2008 JINST 3 S08004 SISSA May 18, 2008 : January 9, 2008 August 14, 2008 : : CCEPTED A ECEIVED http://www.iop.org/EJ/jinst/ UBLISHED R UBLISHINGAND P P XPERIMENTS E HYSICS P NSTITUTEOF I CCELERATOR AND :A 5) assuring very good hermeticity. The overall dimensions ). At the core of the CMS detector sits a high-magnetic- 1 − s | ≤ UBLISHEDBY 2 OLLIDER solid angle. Forward sampling calorimeters extend the pseudo- P η − C cm 27 (10 ADRON 1 H − s 2 − ARGE cm 34 : Instrumentation for particle accelerators and storage rings - high energy; Gaseous : The Compact Muon Solenoid (CMS) detector is described. The detector operates at CERNL BSTRACT EYWORDS HE A K T field and large-bore superconducting solenoidlead-tungstate surrounding scintillating-crystals an electromagnetic all-silicon calorimeter, pixel and andhadron a strip calorimeter. brass-scintillator tracker, a sampling The irondetectors yoke covering of most the of the flux-return 4π rapidity is coverage instrumented to with high values four (| stations of muon © 2008 IOP Publishing Ltd and SISSA CMS Collaboration detectors; Scintillators, scintillation and light emissionCalorimeters; processes; Gamma Solid detectors; state Large detectors; detector systemsParticle for identification particle methods; and Particle astroparticle tracking physics; detectors;circuits; Spectrometers; Control Analogue and electronic monitor systems online;Detector Data control acquisition systems; circuits; Digital Data electronic acquisition circuits;readout concepts; Digital concepts; signal Front-end processing; electronics Electronic for detector detectorand readout; online Modular filtering; electronics; Optical Online detector farms readoutcircuits; concepts; Analysis Trigger and concepts statistical and methods; systems; Computing; VLSI methods; Data Pattern processing recognition, methods; cluster Data finding, reduction calibrationarchitectures; and Detector fitting alignment methods; and Software calibration methods;thermo-stabilization; Detector Detector cooling design and and construction technologiesgrounding; and Manufacturing; materials; Overall Detector mechanics design; Special cables; Voltage distributions. the Large Hadron Collider (LHC)lead) collisions at at CERN. a It centre-of-mass wasties energy conceived up of to 14 to TeV study (5.5 10 TeV proton-proton nucleon-nucleon) (and and lead- at luminosi- of the CMS detector are a length of 21.6 m, a diameter of 14.6 m and a total weight of 12500 t. The CMS experiment at the CERN LHC 2008 JINST 3 S08004 L. Van Lancker, P. Van Mulders, I. Villella, 1 – ii – C. Wastiels, C. Yu Université Libre de Bruxelles, Bruxelles, Belgium O. Bouhali, O. Charaf, B. Clerbaux,R. P. De Gindroz, Harenne, G. G.H. DeJ. Lentdecker, Hammad, Stefanescu, J.P. V. Dewulf, Sundararajan, S. T. C. Elgammal, Vander Velde, Mahmoud, P. Vanlaer, J. L. Wickens Neukermans, M. Pins, R. Pins, S. Rugovac, Yerevan Physics Institute, Yerevan, Armenia S. Chatrchyan, G. Hmayakyan, V. Khachatryan, A.M. Sirunyan Institut für Hochenergiephysik der OeAW, Wien, Austria W. Adam, T. Bauer, T.V.M. Bergauer, Ghete, H. Bergauer, P. M. Glaser,ner, Dragicevic, C. M. J. Erö, Krammer, Hartl, M.M. I. N. Oberegger, Friedl, Magrans M. Hoermann, R. Padrta, de Frühwirth, M. J.H. Pernicka, Abril, Steininger, P. Hrubec, J. Porth, M. Strauss, H. S. A. Markytan, Rohringer, Taurok, S. D. Hänsel, I. Schmid, Uhl, W. T. M. Mikulec, Waltenberger, Schreiner, G. R. Walzel, Jeitler, B. E. Stark, Byelorussian Widl, K. State Neuherz, C.-E. University, Wulz Minsk, Kast- T. Belarus Nöbauer, V. Petrov, V. Prosolovich National Centre for Particle and HighV. Energy Chekhovsky, O. Physics, Dvornikov, Minsk, I. Belarus Emeliantchik, A. Litomin,N. V. Shumeiko, Makarenko, A. I. Solin, Marfin, R. V. Mossolov, Stefanovitch, J. Suarez Gonzalez, A. Tikhonov Research Institute for Nuclear Problems, Minsk,A. Belarus Fedorov, M. Korzhik, O. Missevitch, R. Zuyeuski Universiteit Antwerpen, Antwerpen, Belgium W. Beaumont, M. Cardaci, E. DeP. Langhe, Van Mechelen E.A. De Wolf, E. Delmeire, S. Ochesanu, M. Tasevsky, Vrije Universiteit Brussel, Brussel, Belgium J. D’Hondt, S.M.U. De Mozer, Weirdt, S. O. Tavernier, Devroede, W. Van R. Doninck, Goorens, S. Hannaert, J. Heyninck, J. Maes, CMS Collaboration 2008 JINST 3 S08004 1 L. Dimitrov, V. Genchev, 1 – iii – R.L. Iope, S.F. Novaes, T. Tomei 2 V. Velev, V. Verguilov 1 Institute for Nuclear Research and NuclearT. Energy, Sofia, Anguelov, Bulgaria G. Antchev, I. Atanasov, J. Damgov, N. Darmenov, Ghent University, Ghent, Belgium M. Tytgat Université Catholique de Louvain, Louvain-la-Neuve, Belgium S. Assouak, J.L. Bonnet,S. De G. Visscher, P. Demin, Bruno, D.M. J. Favart, Jonckman, C. D. Caudron, Felix, Kcira, B. T. B. Keutgen, Florins, V.K. E. Lemaitre, De Piotrzkowski, D. Forton, V. Callatay, Michotte, A. Roberfroid, O. Giammanco, X. J. Militaru, Rouby, G. S. N. De Grégoire, Ovyn, Schul, T. Favereau O. Pierzchala, Van De der Aa Jeneret, Université de Mons-Hainaut, Mons, Belgium N. Beliy, E. Daubie, P. Herquet Centro Brasileiro de Pesquisas Fisicas, RioG. de Alves, Janeiro, M.E. Brazil Pol, M.H.G. Souza Instituto de Fisica - Universidade FederalRio do de Rio Janeiro, de Brazil Janeiro, M. Vaz Universidade do Estado do Rio deD. Janeiro, De Rio Jesus de Damiao, Janeiro, V. Brazil Oguri, A. Santoro, A. Sznajder Instituto de Fisica Teorica-Universidade Estadual Paulista, Sao Paulo, Brazil E. De Moraes Gregores, P. Iaydjiev, A. Marinov, S. Piperov, S. Stoykova, G. Sultanov, R. Trayanov, I. Vankov University of Sofia, Sofia, Bulgaria C. Cheshkov, A. Dimitrov, M. Dyulendarova,E. I. Glushkov, Marinova, V. Kozhuharov, L. S. Litov, M. Markov,Z. Makariev, Toteva, M. Mateev, I. Nasteva, B. Pavlov,Institute P. of High Petev, Energy P. Physics, Beijing, Petkov,J.G. China V. Bian, Spassov, G.M. Chen,J. H.S. Wang, M. Chen, Yang, Z. M. Zhang, W.R. Chen, Zhao, H.L. C.H. Zhuang Jiang, B.Peking Liu, University, Beijing, X.Y. China Shen, H.S.Y. Ban, Sun, J. Cai, J. Y.C. Ge, Tao, S. Liu,J. H.T. Ying Liu, L. Liu, S.J. Qian, Q. Wang, Z.H. Xue, Z.C. Yang, Y.L. Ye, 2008 JINST 3 S08004 1 A. Heikkinen, 1 – iv – T. Tuuva 1 T. Lampén, K. Lassila-Perini, V. Lefébure, S. Lehti, T. Lindén, 1 F. Moura Brigido, T. Mäenpää, T. Nyman, J. Nystén, E. Pietarinen, 1 A. Honkanen, J. Härkönen,M. V. Karimäki, Kotamäki, H.M. Katajisto, A. R. Kuronen, P.R. Kinnunen, Luukka, J. S. Klem, Michal, J. Kortesmaa, Laboratoire d’Annecy-le-Vieux de Physique des Particules, IN2P3-CNRS, Annecy-le-Vieux, France G. Bassompierre, A. Bazan, P.Y. David,mel, J. A. Ditta, G. Karneyeu, Drobychev, T. N. LeM. Fouque, Flour, Schneegans, J.P. Guillaud, S. D. V. Sillou, Lieunard, Her- J.P. M. Vialle Maire, P. Mendiburu, P. Nedelec, J.P. Peigneux, K. Skog, K.C. Tammi, Williams E. Tuominen, J. Tuominiemi, D.Lappeenranta University Ungaro, of Technology, Lappeenranta, T.P. Finland Vanhala,M. Iskanius, L. A. Wendland, Korpela, G. Polese, Shanghai Institute of Ceramics, Shanghai, ChinaP.J. (Associated Li, Institute) J. Liao, Z.L. Xue, D.S. Yan, H. Yuan Universidad de Los Andes, Bogota, Colombia C.A. Carrillo Montoya, J.C. Sanabria Technical University of Split, Split, Croatia N. Godinovic, I. Puljak, I. Soric University of Split, Split, Croatia Z. Antunovic, M. Dzelalija, K. Marasovic Institute Rudjer Boskovic, Zagreb, Croatia V. Brigljevic, K. Kadija, S. Morovic University of Cyprus, Nicosia, Cyprus R. Fereos, C. Nicolaou, A. Papadakis, F. Ptochos, P.A. Razis, D. Tsiakkouri,National Z. Institute Zinonos of Chemical Physics andA. Biophysics, Hektor, Tallinn, M. Estonia Kadastik, K. Kannike, E. Lippmaa, M. Müntel, M. Raidal,Laboratory L. of Rebane Advanced Energy Systems, Helsinki University of Technology, Espoo, Finland P.A. Aarnio Helsinki Institute of Physics, Helsinki, Finland E. Anttila, K. Banzuzi, P. Bulteau, S. Czellar, N. Eiden, C. Eklund, P. Engstrom, 2008 JINST 3 S08004 1 , W. Dulinski, 5 1, Y. Patois, P. Prala- 5 C. Maazouzi, V. Mack, 6 A.M. Bergdolt, J.D. Berst, 6 E. Christophel, G. Claus, J. Cof- A. Debraine, D. Decotigny, L. Do- ∗ 3 L. Guevara Riveros, M. Haguenauer, ∗ C. Illinger, F. Jeanneau, P. Juillot, T. Kachelhoffer, 6 – v – G. Gaudiot, W. Geist, D. Gelé, T. Goeltzenlichter, 5 S. Moreau, C. Olivetto, A. Pallarès, E. Bougamont, M. Boyer, P. Bredy, R. Chipaux, M. De- D. Huss, 6 ∗ 6 L. Anckenmann, J. Andrea, F. Anstotz, 5 R. Fang, J.C. Fontaine, 5 P. Graehling, L. Gross, C. Guo Hu, J.M. Helleboid, T. Henkes, M. Hoffer, C. Hoff- A. Albert, E. Locci, J.P. Lottin, I. Mandjavidze, M. Mur, J.P. Pansart, A. Payn, J. Rander, 6 5 D. Bloch, J.M. Brom, J. Cailleret, F. Charles, 1 5 4 DSM/DAPNIA, CEA/Saclay, Gif-sur-Yvette, France M. Anfreville, J.P. Bard, P. Besson, jardin, D. Denegri, J.P. Descamps, Gras, B. G. Hamel Fabbro, de J.L. Monchenault,B. Faure, P. Jarry, Levesy, S. C. Ganjour, Jeanney, F. F.X.J.M. Kircher, Gentit, M.C. Reymond, A. Lemaire, Givernaud, Y. J. Lemoigne, A. Rolquin, Van Lysebetten, P. F. Venault, P. Rondeaux, Verrecchia A. Rosowsky,Laboratoire J.Y.A. Leprince-Ringuet, Ecole Rousse, Polytechnique, Z.H.IN2P3-CNRS, Sun, Palaiseau, France J. Tartas, M. Anduze, J. Badier,P. S. Busson, Baffioni, M. Cerutti, M. D. Bercher,brzynski, Chamont, C. O. C. Bernet, Ferreira, Charlot, Y. U. C. Geerebaert,A. Berthon, Collard, J. Karar, J. Gilly, B. C. Bourotte, Koblitz, Gregory, A. D.N. Lecouturier, Busata, Pukhaeva, A. N. Mathieu, G. Regnault,A. Milleret, Zabi T. P. Miné, Romanteau, P. I. Paganini, P. Semeniouk, Poilleux, Y.Institut Pluridisciplinaire Sirois, Hubert Curien, C. Thiebaux,IN2P3-CNRS, Université J.C. Louis Pasteur Vanel, Strasbourg, France,Université and de Haute Alsace Mulhouse, Strasbourg,J.L. France Agram, R. Blaes, fin, C. Colledani, J.J.P. Ernenwein, Croix, E. Dangelser,U. Goerlach, N. Dick, F.mann, Didierjean, J. Hosselet, F. L. Houchu, Drouhin Y. Hu, M.R. Kapp, H. Kettunen, L. Lakehal Ayat, A.C. Le Bihan, A. Lounis, P. Majewski, D. Mangeol, J.vorio, Michel, C. Racca, Y. Riahi,M.H. Sigward, I. J.L. Sohler, Ripp-Baudot, J. P. Speck, Schmitt,A. R. Zghiche Strub, J.P. T. Schunck, Todorov, R. G. Turchetta, P. Van Schuster, Hove, D. B. Vintache, Schwaller, Institut de Physique Nucléaire, IN2P3-CNRS, Université Claude Bernard Lyon 1,M. Villeurbanne, Ageron, France J.E. Augustin, C. Baty, G.P. Baulieu, Brunet, M. Bedjidian, E. J. Blaha, Chabanat, A.R. Bonnevaux, E.C. G. Della Boudoul, Chabert, Negra, P. R. Depasse, O. Chierici,J. Drapier, V. Fay, M. Chorowicz, Dupanloup, S. C. T. Dupasquier, Gascon,N. Combaret, H. N. El Lumb, D. Mamouni, Giraud, Contardo, C. N. Estre, C. Martin,E. Schibler, Girerd, F. H. Schirra, G. G. Mathez, Smadja, Guillot, S. G. Tissot, R. Maurelli, B. Trocme, Haroutunian, S. S. Vanzetto, B. J.P.Institute Muanza, Walder of Ille, High P. Energy Pangaud, M. Physics and Lethuillier, S.Tbilisi Informatization, State Perries, University, Tbilisi, O. Georgia Ravat, Y. Bagaturia, D. Mjavia, A. Mzhavia, Z. Tsamalaidze 2008 JINST 3 S08004 1 1 7 V. Zhukov ∗ B. Fehr, H. Fesefeldt, G. Fetchenhauer, ∗ 1 – vi – R. Mameghani, A. Meyer, S. Meyer, T. Moers, E. Müller, R. Pahlke, B. Philipps, ∗ J. Vandenhirtz, H. Wagner, M. Wegner, C. Zeidler ∗ Institute of Physics Academy of Science,V. Tbilisi, Roinishvili Georgia RWTH Aachen University, I. Physikalisches Institut,R. Aachen, Germany Adolphi, G.A. Anagnostou, Khomich, R. Brauer, K.doulas, W. Klein, G. Braunschweig, Pierschel, C. F. H. Raupach, Kukulies,M. Esser, S. Thomas, M. Schael, K. L. Weber, B. A. Lübelsmeyer, Feld, Wittmer, Schultz M. von Wlochal W. J. Dratzig, Karpinski, Olzem, G.RWTH Schwering, Aachen A. R. University, III. Siedling, Ostaptchouk, Physikalisches Institut D.F. A, Adamczyk, Aachen, Pan- A. Germany Adolf, G. Altenhöfer,nackels, S. K. Bosseler, Bechstein, A. S. Böhm, M. Bethke, Erdmann, P. H. Biallass, Faissner, O. Biebel, M. Bonte- RWTH Aachen University, III. Physikalisches InstitutF. B, Beissel, Aachen, M. Germany Davids, M. Duda,S. G. Kasselmann, Flügge, G. M. Kaussen, Giffels, T. T. Kress,P. Hermanns, Sauerland, A. A. D. Linn, Stahl, Heydhausen, A. D. S. Nowack, Tornier, Kalinin, L. M.H. Zoeller Perchalla, M. Poettgens, O.Deutsches Pooth, Elektronen-Synchrotron, Hamburg, Germany U. Behrens, K. Borras, A.J. Flossdorf, Mnich, D. C. Hatton, Rosemann, B. C. Hegner, Youngman, W.D. M. Zeuner Kasemann, R. Mankel, A. Meyer, J. Frangenheim, J.H.K. Frohn, Hoepfner, J. C. Grooten, Hof,D. T. E. Lanske, Hebbeker, Jacobi, S. S.D. Hermann, Kappler, Rein, E. M. H. Hermens, Kirsch, Reithler,T. G. Stapelberg, P. H. W. Kreuzer, Szczesny, Hilgers, H. Reuter, Teykal, R. D. Teyssier, H. P. Kupper,J. Tomme, W. Rütten, Tomme, Tutas, H.R. M. Tonutti, S. O. Lampe, Tsigenov, Schulz, H. Schwarthoff, W. Sobek, M. Sowa, University of Hamburg, Institute for ExperimentalHamburg, Physics, Germany F. Bechtel, P. Buhmann,N. Schirm, E. P. Schleper, Butz, G. Steinbrück, G. R. Van Flucke, Staa, R. R.H. Wolf Hamdorf,Institut für U. Experimentelle Holm, Kernphysik, Karlsruhe, Germany R.B. Klanner, Atz, T. U. Barvich, Pein, P.P. Blüm, Dehm, F. G. Boegelspacher, Dirkes, H. M.F. Bol, Hauler, Fahrer, S. Z.Y. U. Heier, Chen, Felzmann, K. S. Kärcher, M. B.G. Chowdhury, Frey, Ledermann, Quast, W. A. S. De K. Mueller, Furgeri, Rabbertz, Boer, Th. E. A. Müller,A. Sabellek, Gregoriev, D. Theel, F. Neuberger, A. W.H. C. Hartmann, Thümmel, Scheurer, Piasecki, A. F.P. Schilling, Trunov, A. H.J. Vest, Simonis, T. Weiler, A. C. Skiba, Weiser, S. P. Weseler, Steck, Institute of Nuclear Physics "Demokritos", AghiaM. Paraskevi, Greece Barone, G. Daskalakis,K. Karafasoulis, N. A. Dimitriou, Koimas, A. G. Kyriakis, Fanourakis, S. Kyriazopoulou, C. D. Filippidis, Loukas, A. T. Markou, Geralis, C. C. Markou, Kalfas, 2008 JINST 3 S08004 A. Gurtu, 10 P. Kovesarki, A. Laszlo, Z.L. Trocsanyi, G. Zilizi 8 1 P. Hidas, D. Horvath, 1 – vii – S. Chatterji, S. Chauhan, B.C. Choudhary, P. Gupta, M. Jha, K. Ranjan, 9 G. Majumder, K. Mazumdar, A. Nayak, M.R. Patil, S. Sharma, K. Sudhakar L. Boldizsar, G. Debreczeni, C. Hajdu, 1 11 R.K. Shivpuri, A.K. Srivastava Bhabha Atomic Research Centre, Mumbai, India R.K. Choudhury, D. Dutta, M.P. Shukla, Ghodgaonkar, A. S. Topkar Kailas, S.K. Kataria, A.K. Mohanty, L.M. Pant, Tata Institute of Fundamental Research —T. EHEP, Mumbai, Aziz, India Sunanda Banerjee, S. Bose, S. Chendvankar, P.V. Deshpande, M. Guchait, G. Odor, G. Patay, F. Sikler, G. Veres, G. Vesztergombi, P. Zalan Institute of Nuclear Research ATOMKI, Debrecen, Hungary A. Fenyvesi, J. Imrek, J. Molnar, D. Novak, J. Palinkas, G.University Szekely of Debrecen, Debrecen, Hungary N. Beni, A. Kapusi, G. Marian, B. Radics, P. Raics, Z. Szabo,Panjab Z. University, Szillasi, Chandigarh, India H.S. Bawa, S.B. Beri,J.B. Singh V. Bhandari, V. Bhatnagar, M. Kaur,University J.M. of Kohli, Delhi, Delhi, A. India Kumar,S. Arora, B. S. Singh, Bhattacharya, M. Maity, Tata Institute of Fundamental Research —B.S. HECR, Mumbai, Acharya, India SudeshnaN.K. Banerjee, Mondal, N. S. Panyam, P. Verma Bheesette, S. Dugad,Institute S.D. for Studies Kalmani, in Theoretical V.R. PhysicsTehran, & Lakkireddi, Iran Mathematics (IPM), H. Arfaei, M. Hashemi, M. Mohammadi Najafabadi, A. Moshaii, S. Paktinat Mehdiabadi N. Mastroyiannopoulos, C. Mavrommatis, J.ofilatos, Mousa, S. I. Tzamarias, Papadakis, A. Vayaki, E. G. Petrakou, Vermisoglou, A. I. Zachariadou Siotis, K. The- University of Athens, Athens, Greece L. Gouskos, G. Karapostoli, P. Katsas, A. Panagiotou, C. Papadimitropoulos University of Ioánnina, Ioánnina, Greece X. Aslanoglou, I. Evangelou, P. Kokkas, N. Manthos, I. Papadopoulos, F.A.KFKI Triantis Research Institute for Particle andBudapest, Nuclear Hungary Physics, G. Bencze, 2008 JINST 3 S08004 1 P. Tem- F. Lelli, V. Gior- 1 1 12 L. Daniello, F. Fabbri, F. Felli, 1 – viii – G. Salemi, C. Sutera, A. Tricomi, C. Tuve 48 M. De Palma, G. De Robertis, G. Donvito, R. Ferorelli, L. Fiore, 25 S. Mersi, M. Meschini, C. Minelli, S. Paoletti, G. Parrini, E. Scarlini, G. Sguazzoni 1 pesta, R. Trentadue, S. Tupputi, G. Zito Università di Bologna e Sezione dell’G. INFN, Bologna, Abbiendi, Italy W. Bacchi,Giacomelli, C. V.D. Battilana, Cafaro, P. A.C. Capiluppi, Benvenuti, A.fiani, Castro, M. I. F.R. Boldini, Cavallo, D’Antone, C. D. G.M. Ciocca, Bonacorsi, G. Dallavalle, S. Codispoti, F. M. Braibant- Fabbri, Cuf- A. Fanfani, S. Finelli, P. Giacomelli, D. Creanza, N. De Filippis, M. Franco, D. Giordano,N. R. Manna, B. Guida, Marangelli, M.S. G. Mennea, Iaselli,pili, S. My, G. N. S. Pugliese, Natali, Lacalamita, S. A. Nuzzo, F. Ranieri, G. Loddo, F. Papagni, Romano, C. G. Pinto, G. Maggi, A. Roselli, Pom- M. G. Maggi, Sala, G. Selvaggi, L. Silvestris, dano, M. Giunta, C. Grandi,F.L. Navarria, M. F. Odorici, Guerzoni, A. L. Paolucci, G. Guiducci, Pellegrini,G. S. A. Torromeo, Perrotta, Marcellini, R. A.M. G. Travaglini, Rossi, G.P. T. Masetti, Veronese Rovelli, G.P. A. Siroli, Montanari, Università di Catania e Sezione dell’S. INFN, Catania, Albergo, Italy M. Chiorboli,F. Noto, S. R. Costa, Potenza, M.A. M. Saizu, Galanti, G. Gatto Rotondo,Università N. di Giudice, Firenze e N. Sezione dell’ Guardone, L. INFN, Bellucci, Firenze, M. Italy Brianzi, G. Broccolo,cardi, E. S. Catacchini, Frosali, V. Ciulli, C. C. Genta, Civinini, G. R. Landi,tini, P. D’Alessandro, L. Lenzi, E. Masetti, A. Fo- Macchiolo, F. Maletta, F. Manolescu, C. Marchet- M. Giardoni, A. La Monaca, B.luigi, Ortenzi, B. M. Ponzio, Pallotta, C. A. Pucci, Paolozzi, A. C. Russo, Paris, L. G. Passamonti, Saviano D. Pier- Università di Genova e Sezione dell’P. INFN, Fabbricatore, Genova, S. Italy Farinon, M. Greco, R. Musenich Laboratori Nazionali di Legnaro dell’ INFN, Legnaro, Italy (Associated Institute) S. Badoer, L. Berti,G. M. Maron, S. Biasotto, Squizzato, S. N. Toniolo, Fantinel, S. Traldi E. Frizziero, U. Gastaldi, M. Gulmini, Laboratori Nazionali di Frascati dell’ INFN,L. Frascati, Benussi, Italy M. Bertani, S. Bianco, M. Caponero, D. Colonna, University College Dublin, Dublin, Ireland M. Felcini, M. Grunewald Università di Bari, Politecnico di BariK. e Sezione Abadjiev, dell’ M. INFN, Abbrescia, Bari, Italy L. Barbone, P. Cariola, F. Chiumarulo, A. Clemente, A. Colaleo, 2008 JINST 3 S08004 1 A. Venturi, 1 1 G. Magazzu, P. Mammini, 48 A. Giassi, S. Giusti, D. Kartashov, A. Kraan, – ix – 13 G. Balestri, A. Basti, R. Bellazzini, L. Benucci, J. Bernardini, L. Berretta, L. Barcellan, M. Bellato, M. Benettoni, D. Bisello, E. Borsato, A. Can- F. Ferri, P. Govoni, S. Magni, M. Malberti, S. Malvezzi, R. Mazza, 1 1 1 A. Neviani, M. Nigro, A. Paccagnella, D. Pantano, A. Parenti, M. Passaseo, 1 S. Bizzaglia, M.T. Brunetti, B. Caponeri, B. Checcucci, R. Covarelli, N. Dinu, 1 INFN e Universita Degli Studi Milano-Bicocca,S. Milano, Banfi, Italy R. Bertoni, M.P. Bonesini, L. Dini, Carbone, G.B. F.M. Cerati, Farina, F. Chignoli, P. D’Angelo, A. De Min, D. Menasce, V. Miccio,N. L. Redaelli, M. Moroni, Rovere, L. P. Sala, Negri, S. M. Sala, R. Paganoni, Salerno, T. D. TabarelliIstituto de Pedrini, Nazionale Fatis, di V. A. Tancini, Fisica S. Nucleare Pullia, Taroni deA. S. Napoli (INFN), Boiano, Ragazzi, Napoli, F. Italy Cassese,P. C. Paolucci, G. Cassese, Passeggio, D. A. Piccolo, Cimmino, L. Roscilli, B. C. D’Aquino, Sciacca, A. L. Vanzanella Università Lista, di Padova D. e Lomidze, Sezione dell’ P.P. INFN, Noli, Azzi, Padova, Italy N. Bacchetta, delori, R. Carlin,F. L. Dal Castellani, Corso, M. P. De Checchia,parini, Giorgi, L. U. M. Ciano, Gasparini, De Mattia, A.A. A. T. Kaminskiy, Giraldo, Colombo, Dorigo, S. P. E. Karaevskii, U. Giubilato, V. Dosselli,M. Conti, Khomenkov, Loreti, F. C. D. M. M. Gonella, Margoni, Fanin, Kostylev, R. Da S. G. Martinelli, A. S. Lacaprara, Galet,F. Rold, Mattiazzo, Gresele, Montecassiano, I. M. F. Mazzucato, Gas- A. Lazzizzera, A.T. Meneguzzo, I. Griggio, L. Modenese, Lippi, P. Guaita, R. Pedrotta, M. Pegoraro, G. Rampazzo,I. S. Reznikov, Stavitskiy, P. Ronchese, M. A. Tessaro, Sancho E.M. Daponte, Zago, P. Torassa, Sartori, F. A. Zatti, P. Triossi, Zotto, G. S. Zumerle Vanini, S. Ventura, L.Università di Ventura, Pavia M. e Sezione Verlato, dell’P. INFN, Baesso, Pavia, Italy G. Belli,D. U. Pagano, S.P. Ratti, Berzano, C. S. Riccardi, P. Bricola, Torre, A. A. Vicini, P. Vitulo, Grelli, C. Viviani Università G. di Musitelli, Perugia e R. Sezione dell’ Nardò,D. INFN, Perugia, M.M. Aisa, Italy Necchi, S.G.M. Aisa, Bilei, F.L. Ambroglini, Fanò, L. M.M. Farnesini, M. Angarano,P. Placidi, Giorgi, V. P. E. Postolache, Lariccia, R. G. Santinelli, Babucci, A. Mantovani, Santocchia, F. D. L. Moscatelli, Servoli, D. Benedetti, D. Passeri, Spiga A.Università M. di Piluso, Pisa, Biasini, Scuola Normale SuperioreP. e Azzurri, Sezione G. dell’ Bagliesi, INFN, Pisa, Italy S. Bianucci, T. Boccali, A. Bocci, L.U. Borrello, Cazzola, F. Bosi, M. F. Ceccanti, Bracci, A. R.F. Brez, Cecchi, F. Fiori, Calzolari, C. R. Cerri, Castaldi, L. A.S. Cucoanes, Foà, R. Dell’Orso, A. D. Gaggelli, Dobur, S. S. Dutta, Gennai, L. Latronico, F. Ligabue, S. Linari, T. Lomtadze, G.A. Lungu, F. Mariani, G. Martinelli, M. Massa, A.G. Messineo, Petrucciani, A. A. Moggi, Profeti, F. F. Raffaelli, Palla, D. F.A.T. Palmonari, Rizzi, G. Serban, G. Petragnani, Sanguinetti, A. S. Sarkar, Slav, G. P.P.G. Segneri, Spagnolo, Verdini, D. M. Sentenac, G. Vos, L. Spandre, Zaccarelli R. Tenchini, S. Tolaini, G. Tonelli, 2008 JINST 3 S08004 14 D. Trocino, V. Vaniev, C. Gargiulo, S. Guerra, 1 14 R. Bellan, F. Benotto, C. Bi- 15 – x – M. Nuccetelli, G. Organtini, A. Palma, R. Paramatti, 14 R. Panero, A. Parussa, N. Pastrone, C. Peroni, G. Petrillo, A. Romero, 15 L. Barone, A. Bartoloni, B. Borgia, G. Capradossi, F. Cavallari, A. Cecilia, R. Sacchi, M. Scalise, A. Solano, A. Staiano, P.P. Trapani, 14 15 M. Ruspa, D. D’Angelo, I. Dafinei, D. Del Re,M. E. Iannone, Di Marco, E. M. Diemoz, Longo, G. Ferrara, M. Montecchi, ino, S. Bolognesi, M.A.R. Borgia, Cirio, C. M. Botta, Cordero, A.F. M. Brasolin, Costa, Dumitrache, N. D. Cartiglia, R. Dattola, R.M. Castello, F. Farano, Marone, Daudo, G. S. G. G. Cerminara, Maselli, Dellacasa,M. E. Ferrero, N. Nervo, Menichetti, M.M. Demaria, Obertino, E. P. G. Mereu, Filoni, Dughera, E. Migliore, G. G. Mila, Kostyleva, V.A. H.E. Monaco, Vilela Pereira, M. A. Larsen, Musich, Zampieri C. Mariotti, Università di Trieste e Sezione dell’S. INFN, Belforte, Trieste, Italy F. Cossutti, G. Della Ricca, B. Gobbo, C. Kavka, A.Chungbuk Penzo National University, Chongju, Korea Y.E. Kim Kangwon National University, Chunchon, Korea S.K. Nam Kyungpook National University, Daegu, Korea D.H. Kim, G.N. Kim, J.C. Kim, D.J. Kong, S.R. Ro, D.C. Son Wonkwang University, Iksan, Korea S.Y. Park Cheju National University, Jeju, Korea Y.J. Kim Chonnam National University, Kwangju, Korea J.Y. Kim, I.T. Lim Dongshin University, Naju, Korea M.Y. Pac Seonam University, Namwon, Korea S.J. Lee Università di Roma I e SezioneS. dell’ INFN, Baccaro, Roma, Italy F. Pellegrino, S. Rahatlou, C. Rovelli, F. Safai Tehrani, A. Zullo Università di Torino e Sezione dell’G. INFN, Torino, Alampi, Italy N. Amapane, R. Arcidiacono, S. Argiro, M. Arneodo, 2008 JINST 3 S08004 – xi – Konkuk University, Seoul, Korea S.Y. Jung, J.T. Rhee Korea University, Seoul, Korea S.H. Ahn, B.S. Hong, Y.K. Jeng,D.H. M.H. Moon, Kang, I.C. Park, H.C. S.K. Kim, Park, J.H. M.S. Kim, Ryu, T.J. K.-S. Kim, Sim, K.S. K.J. Lee, Son Seoul National J.K. University, Lim, Seoul, Korea S.J. Hong Sungkyunkwan University, Suwon, Korea Y.I. Choi Centro de Investigacion y de EstudiosH. Avanzados del Castilla IPN, Valdez, A. Mexico Sanchez City, Hernandez Mexico Universidad Iberoamericana, Mexico City, Mexico S. Carrillo Moreno Universidad Autonoma de San Luis Potosi,A. San Morelos Luis Pineda Potosi, Mexico Technische Universiteit Eindhoven, Eindhoven, Netherlands (Associated Institute) A. Aerts, P. Van der Stok, H. Weffers University of Auckland, Auckland, New Zealand P. Allfrey, R.N.C. Gray, M. Hashimoto, D. Krofcheck University of Canterbury, Christchurch, New Zealand A.J. Bell, N. BernardinoJ.C. Williams Rodrigues, P.H. Butler, S. Churchwell,National R. Centre for Knegjens, Physics, Quaid-I-Azam S. University,Z. Islamabad, Whitehead, Pakistan Aftab, U.H.R. Ahmad, Hoorani, I. I. Ahmed,H. Shahzad, Hussain, W. A.R. Zafar Ahmed, N. M.I. Hussain, Asghar, M. S.National Iftikhar, University Asghar, of M.S. Sciences G. And Khan, Technology, Rawalpindi Dad, Cantt, K. Pakistan M. (Associated Mehmood, Institute) Hafeez, A. A. Ali, A. Osman, Bashir, A.M. Jan, A. Kamal, F. Khan, M. Saeed,Institute S. of Tanwir, Nuclear M.A. Physics, Zafar Polish AcademyJ. of Blocki, Sciences, Cracow, A. Poland Cyz,P. E. Zychowski Gladysz-Dziadus, S. Mikocki, M. Rybczynski, J. Turnau, Z. Wlodarczyk, 2008 JINST 3 S08004 16 S. Shmatov, 17 G. Varner, N. Vaz Cardoso 1 – xii – I. Belotelov, P. Bunin, S. Chesnevskaya, V. Elsha, Y. Er- ∗ A. Ivanov, V. Kudinov, O. Logatchev, S. Onishchenko, A. Orlov, 1 P. Zych 16 W. Zabolotny, Joint Institute for Nuclear Research, Dubna,I. Russia Altsybeev, K. Babich, A. Belkov, Institute of Experimental Physics, Warsaw, Poland K. Bunkowski, M. Cwiok,nowski, K. H. Kierzkowski, Czyrkowski, M. Konecki, R. J. Dabrowski, Krolikowski, I.M. W. Kudla, Dominik, M. Pietrusinski, K. K. Doroba, Pozniak, A. Kali- Soltan Institute for Nuclear Studies, Warsaw, Poland R. Gokieli, L. Goscilo, M. Górski, K. Nawrocki, P. Traczyk, G. Wrochna, P. Zalewski Warsaw University of Technology, Institute of ElectronicWarsaw, Poland Systems, (Associated Institute) K.T. Pozniak, R. Romaniuk, W.M. Zabolotny Laboratório de Instrumentação e Física ExperimentalLisboa, de Portugal Partículas, R. Alemany-Fernandez, C. Almeida,M. N. Bluj, Almeida, S. Da A.S. Mota Araujo Silva,jko, A. Vila A. David Verde, Jain, Tinoco T. Mendes, M. Barata M. Kazana,P. Freitas Silva, Monteiro, P. Ferreira, S. Musella, M. Silva, I. Gallinaro, R. Teixeira, M. Nobrega, J.P. Teixeira, Huse- J. J. Varela, Rasteiro Da Silva, P.Q. Ribeiro, M. Santos, shov, I. Filozova, M. Finger, M. FingerV. Jr., Kalagin, A. A. Golunov, Kamenev, I. V. Karjavin, Golutvin, S. N.V. Gorbounov, Khabarov, I. V. Korenkov, Khabarov, Gramenitski, Y. G. Kiryushin, V. Kozlov, Konoplyanikov, A.V.V. Mitsyn, Kurenkov, K. A. Moisenz, P. Lanev, Moisenz, V.lygin, S. Lysiakov, A. Movchan, A. Petrosyan, E. E. Nikonov, Malakhov, D. Rogalev, I. V. Oleynik, Samsonov, Melnitchenko, V. M. Palichik, Savina, V. R. Pere- Semenov, S. Sergeev, S. Shulha, V. Smirnov, D. Smolin, A.S. Tcheremoukhine, Vasil’ev, A. O. Vishnevskiy, A. Teryaev, E. Volodko, N. Tikhonenko, A. Zamiatin, Urkinbaev, A. Zarubin, P. Zarubin, E. Zubarev Petersburg Nuclear Physics Institute, Gatchina (StN. Petersburg), Bondar, Russia Y. Gavrikov, V. Golovtsov, Y. Ivanov,F. V. Kim, Moroz, V. Kozlov, P. V. Lebedev, Neustroev, G. G. Makarenkov, V. Obrant, Sknar, E. Orishchin, V. A.G. Skorobogatov, Velichko, Petrunin, S. I. Volkov, Y. A. Shcheglov, Vorobyev Smirnov, A. Shchetkovskiy, V. Sulimov, V. Tarakanov,High Temperature L. Technology Center Uvarov, of Researchneering, S. & (HTTC Development RDIPE), Vavilov, Institute of PowerMoscow, Engi- Russia (Associated Institute) D. Chmelev, D. Druzhkin, V. Sakharov, V. Smetannikov, A. Tikhomirov, S. Zavodthikov 2008 JINST 3 S08004 1 N. Smiljkovic 21 V.Kachanov, A. Kalinin, V. Karpishin, I. Kiselevich, 19 ∗ 20 A. Inyakin, 1 D. Maletic, J. Puzovic, 21 J.M. Barcala, J. Berdugo, C.L. Blanco Ramos, 1 V. Zaytsev 1 – xiii – A. Krokhotin, S. Kuleshov, A. Oulianov, A. Pozdnyakov, G. Safronov, L. Dudko, A. Ershov, G. Eyyubova, A. Gribushin, V. Ilyin, V. Klyukhin, 1 18 M. Djordjevic, D. Jovanovic, 21 C. Burgos Lazaro,coles J. Catalán, Caballero N. Bejar, Colino,A. E. M. Calvo, Ferrando, Daniel, B. M. M.C. Delez Cerrada, Fouz, Lopez, La J.M. M. D. Cruz, Hernandez, M.I. Chamizo A. Francia Josa,J. Delgado Llatas, J. Ferrero, Puerta Marin, Peris, J.J. G. Pelayo, J. C. Merino, J.C. Cher- A. Fernandez Puras Garcia Molinero,C. Sanchez, Bedoya, J.J. Yuste Romero, J. Navarrete, J.C. Ramirez, P. Oller, L. Garcia-Abia, Romero, C. O. Villanueva Munoz, Gonza- C. Willmott, A. Khmelnikov, D. Konstantinov, A.V. Korablev, Lukanin, V. Y. Krychkine, Mel’nik, V. A. Molchanov, V. Petrov, Krinitsyn, V. Petukhov,V. A. V. Pikalov, Shelikhov, A. Levine, Ryazanov, V. I. R. Skvortsov, Ryutin, Lobov, S.S. Slabospitsky, Troshin, A. N. Sobol, Tyurin, A. A. Uzunian, A. Sytine, Volkov, S. V. Zelepoukine Talov, L. Tourtchanovitch, Electron National Research Institute, St Petersburg,V. Russia Lukyanov, G. (Associated Mamaeva, Institute) Z. Prilutskaya, I. Rumyantsev, S. Sokha, S. Tataurschikov, I. Vasilyev Vinca Institute of Nuclear Sciences, Belgrade,P. Serbia Adzic, I. Anicin, Centro de Investigaciones Energeticas Medioambientales y Tecnologicas (CIEMAT),Spain Madrid, E. Aguayo Navarrete, M.J. Aguilar-Benitez, Alcaraz Maestre, J. M. Ahijado Aldaya Munoz, Martin, P. J.M. Arce, Alarcon Vega, J. Alberdi, O. Kodolova, N.A. Kruglov, A.L. Kryukov, Sarycheva, I. V. Savrin, Lokhtin, L. L. Shamardin, Malinina, A. V. Sherstnev, Mikhaylin, A. Snigirev, S. K. Petrushanko, Teplov, I. Vardanyan P.N. Lebedev Physical Institute, Moscow, Russia A.M. Fomenko, N. Konovalova, V. Kozlov, A.I. Lebedev, N. Lvova, S.V. Rusakov, A. Terkulov State Research Center of RussianRussia Federation - Institute for HighV. Abramov, Energy S. Physics, Akimenko, Protvino, A.K. Artamonov, Datsko, A. A. Filine, Ashimova, A. I. Godizov, P. Goncharov, Azhgirey, V.Grishin, S. Bitioukov, O. Chikilev, V. Kolosov, M. Kossov, S. Semenov, N. Stepanov, V. Stolin, E. Vlasov, Moscow State University, Moscow, Russia E. Boos, M. Dubinin, Institute for Nuclear Research, Moscow, Russia Yu. Andreev, A. Anisimov,N. Krasnikov, V. V. Matveev, A. Duk, Pashenkov, A. Pastsyak, S.Alexander V.E. Postoev, Solovey, A. Anatoly Gninenko, Sadovski, Solovey, A. D. N. Skassyrskaia, Soloviev, A. Toropin, Golubev, S. Troitsky D. Gorbunov,Institute M. for Theoretical Kirsanov, and Experimental Physics,A. Moscow, Alekhin, Russia A. Baldov, V. Epshteyn, V. Gavrilov, N. Ilina, V. Kaftanov, 2008 JINST 3 S08004 E. Albert, M. Alidra, S. Ashby, 24 J. Lopez-Garcia, H. Naves Sordo, 22 – xiv – T. Rodrigo, D. Rodriguez Gonzalez, A. Ruiz Jimeno, 1 S. Akhtar, M.I. Akhtar, 24 C. Lasseur, E. Laure, J.F. Laurens, P. Lazeyras, J.M. Le Goff, ∗ C. Figueroa, L.A. Garcia Moral, G. Gomez, F. Gomez Casade- G. Benelli, R. Benetta, J.L. Benichou, W. Bialas, A. Bjorkebo, 23 25 I. Ahmed, 24 A. Domeniconi, S. Dos Santos, G. Duthion, L.M. Edera, A. Elliott-Peisert, 26 P. Lecoq, F. Lemeilleur, M. Lenzi, N. Leonardo, C. Leonidopoulos, M. Letheren, 28 M. Eppard, F. Fanzago,A. Frey, M. A. Favre, Fucci, W. H.wig, Funk, Foeth, A. A. Gaddi, R. Ghezzi, F.R. Gagliardi, Folch, D. M. Gomez-Reino N. Gigi, Gastal, Garrido, Frank, M. K. R. Gateau,rez S. Gill, Goudard, Mlot, J.C. Fratianni, J. Gayde, R. A.S. Gutleber, H. M.A. Grabit, R. Giolo-Nicollerat, Ger- H.F. Hall-wilton, Freire, J.P. Hoffmann, J.P. R. Grillet, Hammarstrom, Girod, A. P. M. Gutierrez F. Holzner, Hansen,W. Llamas, Jank, J. Glege, A. Harvey, P. E. A. W. Janot, Honma, Hervé, Gutier- Glessing, P.J.C. D. J. Jarron, Labbé, Hill, Hufnagel, M. D. Lacroix, Jeanrenaud, M. X. P. Lagrue, Huhtinen, Jouvel, R. S.D. Kerkach, Ilie, K. Kloukinas, V. L.J. Innocente, Kottelat, P. Aspell, E.S. Auffray, Beauceron, P. Baillon, F. Beaudette, D. A. Blechschmidt, Ball, C. S.L.son, Bloch, Bally, H. P. N. Breuker, Bloch, Bangert, R. S.E. Bruneliere, R. Bonacini, Carrone, O. Barillère, J. A. Buchmuller, D. Bos,J. Cattai, D. Cogan, Barney, A. M. Campi, J.P. Conde Chatelain, Garcia, Bosteels, T. H. Camporesi,A. Cornet, M. V. E. Boyer, A. De Corrin, Chauvey, M. Caner, A. Roeck, T. Corvo, S. E. Christiansen, Bran- T.S. Cucciarelli, Cano, B. de Di M. Curé, D. Visser, Vincenzo, Ciganek, D’Enterria, C. S. Delaere, Cittolin, M. Delattre, C. Deldicque, D. Delikaris, D. Deyrail, M. Lebeau, M. Liendl, F. Limia-Conde,C. Lourenco, L. A. Linssen, Lyonnet, A. C.lina, Machard, Ljuslin, M. R. Mackenzie, B. Mannelli, N.A. Lofstedt, Magini, A. Meynet G. R. Cordonnier, Marchioro, J.F. Maire, Michaud, Loos, L. J. L.ders, Malgeri, J.A. Mirabito, Martin, R. R. J. Lopez Moser, Ma- F. Mulon, F. Perez, Mossiere, Meijers, E. J. Muffat-Joly, Murer, P. M. Mul- P. Meridiani, Mättig, E. A. Meschi, Oh, T. A. Onnela, Meyer, M. Oriunno, L. Orsini, J.A. Osborne, J.M. Vizan Garcia Instituto de Física de Cantabria (IFCA),I.J. CSIC-Universidad Cabrillo, de A. Cantabria, Calderon, Santander, Spain D. Canodez, Fernandez, J. I. Fernandez Diaz Merino, Menendez, J.munt, Duarte J. Campderros, M. Gonzalez Fernan- Sanchez,A. R. Lopez Gonzalez Virto, J. Suarez, Marco, R. C.P. Marco, Orviz Jorda, C. Fernandez, Martinez P. Rivero, Lobelle A. P. Pardo, Martinez PatinoL. Ruiz Scodellaro, A. Revuelta, del M. Lopez Arbol, Sobron F. Sanudo, Garcia, Matorras, I. Vila, R. Vilar Cortabitarte Universität Basel, Basel, Switzerland M. Barbero, D. Goldin, B. Henrich, L. Tauscher, S. Vlachos, M. Wadhwa CERN, European Organization for Nuclear Research,D. Geneva, Abbaneo, Switzerland S.M. Abbas, Universidad Autónoma de Madrid, Madrid, Spain C. Albajar, J.F. de Trocóniz, I. Jimenez, R. Macias, R.F. Teixeira Universidad de Oviedo, Oviedo, Spain J. Cuevas, J. Fernández Menéndez, I. Gonzalez Caballero, 2008 JINST 3 S08004 1 ∗ 27 32 32 31 31 31 M. Milesi, 33 S. Stoenchev, F. Wittgenstein, 31 G.M. Georgiev, 1 1 G. Viertel, H.P. von Gun- 31 G. Davatz, V. Delachenal, L. Pape, F. Pauss, E. Petrov, 32 K. Stanishev, 34 W. Kastli, A. Kruse, J. Kuipers, 35 31 B. Meier, P. Milenovic, I. Veltchev, M. Spiropulu, G. Stefanini, A. Strandlie, 1 31 28 B. Betev, B. Blau, A.M. Brett, L. Caminada, – xv – 31 A. Maurisset, 32 30 C. Humbertclaude, B. Iliev, D. Pitzl, T. Punz, P. Riboni, J. Riedlberger, A. Rizzi, F.J. Ronga, G. Dissertori, M. Dittmar, L. Djambazov, M. Dröge, C. Eggel, 31 S. Udriot, D.G. Uzunova, 31 31 32 D. Da Silva Di Calafiori, S. Dambach, A. Nardulli, F. Nessi-Tedaldi, B. Panev, 31 31 F. Behner, I. Beniozef, A. Starodumov 29 31 U. Röser, D. Schinzel, A. Schöning, A. Sourkov, 31 31 M.M. Peynekov, 31 P. Rumerio, O. Runolfsson,E. V. Sbrissa, Ryjov, P. H. Scharff-Hansen, P. Sakulin,M. Schieferdecker, D. Schröder, W.D. Schlatter, Samyn, C. B. L.C. Schwick,P. Schmitt, Siegrist, Santos C. C. H.G. Sigaud, Amaral, N. Schmuecker, Schäfer, Sinanis, H. T. I. Sobrier, P. Sauce, Segoni, Sphicas, P. Sempere Roldán, S. Sgobba, A. Sharma, Z. Chen, N. Chivarov, R. Della Marina, H.J. Dimov, Ehlers, R. Eichler, M. Elmiger, G. Faber, K. Freudenreich, J.F. Fuchs, C. Paillard, I.E. Pal, Perez, G. G. Perinic, Papotti, J.F.M. Pernot, G. Pimiä, R. P. Passardi, Pintus, Petagna, M. P. A. Pioppi, Petiot,E. A. Radermacher, P. Patino-Revuelta, Placci, R. Petit, L. Ranieri, V. A. Pollet, G. Petrilli, H. Patras, Raymond,D. Postema, A. P. Ricci, Rebecchi, M.J. B. Pfeiffer, M. J. Price, Ridel, C. Perea R. Rehn, M. Piccut, Principe, S. Risoldi, Solano, A. Reynaud, P. Rodrigues Racz, H. Simoes Rezvani Moreira, Naraghi, A. Rohlev, G. Roiron, G. Rolandi, F. Szoncsó, B.G. Taylor,E. Tsesmelis, O. A. Tsirou, Teller, J. A. Valls,L. I. Thea, Veillet, Van Vulpen, P. M. Vichoudis, E. Vander G. Donckt, Tournefier, Waurick, F.M. Vasey, J.P. D. M. Winkler, M. Wellisch, Vazquez Acosta, Zanetti P. Treille, Wertelaers, M. P. Wilhelmsson, Tropea, I.M. J. Willers, Troska, Paul Scherrer Institut, Villigen, Switzerland W. Bertl, K. Deiters, P.risberger, Dick, Q. W. Erdmann, Ingram, D. H.C.T. Feichtinger, Sakhelashvili, Kaestli, K. D. Gabathuler, Z. Kotlinski, Hochman, S. R. König, Ho- P. Poerschke,Institute D. for Particle Renker, Physics, ETH T. Zurich, Rohe, V. Zurich, Switzerland Aleksandrov, C. Grab, C. Haller,berger, I. J. Horvath, Herrmann, A. M. Hristov, U. Hilgers, Langenegger, P. W. Lecomte, Hintz, E.termann, Lejeune, Hans G. J.D. Hofer, Leshev, Maillefaud, C. Heinz Lesmond, C.F. Hofer, B. Moortgat, Marchica, List, U. I. Nanov, P.D. Horis- Luckey, W.G. Lus- Petrov, P.A. Roykov, F. Stöckli, H. Suter, P. Trüb, ten, S. Waldmeier-Wicki,K. Zagoursky R. Weber, M. Weber, J.Universität Weng, Zürich, Zürich, M. Switzerland Wensveen, E. Alagoz, C. Amsler, V. Chiochia,A. C. Schmidt, Hoermann, S. C. Steiner, Regenfus, D. P. Tsirigkas, Robmann, L. T. Rommerskirchen, Wilke National Central University, Chung-Li, Taiwan S. Blyth, Y.H. Chang, E.A. Chen, A. Go, C.C. Hung, C.M. Kuo, S.W. Li, W. Lin 2008 JINST 3 S08004 41 E. Eskut, 36 N. Sonmez 40 S. Ozkorucuklu, 39 C. Lynch, C.K. Mackay, S. Metson, 42 O. Kaya, 39 – xvi – M. Kaya, G.W.S. Hou, Y.B. Hsiung, Y.J. Lei, S.W. Lin, R.S. Lu, 38 1 A.D. Presland, M.G. Probert, E.C. Reid, V.J. Smith, R.J. Tapper, 42 H. Topakli, M. Vergili, G. Önengüt 37 J.A. Coughlan, P.S. Flower, P. Ford, V.B. Francis, M.J. French, S.B. Galagedera, ∗ Institute of Single Crystals of NationalKharkov, Academy Ukraine of Science, B. Grinev, V. Lyubynskiy, V. Senchyshyn National ScientificUKRAINE Center, KharkovL. Institute Levchuk, S. Lukyanenko, of D. Soroka, P. Physics Sorokin, S. Zub andCentre Technology, for Kharkov, ComplexUnited Cooperative Kingdom (Associated Systems, Institute) UniversityA. Anjum, of N. Baker, the T. Hauer, R. West McClatchey, M. of Odeh, D. England, Rogulin,University A. Bristol, of Solomonides Bristol, Bristol, United Kingdom J.J. Brooke, R.G.P. Croft, Heath, H.F. D. Heath, Cussans, C.S.J. Hill, D. Nash, B. Evans, D.M. Huckvale, R. J. Newbold, R. Jackson, Frazier, Walton N. Grant, M. Hansen, R.D.Rutherford Appleton Head, Laboratory, Didcot, United Kingdom E. Bateman, K.W. Bell,J.F. Connolly, R.M. Brown, B.W. Gannon, Camanzi, A.P.R. Gay, I.T. N.I. Church, Geddes,F.R. Jacob, R.J.S. D.J.A. Greenhalgh, P.W. Jeffreys, Cockerill, R.N.J. L.L. Halsall,Q.R. J.E. Jones, W.J. Cole, Haynes, Morrissey, B.W. J.A. Kennedy, P. Hill, A.L.G.J. Murray, Lintern, Rogers, J.G. A.B. G.N. Salisbury, Lodge, A.A. Patrick, Shah,R. A.J. Stephenson, C.H. Maddox, S. Shepherd-Themistocleous, C.A.X. Taghavi, B.J. I.R. Smith, Pattison, Tomalin, M.J.F. M. Torbet, Xing Sproston, J.H. M.R. Williams, W.J. Pearson, Womersley, S.D. Worm, S.P.H. Quinton, National Taiwan University (NTU), Taipei, Taiwan P. Chang, Y. Chao, K.F. Chen, Z. Gao, J.G. Shiu, Y.M. Tzeng, K. Ueno, Y. Velikzhanin, C.C. Wang, M.-Z. Wang Cukurova University, Adana, Turkey S. Aydin, A. Azman, M.N.A. Bakirci, S. Kayis Basegmez, Topaksu, S. H. Cerci,A. Polatöz, I. Kisoglu, K. Dumanoglu, Sogut, P. S. Kurt, Erturk, K. Ozdemir, N. Ozdes Koca, H. Ozkurt, S. Ozturk, Middle East Technical University, Physics Department, Ankara,H. Turkey Gamsizkan, S. Sekmen, M. Serin-Zeyrek, R. Sever, M. Zeyrek Bogaziçi University, Department of Physics, Istanbul,M. Turkey Deliomeroglu, E. Gülmez, E. Isiksal, 2008 JINST 3 S08004 1 43 C. Matthey, B. Mohr, J. Mumford, S. Otwinowski, ∗ – xvii – Y. Shi, B. Tannenbaum, J. Tucker, V. Valuev, R. Wallny, M. Stoye, J. Striebig, M. Takahashi, H. Tallini, A. Tapper, ∗ 1 R. Stringer, V. Sytnik, P. Tran, S. Villa, R. Wilken, S. Wimpenny, S. Wakefield, P. Walsham, D. Wardrope, M. Wingham, Y. Zhang, ∗ 1 M. Stettler, 1 E. Noah Messomo, M. Noy, A. Papageorgiou, M. Pesaresi, K. Petridis, 30 G. Sidiropoulos, 1 J. Hauser, M. Ignatenko, C. Jarvis, B. Lisowski, Imperial College, University of London, London,M. United Kingdom Apollonio, F.P.M. Arteche, Brambilla R. Hall, Bainbridge, D.G. Britton, G. Davies, M. W. Barber, Della Cameron, Negra, P. D.E.S. G. Barrillon, Dewhirst, Clark, Greder, S. J. I.W. Dris, S. Clark, Batten, C.J. Foudas, D. Greenwood, R. J. Colling, Leaver, Fulcher, G. Beuselinck, D. N. Futyan, P. Hall,A. Cripps, D.J. Lewis, Graham, J.F. Nikitenko, Hassard, B.C.D.R. J. MacEvoy, Price, Hays, X. O. G. Qu,P. Sharp, Maroney, Iles, D.M. E.M. Raymond, V. A. Kasey, McLeod,C. Timlin, Rose, L. M. Toudup, D.G. S. T. Virdee, Khaleeq, Rutherford, Miller,O. M.J. Zorba J. Ryan, F. Nash, Sciacca, C. Seez, Brunel University, Uxbridge, United Kingdom C. Da Via, I.S.J. Watts, Goitom, I. Yaselli P.R. Hobson, D.C. Imrie, I.Boston Reid, University, Boston, C. Massachusetts, Selby, U.S.A. O.E. Sharif, Hazen, L. A. Teodorescu, F. Varela Heering, Rodriguez, S. X. A. Wu Heister, C. Lawlor,Brown University, D. Providence, Rhode Lazic, Island, U.S.A. E.A. Avetisyan, Machado, T. Bose, J. L.D. Rohlf, Nguyen, Christofek, T. Speer, D. L. K.V. Tsang Cutts, Sulak, S. Esen, R. Hooper,University of G. California, Landsberg, Davis, Davis, M. California, U.S.A. R. Narain, Breedon, M. Case, M. Chertok,G. J. Grim, B. Conway, P.T. Holbrook, Cox, W. J. Ko, A. Dolen,J. Kopecky, R. R. Rowe, Lander, Erbacher, M. F.C. Y. Lin, Searle, Fisyak, A. J. E. Lister, Smith, Friis, S. A. Maruyama, Soha, D. M. Pellett, Squires, M. Tripathi,University R. of Vasquez California, Sierra, Los C. Angeles, Veelken LosV. Angeles, California, Andreev, U.S.A. K. Arisaka, Y. Bonushkin, S. Chandramouly, D. Cline, R. Cousins, S. Erhan, D. Zer-Zion University of California, San Diego, LaJ.G. Jolla, Branson, California, U.S.A. J.A. Coarasa Perez, E. Dusinberre, R. Kelley, M. Lebourgeois, J. Letts, E. Lipeles, Y. Pischalnikov, G. Rakness, P. Schlein, H.G. Wang, X. Yang, Y. Zheng University of California, Riverside, Riverside, California, U.S.A. J. Andreeva, J. Babb,W. Gorn, S. G. Campana, Hanson, G.Y.H. D. Jeng, Rick, A. Chrisman, S.C. Satpathy, B.C. Kao, R. Shen, J.G. Clare, Layter, F. J. Liu, Ellison, H. Liu, D. A. Fortin, Luthra, J.W. G. Gary, Pasztor, 2008 JINST 3 S08004 J. Garberson, D. Hale, A. Weinstein, R. Wilkin- 23 1 – xviii – F. Chlebana, I. Churin, S. Cihangir, W. Dagenhart, M. De- 1 M. Albrow, J. Amundson, G. Apollinari, M. Atac, W. Badgett, 1 M.A. Afaq, 1 K. Maeshima, J.M. Marraffino, D. Mason, P. McBride, T. Miao, S. Moccia, N. Mokhov, 1 B. Mangano, T. Martin, M. Mojaver,M. J. Pieri, Muelmenstaedt, A. M. Rana, Norman, M. H.P. Sani, Paar, A. V. Sharma, Petrucci, S. H. Simon, Pi, A. White,University F. of Würthwein, California, A. Santa Yagil Barbara, SantaA. Barbara, California, Affolder, U.S.A. A. Allen, C. Campagnari, M. D’Alfonso, A. Dierlamm, J. Incandela, P. Kalavase, S.A.M. Koay, D. Nikolic, Kovalskyi, V. V. Pavlunin, Krutelyov,S. S. F. Swain, Kyre, Rebassoo, J.R. J. Vlimant, J. Lamb, D. Ribnik, White, S. M. J. Lowette, Witherell Richman, R.California Rossin, Institute Y.S. of Shah, Technology, Pasadena, California, D. U.S.A. A. Stuart, Bornheim, J. Bunn, J.R. Chen, Mao, G. D. Denis, Nae, P. Galvez, I.X. M. Narsky, Su, Gataullin, H.B. M. I. Newman, Thomas, Legrand, T. V. V. Timciuc, Orimoto, Litvine, F. C. Y. van Ma, Rogan, Lingen, S. J. Shevchenko, Veverka, B.R. C. Voicu, Steenberg, marteau, D. Dykstra, D.P. Eartly, J.E.P. Elias, Gartung, V.D. Elvira, F.J.M. D. Geurts, Evans,C. L. I. Giacchetti, Fisk, Grimm, J. D.A. Y. Freeman, Glenzinski, Guo, I.B. Gaines, E. Holzman, O. Gottschalk, E. Gutsche, James, T. H.J. Grassi, A. Jensen, Kowalkowski, D. Hahn, T. M. Kramer, Green, Johnson, S. J. U. Kwan,S. Hanlon, C.M. Joshi, Lusin, Lei, B. R.M. M. Klima, Harris, Leininger, S. S. Kossiakov, T. Los, K. Hesselroth, L. Kousouris, Lueking, S. G. Lukhanin, Holm, son, Y. Xia, Y. Yang, L.Y. Zhang, K. Zhu, R.Y. Zhu Carnegie Mellon University, Pittsburgh, Pennsylvania, U.S.A. T. Ferguson, D.W. Jang, S.Y. Jun, M. Paulini, J. Russ, N. Terentyev, H.University Vogel, I. of Vorobiev Colorado at Boulder, Boulder, Colorado,M. U.S.A. Bunce, J.P. Cumalat, M.E. Dinardo, B.R.U. Drell, Nauenberg, W.T. Ford, K. K. Stenson, Givens, S.R. B. Wagner Heyburn, D. Johnson, Cornell University, Ithaca, New York, U.S.A. L. Agostino, J. Alexander, F.sley, Blekman, C.D. D. Jones, Cassel, V. S. Kuznetsov, Das,J. J.R. Vaughan, J.E. P. Patterson, Wittich Duboscq, D. L.K. Riley, Gibbons, A. B. Ryd, Helt- S. Stroiney, W.Fairfield Sun, University, Fairfield, J. Connecticut, U.S.A. Thom, C.P. Beetz, G. Cirino, V. Podrasky, C. Sanzeni, D. Winn Fermi National Accelerator Laboratory, Batavia, Illinois,S. U.S.A. Abdullin, J.A. Bakken, B. Baldin,M. K. Binkley, Banicz, I. L.A.T. Bauerdick,H.W.K. Bloch, Cheung, A. F. Baumbaugh, G. Borcherding, J. Chevenier, Berryhill, A. P.C. Boubekeur, Bhat, M. Bowden, K. Burkett, J.N. Butler, S. Mrenna, S.J. Murray, C.R. Newman-Holmes, Pordes, C. O. Noeding, Prokofyev, V. N. O’Dell, M. Ratnikova, Paterno, A. D. Ronzhin, Petravick, V. Sekhri, E. Sexton-Kennedy, I. Sfiligoi, 2008 JINST 3 S08004 Y. Gershtein, 49 L. Uplegger, E.W. Vaan- 1 W. Clarida, A. Cooper, P. Deb- 45 – xix – W.J. Spalding, L. Spiegel, M. Stavrianakou, G. Stiehr, ∗ S. Guragain, M. Hohlmann, H. Mermerkaya, R. Ralich, I. Vodopiyanov 44 T.M. Shaw, E.A.L. Skup, Stone, I. R.P. Suzuki, P. Smith, Tan, W. Tanenbaum, L.E. Temple, S. Tkaczyk, dering, R. Vidal, R. Wands,V. Yarba, H. F. Yumiceva, J.C. Wenzel, Yun, J. T. Zimmerman Whitmore, E. Wicklund, W.M. Wu, Y.University Wu, of Florida, J. Gainesville, Yarba, Florida, U.S.A. D. Acosta, P.A. Avery, Drozdetskiy, V. R.D. Barashko, Field,J. P. Konigsberg, Y. A. Bartalini, Fu, Korytov, K. I.K. D. Kotov,Y. P. Pakhotin, Furic, Levchenko, Bourilkov, C. A. L. Prescott, Madorsky, R. K. L. Gorn, Matchev,D. Cavanaugh, Ramond, G. Wang, D. P. J. Mitselmakher, Ramond, S. Yelton Holmes, M. Dolinsky, B.J. Schmitt, B. Kim, Scurlock, S. J. Stasko,Florida Klimenko, International H. University, Stoeck, Miami, Florida, U.S.A. V. Gaultney, L. Kramer, L.M. Lebolo, S. Linn, P. Markowitz, G. Martinez,Florida J.L. State Rodriguez University, Tallahassee, Florida, U.S.A. T. Adams, A.S.V. Gleyzer, Askew, S. O. Hagopian,J. Atramentov, Thomaston V. M. Hagopian, C.J. Bertoldi, Jenkins, W.G.D. K.F. Dharmaratna, Florida Johnson, Institute of H. Technology, Melbourne, Prosper, Florida, U.S.A. M. D. Baarmand, L. Baksay, Simek, University of Illinois at Chicago (UIC),M.R. Chicago, Adams, Illinois, I. M. U.S.A. Anghel, L. Apanasevich, O.E.J. Barannikova, Garcia-Solis, V.E.Bazterra, R.R. C.E. Betts, Gerber, C. Dragoiu, D.J.E. Hofman, Shabalina, A. R. Smoron, Hollis, N. A. Varelas Iordanova, S. Khalatian,The C. University Mironov, of Iowa, Iowa City,U. Iowa, U.S.A. Akgun, E.A. Albayrak, A.S. Ayan, R. Briggs, K. Cankocak, bins, F. Duru, M. Fountain, E.C.R. Newsom, McCliment, E. J.P. Norbeck, Merlo, J. A. Olson, Mestvirishvili, Y. M.J. Onel, L. Miller, Perera, A. I. Moeller, Iowa Schmidt, State S. University, Wang, Ames, T. Iowa, Yetkin U.S.A. E.W. Anderson, H. Chakir, J.M. Hauptman, J. Lamsa Johns Hopkins University, Baltimore, Maryland, U.S.A. B.A. Barnett, B. Blumenfeld, C.Y. Chien,movic, G. M. Giurgiu, Swartz, A. N. Tran Gritsan, D.W. Kim, C.K. Lae, P. Maksi- The University of Kansas, Lawrence, Kansas,P. U.S.A. Baringer, A. Bean,V. Zhukova J. Chen, D. Coppage, O. Grachov, M. Murray, V. Radicci, J.S. Wood, 2008 JINST 3 S08004 S. Muzaffar, 46 – xx – I. Osborne, S. Reucroft, J. Swain, L. Taylor, L. Tuura Northwestern University, Evanston, Illinois, U.S.A. B. Gobbi, M.M. Kubantsev, Szleper, M. A. Velasco, S. Kubik, Won R.A. Ofierzynski, M.University of Schmitt, Notre Dame, E. Notre Dame, Spencer,K. Indiana, U.S.A. S. Andert, Stoynev, B. Baumbaugh,C. B.A. Jessop, Beiersdorf, D.J. L.M. Karmgard, Vigneault, Castle, M. T. Wayne, J. D. Kolberg, Wiand Chorny, J. A. Marchant, Goussiou, N. M. Hildreth, Marinelli, M. McKenna, R. Ruchti, Kansas State University, Manhattan, Kansas, U.S.A. D. Bandurin, T. Bolton, K. Kaadze, W.E. Kahl, Y. Maravin, D. Onoprienko,Lawrence R. Livermore National Sidwell, Laboratory, Z. Livermore, Wan California, U.S.A. B. Dahmes, J. Gronberg, J. Hollar, D. Lange, D. Wright, C.R.University Wuest of Maryland, College Park, Maryland,D. U.S.A. Baden, R. Bard, S.C. Eno, D.ner, Ferencek, F. N.J. Ratnikov, Hadley, F. R.G. Santanastasio, Kellogg, A. M. Skuja, Kirn, T. S. Toole, Kunori, L. E. Wang, Lock- M.Massachusetts Wetstein Institute of Technology, Cambridge, Massachusetts, U.S.A. B. Alver, M. Ballintijn, G. Bauer,I. W. Kravchenko, Busza, W. Li, G. C. Gomez Loizides, Ceballos, T. Ma,G. K.A. S. Roland, Hahn, Nahn, M. P. C. Rudolph, Harris, Paus, G. M. S. Pavlon, Stephans, Klute, J. K. Piedra Sumorok, Gomez, S. C. Vaurynovich, Roland, E.A.University Wenger, of B. Minnesota, Wyslouch Minneapolis, Minnesota, U.S.A. D. Bailleux, S. Cooper, P.G. Cushman, Franzoni, A. W.J. De Gilbert, Benedetti,J. D. A. Mans, Dolgopolov, Gong, R. P.R. Rusack, J. Dudero, S. Grahl, R. Sengupta, Egeland, B. J. Sherwood, Haupt, A. Singovsky, K. P.University Vikas, Klapoetke, of J. Mississippi, Zhang I. University, Kronkvist, Mississippi, U.S.A. Y.M. Kubota, Booke, L.M. Cremaldi, R.D. Godang, Summers, R. S. Watkins Kroeger, M. Reep, J. Reidy, D.A. Sanders,University P. of Sonnek, Nebraska-Lincoln, Lincoln, Nebraska, U.S.A. K. Bloom, B. Bockelman, D.R.C. Claes, Lundstedt, A. S. Dominguez, Malik, M. G.R. Eads, Snow, M. D. Swanson Furukawa, J. Keller, T. Kelly, State University of New York atK.M. Buffalo, Ecklund, Buffalo, I. New Iashvili, York, U.S.A. A. Kharchilava, A. Kumar, M. Strang Northeastern University, Boston, Massachusetts, U.S.A. G. Alverson, E. Barberis, O. Boeriu, G. Eulisse, T. McCauley, Y. Musienko, 2008 JINST 3 S08004 Z. Xie ∗ R. Demina, G. Ginther, Y. Gotra, 1 A.T. Laasanen, C. Liu, V. Maroussov, 1 – xxi – P. Elmer, A. Garmash, D. Gerbaudo, V. Halyo, J. Jones, 47 R. Plano, K. Rose, S. Schnetzer, S. Somalwar, R. Stone, T.L. Watts 1 University of Tennessee, Knoxville, Tennessee, U.S.A. G. Cerizza, M. Hollingsworth, J. Lazoflores, G. Ragghianti, S. Spanier, A. York Texas A&M University, College Station, Texas, U.S.A. A. Aurisano, A. Golyash, T. Kamon,berger C.N. Nguyen, J. Pivarski, A. Safonov, D. Toback, M. Wein- D. Marlow, J. Olsen, P. Piroué, D. Stickland, C. Tully, J.S. Werner, T. Wildish, S.University Wynhoff, of Puerto Rico, Mayaguez, PuertoX.T. Rico, Huang, U.S.A. A. Lopez, H. Mendez, J.E. Ramirez Vargas, A. Zatserklyaniy Purdue University, West Lafayette, Indiana, U.S.A. A. Apresyan, K. Arndt,A.F. V.E. Barnes, Garfinkel, G. L. Bolla, Gutay, D.S. N. Bortoletto, Medved, Ippolito, A. P. Merkel, Y. Bujak, Kozhevnikov, D.H. A.I. Miller, Everett, Shipsey J. M. Miyamoto, Fahling, N. Neumeister, A. Pompos, A. Roy,Purdue A. University Sedov, Calumet, Hammond, Indiana, U.S.A. V. Cuplov, N. Parashar Rice University, Houston, Texas, U.S.A. P. Bargassa, S.J. Lee, J.H.A. Liu, Tumanov D. Maronde, M. Matveev, T. Nussbaum, B.P. Padley, J.University of Roberts, Rochester, Rochester, New York, U.S.A. A. Bodek, H. Budd,S. J. Korjenevski, Cammin, D.C. Miner, Y.S. W. Chung, Sakumoto, P. P. Slattery, De M. Barbaro, Zielinski The Rockefeller University, New York, New York,A. U.S.A. Bhatti, L. Demortier, K. Goulianos, K. Hatakeyama, C. Mesropian Rutgers, the State University of NewE. Jersey, Piscataway, New Bartz, Jersey, U.S.A. S.H.A. Macpherson, Chuang, J. Doroshenko, E. Halkiadakis, P.F. Jacques, D. Khits, A. Lath, The Ohio State University, Columbus, Ohio,B. U.S.A. Bylsma, L.S.G. Durkin, Williams J. Gilmore, J. Gu,Princeton P. University, Killewald, Princeton, New T.Y. Jersey, U.S.A. Ling,N. C.J. Adam, Rush, S. V. Chidzik, Sehgal, P. Denes, 2008 JINST 3 S08004 1 – xxii – Also at CERN, European Organization forNow Nuclear at Research, Universidade Geneva, Federal Switzerland do ABC,Now Santo at Andre, Laboratoire Brazil de l’Accélérateur Linéaire,Now Orsay, at France CERN, European Organization forAlso Nuclear at Research, Université Geneva, de Switzerland Haute-Alsace, Mulhouse,Also France at Université Louis Pasteur, Strasbourg,Also France at Moscow State University, Moscow, Russia Also at Institute of Nuclear ResearchAlso ATOMKI, at Debrecen, University Hungary of California, SanAlso Diego, at La Tata Jolla, Institute U.S.A. of FundamentalAlso Research at - University HECR, of Mumbai, Visva-Bharati, India Santiniketan, India Also at University of California, Riverside,Also Riverside, at U.S.A. Centro Studi Enrico Fermi,Also Roma, at Italy ENEA - Casaccia ResearchNow Center, at S. Università Maria del di Piemonte Galeria, Orientale, Italy Novara, Italy S. Dasu, F. Feyzi, T. Gorski, L.A. Gray, Lanaro, K.S. Grogg, C. M. Lazaridis, Grothe,W.H. M. J. Smith, Jaworski, M. Leonard, P. Klabbers, Weinberg, D. R. J. Wenman Klukas, Loveless, M. Magrans de Abril,Yale University, A. New Mohapatra, Haven, Connecticut, G. U.S.A. Ott, G.S. Atoian, S. Dhawan, V. Issakov, H. Neal, A. Poblaguev, M.E. Zeller Institute of Nuclear PhysicsUzbekistan of the UzbekistanG. Academy Abdullaeva, A. of Avezov, M.I. Sciences, Fazylov,K. E.M. Ulugbek, Olimov, Gasanov, A. Tashkent, A. Umaraliev, B.S. Khugaev, Yuldashev Y.N. Koblik, M. Nishonov, Texas Tech University, Lubbock, Texas, U.S.A. N. Akchurin, L. Berntzon, K.W. Carrell,ill, K. Y. Gumus, Roh, C. A. Jeong, Sill, H. M. Kim, Spezziga, S.W. R. Lee, Thomas, B.G. I. Mc Volobouev, E. Gonag- Washington, R.Vanderbilt Wigmans, University, E. Nashville, Yazgan Tennessee, U.S.A. T. Bapty, D. Engh, C. Florez,S. W. Johns, Pathak, T. P. Sheldon Keskinpala, E. Luiggi Lopez, S. Neema, S. Nordstrom, University of Virginia, Charlottesville, Virginia, U.S.A. D. Andelin, M.W. Arenton, M. Balazs,R. M. Imlay, Buehler, A. S. Ledovskoy, Conetti, D. B. Phillips Cox, II, R. H. Hirosky, Powell, M. M. Humphrey, Ronquest, R.University Yohay of Wisconsin, Madison, Wisconsin, U.S.A. M. Anderson, Y.W. Baek, J.N. Bellinger, D. Bradley, P. Cannarsa, D. Carlsmith, I. Crotty, 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 2008 JINST 3 S08004 – xxiii – Also at Warsaw University of Technology, InstituteWarsaw, Poland of Electronic Systems, Also at Fermi National Accelerator Laboratory,Also Batavia, at U.S.A. California Institute of Technology, Pasadena,Also U.S.A. at University of Minnesota, Minneapolis,Also U.S.A. at Institute for Particle Physics,Also ETH at Zurich, Faculty Zurich, of Switzerland Physics ofNow University at of Instituto Belgrade, de Belgrade, Física Serbia deSantander, Cantabria Spain (IFCA), CSIC-Universidad de Cantabria, Also at Institut für Experimentelle Kernphysik,Also Karlsruhe, at Germany National Centre for Physics,Also Quaid-I-Azam at University, Laboratoire Islamabad, Leprince-Ringuet, Pakistan Ecole Polytechnique,Palaiseau, IN2P3-CNRS, France Also at Alstom Contracting, Geneve, Switzerland Also at Scuola Normale Superiore andAlso Sezione at INFN, University Pisa, of Italy Athens, Athens,Also Greece at Institute of High EnergyTbilisi, Physics Georgia and Informatization, Tbilisi State University, Also at Institute for Theoretical andAlso Experimental at Physics, Central Moscow, Laboratory Russia of MechatronicsAlso and at Instrumentation, Paul Sofia, Scherrer Bulgaria Institut, Villigen,Also Switzerland at Vinca Institute of NuclearAlso Sciences, at Belgrade, Institute Serbia for Nuclear ResearchAlso and at Nuclear State Energy, Research Sofia, Center Bulgaria ofProtvino, Russian Russia Federation - Institute forAlso High at Energy Physics, Nigde University, Nigde, Turkey Also at Mersin University, Mersin, Turkey Also at Marmara University, Istanbul, Turkey Also at Kafkas University, Kars, Turkey Also at Suleyman Demirel University, Isparta,Also Turkey at Ege University, Izmir, Turkey Also at Rutherford Appleton Laboratory, Didcot,Also United at Kingdom KFKI Research Institute forAlso Particle at and University Nuclear of Physics, Debrecen, Budapest, Debrecen, Hungary Also Hungary at Mugla University, Mugla, Turkey Also at Institute for Nuclear Research,Now Moscow, at Russia Lawrence Berkeley National Laboratory,Now Berkeley, U.S.A. at National Institute of PhysicsAlso and at Nuclear University Engineering, of Bucharest, Ruhuna, Romania Matara,Deceased Sri Lanka Corresponding author: Roberto Tenchini) ([email protected] ∗ 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 2008 JINST 3 S08004 1 2 6 6 6 6 ii 26 27 29 30 32 33 33 35 37 43 46 53 54 54 55 55 11 12 13 13 13 14 15 15 17 18 23 23 25 26 – xxiv – 3.1.1 Requirements3.1.2 and operating conditions Overview3.1.3 of the tracker layout Expected3.1.4 performance of the CMS tracker Tracker system aspects 3.2.1 Pixel3.2.2 system general Sensor3.2.3 description Pixel3.2.4 detector read-out The3.2.5 pixel barrel system The3.2.6 forward pixel detector Power3.2.7 supply Cooling 3.2.8 Slow controls 3.3.1 Silicon sensors 2.2.1 Superconducting2.2.2 solenoid Yoke 2.2.3 Electrical2.2.4 scheme Vacuum system 2.2.5 Cryogenic2.2.6 plant Other ancillaries 2.3.1 Cool-down 2.3.2 Charge2.3.3 and discharge cycles Cold2.3.4 mass misalignment Electrical2.3.5 measurements Yoke mechanical2.3.6 measurements Coil2.3.7 stability characteristics Coil warm-up 3.1 Introduction 3.2 Pixel detector 3.3 Silicon strip tracker 1.1 General concept 2.1 Overview 2.2 Main features of the magnet components 2.3 Operating test 1 Introduction 2 Superconducting magnet 3 Inner tracking system Contents CMS collaboration 2008 JINST 3 S08004 90 92 96 96 98 56 62 64 67 73 78 81 82 90 100 103 103 104 105 105 106 106 107 108 109 109 109 110 110 113 114 116 122 122 131 138 145 149 154 156 – xxv – 4.3.1 Barrel:4.3.2 avalanche photodiodes Endcap: vacuum phototriodes 3.3.3 Silicon3.3.4 modules Tracker3.3.5 Inner Barrel and Disks (TIB/TID) Tracker3.3.6 Outer Barrel (TOB) Tracker3.3.7 EndCaps (TEC) Geometry3.3.8 and alignment Detector3.3.9 control and safety system Operating experience and test results 4.5.1 Global4.5.2 architecture The4.5.3 trigger and read-out paths Algorithms4.5.4 performed by the trigger primitive Classification generation performed by the selective read-out 4.6.1 Geometry 4.6.2 Preshower electronics 4.7.1 Safety4.7.2 system Temperature 4.7.3 Dark4.7.4 current HV and LV 4.9.1 Laser-monitoring system overview 3.3.2 Read-out system 4.1 Lead tungstate4.2 crystals The ECAL4.3 layout and mechanics Photodetectors 4.4 On-detector electronics 4.5 Off-detector electronics 4.6 Preshower detector 4.7 ECAL detector control system 4.8 Detector calibration 4.9 Laser monitor system 4.10 Energy resolution 5.1 Barrel design5.2 (HB) Endcap design5.3 (HE) Outer calorimeter5.4 design (HO) Forward calorimeter5.5 design (HF) Read-out electronics5.6 and slow control HF luminosity monitor 4 Electromagnetic calorimeter 5 Hadron calorimeter 6 Forward detectors 2008 JINST 3 S08004 247 156 159 162 165 165 168 174 180 185 197 200 202 207 216 217 222 223 225 225 230 235 236 243 243 248 251 258 259 261 263 265 267 267 271 273 274 279 283 283 – xxvi – 7.1.1 General7.1.2 description Technical7.1.3 design Electronics 7.1.4 Chamber7.1.5 assembly, dressing, and installation Chamber performance 7.2.1 Chamber7.2.2 mechanical design Electronics7.2.3 design Performance 7.3.1 Detector7.3.2 layout Readout7.3.3 electronics Low7.3.4 voltage and high voltage systems Temperature7.3.5 control system Gas7.3.6 system Chamber construction and testing 7.4.1 System7.4.2 layout and calibration procedures Geometry7.4.3 reconstruction System commissioning and operating performance 6.2 Zero degree calorimeter (ZDC) 7.1 Drift tube system 7.2 Cathode strip chambers 7.3 Resistive Plate Chamber system 7.4 Optical alignment system 6.1 CASTOR 8.1 Calorimeter trigger 8.2 Muon trigger 8.3 Global Trigger 8.4 Trigger Control System 9.1 Sub-detector read-out9.2 interface The Trigger9.3 Throttling System and sub-detector Testing fast-control9.4 interface The Event9.5 Builder The Event9.6 Filter Networking and9.7 Computing Infrastructure DAQ software,9.8 control and monitor Detector Control System 10.1 Detector powering 7 The muon system 8 Trigger 9 Data Acquisition 10 Detector infrastructures and safety systems 2008 JINST 3 S08004 285 285 285 286 287 287 287 287 288 289 290 290 290 291 293 297 297 298 299 301 303 305 307 309 317 – xxvii – 10.2.1 Front-end electronics cooling 10.2.2 Cryogenics 10.4.1 Sliding system 10.4.2 Pulling system 10.5.1 DSS Requirements 10.5.2 DSS Architecture 10.5.3 CMS Implementation of DSS 10.6.1 Introduction 10.6.2 Protection systems 10.6.3 Monitoring systems 10.3 Detector cabling 10.4 Detector moving system 10.5 The Detector Safety System 10.6 Beam and Radiation Monitoring systems 11.1 Overview 11.2 Application framework 11.3 Data formats and processing 11.4 Computing centres 11.5 Computing services 11.6 System commissioning and tests 10.2 Detector cooling 11 Computing 12 Conclusions CMS acronym list Bibliography 2008 JINST 3 S08004 1 − s 2 − cm 34 ). 14 TeV is expected to be roughly 100 mb. At = s – 1 – √ ) must reduce the huge rate to about 100 events/s for storage ). This paper provides a description of the design and construction of the CMS detec- 1 − inelastic events/s. This leads to a number of formidable experimental challenges. The s 2 9 − The prime motivation of the LHC is to elucidate the nature of electroweak symmetry break- The LHC will also provide high-energy heavy-ion beams at energies over 30 timesHadron higher colliders are well suited to the task of exploring new energy domains, and the region The total proton-proton cross-section at cm 27 design luminosity the general-purpose detectorsmately 10 will therefore observe an event rate of approxi- and subsequent analysis. The shortfor the time design between of bunch the crossings, read-out 25 and trigger ns, systems. has major implications online event selection process (trigger The Compact Muon Solenoid (CMS)Large detector Hadron is Collider a (LHC) multi-purpose atexisting apparatus CERN. 27-km due The LEP to LHC operate tunnel iston at in presently (ion) the the beams being of constructed Geneva 7 in region. TeV (2.75 the TeV per already It nucleon) will each, with yield a head-on design collisions luminosity of of 10 two pro- Introduction Chapter 1 tor. CMS is installed about 100Lake metres Geneva and underground the close Jura to mountains. the French village of Cessy, between ing for which the Higgs mechanismHiggs is mechanism presumed can to also be shed responsible.energy light scales The on above experimental about the study 1 of mathematical TeV.tries, Various the consistency alternatives new of to forces or the the constituents. Standard Standard Furthermore, Modelthe Model there invoke way at are new toward high a symme- hopes unified for theory.dimensions, discoveries These that the discoveries could could latter pave take often themany requiring form compelling of modification reasons supersymmetry of to or investigate gravity extra the at TeV energy the scale. TeV scale.than Hence at there the are previousextreme accelerators, conditions allowing of temperature, us density, to and parton further momentum extend fractionx (low- the studyof 1 of TeV constituent QCD centre-of-mass matter energy can under are be explored high if enough. the proton energy The andorder the beam to luminosity energy study and physics the atwith design the the luminosity seven-fold TeV increase of energy in scale. thethe energy LHC previous A and have hadron wide a been collider hundred-fold range experiments. chosenthe increase of in detectors. These in physics conditions integrated is also luminosity potentially require over possible a very careful design of (10 2008 JINST 3 S08004 z- plane -y x components. y and x . -axis in the x is measured from the miss T E θ -axis pointing radially inward x b-jets, requiring pixel detectors ’s and τ rejection, and efficient photon and lepton is measured from the . The polar angle 0 r φ π . Thus, the momentum and energy transverse to 1 TeV; 1% at 100 GeV), and the ability to determine un- /2) < – 2 – θ p z-axis points along the beam direction toward the Jura , respectively, are computed from the lntan( T E − = and η T p y-axis pointing vertically upward, and the close to the interaction region; 1% at 100 GeV), wide geometric coverage, ambiguously the charge of muons with tracker. Efficient triggering and offline tagging of isolation at high luminosities; with a large hermetic geometric coverage and with fine lateral segmentation. angles, good dimuon mass resolution (≈ The design of CMS, detailed in the next section, meets these requirements. The main distin- The coordinate system adopted by CMS has the origin centered at the nominal collision point The large flux of particles coming from the interaction regionThe leads detector to requirements high for radiation CMS to levels, meet the goals of the LHC physics programme can be At the design luminosity, a mean of about 20 inelastic collisions will be superimposed on the • Good electromagnetic energy resolution, good diphoton and dielectron mass resolution (≈ • Good charged-particle momentum resolution and reconstruction efficiency in the inner • Good missing-transverse-energy and dijet-mass resolution, requiring hadron calorimeters • Good muon identification and momentum resolution over a wide range of momenta and The imbalance of energy measured in the transverse plane is denoted by axis. Pseudorapidity is defined as the beam direction, denoted by 1.1 General concept An important aspect drivingconfiguration the for detector the design measurement of and the layout momentum is of the muons. choice Large of bending the power is magnetic needed field and the radial coordinate in this plane is denoted by guishing features of CMS are aa high-field homogeneous solenoid, scintillating-crystals-based a electromagnetic full-silicon-based calorimeter. inner tracking system, and inside the experiment, the toward the center of themountains from LHC. LHC Thus, Point the 5. The azimuthal angle event of interest. This implies thatregion around every 1000 25 charged ns. particles will Theother emerge products interactions from of the in an interaction the interaction same underthe bunch response study time crossing. may of be a This confused detectorthis problem with element pile-up those clearly and can from be its becomes reduced electronic more by signal using severein is high-granularity when longer low detectors than occupancy. with 25 good time ns. This resolution,detector The requires resulting electronic effect a channels of require large very number good of synchronization. detector channels. Therequiring resulting radiation-hard detectors millions and of front-end electronics. summarised as follows: 2008 JINST 3 S08004 Muon Detectors Preshower ) crystals with cov- 4 Pixel Detector Silicon Tracker rejection. The energy resolution 0 π 1.1. At the heart of CMS sits a 13-m- to be integrated to ensure robustness and full Superconducting Solenoid – 3 – stations 0. The scintillation light is detected by silicon avalanche 3. 1.2. < | η | Compact Muon Solenoid Figure 1.1: A perspective view of the CMS detector. Electromagnetic Calorimeter Hadron Calorimeter The bore of the magnet coil is large enough to accommodate the inner tracker and the The electromagnetic calorimeter (ECAL) uses lead tungstate (PbWO The overall layout of CMS [1] is shown in figure Very-forward Calorimeter geometric coverage. Each muonin station the consists of barrel several region layersresistive and plate of cathode chambers aluminium (RPC). strip drift chambers tubes (DT) (CSC) in the endcapcalorimetry region, inside. complemented by Theameter. tracking In order volume to is deal with given highdetectors, by track which multiplicities, a CMS provide employs cylinder the 10 layers ofpixel required of detectors 5.8-m silicon granularity are microstrip placed length and close precision. and toparameter the 2.6-m interaction of In di- region charged-particle addition, to tracks, improve 3 the asmuon measurement layers well of momentum of as the resolution silicon impact the using position onlyboth of the sub-detectors secondary muon is vertices. system, shown in using The figure only expected the inner tracker, anderage using in pseudorapidity up to to measure precisely thesuperconducting momentum technology for of the high-energy magnets. charged particles. This forces a choice of long, 6-m-inner-diameter, 4-T superconducting solenoid providingbefore a the large muon bending bending power (12 angle Tm) to is measured saturate by 1.5 the m muon of system. iron, The allowing return 4 field muon is large enough photodiodes (APDs) in the barrel regionpreshower and system vacuum is phototriodes installed (VPTs) in in front the of endcap the region. endcap A ECAL for 2008 JINST 3 S08004 . η (1.1) 8, right 0. in the bar- 3 < 10 [GeV/c] | T < 2.4 p η η | 1.3; the stochas- 1.4. 1.2 < tail-catcher 2 10 , while the HCAL thickness, in . 0 2 X C + Muon system only Muon system Full system Inner tracker only 2 with the HO included), depending on  I E N λ 10

1



-1

-2 T T

)/p (p ∆ 10 10 + 2  (10–15 – 4 – I E S λ √  = [GeV/c] 2 T  p < 0.8 3 E η σ 10 1.1) and with the TOTEM [2] tracking detectors. The expected jet  0 < 2 4. 0. The scintillation light is converted by wavelength-shifting (WLS) fibres 10 2. 3. < < | | η η | | Inner tracker only Muon system only Muon system Full system < 2 10

The CMS detector is 21.6-m long and has a diameter of 14.6 m. It has a total weight of 12500

1

-1

-2 T T

(p )/p ) using the muon system only, the inner tracking only, and both. Left panel: ∆ 10 10 T p t. The ECAL thickness, in radiation lengths, is larger than 25 rel region (HO) ensuring thatlengths. hadronic showers Coverage are up sampledter. to with The nearly a Cerenkov 11 pseudorapidity light hadronic emitted ofcalorimeters interaction in ensure 5.0 the full is quartz geometric fibres provided coverageevent. is by for An detected the even an by higher measurement photomultipliers. iron/quartz-fibre forward of coverage TheTOR, calorime- the is ZDC, forward obtained not transverse with shown energy in additional in figure dedicatedtransverse-energy the calorimeters resolution (CAS- in various pseudorapidity regions is shown in figure interaction lengths, varies in the range 7–11 The ECAL is surrounded byerage a up brass/scintillator to sampling hadron calorimeter (HCAL) with cov- embedded in the scintillatordetected tiles by and photodetectors channeled (hybrid tohigh photodiodes, photodetectors axial via or magnetic clear HPDs) fields. fibres. that This can central This provide calorimetry light is gain complemented is and by operate a in Figure 1.2: The muon transverse-momentum resolution( as a function of the transverse-momentum panel: 1. of the ECAL, for incident electronstic as (S), measured noise in (N), a and beam constant test,points (C) is to terms shown the given in in function figure the figure are determined by fitting the measured 2008 JINST 3 S08004 0). The jets are 5. ) ) 0 V < 5 e | V 2 η G e | 0 (

0 < 3 G ( T 0

E 0 E 0 0 5 2 0 0 1 2 _ 2 . . ) 3 5 V < < ) e | | 4 V η η 3 crystals with an electron impacting G . | | ( e 0

1 0 < < ) ) 0 × G < 4 0 5 ( | 2 %

% . . η ( ( 1 2

| 1 3 1 8 3 . . . 0 2 0

0 = = = 5 S N C 1 0 0 – 5 – 1 /E, as a function of electron energy as measured from 0 0), and very forward jets (3. 0 E) 3. 1 ( σ < | 0 η 5 | 0 5 < 4 0 0 1 0 1 4 3 2 6 5 . 0 8 6 4 2 4 2

...... 0

0 0 0 0 0 0 0 0 0 1 1

) % ( E / ) E (

σ T T E ( σ E / ) 4), endcap jets (1. ) region. The stochastic (S), noise (N), and constant (C) terms are given. 1. 2 < | η 4 mm × Figure 1.4: The jet transverse-energy resolutionjets as (| a function of the jet transverse energy for barrel reconstructed with an iterative cone algorithm (cone radius = 0.5). Figure 1.3: ECAL energy resolution, a beam test. The energy was measured in an array of 3 the central crystal. The points correspond(4 to events taken restricting the incident beam to a narrow 2008 JINST 3 S08004 ) is then determined by the and a picture taken during assembly 2.1 1). The hoop strain (ε – 6 – 0. ∼ 2.2) presents three new features with respect to previous winding is composed of 4coils) layers, or instead maximum of 2 the layers usual (as in 1 the (as ZEUS in [9] the and Aleph BaBar [7] [10] and coils); so-called Delphi insert), [8] is mechanically reinforced with an aluminium alloy; For physics reasons, the radial extent of the coil (∆R) had to be kept small, and thus the • Due to the number of ampere-turns required for generating a field of 4 T (41.7 MA-turn), the • The conductor, made from a Rutherford-type cable co-extruded with• pure aluminium The (the dimensions of the solenoid are very large (6.3-m cold bore, 12.5-m length, 220-t mass). 2.1 Overview The superconducting magnet for CMSof [3–6] 6-m has been diameter designed and to 12.5-mturned reach length through a with a 4-T a 10 field 000-t stored in yoke energy(figure a comprising of1.1). free 5 2.6 bore wheels GJ and The at 2 distinctivestabilised full endcaps, reinforced feature composed current. NbTi of of conductor. The three the The disks flux ratio 220-tKJ/kg), each is between causing cold stored re- a energy mass large and mechanical is cold deformation mass (0.15%) theof during is previous 4-layer energising, high solenoidal well winding (11.6 beyond detector made the magnets. values table from2.1. The a parameters The of magnet thebeing was CMS lowered designed magnet 90 to are be m summarised assembled belowsional in and ground connection tested to to in its its a ancillaries, finalcommissioned surface in position the hall SX5 in CMS during (SX5), autumn the Magnet prior 2006. has experimental to cavern. been fully After and provi- successfully tested2.2 and Main features of the2.2.1 magnet components Superconducting solenoid The superconducting solenoid (see an artistic view in figure Superconducting magnet in the vertical position indetector SX5 magnets: in figure CMS coil is in effect a “thin coil” (∆R/R Chapter 2 2008 JINST 3 S08004 2.5) are critical shows the values of ratio (i.e. mechanical 2.3 /M E . This value is high compared to 3 − 10 × 5 = 170 mm i.e., about half of the total cold 1. s = ε is the mass density. Figure – 7 – δ ratio directly proportional to the mechanical hoop strain , giving ε Y /M , where 2.4. ε E = 2δ Y s 4 MPa), the elastic modulus of the material (mainly aluminium s PR 6. ∆R ∆R ∆R = = 0 2 0 s µ B 2 ∆R ∆R δ = s PR 2∆R = E M = 80 GPa) and the structural thickness (∆R as function of stored energy for several detector magnets. The CMS coil is distinguishably The construction of a winding using a reinforced conductor required technological develop- Y /M mass thickness), according to with magnetic pressure (P Figure 2.1: General artistic viewwith details of of the the 5 supporting modules system (vertical, composing radial the and cold longitudinal mass tie rods). inside the cryostat, the strain of previoussignificant existing figure detector of magnets. merit, i.e.according the This to can be better viewed looking at a more E far from other detectordeformation). magnets when In combining order stored tomust energy provide have and the a necessary structural hoopcracking function. strength, the a insulation, To large especially limit at fractionthe the the of structural border material the shear cannot defined CMS be stress by too coil the far levelof from winding these inside the and considerations, current-carrying the the elements the innovative (the winding external design turns). of mandrel, andby On the the including CMS prevent basis magnet in uses it a the self-supportingthe conductor, structural layers material. (70%) The and magnetic themandrel hoop support only, stress as cylindrical (130 was mandrel the MPa) case (30%) is inof rather shared the the than between previous cold generation being mass of is taken thin shown detector by in solenoids. the figure A outer cross section ments for both the conductorhad [11] to and be the faced winding. mainly related Inmodule-to-module to particular, mechanical the for coupling. mandrel the construction winding The [12], manyproblem the modular problems of winding the concept method module-to-module of [13], mechanical connection. and the the These cold interfaces mass (figure had to face the 2008 JINST 3 S08004 0 X 14 m 13 m 300, 630 and 630 mm 6000 t 250, 600 and 600 mm 2000 t 10 000 t 12.5 m 6.3 m 4 T 41.7 MA-turns 19.14 kA 14.2 H 2.6 GJ Five modules mechanicallyelectrically coupled and 312 mm 3.9 220 t 4.6 T 1.8 K 11.6 kJ/kg – 8 – Iron yoke Cold mass General parameters Table: 2.1 Main parameters of the CMS magnet. Thickness of the iron layers inMass barrel of iron in barrel Thickness of iron disks in endcaps Mass of iron in each endcap Total mass of iron in return yoke Temperature margin wrt operating temperature Stored energy/unit cold mass Outer diameter of the iron flats Length of barrel Layout Radial thickness of cold mass Radiation thickness of cold mass Weight of cold mass Maximum induction on conductor Total Ampere-turns Nominal current Inductance Stored energy Magnetic length Cold bore diameter Central magnetic induction because they have to transmitallowing local the displacements large due magnetic to possible axialinto gaps. force heat, These corresponding displacements causing can to a be 14 premature partiallythe 700 quench. converted upper t, surface A without of construction the methodallowed modules us which and to involved a get the an local machining excellent resin mechanical of impregnation coupling during between the the mechanical modules. mounting 2008 JINST 3 S08004 – 9 – Figure 2.3: The energy-over-mass ratio E/M, for several detector magnets. Figure: 2.2 The cold mass mountedin vertically before the integration vacuum with chamber. thermal shields and insertion 2008 JINST 3 S08004 – 10 – Figure 2.5: Detail ofcontinuity, the false turns interface are region involved. The between modules 2 arethe connected modules. outer through bolts mandrels. and In pins order fixed through to guarantee mechanical Figure 2.4: Cross section ofconductor. the cold mass with the details of the 4-layer winding with reinforced 2008 JINST 3 S08004 5 mm tolerance. Finally, all the elements ± – 11 – 2.6) is composed of 11 large elements, 6 endcap disks, and 5 barrel wheels, To easily align the yoke elements, a precise reference system of about 70 points was installed in the surface assembly hall.coil. The The origin points of werebarrel the made in reference after particular system loading which is the weights theeach coil 1000 foot geometrical t. cryostat in center order with A to of mark the pre-position the on each inner element the detectors, within floor a the was hadronic made showing the position of whose weight goes from 400the t coil for and the its lightest cryostat.of up the to The sub-detectors. 1920 t easy To for relative displacepads the movement each has central of element been wheel, these a chosen. which elements combination Thisallows includes of facilitates choice transverse heavy-duty the makes displacements. air the assembly Two pads system kinds plusof insensitive of grease to either heavy-duty metallic 250 high-pressure dust t air on (40 padswhen the bars) with closing floor or a the and 385 capacity detector, t especially (60A for bars) the special are YE1 solution used. endcap has that been Thispressure is adopted: is 100 protruding not bar) for into favourable have the the for been last vacuum the developedthey tank. 100 in final touch mm order approach of to the facilitate approach, axially-installed the flatelement. final z-stops, grease-pads closing This (working each of assures the element good detector.will is contact Once be pre-stressed before moved with switching on on the 100 toperation 1.23% the inclined to for magnet. floor uphill the by In pulling adjacent a themaximum as strand cavern movements jacking possible well the in hydraulic elements as the system cavern for that are ensures downhill of safe the pushing order by of 11 keeping meters; a this will retaining take force. one hour. The Figure 2.6: A view ofsupports the the yoke vacuum chamber at of an thedisks early superconducting is stage visible. coil. of At magnet the assembly rear, at one SX5. of the The closing central end2.2.2 barrel cap Yoke The yoke (figure were aligned with an accuracy of 2 mm with respect to the ideal axis of the coil. 2008 JINST 3 S08004 2.7. effect, as the eddy currents, quench back – 12 – A bipolar thyristor power converter rated at 520 kW with passive L-C filters is used to power the CMS solenoid. It coversof a 19.1 range kA. of In voltages case fromthe of +26 bus-bar a V resistance to sudden and through -23 switch the V, offInside with free-wheel of the a thyristors the until power nominal power the converter, DC an converter, opening current the of assemblyheat the current of main sinks, decays free-wheel breakers. naturally thyristors, is in mounted installed. onrated naturally to air-cooled In support 20 case kA ofelectrical DC non-opening for power 4 of source minutes. the by Theleaving the main current the use switch discharge solenoid of is breakers, in achieved two the series byenergy redundant with thyristors disconnecting is 20 a the therefore are resistor, kA extracted in by DC a thermalexternal normally-open dissipation L-R to switch the in circuit solenoid the breakers, configuration. cryostat so-called and dump The is resistor. stored designed This magnetic to resistor work without is any active device. It is positioned induced in the external mandrelabove at the the superconducting trigger critical ofsystem, temperature. a which, current This in fast is discharge, case thethe heat of lowest fundamental up a possible basis the thermal superconducting of whole gradients toand the coil and prevents resistive protection temperature the transition increase occurrence of in ofwinding. the the local A superconducting coil, diagram overheating, windings, of aims hence the at reducing powering circuit the keeping with thermal protection stresses is shown inside in the figure 2.2.3 Electrical scheme The CMS solenoid canmandrel. be This represented inductive as coupling allows a for 14 the so-called H inductance mutually coupled with its external Figure 2.7: The electricalcomponents of scheme the of protection is the the magnet dump resistor, with made the of three protection elements. circuit. One of the main 2008 JINST 3 S08004 vacuum 3 dump resistor. The SD /h while the two Root’s pumps 3 mbar of fore vacuum. The smallest 4 − – 13 – and RRR (Residual Resistivity Ratio) of 130, placed inside a 2 /h. The biggest oil diffusion pump, installed via a DN 400 flange on the 3 dump resistor, as a compromise to keep the dump voltage lower than 600 V, and to limit Current leads. The two 20-kAa current cross leads section are made of of 1800 a mm high purity copper braid, having conduit and cooled by circulating helium gas. Without cooling, the current leads are able • current leads chimney, has a nominal flow of 8000 l/s at 10 current evolution is typically exponential,superconducting and state its as time the constant heat isFor load, 7025 current about s, lower 525 but than W, 4 the is kA, coil a fullyrefrigerator. stays FD absorbed in The is by performed the same the in resistor cooling any is case, refrigerator. contactors, as used leaving the in the heat both load dump is cases resistor smallcases, for enough modules the and for either the FD depending in and on series the thedown (FD) SD, to alarms, or using zero, in the taking normally parallel advantage coil open of (SD). current the For can two-quadrant other converter. be adjusted by2.2.4 the operator, or ramped Vacuum system The vacuum system hasvolume been of designed the to coil providerotary cryostat. pumps a It and good consists 2 insulation of Root’slocated inside at pumps, 2 the the that double-primary top 40 provide pumping of CMS the m stations,helium and phase fore equipped connected separator. vacuum The to with rotary to the 2 pumps coil the havehave cryostat a two a via capacity oil flow of the 280 current of diffusion m leads pumps 1000 chimney m and the one delivers 3000 l/s at the phase separator. 2.2.5 Cryogenic plant The helium refrigeration plant for CMS isW specified between for 60 a and cooling capacity 80 of K, 800of and W the simultaneously at plant 4 4.45 have g/s K, been liquefaction 4500 installed, capacity.ate in The cryostat their primary which final compressors interfaces position, the while phase the separatorafter cold and the box, the completion as thermo-syphon, well of were as the moved the magnet underground temporary intermedi- test. heat load These components of were 6.5performance commissioned kW of with that the the cold simulated help box the of hasmode. a coil been cryostat measured which in was cool-down mode not and yet in available. nominal and The operation 2.2.6 Other ancillaries outdoors taking advantage of naturalically air triggered convection by cooling. hardwired The electronicsa fast only so-called discharge in quench, (FD) case and is of for automat- a unrecoverableconstant faults superconductive-to-resistive is which transition, about require 200 fast s. currentAs dumping. An the emergency The FD coil FD button time becomes is resistive alsoAs during available a the to consequence, FD, the this operator energy in is necessitates30 case dissipated a mΩ of inside post-FD need. the cool-down coil, ofthe which the coil heats coil. warm-up up. and The subsequent FD cool-downslow is discharge time. (SD) performed For is on faults triggered involving a through the hardwired 20 electronics kA on power a source, 2 a mΩ 2008 JINST 3 S08004 resistor, dividing by two the potential to ground. – 14 – shows the test layout. grounding resistor. 2.8 Ω to hold a currenttemperature of at 20 the hot kA spot for stays below 5 400 minutes, KGrounding [14]. followed. circuit The by grounding a circuit FD isthe connected without coil across any the circuit solenoid damage, potential, terminals. through asThe It a winding fixes the insulation 1 quality kΩ is monitoredthrough a by 10 continuously measuring the leakage current Quench detection system. The quench detection systemSystem is a (MSS). key The element of role the of Magnettween Safety the two points quench of the detection coil, system whoseThe value is and voltage to duration taps are are detect compared protected a to by adjustable resistive 4.7resistor thresholds. voltage kΩ, bridge 6 be- W detectors resistors. and There differentialEach are detectors. resistor 2 redundant bridge systems, detector For with spans each twoEach system, modules coil there and module one are is detector compared 5 spans with detectors. the two whole other solenoid. modules through two differential detectors. • • 2.3 Operating test The magnet and all itsJanuary ancillaries 2006. were Figure assembled for testing in SX5 and ready for cool-down in Figure 2.8: The layout forconnected the to surface the test cryoplant at (through SX5, the showing proximity only cryogenics), the the vacuum central and barrel. the The power systems. magnet is 2008 JINST 3 S08004 9 × 2.1), . 2.2. A comparison with the expected ◦ 3 longitudinal, plus the vertical and radial × , and 180 ◦ , 90 – 15 – ◦ shows the cool-down curve. The only glitch was due to 2.9 , followed by slow or fast discharges. During these current cycles all the t /d 2.10. One important aspect monitored during the cool-down was the amount of coil shrinkage. In The measured stresses in the tie bars due to the cool-down, causing a shrinkage of the cold 2.11. The tests were carried out through magnet charges to progressively higher currents, 2.3.1 Cool-down The cool-down of the solenoid startedcold on February, mass the to 2nd, 4.6 2006 K and in in a 24 smooth days. way Figure brought the Figure 2.9: Graph ofroom the temperature coil to minimum 4.5 and K. maximum temperatures during the cool-down from an overpressure on a safety releaserestarted. valve that stopped cooling for one night before the system was order to explain this point,made we of refer to longitudinal, the vertical, coillongitudinal and suspension tie axial system tie-rods rods, inside the in 4compensated cryostat Ti vertical strain (figure alloy. gauges tie to The rods, measure magnet the andtie forces is rods. 8 on supported The 2 radial by tie tie rods 2 3 are rods. strain loaded gauges in are The tension placed and tie on flexion. the rods tie To rods are measure at the equipped 0 tension with and flexion strain, mass and putting the tie-bars in tension, are shown in table relevant parameters related to electrical, magnetic, thermal, and mechanical behaviours have been values is provided as well.figure The measured axial and radial shrinkage of the cold mass2.3.2 is shown in Charge and discharge cycles The magnetic tests took placemapping during campaign August in 2006, October 2006. withure additional The tests current during ramps the forsetting the magnet increasing field field dI mapping are detailed in fig- 2008 JINST 3 S08004 45 MPa 20 MPa 20 MPa 27 mm 15 mm 310± 153± 260± Measured value 26 mm 14 mm 315 MPa 167 MPa 277 MPa Expected value – 16 – Cold Mass Shrinkage Longitudinal Radial Tie rod stress due to cool-down Vertical Radial Longitudinal Figure 2.10: Axial (a) and radial (b) shrinkage of the cold mass from 300 K to 4.5 K. Table 2.2: Calculated and measuredto cold the mass cool-down displacements to and 4.5 related K. stresses on tie-rods due 2008 JINST 3 S08004 2.13. The displacement and direction. According to the 2.12 z, in the +z – 17 – 2.15, giving the force measurements on several tie rods. These figures also 2.16. The measured value of Von Mises stress at 4.5 K and zero current is 23 MPa. and figure Figure 2.11: Magnet cycles during the CMS magnet tests in October 2006. 6]. 2.14 Using the strain gauges glued on the cold mass (outer mandrel of the central module, CB0), of the coil’s geometric centrecomputations, is such a found displacement to indicates bemagnetic that 0.4 centre the mm coil in in centre +z. shouldtially be As identically less the loaded. than coil 2 But supporting mm thefigure system off force is the increase hyper-static, during energising theindicate is tie the well rods forces distributed, are computed as not in shown thecalculated all in case for ini- of the a ideally-centred 10-mm model, magnetic showingthe there misalignment, forces. is together no with noticeable forces effect of misalignment on one can determine the Von Misesgiven stress. in The figure cold mass Von Mises stress versus the coil current is The value at 19.1 kAdesign is [3, 138 MPa. These values are in agreement with computations done during recorded. Depending on the levelfor of re-cooling the the current coil at can the be up trigger to of 3 a days. fast discharge,2.3.3 the time needed Cold mass misalignment The support system is designedment, to in any withstand direction the of forcesperformed the created at cold by each mass a step with 10 ofmonitoring respect mm of the to magnetic the magnet the misalign- coil iron assembly magnetic yoke. toThe misalignment misalignment ensure Geometrical is can a surveys of be were good calculated prime positioning.stresses either importance of by during Nevertheless, the analysing magnet the tie the power rods displacementtions test. when of and the the directions coil cold at is mass both energised.use or ends of the of The rectilinear the displacement potentiometers. coil is Results with are measured respect displayed at in to several figures the loca- external vacuum tank wall, by the 2008 JINST 3 S08004 , the t /d is decreasing t /d dI L = V 2.17. Initially the apparent inductance of the – 18 – Figure 2.13: Radial displacement at both ends of the coil in different positions during energising. while increasing the current, as thements iron yoke at reaches the the coil saturation region. endsinductance From in is voltage calculated the measure- and cryostat, results while are givencoil ramping in is up figure 14.7 the H coil at currentjoints, zero at which current, connect a and the regulated then 5 dI it modulesternally decreases together to and, to the for 13.3 coil, each H on module, at the the 18 4 outer kA. layers, radius The are of positioned 21 the ex- resistive external electrical mandrel, in low magnetic field regions. The 2.3.4 Electrical measurements The apparent coil inductance measured through the inductive voltage Figure 2.12: Axial displacement in Zing. at both ends of the coil in different positions during energis- 2008 JINST 3 S08004 at 19.1 kA, 2.18. It appears to 1.6 nΩ – 19 – of about 500 A/s occurs at the very beginning of the discharge. The t /d 2.18. The effect of the mutual coupling of the coil with the external mandrel is clearly visible at Figure 2.14: Force increase on several axial tie rods; the average force at zero current is 45 t. Figure 2.15: Force increase on several radial tie rods; the average force at zero current is 15 tons. resistance measurements of the jointscorresponding indicate to values a ranging maximum dissipation from in 0.7fully the efficient nΩ joint to of remove 0.6 this W. local Thelocal heat specific quench deposit joint of cooling in the system order conductor. is to Asthrough mentioned avoid the that above, quench-back the the process. fast resistive discharge joints The causesgiven generate typical a in a current quench figure decay of at the the coil, nominal current of 19.14 kAthe is beginning of the current fastclearly discharge as that shown a in the high zoomed dI detail of figure 2008 JINST 3 S08004 for a fast discharge 2.19 at the end of a FD at 19.14 kA. Ω – 20 – Figure 2.17: Coil inductance as a function of the magnet current. Figure 2.16: Stresses measured on the CB0 module as a function of the current. During a magnet discharge, the dump resistor warms up, with a maximum measured temper- minimum and maximum temperatures of the coil are displayed in figure at 19.14 kA. Awarmest maximum part, located temperature on difference the coil of centralexternal module 32 radius internal K of radius, the and is the mandrel. measured coldesttemperature part, It tends on located should to on the equilibrate be the coil over noted theThe that between average whole the the cold coil thermal mass 2 gradient temperature hours after is after a mainly the fast radial. trigger discharge at of The 19 the kAature fast is discharge. increase 70 of K. 240°C, resultingAlso in the an coil increase internal electrical of resistance the is total increased by dump up resistance to 0.1 value by up to 19%. 2008 JINST 3 S08004 – 21 – In the case of a fast dump at 19.14 kA, typically half of the total energy (1250 MJ) is dissipated as heat in the external dump resistor. The energy dissipated in the dump resistor as a function of the The effect of both thethrough dump the resistor measurement and of the the magnet348 discharge s electrical time and resistance 498 constant, increasing s which for was was fastis revealed discharges equal visible respectively to at in 177 19 figure kA, s,2.20. 17.5hours 203 kA, The after 15 s, the temperature kA, 263 12.5 trigger recovery s, kA of of and a the 7.5 fast kA. dump dump. This resistor It is is achieved 5 in hours after less the than trigger 2 of a slow dump. Figure 2.19: Minimum anddischarge from maximum 19.1 kA. temperatures detected on the cold mass during the fast Figure 2.18: Magnet current during fastdetails discharge at at the the beginning nominal of field the of discharge. 4 T. The insert shows the 2008 JINST 3 S08004 – 22 – 2.21. The magnet current is precisely measured by the use of two redundant DCCTs (DC current transformer). The peak-to-peakripple stability of of the 2.5% current (0.65 is V). 7has ppm In with order been a to voltage tested gain and onchecked validated the that by operation time, the switching an cryogenic to accelerationsuperconducting refrigerator the of state. can fast the slow take dump This dump the Slow configurationmode Dump full at through Accelerated heat 4 the (SDA) load, kA. cryogenics mode and Itfully was supervisory automatic the has tested system for magnet been in the and final semi-automatic stays the installation in magnet in the the control cavern. system, and it will be magnet current at the trigger ofand a FD is was given measured in for figure each FD performed during the magnet tests Figure: 2.21 Energy dissipated in theatures external of dump the resistor coil and during FD. the mean and maximum temper- Figure 2.20: The normalised dischargeshowing current the as effect of a the function increase of in time magnet for and different external dump initial resistance currents, with current. 2008 JINST 3 S08004 = 6.44 K, g is defined as the maximum g 2.23. The endcap YE+1 disk is = 9.25 K at zero field. At B = 4.6 T (peak field c – 23 – (T= 4.5 K, B= 4.6 T) = 62 kA leading to T c = 7.30 K. The current-sharing temperature T c and compared to the case of a uniformly distributed load on all the Z-stops. To 2.22 Figure 2.22: Axial forces acting on the yoke Z-stops during the coil energising. 2.3.5 Yoke mechanical measurements The elements of the returnjacks, yoke, which barrels are and fixed on endcaps, each are barreland attached and endcaps endcap. with several They into are hydraulic pre-stressed contact locking in24 at order Z-stops to specific between bring the areas each barrels using barrelgives 8900 and the tons. endcap. aluminium-alloy The stresses Z-stop A arein computation blocks. measured figure of on some the There Z-stops; total are the axialallow forces for compressive on uniform these force load Z-stops distribution are and given positioned distortion on during grease magnet pads. energising, During the magnet yokeunder energising, elements the the are displacement compressive of axial the force barrel is yokeYE+1 very elements is limited, while clearly the noticeable displacement onyoke of the the endcaps yoke towards outer end the radius cap interaction of disk elements point. the parallel to disk, The the measurement due axial of to axis the the of distance the axial between detector attraction is the of given barrel in the figure first equipped with rosette strain gauges onat its the inner interface face, between under two thenot adjacent muon exceed segments. 88 chambers MPa. and The near main the stresses bolts measured in these regions2.3.6 do Coil stability characteristics The NbTi superconductor critical temperature is T on the conductor), T temperature for which the currentCMS can the flow, operating with current no is dissipation,done 19 in 143 on the A, a superconducting while short part. the(the sample critical For one current, extracted exposed according from to to the the thei.e., length higher measurements the field), used temperature is in margin I the is inner 1.94 layer K. This of margin the is central a module little higher than the designed one (1.83 2008 JINST 3 S08004 value was confirmed at 9.3 K during cryogenic c – 24 – 2.24) at zero field. The conductor pure-aluminium stabilizer RRR, deduced Figure 2.23: Measured displacement of the yoke during the coil energising. K) because the nominaland current the is expected less conductor than criticalthrough current the advanced was one and from used qualified 7% processes. in to 10% this The lower T kind than of the computation real one (19.5 obtained kA) Figure 2.24: The minimumtime, and with maximum only temperatures a few and amperes voltageat of around of current, 9.3 showing the the K. coil superconducting-to-resistive-state transition as a function of recovery tests (figure from electrical measurements during cool-down, is found to be above 1800. 2008 JINST 3 S08004 – 25 – 2.3.7 Coil warm-up Following the test of the magnetperature on before the lowering. surface, the The coldavoid coil, mass any inside risk had its to due be cryostat, to warmed vacuumformed was degradation up using attached a during to to dedicated the room power the transport tem- supply central (200 operations.interface. V-300 barrel A The DC) Knowing YB0 warm-up to the to was maintain temperature per- integrity ofheat dependence the of of coil/mandrel the both coil the materials, electrical theing temperature resistivity into increase and account for the the a specific given capacityK/hour, the electrical of warm-up power was the is performed calculated. warm-up as supply, shown Tak- discharge, in and the figure limiting2.25. coil the As temperature the temperature wasat warm-up increase was already night done to at as after the 1 70 a fast yoke K.the was Nevertheless, warm-up opened the lasted to warm-up only continue took 3warm-up integration weeks. place exercise activities was only inside The less the maximum than detector. temperature 9 K. gradient Ultimately, across the coil during the Figure 2.25: Measurements of theis coil common warm-up for behaviour all as the a three function curves. of time; the Y-axis scale 2008 JINST 3 S08004 8m of active silicon there will be on 2 1 − s 2 − cm 34 16]. 5. With about 200m 2. < | η | – 26 – 1m. Each system is completed by endcaps which consist of 2 disks in 2cm and a silicon strip tracker with 10 barrel detection layers extending 5m. The CMS solenoid provides a homogeneous magnetic field of 4 T over 4cm and 10. The construction of the CMS tracker, composed of 1440 pixel and 15 148 strip detector 3.1 Introduction The inner tracking systemof of the CMS trajectories is of designedreconstruction charged to of particles secondary provide emerging vertices. a from It precise the surrounds and the LHC efficient interaction collisions, measurement point as and well has a as length a of precise 5. outwards to a radius of 1. Inner tracking system and a diameter of 2. the full volume of theaverage about tracker. 1000 particles At from the morethe LHC than tracker for 20 design each overlapping luminosity bunch proton-proton crossing, of interactions i.e.granularity 10 traversing every and 25ns. fast Therefore a response detector isattributed technology featuring required, to high such the that correct the bunchthe trajectories crossing. on-detector can electronics However, which be these in identifiedthe features turn reliably aim imply requires and of a efficient cooling. keeping high to powerbremsstrahlung, This photon the density is conversion minimum of and in nuclear the direct interactions. conflict amountrespect. A with of compromise The had material to intense in be particle found order fluxThe in to this main will challenge limit also in multiple cause the scattering, severe designto radiation of operate damage the in to tracking this the system harsh was trackinggranularity, environment speed to system. for and develop an radiation detector hardness components expected lead able lifetimetechnology. to of a 10 tracker The years. design CMS entirely These basedbetween tracker requirements on 4. is silicon on detector composed of a pixel detector withthe three pixel detector barrel and layers 3acceptance at plus of radii 9 the disks tracker up in to the a strip pseudorapidity tracker of on each side of the barrel, extending the Chapter 3 area the CMS tracker is the largest silicon tracker ever built [15, modules, required the development of productionnew methods to and the quality field control of procedures500 particle that physicists and physics are engineers detectors. succeeded over A athis period strong unique of collaboration device. 12 of to 15 51 years institutes to design, with develop almost and build 2008 JINST 3 S08004 m in the inner tracker) with µ at a radius of 4cm, falling to 2 m can be used in the outer region of mm µ the strip pitch can be further increased. 180 × at a radius of 115cm. In order to keep the 2 110cm) < per pixel and LHC bunch crossing. At intermediate r – 27 – 4 − < shows the expected fast hadron fluence and radiation dose m, leading to an occupancy of up to 2–3% per strip and LHC 55cm µ ( 3.1 z, respectively, which is driven by the desired impact parameter m thickness as opposed to the 320 80 µ × and the reduced particle flux allows the use of silicon micro-strip detectors -φ r in and allowed the coverage of the large required surfaces with silicon sensors, 2 2 m 55cm) µ < r 5. A precise measurement of secondary vertices and impact parameters is necessary at a radius of 22cm and 3 kHz/mm 150 < 2. 2 × < | η 20cm 5–10 CHF/cm ogy led to large cost savings and to an improved signal-to-noise performance, | CMS is the first experiment using silicon detectors in this outer tracker region. This novel The radiation damage introduced by the high particle fluxes at the LHC interaction regions The operating conditions for a tracking system at the LHC are very challenging. As already ( • sensor fabrication on 6 inch• instead implementation of of the front-end 4 read-out chip in inch industry-standard deep sub-micron wafers technol- reduced• the automation of sensor module assembly and cost use of to high throughput wire bonding machines. with a typical cell size of 10cm bunch crossing. In the outerGiven region the large areas thatincreased in have order to to be limit instrumented thewith in number its length of this and read-out region, therefore channels. also theorder However, electronics the the to noise strip strip maintain is capacitance a length a scales good linear hasfor function signal to the of to outer be the noise tracker strip ratio region length of (500 ascorrespondingly well well. higher above In signal. 10, CMS These usesvoltage. thicker thicker But sensors since silicon the would sensors radiation in levelsbe in principle the chosen have outer such a tracker that are higher the smaller, initial depletion a100 depletion higher V voltages initial to resistivity of 300 can thick V. In and thisthe thin way cell sensors tracker, sizes are with up in an to the occupancy about same 25cmtracker of range also about of satisfy 1%. the requirements These on occupancy-driven position design resolution. choices for the strip approach was made possible by three key developments: is a severe design constraint. Table 3.1.1 Requirements and operating conditions The expected LHC physics programthe [17] trajectories requires of a charged robust, particles efficient withrange and transverse precise momentum reconstruction above of 1GeV infor the pseudorapidity the efficient identificationphysics of channels. heavy Together with flavours the whichhas electromagnetic are calorimeter to and identify produced the electrons in muon and system manychannels muons, the and respectively. of tracker need Tau the leptons to are be interesting a reconstructedreduce signature in the in one-prong event several and rate discovery three-prong from decaypermanently the topologies. stored, LHC tracking bunch In information crossing order is rate to heavily of used 40MHz in the to high about level 100Hz triggermentioned, of each which CMS. LHC can bunch be crossing athitting design luminosity the creates tracker. on average This about leads 1000 particles to a hit rateoccupancy density at of or 1MHz below/ 1%size pixelated of detectors 100 have toresolution, be the used occupancy at is of radii the belowradii order 10cm. 10 For a pixel 60 kHz/mm 2008 JINST 3 S08004 ) 1 6 5 − s 8 10 10 2 − 10 × × 6 3 corresponding to about 10 years (cm 1 − Charged particle flux 10°C. After 10 years of operation it is − 10 years). The fast hadron fluence is a (≈ 7 70 1.8 840 190 1 Dose (kGy) − – 28 – ) 2 − cm 32 4.6 1.6 0.3 0.2 14 (10 Fluence of fast hadrons 4 11 22 75 p-type with a corresponding change in depletion voltage by a few hundred volts 115 (cm) Radius n- to 14TeV and in the Monte Carlo description of the cascade development lead to a safety factor Three different effects had to be considered in the design of a radiation tolerant silicon tracker. The increased detector leakage current can lead to a dangerous positive feedback of the self 5 (2 in regions where the neutron contribution dominates) which was applied to these estimates = s Surface damage is created whenizing the particle, positively charged get holes, trapped in generated a bywhere silicon this the oxide additional passage space layer. of charge This an changes is ion- forface mostly damage instance a simply the concern characteristics scales of with for MOS the thedamage, structures. absorbed front-end dose. Sur- chips i.e. The modifications silicon to sensors are theloss mainly silicon (NIEL) affected and by crystal bulk lead lattice to whichdepending additional are on energy particle caused levels type in by and energy, the non-ionizing butence. band is energy found gap. The to consequences NIEL scale are approximately is an with adoping the increase from complicated fast of hadron process, the flu- leakage current (linear in fluence), a change in the in order to define the design requirements for the tracker. of 1. over the lifetime of thethe tracker, signal and by the roughly creation 10% ofand after additional the 10 read-out trapping years electronics centers of has which LHC toor will running take better reduce [18]. this over into the The account full design andacceptable of lifetime assure fake the of a hit silicon the signal-to-noise rate. sensors ratio detector, Finally, of inparticles transient 10:1 order in phenomena the to due electronic guarantee to circuitry a the candisturb robust generation change or hit of for even instance recognition charge stop the by at the state correct ionizing an of functioning memory of cells the and read-out therefore (single eventheating upset, of the SEU). silicon sensor and thecalled exponential dependence thermal of runaway. the leakage currentthe This on temperature, cooling has system to and bewhole by avoided tracker volume a by will low efficient be operated operating coupling at temperature. or of slightly the below For silicon this sensors reason to it is foreseen that the in the CMS barrel tracker for an integrated luminosity of 500fb of LHC operation [15, make17]. up a substantial Neutrons contribution to generated thetracker by fast close hadron hadronic to fluence, which interactions the actually ECAL in dominateserror in surface. the of the outer ECAL√ The the uncertainties crystals inelastic on proton these proton estimates due cross-section, to momentum the distributions extrapolation and multiplicities to Table 3.1: Expected hadron fluence and radiation(barrel dose part) in different for radial an layers of integrated the luminosity CMS tracker of 500fb good approximation to the 1MeV neutron equivalent fluence [17]. 2008 JINST 3 S08004 m on 2cm, m on 3.2. In µ µ m CMOS µ 3 and 10. 25 m, respectively. 7. µ 4, measurements on a -φ r m and 35 µ 27°C which in turn means that − m. The TIB/TID is surrounded by m on layers 1 and 2 and 120 3.1. At radii of 4. µ m on the first 4 layers and 122 µ µ and has 66 million pixels. 2 m and 141 µ – 29 – 3.3. It is composed of three different subsystems. The Tracker m thick silicon micro-strip sensors with their strips parallel to the beam axis µ m thick micro-strip sensors with strip pitches of 183 The ultimate position resolution of the pixel and strip sensors is degraded by multiple scatter- The radial region between 20cm and 116cm is occupied by the silicon strip tracker, which The read-out chips employed in the CMS tracker are fabricated in standard 0. µ 30°C. A second effect, called reverse annealing, requires to keep the silicon sensors permanently the Tracker Outer Barrel (TOB). It500 has an outer radius of 116cm and consists of 6 barrel layers of In the TID the mean pitch varies between 100 technology which is inherently radiation hardThe due lifetime to of the the thin gate siliconsensors. oxide strip (and tracker For special is efficient design therefore charge rules). collection limitedages they by up to always the 500 need radiation V to damage after be 10 tostability years over-depleted, of the of requiring current silicon LHC bias sensor operation. volt- layouts. Thisat reaches Furthermore, the some the limit point increased of lead leakage the typical currents tomain high of thermal fully voltage the runaway. operational sensors for All 10 will years tests of havehas LHC shown to running. that survive For the the even pixel higher silicon detector radiationsensor strip on doses, the layout. tracker other under-depleted will hand, Its operation re- which lifetime is reacheslayer possible to from due more at to than least a 10 2 different years years for the at third full layer. LHC luminositying in for the the material innermost that istotal necessary about to 60 precisely kW hold for the the sensors,interactions CMS to of tracker) supply and pions the to and electrical cool other power the hadronsfor (in electronics in these and this particles. the material silicon In sensors. reduce addition, significantly Nuclear thisadversely the material affect tracking leads the efficiency to measurement photon accuracy conversionrequirement and of to bremsstrahlung the keep which electromagnetic the calorimeter. amount of It this was material therefore to a a minimum. 3.1.2 Overview of the trackerA layout schematic drawing of thethree CMS cylindrical tracker layers is of shown hybrid incomplemented pixel figure by detector two modules disks surround of theprecision pixel interaction space modules point. points on on each They each side. charged are total particle The the trajectory. pixel It pixel detector is detector delivers described covers three in an detail area high in of section about 1m layers 3 and 4 in the TIB, leading to a single point resolution of 23 expected that this will require a cooling fluid temperature of about is described in detailInner in Barrel section and Disks (TIB/TID)layers, extend supplemented in by radius 3 towards disks 55cm at and each are end. composed TIB/TID of 4 delivers up barrel to 4 in the barrel and radial on the disks. The strip pitch is 80 all structures in the tracker have to− survive temperature cycles between room temperature andwell about below 0°C except forradiation short induced maintenance defects periods. in the Thiseven silicon effect stronger sensors is change which caused can in by leadannealing depletion the to becomes interaction voltage more insignificant of with for serious temperatures damage fluence. roughly and below to Experimentally 0°C an [18]. it is found that reverse trajectory using 320 2008 JINST 3 S08004 φ at 0 X m and 1.7 1.9 2.1 2.3 2.5 m thick µ 1.5 µ 1.3 range the Tracker 3.2). The ultimate z axis) cover the region z (mm) z 1.1 shows the expected reso- the transverse momentum TEC+ 3.4 0.9 0.7 100GeV) ( TID TID 0.5 4, beyond which it falls to about 1 PIXEL 118cm. Beyond this 1. 0.3 ± m thick on the inner 4 rings, 500 | ≈ µ 0.10.1 η m average pitch. Thus, they provide up to 9 | η µ 5cm. Each TEC is composed of 9 disks, carrying TIB TIB 9 hits in the silicon strip tracker in the full range of TOB TOB at -0.1 – 30 – 0 between ≈ X 113. z -0.3 < measurements with single point resolution of 53 6, beyond which it degrades due to the reduced lever arm. 5. The CMS silicon strip tracker has a total of 9.3 million on the disks). The achieved single point resolution of this | 1. m to 184 r 2. -0.5 r | -φ µ r TID TID < | ≈ | ≈ m in TIB and TOB, respectively, and varies with pitch in TID -0.7 η η µ | | 5cm 0 to about 1.8 -0.9 ≈ η 4 of them being two-dimensional measurements (figure 2% up to -1.1 at m and 530 ≈ TEC- in the barrel and − 0 µ X of active silicon area. shows the material budget of the CMS tracker in units of radiation length. It -1.3 2 -2600 -2200 -1800 -1400 -1000 -600 -200 200 600 1000 1400 1800 2200 2600 282cm and 22. < 3.3 0 800 600 400 200 -200 -400 -600 -800 1200 1000 -1000 -1200 z| | -1.5 5. 4 with at least < 2. 2. r (mm) -1.9 -2.1 -2.3 -2.5 -1.7 In addition, the modules in the first two layers and rings, respectively, of TIB, TID, and Figure m, respectively. The TOB extends in < µ | | ≈ η η resolution is around 1 At a transverse momentum of 100GeV multiple scattering in the tracker material accounts for 20 to on rings 5-7) with radialmeasurements strips per trajectory. of 97 TOB as well as rings 1,mounted 2, back-to-back and with 5 a of stereo thesecond angle TECs co-ordinate of carry (z a 100 second mrad micro-strip in detector order module to which provide is a measurement of the lution of transverse momentum, transverse impact parametera and function longitudinal of impact pseudorapidity parameter, [17]. as For high momentum tracks increases from 0.4 up to 7 rings of silicon micro-strip detectors (320 measurement is 230 3.1.3 Expected performance of theFor CMS single tracker muons of transverse momenta of 1, 10 and 100 GeV figure 35 EndCaps (TEC+ and TEC- where the124cm sign indicates the location along the and TEC. This tracker layout ensures| at least acceptance of the tracker ends at strips and 198 m | layers 5 and 6. It provides another 6 Figure 3.1: Schematic crossmodule. section Double lines through indicate the back-to-back modules CMS which tracker. deliver stereo hits. Each line represents a detector 2008 JINST 3 S08004 . η η for the η 0 the effi- ηη 0. At high | ≈ tracks, domi- η ≈ T Outside Other Support Cooling Cables Electronics Sensitive Beam Pipe | p z shows the expected track m for high η 3.5 µ

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22 00

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8 6 4 2 0

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0 0 x/X x/X 0.20.2 1.21.2 0.80.8 0.60.6 1.81.8 1.61.6 0.40.4 1.41.4 Tracker Material Budget the efficiency drop is mainly due tohadrons the in reduced general coverage the by efficiency the is pixel lower forward because disks. of For interactions pions with and the material in the tracker. 30% of the transverse momentum resolutionscattering. while at lower The momentum transverse it is impact dominated parameter by multiple resolution reaches 10 Figure 3.3: Material budget indifferent units sub-detectors of (left panel) radiation and length broken as down a into the function functional of contributions pseudorapidity (right panel). nated by the resolution ofscattering the (similarly first for pixel the hit, longitudinal whilereconstruction impact at efficiency parameter). lower of momentum the Figure it CMS israpidity. tracker For for degraded muons, by single the muons multiple efficiency and isciency pions about decreases as 99% slightly a over due most function to of of gaps the pseudo- between acceptance. the For ladders of the pixel detector at Figure 3.2 Filled circles show the total number (back-to-backthe modules number count of as stereo one) layers. while open squares show 2008 JINST 3 S08004 ηη 22 1.51.5 11 || ηη || , pt=1GeV , pt=10GeV , pt=100GeV 0.50.5 22 µ µ µ 00 3 2

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δ σ /p p ( ) [%] ) e 3.5: Global track reconstruction efficiency for muons (left panel) and pions (right panel) e 3.4: Resolution of several track parameters for single muons with transverse momenta of 1, An independent support and insertion system for the pixel detectors, the central section of Figur of transverse momenta of 1, 10 and 100 GeV. 3.1.4 Tracker system aspects All elements of the CMS trackerHCAL are barrel. housed in The the tracker tracker support support2.38 tube, tube m. which is The is a 30-mm-thick suspended wall large onskins, of cylinder the the 2 5.30 cylinder m mm is long in made with thickness, bytube’s an sandwiching two inner inner 950-1/T300 a surface, carbon diameter 26-mm-high two fiber of carbon Nomex composite fiber core.barrel (TOB) rails and Over are both the attached endcaps entire on (TEC+ length the andpads. TEC-) horizontal of rest The plane. the on tracker these The inner rails trackerbetween by barrel outer means the and of guiding disks adjustable elements (TIB/TID) sliding of are theseto in rails a turn is parallelism between controlled supported the to by guides better the better than TOB. than 0.183 The mrad, angle corresponding Figur 10 and 100 GeV: transverseand momentum longitudinal (left impact panel), parameter (right transverse panel). impact parameter (middle panel), the beam pipe and thetracker inner at elements its of inner the radius. radiationduring monitor This tracker system is spans assembly composed the of to fullthe three form length long installation, of two carbon support the fiber continuous and structures, parallela joined positioning 2266.5-mm-long planes, together of and on each 436-mm-wide which elementdetector. cylinder precision are This which element tracks machined. provides is support for connected and The accurate with central positioning flanges to element the to is pixel the detectors. Two TIB/TID 2420- 2008 JINST 3 S08004 14 F 6 /hour of C 3 35°C and with a pressure drop of up to 8 bar. − and therefore is responsible for a small impact z – 33 – 12°C on the outer surface of the support tube in order and + ) is flushed with pre-chilled dry nitrogen gas at a rate of 3 -φ r °C while the tracker volume needs to be cooled to below 4) ± 18 ( . It has a sufficiently low viscosity even at the lowest required temperature, excellent 10°C inside the tracker volume even when the sub-detectors and their cooling are switched 14 − The outer surface of the tracker tube faces the electromagnetic calorimeter, which is operated The total power dissipation inside the tracker volume is expected to be close to 60 kW. Mainly The full tracker volume (about 25m F 6 10°C. In order to achieve this thermal gradient over a very limited radial thickness, the inside − surface of the tracker support tubebelow is lined with an activeoff, thermal while maintaining screen. a It temperature ensures above a temperature behaviour under irradiation and is extremely volatileeventual (with damages practically no from residues) accidental thus leaks. minimizing liquid The to cooling the system tracker, provides at up a to temperature 77m of down to parameter resolution that is important for good secondary vertex reconstruction. With a pixel cell mm-long side elements aregap coupled between to the it faces of only theto by TIB/TID the and very TEC the precise closing detectors. pinned flangesstrip of connections, These detectors the bridging and side tracker can the elements without be direct are installedThey contact therefore and serve removed structurally several at purposes: decoupled any from time theyof with the provide the no beam silicon support impact pipe, and on they alignment the allowand strip the features they installation detectors. for of are the the used central inner forhoused elements section installation of in and the the radiation inner removal monitor region of system, ofand all the radiation the tracker: monitor. components beam permanently pipe, This or bake-outin system equipment, temporarily the of pixel barrel, core permanent pixel tracks, of disks maintenance, light the inducing but tracker no very will disturbance stiff allow to andfeature the for stable, will volume the installed be occupied quickest extremely by possible valuable theand after silicon intervention radiation some strip damage in years on detectors. this sensors of This will region operation, start during when becoming activation an of issue. components at room temperature and requirescalorimeter good must temperature be stability. kept The at surface of the electromagnetic to avoid condensation. Itthermal also screen reduces consists the of thermal 32plate stress panels. whilst, across separated On the by the supportare 8mm inside, tube powered cold structure. of to fluid Rohacell heat is The foam,controlled, up circulated based several in the on polyimide-insulated a 64 outer resistive temperature thin surface sensors. circuits aluminium to the required temperature.for robustness in The operation, system the CMS is trackerThe is feed-back liquid equipped used with for a refrigeration mono-phase of liquidis the cooling silicon C system. strip and pixel detector as well as the thermal screen This corresponds to a cooling capacity of up to 128 kW. up to one volume exchange per hour. 3.2 Pixel detector 3.2.1 Pixel system general The pixel system iscontributes the precise part tracking of points the in tracking system that is closest to the interaction region. It 2008 JINST 3 S08004 and -φ r . The arrangement 2 46.5 cm. BPix (FPix) z=± 2.5, matching the acceptance < η 34.5 and 2.5< z=± − – 34 – Pseudorapidity η region the 2 disk points are combined with the lowest possible

η

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) s t i H 2 ( y c n e i c i f f E z 3.6 emphasis has been put on achieving similar track resolution in both 2 . In the high m η µ 150 × -range. Figure η The pixel detector covers a pseudorapidity range The vicinity to the interaction region also implies a very high track rate and particle fluences 6 to 15 cm in radius, will be placed on each side at directions. Through this a 3D vertex reconstruction in space is possible, which will be important Figure 3.6:pseudorapidity. Geometrical layout of the pixelsize detector of 100 and hit coverage asfor a secondary vertices function with lowout of scheme track with multiplicity. analog pulse The heightsharing pixel read-out. and system This improves helps has the to a positionoverlapping zero-suppressed separate resolution tracks. due read signal to and charge noise hits as well as to identify large hit clusters from of pseudorapidity z of the central tracker.from The b pixel detector and is tau essential decays,triggering. for and It the forming consists reconstruction seed of of three tracksBPix barrel secondary for layers layers vertices the will (BPix) outer be with track two located≈ endcap reconstruction at disks mean and (FPix). radii high of The level 4.4, 53-cm-long contain 7.3 48 and 10.2 million cm. (18 The million)of FPix the pixels disks 3 covering extending barrel a from layers totalthe and area the full of forward pixel 0.78 disks (0.28) on m each side gives 3 trackingradius point points from over the almost 4.4 cm barrel layer. that require a radiation tolerant design.design For the that sensor this allows led partial to anlayers depleted n+ the operation pixel drift on even of n-substrate the detector at electronsfield very to of high the CMS. collecting particle The pixel fluences. resulting implantover Lorentz is more drift perpendicular For than one to leads the pixel. the to barrel With 4 charge the T spreading analog magnetic pulse of height the being collected read out signal a charge charge interpolation allows 2008 JINST 3 S08004 m 3.7 µ in a ◦ 1632 mm. z=± 23]. concept. The pixels consist away from normal incidence [19]; 600V) after high hadron fluences. ◦ n-on-n m. The forward detectors are tilted at 20 m between implants was chosen. Figure µ µ – 35 – drift. A position resolution of approximately 15 B ~ × E ~ m for the p-stop rings and a distance of 12 In order to allow a replacement of the innermost layers the mechanics and the cabling of the The pixel system is inserted as the last sub-detector of CMS after the silicon strip tracker has The isolation technique applied for the regions between the pixel electrodes was developed µ turbine-like geometry to induce charge-sharing. Theeffect charge-sharing of is particles mainly entering due the to detector the atcharge-sharing an geometric is average angle also of enhanced 20 by the in both directions can be achieved within charge-sharing the between neighbouring depletion pixels. depth The or reduction thetherefore increase a in degradation bias of voltage the will spatial lead resolution to with a radiation reduction damage. of charge-sharingpixel and system has been designedexpect the to innermost allow layer a to yearlyas stay access well operational if as for needed. the atinstallation least forward At along the 2 disks full beam years. LHC are pipe and luminosity divided TheThe to we 6 into 3 pass beyond individual layer a the mechanical barrel beam left pieces pipe mechanics inside are and support the referenced wires a to at TIB right each cylinder. other half. Power,are through brought cooling, precisely to This the machined the optical rails is detector through controls requiredtubes supply as have tube to a well shells. flexible allow as In connection case the that ofslightly needs optical the curved to read-out barrel rails bend lines pixel around by system a the the few beam supply degrees pipe during support insertion ring. following the been installed and after the central section of the beam pipe has3.2.2 been installed and baked Sensor out. description Technological choices The sensors for theof CMS-pixel high detector dose adopt n-implants the introducedis so into placed called a on high the resistance backhigher n-substrate. side costs The due of rectifying to the pn-junction the sensortrons double surrounded ensures sided by a processing high a this signal multi concept chargeFurthermore was guard at the chosen ring moderate double as structure. bias the sided voltages collection processing (< Despiteground of allows the potential. elec- a guard ring scheme keeping all sensor edgesin at close collaboration with themoderated sensor p-spray vendors. [21] for Open the p-stopsduring barrel. an [20] Both extensive were qualification types chosen procedure of for including sensors several the showed test disks sufficient beams radiation and [22, hardness Disk sensors The disk sensors use the p-stoption technique efficiency for and interpixel minimize isolation. theof To pixel maximize 8 capacitance the charge within collec- the design rules of the vendor a width shows a photograph of 4 pixelbetween cells. the The aluminium open and ring the p-stops, implanted the collecting bump-bonding electrode pad are and highlighted. the contact to achieve a spatial resolution in the range of 15–20 2008 JINST 3 S08004 5 ROCs, are implemented on a × 3.8. Most area of a pixel is covered Bump (In) p−Implant Full p−spray dose Contact via Bias dot . The 7 different sensor tiles needed to populate 2 – 36 – Bias grid 2 read-out chips (ROCs) to 2 Aluminium Reduced p−spray × m) to provide a homogeneous drift field which leads to a relatively high capacitance of µ Figure 3.7: Picture of four pixels in the same double column for a pixel disk sensor. The process is completely symmetric with five photolithographic steps on eachThe side sensors to were mini- all fabricated in 2005 on 4 inch wafers. The depletion voltage is 45–50 V A production yield higher than 90% has been achieved and 150 good sensors for each of the The opening on the p-stop rings provides a low resistance path until full depletion is reached a disk blade, ranging from 1 to allow IV (current-voltage) characterizationwhen the of sensor the is over-depleted sensor (10–20 on V over-depletion) wafer to and assure interpixel a isolation. mize high the resistance mechanical path stress on the silicon substrate and the potentialand bowing of the the leakage diced current sensors. is less than 10 nA per cm single wafer. seven flavours are available to the project for module assembly. Barrel sensors The sensors for the pixelphotograph of barrel four use pixels the in a moderatedwith barrel p-spray the sensor technique collecting is shown for electrode in interpixelsmall formed figure (20 isolation. by the A n-implant. The gap between the n-implants is kept Figure 3.8: Photograph of fourreflown. pixel cells. The Indium bumps are already deposited but not yet the order of 80-100 fF per pixel. 2008 JINST 3 S08004 80 pixels [26]. 8 ROCs) and 96 half orientation and a resis- × indicates the opening in the 111i h 3.8 is visible. They provide a high resistance bias dot – 37 – has undergone the bump deposition process. The Indium shows a sketch of the system. 3.8 m 5-metal-layer CMOS process and contains 52× m wide octagons. µ µ 3.9 around the pixel implants visible in figure 7kΩcm (after processing). This leads to a full depletion voltage of 50-60 V of frame 10°C is 90 electrons equivalent with a noise of 170 electrons. 8 ROCs). They were processed in 2005 and 2006 using two different mask sets. − C protocol. Figure × 2 m thick sensors. All wafers for the production of the barrel sensors come from the same µ out. This threshold canThe be trim adjusted bits have individually a for capacitive protection eachto against reduce pixel single SEUs by event by upset 2 means (SEU), orders of which ofat has magnitude four T= shown [26]. trim The bits. mean threshold dispersion after trimming The front end consists of a Token Bit Manager (TBM) chip which controls several read-out The pixel barrel requires two different sensor geometries, 708 full (2 The sensors are processed on n-doped DOFZ-silicon [24] with The sensor shown in figure In one corner of each pixel the so called The dark • Amplification and buffering of the charge signal from• the sensor. Zero suppression in the pixel unit cell. Only signals above a certain threshold will be read chips (ROCs). The pFEC sends thefront 40MHz end clock and and programs fast all control front end signalsit, devices. (e.g. formats The trigger, it pxFED reset) receives to and data the sends frommodules the it located front to in end, the digitizes the electronics CMS-DAQ room event andlinks. builder. are The connected The various to components pFEC, the are front FEC described end and through in pxFED 40 the MHz are following optical sections. VME Read-out chip Sensor signals are read outfabricated by in ROCs a bump commercial bonded 0.25- to the sensors. A ROC is a full custom ASIC Its main purposes are: tivity of about 3. the 285 silicon ingot to provide the best possible homogeneity of all material parameters. bumps are visible as roughly 50 nitride covering the thermal oxide.to the In lateral pn-junction this between region thedose the pixel is implant p-spray reduced. and dose the reaches p-sprayed the inter-pixel region full the level. boron Close modules (1 3.2.3 Pixel detector read-out System overview The pixel read-out and controlmodules/blades system to [25] the consists pixel front ofcontroller end three (pFEC) driver to parts: (pxFED), the a modules/blades a and fast read-outtube/service a control data cylinder. slow link The control link link latter from from from is the the a used pixelthrough standard to front a FEC configure I to end the the ASICs supply on the supply tube/service cylinder punch-through connection to all pixels whichtant allows to on-wafer exclude IV faulty measurements sensors which from are the impor- module production. 2008 JINST 3 S08004 2 − cm 1 − s 34

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E E I L E L Y C T T E L I L U P M N R E P V D A U O R P N R O Figure 3.9: Block diagram of the pixel control and read-out system. D O O A U E A S S C R M P B A doned. DAC) to the TBM chip.values within 5 Pixel clock addresses cycles are (125ns) while transferred the as pulse height 6 information level is analog truly encoded analog. digital variations in the CMOS device parameters. There are a total of 29 DACs on the chip. There are a few architecture inherent data loss mechanisms. The particle detection ineffi- The power consumption depends on the pixel hit rate. At the LHC design luminosity, the • Level 1 trigger verification. Hit information without a• corresponding L1 Sending hit trigger information is and some aban- limited configuration data (analog value of last addressed • Adjusting various voltage levels, currents and offsets in order to compensate for chip-to-chip The ROC needs two supplyThey voltages compensate of for 1.5 differences V inferent and supply lengths, 2.5 voltage improve V. due AC There to power are noise voltageon-chip 6 rejection drops temperature on and sensor in chip strongly allows module reduce voltage the cables intermodule regulators. controlled monitoring of cross-talk. of through dif- the An a module modified temperaturedownloaded I online. without stopping The data ROC acquisition. is ciency has been measured in a high-rateand pion reaches beam. 0.8%, It 1.2% is and in 3.8% fairly respectively good for agreement the with three expectations layers at a luminosity of 10 and 100 kHz L1 trigger rate. ROC contributes with 34 budget before (after) the detector has received a total fluence of 6× 2008 JINST 3 S08004 – 39 – trigger. status. These will be transferred as 2 bit analog encoded digital. • It will control the read-out of the ROCs by initiating a token pass• for each On incoming each Level-1 token pass, it will write• a header The and a header trailer will word to contain the an data stream. 8 bit event number• and the It will trailer distribute will the Level-1 contain triggers, 8 and clock bits to of the ROCs. error Token Bit Manager chip The TBM [27] controls the read-outon of a the group detector of near pixel ROCs.detector to The modules the TBM and is pixel will designed ROCs. control toIn be the the located In read-out case of the of 8 the case or forwardout of disks, 16 of they the ROCs 21 will depending or barrel, be 24 upon mounted ROCs they the onbe depending will layer the on connected disk blade radius. to be side. blades a mounted single and A analog will on TBMa optical control and the flash link the the ADC over group read- which module of the located ROCs that data inthe it will the following: controls be electronics will sent house. to The the front principal end functions driver, of the TBM include Each arriving Level-1 trigger will beNormally placed the on a stack 32-deep will stackhigh awaiting be track its empty associated density token but events, pass. or isfor trigger needed the bursts. to inner Since two accommodate layers there highIn of will burst addition the be rates barrel, two to the analog due two TBMs data to TBMs,addressing will links switch noise, this be per for chip configured module control as also commands pairsROCs. contains in that These a a are control Control Dual commands sent Network. TBM will from Chip. bein the sent The the DAQ over electronics Hub to a house serves the digital to optical as the frontrunning link front a end at from end a TBMs port a Hubs. speed and front The of end commandsa 40 controller will refreshing MHz. be of sent This the using high pixel a speedThere threshold serial are is trim protocol, four mandated bits external, by that write the can onlyis need ports become one to on corrupted internal rapidly each due read/write Hub cycle to port for through for single communicatingeach communicating event command with with upsets. will the the contain ROCs TBMs a and 5-bit within there Hubit the address chip. selects and The a the first 3-bit addressed byte port address. of remainder port, of When the a strips Hub command off is stream addressed, the unmodifiedports onto byte consist the of containing addressed two port. the low The voltage Hub/port outputs differential of address lines the for and external sending passes clock and the Analog data. chain The hit information isbelonging read to out a serially single through trigger.and analog Within digitized such links in packets the in a Front data150 new End packets ns. analog Driver containing value (pxFED) Five is all at values transmittedrepresents the hits are every the same used 25 signal rate. charge. ns to Only Each encodeare the pixel the discrete charge hit levels address signals generated uses are of by 6 truly DACs. a No analog values, pixel ROC while or IDs inside headers are and sent a but addresses ROC every ROC and adds a the header, sixth whether value 2008 JINST 3 S08004 Ω 72 bits). In order to determine thresholds × 36 bit wide) which can be held on demand to enable – 40 – × 72 bits) whose outputs are combined to provide the data now at a × it has hits or not inis order controlled to by make a the token association bit of whichTBM. is hits The emitted differential to electrical by ROCs outputs the possible. of TBM, The the passed ROCstwo sequential from are output read-out ROC multiplexed to by lines. the ROC On and TBM onto back the either to sameAfter one the lines receiving or the the TBM token transmits back a fromstatus header information. the before last From starting ROC the the in TBM ROC theKapton read-out. to chain the cable. the end The ring TBM of sends Kapton thelines a cable pixel are trailer has barrel separated containing a the by ground read-out quiet lines uses meshsignals from the on was the module the found fast back digital to signals. side bethe Nevertheless, and unacceptable end cross-talk and the ring from the a differential LVDS analog analog low signals swing aresent separated digital on from a protocol the separate is digital Kapton and being all(AOH). cable used analog The to instead. signals signal a of path printed On the sector circuit between are board TBM that and houses AOH the is Analog designed Optical with Hybrids a constant impedance of 40 and levels required for themode making state unprocessed machine, ADC FIFO-1 outputtwo can data FIFO-3 alternatively available. memories be (8k operated Thefrequency in output of a from 80 transparent FIFO-2 is MHzacting clocked (twice as into the a common point-to-point operatingare link implemented pxFED-frequency) with (restricted to the in the CMS-DAQ size) system.checking to S-Link data hold interface integrity. selected Parallel Error event to detection fragments the takes andcorresponding place data make flags in them flow are the available spy embedded data for stream in FIFOs DAC from the output FIFO-1 from event to each trailer FIFO-2 ROC and and (on also default accessible representing from the ROC’s VME. temperature) A is selected available as well. and terminated on the AOH. Thesilicon optical strip links tracker. of An the pixel ASIC systemby that are the adapts identical laser the to driver output has those levels been used oflevels added in the used to the for pixel the encoding modules AOH of pixel to addresses the thosewidth pixel is expected to system. crucial separation for A of the clean the identification reconstruction digitized ofdigitizer of levels the hits. input after six is The the 3 ratio full of ns read-out RMS full which chain makes read-out is corrections chain 1:30. from adds The previously a rise-time transmittedby noise at levels baseline equivalent the negligible. variations to of 300 The the electrons laser to drivers. the analog pulse height, dominated Front End Driver Optical signals from thepixel pixel Front End front Digitizer end (pxFED). Aequipped electronics pxFED with (ROCs is an and a optical 9U receiver TBMs) andthe VME are TTC an module. system ADC. digitized It which The can has using ADC be 36 the converts25 adjusted optical at by ns) inputs an LHC for each individually frequency programmed precise supplied phase by timing.set. shift (16 The steps A output within of programmable the offset 10consisting voltage bit-ADC of to is header, processed compensate by trailer, bias a inputaddresses shifts state channel and machine can to number, amplitudes also deliver ROC of pixel be numbers, hit eventfragments fragments pixels are double strobed all column into at numbers FIFO-1 (1k a and read-out deep subject-dependent via resolution VME. of In 5 normalchannels to processing are 8 mode transmitted bits. FIFO-1 to is Event 8 open FIFO-2 and memories data (8k of 4 (5) combined input 2008 JINST 3 S08004 – 41 – In addition, errors areon directly transmitted the to S-Link the supplementary CMS-TTSthe card. rate system of A using double histogramming a column dedicated feature hits.check connector for has This histogram dead been is or implemented intended overloadedenabled, to to columns. be replaces monitor read the The out normal pxFED vianormal ADC VME houses pixel periodically input an event. to There by internal are a test three testthat system pattern DACs every which, of (10-bit) available third when 256 to input generate clocked such channelmost analog a receives of pattern levels the the meaning simulating features same of a the simulated pxFEDstate event. without machine the with This its need adjustable of test parameters, external system the opticalfeatures VME input allows are protocol, signals. to error integrated All detection into test FIFOs, and several the histogramming FPGAsto mounted changes and on improvements. daughter The cards corresponding making firmwareJTAG bus the can connector be pxFED mounted downloaded flexible via on VME the or mother using board.40 a pxFED The modules whole pixel (32 read-out for system the willin barrel consist the and of electronics 8 room. for the Individual forward) modules set can up be in accessed three by 9U VME VME geographicalFront crates addressing. End located Controller The Pixel Front End Controller (pFEC) suppliesprovides clock a and data trigger path information to to thepFEC the front uses front end, the end and same for hardware configurationthe as settings behaviour the of over the standard a mezzanine CMS fiber FEC FEC-CCS (mFEC) opticconverting module the [28]. connection. has FEC been The into The replaced firmware a by pFEC. which aThe Each defines pixel Trigger mFEC specific Encoder board version, performs becomes all two command triggerthe links transmission pixel to functions, standard, the encoding front block TTC end. triggerscontinuously, triggers for to to testing match a purposes. given Within each channel,data command transmission, generate link and are internal a a triggers, one tworead either kilobyte kilobyte operations, output singly, input buffer are or for buffer retransmitted for backthe data from VME receiving. the data front transfer All end time, data,trim for the whether values possible pFEC to write verification. uses the or several To front data minimize of end, transfer pixels the modes. pFEC on calculates the When the transferring fly.values row over pixel number This VME information to results for a in a givenbe nearly command given reloaded link column a in buffer. 50% In 12 reduction this s.14 way, in the s the Another entire to time 2 reload pixel front the s required end frontis are to end trims twice used transfer completely. can to as This trim column load big mode thetrim as is other value the also for configuration the transmit each registers, reason buffer. pixel. that foreither the The a Once return by total return data buffer computer of buffer is control, receives loadedexpected into or the to an row by occur output in number a the buffer, as signal front theSince end well from transfer registers, updating as may it the is be the the TTC anticipated initiated front that system.synchronized periodic end updates to Since may will orbit be single disrupt necessary. gaps event data orFor upsets taking, transmission private are verification orbits. it purposes, the is This number preferableof of is bytes to bytes done transmitted perform returned is through compared small the from totransmitted updates TTC the the address. number initiated front downloads. end. Status bitsstored, Also, are for possible set the review, with should returning an the Hub/port error results condition address of occur. is this compared comparison, to and the these values are 2008 JINST 3 S08004 C data 2 ode n

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L C I M 2 S er f D f U no u V L B CC 2 I C s d shows the block diagram of a CCU Board. The same ring topology configured as a y i r

r ck ck a y b o o ck d l l r ck l o y C C a n l o l a + + h C g g o t t C t m + u u c n n o i + n i i t e r I O O n I 3.10 a a a R S P R t t t p a t a a a a O D Digi D D In the BPix each read-out sector is controlled by a separate CCU node. Eight active and one D local area network as inis the the silicon master strip of tracker thenumber is network of used. slave and CCU uses The nodes, front twotwo and end optical another receiver controller fibers two channels (FEC) to fibers on module to senddata the receive the at return digital timing communication 40 optohybrid and traffic. Mbit/s (DOH) data The (CCUs). in signals transmit the to the direction The a 40 from two MHzCCUs. the transmitter clock FEC channels The and to CCU send control the is clockdistribution ring the in and of the core communication data tracking component and system back developed [29].failure control to for a To units redundant the improve the interconnection system slow FEC scheme reliability control, based against fromCCUs on monitoring a is doubling the implemented. single and signal ring component paths An timing and additional of “dummy” bypassingpreserving CCU of node faulty complete allows functionality. to mitigate a Aelectronics single CCU DOH attached failure node to failure that leads CCU. to The a first two loss CCU of nodes communication in to the all ring provide also the I Figure 3.10: Block diagram ofCCU the nodes is Pixel 9 front for end the control BPix system. and 5 Note for that the FPix. the totalThe number detector front of end control system The CMS Pixel detector front enddetectors control consists system of for four both communication the and barrelcontrols control (BPix) unit a and boards quarter the (CCU forward of Boards). (FPix) the EachFigure detector CCU with board eight Barrel read-out sectors or twelve Forward port cards. channels necessary to control the digital optohybrids on the CCU boards. dummy CCU node build a single control ring. One I the front end read-out electronics andthe three digital output and channels the generate analog the optohybridsThe necessary as FPix signals well control to as ring reset the consists read-out ofnodes chips four control (ROCs) active in 3 and one port one read-out cards, dummy sector. CCU which node. constitute Each a of 45 the active CCU connection between a CCU and achannel port and card two includes reset a signals. bi-directionalgoes 100 to One KHz the reset I read-out signal chips is on for the detector the panels. port card electronics, and the other one 2008 JINST 3 S08004 sides of 285 mm z + − and z + 285 mm to − shows a sketch of a complete support structure 3.11 – 43 – Figure 3.11: Complete support structure half shell with the three detector layers. Aluminium cooling tubes with a wall thickness of 0.3 mm are the backbones of the support Four to five of these tubes are laser welded to an aluminium container which distributes the half shell. structure. Carbon fiber blades with aadjacent thickness cooling of 0.24 tubes mm in are such gluedbeam onto a or the away way top from that or it. bottom theirof of The normal the two ladders tubes directions they have alternate hold. trapezoidal pointing cross either sections to defined the by thecooling azimuthal fluid. angles The resulting manifold provides the necessary cooling of the detector modules to the barrel are separated.sharing Each only side the slow is control divided system. in 16 sectors which operatePixel almost barrel support independently, structure The detector support structure for theequipped three with layers silicon at pixel the modules radii has ofclosest a four, to length seven the and of CMS eleven 570 centimeters interaction mm ranging region. from Figure 3.2.4 The pixel barrel system The pixel barrel system asmounted installed on inside their CMS cylindrical comprises support thewith structure, its barrel length as itself, of well i.e. 570 as mm detector isSupply supply modules much tubes tubes shorter carry than on the services both Silicon along sides. Stripvolume the Tracker to inside beam The the which pipe barrel barrel. it is from The installed. patch supplyof tubes panels the also located full house outside system electronics of for isstallation the read-out 5.60 in tracker and m. the control. presence The Support length of structure the and beam-pipe supply and tubes its are supports. split Electrically vertically the to allow in- 2008 JINST 3 S08004 3.12). direction have a length of 2204 mm (figure z – 44 – − and z + z-direction connected to the stiffener rings (FR4) and the inner The electrical power lines, the electrical control signal and the opti- . Support frames on both ends, which connect the single segments, build Figure 3.12: Overview of a supply tube half shell. 14 F 6 C with C ◦ 10 − The supporting elements of the basic structure are the stainless steel tubes with a wall thick- Printed circuit boards mounted on the the flanges hold the connectors for the module cables ness of 0.1 mm runningand along outer the flanges made outThe gaps of in aluminium. between are filled Thenecessary with tubes rigidity. foamed supply material All with the power the detector and correspondingallows shape with slow a to control the clear guarantee leads layout cooling the are of fluid. the embeddedThe wiring in and motherboards, the also supply which makes tube the hold body. systeminstalled the more This in reliable. optical the hybrids eightresponding for read-out boards the slots at near analog the the and outerpower detector digital and ends on the control carry the bias links, the voltage integrated powertrol are for supply adapter board this boards. boards, (CCU sector. which Board) In The provideindividual is the cor- read-out the central installed. boards slot detector in the From each digital here oflike communication temperatures, the the and pressures eight digital and con- read-out control the sectors. humidity signalsslow Here are control are also brought adapter distributed together all board and slow to to connected control the the by36 signals cables. the single The dedicated fibres optical fibres for are the installed analog in read-out the cable and channels. the The eight fibres for the digital control of the detector a complete detector layer halffilled shell. with These foam flanges and consist covered of by carbon thin fibre fibreglass blades. frames (FR4) thatand are provide control signal fan-out and power distribution to the individual modulesPixel of detector a supply sector. tube. cal signals as well as the coolingtwo fluid supply are tube transferred across parts the of supply a tubes half to shell the in pixel barrel. The about 2008 JINST 3 S08004 2 m µ 3.13). 150 m equipped m pitch. The µ m . The High µ on the left). µ 3.13 on the right, the edges of the 80 pixels of size 100× m diameter. µ – 45 – m thick silicon nitride provide the support of the module. µ A module is composed of the following components (figure Density Interconnect, a flexible lowwith mass a 3 Token layer Bit PCBof Manager with a chip a module trace that and thickness controlsimpedance distributes of matched the signals 6 2 read-out and layer Kapton/copper power of compound tomodule cable the is the with ROCs, powered 21 chips. via traces forms 6 and copper the The 300 coated signals upper aluminium are wires layer of transferred 250 over an six half-shells are equipped with 16 half-modules each (96 in total, seeGeometry figure and components. One or two basestrips madeThe from front 250 end electronics consists of 8 toeach, 16 which read-out chips are with 52× bumpbonded to the sensor. The chips are thinned down to 180 modules will then be connectedadapters through are the mounted MUSR at connector the tosupply circumference the tube in optical is the ribbon first 2204 cable. part mm.the of supply These Only the tube. a supply flexible tube. mechanical The connection length is of made each betweenPixel the barrel barrel detector and modules The barrel part ofmajority the of the CMS modules pixel (672) are detector full consists modules as of seen about in figure 8003.13 detector modules. While the Figure 3.13: Exploded view (middle panel)picture of of a an barrel assembled pixel half detector module full (left module panel). (right panel) and 2008 JINST 3 S08004 3 η , weights 2.2 g plus up to 1.3 g 2 2 0 mm 1 3.14. 26. × 6 0 – 46 – Structure & Cooling Structure & Cabling Sensors & Chips −1 −2 −3 0

0.2 0.1

0.15 0.05 X/X0 0.175 0.125 0.075 0.025 3.15. The assembly requires three slightly different types of cooling channels. A completed full-module has the dimensions 66. The half-disk has 12 cooling channels (each in the shape of a “U”) assembled between a half Figure 3.14: Material budget ofplot the does pixel not barrel contain in contributionsfrom units the from of detector the end radiation pixel flange length to support versus the cylinder, rapidity. supply the tube. The supply tube and cabling Each channel is made by Al-brazing two blocks of Al with the channel for the cooling fluid already for cables, and consumesof 2 a W radiation of length power. inmaterial the The while central support material region. structure of and Sensors the coolingmaterial and fluid as pixel read-out a contribute barrel chips about function amounts of 50 contribute pseudorapidity percent. to one is third The 5 shown distribution of in percent of figure the 3.2.5 The forward pixel detector The FPix detector consists oftion two region. completely They separate are sections,rails. located one inside Each on the section each BPix is sidebeam-pipe supply split of tube vertically and the down but its interac- the are vertical middle mountedjor support so on maintenance wire the separate periods and detector without insertion can so disturbinghalf-cylinder. be the it installed beam-pipe. can around Each also the of be these removed four for sections servicing is called during a ma- Mechanics of a half-cylinder Each half-cylinder consists of a carbonat fiber 34.5 shell cm with from two the half-disksthat IP extend located and from at the 6 its other cm front at to end, 46.5 15 one cm. cm in The radius half-disks from supportring the the shown beam. in actual figure pixel detectors 2008 JINST 3 S08004 attached panels 2°C. The tempera- ≈ 0.02 mbar. Six daisy- ± is 0.49 2 mbar-litre/s. The pressure drop of the 20°C with a rate of 12cc-s the pressure 8 − − at 10 14 F 6 – 47 – 15°C. A single cooling channel with panels mounted on both blade. There are 24 panels, forming 12 blades, in each half-disk. 13 mbar. For C − cooling loop. The pressure drop over a loop (for a flow rate of 0. ± 96 at about is 0. 14 F 2 6 Each of the twelve cooling channels of a half-disk has trapezoidal beryllium Powering up the electronics on one blade increases the temperature by After installing the half-disks in the half-cylinder, the disk position is measured relative to All channels passed a Helium leak test at 1.33× drop is 294 mbar. to each side. The panelsdetectors. support As the explained sensors and above,to read-out the enhance chips cooling charge-sharing. that channels constitute The are thestrong, panels rotated actual stable are to and particle made form relatively of low-mass a support 0.5mmare turbine-like for beryllium. supplied geometry the with actual The C pixel beryllium detectors.sides provides The forms a a cooling subassembly channels called a chained cooling channels form a 1230 sccm) of dry N ture of each ROC is part of thetemperature information detection available sensor. for each The event. pixel Each sensors panelsuring have also machine fiducial has (CMM). marks a Their resistance visible position with is aunits. then coordinate related mea- to reference marks mounted on the half-disk the half-cylinder using a CMMof the and sensors also to by the photogrammetry. CMS detector. This The permits detector relating is the surveyed at position room temperature but operated at Figure 3.15: The FPixturbine-like half-disk geometry cooling is channels apparent. mounted Panels are in mounted the on outer both sides half-ring of structure. the coolingmachined The channels. in the two parts.the The channels are brazed 0.5 parts mm are thick. then The machined average to weight of their the final channels shape. is 8.21 The g. walls of individual cooling channels for a flow of 2600 sccm of dry N 2008 JINST 3 S08004 m. This result has been µ – 48 – 20°C has been measured to be 150 − 3.16. 10°C. The deformation (magnitude and direction) of the panels on a half-disk, when its − The service half-cylinder also contains all the mechanical and electrical infrastructure needed At the end of each service half-cylinder there is an annular aluminium flange that contains reproduced by a finite elementof analysis the of pixels. the We half-disk anticipatealignment and knowing with it the tracks. will pixel be geometry used to a in few the tens final of alignment micronsto before support, the position, final cool, power,tronics control for and providing read bias voltage out to the thethe detector. sensors, read-out power In to chip the particular, via read-out it optical chips, containssignals fibers signals elec- (address for linking and controlling it energy to deposition) the offhalf-cylinder control the also detector room, provides to and the the laser path data drivers for acquisition forsensors cooling system. fluid and sending The necessary read-out the service to chips. remove the heat generated by the holes to pass the power cables,out cooling from tubes, control intermediate and patch monitoringoperation panels cables, of and to the fiber the optic detector read- FPixhalf-cylinder are is detector. mounted shown in on figure The the electronics inner cards surface needed of for the the half-cylinder. A picture of a Figure 3.16: Overview of the Forwardproduction Pixel half-cylinder half-cylinder. facing A the photograph interaction of region the(see (IR). portion below), The of and aluminium the flange, the first the CCU filterThe board boards carbon are fiber not shown. cover at Theinsertion the half-cylinder of end the is beam away mounted pipe from in suspension the aleft wires end survey IR that of fixture. run protects the through the picture. a downstream slot components in during the half-cylinder towards the about temperature changes from 20°C to 2008 JINST 3 S08004 5 35 mm. × 4, and 1× 5, where the first 3, 2× 5, 2× 2, 2× 4, 1× plaquette. A plaquette consists 3.17. A total of 672 plaquettes are 3, 2× 5, has dimensions of 16 mm 2, 2× panels without leaving cracks, five different – 49 – . 3 pie-shaped − m and then diced. Finally, each of the 5 different types of sensors are 5 type plaquettes with a total of 24 ROCs. The sensors are offset on µ hybridization, of the pixel sensors and the pixel unit cells of the ROC is 4 and 2× m thick silicon substrate, whose trace geometry and characteristics (impedance, µ 3,× 2 In order to cover the trapezoidal or The joining, or After delivery from the vendor, the bump-bonded pixel detector module is then installed on Figure 3.17: Sketches of the twothe types plaquettes on of each FPix (left panels side). showing the A different photograph sizes of and an actual numbers 3-plaquette of Forward panel pixel (right detection side). elements - the plaquettes The basic unit of construction for the forward pixel detector is the of a single pixel sensorwire-bonded bump-bonded to to a an very-high-density-interconnect appropriateconnections. (VHDI) number that of provides Read-Out power, Chips control, (ROCs) and and data digit refers to the number ofare attached rows to and a the given second sensor. toThe The the largest panels number plaquette, on the of the 2× columns side of of read-out the chips cooling that channel closest to the IP contain 1× sizes of plaquettes are needed. These are respectively 1× plaquettes or a total of 21IP ROCs. contain 2× The panels on the side of the cooling channels farthest from the the upstream and downstream panelsread-out so periphery. that The two there types are of no panels are cracks shown in in the figure coverage due to the ROC achieved by fine-pitch bumpingdone using on Pb/Sn the 8” solder ROC and wafersby and then backside the grinding flip-chip 4” to mating. sensor 150 wafers. After The bumping, bumping the ROC is wafers are thinned needed. mated to the appropriate numbera of ROCs. module. The For sensor FPix, withmissing the its bumps hybridization ROCs is bump-bonded was at to the done it level in of is industry. a called few The 10 fraction ofa broken, Very High bridged, Density or Interconnect (VHDI).inated The to VHDI a is 300 a two-layerlow intrinsic flexible capacitance, printed and circuit, low lam- cross-talk)ing have digital been control optimized and for analog the output intended signals use to of and convey- from the sensors and ROCs. 2008 JINST 3 S08004 15°C. These cycles − – 50 – forces expected to occur during actual CMS operation. The B ~ × dl ~ I 15°C, include the functionality of the ROC, the integrity of the bump-bond, and − where they undergo 10 temperature cycles between 20°C and The data on each B-grade plaquette are examined carefully. In many cases, the plaquettes The hybridized pixel module is attached and wire bonded to a populated VHDI to become a Once plaquettes are mechanically joined, they are clamped in cassettes that accommodate The completed plaquettes are subjected to a quick plug-in test. Then they are loaded into a The VHDI is made as follows. A bulk 6” silicon wafer is laminated to a flexible sheet con- The effects of thermal cycling and radiation on the assembled plaquettes have been exten- • A - the plaquette is available for• immediate mounting B on - a potential panel; issues have been found• during testing C and - need the further plaquettes analysis; are unsuitable for mounting. m. The adhesive bond between plaquette components is made in a vacuum at 60°C, to soften µ can take up toplaquettes 2 are days monitored to for complete,After electrical depending the operation. upon burn-in the process We is thermalto have completed, load. ensure seen the their no plaquettes During suitability failures are thesetemperature for during subjected of cycles, their the to the a eventual cycling. series mountingthe of on I-V electrical a characteristics tests of panel. theof sensor. These each pixel Other tests, on tests at the measure entire thethe the plaquette ROC operating thresholds assembly, capability. and and We the have noise found individual characteristics remain pixel that valid thresholds the even are pixel after trim trimmed subsequent values via from stepsis the of loaded plaquette the into test assembly the on process. Pixel each Constructioncategories pixel After of Database testing grades: and the the plaquette plaquettes data are graded. We have three main are found to have missed being classified as A-grade due to very minor deficiencies (e.g. slightly taining several VHDI circuits.techniques. Passive components The are wafer of also populated attachedsaw. circuits using The is circuits surface-mount then are solder diced then electrically into tested. individual circuits using a diamond plaquette. The joining is madeof using components parallel is plate fixtures inspected alignedfine using on adjustments a linear on coordinate rails. the measuring The machine. fixtures alignment resulting A in flexible alignments plate between is joined used components for within 100 sively tested. The tests demonstrate thatdue the to adhesive temperature and changes, the and application provide method reliable mitigate strength warping and thermal conductivity. all processing steps such as wirebondingand which the provides electrical VHDI. connections After betweennecessary the wirebonding ROCs due we to encapsulate periodic theencapsulant feet acts of as wirebonds. aharden damping This the force encapsulation wire on is and theat cause wire, eventual room preventing breakage temperature. large [30]. resonantcharacteristics During oscillations Finally of this to the the test work sensor, plaquettes the the undergoassembly read-out quality quick and chip, of testing testing the rate the number is plaquettes of optimized for bad is a pixels evaluated rate and of in missing six terms bonds.Burn-In plaquettes of per Box The day. the the adhesive and prevent air entrapment.which An is air limited cylinder by applies the and compression allowed controls on the the mating bump-bonds. pressure, 2008 JINST 3 S08004 3.18. The – 51 – Figure 3.18: Sketch of a plaquette mounted on a panel showing its several layers. The process by which a panel is assembled is as follows. A single HDI circuit is laminated to There are four types of panels, a right and left 3-plaquette version, and a right and left 4- A panel is built up out of several layers of components. These are shown in figure too many noisy pixels) whichThese are will “promoted” not to be A-gradeon significant and an when declared original grade an usable of on entire A panels.according panel’s or to a quality Current plaquette promotion is plaquette size. to yields, A-grade assessed. from based B, are in the 80% range,Panel varying assembly slightly A panel is formedterconnect from (HDI) three laminated or to four awhose plaquettes beryllium trace plate. attached geometry and to The characteristics HDI an (impedance,intended is assembly low use a cross-talk) of of three-layer have transferring a been flexible digital optimized High printed control for and circuit Density the analog In- output signals. a trapezoidal-shaped 0.5 mm thick beryllium plate.mount Passive solder components techniques. are attached The using Token surface- using Bit a Manager die (TBM) attach is method attached and wire-bonding.the to After the individual functional corner plaquettes and tab burn-in are of tests attachedwire-bonds with the for only HDI to the electrical the TBM, connection. HDI using adhesive for mechanical attachmentplaquette and version. The rightpanel and centerline. left Both handed types versionsplane. are have The required their reason so TBMs for that on the noside “3” opposite panel of and sides a part “4” of blade, projects type and the panels pastother. the is a gaps that line between they in plaquettes are the on eventually mounted vertical one on type opposite are covered bytotal the number active of area panels of in the all eight half-disks is 192. Final detector assembly validation The panels are attached onto thepanels front are and mounted back on of the theon side half-disk the closest cooling opposite channels. to side. the The The interaction 4-plaquette half-disktested. region assembly is (IR), mounted and onto the the 3-plaquette half-service versions cylinder and is again 2008 JINST 3 S08004 port, card by a light- adapter. board Each adapter – 52 – at the end of each panel that plugs into connectors on the fingers of the adapter board. To control and monitor the various ancillary chips and optohybrids, there isThe a port CCU card board contains for the Analog Optohybrid (AOH). Each of the 6 laser diodes of the AOH The control of the ROCs is achieved through the Pixel Front End Controller. Optical signals Monitoring points for temperature are distributed throughout the service cylinder. There are The adapter board has three types of ASICs mounted on it. These are used to passThe the clock, adapter board is connected to another printed circuit board, the weight extension cable. These cablesto are the of ROCs two and types, TBMs, adata power and and cable the control which signals HV distributes to bias the theboard. to panel power the from It the sensors. houses port the card. The electronics(the The other needed port pFEC cable to card and is is interface pxFED) a to the and low-mass transmit front-endthe power printed the supplies chips clock circuit located pixel with signal, in the L1 the VME trigger countingpower and electronics and room. slow bias control The voltages signals port to to the cardas chips the transmits and the front sensors. temperature end It on electronics. also some It monitorsto panels. the distributes the currents the These CMS and functions tracker. voltages are These as ASICs well donetrigger include and by timing the various signal, DCU ASICs the for that gatekeeper monitoring, for are the keeping common TPLL the optical for up regenerating and the downeach links half open service as cylinder, needed. as described above. chip receives data from oneend panel Driver via (FED). its TBM and sends it over its ownare optical sent fiber to from the it Front toadapter board, the then Digital to Optohybrids the TBM on on the the port panel, through card, the through HDIPower and the and the monitoring extension VHDI cables to to the ROCs. the Power connections are made from CAENthe power end supplies of via the half-cylinder cables away thatit from run is the through sent IR along the into wires flange a to at in set the the of port case power/filter card, of boards. in the From the sensor these case bias boards, of voltage. low voltages, and directlyalso to humidity the sensors. adapter board Additional temperaturevoltage and sensors detector are monitoring mounted are on connected the to the panels. DCS High system described and below. low Testing Testing is a key element ofis quality difficult assurance and in error the prone. assembly process. At every While step, rework we is confirm possible, it that we are using only “known good parts”. Electronics chain Each HDI is connected to another flexible printed circuit board, the board serves three blades (or 6receive panels). signals from One the important panels, purpose which of areto mounted the and perpendicular adapter from to board the the is axis electronics to of mountedpigtail the send on service and the cylinder inner surface of the service cylinder. This istrigger done by and a control data signalspFEC. to each panel and return the received control signals back to the 2008 JINST 3 S08004 100 m) to master converters of each DC to 48 V AC – 53 – s) is subject to fine tuning to comply with capacitive load, cable impedance and length µ at 5 MHz. Every card is controlled by an optically decoupled microprocessor for setting and The crates house two types of electronic cards, one of 4 channels of 2.5 V/7 A (A4602) The DC levels are regulated over sense lines. The reaction time of the sensing circuit (typi- Final testing is performed using the real data-acquisition and control hardware and prototype The core of this system, accessed through LAN, is located in the detector control room Ω 600 V/20 mA) for ROC and sensor biasing respectively. Each of these channels contains float- the branch controllers. They are fed2 by kW local (A3486H) 3-phase also 230 suited V for operation at hostile environments. feeding the service electronics ondeliver the 2 supply complex tubes channels (auxiliary of(− power), each while 2 the low other (1.75ing V/7 (A4603H) A pulse-width-modulated DC/DC and switching 2.5 V/15 transformers A)1.75 with and and a 2.5 2 V common lines. high ground The voltage100 return isolation lines for resistance the (ground return versusmeasuring earth voltages, on currents, the ramp racks) times, is trip typically parameters, interlocks and others. cally 200 (typically 50 m). Theallow line for drop a in maximum the of 6 cables V.power, Fourteen amounts feed A4602 to cards, the roughly yielding 32 2 40 V, slots independentgroups while channels of of the of the each regulators auxiliary 12 barrel would port service cardsHV tubes of channels with the (56 forward each A4603H half 2 cards) disks.half DOHs feed The size the and modules) main 64 6 of supplies barrel each of AOHs 12 groups 112 asblades. detector (192 complex well Each modules, LV ROCs, as and and of this 48 these 4 contains forward groups groups groupsthe draws with (135 a digital ROCs) typical (2.5 of V) current each line of 3 respectively. 4.6with disk A The conditions on large during the current bootstrapping analogue reserve where (1.75 of the V) and ROCs the remain 9 supplies A briefly is on in needed an to undefined comply state. It was Testing must keep up withof the driving a assembly plaquette step, requires plaquettedeveloped hundreds production. special read-out of Full hardware characterization thousands andand of software efficiently. that A measurements. software can using carry a USB-based To out datais accomplish these acquisition needed scheme to measurements this, is develop quickly measurement employed programs when we of flexibility modest have procedure. complexity and For duration, the such most as extensive the measurements, burn-in we including use plaquette a testing PCI-based and system characterization, and a software program called Renaissancedata-acquisition [31]. software and constitutes anlishes an end-to-end initial system set of test. parameters for Detailed the testing many DACs also and estab- thresholds3.2.6 in the system. Power supply All needed high and lowof DC the voltages type are CAEN-EASY4000 generated .for by which the This means main system of regulating a is cardshard- (A4601H) commercial also and were firmware modular employed custom were by system designed necessary the [32]. for adaptation CMS Only to small silicon the changes strip pixel in project. tracker (USC55) and consists of one mainThe controller actual (SY1527) power containing supply 3 cards branch are controllersthanks placed (A1676A). in to two their racks radiation of tolerance 5reduce and crates power in magnetic loss close field in proximity resistance. the to cables. the This detector The has power been supply chosen crates are in connected order by to flat cables (≈ 2008 JINST 3 S08004 W from the µ ). 2 z, or vice versa. − 66 million pixels this ≈ for the sense wires. 2 and exits at z 10°C. As for the strip detectors, + − on the HV outputs which can easily W, including about 13 pp µ shielded copper cable was chosen for the . For the total of 2 2 /cm 14 4 mm 10 respectively. The 4 m connection between PP1 and – 54 – Ω on the LV and 50 mV pp is used. To keep the temperature increase of the coolant below 14 F 6 and 4 twisted pair copper lines with 0.1 mm 2 H/m, 0.13 nF/m and 24 µ 0.75 mm s) for over-voltage. side. One barrel loop feeds in parallel 9 thin-walled aluminium pipes, each cooling µ z The pixel system is cooled by a total of 18 cooling loops: 10 for the barrel and 4 for each of Noise levels are typically 5 mV Inductance, capacitance and characteristic impedance between two of the main lines were sensor leakage current at finaladds up fluences to of 3.6 kW. 6× The power load50 on W/m. the aluminium The cooling tubes sensor is temperature thereforeliquid expected will phase to be be cooling about maintained with at C around 2°C, a total flow rate of 1 litre/s is required. the two end disk systems.The coolant For for the the barrel, two thefrom disk the coolant sets same enters on at each side of the interaction region is supplied and reclaimed 8 modules in series. Onequarter disk disks loop the cools 6 in blade parallelturbulent. one loops The quarter are total of connected lengths each serially.rack of of amount the the to The 2 cooling about coolant disks; 80 loops flow inside m, starting resulting at the from in the and pressure pixel drops returning of modules to below is 3.2.8 the 2 bar. pixel cooling Slow controls The safe operation of thecontrols barrel system and (DCS). forward Its pixel detectors tasks is are guaranteed to by monitor the temperatures CMS and Pixel humidities slow at different locations verified that the regulators undergo acurrent regime smooth if transition the from programmed the current limitsactions constant-voltage are (1 to s) approached. the fast Beside constant- over-current microprocessor security controlled crowbars is (100 guaranteed by various solid state fuses (10 ms) as well as be accepted thanks to the LV regulatorsrespectively. in the Of ROCs and major the intrinsically concernsumption small in sensor (2.5 V capacitances the line) overall in design casea were of typical low fast current ROC drops drop activity in likeorder of in of the 2 A some orbit digital Volts gaps. per depending current group on Duecircuit con- local generates to was buffer therefore the over-voltage capacitors. checked cable spikes by The inductance at a integritycurrent full the of simulation loads. the module in cable-module-ROC SPICE This level together served in withor for the measurements the HV on pulsed designs distribution. of (In theare cables one commonly and sector fed the layer-1 by electronic modules40 the layout, m are e.g. other.) from fed grounding the by Finally power one supply acurrent line cards directions 6× to while between the adjacent layer-2,3 patch lines. modules commonly panel Two shielded (PP1) twisted lines pair located for lines in HV for the are the HCAL contained senses in with and the alternating a same cable bunch complex of (0.1 10 mm PP0 (tracker bulkhead) uses Al conductorsand in contains the 26× cable. The auxiliary power cable is also shielded 3.2.7 Cooling The power consumption per pixel amounts to around 55 measured to be 6 2008 JINST 3 S08004 m µ 20) ± 320 ( cm. TOB and the outer m thickness, with substrate µ type silicon micro-strip sen- 25kΩ 3. 20) − 3.3.7) feature a 10 mm hole in the ± 3.1), thin sensors of crystal orientation. This crystal ori- 55 p-on-n 1. 500 ( = 100i h ρ orientation because measurements [38] have wafers due to irradiation is much smaller and 111i h 100i – 55 – h m. µ (Pt1000 RTD) have been chosen. The measurement of humidity is cm. Due to the single sided processing, these sensors show a significant doped float zone silicon with n 8kΩ implantation on the back side of the wafers, covered by aluminium, forms an − 9) of the main CMS DCS. + 4 n = ρ 37]. They have been manufactured on 6 inch wafers in a standard planar process, leading A uniform The monitoring of temperatures and humidities is based on a commercial Siemens S7–300 An additional 96 Pt1000 temperature sensors are read out via the data-acquisition (DAQ) The Barrel and Forward Pixel slow controls system is integrated into the PVSS graphical user In TIB/TID and on the inner 4 rings of the TECs (figure resistivity of bow, which is required to be less than 100 ohmic contact which is connectedpenetrated to by positive the voltage beams up of to the about laser 500 alignment V. Those system sensors (section which are wafer thickness are used, with3 substrate rings resistivity of of the TECs are equipped with thicker sensors of of the detector and to monitoron-detector and electronics. control the high and low voltages necessary for operation ofmodular the mini Programmable Logic Controlleritors (PLC) a system. total The of Siemens 192endcap S7–300 disks. temperature system For mon- and the 8 temperature humidity sensors,a platinum sensors nominal resistance installed resistance temperature in of detection 1 the sensorsbased with kΩ Pixel on barrel detecting and the forward waternected to vapor a induced Wheatstone shear Bridge piezoresistor stresssignal circuit in that [33]. is a This linearly circuit small proportional provides to polymer aRH relative small element humidity and (mV) that (RH) output is between is amplified the con- by fulltracker. the range of same 0% The kind to of PLC 100% conditioninglanguage of electronics [34] the that to is Siemens convert used S7–300 thecalibrated by currents system the physical and silicon is units voltages strip programmed (i.e. ofFor degrees in the the Celsius the temperature purpose for and Statement of temperatures humidity Listfails, avoiding sensors and routines (STL) damage are into percentages to programmed for within the the humidities). cooling) detector PLC in to in that interlock case. case the CAEN the power cooling supplies (shut-off system the (dry airsystem, supply) together with the temperaturepixel read-out dependent chips. voltage The sources temperatures recorded integrated bysystem into the by DAQ means each system of are one passed a of to dedicated the software the slow interface controls [35]. interface (chapter 3.3 Silicon strip tracker 3.3.1 Silicon sensors The sensor elements in the strip tracker are single sided consequently irradiation causes less inter-strip capacitance increase on this material. sors [36, to significant cost reduction perThe unit base area material when is comparedentation was to preferred the over more the traditional moreshown common 4 that the inch built-up wafers. of surface charge on 2008 JINST 3 S08004 type bulk. n 2 pF/cm across all implant. It gradually + p implant width over strip pitch is implantation into the + + p p in the inner and outer barrel, respectively. 2 implant. Each strip implant is connected via a + 9cm p bias ring which encloses the strip region and also × + – 56 – p implant at the cut edge of the sensor and the bias ring, + and 10 junction moves from the strip side of the wafer to the rear value was chosen in order to minimize the strip capacitance n 2 p pn w/ 12cm × m on each side of the strip which pushes the high field region into the µ 3.19): two rectangular sensor types each for TIB and TOB, and 11 wedge- polysilicon bias resistor to a type. At this point, the MΩ p 25, leading to a uniform total strip capacitance per unit length of about 1. 5) 0. , with about 9.3 million of strips [36]. 0. 3.20. This analogue read-out scheme was chosen for several reasons: optimal spatial reso- 2 For all sensors in the CMS strip tracker the ratio of In order to equip all regions in the CMS tracker, 15 different sensor geometries are On the front side, strip shaped diodes are formed by = ± p 5 1. defines the active area of the sensor. w/ side contact. Each implantedinsulated strip by is means of covered a by silicon oxide ancoupling and aluminium nitride of multilayer. the strip This signals from integrated from capacitor which allows thehigh for it strips AC leakage is to currents the electrically after read-out irradiation. electronics, Eachused which metal to is strip make thus has a protected two wire from bond bond the to pads connection on make to each the a end, read-out which wire chippurposes are and bond there in is connection case also of between a the DC the daisy pad two chained connected to sensors sensors the in one detector module. For testing shaped sensor types for TECmodularity and of TID. 256 channels They (two have 128-channel either front-endSince chips 512 multiplexed the or to sensors one 768 read-out are strips, channel). fabricated reflectingsions on the are 6 read-out for inch instance wafers, about they 6 can be made rather large. Typical dimen- 3.3.2 Read-out system The signals from the siliconcuit, sensors the are APV25 amplified, [39]. shaped, Upon andnels a stored are positive by first multiplexed a level custom and trigger integrated transmittedservice decision cir- cavern the via where analogue optical the signals fibers of analoguethe all to to chan- digital full Front conversion analogue End takes information Driver place. tomode (FED) This a subtraction boards read-out as place in scheme well where brings the as itby data can sparsification. optical be links Clock, used as trigger, for well. andfigure accurate control A signals pedestal schematic are and view transmitted of common the silicon strip tracker read-out scheme is given in Due to the radiation damage tochange the crystal to lattice, the bulk material will undergo type inversion and ( sensor geometries [38]. The actual while still maintaining a gooda high metal voltage overhang behaviour of of 4 the tosilicon sensor. 8 oxide The where aluminium the breakdown strips voltage feature isFor much higher, the leading same to reason, stable high the voltagedegrades bias operation. the ring electric is surrounded field by betweenwhich a the are floating guard at ring backplane potentiallayout (high of a voltage) corner and of ground, the active respectively. region Figure of a 3.19 sensor. showsneeded the [36] (figure The total number of silicon198m sensors in the strip tracker is 24 244, making up a total active area of back side metalization, as wellup as to anti-reflective four coating sensors in with a order sufficient to signal achieve on transmission a through fifth sensor. 2008 JINST 3 S08004 – 57 – Bias DC pads AC pads resistors e 3.20: Read-out scheme of the CMS tracker. Figur Bias ring Guard ring e 3.19: Left panel: drawing of one corner of the active region of a wedge-shaped silicon lution from charge sharing, operationalof robustness the full and analogue ease signal, of robustnesshard monitoring against electronics possible due common and to mode reduced the noise, material availability lessneeds budget custom are radiation as shifted out the of analogue the to tracker volume. digital conversion and its power Figur strip sensor for the trackertracker. endcaps. In the Right outer panel: layersThe the silicon Inner sensors Barrel sensor are and geometries paired Outer to utilized Barrelsensors form sensors in utilized exist a for the in single the CMS two first module, types, inner as ofrespectively. ring shown same (Only exist in area in the the and two TEC different different figure. version versions, pitch. is one The shown.) for TID and one for TEC, 2008 JINST 3 S08004 . det C in peak mode and det C · s and to buffer it. A subsequent 38e/pF µ + 270e = peak m bulk CMOS process. Compared to processes µ – 58 – ENC 25 in deconvolution mode, both measured at room temperature [39]. det C · 61e/pF + 430e . Therefore, the noise at operating temperature is about 10% lower. = T √ ∼ More than 100 APV25 chips from all production lots have been irradiatedThe with APV25 X-rays is to fabricated on 8 inch wafers with 360 chips per wafer. MoreAnother than custom 600 ASIC, wafers the APVMUX, is used to multiplex the data streams from two APV25 The APV25 needs supply voltages of 1.25 V and 2.5 V with a typical current consumption deconv 10 Mrad ionizing dose, in excessdegradation of in the pulse expectation shape for or 10 noise years level of has been LHC observed. operation. Nocorresponding significant to 216 000 chips havelems been were manufactured solved, and an probe-tested. average After yield initial of yield 88% prob- was achieved. chips onto one optical channelwhich by interleaving is the then two 20 sentmultiplexers. MS/s to streams into a one laser 40 driver MS/s stream, of the optical links. One APVMUX chip contains 4 such The equivalent noise charge is found to be Front-end ASICs The APV25 has been designed in an IBM 0. with bigger feature sizes, the thinaffected gate by oxide radiation induced inherent charge-up to and this thereby, deepensures in conjunction sub-micron radiation with process tolerance special is]. [40 design much techniques, The less noise APV25 and has 128 power read-out charge channels,deep sensitive each analogue consisting pre-amplifier, pipeline of a which a samples 50ns low pipeline the is CR-RC shaped used signals type to at shaper store thestage the and LHC can data frequency either a for of pass 192 a the 40MHz. signal trigger element a as This latency weighted sampled of at sum up the of to maximum three of 4 (deconvolution consecutive the mode). samples 50ns The which latter pulse effectively is (peak reduces needed mode)correct at or the LHC form high shaping luminosity bunch time in crossing. to order 25ns tosignal The confine up pulse the to signals shape a to charge depends the corresponding linearlyto to (linearity 25 5 minimum better 000 ionizing than electrons particles 5%) in (MIPs,analogue data one on this from MIP the case), all is 128 with equivalent channels of aoutput the gradual at appropriate a time fall rate slice off in of the 20 beyond. pipeline MS/stogether are (mega-samples When multiplexed per with and second) a a as trigger a digital differential is header. bi-directionalwhich current received, the signal, Due channels the are to output the is non-consecutive treeactual and data structure therefore re-ordering processing. of is the necessary An prior analogue internalamplitude to multiplexer and calibration the delay the circuit into order allows the in to amplifier inject inputs charge in order with to programmable beof able about to 65 monitor the mA pulse and shape. 90300 mA mW respectively, leading for to a one totaldominated APV25 power by or consumption the of 2.3 typically front mW around the end per total MOSFET noise channel. transistor for an in The APV25 the channel noise APV25. depends of linearly the Measurements on the analogue haveENC connected shown read-out detector that chain capacitance is Mainly due to the MOSFETENC characteristics, the noise reduces with temperature approximately as 2008 JINST 3 S08004 10mm) and a low bending radius (8cm). For the – 59 – analogue data link up toOpto-Hybrid three (AOH), one transmitters of are which connected sitsthe to close APVMUX a are to transmitted laser each differentially detector driver over module. awhich ASIC distance modulates on The of the electrical an a laser signals few Analogue diode centimeters from currentthe to accordingly the diode. laser and driver, provides For a the programmable bi-directionalmounted bias on digital current a optical to Digital link Opto-Hybrid aand (DOH), set vice converting of versa. the two optical receivers signals and to two electrical transmitters LVDS is [42] Front End Drivers The strip tracker Front End Driver (FED)fibres, is each a 9U corresponding VME to module 2 whichin APV25 receives data or parallel. from 256 96 optical The detector channels opticaldigitized [45]. signals by All are a 96 converted 40MHz, fibres to are 10independently electrical processed bit in levels ADC. 1 by The ns opto-receivers steps. ADC [43]tions sampling After and are point auto-synchronization then applied for to and each the the fibrefor APV common can each data trigger be mode stream, and programmed subtracted. pedestal each correc- APVsequence The separately. of common detector The mode channels samples correction which are is isvalues then essential for calculated re-ordered each for to detector the restore channel following the and step physical digital thresholds of functionality for cluster cluster of finding. finding the are Pedestal FED stored issiderable in implemented look flexibility. in up FPGAs In tables. and zero The can suppressionoutput therefore mode, of be the adjusted which FED with is is con- the afor standard list each for of strip clusters normal in with data the address cluster, taking,for information thus the track and passing signal reconstruction to height the and (8-bit central3.4 resolution) physics DAQ GB/s, only analysis. at those LHC objects In which designOther are this luminosity, modes relevant is way are, reduced however, an available to which input roughly suppresstherefore one data 50 transmit or MB/s additional rate more data per steps per to percent in FED theanalysis. the strip central processing of There occupancy. DAQ chain are about to and a be total used of mainly 450 for FEDs debugging in and the system final system. Optical links Analogue optical links are used toover transmit a the distance data of streams about frombelow) 100 are the transmitted m tracker by to at digital the optical 40 service linksan MS/s. running cavern electrical at distribution Likewise, 40 scheme the Mb/s mainly [41]. since digital they Opticalare timing have links immune minimal and are impact to superior control on electrical to the interference. signals material The (see budgetwell transmitters and InGaAsP are commercially edge-emitting available devices, multi-quantum- selectedproven reliability. for Epitaxially their grown planar good InGaAs linearity, photo-diodesfiber are low itself used threshold as is receivers. current a The and standard, optical are single-mode, grouped non in dispersion shifted ribbons telecommunicationribbon of fiber. cable, 12 which The fibers features fibers a which small in diameter (< turn are packaged in a stack of 8 inside a 96-way 2008 JINST 3 S08004 3.21). m for via µ C protocol [48] is used to send 2 – 60 – ) carrier plate using double sided acrylic adhesive. A poly- 3 O 2 Detector Control Unit (DCU) ASICs [49] on the detector modules are used to monitor the control signals to the APV chips16 as units well so as that to the one other FECchips ancillary ring decode chips. typically the controls One trigger CCU a can set signals control oflocal and up several electronics. provide to tens a of very detector low modules. jitter, The phase PLL adjustable clock signallow to voltages the on the hybrid,sensors, the silicon the sensor hybrid leakage and current, theThe and DCU DCUs the itself. are temperatures For read of this out theavailable purpose, through silicon when each the the DCU control control rings contains rings and eight and the 12 digital detector bit links modules ADCs. so are powered. that theseHybrids readings are only The front-end read-out electronicscalled for hybrid a [50]. detector Due module toare the is needed different mounted in detector onto the modulewhich a geometries CMS are 12 multi silicon mounted different as chip strip types bare module tracker. of dies,are hybrids and packaged Each one components. APVMUX hybrid chip, The carries onevoltages main PLL 4 to features chip the or chips, and of to one 6 the route DCU clock, APV25 hybridfrom chip control the are read-out which and chips data to chips into lines distribute the between cooling the and system. chipshybrid filter and No substrate to the high is remove voltage supply fabricated the is heat as present a onIt the four is CMS layer tracker laminated polyimide hybrids. onto copper The multilayer aimide flex ceramic cable circuit (Al is (figure integrated into the layoutdiameter of and the line hybrid. width. The Large minimal metalized featurederlying sizes through ceramic are holes plate, 120 under from the where chips itsystem. transfer is the removed Three heat through to different the the flex frame un- circuit ofdifferent geometries the types of module (one the into each ceramic the plates, for cooling APV25 different TIB/TID, connector chips TOB orientations (4 and and or different TEC) 6) number make combined of up with the total of 12 differentPower hybrid supplies flavours. Silicon strip modules areservices. grouped into Each 1944 group detector is power supplied groups by in a order power to supply share unit the (PSU) power [32], featuring two low-voltage Control and monitoring Clock, trigger and controlcards [44]. data are These transmittedtracker are in to VME order modules, the to located reduce trackerTiming in trigger Trigger by and latency. the Command Front (TTC) service They system End receive cavern, andital clock distribute as Controller those optical and as close links (FEC) trigger well and as as signals control the possible fromthe signals digital tracker via the to volume. dig- opto-hybrids global the Several to Communication LVDS and token Controlring. Units ring These (CCU) networks] [46 are participate (control custom in rings) ASICs oneis inside token which mounted interface on the a ring network Communicationdetector to and modules. the Control A front-end combined Unit chips. clock Module andchips One (CCUM) trigger CCU [47] signal and on is is each distributed dedicated to detector Phase to module Locked a while Loop set (PLL) the of industry standard I 2008 JINST 3 S08004 50-m-long ≈ 3.3.8). The average power consumption of – 61 – Figure 3.21: Front-endlayers. hybrid layout (example for TEC shown on the left) andregulators, arrangement respectively of 1.25 V (uplators to (0-600 6 V, up A) to andearth). 12 2.5 The V mA). two (up All low-voltage tonique regulators channels to 13 are compensate, share A), up “floating” the to and (return same 4are two V, line return the fanned high-voltage voltage isolated line out regu- drop from and along at the the use thelines. cables. PSU the local The exit sensing two Two into high-voltage wire PSU regulators 8 tech- are984 lines; combined A4601H each boards into silicon are one strip needed to sensor powercrates, power is supply disposed the connected detector on module groups; to 29 (PSM, they one racks, are A4601H“hostile” of around located model). radiation these 10 on and 129 m In EASY magnetic away 4000 total from field the environment, beam powering crossing the region, detector and through operate in a low impedance cables [32]. Thevided 356 by control a rings different requiremodule), set a fully separate of integrated power 110 in at control the 2.5 sameBoth power V. A4601H system This supply and of is modules A4602 the pro- units A4601H (A4602, require unitsregulators, four two the and distinct other 2.5 located 48V (48Vs) on V power for the sources, the channels same one serviceers, per electronics. source crates. CAENs (48Vp) They A3486 for are (“MAO”), both the disposed providedboards by on AC-DC (A4601H the convert- mixed same to racks. A4602)bus Each and lines. EASY provides The 48Vp 4000 first and crate slot 48Vs hosts inand rails, up reset the interlock lines to crate to and (slot 9 the general 0) control hosts reset and one safety systems interlock-card, (section which interfaces the interlock each silicon strip module with 6supplied (4) by APV25 A4601H and chips A4602 is boards about ison 2662 approximately power mW 68 cables. kW, (1845 of The mW). which power The nearly consumptionpower 50% total is is supply foreseen power dissipated to system increase is with dimensioned the tocorresponding aging cope to of with the a detector; up total the to consumption of 60% nearly increase 150 of kW. the low-voltage currents, 2008 JINST 3 S08004 m m µ µ (TEC, 40) 2 m) or two thick µ shows an exploded view and 3.22 m thick graphite (FE779 carbon). For the µ 5) m fabric, cyanate ester resin (CE3)) on a 800 µ – 62 – 125 × front-end hybrid pitch adapter (TOB module). In total 29 different module designs, 15 different sensor 2 silicon sensors near sensor m fabric, cyanate ester resin (CE3)) on a carbon fiber cross piece made of the same far sensor µ m thick carbon fiber frame that surrounds the silicon sensor on all sides is used . For m) silicon sensors from a total of 24 244 sensors. All modules are supported by a frame µ e 3.22: Left panel: exploded view of a module housing two sensors. Right panel: photograph Modules for the inner barrel, the inner disks and rings 1 to 4 in the endcaps are equipped with The module frame provides the stability, safety and heat removal capability needed in the µ 125 × frame (carbon fibre) ceramic cross piece (graphite) Kapton foil Figur of a TEC ring 6 module, mounted on a carrier plate. 3.3.3 Silicon modules Module design The silicon strip tracker is composedent of subsystems 15 148 (TIB, detector TID, modules TOB, distributed TEC).(500 among Each the module four carries differ- either one thinmade (320 of carbon fiber oris graphite, used depending to on insulate the the position siliconsensor from in back the the module plane, tracker. frame i.e. A and bias to Kapton voltageframe provide supply circuit carries the and layer electrical the temperature connection front-end probe to hybrid read-out. the anda In the photograph addition of pitch the a adapter. module TEC Figure module. one sensor, modules in the outer barrelof and two rings sensors, 5 their to corresponding 7 strips inthe are the geometry endcaps connected and have electrically number two via of sensors. wire sensors In the bonds.ring the active 1) Depending case area and on of 17202.4 a mm module varies between 6243.1 mm sensor support and carries the read-outin electronics. the electronics In and addition the it silicon hasone-sensor sensor(s) to modules into remove is the the U-shaped cooling heat and points. generated madetwo-sensor In of modules the (780± a endcaps similar the U-shaped frame support forthick structure the carbon is fiber obtained legs (K13D2U by CFC, gluingthick 5 two graphite (640± cross-piece (FE779 carbon) which holdsa the 550 front end electronics. Inthe the inner TOB, barrel U-shaped module frames5 are obtained by gluing two carbon fiber legs (K13D2U CFC, designs and twelve different hybridpurposes designs special are modules used are in prepared TIB,laser with ray TOB, etched to TID holes traverse and up in TEC. to the five For aluminium modules. alignment back plane to allow a material. 2008 JINST 3 S08004 m m µ µ m thick 3.23. µ m. It also allows µ m narrow lines are etched on a (1.0–1.5) µ m thick glass substrate (Schott D263 glass), cut to – 63 – µ m while all four provide thermal contact between the µ shared the responsibility for wire bonding all modules. The m depending on sensor type) to the APV pitch of 44 µ m–205 (bonding centers) µ m was used for all connections. µ For the TEC and TOB modules the line of bonding wires connecting the hybrid pitch adapter Thin wire wedge bonding is used in several places on the modules to make electrical con- The high voltage supply to the silicon back plane is provided by Kapton bias circuits running The pitch adapter between the front end hybrid and the silicon sensor adjusts the strip pitch Different types of aluminium inserts and precision bushings in the module frames are used Both graphite and carbon fiber fulfil the requirements of high stiffness, low mass, efficient bonding rate was approximately 1 Hz.of Bonding 25 wire (99% aluminium, 1% silicon) with a diameter to the silicon strips, anddamaged by in vibration the during case transport. of two As a sensor protection modules for the the strips TEC of modules the the two silicon sensors, is can glued be nections: APV chip to front-end hybrid,to APV sensor chip (in to pitch case adapter, oftotal pitch 15 two-sensor-modules), adapter to institutes bias sensor, voltage sensor connection to the sensor back plane. In thick aluminium layer deposited on a chromium base, resulting in less thanModule 25 assembly mΩ/. and testing Sensors and front end hybrids arenents glued are to aligned the by frames cameras by surveying high specialIn precision fiducial total gantry marks seven robots. institutes with shared a The the pattern compo- responsibility recognitionwas for algorithm. the about assembly 20 of modules all modules. per The(RMS) day assembly has per rate been gantry achieved robot. and A one example positioning from precision the of quality approximately control 10 can be seen in figure glass (Corning 1737F or G glass) is used. The 10 the correct dimensions, with a pattern of low resistivity aluminium strips. For TIB 300 placing the heat producingadapter front for end TOB electronics and farther TEC away consists from of the a 550 silicon sensors. A pitch module and the cooling pipes. Forand TOB four modules screws two ensure Cu-Be thermal springs contact. give the precision positioning along the legs of theconnection modules of between the the bias silicon voltage sensor toon the and the back the Kapton plane foil carbon is to fiber measure done the support via temperaturesensor wire frame. of and bonds. the the The silicon. Thermal back The probes plane glue are joint is placed between done the with temperature the silicone glueof RTV 3140. the sensor (80 heat removal from the sensors,need and to be radiation compensated hardness. by the glue Differencesare joint in used between the the in frames expansion and module coefficients thegood construction silicon. thermal Several which types conductivity of all and glues comply thermalNovartis), stability. with silicone the Among glue them RTV requirements 3140 are of (Dowcoefficients e. and radiation Corning) g. the to hardness, conductive compensate Epoxy glue for AW EE 106the different 129-4 HV (Araldit, (Polytec) thermal lines between expansion on the the silicon Kapton sensor bias back strips plane (see and below). to position and attach theand modules TEC to modules the are largerfor mounted support a using structures mounting with four precision high points, of precision. better two than being TIB/TID 20 high precision bushings that allow 2008 JINST 3 S08004 m. Each µ 700 mm to − m (RMS) in the module µ ) which in the case of the pitch adapter-sensor z, up/down) for ease of handling and integration. 3 m) for a reference point on the modules is shown O µ 2 – 64 – m thin ceramic Al µ axis. The two innermost layers host double sided modules with a strip pitch z m, while the outer two layers host single sided modules with a strip pitch of 120 After wire bonding each module was tested and graded, using the ARC system [51]. A µ 700 mm along the Each of these sub-assemblies (half-shells)electronics hosts and an thus independent can array be ofother fully services during from equipped final assembly. cooling and to tested before being mechanically coupled to each to a supporting strip (400 production. connection is also glued todone the by graphite dispensing cross Sylgard piece. 186 glue Thebetween on reinforcement the the for near backside the sensor of TOB and the modules the modules,and edge was between the of the the backside two hybrid. sensors APV and For bondings theFor are TIB TOB modules encapsulated modules the no by sensor-sensor reinforcement Sylgard bonds was 186 done. glue across the bondingdetailed wires. description of all tests performedthe and reference. the acceptance Modules criteria for were goodacceptance graded channels criteria A is (due if given to in fewer high thanless noise, 1% than open of 2%. bondings, the oxide The channels defects) remainingreasons and were modules to B were failing reject if graded modules the were the C quality imperfect and failurerelevant mechanical were rate test precision results not was or are used poor stored high in in voltage the thewas behaviour. central experiment. All greater CMS tracker than Other data 97%. base. The yield of module production 3.3.4 Tracker Inner Barrel andIntroduction Disks and (TIB/TID) mechanics The Tracker Inner Barrel (TIB) consists339.0 mm, of 418.5 four mm, and concentric 498.0 cylinders mm+ placed respectively from at the radii beam axis of that 255.0 extendof mm, from 80 cylinder is subdivided into four sub-assemblies (± Figure 3.23: A typical residual distribution (in for the different module assembly centers, indicating a precision of 10 2008 JINST 3 S08004 z) which end 900mm. The − ± or z + 800mm and ± Optical fibres Optical fibres patch panel Electrical power Electrical power patch panels shows a schematic drawing of one (referring to m copper on both sides. between 3.24 µ z . (see below). These service cylinders play a – 65 – margherita Service cylinder Service cylinder (disks are hidden inside) 5. 2. = η Layer 4 shells TIB/TID + with the margherita Silicon detectors are assemblies of three disks placed in Two service cylinders are coupled to the ends of TIB± The silicon detector modules are mounted directly on the structure’s shells and rings. Thus, The TID± All mechanical parts like shells, disks and service cylinders are made of high strength low in a service distribution disk called the Figure 3.24:(TIB/TID-) Schematic nest drawing inside of the thefrom Tracker the TIB/TID+ Outer margherita Barrel subassembly. consist (TOB),signals of one This and copper for controls structure and cables each also and for end. cooling its fluid powering supply Services and twin lines routed slow made of controls, out aluminium optical tubing. fibers for dual role: one is toTracker route Inner out Disks services (TID) from which the sit shells to inside the them. margherita, Figure the other is to support the while a large numberchosen of allows modules for has far to greater be precision integrated of and assembly. tested at The any individual one components of time, a the TIB approach shell, half TIB/TID structure together with its corresponding margherita. disks are identical and each one consiststo of 500 three mm. rings which The span two thesided radius innermost ones. from rings roughly host 200 Just mm back-to-back like modulespendently the while of the TIB the outer shells others one eachcoverage hosts before up individual single to final ring pseudorapidity assembly. can be Together fully the equipped full and TIB/TID testeddeformation guarantee inde- carbon fiber hermetical chosen both foris its instead lightness made and of its conventional low G-10 material fiber budget. epoxy with The 30 margherita 2008 JINST 3 S08004 C 2 30°C) and at high 3mm wall thickness. – 66 – 3.25). The three modules are interconnected through 25°C, while keeping the material budget as low as possible. For the TIB/TID − 3.25), while in the TID arrangements are more varied even though the number of modules Since the position of the ledges defines the position in space of the modules, after the glue some of which not only servicespace, will the be silicon described detector in needs some but detail also in define next its paragraphs. geometric positionCooling in The cooling circuits must be abledown to efficiently to cool about the detectors with a cooling liquid temperature the decision was made to use aluminium piping of 6mm cross section and 0. These pipes are bent into loopsin and parallel. soldered to The inlet/outlet thermal manifoldsledges connection which which connect between are several pipes loops glued and tothe silicon the modules modules pipes. is are On made tightened. each with(figure ledge aluminium there For are the two TIBper threaded cooling M1 each loop holes is loop onto similar. hosts which three modules placedhas in hardened straight the row wholegluing, half the cylinder circuits are is tested surveyed individuallypressure for with (20 leaks a bars). both at precision It cold measuringfor temperatures is machine. the (− only integration after of Before the thecooling survey electrical that circuit parts the vary TIB including from cylinders themodules layer (or detector used TID to for modules. disks) that layer specific The are andmodules layer. dimensions available depend equivalent) The of cooling for on the circuits the the varysided double from amount ones sided a where of individual minimum layers module power of to heat four dissipated dissipationindependent a loops is cooling by much (12 maximum circuits lower. the so of The that TIB/TID in 15 uses casepart a loops of of total an the for of accidental tracker 70 break the is in affected. outer onewhich The of single the TIB cover circuits thus the only is outer a organized small and inwith three inner the module surface ladders only of (the difference cooling the that loop) fourThe the electrical layers. number grouping of which The modules we same now per concept describe cooling applies takes loop this to varies mechanical the with distribution TID into theElectrical account. ring grouping radius. The modules have been groupedwhich together sit electrically. on The any basic givena group cooling consists Kapton loop of (figure circuit three (mother modules tributed. cable) through At which the powering, topdistribution. detector of These biasing a mother and mother cables controls are cablecontrol are then ring sits electrically dis- which a joined distributes CCUM in trigger, clock which agroups and more never takes slow complex straddle care control group two of signals called different to clock,promise the cooling the between loops trigger CCUMs. granularity and and and Control are I complexity ring dimensionedof is so a achieved. that unit Control a called rings reasonable the inoptical com- the DOHM fibers TIB/TID (Digital coming make opto-hybrid from use module) thesignals which front that receives end are all controllers then the distributed (FEC) to signalsthe and up high from converts to them number the 45 of to detector modules electrical modulesin belonging LVDS (15 its to mother DOHM a cables) hardware. via Control CCUs. Ring, TIB/TID Given has implemented redundancy 2008 JINST 3 S08004 0. In each layer, the ) supporting 688 self- = z axis. The wheel has a length z – 67 – 16 mm with respect to the average radius of the layer, thus ± . rods and therefore full coverage within each layer. The rod mechanics are φ 3.26). Disks and cylinders are made of carbon fiber epoxy laminate. The cylinders i Analog signals from the detector front end are converted to optical by analog opto-hybrids Grounding of the TIB/TID relies on the cooling circuits which are made of aluminium. The Modules have been grouped together to keep the number of power supplies down to a man- The wheel is composed by four identical disks joined by three outer and three inner cylin- ageable level. The smallestlargest power comprises group up consists to 12 of modules three (fourtrol mother modules ring cables). (one (i.e. Power there mother groups is are cable) contained nosupply while within straddling unit a the across (PSU) con- control developed for ring the boundaries) tracker and which are also fed supplies by HV a biasingwhich specific for sit power the next detectors. to thethe system silicon is modules completely and optically arewhile decoupled avoiding from connected ground the directly loops. DAQ to which helps the preserve front signal end integrity hybrids.return current Thus wires are connected to thecooling cooling inlet and manifolds outlet for pipes all run mother along cablescontact the and service with DOHMs. cylinder across it. The the margherita, Outside makingground. electrical the Power cable tracker shields volume are these connecteddetector to pipes modules the have are margherita their then which own carbon hosts connected fiber allground. to frame of The directly the the shells connected connectors. CMS to are All the grounded detector front through end the hybrid cooling local manifolds. 3.3.5 Tracker Outer Barrel (TOB) Mechanical structure and layout The Tracker Outer Barrel consistscontained sub-assemblies, of called a single mechanical structure (wheel ders (figure have a core of aramid-fiberaluminium honeycomb. elements The glued joints to between the disks carbonEach fiber and of parts cylinders the on are disks precision realized contains fixtures, with 344two and disks, openings, then and in bolted two which rods together. the cover the rodsof whole are 2180 length inserted. mm, of the and Each TOB inner rod alongtwo and is the outer ends supported radii by the of TOB 555 haslayers mm a with and total average 1160 radii mm, length of respectively. ofgravity 608, With 2360 of cabling 692, mm. the at 780, rods its 868, The are 965, openingsallowing displaced 1080 in for by mm. the overlap Within disks in each form layer, six the detection centers of Figure 3.25: Three TIBunderneath. modules A mounted CCUM module onAlso at a visible the are layer end the of 3 three the analog shell. opto-hybrids string (see interfaces text) The the and modules Kapton fibers. to mother the cable control runs ring. designed in such a way to implement overlap of the silicon sensors at 2008 JINST 3 S08004 m, and a reproducibility between different µ that block the rod against the outer disk surface – 68 – m. z-stops for measurements of the geometrical precision of the µ m of nominal values over the whole TOB dimensions, with µ targets tracker support tube, for a precise measurement of the TOB Figure 3.26: Picture of the TOB wheel. , except the four supporting spheres that stick out laterally in correspon- 3 0 is precisely 1.5 mm. Inside the disk openings, the rod support spheres = z view between neighboring rods is always larger than 1.5 mm or 12 strips, while 22 mm m level. -φ µ × r 1130 × The mechanical structure consists of two 1130 mm long carbon fiber C-shaped profiles, joined The wheel is equipped with after insertion in the wheel. The rod mechanics The rods are self-contained assembliesmodules, providing together support with and their cooling interconnection for and read-out 6 electronics. or 12 silicon detector by several transverse carbon fiber ribs andof plates. 159 All rod components aredence contained of in the an two envelope disks of the wheel, and the disks at the 10 are held by precision elementsstructure. made The of four polyetherimide disks have plasticprecision all that table, been are ensuring assembled a glued in precision a toaluminium on temperature-controlled the elements the room joining carbon on relative disks fiber positions one and cylinder of single of the 100 rod holding elements and the assembled structure. Photogrammetry, theodolites, andbeen 3D used coordinate measurement for systems survey have andafter alignment insertion of of the wheel thepositioning structure. TOB in Some in the of tracker the these referencemovements targets frame, due remain to and deformations visible even of after the loadedmeasured integration structure. before of The starting TIB, wheel rod mechanics to integration, has and monitor beenbeen the possible thoroughly found relative to positioning be of typically the within precisionmaximum 100 elements deviations has observed around 200 the overlap around overlap in the 2008 JINST 3 S08004 3 mm and 3. ± 3 mm in single-sided rods, 3. ± – 69 – m wall thickness, respectively. In addition the design of the µ 3.27). The Communication and Control Unit Module (CCUM) m and 200 µ In single-sided rods, which populate layers 3–6, one detector module is mounted in each of A U-shaped cooling pipe runs around the rod, inside the C-profiles; 24 aluminium inserts are The rod cooling pipes, and the manifolds housed on the outer disks of the wheel, are realized 6 mm in double-sided rods. 7. glued through openings along theinserts provide profiles support to and cooling the to carbon thethe fiber detector rod, modules, and three that per around are side. mounted the in Eachand cooling six detector two positions pipe; is close along supported to these by the four sensor-to-sensorwhich bonds. inserts, the two The Cu-Be close two to springs inserts the on close read-out to theule hybrid, the module positioning; hybrid frame all implement are four pins clamped, inserts on determining haveshaped the a washers precision threaded together of hole with the for a mod- calibrated the torqueing fixation used contact of in between the tightening the module the aluminium to screw heat the ensureOn spreader efficient rod: the cool- on cooling cup- the pipe module side, frame theimpedance and shape of the and the rod the contact, support size which inserts. of in the turn inserts allows is to optimized minimize to the minimize crossthe the section thermal six of positions, the with cooling pipe. thepopulate strips layers 1 facing and the 2, two central detectorsrods plane are and mounted of in the the each outer position, rod. one thebetween inner with In the one the double-sided sensor as backplane and in rods, single-sided the facing which middle the plane backplane of of the rod the is first module. The distance ± in CuNi 70/30 alloy. Thissolder material joints to is be chosen made for relatively itstions; easily, avoiding the corrosion the reliability resistance, use of of and o-rings the as orthe cooling it ferrules TOB, circuits allows in which is the is reliable a pipe the crucial connec- most issue inaccessiblehigh subsystem density for once of the the the tracker, detector material and is (its particularlyminium) fully radiation is so integrated. length compensated for The by of rather the about reduced 1.4 thickness of cmand the is manifolds walls 6 have that 100 times this technology shorter allows: thancooling rod that pipes circuit of has alu- been optimized (asthe already pipes mentioned (the above), cooling to fluid minimize alsomaximize the the gives number cross a of section non-negligible rod contribution of pipes to servedcooling by the performance). a material single An budget), manifold outer and (within diameter to the of constraintscooling 2.2 of mm to the is 6 desired chosen detectors), for 2.5 single-sided mm rod6 for pipes mm double-sided (providing for rod the pipes manifolds; (providing one cooling manifoldvarying to serves between 12 on 8 detectors), average and more and than 22 15 dependingby rod on 44 pipes, cooling the the lines, region actual giving number of an the average TOB. of Overall, 118 the detectors, whole or TOB 550Rod is read-out electrical served chips, design per line. The 6 or 12 modules housedsupply unit. in a The low rod voltage form lines a supplying(AOHs) power the run group, front-end in hybrids i.e. and they the the are Analogue Inter-Connect-Busmiddle supplied Opto-Hybrids (ICB), plane by a a of single 700 the power is mm rod plugged long (figure printed to circuit onealso board end routed sitting of to in the the the ICB.nals final The to destinations front-end clock through hybrids and the and the ICB. AOHs control proceeds The through signals distribution four issued of other by power, PCBs, clock the the and CCUM Inter-Connect-Cards sig- are 2008 JINST 3 S08004 – 70 – 3.28). The choice of including the optical patch panel inside the rod volume The ICB is held in place by small transverse carbon fiber plates; the ICCs and the CCUM are Figure 3.27: Photo of adetector rod modules. frame equipped with electronics components, ready to receive silicon (ICCs). Two ICCs serveICCs one have module different position design and inmodules single-sided two mounted in rods other each and ICCs module double-sided serveICC position, rods, flavours two respectively; in which therefore module the there have TOB. positions. are one in and total two four different plugged to the ICB and screwedthe to module), the which aluminium also provide module a supportand good inserts cooled cooling (on only contact the by to opposite the those side connectorCTRL boards. signals, of that the The plugs ICCs AOHs to receive are the the supported data ICCs.(a lines few In from cm the addition read-out away) to hybrid where distributing and they LVtemperature route power are them information and converted to to from the optical AOHs the signals.optical module The fibers frame ICCs leaving also Kapton the receive circuit AOHs lines travelholders. and carrying inside route the The them carbon only fiber to electrical profiles,lines the lines guided not ICB. for by integrated The dedicated the in plastic sensors. theprofiles, ICB/ICCs while the These distribution line system run with are the insided return the dedicated current rods bias is (one wires integrated per in (size module), thefour and AWG ICB. serving There 8 26) two are lines modules housed six in each). lines in double-sided The inend-panel, LV rods single- the lines each (four and carbon of the serving HV which one fiber lines also module go hostsend each, in in some separate and one connectors temperature multi-service in lines, cable the and plus rod then low-impedanceeight cable. run bias At all lines the together are power to connected supply the backplane toeach back- the the line six powers two or one independent side high-voltage of supplythe the lines CCUM leave rod. in the such The rod a through clock a way andfirst short that control and cable lines which the as plugs last into well rod the as next ofThis the rod a board of LV control lines the houses control ring powering the ring. are The digital connecteddistributes to the opto-hybrids clock the optically and Digital connected the Opto-Hybrid control to Modulethe signals the (DOHM). connected through rods remote a (up control token-ring to 40 system 10). MHzthat and The LVDS-based all protocol fibers length to end of at the the optical sameare fibers location integrated near coming the (figure from CCUM, the where AOHs the is connectorswas chosen of made so the to 12-fiber reduce ribbons the thicknessinactive of volume the between TOB TOB and services TEC. on the TOB end-flanges, so minimizing the 2008 JINST 3 S08004 3.29), are protected by alodyned alu- – 71 – The DOHMs, mounted on the TOB end-flange (figure Figure 3.28: Top panel: photothe of 12-way an optical assembled ribbons double-sided connectedprepared rod, to for showing insertion the the in CCUM AOH the fibers. side, TOB with mechanics; Bottom the side panel: opposite double-sided to the rod CCUMElectrical being is and shown. read-out grouping The grouping of thespanning rods across into two control different rings coolingreduce is cost segments, and designed while material primarily maximizing budget) within the toresults the size avoid recommended in of limit having two of a control 10 or control rings segment CCUMs three ring per containing ring. control (to one This control rings logic ring perin only. the cooling TOB The segment, is average 7.5. with number WithinFED. of a a Again, CCUMs control single a (i.e. ring, read-out exception of rods group are never of rods)minimize spans clustered per the a over in number ring two of groups cooling control unused that channels rings, are in and thein read the FEDs out the grouping (to by TOB is reduce cost). the optimized is same to The 94%. averageby FED In 92 occupancy summary, DOHMs, the and TOB cooled by is 44 made independent of lines. 688 rods readGrounding out by 134 FEDs, controlled In each rod thethe return LV line power of of LVcooling DOHM and manifold bias and serving the is CCUMs, rod: connected andimproved this by inside is connected additional the ground the through connections main CCUM in ground a each connection tothe ICC, short of mounting implemented the through the holes. multi-wire metalization return rod. around cable The line grounding to of is the minium plates of 0.5 mm thickness, which are locally connected to the power return line. 2008 JINST 3 S08004 2 10 mm × 3.26); for the inner . In addition, copper strips as long as the φ – 72 – ground rings: an alodyned aluminium bar of 10 . The connection to the carbon fiber is realized with conductive araldite. The φ The cooling circuits of the different segments are then connected electrically through short Such design of the grounding scheme ensures good electrical connection of mechanical struc- Figure 3.29: Photo of the completedservices z+ on side the of TOB the end TOB.cables flange. The and DOHMs feeding Optical form pipes ribbons the run (green) outer parallel run layer to of out, each the grouped other on in the 16 thermal channels. screen panels. Power multi-wire cables soldered to the radial pipes feedingfor the the manifolds outer (or to layer) the and manifolds themselves, screwed to the square section bent to roundat shape and the equipped outer all radius along0.2 of with mm threaded the thickness holes, TOB, which connect on iseight the both installed locations ground sides. in ring to Gold-coatedsame the copper strip carbon material strips fiber is of structure used to 30and of inner realize mm the cylinders the and width outer electrical disks, connections cylinder, and again betweenwhole in in TOB outer eight are locations cylinders added in and on disks, the outercylinder surface instead, of the which outer is cylinder inside (visible the inthe figure tracking carbon volume, fiber. it was decided to rely on the conductivity of tures and power return lines making efficientand use of carbon the fiber existing parts), conductive materials with (cooling minimal pipes amount of added metallic elements. 2008 JINST 3 S08004 3.30 in the z 2800 mm along ± 1240 mm to ± petals, which in turn are mounted on the disks. – 73 – 5 mm thick. The back plate also serves to make the overall structure 2 mm CFC skins on each side. The back plate provides an additional segments. Each of these segments is attached to the disks and the gaps at ◦ 3.33). Petals can be individually removed from the endcaps without uncabling 5 mm thick CFC panels surrounds the endcaps on the outside and serves as a gas and z-direction. The back plate is covered by another carbon fibre disk, the bulkhead, which 3.32 The disks are Carbon Fiber Composite (CFC) / honeycomb structures. The honeycomb core Ten different module types are arranged in rings around the beam pipe. For reasons of mod- 3.31. Eight U-profiles, referred to as service channels because all services are grouped in their z-direction. The two endcaps are called TEC+ and TEC- (according to their location in the joints between segments are filledskin with made epoxy of glue so 0. that theyenvelope for are the gas atmosphere tight. of A dry thina nitrogen. cylindrical 5 The mm front NOMEX plate core has with 0. the same function and consists of is 16 mm thick NOMEX,is 3.2-92 a with symmetric a layup border of ofHTA CFC epoxy 5131,3K skins potting. (T300) (0.4 mm On impregnated thickness). either withservice side The channels EP121 of skin and epoxy the the material resin. inner is core support CF-fabricsegmented there tube. into The THENAX The four same latter 90 material has a is thickness used of for 3 mm the and is azimuthally thermal shielding for the cold45 mm silicon with volume each and CFC skin isrigid 1. in considerably the thicker. The NOMEX core is ularity they are mounted onDisks substructures 1 to called 3 carry sevening rings on of disks modules, 7 ring and 1 8, isdouble and missing sided on disk modules: disks 9 4 carries two to ringsThis modules 6, 4 provides rings are to space 1 7 mounted information and only. back-to-back perpendicular 2 Rings and are with 1, parallel miss- a 2 to and stereo the 5 angle strip are orientation. of builtPetals 100 up of mrad. so-called To allow easy access to(figures the detector modules theyand/or are disassembling mounted the on entire modulardisks structure. elements, of the A one petals total endcap, of eight on 16 the petals front are face mounted of on the each disk of — the as nine seen from the interaction point — vicinity, join the disks together alongattached their at outer four points periphery, to while an at innerof its support the inner tube. pixel diameter To preserve detector, each the the disk envelope last necessary is three six for (229 the disks mm). insertion have a larger inner radius (309 mm) as compared to the first is, however, mechanically detached from thebulkhead TEC carries and the supported by outer theelectrical connectors tracker connection support of of tube. the all TEC The TEC tofoils cables, the which external close thereby power the cables. forming thermal It screen a is at patch covered the by end panel panels face for with of heating the the tracker support tube. CMS coordinate system). Each endcap consistsindividual of detector nine modules disks are that mounted carry plusnation. substructures an on A additional which sketch two the of disks one servingand endcap as and front/back a termi- photograph of the completed TEC+ is shown in figures the 3.3.6 Tracker EndCaps (TEC) Mechanical structure The endcaps extend radially from 220 mm to 1135 mm and from 2008 JINST 3 S08004 petals. One sector, indicated – 74 – Figure 3.31: Side view of a TEC. (front petals) and eight onfront the and back back face petals, (back longthe petals). petals front for Mechanically and disks there back 1–3 petals are and onBD13, short two disks ones respectively. types 1–3 for each Petals carry disks of on all 4–9. disks sevencarry As rings 4–6 rings described of 3 carry above, modules to rings and 7 2 are (FD78/BD78),have to and labelled a on FD13 7 structure disk and (FD46/BD46), 9 similar those the to on petals carry the disks rings 7 disks, 4 and consisting to 8 7 of (FD9/BD9). a The 10 petals mm NOMEX core sandwiched between Figure 3.30: Left panel: Sketchbeam of axis. one tracker They endcap. are Modules mounted are on arranged trapezoidal in rings sub-structures around called the with a line, consists ofFD13, nine 3 front FD46, petals mounted 2 onBD13, FD78, the 3 1 disk BD46, FD9) sides 2 and BD78, facingpoint. nine 1 the BD9). The interaction back diameter point petals Right of (3 panel: mounted the TECs Photograph in is of the 2.3 a opposite m. TEC side as of seen from a the disk interaction (3 2008 JINST 3 S08004 3 − photos 1, ICB − 3.32 9 mm and a z, one fixed only and y , x C to reduce the effects of coolant gives a temperature ◦ 14 10 F − 6 2 on side B/D and ICB − 3 kg/min of the C – 75 – z. 25 mm. They are embedded in the petal and serve to cool the components on 46 on side B/D, which carries all the connectors for the cables and two CCUM − is done at the outer periphery of the petal. These connections can be undone easily C between petal inlet and outlet. The connection of the petal circuits to the piping ◦ z 57 on side A/C, where the numbers correspond to the number of the ring to which the − 4 mm CFC skins. As viewed from the interaction point the modules belonging to rings 1, 3, 5, 7 0. are mounted on the petal frontwhile side modules (A-side in and rings C-side 2, forthe 4, the front front 6 and and are back back mounted petals, petals, onthe respectively). respectively), the back On petals, back a as side given do, of disk foradjacent each the a rings petal front given are petal, (B-side petals arranged detector and to overlap modules overlap azimuthally D-sideon radially, belonging with for thus inserts to providing in the full the same coverage. main ring. disks Each Detectors using petal in a is three mounted point fixation: one point fixed in Cooling The heat generated by all electronic componentsthe on a silicon petal sensors must be must removed efficiently. be In addition operated at a temperature of about running along in phi, and one fixed only in difference of 2 in case the petal needs to beare removed. connected A in pair parallel. of A longitudinal total pipesare of serves 64 used either longitudinal per 4 stainless endcap. or steel 5 pipes petals, with which 11 mm inner diameter Electrical system design The silicon modules, AOHs andterConnect CCUMs Boards on or the ICBs, petals which areof are connected a mounted to bare on motherboards, front both called petalmain sides In- board equipped of ICB with the petal. ICBs onlyboards In and are figure transmits shown. power and Therewhich signals are provide to five the the individual power modules and boards: of signals rings the for 4 the and other 6, rings and (ICB four smaller boards, radiation damage. The siliconthe detector sensors modules, and for front whichThe carbon end fiber aluminium hybrids of inserts are high for cooled thermal positioningcooling conductivity via the pipe. is modules the used The serve CFC (800 two at inserts W/(m frames the along K)). of of the same the sensors, legs time while of for the the inserts the module oncontains coupling frame the two provide to frame cooling primarily base the are for circuits heat the traversing sinks the cooling point for petal the to front longitudinally the end and next. hybrid. meandering The Each fromwall petal cooling one thickness pipes cooling of are 0. made ofboth titanium back with and an front outer side. diameter Theare of tubing laser 3. is welded pre-bent onto into the the coolinginto proper pipes. the shape. After petals, The input/output having the manifolds milled tubingglue the is them corresponding inserted. to grooves and the Gluing holes pipespetal jigs and a are to CFC used the skin to petal. withare position holes To then the at close machined cooling the the to inserts location the grooves precision of and andthe required the re-establish electronics to for on inserts the module a is integrity positioning. petal glued of is The ontooperation. about the maximum 87 the heat In W, petal load these including from the face. conditions heating a The of mass the inserts flow sensors of after 2. ten years of LHC and ICB 2008 JINST 3 S08004 46 on side B, − 46, the two CCUMs are 2 and ICB − − 46, which must carry a current of up − – 76 – 57 on side A (from left to right). On ICB 57 have six copper layers, while the smaller boards have only four − − C signals. In addition analogue data from the FE hybrids are transmitted 2 3 and ICB − 46 and ICB − 1, ICB − For each low voltage group, two high voltage channels areThe provided. ICB For each HV channel To keep the number of low voltage power supplies and connections relatively small while Figure 3.33: Left photograph: front side of a TEC Petal. Right photograph: back side. limiting the current that must below provided voltage by (LV) one groups, power which supply, are theof modules served rings are by 1 organized individual and in power 2, three supplies. group Thecorresponds 2 LV to contains group 8/11/9 rings 1 (4/8/11) 3, consists 4 modules and orgroup 6 48/44/44 1/2/3. and (24/32/56) finally APVs rings In on 5 total front andto (back) there 7 12 petals belong A. are in to Sensing eleven LV group is power 3. implementedin This rails for the on the electrical ICB low centre voltage ofpower connections. each input power The connectors as group. sense well resistors Capacitances asa are possible are near located voltage the implemented overshoot front-end on caused connectors the by to switching ICB suppress off near ripples the the FE-hybrids. and minimize there are up to four single HV lines, which bias onelayers. or two To limit silicon the modules. contribution to the material budget, the copper layers are rather narrow and thin. connected modules belong). These fourthe boards ground, are the connected various to supply theand voltages transmits main and LVDS and board. the I bias The voltage ICBdifferentially to brings to the the electrical AOHs over devices distances on of the a petal, few centimetres. Figure 3.32: The different ICBs on the two sides of a front petal: ICB and ICB plugged. 2008 JINST 3 S08004 z- 1, − m each, separated µ 57 on front petals and ICB m. Digital and data traces are − µ 3 and ICB − 1, ICB – 77 – − m for the inner four and outer two layers, respectively, µ NTC thermistors are located on ICB_46 on front petals z-direction. 3 on back petals, which has a thickness of 35 − direction, and end at the bulkhead. These cables implement silver-plated aluminium z m thick polyimide layer. µ 2 and ICB Each TEC LV group is supplied by one so-called multiservice cable, which transmits the The connection from the bulkhead to the so-called patch panel 1, located outside of the tracker Two petals, one back and one front petal, are connected in a control ring. The front petal is Low-pass filters are implemented for the traces of the temperature signals that are brought out Kapton cables of about 15 cm length are used to link the petals inside one control ring with − except for the innermost layer of boards ICB by a 100 analogue power and the bias voltageInside and the brings tracker out support signals tube, from powerrun cables temperature along are or the arranged humidity around sensors. the mainconductors TEC to cooling minimize pipes the that impactabout on 5 the A to material 11 budget. A, depending Typicalwith on currents wire the per cross-sections number tailored cable of to APVs range connected. the from differing Therefore needs. three cable types exist, volume, is provided by poweris cables implementing transmitted tinned via copper separate conductors.conductors cables, The are which used control both also power inside break and at outside the the tracker bulkhead. volume. In this case tinned copper The layer thickness amounts to 17 and 25 shielded by power and ground layers. the first in the control loop.CCU, respectively. Both The on Digital back Opto-Hybrid and (DOH) front convertssignals the petals, and optical rings vice signals 1–4 versa. to and electrical Two DOHs LVDS 5–7 are(DOHM), are located which connected on is to a mounted one separate on PCB, the thefor back Digital the petal. Opto-Hybrid DOHs, Module From electrical the signals DOHM, areredundancy which transmitted scheme also to is distributes the implemented the CCUMs on power on thea the ICB. problem, petal. Each so CCU For that can the be the controlfor bypassed ring, functionality redundancy electrically a of purposes in the case only. control of To ring allowis also is located the maintained. on last The CCU the second on DOHM. DOHare the It faulty, is ring the is to needed complete used be control only bypassed, ring in a is fifth this lost. CCU special case. However,via if power cables, two to consecutive ensure CCUs that noiselocated is on not the coupled in Kapton via of these theon lines. silicon In or modules, addition several connected to temperature the to and thermistors humidity theand probes read ICB. are out Two located via 10 the kΩ powerNTC cable of thermistors low are voltage glued group to 2.DCU the Both that cooling on is front inserts and present of back on the petals,ICB_46. ring each four 6 CCUM. 10 For kΩ modules. On back both They petals, petal areside this types, read in sensor a total out is 12 humidity via read hardwired sensor the humidity outthe can sensors via be humidity are connected the sensor distributed to power over is the cableand read TEC of bottom out volume. LV sectors via For group carry front 2. the these petals, relative DCU additional On humidity humidity on along each sensors, the the providing CCUM. detailed information Front on petals the of alleach disks of other the and top withCCUMs. the These DOHM, cables providing consist the of electrical two digital copper signals layers and with the a power thickness for of 35 the ICB 2008 JINST 3 S08004 m, and µ m to a few tens of µ m thick copper path along the ICBs as a reference – 78 – µ 3.4), which needs to be recovered by determining true alignment. 3.23). m thick copper ring, which is glued to the outer radius of each back µ Alignment of the tracker relies on three key components: the various data aboutFor alignment assembly purposes, modules with two sensors are treated as they would have one large The CMS tracker alignment task thus consists of the determination of three translational and The grounding scheme The so-called TEC common ground isof located at a the 5 back cm end of widedisk each and and TEC. It tied 150 is to realized the bymaterial brackets means of that the connect hadron the tracker calorimeterreference support represents points tube a of to very all the solid powerpipes hadron ground. groups, of calorimeter. the the The The petals cooling shields to manifoldspetals of the that and all main the are cables, outer tubes used aluminium that the to shields arethe of connect mounted petal the the on side, TEC cooling are the one connected common TEC, toground analogue the this is ground CF TEC distributed is common skins via ground. implemented of a On per therail. 2 petal. cm disks The wide and This LV and so-called and 20 local HVgeometrical/electrical petal supplies centre of of all power each groups group.once are to referenced The to the digital this local ground localcommon petal of ground. petal a ground. ground Copper strips at control glued the group The tothat is the local connect outer referenced petal all radii of disks ground theground. with of disks and the These each along copper back petal the strips disk service is arecarbon channels provide connected frames connected the via of to short the electrical copper the silicon connection detectors braidsand TEC to are finally to via connected the the the via ICBs TEC ICB a on to common conductiveinsulated the the glue from petals. FE spot the hybrid to The cooling ground. the pipes To bias by avoid Kapton an ground anodized loops, layer the between frames are the electrically cooling3.3.7 inserts and the pipe. Geometry and alignment The deviation of truespecified position in and the engineering orientation drawings depends oftime-dependent: on tracker many the factors modules achieved with assembly from different precision, origin, theiraccess deformation some and due of nominal magnetic them to values field, tracker as out-gassing cooling, ofof stress components from the in track dry nitrogen. parametermodule This resolution position leads (figure and to orientation, a called degradation gathered during the integration process, the Laserordered Alignment by System and increasing the precision alignment and with availability tracks, with time. sensor with identical active area coverage. Thissensor is placement justified by accuracy sensor (figure mask design [36] and achieved three rotational parameters for eachit of the might 15 be 148 tracker necessary modules. toprocessing. To consider achieve additional ultimate precision, parameters, e.g. the sensor bow dueGeometry to single-sided Two methods are mainly usedcoordinate for measurement measuring machines tracker with component a assembly typical precision: accuracy survey of with a few 2008 JINST 3 S08004 10 20 70 150 600 TEC Sensor Module Petal Disc TEC Tube m, which is mandatory for , are foreseen to align TIB, 10 30 µ φ 100 1000 ), 500 (z) φ TOB 140 (r m) of tracker components. Values are given µ m) under good (optimal) conditions for relative µ m, providing additional input for the track based µ – 79 – 3.34) uses infrared laser beams with a wavelength Sensor Module Rod Wheel Tube CMS m (80 µ 10 54 185 350 450 TID . Here special silicon sensors with a 10 mm hole in the backside φ Sensor Module Ring Disc Cylinder Tube 10 180 450 750 TIB Module Shell Cylinder Tube Sensor In each TEC, laser beams cross all nine TEC discs in ring 6 (ray 2) and ring 4 (ray 3) on back The signal induced by the laser beams in the silicon sensors decreases in height as the beams The software description of the position and orientation of the active detector volumes has 3.2. It should be noted that structure deformations due to loading as well as temperature and 1075 nm to monitor the position of selected tracker modules. It operates globally on tracker m. µ = alignment. petals, equally distributed in metalization and an anti-reflective coating arement mounted. of The the beams TEC are discs. usedTOB, for The and the other both internal eight TECs align- with beams respect (raywhich to 4), each is distributed other. established in Finally, by there is 12the a laser link tracker beams to coordinate (six the system. on Muon system each (ray side) 1), with precise position andpenetrate orientation through in subsequent silicon layers in the TECs and through beam splitters in the align- measurements. The measured and expected mountingtable precision from those data are summarizedhumidity in variations have not been taken into account. been validated with surveyrecorded in data various test and and reconstructed integration setups. tracks from testLaser beams Alignment and System cosmic muons The Laser Alignment Systemλ (LAS, figure substructures (TIB, TOB and TEC discs)The and cannot goal determine of the the position system ofometry is individual reconstruction modules. to of generate the alignment tracker information substructures on at a the continuous level basis, of providing 100 ge- photogrammetry with an accuracy of 150 with respect to the next10 level in the hierarchy, e.g. the position accuracy of sensors in modules is track pattern recognition andmovements for can the be High monitored at Level the Trigger. level of In 10 addition, possible tracker structure Table 3.2: Estimated assembly precision (RMS, in 2008 JINST 3 S08004 − µ + µ → Z (100 000). The first is an extension to the well- O – 80 – Figure 3.34: Overview of the CMS Laser Alignment System. Experience from other experiments has shown that collision data are not sufficient to constrain or jets, mass constraints, measurements fromFirst the studies Laser indicate Alignment that System, those and data survey will constraints. provide a unique alignment parameter set. known global Millepede algorithm [52], that takesto all successfully correlations into align account the and most hasa been sensitive shown Kalman 50 000 Filter parameters. [53], The whichaccount second the bridges is most the a important gap novel correlations. approach betweensense In using global that addition and it the local takes HIP algorithms [54] intoparallel. algorithm, by account In which taking only this is into correlations algorithm, local of correlations inalignment parameters between the many modules within times. are a dealt All module, with threefor is implicitly methods the developed by full are in silicon iterating expected pixel the to and be strip able tracker. to provide alignmentcertain constants correlated module movements wellTherefore enough complementary to data obtain a and uniquecosmic constraints muons set need (with of and to alignment without be magnetic constants. halo field) exploited. that muons constrain the for Examples tracker the are barrelTypical modules, tracks endcap. examples or from beam of Beam constraints gas are a and vertex minimum constraint bias for events decay are particles also e.g. under from consideration. ment tubes that partly deflectall the sensors, beams a on sequence TIB ofgenerated. and laser TOB pulses Several sensors. with triggers increasing per Tohundred intensities, obtain intensity triggers optimized optimal are are for needed signals taken to each on get and position,trigger a the is rate full picture signals for of the are the alignment averaged. alignmentdata of system will the be In is tracker taken around total, structure. at 100 Since a regular Hz, the intervals, few this both in will dedicated take runs only andAlignment a during with physics few tracks data seconds. taking. These CMS pursues the development of two novelsolve track-based alignment the algorithms system that allow of to linear quickly equations of order 2008 JINST 3 S08004 9 8 readings 7 5 (in the disk disk number 6 ∆y 5 , 4 LAS Survey Cosmics ∆x 3 2 1 0

0.1 0.3 0.2

-0.1 y [mm] y -0.2 -0.3 ∆ 9 8 7 disk number 6 5 4 rad with each other, which can be taken as an upper – 81 – µ 3 2 1 (around the beam axis) and displacements 0

0.1 0.3 0.2

-0.1 -0.2 -0.3 x [mm] x ∆ m and 80 data points from DSS via a Siemens S7 driver and 10 ∆φ µ 3 9 8 7 disk number 6 shows the results from the three complementary methods. The global degrees 5 9) together with a Finite State Machine written in SMI++, a derivative of the 3.35 4 3 2 1 During integration of the TEC+, deviation of disk positions and rotations from nominal val- -0 power supply parameters, 10

0.1 0.2

-0.1

-0.2

4 [mrad] 0.05 0.15 ∆ φ -0.15 -0.05 Figure: 3.35 TEC+ disk rotation plane) as determined from survey, LAS and cosmic muon tracks. ues have been determined frommuons. survey Figure with photogrammetry, the LAS, and tracks from cosmic former DELPHI control software;LHC experiments. thus The using main the taskmodule of standard low the and control DCS high is softwareOPC to voltage framework control (OLE power for about for and 2000 all Process about powerhigh supplies 100 Automation) voltages for are low protocol. silicon handled, voltage as control well Detectoror as power interdependencies currents fast supplies in ramp of downs via the control, in detector, the 10 case low experimental of and higher cavern than problems, allowed etc. temperatures All this is ensured by evaluating value on the precision of each method. 3.3.8 Detector control and safetyThe system Tracker Detector Safety System (TDSS) anda tracker two Detector pillar Control system. System The (tracker DCS) TDSSLogical is ensures Controller) independently the system, safety, with occupying atemperature large 6 and PLC LHC (Programmable humidity racks. sensors areThe evaluated A tracker and limited out DCS, set of asparameters. of limit The a states around heart interlock of complementary 1000 the power hardwired DCS partner,Control supplies. is And controls, composed Data out Acquisition) monitors of PVSS anAustria, and industrial (Prozessvisualisierungs- SCADA chapter und archives program Steuerungssystem (Supervisory all from ETM important of freedom (absolute position andbeen orientation, fixed torsion by and requiring shear thezero. around average The the displacement values symmetry agree and axis) within rotation have 60 as well as torsion and shear to be from the DCUs situated onand all warning front levels end are hybrids defined andreported for control in temperature, units a relative CCUs. global humidity, voltages, warning Severalshutdown. currents, passive panel alarms etc. Information as and well from are as thethe limits tracker dry that, gas cooling system if plant, are surpassed, crucial the for would thermal safe result running screen, in and beam are automatic conditions accessible from and the tracker DCS and TDSS. 2008 JINST 3 S08004 . 2 m thick layer of silicon [16], and µ – 82 – 25 for all sensor types, the ENC varies between different module 3.36. A linear fit to these data yields the following dependence of 0. = p w/ [16]. Since p w/ In the strip-cluster finding the cuts for the signal-to-noise ratio, S/N, of the cluster seed / The mean most probable S/N values for all module types, together with their strip length, Assuming that a MIP creates 24 000 electrons in a 300 3.3. Measurements performed at low temperature (for the TEC, typically hybrid temperatures 10°C and 0°C were reached for hybrids with six and four APVs, respectively) are plotted + 10°C, while the TIB setup was operated at room temperature. Typical primary trigger rates for All parameters are archived toin ORACLE. the The global TDSS CMS DSS (tracker (DCS) DCS) and system Run is Control system. fully implemented 3.3.9 Operating experience and testPerformance results in test beam experiments The system performance of integrated structureschain of as the well silicon as the strip performance tracker of andtest the its silicon beam data strip experiments modules acquisition at themselves has CERN beencampaigns, and studied performed in the various in Paul May Scherrer and Institutarea, October (PSI), large 2004 Villigen substructures at (CH). of the In TIB, X5energy test TOB test of beam and beam 120 complex TEC GeV in were and theThe exposed a CERN to TIB tertiary west a setup muon secondary comprised beam pion asided with beam strings, prototype plus with muon half-shell four an energies structure double-sided ranging strings, ofthe mounted from layer so-called on 70 3, cosmic a rack, custom to equipped a support with 120 precise structure. GeV. sided mechanical eight For telescope-like and single- the structure TOB, two equipped double-sided with fourback rods, single- and was one used front petal inand [55]. the TEC These beam detectors, setups tests. respectively. corresponded The to− TOB The about and 1% TEC TEC of setup setups the were consisted completethe operated of TIB, pion at TOB beam one a were temperature 600 000 below pionswhich per particles spill are (a delivered) 2.2 corresponding s to long a period mean within occupancy a of 12 s 15 Hz/cm longneighbour SPS strips cycle during / total clusterThe are cluster noise 4/3/5 is for calculated TIB, byby 5/2/5 adding taking for the the single TOB seed strip and noise noise 3/2/5S/N as values of for the in a cluster TEC, quadrature module, noise (TIB, respectively. (TOB). a TEC)distribution, To or Landau determine and distribution the the convoluted most most with probable probable a value value Gaussian of for is the the fitted fitted function to is the quotedpitch signal-to-noise as and the abbreviations S/N. used insensors, the most following, probable are S/N values summarized of inlution 29–33 mode table (36–42) have in3.3. been peak observed For mode [55]. and thin For(38) 19–22 the (thick) and thick (20–24) 25 TEC TOB in (27) OB1 deconvo- (OB2) was modules foundIB1 a in (IB2) S/N peak of modules and typically exhibited 36 deconvolution a mode, S/N respectively of [17], 26 while (30) the in thin peak TIB mode and 18 (20) in deconvolution mode. assuming that the beamequivalent particles noise can charge, be ENC. treated Theof as common the MIPs, mode sensor, subtracted the whichpitch, noise S/N depends depends linearly can on on be the the used capacitance strip to length calculate and the the ratio between strip width and types according to the strip length.table Results for all module typesof except W1TID are summarized in versus the strip length in figure 2008 JINST 3 S08004 n 36) and ± for strip p · 5) 0. + n ( , . − − < e e x < 27) 47) p · ± ± 5) 405 590 0. − + ( + ( n L L ( · · /cm /cm − − e e 9) 2) – 83 – 1. 3. ± ± 6 9 36. 49. = ( = ( : L dec peak electrons for TEC (mean from all APVs in the setup) and (265 ENC 76) ENC ± of the cluster was reconstructed within x 299 ( electrons for TIB (mean from all APVs of TIB2 modules) in peak and deconvolution and p. The uniformity, defined as the ratio between the RMS and the mean of the respective 19) 38) ably, the noisiness of strips dependsread-out on mode external and conditions the such figures as given grounding should and be the regarded as APV estimates only. APV edge strips The common mode noise is the standard deviation of the common mode, calculated per APV The uniformity of the module performance along and perpendicular to the strip direction has Although no dedicated beam telescope was available, efficiency studies have been performed In the following sections the performance of TEC, TIB/TID and TOB during integration is ± ± • Numbers of dead and noisy strips are given below. While dead strips can be identified reli- C communication of all chips, tests of the gain of the optical connections, commissioning (i.e. 173 300 2 the ENC on the strip length from a certain number of events. The( mean common mode noise has been evaluated and amounts to both with the TOBseveral and layers of TEC modules. setups, Efficiencies exploiting of above the 99% fact have been that observed in inbeen all studied both such in studies. cases 2003 with the severalsingle-sided beam TIB strings modules penetrated in equipped a with test IB2 beamportion of modules experiment a at were layer the 3 mounted X5 half-shell, on complex. andstrips, operated a Two the at structure room strips temperature. corresponding read To to out study by theand a uniformity between three across 1000 APVs the and (on 8000 two events were differentcentre collected modules) of per were strip. gravity exposed A to cluster was a associated pion to beam, a strip if the mode, respectively. ( and pitch distribution, was 1.3% for thecluster cluster charge noise, uniformity was with of anfor the increase groups order close of of to 32 1.4%, thegroups adjacent but APV of dropped strips. 32 chip to strips edges. was 0.5% A measured. ifused uniformity The To for calculated investigate of the its separately uniform uniformity the particle along S/N density. the The strips,TOB of cluster a setup position 1.6% muon that along beam on was the was strip operated average couldwas in and be perpendicular the obtained of to from same the that 1.0% test of beam, for theto since TIB their the modules. centre strip of direction The of gravity, clustersaccumulated corresponding the were per to TOB binned bin. modules in length Both 24 intervals the intervals of uniformity according 5 of mm, cluster and charge and about S/N 1500 werePerformance events during found were integration to be 1.4%. Testing during integration consisted typically of checksI of the control ring functionality, tests oftuning the of chip operation parameters),ramping pedestal up runs to in 450 peak V, read-out and ofand deconvolution currents a mode, and functionality bias module check voltage and of hybrid the temperatures temperature through and the humidity DCUs, sensors. described. Two comments apply to all three sub-detectors: 2008 JINST 3 S08004 3.2 3.2 47.23 47.23 ±± ±± 4.567 / 7 4.567 / 7 ] 49.88 49.88 37 31 75 22 37 51 48 26 57 47 − 589.9 589.9 107 20 ± ± ± ± ± ± ± ± ± ± / ndf / ndf 22 ± χχ p0 p0 p1 p1 Strip length [cm] 18 ENC [e 1315 1182 1581 1488 1019 1068 1153 1140 1354 1517 Dec. mode 1681 C communication 16 2 ] 40 47 17 26 − 48 37 23 25 16 21 29 ± ± ± ± 14 ± ± ± ± ± ± ± 931 815 714 741 802 819 971 ENC [e 12 1155 1110 1057 1081 Peak mode 10 1.1 0.5 0.6 0.6 0.4 0.4 0.3 1.1 0.4 ± ± ± ± ± ± ± ± ± 8

25 27

S/N

Common mode subtracted noise [e noise subtracted mode Common

] 1100 1800 1700 1600 1500 1400 1300 1200 1000 Deconvolution mode 20.3 - 18.3 20.3 21.9 20.7 20.0 19.2 24.1 23.0 Dec. mode 1.0 1.3 1.4 0.7 0.5 0.6 0.5 1.1 0.6 ± ± ± ± ± ± ± ± ± – 84 – 36 38 S/N 35.5 25.8 29.5 33.1 31.7 29.2 28.6 42.2 37.8 Peak mode 1.942 1.942 27.34 27.34 ±± ±± 4.428 / 7 4.428 / 7 405 405 36.55 36.55 20 / ndf / ndf 22 χχ p0 p0 p1 p1 Strip length [cm] 18 85.2 88.2 [mm] 110.7 115.2 144.4 181.0 201.8 116.9 116.9 183.2 183.2 Strip length C, the TIB measurements were performed at room temperature. Sensors 16 ◦ 14 m] 80 µ 120 122 183 Pitch [ 12 81–112 113–143 123–158 113–139 126–156 163–205 140–172 10 before insertion and componentsdefects not have fulfilling been observed strict during quality integration.APVs criteria Typical defects (i.e. were are with broken rejected, many optical several fibers, noisy bad or dead strips), and missing or unreliable I show typically an increasedfixed noise noise cut and is are used for frequentlystrips, all flagged although strips. they These as are edge noisy, usually strips fully are especially efficient. included when in the a numbers of flagged 8 • Although all components (petals, rods, single modules in case of the TIB/TID) were tested W4 W5 W6 W7 OB1 OB2 W1TEC W2 W3 Module type IB1 IB2

900 800 700 Common mode subtracted noise [e noise subtracted mode Common

] 1100 1200 1000 Peak mode - Figure 3.36: Equivalent noiseTOB charge and after TEC common module types, mode in subtraction peak versus (left strip panel) and length deconvolution for mode (right all panel). Table: 3.3 Pitch,mode strip subtraction length, for signal-to-noise differenttemperatures ratio module of and types. below 0 equivalent The noise TEC charge and after TOB common measurements are for hybrid of type IB1 andTOB, IB2 layers are 1–4 used are equippedgeometries in abbreviated with TIB, with OB2 W layers sensors, are 1 wedge-shaped layerscorresponding and sensors to 5 used the 2 and in ring. 6 and TEC W1 and with sensors layers TID, have OB1 3 a with sensors. slightly the and different number geometry The 4, in sensor respectively. TID and TEC. In the 2008 JINST 3 S08004 3)% 4 mA ± ± 33°C, respec- + 3.38, left, for all 4)% and (21 3.38, right, indicating ± 23°C and + 75 electrons in this normalization. ± 3.37, left side, the common mode subtracted – 85 – 3.37). In addition, the number of ADC counts in the FED was 2)% in both read-out modes, as shown in figure 0. -axis in figure ± x 5 15°C and mean silicon and hybrid temperatures of about + of complete modules or singlemishandling during chips. insertion or Most cabling. oferable Since the risk, the not problems exchange all of are defective components assumed componentsintroduced bears have by to a any been consid- be following exchanged. handling caused step, Additional such by defectsbelow as could should cabling thus be of the be tracker. regarded The as numbersthe a given single snapshot sub-detectors. reflecting the situation right after integration of The flatness of the noise across the APV is a good indicator for the quality of the grounding. The mean common mode noise, calculated per APV, amounts to (22 During integration a flaw in the crimping of the connectors of the multiservice power cables Strips are counted as noisy or dead if their noise is more than five times the RMS of the , and comprises 18 petals that share nine control rings and four cooling circuits. After integra- φ of the mean intrinsic noisenon-defective in APVs peak of and TEC+). deconvolution mode, respectively (figure The relative spread of the totaldivided noise (before by common the mode subtraction), mean i.e.relative noise, the spread RMS both is of calculated the (2. noise per APV, can be used to quantify the flatness. The TEC Performance during integration The TEC petals were integrated sector-wise,in where one sector corresponds totion one eighth of of one a sector, TEC acoolant read-out at test of the full sector was performed at room temperature, with the tively. was found. After allobserved such during integration connectors was had very robust. beennoise In replaced figure of on both all TECs, stripsdepends the of system on both performance the TECs gainAPV is of (scale shown on the upper for optical chain, deconvolutionconverted to mode. the ENC according noise to the Since was following method: the normalizedand with a to a measured nominal nominal APV the digital noise gain APV digital of output of 1to output MIP/mA 8 for MIPs of thin or the 200 sensors, 000 the electrons. heightdifferent of optical This the method channels digital allows and output a delivers corresponds direct ancharge. comparison approximate of Cross-checks absolute the with measurements calibration from cosmic of muon thethis data equivalent scaling noise performed agrees during with TIB/TID the integration realcapacitance indicate ENC and that within thus 10–20%. on Furthermore, the thestrips strip noise was normalized depends length, to on the i.e. the strip on length strip ofapplied the modules to module of TEC- ring type. data 1 to (8.52 cm). For accountthan for In this addition the TEC+ reason a fact correction the that data. was they noise were ofmode The taken all with per common other APV. To chip mode extract parameter subtraction settings themean was mean common noise, performed mode a subtracted assuming noise gaussian a amounts was to constant fitted 1693 to common the distribution. The resulting that the grounding scheme implemented by the TEC works well. noise above or below the mean noise of the respective APV. Edge strips are counted as noisy, if 2008 JINST 3 S08004 ] - 0.1 4000 - 12 - 0.002) 0.002) 3500 ± ± 15°C. The [ADC counts] 10 − 0.08 3000 3081216 entries Mean = 2049 e Width = 112 e Scaled noise [e 8 Peak Mode Mean = (0.025 Deconvolution Mode Mean = (0.025 2500 0.06 Number of entries = 15070 6 2000 Relative RMS of total noise 1500 4 0.04 1000 2 500 0.02 0 0 5 4 3 2 1

10 10 10 10 10 Number of strips of Number 0 4 3 2 1

10 10 10 10 Number of APVs of Number – 86 – 1 0.9 0.04) 0.03) ]] ± ± -- 40004000 12 0.8

- 35003500

-

[ADC counts] 0.7 10 Peak Mode Mean = (0.22 Deconvolution Mode Mean = (0.21 30003000 0.6 Number of entries = 15070 Scaled noise [eScaled noise [e 3861760 entries Mean = 1693 e Width = 75 e 8 25002500 0.5 Relative common mode noise 0.4 6 20002000 0.3 15001500 4 0.2 10001000 0.1 2 500500 0 4 3 2 1

10

0 00 10 10 10 e 3.38: Ratio between common mode noise and mean intrinsic noise (left panel) and ratio 22 APVs of Number 55 44 33 11

1010

1010 1010 1010 1010 Number of strips strips of of Number Number their noise is more than sevenchannels sigma in above TEC+, the while mean TEC- has noise. 2.7 In per total, mille there of are bad 3.0 channels. TIB per and mille TID of performance bad during integration During TIB/TID integration [56], modulesand and tested AOHs extensively were for assembled functionality, onto(corresponding including half to pedestals, layers a once and string a disks inTID). mother the cable Completed TIB was disks and completed and threeduring half single-sided which layers or the were five structures then double-sidedcomplete were modules subjected half operated layers in to and at the disks a a were burn-in read2–3 silicon out cooling in sensor during cycles a these temperature during tests. climatic of a Typically, theassembled five chamber, about structures day into underwent measurement the complete period. TIB/TID+ After-wards andlast disks TIB/TID- integration and structures half operations and layers were shipped were to performed,cabling CERN, of such where the as the margherita. connection of fibers to the final ribbons and Figur between the RMS of thepeak total and noise deconvolution and mode the for mean all total non-defective APVs noise of (right TEC+. panel), calculated per APV, in Figure 3.37: Normalized commonof mode ring subtracted 1 noise of sensors) all ofDetails are strips both described (scaled TECs in to the (left text. the panel) strip and length the TOB (right panel), in deconvolution mode. 2008 JINST 3 S08004 C to ◦ 10 + 15°C, hybrid temperatures − electrons in the TID. Measure- 24°C and the hybrid temperature 3.37, right. The tail to high noise + 76) ± 14°C (TIB single-sided modules) and APV 1246 ( 10°C and hybrid temperatures of − + – 87 – electrons in the TIB and 87) for deconvolution mode. Scaling and common mode subtraction have been ± 3.39 1233 4°C (TID double-sided modules) to ( electrons. − 112) 30°C. ± + After optimization of the grounding scheme, the noise performance observed in the TIB and During integration, a sensitivity to pick-up noise has been observed, which leads to non-flat, The normalized noise of all TOB strips is shown in figure Due to this wing-like noise structure, a special algorithm has been adopted to evaluate the Only very few permanent defects, corresponding to 0.6 per mille of lost channels, have been 30°C show a mean noise about 20% larger. In contrast to the TEC, a strip is flagged as dead 2049 ranging from ments with a silicon sensor temperature of about TID structures was very good. Fornoise the of TIB all and strips, TID except structures for the two scaledconditions TIB common and half-shells mode three for subtracted half-shells which data for were whichis taken the shown under in proper non-final figure running grounding scheme wasimplemented not as yet previously implemented, described inCMS this conditions, section. with These a data mean have silicon been sensor taken temperature underparameters nominal of set about as intendedfit, for amounts this to temperature range. The mean noise, taken from a gaussian + if its noise isdifferently. below 75% The of total the number averageTIB/TID-. of noise bad of channels the is APV, 4.4 and per APV mille edge in strips TIB/TID+TOB are and performance not during 3.4 integration treated per mille in Fully equipped and tested rods werethe integrated cooling cooling connection was segment-wise. soldered After and acabled, a first and leak functional test a test, was full performed. read-out Thenthese test, the measurements, including cooling the segment pedestals, silicon was was sensor performedabout temperature at was room about temperature. During wing-like common mode subtracted noisefor distributions. layers This 3 sensitivity and is 4, especiallythe which effect pronounced are is equipped worst for with modules single-sided mountedof 4 closest the to APV the highest modules, CCUM. noise and Defining amplitude as within (takenbaseline, a these figure and from layers of counting a merit all parabola the APVs ratio fit with tothe a the wings ratio is noise above about distribution) 1.25 30% to as in theIn “in layers flat the total, 3 noise wings”, 11.4% and the 4 of fraction and of allverified about APVs that APVs 7% in either are and with 1% found adjusted in to clusterincrease layers cuts be in 1/2 or in the and with cluster 5/6, the a width respectively. wings linear and online according occupancy common is to mode negligible. this subtraction criterion. the values It comes from has the been non-flat noise( distributions. The mean noise from a gaussian fit amounts to number of dead and noisyiterative strips. procedure, A and parabola strips is areRMS fitted of flagged to the the as distribution noise of bad fit distribution if residuals of their from each the noise APV fitted deviates in function. moreintroduced an during than TOB ten integration. times Includingbad the the channels number amounts of to noisy 0.6 and per dead mille strips, in the TOB+ number and of 1.9 per mille in TOB-. 2008 JINST 3 S08004 2 A − µ 16]. cm eq n 14 . The radial 1 10 − × 1 for TIB/TID and TEC 2 − 20°C between the irradia- − cm eq n 14 10 15°C. × − 8 . – 88 – (left). However, the required depletion voltage stays . The effect of annealing was simulated by heating the 3.1.1, the silicon strip tracker will suffer from a severe 2 − 3.40 cm eq n 14 for TOB, assuming an integrated luminosity of 500 fb 10 2 − × , and three TIB IB1 modules were subjected to a proton fluence of 2 1 cm − , and one OB2 module was subjected to a neutron fluence of about 2 eq [57]. Two TEC W5 modules were irradiated with a proton fluence of cm n − to 2. eq 2 14 2 n cm − − 10 eq 14 n cm cm × 10 eq 14 eq 5 n n × for explanation) were irradiated with a proton fluence ranging from 0. 10 14 1 14 × 3.3 10 10 e 3.39: Normalized common mode subtracted single strip noise for TIB (left panel) and TID dependence of the fluence both for fast hadrons and neutrons is described in detail in [15, As expected from inversion from n- to p-type doping, the full depletion voltage increased To ensure that both the FE electronics and the silicon sensors can be operated safely and To study the performance of complete irradiated modules, several OB1 and OB2 modules 7 z × × 5 2 about 1. below 500 V, which is thedependence maximum of depletion the voltage depletion for voltage which on the annealing sensors time are was specified. studied The as well and found to be in 0. 1. tion or annealing steps. Measurements were performed at with the fluence, as shown in figure modules for 80 minutes athours. 60°C and To prevent afterwards uncontrolled storing annealing, them the at modules room were temperature stored for at at least two to 0. Irradiation studies As already discussed in detail in section Figur (right panel), in deconvolution mode. Details are described in the text. level of radiation during its 10 year long lifetime: up to 1 and up to 0. and Hadrons are expected to dominatewhile in neutrons backscattered the off inner the part electromagneticfactors of calorimeter of 1.5 dominate the and further tracker, 2.0 outside. up on Safety the to fluence a are radius typically applied of for aboutwith TIB/TID and satisfactory 0.5 m, TOB/TEC, performance respectively. after suchprotons an have irradiation, been several irradiation carried tests out.clotron with of Neutron neutrons the irradiation and Centre de was Recherches usually dua Cyclotron, performed mean Louvain-la-Neuve, energy at which of delivers the 20 neutrons MeV isochronous with (hardness cy- has factor 1.95 been relative to carried 1 out MeV neutrons e.g.26 [58]). MeV at Proton proton the irradiation beam compact (hardness cyclotronand factor of a 1.85 the beam relative Forschungszentrum spot to diameter Karlsruhe, 1 of MeV where 1 neutrons) cm a is with available. a current(table of 100 2008 JINST 3 S08004 m µ ] ] 2 2 m (upper 1.4 /cm /cm µ 2.5 eq eq n n 14 14 1.2 2 1 peak mode deconvolution mode Fluence [10 Fluence [10 SNR versus fluence 3.41. For thick sensors, A/cm, which is in good 1.5 0.8 m (left panel) and 320 17 µ − 0.6 1 10 × 0.4 0.5 27) 0.2 61]. 0. ± 0 0 1 5 0 5 4 3 2 0

30 25 20 15 10 4.5 3.5 2.5 1.5 0.5 79

] [mA/cm density Current

Signal-to-noise ratio Signal-to-noise 3. 3 ( – 89 – ] ] 2.5 2 2 1.4 /cm /cm eq eq n n (right) the dependence of the current density on the fluence is 14 14 2 1.2 3.40 1 1.5 Fluence [10 Fluence [10 proton irradiated (peak) proton irradiated (dec) neutron irradiated (peak) neutron irradiated (dec) 0.8 SNR versus fluence 1 0.6 m (lower curve) sensors for an annealing time of 80 minutes at 60°C. Right panel: 0.4 µ 0.5 0.2 Sr source. Due to an increase of the noise and a decrease of the charge collection efficiency, 0 0 5 0 0 35 30 25 20 15 10

90

600 500 400 300 200 100 e 3.41: Signal-to-noise ratio versus fluence for modules with 500 e 3.40: Left panel: Variation of depletion voltage with fluence for OB1 (triangles), OB2

The leakage current is expected to increase with fluence, leading to a larger heat dissipation Measurements of the signal-to-noise ratio, S/N, of irradiated modules have been performed

Signal-to-noise ratio Signal-to-noise Depletion voltage [V] voltage Depletion and increased noise. In figure shown. The current related damage rate,volume defined and as equivalent the neutron current fluence, increase, amounts scaled to to 20°C, per sensor excellent agreement with the Hamburg modelcorresponding [59], to with a a 10 minimum day at shut 80 down minutes period annealing at time, room temperature. thick sensors (right panel) in peak (filled symbols) and deconvolution mode (open symbols). agreement with literature and measurements from test structures. with a the S/N is expectedfluence to for thick decrease and thin with sensors fluence. inthe both S/N read-out The modes decreased is from dependence shown in 23 ofa figure (35) decrease the to from S/N 15 18 on (24) (21)above to the in 95% 13 deconvolution even accumulated after (18) (peak) 10 was mode, years observed. while of operation These for at figures thin the ensure sensors LHC a [60, hit finding efficiency of Figur Figur and W5 (dots on upper80 curve) minutes and IB2 after (dots each on irradiationcurve) lower and step. curve) 320 modules, The after curves an correspond annealing to time calculations of for 500 Current density, scaled to 20°C, versus fluence after annealing for 80 minutes at 60°C. 2008 JINST 3 S08004 scintil- 4 4.2. – 90 – crystals make them an appropriate choice for operation at 4 ), short radiation length (0.89 cm) and small Molière radius 3 ) crystals mounted in the central barrel part, closed by 7324 crys- 4 29 around the peak wavelength [67]) and the needed uniformity68] [ 2. = at 18°C [65]): at 18°C about 4.5 photoelectrons per MeV are collected in 1 − C 66]. Longitudinal optical transmission and radioluminescence spectra are shown ◦ 1% 2. 4.1. To exploit the total internal reflection for optimum light collection on the photodetector, the The electromagnetic calorimeter of CMS (ECAL)61200 is a lead hermetic tungstate homogeneous calorimeter (PbWO made of Electromagnetic calorimeter tals in each of theAvalanche photodiodes two (APDs) endcaps. are used A as(VPTs) preshower photodetectors in detector in the the is endcaps. barrel placedwhich and The in is vacuum use fast, front phototriodes has of of fine high granularity the andenvironment. density endcap is One crystals radiation crystals. of has resistant, the all allowed driving important criteria the characteristicsphotons in design in of the the of the design LHC postulated a was Higgs the calorimeter boson. capabilityprovided to by This detect a capability the homogeneous is decay crystal enhanced to calorimeter. by two the good energy resolution 4.1 Lead tungstate crystals The characteristics [62] of theLHC. PbWO The high density(2.2 (8.28 cm) g/cm result in alation fine properties granularity and and other a qualitiesduction compact have of calorimeter. been optically progressively clear, In improved, fastof recent leading and these years, to radiation-hard production PbWO the crystals crystals mass [63, isabout pro- of64]. 80% of the The the same light scintillation orderperature is decay of (− emitted time magnitude in as 25 ns. the LHC The bunch light crossing output is time: relatively low and varies with tem- Chapter 4 both APDs and VPTs.420–430 The nm crystals [64, emit blue-green scintillation light with a broad maximum at in figure crystals are polished after machining.makes the For light fully collection non-uniform polished alonghigh crystals, the refractive the crystal index truncated length. (n pyramidal The shape effect is large because of the is achieved by depolishing oneuniform lateral because face. the In crystal the facesthe endcaps, are photodetectors the nearly attached are light parallel. shown collection in Pictures is figure of naturally barrel more and endcap crystals with 2008 JINST 3 S08004 70]. 4.9). The damage reaches a dose-rate dependent – 91 – crystals. 4 crystals with photodetectors attached. Left panel: A barrel crystal with the 4 e 4.2: PbWO The crystals have to withstand the radiation levels and particle fluxes [69] anticipated through- Figur out the duration offormation the of colour experiment. centres dueconsequence Ionizing to is radiation a oxygen produces wavelength-dependent vacancies loss and absorptionlation of impurities bands mechanism, light in through transmission a the without damage the lattice.transparency changes which to with The can the injected practical be scintil- laser tracked light and (section corrected for by monitoring the optical upper face depolished and thepanel: APD An endcap capsule. crystal and In VPT. the insert, a capsule with the two APDs. Right Figure 4.1: Longitudinal opticalright transmission scale) (1, for left production PbWO scale) and radioluminescence intensity (2, equilibrium level which results from a balance between damage and recovery at 18°C [64, 2008 JINST 3 S08004 φ 22 projec- η or 22× -φ and η φ 479. The barrel gran- 1. 0.0174 in < × | η 0. The longitudinal distance | 3. , form a half barrel. and the weight is 67.4 t. φ < | 3 in η | ◦ < . They are mounted in a quasi-projective η 479 at the rear face. The crystal length is 230 mm 2 – 92 – , resulting in a total of 61200 crystals. The crystals , each containing 400 or 500 crystals. Four modules, η η 26 mm 85)-fold in 72]. 4.4). and . The barrel crystal volume is 8.14 m 0 and (2× 4.3 φ at the front face of crystal, and 26× All services, cooling manifolds and cables converge to a patch panel at the external end of In each module, the submodules are held in partial cantilever by an aluminium grid, which The endcaps (EE) cover the rapidity range 1. The centres of the front faces of the crystals are at a radius 1.29 m. The crystals are contained 2 ) with respect to the vector from the nominal interaction vertex, in both the o supports their weight from theby rear. pincers At that the cancel the frontby relative the the tangential submodule displacements. action free of ends The a are submoduleby 4-mm connected cantilever setpins. is together thick Not reduced cylindrical all plate thefrom where submodules a the are total front connected of of to ten.is the the The transmitted submodules cylindrical portion are plate to of but supported the only thebetween aluminium four submodule the grids rows load modules of in taken the at [73].rear the different end front modules Each through by via module the the is grid the cylindricalhoused by supported conical plate on a and webs the spine positioned interspaced front beam. in face Thesupermodule. the of spine supermodule the is The HCAL at provided cylindrical barrel, the with plate allowingmonitoring pads the in system which installation front (see slide and below) of into and support the rails the of supermodule holes each for also single its provides optical the fibres. fixationthe supermodule. of Eighteen the supermodules, each covering 20 between the interaction point and the endcap envelope is 315.4 cm, taking account of the estimated To ensure an adequate performance throughoutradiation LHC hardness operation, the properties crystals quantified are as requiredgreater an to than exhibit induced approximately 3 light times attenuation thehave length crystal been (at length measured high even when to dose the rate) inducetrapolation damage a to is LHC specific, saturated. conditions cumulative Hadrons indicates reduction thatgood of the ECAL light damage performance [71, will transmission, remain but within the the ex- limits required for 4.2 The ECAL layout andThe mechanics barrel part of the ECAL (EB) covers the pseudorapidity range geometry to avoid cracks aligned(3 with particle trajectories, so that their axes make a small angle separated by aluminium conical webs 4-mm thick,1700 are crystals assembled (figures in a supermodule, which contains ularity is 360-fold in have a tapered shape, slightly varying with position in tions. The crystal cross-section correspondsmm to approximately 0.0174 corresponding to 25.8 X in a thin-walled alveolar structure (submodule). Thealuminium alveolar layer, wall is facing 0.1 the mm crystal, thick and anda is two made special layers of coating an of is glass fibre-epoxy applied0.35 resin. mm to inside To the a avoid aluminium submodule, oxidation, and surface.types 0.5 of mm crystals, The between each nominal submodules. submodule contains crystal To only reduceshape. to a the pair number crystal In of of shapes, total, distance different left there is and are rightdifferent reflections 17 types, of such according a pairs single to of the shapes. position in The submodules are assembled into modules of 2008 JINST 3 S08004 ). The 0 X Web 1F 5 crystals (supercrystals, Alveolar structure Connectors Module 1 Web 1R and a length of 220 mm (24.7 Module 2 2 Crystals Web 2 Tablet Web 1F Module 3 Web 1R 28.62 mm – 93 – Web 3 Module 4 Web 2 . The temperature of the system has therefore to be maintained Web 4 1 and the weight is 24.0 t. The layout of the calorimeter is shown − Web 3 3 C ◦ % Crossplate 4) shows the barrel already mounted inside the hadron calorimeter, while 0. Crossplate Figure 4.3: Layout of the ECAL barrel mechanics. Web 4 ± 4.6 8 3. − ( grid, with the crystals pointing at a focus 1 300 mm beyond the interaction point, Grid plate Aluminum Cylindrical -y , a front face cross section 28.62× x 2 shows a picture of a Dee. 4.5. Figure C to preserve energy resolution. The nominal operating temperature of the CMS ECAL is 4.7 ◦ The number of scintillation photons emitted by the crystals and the amplification of the APD 30 mm 05 0. constant to high precision, requiringthe a read-out cooling electronics system and capable of of keeping the extracting± temperature the of heat crystals dissipated and photodetectors by stable18°C. within The cooling system has to complywater with this flow severe thermal to requirement. stabilise The system the employs detector. In the barrel, each supermodule is independently supplied are both temperature dependent.overall Both variation of variations the are response negativebeam to with [74] incident to increasing electrons be temperature. with temperature The has been measured in test figure endcaps crystal volume is 2.90 m in figure giving off-pointing angles ranging from 230× to 8 degrees. The crystals have a rear face cross section or SCs) consisting ofDees. a carbon-fibre Each alveola Dee structure. holdspartial supercrystals Each 3 662 on endcap the crystals. is inner divided andrectangular These outer into are circumference. 2 contained The halves, in crystals or and 138 SCs standard are SCs arranged in and a 18 special shift toward the interaction point by 1.6consists cm when of the identically 4-T shaped magnetic field crystals is grouped switched in on. mechanical The units endcap of 5× 2008 JINST 3 S08004 – 94 – Figure 4.4: Front view of a module equipped with the crystals. Extended tests of the cooling system have been performed with good results [74]. Residual effects caused by a possible variationthe of extreme the case power dissipated of by electronicsconstant the term switched electronics of on were the measured and energy in off. resolutiontemperature due corrections. The to thermal conclusion fluctuations is will that be contributions negligible, even to without the with water at 18°C. Thethermally water decouples runs them through from a the thermal silicongrid, screen tracker, placed connected and in in through front pipes parallel. of embeddedis the in Beyond placed crystals the the which to aluminium minimise grid, the apipes heat distribute 9 flowing the mm from water thick through the a layer read-outclose manifold electronics contact of to with towards insulating a the the set foam very crystals. of front (Armaflex) components aluminium end Return cooling mounted electronics bars. on (VFE) These cards these bars and cards. are absorbBergquist) in the A is heat thermally used dissipated to conductive by provide paste the a (gapfacing good each filler contact board. 2000, between produced This the plate by electronicalso is components coupled produced and to by a the Bergquist). metal cooling plate Both barthe by the dose a gap expected conductive pad in pad and the (ultrasoftcharacter the ECAL gap or gap pad, endcaps loss filler after of have performance. 10 been years irradiated at with the twice LHC and have shown no change in 2008 JINST 3 S08004 Supercrystals Preshower Modules – 95 – Preshower End-cap crystals Figure 4.6: The barrel positioned inside the hadron calorimeter. Crystals in a supermodule Dee Figure 4.5: Layout of themodules, supermodules CMS and electromagnetic endcaps, calorimeter with the showing preshower the in arrangement front. of crystal 2008 JINST 3 S08004 m, which µ ). The configuration of the and a pair is mounted on each crystal. 2 5 mm – 96 – . 4 4.1. Figure 4.7: An endcap Dee, fully equipped with supercrystals. The sensitivity to the nuclear counter effect is given by the effective thickness of 6 4.3 Photodetectors The photodetectors need to be fast,magnetic radiation tolerant field. and be In able addition, toand operate because be in of insensitive the the longitudinal to 4-T small particles light traversing yield them of (nuclear the counter crystals, effect they should amplify magnetic field and the expectedin level of the radiation barrel led and to vacuumgain phototriodes different of choices: in the the avalanche vacuum endcaps. photodiodes phototriodes, Thesurface compared coverage lower to on quantum the the efficiency avalanche back and photodiodes, face internal is of the offset crystals. by their larger 4.3.1 Barrel: avalanche photodiodes In the barrel, the photodetectorsn-type are silicon Hamamatsu behind type the p-n S8148 junction)CMS reverse avalanche structure ECAL. photodiodes (i.e., Each (APDs) with specially APD the developedThey has for bulk are an the operated active at area gain 50and of and 18°C 5× are read listed out in in table parallel. The main properties oftranslates the APDs into at a gain signal 50 from100 MeV a deposited minimum in ionizing the PbWO particle traversing an APD equivalent to about 2008 JINST 3 S08004 C. Each ◦ 2 C A Ω m ◦ 0.2 2% µ µ 5 V 2 ns 2 pF 3 nA 10 5 ± ± 50 nA ± 5 mm < ± 0.5 < 0.1%/V 0.2%/ < 75 45 2.1 5× ± 80 ± ± 340–430 V 6 4 3.1 2. − ) /dT ) V dM 1%/V at gain 50), to keep this contribution · /d 3. dM ' · V /d – 97 – 2 Co irradiation and 1 month of operation at 80 dM 60 n/cm 1/M 13 = 10 V Table: 4.1 Properties of the APDs at gain 50 and 18°C. Cf source to monitor the effectiveness of the screening procedure in selecting A, but that no other properties will have changed. Small samples of APDs were 251 µ Typical dark current Dark current after 2× Breakdown voltage - operating voltage Quantum efficiency (430 nm) Capacitance Excess noise factor Effective thickness Series resistance Voltage sensitivity of the gain/M (1 Temperature sensitivity of the gain (1/M Rise time Dark current Sensitive area Operating voltage The gain stability directly affects the ECAL energy resolution. Since the APD gain has a high For ECAL acceptance each APD was required to be fully depleted and to pass through a to the resolution at the levelstability of of per the mille, voltage the has APDs toelectrical require be a system of very characteristics: the stable order noise, power of ripple, supplyand few voltage system: tens long regulation the of and term mV. absolute This periods. precision, requirementthe applies A for CMS to short custom ECAL all high in the voltage collaboration (HV) withradiation, the power the CAEN HV supply system Company system is [77]. has located To in been remainThe the far designed HV CMS from service channels for high cavern, are some doses 120 floating of mthe and away leads. from use the sense detector. The wires system todesigned is correct for based for this on variations in application a thewith standard (A1520E). voltage the control The drop board crate SY1527 on controller (SY1527) integrate via hostingSY1527 a an 8 on internal PC boards the bus capable expressly and ECAL of differentconcept detector communicating interfaces so control that are each system available HV to (DCS). channelhosted integrate is The on implemented the board a on a single design separate A1520E is module board.500 and based Each V up channel on with to can maximum 9 a give channels current a modular can of bias be 15 voltage mA. to In 50 total, APD there pairs are from 18 0 crates to and 144 boards. Temperature dependence on the bias voltage (α radiation resistant APDs. APD was tested toof breakdown 300. and required The toluminosity screening show LHC conditions and no for testing significant over 99% aimedwith noise of to hadron increase the irradiations ensure up APDs installed [76] to reliable inrisen it a operation the to is ECAL about gain for [75]. 5 expected 10 Based that yearsirradiated on the with tests under a dark high current after such operation will have screening procedure involving 5 kGy of 2008 JINST 3 S08004 = 2.6. | η | , to verify ◦ at ). The mean 2 ◦ n/cm ; one VPT is glued to 26 2 14 ◦ Co source to 20 kGy. 60 10 to the field direction, is typically ◦ capsule, a moulded receptacle with – 98 – m pitch) allowing them to operate in the 4-T magnetic field. µ emission, of less than 10%. Irradiation of VPTs in a nuclear reactor to 4 negative temperature coefficient thermistor from Betatherm, used as temperature showed a loss in anode sensitivity entirely consistent with discolouration of the at the outer circumference of the endcaps and 20 kGy and 7× 2 2 n/cm n/cm 14 13 The operating gain of 50 requires a voltage between 340 and 430 V. The APDs are sorted One 100kΩ All VPTs are tested by the manufacturer before delivery, without an applied magnetic field. The estimated doses and particle fluences for 10 years of LHC operation are 0.5 kGy and 10 10 90% of that in zero field [79]. × drift compensation is possible dueused to to the monitor presence the environment on temperature the for crate adjustments of of the temperature voltage probes setting. according that to can their be operating voltagea into mean bins gain 5 of V 50. wide, and then Each paired pair such is that mounted each in pair parallel has in a Each VPT is 25 mm in diameter, with an active area of approximately 280 mm sensor, is embedded in every tenth APDdiffering by capsule. the There Kapton are length twenty-two and different types by of the capsules, presence of the thermistor. 4.3.2 Endcap: vacuum phototriodes In the endcaps, the photodetectorsResearch are vacuum Institute phototriodes Electron (VPTs) in (type St.a PMT188 Petersburg). single from National gain Vacuum stage. phototriodes are Theseanode particular photomultipliers of devices very having were fine copper developed specially mesh (10 for CMS [78] and have an foam, which is then glued onelectronics the by back Kapton of flexible each printed crystal.position circuit within The the boards capsules submodule. of are Each connected variable capsuleand receives to length, the a the bias dictated protection read-out voltage by resistor. through an the RC capsule’s filter network to the back of eachVPTs crystal. have a One mean Betatherm quantumand thermistor efficiency a is of mean embedded the gain into of bialkaliis each 10.2 photocathode slightly at supercrystal. (SbKCs) reduced zero and of field. The there 22% isrespect When at a placed to 430 modest in nm, the variation a of field strong response overresponse with axial the the in magnetic range angle field, a of of the magnetic the angles response VPT> field relevant axis to of with the 4 T, CMS with endcaps the (6 VPT axis atAll VPTs 15 are also tested onfield receipt up by CMS to to 1.8 determine T.spanning their the Each range response of as device angles a covered is by functionat the measured of endcaps. random, magnetic at In addition, are a at least also setsatisfactory 10% tested of operation of the at in tubes, the angles selected a full with field 4-T of respect CMS. superconducting to magnet, the at5× applied a field, fixed angle ofSample faceplates 15 from every glass production batchThe were faceplates irradiated with were a requiredcorresponding to to show PbWO a transmission loss, integrated over thefaceplate wavelength caused range by the accompanyingto gamma the dose working (100 voltage, with kGy) bothincrease [80]. in gammas anode Irradiations and current, neutrons of attributable showed tubes to no biased the adverse production effects, of apart Cerenkov from light an in the faceplates. 7 2008 JINST 3 S08004 – 99 – 800 V respectively. The high voltage system is based (like the APD + 600 V and + 4.8. The anode sensitivity of a VPT may show a dependence on count rate (anode current) under The system consists of a control and trigger unit located in the Service Cavern, and sets of The VPTs are operated with the photocathode at ground potential and the dynode and anode biased at system) on CAEN SY1527 standard controlwith crates, standard although 12-channel for A1735P the boards, VPTs, eachbias, channel the the rated crates VPT at are gain 1.5 equipped is kV close and to saturation 7However, care thus mA. the must At voltages be the do taken operating not have to toinput minimise be ripple controlled of very and precisely. the noise, since sensitive these preamplifiernetworks would that mounted feed is directly inside into connected the the to supercrystalsusing the (SC), one anode. close SY1527 to crate Filtering thethe equipped is twelve VPTs. achieved with output with just An channels RC two will entiremay A1735P initially endcap be boards. be is used used, biased at On leaving alower four each later bias spare stage, board, voltage. channels. The if only HV noisy The eight fromdesigned channels the spare of develop HV CAEN outputs which power distribution supplies can system is be which transmittedover-current, recovered to provides and by the hard-wired operating SCs sensitive protection via at current a against a crates. custom monitoring. over-voltage Each and crate hosts For up each tosix five output endcap, input cards, cards, this with receiving each the system output HVsystem card is from serving the are housed up power mounted to supplies, in twelve in and SCs. up five twois The to racks served HV (one supplies by and for two distribution coaxial eachCavern cables endcap) to (one the located detector, for in via the intermediate the patch anode, panels. Serviceand one the The Cavern. for cable total cable capacitance the Each length forms dynode) is SC part approximately runningVPTs of 120 via from the m five filter the filter network. Service cards, Inside each an servingis SC five 25% VPTs. the (RMS). HV The They is spread are distributed in therefore to anodethe sorted the sensitivity into highest among six the sensitivities groups VPTs at which the arecircumference. distributed outer on This circumference the arrangement grading endcaps provides with to aacross the roughly the lowest endcaps. constant sensitivities sensitivity at to the the inner transverse energy certain conditions. For example, inHz, the absence following of a a period magneticseveral of field, hours if high the to rate count return operation, rate topercent the falls the to to anode a nominal a sensitivity few value. few may tensoperation), rise The the of suddenly magnitude effect percent. is and of strongly take the In suppressedincorporate effect or the a absent. may presence light Nevertheless, vary pulser of it from system a hasof on a been strong at the few judged least magnetic ECAL prudent 100 field endcaps. to Hz (as of Thisthat pulses in delivers they of a are normal approximately constant kept CMS 50 background “active”, GeV even rate equivalent in energy the to absence all of VPTs, LHC thus interactions. ensuring pulsed light sources mounted on theIII circumference light of emitting each Dee. diodes TheLEDs (type light are LXHL-PR09), is driven whose produced by by peak Luxeon highpulses emission have output amplitudes wavelength current of is 1.2 op-amps 455 A (LT6300 andseven nm. a from LEDs widths and Linear The of associated 80 Technology). drive-circuits. ns.circuits The A These and single are drive LEDs light configured mounted source on singly consists double-sided of orThere printed a in circuit are cluster pairs, boards four of housed with such within enclosures the metal distributed drive- sources. enclosures. around the circumference A of schematic each Dee,figure representation housing of 19 light the system for distributing the light pulses is shown in 2008 JINST 3 S08004 5 crystals × s l e a t s s l y r u C p s l 4

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b E i r m L t o s r i s. f Figure 4.8: Distribution system for VPT stabilisation light pulses. d ( µ 3 ≈ ) or a super-crystal for EB and EE respectively. It consists of five Very Front End (VFE) φ An all-silica optical fibre (CF01493-43 from OFS (Furukawa)) is inserted into a hole drilled The on-detector electronics has been designed to read a complete trigger tower ( 5 The motherboard is located in front of the cooling bars. It connects to 25 photo-detectors Each LVR card [81] uses 11 radiation-hard low voltage regulators (LHC4913) developed by × η s cycle of the LHC circulating beams. µ into the lens of eachlight LED source and are collects combined light into by aa single dual bundle role, that transports acting light alsofrom to as each a diffusing diffusing part sphere sphere of which is the has distributedof distribution to optical network up fibres to of that 220 also the individualcrystal, carry laser detector which the monitoring carries channels laser the system. through monitoring VPT, and the pulses. Light reaches set system the Light is VPT is synchronized via injected reflection to from via pulse the during the front a rear of fraction face the of crystal. of the The a 3 4.4 On-detector electronics The ECAL read-out has toprecision. acquire Every bunch the crossing small digital sums signalsgenerated representing of and the the sent energy deposit to photo-detectors in the with alatency trigger trigger high of system. tower speed are and The digitized data are stored during the Level-1 trigger in boards, one Front End (FE) board,Voltage two Regulator (EB) card or (LVR) and six a (EE) motherboard. Gigabit Optical Hybrids (GOH), one Low and to the temperature sensorsEB using Kapton and flexible EE printed respectively. circuitbias boards In voltage. and the coaxial Two case cables motherboards for of areabout the connected 120m to EB with one the remote CAEN motherboarddistributed sensing. HV distributes and supply In and filtered located the filters by at case a the athe of separate APD distance anode the HV signals. of EE filter Five the of card, theseOne operating hosting cards LVR voltages as and serving for five well five VFE the VPTs the cards each VPTs decoupling plug are are into capacitor installed the for into motherboard. each super-crystal. ST-microelectronics and the RD49 project at CERN. The regulators have built in over-temperature 2008 JINST 3 S08004 800 Mbps

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o o t 40 ns t shaping o ec h for the APD configuration and about 4000e P det − The signals are pre-amplified and shaped and then amplified by three amplifiers with nominal A schematic view of the signal read-out is given in figure Figure 4.9: Schematic viewphotodetectors of (in the the on-detector figure electronics: thePre-Amplifier the case and of scintillation digitized APD light is by is presented),output collected 40-MHz to the by the ADC; signal FE a card, is where radiation-hard shaped datatrigger by pipeline words buffer and are a (LVDS) sent Trigger Multi-Gain adapts Primitives at Generation 25 the (TPG) nsprovide are rate, ADC in performed; while data both are cases transmitted on the receiptoff-detector data of electronics a serializer over Level-1 and trigger; a GOHs the distanceFE laser of cards, diode, about providing sending 100 Level-1 the m. trigger signals (TRG)and A and on out control clock (CTRL a token data). (CLK) fibre signals, ring to together connects the with groups control of data in protection, output current limitation and an inhibit input. The output voltages of 2. tributed to the FE card(DCU) and ASICs on via each the LVR card, motherboardAll interfaced to regulators, to the excluding the VFE FE the card, cards. onepowered monitor providing down all Three power input remotely Detector to and by Control the output an Unit controlvoltage voltages. external distribution interface inhibit. (LVD) of block the to Four FE onepower LVR card, supply cards radiation located can are and about be magnetic connected 30 field by m away tolerant a in Wiener passive racks low low attached voltage to thegains magnet of yoke. 1, 6 and 12.ASIC This developed functionality in is 0. built into the Multi Gain Pre-Amplifier (MGPA) [82], an of 580 mW at 2.5 V.8000e The output pulse non-linearity is less than 1%. The noise for gain 12 is about the MGPA are digitized in paralleldeveloped in by a 0. multi-channel, 40-MHz, 12-bit ADC, the AD41240 [83], and 12.8 pC corresponding to is done by a CR-RC network with a shaping time of contains three programmable 8-bit DACs totest-pulse adjust generator the with baseline an to amplituderead-out the adjustable electronics ADC over by inputs. the means full An of dynamic integrated range. an 8-bit DAC allows a test of the 2008 JINST 3 S08004 04dB 0. ≈ s to the off-detector electronics µ 40 MeV for gain 12. 5 ≈ m technology, adapts the low voltage 7. µ ≈ 25 . In the case of the EE the five strip sums are φ – 102 – 3.3). The GOH consists of a data serializer and laser driver chip, m technology called FENIX. Each VFE card is serviced by a FENIX chip. Thus the µ If the read-out switches to a lower gain as the pulse grows, it is prevented from immediately A radiation-hard buffer (LVDS_RX) developed in 0. The FE card] [84 stores the digitized data during the Level-1 trigger latency in 256-word- The ECAL serial digital data links are based on the technology developed for the CMS The VFE and FE electronics are controlled using a 40-MHz digital optical link system, con- 25 selects the highest non-saturated signal astogether output with and reports two the bits 12 coding bits the of ADC the number. corresponding ADC reverting to the higher gain whencould the be read pulse out falls: at once the thelower higher gain pulse gain for has again, the the declined next read-out to five is the samples. then point forced where to it continue reading out at the deep dual-ported memories, so calledenergy pipelines. sum Five of such pipelines the and 5in the channels 0. logic once to every calculate bunch the energy crossing is are summed integrated in intotransmitted strips an by of ASIC five 5 developed GOHs crystals(TCC), (see along below) while to in the the“fine-grain” off-detector case electromagnetic electronics of bit, Trigger set the Concentrator to EBthe identify Card a electromagnetic energy shower profile sixth candidates of FENIX on the sums thebit trigger basis the is tower. of transmitted five The using strip trigger one towerdata, sums energy GOH ten and sum to 40-MHz calculates together the samples with the per TCC. the channel, On fine-grain are receipt transmitted of in a Level-1 trigger the corresponding differential output signals of the AD41240identical to read-out the channels single are ended integrated CMOS(DCU) into inputs for a on the VFE the measurement FE card, of card. together thenoise with APD Five obtained leakage a with currents the Detector and VFE Control the cardscounts Unit read-out installed for of into gains the 12, supermodules thermistors. 6 is and typically The 1 1.1, respectively. 0.75 This and corresponds 0.6 to ADC Data Concentrator Card (DCC) using antogether identical with GOH. the The LVDS_MUX Clock ASIC and provide Control the Unit interface (CCU) to ASIC the token rings. Tracker analog links (section the GOL, and a12-channel laser NGK diode receiver module with complete an theerating optical at attached link 1310 fibre system. nm pigtail. wavelength It over usesis a single negligible. Fibres, distance mode The of fibre fibres optical about op- links 100 interconnections are m. and operated The at a fibre 800Mbit/s. attenuation of trolled by the off-detector Clock and Controlto System the (CCS) token boards. ring link A board, 12-fibre generatinghas ribbon an 8 is electrical token connected control rings ring, which the connect to tokenlaser groups ring. monitoring of Each eight electronics supermodule to module ten FE (MEM).two cards The consecutive including FE system the cards two has malfunctioning, FE by redundancy, cards means as of ofusing the long two 4 independent as fibres bi-directional each. there optical links, It are provides no level fast one and trigger slow control information functions. and While theof the 40-MHz the fast FE clock, control and the transmits VFE slow the electronics controland as comprises APD well the leakage as configuration currents. the read-out of status information, temperatures, voltages 2008 JINST 3 S08004 φ ◦ mezza- aa SMSM

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DCC DCC DCC Oneset Oneset 86] is illustrated schematically in fig- aa Dat Dat DAQDAQ sector. ◦ TTSTTS FEFEFE SRPSRPSRP 8mFECs 8mFECs 8mFECs CCS CCS CCS – 103 – TTCTTC aa gger gger ii Dat Dat TrTr SLBsSLBsSLBs 9 9 9 TCCTCCTCC plus the fine-grain bit) are time aligned and sent to the regional trigger T E aa DAQ DAQ Dat Dat RCTRCT Dat Dat Figure 4.10: Schematic view of ECAL off-detector electronics. The clock and control system (CCS) board distributes the system clock, trigger and broadcast The trigger concentration card (TCC) [87] main functionalities include the completion of Each TCC collects trigger data from 68 FE boards in the barrel, corresponding to a super- Front End Controller cards (mFEC). The mFEC interfaces optically with a FE token ring. The 4.10. The system is composed of different electronic boards sitting in 18 VME-9U crates (the ure CCS, TCC and DCC modules) andtem). in 1 The VME-6U system crate serves (the both selectivedata the read-out read-out DAQ processor, and and SRP, data sys- the reduction trigger based paths. onIn the In the selective the read-out trigger DAQ flags path, path, computed at the by eachfinalized the DCC SRP and bunch performs system. synchronized crossing, in trigger the primitive TCC generation before started transmission in to the the FE regional boardscommands, calorimeter is configures trigger. the FE electronics andThe provides TTC an interface signals to are the translated trigger andnine throttling encoded system. by suppression of clock8 edges mFECs of and the sent CCS to board the control a supermodule. the trigger primitive generation and their transmissionmezzanines [88] to at the each synchronization bunch and crossing, link theto board classification (SLB) of the each Selective trigger tower Read-out and Processor itstrigger transmission primitives at during each the Level-1 Level-1 latency trigger for accept subsequent signal, reading by and the the DCC. module, storage and of from 48 the FE boardssector. in In the the endcaps corresponding endcaps, to triggerform the primitive a inner computation mapping or is between outer completed part theand in of collected the a the associated pseudo-strips trigger 20 TCCs, trigger towers. which data The musttation encoded from of trigger per- the the primitives trigger (8 different tower bits supercrystals for the nonlinear represen- 4.5 Off-detector electronics 4.5.1 Global architecture The ECAL off-detector read-out and trigger architecture [85, processors by the SLB. The triggersubsequent primitives reading are by stored the in DCC. the In TCCendcap the during region, barrel the a region Level-1 DCC a latency serves single for 4 TCC TCCs is covering interfaced a with 40 1 DCC. In the 2008 JINST 3 S08004 is issued, inhibits new trig- Busy Warning Overflow 5 crystals. The FE card stores the data, in 256- 90] is responsible for collecting crystal data from up – 104 – s. The selected events are read out through the data acquisition µ 4.5.3). Data integrity is checked, including verification of the event-fragment header, in particular the Input and output memory occupancy is monitored to prevent buffer overflows. If a first oc- The data concentration card (DCC) [89, The selective read-out processor (SRP) [91] is responsible for the implementation of the se- The read-out system is structured in sets of 5× to 68 FE boards.diodes). Two extra The FE DCC links also are collectsread-out trigger dedicated flags data to transmitted transmitted the from from read-outusing the the a of TCC programmable SRP laser selective modules read-out monitoring system. and algorithm. data the Whenthe (PN operating A selective SRP in data flags the selective indicate suppression read-out the mode factorFE level read-out. near of suppression 20 For that the is mustresponse application attained be filter of applied with zero to 6 suppression, the consecutive timesample positions crystal samples of and data pass the the of through 6 result a has a is given beenapplied finite compared to digitized impulse to the at a channel. a threshold. gain other If than any the time maximum, then zerodata suppression synchronization is check, not verification ofevent-fragment the parity event-fragment bits. word count Identified andlink error verification errors, conditions, of data triggered the timeouts by or inputincremented buffer event-fragment in memory checks, associated overflows error are counters. flagged Error conditions in are the flagged DCC in error thecupancy DCC registers level event and is header. reached, the Trigger Throttling System (TTS) signal requesting a reduction of the trigger rate. In a second level a TTS signal gers and empty events (eventstransmitted with to just the the central header CMS DAQ words usingof and a 528 trailer) S-LINK64 MB/s, data are while link stored. an interfacereduction. at DCC average a events transmission maximum Laser are data data triggers rate flow (for offrequency crystal 200 and MB/s transparency synchronously is monitoring) with expected will thewhich after are occur LHC ECAL read-out with following gap. data a a TTC No test programmable allowing enable VME data command. access reduction A to is VME physics memory events applied is and used for laser for events these local in DAQ, events, spy mode. lective read-out algorithm. The systemtical is algorithm composed boards by (AB). a The AB singlepartitions. computes 6U-VME the The crate selective flags with read-out are twelve flags composed iden- into of different the 3 calorimeter associated bits, read-out indicating units. the suppression level that must be4.5.2 applied The trigger and read-outThe paths ECAL data, in the form ofsor, trigger for primitives, each are bunch sent to crossing. the Theof Level-1 trigger calorimeter the trigger primitives summed proces- each transverse refer energy deposited to inthe a lateral the single profile tower, trigger and of tower the the and fine-grain electromagnetic consist bit, shower.from which The the characterizes accept global signal, trigger for in accepted about events, is 3 returned system to the Filter Farm where further rate reduction is performed using the full detector data. clock cycles deep memory banks,crossings awaiting after a the Level-1 collision trigger(TPG) occurred. decision pipeline (section during It at implements most most 128 of bunch the Trigger Primitives Generation 2008 JINST 3 S08004 91] so that geometry of φ , η 5 mechanical units (supercrystals). – 105 – 5 crystal sets correspond to the trigger towers. Each trigger tower -oriented strips, whose energy deposits are summed by the FE board trigger φ selective, read-out can be performed by the Selective Read-out Processor [86, After time alignment the ECAL trigger primitives are sent at 1.2 Gb/s to the regional calorime- The TPG logic is implemented as a pipeline, operated at the LHC bunch crossing frequency. In the endcaps, the read-out modularity maps onto the 5× In the barrel, these 5× the HCAL and Level-1 trigger processor. Thecrystals. supercrystals are These divided into groups groups are ofare of 5 contiguous variable composed shape of and several referredthe pseudo-strips to read-out and as structure may pseudo-strips. does extend not Theperformed over match trigger on more the towers the than trigger detector. structure, oneoff-detector only supercrystal. electronics. The the Hence, total pseudo-strip each Since transverse summations endcap FE are energyused board to of is transmit served the the by trigger trigger 6 optical primitives. towercontrol links, As and is 5 in Level-1 of computed the trigger them barrel signals. by being an the electrical serial link transmits theter clock, trigger, via 10-m-long electrical cables,tron/photon where and together jets with candidates HCAL are trigger computed primitives, the as elec- well as the total transverse4.5.3 energy. Algorithms performed by theThe trigger TPG primitive generation logic implementedVFE on boards the to FE determine boards theassigned. combines trigger the The primitives digitized logic and samples must thefrom delivered reconstruct the bunch by the continuous crossing the stream signal to of amplitude successive which digitizations. to they be should assigned be toThe each trigger bunchcrossing primitives are delivered52 to clock the regional cycles, calorimeter of triggersignal which after processing 22 a performed are constant in the latency usedclock of VFE for cycles. and transmission FE The over barrel remaining the electronicsof part has optical the of a fibres digital the total signals. and latency duration cables.there of is Ideally, is only mainly the The a 17 due output signal to of inthis formatting this the case processing and tower the should time resulting output be alignment from is athe a a fine-grain stream word bunch bit. of encoding crossing The zeroes, the endcap exactly pipeline unless summedand 17 is implements transverse clock split very energy between cycles similar in the before. algorithms. the on-detector Theregional and tower In calorimeter trigger off-detector together trigger primitives electronics with are in expected 50 to clock be cycles in delivered to the the endcap case. 4.5.4 Classification performed by theAbout selective read-out 100kB per eventif has all been channels allocated are forvolume, read ECAL out, data. exceeds thisthe The target suppression full by applied a ECAL factor to datameasure of a for of nearly an channel the 20. event, takes energy account Reduction in of of a the energy region, data deposits the in trigger the tower vicinity. sums are For used. the In the barrel the read-out is divided into 5 pipeline to give the total transverseis energy of served the by tower, two called the opticalelectrical main links serial trigger for link primitive. which sending Each transmits FE the the data clock, and control and trigger Level-1 primitives trigger respectively signals. and a third However the sizes of the trigger towers vary in order to approximately follow the 2008 JINST 3 S08004 653 before reaching the first 1. = η before reaching the second plane. Thus about 95% 0 – 106 – X 5-crystal trigger towers. In the endcap, the situation is 5 GeV), then the crystals of this trigger tower (25 crystals in 2. 6. It also helps the identification of electrons against minimum > 2. T < | . η | noise < 5 GeV) then the crystals of this trigger tower and of its neighbour trigger towers , followed by a further 1 653 0 > X T The material thickness of the Preshower traversed at For debugging purposes, the selective read-out can be deactivated and either a global zero The selective read-out algorithm classifies the trigger towers of the ECAL into 3 classes These classifications can be used flexibly to implement a range of algorithms by using differ- (225 crystals in total in the barrelto case) the are read medium with interest no class zero suppression. (E If a trigger tower belongs suppression (same threshold forselective every read-out channel) is or not no applied zerocan the be suppression selective used applied. offline read-out for flags debugging Even are purposes. when inserted the into the data stream and 4.6 Preshower detector The principal aim of the CMSa Preshower detector fiducial is region to 1. identify neutralionizing pions in particles, the and endcaps within improvesgranularity. the position determination of electrons and photons with4.6.1 high Geometry The Preshower is a samplingshowers calorimeter from with two incoming layers: photons/electronstor lead measure whilst radiators the silicon initiate deposited electromagnetic stripPreshower energy is sensors and 20 the cm. placed transverse after shower each profiles. radia- The total thickness of the modularity corresponds exactly to themore 5× complex. The simplified and illustrative description below is given for theusing barrel the case. Level-1 trigger primitives.thresholds. The Trigger energy towers deposited with in an each energytrigger above trigger towers, the tower those higher is threshold with compared are an to classifiedan energy 2 as energy between high below the interest the 2 lower threshold thresholds as as low medium interest interest, trigger and towers. thoseent thresholds with to define the classes, andwithin different each suppression class. levels The for the algorithm read-out currentlyeven of used at the in high channels the luminosity. simulation The provides algorithm adequateinterest data functions class reduction (E as follows: if a trigger tower belongs to the high the barrel case) are readand with it no is not suppression. the neighbour Ifsuppression of a at a about trigger high 3σ tower interest belongs trigger tower, to then the the low crystals interest in class it are read with zero sensor plane is 2 of single incident photons startstrips showering in before the the two second planes sensorsilicon is plane. sensors, orthogonal. The including A orientation the major of effectsLevel-1 design trigger the of consideration performance shower is the that spread, profile of all primaryECAL the lead vertex crystals outer is behind edge spread covered it. of etc. by the For lead the For should inner optimum follow radius the the shape effect of of the the exact profiling of the lead is far less 2008 JINST 3 S08004 divided into 2 61 mm m; a minimum ionizing µ configuration. Around 500 ladders are -y x for 8 micromodules) and an inset shows the , with an active area of 61× 2 – 107 – 63 mm shows a complete ladder (Type-1 4.11 The micromodules are placed on baseplates in groups of 7, 8 or 10 that, when coupled to Figure Each silicon sensor measures 63× The ladders are attached to the radiators in an particle (MIP) will deposit 3.6are fC precisely of glued to charge ceramic in supports,below), this which also and thickness support this (at the is front-end normal in electronics incidence). turnof assembly glued (see the The to sensors an sensors in aluminium the tile directionis that parallel constructed allows to in a the two 2 strips. parts, mmfront-end In overlap with electronics of order a + the to glass supports active improve fibre is part noise insulation known performance in as the a between. tile micromodule. The combination ofan sensor electronics + system motherboardspacing (SMB) between placed silicon above strips the (atwhilst the micromodules, the edges) form spacing in between a adjacent strips ladder. micromodules intwo within adjacent Dees The ladders a join is ladder this normally is spacing 2.5 2.4 is mm. mm, increased For to the 3.0 region mm. where the Figure 4.11: Photograph ofmodule. a complete type-1 ladder, with an inset showing detailscritical, of and a thus a micro- circular shapeon has each side been of chosen. the The beam lead pipe, planes with are the arranged same in orientation two as the Dees, crystal one Dees. 32 strips (1.9 mm pitch). The nominal thickness of the silicon is 320 micromodule. required, corresponding to a totalchannels. of Further around details 4 of 300 the micromodules layout and can 137000 be found individual in read-out [92]. 4.6.2 Preshower electronics Each silicon sensor is DC-coupledtion, to a signal front-end shaping ASIC and (PACE3 [93])192-cell voltage that deep sampling. performs analogue preamplifica- memory Data at 40 is MHz. clocked into an on-chip high dynamic range 2008 JINST 3 S08004 – 108 – of around 3 for a single MIP; with a S/N approaching 10 for a single MIP. Groups of up to 12 ladders are connected via polyimide cables to form control rings. Off- The Preshower-DCC [96] is based on the DCC of the ECAL except it is a modular design For each Level-1 trigger received, 3 consecutive cells of the memory, corresponding to time • Low gain: For normal physics running with a large dynamic range• (0-1600 High fC) gain: with For a MIP S/N calibration purposes [94], with a reduced dynamic range (0-200 fC) but samples on the baseline, near thea peak 20 MHz and multiplexer. after The the PACE3 has peak, a are switchable read gain: out for all 32 channels through The PACE3 are soldered to front-endto hybrids the that SMBs. contain The embedded SMBs contain polyimideThe AD41240 cables digital 12-bit to ADCs data connect that are digitizeK-chip the then data [95]. from formatted 1 and or The 2counter packaged K-chip PACE3. information by also to the a performs data second synchronizationvia packets gigabit Preshower and checks optical transmits ASIC on hybrids the (GOH). known the data Thecontrol as to data, SMB system. the also the adds Preshower-DCC contains (see an bunch/event below) implementation of the CMS tracker detector CCS cards (identical tofor those the of Preshower) the communicate ECAL viaeach except digital control optical not ring. hybrids all The (DOH) FEC full mounted mezzanines Preshower on comprises are 2 4 mounted planes of of the 12 SMBsincorporating control in rings a each. VME host boardhas mounted allowed with a development optoRx12 collaboration [97] withponents mezzanines. but the in TOTEM The a experiment different modular which manner. design uses Thean the optoRx12 Altera incorporates Stratix same an GX com- FPGA NGK that 12-way performs opticalnoise data receiver reduction, deserialization, and pedestal bunch subtraction, crossing common-mode assignment, chargesparsified reconstruction data and from zero suppression up [98]. totransmits The 3 data optoRx12 packets to are the mergeddata event by builder spying another via as FPGA an well on Slink64 asto the interface. allow TTC host The the and board plug-in host VME that of board interfaces. an then alsoprovide additional more provides A mezzanine data board reduction provision mounted power has if with been necessary FPGAs/processors in made that the could on future. the host board 4.7 ECAL detector control system The ECAL Detector Controlparticular System various (DCS) kinds comprises of the environmentalwhich parameters, monitoring will as of generate well the as alarms detectordamaging the and status, the ECAL hardwired detector in safety hardware. interlocks system (ESS), (ESS), It in Precision consists Temperature case Monitoring of (PTM), of the Humidity Monitoring situations following (HM),Low sub-systems: High which Voltage (LV) Voltage (HV), and ECAL could monitoring Safety of lead System the(temperatures to laser in operation, capsules, the temperatures cooling on systemout the and by of printed the the circuit DCUs parameters on boards, the APD VFE leakage and LVR currents) boards. read Further details on the ECAL DCS are available [99]. 2008 JINST 3 S08004 9). 4.2. Therefore a major task for the ECAL DCS – 109 – °C of the crystal volume and the APDs is achieved. The PTM is designed 05) 0. ± 18 ( The whole DCS software is based on the commercial SCADA package PVSS II (chapter A distributed system is built outapplication of is several implemented applications dedicated as towhich a summarizes the the Finite DCS overall sub-systems. ECAL State DCS Every Machine statusDCS and (FSM) supervisor itself is incorporates and linked a linked to FSM. Finally, the tostatus this general and ECAL a alarms CMS and DCS supervisory to supervisory receive level, commands node, which in are order propagated to down to communicate the the relevant sub-systems. 4.7.1 Safety system The purpose of the ESS(expected] [100 to be is around to 25–30°C) monitor andelectronics the the compartment, water air to leakage temperature control detection of the cable, propercally which the perform functioning is VFE pre-defined of routed and safety inside the actions FE the cooling and environment system generatepair interlocks and of in to temperature case automati- sensors of any is alarmbuilt-in placed situation. at redundancy, One the is centre independent of ofLogic each the module. Controller DAQ (PLC) The and situated read-out control system, ininterlock links with the signals and full Service will based Cavern. be on routed In athe to case Programmable cooling the of PLC relevant any crates in critical in orderof reading order to the to hardwired stop ESS switch the PLC off water itself the flow is HV on monitored and a by LV the certain and/or general cooling CMS line. detector4.7.2 safety The system. proper functioning Temperature The number of scintillation photonsboth emitted temperature by dependent, as the described crystals in section andis the the amplification monitoring of of thestability APD the of are system’s temperature andto the read verification out that thermistors, placed the onthan required both 0.01°C. temperature sides In of total the there crystaltemperature are volume, of with ten the a incoming sensors relative and per precision outgoingthe supermodule. better cooling grid water, and Two whereas one immersion two on probes sensors theThe per measure thermal module, read-out the screen one is side on of based the onwhich crystal the functions volume, completely Embedded monitor independently Local the of crystal Monitoring the temperature. to DAQ Board and the (ELMB) control back links. surface developed of In by every addition, ATLAS tenthout sensors crystal fixed by in the the barrel, DCUs and placed onethat on in the the 25 water crystals VFE cooling in boards. system the can endcap, With indeed are this read ensure temperature the monitoring required it temperature has stability4.7.3 been [74]. shown Dark current The APD dark currentstructure will by increase neutrons. during Partelectronics CMS of noise, operation this due due damage to to anneals,current an of bulk but increasing all damage the APD dark channels overall of current, will effect the over be will continuously the silicon be monitored. lifetime an of increase the in detector. The dark 2008 JINST 3 S08004 5). The mean value of the precision 8% within most supermodules, al- 4.12). 1. ≈ ≈ η 15%. In the endcap the VPT signal yield, ≈ – 110 – A comparison of the cosmic ray and high energy electron data demonstrates that the precision All 36 supermodules were commissioned in turn by operating them on a cosmic ray stand The ECAL amplification and digitization electronics located on the VFE electronics cards The main source of channel-to-channel response variation in the barrel is the crystal-to-crystal of the cosmic ray inter-calibrationrising is to better just than above 2% 1.5% at over the outer most end of (corresponding the to volume of a supermodule, the product of the gain,most 25%. quantum efficiency Preliminary and estimates photocathode ofmeasurements the area, of intercalibration has crystal coefficients an light are RMS yield obtainedinformation variation from and reduces of laboratory photodetector/electronics the al- response channel-to-channel [101]. variation10% in to Applying the less endcaps. this than 5% in the barrel andfor less a period than of aboutof one week. approximately 250 A MeV, muon permitting traversingECAL intercalibration the [102]. information full In length to 2006, of nine be120 a supermodules obtained GeV), were crystal in for intercalibrated deposits a with the an high geometrical energy barrel energyoperation. configuration electrons that One (90 reproduced of and the the supermodulesinterval incidence was of of exposed one particles to month. during the CMS the The beam distribution resulting on of two sets differences having occasions, of an separated inter-calibrationthe RMS by statistical coefficients spread precision an are of of 0.27%, in the indicating close individual a measurements agreement, reproducibility (figure within 4.7.4 HV and LV The DCS system operates thethe CAEN independent HV configuration system of the viavoltage HV an and channels OPC the with server. current various delivered set The byECAL of functionalities Safety each voltages, include System channel the can and monitor switch the of off database the the recording HV of via the the individual settings. boardrequire The interlocks. a very stable lowVoltage voltage Regulators to that maintain guarantee constant the signal requiredage stability amplification. Regulator of The Boards the system are signal equipped uses amplification. with Low are The DCUs Low read that Volt- measure via the the voltageswhich and Token are these Ring. operated measurements and monitored Overall by the the DCS. power is supplied by MARATON4.8 crates (WIENER), Detector calibration Calibration is a severe technical challenge forwhich the are operation negligible of at the low CMS precision ECAL.per need Many mille to small is effects be treated approached. with ECAL caregiving the calibration as absolute the is energy level naturally scale, of seen and precision a asas of channel-to-channel intercalibration. composed a relative of few component, The which a essential is global issues referredshowers component, are to in uniformity different locations over in the the whole ECALto ECAL in each and data other. recorded stability, at so different that times are accurately related variation of scintillation light yield which has an RMS of though the total variation among all barrel crystals is 2008 JINST 3 S08004 . γγ → 20 nb) 0 ≈ π mass recon- regions. The η γγ → η ) and S , are abundant (σ r with physics events. As a C e γγ . A complementary method, eν b + t γγ m → A s → e 0 u t → π g p in situ W u e H )/(C A S S

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(the photon coming from inner bremsstrahlung). Entries per bin per Entries γ − µ + µ → The final goal of calibration is to achieve the most accurate energy measurements for elec- Z Figure 4.13: Distribution of the relativesured differences between with the high inter-calibration energy coefficients electrons mea- and those obtained from cosmic ray muons. trons and photons. Different reconstruction algorithmselectromagnetic are objects, used i.e., to unconverted estimate photons, the electronshaving energy and their of converted different photons, own each correction offrom functions. them the simulated data At by present accessingsome the these of generated “algorithmic” the parameters of corrections, corrections the for are Monteprovided example Carlo that obtained the simulation. containment test For corrections, beam this databeing is is used an only used acceptable as to procedure a verify meansother the of cases, interpolating simulation, where and so the extrapolating that, test fromconversions data beam in and taken provides bremsstrahlung effect, in radiation no the the in useful simulation test theof information, beam. is tracker using for In material, information example it that in will can issues beparticularly be related important useful to obtained to channels find from which ways data can takenstep be in of used situ intercalibrating to with regions obtain the of running such the detector. information, ECAL and Two to also one assist another, in are the under investigation: and 2008 JINST 3 S08004 10% the < 4.14). The magni- was assumed, together with a 1 − s 2 − is used as the measure of the crystal ) t cm ( regions of the endcap at high luminosity. 33 η 10 /PN ) t × 2 = APD( – 113 – crystals show a limited but rapid loss of optical trans- L 4 ) = t R( 4 V reverse bias), making them much less sensitive to type inversion + m with µ 7 The evolution of the crystal transparency is measured using laser pulses injected into the tude of the changes isluminosity dose-rate in the dependent, barrel, and to is tensThe expected of performance to per of cent range the in from the calorimetertransparency 1 high changes would or were be 2 they unacceptably per not measured degraded cent and by at corrected these low for. radiation induced crystals via optical fibres.using silicon The PN photodiodes. response PN ispletion type zone normalized photodiodes (≈ were by chosen the because ofthan laser their the pulse very faster narrow PIN magnitude de- photodiodes. measured Thus mission under irradiation due totransmitted light. the production At of the colour ECALbetween working centres damage temperature which and (18°C) absorb annealing the a resultsmission, damage fraction in if anneals the a of and dose dose-rate the the rate is dependent balance transparency constant. equilibrium behaviour In of between the LHC the varying collision conditions optical runs of trans- and LHC running machine the refills result (figure is a cyclic machine cycle consisting of a 10 hourunder coast irradiation followed was by modeled 2 on hours data filling taken time. during The a crystal crystal behaviour irradiation in the4.9 test beam. Laser monitor system Although radiation resistant, ECAL PbWO transparency. The laser monitoring system [69]section. performing Because this of task the is different optical brieflytillation paths light, outlined the and in changes spectra the in of crystal next the transparencyis cause injected a not laser change necessarily pulses in equal response and to to the the the scin- laser change light in which response to scintillation light. For attenuations Figure 4.14: SimulationFor this of illustrative crystal example a transparency luminosity evolution of at LHC based on test-beam results. 2008 JINST 3 S08004 (4.1) 0 for SIC crystals). An 1. ≈ α is characteristic of the crystal which α , α  ) ) 0 t t R( R( 80 Hz, and the pulse timing jitter is less than 3 ns  4.15. This power law describes well the behaviour ≈ = – 114 – ) ) 0 53 for BCTP crystals, and t t ( =440 nm, is very close to the scintillation emission peak, ( 1. S S λ ≈ . The lasers are operated such that the full width at half maximum of the pulses is 3 − shows the basic components of the laser-monitoring system: two laser wavelengths are represents the response to scintillation light and ) t ( 4.16 S 30 ns. The lasers can be pulsed at a rate of =796 nm, is far from the emission peak, and very little affected by changes in transparency, which relationship between the changes can be expressed by a power law, Figure 4.15: Relation between thea transmission given losses crystal. for The scintillation signals light are and followed for during laser the light irradiation for and the recovery. where depends on the production method (α example of this relationship isof given all in the figure crystals that have beenin evaluated the in barrel the for test both beam, low and and this high formula luminosity is at expected to LHC. be4.9.1 valid Laser-monitoring system overview Figure used for the basic source. 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5 ' . & ,$9$,) < < ! e 6 ( ) / > /.=6-,/" r ( . . " >-1'6)CM'" - ) 9 6 6 u ( * - ' = ' g - 6 '=* i "6 - ) 1 , 1 / )/I" ) ' -=//5/(",0.-"%D"1.)-'S"I.*./I5/("=*,/")/(C.S"U5CC" 61*5>)CC1"4DD">-1'6)C'"='5/("*) +-,/6L./I".C.>6-,/5>'$"H " F ( & ' ! " 67." -.'*,/'.$" #$%&" ' & The first laser system was installed in the CERN H4 test beam site in August 2001. The other There are 3 light sources, 2 blue and 1 near infrared. The duplication of the blue source The monitoring light pulses are distributed via a system of optical fibres. A fibre optic switch To provide continuous monitoring, about 1% of the 3.17 The pulse energy of 1 mJ/pulse at the principal monitoring wavelength corresponds to 3 TeV, and a linear attenuator allows 1% steps down to 13 GeV. The pulse intensity instability is LHC beam cycle will bescan used the to entire ECAL inject is monitoring expected light to pulses be about into 30 crystals. minutes. two The laser time systems needed were to installed at H4 in August, 2003. All three laser systems have been used in 1. less than 10% which guarantees a monitoringnormalization. precision of 0.1% by using the PN silicon photodiode provides fault tolerance and allowssource maintenance at of the one wavelength while usedconsists the to of other an track Nd:YLF is changes pump in laser, in its use,a transparency power supply Ti:Sapphire ensuring is and laser that cooler always and unit a available. and its correspondingEach controller, Each transformer, pair and source of a the YLF NESLAB and cooler Ti:S lasersEach for and source an their corresponding has LBO optics its crystal are mounted own inPC on diagnostics, the an based optical Ti:S controllers. 2 table. laser. Further fibre-optic details switches, can internal be monitors found in and [103]. corresponding at the laser directsbarrel the and laser 8 regions pulses in each to endcap).region 1 delivers A the two-stage of distribution light 88 system to mounted each calorimeter on crystal. each regions calorimeter (72 half supermodules in the 2008 JINST 3 S08004 1.1), (4.2) #

( # ( ) E " 4 ( # % % JB # , ? #, $ # : ) ( 6 * # 6 ( > % 0 ( ) ( ) - 4 I , E ( # * . # A 7 0 ( B & ) ' @ ' % #& ( : + F 789# 2 4 E $ I # " > # / ( 3 : * 1 ( > , " ? * ! ! % ) L + = . 6 & , 0 ) # ,%)# ( < 0 0 & 1 ( ; - #> #. ( ) 1 7 0 0 ) K ( # & 5 # & 5 , % + : , $ & $ ) $ % % > # * , ( / ) 6 ) ( ( * / " + + = . % G / . 4.19, showing that elec- 0 / &66)-,*# E , # < 2 0 # ( ; > #- ( #* , ' ( +,# F ) : > ) # H - ( & ( # : + * !30--+3(,01# / ) ) ' $ 9 " $ 6 + % ( #& ' 6 . ) 6 5 8 ( + 0 / & 4 - ( G # / & , & E A , + 2 / / F ( , 4 ( 0 ' " 6 % / #; ) ' & 2 4 " " # ) % $ 0)#8ADE - # ' 4 $ ( C 0 ( & 0 5 #5 " ( 2 6 7 # & ? ) 6 ( + # $ ) ) $ % / #* * 2 " " ( / ; ) #, & ( / 6 & J %  . 0 7 5 - & ) #, 5 ( - 0 6 4 ( the constant term. The individual contribu- E N < & / - 0 : 0 ( % 6. 2 , B = : # 0  C - B : ! 5 ' ( ( & % 9 E . 4 ( + ( $ < + 1 + ( % , 4 2 ) 0 & ) 0+(%,# ! # ! ( # % & & 3 .4!(-.12*.-+13)!+1+-5) " + ( - !"#  # 2 ( -+1&00/#23)#,4#2+66).)',# +'# " " 2 ? $ 2 1 ' & E 6 7 – 116 – ( + - . S " 0 . # " 0&*).# 7 / √ / 1 4 7 $ ? # ( " , " ) 1 # * $  ( * " $ + ) (?#!"#;%).)#.)0&,+C)#*+' ( # / / " % + ( 3 *%4;).# * 0 ) 1 + 1 7 = 2 " ( 0 ( # % ( % ( < - 2 / / & 0 @ 4 +'=)-,)2# & = - #  $ ? ) ! . ! ' ) ( ( & D E σ > ) the noise term, and - JB # . 4.17. The system achieves 0.0074% RMS over 7.5 days operation. C 7 " &('),+-# &'2# * : (  & ) # " " > ) N I - ( 1 I * 5 , $ ( * % % 0 ( / " L % ' % 3 #A)#*))'#+'#B ( * F $ :L: & # ( E 1 ( . # $ + L B , % % . ( # & ( : ) 0 # ) ) + & : )0)-,.45 & * & ( / * 9 , & ( 2 + $ * 0 ( % - % 1 # & &'# / # ) 0 ( & 2 7 . ( " 2 ) ? + - % ' , % $ # )0)-,.4'*# & & 1 64.# ? - % # ( ) )#)66)-,#-&' & $ $ ) % ( % 7 # :# * = , - " $ # $ & ' % for a group of 200 crystals measured for 11.5 days at the wavelength of 440 nm, ( " + ! '

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A beam test in 1999 [105] verified this prediction. N to what is measured in the preshower silicon detector. 75 The contribution to the stochastic term coming from fluctuations in the lateral containment is The contribution to the energy resolution from the preshower device can be approximately The effect of rear leakage is very small. Charged particles leaking from the back of the The photostatistics contribution is given by: 0. 1. non-uniformity of the longitudinal light collection, 2. intercalibration errors, 3. leakage of energy from the back of the crystal. 2. a photostatistics contribution of 2.1%, 3. fluctuations in the energy deposited in the preshower absorber (where present) with respect where is the excess noise factorvalue close which to parametrizes 2 fluctuations for in the the APDs, gain and process. is about This 2.5 factor for has the a VPTs. A value of samples only the beginning of1/E the shower, the resolution is, in fact, predicted to varyThe like constant term The most important contributions to the constant term may be listed as follows: The effects of the longitudinalrequirements light are collection made curve on the havebution crystal been due longitudinal studied uniformity. to in non-uniformity Requiring detail. be thecollection constant less Quite curve term than stringent in contri- 0.3%, the sets region a of limit the on shower the maximum slope of of the longitudinal light expected to be about 1.5% when energy is reconstructed by summing an array of 5 found for the barrel, giving the endcap the photostatistics contributionlargely compensates is for similar, the since reduced the quantum efficiency larger of collection the area photocathode. ofparametrized the as VPT a stochastic term with a value of 5%/ increase in response towards the reardeveloping of showers, the which crystal helps would toachieved otherwise compensate in the cause the rear barrel a leakage by low from depolishingsurface late one energy treatment long is tail. face incorporated of into the The the crystals crystal required to production response a process. designated is roughness.crystals This can also give a directthat signal this in effect the is APDs (nuclear negligibleenergy counter for distribution effect), isolated are but electromagnetic observed test even showers: beam at data no the show highest tails electron on energy the tested high (280 GeV). side of the about 2% when using 3× 2008 JINST 3 S08004 ≈ shows 3 bunch ) has been 1.3 + 1 − s 2 50 MeV. − 5 and ≈ − cm ). Figure ET 33 σ 10 × = 2 , and 30 MeV/channel at the end of the first year 1 − s – 119 – 2 − cm 33 [69]. 10 1 = − s 2 shows the reconstructed amplitude observed with and without pileup L − cm 4.20 34 10 = L region around the point of maximum containment (central impact 2 In the endcap it is intended to sort the VPTs in bins of overall signal yield, which includes the The signal amplitude in the test beam is reconstructed using a simple digital filter. The Neutron irradiation of the APDs in the barrel induces a leakage current which contributes to The shaped signals from the preamplifier output will extend over several LHC bunch cross- The magnitude of pileup noise expected at low luminosity (L 4 mm 1. electronics noise, 2. digitization noise, 3. pileup noise. × 40 MeV/channel in the highestnoise. gain range. The amplitude This reconstruction3 noise makes includes digitization use both samples electronics of taken andchannel-to-channel directly an correlated digitization before event-by-event noise. baseline the Its subtraction signal success using the pulse. is noise evidenced in by This the the procedure sum fact of removes that, 25 the after channels this small is procedure, almost exactlyphotocathode 5 area, times the the quantum noise efficiency in and ayield the single VPT are channel gain. used The [106]. for VPTs the withenergy equivalent larger higher of overall radius the signal regions noise of will be the more endcap. or less This constant, has with a the value result of that the transverse The noise term There are three contributions to the noise term: noise measured, after this amplitude reconstruction, for channels in barrel supermodules is the electronics noise. The evolution of theexperiment leakage has current been and extensively induced studied. noise The over expected theafter contribution lifetime is of one equivalent the year to 8 of MeV/channel operation at of operation at ings. When using a multi-weightssamples method are to used. reconstruct the Pileupsignals signal which amplitude noise overlap [106], will these up samples. occur to if 8 additional time particles reaching the calorimeter cause studied using detailed simulation ofcrossings minimum before bias and events after generatedcrossing the between was 3.5. signal. Figure Thein average the absence number of of any signal. minimumof The the bias fraction electronics events of noise events is per with small,small. bunch a showing signal that beyond at the low Gaussian luminosity distribution the pileup contribution to noise is Energy resolution in the test beam In 2004 a fully equippedolution barrel measured supermodule with was electron tested beams inexpectations having described momenta the above between CERN [107]. 20 H4 and Since beam. 250matrix the GeV/c depends The electron confirmed on shower energy the the energy res- contained particle inperformance impact a position of finite with the crystal respect calorimeter to was4 the studied matrix boundaries, by the using intrinsic events where the electron was limited to a 2008 JINST 3 S08004 5 matrix, × shows an example of 0.5 4.21 , 0.4 2 E (GeV) 0.3 30%) 0. 0.2 + ( trigger. The trigger was roughly centred 2 2  0.1 12 E 0. -0 20 mm  3 case. 5 matrix an energy resolution of better than 0.45% + 3 array of crystals. In this case a resolution of 0.5% – 120 – 2 × -0.1 × ×  E 3 crystals. A typical energy resolution was found to be: -0.2 8% √ × 2. 3 or a 5  -0.3 × = 2  -0.4 E σ  3 2 5 4

-0.5

10 Entries/0.0017 GeV Entries/0.0017 10 10 10 10 is in GeV. This result is in agreement with the expected contributions detailed in the earlier E The energy resolution has also been measured for a series of 25 runs where the beam was The energy resolution was also measured with no restriction on the lateral position of the in- 3 mm) on the point of maximum response of a crystals. In this case a shower containment cor- directed at locations uniformly covering a 3 (± rection was made as a functionin of the incident crystal, position, to as account measuredenergy from reconstruction for in the the either distribution variation of a of energies 3 is the found for amount 120 of GeV electrons energythe after contained energy correction distributions in for before the containment. and matrix. after Figure where correction the for For correction the is case smaller of than reconstruction for in the a 3 5 was measured for 120 GeV electrons. cident electrons except that provided by the 20× part of this section. (Results10% from improvement beam-test of runs the taken noise in performance.) 2006, using the final VFE card, show a where the resolution as a function ofenergy is energy reconstructed when by the summing incident 3 electrons were restricted in this way. The Figure 4.20: Reconstructed amplitude in ECALpileup barrel channels (dashed in histogram) the absence and ofsuperimposed a with on signal, the pileup without dashed (solid histogram. histogram). A Gaussian of width 40 MeV is 2008 JINST 3 S08004 124 area. 2 Fit results: = 0.53 GeV / m = 0.44 % ! Energy (GeV) ! 122 m = 120.0 GeV 20mm × 5 matrix, before and after correction for × 120 118 – 121 – 116 5 crystals With correction Without correction × 5 114 0

2000 1000 6000 5000 4000 3000 Number of events of Number containment, when 120 GeV electrons are incident over a 20 Figure 4.21: Distribution of energy reconstructed in a 5 2008 JINST 3 S08004 η is placed 5.3. Each wedge is 5.1) aligned parallel 3. The HB is divided tail catcher 3, the forward hadron 1. = < | | η η | | = 1.77 m) and the inner extent of sectors, resulting in a segmentation η – 122 – ) sectors. The plates are bolted together in a staggered 5.2), each half-section being inserted from either end of the 5.4). The innermost and outermost plates are made of stainless steel for = 2.95 m). This constrains the total amount of material which can be put in 2 using a Cherenkov-based, radiation-hard technology. The following sections describe 5. = Figure 5.1 shows the longitudinal view of the CMS detector. The dashed lines are at fixed | η | to absorb the hadronic shower. Therefore, an outer hadron calorimeter or values. The hadron calorimeter barrelcalorimeter and as endcaps seen sit from behind the thebetween interaction tracker point. the and outer The the extent hadron electromagnetic of calorimeterthe barrel the magnet is electromagnetic coil radially calorimeter restricted (R (R outside the solenoid complementing the barrel calorimeter. Beyond into two half-barrel sections (figure barrel cryostat of theplane. superconducting Since solenoid the and HB subsequently is verythe hung rigid barrel from compared load to rails is the distributed in cryostat, evenly great the along care the median has rails been [108]. taken to ensureAbsorber that geometry The HB consists ofHB–). 36 identical The azimuthal wedgesto are wedges the constructed which beam out form axis. of thesegmented flat The two into brass numbering half-barrels four absorber scheme (HB+ azimuthal plates ofgeometry and angle the (table resulting (φ wedges in is a shown configurationextent in that of figure contains a wedge no (figure projective dead material for the full radial structural strength. The plastic scintillator is divided into 16 The CMS detector is designedsignatures to of final study states. a wide Theof hadron range hadron calorimeters of jets are and high-energy particularly neutrinos processes important or involving exotic for diverse particles the resulting measurement in apparent missing transverse energy [1]. Hadron calorimeter calorimeters placed at 11.2 m fromto the interaction point extend thethese pseudorapidity subdetectors coverage in down detail. 5.1 Barrel design (HB) The HB is a sampling calorimeter covering the pseudorapidity range Chapter 5 2008 JINST 3 S08004 HF 3. The electromagnetic crystal 1. 3 = | ). The HB effective thickness increases I η | layer are grouped into a single mechanical at φ I 70% Cu, 30% Zn 8.53 g/cm 1.49 cm 16.42 cm λ of material. I λ – 123 – , resulting in 10.6 shows a typical tray. The tray geometry has allowed for construc- HE θ is 5.82 interaction lengths (λ ◦ 5.5 interaction length chemical composition density radiation length sin . The wedges are themselves bolted together, in such a fashion as to 5.2) consists of a 40-mm-thick front steel plate, followed by eight 50.5- 087) 0. ) as 1/ HO 087, HB 0. ) = ( The absorber (table ∆φ , Table 5.1: Physical properties of the HB brass absorber, known as C26000/cartridge brass. ∆η minimize the crack between the wedges to less than 2 mm. mm-thick brass plates, six 56.5-mm-thicktotal absorber brass thickness plates, at 90 and a 75-mm-thick steel back plate. The ( with polar angle (θ Figure 5.1: Longitudinal view(HB), of endcap (HE), the outer CMS (HO) detector and forward showing (HF) the calorimeters. locations of the hadron barrel calorimeter [69] in front of HB adds about 1.1 Scintillator The active medium uses the welllight. known tile The and CMS wavelength hadron shifting calorimeter fibreindividual consists concept elements of to to about bring be 70 handled, out 000 the the scintillator tiles tiles. tray of In unit. a order given Figure to limit the number of tion and testing of the scintillators remote from the experimental installation area. Furthermore, 2008 JINST 3 S08004 shows a -index 1 φ 5.6 -index = 1–4). Trays with segmenta- divisions (φ φ 5.4). Each layer has 108 trays. Figure – 124 – -index 2 and 3 go into the center of a wedge while trays with segmentation of Figure 5.2: Assembled HCAL half-barrel in SX5, the above ground assembly hall. φ individual scintillator trays may becatastrophic replaced damage. Each without HB disassembly wedge of has the four absorber in the event of tion of and 4 go into the edge slots in a wedge (figure cross section of the tray. 2008 JINST 3 S08004 5.3. ) radioactive 60 direction) of the x (or optionally Co 137 thickness 40 mm 50.5 mm 56.5 mm 75 mm material steel brass brass steel – 125 – source tubes, that carry Cs 1-8 9-14 back plate layer front plate Table: 5.2 Absorber thickness in the HB wedges. The HB baseline active material is 3.7-mm-thick Kuraray SCSN81 plastic scintillator, chosen A tray is made of individual scintillators with edges painted white and wrapped in Tyvek LHC ring. for its long-term stability andis moderate located radiation hardness. in front The firstout of [108] layer the and of steel is scintillator made support (layer ofThe plate. 0) 9-mm-thick purpose Bicron BC408. of It layer The was scintillators zero originally arethe is summarized foreseen to EB in sample to table and hadronic have showers HB. a developingleaking The separate in out larger the the read- back inert thickness of material of HB. between layer 16 serves to1073D which correct are for attached late to atile developing is 0.5-mm-thick showers collected plastic with substrate a with 0.94-mm-diameter green plasticY-11) placed double-cladded rivets. in wavelength-shifting a Light fibre machined (Kuraray from groove in each thediameter scintillator. stainless For steel calibration tubes, purposes, each called traysources has 1-mm- through the center(337 of nm) each laser light tile. intopolystyrene. the An The layer cover additional is 9 quartz grooved tiles. to fibre provide The routing is top paths used of for fibres to the to tray inject the is outside ultraviolet covered of with the tray 2-mm-thick and white Figure 5.3: Numbering scheme for the HB wedges. Wedge 1 is on the inside (+ 2008 JINST 3 S08004 – 126 – Figure 5.5: Scintillator trays. After exiting the scintillator, the wavelength shifting fibres (WLS) are spliced to clear fibres also to accommodate the tubes for moving radioactive sources. (Kuraray double-clad). The clear fibre goes tocable an takes optical the connector light at to the end antowers of optical the and decoding tray. unit brings An (ODU). optical the The light ODU arranges to the a fibres hybrid into read-out photodiode (HPD) [109]. An additional fibre enters each Figure 5.4: Isometric viewsampling. of the HB wedges, showing the hermetic design of the scintillator 2008 JINST 3 S08004 5.8. 8 kV at a distance of approximately − thickness 9 mm 3.7 mm 9 mm – 127 – and the actual cabling is shown in figure material Bicron BC408 Kuraray SCSN81 Kuraray SCSN81 5.7 layer 0 1-15 16 Table 5.3: Scintillator in the HB wedges. 5.9. Figure 5.6: Cross-sectional view of a scintillator tray. pixels in a single HPD, the centermost of which is not read-out. A cross sectional view of 2 During the production and assembly process, the WLS fibres are cut, polished, and mirrored. The HPD consists of a photocathode held at a HV of 3.3 mm from a pixelatedelectron silicon in the photodiode. diode The results in20-mm ionization a produced gain by of the the accelerated HPDan of HPD photo- is approximately shown 2000. in There figure are 19 hexagonal The reflectivity of the mirrorthe is fibres used checked in by the measuring calorimeter.controlled test Measuring UV the fibres scanner reflectivity with which of the are the fibresfibres mirror mirrored read with is along out a done by with fusion with photodiodes. splicer. a ClearWLS computer The fibres fibres transmission onto are WLS across spliced fibres. the onto The splice WLS spliceacross is region the is checked splice measured by with is splicing the 92.6% a UVconnector. with scanner. sample This an The of configuration transmission RMS is of called 1.8%. ais pigtail. Next, assembled the In in order optical a to fibres template. get are the glued The fibre into connector lengths a is correct, 10 diamond the fibre pigtail polished. The fibres are measured with the HPD for direct injection of light usingof either the the fibre laser optics or is a shown light in emitting figure diode (LED). A schematic 2008 JINST 3 S08004 5.4. sectors). The rear segment of φ and table towers closest to the endcap transi- 5.10 η source inside a lead collimator. This yields a 4 cm – 128 – 137 Figure 5.7: Schematic of the HB optics. sectors and 0–12 layers for the outer two φ wire source is run through the 4 source tubes and the light yield is measured. 137 towers 1–14 have a single longitudinal read-out. The η tower 15 has three scintillators. Tower 16,in which the is front in front segment of and thescintillator. seven endcap The in (HE) tower the has segmentation one rear. is scintillators The summarized front in figure segment of tower 16 does not have a layer-0 diameter source spot on theFrom tray. the The scanner collimator we determine is the movedThe relative with light light a yield yield computer of of the controlled eachtile individual tile x-y is tiles and motor. 4.5%. the has uniformity A an of Cs RMS eachThe of tray. 4.6%, RMS while of the the transverse ratiowhich uniformity of of can collimated the be source used toto when wire better the source than is calorimeter 2%. 1.3%. is Insystems. completely This addition assembled, means to the can the line moving calibrate sources, wire individual source, tiles there are laserLongitudinal and segmentation LED light injection The tion region (15 and 16)or are 13 segmented scintillators, in due depth. to the The0–11 placement front for of segment the the middle of read-out two tower box 15 and contains the either staggering of 12 the layers (layers UV scanner. The scanner checkslight from the the green fibres is fibre, 1.9%. clear Afterwith fibre, the an splice, pigtail automated is source and inserted scanner mirror. into using the a The tray, the Cs RMS completed of tray is the checked 2008 JINST 3 S08004 – 129 – Figure 5.9: Cross sectional view of an HPD. Figure 5.8: Close up view of the assembled HB wedges, showing the optical cabling. 2008 JINST 3 S08004 ) I plane for one-fourth of the HB, HO, and z , r overlaps with HE thickness (λ 5.39 5.43 5.51 5.63 5.80 6.01 6.26 6.57 6.92 7.32 7.79 8.30 8.89 9.54 10.3 – 130 – range 0.870 – 0.957 0.957 – 1.044 1.044 – 1.131 1.131 – 1.218 1.218 – 1.305 1.305 – 1.392 0.000 – 0.087 0.087 – 0.174 0.174 – 0.261 0.261 – 0.348 0.348 – 0.435 0.435 – 0.522 0.522 – 0.609 0.609 – 0.696 0.696 – 0.783 0.783 – 0.870 η 11 12 13 14 15 16 1 2 3 4 5 6 7 8 9 10 tower Figure: 5.10 The HCAL tower segmentation in the Table 5.4: Tower data for HB.that The tower 16 given overlaps thicknesses with correspond HE. to the center of the tower. Note HE detectors. The shading representsgitudinal the readouts. optical grouping of scintillator layers into different lon- 2008 JINST 3 S08004 E H ) requires HE to handle high (MHz) 1 − s 2 − cm 34 – 131 – 5.12. Only a small part of the calorimeter structure can be used for and 3. Since the calorimeter is inserted into the ends of a 4-T solenoidal magnet, 5.11 | ' η | 3 (13.2% of the solid angle), a region containing about 34% of the particles produced in < Figure 5.11: Hadron endcap (HE) calorimeter mounted on the endcap iron yoke. | η | < 3 the fixation to the magnet iron,is because occupied the with majority muon of the cathode2-t space preshower strip between detector chambers. HE (ES) and is A muon300 attached t) 10-t absorber at and electromagnetic the a calorimeter front strict (EE) requirement facehas with to of made minimize a HE. the non-instrumented The design materials large of alongoped weight HE particle involved in trajectories, (about a order challenge to to providemuon engineers. precise station, positioning and An to of interface minimize the kinematickinematic the endcap scheme influence contains detectors was of a with devel- deformation sliding respect under jointconnection to magnetic between between forces. the the brackets adjacent The interface and interface tube, thesystem are and iron non-magnetic HE disk in back-flange (YE1). order and not to Structural the distort materials hinge the used axial magnetic in field the of interface up to 4 T. counting rates and have highluminosity) radiation at tolerance (10 MRad after 10 years of operation at design the final state. The high luminosity of the LHC (10 the absorber must be made frominteraction a non-magnetic lengths material. to It contain must hadronic alsoleading have showers, to a good the maximum choice mechanical number of of properties C26000 and cartridgeas brass. reasonable shown The cost, in endcaps are figures attached to the muon endcap yoke 5.2 Endcap design (HE) The hadron calorimeter endcaps1. (HE) [108] cover a substantial portion of the rapidity range, 2008 JINST 3 S08004 1) is added 114]. The design ). I 111]. The plates are bolted together – 132 – 5.13). The design provides a self-supporting hermetic construction. The brass plates are The outer layers of HE have a cutout region for installation of the photodetectors and front- to tower 18 [112].optical The elements outer are layers inserted are intothe fixed the optical to elements gaps a must after 10-cm-thick have the a stainless absorber rigid steel structure is support to completely allow plate. assembled; insertion from therefore, The Scintillator any trays position. The scintillation light isminimizes collected by dead wavelength zones shifting becausestructures (WLS) while the fibres at absorber the [113, same can time the be light made can be as easily routed a to solid the photodetectors. piece Trapezoidal- without supporting end electronics. To compensate for the resulting reduction of material, an extra layer (− in a staggered geometry(figure resulting in a configuration79-mm-thick that with contains 9-mm gaps no to accommodate projective theincluding “dead” scintillators. electromagnetic material The crystals, total is length about of 10 the interaction calorimeter, lengths (λ Figure 5.12: Partially assembledtrays HE-minus can absorber be in seen the to CMS be surface inserted hall in (SX5). some of Scintillator the outer sectors. Absorber geometry The design of therather absorber than is single-particle driven energy by resolution,pileup, since the magnetic the need field resolution effects, to and of minimize parton jets fragmentation the in [110, HE cracks will between be HB limited and by HE, 2008 JINST 3 S08004 φ 5.18. 6 and 1. < | η | 087 for 0. × 087 0. 5.16, and the CMS convention for = ∆φ × ∆η – 133 – is shown in figure η 6. 5.17. The scintillators are wrapped with Tyvek and sandwiched 1. | ≥ η | 5.14), 3.7-mm-thick SCSN81 for layers 1–17 and 9-mm-thick Bicron 5.12. Multipixel hybrid photodiodes (HPDs) are used as photodetectors 5.15. These fibres are terminated with aluminium reflectors and distribute 17 for 0. × 17 : Mechanical structure of the HE absorber. Particles enter the calorimeter from the 0. ≈ 5.15. The numbering scheme in ∆φ The tray design is very robust and reliable. The trays are relatively stiff which is very im- The trays are inserted into the gaps in the absorber and fixed by screws. At the back of the × bottom. shaped scintillators (figure BC408 for layer 0, havemachined grooves in with which a the diamond WLS flycollection. fibres cutter are and The inserted. one other The end end endsThe is is of connector covered spliced the with with to fibres the aluminium a are glued topainted clear fibres increase along fibre, is the the which also light narrow is machined edges terminatedboth by and in HE put a calorimeters an into diamond is optical a fly 20 connector. frame 916 cutter.in to and figure The the form scintillator number a of is tray. trays The is total 1368. number The of design tiles of for a tray is presented Figure 5.13 as applied to HE is shown inbetween figure sheets of duraluminum.optical The connectors. stack The contains gaptogether. holes between for the fibres The duraluminum which granularity plates∆η are of is terminated fixed the with by calorimeters brass is spacers screwed portant for insertion into thewas absorber. used To to control excite the the scintillator scintillators.out tray The as quality, light a shown is UV in fed nitrogen figure bythe laser quartz light fibres to to the all connector tiles.signal and induced is The by fanned light a signal chargedfrom particle. produced scintillator by This to a allows electronics, a UV providingtransparency performance an flash due check important in to of technique radiation the the to damage. scintillator entire track Formoving is optical possible further in similar calibration route degradation a and to stainless of monitoring, steel the a tube radioactive is source used to study thecalorimeter, time-dependence boxes of with calibration photodetectors and coefficients. electronics are located in the notch shown in figure due to their low sensitivity to magnetic fields and their large dynamical range. Optical cables transfer signals from the scintillatorbled trays HE to is the shown photodetectors. in The figure partially assem- 2008 JINST 3 S08004 5.10) is, in part, motivated by the radiation environ- – 134 – Figure 5.14: a) Basic structureb) of cross a section scintillator of tile the with 3.7-mm-thickthick a scintillator scintillator for groove for layers to layer 1–17, fix zero. and wavelength Two c) layers shifting cross of fibre, section reflecting of paint the cover 9-mm- the sideLongitudinal surfaces segmentation of the tile. The longitudinal segmentation of HE (figure ment. Correction oforder the to calibration restore coefficients the afterring energy scintillator “29”) resolution. degradation have can 3 The be divisions towersand applied, in 17 nearest depth which in the overlap which beam with are the linefor read-out electromagnetic (27 potential separately. barrel and use calorimeter) The during 28 have other two the plusnot longitudinal towers time yet guard readouts (except be period 16 available. when thethe A electromagnetic absorber special to endcap scintillator partially layer calorimeter correct of (EE)particle for 9 may absorption the mm in different the BC408 response mechanical (layer structure of 0) supporting EE is EE. to installed electrons in and front hadrons of and for 2008 JINST 3 S08004 – 135 – Figure 5.15: The design ofaluminium the calorimeter cover, b) scintillator cut trays: out a) viewa front of tray view the for of layer-0 layers a tray 1–17. tray with without two upper fibres from a tile, c) cut out view of 2008 JINST 3 S08004 x + – 136 – Figure 5.16: Numbering scheme for the tiles in adjacent scintillator trays. direction points to the center of the LHC ring. Figure 5.17: Numbering scheme for the HE wedges as viewed from the interaction point. The 2008 JINST 3 S08004 – 137 – Figure 5.18: Longitudinal and angular segmentationto of the the HE interaction calorimeter. point. The dashed lines point 2008 JINST 3 S08004 1, 0, 3, the − 1. -sectors. 2, φ < interaction − | η | direction are not shows the position φ 0, HB has the minimal 5.19 = except at the barrel-endcap η I positions of the five rings are λ z . φ 5.342 m. At + z-axis) rings. The HO is placed as the first – 138 – and the nominal central 2.686 m and z + 2.686 m, 0, 1 are also not available for HO. The chimneys are used for the cryogenic − + 5.342 m, − 2. The numbering increases with direction and also the space occupied by the stainless steel beams in the Outside the vacuum tank of the solenoid, the magnetic field is returned through an iron yoke The HO is constrained by the geometry of the muon system. Figure + η 1, and sector 4 of ring 1, of HO layers in the ringsdetectors of the closely muon stations follows in that theThe of overall 12 CMS the sectors setup. are barrel The separated segmentation muon by ofiron 75-mm-thick these system. of stainless steel the Each beams return which ring yoke holdthe as has successive layers well 12 of as identical the muon system. The space between successive muon rings in transfer lines and power cables ofposition the the magnet scintillator system. trays Finally, further the constrain mechanical HO structures along needed to available for HO. In addition, the− space occupied by the cryogenic “chimneys” in sector 3 of ring Figure 5.19: Longitudinal and transverselayers. views of the CMS detector showing the position of HO 5.3 Outer calorimeter design (HO) In the central pseudorapidity region, the combinedsufficient stopping containment power for of EB hadron plus showers. HB does To not ensure provide adequate sampling depth for hadron calorimeter is extendedcalorimeter. outside The HO the utilises the solenoid solenoid coil withlengths as an and a additional absorber is tail equal used to catcher 1.4/sinθ toafter called identify HB. late the starting HO showers or and to outer measure the showerdesigned energy in deposited the form of five 2.536 m wide (along respectively absorber depth. Therefore, the central ringof (ring a 0) has 19.5 two cm layers of thickrespectively. HO All piece scintillators other on of rings either iron have side (the aof single tail the HO catcher calorimeter layer iron) at system at a is radial radial thus distance distances extended of of 4.07 to 3.82 m. a m The minimum and total of depth 4.07 11.8 m, sensitive layer in each of these five rings. The rings are identified by the numbers + boundary region. 2008 JINST 3 S08004 z φ 1 and ± slices of a = 0 (ring 0) φ 5.5. In each η . The φ ). However, along the φ shows the dijet integrated shows a schematic view of a values, a region important for 5.22 are given in table 1 for measurements without HO, wide in 5.20 miss T φ ◦ < . The amount of leakage in ring 2 is E | η | . The HO consists of one (rings incident slice (5 φ φ values and the resulting energy deposits in the and . Each ring of the HO is divided into 12 identical η η η = 0.5 (pointing towards the middle of ring 1). The – 139 – η measurement. Figure conforming to the muon ring structure. The rings are η miss T 0.087 in E 2 with increasing + above 500 GeV, is several pb. For these events the HO is useful to T sector. The thickness and position of the iron ribs in the yoke structure E shows distributions of the measured energy scaled to the incident energy = 0 and 225 GeV at 1 and above a certain value. It is clear from the figure that the inclusion of HO φ η + 5.21, there is an excess inE / Energy ). Study of QCD events shows that the cross section for those events, where 5.21 miss T E 1, 0, miss T − 2, − The effect of shower leakage has a direct consequence on the measurement of missing trans- The physics impact of HO has been studied [115] using a simulation of the CMS detector. The sizes and positions of the tiles in HO are supposed to roughly map the layers of HB In the radial direction each HO layer has been allocated a total of 40 mm, of which only ) direction, a tray covers the entire span of a muon ring. Figure sectors and each sector has 6 slices (numbered 1 to 6 counting clockwise) in 2) or two (ring 0) layers of scintillator tiles located in front of the first layer of the barrel muon searches of supersymmetric particles. Module specification HO is physically divided intonumbered 5 rings in layer are identical in all sectors. The widths of the slices along for 200 GeV pions at solid and dashed lines incan the be figure seen indicate in measurements figure without and with HO, respectively. As φ reduces the dijet rate by a factor of 1.5 or more for moderate because of leakage. Theaddition measurements of with HO HO recovers are the morefrom 70 Gaussian effect GeV, increasing of in with nature leakage. energy. The indicating10 mean The that GeV fraction effect the pions of energy of to in 4.3% leakage HO for increases is1 from 300 but visible GeV 0.38% it for at pions. is reduced There due is to some the evidence greater of HB leakage thickness at without larger HO in ring cross section for at least one particledecrease has the leakage and improve the found to be negligible at energies below 300 GeV. verse energy (E electromagnetic calorimeter and in thethe layers energy. of Figure the hadron calorimeter are combined to measure HO tray where one tile isto mapped the to a read-out tower box. of HB and the optical cable from theSingle tray pions is connected of fixed energies are shot at specific (η ± detector. Scintillation light fromshifting the (WLS) tiles fibres is of collected diameterstructure using 0.94 of mm, multi-clad the and return Y11 yoke transported Kuraray by towith splicing wavelength the a the multi-clad photo WLS Kuraray detectors fibre. clear located fibre In onsingle (also order unit of the to 0.94 called simplify mm a diameter) installation tray. Each of tray HO, corresponds the to scintillator one tiles are packed into a 16 mm is available for the detectorstructures. layer, the In rest addition, being the used HO foron modules the are aluminium either independently honeycomb side support supported of from each thefurther steel constrain beams the located shape and segmentation of the HO. to make towers of granularity 0.087× 2008 JINST 3 S08004 | 2 η | = 0.5 η E = 225 GeV Incident Energy/E without HO with HO = 0 and (right panel) 225 GeV at η 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

1

10 10 No. of Events of No. 2 – 140 – = 0.0 η E = 200 GeV Incident Energy/E without HO with HO e 5.21: A simulation of the distribution of the measured energy scaled to the incident energy 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

1

10 10 No. of Events of No. Figur for pions with incident energies of (left panel) 200 GeV at Figure 5.20: Schematic viewgrooves for of WLS a fibres. HOHB. Each tray optically Optical shown independent fibres with (4 from WLS individual theand fibres) tray read-out tiles tile electronics. are and is routed the mapped to to corresponding the a decoder tower box of which contains the photodetector = 0.5. The solid and dashed histograms are measurements without and with HO, respectively. 2008 JINST 3 S08004 3, are + η 2, 2 have 1), are + − − -slice in a 1, boundaries φ + η slice of a ring 1, φ − 268 292 406 1 and ring 1, the 2, Tray 6 − ± − -dimension of any tile η 3, − 327 347 349 4, Tray 5 − 15. Ring in mm 327 347 349 φ Tray 4 ve indices. The − with HO without HO ve number. The tile dimensions along + 332 352 354 Cut (GeV) Tray 3 T Width along – 141 – 1 and trays 3, 4, 5 and 6 in sector 3 of ring Missing E + 343 364 366 boundaries; therefore, part of HO tower 5 overlaps with Tray 2 η . The smallest scintillator unit in HO thus obtained is called for different trays. Each tray corresponds to one sector belong to a plane. The perpendicular distance of this η φ -divisions (i.e. 8 tiles in a tray): φ 0 200 400 600 800 η 274 300 317 -1 -2

1

10 and ring 2 has 5 divisions: 11··· Tray 1

10 10 (pb) σ with or without HO. T 0 1 1 E Layer 2 shows the final layout of all the HO trays in the CMS detector. The length of a ± 0 0 1, 5.6. z-axis is 3.82 m for layer 0 and 4.07 m for layer 1. The tiles in each Ring ± 5.23 ve tower number is the same as the one with Figure Both layers of ring 0 have 8 − sector. 4. Ring 1 has 6 divisions: 5··· 5. Because of the constraints imposed by the gap between ring 0 and rings + with shown in table φ a tile. The scintillator tiles in each are mechanically held together in the form of a tray. the same number of divisions as rings 1 and 2 but with slice, there is a further division along plane from the Figure 5.22: Integrated cross sectionas above a threshold function for of intrinsically missing balanced QCD dijet events Table 5.5: Dimension of tiles along full tray is 2510 mmchimney whereas (trays the 4 shorter and trays, 5 the in sizes sector of 4 which of are ring constrained because of the 2119-mm long. The shorter trays± are constructed without the tileof HO corresponding tower to 4 tower do number not match the barrel tower 4 in the barrel. 2008 JINST 3 S08004 351.2 353.8 359.2 189.1 420.1 545.1 583.3 626.0 333.5 Length (mm) max η 0.087 0.174 0.262 0.307 0.960 1.047 1.135 1.222 1.262 Ring 0 Layer 1 Ring 2 Layer 1 1 2 3 4 11 12 13 14 15 Tower # – 142 – for different rings and layers. The tile sizes, which are η 411.0 430.9 454.0 426.0 331.5 334.0 339.0 248.8 391.5 394.2 Length (mm) max η 0.611 0.698 0.785 0.861 0.087 0.174 0.262 0.326 0.436 0.524 Ring 0 Layer 0 Ring 1 Layer 1 7 8 9 1 2 3 4 5 6 10 Figure 5.23: Layout of all the HO trays in the CMS detector. Tower # constrained by muon ring boundaries, are also given. Table 5.6: HO tile dimensions along 2008 JINST 3 S08004 mm. Figure 5.24 0 1 + − shows a cross section of a tray 5.25 – 143 – sector in each ring has 6 trays. There are 360 trays for φ 1 and 8 tiles in ring 0. The edges of the tiles are painted ± slice of a sector are grouped together in the form of a tray. Each tray contains 2; 6 tiles in rings φ ± The 2 mm plastic sheet on the top has 1.6 mm deep channels grooved on it (on the outer The HO has 95 different tile dimensions, 75 for layer 1 and 20 for layer 0. The total number Figure 5.24: View of a typical tile of HO with WLS fibres inserted in the 4 grooves of the tile. layer 1 and 72 trays for layer 0. to illustrate the different components.with the The holes in plastic the coversthe tiles. (top plastic Specially and covers designed firmly bottom) on countersunk have the screws holes tiles. passing matching through these holes fix side) to route the fibres fromof individual the tiles tray. to an A optical 1.5-mm-widea connector straight placed stainless groove in steel runs a along tube. groove the atcalibrating edge This the the of edge is modules. the used Each top connector for coverassembly has the to two through passage accommodate holes matching of and holes. they a Each are radioactive fixed source to which the scintillator-plastic is employed in 5 tiles in rings with Bicron reflecting white paint forof better a light tray. collection as Further well isolationadjacent as of tiles. isolating tiles The the tiles individual is in tiles achieved aThen by tray are inserting they covered a with are a piece covered single of big withbetween black piece black two of tedler white, tedlar black in reflective between tyvek paper plastic paper. the cover to plates is prevent for 2-mm-thick light and mechanical the leakage. stability bottom one and is This ease 1-mm-thick. package of Figure is handling. placed The top plastic Tiles Scintillator tiles are made from Bicron BC408shows scintillator a plates of typical thickness HO 10 scintillator tile.hole cross The section. WLS Each fibres groove has area a held circular neck inside part of the (of 0.86 diameter tile 1.35 mm in mm)groove width. grooves in inside with each the The quadrant scintillator a grooves of and key are the tile. 2.05-mmof the The deep. grooves grooves are closely Each rounded follow to tile the prevent has quadrant damagegroove to 4 boundary. design the is The identical fibre slightly corners grooves, at different the one for bend thetray. and tile to Since where ease the fibre the tiles insertion. optical are connector The large, is 4 placed grooves at ensure the good end light of the collectionof and tiles less is attenuation 2730 of (2154 light. for layer 1 and 576 for layerTrays 0). All tiles in each 2008 JINST 3 S08004 ) η 1.8 m) is ≈ 5.27). Each tray 5.26). The number 5.7. 8.0 m). A fibre is spliced only if the potential WLS – 144 – ≈ Figure 5.25: Cross section of a HO tray showing the different components. The bunch of fibres fixed to the optical connector is called a pigtail (figure . The fibres from all grooves on one row terminate on one connector (figure spliced to a clear fibre (attenuation length of Figure 5.26: The arrangementcomponents of are scintillation slightly tiles, displaced from plastic their covers true and positions connectors to show in their a matching tray. designs. Pigtails The The light collected by the WLSlocated fibres inserted far in away the on tiles the needsgroove, to muon are be rings. polished, transported to aluminized The photodetectors and captive protected endsWLS using of fibre a the comes thin out WLS polymer of fibres, coating.To the which The minimise tile reside other the through inside end loss a the of slot of the made light on in the transportation, 2-mm-thick the black WLS plastic fibre cover sheet. (attenuation length of light loss is larger than the light loss at a spliced joint. Thus depending on tile length (along 2–3 fibres in each pigtailguiding are grooves made on only of the WLS topconnectors fibres. plastic mounted to The on one clear the end fibres optical of fromη connector the each at tray. tile the In follow a end. the tray,of the Each fibres grooves tray from of trays has the in two tiles different form optical rings two are rows given along in table has 2 pigtails and there area 864 pigtail pigtails is in cut total: tofrom the 720 the proper for scintillator layer length to 1 to the and match optical 144 the connector for at groove layer the length end 0. in of the Each the scintillator fibre tray. plus in the distance 2008 JINST 3 S08004 ≥ = = m 10 core µ θ θ n (≈ 5 10 1 + − − ), sin pb 5 clad 02) and 0. 10 × ± 33 0. = 16 12 10 15 m using high energy electrons ) and the cladding (n ≈ core Fibres/connector 10 MGy. The charged hadron rates will also ≈ m with the protective acrylate buffer. Over 1000 32 24 20 µ m in diameter for the fused-silica core, 630 [108]. This hostile environment presents a consider- – 145 – µ Fibres/tray 5 after an integrated luminosity of 5 30 2 = 10 ± | ± ) contributes to the calorimeter signal. The half-angle η | ◦ per cm 6 5 8 11 Tiles/tray , where NA is the numerical aperture (NA 1 2 0 2 core ± ± Ring # Table: 5.7 Tray specifications for different rings of HO. /2n NA = Figure 5.27: Illustration of an assembled pigtail (not drawn to scale). . The fibres measure 600 trap 2 clad f n − to the fibres. The signal is generated when charged shower particles above the Cherenkov threshold (E ◦ is determined by the refractive indices of the core (n 2 core ◦ n with the polymer hard-cladding, andkm 800 of fibres are usedcutter. The in attenuation the length HF of calorimeters. theseat fibres 90 The is measured fibres to are be cleaved at both ends by a diamond able challenge to calorimetry, and theby design the of necessity the to HF surviveoperation calorimeter in critically was these depends first on harsh and the conditions, foremost radiation preferablyreason guided hardness for of why the at quartz active least fibres material. (fused-silica a Thismedium. core decade. was the and Successful principal polymer hard-cladding) were chosen as the active 190 keV for electrons) generate Cherenkov light, therebyto rendering the the calorimeter electromagnetic mostly sensitive componentcaptured, of showers [116].is A the small refractive fraction index ofangle of the larger the than generated quartz the light critical core. angle19 is (71 q Only light that hits the core-cladding interface at an be extremely high. For the samebeam-line, integrated the luminosity, rate inside will the exceed HF 10 absorber at 125 cm from the years of LHC operation), the HF will experience 5.4 Forward calorimeter design (HF) The forward calorimeter will experienceproton-proton unprecedented interaction particle is deposited fluxes. into the On two forward average,for calorimeters, the 760 compared GeV rest to per of only 100 the GeV detector.maximum Moreover, this at energy the is highest not rapidities. uniformly At distributed but has a pronounced 2008 JINST 3 S08004 ) ) I λ b( ) 10λ 0.175 1 mm 0 ± ≈ 90%) in ). D/D 1 MGy, the φ )( = λ in ◦ a( D 1 MGy) for con- = 0 parameters characterize the radi- b (measuring the total signal), and the and L a a. The in these types of fibres scales as mm in depth) which make a square grid separated (300–500 ppm) HF fibres at 450 nm, the measured λ 70 degrees from normal). Light typically makes five 450 nm at the accumulated dose of 6 – 146 – − 0. 0 5.8). The detector is housed in a hermetic radiation = + − λ 06 modular wedges. Thirty-six such wedges (18 on either side of ◦ and table 3 [117–119]. An accumulated dose of 10 MGy will result in a loss of 5.29 5 dB/m, thus defining 0. 1. (measuring the energy deposition after 22 cm of steel). The absorber ≈ mm wide and 1. b S ≈ 12 0 0. − + 5 and 90 1. ≈ towers (figure 1 mm center-to-center. Long and short fibres alternate in these grooves. The pack- a ) 5.28. The fibres run parallel to the beam line, and are bundled to form 0.175× 0. is the accumulated dose, which is normalized to a reference dose (D ∆φ ± D The entire calorimeter system, with its shielding components, is mounted on a rigid table The calorimeter consists of a steel absorber structure that is composed of 5 mm thick grooved The forward calorimeter is essentially a cylindrical steel structure with an outer radius of Bundled fibres are held in ferrules which illuminate one end of the air-core light guides that The optical attenuation at a wavelength 0 × ∆η with respect to the rest of the CMS experiment. has grooves (0. bounces before reaching the photocathodelight and guide is nearly coupled half to a the standard lightwindow. bialkaline, A 8-stage is read-out photomultiplier lost tube box with in (RBX) a this houses borosilicate 24 glass transport. PMTs Each and services half ofwhich a supports wedge more (10 than 240 tThe with table less is than also 1 designed mmbeam pipe for deflection. at horizontal installation The and separation absorber removal. alone of It is weighs the possible 108 to detector t. align into the forward two calorimeters sections within to clear the ation hardness of a given fibre.values are For high OH plates. Fibres are inserted ingitudinal these segments. grooves. The Half detector ofwhile is the the functionally subdivided other fibres into half run two startsfibres over lon- at are the a read full depth out depth of separately.ated of 22 by the This cm electrons arrangement absorber from and makes (165 thefrom photons, it cm front possible which those of to deposit generated the distinguish a by detector. showersments large hadrons, gener- These fraction on which two of average. produce sets their of The nearlyshort energy in long equal fibre the fibre signals section first section in as 22 is both cm, referred calorimeter as seg- the visible spectrum at the relevant angles (≈ optical transmission by a half, which is the worst case for HF after a decade. by 5. ing fraction by volume (fibre/total)depth. in the first 22 cm is 0.57% and130.0 is cm. twice The as front face large of the beyondfor calorimeter the that is beam located pipe at is cylindrical, 11.2 with mis radius from 12.5 azimuthally the cm interaction subdivided from point. into the The center 20 hole ofthe the beam interaction line. point) This structure make upin the figure HF calorimeters. A cross sectional viewshielding which of consists the of layers HF of 40 is cmA thick shown large steel, plug 40 structure cm in of concrete, the and back 5 of cm of the polyethylene. detector provides additionalpenetrate shielding. through 42.5 cm ofis the necessary shielding to matrix protect (steel,boxes. the lead, photomultipliers The and air-core and polyethylene). light the guide Thiscustom-made front-end consists shielding sheets. of electronics a housed These hollow in tube metal-coated the lined reflectors on read-out are the designed inside to with highly be reflective very efficient (> induced attenuation is ( venience. For example, at a wavelength where 2008 JINST 3 S08004 luminosity and one 1 − s 2 − cm Sv/h on the periphery of the µ 34 – 147 – 5) will experience radiation doses close to 100 Mrad/year, < | η | < 5 The inner part of HF (4. and large neutron fluxes leadingthe to region activation of closest the to absorber the material, beam reaching line several after mSv/h 60 in days of running at 10 Figure 5.28: The crosstends from sectional 125 view to of 13001650 the mm mm. in HF the calorimeter Bundled radial shows direction. fibreslight that (shaded guides The the area) which absorber penetrate sensitive in are the through area routedby beam a from ex- PMTs direction steel-lead-polyethlene the housed measures shielding back in matrix. ofinstalled the Light the for read-out is calorimeter each boxes. detected tower to and air-core interaction Stainless are point is steel accessible at from radioactive 11.2 outside meters sourcein from the mm. tubes the detector front (red for of lines) the source calorimeter are calibration. to the The right. All dimensions are day of cooling down.survive The these active levels elements of of radiation HF withof (quartz limited steel fibres) deterioration. and are borated The sufficiently PMTs polyethylene radiation-hardcally are slabs. insensitive to to shielded neutrons behind HF, and using 40 to Cherenkov cm Further low light energy shielding particles from around from quartz HF the fibres, decaydetector. achieves is of activation A activated practi- levels radionucleids. 10-cm-thick below lead 10 plate,reduces located personal exposure in to front radiation ofperformed from HF with the during the absorber. help operations of Maintenance around semi-automatic of thelocated extractor read-out tools. at detector, boxes the HF is will periphery equipped be of withproperties the radiation of detector, monitors and a with few a referenceluminosity. system quartz (Raddam) fibres to embedded measure in the transmission the absorber, as a function of integrated 2008 JINST 3 S08004 bundle 1.14 1.33 0.96 0.66 0.47 0.34 0.25 0.18 0.13 0.94 0.71 0.11 0.10 A photocathode A ] 2 88 63 46 35 52 50 bundle 551 652 469 324 231 167 120 A [mm fib 85 59 41 30 42 45 N 594 696 491 346 242 171 120 10 10 10 10 10 10 10 10 10 10 10 20 20 ∆φ [degree] – 148 – ∆η 0.111 0.175 0.175 0.175 0.175 0.175 0.175 0.175 0.175 0.175 0.175 0.175 0.300 ) out r , in [mm] (r (286–340) (240–286) (201–240) (169–201) (125–169) (818–975) (686–818) (576–686) (483–576) (406–483) (340–406) (975–1162) (1162–1300) 9 10 11 12 13 Ring No 1 2 3 4 5 6 7 8 Figure 5.29: a) Transverseshows segmentation the of squared the out groove HF holding towers. the radioactive b) source tube. An expanded view ofTable the 5.8: wedge The tower sizes, number ofutilized fibres, are bundle listed sizes and below the for percentagephotocathode each of area photocathode tower. for area towers The 1, air-core 2 light and guides 3. are tapered to better match the 2008 JINST 3 S08004 2000. A ≈ 5.31. The optical 12 HTR, 2 DCC per crate H T R (in UXA) H T R 16 bits H T R @ 80 MHz H T R READ-OUT Crate H T R 5.30. The read-out consists of an H T R 64 bits H T R (ave. rate) @ 25 MHz D C C 5.32. Several PCs in the CMS control Fibers at 1.6 Gb/s 3 QIE-channels per fiber C L K D C C H T R Wall Shield H T R H T R SLINK-64 SLINK-64 H T R H T R – 149 – V M E TTC FE MODULE 32 bits

@ 40 MHz GOL GOL

CCA CCA CCA (ave. rate) 25 MByte/s Rack CPU Rack QIE QIE QIE QIE QIE QIE HPD Trigger Primitives Figure 5.30: Overview of HCAL read-out electronics. CAL TRIGGER REGIONAL (On detector) FRONT-END RBX Readout Box The optical signals from the scintillator-based detectors (HB/HE/HO) are converted to elec- An overview of the HCAL controls is given in figure The configuration database contains the relationships or mapping for all HCAL detector com- optical to electrical transducer followed by aADC fast is charge-integrating transmitted ADC. for every The bunch digital over output athe of gigabit off-detector the digital electronics. optical fibre to In the thetrigger service service cavern, primitives housing which cavern, are the sent signal to ispipelined the for deserialized calorimeter transmission trigger. and to The used the data to DAQ and upon construct trigger a primitives Level-1 are Accept also (L1A) decision. trical signals using multichannel hybriddetailed photodiodes view (HPDs) of which the provide scintillator-based front-end asignals read-out gain from chain of individual is given sampling ining layers figure to are a brought projective calorimeter out towerthat on are interfaces clear mapping to fibres. via individual an opticalfields pixels The decoding on are fibres unit the much correspond- (ODU) HPD. smaller tomatsu a In than R7525HA) cookie the in are forward used the and calorimeter, central quartz-fibre where bundles detector, are the conventional routed magnetic photomultiplier directly to tubes the (Hama- phototube windows. 5.5 Read-out electronics and slowThe control overview of the full HCAL read-out chain is shown in figure room operated through PVSS aredownloads used pedestal to DAC and control timing high parameters and toand low front-ends monitoring and voltages. controls systems The many including of controlsystem. the the system calibration source also These calibration systems drivers,studies the record of LED temperature, detector/calibration pulsers, stability. humidity and and the other laser constants useful forponents: correlation wedges, layers, read-out boxes (RBX), cables, HCAL Trigger (HTR) cards, and calibra- 2008 JINST 3 S08004 HV Laser LV1 DB RBX – 150 – parameters HV Figure 5.32: Overview of HCAL detector controls. drivers Source motor RadMon Figure 5.31: Overview of HCAL read-out/trigger chain and connections to database. The analogue signal from the HPD or photomultiplier is converted to a digital signal by a tion parameters for varioustions components database e.g. has RBX, the QIE,information, slow-controls source etc.) logging, types the and and strength. calibration theinitialization. constants configuration The database (pedestals, condi- downloaded gains, to timing the read-out system duringcharge-integrating the ADC ASIC called the QIE (Charge-Integratorcontains and Encoder). four The capacitors QIE which internally areThe connected integrated charge in from turn the to capacitors the is input, converted to one a during seven-bit each non-linear scale 25 to ns cover period. the 2008 JINST 3 S08004 5.33. The QIE input summarizes the geometry of the trigger towers. 5.9 – 151 – before being sent to the trigger. φ and η The digital outputs of three QIE channels are combined with some monitoring information to When a L1A is received by the HTR through the TTC system, it prepares a packet of data The Level-1 trigger primitives (TPG) are calculated in the HTR modules. The QIE data are The HF towers are summed in Figure 5.33: Contribution ofrepresentative HCAL the resolution curve. FADC quantization error to the resolution,large compared dynamic range with of a the detector. Theresolution ADC over is designed its so multi-range its contribution operation to the is detector negligible, energy as shown in figure characteristics were chosen from testresulted in beam a data per to channel RMS optimize noise speed of and 4600 noise electrons (0.7 performance.create fC) a corresponding This 32-bit to data about word. 180 MeV. The(GOL) 32-bit chip data, at and a transmitted rate using ofservice 40 8b/10b cavern, MHz, the encoding is data off fed is the into receivedcontains the detector by Gigabit the to the Optical Level-1 HCAL the Link Trigger/Read-out pipeline service (HTR) and cavern.primitives board. are also The sent In constructs to HTR the the the board Regional trigger CalorimeterHTR primitives trigger board via for receives Serial data HCAL. Link for These Board 48 mezzanine trigger channels cards. (16 The data fibres) and mayfor host the up DAQ including to a six programmable SLBs. around number the of triggered precision bunch read-out crossing. values and Forfor trigger normal each primitives operations, non-zero the channel HTR will and transmitdata, a 7 each single time trigger covering samples primitive 24 for channels,(DCC). every are The trigger transmitted DCC tower. by is These LVDS the packets to HCALchannels of the Front-End for transmission Driver HCAL (FED) into Data the and Concentrator DAQ. concentrates Card the data from up tolinearized 360 and converted to transverse energy withtime a samples single are look summed. up A table. sumtation. over Two or depth A more is final consecutive made look for up those towers tablelink having is to longitudinal used the segmen- to regional compress calorimeter the trigger. data before Table sending the data across the trigger 2008 JINST 3 S08004 . φ and ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ φ 5 5 5 5 5 5 5 5 5 5 5 η 20 20 20 20 shows the pulse shape for the for- Size η 5.36. The amount of time slewing is 0.087 0.087 0.087 0.090 0.100 0.113 0.129 0.150 0.178 0.150 0.350 0.461 0.525 0.524 0.828 5.35 Detector HB HB, HE HE HE HE HE HE HE HE HE HE HF HF HF HF – 152 – η η | max η 3.000 3.314 3.839 4.363 5.191 1.392 1.830 1.930 2.043 2.172 2.322 2.500 2.650 | 0.087× 0.087× 28 29 30 31 32 16 21 22 23 24 25 26 27 1–15 index 17–20 Tower Table: 5.9 Sizes of the HCAL trigger towers in An additional important effect on the HCAL pulse timing in HB/HE/HO comes from the input The in-situ synchronization of HCAL is performed using the HCAL laser system. The laser Figure 5.34 shows that scintillator tile signals produce relatively fast pulses such that 68% ward calorimeter. The Cerenkov processextremely fast, and so the the pulse phototubes in used HFwhich is in is only important the 10 in ns forward the wide. calorimeter highly The are active HF forward is region thus of subject CMS. only tostage in-time of pile-up the QIE.shape The for QIE large has signals an thandependent amplitude-dependent for on small impedance the ones, noise which as characteristics implies of seenwere the a in chosen QIE, faster figure to so limit pulse the the final timeslew QIE toIn ASICs the for the “medium” the case outer barrel in and calorimeter, exchange endcap for themuch somewhat less noise increased important noise. level so is the a quieter “slow” critical characteristics factor were for chosen for muon thesystem identification HO consists and QIEs. of pile-up a is singleendcap UV at laser once which through can illuminate ato an series the entire of detector half-barrel optical have of been splitters.The HB carefully laser or The can controlled a be quartz to single directed fibres equalize either which the straight lead onto optical a from path scintillator the length block laser to connected each to the wedge. HPD or into the Timing and synchronization The QIE integration clockfine-skewing is of controlled the by integration theeach phase Channel channel’s integration of Control phase each ASIC to correct tower (CCA) forregion relative which differences as in to well allows the as the for time-of-flight differences from machine in the the clock. interaction optical pathlength within This the allows detector. of the pulse is contained within a 25 ns window. Figure 2008 JINST 3 S08004 – 153 – Figure 5.35: Measured pulse shape, energy collected vs. time, for HF. wedge. Within layer 9 of eachflight wedge from is the an interaction arrangement region. of Thismonitored, optical arrangement as fibres allows has which the been mimic timing demonstrated of the in HCAL time-of- testby beam to the data be taking, laser flattened which using and verified the the synchronized timingbe beam. determined illuminated In so the the HO alignment and will HF be detectors, based only on the construction photodetector and can test beam data. Figure: 5.34 MeasuredHB/HE/HO pulse single shapes. event pulse shape from the scintillator tiles, representative of 2008 JINST 3 S08004 3 10 Noise = 3800 e Noise = 5420 e Noise = Noise = 6900 e Testbeam 2003 Particle energy (GeV) 2 10 – 154 – 10 , and possibly beyond. 1 − s 2 − cm 34 1

8 6 4 2 0

16 14 12 10

Signal time delay (n delay time Signal s) to 10 1 − s 2 − A number of techniques capable of providing suitable luminosity information in real time The channel-by-channel bunch synchronization of HCAL will be determined using a his- cm 28 have been identified [17].(HF) while One another, technique called the employs Pixel signalscle Luminosity tracking from Telescope (PLT), telescopes uses the based a on forward set single-crystal hadronPLT of diamond has purpose-built calorimeter pixel parti- not detectors. been At formally theHF time approved, are of but the writing, is ones the under being study. most vigorously The pursued. methods based on signals from the togramming procedure in the serialtion using link the boards beam (SLBs) structure of whichfast the determine LHC. control the The signals event bunch originating and synchroniza- from bunch synchronizationtween the is the TTC front-ends monitored system and using the which HTR. are Onthe transmitted a HCAL in global and scale, the other the data bunch detector stream andsignals. subsystems event be- synchronization is between determined using muons and other correlated physics 5.6 HF luminosity monitor The CMS luminosity measurement will bebunch used to basis monitor in the real LHC’s time performance ongoal and a to for bunch-by- provide the an real-time overallaccuracy normalization measurement with for is an physics update to analyses. rate determine of Theof 1 the design Hz. 5%, average For although luminosity offline every analyses, with reasonable thethese a effort design requirements goal will 1% is must be statistical a be made systematic to met accuracy 10 produce over a a more very accurate large result. range of Both luminosities, of extending from roughly Figure 5.36: Pulse time(solid variation points) as for a severalfrom input function 2003. amplifier of configurations signal compared amplitude with as test measured beam on measurements the bench 2008 JINST 3 S08004 or- 20 sum value is sent to -sum histogram. The sum histogram. The T T E T E -sum data and transmits E T E in which the average fraction of empty rings. Hence two sets of two rings are η rings is filled for use by the LHC. As a result, η – 155 – zero counting -sum histogram, and one additional occupancy histogram. T Two methods for extracting a real-time relative instantaneous luminosity with the HF have Outputs of the QIE chips used to digitize the signals from the HF PMTs on a bunch-by-bunch Although all HF channels can be read by the HLX, MC studies indicate that the best linearity The histograms are transmitted as UDP (User Datagram Protocol) packets from the HLX Each histogram has 3564 bins, one for each bunch in the LHC orbit. Each occupancy- E been studied. The first method is based on towers is used to inferexploits the the linear mean relationship number between the of average interactions transverse energy per per bunch tower and crossing. thebasis luminosity. The are routed second to method a set ofHF 36 HCAL physical Trigger towers. and In Read-out (HTR) order boards, toboard each derive called of the a which HF luminosity services luminosity 24 signal transmitter from (HLX) istaps the mounted HTR, into on an each the of additional raw the mezzanine HTR HF boards.them data to The stream HLX a central and collector collects node channelform over factor standard occupancy as 100-Mbps and the Ethernet. Synchronization The and HLX Linkreadouts boards Boards to (SLBs) have the the used Regional to same Calorimeter interface the Trigger ECAL (RCT) and system. HCAL for occupancy histograms is obtained using just two used for the occupancy histograms. Four rings are combined to form the algorithm has been optimizedrelated to effects. minimize sensitivity Each to ofoccupancy pedestal the histograms drifts, dedicated two gain to sets each changes ofbelow-threshold, of and rings over-threshold-1, the over-threshold-2. other sends following possible In 12 states addition, bitsthe for a HLX of each 15-bit and data a tower: further to enabled- histogram based the on HLX. all 13 There HF are three histogram bin uses twobaseline bytes, design is and to there add the are results four from all bytes desirable per channelscards into bin once a in roughly single every set the 0.37 of s, histograms. time. which is The safely Ethernet within core the inwork 1.45 the s bandwidth. HLX (worst case) automatically Each histogram packages histogram overflow on the spans data the several to type Ethernet make of packets, optimal histogram.transmitted the use at precise of a The rate net- number of eight depending approximately setsmultiple 1.6 of Mbps HLX to histograms boards. an comprise Ethernet The switch aboutof that switch 70 aggregates the multi-casts the kB servers the data from of is data responsible data, tothe for a which CMS publishing and pair is LHC the of control luminosity luminosity roomsserver information server and archives to the nodes. the Fermilab various data One Remote clients, for Operations each such Centerbits, luminosity as (ROC). or section The about (one second luminosity 93 section s).CMS corresponds DAQ An to systems. 2 XDAQ layer on this server makes it possible to communicate with other the input to the HLXone is used to create eight histograms: two sets of three occupancy histograms, 2008 JINST 3 S08004 ◦ ) as absorber and fused [121] Pb-Pb simulations 3 HIJING 5 g/cm 18. ≈ 1%. ≈ 6. Figure 6.1 shows the location of CAS- 6. 126]. < | η | 6.2. The calorimeter and its readout are designed in < – 156 – 2 physics in pp collisions [123]. CASTOR will be installed at 14.38 m from the interaction The main advantages of quartz calorimeters are radiation hardness, fast response and com- 6.1 CASTOR The CASTOR (Centauro Andcalorimeter Strange [120], Object designed Research) for detector thecollisions is very at a forward the rapidity LHC. quartz-tungsten region Itsgramme sampling [122], in physics developed essentially motivation heavy in is ion the baryon-free to andand mid-rapidity complementx proton-proton low- region, and the also nucleus-nucleus the diffractive physics pro- Forward detectors point, covering the pseudorapidity rangeTOR 5. in the CMS forwardthe region. beam pipe The when calorimeter closed, will as shown be in constructed figure in two halves surrounding at 5.5 TeV) can be measured with a resolution better than pact detector dimensions [124], making themin suitable the for the very experimental forward conditions region encountered tromagnetic at showers the in LHC. quartz The calorimeterssignal typical are containement), visible 5–10 i.e. transverse cm are sizes and a of factor aboutcalorimeters 3 hadronic 10 [124]. to and mm 4 elec- A respectively times (for detailed narrowerrical 95% than description specifications those of of in the “standard” the operation (scintillation) quartzand principle and photodetectors) (including tungsten can optimal plates, be found geomet- and in performances references of [125, light-guides, reflectors Tungsten-Quartz plates The CASTOR detector is astructed Cerenkov-based from calorimeter, layers similar of in tungsten concept (W) to plates the (alloy HF. density It is con- Chapter 6 such a way as tothey permit traverse the the calorimeter. observation The of typical the totaltance and cascade range electromagnetic development energies (about of in 180 the TeV the and CASTOR impinging accep- 50 TeV, respectively, particles according as to silica quartz (Q) plates as activea medium. thickness For the of electromagnetic 5.0 (EM) section, mmplates the and have W the plates thicknesses have Q of plates 10.0with 2.0 mm respect mm. and to 4.0 the For mm, direction the of respectively. hadronic the (HAD) The impinging section, W/Q particles, the plates in W are order and inclined to Q 45 maximize the Cerenkov light 2008 JINST 3 S08004 2 ≈ inclination. ). Each readout unit ◦ I λ (0.077 0 X 6.3. The inside surfaces of the light deep. The HAD section has 12 RUs, I . The total number of channels is 224. I λ λ ] reflective foil. The light guide is made out of 2 ) deep. The EM section is divided in two successive I – 157 – λ +TiO 2 ). In the hadronic section, a sampling unit corresponds to I (0.385 λ 0 X (0.77 0 X . In total, the calorimeter has 10 I λ Figure 6.1: Location of CASTOR in the CMS forward region. shows the complicated geometry of the W/Q plates, due to their 45 . Each readout unit consists of 5 SUs and is 0.77 I 6.3 λ In the EM section, each sampling unit corresponds to 2.01 . Both PMTs allow the muon MIP peak to be separated from the pedestal, an important feature 2 for calibration purposes. Beam tests results The energy linearity and resolutionhave as been well studied as at the CERN/SPSsummer spatial tests 2007, resolution in for of 2003 the two [125] final CASTOR and prototypes prototype). 2004 [126] The (as response well of as the in calorimeter tests to end-of- electromagnetic and cm a 0.8 mm stainless steel sheet.The Each PMT light is guide located subtends in 5 the SUsconsideration: in aluminium (i) both housing a the on Hamamatsu EM R7899 the and PMT, top.FEU-187 and HAD (ii) Two sections. produced types a radiation-hard by of multi-mesh, PMTs Research small-size are PMT Institute currently Electron under (RIE, St. Petersburg), with cathode area Light-guides and photodetectors The Cerenkov light, produced bymedium, is the collected passage in sections of (RUs) relativistic alonglight charged guides the onto length particles the of photomultiplier through the (PMT), calorimeters the asguides and shown quartz focused are in by figure covered air-core with Dupont [AlO+ SiO output in the quartz.Figure The combination of one W and one Q plate is called a sampling unit (SU). (RU) consists of 5 SUs and is 10.05 corresponding to 9.24 0.154 RUs and has a total of 20.1 2008 JINST 3 S08004

20–350 GeV pions, and = E 50%. The measured spatial ≈ = 1.7 (6.4) mm. HAD) 20–200 GeV electrons, – 158 – EM( = σ E Figure 6.2: CASTOR calorimeter and support. Figure 6.3: Details of the components and geometry of the CASTOR calorimeter. 50, 150 GeV muons. Good energy linearity for electrons and pions in the full range tested is = hadronic showers has been analysed with E observed. For the EM section,at the high constant term energies, of is theresolution less energy of resolution, than the that electron 1%, limits (pion) whereas performance showers is the stochastic term is 2008 JINST 3 S08004 ◦ 3 for 8. | ≥ η | ). The tungsten plates are oriented 0 ) runs, the expected average absorbed ). The tungsten plates are tilted by 45 X 1 I − λ s 2 − 6.5. The total depth of the combined system cm Figure 6.5: Photograph ofsection. the ZDC HAD 27 – 159 – 128], with pseudorapidity coverage of . The configuration includes 9 mm Cu plates in the front ) I λ ( shows a side view of the ZDC with the EM section in front and the HAD section ) and design-luminosity Pb-Pb (10 1 6.4 − s 140 m on each side of the CMS interaction region at the detector slot of 1 m length, 96 2 e 6.4: The side view of the ZDC show- − ≈ cm Figure 7.5 hadronic interaction lengths ing the EM and HAD sections. Figur 33 ≈ and back of each section.monitor For (BRAN, the Beam TAN’s final RAte of detector Neutrals configurationZDC’s [130]) an will calorimetric LHC be sections. real-time mounted luminosity in The theplates 120 HAD and mm section 24 space layers consists between of the of 0.7 mm 24 diameter layers quartz fibers of (6.5 15.5 mm thick tungsten to optimize Cerenkov-light output. Theplates EM and section 33 is layers made ofvertically. of 0.7-mm-diameter 33 The layers quartz of fibers fibers 2-mm-thick (19 areribbons. tungsten After laid exiting in the tungsten ribbons. platesto the form The fibers a from readout hadronic 6 bundle. individual section This ribbons bundle of are is compressed grouped each and together ZDC glued with requires epoxy into 24 a fiber tube. From there, is behind. A photo of the HAD section is shown in figure 6.2 Zero degree calorimeter (ZDC) A set of two zero degree calorimeters [127, radiation doses is about 180 MGy and 300 kGy, respectively, per data-taking year. neutral particles, are designed toion complement and the pp CMS very diffractive forward studies.and region, hadronic especially Each (HAD) for ZDC sections. heavy haspipes two Two at identical independent ZDCs parts: will themm be electromagnetic width located and (EM) between 607 mm the height twoin inside LHC front the beam neutral of particle the absorberdebris TAN D2 [129]. generated separation The in TAN dipole. the is located pprunning It collisions, the and was combined against (EM designed beam + to2.75 HAD) halo TeV protect spectator calorimeter and magnets should neutrons beam allow with and losses. the aand detectors reconstruction quartz During resolution fibers against of heavy of have the been ion 10–15%. chosen energy forto of Sampling the HF detection calorimeters of and using the CASTOR. energy tungsten The in the quartz-quartzpercent ZDCs fibers loss with [127] a in can design transparency similar withstand in up(10 the to wavelength 30 GRad range with 300–425 nm. only a During few the low-luminosity pp 2008 JINST 3 S08004 (6.2) (6.1) 10 mrad. ≈ 2 5 mm. Such a good position resolution 8%) ≈ + ( 13% 2 +  E E √ 70% √ – 160 – 138%  = = 2 E σ  E σ shows online plots for positrons entering the electromagnetic  6.6 There are a total of 18 readout channels for the two ZDCs. The signals from the ZDCs The response of the ZDC EM and HAD sections has been studied in beam tests at the The performance of both the left and right ZDCs has been studied with electron, pion and where E is in GeV. Positive pionsresponse with of energies the of combined 150 GeV EM+HAD and system. 300can The GeV be pion were parametrized energy used resolution, as to obtained measure by the a Landau fit, where E, again, is inwill GeV. The allow measurement width of of the EM beam showers crossing is angle with a resolution of section of one calorimeter. an optical air-core light guide willtube. carry the light The through radiation full shielding hadronicdirection. to the section photomultiplier For will the consist electromagnetichorizontal of section, direction fibers four from into identical all five towers 33towers identical divided and fiber fiber in each ribbons bundles. the fiber will longitudinal bundle bephototube. These will divided The be 5 in EM mounted and bundles the HAD with will sections aHF: will form Hamamatsu 0.5 be R7525 five instrumented mm phototubes with horizontal air with the gap a sameefficiency bi-alkali type from for photocathode, of the Cerenkov phototube resulting light photocathode as in of of the an about average a 10%. quantum are transmitted through a longunderground counting (210 room m) (USC55). coaxial The cable signalto from to the each the channel QIE front-end will (Charge be HCAL IntegratorAn split, VME analog with and 90% crates sum, Encoder) going proportional in while to the the 10%Level 1 total will trigger energy in be deposition the used in heavy-ion running each forof mode: detector, the making the will interaction coincidence provide trigger point of the is (neutron) signals. sensitive basic signals toright from most both timing of sides the coincidence nuclear and will electromagneticin also cross the section. be heavy A used left- ion as runs.and a for Information fast defining from the vertex scalers real-time trigger, luminosity. willresolution to Finally be of it suppress used the may beam-gas for system be events tuning by possiblewhich to looking the sits improve between at interaction the the the of overall electromagnetic correlation energy beams and between hadronic sections, the near ZDC the and shower the maximum. CERN/SPS BRAN in 2006 detector, [131] andfrom 2007. 20 The GeV to calorimeter 100 is GeV. The foundparametrized energy to as resolution be obtained linear for within the different 2% positron in energies the can range be muon beams in 2007. Figure 2008 JINST 3 S08004 – 161 – Positron Energy, GeV Positron Energy, GeV 0 50 100 150 0 50 100 150 0

5 0

800 600 400 200 25 20 15 10

Resolution, % Resolution, Response, a.u. Response, Figure: 6.6 Online results for positrons fromlinearity, while the 2007 the test bottom beam. panel gives The the topbeam panel energy energy. shows resolution the as response a function of the incoming positron 2008 JINST 3 S08004 z-measuring planes. The of detection planes, the muon chambers had 2 , which in turn decay into 4 leptons, has been called ∗ – 162 – bending plane, and 4 chambers which provide a measurement in the -φ r 2 and are organized into 4 stations interspersed among the layers of the flux 1. 7.1. < | η | In the barrel region, where the neutron-induced background is small, the muon rate is low, Therefore, as is implied by the experiment’s middle name, the detection of muons is of central The CMS muon system is designed to have the capability of reconstructing the momentum direction, along the beam line. The fourth station does not contain the to be inexpensive, reliable, and robust. and the 4-T magnetic fieldstandard is rectangular uniform drift and cells mostly are containedpidity used. in region the The steel barrel yoke, drift drift tube chambers (DT) with chambers cover the pseudora- 2 sets of 4 chambersresolution. in each station The are drift separated cells as much of as each possible chamber to are achieve the offset best by angular a half-cell width with respect to their “gold plated” for the case inmuons, which the all best the 4-particle leptons mass are resolution muons. canare be Besides less achieved the affected if relative than all ease the electrons in leptons by are detecting from radiative muons losses SUSY because in they models, the tracker emphasize material. thewide This discovery angular example, potential coverage and for of others muon muon detection. final states and the necessityimportance for to CMS: precise anddesign robust stages. muon The measurement muon was systemand a triggering. has central 3 theme Good functions: from muon its momentum muonfield earliest resolution identification, solenoidal and magnet momentum and trigger measurement, its capability flux-return areidentification yoke. of enabled The muons. by latter The the also material high- serves thicknessis as crossed shown a by in hadron muons, figure absorber as for a the function of pseudorapidity, and charge of muons over theparticle the entire detectors kinematic range for of muon themuon LHC. identification system CMS was [132]. uses naturally 3 driven types to Due of haveBecause a gaseous the to cylindrical, muon barrel the system section consists and shape of 2 about of planar 25 endcap 000 the regions. m solenoid magnet, the return plates. The firstmuon 3 coordinate stations in each the contain 8 chambers, in 2 groups of 4, which measure the Muon detection is a powerful toolhigh for background recognizing rate signatures expected at of the interesting LHC processes withthe over full Standard the luminosity. Model Higgs For very example, boson the into predicted ZZ decay or of ZZ z The muon system Chapter 7 2008 JINST 3 S08004 . 2 p ◦ 1. 170 and = | η < η | 4 with no θ 2. < < ◦ | η | η F H 7.2) is typically 95–99% 3 5 1st Muon Station . 2nd Muon Station 3rd Muon Station n 4th Muon Statio 2 1 1 1 1 4 3 2 1 2 E E E E M M M M 5 . 2 1 1 E and the beam-crossing time of a muon. Each 6- M 2 2 2 3 E E η L M M A – 163 – C H

1

. A global momentum fit using also the inner tracker

3

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C B B B B 0. 0 M M E M M = | O H η | 0

0 5 0 5 0 5 0

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s h t g n e l n o i t c a r e t n I

values of 0.9 and 2.4. There are 4 stations of CSCs in each endcap, with chambers | η | Because the muon detector elements cover the full pseudorapidity interval Due to multiple-scattering in the detector material before the first muon station, the offline In the 2 endcap regions of CMS, where the muon rates and background levels are high and bending plane. The anode wires run approximately perpendicular to the strips and are also -φ acceptance gaps, muon identification isOffline ensured reconstruction over efficiency of the simulated range single-muon samples corresponding (figure except to in 10 the regions around read out in order to provide measurements of positioned perpendicular to thecathode beam strips line of and each interspersed chamberr run between radially the outward flux and return provide plates. a precision The measurement inlayer the CSC provides robust pattern recognition formatching rejection of of hits non-muon to backgrounds those and in efficient other stations and to the CMS inner tracker. (the transition region between thepunchthrough DT reaches the and system CSC due systems), to theexceeds where amount 16 the of interaction efficiency material lengths in drops. [132]. front of Negligible the muon system, which muon momentum resolution of the standalone muonfor system is transverse about momenta 9% up for to small 200 valuesbetween GeV of [17]. 15% At and 1 TeV 40%, the depending standalone momentum on resolution varies neighbor to eliminate dead spotsway in to the measure efficiency. thefor muon This efficient, time arrangement with standalone also excellent bunch providesand time crossing a their resolution, identification. convenient orientation using were The simple chosen numberdifferent meantimer to stations of circuits, provide into chambers a good single in efficiency muon for each track linking station and together for rejecting muon background hits hits. the from magnetic field is large andWith their non-uniform, fast the response muon time, system fine uses segmentation,between cathode and radiation strip resistance, chambers the (CSC). CSCs identify muons Figure 7.1: Material thickness inpidity. interaction lengths at various depths, as a function of pseudora- 2008 JINST 3 S08004 | η | 1.2). Note 6) of the muon 1. < | η = 10 GeV/c = 50 GeV/c = 100 GeV/c = 500 GeV/c = 1000 GeV/c T T T T T p p p p p μ μ μ μ μ 0 0.5 1 1.5 2 2.5 1

0.9 0.8 0.98 Efficiency 0.92 0.88 0.82 0.96 0.94 0.86 0.84 resolution. T p – 164 – | η | tracks that may stop before reaching the outer 2 stations. In the T resolution is about 15% in the barrel and 25% in the endcap. p T p threshold over a large portion of the rapidity range (| T p = 10 GeV/c = 50 GeV/c = 100 GeV/c = 500 GeV/c = 1000 GeV/c T T T T T p p p p p μ μ μ μ μ Because of the uncertainty in the eventual background rates and in the ability of the muon A crucial characteristic of the DT and CSC subsystems is that they can each trigger on the A total of 6 layers of RPCs are embedded in the barrel muon system, 2 in each of the first 2 Finally, a sophisticated alignment system measures the positions of the muon detectors with 0 0.5 1 1.5 2 2.5 1 of muons with good efficiency and high background rejection, independent of the rest of the

. Left panel: standalone reconstruction (using only hits from the muon system with a vertex 0.8 0.9 Efficiency 0.88 0.82 0.98 0.92 0.86 0.84 0.96 0.94 T T p p system to measure the correctplementary, beam-crossing dedicated time trigger when the system LHC consistingboth reaches the of full barrel resistive luminosity, and plate a endcap com- chamberstrigger regions. (RPC) with The a was RPCs sharp added provide a in fast, independent, and highly-segmented detector. The Level-1 trigger endcap region, there is a planethe of coincidences RPCs between in stations each to of reducecrossing the background, identification, first to and 3 improve to stations the achieve in a time order good resolution for for the bunch trigger to use Figure 7.2: Muon reconstruction efficiency as a function of pseudorapidityconstraint). for selected Right values of panel:tracker). global reconstruction (using hits from both the muonimproves system the and momentum resolution the by an(1 TeV) order both of detector magnitude parts at together low yield momenta. a At momentum high resolution momenta of about 5% (figure that the muon system and thethis redundancy inner enhances tracker fault provide finding independent and muon permits momentum cross-checking measurements; between the systems. system. The RPCs are double-gap chambers,at operated in high avalanche rates. mode to They ensurelution produce good operation than a the fast DTs response, or withfrom CSCs. good multiple hits time They in also resolution a help but chamber. to coarser resolve position ambiguities reso- in attemptingstations, to and make 1 in tracks each of thealgorithm last to 2 work stations. even for The low- redundancy in the first 2 stations allows the trigger respect to each other and to the inner tracker, in order to optimize the muon momentum resolution. 2008 JINST 3 S08004 z- . φ 7.4), each made of 7.3). In each of the 12 projection, is constrained -φ r z-measuring, SL is not present in the fourth coordinate. A muon coming from the interaction ). This value is small enough to produce a negligible discontinuities limits to only 2 (out of 4), the number – 165 – 2 φ z and φ ). In the inner SL, the wires are orthogonal to the beam line -φ r -measuring SL. In this scenario, there still exist limited regions of φ 40 GeV), the probability of electromagnetic cascades accompanying the -measuring SL, passes through the honeycomb plate, then crosses the ≥ φ position along the beam. This third, z coverage, although the supports are placed so as not to overlap in φ At high momenta ( The wires in the 2 outer SLs are parallel to the beam line and provide a track measurement A drift-tube (DT) chamber is made of 3 (or 2) superlayers (SL, see figure The amount of iron in the return yoke was dictated by the decision to have a large and intense The wire length, around 2.4 m in the chambers measured in an in which the combined effect of the point first encounters a parent muon becomes relevant. A2 reliable stations way are to available cope isof with to electromagnetic this have debris. effect a in good Redundancy thehits is tracking regions generated also efficiency where by in needed only neutrons each to and cope stationRedundancy photons is with even obtained in whose the by rate the uncorrelated having several is presence background layersi.e., of much separated the larger drift thickness cells than of per the that station. tube fromenergy The walls, electrons. separation, prompt should The be muons. relatively large thick enough wall to of the decouple DTs, the 1.5 basic mm, units gives against an effective low- decoupling among and measure the station, which therefore measures only the η of stations crossed by a muon. 4 layers of rectangular drift cellsof staggered the design. by half a cell. The SL is thein smallest independent the unit magnetic bending plane ( measuring SL and the second occupancy and to avoid thenumber need of for active multi-hit channels to electronics, an yet affordableprotection value. the against A cell damage tube is was from large chosen a as enough brokenelectromagnetic the to basic wire debris limit drift accompanying and unit the the to to muon partially obtain itself. decouple contiguous cells from the solenoidal magnetic field atother the outside, core would be of insufficient CMS. for reliableTherefore, Two identification detector 2 and additional layers, measurement of layers one a aresectors inside muon embedded in of the CMS. within the yoke the yoke and yoke thereThe the iron are yoke-iron (figure 4 supports muon that chambers arezones per between in the wheel, the chambers labeled of MB1, a MB2, station MB3, generate and 12 MB4. unavoidable dead by the longitudinal segmentation of the ironi.e., barrel the yoke. maximum path The transverse and dimension time380 of of ns the drift, in drift was a cell, chosen gas to mixture be of 21 85% mm Ar (corresponding + to 15% a CO drift time of 7.1 Drift tube system 7.1.1 General description The CMS barrel muon detector consists ofline: 4 stations the forming 3 concentric cylinders inner aroundabout cylinders the beam 172 have 000 60 sensitive drift wires. chambers Itbarrel each is muon possible and system to the because use outer of driftmagnetic cylinder the chambers field. has as low 70. the expected tracking rate There detectors and are for the the relatively low strength of the local 2008 JINST 3 S08004 X

MB/Z/4/1 ϕ Y YB/Z/3/1 MB/Z/4/12 Towards Center of LHC 8. The constraints of MB/Z/3/1 YB/Z/3/12 MB/Z/4/2 0. 7.4). The SLs are glued MB/Z/3/12 Z+ YB/Z/2/1 YB/Z/3/2 < YB/Z/2/12

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MB/Z/3/3 YB/Z/2/3 TC MB/Z/2/3 YB/Z/1/3 TC

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T The many layers of heavy tubes require a robust and light mechanical structure to avoid sig- p the several layers of tubes insidehigh the same station. With thisbetter design, than the 95% efficiency in to the reconstruct pseudorapidity a range covered by 4 stations, i.e., to the outer faces of the honeycomb. In this design, the honeycomb serves as a very light spacer, Figure 7.3: Layout of the CMSeach barrel muon wheel DT are chambers identical in with onechimneys of the the for exception 5 of the wheels. wheels magnet The –1 chambers shortens(bottom) and in the +1 the chambers where MB4 in the chambers 2 presence arechamber of sectors. layout. cut cryogenic Note in that half in to sectors simplify 4 the (top) mechanical and assembly 10 and the global nificant deformations due to gravity inThe the chosen structure chambers, is especially basically in frameless those andcomb that for plate lightness lie that and nearly separates rigidity the horizontal. uses outer an superlayer(s) aluminium from honey- the inner one (figure mechanical stability, limited space, and thecross section requirement of of 13 redundancy led to the choice of a tube 2008 JINST 3 S08004 SLs, since φ ) plane. One can -φ 200 GeV. The 100- = T RPC RPC p – 167 – RPC RPC provides a summary of the general DT chamber parameters. m. This figure makes the precision of the MB1 chamber (the 7.1 µ of 100 -φ r One SL, that is, a group of 4 consecutive layers of thin tubes staggered by half a tube, gives The goal of the mechanical precision of the construction of a chamber was to achieve a m target chamber resolution is achieved by the 8 track points measured in the two µ excellent time-tagging capability, withprovides a local, time stand-alone, and resolution efficient bunch of crossingby a identification. a The few time constant nanoseconds. tagging amount is of delayed the This time size capability equal of to the the tube,the the maximum time electrical possible field, resolution drift-time, and was which the shown iscell gas to optics determined mixture. to be by maintain Within largely a the linear independent relationship angularand of between the range the the drift-time of distance track of interest, from angle, the the wire electronsindependently but of along in this the the each crossing requires entire track of the drift the path.crossing 3 assignment, bunch SLs crossing this by tagging circuit fast is delivers pattern-recognition the performed and circuitry. position its of Together angle with the centre the in ofThis bunch the gravity information SL of is the reference track used system segment assignment. by with the precisions first-level of muon 1.5 trigger mm for and the 20 time mrad,global and resolution respectively. transverse in momentum innermost layer) comparable to the multiple scattering contribution up to Figure 7.4: A DT chamber in position inside the iron yoke; the view is in the (r with rigidity provided by theresolution outer within planes a of station. tubes. Table A thick spacer also helps to improve angular see the 2 SLs with wiresa along honeycomb the plate beam with direction supports andattached attached to the the to other DT perpendicular the chambers to iron via it.chamber yoke. support type. plates In Not glued between to is shown the are bottom the and/or top RPCs, faces, which depending are on 2008 JINST 3 S08004 m µ ch. 582 582 666 666 762 762 764 4576 1144 7440 3800 4760 35960 40832 46400 22156 Sum of 171852 0 0 0 0 0 0 0 7.3). The SLs m required for 2038 2038 2038 2501 2501 2501 3021 3021 3021 µ (mm) Θ Wire length 2379 1989 1989 2379 1989 1989 2379 1989 1989 2379 1989 2379 1989 2379 2379 2379 (mm) Φ m-diameter gold-plated stainless- Wire length µ m thick aluminium tape, glued on a 0 0 0 0 0 0 0 µ 7.1.2). The requirements of 250- Θ 228 190 190 228 190 190 228 190 190 SL concentration in the 10–20% range. The 2 No. of ch. Φ and section 196 196 196 238 238 238 286 286 286 382 382 286 286 372 190 238 m. To avoid corrections to the primary TDC data SL µ – 168 – 7.5 No. of ch. 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 Θ SL No. of 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Φ SL (z) coordinate in the CMS coordinate system. No. of φ m, which is considerably less demanding than the 100 1 8 2 1 1 1 1 1 1 10 10 10 58 58 58 29 µ 250 m nonlinearity can be obtained by operating the tubes at atmospheric pressure m. This figure matches well with the requirements of linearity for the bunch No. of µ µ 7.1.3) identifier. The cell design includes 5 electrodes, 1 anode wire, 2 field chambers gas mixture and by keeping the CO 2 type total shows the drift lines in a cell. The anode is a 50- 7.1.3), the deviation from linearity of the space-time relation in each drift cell must be chamber Φ(Θ) measure the 7.5 MB/1/3/4 MB/1/4/4 MB/1/1/4 MB/1/2/4 MB/-1/3/3 MB/-1/4/3 MB/-1/1/3 MB/-1/2/3 MB/W/4/4 m thick, 23-mm-wide mylar tape that insulates the electrode with respect to the aluminium MB/W/4/S MB/W/2/S MB/W/3/S MB/W/1/S MB/W/4/10 µ MB/W/4/8,12 MB/W/4/9,11 (section less than 100–150 shaping strips, and 2 cathode strips (figure crossing (section the single wire resolution is better than 250 of type Table 7.1: Chambers of the CMS5 DT wheels system. (numbered Notation: –2, MB/wheel/station/sector. –1, W 0, stands 1, for and all 2) and S means any sector (1 to 12, see figure 100- plate set to ground. Bothactivated the glue. conductive and Field insulating electrodes ribbons are are positioned self-adhesive at with the a top pressure- and bottom of the drift cell. Cathodes steel wire. The field electrode is made of a 16-mm-wide, 50- resolution and 150- the mechanical construction. 7.1.2 Technical design Drift cell Figure with an Ar/CO multi-electrode design also ensurespresent this in performance some in regions of the thea presence chambers. single of It tube, the is the stray worth precision notingthe magnetic requirement that wires, field on to is the reach about this position 300 local of performance the in field-shaping electrodes, including 2008 JINST 3 S08004 3600V for wires, + m-thick, 11.5-mm-wide µ m-thick mylar tape. This design µ Figure 7.7: Exploded view ofthe the drift end cells part showing of theand different end-plugs spring contacts fortions. high voltage connec- 7.6) following a technique similar to that used for – 169 – 1200V for cathodes. − e 7.6: Exploded view of the cathode 1800V for strips, and Figur electrodes, glued on the I-beams. allows for at least 3.5the mm extremities separation the mylar of tape the is electrode cutis flush from recessed with the by respect 5 sides to mm. the of I-beamplates the Special ends and tools grounded while the were the I-beam. I-beams. aluminium designed The tape At and only built difference to between glue the the tapes electrode used strips for to the both electrode the strips and the are placed on both sidesthe of strip the electrodes I-beams on (figure the aluminium plates. A cathode consists of a 50- Figure 7.5: Sketch of aof cell the showing cell drift are lines at and ground isochrones. potential. The plates The at voltages the applied top to and the bottom electrodes are aluminium tape insulated from the I-beam by 19-mm-wide, 100- + 2008 JINST 3 S08004 1.2, 1 kV. − − 7.10) is useful mixture and the drift-cell 2 . Under the rough assumption 5 7.1.2. The cell pitch is 42 mm, , allowing them to work within an efficiency 5 – 170 – 7.9). 7.8). This may be compared to the the drift velocity as measured with the Drift 3.6 kV, respectively. + HV connections to the cells and the front-end electronics are located at opposite ends of the The drift cells will operate at a gas gain of 10 The cathode and wire end-plugs were designed to protect against discharges from the border 1.8, and of a uniform drift fieldstrips of should 1.5 be kV/cm, set the to distancesAs a between described voltage the below, larger during various than the electrodes or chambersatisfactory imply equal commissioning performance to that in was 1.7 the obtained laboratories kV with and and the at+ the voltages CERN cathodes of (with cathodes, to B=0), strips, around and wires set to Chamber mechanics and services A chamber is assembled byrequired gluing stiffness. 3 Each (or SL is 2)high, made SLs of 1-mm-thick to 5 an aluminium aluminium aluminium sheets, I-beams,while honeycomb 1.5-mm as thick, plate the separated described to layer by ensure in pitch 11.5-mm- the section the is same 13 time mm. by gluing ForI-beams. together the The 2 pitch aluminium construction and plates of height separated therespectively. of by an An SLs, an I-beam SL array a determine has of full the an parallel largertested independent layer aluminium and gas individually of smaller and before dimensions cells electronics of being is enclosure. achamber. glued built cell, Each to at SL the is assembled honeycomb and plate and/or to thewires. other SL The to HV is formcells fed a via into printed-circuit each HV boards SL (HVB). via Eachplate HVB two separating is 52-pin 2 mounted custom along layers the connectors of edge and of drift distributed the cells aluminium to and the serves drift the 8 cells above and the 8 cells below it. One optics described above provide a linear relationshiprequirement between time for and drift the path. use This of isdrift an the velocity essential chamber using GARFIELD as [134] a2 showed first-level kV/cm that trigger (figure drift device velocity [133]. saturationVelocity occurs Chamber A (VdC) between calculation (figure 1 of and the plateau with a wide threshold range,environment which expected is convenient at for CMS. the A operationfor of computation better large of chambers understanding equipotential in of the lines the [136] roleregion between (figure of the each central electrode. strips and The theand cathodes position is not of mainly by the determined 0 by their the V voltage sizewire equipotential values. of to in the the electrodes The the nearest electrode, gas the gain strips.and is The 1.85 wire/strip mainly kV voltage difference determined to must achieve by be a kept the between gain voltage 1.75 not drop far from from the the expected value of 10 ones just described is thethe width: aluminium tape the is mylar 16-mm tapethe wide. used shaping These of for strips the the are electric electrode set fieldpresence strips to of and is a magnetic the fields. positive 23-mm linearity voltage wide of and the and help space-time to relation, improve most noticeably inat the the end of the cathodeprecision. strips and The to house wire thearound holders wire the holder, protrude which wire. inside is crucial theelectrodes for The cell the to I-beam wire providing the position and 12 high wire mm voltage, end-plug of are pieces, additional shown as in protection well figure as7.7. the The springs Ar-CO connecting the 2008 JINST 3 S08004 m/ns) as functions of electric µ (85%/15%) and for a gas mixture and special care had to be taken to 2 2 37 mm . The measurements were obtained with the 2 × with air impurities corresponding toO 500-ppm VdC, a dedicated reference driftwill chamber be that used for drift-velocity monitoringing dur- CMS running. For comparison,measurements from results135] [ of for ature, pure and gas a mix- simulation with Magboltza [134] for mixture with impurities are also shown. field and gasture pressure Ar/CO for a pure gas mix- Figure 7.9: Measuredvelocities (in and calculated drift s d a 3 e t s

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1.2 1.1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 ] [ cm -Axis z changes the maximum drift time by about 2% with respect to no contamination, z-axis is orthogonal to the wire plane). 7.12. With this type of gas enclosure we can obtain a level of oxygen contamination 2 It is very important that the individual SLs of the DT chambers are gas tight because contami- During SL assembly, before the fifth aluminium plate is glued closing the structure, reference Figure 7.10: Equipotential lineslines in are half labeled of with a the drift potentials cell. in The volts anode (the wire is on the right side. The nation by nitrogen (from air) changes thethe drift signal velocity by efficiency, a when sizeable its amount,1000 contamination while ppm oxygen exceeds reduces of 2000 O ppm. Contamination by air including forming the corners of thealong SL the box. plate border Theplates to front that and form contain back all an necessary of open gasO-rings the connectors, frame, that box HV which seal connectors, have the and is L-shaped signal structure. then profiles outputs,where A equipped glued closed the 3-dimensional with outer with computer aluminium model removable plates of longshown have the in been cover figure gas removed enclosure to for expose one allof SL, details 10–20 of ppm, the downstream of gas the enclosure, 3 is SLs flushed in parallel withblocks are about glued 1 such volume that change their per positionswhen day. with the respect chamber to the is wires completed, can the be wire measured positions precisely. may Thus, be determined by measuring the reference channel. The distance between theof position the where gas the enclosure, wire which entersand determines the the the front-end end side SL plug (corresponding dead and to the area, outer corresponds face to 60 mm on both the HV plane, while the with a sizeable effect on the triggerness of performance the of SLs the is detector. obtained In byC-shaped the gluing profiles DT profiles are chambers, to used the the and gas outer the tight- aluminium ends skins. of Along these 2 profiles sides are of glued the to SL, reference blocks (figure 2008 JINST 3 S08004 Φ-type SLs and one Φ-type SLs for layer 4). The panel thickness Figure 7.12:model of the A gas enclosure of 3-dimensional the SLs. computer – 173 – 7.4) that sustains and gives rigidity to the chamber and provides the e 7.11: Corner blocks of an SL. These The space for the chamber supports and attachments, the passages for alignment, and the Each SL is fully independent with respect to gas tightness, HV, and front-end electronics; Figur pieces also carry the referencespect marks with to re- whichsured. the wire positions are mea- varies from 125 mm for the firstthe three correct stations, dimensions to 178 and mm equipped forthe with the supports the fourth and station. C-shaped for It profiles part is at of delivered the the with electronics. periphery that are usedlocal for read-out and trigger electronicshoneycomb plate. is provided The by channel a isness. approximately channel The as running 2 wide around channels and the parallelfixations deep to border to as the of the the beam honeycomb yoke the line plate supports andremaining thick- themselves, to sides and the houses the yoke the longitudinal steel read-out alignmenttion supports and passages. house). (minicrates trigger the electronics One To kinematic that of ease collect thechamber. chamber the 2 All handling, full the chamber all general informa- services servicesbalconies are for along the connected the chambers on walls are the of locatedwheel same around the is side each CMS thus of barrel cavern an wheel independent, where the on large there subsystem. the is 4 space for the racks and crates. Each marks on the blocks.all the Pressure aluminium and planes to temperaturefront-end form electronics, monitoring a and probes, HV unique distribution ground ground completeeach straps reference, SL. the and that equipment a that connect is Faraday in cage the for gas the enclosures signals, of hence an SL canhoneycomb be panel fully (figure tested beforefixation points it from is which glued itΘ-type is to SL suspended form in in the a the case CMS DT of barrel chamber. layers steel 1, yoke 2, (two SLs and are 3; glued and two to a 2008 JINST 3 S08004 .minicrates A minicrate, as described – 174 – Figure 7.13: Block diagram of the DT electronic system. segments in the same chamber by requiring a spatial matching between segments oc- and briefly summarized, whereas detailed information will be described in the following 8.2. In each TRB are located the Bunch Crossing and Track Identifier (BTI), which φ 7.13 Front-end electronics and HV distribution are physically embedded in the chamber gas vol- ume. Amplified and shaped signals are directly fed to the sections. previously, is an aluminium structurehouses attached both the to first the level honeycomb ofin the of the read-out the minicrates and drift are of the tube the Triggerin trigger chambers Boards electronics. section that (TRB) The and trigger the boards Serverprovides located Boards independent segments (SB), from as each described chamber incorrelates SL, detail and the Track Correlator (TRACO), which curring at the samewhich bunch selects crossing the (BX). best TRB twoicrate. output tracks signals from In all are parallel TRACO fed to candidatesRead the to and Out trigger the sends Boards signals, Server the (ROB), chamber Board data which datato out (SB) are are the of in fed Level-1 the charge Accept to min- of (L1A) theacquisition the trigger read-out chain. time decision system The digitization Chamber and through Control of the the Board chamberROB (CCB) data signals located and merging at related TRB to the configuration centre the of and next theof monitoring. minicrate, stages the allows It minicrate of ends, works the that together data receives withTrigger data Control the from (TTC) CCB system. the link Slow Among board, Control otherand tasks, and on other the global one TTC CCB experiment distributes signals Timing the to and LHC every 40.08 board MHz in clock the minicrate. 7.1.3 Electronics The DT electronics is a complex,out heavily integrated data system, handling, which includes and L1the trigger service electronic logic, electronics, system read- layout such togetherfigure as with the the LV functions and associated HV to systems. each sub-task A is shown description in of 2008 JINST 3 S08004 48)/pF die and ± 2 shows the ASIC 2.5 mm × 7.14 8.2). , common to all channels. Auxiliary th 7.1.3) and to the CMS L1 system through 7.1.3) where data merging is performed. – 175 – in the range 5–200 MHz. Ω m BiCMOS technology [138]. This chip integrates signal pro- 100 µ ≈ 8.2) and to the Read Out Server (ROS, section The ASIC operates with 2 distinct supply voltages, 5 V for the analog section and 2.5 V for The shaper that follows is a low-gain integrator with a small time constant. Its output is Trigger and data signals coming out of the minicrates are collected by VME electronics in- The resulting custom front-end application specific integrated circuit chip (ASIC), named circuits allow the masking ofthus individual stopping channels the at propagation the ofA shaper excessive similar input noise but background (pins faster to A_ENn enable/disable the inchannels trigger that function high output and was state) signals DAQ implemented in electronics. on responsemonitoring to the the a operating cable-driver test conditions stage input. of to the A detector. select temperature probe was also includedthe for output stage, with athe total 2 voltages power and consumption almost ofcarried independent 100 out of on mW the the (25 temperature MAD and mW/ch) ASICanalog signal equally both section rate. on split an the Several between bench average tests and gain have in of been the about field 3.7 in various mV/fC configurations. was For found the for bare chips with (1370 stalled in the iron balconiessection attached to the DTFrom wheels, the respectively wheel to balconies, the data Sector aretem through sent Collector the via (SC, Detector optical Dependent Unit links, (DDU) boththe (section to Sector the Collector CMS (SC) central and acquisition the sys- Drift Tube Track Finder (DTTF, section directly connected to 1other input input of being connected a to latched the discriminator external threshold made pin of V 2 differential gain stages, the Front-end electronics The front-end electronics for the barrel muonfunctions detector must are satisfy to many amplify stringent requirements. the signals Its send the produced results by to the the detector, trigger compare andmust read-out them use chains with a located a short on shaping threshold, the time chamber. and this to Analog signal achieve allows a processing low-gain high operation spatial of resolutionThe while the downstream introducing drift comparator minimal has tubes, noise; to thus be very improvingwhich fast reliability and reduce precise and to the chamber allow influence the lifetime. use ofmust of low be the threshold very signal values, fast, amplitude and it onbe must the transmitted deliver differential time through levels low-cost response. that cables. minimise Besides The mutualthe the interferences output control above and driver and functions, can also several monitoring features ofchannels that the simplify and data the resulting acquisition need have forabout been both power implemented. high consumption reliability The and led large lowpossible. to number cost, of the limited space, necessity and to concerns integrate the front-end electronicsMAD, as was much developed using as 0.8 cessing for 4 channels (480 000 drift pieces were tubes) produced plus with a someblock fabrication ancillary diagram yield better and functions than the in 95%. pinout a Figure chains of 2.5 begins the with TQFP44 a package used chargehaving a for preamplifier GBW it. that product in uses Each excess a of33 of ns 1 the single while GHz 4 gain input (result identical from impedance stage, analog simulation). is folded/unfolded The cascode, feedback time constant is 2008 JINST 3 S08004 Outp1 Outn1 GND Outn2 Outp2 BYP Outp3 Outn3 GND Outn4 Outp4 60)/pF elec- Vdd Vdd VDS VDS VDS VDS DRIV DRIV DRIV DRIV L L L L BIAS D_EnR2 D_EnL2 ONE SHOT ONE SHOT ONE SHOT ONE SHOT m gaps included in the PCB are µ D_EnR1 D_EnL1 GND GND TCH TCH TCH TCH LA LA LA LA WIDTH CTRL GNA GNA Vcc Vcc DISCR DISCR DISCR DISCR f – 176 – Vre W_CTRL Vth T_En BLR BLR BLR BLR T_OUT TEMP PROBE SHAPER SHAPER SHAPER SHAPER Figure 7.14: Block diagram of the MAD ASIC. 105 sparks at 3.6 kV amplitude with 1 spark/s on all channels). Vcc Vcc > PA GNA PA PA PA GNA The above figures enable front-end operation at a threshold well below 10 fC (the value used The chip performance is somewhat degraded when it is mounted on a front-end board (fig- In1 In3 In2 In4 Vcc 7.15): the gain reduces to 3.4 mV/fC and noise and crosstalk increase to (1850± GNA GNA A_En1 A_En3 A_En2 A_En4 2 mV total error. ure trons and 0.2%, respectively. Thesemade effects of are an caused external by resistorcapable the and of input diodes dissipating that protection the together network, energy(biased with which stored 100 is at in 3.6 the kV) 470sparks to pF (ASICs the capacitors survive ASIC that inputs. connect the This detector protection wires is effectiveduring test even beams in was the 5 fC) case40 when pF. of connected The propagation to repeated delay the of detector, the which(time chip has walk is a is less less maximum than than 5 capacitance 7 ns of ns). withcharge little The pulses dependence rate on capability (just signal of below amplitude the MAD saturation)interleaved ASIC at largely signals, exceeds 2 demand: so MHz 800 there fC rate isforeseen do a per not wide drift affect tube safety the during margin efficiency CMS with operation. in respect detecting to 5 the fC total rate (about 10 kHz) electrons ENC. Another key characteristicis for less operation than with 0.1%; low moreover,± the signals baseline is restorer the and crosstalk, the which comparator offsets sum up to less than 2008 JINST 3 S08004 in 10 2 − cm 10 s, and of the need µ m. µ – 177 – 7.1.3, together with the DT muon trigger electronics. -rays to simulate the behaviour in a CMS-like environment. γ m CMOS technology. This highly programmable TDC is based µ Figure 7.15: Front-end board (FEB). 3000 hours on 20 FEBs and related circuits without revealing any fault. > The number of HPTDCs per ROB has been decided following a compromise between the Finally, the radiation tolerance and overall reliability of the front-end board and associated Read-Out Boards are built around a 32-channel high performance TDC, the HPTDC, which Read-out electronics The electronics of the read-out system ofsignals the CMS generated DTs is in responsible the for the driftsystem. time chambers digitization of and The the for time the digitization datalocated of transmission in minicrates, to the as higher signals described levels is in of section performed the at DAQ the Read-Out Boards (ROB [140]), electronics were investigated [139]. Radiationhigh-energy neutrons, testing involved protons, a and seriesThe of results tests can with be thermal summarized and naked dies), in very latch-up little immunity sensitivity to (undetected SEUsfor SELs (only the a even whole few with thousand detector spurious heavy lifetime), counts/channel ionsthan and calculated foreseen on tolerance in 10 to years total of CMS integrated operation.125°C dose was In orders carried addition, out of accelerated for ageing magnitude in higher a climatic chamber at Two FTP cables arethe used towers to beside send the digitized CMSROS data merges wheels from data where each coming the minicrate from Read-OutDetector chambers to Dependent Server Units of the (DDU) (ROS) one in rack boards the wheel USC55 are 30copper sector control located. m room, links through performing into away a the Each multiplexing 60 in 70-m of optical optical 1500 requirements links. link both of to The the the Read-Out expected Systemsaverage trigger occupancy have rates of been (100 0.76% kHz) developed in at according the the to whole high the detector, luminosity a of L1 LHC, trigger latency with of an 3.2 number of unused channels whencomponents when the it granularity is too is big. too Finally,token each small ring ROB has passing and 4 scheme, the HPTDCs where connected multiplication one in of of a clock them common synchronous is configured as a master to control the token of the of operating in anyears environment of where activity. the integrated neutron fluence will reachis 10 the third generation of TDC’sbeen developed by implemented the in CERN IBM Microelectronics 0.25 groupon the [141], and Delay it Locked has Loopcorresponds to (DLL) 265-ps principle, resolution, providing when itresolution a is is time enough clocked bin to at obtain of the a LHC 25/32 single 40.08-MHz ns wire frequency. position = This resolution 0.78 time of 250 ns, which 2008 JINST 3 S08004 4 4

E S S C C O M O S S R R V T T E

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V w V 3 . o 5 3 P TTC+Slow control Figure: 7.16 Sketch of the read-outelectronics and located trigger inside a minicrate. in four groups of sixFIFO channels read-out each, performing a so-called pooling CEROS, searchthe controlled for events, by the discarding an next headers FPGA event and that toreducing trailers be accordingly manages of read. the the those data These overhead. channels FPGAs without also timing filter or error information, to simulate 10 years of CMSDDU activity, [143]) gave is no the faults. last Theof component DT 5 of Front-End-Driver VME64X (FED, the also 9U DT called serial read-out boards optical electronics. housed connections in The from the DTformatted 12 FED CMS event system ROS, service fragment consists corresponding cavern; to to each thesynchronization an CMS board with common entire collects the DAQ DT data trigger through wheel, through timing system a signal, and is S-Link the L1 transmits transmitter guaranteed trigger module. a by acceptthe and the FED The fast TTC board. commands, that The network, are layout providing distributed of to the the the board LHC different is parts depicted of in figure read-out data chain. Theavoids that token the ring failure scheme in one issoftware of bypassing designed the systems TDCs following have interrupts a been the implemented. failsafe whole ROB mechanism, operation. which Both hardware and number of ROBs per minicrate.are all The connected smallest to minicrate the has ControlControl Board 3 (CCB) (TTC) ROBs that signals. and manages, the among As biggest others, can the has Timing be 7. and seen Trigger They in figure minicrate are connected tobeginning the of ROBs this to section, receive FTP TTLLocated cables translated in connect hit the the signals. barrel outputfive tower of As minicrates), racks the described so ROBs there at each to are the the ROS9U 60 receives ROS boards ROS boards 25 have boards, to channels 12 [142]. multiplex ofnumber, data per the link coming status wheel, LVDS from and copper 1 other the ROB-ROS per information, ROBs, link.feature and sector adding of send necessary These (four the them information to to ROS of the boardtemperature DDU ROB is monitoring, through that a and it fast a link. also 512ability Another kB includes in memory a case to power of test supply transmission and protection errors. perform circuitry, data current In flow and Figure snapshots for trace- 2008 JINST 3 S08004 voltage to the CC 4.2 kV (2.5 mA maximum + 2.2 kV (1 mA maximum output current), a − and the A3100 to power the Sector Collector Crates. – 179 – DD A. µ Figure 7.18: Scheme of the DDU architecture. voltages to the chamber front-end electronics and the V DD and V 15V (1.5 A maximum output current). The A877 HV outputs are subdivided into 12 ± CC The DT LV system uses three different types of CAEN Easy3000 modules: the A3009 to The data rate in each DT FED board is limited by the maximum rate the CMS DAQ can mini-crates, the A3050 for the mini-crate V The control of the(Mod. Easy3000 A1676A) power plugged supply in system a is SY1527 done mainframe remotely located using in a the branch control controller room. Each A1676A provide V groups (8 for the special A877channels. boards Each powering macro-channel the supplies MB4 4 chambers) HVare conventionally channels divided called per into macro- layer: 2 groups), 2 1 anodes strip (theis and wires hardware 1 of limited cathode. each to layer For 100 all HV channels, the maximum output current accept from an S-Link connectionto (about deal 200 with Mbytes/s). the expected The DT number event size of (7 boards kbytes/event) has at been 100High chosen kHz Voltage trigger and rate. Low Voltage systems The CAEN SY1527 universal multichannel powervoltages supply (HV systems and are LV) used to to the supply muonof high DT and A876 chambers. low master The basic boards modules andhoused of in A877 the the DT remote HV SY1527 boards. system mainframe. consist Eachand A of monitoring, maximum them to supplies a of high maximum 8 voltages ofchamber A876 and 4 (two low master independent in voltages, A877 boards controls the remote can boards, caseseparate be each of non-powered one mechanical MB4 crate powering of sitting one in Sectors DT racksdelivers 4 to on or each the towers A877 10). next HV to board: The theoutput a wheels. A877 current), positive The remote HV a A876 in negative boards the HV are range indual from located the 0 LV range in of to from a 0 to 2008 JINST 3 S08004 800 time [ns] 600 7.21). 400 200 5%), deviation from linear drift ± 0 7.22), wire positions and comparison events in a few hours. With such a large 6 0

-200

80 60 40 20 10 120 Entries 100 140 ≈ m (figure Figure 7.20: Drift Timewith distribution a disconnected of cathode. a cell µ = 3 A; = 4 A; = 3 A; = 30 A; 0 0 0 0 – 180 – 7.20) and disconnected strips (figure 800 and time [ns] 7.19 600 7.23). 400 200 0 e 7.19: Drift Time distribution of a good crate. Beside efficiencies, other relevant working parameters are measured from cosmic-ray data, as

• VCCMC = 5.8 V, software current limit• i VDDMC = 4 V, software current limit• i VCCFE = 5.2 V, software current limit• i VDDFE = 2.6 V, software current limit• i VSC = 2.6 V, the current limit depends on the number of SC and ROS boards plugged in the 0 -200

50 Entries 100 350 300 250 200 150 cell. Wire position corresponds to time 0. Figur branch controller can handle up to48 6 V DC Easy3000 that crates. is The provided byare Easy3000 the delivered: crate CAEN is AC/DC powered converter A3486S by module. external The following voltages 7.1.4 Chamber assembly, dressing, andChamber installation assembly Mass chamber assembly was started inJune January 2006, 2002 with and a was constant fully production completed rateof for (spares a all included) good the in sample four production of sitesit cosmic involved. to muons The CERN. collection allowed In full each testing laboratorywhich cosmic-ray of covered events a the were full constructed triggered acceptance chamber, by of before anable the external during sending chamber. scintillator chamber system assembly, Since drift final times minicrateTypical were trigger electronics measured was rates with not were external avail- TDCs 50–100 and Hz,data a sample resulting it custom in was DAQ. possible to spotlike and disconnected cure cathodes problems (figures which could not be detected in previous tests, with CCD measurements during assembly, relative100 alignment Hz of per layers, and cell, noise see (typically figure below calibration stability (drift velocity measured to be stable within parametrization, measured to be well within 100 2008 JINST 3 S08004 0 2 8 1 6 1 4 1 cell n. 0 m in the full cell 9 2 µ 1 distance from wire [mm] 0 1 100 0 8 ± 8 6 0 7 4 2 0 6 0 0

0.1 0.2 0.3

-0.1 -0.2 -0.3 Mean residual [mm] residual Mean 0 5 range. Figure 7.22: Residualsdistance as from the a wire, functionpendence indicating of well a within linear the de- 0 – 181 – 2525 4 2020 0 3 position (mm)position (mm) 1515 1010 0 2 55 00 0 1 -5-5 0 -10-10 0

60 50 40 30 20 10 90 80 70 -15-15 [Hz] Noise 7.1.4. After going through the alignment procedure, chambers are equipped with gas 7.1.3), minicrates-related items and external protections are installed at this stage. -20-20 At a first stage chambers are assigned to a particular position in CMS, depending on their After dressing the chamber the following tests were performed: • High voltage long term tests; • Gas tightness tests; 1 -25-25

0.9 0.8 efficiency 0.85 0.95 Figure: 7.21 Single cellcell efficiency (red for dots) and a for a good cellstrip with (green a disconnected dots). orientation. Before any test,in each section chamber undergoes thecomponents optical (cooling alignment pipes, gas procedure manifolds, described PADC pressure meters),like HV stickers, cables protectors, and additional grounding items straps,(section etc. Basically all components except for the minicrates Chamber dressing All chambers, built andand fully commissioning tested prior at to the installation inCERN production the (an sites, experiment. MB2 were type Since sent the chamber arrival arrived272 to of in more CERN the summer chambers first for 2000, (including chamber prepared final spares) at forto testing have a a been test continuous received beam workflow of from [144]), dressing all a and total four testing. of production sites, leading Figure 7.23: Typical hit rate distributionwith in cosmic one rays. layer, as This measured rate during is the dominated test by of noise a and SuperLayer is typically below 100 Hz per cell. 2008 JINST 3 S08004 . Last C bus system 2 ready to install 7.24). This bench had 7.4). All the 250 DT-chambers positions 7.1.3). All signal cables from the chamber to – 182 – m and the position of the forks relative to the chamber µ 40 < σ tube as the light-passage. Each fork has 10 LEDs, 6 and 4 respectively, 2 65 mm 1200 V for cathodes) for a minimum of 6 weeks. The time constant of the chamber × − At this point the chamber has passed all tests and can be considered The primary aim of the alignment is to give the positions of the anode wires but this is not The high voltage long term test consists of a continuous monitoring of the high voltage per- Finally a cosmic test stand has been set up with trigger scintillators, independent cabling, LV Once this first certification step is passed, the chamber dressing is completed and the chamber • Cosmic-muon tests. are recorded by this system viabers optical and connections specially using designed LED video-cameras light fixed sources tocalled mounted the on forks return the are yoke cham- of mounted the on barrel.rectangular the Four 50 side-profile LED-holders of the honeycombon structure each side (two of per the side), fork. using The the control of the LEDs (on-off, current) is performed via I the minicrate are installed andof tested, the minicrate and is then tested theconnections at minicrate are this itself checked, stage is for as inserted. thelocal well first electronics The as chain. time performance configurability together and with a data real processing chamber. performance All ofdressing internal the steps are full performed (installation ofbers carters are and coupled additional protections) together and to then RPCs, DT forming cham- an installable barrel muonChamber package. survey To determine the chamber positions in theposition CMS monitoring coordinate system Alignment and System to was follow built their (section movements a integrated in the minicrate. directly possible. On thecorner other during hand the all chamber the construction.corner wire blocks To positions a establish calibration are the bench measuredtwo connection functions. was with between built The respect the at first to LEDs one the theallowing and was CERN the SL to the ISR full-chamber measure site geometry, the including (figure cornertheir the block relative planarity, positions positions with to of respect be the tochamber measured. superlayers each coordinate in other, system stretched 3D The on and the second corner blocks.could function observe The was bench the contained LEDs to video-cameras that and measure photogrammetrythe the LEDs targets by to LED photogrammetric measure methods. positions the The in corner benchfrom allowed blocks MB1 the us to with to MB4. measure respect all The to the full typescampaign bench of was by chambers calibrated the and CERN recalibrated survey before group. eachany Also, chamber significant additional calibration LEDs deformation were of mounted the onlocations bench the of bench itself. the to corner detect The blocks precision was of the bench measurements for the formance (electric current) under the nominal valuesfor for strips, all and components (3600 V forwith wires, the 1800 final V gas connections isdegradation has also been computed observed as with a respect measurement to of the gas values tightness. measured at No theand significant HV sites. supplies and several HPTDCs, capableseveral of millions measuring one of chamber triggers at a in time,of a and almost few registering all hours. kind The of problems later related analysis to of the these chamber data itself allowsis and the its declared recognition internal ready electronics. for minicrate installation (section 2008 JINST 3 S08004 Φ- EntriesEntriesMeanMean 264 264 -0.04883 -0.04883 RMSRMS 0.2285 0.2285 -deviation X [mm] φ ∆ in the ratio 85/15 2 Φ-type SL corner block positions for

0

-1.5 -1 -0.5 0 0.5 1 50 40 30 20 10 Number of chambers of Number from the nominal design valuetype superlayers. for the two Figure 7.25: Distribution of the – 183 – m. Both values are within the acceptable range defined by physics requirements. µ shows the result of the residual distributions of 70 7.25 < The gas is also analysed independently for each of the 5 wheels and consists of a measurement σ Figure 7.24: The chamber calibration benchthe in CERN ISR Lab. was all measured chambers. Gas system For the DT chambers a safe and inexpensive gas mixture is used, namely Ar/CO Figure volume. The gas isinto distributed 5 in lines parallel to to feed all each50 drift chambers of cells on the the in 5 wheel; barrel four (3) wheels;within steps: on (2) the the (1) SL on chambers a the the it long is wheel main tube split it lineis with into is small 50 is 3 split holes lines l/h split into distributes to for the 50 feed gas each lines thewith over 3 chamber. to the a SuperLayers; feed drift cleaning Due (4) the cells. station to The is the nominalrun used. flow large at It total constant is number absolute foreseen of to pressure 250inside add inside the chambers, about the chamber. a 10% The chambers, closed fresh pressure to loop is gasoutlet avoid regulated daily. circuit of any for The each each variation line gas wheel. of at system There the the is aretwo gas drift flowmeters distribution sensors at velocity rack at the on inlet the the and wheel. inlettotal. The and gas They outlet pressure should gas is ensure also manifolds a measuredneeded on safe with for the and unaccessible chambers, chambers. redundant measurement To amounting be of to ablea the to 1000 return analyze pressure sensors the line at in gas brings every actually chamber, present acontrolled as in sample multiway every chamber, valve to permits the the gaswheel, selection for room. of analysis. the There desired is chamber one or such the line gas per arrivingof wheel at the and the oxygen a and of remotely theparameter humidity of content the of DT the chambers, gas, thechamber as drift (VdC), well which velocity. features as The a a drift very direct velocityin homogeneous, measurement is a constant, of measured known region the with and where main a adjustable two electric small field thin drift beams of electrons from a beta-source cross the chamber volume and 2008 JINST 3 S08004 used to cradle demonstrate that the 7.8 7.26). Pneumatic movements – 184 – 7.26. The first chambers were installed in the bottom sectors of Wheel +2 in July 2004 and the trigger a counter outsidethe the signal chamber. from the The anode distributionbeing wire well of of known times the by between chamber construction, the istwo by sources, recorded. measuring trigger one the signal The reads distance and distance directly in the betweenaccurately time by drift the between accumulating velocity. two the data Variations beams for peaks of about from the 5 the drift min. velocity The can data be shown in monitored figure insert the chamber in its location inside the iron slot. Figure 7.26: Installation of MB1 station on Wheel -2. The yellow frame is the absolute values measured with themonitoring VdC of agree the with drift the velocity expectation.the is drift The that velocity special to one monitor merit does it. of not a need direct to know whichChamber impurities installation are in CMS affecting The main installation tool isthat a can platform be) (cradle anchored with to the interfaceallow pads same the mounted support precise on rail the alignment as wheelthe of in (figure cradle the the and iron chamber those pockets with inelectric respect the motor. to iron The the pockets installation of are iron thein aligned, pockets. figure chamber the in chamber Once the is MB1 the pushed station rails of into on Wheel position -2 with sector an 11surface is installation shown was completedsectors in 1 Wheel and 7, -2 which could in notfor December be handling filled 2006. during on the the surface Installation heavy since lowering these completion, operation, parts was for of made the wheel underground. were reserved 2008 JINST 3 S08004 0 7.27). 2.5 5 =0 deg =15 deg ! ! . The cathode o m (figure µ Distance to the wire [mm] 7.5 HV:3600/1800/-1200 V and 15 7.19) are both signs of 10 o 147], with cosmic-rays deviations from linearity =0 α 12.5 146, 7.28 15 17.5 20 being the meantime obtained from the time 0

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m/ns. 1 one can easily observe an average spatial resolution of 170 t ) generated by the incoming muon in 3 consecutive, staggered layers. The µ , 3 t 81512 0.1125E+05 , m, which corresponds to a trigger jitter smaller than 5 ns. = ( 2685. / 22 2 MT 340 m. The position of the t µ σ , µ 1 · t MT 2 3 100 320 √ 170 ± Entries Magnet Test and Cosmic Challenge Constant Mean Sigma = = t t 7.29). The geometrical acceptance associated with the presence of the I-beam is clearly seen σ e 7.27: Gaussian fitted 300 0 σ Silicon Beam Telescope data can also be used to measure precisely the chamber efficiency

4000 2000 8000 6000

12000 10000 Entries peak allows the determinationdrift velocity of of 54.4 an average with Figur the saturation of the drift velocity.layers Under the assumption that the time resolution is the same in all are within smoothness of the drift time box and the fast drop of the trailing edge (figure completely installed and equippedDAQ with system. final hardware, was tested together with theTest beam final data: CMS chamber performance Several dedicated muon test beamdifferent runs conditions. were Single set cell uppersion spatial in of resolution the order could to be test determined chamber [144] performance simply under by the dis- (figure by the drop of efficiency in that region. In the rest of the cell the efficiency is always higher than 7.1.5 Chamber performance Chamber and trigger performances have beenbefore thoroughly analyzed mass at production various stages, (with on andtest prototypes without beams external magnetic and field withboth [145]), the at on CERN production final sites chambers Gamma and with so-called Irradiation at Facility the commissioning [144, of the installed chambers, and finally with the of the signals ( Using a Silicon Beam Telescope, it wason possible the to SL measure the and deviation the from reconstructed the extrapolated position. hit As can be seen in figure 2008 JINST 3 S08004 146], 7.33. This 7.32), and tested both at 7.30. It is reasonably stable, for various filter values of the gamma source, 7.31 – 186 – 50 Hz, and does not vary much with channel number. Also the effect of higher noise ≈ at values of levels, generated at the CERN Irradiationwalls Facility, at by chosen photo-conversion rates, in both thereconstruction on chamber reconstruction efficiency aluminum and is trigger shown efficiency, was in studied. figure The SL segment 99.5%. The typical intrinsic averagetest noise, beam as in measured dedicated during random chamber trigger construction runs or [146], during is a shown in figure Figure 7.29: Efficiency aschamber a surface; function (bottom) with of an the expanded scale distance excluding to the I-beam the region. wire (top), for tracks orthogonal to showing no significant dependence of theeven reconstruction algorithm at on noise the rates gamma irradiation higherLHC level, than operations. the maximum Since levelsstray expected the magnetic in fields chambers any are are present, DT the operatedwere chamber impact carefully during in of simulated normal the (finite the radial element iron and analysisdedicated program longitudinal yoke muon ANSYS, components test of figure of beams the CMS, where field whereand the during chambers important the were CMS operated inside Magnetelectron a Test and drift magnetic Cosmic lines field Challenge, caused [145, by withdistortion a comsic can field rays. be of The roughly 0.5 distortion T approximated of parallel bya the a to rotation rotation the of of wires the the can drift driftmaximum be cell lines seen drift around with in path the respect figure and wire, to simulating timewhich the is go direction generated, through of together the the with I-beam incidentof a region particles. the drop where four A of the layers change efficiency drift minimizes in for lines the the inclined do impact tracks not on reach track the measurement wire. of this The last staggering effect. In the case of 2008 JINST 3 S08004 6 (source filter) 5 10 log 4 3 values (0.7–0.8 T) occur in the 2 r 1

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7 / 4 / Z / B M • exercise the reconstruction software under realistic conditions. e 7.44: Event displays from the MTCC. Left panel: muon reconstructed in a DT sector in 4. Take data with other CMS subsystems. Figur conjunction with Tracker activity.chambers. Right panel: muon track passing through both DT and CSC For the DTs (as well assector 10 for and the the adjacent barrel sector RPCs) 11, three bothaccounted in instrumented for YB+2, 14 sectors along DT were with chambers, sector read-out, corresponding 10 the to inchamber about YB+1 bottom performance (figure 10 previously 000 carried channels. out Beside thetunity in cross-check to test of test beams, the MTCC reconstruction data algorithmsand provided for to a different observe unique magnetic for oppor- field the strengths first (figure time tracks combined in different detectors (figure Figure 7.43: The MTCC exploitedand in YB+2 (sectors the 10, barrel 11) region instrumented three with sectors DTs and in RPCs. wheels YB+1 (sector 10) 2008 JINST 3 S08004 positions z 8.2) failing z. Thus signals gener- 7.1.5, were released by the trigger view changes, acquiring a Lorentz angle. -φ r – 195 – drift tube at a given distance from the wire but at different -φ r 7.1.5, because of the radial component of the magnetic field between the solenoid This efficiency was found to be about 65–70% in all stations, independent of the magnetic The observed lower efficiency of the DTLT can be explained by the fact that, while the trigger While procedures for the synchronization of the DT system in stand-alone were studied in To study the efficiency of the DT Local Trigger (DTLT), events were selected by requiring sector collector and thus used to compute the DTLT efficiency. field. The measurements obtainedhigher using efficiency, of 40 the order MHz of bunchedconsidered. 85% muon or beams more, and [148] for provided which a only triggers much at the correctsystem BX is were clocked every 25 ns,properly cosmic synchronized rays by occur choosing atwith the any time. respect best to phase In bunched higher which beams levelrandom maximizes the triggers. the arrival BTIs number time can In be of of thesuch HH the case conditions triggers muons of the rate thus cosmic of rays, makingthe Low-quality this the trigger associated is segments BX BTI released not can synchronization by possible, easilytrigger itself the fluctuate. due Sector BTIs meaningless. Collector to increases, As in each the and only In station, also correlated we trigger also expect segments an were increase in released TRACOs by (section the The angle is increasingly largerated as by the muon B hits radial in componentwill increases a appear along at different times. Thefor effect the has muon implications both track forthe reconstruction the MTCC trigger and a synchronization it and total should ofat be several 159 calibrated values million of out cosmic-muon the before eventsand B LHC 4 (48 field. T start-up. million (93 Data million DT were events During triggered)effect collected at in were at 3.8 an and collected 0 T MB1 4 T), and (as whichtriggered) an a allowed MB2 have reference), a chamber. been then detailed Some at taken mapping 15 of 2, withpointing million the 3, the to Lorentz events 3.5, the MB1 at angle centre 3.8, local 0 of T trigger thetrigger and configured timing CMS 3.8 studies T barrel to in (1.6 (LHC select the million beam DT-CSC only overlap, DT interactionas in muon point): in particular a segments this also LHC the sample run. muon is time-of-flight specific is for the same Phase I of the MTCC,in in tools Phase for II fine (duringthe inter-synchronization the analysis magnetic of of field the the mapping muon DTproven operations) trigger detectors to effort data be (DT, was at sensitive CSC put to the and desynchronization chamber by RPC). output a as In few nanoseconds. function particular ofthe RPC-originated L1A presence has of the RPCtriggers. triggers In RBC1 such (for events, wheelwhenever track possible, YB+1) segments using or were TDC RBC2 reconstructed hits. (forstation, in If RPCs the each more in one muon than with wheel station one the YB+2) independently, trackwas largest segment number computed was of for reconstructed associated each in hitssegment, a muon was given taken. and station The separately, comparing efficiency by them ofsame counting with the muon events DTLT station. events with Accepting which a a alsocosmic trigger reconstructed rays had regardless are muon of likely a to its generate trigger BX triggersis position segment in intrinsically was nearby at not dictated BXs, as by any synchronized. with the BX non-bunched Only(HH), fact particles High-Low in correlated that the (HL) system trigger the or segments, Low-Low namely (LL), of as quality defined High-High in section scribed in section and endcap disks, the electron drift direction in the 2008 JINST 3 S08004 7.45 (left) 7.45 values, the 0 0 3 0 2 0 T0 correction (ns) 1 of the event to obtain the ef- 0 -correction time, obtained as the Trig 0 -10 values. This can be seen in figure 0 -20

1 -30 0 DTLT efficiency DTLT 0.4 0.2 0.8 0.6 z-position of the track in the chamber, with and 7.1.5. The largest effect in the barrel is expected to – 196 – 0 5 for all track segments in a station, for events triggered 0 4 0 0 3 All tracks tracks with trigger 0 2 T0 correction (ns) 0 1 correction of the reconstructed track segments in events triggered 0 0 -10 -20 -30 is the time correction to be added to the t 0 -40

shows this effect for the two MB1 stations in Wheel 2, displaying the BX value

-50 0 tracks / ns / tracks 500 400 300 200 100 7.46 The magnetic field modifies the shape of the field lines in the drift cell, thus affecting the The quantity t Figure Consequently, one expects that muons crossing the detector at the “correct time” (for which , obtained by the ratio of the two histograms shown on the left. 0 (right) which shows the DTLT efficiency as a function of the t by the barrel RPC,best superimposed trigger to efficiency is the obtained one only for at some events preferred which t also had a DT local trigger. The fective time at which theminimizing given the muon space crossed resolution the of detector.shows the It the reconstructed can track distribution be segment of computed in the event-by-event a t by station. Figure ratio of the two distributions previously described.They correspond Two peaks to at the efficiency case around in 90%BTIs which are the are visible. muon synchronized. crosses the The detectorefficiency two at can the peaks “correct correspond be time” to very for two which low,efficiency adjacent as is BXs. therefore in explained this For by case other thethe t the fact “correct that time” system cosmic at is which rays not the occur BTIs at synchronized. have random maximum time The efficiency. with observed respecteffective DTLT to drift velocity, as discussed in section the BTIs behave as perfectly synchronized toas the such clock) will a be condition detected is withthe the the highest detector same efficiency, as out in of the suchsynchronization bunched of a beam the “correct tests. system is time” On not will the optimised. be other hand, detected muons with crossing lower efficiency, as for them the occur in station MB1 ineffective Wheels drift +2 velocity, if and large -2. enough, couldvalue From make by the the one point BX unit. determination of less view precise, of and the shift DTLT, its a change of the to correlate segments amongsynchronized the system, two which will superlayers turn of into a a DTLT efficiency given loss. station, with respect to a perfectly determined by the DTLT as a function of the Figure: 7.45 Left panel: distributionby of RPC t (solid line).superimposed The (dashed distribution line). of the Right panel: samet quantity DT for local trigger events also efficiency as triggered a by function the of DT the is quantity 2008 JINST 3 S08004 6. 1. < | η | z-direction of 100 1 are also detected by 4 crosses 3 or 4 CSCs. 0 2. 2. 5 < < | | width. Following the original 0 η η | | ∆φ 7.48). The de-scoped 72 ME4/2 < -50 2 segment position in Theta SL (cm) segment position in Theta SL and B = 0 B = 4T -100 in the CMS coordinate system) is obtained 7.47

9 8 -150 trigger BX 9.4 9.2 trigger 8.8 8.6 8.4 8.2 7.8 7.6 MB1, wheel 2 2, muons are detected by both the barrel drift 7.50). The largest chambers, ME2/2 and ME3/2, 1. z, where the stray field components are larger. This < , and the number of wires is about 2 million. There | – 197 – 3 η | 100 < 50 m 9 > 0 5 ; all chambers, except for the ME1/3 ring, overlap and provide φ 0 7.49). Wires run azimuthally and define a track’s radial coordinate. in ◦ -50 segment position in Theta SL (cm) segment position in Theta SL in size. The overall area covered by the sensitive planes of all chambers 2 or 20 B = 0 B = 4T -100 ◦ 5 m , the gas volume is

2

9 8 1. -150 trigger BX trigger 8.4 8.2 7.8 7.6 9.4 9.2 8.8 8.6 MB1, wheel 1 × -coverage. A muon in the pseudorapidity range 1. 4 φ The CSCs are multiwire proportional chambers comprised of 6 anode wire planes interleaved Figure 7.46: BX determined by the DTLT as a function of the track position in the the muon station, with and withoutof magnetic the field, B-field for is MB1 in expected. Wheel Onan 1 the influence on right, of the the the left, same magnetic where quantities field no are on effect shown the for drift MB1 velocity in is Wheel expected. 2,without where magnetic field. Whileis no a clear slight effect delay is of visible theof in average the MB1-Wheel BX wheel, corresponding value 1, to which in larger tendsdelay MB1-Wheel values to is 2 of increase at there as most the of track the order approaches of the 0.3 edge units of BX. 7.2 Cathode strip chambers At the time of thechambers LHC (CSC) start-up, arranged the in CMS groups EndcapME2/2, Muon as 36 system follows: ME3/1, will 72 consist 72 ME1/1, of ME3/2, 72 468 and ME1/2, cathode 36 72 strip ME4/1 ME1/3, (figures 36 ME2/1, 72 chambers will not be available during earlyand years cover of either CMS operation. 10 Thecontiguous chambers are trapezoidal In the endcap-barrel overlap range, 0. are about 9000 high-voltage channels inwith the 12-bit system, signal about digitisation, 220 000 and cathode about strip 180 000 read-out anode channels wire read-out channels. tubes (DT) and endcap CSCs. In the baseline design, muons with CSC idea [149], the muon coordinate alongby the interpolating wires charges (φ induced on stripsare (figure about 3. is about 5000 m resistive plate chambers (RPC); however, in the initial detector this coverage is reduced to among 7 cathode panels (figure Strips are milled on cathode panels and run lengthwise at constant 2008 JINST 3 S08004

0

7.380 m 3.800 m 4.020 m 5.975 m 1.200 m 7.100 m 4.885 m 2.950 m 2.864 m 1.300 m 1.930 m

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m 0 8 9 . 4 1 in ◦ provide contiguous coverage in Figure 7.48: The ME2spanning station 10 of CSCs. The outer ring consists of 36 ME2/2 chambers, each Figure 7.47: Quarter-view ofsystem the are highlighted. CMS detector. Cathode strip chambers of the Endcap Muon 2008 JINST 3 S08004 for ME1/1 and ME1/2 chambers and about ; 2 -φ Figure 7.50: A schematic viewillustrating of the a principle single of gap CSCinterpolating operation. charges By induced on cathode strips by avalanche positive ions near aobtain wire, one a can precise localisationalong the of wire direction. an avalanche r – 199 – at the first-level trigger. -φ r m off-line spatial resolution in µ m for all others. µ 150 level trigger. With such ansimple majority efficiency rule per ensures chamber that the andcrossing reconstructed 3–4 number muons CSCs will in be more on assigned than a the 99% muon correct of bunch track cases; path, a at estimated random hit rates up to 1 kHz/cm The CSCs provide the functions of precision muon measurement and muon trigger in one The performance requirements for the CMS cathode strip chamber system include the fol- run lengthwise (radially). The 144 largest • About 75 • At least 99% efficiency per chamber for• finding track At stubs by least the 92% first-level trigger; probability per chamber of identifying correct bunch crossings by the first- • About 2 mm resolution in • Reliable and low-maintenance operation for at least 10 years at the full LHC luminosity, i.e., Figure 7.49: Layout of a CSCzoidal made panels. of The 7 panels trape- form 6 gasplanes gaps of with- sensitive anode wires.the The top cut-out in panel reveals anodestrips. wires Only and a cathode few wirestheir are azimuthal shown to direction. indicate ∆φ Strips ofCSCs constant are 3.4 mand long up along to the 1.5 m strip wide direction along the wire direction. device. They can operate atrequire high precise rates gas, and in temperature, large ornatural and pressure for non-uniform control. measurements magnetic in fields. Moreover, the a They endcap radial do region, fan-shaped can not strip be easily pattern, arrangedlowing: on the cathode planes. 2008 JINST 3 S08004 7.51). m-thick copper on their outer µ – 200 – m on such spans. This specification arises from the desire to keep gas-gain µ 300 ± Figure 7.51: Mechanical design of the CMS cathode strip chambers (exploded view). FR4 cathode gap bars are glued to both sides of every other panel (panels 1, 3, 5, 7 in fig- Six of the panels have a pattern of 80 strips milled on one side. Strips, being radial, have The mechanical structure is based on seven 16.2-mm-thick trapezoidal panels (figure 7.51) so that when the panels are stacked together, these cathode bars define 6 gas gaps of surfaces, forming the cathode planes. ure 9.5 mm. To provide additional support,ber there centreline. are 4 spacers When placed all betweenalong 7 panels the along panels the chamber are cham- perimeter putchamber (through together, centreline the holes (through entire holes in in stack the themore is cathode than spacers). tightened 60 gap Such cm down an of bars) with unsupported arrangement and bolts length.the ensures Measurements at required that show no 4 that panel most points has of the along panels the are flat within a pitch that varies from 8.4 mm at the narrow chamber end to 16 mm at the wide end. The gap variations within a factor of 2. The panels are made ofskins a commercially 12.7-mm-thick glued polycarbonate on honeycomb eachused core side. for with printed FR4 two circuit is 1.6-mm boards. a FR4 fire-retardant The fibreglass/epoxy FR4 material skins widely are clad with 36- 7.2.1 Chamber mechanical design The 72 ME1/1 chambers and the largerBelow, 396 we chambers describe have somewhat the different design mechanical of designs. end the larger of chambers this using section, ME2/2 aschambers. summarise an the example and, ME1/1-specific then, features at that the distinguish them from the other 2008 JINST 3 S08004 is m µ 4 m in diameter, µ m (rms). Milling µ component is a non- 2 7.51) around which an- . The CO 4 1% of the chamber volume per day at an 10%CF < + 2 10%, while wire spacing variations are less than ± – 201 – panels (panels 2, 4, 6 in figure 50%CO + /min for the largest chambers whose gas volume is about 3 anode to make the groove edges smoother (otherwise, sharp edges and 2 cm ◦ < m. Wires found to fall outside of these specifications were replaced. µ Three of the panels are so-called After winding, the wires were first glued and then soldered to anode bars 4.75 mm in height Each wire plane is sub-divided by spacer bars into 5 independent HV segments, which allows After stacking the panels and tightening the bolts (with O-rings), continuous beads of RTV Side plates made of 3.2-mm-thick Al extrusions were attached around the chamber perimeter. The nominal gas mixture is 40%Ar 150 was done with a cutter tilted atburrs 45 might provoke sparking and discharges). ode wires were wound (these panelswound do wires not directly have gap on bars). a Aminute; panel specially one by designed rotating panel winding it could machine around bewire its completed spacing long (about of axis 1000 about at wires 3.2 a onand mm speed each attached was of side) to defined about in by the 5 less combs: panel turnswere than edges threaded per stretched 4 during at rods 250-g hours. winding. running tension the (about The Gold-plated full 70%without tungsten of panel any the wires, length intermediate elastic 50 limit) supports. and run6 The their electrostatic kV full length stability (the up limit nominal to for 1.2wire operational m the tension point longest non-uniformity is wires does 3.6 is not kV). above exceed Based on measurements during production, the flammable quencher needed to achieve large gas gains, while the main function of the CF ± (half of the gas gap).An The automated anode soldering bars machine are allowed made forwires of soldering make copper-clad 1 at FR4 anode a and read-out speed carry channel ofto the with the 3.5 a electric wire s width artwork. groups per of on about joint. one end 5 Groups and cm. signals of High are 16 voltage read (HV) out on is theus distributed other to end via independently 1 regulate nF blocking orbars capacitors. turn were inserted off (and HV prior on to their anyguard installation), wires of 8 were the wires inserted were 5 in removed. sections. placeedge Two of gold-plated In effects. the 200- first places and The where eighth very the thinwere spacer first wires to that and be were left last removed unguarded, to wireswires, eliminate the in electric which each field would plane on provoke them arepanel discharges. would also supports be thicker. and much Such larger the If plane than individual thechamber segmentation, for HV performance edge the control because very rest over thin robust. of of smaller wires the the wire-plane intermediate sections, makes the overall sealant were applied along thethe outer bolts seams and between the the RTV panels sealopened, make and serviced, the gap and chambers bars. hermetic. resealed. The Should Gas O-ringsgap it enters around be bar, into necessary, flows one a from of chamber one can theexits plane be outer from to the gas last another gaps gas in via gap an a viaafter inlet an zigzag installation outlet in manner in of a via a the cathode gap special chambers, bar.over-pressure holes The was of in leak required 7.5 rate, the to mbar measured panels, during (e.g., be then production200 and litres). They stiffen the chamber and connect the top and bottom copper skins to form a Faraday cage. to prevent polymerisation on wires.elsewhere [150]. A detailed discussion of the gas optimisation can be found between strips is about 0.5 mm. The precision of milling was better than 50 2008 JINST 3 S08004 ). . A minimum 2 4 10 × 9.5 m ≈ (left). The constant-fraction dis- 7.55 7.53). Unlike the other CSCs, the ME1/1 m, and wire spacing is 2.5 mm, so the nominal µ (figure ◦ – 202 – 29 = (right)). L α 7.52 -coordinate. -φ r (left) shows the chamber gas gain vs. high voltage. The nominal operating HV 7.52 shows a schematic layout of the custom-made trigger and read-out electronic boards 7.54 The 72 ME1/1 chambers have differences in their mechanical design with respect to the other An anode front-end board (AFEB) has one 16-channel amplifier-discriminator application- Figure CSCs. The gas gap isHV 7 for mm, these wire diameter chambers is isazimuthal, 30 somewhat lower: but are 2.9 kV. tilted Most bychambers notably, an the are inside ME1/1 angle the anode CMS wires solenoidcompensates are and for not see the its Lorentz strong and anglemeasurement uniform so of 4 that the T electrons axial drift field. parallel The to wire tilt the strips, enabling7.2.2 a precise Electronics design Figure developed for the CSC system. specific integrated circuitexponent (ASIC). tail cancellation The designed amplifier toof suppress has positive the ions away slow a from signal the 30-ns anode componentwire wires), associated group about shaper with 7 capacitance mV/fC a of (semi-Gaussian sensitivity, 180 drift and pF 1.4 withsees fC for noise about the 2- at 12% largest a chambers. of typical the With thesignal total 30-ns as avalanche seen shaping charge, at time, i.e., the an an output AFEB of average this of amplifier about is shown 130 in fC. figure A typical chamber Figure 7.52: Left panel: CSCvs. gas high gain voltage vs. (the high overall voltage. sensitive Right area panel: of all ME2/1 6 chamber planes singles in rate this chamber is ionising particle (MIP) producesan about avalanche 100 is electrons about 1 inelectronics pC. have a a As very gas is high gap, efficiency shown andof thus below, an adequate at the the signal-to-noise this chambers ratio. charge operational extends The per to point, operationalpulses range MIP 3.9 the at about kV. in cathode Typically, 3.9–4.0 and we kV anode (figure start seeing a sharp rise in the rate of spurious criminator has a threshold nominally setless than at 3 20 ns for fC the (input 60–600 equivalentper fC charge) signal chamber. range. and Further Depending its details on slewing on chamber time the size, is there AFEB are design 12 and to performance 42 AFEBs can be found elsewhere [151]. was chosen to be 3.6 kV, which corresponds to a gas gain on the order of 7 2008 JINST 3 S08004 – 203 – , all ionisation electrons arrive near the same point. L α Figure 7.54: Schematic layout of the CSC trigger and read-out electronics. Figure 7.53: Left panel:toward the if anode wires the in ME1/1carried the wires sideways strong by were magnetic the field Lorentz not force. normal tilted,the The to direction electrons ionisation the and drift plane electrons, size upwards of of or as the the downwardswith. shift they drawing, and would would These drift depend on be on sideways how whether displacements far away wouldby they spread tilting were the the from wires charge the at over wires the the Lorentz to anode angle begin wires. Right panel: 2008 JINST 3 S08004 7.55 (16 strips) = 96 (left)): 16-channel amplifier- 7.56 – 204 – information is stored in a FIFO. Upon receiving a CMS-wide Level- yes/no s. The temporal length of the raw-hit record transmitted to the DAQ can be as µ Every 25 ns, in synchronization with the LHC collisions, all AFEB outputs, 40-ns-long step The ALCT board has another important function. Based on the information from all anode For the cathode strips, 1 cathode front-end board (CFEB) serves (6 planes)× channels and has 6 parallel chains of the following chips (figure pulses, are sampled bychamber. an The recorded FPGA-based anode local charged track (ALCT) board, 1 board per Figure 7.55: Left panel:schematic event display muon showing signals anode signals asALCT in seen the board 6 at FPGA planes logic the of apredefined is AFEB CSC patterns programmed amplifier (small (grey dark to cells) output. squares). scan consistent The withmust the Right be muons chamber present originating panel: in and from at the search a least interaction for 4 point. planes hits Hits for falling an inside ALCT pattern to be found. 1 Accept (L1A) triggerextracted command, and reported the to recorded thea information DAQ. collision The within is latency the 3.2 of the properlarge L1A time as command 800 window with ns. is respect to the time of channels, the FPGA code constantly (everythat 25 ns) would searches be for consistent patterns ofto with hits muon be among tracks the valid, 6 originating we planes (right) from illustrates require the how that patterns interaction are hits point. identifiedlarge from in neutron-induced the For at photon presence a background, of least pattern spurious a 4 single-plane substantialHowever, hits. rate these planes Due of hits, be to such a being single-plane presentlike hits completely in is patterns. uncorrelated, the expected. Found would pattern. patterns, notdownstream called typically to Figure ALCTs, the line are muon up trigger Level-1 primitives. triggerprimitives. to electronics form They that The are track- builds time transmitted muon it further tracktime). takes candidates Each from to ALCT these board form can anthe find expected anode up chamber track to track 2 trigger occupancy such at primitive patterns the is per nominal 225 bunch LHC crossing, luminosity. ns which (including is drift adequate for shaper ASIC, 16-channel switched capacitorchannel array comparator ASIC. (SCA) There ASIC, are 12-bit 4 1-channel to 5 ADC, CFEBs and per 16- chamber. 2008 JINST 3 S08004 (CLCT) s following a collision, µ cathode local charged track 300-pF strip capacitance is typically 1.5 fC. ≈ – 205 – s. Upon receiving the L1A command 3.2 µ (right)). The CFEB sees about 8% of the total avalanche charge, i.e., 7.56 signal tail due to the slow drift of positive ions. After convolution with the t 50 ns = 4.8 -function input pulse. The undershoot is intended to compensate for the long tail × δ The amplifier-shaper ASIC has 100-ns shaping time and a sensitivity of 0.85 mV/fC over a The output from this chip is split into 2 pathways. One leads to the SCA chip [152], which Figure 7.56: Left panel:response to basic a functional diagram of a CFEB and the CFEB amplifier-shaper linear range up to 1 V.The The shaping equivalent noise is level based at onpensate a for semi-Gaussian the transfer 1/ function with an undershoot designed to com- present in muon hitwires. signals resulting Right from panel: theare signals slow oscilloscope from traces drift a and of muon the positivevertical 6 track offset ions lines for on of away ease 6 dots of from contiguous viewing. are the strips digitised anode outputs. in a The signals layer. have an The arbitrary 4 curves current pulse produced in aand chamber has by no a tail muon, (figure the amplifier-shaper signal peaks around 150 ns about 100 fC on average. samples the waveform of each stripanalog signal information every on 50 its ns in capacitors.channel, sync or with The 96 the depth LHC of clock this and analog stores this memory is 96 capacitor cells per 8 or 16 consecutive samplesand from digitised the individually proper by time the 12-bit rangevia flash among an ADCs. the intermediate The SCA digital digital capacitors data informationto are buffer. is happen, retrieved passed For the to the L1A the digitisation signal DAQ primitive decision and must described subsequent be below. read-out in by coincidence the with DAQ the 2008 JINST 3 S08004 - ◦ - or 30 ◦ strip signal l cathode local Q with a threshold − r c Q Q 0 (as shown here), the > l Q − r Q , and right-to-left r Q 0, and (left)). − > c r Q Q 7.57 − c Q – 206 – 0, CLCT), up to 2 per bunch crossing. These 2D-LCTs are > l Q , central-to-right − l c Q Q − (right)). There is 1 TMB per chamber and up to 2 CLCTs per bunch c Q 7.57 threshold, > c Q is a pattern of half-strip hits consistent with a muon track. . For each bunch crossing, an MPC performs a preliminary sorting of all received φ The second amplifier-shaper output goes to the comparator network. This chip compares Raw data are collected by the DAQ motherboards (DMB) located in the peripheral crates. The TMB also matches ALCT and CLCT patterns found within a chamber to make correlated Comparator half-strip hits are sent to the trigger motherboard (TMB). Like the ALCT board, Figure 7.57: Left panel:each a group simplified of schematic 3 of adjacent the strips, idea comparators behind compare the the comparator central network. strip signal For and with the central-to-left differences. If hit position is somewhere withincharged track the right half of the central strip. Right panel: a signals on triplets of adjacentmeans strips of at such the comparisons, time the when comparatorhalf network signals can of reach identify a their a strip maximum muon width, amplitude. hit independent location“bell”-like), of By to and the within the signal one strip amplitude, width the induced itself charge [153] shape (figure (as long as it is There is one DMBtime for window up each to chamber. 32 bunch The crossings long, data ALCT consist and CLCT of decisions anode in the and same comparator window, and hits within a correlated 2D-LCTs and finds the 3to best-quality the candidates muon — L1-trigger these electronics. are then sent further upstream crossing can be found perhalf-strip TMB. hits As must in be the present ALCTmounted from pattern at on search, least for the 4 a chambers, planes. CLCT butendcap pattern Unlike are steel to the disks. in be ALCT peripheral found, boards, VME the crates TMBs are mounted not along the2-dimensional outer LCTs rim (2D-LCT of = ALCT× the sent to muon portsectors cards in (MPC), each of which serves 9 chambers covering either 60 the TMB searches for patternstracks of of interest half-strip (figure comparator hits that would be consistent with muon 2008 JINST 3 S08004 A µ sector, 1 bunch ◦ ± 1 MeV pho- L1A coinci- ≈ shows a muon event as detected A can be measured with a precision 7.58 µ in the CSCs. The GIF at CERN has a 2 – 207 – A. µ 10 < A current for individual channels as long as the average consumption does not exceed 40 It is important to note that the CSC read-out is intrinsically zero-suppressed. The anode raw A high-energy muon beam provides a test environment with maximum control, but it can During the CMS Magnet Test and Cosmic Challenge (MTCC) in 2006, a substantial part At the design LHC luminosity, we expect on average to find track stubsOperation in 2 of chambers the for peripheral VME crates is supported by clock-control boardsThe (CCB) HV and system is custom made and provides channel-by-channel regulated voltage up to At the design LHC luminosity, we expect a large neutron flux in the underground cavern, µ digitised strip signal waveforms (eightelectronic or boards sixteen is 50-ns also time aa samples). part detector-dependent of The unit the status event (DDU) record. of board,the the CMS The then various filter data to farm collected a to by data beevent the size processed concentration DMB per by card are chamber the is passed (DCC), CMS about to and high-level 5 trigger finally kBytes. (HLT) to software. The expected data in a particular chamber are passedwith downstream the only if L1A there signal. is Likewise, anwaveforms, ALCT the pattern cathode are in information, passed coincidence comparator downstream hits to and the digitised strip DAQ signal only if there was a similar CLCT× dence. The coincidence window is programmable, but is nominally set at 75 ns, i.e., of 100 nA, while the precision100 for larger currents is aboutper 1%. channel. The system The can maximum provideHV expected more segment current is than at the design LHC luminosity for the7.2.3 most-loaded Performance The results presented in thisenergy section muon beams come at from CERN, teststhe with conducted Gamma cosmic-ray Irradiation with muons Facility final-design in (GIF). CSCs a in lab high- or in situexpose after installation, only and a at smallallowed portion us of to a study chamber. chamberperformance performance over We the in typically entire chamber the used area, presence for 100–300with many of GeV cosmic-ray years bremsstrahlung beams, we muons have radiation. at which tested various individual also research To large chambers study laboratories. of CMS was operated as a unified system. The CSC subsystem was represented by a 60 crossing. each L1A signal. With theHLT maximum is CMS estimated L1A to rate be of around 100 1 kHz, GB/s. the data flow ratecustom from crate CSCs controllers. to Ascontrol its commands name (like L1A implies, signals). the CCB distributes the LHC4.0 clock kV and with all about CMS 10 V precision. Currents of less than 10 or 36 chambers. This allowedoperating us simultaneously to with obtain other in CMS subsystems. situ Figure performance results for a large number of CSCs by CSCs at the MTCC. which upon thermalization and capture is predicted to result in a substantial flux of tons. Of the photonswill that give rise enter to a large chamber, rates about of random 1% hits will up convert to to 1 electrons. kHz/cm These electrons 2008 JINST 3 S08004 0.03)%. For the (left). The same figure 7.59 Bq. Tests at the GIF allowed 12 CLCT) averaged over the entire 10 × 7 0. ≈ – 208 – L1A coincidence. If an LCT is not found, there will not be a coincidence, and no raw The anode signal efficiency of a single plane is shown in figure The overall efficiency of finding 2D-LCT patterns (ALCT× Figure 7.58: Part ofMTCC. a Only those CMS chambers event containing display muon hits showing are a displayed. muon event detectedCs-137 by source CSCs of 0.7 during MeV the photons with an intensity of us to study the chamberthese performance facilities for in chamber-ageing an studies. environment of high random-hit rates.Trigger We primitives also used It is important to noteonly that the muon the trigger, efficiency but of also theby finding DAQ an trigger path. LCT× primitives As was (LCTs) described directlyhits earlier, the affects will CSC be not read-out recorded is and driven available for the offline reconstruction. also shows the efficiency fortrack. finding The ALCTs, desired patterns ALCT-finding efficiency of offinding 99% hits efficiency is in is reached 6 about above 3.4 99.9%. planes kV. These consistent Ata results 3.6 with small were kV, the a area obtained ALCT- muon of for test-beam aabout muons chamber 50 going free V through of higher. This dead is zones. because the For cathode CLCT signal patterns, is similararea somewhat of smaller results many than are chambers the was achieved studied anode at with signal. cosmic-raykV, the muons average at 2D-LCT the MTCC. efficiency At in the 60.07% nominal ME2/2 HV of chambers of events was 3.6 with found missing to 2D-LCTs be in (99.93± ME2/2 chambers, the majority of tracks (reconstructed 2008 JINST 3 S08004 (right) coordi- x 7.60 0.5 cm along (left, top)) has ≈ 7.61 is the strip width. w coordinates of 2D-LCTs found in 14w, where y) 0. , x ( ≈ are the local chamber coordinates across 12 y √ (left). The observed spread of / and x 7.60 w/2) ( – 209 – coordinates in the ME2 station as predicted from the y) , x ( 11 in strip width units, which is better than the desired 2 mm 0. axis is noticeably broader due to a much coarser wire group ≈ y σ coordinates are shown in figure y) , x ( The time distribution of anode signals from a single chamber plane (figure For studying the intrinsic CLCT-localisation precision, we used a test chamber in a muon To test whether the found LCTs are indeed associated with the muons going through the axis is consistent with the expected multiple scattering of cosmic-ray muons penetrating the x nate corresponding to the average ofshows all muons the that residuals can between generate such thedistribution a is Si-based pattern. Gaussian track Figure and has coordinate andfor the even CLCT-based the coordinate. widest 16-mm The strips.muon In trigger the firmware, more CLCT conservative patterns approach are currently localisedthe within implemented CLCT a in spatial half-strip. the resolution Therefore, is in approximately this approach an RMS of about 11 ns. Clearly this is too wide for a chamber hit to be assigned unambiguously to ME2/2 chambers and the muon track the endcap steel disks. As isthat. shown below, The the intrinsic distribution precision alongsegmentation of of the 5 CLCT cm, localisation which is defines better the than precision of ALCT localisationbeam in and these a chambers. telescope of Si micro-strip detectorsthrough to the precisely test determine chamber. the To position achieve of the a best muon results, going a given CLCT pattern is assigned an chambers, we looked at the relative distance between the 2D-LCTs in the ME1 andthe ME3 cathode stations. strips (Here andpredicted anode wires, respectively.) The 2D-residuals between the measured and Figure 7.59: Left panel:finding efficiency single-plane (filled anode circles) vs. signalin high efficiency ME2/2 voltage. chambers (open for Right events circles) when panel: no and LCT6 predicted was ALCT chambers). position found pattern in The of these dashed muon chambers lines (superimposed tracks results indicatebands for where separating wire independent planes HV segments. of the ME2/2 chambers have inefficient using the ME1 andseparating ME3 the LCT chamber high-voltage stubs) segments were (figure found7.59 (right)). to cross ME2/2 chambers in inefficient bands 2008 JINST 3 S08004 axis along the strips. The observed y – 210 – axis runs along the wires and the x Figure 7.61: Left panel:(top) and time for distributions the of 3rd earliest theoffset. hit response in The an shaded of band ALCT a indicates pattern the (bottom). singleRight 25-ns The plane window, panel: horizontal the to scale time has between a probability an bunch passing for crossings arbitrary 25-ns at muon correct clock the on LHC. bunch an crossing ALCT board tagging and vs. the relative LHC 25-ns phase clock. shift between the spread is consistent with multiple scattering ofCLCT cosmic-ray muons and in the ALCT steel spatial disks and resolutions.muon the expected coordinate and Right the panel: coordinate predicted residualsThe by residuals between the are Si the shown beam CLCT in telescope units in pattern-defined of a strip 300-GeV width. muon beam. Figure 7.60: Left panel:muon-track 2D-coordinate positions. residuals The between LCTs found in ME2/2 chambers and 2008 JINST 3 S08004 (left, bottom)) is a 7.61 shows an example of a badly 7.63 (right) shows the accuracy required for 7.61 – 211 – 5 ns, the use of which results in a bunch-tagging efficiency < σ 5 ns. CLCTs tend to have slightly worse timing properties due to the ± 7.62) show that the ALCT-finding and bunch-tagging efficiencies remain very robust even Results obtained from a CSC irradiated with 0.7 MeV photons in a muon beamDuring at 300-GeV the muon-beam tests, GIF a 30-cm-thick steel slab was moved in front of the test Figure 7.62: Left panel:panel: ALCT-finding efficiency efficiency of vs. correct rate bunch tagging ofshow vs. the random rate range of hits of random per rates hits wire per expected wire in group. group. different chambers The Right at shaded full areas LHC luminosity. the correct bunch crossing. We overcomeThe this problem time by distribution making for use of the all 3rd 6 earliest planes in hit a in chamber. an ALCT pattern (figure much narrower Gaussian with of 98–99%, well above the desiredaligning 92% the phase level. of Figure the 25-ns clockof on phase an misalignment ALCT board is with theslower LHC CFEB clock. shaping The time acceptable and range smallerthe amplitude ALCT of pattern strip to signals, the so matched we 2D-LCT. assign the time tagged by (figure at random-hit rates far exceeding those expected at full LHC luminosity. chamber to study the effect oftrigger bremsstrahlung level. radiation on In the offline reconstruction analysischarge of of muon clusters strip stubs observed data, at the we in classifiedthe only each fraction 1 muon of plane) as “clean” either or muons99.5% “clean” otherwise was efficiency. (multiple “contaminated.” 94% With and the Without CLCTCLCT-finding steel the patterns efficiency slab, steel were remained the formed very slab, fraction high from“contaminated” of (98.9%). half-strips muon “clean” with where Figure muons a the muon dropped track to is 80%, nevertheless successfully while identified. the 2008 JINST 3 S08004 (7.2) 56 shows the track 17. = λ , is the cathode-anode spacing, and  ) h ) λ 2 λ 2 K ( K 2 ( 2 59. tanh 3 tanh 17. K − = + 1 1 – 212 – λ  1 K = λ d dQ 1 Q are defined by the chamber geometry. 3 K is the coordinate across a strip and x , and 2 K , 1 K /h, in which x = λ Given the geometry of the CSCs, most of the induced charge is shared among 3–4 strips. As described earlier, apeaks strip in signal about 150 waveform ns is and sampled comes back and very digitised close to every the 50 baseline ns. within the next The 150 signal ns so that the where the coefficients position extrapolated from the Sithat beam corresponds telescope. to an This average event track was position assigned a 6-layer CLCTSpatial code resolution based on digitised strip signals An avalanche on a wirethe induces induced charge charge on can a be cathode parameterized plane. by the In so-called a Gatti first function approximation, [155]: the shape of Figure 7.63: A sample CSC event ofThe a left muon side accompanied of by the substantial plot bremsstrahlung shows the radiation. of charge the (blocks just 6 above the chamber axes) layers, onStrips each while with of the charge the 32 above right strips the in side trigger each the shows threshold half-strip are the “peaks” marked information are with marked from light with the shading dark below anode squares. the wire The axes, vertical groups. while line at 2008 JINST 3 S08004 (7.3) , which is , for chamber CSC i σ σ m at nominal HV. The µ plus alignment errors. Clearly, m, . µ 33 /w) x 1 = ( (left)) is about 80 2 6 i σ √ ∑ 7.64 80/ = 213 – ≈ – (right) shows single-plane resolutions, /w) x ( 1 7.64 2 CSC σ m per 6-plane chamber is within reach. µ e 7.64: Left panel: ME1/1 chamber single-plane resolution vs. HV. Right panel: ultimate By design, ME1/1 and ME1/2 chambers have narrower strips and thus deliver better resolu- The single-plane spatial resolution of the larger CSCs (with very wide strips up to 16 mm) 6-plane chamber resolution is estimated to be tion. The ME1/1 single-plane resolution (figure Figur large CSC offline resolutions perwith plane different for strip different widths muon passage foroverall 6-plane points data CSC across (closed resolutions a are symbols) strip shown and by for open simulation areas symbols (solid and lines). dashed lines. Theoverall pulse expected duration is roughlythe 300 spatial ns. coordinate, Such time, a and 2-dimensionalinto charge cluster account cluster charge. empirical can corrections To be achieve forwaveform, fit strip-to-strip the to the cross-talk, best obtain electronic-noise induced correlations possible charge between resolution, shape, nearbyelectronic we time pedestal the samples, take and and time gain structure calibrations. of the signal the desired resolution of 75 depends very strongly oncentre the will muon be measured coordinate poorly across (andhand, the a muons wider hitting strip. the between strip, the strips Muonstook worse will the that advantage be measurement). pass measured of On nearly through the this equallyare other a feature well staggered strip for in by any our strip one design.chamber width. half resolution, We of appear In as the the nearlywith strip larger straight-through poor pitch. chambers, tracks. resolution strips in If odd High-energy in suchversa. planes, muons, adjacent a Therefore, it by for muon will planes combining goes have which measurements very through fromsegment we good areas is 6 measurements need accurately planes localised. in with the even Figure proper planes, best weighting,regions and a with muon vice different track strip widthsestimated and by the resulting combined 6-plane resolution, 2008 JINST 3 S08004 r 7.65 (7.4) of the ratio m (figure ) r . µ (  w f ) 200 left threshold used by the < Q , T m almost independent of p µ left right Q Q 80 − ≈ min( right − Q centre Q  1 2 m goal. µ = r – 214 – 40 GeV, one need not measure muon coordinates with < where T (left)). A simplified algorithm for hit-position reconstruc- p , ) r ( 7.65 w 0.5 mm. This holds true for a muon momentum measurement in f ≈ = on 3 adjacent strips (centre, right, and left strips): Q measured /w) x ( algorithm localises muon stubs in a chamber with a precision of e 7.65: Left panel: deterioration of spatial resolution (ME1/1 chambers) with increasing rate Even at the highest rates expected at the LHC, the CSC resolution will stay well within This The expected combined resolution for a 6-plane chamber is built from the charges the design specifications (figure tion that does not usetions/calibrations any was fitting, iterative tested procedures, on orsimple the chamber- and or 12 fast, electronics-specific this largest correc- algorithm chambers ischambers specifically are in identified targeted the by for directly MTCC the accessing HLT. First, cosmic-ray theDAQ. Then, ALCT- 2D-track runs. and the segments CLCT-pattern records in coordinate available the Being is in calculated the by using a simple analytical function a precision much better than the stand-alone muon system, for associatingand stand-alone for muons the with tracks ultimate in muoninformation the from momentum central the tracker, measurement, central tracker which and is the achieved muon system. by means of combining the hit position in a chamber, better than the 150- (right)), which is moreHLT than is adequate 40 for GeV. Due thefor to HLT. The muons the with highest muon transverse muon multiple momenta scattering in the calorimeters and in the steel disks, Figur of signals. The resolutionexpected remains at well the within LHC. the Right designtracks panel: specs vs. even expected muon at 6-plane coordinate rates chamber far acrosswith resolution a exceeding a for simplified those nearly strip and perpendicular fast as reconstruction evaluated specifically from targeted for the the single-plane HLT. resolution obtained 2008 JINST 3 S08004 2400 ≈ . Analog components of the elec- 2 − cm 12 to 10 10 . No SEL was observed on any FPGA during testing. – 215 – 2 − cm 11 10 3× ≈ of sensitive area. The total number of read-out channels is about 400000. During 20 Gy for on-chamber boards and 2 Gy for peripheral crate electronics. The integrated 2 ≈ All electronic chips and components were tested with radiation doses far exceeding the 10 Ageing studies were conducted [156] by irradiating CSCs at the GIF for several months. The To test the stability of electronic board performance, we dealt separately with 2 distinct radi- 5000 m tronics may suffer a steady anddigital permanent electronics deterioration are in Single performance, Event while Effects the (SEE),Event main including Latching danger Single (SEL). Event for Upsets Upon (SEU) an anding SEE Single the occurrence, the FPGAs electronics or can cyclingoccurrences. typically the be power: reset by SEEs reload- can thus be characterisedLHC-year by the equivalent meantime [158]. between Forformance was final-design observed boards, (noise, gain, no threshold,SEEs significant etc.). using typical deterioration All fluences digital-electronic of in FPGAs analog wereSEU per- tested rates for were dominated bysignificantly the by control introducing logic a on design thesingle with CFEB CFEB triple-voting was boards. logic. measured and The The extrapolated SEUCFEBs mean to rate time be in was between 700 our lowered h SEEs system, at on therunning, a a LHC which single neutron is fluence. an CFEB acceptable With will rate, fail and will due need to to be an reset. Reliability SEU about every 30 min duringExtensive LHC testing of prototypestechnology has would shown meet all that performance thethe requirements construction CMS and budget. could Endcap There be are Muon built 468≈ System six-plane within CSCs the based in constraints the on of system, CSC with CSC planes comprising the years of construction andoperation commissioning, (e.g., not the a CMS single CSCsconfirmed wire have the out proven expected of to performance. about be 2000000 As36 very chambers an in reliable and example, the in cosmic-ray analyses system muons of has showed that the ever chambers snapped) first had and data a have taken 99.9% efficiency in to situ detect with muon- Radiation tolerance The high radiation rates atelectronics the were LHC designed could to result betests in robust. of devastating To chamber problems; validate ageing thus, the and the electronic design, board detectors we radiation and carried damage. out a seriesprototype of gas detailed system operated involume exchanges recycling per mode day with as about envisionedshowed 5% for little fresh full-system gas change added operation in in (2charge each gas on 1-volume gas gain, the cycle). wires The dark was chambers about current,luminosity 0.4 in and C/cm, the corresponding spurious worst to areas pulse about closest 50layer rate. to of years the deposits of beam on The operation line. the at total cathode Upon full surfaces,being accumulated opening LHC but slightly the not chambers, conductive on we the (established anode observed by wires.affect a a performance The (e.g., small deposits by on reduction the the of cathodes, Malter resistance effect [157]). between strips), did not ation components: total ionisation doseyears and is neutron fluence. Theneutron total flux ionising over 10 dose years for ranges 10 from LHC about 10 2008 JINST 3 S08004 and up 160]. An RPC is capable cm Ω· 10 10 2 mm 2 mm × 1–2 . 2 Hz/cm lists the basic construction and operating parameters – 216 – 3 7.2 m. µ Table 7.2: Basic construction parameters. Figure 7.66: Layout of a double-gap RPC. Bakelite thickness Bakelite bulk resistivity Gap width 150 ≈ 162]. The total induced signal is the sum of the 2 single-gap signals. This allows gaps, operated in avalanche mode with common pick-up read-out strips in between (fig- The CMS RPC basic double-gap module consists of 2 gaps, hereafter referred as 7.66)[161, 7.3 Resistive Plate Chamber system Resistive Plate Chambers (RPC) are gaseousresolution parallel-plate with detectors a that time combine adequate resolution spatial comparableof to tagging that the time of of scintillators an [159, ionisingLHC event in bunch a crossings much shorter (BX). time Therefore, thanidentify the unambiguously a 25 the fast ns relevant between BX dedicated to 2 muon which consecutive the a trigger muon high device track rate is based and associated on background even in expected RPCstime the at and presence can the position of of LHC. a Signals muon from hitthe such with BX devices the directly assignment required provide accuracy. to A the candidate triggerin based tracks an on and environment RPCs where estimate has rates to the may provide transverse reach momenta 10 with high efficiency track segments (input to thetrigger Level-1 and trigger) offline and was the spatial resolution attainable at the high-level of the CMS double-gap RPCs. down ure the single-gaps to operate atciency higher lower than gas for a gain single-gap. (lower Table high voltage) with an effective detector effi- 2008 JINST 3 S08004 = η 164]. show 7.67). lists some 7.69 7.5 and = 1.6 are built. η 7.68 ). Figures φ in ◦ 7.3), each one 2455 mm long in the beam region is significantly higher, well beyond the limit – 217 – η 7.4. particles, which may stop inside the iron yoke. In the endcap region, the baseline design T In the first and second muon stations there are 2 arrays of RPC chambers located internally In total there are 480 rectangular chambers (table Physics requirements demand that the strips always run along the beam direction and are Extensive ageing tests have been performed over the past years with both neutron and gamma p and externally with respect toand the RB1out Drift Tube and (DT) RB2out chambers: atchambers, RB1in larger both and radius. RB2in located at In on smallerRB4–). the the radius third A inner and special side fourth case ofand stations is RB4– the RB4 there –. DT in are Finally, in sector layer again sectors 4, 2 (named 9 which RPC and RB3+ consists 11 and there of is RB3–, 4 only chambers: RB4+ 1 RB4 RB4++, and chamber. RB4+, RB4–, Results confirm that over a period equivalentis to expected 10 while CMS-operation all years, other no characteristic efficiencylayers degradation parameters stay of well RPC within chambers the project aresecond specifications. embedded muon Six in stations the and barrel 1allows iron the in trigger yoke, each algorithm 2 of to located the performlow in the 2 reconstruction each last always of stations. on the the basis Theforesees first of the redundancy and 4 instrumentation in layers, of the even the for first2.1. iron 2 disks However, stations with in 4 the layers firstIn of addition, RPCs phase, the to due background cover to rate the budget inreached region limitations, the up during only high to the 3 ageing layers test.conditions up is to ongoing. Additional R&D to certify the detector performance7.3.1 under such Detector layout Barrel system In the barrel iron yoke, theaxis) RPC that are chambers approximated form with 6 concentric coaxial dodecagon arrays sensitive arranged cylinders into (all 4 around stations the (figure beam direction. Exceptions are theare chambers 2055 in mm sector long 3 of toRB3 have wheel allow widths –1 passage 2080, 2500, and of and sector the 1500depend 4 mm, on magnet respectively. of location) The cooling are wheel widths chimney. given of +1, in the which Chambers table RB4 chambers RB1, (which RB2, and divided into 2 parts for chamberstrigger algorithm, RB1, have RB3, strips divided and into RB4. 2 parts+1, The (RB2in 0, in RB2 wheels and chambers, +2 –1) and a and –2 special andEach into case RB2out chamber 3 in for therefore wheels parts the consists (RB2out in ofbeam wheels either direction +2 2 to and or cover –2 3 the and double-gap activethe RB2in modules area. front-end in mounted electronics For wheels sequentially boards each +1, in are double-gap located 0, the module atwith and (up the respect –1). strip to to end, 96 the which strips/double-gap), minimises interaction the point.to signal the The arrival outer time strip ones widths to increase preserve projectivity accordingly (each from strip the covers inner 5/16 stations sources to verify long term detector performance in the LHC background environment [163, global information regarding the barrel detector. schematic views of chamber modules with 2 and 3 double-gaps, respectively. Table 2008 JINST 3 S08004 60 60 24 36 36 24 120 120 480 Total - - 12 12 12 12 24 24 96 W–2 - - 12 12 12 12 24 24 96 W–1 - - 12 12 12 12 24 24 96 W0 – 218 – - - 12 12 12 12 24 24 96 W+1 - - 96 12 12 12 12 24 24 W+2 Table 7.3: Number of RPCs for different wheels. Total RPC RB1in RB1out RB2/2in RB2/2out RB2/3in RB2/3out RB3 RB4 Endcap system In the forward and backward regions ofLike the in CMS the detector, barrel, 3 iron 2 disks complementary constitute muon the detector endcap systems yokes. are deployed for robust muon identifi- Figure 7.67: Schematic layout of+2, one respectively. of Each the wheel 5 is barrel divided wheels, into 12 which sectors are that labeled are –2, numbered –1, as 0, shown. +1, and 2008 JINST 3 S08004 2000 mm 2 480 1020 80 640 2400 m 2000 mm 2000 mm 1500 mm 2500 mm as to avoid dead space at chamber edges. Except φ – 219 – Number of strips Number of stations Total surface area Number of double-gaps Table: 7.4 Widths of the RB4 chambers. RB4+ RB4++ RB4– RB4– – RB4 2000 mm 1500 mm 2000 mm 2500 mm 1500 mm 1500 mm 1500 mm 1500 mm Table 7.5: Barrel RPC system global parameters. 7.70. They overlap in S5–S7 S8 S12 S9, S11 S10 S4 Sector S1–S3 Figure 7.68: Schematic layout of chamber module with 2 double-gaps. view of figure -φ r cation: cathode strip chambers (CSC)yield and 4 RPCs. CSC They stations are (ME1–4)gaps mounted and, in on for every both the station faces initial have of detector,the a the 3 trapezoidal disks RPC shape to stations and (RE1–3). are arranged The in double- 3 concentric rings as shown in 2008 JINST 3 S08004 . As mentioned ◦ shows a schematic layout 7.71 , all others span 10 φ 6) has been staged until the LHC is 1. . in 1 ◦ ≈ − s 2 η − cm 34 – 220 – layout of RPC station RE2 on the back side of the first -φ r part of the RPC system (beyond η Figure 7.69: Schematic layout of chamber module with 3 double-gaps. Station RE1 is mounted on the interaction point (IP) side of the first endcap disk (YE1), before, the high underneath the CSC chambersYE1 of and ME1. on the StationsCSC IP stations RE2 side 2 and of and 3 YE3, 3 are respectively. are mounted mounted They on on remain both the uncovered faces back since of side YE2. the of corresponding Figure Figure 7.70: Left panel:endcap schematic yoke. Right panel: RPC stationbeen RE2 staged on and the is back absent side here. of the YE-1 yoke. The inner ringfor has station 1, the chambers of the innermost ring span 20 scheduled to deliver its design luminosity of 10 2008 JINST 3 S08004 7.72). section spacer frame (figure 2 16 mm × RPC chambers are projective to the beam line, ◦ – 221 – Figure 7.72: A view of an endcap RPC chamber. Figure 7.71: Schematic layout of the CMS endcap for the initial muon system. of the CMS endcap definingconsists the of nomenclature a of double-gap the structurehoneycomb enclosed muon panels in stations. of a 6 Each flat mm endcap trapezoidal thickness RPC shaped each box chamber and made a of 16 2 aluminium The strip panel, sandwiched inStrips between the run gas radially gaps, and haschambers copper are (n strip radially sections = segmented on 1–3). into a G10 3 support. The trigger 32 sections strips for of the the REn/2 10 and REn/3 following a homothetic pattern.end Besides electronics, the services, different trigger, mechanical and read-out shapethe schemes barrel and of system. assembly, the To the an endcap front- operator, RPC the system CMS are barrel identical and to endcap RPC systems look identical. 2008 JINST 3 S08004 input impedance to match the characteristic – 222 – m CMOS technology [165]. Each chip is made of 8 identical µ 7.73. Figure 7.73: Block diagram of RPC read-out electronics. 10 ns. The discriminator is followed by a one-shot circuit. This produces a pulse shaped ≈ The FEBs house two (barrel version) or four (endcap version) front-end chips, which are Since accurate RPC timing information is crucial for providing an unambiguous bunch cross- Gamma-irradiation tests showed no performance degradation of either the front-end chip or 7.3.2 Readout electronics Front-end electronics The read-out strips arediscriminated, connected signals to are Front-End sent BoardsThe unsynchronized (FEB). LBs to After synchronize Link having the Boards beenelectronics signals (LB) amplified located with placed and in the around the CMS the 40-MHz countingblock room detector. LHC diagram over clock a of 90-m figure and optical transmit link at them 1.6 to GHz, as the shown trigger incustom the ASICs designed in AMS 0.8 channels, each consisting of an amplifier,The zero-crossing preamplifier discriminator, is one-shot, a and trans-resistance LVDS stage driver. with 15-Ω impedance of the strips.2 It mV/fC. is followed by a gain stage to provide aning assignment overall charge of sensitivity the of event,timing the response zero-crossing amplitude-independent. discrimination In technique fact, wasnamic considering adopted that range to the (from RPC make few signals the tens havebelow a of 1 wide fC ns, dy- to while the 10walk simpler pC), of leading-edge the discrimination implemented technique architecture wouldat provides have 100 a provided time ns a walk time todriver mask is possible used to after-pulses send that the may signals to follow the the LB avalanche in differentialthe pulse. mode. control Finally, electronics an on the LVDS (0.4 eV–10 FEB MeV) [166]. and with Moreover, more testssustain with energetic the expected thermal neutrons CMS and (65 operational MeV), fast conditions have reactor [167]. certified neutrons that the circuit can 2008 JINST 3 S08004 . In cooperation with the 2 neutrons/cm 11 10 and 5· 2 – 223 – 7.74)[168]. 7.6. protons/cm 10 10 Figure 7.74: Technical Trigger schematic layout. The HV and LV systems are both based on a master/slave architecture. The master, called The RBC collects 96-strip OR signals from the barrel LBs and produces a “local” sector- ATLAS, ALICE, and LHCb groups,power the system CMS able collaboration to developed operate in apower supplies such new are conditions. design collected The for in main an table requirements RPC for the RPC HV and LV the mainframe, is devoted to controlling and monitoring one or more slaves and is placed in a RPC technical trigger electronics Study of the detectorThe performance RPC is trigger a system crucial wasTherefore, designed aspect to all during identify interconnections the muon among tracks detector-commissioning theprojective starting phase. vertex LBs from geometry, and the not interaction trigger adequate point. for electronicstrigger (Technical triggering were Trigger on in optimised the cosmic following) to rays. has been fulfilboards: Therefore, implemented a by an the means RPC-based of RPC 2 types Balcony of(TTU) Collector electronic located (RBC) in housed the counting in room the (figure cavern and the Technical Trigger Unit based cosmic trigger totransmits be the used ORs during optically commissioning towheel-level or the cosmic TTU calibration trigger boards is of in produced the the andA sent detector. Counting proper as Room algorithm a The (30 for Technical fibres Trigger RBC searching to in for the total), cosmic-muon CMS where tracks Global is a Trigger. implemented in the7.3.3 TTU. Low voltage and highGeneral voltage requirements systems The RPC power systems operate inradiation a flux. hostile environment Large due portions toplaced of the around high the the magnetic barrel power field wheels systems1 and and are high the T near endcap with disks. the radiation detectors In around these on 5· areas the the balcony magnetic racks field can reach 2008 JINST 3 S08004 A µ A. This µ 20 MHz) LV 7 V 3 A < 100 mA 100 mV 7.7. from 0 to 7 V 10 mV pp at load (freq < A µ 20 MHz) 10 V HV < 1 mA 12 kV < 0.1 – 224 – from 0 to 12 kV (freq 100 mV pp at load < Table: 7.6 HV and LV power supply requirements. The A3512 double-width board is equipped with 6 floating 12 kV/1 mA channels Maximum Current Ripple Programmable Voltage Current monit. precision Voltage monit. precision Maximum Voltage Past experience with RPC detector systems, however, suggested that it is important to have current resolution allows theevery Detector chamber Control with System an accuracy (DCS)per of to at chamber). study least the 1/10 In of currentchannel the the behaviour supplies measured barrel of 2 current there (between chambers. is 10budget availability. and 1 In A 20 this HV summary of last channel the case, per HV systems an chamber, is upgrade while given of in in table the the system endcap will region depend 1 on future the HV power supplies inthe an possibility accessible of area. removing In aRPC case channel collaboration of during decided unsustainable operation to high keep should currentbut the be on to master/slave available. a move architecture all detector, for Therefore, HV both system the the components CMS into HV the and control LV room. systems HV and LV system description The system is based onSY1527 the (mainframe) EASY which (Embedded houses up Assembly to SYstem) 16crates project. branch (slaves). controller It boards The (A1676A) is EASY3000 and made crate of can ofDAC). EASY3000 Each house a EASY3000 different master boards board (high operates and asthe low a voltage, mainframe. channel ADC, of and the The A1676Aindependently EASY and the architecture can channel be regulators foresees and accessed 2 the through external independent control world through logic. 48-V a The power serial EASY port suppliesand system and control is to an the connected ETHERNET3 power whole to interface system the that withsophisticated various allows OPC software the protocol. from user a to very monitor easy TELNET interface to a more HV hardware. of either positive or negative polarity.loops. The 6 The channels board have an isthe independent designed 0–12 return with kV to an avoid range ground output with voltage 1 that V can resolution and be with programmed a and monitored monitored current in resolution of 0.1 safe and accessible areaare like designed the to control be room. modularto and The work in multi-functional slaves a to can hostile accept betolerant and both electronics. located inaccessible HV near area and the and LV detector are boards. based and on These radiation-tolerant have and magnetic-field- 2008 JINST 3 S08004 ) d ) and digital (LV a . Water vapour is added to the 6 6 36 36 14 216 432 Endcap Endcap 80 14 60 20 480 720 and 0.3% SF Barrel Barrel 10 H 4 – 225 – iC ), 3.5% 4 F 2 HV boards Easy3000 Crates LV channels LV boards Easy3000 Crates HV channels Table 7.8: Summary of LV systems. Table: 7.7 Summary of HV systems. H 2 channel per chamber. However, for the endcap detector, at the start-up d are distributed between 2 chambers. A summary of the LV systems is given in The CAEN A3009 board is a 12-channel 8V/9A power-supply board for the d and 1 LV a and 1 LV Each chamber is supplied by 2 LV lines for the front-end analog (LV Additional sensors are available on each front-end board; they are read out through the LB 7.8. a electronics to monitor the temperature. 7.3.5 Gas system Test results [169] showedmixture that of RPCs 96.2% are R134a suitablygas (C operated mixture with to a maintain 3-component a relative non-flammable humidity of about 45% and to avoid changes of the bakelite EASY Crate. It was developed foroutput-voltage operation range in is magnetic fields 1.5–8 and Valarms radioactive with and environments. protections. 5-mV The The monitor output resolution; current channel is monitored control with includes 10-mA various resolution. 7.3.4 Temperature control system RPC operation is sensitive to bothare temperature constantly and monitored atmospheric to pressure. compensate Therefore, in thenetwork real chambers of time 420 for the sensors detector located operating insideThe point the AD592BN (HV barrel value). sensor chambers A is (Analog available Devices)about to can 0.5°C, monitor better the work than temperature. in the a CMSequipped hostile requirement with a (1°C). environment 12-V Sensors with input are a stage. read resolution out of by a 128-channel ADC LV hardware. table 1 LV parts. To avoid ground loopscorrespondence on between the LV detector, channel it andthere is chamber. is important 1 This to LV preserve, is when achieved possible, in a the 1-to-1 barrel system, where 2008 JINST 3 S08004 6 , and 0.3% SF 10 H /h /h 3 4 3 3 iC 14 m 3 mbar 10 m 0.2 m 7.9. 250 (barrel) + 144 (endcaps) 96.2% R134a, 3.5% 7.75) extends from the surface gas building SGX to – 226 – Figure 7.75: Closed-loop circulation system. Table: 7.9 Main gas parameters of the CMS RPC system. The system consists of several modules: the primary gas supply, mixer and closed-loop cir- Fresh gas replenishing rate Number of gas channels Gas volume Gas mixture composition Internal chamber pressure above atmosphere Nominal flow rate resistivity. The basic functionappropriate proportions of and to the distribute the gas mixturevolume system to and the is individual the chambers. to use The mix of largemandatory. detector the The a main relatively different gas-system expensive gas parameters gas are components mixture given in in make table the a closed-loop circulation system culation system, gas distributors toThe full the closed-loop chambers, circulation purifier, system (figure pump,the and USC55 service gas-analysis cavern station and [132]. UXC55 experimental cavern. Mixer The primary gas supplies and thegases mixer is are controlled situated by in mass-flow the meters. SGX building. Flows are The flow monitored of by component a computer-controlled process, 2008 JINST 3 S08004 7.76). . Each ◦ . A section 7.77a). The ◦ 330 406 251 347 1334 type (l/h) total flow per station sections of 30 7.77b). In RE2 and RE3 φ sections of 60 φ 27.5 33.9 20.9 28.9 channel flow (l/h) Operating 7.10). 41.2 50.8 31.4 43.4 per gas Volume channel (l) – 227 – 12 12 12 14 50 of gas number channels (l) 20.6 25.4 31.4 43.4 Volume per RPC fraction increases beyond the flammability limit. For fast detector filling, 24 24 12 12 72 RPCs in that station 10 H 4 iC RB1 RB2 RB3 RB4 Total Station Table: 7.10 Chamber volumes and gas flow for a single wheel of the barrel detector. instrumentation are located in the USC (accessible at any time); distribution racks near the detector. The high density of the used mixture generates a hydrostatic pressure of about 0.3 mbar/m Each endcap detector consists of 3 disks, RE1, RE2, and RE3, with a total of 216 double- • the manifolds for the chamber-gas supplies and channel flow meters are mounted in the • the purifier, gas input, and exhaust gas connections• are located the in pressure the controllers, SGX separation building; of barrel and endcaps systems, compressor, and analysis contains 6 chambers and is suppliedgas with flow 2 in gas the lines up forquality. gap the is up In in and the the down RE2 opposite gapssection (figure and sense contains to RE3 3 that stations, chambers in the of the chambers thering, down i.e., external are gap an ring divided to RE2 and into improve section the the 12 includes corresponding average 3 3 gas RE2/2 chambers and of 3 the RE2/3 internal chambers (figure above atmospheric pressure. Since the total RPCsplit detector into height 2 is about zones 15 (top m, and theEach bottom) barrel barrel that detector muon have is independent station pressure has regulation an systemssupplied independent (figure gas in line. parallel The from 2 the RPCchannels same chambers (50 located patch per in panel wheel) a sitting for station nearby. are the full This barrel configuration detector leads (table to 250 gas parallel rotameters are used, insteadnewal of in the about mass-flow 8 controllers, hours. yielding a complete volume re- Closed-loop circulation The mixed gas is circulated intion a loop common is closed distributed loop among for 3 the locations: barrel and both endcaps. The circula- gap chambers. Each disk is36 composed chambers of each. 2 In concentric the rings RE1 (i.e., rings for the REn: chambers REn/2 are and divided REn/3) in of 6 which constantly calculates and adjustsmixture the is mixture maintained percentages non-flammable suppliedmatically to by if the permanent the system. monitoring. The The gas gas flow is stopped auto- 2008 JINST 3 S08004 – 228 – sectors, while in RE2 and in RE3 (b) sectors are composed of 3 chambers of the internal ring ◦ as well there are 2 gas linessense per between section the (for two. the The up and totaltable down number7.11. gaps) of and channels the and flows the are in relative the gas opposite flows are summarised in Figure 7.77: In each endcap disk60 the RPC detectors are dividedand in the 2 corresponding rings. 3 RE1 of (a) the is external divided ring. into Every sector is supplied by 2 independent gas lines. Figure 7.76: The 2 zones intoby which a a gas wheel line. is sub-divided. Each station (2 chambers) is supplied 2008 JINST 3 S08004 122 178 324 324 948 type (l/h) Total flow per module ) single-gap RPCs whose 2 20.4 29.6 13.5 13.5 channel flow (l/h) Operating 50 cm × 30.6 44.4 20.3 20.3 per gas Volume channel (l) – 229 – 12 12 24 24 72 of gas Number channels (l) 5.1 7.4 5.1 8.4 5.1 8.4 Volume per RPC 36 36 36 36 36 36 216 RPCs in that module RE/1/2 RE/1/3 RE/2/2 RE/2/3 RE/3/2 RE/3/3 Total Module Table: 7.11 Chamber volumes and gas flows for a single endcap of the CMS RPC system. Pressure regulation system and gas distribution in UXC Pressure regulation is achieved in theown USC pressure area control for and each of protection the systemat 2 consisting the zones. of bottom bubblers Each located of height in section the the hasdifferences wheels/disks. distribution its in The racks the oil 2 level is zones.The adjusted supply to The and return account distribution lines for racks for the each are(only hydrostatic station installed at are pressure equipped the at with inlet). the a mass-flow bottom The metervalves flow of and are measurements a used each needle allow for wheel/disk. valve the the detection flow adjustment of between possible different leaks, stations. while thePurifier needle Results from long term tests performedin by the CMS RPC showed chambers that are the high impurity enough concentrationsremoved to produced from influence the the detector mixture. performance Therefore, ifsystem they to is are achieve not equipped a properly with high a recycling purifierthe rate module 3 the containing cleaning closed-loop 3 circulation agents cleaning are agents.is contained filled In in with the 2 first a purifiers. running 0.5-nm phase 25% molecular Both Cu-Zn sieve, the filter while (type purifiers the R12, are second BASF), 24-l 25% is(type Cu cartridges. 6525, filled filter Leuna). with (type The During R3-11G, the first the BASF), following and high combination: 50%2 luminosity Ni-Al2O3 separate running filter period 24-l the cartridges, second the purifier first willcontaining containing be the the split 6525 R12 into Leuna and filter. R3-11G Each2 cleaning purifier identical agents is cartridges and equipped are the with present second an allowing automatic the regeneration regeneration system: of a cartridge whileGas-quality the monitoring other is in use. Two independent systems aregain in monitoring preparation system to [170] continuously is monitor based the on gas quality. several small The (50 gas- working points (gain and efficiency) areprovide continuously a monitored online. fast and The accurate system is determination designed of to any shift in the working points. The small single-gap 2008 JINST 3 S08004 293 K = 0 coordinate x ) was used and water the distribution of the 6 7.78 , and 0.3% SF 10 H 4 )[173] at given reference values (T iC eff – 230 – , 3.5% 4 F 2 H 2 the efficiency distribution at HV = 9.3 kV for the first 27 endcap chambers is shown. 1010 mbar). 7.79 = 0 The chamber response uniformity was also studied by performing track recognition through The final gas mixture (96.2% C The tracking capabilities of the test telescope provided a full characterisation of the detectors First, the chamber efficiency was studied with the “coincidence” method by evaluating the Details regarding the quality certification procedures have been reported elsewhere [172]. • selection of electrodes and resistivity certification; • certification of single-gaps and double-gaps; • chamber testing. maximum efficiency for all the barrel RPCsIn is figure shown. The mean value of the distribution is 97.2%. the telescope. Muon trajectories were reconstructed in 2-dimensional views, where the and P vapour was added to keep the gas relative humidity at a valuein of terms of about efficiency, 45%. cluster size, and noiseresolution rate. were Also the studied. chambers’ local efficiency and Rigourousapplied the at and spatial all automatic test protocols sites in were order developed to and accept chambers systematically thatratio satisfied between the the CMS number requirements. of eventswindow in which (100 an ns) RPC and module had the at total least number 1 fired of strip recorded in the events. trigger In figure RPCs are divided into several sub-groupssystem supplied (i.e., with fresh gas gas coming mixture, input from to differentclosed-loop the parts chambers circulation). of in the closed-loop The full circulation, second and returnquantitative gas from gas the monitoring chemical system analyses [171] with performsand a specific both set-up fluoride qualitative electrodes. that and includes Inequipped a the with underground gas manual service chromatograph, cavern valves pH (USC),wheel. allow sensors, many In the sampling the analysis surface points gas of building (SGX),as the sampling well points gas as are available mixtures the to status that monitor of the return effectiveness each cartridge from in every the half purifier module. 7.3.6 Chamber construction and testing In view of the extremelyimpressive large-scale quality production control (a and factor certification of protocolsdifferent were levels: 10 set greater along than the in production past chain experiments), at many Only a short summary of the chamber testing results is given below. Chamber performance at the test sites Several RPC test stands weredetectors in could operation. be placed Each horizontally and telescopeof read consisted out cosmic of in muons. coincidence a with Two tower sets thefor in passage of triggering which of scintillators, purposes. the several at crossing Atmospheric the and topduring environmental and the conditions the were tests. bottom continuously of monitored Thesevariations the to values telescope, evaluate the were were effective high used used voltage (HV to scale the applied HV for temperature and pressure 2008 JINST 3 S08004 7.80. is shown eff coordinate by the chamber position in y – 231 – Figure 7.79: Efficiency at HV = 9.3 kV for the first 27 endcap chambers. the profile histogram of the cluster-size distribution as a function of the HV Figure 7.78: Distribution of plateau efficiency for all the barrel chambers. 7.81 The chamber cluster size is defined as the average value of the cluster-size distribution. In is defined by the strip positionthe along tower. the chamber Details and about the The the track-impact pattern recognition point algorithm onnearest have the cluster been centre chamber presented was evaluated. under elsewhere A [174]. test chambertrajectory was matched was considered the efficient also fired if strip. determined the reconstructed A and muon typical the strip-by-strip efficiency distance plot is to shown the in figure for all the barrel chambers.knee of A the chamber efficiency was plateau. accepted if the cluster size was below 3 strips at the Figure 2008 JINST 3 S08004 . eff portion of the ◦ = 9.6 kV for a barrel chamber. eff – 232 – Figure 7.80: Local efficiency at HV The RPC Balcony Collector (RBC) board provided a cosmic trigger with a selectable majority Figure 7.81: Profile histogramThe of dots the and chambers’ bars cluster-size arespectively. distribution as the a average and function the of HV root-mean-square of the cluster-size distributions,Magnet Test re- and Cosmic Challenge (MTCC) During the summer and fall ofin 2006 the a SX5 experimental first surface integrated hall. testfirst For of the positive an RPC endcap entire system, CMS disk 3 “slice” were barrelpower was sectors involved system performed and in configuration, a the 60 and test. CMScontrol DAQ The system software, chambers (DCS) data were were quality implemented operated monitor for with the (DQM), detector their and read-out final detector and control. level of signals from the 6 RPClevel barrel of chambers. A 5/6, trigger and rate ofsurface. 13 about Hz/sector 30 Hz/sector The for for RBC a a majority triggers. trigger 6/6 majority was was well found synchronized while with operating the the other detector muon on detector the (DT and CSC) 2008 JINST 3 S08004 shows the the chamber 7.82 7.85 = 9.6 kV. eff shows the overall noise distribution for all the 7.84 – 233 – is shown for some RPC stations. eff = 9.6 kV, while figure eff Figure 7.83: Barrel chamber noise profile at HV at HV 7.83 The RPC efficiency can be studied by extrapolating DT segments to the corresponding RPC Results are in agreement with those obtained during testing at construction sites and fully Several millions of events were collected with different trigger configurations. The DQM Specific runs were taken before and during the test to evaluate the noise rate. Preliminarily, Figure 7.82: Iguana muon reconstruction: RPC-fired strips are in red and DT hits in green. barrel strips involved in the test. layer and by requiring matching hits within an appropriate width. In figure efficiency as a function of the HV meet the design specifications. was used successfully during theand MTCC. the It chamber allowed behaviour the in online terms checking of of cluster the size, quality number of of the clusters, data etc. Figure event display of a typical cosmic muon triggered by the RBC andall the crossing threshold both values RPCs on and the DTs. front-endconfiguration electronic with discriminators higher were set efficiency. to The achievein the chamber figure best noise noise rate profile for a barrel station is shown 2008 JINST 3 S08004 3 10 2 HV_eff(KV) 10 Noise (Hz/cm^2) 3414 3414 1.584 1.584 0.3431 0.3431 RB2IN_B RB2OUT_B RB2OUT_M RB2IN_F RB2OUT_F 10 B = 0.0 T B = 3.5 T Entries Entries Mean Mean RMS RMS Noise_Histos106_10_26_9_24_45.txt Noise_Histos106_10_26_9_24_45.txt Efficiency For Chambers W2 S10 1 – 234 – , estimated by means of DT segment extrapolation. eff Noise Hz/cm2 -1 10 8.8 9 9.2 9.4 9.6 9.8 10 10.2 80 60 40 20

100 -2 10 Efficiency

80 60 40 20

180 160 140 120 100 Entries Figure 7.85: Global efficiency vs. HV Figure 7.84: Noise distributions inincluded 2 in different the magnetic distribution. fields. All strips of the barrel stations are 2008 JINST 3 S08004 m for the inner cham- µ . The required alignment precision for the endcap φ r – 235 – m in µ 7.2). After assembly, all chambers were tested with cosmic muon m for the outer chambers of Station 4. To this end, after following strict µ m, while for the barrel the precision varies from 150 µ duction of the chamber parts,relative such shifts as in mis-positioning the layer-superlayer ofternal assembly. wires components or The of relative strips a positioning chamber within was of atolerances measured the (section layer during7.1 different construction and and in- to be withindata the and showed required good correlation between thosefits. measurements and Furthermore, the the results geometry of of muon the track bly DT hall chambers was using measured optical atdrawings the and CERN and survey ISR cosmic techniques. assem- datanecessary. These to data provide are corrections compared to with the nominal construction chamber geometry when static deformations of the steel support.results This in effect, together displacements with of the the installationup chambers tolerances, to in the several different millimetres barrelinstallation, with wheels survey respect and and to photogrammetry endcap measurements their disks weredisk. of nominal performed detector for These each positions. measurements wheel provide and muon After an chamber chamber initial in geometry the — different positionstatic yoke steel structures and deformations — orientation [175]. which of absorbs each installation tolerances and the return yoke, at the levelchambers. of The a few new centimetres. detector geometry Theymeasurements of result resulting the in from optical further the system displacement magnetic and of forces track-based the alignment is techniques. accessed with factors can cause dynamic misalignments at the sub-millimetre level. There are several potential sources of misalignment in the muon spectrometer, from chamber The Muon Alignment (MA) system was designed to provide continuous and accurate mon- • Chamber construction tolerances. These are unavoidable geometrical tolerances in the pro- • Detector assembly, closing tolerances. Gravitational distortions of the return yoke lead to • Solenoid effects. Magnetic field distortions lead to almost perfect elastic deformations of • Time-dependent effects. During operation, thermal instabilities and other time-dependent bers of Station 1 to 350 chamber construction specifications, CMS combines precise surveyments, and measurements photogrammetry measure- from anbased opto-mechanical on system, muon tracks and (both the from cosmic results rays of and alignment from pp algorithms production collisions) to crossing final the detector spectrometer. operating conditions, including: itoring of the barrel andthem endcap and muon the inner detectors tracker among detector. themselves To fulfil as these well tasks as the system alignment is between organized in separate blocks: 7.4 Optical alignment system For optimal performance of the1 muon TeV, the spectrometer different [132] muon over chamberstracking the must system entire be to within momentum aligned a range with few hundred up respectchambers to to is 75–200 each other and to the central 2008 JINST 3 S08004 . φ staggering in ◦ staggering in ◦ 900 photo-detectors ≈ alignment planes with 60 -z alignment planes with 60 r -z r – 236 – shows schematic longitudinal and transverse views of CMS, with 7.86 The system must generate alignment information for the detector geometry with or without The basic geometrical segmentation consists of 3 . This segmentation is based on the 12-fold geometry of the barrel muon detector. Within each Figure 7.86: Schematic view of thecontinuous alignment and system. dotted Left lines panel: show longitudinal differentbarrel view optical muon of detector. light CMS. The paths. The crossing Right lines indicate panel: the transverse view of the local systems for barrel andbers, endcap and muon a detectors link to system monitormonitoring that the of relates relative the the positions detectors. muon of and the central cham- tracker systems and allows simultaneous collisions in the accelerator. Themagnetic dynamic field range between of 0 and the 4 systeming T. allows Its detector it goal geometry to is with to work respect provide indisentangle independent to the geometrical monitoring an solenoidal of errors internal the from light-based CMSapproach, track- sources reference e.g., of system. knowledge of uncertainty This the present will magnetic in field, help material the to description, track-based and drift alignment velocity. φ plane, the 3 trackingare sub-detectors linked of together. CMS Figure (central tracker, barrel and endcap muon detectors) the light paths indicated.stand-alone mode, Furthermore, in which the they barrelsub-detector. provide The and reconstruction layout of of endcap the the monitoring optical full pathswhile systems allows geometry the only of can monitoring one of each work sixth each independent of of in thesensors selected 250 CSCs DT located chambers, in in the the 4 regionand endcap between muon stations the detectors are muon to directly barrel be monitored. aligned wheels with Alignment and respect endcap to disks each allow other. the7.4.1 tracker System layout and calibrationThe procedures optical network uses two10 000 types LEDs of and 150 light laser sources: beams together with LEDs precise and measuring devices: laser beams. It is composed of 2008 JINST 3 S08004 . ◦ 40 < every 60 φ 288 pixels with 12 × z-bars. LED-holders were mea- rad]. [176 The MABs are fixed µ rad. µ m and 50 7.87) is based on the measurement of all the µ m and 50 µ – 237 – 7.88), the initial MAB positions on the barrel wheels were 7.1.4. Each LED-holder and video-sensor was individually planes parallel to the beam line and distributed in -z r m. Long term measurements showed good stability of the centroids and coordinate are measured with respect to 6 calibrated carbon-fibre bars (z- µ tube as a light passage. Each fork contains 10 LEDs, 6 and 4, respectively, z 2 65 mm 2, are equipped with extra alignment sensors and light sources that connect the barrel × pixel size, were calibrated to absorb residual response non-uniformities and the intensity m. As an important by-product, the calibration also provides the full geometry, including 2 µ 600 analog sensors (distance sensors and inclinometers), complemented by temperature, m Once MABs were installed (figure The control, read-out, and data preprocessing [177] are performed by a network of local The 4 corners of the DTs are equipped with LED light sources. Four LED-holders, or forks, µ 70 ≈ < 12 m precision, as described in section µ determined by photogrammetry measurements. minicomputers (1 per MAB, 36 in total)minicomputers that are makes connected it to possible the to main run control themagnetic PC full fields. via system an in The Ethernet parallel. network main The capable control of PC working in synchronizes the operation of the light sources mounted on nonlinearities. The video cameras, consistingbled of in a an video aluminium sensor box,Fully and instrumented were a MABs also single-element containing calibrated lens the to assem- necessarya determine number special of bench, their where survey inner the fiducials geometrical whole werewere geometry calibrated parameters. determined of on with the overall structure, accuracies positions, of and orientations 70 of elements sured and the position ofwith the an light accuracy centroid of was 10 light determined intensity with distributions. respect CMOS to miniature the× video holder sensors, mechanics containing 384 monitoring system with the endcap and tracker detectors. are rigidly mounted on theangular side-profile 50 of the honeycombon structure each (2 side. per side) There andforks are use with 10 the respect 000 to rect- light the sourcesof chamber mounted geometry on was the measured DT onthe chambers. planarity, a trapezoidity, dedicated and The the bench position relative with positions of a of the superlayers precision for each DT chambercalibrated with before its assembly on the DT chambers or MABs and bars) sitting on the outerwheels, surface YB± of the vacuum tank of the solenoid. The MABs in the external to the barrel yoke formingEach 12 structure contains 8on specially the designed DT video chambers. camerasMABs that Extra in observe light different LED sources planes and sourcesMAB forming video-cameras mounted positions a in in closed specific the optical MABs network serve to (called connect diagonal connections). The and humidity and Hall probes.are The described system below. is structured into three basic blocks whoseMuon main barrel features alignment The monitoring of the barrel muon detector (figure 250 DT chamber positions with respect toMABs a (Module floating for network the of Alignment 36 of rigidmechanical Barrel). reference structures, The rigidity called MAB design of was the optimisedterm to structures achieve measurements adequate under showed deviations load below and 100 in thermal and humidity gradients. Long 2008 JINST 3 S08004 – 238 – Figure 7.88: Installation of the MABs on wheel YB+2. Figure 7.87: Schematic view of thethe barrel MAB monitoring structures. system showing the optical network among 2008 JINST 3 S08004 m in µ z. From -position z-sensors z-sensors r plane and in -φ r m for chambers in the same µ 1 mm. ≈ z-bars, read out the temperature and humidity shows a photograph of a complete SLM on sta- plane are the Straight Line Monitors (SLM). Each – 239 – -φ 7.90 r position accuracy of 100 -φ 7.89). The system measures one sixth of all endcap cham- r -sensors for monitoring radial chamber positions, shows the location of proximity sensors on the outer ring of r 2 cm with an accuracy of ≈ 7.90 accuracies are directly coupled, the required accuracy in the -φ z-axis along the outer cylindrical envelope of CMS at 6 points separated by r m between barrel sectors. The current understanding of its performance is displacement due to the deformation of the iron yoke disks caused by the µ 7.4.3. coordinates (figure z and z r , and . Furthermore, every CSC and alignment device is equipped with photogrammetry r coordinate alignment is handled by optical SLMs and transfer lines. Transfer laser lines φ , m. The φ φ µ . The SLMs run across the surface of one sixth of all the CSCs, along radial directions, and φ The system uses a complex arrangement of 5 types of sensors for the transferring and moni- Based on simulation, the barrel monitoring system should provide a stand-alone measurement The 400 in . Because the ≈ ◦ -φ SLM consist of 2 cross-hair lasers,each end, which and emit provide a straight nearly reference radialOptical lines laser Position that beam are Sensors, across picked DCOPS up 4 [179]). by chamberspositions 2 from relative This optical to arrangement sensors the (Digital provides CCD laser references for lines. the Figure chamber bers. The main monitoring tools within the toring of the DT chambers and the read-outthe of the light images sources taken by mounted the on cameras. the The minicomputers MABs control and the strong and non-uniform magnetic field inaccommodate a the dynamic endcaps range requires of the alignment sensors to be able to sensors, perform the image read-out andsources. digitisation, The and results calculate are the transferred image to the centroidscentral main of CMS control the units. PC, light which is connected to the corresponding of the barrel chambers with ansector average and about 250 r is discussed in section Muon endcap alignment The muon endcap alignmentthe system actual [178] positions is ofultimately the designed within 486 to the CSCs absolute continuously relative coordinates andmounted of to accurately CMS. on each Due the monitor other, to endcap relative the yokecentimetres, to large undergo magnetic when the substantial field, the tracking motion the field system, and chambers isdeformation deformation, and switched and on on the and monitor order off. the of The absolute a alignment positions few system of must measure the the CSCs disk in the simulations, the required absolute alignment accuracies were found to run from 75 to 200 tion ME+2. The figure also indicates link transfer lines on oppositea sides laser of beam a disk. defines a Both direction laser in lines space have a that similar is basic picked configuration: up by several DCOPS precisely mounted 60 for axial distance measurements betweenmechanical stations, support and assembly a (transfer clinometer plate)are for onto mounted. monitoring which The the lasers, inset tilt reference in of DCOPS,the figure and the ME+1 station, which monitorare the necessary azimuthal because distance the between outer neighbouring ringoverlap chambers. of in ME1 These chambers is the only ring for which the CSCs do not run parallel to the CMS targets to allow absolute magnet-off measurements. 2008 JINST 3 S08004 sen- z m step size. m for µ µ coordinate measurements are sensors and 53 z r and r m for µ – 240 – m. Every DCOPS comprises 4 linear CCDs, each with µ 50 ≈ m pixel pitch. The CCDs are basically arranged in the shape of a square and µ m. µ All analog sensors were calibrated with a 1D precision linear mover with 6.4 can be illuminated by cross-hair lasers from either side. The 2048 pixels and 14 performed by analog linear potentiometers andtubes optical of distance calibrated devices length. in contact with aluminium The uncertainty in the absolutesors distance [180]. calibration is Calibration 100 for opticalof DCOPS the consisted mount in hole determining for thejected a distance pixel pitch reference from of the dowel each surface of pin the tovariable 4 light the CCDs. source first This was at active done CCD the onsimple a pixel focus calibration geometry and of bench reconstruction, where measuring a a based the parabolic fibre-bundle on pro- mirrormask coordinate-measuring-machine and illuminated sensor data a mounts, for mask determined the the with physical30 calibration 8 pixel to optical positions. 50 slits. Calibration errors A were typically Figure 7.89: Visualisation of the geometry andThe components square of objects the muon represent endcap optical alignmenteach sensors system. endcap (DCOPS) station. for monitoring 3 straight laser lines across on CSCs or transfer plates toof reference dowel their pins own positions. and Mounting dowel accuracies holes due are to tolerances 2008 JINST 3 S08004 -planes φ 3.3.7). Three pillars, acting as 2. Figure 7.91 (left) shows the LD = 3 cone. The link measurement network η z, and Tiltmeter). The insert indicates the location , – 241 – 1 wheels of the endcap muon spectrometer (link disks, LD); and the The ARs are rigidly attached to the endcap tracker detectors, TECs, through a purely me- apart; this segmentation allows a direct reference of each muon barrel sector with the tracker ◦ MAB structures attached at the external barrel wheels, YB± is complemented by electrolytic tiltmeters,calibrated proximity length, sensors magnetic in probes, and contact temperature with sensors. aluminium tubes of chanical connection with the instrumented silicon volume (section detector and provides a directtion, reference ME1. also to Each the plane endcap consistsz-side alignment of of lines 4 the in quadrants CMS the (figure detector, first7.86)ence and endcap resulting structures: generated sta- in rigid by 12 carbon-fibre 36 laser annular laser paths:rings, structures sources. placed AR) 6 at The on and both each system at ends uses of the 3 the YE± types tracker of (alignment refer- of proximity sensors on ME+1. Link system The purpose of the link alignmenteter system is and to the measure tracker the in relative position aenvironment of common of the CMS very muon coordinate spectrom- high system. radiationhigh It and precision is measurements magnetic over designed long field, to distances. meet work Asensors, in tight distributed ASPDs network a space of (amorphous-silicon challenging opto-electronic constraints, position position detectors) and [181], provide ter placed and around tracker the volumes muon are spectrome- connected60 by laser lines. The entire system is divided into 3 and AR carbon fibre structures installed in the inner support fixations, connect the last instrumented disk of each TEC with the corresponding AR, at Figure 7.90: Close-up ofcross-hair one laser, of DCOPS, the and analog 3 sensors Straight (r Line Monitors (SLM) on the ME+2 station with 2008 JINST 3 S08004 m resolu- µ = 3 cone during the η rad. Long term mea- µ rad; mechanical offsets µ 80% transmittance for the ≥ (right). The position and orientation of the ARs m, respectively, for the different sensor types. The – 242 – 7.91 µ m oriented perpendicularly. With m and 20 m. Distance measurement devices (optical distance sensors and µ µ µ e 7.91: Left panel: Link Disk and Alignment Ring installed in the inner The ASPDs are 2D semitransparent photo-sensors, which consist of 2 groups of 64 silicon The light sources (collimators) and specific optical devices housed on the alignment reference m. The location, centre position, and orientation of the ASPD with respect to reference pins in µ both ends of the tracker volume, see figure first closing of the detector in summerin 2006, the MTCC TEC period. end Right flange. panel: Alignment Ring mounted with respect to the TECusing disks the 9 external and survey 10angular fiducials were orientations prior measured are to monitored with by the a highLaser TEC coordinate-measurement precision sources machine tiltmeters assembly originating placed and at at instrumentation. the thesensors AR on AR and Changes the TEC and first in disk running endcap 10. along disk, ME1, the and inner on detector the external boundarymicro-strips barrel reach wheel. with ASPD a pitch of685 430 nm wavelength used in thewithout system, significant they distortions allow in multi-point the measurements beam along the direction. light The path intrinsic position resolution is about 2 tion linear movers and pre-measured calibrationcalibration fixtures. [182] The uncertainties are in below absolute and 50 relative surements were performed after beam adjustments. Beam pointing stability, including temperature their mechanical mount are measured withwith a an non-contact overall CMM accuracy (Coordinate of Measuring 15 Machine) intrinsic accuracy of the tiltmeters sensors, after calibration, is about 2 Figur linear potentiometers) already mounted in their final mechanics were calibrated using 2 inherent to the mechanicaltogrammetry mounts techniques. and assembly tolerances are determined by surveystructures and (AR, LD, pho- and MABs) createcollimator the laser is beam focused paths to with thegation its layout path working described to above. distance avoid Each to beam-shape-induced ensurecalibration bias [183] in Gaussian of the beam position the profiles reconstruction. laser alonginstrumented rays The with the for adjustment a propa- the and precise AR surveywere and network adjusted LD that to structures their mimics were nominal done the geometry on nominal with a detector a dedicated geometry. precision bench better Beams than 100 2008 JINST 3 S08004 m. µ – 243 – rad. The adjustment and calibration accuracy was limited µ rad due to the finite dimension of the structures combined with the intrinsic accuracy µ Survey and photogrammetry measurements are also performed during the installation of the The control, read-out, and data preprocessing are performed by two types of electronic COCOA has proved its robustness through its extensive use in CMS for several design studies, effects, was found to be betterto than 30–100 30 of the survey and photogrammetry measurement techniques of 70 alignment structures in the detector. Anmilliradians installation is accuracy needed to of ensure the correct order functionalityCMS of of assembly the a system, tolerances few taking of millimetres into the and account big the standard endcap disks and barrel wheels. boards. Analog sensors read-outboard) and cards laser [184]. control For use the standardcards read-out were ELMB of developed. (embedded ASPD LEBs sensors, local are intelligent custom monitor imagingto made acquisition 4 LEB boards ASPD (local made to sensors. electronic read board) They andCAN are control communication up based protocol on to Hitachi connect micro-controllers. the front-end ELMB electronics and and LEB the boards main use control the 7.4.2 PC unit. Geometry reconstruction The DAQ, monitoring, and control softwareenvironment. are Data integrated are into recorded the in DCS anples (detector online by Oracle control specialised database system) programs and subsequently thatvalues converted perform into into database ntu- meaningful queries and physical applygeometry quantities. calibrations reconstruction, to which This convert is raw provides handledAlignment) the by [185], necessary COCOA an (CMS information offline Object-Oriented program forsystem. Code to global for Due simulate Optical to and the reconstructalignment the unknown systems movements complex will of optical not different measure alignment yse the CMS the expected structures, observed nominal the changes values. in sensors The theserotations of aim measurements that the of caused to optical them. COCOA determine is The which approach to aresystem adopted anal- the of by displacements COCOA equations and/or to that tackle relate thisparameters the problem is measurement of to values all solve to the the all objectsone the does that positions, not make rotations, need and up to internal know thesurement the system. value explicit form with In of respect the fact, to equations, each toof but the object solve only propagation parameter. the the of derivatives COCOA system of light uses each of toequations a mea- calculate through equations, geometrical numerically a approximation nonlinear these least derivatives squares and method. then(about Due 30 solves to 000), the the big system large matrices of number are of needed.Library parameters COCOA [186]. in matrix CMS manipulations are based on the Meschach as well as for thegeometry, analysis will of be used several as test input benchesstudies geometry based and on for magnet muon track test tracks reconstruction results. from as cosmic well Its rays as and output, for from the further pp aligned alignment collisions. 7.4.3 System commissioning and operatingA performance first test ofperformed the between large June superconducting and November solenoid 2006,achieved magnet during (section which in stable 3.3). the operation at CMS The full detector alignment field was sensors, (4 T) successfully read-out, was and DAQ software were commissioned 2008 JINST 3 S08004 -φ r side of the detector. 7.93. Note that the 7.92, the nose is pulled z-stops, which prevent the m. This explains the radial µ 800 ≈ – 244 – 16 mm at 4 T. The various 7.92. At 4 T, the elastic deformation of the barrel yoke, ≈ z-stops between endcap and barrel, positioned at nearly half side with respect of the plane of the interaction point, is about m. µ 5% of the muon spectrometer. The measured relative movement ≈ shows the elastic compression of the barrel wheels versus the magnet m over the entire test period, with changes in position showing a good µ 7.93). Endcap disk deformations are predicted by finite element analysis m, while expanding azimuthally by 7.92 µ 600 ≈ direction towards the solenoid seem to stabilise after the first 2.5–3 T are reached. This compression of the face ofouter edge ME+1 (figure and the larger bending angles at mid-radius than at the (FEA) using the ANSYSagreement program for [3]. all displacements The and measurements deformations, are as shown in in reasonable figure quantitative direction did not exceed 60 The behaviour of the endcapmagnetic field disk near the is end of more the complicated.the solenoid, endcap strong disks magnetic Due towards forces the pull to center the of the central thetowards portions detector. strong the of As interaction shown gradient in point, figure in the the magnitudethe of magnet the current, compression reaching is up perfectlydisks to from correlated getting with pushed into eachto other bend and into onto the a barrel cone wheels, shape.the cause disk The the radius, endcap cause disks the sidethem of by the YE1 disk facing the barrel to compress radially around current as recorded in the secondcompression phase of of the the barrel Magnet Test spectrometer,barrel period. an chambers Despite important the during measurement large the was overall the whole stability data-taking of period. the The relative movements in the did not exceed 50 The effects of thermal changescorded (day-night for variations) the for conditions present DThall during and and the CSC power test, chambers on with were only the re- detector in the surface assembly Two effects were observed. The first(the is positions the before change any in magnet thez operation). original positions The of displacements the of structures compression the is structures along permanent, the meaningstates, it and is it not is reversed/recovered interpreted inacting as subsequent on the magnet the final off closing iron.experience of and the cannot These be structures measured extrapolated due to displacements to other the scenarios. areThe magnetic second specific effect forces is to the the almostnet-off perfectly first states, elastic as CMS deformations illustrated between in closing magnet-on figure measured and at mag- the end of the2.5 +z mm. Figure correlation with temperature. Although athe movement physics of analysis this magnitude pointalignment is of system. not view, relevant its from measurement illustrates the good resolution of the • Measurement of relative movements due to thermal changes. • Measurement of the displacements and deformations of the yoke structures. This allowed the first full-scale dynamicas test the of the main system. features The of performanceare the of summarised yoke the below: displacement system and as deformation well were studied. The relevant results during this test period for about one third of the system, instrumented at the +z 2008 JINST 3 S08004 300 ≤ 7.94. As in the case of the barrel – 245 – z-stops, between the ME1 and barrel wheels, were not included in the FEA, which 2.5 mrad relative to the vertical, as sketched in figure ≈ front explains the difference.presence The of difference the between carts that top support and the disks. The bottom rest is of also the explained endcapof by stations on the YE+2 andchambers, YE+3 with experience stable a 4 T maximum field, bending the angle observed relative movements were very small. The test of the magnetthe was yoke divided was into open 2 to extract phases, thetest separated inner of by detectors, the a tracker, reproducibility and short in ECAL period the modules.compatibility during closing This of procedure which allowed measurements and a tolerances, between as the wellat two as the phases. level the of study Reproducibility a of in few the the millimetresfor for closing the the was barrel endcap wheels disks. and aboutof an The a order particular solid of understanding magnitude conditions higher of of reproducibilityInstead, the for the the test system process did was of not closing able thesured allow to different in reproduce the structures. the the establishment first same period. magnetic-force-induced effects as mea- e 7.92: Deformations of endcap disks and barrel wheels vs magnet current cycling. Left From this test we conclude that the system operates adequately under magnetic fields both in • Detector closing tolerances and reproducibility. m and the measurement accuracy has been validated against results from photogrammetry and µ terms of dynamic range and measurement performance. The system precision achieved is Figur panel: The bottom plotMagnet shows Test the period. magnet The powering top cycleaction plot exercised point. shows during Right the the panel: measured first YE+1 Thesecond phase nose bottom phase plot compression of shows towards of the the the the magnet inter- compression Magnet powering towards cycle Test the exercised period. interaction during point. the The top plot shows the calculated approximate YB+2 cosmic ray tracks. 2008 JINST 3 S08004 z-stops Figure 7.94: Currentdeformation understanding due of to magnetic disk forcesalignment based system on measurements. The (red) prevent the disksinto each from other. getting Note that pushed ing the angle indicated bend- is exaggeratedposes. for Its measured illustrative magnitude pur- is 2.5 mrad. – 246 – plane at full magnetic -z r e: 7.93 Comparison of the YE+1 disk Figur deformations in the field (4 T) measured by(left the panel) alignment and predictions system from finite element analysis (right panel). The vertical linesspond corre- to 0 magnetic field. 2008 JINST 3 S08004 ). Since it is impos- 1 − s 2 − cm 34 for the combined L1 Trigger and HLT. The 6 – 247 – The L1 Trigger has local, regional and global components. At the bottom end, the Local Trig- The LHC provides proton-proton andthe beam heavy-ion crossing collisions interval at is high 25on ns, interaction luminosity, corresponding rates. several to collisions a For occur crossingsimultaneous protons frequency at pp of each collisions 40 crossing at MHz. of the Depending nominal the design proton luminosity bunches of (approximately 10 20 Trigger sible to store and processevents, the a drastic large rate amount reduction ofwhich has data is to associated the be with start achieved. the ofLevel-1 resulting This the (L1) high task Trigger physics number is [187] event performed of and selectionger by High-Level process. consists Trigger the of (HLT) The trigger custom-designed, [ 188], largely rate system, respectively. programmable issystem electronics, The implemented reduced whereas Level-1 in the in Trig- a HLT two is filter farm a stepstion of software called capability about is one thousand designed commercial to processors. be The at rate least reduc- a factor of 10 Chapter 8 design output rate limit ofmaximal the output L1 Trigger rate is of 100ger 30 kHz, uses kHz, which coarsely translates assuming segmented in an datahigh-resolution practice from approximate data to in the safety a pipelined calorimeters calculated factor memories and in ofcomplete the the three. read-out front-end muon electronics. data system, The The and while HLT has can L1the holding access therefore the Trig- the to analysis perform the off-line complex software calculations ifwill required similar evolve for to with specially time those interesting and events. made experience Sincein in they HLT algorithms ]. [189 are not For described reasons here. ofwhere More flexibility possible, information the may but be ASICs L1 found and Triggerwhere programmable hardware speed, memory is density lookup implemented and tables in radiation (LUT) FPGATrigger resistance are technology Supervisor requirements also [190], are widely controls important. used the configuration A and software operation system, of the the trigger components. gers, also called Trigger Primitive Generatorstrigger (TPG), towers are and based track on segmentsgers energy or combine deposits hit their in patterns information calorimeter and in use muon patternsuch chambers, logic as to respectively. electron determine Regional or ranked and Trig- muon sortedtion candidates trigger of in objects energy limited spatial or regions. momentumL1 and parameter The measurements, rank quality, based is which on determined reflectsand detailed as the knowledge on a level of the func- of the amount detectors confidence of and attributed information trigger to available. electronics the The Global Calorimeter and Global Muon Triggers 2008 JINST 3 S08004 74 each trigger 1. = | η | -veto bits and information relevant for muons in the – 248 – τ 087. Beyond that boundary the towers are larger. The s. The processing must therefore be pipelined in order to 0. µ × 087 8.1. The L1 Trigger has to analyze every bunch crossing. The allowed Figure 8.1: Architecture of the Level-1 Trigger. )-coverage of 0. φ , and attach the correct bunch crossing number. In the region up to T form of minimum-ionizing particle (MIP) and isolationdetermines (ISO) the bits. highest-rank The calorimeter Global trigger Calorimeter objects Trigger across the entire detector. enable a quasi-deadtime-free operation. Thetors, L1 partly Trigger in electronics the is underground housed controlexperimental partly room cavern. on located the at detec- a distance of approximately 90 m from the 8.1 Calorimeter trigger The Trigger Primitive Generators (TPG) makepipeline. up For the triggering first purposes or the local calorimetersthe step are transverse of subdivided energies in the measured trigger Calorimeter in towers. Trigger ECALtower The crystals E TPGs or sum HCAL read-out towerstower to has obtain an the (η trigger TPG electronics is integratedhigh-speed with serial the links calorimeter to read-out. theelectrons/photons, Regional transverse The Calorimeter energy Trigger, TPGs sums, which are determines transmitted regional candidate through L1 Trigger latency, between a giventhe bunch detector front-end crossing electronics, and is the 3.2 distribution of the trigger decision to determine the highest-rank calorimeter and muonthem objects to across the the entire Global experiment Trigger, andto the transfer reject top an entity event of orgorithm the to calculations Level-1 and accept hierarchy. on it The the forby readiness latter further the of takes Trigger evaluation the the Control by sub-detectors System decision and the (TCS).sub-detectors the The HLT. through The Level-1 DAQ, Accept which the decision (L1A) is Timing, is decision determined Trigger is basedTrigger and communicated is on Control to depicted al- (TTC) the in system. figure The architecture of the L1 2008 JINST 3 S08004 4 trigger towers except requires passing of two × m CMOS ASIC chips named FENIX. An off- µ – 249 – 8.2) starts by determining the tower with the largest energy 5 are determined by the trigger. A non-isolated e/γ 2. 5 crystals. The matrix is dimensioned such that it also allows for the detection of trigger algorithm (figure | ≤ η × | The front-end modules of the hadron calorimeter contain Charge Integrator and Encoder The e/γ within per region are forwarded to the GCT. detector Trigger Concentrator Card (TCC)barrel collects and the 48 primitives from boards 68 inand front-end the encoding, boards endcaps store in through the the optical trigger primitives links.by during The the dedicated L1 TCCs daughter latency finalize time boards, the and theL1A TPG transmit signal. them Synchronization generation to The and the SLBs Link RCT synchronize the Boardscrossing trigger (SLB), structure. data upon through circuits reception Each that of histogramConcentrator trigger the a Card LHC tower (DCC) bunch performs is the aligned opto-electronicinput conversion with and data deserialization the streams of bunch the and serial crossing sendsClock and zero the Control read-out signal. System data (CCS) collectedTCC, A boards the from Data distribute DCC the the and front-end clock, the boards9U the on-detector VME to electronics. L1A crates the and for The the control DAQ. ECAL barrel signals TPG and to hardware six the is for the contained endcaps. in(QIE) twelve ADC chips to digitizeto the the signals HCAL from Trigger the and photo Readoutearizes, detectors. (HTR) filters boards. Optical and Each links converts HTR transmit thevalues board the input of processes data data front 48 channels. and to back generate Itfiltering towers lin- the algorithm. are HCAL added As trigger and for primitives.data the the are The bunch ECAL, collected crossing energy the by number primitives a areEach is crate sent DCC. assigned houses to by The 18 the a HCAL HTR boards RCT peak trigger and by electronics one SLBs, DCC. is and contained read-out inRegional 26 Calorimeter Trigger 9U VME crates. The Regional Calorimeter Trigger [191] determinesergy electron/photon sums candidates per calorimeter and region. transverse Information en- relevantwith for minimally muons ionizing about particles isolation is and also compatibility calculated.in A HF region consists where of a 4 regionsummed is in one each tower. trigger tower. Electromagnetic and hadronic transverse energies are Calorimeter trigger primitive generators The ECAL on-detector front-endsignals electronics from boards, the very each front-end electronics serving locatedmost at 25 of the the crystals, rear TPG of receive pipeline the in detector the six modules. ADC radiation-hard They 0.25 contain deposit and is appliedhighest across deposit the in entire one of ECALe/γ the region. four broad The side energy neighbours is of then the added. tower Isolated with and the non-isolated next- shower profile vetoes. Thelateral first extension one of is a based shower.matrix on The of a fine-grain 2 bit fine-grain is crystal setbremsstrahlung energy by due profile the to reflecting TPG the the if magneticenergies the field. in shower the is The contained hadronic second in andallowed one a in for is the that based ratio. electromagnetic on sections. theall An ratio eight isolated A of neighbouring electron/photon typical the towers. candidate maximal deposited electromagnetic has value In towers to of addition, surrounding pass 5% at the the is least hit previouse/γ tower one vetoes is quiet for required. corner Four made isolated of and four four groups non-isolated of five 2008 JINST 3 S08004 3 7. 12 × 0. × × 3 cells 0 × 5. = 4 tower region. ∆φ × -veto bit set. After × τ ∆η candidates. -strip combined to make a 3 -veto bit is set unless the pattern φ -directions. These are compared τ φ Figure 8.3: Electron Isolation Card. 8.3. -strip. Mini-clusters adjacent or diagonally φ – 250 – 0 (not in HF). 3. 2 contiguous trigger towers within a 4 × < | η | jets from the central HCAL and four jets from HF are forwarded and half the detector, respectively, in these directions. The cell at -veto bits for the identification of jets from one- and three-prong τ τ ◦ -strips are transferred in opposite (the scalar transverse energy sum of all jets above a programmable jet if none of the corresponding RCT regions had a φ τ T -jet only at τ , spanning 40 η e 8.2: Electron/photon algorithm. and φ The RCT hardware consists of 18 regional 9U VME crates and one 6U clock distribution Jets are found by a four-stage clustering technique based on jet finders operating in 2 The RCT also sums the transverse energy in a given region of the central calorimeter (HF is Figur =0 is duplicated. In the first stage mini-clusters are created by summing energies within 2 -decays, which are narrower than ordinary quark/gluon jets. A Jets can be classified as crate located in the underground control room. Each crate covers a region of cells in η threshold). It also provides the highest-rank isolated and non-isolated e/γ of active towers corresponds to at most 2 Receiver cards are plugged intoECAL the and rear HCAL primitives. of The the HFserial regional primitives input are crates. data directly are received Seven on converted cards to atransmission per 120 Jet/Summary on card. MHz crate a parallel The receive 160 data, the MHz deskewed, custom linearizedand and monolithic one summed backplane Jet/Summary before to Card seven (JSC) Electron mountedthe Isolation at algorithm Cards calculations. the (EIC) front An side EIC of is shown the in crate. figure Different ASICs perform Global Calorimeter Trigger The Global Calorimeter Trigger determines jets,energy, the total jet transverse counts, energy, the and missing transverse H if a central cell has more energyclusters than in neighbouring each cells. of In the theagainst second two stage the the three existing largest mini-clusters mini- on the receiving not included) and determines adjacent to a largerclusters mini-cluster that are survive have their removed. three adjacent cells In in the the receiving third and fourth stages the received mini- τ cell. A jet is classified as a sorting, up to four jets andto four the GT. The magnitude and direction of the missing energy and the total transverse energy are 2008 JINST 3 S08004 4. 2. | ≤ η | -projection and hit φ -thresholds and optionally also T E data from one half of the RCT crates on 27 fibres – 251 – 1 at the startup of LHC. The design coverage is 2. | ≤ η | TCA industry standard [193]. An active custom backplane based on the µ -projection. The endcap CSCs deliver 3-dimensional track segments. All cham- η )-regions are computed. Muon MIP/ISO bits are received from the RCT along with 5. Twelve jet counts for different programmable ’s, jets and energy sums, the GCT also handles MIP/ISO bits for muons. They are φ , < | η data and are forwarded to the GMT through a dedicated muon processing system. Apart | All GCT electronics is located in the underground control room. The large amount of data processed by three muon processingThe cards, processor which design receive is 6 built muonarchitecture on fibres based an each on evolution from the of Source the Cards. leaf concept and uses a modular, low-latency computed from the regional transverse energywithin sums in the two coordinates transverse to the beam the e/γ from triggering, the GCT also acts ascapability the to read-out monitor system rates for the for RCT. certainthe The trigger GCT LHC has algorithms luminosity in and as addition from seen the those by deduce the CMS information trigger about system. from the RCT crates are transmitted252 electronically to optical 63 fibres. Source Cards, which Theconfigured reorder as core the data electron of onto or the jetto GCT cards. perform processing Several complex is Leaf tasks Cards performed such canfor by as be jets. Leaf the connected Each jet Cards, with electron finding. each which leaf otherand card There can sorts in receives are be them. order the two Each e/γ Leaf jet card Cardscards. receives for 30 electrons regional They and sum perform fibres six sorting from the three and jet RCT data crates clustering compression. via and They thethem also source transmit calculate to the partial the energy jet Wheel sums candidatesand Cards. and jet to Wheel counts A Cards two and Concentrator and Wheel forward Cardin performs Cards the finally the for boundaries final collects between sorting the groupsand for data of jet electrons/photons, from three count completes all quantities Leaf the and Electron Cards, sendsinvolving jet Leaf sorts the e/γ finding all final jets, results to calculates the the GT global and energy the DAQ. In addition to the tasks principle of a crosspoint switch allows athen programmable transmitted routing to of the the GMT 504 on MIP/ISO 24 bits, links. which are 8.2 Muon trigger All three muon systems –chambers the provide DT, local the trigger information CSC in and the form the of RPC track – segments in take the part in the trigger. The barrel DT different (η patterns in the ber types also identify theTrigger consists bunch crossing of the from DT whichassign and an physical CSC event parameters to originated. Track them. Finders,timing The which In resolution, Regional join addition, deliver Muon segments the their RPC to ownMuon trigger complete Trigger track chambers, tracks then which candidates and combines have based the excellent information onmomentum from regional resolution the hit three and sub-detectors, patterns. efficiency achievingcoverage an compared The of improved Global to the muon the trigger stand-alone is systems. The initial rapidity 2008 JINST 3 S08004 8.4): Bunch Φ-type superlayer Θ-type superlayers ) and the other for the coordinates. The TRACO φ m Gate Array technology. The µ consists itself of two components, the view delivered by the θ – 252 – Φ-type superlayers, measuring Φ-type superlayer and 12 BTIs in the outer Figure 8.4: Drift Tube Local Trigger. ). The first one processes the output from the TRACO, whilst the The TS has two components, one for the transverse projection (TSφ The DT chambers have two m Standard Cell technology. There are a few hundred BTIs per chamber. µ longitudinal projection (TSθ second uses directly thepresent output in of the the three BTIs innermost of muon the stations. The TSφ trigger data of at mosttransmitted two to track the segments TS, per whose purpose bunch is crossing to reconstructed perform by a each track TRACO selection are in a multitrack environment. Drift Tube local trigger The electronics of theand DT Track Identifiers local (BTI), trigger Track Correlatorstors consists (TRACO), (SC). Trigger of While Servers four (TS) the and SCs basicread-out Sector are components electronics Collec- placed is (figure on housed the in sides minicratesplemented on of in the the custom-built front integrated experimental side circuits. cavern, of allof The each other the BTIs chamber. trigger are chambers. All interfaced and devices Using to are the thepassage im- signals front-end of from electronics the the muon. wires Each theyof BTI generate searches staggered a for drift trigger coincident, tubes at aligned in hits atimer each in fixed technique the chamber time [194], four after superlayer. which equidistant the uses planes Theany the association three fact of adjacent that planes. hits there is From islar the based a direction associated on fixed are hits, a relation determined. track mean- between segments Theresolution the defined spatial better drift by resolution than position times of 60 and of one mrad. angu- BTI0.5 The is BTI better algorithm than is 1.4 implemented mm, in the a angular 64-pin ASIC withattempts CMOS to correlate the trackthe segments measured TRACO in defines each a ofhierarchy. them. new Four segment, If BTIs a enhancing in correlation theare the can connected inner angular be to found, resolution one TRACO. andThe The producing TRACO number is a of implemented TRACOs in quality is a 240-pin 25 ASIC for with the CMOS largest 0.35 muon chamber type. 2008 JINST 3 S08004 groups the -coordinate, the anode electronics to φ -sectors of CMS are sent to Sector Col- ◦ – 253 – shows the principles of the cathode and anode trigger electronics and the bunch 8.5 have a higher momentum than in the barrel, which gives rise to more bremsstrahlung T p The requirement of robustness implies redundancy, which introduces, however, a certain An electric charge collected by the anode wires induces a charge of opposite sign in the Track Sorter Slave (TSS) and thethe Track best Sorter quality Master and (TSM). the Thethe smallest TSS bending TRACOs preselects angle in the based order tracks on to with is a then save reduced activated processing preview and data time. the setpreview TRACO coming data A is are from select also allowed sent to line to send the inpreview TSM the the words for full a from TRACO second data with the stage to processing. TSSs. the themomentum. The best TSM. TSM The analyzes The track There up output corresponding to is consists seven one of TSM the two per tracks muon with station. the highest In transverse the longitudinal view the TSθ crossing assignment. information from the 64and BTIs a per quality chamber. bit. From Aindicating logic the each position OR BTI of of the two groups muon bits of and are eight 8 quality bits received, bits. is a applied.amount trigger The of bit output noise data or consistCOs duplicate of and tracks 8 the bits different giving parts rise oftrigger the to and TS false also contain the triggers. complex read-out noise data and Thereforelector from ghost each reduction (SC) the of mechanisms. units, BTIs, the The sixty where the 30 thequality TRA- trigger — is information coded — and the transmittedFinder position, to (DTTF), transverse the through DT momentum high-speed regional optical and trigger, links. track called the Drift Tube Trigger Track Cathode Strip Chamber local trigger The endcap regions are challenginga for given the trigger since manyphotons. particles In are addition, present photon and conversions in muonsfrequently. a Therefore at high-radiation the (neutron-induced) CSCs consist environment occur ofwhich six can layers be equipped correlated. with Muon anode track wires segments,of and also called positions, cathode Local strips, angles Charged Tracks and (LCT), consisting bunchorthogonal anode crossing and information cathode are views. first Theyhit. are determined then separately The correlated in cathode in the time electronicsidentify and nearly the is in bunch optimized the crossing number with to of high measure layers efficiency. the cathode strips nearby. The triggera electronics resolution determines of half the a centre stripthat of width, at gravity between least of 1.5 four the and layers charge are 8strip with hit, mm, widths. the depending Due position on to of the the a radius.over finite muon an By drift can interval demanding time of be the more determined than anode with twoare signals a bunch required, in resolution crossings. since the of in As six contrast 0.15 for chamber to the neutron-induced layersin cathodes, background are at at a least spread real least four out muon four coincident leaves hits layers coincident(pre-trigger) signals with is a probability used that to exceedsA identify 99%. validation the Actually of crossing, a the in coincidence tracksignals of order occurs are two to if signals found. allow in for theORed. In long following Figure order drift two to time bunch reduce hits crossings the to at number least arrive. of four trigger coincident channels 10 to 15 anode wires are 2008 JINST 3 S08004 10 5 1 -coordinate in the bending plane, φ 55 – 254 – -value and the bunch crossing number. The best two LCTs of each η , a rough b φ The track segments from the cathode and anode electronics are finally combined into three- The hardware of the CSC local trigger consists of seven types of electronics boards. Cathode Figure: 8.5 Cathode StripAnode Chamber LCT Local formation from Trigger: wire (a) group hits, Cathode (c) LCT Bunch formation crossing assignment. from strips, (b) dimensional LCTs. They are characterized by thethe high-precision bending angle chamber are transmitted to the regionaljoins CSC trigger, segments called to the complete CSC tracks. Track Finder (CSCTF), which and anode front-end boardsfinding (CFEB boards and (ALCT) latch AFEB) the amplifythat anode hits are and at consistent digitize 40 with the MHz, havingsend find signals. originated hit the at patterns anode Anode the in information the vertex, LCT- tocards. six and the chamber determine The Cathode layers the CLCT LCT-finding plus bunch circuits Trigger crossing.TMB look Motherboard circuits for They perform (CLTC/TMB) strip a hit time coincidence patternsis of consistent cathode found, with and they high-momentum anode send LCT tracks. information. theLCTs The based If information on a to quality coincidence cuts. the In Muon orderif to Port two cancel Cards out or ghosts (MPC). more a The LCTs coincidence withmuon TMB are RPC station found. hits selects sector, is selects up A established the to MPC best two receivesthem two over the or optical three LCTs links LCTs from to depending the the onrecorded CSC CLTC/TMBs the of Track by station Finder. one number DAQ The endcap and motherboards anode sends and (DAQMB)(DDU) cathode and LCTs belonging transmitted and to to the the raw the DAQ hits system CSCthe are upon L1A detector-dependent reception decision, units of the a bunch crossing L1A numberClock signal. and and The Control bunch Boards counter LHC (CCB). reset timing The signals reference, front-end arechambers. boards distributed and by The the the ALCTs rest are of mounted the directlydisks. on local the The trigger optical electronics fibres is to housed theASIC in control implemented 48 room in depart peripheral the from crates CLCT there. on module, Except the the for CSC endcap the trigger comparator-network electronics is builtResistive in Plate FPGA technology. Chamber trigger The RPCs are dedicated triggerDT detectors. and Several layers CSC of tracking double-gapof chambers, RPCs the are six two mounted in on innermost the the muonthe central stations, forward region one parts (one (two on layer the layers on inside on the of the inside the of inside two each and outermost station). outside stations) Their and main advantage four is in their excellent 2008 JINST 3 S08004 of T . As p φ ghost busting and electric charge, after having es- T p and quality. The DTTF and the CSCTF T p – 255 – , which are each subdivided in 144 segments in η at several points along the track to determine the bending and thus the 24. Their signals can also be taken into account by the RPC trigger in φ 1. < | η | The track finding principle relies on extrapolation from a source track segment in one muon The RPC trigger is based on the spatial and temporal coincidence of hits in several layers. The RPC signals are transmitted from the FEBs, which contain ASICs manufactured in 0.8 . Therefore the RPC strips run parallel to the beam pipe in the barrel, and radially in the endcaps. m BiCMOS technology, to the Link Boards (LB), where they are synchronized, multiplexed, T p µ opposed to the DT/CSC, there iscluster no reduction. local The processing Pattern on Comparator a Trigger chamberfour (PACT) logic apart muon] [195 from stations compares synchronization to strip and predefined signals patterns oftablished all in at order least to three assign coincident hits ina time minimum in four number planes. of Spatially hit thethe PACT planes, muon. algorithm requires which Either varies 4/6 depending (fourparameter out on reflects of the six), the trigger 4/5, numbers tower 3/4patterns. and of or The on 3/3 hit outer the hit layers. section layers of are themagnet For minimally hadron coil six required. calorimeter up (HO) planes A to consists quality there of are scintillators placed typically after 14 the 000 possible logic is also necessary. Theregions. RPC The muon best candidates four are barrel sorted andThe the separately best RPC in four data the forward barrel record muons and are isindividual sent forward trigger generated to boards. the on Global the Muon Data Trigger. Concentrator Card, which receivesDrift data Tube from and Cathode the Strip Chamber track finders The regional muon triggerTrack based Finder on (DTTF) in the the precision barrelThey [197] tracking and identify chambers the muon CSC consists candidates, Track of Finder determinecandidates (CSCTF) the are their in Drift the sorted transverse endcaps by Tube momenta, [198]. rank, locationseach which deliver and up is quality. to a four function The muons of to the Global Muon Trigger. station to a possible target segmentinating in at another the station according vertex. to If a a pre-calculated compatible trajectory target orig- segment with respect to location and bending angle is serialized and then sentcontrol via room. 1732 optical The links 1640the to LBs complex 108 are PACT housed Trigger logic in which Boards fitsSince 136 in duplicate into Link 12 tracks a may Board trigger be large Boxes. found crates FPGA. due in The to There the Trigger are the algorithm Boards 396 concept and contain PACT the chips geometry, in a the system. timing resolution of about 1 ns,triggering which purposes ensures an the unambiguous measurement bunchmagnetic crossing of field, identification. muons the are For bent momentum in thethe of plane azimuthal a transverse coordinate to particle the LHC is beams. also It is important. sufficient to measure InThere are the about 165 000 strips inchannels total, each. which are connected to front-end boards (FEB) handling 16 It is segmented in 33 trigger towers in order to reduce rates and suppresslow-quality background RPC triggers. [196]. The The optical algorithm links requirestrigger from HO the boards, confirmation four and for HO HTR the boards signals areRPC received plane, are by with treated the the RPC and required number incorporated of in planes the hit increased PACT logic by one. like an additional 2008 JINST 3 S08004 -value η assignment η is nevertheless possible by deter- η -information coming from the DT lo- 12 half-width sectors, whereas the four η × -values, is performed by 12 η -superlayers. Both for the DTTF and the CSCTF, θ 8.6. While the CSCTF incorporates 3-dimensional – 256 – is performed by 72 sector processors, also called Phi φ status is therefore necessary. The sector processors attempt . The central wheel has 2 φ , with the goal to refine η Figure 8.6: Track Finder extrapolation scheme. -projection. A coarse assignment of -sectors. In the overlap region between the DT and CSC chambers, around φ ◦ 6 60 -sectors in ◦ × second track segment 1, information from both devices is used. In the DTTF the track finding in The track finding in | ≈ η the track finder logic fitsorganized into in high-density sectors FPGAs. and wedges. Forwedge the There has are regional six twelve trigger 30 horizontal the wedges DT parallel chambers to are the beams. Each can be assigned using the information from the outer wheels are subdivided inpartitioned 12 in full-width 2 sectors each. In| the two endcaps the track finding is Track Finders (PHTF). Per chambertrigger they through receive optical at links. mostthe two segments The track inside segments segment from a informationpresent the is sector, in DT composed its a local of bending chamber, the thebut angle at second relative and the one position a subsequent is of quality one, sentindicate code. provided not this that at in If the that bunch there crossing crossing are no from two other which segment segments it occured. originated A tag bit to spatial information from the2-dimensionally CSC in chambers the in the track finding procedure, the DTTF operates to join track segments topre-calculated. form Extrapolation complete windows, tracks. which aretracks The adjustable, can are cross parameters stored sector of in boundaries, allcancellation look-up therefore scheme compatible tables. data to segments are avoid Muon are duplicated exchanged tracks between has sector to processors be and incorporated. a found, it is linked to theto source four segment. muon A stations maximum is numberThe of joined extrapolation compatible to principle track form is segments a shown in in up complete figure track, to which parameters are then assigned. mining which chambers were crossed by the track. In most cases an even more refined units, also called Etamethod is Track used, Finders since (ETTF). for A muon pattern stations matching 1, 2 rather and than 3 an the extrapolation 2008 JINST 3 S08004 are η and qual- T p assignment, through T p – 257 – -information from up to three muon stations. The data are φ -sector, is delivered to a first sorting stage, the Wedge Sorter (WS). -projection, if possible. For each wedge, the combined output of the ◦ φ -values and quality for at most 12 muon candidates corresponding to a maximum of η The DTTF data are recorded by the data acquisition system. A special read-out unit, the As for the DTTF, the core components of the CSCTF are the sector processors. They receive, - and )-coordinates. Then nearly all possible pairwise combinations of track segments are tested for φ φ , PHTFs and the ETTFs, whichthe consists of the transverse momentumtwo including track the electric candidates charge, per 30 There are twelve of these sorters, which have to sort at most 144 candidates in total by matched with those of the ity. Suppression of remaining duplicatequality candidates filtering found is by also adjacent performed sectorat by processors these most units. and 24 track in The total, twofour highest-rank are candidates muons then in found transmitted the in to entire each thefor central WS, matching final region, with Barrel which the Sorter are RPC (BS). and then The CSC delivered candidates. latter to selects the the Global best DAQ Muon Concentrator Trigger Card (DCC) has beensix developed. It Data gathers Link the Interface datacontained from Boards in each (DLI). three wedge, racks through Each in DLI thehouse control serves the room. electronics two for Two two wedges. racks wedges contain as(TIM) six well The in track as each DTTF finder a of crate crates, these electronics controller. which crates There is each the to is distribute central also the one crate clock Timing and containing Module other theLHC timing BS, signals. machine clock the The and third DCC, the rack a houses Trigger Control TIM System. module and boardsthrough for interfacing optical with links, the thesector LCT processor data receives from upME3 the to and Muon six ME4. Port LCTs Up Cards fromdata to in are ME1 four latched the and track and peripheral synchronized, segments three and(η are crates. LCTs the also original each transmitted LCT Each from from information is stations DTconsistency converted with station ME2, to a MB2. reflect single global track Firstdata in the the exchange processors’ between extrapolation neighbour units. processorsthe is In extrapolation contrast performed. results to and Complete the redundant tracks DTTF,processor tracks no are are canceled selected assembled as and from in assigned kinematic the andSRAM DTTF. quality look-up The parameters. tables, best The is three based muons on per the cal trigger is contained in a bit pattern representing adjacent chamber areas. The tracks in collected in a detector-dependent unithoused (DDU) in a for single the crate read-out. in(CCB) the similar The counting to twelve room. the sector This ones processors cratecrossing in also are reset, the contains local bunch a CSC crossing Clock trigger zero andbackplane electronics, Control and a which Board other distributes maximum the timing of clock, signals.which 36 bunch determines candidate Over the best the tracks four custom-developed is muons GTL+ transmitted in the to two the endcaps and forward sendsGlobal Muon them Muon to Sorter Trigger the board, GMT. The purpose of the Global Muonand Trigger suppress [199] background is by to making improve use trigger ofsystems. efficiency, reduce the complementarity trigger It and rates receives redundancy for of the everybarrel three bunch muon RPCs, crossing and up to up four to muon four candidates each each from from the the DTs CSCs and and endcap RPCs. The candidate information 2008 JINST 3 S08004 8.7). 35. A muon 0. × 35 8.7. Three Pipeline 0. jets, as well as global = τ ∆φ × ) of the transverse energies of T ∆η technical. triggers The core of the GT thresholds to single objects, or of requiring the jet – 258 – T E or T and quality. Cancel-out units reduce duplication of muons )-coordinates, and quality. For muons, charge, MIP and ISO p φ η , and a quality code. From the GCT it also receives isolation and ,(η φ T , η or E T p and charge, T p The GT has five basic stages: input, logic, decision, distribution and read-out. The corre- multiplicities to exceed defined values. Since location and quality information is available, more bits are also available. sponding electronics boards use FPGAthe GMT, technology are [201]. housed in AllSynchronizing one Buffer of (PSB) central them, input 9U boards as high receive well thealign crate, calorimeter as them which trigger in the objects is time. from boards shown the The in of GCTPSB muons and figure board are can receive received direct from trigger the signalscial GMT from purposes through sub-detectors such or the as the backplane. TOTEM calibration. experimentis An for These the additional spe- Global signals Trigger are Logic called (GTL)basic stage, in algorithms which consist algorithm of calculations applying are performed. The most jets above a programmable threshold,representing and particles twelve and threshold-dependent jets jet arecharacterized multiplicities. ranked by their and Objects sorted. Up to four objects are available. They are is considered isolated if itslow energy a deposit defined in threshold. the calorimetercandidates DT region based and from on CSC which their candidates it spatial are emergedmerged. coordinates. is first Several If be- matched merging a with options match barrel are isrameters, possible and possible, taking and forward the into can RPC kinematic account be parameters the selected strengths are are individually of for optionally the all individual suppressed muon of based systems. these on Unmatched pa- in candidates the overlap region betweenby the both barrel the and DT the and CSC endcaps,the triggers. where vertex, Muons the in are same order back-extrapolated muon through toGMT may the retrieve be calorimeter output the regions reported and corresponding to can MIP beby and taken transverse ISO into momentum bits, account and which by quality, aretogether the first then to Global separately added deliver Trigger. in to four the Finally, the final barreldata the candidates and and muons the to forward are output the record. regions, sorted GT. The andThe A GMT then 16 electronics read-out muon is processor cables housed are in collects the directly theslot same connected crate to input wide as the front muon the GMT panel. GT logic (figure board, TheThe which logic MIP/ISO has itself, a bits which special from is four the VME containedBuffer GCT in (PSB) FPGA are input chips, received modules, only and which occupies synchronized1.4 are one Gbit/s by also slot. serial three used links Pipeline in and Synchronizing theThe are MIP/ISO mounted GT. The at bits PSB the are back transmitted boardson of from receive the the the the GT crate, PSBs bits backplane. behind to via the the wide logic logic board front by panel. GTL+ point-to-point links 8.3 Global Trigger The Global Trigger] [200 objects takes delivered the by decision the to GCT(isolated accept and and or GMT. non-isolated reject These ), an objectsquantities: muons, consist event total at in central and candidate-particle, L1 and missing such transverse based forward energies, as on hadronic the e/γ trigger jets, scalar sum (H consists of minimally ionizing particle bits for each calorimeter region sized 2008 JINST 3 S08004 8.8. Different subsystems may be operated – 259 – Figure 8.7: Global Trigger central crate. 8.4. A Timing Module (TIM) is also necessary to receive the LHC machine clock The TCS architecture is represented in figure complex algorithms based ongraphical topological interface conditions [202] can is used also tocalculations be set are programmed up sent the into to trigger the the algorithmnumber Final menu. logic. of Decision The algorithms Logic results A that (FDL) of can the in beaddition algorithm executed the be in form received parallel directly of is from one 128. the dedicated bit Uptrigger PSB per to board. mask 64 algorithm. is For technical applied, normal The trigger physics and bits data the taking mayand L1A a in decision tests single is of taken individual accordingly. subsystems For upL1A commissioning, calibration to signals eight can final be ORs issued. canby be two The applied L1A_OUT distribution and output of correspondingly boards, the provided eight scribed that in L1A section it decision is to authorized the byand subsystems the to is Trigger distribute Control performed it System to de- GT the data boards. records, Finally, appends the the Globaldata GPS acquisition Trigger for event Frontend read-out. time (GTFE) received board from collects the the machine, and sends them to8.4 the Trigger Control System The Trigger Control System (TCS)the [203] status controls of the the sub-detector delivery read-out ofsignals systems the provided and by L1A the the signals, data Trigger acquisition. dependingreset Throttle The on System commands, status (TTS). is and The derived from TCS controlsTrigger also the and issues Control delivery synchronization distribution and of network [204], test which is and interfaced calibration to the triggers. LHC machine. It uses the Timing, independently if required. For thisresenting purpose a the subsystem experiment or is a dividedalso major into called component 32 a of partitions, it. TCS each partition. rep- Eachrently. partition For Within commissioning is such and assigned a testing to TCS up asignals to partition partition eight distributed all TCS group, in connected partitions partitions different are available, operate time with concur- slots their own allocated L1A by a priority scheme or in round robin mode. 2008 JINST 3 S08004 overflow disconnected, .error The signals are generated by the Fast Merg- – 260 – and ready , busy Figure 8.8: Trigger Control System architecture. synchronization loss, The central TCS module, which resides in the Global Trigger crate, is connected to the LHC During normal physics data takingbe there is operated only centrally one as single(LTC). TCS members Switching partition. of between Subsystems a central may partition either andface) or local module, privately mode which through provides is the a performeddestinations interface Local by for between Trigger the the the Controller TTCci respective transmission trigger (TTC ofand control the CMS control. module L1A inter- The and TTC signal the Encoder and andthe other Transmitter (TTCex) TTCci fast module and commands encodes drives the for optical signals synchronization splitters receivedTTC from with machine a laser interface transmitter. (TTCmi). Theceivers LHC (TTCrx) At clock containing is the low-jitter received quartz destinations from PLLs. the theof The the TTC Beam LHC signals Synchronous sends the Timing are (BST) GPS received system time. by TTC re- machine through the TIM module,ules to through the the FDL through LA1_OUT the boards.(sTTS) GT and backplane, an The and asynchronous TTS, (aTTS) to to branch. 32end which electronics TTCci The of it sTTS mod- 24 collects is sub-detector status partitions also informationemulators. and connected, from up the has to The eight front- a tracker status synchronous andwarning, signals, preshower front-end coded buffer in four bits, denote the conditions ing Modules (FMM) through logicaland are operations received on by up four conversion toaTTS boards runs 32 located under groups in control a of of 6U the fourger crate DAQ sTTS software electronics. next and binary to monitors It the signals the GT receives behaviour central andmatch of crate. the sends the TCS read-out The status and partitions. information trig- It concerningthe is the status coded 8 signals in DAQ different a partitions, protocols similar which resources are way due executed. as to the For excessive sTTS. trigger example, Depending rates, incausing on prescale them. case the factors A of meaning may loss warning of be of on synchronization appliedminimal the would in spacing use initiate the of of a FDL reset L1As to procedure. are algorithms maximum General L1 also trigger output implemented rules rate of in for 100 theters kHz TCS. is are estimated The provided to in total be the below deadtimein 1%. TCS. estimated the The Deadtime at surface and central control monitoring the board coun- room sends the3564, to total the the L1A orbit DAQ count, number, Event the the Manager event bunch (EVM)other number crossing information. located for number each in TCS/DAQ the partition, range all from FDL 1 algorithm to bits and 2008 JINST 3 S08004 , 1 − 9.1. s 2 − cm 34 2 kByte (for pp ≈ 9.1. Each data source and Monitor Control Filter Systems Readout Systems 100 GB/s Hz. At the design luminosity of 10 2 Detector Front-Ends – 261 – Computing Services Builder Network

Event Level 1 Trigger Manager Figure 9.1: Architecture of the CMS DAQ system. Hz Hz 100 GByte/s coming from approximately 650 data sources, and must provide 5 2 10 10 40 MHz ≈ The read-out parameters of all sub-detectors are summarized in table The architecture of the CMS Data Acquisition (DAQ) system is shown schematically in figure Data Acquisition The CMS Trigger and DAQ systemthe is LHC designed bunch to crossing collect frequencycessing and of and analyse 40 the analysis MHz. detector is The information onthe rate at the LHC of order rate events of of to a proton be1 collisions few recorded MByte will 10 for of be offline zero-suppressed around pro- data 20to in per the bunch reduce crossing, CMS the producing read-out incoming approximately systems.information average The coming data first from level rate the trigger to calorimeters isteresting a designed and signatures. maximum the Therefore, of muon the chambers, 100 DAQfor and kHz, system a selecting must by data events sustain flow processing with a of fast in- maximumenough trigger input computing power rate for of a 100 softwarerate kHz, filter of system, stored the events High by Level Triggersent a (HLT), to factor to a of reduce computer the 1000. farm (Event Inoffline Filter) CMS that reconstruction all performs software, events physics that selections, to using pass filterof faster the events the versions Level-1 of and CMS (L1) the achieve Data trigger the are Acquisitionrespective required Technical System Design output and Report of rate. [188]. the The High design Level Trigger is describedto in the detail DAQ in system the is expected to deliver an average event fragment size of Chapter 9 2008 JINST 3 S08004 9.2. The 3 3 2 40 56 32 10 458 3 3 2 40 56 32 10 626 Builder Control Network Builder Data Network Builder Manager Builder Unit Computing Service Network Detector Control System Detector Control Network DAQ Service Network Data to Surface Event Manager FED Builder Front-End Controller Front-End Driver Front-End System Filter Farm Network Front-End Readout Link Filter Subfarm Global Trigger Processor Level-1 Trigger Processor Regional Trigger Processor Readout Manager Readout Control Network Run Control and Monitor System Readout Unit Trigger Primitive Generator Timing, Trigger and Control synchronous Trigger Throttle System asynchronous Trigger Throttle System 9 k 54 54 RM RCN RCMS RU TPG TTC sTTS aTTS Acronyms BCN BDN BM BU CSN DCS DCN DSN D2S EVM FB FEC FED FES FFN FRL FS GTP LV1 RTP 36 k 440 250 (merged) 1500 n/a n/a ≈ ≈ ≈ s latency) via the Timing, Trigger and Control µ – 262 – DCS DCN FEC DSN DSN RCMS Control column *10000 *700 *512 *64x8 *64x8 *8 21 k 72 k 76 k 540 8 8 8.6 k 732

≈ ≈ ≈ ≈ FFN FU RU BU D2S FED FES FRL-FB DAQ BDN CSN column *8 *8 66 M 15840 55 M n/an/a n/a n/a 500 k 9.3 M 9072 9072 3072 192 k 195 k 48820 60 75848 TPG TTC sTTS aTTS RCN BCN Table: 9.1 Sub-detector read-out parameters. 144384 4512 1128 ≈ ≈ ≈ ≈ channels FE chips detector data links sources (FEDs) links (FRLs) number of number of number of number of data number of DAQ *8 207], the corresponding data are extracted from the front-end buffers and Trigger & LV1 RTP GTP EVM RM-BM Data Flow Control A schematic view of the components of the CMS DAQ system is shown in figure CSC, DT Track Finder Total ECAL HCAL Muons CSC Muons RPC Muons DT Global Trigger sub-detector Tracker pixel Tracker strips Preshower collisions at design luminosity). Innominal size. some case two data sources are merged in order to reach this Figure 9.2: Schematic of the functionalis decomposition not of the shown DAQ. for The clarity. multiplicity of each entity various sub-detector front-end systems (FES) store dataUpon continuously arrival in 40-MHz of pipelined a buffers. (TTC) synchronous L1 system trigger [204, (3.2 pushed into the DAQ system by the Front-End Drivers (FEDs). The data from the FEDs are read 2008 JINST 3 S08004 as a luminosity section 9.4). The DAQ system – 263 – it is foreseen to operate at a maximum L1 rate of 50 kHz, 1 − s 2 − LHC orbits, corresponding to 93 s), during which trigger thresholds cm 20 slices, each of which is a nearly autonomous system, capable of han- 33 10 × For the first LHC run, the Event Filter is foreseen to comprise 720 PC-nodes (with two quad- The required computing power of the filter farm to allow the HLT algorithms to achieve the The DAQ system includes back-pressure all the way from the filter farm through the event The event builder assembles the event fragments belonging to the same L1 from all FEDs into corresponding to 4 installed DAQthe slices. HLT algorithms It will has demand a beencore. mean estimated processing This [189] time implies of that around for under 50 thebe these ms 50-kHz deployed conditions on DAQ for a system the 3-GHz that HLT. After Xeon an optimising CPU- estimated equivalent the required of trigger about computing selection 2500 for power the CPU-cores isoperating LHC must at expected design a luminosity, to 100 the be kHz L1 roughly rate. twice as much forcore 8 processors) DAQ for slices 50hardware, kHz the operation. additional filter Based farm on nodescured. for initial The 100 design experience kHz of and operation the atprocessing. evaluation DAQ system design of allows luminosity candidate for will this be gradual pro- expansion in event building rate and 9.1 Sub-detector read-out interface The design of thethe FED central is DAQ sub-detector system specific, has however, been a common implemented. interface The from the hardware FED of to this interface is based on S- fixed period of time (set toand 2 pre-scales are not changed. Theeach GTP luminosity counts section the and live-time records (in them numbers in of the bunch Conditions crossings) Database for fordesign later rejection analysis. factor of 1000 isLHC substantial luminosity and corresponds of to 2 O(1000) processing nodes. At the can be deployed in updling to a 8 12.5 kHz eventunderground rate. to the The surface event building builder (SCX), is where also the filter in farm charge is of located. builder transporting to the the data FEDs. from the size Back-pressure and from rate of the events, may down-stream givewhich event-processing, rise would or to result buffer variations overflows in in in data the the corruption sub-detector’s(TTS) front-end and protects electronics, against loss these of buffer overflows. synchronization. It The providesfront-ends fast Trigger-Throttling to feedback System the from any Global of Trigger the Processor sub-detector overflow. (GTP) so During that operation, the trigger trigger canutilize thresholds be the and available throttled DAQ before pre-scales and buffers HLT will throughput capacity. belead However, instantaneous optimized to fluctuations L1 in might trigger order throttling to and fully introduce dead-time. CMS has defined a into the Front-end Read-out Links (FRLs)of that are FRLs able to corresponding merge to dataconfiguration, from the there two CMS FEDs. are The 512 read-out number FRLs. parametersthe TOTEM These of experiment additional [2], table and inputs for9.1 are inputsread-out from usedis local and for 458. trigger FRL combined units, electronics among operation are others. In with located The in the sub-detector the “baseline” underground electronics room (USC). a complete event and transmits itThe to event one builder Filter is Unit (FU) implementedcomprises in in the a two Event number stages Filter of (referred for components, further to processing. as which FED-builder are and described RU-builder) below and (section , , . , . t t r - s e e a n n h n h . s s r e t l a n e r m n i t t t B h o o g r e c e u p e e t h d v i i i n n k t d e t t p n d p v h l n o wi h e e i a m a t v a e u e n n a 4 i r u v v r a i i s n w e a s d d i e e r e m u B c t u s , o t t r e e i e n s a s d r s t e h e a m o r d e h a D b y l e d e s o s z n t z f a s t e n r i E f b o i r . d e s m a c s s a s F u c g k e t o n m e u r n c t e i g m t o a o n a j p k 8 o e t i r n o t e h s n r n l x d n i d l t s w o d g i t h a u a t h 8 o t t b l r r t n p t i . e s n i c p a h wi n a s e a p e t w t d i t n e e e p u e o t m r l c n r d wi u n l i n l v b e i L i l a a b n o C n wi o m o e wi , a , n a v a a c s Gb r u e R s e c g s t t r s - a z r , t k NI t a i F t e d o n g m h ’ e c a - r s 0 r e t g h n r n e s d . n w f e h i fi t l a t r c e i L n n o t l 4 f i t Da i y h i n c f m e a wi t t a r r g a e R u e r l m e t g d n t . r u o y n e l a i F h g t h d m a a B i u k i t m o p c s p t g r a e r t T i r t p e u e s M f a r r o a t h r wi o r n r D f r n r h n n e . f ’ B c p i e t f e o e e f r e a E o w s e r a s o e s h r t p d h m t s n e d t F t e n u l e t d t t D- e n a o l i i e s f i r e h l e i r f n a f t n e r n s E o u g n c a u i e r h s e d c r o t e h o t t e F i v n B t d s B e e f s 8 r s r T m a s f e n i d y x wi e n e h D Q c . g e d t u r o s s wh D t c n a 8 y o E e a n h a a x A As c n l o r t E n e a F e e c o e b f l e c wi b n . z D % F r n i c h 8 i d a s a e f t e 0 d c e o , e t x l 6 s k r L p e e i o h r a s 8 5 h a f fi n 5 t t h t h c r t a R p a f e o c t t o o 2 e r i u a r e o e u l F y n . f p d k t l w v t t d l , k g r 4 t h i o o l c wi e a e s a e l , s t i s o g n e u . a ws i t h e n i c h u h d s g u p t o n i i o d h p i t b n h m l o t c e r o r e m c F B 2008 JINSTf 3 S08004 h a t e c . o r e p n e o y h r t s d y n r o s d h m m o g h t m f T e u e b w U t wi i M a 5 t e n t wi n g T s r b s m r i r o R % s e s . e . . fi fi a n g e e u 5 t m e a i 5 e r w g e e b e n s o m h h s t i e e 9 l h . h g t d d r t i o a e t g t g r m e F T T g t s o e o c e p e e i r a r f r o u n y e e r F o a h h p s t m a o wh p p r n l t r o m f t , , , , t t t t t ) - f r s s s s e e e e e e d n o o d t s s s t e i e w Q u n n t t e r n e n o h d a h h h h r n r n C i i i k Hz u n o n e e t a t t t p y g a c A e r e a a r i u i t o e b t h h v v d t a d r t r t s o , o o l M u - p D s s e s NI s e e c e a m n e I t s a u y m / t p i g r t n 6 o u k a d t w m e e p r e u l y i c g C s l r a t c n k o 6 B r t s ( e l e t E M t i s h i c / e a n r o h b i a e e o P t t p t n u t i n t r a f n t r k . d , . n c o i i n n - m M f u a a t r p r r e d c d s y r r s y n n r t b n a k o t n d w n r t e o a o e e e g y c 8 b o ; t o c r u u t e 4 o m h f r a e n o n u i p d g s o 2 e c r a w c f c e g c o h 6 t e l c u a l d r e t p M t e t e f . r : i e t 5 n b l u m y fi l e v e o e d n s e e u a u a u n s s e o e b i e o l g n n b f p n n w e i s e c wi i b e e e z m Ds n e h h a b B o o s o o r f c h s a o i c a C s t l t r h l n l t o B c a c f E a s a c e y n t d fl m s s e e a o r u c o f 4 e l k i n g e r i F r o e 8 t l r u c i e d v t 6 D n p t d , h a M a n i a d t l o h e a x e t k 2 a e p m s e i i h e n y t E c t t i g n t a n i k r l n 8 . d c w l i s i u h e s y t s e a ; C n F d o c n s t t o n o i , t e i e a L l n e b u v t s i VDS r n B t s a e - u C i i o e s v o i t d z s d h y t a e r o o i L NI S u p r b e n u d n , p t t 8 m s w o n i , y T p a b c e s e e e NI b c t l o o D e x r d r m I t e c r e p t L . l h h e p e C On I p r t 8 y r n t u E u t M n e s I d m u n I t C p f u . n e R t a R e o C n ) s F e . e n m f o P o h C e n m m C M f s n g F s a v s f m t P i a e s C r n n s o i i wh k o r P o n P e m e h i e r d e e e x s t i u t e s c f c a r d d e r e d c b o d g r r I h f a , h r k r c t v t p i a e d h a , u y a a . n a Hz h e e t fi t . t c e a o e 4 a a T t e e v p r e g t t o t m o s f n s y d c w l f s p s l h e wi M f o p l e M n n . n a a i d . e n k r e i o k a s r s e y i l r u f u r c a f 6 t i wi o g n m m f p o z n i c h u l b p a i h i a t a t b i i s o e e t o 6 e h t o o a x l l p e s p / e p s c s e b B F o , T h e g s c e c t r t e b s o c o l s t s l k i C i e s s i n ( e b . n a e e a i r l s d w s i a o c n . S s e L a i r b e l t r y c l d a r a D h e k b i m e d s o a k a r f n l i v t h d e r a . 4 e / s c e s R c r a y i d wh n x n E s b s e , o o t s D2 . o i e l s n r a 6 d i a s a c m e i l F f a ( B i s fi d a F v l d d z y e h t d r o g I a h h M B c p e k i i r i r h r u r r l d r e g t n c c t e C p o c o e c c f s k n s r M u a r a e c C a e a a f c a t f e c n r B o e e i h a o a e s n c a c c r o h r c s v n P h o e p C e B f n r h d t a t i 1 i 0 NI h t T E c r y e B e h t r y c e p o d g C c r c D d s c h i L 8 , L T e d . b c p e k i y r p s i L e L t u d - t e o . n NI i D t a L , r e 4 s t d e s l E i d t . R e l p R ) v e u n s n i c d R n l e R NI l p e e 4 e r E g i h b R i t t i F F wh o F e p p g e n o e u s v e F p d 6 h a F fi t P F g n r wh t t F i u i s n m s b e n r s v o c i l wn c l e 2 e e B e e i o , o n p a e o o d e e a c a l e e e e e a o h o e o y i t n f m 1 h h h l . h p a f c t t i p r n v t e m h h h h h h C d e e s o 3 e u r i c 5 t i T e r a 8 T u r a t r l i t I s D a Figure 9.4: Photographcard, LVDS of cable and S-link64 compact-PCI FRL sender with card embedded LANai2XP NIC. Connected to the NIC are fibres thatinput go switch. to the FED Builder h g e . f e k p o T T T T T i m d n v t y s o e t e e a a e r a g z . . E C n r f n a e i i b o n o n y i r h e s n s h h h h o i o g F s t f B t M t o o h s i C i 8 i a t t F c b a P wh t c v t a t l – 264 – 9.4. and 9.3 PMC-Link (576) Myrinet LANai 2XP FED crate VME-PCI Input-FED Builder 6x(256x256) Switch 2x2.5 Gb/s link Optical Cable USC-SCX ~ 200 m FED Builder liks 6x(256x256) Switch FB-RUI Fibers ~ 20m RUI-PCI (576) Myrinet LANai 2XP S-Link64 LVDS S-Link64 LVDS adapter (680) cable LVDS (Dual) LVDS-FED merger (576) FED-PC FED Builder system Detector FrontEnd Driver FED Frontend Readout Link FRL e 9.3: Diagram of a generic sub-detector The physical implementation of one element of the sub-detector read-out interface and its Figur read-out into the FED builder. Link64 [208]. The FED encapsulates thedata data received structure from by the front-end adding electronicsfragment. a in a header The common header and and a trailerprocess, trailer partially consists that such of mark as event the information theCRC used beginning event (Cyclic in and the Redundancy number the event Check) derived end building ofinspected from of the in data an the the record. event Event TTC Filter. The L1A payload signals. of the event The fragmentsFED trailer is builder includes only port is a shown in figures The S-Link64 Sender card The S-Link64 Sender cardplugged into is the sub-detector a FED. custom Itthe receives developed data CRC from Common in the order FED Mezzanine via to1.6 Card an check kByte S-Link64 (CMC), of transmission port data and errors directly checks before overto generating the interface back-pressure S-Link. with to a the The FED. copperconductor card The round cable is cable CMC which v98 able manufactured has can by to an 3M) have buffer comprises LVDSshielded. a 14 converter up twisted The maximum pairs, to link length which provides are of feedback individually matic 11 lines self in m. test. order The to This nominal signal cable data back-pressure64 transfer (Multi- and bits), rate which to over the is initiate LVDS twice an cable the is auto- maximum 400 MByte/s sustained (50 design MHz throughput clock, of the DAQ system. 2008 JINST 3 S08004 s, µ s. Each FED µ l r s s n 1 s a n a i e

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Error and terface The FRL receives event fragments and checks the CRC in order to check transmission errors The FRL card also provides monitoring features, such asUp the to ability to 16 spy FRL on cards a are fraction of placed in a crate with a Compact-PCI backplane. Each crate is a FED has to beindicate able that to synchronization accept was 2 lost moreattempts or triggers to an after recover error asserting automatically Busy occurred from state. these in states the Out-Of-Sync by front-end and issuing electronics. Error a L1-Resync The or GTP L1-Reset command provides fast signals indicating theOf-Sync state of the read-out.are generated The according states to the amountif of more internal triggers data can buffering be available accepted. and are Given used the to trigger indicate rules (section The TTS provides the feedbackIt from is all a FEDs hardwired and their system, associated acting front-end on systems the to dataflow with the a GTP. reaction time of less than 1 The Front-end Read-out Link The FRL is a custom 6Uwhich Compact-PCI handles card up (figure to two64-bit/66-MHz LVDS PCI cables; connector an for a output Network interface Interfaceinterface to Card which (NIC); the is and FED a a Builder configuration PCI andthe implemented bus control FRL as interface a board connected is to the performedEP1S10F672C6 Compact-PCI by for backplane. two the main FPGAs The logic). (Altera function EP20K100EFC324-1 of for the PCI bridgeover the and LVDS cable. In the caseare where merged. the FRL Data receives are data buffered from in twoblocks FEDs, memories via the of the two 64 onboard data kByte PCI records bus. size and pushed into the NICevents in via fixed the size Compact-PCI bus, and to accumulate histograms of quantities such asconnected fragment to size. a PC viaHartmann a Elektronik), compact which PCI is bridge used (StarFabric forcrates CPCI/PCI configuration, in system control total. and expansion monitoring. board from There are 50 FRL 9.2 The Trigger Throttling System and sub-detector fast-control in- 2008 JINST 3 S08004 9.7). It has three main and 9.6

Figure 9.7: Photograph of a FMM module.

BIT -(Z – 266 –

' T0#) OMPAC ! # *4 YBUS NALBUS ER Y EMOR E T TION BIT-(Z - BIT-(Z )N YT IDGE EMOR &0'! &0'! -B - 0#)BR &--FUNC

e 9.6: Block diagram of the FMM.

ERS ANSMITT TR

ERS EIV EC 6$3R 2*, The FMM is a custom-built 6U compact-PCI card (figures The FMM also provides extensive monitoring capabilities in order to diagnose the causes for G

6$3 2*, O Figur R ESET 2 &0'! E 0 2 via the TTC system. Thesetwisted fast pairs TTS using signals the LVDS are signaling transmitted standard. over shielded RJ-45 cables withThe four Fast Merging Module For flexibility, FEDs are grouped intoeach 32 other. TTC partitions The which Level-1 maypartitions Trigger be and operated Control independently separately System of receives separatelyfrom trigger distributes all throttling triggers FEDs signals to in these for aing TTC 32 each partition Modules TTC TTC thus (FMMs), partition. need have to beenup TTS be designed merged to signals with for 20 low this inputs latency. task. andpendent Dedicated have groups Fast These quad of Merg- modules outputs. 10 can inputs Optionally,FEDs, FMMs with merge FMMs two can and are independent be cascaded monitor twin in configured outputs. two to layers. For merge partitions two with inde- more thancomponents: 20 a PCI Interface FPGA,MHz a internal main clock logic of FPGA the FMM andnized is an to not on-board the synchronized internal memory clock to block. by theare requiring The LHC then two 80 clock. successive merged samples by Input in selecting signals the the arethe same highest synchro- signal state. priority priorities The input listed input signal above. signals from Optionally,if the Out-of-Sync the input enabled number signals inputs are of according only inputs to taken in into Out-of-Sync account state exceeds a programmabledead-times. threshold. Each stateresolution) transition in at a the circular inputs bufferthe is memory states that detected Warning can and and Busy hold stored areoutput(s). up with counted to with a 128 25 k time-stamp ns transitions. (25 resolution for ns The each times input spent channel in and for the 2008 JINST 3 S08004 512 FRLs generate event ≈ 9.8. The event builder is com- – 267 – 2 kByte and the FED-builder is in charge of transporting ≈ 16 kByte. The super-fragments are then stored in large buffers in Read-out ≈ 72 networks. There can be up to 8 RU-builders, or DAQ slices, connected to 9.2). It reproduces the LHC beam structure, generates random or clocked triggers up In normal data taking mode, triggers from the global trigger are distributed to the FEDs via the The Global Trigger Processor emulator (GTPe) [205] emulates the functionality of the GTP FMM cards are configured, controlled and monitored by a PC via a compact-PCI interface TTC. When using the GTPe, special testto triggers a are sent trigger directly distributer to the card FRLcrate. which crates Because distributes via the a the lemo FEDs trigger cable are over notby the being the backplane used trigger in to distributer this all card mode, the and busysubset FRLs sent signals of in from to the the sTTS a FRLs dedicated signals. are setand collected of A FMM instead modules of dedicated for reading mode fast out of mergingpredefined the of table. the FEDs, this In FRL the this firmware FRL way, the handles generates full data the central fragments DAQ GTPe system with test can sizes be triggers according tested. to a 9.4 The Event Builder A schematic view of theposed Event of Builder two system stages: is the shownfragments FED-builder in and with the figure an RU-builder. Each average ofthese size the fragments to of the surfacean building (SCX) average and size assembling of them into 72 super-fragments with to 4 MHz, respects theS-Link64 trigger and rules, receives applies and partitioning, handlesmentation transmits is sTTS the based and GTPe on aTTS the data Generic-III backpressure fragment PCI over signals. card [206] and The an hardware interface imple- module GTPe-IO. Units (RU), waiting for thewith multiple second 72× stage of event building (RU-builder), which is implemented (StarFabric CPCI/PCI system expansion board fromprises Hartmann 8 Elektronik). FMM The crates total with system up com- order to to 9 merge FMMs the in TTS each signals crate. of all A TTC total partitions of of 60 CMS. FMM modules9.3 are needed in Testing In order to test and commissiondetector the DAQ central systems, DAQ system a independently number ofused the of in GTP standard additional and data components of taking. have the sub- been developed. These are(see not figure the FED-builder layer. Eachevent FED-builder by is event in basis, to charge the ofevent RU-builders go distributing and to ensures the one that super-fragments, and all on only super-fragmentsnetwork. an corresponding one to DAQ The slice, one complete and are event readan is by architecture then one with transferred Builder two-stage to Unit event a (BU)slice building, of single by the the unit slice RU-builder full of while size the the systemmented Event traffic can with Filter. load be commodity By to progressively equipment, utilising the deployed interfaces. including second processing stage The processing nodes, is nodes optimized. network areLinux switches The server operating and PC’s event system. with network builder PCI is busses imple- to host the NICs. They run the 2008 JINST 3 S08004 output NICs 9.9). The NIC M FED-builders. In the baseline M × N switches to form 2 rails (figure input NICs hosted by the FRL, M N × – 268 – N equals the number of DAQ slices, which is 8 for the full system. M Figure 9.8: Schematic view of the Event Builder. FED-builder comprises M 8 and × ≤ N N The software running on the NICs has been custom developed in the C language. The FED- The event builder is lossless and when necessary back-pressure is propagated up to the FRL The FED-builder stage is implemented using multiple (M3F2-PCIXE-2 based on the LANai2XP)data has rate each. two Each bi-directional rail fibre oflarge optic one amount NIC ports, of is small with connected physical to 2 switches, an Gbit/s a independentThis single switch. 2-rail large configuration In switching practice, doubles fabric instead the is of used bandwidth a per to rail 4 (see Gbit/s below). per FRLbuilder and input provides NICs redundancy. are programmed to readfabric, fragments with from the a FRL and destination tolook-up assigned send table. them on to the the The switch basis FED-buildergrammed of to output concatenate the NICs fragments with fragment are the event hosted same event number by number and from the all a RU-builder the PCs. connected predefined input cards, They are pro- hosted by the RU PCs, and two independent In general, one configuration, and subsequently to the FED, which can throttle the trigger via theThe TTS. FED-Builder stage The FED Builder is based oncrossbar Myrinet switches [209], and an NICs, interconnect connected technology byrouting point for to clusters, and point composed flow bi-directional of links. control It atRISC employs processor. the wormhole link level. The LANai ASIC on the NIC contains an embedded 2008 JINST 3 S08004 9.10). , , . , . t t r - s e e a n n h n h . s s r e t l a n e r m n i t t t B h o o g r e c e u p e e t h d v i i i n n k t d e t t p n d p v h l n o wi h e e i a m a t v a e u e n n a 4 i r u v v r a i i s n w e a s d d i e e r e m u B c t u s , o t t r e e Input-FED Builder CLOS-256 2x2.5 Gb/s Optical link USC Optical Cable ~ 200 m Output-FED Builder CLOS-256 i e n s a s d r s t e h e a m o r d e h a D b y l e d e s o s z n t z f a s t e n r i E f b o i 16 (Xbar32) cross-bars. Three r . d e s m a c s s a s F u c g k e t o n m e u r n c t e i g m t o a o n a j p k 8 o e t i r n o t e h s n r n l x d n i d l t s w o d g i t h a u a t h 8 o t t b l r r t n p t i . e s n i c p a h wi n a s e a p e t w t d i t n e e e p u e o t m r l c n r d wi u n l i n l v b e i L i l a a b n o C n wi o m o e wi , a , n a v a a c s Gb r u e R s e c g s t t r s - a z r , t k NI t a i F t e d o n g m h ’ e c a - r s 0 r e t g h n r n e s d . n w f e h i fi t l a t r c e i L n n o t l 4 f i t Da i y h i n c f m e a wi t t a r r g a e R u e r l m e t g d n t . r u o y n e l a i F h g t h d m a a B i u k i t m o p c s p t g r a e r t T i r t p e u e s M f a r r o a t h r wi o r n r D f r n r h n n e . f ’ B c p i e t f e o e e f r e a E o w s e r a s o e s h r t p d h m t s n e d t F t e n u l e t d t t D- e n a FRL-PCI Link Myrinet LANai2XP o l i i e s f i r e h l e i r f n a f t n e r n s E o u g n c a – 269 – u i e r h s e d c r o t e h o t t e F i v n B t d s B e e f s 8 r s r T m a s f e n i d y x wi e n FRL-FB Fibers ~ 20m e h D Q c . g e d FB-RUI Fibers ~ 20m RUI-PCI Myrinet LANai 2XP t u r o s s wh D t c n a 8 y o E e a n h a a x A As c n l o r t E n e a F e e c o e b f l e c wi b n . z D % F r n i c h 8 i d a s a e f t e 0 d c e o , e t x l 6 s k r L p 8 FED builder with a two-rail network. e e i o h r a s 8 5 h a f fi n 5 t t h t h c r t a R p a f e o c t t o o 2 e r i u a r e o e u l F y n . f p d k t l w v t t d l , k g r 4 t h i o o l c wi e a e s a e l , s t i s o g n e u . a ws i t h e n i c h u h d s g u p t o n i i o d h p i t b n h m l o t c e r o r e m c F B f h a t e c . o r e p n e o y h r t s d y n r o s d h m m o g h t m f T e u e b w U t wi i M a 5 t e n t wi n g T s r 8 FED-builders. The use of a large switching fabric allows for a high b s m r i r o R % s e s . e . . fi fi a n g e e u 5 t m e a i 5 e r w g e e b e n s o m h h s t i e e 9 l h . h g t d d r t i o a e t g t g r m e F T T g t s o e o c e p e e i r a r f r o u n Figure 9.9: 8 × y e e r F o a h h p s t m a o wh p p r n l t r o m f t , , , , t t t t t ) - f r s s s s e e e e e e d n o o d t s s s t e i e w Q u n n t t e r n USC e n o h SCX d a h h h h r n r n C i i i k Hz u n o n e e t a t t t p y g a c A e r e a a r i u i t o e b t h h v v d t a d r t r t s o , o o l M u - p D s s e s NI s e e c e a m n e I t s a u y m / t p i g r t n 6 o u k a d t w m e e p r e u l y i c g C s l r a t c n k o 6 B r Figure 9.10: The FED builder stage switching fabric (only 1 rail is shown). t s ( e l e t E M t i s h i c / e a n r o h b i a e e o P t t p t n u t i n t r a f n t r k . d , . n c o i i n n - m M f u a a t r p r r e d c d s y r r s y n n r t b n a k o t n d w n r t e o a o e e e g y c 8 b o ; t o c r u u t e 4 o m h f r a e n o n u i p d g s o 2 e c r a w c f c e g c o h 6 t e l c u a l d r e t p M The physical switching fabric is composed of six Clos-256 enclosures per rail (figure t e t e f . r : i e t 5 n b l u m y fi l e v e o e d n s e e u a u a u n s s e o e b i e o l g n n b f p n n w e i s e c wi i b e e e z m Ds n e h h a b B o o s o o r f c h s a o i c a C s t l t r h l n l t o B c a c f E a s a c e y n t d fl m s s e e a o r u c o f 4 e l k i n g e r i F r o e 8 t l r u c i A Clos-256 enclosure is internallyClos-256 composed enclosures of are two located layers in of theare 16× underground in electronics the room surface (USC), DAQ whilerail, building the bundled (SCX). other in They three 12 are cables. connected Thethe by Clos-256 system 768 enclosures has are 200 partly ports m populated to opticalconfigured with accommodate fiber linecards. as a pairs Currently, 72 per total times of 8× 576 FRLs and 576 RU PCs. 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Builder Units Filter Units FED DAQ links FED Builders Readout Units 288

512 72 'Front' view Detector Front-Ends Readout Builder Network 1 1 RU 1 FU BU 16 kByte from 72 data sources and build them into – 270 – ≈ TTC TPD sTTS aTTS 9.11. A RU-builder is made up of a number of Read-

rigger Event

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1.4 Tbit/s, satisfying the CMS DAQ requirements. A maximum peak

EVM BDN BU FU 8 RU ≈ FED>P 2 Tbit/s is possible, if fully exploiting the FRL and Myrinet bandwidth, and using 8x8 FB switches 'Side' view ≈ 1 The Myrinet NIC can transfer 4.0 Gbit/s data rate over the two optical rails. For random traffic In the baseline configuration the number of RUs per RU-builder is 72 and there is a factor of 4 traffic shaping in the FED-builders. The RU-builder stage The RU-builder stage assemblescollect super-fragments event into superfragments of complete average events. size Each RU-builder must re-configurability of the FED-builders inthe software, super-fragment composition which and enables traffic rerouting traffic in balancing case by of redefining a hardware failure. the network efficiency isthroughput approximately of about 60%, 300 MBbyte/s due per node toaverage is head-of-line of achieved for 2 blocking. variable sized kBytes fragments by with Anthe using a nominal event FED-builder two stage rails building [210]. is Hence,throughput the of sustained aggregate throughput through complete events at a ratevarious of components 12.5 is kHz. shownout in A Units figure diagram (RU), Builder of Units oneswitching (BU) network. slice and The of a EVM the supervises single the RU-builder, Eventfrom data indicating Manager flow the in its (EVM) GTP the via connected RU-builder and a together receivessubsequently dedicated by a FED-builder. collects data a record The the EVM super-fragments allocates fromsent events to all on the request RUs. Filter to Units a From (FU). BU, the which BUs the completemore events FU are nodes. The RU, BU andthe EVM PC software nodes. components can In be the distributedbuilt baseline, in by there various the ways are BU on two software layers component ofto in PCs: the as same RUs BU-FU. PC and The that BU-FUs. runs RU Here,and the nodes the 4 filter GByte are events unit of are server (FU) main software, memory PCs referred (Dellfor with PowerEdge the 2950). two input They 2 from host the GHz a FED-builder Myrinet dual-core and NIC a Xeon (M3F2-PCIXE-2) 4-port processors GbE NIC (e5120) (PEG4I-ROHS Quad port copper Gigabit 2008 JINST 3 S08004 240 MByte/s per ≈ 360 MByte/s per RU node by ≈ – 271 – them to worker nodes for further processing; (High Level Trigger, “HLT”); from online event processing in the HLT; calibration and DQM; configuration; the Meyrin site. The RU-builder is based on TCP/IP over Gigabit Ethernet. The design choice of TCP/IP over For the event builder with 2 Ethernet links per RU node, a throughput of The Event Filter complex: • performs basic consistency checks on the event• data; runs offline-quality reconstruction modules and filters to process and select events for storage • generates, collects, and distributes Data Quality Monitoring (DQM) information• resulting serves a subset of the events to local and• remote online routes consumers selected (EventServer, events ES) to for local storage in several online• streams according transfers data to from their local storage trigger at the CMS site to mass storage in the CERN data centre at • collects events accepted by the Level-1 Trigger system from the Event Builder and distributes RU node has been achievedincreased, at if the needed nominal for higher super-fragment trigger size rate of or 16 larger event kBytes sizes, [211]. to This can be Ethernet PCI Express Server AdapterNIC from are Silicom cabled Ltd.). to the Inat network the least switch, baseline, 200 which two MByte/s is links per sufficient of RU torequired node. the throughput satisfy A 4-port is the single 50 throughput ethernet MByte/s. requirement link The for of switches EVB switching each (Terascale network E-1200 BU-FU is router node implemented from is with Force10), sufficient, eight as one E-1200 the per DAQ-slice. Gigabit Ethernet has the advantageevent of builder using over Ethernet standard close hardware to and wirecontrol speed, software. is typically packet When not loss operating occurs propagated an becausereliable from hardware transport flow end-point service that to removes end-point the needwith through for lost the the packets. event switches. building It application to also TCP/IPamount detect provides of provides and host flow deal resources. a control Roughly and 20% congestion ofwhen a control. using 2 jumbo-frames GHz TCP/IP Xeon (MTU=9000 uses CPU Bytes). core a is substantial required to transmit 1 Gbit/s, installing a third Ethernet link per RU node.to 1/4 At a of nominal the throughput RU of 60 throughput,on MByte/s, the the corresponding event BU-FU building event tasks filter consume nodes. roughly 10% of the CPU resources 9.5 The Event Filter The primary goal ofrate the of Event 100 Filter kHz to complexpreserving a interesting is manageable physics to events level and reduce for not the the introducing mass additional nominal experiment storage Level-1 dead-time. and Trigger offline accept processing systems while 2008 JINST 3 S08004 GPN

CDR 9.12. The Event

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DQM BU-FU PC – 272 – Rec. FU-EP FU-RB BU 9.7). As mentioned above, there are three separate appli- Raw Figure 9.12: Architecture and data flow of the Filter Farm. Event Builder Control network (CN) 64 x N BU FU RU The filter farm is logically subdivided into groups of processing nodes (Builder/Filter Unit, cations, the Builder Unit (BU),(EP). the The RB Filter is Unit responsible for “Resourceprocesses, managing Broker” memory and (RB) resources the and for communication input the with andis Event output the handed Processor to/from Event the by Builder HLT the and RB, thereconstruction data upon framework logger. (CMSSW) request, [212] A to to complete thecode steer event forming Event the the Processor HLT selection. execution (EP). of Multiple The EPconcurrent reconstruction processes execution EP and can and process coexist selection thus in uses saturate a the single the processor processing CMS to CPU provide resources. Event processing The EP reconstruction and selection algorithmsby are a configuration configured management at system the based on startThe Oracle of and reconstruction, each working selection, under data-taking and run run, control analysis supervision. modulesobtain specified calibration in constants the and configuration other arestandard instructed time-dependent access to information methods from supported an by Oracle the reconstruction database framework. using Architecture and data flow The architecture of theFilter CMS hardware Event consists Filter of isselection a schematically (Filter large illustrated Farm), farm in and of figure aThe processors data Builder (on Unit logging (BU), the system belonging order connected tocopies to the of of event the a 1000), builder, Filter Storage delivers Unit running complete Event Area events Processors thelogically Network to (FU-EP) HLT separate via (SAN). one switch the of Filter fabric multiple Unit provides Resource thenodes. Broker connectivity (FU-RB). These A from data the logging Filter nodes Unitsbandwidth are to of connected the 1 to data GByte/s a logging and Fibre-Channel has SAN, a that capacity is of capable several of hundred a TBytes. BU-FU). Each peak BU-FU hosts an identical set ofon software the modules XDAQ in online a framework distributed environment (section based 2008 JINST 3 S08004 – 273 – Each data logger node hosting a SM is responsible for direct management of its disk pool in Each reconstruction or selection algorithm runs in a predefined sequence, starting from raw • CMS Technical Network (CMS-TN); • CERN general purpose network (CERN-GPN); data unpacking modules, which deal withdata sub-detector is specific formatted raw-data into formats. C++ Theusing binary objects the raw- associated FED with block sub-detector identifiers.event channels data Reconstruction through structure. a modules A full channel can historyIn map attach addition, of reconstructed bookkeeping the objects information execution is of to maintained the the by by HLT each a is EP attached supervising process, to system and each periodically topath. accepted collected provide event. When full a accounting decision of isinformation events reached, accepted produced accepted and by events, rejected comprising the by rawprocess. HLT, each data are and HLT event handed reconstruction back to the RB forMonitoring transfer to the data logging The operation of unpacking anditored reconstruction using modules the running Physics in and themodules Data Event may Quality Processors be Monitoring is executed mon- infrastructure infeedback (DQM). the about Additional process, the analysis outside quality the ofDQM the normal on data selection the using sequences, individual the FU to same nodes provideproviding infrastructure. is a fast periodically Information DQM forwarded Collector collected to functionality by the (DQMC). the data logging system via the RB, Data logging and Event Server Events accepted for storage by onethem of to the the EP Storage processes Manager arenetwork. (SM) transmitted The process to SM the running is RB, in responsible which thegranularity of forwards data managing of logger the event various data nodes online for via streams transfer,disk the to processing streams data provide and for logging an bookkeeping. physics appropriate The orcesses data calibration carrying logger data, out supports calibration and both or network monitoring streamsby tasks. a for The consumer the network process usage streams connecting are of totion created consumer the with “on pro- EventServer multiple demand” (ES) SMs, function the ES ofServer is each Proxy multiplexed SM. (ESP). across In File the normal and various network opera- sub-farm streams SMs can by deal a transparently caching with Event event datathe or storage DQM data. area network.data This transfer, via includes the correct Central Data interleaving Recordingdistribution of (CDR) to write network remote to transactions sites. the of offline systems the for SM analysis and and 9.6 Networking and Computing Infrastructure Networking Infrastructure The general networking infrastructure of the experiment is based on Ethernet and is separated into: 2008 JINST 3 S08004 11) system at the CERN Meyrin site using a mini- – 274 – The LHC-TN allows data exchange between some of the CMS equipment and the LHC con- Database services are provided by a 6-node Oracle Real Application Cluster. These four networks are interconnected. In addition there are the dedicated DAQ event build- The CMS-TN is a general purpose network connecting all machines directly related to the The CERN-GPN is the CERN-site network. The GPN will be used at all placesThe to CDR connect connects to the Tier0 (chapter • Connection to the Central Data Recording (CDR); • LHC technical network (LHC-TN). 9.7 DAQ software, control andAs monitor stated previously, the CMS DAQ is designedbe in staged a way as such the that LHC its hardware acceleratorthroughput. implementation luminosity can increases Thus as the well CMS asa DAQ the diverse online experiment’s hardware software need base. must for higher The bedata online highly acquisition software scalable encompasses components, and a must the distributedof also processing run the support environment, control DAQ have and adoptedcommon the and the detector standardized central control software online technologies system.maintenance software in and frameworks evolution order of All with to the detector reduce subsystems the read-out the philosophy system effort over of the associated long using with lifetime of the the experiment. mum of 10 Gbit/s. A setone of on 8 the triple-homed CDR servers switches) (one connection are on dedicated the to DAQ, this one task. to CERN-TN, Thesetrols. are the Storage The Manager CMS-TN nodes. mented interconnects in with the backbone the routers. CERN-GPN and the LHC-TN usingComputing a infrastructure filter imple- As previously discussed, theall DAQ system rack mounted comprises PCs. thousands All ofLinux PCs computing OS. are nodes. The Intel x86 PC These based,independently cluster are from running includes the the CERN-GPN. a CERN System distribution global installationaddition of is file around the done server a with Redhat hundred and the PCs Quattor other are toolkit used services [213]. for In to DCS, running be Microsoft able Windows. to operate ing networks (Myrinet and Ethernet) andconnection dedicated to networks any for of equipment those control four. which have no operation of the experiment. Ituration, is control used and for monitoring system of administrationfrom all outside, of online but all can applications. computers be and This reachedhave through for network one dual-homed config- is connection Application not Gateway to accessible (AG) CMS-TN machines, directly and which as one a to distributed CERN-GPN backbone switches. with two Theers routers CMS-TN in located a is in rack implemented are SCX, served and by twobackbone a in routers. switch USC. in The that Typically desktop all rack. computers comput- Each in switch the has control two Gigabit room Ethernet are uplinks also tovisitors connected the (wired to or the wireless), CMS-TN. who will usenetwork the will application typically gateways provide to 1 connect Gbit/s to connections the to CMS-TN. This the GPN backbone. 2008 JINST 3 S08004 9.5). The EVM interfaces to the trigger read-out – 275 – XDAQ Applications are modeled according to a software component model [216] and follow All configuration, control and monitoring can be performed through the SOAP/http [217] The generic event builder application consists of the main XDAQ components: a read-out unit Data transmission in the XDAQ programming environment is carried out by special appli- XDAQ Framework The XDAQ (Cross-Platform DAQ Framework) framework [214] is designeddistributed for data the acquisition development of systems. XDAQthe includes “executive“ a that distributed provides processing applications environmentfiguration called with control the and monitoring. necessary functions Writtenasynchronous entirely for communication in communication, in C++, con- a it platform providesfor independent applications fast with way, and including efficient, predictable the buffer use allocation,anism support of for memory for zero-copy pools an operation and event-driven aprocessing processing dispatching node mech- in scheme. the data acquisition A network. copy of thea executive prescribed process interface. runs They onically are every at compiled run-time and into thecomponents, object a even code of running the is executive same loaded using application and class, the may configured XML coexist dynam- in schema a [221]. singleprotocol, executive widely process. Multiple used application in Webvectors enabled and histograms applications. are exportable A and richservices. can set be Additional inspected utility of by components data clients provide structures, through support the for including executive hardware lists, SOAP and database access. XDAQ Applications and Libraries XDAQ components [219] developed forBuilder CMS (EVB), sub-detector include electronics applications configuration and such monitoring componentsand as (FEC central the and DAQ FED), applications. distributed Event (RU), a builder unit (BU) and andevices event are manager forwarded (EVM). to Data that the areevents read-out recorded unit until by application. custom it read-out A receives RUcollects a buffers the data control event fragments from message belonging subsequent to to single acomplete forward event. single event The a from BU all provides specific an the event interface RUsalgorithms to and fragment and the combines provide event to them data data into processors a persistency a that (section BU. apply event-filtering A BU electronics and so controlsRUs the and BUs. event building For efficient processfollowed. transmission by of The mediating binary event (i.e. builder controlhardware event) is messages and data a is the between also generic I2O used application specification in that local [218] can data is acquisition run systems, on such acation as sub-detector wide components test range beams named of [215]. peer underlying executive transports. as being capable Peer of resolving transportsmunication addresses register between as XDAQ well themselves applications as is with transmitting then and thewhen accomplished receiving by data. XDAQ invoked, using Com- redirects an executive the functionthe that, outgoing data message over to the the associatedprotocol medium. proper or peer-transport network In that and this can way innication be the turn technologies. framework extended delivers is at Baseline independent any peertransmission of time transports using any to have an transport accommodate been asynchronous newly TCP/IP implemented appearing protocol for commu- and efficient for binary simple data message handling using the 2008 JINST 3 S08004

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n d l d e s t a A o p C a D A Libraries and device drivers have been developed that provide generic user access to VME and PCI modules andCMS support custom Myrinet. front end devices, Additionalto persistent XDAQ interface monitoring components the message XDAQ include support SOAP environment and support to a for the gateway Detector the application Control System (section HyperDAQ An extension to the XDAQ framework,an HyperDAQ [220], entry exploits point the into http XDAQ protocol executives.used which A creates to combination of discover HyperDAQ and newthe Peer-to-Peer XDAQ technology, data applications content providing providers datadistributed as content, online they cluster become presents available can tocan (figure become the be an explored user by access links navigating point fromHyperDAQ to system one from has application which proved to to the another be assystem entire invaluable the integration in distributed links tests. debugging system become and available. monitoring The the DAQ during full Run Control System The Run Control System configuresand and interfaces controls the to online the applications Detector of Control the Systems. DAQ components It is an interactive system furnishing diagnostic SOAP XML message format, however the frameworkoptimisation is of independent this of layer the is peer transparent transport to used, the so rest of the XDAQ applications. Figure 9.13: Example HyperDAQ page.brings up Clicking monitoring on information the for RU the Read-out application Unit in application. the HyperDAQ page 2008 JINST 3 S08004 9.7). 9.14). – 277 – The FM has available a finite state machine, an interface for remote invocation, and a set of In the following a few key components of Run Control are discussed. The Run Control structure is organized into eleven different sub-systems, with each sub- Run Control applications and services are implemented in Java as components of a common In RCMS the basic unit is the Function Manager (section 9.7). The interfaces are specified For the baseline DAQ system, ten PCs running Linux are sufficient to control the experiment. The services and tools provided by RCMS comprise: • Function Manager Framework; • Resource and Account Management Services; • Configurator; • Log Message Collector. Function Manager A hierarchical control tree, with asub-system, central controller structures on the the top flow and of oneusing or a commands more common and controllers design for paradigm, state each the information. so-called “Function The Manager” (FM). controllers areservices written to start, configure andfrom control a remote DBMS. processes The and FMmodel to has is access been the configuration adopted basic information bythe the element central sub-system in controller for in the the the first control control level tree tree. of (figure FMs which A are standardized directly steered state by machine and status information and providing theto manage, entry running point on for O(1000) control. PCs. There are O(10000) applications system corresponding to a sub-detector orcentral self-contained DAQ component, e.g. or the global Hadronprovides Calorimeter, trigger. a uniform The API to Runstate-machine common Control models tasks for and like process storage Monitoring control and and System access retrieval (RCMS) to of the process framework, online configuration monitoring data, web system. application “RCMS” provided byand the framework. distributed system The Run to Control runadding is additional on designed hardware. multiple as machines, a scalable thus the system canwith be the easily Web Service expanded Description by Language (WSDL)Services using (WS). the Axis Various Web [222] implementation Service ofmented clients Web to including Java, provide LabView access andimplementation to Perl of the the have Java Run been Servlet Control imple- technologyhas Tomcat services. [223], been by the chosen The Apache as publicly Software theOracle Foundation, available and official platform MySQL reference to are supported run by the the Run RCMS framework. Control web-applications.A For special persistency copy of both theaccept XDAQ executive, SOAP the commands job from control, the is runOne always common control running database to on (Oracle) start is each and shared onlineuration configure by node management additional all across to XDAQ online sub-systems executives. processes is and achieved RCMS using installations. global configuration Config- keys (section 2008 JINST 3 S08004 1 8$! 1 42+ &%$ 8$! 1 8$! !, 1 E &%# %# V T ES 8$! T TS OIN YP TR ONEN !, OMP EL&-ANDHA (# EMEN V ECIFIC E ST Y EMC O, ST OL3 EMSP DSETOFINPUTANDSTA EST TR ST ON FAC TIONS $4 ER TA T UN# ON LINESY  IN SUB SY   2 SER'5) TASTANDAR W #%3 O R – 278 – EL&- EL&-S EL&-S OMIMPLEMEN V V V #3# E E E OIMPLEMEN , 7%"" , T , CUST 2%3/52 1 8$! 1 20# 8$! && 1 # 8$! '4 2" 1 8$! 1 1 /0 8$! 4 1 &" $! 8$! Users have to be authenticated to get access to the RCS resources. The resource service manages the configurations based onusers can RCMS be user run accounts. simultaneously in Multiple the same configurations instance by of multiple the RCMSConfigurator web-application. In order to create centralconfigurator DAQ application configurations has for been different developed. data taking The scenarios, configurations the can CMS be DAQ tailored for reading out Resource and Account Management Services The Resource Service (RS) storescesses all information of necessary the to DAQ startpersistent and and in sub-detectors. configure the the DBMS online The both pro- ment data as as is blobs a represented and collection optionally as ofand as configurations, Java one relational where objects or tables. a which more configuration RCS are functioneach is views manager made sub-system. one the implementations or Each experi- for more sub-system control. groups hassource its of definition The own resources of configuration schema a is instance specific runconfiguration of to of is the RS a then in given the the sub-system seta DBMS. is of “configuration The resolved configurations key” re- via of to a allchanges a key to participating given configurations mechanism. global sub-systems. and global key The keys The identifying sub-systems are the versioned register and configuration trackable. of the global run. All Figure 9.14: The RC hierarchy showing thethe full next DAQ layer system. (Level The 1) Top Function ofFunction Manager Function Managers. controls Managers The who sub-detector in Function turnsystem Managers control component are the resources. responsible Level for 2 managing (sub-detector the level) online 2008 JINST 3 S08004 9.2) and safety-related – 279 – 9.15) for combined operation. These sub-detector DCS subsystems handle all The DCS provides both bookkeeping of detector parameters (table Each subsystem has its own instance of a LMC. A central LMC concentrates the messages of The Detector Control Systems of individual sub-detectors are connected to the central DCS functions, including alarm handling and limiting the control of critical components via a software the individual detector electronics suchtronics as the both CAEN commercial high-voltage and power custom suppliesmon made. and for The all other low-voltage sub-detectors elec- system whereas and theAdditional components the cooling such systems gas as are system front-end built are detector individually com- read-out by links each are sub-detector. also monitored by the DCS. specific sub-sets of FEDs with specificfigurations throughput requirements, and using different different sub-sets FED-Builder of con- be the adapted available event to builder different hardware. versionsprocess The of and parametrising configurations parameter tens can settings of of thousandsby applications the factorizing on online the thousands software of structure hosts components. ofresentations is the of largely The DAQ simplified the system DAQ and configurationsdatabase of are which the stored also software in holds settings. the anectivity. CMS The representation Templates DAQ structural of of hardware rep- the software and available parameterssoftware configuration hardware for template components all database. and software The components theirIt are CMS con- automatically stored DAQ calculates configurator in application application a parameters reads such separate formation from as of those the both depending underlying databases. on hardware theconfiguration and connectivity creates files in- the for Java the objects of XDAQstored executive the in processes the Resource Resource Service. are Service generated XML database.to from The generate CMS these configurations DAQ for Java configurator test-bed objects application hardware. can and also be used Log Message Collector The Log Message Collector (LMC) isand a log4c web compliant application applications. to collectC++ The logging applications LMC information from has and log4j receiver log4j modules messagesAppender for used modules log4c with are messages implemented Java used for applications with messages TCP in can socket, XML be TCP stored and socket on in hub filesders binary with and can format. a JMS be File connections. active Appender, concurrently. or Log Log in messages a are DBMS filtered with by a severity DB inthe Appender. the subsystems Appen- appender and modules. forms the entryChainsaw log point message for viewer. the visualization client of messages, e.g. the Apache 9.8 Detector Control System Function The main purpose ofthe the CMS Detector experiment, Control so Systemincludes that all (DCS) high subsystems is involved quality in to the dataelectronics control ensure is on and and the taken monitor off of with correct the the detector the detector, operation and its apparatus. of the active elements, overall the environment. 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2008 JINST 3 S08004

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OMMANDS &3-# The DCS has to communicate with external entities as well, in particular the DAQ run control, and serves as the interfacefeatures between provided the by CMS the experiment DCSmust and function are the continually needed on LHC at a accelerator. 24-hour alland basis Many times, redundant during of and the software the entire as and year. anon-critical To hardware ensure result nodes systems this selected can continuity are be parts UPS implemented recovered ofsoftware in recovery in the system. the DCS critical order areas, of however minutes even thanks to a CMS specific automated access control. Themajor alarm problems handling that would and otherwise automated initiateoperator Detector actions in Safety advance are that System some designed (DSS) action actions, in ismessaging”) and needed. system a warn that The the warns way alarm DCS handling to users includes (fortem an anticipate example parameters. SMS a (mobile These sub-detector “text SMS expert) messages about may abnormalalert require sys- SMS, an and acknowledgment by the replying status to ofso the both received that the alerts the and operators acknowledgment’s in isDCS displayed the also in control collects the room control relevant are room information awarethe from Oracle that DSS. Portal experts Monitoring web are of pages investigating DCS that the allow parameters alarms. users is to possible The analyse via both real time and archived data. Figure 9.15: Outline of theECAL Detector as Control an System example hierarchy. of Shown a are sub-detector all control. global services and 2008 JINST 3 S08004 2 10 / 9 2 / 1 5 15 PCs / PLCs 16 7 5 2 2 3 4 2 / 1 1 1 / 2 CAN (Wiener) CAEN OPC custom: PSX Simatic S7 CANopen-ELMB OPC CAEN OPC, Siemens S7 CAEN OPC, Siemens S7 custom: PSX CAEN OPC ELMB, custom Wiener OPC, CAN, SNMP custom: PSX Wiener and CAEN OPC custom: HV controller, Peripheral crate ctr CAEN OPC custom CAEN OPC CAEN OPC same as LV custom custom custom Simatic S7, PSX Drivers – 281 – 100 k params ≈ 1600 params CAEN OPC ≈ 80 k params ≈ 1 k params 200 params ≈ 12 k params ≈ ≈ 600 params 2600 params 4500 params ≈ ≈ ≈ 2 k sensors Temperature: 200 sensors LV: 200 channels 10 k LEDs, 150 lasers ≈ rack control: 10 k params LHC interface: 1 k params cooling and ventilation DSS Front end: 21 k params LV: HV: Cooling: FE monitoring: ESS: PTM/HM: HV: 4 k channels LV: 4 k channels + 365 ctrlTemperature: ch, 1100 160 sensors k paramsDCUs: 18 custom: k channels, PSX HV: 192 channels, 384 params LV: 192 channels, 384 params HV: 11 k channels, 218 kLV: 8 params k params Peripheral crate controller: 24 k paramsHV: 15 k channels - 110LV: 1100 k channels params - 10 k parameterstrigger: CANopen-ELMB OPC HV: 1200 channels LV: 1400 channels sensors: CAEN OPC 500 channels Front end: 50 k params HV: 450 channels, 3500 params LV: 270 channels, HSS: 220 params Monitored Parameters Table: 9.2 Summary of detector parameters that are specific to each sub-detector. Central DCS Services Pixel tracker Alignment ECAL Strip tracker HCAL muon DTs muon RPCs Sub-detector muon CSCs Implementation The DCS software is based onJoint the Controls Siemens commercial Project SCADA (JCOP) packagePVSS-II PVSS-II via framework various and supported [224]. the drivers OPC CERN (OLE forS7, Industrial Process Automation) SNMP, controls [225] or protocol, hardware Siemens Modbus. isacross The all interfaced LHC JCOP by experiments. framework provides Thisitor framework common the includes solutions most PVSS-II to commonly componentsadditional similar used to hardware control problems commercial and devices hardware mon- designed (CAEN and at Wiener) CERN as like well the as widely control used for ELMB (Embedded Local 2008 JINST 3 S08004 9.15). 9.7) using the PVSS native interface – 282 – The DCS is a distributed system and comprises all control applicationsPVSS-II dedicated includes to a sub- proprietary database that is used to store in real time the values of all During normal physics data taking the DCS will act as a slave to run control and will there- The control application behaviour of all sub-detectors and support services are modeled as The different control systemswhose of top the node experiment is have referredensure been a to integrated homogeneous as and into the coherent a use CMS of single DCS the control DCS Supervisor. tree, ]. [226 CMSsystems, has communicating put via policies the PVSS into proprietary100 place PCs network to with protocol. the In majority total of there them will running be Microsoft around Windows, although Linuxthe is parameters also supported. defining theThe current configuration state of of PVSS-II the itselfof system is data, (e.g. also an high-voltage stored external settings, Oracle invalues alarms, of database this parameters etc.). is database. from used PVSS For to toconditions Oracle static store tables. database, and configuration Selected which large data, data contains amounts from and DCSthe all to is the offline archive exported measured to data reconstruction. the describing CMS management the The tools detector DCS which environment has access web needed control support for for system account uses management. the LDAPfore and have to Oracle receive identity commandsbetween and DCS send and back external entities status isThe information. provided PSX by is A a the communication SOAP CMS mechanism server specificand implemented PVSS JCOP with SOAP framework, XDAQ interface (section and (PSX). allows access to the entire PVSS-II system via SOAP. Monitoring Board). It also providesby a JCOP, Data PVSS-II Interchange offers Protocol the (DIP). possibilityhas For developed hardware of sub-detector not implementing specific covered new software. drivers and components, and CMS Finite State Machine (FSM) nodes,detector using controls the are FSM organized toolkit in provided a byof tree-like FSM the the node detector, JCOP where hierarchy framework. commands representing The the flow down logical and structure states and alarms are propagated up (figure 2008 JINST 3 S08004 9000 2200 2300 1000 1250 1250 4000 1500 Power (kW) – 283 – gives an overview of the power requirements for CMS. includes very different systems, ranging from basic site facilities 10.1 Table 10.1: Power requirements for CMS. Low voltage to front-end electronics Magnet and cryogenics Ventilation stations Surface cooling stations Underground cooling stations Total steady-state consumption System General site services Electronics racks infrastructures With the exception of the cooling stations, the racks system is the most important client in to more detector-specific and safety-related services.described. In this section, the main general systems are 10.1 Detector powering CMS, like any other modernfront-end particle electronics physics detector, (FEE), needs for considerableand electronics electrical finally racks for power auxiliary for in services its counting (cranes, ventilationetc.). rooms and cooling and Different stations, in lifts power and site sources accessvaluable control facilities, equipment are centres, that available must on stay site.for on in a Uninterruptible case short of Power period, power Systemsstandard disruption, before (UPS), network secure being power. for power backed-up Table for by specific a users diesel engine. Common users are connected to The common term Detector infrastructures and safety systems Chapter 10

2008 JINST 3 S08004

t e n r e h t E C C US UX S DC S describes the logic behind the DS 10.1 RSS Premium PLC CAN bus – 284 – fire extinguisher (option) ST/MA AFDCIE from monitoring board h/w RSS loop s TS/EL Power distribution TS/EL Bu Twido PLC

Figure 10.1: Control loops for rack powering.

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g n i r o t i n o m e t a r c + h c t i w s l a m r e h t terms of power. Rowspiloted of by racks a are dedicated fed PLC, bypower and the power a whole bus-bars. control system cable Each run beinginets single from located this provide rack in box single-phase, has to a three-phase the a box or power mainPLC attached distributor three-phase breaker cabinet is to + inside controlled the neutral each by rack. bus-bar. current the Cab- distribution.can Detector A be Control The switched System breaker on-off upon (DCS) DCS viaMoreover, request a a and hardwired network the connection connection. status to of the Single eachof Detector racks breaker smoke Safety is or System known a (DSS) by high secures DCS temperature the as is system well. detected in inside case a rack. Figure power controls. 2008 JINST 3 S08004 shows 10.2 25°C for the Preshower, Pixel and 50 60 − 100 300 150 1600 Power (kW) 15°C to − – 285 – Muon Barrel HCAL and Yoke Barrel ECAL Rack system Tracker, Pixel, Preshower System Muon Endcaps Table: 10.2 Cooling power for different sub-systems. fluid at temperature ranging from 14 F 6 Chilled water at 14°C is produced at the surface in the SU5 building and then transferred 10.2 Detector cooling 10.2.1 Front-end electronics cooling The CMS front-end electronicsamount dissipates of some heat 800 is kW interceptedand by in cooling by the water C experimental at cavern. 18°C for This the ECAL, huge HCAL and Muon systems, Tracker systems. In addition, some 1600 kW are dissipated by the rack system. Table the power dissipated by each system. to the USC55 coolingexchangers, plant, pumps where and five controls, independent produce waterThe and circuits, Tracker, distribute Pixel, each water and at one Preshower 18°Cthey with systems have its to have their own the on heat- own experiment theirmonitored cooling cavern. primary by cabinets side the in chilled central DCS water UXC55 viacrucial at to ethernet parameters 6°C, shorten connection such and to the as TS/CV transfer flow controlof rate, lines. units. need. temperature, The and Loss Cooling DSS dew of monitors status point,cooling coolant is loop. in is order detected to by take measuring actions the in fluid case level in the10.2.2 expansion tanks of every Cryogenics The cryogenic plant at the CMS siteCMS has superconducting the function coil. to cool The down refrigeratorK, and keep plus system at 4500 can 4.7 W deliver K at the a 60 230used cooling t K to of power to the cool of cool the 800 the 20 coil’s Wweeks, thermal kA at screens, with 4.7 coil in a current addition maximum leads. to thermal thetemperature Cooling gradient 4 rises the inside to g/s 70 of coil the K liquid down cold and helium fromliquid mass 3 helium room of days storage temperature are 30 tank necessary takes K. sits to 3 close Inwithout bring to case warming the the up cold of coil the mass a cryostat coil. down to quench, to allow the 4.7 a K. slow A discharge 6000 from l full current 2008 JINST 3 S08004 – 286 – 10.2). Figure 10.2: YB+2 and YE+1 cable-chains in UXC55 basement trenches. Cables are labeled and stored in a database with web interface, that allows identification of • HV cables; • LV cables for DC power to FEE; • FEE read-out cables; • optical fibres read-out; • monitoring and control (DCS) cables; • general pourpose power cables (230-400 V AC); • safety system cables (DSS) for hard-wired signals and interlocks. 10.3 Detector cabling Due to the specific CMS design, withfor one each central element side (YB0) moving that on is the fixedoptical cavern and fibres floor 6 have mobile during to elements shut-down run periods, through power hugedisconnecting cables, cable-chains everything coolant, in (figure gas order and to open and close the detector without each cable by sub-system, type, length,can starting be point, summarised endpoint as and follows: routing. The main cable types The cable-trays include also thedata-base. gas-sniffer soft-pipes. Some 30 000 cables are referenced in the 2008 JINST 3 S08004 10.4). 10.3) have rubber sealing rings that – 287 – Normal operation of the experiments proceeds with the DCS which monitors and controls For emergency situations though, the LHC experiments are equipped with the CERN Safety any deviation from normal operationensuring or a the safe occurrence operation of of theto anomalies. experiment. a In The very DCS this detailed is respect, level designed andmakes the such the in DCS as system a is to quite highly monitor complex granular and and way, thus react a vulnerable. up necessary feature which onSystem. the other The hand CSSoxygen is deficiency, etc. designed that could to endanger reliably theto human detect the life, CERN and the fire will brigade. transmit main a The hazards, correspondingof CSS, alarm however, the does like equipment. not smoke, foresee immediate flammable actions for gas, the protection prevent air losses. The system cansealing be used increases with somewhat compressed the air bottles frictiondown only. to factor, At around the which same 0.4% lies time, once around this with moving practically 0.8% has no before begun. friction. moving The and grease goes pad system produces a10.4.2 final approach Pulling system The pulling system consists of awhich hydraulic the strand jack two system in and the includesslope center 6 of jacks are the with pivotable) strands cavern and (of (1.234%) acapable and strand of the safely storage friction pulling mandrel. of uphill TakingWhereas 2.5% the into going of airpads account uphill the and is the maximum cable a load, chain, purea which pulling, the is smooth, going system 2600 downhill constant t must needs (3 movement be a endcapscontrol of retaining unit. together). force the in load. order to This produce was integrated into the design10.5 of the hydraulic The Detector Safety System The Detector Safety Systemexperiments (DSS) together is with a the commondetector CERN development and IT carried the department. out experimentalDetector The equipment by Control purpose from the System (DCS) of hazards. 4 and the the large The CERN DSS LHC Safety DSS is System works to (CSS) (figure complementary protect to the the 10.4 Detector moving system The CMS moving systemrobustness, has preciseness, been easyness designed inbeen according handling determined to on and the the compactness. one following handhand by criteria: The by the the boundary weight friction, affordability, and conditions the dimensions slope have of and the the assemblies size and of on the the cavern. other 10.4.1 Sliding system In order to limit frictionair and thus pad the system power for offinal the the approach pulling long (up system, to CMS movements has 10 (10movement chosen cm). perpendicular cm a to In heavy to the duty addition, 10 beam. these m) systems and The allow, without air a any pads flat additional (figure grease structure, pad system for the 2008 JINST 3 S08004 – 288 – Figure 10.3: A transport beam for barrel rings with 4 air pads fixed on it. Equipment protection is the purpose of the DSS which triggers automatic actions in order to • high reliability and availability to make the system simple and robust; avoid or to reduce eventualpotentially damage dangerous to situations. the The experimental DSS equipmentthe is when DSS designed it actions to detects have be to abnormal simple becase and and fast that reliable and smoke and quite is consequently coarse, detected. e.g.,(e.g., In cutting smoke order the detection) to power and do to triggers so, actions theDSS on the entire actions the DSS cavern thus main in partially will infrastructure, the recuperates in as signals general cuttingexperimental from disrupt the equipment, the the 18 will data CSS kV increase taking, supply. the but in overall data the long taking run, efficiency of by avoiding the damage experiment. 10.5.1 to DSS Requirements In order to fulfill its purpose, the DSS has the following characteristics: 2008 JINST 3 S08004 – 289 – ments; The front-end is a redundant array of two Siemens S7-400 H PLCs. These PLCs interpret • operational independence of all other systems, running• in stand autonomy alone from system outside mode; services, especially power supply• and computer input network; from its own sensors and actuators• (nevertheless some are capability owned of by immediate the and CSS); automatic actions; • flexibility to be adopted and configured in order to adapt to the evolving• needs of the full experi- integration into the DCS. 10.5.2 DSS Architecture The DSS consists of two main pillars: the front-end and thethe back-end. signals coming from the connectedActuators, sensors attached according to to a the programmablechannels, output alarm-action processing of matrix. the the alarm-action PLCs matrixSuch trigger and a actions. modifying cycle the will The take stateresponse about PLCs of time 500 the are below ms, outputs scanning one allowing accordingly. all the second.digital DSS input inputs, Different to analogue type react inputs of to (4–20 sensors mA) anyate and can hazardous completely PT100 be situation independent temperature connected with from probes. to a the The back-end thealso front-end and connected can DSS to is oper- that an thus are uninterruptible the power safety supply relevant which part gives the of DSS the autonomy DSS. of It several is hours. Figure 10.4: Context diagram of the DSSSystem system, (CSS), showing its the rôle Detector with Control respect System totion the (DCS) network CERN and is Safety other provided by technical the services. Data The Interchange interconnec- Protocol (DIP). 2008 JINST 3 S08004 – 290 – rack extinguishing system, as well as the water mist system. 2 In addition to the protection of the racks, the DSS also directly safeguards the sub-detectors The back-end of the DSS consists of a standard PC running the PVSS software. It serves as interface between the frontand end and data the analysis, operator. e.g. The thecriteria, back-end possibility trending provides to tools tools and retrieve for the and post possibilityalarm display mortem to priority. data filter However, based it alarms is on according not to user-definedperformed necessary criteria selection as for such automated the as actions user time, in to origin, the initiate DSS any DSS front-end. actions, as these are10.5.3 all CMS Implementation of DSS Due to the rather largetwo number completely of separate input entities. channelsin One for the entity the USC collects CMS cavern input experiment, andeach channels the the equipped from DSS surface the with is buildings equipment split a andwired housed into one set input entity and of output. for redundant the Thehoused PLCs, UXC USC/surface in system cavern. are a consists stand rack, Both of alone 6 where systems, digital Detector the and input Safety UXC channels, communicate Units system (DSU) 64 only consists each The analogue via bulk of or amount hard 10 of PT100 DSU’s. signals input originateslow A form channels the voltage typical and 230 system. DSU V a rack is The few power madedetection distribution about digital alarm of system 200 output and and 224 from racks channels. an the in alarmthe the from UXC cavern the USC will power give cavern as distribution produce additional boxbox signals each the (TWIDO). and an status a The of individual signal the about electrical smoke in 200 breaker caseduring racks inside the of the in LHC TWIDO an operation. electrical Concerning fault the sinceabout low the voltage 180 supply racks status- for and in the electrical-fault the UXC bits, UXC racks,rack and the cavern individually. it DSS are is receives not able accessible to cut the low voltage power supply tovia each a number of sensors.the vicinity These are of temperature them, sensors flowvacuum placed tank meters of directly measuring the on their solenoid, the cooling etc.of sub-detector circuit, Since the or the water DSS, in functioning leak every of sub-detector detectors theactions shall DCS inside in send is the case a mandatory the for status the DCS bitaction operation of to is a DSS, to sub-detector such cut or that the the DSSexample, power central can triggering to DCS take the part is appropriate CO of not the functioning. detector The equipment, typical but DSS other actions can be10.6 taken as, for Beam and Radiation Monitoring10.6.1 systems Introduction The Beam and Radiation Monitoringtection systems (BRM) function [227] for perform CMS. both Toof a this which monitoring end, can and multiple be a and used pro- redundant tocan systems initiate be LHC have used beam been aborts for installed, and/or fast some CMSof beam/detector equipment the optimisations. control, received radiation others All dose of in systems which various will regions provide of long the term CMS detector. monitoring 2008 JINST 3 S08004 and z , positioned on either 230] where they have 3 intervals at large radius ◦ 0.4 mm × 10 , on either side of the IP behind the 3 10.5. × s time scales. The BCM1L diamonds are µ 0.4 mm × 10 – 291 – × 14.4 m. On each side of the IP, a set of eight sensors ± per beam. Even very small fractional losses of this beam risk 14 1.8 m, close to the beam pipe and the inner-tracker pixel detectors ± position of z axes. The BCM2L comprise eight diamonds at 45 y values of and z x s. Additionally, the BRM systems provide monitoring and tuning data to permit op- µ 3) at a radius of 4.5 cm. The second protection system is the BCM2L. This is a set of While radiation damage can lead to long term effects, the most likely damage scenarios in- In designing the BRM, CMS imposed several design constraints; namely to implement sys- The CMS experiment sits in an unprecedentedly high radiation field for a HEP experiment and In CMS there are two protection systems foreseen for initial LHC operation. The first is the much effort has gone into the designNevertheless, and construction the of systems LHC with very is highproton radiation designed tolerance. intensities to in run excess of withcausing 10 362 serious MJ damage to of detector stored elements.designed for energy Whilst machine the in protection, LHC CMS one requirements itself dictate beam hasrelated that extensive problems and CMS instrumentation as must with be they able develop to andable detect to beam- to assert log beam aborts data ifaccumulated and required. dosage perform and In post-mortem potential addition, longer analyses CMShas term must in implemented damage be the the to BRM the case systems. detector of elements. accidents To and this end understand CMS the volve very fast burstssystems of must radiation/energy-dissipation be in sensitive detector tochanges elements. very at fast the changes Thus 25 in ns theorder beam level, protection 3–40 conditions; though the the initially BRM deployed systemserator protection intervention can to systems detect diagnose will and react improveused beam in conditions. to times monitor In of integrated addition, dose all and BRM detector systems can component be aging over the yearstems of which LHC can operation. stay aliveof at CMS any operations; that time have when readout beamLHC and machine may post-mortem protection capabilities be systems; extremely in close and the to thatrange those LHC offer for of a independently protection the high of and degree the of monitoringtem, state redundancy scenarios. and summarised a Given in wide these table dynamic constraints,10.3,sub-system the locations has BRM in been protection CMS are implemented. sys- also represented The in BRM figure system, its nomenclature and 10.6.2 Protection systems The protection systems are basedto on chemical those vapour that deposition have diamondproven been detectors to [228] widely be similar used radiation in hardto recent [231], be fast collider inserted enough experiments into to areas [229, services. match close beam to abort key scenarios, detector and components small without enough adding substantial materialBCM1L or made of four polycrystallineside diamonds, of the each IP 10 at (chapter twelve polycrystalline diamonds, eachTOTEM 10 T2 detector at a are deployed at an outerBCM radius refers of to 29 cm Beam and Conditions an Monitor, additional the four index at an 1 inner or radius 2 of refers 5 to cm. the Here two locations in arranged on the L indicates that these detectorsmonitors, typically are integrating used the in leakage current a over leakage current measurement mode as relative flux 2008 JINST 3 S08004 233] that is read out asynchronously with respect to – 292 – s sampling. The BCM1L readout uses the same LHC BLM back-end s LHC orbit, allowing user-configurable sampling, so that the sampling µ µ Figure 10.5: Layout of CMS BRM sub-systems. axes at small radius. The BCM1L and inner BCM2L diamonds measure a rate y , x The diamonds used for BCM1L and BCM2L are essentially identical, but the two systems In the event of a beam abort initiated by CMS, or by any of the other LHC (or experiment) Using a set of thresholds in the readout systems and a combinatorial logic to reduce sensitivity which is dominated by pp interactionsbeam-spot and at are the expected IP. The to be outer largely BCM2L sensitive diamonds to are beam-halo hidden rates. fromdiffer the in the readout(BLM) methods electronics adopted. and data The processingthe BCM2L [232, LHC uses machine a with 40 standard LHC Beam Loss Monitor to individual noise events, aLHC hardware machine beam via abort the Beam signal Interlock canorbits. System be [234], A generated leading lower to threshold and the value transmitted dumpingto can to of initiate be the the high used beams and/or to within low send voltage 3 hardware ramp-downs. signals to CMS sub-detectorprotection clients systems, a full historyto of the the LHC BCM1L control and room. BCM2L signals is produced and transmitted electronics, but uses an additionalsynchronized mezzanine with the card 89- to providecan sub-orbit sampling. be matched The to readout theabort is gap, LHC which bunch must trains. be keptbeam In empty dump. to addition avoid the a BCM1L spray of allows particles sampling being of directed the at CMS LHC during a and four on the 2008 JINST 3 S08004 8 8 8 2 18 24 32 Many Number of Sensors , positioned on 3 N/A 0.5 mm Standard LHC Standard LHC Standard LHC CMS Standalone CMS Standalone CMS Standalone CMS Standalone 5× LHC or CMS type Readout + Interface Function Protection Protection Monitoring Monitoring Monitoring Monitoring Monitoring Monitoring s s µ ns ns ns µ 1 s ∼ ∼ ∼ 5 months 40 200 ps ∼ 10.3: the BCM1F and BCM2F are also based upon – 293 – Sampling Time 1.8 m at a radius of 4.5 cm, in close proximity to the BCM1L 1.8 m 1.8 m ± 175 m 10.9 m 14.4 m 14.4 m Location z=± z=± z=± z=± z=± z=± Front of HF Pixel Volume Pixel Volume CMS and UXC CMS and UXC Upstream of IP5 Behind TOTEM T2 Behind TOTEM T2 Distance from IP (m) values of z BSC BPTX BCM2F BCM1F BCM2L BCM1L Passives RADMON sub-system (Sensor type) (TLD+Alanine) (Scintillator Tiles) (RadFets+SRAM) The BCM1F, BSC and BPTX are sensitive to time structure below the 25-ns level; as such The BCM1F consists of four single crystal diamonds, each 5× (Button Beam Pickup) (Single Crystal Diamond) (Polycrystalline Diamond) (Polycrystalline Diamond) (Polycrystalline Diamond) diamond sensors, but with readoutsCounters able (BSC) to are resolve a the series sub-bunchButton structure, of Beam the scintillator Pickup Beam (BPTX) tiles is Scintillator designed designed to totiming provide provide of precise hit information the and on beam, the coincidence bunch and rates,radiation structure field the and the within RADMON the and CMS Passives cavern. systems give calibrated informationthey on also the provide technical trigger inputs intothe the BPTX global and CMS BSC trigger. provide In zero- particular,of the and these inputs systems minimum-bias from are triggers, sensitive respectively. to Additionally, alla all foreseen single three beam intensities low including intensity the bunch LHCintensity pilot injection. is beam, injected where for studies or to confirm parameter settings prior to full 10.6.3 Monitoring systems Several monitoring systems are listed in table detectors. The BCM1F is used as“bursts” a of diagnostic beam tool to loss flag over problematic verythe beam short principle conditions periods damage resulting of scenarios in time. for the Suchto CMS beam the detector losses optimal systems. are position The expected in location to terms ofthe be of the IP one (i.e. BCM1F timing of 6.25 is separation ns close between from ingoinga the and very IP). outgoing good The handle particles gated on rate from the informationproducts. comparative from rate the of BCM1F The background should from therefore sensor give beam is halo to connected that from to lumonisity the JK16 radiation hard amplifier [235], after which the either side of the IP at Table: 10.3 The sub-systems to betop deployed to as bottom in part increasing of time the resolution. initial BRM. The table is ordered from 2008 JINST 3 S08004 10.6. Good separation can – 294 – 10.7. The BSC1 is located on the front of the HF, , with an inner radius of 22 cm and an outer radius of φ 80 cm, which in addition to providing rate information, will also provide ≈ 55 cm and ≈ The detector is sensitive to one MIP and has a timing resolution for single hits of a few In a similar vein to the BCM1F, the BCM2F is composed of four diamonds at the BCM2L The Beam Scintillator Counters (BSC) are a series of scintillator tiles designed to provide 10.9 m from the IP, and consists of two types of tiles. Next to the beampipe are the disks, ± signal is transmitted to the countingcomponents room [236]. over an analog optical link built from the tracker optical ns. The performance of the front end electronics is shown in figure Figure: 10.6 MIPfunction response of of bias voltage BCM1F of single-crystaltude the diamond indicates sensor. the with The noise. front-end superposition of electronics, histograms as around a 0-V output ampli- be seen between the signalvoltage across and the the sensor. The noise. back-end readoutinformation The produces independently rate, pulse of multiplicity, timing height the and CMS was coincidence DAQ.into found However, there the to is event saturate stream the via possibility at a to 100 standard feed V CMS information SLINK. bias location, read out byinformation a at fast this digitiser. location, as Thebunch the aim level [237]. digitiser of Whilst can this this sample will system atperiods not is of 1 be enhanced to GHz, MIP-sensitive, background. it giving provide will information additional help on resolve diagnostic the the timing sub- structure of hit and coincidence rates, withscintillators a and design PMTs similar used to for the thoseof BSC used the are at recycled scintillator previous from experiments tiles OPAL [239]. [238]. are The The layout shown and in geometry figure segmented into 8 independent slices in at 45 cm. The primarybeam function conditions. of In the addition, disks there is arebetween to four large provide area the “paddles” rate further information out, corresponding at a to radial the distance of coincidence information which cancalibration be purposes. used The to area covered tag by thecan halo BSC be muons is indicative about passing 25% of through of activity the the tracker; within therefore detector, this these for tiles bunch crossing, and can be used to provide a minimum- 2008 JINST 3 S08004 z – 295 – In parallel to the oscilloscope based read-out, the signals from the BPTX will also be discrim- At 18 locations around the CMS cavern, RADMON] [241 detectors are installed. The RAD- An oscilloscope-based read-out was chosen for the BPTX and developed in common with The Beam Timing for the experiments (BPTX) is a beam pickup device specifically installed 14.4 m from the IP. The BSC2 consists of two tiles on each side of the IP, with a minimum ± position to be calculated from thethe relative IP. phases The of BPTX the can BPTX alsoof measurements beam detect on which problems opposite has with sides drifted of the into bunch the structure, neighbouring RF and bucket. measure theinated proportion and sent as three technicalflags trigger on inputs each to bunch the crossing CMSis as global occupied; to trigger. c) whether: This both will beams a) providewhether are bunch three occupied. collisions in can beam The occur 1 flag in where iscommissioning this both occupied; of bunch beams b) the crossing, are bunch trigger and occupied system. in therefore is beam provides indicative 2 of a zero-bias trigger for MON detectors each provide well calibrated measurements of: a) the dose and dose rate using to provide the experimentsstandard with button the monitor timing used structureTwo everywhere of are around the installed the for LHC LHC CMS: beam. 175 ringbeampipes, m and for This left therefore the and beam the beam right timing pickup upstreamtiming position measurement is of measurement, is monitors. a the only the IP. of four At the this buttonsconnected incoming location (left, together. beam. there right, This are To up, two is optimise down) done the timing, of to at the the maximise pickup price the of have signal loosing been strength the electrically and position information. hence the resolutionATLAS on [240]. the Thebunch BPTX and will its intensity. provide The phases accurate ofphase information all of the each on experimental bunch clocks with the can a be precision timing compared better and to than the 200 phase measured ps. of This will each also allow the interaction-point inner radius of 5 cmto and distinguish a between maximum ingoing outer and radius outgoingdifference of particles between 29 along them. cm. the beamline, The The as rates primary thereincoming at function is (beam this of a halo location the 4-ns only) can BSC2 timing or therefore is outgoing be (collision tagged products as and beam to halo). whether they are Figure 10.7: Layout of thefor Beam BSC1, Scintillator the Counters right-hand tiles. panel The forthe left-hand panel right-hand BSC2. shows panel. The the locations layout of the BCM2 sensors can also bebias seen in trigger for commissioning andat systematic studies. The BSC2 is located behind TOTEM T2 2008 JINST 3 S08004 – 296 – The integrated radiation dose throughout the CMS cavern will be measured during each run RadFETs; b) the hadronSRAM; flux c) with the energies 1-MeV-equivalent above neutronstalled 20 fluence MeV all using and around pin the the diodes. single LHCCMS event ring, will RADMON upset be and detectors integrated rate in into are using the and in- read experimental out insertions. via the The accelerator-wide RADMON RADMONperiod system. detectors with at passive dosimetry.will This be allows used to to validate map the theother simulations measurements. radiation of the The field anticipated dosimeters throughout doses. chosen the are This gives cavern TLDs an and and absolute Alanine. scale to the 2008 JINST 3 S08004 man- large scale, supporting efficient approaches – 297 – highly, flexible allowing any user access to any data item ,ageability both in the operation of computing resources for physics, and in terms of software with the fine granularityscientific of computing. the This CMS requires detector, a impliesto system data a of reduction volume and of pattern recognition. data unprecedented in recorded or calculated during thequired which lifetime supports of a the wide variety experiment.must of data A evolve processing software along tasks in framework with a ison the consistent re- discovery way, goals and of which new of phenomena, the undercannot new experiment. be experimental wholly conditions, defined Since analysis in requirements the advance. CMS programme centres The nature of the CMS experimental programme poses several challenges for the offline The users of the system, and the physical computer centres it comprises, are distributed world- • The requirement to analyse very large statistics datasets in pursuit of rare signals, coupled • The system is required to be • A complex distributed system of such large scale must be designed from the outset for wide, interconnected by high-speed international networks.iments, the Unlike majority previous of generations data of storage exper- laboratory. and A processing fully resources distributed available to computing CMS modelsystem lie has is outside based therefore the upon been host Grid designed middleware, from withaged the the through common the outset. Grid Worldwide LHC services The Computing at Grid centres (WLCG)LHC defined project and experiments, [242], man- computing a centres, collaboration and between middleware providers. computing system: 11.1 Overview The CMS offline computingrecorded system data for must the support lifetime of the thefrom storage, experiment. the The transfer data system accepts and acquisition real-time manipulation systemperforms detector information at of pattern the the recognition, experimental event site;activities filtering, of ensures the safe and collaboration. curation data The ofdata, reduction; system and the access also supports raw to supports data; the conditions production and physics and calibration distribution information analysis of and other simulated non-event data. Computing Chapter 11 2008 JINST 3 S08004 for both disk storage ,analysers producing Event. The Event provides access to event data, producers which add new of the system, of 15 years or more, implies input and output modules – 298 – longevity physics modules, which may read data from it, or add new used in online triggering and selection; filters construction and maintenance. The several generations of underlying hardwareduring and the software, lifetime of and the many system. changes of personnel, of events; At each level, the design challenges have been addressed through construction of a modular The central concept of the CMS data model is the The Event is used by a variety of • An event data model and corresponding application• framework; Distributed database systems allowing access to non-event data; • A set of computing services, providing tools to transfer, locate, and process large collections • Underlying generic Grid services giving access to• distributed computing Computer resources; centres, managing and providing access to storage and CPU at a local level. summary information from an event collection; and and DAQ. Key components of the computing system include: system of loosely coupled componentsbility with to well-defined very interfaces, large event and samples with [243]. emphasis on scala- 11.2 Application framework The CMS application software musttasks, perform and a is variety used in of both event offline and processing,it online can selection contexts. be and developed The and analysis software maintained must be bychosen sufficiently a architecture modular large consists that group of of a geographically common dispersed framework which collaborators.environment, is physics The adaptable for modules each which type of plug computing service into and the framework utility via toolkit ainterface, which well-defined and decouples other interface, environmental and the constraints a [212]. physics modules from details of event I/O, user the recorded data from amay single include triggered raw digitised bunch data, crossing,simulated reconstructed and crossings. products, The to Event or new also high-level data contains analysisthe information derived provenance describing objects, from of the for origin all it. of real derived the data or This rawto products. data, unambiguously The and identify inclusion how each of event provenance contributing informationa to allows record a users final of analysis the was software produced; configuration itdata and includes product. conditions Events / are calibration physically setup stored used as to persistent produce ROOT files each [244]. new data, with provenance information automaticallyfunction included. relating Each to module the performs selection,exist, a well-defined reconstruction each or with analysis a ofdata specialised the products interface. Event. into the Several event; These module include: types 2008 JINST 3 S08004 primary datasets, Output 3 Output Output 1 Output 2 Output ParameterSet N N Module B Module Module A Module Config file Config Schedule – 299 – Database(s) Module B1 Module Module A1 Module EventSetup Figure 11.1: Modules within the CMS Application Framework. Event InputSource The RAW data will be classified by the online system into several distinct Modules are insulated from the computing environment, execute independently from one an- other, and communicate only thoughindependently. the A Event; complete this CMS allows application is modulesmore constructed to ordered by be sequences specifying developed to of and the modules verified Framework throughration one which for or each each. Event must The flow,access Framework along to configures with global the the services modules, configu- and schedules utilities (figure their11.1). execution, and provides 11.3 Data formats and processing In order to achieve the requireduse level of of several data event reduction, formats whilstformats maintaining with flexibility, are differing CMS levels makes used of for detailseveral heavy-ion and steps, data. precision. typically carried Other out The specialised at process different event computer of centres. data reduction andRAW format analysis takes place in RAW events contain the fulldecision recorded and information other from metadata. the RAW detector,(nominally data plus is 300 accepted a Hz into record for the of ppoutput offline the collisions). system of trigger at An CMS the extension HLT Monte output ofstorage, Carlo rate the and simulation RAW is data tools. designed format toadditional is The Monte occupy used Carlo around RAW to truth 1.5 data information). store MB/event is the (2 permanently MB/event archived for in simulated data, safe due to based upon the triggeradvantages, signature. including the possibility Event of classificationthe assigning case at priorities of backlog, for the and data balancing earliest reconstruction of dataone and possible placement or transfer at stage more centres in outside flexible has CERN. “express CMS several will streams”or also used anomalous define events. for prompt calibration and rapid access to interesting 2008 JINST 3 S08004 is required in order non-event data – 300 – physics objects, plus a full record of the reconstructed hits Conditions data are produced and required by both online and offline applications, and have Reconstruction is the most CPU-intensive activity in the CMS data processing chain. The re- to interpret and reconstruct events.data, CMS generated makes during use of the four constructiontion types data, of of comprising the non-event programmable data: detector; parameters related equipment construction including to management calibrations, detector data; operation; alignments and configura- and conditionslattermost data, detector category. status information. We concentrate here ona the well-defined interval of validitybe (IOV). derived For from instance, prompt calibration reconstructionHLT constants system of and for a for a subset subsequent reconstruction given of and run recordedNon-event analysis data at may events, computing are and centres held then around in the used world. applications. a both New number by conditions of data, the central including Oracle calibrationmay and databases, be alignment for replicated constants access between produced by offline, the online databasesplace via and as the offline required. FroNTier system Conditions [245] which data uses access a at distributed network remote of sites caching http takes proxy servers. RECO format Reconstructed (RECO) data is produced by applyingpression several algorithms levels of to pattern recognition the andcorrection RAW com- of data. the the digitised These data; algorithmsstruction; cluster- and and include: track-finding; particle primary ID, detector-specific and using secondary filtering a vertex variety and recon- of algorithms operating on cross-detectorsulting information. RECO events contain high-level and clusters used to produce them.tion of Sufficient new information calibrations is or retained algorithmsin to without allow pattern recourse subsequent recognition applica- to or RAW data, eventleast though once formats basic per will improvements year. probably RECO require events are re-production foreseen of to occupy the around RECO 0.5AOD data MB/event. format at AOD (Analysis Object Data) isphysics the analyses whilst compact occupying analysis sufficiently format, smallbe storage designed held so to at that allow many very a centres. largesufficient event wide additional samples AOD range may events information of contain to the100 allow parameters kB/event, kinematic of small high-level enough refitting. physicsto to objects, be allow This held plus a at format complete computing willeither centres copy outside in require of CERN. bulk around the AOD production, data experimental or isseveral data analysis in produced in datasets. by a AOD filtering skimming format of process RECO which data, may also filter aNon-Event data primary dataset into In addition to event data recorded from the detector, a variety of 2008 JINST 3 S08004 2 2 2

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a i c 0 m n t r r E H 0 m 1 a C a P 1 a ( e ~ permanent mass storage; centre must keep pace withinput the buffering to average absorb rate fluctuations of in data data rate; recording, and must provide sufficient “safe” for deletion from Tier-0 buffersof until these it is is CERN held computing at centre, at playing least the two role independent of sites. a Tier-1.) (One O r e ~ C t The CMS computing model depends upon reliable and performant network links between During the LHC low-luminosity phase, the Tier-0 is intended to be available outside data- r ( t s s • Accept data from the online system with guaranteed integrity• and Carry latency, out and prompt reconstruction copy of it the RAW to data to produce first-pass RECO datasets. The • Reliably export a copy of RAW and RECO data to Tier-1 centres. Data is not considered 11.4 Computing centres The scale of the computingat system one is site. such that Thelaborating it system institutes could is around not, built the using even world. in computingcentres, principle, similar resources CMS to be proposes at that hosted to a originally devised use entirely range in0 a of the centre MONARC hierarchical scales, working at architecture group provided CERN, of], [246 by a with Tiered col- few aat single Tier-1 institutes. Tier- centres A at representation national of computing the facilities, dataflow between and centres several is Tier-2 centres shown in figure sites. In the casemented of as an transfers optical between private network Tier-0centres (LHC-OPN) and typically]. [247 takes Tier-1 Data place centres, transfers over these general-purpose between national Tier-1 network and and links Tier-2 international are research networks. imple- Tier-0 centre A single Tier-0 centre is hosted at CERN. Its primary functions are to: taking periods for second-passluminosity reconstruction running will and require other the use scheduledCMS of facility processing the used Tier-0 activities. only for for most well-controlled High- of batch the work; year. it is The not Tier-0 is accessible a for common analysis use. 2008 JINST 3 S08004 – 302 – outside CERN distributed across the centres.sibility for Each a Tier-1 fraction takes of long-term the custodial CMS respon- dataset; the CMS simulated and RECOtransfers data, these and data to a any complete Tier-2 copy centre which of requires the them AOD for data. analysis; It canallow rapidly reproduction of RECO datasets using improved algorithms or calibrations; a Tier-1 can support high-statisticscentre. analysis projects which would be infeasible at a Tier-2 centres, and access to asupport flexible final-stage CPU analysis farm; requiring repeated in passes particular, over the a Tier-2 reduced centres dataset; are designed to studies; storage. Since each Tier-1 centre holds unique RAW and RECO datasets, it must be capable of serving • Provide long-term safe storage of RAW data from CMS, providing a second complete copy • Store and serve to Tier-2 centres simulated and derived data. Each Tier-1 holds a fraction of • Carry out second-pass reconstruction: a Tier-1 provides access to its archive of RAW data• to Provide rapid access to very large data samples for skimming and data-intensive analysis: • Support of analysis activities, including local storage of data samples transferred from Tier-1 • Support of specialised activities such as offline calibration and alignment tasks, and detector • Production of Monte Carlo data, and its transfer to an associated Tier-1 centre for long term Tier-1 centres A few large Tier-1 centres arethe hosted world. at collaborating These national centres labssis are and operated on computing by extremely centres a reliable around professional deliverybatch staff of CPU on data-intensive facilities, a processing a 24/365 services. mass basis,international storage Each network with system links site including the including a provides empha- a robotic large dedicateda tape Tier-1 link archive, are to and to: the very LHC-OPN. high The speed primary functions of data to any CMS Tier-2.serving, the However, for Tier-1 serves the a purposesgeographical proximity. of defined Monte set Carlo of data a receipt few and “associated” AOD Tier-2 data centres,Tier-2 centres usually defined by Several Tier-2 centres ofdivides varying its sizes resources are between hosted thesubject at local to less user CMS stringent community institutes. requirements and onthem CMS availability A feasible and as data to Tier-2 a security manage centre than whole. with a typically of the Tier-1 Tier-2 a resources centre, centres Tier-2 available making centre are to may a include: typical University group. The functions 2008 JINST 3 S08004 11.3. Data Dataset Location Catalogs Local File CMS Data Data Access Bookeeping and Storage Management Data Transfer and Placement

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Data Set Production Database Parameter Workflow Management Workflow Grid Grid Grid Systems Grid Job Figure 11.3: Overview of the CMS Computing Services. Workload Workload Monitoring Logging and Management Management Bookkeeping A number of CMS-specific distributed computing services operate above the generic Grid CERN Analysis Facility In addition to theCPU Tier-0 resources centre, with CERN rapid also accessanalysis to hosts when the an required, entire and Analysis CMS a Facility variety dataset. ofitoring) which This other related specialised to centre combines functions the supports flexible (calibration, operation fast performance of turn-around mon- theaccess CMS capabilities detector. of The centre a effectively Tier-1 combines with the the rapid flexibility data of a very large Tier-2. 11.5 Computing services Grid computing The integration of theupon resources at Grid CMS middleware computing whicheach centres presents WLCG into a (Worldwide LHC a standardised Computing single Grid) interfacedata coherent site. to access system The with storage Grid relies robust allows and security remote and CPUin job accounting. the submission facilities WLCG The and at Technical detailed Design architecture Report of [242]. the Grid is described layer, facilitating higher-level data andCMS-specific workload software management agents functions. toalso These run provides services at specialised require some user-intelligible sites,monitoring, interfaces in to and addition the tools Grid to forprocessing. for automated generic An analysis steering Grid overview job and of services. the submission monitoring CMS and of Computing CMS Services large-scale components data is production shown in and figure 2008 JINST 3 S08004 allows users to track, provides a standardised and queryable provides the mapping between file blocks to the is responsible for the physical movement of file- – 304 – dataset, a logical collection of data grouped by physical- job bookkeeping and monitoring system at each site map logical files onto physical files in local storage. Dataset Bookkeeping System Data Location Service file, block an aggregation of a few TB of data files, representing the smallest event, collection roughly corresponding to an experiment “run” for a given data transfer and placement system parameter set management, system implemented with either global or local scope accord- Local File Catalogues To provide the connection between abstract datasets and physical files, a multi-tiered cata- The A unit of operation of the data transfer system. logue system is used.means of The cataloguing and describingfor event data the [249]. end user, It is answeringond the catalogue the principle system, question means the “which of dataparticular data sites discovery of at this which type they are existssites. located, in taking the into account system?” the possibility A of sec- replicas at multiple monitor, and retrieve output from jobsThe currently system submitted also to provides and abased executing at uniform submission remote interface tools. sites to [250]. automated a In installation variety addition, of of standard a CMS Grid-based suite applications and and of local libraries software at batch-system remote distribution sites. toolsBulk provide workflow facilities management for For very large-scale data processingconstruction), (including a Monte specialised Carlo bulk production, workflow skimmingsystem management comprises and tool a has event collaborative distributed re- been network developed. of0, automated The job Tier-1 managers, and ProdAgent operating Tier-2 at sites Tier- ]. [250 The system provides facilities for large-scale Grid job submission, dataset definition; and Data management CMS requires tools to cataloguephysical the data data files which on exist, sitesites. to storage In track systems, order the and to location todefines simplify of manage higher-level the the concepts and data including: corresponding monitor management the problem,meaningful flow the criteria; of data data management between system therefore blocks between sites on demand;system it must is schedule, currently monitor implemented and byinterfaces verify the at the PhEDEx CMS system movement sites, [248]. of ensuringoperation data optimal for This in the use data conjunction of management with the systemdefined the is available sites, storage that bandwidth. where the they collaboration The will will remain baseline explicitly for mode place access of datasets by at CMS applications untilWorkload removed. management Processing and analysis ofremote data at site sites via is thenecessary typically Grid setup, performed workload by executes management submission a system.arranges of CMSSW for any batch application produced A jobs data upon to to standard data belogging made a job present accessible information. via wrapper on This Grid process data local performs management is tools, storage supported the and by at provides several the CMS-specific services. site, ing to the application, allows the storagesubmitted and to tracking the of Grid. the A configuration lightweight of CMSSW applications 2008 JINST 3 S08004 100 million events) at around twenty CMS – 305 – Tier-1 and Tier-2 centres in the weeks preceding the challenge, and upload to CERN; application of calibration constants from theinto offline around database, ten and datasets; splitting the event sample The relatively large cost of the computing system dictates that centres must build up their In 2006 and 2007, CMS carried out large-scale Computing, Software and Analysis challenges • Preparation of large Monte Carlo datasets (≈ • Playback of the MC dataset for prompt Tier-0 reconstruction at around 100 Hz, including the interface to the CMS data catalogueslogging and and data status management information. system, A and highlyto handling automated of system allow such large the as flows CMS ProdAgent of is datadata essential processing operations in team. order system to be controlled and monitored by aUser workflow moderately-sized management For a genericable CMS [250]. physicist, It allows to a submitdata dedicated user-specific previously jobs transferred tool to to a (CRAB) remote auser computing environment, close for element it storage which provides workflow can element. data-discovery and access managementalso data-location CRAB manages services, is takes status and reporting, care Grid avail- monitoring, infrastructure. of andstorage It user interfacing element. job with output Via the which a can be simplemote put configuration sites on file, as a a user-selected easily physicist asas can he much thus can as access access possible. data local available There data:submitted on to is all re- the also infrastructure Grid a complexities but client-server to arethe architecture a hidden user, available, dedicated interacting to so CRAB with him server, the the which, Grid job in services. is turn, not handles directly the job on behalf of 11.6 System commissioning and tests It has been recognised sinceganisation of the the very experiment start computing systems of wouldsystem preparations be must a for be key LHC designed challenge. that with Eachrealistic component attention the scale. of to construction the The both and reliance scalability or- on andmany distributed flexibility, advantages, computing, and but using rigorously adds the tested further relatively at complexity newsystem in Grid located controlled approach, primarily deployment has at and a testing single compared site. to a resources in a carefully controlled way;resources the rapidly will falling price only of become hardwareresources dictates available that is shortly full-scale a before strong requirement. theyfull-system are The tests emphasis (“data required, in challenges”) and CMS over that has thein a last been efficient realistic three on use way. years, a of exercising series all of available increasing components scale (CSA06, CSA07). The scale ofmance, the two respectively, with tests the was set computing at systemfour 25% operated weeks. and continuously 50% at The of this challenges thetools. level nominal were for Typical 2008 targets carried more perfor- for out than the using tests were: realistic application software and computing 2008 JINST 3 S08004 – 306 – 11.4). CMS will finalise its data challenge programme with additional scale Figure 11.4: Dataflow from CERN during the CSA07 Data Challenge. reconstruction and skimming operations at several sites; Overall, many of the key metrics for success in the challenges were met: the reconstruction • Distribution of AOD and RAW to all Tier-1 centres, and subsequent alignment /• calibration, Transfer of skimmed data to Tier-2 centres and running of physics analysis jobs. rate at the Tier-0 exceeded 100 Hz forfrom periods of CERN time; (figure an export rate oftests over 350 during MB/s was 2008, achieved which arewith in data the challenges, final continuous stages programmesincreasing of are hardware preparation under resources at way at to theand the deploy, time high-speed computing commission of data and centres, network writing. links test andungoing between In the to review, them. parallel with debug many The new and CMS lessons computing demonstrate expected model to reliable itself be is learnt also as detector under data begins to flow. 2008 JINST 3 S08004 of active silicon, has been integrated into 2 – 307 – The silicon-strip inner tracker, with about 200 m At the time of this paper,After the more apparatus than is 10 essentially completed years and of installed. design and construction, the CMS magnet has been constructed The ECAL, comprising over 75 000 lead tungstate crystals, is the largest crystal calorime- The entire HCAL has been completed and commissioned on the surface. The HCALThe modules various components of the Muon System (drift tubes, cathode strip chambers, resistive In the very forward region, the Zero Degree Calorimeter hasThe been off-detector completed electronics and are CASTOR currently being installed and operations forCommon trigger data-acquisition commis- runs with various sub-detectors, sometimes using cosmic rays, are and successfully tested. Most ofmeasured the during magnetic, the electrical, tests are mechanical,largest in and superconducting good cryogenics solenoid agreement ever parameters built with for calculated aphysics, values. physics total experiment stored The in energy, and CMS terms stored of magnet bending energy is power per the for unit of cold mass. The Compact Muon Solenoid detectormance has of been the described apparatus in has detail. been described The elsewhere expected [17]. physics perfor- Conclusions Chapter 12 its support tube, commissioned, and thoroughlylent, tested fulfilling with the cosmic design rays. specifications. Its2007. performance The All is the silicon excel- pixel tracker modules wasmid-2008. are installed completed; into it CMS is in planned december to install the Pixel detectorter into ever CMS built. in Thecalibrated crystals using cosmic in rays the and barrel aboutsure a part, the third energies comprising in ranging over particle from beams, those 60trons. deposited demonstrating 000 by the An minimum crystals, ability ionising energy to have particles mea- resolution been tohas of high-energy inter- been elec- 0.5% installed for in 120 GeV theinserted electrons experiment into has and the been is experiment in attained. being 2008. commissioned. The The ECAL endcaps barrel are foreseenare currently to being be commissioned in the experiment proper. plate chambers) have been completed. A significantsioned fraction and of the tested Muon on System has surface beenand with commis- being cosmic commissioned rays, in-situ. and it is now being integrated intois the expected to experiment be completed in 2008. sioning are taking place. regularly taking place at the experimentsions and at will LHC continue in into mid-2008. spring 2008 in anticipation of colli- 2008 JINST 3 S08004 – 308 – We also acknowledge the important contributions provided by the following institutes: Re- The design, construction, installationwithout and the devoted commissioning efforts of of our CMSfrom numerous technical all would colleagues the have from CMS been the Institutes. CERNand impossible departments The and all cost other of the systemsported detectors, without by computing the which infrastructure, financing agencies data CMS involved acquisition trian in would Federal the not experiment. Ministry be We of are Science able particularly(Brazil); and indebted to Bulgarian Research; to: Ministry operate, FNRS Aus- of and Education was FWO andMinistry generously (Belgium); Science; of CERN; CNPq sup- Science CAS and and and FAPERJ NSFC Technology;NICPB; (China); Academy University Croatian of of Finland, Finish Cyprus; Ministry Estonianand of Education Academy CNRS/IN2P3 and (France); of Helsinki Institute BMBF Sciences of and and Technology Physics; (Greece); DESY CEA NKTH (Germany); (Hungary); DAE General and Secretariat DST(Italy); (India); for IPM KICOS Research (Iran); (Korea); and UCD CINVESTAV (Ireland); (Mexico); INFN PAECtific (Pakistan); Research State (Poland); FCT Commission (Portugal); for JINRMinistry Scien- (Armenia, of Belarus, Education Georgia, and Ukraine, Science Uzbekistan), ofEnergy; the Ministry Russian of Federation, Science Russian and FederalCiencia Environmental Agency y Protection of Tecnologia of Atomic (Spain); the ETHZ,Council Republic PSI, (Taipei); of TUBITAK and University Serbia; TAEK (Turkey); of STFC Oficina Zurich (United de Kingdom); (Switzerland); DOE and National NSF Science (USA). search Institute of Applied Physicalnology Problems, of Minsk, China, Belarus; Hefei, University Anhui, forversity China; Science of Digital and and Technology, Tech- Computer Tampere,rea; Systems Finland; Benemerita Laboratory, Universidad Tampere Seoul Autonoma Uni- National de Puebla,Zhukovsky, University Puebla, Russia; of Mexico; Russian Myasishchev Education, Design Federal Bureau, Seoul,Physics, Nuclear Ko- Centre, Snezhinsk, Scientific Russia; Research Kharkovclyde, Institute State Glasgow, United for University, Kingdom; Technical Kharkov, Virginia Polytechnic Ukraine; InstituteVirginia, USA. University and State of University, Blacksburg, Strath- Acknowledgements 2008 JINST 3 S08004 – 309 – Algorithm Board Alternating Current Analog to Digital Converter Anode Front-End Board, CSC system Application Gateway Anode Local Charged Track trigger primitive,Analysis CSC Object system Data - a compactAnalog event Opto-Hybrid format for physics analysis Avalanche Photo-Diode Application Programming Interface Analogue Pipeline (Voltage mode), front-end read-outApplication chip Specific of Integrated Tracker Circuit A Toroidal LHC ApparatuS experiment Asynchronous Trigger Throttle System American Wire Gauge Barrel Muon system Back Disk Back Petal Barrel Pixel Branching Ratio Beam RAte of Neutrals Beam Synchronous Timing Bunch and Track Identifier trigger primitive,Builder DT Unit system Bunch Crossing Bunch Crossing Number Centauro And Strange Object Research Cosmic Challenge Clock and Control System Communication and Control Unit Communication and Control Unit Module Central Data Recording Carbon Fiber Composite AC ADC AFEB AG ALCT AOD AOH APD API APV ASIC ATLAS aTTS AWG BMU BD BP BPix BR BRAN BST BTI BU BX BXN CASTOR CC CCS CCU CCUM CDR CFC AB CMS acronym list 2008 JINST 3 S08004 – 310 – online with offline software Cathode Front-End Board of the CSCCathode system Local Charged Track trigger primitive,Coordinate CSC Measuring system Machine Common Mode Noise Complementary Metal Oxide Semiconductor Compact Muon Solenoid experiment CMS SoftWare framework Consistent Online Software INtegration Environment, project integrating Central Processing Unit CMS Object-oriented Code for optical Alignment CMS Remote Analysis Builder Cosmic Rack, a set of TOBCyclic rods Redundancy Check error detection Cathode Strip Chamber muon system Cathode Strip Chamber Trigger Track Finder Data to Surface Digital to Analog Converter Data Acquisition Data Acquisition Motherboard, CSC L1 trigger Database Management System Direct Current Data Concentrator Card DC Current Transformer Detector Control System Detector Control Unit Detector Description Database Data Description Language Detector Dependent Unit in DAQ system Data Interchange Protocol (CERN) DAQ MotherBoard of CSC system Diffusion Oxygenated Float Zone Digital Opto-Hybrid Digital Opto-Hybrid Module Data Quality Monitoring Data Quality Monitoring Collector Detector Safety System Drift Tube muon system Drift Tube Trigger Track Finder, DT L1Electromagnetic trigger Calorimeter (Barrel) Electromagnetic Calorimeter Event Data Model Engineering Database Management System CFEB CLCT CMM CMN CMOS CMS CMSSW COSINE CPU COCOA CRAB CRack CRC CSC CSCTF D2S DAC DAQ DAQMB DBMS DC DCC DCCT DCS DCU DDD DDL DDU DIP DMB DOFZ DOH DOHM DQM DQMC DSS DT DTTF EB ECAL EDM EDMS 2008 JINST 3 S08004 – 311 – bytes) 9 bits) 9 Electromagnetic Calorimeter (Endcap) Electromagnetic Isolation Card, regional calorimeter trigger Embedded Local Monitoring Board (ECAL) Equipment Management DataBase Endcap Muon system Equivalent Noise Charge Event Processor Endcap preShower detector, also Event Server Event Server Proxy ECAL Safety System Eta Track Finder, DT regional muonEVent trigger Builder Event Filter Farm Event Manager FED builder Front Disk Final Decision Logic, L1 Global Trigger Front-End Front-End Board Front-End Card, Front End Controller Front-End Driver Front-End Electronics Front-End System ECAL front-end read-out ASIC Event format comprising the union ofFilter RAW Farm and RECO data Fast Merging Module First In First Out buffer Front Petal Field Programmable Gate Array Forward Pixel Front-End Read-out Link Finite State Machine Foil screened Twisted Pair cables Filter Unit Gigabit (10 Gigabyte (10 Gain BandWidth product Computer program for hadron shower calculations Global Calorimeter Trigger (L1) Gamma Irradiation Facility Global Muon Reconstructor Global Muon Trigger (L1) EE GB EIC ELMB EMDB EMU ENC EP ES ESP ESS ETTF EVB EVF EVM FB FD FDL FE FEB FEC FED FEE FES FENIX FEVT FF FMM FIFO FP FPGA FPix FRL FSM FTP FU Gb GCALOR GCT GIF GMR GMT GBW 2008 JINST 3 S08004 – 312 – bytes) 3 bits) 3 Semiconductor heavy-ion collisions Giga Optical Hybrid Gigabit Optical Link General Purpose Network (CERN campus) Global Trigger (L1) Global Trigger Front-end board (L1) Global Trigger Logic board (L1) Gunning Transceiver Logic, upgraded version, developed by Fairchild Global Trigger Processor Global Trigger Processor emulator Graphical User Interface Beamline at CERN Hadron Calorimeter Hadron Calorimeter (Barrel) High Density Interconnect Hadron Calorimeter (Endcap) Hadron Calorimeter (Forward) High Gain Heavy Ion(s) Heavy Ion Jet INteraction Generator, Monte Carlo event generator for Hits and Impact Point alignment method,High-Level also Trigger Highly Ionizing Particle Humidity Monitoring Hadron Calorimeter (Outer Barrel) Hybrid Photo-Diode HyperText Mark-up Language HCAL Trigger and Read-out High Voltage Interactive Graphics for User ANAlysis Inter-Integrated Circuit InterConnect Board (TEC), InterConnect Bus (TOB) InterConnect Card Input/Output Interval Of Validity Interaction Point or Internet Protocol Isolation bit in muon trigger Intersecting Storage Ring collider at CERN Joint controls Project at CERN Jet Summary Card, in Regional CalorimeterJoint Trigger Test Action Group kilobit (10 kilobytes (10 C 2 GOH kB GOL GPN GT GTFE GTL GTL+ GTP GTPe GUI H2 HCAL HB HDI HE HF HG HI HIJING HIP HLT HM HO HPD HTML HTR HV IGUANA I ICB ICC I/O IOV IP ISO ISR JCOP JSC JTAG kb 2008 JINST 3 S08004 bytes) 6 – 313 – bits) 6 Monte Carlo simulation program/technique, also Mini-CrateMuon of system DT (Endcap) system or Monitoring Element Monitoring Electronics Module mezzanine Front End Controller Multiple Gain Pre-Amplifier chip, ECAL Algorithm for tracker alignment Minimum Ionizing Particle Metal Oxide Semiconductor Metal Oxide Semiconductor Field Effect Transistor Muon Port Card, CSC L1 trigger Magnet Safety System Mean Time Magnet Test Cosmic Challenge Maximum Transfer Unit Network Interface Card Non-Ionizing Energy Loss Online to Offline Object Database Management System Online Master Data Storage OLE for Process Automation Offline ReConstruction OFfline subset, conditions database Level-1 hardware-based trigger Level-1 Accept Local Area Network Laser Alignment System LHC Computing Grid (a common computingLocal project) Charged Track trigger primitive ofLightweight CSC Directory system Access Protocol Light Emitting Diode Large Electron Positron collider at CERN Low Gain Large Hadron Collider Least Significant Bit Lookup table Local Trigger Controller Low Voltage Low Voltage Distribution Low Voltage Differential Signaling Low Voltage Regulator Module Alignment Module Alignment of Barrel Megabit (10 Muon system (Barrel), also Mother Board or Megabyte (10 ME MEM mFEC MGPA MILLEPEDE MIP MOS MOSFET MPC MSS MT MTCC MTU NIC NIEL O2O ODBMS OMDS OPC ORCOF MC L1 MB L1A LAN LAS LCG LCT LDAP LED LEP LG LHC LSB LUT LTC LV LVD LVDS LVR MA MAB Mb 2008 JINST 3 S08004 – 314 – bytes) 15 Offline ReConstruction ONline subset, conditions database Operating System Point 5 collision area of LHC Preshower front end ASIC PAttern Comparator Trigger, RPC system Petabyte (10 Personal Computer Printed Circuit Board Peripheral Component Interconnect Pixel Detector Parton Density Function, also Probability DistributionPhi Function Track Finder, DT regional muonProgrammable trigger Logic Controller Programmable Logic Device Phase-Locked Loop Patch Panel Pixel Luminosity Telescope Proton Synchrotron Pipeline Synchronizing Buffer, L1 Global TriggerPVSS and SOAP Global Interface Muon Trigger Precision Temperature Monitoring, ECAL Primary Vertex Prozessvisualisierungs- und Steuerungs-System Charge Integrator and Decoder, ECAL frontendQuartz electronics Phase-Locked Loop Event format from the online containingRead-out full Unit detector Builder, and also trigger Resource data Broker Regional Calorimeter Trigger (L1) Run Control System Event format for reconstructed objects suchRelative as Humidity tracks, vertices, jets, etc. Reduced Instruction Set Computer Root Mean Square ReadOut Board, DT system ReadOut Chip, pixels ReadOut Server board, DT system Resistive Plate Chamber muon system Resource Service Read-out Unit Storage Area Network Sector Collector, DT muon L1 triggerSwitched or Capacitor Super Array Crystal, buffer, ECAL CSC system Supervisory Control And Data Acquisition ORCON OS P5 PACE PACT PB PCB PCI PD PDF PHTF PLC PLD PLL PP PLT PS PSB PSX PTM PV PVSS QIE QPLL RAW RB RCT RCS RECO RH RISC RMS ROB ROC ROS RPC RS RU SAN SC SCA SCADA PC 2008 JINST 3 S08004 – 315 – bytes) bits) 12 12 Surface Control eXperimental building at P5 Slow Dump Accelerated Single Event Lathcup Single Event Upset SubFarm Manager Subset of events selected from aSychronization larger and set Link Board SuperModule (ECAL) or Storage Manager (DAQ) System Mother Board Surface Mounted Device Short Message Service (mobile phones) Signal to Noise ratio Simple Network Management Protocol Simple Object Access Protocol Super Proton Synchrotron Selective Read-out Processor Silicon Strip Tracker Standard Template Library Synchronous Trigger Throttle System Secondary Vertex Surface hall at Point 5 forTracking CMS telescopes of TOTEM Event index information such as run/eventTerabit number, (10 trigger bits, etc. Terabyte (10 Token Bit Manager Telecom Computing Architecture Trigger Concentrator Card Transmission Control Protocol Trigger Control System Time to Digital Converter Technical Design Report Tracker Detector Safety System Tracker EndCap Track-Finder, muon L1 trigger Tracker Inner Barrel Tracker Inner Disks Timing Module, Global Trigger and DriftTrigger Tube MotherBoard, Trigger CSC Track Finder L1 trigger Technical Network Tracker Outer Barrel TOTal Elastic and diffractive cross section Measurement Tracker Pixel Detector SCX TBM SDA SEL SEU SFM Skim SLB SM SMB SMD SMS S/N SNMP SOAP SPS SRP SST STL sTTS SV SX5 T1, T2 TAG Tb TCA TCC TCP TCS TDC TDR TDSS TEC TF TIB TID TIM TMB TN TOB TOTEM TPD TB 2008 JINST 3 S08004 – 316 – Trigger Primitive Generator Track Correlator, DT L1 trigger Trigger and Data Acquisition project Token Ring Link Board Trigger Server, DT L1 trigger Track Sorter Master, DT L1 trigger Track Sorter Slave, DT L1 trigger Trigger Timing and Control TTC Encoder and Transmitter TTC Machine Interface TTC Receiver Trigger Throttling System User Datagram Protocol Underground Service Cavern at Point 5Underground for eXperimental CMS Cavern at Point 5Very for Front CMS End Very High Density Interconnect Versa Module Eurocard Vacuum PhotoTriode Wide Area Network Worldwide LHC Computing Grid WaveLength Shifting Software framework for CMS Data Acquisition eXtensible Markup Language Yoke (Barrel) Yoke (Endcap) Zero Degree Calorimeter TPG TRACO TriDAS TRLB TS TSM TSS TTC TTCex TTCmi TTCrx TTS UDP USC55 UXC55 VFE VHDI VME VPT WAN WLCG WLS XDAQ XML YB YE ZDC 2008 JINST 3 S08004 Nucl. 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