PoS(EPS-HEP 2013)488 http://pos.sissa.it/ ope with the corresponding of micromegas detectors for N needs to be upgraded. In oresees a luminosity increase 2 onstruction of the chamber as well 00 m hown. ectors have been chosen as the main e to the trigger. We describe the R&D sics -EPS-HEP2013 ) large micromegas detectors at CERN 2 2.4 m × e Commons Attribution-NonCommercial-ShareAlike Licence. † ∗ michele.bianco@cern.ch Speaker. on behalf of MAMMA (Muon ATLAS Micromegas Activity) Collaboration. efforts that led to the construction of the first (1 by a factor 3 comparedrate to increase, the the LHC Muon luminosity Systemthe design of first the value. station ATLAS of experiment To the at c hightracking chambers CER rapidity but region, will, micromegas at det the same time, also contribut The luminosity upgrade of the Large Hadron Collider at CERN f the ATLAS upgrade. The technical solutions,as adopted results in on the the c detector performance with cosmic rays are s and outline the next steps towards the construction of the 12 ∗ † Copyright owned by the author(s) under the terms of the Creativ c

CERN, Switzerland E-mail: Michele Bianco Development of large size Micromegas detectorsthe for upgrade of the ATLAS experiments. The European Physical Society Conference on18-24 High July Energy 2013 Phy Stockholm, Sweden PoS(EPS-HEP 2013)488 . In ing be- year distance / 1 m rays, show- − ergy deposit µ δ f b Michele Bianco 150 ade readout electrode st be upgraded to eloped in the mid- und estimations, a s by charged parti- , the drift electrode a layer of resistive l phases which will ue to , where the signal is TLAS muon system lification mesh. The ng shutdown in 2018 a way the MM become electrons in the conver- ctors, to be installed on nosecond is required. As ctors. out electrode which is not nd it typically takes several m is applied. The electrons, ed. exceeding the design value of p of a few millimetres thickness 1 − s 2 − cm 34 10 × 2 98%. ≥ per plane, for each of the two planned 4-layer multi-plane m µ allowing the ATLAS experiment [3] to collect approximately 100 1 − s 2 − cm 34 tween the MS and the ID track for the combined muon reconstruction. ers, etc). detector that will replace the Small Wheel. The highly ionizing particles, produced in the LHC collisions, leads to large en The Micromegas (Micro-MEsh Gaseaus Detector) MM technology was dev The Large Hadron Collider (LHC) [2] complex will be upgraded in severa 10 * Measure the second coordinate with a resolution of 1–2 mm to facilitate the match * High single plane detection efficiency * Resolution better than 100 * Efficiencies and resolutions should not degrade at very high momenta (d × allow the physics program to bethe significantly accelerator extended. luminosity After will the be expected lo increased to 2–3 and an increasing probability forthe spark New occurence Small Wheel, [5]. astrips on For spark top the protection of MM a system thin dete hasspark-insensitive insulator been directly [6]. above developed the adding The readout electrode, signals inanymore are such directly exposed capacitively to coupled the to charge created the in read the amplification region. 1 Development of large size Micromegas 1. Introduction dle of the 1990’s [1]. Itacting consist of as a conversion planar and (drift) electrode, drift a gas region, ga and a thin metallic mesh at typically 100– order to take advantage of thehave improved better LHC performance operation at the the ATLASwill expected detector need mu high major luminosity. improvements in In thelist particular, highest of the rapidity requirements A for region. these Based new on detector backgro has been estabilished [4]: from the readout electrode, delimiting the amplificationand region. the In amplification the mesh beginning were at negativewas high at voltage ground (HV) potential. potentials and The the MMcles traversing operation the is drift based space where on an theproduced electric ionization field by of of the few ionization, the hundred drift ga V/c towards thecreated mesh by and means of the an amplification electric region fieldsion of gap about depends 40–50 kV/cm. on the The drift drifttens of gas, of the the nanoseconds, drift while distance, for and the thea amplification drift conseguence process field a a a fast fraction pulse of of aThe electrons na ions on the that readout are strip produced isions produc in evacuation needs the about avalanche 100 ns, process, till move very back fast compared to to the other amp dete 2. The Micromegas thecnology for the ATLAS New Small Whell upgr PoS(EPS-HEP 2013)488 d not to . In order [7]. In the 2 cation mesh lly shown in m needed to as- scheme is the n the resistive Michele Bianco ulted in a more tive strips while ical precision, a readout strips are field lines between ace of 3 vantages for large-area eposited. The mesh sits t boards, and the drift panel t a part of the drift panel. uickly to ground through the ation the mesh is not part of the thick layer of insulator, followed by the m ) construction µ 2 ) has been built at CERN laboratories with the 2 3 2.4 m 2.4 m × × Internal structure of the MM readout boards, in this cinfigur the size of the individual PCBs. With the mesh decoupling from the readout structure,two types of panels are Another difference for the MM detectors for the NSW from the original MM The mesh decoupling from the readout structure, presents several ad Figure 1 shows schematically the internal structure of a readout PCB. The The realization of the ATLAS NSW, requires the production of large size MM * The mesh size is only limited to he mesh fabrication size and stretching machines an * It facilitates detector opening and cleaning. * It separates PCB production from mechanical construction. detectors: current layout, the largest MM will have a trapezoidal shape, with a surf help of the PH-DT-EO unit and the CERN PCB workshop. semble an operational detector, the readoutwhich panel, comprises carrying the the drift readou electrodeFig. 2. and the amplification mesh. This is schematica resistive strips. On top of theon these resistive strips support the pillars, however mesh it support is pillars not are a d part of the readout PCB bu to prove the ability toworking construct prototype a with detector the of dimensions (1 that size with the adequate mechan HV distribution configuration. In thisthe scheme, amplification positive mesh HV is is connectedstable applied to to detectors, ground. the the In resis spark-induced this currentmesh, operation can without mode, be mesh which potential evacuated res variations. verythe q Moreover amplification the mesh better and focusing thestrip. of resistive Finally, the in strips the leads MM to layoutis a for not the better integrated in ATLAS charge New the collection Small readout Whell o structure. upgrade the amplifi 3. The large MicroMmgas chamber (1 readout PCB drawn on 0.5 mm thick PCBs and then covered by a 64 Figure 1: Development of large size Micromegas PoS(EPS-HEP 2013)488 ranite covered by a Michele Bianco um frame was nite table. The of the electrode nd line of epoxy ars were precisely rated into the drift ( n the gaps between ith honeycomb and + nel production, can ( structural form after $ + s realized by use of anite table. ith a vacuum sucking $ ding glue was used to rovisions for vacuum m creeping under the *% me height as the mesh l which kept the panel ) *% ( ) completely. The second ' ( tem, but in this case, the electorde) to be glued to and 4 for the drift). The % ' & , while the readout boards rom the short sides of the % % enings into the mesh at the & $ % # $ e panel interconnections. To d readout panels in open (left) " # by specialized company. For ! " ! cm / ..( ,- N 1( /0

4 ( ; : ( 9 $ ( ( 2 + 1 ( $ 678 0- + 5 / ( 4 $ $ + $ *- *% ( &++ . & ) 3 *% - ( , ) ' ( % ' & % % & $ % # $ " # ! " ! =( 3< high pillars, ii) a solid profile is embeded in the drift panel frame onto the mesh m µ Schematics of a single MM plane assembly showing the drift an thick mylar foil. The mylar foil with a grid of small holes, was sealed against the g m In correspondence of the solid profile embeded in the drift panel, an alumin Each panel would be composed of a stiffening structure onto wchich either By means of the sucking system the PCBs were retained and fixed on the gra The main differences between readout and drift panel, involved in the pa µ be summarized as follow: i) the skinshave of the the 128 drift panels have flat surfaces the glueing a cyanolit-basedglue. glue The is mesh used, is also andsupport glued the frame. to mesh As the last drift is step, panel before secured spacers,place the with the chamber of latter assembly, the a three have drift small seco the panel op sa spacers were made to create the passages for th frame will be installed, iii) an open channel that serves as gas manifold is integ panel frame, only on the shorter sides. attached were the mesh was glued with a tension of about 10 and closed (right) position. Figure 2: Development of large size Micromegas structure would be glued. Stiffeningspacers panels while consist the of electrodes aluminum consistPCBs bars of that filled 8 compose w PCBs the (4 readoutchamber. for panel The the host assembly readout of 4096 the plane strips panels whichsystem. was are done read on The a f vacuum granite table175 sucking equipped system w was made by a thin layer of a mesh fabric table. The PCBs (both inthe case honeycomb of were the placed readout electrode face that downthe in on boards cas the were of mylar closed drift foils andboards. by and tape aligned, as tha well the PCB edges to prevent glue fro aluminum profiles were glued to the boardsglue using the epoxy honeycomb glue, on while the an readout expan face boards, of the each glue panel take was 24 gluedpositioning hours using of to tha the cure same half-panel technique already ofat built, the a was sucking fixed controlled sys distance by stiff-back .sucking. too The For stiff-back this isaluminum a exercise bars tool a equipped with with simplified a sucking stiff-back heads flatmachined structure approximately and lower every glued was surface 25 together and used, cm. with longitudinal p it Thethe bars, b curing stiff wa of enough the to keep glue; their thus forming a plane that matches the surface of the gr PoS(EPS-HEP 2013)488 he s done struction, a a signal with Michele Bianco intillators, about r algorithm hence r multiple clusters g the long chamber (SRS) [9] developed ch SRS DAQ unit can the large Micromegas g to the study of inter- m the trigger coverage mputer via an ethernet f large chamber, a long The FEC board receives /580 Volt. the collected clusters. A readout side of the large r after the assembling. hip [8] using an adapter r clusterization algorithm n produce current bridges trip position is shown for all ted strips are merged into a ), indeed the events fall mostly in Θ 2 cos ∝ 3% gas mixture with a flow of about 10 l/hour, / 5 97 2 CO / Ar distance between the mesh and the readout structure, the final assembly wa large, were positioned above the chamber to provide a cosmic muon trigger. T m The 3D rendering and a picture of the large Micromegas chambe 2 µ 1.5 m Since no test-beam were available at CERN at the time of the large chamber con × Figure 3: in controlled clean room of classproject 10000. and the In final Fig. chamber 3 after the the 3D assembling view are rendering shown. of scintillator configuration with rispect to theest. chamber, was The changed chamber accordin was operated with 4. First large MicroMegas chamber characterization dedicated cosmic stand was0.25 installed in the RD51 laboratoryt. Three planar sc the drift plane was set toThe 300 data Volt while acquisition the was resistive strips basedat were on set CERN. the at The 560 so-called detector Scalable readout(ADC) Read-out was and System FrontEndConcentrator done (FEC) through cards to the digitizethe APV25 the external analog readout data. trigger c signal aslink. a Both NIM ADC and or FEC LVDS boards signalread-out are and 2048 installed in reads detector a out channels, standard to 6U samechamber. Eurocrate. a number To Ea provide co of the strips cosmic hosted trigger, theside by three a each scintillator the were center aligned of alon theruns chamber. was To recorded, assess for the each uniformity chamber ofThe readout the studies side. responce of o the chambercluster performances is are a based group on of the firedis properties strips initiated of with with charge a above scan a overa given all pulse-height threshold. strips that Ou in passes the detector. acluster, A and predefined strip the threshold. is clusterization selected Neighboring continues ifselects selec also it clusters with if contains no one more strip thanper one fails event. hole, the made selection. by a Ou singleIn strip, Fig. and 4, allows for fo one ofevents the and readout side, for the events number with of onlyconvoluted cluster one versus with the cluster. the s The cosmic obtained rays profile angular comes distribution fro ( Development of large size Micromegas assure the cleanliness during the assembly andover avoid the dust 128 particles that ca PoS(EPS-HEP 2013)488 . ◦ Michele Bianco r were selected, arge versus strip as turned by 90 as observed along can was performed. ilt and its first cham- chamber thecnology response through the signals and their rise moothly operated and n the events with only s, as a function of the chamber under test. the performed surface scan nction of the distance from the front 1000 No Cuts Single Cluster Events 500 Cluster Position [strip] 0 6 -500 Large Chamber Cluster Profile -1000 0

800 600 400 200

2000 1800 1600 1400 1200 1000 Clusters [entries/20 strips] [entries/20 Clusters Number of clusters vs strip position for one side of the large Number of cluster and cluster charge vs strip position as a fu Figure 4: The construction and assembly of the largest Micromegas chamber ever bu In order to analize the chamber responce along the strip lengh a surface s end. 5. Conclusion Figure 5: Development of large size Micromegas the center of the chamber.one The cluster are trigger selected. coverage became more evident whe ber characterization with cosmics wereshows presented. a The reasonably uniform chamber responce built over wasno the s signal full reduction detector area. was observed With here over presented the is 1 fully suitable m for strip the lengh. upgrade of The the Micromegs ATLAS NSW. By moving the turned scintillator, events impingingthe in whole a detector specific was part of testedcluster the in detecto distribution, different the steps. cluster At chargetime each as were step, studied. well the as A chamber uniform thethe behaviour shape whole in strip of spatial, leght. the charge In acquired andposition Fig. time 5 are responce the w presented, Micromegas while clusterdistance distribution in from and Fig. the cluster front ch 6 end the are shown. signal shape for different step The trigger configuration was modified, the scintillator closest to the chamber w PoS(EPS-HEP 2013)488 Michele Bianco d. C-2013-006 rge Hadron Collider, JINST 3 (2008) lerator and Experiments, JINST 3 ctronics Design Group (2001), pg. 20, egas detector for the upgrade of the ATLAS k, Micro-Pattern Gaseaus Detectors, Nucl. f. gas chamber for high-rate applications, 1-wg5/srs/default.aspx. 7 Signal shape for three differents distance from the front en Figure 6: ATLAS-TDR-020-2013. Nucl.Instrum.Meth. A640 (2011) 110-118 muon system, Nucl.Instrum.Meth. A617 (2010) 161-165 http://hep.ucsb.edu/people/affolder/User Guide 2.2.pd Instrum. and Meth. A376 (1996) 29-35. (2008) S08001 S08003. [5] H. Raether, Z. Phys 112 (1939)[6] 464. T. Alexopoulos, et al.,A spark-resistant bulk-microme [7] T.Alexopoulos, et al., Development of large size Microm [8] L. Jones, APV25-S1: User guide version 2.2, RAL Microele [9] Scalable Readout System, https://espace.cern.ch/rd5 [2] LHC Collaboration, The CERN Large Hadron Collider : Acce [3] ATLAS Collaboration, The ATLAS Experiment at the CERN La [4] ATLAS Collaboration, ATLAS New Small Wheel TDR, CERN-LHC [1] Y. Giomataris, P. Rebourgeard, J.P. Robert and G.Charpa References Development of large size Micromegas