Fourth International Conference on « New developments in photodetection » Beaune, France, 19-24 June 2005

• Getting started • List of participants – Official photo • Oral presentations • Poster Sessions – Best poster awards • Photos from the conference • Sponsorship • Exhibitors – List of participants - Photos

See also http://beaune.in2p3.fr

Fourth International Conference on « New developments in photodetection » Beaune, France, 19-24 June 2005

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Fourth International Conference on « New developments in photodetection » Beaune, France, 19-24 June 2005

PARTICIPANTS LIST

Title Name Surname Institut Country email Mr. Aicher Klaus-Peter HAMAMATSU PHOTONICS Deutschland Germany Dr. Akindinov Alexander ITEP Russia [email protected] Dr. Alexey Stoykov Paul Scherrer Institut Switzerland [email protected] Mr. Alibert Claude CEM2 France [email protected] Mr. Appleby Graham Victoria University of Wellington, New Zealand New zealand [email protected] Dr. Arisaka Katsushi UCLA, Department of Physics and Astronomy USA [email protected] Mr. Atac Muzaffer Fermilab USA [email protected] Mr. Bar Doron Soreq NRC Israel [email protected] Dr. Barbi Mauricio University of Regina Canada [email protected] Mr. Barnyakov Mikhail The Budker Institute of Nuclear Physics Russia [email protected] Mr. Barriere Nicolas CESR France [email protected] Mr. Basset Marco INFN - sezione di Trieste (ITALY) Italy [email protected] Pr. Bazarko Andrew Princeton University USA [email protected] Dr. Ben-dov Yair Negev Nuclear research center Israel [email protected] Dr. Bennati Paolo University of Rome "La Sapienza" Italy [email protected] United Dr. Bergonzo Philippe CEA-LIST kingdom [email protected] Mr. Bernard Frédéric Saint Gobain Cristaux France [email protected] Mr. Billot Nicolas CEA-Saclay/SAp UMR-AIM France [email protected] Mr. Birkel Marc HAMAMATSU France Mr. Blanco Alberto LIP - Coimbra Portugal [email protected] Dr. Blazej Josef Czech Technical University in Prague Czech republic [email protected] Mr. Bordessoule Michel Synchrotron Soleil France [email protected] Dr. Borrel Véronique CESR France [email protected] Mr. Bosch Léon PHOTONIS-DEP Netherlands [email protected] Mr. Bourgeois Philippe CEA/DSM/Dapnia France [email protected] Dr. Bourgoin Jacques c. GESEC R&D France [email protected] Pr. Breskin Amos Weizmann Institute of Science Israel [email protected] Mr. Britvitch Ilia ETH, Zurich Switzerland [email protected] The Mr. Bruijn Ronald Nikhef/UvA netherlands [email protected] Mr. Buzhan Pavel MEPHI Russia [email protected] Mr. Buzzi Christophe EADS SODERN France [email protected] Pr. Camin Daniel v. Physics Department of the University and INFN Italy [email protected] Mr. Castay jérome OPTOPRIM France Mr. Castera Alain I.P.N.L. France [email protected] Dr. Chakraborty Dhiman Northern Illinois University USA [email protected] United Mr. Chamonal Reinhardt University of Edinburgh kingdom [email protected] Mr. Chandraeskharan Rico ETH Zurich (Swiss Federal Institute of Technology) Switzerland [email protected] Dr. Chechik Rachel Weizmann Institute of Science Israel [email protected] United Dr. Cheung Jessica National Physical Laboratory kingdom [email protected] Mr. Courrech Jean luc CESR / GIATHE France [email protected] Dr. Couture Aaron GE Global Research USA [email protected] Mr. Dautremer Thomas CEA/Saclay France [email protected] Dr. De la taille Christophe in2p3/LAL Orsay France [email protected] Mr. De sio Antonio Department of Astronomy and Space Science Italy [email protected] Mr. Deiters Konrad PSI Switzerland [email protected] Mr. Delagnes Eric CEA DAPNIA France [email protected] Mr. Depasse Pierre IPN Lyon France [email protected] Mr. Di Mario Gianni Caen Italy Mrs. Dinu Nicoleta Istituto Nazionale di Fisica Nucleare Italy [email protected] Mr. Dirks Bob CEA/DSM/DAPNIA Service d'Astrophysique Saclay France [email protected] Pr. Dolgoshein Boris Moscow Engineering and Physics Institute Russia [email protected] Mr. Dornic Damien IPN d'Orsay France [email protected] Ms. Doyeux Kaya SPP/DAPNIA CEA SACLAY France [email protected] Dr. Drobychev Gleb Institute for Nuclear Problems Belarus [email protected] Dr. Dussoni Simeone INFN and university of Genoa Italy [email protected] Mr. Errando Manel IFAE (Barcelona) Spain [email protected] Mr. Farr William Jet Propulsion Laboratory USA william.farr@jpl.nasa.gov Mr. Faure Jean-louis Saclay DAPNIA-SPP Switzerland [email protected] Pr. Ferenc Daniel University of California Davis USA [email protected] United Mr. Ferguson Ian Photek Limited kingdom [email protected] Mr. Ferrero Andrea Dip. di Fisica Generale "A. Avogadro" and I.N.F.N. - Torino Italy [email protected] Dr. Finocchiaro Paolo INFN-LNS Italy [email protected] Dr. Fitzgerald Carrie Naval Research Laboratory USA [email protected] Mr. Fontaine Christophe PHOTONIS France Mr. Forot Michael Service d'Astrophysique CEA Saclay France [email protected] Dr. Frach Thomas Philips Research Laboratories Germany [email protected] Mr. Francois Moreau IN2P3 - LLR France [email protected] Mr. Gaglione Renaud Laboratoire de Physique Corpusculaire France [email protected] Mr. Gambicorti Lisa Department of Astronomy and Space Science Italy [email protected] Mr. Genolini Bernard IPN Orsay France [email protected] Dr. Gevin Olivier CEA/DAPNIA France [email protected] Mr. Gharbi Mohammed Alimtronic France Pr. Godinovic Nikola University of Split Croatia [email protected] Dr. Goret Philippe DSM/DAPNIA/SAp France [email protected] Dr. Gorodetzky Philippe APC - College de France France [email protected] Mr. Guerin Daniel PHOTONIS France Dr. Guyonnet Jean-louis IReS/IN2P3 France [email protected] Mr. Gys Thierry CERN Switzerland [email protected] Dr. Hanson Kael University of Wisconsin - Madison USA [email protected] Mr. Hayashida Masaaki Max-Planck-Institute for Physics Germany [email protected] Dr. Herbert Deborah INFN Pisa Italy [email protected] Mr. Hermann German Max-Planck-Institut fuer Kernphysik Germany [email protected] Mr. Hermel Richard IN2P3 / LAPP France [email protected] United Dr. Hobson Peter Brunel University kingdom [email protected] Mr. Horeau Benoît CEA Saclay DAPNIA/SAP France [email protected] Mr. Hota Yuji HAMAMATSU Japan Mr. Houmani El mamouni IPN LYON France [email protected] Dr. Isenhower Donald Abilene Christian University USA [email protected] Dr. Ivantchenko Vladimir CERN Switzerland [email protected] Pr. Jackman Richard a. University College London France [email protected] Dr. Jaeger Jean-jacques APC / IN2P3 France [email protected] Dr. Jarron Pierre CERN Switzerland [email protected] Mr. Jeanneau Fabien CEA / DAPNIA France [email protected] Dr. Joram Christian CERN Switzerland [email protected] Pr. Kanno Ikuo Kyoto University Japan [email protected] Mr. Karakash Alexander MEPhI Russia [email protected] Mr. Karar Akli LLR Ecole Polytechnique France [email protected] United Dr. Kardynal Beata Toshiba Research Europe Ltd. kingdom [email protected] Mrs. Keters Marijke Canberra Semiconductor NV Belgium [email protected] Mr. Kim Min suk Dept.of Electronics & Information Engineering, Korea Univ. Korea [email protected] Mr. Klemin Sergey PULSAR Russia [email protected] Pr. Kooijman Paul NIKHEF Netherlands [email protected] Pr. Krizan Peter University of Ljubljana Slovenia [email protected] Mr. Krutov Al ATI USA [email protected] Mr. Le du Patrick CEA DAPNIA France [email protected] Dr. Lecomte Roger Université de Sherbrooke Canada [email protected] Mr. Li Yan CEA/DAPNIA/SEDI France [email protected] Dr. Limousin Olivier CEA SACLAY France [email protected] Dr. Linga Krishna Amplification Technologies Inc USA [email protected] Mr. Lorenz Edouard ETH ZÜRICH, Institut for Particle Physics Switzerland [email protected]; [email protected] Mr. Lubsandorzhiev Bayarto Institute for Nuclear Research RAS Russia [email protected] Mrs. Luengo Sonia La Salle, School of Engineering Spain [email protected] Mr. Luong Laurent HAMAMATSU PHOTONICS France France [email protected] Dr. Lutz Gerhard MPI Semiconductor Laboratory Germany [email protected] Mr. Lyashenko Alexey The Weizmann Institute of Science Israel [email protected] Mr. Maemonier Carole PHOTONIS France [email protected] Ms. Mañez Nuria LISIF, Université Pierre et Marie Curie France [email protected] Mr. Mangeot Philippe CEA/DSM/DAPNIA France [email protected] Dr. Mangin-brinet Mariane L.P.S.C. France [email protected] Mr. Mayer Markus HAMAMATSU PHOTONICS France - Swiss Sales Office Switzerland Mr. Mcclish Mickel Radiation Monitoring Devices, Inc. USA [email protected] Mr. Menard Laurent Institut de Physique Nucléaire d'Orsay France [email protected] Ms. Merck Christine Max-Planck-Institute for Physics Germany [email protected] Dr. Michalet Xavier Chemistry & Biochemistry Dpt/UCLA USA [email protected] Dr. Migdall Alan NIST USA [email protected] Dr. Mikulec Bettina University of Geneva Switzerland [email protected] [email protected]; Dr. Millaud Jacques Lawrence Livermore National Laboratory USA [email protected] Dr. Mirzoyan Razmick Max-Planck-Institute for Physics Germany [email protected] Mr. Montagne Jean François HAMAMATSU France Mr. Montarou Gérard Laboratoire de Physique Corpusculaire France [email protected] Dr. Mosca Luigi DSM / DAPNIA at CEA - Saclay France [email protected] Pr. Moszynski Marek Soltan Institute for Nuclear Studies Poland [email protected] Mr. Moussant Cyril PHOTONIS France Dr. Mozzanica Aldo Dipartimento di Chimica e Fisica - Università di Brescia Italy [email protected] Dr. Muller Hans CERN Switzerland [email protected] Mr. Musienko Yuri Northeastern University(Boston)/CERN Switzerland [email protected] Mr. Nakayama Hiroyuki University of Tokyo / Aihara-lab Japan [email protected] Dr. Nappi Eugenio INFN - Sezione di Bari Italy [email protected] Mr. Nedelec Patrick LAPP France [email protected] Mr. Neyret Damien CEA Saclay DAPNIA/SPhN France [email protected] Mr. Nguyen trung Thi Institut de Physique Nucléaire France [email protected] Mr. Otte Nepomuk MPI für Physik Germany [email protected] Pr. Paic Guy Instituto de Ciencias Nucleares UNAM Mexico [email protected] Pr. Pani Roberto University La Sapienza- Dept of Experimental Medicine Italy [email protected] Dr. Pegna Raffaello INFN Italy [email protected] Mr. Pellion Denis CESR/GIATHE France [email protected] Mr. Periale Luciano INAF - CERN Italy [email protected] Pr. Petrolini Alessandro University of Genova and INFN Italy [email protected] Mr. Philippe Rebourgeard CEA SACLAY France [email protected] Dr. Piccioli Alessio INFN Italy [email protected] Pr. Pignatel Giorgio UNIVERSITA' DI PERUGIA Italy [email protected] Mr. Plein Manfred Wiener Germany Mr. Popov Vladimir Jefferson Lab USA [email protected] Ms. Popova Elena Moscow Engineering and Physics Institute Russia [email protected] Dr. Prata Michele INFN - Sezione di Pavia Italy [email protected] Ms. Puill Véronique CNRS/In2p3/LAL France [email protected] Dr. Rabin Michael Los Alamos National Laboratory USA [email protected] Dr. Rappoport Vitaliy Siemens USA [email protected] Mr. Raux Ludovic LAL Orsay France [email protected] Ms. Reboli Anne CEA/DAM/DIF/DASE/SRCE/CA France [email protected] Mr. Reiche Soeren RADOS Germany [email protected] Mr. Renker Dieter Paul Scherrer Institute Switzerland [email protected] Dr. Reznik Alla Sunnybrook&Women’s College Health Sciences Centre Canada [email protected] Marie- Ms. Ricol charlotte IPN LYON France [email protected] Dr. Rocard Francis CNES France [email protected] Mr. Rochas Alexis Id Quantique Switzerland Dr. Rossella Massimo INFN - Sezione di Pavia Italy [email protected] Dr. Rozsa Csaba Saint-Gobain Crystals USA [email protected] Mr. Ryu Jun seok Dept.of Electronics & Information Engineering, Korea Univ. Korea [email protected] Mr. Sadygov Ziraddin Joint institute for nuclear recearch Russia [email protected] Pr. Saveliev Valeri Obninsk State University Russia [email protected] Dr. Schanne Stéphane CEA Saclay, DSM/DAPNIA/SAp France [email protected] Mr. Scheu Simon Physik-Institut Switzerland [email protected] Dr. Sefkow Felix DESY Germany [email protected] Pr. Seliverstov Dmitry Petersburg Nuclear Physics Institute Russia [email protected] Dr. Sellai Azzouz Physics Dept, Sultan Qaboos University Oman [email protected] Dr. Shibamura Eido Saitama Prefectural University Japan [email protected] Dr. Singovski Alexander University of Minnesota Switzerland [email protected] Mr. Stassi Patrick LPSC France [email protected] Paul Scherrer Institut/Laboratory for Muon Spin Dr. Stoykov Alexey Spectroscopy Switzerland [email protected] United Dr. Stubberfield Ron ETL kingdom Pr. Swain John Dept. of Physics, Northeastern University USA [email protected] Mr. Tanaka Takaaki ISAS / JAXA Japan [email protected] Pr. Tao Charling CPPM/IN2P3/CNRS et Université de la Méditerranée France [email protected] Dr. Tapan Ilhan Uludag University Turkey [email protected] Ms. Tarasova Oxana DESY Germany [email protected] Dr. Tardocchi Marco Department of Physics, Università di Milano-Bicocca Italy [email protected] United Mr. Tartoni Nicola Diamond Light Source kingdom [email protected] Dr. Tavernet Jean-paul LPNHE - Universite Paris 6 France [email protected] Mr. Thea Alessandro INFN and University of Genova, MPI Munich Italy [email protected] Dr. Thon Andreas Philips Research Laboratories Germany [email protected] Dr. Tokanai Fuyuki Yamagata Unviversity Japan [email protected] Jean- Mr. Trama christophe CEA/Saclay France [email protected] Mr. Valle Riccardo National Institute of Nuclear Physics Italy [email protected] Dr. Vallerga John Space Sciences Laboratory USA [email protected] Dr. Vanel Jean-charles LLR / IN2P3 France [email protected] Dr. Vartsky David Soreq NRC Israel [email protected] Mr. Vert Pierre-etienne Laboratoire de Physique Corpusculaire France [email protected] Dr. Verzellesi Giovanni INFM and University of Modena and Reggio Emilia Italy [email protected] Mr. Veziant Olivier LPSC France [email protected] Mr. Vogel Wilfried HAMAMATSU France Dr. Watanabe Shin ISAS/JAXA Japan [email protected] United Mr. Wright Tony Electron Tubes Ltd kingdom [email protected] Dr. Wyllie Kenneth CERN Switzerland [email protected] United Mr. Yaselli Ignacio Brunel University kingdom [email protected] Mr. Yoshizawa Yuji HAMAMATSU PHOTONICS K.K Japan Mr. Yvernault Philippe FEMLIGHT France [email protected] Pr. Ziemons Karl Research Center Juelich / ZEL Germany [email protected]

Fourth International Conference on « New developments in photodetection » Beaune, France, 19-24 June 2005

Posters Sessions

Poster Session I - PMT+HPD+APD

PI-2 Shibamura Eido Photon-to-electron conversion efficiency and reflectance of photomultiplier tubes as a function of incidence angle of photon PI-3 Bazarko Andrew Photomultiplier tubes in the MiniBooNE experiment

PI-4 Rossella Massimo Behaviour in High Magnetic Fields of Fine-mesh Photodetectors for Fast Time-of-flight detectors PI-5 Bruijn Ronald Alternative to large PMTs in underwater neutrino telescopes: An array of small tubes PI-6 Ferenc Daniel The ReFerence Flat-Panel Photon Detector

PI-7 Genolini Bernard A 0.35 µm CMOS Large Dynamic Gain Amplifier for Fast Signal Digitization PI-8 Hanson Kael The design of the icecube digital optical module Tarasova Oxana Production and Testing of Digital Optical Modules (DOMs) for the IceCube Experiment PI-10 Pegna Rafaello The DRS DAQ: a Low Power Digitizing System in the GHz Range

PI-11 Rossella Massimo Performance and behaviour of photomultiplier tubes at cryogenic temperature PI-12 Yaselli Ignacio Simulation of the time response of a vacuum phototriode in a magnetic field and a comparison with experimental data Part 1 & Part 2 PI-13 Mirzoyan Razmick Very High Quantum Efficiency PMTs with Bialkali Photocathode

PI-15 Errando Manel Ageing studies on hybrid photodiodes with Cs activated GaAsP photocathode PI-16 Lubsandorzhiev Baryato Some historical issues of photomultiplier tube invention

PI-17 Blazej Josef Gallium based avalanche photodiode optical crosstalk

PI-18 Depasse Pierre Final calibration results of CMS electromagnetic calorimeter photodetectors

PI-19 Stoykov Alexey Avalanche micro-pixel photodiodes with surface drift of charge carries The use of avalanche microchannel photodiodes in a scintillating fiber muon beam profile monitor PI-20 Swain John Multipixel Geiger-mode avalanche photodiodes with high quantum efficiency and low excess noise factor PI-21 Borrel Veronique APD detectors for biological fluorescence spectroscopy

PI-23 Brivitch Ilia Recovery time of the Gieger mode Avalanche Photodiodes

PI-24 Lecomte Roger Performance of Recent Avalanche Photodiodes with Phoswich Detectors for High-Resolution Positron Emission Tomography PI-25 Muller Hans Front end electronics for PWO-based PHOS calorimeter of ALICE

PI-26 Tapan Ilhan A ZnS-Si isotype hetero-junction avalanche photodiode structure for scintillation lights detection PI-27 Merck Christine Timing Properties of an Avalanche Diode for Single Photon Counting PI-28 Renker Dieter Investigation of a Photon Counting Avalanche Photodiode from Hamamatsu Photonics PIII-16 Manez Nuria Material optimization for X-ray Imaging detectors

PIII-14 Verzellesi BJT-based detector on high-resistivity silicon with integrated Giovanni biasing structure

Poster Session II - MAPMT + MCPMT

PII-1 Ménard Laurent Intraoperative beta probe for brain tumor surgery

PII-2 Drobychev Gleb Studies of the aluminum oxide based microchannel plates

PII-4 Ferguson Ian Picosecond Time Response of Microchannel Plate PMT Detectors

PII-5 Pani Roberto Lanthanum scintillation crystals for gamma ray imaging Performance measurements of a compact scintillation camera based on multiPSPMT read-out PII-6 Basset Marco MGR: an innovative, compact and low-cost cosmic ray tracking detector PII-7 Chamonal Reinhardt Performance of 8-stage and 12-stage Multianode Photomultipliers

PII-8 Gambicorti Lisa Optical adapters to improve the collection efficiency of the Multi- Anode PhotoMultipliers detectors PII-9 Luengo Sonia SPD Very Front End Electronics

PII-12 Mozzanica Aldo Design, Simulation and Prototype Results of the FAST Detector : an Innovative Scintillating Fiber Tracker PII-13 Popov Vladimir A Novel Readout Concept for Multianode Photomultiplier Tubes with Pad Matrix Anode Layout PII-14 Veziant Olivier Tests of the AMS RICH prototype with secondary ions at CERN

PII-15 Hermel Richard Front End electronics for calorimetry in space

PII-19 Rowland-Fitzgerald Carrie Gamma-ray Imaging with Position Sensitive Silicon Detectors

PII-20 Schanne Stephane The ECLAIRs micro-satellite for gamma-ray bust multiwavelength observations PII-21 Barriere Nicolas MAX, a space borne gamma ray telescope for nuclear astrophysics based on a Laue diffraction lens PII-23 Tardocchi Marco Comparison of Cadmium-Zinc-Telluride semiconductor and Yttrium-Aluminum-Perovskite scintillator as photon detectors for epithermal neutron spectroscopy PII-24 Kim Min Suk Comparison of measured backscatter factors with Monte Carlo simulations for low energy x-ray PII-25 Scheu Simon Studies on wrapping materials and light collection geometries in plastic scintillators PII-26 Trama Jean-Christophe ADONIS: a new digital signal processing concept for HpGe gamma spectrometry PII-27 Limousin Olivier Simbol-X: a formation flying mission for hard X-ray astrophysics

Poster Session III - SiPM + Solid State + Gas

PIII-1 Karakash Alexander Timing by silicon photomultiplier: a possible application for TOF measurements PIII-2 Herbert Deborah The Silicon Photomultiplier as a photodetector for scintillator applications PIII-3 Otte Nepomuk Using Silicon Photomultipliers in Astrophysics

PIII-9 Kim Kwang Design of Pixellated Scintillator on PIN type Photodiode Hyun for Digital Mammography PIII-10 Bergonzo Philippe Synthetic diamond devices for radiotherapy dosimetry applications

PIII-12 Pignatel Giorgio An improved PIN photodetector with integrated JFET on high- resistivity silicon PIII-13 Vartsky David An efficient, large-area fast-neutron imaging & timing detector

PIII-18 Sellai Azzouz Effect of Temperature and Inhomogeneity on the Yield of PtSi-n-Si Photodetectors

PIII-21 Appleby Graham New Oxychloride Glass-Ceramic X-ray Storage Phosphors

PIII-22 Bordessoule A fast gaseous integrating detector for small angle X-ray scattering Michel chemical kinetic experiment at SOLEIL PIII-23 Tokanai Fuyuki Developments of Imaging Capillary Plate Gas Detector

PIII-24 Periale Luciano A Study of the Operation of Specially Designed Photosensitive Gaseous Detectors at Cryogenic Temperatures PIII-25 Prata Michele Development of gas avalanche photodetector operating at cryogenic temperature PIII-26 Lyashenko A Advances in gaseous photomultipliers for the visible spectral range

Fourth International Conference on « New developments in photodetection » Beaune, France, 19-24 June 2005

Oral Presentations

Sunday, June 19

15:00- Registration 15:40

15:40- Tutorial Interaction Particle Matter V. Ivanchenko 17:10 40'+10'+40' Part 1 & Part 2

17:10- Tutorial Photodetection P. Mangeot 18:50 40'+10'+40'

Monday, June 20

Tutorial Electronics C. De la Taille 08:50-10:10

10:10-10:40 Coffee break

10:40-11:00 Conference Opening P. Bourgeois

11:00-11:40 General talk Mars exploration F. Rocard

11:40-12:20 General talk Astrophysics E. Lorenz

12:20-14:00 Lunch

14:00-14:40 General talk Medical/Bio R. Lecomte

14:40-15:20 Review talk Review on gaseous photomultipliers A. Breskin

Session 15:20-15:40 PMT Photoelectron backscattering in vacuum phototubes B. Lubsandorzhiev

15:40-16:10 Coffee, Poster I & Exhibition

16:10-16:30 R&D of microchannel plate phototubes M. Barnyakov

17:10-17:30 Fast Time Response PMT series Y. Yoshizawa Session PMT 17:30-17:50 New Photonis XP20D0 photomultiplier for fast timing in M. Moszynski nuclear medicine

18:20 Departure for the Welcome Coktail@Hospices de Beaune 19:30 GROUP PHOTO, then DRINK

Tuesday, June 21

08:30-08:50 Recent Advances of Planar Silicon APD Technology M. McClish

08:50-09:10 APD photodetectors in the Geiger photon counter mode V. Pellion

09:10-09:30 Application of avalanche photodiodes for the measurement A. Reboli Session APD of actinides by alpha liquid scintillation counting

Detection of DUV Light at High Quantum Efficiency with 09:30-09:50 R. Chandrasekharan Large Area Avalanche Photodiodes (LAAPDs)

CMOS-based single photon detectors and potential 09:50-10:10 A. Rochas applications 10:10-10:40 Coffee, Poster I & Exhibition

10:40-11:20 Review talk Review on SiPM D. Renker Resent Development and Study of Silicon Photomultiplier 11:20-11:40 V. Saveliev (SiPM)

11:40-12:00 Session The gain, photon detection efficiency and excess noise Y. Musienko SiPM factor of multipixel Geiger-mode avalanche photodiodes

12:00-12:20 Test and acceptance procedures for large-scale batches of E. Popova Silicon Photomultipliers

12:20-14:00 Lunch

14:00-14:30 Poster I & Exhibition

14:30-14-50 The SAM GHz Sampling chip for the HESS 2 experiment E. Delagnes Session PMT Characterisation of improved photocathode in large 14:50-15:10 D. Dornic hemispherical photomultiplier 15:10-15:30 Ground-based photon counting optical detection for the W. Farr Session 2010 Mars Laser Communications Demonstration 15:30-15:50 Others Development of GaN photocathodes for UV detectors J. Vallerga

15:50-16:20 Coffee, Poster I & Exhibition

The quantum efficiency of photo-charge generation in a-Se 16:20-16:40 A. Reznik avalanche photodetectors Session Others 16:40-17:00 Very high position resolution gamma imaging with A. Blanco Resistive Plate Chambers

17:00-19:00 Round table (Yoshizawa / Pierlot / Stubberfield / Reiss) E. Lorenz

20:00-23:59 Fête de la Musique in Beaune/France

Wednesday, June 22

08:40-09:00 Detecting photons - properties and challenges J. Cheung

09:00-09:20 Fast read-out of the COMPASS RICH CsI-MWPC chambers using APV25 D. Neyret amplifier chips Session Others

09:20-09:40 Transmission of analogue signals over fiber optics using the optically- D. Camin coupled current-mirror architecture

09:40-10:10 Photo-Sensors for UHECR observation from space A. Petrolini

10:10-10:40 Coffee, Poster II & Exhibition

Session A noiseless kilohertz frame rate imaging detector based on microchannel 10:40-11:00 Others B. Mikulec plates read out with the Medipix2 CMOS pixel chip

11:00-11:20 Design and status of COMPASS FAST-RICH A. Ferrero

11:20-11:40 Multi-anode PMT readout: OPERA_ROC and its relatives... C. de La Taille Session MAPMT 11:40-12:00 An Application Specific Integrated Circuit for Multi Anodes PMT R. Gaglione

12:00-12:20 Tests of the Burle 85011 64-anode MCP PMT as a detector of Cherenkov P. Krizan photons

12:20-14:00 Lunch

14:00-14:40 Poster II & Exhibition

14:40-15:00 Development of Avalanche-Drift and Avalanche-Pixel Detectors for Single G. Lutz Photon Detection and Imaging in the Optical Regime

15:00-15:20 Session Pixel Photon-Counting H33D Detector for Biological Fluorescence Imaging X. Michalet

15:20-15:40 Recent achievements on the HERSCHEL/PACS bolometer arrays N. Billot

15:40-16:10 Coffee, Poster II & Exhibition

16:10-16:30 IDeF-X v1.0: a new sixteen-channel low noise analogue front-end for O. Gevin Cd(Zn)Te detectors

16:30-16:50 Automatic mapping of the leakage current in pixelated CdZnTe and CdTe B. Dirks detectors

Session 16:50-17:10 CdTe Development of CdTe Pixel Detectors for Compton Cameras S. Watanabe

17:10-17:30 Energy Subtraction Method with Filtered X-ray for the Detection of I. Kanno Contrast Media

Data analysis and performances of Compton coded mask telescopes: 17:30-17:50 M. Forot application to the Integral/IBIS telescope

17:50-18:50 Winery visit Thursday, June 23

08:30-08:50 Development of HPDs for applications in physics and medical C. Joram imaging 08:50-09:10 The Novel Light Amplifier Concept D. Ferenc

09:10-09:30 Development of a 13-inch HAPD for a next generation water H. Nakayama Session HPD Cherenkov detector 09:30-09:50 Production of 500 Pixel Hybrid Photon Detectors for the T. Gys RICH counters of LHCb Development of HPDs with a 18-mm-diameter GaAsP 09:50-10:10 photocathode and an avalanche diode anode for the MAGIC- M. Hayashida II telescope 10:10-10:40 Coffee, Poster III & Exhibition

10:40-11:00 Session HPD The front-end electronics of the LHCb Ring-Imaging- K. Wyllie Cherenkov system 11:20-11:40 Diamond based photoconductors for deep UV detection A. De Sio

11:40-12:00 Diamond UV photoconductive devices: high gain, high speed R. Jackman and solar-blind 12:00-12:20 UV photorepsonse and electrical properties of diamond p-n P. Bergonzo junctions 12:20-14:00 Lunch

14:00-14:40 Poster III & Exhibition

14:40-15:00 Studies of silicon photodetectors for hadron calorimetry at the D. Chakraborty next electron-positron linear collider Three advanced designs of avalanche micro-pixel Z. Sadygov 15:00-15:20 Session SiPM photodiodes: their present status, maximum possibilities and limitations High-efficiency and low noise scintillation detector for A. Akindinov 15:20-15:40 ionizing particles START (scintillation Tile with MRS APD Light ReadouT) 15:40-16:10 Coffee, Poster III & Exhibition

16:10-16:30 Large area silicon photomultipliers: performance and B. Dolgoshein applications 16:30-16:50 Session SiPM A new generation of low-voltage single photon micro-sensors P. Finocchiaro with timing capability 16:50-17:10 Solid State Photomultipliers for Photon Counting A. Muzaffer

17:10-17:50 Review talk RICH04 a summary G. Paic

17:50 Conference Dinner

Friday, June 24

08:50-09:30 Overview Photon Counting Detector Metrology Efforts at NIST A. Migdall

09:30-09:50 Superconducting photon detectors for quantum information A. Migdall applications

Session SPE Single photon detectors based on quantum dot field effect 09:50-10:10 transistors – from principle of operation to single photon B. E. Kardynal counting

10:10-10:40 Coffee, Poster III & Exhibition

10:40-11:20 Review talk Conference Summary K. Arisaka

P. Bergonzo 11:20-12:00 Review talk Ruffignac’s Mammouth (Chambellan)

12:00-12:20 Conference Closing P. Nédélec

12:20-14:00 Buffet

TALKS SESSION 1

PMT Review talk

Review on gaseous photomultipliers

A. Breskin

Department of Particle Physics, The Weizmann Institute of Science, Particle Physics Department, 76100 Rehovot, Israel Email: [email protected]

- 2 - Photoelectron backscattering in vacuum phototubes

B.K Lubsandorzhiev, R.V. Vasiliev, Y.E. Vyatchin

Institute for Nuclear Research RAS, pr-t 60-letiya Oktyabrya 7A, 117312 Moscow, Russia Email: [email protected]

In this article we describe the results of extensive studies of photoelectron backscattering effect in vacuum phototubes: classical photomultipliers (PMT) and hybrid phototubes (HP) - hybrid photodiodes (HPD) or phototubes with luminescent screens. Vacuum phototubes are used widely in an overwhelming majority of experiments in astroparticle and high energy physics where precision timing plays a crucial role. The late pulses occurring in PMTs and HPs are attributed to photoelectron backscattering and distinguished from afterpulses. The late pulses are measured in a number of PMTs and HPs with various photocathode sizes covering 1-50 cm range and different types of dynode materials and construction designs. It's shown that late pulses constitute about 3-5% of total single photoelectron response of PMTs. It is demonstrated also that late pulses are general features of all vacuum photodetectors - PMTs and PHs. Anode afterglow effect and its influence on PMT timing were studied too.

- 3 - R&D of microchannel plate phototubes

A.Yu. Barnyakov, M.Yu. Barnyakov, V.S. Bobrovnikov, A.R. Buzykaev, D. Cygankov, S.A. Kononov, E.A. Kravchenko, A.P. Onuchin, V.A. Rodiakin

Budker Institute of Nuclear Physics, Acad. Lavrentiev prospect 11, 630090 Novosibirsk, Russia Email: [email protected]

PMTs based on microchannel plate (MCP) are used in Cherenkov ASHIPH counters of the KEDR detector [1,2]. These PMTs are manufactured in Novosibirsk. We have investigated stability of PMT parameters during 3 years [3].

New design of PMT has been developed. Now we use MCP with 6mkm channel diameter versus 8mkm diameter used before. That decreases the sensitivity of PMT to magnetic field. The gap between photocathode and MCP has been increased from 0.2 to 0.7mm. That allows to supply much higher voltage on the gap and to achieve higher collection efficiency for PMT with the photocathode protection.

The comparison of properties of “new” and “old” designs was performed.

Two options of 'new' design are manufactured: PMT with the thin Al layer on MCP entrance which prevents the bombardment of photocathode by feedback ions and PMT without it [4].

Aging of both MCP PMT designs was studied [4]. The influence of the prevention layer on photocathode lifetime and collection efficiency of photoelectrons was investigated.

The measurement of absolute collection efficiency has been performed.

[1] A.R.Buzykaev, et al., "Aerogel Cherenkov counters with wavelength shifters and micro-channel plate photo-tubes", Journal of Non-Crystalline Solids 225(1998)381

[2] M.Yu.Barnykov, et al., "Development of aerogel Cherenkov counters with wavelength shifters and phototubes", Nucl. Instr. and Meth. A419(1998)584

[3] A.Yu.Barnyakov, et al., "The status of the KEDR ASHIPH system", Nucl.Instrum.Meth. A518(2004)597

- 4 - [4] M.Yu.Barnyakov, et al., "Aerogel Cherenkov counters for the KEDR detector", Nucl. Instr. and Meth. A453(2000)326

- 5 - The SAM GHZ-Sampling Chip for the HESS 2 experiment

E. Delagnes, Y. Degerli, P. Goret, P. Naymann, F. Toussenel

CEA/DAPNIA, CE SACLAY. BAT141, 91191 Gif sur yvette, France Email: [email protected]

The HESS-2 front-end electronics, with its 20 GeV energy threshold, will require a much higher acquisition rate capability and a larger dynamic range than was relevant for HESS-1. These constraints led to the development of a new ASIC, called SAM for Swift Analog Memory, to replace the ARS used for HESS-1. The SAM chip features 2 channels for the low/high gain outputs of a PMT, each channel having a depth of 256 analog memory cells. The sampling frequency is adjustable from 0.7GS/s up to 2GS/s and the read-out time for one event is decreased from 275 microsecs down to 2.3 microsecs. The input bandwidth and dynamic range are increased up to 300 MHz and 12 bits respectively. We expect that ADC's will be ultimately implemented on the chip. The first prototypes of the SAM chips have been produced and are under testing, preliminary results will be given.

- 6 - Characterisation of improved photocathode in large hemispherical photomultiplier

1 1 1 1 D. Dornic , B. Genolini , T. Nguyen Trung , J. Pouthas , C. Moussant2

1Institut de Physique Nucléaire, IN2P3-CNRS, Université Paris-Sud d'Orsay, 91406 Orsay Cedex, France 2Photonis, Avenue Roger Roncier, 19106 Brive La Gaillarde, France Email: [email protected]

This document presents a study about improved photocathode on large hemispherical photomultiplier (PMT) for astroparticle and neutrino experiments. Photonis has developed a new photocathode process to improve quantum efficiency. The process has been applied on some samples of XP1805, the 9 inches PMT used in the AUGER experiment. Those samples were compared to the standard AUGER PMT production. The current measurements of the photocathode sensitivity were performed in the blue domain (standard Corning blue). They show a mean improvement of around 20%.

On spring 2005, it is planed to confirm those results by comparative measurements of the relative detection efficiency on a sample of new and standard photomultipliers XP1805. Other measurements will be performed in order to determine if the new process could have drawback effects on important parameters such as noise and afterpulses. The noise level and the noise rate decay time after exposure (dazzling effect) will be investigated. The main afterpulses characteristics (the counting rate, timing and amplitude distributions) will be also compared for some new and standard XP1805 photomultipliers.

- 7 - Fast Time Response PMT series

Y. Yoshizawa

Hamamatsu Photonics, 314-5, Shimokanzo, 438-0193 Iwata, Japan Email: [email protected]

Hamamatsu Photonics developed new PMTs, which have fast time response. It includes 1 inch and 2 inch PMTs. These are suitable for applications, which need fast timing resolution, such as TOF counter in HEP experiment and PET (Positron Emission Tomography) in medical instrument. Both PMTs were designed by our computer simulation technology while taking into account of simple PMT configuration, which can lead to easy assembling and production of the PMTs. The fast time response is key parameter for those PMTs. We confirmed that typical TTS (Transit Time Spread) of 1 inch and 2 inch PMTs are about 270 ps and 250 ps, respectively. These values are almost the best ones among the conventional PMTs. Other preliminary test results are shown in the presentation.

- 8 - New Photonis XP20D0 photomultiplier for fast timing in nuclear medicine

M. Moszynski1, M. Gierlik1, M. Kapusta1, A. Nassalski1, T. Szczesniak1, Ch. Fontaine2, P. Lavoute2

1Soltan Institute for Nuclear Studies, Swierk, PL 05-400 Otwock, Poland 2Photonis. Av. Roger Roncier, B.P. 520, F 19106 Brive La Gaillarde Cedex, France Email: [email protected]

Growing interest in the time-of-flight positron emission tomography (TOF PET) prompts the study of a new Photonis XP20D0 photomultiplier, equipped with a screening grid at the anode, in application to a fast timing with LSO and LaBr3 crystals. The importance of the grid and a high quantum efficiency of the XP20D0 are discussed, which allows getting time resolution of 230 ps and 200 ps for 511 keV annihilation quanta with LaBr3 and LSO crystals, respectively. A high time resolution observed with LSO makes good prospects to its application in TOF PET.

- 9 - TALKS SESSION 2

APD

- 10 - Recent Advances of Planar Silicon APD Technology

M. McClish1, R. Farrell1, R. Myers1, F. Olschner2, G. Entine1, K. S. Shah1

1Radiation Monitoring Devices Inc., 44 Hunt Street, Watertown, MA 02472, USA. 2Cremat Inc., Watertown, MA 02472 USA Email: [email protected]

Radiation Monitoring Devices previously reported to have fabricated, using a planar process, silicon avalanche photodiodes (APDs) and position sensitive APDs (PSAPDs) that can be used for direct or scintillation based spectroscopic and imaging applications. We have developed high gain (~1000), high quantum efficiency (40 – 70% in the 200 to 900 nm region), relatively low noise, and magnetically insensitive APDs up to 45 cm2 in area and PSAPDs up to 1 cm2 in area. Since initially reported, these detectors have begun to be implemented in applications such as positron emission tomography (PET) and single photon emission computerized tomography (SPECT) for medical imaging, high-energy physics experiments as water Cherenkov detectors and liquefied noble gas calorimeters, and receivers for long-range optical communication at near infrared (IR) wavelengths. Also, our PSAPDs have been combined with photocathode structures, similar to a photomultiplier tube (PMT), to fabricate hybrid devices. Here we present a small review and a sample of results showing various applications utilizing our planar processed APDs and PSAPDs.

- 11 - APD photodetectors in the Geiger photon counter mode

V. Borrel

GIATHE/CESR, 9 av Colonel Roche BP 4346, 31029 Toulouse cedex, France Email: [email protected]

The best detector in cerenkov experiments still remains the PM tube, thanks to its characteristics of sensitivity and speed. But its disadvantages are its low quantum efficiency and its costs.

We are currently exploring the field of solid state silicon detectors, used in the geiger photon counter mode. We have conducted a series of tests using standard APD, but with an electronic circuitry to rise the polarisation towards the Geiger mode. Thus, we have measured gains around 10 E+4.

With our current devlopments, both in command circuitry and in the geometry of the photodetector itself, we should reach values such as 10 E+6 for the gain and 80 percent for the quantum efficiency. As the photodiode is polarized over its own breakdown bias, a single photon passing through it may start an electron avalanche resulting in about 10 E+6 electrons collected. After that, the diode should recover as soon as possible to be available for the next photon.

This process is under modelling: electrical diagrams (PSPICE), differential equations(VHDL AMS) and components physics equations (SABER) are needed to reproduce closely the physical processes and to allow optimisation and improvment of the electronics both for triggering and for reading the detectors. Our most promissing results will be presented.

- 12 - Application of avalanche photodiodes for the measurement of actinides by alpha liquid scintillation counting

A. Reboli1, J. Aupiais1, J.C. Mialocq2

1CEA Bruyères-le-Châtel, Département Analyses et Surveillance de l’Environnement, BP 12, 91680 Bruyères-le-Châtel, France 2CEA Saclay, DSM/DRECAM/SCM/URA 331 CNRS, 91191 Gif-sur-Yvette Cedex, France Email: [email protected]

Alpha emitters analysis using liquid scintillation spectroscopy is often used when sensitivity and fast samples preparation are the important points. A more extensive use of this technique is until now limited by its poor resolution compared to alpha particle spectroscopy with semiconductor detectors[1]. To improve the resolution and thus promote this method for the measurement of actinides in environment, we have tested silicon avalanche photodiodes (APD) as new detectors for scintillation photons.

The set-up consists of a large area avalanche photodiode (16 mm diameter) coupled to a thin vial containing alpha-emitters within a liquid scintillation cocktail. After optimization of several parameters like bias voltage, temperature, counting geometry and composition of the scintillating cocktail, energy resolutions have been found to be better than those obtained with standard photomultiplier tubes (PMT): 5% (200 keV FWHM) for Th232 and 4.2% (240 keV FWHM) for Pu236. Our results show that the improvement is due to less fluctuations associated with light collection since the spatial response of APDs is more uniform than that of PMTs [2]. The expected gain on quantum efficiency (80% for APDs instead of 25% for PMTs) is nullified by a corresponding increase on electronic noise and excess noise factor.

Significant better results are foreseen by using green scintillators (450-550 nm wavelengths region) with larger Stokes-shift and blue-enhanced APDs which reache their maximum quantum efficiency in this region.

[1] G.T.Cook, C.J.Passo Jr. and B.Carter, Handbook of radioactivity analysis, Second edition, Elsevier/Academic Press, 2003

[2] B.Koren and M.Szawlowski, Laser Focus World, 1998

- 13 - Detection of DUV Light at High Quantum Efficiency with Large Area Avalanche Photodiodes (LAAPDs)

R. Chandrasekharan

Institute for Particle Physics, ETH Zurich, ETH Hoenggerberg, HPK F 25, CH-8093 Zurich, Switzerland Email: [email protected]

Large Area Avalanche Photodiodes (LAAPDs) were used for a series of systematic measurements of the scintillation light in Ar, Kr, and Xe gas. Absolute quantum efficiencies are derived. Values for Xe and Kr are consistent with those given by the manufacturer. For the first time we show that argon scintillation (128 nm) can be detected at a quantum efficiency above 40$\%$. Low-pressure argon gas is shown to emit significant amounts of non-UV radiation. The average energy expenditure for the creation of non-UV photons in argon gas at this pressure is measured to be below 378 eV.

See also Detection of noble gas scintillation light with large area avalanche photodiodes (LAAPDS) By R. Chandrasekharan, M. Messina, A. Rubbia (Zurich, ETH),. Dec 2004. 16pp. e-Print Archive: physics/0412155

- 14 - CMOS-based single photon detectors and potential applications

A. Rochas, A. Pauchard, O. Guinnard, L. Monat, and A. Matteo

IdQuantique, Chemin de la Marbrerie 3, 1227 Carouge-geneve, Switzerland Email: [email protected]

New solid-state single photon detectors suited for the visible spectral range will be presented [1,2]. The sensors are based on avalanche photodiodes (APDs) biased above the breakdown voltage in the so-called Geiger mode. They are fabricated using Complementary Metal-Oxide-Semiconductor (CMOS) process, a technology widely used in the microelectronics industry. Using this technology, detectors [3] or detector arrays [4] and front-end electronics can be integrated on the same silicon chip. Many of the functionalities (e.g. voltage conversion and read-out) are done directly at the chip level, thus almost completely removing the need for discrete electronic components and expensive assembly. In addition to the high degree of miniaturization and low fabrication cost, the complete integration leads to a dramatic reduction of the parasitic capacitances. This allows one to maintain the afterpulsing probability at a low level (less than 2%) and to reduce the dead time up to 15ns. The cleanliness of the fabrication process leads to a very low intrinsic noise level: at room temperature, the dark count rate is typically 200Hz for a sensitive area of 20um in diameter. Because these detectors have thin active regions, the photon detection probability peaks in the blue/green at almost 35% and is limited to a few percents in the red and near-infrared regions. This is the price to pay in order to achieve best-in-class timing resolution of 40ps, which makes these detectors essential for applications in which the photons must be detected with a very high timing accuracy. Besides, these detectors do not suffer from memory effects found in photomultiplier tubes and are not damaged by ambient light. The modules are currently used in biological/chemical instrumentation, quantum optics, aerospace and defense applications. The potential of these sensors will be demonstrated for several applications including single-molecule spectroscopy, diffuse optical tomography and time-resolved confocal microscopy.

[1] http://www.idquantique.com/spcm-vis.html

[2] http://www.idquantique.com/spcm-vis-10.html

[3] A.Rochas et al., Review of Scientific Instruments, Vol.74, 2003, pp. 3263-3270

[4] A.Rochas et al., IEEE Photonics Technology Letters, Vol.15, No.7, 2003, pp. 963-965

- 15 - TALKS SESSION 3

SiPM

- 16 - Review talk SiPM Review on SiPM D. Renker

Paul Scherrer Institute, Villigen PSI, CH-5232 Villigen, Switzerland Email: [email protected]

- 17 - Resent Development and Study of Silicon Photomultiplier (SiPM)

V. Saveliev

Obninsk State University, Studgorodok 1, 249040 Obninsk , Russia Email: [email protected]

Review of recent developments and results from the study of a Silicon Solid State Photomultiplier (SiPM), different types are presented including enhansment to blue reagion of light.

The basis of this new type of photodetector is a fine structure of microcells operating in the Geiger mode with an internal gain greater than $106$, and integrated quenching mechanism. Common signal output allows for the detector to be operated in the proportional mode, and to reach a dynamic range of $1.5*103$.

Such photodetectors have shown single photon response at room temperature with fast timing up to ~50 ps. They are compact, robust and non sensitive to magnetic fields.

Results show the detection of low intensity light in single photon mode and the detection of minimal ionizing particle using a scintillation tile for the hadron calorimetry.

The silicon photomultiplier is suitable for wide application in scintillation calorimetry, medical applications as positron emission tomography etc…

[1] V.Saveliev, V.Golovin, Silicon Avalanche photodiodes on the base of metal-resistor-semiconductor (MRS) structures, NIM A442 (2000) 223

[2] V.Saveliev, Novel type of avalanche photodetector with Geifger mode operation, NIM A 518 (2004) 560

[3] V.Saveliev The resent development and study of silicon photomultiplier NIM A 535 (2004) 528

- 18 - The gain, photon detection efficiency and excess noise factor of multipixel Geiger-mode avalanche photodiodes

Y. Musienko, S. Reucroft, J. Swain

Department of Physics, Northeastern University, Boston, MA 02115, USA Email: [email protected]

Recently developed multipixel Geiger-mode avalanche photodiodes (MPGM APDs) are very promising candidates for many HEP, astrophysical and medical applications. They have many advantages over conventional photosensors (such as PMTs, APDs and PDs) because of their compact size, low power consumption, high gain, reasonably high QE in the green and red regions of the optical spectrum, non- sensitivity to magnetic field, etc. However the measurement technique for characterization of these devices has not been well developed. In this work we propose a method to characterize MPGM APDs and present systematic studies of new devices from three different manufacturers. The basic properties of MGPM APDs such as gain, photon detection efficiency, excess noise factor and noise, as well as their dependence on operating voltage have been measured and compared to those of a PMT XP2020. Spectral response was measured in the range 350-800 nm. It was shown that despite very good pixel-to pixel gain uniformity, the excess noise factor of these APDs can be significantly greater than one.

- 19 - Test and acceptance procedures for large-scale batches of Silicon Photomultipliers

V. Balagura, B. Bobchenko, P. Buzhan, M. Danilov, B. Dolgoshein, L. Filatov, M. Groll, A. Ilyin, A. Karakash, S. Klemin, P. Komissarov, V. Korbe,l V. Morgunov, E. Popova, V. Rusinov, F. Sefkow, E. Tarkovsky

Moscow Engineering and Physics Institute, Kashirskoe shosse 31, 115409 Moscow, Russia Email: [email protected]

The Silicon Photomultiplier (SiPM) is a recently developed novel type of photodetector. After several years of R&D studies the SiPM is now ready for usage in different applications. One of these is the Analogue Tile Hadron Calorimeter (HCAL) for the International Linear Collider (ILC). SiPMs have been studied already at DESY as part of a small HCAL prototype and gave very promising results. Now a large scale HCAL prototype is under construction, containing few thousands of SiPMs.

Basic SiPM characteristics to be determined before installation are the following: photon detection efficiency, gain, inter-pixel crosstalk, single pixel resolution, dynamic range, dark rate and dark current. New test procedures and acceptance criteria have to be developed, and new test benches have to be created for SiPMs as a novel type of a photodetector.

One of the most important SiPM characteristics is the single pixel pulse height spectrum. A special test bench to measure such spectra has been built at ITEP. It is a computer-controlled setup which provides the possibility to measure 15 SiPMs mounted on precision plates simultaneously, with automatic subsequent data processing. More than 500pc/week can be tested at this setup.

Another special test bench for the initial SiPM selection directly on the uncut wafer has been built by MEPHI/Pulsar. Each wafer consists of about 1000 SiPMs. Compared with the above-mentioned ITEP setup, this pre-selection test bench is simpler, and a faster procedure not relying on single pixel spectra is used. The setup has a maximum acceptance capability of 1000 pieces per day. Such a pre-selection allows to avoid mounting of bad SiPM chips on the precision plates and thus significantly reduces cost and time consumption of the overall procedure.

The results of such a two-step test procedure are presented for 5000 measured SiPM chips.

- 20 - Studies of silicon photodetectors for hadron calorimetry at the next electron-positron linear collider

D. Chakraborty

Northern Illinois University, Physics Dept., Faraday Hall West, 60115 Dekalb, Usa Email: [email protected]

Our group at the Northern Illinois Center for Accelerator and Detector Development/Northern Illinois University has been investigating the possibility of using solid-state photodetectors for a finely segmented scintillator-based hadron calorimeter in a detector at the proposed International Linear Collider. We have tested similar devices from two different sources: "SiPM"s from MEPhi/Pulsar and "MRS"s from CPTA. We have carried out extensive studies of the signal and noise characteristics as functions of bias voltage, linearity, and uniformity of response. Effects of fiber positioning and angle as well as those of irradiation, temperature variations, and magnetic fields up to 4.5 Tesla have also been studied in detail. We find that performancewise these devices meet our needs, although cost remains somewhat of a concern.

- 21 - Three advanced designs of avalanche micro-pixel photodiodes: their present status, maximum possibilities and limitations

Z. Sadygov

Joint institute for nuclear research, Joliot-Curie str.6, 141980 Dubna, Moscow region, Russia Email: [email protected]

The basic physical principles which result in appearance of the novel avalanche photodiodes with local feedback/suppression of avalanche gain are analyzed. The first proposed three different designs of avalanche micro-pixel photodiodes (AMPD) are considered from the point of view of their advantages, restrictions and opportunities of mass production. The first design of AMPD contains common silicon wafer on which a matrix of independent p-n-junctions (micro-pixels) with individual surface resistors are created. The individual resistors provide discharge of each micro-pixel to common metal grid (electrode). Second design is an avalanche photodiode with independent micro-pixels in which local suppression of avalanche process is carried out due to the limited conductivity of the individual surface drift channels formed along the silicon- silicon oxide boundary. This design is considered as prototype of future super-fast avalanche CCD matrix capable to work in single photon detection mode. Third design contains a matrix of deep buried multilayer pixels with individual suppression of avalanche process in independent vertical channels. Using the latest design an AMPD with super-high density of micro-pixels (more than 104 pixel/mm2) and high fraction (up to 90%) of active sensitive area may be produced.

- 22 - High-efficiency and low noise scintillation detector for ionizing particles START(Scintillation Tile with MRS APD Light ReadouT)

A. Akindinov

ITEP, B. Cheremushkinskaya 25, 117259 Moscow, Russia Email: [email protected]

High-efficiency and low noise scintillation detector for ionizing particles START (as abbreviated from Scintillation Tile with MRS APD Light ReadouT) has been developed for many purposes MIP registration.

Scintillation light in START is detected by MRS APDs (Avalanche Photo-Diodes with Metal-Resistor- Semiconductor Structure), operated in the very high gain Geiger mode. START is assembled from 150x150x15 mm**3 scintillating plate, two MRS APDs (implemented inside plastic plate) and one piece of WLS optical fiber stacked in circular coil inside the plastic. FEE card is mounted directly on a detector body. START has confirmed its operational consistency, over 99% efficiency for MIP registration, good homogeneity and very low intrinsic noise of about 10**-2 Hz. First full scale mosaic array of STARTs of around 1m**2 area has been built and is now under test.

- 23 - Large area silicon photomultipliers: performance and applications

B.Dolgoshein, On behalf of MEPHI-Pulsar-MPI(Munich) Collaboration: P. Buzhan, B. Dolgoshein, L. Filatov, A. Ilyin, V. Kaplin, S. Klemin, .A. Karakash, R. Mirzoyan, N. Otte, E. Popova, V. Sosnovtsev, M. Teshima

Moscow Engineering and Physics Institute, Kashirskoe Shosse,31; 115409 Moscow, Russia Email: [email protected]

The large Silicon Photomultipliers(SiPM'S) with an area up to 10x10 mm2 are considered and their optimal parameters,such as gain,dark rate, afterpulsing probability and optical crosstalk are discussed.The 3x3 mm2 SiPM is described and its performance is demonstrated.

Finally three examples of 3x3 mm2 SiPM applications are given:

- Transition Radiation X-Rays detection

- Detection of PET gammas using LSO cristal

- Time of flight application

Corresponding experimantal results are presented and discussed.

- 24 - A new generation of low-voltage single photon micro-sensors with timing capability

P. Finocchiaro

INFN Laboratori Nazionali del Sud, Via S.Sofia 64, 95125 Catania, Italy Email: [email protected]

Our project aims at proving that single photon sensing can be made accessible in form of cheap off-the-shelf micro-devices with micro-optical/ micro-mechanical coupling systems.

In order to achieve this challenging goal, we are making use of different micro-technologies, not yet fully established but promising and innovative in and of themselves, and to combine them into a more challenging micro-technology capable of bringing the single photon handling to the shelf. Moreover, the technology we would like to implement should make it possible to provide the photonic sensors we aim at in a ready-to-go fashion, that is in such a way that what one needs, in the standard cases, is to couple the sensor to the light source, provide the power supply (low voltage) and use the output signals.

Photon handling is nowadays considered an emerging issue, mainly, but not exclusively, in the field of telecommunications. The possible applications are so many that a full branch of science and technology is dedicated to it, namely photonics.

After developing and testing single channels and small arrays, we are going to develop arrays of Single Photon Avalanche Detectors (SPAD) operating at low voltage and fabricated in silicon planar technology, starting from the know-how we already acquired by producing and testing few-channel sensors. On top of this, in order to match the performance of the proposed detectors with those of the systems where the photons are produced and conveyed, we want to improve and finalize our emerging technology of Deep Lithography with Ions (DLI) for the fabrication of micro-mechanical and micro-optical components, perfectly suitable for the coupling to the silicon micro-sensors.

- 25 - Solid State Photomultipliers for Photon Counting

M. Atac

Fermilab, P.O. Box 500, 60510 Batavia, Usa Email: [email protected] [email protected]

Solid State Photomultipliers (SSPM/VLPC) have been developed for scintillating fiber tracking, medical imaging and Astroparticle Physics. These devices can count down to a single photon with quantum efficiency; around 80% for 530 nm wavelength with a dynamic range of 3000 simultaneous photoelectrons. They provide gains of around 3x104 with count rate capabilities of 107 /mm2.sec. at 6.5K. They are insensitive to magnetic fields. Experiment E835 has successfully used about 900 of the VLPCs for their scintillating fiber tracking in 1996 and presently the D0 Experiment is using more than 80,000 VLPCs for scintillating fiber tracking successfully at Fermilab. Rate capabilities and other properties of these devices and their applications are going to be presented.

- 26 - TALKS SESSION 4

MAPMT

- 27 - Design and status of COMPASS FAST-RICH

A. Ferrero for the COMPASS FAST-RICH group

Universita' di Torino, V. P. Giuria 1, 10125 Torino, Italy Email: [email protected]

We are developing a fast photodetection system for RICH detectors, based on UV extended Multi-Anode Photo-Multiplier Tubes (MAPMT) and a custom, low dead-time readout electronics. The Cherenkov photons are concentrated on the MAPMT photocatode by an optical system that preserves the position information. The ratio between the collection and the photosensitive surfaces is approximately 9 in our design, larger than in previous applications.

A new frontend electronics, based on a modified version of the MAD4 discriminator chip, is being designed to digitize the MAPMT signals.

We report about the design of the photodetection system and of the associated readout electronics, and on the preliminary test beam results.

- 28 - Multi-anode PMT readout: OPERA_ROC and its relatives...

S. Blin, J. Fleury, C. de La Taille, G. Martin-Chassard, L. Raux, N. Seguin-Moreau

LAL Orsay CNRS/IN2P3, bât. 200, Centre universitaire, 91898 Orsay, France Email: [email protected]

The 64ch multi-anode Hamamatsu is an increasingly popular photodetector chosen by several large physics experiments like OPERA, LHCb, ATLAS. For the OPERA neutrino experiment, the target tracker scintillating fibers are read with ~1000 MAPMT and dedicated ASICs OPERA_ROC which exhibits the following characteristics:

* auto-trigger on 1/3 photoelectron with fast 15 ns shaping. 1% photoelectron noise andthreshold spread. "Ored" trigger output with mask capability

* measure charge up to 100 photoelectrons with % linearity

* multiplexed output of charge measurement with 150ns shaping,low noise and pedestal dispersion

* gain correction from 1 to 4 with 6 bits acccuracy to correct for PM non-uniformity

The ASIC has been realized in BiCMOS AMS 0.8µm and 3400 chips have been produced in 2003 to equip the detector. It houses 32 channels and dissipates 185 mW.

A version with the 32 digital outputs has also been produced for medical imaging applications with counting rate capability of 2-5 MHz.

In 2004, with the termination of the 0.8µm process, one channel has been moved to 0.35µm SiGe BiCMOS technology together with a faster shaping stage that should allow counting up 20MHz. A 64channel ASIC will be submitted in june 05 in view of equipping the roman potsluminometry monitors of ATLAS.

The talk will present design and experimental results on OPERA_ROC chip and recent resultson the SiGe upgrades.

- 29 - A new high open-area-ratio position sensitive microchannel plate photomultipliler tube

S. Moulzolf, P. Hink, P. Mitchell, R. Caracciolo, R. Thompson

BURLE INDUSTRIES, INC.,: 1000 New Holland Ave, 17601 Lancaster, pa, Usa Email: [email protected]

Large area close packed arrays of position sensitive photomultiplier tubes are of interest for use in important photon counting devices such as medical imagers and high energy physics detectors. These applications typically require minimal dead-space, good uniformity, excellent temporal resolution and high count rates. Also, some applications may require operation in high magnetic fields. To fill this need, Burle Industries has developed a new large format, high open-area-ratio (OAR) microchannel plate photomultiplier tube (MCP- PMT) with a square geometry in its PLANACON family. This PMT device has a 53.8 cm square active area with an 86% OAR. Furthermore, the device is extremely compact and light at a thickness of < 12 mm and mass of 68 g. This new device presents a significant improvement over the current design that has a 66% OAR, 17 mm thickness and 128 g mass. Prototypes having 8x8 pixilated anode arrays have been fabricated and characterized. We will show typical data for cathode spectral response, cathode and anode uniformity, single photon pulse and timing characteristics, and magnetic field sensitivity. We will also present an overview of a prototype module that allows for simple optimization of the voltage-divider-network for specific applications. This module supplies ribbon connector sockets for the multi-anode interface and a separate connector for plug-in or remote VDN circuit boards/power supplies. Because the module electronics are completely contained within the footprint of the MCP-PMT, they do not alter the device OAR. Preliminary results on a 32x32 pixilated anode device will also be presented.

- 30 - An Application Specific Integrated Circuit for Multi Anodes PMT

R. Gaglione, G. Bohner, J. Lecoq, G. Montarou, L. Royer

Laboratoire de physique corpusculaire, 24 avenue des Landais, 63177 AUBIERE cedex, France Email: [email protected]

The main purpose of this developpment is to build an "intelligent sensor", composed of one multianode PMT, four custom front-end analog chips with embedded analog to digital converter and a pre-processing logical unit. The idea of that design is to improve as much as possible the treatment speed of signals of the PMT. This design should be compact to fit the PMT dimensions, in order to combine them together to form an assembly which will be used in medical imaging research, especially for gamma-ray camera.

Two ASIC prototypes have been made and tested, and an improved version is sheduled. The digital part is under developpement.

This work is a part of a Ph.D. thesis and of a collaboration between CNRS and Hamamatsu Photonics.

- 31 - Tests of the Burle 85011 64-anode MCP PMT as a detector of Cherenkov photons

P. Krizan et al

University of Ljubljana and J. Stefan Institute, Jadranska 19, SI-1000 Ljubljana, Slovenia Email: [email protected]

The present paper reports on experimental investigation of a novel type of photon detector, the BURLE 85011 multianode micro-channel plate PMT, in an aerogel based RICH detector of the proximity focusing type. Such a detector is being considered in connection with an upgrade of the BELLE particle identification system at KEK. One of the essential components of such deviceis a photon detector which can operate in a magnetic field of 1.5 T. Since photon detectors based on the microchannel plate technology are good potential candidates, the 64 channel BURLE 85011 multianode micro-channel plate PMT was tested in a pion beam and on the bench.

Beam test studies of a similar device, with flat pannel PMT Hamamatsu 8500 as photon detectors, were reported recently [1]. The present paper describes measurements and results obtained with the new photon detector in the same pi2 beam at KEK. From the photon hit position and the measured direction of the incident charged particle, the Cherenkov angle is calculated.

Fitting the angular distribution with a Gaussian function and a linear background yields the average value and standard deviation of the measured Cherenkov angle, as well as the number of photons per ring section, covered by the counter. From the measured resolution in Cherenkov angle for singlephotons (13 mrad) and the measured number of photons per ring (around 7) we conclude that such a counter would allow for a 4 sigma pi/K separation at 4 GeV/c.

The uniformity of the response of the photon detector over its active surface as well as a possible cross-talk between the individual detectorpads was studied in a separate study on the bench. The surface was scanned with a LED light source focused by a microscope to a 30mum diameter light spot. We have observed that at the edges of pads charge sharing becomesan important effect. Another interesting effect has been observed with photons entering the PMT at an angle with respect to the normal incidence. For inclined incidence, one observes reflection images of the counting pad. These counts are due to single or double reflection of the photon on the structure of the micro-channel plate and the entrance window. The dependence of the distance between these pad images on the photon beam inclination angle confirms such an interpretation. As the fraction of hits in these reflection images is about 7-8%, their impact on position resolution at 18 deg. incident angle (typical for the present beam test) produces a 10% degradation of angular resolution, while their impact on timing resolution could be obtained from the estimated delay of 40 ps for such reflected photons.

[1] T. Matsumoto et al, Nucl. Instr. and Meth. A 518 (2004) 582

- 32 - - 33 - TALKS SESSION 5

DIAMOND

- 34 - Diamond 2D Detectors for Deep-UV Monitoring

G. Mazzeo, S. Salvatori, G. Conte

INFM and Dept. of Electronic Engineering, University of Rome “Roma Tre”, Via della Vasca Navale 84, 00146 Rome, Italy Email: [email protected]

The interest for high performance UV sensors for operation in the deep UV region of the electromagnetic spectrum is growing more and more interesting. This arises from the increasing industrial use of intense laser sources in areas that include micro-machining and ULSI photolithography, demanding high radiation hardness and long lifetime that conventional semiconductors can’t offer. Owing to the high cohesive energy, diamond deposited by chemical vapor deposition (CVD) techniques appears as the elective material for such kind of application although long irradiation of a few mJ/cm2 have shown degradation in the film quality. Notwithstanding this evidence, polycrystalline diamond UV detectors are under development with the aim of improving their performance.

High quality, 1 cm2 large and 100 um thick, polycrystalline diamond deposited by a microwave CVD process has been used in this work. Chromium deposits have then been realised by physical vapour deposition on both the diamond surfaces. Fine line photolithography has been then used to define crossed Chromium strips.

A Neweks PSX100 ArF laser (4.5 mJ per pulse, FWHM=3 ns, 10-100 Hz, spot size 2x3 mm2) has been used to shine light on the realized device and to test the pixel-by-pixel performance in respect of the beam intensity variations for photon fluxes between 0.1 uJ/cm2 and 0.2 mJ/cm2. The photocurrent signal has been recorded as the voltage across the 50W input impedance of a Le Croy Wavepro 960 digital sampling oscilloscope. To study the response of the whole multi-strip matrix under UV irradiation an addressing, shaping and reading electronics has been also developed to monitor the beam’s shape in CW or modulated irradiation.

The characterization results will be presented and discussed on the basis of single pixel homogeneity and whole matrix response as a function of beam intensity and chopping frequency.

- 35 - Diamond based photoconductors for deep UV detection

A. Balducci2,M. Bruzzi3,A. De Sio1, M. G. Donato4, G. Faggio4, M. Marinelli2, G. Messina4, E. Milani2, M.E. Morgada2, E. Pace1, G. Pucella2, S. Santangelo4, M. Scoccia2, S. Scuderi5, A. Tucciarone2, G. Verona- Rinati2

1Dip. Astronomia e Scienza dello Spazio, Università di Firenze, L.go E. Fermi 2, 50125 Firenze, Italy 2INFN - Dip. di Ing. Meccanica, Università di Roma "Tor Vergata", Via del Politecnico 1, 00133 Roma, Italy 3INFN - Dipartimento Energetica Via S. Marta 3, 50139 Firenze, Italy 4INFM, Dip. Meccanica e Materiali, Università di Reggio Calabria, Reggio Calabria (Italy) 5Osservatorio Astrofisica di Catania,Catania (Italy) Email: [email protected]

This work summarise the results obtained by our collaboration in the aim of the realization of a bidimensional deep UV sensor based on synthetic diamond. All the expertises needed for such purpose are included in our collaboration. The growth of the material is obtained with the tubular MWCVD reactor at the Rome "Tor Vergata" University laboratories with which both eteroepitaxial polycrystalline diamond films and omoepitaxial single crystal diamond can be realized. The samples are characterized with cathode luminescence (CL), photoluminescence (PL), Raman and thermally stimulated currents (TSC) techniques. The selected material is used for the realization of photoconductive single pixel and 2D array devices evaporating metal contacts on the sensitive surface.

The electro-optical characterization of the devices is realized in a wide spectral interval ranging from 2400nm to 30nm. In the extreme UV region (20-100 nm) a gas discharge source and a toroidal grating vacuum monochromator with 5Å wavelength resolution were used. In the 120-250 nm spectral range the device responsivity was measured in continuous mode by using a deuterium lamp and a 0.5 m vacuum monochromator. In the 210-2400 nm range an Optical Parametric Oscillator (OPO) tunable laser producing 5 ns pulses was used as light source.

Time response, signal to noise ratio, sensitivity and visible blindness are reported in order to evidence the good results attained but also the major problems on which the community should be focused.

- 36 - Diamond UV photoconductive devices: high gain, high speed and solar-blind

S. Curat, R. B Jackman

University College London, London Centre for Nanotechnology, Torrington Place, WC1E 7JE London, Uk Email: [email protected]

Diamond has been proposed as an ideal candidate for solar-blind deep UV detectors for many years, principally because of its wide (5.5eV) band gap. The emergence of CVD techniques for the formation of large area diamond films, at modest costs, led to considerable commercial interest in the realisation of such devices. Despite the publication of many papers relating to the provision of diamond UV photoconductive detectors, few examples of devices which combine good spectral selectivity, good gain and rapid turn-off times currently exist. This problem relates to the defective nature of most of the types of diamond that have been used. We have pioneered a generation of dramatically improved devices, using a post-growth passivation treatment to engineer the properties of the detector. We can achieve photoconductive gain levels of several thousand, more than six decades of discrimination between deep UV and visible light and under some conditions operation at MHz frequencies.

This paper will review the methods that we have used and show the performance of diamond detectors when exposed to steady-state and pulsed laser light fluxes. We have recently studied carrier transport within these structures using impedance spectroscopy and optical Hall effect measurements. These results will discussed in terms of the ultimate device performance levels that can be expected. The radiation hardness of the devices will also be considered. The prospects for photoconductive devices compared to those based on diamond semiconductor junctions will be addressed.

- 37 - UV photorepsonse and electrical properties of diamond p-n junctions

M. Nesládek1, P Bergonzo1, S. Koizumi2, K. Haenen3, V. Mortet3

1Commissariat à l'Energie Atomique, CEA, Saclay, DRT, 91191 Gif Sur Yvette, France 2Advanced Materials Laboratory (AML), National Institute for Materials Research (NIMS), 1-1 Namiki, Tsukuba, 305-0044, Japan 3Institute for Materials Research, IMO, Limburgs Universitair Centrum, Wetenschapspark 1, B-3590 Diepenbeek, Belgium Email: [email protected]

Junction type of detectors based on wide band gap semiconducting diamond are very interesting for space solar blind UV applications. Recently diamond p-n junctions have been fabricated at NIMS and IMO-LUC.

The UV photoresponse of p-n and p-i-n diodes made of CVD diamond, composed of P- and B-doped layers have been studied. The device has been grown by homoepitaxy on Ib diamond substrates, doped with boron and further processed including mesa structures pattering by FIB and dry etching techniques. The diode characteristics have shown very high rectification, over 10 decades in magnitude and photoresponse with a rejection factor between the UV and visible part of the spectra with at least 6 decades in magnitude.

Also we attempt to construct for the first time CVD diamond n-type Schottky photodetectors with an advantage of responses in VUV range compare to pin junction detectors where light in VUV range is strongly absorbed in the top p-type layer.

We model the photoresponse taking into account the recombination of the minority carriers at the top surface and the drift currents in the junctions. The photorepsonse and the recombination lifetime for various p-i-n structures and Schottky diodes is discussed to with relation to the device optimisation.

Finally we compare the junction photoresponse with novel MSM structures, based on single crystal free standing CVD diamond wafers.

[1] Milos Nesladek 2005 Semicond. Sci. Technol. 20 R19-R27, 2005

- 38 - TALKS SESSION 6

OTHERS

- 39 - Ground-based photon counting optical detection for the 2010 Mars Laser Communications Demonstration

W. Farr

Jet Propulsion Laboratory, 4800 Oak Grove Dr. 161-135, 91109 Pasadena, ca, Usa Email: [email protected]

In 2009 NASA plans to launch the Mars Telecommunications Orbiter (MTO), which will function as the first dedicated Mars orbiting telecom relay satellite beginning in 2010. This orbiter will support future high data return volume Mars exploration missions, such as Mars Science Laboratory. Although primarily a radio- frequency communications relay, the MTO will also carry a payload to demonstrate the first deep-space optical communications link, the Mars Laser Communications Demonstration (MLCD). A goal of this demonstration is to transfer both science and link characterization test data from Mars orbit to Earth over a near-infrared optical link at data rates from one to over thirty megabits per second, including both night-time and daytime operations.

The optical receive terminals for the MLCD will be ground based, and require the use of photon counting optical detectors to meet mission requirements. These terminals are being implemented and managed by the Jet Propulsion Laboratory, California Institute of Technology. One receive terminal shall utilize the 5 meter diameter Hale telescope at the Palomar Observatory located in the mountains in the southwestern United States. The challenges of matching this large aperture telescope to a high bandwidth photon counting detector will be discussed, including laboratory test results of a simulated end-to-end optical link under MLCD operational scenarios.

- 40 - Development of GaN photocathodes for UV detectors

O. Siegmund

Space Sciences Laboratory / University of California, 7 Gauss Way, 94720 Berkeley, Usa Email: [email protected]

We have made substantial progress in the development of GaN photocathodes, including crystalline and polycrystalline GaN and InGaN coatings grown by CVD on sapphire. In addition GaN, grown by MBE, on sapphire and MgF2 have been assessed. GaN, InGaN and GaN on MgF2 photocathodes have been developed with efficiencies up to 70% and cutoffs at ~380nm, with low out of band response, and high stability. Samples have been processed and tested in-situ to establish cathode process parameters, and some have been integrated into sealed tubes for long term evaluation. We have test, processing and measurement capabilities to encompass opaque and semitransparent QE as well as angular dependence, all in the same environment. Key factors in cathode activation include cleaning techniques, degassing, vacuum scrubbing and surface activation with alkali metal (Cs).

We have achieved efficiencies as high as 70% for GaN at the shortest wavelengths (120nm), dropping off to around 15% at 360nm. This is markedly improved over early attempts where the long wavelength quantum efficiency was poor, and the drop off going from short to long wavelengths was severe (2 orders of magnitude). The out of band quantum efficiency drops extremely fast above 380nm to a value of about 10^-4 just above 400nm and further decreasing to 10^-5 at 500nm, and <10^-6 at 600nm showing reasonable “solar blindness”.

We also find that polycrystalline GaN performs as well as crystalline GaN, thus permitting use of a wider variety of potential cathode substrates. Indeed GaN was grown on MgF2 windows (with a correspondingly shorter cutoff wavelength). Although processing conditions had to be changed, we were able to get GaN on MgF2 that was robust enough to operate as a photocathode – albeit at somewhat lower efficiency than GaN. InGaN has also been tested also seems to work but again we have not optimized the process yet. Other interesting data show that even after air exposure, we can recover most of the activated GaN QE by a simple vacuum bakeout of the cathode (with a secondary effect of reducing the “red end” QE) thus encouraging our expectations of the robustness of GaN. Furthermore, we have affirmed the longevity of our activated GaN in sealed tube devices over 2 years with no degradation.

Other measurements include evaluations of angular QE response. These indicate increases in QE are possible at grazing input angles, and give us a probe to determine the electron mean free path in GaN samples. Early indications seem to favor the use of MBE grown materials for the best electron mobility and negative electron affinity.

We will discuss our plans to further develop this GaN technology and to fabricate imaging photon counting devices with microchannel plates and high fidelity electronic readout systems.

- 41 - The quantum efficiency of photo-charge generation in a-Se avalanche photodetectors

A. Reznik1, B. J. M. Lui1, J. A. Rowlands1, Y. Ohkawa2, K. Tanioka2

1Sunnybrook & Women’s College Health Sciences Centre, SWCHSC, Imaging Research, 2075 Bayview Avenue, M4N3M5 Toronto, Canada 2NHK Science & Technical Research Laboratories, Tokyo, Japan Email: [email protected]

The quantum efficiency of photo-charge generation in a-Se photodetectors has been investigated for wavelengths of excitation between 380 and 700 nm, in both the sub-avalanche and avalanche regimes. The observed electric field dependence of quantum efficiency and photodetector gain revealed two distinct generation mechanisms for band-to-band and sub-band excitations that are due to the different nature of optical transition in each case. For band-to-band excitation the Onsager geminate pair dissociation model fits our experimental results, although for photon wavelengths shorter than 430 nm the creation of light-induced traps should be taken into account. For sub-band excitation, our results on quantum efficiency can be explained by the field enhanced delocalization of states. A theoretical model of this mechanism has been developed.

Our results show that a-Se is a promising material for use as a photodetector in indirect X-ray and nuclear medicine imaging devices due to its extremely high and stable avalanche gain.

- 42 - Very high position resolution gamma imaging with Resistive Plate Chambers

A. Blanco1, N. Carolino1, C.M.B.A. Correia2, L. Fazendeiro1, Nuno C. Ferreira3, M.F. Ferreira Marques4,5, R. Ferreira Marques1,6, P. Fonte1,5, C. Gil4, M. P. Macedo2,5

1LIP, Laboratório de Instrumentação e Física Experimental de Partículas, 3004-516 Coimbra, Portugal 2CEI, Centro de Electrónica e Instrumentação, Univ. Coimbra, 3004-516 Coimbra, Portugal 3IBILI, Instituto Biomédico de Investigação de Luz e Imagem, Faculty of Medicine, 3000, Coimbra Portugal 4ICEMS, Departamento de Física, Universidade de Coimbra, 3004-516 Coimbra, Portugal 5ISEC, Instituto Superior de Engenharia de Coimbra, 3031-199 Coimbra, Portugal 6Departamento de Física, Universidade de Coimbra, 3004-516 Coimbra, Portugal Email: [email protected]

In this study we present experimental and simulated results from a first prototype of a positron emission tomography (PET) system based on the resistive plate chamber technology. The prototype is aimed at validating the expectations, derived from simulations, of a system with sub-millimeter spatial image resolution and very small parallax error, which may be useful for the imaging of small animals.

The system is composed of two counting heads, each containing 16 single-gap RPC counters, stacked in a common mechanical frame. The counters are made from copper (on a PCB) and glass (anode) electrodes. The transverse coordinate is sensed in each counter by 32 1-mm wide signal pickup strips, covering an area of 32x10 mm2.

Corresponding strips are grouped together for all counters and readout by charge-sensitive electronics, allowing precise interstrip position interpolation. The charge induced in the cathodes indicates the counter where the interaction takes place, allowing precise identification of the photon interaction point in the transaxial plane. The system comprises 96 charge-sensitive channels.

By imaging a point-like 22Na source located at different positions in the transaxial plane, a uniform system resolution of 0.52 mm FWHM was demonstrated, validating positron range simulations from several authors. A corresponding image resolution of 0.31 mm FWHM was obtained after reconstruction by an ML-EM type algorithm.

The expected performance of a small-animal PET scanner based on this technology will be discussed, including the advantages arising from the intrinsic time resolution of 300ps.

- 43 - Detecting photons - properties and challenges

J. Cheung, C. Chunnilall, N. Fox

National Physical Laboratory, Hampton Road, TW11 0LW Teddington, Middlesex, United kingdom Email: [email protected]

This paper will report on the work being carried out on detector characterisation at the National Physical Laboratory in the UK. It will discuss the importance of traceability and give an overview of the facilities that exist for detector characterisation from the UV (200 nm) to the near IR (20 um) for spectral responsivity, linearity and uniformity. The paper will focus on the development of a new technique based on correlated photons. Correlated photons produced via parametric downconversion can be used to directly measure the quantum efficiency of photon counting detectors. The main drivers for these metrological techniques are the rapidly progressing field of quantum information processing which requires the development of single photon counting detectors which must perform at quantum efficiency levels of greater that 99%, and the wider use of optical technologies in the photon counting regime. Photodetection in the fields of biology, nuclear physics and astrophysics will also benefit from this work. The potential of this technique for realising primary radiometric scales will also be briefly discussed.

Related papers: J. Y. Cheung, M. P. Vaughan, J. R. M. Mountford and C. J. Chunnilall. Correlated photon metrology of detectors and sources. Proceedings of SPIE, 2004, 5161, 365 – 376

- 44 - Fast read-out of the COMPASS RICH CsI-MWPC chambers using APV25 amplifier chips

P. Abbon1, H. Deschamps1, E. Delagnes1, F. Kunne1, A. Magnon1, D. Neyret1, S. Panebianco1, P. Rebourgeard1, S. Gerasimov2, B. Ketzer2, I. Konorov2, S. Paul2, N. Kravtchuk3

1DSM-DAPNIA, CEA Saclay, F-91191 Gif-sur-Yvette, France 2Technische Universität München, Physik Department, D-85748 Garching, Germany 3JINR Dubna, 141980 Dubna, Russia Email: [email protected]

The COMPASS [1] experiment at CERN takes advantage of a Ring Imaging Cherenkov (RICH) detector to identify particles scattered from the beam-target interactions, and in particular recognize kaons from pions. The photon detection of this RICH detector is based on Multi-Wires Proportional Chambers (MWPC) coated with CsI, a 2-dimensional photon detection is performed by reading signal on pads located on the photocathodes. The read-out is actually provided by an electronics system based on Gassiplex chips, however this system has an integration time around 3 to 5 micro-second, which generates a sensible background level at high beam intensity. A project has been proposed to replace this electronics by a system based on APV25-S1 chip [2], which has been designed for CMS Silicon tracker. This pipelined amplifier allows us to shorten the effective time gate, while reducing the electronics noise level and the read-out dead time. Prototype boards have been built to equip a whole RICH photon-detector, and tests on the RICH detector have been made in nominal condition, showing an important improvement of the signal to background ratio. The project will be presented and an overview of the tests results will be given.

[1] G. Baum, et al., COMPASS: A proposal for a COmmon Muon and Proton Apparatus for Structure and Spectroscopy, CERN/SPSLC 96-14, SPSC/P 297 (March 1996)

[2] M. J. French, L. L. Jones, Q. Morrissey, A. Neviani, R. Turchetta, J. Fulcher, G. Hall, E. Noah, M. Raymond, G. Cervelli, P. Moreira, G. Marseguerra, Design and results from the APV25, a deep sub- micron CMOS front-end chip for the CMS tracker, NIM A466 (2001) 359-365

- 45 - Transmission of analogue signals over fiber optics using the optically-coupled current-mirror architecture

D.V.Camin, V. Grassi and M. Squerzoni

Institution/Laboratory: Physics, Department of the University and INFN, Via Celoria 16 , 20133 Milan, Italy Email: [email protected]

The Optically-Coupled Current-Mirror (OCCM) is a novel feedback-circuit architecture that incorporates optical links in its forward and feedback paths. The input-stage is a passive dipole consisting only on the back-to-back connection of a diode and a photodiode galvanically isolated from the receiving-end, which is located at ground potential. The input stage has low impedance, which is the ideal situation for a current- sensitive device. In addition, being passive, there is no need to bring a low voltage power supply to the isolated and possibly HV-biased input-stage, as it is required by standard circuit architectures; this feature definite simplifies the circuit’s burden. The operation of the OCCM with its input-stage cooled to cryogenic temperature (LAr, LXe), improves the circuit linearity as all non-radiative processes in the LED are strongly suppressed. A very large dynamic range can be achieved by connecting in series two or more input stages, each one having different gain. The first result obtained with the OCCM was the readout with high- resolution of the quasi-DC, minutes long component of the anode current left by stars transiting trough the 880 cathode-grounded PMTs of the first two telescopes at the Pierre Auger Observatory. Optimization of the OCCM for large signal bandwidth allowed us to reach 30 MHz. Latest results will be presented.

- 46 - Photo-Sensors for UHECR observation from space

A. Petrolini et al

University of Genova and INFN, Via dodecaneso 33, I-16146 Genova, Italy Email: [email protected]

It is most likely that the next generation of experiments for the study of the Ultra High-Energy Cosmic Rays (UHECR), that is cosmic particles reaching the Earth with energies in excess of 10**19 eV, will consist of space-based experiments. The observation from space of the Extensive Atmospheric Showers (EAS) produced by UHECR is a big challenge, because the faint signal must be extracted from a large background by an experimental apparatus operating in space.

The required photo-sensor need single photon sensitivity in the near-UV and must be fast enough (fractions of microseconds) and suitably pixelized (order of the millimetre) to be able to follow the space-time development of the EAS.

Moreover these sensors must allow close packing with negligible dead areas of hundreds of thousands of channels on large surfaces (a few meters). Finally they must withstand operation in space for a few years with a high reliability and operational stability in the harsh space environment.

In this presentation the requirements for the photo-detector for such a kind of space missions will be firstly briefly discussed. Secondly the options adopted for the photo-detectors (both sensors and associated electronics) of the first generation of proposed experiments will be critically reviewed. In particular the solutions adopted for the design of the photo-detector of the EUSO experiment will be presented. In that case the photo-detector is built from elementary-cells housing four Hamamatsu MAPMT and all the associated electronics (including the ASIC) in a totally autonomous assembly. The prototypes developed will be presented, including the dedicated front-end ASIC for the MAPMT readout.

Finally an attempt will be done to identify the required R&D towards sensors for the next generation of experiments.

- 47 - TALKS SESSION 7

HPD

- 48 - Development of HPDs for applications in physics and medical imaging

Braem, E. Chesi, C. Joram, J. Séguinot, P. Weilhammer (for the CIMA collaboration and the C2GT initiative)

CERN, PH departement, 1211 Geneve 23, Switzerland Email: [email protected]

We discuss the design, construction and first results of two Hybrid Photon Detectors under development for applications in neutrino physics and Positron Emission Tomography. The concept of a large almost spherical HPD is being developed as instrumentation of a next generation underwater Cherenkov detector array. Its main advantages compared to a conventional hemispherical PMT are the considerably increased viewing angle, minimum transit time spread, high gain stability and immunity to the earth magnetic field, intrinsic to the design. A proximity focused ceramic HPD with a flat sapphire entrance window has been developed in the framework of a conceptual design study of a novel 3D Axial PET scanner. The ‘PET-HPD’ is equipped with custom designed fast front-end electronics, allowing sequential and sparse mode readout of its 208 pads. Prototypes of both HPDs are being built in a dedicated vacuum deposition facility at CERN.

- 49 - The Novel Light Amplifier Concept

D. Ferenc, D. Kranich, A. Laille, E. Lorenz (Presented by D. Kranich)

University of California Davis, Physics department, One Shields Avenue, 96616 Davis, Usa, ca Email: [email protected]

We will discuss the development of the Light Amplifier—an inexpensive and robust solution for the photoelectron readout in highly focusing hybrid photon detectors (HPDs), like e.g. the ReFerence flat-panel photosensors, or some large hemispherical HPDs. In a Light Amplifier, the photoelectron sensor is a scintillator coupled to optical fiber readout. The strong electron focusing allows us to use a small-area scintillator, which will, in turn, provide efficient optical coupling to the optical fiber. The other end of the optical fiber may be coupled to a Geiger-mode avalanche photodiode (G-APD), respectively to a G-APD matrix, in case of a large area device. These secondary photosensor(s) should be placed outside the vacuum enclosure, which results in a particularly simple and robust construction, without any electronic components enclosed in the vacuum panel or tube. That dramatically simplifies thermal processing, and keeps away from cross-contamination between the semiconductor sensor and the photocathode.

This concept is quite general, and may be applied to any vacuum photosensor with strong photoelectron concentration. One example studied by our group is the ReFerence flat-panel photon detector, another is the large Quasar (or Philips Smart-PMT) hemispherical HPD. We will report on the results of first experiments.

- 50 - Development of a 13-inch HAPD for a next generation water Cherenkov detector

H. Nakayama, A. Kusaka, H. Kakuno, T. Abe, M. Iwasaki, H. Aihara (U. of Tokyo), M. Shiozawa (ICRR), M. Tanaka (KEK), H. Kyushima, M. Suyama, Y. Kawai (HPK)

University of Tokyo/Aihara-lab, 7-3-1 Hongo, Bunkyo-ku, 113-0033 Tokyo, Japan Email: [email protected]

We have developed a 13-inch Hybrid Avalanche Photo Diode (HAPD) for photo sensors in next generation water Cherenkov type detectors. The next generation water Cherenkov detectors are designed to have Megaton-level total mass to improve the sensitivity of neutrino physics measurement, and need more than ~100,000 photo sensors with high performance. Major requirements for the photo sensors are, good time resolution, single photon sensitivity, and low cost. We consider the HAPD with large photocathode is one of the best solutions to those requirements.

The HAPD is a Hybrid Photo Detector with an avalanche diode as its anode. The HAPD gives good time resolution due to the absence of dynodes used in PMTs. The avalanche diode gain enables the HAPD to have sufficient gain for single photon detection.

We fabricate for the first time prototype HAPDs with a large photocathode of 13-inch. Our study shows that the HAPD has good time resolution of <1ns, good sensitivity for single photon detection, wide dynamic range, and good uniformity on the photocathode. The HAPD is also expected to be less expensive than PMT because of its simpler structure.

A dedicated readout system to achieve high S/N and good time resolution is also under development. The system consists of 1) wide bandwidth preamplifier ASIC, 2) AMC (Analog Memory Cell) ASIC and FADC as a high speed sampling system, and 3) FPGA for DSP (Digital Signal Processing).

We present the R&D status of our 13-inch HAPDs. We also show the performance of the readout system.

- 51 - Production of 500 Pixel Hybrid Photon Detectors for the RICH counters of LHCb

T. Gys, on behalf of the LHCb-RICH group

CERN, PH Department, CH-1211 Geneva 23, Switzerland Email: [email protected]

The LHCb experiment will make high precision studies of CP violation and other rare phenomena in B meson decays. Particle identification from a few to ~100 GeV/c is essential for this physics programme, and will be delivered by two Ring Imaging Cherenkov (RICH) detectors. The pixel Hybrid Photon Detector (HPD) has been developed to detect the Cherenkov light. The device is a vacuum photon detector equipped with cross-focussing electron optics and a custom anode for photoelectron detection. The anode consists of a finely segmented silicon pixel detector bump-bonded to a binary readout chip. This flip-chip assembly is packaged into a custom ceramic carrier and is consequently fully encapsulated in the tube vacuum. This concept results in a high efficiency device with excellent spatial resolution and a large active area.

The production of the 500 such devices that are required to cover the 2.6m2 photon detection surface of the LHCb RICH detectors is ongoing. In addition to the basic photon detection requirements, the HPD's must comply with the overall integration and environmental constraints of LHCb. These result in tight mechanical tolerances for optimal HPD close-packing and for compatibility with individual magnetic shields. The shields are used to minimize HPD image distortions induced by the fringe magnetic flux density of the LHCb dipole magnet. A pre-series of HPD's fulfilling all the above requirements has been manufactured and their detailed performance assessed in the laboratory. Their successful operation, confirmed in a test beam, will be summarized. Magnetic distortion measurements and correction strategies will also be presented.

- 52 - Development of HPDs with a 18-mm-diameter GaAsP photocathode and an avalanche diode anode for the MAGIC-II telescope

M. Hayashida, R. Mirzoyan, M. Teshima

Max-Planck Institute for Physics, Foehringer Ring 6, 80805 Munich, Germany Email: [email protected]

The MAGIC-I telescope of 17 m diameter, the largest Imaging Air Cherenkov Telescope (IACT) in the world has been in operation at Canary island LaPalma with a low trigger threshold of about 30 GeV for cosmic gamma rays. In the future High Quantum efficiency (HQE) Hybrid photosensors should allow us to access even a lower energy in the upgraded project with a second 17 m IACT, MAGIC-II. The Hybrid Photon Detector (HPD) has been developed over several years in the collaboration with Hamamatsu Photonics [1][2]. The new prototype of 18 mm window HPDs has been produced recently according to requirement for the MAGIC project. GaAsP is used as photocathode material. The QE reaches about 50 % at the peak wavelength of around 500 nm. Using a wavelength shifter coating allows to enhance the UV- sensitivity. A fast avalanche diode, acting as an electron bombarded anode with internal gain, provides very fast output pulses. The HPD gain can be adjusted between 2 to 8x10**4. Application of these HPDs can be seen as an equivalent increase of the reflector diameter of MAGIC from 17 m to 24 m. The effect of starlight and night sky background light, which may cause the degradation of GaAsP photocathode during the operation, was examined in a simulation with realistic conditions. We found that the GaAsP photocathode is expected to have a sufficiently long lifetime to survive the adverse background light for ten years of operation. In this talk, we will report on the performance and application scheme of this type of HPDs for the MAGIC-II Telescope.

[1] R. Mirzoyan et al. NIM, A442 (2000) 140-145

[2] E. Lorenz et al. NIM, A504 (2003) 280-285

- 53 - The front-end electronics of the LHCb Ring-Imaging-Cherenkov system

K. Wyllie on behalf of the LHCb RICH group

CERN, Route de Meyrin, CH-1211 Geneva, Switzerland Email: [email protected]

The LHCb experiment at the CERN Large Hadron Collider will use Ring-Imaging-Cherenkov (RICH) detectors [1] for particle identification. By measuring rings of Cherenkov photons generated by elementary particles traversing a radiative medium, these particles can be identified across a wide range of momenta. The photons will be measured by a new type of detector, the pixel hybrid photon detector (HPD) [2]. In total, 500 HPDs will be used covering an area of 2.6m2 divided into 500,000 channels.

Specific readout electronics have been developed for processing the data from the HPDs, and this paper will describe the design and testing of these devices together with the final system to be used in the experiment. Emphasis will be on the application-specific integrated circuits that are encapsulated within the HPDs, allowing high channel density and low noise. These are subject to the strict requirements of efficient photon- detection and reliability within the harsh environment of the experiment. The chips contain both analog and digital signal processing and are fabricated in a commercial CMOS technology with additional layout features to enhance their long-term reliability. Special interconnect techniques developed for this application will also be described. Finally, the additional electronics infrastructure to read out the full system of 500,000 channels will be outlined, including data transmission and power distribution.

[1] LHCb RICH Technical Design Report, CERN/LHCC 2000-037, September 2000

[2] M. Alemi et al., Nucl. Instr. and Meth. A 449 (2000) 48

- 54 - TALKS SESSION 8

CdTe

- 55 - IDeF-X v1.0: a new sixteen-channel low noise analogue front- end for Cd(Zn)Te detectors

O. Gevin, F. Lugiez, O. Limousin, P. Barron, B.P.F Dirks, E. Delagnes

CEA/DAPNIA, CEN Saclay, 91191 Gif sur yvette, France Email: [email protected]

Joint progresses in Cd(Zn)Te detectors, microelectronics and interconnection technologies open the way for a new generation of instruments for physics and astrophysics applications in the energy range from 1 to 1000 keV. Even working between –20 and 20°C, these instruments will offer high spatial resolution (pixel size ranging from 300  300 µm² to few mm²), high spectral response and high detection efficiency. To reach these goals, reliable, highly integrated, low noise and low power consumption electronics is mandatory. Our group is currently developing a new ASIC detector front-end named IDeF-X, for modular spectro-imaging system based on the use of Cd(Zn)Te detectors. We present the most recent version of IDeF-X which is a sixteen channels analogue readout chip intended for use with low capacitive detectors. It has been processed with the standard AMS 0.35 µm CMOS technology. Each channel consist of a CSA, a pole zero cancellation stage, a variable peaking time Sallen & Key type filter and an output buffer. The CSA is designed to be DC coupled to detectors having a low dark current at room temperature and the compensation stage is continuously self adapted to this dark current.

- 56 - Automatic mapping of the leakage current in pixelated CdZnTe and CdTe detectors

B.P.F. Dirks, O. Gevin, O. Limousin, F. Lugiez

CEA/DSM/DAPNIA Saclay, L'Orme de Merisiers, Bât. 709, 91191 Gif-sur-yvette, France Email: [email protected]

In the field of the research and development of a new generation X-ray cameras for space applications we focus on the use of pixelated CdTe or CdZnTe semiconductor detectors covered with 64 (0.9*0.9 mm^2) or 256 (0.5*0.5 mm^2) pixels, surrounded by a guard ring. A critical parameter in the characterisation of these detectors is the leakage current per pixel under polarisation (~ 50-500 V/mm). Each pixel is read-out with an integrated spectroscopy channel of the multi-channel IDeF-X ASIC currently developed. The design and functionality of the ASIC depends directly on the direction and value of the current. A dedicated and highly isolating electronics circuit is developed to automatically measure the current per pixel, which is in the order of tens of pico-amperes. Leakage current maps of different detectors and at various temperatures are presented and discussed.

- 57 - Development of CdTe Pixel Detectors for Compton Cameras

S. Watanabe, T. Tanaka, K. Oonuki, T. Mitani, S. Takeda, T. Kishishita, K. Nakazawa, T. Takahashi (ISAS/JAXA), Y. Kuroda, M. Onishi (MHI)

ISAS/JAXA, 3-1-1 Yoshinodai, 229-8510 Sagamihara kanagawa, Japan Email: [email protected]

Compton cameras are the most promising approach for the detection of gamma-rays from sub-MeV to MeV. We have been developing Compton cameras based on semiconductor detectors in order to explore gamma- ray universe in these energy bands. In our Compton cameras, double-sided silicon strip detectors (DSSDs) and cadmium telluride (CdTe) pixel detectors are combined. Semiconductor detectors with high energy resolution can improve angular resolution of Compton cameras, and can also extend an energy coverage down to the sub-MeV region as low as 100 keV. CdTe pixel detectors play an essential role as absorber detectors. By using our gold stud bump bonding technology, we have realized CdTe pixel detectors and have examined their basic properties. The energy resolution of 2.4 keV (FWHM) at 122 keV was achieved with an 8 x 8 CdTe diode type pixel detector with a pixel size of 2 mm x 2 mm and a thickness of 0.5 mm. Low noise analogue ASICs, VA32TAs, are utilized to read out signals from the pixel detectors. Furthermore, we have demonstrated a performance of the Compton camera, consisting of stacked DSSDs and CdTe pixel detectors. We obtained Compton reconstructed images and spectra of gamma-rays from 80 keV to 662 keV. The angular resolution of the Compton image was ~ 4 degree (FWHM) for 511 keV gamma-rays. In this presentation, we will report our developments of the CdTe pixel detectors and the results of the Compton cameras.

[1] S. Watanabe et al., "Si/CdTe Semiconductor Compton Camera" in Proc. IEEE, Nuclear Science Symposium”, Rome, 2004

[2] T. Tanaka et al., "Development of a Si/CdTe semiconductor Compton telescope" in Proc. SPIE, vol. 5501, 229-240, 2004

- 58 - Energy Subtraction Method with Filtered X-ray for the Detection of Contrast Media

I. Kanno1, M. Takahashi1, H. Aoki2 and H. Onabe2

1Graduate School of Engineering, Kyoto University, Sakyo, Kyoto 606-8501, Japan 2Raytech Corporation, Utsunomiya, Tochigi 321-0904, Japan Email: [email protected]

For the detection of contrast media, such as Iodine, in tumors with low dose exposure, we proposed a filtered x-ray energy subtraction method [1]. In this method, an x-ray filter made of Lanthanum with its K-edge a little above the one of Iodine was employed to cut x-rays with higher energy out and to make x-ray spectrum sensitive to the thickness of Iodine. In Ref. [1], we firstly measured x-ray spectra, which passed through water phantom and Iodine layer, with a Ge detector and reproduced them by a calculation code. The thickness of Iodine and relative dose exposure were estimated based on the energy information of the calculated x-ray spectra.

In this paper, energy subtraction method with filtered x-ray measured by a CdZnTe (CZT) detector is reported: a Ge detector is not very promising in medical application due to the size of its cryogenic system. The voltage of x-ray tube was 50 kV to make the x-ray spectrum sensitive to the Iodine thickness. The energy range from 27 keV to 39 keV of the measured x-ray spectra was employed for the estimation of the Iodine thickness. The energy spectra measured by the CZT detector have some distortion 26 keV below the incident energy of the x-ray spectra. Due to the tube voltage of 50 kV, however, we could avoid the distortion and use measured energy spectra without any corrections.

The estimated thickness of Iodine contrast media from the x-ray spectra measured by the CZT detector is shown. Even in the presence of Aluminum as a substitution of bones, the thickness of Iodine could be estimated.

[1] I. Kanno, S. Maetaki, H. Aoki, S. Nomiya and H. Onabe, J. Nucl. Sci. Technol., 40, 457 (2003)

- 59 - Data analysis and performances of Compton coded mask telescopes: application to the Integral/IBIS telescope

M. Forot

Service d'Astrophysique CEA Saclay, Orme des Merisiers Bât 709 , 91191 Gif sur yvette, France Email: [email protected]

The INTEGRAL IBIS instrument is a coded aperture telescope with a dual detection layer operating in the range 15 keV - 10 MeV. In the IBIS Compton Mode, true Compton scatterings appear as two events detected into the two independent detectors ISGRI(CdTe) and PICSIT(CsI) within a given coincidence window.

The Compton mode allows us to construct images and perform polarization, spectral and temporal studies of astrophysical sources. But it happens, that an event recorded by ISGRI is mistakenly associated with an independent event detected by PiCsIT if both events occur within a time gap shorter than the coincidence window. To avoid false source detection these spurious events have to be substracted.

In this contribution we present the IBIS Compton mode performances in terms of spatial resolution (5'), spectral resolution (20% at 511 keV) and sensitivity between 150 keV and 1 MeV followed by the description of the data analysis method.

- 60 - TALKS SESSION 9

Pixel

- 61 - Development of Avalanche-Drift and Avalanche-Pixel Detectors for Single Photon Detection and Imaging in the Optical Regime

G. Lutz, P. Holl, M. Laatiaoui, C. Merck, H.G. Moser, N. Otte, R.H. Richter, L. Strüder

MPI Semiconductor Laboratory, Otto Hahn Ring 6, D 81739 München, Germany Email: [email protected]

The motivation for the development of detectors capable of time resolved imaging of optical photons comes from experiments in particle physics and astrophysics. On the one hand high energy particle showers generated by cosmic radiation are to be reconstructed by observing fluorescence and Cherenkov light. On the other hand rapidly varying astronomical objects are to be observed by looking at the time dependence of their optical emission. In both cases single photon efficiency, position and time resolution is of utmost importance.

The devices under development make use of a new concept in which the electron generated in a large sensitive area is lead towards a small area avalanche structure. This large area device can be a drift device with the avalanche structure in its center. The device can work in proportional or limited Geiger mode and a number of cells can be combined to a macro-cell. When adding all signals within this macro cell, its pulse height is a measure of the number of photons arriving in the macro-cell. Alternatively the avalanche structure can be implemented into a CCD type device.

The project is in the design and development stage; first production pre-tests are under way. The devices will be produced entirely in our laboratory, which has available a complete production line for double sided planar silicon processing. Many simulation studies have shown the validity of the concept. Some of them will be presented in order to illustrate the working principles and expected properties of the devices.

- 62 - Photon-Counting H33D Detector for Biological Fluorescence Imaging

X. Michalet1, O. Siegmund2, J. Vallerga2, P. Jelinsky2, J.E. Millaud3, S. Weiss1

1UCLA Dpt of Chemistry & Biochemistry, 607 Charles E Young Drive East, 90095 Los angeles, Usa 2Space Science Laboratory, UCB, Berkeley, CA 3Lawrence Livermore National Laboratory, Livermore, CA [email protected]

As a first step towards a wide-field, time-resolved single-molecule fluorescence detector, we have developed a high-temporal and spatial resolution, high-throughput 3-dimensional detector (H33D) for biological imaging of fluorescent samples. The design is based on a 25 mm diameter S20 photocathode followed by a 3-microchannel plate stack, read out by a cross delay line anode, using the SOHO-UVCS/SUMER mission design timing electronics to determine the (X, Y) position of the electron cloud impact generated by each detected photon [Siegmund et al, 1994]. The precise timing (t) of each detected photon with respect to the exciting laser pulse is obtained with a commercial TDC. A front-end FPGA allows synchronization of all information and time-stamping (T) of each event before asynchronous transfer to a computer. The H33D detector supports a 500 kHz global count rate, 10 kHz local count rate, 100 ps timing resolution and 100 um spatial resolutions. We describe the bench performance of the H33D detector, as well as preliminary imaging results obtained with fluorescent beads, quantum dots and live cells and discuss applications of future generation detectors for single-molecule imaging and high-throughput study of biomolecular interactions [Weiss, 1999].

[1] Siegmund et al, SPIE, 2280, 89-100 (1994)

[2] Weiss, Science 283, 1676-1983 (1999)

- 63 - Recent achievements on the HERSCHEL/PACS bolometer arrays

N. Billot, B. Horeau, P. Agnese, O. Boulade, C. Cigna, E. Doumayrou, J. Lepennec, J. Martignac, J.L. Pornin, V. Reveret, L Rodriguez, M. Sauvage, F. Simoens, L. Vigroux

CEA/DSM/DAPNIA/Sap, L'Orme des Merisiers, 91191 Gif-sur-yvette, France Email: [email protected]

New types of monolithic Si bolometer arrays sensitive in the far Infrared and Submillimeter range have been developped and manufactured by CEA/LETI/SLIR in Grenoble since 1997, and will be integrated in the PACS instrument (Photodetector Array Camera and Spectrometer) of the ESA's Herschel Space Observatory (launch date 2007). The main objective of Herschel is to understand the mechanisms that govern galaxy and star formation by observing thermal emission from interstellar dust particles in the wavelength range 60-670 microns. The very high impedance bolometers used for the PACS photometer (60-210 microns) are based on an all Silicon technology development that takes advantage of Si micromachining techniques maturity. The two focal planes consist of tiled matrices manufactured by blocks of 16x16 pixels and for the first time in bolometers' history, the readout cold electronics circuit (300 mK) includes a `16 to 1' multipexing function that allows the implementation of a large number of pixels in a confined focal plane and reduces the number of electronics lines. Another advantage of having closely packed pixels is to instantaneously achieve Nyquist sampling of the field of view. Finaly, instead of Winston cones, electromagnetic absorption is optimized using a reflecting surface and a quarter-wave cavity.

We first describe the bolometer arrays and their multiplexing cold electronics (300 mK). Then we detail the sub-modules tests and present the performances achieved in the laboratory (NEP, 1/f noise, response time).

- 64 - TALKS SESSION 10

SPE

- 65 - Overview

Photon Counting Detector Metrology Efforts at NIST

A. Migdall1, J. Fan1, M. Ware2, S. Nam3, S. Castelletto4, and J. Cheung5

1Optical Technology Div., NIST, Gaithersburg, MD 20899 USA 2Brigham Young Univ. Physics and Astronomy Dept. N283 ESC Provo, UT 84602 3Quantum Electrical Metrology Div. NIST, 325 Broadway, Boulder, CO 80305 USA 4Istituto Elettrotecnico Nazionale G. Ferraris, Strada delle Cacce 91, 10135, Torino, Italy 5Quality of Life Division (DQL), NPL, Hampton Road, Teddington, Middlesex, U.K.TW11 0LW Email: [email protected]

NIST is building a facility for the characterization of photon-counting detectors in support of the requirements of a number of quantum information applications. This facility is being used to develop improved photon counting detector metrology methods and also to facilitate the development of better photon counting detectors. The facility is intended to allow and encourage interactions between NIST and other metrology labs and detector developers. In the area of metrology, our current efforts involve photon- counting measurements based on conventional detector standards tied to a cryogenic radiometer and measurement methods based on photon pair production via parametric downconversion. This second method is an inherently absolute scheme well suited to photon counting. We are working toward verifying the detection efficiency measurement uncertainties to the 0.1% level. In the detector development arena, we are characterizing a NIST constructed photon number resolving detector currently optimized for 1550 nm and commercial prototype InGaAs avalanche photodiodes also optimized for photo counting at 1550 nm. We will describe our efforts and progress in these areas, as well as summarizing the past and future of our NIST photon counting workshop.

- 66 - Superconducting photon detectors for quantum information applications

S. W. Nam

NIST, 325 Broadway, 80305 Boulder, co, Usa Email: [email protected]

New quantum-based communication and measurement systems that use single and correlated photons are an active area of research. The current tools to calibrate the components in these systems are inadequate for these emerging applications. For accurate calibrations, high speed, low noise, and high quantum efficiency single photon detectors are needed. I will describe our work on two types of superconducting detectors, the Single Photon Superconducting Detector (SSPD) and superconducting

Transition-Edge Sensor (TES). An SSPD is an ultra-thin, ultra-narrow (nm scale) superconducting meander that is current biased just below its critical current density. When a photon is absorbed, a hot spot is formed that causes the superconductor to develop a resistance and consequently a voltage pulse. Recently, we have begun to collaborate with the University of Rochester, Moscow State Pedagogical University, MIT, and BBN to package SSPDs in a system appropriate for Quantum Key Distribution systems. By cooling to 100mK temperatures, a superconducting TES photon counter is capable of determining the number of photons that have been absorbed from a faint pulse of light. By exploiting the sharp superconducting-to- normal resistive transition of tungsten at 100mK, these voltage-biased TES single photon counters give an output current pulse that is proportional to the cumulative energy in an absorption event. This proportional pulse-height enables the determination of the energy absorbed by the TES and the direct conversion of sensor pulse-height into photon number. I will discuss our recent results of using a TES in quantum information applications and our progress towards developing detectors with quantum efficiencies approaching 100%.

- 67 - Single photon detectors based on quantum dot field effect transistors – from principle of operation to single photon counting

B. E. Kardynal1, A. J. Shields1, N. S. Beattie1,2, I. Farrer2, D. A. Ritchie2

1Cambridge Research Laboratory, Toshiba Research Europe Ltd, 260 Cambridge Science Park, Cambridge CB4 0WE, UK. 2Semiconductor Physics Group, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK. Email: [email protected]

In this presentation we show the recent results of optimisation of single photon detectors based on GaAs/AlGaAs HEMT transistors with InAs dots 1). Single photon detectors based on quantum dots rely on the sensitivity of small electronic devices such as field effect transistors (FETs) or resonant tunnelling diodes (RTDs) to local electrostatic potentials. Quantum dots placed in close proximity to the conducting channel of an n-type field effect transistor act as centres of localised negative charge, which controls the conductance of that channel. In a device with an electrically active area of the order of 1 – 2 ?m, a single photo-hole captured by a dot changes the electrostatic potential sensed by the channel enough to lead to measurable increase of the current of the device. We show that the single-photon induced current change can be as large as 100 nA at 4K 2) and we will discuss the dependence of that signal on detector design parameters (separation between the conducting channels and the dots and carrier concentration of the channel) and temperature of operation. In order to perform photon counting with quantum dot single photon detectors (both FET and RTD) we have built a transimpedance amplifier with the input stage of the amplifier near the detector at 4K 3). We discuss the design of the amplifier, whose low-pass 3dB point can be tuned from 100 kHz to 15 MHz to match the speed of the device. By increasing the single photon response signal of the device we reduced the jitter of the detection time to 6.5 ns. This value can be further decreased by reduction of the device capacitance. We show that since the dots capture an electron after capturing a hole, we do not need any conditioning pulses to achieve continuous operation of the device. Although the photo-hole is captured in the dots the photon absorption takes place in the surrounding semiconductor layers. In initial studies the absorption was confined to the 20 nm channel of the device. We report here the introduction of a 200 nm thick absorber layer under the channel of the device increasing the absorption efficiency for photons of 684 nm wavelength from 4% to 30%. Using the amplifier discussed above we found the counting efficiency of the FET is about 2% at 684nm. However, as 75% of the loss arises due to reflection at the gate on the top surface of the device, this figure could be increased to 8% by using a transparent gate contact. The dark count rate is very low for a semiconductor single photon detector, typically 10-16 counts/sec, due to the absence of avalanche processes within the detector. In the presentation we discuss mechanisms contributing to the dark count rate of quantum dot devices. Finally based on our current understanding of the principle of the operation of the detector we would like to discuss the real limitations of the operation of the detectors as opposed to the current technological ones.

[1] A. J. Shields et al Appl. Phys. Lett. 76, 3673 (2000)

[2] N. S. Beattie et al Phys.Rev.B 70, 081304(R) (2004)

- 68 - [3] B. E. Kardynal et al. Appl. Phys. Lett. 84, 419 (2004)

Review talk

RICH04 a summary

G. Paic

Instituto de Ciencias Nucleares UNAM, Circuito ext CU 0543, Mexico Email: [email protected]

The RICH 2004 workshop held in Playa Del Carmen, Mexico in December 2004 has abunded with a number of new developments. The main results of the workshop concerning the building of RICH detectors for LHCb, ALICE, PHENIX will be reviewed as well as the the recent advances in the aerogel radiators, use of multiGEM detectors and other results.

- 69 - POSTER SESSION I

PMT+HPD+APD PI-1

A test bench for precise timing measurements of single photoelectron in large hemispherical photomultiplier

D. Dornic, B. Genolini, T. Nguyen Trung, J. Pouthas

Institut de Physique Nucléaire d'Orsay, IN2P3-CNRS, Université Paris-Sud d'Orsay, 91406 Orsay Cedex, France Email: [email protected]

Accurate measurement of the timing properties of large photomultiplier (PMT) is crucial in neutrino experiments. This document describes a test bench developed for this purpose.

The pulse light is generated by the excitation of a scintillator by alpha particles of a 241Am source. The scintillator is an ultra fast plastic one, the BC422Q in which the increase percentage of benzophenone decreasesthe light output but largely improves the timing properties. The counting rate depends on the activity of the source and can be increased up to 1 kHz and even more.

The trigger is made with an ultra fast PMT (Photonis XP2020) coupled through a light guide to the scintillator. The direct coupling provides a large number of photoelectrons in this control PMT, reducing its intrinsic jitter to an hundred of pico seconds.

The PMT to be measured is placed at a large distance from the source in order to provide a quasi parallel light. The injected light level ranges from 1 (with a low yield down to few percents of non zero pulses) to a few photoelectrons by changing the distance between the scintillator and the measured PMT.

The intrinsic resolution of the bench has been determined with a second fast PMT (XP2020) used as the measured PMT. The resolution is found less than 400 ps (RMS). This bench not only provides a fast pulsed source but is also very stable and noiseless.

- 2 - PI-2

Photon-to-electron conversion efficiency and reflectance of photomultiplier tubes as a function of incidence angle of photon

E. Shibamura1, S. Sasaki2, H. Tawara2, K. Saito2, M. Miyajima3

1Saitama Prefectural Univ., College of Health Science, Sannomiya 820, 343-8540 Koshigaya Japan 2High Energy Accelerator Research Organization, Japan 3Advanced Research Center for Science and Engineering, Waseda University, Japan Email: [email protected]

Reflectivity and photon-to-electron conversion efficiency have been measured for three photomultiplier tubes, of witch windows are a borosilicate-glass with a bialkali photocathode(R878, Hamamatsu Photonix), a synthetic silica with a multialkali photocathode(R375), and a borosilicate-glass with a Sb-Cs photocathode(7696). A measurements were made by using a collimated light source with three-color LED. The peak wavelengths of emission were 640 nm for red, 525 nm for green, and 470 nm for blue lights. The LED was driven by current pulses with duration less than 1 second at a frequency of about 100 Hz. A light guide made of acrylic resin with a cross-section of 24-cornered hemi-regular polygon was attached to one of the above PMTs. The light guide with a refractive index similar to that of the PMT window enabled the measurements for incident angle to the photocathode from 15 degree to 75 degree with a step of 15 degree. These three PMTs showed a similar tendency for the three wavelengths in the photon-to-electron conversion efficiency and in the reflectance. The conversion efficiency was almost the same at 15 and 30 degrees and was maximum at 60 degree. The reflectance was almost the same at 15 and 30 degrees and was maximum at 45 degree. The reflectance was in good agreement with that calculated by treating the photocathode of the PMT as a thin film with a complex refractive index. Also the measured photon-to-electron conversion efficiency was consistent with the calculated absorptivity of the photon by the thin film.

- 3 - PI-3

Photomultiplier tubes in the MiniBooNE experiment

A. Bazarko

Princeton University, Dept of Physics, Jadwin Hall, 08544-0708 Princeton, nj, Usa Email: [email protected]

The MiniBooNE experiment at Fermilab is a neutrino oscillation search (muon to electron neutrino appearance), whose detector is a 12 m spherical tank of mineral oil instrumented with 1520 Hamamatsu R1408 and R5912 20-cm photomultipliers with custom-designed bases.

Measurements of dark rate, double-pulse rate, and charge and time response resolution were performed on all of the tubes to qualify them for placement in the detector and determine their operating voltage. The angular dependence of the response was measured for eight additional tubes.

These measurements and operational experience in the context of the MiniBooNE oscillation search will be described.

- 4 - PI-4

Behaviour in High Magnetic Fields of Fine-mesh Photodetectors for Fast Time-of-flight detectors

M. Bonesini1, F. Strati1, G. Baccaglioni2, F. Broggi2, G. Volpini2, G. 4 Cecchet3, A. De Bari3, R. Nardo’3, M. Rossella3, S. Dussoni4, F. Gatti , R. Valle4

1 INFN – Sezione di Milano, Dipartimento di Fisica G. Occhialini, Piazza Scienza 3, Milano, Italy 2LASA (INFN - Sezione di Milano) via Fratelli Cervi 201, Segrate, Italy 3INFN – Sezione di Pavia, Dipartimento di Fisica Nucleare e Teorica, via A. Bassi 6, Pavia, Italy 4 INFN – Sezione di Genova, Dipartimento di Fisica, via Dodecaneso 33, Genova Email: [email protected]

The operation inside high magnetic fields (O(1 Tesla)) of fast scintillator-based time-of-flight detectors puts severe requirements on the properties of the used photodetectors, in term of gain and timing properties. In addition rate effects may complicate the situation (as in MICE R&D experiment at RAL). The analog signal from PMTs is usually fed, after a high quality coax cable, to a splitter chain that divides the signal to the ADC line and to a leading edge discriminator followed by the TDC line. The time-of-flight measurement is achieved combining leading-edge time measurements (from the TDC) with pulse-height information for time-walk corrections (from the ADC). Aside the characteristic scintillator properties, the intrinsic Transit Time Spread (TTS) is the main limit to the detector time resolution, that can be improved increasing the photoelectron statistics of the PMT. Taking account the few available PMTs that can operate inside strong magnetic fields, this points to a systematic study of PMT gain (G), timing characteristics (TTS) and rate effects as a function of magnetic field intensity.

Systematic studies have been done with 1”, 1.5” and 2” Hamamatsu fine-mesh photomultipliers, using a refurbished resistive dipole magnet at LASA (INFN Milano), allowing fields up to 1.2 T with an open gap of 12 cm.

A fast laser pulse from a PLP-10 Hamamatsu laser (~405 nm, 60 ps FWHM, repetition rate up to 100 MHz) or a custom made system based on a fast AVTECH pulser and a NICHIA NDHV310 laser diode (~401 nm, 150ps-1ns FWHM, repetition rate up to 1 MHZ) is sent to the photocathode of the PMT under test, after a system of removable optical filters via a CERAM OPTEC UV 100/125 optical fiber (with a minimal dispersion ~ 15 ps/m). In this way optical signals of different intensities (1-2000 p.e.) can be delivered to the PMT under test. Tests were usually done with a signal corresponding to a MIP, crossing a typical scintillator counter (300 p.e.). Gain and timing measurements are done with a dedicated VME based system.

Final results on gain, timing and rate effects as a function of the magnetic field and PMT axis orientation wrt B field direction are reported.

- 5 - PI-5

Alternative to large PMTs in underwater neutrino telescopes: An array of small tubes

R. Bruijn, P. Kooijman

NIKHEF, Kruislaan 409, 1098 SJ Amsterdam, The netherlands Email: [email protected]

We report on the investigation of the use of an array photomultiplier tubes as the basic optical module in an underwater neutrino telescope. The array will finally consist of 15 to 20 3.5" phototubes housed in a glass cylindrical pressure vessel. Simulations of the response to muons traversing a cubic kilometer detector will be presented. First results on a prototype array are presented. In particular the readout using the time over threshold summed for the array of tubes are presented. This readout has the advantage of combining the hit multiplicity of the array in the output signal height with pulseheight of the individual hits in the timestructure of the pulse. It is foreseen to modulate an optical clock signal with this signal in order to read out the array via a single fibre.

- 6 - PI-6

The ReFerence Flat-Panel Photon Detector

D. Ferenc, D. Kranich, A. Laille, E. Lorenz (Presented by D. Ferenc)

University of California Davis, Physics department, One Shields Avenue, 96616 Davis, Usa, ca Email: [email protected]

Photosensors play a key role in particle astrophysics, medical imaging, nuclear radiation monitoring, some classes of analytical instrumentation, and nuclear proliferation control. Except of physics, all these areas present real (i.e. large and steady) potential markets for new, inexpensive, high-quality, industrially mass- produced photosensors.

The proposed new ReFerence Flat-Panel technology essentially combines three fully established and well- understood technologies: (1) the flat-panel plasma and field-emission TV-screen assembly, (2) the large-area photocathode deposition, and (3) the semiconductor particle sensor production.

After verifying the basic functionality of a ReFerence pixel in a series of single-pixel vacuum-unsealed prototype tests, as reported at previous meetings, in 2003 we started with the development of fully functional vacuum-sealed flat-panel ReFerence prototypes. The principal goal of that effort is to demonstrate the feasibility of an industrial mass-production technology. We report on the development of a series of gradually improving ReFerence panel prototypes, fabricated in a way that closely approaches the ultimate industrial processing. One of the main problems we encountered was with the hot Indium vacuum sealing technique. We developed a new glass-to-glass sealing technique, based on a vacuum-evaporated multi-layer structure consisting of Chromium, Gold, and Indium. Specifically, the Indium surface is now protected from oxidation with a thin Au2-In intermetallic compound layer.

- 7 - PI-7

A 0.35 µm CMOS Large Dynamic Gain Amplifier for Fast Signal Digitization

B. Genolini, L. Raux, C. de La Taille, J. Pouthas

IPN Orsay, 15 rue G. Clemenceau, 91406 Orsay cedex, France Email: [email protected]

A wide band large dynamic gain amplifier has been developed for the readout of photomultiplier tubes in astroparticle experiments like the Pierre Auger Observatory [1]. The circuit was produced with AMS 0.35 µm CMOS technology. It has a linear response for input signal amplitudes ranging from 1 mV to 7 V. It provides gains of 0.1, 1 and 10 to split the dynamic range into 3 overlapping ranges of 10 bits. Each amplifier can measure signals with durations of several microseconds with a very good baseline stability, even for an input charge of tens of nano Coulombs. The amplification is performed by current feedback amplifiers with a bandwidth of 60 MHz. The input impedance, which matches coaxial cables, remains stable over more than 1 GHz, and over the input range.

A prototype was submitted in April 2004 and successfully tested. The linearity on the working range is better than 1 %. It was also successfully tested on the Auger surface detector element installed at Orsay (Cerenkov water tank equipped with Photonis XP1805 large photomultiplier tubes).

The final circuit is foreseen to include other elements for which simulations have been performed:

• an internal calibration to be submitted for foundry in April 2005. It is adapted from the ATLAS liquid argon calorimeter calibration,

• a shaping to compensate for the effects of the coupling capacitance placed at the output of the photomultiplier tubes. The simulation relies on events acquired on the Orsay tank.

A solution integrating the digitization on the same chip is also discussed. For this purpose, a 100 MSPS FADC has been designed and submitted in December 2004.

[1] B. Genolini et al, Low power high dynamic range photomultiplier bases for the surface detectors of the Pierre Auger Observatory, NIMA 504 (2003) 240-244

- 8 - PI-8

The design of the icecube digital optical module

K. Hanson

University of Wisconsin, 1150 University Ave, 53706 Madison, Wisconsin, Usa Email: [email protected]

The first string of 70 in the IceCube neutrino observatory was deployed at the South Pole site in January 2005 and is now taking data. An IceCube string is composed of 60 digital optical modules (DOMs) each of which is an integrated package of a large area photomultiplier tube, high voltage unit, LED flasher calibration board, and embedded digital data acquisition system encased inside a glass pressure housing. The DOM posed a challenging design problem that had to simultaneously meet the extremes of high reliability in a remotely-deployed high pressure and low temperature environment, low power, wide dynamic range from single photon hits emitted by passing cosmic ray muons to tens of thousands of photons from immense electromagnetic showers, and fast time tagging of events to nanosecond precision. In addition the DOM had to be cost effective and reliably producible in quanties of several thousand units. This talk reviews these goals and the successful design that emerged.

Production and Testing of Digital Optical Modules (DOMs) for the IceCube Experiment

O. Tarasova for IceCube collaboration

DESY, Platanenallee 6, 15738 Zeuthen, Germany Email: [email protected]

The first string of IceCube - a kilometer-scale, high energy neutrino detector - was deployed in January this year deep in the Antarctic ice. At completion, IceCube will consist of at least 70 strings each with 60 Digital Optical Modules (DOMs) and a surface array of 280DOMs.

2004 was the first year of real production and testing of these DOMs: 400 DOMs were produced worldwide and a series of tests such as basic functionality, phototube dark noise, optical sensitivity, linearity, time resolution, and high voltage tests were performed in special dark freezer laboratories at temperatures ranging from +25C to -55C. 280 DOMs were sent to the South Pole for deployment and tested there again prior to deployment. Now frozen in the ice, the DOMs are showing exceptionally promising functionality.

Here DOM testing procedures and corresponding results are discussedand data from the first in-ice string are presented.

- 9 - PI-9

Testbench to Characterize the Pixels of the MAGIC Telescope

F. Lucarelli1, P. Antoranz2, M. Camara1, J.M. Miranda2, M. Asensio3, J.A. Barrio1, M. V. Fonseca1

1Departamento de Física Atómica, Molecular y Nuclear, Universidad Complutense de Madrid, Spain 2Departamento de Física Aplicada III, Universidad Complutense de Madrid, Spain 3Dpto. Infra., I. Sistemas Aeroespaciales y Aerop., Universidad Politécnica de Madrid, Spain Email: [email protected]

Photomultipliers (PMT) and hybrid photon detectors (HPDs) have a wide range of applications, from nuclear medicine to nuclear physics. In particular, they are commonly used in high energy physics and astrophysics. The MAGIC telescope is an example of their applications. This paper presents a test system for the characterization of the transient response of the photodetectors used as fast light sensors in the telescope.

This testbench consists of a short pulse generator, a well characterized blue LED, a polarization board for the PMT or HPD and an automatized DAQ made through a digital oscilloscope.

Two prototypes of pulse generator have been tested. One based in the hysteresis cycle of a Trigger Schmidt inverter, and the other based in the fluorescence or phosphorescence produced in some materials when hit by a charged particle or by gamma rays present in the atmosphere. In the former, the frequency and pulse amplitude can be electrically controlled by means of variable resistors. In the latter, the statistical behaviour of the radiation randomises the frequency. Both prototypes were proved to reach up to 10 ns pulse width.

These pulse generators were applied to a blue LED, whose peak wavelength was chosen to be the same of the Cherenkov radiation (~ 470 nm). The low duty cycle of the pulse (<0.03%) allows us to directly apply the light to the high sensitive photomultiplier without risk of damages, and to simulate the real work conditions of the pixel inside the telescope.

Radiation diagrams of the blue LED have been made. This, together with the known quantum efficiency of the PMT and the spectral emission of the LED, allows us to calculate the charge accumulated in the anode of the photomultiplier under test conditions. Therefore, in addition to the time response characteristics, we had an initial estimation of the voltage obtained in the PMT under illumination.

The pulsed signal supplied by the photodetector has been studied in detail. The fast response needed and therefore the high frequencies involved into the signal treatment makes advisable to use microstrip lines in the polarization and signal paths of the transmission chain devices. In order to obtain a) the most suitable output amplitude, b) the wider dynamic range and c) the lower noise and distortion, some commercial amplifiers have been tested.

- 10 - - 11 - PI-10

The DRS DAQ: a Low Power Digitizing System in the GHz Range

R. Pegna, A. Piccioli, R. Paoletti, N. Turini

INFN Pisa, Largo Bruno Pontecorvo 3 Edificio C polo Fibonacci, 56100 Pisa, Italy and University of Siena Email: [email protected]

We present a waveform digitizing system based on the Domino Ring Sampling Chip [1] and its implementation in a Mezzanine Card. This system is suitable for experiments in which the waveform sampling of high-speed PMT signals is crucial like the Gamma-Ray MAGIC Telescope [2].

The principle of operation, the test and the performance of the system are described.

We present also results of Night Sky Background [3] measurements performed using the Domino DAQ on the photomultipliers of the Magic Telescope camera.

The Domino ring capacitors are sampling input signals up to a maximum frequency of 4.5 GHz and are locked to an external reference clock. This feature results in a fine timing resolution sampling of the PMT signals, relevant also in other fields like Medical PET. The analog waveform is stored in capacitive sampling cells fabricated in a 0.25 $\mu$m CMOS process and read out at 40 MHz with an external 12 bit flash ADC.

The design is optimized for a multi-channel DAQ based on a 9U VME board [4] with parallel sampling of 32 input channels upon a common trigger pulse.

[1] S. Ritt, Electronics for the MEG experiment, Nucl. Instr. And Meth. A494 (2002) 520-525

[2] Commissioning and first tests of the MAGIC telescope, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Volume 518, Issues 1-2, 1 February 2004, Pages 188-192 C. Baixeras, D. Bastieri, C. Bigongiari, O. Blanch, G. Blanchot, R. Bock, T. Bretz, A. Chilingarian, J. A. Coarasa, E. Colombo et al

[3] Determination of the night sky background around the Crab pulsar using its optical pulsation Astroparticle Physics, Volume 22, Issue 1, October 2004, Pages 95-102 E. Oña-Wilhelmi, J. Cortina, O. C. de Jager and V. Fonseca

- 12 - [4] Virtual prototype method used in design of electronic circuitry for CDF, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Volume 518, Issues 1-2, 1 February 2004, Pages 491-492 Bill Ashmanskas, Mircea Bogdan, Henry Frisch, Ted Liu, Harold Sanders and Mel Shochet

- 13 - PI-11

Performance and behaviour of photomultiplier tubes at cryogenic temperature

M. Prata, M.C. Prata, G.L. Raselli, M. Rossella, C. Vignoli

INFN – Sezione di Pavia – Via Bassi, 6 - 27100 Pavia - Italy Email: [email protected]

Noble-gas liquids, such as xenon and argon, have been recently proposed as light scintillators in some experiments dedicated to neutrino physics and dark matter research. These experiments need the use of large-area high-sensitivity light detectors directly immersed in the liquid phase and operating at cryogenic temperatures.

We carried out a detailed investigation about the use of conventional and dedicated photomultiplier tubes in collaboration with two manufacturers: Electron Tubes Ltd. and Hamamatsu.

Different photomultiplier samples were tested and characterized at the liquid nitrogen temperature (77 K). Besides the capability of the devices to withstand the thermal shock from room to cryogenic temperature, we studied the behaviour of the photocathode and the multiplier chain separately. Good quantum efficiencies can be achieved with multialkali photocathodes, while the resistivity of conventional bialkali photocathodes is cause of a non-linear response at low temperature. The resistivity drawbacks can be avoided at manufacture by the use of nearly transparent platinum undercoatings. The behaviour of the multiplier chain is also strongly affected at low temperature, resulting in a wide range of gain losses (from -20% to -80%). The compensation of the gain losses with an increase of the power supply results in an increase of the dark count rate.

- 14 - PI-12

Simulation of the time response of a vacuum phototriode in a magnetic field and a comparison with experimental data

I. Yaselli, P.R Hobson

Brunel University, School of Engineering and Design, UB8 3PH Uxbridge, Uk Email: [email protected]

Vacuum phototriodes (VPT) are low gain single-stage photomultipliers that can operate in strong magnetic fields. Their simple planar electrode geometry results in a very fast time response to light. We have simulated a VPT using the ion transport software SIMION which we have extended with our own code to allow us to generate and track secondary electrons produced at the dynode. Using these programs we have determined the timing response for a delta-function light pulse as a function of VPT gain. One of the challenges in realistically simulating current VPT devices, for example those used in

High Energy Particle detectors such as the CMS endcap electromagnetic calorimeter, is that extremely fine anode meshes (of order 10 µm hole spacing) are used. By using separate instances of our geometric VPT model with radically different resolutions we can cope with the macroscopically large distances between electrodes and fully resolve the complex field near the mesh without needing to refine an enormous potential array.

We compare our simulated data on the time development of the signal with experimental data from real VPT devices obtained by illuminating the photocathode with a laser diode light source providing 60ps pulses at a wavelength of 435 nm.

- 15 - PI-13

Very High Quantum Efficiency PMTs with Bialkali Photocathode

R. Mirzoyan, M. Laatiaoui

Max-Planck-Institute for Physics, Foehringer Ring 6, 80805 Munich, Germany Email: [email protected]

The classical PMTs were invented in the mid 1930's. Their very low quantum efficiency (QE) of only < 1% at the beginning soon has been increased to the level of a few percent and in the mid 1960's to the level of ~ 25 % in the peak. Since then one can not report any significant increase of the QE. Also today the classical PMTs of relatively small size (< 1.5") with semi-transparent bialkali photo cathode show a QE of ~ 25-27 % in the peak. On the other hand there are few commercially available bialkali PMTs of 2"-3" size that demonstrate QE of 33-35 % in the peak. We have asked the PMT manufacturers Hamamatsu, Photonis and Electron Tubes to send us few samples of their PMTs with highest QE for measuring them in our laboratory. In this report we want to show the results of our comparative measurements. In fact, we have measured QE values as high as 33-35 % in the peak with few samples from different manufacturers. Also, we want to report on the modest increase of the QE of flat-window PMTs of 5-7 % after sand-blasting of the front glas. On the other hand earlier we have shown experimentally that by coating the front window of a hemi- spherical PMT with a milky scattering layer one can increase the QE on ~ 20 % [1]. Here we want to speculate that if the industry could apply the above mentioned known technology of the very high QE bialkali PMTs also to the hemi-spherical PMTs then together with the milky coating one could achieve QE peak values in the range of ~ 40 %. Note that this value is coming close to the QE of the hybrid photo-diodes with GaAsP photocathode and as one knows the latter are by about an order of magnitude more expensive.

[1] D. Paneque, et al., “A method to enhance the sensitivity of photomultipliers for air Cherenkov telescopes”. NIM A 504 (2003) 109

- 16 - PI-14

Design, modelling and testing of electro-optical transmitters for the central pixel of MAGIC telescope camera

M. Asensio1,3, F. Lucarelli1, P. Antoranz2, J.M. Miranda2, M. V. Fonseca1

1Departamento de Fisica Atomica, Molecular y Nuclear, Universidad Complutense de Madrid 2Departamento de Fisica Aplicada III, Universidad Complutense de Madrid 3Dpto. Infra., I. Sistemas Aeroespaciales y Aerop., Universidad Politecnica de Madrid Email: [email protected]

The MAGIC (Major Atmospheric Gamma-Ray Imaging Cherenkov) telescope is a 17m imaging detector with very high light sensitivity. One of its main goals is the observation of pulsars, whose emission period can vary from less than one hertz to some hundreds of hertz. Our main purpose is to detect the optical pulsed signal of the Crab pulsar, which has a frequency of about 30 Hz and a pulse width of about 3 ms.

In this work we have built an electro-optical system for the transmission of low frequency analogue signals through optical fibre. The light received by the photomultiplier is well determined by measuring the current supplied by the anode, as the electro-optical characteristics of the tube are known. The current is then driven into a transimpedance amplifier that polarizes an infrared LED (l=850 nm), therefore converting the pulse into an optical analog signal. This pulse is transmitted by means of a multi-mode optical fibre and finally amplified and filtered by the receiver.

The whole system has been tested using a pulse generator resembling the type of signal we expect from the pulsar. Time domain calibrations have been done in order to: a) obtain a fixed relation between the received pulse and the final data; therefore the loss due to the optical fibre length can be corrected and b) enhance the dynamical range of the system, covering the whole range of currents supplied by the photomultiplier. Frequency domain tests showed the low distortion caused by the whole system at the desired frequencies, even after the introduction of some filters to avoid the high frequency noise and the DC current due to the night sky background.

- 17 - PI-15

Ageing studies on hybrid photodiodes with Cs activated GaAsP photocathode

M. Errando and M. Martinez

IFAE, IFAE Ed. Cn. Campus UAB, 08193 Bellaterra, Spain Email: [email protected]

Hybrid photodiodes (HPD) are nowadays one of the most favorable options for the detection of Cherenkov photons. To reach high quantum efficiencies (QE), monocrystalline GaAs or GaAsP photocathodes are used. Prototypes of HPDs with a Cs activated GaAsP photocathode specially developed for Imaging Atmospheric Cherenkov Telescopes have shown a peak QE up to 45% at 500nm, but no extensive studies on the ageing properties of these devices have been performed. Because of the high operating voltages of HPDs -up to 10 kV- the damage effects of ion feedback are maximized, but a passive ageing -also present if the HPD is not operated- has also been observed. A theoretical approach to the most relevant ageing sources will be presented, including ion feedback and possible passive ageing sources such as evaporation and diffusion of the Cs activation layer and contamination of the electronegative surface by residual gases present on the vacuum tube. The effect of the storage and operation temperature on the lifetime of the prototype HPDs will be studied both theoretical and experimentally, and the concentration of residual gases on the vacuum tube will be measured using the afterpulses caused by ion feedback impacts. The possibility of disentangling between the causes of the photocathode damage will also be discussed and some experimental tests will be proposed and its results presented.

- 18 - PI-16

Some historical issues of photomultiplier tube invention

B.K.Lubsandorzhiev

Institute for Nuclear Research RAS, pr-t 60-letiya Oktyabrya 7A, 117312 Moscow, Russia Email: [email protected]

We review some historical aspects of photomultiplier tube invention. The paper is our tribute to the memory of great Soviet-Russian physicist and engineer Leonid Aleksandrovitch Kubetsky whose life and scientific activities are described briefly. Particular effort are made to shed light on controversial issue of who invented photomultiplier tube. It is asserted that if to recognize L.A.Kubetsky's priority on photomultiplier tube invention the Beaune Conference would be held on the eve of 75th Anniversary of that great event.

- 19 - PI-17

Gallium based avalanche photodiode optical crosstalk

J. Blazej, I. Prochazka, K. Hamal, B. Sopko, D. Chren

Czech Technical University in Prague, Brehova 7, 115 19 Prague 1, Czech Republic Email: [email protected]

Solid state single photon detectors based on avalanche photodiode are getting more attention in various areas of applied physics: optical sensors, quantum key distribution, optical ranging and Lidar, time resolved spectroscopy, X-ray laser diagnostic, and turbid media imaging. Avalanche photodiodes specifically designed for single photon counting semiconductor avalanche structures have been developed on the basis of various materials: Si, Ge, GaP, GaAs and InGaP/InGaAs at the Czech Technical University in Prague during the last 20 years. They have been tailored for numerous applications. Trends in demand are focused on detection array construction recently. Even extremely small arrays contain a few cells are of great importance for users. Electrical crosstalk between individual gating and quenching circuits and optical crosstalk between individual detecting cells are serious limitation for array design and performance. Optical crosstalk is caused by the parasitic light emission of the avalanche which accompanies the photon detection process. We have studied in detail the optical emission of the avalanche photon counting structure in the gallium based photodiodes. The timing properties and spectral distribution of the emitted light have been measured for different operating conditions to qualify optical crosstalk.

- 20 - PI-18

Final calibration results of CMS electromagnetic calorimeter photodetectors

P. Depasse, H. El Mamouni, J. Fay, S. Gascon-Shotkin, B. Ille

Institut de Physique Nucléaire de Lyon, 4 rue Enrico Fermi, 69622 Villeurbanne, France Email: [email protected]

The Compact Muon Solenoid is one of two generic detectors currently being constructed for the Large Hadron Collider at CERN foreseen to begin data taking in 2007. The electromagnetic calorimeter consists of a barrel and endcaps. These are made of PbWO4 scintillating crystals. In the barrel, the scintillation signal is read out by Hamamatsu avalanche photodiodes, connected in parallel in a structure called a "capsule". Each of the 61200 channels must be equipped with a capsule, the reliability of which must be assured since they will be inaccessible during the life of the experiment. The capsule production is now finished. We present the final calibration and performance statistics.

- 21 - PI-19

Avalanche micro-pixel photodiodes with surface drift of charge carries

I. Britvitch, D. Renker, Z.Ya. Sadygov, R. Scheuermann, A. Stoykov

Paul Scherrer Institut/Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, CH-5232 Villigen psi, Switzerland Email: [email protected]

Avalanche Micro-pixel Photo Diodes (AMPDs) are produced on the basis of standard MOSFET technology.

The AMPD consists of a matrix of independent p-n - junctions for photoelectron amplification by a local avalanche process.

Each element of the matrix is connected with a common drain electrode by an individual surface drift channel to provide transfer of the multiplied charge carriers along the Si-SiO2 boundary.

Experimental results with the two (p-on-n and n-on-p) novel devices of this type are presented.

The use of avalanche microchannel photodiodes in a scintillating fiber muon beam profile monitor

A. Stoykov, R. Scheuermann, T. Prokscha, Ch. Buehler, Z.Ya. Sadygov

Paul Scherrer Institut/Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, CH-5232 Villigen psi, Switzerland Email: [email protected]

A position--sensitive detector (the Muon Beam Profile Monitor - muBPM) for nonrelativistic muon beams and to be used in high magnetic fields was developed. The muBPM consists of a grid of 20 scintillating fibers probing the muon beam intensity along the two orthogonal directions perpendicular to the beam axis.

The fibers are readout by avalanche microchannel photodiodes (AMPDs).

The use of AMPDs results in a compact design of the device, its insensitivity to magnetic fields, and the ability to handle high event rates. The muBPM was successfully utilized in the measurement of the muon beam profiles in magnetic fields up to 4.8 Tesla and at event rates as high as 3*106 1/s per channel.

- 22 - - 23 - PI-20

Multipixel Geiger-mode avalanche photodiodes with high quantum efficiency and low excess noise factor

E. Gushchin1, M. Khabibullin1, Y. Kudenko1, A. Kuznetsov2, O. Mineev1, Y. Musienko2, S. Reucroft2, J. Swain2, M. Vlasov1, N. Yershov1

1Institute for Nuclear Research, Moscow, Russia 2Department of Physics, Northeastern University, 360 Huntington Ave, MA 02115 Boston, Usa Email: [email protected]

We have studied the performance of two different 1 mm-squared area multipixel Geiger-mode avalanche photodiodes (MPGM APDs) recently developed by CPTA (Moscow). One of the devices was developed for the detection of UV and blue light, the other has a peak sensitivity in the green/red region. Both devices show >35% photon detection efficiency at peak sensitivities (470 nm and 650 nm, respectively) with moderate cooling. The excess noise factors were measured to be from 1 to 1.3 in the working range for both devices. The results of scintillation light detection from an LSO crystal as well from plastic scintillator will be presented.

- 24 - PI-21

APD detectors for biological fluorescence spectroscopy

V. Borrel

GIATHE/CESR, 9 av Colonel Roche BP 4346, 31029 Toulouse cedex, France Email: [email protected]

Fluorescence spectroscopy is a very convenient and widely used method for studying the molecular background of biological processes. Chromophores are included inside the structure under study, a flash of laser light induces fluorescence (Fluorescence Recovery After Photo-bleaching, the decay of which yields informations on polarity, speed of rotation, speed of diffusion as well as time and spatial evolutions of interactions between molecular species. The method can even be operated for studying living cells.

This is classically performed with a PM-based system. Since for biological reasons an important decrease of the excitation of the cells is needed, their fluorescence response becomes fainter and a significant evolution of the detectors capabilities is welcome.

We present here results obtained with an APD-based system. The small sensitive area of detection allows a very significant improvement in signal/noise ratio,improvement in gain, and the opening towards new parameters.

With these new detectors we begin the study of information transmission between cells through morphine receptors.

This works is conducted by both electronicians and biophysicists, so results and technics in both fields will be presented.

- 25 - PI-22

XPAD: a pixel detector for material sciences

S. Basolo2, J.-F. Berar1, N. Boudet1, P. Breugnon2, B. Caillot1, J.-C. Clemens2, P. Delpierre2, B. Dinkespiler2, I. Koudobine2, Ch. Meessen2, M. Menouni2, Ch. Mouget1, P. Pangaud2, R. Potheau2 and E. Vigeolas2

1Laboratoire de cristallographie-CNRS, BP166, 38042 Grenoble cedex 9, France 2CPPM-IN2P3, 163 avenue de Luminy, 13288 Marseille, France Email: [email protected]

Currently available 2D detectors do not make full use of the high flux and high brilliance of third generation synchrotron sources. For this reason numerous experiments are still performed using slits and photomultipliers that allow only point detection. At the present time, the 2D detectors in most common use are CCD cameras with indirect photon detection.

The XPAD photon counting detector has been developed for materials science and small angle scattering experiments similar to those performed on the CRG-D2AM beamline at ESRF [1]. At the time, its prototype is built of 8 modules of 8 chips for a total area of about 6.8x6.8 mm2 and 200x192 pixels.

Recent results of powder diffraction of CaSrX zeolite [2] have prooved that such 2D detectors present a new opportunity to improve the quality of our measurements. SAXS results will also be presented and compared to CCD ones.

[1] J.-F. Berar, L. Blanquart, N. Boudet, P. Breugon, B. Caillot, J.-C. Clemens, P. Delpierre, I. Koudobine, C. Mouget, R. Potheau and I. Valin, J. Appl. Cryst. 35 (2002) 471-476

[2] S. Basolo, J.-F. Berar, N. Boudet, P. Breugnon, B. Caillot, J.-C. Clemens, P. Delpierre, B. Dinkespiler, I. Koudobine, Ch. Meessen, M. Menouni, Ch. Mouget, P. Pangaud, R. Potheau and E. Vigeolas, accepted in IEEE Trans. Nucl. Sci., conference IEEE-2004, Rome

- 26 - PI-23

Recovery time of the Gieger mode Avalanche Photodiodes

I. Britvitch

ETH, Zurich, OFLC/009 Paul Scherrer Institute, 5232 Villigen psi, Switzerland Email: [email protected]

A lower energy threshold for ground-based Cherenkov telescopes together with an improved precision in measuring the energy spectrum are the keys for a breakthrough in gamma-ray astrophysics in the GeV domain. Such improvements will allow gamma-ray energies to be covered which overlap the range covered by satellite experiments. The MAGIC (Major Atmospheric Gamma Imaging Cherenkov telescope) collaboration proposes an upgraded image camera for the telescope now successfully operating in La Palma.

Avalanche photodiodes working in Geiger mode (GMPD) are currently under consideration as a possible photodector option for a new image camera. An important issue is the dead time of these devices because of the high background count rate caused by star light.

We report on the properties and especially the recovery time measurements of GMPD prototypes from different producers.

- 27 - PI-24

Performance of Recent Avalanche Photodiodes with Phoswich Detectors for High-Resolution Positron Emission Tomography

R. Lecomte¹, C. M. Pepin¹, D. Rouleau¹, J. Cadorette¹, P. Bérard¹, M. D. Lepage¹, F. Bélanger², J.-D. Leroux², J.-B. Michaud², S. Robert², H. Semmaoui², M.-A. Tétrault², N. Viscogliosi², R. Fontaine², D. E. MacSween³, M. Davies³, H. Dautet³

¹Department of Nuclear Medicine and Radiobiology, Université de Sherbrooke, Sherbrooke, QC, Canada ²Department of Electrical and Computer Engineering, Université de Sherbrooke, Sherbrooke, QC, Canada ³PerkinElmer Optoelectronics, Vaudreuil, QC, Canada Email: [email protected]

Molecular imaging of small laboratory animals, primarily mice, with positron emission tomography (PET) requires an intrinsic spatial resolution on the order of 1 mm to reach an image definition equivalent to that currently obtained in humans with clinical PET scanners. Such high resolution can be achieved using avalanche photodiodes (APD) coupled to a stack of high luminosity scintillators in a phoswich configuration, either to increase the pixel detector density or improve the depth-of-interaction measurement. New high performance reach-through APDs with low noise (~0.5 pA/Hz½ at gain 100) and low breakdown voltage (~275 V) for improved reliability at high gain were designed by PerkinElmer Optoelectronics for efficient coupling with 2x2 mm² pixels. The devices were investigated with a variety of crystals and phoswich assemblies spanning a wide range of scintillation characteristics. In this paper, we compare the energy, timing and phoswich crystal identification performance obtained with these APD-based detectors using traditional nuclear spectroscopy analog techniques and modern digital signal processing algorithms. Whereas little gain in energy resolution relative to PMT-based detectors has been observed, sizeable gains in coincidence timing resolution were achieved, respectively reaching 10 ns FWHM and less than 2 ns FWHM with BGO-BGO and LSO-LSO APD-based detectors. By fully exploiting the features of the APD-scintillator detector response, digital phoswich crystal identification with error rates <0.5% was achieved with all crystal combinations.

- 28 - PI-25

Front end electronics for PWO-based PHOS calorimeter of ALICE

H. Muller1, R. Pimenta1, Q. Li5, D. Budnikov4, I. Sibiryak3, A. Vinogradov3, M. Ippolitov3, D. Rohrich6, B. Skaali2

1CERN, Division PH, Geneva, Switzerland 2Department of Physics, University of Oslo, Norway 3Kurchatov Institute, Moscow, Russia 4RFNC VNIIEF, Sarov, Russia 5Huazhong University of Science and Technology, Wuhan, Rep. o. China 6Department of Physics, University of Bergen, Norway Email: [email protected]

The electromagnetic Photon Spectrometer (PHOS) of ALICE consists of five PbWO4 arrays of 56*64 crystals, operated at -25 C with signal conversion via APD diodes and charge sensitive preamplifiers. We describe here the new 32-channel shaper/digitizer and readout electronics, situated below the crystals in an isolated warm volume in geometrical correspondence to 2 parallel rows of 16 crystals per card.

Each of these Front End Electronics (FEE) cards cover a 14 bit dynamic range of 5 MeV…80 GeV per channel with a RMS noise level of 3 MeV or 600 electrons. Dual gain shapers produce semi-gaussian input to 10 bit Altro digitizers with embedded multi-event buffers. The data readout is mastered by an external Readout Control Unit (RCU) which has address mapped access to data memories and to control registers of the FEE cards via a custom GTL bus. Programmable high voltage controllers on the FEE card allow for precise calibration of all 32 APD gains. Co-designed with the TRU trigger cards, each FEE card generates 8 fast analog signal sums of 2*2 crystal as input to the trigger cards. With 112 FEE and 8 TRU’s embedded inside PHOS module the dissipated power of 1 kWatt is extracted via a leakless water cooling system.

- 29 - PI-26

A ZnS-Si isotype hetero-junction avalanche photodiode structure for scintillation lights detection

I. Tapan, M.A. Afrailov and F. Kocak

Department of Physics, Uludag University, Fen Edebiyat Fakultesi, Fizik Bolumu, 16059 Bursa, Turkey Email: [email protected]

In this work, we have developed a Zinc sulfide-Silicon (ZnS-Si) isotype hetero-junction avalanche photodiode structure that has very high quantum efficiency and very low excess noise factor for photons of wavelength in the region from 340 to 800 nm. This structure is suitable for scintillating crystals used in particle physics experiments, emit light in the wavelength region of 400–550 nm. The signal generation process has been performed in a well-defined device geometry, which consist of successive layers of p+ - type ZnS, p -type Si, n -type Si, n- -type Si and n+ -type Si semiconductors, by a Monte Carlo simulation code. Based on this work, we offer a new avalanche photodiode structure for scintillation lights detection.

- 30 - PI-27

Timing Properties of an Avalanche Diode for Single Photon Counting

C. Merck, P.Holl, M. Laatiaoui, G.Lutz, H.G. Moser, N. Otte, R.H. Richter, L. Strueder

Max-Planck-Institute for Physics, Foehringer Ring 6, 80805 Munich, Germany Email: [email protected]

A new concept for a silicon single photon counter has been developed at the Semiconductor Laboratory of the Max-Planck-Institute for Physics and Extraterrestrial Physics. The concept combines the principles of a drift diode and an avalanche diode. The electron which is generated by an incoming photon has to drift to the small avalanche region. In order to provide high efficiency and good timing properties, the electrons have to be focussed properly with short time jitter. Therefore, drift and timing properties have been investigated and studied using simulations.

- 31 - PI-28 Investigation of a Photon Counting Avalanche Photodiode from Hamamatsu Photonics I. Britvitch1, Y. Moussienko2, D. Renker1, A. Stoykov1

1Paul Scherrer Institute, Villigen PSI, CH-5232 Villigen, Switzerland 2Northeastern University, Boston, US Email: [email protected]

Multi-cell avalanche photodiodes operating in Geiger-mode have shown to be a very promising alternative to photomultiplier tubes for the detection of single photons at room temperature. Like a photomultiplier they have high gain and a fast rise time and they are insensitive to pickup. Beyond it they operate in high magnetic fields, are compact and need a relative low bias voltage. It is expected that the MOS production technique makes them cheap. Recently PSI and Hamamatsu Photonics worked together for the development of a radiation hard APD for CMS ECAL and had a very good success. The development continued based on a similar design for a photon counting multielement Geiger-mode APD with a area of 1x1 mm**2. The properties of this device have been measured and will be reported.

- 32 - POSTER SESSION II

MAPMT+MCPMT+CdTe

- 33 - PII-1

Intraoperative beta probe for brain tumor surgery

L. Menard1, S. Bonzom1, S. Palfi2, S. Pitre3, M.A. Duval3, R. Siebert3, Y. Charon1

1Paris VII 2Hôpital Henri Mondor, Créteil 3Institut de physique nucléaire d’Orsay Email: [email protected]

Surgery is still considered the primary therapeutic procedure for high grade gliomas and several recent clinical studies have shown that gross total tumor resection is directly associated with longer and better survival when compared to subtotal resection. Considering this context and based on a first experience in radio-guided surgery [1,2], we are currently developing an intraoperative positron imaging probe specifically designed to help neurosurgeons to locate residual radiolabeled brain tumor (with 18F-FDG or FET) after the bulk has been excised. Our detector was conceived to be compact and electrically safe in order to be easily used inside the operative wound jointly to other surgical tools.We chose to build our  imaging probe around plastic scintillating multiclad fibers which optimize the detection of positrons emitted by tumor while significantly reducing annihilation gamma rays background noise. Scintillating fibers are disposed on two concentric rings and are thermally fused to a 2 m length optical fiber bundle to export the signal outside of the operative wound until a multi-channel PMT. To eliminate the  background noise, each detection pixel is composed of 2 scintillating fibers: 1 on the internal ring and 1 on the external ring which is beta shielded wich a thin inox layer. The + distribution is obtained in real time by subtracting the signal from these 2 fibers for each detection pixel. Monte Carlo simulations using MCNP were realized on a voxelised anthropomorphic brain phantom with different tumor seeking radiotracers to optimize the detector geometry in a realistic clinical environment. A first prototype of the probe composed of 4 detection pixels is currently under development. Its experimental beta and gamma sensitivities were measured using 204Tl and 22Na point sources.Simulations show that optimal performances are obtained with 2 mm diameter and 0.5 mm length scintillating fibers. This geometry provides a gamma ray rejection efficiency of 99.9% for a tumor to tissue ratio of 3:1. These results were confirmed by experimental measurements. With a homogeneous 18F-labeled tracer distribution in the tumor margins and a detector placed in contact with the tissues, the probe sensitivity is 11 cps/nCi/mm3 for each detection pixel. The theoretical minimum radiotracer detectable concentration achieved with 18F-FET is 1.8 nCi/mm3 for an acquisition time of 5 s. This minimum value has to be compared to the 2.9 nCi/mm3 average concentration of 18F-FET in the bulk of the tumor and is expected to be sufficient to help surgeons to detect residual lesions in the resection margins of the tumor. In addition to these promising performances, we are performing experimental measures on radioactive phantom to validate the operating parameters of the probe in a clinical context.

[1] L. Ménard, et al., "Performance characterization and first clinical evaluation of an intra-operative compact imager", IEEE Trans. Nucl. Sci., NS46(6), 2068-2074 (1999)

- 34 - [2] S. pitre, et al., “A hand-held imaging probe for radioguided surgery: physical performances and preliminary clinical experience. Eur J. Nucl Med, 30:339-343

- 35 - PII-2

Studies of the aluminum oxide based microchannel plates

G. Drobychev, A. Barysevich, K. Delendik, A. Karneyeu, K. Rudov, O. Voitik

Institute for Nuclear Problems, 11 Bobruiskaya St., 220050 Minsk, Republic of belarus Email: [email protected]

Microchannel plates (MCP) recently became widely used in different fields of science and technology. They have good operational parameters, such as short response time (<1 ns), good spatial resolution, sensitivity up to single electron mode, high radiation hardness, ability to work in strong magnetic fields.

We propose new kind of MCP on a basis of anodic aluminum oxide. It is being formed by electrochemical oxidation of aluminum in electrolytes [1].

This work presents results of the research on the Al2O3 based MCPs. We studied MCPs that have various geometric parameters (thickness, channel diameter to length ratio, effective surface, etc.). The properties of MCPs as radiation detectors were studied in direct current mode as well as in pulse - height mode.

[1] Delendik K. I., Voitik O. L. Anodic alumina as material for high-aspect ratio microstructures // Proceeding of Fourth International Workshop on High-Aspect-Ratio Micro-Structure Technology. June 2001. Baden-Baden, Germany. 2pp.)

- 36 - PII-3

Extending the operation of a position-sensitive photomultiplier tube to 1 million cps

A. Fallu-Labruyere1, H. Tan1, W. Hennig1, Y.X. Chu1, M. Momayezi2 and W.K. Warburton1

1XIA LLC, 8450 Central Ave, Newark, CA 94560 2Bridgeport Instruments LLC, Oakland CA USA. Email: [email protected]

While position sensitive photomultiplier tubes (PSPMTs), coupled to fast scintillators, are widely used as photon detectors in applications such as medical imaging systems (PET, gamma camera, etc.) where it is desirable to combine good time resolution with the capability of locating the point of photon interaction, their count rate limitations (of order of tens of thousand cps) have precluded their use in more demanding applications. Recently, in a neutron imaging application, we found that, by using custom designed fast anode and dynode readout circuits, coupled to a fast digital pulse processing board, we could operate a PSPMT at rates approaching 1 million cps while retaining good position resolution, linearity and time resolution. These developments therefore significantly extend the range of PSPMT application.

A PSPMT consists of a photocathode sensitive to the scintillation light wavelength, multiple dynodes for photo-electron multiplication, and a pair of crossed multi-wire anodes. The wires in each anode are interconnected via a chain of resistors, both ends of each chain being terminated by a resistor that converts the collected photocurrents into voltages. For each photon interaction event within the scintillator, the ratio of the difference between a pair of anode end voltages to their sum provides an interpolated position measurement along one axis and hence a projection of the event’s location on the photocathode. For each and every events, time of interaction is provided using the last dynode. In this work these interpolation computations were performed in real time for each interaction using an XIA Pixie-4 gamma ray spectrometer.

In this paper, we first describe our custom fast anode and dynode trans-impedance circuits, which can accommodate input event rates of order one million counts per seconds while sustaining good position resolution. Using data collected from both a 3-inch and a 5-inch PSPMT (Hamamatsu R2486 and R3292, respectively), we report their linearity, quantum efficiency, and time and position resolution as a function of the number of incident photons, as well as the dependency of photo-electron time of flight on photocathode interaction location. These results combine to show that, with proper signal handling and processing, the useful input counting rate capability of this family of PSPMTs can be extended by a factor of 20 compared to previously reported results.

- 37 - PII-4

Picosecond Time Response of Microchannel Plate PMT Detectors

J. Milnes

Photek Ltd, 26 Castleham Road, TN38 9NS St leonards on sea, Uk Email: [email protected]

The output pulse width and jitter in the time response of photomultiplier tubes (PMT) is severely reduced in microchannel plate models compared to more standard dynode chain PMTs due to a vastly reduced variation in the path length of the electrons through the amplifying system. Typically the jitter can be < 50 ps and pulse widths in the region of 200 ps compared to the nanosecond domain occupied by the best conventional PMTs Photek manufacture PMTs with one, two or three microchannel plates depending on the gain required, and also use the same structure without any microchannel plates to work as simple photodiodes. We illustrate advances in pulse rise time and width and demonstrate the dependence of the leading and trailing edges of the output pulse on the design of the PMT. We use a time correlated single photon counting module to show the variation in the jitter of the time response.

- 38 - PII-5 Lanthanum scintillation crystals for gamma ray imaging R. Pani1, P. Bennati1, M.Betti1, M.N. Cinti1, R.Pellegrini1, M.Mattioli2, V. Orsoline Cencelli2, F. Navarria2, D. Bollini2, G. Meschini2 and F. de Notaristefani2 1Dipartimento di Medicina Sperimentale e Patologia dell’Università “La Sapienza”, viale Regina Elena 324, 00161 Rome, Italy 2INFN Scintirad collaboration Email: [email protected] The availability of new scintillation materials as LaBr:Ce and LaCl:Ce, which are characterized by very high energy resolution values and light yield higher than NaI(Tl), makes possible to build low cost detectors optimizing the compromise between detection efficiency and spatial resolution. In addition to 49000ph/MeV and 62000ph/MeV respectively, at a wavelength suited to photocathode, the more important characteristic is surely represented from the scintillation light yield proportionality as a function of incident gamma ray energy. This involves an absolute innovation in X and gamma ray imaging giving the possibility to obtain energy resolution values nearly halved regarding the past (6-7% at 140 keV and 3% at 511 keV). Moreover they show scintillation time decay of approximately 25ns. From the point of view of radiation absorption, the crystals offer a behavior close to the NaI(Tl). The photodetector consists of new position sensitive PMT Hamamatsu H8500 Flat Panel. This tube, whose charge multiplication and positioning system is based on metal channel method, introduces characteristics strongly innovative which: charge intrinsic spread less than 1 mm, extreme compactness (15 mm thickness and 1 mm peripheral dead zone) and 1.5 mm photocathode glass window, that highlights the imaging performance of such crystals. In this paper we present preliminary results obtained from a series of such crystals like one inch square LaCl:Ce and two inch square LaBr:Ce coupled to PSPMT by light guide or by integral assembly respectively. Imaging performance were also compared with the analogous ones obtained by NaI(Tl) pixelleted crystal and NaI(Tl) continuous crystal integral assemblied with a Flat Panel PMT. Spatial resolution measurements were performed filling two capillaries with 99mTc and intrinsic spatial resolution values resulted between 0.7 and 1.3 mm for all crystal configurations investigated. In particular MTF curves of planar Lanthanum crystals shown superior image performances with respect to pixellated detectors. Finally energy resolution measurements were performed on one inch diameter by one inch thick LaBr:Ce crystal optimized for spectrometric studies. 6% energy resolution value at 140keV was carried out.

Performance measurements of a compact scintillation camera based on multiPSPMT read-out R. Pani1, M. Betti1, M.N. Cinti1, P. Bennati1, R.Pellegrini1, A. Bigongiari2, G. Passuello2, M. Pieracci2 1Dipartimento di Medicina Sperimentale e Patologia dell’Università “La Sapienza”, viale Regina Elena 324, 00161 Rome, Italy 2CAEN S.p.A., Viareggio-Lucca, Italy Email: [email protected] IMI (Integrated Mammographic Imaging) is technological transfer project, from INFN and Universities to Italian industries, and it consists in the development of a new gamma camera specifically designed for the functional breast imaging. It was projected to overcome present limitations offered by standard imaging detectors (Anger camera). The scintillation camera design, based on an array of 1” PSPMTs Hamamatsu H8520-C12 closely packed, allows to assemble very compact detectors without limitation in active area and light weight. In this paper we present the results obtained by a 6x7 PSPMT high spatial resolution gamma camera, comparing its performances with a previously developed 4x4 PSPMT gamma camera prototype. Both the gamma imagers were based on PSPMTs with 12 crossed wire anodes and a photocathode with 0.8 mm glass window thickness. The PSPMT array was coupled to a NaI(Tl) scintillation matrix, 2x2x6 mm3 individual pixel and 3 mm glass optical guide. Signal read out logic consists of 42 independent resistive chains, one for each PSPMT, for the position determination. The calibration results show a very good identification of each individual crystal in the active area and in neighboring tubes as well. It allowed a better LUT correction of the final image with a consequent contrast enhancement. Very good performances were also carried out in term of spatial resolution, energy resolution, position linearity and uniformity counting. The imaging features were also compared with the analogous ones obtained by Hamamatsu H8500 Flat Panel PSPMT with the same scintillation crystal coupling. Such tube represents the last advancement in position sensitive photodetection. It allows to improve pulse height uniformity response, through reducing cracks in close packing assembly.

- 39 - PII-6

MGR: an innovative, compact and low-cost cosmic ray tracking detector

M. Basset1, G. Giannini1, M. Bari1, S. Ansoldi1, G. Scian1, A. Zuccaro1, S. Blasko2, R. Battiston2, M. Menichelli2, E. Fiori2

1University or INFN of Trieste, Padriciano, 99, 34012 Trieste, Italy 2University or INFN of Perugia – Italy Email: [email protected]

We will illustrate the design, assembly and test of an innovative, compact and low cost cosmic ray tracking detector developed at the INFN laboratories of Trieste and Perugia (Italy), which makes use of the most recent technologies for scintillating fibres and multianode photomultiplier tubes.

The detector has been designed in particular for underground investigation: it lies inside a cylinder made of aluminium and can be lowered down a 20 cm diameter hole drilled into the ground, reaching a depth of 10- 30 m. It measures the cosmic ground penetrating muon flux as a function of the direction to obtain information about the density of the material through which the cosmic rays travel before reaching the detector itself.

The whole instrumentation (that is, the detector, a computer for data acquisition and a power supply), is simple to install and easy to handle. It could be useful in geology, archaeology, and speleology.

In the last few months we tested the performance of the detector in two different italian archaeological sites (Aquileia -UD- and Fiumicino - RM-). The acquired data are being analyzed in these weeks and will be presented in this work.

- 40 - PII-7

Performance of 8-stage and 12-stage Multianode Photomultipliers

S. Eisenhardt

University of Edinburgh, School of Physics, Mayfield Road, EH9 3JZ Edinburgh, Uk Email: [email protected]

The 64-channel Multianode Photomultiplier (MaPMT) has been evaluated as a candidate photo-detector for the LHCb Ring Imaging Cherenkov (RICH) counters. The newly available 8-dynode stage MaPMT was tested in particle beams at CERN. The MaPMT signals were read out directly with the Beetle1.2 chip which was designed for the LHCb environment and operates at 40MHz. The photon yield and signal losses were determined for a cluster of 3x3 close-packed MaPMTs. The photon yield matched well the results from simulation after corrections had been applied.

The performance of the 8-stage MaPMT was compared to that of the 12-stage MaPMT which has a larger intrinsic gain. The Beetle1.2MA0 readout chip was custom designed to match the dynamic range of the 12- stage device.

- 41 - PII-8

Optical adapters to improve the collection efficiency of the Multi-Anode PhotoMultipliers detectors

L. Gambicorti1,2, P. Mazzinghi2,3, E. Pace1,2

1Dep. of Astronomy, University of Florence, L.go E.Fermi 2, 50125 Firenze, Italy 2INFN Section of Florence, Italy 3Istituto Nazionale di Ottica Applicata, Italy Email: [email protected]

Aim of this work is to describe the optical system developed, with ray- tracing simulations, to improve the collection efficiency of Multi-Anode PhotoMultipliers (MAPMTs) detectors from Hamamatsu corp., used in nuclear, cosmic-rays and neutrino physics experiments. These optical collectors have imaging and filtering capability. Such characteristics allow to improve the collection efficiency of detectors, focusing all photons inside the sensitive area, and also to improve the signal to noise ratio by limiting the wave band to the region of interest. This filter properties allow to avoid background photons from nearby spectral regions and it is studied to minimize the wavelength shifting respect to the increasing of the incident angle. The spectrum of transmissivity have been realized with an high transparency in wavelength range of interest and with a sharp cutoff outside.

In this work the application on different typologies of PMT have been studied. In particularly the collection efficiency of the 64-channel PMT was improved from 45% to 65% using our optical adapters. On an electrostatic-focusing PMT, with an efficiency of 74%, the application of our innovative solutions have enhance this efficiency exceeding 90%, including the band pass filter and keeping the mass below 25g. First prototypes have been realized.

- 42 - PII-9

SPD Very Front End Electronics

S. Luengo

La Salle, School of Engineering, Quatre Camins Street, 30th, 08022 Barcelona, Spain Email: [email protected]

The SPD (Scintillator Pad Detector) is part of the LHCb calorimetry [1] system that provides high energy hadron, electron and photon candidates for the first level trigger (Level 0 Trigger).

The SPD is designed to distinguish electrons and photons for the LHCb first level trigger. This detector is a plastic scintillator layer, divided into about 6000 cells of different size to obtain better granularity near the beam [2]. Charged particles will produce, and photons will not, ionisation in the scintillator. This ionisation generates a light pulse that is collected by a WaveLength Shifting (WLS) fibre that is coiled inside the scintillator cell. The light is transmitted through a clear fibre to the readout system that is placed at the periphery of the detector. Due to space constraints, and in order to reduce cost, these 6000 cells are divided in groups using a MAPMT [3] of 64 channels that provides information to the VFE readout electronics.

The SPD signal has rather large statistical fluctuations because of the low number (20-30) of photoelectrons per MIP. Therefore the signal is integrated over the bunch length of 25ns. Since in average about 85% of the SPD signal is within 25ns, 15% of a sample is subtracted from the following one using an operational amplifier.

The SPD VFE readout system that will be presented, consists of the following components. A specific ASIC[4] integrates the signal, makes the signal-tail subtraction, and compares the level obtained to a programmable threshold (to distinguish electrons from photons). A FPGA programmes the ASIC threshold and the value for signal-tail subtraction. Finally a LVDS serializer, sends the information to the first level trigger system.

[1] D. Breton “The Front-End Electronics for LHCb calorimeters”, X Int. Conf. on Calorimetry in Part. Phys., CALOR 2002, Pasadena

[2] S. Amato et al., “LHCb Technical Design Report”, CERN/LHCC/2000-0036, 2000

[3] O. Dechamps et al, “Study of multianode photomultipliers for the electromagnetic calorimeter preshower read out of the LHCb experiment”, 3th Int. Conf. on New Developments in Photodetection, Beaune, 2002

- 43 - [4] D. Gascon et al, “Discriminator ASIC for the VFE SPD of the LHCb Calorimeter”, LHCB Technical Note, LHCB 2004-xx

- 44 - PII-10

A noiseless kilohertz frame rate imaging detector based on microchannel plates read out with the Medipix2 CMOS pixel chip

B. Mikulec1, A. G. Clark1, J. B. McPhate2, J. V. Vallerga2, A. S. Tremsin2, O. H. W. Siegmund2

1University of Geneva, 24, quai Ernest-Ansermet, 1211 Geneva 4, Switzerland 2Space Sciences Laboratory, U.C. Berkeley, USA Email: [email protected]

A new hybrid imaging detector is described that is being developed for the next generation adaptive optics (AO) wavefront sensors for ground-based telescopes. The detector consists of proximity focused microchannel plates (MCPs) read out by the Medipix2 CMOS pixel ASIC developed at CERN in the framework of the Medipix2 Collaboration. Each pixel of the Medipix2 device comprises pre-amplifier, window discriminator and 13-bit counter. The 256 x 256 Medipix2 array can be read out noiselessly (photon counting) in 266 microseconds, making use of the parallel bus. The Medipix2 is abutable on 3 sides to produce 512 x (n*256) pixel devices. The readout can be electronically shuttered down to a temporal window of a few microseconds.

The detector has been evaluated for a range of incident particles. Good quantum efficiencies can be achieved from charged particles over X-rays (open faced with opaque photocathodes) down to optical wavelengths (sealed tube with semi-transparent GaAs photocathode).

Both technical aspects and measurement results of the project will be presented.

- 45 - PII-11

Study of Multianode Photomultipliers for the electromagnetic calorimeter preshower read out of the \LHCB\ experiment

S. Monteil

LPC Clermont-Ferrand, Université Blaise Pascal/IN2P3, 24 avenue des Landais, 63177 Aubière, France Email: [email protected]

The \LHCB\ experiment is dedicated to the study of the CP symmetry violation in the system of the beauty particles. \LHCB\ is a 20 meters long spectrometer to be installed on the \LHC\ machine comprising from the interaction point vertex and tracking detectors, RICH and calorimetric systems and eventually muon detectors. Of major importance for the first level of trigger is the preshower of the electromagnetic calorimeter meant to select electrons, hadrons or photons. The preshower consists in a lead sheet corresponding to 2.5 radiation lengthes followed by a plastic scintillator plane. The scintillator signal is extracted with wavelength-shifting fibres. A comprehensive study has been conducted to define the best photodetector candidate to read out the light of the 6000 detector cells. The choice has been made for 64-anode photomultipliers with eight stages of electron amplification from the Hamamatsu Company. The number of stages has been defined according to the multiplicity of hits in the detector in the \LHC\ environnement. A dedicated test bench has been designed to evaluate the long term stability performance of the photomultipliers and demonstrated a prematured aging of the photodetector under its operation at large gains. Furthermore, the behaviour of this type of photomultipliers in magnetic field has been studied in details and will be also adressed in the talk. It showed up a critical issue for the correct operation of the detector read-out and the problem has been solved by redesigning the mechanical structure hosting the photomultipliers. Eventually, the generic performance of the photomultiplier in terms of gain, linearity, uniformity and electronic cross-talk between channels will be reported as well as the results of the test bench designed at laboratory to qualify the 120 64-anodes photomultipliers now produced for the experiment.

Electronics Read-Out of The Calorimeter Preshower of the \LHCB\ experiment

S. Monteil

LPC Clermont-Ferrand, Université Blaise Pascal/IN2P3, 24 avenue des Landais, 63177 Aubière, France Email: [email protected]

The \LHCB\ experiment is dedicated to the study of the CP symmetry violation in the system of the beauty particles. \LHCB\ is a 20 meters long spectrometer to be installed on the \LHC\ machine comprising from the interaction point vertex and tracking detectors, RICH and calorimetric systems and eventually muon detectors. Of major importance for the first level of trigger is the preshower of the electromagnetic calorimeter meant to select electrons, hadrons or photons. The preshower consists in a lead sheet corresponding to 2 radiation lengthes followed by a plastic scintillator plane. The scintillator signal is extracted with wavelength-shifting fibres, read by more than one hundred 64-anodes photomultipliers(PMT). The Read-Out electronics consists first in a Very-Front-End board (VFE) embedded in the detector and dealing with 64 channels which integrates the charge given by each tube channel for 25 ns each 25 ns, with a very small dead time. The analogical integrated signals are sent to an off-detector Front-End board aimed at digitazing the VFE output and at realizing the appropriate treatment of the signals before it is used in the first level of trigger of the experiment and sent to the general data acquistion system. Following the comprehensive study which has been conducted to define the best photodetector candidate, the initial Very Front-End electronics design has been deeply redefined to account for the prematured aging of the tubes in the \LHC\ environnement. A correct operation of the tube actually requires a gain of the amplification chain of the

- 46 - chips of $26000 \; \Omega$, which made it a challenging electronics achievement. The latest developments of the electronics read- out chain will be addressed in this talk together with the status of the production.

PII-12

Design, Simulation and Prototype Results of the FAST Detector: an Innovative Scintillating Fiber Tracker

A. Mozzanica1, M. Corradini1, M. Leali1, E. Lodi Rizzini1, L.Venturelli1, M. Basset2, E. Vallazza2, M. Caccia3, M. Prest3

1Universita' degli Studi di Brescia, Dipartimento di Chimica e Fisica per L'Ingegneria e per i Materiali 2INFN, sezione di Trieste 3Universita' degli Studi dell'Insubria, Dipartimento di Scienze Fisiche e Matematiche Email: [email protected]

The ASACUSA Collaboration is preparing a new period of measurements of the antiproton interactions at the AD machine of the PS complex at CERN.

The main fields of investigation concern test of CPT violation by spectroscopy of antihydrogen and antiprotonic helium, atomic collision and nuclear physics experiments. For the measumement of pbar- nucleus cross section at low energy a specific detector must be realized with the main shortcoming due to the very short duty cycle of the beam interaction with the target (300 ns every 180 seconds of antiprotons accumulation).

The charged tracks coming out from each pbar-nucleus annihilation event should be reconstructed along the gaseous target (a cylinder 50 cm long with a diameter of 30 cm) and the different events (up to 10) occuring during the spill should be separated with very good time resolution in order to associate each track to a single event. To cope with these requirements, the FAST detector (Fiber Antiproton Scintillation Tracker) has been designed with 6 layers of fibers surrounding the target in a cylindrical geometry providing up to 2 space points to reconstruct the track and solving the hit ambiguities. The fibers are read out with multianode PMT produced by Hamamatsu and the anode output is amplified and shaped with VLSI ASICs manufactured by IDEAS.The ASIC output is sampled with a clock in order to extract the hit and time information by a set of Xilinx FPGAs.

This paper presents the design, the simulation of the expected performances in terms of track reconstruction capability and the results of the tests of a prototype in terms of efficiency and spatial resolution measured with a high resolution silicon microstrip telescope. The time resolution is correlated with these quantities measuring the time information both with commercial TDCs and the proposed DAQ system.

- 47 - PII-13

A Novel Readout Concept for Multianode Photomultiplier Tubes with Pad Matrix Anode Layout

V. Popov, S. Majewski and B. Welch

Thomas Jefferson National Accelerator Facility, 12000 Jefferson Avenue, VA 23606 Newport news, Usa Email: [email protected]

We have developed a new readout concept for multianode photomultiplier tubes with pad matrix anode layout. The pad matrix anode layout is one of the most common for modern Multianode Photomultiplier Tubes. This multianode style is used in R5900-M64, flat panel H8500 and H8900 PMT from Hamamatsu Photonics, as well as in Burle PLANACONâ„¢ photomultiplier tube family. These tubes could have from 64 to 1024 anode pads. The number of readout channels quickly increases in systems utilizing many of these PMTs. In order to reduce the number of active channels to be read it may be used one of known technique: 2-D charge division network (S.R.Cherry et al., US patent No: 5,719,400) or, developed in Detector Group of Jefferson Lab. a two-dimensional decoupling resistive matrix circuit (V.Popov, US patent No: 6,747,263 B1), but both methods provides an anode output signals analog conversion without respect of possible anode to anode gain tolerance. The anode gain variation factor 3 to 5 is a common to some of photomultiplier tube models it causes a specific distortion of obtained raw image and could limit a detector spatial resolution. We have developed a novel economical readout concept which combine an active channel reduction factor of a two-dimensional decoupling resistive matrix circuit and include an anode gain correction to equalize anodes output gain prior to analog signal conversion. This readout circuit was applied in a several compact gamma cameras designed and build in Detector Group of Jefferson Lab. In result we obtained a better uniformity of raw image, a better spatial resolution, and improved energy resolution. Results of evaluation a small gamma camera made of 2x2xH8500 Hamamatsu PSPMT and pixellated NaI(Tl) scintillator crystal array are presented.

- 48 - PII-14

Tests of the AMS RICH prototype with secondary ions at CERN

O. Veziant for the AMS-RICH collaboration

LPSC, 53, avenue des Martyrs, 38026 Grenoble, France Email: [email protected]

The AMS experiment will be installed on the International Space Station in 2008. It will include a proximity focusing Cherenkov imager (RICH) to perform isotope separation for light nuclei between 1 and about 10 GeV/c and element identification up to beyond Fe (Z=26) over a momentum range extending from threshold up to the upper limit of the spectrometer capability (TeV/c per nucleon). The architecture of the counter consists of a solid state radiator plane at the top, combining silica aerogel and sodium Fluoride (NaF) Cherenkov radiators, separated from the photodetector plane by a drift space for Cherenkov ring expansion. The detector plane includes 680 16-anode PMTs, corresponding to 10880 readout channels. A prototype of the counter including 96 PMTs has been built and tested at the CERN SPS, using secondary beams of ion fragments obtained from primary beams of Lead (Pb) and Indium (In) ions at 20 and 158 GeV/c per nucleon respectively. The response of the prototype to these ions has been studied for various radiators (silica aerogels with refraction index 1.03 to 1.05 and NaF). Cherenkov rings associated to ions over the covered range of mass have been observed, the charge and mass resolutions of the prototype have been evaluated from the analysis of the 5 million and 11 million events recorded during the two experimental runs respectively. The results obtained with the prototype will be presented together with the design and the expected performances of the final detector.

[1] The AMS collaboration, J.Alcaraz et al.,Phys. Rep. 366(2002)331

[2] M. Buenerd on behalf the AMS-RICH collaboration "The AMS-02 RICH Imageur Prototype, In- Beam Tests with 20 GeV/c per Nucleon Ions"

Prepared for 28th International Cosmic Ray Conferences (ICRC 2003), Tsukuba, Japan, 31 Jul - 7 Aug 2003

Published in “Tsukuba 2003, Cosmic Ray” 2157-2160

- 49 - PII-15

Front End electronics for calorimetry in space

S. Rosier-Lees

LAPP, 9 Chemin de bellevue, BP 110, 74941 Annecy le vieux, France Email: [email protected]

A front end read-out electronic system has been developed for the electromagnetic calorimeter (ECAL) of the AMS experiment. AMS should be installed on the ISS (International Space Station) in 2007 and will record several billions cosmic rays per year of operation. The ECAL frond-end read-out was designed with a dynamic range of 60,000 to allow to measure minimum ionizing particles and high energy (more than 1 TeV) electromagnetic showers as well. The 3D imaging electromagnetic calorimeter (ECAL) consists of 9 modules made of a sandwich of lead foils and of layers of scintillating fibers glued together. The fibers are read alternatively at one end and the other by 324 4-anodes square PMT's. Eventually, the detector must be operated in space, thus the electronics must be a low power consumption device, must sustain vibrations and must be able to work in vacuum with temperatures from -30deg C to +40. The system comprises also an analog topological trigger for the detection of gamma-ray showers. It will be described in detail with the main challenges encountered to meet the required physics performances. The analog trigger performances have been measured at CERN in September 2004 using electron, pion and proton beams for energy ranges from 3 to 8 GeV. The results obtained will be presented and compared with the expectations.

- 50 - PII-16

A Project for a High-Efficiency Direction-Sensitive Photo- Detector to be used in Underwater Neutrino Telescopes

M. Taiuti On behalf of the NEMO Collaborations

INFN and Università di Genova, via Dodecanneso 33, I-16100 Genova, Italy Email: [email protected]

The detection of high energy neutrinos (>1 TeV) originating from galactic and extra-galactic sources requires a large amount of matter to convert it into a charged muon and to reconstruct the muon track. Large volumes of water located at large depth could be instrumented with optical module and become very efficient detectors. Several projects in the detection of high energy neutrinos have been developed in the past years and a large volume (1km3) detector to be deployed in the Mediterranean Sea is under study.

Important components of the detector are the photomultipliers required to detect the Cherenkov light emitted by muons. To efficiently cover the 1km3 detection volume it is necessary to deploy several thousand of photomultipliers whose main requirements are a quite large photocathode area, high gain, low noise and good timing also for single photo-electrons.

In this talk it is presented the development of a new photo-detector to be employed in water neutrino detectors where large detection area and good background suppression are required. The design includes an emispherical photomultiplier position-sensitive coupled to a direction-sensitive light-guide system.

The optical module performances and the response of the new detector are also discussed.

- 51 - PII-17

Surface currents of CdZnTe and CdTe pixelated detectors

B.P.F. Dirks, O. Gevin, O. Limousin, F. Lugiez

CEA/DSM/DAPNIA Saclay, L'Orme de Merisiers, Bât. 709, 91191 Gif-sur-yvette, France Email: [email protected]

The next generation hard X-ray cameras for astrophysics will be built with pixelated CdTe or CdZnTe semiconductor detectors covered with 64 (0.9*0.9 mm^2) or 256 (0.5*0.5 mm^2) pixels, surrounded by a guard ring. The dedicated multi-channel read-out ASIC, IDeF-X, is developed in a such a way that if connected to the pixel electrodes, potential differences may exist of zero to a few tens of millivolts between pixels, and zero to three volts between pixel and guard ring. This gives rise to surface currents that may drastically influence the functionality or noise performances of the ASIC. In this paper, the surface current is characterized for different configurations of the read-out electronics using a special low-current measurement setup.

- 52 - PII-18

Improvements of Energy Resolution in Polycrystalline CdZnTe X-ray Detectors

KiHyun Kim1, TaeRok Jung1, SunUng Kim2

1Samil-Pharm Coperation/Central Research Center, 990-1, Bangbae-Dong, Seocho-Ku, 137-061 Seoul, Korea 2Dept. of Display and Semiconductor Physics, Korea University, ChungNam, 339-800, Korea Email: [email protected]

Recent developments in digital technology have resulted in increased interest in semiconductor devices for radiological applications. The CdZnTe material has high stopping power due to its high mass density (5.8 g/cm^3) and effective atomic number Z of 49.6. To overcome restriction of single CdZnTe on large area, we tried to deposit high resistivity poly-CdZnTe (polycrystalline CdZnTe) layers by thermal evaporation method on carbon substrate.

The merits of Ohmic type electrode is reduction of hole tailing effect by the replacement of the trapped carriers with injected charge carriers with injected charge carriers from the contacts but have a disadvantage in the suppress of leakage currents.

In our previous publications, we showed successful deposition of poly- CdZnTe:Cl layer which have high resistivity over 5 x10^9 Ohm cm. Nevertheless, the dark leakage currents of these layers are high to operate high sensitivity X-ray detectors. In this study, to suppress the dark currents, blocking layers using Schottky barrier was investigated.

The Schottky barrier was formed using indium after specific surface treatment conditions. The dark currents were 13 nA/cm^2 at 40 V and the signal current was increased by 200 nA/cm^2 under visible light illumination. The ideality factor n calculated from the slope of Log J vs. V plot is 1.08 implying that recombination and thermionic emission is dominate transport mechanism. The barrier height was 0.798 eV. Considering the work function of indium ( 4.2 eV) and electron affinity of CdZnTe (4.5 eV), the Fermi levels lied in middle of energy gap. In energy spectrum analysis of 241 Am using MCA, we can clearly separated energy peak of 14, 18, 21 keV and 59.54 keV. The FWHM (full width half maximum) of 59.54 keV is 2.5 keV.

The aim of this works is to find out the reproducible Schottky barrier formation conditions and the relations between dark currents and energy resolutions in poly-CdZnTe X-ray detectors.

- 53 - PII-19

Gamma-ray Imaging with Position Sensitive Silicon Detectors

C. M. Rowland Fitzgerald, J. D. Kurfess, B. F. Phlips, E. A. Wulf, and E. I. Novikova

Naval Research Laboratory, Space Sciences Division Code 7650, 20375 Washington, dc, Usa Email: [email protected]

The achievements expected from the next generation of gamma-ray instruments depend on the development of new technologies in gamma-ray detection. Fields including high energy astrophysics, homeland security, nuclear physics, nuclear non-proliferation, and nuclear medicine all would benefit from gamma-ray detectors with improved sensitivity as well as superior spatial and spectral resolution. In order to meet this demand, the development of a prototype stacked silicon strip detector has begun at the Naval Research Laboratory. The instrument is based on the 3-Compton energy reconstruction technique, and will use thick double-sided silicon strip detectors. Data obtained from the characterization and testing of the prototype instrument's individual silicon wafers will be presented along with results from GEANT simulations.

- 54 - PII-20

The ECLAIRs micro-satellite for gamma-ray bust multiwavelength observations

S. Schanne

CEA Saclay, DSM/DAPNIA/Sap, Bât 709, 91191 Gif sur Yvette, France Email: [email protected]

Since 1997 we know that gamma-ray bursts (GRB), among which at least the long-duration ones, are the most energetic events in the Universe and occur at cosmological distances. The ECLAIRs micro-satellite, to be launched in 2009, will provide multi-wavelength observations of GRB, for studies of their astrophysical origin and for their use as cosmological probes. Furthermore in 2009 ECLAIRs is expected to be the only space borne instrument capable of delivering a GRB trigger in near-realtime with sufficient localization accuracy in order to perform GRB follow-up observations with the powerful ground based robotic telescopes available by then.

A "Phase A" study of the ECLAIRs project has recently been launched by the French Space Agency CNES, aiming at a detailed mission design and a selection for flight in 2006. This paper presents the concept of the ECLAIRs mission as a payload onboard a CNES micro-satellite of the successful "Myriade" family. The ECLAIRs main instrument, the X/gamma-ray camera (CXG) has a wide field of view of about 2 sr and will detect about 100 GRB per year in the 4-50 keV energy band. It will localize the GRB on the sky with an accuracy of about 10 arcmin and transmit this information in near real-time on ground via a continuous low data-rate telemetry stream for ground-based follow-up observations. The CXG is inspired from the INTEGRAL imager IBIS, and uses a CdTe detection plane covering about 1000 cm^2, placed 35 cm below a coded mask. A second instrument onboard ECLAIRs, the optical camera (UDV), is sensitive to magnitude- 15 stars and covers 1/4th of the CXG field of view. It will observe the prompt emission and a possible precursor of about 10 GRB per year in the visible-band. The UDV acquires images continuously at a rate of about 5/s, dumped into an on-board memory. In case of a GRB trigger issued by the CXG, a memory seek- back of the GRB optical precursor is launched. All photons acquired by the CXG and visible-band images during GRB events are sent to ground when a ground-station supporting the high data-rate telemetry is reachable.

- 55 - PII-21

MAX, a space borne gamma ray telescope for nuclear astrophysics based on a Laue diffraction lens

N. Barriere1, P. von Ballmoos1, G. Skinner1, P. Bastie2, K. Andersen2, N. Abrosimov3, H. Halloin4, J. M. Alvarez7, S. Boggs5, T. Courvoisier6, M.Harris1, M. Hernanz7, J. Isern7, P. Jean1, J. Knšdlseder1, B. Smither8, P. Ubertini9, G. Vedrenne1, G. Weidenspointner1

1Centre d'Etude Spatiale des Rayonnements, 9 avenue du Colonel Roche, BP 4143, 31028 Toulouse Cedex 4, France 2Institut Laue Langevin, 6, rue Jules Horowitz BP 156 - 38042 Grenoble Cedex 9 - France 3Institut für Kristallächtung, Max-Born-Strasse 2, D-12489 Berlin - Germany 4Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85748 Garching - Germany 5Space Sciences Laboratory #7450, University of California, Berkeley, CA 94720-7450 - USA 6ISDC, Chemin d'Ecogia 16, 1290 Versoix - Switzerland 7Institut d'Estudis Espacials de Catalunya, Despatx 201 Edifici Nexus C/ Gran Capitˆ, 2-4, 8034 Barcelona - Spain 8Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439. - USA 9Istituto di Astrofisica Spaziale e Fisica Cosmica, Via del Fosso del Cavaliere 100, 00133 Roma - Italy Email: [email protected]

In 2001, the CLAIRE mission demonstrated the feasibility of a crystal diffraction gamma ray lens for nuclear astrophysics with the detection of photons from the Crab nebula during a balloon flight. It was the first time that gamma rays were focused, and thus it has opened new perspectives in a domain where all existing instruments have had their collecting area equal to the detector surface because focusing has previously been impossible.

The next step towards the nuclear astrophysics of tomorrow has now commenced with MAX, a space borne gamma ray lens. MAX which is currently in pre-phase A at CNES (the French space agency), features a Laue diffraction lens composed of more than 8000 germanium and copper crystals and makes use of the latest developments in satellite formation flying to achieve a 86m focal length. At the focus, a stack of high purity stripped germanium detectors will perform the spectroscopy and the 3-D positioning of detected events. This will allow location of the source and so rejection of any event coming from elsewhere than the lens. For the first time in nuclear astrophysics, a space borne instrument will associate a large collecting area with a small detector volume, making possible unprecedented sensitivities.

The instrument is designed to observe simultaneously in two wide energy bands: the primary scientific objective of MAX will be the study of Type Ia supernovae by measuring intensities, energy shifts and shapes of their nuclear gamma ray lines, particularly the 56Ni decay chain, which is in the highest energy bands: 800 - 900 keV. In the lower one, 450 - 530 keV, MAX will extend the exploration of the e-e+ annihilation sky (emission at 511 keV), where the ESA mission INTEGRAL is currently identifying potential positron sources in our Galaxy.

- 56 - - 57 - PII-22

High spatial resolution and wide-band imaging spectrometer with scintillator-deposited charge-coupled device (SD-CCD)

N. Anabuki, E. Miyata, K. Mukai, N. Tawa, T. Miyauchi, H. Tsunemi and K. Miyaguchi

Osaka University, 1-1 Machikaneyama, 560-0043 Toyonaka, Japan Email: [email protected]

We report on a newly-developed photon counting detector possessing unprecedented spatial resolution and moderate energy resolution in very broad band (0.1-100 keV): the scintillator-deposited CCD (SD-CCD). It is a good mix of an X-ray CCD and a scintillator, which is directly deposited on the surface of the CCD. The CCD properly works as a soft X-ray (< 10 keV) detector. On the other hand, the majority of X-rays having energy above 10 keV pass through the CCD.

However, they can be absorbed in the scintillator and emit visible light, the amount of which is proportional to the energy of the incident X-rays. Therefore, the SD-CCD also works as a hard X-ray imaging spectrometer using the visible light.

In order to maximize the amount of visible light detected by the CCD, we have employed the SD-CCD that is formed columnar crystal of CsI(Tl) on the front surface of a back-illuminated CCD (BI-CCD). The emission spectrum from CsI(Tl) ranges between 350 and 700 nm with the peak wavelength at 550 nm where the BI-CCD has the detection efficiency of more than 85 %. As a result, the spectral resolution of 28.4 % at 22.1 keV and 25 % at 59.5 keV have been achieved. To examine the imaging capability of the SD-CCD fabricated, we performed a demonstrative experiment with a sharp edge and determined the spatial resolution to be 10 micron with 24 micron pixel CCD.

We will perform the balloon-born experiment of the SD-CCD with the supermirror (NUSMIT) at Brazil in November 2005. In order to verify the SD-CCD, we will perform the test balloon experiment without the supermirror in May 2005 in Japan.

[1] E. Miyata, K. Tamura, Jpn. J. Appl. Phys. 42 (2003) L1201

[2] E. Miyata et al., Proc. SPIE 5501 (2004) 56

[3] E. Miyata et al., NIMPA 525 (2004) 122

- 58 - PII-23

Comparison of Cadmium-Zinc-Telluride semiconductor and Yttrium-Aluminum-Perovskite scintillator as photon detectors for epithermal neutron spectroscopy

M. Tardocchi1, A. Pietropaolo2, C. Andreani2, G. Gorini1, S. Imberti2, E. Perelli-Cippo1, R. Senesi2, N. Rhodes3, E. M. Schooneveld3

1INFM and Università degli Studi di Milano-Bicocca, Dipartimento di Fisica “G. Occhialini”, Milano, Italy 2INFM and Università degli Studi di Roma “Tor Vergata”, Dipartimento di Fisica, Roma, Italy 3Rutherford Appleton Laboratory, ISIS Facility, Chilton, UK Email: [email protected]

The range of applications of epithermal neutron scattering experiments has been recently extended by the development of the Resonant Detector (RD). The RD, first proposed in the 1980’s, has been revisited for neutron spectroscopy experiments at spallation pulsed neutron sources in the eV energy region. The RD consists of the combination of an analyzer foil and a photon counter. Resonant neutron absorption in the analyzer foil results in prompt emission of X- and gamma-rays, which are detected by a photon counter. The energy of the incoming neutrons can thus be reconstructed via the time of flight technique. Several combinations of analyzer foils and photon detectors have been studied and tested in the last five years of research on the RD. The best results have been obtained with the combination of a natural uranium or gold foil and i) Cadmium-Zinc-Telluride (CZT) semiconductor, ii) Yttrium-Aluminum-Perovskite (YAP) scintillators. Here we compare the performance of the CZT semiconductor and YAP scintillator as RD units.

The detectors are installed on the VESUVIO spectrometer at the ISIS spallation neutron. The first RD unit consists of a uranium analyzer foil attached to a YAP crystal (35 mm diameter by 6.4 mm thickness), which was directly glued to a standard photomultiplier tube. A second RD unit is made with a uranium foil attached to a commercial CZT detector made of a CdZnTe crystal (5 x 5 x 5 mm3) coupled to a preamplifier. The analyzer foils were each 60 um thick. The scattering samples were lead, which is routinely used for calibration in this kind of experiments, and ZrH2. The collected time of flight spectra indicate that both RD units, which have similar gammadetection efficiency, can be used to detect epithermal neutrons of energy in the range from 1 eV up to 100 eV. It was found that the signal to background ratio of the measurement can be improved via pulse height discrimination on the gamma energy. The advantages/disadvantages of the choice of a RD based on YAP or CZT are discussed together with some potential applications.

- 59 - PII-24

Comparison of measured backscatter factors with Monte Carlo simulations for low energy x-ray

M. S. Kim, J. S. Ryu, S. W. Park, Y. Yi

Dept.of Electronics & Information Engineering, Korea Univ., B-238 school of Biotechnology 5-1 Anam- dong, Sungbuk-ku, 136-701 Seoul, Korea Email: [email protected]

Experimentally determined values of x-ray backscatter factors (BSFs) are presented in comparison with Monte Carlo simulations in this paper. Measurements were made for x-rays generated at voltages between 50 kVp and 150 kVp and various phantoms different in shape, size, and composition. To study the influence of the irradiation geometry on the backscatter factors, the measurements were performed for different photon beam field diameters at the phantom front face. The phantoms were placed on the irradiation bench of the x- ray unit at a fixed distance of 100cm from the focal spot. In this paper, the experimental determination of backscatter factors is based on a measuring technique using an ionization chamber. The generalized particle transport program MCNP4C code has been used for Monte Carlo simulations. Measured results are analyzed and discussed in comparison with simulated values and we acquired phantom images using a 512 channel linear array photo-detector.

- 60 - PII-25

Studies on wrapping materials and light collection geometries in plastic scintillators

S. Scheu

Physic Institute, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland Email: [email protected]

The KOPIO experiment at BNL intends to measure the branching ratio of the ultra-rare(SM branching ratio about 3E-11) decay K0 -> pi0 + 2nu with a precision of O(10%).

Highly efficient veto systems are required to keep background from kaon decays with additional photons or charged particles under control. The charged-particle veto system comprises ~40 m2 organic scintillator operated in vacuum and aims at efficiencies >99.99%.

To reach the required ~50 keV detection thresholds a very high light-collection efficiency has to be achieved. We report on our extensive studies of different wrapping materials and light collection geometries.

- 61 - PII-26

ADONIS: a new digital signal processing concept for HpGe gamma spectrometry

E. Barat, T. Dautremer, L. Laribière, J.Ch. Trama

CEA/Saclay, DETECS/SSTM/LETS, Bâtiment 451, 91191 Gif-sur-yvette, France Email: [email protected]

In radiation measurement, gamma spectrometry among others, the front end signal processing has been based on usual linear shaping filter for a long time. Recently, digital units have appeared in the field of gamma spectroscopy, but they still rely on the same kind of shaping but in digital version. In this paper we present the ADONIS project: an innovative work dedicated at renewing the filtering concepts to detect and measure pulses arriving at random time in a noisy environment. The innovation lies in the modelling of this problem as a Jump Markov Linear System. The jump is the occurrence of a pulse in the signal.

From this model, we developed an algorithm which makes possible the on-line estimation of the detector signal without having to temporally enlarge the pulses. This algorithm provides the user with Xk/N=Argmax p(Xk/ y1, y2,….., yN), maximum a posteriori estimate of the desired information Xk which is the denoised short-time image of the pulse. This allows us to dramatically increase the compromise throughput vs resolution, gaining a 10 factor on the admissible input count rate on an commercial HpGe followed by a reset preamplifier (2 to 3 millions counts per second admissible, without having reached the algorithm limit).

The algorithm first determines whether there is a pulse or not at each time, then conditionally to this information, it performs an optimal bi-modal Kalman smoother.

To validate the concept we built a real time demonstrator, that could sample at a 10 Mhz pace a signal after the aforementioned HpGe sensor, and on-line process it with our algorithm.

The first lab version of this hardware and sofware system, called Adonis S1 has been tested on a variety of applications, the present paper will focus on the ability to give a precise estimate of a reference gamma source, disturbed by growing intensity gamma noise. It was for example possible to continuously monitor a 60Co source (7600 cps ICR) perturbed by a 137Cs (from 0 to 1600000 cps ICR), while maintaining a good resolution (from 1,8 keV @ 1332 keV to 3,2 keV @ 1332 keV). The reference activity was quantitatively good (2,7 % peak-peak dispersion for all the perturbating activity range).

- 62 - PII-27

Simbol-X: a formation flying mission for hard X-ray astrophysics

P. Ferrando, on behalf of the Simbol-X collaboration

CEA/Saclay, DSM/DAPNIA/SAp, Bât. 709, 91191 Gif-sur-Yvette,France E-mail: [email protected]

SIMBOL-X is a hard X-ray mission, operating in the 0.5-70 keV range, which is proposed by a consortium of European laboratories in response to the 2004 call for ideas of CNES for a scientific mission to be flown on a formation flying demonstrator. Relying on two spacecrafts in a formation flying configuration, SIMBOL-X uses a 30 m focal length X-ray mirror to focus for the first time X-rays with energy above 10 keV, resulting in a two orders of magnitude improvement in angular resolution and sensitivity in the hard X- ray range with respect to non focusing techniques. The SIMBOL-X revolutionary instrumental capabilities will allow to elucidate outstanding questions in high energy astrophysics, related in particular to the physics of accretion onto compact objects, or to the acceleration of particles to the highest energies. The focal plane instrument is made of two superposed new technology detectors in order to cover the full energy range of Simbol-X and its 6 arc minutes field of view. Each detector is made of about 10,000 pixels of 500 microns size. The top detector is a 500 microns thick Silicon Drift

Detector with a DEPFET integrated in each pixel, allowing very fast reading and operation at room temperature. It will detect X-rays with a high spectral resolution up to about 17 keV. The high energy detector is made of an array of, presently, 37 one square cm modules. Each module consists of a 2 mm Cd(Zn)Te crystal, with 256 pixels defined by a a segmented anode, hybridised to its read-out electronics with dedicated ASICs. The detector assembly is protected against background by an active shielding, and will be operated at about -20° C. The mission is currently in final assessment study in CNES, and is expected to start a competitive phase A study in autumn 2005, leading to a flight decision at the end of 2006. The mission science objectives, instrumentation, and status will be presented.

- 63 - POSTER SESSION III

SiPM+Solid State+Gas

- 64 - PIII-1

Timing by silicon photomultolier: a possible application for TOF measurements

P. Buzhan, B. Dolgoshein, A. Karakash, V. Kaplin, V. Kantserov, F. Kayumov, S. Klemin, N. Kondratieva, A. Pleshko, E. Popova

Moscow Engineering and Physics Institute, Kashirskoe Shosse,31, 115409 Moscow, Russia Email: [email protected]

The Silicon Photomultiplier(SiPM) is intrinsically a very fast device,its single photoelectron timing resolution is about of 100ps FWHM.Therefore a real properties of the system Scintillator+SiPM is determined mostly by timing properties of the scintillator+light collection system.

We present the experimental results for timing properties of SiPM+scintillator(or Cherenkov radiator)for two cases:

1.Timing resolution of a few GeV electron beam with a fast plastic scintillator or Cherenkov radiator+SiPM with a size of 1x1mm2 and 3x3 mm2

2.Time of flight resolution for detection of 511 KeV photons by two LSO cristals+SiPM(3x3 mm2),as aposiible application for PET.

- 65 - PIII-2

The Silicon Photomultiplier as a photodetector for scintillator applications

D.J. Herbert, N. D'Ascenzo, N. Belcari, A. Del Guerra, V. Saveliev

INFN Pisa, Largo Pontecorvo, n.3, 56123 Pisa, Italy Email: [email protected]

The SiPM (Silicon Photomultiplier) APD represents an interesting advance in photodetection and could soon be a rival to traditional PMTs in many applications. The MRS (Metal-Resistor-Silicon) structure SiPM produced by CPTA, Russia has been characterised and tested for possible use in scintillator light detection in medical applications.

The MRS SiPM is effectively an avalanche photodiode operated in Geiger mode. In normal Geiger-mode detectors, a very large current signal is produced regardless of the size of the input, giving just logical rather than proportional information. However, the SiPM is subdivided into a large number (1400) of microcells that act as independent and virtually identical Geiger-mode photodiodes. The outputs of all these individual microcells are connected so that the total output signal is the sum of the signals from all of the microcells that were fired. In this way proportional information can be obtained. As a consequence of their design, these detectors have potentially very fast timing, high gain (1E5 – 1E6) at low bias voltage (~50V), have an excellent single photoelectron resolution, are low noise and like other APDs, can be small, rugged and insensitive to magnetic fields. They are operated at room temperature.

We present a summary of measurements of the devices' primary operating characteristics and results of the application to scintillator readout. In particular, we use 1mm x 1mm pixels of LSO and BGO illuminated with 511keV photons to assess their suitability for PET (Positron Emission Tomography) systems.

From the measurements made and presented here, the SiPM is found to have a very low detection efficiency, being as low as ~2% at 420nm. The reasons for this low efficiency are discussed and ways to overcome the problem explored. An alternative SiPM structure that eliminates some of these limitations has also been tested and compared with the CPTA device. The energy resolution at 511 keV from a small LSO pixel, measured with the alternative SiPM, is found to be comparable with that measured with a conventional PMT.

- 66 - PIII-3

Using Silicon Photomultipliers in Astrophysics

N. Otte, R. Mirzoyan, M. Teshima, G. Lutz, B. Dolgoshein, E. Popova, S. Klemin

Max Planck Institut für Physik, Föhringer Ring 6, 80805 Munich, Germany Email: [email protected]

Recently several groups have developed a new type of photon detector - the silicon photomultiplier (SiPM). The SiPM has remarkable features like large gain (106), low operation voltage and currently achieved photon detection efficiencies are comparable to that of conventional bialkali photomultiplier tubes.We want to use SiPMs in high energy astrophyiscs experiments like MAGIC and EUSO. In both types of experiments light is observed which is emitted in air showers initiated by cosmic rays.We are currently developing the SiPM in two different directions a) front illuminated together with MEPhI and the Pulsar Enterprize, Moscow, and b) back illuminated together with the Semiconductor Laboratory attached to the Max-Planck- Institute for Physics.If SiPMs are used in these experiments they have to fulfill several criteria like e.g. large enough size (5x5mm2 - 10x10mm2), dynamic range, high efficiency in the blue and capability to cope with a large background (the light of night sky). On the other side one has also to study the intrinsic features of the SiPM and their impact on the physics outcome of the experiment. Some of the most important characeristics under question are the optical crosstalk and the dark noise of the sensor. We discuss these issues and their impact on the experiments.

Wavelength Dependent Photon Detection Efficiency Measurement of Silicon Photomultipliers

N. Otte, J. Hose, A. Thea, O. Kalekin, R. Mirzoyan

Max Planck Institut für Physik, Föhringer Ring 6, 80805 Munich, Germany Email: [email protected]

New challenging experiments in high energy phyiscs and astrophysics like EUSO and MAGIC demand photon sensors with high detection efficiencies for single photons (>40%) and easier operation conditions.The silicon photomultiplier (SiPM), also called Geiger-APD (G-APD), which has been developed by several groups, is a promising photon sensor candidate for such experiments. In addition to high single photon detection efficiency the SiPM has other favorable features like insensitivity to magnetic fields, mechanical robustness and low pickup as well as a low operation voltage (<100V). These properties, once larger area detectors become available and mass production is established, makes the SiPM superior to conventional photomultiplier tubes for many applications.The key question to be answered for every photon detector is the photon detection efficiency (PDE). Other parameters of importance for SiPMs are the interpixel "optical" crosstalk, dark noise and the recovery time of single cells.The dependence of all these parameters as a function of voltage and temperature have to be understood.We have constructed an experimental setup to quantify the PDE and related parameters as a function of wavelength.Basically, the setup consists of a fast light pulser of discrete wavelength whose light is injected into an itegrating sphere.

- 67 - The SiPM under investigation and a calibrated PiN diode are both optically coupled the sphere and the signals compared. The method and results from measurements of different SiPMs will be presented.

- 68 - PIII-4

Especial Bump Bonding Technique for Silicon Pixel Detectors

E. Cabruja

CNM-IMB, Campus UAB, 08193 Cerdanyola del vallès, Spain Email: [email protected]

In this talk we will present a novel high density bumping technique based on electrodeposition of the bump materials, which can be used for silicon pixel detectors packaging.

Silicon Pixel detectors have been designed and manufactured at CNM using high resistivity 300 and 800µm thick silicon wafers which have been flipchipped on a MedipixII® single photon counting read-out chip.

The foreseen applications are Medical Imaging and X-Ray systems. The new bumping technique developed will greatly improve the simplicity and the cost of the packaging process.

- 69 - PIII-5

Polycrystalline diamond UV and X-ray detectors performance

I. Ciancaglioni, M.C. Rossi, G. Conte

Dept. of Electronic Engineering, University of Rome “Roma Tre”, Via della Vasca Naval 84, 00146 Rome, Italy Email: [email protected]

Polycrystalline diamond devices with different structures have been realized for high energy photon detection such as deep UV and soft X-ray. In particular, diamond films grown by chemical vapour deposition (CVD) techniques can be deposited on large area and exploited for image detection. These applications are related to the unique properties of this wide band gap material, such as small leakage current, visible blindness, lattice rigidity, radiation hardness and fast response time.

The interaction between a diamond sample and a ionising radiation beam, both UV (193ìm) and X-ray (8.06keV), is here analysed with the aim to study the role of surface and bulk defects in determining the linearity region of the dosimeter’s response. In particular will be analysed the response to a chopped X-ray beam in order to evaluated the photoconductive decay of traps localization.

A simple photogeneration model will be used to elaborate and discuss the observed results. The relationship among the charge carriers generation processes, material quality, surface morphology and photoconductivity linearity response will be presented as the result of a 73ìm and 400ìm thick, metal-diamond-metal structure.

- 70 - PIII-6

Quantum dot infrared Photodetectors

P. Aivaliotis, L.R. Wilson, J. Cockburn, E. Zibik, J.P.R. David*, M. Hopkinson, and C. Groves

Sheffield University, Sir Frederick Mappin Building, Mappin Street, S1 3JD Sheffield, Uk *E-mail [email protected] Email: [email protected]

Quantum dot infrared photodetectors (QDIPs) are a fast emerging technology for long wavelength (5µm < λ < 20µm) detection applications including night vision, thermal imaging, medicine and chemical analysis. The interest in QDIPs is fuelled by a number of intrinsic advantages which they hold over competing technologies, such as HgCdTe interband and QWIP intraband detectors. Most notably, as QDIPs utilise bound-bound or bound-continuum transitions they may be grown using common III-V materials and thus benefit from mature growth technology, high uniformity and low cost. QDIPs, unlike their quantum well counterparts, are intrinsically sensitive to normally incident radiation, making them particularly attractive for use in large focal-plane arrays. Additionally, the improved confinement in a QDIP increases the carrier relaxation time which in turn leads to greater responsivity.

In this paper we report photoresponse and dark current characteristics of a range of n+-i-n+ dots-in-a-well (DWELL) QDIPs grown by MBE. InAs dots comprising 2.2, 2.55 and 2.9 monolayers of InAs were grown within an In0.15Ga0.85As well, which lowers the ground state of the dot with respect to the GaAs conduction band edge thus yielding lower thermionic emission [1]. The dots were grown in-situ via the Stanski- Krastanov growth mode at a dot density of ~1011 cm-2, and were doped to either 1e- or 2e- per dot to supply carriers for photoexcitation. Five layers of dots were grown to increase the absorption without adversely affecting the dark current performance.

FTIR measurements show two colour absorption at λ ≈ 5µm and λ ≈ 9µm for all layers, which coincide approximately with the atmospheric windows in the infrared range. Additionally the results show that the energy corresponding to the absorption peaks increases with the number of InAs monolayers, thought to be due to an increase in the size of the InAs dot. The control over the absorption wavelength during growth is in addition to bias tunability of the absorption wavelength via the quantum-confined stark effect.

Responsivities of the order of 1A/W have been measured on one of the current layers at wavelengths of 8.62µm and 10.42µm, corresponding to the peak absorption wavelengths for positive and negative bias.

[1] Krishna et al. “Three colour InAs/InGaAs quantum dots in a well detector,” Appl. Phys. Lett., vol. 83, pp. 2745-2747 (2003).

- 71 - PIII-7

Photoresistors on the base of new TlGa1-xFexS2 single crystals

E.M. Kerimova, S.N. Mustafaeva, P.M. Iskemderova

Institute of Physics, National Academy of Sciences of Azerbaijan, G. Javid pr. 33, AZ-1143 Baku, Azerbaijan Email: [email protected]

Determination of composition-property behaviour offers a scope for carrying out purposeful search of new semiconductive photodetectors having a given package of physical properties.

The aim of this paper is the study of photoelectric properties of TlGa1-xFexS2 single crystals depending of its composition x (x=0; 0,01; 0,02).

Initial TlGaS2 single crystals have been grown by modified Bridgemen method. Doping of TlGaS2 crystals by Fe are carried out during the synthesis. Defferential-thermal analysis and difractometric study of synthesis products show that Fe is included in Ga subdivision. Grown TlGa1-xFexS2 single crystals undergo quantative microroentgenspectral analysis by the device "CAMECA-MS-46", which shows rather uniform destrubition of Fe ions for and wide of ampoules (ingot). Obtained single crystals are laminated. For preparation of measurable samples there have been spalled plane-parallel plates in thickness 0,1 mm and cut out samples through an area 2„e2 mm2. Their contacts are made by melting In in lateral ends. The light on the single crystal falls in the direction which is perpendicular to the plane of natural spall, and external electric field (102„i103 V/cm from ohmic range of VAC) is applied along the crystal layers.

Study of spectral dependences of photocurrent of TlGaS2 single crystals shows that with the temperature rise from 300 up to 383 K photocurrent maximum shifts from 2,70 to 2,82 V. Besides, there have been observed broadening of main band of intrinsic photoconductivity and wide impurity band in energy interval 1,3„i2,2 eV appears on photocurrent spectra.

Partial substitution of Ga ions in TlGaS2 lattice by Fe ions in quantity of 1 at. % brings about the full frequency change of photocurrent spectra. The main band of intrinsic photoconductivity observed in 2,6„i2,9 eV before Fe introduction is depressed and manifested in weak short-wave circuit arm through new band of maximum sensibility in low-energy spectrum range (1,3„i2,6 eV) appearing after Fe introduction. The new band of maximum spectral sensitivity in TlGa0,99Fe0,01S2 shifts sharply in the direction of long waves (from 1,98 up to 1,70 eV) with temperature rise from 300 up to 369 K. For TlGa0,98Fe0,02S2 composition energy position of photocurrent maximum (hƒÞ=1,90 eV) in 300„i350 K do not depend on temperature. This peculiarity offers scope for using obtained composition for registration of monochromatic radiation hƒÞ=1,90 eV in temperature range 300„i350 K.

- 72 - Thus obtained experimental results show that at the expense of partial substitution Ga„_Fe in TlGaS2 lattice one can modify substantially photocurrent spectra, also control photocurrent maximum energy of TlGa1- xFexS2 single crystals by temperature variation.

PIII-8

New type of photodetectors with selective spectral photosensitivity

S. Kh. Khudaverdyan, J. G. Dokholyan, A. A. Kocharyan, D. S. Khudaverdyan

State Engineering University of Armenia, 105 Teryan str., 375009 Yerevan, Armenia Email: [email protected]

A new type of ptotodetectors is proposed, in which the selective spectral photosensitivity is realized by structures with the opposite directed barriers on both sides of the thin high resistance layer.

At the illumination of the structure through the transparent metal contact, the integral flow of the electromagnetic radiation is absorbed in the depletion region of potential barriers of the junctions, which give the opposite contribution to the photoresponse of the structures. The photoresponse depends on the barriers width, which, in its turn, depends on the external voltage.

The change of the external voltage brings to the change of the potential barrier width and, consequently, to the change of the range of the spectral sensitivity of each of these barriers. The difference of these ranges of the spectral sensitivity at two different values of the voltage determines the strip of the spectral sensitivity Äl. Changing the external voltage, it is possible to change Äl and to choose the necessary strip of the spectral sensitivity.

The experiments on the CdTe and Si basis were carried out. The structures on the basis of these materials allowed to register the narrow strips of the spectrum within the spectral sensitivity of the initial materials.

- 73 - PIII-9

Design of Pixellated Scintillator on PIN type Photodiode for Digital Mammography

Kim Kwang Hyun

KAERI, 150, Dukjin-dong, Yusung-gu, 305-353 Daejon, Korea Email: [email protected]

From the measurement results and analysis of scintillator coupled CMOS APS imager for mammography conditions, we designed new detector module based on 2-D pixellated scintillator on PIN type photodiode array. Two scintillators of CsI(Tl) and ZnSe(Te) are considered to build columnar structured on pixel pitch of 50 §, and candidate photodiodes are both front-side illumination and back-side illumination. From experiments and calculation, we derived semi-empirical MTF model which can predict the performance of new designed detector. This model reflects the contribution of the ratio of initial dark signal to an output signal response to X-ray exposure to the spatial resolution of the sensor. Using F value based on the ratio, it is possible to estimate the expected resolution for a given scintillator and sensor properties.

In this experiment we used FOP-CsI(Tl)-HRTM of 22 cycle/mm as a scintillator and RadEyeTM CMOS APS imager with pixel pitch of 48 §. These were optically coupled together and exposed by two X-ray conditions of 28 kVp and 80 kVp, and system resolutions of Modulation Transfer Function (MTF) were measured and compared to two calculated MTF. From this new model the minimum light output from the scintillator was derived so as to have its high intrinsic resolution when it is coupled to sensor. With the new MTF model and theoretical calculation, the performance of the new detectors predicting the resolution will be predicted in detail. To build columnar structured scintillator pixellated directly on 2-D PIN photodiode array, the suggested fabrication process will be also announced in detail.

- 74 - PIII-10

Synthetic diamond devices for radiotherapy dosimetry applications

P. Bergonzo, M-J. Guerrero, D. Tromson, C. Mer, C. Descamps, B. Bazin, M. Nesladek

CEA-Saclay – LIST, DETECS - Bât 451, 91191 Gif-sur-yvette, France Email: [email protected]

CVD diamond is a remarkable material for the fabrication of radiation detectors. Radiation hardness, chemical resistance and high temperature operation capabilities of diamond motivate its use for the fabrication of devices operating in hostile environments such as that encountered in nuclear industry and high energy physics. Its potentialities for such applications have been well documented and recent studies have led to the developments of a few applications that are addressing specific industrial needs.

One particular interest of diamond stands in the fact that its atomic number is close to that of human tissues. This implies that the response of a diamond device to radiation is equivalent to that received by the human body. It thus enables the straightforward measurement of the dose for radiotherapy applications. However, this requires high reproducibility and linearity. It is widely observed that exposure to radiation is modifying the initial performances of diamond detectors and priming structures is therefore required to obtain the required linearity. However the nature of defects in the material strongly influences the type of priming required. This paper will address this problem from the study of defect levels and their influence on the device response. In fact, one parallel perspective is the use of diamond as a thermoluminescent dosimeter if the defect level concentrations are stable and controllable. We will propose new techniques such as the incorporation of doping impurities during growth as well as the optimisation of the device characteristics for such applications.

- 75 - PIII-11

Radionuclide Imaging Using Electron Multiplying CCD Based Detector

V. Nagarkar

RMD, Inc, 44 Hunt Street, 02472 Watertown, Usa Email: [email protected]

Traditionally charge coupled devices (CCDs) are used as integrating detectors to acquire high resolution images with enhanced signal to noise ratio. However, the recent development of an electron multiplying CCD (EMCCD) has enabled their use in photon counting applications. These new devices combine high spatial resolution and low noise properties of a conventional CCD, with internal gain of an avalanche photodiode (APD). Additionally, the device design allows it to be operated at a very high frame rate of 500 frames per second or higher, without introducing any significant noise. At RMD we are utilizing unique properties of EMCCDs for their use in nuclear medicine applications. This paper will describe the design of a detector based on thick microcolumnar CsI(Tl) scintillator coupled to a specially designed EMCCD camera. The imaging performance of this detector along with its efficacy for radionuclide imaging will be discussed.

- 76 - PIII-12

An improved PIN photodetector with integrated JFET on high- resistivity silicon

G.F. Dalla Betta, C. Piemonte, M. Boscardin, P. Gregori, N. Zorzi, A. Fazzi, G.U. Pignatel

Universita' di Perugia, DIEI - via G.Duranti 93, 06125 Perugia, Italy Email: [email protected]

We report on a test-structure made on n-type high-resistivity silicon, consisting of a 0.8mm2 PIN diode monolithically integrated with a Junction Field Effect Transistor (JFET) in the tetrode configuration (W/L=100um/6um). The JFET is a fully-implanted device with circular geometry. A deep p-well acts as the bottom-gate and isolates the transistor from the high-resistivity substrate. The PIN+JFET device is intended as a detector for X-rays and gamma-rays. In case of high energy photons, it might be coupled to a scintillator to improve the efficiency. Besides being suitable as a stand-alone detector for spectroscopy, it can be used as an active pixel in linear or 2D arrays for imaging applications. In particular, we are currently investigating its operation as the main element of a gamma camera for scinto-mammography, composed of a 2D array of detectors with 2mm pitch, coupled to pixellated CsI(Tl) crystals able to convert 99Tc 140keV photons into light photons centered at 550nm wavelength.

We have already reported on previous versions of such a device, which could be effectively operated as an X-ray detector, although its noise performance was degraded by the presence of excess white noise in the JFET [1,2]. The best result we obtained for the equivalent noise charge was 60 rms electrons at room temperature. The reason for this excess noise has been thoroughly investigated both experimentally (Electrical tests and SIMS measurements of the doping profiles) and with the aid of TCAD numerical simulations. The problem has now been fully understood: the depletion of the bottom-gate, whose doping profile was not adequately concentrated and deep, caused a bias-dependent series resistance, this contributing Johnson noise to the transistor. In order to fix the problem, an improved fabrication technology has been developed, featuring a high-energy (1MeV) boron implantation to realize the bottom gate. Devices fabricated within this new process are fully functional with good static (pinch-off voltage, transconductance) and capacitance parameters. The leakage current of the diodes is very low (~0.5nA/cm2 at full depletion). Dedicated measurements prove that the JFET bottom-gate is not depleted any more and, in fact, is almost as effective as the top-gate in depleting the transistor channel. In this condition, the JFET thermal noise is determined only by the transconductance, as predicted by basic theory. Noise measurements on the JFET are under way to confirm the above assumption. Moreover, a complete noise and spectroscopic characterization of the new PIN+JFET test structure have been planned. Experimental results will be presented at the Conference and issues dealing with the integration of the device in 2D arrays for scinto-mammography will also be addressed.

- 77 - PIII-13

An efficient, large-area fast-neutron imaging & timing detector

D. Vartsky1, I. Mor1, M. B. Goldberg1, D. Bar1, G. Feldman1, V. Dangendorf2, K. Tittelmeier2, A. Breskin3, R. Chechik3

1Soreq NRC, Yavne, Israel 2Physikalisch-Technische Bundesanstald (PTB), Brunschweig, Germany 3Weizmann Institute of Science, Rehovot, Israel Email: [email protected]

We describe an efficient, large-area-detector for sub-mm spatial imaging and few-ns-timing of fast neutrons, capable of loss-free operation at very high neutron-flux intensities. The detector is based on an integrative (as opposed to single-event counting) optical technique, which permits neutron energy-resolved imaging via time gated optical readout.

The neutron detector consists of a fast plastic (polystyrene) scintillator fiber screen, 200x200x20 mm3 in dimensions. The reason for using scintillating optical fibers, rather than a plain plastic scintillator slab, is to maintain the position resolution, independent of screen thickness. The fiber diameter in the screen was 250 µm. A neutron interacts in the fibers and transfers part of its energy to a proton, which produces scintillations in the fiber. A fraction of this light travels along the fiber and is emitted at its ends. The light is transported via a front-coated mirror and viewed by a CCD camera through a custom designed large-aperture lens (150mm F#1) and a nanosecond-gated image-intensifier.

The detector was tested at the PTB cyclotron using a broad-energy spectrum (2-16 MeV), pulsed neutron beam produced by a nanosecond-pulsed deuterium beam hitting a thick Be target. The measurement of the time of flight of the neutrons is performed by varying the delay time of the image intensifier gate relatively to the accelerator pulse.

In this experiment we studied various detector parameters, such as efficiency, spatial and energy resolution and by exploiting resonances in neutron cross-sections we performed element-specific neutron radiography which permits imaging of elements such as C, O and N.

We demonstrated that at high spatial frequency the modulation transfer function of scintillating fiber screen is superior to that obtained using a plain scintillating slab screen of same thickness. The dependence of the spatial resolution on neutron energy was studied experimentally and compared to that obtained using GEANT simulation.

- 78 - The neutron energy resolution of this system is dependent mainly on the time width of the image intensifier gate. We demonstrated that with 15-20 ns gate width it is possible to resolve elements such as carbon and nitrogen from other elements and to obtain element specific images by fast neutron resonant radiography.

- 79 - PIII-14

BJT-based detector on high-resistivity silicon with integrated biasing structure

G. Verzellesi1, G. Batignani2, S. Bettarini2, M. Boscardin3, L. Bosisio4, G.F. Dalla Betta5, C. Piemonte3

1University of Modena and Reggio Emilia, Department of Information Engineering, via Vignolese 905, 41100 Modena, Italy, and INFN Bologna 2University of Pisa, Department of Physics ”E. Fermi”, and INFN Pisa, Largo Pontecorvo, 3, 56127 Pisa, Italy 3ITC-irst, Microsystems Division, via Sommarive, 18, 38050 Povo di Trento, Italy 4University of Trieste, Department of Physics, and INFN Trieste, Via.A. Valerio, 2, 34127 Trieste, Italy 5University of Trento, Department of Information and Communication Technology, via Sommarive, 14, 38050 Povo di Trento, Italy Email: [email protected]

When applied to the detection of ionizing particles or to X-ray spectroscopy, bipolar phototransistors require to be biased at a suitable quiescent current, allowing the phototransistor to operate in its high-current-gain region. Signal charges generated by the ionizing radiation are in fact generally too small to drive, by themselves, the phototransistor into the active forward region.

In this paper, a novel method for biasing phototransistor-based radiation detectors on high-resistivity Si is presented, that relies on the integration into the detector base of a pnp transistor acting as a current source. The proposed approach can be extended in a natural way to the biasing of npn detector arrays, allowing different detectors to be biased at the same quiescent current, by connecting all the biasing pnp transistors with a diode-connected reference transistor (integrated onto the same chip), so that they form a current- mirror circuit.

Relying on two-dimensional numerical device simulations, several test structures have been designed and fabricated, including single BJT detectors and detector arrays with pnp biasing transistors connected in the current-mirror configuration. The electrical characterization of fabricated structures shows that both single detectors and detector arrays are operational and behave in good agreement with simulations, thus demonstrating the feasibility of the proposed approach. Results will also be shown from the characterization of the optical and X-ray detection properties of the proposed structures.

- 80 - PIII-15

Characterization of GaAs based detectors

I. A. Sokolov

A.F. Ioffe Physico-Technical Institute Russian, Academy of Sciences, Polytekhnicheskaya 26, 194021 St.- petersburg, Russia Email: [email protected]

GaAs detectors for registration of X-radiation and gamma radiation are found applications in medicine and for the tasks of high-energy physics. Since the registered signals are small enough the main problem of such devices can be formulated as follows - realization of maximal detector volume keeping constant low noise level. The capacity and return current should be minimized. The is achieved via (i) fabrication of GaAs layers with low amount of defects and low carrier concentration, and (ii) structure optimization and creation of contacts with low resistance.

The non-steady-state photoelectromotive force effect [1] was used for characterization of transport parameters of ultra-pure GaAs thin films grown on semi-insulating gallium arsenide wafers using gas-phase epitaxy technique. Such structures are used for fabrication GaAs detectors for registration of X-radiation and gamma radiation.

The mechanism responsible for the effect can be described as follows (Fig. 1). Illumination of a photoconductive sample by an interference pattern I(x) formed by two coherent light beams produces a nonuniform excitation of free carriers. Diffusion of the photoexcited carriers towards the dark regions leads to charge redistribution between traps. A space charge field grating Esc(x) arises; this grating is spatially shifted by 900 relative to the optical interference pattern and photoconductivity distribution. For the steady- state conditions the current j = (((x)Esc(x) = 0. Small vibrations of the light along the grating vector excites an alternating current through the short-circuited crystal because of the time-dependent phase shift between oscillating spatially-periodic free carriers and fixed space charge field distributions.

The structures were fabricated at A.F. Ioffe Physico-Technical Institute (laboratory of Yu.V. Zhilyaev). For our experiments we choose the GaAs sample with the layer thickness of 400 microns, n = 2 1012 cm-3. The experiments can be carried out only in the geometry of Michelson interferometer at the illumination wavelength of 532 nm. The modulation frequency was f = 1 kHz and the light power of the signal and reference beam on the sample’s surface was about 20 mW, the inter-electrode distance was 2,5 mm. The dependence of the signal photocurrent amplitude versus spatial frequency of the interference pattern was measured. Note, that the signal peaks for the spatial frequency of the interference pattern K equal to the inverse diffusion length of photocarriers. The value of diffusion length of the as grown structure was estimated to be LD = 40

- 81 - PIII-16

Material optimization for X-ray Imaging detectors

N. Mañez1, G.C. Sun2, H. Samic3, B. Berjat2, N. Kanoun2, J.C. Bourgoin4

1Laboratoire des Instruments et Systèmes Ile de France, Université Pierre et Marie Curie (Paris 6), 3 rue Galilée, 94200 Ivry s/Seine, France 2Institut de Minéralogie et Physique de la Matière Condensée, Université Pierre et Marie Curie (Paris 6), 140 rue de Lourmel, 75015 Paris, France 3Department of Physics, University of Sarajevo, 7100 Bosnia & Hertzegovina. 4GESEC R&D, 68 avenue de la Forêt, 77210 Avon, France Email: [email protected]

Materials of atomic number Z as high as possible are considered for solid state X-ray imaging detectors in order to absorb the radiation efficiently. However, the energy and yield of the fluorescence photons increase with Z [1], so that the contrast and spatial resolution of an image decreases with Z. We shall show that the Z value which optimizes the absorption and the image contrast for a given spatial resolution corresponds to GaAs. Now that the GaAs material (thick epitaxial layers) necessary to make pixel detectors exists [2,3], we shall illustrate the improvements this material brings by comparing, in case of a pixel size adapted to mammography (50 to 100 µm), the spatial resolution and contrast, with that obtained using CdTe and CsI based detectors. Using the model of Rose [4] which gives the threshold signal-to-noise ratio corresponding to the minimum detectable contrast, we evaluate the minimum size of the object and the minimum absorption difference for a given object which can be detected with detectors made of GaAs, CdTe and CsI.

[1] S. A. Moszkowski, Alpha-, Beta-, and Gamma- Ray Spectroscopy, edited by Kai Siegbahn, pp.570, North-Holland Publishing Company, Amsterdam, 1965

[2] G.C. Sun, H. Samic, V. Haguet, J.C. Pesant, J.P. Montagne, M. Lenoir, J.C. Bourgoin, "Performances of epitaxial GaAs p/i/n structures for X-ray imaging", Nuclear Instruments and Methods in Physics Research A 487, 102(2002)

[3] G.C. Sun, N. Talbi, C. Verdeil, J.C. Bourgoin, Suitability of epitaxial GaAs for X-ray imaging", Applied Physics Letters, 85(12), 2399(2004)

[4] A. Rose, Vision: Human and Electronic (Plenum, New York) (1973)

- 82 - PIII-17

Characteristic Analysis and Image Correction of High Resolution Digital X-ray Camera System Based on Scintillator Detectors for Phase-Contrast Imaging

Huang Zhifeng1, Li Zheng1, Zhang Di1, Kang Kejun1, Li Gang2, Chen Yu2

1Department of Engineering Physics, Tsinghua University, Building of Engineering Physics 214, Beijing, China, 100084 2Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China,100049 Email: [email protected]

X-ray phase contrast imaging is a state-of-the-art technique. Compared with the conventional absorption contrast imaging, it is more sensitive, especially for imaging weakly absorbing samples (especially low- atomic-number elements, such as hydrogen, carbon, nitrogen, and oxygen), less harmful and almost 1000 times higher by resolution. So it has great potential to reveal the structures inside soft tissues, organic materials etc. Resolution of a few micrometers is achieved, so a very high resolution digital X-ray camera system based on scintillator detectors is required to suitable to the phase contrast imaging. This paper will firstly analyze the characteristic of scintillator detectors for the X-ray photons with information of contrast shift in two phase contrast Imaging method: diffraction enhanced method and in-line method. Then try to find out the choice strategy of detectors for the appropriate resoluction, according to the their own principles. At last, several correction methods for the detector-induced artifacts are applied to improve image quality. A series of experiments are done to validate them at the Beamline 4W1A and TOP station of the Beijing Synchrotron Radiation Facility (BSRF) in China.

[1] Huang zhifeng,Li Zheng,Kang Kejun, The Application of Digital Tomosynthesis to the CT Nondestructive Testing of Long Large Objects,Developments in X-Ray Tomography IV, edited by Ulrich Bonse, Proc. of SPIE(SPIE, Bellingham, WA, 2004), V.5535, PP514-521,2004

- 83 - PIII-18 Effect of Temperature and Inhomogeneity on the Yield of PtSi- n-Si Photodetectors A. Sellai

Sultan Qaboos University, Physics Dept, PO Box 36, Sultan Qaboos University, 123 Muscat, Oman Email: [email protected]

The internal photoemission yield in Schottky barrier (SB) photodetectors is intimately linked to the SB height. The vast majority of electrical measurements reported in the literature, concerning SB diodes, are consistently interpreted on the basis of non-homogeneous or spatially distributed BH. The objective of the present paper is to report the effect of spatial inhomogeneity and temperature on the yield of PtSi/n-Si Schottky photodetectors in the spectral region (0.8 ƒÝm ¡V 1.55 ƒÝm) where internal photoemission in the dominant detection mechanism.

In this context, the current-voltage (I-V) characteristics of PtSi/n-Si Schottky diodes are measured over a wide temperature range (20 K ¡V 290 K) with the lower temperature end extended to 20 K, much lower than what is usually reported in literature. The I-V results show, as expected, strong temperature dependence but appear to be in discordance with thermionic emission theory at very low temperatures. The starting point in analyzing our I-V-T data is simple thermionic emission theory. First, following the conductance method of Werner [1] the series resistance (Rs) and ideality factor (n) were extracted. Contrary to Rs, n shows a remarkable increase as the temperature is lowered from 290 K to 20 K. Although the Ln(I)-V plots, corrected for series resistance, exhibit excellent linearity over the wide voltage and temperature ranges, the apparent barrier heights derived from these plots vary between 0.60 V and 0.82 V. To address these ¡§abnormal¡¨ experimental behaviors arising in this simple approach, the I-V-T results are adequately interpreted in the context of a modified thermionic model that takes into account the spatial inhomogeneity of the BH. The most interesting form of non-homogeneity, as reported by Tung [2], is the presence of locally non-uniform regions or patches consisting of both low and high SBs. A Gaussian distribution of the barrier potential of the form: has been successfully used to satisfactorily describe the strong variations of both the SBH and ideality factor with temperature. This is a more physically based interpretation as compared to alternative empirical approaches such as the T0-parameter or the flatband models. Our analysis, in this context, gave a mean barrier height of 0.78 V with a standard deviation of 30mV.

Since the total current, including the photocurrent, is the sum of currents flowing in each individual patch, it is expected that the photodetector efficiency in a non-homogeneous case to exhibit behavior that deviates from a uniform SBH. The calculated internal yield in the spectral range 0.8 ƒÝm ¡V 1.55 ƒÝm taking a Gaussian BH distribution into account shows, however, no significant deviations - except at cut-off wavelengths, from the yield obtained assuming a homogeneous (a mean BH) Schottky contact. The quantum efficiency results obtained assuming temperature dependent electron-electron and electron-phonon scattering events show, however, significant temperature dependence in disagreement with the well-known Fowler expression.

[1] J. H. Werner, Appl. Phys. A47, 291-300, 1988

- 84 - [2] R. T. Tung, Phys. Rev. B45, 13509-13523, 1992

PIII-19

Influence of the substrate surface texture on the quantum efficiency of thin CsI photocathodes

M. A. Nitti1, A. Valentini1, D. S. Sutherland2,E. Nappi1

1INFN-Sezione di Bari, c/o Dipartimento Interateneo di Fisica, Via Amendola 173,70126 Bari, Italy 2Department of Applied Physics, Chalmers University of Technology, S-41296 Go¨teborg, Sweden Email: [email protected]

Morphology, roughness and photoemissive properties of photocathodes (PCs), based on evaporated and ion beam sputtered CsI films, have been investigated. The film thickness has been fixed to 50 nm, not much higher than CsI photoelectron escape length. Film surface morphology and roughness have been analysed by means of atomic force microscopy. In order to change the film morphological surface properties, substrates with different roughness have been used. In particular, with respect to our previous investigations, a new type of material has been included. It presents a very high roughness density, obtained by depositing nanostructured polymer colloidal particles on a PolyEthylene Terephthalate (PET) foil. This foil has been put on a rigid support and covered with a very thin metal layer before CsI deposition.

New investigation results concerning the surface roughness effect on the PET PCs quantum efficiency confirm our previous ones.

- 85 - PIII-20

Scintillation photodiode detectors on a base of CsI:Na crystal with radiation hardness up to 1 mrad for high energy physics

L.A. Andryustchenko, A.M. Kudin, Yu.A. Borodenko, V.V. Nekrasov, A.I. Mitichkin, E.A. Kudin

Institute for Scintillation Materials, NAS of Ukraine, 60 Lenin Ave., Kharkov, Ukraine Email: [email protected]

Detection of ionizing radiation by scintillation photodiode detectors is more suitable in high energy physics especially when detector is used in magnetic field. In well known experiments as BaBar and BELLE a calorimeter consists from CsI:Tl crystals coupled with silicon PIN photodiode. CsI:Na crystal has an obvious advantage in comparison with CsI:Tl such as shot decay time (630 nanosecond instead of 1000) and very good radiation hardness (critical dose D = 1 MRad instead of 0.01 MRad). A unique property of CsI:Na crystal is the fact that energy resolution doesn’t worse after irradiation by critical dose [1].

Essential disadvantage of CsI:Na scintillator is the fact that it must be coupled with photomultiplier because luminescence spectrum is not in good conformity with the spectral sensitivity of the silicon PIN photodiode. Recently we have shown that protective coating on the surface of crystal can play a role of wavelength shifter (WLS) [2] and improve the axial uniformity of long size CsI:Tl detector.

In this report we consider the problem how to increase the light output of the assembly on the base of CsI:Na crystal and Si PIN photodiode. It has been shown that immersion layer between crystal and photodiode can increase the light output if transparent silicon oil contains a WLS dopand. The photopeak shifts to high energy side but retains its shape. Improvement of energy resolution takes place due to increasing of light output only. Contrary to transparent immersion layer thixotropic one increases the light output slightly but improves the energy resolution more.

For long size CsI:Na scintillator the best solution is to apply WLS coating to all sides of detector excluding output window in combination with thixotropic WLS immersion layer. In this case the energy resolution depends on axial uniformity of light yield mainly. It is possible to achieve the value of nonuniformity better then 1 % [2].

[1] Hitlin D.G., Eigen G. Heavy scintillators for scientific and industrial applications. Frontieres, France (1992) 467.

[2] Andryustchenko L.A., et al. NIM A 486 (2002) 40.

- 86 - PIII-21

New Oxychloride Glass-Ceramic X-ray Storage Phosphors

G.A. Appleby1,2, A. Edgar1,2, and G.V.M. Williams2,3

1Victoria University of Wellington, P O Box 600, New Zealand 2MacDiarmid Institute for Advanced Materials and Nanotechnology 3Industrial Research Limited, Lower Hutt, Wellington, New Zealand Email: [email protected]

Imaging plates made from x-ray storage phosphor (XRSP) [1] materials are solid-state replacements for photographic film in x-ray radiography [2]. New glass-ceramic XRSP’s have been shown to have several advantages over existing commercial imaging plates. Materials studied so far consist of a fluorozirconate glass matrix containing a nanocrystalline phase of a europium doped bromide or chloride salt - the latter materials showing a sensitivity to x-irradiation of up to 80% of that of the well-known XRSP BaFBr:Eu2+ [3, 4].

Recently, a new glass-ceramic consisting of a lithium borate glass matrix containing orthorhombic BaCl2:Eu2+ nanocrystallites has been discovered, which shows promise as a new XRSP. The addition of fluoride results in the formation of a minor phase of BaFCl:Eu2+, which is a superior XRSP to BaCl2:Eu2+ and is a phase that, like BaFBr:Eu2+, has not been found in the fluorozirconate glass.

In this paper, we present the performances of new lithium borate glass-ceramic family containing nanocrystalline BaFCl:Eu2+ or BaFBr:Eu2+, with a particular focus on applications for x-ray imaging, including stimulation and conversion efficiency, storage time, readout time and spatial resolution.

[1] Schweizer, S., Physics and Current Understanding of X-ray Storage Phosphors. Physica Status Solidi, 2001. 187(2): p. 335-393

[2] Rowlands, J.A., Physics of Computed Radiography. Phys. Med. Biol, 2002. 47: p. R123-R166

[3] Schweizer, S., et al., Photostimulated luminescence in Eu-doped fluorochlorozirconate glass ceramics. Applied Physics Letters, 2003. 83: p. 449-451

[4] Edgar, A., et al., New materials for glass ceramic x-ray storage phosphors. Current Applied Physics, 2004. 4/2-4: p. 193-196

- 87 - PIII-22

A fast gaseous integrating detector for small angle X-ray scattering chemical kinetic experiment at SOLEIL

M. Bordessoule1, T. Bucaille1, G. Chaplier2, S. Hustache1, M. Lemonnier2, A. Jucha2, K. Medjoubi1, S. Megtert2, J. Perez1, P. Vachette2

1Synchrotron SOLEIL, L'Ome des Merisiers, 91192 Gif sur Yvette cedex, France 2LURE, 91405 Orsay cedex, France Email: [email protected]

With high photon fluxes delivered by third generation synchrotron sources like Soleil, high resolution studies of fast kinetics in chemical reaction are now possible. The one-dimensional gaseous photon integrating detector presented here is designed for Small Angle X-ray Scattering (SAXS) on isotropic samples. Detector’s internal structure consists of a conversion region and of an amplification gap based on CAT technology [1]. The detector is filled with Xe-C2H6 mixture at a pressure of 1.5 bars. The read-out electrode structure takes advantage of the independence on the azimuthal angle of the scattering from isotropic samples, thanks to 128 concentric strips. The strips are connected to two chips with 64 integrating multiplexed preamplifier channels each. Thanks to the variable gain of this electronics, the detector can be sensitive can be sensitive to a few photons per channel only, up to 10^5.

The detector is able to measure images every millisecond with an efficiency better than 50% and a spatial resolution less than 800µm at 12 keV. Performances and images obtained under X-ray tube irradiation will be presented.

[1] «The C.A.T. Pixel Proportional Gas Counter Detector», M.Lemonnier et al., J.Phys.III France 6 (1996) 337-347

- 88 - PIII-23

Developments of Imaging Capillary Plate Gas Detector

F. Tokanai, T. Atsumi, T. Endo, Y. Fujita, Y. Ohishi, T. Okada, S. Gunji, H. Sakurai, H. Toyokawa, M. Suzuki, K. Hirota, S. Kishimoto

Faculty of Science, Yamagata University, 1-4-12 Kojirakawa, Yamagata, 9908520 Yamagata , Japan Email: [email protected]

The glass capillary plate (CP) is one of the hole-type micro-pattern gas detectors. It consists of two- dimensional arrays of fine glass capillaries with an effective area ranging from 10 to 100 mm in diameter. The channel diameter is in the range of 1 to 1000 micrometers with a thickness range of between 0.2 and 2 mm. In general, it is widely used as a flow controller for gas and liquid, a particle filter, as well as optical and X-ray collimators. Using this CP gas detector, we have been developing the real two-dimensional imaging gas detectors for an X-ray photoelectron imager for cosmic X-ray polarimetry and a gaseous photomultiplier (PMT) with a bi-alkali photocathode for application to cellular function analysis. In this 2D imaging gas detector, we utilize the gas scintillation light emitted from the capillary plate. The light is detected using an image intensified CCD camera or a cooled CCD camera, coupled to the lens system. In this paper, we will describe the characteristics and recent development of the imaging CP gas detector.

- 89 - PIII-24

A Study of the Operation of Specially Designed Photosensitive Gaseous Detectors at Cryogenic Temperatures

L. Periale1, V. Peskov2, C. Iacobaeus3, B. Lund-Jensen4, P. Pavlopoulos2, P. Picchi1, A. Pietropaolo1

1CERN, Geneva, Switzerland 2Pôle Universitaire Leonardo de Vinci, La Défense Cedex, 92916 Paris, France 3Karolinska Institute, Stockholm, Sweden, 4Royal Institute of Technology, Stockholm, Sweden Email: [email protected]

In some experiments and applications there is need for large-area photosensitive detectors operating at cryogenic temperatures. Examples could be: the ICARUS experiment, WIPMs search LAr/Xe detectors, noble liquid scintillating calorimeters and cryogenic PETs. Nowadays, vacuum PMs are usually used for this purpose. The main drawbacks of these detectors are: the high cost and sensitivity to magnetic fields (desirable for some experiments).

In attempts to overcome these drawbacks we have developed special designs of planar photosensitive gaseous detectors able to operate at cryogenic temperatures. Such detectors are much cheaper PMs and are insensitive to magnetic fields. We will report our new and yet unpublished results on the operation of sealed gaseous detectors with reflective and semitransparent CsI photocathodes inside LAr and LN2. Results of systematic measurements of their quantum efficiencies, the maximum achievable gains and long-term stabilities will be presented. In addition the operation of gaseous detectors combined with other solid photocathodes was also studied.

Finally, the results on the operation of windowless photosensitive detectors placed either in cooled gases or directly in vapors a few cm above the noble liquid level will be presented. Based on obtained results a comparison will be done between the sealed and windowless photosensitive gaseous detectors. Note that the windowless detectors could also be used for the detection of the charge tracks. As an example we will describe our first experiments with muon’s charge track extraction from the LAr and detected by a specially developed G10 based hole-type detector.

The successful operation of these detectors open realistic possibilities in replacing PMs by photosensitive gaseous detectors in some applications dealing with cryogenic liquids, for example in experiments using noble liquid TPCs or noble liquid scintillating calorimeters.

- 90 - PIII-25

Development of gas avalanche photodetector operating at cryogenic temperature

S. Bricola1, R. Brunetti1, E. Calligarich1, M. Cambiaghi1,2, C. De Vecchi1, R. Dolfini1,2, A. Menegolli1,2, M. Prata1, M.C. Prata1, G.L. Raselli1, M. Rossella1, C. Vignoli1

1Istituto Nazionale di Fisica Nucleare (INFN) Sezione di Pavia, Via Bassi 6, I-27100 Pavia, Italy 2Dipartimento di Fisica Nucleare e Teorica, Università degli Studi di Pavia, Via Bassi 6, I-27100 Pavia, Italy Email: [email protected]

We are interested in developing a photodetector sensitive to liquid noble gas scintillation light which is able to operate in cryogenic environment down to liquid nitrogen temperature (77 K). It should be a simple device, economic, compact, with a photocathode surface comparable to the photomultipliers’ one. It should be able to produce fast signals with the purpose of timing and triggering. It could offer a cheap alternative to the photomultipliers use in big volume liquid noble gas Time Projection Chamber (TPC).

We studied the possibility to couple a standard photocathode to a suitable electron multiplication system in gas. In the first part of the programme the gas avalanche multiplication at cryogenic temperature and low pressure was studied with a small wire chamber prototype. The second part of the programme foresees the production of a multialkali photocathode able to operate at low temperature.

We present the results of the evaluation of the maximum gain attainable in gas employing pure argon and argon/methane mixture and we report on aging effects at low temperature. The second part of the programme is in progress and preliminary results are presented.

This work has been carried out within the PRIN (Progetti di ricerca scientifica di Rilevante Interesse Nazionale) and funded by MIUR (Ministero dell’Istruzione, dell’Università e della Ricerca), by the Universities of L’Aquila, Napoli, Padova and Pavia, and by INFN.

- 91 - PIII-26

Advances in gaseous photomultipliers for the visible spectral range

A. Lyashenko1, D. Mörmann1, A. Breskin1, R. Chechik1, F.Amaro2, J.Veloso2, J.dos Santos2

1Department of Particle Physics, The Weizmann Institute of Science, Particle Physics Department, 76100 Rehovot, Israel 2Physics Dept., University of Coimbra, 3004-516 Coimbra, Portugal Email: [email protected]

We present recent advances in the study of visible-sensitive gas avalanche photomultipliers operating at atmospheric pressure with bialkali photocathodes. Appart from technical issues concerning the sealed-mode operation, the main challenge in realization of such devices has been the matching of the electron multiplier to the photocathode. In particular it is crucial to reduce the avalanche-induced positive-ion flux impinging on the photocathode; it induces excessive feedback pulses, limiting the gain and moreover, modifying the surface composition of the photocathode resulting in Quantum Efficiency(QE) degradation.

Our visible-sensitive gaseous photomultipliers comprise a cascade of Kapton-made GEMs, optimized for the operation with a bialkali photocathode. These electron multipliers provide high gain, due to the suppression of photon feedback, have ns time resolution and present good localization properties.

We report on the introduction of an ion-gate electrode, between the photocathode and the cascaded multiplier, that reduced the ion backflow to the photocathode by a factor of ~104. This enabled the breakthrough of a stable operation of a visible-sensitive gaseous photomultiplier, with single-photon sensitivity, at a gain of 106.

We will report on our extensive study of other solutions for ion blocking, that will permit DC operation with bialkali and other visible-sensitive photocathodes. These include the introduction of other multipliers with special electrodes operated as dedicated ion-trapping devices: MHSPs and R-MHSPs. The first is a GEM- like electrode with extra anode multiplying strips and the latter is a GEM-like electrode with extra ion- repulsing cathode strips, patterned at their bottom. An ion-backflow reduction of about 103 has already been demonstrated with the novel cascaded multipliers.

The aging of bialkali photocathodes was studied under accelerated ion flux; a 20% aging was observed at an accumulated ion charge of 2 C/mm2; assuming a quantum efficiecy of 30%, this results in ~13 years of operation under a gain of ~105 at a photon flux of 1kHz/mm2.

- 92 - Further developments in the production of GEM and GEM-like electrodes made of ceramics and Si will be reported, in view of the sealed mode operation. Other photocathodes will be discussed.

- 93 -

Fourth International Conference on « New developments in photodetection » Beaune, France, 19-24 June 2005

Best Poster Awards

• Session I - Poster PI-8: Hanson Kael from University of Wisconsin - Madison and Tarasova Oxana from DESY

• Session II: -Poster PII-5: Pani Roberto from University La Sapienza- Dept of Experimental Medicine

• Session III - Poster PIII-23: Tokanaï Fuyuki from Yamagata University

Fourth International Conference on « New developments in photodetection » Beaune, France, 19-24 June 2005

To see the others photos of Beaune 2005, go manually to the “Photos” directory on the cd.

DSM Direction des Sciences de la Matière

Fourth International conference on « New developments in photodetection » Beaune, France, 19-24 Juin 2005 Sponsorship

Centre National de la Recherche Scientifi que

Commissariat à l’Energie Atomique DSM Direction des Sciences de la Matière

Université de Savoie

International Science and Technology Center

Id Quantique

Istituto Trentino Di Cultura DSM Direction des Sciences de la Matière

Fourth International conference on « New developmentsdevelopments iinn pphotodetectionhotodetection » Beaune, France, 19-24 JuinJuin 2005

ALIMTRONICALIMTRONIC Alimentation basse etet haute ttensionension Alimtronic-Wiener-Caen

Burle Industries Inc. Electron Tubes Limited

Hamamatsu Photonics

Higler Crystals

Hi-Tech Detection Systems

ISEG Spezialelektronik GmbH

Photonis-DEP OPTOPRIM

SensL : SiPMs & Photon Counting

Systems Development and Solutions

« Lycée Viticole de Beaune »

Fourth International Conference on « New developments in photodetection » Beaune, France, 19-24 June 2005

Company Participants Name Web Site & e-mail Name E-mail ETL www.electrontubes.com Tony Wright [email protected] [email protected] Ron Stubberfield [email protected] HAMAMATSU www.hamamatsu.fr Marc Birkel [email protected] [email protected] Peter Aicher [email protected] Wilfrid Vogel [email protected] Laurent Luong [email protected] Marcus Mayer [email protected] Yuji Yoshizawa Yuji Hota ISEG www.iseg-hv.de Ludwig Christians [email protected] [email protected] SDS www.sdshv.com Bernard Leibovici [email protected] Paul Reiss www.corel- Alimtronic electronique.com Mohammed Gharbi [email protected] Wiener www.wiener-d.com Manfred Plein [email protected] Caen www.caen.it Gianni Di Mario [email protected] PHOTONIS www.photonis.com Carole Marmonier [email protected] Christophe Fontaine [email protected] Daniel Guerin [email protected] Léon Bosch [email protected] Cyril Moussant [email protected] HTDS www.htds.fr Michel Herrero [email protected] [email protected] Maxime Pierlo [email protected] Jérôme Barbier [email protected] Denis Boireau [email protected] OPTOPRIM www.optoprim.com Patrice Benoit [email protected] Jérome Castay [email protected] Id Quantique www.idquantique.com A. Rochas [email protected] [email protected] SensL www.sensl.com Joseph O'Keeffe [email protected] [email protected] Hilger Crystals www.hilger-crystals.co.uk Dennis Day [email protected] [email protected]

Fourth International Conference on « New developments in photodetection » Beaune, France, 19-24 June 2005

Exhibitors

4th International Conference on New Developments in Photodetection - Palais des Congrès, Beaune, France - June 19-24, 2005 A Large Dynamic Range Integrated Front-End for Photomultiplier Tubes B. Genolini1, L. Raux2, C. de La Taille2, J. Pouthas1 , V. Tocut2 1 IPN Orsay, IN2P3-CNRS, Université Paris-Sud, 91406 Orsay Cedex, France 2 LAL, IN2P3-CNRS, Université Paris-Sud, Bat. 200, 91898 Orsay Cedex, France

A cost effective « system on chip » design for PMTs

High Large voltage 10 dynamic range: -Input range = 7 V 1 FADC Base -16 bits -Overlap between ranges: Reduce the number of cables 0.1 >75 LSB High voltage and signal through the same cable Calibration Auto/cal switch mode (Pierre Auger Observatory requirements) 75 Ohm impedance

P M Built-in calibration adapted from the Atlas liquid Argon calorimeter (sched. Dec 2005) Signal digitization by a 100 MSPS FADC – submitted in January 2005 – under test

Measurements: Submission of April 2004 AMS 0.35 µm CMOS High linearity and low noise Gain 0.1 Gain 1 Gain 10

Measurement 1 2 1 2 1 OTA 1 Residuals Measurement Measurement

0.8 (%) Residuals 0.8 1.8 Residuals 0.8 0.9 1.8 V + Biasing with a slow OTA Bias 0.6 1.6 0.6 1.6 0.6 - CFOA 0.8 (transimpedance amplifier) 0.4 1.4 0.4 1.4 0.4 buffers 0.7 Design based on CFOA 0.2 0.2 1.2 Residuals (%)

Residuals 0.2 0.6 1.2 Residuals (%) Vdd + (current feedback amplifiers) 0 0.5 1 0 1 0 - Vdd -0.2 0.4 0.8 -0.2 0.8 -0.2

× 10 (V) amplitude OUTPUT -0.4 (V) amplitude OUTPUT -0.4 OUTPUT amplitude (V) amplitude OUTPUT 0.3 0.6 0.6 -0.4 -0.6 -0.6 0.4 -0.6 MP1 MP2 0.2 0.4 in+ in- -0.8 0.2 -0.8 0.2 -0.8 + Rg e 0.1 -1 out_ota 0 0 -1 0 -1 - 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0 50 100 150 200 250 300 350 400 idc_cascod idc R × 1 in- f INPUT amplitude (V) INPUT amplitude (V) INPUT amplitude (mV) MN_ MP_Out Vcascode C Linearity limit Linearity limit: Linearity limit: in+ MP_In + Input: >5 V Input: 1.3 V Input: 230 mV - Vss_bulk MN1 MN2 Output: > 1 V Output: 1.7 V Output: 1.4 V Vss × 1 Vss Gain 0.2 Gain 1.3 Gain 6.2 lk Vss_bu Out. noise RMS: 90 µV Out. noise RMS: 90 µV Out. noise RMS: 430 µV Over 175 MHz Over 175 MHz Over 175 MHz

Estimated power absorption: Linearity better than 1 % over the measured range less than 2 mW (<400 µA on 5 V) Equivalent input noise < 50 µV RMS (below 50 MHZ - Nyquist frequency For 100 MSPS) A single cable for Measurements on the Orsay signal and high voltage Cerenkov water tank (Auger) 3 m long cable 25 Ω Fall time distribution Digitizing ZC 75 Ω Anode (CH1) LED CC oscilloscope 500 Standard base G 1 (CH3) 100kΩ Single cable 100kΩ (50 Ω input) G0.1 (CH2) G10 (CH4) 400 Single cable + G10 Matacq FADC PMT Occurences 12 bits, 2 GSPS 300 LAL Orsay (IN2P3-CNRS), High DAPNIA Saclay (CEA) - (France) voltage 200 Passive CH1 100 PMT gain: splitter around 3×106 G0.1 0 0 5 10 15 20 25 CH2 Fall time (ns) Noise: negligible influence G1 - difference between a standard base / system with single cable Cable bandwidth: no effect CH3 measured over 300 MHz bandwidth, dominated by the 25 Ω series Theplot aboveshows thefalltimedistribution resistor. for LED signals at 5 photoelectrons, with G10 - Measurement with the preamplifier, on the highest gain: no change different configuration: standard base, CH4 detected on 300 MHz bandwidth configuration with a single cable, highest amplification at the single cable configuration. There is no significant bandwidth reduction. 12 m3 water tank

Gain 0.1 Large bandwidth for Conservation of the signal shape 1.6 Curves rescaled to the input 100 MSPS digitization 1.4 Linear up

Auger fall time bandwidth Auger fall time bandwidth 1.2 to 7 V Saturation level on gain 1 Nyquist for Nyquist for

100MSPS 100MSPS Output amplitude (V) 200 1 40 150 20 0.8

Gain (dB) 100

0 (deg) Phase 200 ns 50 0.6 -20 0 -40 Gain 0.1 -50 Gain 0.1 0.4 -60 Large amplitude (6V input) -100 Gain 1 Gain 1 Large width -80 0.2 Gain 10 -150 Gain 10 2345678 Fast recovery -100 -200 Input amplitude (V) 5 6 7 8 5 6 7 8 10 10 10 10 10 10 10 10 Frequency (Hz) Frequency (Hz) http://beaune.in2p3.fr/beaune05/cdrom/Photos/Exhibitors/hilger.jpg

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http://beaune.in2p3.fr/beaune05/cdrom/Sessions/Photos/bergonzo.jpg (2 sur 2)11/07/2005 13:12:59 Concluding remarks

Fourth International conference on « New Developments in Photodetection » Beaune, France, 19-24 Juin 2005 Beaune 05 year Present 250 208 participants 1996 161 1999 173 200 2002 150 2005 208 150 250

100 200

50 Participants vs Year 150 0 100 1994 1996 1998 2000 2002 2004 2006 50

0 french euro Other Totol Talk-Poster sessions

• 3 tutorials • 6 reviews, overviews

• Among 160 abstracts submitted – 57 presentations – 3 Poster sessions ~ 61 posters Poster sessions

• 3 “best” posters - 3 awards – Congratulations to the 4 winners

K. Hanson & O. Tarasova R. Pani F. Tokanai Thanks to: • Beaune staff – Laure, Patricia – Laurence, Claudine, Monique – Joel, Gildas, Jean-Claude

• Palais des Congrès – Claudine, Virginie – Vincent & technical staff

• Young generation of φ – Kaya Doyeux (CEA) – Marie-Charlotte Ricol (IPNL)

• Young generation of φ – Web site: Martial Chartoire – Affiche: Gérard Dromby – The one I forgot! Thanks to: • Manufacturers – Exhibition – All companies – Wine & Food shops • Tutorial speakers • Overview speakers • Speaker & Poster(wo)men • E. Lorenz for the Round Table • K. Arisaka for his huge work for a Summary • Advisory Committee • All of you

• Sorry for the too HOT exhibition Hall temperature CD-Web-Proceedings • CD-rom: talks+poster+extra – send to you soon in 2-3 weeks, pdf •Web – Pdf next week • Talks & Posters papers : – Publish only « good » papers (techn+scientific) – Size max = 4 pages – Deadlines: • July 14, 2005: first version • September 15: final version • Referees Next edition

• Beaune – NDIP08 • Somewhere in France – Beaune –… – Don’t forget to VOTE – This Conference is yours

– Merci, au revoir et a bientôt… http://beaune.in2p3.fr/beaune05/cdrom/Sessions/Photos/delataille.jpg

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Dominique CHAMBELLAN, Jacques de SANOIT

Presented by Philippe Bergonzo

1 Contents

• Rouffignac region

• Rouffignac cave

• Rouffignac works

• Black pigment drawings

• Portable XRF method

• Choice of drawings for analysis

• XRF data treatment

• Quantitative analysis

• Conclusions

• References The painter

SSTM / Réf présentation : Rouffignac Date 21/06/05 2 Rouffignac region Localisation

SSTM / Réf présentation : Rouffignac Date 21/06/05 3 Rouffignac cave 12°C and 95 % humidity

SSTM / Réf présentation : Rouffignac Date 21/06/05 4 Rouffignac cave Map of the underground

SSTM / Réf présentation : Rouffignac Date 21/06/05 5 Rouffignac cave The railway station

SSTM / Réf présentation : Rouffignac Date 21/06/05 6 Rouffignac cave A family affair

• Charles Plassard : owner (1929) discoverer (1956)

• Louis Plassard : current owner and discoverer (1956)

• Marie Odile and Jean Plassard : S.A.R.L. Grotte de Rouffignac

• Frédéric Plassard : specialist of parietal art

SSTM / Réf présentation : Rouffignac Date 21/06/05 7 The Rouffignac Cave Pehistorians’ affair (1956)

• Louis-René Nougier (discoverer in 1956)

• Romain Robert (discoverer in 1956)

• Abbé Henri Breuil (1877-1961)

• Claude Barrière (inventory of works, 1982)

SSTM / Réf présentation : Rouffignac Date 21/06/05 8 Rouffignac works The discovery

1575 « On voit des paintures en plusieurs endroits, plusieurs sortes de bestes grandes et petites » ("Thou shall see in several places several sorts of small and big animals") (La cosmographie universelle de tout le monde par François de Belle-Forest) in the 1930’s « J’ai vu une tête de cheval diablement bien faite » "I saw an horse head well drawn" (Mrs Jeanne Plassard)

26 June 1956 « Eh ! Toto viens voir »

(Romain Robert, Louis-René Nougier, Charles et Louis Plassard)

SSTM / Réf présentation : Rouffignac Date 21/06/05 9 A picture of 1956 Opinion of the Boss (Abbé Breuil)

L.R Nougier

Abbé Breuil R. Robert

SSTM / Réf présentation : Rouffignac Date 21/06/05 10 Rouffignac works

Engraved work Drawn work

Mammoth «The Patriarch» Woolly rhinoceros N° 183

SSTM / Réf présentation : Rouffignac Date 21/06/05 11 Rouffignac works An impressive inventory (Jean Plassard, 1999)

• Mammoths …………….….158 • Bisons…………………….…28 • Horses…………………….…16 • Ibexes………….……………12 • Rhinoceros …………………11 • Humans…………………....…4 • Snakes……….. …………..…6 • Bear….…………….…………1

SSTM / Réf présentation : Rouffignac Date 21/06/05 12 Rouffignac works Dating

No direct dating was realized

Estimation compared with the other nearby sites presenting resemblances (Les Combarelles, Bernifal, Fond de Gaume)

13000 – 15000 years B.C.

SSTM / Réf présentation : Rouffignac Date 21/06/05 13 A double problem for black drawings

¾ Problem of black pigment composition

The composition of pigments remains unknown. Need for verifying the presence of manganese and to complete the analyses of 1956. (Graziosi, La Nature, 1956)

¾ Problem of direct dating of works

Need for identifying possible charcoal for radiocarbon dating (CEA\LSCE-Gif-sur-Yvette)

SSTM / Réf présentation : Rouffignac Date 21/06/05 14 Choice of the drawings for analysis

• Short period of time 20 paintings (40 measurements)

• Accessibility to drawings Cavity of the wall

• Quantity of pigment Thickness and width of lines

SSTM / Réf présentation : Rouffignac Date 21/06/05 15 XRF method X-Ray Fluorescence

• Non destructive method • Analysis of elements • Use X-ray generator • Use X-ray radioactive sources (109Cd , 55Fe or 241Am) • Analysis of the whole depth of the sample • Very successful method for elements (Z > 15) • Not useful method for light elements (Z < 15)

SSTM / Réf présentation : Rouffignac Date 21/06/05 16 Rouffignac XRF experimental arrangement

SSTM / Réf présentation : Rouffignac Date 21/06/05 17 The portable measurement device Front view

SSTM / Réf présentation : Rouffignac Date 21/06/05 18 The characteristics of the portable XRF system

• X-Ray generator (BulletTM 40 keV, Moxtek)

• SDD Detector (Röntec 1102) with a Peltier effect cryostat

• Analysis area: 4 mm x 6 mm

• Positioning system: projection of a cross of light on the sample.

2 • Analysis depth ~ 10 µm (e1/2= 4 µm or 20 g/m )

• Counting time: 300 s for one spectrum

• Electric consumption: 6.5 A / 2V (80 W).

SSTM / Réf présentation : Rouffignac Date 21/06/05 19 SSTM / Réf présentation : Rouffignac Date 21/06/05 20 Choice of drawings for analysis The three rhinoceros freeze

SSTM / Réf présentation : Rouffignac Date 21/06/05 21 Choice of drawings for analysis The horse over the flint nodule

SSTM / Réf présentation : Rouffignac Date 21/06/05 22 Choice of drawings for analysis The ten mammoths freeze

SSTM / Réf présentation : Rouffignac Date 21/06/05 23 Choice of drawings for analysis Some animals from the “Grand Plafond” (Cl. Barrière, 1982)

SSTM / Réf présentation : Rouffignac Date 21/06/05 24 Underground Laboratory

• No taking samples (non destructive analysis).

• No contact with the drawings (distance 10 mm).

• We can multiply analysis without damaging the artistic patrimony

SSTM / Réf présentation : Rouffignac Date 21/06/05 25 Exemple 1 The horse over the flint stone (Galerie Henri Breuil)

Mn Kβ Fe Kα

5 1,2x10 Cheval 186 paroi dessin + paroi 9,0x104 Mn Kα

6,0x104 tage / 300 s p

Com K Kα 3,0x104 Si Kα Ti Kα Fe Kβ Ar Kα Ca Kα Ti Kβ

0,0 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,5 6,0 6,5 7,0 7,5 Energie (keV)

SSTM / Réf présentation : Rouffignac Date 21/06/05 26 Exemple 2 Bison N° 100 (Grand Plafond)

Ca Kα BISON 100 3,00x105 paroi dessin + paroi Mn Kα

5

s 2,25x10 300

/

5

age 1,50x10 t Ca Kβ Mn Kβ p

m Fe Kα o C 7,50x104

Ti Kα Ti Kβ Fe Kβ 0,00 2,5 3,0 3,5 4,0 4,5 5,0 5,5 6,0 6,5 7,0 7,5 Energie (keV)

SSTM / Réf présentation : Rouffignac Date 21/06/05 27 Exemple 3 Mammoth N° 107 «the Grand Father» (Grand Plafond)

6x105 Ca Kα Mammouth 107

5x105 paroi paroi + dessin

4x105 00 s 3

3x105 ge / ta

p 5

m 2x10 Mn Kα Co Ca Kβ Mn Kβ 5 1x10 Fe Kα

0

2,5 3,0 3,5 4,0 4,5 5,0 5,5 6,0 6,5 7,0 7,5 E (keV)

SSTM / Réf présentation : Rouffignac Date 21/06/05 28 Exemple 4 The horse N°87 «Graziosi’s sample, 1956» (Grand Plafond)

Ca Kα 1,50x105

Cheval 87 5 1,25x10 paroi dessin + paroi 1,00x105 0 s 30 /

7,50x104 ge a t Mn Kα

mp 4 o 5,00x10 C Mn Kβ Ca Kβ Fe Kα 4 2,50x10 Ti Kα Fe Kβ Ti Kβ

0,00 2,53,03,54,04,55,05,56,06,57,07,5 Energie (keV)

SSTM / Réf présentation : Rouffignac Date 21/06/05 29 Quantitative analysis Hypothesis

X-Ray generator (Moxtek)

Cliff : Homogeneous mixture

of CaCO3 , 6 H2O + 7% H O Detector SDD 2 + TiO + MnO + Fe O (Semi-Conductor Drift Detector) 2 2 2 3

Painting = homogeneous mixture of 3 oxides (TiO2 + MnO2 + Fe2O3) + H2O

SSTM / Réf présentation : Rouffignac Date 21/06/05 30 Comparaison Simulation / Experiments Pure elements

SSTM / Réf présentation : Rouffignac Date 21/06/05 31 Compared spectra Simulation / Experience

Taken into account: CaCO3 , H2O, TiO2 , MnO2 et Fe2O3 Negligible elements: Si, Ni et Cu.

SSTM / Réf présentation : Rouffignac Date 21/06/05 32 Quantitative analysis Data treatment

• Data: 3 oxides (TiO2, MnO2 et Fe2O3) for the cliff and for the painting give 6 counting rate.

• Subtraction of the Mn Kβ contribution into Fe Kα for painting and cliff (the two peaks are overlapped on the fluorescence spectrum).

• Subtraction of the contribution of the cliff spectrum into the painting spectrum.

• Calculation of mass thickness using standardization curves obtained at the laboratory

SSTM / Réf présentation : Rouffignac Date 21/06/05 33 Sensitivity of the measurements

Cliff

- Detection limit : 0.007 % (for 300 s counting time)

- Typical values : TiO2 0.05 % MnO2 0.1 % Fe2O3 1 %

Paintings

- Detection limit: 0.005 g/m2 (for 300 s counting time) - Observed range: 0.06 à 12.8 g/m2 (0.01 à 2 µm) - Mean value: 3.6 g/m2

- Typical composition 5% de TiO2 75% de MnO2 20% de Fe2O3

SSTM / Réf présentation : Rouffignac Date 21/06/05 34 Uncertainties of measurements

• Statistical uncertainties on counting rates give a maximum value of σ = 1 %.

• Reproducibility with repositioning on a flat and homogeneous rock give σ = 1.6 %.

• Deconvolution of small intensity fluorescence peaks give a maximum value of σ = 10 %.

• The lack of the rock flatness can induce an uncertainty of σ = 10 %.

• No direct access to the measurement of the cliff just under the painting. The lack of homogeneity of the chemical composition of the cliff can induce a σ = 10 %.

Don’t forget ! Unfortunatly, ARCHAEOLOGY is not METROLOGY !!!

SSTM / Réf présentation : Rouffignac Date 21/06/05 35 Summary of the results

100%

90%

80%

70%

60% % Fe2O3 50% % % MnO2 % TiO2 40%

30%

20%

10%

0% BISON100 RH185 MAM107 BOUQ102 MAM121 CHEV186 MAM199 CHEV87 RH183 MAM194

12

10

8 Mass thickness 6 (g/m2) 4

2

0 B IS O N1 0 0 RH1 8 5 M A M 1 0 7 B O UQ 1 0 2 M A M 1 2 1 CHE V 1 8 6 M A M 1 9 9 CHE V 8 7 RH1 8 3 M A M 1 9 4

SSTM / Réf présentation : Rouffignac Date 21/06/05 36 Conclusions

• Systematic presence of manganese in the pigments of the black drawings

• Confirmation of the 1956 destructive analysis (Graziosi)

• A Monte-Carlo simulation allowed a quantitative approach

• The manganese ore does not result from a single source

• No drawing was made exclusively with black charcoal

• Need for other techniques to identify organic carbon possibly associated with mineral pigments (Raman spectroscopy)

SSTM / Réf présentation : Rouffignac Date 21/06/05 37 References….

• Paolo Graziosi. Analyses chimiques des peintures de la grotte de Rouffignac. revue « La nature », 1956.

• Claude Barrière. L’art pariétal de Rouffignac, Ed. Picard, 1982.

• Marie Odile et Jean Plassard. Visiter la grotte de Rouffignac. Ed. Sud Ouest, 1995.

• Jean Plassard. Rouffignac, le sanctuaire des mammouths. Ed. Seuil, 1999.

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