TITLE F Sauli-Short Courses-IEEE-NSS 2002 -PART 2 LARGE

TITLE F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 LARGE AREA DEVICES: SPARK COUNTERS PARALLEL PLATE COUNTERS RESISTIVE PLATE CHAMBERS HIGH ACCURACY TRACKERS: GAS MICROSTRIP CHAMBERS MICROPATTERN DETECTORS GAS ELECTRON MULTIPLIER 1

PESTOV COUNTERS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 SPARK (PESTOV) COUNTERS GOOD TIME RESOLUTION ---> THN GAP GOOD EFFICIENCY---> THICK GAS LAYER THIN GAP (100 µm) AND HIGH PRESSURES (~10 bar) HIGH RESISTIVITY ELECTRODE (PESTOV GLASS, 109 Ω cm DESIGNER’S GAS MIXTURE FOR WIDE SPECTRUM PHOTON ABSORPTION: Yu. Pestov Nucl. Instr. and Meth. 196(1982)45 HIGH-PRESSURE GAS VESSEL METAL CATHODE C 3 H 6 SEMI-CONDUCTING GLASS ANODE SIGNAL PICK-UP STRIPS Yu. Pestov et al, Nucl. Instr. and Meth. A 456(2000)11 H. R. Schmidt, Nucl. Phys. B (Proc. Suppl. ) 78 (1999) 372 2

PESTOV COUNTERS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 SPARK COUNTER PERFORMANCES 100 µm GAP 12 BAR PRESSURE EFFICIENCY TIME RESOLUTION HV (k. V) E. Badura et al, Nucl. Instr. and Meth. A 379(1996)468 PHYSICAL ORIGIN OF TAILS IN THE TIME RESPONSE OF SPARK COUNTERS: A. Mangiarotti and A. Gobbi, Nucl. Instr. and Meth. A 482(2002)192 3

PESTOV COUNTERS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 ALICE TIME-OF-FLIGHT PROTOTYPE SINGLE LONG COUNTER IN CYLINDRICAL VESSEL 4

PESTOV COUNTERS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 PHOTON-MEDIATED AVALANCHE SPREAD (DE-LOCALIZATION) CHARGE SPECTRA BEFORE AND AFTER IRRADIATION: COUNTER FORMATION: LONG-TERM EXPOSURE TO STRONG RADIATION POLYMER COATING ON ELECTRODES INCREASES THE WORK FUNCTION CHARGE CAN THIS BE UNDERSTOOD AND EXPLOITED FOR OTHER DETECTORS? 5

RESISTIVE PLATE CHAMBERS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 RESISTIVE PLATE COUNTERS (RPC) R. Santonico and R. Cardarelli, Nucl. Instr. and Meth. 187(1981)377 R. Santonico and R. Cardarelli, Nucl. Instr. and Meth. A 263(1988)20 READOUT STRIPS X HV INSULATOR GRAPHITE COATING HIGH RESISTIVITY ELECTRODE (BAKELITE) GAS GAP GND READOUT STRIPS Y Initial condition after applying high voltage Surface charging of electrodes by current flow through resistive plates After a discharge elctrons are deposited on anode and positive ions on cathode I. Crotty et al, Nucl. Instr. and Meth. A 337(1994)370 6

RESISTIVE PLATE CHAMBERS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 RESISTIVE PLATE CHAMBERS SYSTEMS BABAR IFR (SLAC) C. Lu, RPC Workshop, Coimbra 2001 7

RESISTIVE PLATE CHAMBERS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 RPC MUON DETECTOR FOR CMS (CERN LHC): R (cm) 700 600 BARREL RPCs ~ 400 m 2 500 400 300 200 100 200 400 600 800 1000 1200 Z (cm) FORWARD RPCs 8

RESISTIVE PLATE CHAMBERS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 TRANSITION AVALANCHE TO STREAMER NORMAL AVALANCHE PHOTON MEDIATED BACKWARD PROPAGATION: STREAMER 10 m. V 80 m. V 200 m. V R. Cardarelli, V. Makeev, R. Santonico, Nucl. Instr. and Meth. A 382(1996)470 9

RESISTIVE PLATE CHAMBERS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 RPC RATE CAPABILITY: AVALANCHE VS STREAMER OPERATION STREAMER MODE: AVALANCHE MODE: 3. 5 109 Ω cm r = 3 1011 Ω cm R. Arnaldi et al, Nucl. Physics B (Suppl) 78 (1999) 84 10

RESISTIVE PLATE CHAMBERS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 RPC RATE CAPABILITY: DEPENDS ON GAIN AND ELECTRODES RESISTIVITY MATERIAL VOLUME RESISTIVITY (Ω. cm) Pestov glass 109 -1010 Phenolic (Bakelite) 1010 -1011 Cellulose 5. 10 12 Borosilicate glass 10 13 Melamine 2. 10 13 PROPORTIONAL (AVALANCHE) OPERATION: P. Fonte, Scientifica Acta XIII N 2(1997)11 11

RESISTIVE PLATE CHAMBERS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 GAP DEPENDENCE THE SEPARATION AVALANCHE-STREAMER DEPENDS ON THE GAP: 3 mm SMALL ADDITIONS OF ELECTRO-NEGATIVE GASES EXTEND THE SEPARATION: 2 mm R. Santonico, Scient. Acta XII N 2(1997)1 P. Camarri et al, Nucl. Instr. and Meth. A 414(1998)317 12

RESISTIVE PLATE CHAMBERS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 RPC: INDUCED CHARGE DISTRIBUTION 2 mm gap STREAMER MODE V. Barret (ALICE di-muon trigger RPC) RPC Workshop, Coimbra 2001 13

RESISTIVE PLATE CHAMBERS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 RPC: INDUCED SIGNAL CLUSTER SIZE EFFECT OF ELECTRODE SURFACE RESISTIVITY Y. Hoshi et al, RPC Workshop, Coimbra 2001 SIGNAL PROPAGATION IN RESISTIVE PLATE CHAMBERS: W. Riegler and D. Burgarth, Nucl. Instr. and Meth. A 481(2002)130 14

RESISTIVE PLATE CHAMBERS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 IMPROVING THE ELECTRODE SURFACE: LINSEED OIL TREAT THREAT COATING THE BAKELITE PLATES WITH A THIN LAYER OF LINSEED OILCONSIDERABLY IMPROVES PERFORMANCES (SMOOTHING OF LOCAL DEFECTS? ) R. Santonico and R. Cardarelli, Nucl. Instr. and Meth. 187(1981)377 SINGLE RATES vs HV: AVERAGE CURRENT vs HV: NON-OILED AFTER OIL TREATMENT M. Abbrescia et al, Nucl. Instr. and Meth. A 394(1997)13 15

RESISTIVE PLATE CHAMBERS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 BABAR RPCS: FAST EFFICIENCY DROP PROBLEM OF QUALITY CONTRON IN LINSEED OIL COATING AND POLYMERIZATION DROPLETS, STALAGMITES, PILLARS, FRAMES C. Lu, RPC Workshop, Coimbra 2001 16

RESISTIVE PLATE CHAMBERS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 OPTIMIZATION OF RPC PARAMETERS INCREASING THE GAP PROVIDES BETTER EFFICIENCY PLATEAUX (BUT WORSE TIME RESOLUTION) RPC SIMULATION STUDIES: M. Abbrescia et al, Nucl. Instr. and Meth. A 409(1998)1 17

RESISTIVE PLATE CHAMBERS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 MULTIPLE GAP RPC: BETTER EFFICIENCY AND TIME RESOLUTION HV GND DOUBLE GAP FWHM=1. 7 ns SINGLE GAP FWHM 2. 3 ns M. Abbrescia et al, Nucl. Instr. and Meth. A 431(1999)413 18

IONIZATION RESISTIVE PLATE CHAMBERS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 MULTI-GAP RESISTIVE PLATE CHAMBERS WIRED “OR” BETWEEN SEVERAL GAPS s ~ 68 ps P. Fonte et al, Nucl. Instr. and Meth. A 449 (2000) 295 19

RESISTIVE PLATE CHAMBERS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 MULTIGAP RPC SEVERAL RESISTIVE ELECTRODE PLATES WITH NARROW GAPS ALL INTERNAL PLATES ARE FLOATING (SET AT PROPER VOLTAGE BY ELECTROSTATICS) E. Cerron Zeballos et al, Nucl. Instr. and Meth. A 374(1996)132 HV FLOATING GND A. Akindinov et al, Nucl. Instr. and Meth. A 456(2000)16 20

RESISTIVE PLATE CHAMBERS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 RPCs: OPEN PROBLEMS QUALITY CONTROL (LINSEED COATING) CHANGE OF RESISTIVITY WITH TIME (WATER DRYING? ) TEMPERATURE DEPENDENCE OF RESISTIVITY RADIATION DAMAGE OF BAKELITE RADIATION-INDUCED GAS POLYMERIZATION GENERAL QUESTION: HOW TO MONITOR RESISTIVITY AND PERFORMANCE CHANGES? 21

MSGC F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 MICRO-STRIP GAS CHAMBER (MSGC) Drift electrode THIN ANODE AND CATHODE STRIPS ON AN INSULATING SUPPORT Anode strip 200 µm Glass support Back plane Cathode strips A. Oed Nucl. Instr. and Meth. A 263 (1988) 351. 22

MSGC F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 MSGC: SIGNAL FORMATION 3 -D READOUT (ANODE 3, CATHODES, BACKPLANE) LIGHT CONSTRUCTION: 23

MSGC F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 MSGC PERFORMANCES EXCELLENT RATE CAPABILITY AND MULTI-TRACK RESOLUTION RATE CAPABILITY > 106/mm 2 s SPACE ACCURACY ~ 40 µm rms 2 -TRACK RESOLUTION ~ 400 µm 24

MSGC SYSTEMS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 MSGC SYSTEMS: NEUTRON SPECTROMETER AT ILL-GRENOBLE Ring of 50 MSGCs operated in 3 He-CF 4 (3. 1 bar-0. 8 bar) 25

MSGC SYSTEMS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 CMS MSGC TRACKER (CERN LHC) BARREL ~5500 modules FORWARD ~ 5000 modules CANCELLED (IN FAVOUR OF SILICON) 26

MSGC DISCHARGES F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 MSGC: DISCHARGE PROBLEMS For detection of minimum ionizing tracks a gain ~ 3000 is needed In presence of heavily ionizing particles background, the discharge probability is large ON EXPOSURE TO a PARTICLES 27

MSGC DISCHARGES F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 MSGC DISCHARGE PROBLEMS: FULL BREAKDOWN MICRODISCHARGES 28

MSGC DISCHARGES F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 MSGC: DISCHARGE MECHANISMS FIELD EMISSION FROM CATHODE EDGE VERY HIGH IONIZATION RELEASE: AVALANCHE SIZE EXCEEDS RAETHER’S LIMIT Q ~ 107 CHARGE PRE-AMPLIFICATION FOR IONIZATION RELEASED IN HIGH FIELD CLOSE TO CATHODE 29

NEW MICROPATTERN F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 NEW MICRO-PATTERN DETECTORS MICRO-GAP CHAMBER MICRO-GROOVE CHAMBER R. Bellazzini et al Nucl. Instr. and Meth. A 335(1993)69 R. Bellazzini et al Nucl. Instr. and Meth. A 424(1999)444 30

NEW MICROPATTERN F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 NEW MICRO-PATTERN DETECTORS MICROMEGAS: COMPTEUR A TROUS (CAT) Thin-gap parallel plate chamber Y. Giomataris et al Nucl. Instr. and Meth. A 376(1996)29 Single hole proportional counter F. Bartol et al, J. Phys. III France 6 (1996)337 31

NEW MICROPATTERN F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 MICRO-PATTERN PIXEL DETECTORS MICRODOT: MICRO-PIN ARRAY (MIPA): Metal electrodes on silicon S. Biagi et al Nucl. Instr. and Meth. A 361(1995)72 REVIEW: Matrix of individual needle proportional counters P. Rehak et al, IEEE Trans. Nucl. Sci. NS-47(2000)1426 F. Sauli and A. Sharma: Micropattern Gaseous Detectors, Ann. Rev. Nucl. Part. Sci. 49(1999)341 32

NEW MICROPATTERN F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 DISCHARGE POINT IN MICROPATTERN DETECTORS ALMOST THE SAME IN ALL TESTED DEVICES: LAW OF NATURE! A. Bressan et al Nucl. Instr. and Meth. A 424(1999)321 33

GEM F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 GAS ELECTRON MULTIPLIER (GEM) Thin, metal-coated polymer foil with high density of holes: 100÷ 200 µm Typical geometry: 5 µm Cu on 50 µm Kapton 70 µm holes at 140 mm pitch F. Sauli, Nucl. Instrum. Methods A 386(1997)531 34

GEM F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 GEM DETECTOR: - multiplication and readout on separate electrodes - electron charge collected on strips or pads: 2 -D readout - fast signal (no ion tail) - global signal detected on the lower GEM electrode (trigger) Cartesian Small angle Pads A. Bressan et al, Nucl. Instr. and Meth. A 425(1999)254 35

GEM F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 MULTIPLE GEM STRUCTURES Cascaded GEMs permit to attain much larger gains before discharge Double GEM Triple GEM C. Buttner et al, Nucl. Instr. and Meth. A 409(1998)79 S. Bachmann et al, Nucl. Instr. and Meth. A 443(1999)464 36

GEM F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 SINGLE-DOUBLE-TRIPLE GEM GAIN Multiple structures provide equal gain at lower voltage The discharge probability on exposure to a particles is strongly reduced DISCHARGE PROBABILITY WITH a : For a gain of 8000 (required for full efficiency on minimum ionizing tracks) in the TGEM the discharge probability is not measurable. S. Bachmann et al, Nucl. Instr. and Meth. A 479 (2002) 294 37

GEM F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 FAST ELECTRON SIGNAL (NO ION TAIL) The total length of the detected signal corresponds to the electron drift time in the induction gap: Full Width 20 ns (for 2 mm gap) Induced charge profile on strips FWHM 600 µm Good multi-track resolution 38

GEM F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 COMPASS TRIPLE GEM CHAMBERS • Active Area 30. 7 x 30. 7 cm 2 • 2 -Dimensional Read-out with 2 x 768 Strips @ 400 µm pitch • 12+1 sectors GEM foils (to reduce discharge energy) • Central Beam Killer 5 cm Ø (remotely controlled) • Total Thickness: 15 mm • Low mass honeycomb support plates B. Ketzer et al, IEEE Trans. Nucl. Sci. NS-48(2001)1065 C. Altumbas et al, Nucl. Instrum. Methods A 490(2002)177 39

GEM F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 2 -DIMENSIONAL READOUT STRIPS Two orthogonal sets of parallel strips at 400 µm pitch engraved on 50 µm Kapton 80 µm wide on upper side, 350 µm wide on lower side (for equal charge sharing) 400 µm 80 µm 350 µm 40

GEM F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 20 TRIPLE GEM DETECTORS BUILT FOR COMPASS AT CERN (2001 -2002) BEAM: 107 Particles/second ~ 10 Tracks/event 50 µm accuracy 10 ns Time resolution 41

GEM F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 DETECTED CHARGE FOR MINIMUM IONIZING TRACKS Gain ~ 8000 Y-coordinate X-coordinate 42

GEM F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 CLUSTER CHARGE CORRELATION Very good correlation, used for multi-track ambiguity resolution s ~ 10% X-Y Cluster charge correlation: 43

GEM F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 SPACE AND TIME RESOLUTION Time resolution: Space resolution: s = 12. 4 ns s = 57 µm Time resolution: computed from charge signals in three consecutive samples (at 25 ns intervals) s = 12. 4 ns Traks fit with two TGEM and one silicon micro-strip After deconvolution s = 46± 3 µm 44

GEM F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 GEM TIME RESOLUTION Triple GEM with pad readout for LHCb muon detector G. Bencivenni et al, Nucl. Instr. and Meth. A 478(2002)245 45

GEM APPLICATIONS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 GEM APPLICATIONS FAST X-RAY IMAGING Using the lower GEM signal, the readout can be self-triggered with energy discrimination: A. Bressan et al, Nucl. Instr. and Meth. A 425(1999)254 F. Sauli, Nucl. Instr. and Meth. A 461(2001)47 9 ke. V absorption radiography of a small mammal (image size ~ 60 x 30 mm 2) 46

GEM APPLICATIONS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 GEM: HIGH PRESSURE OPERATION Neutron detection in He 3? A. Bondar, A. Buzulutskov, L. Shekhtman, V. Snopkov and A. Vasiljev, Subm. Nucl. Instr. and Meth. (2002) 47

GEM APPLICATIONS X-RAY POLARIMETER Charge asymmetry: F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 GEM chamber with pad readout to detect the direction of the photoelectron produced by X-rays 5. 9 Ke. V unpolarized source 5. 4 Ke. V polarized source E. Costa et al, Nature 411(2001)662 R. Bellazzini et al Nucl. Instr. and Meth. A 478(2002)13 48

GEM APPLICATIONS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 PHOTON DETECTION WITH MULTI-GEM Multiple GEM detectors permit to achieve very large gains (106) in photocathode-friendly pure noble gases or poorly quenched mixtures. Reduced transparency strongly suppresses photon and ion feedback A. Buzulutskov et al, Nucl. Instrum. Methods A 443(2000)164 Large area position-sensitive photomultipliers R. Chechik et al, Nucl. Instr. and Meth. A 419(1998)423 49

GEM APPLICATIONS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 GEM OPERATION IN CF 4 Photoelectron extraction from Cs. I: A. Breskin, A. Buzulutskov, R. Chechik Nucl. Instr. and Meth. A 483(2002)658 50

GEM APPLICATIONS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 SEALED GEM PHOTOMULTIPLIER Semi-transparent Cs. I photocathode Single photo-electron signals: A. Breskin et al, Nucl. Instr. and Meth. A 478(2002)225 51

GEM APPLICATIONS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 GEM OPTICAL IMAGER Scintillation light in a multiple GEM detector recorded by a CCD camera - particle tracks Proton and Triton tracks by neutrons in 3 He F. A. F. Fraga et al, Nucl. Instr. and Meth. A 478 (2002) 357 52

GEM APPLICATIONS F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 TIME-RESOLVED PLASMA DIAGNOSTIC PINHOLE GEM CAMERA WITH PIXEL READOUT: Plasma emission (~ 1. 5 ke. V) sampled at 10 k. Hz FIRST OBSERVATION OF PLASMA ROTATION BEFORE DUMP! Courtesy D. Pacella, Princeton Plasma Physics Laboratory D. Pacella et al, Rev. Scient. Instrum. 72 (2001) 1372 R. Bellazzini et al, Nucl. Instr. and Meth. A 478(2002)13 53

BIBLIOGRAPHY F. Sauli-Short Courses-IEEE-NSS 2002 -PART 2 BASIC BIBLIOGRAPHY IONIZATION CHAMBERS AND COUNTERS, D. H. Wilkinson (Cambridge Univ, Press, 1950) ELECTRON AND NUCLEAR COUNTERS, S. A. Korff (Van Nostrand, New York 1955) BASIC DATA ON PLASMA PHYSICS, S. C. Brown (Wiley, New York 1959) ELECTRON AVALANCHES AND BREAKDOWN IN GASES, H. Raether (Butterworth, London 1964) COLLISION PHENOMENA IN IONIZED GASES, E. W. Mc. Daniel (Wiley, New York 1964) ATOMIC AND MOLECULAR RADIATION PHYSICS, L. G. Christophorou (Wiley, New York 1971) SPARK, STREAMER, PROPORTIONAL AND DRIFT CHAMBERS, P. Rice-Evans (Richelieu, London 1974) PRINCIPLES OF OPERATION OF MULTIWIRE PROPORTIONAL AND DRIFT CHAMBERS, F. Sauli (CERN 77 -09, 1977) TECHNIQUES AND CONCEPTS OF HIGH-ENERGY PHYSICS, ed. by Th. Ferbel (Plenum, New York 1983) TECHNIQUES FOR NUCLEAR AND PARTICLE PHYSICS EXPERIMENTS, W. R. Leo (Springer-Verlag, Berlin 1987) RADIATION DETECTION AND MEASUREMENTS, G. F. Knoll (Wiley, New York 1999) RADIATION DETECTORS, C. F. G. Delaney and E. C. Finch (Clarendon Press, Oxford 1992) SINGLE PARTICLE DETECTION AND MEASUREMENT, R. Gilmore (Taylor and Francis, London 1992) INSTRUMENTATION IN HIGH ENERGY PHYSICS, ed. by F. Sauli (World Scientific, Singapore 1992) PARTICLE DETECTION WITH DRIFT CHAMBERS, W. Blum and l. Rolandi (Springer-Verlag, Berlin 1993) PARTICLE DETECTORS, K. Grupen (Cambridge Monographs on Part. Phys. 1996) REVIEW ARTICLES G. Charpak and F. Sauli: High-resolution electronic particle detectors, Ann. Rev. Nucl. Part. Sci. 34(1984)28 J. Va’vra: Wire chambers aging, Nucl. Instr. and Meth. A 323(1992)34 F. Sauli and A. Sharma: Micropattern Gaseous Detectors, Ann. Rev. Nucl. Part. Sci. 49(1999)341 GAS DETECTORS DEVELOPMENT WEB PAGES: http: //www. cern. ch/GDD MSGC, GEM Bibliography Papers 54