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Advances in the TGEM: A Thick GEM-like gaseous multiplier C. Shalem, R. Chechik, N. Advances in the TGEM: A Thick GEM-like gaseous multiplier C. Shalem, R. Chechik, N. Ben-Haim, K. Michaeli & A. Breskin The Weizmann Institute of Science, Rehovot, Israel A robust, high-gain gaseous electron multiplier 30 years of “Hole-multiplication” history: Breskin & Charpak NIM 108(1973)427 (discharge in glass capillaries); Lum et al. IEEE NS 27(1980)157, Del Guerra et al. NIMA 257(1987)609 (Avalanches in holes); Bartol, Lemonnier et al. J. Phys. III France 6(1996)337 (CAT); Sakurai et al. NIMA 374(1996)341, Peskov et al. NIMA 433(1999)492 (Glass Capillary Plates); Sauli NIM A 386(1997)531 (GEM); Ostling, Peskov et al, IEEE NS 50(2003)809 (G-10 “Capillary plates”). 1 1 C. Shalem et al, IEEE 2004, Rome

Expanding the standard GEM… Standard GEM TGEM* 1 mm n n n 2 Microlithography Expanding the standard GEM… Standard GEM TGEM* 1 mm n n n 2 Microlithography + etching High Spatial resolution (tens of microns); VGEM~400 V >103 gain in single GEM 106 gain in cascaded GEMs Fast (ns) Low pressure – gain~30 1 mm n n n n PCB tech - etching + drilling Simple and robust VTGEM~2 KV (at atmospheric pressure) 105 gain in single- & 107 double-TGEM Sub-mm to mm special resolution Fast (ns) Low pressure (<1 Torr) gain 104 *Similar approach to Peskov’s “optimized GEM” C. Shalem et al, IEEE 2004, Rome, October 18 2

Thick GEM-like multipliers Manufactured by standard PCB techniques of precise drilling in G-10 (and Thick GEM-like multipliers Manufactured by standard PCB techniques of precise drilling in G-10 (and other materials) and Cu etching. Atmospheric pressure geometry Hole diameter d=0. 3 mm Distance between holes a=0. 7 mm Thickness t=0. 4 mm 0. 1 mm Low pressure geometry Hole diameter d=1 mm Distance 3 cm between holes a=1. 5 mm Thickness t=1. 6 mm Cu G-10 0. 1 mm rim to prevent discharges Important for high gains! 3 C. Shalem et al, IEEE 2004, Rome, October 18 3

TGEM: principle of operation Multiplication of electrons induced by radiation in gas or from TGEM: principle of operation Multiplication of electrons induced by radiation in gas or from solid converters (e. g. A photocathode) Edrift ETGEM Etrans Garfield simulation of electrons multiplication in Ar/CO 2 (70: 30) Multiplication inside holes reduces secondary effects, Each hole acts as individual multiplier 4 C. Shalem et al, IEEE 2004, Rome, October 18 4

Electric fields Maxwell & Garfield software E~4 (KV/cm) E~25 (KV/cm) multiplication Hole length TGEM: Electric fields Maxwell & Garfield software E~4 (KV/cm) E~25 (KV/cm) multiplication Hole length TGEM: VTGEM~2 KV ( for comparison, in GEM: VGEM~400 V) 5 C. Shalem et al, IEEE 2004, Rome, October 18 5

TGEM - Photon detector A reflective photocathode on top of the TGEM’s surface Surface TGEM - Photon detector A reflective photocathode on top of the TGEM’s surface Surface field > 5 k. V/cm • Full photoelectron extraction • High effective QE 6 Slightly reversed E • good photoelectron collection! • Low sensitivity to MIPS C. Shalem et al, IEEE 2004, Rome, October 18 6

Single-TGEM: Gain example: TGEM with reflective Cs. I photocathode n n n 7 Single-photon Single-TGEM: Gain example: TGEM with reflective Cs. I photocathode n n n 7 Single-photon detection no photon feedback Rise time < 10 ns C. Shalem et al, IEEE 2004, Rome, October 18 7

Double-TGEM: Gain Important: high Etrans Large transfer gap 5 mm n n 8 Higher Double-TGEM: Gain Important: high Etrans Large transfer gap 5 mm n n 8 Higher gain at lower VTGEM Higher stability C. Shalem et al, IEEE 2004, Rome, October 18 8

Electron Transfer efficiency e Transfer efficiency the ability to focus electrons into the TGEM Electron Transfer efficiency e Transfer efficiency the ability to focus electrons into the TGEM holes Important! e affects energy resolution, detection efficiency, effective QE F f 9 Method: Pulse-counting of the fraction of single-eevents reaching the TGEM bottom, Compared to GEM, very high fields are reached at the TGEM surface already at low VTGEM good e- extraction in all gases. C. Shalem et al, IEEE 2004, Rome, October 18 9

Counting rate § Reflective Cs. I photocathode § UV photons (185 nm) § Total Counting rate § Reflective Cs. I photocathode § UV photons (185 nm) § Total current limit 4*10 -7[Amp/mm 2] 10 C. Shalem et al, IEEE 2004, Rome, October 18 10

TGEM: Low pressure operation § low pressure isobutane § semi-transparent Cs. I photocathode Single TGEM: Low pressure operation § low pressure isobutane § semi-transparent Cs. I photocathode Single TGEM 10 Torr Isobutane Gain~105; Rise time~5 ns 11 C. Shalem et al, IEEE 2004, Rome, October 18 11

TGEM: Low pressure operation § low pressure isobutane § semi-transparent Cs. I photocathode 12 TGEM: Low pressure operation § low pressure isobutane § semi-transparent Cs. I photocathode 12 C. Shalem et al, IEEE 2004, Rome, October 18 12

Applications atmospheric pressure A robust, simple multiplier, fast , sub-mm localization Many possible applications Applications atmospheric pressure A robust, simple multiplier, fast , sub-mm localization Many possible applications with moderate localization accuracy : 1. 2. 3. 4. 5. 13 Simple UV detectors for RICH Neutron detectors X-ray imaging Simple particle tracking over large area TPC readout C. Shalem et al, IEEE 2004, Rome, October 18 13

Applications: low-pressures Unique: high gain, fast multipliers at sub-Torr pressures ! - Nuclear Physics: Applications: low-pressures Unique: high gain, fast multipliers at sub-Torr pressures ! - Nuclear Physics: localization and timing of heavy ions - Novel detectors of low-energy ions ion avalanche Readout strips Dielectric Secondary electrons Secondary electron emitter readout strips/pads TGEM: INTENSIVE R&D IN PROGRESS ! 14 C. Shalem et al, IEEE 2004, Rome, October 18 14

The end C. Shalem et al, IEEE 2004, Rome, October 18 15 The end C. Shalem et al, IEEE 2004, Rome, October 18 15

TGEM conduction area 15 C. Shalem et al, IEEE 2004, Rome, October 18 16 TGEM conduction area 15 C. Shalem et al, IEEE 2004, Rome, October 18 16

Transfer efficiency the ability to collect a photoelectron and transfer it through the TGEM Transfer efficiency the ability to collect a photoelectron and transfer it through the TGEM Counting mode measurement 16 C. Shalem et al, IEEE 2004, Rome, October 18 17

reflective photocathode n n 17 Current mode measurement TGEM Coated with reflective photocathode - reflective photocathode n n 17 Current mode measurement TGEM Coated with reflective photocathode - 3000 A Cs. I Electrons are extracting from surface into the holes Edrift = 0 Close to 100% PC area at cross mode ETGEM = multiplication C. Shalem et al, IEEE 2004, Rome, October 18 18

Modes of operation S. T. PC 18 Reflective PC C. Shalem et al, IEEE Modes of operation S. T. PC 18 Reflective PC C. Shalem et al, IEEE 2004, Rome, October 18 19

Transfer efficiency semi-transparent photocathode n n 19 Double coated semi-transparent PC Factor 4 between Transfer efficiency semi-transparent photocathode n n 19 Double coated semi-transparent PC Factor 4 between electrons current in both sides C. Shalem et al, IEEE 2004, Rome, October 18 20

Modes of operation (S. T PC) field map – transfer mode E=0. 3 kv/cm Modes of operation (S. T PC) field map – transfer mode E=0. 3 kv/cm 20 (reflective PC) PC field map – reflective mode E=1 kv/cm C. Shalem et al, IEEE 2004, Rome, October 18 21

n n n 21 S. T. photocathode Semi-transparent photocathode (300 A Cs. I coated n n n 21 S. T. photocathode Semi-transparent photocathode (300 A Cs. I coated quartz crystal) Lower QE Edrift ~ 0. 4 kv/cm C. Shalem et al, IEEE 2004, Rome, October 18 22

reflective Cs. I PC 22 C. Shalem et al, IEEE 2004, Rome, October 18 reflective Cs. I PC 22 C. Shalem et al, IEEE 2004, Rome, October 18 23