A gaseous imaging detector based on thick GEMlike

A gaseous imaging detector based on thick GEM*-like (THGEM) multipliers R. Chechik, A. Breskin, C. Shalem, G. Guedes & M. Cortesi Weizmann institute of science, Rehovot, Israel V. Dangendorf Physikalisch Technische Bundesanstalt, Braunschweig, Germany D. Vartsky & D. Bar SOREQ NRC, Yavne, Israel MOTIVATION: Robust, economic, large-area radiation imaging detectors FAST, HIGH-RATE, MODERATE LOCALIZATION RESOLUTION ----------- *GEM: Gas Electron Multiplier PSD 7 Liverpool 2005 A. Breskin

Thick GEM-like multipliers: THGEM R. Chechik et al. NIM A 535 (2004) 303 -308 & R. Chechik et al. Physics / 0502131(NIM A, in press) Manufactured by standard PCB techniques of precise drilling in G-10 (+ other materials) and Cu etching. ECONOMIC & ROBUST! Hole diameter d=0. 3 - 1 mm Distance between holes a=0. 7 - 7 mm Plate thickness t=0. 4 - 3 mm Standard GEM THGEM 103 gain in single GEM 0. 1 mm F. Sauli 105 gain in single-TGEM 1 mm Cu G-10 0. 1 mm rim: prevents discharges high gains! PSD 7 Liverpool 2005 (An improved “optimized GEM” of Peskov & Periale) A. Breskin

The THGEMs : A small THGEM costs ~3$ /unit. With minimum order of 400$ ~120 THGEMs. ~10 times cheaper than standard GEM. PSD 7 Liverpool 2005 A. Breskin

HOLE-MULTIPLICATION Multiplication within HOLES: • Avalanche confined within a small volume • Secondary effects confined/reduced high gains • True pixilated structures • Possibility to CASCADE multipliers high gains GAS 1 e- in “hole multipliers”: n. Breskin, >104 e-s out Charpak NIM 108(1973)427 discharge in glass capillaries n. Lum et al. IEEE NS 27(1980)157, & Del Guerra et al. NIMA 257(1987)609 Avalanches in holes n. Sakurai et al. NIMA 374(1996)341, & Peskov et al. NIMA 433(1999)492 Glass Capillary Plates n. Sauli NIMA 386(1997)531 GEM n. Ostling, Peskov et al, IEEE NS 50(2003)809 G-10 “Capillary plates” n. Chechik et al. NIM A 535(2004)303 & Physics/0502131 Thick GEM-like (THGEM) Electric field in the holes >20 k. V/cm PSD 7 Liverpool 2005 A. Breskin

THGEM detector configuration Can operate in single-multiplier and in cascaded-multiplier modes Resistive layer (optional) Radiation gas conversion e- . ereadout THGEM PSD 7 Liverpool 2005 Radiation surface conversion Converter e. g. photocathode A. Breskin

Single-THGEM multiplier: gain Example: THGEM photon detector with reflective Cs. I photocathode • • Gain 104 -105 Single-photon detection no photon feedback Rise time < 10 ns Good electron collection eff. Low sensitivity to charged particles (like with REF-GEM) Rate capability: 10 MHz/mm 2 sub-mm localization resolution pc 105 R. Chechik et al. Physics / 0502131(NIM A) PSD 7 Liverpool 2005 A. Breskin

THGEM: CASCADED OPERATION C. Shalem et al. in preparation An efficient electron focusing into the hole and its transfer into a successive element Already @ “low” THGEM voltages/gains Edrift =0 PSD 7 Liverpool 2005 A. Breskin

Double-THGEM multiplier: Gain R. Chechik et al. Physics / 0502131(NIM A) 107 Single photoelectrons 10 ns Fast signals in atm. pressure Ar/30%CO 2 Double TGEM ( t=1. 6 mm d=1 mm, a=1. 5 mm) Total gain=~ 106 • Higher total gain (106 -107) • >103 higher gain at same VTGEM • Better stability PSD 7 Liverpool 2005 EXOTIC: gains > 104 @ sub-Torr pressures! A. Breskin

THGEM: energy resolution C. Shalem et al. in preparation E resolution similar to standard GEM PSD 7 Liverpool 2005 A. Breskin

A VERY FLAT IMAGING DETECTOR ~10 mm radiation readout converter THGEM Resistive layer PSD 7 Liverpool 2005 100 x 100 mm 2 THGEM With 2 D delay-line readout f 0. 3 mm holes A. Breskin

THGEM: RESISTIVE ANODE READOUT • In some applications simple & economic readout is OK (e. g. delay-line, resistive etc) • The induced signal should match the readout-pixel size • Signal broadening: induction gap length & resistive anode • Resistive anode: charge spread & electrical decoupling & spark protection THGEM charge cloud in induction gap resistive anode Q 0 Resistive anode charge transmission: QRO / Q 0 depends on surface resistivity For 3 M /square ~70% (e. g. sprayed C-paint) For 30 M /square ~95% (e. g. evaporated Ge) PSD 7 Liverpool 2005 insulator QRO readout board 2 mm A. Breskin

THE 2 D 100 x 100 mm THGEM d = 2, 6 mm fwhm: 5, 1 mm d d = 1, 0 mm fwhm: 2, 0 mm 2 mm pitch PSD 7 Liverpool 2005 A. Breskin

The delay-line readout 100 x 100 mm • Signal induction to pads (“diamonds”) printed on two sides of a 0. 5 mm thick pickup PCB electrode • Different pad sizes to ensure equal induced charge: 2 mm pitch front side pads: 0, 5 mm back side pads: 1, 5 mm • Non-overlapping pads on front and backside to minimize capacitive cross talk • Delay-line with SMD-elements integrated to the electrode C L 2 C 1 “X” & “Y” DL-signals front side back side Z = 100 , d = 2, 7 ns total length: 135 ns (1. 35 ns/mm) PSD 7 Liverpool 2005 A. Breskin

THGEM: EXAMPLES OF 2 D X-RAY IMAGES X-rays • Double-THGEM 0. 4 mm thick; 0. 7 mm pitch; F 0. 3 mm 1 mm mask • 2 D delay-line readout • Ar/CO 2 (30%) • 6 ke. V x-rays • conversion in gas X-Y read out 10 mm Sub-mm resolution F 1. 4 mm PSD 7 Liverpool 2005 5 mm RAW DATA! F 1 mm A. Breskin

THGEM: applications LARGE-AREA DETECTORS, ROBUST, MODERATE COST ns, sub-mm, MHz/mm 2 • Particle tracking at moderate (sub-mm) resolutions • Single-photon imaging; e. g. in Ring Imaging Cherenkov (RICH) detectors R. Chechik et al. Physics / 0502131(NIM A) • Moderate-resolution, fast (ns) x-ray and n imaging PSD 7 Liverpool 2005 A. Breskin

Fast-n imaging with cascaded GEMs V. Dangendorf et al. NIM A 542(2005)197 TOF material-sensitive radiography Image of C phantom and wrench using 2 -10 Me. V n’s, Polyethylene converter and 3 -GEM detector resistive layer on insulator conversion gap neutron 2 - 10 Me. V 2 -sided PCB (pads / delay lines) proton 1 mm PE neutron-converter gas: 1 bar Ar/CO 2 70/30 % 10 x 10 cm 2 3 GEMs ~ 12 mm PSD 7 Liverpool 2005 Delay-line readout C s=0. 4 mm NEXT: 30 x 30 cm 2 cascaded THGEMs A. Breskin