Efficient ion blocking in gaseous detectors Efficient ion blocking in gaseous detectors and its application to and its application to and its application to and its application to visible visible- -sensitive gaseous photomultipliers sensitive gaseous photomultipliers A. Breskin, A. Lyashenko and R. Chechik Weizmann Institute of Science, Rehovot, Israel & J.M.F. dos Santos, F.D. Amaro and J.F.C.A. Veloso J.M.F. dos Santos, F.D. Amaro and J.F.C.A. Veloso University of Coimbra Portugal University of Coimbra, Portugal ION BLOCKING & visible-sensitive gas-PMs RD51 Amsterdam 4/08 A. Breskin
Secondary effects in gaseous detectors Secondary effects in gaseous detectors Time Projection Chamber (TPC) Time Projection Chamber (TPC) Gaseous Photo-Multiplier (GPM) Gaseous Photo Multiplier (GPM) onizing particle GAS incident photon + + ioniz h ν h + + E PC + secondary secondary drift dynamic + emission emission track distortions ions + photons + + + E ions avalanche E E + + + + GAS avalanche readout plane readout plane d t l Ions � � secondary e emission Ions � � ion feedback pulses � ion feedback pulses � dynamic track distortions � gain & performance limitations ION BLOCKING & visible-sensitive gas-PMs RD51 Amsterdam 4/08 A. Breskin
IBF: Ion Back-Flow Fraction IBF: The fraction of avalanche-generated ions back- flowing to the drift region or to the photocathode � Major efforts to limit ion backflow 1. GATING � operation in “gated-mode” � deadtime, trigger 2. NEW e - - MULTIPLIERS � operation in DC mode 2 NEW MULTIPLIERS � ti i DC d (cascaded - GEM* , MICROMEGAS…&: OTHERS ) � Challenge: BLOCK IONS WITHOUT AFFECTING � Challenge: BLOCK IONS WITHOUT AFFECTING ELECTRON COLLECTION *GEM: Gas Electron Multiplier - Sauli, NIM A 386, (1997) 531. ION BLOCKING & visible-sensitive gas-PMs RD51 Amsterdam 4/08 A. Breskin
Visible Visible- -sensitive gaseous photomultipliers: sensitive gaseous photomultipliers: Ion Ion- -feedback development feedback development γ eff : ion feedback coeff. if - stable operation of visible sensitive GPM eff IBF G 1 γ ⋅ ⋅ < + + ~0.03, Gain ~ 10 5 => IBF < 3.3*10 -4 Ar/CH 4 (95/5), γ eff ), γ 4 ( , + Visibile-sensitive gas photomultiplier review: M. Balcerzyk et al., IEEE Trans. Nucl. Sci. Vol. 50 no. 4 (2003) 847 ION BLOCKING & visible-sensitive gas-PMs RD51 Amsterdam 4/08 A. Breskin
IBF in cascaded GEM GPMs (high E drift ) High E drift (>0.5 kV/cm) needed to efficiently extract photoelectrons B Bachman et al. NIMA438(1999)376 5% h l NIMA438(1999)376 5% @ 0 5kV/ @ 0.5kV/cm, Gain ~10 5 G i 10 5 Breskin et al. NIM A478(2002)225 2-5%@ 0.5kV/cm, Gain ~10 5 Bondar et al. NIM A496(2003)325 3% @ 0.5kV/cm, Gain ~ 10 5 N Need another factor of 100!!! d th f t f 100!!! ION BLOCKING & visible-sensitive gas-PMs RD51 Amsterdam 4/08 A. Breskin
The Microhole & Strip plate (MHSP) 30 µ m 30 µ m 70 µ m Two multiplication stages on a single, 70 double-sided, foil 100 µ m 140 µ m R&D: Weizmann/Coimbra R&D: Weizmann/Coimbra 100 µ m 210 µ m hv photocathode E drift V V A-C V C-T A C E trans cathode mesh ~80% of avalanche ions are trapped by cathode strips and plane Veloso et al. Rev. Sci. Inst. A 71 (2000) 237. ION BLOCKING & visible-sensitive gas-PMs RD51 Amsterdam 4/08 A. Breskin
The benefit of MHSP in a cascade The benefit of MHSP in a cascade 3GEM 3GEMs+MHSP MHSP 4GEMs IBF: 20% @ Gain > 10 5 IBF: 3% @ Gain > 10 5 7 times lower than with cascaded GEMs 7 times lower than with cascaded GEMs Maia et al. IEEE NS49 (2002) Mörmann et al. NIM A516 (2004) 315 Maia et al. NIM A504(2003)364 ION BLOCKING & visible-sensitive gas-PMs RD51 Amsterdam 4/08 A. Breskin
Reverse Reverse- -biased MHSP (R biased MHSP (R- -MHSP) concept MHSP) concept Ions are trapped by negatively biased cathode strips R-MHSP Flipped-R-MHSP electrons 410V 70V C A +++ ++ ions C Can trap only ions from l f Can trap its own ions successive stages Roth, NIM A535 (2004) 330 Lyashenko et al., JINST (2006) 1 P10004 Breskin et al. NIM A553 (2005) 46 Lyashenko et al., JINST (2007) 2 P08004 Veloso et al. NIM A548 (2005) 375 ION BLOCKING & visible-sensitive gas-PMs RD51 Amsterdam 4/08 A. Breskin
BETTER ION BLOCKING: BETTER ION BLOCKING: “COMPOSITE” CASCADED MULTIPLIERS: “COMPOSITE” CASCADED MULTIPLIERS: COMPOSITE CASCADED MULTIPLIERS: COMPOSITE CASCADED MULTIPLIERS: 1st R-MHSP or F-R-MHSP: ion defocusing (no gain!) Mid Mid GEMs: GEMs: gain in Last MHSP: extra gain & ion blocking R-MHSP/GEM/MHSP F-R-MHSP/GEM/MHSP ION BLOCKING & visible-sensitive gas-PMs RD51 Amsterdam 4/08 A. Breskin
IBF in “composite” micro-hole multipliers IBF measured with 100% e-collection efficiency Gas PMT conditions (high drift field) TPC conditions (low drift field) -2 -1 10 10 E E =0 5kV/cm drift =0.5kV/cm E E drift =0.2kV/cm 0 2kV/ -2 10 BF BF -3 IB -3 IB 10 10 10 10 F-R-M HSP/GEM /M HSP -4 10 F-R-M HSP/GEM /M HSP R-M HSP/GEM /M HSP R-M HSP/GEM /M HSP Ar/CH Ar/CH 4 (95/5), 760 Torr 4 (95/5), 760 Torr Ar/CH A /CH (95/5) 760 T 4 (95/5), 760 Torr -4 10 -5 10 5 2x10 3 4 5 10 10 10 2 3 4 10 10 10 Total gain Total gain IBF=1 5*10 -4 @ Gain=10 4 IBF=1.5 10 @ Gain=10 IBF=3*10 -4 @ Gain=10 5 IBF=3 10 @ Gain=10 IBF is 100 times lower than with 3GEMs IBF is 100 times lower than with 3GEMs Lyashenko et al., JINST (2007) 2 P08004 ION BLOCKING & visible-sensitive gas-PMs RD51 Amsterdam 4/08 A. Breskin
New ideas for ion blocking R&D in course @ WEIZMANN/COIMBRA ) 30 µ m 70 µ m 100 µ m 140 µ m 100 µ m 210 µ m � NEW! “COBRA”: GEM-LIKE PATTERNED NEW! COBRA : GEM LIKE PATTERNED ION-SUPPRESSING ELECTRODES (R. d’Oliveira, CERN) ION BLOCKING & visible-sensitive gas-PMs RD51 Amsterdam 4/08 A. Breskin
IBF suppression with “Cobra” IBF suppression with “Cobra” 0 10 Flipped-Cobra/2GEM -1 10 IBF= 2.7*10 -5 -2 10 Gain=10 4 IBF 3*10 -6 IBF= 3*10 -6 F IBF -3 3 TPC 10 Gain=10 5 -4 10 GPM -5 5 10 E drift =0.5kV/cm 700 Torr Ar/CH 4 (95/5) -6 10 3 4 5 6 10 10 10 10 Total Gain Total Gain IBF 1000 times lower than with GEMs, best results ever achieved Though Though, presently at the expense of electron collection (~20%) presently at the expense of electron collection ( 20%) ION BLOCKING & visible-sensitive gas-PMs RD51 Amsterdam 4/08 A. Breskin
IBF reduction summary IBF reduction summary TPC (E drift =0.1-0.2kV/cm, TPC (E drift 0. 0. kV/cm, GPM (E drift =0.5kV/cm, GPM (E drift 0.5kV/cm, Gain=10 4 ) Gain=10 5 ) Detector IBF Collection IBF Collection type type efficiency ffi i efficiency ffi i 3GEM 0.5% 100% 5% (20%) * 100% 4GEM 100% 2% 100% (0.01%) ** R MHSP/ R-MHSP/ 0 08% 0.08% 100% 100% 0 1% 0.1% 100% 100% GEM/MHSP F-R-MHSP/ 0.015% 100% 0.03% 100% GEM/MHSP “Cobra”/ 0.0027% 20% 0.0003% 20% 2GEM 2GEM * Reflective PC **Gated mode ION BLOCKING & visible-sensitive gas-PMs RD51 Amsterdam 4/08 A. Breskin
Visible Visible- -sensitive GPM sensitive GPM Test detector setup p UHV compatible materials Sealed detector Sealed detector Bi-alkali PC Base plate made in Novosibirsk ION BLOCKING & visible-sensitive gas-PMs RD51 Amsterdam 4/08 A. Breskin
Visible Visible- -sensitive GPM: Gain Divergence sensitive GPM: Gain Divergence 4 10 E drift =0.5kV/cm K-Cs-Sb QE=22%@375nm @ 3 3 10 al gain G meas 2 10 Tota G 1 10 700 Torr Ar/CH 4 (95/5) 0 10 200 220 240 260 280 300 320 340 V GEM [V] K-Cs-Sb, Na-K-Sb, Cs-Sb : Current deviates from exponential Max Gain ~ few 100, IBF~10% D. Mörmann et al.,NIM A 504 (2003) 93 ION BLOCKING & visible-sensitive gas-PMs RD51 Amsterdam 4/08 A. Breskin
Gated operation of visible Gated operation of visible- -sensitive GPM sensitive GPM Ion gating electrode G in 10 6 Gain~10 6 GATED MULTI GEM GATED MULTI-GEM GAIN: ~ 100 in DC mode (ion feedback limit), IBF~10% ~10 6 in ion gating mode; IBF~10 -4 ~10 6 in ion-gating mode; IBF~10 4 A.Breskin et al. NIM A553 (2005) 46-52 ION BLOCKING & visible-sensitive gas-PMs RD51 Amsterdam 4/08 A. Breskin
DC operation of visible DC operation of visible- -sensitive GPM sensitive GPM Flipped Cobra Flipped Cobra + 2GEMs GEMs 6 6 10 Flipped-Cobra/2GEM K-Cs-Sb E drift =0.5kV/cm 5 10 700 Torr Ar/CH4 (95/5) in UV-LED 375nm otal Gai Gain~10 5 4 10 CsI 3 10 To K-Cs-Sb (QE~40%) 2 CsI 10 Exponential fit of Exponential fit of 50 1 10 0 K-Cs-Sb PC K-Cs-Sb K C Sb 200 200 250 250 300 300 350 350 40 V GEM [V] DC Gain limit~100 QE [%] 30 in cascaded GEMs 20 10 Gain >10 5 in DC mode � 0 300 400 500 600 single photon sensitivity Wavelength [nm] But: e - collection efficiency ~ 20% ION BLOCKING & visible-sensitive gas-PMs RD51 Amsterdam 4/08 A. Breskin
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