Скачать презентацию Efficient ion blocking in gaseous detectors and its Скачать презентацию Efficient ion blocking in gaseous detectors and its

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Efficient ion blocking in gaseous detectors and its application to visible-sensitive gaseous photomultipliers A. Efficient ion blocking in gaseous detectors and its application to visible-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 University of Coimbra, Portugal RD 51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs A. Breskin

Secondary effects in gaseous detectors Gaseous Photo-Multiplier (GPM) Ions secondary e emission feedback pulses Secondary effects in gaseous detectors Gaseous Photo-Multiplier (GPM) Ions secondary e emission feedback pulses gain & performance limitations RD 51 Amsterdam 4/08 Time Projection Chamber (TPC) Ions dynamic track distortions ION BLOCKING & visible-sensitive gas-PMs A. Breskin

IBF: Ion Back-Flow Fraction IBF: The fraction of avalanche-generated ions backflowing to the drift IBF: Ion Back-Flow Fraction IBF: The fraction of avalanche-generated ions backflowing 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 (cascaded-GEM*, MICROMEGAS…&: OTHERS) Challenge: BLOCK IONS WITHOUT AFFECTING ELECTRON COLLECTION *GEM: Gas Electron Multiplier Sauli, NIM A 386, (1997) 531. RD 51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs A. Breskin

Visible-sensitive gaseous photomultipliers: Ion-feedback development geff : ion feedback coeff. if - stable operation Visible-sensitive gaseous photomultipliers: Ion-feedback development geff : ion feedback coeff. if - stable operation of visible sensitive GPM Ar/CH 4 (95/5), RD 51 γeff+ ~0. 03, Gain ~ 105 => IBF < 3. 3*10 -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 Amsterdam 4/08 A. Breskin

IBF in cascaded GEM GPMs (high Edrift) High Edrift (>0. 5 k. V/cm) needed IBF in cascaded GEM GPMs (high Edrift) High Edrift (>0. 5 k. V/cm) needed to efficiently extract photoelectrons Bachman et al. NIMA 438(1999)376 5% @ 0. 5 k. V/cm, Gain ~105 Breskin et al. NIM A 478(2002)225 2 -5%@ 0. 5 k. V/cm, Gain ~105 Bondar et al. NIM A 496(2003)325 3% @ 0. 5 k. V/cm, Gain ~ 105 Need another factor of 100!!! RD 51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs A. Breskin

The Microhole & Strip plate (MHSP) Two multiplication stages on a single, double-sided, foil The Microhole & Strip plate (MHSP) Two multiplication stages on a single, double-sided, foil R&D: Weizmann/Coimbra hv photocathode E drift VC-T VA-C 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. RD 51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs A. Breskin

The benefit of MHSP in a cascade 3 GEMs+MHSP 4 GEMs IBF: 20% @ The benefit of MHSP in a cascade 3 GEMs+MHSP 4 GEMs IBF: 20% @ Gain > 105 IBF: 3% @ Gain > 105 7 times lower than with cascaded GEMs Mörmann et al. NIM A 516 (2004) 315 RD 51 Amsterdam 4/08 Maia et al. IEEE NS 49 (2002) Maia et al. NIM A 504(2003)364 ION BLOCKING & visible-sensitive gas-PMs A. Breskin

Reverse-biased MHSP (R-MHSP) concept Ions are trapped by negatively biased cathode strips R-MHSP Can Reverse-biased MHSP (R-MHSP) concept Ions are trapped by negatively biased cathode strips R-MHSP Can trap only ions from successive stages Lyashenko et al. , JINST (2006) 1 P 10004 Lyashenko et al. , JINST (2007) 2 P 08004 RD 51 Amsterdam 4/08 Flipped-R-MHSP Can trap its own ions Roth, NIM A 535 (2004) 330 Breskin et al. NIM A 553 (2005) 46 Veloso et al. NIM A 548 (2005) 375 ION BLOCKING & visible-sensitive gas-PMs A. Breskin

BETTER ION BLOCKING: “COMPOSITE” CASCADED MULTIPLIERS: 1 st R-MHSP or F-R-MHSP: ion defocusing (no BETTER ION BLOCKING: “COMPOSITE” CASCADED MULTIPLIERS: 1 st R-MHSP or F-R-MHSP: ion defocusing (no gain!) Mid GEMs: gain Last MHSP: extra gain & ion blocking R-MHSP/GEM/MHSP RD 51 Amsterdam 4/08 F-R-MHSP/GEM/MHSP ION BLOCKING & visible-sensitive gas-PMs A. Breskin

IBF in “composite” micro-hole multipliers IBF measured with 100% e-collection efficiency TPC conditions (low IBF in “composite” micro-hole multipliers IBF measured with 100% e-collection efficiency TPC conditions (low drift field) IBF=1. 5*10 -4 @ Gain=104 Gas PMT conditions (high drift field) IBF=3*10 -4 @ Gain=105 IBF is 100 times lower than with 3 GEMs Lyashenko et al. , JINST (2007) 2 P 08004 RD 51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs A. Breskin

New ideas for ion blocking R&D in course @ WEIZMANN/COIMBRA ) NEW! “COBRA”: GEM-LIKE New ideas for ion blocking R&D in course @ WEIZMANN/COIMBRA ) NEW! “COBRA”: GEM-LIKE PATTERNED ION-SUPPRESSING ELECTRODES (R. d’Oliveira, CERN) RD 51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs A. Breskin

IBF suppression with “Cobra” IBF=2. 7*10 -5 Gain=104 IBF=3*10 -6 Gain=105 IBF 1000 times IBF suppression with “Cobra” IBF=2. 7*10 -5 Gain=104 IBF=3*10 -6 Gain=105 IBF 1000 times lower than with GEMs, best results ever achieved Though, presently at the expense of electron collection (~20%) RD 51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs A. Breskin

IBF reduction summary TPC (Edrift=0. 1 -0. 2 k. V/cm, Gain=104) GPM (Edrift=0. 5 IBF reduction summary TPC (Edrift=0. 1 -0. 2 k. V/cm, Gain=104) GPM (Edrift=0. 5 k. V/cm, Gain=105) Detector type IBF Collection efficiency 3 GEM 0. 5% 100% 5% (20%)* 100% 4 GEM 100% 2% (0. 01%)** 100% R-MHSP/ 0. 08% GEM/MHSP 100% 0. 1% 100% F-R-MHSP/ 0. 015% GEM/MHSP 100% 0. 03% 100% “Cobra”/ 2 GEM 20% 0. 0003% 20% 0. 0027% * Reflective PC RD 51 Amsterdam 4/08 **Gated mode ION BLOCKING & visible-sensitive gas-PMs A. Breskin

Visible-sensitive GPM Test detector setup UHV compatible materials Sealed detector Bi-alkali PC Base plate Visible-sensitive GPM Test detector setup UHV compatible materials Sealed detector Bi-alkali PC Base plate made in Novosibirsk RD 51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs A. Breskin

Visible-sensitive GPM: Gain Divergence Gmeas G K-Cs-Sb, Na-K-Sb, Cs-Sb : Current deviates from exponential Visible-sensitive GPM: Gain Divergence Gmeas G 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 RD 51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs A. Breskin

Gated operation of visible-sensitive GPM Ion gating electrode Gain~106 GATED MULTI-GEM GAIN: ~100 in Gated operation of visible-sensitive GPM Ion gating electrode Gain~106 GATED MULTI-GEM GAIN: ~100 in DC mode (ion feedback limit), IBF~10% ~106 in ion-gating mode; IBF~10 -4 A. Breskin et al. NIM A 553 (2005) 46 -52 RD 51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs A. Breskin

DC operation of visible-sensitive GPM Flipped Cobra + 2 GEMs K-Cs-Sb Gain~105 Cs. I DC operation of visible-sensitive GPM Flipped Cobra + 2 GEMs K-Cs-Sb Gain~105 Cs. I K-Cs-Sb DC Gain limit~100 in cascaded GEMs Gain >105 in DC mode single photon sensitivity But: e- collection efficiency ~ 20% RD 51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs A. Breskin

DC operation of F-R-MHSP/GEM/MHSP with K-Cs-Sb photocathode Gain ~105 at full photoelectron collection efficiency DC operation of F-R-MHSP/GEM/MHSP with K-Cs-Sb photocathode Gain ~105 at full photoelectron collection efficiency First evidence of DC high gain operation of visible-sensitive GPM RD 51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs A. Breskin

Summary Cascaded Patterned Hole Multipliers (PHM) significant improvement in ion blocking in gaseous detectors Summary Cascaded Patterned Hole Multipliers (PHM) significant improvement in ion blocking in gaseous detectors of importance in: Tracking detectors (TPC) & Gaseous Photomultipliers with MHSP/GEM-based CASCADED MULTIPLIERS • • 100 times lower IBF than with cascaded GEMs with full efficiency for collecting primary electrons! Gain >105 reached with visible-sensitive K-Cs-Sb PC with Cobra/GEM-based CASCADED MULTIPLIERS • • 1000 times lower IBF than with cascaded GEMs with so-far low e- collection efficiency – Gain >105 reached with visible-sensitive K-Cs-Sb PC First evidence of high-gain DC operation of visible-sensitive GPM Further work: • • Optimization of COBRA Double-sided patterned hole-multipliers RD 51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs A. Breskin

K-Cs-Sb stability in gas RD 51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs A. K-Cs-Sb stability in gas RD 51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs A. Breskin