A. Breskin RD51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs Efficient ion blocking in gaseous Efficient ion blocking in gaseous detectors and its application to detectors and its application to visible-sensitive gaseous visible-sensitive gaseous photomultipliers 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
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A. Breskin RD51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs Efficient ion blocking in gaseous detectors and its application to visible-sensitive.
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A. BreskinRD51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs
Efficient ion blocking in gaseous Efficient ion blocking in gaseous detectors and its application to detectors and its application to
A. BreskinRD51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs
Sealed detector
Test detector setup
Base plate made in Novosibirsk
Visible-sensitive GPMVisible-sensitive GPM
UHV compatible materials
Bi-alkali PC
A. BreskinRD51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs
Visible-sensitive GPM: Gain Divergence Visible-sensitive GPM: Gain Divergence
200 220 240 260 280 300 320 340100
101
102
103
104
700 Torr Ar/CH4 (95/5)
Edrift
=0.5kV/cm
Tot
al g
ain
VGEM
[V]
K-Cs-Sb QE=22%@375nm
G
Gmeas
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
A. BreskinRD51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs
A.Breskin et al. NIM A553 (2005) 46-52
Gated operation of visible-sensitive GPMGated operation of visible-sensitive GPM
GATED MULTI-GEM
Gain~106
GAIN: ~100 in DC mode (ion feedback limit),IBF~10% ~106 in ion-gating mode; IBF~10-4
Ion gating electrode
A. BreskinRD51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs
DC operation of visible-sensitive GPMDC operation of visible-sensitive GPM
Gain >105 in DC mode single photon sensitivity
But: e- collection efficiency ~ 20%
300 400 500 6000
10
20
30
40
50
QE
[%]
Wavelength [nm]
K-Cs-Sb PC
K-Cs-Sb 200 250 300 350101
102
103
104
105
106
K-Cs-Sb (QE~40%) CsI Exponential fit of Exponential fit of
Flipped-Cobra/2GEME
drift=0.5kV/cm
700 Torr Ar/CH4 (95/5)UV-LED 375nm
Tot
al G
ain
VGEM
[V]
Gain~105
K-Cs-Sb
CsI
DC Gain limit~100 in cascaded GEMs
Flipped Cobra + 2GEMs
A. BreskinRD51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs
DC operation of F-R-MHSP/GEM/MHSPDC operation of F-R-MHSP/GEM/MHSP with K-Cs-Sb photocathodewith K-Cs-Sb photocathode
Gain ~105 at full photoelectron collection efficiencyFirst evidence of DC high gain operation of visible-sensitive
GPM
200 220 240 260 280103
104
105
106
K-Cs-Sb (QE~27%@375nm) CsI Exponential fit of Exponential fit of
F-R-MHSP/GEM/MHSPE
drift=0.5kV/cm
700 Torr Ar/CH4 (95/5)UV-LED 375nm
Gai
n
VAC2
[V]
A. BreskinRD51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs
SummarySummary 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
A. BreskinRD51 Amsterdam 4/08 ION BLOCKING & visible-sensitive gas-PMs