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RICH04 Mexico A. Breskin
Ion-induced effects inIon-induced effects in GEMGEM & & GEM/MHSPGEM/MHSP- gaseous photomultipliers- gaseous photomultipliers
for the for the UVUV & & visiblevisible spectral range spectral range
http://www.weizmann.ac.il/home/detlab
A. Breskin, D. Mörmann, A. Lyashenko and R. ChechikDepartment of Particle Physics, The Weizmann Institute of Science
76100 Rehovot, IsraelF.Amaro, J.Maia, J.Veloso and J.dos Santos
Physics Dept., University of Coimbra, 3004-516 Coimbra, Portugal
RICH04 Mexico A. Breskin
Gaseous Photomultipliers (GPM)Gaseous Photomultipliers (GPM)Gas 1 atm (F.Piuz et al)
Problems with wire chambers:open geometryopen geometry - Photon and ion feedback gain limitations- Damage to the photocathode
CsI on readout pads
photocathode
I will discuss only our work!
Possible solution: closed geometryclosed geometry
Cascaded GEM & othersCascaded GEM & others
RICH04 Mexico A. Breskin
Multi-GEM GPMMulti-GEM GPM
• largely reduced photon feedback compared to “open” geometry
• no photon feedback• thick pc: easier production• low sensitivity to charged particles!
Semitransparent Photocathode
A. Buzulutskov et al. NIM A 443 (2000)164 D. Mörmann et al. NIM A 478 (2002) 230
higher QE!
• high 2D precision [0.1-0.2 mm] • high gain [>105] single photon sensitivity!• fast signals [ns] good timing
Reflective Photocathode
RICH04 Mexico A. Breskin
Multiplication in multi-GEM structuresMultiplication in multi-GEM structures
For a given total gain: a larger number of GEMs permits operation @ lower V GEM
HIGHER STABILITY
D. Mörmann et al. WIS
RICH04 Mexico A. Breskin
Electron transmission into holesElectron transmission into holes
0.7 1.0 1.4 1.9 2.6 3.7 5.2 7.3 10 14 20kV/cm
VGEM=500VVGEM=300VVGEM=100V
Good extractionE drift
E GEM
high VGEM
high surface field
low backscattering
=> optimal operation at high VGEM
E>2
RICH04 Mexico A. Breskin
- Reflective PC (compared to ST), higher QE, low sensitivity to ionizing BG radiation- High optical opacity of multi-GEM, no photon-feedback- Reduced ion back-flow (compared to MWPC)
- Reduced secondary effects high gains 106 - 107
- Operation with large variety of gases, noble gases, CF4, etc
- Fast: with CF4 = 1.6ns w\single electrons
= 0.33ns w\150 electrons
GPMs: highlightsGPMs: highlights
e-
50mV 10ns
gain 105, no photon feedback.
Refl. CsI, 1 atm CF4
3 GEM, single electron pulses.
With reflective PC:low sensitivity to ionizing background radiation
RICH04 Mexico A. Breskin
Examples of GEM-GPM applicationsExamples of GEM-GPM applications
• Hadron-Blind Detector (HBD) for PHENIX
(I. Tserruya et al. Weizmann)• UV imaging detectors of
LXe scintillators for Dark-Matter experiments
(XENON, E. Aprile et al. Columbia Univ.)
• UV imaging detectors for a fast LXe Gamma-camera for PET ) D. Thers - Nantes/A.B.-Weizmann)
GPM
LXe
LIQUID Xe
Xe GAS
RICH04 Mexico A. Breskin
Visible-range Gaseous PhotomultipliersVisible-range Gaseous Photomultipliers
Real challenge: GPMTs for the visible range!
Photocathodes(e.g. bi-alkali)
are very chemically reactive.
Cannot operate in flow-mode!
Solution:Visible-range GPMTs => sealed
mode D. Mörmann et al. NIM A504 (2003) 93
UV
visible
UV: established techniquevarious ~“air-stable” photocathodes
RICH04 Mexico A. Breskin
GPMT for visible lightGPMT for visible lightsealed 3 Kapton-GEMs & KCsSb PC Sealing in gas: In/Sn; 130-1500C
D. Mörmann et al. NIM A504 (2003) 93M.Balcerzyk et al. IEEE TNS 50 (2003) 847
QE in Ar/CH4 (95/5) ~ 70% of QE in vacuum (backscattering)
best expected ~20% @360-400 nm
QE in transmissive mode Ar/ CH 4 95 /5 %
Wavelength [nm]
300 400 500 600
15
10
5
Q E
%
13% = best QE measured after sealing.2 weeks stability
under development: Silicon, ceramicExpected higher stability
Sealed detector package with semitransparent K-Cs-Sb PC
Best sealed GPMT: QE = 6% @ 365nm stable for 1 month
~2”
RICH04 Mexico A. Breskin
Ion feedback: photocathode-dependent (band gap, electron affinity) gas-dependent (ion species, PC surface processes) field-dependent (ion velocity)
No significant feedback observed with CsI Significant with efficient secondary electron emitters, e.g. visible photocathodes
Gain limitation by ion-feedbackGain limitation by ion-feedback
K-Cs-Sb:Current deviates from exponential
100mV/div 400s/div
Recently measured: SEE Probability = 0.05 – 0.5 electron/ion in Ar/CH4 mixtures(Gas dependent, Ar is worst)
1 atm Ar, 1 GEM ST PC
RICH04 Mexico A. Breskin
Drawbacks of ion-photocathode interactionDrawbacks of ion-photocathode interaction
• Secondary avalanches due to ion feedback
gain limits, imaging problems (observed in K-Cs-Sb)• Photocathode damage due to ion sputtering
observed in both: CsI and K-Cs-Sb
Major efforts to limit ion backflow
RICH04 Mexico A. Breskin
Ion back-flow in multi-GEMIon back-flow in multi-GEM
Tracking detectors & TPCs
Electron’s path Ion’s back-flow
Back-flowing ionsDistort the E-field
Ed can be kept relatively LOW reduces ion back flow to a few % levelsEd cannot be too low keep e-diffusion low localization resolution
Ed
S.Bachman et al. NIMA438(99)376: 5% @ 0.5kV/cm A.Breskin et al. NIM A478(2002)225 2-5%@ 0.5kV/cmA.Bondar et al. NIM A496(2003)325 3%@ 0.5; 0.5% @ 0.1 kV/cm (GEMs with small holes)
RICH04 Mexico A. Breskin
Electron’s path Ion’s back-flow
Ion back-flow in multi-GEMIon back-flow in multi-GEM
Attempts to reduce the ion back-flow: variables VGEM ; Etrans ; Eind
E @ photocathode must be high for good e-extraction; best @ high VGEM Ion back-flow 10-20% at best…!
-
(without affecting e- transfer)
Detectors with solid converters
D. Mörmann et al. NIM A516 (2004) 315
RICH04 Mexico A. Breskin
The Microhole & Strip Plate (MHSP)The Microhole & Strip Plate (MHSP)
Foil:5m copper on both sides of 50m Kapton Bi-conical holes: 50/70m (inner/outer) diameter Anode-strip pattern:175m pitch /15m strips Production: similar to GEM technology (CERN)
Two multiplication stages on a single, double-sided, foil J.M.Maia et al. IEEE NS49 (2002)J.M.Maia et al. NIM A504(2003)364
R&D in course: Weizmann/Coimbra
RICH04 Mexico A. Breskin
Ion back-flow: MHSP vs GEMIon back-flow: MHSP vs GEM
All ions flow back Some ions flow back but others flow towards the strip cathodes and bottom cathode
Multi-GEM GEM & MHSP
anode bottom cathodeA C
GEM & MHSP: ion flow reduced to 2-3% levels!
J.Maia et al. NIM A523(2004)334
RICH04 Mexico A. Breskin
MHSP simulationMHSP simulation
Simulations:Oleg Bouianov Bouianov
photocathode
cathode mesh
hv
VC-T
VA-C
E trans
E drift
CA
RICH04 Mexico A. Breskin
The multi-GEM & MHSP photomultiplierThe multi-GEM & MHSP photomultiplierJ. Maia et al. NIM A523(2004)334
High gain and low ion back flow: 2-3%
1E+04
1E+05
1E+06
1E+07
1E+08
80 120 160 200 240 280Vac [V]
Eff
ectiv
e G
ain
EInd=- 5.0 kV/cm
Vhole
ET1= 3.0 kV/cm
ET2=ET3 =2.0 kV/cm
VGEM1=345 VVGEM2=VGEM3=310 V
Ar/5%CH4 p=760 Torr
300 V
250 V
200 V
Current-mode UV-light
1E+04
1E+05
1E+06
1E+07
1E+08
80 120 160 200 240 280Vac [V]
Eff
ectiv
e G
ain
EInd=- 5.0 kV/cm
Vhole
ET1= 3.0 kV/cm
ET2=ET3 =2.0 kV/cm
VGEM1=345 VVGEM2=VGEM3=310 V
Ar/5%CH4 p=760 Torr
300 V
250 V
200 V
Current-mode UV-light
0.01
0.1
1
1E+02 1E+03 1E+04 1E+05 1E+06Effective Gain
Ion
bac
k-fl
ow
rat
io
ET1 =1.0 kV/cm
ET2 =E T3 =0.25 kV/cm
Eind -=5.0 kV/cm
Ar/5%CH4 p=760 Torr
VGEM1 =350 V
VGEM2 =V GEM3
250 V
300 V
280 V
350 V
V GEM3 315 V
V hole
2-3%
0.01
0.1
1
1E+02 1E+03 1E+04 1E+05 1E+06Effective Gain
Ion
bac
k-fl
ow
rat
io
ET1 =1.0 kV/cm
ET2 =E T3 =0.25 kV/cm
Eind -=5.0 kV/cm
Ar/5%CH4 p=760 Torr
VGEM1 =350 V
VGEM2 =V GEM3
250 V
300 V
280 V
350 V
V GEM3 315 V
V hole
2-3%
RICH04 Mexico A. Breskin
Ion back-flow reduction: reversed-MHSP & GEMIon back-flow reduction: reversed-MHSP & GEMJ.Veloso et al. WIS/Coimbra IEEE 2004
IBF R&D IN PROGRESS!
R-MHSP
MHSP
MHSP: gain & ion blocking
R-MHSP: ion defocusing*
WIS/Coimbra
IBF: Ion Backflow Reduction
R-MHSP
Gain=30
~1200 ions/e
~300 ions/e
30 x gain4 x ions!
R-MHSP: Roth, Vienna 04
C
C
C
RICH04 Mexico A. Breskin
Gain of 1st element: 20-30
Other ion-suppression ideasOther ion-suppression ideas
RICH04 Mexico A. Breskin
Ion backflow (reflective photocathode)Ion backflow (reflective photocathode)
Gain of R-MHSP1 ~ 30
RICH04 Mexico A. Breskin
1. Gate open
=> electron transfer
2. Gate closed, after electron transfer,
=> ions are stopped
Ion GatingIon Gating
E1
E2
Feedback pulses
0 10 20 30 40 50 60 70 80 9010-5
10-4
10-3
10-2
10-1
100
ion feedbackpulse mode and ion countingCH
4 100torr
real
tive
ion
feed
back
VGate
[V]
all VGEM
=260V
all Etrans
=0.5kV/cm
gain 7x105
Non-gated GEM: at best 10% ion-feedback Gated GEM: ion suppression to 10-4 levels!
10-4
Problem: dead time! (s)
D. Mörmann et al. NIM A516 (2004) 315
RICH04 Mexico A. Breskin
Gated GPMT for visible lightGated GPMT for visible light
D. Mörmann et al. WIS 2004
1800 1900 2000 2100 2200 2300
0.1
1
10
100
250 260 270 280 290 300 310 320 330 340102
103
104
105
106
107
m430_gain_bi-alkali
gain
VGEM
[V]
4-GEM gainAr/CH
4 (95:5) 700torr
gated operation with bi-alkali
singleelectrons
Vres
[V]
pul
sehe
ight
>105
GAIN: 100-1000 in DC mode (ion feedback limit) >105 in ion-gating mode
A breakthrough!
RICH04 Mexico A. Breskin
Ion-suppression: summaryIon-suppression: summary
At gain ~ 105
Multi-GEM: IBF = 10-1 – 2 10-1
Multi-GEM & MHSP: IBF = 2 10-2 Multi-GEM & MHSP & R-MHSP: IBF = 1-3 10-3
Gated multi-GEMs: IBF = 10-4
Photocathode life-time, TPC , depends on the total ion’s accumulated charge on the photocathode: TPC (GEM-like GPM) = TPC (MWPC GPM) x 1/IBF Operate at minimal possible gain!
RICH04 Mexico A. Breskin
K-Sb-Cs photocathode ageingK-Sb-Cs photocathode ageing
CsI
CsBr
KCsSb
4-GEM / semitransparent photocathode a small fraction of ions hit the pc slow aging
parallel-grids / semitrans. photocathode all ions hit the pc faster aging !
Aging of K-Cs-Sb under avalanche-ion bombardment in Ar-CH4(5%)
RICH04 Mexico A. Breskin
SummarySummary
• GEM photomultipliers (GPM): - a mature concept in the UV - important progress in the visible• Other advanced “hole-multipliers”: MHSP, TGEM
(talk by Rachel Chechik)• Ion blocking: cascaded GEM/MHSP/RMHSP – 10-3
importat also for TPCs!
RICH04 Mexico A. Breskin
FIN
RICH04 Mexico A. Breskin
GPM
LXe
SiO2 entrance window (3mm)
PTFE Wall
Thermal Screen
Metallic Micromesh
Anode plane
Cathode wire plane
HV 20kV
Liquid Xenon
Xenon gas
511 keV Gamma ray
HV [1-2] kV
9 cm
LXe-gaseous PMT gamma-camera for PETLXe-gaseous PMT gamma-camera for PET
SUBATECH-Nantes/WEIZMANN
RICH04 Mexico A. Breskin
Replace
Suggested GEM in the XENON DetectorSuggested GEM in the XENON DetectorThe XENON Dark Matter search: E. Aprile et al. Columbia Univ. astro-ph/0207670
1 ton liquid Xe detector with multi-GEM GAS PHOTOMULTIPLIER
Xe GAS
LIQUIDXe
Primary scintillation:Photo-effect in LIQUID & GAS
Secondary scintillation: Induced by electrons extracted fromLIQUID & drifting in GAS
WIMPS
RICH04 Mexico A. Breskin
A single 100 MeV electron identified by a “Cerenkov signal” in the HBD
Suggested PHENIX HBDSuggested PHENIX HBD
Simulation Real life.…
A single event recordedin the STAR TPC showing hundreds of particles:most of them HADRONS
e-
GEM-photodetectorinsensitive to particles!
HBD
RICH04 Mexico A. Breskin
TPC/HBD for RHIC-PHENIXTPC/HBD for RHIC-PHENIX
Drift regions
HV plane (~ -30kV)Grid
TPC Readout Plane
Readout PadsDR ~ 1 cm f ~ 2 mm
Large area UV detector3-GEM/CsI
I. Tserruya et al, WIS
GOAL: identification of a few low-mass e-pairs out of hundreds of Hadrons / collision
RICH04 Mexico A. Breskin
Ion feedback to the ST photocathodeIon feedback to the ST photocathode
Ion feedback as a functionof the drift field
0.1 1
10-3
10-2
10-1
VT / V
GEM = 1.0
Gain = 3000
VT / V
GEM = 0.5
Gain = 5000
3GEM
Ion f
eedbac
k :
I
C /
I A
ED ( kV/cm )
102 103 104 1050.00
0.05
0.10
0.15
0.20
0.25
4GEM
3GEM
VD = V
GEM
VT / V
GEM = 0.5
ED ~ 0.6 kV/cm
Ion f
eedbac
k :
I
C /
I A
Gain
Dependence on the gain:3GEM vs 4GEM
TPC
Breskin et al. NIM A478(2002)225
GPM
“standard” GEMs
101 102 103 104 105
0.01
0.1
Hole diameter effect
Ar/CF4 (90/10)
3GEM+PCBE
D = 0.5 kV/cm
80-80-80 80-40-80 40-40-80 40-40-40
Ion
feed
back
: I
C /
I A
Gain
Breskin et al. NIM A478(2002)225
Bondar et al NIMA
Factor 2-3 IBF reduction
RICH04 Mexico A. Breskin
Ion back-flow in multi-GEM with reflective pcIon back-flow in multi-GEM with reflective pc
0.0
0.2
0.4
0.6
0.8
1.0
0 2 4 6 8 10 12102
103
104
105
106
107
ion b.
gain
ion backflow4GEM with refl. CsIV
GEM4=200V
Ar/CH4 (95:5) 760torr
Etrans
=2kV/cm
m274_ionfeedback_Eind 16.5.02
gain
Eind
[kV/cm]
ion
back
flow
Variable:Induction field
10% at best-75 -50 -25 0 25 50 75 100
0.15
0.20
0.25
0.30
0.35
ion feedback4GEM with refl. CsIAr/CH
4 (95:5) 760torr
gain = 2x105
m272_ionfeedback_ArCH4
ion
fee
db
ack
VGEM4
- VGEM3
[V]
Variable:GEM voltage
0.0
0.2
0.4
0.6
0.8
1.0
0 1 2 3 4 5 6102
103
104
105
106
107
gain
ion b.
ion backflow4GEM with refl. CsIAr/CH
4 (95:5) 760torr
m273_ionfeedback_Etrans
ga
in
Etrans3
[kV/cm]
ion
ba
ck-f
low
Variable:transfer field
D. Mörmann et al. NIM A516 (2004) 315