ion-induced effects in gem & gem/mhsp - gaseous photomultipliers

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


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 geometryCascaded GEM & othersCascaded GEM & others


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


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


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


- 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: highlightse-

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


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


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


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”


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


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


Ion back-flow in multi-GEMIon back-flow in multi-GEMTracking 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)


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


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


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


MHSP simulationMHSP simulation

Simulations:Oleg Bouianov Bouianov

photocathode

cathode mesh

hv

VC-TVA-C

E trans

E drift

CA


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]

Effe

ctiv

e Ga

in

EInd=- 5.0 kV/cm

Vhole

ET1= 3.0 kV/cm

ET2=ET3 =2.0 kV/cmVGEM1=345 V

VGEM2=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]

Effe

ctiv

e Ga

in

EInd=- 5.0 kV/cm

Vhole

ET1= 3.0 kV/cm

ET2=ET3 =2.0 kV/cmVGEM1=345 V

VGEM2=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

back

-flow

ratio

ET1 =1.0 kV/cmET2 =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

back

-flow

ratio

ET1 =1.0 kV/cmET2 =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%


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 blockingR-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


Gain of 1st element: 20-30

Other ion-suppression ideasOther ion-suppression ideas


Ion backflow (reflective photocathode)Ion backflow (reflective photocathode)

Gain of R-MHSP1 ~ 30


1. Gate open => electron transfer2. 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


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!


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!


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%)


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!


FIN


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


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


A single 100 MeV electron identified by a “Cerenkov signal” in the HBD

Suggested PHENIX HBDSuggested PHENIX HBDSimulation Real life.…

A single event recordedin the STAR TPC showing hundreds of particles:most of them HADRONS

e-

GEM-photodetectorinsensitive to particles!

HBD


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


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 / VGEM = 0.5Gain = 5000

3GEM

Ion

feed

back

: 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

GEMV

T / V

GEM = 0.5

ED ~ 0.6 kV/cm

Ion

feed

back

: 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


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

0.35ion feedback4GEM with refl. CsIAr/CH

4 (95:5) 760torr

gain = 2x105

m272_ionfeedback_ArCH4

ion

feed

back

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

gain

Etrans3

[kV/cm]

ion

back

-flo

w

Variable:transfer field

D. Mörmann et al. NIM A516 (2004) 315

ion-induced effects in gem & gem/mhsp - gaseous photomultipliers

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