Fabio Sauli-CERN

1

IEEE-NSS Rome 04

F. Sauli, T. Meinschad, L. Musa, L. RopelewskiCERN, GENEVA, SWITZERLAND

PHOTON DETECTION AND LOCALIZATION WITH THEGAS ELECTRON MULTIPLIER (GEM)

Fabio Sauli-CERN

2

IEEE-NSS Rome 04

GEM 1

GEM 2

ED

ET1

EI

DRIFT

READOUT

DRIFT

TRANSFER 1

INDUCTION

GEM 2

ET2 TRANSFER 2

REFLECTIVE PHOTOCATHODE ON UPPER GEM SIDE: no photon feedback

MULTIGEM DETECTORS: VERY HIGH GAINSSingle photoelectron detection with internal photocathode

S. Bachmann et al, Nucl. Instr. Methods A 443(1999)464

R. Bouclier et al, IEEE Trans. Nucl. Sci. NS44(1997)646

D. Mörmann et al, Nucl. Instr. Methods 478(2002)364

Fabio Sauli-CERN

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IEEE-NSS Rome 04

Quartz window(inverted) drift field gridGEM1 CsI-coated

GEM2

GEM3

Anode strip readout

Collimator-attenuator

T0

EFFICIENCY AND RESOLUTION FOR UV PHOTON DETECTIONMulti-GEM with Cesium Iodide coating on upper side of first GEM:

Hydrogen UV lamp

R

C

HV

r

ADCs

Fabio Sauli-CERN

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IEEE-NSS Rome 04

SINGLE PHOTON DETECTIONPulse height spectra at decreasing UV source intensity:

Single photoelectron spectra:Multiple photoelectron spectra:

BEAM ATTENUATION

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SINGLE PHOTOELECTRON POSITION ACCURACY: Two positions of collimated beam 200 µm apart

200 µm

160 µm FWHMBeam ~ 100 µm FWHM

Intrinsic accuracy ~ 50 µm rms

T. Meinschad, L. Ropelewski and F. Sauli, Vienna Conference (Nucl. Instr. and Methods, in press)

Fabio Sauli-CERN

6

IEEE-NSS Rome 04

Hexaboard readout: matrix of hexagonal pads interconnected along three projections at 120º

U

V

W

GEM RICH: MULTIPLE PHOTONS Hexaboard closeup: 520 µm Ø pads

S. Bachmann et al Nucl. Instr. and Meth. A 478 (2002) 104

Fabio Sauli-CERN

7

IEEE-NSS Rome 04

HEXABOARD DETECTORStandard assembly for 10x10 cm2 GEMs, 3x128 strips

3x16 strips readout: fast charge amplifier+ALTRO (FADC, 10 bit-25 MHz sampling)

B. Mota et al, Nucl. Instr. and Methods, in press (2004)

16 strips8.3 mm

16 strips16 strips

ALTRO:

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IEEE-NSS Rome 04

SINGLE PHOTON EVENT:

16 strips8.3 mm

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IEEE-NSS Rome 04

SINGLE PHOTON CLUSTER WIDTH (rms)

~ 0.5 pads (250 µm) Charge sharing (520 µm pad rows)

Fabio Sauli-CERN

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IEEE-NSS Rome 04

DOUBLE PHOTON EVENT:

1.1 mm

2.4 mm

1.3 mm

Fabio Sauli-CERN

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CHARGE CORRELATION BETWEEN THE PROJECTIONS:

SINGLE PHOTON CLUSTERS

U-V

W-U

V-W

Fabio Sauli-CERN

12

IEEE-NSS Rome 04

DETECTION OF INTERNAL SCINTILLATION IN XENON

CsI - Quad-GEM in pure Xenon X-ray

Scintillation

Ionization

G. Charpak, S. Majewski and F. Sauli, Nucl. Instr. and Meth. 126(1975)381

L. Periale, V. Peskov, P. Carlson, T. Francke, V. Pavlopulos, P. Picchi, F. Pietropaolo, Nucl. Instr. and Meth. 478(2002)377(See also V. Peskov N25-3)

0

10

20

30

40

50

60

70

5 6 7 8 9 10

CsI Quantum Efficiency (%)

Photon energy (eV)

CsI QE

CsI QE+Xe scint

Xe scintillation

Xe scintillation yield (AU)

Fabio Sauli-CERN

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IEEE-NSS Rome 04

22 keV from 109Cd

Primary scintillation

PRIMARY SCINTILLATION IN XENON-CsI

Fabio Sauli-CERN

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LOW DRIFT FIELD: PRIMARY SCINTILLATION

TIME DIFFERENCE PROMPT- MAIN PULSE

Efficiency 2% for 5.9 keV 10% for 22 keV

Fabio Sauli-CERN

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IEEE-NSS Rome 04

Secondary scintillation

HIGH DRIFT FIELD: SECONDARY SCINTILLATION

Fabio Sauli-CERN

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IEEE-NSS Rome 04

TIME DIFFERENCE PROMPT- MAIN PULSEHIGH FIELD: SECONDARY SCINTILLATION

5.9 keV X-rays

Efficiency for 5.9 keV 20% at 1.3 kV/cm 66% at 1.9 kV/cm 76% at 2.5 kV/cm

Fabio Sauli-CERN

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IEEE-NSS Rome 04

CONCLUSIONS

MULTI-GEM DETECTORS WITH CsI PHOTOCATHODE:

HIGH GAIN-EFFICIENT UV PHOTON DETECTION

VERY GOOD POSITION ACCURACY ~ 50 µm rms

WITH HEXABOARD READOUT:

GOOD MULTI-HIT RESOLUTION ~ 2 mm

GEM-CsI FOR DETECTION OF SCINTILLATION IN Xe

EFFICIENCY FOR PRIMARY SCINTILLATION ~ 10% FOR 22 keV

EFFICIENCY FOR SECONDARY SCINTILLATION ~ 80% FOR 5.9 keV

TOWARDS A PARALLAX-FREE X-RAY DETECTOR?

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IEEE-NSS Rome 04

SECONDARY SCINTILLATION IN XENON

C.A.N. Conde et al, IEEE Trans. Nucl. Sci. NS-24 (1977) 221

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IEEE-NSS Rome 04

Manufactured by CERN-EST workshops

31 cm

Large size Hexaboard for MICE (Muon Ionization Cooling Experiment):

V. Ableev et al, Nucl. Instr. and Meth. A518(2004)113

Fabio Sauli-CERN

20

IEEE-NSS Rome 04

Gas Electron Multiplier (GEM)

F. Sauli, Nucl. Instrum. Methods A386(1997)531

70 µm 140 µm

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5 MeV TRACKS AT LOW FIELD

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(PURE) XENON DRIFT VELOCITY (ONE BAR)

Fabio Sauli-CERN

23

IEEE-NSS Rome 04

ELECTRON DIFFUSION IN XENON