F.Sauli, T.Meinschad, L.Musa, L.Ropelewski

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PHOTON DETECTION AND LOCALIZATION WITH THE GAS
ELECTRON MULTIPLIER (GEM)
F. Sauli, T. Meinschad, L. Musa,
L. Ropelewski CERN, GENEVA, SWITZERLAND
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REFLECTIVE PHOTOCATHODE ON UPPER GEM SIDE no
photon feedback
MULTIGEM DETECTORS VERY HIGH GAINS Single
photoelectron detection with internal
photocathode
R. Bouclier et al, IEEE Trans. Nucl. Sci.
NS44(1997)646
S. Bachmann et al, Nucl. Instr. Methods A
443(1999)464
D. Mörmann et al, Nucl. Instr. Methods
478(2002)364
3
T0
Collimator-attenuator
Quartz window
(inverted) drift field grid
GEM1 CsI-coated
GEM2
GEM3
Anode strip readout
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SINGLE PHOTON DETECTION Pulse 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
T. Meinschad, L. Ropelewski and F. Sauli, Vienna
Conference (Nucl. Instr. and Methods, in press)
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GEM RICH MULTIPLE PHOTONS
Hexaboard closeup 520 µm Ø pads
Hexaboard readout matrix of hexagonal pads
interconnected along three projections at 120º
U
V
W
S. Bachmann et al Nucl. Instr. and Meth. A 478
(2002) 104
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HEXABOARD DETECTOR Standard assembly for 10x10
cm2 GEMs, 3x128 strips
3x16 strips readout fast charge amplifierALTRO
(FADC, 10 bit-25 MHz sampling)
ALTRO
B. Mota et al, Nucl. Instr. and Methods, in
press (2004)
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SINGLE PHOTON EVENT
16 strips 8.3 mm
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SINGLE PHOTON CLUSTER WIDTH (rms)

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

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DOUBLE PHOTON EVENT
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CHARGE CORRELATION BETWEEN THE PROJECTIONS
SINGLE PHOTON CLUSTERS
U-V
W-U
V-W
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DETECTION OF INTERNAL SCINTILLATION IN XENON
CsI - Quad-GEM in pure Xenon
X-ray
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)
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PRIMARY SCINTILLATION IN XENON-CsI
22 keV from 109Cd
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TIME DIFFERENCE PROMPT- MAIN PULSE
LOW DRIFT FIELD PRIMARY SCINTILLATION
Efficiency 2 for 5.9 keV 10 for 22 keV
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HIGH DRIFT FIELD SECONDARY SCINTILLATION
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TIME DIFFERENCE PROMPT- MAIN PULSE HIGH 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
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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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SECONDARY SCINTILLATION IN XENON
C.A.N. Conde et al, IEEE Trans. Nucl. Sci. NS-24
(1977) 221
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Large size Hexaboard for MICE (Muon Ionization
Cooling Experiment)
Manufactured by CERN-EST workshops
31 cm
V. Ableev et al, Nucl. Instr. and Meth.
A518(2004)113
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Gas Electron Multiplier (GEM)
70 µm
140 µm
F. Sauli, Nucl. Instrum. Methods A386(1997)531
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5 MeV a TRACKS AT LOW FIELD
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(PURE) XENON DRIFT VELOCITY (ONE BAR)
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ELECTRON DIFFUSION IN XENON