1. PHOTON DETECTION AND LOCALIZATION WITH THE
GAS ELECTRON MULTIPLIER (GEM)
F. Sauli, T. Meinschad, L. Musa, L. Ropelewski
CERN, GENEVA, SWITZERLAND

2. 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. EFFICIENCY AND RESOLUTION FOR UV PHOTON DETECTION
Multi-GEM with Cesium Iodide coating on upper side of first GEM:
Hydrogen UV lamp R C HV r
ADCs T0
Collimator-attenuator
Quartz window
(inverted) drift field grid
GEM1 CsI-coated
GEM2
GEM3
Anode strip readout

4. SINGLE PHOTON DETECTION
Pulse height spectra at decreasing UV source intensity:
Multiple photoelectron spectra:
Single photoelectron spectra:
BEAM ATTENUATION

5. SINGLE PHOTOELECTRON POSITION ACCURACY:
Two positions of collimated beam 200 µm apart
200 µm
160 µm FWHM
Beam ~ 100 µm FWHM
Intrinsic accuracy
~ 50 µm rms
T. Meinschad, L. Ropelewski and F. Sauli, Vienna Conference (Nucl. Instr. and Methods, in press)

6. U V W 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

7. Standard assembly for 10x10 cm2 GEMs, 3x128 strips
HEXABOARD DETECTOR
Standard assembly for 10x10 cm2 GEMs, 3x128 strips
3x16 strips readout: fast charge amplifier+ALTRO (FADC, 10 bit-25 MHz sampling)
16 strips
8.3 mm
ALTRO:
B. Mota et al,
Nucl. Instr. and Methods,
in press (2004)

8. SINGLE PHOTON EVENT:
16 strips
8.3 mm

9. SINGLE PHOTON CLUSTER WIDTH (rms)
~ 0.5 pads (250 µm)
Charge sharing (520 µm pad rows)

10. 1.1 mm
2.4 mm
1.3 mm
DOUBLE PHOTON EVENT:

11. CHARGE CORRELATION BETWEEN THE PROJECTIONS:
SINGLE PHOTON CLUSTERS
U-V
W-U
V-W

12. DETECTION OF INTERNAL SCINTILLATION IN XENON
CsI - Quad-GEM in pure Xenon
Scintillation
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)

13. PRIMARY SCINTILLATION IN XENON-CsI
22 keV from 109Cd
Primary scintillation

14. TIME DIFFERENCE PROMPT- MAIN PULSE
LOW DRIFT FIELD: PRIMARY SCINTILLATION
Efficiency
2% for 5.9 keV
10% for 22 keV

15. HIGH DRIFT FIELD: SECONDARY SCINTILLATION

16. 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

17. 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?

18. SECONDARY SCINTILLATION IN XENON
C.A.N. Conde et al, IEEE Trans. Nucl. Sci. NS-24 (1977) 221

19. 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

20. Gas Electron Multiplier (GEM)
F. Sauli,
Nucl. Instrum. Methods A386(1997)531

21. 5 MeV a TRACKS AT LOW FIELD

22. (PURE) XENON DRIFT VELOCITY (ONE BAR)

23. ELECTRON DIFFUSION IN XENON