Post on 23-Feb-2016
description
Hiroyuki Sekiya Jul. 31st 2008, Philadelphia, ICHEP2008
Development of Gaseous Photomultiplierwith GEM/μPIC Hiroyuki Sekiya ICRR, University of Tokyo
E-mail: sekiya@icrr.u-tokyo.ac.jp
Abstract: We are developing a new photon detector with gas amplification devices. A semitransparent CsI photocathode is combined with 10cm×10cm GEM/μPIC for the first prototype which is aimed for the large liquid Xe detectors. Using Ar+C2H6
(10%) gas, we achieved the gas gain of 105 which is enough to detect single photo-electron. We, then, irradiated UV photons from a newly developed solid scintillator, LaF3(Nd), to the detector and successfully detected single photo-electron.
1.MotivationRecently, large area micro pattern gaseous detectors such as GEM, Micromegas, and μPIC have been developed and successfully operated. 30cmGEM30cmμ-PIC
These devices with photocathode can realize a gaseous photomultiplier for future large volume detectors.
Possible features Large areaLow costSmall volume
Position sensitiveLow background
Handling bialkali photocathodes requires special equipments,
therefore, we use the CsI for the first step. In particular, the quantum efficiency of the CsI matches the liquid/gas Xe scintillators; thus, dark matter and neutrino experiments are the targets of this photon detector.
2.Prototype Detector
Window/photocathode
•MgF2 54Φ×5t•Al electrode (edge10mm)•CsI evaporated by Hamamatsu
GEMμPIC
10cmGEM10cmμ-PIC
•Advanced MSGC•PCB technology (Toshiba, DNP)•10cm×10cm•256×256 strips merged to 4×4
Structure of μ-PIC
400μm
anode
cathode
•SMASH (plasma etched GEM) (SciEnergy Co., Ltd.)•100μm Liquid Crystal Polymer•10cm×10cm•140μm pitch, 70μm Φ
2GEMs + μPIC System for suppression ion/photon feedback high gain operationGas: Ar + C2H6 ( 90 : 10 ) 1atm
6.Conclusions and ProspectsSuccessfully operated with the stable gas gain of 105 .UV lights from LaF3(Nd) were detected. Has enough sensitivity to single photo-electron.The quantum efficiency of this semitransparent photocathode is 2% as expected.To increase the QE, a reflective photocathode (300nm-thick CsI evaporated to one side of GEM ) is tested now.
Many additional tests such as the uniformity, the longtime stability, and the detection efficiency should be conducted.
w
4. LaF3(Nd) – VUV source
• For liquid Xe : UV enhanced bialkali photocathode• QE ~ 30%@172nm
Response to the “SLS “
Reference Detector PMT R8778 (Hamamatsu)
•λpeak =172nm •100 photons/MeV(gamma)•100 photons/241Am (5.5MeV α) →”Standard Light Source”
150 160 170 180 190 200 210 220 230 240 250 260
10.90.80.70.60.50.40.30.20.10.0
wavelength(nm)
Newly developed VUV scintillator (Yoshikawa grope, IMPAM, Tohoku Univ.) Optical spectrum
-1300V gain =2.2x106
wavelength(nm)160 180 200 220 240 260
100
10
1
QE (by Hamamatsu )
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5.Performance for VUV
Typical signal after 1V/pC charge amplifier
“SLS” attached to the MgF2 window of the prototype detector
120mV/1V×1pC/(1.602×10-19pC)/ (2.6×105)
=2.9 p.e signal
gain =2.6x105
spectrum in p.e. spectrum in mV
•Has sensitivity to 1p.e. •QE is about 2% as expected.
3.Electron multiplication The gas gain of the detector was examined with 5.9keV Xray
10 MΩ
20 MΩ
1MΩ
100pF
500MΩ
20μmAl
6mm
2mm
6mm
12mm-HV
20 MΩ
20 MΩ
+HV
-HV
100pF
55Fe
0.3kV/cm
0.3kV/cm
Results
Stable operation with the gain of 2.6 ×105 was achieved without any discharges
The uPIC which is not good one (reused, old product ) limit the gain.
25μm Mylar ® tape window (only for this measurement)
gas gain =10000
Typical Spectrum
[μPIC] A.Takada et al., Nucl. Instr. and Meth A. 573 (2007) 195[GEM/SMASH] SciEnergy Co., Ltd. http://www.scienergy.jp[This detector] H.Sekiya, Proc. of the International Workshop on new Photon-Detectors, Proceedings of Science, PoS(PD07)028
References
30 % @172nm
wavelength(nm)
ref. CsIB.K. Singh et al., NIMA 581(2007) 651
QE
(%)
wavelength(nm)
trans. CsI
172
Hamamatsu catalog
2 % @172nm
QE(%)
Au-plated GEM for CsI evaporation
120mV