Hiroyuki Sekiya Oct. 4 th 2007 Hamamatsu, JAPAN NNN07 Development of Gaseous Photomultiplier with GEM/μPIC Hiroyuki Sekiya ICRR, University of Tokyo Abstract: We are developing a new photon detector with gas amplification devices. The transmissive CsI photocathode is combined with 10cm×10cm GEM/μPIC for the first prototype which is aimed to apply to the large liquid Xe detectors. Using Ar+C 2 H 6 (10%) gas, we achieved the gas gain of 10 5 which is enough to detect single photoelectron. We, then, irradiate UV photons with the Excimer Xe lamp to the prototype detector and we successfully detected the UV photons. 1.Motivation Recently, large area micro pattern gaseous detectors such as GEM, Micromegas, and μPIC have been developed and successfully operated. 30cmGEM 30cmμ-PIC These devices with photocathode can realize a gaseous photomultiplier for future large volume detectors. Possible features Large area Low cost Small volume Position resolution Low background Handling the 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 MgF 2 54Φ×5t Al electrode (edge10mm) CsI evaporated by HPK GEM μPIC 10cmGEM 10cmμ-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 operation Gas: Ar ＋ C 2 H 6 （ 90 ： 10 ） 1atm 3.Gas Gain Measurement In the beginning, the gas gain of the detector was examined. 10 MΩ 20 MΩ 1MΩ 100pF 500MΩ 20μmAl 6mm 2mm 6mm 12mm -HV 20 MΩ +HV -HV 100pF 5.9keV Xrays of 55 Fe were irradiated Signals Charge amplifiers were used. CP581(11V/pC) for GEM2 CP515-1(5V/pC) for μPIC 0.3kV/cm gas gain =600 gas gain =600 GEM2 μPIC cathode μPIC cathode Results GEM HV dependence μPIC HV dependence Although the signals were saturated, 400V was successfully applied to the μPIC without any discharges → Stable operation with the gain of Output of the amplifier was saturated. Can still apply higher HV. 4.Light Detection The UV light test was conducted with a Xe 2 ∗ Eximer Lamp. (Ushio H0016) 1mmΦcollimater low gas gain(=600) operation without charge amplifiers GEM2 μPIC cathode 2mV 100μs 137 Cs 662keV irradiation Air leak to the path Light OFF 10mV 100μs 10mV 100μs Light ON! GEM2 μPIC cathode 18kHz Oscillation was observed!Light attenuation was confirmed. Amplitude became 1/4 λ mean =172nm 18kHz dielectric disharge Too strong intensity Ion feedback 5.Conclusions and Prospects References [μPIC] A.Takada et al., Nucl. Instr. and Meth A. 573 (2007) 195 [GEM/SMASH] SciEnergy Co., Ltd. [This detector] H.Sekiya, Proc. of the International Workshop on new Photon- Detectors, Proceedings of Science, PoS(PD07)028 The gas gain of 10 5 with the suppression of ion feedback flow is achieved, which enable the detection of single photo-electron. The UV light was successfully detected. → A milestone in the realization of 10cm-size gas PMTs Many additional tests such as the uniformity, the longtime stability, the detection efficiency should be conducted. 10cm size transmissive/reflective photocathodes will be tested. Bialkali photocathodes for visible light will be developed. 25μm Mylar ® tape window (only for this measurement)