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12-16 September 2005
University of Liverpool
Europe/Zurich timezone

Micro Pixel Chamber Operation with Gas Electron Multiplier

14 Sep 2005, 10:15
University of Liverpool

University of Liverpool

Greenbank Conference Park
Contributed Talk New Gas-based Tracking Detectors S7 : Novel Photon Detection Systems


Mr Kaori Hattori (Cosmic Ray Group, Dept. of Physics, Kyoto Univ.)


We are developing a micro-Time Projection Chamber (micro-TPC) based on a micro-pixel chamber (μ-PIC). A Micro-TPC is employed for an electron-tracking Compton camera [1,2]. A μ-PIC is a fine pixel-type two-dimensional imaging detector with a pixel pitch of 400μm and it has a detector area of 10×10cm2. We achieved a maximum gas gain of 15,000 and stable operation over 1,000 hours at a gas gain of 5,000. However, the stable gas gain of 5,000 is not high enough for detecting Compton-recoil electrons, dE/dx of which are the same as that of minimum ionizing particles (MIPs). A required gas gain for MIP detection is 2 – 4 times as large as the achieved one. Therefore, a hybrid detector consisting of a μ-PIC and a gas electron multiplier (GEM) is employed for realizing the required gain. A GEM is installed just above a μ-PIC and operated at a low gas gain (less than 50). We plan to use a GEM temporarily until a gas gain of a μ-PIC reaches the aimed gas gain alone by improvements of the electrode structure and manufacturing process. We used a GEM developed by Center for Nuclear Study, the University of Tokyo. The GEM consist of 50μm a thick kapton foil, and copper clad on each side, 70μm holes arranged with 140μm between centers, with detection area of 10×10cm2. Operating a μ-PIC at a gas gain of 2.5×103, we achieved a maximum total gas gain of more than 105, and energy resolution of 1.2keV (21%) FWHM at 5.9keV (at a gas gain of 3.3×104). Long-term stability over 170 hours was also confirmed at a total gas gain of 2.0×104 (the μ-PIC was operated at a gas gain of 2.0×103, the GEM at 10). We achieved enough stable gain to detect MIPs and detected cosmic ray muons by micro-TPC. The ion feedback was suppressed to less than 10%, when GEM was operated at a gas gain of 10, which enables us to detect tracks of particles at higher rates. Now we are developing a larger μ-PIC with a detection area of 30×30cm2 and GEM with that of 28×25cm2. The larger hybrid detector will increase detection efficiency of detecting charged particles, and enable us to measure longer tracks.

Primary author

Mr Kaori Hattori (Cosmic Ray Group, Dept. of Physics, Kyoto Univ.)

Presentation materials