P oS(TIPP2014)300 Development of a GEM-based TPC for H-dibaryon Search at J-PARC

for the J-PARC-E42 Collaboration We developed a TPC using GEMs and a gating grid to search for the H-dibaryon at J-PARC with high rate hadron beams up to 106 count per second (cps) / cm2. The TPC consists of an octagonal-shape drift cage filled with Ar-CH4 (90:10) gas, and an end cap detector consisting of a gating grid, a triple GEM stack, and readout pads. The TPC is operated in the magnetic field of 1 T. We built a small prototype TPC and performed tests. The hit position shift due to ion backflow was suppressed within 0.2 mm at the beam rate up to 5 × 105 cps/cm2. The hit detection efficiency was better than 90 % up to the beam rate of 3 × 106 cps/cm2. The horizontal position resolution was improved by 40−50 % in the magnetic field from 0 to 0.68 T at a laser test