High-rate performance of a time projection chamber for an H-dibaryon search experiment at J-PARC

Kim, S. H.*; Ichikawa, Yudai   ; Sako, Hiroyuki   ; Hasegawa, Shoichi   ; Hayakawa, Shuhei*; Nanamura, Takuya*; Sato, Susumu  ; Tanida, Kiyoshi   ; Yoshida, Junya; 11 of others*

We have developed a gas electron multiplier (GEM)-based time projection chamber (TPC) for the H-dibaryon search experiment at J-PARC. High-rate beam particles enter a TPC gas volume of approximately 0.2 m, in a direction perpendicular to the electric field. A long-rectangular hollow section is located inside the TPC volume to accommodate a diamond target. We commissioned the TPC using 230 MeV protons with beam rates of up to 1 MHz. The TPC data acquisition system collected 5768 pad signals in full readout mode, with almost 100% efficiency, at a preset trigger rate of 230 Hz. We operated the TPC in an Ar/CH gas mixture (90/10) without a magnetic field. The spatial resolutions on the pad plane are measured to be 400-700 m, which correspond to 230-300 m in a magnetic field of 1 T. We confirmed high tracking capability at beam rates of up to 1 MHz.