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

J-PARCにおけるHダイバリオン探索実験のためのタイムプロジェクションチェンバーの高計数率特性

Kim, S. H.*; 市川 裕大   ; 佐甲 博之   ; 長谷川 勝一   ; 早川 修平*; 七村 拓野*; 佐藤 進  ; 谷田 聖   ; 吉田 純也; 他11名*

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.