Development of a Time Projection Chamber (TPC) using Gas Electron Multiplier (GEM) for use as an active target

A Time Projection Chamber (TPC) for use as an active target has been developed. The TPC is used for nuclear experiments using unstable nuclear beam and is intended to measure a recoil nucleus in forward scattering whose energy is very small. It is designed to have two field cages and beams pass between the cages in order to decrease distortion of the electric field inside the TPC due to the ions created along the beam track. A Gas Electron Multiplier (GEM) is utilized for signal amplification. A performance test was carried out using ⁴ He²⁺ with 7.5 MeV/u in 12UD Pelletron tandem accelerator at the University of Tsukuba Tandem Accelerator Center. From the test, energy resolution of 4%, position resolution of 80 μm in the drift direction and of less than 700 μm in the transverse direction were obtained.