Commissioning of a portable ionization chamber at high counting rate using heavy ion beams

A fast ionization chamber with a high counting rate was commissioned at the 8 MV tandem accelerator complex of Kyushu University in Japan. Heavy ion beams consisting of 12C and 16O with Ebeam = 36 MeV were used to investigate the detector performance. By using various beam intensities ranging from 103 to 106 particles per second (pps), the maximum counting rate of the ion counter was measured to be about 8 × 105 pps. The detector performance under different gases was also investigated using two common gases in the ionization chamber: isobutane and P-10 gases. The results show that the negative effects due to pileups, which are often observed at high counting rates, can be greatly reduced when P-10 gas is used.