Research of the neutron damage and measurement of the energy distribution of ray under the carbon-ion beam therapy

Yamaguchi, Mitsutaka; Torikai, Kota*; Shimada, Hirofumi*; Kawachi, Naoki; Kamiya, Tomihiro; Suzuki, Yoshiyuki*; Yoshida, Yukari*; Sato, Takahiro; Suzui, Nobuo; Fujimaki, Shu; Ishioka, Noriko; Arakawa, Kazuo*; Nakano, Takashi*

Measurement of the energy distribution of ray under the Carbon-Ion Beam Therapy environment was carried out in order to measure the background for positron annihilation ray peak in the use of in-beam monitoring. In this fiscal year, we studied the effect of the thermal neutron in the irradiation room against a CdTe semiconductor detector. Carbon-ion beam was irradiated on a water phantom and the energy spectrum of ray was measured. The 559 keV ray peak which is emitted from the neutron absorption reaction of Cd-133 are observed in the spectrum. For the case using the boron-paraffin block, the peak is clearly disappeared and the continuous component of the spectrum under the 511 keV annihilation peak decreased and the S/N ratio was refined. Neutron damage of the detector was not observed after the 20 hours use in the 108 pps beam environment.