Measurements of neutron- and photon-production cross sections from heavy-ion reactions on tissue equivalent elements

Uozumi, Yusuke*; Shigyo, Nobuhiro*; Kajimoto, Tsuyoshi*; Hirabayashi, Keiichi*; Uehara, Haruhiko*; Nishizawa, Tomoya*; Satoh, Daiki   ; Sanami, Toshiya*; Koba, Yusuke*; Takada, Masashi*; Matsufuji, Naruhiro*

In the heavy-ion radiotherapy, considerable discussion has been attracted regarding the potential for second cancer induction by secondary neutrons produced from the primary heavy-ion fragmentation. It is important to measure energy-angle double-differential cross sections (DDXs) of neutron- and photon-productions in heavy-ion nuclear reactions. Since it is notoriously hard to measure the spectral cross sections of neutrons in an energy range of around 1 MeV where the RBE value reaches at its maximum. In the project by last year, experiments were carried out at the synchrotron HIMAC of NIRS, Japan. The beams were C and O of 290 MeV/u and bombarded a carbon target. In measurements of neutrons and photons were used liquid scintillator detectors of 5" and 2". We have succeeded to lower the neutron energy threshold down to 0.6 MeV. The present results for neutron productions are in reasonable agreements with PHITS. Since our goal in technical aspects has been fulfilled, measurements will be continued for other reactions.