Development of the photonuclear reaction model in the PHITS code

Noda, Shusaku; Hashimoto, Shintaro  ; Sato, Tatsuhiko   ; Fukahori, Tokio  ; Chiba, Satoshi*; Niita, Koji*

Medical linac is commonly used in photonthereapy. High energy photons can induce the photonuclear reaction generating proton and neutrons. Improvement of the PHITS code is needed to accurately estimate the dose rate for the human body. In this study, we developed the PHITS code to applicable to the incident photon energy of 140 MeV; (1) adopted the evaluated photonuclear data file (JENDL/PD-2004), (2) improved the evaporation model for the light nuclei excited by photon, (3) developed the quasideuteron process in the JAERI Quantumn Molecular Dynamics (JQMD) model. Owing to these improvements, PHITS can handle the photonuclear reaction against the incident photon energy below 140 MeV. As an example, the photon-induced proton/neutron-emission cross sections are well reproduced using improved PHITS.