Establishing a model for the number of generated neutron using irradiated protons to a target in an accelerator-based neutron source for boron neutron capture therapy.

An accelerator-based neutron source for boron neutron capture therapy (BNCT) is installing into National Cancer Center Hospital. In clinical situations, controlling the number of generated neutron is important for BNCT in order to provide an adequate radiotherapy. The purpose of this study is to establish a model for the number of generated neutron using irradiated protons to a target in the neutron source. Experiments were performed with an accelerator-based neutron source with a solid-state Li target (Cancer Care Intelligence systems, Inc.). A maximum thermal load to the target reaches 50 kW to acquire sufficient neutrons for BNCT. According to previous studies, the thermal load induces decrement of the Li target thickness, and its decrement induces reduction of the number of generated neutron per unit of proton current. Thus, the model was established by considering the thermal loads in this study. The calculated neutron flux using the model was compared with the measured one. Mean difference and standard deviation between the calculated and the measured neutron flux was (0.0±1.0)%. The model might be able to reflect interactions between the target and protons adequately. Therefore, the accelerator-based neutron source has a potential to perform BNCT using the model.