Accelerator based neutron source for boron neutron capture therapy

This paper describes the current state of acceleration neutron sources for boron neutron capture therapy (BNCT), and introduces cyclotron-based epithermal neutron source at the Kyoto University reactor. The accelerator neutron sources for BNCT are classified by the energy of protons or deuterons used in reaction and acceleration, as well by the type of targets. The classification by the energy is as follows; (1) D-D, D-T fusion reaction, (2) low-energy protons (< 3 MeV), (3) medium energy protons (3 MeV < proton energy < 11 MeV), and high energy protons (>11 MeV). In (2), electrostatic accelerator or high-frequency accelerator is used, and a system using lithium as a target is studied. In (3), a system using beryllium as a target is studied. In (4), neutron sources using a tungsten or beryllium target have been proposed. In the cyclotron-based epithermal neutron sources in the Kyoto University reactor, by paying attention to 30 MeV proton projectile beryllium reaction, high energy neutrons are decelerated and shaped to the epithermal neutrons suitable for medical treatment. The deceleration system is composed of lead and iron, fast neutrons up to 28 MeV are decelerated with small absorption. The shaping system is composed of aluminum and calcium fluoride, and they are shaped in the epithermal neutron region. The spectrum obtained by the accelerator has a peak of 10-20 keV, and harder than the spectrum of the Kyoto University reactor neutron. Epithermal neutron flux is higher in the accelerator neutron sources by about 1.5 times. (A.O.)