Study on the under-surgery neutron irradiation field using near-threshold 7Li(p, n)7Be neutrons. Application of accelerator for boron neutron capture therapy

Nuclear reaction 7Li(p, n)7Be using 2.5 MeV proton has been investigated in research fields of neutron source for accelerator-based neutron capture therapy considering neutron yield and spectrum. The nuclear reaction using proton of near-threshold energy (1.881 MeV), however, is discussed in Western countries, recently. Epithermal neutrons (0.5 eV-10 keV) which need for neutron capture therapy are able to generate effectively by a small moderator system, although the maximum energy of neutron and the neutron yield caused by the proton of near-threshold energy decrease. Benchmark experiments carried out with acceleration voltage 1.89 MV and average proton current 330 μA. The depth dose distributions of epithermal neutron in water phantom are measured by the saturated activity of gold wire with and without Cd cover. The surface dose distributions of water phantom are able to control by adjusting the distance between Li target of proton and the surface of water phantom. The depth dose distributions are calculated by monte carlo code MCNP-4B for comparison with the measured values. (M. Suetake)