Characterization of a real-time neutron detector for boron neutron capture therapy using a thin silicon diode

A real-time neutron detector was developed to measure an intense neutron beam, based on both a thin silicon sensor and an extremely thin neutron converter for boron neutron capture therapy (BNCT). Neutron response function and detection efficiency were evaluated at the BNCT facility. The response function consists of neutron events, detecting both triton particles produced from the Li-6 (n,t)He-4 reaction and alpha particles from the B-10 (n,alpha)7Li reaction. The detector is able to clearly separate the BNCT neutron beam from coexisted gamma rays. A depth distribution of slow neutron flux in an acrylic block was experimentally obtained. While the relative depth distribution of over 20 mm in depth is in line with the results of the neutron activation measurements of gold, the absolute values are around 17% smaller than the corresponding neutron activation results, which was due to the incomplete evaluation of the neutron detection efficiency and angular-dependent response of the neutron detector.