Response Function of Active Thermal Neutron Detector for Boron Neutron Capture Therapy Using Back-Illuminated Thin Si PIN Diode

A lithium fluoride (LiF)-silicon (Si)-based neutron detector was developed for real-time measurement of neutron beams for boron neutron capture therapy (BNCT). Detection efficiencies for thermal neutrons were measured at the national standard neutron field in Japan and simulated using a Monte Carlo simulation code to evaluate the absolute BNCT neutron fluence rates. The simulation neutron detection efficiencies agreed excellently with the experimental results, within an experimental error of 3%. The simulation results reproduced well the peaks of tritons and alpha particles emitted from the 6Li(n,t)4He reaction, peak of the protons produced by the $^{14}\text{N}$ (n,p) $^{14}\text{C}$ reaction in air, and distribution of alpha particles produced by the neutron capture reactions of dopant boron. The active BNCT neutron detector was characterized based on the experimental and simulation results.