Spectrometer design of low energy neutrons for boron neutron capture therapy

We designed a neutron spectrometer to measure low-energy neutron beam for boron neutron capture therapy (BNCT) without exchanging thicknesses of neutron moderator. The spectrometer consists of a boron carbide block as a neutron moderator and nine thin neutron silicon sensors with variable detection efficiency. Using the Monte Carlo technique, we simulated the spectrometer's neutron energy response functions. It represented sharp rise in the response functions with various lower limits of neutron energies distributed over a wide range of neutron energy from a thermal energy to a few 100 keV. The lower limit of neutron energy was dependent on a depth in the boron carbide block. By applying thicker enriched ⁶LiF neutron converter and covering the deep positioned neutron sensors with polyethylene plates, neutron detection efficiencies were increased to be able to measure the BNCT neutron beam in a short time.