NEUTRON SPECTROMETRY AND DOSIMETRY FOR BORON NEUTRON-CAPTURE THERAPY

Techniques are described that are used for neutron energy spectrometry of beams of intermediate energy neutrons being set up for boron neutron capture therapy (BNCT) research. These include high resolution proton and alpha recoil spectrometry (in the energy range from 10 keV to 15 MeV), activation detectors and spectrum modification using a variety of scattering materials. As an example, results of measurements made recently on the HB11 filtered beam in the JRC, Petten, High Flux Reactor (HFR) are given. The total fluence rate in this beam (determined from activation detector measurements) is 4.95 x 10(8) cm-1.s-1, which corresponds to a neutron kerma rate in tissue of 1.59 Gy.h-1. In the energy range above 10 keV, the fluence rate is only 0.912 x 10(8) cm-1.s-1 (about a fifth of the total), but corresponding to over 92% of the total neutron kerma rate in tissue. Consequently, these measurements highlight the importance of making high resolution spectrum measurements using recoil counters for BNCT beams.