Spectrum measurements in 15 MeV neutron therapy beams

Abstract

Energy spectra in collimated DT neutron beams have been investigated using an organic scintillator proton recoil spectrometer incorporating pulse shape discrimination against y-rays. Measurements covered the energy range 0.5-15 MeV. A Monte Carlo program was used to generate corrections for a-particles produced by neutron interactions with the carbon atoms of the scintillator which affect the spectrum below 3.5 MeV neutron energy. The influence of collimator shape and composition was investigated in geometry which simulated therapy conditions. The variations in spectrum quality were determined along the central axis and in a penumbra region in a tissue-equivalent phantom. The results are discussed with reference to DT neutron therapy.