Neutron intensity monitor with activation foil for p-Li neutron source for BNCT – Feasibility test of the concept

Abstract

Proton-lithium (p-Li) reaction is being examined worldwide as a candidate nuclear production reaction for accelerator based neutron source (ABNS) for BNCT. In this reaction, the emitted neutron energy is not so high, below 1MeV, and especially in backward angles the energy is as low as about 100keV. The intensity measurement was thus known to be difficult so far. In the present study, a simple method was investigated to monitor the absolute neutron intensity of the p-Li neutron source by employing the foil activation method based on isomer production reactions in order to cover around several hundreds keV. As a result of numerical examination, it was found that 107Ag, 115In and 189Os would be feasible. Their features found out are summarized as follows: 107Ag: The most convenient foil, since the half life is short. 115In: The accuracy is the best at 0°, though it cannot be used for backward angles. And 189Os: Suitable nuclide which can be used in backward angles, though the gamma-ray energy is a little too low. These would be used for p-Li source monitoring depending on measuring purposes in real BNCT scenes.