The Study of Gamma-Rays Associated with Fast Neutron Interactions in Extended Assemblies

Abstract

The thesis is written in two parts. The first part describes the experimental measurements on the ϒ-rays emitted following the inelastic scattering of 14 MeV neutrons in both small and extended samples of the possible fusion reactor materials Iron and LiF. The source neutrons were produced by the 3H (ad,n) 4He reaction at an incident deuteron energy of 120 Kev using a S.A.M.E.S. type J accelerator. The ϒ-rays were detected using a shielded NaI(T1) scintillation counter and the spurious background was reduced by suitably gating theϒ-ray signals by a time of flight system based on the detection of the 4He-particle associated with the instant of neutron production. Differential ϒ-ray production cross—sections were measured for the small samples, the results of which were analysed using a least squares fit and were used as a control with which to compare the differential cross-section measurements for the extended samples. In each case the results are compared with the predictions of a Monte Carlo type of calculation which took into account multiple neutron scattering and Compton degradation of the ϒ-ray energy at various angles to the neutron beam direction. The second part of the thesis is concerned with a detailed feasibility study of the possible implementation of a similar experiment on the 3 MeV Dynamitron using neutrons from the D(d,n) 3He reaction. The detection of the 3He-particles in the presence of large numbers of scattered deuterons is considered and a design for a suitable magnetic discriminator system is presented. The suitability of various deuterium targets is considered and an experimental investigation into the behaviour of a heavy ice target is shown to be promising. A complete design for a suitable experimental arrangement is given.