MEASUREMENTS OF 14-MeV NEUTRON TRANSMISSION THROUGH LITHIUM HYDRIDE LAYERS BY NEUTRON ACTIVATION ANALYSIS

The paper presents the results of experiments in 14-MeV neutron transmission through lithium hydride layers 25 cm thick. Measurements were performed by neutron-activation analysis using NG-12I neutron generator. The neutron generator operated in static mode. In order to determine 14-MeV neutron transmission through sample layers and to evaluate neutron spectrum changes we have used neutron-activation detectors based on the following activation reactions: 19F(n,2n)18F, 27Al(n,α)24Na, 64Zn(n,p)64Cu, 115In(n,n')115mIn, 65Cu(n,2n)64Cu, 63Cu(n,γ)64Cu. The activity of irradiated neutron-activation detectors was measured by the gamma-spectrometer with a semiconductor HPGe-detector. Neutron yield from the generator target was determined by monitor readings with fluoroplastic neutron-activation detector. The average 14-MeV neutron flow from the target came up to ~1010 n/s. The experimental geometry and measurement results are described. Based on measurement data we determined the number of reactions for each neutron-activation detector, as well as coefficients of 14-MeV neutron transmission through lithium hydride layers of different thickness. The obtained results can be used to validate neutron-physical calculations and to update neutron constant libraries.