The Gamma Rays Associated with the Inelastic Scattering of 14 Mev Neutrons in Large Samples of Iron and Concrete

Abstract

Iron and concrete will be used in fusion reactors and multiple scattering processes are important. The angular distribution of gamma rays following inelastic scattering of 14 MeV neutrons in iron and concrete have been measured. An associated particle time of flight system was used to gate the gamma ray signals. The 14 MeV neutrons were produced by the T(d,n)4He reaction. The neutron flux was monitored by counting the alpha particles associated with the neutrons. The gamma rays were detected by a Nal(Tl) scintillator mounted on a 56 AVP photo-multiplier tube. The samples varied in thickness from 2cms to 10.5cms. The differential cross-sections between 20° and 90° were measured. The increase in cross-sections a due to multiple scattering effects was found to obey the law σ = σoeαx where x is the sample thickness in mean free paths and α has an average value of 0.35 (mean free paths)−1. The concrete results show that the angular distributions are strongly anisotropic.