Anisotropy in the Scattering of Thermal Neutrons in Crystalline Moderators—Beryllium Oxide

Anisotropy in the scattering of thermal neutrons from beryllium oxide has been investigated. Elastic differential scattering cross sections have been calculated by replacing the δ function occurring in the expression by a Gaussian. The effect of changing the width of the Gaussian on the differential cross section has also been studied. Anisotropy in inelastic scattering has been calculated for coherent one-phonon and incoherent one- and two-phonon processes. Using these differential cross sections, we have calculated the energy distribution of neutrons scattered along different directions by a beryllium oxide slab and these results are compared with corresponding measured results. The agreement between the two sets of results is found to be good.