EVALUATION OF COHERENT AND INCOHERENT THERMAL-NEUTRON SCATTERING CROSS-SECTIONS FOR POLYCRYSTALLINE BISMUTH

A lattice-dynamical study was performed for the real and the reciprocal lattice to derive the form function and other lattice parameters necessary for calculating coherent scattering cross-sections for thermal neutrons in polycrystals of bismuth. The incoherent neutron scattering cross-sections were derived from generated scattering law data S(alpha, beta), which were calculated by the code GASKET. Both components were placed in Evaluated Nuclear Data File (ENDF) formats for further handling with the nuclear data processing system NJOY to generate pointwise cross-sections and to collapse these into multigroup data sets using a realistic weighting function. These data are needed for the calculation of neutron transport and radiation heating in a planned superthermal neutron source for the production of ultracold neutrons.