Inelastic scattering of fast neutrons by chromium, nickel, yttrium, zirconium and tungsten nuclei

The authors obtained the energy spectra of neutrons undergoing inelastic scattering by chromium, nickel, yttrium, zirconium, and tungsten nuclei for five scattering angles: 30 deg., 60 deg., 90 deg., 120 deg. and 150 deg. The measurements were made with a KG-300 cascade generator using the time-of-flight method. The initial energy of the neutrons was 14.4 MeV and the resolution 3 nsec/m at the half-height of the gamma peak. Knowing the energy spectra of the inelastically scattered neutrons it was possible to determine the differential cross-section of the inelastically scattered neutrons for different spectrum energy intervals and to calculate the averaged temperature Teff on the basis of the two neutron spectra from the reactions (n, n') and (n, 2n) and the temperature T of the residual nucleus after evaporation of the first neutron - i. e. the temperature characterizing inelastic scattering in a multi-level nucleon system. On the basis of the known angular distribution of the inelastically scattered neutrons the authors determined the relationship between the contributions of direct processes, characterized by small incident neutron energy losses, and of processes involving a compound nucleus. (author)