Gamma-Ray Cross Section Standards in the MeV Energy Range and 56Fe Inelastic Scattering

An accurate knowledge of neutron-induced -ray production cross sections is important in enabling the determination of absolute cross sections from relative measurements of -ray yields. Such data have a variety of uses, for example, in determining reaction cross sections for activation of materials used as integral neutron flux detectors, and in measuring photon production necessary to evaluate -ray heating in nuclear systems. Such data also find application in neutron-induced -ray detection and assay systems and in planetary exploration where cosmic-ray-neutron-induced photon production is used to determine elemental composition of soils. In our work using the GEANIE -ray spectrometer at the WNR facility of LANSCE, we observed discrepancies outside of the error estimates for evaluations of the natFe(n,n1) cross section for the 847-keV ray and for other reactions that are taken as standards. We have performed measurements relative to the natCr(n,n1) 1434-keV ray absolute cross section measurements using the 235U(n,f) and 238U(n,f) reactions to determine the neutron fluence.