NEUTRON INELASTIC SCATTERING CROSS SECTIONS FOR Ni AND Cr DETERMINED FROM THE (n,n'γ) REACTION
Department of Electrical Engineering
Akita National College of Technology
Iijima, Akita-shi 011, Japan
Department of Nuclear Engineering, Tohoku University
Aramaki Aoba, Sendai, Miyagi-ken 980, Japan
Absolute 125-deg differential gamma-ray production cross sections have been measured for about 400 gamma rays produced in natural nickel and chromium by the (n,n'γ) reaction in the incident neutron energy range from 4.1 to 5.6 MeV. Gamma-ray yields were measured by a 80 cm3 high purity Ge detector housed in a lead shield surrounded by lithium carbonate and boric acid. The pulsed beam time-of-flight (TOF) techniques was used for background reduction. Angle-integrated gamma-ray production cross sections were inferred from the differential measurements using gamma-ray angular distributions obtained from compound nucleus statistical model calculations. On the basis of the angle-integrated cross sections and measured branching ratios, neutron inelastic scattering cross sections were deduced for 28 and 40 energy levels in natural nickel and chromium, respectively. These results are compared with the evaluated nuclear data files, JENDL-3 for Cr and ENDF/B-IV for Ni. The present measurements indicate that for inelastic scattering to the second excited state (4+) in Cr-52 and Ni-58, the cross sections are significantly overestimated in the evaluated nuclear data files.
KEYWORDS: Nuclear reaction Ni(n,n'γ) and Cr(n,n'γ), σ(n,n'γ), deduced levels, high purity Ge detector, natural targets.