Inspection of ⁵⁶Fe γ-Ray angular distributions as a function of incident neutron energy using optical model approaches

¹ Department of Physics, U.S. Naval Academy, 21666 Annapolis, Maryland, USA
² Department of Chemistry, University of Kentucky, 40506 Lexington, Kentucky, USA
³ Department of Physics, University of Dallas, 75062 Irving, Texas, USA
⁴ Department of Physics & Astronomy, University of Kentucky, 40506 Lexington, Kentucky, USA

^a e-mail: vanhoy@usna.edu
^b e-mail: ap.ramirez@uky.edu
^c e-mail: hicks@udallas.edu

Published online: 13 September 2017

Abstract

Neutron inelastic scattering cross sections measured directly through (n,n) or deduced from γ-ray production cross sections following inelastic neutron scattering (n,n^′γ) are a focus of basic and applied research at the University of Kentucky Accelerator Laboratory (www.pa.uky.edu/accelerator). For nuclear data applications, angle-integrated cross sections are desired over a wide range of fast neutron energies. Several days of experimental beam time are required for a data set at each incident neutron energy, which limits the number of angular distributions that can be measured in a reasonable amount of time. Approximations can be employed to generate cross sections with a higher energy resolution, since at 125^o, the a₂P₂ term of the Legendre expansion is identically zero and the a₄P₄ is assumed to be very small. Provided this assumption is true, a single measurement at 125^o would produce the γ-ray production cross section. This project tests these assumptions and energy dependences using the codes CINDY/SCAT and TALYS/ECIS06/SCAT. It is found that care must be taken when interpreting γ-ray excitation functions as cross sections when the incident neutron energy is < 1000 keV above threshold or before the onset of feeding.