Gamma Ray Spectra from Thermal Neutron Capture on Gadolinium-155 and Natural Gadolinium

Natural gadolinium is widely used for its excellent thermal neutron capture cross section, because of its two major isotopes: $^{rm 155}$Gd and $^{rm 157}$Gd. We measured the $gamma$-ray spectra produced from the thermal neutron capture on targets comprising a natural gadolinium film and enriched $^{rm 155}$Gd (in Gd$_{2}$O$_{3}$ powder) in the energy range from 0.11 MeV to 8.0 MeV, using the ANNRI germanium spectrometer at MLF, J-PARC. The freshly analysed data of the $^{rm 155}$Gd(n, $gamma$) reaction are used to improve our previously developed model (ANNRI-Gd model) for the $^{rm 157}$Gd(n, $gamma$) reaction, and its performance confirmed with the independent data from the $^{rm nat}$Gd(n, $gamma$) reaction. This article completes the development of an efficient Monte Carlo model required to simulate and analyse particle interactions involving the thermal neutron captures on gadolinium in any relevant future experiments.