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: Gd-155 and Gd-157. We measured the gamma-ray spectra produced from the thermal neutron capture on targets comprising a natural gadolinium film and enriched Gd-155 (in Gd2O3 powder) in the energy range from 0.11 MeV to 8.0 MeV, using the ANNRI germanium spectrometer at MLF, J-PARC. The freshly analyzed data of the Gd-155(n,gamma) reaction are used to improve our previously developed model (ANNRI-Gd model) for the Gd-157(n,gamma) reaction [K. Hagiwara et al. [ANNRI-Gd Collaboration], Prog. Theor. Exp. Phys. 2019, 023D01 (2019)], and its performance confirmed with the independent data from the Gd-nat(n,gamma) reaction. This article completes the development of an efficient Monte Carlo model required to simulate and analyze particle interactions involving the thermal neutron captures on gadolinium in any relevant future experiments.