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: 155Gd and 157Gd. We measured the γ-ray spectra produced from the thermal neutron capture on targets comprising a natural gadolinium film and enriched 155Gd (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 155Gd(n, γ) reaction are used to improve our previously developed model (ANNRI-Gd model) for the 157Gd(n, γ) 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 natGd(n, γ) 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.