The 209Bi(nth, )210Bi and 209Bi(nth, )210m,gBi Cross Sections Determined at the Budapest Neutron Centre

Abstract

The neutron total capture cross section of 209Bi together with the cross sections to the ground state and the isomeric state were determined at the cold neutron beam PGAA-NIPS facilities at the Budapest Neutron Centre. For the measurements we used a coaxial HPGe detector with Compton suppression. The partial gamma-ray production cross sections were deduced relative to the partial capture cross section for the 4055 keV transition following 209Bi(n, gamma). This partial cross section was measured with a bismuth nitrate sample with respect to nitrogen as a comparator. The total capture cross section resulting from the primary transitions is lower than the one deduced from the transitions feeding the isomeric and the ground state. Since the multipolarity of the main transition feeding the ground state is not known, the uncertainty on the capture cross section to the ground state is rather large. We also compare the total capture thermal cross section with the value deduced from resonance parameters and discuss the impact of the branching ratio on the analysis of prompt capture cross section measurements using the total energy detection principle.