Prompt gamma rays of terbium induced by inelastic scattering of fission neutrons

Abstract

Prompt gamma rays of terbium emitted after (n,nʹγ) inelastic scattering reactions induced by irradiation of a terbium(III) hexahydrate (TbCl3·6H2O) sample with a beam of fission neutrons were investigated with the instrument FaNGaS (Fast Neutron-induced Gamma-ray Spectrometry) at an angle of 90° between neutron beam and detector. At sample position, the fast-neutron flux was 1.13 × 108 cm−2 s−1 and the neutron beam has an average energy of 2.30 MeV. We identified 124 prompt gamma lines from the 159Tb(n,nʹγ)159Tb reaction. Presence of prompt gamma rays from oxygen and chlorine was used for a concise verification of recently published results. Relative gamma-ray intensities, effective cross sections and fast-neutron spectrum-averaged partial production cross sections of the gamma lines are given including comparisons with available literature data. We found a reasonable agreement and the multitude of unreported lines adds decisive value to nuclear spectroscopy. Additionally, we estimated the detection limit of terbium as 1 mg for a counting time of 12 h.