Measurement of thermal neutron cross section and resonance integral for the 170Er(n, γ)171Er reaction by using a gold monitor

Abstract

The thermal neutron cross section (σ0) and the resonance integral (I0) of the reaction 170Er(n,γ)171Er were measured by an activation method using a reaction 197Au(n,γ)198Au as a single comparator. The high-purity natural erbium (natEr) and gold (197Au) foils with and without Cd cover with the thickness of 0.5mm were irradiated in a neutron field of the Pohang neutron facility. The induced activities in the activated foils were measured with a well calibrated coaxial HPGe detector. The thermal neutron cross section for the 170Er(n,γ)171Er reaction has been determined to be σ0=7.80±0.35 barn, relative to the reference value of 98.65±0.09 barn for the 197Au(n,γ)198Au reaction. By assuming the cadmium cut-off energy of 0.55eV, the resonance integral for the 170Er(n,γ)171Er reaction is I0=40.4±2.8 barn, which is determined relative to the reference value of 1550±28 barn for the 197Au(n,γ)198Au reaction. In order to improve the accuracy of the experimental results the epithermal neutron spectrum shape factor (α) was determined, and the necessary corrections for the counting loss caused by γ-ray attenuation (Fg), the thermal neutron shelf-shielding (Gth), the resonance neutron self-shielding (Gepi) effects, the γ-ray coincidence summing effect, as well as neutron flux fluctuation. The present results are compared with the reference data and discussed.