Measurement of thermal neutron cross-sections and resonance integrals for 71Ga(n,γ)72Ga and 75As(n,γ)76As by using 241Am–Be isotopic neutron source

Thermal neutron cross-sections and resonance integrals for the 71Ga(n,γ)72Ga and 75As(n,γ)76As reactions were measured by the activation method. The experimental samples with and without a cylindrical Cd shield case in 1 mm wall thickness were irradiated in an isotropic neutron field of the 241Am–Be neutron source. The induced activities in the samples were measured by high-resolution γ-ray spectrometry with a calibrated reverse-electrode germanium detector. Thermal neutron cross-sections for 2200 m/s neutrons and resonance integrals for the 71Ga(n,γ)72Ga and 75As(n,γ)76As reactions have been obtained relative to the reference values, σ0=13.3±0.1 b and I0=14.0±0.3 b for the 55Mn(n,γ)56Mn reaction as a single comparator. The necessary correction factors for gamma attenuation, thermal neutron and resonance neutron self-shielding effects were taken into account in the determinations. By defining Cd cut-off energy 0.55 eV, the results obtained were: σ0=4.41±0.18 b and I0=32.3±2.3 b for 71Ga(n,γ)72Ga, and σ0=4.15±0.24 b and I0=63.5±3.8 b for 75As(n,γ)76As. These results are discussed and compared with previous measurements and the evaluated data in ENDF/B-VI and JENDL-3.2. Thermal neutron cross-sections for 71Ga(n,γ)72Ga and 75As(n,γ)76As reactions are in good agreement with the recent measurements. However, the discrepancies between present results and some of old experimental data for resonance integrals for both reactions are within about 8–58%.