Determination of thermal neutron cross-section and resonance integral for the 75As (n, γ)76As reaction by activation method using 55Mn (n, γ)56Mn as a monitor Original Research Article

Nuclear constants for use in reactor activation analysis especially (n, γ) cross-sections and absolute gamma intensities, are known to show a rather large scatter in literature. Thermal and resonance cross-sections for the 75As (n, γ)76As reaction is determined by the method of foil activation using 55Mn (n, γ)56Mn as a reference reaction. The experimental sample with and without a cadmium cover of 1-mm wall thickness was irradiated in the isotropic neutron field of the outer irradiation sites 7 of Ghana Research Reactor-1 facility which is a miniature neutron source reactor designed by the Chinese. The irradiation channel used has a neutron spectral parameter (α) found to be (0.037 ± 0.001). The induced activity in the sample was measured by gamma ray spectrometry with a high purity germanium detector. A standard solution of Arsenic was used for the analysis. The necessary correction for gamma attenuation, thermal neutrons and resonance neutron self-shielding effects were not taken into account during the experimental analysis because they were negligible. By defining cadmium cut-off energy of 0.55 eV, the result for 75As (n, γ)76As reaction was found to be: thermal neutron cross-section σ0 = (4.28 ± 0.19) b and resonance integral I0 = (61.88 ± 1.07) b.