Measurement of fast neutron induced (n,γ) reaction cross-section of 152Sm, 154Sm and 150Nd in the energy range of 0.8 to 2 MeV

Abstract

The (n,γ) reaction cross-section of rare earth stable fission products, such as 152Sm, 154Sm and 150Nd, in the neutron energy range of 0.8 to 2 MeV, obtained from 7Li(p,n)7Be reaction, was measured by neutron activation followed by off-line gamma-ray spectrometry. Natural strontium (natSr) has been established as a fast neutron flux monitor in this work, by measuring the natSr(n,γ+n,n′)87Srm reaction cross-section using 127I(n,γ)128I as monitor reaction. The cross-section for 86Sr(n,γ)87Srm has been determined for the first time to the best of our knowledge. The excellent decay properties of 87Srm and opposite energy dependence of 86Sr(n,γ)87Srm and 87Sr(n,n′)87Srm reactions makes natSr an excellent candidate for neutron flux monitor for wide neutron energy range. The measured (n,γ) cross-section data from the present study has been compared with the literature data, which is very limited along with large scatter in the energy range of 1–2 MeV for these nuclei. The results from the present study, clearly show a need for fresh cross-section evaluations for 152Sm(n,γ)153Sm. For, 154Sm(n,γ)155Sm and 150Nd(n,γ)151Nd reactions, the present data align with one of the data groups among the two which can be broadly identified having difference of about more than ∼50%. The present experimental data has been compared with TALYS 1.96 theoretical model calculations based on Fermi gas level density prescriptions which shows that the cross section values are close to the experimental data at some of the neutron energies. A comparison of the data on fast neutron capture cross-section for N = 90 isotones from the present study and from the literature showed a systematic decrease in the cross-section value with increasing neutron richness of the target nucleus. The cross-section data could be scaled with neutron-proton asymmetry parameter to show a nearly linear behaviour on a logarithmic scale. The data for 154Sm (N = 92) was also observed to follow the same trend.