Measurements of Thermal Neutron Capture Cross Sections of Low Abundance Stable Isotopes

Abstract

We measure the thermal neutron capture cross sections of low abundance stable nuclei. The experiments are done with natural foils with known relative isotopic abundances. The cross sections can be obtained by comparing the yields of ’s from the neutron captures by various isotopes. The thermal neutron capture cross sections for isotopes with high abundances are already well measured, and we can obtain the cross sections for nuclei with low abundances which are not known or measured with large errors by simply getting the ratios of gamma yields. For the cross sections of the 152 Gd(n; ) reaction at thermal neutron energy, there are only two old measurements, 1100 100 barn and 735 10 barn, and there is a big discrepancy in the two values. We have measured the neutron capture cross section of the 152 Gd with a natural gadolinium foil. The cross section was obtained by comparing the yields of ’s from the neutron captures by 158 Gd. We have obtained a new cross section value of 614.7 57.8 barn for the 152 Gd(n; ) reaction.