Statistical Analysis of Fast Neutron Total Cross Sections of Silicon, Phosphor, Sulfur, and Chlorine

Abstract

The neutron total cross sections of silicon, phosphor, sulfur, and chlorine in the energy range from 3 to 5 MeV have been measured with an energy resolution of 20 to 50 keV, and the variations of the cross sections with energy have been analyzed statistically under the assumption that the variations arise from the fluctuation of the neutron widths and spacings of the resonances which are covered by the energy resolution. The average spacings D , which are obtained by the present analysis, are 1.3 0.13, 0.54, and 0.04 keV for silicon phosphor, sulfur, and chlorine, respectively. These values agree well with those calculated by Cameron's semi-empirical formula. The neutron strength functions \({\langle}{\varGamma_{n}}^{0}{\rangle}/D\), which are obtaind also by the present analysis, are 2.9, 3.9, 3.8, and 4.7×10 -4 for the respective elements, and are consistent with those obtained by the low-energy-neutron experiments. The correlation between the fluctuation of the total cross sections and the energy are obtained, and it is pointed out that there appear no signs of the fluctuations due to the existence of the large resonances, the width of which are comparable with or larger than the energy interval of about 100 keV.