Fluctuations in the neutron cross sections of Si

Abstract

The total neutron cross section, the 15° and 30° neutron elastic scattering cross sections, the (n, α) cross sections for the four most energetic alpha groups and the (n, p) cross sections for the four most energetic proton groups have been measured for Si with 30 keV resolution in the energy range 6.7 to 13.4 MeV. The average (n, p) and (n, α) cross sections agree within errors with the values obtained from a Hauser-Feshbach calculation. A fluctuation analysis was performed to determine the origin of the fluctuations in the cross sections. The magnitude of the fluctuations and the lack of correlation between fluctuations in different partial cross sections may be explained by Ericson interference effects. The results of the Hauser-Feshbach calculation and the fluctuation analysis indicate that direct interaction contributions to the (n, p) and (n, α) cross sections are small in this energy region. No evidence for intermediate states was found.