Systematics and empirical expressions for neutron emission from thick targets inα-induced reactions

Abstract

The effect of two initial exciton (particle-hole) configurations, namely 4p0h and 5p1h, on the angular distribution of neutron emission from $\ensuremath{\alpha}$-induced reactions on various thick targets have been analyzed. In the angular distribution of emitted neutrons the relative contribution of the 4p0h configuration is found to vary as the cosine of the angle of emission. Using such dependence, empirical expressions are developed for the total neutron yield, energy spectra, and angular distribution of neutrons in $\ensuremath{\alpha}$-induced reactions in the 25\char21{}200-MeV energy range. These expressions are based on empirical fits to the hybrid model calculations of neutron emission from target elements in the mass range $^{9}\mathrm{Be}$ to $^{209}\mathrm{Bi}$. The results of these calculations are compared with experimental data showing fairly good agreement. The empirical expressions provide a simple, fast, and reliable tool for calculating neutron emission essentially required for radiation shield design and other applications.