VEGAS: A Monte Carlo Simulation of Intranuclear Cascades

Abstract

The model dependence of the Monte Carlo simulation of intranuclear cascades generated by nucleons up to \ensuremath{\sim}380 MeV incident on complex nuclei has been investigated. Differences in the details of the Monte Carlo procedure between this work and previous intranuclear-cascade calculations are discussed. The specific effects that were investigated are those attendant upon the introduction of refraction of cascade particles when going through regions of varying potential energy, and upon the change in the nuclear density distribution from that of a uniform-density sphere to one with a diffuse surface similar to that consistent with electron-scattering experiments. Among the calculated quantities discussed are reaction cross sections, excitation energies of cascade products, spallation cross sections, energy and angular distributions of emitted particles, and linear and angular momentum transfers. The introduction of the diffuse-surface-density distribution improves agreement with available experimental data. At incident energies below \ensuremath{\sim}200 MeV and for medium and heavy nuclei, best agreement with experimental data is obtained when refraction and reflection are neglected. Possible reasons for this result are discussed.