Comparison of Monte Carlo and continuous slowing-down approximation treatments of 1-keV proton energy deposition in N2

Abstract

Monte Carlo (MC) and continuous slowing-down approximation (CSDA) calculations of proton energy deposition are compared for the same set of detailed atomic cross sections (DACS). It is found that the MC and CSDA results for the gross features of energy deposition, such as the eV/ion pair, and efficiency for excitation of a given state, are in reasonably good agreement. The spatial apportionment of energy shows disparities, particularly for particles which have degraded to energies less than about 100 eV. Energy spreading of the proton beam is found to be appreciable in the MC calculation, but appears to have a relatively small influence on the spatial distributions of excitation in comparison with CSDA, especially for high-lying states. Range straggling is found in the MC calculations, but it also appears to have only a small influence on the final results when compared with CSDA. Significant differences appear in the mean proton and hydrogen beam fraction obtained from MC and from CSDA. For the convenience of applications, the proton and hydrogen differential flux at each depth in the gas obtained from the MC results is represented analytically.