Atomistic modeling of the channeling process with and without account for ionising collisions: A comparative study

This paper presents a quantitative analysis of the impact of inelastic collisions of ultra-relativistic electrons and positrons, passing through oriented crystalline targets, on the channeling efficiency and on the intensity of the channeling radiation. The analysis is based on the numerical simulations of the channeling process performed using the MBNExplorer software package. The ionising collisions, being random, fast and local events, are incorporated into the classical molecular dynamics framework according to their probabilities. This methodology is outlined in the paper. The case studies presented refer to electrons with energy $\E$ ranging from 270 to 1500 MeV and positrons with $\E=530$ MeV incident on thick (up to 1 mm) single diamond, silicon and germanium crystals oriented along the (110) and (111) planar directions. In order to elucidate the role of the ionising collisions, the simulations were performed with and without account for the ionising collisions. The case studies presented demonstrate that both approaches yield highly similar results for the electrons. For the positrons, the ionising collisions reduce significantly the channeling efficiency. However, it has been observed that this effect does not result in a corresponding change in the radiation intensity.