Positron channeling in quasi-mosaic bent crystals: atomistic simulations vs. experiment

Abstract

This paper presents the results of a comprehensive study of an ultra-relativistic positron beam deflection by an oriented quasi-mosaic crystal. The analysis was performed for the positron energy of 530 MeV incident on the quasi-mosaic bent Si(111) crystal. This particular case was chosen because it has recently been studied experimentally at the Mainz Microtron MAMI. The results of the relativistic molecular dynamics simulations were compared with the experimental observations, revealing a high degree of agreement. The study examined the presence of planar channeling, de-channeling, volume reflection, and volume capture processes in the angular distribution of deflected positrons for various beam-crystal alignments. Predictions have been made for certain crystal orientations for which there is no experimental data. Our simulations have also focused on analysing the influence of the anticlastic deformation of the bent crystal on the beam deflection by an oriented quasi-mosaic crystals.

Graphical Abstract caption: Schematic representation of the geometry of a ‘quasi-mosaic’ bent crystal slab and its orientation with respect to an incident beam.