Small-angle scattering of swift electrons and positrons in a crystal

Features of small-angle scattering of charged particles by the crystal structure and two-dimensional angular distribution are studied on the basis of Monte-Carlo calculations of 20 MeV electron and positron transmission through a <001> MgO single crystal. An accurate method for calculation of the charged particle scattering in a heterogeneous electron gas in the crystal is proposed. The analytical conditions under which the string-effect influences the small-angle scattering are derived and comparison is carried out with well-known experimental data. (author)