Secondary electron emission from beryllium irradiated by plasmas in a magnetic field

Abstract

A Monte-Carlo simulation model of secondary electron emission from beryllium is combined with the kinetic equation analysis for the Lorentz force perpendicular to an oblique magnetic field and the acceleration due to the sheath electric field normal to the surface. The emphasis is put on the energy distribution of secondary electrons entering into an edge plasma after their transport in the sheath, as well as the effective secondary electron yield. Some of the secondary electrons emitted from the surface return to the surface within their first gyration, resulting in low effective secondary electron yield. The higher the energies of the secondary electrons or the lower the temperature of the edge plasma electrons, the more the secondary electrons return to the surface. Lowering of the yield is accompanied by a low-energy shift of the energy distribution.