Scaling of particle reflection coefficients

Previously published data on particle backscattering from surfaces under normal incidence conditions is reviewed in order to arrive at a general scaling relationship in terms of projectile energy and the masses of the colliding species. A single empirical formula is proposed which, with suitable coefficients, represents the available data base and provides a basis for interpolation and extrapolation. The formula is intended for use in codes for the modelling of particle recyling in fusion reactor devices. Attention is focused primarily on light projectile (H, D, T, He) reflection from candidate plasma facing materials and covers an energy range from tens of eV to 100 keV to encompass situations of interest in a fusion device. We also review briefly the case of self-ion reflection. (orig.)