A coupled energy-angle Fokker-Planck decomposition scheme for ion transport

A method for describing highly forward peaked scattering and transport of ions in random (as opposed to crystalline) solids is presented. It is based on a generalized decomposition scheme that separates the singular peaked component of the scattering cross-section using a Fokker-Planck formalism, leaving a relatively smooth Boltzmann collision integral. A suitability modified energy dependent Legendre expansion scheme is introduced to deal with the truncated angular domain in the collision integral resulting from the decomposition. A complete library of multigroup cross-section moments as well as Fokker-Planck coefficients is developed for use with a specially constructed transport code as well as the MCNP Monte Carlo code. Outstanding accuracy is achieved for ion implantation profiles and average range when compared with established results