Electron transport: Multiple and plural elastic scattering

We present a new approach to small angle multiple and plural scattering of electrons applicable for all step sizes in atomic and compound matter Using the screened Rutherford law to describe single scattering and the momentum transfer as the ''angular'' variable, a simple analytical expression for the multiple scattering distribution is found. The parameters of this distribution are fixed by a chi(2)-fit to the distribution calculated by the Monte Carlo technique. The validity of the small angle approximation is investigated. It is found, that at very large step sizes, the multiple scattering distribution becomes a Gaussian. The new approach is implemented in the EGS4 code system and tested in a variety of geometries. It is found, that the new multiple scattering subroutine is 2-3 times faster as the standard EGS4 one.