SUSPRE - How It Works 1
SUSPRE is based on the PRAL algorithm which is a solution to the Boltzmann Transport equation.
Basically, particles arrive at a surface with energy E0, they lose energy as they penetrate the solid. When they have no energy left they stop and form a statistical range distribution which can be characterized by a set of moments - here we assume that two moments are enough to describe the profile, the mean and the standard deviation.
As the ions slow down they lose their energy in the solid and it takes up this energy into target recoils which further spread the energy into the solid creating displacements of the target atoms. This results in damage of the irradiated solid.
Boltzmann Transport equation animation (click to enlarge)