Calculation of radiation effects in solids by direct numerical solution of the adjoint transport equation

The ‘adjoint transport equation in its integro-differential form’ is derived for the radiation damage produced by atoms injected into solids. We reduce it to the one-dimensional form and prepare it for a numerical solution by: 1. - discretizing the continuous variables energy, space and direction, 2. - replacing the partial differential quotients by finite differences and 3. - evaluating the collision integral by a double sum. By a proper manipulation of this double sum the adjoint transport euation turns into a (very large) set of linear equations with tridiagonal matrix which can be solved by a special (simple and fast) algorithm. The solution of this set of linear equations contains complete information on a specified damage type (e.g. the energy deposited in a volume V) in terms of the function D(i,E,c,x) which gives the damage produced by all particles generated in a cascade initiated by a particlee of type i starting at x with energy E in direction c. It is essential to remark that one calculation gives the damage function D for the complete ranges of the variables {i,E,c and x} (for numerical reasons of course on grid-points in the {E,c,x}-space). This is most useful to applications where a general source-distribution S(i,E,c,x) of particles is given by the experimental setup (e.g. beam-window and and target in proton accelerator work. The beam-protons along their path through the window — or target material generate recoil atoms by elastic collisions or nuclear reactions. These recoil atoms form the particle source S). The total damage produced then is eventually given by: Image A Fortran-77 program running on a PC-486 was written for the overall procedure and applied to some problems.