Computer simulation of a fast atom/ion source

Calculations of ion and atom spatial and energy/angle distributions are presented for various initial beam profiles and a range of initial energies and pressures, after travelling through the charge exchange cell of a special source of fast heavy particles. The distributions were calculated, using a Monte-Carlo simulation programme with accurate numerical integration of the scattering angles under the influence of a Thomas-Fermi potential in the Moliere approximation, for elastic scattering with a proper dependence of the charge transfer cross-section on ion energy. A comparison is made with an experimentally obtained spatial distribution for the particular pressure 0.001 torr. The simulation results show that elastic scattering has virtually no effect on the energy/angle distributions but does modify the beam profile and strongly affects the loss of particles from the beam. Thus any energy distribution in the detected beam must have been present originally and is not produced by elastic scattering. (author)