ENERGY-DISTRIBUTIONS OF PARTICLES TRANSMITTED THROUGH FREE FOILS AT OBLIQUE-INCIDENCE

Energy loss distributions of particles transmitted through free mylar foil of 25 mu g/cm(2) thickness for 10-25 keV protons incident at angl es 0 less than or equal to theta(0) less than or equal to 60 degrees a re measured. An analytical treatment is made using the Fokker-Planck a pproximation for the kinetic equation. Different factors that can affe ct energy loss distributions were taken into account: energy stragglin g during inelastic collisions, path length fluctuations due to multipl e eleastic collisions and foil thickness fluctuations. A simple formul a for the energy spectra FWHM is derived comprising all aforesaid fact ors. It is shown that the dependence of FWHM on these factors as funct ion of theta(0) is different. So possible contribution of each factor can be evaluated from angle measurements of FWHM. Comparison of the an alytical result with the experiment as well as computer simulations us ing TRIM-like code shows that the main contribution to measured FWHM i s due to fluctuations of the inelastic energy losses.