FLUCTUATIONS IN COLLISION CASCADES - ION-BEAM MIXING

We have studied the consequences of statistical fluctuations in collis ion cascades on mixing of atoms in dense collision cascades, The distr ibutions of energy densities in spherical and cylindrical spikes are o btained from Monte Carlo simulations of collision cascades where a sim ple model is used for grouping recoils into separate subcascades. The subcascades are approximated as either spherical or cylindrical. In th e latter case we find a decrease by a factor of ten and two in the mix ing rate when Au is mixed by 7 MeV Ag and 650 keV Kr ions, respectivel y, if the mean energy deposition is used instead of distribution. New experimental results from 7 MeV Ag ion bombardment of Au-Pt multilayer s at 12 and 300 K are reported. The calculated values for mixing races agree with the measured values.