BACKSCATTERING OF SLOW POSITRONS FROM SEMIINFINITE ALUMINUM

Monte Carlo simulation for 1-10 keV positron backscattering from semi- infinite aluminum with normal angle of incidence is reported. The elas tic scattering cross sections have been obtained from the modified Rut herford differential cross section where the numerical coefficient in the atomic screening parameter is taken to be variable. To model inela stic scattering, we have investigated for the first time the effects o f continuous slowing down through collisions with conduction electrons . Attention has also been paid to effects of changing the angle of inc idence. Our simulated results and the available experimental data are found to be in reasonable agreement, and show that the energy dependen ce of the backscattered fractions can be fitted with a simple function : B(E) = 0.0187997 In E+0.102644. This suggests that both the transpor t model and the scattering cross sections used in the present work are reliable. (C) 1998 American Institute of Physics. [S0021-8979(98)0670 6-1].