ELECTRON BACKSCATTERING AND SECONDARY-ELECTRON EMISSION FROM CARBON TARGETS - COMPARISON OF EXPERIMENTAL RESULTS WITH MONTE-CARLO SIMULATIONS

Electron backscattering (EBS) and secondary electron emission (SEE) yield have been measured for bulk carbon with a density of 1.8 g cm-3, for primary electron energies in the range from 100 to 500 eV and from 12 to 1 000 eV respectively. The backscattering results were in agreement with an empirical formula to within 2%. The SEE yield value was 0.04 at lowest measured energy (12 eV) and reached a maximum value of 0.54 at about 300 eV. The backscattering coefficients and SEE yield have also been calculated using a Monte Carlo simulation for the energy range from 12 to 1000 eV. In the simulation, two different energy loss characteristics were used. The first was obtained from a set of optical data and gave good agreement with the experimental SEE yield but poor agreement with the backscattering data. The second was obtained from a modified Bethe energy loss function which fitted the backscattering data well. Using the Bethe loss function for each primary electron, the SEE yield was calculated for every path length between scattering events by dividing the primary electron energy lost per unit path length by the average energy required to create a secondary electron. The SEE data was fitted on the assumption that the average energy to create a secondary varied with primary electron energy according to a four parameter function. Comparison of the calculated SEE yield with the experimental SEE yield, as a function of incident angle of the primary beam, was good over the energy range from 100 to 500 eV.