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) yi eld have been measured for bulk carbon with a density of 1.8 g cm-3, f or primary electron energies in the range from 100 to 500 eV and from 12 to 1 000 eV respectively. The backscattering results were in agreem ent 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 ra nge from 12 to 1000 eV. In the simulation, two different energy loss c haracteristics 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, th e SEE yield was calculated for every path length between scattering ev ents by dividing the primary electron energy lost per unit path length by the average energy required to create a secondary electron. The SE E data was fitted on the assumption that the average energy to create a secondary varied with primary electron energy according to a four pa rameter function. Comparison of the calculated SEE yield with the expe rimental SEE yield, as a function of incident angle of the primary bea m, was good over the energy range from 100 to 500 eV.