PLURAL AND MULTIPLE SCATTERING OF FAST ELECTRONS IN GASES.

The scattering of fast electrons in nitrogen and argon has been investigated under conditions resulting in approximately 1 to 100 small angle scattering collisions. Experimental measurements have been made of the spatial distribution of the scattered electrons for highly collimated incident electron beams. Electron energies of 20, 40 and 100 keV and gas target thickness of 3 to 1000 torr-cm at room temperature were used. The experimental distributions are much wider than predicted for single scattering and were approximately Gaussian for thick targets with many electron collisions. The dependence of the measured half current beam width on the target thickness varied from a 32 power law at small target thicknesses to a 12 power law in thick targets. Direct analog Monte Carlo calculations have been made based on a screened cross-section including the large contribution by inelastic collisions at very small scattering angles. Despite the approximate nature of the cross-section data the calculated spatial distributions of scattered electrons agree well with the experimental results except at the smallest target thicknesses where the calculated distributions are wider than the experimental results. Author