Polarized electrons by Mott scattering at bulk targets

Abstract

Mott 120° double scattering experiments with bulk gold targets and energy filtering of the scattered electrons have been performed in the energy range 22–48 keV. The polarization degrees are the largest experimental values hitherto published for Mott scattering in this energy range but they are smaller than the theoretical Sherman function computed very accurately some time ago. However, deviations of experimental values from theoretical ones do not exceed 20%. The filter method introduced here is based on the assumption that the mean path of plurally scattered electrons in the target is considerably larger than of singly scattered electrons. Hence, the probability of additional inelastic scattering events is larger in the case of plural than in the case of single scattering. That is why nearly all elastically large-angle scattered electrons are singly scattered electrons with a large polarization degree. The influence of the small angle multiple scattering may be neglected for the present. Mott scattering by bulk targets and the selection of the elastically scattered electrons by energy filtering give a simple source of nearly monoenergetic electron beams of high intensity with a well-reproducible and large polarization degree (0.27 at 32 keV).