Two contributions to the ratio of the mean secondary electron generation of backscattered electrons to primary electrons at high electron energy

Abstract

Based on the main physical processes of secondary electron emission, experimental results and the characteristics of backscattered electrons (BE), the formula was derived for describing the ratio (β angle ) of the number of secondary electrons excited by the larger average angle of emission BE to the number of secondary electrons excited by the primary electrons of normal incidence. This ratio was compared to the similar ratio β obtained in the case of high energy primary electrons. According to the derived formula for β angle and the two reasons why β > 1, the formula describing the ratio β energy of β to β angle , reflecting the effect that the mean energy of the BE W AV p0 is smaller than the energy of the primary electrons at the surface, was derived. β angle and β energy computed using the experimental results and the deduced formulae for β angle and β energy were analyzed. It is concluded that β angle is not dependent on atomic number z, and that β energy decreases slowly with z. On the basis of the two reasons why β > 1, the definitions of β and β energy and the number of secondary electrons released per primary electron, the formula for β E-energy (the estimated β energy ) was deduced. The β E-energy computed using W AV p0, energy exponent and the formula for β E-energy is in a good agreement with β energy computed using the experimental results and the deduced formula for β energy . Finally, it is concluded that the deduced formulae for β angle and β energy can be used to estimate β angle and β energy , and that the factor that W AV p0 increases slowly with atomic number z leads to the results that β energy decreases slowly with z and β decreases slowly with z.