Computer modeling of the Schottky electron source

A computer modeling program that is able to imitate the polyhedral shape of the ZrO/W(100) Schottky cathode is used to compute emission parameters such as the electric field distribution and reduced brightness Br for the various observed end form shapes. This program includes the electron–electron interactions in the beam and their effect on Br. A relationship between the axial field factor β = F/Ve and the axial lens factor K = (I′/J)1/2 (where F, Ve, I′, and J are the applied electric field, extraction voltage, beam angular intensity, and surface current density, respectively) was obtained from the data which allow β, K, and the work function to be calculated from experimental I′(Ve) data. In addition, an empirical relation, independent of the end form shapes, was obtained that allows Br to be calculated from the intrinsic reduced brightness. Experimental energy distribution measurements are presented which allows one to compare the energy spread and Br values for emitters with various values of β. An e...