ショットキー放出型電子銃の電子軌道解析と収差の評価

Abstract

Electron trajectories in a Schottky-type field emission gun were traced by solving the equation of motion directly, and the size and position as well as the divergence angle of the effective source were examined projecting the asymptote of each trajectory in the field-free space behind the anode back toward the cathode. The numerical analysis, combined with the field determination by the surface charge method, allowed the estimation of the influences of spherical and chromatic aberrations on the effective source size. The aberrations largely vary with the second anode voltage and restrict the beam angle giving the attainable minimum source size.