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 emission electron gun were traced with numerical method at different positions of the extraction electrode as keeping the tip field constant. The aberrations of the electric field lens were examined using a relation between the size and the divergence angle of the virtual source estimated from the minimum cross section of the asymptotes of the traced trajectories in a field-free space behind the extraction electrode. The aberrations are reduced as decreasing a distance between the cathode tip and the extraction electrode. The reduction is caused by a divergence field lens in front of the tip facet of the cathode.