电子枪理论研究的新进展

Advances in electron gun theory research

本文简要回顾了电子枪发展的历史,评述了电子枪理论研究方面的新进展,重点介绍了日本学者Fujita和Shimoyama的新近研究成果。最新的研究表明,对冷场发射和扩展的肖特基发射电子枪,存在阈值电流。当束流Ib增大,超过阈值电流时,枪的表观亮度逐渐下降。当对整个电子光学柱体进行评价时,必须把亮度和束流的函数关系考虑在内。这时会出现关于电子枪的若干新概念。整个电子光学柱体的电子探针性质曲线由三个区域组成,即:(1)恒定束斑(d)区;(2)d∝I3b/8区;(3)d∝I3b/2区。以往的理论只指出了3/8次方区的存在。3/2次方区的存在是一个新的发现。它解释了历史上曾注意到的一个事实,即当应用的束流进入μA量级时,扩展的肖特基发射和冷场发射枪的性能反而不如传统的钨丝热发射枪。

In this paper, we recalled briefly the history of the development of electron gun, reviewed the advances in electron gun theory research, with stress on the introduction of the research work carried out by Fujita and Shimoyama. In their work, some new concepts such as electron gun focal length, spherical aberration of dectren sun, and threshold current of SE and CFE gun, have been proposed. Formulas were presented to estimate the brightness reduction as a function of the beam current. It is shown that the probe property curve consists of three segments in the order of increasing beam current： （1） the constant probe size region; （2） the brightness limited region, d～I3/8b ; （3） the angular current intensity limited region, d～I3/2b . The existence of the last region is a new discovery.