宽束和细束电磁复合聚焦球面阴极透镜的象差理论

本文研究了对宽束和细束阴极透镜普遍适用的电磁复合聚焦球面阴极透镜的象差理论。在考虑物场和象场弯曲以及阴极面上磁场和横向电场不为零的情况下,导出了任意理想象面上的一级近轴横向象差和包括色象差在内的全部三级横向象差矩阵公式。所得的结果较为完整、普遍。本文详细讨论了宽束和细束阴极透镜的关系,并用轨迹法和变分法严格证明了:当考虑阴极面逸出电子具有一定的初能量和初角度分布,并采用准规范化电位表示的近轴轨迹方程来讨论系统的理想成象时,宽束和细束两类阴极透镜从象差理论以至导出的三级横向象差、象差系数表示式都可以统一起来。本文采用矢量描写轨迹,运用矩阵表示象差,形式简洁,象差系数积分收敛,适合于计算机计算。 关键词：

ON THE ABERRATION THEORY FOR WIDE AND NARROW ELECTRON BEAMS IN A COMBINED ELECTROMAGNETIC FOCUSING SPHERICAL CATHODE LENS SYSTEM

In the present study, an aberration theory for both wide and narrow electron beams in a combined electromagnetic focusing spherical cathode lens system is discussed. The general formulae of aberration coefficients for first and third order transversal geometrical and chromatic aberrations on any ideal image plane have been derived under following conditions, i.e., when the objective and image fields have finite curvatures and when the cathode is immersed in magnetic and transversal electric fields. Based on the variational analysis method and the trajectory calculation method, the relationship between the wide electron beam slstem and the narrow electron beam system has been considered in detail. It has been shown that these two different electron beam systems can be treated equally and their aberration equations and coefficients can be expressed in a universal form, if one considers the definite energy and angular initial distributions and utilizes the first order linear trajectory equation. In the present paper, electron frajectories are described in the vector form. The aberrations are expressed in the matrix form and are thus appropariate for computer calculations.