在给定探针直径的条件下获取最大的上靶束流

Maximum Electron Probe Current for a Given Probe Diameter

对于一个电子探针系统，我们在考虑了它的球差、色差、衍射以及高斯斑大小的条件下，推导出了一个获得最佳放大倍数和孔径角的公式，这些最佳值可确保该系统在给定探针直径的条件下获得最大的上靶束流。本文中还将阐明：给定束径下使束流最大的最佳条件可同时满足在束流一定时使束径达到最小。本文并以一个实例说明上述公式的使用。

An equation is derived for the optimum magnification and optimum aperture angle of an electron probeforming system. Using this equatio, one can obtain the maximum probe current for a probe of given diameter,taking into consideration the spherical, chromatic and diffraction aberration as well as the gaussian probe size.Itis shown that the optimum condition for the maximum probe current for a given probe diameter is the same asthat for a minimum probe diameter for a given probe current. An example is given here to explain how to usethe equation in electron gun design.