COMPUTER-AIDED DESIGN OF AXISYMMETRIC ELECTROSTATIC LENSES

Abstract

A CAD system named GUNSMITH is developed to design axisymmetric electrostatic lenses. The system runs on any IBM compatible computer with CGA graphic card, 640 kbyte of main memory, two floppy disc drives or one floppy drive and one hard disc drive, though an AT with a math coprocessor chip is recommended. It can calculate the most important properties of a charged particle optic, namely: - the axial and the radial potential function, - the first order optical properties, - the transfer matrix and its derivates, - the magnification, - the chromatic aberration and - the particle density of the beam as well within a reasonably short time. Using the system described here the engineer can compare the effects of different electrode shapes without the expense of building an actual optical system. To test the GUNSMITH we have calculated the properties of some electrostatic lenses, and the results agree very well with the literature and with the experiments. For example the GUNSMITH was used to calculate the parameters of a SIMS ion gun, and the comparisons with the measurements also show fair agreement.