COMBINED CALCULATION OF LENS ABERRATIONS, SPACE-CHARGE ABERRATIONS, AND STATISTICAL COULOMB EFFECTS IN CHARGED-PARTICLE OPTICAL-COLUMNS

Optimizing a charged particle optical system utilizing a high brightne ss source requires the inclusion of the effect of Coulomb interactions in the evaluations. A new computer program package, named ANALIC, has bean developed to perform the combined calculation of lens aberration s, space charge aberrations, and statistical Coulomb effects in a comp lete instrument. By making use of an analytical slice method, valid fo r weak/incomplete collisions, to calculate the Coulomb interactions, t he program combines reasonable accuracy with high speed. Using ANALIC, an optical system with an arbitrary number of lenses and apertures, a n arbitrary mode of imaging, and an arbitrary distribution of the beam energy can be analyzed directly. The functions, features, organizatio n, and calculation approach of the program are reported. As an example of the use of the program, a four lens electron probe instrument is a nalyzed for the demonstration of the combined calculation and optimiza tion process of a particle optical system. (C) 1996 American Vacuum So ciety.