Accurate Calculation of Properties of the Two-Tube Electrostatic Lens III. Aberration Coefficients

Abstract

Using numerical methods, electric fields and meridional electron trajectories have been calculated for the two‐tube electrostatic lens with sufficient precision to determine values for all the third‐order and several of the fifth‐order aberration coefficients for meridional trajectories. The aberration coefficients are expressed in a form which is intrinsic to the lens and do not depend on a particular object and aperture position. Results were obtained for voltage ratios of 2, 5, 10, 20, and 40.