Analysis of a range of symmetrical three-aperture electrostatic lenses

1 October 1972

journal article
Published by Institute of Electrical and Electronics Engineers (IEEE) in IEEE Transactions on Electron Devices

Vol. 19 (10) , 1075-1084
https://doi.org/10.1109/t-ed.1972.17552

Abstract

The three-aperture electrostatic lens was investigated in great detail. The potential along the axis was obtained using the relaxation technique. The cardinal points and coefficients of spherical and chromatic aberration were numerically calculated from the axial potential distribution using the classical Scherzer and Glaser formulas. The results are given for a range of lenses and for a series of voltage ratiosV_{1}/V_{2}where V1and V2are the potentials of the inner and outer electrodes, respectively. The ratio of the aperture radiiR_{2}/R_{1}is varied from 0.25 to 1 in steps of 0.25. The separation of the electrodesS/R_{1}is varied from 0.5 to 3 in steps of 0.5, and the thickness of the central electrodeT/R_{1}is varied from 0.25 to 2 in steps of 0.25. The influence of all these parameters on the cardinal points and aberration coefficients is discussed and comparison is made with published experimental and theoretical results.

Keywords

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