Analysis of an electrostatic column used to produce a microfocused ion beam.

This memorandum presents an analysis of an asymmetric three- element electrostatic column designed to produce a microfocused gallium ion beam. The study includes both theoretical calculations and experimental measurements from working columns. Even though the column design has low chromatic aberration, the spot size is dominated by this aberration throughout the usual range of operation. The column can generate gallium current densities in excess of 1.5 A/cm sup 2 into a 0.2micron spot size.