A theoretical study of the effects of insulators on electron transport through electrostatic tube lenses

Using the computer program SIMION 6, we have studied the effects of spuriou s insulator charging on the trajectories of electrons through electrostatic tube lenses. We considered lens elements with flat ends, spaced a distance g apart, whose inner diameter D=10g. For the standard cases of drift tubes , two-element lenses, and einzel lenses, we found that charging effects are eliminated if t/g >3.5, where t is the distance between the lens inner dia meter and the charged spacing insulator. (C) 2001 American Institute of Phy sics.