Synthesis of focusing-and-deflection columns

Szilagyi and Szep have demonstrated that focusing lenses of high performances can be constructed from a column of circular plate electrodes. It has already been shown that additional quadrupole components can bring about substantial improvements in the focusing of charged particle beams. In this article, that design procedure is expanded to columns capable of both focusing and deflecting particle beams by just introducing additional dipole components. Two sample designs, one for negative ions and one for electrons, are presented showing that in both cases a ± 2.3 mrad diverging beam can be focused down to a spot of less than 50 nm in radius over a scanning circular area of radius 0.25 mm.