Synthesis of electrostatic multielectrode deflectors

Synthesis of electrostatic deflectors with given source parameters, first-order properties, and minimum aberrations can be realized by using the cubic spline method or the a priori given multielectrode approach. Synthesis of electrostatic deflectors was successfully achieved previously by using the cubic spline method. In this paper we present synthesis of electrostatic deflectors based on the a priori given multielectrode approach for the purpose of obtaining the minimum beam spot size through a sequential optimization technique. Our calculations show that the third-order geometrical deflection aberrations can be reduced by about two to three orders of magnitude using a multielectrode deflector with three units or five units, each having short cylindrical segments with geometrically octupole symmetry.