Computer Aided Design for Low Aberration Three Electrode Electrostatic Lens

Abstract

A computational investigation is carried out in the field of charge particle optics with the aid of
the numerical analysis method using personal computer. The work concerned with the design of three
electrode unipotential electrostatic lens with low spherical and chromatic aberration .
The axial electrostatic potential distribution is determined by using polynomial functions of the
third and forth order from which the paraxial ray equation is solved to obtain the trajectory of
particles that satisfy the suggested potential function.
From the knowledge of the first and second derivatives of the axial potential distribution the
spherical and chromatic aberration are determined, the electrode shape of electrostatic lens was then
determined from the solution of the paraxial ray equation.