Computer Aided Design of Three Electrode Electrostatic Unipotential Lens

The present work has been concerted on the simulation of focusing electron beam by finding the optimum design of an electrostatic uni potential lens with optimum low values of spherical and chromatic aberration coefficient. Computational theoretical investigation has chivied in the field of non-relativistic charged particles optics with the aid of the personal computer and numerical method under the absence of space - charge, the potential field distribution of un potential lens have been represented by using some of analysis functions, the paraxial ray equation have been solved for proposed fields to determine the trajectory of the electron beams in the lens. The spherical and chromatic aberration coefficients computed from the axial potential distribution and its first and second derivative the electrodes shape of the low aberration un potential lens has been determined in two and three dimension, its benefited from the optimum design for the three electrode un potential lens have a low a aberration values so it is possible to use this lens in making an optical system which can be used in focusing of charge particles.