The Influence of Electrode Angle on the Minimization of the Aberration Coefficients of the Two Electrodes Electrostatic Immersion Lens

This paper deals with the electron optical properties of a set of asymmetrical electrostatic immersion lenses with two electrodes which have been designed using different angles (θ) of the outer lens electrodes as well as air gaps (S) between the electrodes of each lens. It was found that the angle of the outer electrode and the air gap have a clear effect on the electron optical performance of such lenses. In addition to that, it was noticed that the better electron optical properties occurred when the angle of the outer electrode equals (θ = 0°) and the air gap equals (S = 11 mm). The results of the preferable design of the present work were compared with those in published papers in terms of the optical properties. It was found that the results are in good agreement with each other.