Inverse Design of Magnetic Electron Lenses Using a Gray Field Model

The Gray-field model has been considered in the present work to represent the axial magnetic field strength and its corresponding magnetic flux density distribution of symmetrical double polepiece magnetic lenses. The well-known parameters of magnetic lenses have been investigated with the aid of the Gray-field model. These parameters are the air gap width, bore diameter, and the excitation of the lens. The influence of each parameter on the optimization process of the objective focal properties and polepiece profile has been investigated. The results have been checked with the aid of well-known electron optics computer programs and good agreement have been achieved.