Effect of pole piece shape on properties of the symmetrical objective magnetic lenses

A theoretical computational study has been carried out to describe the optimization for the symmetrical double pole piece magnetic lenses, under the absence of magnetic saturation by analysis. The study depends on design of pole piece shape for double pole piece magnetic lenses. By study the variation of the parameters air-gap width(S), axial bore diameter (D) and lens excitation (NI) for the tapered cylindrical, the tapered spherical and conical double pole piece magnetic lenses. The magnetic field distribution has been used to study the objective focal properties. Double pole piece magnetic lens with tapered spherical pole piece has shown the most favorable objective properties among the three unsaturated lenses.