Computational Study of Magnetic Lens and Deflector with a Field Distribution of The Form B(z) ∝ z-n

The analytical method is used to derive the formulae of optical properties for magnetic lens and deflector From these formulae, the optical properties are computed for both magnetic lens and deflector. The minimum spherical and chromatic aberration coefficients (axial, magnification and rotation chromatic aberration coefficients) are selected from the results of calculation for both magnetic lens and deflector. m The inverse power law model is adopted to obtain the axial field distribution of magnetic lenses. The moving objective lens concept is used in the computation of the deflection field distribution for magnetic deflector. The first and third orders optical properties for magnetic lens and deflector are studied. Also, the minimum values of optical properties are obtained by changing the order n and the index of the zero corresponding to each value of n.
The computation for magnetic lens and deflector shows that the focal length, spherical and axial chromatic aberration coefficients are proportional with the value of z at the focus. As well, the best magnetic lens and deflector which gives rise to minimum spherical and axial chromatic aberration coefficients are found at n=4. Also, it is noticed that the increasing of the values of the index of the zero for each value of n, for magnetic lenses and deflectors, leads to reduce the spherical and axial chromatic aberration coefficients. Additionally for magnetic lens and deflector, the magnification and rotation chromatic aberration coefficients have constant values, for each value of n, corresponding to each index of the zero.