Accurate computation of magnetic lenses with FOFEM

First-order finite element method (FOFEM) is used for computations of rotationally symmetric magnetic electron lenses with saturated materials. An overview of local and global errors in the axial flux density distribution in the first-order finite element method is given, and the coefficient computation in FOFEM providing the best axial fields are shown. The quality of computed results is illustrated on several typical problems. It is shown that with graded dense mesh accurate results can be obtained fast and with small memory requirements.