On magnetic lens computations with FEM and BEM

The aim of the paper is to compare the Boundary Element Method and the first-order Finite Element Method (FEM) for the computation of rotationally symmetric magnetic electron lenses. It is shown that the FEM is accurate for the computation of open lenses and the computation accuracy at off-axis points is sufficient to get aberrations from ray tracing. Open lenses can be satisfactorily computed with the FEM if we use meshes with a large number of points and if we define sufficiently distant boundaries, eventually if we apply both the Dirichlet and Neumann boundary condition. It is also shown that the FEM allows fast and accurate computation of saturated magnetic electron lenses.