Design of Wien filters with high resolution

The design of a compact high-energy resolution device based on a symmetrical double Wien filter is presented. An accurate version of the boundary element method (BEM) is employed to model the shape and behaviour of the filters very precisely. Using a direct ray tracing technique, we investigate the geometrical aberrations in the basic filter, in which dipole and quadrupole electric fields and a dipole magnetic field are present. The additions of a quadrupole magnetic component along with some slight modifications in the geometry produce a drastic reduction in the aberrations.