Imaging electron energy filter

Abstract

The invention relates to an electron energy filter for electron microscopes as well as to an electron microscope equipped with such a filter. The filter comprises three sector magnets with the deflection field in the first sector magnet being homogeneous. The deflection field in each of the two other sector magnets is an inhomogeneous gradient field. To generate the gradient field, the pole pieces of the two other sector magnets have the form of segments of truncated double cones. The electron beam passes the first homogeneous sector magnet twice. Multipole elements are arranged in front of, behind and between the three sector magnets. The filter has a large dispersion also for high-energy electrons while at the same time providing a compact configuration. All second-order aberrations and the significant second-rank aberrations are corrected by means of the multiple elements.

Dependencies are inferred from the claim text.