Measuring and correcting aberrations of a cathode objective lens

In this paper I discuss several theoretical and practical aspects related to measuring and correcting the chromatic and spherical aberrations of a cathode objective lens as used in Low Energy Electron Microscopy (LEEM) and Photo Electron Emission Microscopy (PEEM) experiments. Special attention is paid to the various components of the cathode objective lens as they contribute to chromatic and spherical aberrations, and affect practical methods for aberration correction. This analysis has enabled us to correct a LEEM instrument for the spherical and chromatic aberrations of the objective lens.

Research highlights
► Presents a comprehensive theory of the relation between chromatic aberration and lens current in a cathode objective lens.
► Presents practical methods for measuring both spherical and chromatic aberrations of a cathode objective lens.
► Presents measurements of these aberrations in good agreement with theory.
► Presents practical methods for measuring and correcting these aberrations with an electron mirror.