Simulation of a mirror corrector for PEEM3

A third generation aberration-corrected Photoemission Electron Microscope is being designed at the Advanced Light Source. An electron mirror is used for the correction of the lowest order spherical and chromatic aberrations. Two very different methods, one using finite-element method and ray-tracing technique and the other using charge ring method and differential algebra technique, have been employed to simulate the electrostatic field and the behavior of the electron beam. Good agreement has been obtained between the two methods and a tetrode mirror has been found to effectively correct the spherical and chromatic aberrations. Operating at 20 kV, the point resolution for 100% transmission reaches 50 nm with the mirror corrector, a significant reduction from that of 440 nm without correction. The highest resolution achieved is 4 nm at 2% transmission, as opposed to 20 nm at 1% transmission without correction.