Potential distribution and focusing properties of toroidal deflection plates: Application to simultaneous energy and angle-resolved charged particle spectroscopy

Abstract

The potential distribution of toroidal deflection analysers is calculated in a new way which enables the determination of potential distributions to be made up to any desired order of accuracy. The calculations are valid for all kinds of toroidal analysers and can be applied to either “radial” particles that move at or about the (equatorial) plane of symmetry or “axial” particles that move at or about meridian planes that contain the axis of symmetry. The latter are of special interest because they enable the use of position-sensitive detectors. In both cases the particles are moving at or about circular main paths. For “axial” particles this can only be realized by adapting the shape of the deflection plates to non-circular cross-sections in meridian planes. Both potential calculations and numerical particle trajectory calculations are carried out to show that (for “axial” particles) better results are obtained for deflection plates adapted as above compared with the commonly used circular deflection plates. Calculations are carried out with reference to the EARISS analyser, which is the first analyser known to be equipped with such adapted deflection plates.