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Novel and traditional fringing field correction schemes for the hemispherical analyser: comparison of first-order focusing and energy resolution

Strong fringing fields at the entry and exit of a real hemispherical deflector analyser (HDA) significantly degrade the 180° first-order focusing conditions, one of the central advantages of the ideal-field HDA. Over the past 50 years, traditional approaches to cure this problem have primarily sought to suppress these fields by improving field termination conditions typically requiring the unwieldy use of additional electrodes. Recently, Zouros et al (2006 Meas. Sci. Technol. 17 N81–N86) have shown in simulation that a simple repositioning of the HDA entry when appropriately biased results in the effective utilization of the intrinsic lensing properties of these fields to restore and even improve first-order focusing. Here, we investigate in simulation the efficacy of the new controlled lensing approach and compare it to the traditional Herzog and Jost field corrector approach. HDA focusing properties and energy resolution are reported as a function of entry angle, source extent and hemispherical interelectrode separation. For all cases considered, HDAs using controlled lensing always came out ahead demonstrating superior focusing along the 180° deflection plane and improved energy resolution.