Control of Parasitic Aberrations in Multi-pole Optics

A method is described to find the optimal 4th order setup of a quadrupole-octupole 3rd order aberration corrector. Given accurate measurements of aberrations to 5th order, stimulus/response experiments can be used to synthesize pure controls for each measured aberration up to 4th order, including those which are caused by parasitic e®ects { symmetry violations, misalignments, construction mistakes, post-construction drift or other problems.

By: Philip E. Batson

Published in: Journal of Electron Microscopy, volume 58, (no 3), pages 123-130 in 2009

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