Premium
High‐order and multipole aberrations by aberration integral and direct ray‐tracing methods
Author(s) -
MUNRO E.,
ZHU X.,
ROUSE J.
Publication year - 1995
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1111/j.1365-2818.1995.tb03628.x
Subject(s) - paraxial approximation , chromatic aberration , multipole expansion , physics , ray tracing (physics) , optics , spherical aberration , quadrupole , electrostatic lens , electron optics , lens (geology) , optical aberration , spherical harmonics , quadrupole magnet , electron , chromatic scale , beam (structure) , wavefront , atomic physics , quantum mechanics
SUMMARY This paper describes methods for computing high‐order aberrations and multipole aberrations in electron optical systems. Two approaches are discussed – the first involves obtaining aberration integrals for the high‐order aberration coefficients, in terms of paraxial rays and axial field functions, while the second method uses direct ray‐tracing through fields computed accurately by finite element or finite difference methods. The methods are illustrated by several examples, including a wide‐angle focusing and deflection system with fifth‐order aberrations, a combined magnetic and electrostatic lens, a ‘supertip’ ion source, an electron mirror with negative spherical and chromatic aberration, and a chromatically corrected quadrupole lens.