CANONICAL ABERRATION THEORY IN ELECTROMAGNETIC MULTIPOLES

In a 2N-pole electromagnetic system, defining the electron optical Hamiltonian function, we have derived both general algebraic expressions (arbitrary N) and special numerical formulas (N = 3,4,5,6,7) for different aberrations from lower to higher order (i.e., the order of N - 1, N + 1, 2N - 3, 2N - 1, 3N - 5). The so-called canonical aberration theory in electromagnetic multipoles has thus been developed, which allows us to deduce angular dependencies of different aberrations and to examine the possibility for spherical correction of a round lens by using multipoles.Physics, AppliedSCI(E)0ARTICLE125968-59756