ABSTRACT
Abstract. The asymptotic aberration coefficients of the primary aberrations of electron lenses can be written as polynomials in reciprocal magnification (or object position). Expressions are available for the polynomial coefficients of a doublet in terms of those of the individual members of the doublet for both geometrical and chromatic aberrations. Here, these expressions are used to search for favourable lens doublet configurations when the chromatic aberration is the most important
1. Introduction That the asymptotic aberration coefficients of electron lenses can be written as polynomials in reciprocal magnification m (m = liM, where M denotes the magnification) can be seen immediately from the integral expressions for these coefficients. For the chromatic aberration coefficients the regular axial chromatic aberration coefficient is quadratic in m and the chromatic aberration of distortion is linear. The anisotropic aberration of magnetic lenses is independent ofm.
