The concept of an electrostatic (a magnetostatic) ordinary multipole has been extended to that of an electrostatic (a magnetostatic) generalized multipole which consists of a closely placed electrostatic ordinary multipole and electrostatic round lens (or closely placed magnetostatic ordinary multipole and magnetostatic round lens). The definition of the M function for an ordinary multipole has been extended to that of the M function for its corresponding generalized multipole. The relation between the symmetry group of an ordinary multipole and that of its corresponding generalized multipole and the relation between their constraint relations among their mth partial harmonic potentials have been derived. The following conclusion is derived: if an electrostatic deflector-multipole and an electrostatic round lens are placed in close proximity, one cannot assert that this combined system can always be treated by the aberration theory of a combined focusing-deflection system. [References: 9]
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