One class of electrostatic fields perfectly conserving the parallelism of planar homogeneous beams of charged particles

Electrostatic systems whose field is a superposition of two two-dimensional fields with the plane of symmetry (midplane) in common are considered. It is assumed that these fields overlap in the region through which a charged particle beam passes. The basic property of these systems is that they perfectly (without angular aberrations) conserve the parallelism of charged particle beams that are homogeneous in terms of energy-to-charge ratio and pass in the midplane of the field. A four-electrode system where each of the electrodes consists of two plates symmetric with respect to the midplane is an example of the new-class electrostatic systems. (C) 2000 MAIK "Nauka/Interperiodica".