A nonaberrational lens and aberration correctors

A nonaberrational four-electrode lens for forming an ion beam for mass separators or spectrometers is described. A lens is a modification of a transaxial lens in which the circular gaps between the electrodes are replaced by elliptical gaps. The lens transforms an axially symmetrical beam into a ribbon-type beam. The lens parameters have been found using the phase diagram method. Using the same method, a new aberration corrector for electrostatic lenses and a new sector magnet aberration corrector are developed.