Focusing Properties of Quadrupole Lenses

Abstract

The properties of electrostatic quadrupole lenses are investigated both theoretically and experimentally. A method for measuring the effective lens length is developed and used. Previously reported (6) focusing equations for the two lens system provide an implicit solution involving trigonometric and hyperbolic functions. A nomograph was designed as an aid in carrying out this solution numerically. The two lens system was evaluated for various combinations of object distance, lens separation and image distance. Measured values of focal strengths were compared to theoretical values. Finally, measurements were made on the effective focal strength as a function of radial displacement from the central axis.