A A Trubitsyn, E Yu Grachev, E G Kochergin
An approach to modeling cathode lenses with arbitrary electrode configurations is developed, in which the electric field on the symmetry axis is calculated using the boundary element method. Criteria for the telescopic mode of idealized and real cathode lenses are determined. A telescopic mode is observed for the first time in a lens with a small-diameter cathode. Algorithms for numerical modeling of cathode lenses are optimized, and a lens with a small-diameter cathode is numerically studied. A design for an electron gun with a thermionic cathode that provides high brightness is proposed.