Electrostatic Focusing of an Electron Sheet Beam in a Symmetric Planar Structure

摘要

The relative merits of electrostatically focused electron-sheet beams are evaluated with respect to their use in both 0-type and transverse-field devices. Several practical structures for attaining this type of focusing are described. The parameters of interest in a symmetric planar electrostatic-focusing structure--beam perveance, transverse resonant frequency, beam stiffness, and the condition of beam instability--are evaluated analytically as a function of focusing-structure dimensions and applied focusing voltages. The analytic calculations are compared with digital-computer solutions of the paraxial-ray equation as well as with experiment. The beam motion in the unstable region and the electron motions within the beam are also investigated by analog-computer solutions of the paraxial-ray equation. Finally, methods for containing lateral beam spread are discussed. (Author)