ELECTRON BEAMS IN THE GRADIENT MAGNETIC FIELD: CONTROL FOR CONVERTING LONGITUDINAL MOTION INTO TRANSVERSAL

Abstract

The motion of electrons in the cylindrical magnetic field of the magnetron gun with a gradient-type potential is considered. The formation of a beam with an energy of 55 keV in such the magnetic field has been studied. It is found that in the selected field, the initial motion of electrons along the longitudinal axis is converted into radial motion. It is determined that such the transformation is due to the influence of the solenoidal magnetic field with large longitudinal gradient. The transformation of the longitudinal direction of motion into the transverse one is stable in the energy range of 20...55 keV of electrons and in the range of 5...55 mm of radial dimensions of the particle beam. The modes of operation of the gun, in which the particle undergoes a stable transformation of the direction of motion, are studied numerically. It is shown that for the given electron energy and the fixed magnetic field, the parameter that determines the rotation of particles is the magnetic field gradient at the boundary of the entry region. It is found that the rotation effect takes place for the range of radial beam sizes, which leads to particle focusing. The possibility is shown to control the vertical coordinate of a focused beam on the basis of field adjustment as the whole. Based on the model of electron flow motion, the characteristics of the resulting electron beam are considered. It is shown that the beam, having radial dimensions of 5...55 mm, is focused vertically on the section of 1 mm.