Controlling the transverse dimensions of the electron beam in the solenoidal field of a magnetron gun

Abstract

The results of the study on the formation of transverse dimensions of an electron beam by a magnetron gun with a secondary emission cathode in the voltage range of 25..90 kV are presented. Investigations of the formation of electron beams in electron sources with cold metal cathodes operating in the secondary emission regime are carried out. The electron source is a magnetron gun. The principle of operation of such gun s is based on the reverse bombardment of the cathode by electrons returned by the magnetic field, the formation of an electron cloud near the cathode a nd the formation of a beam in crossed electric and magnetic fields. Their main difference from thermionic guns is the large current density from a unit of the cathode’s cross-sectional area ~ 50 A/cm² and a long service life. Therefore, the search and investigation of electron sources with a long service life is an urgent task. On the basis of a magnetron gun with a secondary-emission cathode, an electron accelerator is created in which an axial electron beam is used to irradiate metal targets and the inner cylindrical surface with a radial electron beam. The article presents the experimental data and the results of modeling calculations on the formation and control of the electron beam distribution by a magnetron gun with a secondary-emission cathode in motion in a solenoidal magnetic field. The dependence of the formation of the radial dimensions of the electron beam on the amplitude and gradient of the solenoidal magnetic field in the gun, which grows or falls in the channel of the beam transport, is studied. The results of numerical simulation of the motion of a tubular electron beam in a magnetic field of a solenoid are presented. Based on the motion model of the electron beam, the characteristics of the resultant electron beam are considered. It is shown that the diameter of the beam can be adjusted by varying the control magnetic field. The results of numerical modeling on the motion of a tubular electron flux in a magnetic field of a solenoid are given. The possibility of controlling the transverse dimensions of the beam is studied.