A Wide Dynamic Range Crossed-field Gun†

Abstract

ABSTRACT Generally, a short Kino gun can give an electron beam with optimum launching conditions only for the designed value of the cathode current density. For other values of the cathode current density the beam has a y component of velocity and it enters the interaction region with cycloid formation. Also, the y location of the beam changes with the cathode current density. This is true unless the various parameters, including the magnetic field, are simultaneously changed. A transformer is described which, when placed at the gun exit, helps in launching beams of widely different cathode current densities under optimum conditions, without changing the magnetic field. The gun-transformer combination thus results in a wide dynamic range gun. The same gun can be used for CW and pulsed operations. The transformer allows electronic control of the level at which the beam is injected into the interaction region, thus providing control of gain, efficiency and noise. Heretofore, this level was varied by adjusti...