Effect of cathode magnetic field on beam characteristics

The effect of the cathode magnetic field on the linear electron beam is under investigation both theoretically and experimentally. When the electron beam is confined by the periodic permanent magnet (PPM), the characteristics of the electron beam are affected by several PPM system parameters. The peak magnetic flux density, period of PPM, initial beam radius, initial velocity direction when the electron beam enters the main PPM magnetic field region, and the magnetic flux at the cathode are the main parameters. In this paper we focused on the effect of magnetic flux at the cathode. When the electron gun is operated in the confined flow, this effect is very critical, especially for the beam radius and ripple.