Effect of voltage ripple on the electron beam of a strip-type electron gun

Ripple in HV power supply is inevitable. In this current work, the effect of ripple present in the accelerating voltage on the dynamics of an electron beam from a strip-type electron gun is investigated. A comparative study has been performed by 3D simulation of the electron trajectories from the strip electron gun using SIMION 7 for AC and DC modes of filament-heating. In both the cases, it has been found that the average width of the electron beam increases considerably due to its width-wise oscillation leading to a decrease in its average power density even in the presence of about 1.2% rms ripple in the accelerating voltage. In the AC mode of filament-heating, the beam oscillates along the length due to the filament current-generated magnetic field. Thus, in case of AC filament-heating, length- and width-wise oscillations result in the formation of a larger molten pool required for processing large raw material for metal purification purposes. The inherent ripple in the accelerating voltage is shown to be useful in avoiding material sputtering, yet maintaining a high evaporation rate.