Design of a Cusp Gun With Two Control Electrodes Biased at Different Voltages

A cusp gun with two coaxial control electrodes biased at different voltages was optimized through parametric simulations for a gyrotron traveling-wave amplifier aiming to achieve an output power of 10 kW at a central operating frequency of 220 GHz. The on and off of the electron beam are controlled by applying an appropriate bias to the electrodes. An annular axis-encircling electron beam with a current of 1.5 A, a pitch factor of 1.23, was simulated when the gun was operated at 70 kV. The pitch-factor spread was improved from 5.0% to 3.4% by adjusting the different bias voltages applied to the control electrodes.