Systematic Design Study of the Elliptical Sheet Beam Electron Gun for Terahertz TWT Applications

Abstract

The design methodology of a sheet beam electron gun has been discussed and, subsequently, used for the design of a gun intended for use in a 0.3 THz traveling wave tube amplifier. The initial gun design parameters have been calculated analytically using a theoretical approach. Then, starting with these calculated parameters, the designed gun is then simulated using a commercial 3-D simulation code “CST Particle Studio” and optimized to get the target beam parameters. The circular-shaped cathode with an elliptically shaped beam-focusing electrode and elliptically shaped anode has been used to produce the good laminar elliptical sheet beam. The effect of varying the several parameters, such as height, width, and distance of focusing electrode, cathode-anode distance, and anode height have been studied to investigate their sensitivity on the target beam parameters. The simulation results predict that the designed sheet beam electron gun produces an elliptical beam with a desired beam cross section of 0.33 mm × 0.066 mm at a beam-waist position of 6.61 mm from the curved cathode emission surface corresponding to the beam parameters of 12 kV beam voltage and 55 mA beam current.