Field Emitter Array Electron Gun for Traveling Wave Tubes

Abstract

This paper describes the structure, the fabrication process and the test of an FEA electron gun. A three-dimensional electromagnetic simulation program MAFIA was used to design the FEA electron gun, and the electron beam trajectory was simulated under initial condition of emitted electron half angle of 30 degrees. The designed FEA electron gun, Fig. 1 shows its photo, includes cathode, Wehnelt electrode, focusing electrode and anode. The FEA chip was mounted on the cathode electrode. The Wehnelt electrode, forced on the gate of FEA, extracts the electron and focuses the electron beam. The extracted electron beam, refocused by the focusing cylinder electrode and then transmits through the anode hole. In fabrication of the electron gun, many welding processes were used and which usually produce a mass of quantity of heat, if the weld point is very close to the cathode, or the weld power is very high, the high temperature resulted from welding will do great harm to the FEA, and sometime even leads to the short between the tips and the gate, so more attention must be paid on the welding technics