Sheet Beam Electron Gun with High Current for 220 GHz TWT

In this paper, a new structure of sheet beam electron gun with 0.55 mm 2 elliptical cathode is proposed for 220 GHz traveling wave tube (TWT) with the help of 3-D simulation software CST. By optimizing the size of the external ellipse structure of the focusing electrode, the desired sheet beam compression ratio is constructed easily and quickly. The simulation results show that the current and anode voltage of the electron gun are 152 mA and 22 kV, respectively. The current density of cathode emission surface can reach $\sim 27.6\mathrm{A}/\mathrm{cm}^{2}$ , the position of beam waist is located at 9.8 mm on the z-axis, and the beam size at the beam waist is $\mathbf{0.58}\ \mathbf{mm}\times \mathbf{0.1}\mathrm{mm}$ . The current of the tested cathode reaches $\sim \mathbf{154} \ \mathbf{mA}$ , which is consistent with the simulation result (152 mA). This proposed sheet beam electron gun is suitable for aT-type staggered double-vane TWT.