Integrated Planar Three-Beam Electron Optics System for 220-GHz Folded Waveguide TWT

Abstract

An integrated planar three-beam electron optics system is designed for our 220-GHz cascaded folded waveguide TWT. First, a planar three-beam gun is designed based on Pierce theory and Vaughan’s synthesis method with simplification of the focus electrode and the anode to facilitate manufacture and assembly, which is characteristic with 20 kV, ${3} \times {0.1}$ A, and beam radius of 0.1 mm. Simulation results show that the gun model performs well. Next, a uniform magnetic focusing structure used for constraining the three-beam array with adjacent beam separation of 8 mm is designed. Magnetic saturation analysis of the pole piece and structure parameters optimization of the magnets is considered thoroughly, which may guarantee the transport stability of the three-beam array and keep down the volume of the magnet. Simulation results show that the transmission of three-beam array up to 18 mm is 100% with the maximum ripple of 11.2% in the designed focusing structure. And the integrated planar three-beam electron optics system is verified as a stable system with the beam characteristics analyses of matching error, beam voltage fluctuation, and variation of peak ${B}_{z}$ .