Electron optics design and experiment of G-band TWT

This paper introduces the design method and experiment of intensive beam electron optics which contains an electron gun and a magnetic focusing system for a 220GHz folded waveguide TWT. Pierce type electron gun is used. The thermal initial velocity effects as well as the beam waist radius and gunshot distance are considered for the design of electron gun. The period permanent magnet (PPM) system which contains the U-type magnet is simulated by Microwave Tube Simulation Suite (MTSS) and Opera 3D software. The simulation result shows that the transmission current in the tunnel of 0.12mm radius is 53mA with about 90% transmission rate. The experiment achieves about 82.7% of transmission rate and 45mA of transmission current.