Design of Electron Optics System for G-band Traveling Wave Tube

Abstract

Electron optics system (EOS) for G-band traveling wave tube (TWT) is designed, and the design process of electron gun and permanent magnetic focusing system are described. Firstly, according to the particle-in-cell (PIC) simulation results of high frequency structure, we design an electron gun which can emit enough current whose quality is good. Secondly, combining with Piers theory, the structure of permanent magnetic focusing system which matches the electron gun is designed. The simulation results show that the passing rate of electron beam is high and its ripple is low. Basic parameters of EOS are as follows: the current emitted from the surface of cathode is greater than 70 mA when operating voltage is 17 kV. The length and radius of drift tube are 45 mm and 0.2 mm, respectively. Magnetic field (B) is about 6000 Gauss on the central axis. At last, the experimental results show that the passing rate of the electron beam is higher than 70%.