Design and Simulation of Electron Optics System for 0.34 THz Traveling Wave Tube

Electron optics system (EOS) for 0.34 THz 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 tracking code simulation results, we design an electron gun that can emit enough current whose quality is good. Secondly, combining with Peirce theory, the structure of focusing magnetic field which matches the electron gun is designed. Basic design parameters of 0.34 THz EOS are as follows: the current emitted from the surface of the cathode is greater than 25 mA when operating voltage is 23.8 kV. The length of drift tube is longer than 60 mm and the radius is 0.08 mm. The peak value of the magnetic field is about 6200 Gauss, and the period length of the magnetic focusing system is 3.4 mm. At last, the simulation results show that the passing rate of the electron beam is 100% and the filling ratio is about 55%.