Study Of 220GHZ Coupled-cavity Extended Interaction Klystron

Terahertz(THz) is electromagnetic wave with band of frequencies from 0.1 to 10 terahertz, and wavelength range from 0.03 to 3mm. Terahertz wavelength lies between infrared radiation and microwave radiation in the electromagnetic spectrum. Because of its own characteristics, THz has wide and important applications, and it became one of the most hot research fields.It is of importance to research the THz source because it is one of the key factors of THz technology. Extended interaction klystron(EIK) is one of sources which can work in THz region. Firstly, we analyze the basic theory of the EIK. Based on the theory, we design a 220 GHz three cavity structure coupled cavity extended interaction klystron and simulate the possibility of its work. The electron channel adopts rectangular structure,the input cavity adopts bell mouth input window structure and the output cavity adopts rectangular waveguide output window structure.Secondly, we did cold cavity simulation of the high-frequency structure using CST software. First, we analyzed its dispersion characteristics, coupling impedance, the characteristic impedance with the change of structure parameters of the cavity to identify the appropriate parameters by the cold cavity simulation of single period extended interaction resonator. By researching its dispersion curve we derived the range of operating parameters. And then the multi-gap cavity cold simulation was done to identify its work patterns and the field distribution of its 2π pattern. Finally, we analyzed the cold cavity characteristics of the input cavity, the middle cavity and the output cavity and calculate their intrinsic quality factor.Thirdly, we did the hot cavity simulation of the EIK by the 3D software MAGIC combined with the cold cavity work parameters. We analyzed each work parameter’s effect on output power. By optimizing the operating parameters we found a best group. The result was that when with an input wave of 220.248 GHz, 13.4kV of working voltage,63A/cm2 of current density, 34 mA of working current, 53 mW of input power and 0.5T of magnetic field, its output peak power was 21.468 W, with average power 10.734 W, gain of 35 dB, efficiency of 2.36% and 3dB of 180 MHz.The simulation results show that the EIK in this paper can work under appropriate work parameters. All of these lay the foundation for the next manufacture and research of the higher frequency EIK.