The Research Of THz Extended Interaction Klystron Based On The Ladder Structure

With the rapid development of science and technology, the unique properties and advantages of THz wave were also gradually found. But at present, the broadband and miniaturization of high-power THz radiation source are the real bottlenecks restricting the next application.In this paper, terahertz multi-cavity extended interaction klystron(EIK) is designed and analyzed. The EIK uses the coupled ladder structure as its high frequency system, and the input and output cavity is multi-gap couple connected by standard waveguide. Each cavity is connected by drift section.The main work of this paper is as follows:First, the characteristics and application of terahertz wave is described. The present development situation and the future development trend of the terahertz field is analyzed. The principles of the traditional klystron and EIK are presented.Then, the ladder structure is simulated to get the dispersion curve and coupling characteristics, using HFSS and CST simulation software. The equivalent axial electric field of the ladder structure is derived, and the coupling impedance is obtained. The relationship between the characteristic impedance and the coupling impedance is analyzed. The S-parameter of the input and output cavity is analyzed. Furtherly, we compared the high frequency characteristics of different coupled cavity structures.Finally,based on the results of the above, the 3D simulation model is built using the 3D particle-in-cell code. We investigated the output performances of the EIK operating on the different parameters, including the drift length, the type of the middle cavity, the power and frequency of the input signal, and beam parameters. The simulation results showed the stable output power will be obtained adopting the middle cavity with matched waveguide load. The operating parameters of the 0.22 THz EIK are summarized as follows. The operating mode is 2π, beam voltage is 13 kV, current is 0.07 A, the average input power is 7 mW, the average output power is 20 W, the gain is 34.6 dB, the efficiency is 2.2%. The simulation results laid a foundation for the further processing and experiment.