Simulation Design Of An X-band High-impedance Relativistic Klystron Amplifier

The coherent power combing is a significant trend of the development of high-power microwave technology. The high-impedance relativistic klystron amplifier based on the hot cathode, of high power, long pulse, high efficiency and steady amplitude and phase, is one of the promising candidates for the high-power microwave coherent power combing. In the dissertation, an X-band high-impedance relativistic klystron amplifier is designed by Particle-in-Cell(PIC) method, which provides reference for the further investigation. The main conclusions include:1. An X-band high-impedance relativistic klystron amplifier with coaxial output structure is proposed. Compared the klystrons with radial output structure, the klystron in the dissertation has the advantage of compact structure and high power capacity which is suited for high power microwave generation and application.2. The cavities of the klystron are investigated by cold cavity analysis method and hot cavity test method, and then the RF structure of the X-band high-impedance relativistic klystron amplifier is modeled by PIC code. The operation characteristics of the klystron are studied systematically and the influences of the geometry parameters and the operation conditions on the characteristics of the device are investigated. The key problems of the matching absorption in the input cavity, excessive modulation in the middle cavities and the beam-wave conversion efficiency are discussed and resolved. With the optimized structure of the klystron, an output microwave with an average power of 105 MW and frequency of 11.424 GHz is generated by a beam with the voltage 520 kV and current 460 A. With guiding magnetic field 0.4 T, the efficiency reaches 43.5 % and the gain is 50 dB.3. A high perveance and area compression electron optics system is designed for the requirement of the klystron. The static electricity characteristic of the gun is optimized by a big curvature radius focusing electrode and the anode to reduce the electric field. A match magnetic focus system is designed by SUPERFISH, with which the electron beam can be well focused. A solid beam is obtained with a radius of 3 mm, and the beam voltage and current are 525 kV and 328 A. The fluctuation on the beam is small with favorable laminar flow characteristic, and the transmission, the perveance and the area compression are 100 %, 0.9 μp and 97, respectively.