The Reserch On RF Structure And Beam-wave Interaction Circuit Of Millmeter Klystron

As vacuum electronic devices constantly develop into high power, high frequency and miniaturization, based on traditional devices, all kinds of new type device are produced. In order to realize broadband under low peak power, multiple-beam klystron is developed; In order to obtain high power output under high working frequency, sheet beam klystron is developed; In order to overcome the traditional klystron size decrease difficulty at high frequency, extended interaction klystron is developed. As a new type of vacuum electronic devices, sheet-beam extended interaction klystron hold great promise in the millimeter and sub-millimeter regimes, and both sheet-beam and coupled-cavity traveling-wave circuit have been considered.In this dissertation, the RF structure and beam-wave interaction system of traditional klystron and W-band sheet-beam extended interaction klystron have been deeply and detailedly studied using CST Microwave Studio and MAGIC. The main work includes the following three aspects:1.For the analysis of general theory and basic parameters of klystron cavity, the relationship between the structure parameters and electric parameters is established using equivalent circuit of klystron cavity. Then a 2.856 GHz cavity is preliminary designed and optimized using MAGIC. Through the research work, the design method of reentrant cavity is formed.2.Based on the basic theory and design method of reentrant cavity, a S-band traditional klystron is designed. Then, a five-cavity S-band klystron design has been completed with the code MAGIC, as well as device stability and characteristics of beam-wave interaction. The impact of second harmonic cavity and long drift tube on klystron’s efficiency is deeply and detailedly studied.3.The W-band sheet-beam extended interaction klystron is studied. A W-band sheet-beam five-cell extended interaction cavity working in 2? mode is designed using CST Microwave Studio and MAGIC. The impact of key structure parameters of five-cell cavity on characteristic impedance and resonant frequency are studied, as well as device stability and characteristics of beam-wave interaction. With a 19.5kV, 3.5A sheet beam, the W-band sheet-beam klystron is proved to be capable of generating an output power about 8kW and a gain of 23 d B.According to the research work on tranditional klystron and W-band sheet-beam extended interaction klystron, the method of klystron from cavity design to whole tube simulation is set up. Especially, for the design and simulation of RF structure and beam-wave interaction system, several valuable and important results are obtained, which provide a good guide for developing higher performance of sheet-beam extended interaction klystron in the future.