Study On The Influences Of The Electron Beam On The Resonant Frequency And Electromagnetic Field Distribution In A Cavity

The high power klystron is a microwave vacuum device based on the principle of velocity modulation converting the electron beam energy to the microwave energy, which is a wide range of applications in areas such as broadband radar systems, electronic warfare and communications systems.The resonant cavity is the main core components of the klystron. The klystron resonant cavity can be divided into three categories, the input cavity, the middle of the cavity and the output cavity.The function of the input cavity is inputing the microwave signal, and producing microwave electric field in the cavity gap as to modulate electron beam. The function of the middle cavity is to improve the gain, bandwidth and efficiency of the klystron. The function of the output cavity is to convert the cluster electron beam energy into microwave energy. As a high-frequency interaction circuits of the klystron, the resonant cavity’s characteristics have a decisive impact on efficiency, gain and bandwidth performance of the klystron. When the klystron works, the electron beam will through the resonant cavity, which makes the resonant cavity’s performance change. The eigenvalue problem of the resonant cavity is an important topic of electromagnetic engineering fields. On the one hand, the different modes analysis of the cavity field is directly related to this issue, on the other hand, the optimization design of many cavity is often based on the solving of the problem. The size of the resonant frequency, the distribution of the electromagnetic field and the analysis of the various modes are the most important reference when studying these cavities. This article studies the influence of the resonant frequency and electromagnetic field distribution in the resonant cavity traversed by electron beam. The contents of this paper are as follows.Firstly, we briefly describe the structure, working principle and the the development of the klystron as well as the theory of the resonant cavity.Secondly, through zoning, a physical model of the resonant cavity filled with the electron beam was established. On the basis of the original wave equation, the electromagnetic field distribution of the electron beam region and the vacuum region are educed in the boundary matching conditions. And the eigenfrequency equations of the TM0m0mode are educed by further educing.Thirdly the resonant frequency of the TM010mode and the TM020mode changes with the plasma frequency can be got by calculating. And uses a graphical method for solving the eigenvalue equation to verify the calculation results. The results show that with the increasing of the plasma frequency, the resonant frequency will continue to increase. When the plasma frequency exceed40GHz, the resonant frequency o changes little. Finally, The resonant cavity’s electromagnetic field distribution of the TM010mode and the TM020changes with the plasma frequency also can be got by simulating. When the plasma frequency increases, it will make the electromagnetic field distribution change. And the results show that, when the plasma frequency exceeds the resonant frequency, the electromagnetic field distribution of the resonant cavity will change greatly, which will have an important impact on the stability of the high power klystron. The impact of the law of the resonant cavity filled with electron beam also applies to other types of high-power microwave source. So it will have important reference value for the development of the klystron and other types of microwave sources.