| High-power microwave power synthesis technology is an important research direction to improve the pulse energy and power of high-power microwave devices.The relativistic klystron has the advantages of high power,high gain,high efficiency and phase stability.It is one of the ideal devices for power synthesis.With the urgent need of related applications,relativistic klystron is developing towards higher frequency.In the high frequency range,the relativistic klystron with conventional cylindrical structure is difficult to achieve high power microwave output.In order to break through the power limitation,a Ka-band coaxial multibeam relativistic klystron amplifier is proposed in this paper.In this paper,the high frequency structure and beam wave interaction characteristics of Ka-band coaxial multibeam relativistic klystron amplifier are studied by theoretical analysis and numerical simulation.The research content of this paper is divided into the following aspects:Firstly,the transmission process of the strong current relativistic electron beam in the drift tube is theoretically analyzed.Compared with the cylindrical structure,the coaxial structure is more conducive to the interaction between the electron beam and the resonant cavity.The electronic load conductance of the interaction between the electron beam and the coaxial cavity is studied.Based on the numerical analysis of the conductance formulas of different modes of common double gap and three gap coaxial resonators,the best value range of gap transition angle of beam wave interaction in each mode is found,which guides the design of devices in theory.Secondly,in order to produce multi beam electron beam with high efficiency and good quality factor in Ka-band,a multi beam diode system is designed,and its parameters are optimized by simulation and experiments.Under the experimental condition of the voltage of 507 kV,we have obtained a multibeam electron beam with total beam current of 2.8kA,injection drift current of 2.48 kA and efficiency of 88.5%.The feasibility of high efficiency introduction of high current multibeam in Ka-band is verified,which provides a reliable multibeam source for the subsequent coaxial multibeam relativistic klystron.Thirdly,the high frequency characteristics of Ka-band coaxial multibeam relativistic klystron amplifier are studied by combining 3D theory with electromagnetic simulation software.The influence of the structural parameters of the coaxial cavity on the resonant frequency,working mode and characteristic impedance is studied,and the variation law between them is found,which provides theoretical and simulation guidance for the overall design of Ka-band coaxial multi beam relativistic klystron amplifier.Finally,the input cavity,the middle cavity and the output cavity are simulated by using the Chipic three-dimensional particle simulation software,and the optimal structural parameters of each cavity and the optimal length of drift tube are obtained.The coaxial multibeam relativistic klystron amplifier was simulated by three-dimensional electromagnetic simulation software.Under the condition of electron beam pressure of 500 kV,beam current of 2kA,input microwave power of 1.2kW and axial uniform magnetic field of 1T,we have obtained microwave with output power of 250 MW,efficiency of 25%,gain of 53 dB and bandwidth of-3dB of 80MHz... |
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