Research On High Harmonic Interaction System Of W-Band Gyrotron

As one of the most mature tube types in the electron cyclotron maser devices,gyrotron has important application value in industry,military and scientific research.For example,the gyrotron with frequency higher than 24GHz is used for material processing,the W-band gyrotron can be applied in the active denial system,and the170GHz gyrotron is used in the field of thermonuclear fusion.In view of the different application scenarios of gyrotron with different output power,in this paper,two kinds of high frequency interaction cavities with operating frequency in 94GHz and output power of 10kW and 150kW are designed,respectively.In order to reduce the requirements on working magnetic field,the interaction cavity adopts the second harmonic operation and the gradual complex cavity structure with the function of suppressing mode competition.In this paper,the beam-wave interaction cavity of gyrotron is studied as follows:1.The instability of the electron cyclotron master,the theoretical foundation of the gyrotron,is explored.It is precisely because of the existence of the relativity effect that the cyclotron frequency of the electron is related to the speed of the electron.So under the certain conditions,the cyclotron beam will occur clustering effect and exchange energy with the high-frequency field.2.Two major theories supporting the continuous study of the interaction cavity of gyrotron are analyzed:linear theory and self-consistent nonlinear theory.The linear theory based on the linear equations of vlasov and maxwell's equations is indispensable to the design of interaction cavity.The first-order transmission line equation of the cylindrical cavity based on the coupled wave theory,and the boundary conditions satisfying the specific cavity structure,together with the motion equation of the electrons in the interacting cavity,provide a theoretical formula for calculating the interaction efficiency.3.Through mode analysis,the pair of high-order mode TE_7.2/TE_7.3 is selected as the operating mode.The high-order mode is conducive to increasing the cavity size,reducing the processing difficulty,and improving the power capacity.4.A second harmonic complex cavity gyrotron with low voltage,low current and low magnetic field is designed.The structure of the interaction cavity is designed through the cold cavity simulation program,and the high frequency characteristics of the operating mode and the nearby competitive mode are analyzed,so as to further verify the rationality of the cavity structure and the operating mode.Meanwhile,the variation of resonant frequency and quality factor under the change of cavity structure parameters are analyzed.Through the hot cavity simulation program,the interaction efficiency and output power are simulated,and the influences of the working parameters related to the electron beam such as voltage,current,pitch factor,beam quality,working magnetic field and main cavity structure on the interaction are explored.Finally,a high frequency interaction cavity with interaction efficiency of 32.9%and output power of16kW is designed.5.The complex cavity gyrotron operating at second harmonic of the cyclotron frequency with output power of 150kW is designed through numerical simulation.The structure of the cavity is simulated by cold cavity program,and the high frequency characteristics of the competitive mode are analyzed.The change of the interaction efficiency under the key working parameters is simulated to find the best efficiency point.Finally,a high frequency interaction cavity with interaction efficiency of 34.83%and output power of 173kW is designed.