Study On S-band Tunable Relativistic Magnetron With Axial Diffraction Output

With the development of high power microwave technology, frequency tuning hasbecome an important development direction for high power microwave sources. Therelativistic magnetron (RM) is one of the high power microwave sources for emphasisresearch, owing to its simple structure, high efficiency and suitable application for longpulse and high repetition frequency, as well as its convenience for frequency tuning. Inthe thesis, a tunable relativistic magnetron based on rising-sun structure with axialdiffraction output is investigated on the aspects of theoretical analysis, particlesimulation and engineering designs of the device. The dominant contents of the thesisare as follows:Firstly, field analysis method is used to deduce the dispersion relation of therising-sun magnetron with sector cavities, as well as the expression of the field function.The dispersion relation is then extended to the general case in which the rising-sunmagnetron can be with multi-group cavities of different shapes and sizes. Then theeffects of the structure parameters on the cutoff frequency of π mode and the modeseparation are examined. The results show that the relative errors of the cutofffrequencies of π mode between theorety and simulation are less than1%; Cutofffrequency of π mode is in direct proportion to cathode radius Rc, anode radius Raandbig cavity angle θ1, but in inverse proportion to small cavity radius Rd0, big cavity radiusRd1and small cavity angle θ0; The radial structure parameters, the effects of which onfrequency are sorted in descending order, are as follows: anode radius, big cavity radius,small cavity radius and cathode radius; In the angular structure parameters, the effect ofbig cavity angle on frequency is greater than that of small cavity angle. In addition, themode separation γ is proportional to big cavity radius Rd1, but is inversely proportionalto cathode radius Rc, small cavity radius Rd0, and small cavity angle θ0, and the modeseparation γ increases firstly and then decreases with the increase of anode radius Raorbig cavity angle θ1. As for the tunability of the RM, the feasibility of10-cavityrising-sun magnetron and frequency tuning with small cavities applied in tunable RMare analyzed.Secondly, the softwares of high-frequency field analysis and3-D particlesimulation are used to analyze the operating performance of the rising-sun RM withsector cavities and to optimize the axial diffraction output structures of the RM. Underthe condition of the applied voltage of350kV, the diode current of6.17kA and theapplied magnetic field of0.3T, the output microwave power is868MW and the powerconversion efficiency can reach40%, while the resonant frequency of π mode is3.34GHz and the radiation mode is TE51. Then the frequency tuning performance of thedevice is investigated. Under the condition of the applied voltage of350kV and the applied magnetic field of0.3T, when the small cavity radius extends from25.1mm to36.1mm, the resonant frequency of π mode extends from3.72GHz to2.98GHz (about20%relative bandwidth), while all the output microwave power is above530MW andall the power conversion efficiency is above20%. And then the frequency tuningperformance of the device is improved by adjusting the operational parameters properly.In the20%relative bandwidth, the lowest output microwave power is improved from530MW to600MW, and the lowest power conversion efficiency is improved from20%to26%, while the highest power conversion efficiency keeps at40%.In the last part of the thesis, the engineering designs of the device, including thedesigns of the frequency tuning mechanism, the vacuum sealing and the magnetic fieldsystem, are investigated preliminarily.