Investigation Of An Improved Coaxial Relativistic Magnetron

In order to develop a high power microwave?HPM?source which has the advantages including compact structure,good frequency tunability,low-order and controllable output mode,less sensitive parameters,high power conversion efficiency and so on,an improved coaxial relativistic magnetron?RM?with all-cavity extraction?ACE?structure proposed in this paper is systematically and thoroughly investigated in the aspects of theory,simulation and experiment.The main research results of this paper are listed as follows.1.Relevant theoretical studies are carried out on the improved coaxial RM with ACE structure.Firstly,based on the Helmholtz equation and the field matching method,the dispersion relation of a rising sun magnetron with sector and rectangular cavities is derived.And the dispersion relation is then generalized to a general case,in which the rising sun magnetron has multi-group cavities of different shapes and sizes.It has universal significance,because various kinds of dispersion relations of RMs can be summarized as a uniform expression.Then,based on the Helmholtz equation and the field matching method,the necessary conditions for generating coaxial TEM mode,left and right circularly polarized TE_n1 modes in the RM with ACE structure are derived for the first time.And the necessary conditions are then generalized to a general case,in which the RM has any type of periodic-symmetric-cavity extraction?PSCE?structures.It has universal significance,because the necessary conditions can be applicable for all possible excited modes and provide a theoretical foundation for outputting HPM with any given single mode.Finally,based on the cut-off condition and start-oscillation condition of RM,the value ranges of resonant cavity structure parameters are derived with the given operating parameters including applied voltage,magnetic field,frequency,mode number,and so on,and the conclusions of the corresponding monotonicity analysis are also given.The theoretical analysis takes the reverse thinking from operating parameters to structural parameters as a starting point,and its results can be applicable for the RM with any type of resonant cavity structures,so that a new method for designing the resonant cavity structure of a RM is provided.2.Relevant simulation studies are carried out on the improved coaxial RM with ACE structure.Firstly,the improved coaxial RM for outputting the coaxial TEM mode is simulated.Simulation analysis shows that the improved coaxial RM has the advantages including compact structure,good frequency tunability,low-order output mode,less sensitive parameters,high power conversion efficiency and so on.Then,the improved coaxial RM for outputting the coaxial circularly polarized TE₁₁ mode and the coaxial circularly polarized TE₂₁ mode respectively are simulated for the first time.Finally,the improved coaxial RM with PSCE structure for outputting the coaxial linearly polarized TE₁₁ mode is simulated.Research results show that compared with the ACE structure,the PSCE structure not only inherits the advantages of the ACE structure,but also makes it easier to output the coaxial linearly polarized TE₁₁ mode,and on this basis,it is easier to output HPM in a higher frequency band.The typical simulation results for outputting the coaxial TEM mode show that under the applied voltage of 220 kV and the applied magnetic field of 0.4 T,the HPM can be obtained with the frequency of 4.3 GHz,the output power of 480 MW and the power conversion efficiency of 56.8%.The typical simulation results for outputting the coaxial circularly polarized TE₁₁ mode show that under the applied voltage of 280 kV and the applied magnetic field of 0.4 T,the HPM can be obtained with the frequency of 4.2 GHz,the output power of 422 MW and the power conversion efficiency of 49.1%.The typical simulation results for outputting the coaxial circularly polarized TE₂₁ mode show that under the applied voltage of 340 kV and the applied magnetic field of 0.4 T,the HPM can be obtained with the frequency of 4.056 GHz,the output power of 558 MW and the power conversion efficiency of 49.9%.The typical simulation results for outputting the coaxial linearly polarized TE₁₁ mode show that under the applied voltage of 220 kV and the applied magnetic field of 0.4 T,the HPM can be obtained with the frequency of 4.4GHz,the output power of 208 MW and the power conversion efficiency of 46.6%.3.Relevant experimental studies are carried out on the improved coaxial RM with ACE structure.The improved coaxial RM for outputting the coaxial TEM mode and the coaxial circularly polarized TE₁₁ mode respectively are investigated experimentally for the first time,in which the microwave frequencies and the microwave modes obtained by the theory and simulation calculations of this paper are verified.The typical experimental results for outputting the coaxial TEM mode show that under the applied voltage of 293 kV,the voltage pulse width of 80 ns and the applied magnetic field of0.48 T,the HPM with quasi-single mode can be obtained with the frequency of 4.3 GHz,the output power of 309 MW,the pulse width of 50 ns and the power conversion efficiency of 20.6%.The typical experimental results for outputting the coaxial circularly polarized TE₁₁ mode show that under the applied voltage of 302 kV and the applied magnetic field of 0.32 T,the HPM with quasi-single mode can be obtained with the frequency of 4.21 GHz and the output power of 203 MW.