Research On Efficient And Compact Dual Frequency Relativistic Magnetron Based On Beat Wave

The High Power Microwave（HPM）is a new science,based on pulsed power technology,relativistic electronics and plasma physics in the 1970 s,which has broad application prospects in the fields of national defense,energy,aerospace,high-energy physics,etc.With the development of related technologies and the traction of effects,HPM is developing from lab researches to engineering applications.Driven by application requirements,compactness and beat waves are two important research directions for HPM.The relativistic magnetron has advantages in compactness and miniaturization.Due to the low working magnetic field,it is convenient for permanent magnet packaging,which is obvious advantages when applied to mobile platforms.In this context,the purpose of this dissertation is to explore a technological approach to an axially cascaded dual-frequency relativistic magnetron.This technical approach ensures compactness through the common magnetic field and integration of output port,achieves high efficiency through independent beam-wave interaction,and satisfies the beat-wave conditions through reasonable power distribution and frequency selection,which lay the foundation for a compact high-power microwave beat-wave system in the future.Focusing on the requirement of beat wave,taking into account both high efficiency and compactness,this dissertation conducts in-depth research on axial series dualfrequency relativistic magnetron from theory,simulation and experiment.The main research results and innovations are as follows:1.According to the structural characteristics of relativistic magnetron,the technical route of relativistic magnetron with axial series dual frequency resonance system is proposed,whose advantages are sharing the magnetic field bunching system and integrating the ouput structure.The feasibility of establishing dual-frequency resonance under the same operating parameters and the allowable frequency interval range of the dual-frequency system are determined by analyzing the dispersion relation and selfexcited oscillation conditions of the dual-frequency resonant system.Meanwhile,the electric power distribution of the dual-frequency resonant system under the common working condition is analyzed,and it is pointed out that if the electric power distributed by the dual-frequency resonant system is as consistent as possible,the dual-frequency resonant system is required to have the same level of externl load value,which provides bases for the design of an efficient and compact dual-frequency relativistic magnetron based on beat waves.2.The mechanism and distribution characteristics of the self-magnetic field in the dual-frequency resonance system are studied,and it is pointed out that the influence of the self-magnetic field excited in the dual-frequency resonance system cannot be ignored.Meanwhile,the self-magnetic field is introduced into the physical model of beam-wave interaction,which further confirms the electron axial drift caused by the self-magnetic field.To solve the problem of the axial drift of the electron beam,three solutions are proposed:（1）under the condition of a certain diode voltage,a higher axial magnetic field is selected,that is,increase the impedance of the resonant system to suppress the self magnetic field,so as to suppress the axial drift speed of the electron beam;（2）Reduce the external load quality factor of the resonant system and reduce the high-frequency field of the resonant system to increase the impedance of the resonant system,so as to suppress the self magnetic field and reduce the axial drift velocity of the electron beam;（3）The end space structure is introduced to optimize the distribution of high-frequency field,and the axial drift of electron beam is restrained by pulling the axial velocity distribution of electron beam.The effectiveness of the method is verified by particle PIC simulation.3.Based on the dual frequency resonant system,the output structure of dual frequency relativistic magnetron is explored,and a compact diffraction output structure based on ridged circular waveguide is proposed,which is integrated with the radial all cavity extraction structure to realize the dual fundamental mode output of dual frequency relativistic magnetron.While ensuring the compact output structure,two sets of independent output structures can output microwave with low value coupling,which meets the requirements of dual frequency relativistic magnetron for output structure.4.According to the research of dual frequency resonant system and output structure,a design scheme of efficient and compact dual frequency relativistic magnetron based on beat wave is proposed,and its operation mechanism and output characteristics are studied by particle simulation.The simulation results show that,driven by a diode voltage of400 k V and an axial magnetic field of 0.44 T,two high-power microwaves are output,with frequencies of 2.05 GHz and 2.35 GHz,and microwave powers of 740 MW and 876 MW,respectively.The efficiency reaches 43%,and its power level and frequency interval meet the beat wave synthesis conditions.5.The experiments of the radial extraction relativistic magnetron of the permanent magnet packing and the diffraction full cavity output relativistic magnetron were carried out respectively.Based on this,a dual-frequency relativistic magnetron system is built,and the corresponding experimental research is carried out to obtain the experimental results.As follows: When the diode voltage is 487 k V and the working current is 12 k A,the dual-frequency relativistic magnetron system radiates two columns of high-power microwaves,the frequencies are 2.45 GHz and 2.95 GHz,the microwave power is 402 MW and 560 MW,and the device efficiency is 16.5%.Meanwhile,an obvious beat wave phenomenon is observed in the experiment.The experimental results show that:（1）Under the condition of the same cathode and anode radius,when the frequency interval is500 MHz,the π-mode fundamental wave of the dual-frequency resonant system still has a common working range.（2）The dual-frequency relativistic magnetron establishes resonance almost simultaneously.（3）The dual-frequency relativistic magnetron outputs two high-power microwaves at the same level.The experiment verifies the feasibility of the axial cascade technical scheme.