Study On The High-efficiency Relativistic Magnetron

The relativistic magnetron is direct extrapolation of ordinary magnetron in high voltage and large current direction,it has the characteristics of high power capacity,stable operation,simple structure,and thus become a hotspot in the field of high power microwave.The early research on relativistic magnetron focused on its output power,ignoring the efficiency of relativistic magnetron.The requirement of practicality makes the efficiency of relativistic magnetron become the focus of magnetron research.The magnetron with diffraction output(MDO)has a series of advantages,such as compact structure,good angular uniformity,high power output,and so on.It has become the mainstream of relativistic magnetron research.Therefore,in this paper,we have carried out a comprehensive and in-depth research on the MDO,including theoretical analysis,structural design and particle simulation.Firstly,the development history and research status of relativistic magnetron are introduced on the premise of full investigation.Five kinds of diffraction output structures are introduced in this paper.The explosive cathode,cathode priming technology and transparent cathode are introduced.Secondly,the theoretical analysis of relativistic magnetron is carried out.The basic structure of the axial output of relativistic magnetron is introduced,and the process of electronic steady motion in magnetron is described.The interaction between electron and field in the high frequency structure of magnetron is analyzed.The cutoff condition and synchronization condition of magnetron are deduced.The dispersion relation of relativistic magnetron is derived by means of circuit analysis,and the mode spectrum of the A6 system is drawn.Some special physical problems in relativistic magnetron are explained,that is,the generation and influence of plasma in relativistic magnetron,the influence of angular magnetic field of axial current,and the influence of strong highfrequency field.Finally,the simulation study of L-band relativistic magnetron is carried out.The particle-in-cell(PIC)simulation is briefly introduced,and the preliminary modeling design is carried out.The parameters of the magnetron are optimized after the voltage and magnetic field are determined.The cathode priming technique is introduced to accelerate the vibration of the π mode and restrain the competition of other modes.The length and width of the emission region,the deviation angle between the emission region and the anode vane,and the extended length of the cathode are four important parameters for cathode emission.The four parameters are optimized in simulations,and the highest efficiency optimization value is obtained: when the applied voltage and magnetic field are 520 kV and 0.3 T,respectively,MDO radiates microwave of 2.19 GW at 1.577 GHz and the corresponding power efficiency is 61%.The endcaps are introduced to limit the leakage current.The structural parameters of the cathode endcaps are optimized by CST and MAGIC.And the optimized results are obtained: working at an applied voltage of 563 kV and a magnetic field of 0.34 T,the MDO radiates microwave of 2.13 GW at 1.589 GHz,and the corresponding power conversion efficiency is 75.5%.Based on the optimized structure,the effect of different DO on the efficiency of magnetron is compared.It is concluded that the stepped mode conversion DO can achieve higher power conversion efficiency in this magnetron structure.