| High power,high efficiency and miniaturization have become the trends of most high power microwave sources these days.High power microwave sources operate under intense relativistic electron beam.As a magnificent component of high power microwave sources,the optimization of volume,weight and energy consumption of the Periodic Permanent Magnets(PPM)is of great significance to the high power microwave sources.PPM have the advantages of light weight,no power consumption and small stray magnetic field and can meet the requirements of small volume,light weight and low energy consumption of microwave tube.Therefore,based on the high power PPM focusing system,the transmission characteristics of intense relativistic electron beam in PPM,the design of the Pierce electron gun generating the real electron beam,the design of the structure of the PPM and the optimization of transition zone are studied in this thesis.Therefore,the main purpose of the research on PPM system is to ensure the passing rate of electron beam and reduce the fluctuation.Firstly,the research background and the significance of intense relativistic electron beam PPM focusing system are summarized and the theory of periodic permanent magnetism focusing system is introduced including the theory of PPM focusing the electron beam,the design methods of PPM,transition zone and the electron gun.Secondly,the transmission characteristics of intense relativistic electron beam in PPM system are studied.Based on the change of its own magnetic field of the beam and the electron mass under the relativistic condition,the relationship between the beam parameters and the peak value of the periodic magnetic field ensuring the stable transmission of the electron beam is obtained by force analysis of the outermost electron,obtaining the Brillouin magnetic field correction factor as well.Then,the correctness of the conclusion is verified by particle simulation.The ideal intense relativistic electron beam of 500kV,3.6kA can transmit stably under the relativistic PPM peak magnetic field,which meets the relationship between the peak magnetic field and the beam current and voltage and verifies the correctness of the theoretical analysis.Thirdly,an intense relativistic electron beam PPM focusing system is initially designed.The effect of the peak magnetic field on the transmission of electron beam is studied in the case of electron injection from the gun,that is,consider the effects of non-laminar flow and other conditions.The modified Vaughan iterative synthesis method is used to design the electron gun generating the actual electron beam,and the integrated simulation is established with the PPM of constant peak magnetic field.And the result shows that when the magnetic field strength is 1.1 times of the theoretical value,the injection rate of the beam is 100%with almost no fluctuations.Finally,the intense relativistic electron beam PPM focusing system is optimized through the design of the PPM transition zone magnetic field.After the effect of the field period on the condition of electron transmission is studied,the principle of selecting the period is determined.Based on the chosen period,the influence of the magnetic field peak value on the fluctuation of the intense relativistic high current is studied,offering the range of the magnetic field peak value in the transition zone,that is,when the peak value of the constant magnetic field of PPM is 0.9-1 times of the theoretical cycle magnetic field peak value,the second magnetic field peak value of the transition zone is 0.8-1 times of the constant magnetic field peak value,and the first magnetic field peak value is 1-1.2 times of the constant magnetic field peak,the electron injection fluctuation can be improved and the weight and volume of PPM are relatively reduced. |
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