| Permanent magnetic field focusing has proved to be a useful method of focusing in present-day microwave tube ,and is one of the important compose of electronic optics of the microwave tube. The dissertation presents a new type of focusing structure of part filled in periodic permanent magnet on demand of high-power travelling wave tube, adopts finite element method to calculate it,uses the PIC tool of MAGIC to simulate electro-transmission channel, experiments with Gauss testing apparatus. Firstly, the author analyses the theory of full filled in periodic permanent magnetic field focusing system and the principia of designing PPM focusing system and how to choose primary parameter in detail, and then conclude formula of part filled in periodic permanent magnetic focusing system based on the theory of PPM and characteristic of part filled in PPM focusing system, reasonably designs magnetic system. Secondly,the author computes by the design parameter with FEMM program,and studies primary parameter to influence on magnetic field distributing, researches the method of minute adjust on magnetic field distributing. Lastly,the authod uses the PIC tool of MAGIC to simulate electron beam movement in part filled in periodic permanent magnet, the result is consistent with the theoretical prediction of the PPM focusing electron beam, and thoroughly probes into the factor of influence on focusing electron beam , finally confirms swell coefficient of magnetic field intensity.The mainly innovation of the thesis is that the author researches into part filled in periodic permanent magnetic field focusing , and validates rationality and feasibility of this structure according to design parameter, moreover confirms swell coefficient of magnetic field intensity based on thoroughly researching into focusing electron beam. The calculated result has been adopted on correlative project team. The heat testing result of travelling wave tube has attest to credibility of the conclusion . |
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