Multimode Time Domain Analysis of Terahertz Second Harmonic Cyclotron Oscillator *
Received:November 21, 2018  Revised:July 17, 2019  download
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Author NameAffiliationE-mail
WANG Xue-Wei Chinese Academy of Sciences,Key Laboratory of High Power Microwave Sources and Technologies,Institute of Electronics wxwuestc@163.com 
XUE Qian-Zhong Key laboratory of Science and Technology on High Power Microwave Sources and Technologies Institute of Electronics, Chinese Academy of SciencesUniversity of Chinese Academy of Sciences qianzhong_xue@mail.ie.ac.cn 
ZHANG Shan Key laboratory of Science and Technology on High Power Microwave Sources and Technologies Institute of Electronics, Chinese Academy of SciencesUniversity of Chinese Academy of Sciences  
ZHAO Guo-Hui Key laboratory of Science and Technology on High Power Microwave Sources and Technologies Institute of Electronics, Chinese Academy of SciencesUniversity of Chinese Academy of Sciences  
LIU Gao-Feng Key laboratory of Science and Technology on High Power Microwave Sources and Technologies Institute of Electronics, Chinese Academy of SciencesUniversity of Chinese Academy of Sciences  
Abstract:Medium-power gyrotron operating in high frequency usually works at harmonics to reduce the required magnetic field strength. However, high harmonic modes suffer from low beam-wave interaction efficiency and from additional competition with neighboring fundamental modes. Start currents provide self-excitation conditions for the only operating mode, which can be referred to the methods providing the linear selection of modes. However, as the amplitude of modes grow they may cause some saturation effects, e.g. mode interaction. In order to observe the interaction phenomenon in the nonlinear stage, multimode computation in time domain is needed. In this paper, the suitable operating point is determined according to the start current. Hot cavity simulation is carried out based on both frequency domain single mode theory and time domain multimode theory. The gyrotron reached a steady state where both TE261+ and TE261- modes oscillate at 393.87GHz in time domain theory while TE261- cannot oscillate in frequency domain theory when the beam voltage is15kV,the magnetic field is 7.185 T, and beam current is 0.25A. TE261+ mode dominated the final oscillation, which output power and efficiency are 136.8W and3.6%, respectively. The output characteristics of the operating mode obtained by the two theories are identical.
keywords:starting current, harmonics, THz, multimode btime domain calculation
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Copyright:《Journal of Infrared And Millimeter Waves》