The Simulation Of Beam-Wave Interaction In Third Harmonic Gyrotron

With the rapid development of science and technology, the application ofelectromagnetic spectrum is expanding constantly. Millimeter wave technology is moreand more mature, THz technology has become a new trend in science and technology.Terahertz science and technology have the important application and academic value inthe development of the national economy, security, and information science andtechnology. It is a very important cross-frontier disciplines. Now most countries in theworld have done a lot of research on terahertz science and technology, among them, thework of the United States, Germany, Russia have reached the advanced level of worldclass. The terahertz science and technology also attracts high attention and becomes ahot areas for scholars in China.As one of the terahertz radiation sources, gyrotron has broad application interahertz imaging, radar, communication and plasma heating, which can output the highpower and efficiency is the most promising. Gyrotron based on the free electronstimulated emission mechanism is a fast wave device, it principles to overcome thesetback that the traditional microwave tube encountered in the millimeter andsub-millimeter expansion. And it plays a significant role in promoting the developmentand application of terahertz science and technology. Thus the research on gyrotron playsan major role in the study of terahertz science and technology.A0.6THz third harmonic gyrotron will be designed and analyzed in this paper,and the contents are as follows:1. The complex cavity is chose as the high frequency structure to lock the mode.Then the advanced TE15.9mode is selected to increase the power capacity of the cavity.While the gyrotron work with the third harmonic，the magnetic field can be reduced tothe1/3when the gyrotron work with fundamental harmonic.2. HFSS and the multimode simulation software for cold cavity are used to get theappropriate high frequency structure for0.6THz gyrotron. And the changes of structureparameters on the complex cavity system are also analyzed.3. Based on the linear theory, the mode competition is detail analyzed. Then choose the appropriate guiding center radius,working current and operating magneticfield can effectively inhibit the mode competition4. Repeated simulate and optimize the beam-wave interaction, then significantimpact on the efficiency of interaction is analyzed which due to the changes of voltage,current, the guiding center radius and coefficient of magnetic field. Finally, with asingle output TE15.9mode and high interaction efficiency, the structure parameters andelectrical parameters are get.