Research On High Frequency System Of High Power Gyrotron With Frequency Tuning

Gyrotron is a fast wave microwave device based on electron cyclotron resonance excited radition mechanism,which can realize high-power output in the millimeter wave band and the sub-millimeter band.At present,the gyrotron with frequency of110GHz to 170GHz is mainly used in the plasma heating device.However,the traditional gyrotron usually works at a point frequency,so it is difficult to meet the requirement of controlling the instability of magnetic fluid in plasma electron cyclotron heating.Therefore,the gyrotron having the frequency tuning function has a wider application prospect.In this paper,a 140 GHz gyrotron operating in high order mode is selected for frequency tuning analysis and beam-wave interaction study.The main contents are as follows:1.The basic structure of the gyrotron,the principle of frequency tuning and the research status at home and abord are introduced.2.Analyze the open cavity of the slowly varying section,design the structure size of the resonant cavity according to the working frequency of 140GHz and the TE_22,6working mode.The influence of dimensional change on high frequency characteristics shows that the angle of the input and output and the length of the interaction zone have a great influence on the reaonant frequency and quality factor.3.The effects of coupling and starting current on mode competition are analyzed respectively.The method of frequency tuning is given,and the frequency hopping operation is realized by changing the working magnetic field.4.Combined with the nonlinear calculation software,the beam-wave interaction analysis of the gyrotron working in 140 GHz,TE_22,6,12,6,1 mode is carried out.For the analysis of the results,choose the best working parameters.5.Set up the test platform and carry out the test on the gyrotron.The output power is 560kW,the efficiency is 29.4%and the operating frequency is 140.2GHz.When the magnetic field is changed,the gyrotron can work in TE_22,6,3 mode with output power 450kW efficiency of 23.59%and operating frequency of 141.237GHz.