Simulation Study On Terahertz Gyrotron Of High Harmonic Quasi-optical Cavity

It is extremely important to look for high power,high frequency microwave source with the continuous development of terahertz technology.The gyrotron is a kind of high power microwave devices developed based on the electron cyclotron mechanism.It was divided into two types of gyro amplifier and cyclotron oscillator.Among them,the cyclotron oscillator is a kind of important high power microwave radiation source.However,with the increasing working frequency,the traditional cyclotron oscillator with circular waveguide resonator has the gradually increased mode density,which leads to some problems such as serious mode competition,small power capacity,less output power,difficult to process and so on.Simultaneously,the increasing working frequency also leads to an increase in the magnetic field requirements of the cyclotron oscillator.Therefore,in order to suppress the mode of competition effectively and reduce the requirements of the magnetic field,this paper uses high harmonics and adopts the confocal quasi-optical waveguide,which has a mode selection feature,as the resonant cavity of the cyclotron oscillator.The specific work of this paper is as follows:Firstly,the theory and structure analysis of the confocal quasi-optical waveguide are carried out,and the HE_On mode has been selected as working mode by using the diffraction characteristics of the confocal quasi-optical waveguide.Then,a research method suitable for studying the gyrotron with a quasi-optical waveguide cavity is proposed based on the theory of slowly varying open resonator and the nonlinear theory of gyrotron,which lays the theoretical foundation and provides the research tool for the later study of the 0.3THz high-order harmonic quasi-optical cavity gyrotron.Secondly,the 0.3THz high-order harmonic quasi-optical cavity gyrotron is designed in detail based on the basic theory of quasi-optical cavity gyrotron and the C++Builder calculation program.Finally,the detailed design parameters of gyrotron are obtained by choosing the working mode and the structure size and optimizing the working parameters.At last,a double anode magnetron injection gun has been designed based on its theory and the particle simulation software,which can obtain an electron beam that has an injection voltage of 60 kV,a current of 2.5A,a transverse longitudinal velocity ratioof 1.8 and a radius of 0.3mm of the electron beam guiding center.It basically meets the requirements of 0.3THz second harmonic quasi-optical cavity gyrotron for electron beam.By using PIC simulation software to model and to simulate,the simulation result of05 HE mode second harmonic quasi-optical cavity gyrotron shows that the output power is 20 kW,the frequency is 301.12 GHz,when the working magnetic field is5.89 T.