Research On Quasi Optical Mode And Matching Technology Of Gyrotron

Electron cyclotron resonance heating(ECRH)has become the basic auxiliary heating method for many tokamak devices.In the ECRH,a high-power Gyrotron,which needs to output energy horizontally,is used as a microwave source to cope with energy transmission of subsequent transmission lines.Thus,a quasi-optical mode converter needs to be used in the mode conversion section in the gyrotron.In addition,the operating mode of these high-power Gyrotron is mostly high-order rotational polarization mode.High-order rotational polarization modes are not easily transmitted at low loss and therefore need to be converted to Gaussian beams by a quasi-optical mode converter.However,if it is used in Vlasov radiators that are suitable for fundamental mode and higher-order symmetry modes,the wall current distribution at the notch of the radiator will be uneven,and the spatial radiation area will be too large and cluttered,and the subsequent mirror design will not be used..The Denisov radiator,due to the presence of an internal disturbance structure,allows the working mode to couple out a number of modes that are mixed in a certain proportion.These modes generate a Gaussian beam after being superimposed at the incision of the radiator.And if it is possible to design radiators with good Gaussian content and energy transmission efficiency,the subsequent mirrors can use a simple regular beam-focusing mirror,which can greatly reduce the difficulty of mirror processing.Therefore,this article focuses on the design of Denisov radiators.The main work of this article is as follows:1.It mainly studies the design method of radiators.The method of geometrical optics analysis of the electromagnetic wave propagation on the inner wall of the radiator to obtain a spiral incision;By deducing the two-dimensional Gaussian formula to obtain the Gaussian beam composition mode and the power relationship between these modes,the design method of the internal disturbance structure of the radiator is obtained;The modeling and simulation of Vlasov radiators and Denisov radiators for 94GHz and TE6,2 are performed.The simulation results show that the Denisov radiators have great advantages for the transmission of high-order rotation polarization modes.2.The accurate distribution of spatial field is obtained mainly by the vector diffraction theory combined with the aperture area method.The ABCD principle of Gaussian beam propagation principle is studied.Finally,for the depth phase correction,the method of obtaining the phase perturbation using the KSA algorithm is introduced.3.For the radiator in the quasi-optical mode converter with an initial diameter of 49mm,a working mode of 94GHz and a working frequency of TE22,6,a seven-stage disturbance structure,five-stage disturbance structure,and three-stage disturbance structure are designed in combination with numerical calculations;FEKO simulation software to verify.Finally,based on the three-stage disturbance radiator with the best energy transmission efficiency,the subsequent matching mirror is designed.The mirror system of this article consists of two mirror surfaces.The first stage mirror surface is a parabolic cylinder surface mirror;the second stage mirror surface is an elliptic parabolic surface mirror.This paper presents the numerical calculation results and simulation verification results of the mirror and output window.