Research Of Electron Cyclotron Resonance Heating Transmission And Launcher System On J-TEXT

Plasma is a good conductor with a certain electrical resistivity, and it can be heated by the resistance effect. However, the resistivity of the plasma decreases with the increasing of its temperature, and will reduce the efficiency of the conventional ohmic heating. Thus to achieve the required temperature(~ 10 ke V) for fusion reactions, auxiliary heating should be used. Since electron cyclotron waves(ECWs) can be easily coupled to the plasma for local heating and the launcher for beam injection can be far away from the plasma, the electron cyclotron resonance heating(ECRH) has been widely used in many magnetic confinement fusion devices.J-TEXT is a medium tokamak device on Huazhong University of Science and Technology, which is mainly used for personal training in the fusion field. To improve the plasma parameters of J-TEXT tokamak, a 1.2 MW ECRH system with 6 subunits was introduced from the Culham Science Center in 2013 through international cooperation, and the reconstruction of the system was started in 2014. As important parts of the ECRH system, the transmission lines and the launcher are used to efficiently transmit and inject the waves into the plasma with the desired polarization and injection angles which are determined by the requirements of physics experiments. The main work of this article consists of the design and layout of the whole transmission lines, construction and alignment of the first transmission line, the design of a polarization-controlled launcher, and the design of a high reliability arc detector for the safety operation of the gyrotron and the transmission line.This paper briefly introduces the transmission theory of the ECWs on J-TEXT tokamak. Based on this, analysis of the waveguide parameters and the material selection of the waveguide are given, and the mechanical structure of the TE02-TE01, TE01-TE11, and TE11-HE11 mode convertors are analyzed. The layout of transmission lines and the construction of the first transmission line with a length about 35 meters are presented according to the relative location between the tokamak and the ECRH hall. In addition, we design a set of arc detector with high reliability for the arc protection of the gyrotron and the transmission line. After about 200 times of test, the maximum delay of the arc detector is 3.2 microseconds and the average delay is 2.8 microseconds, the test results indicate that the detector can meet the protection requirements.Finally, we design a launcher for beam injection with the quasi-optical theory. The main parts of the launcher include a polarizer, an ellipsoidal mirror and a steerable flat mirror. The polarizer was used to change the polarization of the wave, and then the beam was focused by the ellipsoidal mirror. The injection angle of the wave can be adjusted with the steerable mirror. After assembly, test and calibration of the launcher, the feasibility and accuracy of the launcher are verified by comparing the experimental results with the theoretical calculation.