Design Of The Electron Cyclotron Wave Mode Analysis Unit Based On Directional Couplers

Electron cyclotron resonance heating(ECRH)is widely accepted by magnetic confinement fusion field due to its high coupling efficiency,simple coupling principle,highly localized power deposition and launcher away from plasma.Considering the gyrotron,as the wave source which generates electron cyclotron(EC)wave in ECRH system,is urgent to be provided with the ability to analyze the wave mode in real time in case increased rates of the parasitic mode threat the system,an EC waves mode analysis unit is designed based on threeport broadband directional couplers.High power tests with this unit are carried out on the 105 GHz ECRH system on J-TEXT and HL-2M devices respectively,and the test results provide the EC waves mode information of the gyrotron.The main work of this article includes:Brief introduction to the close relationship between tokamak device and ECRH system and the necessity to analyze the EC wave mode in real time.Some existing methods of mode analysis are also given.List of the basic design principle of directional coupler,which is the main part of the EC wave mode analysis unit.The design principle of directional coupler in this article includes small aperture coupling theory and phase addition theory under multi-hole coupling,which offer a theoretical basis for design of coupling parameters.The design of directional coupler in the EC wave mode analysis unit.This part models the single-port directional coupler first,then calculates and optimizing the coupling parameters according to this model.These parameters are also utilized in three-port directional couplers.Finally,two three-port directional couplers are fabricated after their structure is confirmed.An evaluation about the real performance of the directional couplers is given.The high power tests of EC wave mode analysis unit carried out on the 105 GHz ECRH system on J-TEXT and HL-2M tokamaks respectively.