EAST ICRF Antenna Measurements And The Investigation Of Interactions Between Antenna And Edge Plasma

Ion cyclotron radio frequency(ICRF)heating is one of the auxiliary heating methods in the Tokamak fusion devices.Using ICRF waves to efficiently heat ions and electrons in the plasmas has been successfully demonstrated in EAST and other Tokamak devices.The ICRF antenna is a key component directly facing the plasmas,the ICRF coupling and heating efficiency is greatly influenced by the parameters of the edge plasma.In addition,the excitation of ICRF waves may change the parameters distribution of edge plasmas.In this thesis,the coupling and the interaction between ICRF antenna and the edge plasmas are investigated based on the antenna coupling resistance obtained by means of antenna impedance measurement system.At first,a new ICRF antenna impedance measurement system has been designed and built up based on the voltage and current probes(?/? probes).The principle of the measurement method is described,and the appropriate size and location of V/I probes in the transmission lines are determined.The impact of the amplitude and phase measurement error on the impedance calculation is evaluated.It is found that the small phase measurement error(2°)has an important impact on the impedance calculation results.The test results with low power(several watts)have the large relative deviations(exceeds 100%)compared with calculation results for a load that has a large reflection coefficient|?|>0.9,and the large deviation is mainly ascribed to the uncertainty of phase measurement.Therefore,it is necessary to find an appropriate impedance calculation method to obtain the accurate phase of V/I probes when the phase detector gives the illogical results.Secondly,the method based on power,amplitude of voltage and current probes has been used for the antenna impedance calculation instead of the phase detector.The simulation results indicate that 10%of power measurement error will lead to less than 10%of relative resistance error for an arbitrary load,which demonstrates the feasibility of this calculation method.Finally,the experiments of the ICRF antenna coupling and the interaction between antenna and edge plasmas have been carried out by using the impedance measurement system.The effects of various parameters(including core density,gap,IP,ICRF power)on the antenna loading are analyzed and investigated,and the experimental results are in agreement with those of the theoretical simulations.The evolution of the edge density distribution with ICRF power is also investigated by numerical simulation with Comsol program,the results show that the ICRF induced sheath potential is the cause of theasymmetry of density distribution along poloidal direction in front of antennas.The temperature distribution of the antenna limiter from IR camera indicates that the asymmetry of temperature distribution along poloidal direction depends on the magnetic direction,which supports the explanation of physics mechanism of impact of the ICRF sheath on the density evolution.