Experimental Study Of Electron Temperature Fluctuations On J-TEXT Tokamak

In the magnetic confinement nuclear fusion device,the heat and particle losses are related with the anomalous transport which is driven by the turbulence.In recent years,lots of researches focused on the turbulent transport.However,many questions remain regarding the turbulence state in a fusion plasma relating to the mechanisms responsible for creation,evolution,and saturation of the turbulent spectrum,as well as the detailed physics governing the turbulence-driven contribution to transport of heat and particles.Therefore,it is value to continue the experimental research on turbulence and heat transport.In this paper,a series of related experimental researches on turbulent are carried out by measuring the fluctuations of electron temperature with the correlation electron cyclotron emission(CECE)diagnostic on JTEXT.First part of this paper focuses on the effect of static m/n=2/1 magnetic island on turbulence.The resonant magnetic perturbation(RMP)is used to excite the static magnetic island here.It is found that the amplitude of electron temperature fluctuations and density fluctuations in the island decrease significantly when the magnetic island is excited.By scanning the phase of the magnetic island,it is found that the fluctuation level of electron temperature fluctuations at the X point magnetic of island is basically the same as that before the excitation of the magnetic island.The level of turbulence at X point is significantly higher than that at O point.The experimental results show that the magnetic island can significantly affect the plasma background gradient and then change the turbulence distribution.Secondly,first dedicated experiments have been carried out on the J-TEXT tokamak for investigating the electron thermal transport and plasma fluctuations before and during Electron Cyclotron Resonance Heating(ECRH).It is found that the electron thermal diffusivity and the long-wavelength electron temperature fluctuations significantly increase in the ECRH-assisted Ohmic plasmas.The electron thermal diffusivities increase almost linearly with the ECRH power for the same discharge parameters,while the temperature fluctuations become broader at the same time.All these results suggest that long-wavelength the temperature fluctuations play an important role in electron thermal transport.The electron thermal diffusivities and the bandwidth of the electron temperature fluctuations decrease simultaneously as density increases in Ohmic plasmas,but the same trend is not found for ECRH-assisted Ohmic plasmas.It shows that the turbulence mode driving electron heat transport changed.The short-wavelength electron temperature fluctuations also play an important role on electron thermal transport.Finally,the linear stability analysis is preformed using the Gyrokinetic Electromagnetic Numerical Experiment(GENE)code.The simulation results of related magnetic island experiment further explain and verify the experimental conclusion.The simulation results of related ECRH experiment show that in ECRH-assisted ohmic plasmas,TEM is the dominant turbulence leading to the increase of electron heat transport and electron temperature fluctuation at lower density.However,at high density,TEMs tends to be suppressed,ETGs may become the dominant turbulence driving electron heat transport in ECRH-assisted ohmic plasmas.