Study Of Electron Mode Turbulence Characteristics In EAST Tokamak

Electron thermal transport has always been an important problem to be solved in magnetic confinement thermonuclear fusion.Electron heat transport is mainly related to electron mode turbulence,including trapped electron mode（TEM）turbulence and electron temperature gradient mode（ETG）turbulence.The wavelength of electronic mode turbulence is generally larger than the electron gyro-radius,and only a few diagnosis can monitor the high wavenumber turbulence in the experimental study.At present,our understanding of electronic mode turbulence is still very scarce in both theoretical and experimental measurements.In this paper,we use the four-channel CO₂ laser coherent scattering diagnosis system to synchronously measure the multi-scale poloidal turbulence（density fluctuation）in different regions of the EAST tokamak.This experimental study is unique in the world,and it is of great significance to explore the anomalous transport of magnetic confinement fusion plasma.In the first chapter,the significance of magnetic confinement thermonuclear fusion is introduced,and the principle and components of tokamak device are simply introduced.The anomalous transport in controlled fusion experiment is the important factor that restricts the realization of thermonuclear fusion.In this paper,plasma turbulence,which causes anomalous transport,is briefly introduced,and its research status is explained.In the second chapter,the development of turbulence research is briefly introduced according to development of nuclear fusion,and the current research status of turbulence is explained.After that,two phenomena in tokamak device—high confinement mode and stiffness of electronic temperature profile are briefly introduced.In chapter three,the EAST tokamak device is briefly introduced.The basic principle and characteristics of coherent scattering are briefly explained,and the diagnostic system of poloidal CO₂ laser coherent scattering installed on EAST device is introduced in detail.At present,the system can measure density fluctuations at different wavenumbers(k=10-30cm^-1)in different regions（ρ～0-0.4 andρ～0.4-0.8）simultaneously.Finally,the signal processing methods and their physical meanings are briefly explained.In the fourth chapter,we monitor the electronic mode turbulence characteristic in the L-mode and H-mode discharge states,and analyze and compare the turbulence characteristic.e.g.turbulence intensity,power spectrum characteristics and cross-correlation structural characteristics.In subsection 4.2,under the low confinement mode（L-mode）of the stable ramp-up process with low hybrid power,we study short-scale turbulence characteristics variations with L_ne and L_Te,and find that there is a certain relationship between the stiffness of electronic temperature profile and the change of turbulent spectrum structure,and make corresponding exploration for this phenomenon.In chapter five,the main work of this paper is summarized.Based on the understanding of electronic mode turbulence in tokamak and current research,the future research work is prospected.