Study of turbulence modulation and core density peaking with CO2 laser collective scattering diagnostics in the EAST tokamak

We report experiments designed to help us understand the interaction between electron-scale turbulence and plasma poloidal flow in tokamaks. Multiple electron-scale turbulence (for ) in the plasma radial region (ρ = 0–0.8) is simultaneously monitored by CO2 laser collective scattering diagnostics in the EAST tokamak. In the stable discharge phase with electron cyclotron resonance heating (ECRH) power modulation and constant neutral beam injection (NBI), a periodic change in the core density peaking factor can be obtained. We note that the intensity of turbulence and the core density peaking factor show a negative correlation, while the poloidal rotation speed is inversely proportional to the intensity of electron-scale turbulence. The correlation between turbulence and plasma flow is found to be closely related to the density peaking factor. The quasi-linear theory of electron-scale turbulence-driven intrinsic poloidal rotation is adopted, and it shows that plasma flow may exhaust the free energy of turbulence through Reynolds stress. Besides, by comparing the plasma flow shear and spatial cross-correlation of turbulence we observed that the spatial structure of turbulence at is more sensitive to flow shear than that of turbulence at . The possible mechanism for controlling the core density peaking, together with the unchanged density gradient in the outer plasma region 0.5–0.8) are favorable for controlling the fusion reaction rate if they can be extrapolated to burning plasma. The results for ECRH power modulation experiments without NBI are listed and analyzed simultaneously; these serve as a comparison and enrich the physical picture.