An experiment was conducted on the Experimental Advanced Superconducting Tokamak (EAST) to investigate the properties of stiff transport in an electron-heated H-mode plasma, using a power deposition scan with electron cyclotron resonance heating (ECRH). During this experiment, a shift in lower hybrid wave heating power and driven current from the plasma core to the outer regions was observed, accompanied by a change in the local magnetic shear. Transport analysis reveals a reduction in the normalized effective electron thermal diffusivity () at larger minor radii when ECRH was applied off-axis, in alignment with the turbulent instability analysis. A threshold for the stiff transport is identified around on EAST, above which the electron heat flux (qe) increases sharply with . Moreover, experimental and simulation results indicate that the change in ECRH power deposition influences local micro-instability turbulence, resulting in the transition of TEM to ITG modes, thereby affecting the plasma performance. These findings provide important insights for optimizing plasma performance, improving confinement, and advancing our understanding of plasma transport in future fusion reactors.
This paper investigates the properties of stiff transport in an electron-heated H-mode plasma on the Experimental Advanced Superconducting Tokamak (EAST). The study found that applying off-axis electron cyclotron resonance heating (ECRH) can reduce the normalized effective electron thermal diffusivity at larger minor radii, and identify a threshold for stiff transport. The findings provide insights for optimizing plasma performance and understanding transport in future fusion reactors.