New Small-ELM H-mode Regimes for Steady-state High-performance Operations in EAST

A stationary high-confinement (H$_{\mathrm{98y2}}$\textasciitilde 1.1) fully non-inductive H-mode regime characterized by high-frequency (2kHz) small ELMs (divertor peak heat flux \textasciitilde 2MW/m$^{\mathrm{2}})$ at relatively low pedestal collisionality ($\nu $*$_{\mathrm{e}}$\textasciitilde 1) and optimized high internal inductance (l$_{\mathrm{i}}$\textasciitilde 1.1) plasma has been recently achieved with high heating power (source power \textasciitilde 9MW) in EAST. This regime was obtained at high triangularity $\delta $ (0.55), high q$_{\mathrm{95}}$ (6) and high $\beta_{\mathrm{p}}$ (1.6), close to the parameter space of the grassy ELM regime in JT-60U. The relatively low plasma current, high q$_{\mathrm{95}}$, $\beta_{\mathrm{p}}$, and therefore high bootstrap current fraction (\textgreater 30{\%}) make it a suitable regime to achieve steady-state operation with low disruptivity, good reproducibility and robustness. The access to this regime is insensitive to the change of toroidal torque or plasma density in the explored parameter range. Benefiting from the optimized high l$_{\mathrm{i}}$ and high $\beta _{\mathrm{p}}$, good core energy confinement has been achieved even at low core toroidal rotation ($V_{t}$ down to 10 km/s). Good density control has been achieved at a line-averaged density up to 76{\%} Greenwald. Impurity concentration and core radiation were maintained at an acceptably low level, suggesting that sufficient particle exhaust can be driven by the high-frequency small ELMs.