Abstract
A world-record duration of 310s H-mode plasma (H98y2>1.3, ne/nGW>0.6, fBS>50%) has been recently achieved on EAST, exploiting the device's improved long pulse capabilities. The experiment demonstrates good control of impurities, core/edge MHD stability, and heat exhaust with an ITER-like tungsten divertor and zero injected torque, establishing a milestone on the path to steady-state long-pulse high performance scenarios in ITER and CFETR. Important synergistic effects are leveraged towards this result, which relies purely on RF power for heating and current drive. On-axis Electron Cyclotron Heating enhances the heating and current drive from Lower Hybrid Wave injection, increasing confinement quality and enabling fully non-inductive operation at high density (ne/nGW ~60%) and high poloidal beta (βP ~2.5). A small ELM regime facilitates the RF power coupling to the H-mode edge and reduces divertor sputtering/erosion. The very high energy confinement quality (H98y2>1.3) is achieved with a slightly reversed magnetic shear and an internal transport barrier (ITB) in the Te profile, at rho~0.3. Transport analysis suggests that TEMs dominate in the core region, and reveals that these EAST plasmas are limited by ITG turbulence in the outer region (rho>0.7). The detailed physics processes (RF synergy, core-edge integration, confinement properties, etc.) of the steady-state operation will be illustrated. The latest experiments will also be discussed, where a broader current profile with qmin>2 and li~0.7 is obtained by early heating using off-axis ECH, and is sustained with combined LHW, ICRF and NBI powers. Based on this high qmin profile, future experiments will pursue the formation and sustainment of an ITB at larger radius, in order to further extend the fusion performance of long pulse plasmas on EAST.
