Confinement improvement in the high poloidal beta regime on DIII-D and application to steady-state H-mode on EAST

Systematic experimental and modeling investigations on DIII-D show attractive transport properties of fully non-inductive high beta(p) plasmas. Experiments on DIII-D show that the large-radius internal transport barrier (ITB), a key feature providing excellent confinement in the high beta(p) regime, is maintained when the scenario is extended from q(95) similar to 12 to 7 and from rapid to near-zero toroidal rotation. The robustness of confinement versus rotation was predicted by gyrofluid modeling showing dominant neoclassical ion energy transport even without the E x B shear effect. The physics mechanism of turbulence suppression, we found, is the Shafranov shift, which is essential and sets a beta(p) threshold for large-radius ITB formation in the high beta(p) scenario on DIII-D. This is confirmed by two different parameter-scan experiments, one for a bN scan and the other for a q(95) scan. They both give the same beta(p) threshold at 1.9 in the experiment. The experimental trend of increasing thermal transport with decreasing beta(p) is consistent with transport modeling. The progress toward the high beta(p) scenario on Experimental Advanced Superconducting Tokamak (EAST) is reported. The very first step of extending the high beta(p) scenario on DIII-D to long pulse on EAST is to establish a long pulse H-mode with ITB on EAST. This paper shows the first 61 s fully non-inductive H-mode with stationary ITB feature and actively cooled ITER-like tungsten divertor in the very recent EAST experiment. The successful use of lower hybrid wave as a key tool to optimize the current profile in the EAST experiment is also introduced. Results show that as the electron density is increased, the fully non-inductive current profile broadens on EAST. The improved understanding and modeling capability are also used to develop advanced scenarios for the China Fusion Engineering Test Reactor. Overall, these results provide encouragement that the high beta(p) regime can be extended to a lower safety factor and very low rotation, providing a potential path to high performance steady state operation in future devices. Published by AIP Publishing.