To address the needs for a fusion pilot plan design, DIII-D/EAST joint experiments on DIII-D have demonstrated high normalized beta βN ∼ 4.2, toroidal beta βT ∼ 3.3% with qmin > 2, q95 ⩽ 8 sustained for more than six energy confinement times in high poloidal beta regime. The excellent energy confinement quality (H98y2 ∼ 1.8) is achieved with an internal transport barrier at high line-averaged Greenwald density fraction fGr > 0.9. The trapped gyro-Landau fluid (TGLF) modeling of the transport characteristics shows that the beam-driven rotation does not play an important role in the high confinement quality. The modeling also captures very well several transport features, giving us confidence in using integrated modeling to project these experimental results to future machines. The high-performance phase is terminated by fast-growing modes triggered near the n = 1 ideal-wall kink stability limit. New radio frequency (RF) capabilities for off-axis current drive could remove the residual ohmic current to achieve a fully non-inductive state, and improve the mode–wall coupling to increase the ideal-wall βN limit, enabling sustainment of the fully non-inductive high performance plasma in stationary conditions.
This paper discusses the achievement of high-performance fusion plasmas with high normalized beta and toroidal beta on the DIII-D tokamak. The experiments demonstrated excellent energy confinement with an internal transport barrier, and the modeling captured key transport features. However, the high-performance phase was limited by instabilities near the ideal-wall kink stability limit. The paper suggests that new RF capabilities could help sustain the high-performance state.