Results of the 2022 U.S. Joint Research Target on Intrinsically Non-ELMing Enhanced Confinement Regimes

Intrinsically non-ELMing enhanced confinement regimes exhibit steady high confinement while avoiding ELMs and associated material erosion. Five JRT working groups further developed non-ELMing regimes for future application through new DIII-D experiments and comprehensive simulations of DIII-D and NSTX discharges. A new multi-machine non-ELM database with over 500 discharges identifies gaps with respect to ITER Q=10 and Fusion Pilot Plant equivalent targets and compares operating spaces and figures of merit across regimes. The database includes Standard and Wide-Pedestal QH-Mode (WPQH-Mode) in DIII-D, I-Mode in DIII-D and Alcator C-Mod, Wide and Enhanced Pedestal H-Modes in NSTX, and others. The roles of pedestal instabilities are elucidated using simulations ranging from fluid/MHD to global full-f gyrokinetic. I-Modes were achieved at record powers up to 11.9 MW using β feedback control in DIII-D. SOLPS-ITER simulations led to a new validated understanding of WPQH-Mode impurity sourcing, revealing the impacts of both high boundary temperatures and drifts. Measurements show the impurity confinement time increases with charge Z, approaching neoclassical values at high Z. Recent WPQH-Mode experiments reduced impurity sourcing of carbon and tungsten using divertor dissipation, and in hydrogen plasmas achieved record low carbon Z_eff ~ 2. Adding carbon powder closely matched hydrogen and deuterium WPQH-Modes. Measured turbulence increases the electron contribution to nearly double the divertor heat flux width relative to Eich scaling, in turbulence-limited QH-Modes over a range of plasma currents, matched by XGC gyrokinetic simulations. Scaling arguments suggest turbulence-limited non-ELMing pedestals may naturally arise in future machines – bringing new benefits, including high confinement, favorable power scaling, internal transport barriers, broader heat flux widths, and compatibility with strong electron heating in future burning plasmas.