Pellet-fueled I-mode plasmas in ASDEX Upgrade

Abstract This letter reports on the efforts carried out at ASDEX Upgrade tokamak to integrate I-mode plasmas with pellet fueling and increase Greenwald fraction f GW , two important requirements for any DEMO operational scenario. For first time, stationary have been achieved core has increased up 0.8. Larger were not due technical constraints rather than a physics-based limit. Pellet-fueled exhibit enhanced edge density, while temperature are reduced. Nonetheless, normalized gradients remain I-mode-like, namely shallow density steep temperature. The energy confinement time is found obey distinct dependencies: < 0.4 it rises increasing > plateaus or even decreases pellet-fueled plasmas. Similarities Ohmic L-mode dependency discussed.