Characterization of Type-I ELMs in tangential co-, balanced- and counter- plus perpendicular NBI heated plasmas on JT-60U

Abstract

Effects of plasma rotation and losses of fast ions on Type-I ELM characteristics have been systematically studied in the JT-60U tokamak, scanning combinations of NBI (tangential co-, balanced- and counter-NBI plus perpendicular NBI) in the three types of plasma configurations (corresponding toroidal field ripple at the plasma edge, δr ∼ 0.4, 1.0 and 2.0%). New findings on the Type-I ELM characteristics are as follows: smaller ELM energy loss normalized by pedestal stored energy, ΔWELM/Wped, and faster ELM frequency, fELM, are confirmed in the counter-NBI in comparison with the co-NBI discharges. Nevertheless, the power loss due to ELM, PELM (= ΔWELM × fELM), normalized by heating power crossing the separatrix, PSEP, is constant regardless of the direction of the momentum injection at each plasma configuration. In contrast, the PELM/PSEP decreases with increasing δr. The relationship between ELMs, rotation and the losses of fast ions are discussed.