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P: Plasmaphysik

P 5: Magnetischer Einschluss I

P 5.4: Fachvortrag

Dienstag, 9. März 2004, 11:50–12:10, H\"orsaal D

Stationary ELM-free H-mode in ASDEX Upgrade — •W. Suttrop¹, T. Kurki-Suonio², A. Stäbler¹, G.D. Conway¹, M. Maraschek¹, C.F. Maggi¹, H. Meister¹, and R. Neu¹ — ¹Max-Planck-Institut für Plasmaphysik, EURATOM Association, D-85740 Garching — ²Euratom-TEKES Association, Helsinki University of Technology, FIN-02015 HUT

The planned first reactor-size fusion experiment ITER (International Thermonuclear Experimental Reactor) will rely on the High Confinement Mode (“H-mode”) regime for its target of Q=10 (ratio of fusion power and external heating power). Helium ash and impurity exhaust are mainly due to an intermittent edge localized MHD instability (“ELMs”) which can also lead to large momentary heat fluxes that are a challenge for the power handling capability of plasma facing components. “Quiescent H-mode” (QH-mode) is a new H-mode regime without ELMs, obtained in several tokamaks (DIII-D, ASDEX Upgrade, JET, JT-60U) with neutral beam injection in direction opposite to the plasma current, which causes a strong population of beam ions outside of the core plasma, and a significant radial current from lost ions. The impurity content in the plasma is higher than in normal injection direction but similar in ELMy and QH-mode phases with reversed injection, indicating comparable levels of particle transport across the transport barrier. This may be connected with benign continuous MHD activity observed instead of ELMs. The edge pressure can be higher than in ELMing H-mode plasmas indicating improved MHD stability. The physics of QH-mode and its extrapolation to a reactor-size plasma are discussed.