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AbstractAbstract
[en] Edge Localized Mode (ELM) measurements in the tokamaks, including JT-60U, DIII-D, ASDEX-U and JET, are reviewed. An ELMy H-mode operation having Type-I ELMs is nominated as the reference inductive operational scenario for ITER (QDT=10), which is normally observed for the best performing H-mode in many tokamaks,. However, the ELMs produce pulsed heat and particle fluxes that can lead to a rapid erosion of the divertor plate. It is estimated that the peak heat flux to the divertor would reduce the lifetime of the divertor to several hundred shots in ITER (e.g. an acceptable divertor lifetime could be realized only by an upper limit of ELM energy loss normalized by pedestal stored energy, ΔDWELM/Wped ∼ 5-6%). Approaches to control the Type-I ELMs, such as '' Ergodization '' on DIII-D, '' Pace making by a shallow pellet injection '' on ASDEX-U, '' Vertical motion '' on TCV, have been successfully demonstrated in many tokamaks. On the other hand, finding alternative scenarios to Type-I ELMy H-mode operation are also a key area of research for current tokamaks. Specifically, '' Quiescent H-mode (QH-mode) '' on DIII-D, ASDEX-U and JT-60U, and '' Grassy ELMs '' on JT-60U demonstrated a high confinement (being comparable to that of Type-I ELMy H-mode plasmas at similar parameters) in the absence of large, ELM induced, transient heat/particle fluxes to the divertor targets. ELM dynamics measurements in the SOL at the midplane show large, rapid variations of the SOL parameters. Recent data from a fast resolved measurements, such as scanning probe, radial interferometer chord, BES and tangentially viewing fast-gated camera at the midplane, suggest a filamentary structure of the perturbation with fast radial propagation in later phases and parallel propagation of the ELM pulse at around the sound speed of pedestal ions. The results are qualitatively consistent with nonlinear ballooning theory, although a more quantitative physics understanding, including detailed structures of radial electric field, edge current and neutral penetration, is needed to develop the edge condition to minimize ELM energy loss. (author)
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[33 p.]; 2007; 1 p; IEA Large Tokamak IA Workshop on Edge Transport in Fusion Plasmas; Cracow (Poland); 11-13 Sep 2006; Also available at http://www.ifpilm.waw.pl; 13 refs.
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