Session 7F - DIII-D: Edge and H-Mode.
ORAL session, Thursday morning, November 14
Vail Room, Adam's Mark
Three classes of Edge Localized Modes, or ELMs, simply labeled Types I, II, and III, in the \hboxDIII--D work, are widely observed. Type I ELMs are distinguished by the fact that their frequency increases with increasing input power. A scaling for the Type I ELM energy loss predicts 3% for ITER. The frequency of Type III ELMs decreases with increasing input power. The energy loss per Type III ELM is a factor of 2 to 4 below that for Type I at the same input power. Experiments on \hboxDIII--D suggest that proximity to the H--mode threshold power is the critical parameter for Type III ELMs. In contrast to Type I ELMs, the pressure gradient near the separatrix at a Type III ELM is often well below the ideal ballooning mode limit. Medium n magnetic precursor oscillations are observed with Type III ELMs, while no magnetic precursors are observe with Type I ELMs. Type II ELMs have very high frequency and low energy loss compared to Type I ELMs. Type II ELMs do not require low input power in contrast to Type III ELMs. Type II ELMs are associated with edge second stability in combination with either high q or high \beta_P.