Aachen PK 2003 – scientific programme

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P: Plasmaphysik

P IV: HV IV

P IV.1: Invited Talk

Tuesday, March 18, 2003, 11:00–11:30, FO1

Understanding of Plasma boundary turbulence — •Bruce Scott — Max-Planck-Institut fuer Plasmaphysik, Euratom Association, Boltzmannstr. 2, D-85748 Garching

Self consistent computations of electrons and ions in closed magnetic flux surface geometry under the fluid drift approximation are presented. These relatively low frequency (few 100 KHz) and medium scale (few mm to cm) motions are believed to be responsible for the observed noncollisional losses of particles and thermal energy in magnetically confined laboratory plasmas. Since several mechanisms are at play, well founded computations must be constructed without regard to the particular type of eigenmode which may result. The computations show various mode types in their expected parameter regimes in the small amplitude linear regime. There are important differences, however, in the fully developed turbulence due to the presence of a nonlinear instability. The physics of the turbulence is diagnosed in the context of statistically saturated turbulence. Measurements of various cross correlations and directly of energy transfer mechanisms are found to be the most useful. The results are very compatible with observations of low frequency fluctuations in the plasma parameters for both edge and core turbulence. Many features can be explained, but at the same time one of the more enlightening results of these computations is the extent to which favourite scenarios to explain experimental features are found to be nonfunctional. This points the way to the construction of more general models which will have better chances to deliver the types of predictions one requires to assess the performance of next generation fusion experiments.