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P: Plasmaphysik

P III: HV III

P III.1: Hauptvortrag

Dienstag, 3. April 2001, 15:00–15:30, 2053

Turbulence in the Edge of Fusion Plasma — •Andreas Zeiler — Max-Planck-Institut für Plasmaphysik, Centre for Interdisciplinary Plasma Science, D-85748 Garching

During the last years it became increasingly evident that the confinement in the core of tokamak plasma is closely linked to stiff temperature profiles confirming theoretical predictions based on critical gradient models. As an important implication of these models the core temperature is expected to be proportional to the temperature at the top of the edge pedestal, where the transition between core and edge confinement occurs, emphasizing the crucial importance of plasma edge turbulence on the total confinement. The scaling properties of the edge turbulence are largely controlled by the drive and saturation mechanisms. Whereas resistive ballooning modes and drift wave instabilities drive the turbulence in the outer and relatively cool edge toroidal ion temperature gradient modes start to dominate towards the top of the edge pedestal marking the transition from edge to core confinement. Electromagnetic effects have a crucial impact on the saturation mechanisms which terminate the growth of the linear instabilities and therefore determine the stationary fluctuation level. Whereas in the resistive ballooning case the magnetic field supports the sheared velocity field originating from the linear instability and delays the nonlinear break-up, reconnection of perturbed magnetic field lines arises as an independent saturation mechanism in ion temperature gradient turbulence. The fully developed turbulence and the impact of the underlying physical mechanisms is studied by three-dimensional simulations of the complete electromagnetic two-fluid system.