Numerical investigations of edge plasma flows in the Tore Supra tokamak

Abstract

The 2D boundary layer code TECXY has been used to simulate edge plasma parameters in the Tore Supra tokamak. Experimental situations have been analysed when the plasma contact point is shifted to different poloidal positions (limiter at bottom, top, outboard and inboard midplane) as well as the edge plasma conditions during lower hybrid RF power scan experiments. With the results of the calculations it was possible to reproduce experimentally observed changes to the flow pattern in the scrape-off-layer (SOL) for different plasma positions. These changes can be associated with the dependence of the radial electric field and the corresponding E × B drift velocity on the limiter position as well as to the poloidal asymmetries of the input particle flux. However, the code results with ‘standard radial transport’ did not show the large changes to the SOL widths as observed in the experiment. In order to reproduce in the calculations the observed differences in the SOL width, it was necessary to assume strong convective (or diffusive) radial plasma flow localized at the outboard midplane.