Influence of different DED base mode configurations on the radial electric field at the plasma edge of TEXTOR

Abstract

The influences of resonant magnetic perturbations (RMPs) on the poloidal rotation at the edge of a tokamak are investigated. Specific results are displayed for the tokamak TEXTOR with the dynamic ergodic divertor (DED). The latter can be operated in three different base mode configurations, namely 12/4, 6/2 and 3/1. The base mode configurations distinguish themselves by resonating with different island chains and having distinctly different penetration depths. Calculations predict a strong influence of the DED base mode configurations on the strength of the poloidal plasma rotation. The interpretation of the results emanates from the electron and ion drift motions in partially stochastic magnetic fields. Generally, RMPs cause incomplete magnetic chaos; the latter influences the drift motion of electrons and ions differently. By virtue of the formed ambipolar electric field, the poloidal plasma rotation is directly connected via the radial force balance. With increasing current in the DED perturbation coils the electron and ion last closed drift surfaces as well as internal drift surfaces break up differently for each species. These break-ups, as well as the changes in the poloidal rotation in dependence on the electron and ion temperatures, are investigated in detail.