Modeling of the dynamic ergodic divertor of TEXTOR-94

A Dynamic Ergodic Divertor (DED) is under construction for TEXTOR-94. The ergodization will be achieved by a set of 16 in-vessel perturbation - plus two compensation - coils located at the high field side of TEXTOR-94. The coils follow helically the resonant magnetic field lines for one toroidal turn and are individually fed outside the vessel allowing a large flexibility for possible connections. The DED-system will operate at de or several fixed frequencies up to 10 kHz. Different and adapted modeling efforts have been undertaken both for the ergrodic area and the laminar zone. The basic techniques for the ergodic zone are held fine mapping and field line tracing; the analysis provides the magnetic field structure in form of Poincare plots and the transport coefficients for the magnetic field lines. For the laminar zone a modeling is used which takes into account the typical aspects of the scrape-off layer physics. A low frequency operation of the DED will distribute the heat flux over the relatively large area of the divertor target plate. The calculations show that the high frequency operation should impose a torque on the plasma edge which is of similar size as the one imposed by tangential NBI. (C) 1999 Elsevier Science B.V. All rights reserved.