Modelling with the 2D multifluid code TECXY of TEXTOR discharges in the presence of DED

A study of the influence of the dynamic ergodic divertor (DED) on transport and radiation of intrinsic carbon in TEXTOR has been done, based on calculations with the 2D multifluid code TECXY and experimental data from spectroscopic diagnostics involving the brilliances of lines en-fitted by C+2 and C+4 lines in the UV range. This allows the investigation of the radiation properties of carbon and the contamination of the main plasma for a variety of experimental conditions. The physical model in the TECXY code was extended to incorporate the increased radial transport in the stochastic magnetic field applying a model of 'optimal paths'. Two DED operational modes (m/n = 12/4 and 3/1), both resonant at the q = 3 surface, have been experimentally studied so far. In the present paper we have concentrated on the 12/4 mode of operation. The radial decay length of the 12/4 mode is very short. In order to maximize the field penetration, the plasma column has to be shifted horizontally towards the high field side. Both the simulation and the experimental evidence indicate that the main changes are related to the horizontal shift of the plasma column rather than to the stochastic transport itself. A high recycling regime with good impurity screening is predicted for an un-shifted position of the plasma column as foreseen for the future 6/2 mode operation.