Study and simulation of carbon impurity dynamics near the ergodic divertor in Tore Supra

In the past few years, effects induced by the ergodic divertor such as impurity screening and transport modifications in the plasma edge have been used to achieve high radiation, low contamination regimes. A crucial issue in understanding these effects is that of impurity generation and propagation across the plasma edge, especially in the vicinity of the Ergodic Divertor (ED) neutralizer plates. A variety of diagnostic tools and techniques are used for this purpose. In the case of Tore Supra, interpretation of spectroscopic data is strongly complicated by the complex geometry of the ED, leading among other effects to the total lack of uniformity of the sources. Indeed, due to the specific pattern of impurity sources on the neutralizers and to their particular orientation with respect to the local magnetic field, densities of lowly ionised impurities are deeply modulated on the sub-centimeter scale in both directions perpendicular to the magnetic field. Because of this, accurate 3-D simulations are essential for the evaluation of experimental signals. (authors)