Düsseldorf 2007 – scientific programme
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P: Fachverband Plasmaphysik
P 20: Plasma-Wand-Wechselwirkung
P 20.4: Talk
Thursday, March 22, 2007, 15:30–15:45, 6C
Numerical investigation of impurity transport in the ergodized edge plasma at TEXTOR-DED — •Heinke Frerichs1, Derek Harting1, Detlev Reiter1, and Yühe Feng2 — 1Institut für Plasmaphysik, Forschungszentrum Jülich GmbH, EURATOM Association, Trilateral Euregio Cluster, D-52425 Jülich — 2Max-Planck-Institut für Plasmaphysik, D-17491 Greifswald
Recent numerical studies of impurity transport in the ergodized edge plasma for the tokamak TEXTOR-DED are discussed. The dynamic ergodic divertor (DED) at TEXTOR induces a complex 3D magnetic field structure at the plasma boundary, which brakes symmetry between neutral and charged particle transport and, hence, leads to an intrinsically 3D transport problem. Calculations for TEXTOR-DED are performed with the 3D Monte Carlo code package EMC3/EIRENE. The effect of the DED on impurity production and transport is investigated and sensitive model parameters are identified. In particular the frequently neglected finite population of electronically excited states of impurity ions (``corona approximation'') within the transport code instead of a more sophisticated collisional-radiative model leads to a significant overestimation of the radiated power for TEXTOR conditions. A pronounced reduction of the carbon density at the inner simulation boundary (inside the last closed flux surface) after turning on the DED magnetic perturbation field is robustly predicted, despite an enhanced sputtered flux. However, experimentally this strong screening effect has not yet been identified.