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P: Fachverband Plasmaphysik
P 19: Poster II
P 19.24: Poster
Thursday, March 31, 2022, 16:00–17:30, P
Assessment of NII line ratio method for analysis of nitrogen enrichment in the W7-X divertor — •F. Henke, M. Krychowiak, R. König, F. Reimold, D. Gradic, and T. Sunn Pedersen — Max Planck Institute for Plasma Physics, Wendelsteinstr. 1, 17491 Greifswald, Germany
Impurities are of great importance in fusion plasmas. At the plasma edge, their radiation provide an advantageous cooling and dissipation, whereas they can negatively impact the energy confinement and dilute the fusion fuel in the plasma core already at small concentrations.
Because the divertor of Wendelstein 7-X consists of graphite, the intrinsic impurity carbon is utilized as the main radiator. As tritium retention rules out carbon for the choice of wall material in a future reactor, seeded gases will be crucial for successful divertor operation.
In order to study the impurity screening capabilities of the divertor of Wendelstein 7-X, we analyse nitrogen seeding experiments via a NII line ratio model in the plasma edge and Charge Exchange Recombination Spectroscopy (CXRS) in the plasma core with the goal of estimating an enrichment coefficient of nitrogen in the divertor cN,divertor / cN,core.
Due to the complexity of the W7-X divertor plasmas and geometry, the passive NII line ratio model is subject to considerable uncertainties. The assessment of this method as well as possible model and diagnostics upgrades for its application in future experiment campaigns are discussed in this work.