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P: Fachverband Plasmaphysik

P 5: Poster I

P 5.24: Poster

Dienstag, 31. August 2021, 14:00–16:00, P

Spectroscopic investigation of W7-X detachment induced via nitrogen seeding — •Frederik Henke, Maciej Krychowiak, Ralf König, Felix Reimold, Dorothea Gradic, and Thomas Sunn Pedersen — Max Planck Institute for Plasma Physics, Wendelsteinstr. 1, 17491 Greifswald, Germany

As power exhaust is one crucial aspect of a future fusion power plant, dissipation of the localized heat fluxes striking the divertor is needed. The regime, in which a large fraction of the input power is radiated isotropically into full solid angle while the peak heat- and particle-fluxes to the target are strongly reduced, is called detachment.
Stable detachment is accessible via two different paths in the island divertor of W7-X. First, increasing the density via hydrogen fueling can lead to the transition into the detachment regime with carbon as the intrinsic impurity being the main radiator. Because in a future power plant carbon will not be used at any first wall components due to strong tritium retention, extrinsically seeded low-Z impurities are investigated as the second way to reach detachment.
In this work nitrogen seeding experiments are analyzed applying a spectroscopic line-ratio model of singly ionized nitrogen to measure the local plasma parameters electron density n_e, electron temperature T_e and impurity concentration c_Z. From the analysis of data acquired in the previous operation campaign possible upgrades of the diagnostic, as well as extensions of the physics model to i.e. analyse carbon radiation are explored.