Greifswald 2024 – scientific programme

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P: Fachverband Plasmaphysik

P 15: HEPP V

P 15.4: Talk

Wednesday, February 28, 2024, 15:20–15:45, ELP 6: HS 3

Investigations of impurity concentration in seeded divertor plasmas of W7-X via line ratio spectroscopy — •Frederik Henke, Maciej Krychowiak, Felix Reimold, Ralf König, Dorothea Gradic, Erik Flom, and Victoria Winters — Max Planck Institute for Plasma Physics, Wendelsteinstr. 1, 17491 Greifswald, Germany

In future fusion power plants, managing power exhaust in the divertor poses a significant challenge, requiring seeding of extrinsic impurities. Retaining these impurities at the plasma edge is crucial to avoid fuel dilution and radiative energy losses in the core, limiting the reactor's operational space.

Ongoing research explores power exhaust scaling with spectroscopically measured impurity concentration and machine parameters in tokamak plasmas. This study focuses on measuring multiple spectral lines of the same impurity ion using passive divertor spectroscopy, employing their ratios to reconstruct local plasma parameters.

W7-X's recent operational campaign featured experiments with various seeded impurity species, revealing challenges in the analysis. Notable variations in measured line ratios among different magnetic configurations indicate distinct local plasma parameters. Due to different plasma conditions in the divertor, line-ratio analysis methods require re-validation. This study presents initial results of impurity concentrations, discussing factors influencing the diverse behavior of line ratio measurements.

Keywords: Spectroscopy; Divertor; Detachment; Power Exhaust; Impurities