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Impurity sources and fluxes in W7-X: from the plasma-facing components to the edge layer

W7-X Team; Wang, E.; Brezinsek, S.; Sereda, S.; Buttenschön, B.; Barbui, T.; Dhard, C. P.; Endler, M.; Ford, O.; Flom, E.; Hammond, K. C.; Jakubowski, M.; Krychowiak, M.; Kornejew, P.; König, R.; Liang, Y.; Mayer, M.; Naujoks, D.; Neubauer, O.; ... mehr


Wendelstein 7-X (W7-X) is a nearly full-carbon machine with graphite divertors, baffles and shields in Operation Phase 1.2b (OP 1.2b). Divertor spectrometer measurements showed that an amount of helium and oxygen impurities existed in the predominately hydrogen plasma, which resulted in a high carbon impurity level by enhanced physical and chemical sputtering by these impurities in comparison with the pure impinging proton yields. In order to improve the wall conditions, especially to reduce the oxygen content, boronizations were applied in OP1.2b. After the boronization, an oxygen decrease by more than an order of magnitude was observed. Helium disappeared in comparison with OP1.2a due to reduced application of helium wall conditioning after introduction of boronizations. The overall radiation normalized to line integrated density was reduced by a factor of six. In addition, local CH4 injection was applied in the divertor in order to quantify the chemical sputtering by hydrogen on divertor plates. The experimentally determined effective D/XB of the A–X band of CH resulting from CH4 was ${\left[\tfrac{{D}}{{X}{B}}\right]}_{{{A}}^{2}{\rm{\Delta }}\to {{X}}^{2}{\rm{\Pi }}}^{{\rm{C}}{{\rm{H}}}_{4}\to {\rm{C}}{\rm{H}}}=16$ at T e ≈ 20 eV and n e ≈ 5 × 1018 m−3. ... mehr

DOI: 10.1088/1402-4896/ab4c04
Zitationen: 18
Web of Science
Zitationen: 17
Zitationen: 17
Zugehörige Institution(en) am KIT Institut für Angewandte Materialien – Angewandte Werkstoffphysik (IAM-AWP)
Institut für Hochleistungsimpuls- und Mikrowellentechnik (IHM)
Publikationstyp Zeitschriftenaufsatz
Publikationsmonat/-jahr 01.2020
Sprache Englisch
Identifikator ISSN: 0031-8949, 1402-4896
KITopen-ID: 1000121070
HGF-Programm 31.03.02 (POF III, LK 01) Plasma Heizsysteme
Erschienen in Physica scripta
Verlag Royal Swedish Academy of Sciences
Band 2020
Heft T171
Seiten 014040
Projektinformation EUROfusion (EU, H2020, 633053)
Nachgewiesen in Scopus
Web of Science
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