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Observation of impurity accumulation and its compatibility with high plasma performance in W7-X

Zhang, D. ; Buttenschön, B.; Jablonski, S.; Kubkowska, M.; Ford, O.; Alcusón, J. A.; Beidler, C. D.; Burhenn, R.; Beurskens, M. N. A.; Langenberg, A.; Pablant, N.; Reimold, F.; Rahbarnia, K.; Smith, H. M.; Wegner, Th; Wurden, G.; Bozhenkov, S. A.; Feng, Y.; Brunner, K. J.; ... mehr

Abstract (englisch):

At the W7-X stellarator, the bolometer system has measured an intensive radiation zone in the inner plasma region (at a normalized radius ρ ∼ 0.3–0.4) in the hydrogen plasma generated by electron cyclotron resonance heating; it differs from the normal plasma radiation distribution with an edge-localized emission zone. Spectroscopic diagnostics have recorded high-Z elements such as iron. This phenomenon happens in the plasma phases after gas supply turn-off, which results in all impurity relevant diagnostic signals increasing for several seconds. Despite the enhancement of the core radiation, the plasma energy confinement is improved. A transport analysis shows that this impurity radiation behavior is associated with a low diffusion coefficient (D∼ 0.02 m2 s−1) and a reversal of the convection around the radial position of the emission peak, which, under normal conditions, separates the zones of outward convection in the central (|V| ∼ 0.1 m s−1) and inward convection in the outer region (|V| ∼ 0.3 m s−1). An impurity accumulation around this radial position has been identified. The transport coefficients obtained are comparable with the theoretical predictions of collisional impurity transport. ... mehr

Verlagsausgabe §
DOI: 10.5445/IR/1000161906
Veröffentlicht am 04.09.2023
DOI: 10.1088/1361-6587/acf0e7
Zitationen: 1
Zitationen: 1
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Hochleistungsimpuls- und Mikrowellentechnik (IHM)
Publikationstyp Zeitschriftenaufsatz
Publikationsdatum 01.10.2023
Sprache Englisch
Identifikator ISSN: 0741-3335, 1361-6587
KITopen-ID: 1000161906
HGF-Programm 31.13.02 (POF IV, LK 01) Plasma Heating & Current Drive Systems
Erschienen in Plasma Physics and Controlled Fusion
Verlag Institute of Physics Publishing Ltd (IOP Publishing Ltd)
Band 65
Heft 10
Seiten Art.-Nr. 105006
Projektinformation EUROfusion (EU, EU 9. RP, 101052200)
Vorab online veröffentlicht am 29.08.2023
Schlagwörter impurity accumulation, impurity outward convection, impurity inward convection, suppression of ITG turbulence, high plasma performance, plasma radiation, W7-X stellarator
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