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The Langmuir probe system in the Wendelstein 7-X test divertor

W7-X Team; Rudischhauser, L.; Endler, M.; Höfel, U.; Hammond, K. C.; Kallmeyer, J. P.; Blackwell, B. D.; Gantenbein, Gerd; Huber, Martina; Illy, Stefan; Jelonnek, John; Kobarg, Thorsten; Lang, Rouven; Leonhardt, Wolfgang; Mellein, Daniel; Papenfuß, Daniel; Scherer, Theo; Thumm, Manfred; Wadle, Simone; Weggen, Jörg

Abstract:
The design and evaluation of the Langmuir probe system used in the first divertor operation phase of Wendelstein 7-X is described. The probes are integrated into the target plates and have individually facetted surfaces to keep the angle of incidence of the magnetic field within an appropriate range for different magnetic configurations. Multiple models for the derivation of plasma parameters from current–voltage characteristics are introduced. These are analyzed with regard to their assumptions and limitations, generalized, and adapted to our use case. A detailed comparison is made to determine the most suitable model. It is found that the choice of model has a large impact, for example, resulting in a change in the inferred temperatures of up to a factor two. This evaluation is implemented in a Bayesian modeling framework and automated to allow for joint analysis with other diagnostics and a replacement of ad hoc assumptions. We rigorously treat parameter uncertainties, revealing strong correlations between them. General and flexible model formulations permit an expansion to additional effects.



Zugehörige Institution(en) am KIT Institut für Hochleistungsimpuls- und Mikrowellentechnik (IHM)
Institut für Angewandte Materialien - Angewandte Werkstoffphysik (IAM-AWP)
Publikationstyp Zeitschriftenaufsatz
Publikationsmonat/-jahr 06.2020
Sprache Englisch
Identifikator ISSN: 0034-6748, 1089-7623
KITopen-ID: 1000121082
HGF-Programm 31.03.02 (POF III, LK 01)
Plasma Heizsysteme
Erschienen in Review of scientific instruments
Band 91
Heft 6
Seiten 063505
Projektinformation EUROfusion (EU, H2020, 633053)
Nachgewiesen in Scopus
Web of Science
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