SMuK 2023 – scientific programme
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P: Fachverband Plasmaphysik
P 10: Magnetic Confinement III/HEPP V
P 10.3: Talk
Wednesday, March 22, 2023, 11:55–12:20, CHE/0091
Experimental Exploration of a Two Point Model for the Island Divertor of Wendelstein 7-X via Helium Line Ratio Spectroscopy — •Erik Flom1, 3, Tullio Barbui2, Oliver Schmitz1, Maciej Krychowiak3, Ralf König3, Marcin Jakubowski3, Sergei Bozhenkov3, Valeria Perso3, Felix Reimold3, and The Wendelstein 7-X Team3 — 1UW-Madison, Madison, WI, USA — 2PPPL, Princeton, New Jersey, US — 3Max Planck Inst. for Plasma Physics, Greifswald, Germany
Understanding the basic plasma parameters of temperature and density, as well as their gradients in the scrape-off layer (SOL), is a topic critical for providing information about the performance of a divertor concept. The stellarator Wendelstein 7-X features a novel resonant island divertor with an adjustable rotational transform of ι = 2π (5/6, *, 5/4). In order to study the performance of this divertor concept, an active spectroscopy system on an atomic helium beam [1] was developed and installed on the stellarator [2]. The diagnostic was successfully operated in the first two divertor campaigns of the device in two magnetically connected modules. In this work, a database analysis of experiments from the operational phase OP1.2b is performed and systematic trends in divertor performance are discussed within the framework of a two-point, single-fluid model [3]. Particular focus is applied to separatrix vs. target density scaling and evidence for a *high-recycling* conduction limited regime, as well as an exploration of the validity of the helium beam as a downstream proxy given its displacement from the strike line poloidally.