Greifswald 2024 – scientific programme
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P: Fachverband Plasmaphysik
P 15: HEPP V
P 15.3: Talk
Wednesday, February 28, 2024, 14:55–15:20, ELP 6: HS 3
Towards the Next-Step Island Divertor for W7-X Stellarator: Heat Exhaust Perspective — •Amit Kharwandikar1, Dirk Naujoks1, Felix Reimold1, Ralf Schneider2, and The W7X-Team1 — 1Max Planck Institute for Plasma Physics, Greifswald — 2Universität Greifswald, Greifswald
The Wendelstein 7-X (W7-X) stellarator implements the island divertor concept and has demonstrated the viability of using magnetic islands as a exhaust solution for low-shear stellarators. During the experiments, the divertor design revealed challenges in two aspects in particular: unexpected hotspots that limited operation and a poor neutral particle exhaust, motivating an investigation of new geometries to advance the W7-X island divertor. Early stages of such an exploratory challenge calls for fast and simple tools to scan the large 3D design space. In the same spirit, this contribution proposes a framework to analyse the heat flux compatibility of new divertor geometries.
The problem is approached in 2 steps - first, obtaining a simple picture of heat transport in an island scrape-off layer (SOL) to build fast predictive models of target heat flux distribution, followed by shape exploration of target geometries. In terms of tools, we utilize the Monte-Carlo code for 3D SOLs, EMC3-Lite, and compliment it with a newly developed empirical approach - Simple model for loads in island divertor (SMoLID) - based on estimating the SOL width and perpendicular transport length scales for a given magnetic topology and plasma conditions. Eventually, these tools are applied to investigate the heat load compatibility of certain "closed" divertor geometries.
Keywords: Wendelstein 7-X; heat transport; Island divertor; 3D SOL; divertor geometry optimization