Recent progress towards a quantitative description of filamentary SOL transport

• Published in: arXiv.org 2020-05
• Main Authors: Carralero, D, Siccinio, M, Komm, M, Artene, S A, D'Isa, F A, Adamek, J, Aho-Mantila, L, Birkenmeier, G, Brix, M, Fuchert, G, Groth, M, Lunt, T, Manz, P, Madsen, J, Marsen, S, Müller, H W, Stroth, U, Sun, H J, Vianello, N, Wischmeier, M, Wolfrum, E, ASDEX Upgrade Team, Team, COMPASS, Contributors, JET, the EUROfusion MST team
• Format: Article
• Language: English
• Subjects: Deuterium; Filaments; Ion temperature; Plasmas (physics); Sheaths; Temperature distribution; Tokamak devices
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2005.06250

A summary of recent results on filamentary transport, mostly obtained in the ASDEX-Upgrade tokamak (AUG), is presented and discussed in an attempt to produce a coherent picture of SOL filamentary transport: A clear correlation is found between L-mode density shoulder formation in the outer midplane and a transition between the sheath limited and the inertial filamentary regimes. Divertor collisionality is found to be the parameter triggering the transition. A clear reduction of the ion temperature takes place in the far SOL after the transition, both for the background and the filaments. This coincides with a strong variation of the ion temperature distribution, which deviates from Gaussianity and becomes dominated by a strong peak below \(5\) eV. The filament transition mechanism triggered by a critical value of collisionality seems to be generally applicable to inter-ELM H-mode plasmas, although a secondary threshold related to deuterium fueling is observed. EMC3-EIRENE simulations of neutral dynamics show that an ionization front near the main chamber wall is formed after the shoulder formation. Finally, a clear increase of SOL opacity to neutrals is observed associated to the shoulder formation. A common SOL transport framework is proposed account for all these results, and their potential implications for future generation devices are discussed.