SOL Transport and Filamentary Dynamics in High Density Tokamak Regimes

Antti Hakola, Nicola Vianello (Corresponding author), Daniel Carralero, Cedric Tsui, Volker Naulin, Matteo Agostini, J Boedo, Benoit Labit, Christian Theiler, Diego Aguiam, Scott Allan, Matthias Bernert, Stefan Costea, Istvan Cziegler, Hugo de Oliveira, Joaquin Galdon-Quiroga, Gustavo Grenfell, Codrina Ionita, Heinz Isliker, Alexander KarpushovJernej Kovacic, Bruce Lipschultz, Roberto Maurizio, Ken McClements, Fulvio Militello, Jeppe Olsen, Jens Juul Rasmussen, Timo Ravensbergen, Holger Reimerdes, Bernd Schneider, Roman Schrittwieser, Monica Spolaore, Kevin Verhaegh, Jose Vicente, Nick Walkden, Wei Zhang, Elisabeth Wolfrum

    Research output: Chapter in Book/Report/Conference proceedingConference abstract in proceedingsScientific

    Abstract

    Addressing the role of scrape off layer filamentary transport is a subject of intense studies in fusion science. Intermittent structures dominate transport in L-Mode and strongly contribute to particle and energy losses in H-mode. The role of convective radial losses has become even more important due to its contribution to the shoulder formation in L-Mode, describing the progressive flattening of the density scrape off layer profile at high density [1]. Investigation of this process revealed the strong relationship between divertor conditions
    and the upstream profiles, mediated by filaments dynamics which varies according to the downstream conditions. Preliminary investigations suggested that similar mechanisms occur in H-Mode [1] and that filaments contribute the SOL transport in H-mode density limit (HDL) as well [4]. The present contribution will report on results obtained on ASDEX-Upgrade and TCV tokamaks, to address the role of filamentary transport in high density regimes both in L- and H-Mode. The combined results enlarge the operational space, from a device with a closed divertor, metallic first wall and cryogenic pumping system to a carbon machine with a completely open divertor. The mechanism of shoulder formation
    and the role of filaments have been tested against variation of plasma current, magnetic configuration (single and double null plasmas), and divertor neutral densities, through modification of cryopump efficiency. At constant magnetic field the density decay length increases with filament-size independently of the plasma current for both machines in L-mode, consistently with the fact that upstream profiles and divertor neutral pressure exhibit the same trend with normalized Greenwald fraction.
    In H-Mode fuelling is insufficient to cause flattening of SOL profiles in the inter-ELM phases since large neutral pressure is needed. Consistently inter-ELM blob size in AUG are found larger whenever the cryopumps is switched off. The resulting picture suggests a complex relationship between divertor and upstream profiles, where filaments are modified by divertor conditions as well as by neutral particles interaction.
    Original languageEnglish
    Title of host publication27th IAEA Fusion Energy Conference
    Subtitle of host publicationProgramme and Abstracts
    PublisherInternational Atomic Energy Agency IAEA
    Pages396-397
    Publication statusPublished - Oct 2018
    MoE publication typeNot Eligible
    Event27th IAEA Fusion Energy Conference, FEC 2018 - Ghandhinagar, Ahmedabad, India
    Duration: 22 Oct 201827 Oct 2018
    Conference number: 27
    https://www.iaea.org/events/fec-2018

    Conference

    Conference27th IAEA Fusion Energy Conference, FEC 2018
    Abbreviated titleFEC
    CountryIndia
    CityAhmedabad
    Period22/10/1827/10/18
    Internet address

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