Collective Thomson scattering measurements of fast-ion transport due to sawtooth crashes in ASDEX Upgrade

TitleCollective Thomson scattering measurements of fast-ion transport due to sawtooth crashes in ASDEX Upgrade
Publication TypeJournal Article
Year of Publication2016
AuthorsJ. Rasmussen, S.K Nielsen, M. Stejner, J. Galdon-Quiroga, M. García-Muñoz, B. Geiger, A.S Jacobsen, F. Jaulmes, S.B Korsholm, N. Lazanyi, F. Leipold, F. Ryter, M. Salewski, M. Schubert, J. Stober, D. Wagner, ASDEX-Upgrade Team, EUROfusion MST1 Team
JournalNuclear Fusion

Sawtooth instabilities can modify heating and current-drive profiles and potentially increase fast-ion losses. Understanding how sawteeth redistribute fast ions as a function of sawtooth parameters and of fast-ion energy and pitch is hence a subject of particular interest for future fusion devices. Here we present the first collective Thomson scattering (CTS) measurements of sawtooth-induced redistribution of fast ions at ASDEX Upgrade. These also represent the first localized fast-ion measurements on the high-field side of this device. The results indicate fast-ion losses in the phase-space measurement volume of about 50% across sawtooth crashes, in good agreement with values predicted with the Kadomtsev sawtooth model implemented in TRANSP and with the sawtooth model in the EBdyna_go code. In contrast to the case of sawteeth, we observe no fast-ion redistribution in the presence of fishbone modes. We highlight how CTS measurements can discriminate between different sawtooth models, in particular when aided by multi-diagnostic velocity-space tomography, and briefly discuss our results in light of existing measurements from other fast-ion diagnostics.





Alternate TitleNucl. Fusion

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