Collective Thomson scattering measurements of fast-ion transport due to sawtooth crashes in ASDEX Upgrade. (22nd July 2016)

• Record Type: Journal Article
• Authors: Rasmussen, J.; Nielsen, S.K.; Stejner, M.; Galdon-Quiroga, J.; Garcia-Munoz, M.; Geiger, B.; Jacobsen, A.S.; Jaulmes, F.; Korsholm, S.B.; Lazanyi, N.; Leipold, F.; Ryter, F.; Salewski, M.; Schubert, M.; Stober, J.; Wagner, D.
• Other Names: collab.; collab.
• Is Part Of: Nuclear fusion. Volume 56:Number 11(2016:Nov.)
• Publication Date: 2016-07-22
• Subjects: fast ions in tokamaks -- collective Thomson scattering -- fast-ion velocity distribution function -- sawtooth instabilities; Nuclear fusion -- Periodicals; 621.48405
• DOI: 10.1088/0029-5515/56/11/112014
• Languages: English
• ISSNs: 0029-5515

Abstract

Abstract: 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.