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Integrated modelling of sawtooth cycles and fishbone oscillations in ASDEX Upgrade plasmas.

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Title: Integrated modelling of sawtooth cycles and fishbone oscillations in ASDEX Upgrade plasmas.
Authors: Stefanelli, F.1 (AUTHOR) federico.stefanelli@ipp.mpg.de, Fable, E.1 (AUTHOR), Angioni, C.1 (AUTHOR), Bergmann, M.1 (AUTHOR), Brioschi, D.1 (AUTHOR), Gude, A.1 (AUTHOR), Igochine, V.1 (AUTHOR), Lauber, P.1 (AUTHOR), Samoylov, O.1 (AUTHOR), Stucchi, R.1 (AUTHOR), Tardini, G.1 (AUTHOR), Weiland, M.1 (AUTHOR), Zohm, H.1 (AUTHOR)
Source: Nuclear Fusion. 2026, Vol. 66 Issue 7, p1-23. 23p.
Subjects: Plasma instabilities, Fast ions, Neutral beams, Turbulent flow, Plasma dynamics, Tokamaks
Abstract: An integrated model of sawtooth cycles is presented, which includes also the effects of fishbone oscillations in between the sawtooth core collapses. All phases of a sawtooth cycle are modelled, with the onset predicted by the Porcelli model, the post-crash current and q profiles with the flat current model, and the recovery phase with TGLF and NCLASS. It will be shown that TGLF significantly overestimates turbulent transport throughout the whole sawtooth period, and an additional turbulence stabilisation mechanism, which could be driven by fast particle effects, has to be invoked to recover the correct fluxes. The collapse of the temperature and density profiles is obtained with MHD-driven anomalous diffusivity applied within the q = 1 surface at the crash time. The redistribution of fast particles and rotation is modelled as well. The fishbone onset criterion and induced radial transport and radial electric field are also modelled. Notably, the fishbone-induced radial electric field predicted by reduced models is found to have little effects on core turbulence. The results are validated on AUG discharges in presence of neutral beam injection and electron cyclotron heating schemes. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:An integrated model of sawtooth cycles is presented, which includes also the effects of fishbone oscillations in between the sawtooth core collapses. All phases of a sawtooth cycle are modelled, with the onset predicted by the Porcelli model, the post-crash current and q profiles with the flat current model, and the recovery phase with TGLF and NCLASS. It will be shown that TGLF significantly overestimates turbulent transport throughout the whole sawtooth period, and an additional turbulence stabilisation mechanism, which could be driven by fast particle effects, has to be invoked to recover the correct fluxes. The collapse of the temperature and density profiles is obtained with MHD-driven anomalous diffusivity applied within the q = 1 surface at the crash time. The redistribution of fast particles and rotation is modelled as well. The fishbone onset criterion and induced radial transport and radial electric field are also modelled. Notably, the fishbone-induced radial electric field predicted by reduced models is found to have little effects on core turbulence. The results are validated on AUG discharges in presence of neutral beam injection and electron cyclotron heating schemes. [ABSTRACT FROM AUTHOR]
ISSN:00295515
DOI:10.1088/1741-4326/ae6e55