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Low frequency sawtooth precursor activity in ASDEX Upgrade

Gergely Papp (Institutionen för teknisk fysik, Nukleär teknik) ; Gergö Pokol ; Gabor Por ; András Magyarkuti ; Nóra Lazányi ; László Horváth ; Valentin Igochine ; Marc Maraschek ; ASDEX Upgrade Team
Plasma Physics and Controlled Fusion (0741-3335). Vol. 53 (2011), 6, p. 065007.
[Artikel, refereegranskad vetenskaplig]

This paper describes the precursor activity observed in the ASDEX Upgrade tokamak before sawtooth crashes in various neutral beam heated plasmas, utilizing the soft x-ray diagnostic. In addition to the well-known (m, n) = (1,1) internal kink mode and its harmonics, a lower frequency mode is studied in detail. Power modulation of this mode is found to correlate with the power modulation of the (1, 1) kink mode in the quasistationary intervals indicating possible nonlinear interaction. Throughout the studied sawtooth crashes, the power of the lower frequency mode rose by several orders of magnitude just before the crash. In addition to its temporal behaviour, its spatial structure was estimated and the most likely value was found to be (1, 1). A possible role of this mode in the mechanism of the sawtooth crash is discussed.

Nyckelord: tokamak, ASDEX Upgrade, sawtooth, MHD, LFSP, X-ray, STFT, bicoherence, wavelet, bandpower

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Denna post skapades 2011-05-23. Senast ändrad 2011-05-23.
CPL Pubid: 140929


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Institutioner (Chalmers)

Institutionen för teknisk fysik, Nukleär teknik (2006-2015)


Hållbar utveckling

Chalmers infrastruktur

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