Low frequency sawtooth precursor activity in ASDEX Upgrade
Journal article, 2011

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.

X-ray

sawtooth

bicoherence

ASDEX Upgrade

bandpower

tokamak

LFSP

STFT

wavelet

MHD

Author

Gergely Papp

Chalmers, Applied Physics, Nuclear Engineering

Gabor Por

András Magyarkuti

Nóra Lazányi

László Horváth

Valentin Igochine

Marc Maraschek

ASDEX Upgrade Team

Plasma Physics and Controlled Fusion

0741-3335 (ISSN) 1361-6587 (eISSN)

Vol. 53 6 065007-

Driving Forces

Sustainable development

Subject Categories

Physical Sciences

Fusion, Plasma and Space Physics

Areas of Advance

Energy

Roots

Basic sciences

DOI

10.1088/0741-3335/53/6/065007

More information

Created

10/7/2017