Bidirectional tornado modes on the Joint European Torus

Journal Article · Sat Dec 15 04:00:00 EST 2007 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2804084· OSTI ID:21072696

Sandquist, P; Sharapov, S E; Lisak, M; Johnson, T ^[1]

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1. EURATOM-VR Association and Department of Radio and Space Science, Chalmers University of Technology, SE-412 96 Goeteborg (Sweden)

In discharges on the Joint European Torus [P. H. Rebut and B. E. Keen, Fusion Technol. 11, 13 (1987)] with safety factor q(0)<1 and high-power ion cyclotron resonance heating (ICRH), monster sawtooth crashes are preceded by frequency sweeping 'tornado modes' in the toroidal Alfven eigenmode frequency range. A suite of equilibrium and spectral magnetohydrodynamical codes is used for explaining the observed evolution of the tornado mode frequency and for identifying temporal evolution of the safety factor inside the q=1 radius just before sawtooth crashes. In some cases, the tornado modes are observed simultaneously with both positive and negative toroidal mode numbers. Hence, a free energy source other than the radial gradient of the energetic ion pressure exciting these modes is sought. The distribution function of the ICRH-accelerated ions is assessed with the SELFO code [J. Hedin et al., Nucl. Fusion 42, 527 (2002)] and energetic particle drive due to the velocity space anisotropy of ICRH-accelerated ions is considered analytically as the possible source for excitation of bidirectional tornado modes.

• OSTI ID: 21072696
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 12 Vol. 14; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ANISOTROPY
DISTRIBUTION FUNCTIONS
EQUILIBRIUM
EXCITATION
FREE ENERGY
ICR HEATING
JET TOKAMAK
MAGNETOHYDRODYNAMICS
PLASMA
PLASMA CONFINEMENT
PLASMA INSTABILITY
RF SYSTEMS
S CODES
SAFETY
SAWTOOTH OSCILLATIONS
TAIL IONS
THERMONUCLEAR REACTORS