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Bidirectional tornado modes on the joint european torus
KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.ORCID iD: 0000-0002-7142-7103
2007 (English)In: Physics of Plasmas, ISSN 1070-664X, Vol. 14, no 12Article in journal (Refereed) Published
Abstract [en]

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 , 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.

Place, publisher, year, edition, pages
2007. Vol. 14, no 12
Keyword [en]
toroidal alfven eigenmodes, orbit width, energetic ions, jet tokamak, toroidicity, plasmas, stabilization, instabilities, discharges, excitation
URN: urn:nbn:se:kth:diva-17191DOI: 10.1063/1.2804084ISI: 000251988200026ScopusID: 2-s2.0-37549051247OAI: diva2:335234
QC 20100525Available from: 2010-08-05 Created: 2010-08-05Bibliographically approved

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