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Published on: August 15, 2014
Demonstration of effective control of fast-ion-stabilized sawteeth by electron-cyclotron current drive
M Lennholm1, L-G Eriksson, F Turco
1Association EURATOM-CEA, DSM/IRFM, CEA/Cadarache, 13108 St. Paul-lez-Durance, France.
Abstract:
In a tokamak plasma, sawtooth oscillations in the central temperature, caused by a magnetohydrodynamic instability, can be partially stabilized by fast ions. The resulting less frequent sawtooth crashes can trigger unwanted magnetohydrodynamic activity. This Letter reports on experiments showing that modest electron-cyclotron current drive power, with the deposition positioned by feedback control of the injection angle, can reliably shorten the sawtooth period in the presence of ions with energies >or=0.5 MeV. Certain surprising elements of the results are evaluated qualitatively in terms of existing theory.
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