Fast-ion losses due to high-frequency MHD perturbations in the ASDEX upgrade tokamak

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Garcia-Munoz, Miguel
Fahrbach, H. U.
Guenter, Sibylle
Igochine, Valentin
Mantsinen, Mervi J.
Maraschek, M.
Martin, Piero
Piovesan, Pablo
Sassenberg, Karl
Zohm, H.
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American Physical Society
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Time-resolved energy and pitch angle measurements of fast-ion losses correlated in frequency and phase with high-frequency magnetohydrodynamic perturbations have been obtained for the first time in a magnetic fusion device and are presented here. A detailed analysis of fast-ion losses due to toroidal Alfven eigenmodes has revealed the existence of a new core-localized magnetohydrodynamic perturbation, the sierpes mode. The sierpes mode is a non-Alfvenic instability which dominates the losses of fast ions in ion cyclotron resonance heated discharges, and it is named for its footprint in the spectrograms ("sierpes" means "snake" in Spanish). The sierpes mode has been reconstructed by means of highly resolved multichord soft-x-ray measurements.
Alfven instabilities , Scintillator probe , Neutral beam , Modes , Diagnostics , Transport , Plasmas , particles , Eigenmode , Driven
García-Muñoz, M., Fahrbach, H. U., Günter, S., Igochine, V., Mantsinen, M. J., Maraschek, M., Martin, P., Piovesan, P., Sassenberg, K. and Zohm, H. (2008) 'Fast-ion losses due to high-frequency MHD perturbations in the ASDEX upgrade tokamak', Physical Review Letters, 100(5), 055005 (4pp). doi: 10.1103/PhysRevLett.100.055005
© 2008, American Physical Society