Observations of toroidicity-induced Alfvén eigenmodes in a reversed field pinch plasma

High frequency peaks in the spectra of magnetic field signals have been detected at the edge of Extrap-T2R [P. R. Brunsell, H. Bergsåker, M. Cecconello, J. R. Drake, R. M. Gravestijn, A. Hedqvist, and J.-A. Malmberg, Plasma Phys. Controlled Fusion, 43, 1457 (2001)]. The measured fluctuation is found...

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Published in:Physics of plasmas 2005-04, Vol.12 (4), p.042502-042502-10
Main Authors: Regnoli, G., Bergsåker, H., Tennfors, E., Zonca, F., Martines, E., Serianni, G., Spolaore, M., Vianello, N., Cecconello, M., Antoni, V., Cavazzana, R., Malmberg, J.-A.
Format: Article
Language:English
Subjects:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ALFVEN WAVES
excitation
FLUCTUATIONS
mode
particles
PLASMA
PLASMA DENSITY
PLASMA DIAGNOSTICS
REVERSE-FIELD PINCH
rotation
spectra
tokamaks
transport
TURBULENCE
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Summary:High frequency peaks in the spectra of magnetic field signals have been detected at the edge of Extrap-T2R [P. R. Brunsell, H. Bergsåker, M. Cecconello, J. R. Drake, R. M. Gravestijn, A. Hedqvist, and J.-A. Malmberg, Plasma Phys. Controlled Fusion, 43, 1457 (2001)]. The measured fluctuation is found to be mainly polarized along the toroidal direction, with high toroidal periodicity n and Alfvénic scaling ( f ∝ B ∕ m i n i ) . Calculations for a reversed field pinch plasma predict the existence of an edge resonant, high frequency, high- n number toroidicity-induced Alfvén eigenmode with the observed frequency scaling. In addition, gas puffing experiments show that edge density fluctuations are responsible for the rapid changes of mode frequency. Finally a coupling with the electron drift turbulence is proposed as drive mechanism for the eigenmode.
ISSN:1070-664X
1089-7674
1089-7674
DOI:10.1063/1.1861896