Investigation of fast particle driven instabilities by 2D electron cyclotron emission imaging on ASDEX Upgrade

I.G.J. Classen, Ph. Lauber, D. Curran, J.E. Boom, B.J. Tobias, C.W. Domier, N.C. Luhmann, H.K. Park, M. García-Munoz, B. Geiger, M. Maraschek, M.A. Zeeland, van, S. Graça, da

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19 Citations (Scopus)

Abstract

Detailed measurements of the 2D mode structure of Alfv´en instabilities in the current ramp-up phase of neutral beam heated discharges were performed on ASDEX Upgrade, using the electron cyclotron emission imaging (ECEI) diagnostic. This paper focuses on the observation of reversed shear Alfv´en eigenmodes (RSAEs) and bursting modes that, with the use of the information from ECEI, have been identified as beta-induced Alfv´en eigenmodes (BAEs). Both RSAEs with first and second radial harmonic mode structures were observed. Calculations with the linear gyro-kinetic code LIGKA revealed that the ratio of the damping rates and the frequency difference between the first and second harmonic modes strongly depended on the shape of the qprofile. The bursting character of the BAE type modes, which were radially localized to rational q surfaces, was observed to sensitively depend on the plasma parameters, ranging from strongly bursting to almost steady state.
Original languageEnglish
Article number124018
Pages (from-to)124018-1/10
Number of pages10
JournalPlasma Physics and Controlled Fusion
Volume53
Issue number12
DOIs
Publication statusPublished - 2011

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