|Title||Investigation of fast particle driven instabilities by 2D electron cyclotron emission imaging on ASDEX Upgrade|
|Publication Type||Journal Article|
|Year of Publication||2011|
|Authors||I.G.J. Classen, P. Lauber, D. Curran, J.E Boom, B.J Tobias, C.W. Domier, NC Luhmann, Jr., H.K Park, M.G Munoz, B. Geiger, M. Maraschek, M.A VanZeeland, S. da Graca|
|Journal||Plasma Physics and Controlled Fusion|
|Type of Article||Article|
|Keywords||ALFVEN MODES, CASCADES, EIGENMODES, STABILITY, TOKAMAK|
Detailed measurements of the 2D mode structure of Alfven 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 Alfven-eigenmodes (RSAEs) and bursting modes that, with the use of the information from ECEI, have been identified as beta-induced Alfven 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 q-profile. 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.
|Alternate Title||Plasma Phys. Control. Fusion|
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