|Title||Velocimetry analysis of type-I edge localized mode precursors in ASDEX Upgrade|
|Publication Type||Journal Article|
|Year of Publication||2014|
|Authors||P. Manz, J.E Boom, E. Wolfrum, G. Birkenmeier, I.G.J. Classen, N.C Luhmann, Jr., U. Stroth|
|Journal||Plasma Physics and Controlled Fusion|
|ISBN Number||0741-3335; 1361-6587|
When the electron transport barrier remains in its final shape before a type-I edge localized mode (ELM) crash in ASDEX Upgrade, ELM precursors appear as electron temperature fluctuations. In order to relate these precursors to an instability, spatial scales, parity and the cross-phase between electron temperature and radial velocity fluctuations are evaluated by means of velocimetry of measured 2D electron temperature fluctuations. A comprehensive comparison with properties of different instabilities points to microtearing modes. Bispectral analysis indicates a nonlinear coupling of these precursors to a ballooning-type mode prior to the ELM onset.
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