|Title||Characterization of edge profiles and fluctuations in discharges with type-II and nitrogen-mitigated edge localized modes in ASDEX Upgrade|
|Publication Type||Journal Article|
|Year of Publication||2011|
|Authors||E. Wolfrum, M. Bernert, J.E Boom, A. Burckhart, I.GJ Classen, G.D Conway, T. Eich, R. Fischer, A. Gude, A. Herrmann, N.CLuhmann Jr., M. Maraschek, R. McDermott, H.K Park, T Pütterich, J. Vicente, B. Wieland, M. Willensdorfer, ASDEX Upgrade Team|
|Journal||Plasma Physics and Controlled Fusion|
Edge localized modes (ELMs) with high frequency and low power loss (type-II ELMs) occur in high triangularity, near double null configurations in ASDEX Upgrade with full tungsten plasma facing components. The transition from type-I to type-II ELMs is shown to occur above a collisionality threshold. For the first time the characteristic MHD fluctuations around 40 kHz have been localized. The fluctuations are observed in a wide region extending from the pedestal inward to normalized poloidal radius ρ pol = 0.7. Their amplitudes on the low-field side of the plasma exhibit maxima above and below the mid-plane. The fluctuations move in the electron drift direction and lead to a reduced edge electron temperature gradient. The reduction in the edge pressure gradient is connected with these MHD fluctuations, which affect the electron temperature but not the electron density profiles. A comparison with nitrogen-mitigated type-I ELMs in the same plasma shape shows that core profiles are also affected. The electron temperature profile is self-similar for type-I and nitrogen-mitigated type-I ELMs but is not self-similar in the case of type-II ELMs.
|Alternate Title||Plasma Phys. Control. Fusion|
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