Characterization of edge profiles and fluctuations in discharges with type-II and nitrogen-mitigated edge localized modes in ASDEX Upgrade

TitleCharacterization of edge profiles and fluctuations in discharges with type-II and nitrogen-mitigated edge localized modes in ASDEX Upgrade
Publication TypeJournal Article
Year of Publication2011
AuthorsE. 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
JournalPlasma Physics and Controlled Fusion
Volume53
Issue8
Number8
Pagination085026
Abstract

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.

DOI10.1088/0741-3335/53/8/085026
Division

FP

Department

PDG

PID

96834303cba945bc786624fc66aecfbd

Alternate TitlePlasma Phys. Control. Fusion

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