The role of temperature fluctuations in the dynamics of type-I and type-II edge localized modes at ASDEX Upgrade

TitleThe role of temperature fluctuations in the dynamics of type-I and type-II edge localized modes at ASDEX Upgrade
Publication TypeJournal Article
Year of Publication2013
AuthorsI.G.J. Classen, J.E Boom, A.V. Bogomolov, E. Wolfrum, M. Maraschek, W. Suttrop, P.C de Vries, A.JH Donne, B.J Tobias, C.W. Domier, NC Luhmann, Jr., ASDEX-Upgrade Team
JournalNuclear Fusion
Volume53
Number7
Pagination073005
Abstract

Two-dimensional temperature measurements using the electron cyclotron emission imaging diagnostic at ASDEX Upgrade revealed a variety of temperature fluctuations associated with type-I and type-II edge localized modes (ELMs). The characteristics and dynamics of these modes, and their role in the ELM cycle, are presented. During type-I ELMs, different phases of distinct mode activity have been identified. At the onset of the ELM crash, a short lived mode is observed in the pedestal region. During the actual crash phase, multiple filamentary structures are observed just outside the separatrix. A third type of fluctuation, the inter-ELM mode, is often observed in between type-I crashes. The occurrence of this mode tends to lengthen the ELM period. During type-I ELM suppression with magnetic perturbation coils, smaller crash events become more frequent, replacing the large type-I crashes. In type-II ELMs, temperature crashes are absent altogether, and a continuous broadband fluctuation in the 20–60 kHz range, showing beat wave like behaviour, is observed. The similarities between the characteristics of this mode and the inter-ELM mode suggest that it is the same instability. In type-I ELMs it delays the next crash, in type-II ELMs it might be responsible for the complete absence of crash events.

URLhttp://stacks.iop.org/0029-5515/53/i=7/a=073005
DOI10.1088/0029-5515/53/7/073005
Division

FP

Department

PDG

PID

ced084f9d0677c7fab0c2d1427910132

Alternate TitleNucl. Fusion

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