L to H mode transition: on the role of Z(eff)

TitleL to H mode transition: on the role of Z(eff)
Publication TypeJournal Article
Year of Publication2014
AuthorsC. Bourdelle, C.F Maggi, L. Chone, P. Beyer, J. Citrin, N. Fedorczak, X. Garbet, A. Loarte, F. Militello, M. Romanelli, Y. Sarazin
JournalNuclear Fusion
Volume54
Issue2
Pagination022001
Date PublishedFeb
ISBN Number0029-5515; 1741-4326
Abstract

In this paper, the nature of the primary instability present in the pedestal forming region prior to the transition into H mode is analysed using a gyrokinetic code on JET-ILWprofiles. The linear analysis shows that the primary instability is of resistive nature, and can therefore be stabilized by increased temperature, hence power. The unstable modes are identified as being resistive ballooning modes. Their growth rates decrease for temperatures increasing towards the experimentally measured temperature at the L-H transition. The growth rates are larger for lower effective charge Z(eff). This dependence is shown to be in qualitative agreement with recent and past experimental observations of reduced Z(eff) associated with lower L-H power thresholds.

DOI10.1088/0029-5515/54/2/022001
Division

FP

Department

CPP-HT

PID

243547f2c07e1c57e76e9b4147717183

LabelOA

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