Chapman, Sandra C., Dendy, R. O., Todd, T. N., Watkins, Nicholas W., Webster, A. J., Calderon, F. A. and Morris, J. (2014) Relationship of edge localized mode burst times with divertor flux loop signal phase in JET. Physics of Plasmas, 21 (6). Article number 062302. doi:10.1063/1.4881474 ISSN 1070-664X.

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Abstract

A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM.

Item Type:	Journal Article
Subjects:	Q Science > QC Physics
Divisions:	Faculty of Science, Engineering and Medicine > Science > Physics
Library of Congress Subject Headings (LCSH):	Edge-localized modes, Tokamaks
Journal or Publication Title:	Physics of Plasmas
Publisher:	American Institute of Physics
ISSN:	1070-664X
Official Date:	June 2014
Dates:	Date Event June 2014 Published 3 June 2014 Available 20 May 2014 Accepted 17 April 2014 Submitted
Volume:	21
Number:	6
Number of Pages:	9
Article Number:	Article number 062302
DOI:	10.1063/1.4881474
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Open Access (Creative Commons)
Date of first compliant deposit:	27 December 2015
Date of first compliant Open Access:	27 December 2015
Funder:	Engineering and Physical Sciences Research Council (EPSRC), Culham Centre for Fusion Energy (CCFE), Euratom, Research Councils UK (RCUK)
Grant number:	EP/I501045 (EPSRC)
Contributors:	Contribution Name Contributor ID Research Group JET EFDA Contributors, UNSPECIFIED

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