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Spectra of magnetic perturbations triggered by pellets in JET plasmas

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European Fusion Development Agreement, JET Project (Including: Poli, F. M. (Francesca), Lang, P. T., Sharapov, S. E. (Sergei E.) and Koslowski, H. R.). (2010) Spectra of magnetic perturbations triggered by pellets in JET plasmas. Nuclear Fusion, Vol.50 (No.2). p. 5004. ISSN 0029-5515

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Official URL: http://dx.doi.org/10.1088/0029-5515/50/2/025004

Abstract

Aiming at investigating edge localised mode (ELM) pacing for future application on ITER, experiments have been conducted on JET injecting pellets in different plasma configurations, including high confinement regimes with type-I and type-III ELMs, low confinement regimes and Ohmically heated plasmas. The magnetic perturbations spectra and the toroidal mode number, n, of triggered events are compared with those of spontaneous ELMs using a wavelet analysis to provide good time resolution of short-lived coherent modes. It is found that—in all these configurations—triggered events have a coherent mode structure, indicating that pellets can trigger an MHD event basically in every background plasma. Two components have been found in the magnetic perturbations induced by pellets, with distinct frequencies and toroidal mode numbers. In high confinement regimes triggered events have similarities with spontaneous ELMs: both are seen to start from low toroidal mode numbers, then the maximum measured n increases up to about 10 within 0.3 ms before the ELM burst.

Item Type:	Journal Article
Subjects:	Q Science > QC Physics
Divisions:	Faculty of Science > Physics
Library of Congress Subject Headings (LCSH):	Plasma jets -- Research, Wavelets (Mathematics), Toroidal magnetic circuits, Plasma confinement devices, Tokamaks
Journal or Publication Title:	Nuclear Fusion
Publisher:	Institute of Physics Publishing Ltd.
ISSN:	0029-5515
Official Date:	15 January 2010
Volume:	Vol.50
Number:	No.2
Page Range:	p. 5004
Identification Number:	10.1088/0029-5515/50/2/025004
Status:	Peer Reviewed
Access rights to Published version:	Open Access
Funder:	Engineering and Physical Sciences Research Council (EPSRC)
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URI:	http://wrap.warwick.ac.uk/id/eprint/2673