Magnetic island localization for NTM control by ECE viewed along the same optical path of the ECCD beam

TitleMagnetic island localization for NTM control by ECE viewed along the same optical path of the ECCD beam
Publication TypeJournal Article
Year of Publication2009
AuthorsW.A Bongers, A.PH Goede, E. Westerhof, J.W Oosterbeek, N.J Doelman, F.C Schüller, MR de Baar, W. Kasparek, W. Wubie, D. Wagner, J. Stober
JournalFusion Science and Technology
Volume55
Number2
Pagination188-203
Date PublishedFeb
Type of ArticleArticle
ISBN Number1536-1055
Accession NumberISI:000263009800006
KeywordsASDEX UPGRADE, CURRENT DRIVE, DESIGN, DISCHARGES, ECHR/ECCD, ELECTRON-CYCLOTRON WAVES, feedback control, FEEDBACK-SYSTEM, GUIDES, INSTABILITIES, NEOCLASSICAL TEARING MODE, NTM stabilization, STABILIZATION
Abstract

Neoclassical tearing modes (NTMs) deteriorate high-pressure tokamak plasma confinement and can be suppressed by electron cyclotron current drive (ECCD). In order to obtain efficient suppression, the ECCD power needs to be deposited at the center of an NTM magnetic island. To enhance efficiency, this power also needs to be synchronized in phase with the rotation of the island. The problem is that of real-time detection and precise localization of the island(s) in order to provide the feedback signal required to control the ECCD power deposition area with an accuracy of 1 to 2 cm. Existing schemes based on mode location, equilibrium reconstruction, and plasma profile measurements are limited in positional and temporal accuracy and moreover will become very complex when applied to ITER. To overcome these limitations, it is proposed to provide the feedback signal from electron cyclotron emission (ECE) measurements taken along the identical line of sight as traced by the incident ECCD millimeter-wave beam but in reverse direction. Experiments on TEXTOR have demonstrated a proof of principle. These measurements motivate the further development and the implementation of such an ECCD-aligned ECE system for NTM control in larger fusion machines. Possible implementation of such a system on ASDEX-Upgrade, based on waveguides equipped with a fast directional switch, is presented in this paper. Possible further development for ITER is also discussed.

URL<Go to ISI>://000263009800006
Division

Fusion Physics

PID

3ca0185e51a5a2856d6f124b53ad61a9

Alternate TitleFusion Sci. Technol.

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