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(EX8/5) Error Field Mode Studies on JET, COMPASS-D and DIII-D, and Implications for ITER

   
R. Buttery ¹, M. de Benedetti ⁴, D. Gates ^1*, Y. Gribov ⁵, T. Hender ¹, R. J. La Haye ³, P. Leahy ¹, J. A. Leuer ³, A. W. Morris ¹, A. Santagiustina ², J. T. Scoville ³, B. Tubbing ^2**, and the JET², COMPASS-D¹ and DIII-D³ Teams
     
¹ EURATOM/UKAEA Fusion Association, Culham Science Centre, Oxon, UK
² JET Joint Undertaking, Oxon, UK
³ General Atomics, San Diego, USA
⁴ Imperial College, London, UK
⁵ ITER-Naka Joint Working Site, JAPAN
^* now at Princeton University, NJ 08543, USA
^** now at European Commission, Brussels

Abstract
New experiments on COMPASS-D , DIII-D  and JET  have identified the critical scalings of error field sensitivity and harmonic content effects, enabling predictions of the requirements for larger devices such as ITER . Thresholds are lowest at low density, a regime proposed for H mode access on ITER. Results suggest a moderate error field sensitivity ( $\delta B/B \sim 10^{-4}$) for ITER, comparable with the size of its intrinsic error, although there are uncertainties in scaling behaviour. Other studies on COMPASS-D and DIII-D show that sideband harmonics to the (2,1) component play an important role. Thus a correction system for ITER will be important, with flexibility to correct sidebands desirable, possibly assisted by beam rotation. Such a system has been designed and is capable of reducing multiple harmonic error levels to $\sim 2\times 10^{-5}$.

 

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