Plasma and Fusion Research

Volume 5, S2018 (2010)

Regular Articles

Overview of ELM Control by Low n Magnetic Perturbations on JET

Yunfeng LIANG¹⁾, Hans-Rudolf KOSLOWSKI¹⁾, Stefan JACHMICH²⁾, Alberto ALFIER³⁾, Christopher G. GIMBLETT⁴⁾, Eric NARDON⁴⁾, Philippa K. BROWNING⁵⁾, Peter DEVOY⁵⁾, Thomas EICH⁶⁾, Carine GIROUD⁴⁾, Geoffrey MADDISON⁴⁾, Peter T. LANG⁶⁾, Mikhail P. GRYAZNEVICH⁴⁾, Derek HARTING¹⁾, Martin HEYN⁷⁾, Samuli SAARELMA⁴⁾, Youwen SUN¹⁾, Ronald WENNINGER⁶⁾, Christopher WIEGMANN¹⁾, Tao ZHANG¹⁾ and JET-EFDA Contributors

1): Forschungszentrum Jülich GmbH, Association EURATOM-FZ Jülich, Institut für Energieforschung - Plasmaphysik, Trilateral Euregio Cluster, D-52425 Jülich, Germany
2): Association EURATOM-Belgian State, Koninklijke Militaire School - Ecole Royale Militaire, B-1000 Brussels Belgium
3): Associazione EURATOM-ENEA sulla Fusione, Consorzio RFX Padova, Italy
4): EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxon, OX14 3DB, UK
5): School of Physics and Astronomy, University of Manchester, Manchester, UK
6): Max-Planck-Institut für Plasmaphysik, EURATOM-Assoziation, D-85748 Garching, Germany
7): Abteilung Plasmaphysik Institut für Theoretische Physik TU-Graz, EURATOM- ÖAW

(Received 8 December 2009 / Accepted 5 February 2010 / Published 10 December 2010)

Abstract

A series of ELM control experiments have been performed on JET aiming at a better understanding of the plasma response to applied magnetic perturbations. The dynamics of the edge profiles with applied n = 1 fields have been studied in the type-I ELM H-mode plasmas. Typically, the pedestal density decreased by about 20 % when the n = 1 perturbation field was applied (So called pump-out effect). However, there is no influence of the n = 1 fields on the recovery rate of the pedestal pressure, but the ELM crash occurs earlier and at a lower level of the pedestal pressure and pressure gradient. The compensation of the density pump-out has been demonstrated using either gas fuelling or pellets injection in low triangularity H-mode plasmas. Strong toroidal rotation braking by more than 60 % has been observed, and found to be independent on the safety factor. The calculated Neoclassical Toroidal Viscosity (NTV) torque profile in the ν regime including the boundary effect is in agreement with the observed torque profile induced by the n = 1 fields on JET. No complete ELM suppression was observed by application of either n = 1 or n = 2 fields with a Chirikov parameter above one at √ Ψ ≥ 0.925, which is one of the important criteria for the design of ITER ELM control coils.

Keywords

Type-I ELM, H-mode, RMP, Density pump-out, MHD stability

DOI: 10.1585/pfr.5.S2018

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This paper may be cited as follows:

Yunfeng LIANG, Hans-Rudolf KOSLOWSKI, Stefan JACHMICH, Alberto ALFIER, Christopher G. GIMBLETT, Eric NARDON, Philippa K. BROWNING, Peter DEVOY, Thomas EICH, Carine GIROUD, Geoffrey MADDISON, Peter T. LANG, Mikhail P. GRYAZNEVICH, Derek HARTING, Martin HEYN, Samuli SAARELMA, Youwen SUN, Ronald WENNINGER, Christopher WIEGMANN, Tao ZHANG and JET-EFDA Contributors, Plasma Fusion Res. 5, S2018 (2010).