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Abstract

The formation of internal transport barriers (ITBs) has been experimentally associated with the presence of rational q surfaces in both JET and ASDEX Upgrade. The triggering mechanisms are related to the occurrence of magnetohydrodynamic (MHD) instabilities such as mode coupling and fishbone activity. These events could locally modify the poloidal velocity and increase transiently the shearing rate to values comparable with the linear growth rate of ion temperature gradient modes. For JET reversed magnetic shear scenarios, ITB emergence occurs preferentially when the minimum q reaches an integral value. In this case, transport effects localized in the vicinity of zero magnetic shear and close to rational q values may be at the origin of ITB formation. The role of rational q surfaces in ITB triggering stresses the importance of q profile control for an advanced tokamak scenario and could assist in substantially lowering the access power to these scenarios in next step facilities.

Additional information

Authors: JOFFRIN E, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);GARBET X, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);HUYSMANS G T A, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);MAGET P, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);CHALLIS C D, EURATOM-UKAEA Fusion Association, Culham Science Centre, Abingdon (GB);HAWKES N C, EURATOM-UKAEA Fusion Association, Culham Science Centre, Abingdon (GB);HENDER T C, EURATOM-UKAEA Fusion Association, Culham Science Centre, Abingdon (GB);HOWELL D F, EURATOM-UKAEA Fusion Association, Culham Science Centre, Abingdon (GB);SHARAPOV S E, EURATOM-UKAEA Fusion Association, Culham Science Centre, Abingdon (GB);GUNTER S, Max-Planck-Institut fur Plasmaphysik, IPP-EURATOM Association, Garching (DE);LAZZARO E, Istituto di Fisica del Plasma del CNR, Assoc. Euratom-ENEA-CNR per la Fusione, Milano (IT);CONWAY G D, Max-Planck-Institut für Plasmaphysik, IPP-EURATOM Association, Garching (DE);GÜNTER S, Max-Planck-Institut für Plasmaphysik, IPP-EURATOM Association, Garching (DE);MARACHEK M, Max-Planck-Institut für Plasmaphysik, IPP-EURATOM Association, Garching (DE);PEETERS A G, Max-Planck-Institut für Plasmaphysik, IPP-EURATOM Association, Garching (DE);PINCHES S D, Max-Planck-Institut für Plasmaphysik, IPP-EURATOM Association, Garching (DE)
Bibliographic Reference: An article published in: Nuclear Fusion 43 (2003) pp.1167�1174
Availability: This article can be accessed online by subscribers, and can be ordered online by non-subscribers, at: http://stacks.iop.org/NF/43/1167
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