Author:
Puiatti M.E.,Valisa M.,Agostini M.,Auriemma F.,Bonomo F.,Carraro L.,Fassina A.,Gobbin M.,Lorenzini R.,Momo B.,Scaggion A.,Zaniol B.,Alfier A.,Apolloni L.,Baruzzo M.,Bolzonella T.,Bonfiglio D.,Canton A.,Cappello S.,Cavazzana R.,Bello S. Dal,De Masi G.,Escande D.F.,Franz P.,Gazza E.,Guo S.,Innocente P.,Marchiori G.,Marrelli L.,Martin P.,Martines E.,Martini S.,Menmuir S.,Novello L.,Paccagnella R.,Piovesan P.,Piron L.,Predebon I.,Ruzzon A.,Sattin F.,Scarin P.,Soppelsa A.,Spizzo G.,Spagnolo S.,Spolaore M.,Terranova D.,Veranda M.,Vianello N.,Zanca P.,Zanotto L.,Zuin M.
Abstract
An interesting result of magnetic chaos reduction in RFX-mod high current discharges is the development of strong electron transport barriers. An internal heat and particle transport barrier is formed when a bifurcation process changes the magnetic configuration into a helical equilibrium and chaos reduction follows, together with the formation of a null in the q shear. Strong temperature gradients develop, corresponding to a decreased thermal and particle transport. Turbulence analysis shows that the large electron temperature gradients are limited by the onset of micro-tearing modes, in addition to residual magnetic chaos. A new type of electron transport barrier with strong temperature gradients develops more externally (r/a = 0.8) accompanied by a 30% improvement of the global confinement time. The mechanism responsible for the formation of such a barrier is still unknown but it is likely associated with a local reduction of magnetic chaos. These external barriers develop primarily in situations of well-conditioned walls so that they might be regarded as attempts towards an L–H transition. Both types of barriers occur in high-current low-collisionality regimes. Analogies with tokamak and stellarators are discussed.
Subject
Condensed Matter Physics,Nuclear and High Energy Physics
Cited by
26 articles.
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