Internal and external electron transport barriers in the RFX-mod reversed field pinch
2011 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 51, no 7, 073038- p.Article in journal (Refereed) Published
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. Â© 2011 IAEA, Vienna.
Place, publisher, year, edition, pages
2011. Vol. 51, no 7, 073038- p.
Bifurcation process, Electron transport, External electrons, Global confinement, Helical equilibria, High-current, High-current discharges, Internal heat, L-H transition, Magnetic configuration, Particle transport, Reversed field pinch, Electron transitions, Electron transport properties, Particle separators, Thermal gradients, Electron temperature
Fusion, Plasma and Space Physics
IdentifiersURN: urn:nbn:se:kth:diva-50844DOI: 10.1088/0029-5515/51/7/073038ISI: 000291933300040OAI: oai:DiVA.org:kth-50844DiVA: diva2:466363
QC 201112162011-12-152011-12-082011-12-16Bibliographically approved