Issue
EPL
Volume 87, Number 5, September 2009
Article Number 55002
Number of page(s) 5
Section Physics of Gases, Plasmas and Electric Discharges
DOI http://dx.doi.org/10.1209/0295-5075/87/55002
Published online 24 September 2009
EPL, 87 (2009) 55002
DOI: 10.1209/0295-5075/87/55002

Multi-scale physics mechanisms and spontaneous edge transport bifurcations in fusion plasmas

C. Hidalgo1, M. A. Pedrosa1, C. Silva2, D. Carralero1, E. Ascasibar1, B. A. Carreras3, T. Estrada1, F. Tabarés1, D. Tafalla1, J. Guasp1, M. Liniers1, A. López-Fraguas1, B. van Milligen1 and M. A. Ochando1

1   Laboratorio Nacional de Fusión, EURATOM-CIEMAT - Madrid, Spain, EU
2   EURATOM-IST - Lisbon, Portugal, EU
3   BACV - Oak Ridge, TN, USA

carlos.hidalgo@ciemat.es

received 28 July 2009; accepted in final form 3 September 2009; published September 2009
published online 24 September 2009

Abstract
The magnitude of radial transport in magnetic confinement devices for controlled nuclear fusion suffers spontaneous bifurcations when specific system parameter values are exceeded. Here we show, for the first time, that the correlation length of the plasma potential becomes of the order of the machine size during the edge bifurcation itself, quite unlike the density fluctuations. The mechanism governing the development of this bifurcation, leading to the establishment of an edge transport barrier, is still one of the main scientific conundrums facing the magnetic fusion community after more than twenty years of intense research. The results presented here show the dominant role of long-range correlations when approaching the Low to High confinement edge transition in fusion plasmas. This is in line with the expectation that multi-scale interactions are a crucial ingredient of complex dynamics in many non-equilibrium systems.

PACS
52.35.Ra - Plasma turbulence.
52.35.-g - Waves, oscillations, and instabilities in plasmas and intense beams.
52.55.-s - Magnetic confinement and equilibrium.

© EPLA 2009