Electrostatic transport in L-mode scrape-off layer plasmas of Tore Supra tokamak. II. Transport by fluctuations
- Center for Energy Research, University of California San Diego, La Jolla, California 92093 (United States)
- Commissariat a l'Energie Atomique et aux Energies Alternatives, Institut de Recherche pour la Fusion Magnetique Controlee, F-13108 Saint-Paul-Lez-Durance (France)
- Department of Applied Physics, Ghent University, St. Pietersnieuwstraat 41, B-9000 Gent (Belgium)
The turbulent transport of particles is investigated using rake probes at the top of the scrape-off layer (SOL) of circular ohmically heated L-mode plasmas in the Tore Supra tokamak [G. Giruzzi et al., Nucl. Fusion 49, 104010 (2009)]. Both radial and poloidal non-linear fluxes are estimated by means of two reciprocating arrays separated toroidally by 120 Degree-Sign . The time average of the radial (poloidal) flux is positive (negative) through the whole SOL profile. The respective effective transport velocity are about {sub t} Almost-Equal-To 30m s{sup -1} and {sub t} Almost-Equal-To -60m s{sup -1} close to the last closed flux surface. Both components present a standard deviation about 10 times higher than their respective mean amplitude, and time-distributions highly skewed toward values of the same sign as their mean values. The existence of a nonlinear poloidal flux is associated with the local tilt of filament eddies due to electric and magnetic shear. At the last closed flux surface, where plasma filaments experience their early life, the orientation of the velocity field is consistent with structure dynamics which originate from the outboard midplane and spread along field lines toward the rest of the poloidal section. The localized tilt of the eddy structures corresponds to the effect of the magnetic shear. Further into the SOL, the orientation of the velocity field evolves along radius in agreement with a simple model of propagating filaments progressively tilted by an electric shear. The combined effects of electric and magnetic shear on the eddy tilting have potentially a crucial impact on the existence of a Reynolds stress {sub t} component, which is strongly poloidally asymmetric at the edge of tokamak plasmas.
- OSTI ID:
- 22072557
- Journal Information:
- Physics of Plasmas, Vol. 19, Issue 7; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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