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Marseille, France

Ghendrih Ph.,French Atomic Energy Commission | Auphan T.,LATP | Bensiali B.,M2P2 | Bilanceri M.,French Institute for Research in Computer Science and Automation | And 17 more authors.
Journal of Nuclear Materials | Year: 2013

The ballooned nature of cross-field transport is shown to govern the steady state divertor imbalance of the energy flux leading to a factor 10 between the low field side and high field energy flux. An even stronger ratio is found for the divertor temperatures. Conversely the particle flux is expected to be a factor 10 larger on the high field side than on the low field side. The transition to detachment, close to divertor thermal collapse, exhibits several constraints to maintain steady state solutions. These constraints, related in particular to a large drop of the divertor density upon detachment, are shown to strongly correlate the pressure and particle flux variation along the field line and consequently the various loss channels. This delicate balance between different mechanisms is a possible understanding of the difficulty reported in detached plasma operation and simulation. © 2013 Elsevier B.V. All rights reserved.

Schwander F.,M2P2 | Chiavassa G.,M2P2 | Ciraolo G.,M2P2 | Ghendrih P.,French Atomic Energy Commission | And 5 more authors.
Journal of Nuclear Materials | Year: 2011

The transition between the core and scrape-off layer of a tokamak corresponds to a marked momentum shear layer, owing to sheath acceleration on limiters which drives near-sonic flows along the plasma magnetic field in the scrape-off layer, and a parallel shear flow instability can possibly be triggered. The possibility of this instability driven by the velocity gradient is investigated numerically, using a minimum model of particle and parallel momentum transport in the edge of a tokamak, in a computational domain modelling a limiter plasma with background turbulence modelled as an effective diffusion. It is found that unstable regions can exist in the vicinity of a limiter, in agreement with experimental findings, when momentum radial transport - and therefore coupling between SOL and core flows - is sufficiently weak. Instability is reinforced by core rotation, and is found to be maximum downstream of the limiter (with respect to the core plasma flow). © 2010 Elsevier B.V. All rights reserved.

Fedorczak N.,French Atomic Energy Commission | Gunn J.P.,French Atomic Energy Commission | Ghendrih P.,French Atomic Energy Commission | Ciraolo G.,M2P2 | And 4 more authors.
Journal of Nuclear Materials | Year: 2011

A consistent description of scrape-off layer transport is built from multi-diagnostic observations in ohmic discharges in Tore Supra. Fast imaging reveals the existence of relatively large filamentary structures on the low field side but not on the high field side of the torus. These filaments can exist either on open or closed magnetic flux surfaces and have a finite parallel extent from the outboard midplane. Probe electrostatic turbulence measured at the top of the plasma corresponds to the ExB convection of density burst, understood as the signature of filament propagation. Independent experiments on time-averaged parallel flows measured with a Mach probe lead to a poloidal mapping of the strongly asymmetric radial flux. This flux is centered at the outboard midplane and its poloidal half width is about 50°. The local turbulent flux on the top is consistent with the mapping. © 2010 Elsevier B.V. All rights reserved.

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