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Cross-field blob transport in tokamak scrape-off-layer plasmas

2002; American Institute of Physics; Volume: 9; Issue: 1 Linguagem: Inglês

10.1063/1.1426394

1527-2419

D. A. D’Ippolito, J. R. Myra, S. I. Krasheninnikov,

Nuclear reactor physics and engineering

Recent measurements show that nondiffusive, intermittent transport of particles can play a major role in the scrape-off-layer (SOL) of fusion experiments. A possible mechanism for fast convective plasma transport is related to the plasma filaments or “blobs” observed in the SOL with fast cameras and probes. In this paper, physical arguments suggesting the importance of blob transport [S. I. Krasheninnikov, Phys. Lett. A 283, 368 (2001)] have been extended by calculations using a three-field fluid model, treating the blobs as coherent propagating structures. The properties of density, temperature and vorticity blobs, and methods of averaging over ensembles of blobs to get the average SOL profiles, are illustrated. The role of ionization of background neutrals in sustaining the density blob transport is also discussed. Many qualitative features of the experiments, such as relatively flat density profiles and transport coefficients increasing toward the wall, are shown to emerge naturally from the blob transport paradigm.