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(EX/P4-05) Edge Transport and its Interconnection with Main Chamber Recycling in ASDEX Upgrade

A. Kallenbach1), R. Dux1), J. Gafert1), G. Haas1), L. Horton1), M. Jakobi1), B. Kurzan1), H.W. Mueller1), R. Neu1), J. Neuhauser1), R. Pugno1), T. Puetterich1), V. Rohde1), W. Sandmann1), S.-W. Yoon1), ASDEX Upgrade Team1)
1) Max-Planck Institut für Plasmaphysik, Garching, Germany

Abstract.  Edge transport in ASDEX Upgrade H-mode discharges is studied using Thomson scattering measurements with high spatial resolution in combination with spectroscopic recycling- and erosion measurements and Langmuir probes. The simultaneous measurement of electron temperature and density profiles allows to correct uncertainties in the separatrix position using power balance and parallel conduction. During gas puffing, a shoulder is observed in the density profiles extending far into the SOL. Radial ion fluxes lead to neutral recycling at the wall, which subsequently fuel the edge plasma forming a loop for the radial particle flux. The recycling and corresponding impurity release is measured with various lines of sight of the visible spectroscopy, allowing to determine in-out ratios and also toroidal distributions over limiters. Modelling with the B2.5 fluid code is used to find a coherent description of the underlying transport processes. In the hot edge region between the pedestal top and the outer transport barrier foot (Te > 20 eV) a constant ratio of the electron density and temperature gradient lengths is found, $ \eta_{e}$ $ \sim$ 2, indicating profile stiffness effects.

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IAEA 2003