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M. Kaufmann, H.-S. Bosch, A. Herrmann,
A. Kallenbach, K. Borrass, A. Carlson, D. Coster,
J. C. Fuchs, J. Gafert, K. Lackner, J. Neuhauser,
R. Schneider, J. Schweinzer, W. Suttrop, W. Ullrich,
U. Wenzel, and ASDEX Upgrade Team
Max-Planck-Institut für Plasmaphysik, EURATOM-IPP Association, Garching und Berlin, Germany
Abstract. In 1997 the new `LYRA' divertor went
into operation at ASDEX Upgrade and the neutral beam heating power was
increased to 20 MW by installation of a second injector. This leads to the
relatively high value of P/R of 12 MW/m. It has been shown that the ASDEX
Upgrade LYRA divertor is capable of handling such high heating
powers. Measurements presented in this paper reveal a reduction of the
maximum heat flux in the LYRA divertor by more than a factor of two compared
to the open Divertor I. This reduction is caused by radiative losses inside
the divertor region. Carbon radiation cools the divertor plasma down to a few
eV where hydrogen radiation losses become significant. They are increased due
to an effective reflection of neutrals into the hot separatrix
region. B2-Eirene modelling of the performed experiments supports the
experimental findings and refines the understanding of loss processes in the
divertor region.
IAEA 2001
