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A. Kallenbach, A. Bard, K. Krieger, J. Roth,
U. Wenzel and the ASDEX Upgrade Team
Max-Planck-Institut für Plasmaphysik, EURATOM Association, D-85748 Garching and Berlin
Abstract. Chemical erosion of carbon is investigated in the outer Divertor II
of the ASDEX Upgrade tokamak for ion flux densities up to
1023m- 2s- 1 and up to reactor-relevant values of the power per major plasma
radius,
P/R 
12MW/m. Surface temperatures are relatively low and do
not exceed 100
oC at the position of the measurements. The erosion
yields calculated from CH molecular line emission exhibit a pronounced
hydrogen flux dependence and an isotope effect, resulting in lower yields for
higher fluxes and a factor of 2 higher yields for deuterium in comparison to
hydrogen. Corresponding yields derived from carbon ion lines corroborate
these results. The observed parameter dependences of the chemical erosion
yields can be described with the analytical model of Roth and Garcia-Rosales,
Nucl. Fusion 36 (1996), if an additional, empirical time constant for the
hydrogenation process is introduced.
IAEA 2001
