High Resolution Main-ion Charge Exchange Spectroscopy in the DIII-D H-mode Pedestal

Authors: B.A. Grierson, K.H. Burrell, C. Chrystal, R.J. Groebner, S.R. Haskey, D.H. Kaplan

Abstract:  A new high spatial resolution main-ion (deuterium) charge-exchange spectroscopy system covering the tokamak boundary region has been installed on the DIII-D tokamak. Sixteen new edge main-ion CER sightlines have been combined with nineteen impurity sightlines in a tangentially viewing geometry on the DIII-D mid- plane with an interleaving design that achieves 8 mm inter-channel radial resolution for detailed profiles of main-ion temperature, velocity, charge-exchange emission and neutral beam emission. At the plasma boundary, we find a strong enhancement of the main-ion toroidal velocity that exceeds the impurity velocity by a factor of two. The unique combination of experimentally measured main-ion and impurity profiles provide a powerful quasi-neutrality constraint for reconstruction of tokamak H-mode pedestals.
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