Measurement of deuterium density profiles in the H-mode steep gradient region using charge exchange recombination spectroscopy on DIII-D

Recent completion of a thirty two channel main-ion (deuterium)charge exchange recombination spectroscopy (CER)diagnostic on the DIII-D tokamak [J. L. Luxon, Nucl. Fusion42, 614 (2002)] enables detailed comparisons between impurity and main-ion temperature, density, and toroidal rotation. In aH-mode DIII-D discharge, these newmeasurement capabilities are used to provide the deuterium density profile, demonstrate the importance of profile alignment between Thomson scattering and CERdiagnostics, and aid in determining the electron temperature at the separatrix. Sixteen sightlines cover the core of the plasma and another sixteen are densely packed towards the plasma edge, providing high resolutionmeasurements across the pedestal and steep gradient region inH-mode plasmas. Extracting useful physical quantities such as deuterium density is challenging due to multiplephotoemission processes. These challenges are overcome using a detailed fittingmodel and by forwardmodeling thephotoemission using the FIDASIM code, which implements a comprehensive collisional radiativemodel.

Source: Review of Scientific Instruments - September 26, 2016 Category: Physics Authors: S. R. Haskey, B. A. Grierson, K. H. Burrell, C. Chrystal, R. J. Groebner, D. H. Kaplan, N. A. Pablant and L. Stagner Source Type: research