EUV Spectroscopy During the DIII-D Tungsten Divertor Campaign*

Two toroidal rings of tungsten-coated tile inserts were installed in the DIII-D lower divertor and a range of L- and H-mode plasma discharges were compared during a dedicated two week run campaign. A high resolution (1340 spectral channels) variable-ruling grating spectrometer viewing the core of the plasma was used to study the spectral region 10-70 {\AA}; a second spectrometer viewing $\sim20-150 {\AA}$ was also used. At DIII-D core plasma temperatures 2-3 keV, several emission lines from W38+ through W43+ were identified, including a quasi-continuum feature of W near 50 {\AA} whose structure depends on core $T_e$. Molybdenum (TZM substrate) emissions between 20-30{\AA} and near $\sim70{\AA}$ were also observed. ADAS calculations are used to guide the identification of W emission lines for the measured core plasma $T_e$ and $n_e$ profiles. The behavior of W emissions during both “benign”, pellet injection, and impurity accumulation conditions will be presented.