Diagnostics for local spectroscopic measurements in the divertor region of the Alcator C-Mod and DIII-D tokamaks

Local measurements of line emission of either intrinsic or gas puffed impurities will be performed around and below the X point. Such spectroscopic measurements, together with divertor Thomson scattering and bolometric imaging will enable estimates of divertor impurity particle distributions and power losses. A proposed multilayer mirror (MLM) diagnostic mounted inside the tokamak vessel will measure XUV (100-200 Å) emission from impurities at multiple locations in the divertor region of the C-Mod tokamak. A prototype of this instrument measuring N V at 162.6 Å is scheduled to be installed on C-Mod with a single chordal view of the X point. A multichordal/ multispectral device using MLMs and gratings has been designed for the DIII-D tokamak. The instrument will measure the resonance emission of C II to C VI from 40-2000 Å, thus enabling a more direct and reliable estimate of the impurity content in the divertor. At DIII-D, the device will be mounted on a port below the mid plane avoiding spectroscopic contamination from the core plasma.