MULTICHORD SPECTROSCOPY OF THE DIII-D DIVERTOR REGION

A multichannel spectrometer with high spectral resolution (0.01 nm) and high temporal resolution (0.5 ms) has been configured to collect data simultaneously from eight viewchords spanning the divertor region of DIII-D. Fiber optically coupled to a wide-field lens with a vertical view of the vessel floor, the instrument will be capable of differentiating the behavior of impurity line emission at the inner and outer divertor strike points, on and off the Advanced Divertor Program ring, on the face of the Divertor Material Exposure System probe, and in the region of the lower centerpost. Used with a coarse grating (300 grooves/mm), spectral coverage of each spatial channel is 15 nm with 0.3 nm resolution; used in high order with a 1200 groove/mm grating, the instrument is capable of resolving Doppler profiles. Spatial variation of gas recycling and impurity influx will be studied for both single- and double-null divertor configurations in low and high density operating regimes.