Preliminary Measurements with the Ultra-Fast Charge Exchange Recombination Spectrometer (UF-CHERS) on DIII-D

A dual-channel, high throughput (1 mm$^2$-ster), high efficiency, customized spectrometer (UF-CHERS) has been deployed at \hbox{DIII-D} to measure ion temperature and parallel velocity fluctuations through detection of the beam-excited CVI charge exchange line near \hbox{529 nm} at \hbox{0.25 nm} resolution. Turbulence-relevant time resolution of \hbox{1 $\mu$s} is achieved with cooled avalanched photodiode detectors (APDs). Initial measurements obtained during the 2010 \hbox{DIII-D} experimental run campaign demonstrate detection of the charge exchange and edge emission at near photon-noise-limited performance, although signal levels are lower than estimated. The Doppler broadened spectrum, time evolution, radial variation, and cross correlation with BES-measured density fluctuations from \hbox{L-mode} discharges are presented to assess signal levels and noise characteristics. Hints of GAM-induced temperature fluctuations are observed. Upgrades to the optics and detectors for improved signal-to-noise are evaluated.