Ultrafast spectroscopy diagnostic to measure localized ion temperature and toroidal velocity fluctuations

Uzun Kaymak, İlker Ümit
Fonck, R. J.
McKee, G. R.
Schoenbeck, N.
Smith, D.
Winz, G.
Yan, Z.
A dual-channel high-efficiency, high-throughput custom spectroscopic system has been designed and implemented at DIII-D to measure localized ion thermal fluctuations associated with drift wave turbulence. A large-area prism-coupled transmission grating and high-throughput collection optics are employed to observe C VI emission centered near lambda = 529 nm. The diagnostic achieves 0.25 nm resolution over a 2.0 nm spectral band via eight discrete spectral channels. A turbulence-relevant time resolution of 1 mu s is achieved using cooled high-speed avalanche photodiodes and ultralow-noise preamplifiers. The system sensitivity is designed to provide measurements of normalized ion temperature fluctuations on the order of delta T-i/T-i <= 1%. (C) 2010 American Institute of Physics. [doi:10.1063/1.3479114]