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Wide-field turbulence imaging with beam emission spectroscopy

McKee, G. R.
Fonck, R. J.
Shafer, M. W.
Uzun Kaymak, İlker Ümit
Yan, Z.
Imaging of the size, shape, time-averaged, and time-resolved dynamics of long-wavelength density turbulence structures is accomplished with an expanded, high-sensitivity, wide-field beam emission spectroscopy (BES) diagnostic on DIII-D. A 64-channel BES system is configured with an 8 X 8 grid of discrete channels that image an approximately 7 X 9 cm region at the outboard midplane. The grid covers multiple correlation lengths and each channel shape matches the measured radial-poloidal correlation length asymmetry of turbulent eddies. The wide field 8 X 8 imaging capability allows for sampling of essentially the full two-dimensional spatial correlation function for typical plasma conditions. The sampled area can be radially scanned over 0.4 < r/a < 1, including the core ((n) over tilde /n < 1% ), pedestal, and scrape-off-layer. The resulting time-resolved visualizations of turbulence and flows provide critical data on turbulence dynamics. (C) 2010 American Institute of Physics. [doi:10.1063/1.3495788]