TITLE

Detection of zonal flow spectra in DIII-D by a dual-channel Doppler backscattering system

AUTHOR(S)
Schmitz, L.; Wang, G.; Hillesheim, J. C.; Rhodes, T. L.; Peebles, W. A.; White, A. E.; Zeng, L.; Carter, T. A.; Solomon, W.
PUB. DATE
October 2008
SOURCE
Review of Scientific Instruments;Oct2008, Vol. 79 Issue 10, p10F113
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
Doppler backscattering (DBS) has been successfully used to measure the E×B flow velocity and local intermediate wavenumber density fluctuation levels in the DIII-D tokamak. Depending on the launch angle and the frequency of the probing beam, the signal backscattered from the plasma cut-off layer is sensitive to density fluctuations at a specific perpendicular wavenumber (1<=k⊥ρs<=4). Due to the localization and high time resolution for poloidal flow measurements, DBS is well suited to detect stationary and time-dependent shear flows [zonal flows (ZFs)]. We present a novel scheme to measure ZF spectra using a dual-channel DBS system capable of simultaneously probing two minor radii separated by a distance of 0.2 cm<Δr<3 cm. Frequency spectra of geodesic acoustic modes and low frequency ZFs (f<=10 kHz) have been obtained for 0.6
ACCESSION #
35150132

 

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