Space-Time Statistics of the Turbulence in a Tokamak Edge Plasma

摘要

The results of a study of the statistical space-time properties of the turbulence observed in the edge region of the PRETEXT Tokamak are reported. A local estimate of the wavenumber-frequency spectra S(k, omega ) for poloidal (k/sub y/) and toroidal (k/sub z/) wavenumbers is determined for the range .5 cm exp -1 < k < 7.5 cm exp -1 for both potential and density fluctuations obtained from spatially fixed Langmuir probe pairs. The S(k/sub y/, omega ) spectra are dominated by low frequencies (< 200 kHz) and small wavenumbers (< 3 cm exp -1 ) and appear broadened about an approximately linear statistical dispersion relation, anti k( omega ). The broadening is characterized by a spectral width sigma/sub k/( omega ) (rms deviation above anti k( omega )) which is of the order of anti k( omega ). The turbulence appears to propagate poloidally with an apparent mean phase velocity of 1 to 2 x 10 exp 5 cm/s in the ion diamagnetic drift direction. Measurements of the fluctuation-induced particle transport reveal the particle flux to be outward and resulting primarily from the low frequency, long wavelength components of the turbulence. A particle diffusion coefficient D/sub x/, estimated from measured particle flux and density profiles, is of the order of that estimated for Bohm diffusion, but appears to increase with density. (ERA citation 10:006032)