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(κ,ω) for poloidal (ky)an d toroidal (kz) wavenumbers is determined for the range 0.5 cm−1 < k < 7.5 cm−1, for both potential and density fluctuations obtained from spatially fixed Langmuir probe pairs. The S(ky, ω) spectra aredominated by low frequencies ( < 200 kHz) and small wavenumbers (< 3 cm−1) and appear broadened about an approximately linear statistical dispersion relation, (ω). The broadening is characterized by a spectral width σk (ω) (root-mean-square deviation about (ω)) which is of the order of (ω). The turbulence appears to propagate poloidally with an apparent mean phase velocity of (1–2) × 105 cm·s−1 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 Dx, estimated from the measured particle flux and density profiles, is of the order of the coefficient estimated for Bohm diffusion, but appears to increase with density.
Experimental study of particle transport and density fluctuations in LHD