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, w) for poloidal (k y ) and toroidal (k z ) 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(k y ,co) spectra are dominated by low frequencies (< 200 kHz) and small wavenumbers (< 3 cm" 1 ) and appear broadened about an approximately linear statistical dispersion relation, k (co). The broadening is characterized by a spectral width a k (co) (root-mean-square deviation about k (to)) which is of the order of k (CJ). The turbulence appears to propagate poloidally with an apparent mean phase velocity of (1 -2) X 10 s 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 D x> 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.

A reversal has been observed in the mean phase velocity of the turbulent fluctuations in the edge plasma of the TEXT tokamak. The observations can be described by a model in which the wave velocity in the lab frame is dominated by a nonuniform Er×B velocity and a gradient driven drift. The measurements also exhibit a localized instability which occurs in the region of maximum velocity shear.

Particle transport in an ohmically heated tokamak plasma was investigated in the Texas Experimental Tokamak (TEXT). Spectroscopic measurements of the electron source were used with electron density measurements to derive particle confinement times from the continuity equation. Scalings were developed for particle confinement time with electron density, plasma current, toroidal field, and plasma positioning. Simultaneous measurement of electrostatic fluctuations with Langmuir probes may suggest a correlation between edge particle transport in TEXT and electrostatic turbulence. In addition, two major features of transport were isolated. First, transport is poloidally asymmetric at least in the plasma edge. Secondly, in some cases, the particle confinement scalings are closely associated with the scalings for recycling at particular surfaces. Similarities of the TEXT global particle confinement time scalings to those observed in other tokamaks may allow the conclusions of this work to be extended to other devices.

The nonlinear coupling coefficient and the energy transfer associated with three-wave interactions are computed from measured data of the turbulent edge plasma of the Texas Experimental Tokamak(TEXT) [Nucl. Technol. Fusion 1, 479 (1981)]. The results show the presence of three-wave interactions. The interactions cause energy to cascade away from the dominant waves of the spectrum primarily toward lower, but also toward higher frequencies. The results are obtained with a new digital spectral analysis technique based on the estimation of higher-order cumulants. The method is discussed and tested on a simulation experiment. The same technique is useful for neutral fluids as well.