We study the turbulent dynamics of a helium plasma in a nonconfining cylindrical configuration. Our experimental setup allows us to analyze particle transport in different plasma regions. We find that, whereas the transport is diffusive in the innermost regions of the plasma, distinctive non-diffusive features appear in regions away from the center. Indeed, at the plasma edge we find that particle flux exhibits a power-law distribution of avalanche durations, intermittency, and long-term correlations.

Experimental evidence of parallel flows dynamically coupled to radial turbulent transport is reported in a linear plasma machine (SLPM). Probability density functions (PDFs) for parallel flows and transport are different. PDFs for transport show clear non-gaussian features with large and sporadic bursts and PDFs of parallel flows are rather gaussian. Plasma profiles of parallel Mach number (in the range 0.1-0.3) show gradients dM || /dr comparable to 1/L n . Experimental results show that the dynamical coupling between transport and flows shows differences at different plasma radii. The degree of coupling also shows variations with plasma heating conditions. These findings suggest that, although turbulence can be considered as quasi-bidimensional in magnetized plasmas, parallel dynamics still play an important role in the regulation of radial transport.

It is shown that the statistical and correlation properties of the local turbulent flux measured at different radial locations of the cold, weakly ionized plasmas inside the Santander Linear Plasma Machine [Castellanos et al., Plasma Phys. Control. Fusion 47, 2067 (2005)] are consistent with diffusive-like transport dynamics. This is in contrast to the dynamical behavior inferred from similar measurements taken in hotter, fully ionized tokamak and stellarator edge plasmas, in which longterm correlations and other features characteristic of complex, non-diffusive transport dynamics have been reported in the past. These results may shed some light on a recent controversy regarding the possible universality of the dynamics of turbulent transport in magnetized plasmas.

Shows the possibility of generating magneto-active plasmas in a waveguide by the use of electromagnetic waves launched transversely to the static magnetic field for ordinary and extraordinary polarisation. With extraordinary polarisation, plasmas of densities of about 1017 m-3 can be obtained at low power levels. The working gas was argon and the static magnetic field about 0.09 T. Plasma density is limited by the frequency of the incident waves (2.45 GHz in the authors' case) and not by the mechanism of wave transformation.

A b s t r a c tA view of the experimental techniques used in the characterization of fluctuations in the plasma boundary region of magnetic confinement systems by Langmuir probes is given. In particular, recent experimental developments for the measurement of electron temperature fluctuations are discussed. I n t r o d u c t i o nCharacterization of fluctuations and fluctuation driven particle and energy fluxes requires experimental techniques for measuring the variations in parameters such as density, temperature and magnetic and electric fields with good temporal and spatial resolution. With the present state of the art in plasma diagnostics this kind of measurement is mostly limited to the plasma edge where material probes can be used.Electrostatic fluctuations induced particle transport, computed assuming a negligible level of temperature'fluctuations (i.e. fs M 5, and 61 M & where fs is the ion saturation current fluctuations is the electron density fluctuations and and 6, are the floating and plasma potential fluctuations respectively), is large enough to account for the total particle transport in the plasma boundary region in tokamaks and stellarators [27]. However, a more complete picture of particle and energy transport due to fluctuations requires a better knowledge of the level of electron temperature fluctuations. Furthermore, the presence of electron temperature fluctuations can significantly affect the interpretation of the Langmuir probe data [ll]. p,-3 M e a s u r e m e n t s of electron temperature fluctuations First measurements of electron ternperature.fluctuations were carried out using slow swept double Langmuir probe technique, fitting the current fluctuations as a function of the bias voltage [21], [16]. However, the interpretation of temperature fluctuation measurements provided by this method presents some difficulties clue to the fact that gradients in the fluctuating quantities between probes are not necessarily negligible [8]. A modified triple probe technique has been developed [25] which reduces the phase delay errors introduced by finite probe tip separations in the so called standard triple probe method [9]. The main difficulty of the multiple probe measurements is t o avoid the effects of probe shadowing while reducing the phase delay and decorrelation effects. To address this problem, a time domain triple probe method has been recently proposed which uses high speed switching of Langmuir probe potential to get all triple probe quantities at a single probe position [17].