High-frequency electrostatic waves have been observed in a two-electron-temperature plasma. Both bi-Maxwellian and Maxwellian-waterbag models were found to be inadequate in explaining the observed dispersion and damping rates. However, modelling of the hot electron component with a κ-distribution function confirms that the experiments represent observation of the electron-acoustic wave in the laboratory.

In the BLAAMA" device a wealdy ionized hydrogen plasma is produced by electrons accelerated from a hoL negatively biosed tungsten filament and confined in a toroidal magnetic field of strength up to 0.4 T. The plasma is turbulent, with relative fluctuation levels in ne, # and Tc of 10% or more. The time-averaged state exhibits nested toroidal surfaces of constant potential and pressure, which requires an anomalous cross-field cumeat to remove the spacecharge injected by the cathode and the charge accumulated due to the VB-and C U N ~U E drifts. Typical plusma parameters me n, -10l6 m-3, T, .. 1-20 eV, Z -I eV. The cross-field diffusion coefficient is typically DI -30 m2 s-' -IO4 x Of"""' -10' x DY". Evidence is presented in support of the hypothesis that the placma goes turbulent beuuse it needs to develop an anomalous current channel. nnd this turbulence in tum determines the plasma transport and the time-averaged state.

Electron energy distributions (EED) in strongly magnetized (∼0.3 T), low-pressure (∼0.2 Pa) helium plasmas of the toroidal device “Blaamann” [K. Rypdal et al., Plasma Phys. Controlled Fusion 36, 1099 (1994)] have been measured. In the analysis of measurements, one applies a simplified expression for the limit of a strongly magnetized plasma relating the electron energy distribution to the first derivative of electron probe current with respect to the probe potential. It is shown that for the conditions investigated this approximation gives the same electron densities and slightly lower temperatures (up to 10%) as the kinetic theory for arbitrary magnetic field strength. Cylindrical probes, which are oriented along and perpendicular to the magnetic field, are used in the measurements. It is shown that these probes give nearly identical results. However, the probe that is oriented perpendicular to the magnetic field can give the electron energy distribution in a wider energy range and with better accuracy. The cross-field diffusion coefficient of electrons near the probe is estimated and shown to be classical.

The formation of ion phase space vortexes in the ion two stream region behind electrostatic ion acoustic shocks are observed in a laboratory experiment. A detailed analysis demonstrates that the evolution of such vortexes is associated with ion-ion beam instabilities and a nonlinear equation for their initial evolution is derived. The results are supported by a numerical particle simulation. Also the possibility of vortex excitation by ion bursts and coalescence of two vortexes are demonstrated. The effects of finite ion temperature, particle trapping and charge exchange collisions are discussed and the results related to ionospheric observations.

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