Positive/negative ion plasmas, composed of Ba+, SF 6-, and residual electrons, were observed to display characteristics of strong turbulence. Experiments on the UCI Q machine linked the presence of negative ions (and the depletion of electrons) with large density fluctuations (δn/ n≃1), large-amplitude, low-frequency electrostatic noise (f≤20 kHz), and rapid transport of ions across magnetic field lines (DL⊥≃104 cm2/sec). Ion velocity distributions were heated parallel to and cooled perpendicular to the confining magnetic field. The partial pressure of gaseous SF6 was shown to serve as a regulator of plasma turbulence. Turbulence levels could be smoothly varied from quiescent states (δn/n≃0.01) to strongly turbulent states (δn/n≃=0.01). © 1993 American Institute of Physics.

We report measurements of test particle diffusion in velocity space. Test particles are created and examined using the method of optical tagging, an extension of laser-induced fluorescence. In quiet plasma conditions (δn/n ≤ 0.01%) results show diffusion to be linear with density in agreement with classical theory. Measurements taken in the presence of drift waves (δn/n ≃ 6%) show resonant particle interactions. Applications to magnetospheric phenomena will be discussed. © 1992 IEEE

Direct measurements of velocity-space transport coefficients, which may be interpreted as the Fokker-Planck coefficients, in the direction of the confining magnetic field are reported. The measurements were made using the techniques of laser-induced fluorescence and optical tagging, which allow ions to be followed in phase space. The results show that in a plasma with nearly only thermal fluctuations the data agree well with test particle calculations made by N. Rostoker for classical collisional processes. In the presence of larger-amplitude drift-wave fluctuations there is a pronounced enhancement of the velocity diffusion coefficient at a velocity less than the thermal speed. © 1992 The American Physical Society.

Parametric decay of lower hybrid pump waves into daughter lower hybrid waves and electrostatic ion-cyclotron waves was observed above instability threshold power levels in a fully ionized plasma. The ion velocity distribution function was measured in time and space by the nonperturbing techniques of laser-induced fluorescence and ion optical tagging. Significant ion heating, Ti up to 6Ti0, and cross-field transport were observed in the regime 012pi. © 1983 The American Physical Society.