ADJUSTABLE LEVELS OF STRONG TURBULENCE IN A POSITIVE-NEGATIVE ION-PLASMA

Positive/negative ion plasmas, composed of Ba+, SF6-, 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 (deltan/n congruent-to 1), large-amplitude, low-frequency electrostatic noise (f less-than-or-equal-to 20 kHz), and rapid transport of ions across magnetic field lines (D(perpendicular-to) congruent-to 10(4) 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 (deltan/n congruent-to 0.01) to strongly turbulent states (deltan/n congruent-to 1).