CONFINEMENT AND TURBULENT TRANSPORT IN A PLASMA TORUS WITH NO ROTATIONAL TRANSFORM

In the BLAAMANN device a weakly ionized hydrogen plasma is produced by electrons accelerated from a hot, negatively biased 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 n(e), phi and T(e) of 10% or more. The time-averaged state exhibits nested toroidal surfaces of constant potential and pressure, which requires an anomalous cross-field current to remove the space-charge injected by the cathode and the charge accumulated due to the delB- and curvature drifts. Typical plasma parameters are n(e) approximately 10(16) m-3, T(e) approximately 1-20 eV, T(i) approximately 1 eV. The cross-field diffusion coefficient is typically D(perpendicular-to) approximately 30 m2 s-1 approximately 10(4) x D(perpendicular-to)classical approximately 10(1) x D(perpendicular-to)Bohm. Evidence is presented in support of the hypothesis that the plasma goes turbulent because it needs to develop an anomalous current channel, and this turbulence in turn determines the plasma transport and the time-averaged state.