BOUNDARY EFFECTS IN ROTATING-PLASMA EXPERIMENTS

The problem of current continuity and viscous drag at the boundaries in rotating-plasma experiments is discussed. A hypothetical model having a steady state with axial symmetry is emphasized; it is shown that the discharge impedance derived from this model does not agree with many observations. The Homopolar III'' experiment is described in which the flux surfaces were strongly convex and parallel to the toroidal-shaped electrodes. In this way friction at the insulators was reduced. But the structure of the discharge deviated drastically from axial symmetry near the outer surface. Several studies led to the conclusion that the flow pattern probably involved secondary flows. A detailed analysis of this structure was not possible. It was also found that the rotational speed could not be raised above a few cm/ mu sec because the insulators failed in spite of the special design of the experiment. 28 references. (auth