STEADY-STATE TOROIDAL PLASMA AROUND A SPHERICAL ANODE IN A MAGNETIC-FIELD

When a positive potential is applied to a spherical electrode in the presence of a low-pressure gas in a uniform magnetic field, a stable toroidal plasma can form around the anode. This plasma is produced by electrons which are trapped in the combined electric and magnetic fields. We present observations of some of the basic properties of this plasma as measured using electrostatic probes and a low-light-level camera. We interpret these measurements in terms of an extended treatment of electromagnetic which have been predicted to exist in this system. © 1990 The American Physical Society.