The interaction of a conducting object with a supersonic plasma flow: ion deflection near a negatively charged obstacle

An experimental study of the interaction of a conducting object with a flowing plasma is described. Particular attention is given to the deflection of ions in the sheath of a negatively charged body. The experiments were conducted in a double plasma device in which a relatively weak longitudinal magnetic field may also be present. For the particular conditions used in these experiments, it was found that ion deflection occurs primarily near the edge of the body. A simple physical model is discussed which accounts for the observed dependences of the convergence of ion streams on the body potential and ion beam velocity. A density rarefaction wave is also observed in the wake region, which propagates into the ambient plasma at roughly the ion acoustic Mach angle. Finally, some preliminary observations of the spatial distribution of plasma noise in the wake region are presented.