Study of the Ion—Vortex-Ring Transition

Abstract

The velocity of bare ions and vortex rings in the region of the ion-vortex-ring transition as a function of applied electric field was experimentally studied and is described in detail. The velocity at which a bare ion produces quantized vortex rings has been determined. In the case of negative ions under pressure, this critical velocity is related to the radius of the negative-ion bubble. It was also found that creation of vortex rings by bare ions requires a considerably larger electric field than that necessary to support a singly charged vortex ring. An effect associated with the radioactive source (for producing ions) was observed which allowed vortex rings to be produced in the source region with comparatively weak electric fields. Vortex rings having a radius as small as 37 Å were studied, and no deviation from the classical hydrodynamic equation was observed. The data indicate that the vortex core size may be pressure- and temperature-sensitive.