Electrostatic confinement of dust grains in a spherical electrostatic potential

Summary form only given, as follows. Negatively charged dust particles have been confined in vacuum in the spherical electrostatic potential surrounding a small aluminum sphere biased positively. The confinement system is similar to one in which dust is confined in orbits in the logarithmic potential around a biased wire. The spherical geometry results in a nearly Keplerian potential. The purpose of the experiment is to investigate orbital phenomena in celestial mechanics such as the occurrence of orbital resonances and chaotic dynamics. The dust particles are hollow glass microballoons 50 microns in diameter. These are dropped past an emissive filament and are charged to a potential of -30 volts corresponding to a charge of /spl sim/6/spl times/10/sup 5/ electrons. The particles drop into a rectangular chamber with a 12.7 mm diameter aluminum sphere in the center. The particles are trapped by increasing the potential on the sphere from zero to -10 kV. The precession due to gravity is reduced by applying an additional upward electrostatic force created by biasing the upper and lower surfaces of the trap. The potential on the stalk supporting the sphere is approximately matched to a 1/r potential by biased concentric cylinders. Particles are observed to be trapped for several minutes before striking the center conductor. The orbital motion is visible and has been videotaped.