Experimental studies of charged dust particles

Measurements of the charge on individual dust grains of glass and copper have been made in a double plasma device with monoenergetic primary electrons and a tenuous plasma. In conditions where the current collected by grains is dominated by the primary electrons, the grains charge to the potential which repels the primary electrons. The charging potential is reduced from this value when the fast electrons are sufficiently energetic to release a comparable current of secondary electrons. In addition, confinement of charged dust has been investigated in evacuated electrostatic traps consisting of a center electrode at high potential within a grounded enclosure. The confinement time of particles orbiting the center conductor may be an hour or ∼105 orbits. The orbits are visible and the effects of perturbations have been videotaped.