Observation of the structure and its formation process of a new volumetric Coulomb cloud composed of different multiple dust layers

A three-dimensional funnel-shaped dust cloud composed of multiple layers with different sized dust particles has been clearly observed in a new configuration of DC glow discharge. The Coulomb crystal-like cloud seems to be supported against gravity by the electric field in the thick sheath above the mesh cathode, in which the heavier layer of dust cloud seems to push the sheath to have a greater electrostatic force. The structural formation process of such a new volumetric Coulomb cloud was observed by a video imaging technique with laser light scattered by moving dust particles. They seem to be transported from the far outside, attach to the lateral surface of the funnel, and build up. The cloud is observed to expand radially outward on the horizontal layer.