Observation of individual particles and Coulombic solids in a microdischarge

Spherical particles /spl sim/10-35 /spl mu/m in diameter are intentionally introduced into a cylindrical microdischarge device fabricated in Al or Si. Having a diameter of 400 /spl mu/m, this device is viewed along its axis with a microscope and charge-coupled device camera. Individual particles suspended in discharges in Ne are readily observable and form stable spatial patterns (in the plane transverse to the microdischarge axis) determined by the interplay of electrostatic and ion drag forces. Microdischarges may well provide an ideal testbed for exploring the application of well-characterized particles as in situ probes of plasmas.