Observation of individual particles and Coulombic solids in a microdischarge

Spherical particles similar to 10-35 mu m in diameter are intentionally int roduced into a cylindrical microdischarge device fabricated in Al or Si. Ha ving a diameter of 400 mu m, this device is viewed along its axis with a mi croscope and charge coupled device camera. Individual particles suspended i n discharges in Ne are readily observable and form stable spatial patterns tin the plane transverse to the microdischarge axis) determined by the inte rplay of electrostatic and ion drag forces. Microdischarges may well provid e an ideal testbed for exploring the application of well-characterized part icles as in situ probes of plasmas.