PLASMA CRYSTAL - COULOMB CRYSTALLIZATION IN A DUSTY PLASMA

A macroscopic Coulomb crystal of solid particles in a plasma has been observed. Images of a cloud of 7-mum ''dust'' particles, which are cha rged and levitated in a weakly ionized argon plasma, reveal a hexagona l crystal structure. The crystal is visible to the unaided eye. The pa rticles are cooled by neutral gas to 310 K, and their charge is >9800e , corresponding to a Coulomb coupling parameter GAMMA > 20 700. For su ch a large GAMMA value, strongly coupled plasma theory predicts that t he particles should organize in a Coulomb solid, in agreement with our observations.