Growth of ordered dusty structures in the glow discharge
  In plasma of direct-current glow discharge the dependence of ordered dusty structure volume, shape and density on plasma conditions were investigated. The structure is formed in a field of volume charge. In experimental investigations we used the aluminum oxide macroparticles with diameter up to 60 microns (size distribution function was not determined). Discharge tube was established vertically, has an internal diameter 2.6 cm and space gap between electrodes 45 cm. Particles were injected from the top end of the discharge tube into the plasma of spectral purity neon. Repeatability of randomized experiment results was better than 5% of the measured values. The areas of existence of various dusty ordered structures and their dependence on physical conditions in plasma (discharge current and pressure) were determined. When the interparticle distance in the structure is constant and particle positions have good time stability this structure was defined like "plasma crystal". Otherwise, we observed process of the "dusty crystal" melting and in that case structure was defined like "dusty liquid". Experimental data were obtained by using computer-based measure system, which lets us to see, record and analyse images of the macroparticle structure in "laser sheet" cross section. Experimental investigations of dusty structure growth by consistent dosed injections of the macroparticles into the glow discharge plasma are carried out. These experiments with good statistical reliability showed that the mean interparticle distance inside the structure is constant regardless of the structure volume. Invariability of the structure volume during the process of dusty crystal melting was established. 
Anatoly Khakhaev, Sergey Podriadtchikov