Experimental study of dust interactions in plasma of RF- discharge

Summary form only given. The particle charge is an important parameter determining physical properties of complex plasmas, and has a significant influence on the thermal energy acquired by a dust particle due to various mechanisms. The magnitude of charge is crucial for particle trapping and levitation as well as for the formation of ordered dusty structures in a laboratory plasma.The results of measurements of the charge on dust suspended in laboratory rfdischarge plasma are presented. Experiments were performed for both small-size clusters of particles (consisting of 11-29 particles) and large quasi-twodimensional systems (monolayers of about 1500-2000 particles) forming in the sheath region of rfdischarge in a wide range of dusty plasma conditions (with different sizes, kinetic temperature and concentration of dust, coupling parameter, pressure of neutral gas, and etc). The magnitudes of dust charges were derived from the interaction potential profiles of dust particles, their characteristic oscillation frequencies and the confining field parameters obtained by two methods: one based on a solution of the inverse Langevin problem1 and another one on studying mass transfer processes in dusty subsystem. The values of the particle charge Z, obtained by the ways above, are their lowest estimate, because the results of measurements at distances close to the mean interparticle distance does not fully take into account the possible screening of the particles. A highest estimate of the particle charge was derived from equations of the near-electrode layer theory. To compare the particle charges, obtained in the considered experiments, with the collisionless theory we estimated their values in the OML approach for isotropic and anisotropic plasma. Finally, we compared the experimentally obtained particle charges with the results of calculations of the dust charge in argon using the molecular dynamics technique in the case of isotropic plasma with an electron temperature 2- 5 eV.