Self-excited nonlinear oscillations of dust particles in small assemblies

Summary form only given, as follows. Summary form only given. Self-excited nonlinear oscillations of dust particles floating in an RF plasma are described. Small assemblies of 2 and 3 dust particles are levitated in the sheath, above the powered electrode due to the equilibrium between the electrostatic, the gravitational, the friction and the ion drag forces. In a very narrow range of pressures, spontaneous oscillations of the particles are observed. The evolution in time of the particle trajectory is recorded using a high speed camera. The dynamics are investigated by reconstructing the attractor of the trajectory of the particles These experimental results may be used as a diagnostic tool for deducing the ion drag force acting on the particles and to evaluate the ion focusing effect produced by the particles as ions flow vertically past them in the plasma sheath.