Dynamics of dust particles in plasma sheaths

Abstract

A large number of laboratory observations reveal the formation of ordered linear chains and sheets composed of charged dust grains levitated in the sheath region of radio-frequency or dc plasma discharges at very low pressures. At higher pressures, three-dimensional structures are typically formed. Recently, a number of low gas pressure experiments have explored the generation of large amplitude vertical oscillations by lowering either the background pressure or the plasma power below a threshold value, or by imposing an external force that arises from a low-frequency sinusoidal voltage in the sheath region. A theoretical model is presented that successfully describes the phenomenology in various experiments, including the observed self-excited oscillations, nonlinear resonance and parametric oscillations. A new forcing mechanism, namely the modulational forcing, for exciting nonlinear resonances is proposed.