Dust clusters in complex plasmas

Abstract

Dust cluster is a stable structure of negatively charged dust particles formed in complex plasmas. This paper briefly describes the dynamics of these objects. Dust clusters are confined by external applied and or self consistent electrostatic plasma fields. Dust cluster may be regarded as energy storage device which stores plasma thermal energy in the electrostatic fields of cluster. This energy is recovered when the cluster explodes upon removal of the confining potential. In this paper a model for the dust cluster explosion in the afterglow phase of a complex plasma discharge is described. The model is tested by MD simulations of dust particles in a confining potential. The nature of the explosion (caused by switching off the discharge) and the concomitant dust acceleration is found to depend critically on the pressure of the back ground neutral gas. At low gas pressure, the explosion is due to unshielded Coulomb repulsion between dust particles and yields maximum acceleration while in the high pressure regime it is due to shielded Yukawa repulsion and yields much feebler acceleration. These results are in agreement with recent experimental findings. The simulations also confirm a recently proposed electrostatic (ES) isothermal scaling relation, P_E∝V^-2_d (where P_E is the ES is pressure of the dust particles and V_dis the confining volume).