Controlling equilibrium dust charge in a complex plasma with AC signals*

Reproducible displacements in the equilibrium position of clouds of charged microparticles (dust) suspended in an argon, DC glow discharge have been observed in response to AC signals applied to a confining electrode. The applied signals are low power (mW), unbiased, and at frequencies approaching the ion-neutral collision rate. Probe measurements indicate that surfaces in the plasma experience a sizable increase (50% or greater in some cases) in incident ion flux, reducing the floating potential of the surfaces relative to the plasma. A theoretical model is presented which demonstrates how an unbiased AC field may produce a net increase in ion flux, and the effect of these signals on background plasma parameters, fields, and instabilities is examined in order to determine whether these displacements are the result of a controlled change in dust charge.