Laboratory experiments in dusty plasmas

Abstract

We describe a rotating‐drum dust‐dispersal device, which we have used in conjunction with an existing Q machine, to produce extended, steady‐state, magnetized dusty plasma columns. This device is capable of generating dusty plasmas in which as much as ∼90% of the negative charge is attached to dust grains of 1–10 μm size with dust densities up to ∼104 cm−3. Langmuir probes were used to determine how the negative charge is divided between free electrons and dust grains. This paper reports the results of three experimental investigations performed with this dusty plasma device (DPD): (1) the effect of closely packed grains, i.e., the reduction in grain charge that occurs when the intergrain spacing is on the order of or less than the plasma Debye length; (2) the effect of negatively charged dust on the electrostatic ion‐cyclotron instability; and (3) the levitation of charged dust in a double layer and the observation of a ‘Coulomb lattice,’ i.e., strongly coupled dusty plasmas.