A. Barkan

Laboratory observation of the dust‐acoustic wave mode

A laboratory observation of the dust‐acoustic instability is reported. The results are compared with available theories.

EXPERIMENTS ON ION-ACOUSTIC WAVES IN DUSTY PLASMAS

Abstract An experiment is described on ion-acoustic (IA) waves in dusty plasmas, which was performed in the dusty plasma device (DPD) of Xu et al. (Rev. Sci. Instrum. 63, 5266, 1992). It is found that, as expected, the presence of negatively charged dust grains increases the phase velocity of the waves and, at the same time, also reduces the strength of the collisionless (Landau) damping to which the waves are subjected.

Laboratory studies of waves and instabilities in dusty plasmas

Theoretical and experimental studies of low-frequency electrostatic waves in plasmas containing negatively charged dust grains are described. The presence of charged dust is shown to modify the properties of ion-acoustic waves and electrostatic ion-cyclotron waves through the quasineutrality condition even though the dust grains do not participate in the wave dynamics. If the dust dynamics is included in the analysis, new “dust modes” appear—dust acoustic and dust cyclotron modes. The results of laboratory experiments dealing with dust ion acoustic (DIA) waves and electrostatic dust ion cyclotron (EDIC) waves are shown. These modes are more easily excited in a plasma containing negatively charged dust. Finally, observations of dust acoustic (DA) waves are presented and measurements of the dispersion relation are compared with one obtained from fluid theory.

Dust acoustic waves in a direct current glow discharge

An experimental investigation of dust acoustic (DA) waves in a dc glow discharge plasma is described. The glow discharge is formed between a 3 cm anode disk and the grounded walls of a 60 cm diameter vacuum chamber which is filled with nitrogen gas at a pressure of about 100 mTorr. Dust located on a tray in the chamber is attracted into the plasma where it is trapped electrostatically. The dust acoustic waves were produced by applying a modulation signal (5–40 Hz) to the anode. The wavelength of the DA waves was measured from single frame video images of scattered light from the dust grains. The measured dispersion relation is compared with theoretical predictions.

Laboratory experiments on electrostatic ion cyclotron waves in a dusty plasma

Abstract Current driven electrostatic ion cyclotron (EIC) waves have been observed in a dusty plasma laboratory experiment. The theoretical prediction that a substantial amount of negatively charged dust makes the plasma more unstable to the EIC instability appears to be borne out by the experimental results.

Confinement of dust particles in a double layer

Negatively charged, micron‐sized dust grains have been electrostatically confined in the high‐potential region of an anode double layer formed in a single‐ended Q‐machine plasma. The levitated dust grains are large enough to be visually observed in the scattered light from the plasma source. The various forces on a dust grain in a plasma, i.e., gravitational, electric, ion drag, and neutral drag are estimated based on the measured plasma and dust parameters. The possibility of observing a Coulomb lattice in such a setup is discussed.

Experiments on waves and instabilities in dusty plasmas

Laboratory experiments on waves in dusty plasmas performed at the University of Iowa are described. All of the experiments deal with low-frequency electrostatic waves and include studies of (i) electrostatic dust ion cyclotron (EDIC) waves, (ii) dust ion acoustic (DIA) waves and (iii) dust acoustic (DA) waves.

POTENTIAL RELAXATION INSTABILITY AND ION ACOUSTIC WAVES IN A SINGLE-ENDED Q-MACHINE DUSTY PLASMA

Abstract The potential relaxation instability (PRI) is excited when the cold endplate of a single-ended Q-machine is biased positively. If a sufficient concentration of negatively charged dust is present, the PRI is eliminated and the current-driven ion acoustic (IA) instability is observed. As the concentration of the negatively charged dust is increased, the frequency of the IA waves also increases, in agreement with theoretical predictions.

Experiments on ion and dust acoustic waves

A summary of recent experimental work performed by our group at the University of Iowa on current-driven dust ion acoustic (DIA) and dust acoustic (DA) waves is given. A discussion of relevant theoretical work is also included.

Laboratory experiments in dusty plasmas

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.