The effect of electrode heating on the discharge parameters in complex plasma experiments

Land, Victor; Carmona-Reyes, Jorge; Creel, James; Schmoke, Jimmy; Cook, Mike; Matthews, L. S.; Hyde, Truell

doi:10.1088/0963-0252/20/1/015026

Cited by 2 publications

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References 30 publications

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“…By assuming force balance between gravity and the electrostatic force, the dust levitation height is obtained. The importance of the dust charge variation is investigated.In experiments at the Center for Astrophysics, Space Physics and Engineering Research (CASPER), complex plasma bi-layers were formed in a modified Gaseous Electronics Conference (GEC) RF discharge in argon, the geometry of which has been described elsewhere [1]. By adjusting the discharge power, the distance between the two layers was affected, as illustrated in figure 1.…”

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The effect of dust charge variation, due to ion flow and electron depletion, on dust levitation

Land

Douglass

Qiao

et al. 2011

AIP Conference Proceedings

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Using a fluid model, the plasma densities, electron temperature and ion Mach number in front of a powered electrode in different plasma discharges is computed. The dust charge is computed using OML theory for Maxwellian electrons and ions distributed according to a shifted-Maxwellian. By assuming force balance between gravity and the electrostatic force, the dust levitation height is obtained. The importance of the dust charge variation is investigated.In experiments at the Center for Astrophysics, Space Physics and Engineering Research (CASPER), complex plasma bi-layers were formed in a modified Gaseous Electronics Conference (GEC) RF discharge in argon, the geometry of which has been described elsewhere [1]. By adjusting the discharge power, the distance between the two layers was affected, as illustrated in figure 1. It is clear that the inter-layer separation is decreased by increasing the discharge power. Figure 2 shows the levitation height above the electrode surface for each particle size, for a similar FIGURE 1. Three frames illustrating the bi-layer experiments, as discussed in the text. The upper layer consists of 6.5 micron diameter melamine-formaldehyde (MF) particles, while the lower layer consists of 11.9 micron MF dust particles. FIGURE 2. The levitation height above the powered electrode for the two layers in a complex plasma bi-layer as the applied discharge power is varied. The experiment was performed in argon at 25 Pa.experiment. In this case, the distance between the layers is decreased to half a millimeter, which is the approximate Debye length for this discharge [2]. Even though the intent of the experiment, namely to influence the inter-layer distance, was achieved, upon further investigation, the levitation height of the particles could not be analytically reproduced using Orbital Motion Limited (OML) theory [3] and the usual assumption of a linear electric field [4].In order to insure the above results were not due to any bi-layer interaction, the experiment was repeated for different sizes separately, at a pressure of 20 Pa. These results are shown in figure 3, against the driving potential, V RF (The power is proportional to V 2 RF ). Although the levitation height of the smaller particles does not change much, the larger particles initially move up quickly with increased power, before reaching a constant levitation height. FIGURE 3. The levitation height of single layer plasma crystals consisting of MF particles of different diameters, plotted versus the applied amplitude of the driving potential, V RF . Each crystal was separately suspended in the discharge, but the results are plotted together.

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confidence: 99%