Transport mechanisms and experimental evidence of positively charged dust particles in an argon plasma

Abstract

Summary form only given. It is well known that dense particle clouds often reside within the steady-state plasma; however, particle transport in the critical post-plasma period has not yet been fully explored. To better understand and characterize particle behavior, charge and transport properties of dust particles in an argon plasma, contained within a gaseous electronics conference (GEC) reference cell, were studied in the steady-state and post-plasma regimes of a 500 mTorr, 25 W argon discharge. Using separate water chillers to control independently the temperatures of the upper and lower electrodes, various temperature gradients were imposed on the plasma and thermophoretic transport of the particle clouds observed for both steady and decaying discharges. Next, using a pulsed rf power supply and a tuned Langmuir probe, the decay times of electrons and ions were measured in the afterglow. Finally, utilizing high-speed video (1000 frames per second) in concert with 10 mW He-Ne laser light, post-plasma particle trajectories were observed for various electric fields and electrode temperatures. Results were then compared to calculations from a net force model that included gravity, the electric field, fluid flow, ion drag, and thermophoresis.