Orbiting Dust Particles in Unmagnetized Plasma Multi-Rings

Strongly coupled dusty plasma multi-rings were generated using a grooved radio frequency (RF) electrode embedded in an Argon plasma. These unmagnetized 2-D plasma systems had a regular lattice structure and distinct sections consisting of one to four concentric rings. Dust particles in each ring section had the tendency to move azimuthally about the center of the electrode, allowing for the angular velocity to be calculated. It was found that when the particles traveled through sections with more rings, the angular velocity of the particles decreased. The decrease in particle velocity in sections with a higher number of particles was determined to be consistent with the continuity equation from fluid dynamics. Interestingly, contrary to many rotating dusty plasma systems where the whole system rotates, or the particles tend to swirl in dust clouds, it was observed that the multiring segments were essentially stationary in the confining potential sheath as the individual dust particles progressed through the various sections of the multiring.