Strongly-Coupled Dusty Plasmas

University Of Iowa, Iowa City IA

Investigators

Abstract

A fundamental experimental study is proposed for nonequilibrium dynamics, viscoelastic behavior, and waves in strongly-coupled dusty plasma. Strongly-coupled plasma is ionized gas in which the interparticle potential energy is greater than the particle kinetic energy. Under these conditions, plasma behaves like a crystal or liquid, unlike more familiar weakly-coupled plasmas which behave like a gas. Dusty plasma consists of micron-size particles of solid matter suspended in a plasma consisting of electrons and ions. Due to collecting electrons and ions from the plasma, particles become highly charged. Typically, Q = -10,000 e for a 10 micron diameter sphere. This large charge produces a large interparticle repulsion. This large repulsion, combined with cooling the particles with gas drag, provides strong coupling. The size of the particles allows direct imaging and particle tracking using video micrography. Experiments are done with both 2D and 3D suspensions of microspheres. For 2D, the electric field of a plasma sheath levitates particles in the presence of gravity, yielding a single layer of particles. Discoveries made with this 2D system will help in understanding 2D physics in other areas of physics as well. For 3D, forces due to gas temperature gradients are applied to offset gravity, yielding a 3D suspension called a "Coulomb ball." Laser beams can push and manipulate particles in different ways to heat them, drive shear flows, and excite waves. A combination of this manipulation and gas friction provides a driven-dissipative system. This allows nonequilibrium systems to be studied experimentally at a fundamental level that is usually possible only in theory. An experimental program is proposed for these fundamental physics topics: * Nonequilibrium fluctuations in 2D * Equilibration of 3D expanding plasma * Viscoelastic 2D physics * Interfaces in 3D under extreme shear. * Solitary waves in 2D crystal. Other impacts of the research activity include: * K12 outreach presentations in the "Hawk-Eyes on Science" series. * Participation of faculty of a non-PhD-granting institution. * Incorporating research topics in the teaching curriculum This proposal was submitted to the NSF-DoE Partnership in Plasma Science and Engineering joint solicitation 08-589. This award is being funded by the Plasma Physics Program in the Division of Physics.