Events at Physics
Beyond the usual electrons and ions, low-temperature plasmas can also contain charged particles of solid matter, ranging in size from nanometers to microns. They gain a large charge by collecting more electrons than ions from the ambient plasma. In fusion these solid particles are found immersed in the plasma of the divertor region of tokamaks. In semiconductor manufacturing they are called “particulates,” and they grow spontaneously and represent a contamination problem. Astronomers call these solid particles “dust,” and they are found in the plasma of the interstellar medium where they are the precursors of terrestrial planets like Earth. In this talk I review these diverse examples of dusty plasma, and then I present a fundamental physics experiment intended to probe the extreme properties of plasmas that are dominated by Coulomb collisions. A shear flow in this “strongly coupled” plasma results in localized viscous heating, a phenomenon that has long been predicted theoretically for both plasmas and fluids but never observed until now.