In nature, matter naturally exists in one of four states. The most common (and perhaps least familiar) of these states is a plasma; an ionized gas composed of ions, electrons and neutral particles. This state of matter exhibits several complex phenomena and has numerous practical applications, impacting nearly every aspect of our everyday lives. Nearly all plasmas that occur, both in nature and in the laboratory setting, contain small particles of matter (dust). When this particulate matter enters a plasma, it becomes charged through interactions with the electrons and ions in the background plasma. Once charged, this third charged species fully interacts with the other plasma components and self-consistently alters the properties of the surrounding plasma. The resulting system is known as a dusty plasma, a non-linear system that is notably more complex than the traditional plasma and supports a wide range of new plasma phenomena including new wave modes and strongly coupled phenomena.
In ground-based experiments, the high mass of the dust leads to sedimentation effects, resulting in the dusty plasma system being compressed. To reduce sedimentation effects, it is necessary to perform experiments in a microgravity environment, such as in the ISS based experiment facility "Plasma-Kristall-4" (PK-4). In the PK-4 facility, particles are injected into a dc glow discharge plasma and flow along an axial electric field. Upon the application of polarity switching (a periodic oscillation of the electric field), a sudden change in the bulk motion and spatial ordering of the dust is observed. In some cases, this change is accompanied by a change in the thermal state of the dust component.
In this talk, Jeremiah Williams, professor of physics at Wittenberg University and =program director in plasma physics at the U.S. National Science Foundation, will present a brief introduction to plasmas and dusty plasmas, highlighting how these systems are relevant to your everyday lives and provide a unique system to study a wide range of physical phenomena. He will also present the results of a series of experiments and numerical simulations to understand the change in the thermal state that has been observed in the PK-4 microgravity laboratory on the International Space Station.
Join us on Friday, Nov. 8, for this exciting presentation from Williams. Lunch will be available in Hayes 216 from 11:45 a.m. to 12:15 p.m. and the presentation will begin in Hayes 211/213 at 12:10 p.m. We hope to see you there!