An Effective Potential Approach to the Modeling of Concentrated Dusty Plasmas

University Of Memphis, Memphis TN

Investigators

Abstract

Dusty plasmas are comprised of electrons, ions and charged micro/nanometer-sized grains interacting with each other predominantly through electrostatic forces. This computational research project will focus on the impact of the space charge effect -- the distortion of grain-ion forces due to other charges being present in the vicinity -- on individual grains and on the drag force exerted by ions on grains. The broader implications of this research will fortify the prediction capabilities of researchers working on plasma-based semiconductor manufacturing processes where dust formation is a serious contamination issue, the understanding of astrophysical processes such as asteroid and planet formation where highly charged grains coalesce and grow, and modeling of thermonuclear fusion reactors where wall material ablation may interfere with the sustenance of the fusion core. The educational and outreach activities of this project will result in interactive software tools designed for high school and undergraduate students to develop an intuitive sense about dusty plasmas. As part of an outreach program called "Girls Experiencing Engineering" to increase the participation of female students in science and engineering, the project team will conduct a week-long event that will provide opportunities of programming, lab demos and scholarly presentations. A modeling investigation will be carried out to study the effect of a high concentration of space charge (grains, ions and electrons) and the plasma electric field on the charging of and the ion drag on an individual grain immersed in a dusty plasma. The central hypothesis to this effort is that the complex multi-body electrostatic interaction between grains and ions/electrons can be captured by an effective potential that is derived by averaging over all possible configurations of space charge around an individual grain. The effective potential will be used in a Langevin framework to capture the interplay of electrostatic interactions (effective potential), neutral drag and Brownian diffusion. Grain charging and ion drag models will be developed by analyzing the grain-ion collision time distribution and grain-ion impact force distribution inferred from Langevin Dynamics simulations. The developed models will be tested against published experiments and data obtained from PK-4 measurement campaigns of grain charging and ion drag. The project is expected to unravel basic aspects of correlated grain motion of relevance to dense granular systems. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.