Abstract View
Grain Charging Rate in High Ion Concentrated Dusty Plasma Using Langevin-Dynamic Simulations
RANGANATHAN GOPALAKRISHNAN, Vikram Suresh, Zhibo Liu, The University of Memphis
Abstract Number: 186
Working Group: Dusty Plasma
Abstract
Grain charging is modeled in instances wherein the ions are dense and strongly coupled (i. e.) Γi>1: Γi ≡ (e2/(4πεoni-1/3kbTi)). Langevin Dynamics is used to simulate the motion of multiple ions around a negatively charged grain in a periodic domain for 101 - 105 Pa. The ion flux coefficient is calculated using the grain-ion collision time distribution and the grain-ion pair correlation function g(2)(r) is used to deduce the influence of the ion space charge on the collision of individual ions with the grain during charging. In addition to Γi, the ion flux coefficient is influenced by the diffusive Knudsen number KnD [√(mikbTi)/(ni-1/3fi)] (an ion-neutral gas interaction parameter) and χp ≡ (ap/ni-1/3) that compares the size of the grain to the mean inter-ion spacing). We also demonstrate that an effective grain-ion potential computed using g(2)(r) according to the effective potential theory accurately describes the grain-ion dynamics in a binary framework for Γi<~20, without the need to simulate multiple ions. Ion concentration has a significant effect across different ion coupling regimes and the analysis of the pair-correlation functions reveals the perturbation of ion structure in the plasma by the presence of grains. We hope our model development will spark experimental validation efforts.
We thank The University of Memphis High Performance Computing Cluster for providing computational resources to carry out this research. Partial support for this work was provided by US National Science Foundation (NSF) PHY Grant Award Number 1903432 under the Directorate of Mathematical & Physical Sciences.