Abstract
Transport properties of high-energy-density plasmas are influenced by the ion collision rate. Traditionally, this rate involves the Coulomb logarithm, . Typical values of are in kinetic theories where transport properties are dominated by weak-scattering events caused by long-range forces. The validity of these theories breaks down for strongly coupled plasmas, when is of order one. We present measurements and simulations of collision data in strongly coupled plasmas when is small. Experiments are carried out in the first dual-species ultracold neutral plasma (UNP), using and ions. We find strong collisional coupling between the different ion species in the bulk of the plasma. We simulate the plasma using a two-species fluid code that includes Coulomb logarithms derived from either a screened Coulomb potential or a the potential of mean force. We find generally good agreement between the experimental measurements and the simulations. With some improvements, the mixed and dual-species UNP will be a promising platform for testing theoretical expressions for and collision cross-sections from kinetic theories through measurements of energy relaxation, stopping power, two-stream instabilities, and the evolution of sculpted distribution functions in an idealized environment in which the initial temperatures, densities, and charge states are accurately known.
- Received 30 March 2018
- Revised 15 November 2018
DOI:https://doi.org/10.1103/PhysRevE.99.053206
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