Strong Coulomb coupling influences ion and neutral temperatures in atmospheric pressure plasmas

• Published in: Plasma sources science & technology Vol. 31; no. 12; pp. 125005 - 125017
• Main Authors: Acciarri, M D, Moore, C, Baalrud, S D
• Format: Journal Article
• Language: English
• Published: United States IOP Publishing 01.12.2022
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; atmospheric pressure plasmas; CAPP; fast neural heating; fast neutral heating; strong correlations; strongly coupled
• ISSN: 0963-0252; 1361-6595
• DOI: 10.1088/1361-6595/aca69c

Abstract Molecular dynamics simulations are used to model ion and neutral temperature evolution in partially-ionized atmospheric pressure plasma at different ionization fractions. Results show that ion–ion interactions are strongly coupled at ionization fractions as low as 10 −5 and that the temperature evolution is influenced by effects associated with the strong coupling. Specifically, disorder-induced heating is found to rapidly heat ions on a timescale of the ion plasma period (∼10 s ps) after an ionization pulse. This is followed by the collisional relaxation of ions and neutrals, which cools ions and heats neutrals on a longer (∼ns) timescale. Slight heating then occurs over a much longer (∼100 s ns) timescale due to ion-neutral three-body recombination. An analytic model of the temperature evolution is developed that agrees with the simulation results. A conclusion is that strong coupling effects are important in atmospheric pressure plasmas.