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1. Controlling plasma produced fluxes to liquid surfaces by acoustic structuring: applications to plasma driven solution electrochemistry

   https://doi.org/10.1088/1361-6595/adb783  

   Doyle, Scott_J; Dias, Tiago_C; Meyer, Mackenzie; Kushner, Mark_J (March 2025, Plasma Sources Science and Technology)

   Abstract Plasmas interacting with liquid surfaces produce a complex interfacial layer where the local chemistry in the liquid is driven by fluxes from the gas phase of electrons, ions, photons, and neutral radicals. Typically, the liquid surface has at best mild curvature with the fluxes of impinging plasma species and applied electric field being nominally normal to the surface. With liquids such as water having a high dielectric constant, structuring of the liquid surface by producing a wavy surface enables local electric field enhancement due to polarization of the liquid, as well as producing regions of higher and lower advective gas flow across the surface. This structuring (or waviness) can naturally occur or can be achieved by mechanical agitation such as with acoustic transducers. Electric field enhancement at the peaks of the waves of the liquid produces local increases in sources of reactive species and incident plasma fluxes which may be advantageous for plasma driven solution electrochemistry (PDSE) applications. In this paper, results are discussed from a computational investigation of pulsed atmospheric pressure plasma jets onto structured water solutions containing AgNO₃as may be used in PDSE for silver nanoparticle (NP) formation. The solution surface consists of standing wave patterns having wavelength and wave depth of hundreds of microns to 1 mm. The potential for structured liquid surfaces to facilitate spatially differentiated chemical selectivity and enhance NP synthesis in the context of PDSE is discussed. 

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2. Two-fluid approach to weak plasma turbulence

   https://doi.org/10.1088/1361-6587/ac2e40  

   Yoon, Peter H (November 2021, Plasma Physics and Controlled Fusion)

   Abstract Weakly turbulent processes that take place in plasmas are customarily formulated in terms of kinetic theory. However, owing to an inherent complexity associated with the problem, thus far the theory is fully developed largely for unmagnetized plasmas. In the present paper it is shown that a warm two fluid theory can successfully be employed in order to partially formulate the weak turbulence theory in spatially uniform plasma. Specifically, it is shown that the nonlinear wave-wave interaction, or decay processes, can be reproduced by the two-fluid formalism. The present finding shows that the same approach can in principle be extended to magnetized plasmas, which is a subject of future work. 

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3. Construction of a linear plasma device for studying helicon plasmas relevant to plasma-wakefield accelerators

   https://doi.org/10.1088/1361-6595/ab7852  

   Green, Jonathan; Schmitz, Oliver (April 2020, Plasma Sources Science and Technology)
4. Plasma-based global pathway analysis to understand the chemical kinetics of plasma-assisted combustion and fuel reforming

   https://doi.org/10.1016/j.combustflame.2023.112927  

   Johnson, Praise N.; Taneja, Taaresh S.; Yang, Suo (July 2023, Combustion and Flame)

   Pepiot, Perrine (Ed.)

   The Global Pathway Analysis (GPA) algorithm helps analyze the chemical kinetics of complex combustion systems by identifying important global reaction pathways connecting a source species to a sink species through various important intermediate species (i.e., hub species). The present work aims to extend GPA algorithm to plasma-assisted combustion and fuel reforming systems to identify the dominant global pathways in such systems at various conditions. In addition, the present study extends the ability of GPA algorithm to identify reaction cycles involving the excitation of high-concentration species (e.g., O2, N2, and fuel) to their vibrational and electronic states and the subsequent de-excitation to their ground state, based on their significance on the reactivity of plasma-assisted systems in terms of gas heating and radical production. Provisions are made in the GPA algorithm to evaluate the reactivity of identified reaction pathways and cycles based on the element-flux transfer (i.e., dominance), heat release, and radical production rate. The newly developed Plasma-based Global Pathway Analysis (PGPA) algorithm is then used to analyze the plasma-assisted combustion of ammonia and reforming of methane. The PGPA analyses elucidated the significance of vibrational-translational cycles on the reactivity of NH3/air mixtures. Further, analyses on the production of NO ascribed the early reforming of NH3 to N2 and H2 in impeding the production of NO during plasma-assisted NH3 ignition. Lastly, the enhanced reforming of CH4/N2 mixtures using plasma has been attributed to electron impact dissociation of CH4 when compared to thermal reforming. In contrast, conventional path-Flux analysis (PFA) was found to require significant manual effort and pre-analysis intuitions from expert knowledge, making it arduous to provide valuable insights into plasma chemistry. The user-friendly and automated nature of PGPA thus provides a valuable tool for assessing the kinetics of plasma-assisted systems helpful in analyzing and, further, a foundation in reducing plasma-assisted chemistry, without the needs of expert knowledge. 

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5. Hand-generated piezoelectric mechanical-to-electrical energy conversion plasma

   https://doi.org/10.1063/5.0018967  

   Jaenicke, Olivia K.; Hita Martínez, Federico G.; Yang, Jinyu; Im, Seong-kyun; Go, David B. (August 2020, Applied Physics Letters)