Browsing by Author "Schröter, Sandra"

Now showing 1 - 3 of 3
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    Concepts, Capabilities, and Limitations of Global Models: A Review
    (Weinheim : Wiley-VCH, 2016) Hurlbatt, Andrew; Gibson, Andrew Robert; Schröter, Sandra; Bredin, Jérôme; Foote, Alexander Paul Stuart; Grondein, Pascaline; O'Connell, Deborah; Gans, Timo
    For researchers wishing to generate an understanding of complex plasma systems, global models often present an attractive first step, mainly due to their ease of development and use. These volume averaged models are able to give descriptions of plasmas with complex chemical kinetics, and without the computationally intensive numerical methods required for spatially resolved models. This paper gives a tutorial on global modeling, including development and techniques, and provides a discussion on the issues and pitfalls that researchers should be aware of. Further discussion is provided in the form of two reviews on methods of extending global modeling techniques to encompass variations in either time or space.
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    The formation of atomic oxygen and hydrogen in atmospheric pressure plasmas containing humidity: Picosecond two-photon absorption laser induced fluorescence and numerical simulations
    (Bristol : IOP Publ., 2020) Schröter, Sandra; Bredin, Jérôme; Gibson, Andrew R.; West, Andrew; Dedrick, James P.; Wagenaars, Erik; Niemi, Kari; Gans, Timo; O’Connell, Deborah
    Atmospheric pressure plasmas are effective sources for reactive species, making them applicable for industrial and biomedical applications. We quantify ground-state densities of key species, atomic oxygen (O) and hydrogen (H), produced from admixtures of water vapour (up to 0.5%) to the helium feed gas in a radio-frequency-driven plasma at atmospheric pressure. Absolute density measurements, using two-photon absorption laser induced fluorescence, require accurate effective excited state lifetimes. For atmospheric pressure plasmas, picosecond resolution is needed due to the rapid collisional de-excitation of excited states. These absolute O and H density measurements, at the nozzle of the plasma jet, are used to benchmark a plug-flow, 0D chemical kinetics model, for varying humidity content, to further investigate the main formation pathways of O and H. It is found that impurities can play a crucial role for the production of O at small molecular admixtures. Hence, for controllable reactive species production, purposely admixed molecules to the feed gas is recommended, as opposed to relying on ambient molecules. The controlled humidity content was also identified as an effective tailoring mechanism for the O/H ratio.
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    Numerical study of the influence of surface reaction probabilities on reactive species in an rf atmospheric pressure plasma containing humidity
    (Bristol : IOP Publ., 2017) Schröter, Sandra; Gibson, Andrew R.; Kushner, Mark J.; Gans, Timo; O’Connell, Deborah
    The quantification and control of reactive species (RS) in atmospheric pressure plasmas (APPs) is of great interest for their technological applications, in particular in biomedicine. Of key importance in simulating the densities of these species are fundamental data on their production and destruction. In particular, data concerning particle-surface reaction probabilities in APPs are scarce, with most of these probabilities measured in low-pressure systems. In this work, the role of surface reaction probabilities, γ, of reactive neutral species (H, O and OH) on neutral particle densities in a He-H2O radio-frequency micro APP jet (COST-APPJ) are investigated using a global model. It is found that the choice of γ, particularly for low-mass species having large diffusivities, such as H, can change computed species densities significantly. The importance of γ even at elevated pressures offers potential for tailoring the RS composition of atmospheric pressure microplasmas by choosing different wall materials or plasma geometries.