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Uncertainty and error in complex plasma chemistry models

Turner, Miles M. (2015) Uncertainty and error in complex plasma chemistry models. Plasma Sources Science and Technology, 24 (3). 035027. ISSN 1361-6595

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Abstract

Chemistry models that include dozens of species and hundreds to thousands of reactions are common in low-temperature plasma physics. The rate constants used in such models are uncertain, because they are obtained from some combination of experiments and approximate theories. Since the predictions of these models are a function of the rate constants, these predictions must also be uncertain. However, systematic investigations of the influence of uncertain rate constants on model predictions are rare to non-existent. In this work we examine a particular chemistry model, for helium-oxygen plasmas. This chemistry is of topical interest because of its relevance to biomedical applications of atmospheric pressure plasmas. We trace the primary sources for every rate constant in the model, and hence associate an error bar (or equivalently, an uncertainty) with each. We then use a Monte Carlo procedure to quantify the uncertainty in predicted plasma species densities caused by the uncertainty in the rate constants. Under the conditions investigated, the range of uncertainty in most species densities is a factor of two to five. However, the uncertainty can vary strongly for different species, over time, and with other plasma conditions. There are extreme (pathological) cases where the uncertainty is more than a factor of ten. One should therefore be cautious in drawing any conclusion from plasma chemistry modelling, without first ensuring that the conclusion in question survives an examination of the related uncertainty.

Item Type:Article (Published)
Refereed:Yes
Subjects:Physical Sciences > Plasmas
Mathematics > Mathematical models
Physical Sciences > Plasma processing
Physical Sciences > Chemistry
DCU Faculties and Centres:Research Initiatives and Centres > National Centre for Plasma Science and Technology (NCPST)
DCU Faculties and Schools > Faculty of Science and Health > School of Physical Sciences
Publisher:Institute of Physics
Official URL:http://dx.doi.org/10.1088/0963-0252/24/3/035027
Copyright Information:© 2015 IOP
Use License:This item is licensed under a Creative Commons Attribution-NonCommercial-Share Alike 3.0 License. View License
Funders:Science Foundation Ireland. Grant number: 08/SRC/I1411, European Cooperation in Science and Technology. Grant number: MP1101
ID Code:20652
Deposited On:16 Jun 2015 10:34 by Miles Turner. Last Modified 16 Jun 2015 10:34

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