Title: Molecular admixtures and impurities in atmospheric pressure plasma jets

Abstract

A more complete understanding of reactive chemistry generated by atmospheric pressure plasma jets (APPJs) is critical to many emerging medical, agricultural, and water treatment applications. Adding molecular gases to the noble working gas which flows through the jet is a common method to tailor the resulting production of reactive oxygen and nitrogen species (RONS). In this paper, results are discussed from a computational investigation of the consequences of H₂O and O₂ admixtures on the reactive chemistry of He APPJs flowing into humid air. This investigation, performed with a 2-dimensional plasma hydrodynamics model, addresses the RONS that are initially produced and the evolution of that chemistry on longer time scales. Without an admixture, the impurities in 99.999% pure helium are a major source of RONS. The addition of H₂O decreases the production of reactive nitrogen species (RNS) and increases the production of reactive oxygen species (ROS). The addition of O₂ significantly decreases the production of RNS, as well as hydrogen-containing ROS, but increases the production of ROS without hydrogen. This selectivity comes from the lower ionization energy of O₂ compared to N₂ and H₂O, which then allows for charge exchange reactions. These charge exchange reactions change the RONS which are producedmore » in the afterglow by dissociative recombination. The consequences of impurities were also examined. Humid air impurities as low as 10 ppm in the helium can account for 79%-98% of the production of most RONS in the absence of an intentional admixture. The degree to which the impurities affect the RONS production depends on the electrode configuration and can be reduced by molecular admixtures.« less

Authors:

Lietz, Amanda M.  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-6423-5042"

Kushner, Mark J. ^[1]

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+ Show Author Affiliations

1. Univ. of Michigan, Ann Arbor, MI (United States)

Publication Date:

Thu Oct 18 00:00:00 EDT 2018

Research Org.:

Univ. of Michigan, Ann Arbor, MI (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Fusion Energy Sciences (FES); National Science Foundation (NSF)

OSTI Identifier:

1612092

Alternate Identifier(s):

OSTI ID: 1478129

Grant/Contract Number:  

SC0014132; SC000319; PHY-1519117

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Applied Physics

Additional Journal Information:

Journal Volume: 124; Journal Issue: 15; Journal ID: ISSN 0021-8979

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Physics; Hydrodynamics; Electron impact ionization; Ionization processes; Ions and properties; Partial differential equations; Plasmas; Charge exchange reactions; Chemical reactions; Recombination reactions