Nonequilibrium effects of diluent addition in a recombining argon plasma

Journal Article · Sun Feb 28 23:00:00 EST 1993 · Physics of Fluids B; (United States)

DOI:https://doi.org/10.1063/1.860503· OSTI ID:6817218

Gordon, M H ^[1]; Kruger, C H ^[2]

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1. University of Arkansas, Department of Mechanical Engineering, Fayetteville, Arkansas 72701 (United States)
2. Stanford University, High Temperature Gas Dynamics Laboratory, Stanford, California 94305 (United States)

Spectroscopic and calorimetric measurements have been made using a 50 kW radio frequency inductively coupled plasma torch operated at atmospheric pressure with maximum temperatures and electron densities near 8500 K and 3[times]10[sup 21] m[sup [minus]3], respectively. The plasma flowed through a water-cooled quartz test section which enabled the study of nonequilibrium effects on both a recombining pure argon plasma and a recombining argon plasma with hydrogen, nitrogen, or neon. The pure argon plasma is found to be well described by a partial equilibrium model in which the free and bound-excited electrons are in mutual equilibrium irrespective of possible departures from equilibrium with the ground state. The addition of just tenths of a percent of either atomic hydrogen or nitrogen (but not neon, in contrast) is found to significantly affect the plasma's state of equilibrium for electron densities roughly less than 10[sup 21] m[sup [minus]3] because of a nearly gas-kinetic reaction between argon's first excited state and the diluent's ground state. This quenching'' reaction provides a depopulating mechanism for argon's first excited state and thereby inhibits the establishment of partial equilibrium which then invalidates several common diagnostic methods. The extent of quenching depends on the particular diluent, the amount of diluent relative to the electron number density, and on the temperature. These experimental observations are supported by an appropriately modified argon collisional--radiative model.

• DOE Contract Number: FG03-88ER13957
• OSTI ID: 6817218
• Journal Information: Physics of Fluids B; (United States), Journal Name: Physics of Fluids B; (United States) Vol. 5:3; ISSN PFBPEI; ISSN 0899-8221
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700330* -- Plasma Kinetics
Transport
& Impurities-- (1992-)
ARGON
CALORIMETRY
COLLISIONS
DILUTION
ELECTROMAGNETIC RADIATION
ELECTRON DENSITY
ELEMENTS
ENERGY LEVELS
FLUIDS
GASES
GROUND STATES
HYDROGEN
NEON
NITROGEN
NON-EQUILIBRIUM PLASMA
NONMETALS
PLASMA
QUENCHING
RADIATIONS
RADIOWAVE RADIATION
RARE GASES
SPECTROSCOPY