Nonequilibrium discharges in air and nitrogen plasmas at atmospheric
Charles H. Kruger, Christophe O. Laux, Lan Yu, Denis M. Packan, and
High Temperature Gas Dynamics Laboratory, Mechanical
Engineering Department, Stanford University, Stanford, CA 94305, USA
Abstract: Diffuse glow discharges were produced in low temperature
(<2000 K) atmospheric pressure air and nitrogen plasmas with electron
number densities in excess of 1012 cm3, more than six orders of
magnitude higher than in thermally heated air at 2000 K. The measured
discharge characteristics compare well with the predictions of a two-temperature
kinetic model. Experimental and modeling results show that the steady-state
electron number density exhibits an S-shaped dependence on the electron
temperature, a behavior resulting from competition between ionization
and charge-transfer reactions. Non-Maxwellian effects are shown to be
unimportant for the prediction of steady-state electron number densities.
The power requirements of DC discharges at atmospheric pressure can
be reduced by several orders of magnitude using short repetitive high-voltage
pulses. Between consecutive pulses, the plasma is sustained by the finite
rate of electron recombination. Repetitive discharges with a 100-kHz,
12-kV, 10-ns pulse generator were demonstrated to produce over 1012
electrons/cm3 with an average power of 12 W/cm3, 250 times smaller than
a DC discharge at 1012 cm3.
* Lecture presented at the 15th International Symposium
on Plasma Chemistry, Orléans, France, 9-13 July 2001. Other presentations
are presented in this issue, pp. 317492.
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