Measurement of a Planar Discharge and Its Interaction With a Neutral Background Gas.
NAVAL RESEARCH LAB WASHINGTON DC
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The effect of a weakly ionized glow discharge plasma on the temperature and density of a neutral background gas has been investigated. The particular discharge studied is a magnetically confined 50 cm x 60 cm x 3 cm planar sheet plasma produced using the Agile Mirror system at the U.S. Naval Research Laboratory. Most previous glow discharge work has concentrated on either the DC characteristics, or on the very early evolution 1 - 2 microseconds of the discharge. This paper analyzes the results of time-resolved measurements made over intermediate 5 - 300 microseconds timescales. Measurements made of an air discharge produced using a V sub D 4.5 kV anode-cathode voltage, P sub N approx. 120 mTorr background gas pressure, and B 250 G external magnetic field reveal an n sub e 10exp 12cu cm, T sub e 1 eV negative glow plasma. Measurements made on an air discharge produced using V sub D approx. 2-3 kV, P sub N approx. 208 mTorr, and B approx. 250 G reveal an n sub e 10exp 11cu cm, T sub e 1-3 eV plasma with distinct negative glow, Faraday dark space, and positive column regions. Analysis of time-resolved potential, temperature, and spectroscopic data reveal that the higher pressure discharge transitions after approx. 100 microseconds into a homogeneous negative glow discharge. Quantitative analysis of the discharge taking into account the important ionization and loss processes, and using measurements of discharge current, voltage, and local electric field, confirms that a 50 reduction in neutral gas density due to heating of the background gas is responsible for the transition.
- Physical Chemistry
- Atomic and Molecular Physics and Spectroscopy