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Comparison of an atmospheric pressure, radio-frequency discharge operating in the α and γ modes

X Yang1, M Moravej1, G R Nowling1, S E Babayan2, J Panelon2, J P Chang1 and R F Hicks1

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The α and γ modes of an atmospheric pressure, radio-frequency plasma have been investigated. The plasma source consisted of two parallel electrodes that were fed with helium and 0.4 vol% nitrogen. The transition from α to γ was accompanied by a 40% drop in voltage, a 12% decrease in current and a surge in power density from 25 to 2083 W cm−3. Optical emission confirmed that sheath breakdown occurred at the transition point. The maximum light intensity shifted from a position 0.25 mm above the electrodes to right against the metal surfaces. The average density of ground-state nitrogen atoms produced in the atmospheric plasma was determined from the temporal decay of N2(B) emission in the afterglow. It was found that 5.2% and 15.2% of the N2 fed were dissociated into atoms when the plasma was operated in the α and γ modes, respectively. The lower efficiency of the γ discharge may be attributed to the non-uniform distribution of the discharge between the electrodes.


PACS

52.80.Pi High-frequency and RF discharges

52.70.Kz Optical (ultraviolet, visible, infrared) measurements

52.80.Hc Glow; corona

52.50.Dg Plasma sources

52.25.Os Emission, absorption, and scattering of electromagnetic radiation

52.25.-b Plasma properties

Subjects

Instrumentation and measurement

Plasma physics

Dates

Issue 2 (May 2005)

Received 23 July 2004

Published 22 March 2005



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