AVS 49th International Symposium
    Plasma Science Tuesday Sessions
       Session PS1-TuA

Invited Paper PS1-TuA1
Microhollow Cathode Discharges@footnote 1@

Tuesday, November 5, 2002, 2:00 pm, Room C-103

Session: Microdischarges
Presenter: K.H. Schoenbach, Old Dominion University
Authors: K.H. Schoenbach, Old Dominion University
M. Moselhy, Old Dominion University
W. Shi, Old Dominion University
R. Bentley, Old Dominion University
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By reducing the dimensions of hollow cathodes into the hundred micrometer range, stable, direct current, high (atmospheric) pressure glow discharges in rare gases, rare gas-halogen mixtures and in air could be generated. The electron energy distribution in these microdischarges is non-maxwellian, with a pronounced high-energy tail. The high electron energy together with the high gas density, which favors three-body collisions, is the reason for an efficient excimer generation in rare gas and rare gas-halogen microplasmas. Excimer efficiencies of up to 8% have been measured for Ar, Xe, ArF, and XeCl with a radiant excimer emittance on the order of 1 W/cm@super 2@. Pulsing Xe discharges with 20 ns electrical pulses has led to an increase in radiant excimer emittance to 15 W/cm@super 2@, and a simultaneous increase in efficiency to more than 20%. Operating the discharges in an abnormal glow mode has allowed us to generate microdischarge arrays without individual ballast. Stable atmospheric pressure plasmas are not only obtained with microhollow cathodes but also in electrode geometries with planar cathode, and large diameter, ring-shaped anodes, separated by approximately 100 @micron@. Discharges in such geometries show for pressures on the order of 100 Torr self-organized regular plasma patterns. With increasing pressure the individual plasma structures merge into a homogeneous surface plasma with similar excimer emission characteristics as that obtained with microhollow cathode discharges. Applications of these plasmas are excimer lamps, potentially micro-excimer lasers, and electron emitters. @FootnoteText@ @footnote 1@This work is supported by the NSF under Grant # CTS-0078618 and INT-0001438.