ATMOSPHERIC GLOW DISCHARGE PLASMAS USING A MICROHOLLOW CATHODE DEVICE

Glow discharges are known to have relatively high electron densities even while maintaining stability. Applications of these discharges are numerous and include plasma reflectors and absorbers of electromagnetic radiation, surface treatment, thin film deposition and gas lasers. Microhollow cathode devices have been shown to be excellent high electron density (up to 10(16) /cm(3)) sources of glow plasma atmospheric air discharges. Under pD conditions on the order of 10 Torr-cm the radial electric field created in the microhollow overtakes the axial electric field, oscillating electrons across the diameter of the hole. This effect leads to a glow discharge formed above the surface of the microhollow cathode. This geometry allows for large area arrays of highly stable glow discharges operated in parallel at atmospheric pressure. The University of Missouri-Columbia is currently developing a stable high-density large surface area plasma source. A microhollow cathode device with Cu electrodes, an Al2O3 substrate, and laser drilled 125 mu m cathode holes has been fabricated and investigated as a glow discharge plasma source. Illustrated are the physics behind the microhollow cathode relating to its high electron density, operation in atmospheric pressure, and generation of several discharges in parallel. Also presented are the conclusions of several studies on the operation on variants of hollow cathode geometries.