Spring 2000

ME/IE 8773-8774

MICROHOLLOW CATHODE DISCHARGES
by

Karl H. Schoenbach, Ph.D.
Eminent Professor
Physical Electronics Research Institute
Department of Electrical and Computer Engineering
Old Dominion University
Norfolk, VA 23529

Wednesday, February 9, 2000
3:35 - 4:25 p.m.
Room 108 ME
Broadcast on UNITE Channel A
Coffee will be available in 152 ME following the seminar

Microhollow cathode discharges are nonthermal discharges between perforated metal electrodes separated by a dielectric film. Gas discharges in these microcavities, with diameters of the cathode opening on the order of hundred micrometers, were found to operate in a stable glow mode even at pressures at and above atmospheric, and electrical power densities of hundreds of kW/cm3. The large concentration of high-energy electrons generated in the cathode fall, in combination with the high neutral gas density favors excimer formation. Excimer light emission has been observed from the deep UV (128 nm) in argon discharges to 308 nm in xenon chloride with efficiencies between 1% and 10%. Parallel operation of the microdischarges offers the possibility to use them as dc-excimer lamps, with applications in UV curing and polymerization, photolithography, photo-chemistry, photo-deposition, photo-annealing, and pollution control. Besides as UV light sources, and possibly as micro excimer lasers, microhollow cathode discharges may also be used as current controlled plasma cathodes for large volume, high-pressure glow discharges. Direct current glow discharges in atmospheric air between plane parallel electrodes have recently been generated with this method.

Karl H. Schoenbach received the Diploma degree in physics and the Dr.rer.nat. degree in physics in 1966 and 1970, respectively, from the Technische Hochschule Darmstadt (THD), Germany. From 1970 to 1978, he was working at the THD in the areas of high-pressure gas discharge physics and on the dense plasma focus. From 1979 to 1985, he held a faculty position at Texas Tech University, where he was involved in research on fast opening switches, especially electron-beam and laser controlled diffuse discharge opening switches. In 1985, he joined Old Dominion University in Norfolk, VA. He was active in research on photoconductive switches until 1993, and has now concentrated his research efforts on high-pressure glow discharges, and on environmental and medical applications of pulse power technology. He has chaired a number of workshops and conferences, most recently the "First International Symposium on Nonthermal Medical/Biological Treatments using Electromagnetic Fields and Ionized Gases." He was elected Fellow of IEEE in 1994 for "contributions to the research and development of very-high-power electronic devices."

Faculty Host: Prof. Joachim V.R. Heberlein