EXCITATION OF GASES WITH A MICROWAVE RESONANT LINE.
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Date
1965
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Publisher
Ohio State University
Abstract
In the radiofrequency excitation of gases, it is important to avoid excessive concentrations of the electromagnetic field, resulting in arc discharges which have a low impedance and reflect much power. A fairly uniform field just strong enough to maintain glow is often more desirable. At the frequencies at which power can be generated cheaply (for example, at 2450 Mc/sec with a diathermy machine), cavities are rather large, and it is difficult to couple the electrical power into them efficiently and also to get the radiation or excited atoms out. Much more satisfactory results have been obtained with a parallel-wire half-wavelength transmission line, shorted at the ends and fed at the middle. The gas to be excited is placed between the transmission lines, and voltage standing-wave ratios of less than 1:1 have been obtained at the feed-in line at power levels of 120 watts. An intense glow is produced, suitable for a spectroscopic source or for the production of free radicals or excited electronic states. For some applications, more than one half-wavelength of transmission line is desirable, or several parallel wires may be used in a multipole arrangement.
Description
Author Institution: Department of Physics and Astronomy, University of Tennessee; Department of Physics, Wofford College Spartanburg, South Carolina