Substantial changesin the characteristics of a microwave plasma due to combiningargon and hydrogen

Abstract

Upon the addition of 5% argon to a hydrogen plasma, theLyman α emission was observed to increase by about anorder of magnitude, whereas xenon control had no effect. Witha microwave input power of 40 W, the gas temperature of anargon plasma increased from 400 to over 750 °C withthe addition of 3% flowing hydrogen, whereas the400 °C temperature of a xenon plasma run underidentical conditions was essentially unchanged with the additionof hydrogen. The average hydrogen-atom temperature of theargon-hydrogen plasma was measured to be 110-130 eV versus≈3 eV for pure hydrogen or xenon-hydrogen. Mechanismssuch as Stark broadening or acceleration of charged species dueto high fields (e.g. over 10 kV cm-1) cannot be invoked toexplain the results with argon since the electron density waslow and no high field was observationally present. The electrontemperature Te for the argon-hydrogen andxenon-hydrogen plasmas was 11 600±5% and 6500±5% K, respectively, compared to 4800±5% and 4980±5% K for argon and xenon alone, respectively. The observationof higher temperatures corresponding to three possiblyindependent plasma parameters for only argon with hydrogen maybe explained by the release of energy from atomic hydrogen by aresonant nonradiative energy-transfer mechanism.