Production of metastable and resonant atoms in rare-gas (He, Ne, Ar) radio-frequency and microwave-sustained discharges
1988; NRC Research Press; Volume: 66; Issue: 8 Linguagem: Inglês
10.1139/p88-122
ISSN1208-6045
AutoresA. Ricard, C. Barbeau, A. Besner, Jan Hubert, J. Margot-Chaker, Michel Moisan, G. Sauvé,
Tópico(s)Quantum, superfluid, helium dynamics
ResumoRadial density distributions of excited atoms in plasma columns of helium, neon, and argon, sustained by a travelling electromagnetic surface wave, are examined as a function of frequency over the range 200 kHz – 2450 MHz. This investigation is conducted using an end-on measurement method. At low frequencies (<50 MHz), these radial distributions show a maximum at the axis (J 0 Bessel-like behavior), whereas as frequency is increased beyond 50 MHz up to 2450 MHz, the radial distributions flatten and finally exhibit a minimum at the axis with a maximum close to the tube wall. Comparison with a DC positive column plasma, working under the same gas-pressure and tube-diameter conditions, is made as a function of cross-section average electron density. The surface-wave discharge operated in the microwave frequency range (>300 MHz) yields larger cross-section average densities for atoms in a metastable or resonant state, typically a factor of 2–3 at 10 11 electrons∙cm −3 . This result arises because the two types of discharges have different radial-density distributions for excited atoms.
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