Multitube surface-wave discharges for increased gas throughput at atmospheric pressure

Abstract

Large diameter (>10 mm) microwave discharges at atmospheric pressure are often constricted transversely and, when large gas flow rates are used, unstable as far as microwave power coupling is concerned. A group of small bore tubes can be used instead to provide the same gas throughput and ensure a higher probability of interaction of molecules to be processed with the carrier gas. The solution presented provides equal power sharing in these small diameter plasma columns and it employs preferably a single microwave field applicator, therefore enabling one to use only one power generator and yielding a compact system. This scheme is based on the properties of surface-wave sustained plasmas and it calls on basic principles of waveguide circuitry.

Absolute atomic oxygen density measurements by two-photon absorption laser-induced fluorescence spectroscopy in an RF-excited atmospheric pressure plasma jet

“…This point is supported by the work of Jeong et al [15], who performed axially resolved optical emission and ultraviolet (UV) absorption measurements of O 2 OES gives direct access only to excited particles, and conclusions on the atomic ground state density (exceeding that of excited states by several orders of magnitude) require rather complex models of approximative character. Furthermore, OES only provides line-of-sight integrated information, unless tomographic methods (e.g.…”

“…With these data, we derived the two-photon excitation cross-section ratio σ (2) (Xe)/ J σ (2) J →J (O) = 1.9 from the measured calibration factor, where J is the total angular momentum quantum number of the upper fine structure levels; we estimate the overall uncertainty to be ∼20%.…”

“…with the 'normalized' fluorescence signal S (integrated over fluorescence wavelength, excitation wavelength and interaction time, and normalized to the squared laser pulse energy), the photon energy hν, the effective branching ratio a of the observed fluorescence transition, the transmission T of the detection optics and the detector's quantum efficiency η for the fluorescence wavelength, and the two-photon excitation cross section σ (2) . For low pressure media (collisionless case) the calibration factor χ depends only on atomic cross sections and experimental constants.…”

“…Their application is often limited due to their non-uniformity. This shortcoming may be overcome by recently developed discharges: the atmospheric pressure glow (APG) [1,2] in dielectric barrier discharges and the atmospheric pressure plasma jet (APPJ) [3], the latter source being the object of this study.…”

Spectroscopic measurements of electron density in atmospheric-pressure surface wave sustained discharge in argon

“…In the last decades, field applicators for such sources were developed, investigated and implemented in practice (see e.g. [1,2,3]). In the present investigations we used a surfaguide-type plasma source, based on WR 430 standard waveguide.…”