A dielectric barrier discharge generated by flowing inert gas (helium) ionized by a high-voltage source through a cylindrical reactor working at atmospheric pressure has been studied and an electrical model characterizing this discharge is proposed. A sinusoidal voltage of up to 2 kV peak to peak with frequencies from 10 to 125 kHz has been applied to the discharge electrodes. The proposed model considers the geometry of the reactor and dielectric materials. From experimental and analytical results, a semi-empirical relation of the breakdown voltage is presented as a function of the operating frequency. The microdischarge regime is characterized by a dynamic equivalent capacitance.

This paper proposes a new system to ignite and to sustain a plasma discharge for different reactor configurations, using a single-series parallel high-frequency resonant converter. The different operation modes are analyzed, and their performance is verified in two applications: an equilibrium plasma discharge (electric arc) and a nonequilibrium plasma discharge (electric barrier at atmospheric pressure) with intensity current and voltage amplitude varying from 135 mA and 1050 V to 600 mA and 502 V, and operating the reactors at 60 Hz, 14 kHz, and 40 kHz. The principal features and results are remarked, such as its ease of adaptation to several regimes of discharge, by simply changing the operational frequency.Index Terms-Arc discharge, dielectric barrier discharge, equilibrium discharge, glow discharge, nonequilibrium discharge, resonant converter.

In this paper, a detailed diagnostic of an ac glowto-arc discharge transition is presented. The behavior of the temporal evolution of voltage and current discharges is studied under an atmosphere of helium-methane. In order to determine the rotational temperature, an optical emissionspectroscopy analysis from glow-to-arc regime discharge is carried out, where the OH and C 2 bands, respectively, which are situated at 306.357 nm (A 2 Σ + , ν = 0 → X 2 Π, ν = 0) and 516.52 nm (d 3 Π g , ν = 0 → a 3 Π u , ν = 0), are used. Several metallic atomic lines were used to calculate the electron temperature. The principal discharge parameters, such as temperature and electron density in the arc regime, are determined. As an application of this glow-arc discharge, the synthesis of carbon nanofibers is reported.Index Terms-Carbon nanofibers (CNFs), glow-arc, highfrequency discharge, swan band, UV-OH band.

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