A. V. Pipa

The simplest equivalent circuit of a pulsed dielectric barrier discharge and the determination of the gas gap charge transfer

The concept of the simplest equivalent circuit for a dielectric barrier discharge (DBD) is critically reviewed. It is shown that the approach is consistent with experimental data measured either in large-scale sinusoidal-voltage driven or miniature pulse-voltage driven DBDs. An expression for the charge transferred through the gas gap q(t) is obtained with an accurate account for the displacement current and the values of DBD reactor capacitance. This enables (i) the significant reduction of experimental error in the determination of q(t) in pulsed DBDs, (ii) the verification of the classical electrical theory of ozonizers about maximal transferred charge q(max), and (iii) the development of a graphical method for the determination of q(max) from charge-voltage characteristics (Q-V plots, often referred as Lissajous figures) measured under pulsed excitation. The method of graphical presentation of q(max) is demonstrated with an example of a Q-V plot measured under pulsed excitation. The relations between the discharge current j(R)(t), the transferred charge q(t), and the measurable parameters are presented in new forms, which enable the qualitative interpretation of the measured current and voltage waveforms without the knowledge about the value of the dielectric barrier capacitance C(d). Whereas for quantitative evaluation of electrical measurements, the accurate estimation of the C(d) is important.

Analysis of the Mid-Infrared Spectrum of the Exhaust Gas From an Atmospheric Pressure Plasma Jet (APPJ) Working With an Argon–Air Mixture

The mid-infrared (IR) absorption spectrum of the exhaust gas of an atmospheric pressure plasma jet operated in Ar with the admixture of 0.1% of air has been monitored in the spectral region from 4000 to 750 cm^-1. The absorption features of CO₂, CO, NO, NO₂, N₂O, HNO₂, and HNO₃ were identified using a Fourier transform IR spectrometer combined with a multipass cell with 30-m absorption path length. The production rates of these molecules to be in the range of 0.5 to 4 times10¹⁸ molecules s^-1 were estimated.

Spatial distribution of charged particle emission in a copper-chromium high-current vacuum arc

Summary form only given. Vacuum circuit breakers are widely used in high-power systems, because they are compact, reliable and provide excellent switching capabilities even at high currents up to tens of kA. The main tendency of vacuum circuit breaker development is nowadays to extend their ability to operate even at higher voltages and higher currents. Despite numerous studies of the vacuum arc properties there is still a lack of spectroscopic investigations of high-current vacuum arcs for advanced switching applications. Nevertheless fundamental investigations are required for a deeper understanding of the plasma properties and the physical processes taking place during current interruption.This contribution presents results obtained by optical emission spectroscopy applied to a high-current vacuum arc model experiment. The experimental setup allows to reproduce the arc behavior observed in real circuit breakers at 50 Hz sinusoidal currents with peak values of 2.3 kA. Copper Chromium (Cu-Cr) electrodes with 20 mm diameter are used, which are separated at a controlled velocity of 1.1 m/s to ignite the discharge. Overview spectra as well as highresolution spectra are shown (spectral resolution down to 30 pm). The optical emission spectroscopy is accompanied by high-speed video imaging to observe the arc behavior in general. By imaging of axial and radial sections of the arc onto the entrance slit of a spectrograph, spatial distributions of neutral and charged particle emission can be determined. In case of electrodes made of Cu-Cr alloys it is possible to detect emissions from Cu I, Cu II, Cu III as well as Cr I, Cr II and Cr III. Due to the multitude of partly overlapping spectral lines line identification is an important issue before conclusions can be drawn. Along the arc axis different zones can be discriminated where different ionization stages achieve maximum emission. To give an example, neutral atoms radiate strongly in the vicinity of the electrodes, which is an expected behavior due to the eroded electrode material and the correspondingly high particle density. The results can reveal new information about charge distribution in the gap and describe elementary processes which are taking place in switching plasmas during current interruption giving options to increase the interruption behavior in future.

PPPS-2013: This is a sample abstract submission dielectric barrier discharges: Pulsed breakdown, electrical characterization and Chemistry

Summary form only given. The application of atmospheric pressure discharges in new fields like environmental protection, surface treatment or life-sciences requires a profound knowledge on the plasma parameters and properties. This includes (1) the characterization of the breakdown processes triggering plasma chemistry, (2) the proper determination of the electrical parameters and (3) the description of the dominant chemical pathways. The contribution aims to present new approaches regarding these three topics for pulsed driven Dielectric Barrier Discharges in particular. It will be shown by fast electrical, optical and spectroscopic methods that the ignition, breakdown statistics and spatio-temporally resolved development of pulsed DBD microdischarges is controlled by the properties of the power supply (duty cycle, frequency, amplitude varied) as well as the composition of the gas1. In particular the starting point of the microdischarge ignition can be changed which is a new effect in DBDs caused by electric field rearrangement in the gap due to positive ion development. Surface processes at the dielectric barriers influencing this behavior will be discussed, too. The determination of electrical parameters such as discharge current, gas gap voltage, instantaneous power and energy as well as the charge transferred through the gas gap based on a simple equivalent circuit will be presented. The proposed approach accurately accounts the displacement current and key capacitance values, which inexactly determination are a source of experimental errors in particular in case of pulsed driven DBDs. The presented approach is consistent with sinusoidal-voltage driven or miniature pulsed driven DBDs. We believe that these new insights on electrical characterization are an important input for those who are working with DBDs, since the electrical parameters are mandatory information. The characterization of the dominant chemical pathways of advanced plasma processes is usually focused on the volume processes only. This contribution will discuss several examples which shall emphasize, that secondary effects must be considered, too. These shall cover the topics of adsorption-enhanced VOC conversion by DBD plasma treatment, NOx conversion and indirect plasma treatment of liquids for antimicrobial and chemical decontamination.

Dielectric barrier discharges: Pulsed breakdown, electrical characterization and Chemistry

The application of atmospheric pressure discharges in new fields like environmental protection, surface treatment or life-sciences requires a profound knowledge on the plasma parameters and properties. This includes the characterization of the breakdown processes triggering plasma chemistry, the proper determination of the electrical parameters and the description of the dominant chemical pathways. This contribution aims to present new approaches regarding these three topics for pulsed driven Dielectric Barrier Discharges (DBDs) in particular. Fast electrical, optical and spectroscopic methods enable the study of ignition, breakdown statistics and spatio-temporally resolved development of pulsed DBD microdischarges. The determination of electrical parameters such as discharge current, gas gap voltage, instantaneous power and energy as well as the charge transferred through the gas gap is based on a simple equivalent circuit which is consistent with sinusoidal-voltage driven or miniature pulsed driven DBDs. The characterization of the dominant chemical pathways of advanced plasma processes discusses also several examples including secondary effects, such as adsorption-enhanced VOC conversion by DBD plasma treatment.