A time-resolved imaging and electrical study on a high current atmospheric pressure spark discharge

Abstract

A time-resolved laser induced fluorescence study on the ion velocity distribution function in a Hall thruster after a fast current disruption Phys. Plasmas 16, 043504 (2009) We present a time-resolved imaging and electrical study of an atmospheric pressure spark discharge. The conditions of the present study are those used for nanoparticle generation in spark discharge generator setups. The oscillatory bipolar spark discharge was generated between two identical Cu electrodes in different configurations (cylindrical flat-end or tipped-end geometries, electrode gap from 0.5 to 4 mm), in a controlled co-axial N 2 flow, and was supplied by a high voltage capacitor. Imaging data with nanosecond time resolution were collected using an intensified CCD camera. This data were used to study the time evolution of plasma morphology, total light emission intensity, and the rate of plasma expansion. High voltage and high current probes were employed to collect electrical data about the discharge. The electrical data recorded allowed, among others, the calculation of the equivalent resistance and inductance of the circuit, estimations for the energy dissipated in the spark gap. By combining imaging and electrical data, observations could be made about the correlation of the evolution of total emitted light and the dissipated power. It was also observed that the distribution of light emission of the plasma in the spark gap is uneven, as it exhibits a "hot spot" with an oscillating position in the axial direction, in correlation with the high voltage waveform. The initial expansion rate of the cylindrical plasma front was found to be supersonic; thus, the discharge releases a strong shockwave. Finally, the results on equivalent resistance and channel expansion are comparable to those of unipolar arcs. This shows the spark discharge has a similar behavior to the arc regime during the conductive phase and until the current oscillations stop. V C 2015 AIP Publishing LLC. [http://dx

Observation of fine-ordered patterns on electrode surfaces subjected to extensive erosion in a spark discharge

“…Each and every spark only affects a part of the electrode surface, as is obvious from the substantial difference between the diameter of the spark channel and that of the electrode (e.g. (Bazelyan & Raizer, 1997;Palomares, Kohut, Galbács, Engeln, & Geretovszky, 2015)). The fact that the electrode pattern begins to emerge only after a large number (10 5 -10 6 ) of spark events also suggests that each spark event only contributes a small part of the whole pattern.…”

Characteristics of an Overstressed Discharge of Nanosecond Duration between Electrodes of Chalcopyrite in High Pressure Nitrogen

“…The intensive group of spectral lines and bands of the nitrogen molecule is visible in the spectral range of 290-410 nm (lines and bands 14-35; The radiation spectra of plasma also showed a characteristic spectral line with the wavelength of 500.5 nm N II, which is often observed in the radiation spectra of nanosecond discharges in an atmospheric pressure air [17].…”

Parameters of Nanosecond Overvoltage Discharge Plasma in a Narrow Air Gap between the Electrodes Containing Electrode Material Vapor

“…Small bipolar peaks of the voltage pulse had the amplitudes of the positive and negative components up to 15-20 kV. The current pulses of the nanosecond discharge consisted of The spatial, electrical, and some emission parameters of the bipolar nanosecond discharge between metal electrodes (Zn, Cu, and Fe at = 0.5÷4 mm) in the nitrogen atmosphere at a pressure of 1 atm were studied in works [12,13]. The results obtained there correlate with the results of our experiments.…”

“…The parameter of those "pointsource" lamps have been most completely studied, when exciting an overvoltage discharge 1-2 ns in duration, which is ignited making use of unique pump oscillators [9]. Less studied are the parameters of nanosecond discharges between metal electrodes for systems with a low inhomogeneity of the electric field strength distribution in the discharge gap [10][11][12][13]. Such conditions are created, when a system of electrodes of the "sphere-sphere" type is used, and the curvature radius of the working electrode surface is comparable with the distance between the electrodes [14].…”