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This paper reports the ongoing effort on development of efficient, compact pulsed corona sources for pollution control applications. The system comprises an all-solid 4 kW average-power nanosecond pulser and a plasma reactor. The pulser is based on a single-stage magnetic compressor generating ~50 kV, 1-5 J and 50-100 ns pulses across a multi-wire reactor having an impedance of approximately 100 [ohms], at pulse repetition frequency of up to 1 kHz. The principle of operation of the compressor is described. Equivalent circuits for two consecutive operation stages of the compressor accounting for nonlinear processes in magnetic switches are presented and analyzed. It was found that for the given topology, the optimal ratio of the primary and secondary capacitances is less than 'classical' unity value that is characteristic for most magnetic compression systems. The freewheeling diode was constructed from UX-FOB diodes chosen on the basis of the comparison of forward losses of several fast recovery diodes at pulsed conditions. Electrostatic analysis of a complex reactor structure was reduced to a simple problem of coaxial electrodes. This allowed for the implementation of a simplified corona model integrated into a PSpice simulation. The simulated waveforms bear close resemblance to their experimental counterparts. It was found that the reactor breakdown voltage decreased considerably with the increase of the pulse repetition frequency. In several cases, the latter effect was clearly associated with ozone build-up. Index Terms--Pulsed corona, magnetic compression, electrostatic analysis, streamer, forward drop, ozone.

An indoor two-wire transmission line (TL) was used to investigate the development of corona discharge during the propagation of a short HV pulse, for both polarities. The pulse voltage peak ranged from 40 to 100 kV with a pulse width of 5 ns at the full-width half-maximum points. The charge per unit length q was derived from the measurement of the voltage and current at the beginning of the TL. The q-v hysteresis curves were used to analyze the properties of the corona developed along the TL. It was found that at peak voltages much higher than the corona onset voltage, the q-v curves’ characteristics were similar to those found for μs surge pulses at overhead transmission lines. For peak voltages close to the corona onset, the corona exhibited charge neutralization oscillations and the charge buildup delay time vanished. It was also found that the positive corona is up to about six times more dissipative than the negative one, even though the negative corona onset voltage was somewhat lower than the positive, and q at the peak voltage is similar for both polarities. [ABSTRACT FROM AUTHOR]

An inductive-based power supply (240 μH, 50 kA) was used for the investigation of the foil explosion process in the time range of 0.05 msexpl<0.2 ms. The foil current for these experiments was set between 10 kA and 27 kA. The foil thickness was 10 μm and its length was 5 cm. Images of the exploding foil captured by a fast framing camera show that the radiation of the exploding foil discharge starts on the voltage rise. The peak voltage Vpeak decreases with an increasing time to explosion and a decreasing current density: Vpeak=2.8 kV at j=9.1 MA/cm2 and Vpeak=1.75 kV at j=5.3 MA/cm2. A phenomenological model was suggested for the experimental data interpretations. Contrary to the previous model, we assume that the breakdown initiates with cathode spots instead of a breakdown by a bulk discharge. We suggest that the plasma appearance is related to the ejection of a metal vapor during the metal boiling. The high temperature of the vapor permits ignition of the cathode spots even at a low electric field. It results in the arcing in the metal vapor and bypassing the liquid pieces of the foil. [ABSTRACT FROM AUTHOR]