Investigation of Operational Regimes of a High-Power Pulsed Corona Source with an All-solid State Pulser

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 Omega, 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.