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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.

A technical overview of a European project on pulsed corona (PC) treatment of polluted streams is presented. Versatile high-power systems that are capable of cleaning both aqueous and gaseous streams in heterogeneous media, in either a corona above water reactor or an aerosol reactor, have been developed. Both reactors are capable of high-phenol removal yields from aqueous streams and increase the biochemical oxygen demand/chemical oxygen demand ratio for several nonbiodegradable wastewaters to such degree that further biodegradation becomes possible. The PC combined with a catalyst is capable of cleaning gaseous streams that are polluted by toluene, styrene, and malodorous constituents. Reduction rates of toluene that are higher than 99% have been achieved, and very high odor removal efficiency has been demonstrated. The reliable operation of high-power all-solid-state compact nanosecond pulsers has also been demonstrated. For the second phase of the project, a high-power pulser was designed. One compression stage suffices for the formation of 60-kV 3-J pulses across a reactor that has a discharge impedance of approximately 100 [ohm] at a pulse repetition frequency of up to 500 Hz; the rise time is 15 ns, and the duration is 100 ns. The system scale-up is also analyzed. The estimated price of water treatment in systems that were scaled up to 50 [m.sup.3]/h is 2 [euro]/[m.sup.3]. Incineration of aqueous organic waste streams can cost 500 [euro]/[m.sup.3] or more, depending on the nature of the contamination, so the PC water-treatment technology may become highly competitive. It is planned in the future to investigate the cleaning efficiency of the developed processes with different industrial wastes, both at laboratory conditions and in the field. Index Terms--Catalyst, fast solid-state switching, heterogeneous media, magnetic compression, pulsed corona (PC), streamer.

Pulsed corona (PC) offers real promise for the degradation of pollutants in gas and water streams. Understanding discharge physics is necessary for developing corona applications. This paper presents an investigation of the dependence of PC current and radiation on pulse repetition rate (PRR). The study was carried out in a wire-to-wire geometry. A corona device with a central high-voltage electrode and two symmetrical grounded electrodes was used for model experiments. A nanosecond solid-state pulse generator SM-2N (100 kV, 5 ns, PRR up to 300 Hz) was used for driving PC discharge. A model expression relating the removal efficiency with PRR is presented. The removal efficiency falls with the increase of PRR at a 'constant' flow rate or 'constant' residence time. There is satisfactory agreement between the calculated data and the experimental results. Index Terms--Atmospheric pressure corona, removal efficiency, repetition rate.

Propagation of short high-voltage pulses along a 6-mlong twin line was studied in the presence of corona discharge. The experimental setup included a twin-line arrangement, a 100-kV, 5-ns pulse generator, voltage and current probes, and photomultipliers. The dependencies on line geometry and wire conductivity and on pulse voltage and polarity have been studied. PSpice and electrostatic simulations are presented; the latter are compared to still photos of corona discharge. Of most interest was the finding that the discharge was very much asymmetric when one of the pulser's terminals was grounded, even when the line height was much greater than the distance between the wires. This effect will be pronounced to heights of hundreds of meters. Pulsed corona study on NiCr resistive wires revealed intense pulse decay: only 1% of the launched energy reaches the end. Index Terms--Dispersion, electromagnetic wave, potential coefficients, pulsed corona, twin line.

The system comprises either a nanosecond solid-state operating switch (SOS)-generator (see, e.g., Rukin, 1995) or a RADAN pulsed power source (see, e.g., Mesyats et al., 1993) that charges resonantly a short pulse-forming line (PFL) through a decoupling inductor, an active converter, a matched load, and several built-in voltage and current probes. The active converter comprises an additional 1-ns PFL charged through a peaking spark gap (SG) and a secondary decoupling inductor by the first PFL, and two SGs (chopping and peaking gap). The peaking SG and active converter are set in one body and operate in N2 at pressure up to 6 MPa. Driven by RADAN, the converter generates bipolar subnanosecond pulses having peak-to-peak amplitude up to 270 kV across 46.6-[ohm] load. The pulsewidth of each half wave of bipolar pulses on full-width at half-maximum is 280 ps, with the risetime of the first half wave of about 160 ps. The SGs' gaps can be regulated without system depressurizing (a technique adopted from Shpak et al., 1996). Circuit analysis accounting for the distributed character of the components and numerous parasitic parameters is presented. Mapping of main SG parameters (gap distance and pressure) was performed. Waveforms probed at different locations of the pulser systems, from the SOS-generator and from the RADAN to the load, are shown. The bipolar subnanosecond pulses had very stable rise, while the fall jitter was around 50 ps. The experimental results are in fair agreement with the simulation. Pulsers were tested with a transverse electromagnetic horn antenna. An effective potential of 910 kV was obtained. Index Terms--Closing switch, electrode erosion, electromagnetic radiation, pulse generation, spark gaps, time-domain measurements.

An overview of the electro-thermal-chemical launcher (ETC) research program at the Propulsion Physics Laboratory, Soreq NRC, Israel is presented. The main avenue explored is a detailed study of solid propellant ETC (SPETC) performance and optimization. A better knowledge of the physical phenomena taking place inside the device and in parallel efforts to tackle the engineering aspects of specific weapon systems based on the SPETC concept. Theoretical and experimental tools have been developed. Permanent efforts toward developing optimal and efficient components for such systems are invested. A second avenue is the design and the construction of a small-caliber ETC demonstrator, as an answer for present military demands for urban combat conditions. All system options are dealt with including a novel inductive pulse power supply. Index Terms--Ballistic codes, electro-thermal-chemical, inductive storage system, low-plasma energy, plasma injector.

The system comprises an all solid-state compact nanosecond pulser and a plasma reactor. The pulser makes use of magnetic compression techniques. Owing to a fast switching at the feed of the HV transformer provided by an ABB GCT switch, one compression stage suffices for the forming of 45-kV, 100-ns pulses across a 120-[ohms] resistive load at a PRF of up to 1 kHz; the risetime is 15 ns. Plasma reactor is capable of handling both gases and liquids by adding small amounts of atomized water to the gas discharge, in the case of gas, or atomizing polluted liquid itself. In both cases, the treatment is conducted in heterogeneous media. Circuit analysis of compressor and charging system accounting for nonlinear processes in magnetic switches and numerous parasitic parameters is presented. Mechanical and electrical designs are detailed. Typical voltage and current waveforms, volt-ampere characteristics, corona discharge appearance, and light emission characteristics are presented. At operation on a resistive load, the compressor efficiency was found to be approximately 80%, which allowed for air cooling. The experimental results obtained with a resistive load are in fair agreement with the circuit simulation. A novel magnetic compressor circuit improving the coupling to PC discharge is proposed and evaluated. Index Terms--Fast solid-state switching, heterogeneous media, magnetic compression, pulsed corona.

The system comprises a nanosecond solid-state opening swish (SOS) generator that charges resonantly a short pulse-forming line (PFL) through a decoupling inductor, one or two pulse-compression stages based on high-pressure gas spark gaps (SGs), a matched load and several built-in voltage and current probes. Weighing less than 50 kg, the pulser provides up to 160-kV subnanosecond pulses at a 37.5-[OMEGA]load at a repetition rate of up to 300 Hz. The pulsewidth can be regulated from 2 ns down to 300 ps without SG depressurization. The rise-and fall times are 180 and 100 ps, respectively. Alternatively, unipolar or bipolar output can be provided. The latter was formed by a synchronous operation of SGs located at the beginning and at the end of a PFL; thus, an active conversion of unipolar to bipolar output was realized. The load peak-to-peak voltage was almost two times as high as the amplitude of the anipolar pulse. In the active converter, a virtually identical electrical field stress across the switching SGs was achieved, which alone provided its stable operation. Circuit analysis accounting for distributed character of the components and numerous parasitic parameters is presented. Voltage and current measurement means were developed and time-domain calibrated. Waveforms probed at different locations of the pulser system, from the SOS generator to the load, are presented. The experimental results are in fair agreement with PSpice simulations used for the hardware design. Life test of a one-stage compressor with two types of electrode systems was performed, and the results are reported. The pulser was tested with a TEM horn antenna. The effective potential (field multiplied by distance) of this radiation source is 640 kV in far field. Index Terms--Closing switch, electrode erosion, pulse generation, spark gaps (SGs), time-domain measurements.

A laboratory repetitive inductive storage power supply (ISPS) for the ignition of an electrothermal-chemical (ETC) gun is described. It is designed for delivering to an electrothermal load an energy of 400 kJ in a shot under the assumption that this energy suffices for an effective ignition of advanced consolidated propellants accounting for temperature compensation. The ISPS is battery-based. The battery has a peak power of 5 MW and is able to charge a cylindrical coil to 700 kJ. Fringe fields of the coil with and without ferromagnetic screens in static and transient conditions are analyzed using numerical simulation. A conclusion is drawn that a screen of reasonable weight cannot reduce the stray field below a susceptibility level of electronic devices that should be shielded individually. A hybrid repetitive opening switch (OS) rated 50 kA, 4 kV, 70 [micro]s breaking time is described. A commercial vacuum circuit breaker serves as the first stage. At a desired moment, it is opened, and the current is transferred to the second stage, which is an integrated gate-commutated thyristor (IGCT) that finally breaks the current. The IGCT turnoff is assisted by an inverse current injection into the second stage. The main benefit of this technique is a dramatic reduction (by a factor of ten) in the quantity of semiconductor devices in the second stage. The OS design, assisted by PSpice simulations coupled with field analysis of nonlinear magnetic components is described. Test results (1) are presented. Overall, this work supports an earlier conclusion that an 0.5-MJ ISPS, capable of delivering the first round of an eight-shot burst in 0.3 s, will occupy 0.6 [m.sup.3] net volume and weigh 1000 kg. Index Terms--Electrothermal gun, fringe field, inductive storage, opening switch.

Visual appearance, electrical performance, and chemical activity of a 50-MW 100-kV 22-ns pulsed corona were studied in simulated air-S[O.sub.2] gas mixture in a coaxial reactor. Infrared and mass spectrometers and electrochemical sensors were used for gas diagnostics; solid byproducts were identified using X-ray fluorescent spectrometry. Electrochemical sensors were employed for the measurement of initial concentration, before the discharge commencement. The removal efficiency of S[O.sub.2] in dry and humid air-S[O.sub.2] mixtures was studied. The removal efficiency of S[O.sub.2] decreased at lower pollutant concentration and higher frequency, while the pulse energy was kept invariant. Removal efficiency in dry mixtures was 25 g/kWh; in humid air, it was several times greater, which is attributed to the influence of OH radicals. In dry mixtures, the removal efficiency was much higher at positive polarity. Traces of many compounds were found and identified in treated gas. Ozone was produced in large concentrations both in dry and humid mixtures. Dependence of its formation rate on the pulsed power, and on the voltage polarity was studied. The precipitation of a yellowish powder identified as sulfur was observed. It is ascribed to cleavage of bonds of the S[O.sub.2] molecule by energetic species and confirmed by experiments with dry [N.sub.2]-S[O.sub.2] and Ar-S[O.sub.2] mixtures. Index Terms--IR spectrometry, mass spectrometry, nonthermal plasma, pulse power systems, pulsed corona, waste treatment.

A two-stage opening switch comprising of a vacuum switch as the first stage and a high voltage fuse in series with a silicon controlled rectifier (SCR) as the second stage is presented. The switch offers low resistance of 20 [Mu][ohms] during charge intervals of several hundred milliseconds, controlled time to opening, minimal fuse size, and a relatively fast opening of 0.25-0.7ms. It serves as a closing switch as well. In a series of experiments, the current of 30-40 kA was commutated routinely from a 0.13 mH inductor into a resistive load at a voltage of 3000 V. Various quenching media were examined. The liquids were found to yield maximum inductively generated voltage and transfer efficiency. A strong correlation exists between the fuse performance and the pressure generated in the fuse. This dependence is used as a guideline in fuse design. It was found that a 2-3 ms fuse conduction time suffices for the recovery of the vacuum switch. A PSpice circuit simulation using an action-dependent fuse model is in good agreement with experimental results. A semi-empirical fuse model based on electron-ion recombination mechanism of the fuse resistance change is proposed. This model is integrated into PSpice circuit simulation. The calculations are in fairly good agreement with experimental results.

The influence of eddy currents on the energy transfer from a storage coil to a resistive load in systems with a long charge was studied. The magnetic diffusion equation for a current exponential fall in an infinite slab, as a model problem, was solved analytically. The dependence of the energy loss on the slab characteristics and time constant of the current decay was determined. More complicated cases of cylindrical coils were treated numerically. Both electromagnetic and stress analyses were performed. A jellyroll coil was found to be superior to a pancake coil in terms of discharge efficiency. A jellyroll coil of the Brooks type is able to supply to the load approximately 25% more energy than a pancake coil of identical size, providing both carry the same current. However, the energy density of a pancake coil is approximately 20% higher than that of a jellyroll coil, if the coils are charged up to the limit of their mechanical strength. To calculate the discharge efficiency of a pancake coil, a time-consuming transient analysis could be replaced by a dc or low-frequency ac analysis. Discharge efficiency increases for a faster charge, whereas the total transferred energy decreases, owing to a slight field diffusion into conductors. The experiments with a pancake coil yielded results in close agreement with the theoretical analysis.

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 ms