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Non-thermal plasma (NTP) is a promising biomedical tool for application to wound healing. However, there is limited scientific evidence that confirms its efficacy to inhibit scar formation. This study aims to investigate the role of non-thermal plasma in scar formation. Two full-thickness dorsal cutaneous wounds of rats were treated with either a non-thermal helium plasma jet or helium. It was determined that the non-thermal plasma jet accelerated the wound healing process from 5 days after surgery (day 5: 41.27% ± 2.351 vs 54.7% ± 5.314, p

In this paper, we present a new method that views offline handwritten chinese character recognition (HCCR) as a Re-identification (ReID) task. We introduce a print dataset as the target that needs to be retrieved, and make the test set of offline HCCR as the object of interest. According to ReID’s scene, the goal is to find the most similar print sample as the prediction result for each object of interest. We also employ triplet loss for metric learning, and train model together with cross-entropy loss, which has a good effect on improving performance. Compared with the classification model, the experimental results show that our method achieves much better results in few-shot learning, whose dataset is randomly selected from overall datasets. When the training set used is 5% of HWDB1.1, the gap between them even reached 9.8%. At the same time, it also obtains an accuracy of 97.69% on ICDAR-2013 offline HCCR competition dataset.

All types of seismic sources have a common feature in which large energy is released into water in a short time to produce an intense acoustic pulse. For plasma sparker, the discharge time is mainly determined by the discharge circuit parameters. Providing an accurate prediction of the acoustic pulse is difficult because of the complex plasma discharge process and unclear initial bubble condition. This paper presents the first experimental study on the influence of electric pulse width on acoustic pulses, especially the expansion pulse. Three comparative experiments are conducted to investigate the effect of electric pulse and to determine the minimum acoustic pulse width produced by a plasma sparker. One of the main results is that only the amplitude of the expansion pulse can obviously be changed if the electric circuit parameters are fixed, especially the capacitance of the energy storage capacitor. Meanwhile, the smaller the energy storage capacitor is, the shorter is the electric pulse and the narrower is the expansion pulse. The maximum pressure of an expansion pulse generated by a small capacitor is larger than that generated by a large capacitor under the same energy. The expansion pulse width decreases quickly when the energy dissipation on the load speeds up, and approaches the minimum value around several microseconds when the energy dissipation rate on the load is over 2 J/ $\mu$ s, and the corresponding electric pulse width is on the order of hundreds of nanoseconds.

Wide Electrostatic Precipitator (having plate-to-plate spacing 400 mm or more) is one of a promising ways to improve existing ESPs, yet its large-scale application has been limited because of potential collection efficiency reduction. This article focus on study the electrohydrodynamic flow inside the ESP and the particle collection efficiency by using Particle Image Velocimetry and Electrical Low Pressure Impactor respectively when several different electrode geometries were applied, in order to increase wide ESP efficiency. Results showed that geometry with juxtaposed high voltage wires provided best performance of the wide ESP (both in collection efficiency and running cost) among our tests.

The plasma sparker has been applied in oceanic high-resolution seismic exploration for decades. Normally it is towed on the water surface. This is suitable for shallow water, but if the water depth is great, the resolution will decrease dramatically, especially in the horizontal direction. This paper proposes the concept of a deep-towed plasma sparker and presents an experimental study of plasma sparker performance in terms of electric parameters, bubble behavior, and acoustic characteristics. The results show that hydrostatic pressure at a source depth ranging from 1 to 2000 m has a negligible influence on the electric parameters but a strong influence on bubble behavior, wherein both the maximum bubble radius and oscillation period are decreased. The collapse pulse vanishes when the source depth reaches 1000 m or deeper, and no bubble oscillation can be distinguished. The source level (evaluated by the expansion pulse) is also decreased as the source depth increases; moreover, the greater the discharge energy, the smaller the source level loss. The discharge energy per electrode should be greater than 20 J for the deep-towed plasma sparker, which can make the source level loss induced by hydrostatic pressure smaller than the transmission loss. The fast Fourier transform (FFT) results show that the dominant energy is around 20 kHz, which is mainly induced by the expansion pulse and its oscillation. According to the simulation results, the fundamental frequency of the acoustic waveform increases with source depth in accord with a log linear trend, and also reaches tens of kilohertz in deep water. So, before the development of deep-towed plasma sparker, a new technical solution will need to be developed to solve this problem.

Electrostatic precipitator (ESP) units have wide application in lots industries processes as gas filtration devices. Regarding their high efficiency, further improvement is still required. Wide ESP (plate-to-plate distance greater than 400 mm) is one of a promising way to improve existing ESP due to its ability to reduce equipment investment significantly. However, its large-scale application has been limited because it may potentially lead to collection efficiency reduction. This article focuses on the study of two major effects when several different electrode configurations are applied. The electrohydrodynamic (EHD) flow pattern inside ESP and particle collection efficiency were investigated by using particle image velocimetry (PIV) and electrical low pressure impactor (ELPI) respectively. Results suggested that the collection efficiency of wide ESP is rather complicated and highly related to inner gas flow pattern.

This paper describes an efficient, repetitive nanosecond pulsed power generator using a Transmission-Line-Transformer (TLT) based multiple-switch technology. Within this setup, a 10-stage TLT and ten high-pressure spark-gap switches are adopted. At the input side, ten spark-gap switches are interconnected in series via the TLT, so that all the spark-gap switches can be synchronized automatically. At the output side, all the stages of the TLT are connected in parallel, thus a low output impedance (5 ¿) is obtained, and a large output current is realized by adding the currents through all the switches. Experimental results show that 10 spark-gap switches can be synchronized within about 10 ns. The system has been successfully demonstrated at repetition rates up to 300 pps (Pulses Per Second). Pulses with a rise-time of about 11 ns, a pulse width of about 55 ns, an energy of 9-24 J per pulse, a peak power of 300-810 MW, a peak voltage of 40-77 kV, and a peak current of 6-11 kA have been achieved with an energy conversion efficiency of 93-98%

In this paper, the matching between a pulsed-power modulator and a streamer plasma reactor is discussed. The total process of energizing the reactor is divided into three different steps: before, during, and after plasma generation. Equivalent circuit models are used to obtain insight in the relevant mechanisms. Experiments are used to validate the results of the modeling. Based upon the results, design criteria are derived that can be used to design energy efficient streamer plasma systems.

A prototype of pulse-width-modulated plasma sound source with four independent outputs has been designed and tested, in which the main circuit includes a switched DC source for realizing effective capacitor charging and four independent discharging units for pulse forming. Each two outputs are isolated by high voltage diodes connected both at the two terminals of energy storage capacitors. The maximum energy per pulse per unit is in the range of 50 to 500 J, which means 200 to 2000J per pulse in total. The delay time between each two outputs can be changed from 5 to 200 μs by controlling the trigger signals of SCRs. The field test results show that larger delay time generates longer acoustic pulse width and smaller pulse amplitude. The spectrum results indicate the lower fundamental frequency for larger time interval.

For pulsed corona plasma applications, it becomes important to develop pilot systems with large average power and high-energy conversion efficiency. Since the beginning of 2000, we have been working on an industrial corona plasma system with tasks of 10-30 kW in average power and higher than 90% of total energy conversion efficiency. The pulsed-power source should have the following specifications: rise time of 10-25 ns, pulsewidth of 50-150 ns, pulse repetition rate of up to 1000 pulses per second, peak voltage pulse of 70 kV, peak current of 3.5 kA, dc bias voltage of 10-35 kV, and energy per pulse of up to 30 J. Sixteen parallel wire cylinder reactors are used to match the source. Gas and reactor temperatures can be controlled individually with water flow around the outside of those cylinders. The system is designed for gaseous oxidation and electrostatic dust precipitation. The system has been used for up to 17 kW in average power. This paper reports the system in detail, discusses issues related to the matching between the source and the reactor, and presents an example of industrial demonstrations on odor abatement at 1000 m3/h. Finally, this paper also gives a general guideline for design of corona plasma systems

In this paper a large-scale pulsed corona system is described in which pulse parameters such as pulse rise-time, peak voltage, pulse width and energy per pulse can be varied. The chemical efficiency of the system is determined by measuring ozone production. The temporal and spatial development of the discharge streamers is recorded using an ICCD camera with a shortest exposure time of 5 ns. The camera can be triggered at any moment starting from the time the voltage pulse arrives on the reactor, with an accuracy of less than 1 ns. Measurements were performed on an industrial size wire-plate reactor. The influence of pulse parameters like pulse voltage, DC bias voltage, rise-time and pulse repetition rate on plasma generation was monitored. It was observed that for higher peak voltages, an increase could be seen in the primary streamer velocity, the growth of the primary streamer diameter, the light intensity and the number of streamers per unit length of corona wire. No significant separate influence of DC bias voltage level was observed as long as the total reactor voltage (pulse + DC bias) remained constant and the DC bias voltage remained below the DC corona onset. For those situations in which the plasma appearance changed (e.g. different streamer velocity, diameter, intensity), a change in ozone production was also observed. The best chemical yields were obtained for low voltage (55 kV), low energetic pulses (0.4 J/pulse): 60 g (kWh)−1. For high voltage (86 kV), high energetic pulses (2.3 J/pulse) the yield decreased to approximately 45 g (kWh)−1, still a high value for ozone production in ambient air (RH 42%). The pulse repetition rate has no influence on plasma generation and on chemical efficiency up to 400 pulses per second.

Repetitive pulsed power techniques have enormous potential for a wide range of applications, such as nano-particle and hydrogen production, gas and water processing and sterilization, and generation of X-ray, EUV, and high-power acoustics. This paper presents the state of the art of our activities on repetitive ultra-short and microsecond pulsed power sources, pulsed thermal and streamer corona plasmas. Critical circuit elements are heavy-duty thyristors, transmission line transformers, and triggered spark-gap switches.

Pulsed plasma techniques serve a wide range of unconventional processes, such as gas and water processing, hydrogen production, and nanotechnology. Extending research on promising applications, such as pulsed corona processing, depends to a great extent on the availability of reliable, efficient and repetitive high-voltage pulsed power technology. Heavy-duty opening switches are the most critical components in high-voltage pulsed power systems with inductive energy storage. At the Ioffe Institute, an unconventional switching mechanism has been found, based on the fast recovery process in a diode. This article discusses the application of such a "drift-step-recovery-diode" for pulsed corona plasma generation. The principle of the diode-based nanosecond high-voltage generator will be discussed. The generator will be coupled to a corona reactor via a transmission-line transformer. The advantages of this concept, such as easy voltage transformation, load matching, switch protection and easy coupling with a dc bias voltage, will be discussed. The developed circuit is tested at both a resistive load and various corona reactors. Methods to optimize the energy transfer to a corona reactor have been evaluated. The impedance matching between the pulse generator and corona reactor can be significantly improved by using a dc bias voltage. At good matching, the corona energy increases and less energy reflects back to the generator. Matching can also be slightly improved by increasing the temperature in the corona reactor. More effective is to reduce the reactor pressure.

A triggered spark-gap switch together with a LCR trigger circuit has been developed in order to produce high levels of pulsed corona plasma at high-repetition rate and with a long lifetime. The spark-gap switch is flushed in air with a gas flow rate of up to 100 m 3 /h. Experiments are carried out up to 10 kW average output power, 12 J/pulse, and 900 pps (pulses per second).

We present our results on high-power repetitive pulse sources for continuous operation. Two 1-10-kW systems using advanced spark gap technology and a transmission line transformer have been tested for several hundred hours at a 60-MW pulse level. High reliability and above 90% overall efficiency are realized. Introducing a DC-bias, we designed a 30-kW hybrid system for industrial corona applications. The DC bias allows better matching, faster spark gap recovery, and higher power.

A new sparker system based on pulsed spark discharge with a single electrode has already been utilized for oceanic seismic exploration. However, the electro-acoustic energy efficiency of this system is lower than that of arc discharge based systems. A simple electrode structure was investigated in order to improve the electro-acoustic energy efficiency of the spark discharge. Experiments were carried out on an experimental setup with discharge in water driven by a pulsed power source. The voltage–current waveform, acoustic signal and bubble oscillation were recorded when the relative position of the electrode varied. The electro-acoustic energy efficiency was also calculated. The load voltage had a saltation for the invaginated electrode tip, namely an obvious voltage remnant. The more the electrode tip was invaginated, the larger the pressure peaks and first period became. The results show that electrode recessing into the insulating layer is a simple and effective way to improve the electro-acoustic energy efficiency from 2% to about 4%.

An intense luminescence flash can be induced during the collapse phase of bubbles generated by pulsed discharge in water. To gain insight into this special phenomenon, we experimentally investigated the optical characteristics and luminescence temperature inside collapsing bubbles. The duration of the luminescence flash generated by pulsed discharge was around tens of microseconds, which was confirmed by high-speed recording and the photodiode output, and the inception time of the luminescence flash was approximately 32.5 μs before the bubble collapsed to its minimum size. The temperatures of the luminescence flash at discharge energies of 25 and 30 J/pulse calculated according to the two-line radiance ratio method were 6673 and 6728 K, respectively.

In this article we discuss a 10 kW high-voltage pulse generator for producing corona-induced plasma. The generator mainly consists of a three-step resonant charging circuit switched by thyristors, a transmission line transformer, and a triggered spark-gap switch. Voltage pulses of 30–100 kV with a rise time of about 20 ns, a pulse duration of 50–250 ns, pulse repetition rate of 1–900 pulses per second, energy of up to 12 J/pulse, and an average power of up to 10 kW have been achieved with a total energy transfer efficiency of about 80%–90%. At each frequency, the deviation of the energy per pulse is around 1.0%. Moreover, the generator has been tested for more than 100 h for both industrial demonstrations and laboratory investigations at an average output power of 1–10 kW.

The paper discusses the relationship between corona discharge modes and pollution emission control. It also discusses the optimization of corona plasma reactor and high-voltage pulse generator.

This research concentrates on the application of pulsed corona discharges to crack heavy tar components (hydrocarbons) of thermally generated biogas into lighter ones. The method has the advantage that it can operate at a high temperature and be retrofitted to existing installations. The corona discharge is energized by 100-150-ns-wide voltage pulses (100 kV) at a continuous repetition rate of 600-1000 pulses per second. The power dissipated by the corona discharges is 1.5 kW average and 50 MW peak in each pulse. To be cracked by discharges, the hydrocarbons of the tar mixture need to be gaseous, and therefore, the corona reactor must operate at a high temperature. During this first phase of the program, the reactor runs at a modest temperature of up to 200/spl deg/C. The reactor is a 3-m-long stainless steel cylinder, 0.25-m diameter with a corona wire along the axis. The pressure is 1 atmosphere.

This letter presents an experimental observation of luminescence flash at the collapse phase of an oscillating bubble produced by a pulsed discharge in water. According to the high speed records, the flash lasts around tens of microseconds, which is much longer than the lifetime of laser and ultrasound induced luminescence flashes in nanoseconds and picoseconds, respectively. The pulse width of temperature waveform and minimum radius calculated at the collapse phase also show that the thermodynamic and dynamic signatures of the bubbles in this work are much larger than those of ultrasound and laser induced bubbles both in time and space scales. However, the peak temperature at the point of collapse is close to the results of ultrasound and laser induced bubbles. This result provides another possibility for accurate emission spectrum measurement other than amplification of the emitted light, such as increasing laser energy or sound energy or substituting water with sulphuric acid.

For using multi-switches in parallel, external forced trigger is usually required to synchronize all of them. This paper describes a generator with 20 spark-gap switches without using external triggers. The generator mainly consists of a 20-stage transmission line transformer (TLT), 20 energy storage capacitors, and 20 high-pressure spark-gap switches. At the input side of the TLT, all switches, capacitors and TLT cables are inter-connected to synchronize them automatically. All switches are made of three electrodes and are assembled in one 2 bar compact chamber. The TLT consists of 100 RG218 cables. The capacitors are charged up to 50 kV during 20–50 µs with a total energy per pulse of 140 J. As a result, the output peak power is estimated to be about 5 GW. At the output side of the TLT, a variety of output options are possible. For the present design, output peak voltage, current and impendence are in the range of 50–250 kV, 1–50 kA and 1–250 Ω, respectively. Up to 100 independent simultaneous outputs can also be realized under the same peak power.

Electrohydraulic discharge (EHD) can generate localized plasma emitting high intensity ultraviolet, and generating shock wave and active species. It is a multiple mode-of-action approach of sterilization and disinfection. Based on a homemade experimental setup, including all solid-switch capacitive pulsed power source and multi-electrode EHD reactor, we experimentally investigate the mechanism of EHD for chlorella inactivation. Typical energy range of the pulse power source is 5–500J with a repetition rate of 1–10Hz. Mono-current pulse wave is applied on the EHD reactor. We also design a multiple electrode configuration to increase the chlorella inactivation efficiency of over 90%. Besides, a monochromator combined with PMT and a high speed CCD camera system are used to detect the ultraviolet emission and pulsed plasma induced bubble growth process, respectively. After discharging, the concentration of chlorophyll measured by UV-visible spectrophotometer rises, which is caused by the broken up of chlorella cell.

This article presents our recent research on a new multiple-switch pulsed power technology. With this technique, multiple spark-gap switches can be synchronized automatically, like in Marx generator. However, in contrast to a Marx, Pulsed power can be produced either at a high voltage or with a large current, or it can be used to drive multiple independent loads simultaneously. It is promising for the development of an efficient large pulsed power supply with an increased lifetime. Through use of this technique, an efficient ten-switch prototype system has been successfully developed. Experimental results show that 10 spark-gap switches can be synchronized within about 10 ns. The system has been successfully demonstrated at repetition rates up to 300 pps (Pulses Per Second). Pulses with a rise-time of about 11 ns, a pulse width of about 55 ns, an energy of 9 J-24 J per pulse, a peak power of 300 MW-810 MW, a peak voltage of 40–77 kV, and a peak current of 6 kA-11 kA have been achieved with an energy conversion efficiency of 93%–98%.

Streamer plasmas can be used to remove pollutants from gases. As a result of the complex mechanisms involved during streamer initiation and propagation, the related knowledge is incomplete. During the last few years, extensive research was performed to determine typical streamer properties (such as velocity and dimensions) as a function of various pulse parameters. During the study, as presented in this paper, typical streamer velocities and diameters in the range of 105-106 m/s and 0.5-3.0 mm, respectively, were found.

Summary form only given. Long lifetime heavy duty (1 GW/1 kHz) pulsed power sources become more and more attractive for industrial applications such as gas/water cleaning, etc. One critical issue associated with such kind of source is the heavy switching duty. This paper describes a multiple switches based large scale prototype setup. It consists of ten high-pressure spark gap switches and a ten-stage transmission-line-transformer (TLT). By means of the TLT, the ten spark gap switches are able to share the heavy switching duty identically and simultaneously. At the switching side, the ten spark gap switches are interconnected via the TLT, and are put into one cavitv. At the output side the TLT is put in parallel, thus it has very low output impedance, i.e. 5 Omega. This prototype has been successfully demonstrated. In this paper, the development and testing results will be presented.

The Blumlein generator has been one of the most popular pulsed-power circuits. The pulse forming lines are charged simultaneously, and then discharged via a single switch, such as a spark gap. The generator can be used for single pulse or at a high repletion rate. However, for large pulsed power generation, one critical issue for such a single-switch based circuit topology is related to large switching currents. In this article, we propose a novel Blumlein circuit topology based on multiple switches. The pulsed forming lines are charged in parallel and then are synchronously commutated via multiple switches. No special synchronization trigger circuit is needed for the proposed circuit topology; this robust circuit topology is simple and very reliable. A prototype multiple-switch Blumlein generator with two spark-gap switches has been experimentally evaluated with both resistive and corona plasma loads. In terms of the switching currents, it is observed that the two switches can be synchronized within 2–3 ns. The energy conversion efficiencies are 82% and 76.8% for a matched resistive load and a plasma reactor, respectively.

A triggered multiple-gap spark gap switch has been developed and tested under atmosphere. By means of an LCR trigger circuit, the multiple-gap switch can be used very reliably. For the same switching voltage (35.5 kV), with increasing the number of gaps from 2 to 6, the switching current rise time is reduced from 13.5 to 6 ns, and the energy efficiency is increased from 87% to 92%. An eight-gap switch was also tested, and the switching current rise time is much smaller than the usable rise time of the current probe (3.5 ns). One interesting application of the multiple-gap switch is to improve the switching performance in the multiple-switch and transmission lines based pulsed power circuit. To verify this application, a six-gap switch was tested. In contrast to a single-gap switch, the output current rise time was improved from 21 to 11 ns by the six-gap switch.

This paper discusses some critical issues when developing industrial corona plasma systems. Based on streamer generation and interaction between power sources and reactors, the power conditions for streamer corona plasma generation can be basically divided into two groups, namely ultra-short and high-frequency oscillation DC/AC sources. Today, single- and multiple-switch circuit topologies become available to scale the ultra-short pulsed-power system up. DC/AC sources are being introduced into the market. With regard to processing conditions and costs of the power sources, this paper presents their advantages and drawbacks. In order to develop very large scale plasma systems, a new energization technique to integrate the power source and the reactor has been developed for energization of multiple reactors. Today, various options are available for industrial plasma applications, and the data available would be sufficient enough to carry out commercial-scale designs for both odour emission control and exhaust gas cleaning.

A transmission line transformer (TLT)-based multiple-switch circuit topology was recently proposed for pulsed-power generation. By means of a TLT, multiple spark-gap switches can be synchronized in a short time (ns). It is attractive to be used to design a long-lifetime repetitive large pulsed-power source (100 kW, 1 kHz) for various kinds of applications, such as corona plasma-induced gas cleaning. To gain insight into the synchronization principle and switching behavior of the individual switch, an equivalent circuit model was developed and an experimental setup with two spark-gap switches and a two-stage TLT has been constructed. We observed that in terms of switching currents, the two switches can be synchronized within 2–3 ns. The equivalent circuit model approximately fits the experimental results

A critical component for pulsed power sources is the switch. Main related issues are life-time, stability, cost, repetition rate, hold-off voltage and current ratings. This paper discusses these problems, presents a high repetition rate (1-1000 pps), large average power (1-10 kW), and long-life time spark-gap switch. Due to its coaxial design, the inductance of the switch is low, enabling fast switching, i.e. less than 5 ns voltage rise-time. The switch is used with a LCR trigger circuit. It is observed that the switch has a good stability, and its lifetime is estimated to be in the order of 4·1010 shots. (6 pages)

This paper discusses some critical issues of developing industrial streamer corona plasma systems for gas cleaning. Based on streamer generation and interaction between powar sources and reactors, two energization methods, namely hybrid-pulsed power source (HPPS) and DC-superimposed; high-frequency AC oscillation (DC/AC), were developed for industrial applications. As an example, a resalt of an industrial investigation on odor emission abatement is presented. The data available is sufficient enough for the commercial-scle design of a corona plasma system for DeNO x , DeSO 2 , deodorization and dust removal. We foresee that by retrofitting available ESPs, plasma-based gas-cleaning systems will be applied in the near future to simultaneously remove polluting gases, heavy metals, and particles.

This paper discusses novel pulsed circuit topologies for pulsed corona plasma generation. As a general principle, decrease of output impedance of pulsed power source leads to scale up of corona plasma power. DC superimposed pulse energization provides advantages of decrease of switching duty, increase of average power, and improvement of matching. Critical circuit elements include pulse forming networks (PFNs), triggered spark-gap switches and transmission line transformers (TLTs). Two main circuit topologies are based on single and multiple switches. The TLTs are used for both impedance matching and synchronization of the multiple switches.

Publisher Summary This chapter reviews the state-of-the-art of power conditions for streamer–corona plasma applications. It also discusses some critical issues when developing industrial systems. Based on streamer generation and interaction between power sources and reactors, the power conditions can be divided into two groups—namely, hybrid pulsed-power system (HPPS) and DC/AC. Today, single- and multiple-switch circuit topologies have become available to scaleup the HPPS system. DC/AC sources are being introduced into the market. Over the past 20 years, pulsed corona plasma system was expected to be integrated together with electrostatic precipitator for a simultaneous removal of dusts, SO 2 , NO x , and heavy metals from exhaust gases. The data available would be sufficient enough for commercial-scale design for either odor-emission control or exhaust-gas cleaning. By retrofitting available electrostatic precipitation (ESP), a plasma-based gas cleaning system to simultaneously remove polluting gases, heavy metals, and particles will be applied in the near future.

We are concentrating on the development of pulsed corona discharges to crack heavy tar components (hydrocarbons) into lighter ones. The method has the advantage that it can operate at a high temperature, and be retrofitted to existing installations. The corona discharge is energized by 100-150 ns wide voltage pulses (100 kV) at a continuous repetition rate of 600-1000 pulses per second. The power dissipated by the corona discharges is 1.5 kW average and 50 MW peak in each pulse. To be cracked by discharges, the hydrocarbons of the tar mixture need to be gaseous and therefore, the corona reactor must operate at a high temperature. In the first phase of the experiments the reactor will run at a modest temperature of 150/spl deg/C. The reactor is a 1-3 m long stainless steel cylinder, 0.25 m diameter with a corona wire along the axis. The pressure will be 1 atmosphere.

In this paper, the electrical characteristics of the positive pulsed corona in a wire-cylinder type reactor are investigated. The injected energy and charge into the discharging volume per pulse and per unit length of corona emitting wire are adopted to evaluate the power source, electric circuits, and the corona wire. The discharging current lasts from several hundred nanoseconds to a few microseconds. The current, power peak values, and the injected energy and charge per pulse per unit length of emitting wire can reach up to 60 A/m, 5 MW/m, 480 mJ/m, and 8 /spl mu/C/m, respectively. The energy conversion efficiency related to the output energy from the pulse forming capacitor and the energy delivered to the discharging volume can reach up to 90%. All results are obtained at room temperature and in air. >

This paper presents novel circuit topologies based on multiple switches and transmission line transformers (TLTs). The proposed pulsed power circuit topologies produce high levels of pulsed power either at higher voltages or at higher currents. The TLTs are used for impedance matching and synchronization of multiple switches. This paper also presents our first experimental results to verify the circuit topologies.

This paper discusses a high-voltage pulse generator for producing corona plasma. The generator consists of three resonant charging circuits, a transmission line transformer, and a triggered spark-gap switch. Voltage pulses in the order of 30-100 kV with a rise time of 10-20 ns, a pulse duration of 100-200 ns, a pulse repetition rate of 1-900 pps, an energy per pulse of 0.5-12 J, and the average power of up to 10 kW have been achieved with total energy conversion efficiency of 80%-90%. Moreover, the system has been used in four industrial demonstrations on volatile organic compounds removal, odor emission control, and biogas conditioning.

The authors present their recent results on high power repetitive pulse sources for continuous operation. Two 1-10 kW systems using spark gap technology have been tested for several hundred hours at a 60 MW pulse level. High reliability and above 90% overall efficiency are realized. Introducing a DC-bias, they designed a 30 kW hybrid system for industrial corona applications. The DC bias allows better matching, faster spark gap recovery and higher power.

With regard to pollution emission control, there are two critical issues that are blocking corona plasma industrial applications. The first one is the capacity of repetitive pulse power techniques, and the second is the total energy consumption. Worldwide research and development on industrial corona plasma systems were very much dependant on individual empirical experience. Systems were not designed at an optimized operation. To the authors' knowledge, no group has tried to bridge the gap between the fundamental characteristics of corona plasma, chemical reactions, pulsed power generators and the corona plasma reactor. This paper discusses their recent work in developing industrial corona plasma systems for industrial applications. (4 pages)

This paper gives an overview of the Eindhoven pulsed corona pilot unit and discusses results from laboratory and on-site tests on the cleaning of biogas. The unit can operate under polluted conditions and can easily be integrated in various industrial processes. The corona discharges are energized by 100-200 ns wide voltage pulses (100 kV) at a repetition rate of maximum 1000 pulses-per-second. The power dissipated by the corona discharges is typically 50 MW peak in each pulse, the energy per pulse is max. 3 J. It is shown that: (i) the pilot corona unit has proven to be reliable under laboratory conditions and during industrial on-site tests; (ii) tar components in biogas can be removed at energy densities between 39 and 154 J/L, depending on the component type; and (iii) heavy tar components in industrial biogas are converted at energy densities of 148-161 J/L.

Streamer properties such as their velocity, diameter, intensity and density, can be obtained by analysis of temporal and spatial resolved ICCD imaging. In this paper, experimental results on streamer generation and propagation as a function of several high-voltage pulse and reactor parameters are described. Experiments were performed on a large scale wire–plate reactor in ambient air. The set-up allows for independent variation of the parameters over wide ranges. The minimum gate time of the ICCD camera is 5 ns, allowing for a high temporal resolution. The camera can be triggered with a precision of 1 ns. Both negative and positive polarity pulses are investigated. The most important conclusions are as follows. (1) The streamer velocity ((0.5–2.5) × 106 m s-1) increases if the applied electric field and/or the voltage rise rate is increased. (2) The same is true regarding the velocity ((0.2–1.2) × 105 m s-1) with which the streamer diameter (0.7–3.0 mm) increases during propagation. (3) Typical properties (velocity, diameter, etc) of negative and positive polarity streamers vary less than 25%, especially when the applied electric field is high. (4) As long as the dc bias voltage is below the dc corona onset value it does not have a separate effect on the visual streamer properties. Only the total voltage (peak voltage + dc) is of importance. (5) A simple model was used to determine the electric field in the secondary streamer channel. It was found that in the light emitting part of the secondary streamer the electric field is approximately 21.5 kV cm-1. In the remainder (dark part) of the channel the electric field is around 6.5 kV cm-1. This paper shows mainly experimental findings. Not all observed relations and phenomena could be explained. This is partly caused by the fact that current theoretical and numerical models are not yet able to describe the experimental situation as used during this study.

High-power semiconductor opening switches are the most critical components in nanosecond pulsed power systems with inductive energy storage. For industrial applications, such as pulsed corona processing, a long lifetime, high repetition rate, high efficiency and high reliability are required. At the Ioffe Institute, an unconventional switching mechanism has been found, based on the very fast recovery process in a silicon p/sup +/p'nn/sup +/ diode. This paper describes the application of such a 'drift-step recovery diode' for high-power pulsed corona plasma generation. The principle of the diode-based nanosecond pulse generator is discussed in detail. The generator is coupled to a wire-plate corona reactor via a transmission-line-transformer, which has the following advantages: (i) increase of the output voltage, (ii) impedance transformation to improve the matching with the reactor, (iii) protection of the switch against reflections and mismatches, (iv) limitation of the switch current during short-circuit or breakdowns, and (v) easy coupling with a DC-bias voltage. The developed circuit has been tested at both a matched resistive load and a wire-plate pulsed corona reactor. Various ways to improve the matching with the reactor have been evaluated. We found that superposition of the pulse on a DC-bias voltage gives the best result. For example: without DC-bias, more than 50% of the energy-per-pulse reflects back to the source. However, the reflected energy could be reduced to

In this paper, the effects of the applied voltage modes on the positive corona discharge morphology and NO removal characteristics from air streams are experimentally investigated. By using a DC superimposed high frequency AC power supply (10-60 kHz), a uniform streamer corona can be generated, which is also less sensitive to electrode mis-arrangements. Hermstein glow can he transferred to streamer corona if the peak-to-peak voltage is larger than 1.0 kV at the voltage change rate of 0.2 kV//spl mu/s. A significant amount of NO removal is observed under streamer corona. For the Hermstein glow, the removal is negligible. Moreover, the basic principle for designing AC/DC energized streamer corona is also presented in this paper.

Transmission line transformers (TLTs) are usually used for impedance match. In this paper, we present a novel circuit topology based on multiple switches and TLTs for both the impedance match and synchronization of multiple switches. In contrast to the Marx pulse generator, our proposed pulsed power systems produce high levels of pulsed power not only at higher voltages but also at higher currents.