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Surface-dielectric-barrier discharges (SDBDs) can be applied for a wide range of applications, such as ozone generation, surface treatments, and air-pollutants removal. An important advantage of the SDBD plasma is that relatively low high-voltage (HV) pulses (<10 kV) are needed to generate the plasma. They are effective in removing a wide range of pollutants. Despite their high energy efficiency, plasma decomposition generally results in the reaction by-products and the formation of ozone and nitrogen oxides. This drawback can be overcome by combining the SDBD plasma with catalysis. In this paper, a novel plasma-catalytic topology is proposed for the purpose of on-demand air purification. The main idea of the plasma-catalytic reactor is that both the plasma and the catalytic function are configured as planar structures which are positioned in parallel to each other. The plasma is generated along a planar dielectric structure. We use an SDBD for this purpose. Plates coated with the catalytic material are positioned in parallel to the SDBD plates. The air to be treated is flushed along the plates. There are no restrictions to the type or combination of catalysts used; the catalysts and their specifications can be chosen freely. We have developed a modular plasma-catalytic SDBD reactor to handle large flows, which can be scaled up and scaled down easily. To energize the plasma, an SDBD power modulator was developed. The modulator is able to generate a HV output pulse over an SDBD plasma load with a magnitude adjustable from 4.78 to 6.95 kV. The pulse rise time is about $1~\mu \text{s}$ and its ramp is about 6 kV/ $\mu \text{s}$. The energy per pulse then ranges from 1.1 to 17.4 mJ. The output power can be adjusted up to 48 W at a repetition rate of 5.5 kHz. The maximum possible pulse repetition rate is 22 kHz, but it is limited to 5.5 kHz due to the limited current rating of the available dc power supply. The total energy efficiency of the power modulator is 68%. A single modulator unit can power up to two SDBD reactor plates of $100\times 150$ mm size, having plasma at both sides of the plate. The operational efficiency of the developed SDBD catalytic reactor has been investigated by studying the removal of NOx and ethylene. The removal efficiency of NOx and ethylene is determined as a function of energy density and operational parameters, such as their initial concentrations and the gas flow rate. [ABSTRACT FROM AUTHOR]

Water can be activated by applying plasma to water, for instance, by creating plasma inside (bubbles in) the water, or along a water surface. Plasma-activated water (PAW) typically contains hydrogen peroxide, nitrates, nitrites, and peroxynitrite, and typically has a pH ranging from 2 to 4. The components of PAW and the low pH have proven synergistic antimicrobial effects against bacteria, biofilms, yeasts, and other microorganisms. This paper describes a power modulator and a plasma reactor system for high-yield production of PAW at high production rate. A compact and solid-state dual resonant system has been realized and successfully demonstrated for industrial PAW production. The system generates up to 80-kV (theoretical 120 kV is possible) dual-resonant high-voltage pulses with an oscillation frequency up to 2 MHz, pulse repetition rate > 20 kHz, and an average power of 800-W continuous. In addition to the power modulator, the PAW production system consists of a transient arc plasma reactor and a loop system. Depending on the application, the system is able to activate 10–100 L/h. The disinfecting properties of the PAW production system have been verified by experiments on the reduction of Staphylococcus Epidermidis. Directly after its production, the log reduction of S. Epidermidis can be as high as >8 log. During a period of at least 40 min after its production, the PAW has “mild” disinfecting properties, being able to deactivate S. Epidermidis by 3–4.1 log. [ABSTRACT FROM PUBLISHER]

In this paper, we describe a novel multiple-switch pulsed-power technology. The basic idea is that the heavy switching duty is shared by multiple switches. The multiple switches are interconnected via a transmission line transformer, in such a way that all switches can be synchronized automatically and no special external synchronization trigger circuit is required. It can produce either exponential or square pulses, with various voltage and current gains and with a high degree of freedom in choosing output impedances. The topology has been implemented on a prototype with ten spark-gap switches. Pulses with a rise time of 10 ns, a width of 55 ns, a peak power up to 810 MW, a peak voltage of 77 kV, and a peak current of 11 kA have been achieved at a repetition rate of 300 pps. The energy efficiency of the circuit is about 93%. In addition to spark gaps, any overvoltage-controlled switch can be applied in this topology. As an example, we demonstrate the synchronous switching of multiple thyristor switches for current multiplication. The proposed multiple-switch topology can also be applied in a Blumlein configuration for an inductive voltage adder and a linear transformer driver. [ABSTRACT FROM AUTHOR]

Gas-cleaning techniques using nonthermal plasma are slowly introduced into industry nowadays. In this paper, we present a novel power modulator for the efficient generation of large-volume corona plasma. No expensive high-voltage components are required. Switching is done at an intermediate voltage level of 1 kV with standard thyristors. Detailed investigations on the modulator and a wire-plate corona reactor will be presented. In a systematic way, modulator parameters have been varied. Furthermore, reactor parameters, such as the number of electrodes and the electrode-plate distance, have been varied systematically. The yield of 0 radicals was determined from the measured ozone concentrations at the exhaust of the reactor. [ABSTRACT FROM AUTHOR]

Industrial application of nanosecond pulsed corona technology for air purification requires high volume, high-power plasma reactors. Cylinder-wire type reactors require multiple cylinders to meet these demands. Variations in pulse waveforms per cylinder, misalignment of wires, and jitter in streamer inception could lead to an uneven energy distribution over the cylinders. Nanosecond ICCD imaging is applied to a semi-industrial scale pulsed corona reactor to study streamer inception and propagation of the streamer plasma simultaneously in 16 cylinders. The images show streamer inception of all cylinders within 9 ns. Streamer propagation and intensities are very similar for all cylinders. [ABSTRACT FROM PUBLISHER]

Industrial application of nanosecond pulsed corona technology for air purification requires high volume, high power plasma reactors. Cylinder-wire type reactors require multiple cylinders or very long reactors to meet these demands. In this article, we focus on the characterization of a pulsed corona plasma in a long (4.5 m) plasma reactor. The reactor cylinder acts as a coaxial transmission line wherein high-voltage pulses propagate with close to the speed of light. Interactions between plasma generation and reflection behavior inside the reactor are expected and therefore investigated. A 4.5-m-long corona reactor is constructed and equipped with voltage and current sensors at multiple positions along the reactor length. A lumped element SPICE model is developed to simulate the reflection behavior. Strong reflections at the end of the reactor are observed for pulse rise times which are shorter than the transient time of the reactor. Plasma generation and energy distribution in the reactor, as well as impedance matching between source and reactor, are affected by these reflections. We investigate the role of the input voltage and rise time and analyze the electrical characterization, impedance characterization, and reactor efficiency. [ABSTRACT FROM AUTHOR]

In this paper, we present the final implementation of our 0–50-kV picosecond rise time 0.5–10-ns pulse generator. The pulse generator will be used in future work to generate a (sub)-nanosecond streamer plasma for air purification research. The pulse generator is a single-line pulse generator with an oil spark-gap (SG), which generates 0.5–10-ns pulses with a 200-ps rise time and can operate at repetition rates of over 1 kHz into a 50- \Omega load. It is an improvement over the first implementation of our nanosecond pulse generator that we designed and verified experimentally in previous work. In this paper, we evaluate the performance of the final design. Furthermore, we present 3-D electromagnetic simulations of the nanosecond pulse generator and show that the simulations are in good agreement with the measurements. A variation in pulse duration from 0.5 to 10 ns is possible and the output pulses are square shaped without the large plateau behind the main pulse that was present in the pulses from the first implementation of the nanosecond pulse generator. At high voltages, the pulse top becomes less flat due to a time-dependent mismatch in the spark-gap. Furthermore, investigation of electrode erosion of the oil spark-gap shows that the erosion rate of the electrodes is in the range of 200–600 \mu \mathrmcm^3 \cdot \mathrmC^-1 for the electrode that is mainly the cathode and 100–300 \mu \mathrm{cm}^{3} \cdot \mathrm{C}^{-1}$ for the electrode that is mainly the anode, respectively. This is almost an order of magnitude higher than most gas spark-gap studies show for brass electrodes. Therefore, electrode erosion in the oil spark-gap will be a limiting factor on the lifetime of the system. We designed a new electrode with a stainless steel head to increase this lifetime. [ABSTRACT FROM PUBLISHER]

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 as, pulsewidth of 50-150 as, 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. [ABSTRACT FROM AUTHOR]

Presents a study which described the high-power repetitive pulse generation technology sources for power transmission. Reliability of the generators; Electric generation procedures in high-voltage circuits; Performance of a spark-gap switch.

This paper introduces the work undertaken to reliably use off-the-shelf differentiating voltage probes attached to coaxial transmission lines. The results obtained prove that indeed such probes are a valid and simple instrument for measuring nanosecond and subnanosecond voltage impulses. As a bonus, this paper also highlighted an important challenging phenomenon that appears whenever an attempt is made to measure fast voltage impulses with a differentiating probe positioned too close to the closing switch of a pulse forming line generator. [ABSTRACT FROM AUTHOR]

A compact magnetic pulse compression (MPC) topology with only two magnetic cores and a continuous repetition rate of 20 kHz is presented. The demand for higher average output powers of pulsed power systems can be achieved by an increase of the pulse rate frequency (PRF). The PRF is often limited by the switching speed or recovery of the main switch and also the complex behavior of the magnetic materials. With the advent of insulated gate bipolar transistors and the nanocrystalline soft magnetic material, PRFs of tens of kilohertz are feasible if a suitable MPC topology is applied. The presented MPC is based on an existing topology that has been significantly improved to enable high-frequency pulse generation. A design method using 3-D magnetostatic and transient magnetic simulations is introduced to enable optimization of the magnetic switching components. A 20 kHz, 60 kV, and 52 ns full width at half maximum (FWHM) MPC generator is designed, built, and tested for a $100~\Omega $ load. Simulations suggest that a PRF up to 50 kHz is achievable, but continuous operation will likely be limited by thermal management. [ABSTRACT FROM AUTHOR]

By the application of pulsed corona discharges in a carbon dioxide atmosphere over a water film, the formation of methane has been observed under mild reaction conditions, without the application of a dedicated catalyst. Methane is proposed to result from hydrogenation of carbon monoxide and possibly also carbon dioxide at the NiCr alloy high-voltage electrodes, the precursors being formed by plasma-induced decomposition of carbon dioxide and water. Applying energy densities up to 46 kJ/L has yielded methane levels of approximately 440 ppm at a production efficiency of 398 pmol/J. The observed plasma chemistry occurs at ambient pressure, while gas phase heat is cooled away by the water film, the latter being thermally nearly unaffected. [ABSTRACT FROM PUBLISHER]

Matching a pulse source to a plasma load is one of the main challenges to overcome to maximize the full potential of pulsed discharges for air purification applications. In this paper, we propose experiments that investigate the matching of a nanosecond pulse source to a corona plasma reactor that is aided by a high voltage on a tertiary electrode. The corona plasma reactor is a wire-cylinder reactor, as is commonly used in pulsed power plasmas. A tertiary electrode is situated on a dielectric layer against the cylinder of the reactor. On this tertiary electrode, we can apply a pulsed RF or dc voltage to provide an additional plasma and bias voltage in the corona plasma reactor. The pulse source that energizes the main corona plasma is the nanosecond pulse source of Kumamoto University, Japan. In this paper, we show the results of experiments with a dc voltage on the tertiary electrode. We varied the amplitude of the pulsed voltage as well as the dc voltage and investigated their effect on the corona plasma with energy and ozone measurements. The results show that the matching to the reactor increases with increasing dc voltages. However, the matching effect decreases with higher repetition rates. Furthermore, ozone measurements confirmed that a better matching also results in a higher ozone production, but in a lower ozone production energy yield. [ABSTRACT FROM PUBLISHER]

In this paper, a compact circuit topology is presented for pulsed power generation with a semiconductor opening switch (SOS). Such circuits require the generation of a fast forward current through the diode, followed by a reverse current that activates the recovery process. In general, magnetic switches are used to switch the diode current from forward to reverse. Therefore, adjustment of the output voltage of an SOS pulser is difficult. This paper introduces a circuit that allows an adjustable output voltage of the pulser. A solution is realized with a premagnetizing circuit on the primary winding of a pulse transformer (PT), so that a third winding is not needed. The primary capacitor voltage can now be varied while maintaining proper saturation of the PT. [ABSTRACT FROM PUBLISHER]

In this paper, we present the first implementation of our 0–60-kV picosecond rise time 1–10-ns pulse generator. The pulse generator will be used in future work to generate a (sub-)nanosecond streamer plasma for air purification research. The first implementation of the pulse generator is a single-line pulse generator with an oil spark-gap, which generates 5 ns pulses with a 200 picosecond rise time and can operate at repetition rates of over 1 kHz into a 50 \Omega load. In this paper, we evaluate its performance and describe how we measure the very short pulses with an integrated and calibrated D-dot sensor. Furthermore, we present 3-D EM simulations of the 5 ns pulse generator and show that the simulations are in good agreement with the measurements. We previously described methods to flexibly vary the pulse duration of the pulse source by (artificially) changing the length of the pulse forming line (PFL). Here, we test these methods and find that changing the length of the outer conductor of the PFL and inserting magnetic material at the end of the PFL is a suitable method to change the pulse duration. Finally, we measure the breakdown voltages of the oil spark-gap and discover that higher pulse repetition rates are possible at higher oil pressures and smaller gap distances. [ABSTRACT FROM AUTHOR]

In this paper, we present a design approach of a single-line nanosecond pulse source by using a thorough analytical investigation and by verification with CST MICROWAVE STUDIO. Through detailed analysis and simulation, we arrive at a design for a fast rise time variable pulse duration pulse source which is able to produce 1–10 ns pulses with tens of kilovolt amplitude and less than hundreds of picoseconds rise time. This variable pulse duration is achieved by using telescopic antennas and ferrites in the pulse-forming line of the pulse source. Finally, we present a first implementation of a 5-ns pulse source with an oil spark gap for fast switching. [ABSTRACT FROM AUTHOR]

In this paper, we present a solid state 0–120 kV microsecond pulse charger for our nanosecond pulse generator refid="ref1"/. The pulse-forming line (PFL) of our nanosecond pulse generator must be charged with microsecond pulses to prevent pre-firing of its oil spark gap. The pulse charger consists of two identical compact pulse charger modules with integrated electronics. The electronic circuits are mounted on a compact printed circuit board and consist mainly of a number of parallel connected insulated-gate bipolar transistors (IGBTs) that switch a primary capacitor bank into a pulse transformer. Each pulse charger module can generate 60 kV microsecond pulses at 1 kHz repetition rate. When connected in series, they are able to deliver up to 120 kV into a 100 pF load. This 100 pF load is the PFL of our nanosecond pulse generator at its maximum length of 1 m. The pulse charger is able to operate in a harsh electromagnetic interference environment as a result of its compact layout and optical triggering of the IGBTs. [ABSTRACT FROM PUBLISHER]

Although pulsed corona technology for air purification is widely investigated by the lab experiments, large-scale application has yet to be proven. Industrial systems require large flow handling and thus, high corona power. An autonomous semi-industrial scale pilot wire-cylinder type corona reactor has been constructed for air purification demonstrations. The reactor is powered by a 10-kW spark gap-based pulsed power supply, capable of generating 60-kV 100-ns wide pulses with 1-kHz repetition rate. The pulses are optionally superimposed on a 0–30-kV dc bias to enable electrostatic precipitation. The system has been successfully applied during several field and lab experiments. Conversion data as a function of energy density are presented for NOx, NH3, H2S, toluene, limonene, and fine dust removal. The system proves feasibility of large-scale air purification by pulsed corona. [ABSTRACT FROM AUTHOR]

Nanosecond pulsed electric fields (nsPEFs) have been found to induce either cell death or cellular changes to a wide range of cells. However, for the current way of delivering the electric field to the cell (by electrodes contacting the cell culture), cells need to be placed in low-conductivity media unsuitable for maintaining cell growth. Here, we present a novel device for noncontact exposure of cells to nsPEF. The cells can be treated in their native cell culture medium and culture vessel. A single-turn loop antenna is designed that can contain a cylindrical cell culture vessel. The electric field within the loop is created by magnetic induction and depends on the time derivative of the current through the loop. To generate the required field strength of 10 kV/cm with duration of \sim6~ns, a fast high-voltage, low-inductance RLC circuit is developed. A fast rising current of 100 A/ns is achieved in this circuit. The developed method is used for the nsPEF treatment of either adherent [Chinese hamster ovary (CHO-K)] or suspension (CHO-S) cells in their native culture medium and vessel. We discovered that nsPEF enhances cell proliferation. This novel effect of nsPEF has significant applicability in improving the yield and lowering the cost of cell cultures and bioreactors. [ABSTRACT FROM AUTHOR]

In this paper, pulsed-power technology was applied to plasma printing, which is a maskless plasma patterning solution that is being developed for the fabrication process of printed electronics. A high-voltage pulse source was developed and applied to a high-speed plasma printer to improve the speed of plasma printing. Experiments on plasma printing were used to compare the performance of the pulse source with the currently used alternating-current source. From plasma experiments, an electrical plasma model was derived for the plasma printer. Different parameters were investigated, such as the plasma energy as a function of gap distance, applied voltage, and the total amount of plasma that was generated. From these experiments, a connection was made between the plasma energy and the print effectiveness to arrive at optimal parameter values for fast plasma printing. It was concluded that higher plasma energy leads to higher print effectiveness, which leads to an increase in plasma print speed by a factor of 10 when using the pulse source. Moreover, scaling the PlasmaPint technology to reach higher print speeds is achievable by using more print heads or print heads with more tips. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

A spark discharge generated by a 5-ns high-voltage pulse of 21 kV with a rise-time of 200 ps in a 1-mm gap between half-sphere steel electrodes was investigated in N2–O2 gas mixtures at atmospheric pressure. We compared short exposure and long exposure ICCD images of the discharge, as well as single shot images and accumulated images. At high repetition rates more discharge channels form due to higher background ionization. The influence of the O2 concentration between 0.1 and 10 vol% O2 in N2 is insignificant. [ABSTRACT FROM PUBLISHER]

Dielectric barrier discharges generated in a coaxial tip to cylinder configuration at atmospheric pressure by a 5-ns high-voltage pulse with sub-ns rise time were investigated with a fast intensified CCD camera. Different discharge characteristics were found for the breakdown during the pulse itself and in the subsequent reflections of the pulse. There is a transition from a complete diffuse regime to a breakdown in constricted channels, which finally cross the whole gap. [ABSTRACT FROM PUBLISHER]

Surface dielectric barrier discharges (SDBDs) provide homogeneous plasma over a large surface area. This allows surface treatments of foils, textiles, or fibers. In this paper, we present results of a study to characterize the pulsed performance of SDBD by fast imaging of the plasma development. [ABSTRACT FROM AUTHOR]

High current sparks are created in argon and air using a high-voltage pulse of 16-ns duration. Shadowgraphy is applied to image density fluctuations. Shock waves become visible \sim100 ns after the pulse; they expand with a velocity somewhat higher than the speed of sound. The filamentary core of the discharge shows heating that diffuses outward slowly and develops into microturbulences. They remain visible up to 3 ms. In air, the current remains lower than that in argon, and shocks only emerge from the electrodes. No indication of absorption is found; probably gas heating is observed near the electrodes. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]