Nanosecond Pulse Power Supply Research Articles

Air disinfection by nanosecond pulsed DBD plasma

Atmospheric pressure dielectric barrier discharge (DBD) plasma is an emerging and promising technique for air disinfection in public environments. Power supply is a crucial factor but it remains unclear about its impacts on the air disinfection performance of plasmas. In this work, a nanosecond (ns) pulsed power supply was applied to drive an in-duct grating-like DBD array to achieve fast single-pass air disinfection. The influence of pulse parameters and environmental factors on both the discharge characteristics and the single-pass bacterial inactivation efficiency were uncovered. At a close relative humidity (RH) level, the efficiency was dominated by the discharge power, namely, specific input energy could serve as the disinfection dose. A higher frequency, shorter pulse rising time, and suitable pulse width are preferred to obtain a higher Z value. The pulsed source was not notably superior to an alternating current source, or even worse at a low voltage frequency at the same discharge power. Airflow humidity was a predominant factor to improve the efficiency and a single-pass efficiency of ∼ 99% and a Z value of 2.2 L/J were achieved under an optimal RH of 50%–60%. This work provides fundamental knowledge of ns-pulsed DBD on discharge characteristics and air disinfection behaviors.

Effectiveness of Noble Gas Addition for Plasma Synthesis of Ammonia in a Dielectric Barrier Discharge Reactor

Non-thermal plasma driven ammonia synthesis has great potential for future industrial applications due to its low theoretical energy requirements. To achieve technological advancement and environmental sustainability, it is crucial to boost the energy yield in plasma-assisted ammonia synthesis. Therefore, optimizing energy transfer and utilization are key strategies for enhancing energy efficiency. In this study, dielectric barrier discharge driven by a nanosecond pulsed power supply is used to enhance plasma-assisted ammonia synthesis by controlling the energy transfer through the addition of noble gases. It was found that the addition of noble gases changed the plasma characteristics, significantly improved the uniformity of the discharge, and achieved a high energy yield for ammonia synthesis. The effects of additive amounts of argon (Ar) and helium (He), as well as the pulse parameters including the pulse voltage, pulse repetition frequency, pulse width, and pulse rise time on the energy yield of ammonia synthesis are discussed. The inclusion of noble gases expanded the pathway for gas-phase reactions, with the active components of critical reactions examined through optical emission spectra. This analysis revealed an increased presence of both N2+ and N2* particles in the reaction’s rate-limiting step, attributed to the addition of noble gases. Finally, a zero-dimensional (0D) plasma chemical kinetic model was established to investigate the influence of Ar addition on the reaction mechanism of ammonia synthesis.

A nanosecond pulse power supply for grid-controlled electron gun used in HALF

Hefei Advanced Light Facility (HALF) uses a grid-controlled thermionic cathode gun as its electron source of the linear accelerator. The nanosecond grid-controlled power supply is an important part of the electron gun power supply system, and its performance will affect the quality of the beam. To achieve the requirements of the electron gun for nanosecond pulse power supply, we use the series-parallel multi-stage avalanche transistor scheme to achieve nanosecond fast pulse output. The test results show that the power supply not only can meet the requirements of HALF for its electron gun but also have good waveform repeatability and amplitude stability.

Removal of toluene via non-thermal plasma generated by applying rare-earth tungsten electrode and nanosecond pulsed power supply.

The objective of this investigation is to evaluate the characteristics associated with degradation of toluene through the utilization of non-thermal plasma (NTP) generated via application of a low-work-function electrode and nanosecond pulsed power supply. Initially, a comparative analysis is made between toluene removal efficiency utilizing the low-work-function electrode and that achieved with the conventional stainless-steel electrode. The outcomes demonstrate that NTP generated by the low-work-function electrode exhibits markedly superior removal efficiency for toluene in comparison to the stainless-steel electrode operating at the same voltage. Subsequently, the impacts of voltage, pulse frequency, and initial concentration of toluene on the removal efficiency and production of by-products are investigated. It is found that as the voltage and frequency increase, the removal efficiency also increases, and a maximum toluene removal efficiency of 87.2% is achieved at a voltage of 12,000V and pulse frequency of 2000Hz. The removal efficiency first increases and then decreases with increasing toluene initial concentration. The investigation also finds that energy yield is negatively correlated with voltage and pulse frequency and positively correlated with the initial concentration. Finally, the reaction products were subjected to quantitative analysis using GC-MS. Based on the analysis results, potential reaction pathways are inferred.

Study of coaxial-dual-gap dielectric barrier discharge based on capillary: discharge characteristics and Escherichia Coli decontamination.

The medical capillary catheters occupy a high proportion of medical diagnosis, monitoring and treatment devices, and will cause serious cross-infection without being disinfected adequately. This paper presents a new plasma structure for efficient inactivation of harmful microorganisms in medical capillaries. An innovative coaxial-dual-gap dielectric barrier discharge (CDG-DBD) reactor powered by nanosecond-pulsed power supply was designed for disinfection of Escherichia Coli (E. coli) inside and outside medical capillary catheters in this work. Atmospheric helium plasma (AHP) and atmospheric air plasma (AAP) were successfully obtained inside and outside capillary (0.6mm inner diameter and 1.0mm outer diameter), respectively. The electrical and optical characteristics of AHP and AAP were investigated. As the threshold of applied voltage amplitude (Uamp) was below 7.0kV, only one helium glow discharge was generated inside the capillary at the rising and falling stages of pulse voltage. As the Uamp exceeded the threshold, two helium glow discharges were generated that further caused generation of air discharge. Under the Uamp of 9.0kV, the production of AHP lowered the breakdown voltage in air gap, resulting in the formation of high-volume and uniform AAP, which was conducive to the realization of full inactivation. The inactivation rates of E. coli reached 98.13% and 99.99% by 2min AHP and 0.5min AAP treatment, respectively. The electrical stress of AHP and the reactive oxygen and nitrogen species (RONS) produced by AAP were contributed to the inactivation of E. coli. The results of SEM show that plasma treatment can destroy the cellular structure of E.coli.

All-Solid-State Nanosecond Pulse Power Supply Based on BLTs and Pulse Transformer for DBD Application

Nanosecond(ns) pulses have been proven to drive DBD more efficiently. However, since the DBD device is a capacitive load, which will cause distortions in the pulse waveform of the power supply. To maintain the ns pulse waveform, a parallel resistor is normally set to overcome the influence of DBD loads in the traditional methods, which will cause extra energy loss. This paper proposed a bipolar ns pulse power supply for DBD based on Blumlein transmission lines (BLTs) and pulse transformer. It does not need to set a parallel resistor and can adapt well to the load characteristics of DBD. This topology can output bipolar ns pulses on DBD loads with a rise time of 100 ns, a pulse width of 300 ns, an adjustable amplitude of 0-5 kV, and a maximum repetition frequency of 20 kHz. In this context, the operating characteristics of the circuit are derived based on the lossless transmission line model and Laplace transform, and then the correctness of the theoretical derivation is verified by the prototype. The results showed that the proposed ns power supply can drive DBD loads with adjustable output voltage amplitude and frequency.

Nanosecond-pulsed plasma jet in air and air/helium mixtures: Plasma properties and anticancer effect

Nanosecond-pulse power has the characteristics of quickly increasing applied power, short pulse width, and considerably high-energy electrons. In this study, we investigated the different air/helium mixture ratios of nanosecond-pulsed-power-driven plasma jet discharge characteristics and the physicochemical properties of the gaseous and aqueous phases. Results showed that the length and luminescence intensity of the plasma increased with decreasing air ratio. Notably, there is a maximum inflection point in N2O5 of Fourier transform infrared spectrometry detection and concentration of H2O2 at 70% air ratio. Furthermore, we used drug-resistant ovarian cancer cells (A2780/ADR) as a model to detect the anticancer effect, with the results indicating that 70% air ratio is the best condition to inhibit cell growth and induce cell apoptosis. Our research indicates that the air discharge driven by a nanosecond-pulse power supply has potential application in an ovarian cancer drug-resistant tumor cell therapy.

A unipolar compact nanosecond pulsed power supply with high power factor for dielectric barrier discharge applications.

A high voltage with a very short duration and fast rising time is beneficial to generate uniform and diffuse plasma in dielectric barrier discharge (DBD) loads, and a power supply with a high power factor (PF) can reduce the impact on the power grid. According to two requirements, a unipolar high voltage pulsed power supply with power factor correction (PFC) is proposed in this paper. The power supply consists of a unipolar pulse high voltage generating unit, a PFC unit, and a driving circuit. By introducing a feedback clamping diode and a reverse current blocking diode in a flyback converter, repetitive nanosecond pulses are generated in the unipolar pulse high voltage generating unit. Because a discontinuous current mode strategy is adopted in the PFC unit and the driving signal is shared by the two units, a compact structure of the power supply is achieved, and a high PF is obtained. To validate the proposed pulsed power supply, an experimental setup is built for a DBD excimer lamp. The results show that the proposed power supply has the capability of not only providing a unipolar nanosecond pulse high voltage for the DBD excimer lamp but also achieving PF close to 1 and total harmonic distortion of less than 24%.

Decomposition of hexane and benzene by dielectric barrier discharge plasma and reaction temperature: Comparison of performance of DC nano-second pulsed power supply and AC high voltage power supply

The VOC decomposition performance of a dielectric barrier discharge plasma powered by a DC nano-second pulsed power system was compared with that of an AC high voltage power system. Benzene and hexane were selected as a representative aromatic VOC and a chain-structured VOC, respectively, and the decomposition of each VOC was conducted at the same applied voltage in both systems. The energy of electrons released from the plasma was analyzed, and the ozone production ability was evaluated under a constant applied voltage at different temperatures. Compared with AC high voltage system, the DC nano-second pulsed power system had about 32 times, 26 times, and 30 times better performances for ozone production yield, benzene decomposition yield, and hexane decomposition yield, respectively. For benzene decomposition, the ring cleavage reaction was constant at all reaction temperatures. On the other hand, the mineralization of hexane was largely improved by higher temperatures, because the dehydrogenation reaction was accelerated. Consequently, benzene decomposition was easier than hexane decomposition at the same energy.

Study on discharge characteristics and improving surface hydrophobicity of epoxy resin by nanosecond pulse excited argon/hexamethyldisiloxane jet array

Surface flashover of insulating materials induced by pollution and moisture environment is one of the main reasons for the damage of power system and electrical equipment. The improvement of the insulating materials surface hydrophobicity is key important, which can prevent the pollutants and water attachment, and enhance the insulating performance. In this paper, the super-hydrophobic film is formed on the surface of epoxy resin by a one-dimensional (1D) argon (Ar) jet array driven by nanosecond pulse power supply with hexamethyldisiloxane (HMDSO) addition. The influences of the processing time and HMDSO content on the epoxy resin surface hydrophobicity are investigated. It shows that with 0.04 % HMDSO, the jet array achieves a best hydrophobic treatment effect on the epoxy resin surface. After 60 s treatment, the apparent contact angle (ACA) of the epoxy resin surface increases from 60.3° of the untreated surface to 150.0°. The wettability of epoxy resin surface does not change too much as the treatment time beyond 60 s. The maximum ACA value 153.4° appears at 120 s processing time, which is just slightly higher than that of 60 s treatment time. The epoxy resin surface morphology and chemical feature before and after plasma processing are characteristics by the scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infra-red spectroscopy and X-ray photoelectron spectroscopy. It shows that the treated epoxy resin surface is covered with dense coral like particles in nanoscales, the original C=O、C-H and other organic functional groups are replaced by Si-(CH3), Si-O-Si and other silicon containing groups, and the Si content increases from 0.4% to 28.0%. The experimental results provide important references to develop jet array as an efficient tool to enhance the surface hydrophobicity and insulating performance of insulating materials.

Development of a micro-electrochemical machining nanosecond pulse power supply.

Micro-electrochemical machining (micro-ECM) has been widely used for microscale and nanoscale processing of materials. The performance of the nanosecond pulse power supply is directly related to the precision of micro-ECM, which is one of the core technologies for micro-ECM. In this work, a nanosecond pulse power supply, with adjustable pulse frequency, duty cycle, and voltage, was designed with an STM32F103VET6 single-chip microcomputer as the control core and a metal-oxide-semiconductor field-effect transistor as the chopper switch component. The performance test has shown that the power supply can produce a continuous pulse with the highest frequency of 8MHz, the shortest pulse width of 50ns, the maximum peak current of 12A, and the maximum voltage of 10V. As compared with the power supply reported in the literature, the present power supply demonstrated the enhanced output current and improved waveform of the nanosecond pulse output, which could result in better machining accuracy and efficiency for micro-ECM.

Bipolar nano-second pulse power supply for electrochemical micromachining of tungsten carbide without tool wear

Electrochemical machining (ECM) of tungsten carbide (WC) alloy using bipolar pulses with a neutral electrolyte (NaNO3 aq) was successfully proposed in recent years. However, tool electrode wear always occurs during machining in the period of negative pulses. To solve this problem, a method of ECM with sacrificial auxiliary electrode using bipolar current is presented. This paper is focusing on the development of nano-second pulse bipolar power supply for this method. Firstly, positive and negative nanosecond pulses are obtained with the method of DC voltage chopping by using a multi-channel high-speed switch composed of gallium nitride (GaN) transistors. Then, these pulses are accordingly distributed onto the electrodes between tool electrode, workpiece electrode and auxiliary electrode during ECM in different time. During the period of positive pulses, the workpiece anode and tool cathode form a circuit for ECM, which dissolve the workpiece and form a passive film (tungsten oxide) on tungsten carbide; during the period of negative pulses, the workpiece cathode forms a loop with the auxiliary anode, resulting in hydrogen evolution reaction on the surface of workpiece, so as to weaken the adhesion of the passive film and improve the pH value of the electrolyte close to the machining area on workpiece surface to dissolve the tungsten oxide. ECM experiments were carried out with the developed power supply, and the micro holes are successfully machined on the surface of tungsten carbide without tool wear, which verifies the feasibility of the presented method and designed bipolar pulse power supply.

Experimental Study on Ignition Characteristics of RP-3 Jet Fuel Using Nanosecond Pulsed Plasma Discharge

A study on forced ignition characteristics of RP-3 jet fuel-air mixture was conducted around a constant volume combustion vessel and a nanosecond pulsed plasma discharge power supply. Experiments were carried out at different initial pressures (pu = 0.2, 0.3, 0.5 atm), equivalence ratios (ϕ = 0.7, 0.8, 1.1), steam concentrations (ZH2O = 0%, 10%, 15%) and oxygen concentrations (ZO2 = 13.5%, 16%, 21%). The relationship between ignition probability and ignition energy is investigated. The experimental results show that the decrease in pressure, equivalence ratio, oxygen concentration and the increase in steam concentration all lead to an increase in minimum ignition energy (MIE). In order to further analyze the experimental data, one existing fitting equation is reformed with the initial conditions taken into account. Multivariate fitting is carried out for different conditions, and the fitting results of ignition probability are in good agreement with the experiments. The MIE results under different experimental conditions are figured out with the new fitting equation. The impact indexes, which stand for the effects of different factors, are also calculated and compared in present work.

Synthesis of Silicon and Silicon Carbide Nanoparticles by Pulsed Electrical Discharges in Dielectric Liquids

Silicon carbide (SiC) has been widely used in many applications, which require high mechanical endurance or high electrical resistance. It also serves as a basic material for light emitting diodes. Here, we present an in-liquid plasma method to produce SiC nanoparticles. A sustained spark-discharge in a dielectric liquid, which is energized by a nanosecond pulsed power supply, is established for the synthesis. To provide Si and C, we employed graphite and silicon as electrodes and cyclohexane (CHX) and tetramethylsilane (TMS) as dielectric liquids. For a reasonable comparison, we tested various combinations of electrode and liquid, namely Si-to-C in CHX, Si-to-Si in CHX, and C-to-C in TMS. We found that discharges in CHX produce Si particles encapsulated in C-shell and Si nanoparticles in C-matrix. Meanwhile, discharges in TMS consistently produce SiC nanoparticles with an average size of ~ 10 nm, regardless of the electrode material.

Experimental investigation on DBD plasma reforming hydrocarbon blends

To improve the ‘detonation-supporting’ performance of fuel-rich catalytic combustion products, DBD plasma, stimulated by adjustable nanosecond pulse power supply, was used to further regulate the components and concentrations of the hydrocarbon blends. In this paper, the parameters including load voltage, frequency, rising (falling) edge, pulse width and feeding flow rate were changed respectively, and the corresponding concentration and proportion change of the components in blend gas were investigated. According to the experiment result, it was found that when the discharge frequency is low, the plasma mainly promotes the transformation of light gaseous substances, while it mainly promotes the conversion to heavy hydrocarbons when the frequency is larger. Increasing load voltage will strengthen this trend. The controlling and reforming effect of plasma on the blend gas will decrease with the increase of voltage rising (falling) edge and the feeding flow rate. The regulation effect will be strengthened with the increase of pulse width under 200 ns. With the increase of discharge intensity, the ‘carbon’ settles on the walls of the reactor, which will change the dielectric constant, leading to the loss of control of the discharge.

Research on the characteristics of atmospheric pressure air pulse gas-liquid discharge using a needle-water electrode

In this paper, a nanosecond pulse power supply is employed to excite the gas-liquid discharge in atmospheric air, and the discharge characteristics, plasma characteristics and the composition of activated water under different pulse parameters are studied. The results show that the discharge consists of three stages in one pulse period, among which the two discharges that occur during the pulse duration and the falling edge are stronger, and the discharge on the rising edge is weaker. When the pulse voltage increases, the discharge current, average power, luminous intensity and spectra intensity all gradually increase. When the frequency increases, the discharge current is almost unchanged, but the power increases significantly, the discharge luminous and spectra intensity also increase. The increase of the voltage rising edge time will weaken the discharge intensity, and the corresponding luminous intensity and spectra intensity will be weakened. The increase of the voltage falling edge enhances the discharge, and the luminous intensity and emission spectra intensity increase. When the pulse voltage, frequency and falling edge time increase, the concentration of H2O2, \begin{document}${\rm{NO}}_2^ - $\end{document} and \begin{document}${\rm{NO}}_3^ - $\end{document} gradually increases. The increase of the rising edge time results in the decrease of the three active species concentrations. These results are helpful to understand the mechanisms of gas-liquid discharge characteristics under different conditions, so as to control plasma and solution activity, which will promote further practical application of nanosecond pulse gas-liquid discharge.

Physical and chemical properties of a magnetic-assisted DC superimposed nanosecond-pulsed streamer discharge plasma

In the present work, a magnetic-assisted DC superimposed nanosecond-pulsed streamer discharge (DC-NPSD) with a 0.4 T parallel magnetic field is developed that achieves good performance for ozone production and toluene degradation. The influence of the assisted parallel magnetic field on the electrical characteristics, streamer propagation behavior, reactive species generation and plasma chemical properties of the DC-NPSD are systematically investigated. The experimental results indicate that better impedance matching of a nanosecond pulsed power supply and a discharge reactor can be realized by superimposing DC voltage (U DC), which facilitates reactive species production and toluene degradation. The discharge current, input energy and reactive species production can be further enhanced by the application of a parallel magnetic field under different pulse and DC voltage conditions. There are two distinct streamer phases in the DC-NPSD: a primary streamer (PS) with longer propagation distance and higher propagation velocity and a secondary streamer (SS) with shorter propagation distance and lower propagation velocity. The propagation velocities of both the PS and the SS increase with increasing U DC. Only PS propagation velocity is accelerated by a parallel magnetic field; however, that of the SS remains almost constant with or without a magnetic field. Both ozone generation and toluene degradation performance are improved by a magnetic field, which is attributed to the lengthened electron motion path under the action of Lorentz force and the constraint effect on energetic electrons in the presence of a parallel magnetic field.

Influence of dielectric materials on discharge characteristics of coaxial DBD driven by nanosecond pulse voltage

The dielectric material is one of the important influencing factors for the dielectric barrier discharge (DBD) characteristics and its application effects. The glass, quartz, polycarbonate (PC), and polytetrafluoroethylene (PTFE) materials are selected as dielectric materials of a coaxial DBD reactor. A nanosecond (ns) pulse power supply is used to drive the coaxial DBD reactors and the influences of dielectric materials on the optical, electrical, and temperature characteristics of DBDs are recorded. The mechanisms of the effects of the dielectric materials on the DBD characteristics are analysed by equivalent electrical model and heat conduct model. From the observation of the discharge, all of the discharges are in the diffuse mode without filament and the coaxial DBD with glass dielectric barrier are more homogenous. With the electrical analysis, it is found that the glass dielectric barrier with larger relative permittivity compared with the other materials leads to a better discharge uniformity and a higher power deposition in gap. At the same applied voltage, the coaxial DBD reactor with glass dielectric barrier also has the highest energy efficiency, which can reach 70.8% at 24 kV peak applied voltage. The operation temperatures of the coaxial DBD reactors after 900 s discharge with different dielectric materials are compared. The coaxial DBD reactor with glass dielectric barrier has the highest outside wall temperature at 78.0 °C. The reactor with PTFE dielectric barrier has the lowest operation temperature at 58.2 °C. With the heat conduct analysis, the results show that the coaxial DBD reactor with glass dielectric barrier has the highest the inner barrier tube temperature at 137.9 °C and has the lowest heat loss power rate at 29.2% under thermal balance. The reported work provides important reference for the selection of dielectric materials for DBD reactors and for the optimization in the industrial application.

A parametric and compact nanosecond pulsed power generator for liquid phase discharge.

Nanosecond pulsed liquid discharge has attracted significant attention in various applications, in which adjustable parameters and compact volume of nanosecond pulsed power are essential for the convenience of researchers. In this paper, a compact volume (0.6 × 0.8 × 0.4 m3) nanosecond pulsed power supply is built for the liquid discharge with the capacity charging power supply technology. Moreover, a high-frequency induction feed control system is adopted to achieve synchronizations between insulated gate bipolar transistors to realize the adjustable pulse width and frequency. A non-inductive resistor is used to test the properties of the nanosecond pulse power supply, and results show that the rising time of nanosecond pulse power is 100 ns with the pulse width in the range of 4 µs to ∼100 µs, and the output pulse voltage and repetition frequency are 0 kV-20 kV and 1 Hz-300 Hz, respectively. Moreover, the needle-to-needle electrode discharge in the liquid phase is successfully excited by this power supply with different working conditions.

NOx production in plasma reactors by pulsed spark discharges

Nitrogen fertilizers are important for modern agriculture, among which nitric acid is a basic chemical for ammonium nitrate production. Herein, NOx was produced from N2 and O2 using a spark discharge technology with point-to-point and circle-to-plate types of plasma reactors driven by a nano-second pulsed power supply. NOx could be produced with an energy efficiency of 0.09 mol kWh−1 under the gases of 50%/50% N2/O2, while NO2 selectivity increased with increasing energy density. The gas temperatures in the spark channels were estimated using the Gibbs free energy equation. Based on kinetics calculations, the reactions of N with O2 and O with NO were the major reactions for NOx production.