kV Pulse Research Articles

The anti-biofouling behavior of high voltage pulse electric field (HPEF) mediated by carbon fiber composite coating in seawater

One of the most important research areas in the marine industry is to investigate new and effective anti-biofouling technologies. In this study, high voltage pulse electric field (HPEF) mediated by carbon fiber (CF) composite coating was utilized to prevent the fouling of bacteria, microalgae and barnacle larvae in seawater. The plate count, 2, 3, 5-triphenyl-tetrazolium chloride (TTC) reduction assay and neutral red (NR) staining and larval motility detection showed that the inactivation rates were at the highest levels, which reached 99.1%, 99.9%, 99.7%, 98.7% and 85% respectively for Pseudomonas sp., Vibrio sp., iron bacteria, Navicula sp. and the second stage nauplii of Balanus reticulatus, under the HPEF with 19 kV pulse amplitude, 23.15 kHz frequency and 0.5 duty cycle. The field-emission scanning electron microscopy (FE-SEM) of Navicula sp. revealed that the HPEF brought about the cell lysis and the cell organic matter release on the coating, which could be the mechanism of the inactivation by the HPEF. Additionally, the FE-SEM and Raman spectroscopy indicated that the HPEF hardly damaged the coating.

Hydrophilicity modification of aramid fiber using a linear shape plasma excited by nanosecond pulse

In this paper, a linear shape nanosecond pulsed dielectric barrier discharge is generated at atmospheric pressure for improving the hydrophilic property of aramid fibers. The discharge images, waveforms of voltage and current, and optical emission spectra of discharge are obtained to investigate plasma characteristics, and the water contact angles, scanning electron microscopy, and X-ray photoelectron spectroscopy are employed to estimate the modifying effects of plasma and investigate modification mechanisms. It is found that 75 s is an optimal treatment time in air under 2 mm discharge gap, 28 kV pulse peak voltage, and 100 Hz pulse repetition rate, and the energy density of discharge is about 2.1 J/cm2. The improvement of aramid fiber hydrophilicity is due to the increasing of surface roughness and the formation of polar functional groups such as CN and OCO. Besides, the content of O2 has an obvious influence on plasma treatment, and CC is more easily oxidized under a high O2 concentration owing to the role of O atoms.

POWERFUL GENERATORS OF HIGH-VOLTAGE PULSES WITH NANOSECOND FRONTS

Purpose. Purpose of the article is to show the possibility of joint efficient operation of semiconductor switches and spark arresters in high-powerful high-voltage generators for obtaining nanosecond and shorter pulse fronts on a high-voltage load. Methodology. The variants of generators of power high-voltage pulses with semiconductor switches in the form of IGBT-transistors, SOS-diodes and spark dischargers as pulse front peaking spark gaps are considered. A scheme is proposed for such a generator of high-voltage pulses with nanosecond front on the basis of a linear pulsed transformer in the Tesla scheme. Results. On the complex load of the generator in the form of a serial connection of a gas bubble in water with a discharge in it and a layer of water under the bubble, voltage pulses with an amplitude of 23 kV and current pulses with an amplitude of 15 A were obtained. In this case, the pulse front, both voltage and current, on the levels 0.1-0.9, was approximately 10 ns, and the repetition rate of pulses in the load ranged from 1200 to 5000 pulses per second. Originality. A scheme is proposed for a generator of high-voltage pulses with a nanosecond front. The difference of the proposed generator with a nanosecond front, high pulse repetition rate, using its high-voltage and low-voltage circuits in the discharge circuit, is the presence in its composition of a linear pulse transformer and a system of peaking of pulse front using SOS diodes and spark gaps. Practical value. These generators considered in this work can find wide application in high-voltage technologies, including decontaminating water treatment, water purification by electric discharges.

The effect of high voltage pulse electric field (HPEF) on attachment of diatom on graphene composite coating and carbon fiber composite coating in marine environment

With increasing restrictions of environmental regulations and safety concerns on the traditional poisonous coatings, it is highly desirable to develop a new green anti-biofouling method in marine environment. In this paper, graphene composite coating and carbon fiber (CF) composite coating connected with high voltage pulse electric field (HPEF) were developed to inhibit the attachment of diatoms. The polarizing microscopy showed that the attachment rates of Thalassiosira and Navicula reached the lowest levels which were 0.23 cells mm−2 and 6.06 cells mm−2 on the graphene composite coating, 0.38 cells mm−2 and 4.17 cells mm−2 on the CF composite coating, under the HPEF with 1 h duration, 23.15 kHz frequency, 0.5 duty cycle and 19 kV pulse amplitude. While the attachment rates of Thalassiosira and Navicula were 21.21 cells mm−2 and 61.89 cells mm−2 on the graphene composite coating, 22.75 cells mm−2 and 62 cells mm−2 on the CF composite coating, without HPEF. Scanning electron microscopy (SEM) revealed that HPEF disintegrated the diatom cells, which could underlie the considerable inhibition of the diatom attachment by the HPEF. Additionally, the hardness, flexibility and shock resistance tests indicated that graphene and CF could considerably increase the mechanical properties of epoxy resin coating. HPEF stimulation had no obvious effect on the mechanical properties of the composite coatings.

Trap distribution of electron beam irradiated epoxy resin under repetitive pulse voltage

Epoxy resin has been widely used as dielectric material in irradiation environment, such as nuclear power plants, aerospace equipment and superconducting power apparatus. This paper investigated the effects of different electron beam irradiation doses on the trap distribution of epoxy resin under repetitive pulse voltage. Samples were irradiated at room temperature (20 °C) in air by high energy electron beam of 7.5 MeV with beam density ranging from 0.35 to 0.45 mA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The total irradiation dose was 0, 100, 500 and 700 kGy, respectively. The corona charging was performed under ± 6 kV pulse voltage with different pulse frequencies in atmospheric air with relative humidity of 20%. The surface potential was collected through an electrostatic voltmeter to obtain the trap distribution at room temperature, and the isothermal discharge current of the samples processed with different irradiation dose was measured to calculate the trap distribution in liquid nitrogen (LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ). The experimental results indicate that both at room temperature and in LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , the trap level decreases first and then increases with the increase of irradiation dose. The trap level and the trap density have the positive correlation with pulse voltage frequency. At room temperature, the electron traps have higher energy level and deep trap density, but have lower shallow trap density than the positive charge traps.

Nanosecond Pulsed Plasma Brush for Bacterial Inactivation on Laminate

An array of nonthermal atmospheric-pressure helium plasma jets, in the shape of a brush, was generated in air when a rectangular, 0.1 mm thick anode was powered by 150 ns, 9.5 kV pulses at 2 kHz. With helium as the working gas at 1 slpm, each of the 11 jets of the plasma brush was 1 mm in width, and up to 1 cm long. The jets were spaced 4 mm apart, resulting in a lateral length of 51 mm. The bactericidal effect of the plasma brush was studied against Acinetobacter baumannii and Staphylococcus aureus inoculated on surfaces, including agar and laminate. The impact of humidity in the working gas, substrate type (agar versus laminate), and surface condition (wet versus dry) on the plasma-induced bactericidal effect was evaluated. In a humid discharge, bacterial inactivation was maximized at 0.6 log (75%), whereas adding water to the laminate surface before treatment yielded a 4 log (99.99%) reduction in bacterial viability. In addition, reactive plasma species, including excited O, NO, and OH were evaluated using optical emission spectroscopy for all plasma treatment conditions on laminate.

Ignition and dynamics of nanosecond pulsed helium streamers over a water electrode

Applications of atmospheric pressure non-equilibrium plasma jets for a variety of biomedical applications have motivated fundamental studies of the gas-phase plasma in the presence of water. The initiation of guided streamers, excited with 164 ns, 5.2 kV pulses, as well as the dynamics of the streamer were investigated using a micro-hollow needle-to-plate configuration with and without water. Addition of water to the ground plate results in the enhanced ionization at the needle anode, earlier streamer formation, greater total energy deposition, and stronger emissions by excited states including N2, N2+, OH, and O. Importantly, spatiotemporally-resolved emission spectroscopy reveals that excitation transfer via collisions with heavy particles played an important role in the production of OH(A2Σ) in addition to direct electron impact.

Runaway electrons during subnanosecond breakdowns in high‐pressure gases

The parameters of runaway electrons produced in nanosecond high-voltage discharges in different gases (air, nitrogen, sulphur hexafluoride, krypton, argon, methane, neon, hydrogen, helium) at atmospheric and higher pressure were studied. An optical analysis was also performed to investigate the ionisation dynamics in diffuse discharges in nitrogen and nitrogen-containing mixtures. At breakdown of a point-to-plane gap by nanosecond (≃2 ns) high-voltage (≃200 kV) pulses of negative voltage polarity and gas pressure above 0.1 MPa, a supershort avalanche electron beam (SAEB) was detected by a collector behind the flat anode. For pressure >0.1 MPa of nitrogen and other gases it is shown that the maximum pressure for SAEB registration decreases with increasing the voltage pulse rise time. Therefore, to detect a SAEB at atmospheric and higher gas pressure, one should use voltage pulses with an amplitude of hundred kilovolts and rise time of ∼1 ns and shorter. The experimental research in the dynamics of optical radiation from the discharge plasma shows that the breakdown in which runaway electrons are produced develops as an ionisation wave.

Simulation of a non-equilibrium helium plasma bullet emerging into oxygen at high pressure (250–760 Torr) and interacting with a substrate

A two-dimensional computational study of a plasma bullet emanating from a helium gas jet in oxygen ambient at high pressure (250–760 Torr) was performed, with emphasis on the bullet interaction with a substrate. Power was applied in the form of a trapezoidal +5 kV pulse lasting 150 ns. A neutral gas transport model was employed to predict the concentration distributions of helium and oxygen in the system. These were then used in a plasma dynamics model to investigate the characteristics of the plasma bullet during its propagation and interaction with a substrate. Upon ignition, the discharge first propagated as a surface wave along the inner wall of the containing tube, and then exited the tube with a well-defined ionization front (streamer or plasma bullet). The plasma bullet evolved from a hollow (donut-shaped) feature to one where the maximum of ionization was on axis. The bullet propagated in the gap between the tube exit and the substrate with an average speed of ∼2 × 105 m/s. Upon encountering a metal substrate, the bullet formed a conductive channel to the substrate. Upon encountering a dielectric substrate, the bullet turned into an ionization wave propagating radially along the substrate surface. For a conductive substrate, the radial species fluxes to the surface peaked on the symmetry axis. For a dielectric substrate, a ring-shaped flux distribution was observed. The “footprint” of plasma-surface interaction increased either by decreasing the gap between tube exit and substrate, decreasing the relative permittivity of an insulating substrate, or decreasing pressure. As the system pressure was lowered from 760 to 250 Torr, the discharge was initiated earlier, and the plasma bullet propagation speed increased. A reverse electric field developed during the late stages of the ramp-down of the pulse, which accelerated electrons forming a brief backward discharge.

Development of a compact generator for gigawatt, nanosecond high-voltage pulses.

A compact generator producing 2.2-ns 1.5 GW high-voltage pulses was developed. The generator employed a 27.6 Ω, 0.9 ns pulse-forming-line (PFL), which was charged by an iron core transformer with a turn ratio of 2:33.5 and a coefficient of 0.94. A 1.2 μF, 20 kV capacitor and a hydrogen thyratron were used in the primary circuit. When the thyratron closed at 14.5 kV, 3.4% of the energy stored in the capacitor was delivered to the PFL in 850 ns, producing a peak voltage of up to ∼500 kV. In addition, the principle of triple resonance transformation was employed by adding a 50 pF tuning capacitor and a 1.15 mH inductor between the transformer and the PFL, which led to a significant reduction of the duration and peak value of the transformer voltage without reducing that in the PFL. Meanwhile, an adjustable self-break oil switch was applied. By using transmission lines with impedance overmatched to that of the PFL, the generator delivered a 512 kV pulse across an electron beam diode, generating radiation with a dose of 20 mR/pulse at 20 cm ahead of the diode. The generator provides an excellent ultra-short radiation pulse source for the studies on radiation physics.

Comparative study of electrical breakdown properties of deionized water and heavy water under pulsed power conditions.

A comparative study of electrical breakdown properties of deionized water (H2O) and heavy water (D2O) is presented with two different electrode materials (stainless steel (SS) and brass) and polarity (positive and negative) combinations. The pulsed (∼a few tens of nanoseconds) discharges are conducted by applying high voltage (∼a few hundred kV) pulse between two hemisphere electrodes of the same material, spaced 3 mm apart, at room temperature (∼26-28 °C) with the help of Tesla based pulse generator. It is observed that breakdown occurred in heavy water at lesser voltage and in short duration compared to deionized water irrespective of the electrode material and applied voltage polarity chosen. SS electrodes are seen to perform better in terms of the voltage withstanding capacity of the liquid dielectric as compared to brass electrodes. Further, discharges with negative polarity are found to give slightly enhanced discharge breakdown voltage when compared with those with positive polarity. The observations corroborate well with conductivity measurements carried out on original and post-treated liquid samples. An interpretation of the observations is attempted using Fourier transform infrared measurements on original and post-treated liquids as well as in situ emission spectra studies. A yet another important observation from the emission spectra has been that even short (nanosecond) duration discharges result in the formation of a considerable amount of ions injected into the liquid from the electrodes in a similar manner as reported for long (microseconds) discharges. The experimental observations show that deionised water is better suited for high voltage applications and also offer a comparison of the discharge behaviour with different electrodes and polarities.

Ultralow Capacitance Transient Voltage Suppressor Design

A novel transient voltage suppressor (TVS) that features ultralow capacitance is proposed. This structure is able to reduce the input capacitance by 21.1%, and is designed to protect against electrostatic discharge (ESD) issues for high-speed ports. The device is also able to withstand IEC 61000-4-2 contact testing at ±14 kV and transmission line pulse (TLP) testing at 20 A. The device is fabricated using a typical planar Bipolar-CMOS-DMOS (BCD) process. By slotting the doping well to decrease the concentration of diodes, a TVS with an ultralow $C_{j}$ is obtained without the need to add to the process procedures or without damaging the ESD capability.

Analysis of inactivation saccharomyces cerevisiae by 13 μs, 200 ns and 2 ns pulsed electric fields

The effect of the pulse width change is studied on the membrane voltage and energy of cell membranes and organelles membrane under the high voltage pulse electric field. The sterilization effect of saccharomyces cerevisiae (CICC31180) changes with the quantity of the 13 s, 200 ns or 2 ns pulses. The results showed that with the increase of the quantity of pulses, the sterilization effect was enhanced. The yeast concentration decreased by 4.3 orders of magnitude after 50, 13 s width, 14 kV pulses treatment while by 2.8 orders of magnitude after 500, 13 ns width 200 kV pulses treatment, by 2.6 orders of magnitude after 500, 13 ns width 200 kV pulses treatment. The survival rate logarithmic relation with the pulse number was not linear. The survival rate logarithmic decreased slowly when the pulse number increased to a higher value. Under the same survival rate logarithmic decrease, the loss of energy in coaxial electrode was lower in 2 ns pulses than 13 s or 200 ns pulses.

DEPENDENCY OF THE HARM ROOT PLANTS FROM DEPTH OF THEIR FINDING AND MOISTURE OF THE LAND UNDER ELECTRIC PROCESSING

The ecological clean way of the destruction weeds by pulse of high power is offered. The methods of the study of the influence high-tension pulse to root system of the rubbish plants and methods of the determination degree damages of the root system after influence are brought. The methods of the study of the influence high-tension pulse to root system of the rubbish plants and methods of the determination degree damages of the root system after influence are brought. Dependencies degree damages root бодяка field from depth of its location and moisture of ground at voltage of the processing 20 kV and energy pulse 10 J are received.

Optical investigations of pulsed sparks in soil near electrode

Experimental results of laboratory investigation of nonlinear processes in moist soil near electrode simulating grounding of electric power facilities are presented. A method of optical recording of spark formation in the soil is developed. Investigations were carried out at voltage of 20-50 kV and current pulse duration of tens of microseconds. The critical electric field and delay of sparks beginning in soil in depending on the electrode construction, moisture and impulse duration are obtained. The images of sparks in soil are obtained for the first time.

High-voltage sharp-recovery 4H:SiC drift diodes: Theoretical estimation of limiting parameters

A simple mathematical model of 4H:SiC sharp-recovery drift diodes with a p +-p-n 0-n + structure. With this model, the limiting electrical parameters of high-voltage (2–10 kV) pulse generators built around these diodes are theoretically estimated.

Stabilization of ion beam generation in a diode with self-magnetic insulation in double-pulse mode

AbstractThe paper presents the results of statistical studies of ion beam generation in different geometry diodes with explosive emission cathode in a mode of self-magnetic insulation. The experiments were carried out using the TEMP-4M pulsed ion beam accelerator during its operation in both unipolar pulse mode (100 ns, 250–300 kV) and bipolar-pulse mode with the first negative (300–600 ns, 100–150 kV) followed by a second positive (120 ns, 250–300 kV) pulse. It is found that the standard deviation of the total energy and energy density of the beam does not exceed 10–11%, while the same shot-to-shot variation in ion current density was found to be 20–30%. The mechanism of the energy density stabilization from pulse to pulse may be associated with the charge exchange between accelerated ions and stationary molecules and formation of accelerated neutrals. We observed a high correlation between the energy density (or total beam energy) and the duration of the first voltage pulse. We performed analysis of Blumlein statistical performance when the Blumlein was terminated with a resistive load and with a self-magnetically insulated ion diode. A characteristic feature of Blumlein operation in the double-pulse mode is an excellent reproducibility of breakdown of the preliminary spark gap, the variation in breakdown voltage is &lt;2%. At the same time, the shot-to-shot variation in the breakdown voltage of the main spark gap in both bipolar- and unipolar pulse mode is 3–4 times higher than that for the preliminary spark gap. To improve the statistical performance of the main spark gap we used the first voltage pulse at the output of Blumlein to trigger the main spark gap. The new trigatron-type regime of the main spark gap operation showed a better reproducibility of the first pulse duration, with the time jitter not exceeding 10 ns in a set of 50 pulses.

Design and construction of a ±100 kV gas switch for linear transformer drivers

In this paper, the design, installation, and performance of a ±100 kV gas switch for linear-transformer-driver (LTD) are presented. LTD demands require gas switches that can be operated at a 200 kV DC voltage, and require trigger jitter and inductance as small as possible. A field distortion switch has been designed based on the L3 switch, the design criteria of switch electric field and trigger system are explained in detail. A two dimensional plasma model is developed to analyze the contribution of trigger system to the closing of gas switch. An experimental platform was built to test the self breakdown and triggered breakdown characteristics of the switch. When the switch is charged to ±100 kV and is triggered by a -120 kV pulse with a 30 ns rise time, the delay time is 78 ns and the jitter is 1.6 ns. A comparative test was done to research the function of UV preionization gap, the test results shown that the UV preionization gap can reduce the switch delay time and jitter, it can effectively improve the trigger performance of the switch. Meanwhile, using the short-circuit discharge, the inductance and impedance were measured, the switch inductance is about 30 nH, and the impedance is varied from 50mΩ to 30mΩ.

A multi-functional high voltage experiment apparatus for vacuum surface flashover switch research.

A multifunctional high voltage apparatus for experimental researches on surface flashover switch and high voltage insulation in vacuum has been developed. The apparatus is composed of five parts: pulse generating unit, axial field unit, radial field unit, and two switch units. Microsecond damped ringing pulse with peak-to-peak voltage 800 kV or unipolar pulse with maximum voltage 830 kV is generated, forming transient axial or radial electrical field. Different pulse waveforms and field distributions make up six experimental configurations in all. Based on this apparatus, preliminary experiments on vacuum surface flashover switch with different flashover dielectric materials have been conducted in the axial field unit, and nanosecond pulse is generated in the radial field unit which makes a pulse transmission line in the experiment. Basic work parameters of this kind of switch such as lifetime, breakdown voltage are obtained.

Effect of Ion Irradiation on the Structural Properties and Hardness of a-C:H:Si:O:F Films

Amorphous carbon-based thin films, a-C:H:Si:O:F, were obtained by plasma immersion ion implantation and deposition (PIIID) from mixtures of hexamethyldisiloxane, sulfur hexafluoride and argon. For PIIID the sample holder was biased with negative 25 kV pulses at 60 Hz. The main system parameter was the proportion of SF6 in the reactor feed, Rsf. To allow comparison to growth without intentional ion implantation, some films were also grown by plasma enhanced chemical vapor deposition (PECVD). The objectives were to investigate the effects of fluorine incorporation and ion implantation on the film's chemical structure, and principally on the surface contact angle, hardness and friction coefficient. Infrared and X-ray photo-electron spectroscopic analyses revealed that the films are essentially amorphous and polymer-like, and that fluorine is incorporated for any non-zero value of Rsf. Choice of RSF influences film composition and structure but ion implantation also plays a role. Depending on Rsf, hydrophilic or hydrophobic films may be produced. Ion implantation is beneficial while fluorine incorporation is detrimental to hardness. For ion implanted films the friction coefficient falls about one third as Rsf is increased from 0 to 60%. Films prepared by PIIID without fluorine incorporation present fairly low friction coefficients and hardnesses greater than those of conventional polymers.