High Current Pulsed Arc Research Articles

Characteristic simulation of underwater microsecond high-current pulsed arc discharge plasma

Modeling analysis of underwater pulsed arc discharge can predict the characteristics of plasma channels, providing theoretical guidance for the practical application of underwater pulsed discharge. Due to the complexity of experimental diagnostics for ‘kA’-level underwater pulsed discharge, there is currently a lack of precise experimental data to support the initial value selection and result optimization of the modeling. This paper established a plasma channel model for underwater pulsed arc discharge. In conjunction with the Saha ionization equilibrium equation, the model was capable of simulating the current, pressure, temperature, and electron density of the channel after gap breakdown. By utilizing spectroscopic diagnostic data and a multi-objective optimization algorithm, the initial values and key parameters of the model were reasonably determined. The simulation results were in good agreement with the experimental diagnostic results, reasonably representing the trends in electron density and blackbody radiation temperature. Moreover, the model was applicable for reasonably explaining the emission spectral mechanism of the arc channel and shock waves prediction under different discharge conditions.

Numerical simulation of high-current pulsed arc discharge in air

A computational model of high-current pulsed arc discharge in air is proposed. This is, in general, a 2D model which takes into account the gas dynamics of the discharge channel, real air thermodynamics in a wide range of pressures and temperatures, the electrodynamics of the discharge including the pinch effect, and radiation. The 1D version of the model is tested and verified on several numerical and experimental works reported recently. It is concluded that low and moderate current discharges are satisfactorily described with the model. The model was then applied to simulate the electric discharge in air for the currents 1–250 kA and characteristic rise times in 13–25 µs, and the results of the calculations were compared with experimental ones. It was concluded that most characteristics of the discharge are predicted well. Namely, the arc column radius and shock wave position agree well with experimental data for all the current amplitudes and rise times considered. Radial distributions of temperature and electron density also satisfactorily agree with experimental data. It was found that the pinch effect should be considered for currents higher than 100 kA.

High-current arc discharge in air

Computational model of high-current pulsed arc discharge in air is proposed. This is, in general, two-dimensional model with taking into account gas dynamics of the discharge channel, real air thermodynamics in a wide range of pressure and temperature, electrodynamics of the discharge including pinch effect, and radiation. The developed model was applied to simulate the electric discharge in air for the currents of 1 - 250 kA and characteristic rise times in 13 - 25 µs, and results of calculations were compared with experimental ones. It was concluded that most of characteristics of the discharge are predicted well. Namely, arc column radius and shock wave position agree well with experimental data for all current amplitudes and rise times considered. Radial distributions of temperature and electron density also satisfactorily agree with experimental data. It was found that pinch effect should be considered for currents higher than 100 kA.

The Impact of Pulse Plasma Treatment on the Operating Characteristics of Steel 40X10C2M: Experiment and Numerical Simulations

This paper presents a study of operating characteristics of steel 40X10C2M after treatment it of high-energy plasma pulses. The steel is used to manufacture the elements of ships' power plants. For pulsed plasma treatment of steel samples, we used an electrothermal plasma accelerator (ETPA). A high-current pulsed high-pressure arc discharge was initiated in a restricted dielectric chamber of ETPA. The discharge duration was 1.4 ms, the maximum current reached the value of 5 kA, the discharge voltage was up to 5 kV. We investigated the microhardness and microstructure of the processed (modified) layer and determined the optimal parameters of steel processing that provide the best characteristics of the modified layer when the microhardness increases by ≈ 5 times. Microhardness maxima were discovered in the depth of the modified layer. The paper studies the possibilities of controlling the maxima localization to form the desired performance characteristics of the treated layer. Mathematical modeling of rapid pulsed heating of the steel surface layer is performed within the framework of the two-phase "melt-solid" model, taking into account the dynamics of the thermodynamic characteristics of steel. For this purpose, we used the classical equation of thermal conductivity with varying steel parameters: density, heat capacity, and coefficient of thermal conductivity during the transition of a substance from the liquid to the solid phase. Within the chosen mathematical model, numerical calculations of the rapidly pulsed heating phenomenon of the steel surface were performed, taking into account melting and solidification in the Comsol Multiphysics package using the finite element method. The numerical simulation results are in good agreement with the experimental distribution of the microhardness of the treated steel layer deep into the sample.

Surpassing Cu–Ta Miscibility Barriers Using a High‐Current Pulsed Arc

AbstractThe improvement of many applications in the fields of catalysis, surface and coatings technology, biomedicine, and fuel cells depends on the advances in nanoalloy research. Here, a structural and thermal study of nanostructures of Cu–Ta particles produced using a high‐current pulsed arc (HCPA) is presented. Structural analysis performed utilizing electron microscopy and X‐ray spectroscopy shows the formation of distinctive single crystals with grain sizes larger than 100 nm. Notably, these grains exhibit evidence of a variation of the characteristic immiscibility of Cu and Ta, as found in the bulk scale. The nonequilibrium HCPA method appears to offer a way to surpass miscibility barriers in bimetallic alloys. This technique also allows the synthesis of oxygen‐free powders in sufficient quantities to perform a variety of characterization measurements. The detailed Cu–Ta alloy crystals and oxidation temperature in a high purity oxygen atmosphere and the stability at high temperatures in argon are analyzed.

Electrical and spectral energy measurement techniques of pulsed continuous spectrum radiation sources

The techniques of total spectral energy and electrical measurements of high-current pulsed arc discharge are presented and substantiated. On the example of a flash lamp, three working circuits were reviewed and the following values were obtained: time dependences for circuit electrical parameters, values of the energy deposition into plasma, and radiative efficiencies for different spectral ranges.

Characteristics of N<inf>2</inf>/O<inf>2</inf> reaction in spark gap switch: The effect of high-current pulsed arc

Compressed air is used in spark gap switches as an insulating gas. Triggered by nanosecond pulsed voltage, the streamer bridges the electrode gap in the switch. During the streamer-arc transition, the spatial distribution of the arc changes drastically. The nitrogen and oxygen in the compressed air will react with each other under high temperatures. Damaging effects in the switch are caused by arc reaction. In this paper, by adjusting the parameters of the high-energy pulse discharge circuit, the arc is produced with different current waveform in the spark gap switch, while the gaseous product is analyzed. The results show that, when current pulse-width remains constant, the amount of transferred charge is approximately linear with the production of nitrogen oxides. The proportion of NO is higher when the current pulse-width is shorter. The concentration of nitrogen oxides is determined by the chemical reaction, which relies on the dynamic change of the impulse arc. During the arcing time, there is the collision dissociation reaction in the local thermodynamic equilibrium (LTE) plasma, leading to the production of gas atoms and excitation molecules. In the boundary of the arc channel, the nitrogen oxides formation reactions mainly occur in the arc quenching period. According to the characteristics of the high-current arc, a simplified analysis of chemical kinetics on the reactions of nitrogen and oxygen is implemented to expound the effect of pulsed arc on the gas composition.

Characterization of high-current pulsed arcs ranging from 100–250 kA peak

In this paper, we present the laboratory study on three experimental setups that produce a free arc channel subjected to the transient phase of a lightning current waveform. This work extends the high-current pulsed arc characterization performed in previous studies for peak levels up to 100 kA. Eleven high-current waveforms with peak value ranging from 100–250 kA with different growth rates and action integrals are studied, allowing the comparison of different test benches. These waveforms correspond to standard lightning ones used in aircraft certification processes. Hydrodynamic properties such as arc channel evolution and shock-wave propagation are determined by high-speed video imaging and the background-oriented Schlieren method. The arc diameter reaches around 90 mm at 50 μs for a current of 250 kA peak. Space- and time-resolved measurements of temperature, electron density and pressure are assessed by optical emission spectroscopy associated with the radiative transfer equation. It is solved across the arc column and takes into account the assumption of non-optically thin plasma at local thermodynamic equilibrium. For a 250 kA waveform, temperatures up to 43 000 K are found, with pressures in the order of 50 bar. The influence of current waveform parameters on the arc properties are analyzed and discussed.

Multiply charged metal ions in high current pulsed vacuum arcs

We show that vacuum arc plasma discharges with a current of several kiloamperes and duration of a few microseconds can generate multiply charged metal ions with charge states greater than 10+. The physical mechanism behind this is discussed, suggesting an optimum arc current for higher charge states depending on the pulse duration and cathode material. Measurements of ion mass-to-charge ratio and images taken with nanosecond resolution suggest that, higher charge state ions are produced at characteristic distances of ∼10 mm from the cathode as the arc current peaks, and the process responsible for their generation is additional ionization as the discharge is pinched by its self-magnetic field. The maximum and mean ion charge states reveal a considerable increase for the all cathode materials studied: magnesium, aluminum, zirconium, tin, tantalum, gold, lead, and bismuth. For bismuth ions, the maximum charge state reaches a record-breaking value of 17+ and the mean of the charge state distribution is 12.6+. The results obtained are of interest for vacuum arc discharge physics and for ion beam technologies.

Use of a probing pulsed magnetic field for determining plasma parameters

A novel, simple, and readily usable method is proposed for measuring the electrical conductivity and temperature of a plasma. The method is based on the interaction of the test plasma with a pulsed magnetic field. The electric signals induced by the magnetic field in the circuits of two probes (miniature solenoids), one immersed in the test plasma and the other placed outside the plasma, provide data for estimating the plasma parameters. The method was verified experimentally by determining the parameters of the plasma flows generated in the cathode spots high-current pulsed vacuum arcs that were used to form cylindrical shells of bismuth Z-pinch plasma.

Characterization of a high current pulsed arc using optical emission spectroscopy

In this paper, we present the investigation realized on an experimental setup that simulates an arc column subjected to the transient phase of a lightning current waveform in laboratory conditions. Optical emission spectroscopy is employed to assess space- and time-resolved properties of this high current pulsed arc. Different current peak levels are utilised in this work, ranging from 10 kA to 100 kA, with a peak time around 15 µs. Ionic lines of nitrogen and oxygen are used to determine the radial profiles of temperature and electron density of the arc channel over time from 2 µs to 36 µs. A combination of 192 N II and O II lines is considered in the calculation of the bound–bound contribution of the absorption coefficient of the plasma channel. Calculations of the optical thickness showed that self-absorption of these ionic lines in the arc column is important. To obtain temperature and electron density profiles in the arc, we solved the radiative transfer equation across the channel under an axisymmetric assumption and considering the channel formed by uniform concentric layers. For the 100 kA current peak level, the temperature reaches more than 38 000 K and the electron density reaches 5 × 1018 cm−3. The pressure inside the channel is calculated using the air plasma composition at local thermodynamic equilibrium, and reaches 45 bar. The results are discussed and utilised to estimate the electrical conductivity of the arc channel.

Preparation of ultrafine Cu3Si in high-current pulsed arc discharge

The results of experimental research into ultrafine copper silicide production in plasma high-current pulsed arc discharge are shown. According to X-ray diffraction, the product consists primarily of η″-Cu3Si (81%) and contains copper and silicon. A study of the material by transmission electron microscopy reveals the formation of elongated pointed copper silicide crystals with cross-sectional dimensions of approximately 250 nm. The presented method of preparation of copper silicide allow one to obtain grams of the ultrafine product per one operating cycle of the system, the duration of which is about 0.5 ms. The materials prepared may be used in the power industry, for example, for the manufacture of electrode systems of power supplies.

Electrical and hydrodynamic characterization of a high current pulsed arc

High current pulsed arcs are of significant industrial interest and, aiming to reduce time and cost, there is progressively more and more need for computation tools that describe and predict the behaviour of these arcs. These simulation codes need inputs and validations by experimental databases, but accurate data is missing for this category of electric discharges. The principal lack of understanding is with respect to the transient phase of the current, which can reach thousands of amperes in a few microseconds. In this paper, we present the work realized on an experimental setup that simulates in the laboratory an arc column subjected to five levels of high pulsed current, ranging from 10 kA to 100 kA, with the last one corresponding to the standard lightning current waveform used in aircraft certification processes. This device was instrumented by high speed video cameras to assess the characteristic sizes of the arc channel and to characterize the shock wave generated by the arc expansion. The arc channel radius was measured over time during the axisymmetric phase and reached 3.2 cm. The position and velocity of the shock wave was determined during the first 140 μs. The background-oriented schlieren method was used to study the shock wave and a model for the light deflection inside the shock wave was developed. The mass density profile of the shock wave was estimated and showed good agreement with Rankine–Hugoniot relations at the wave front. Electrical measurements were also used to estimate the time-dependent resistance and conductivity of the arc for times lasting up to 50 μs.

Determination of plasma parameters with a probing magnetic field pulse

An experimental technique for the determination of electric conductivity and temperature of plasma is presented. The technique is based on comparing the signals that are produced by a pulsed magnetic field in the circuits of two probes located within the studied plasma and outside of it. The proposed technique for the measurement of plasma parameters was tested experimentally in the context of measuring the electric conductivity and temperature of plasma flux formed in cathode spots of a high-current pulsed vacuum arc with a magnesium cathode.

High-Speed Imaging and Radiative Energy Measurements of a High-Current Pulsed Arc in Air

A high-current pulsed arc struck between a 100-mm electrode gap in open air was experimentally studied by time-resolved imaging. The arc was created by a discharge current with an amplitude of 10 kA and a duration of about 10 ms. A high-speed camera was used to investigate the dynamic behavior of the arc. The images extracted from the video show in particular strong interaction between the anode and cathode jets.

Dense Metal Plasma in a Solenoid for Ion Beam Neutralization

Space-charge neutralization is required to compress and focus a pulsed high-current ion beam on a target for warm dense matter physics or heavy ion fusion experiments. We describe an approach to produce dense plasma in and near the final focusing solenoid through which the ion beam travels, thereby providing an opportunity for the beam to acquire the necessary space-charge compensating electrons. We use a high-current (>;4 kA) pulsed vacuum arc plasma from a ring cathode near the edge of the solenoid. The plasma distribution is characterized by photographic means, by an array of movable Langmuir probes, by a small single probe, and by evaluating Stark broadening of the Balmer H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">β</sub> spectral line. The plasma is produced at several cathode spots distributed azimuthally on the ring cathode. It is shown that the plasma is essentially hollow, as determined by the structure of the magnetic field, although the plasma density exceeds almost everywhere in the volume defined by the solenoid. The plasma is nonuniform and fluctuating. However, since its density exceeds the ion beam density, it is believed that this approach could provide a practical solution to the space-charge neutralization challenge.

Production of highly ionized species in high-current pulsed cathodic arcs

Time resolved optical diagnostic techniques were used to study the production of highly ionized species in aluminum plasma produced by a centered-triggered high-current pulsed cathodic arc. Controlling the spacing between cathode spots enabled a correlation between a reduction in the mean charge state and an increase in the spacing of cathode spots to be observed. As the cathode current was increased, the distances between spots were reduced and these charge states were produced for longer times. Strong cathode spot coupling is proposed as a mechanism for the production of high charge states.

Synthesis and characterization of silver–carbon nanoparticles produced by high-current pulsed arc

In this paper, we report the formation of silver–carbon encapsulated metal nanoparticles (EMN's) using a high-current pulsed arc system in an argon atmosphere. The deposits were studied by Optical Extinction Spectroscopy (OES), X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM); the chemical analysis of the deposits was performed using Energy Dispersion X-ray spectroscopy (EDX). Using the total nanoparticle diameter, the bulk crystalline density of silver and an estimate amorphous carbon (a-C) density we have calculated the size of the silver nucleus and the thickness of the a-C coating as a function of the argon gas pressure. The OES spectra of the EMN's exhibited two peaks characteristic of the Surface Plasmon Resonance (SPR) of elongated/very close silver nanoparticles; a subsequent thermal annealing strongly increased the SPR peaks. The double peak SPR spectra were modeled using calculations based on the existence of silver nanoparticles in the form of prolate spheroids. The main advantage of our preparation method is that the metal nanoparticles are encapsulated in a-C from the beginning and this layer acts as an efficient chemical barrier.

Cathode-Spot Dynamics in a High-Current Pulsed Arc: A Noise Study

Cathode spots are the locus for plasma production in cathodic vacuum arcs, and measurements of the discharge voltage provide information about the physics. The voltage noise and cathode-erosion patterns of a high-current pulsed titanium arc were studied as a function of time, current, and pulse shape. Enhanced noise and a 1/f <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> trend in the spectral power density were observed when cathode spots are close together at the initiation of an arc for fast rising currents (>1.3 kA in 30 mus) or when the total current exceeds a threshold value of 1.6 kA. We propose a model in which the individual currents associated with the spot substructure can act as noise generators coupled via magnetic fields or coherent spot nucleation.

Oriented graphite layer formation in Ti/C and TiC/C multilayers deposited by high current pulsed cathodic arc

Ti/C and TiC/C multilayers with periods ranging from 2 to 18 nm were grown by filtered high current pulsed cathodic arc. The growth was monitored in situ by ellipsometry and cantilever stress measurements. The ellipsometry results reveal that the optical properties of the carbon vary as a function of thickness. Correspondingly, the stress in each carbon layer as measured in situ exhibits two well defined values: initially the stress is low and then takes on a higher value for the remainder of the layer. Transmission electron microscopy shows that the initial growth of carbon on Ti or TiC layer is oriented with graphitic basal planes aligned parallel to the interface. After 2–4 nm of growth, the graphitic structure transforms to amorphous carbon. Electron energy loss spectroscopy shows that the carbon layer simultaneously undergoes a transition from sp2 rich to sp3 rich material.