High-current Arc Discharge 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 investigation of regimes of current transfer to anodes of high-pressure arc discharges

Unified 1D numerical modeling of high-pressure high-current arc discharges is revisited. Two regimes of current transfer to anodes are investigated. The “passive anode” regime occurs for low and moderate anode surface temperatures Ta. The energy flux from the plasma to the anode surface, qpl, depends on Ta rather weakly in this regime and may be conveniently expressed in terms of the local current density jc, and the so-called anode heating voltage Uh. Uh is independent of the arc length and the cathode surface temperature, although it weakly varies with jc between approximately 6 and 8.5 V for jc in the range from 105 to 108 A m−2. In the “active anode” regime, qpl is higher than in the passive anode regime and varies with Ta. The active anode regime may occur on hot refractory anodes, such as those of high-intensity discharge lamps, when Ta exceeds approximately 3000 K and the thermionic electron emission from the anode comes into play. The latter causes an increase in the electron density near the anode. One consequence is the increase in the electron energy transport from the bulk plasma to the near-anode layer by electron heat conduction. The other effect contributing to increase in qpl is the formation of a negative near-anode space-charge sheath with a positive voltage drop. In non-stationary simulations, the active regime occurs via the development of a thermal instability similar to that causing the appearance of spots on thermionic arc cathodes. The occurrence of the active regime is strongly affected by parameters, in particular, by the distance between the anode surface and the cooling fluid.

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.

Studies of initiation and quenching of extensive high-current discharges

The system has been developed for initiating and quenching the arc discharges by means of moving apart the initially closed electrodes at a variable speed. The experimental studies of the extensive high-current electric arc discharges were performed in the atmospheric air. By means of optimizing the process of moving apart the electrodes and matching their sizes and shapes, it is possible to increase up to ten times the length of the stably burning high-current arc without using the external magnetic field for its stabilization.

Следы на пленках и многозарядные кластеры

When conducting experiments on the electric explosion of titanium foil in water, a “strange” radiation was detected, leaving dotted traces on the film. The velocity of the carriers of this radiation was estimated as 20–40 m/s, and their energy, estimated by the Coulomb drag mechanism, turned out to be equal to 700 MeV. Subsequently, it was found that similar traces are formed at various types of high-current arc discharges, both of artificial and natural origin. Many solutions have been proposed to explain the nature of “strange” radiation, but none of them describes the details of the process of formation of dotted traces. We believe that these traces on the film could appear due to the action of charged micron-sized clusters. The possibility of the existence of clusters in the form of a nucleus from a certain number of similarly charged ions enclosed in a spherical shell of water molecules is shown. The force of the Coulomb repulsion of ions is compensated by the compression force of the shell polarized by the inhomogeneous electric field created by the nuclear charge. As the cluster approaches the surface of the film, a cluster with a small charge separates from it. It is accelerated in the electric field of a “large” cluster to energy of about 1 GeV. Having received a recoil momentum, a large cluster moves away from the film, braking in an inhomogeneous electric field, and then “falls” onto it again, and the process is repeated.

“Strange” particles and micro-sized ball lightning in some electric discharges

When conducting experiments on the electric explosion of titanium foil in water, a “strange” radiation was detected, leaving dotted traces on the film. The velocity of the carriers of this radiation was estimated as 20–40 m/s, and their energy, estimated by the Coulomb drag mechanism, turned out to be equal to 700 MeV. Subsequently, it was found that similar traces are formed at various types of high-current arc discharges, both of artificial and natural origin. Many solutions have been proposed to explain the nature of “strange” radiation, but none of them describes the details of the process of formation of dotted traces. We believe that these traces on the film could appear due to the action of charged micron-sized clusters. The possibility of the existence of clusters in the form of a nucleus from a certain number of similarly charged ions enclosed in a spherical shell of water molecules is shown. The force of the Coulomb repulsion of ions is compensated by the compression force of the shell polarized by the inhomogeneous electric field created by the nuclear charge. As the cluster approaches the surface of the film, a cluster with a small charge separates from it. It is accelerated in the electric field of a “large” cluster to energy of about 1 GeV. Having received a recoil momentum, a large cluster moves away from the film, braking in an inhomogeneous electric field, and then “falls” onto it again, and the process is repeated.

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.

Interaction of Arc Discharges with a Melt in Ultrahigh-Power Electric Arc Furnaces

Mathematical simulation is performed to study the electrodynamic and gasdynamic processes of the interaction of arc discharges with the molten slag and metal in an electric arc furnace. The maximum forces that determine the penetration of ac arc discharges into the melt are calculated. Maecker’s theory is adapted to high-current arc discharges.

Obtaining of High-Power Electron Beams in a Plasma Anode Source Powered by the Marx Generator with Matched Loads

Experiments have been carried out to obtain high-power microsecond electron beams with high energy using an electron beam source with an explosive emission cathode and a plasma anode. The beam was formed and transported in a longitudinal magnetic field. The voltage source was the Marx generator with stages based on artificial long lines with matched loads connected to them. The possibility of realization of operation modes of the electron beam source with quasi-constant values of the accelerating voltage and current without highcurrent arc discharge formation in the interelectrode gap is demonstrated. Electron beams with circular and rectangular cross sections of ~100–200 cm2 with current up to 1–1.5 kA and duration of 5 μs were obtained at a quasi-constant accelerating voltage of 200 kV. The rotation of the beam around its axis was recorded. The possibility of electron beam extraction through a foil window into the atmosphere has been tested.

Synthesis of Quasicrysalline Powders and Coatings by Vacuum Arc Plasma Evaporation

Quasicrystalline coatings of the Al–Cu–Fe system were obtained by sputtering the cathode using a pulsed high-current low-pressure arc discharge followed by deposition on a hot (600°C) and cooled substrate (25°C). The surface morphology, chemical and phase composition of evaporation products in the powder form and the resulting coatings were studied. Powders and coatings were also annealed and the phase composition change was studied. It was found that during the evaporation process a significant change in chemical composition occurs in the form of loss of Al from the surface of particles and coating, that leads to a decrease in the content of the ψ-phase. However, subsequent annealing and spraying onto a hot substrate leads to an increase in the ψ-phase, as well as the density and hardness of the coatings.

Effect of low-temperature ion nitriding on microhardness, roughness and residual stresses in the surface layer of Ti-6Al-4V

The paper presents the results of two experimental series with low-temperature nitriding of VT6 titanium alloy in a non-self-maintained high-current arc discharge and in a glow discharge in different regimes. It is shown that microhardness and depth of a surface layer are significantly impacted by the temperature of treatment. The value of surface roughness of the samples is also affected, with a temperature rise from 450 to 600°C resulting in a surface roughness increase by 2–2.5 times. The temperature of nitriding affects the sign and magnitude of residual stresses in a surface layer.

Ion Angular and Initial Energy Distributions in Arc Discharge Deuterium Ion Source

Ion beams of hydrogen isotopes are of interest for accelerator and surface modification technologies. One of the methods of the generation of hydrogen-isotope ion beams is by using a high-current arc discharge ion source with hydrogen-saturated electrodes. The divergence of an ion beam is determined by the initial energy and angular distributions of ions. Some applications require ion beams with a divergence of 100 mrad or less. This paper analyzes the initial energy and angular distributions of ions in an ion source based on an arc discharge with a deuterated zirconium electrode. The analysis shows that the angular distribution of deuterium ions, compared to zirconium ions, is much broader and that the initial energy of zirconium ions in the ion beam is greater than the initial energy of deuterium ions.

Синтез квазикристаллических порошков и покрытий методом вакуумного плазменно-дугового испарения

Quasicrystalline coatings of the Al-Cu-Fe system were obtained by sputtering the cathode using a pulsed high-current low-pressure arc discharge followed by deposition on a hot (600 ° C) and cooled substrate (25 ° C). The surface morphology, chemical and phase composition of evaporation products in the form of powder and the resulting coatings were studied. Powders and coatings were also annealed and the phase composition variation was studied. It was found that during the evaporation process a significant change in the chemical composition occurs in the form of loss of Al from the surface of the particles and the coating, which leads to a decrease in the content of the ψ phase. However, subsequent annealing and sputtering on a hot substrate lead to an increase in the ψ phase, as well as the density and hardness of the coatings.

Influence of Ion Nitriding Regimes on Diffusion Processes in Titanium Alloy Ti-6Al-4V

The paper reports on the results of two-stage-experiments of low-temperature ion nitriding of the Ti-6Al-4V titanium alloy in a non-self-sustained high-current arc discharge and in a glow discharge under various conditions. The diffusion of nitrogen into the interior of the material was determined by the thickness of the layer being modified. It was established that the depth of the nitrided layer greatly depends on temperature, composition of the working medium, as well as on process duration. When treated in non-self-sustained high-current arc discharge, the depth of the nitrided layer increases from 4 to 17 μm, and in the glowing discharge the depth increases from 9 to 13 μm. The nitriding temperature affects the sign and magnitude of the residual stresses.

Increase in the Acceleration Efficiency of Solids in a Hybrid Coaxial Magnetoplasma Accelerator

It is shown that in a hybrid coaxial magnetoplasma accelerator with a channel length of 350 mm and a diameter of 23 mm, the acceleration velocity and the energy conversion efficiency increase as the length of the plasma structure formation channel filled with a gas-generating material decreases from 17 to 9 mm. It is found that it is reasonable to use paraffin as the gas-generating material as it has a less significant deionizing effect on the high-current arc discharge and hence causes a less significant decrease in the discharge current intensity and an increase in conductive and inductive electrodynamic forces.

Investigation of low-temperature ion nitriding technology of titanium alloy Ti-6Al-4V

The paper presents the results of low-temperature nitriding in non-self-maintained high-current arc discharge and in glow discharge. Measurement results of microhardness across the depth of a nitrated layer are given. It is found that the depth of a nitrated layer depends on treatment temperature. The temperature increase from 450 to 600 °C during nitriding in non-self-maintained high-current arc discharge leads to the increase in the depth of a nitrated layer from 10 to 24 μm, and from 10 to 22 μm when treated in a glow discharge. The paper also describes data on residual stress in a surface layer of samples after low-temperature ion nitriding.

Producing of aluminum boride in plasma of high-current impulse arc discharge

The experimental investigations were conducted on producing ultradisperse materials in a beam of electrodischarge plasma that contained aluminum and boron. A beam is generated by a high-current impulse accelerator of plasma and flows into an inert atmosphere (argon). According to the quality X-ray diffraction analysis, the produced powder material consists of aluminum and aluminum boride α-AlB12.

Methods for increasing the service life of electrodes in the arc plasmatorches

Results of experimental studies of electrode erosion in high-current arc discharges are presented. Available data on the service life of electrodes in the arc plasma generators sometimes are contradictory and do not give the whole pattern on the relationship of specific erosion of the electrode material with the basic determining parameters of the plasmatorch. The real ways to increase the duration of plasmatorch operation before electrode replacement have been proposed.

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.