Arc Discharge Current Research Articles

In-situ X-ray imaging of the breakup dynamics of current-carrying molten metal jets during arc discharge

The flow dynamics of current-carrying molten metal jet breakup during arc discharge serves as mass and heat sources in wire-arc-based metal deposition processes, thereby optimizing the resultant product quality. However, the spatiotemporal flow interaction between the molten metal jet and the surrounding arc plasma remains unclear. Here, using in-situ synchrotron X-ray imaging, we simultaneously track surface deformation and internal flow in molten aluminum jets during argon arc discharge. We reveal that modulating the magnitude and path of the arc discharge current can accelerate the jet velocity by 200–300% beyond its initial injection speed, thereby facilitating significant jet elongation. Our results provide consistent evidence that the jet flow dynamics are predominantly governed by the interaction between the arc discharge current and its coaxial self-induced magnetic field. This study establishes a framework at the intersection of fluid dynamics and electromagnetism, contributing to optimized control and precision in wire-arc-based applications.

Features of the formation and diagnostics of powerful metal ion beams with submillisecond duration

The article presents the results of experimental studies on the formation of repetitively-pulsed beams of titanium ions with submillisecond pulse duration from the continuous vacuum arc discharge plasma. The influence of ion-electron emission on the overestimation of the measured ion current with a power density of tens and hundreds of kilowatts per square centimeter was studied using various methods. It has been established that at an average energy of titanium ions of about 80 keV, due to ion-electron emission, the measured current is three times higher than the real ion beam current. Complicating the measurement of the current and energy parameters of the ion beam, the ion-electron emission ensures the neutralization of its space charge during the entire duration of the pulse. An increase in the ion current density due to ballistic focusing to more than 1 A/cm2 does not change the ion-electron emission coefficient. It is shown that, as a result of incomplete ion beam space charge neutralization, its crossover is shifted by 20 mm beyond the geometric focus of the system. The possibility of forming submillisecond high-intensity titanium ion beams with a current density exceeding 2.8 A/cm2, a power density exceeding 200 kW/cm2, and a pulse energy exceeding 100 J has been experimentally demonstrated. Data are obtained on the change in the current density over the ion beam cross-section depending on the accelerating voltage amplitude, the vacuum arc discharge current, and the distance from the focusing electrode.

Synthesis and in situ oxidation of copper micro- and nanoparticles by arc discharge plasma in liquid

This work presents a one-step controlled method for the synthesis of copper oxide nanoparticles using an arc discharge in deionized water without subsequent thermal annealing. The synthesis conditions were varied by changing the arc discharge current from 2 to 4 A. Scanning electron microscopy images of samples synthesized at discharge current of 2 A revealed the formation of tenorite (CuO) nanopetals with an average length of 550 nm and a width of 100 nm, which had a large surface area. Arc discharge synthesis at 3 and 4 A current modes provides the formation of a combination of CuO nanopetals with spherical cuprite (Cu2O) nanoparticles with sizes ranging from 30 to 80 nm. The crystalline phase and elemental composition of the synthesized particles were identified by X-ray diffraction analysis, Raman spectroscopy and Energy dispersive analysis. As the arc discharge current was raised from 2 to 4 A, two notable changes occurred in the synthesized particles: the Cu/O ratio increased, and the particle sizes decreased. At 4 A, the synthesized particles were from 30 to 80 nm in size and had a spherical shape, indicating an increase in the amount of cuprite (Cu2O) phase. The optical band gap of the aqueous solutions of copper oxide particles also increased from 2 to 2.34 eV with increasing synthesis current from 2 to 4 A, respectively. This suggests that the proposed synthesis method can be used to tune the band gap of the final material by controlling the Cu/O ratio through the current of arc discharge. Overall, this work demonstrates a novel approach to the synthesis of copper oxide nanoparticles with controllable CuO/Cu2O/Cu ratios, which has the potential to be useful in a variety of applications, particularly due to the significant enhancement of photocatalytic abilities and widen the working spectral range.

Discharge characterization and technological application of an arc ion plating with a hollow cathode vacuum arc

In an effort to reduce macroparticle defects in arc ion plating, a hollow cathode vacuum arc was added to an arc ion plating deposition chamber, so that the discharge from the hollow cathode vacuum arc was between the target and the substrate. AlTiN coatings were deposited using this technique (hollow cathode vacuum arc enhanced arc ion plating or HCVA-AIP) on high-speed steel substrates, and analyzed using scanning electron microscopy and X-ray diffraction. The hollow cathode vacuum arc was found to reduce the number and size of macroparticles in the deposited coatings and to increase the deposition rate. The hollow cathode vacuum arc also reduces the arc ion plating target voltage, by up to 29% (to 12 V) under the conditions studied here. Using this technique, the rate of Al ionization in the target is enhanced, resulting in the formation of AlN in the coating. This effect is strengthened at a higher hollow cathode vacuum arc discharge current.

Физические особенности формирования плазмы в протяженном полом аноде импульсного несамостоятельного дугового разряда

The paper investigates the characteristics of a pulsed arc discharge of low (≈ 1 Pa) pressure with thermal emission and hollow cathodes in an argon atmosphere. It is shown that a pulsed discharge is stably initiated in an extended, 1.2 m long and 0.6 m in diameter, hollow anode with a volume of about 0.3 m3 at increased (100-300) V combustion voltages and allows reaching currents up to 800 A with a pulsed with a capacity of up to several tens of kilowatts. An increase in the combustion voltage of the discharge from 100 to 300 V leads to a decrease in the inhomogeneity of the plasma concentration distribution over the height of the hollow anode by more than an order of magnitude. An increase in the value of the induction of the axial magnetic field due to an increase in the magnetic coil current from 0.2 to 2 A leads to an increase in the non-self-sustained arc discharge current by 20% at an increased (300 V) discharge voltage.

Широтная и амплитудная модуляция тока пучка для управления его мощностью в течение импульса субмиллисекундной длительности

Methods for controlling the power electron beam in a source based on a low-pressure arc discharge with layer stabilization of the emission plasma boundary are described. The control is carried out by the method of amplitude and latitude modulation within the duration of the beam current pulse with a time resolution of 10 μs at a submillisecond pulse duration. Two ways to control the power of the electron beam are implemented: the first one is based on changing the concentration of the emission plasma by modulating the arc discharge current, the second method uses grid control (the mode of operation of the plasma triode) at the constant discharge current. Simplified diagrams of the power supply sources of the discharge and intergrid control voltage, typical oscillograms of the main currents of the discharge system, a graph of a quick-acting power change, and a control characteristic of a plasma triode are presented.

Energy density distribution of a modulated electron beam in a source with a plasma cathode based on a low pressure arc

The article presents the results of studies devoted to the study of the energy density distribution in the amplitude-modulated regime of electron beam generation. It is shown that in the first ≈ 50 μs of the duration of the beam current pulse, its spatial rearrangement occurs, due to the development of the arc discharge current. Thus, the rearrangement of the arc current, which develops from the axis of the system, leads to an axial diving of the emission current density and the beam current density on the target. With the development of the arc current, the energy density on the target on the axis of the system decreases and after ≈ 50 μs takes on a steady-state value, which can change only as a result of a change in the conditions for generating an electron beam or the transition to a modulated regime of electron beam generation. It has been experimentally shown using calorimetric measurements that the shape of the electron beam current pulse with its amplitude modulation with a pulse duration of more than 100 μs has little effect on the distribution of the beam energy density in the target region.

Investigation of the aluminum electrodes erosion of a plasma gun during the operation of a high-current vacuum arc discharge

The aim of this work was to obtain magnitude quantitative estimates of the “closed-type” plasma gun aluminum electrodes erosion that occurs during the course of a high-current vacuum arc discharge. The experimental setup consisted of two current generators. The first generator capable of generating a current with an amplitude of up to 450 kA and a rise time of 500 ns was used as a current source for a plasma gun. The second one was used as an X-ray radiograph to visualize the object under study in the soft X-ray range (hv ≈ 0.5–3 keV). Quantitative distributions of the plasma linear mass are obtained both along the radius and along the length of the jet at different times. It was shown that the erosion properties of the electrode material are related to the current characteristics of the arc discharge current.

Preparation of Metal Nitride Particles Using Arc Discharge in Liquid Nitrogen.

A simple process to synthesize metal nitride particles was proposed using submerged arc discharge plasma in liquid nitrogen. Gibbs standard free energy was considered for the selection of the nitride-forming materials. In this study, titanium (Ti) and aluminum (Al) electrodes were used as raw materials for nitride particle preparation. Liquid nitrogen acted as a dielectric medium as well as a nitridation source in this process. A copper electrode was also used as a non-reactive material for comparison with the reactive Ti and Al electrodes. As the operating conditions of the experiments, the arc discharge current was varied from 5 A (low-power mode) to 30 A (high-power mode). The formation of titanium nitride (TiN) and aluminum nitride (AlN) was confirmed in the particles prepared in all experimental conditions by X-ray powder diffraction (XRD). The observation using a field emission scanning electron microscope (FE-SEM) and a field emission transmission electron microscope (FE-TEM) indicated that the synthesized TiN particles showed a cubic morphology, whereas AlN particles containing unreacted Al showed a spherical morphology. The experiments using different metal electrode configurations showed that the anode generated most of the particles in this process. Based on the obtained results, a particle formation mechanism was proposed.

Extended Cylindrical Low-Pressure Arc Discharge Plasma Emitter for Generation of a Radially Diverging Electron Beam

The paper presents the results of studies of processes of generation of a beam-plasma formation in an extended cylindrical hollow mesh anode with a diameter of 115 mm and a length of about 1 m of a non-self-sustaining low-pressure arc discharge with thermionic and hollow cathodes. The probe method was used to measure the longitudinal distributions of the plasma parameters inside the mesh hollow anode of the arc discharge for burning conditions with/without a flow of ions injected from the plasma of the main glow discharge, for which the hollow anode was the plasma emitter of electrons. The distributions of the ion current density on the probe inside the cylindrical anode of the arc discharge (electron emitter) as functions of the operating pressure, the longitudinal magnetic field in the hollow cathode of the arc plasma source, and the arc discharge current are experimentally determined. In an extended plasma emitter, unequal conditions of plasma formation are formed, leading to the formation of a potential barrier for the propagation of the arc plasma. The emission of ions from the glow discharge plasma in the beam-plasma formation allows the inhomogeneity of the plasma formed in the hollow plasma emitter to be reduced significantly. The results obtained show the possibility of forming relatively uniform extended beam-plasma formations inside the extended mesh anode of the arc discharge under conditions of injection of an external ion flow through the mesh cells.

Spectroscopic Measurement of Arc‐Discharge Argon Plasma Plume Injected into Water

The electron temperature and the density of argon arc plasma plume injected into water were observed through optical emission spectroscopic measurement. Argon arc plasma jets were generated with a DC arc current of 40–200 A by a non‐transferred arc discharge plasma torch under atmospheric pressure, and ejected through a nozzle on the anode into water or gas‐phase argon. The electron temperature of the plasma plume was determined by the Boltzmann plot with line intensity measurement of atomic argon lines, while the electron density is examined with the Stark broadening measurement of Hα line. It was found that the electron temperature increased from approximately 6500–8000 K, and the electron density also increased up to the order of 1016cm−3, as the discharge current increased for the underwater argon arc plasma plume, both of which were observed at 20 mm in the downward direction from the plasma generator nozzle. In addition, the electron temperature of the underwater plasma plume was slightly lower than that of the gas‐phase argon plasma plume, while the electron density of the underwater plasma was slightly higher than that of the gas‐phase plume. Longitudinal variation of the electron temperature and density of the underwater plasma plume was also observed, and the lowering rate was found to depend on the arc discharge current. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Maximal current of a pulsed constricted arc discharge operating in the forevacuum plasma electron source

The paper presents results of investigation of maximal current of the pulsed constricted arc discharge generating emission plasma in the forevacuum plasma electron source. Distinctive feature of the forevacuum plasma electron source is the absence of pressure differential between region of formation of emission plasma and the region of acceleration and propagation of electron beam. Therefore, the operating conditions of the constricted arc in the forevacuum plasma source are significantly different from the conditions in the plasma electron sources generating electron beams at pressure 10–3–10–1 Pa. The constriction of the positive column of the arc discharge provides, as it known, to reduce influence of instability and chaotic behavior of the cathode spot of the arc on the formation of emission plasma. In the investigated pressure range 3–20.5 Pa, the maximal current of the constricted arc discharge has been limited either by extinction of the arc or by initiation of the cathode spots on the constricting electrode and transition of the arc operation to the cascade mode. Increase of gas pressure and the use of working gas with larger ionization cross section (e.g. argon) have provided increase of the maximal arc current. The increase in the constricting channel diameter has provided the increase of maximal current and provided lower minimal gas pressure, at which stable operation of the constricted arc ensured. The decrease of length of the constricting channel has provided noticeable increase in the maximal arc current only at gas pressure more than 12 Pa.

Multi-layered gradient (Zr,Nb)N coatings deposited by the vacuum-arc method

Multi-layered gradient (Zr,Nb)N coatings were deposited with vacuum-arc evaporation of pure Zr and Nb metal cathodes. The gradient of the Nb concentration through the thickness was obtained by varying the arc discharge current with a Nb cathode within 80–150 A under the constant pressure of a working Ar/N2 gas mixture and a constant current of arc discharge with a Zr cathode. These coatings were studied by scanning and transmission electron microscopes, X-ray diffraction analysis, micro- and nanoindentation, and tribological measurements. The synthesized coatings show a high hardness, relatively low Young's modulus, relatively high H/E ratio, a high degree of elastic recovery, low surface roughness, a low friction coefficient, and a low wear rate. These coatings also feature a multiphase and multi-layered nanocrystalline structure with alternation of only layers with higher and lower Nb concentration.

Thermal regime of the cathode in a vacuum-arc discharge during coating deposition

The questions of stabilizing the cathode temperature in a vacuum-arc discharge are discussed. A model and a method for calculating the temperature of the working surface of the cathode end, eroded under the action of cathode spots, are presented. Stabilization of the cathode temperature is carried out by changing the arc discharge current during the operation of the evaporator in accordance with the obtained regularity or design solutions.

Surface modification of Al by high-intensity low-energy Ti-ion implantation: Microstructure, mechanical and tribological properties

A high-intensity metal ribbon ion beam was generated using plasma immersion extraction and the acceleration of the metal ions with their subsequent ballistic focusing using a cylindrical grid electrode under a repetitively pulsed bias. To generate the dense metal plasma flow, two water-cooled vacuum arc evaporators with Ti cathodes were used. The ion current density reached 43 mA/cm2 at the arc discharge current of 130 A. High-intensity ion implantation (HIII) with a low ion energy ribbon beam was used for the surface modification of the aluminium. The irradiation fluence was changed from 1.5 × 1020 ion/cm2 to 4 × 1020 ion/cm2 with a corresponding increase in the implantation temperature from 623 to 823 K. The structure and composition of the Ti-implanted aluminium were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDX). The mechanical properties and wear resistance were measured using nanoindentation and “pin-on-disk” testing, respectively. It was shown that the HIII method can be used to form a deep intermetallic Al3Ti layer. It has been established that a thin (0.4 μm) modified layer with a hcp Ti(Al) structure is only formed on the surface at 623 K, while the formation of the ordered Al3Ti intermetallic phase occurs at the implantation temperatures of 723 and 823 K. Despite the significant ion sputtering of the surface, the thickness of the modified layer increases from ~1 μm to ~6 μm, and the implantation temperature rises from 723 to 823 K. It was found that the homogeneous intermetallic Al3Ti layer with a thickness of up to 5 μm was formed at 823 К. The mechanical and tribological properties of the aluminium were substantially improved after HIII. For the Ti-implanted aluminium, the hardness of the surface layer increases from 0.4 GPa (undoped Al) to 3.5–4 GPa, while the wear resistance increases by more than an order of magnitude.

Determination of hafnium in zirconium materials

An arc atomic emission technique of hafnium determination in zirconium is developed and tested. The study was carried out on a PGS-2 spectrometer equipped with MAÉS analyzer and information processing software «Atom 3.3». («VMK-Optoélektronika», Novosibirsk). Excitation of spectra of pre-oxidized metal was carried out using a medium-frequency generator «Vesuvius» («VMK-Optoélektronika», Novosibirsk). Analytical line of hafnium was free of spectral overlap with the lines of zirconium. We have set a current of the AC arc discharge (20 A), exposure time (30 sec) and the form of the electrode into which the sample is placed («narrow crater») are selected. The effect of buffering additives (graphite powder, bismuth fluoride) on the intensity of the analyte lines was studied. It is shown that high sensitivity of the analyte is observed for oxidized material without additives. Reduction of the random error attributed to the influence of conditions of spectrum excitation and sample preparation is achieved using the intensity ratio of the analyte line and zirconium as an analytical signal. Recommendations regarding preparation of the samples for calibration are given. The lower limit of the determined concentration is 0.01% with a relative standard deviation in repeatability 3%.

Generation of uniform low-temperature plasma in a pulsed non-self-sustained glow discharge with a large-area hollow cathode

Generation of plasma in a pulsed non-self-sustained glow discharge with a hollow cathode with an area of ≥2 m2 at gas pressures of 0.4–1 Pa was studied experimentally. At an auxiliary arc-discharge current of 100 A and a main discharge voltage of 240 V, a pulse-periodic glow discharge with a current amplitude of 370 A, pulse duration of 340 μs, and repetition rate of 1 kHz was obtained. The possibility of creating a uniform gas-discharge plasma with a density of up to 1012 cm−3 and an electron temperature of 1 eV in a volume of >0.2 m3 was demonstrated. Such plasma can be efficiently used to treat material surfaces and generate pulsed ion beams with a current density of up to 15 mA/cm2.

Spectroscopic determination of the composition of a 50 kV hydrogen diagnostic neutral beam.

A grating spectrometer with an electron multiplying charge-coupled device camera is used to diagnose a 50 kV, 5 A, 20 ms hydrogen diagnostic neutral beam. The ion source density is determined from Stark broadened Hβ emission and the spectrum of Doppler-shifted Hα emission is used to quantify the fraction of ions at full, half, and one-third beam energy under a variety of operating conditions including fueling gas pressure and arc discharge current. Beam current is optimized at low-density conditions in the ion source while the energy fractions are found to be steady over most operating conditions.

Preparation of carbon nanomaterials using two-group arc discharge plasma

Carbon nanomaterials were prepared using two-group arc discharge plasma method in this study. A combination of an alternating current (AC) arc discharge plasma and a direct current (DC) arc discharge plasma in a fluidized bed was used, in which propane was cracked into carbon blacks (CB) with controlled structure and hydrogen. The effects of parameters such as electrode type, frequency of AC arc discharge, current of DC arc discharge and gas flow ratio (propane/argon) on the synthesis and properties of CB were investigated. A systematic study of the size, morphology, microstructure and surface chemical composition of CB was conducted using various characterization techniques. By using this process, spherical and hydrophobic CB with a narrow size distribution, high degree of graphitization and large specific surface area were produced under optimal experimental conditions. Then, as-prepared CB were used to adsorb heavy-metal ions in water and to reinforce the engineering plastic. The results verified that the adsorption rate of the Cr (VI) ion was increased significantly and that the CB enhanced the electrical and mechanical properties of acrylonitrile–butadiene–styrene (ABS)/natural rubber (NR) composites.

Experimental investigation of the relation between H− negative ion density and Lyman-α emission intensity in a microwave discharge

A new mechanism for producing negative ions in low density and low power hydrogen plasmas was proposed recently. It refers to anion formation due to collisions between hydrogen atoms being in the first excited state. The proposed mechanism was indirectly supported by the quadratic relation observed between the extracted negative ion current and Lyman-α radiation of a filament-driven arc discharge, when borrowed data from the literature were combined. The present work provides experimental data comparing directly the absolute negative ion density and Lyman-α radiation in an ECR-driven hydrogen plasma source. The previously mentioned quadratic relation is not observed in the specific source studied, underlying the difficulty of distinguishing between the proposed mechanism and other negative ion production paths.