Arc Discharge Parameters Research Articles

Generation of multiply charged metal ions in a high current short pulse vacuum arc

We have studied the plasma composition of a high current short pulse vacuum arc discharge with different cathode materials: lanthanum, gadolinium, lead, silver, and tin. We find that for optimal vacuum arc discharge parameters – arc current pulse duration about 2 μs and amplitude about 3 kA – the maximum ion charge state is 11+ and mean ion charge state from 7.8+ for tin to 9.6+ for lanthanum. The mean ion charge state for different materials depends on the discharge voltage and the energy required for ionization to maximum charge state. The cathode surface heats to a temperature of 700 °C–1100 °C in the course of the arc current pulse, depending on the cathode material, and the cathode surface of low melting point metals such as lead and tin melts to a depth of 5 μm and 10 μm, respectively. Surface melting does not lead to change in plasma ion composition, since the ion flux from the cathode considerably exceeds the evaporated atom flux.

Studying the effect of the argon flow introduced into the arc discharge in the atomic-emission spectrometry of powdered samples using the spillage-injection method

Atomic emission spectral analysis of a powder sample by the method of spillage-injection into the plasma of an arc discharge burning in air is accompanied by the formation of cyanide, nitride and oxide compounds which form molecular bands in the spectrum thus impeding measuring the intensity of the analytical lines of the elements to be determined. Feeding an argon flow into the arc discharge can reduce the amount of spectral interference and increase the plasma temperature, which promotes more a complete evaporation of the analyzed sample injected into the arc discharge and, accordingly, increases the degree of ionization of the elements and the intensity of ion spectral lines. The aim of the study was to develop a device for argon introduction into the arc discharge zone and simultaneous sample delivery by a spillage-injection method, as well as to study the effect of argon consumption on arc discharge parameters and emission spectra of powder samples. The argon input device (up to 2.25 L/min) is developed on the basis on glass funnels, the geometric dimensions of which are selected with the goal of gaining the maximum intensity of spectral lines and reduced intensity of molecular bands at the minimal argon consumption. The study carried out on a «Grand Potok» spectrometer demonstrated that with an increase in argon consumption, the intensity of SiO molecular bands decreases, the plasma temperature increases by 350 – 540 K, and the intensity of ion and atomic lines with the ionization energy above 8 eV increases by more than 4.7 and 2.9 times, respectively. The developed device can be used in analysis of geological materials to improve the metrological characteristics of the results of atomic emission spectral analysis.

The effect of magnetic field variations on the spectral properties of tornado plasma

At atmospheric pressure and at a frequency of 9.1 kHz, a constructed magnetically stabilized tornado gliding arc discharge (MSGAD) system was utilized in this study to generate a non-thermal plasma with an alternating voltage source from 2,4,6,8 to 10 kV. Argon gas was used to generate the arc plasma with an adjustable flow rate using a flow meter regulator to stabilize the gas flow rate to 2 L/min. A gliding plasma discharge is achieved by a magnetic field for the purpose of a planned investigation. The influence of the magnetically stabilized tornado gliding arc discharge parameters such as magnetic field and applied voltage on microscopic tornado plasma parameters was studied. The electron temperature1was measured using a Boltzmann plot and the electron1density was1determined by the Stark1broadening method. The electron temperature ranged from 0.818 eV to 1.495 eV, and the electron density varied from 1.37 × 1018 cm−3 to 2.49 × 10 18 cm−3 at a magnetic coil with 350 turns. Subsequently, the electron temperature increased to a range of 1.029 eV–1.794 eV, and the electron density reached a range of 1.53 × 1018 cm−3 to 2.89 × 1018 cm−3 at a magnetic coil with 500 turns. It can be observed that the plasma properties exhibit a rise as the number of turns of the coil and the applied voltage increase.

Numerical Analysis of the Influence of Evaporation of the High- and Low-Melting-Point Anode Materials on Parameters of a Microarc Discharge

We present the results of numerical studies of the influence of evaporation of anode material on the main characteristics of an arc discharge. Calculations were carried out for an arc discharge in helium as a buffer gas with high-melting-point (using graphite as an example) and low-melting-point (using copper as an example) anodes. The dependences of the main arc-discharge parameters on current density are presented. It is demonstrated that intense evaporation of particles of the anode material into the discharge gap occurs upon reaching the melting point of the anode surface. As a result, the plasma-forming ion is replaced, i.e., the carbon ion in the case of the graphite anode or a copper ion in the case of the copper anode becomes dominant. In the process, a jump in the potential is observed in the dependence of voltage on current density (the volt–ampere characteristic, VAC). Distribution of the main plasma parameters along the discharge gap is presented for different points in the VAC.

Arc characteristics in short electrical arc high-efficiency milling for GH4169

To solve core problems of slow arc response and unstable combustion, arc movement characteristics and arc action rules in short electrical arc milling are studied using a high-speed acquisition system and the Phantom high-speed camera in this article. To improve arc reignition, the characteristic parameters of arc discharge are determined as a discharge gap of 0.053 mm and discharge time of 2180 μs. A short electrical arc milling experiment with nickel-based superalloy GH4169 is carried out, confirming that the continuous stable discharge of the arc can easily produce a material removal rate of 40 g/min and a tool wear ratio of 0.8%. An SU8010 scanning electron microscope and energy spectrum analyzer are then used to study the erosion mechanism of GH4169 in short electrical arc milling. This article aims to expand the processing range of short electrical arc machining in the field of special material processing to provide experimental and theoretical bases for the development of short electrical arc milling technology theory and methods.

Formation of pulsed large-radius electron beam in the forevacuum pressure range by a plasma-cathode source based on arc discharge

The research on generation and propagation of large-radius low-energy (up to 10 keV) electron beam with millisecond pulse duration by the plasma-cathode electron source in the forevacuum pressure range (3–30 Pa) is presented. An arc discharge with cathode spot has been used to generate emission plasma with millisecond pulse duration. Large hollow anode and ball-shaped redistributing electrode have provided formation of arc plasma with emission surface of 100 cm2; emission plasma boundary has stabilized by metallic mesh. It is established, that gas type and gas pressure affect the parameters of the arc discharge. In case of gases with greater ionization cross section (argon, nitrogen), an increase of gas pressure has led to a decrease of arc voltage and to an increase of emission plasma density. Gas with small ionization cross section (helium) had weak effect on the arc discharge parameters. An increase of emission window in the anode has provided an increase in radius of the electron beam and an increase of efficiency of electron extraction from the arc plasma; on the other hand it has led to an increase of influence of back-streaming ion flow on the electron emission and led to a decrease of maximal operating gas pressure. Reducing the geometric transparency of the emission mesh, as well as the use of gas with small ionization cross section have provided an increase in the maximal operating pressure of the source of large-radius electron beam. It is established, that in the forevacuum pressure range, large-radius electron beam is efficiently generated in the investigated range of distances from the extractor up to 35 cm.

Generation of Millisecond Low-Energy Large-Radius Electron Beam by a Forevacuum Plasma-Cathode Source

We describe our research on the generation and formation of low-energy (up to 11 keV) large-radius (up to 3.5 cm) electron beams with pulse duration up to 10 ms, in the forevacuum pressure range (4–25 Pa). The electron beam was formed by extraction from a cathodic arc plasma of millisecond pulse duration using a dc accelerating voltage. To increase the efficiency of electron emission from the plasma, the anode of the plasma source was divided into hollow and plane parts, and the current through the hollow part was limited. When using a redistributing electrode and limiting the current through the hollow part of the anode, the working gas and the gas pressure affect the arc discharge parameters. On the other hand, limiting the current through the hollow part of the anode yields increased efficiency of electron emission from the plasma and provided control of the electron extraction efficiency as well as maximum tolerable gas pressure at the selected beam current. We have generated the electron beam with current up to 23–25 A at pulse duration up to 10 ms in the forevacuum pressure range 4–25 Pa. The electron beam energy per pulse reaches 1800–2000 J.

A Single-Ended Ultra-Thin Spherical Microbubble Based on the Improved Critical-State Pressure-Assisted Arc Discharge Method

Hollow core microbubble structures are good candidates for the construction of high performance whispering gallery microresonator and Fabry-Perot (FP) interference devices. In the previous reports, most of interest was just focused on the dual-ended microbubble, but not single-ended microbubble, which could be used for tip sensing or other special areas. The thickness, symmetry and uniformity of the single-ended microbubble in previous reports were far from idealization. Thus, a new ultra-thin single-ended spherical microbubble based on the improved critical-state pressure-assisted arc discharge method was proposed and fabricated firstly in this paper, which was fabricated simply by using a commercial fusion splicer. The improvement to former paper was using weak discharge and releasing pressure gradually during the discharging process. Thus, the negative influence of gravity towards bubble deformation was decreased, and the fabricated microbubble structure had a thin, smooth and uniform surface. By changing the arc discharge parameters and the fiber position, the wall thicknesses of the fabricated microbubble could reach the level of 2 μm or less. The fiber Fabry-Perot (FP) interference technique was also used to analyze the deformation characteristic of microbubble under difference filling pressures. Finding the ends of the microbubbles had a trend of elongation with axial compression when the filling pressure was increasing. Its sensitivity to the inner pressure of microbubble samples was about ~556 nm/MPa, the bubble wall thickness was only of about 2 μm. Besides, a high whispering gallery mode (WGM) quality factor that up to 107 was realized by using this microbubble-based resonator. To explain the upper phenomenon, the microbubble was modeled and simulated with the ANSYS software. Results of this study could be useful for developing new single-ended whispering gallery mode micro-cavity structure, pressure sensors, etc.

Structure and morphology of copper oxide composite materials synthesized by the arc discharge method

Copper oxide is a semiconducting compound with a narrow band gap and is used for photoconductive and photothermal applications. Most of the synthesis methods for the preparation of copper oxide composite materials either are unsuitable for mass fabrication or inevitably introduce unwanted impurities. In this work, we report on the synthesis of copper oxide composite materials by the arc discharge method with a pure copper rod as the anode and graphite as the cathode. Ion beam analysis techniques, particle-induced X-ray emission and Rutherford backscattering spectrometry were used to probe the impurities in the copper oxide composites. Ion beam analysis results revealed copper and oxygen as constituent elements with no impurities. X-ray diffraction results discovered the presence of CuO, Cu2O and Cu phases in the composite materials. The morphology of the as-synthesized copper oxide was studied by scanning electron microscopy. Results clearly demonstrated that spherical particles were obtained with an average diameter of 14 [Formula: see text]m (range 2–85 [Formula: see text]m), 35 [Formula: see text]m (range 20–100 [Formula: see text]m) and 50 [Formula: see text]m (range 30–120 [Formula: see text]m) for the arc current of 60 A, 80 A and 95 A, respectively. It was found that the morphology can be controlled by the arc discharge parameters, e.g. a lower arc discharge current contributed to a smaller particle size. This is because the electric arc current influences the nucleation and the growth of the spherical structures. Due to its simplicity of synthesis, the proposed arc discharge is a promising technique for the fabrication of copper oxide composite materials for optical and electrical applications.

Morphological and structural features of materials formed in carbon plasma of arc discharge

The method of electric arc synthesis is used to obtain nanoparticles encapsulated in a carbon matrix. The properties of the entire material depend on the properties of the carbon matrix. In this paper, the structural characteristics of a carbon material synthesized at various arc discharge parameters are investigated. It is established that in the arc discharge a material containing amorphous and graphite-like carbon structures is synthesized, including in the form of graphene fragments folded into stacks, twisted into rolls and in the form of closed forms. Interplanar distances in graphite-like structures and interatomic distances in amorphous structures are determined. It is established that the pressure of the buffer gas determines the size of the soot globules and the volume fractions of graphite-like and amorphous structures, and the current strength affects the internal structure and determines the size of graphene planes in graphite-like structures.

The reaction of arc discharge parameters to the selection of electrons from the emission plasma in an electron accelerator with a grid plasma cathode

In the electrode system of an electron source with a plasma cathode, which allows the generation of a pulse-periodic electron beam of a large cross section from vacuum to the atmosphere through the outlet foil window, investigations have been made of the effect of electron extraction from the emission plasma on the parameters of a low-pressure arc discharge in which this plasma is generated. The work of the plasma cathode in different modes of electron beam generation is compared, namely, with the use of both a wide-aperture two-electrode electron-optical system (EOS) characterized by high beam current losses on the ribs of the support grid and a multi-aperture two-electrode EOS, when a metal mask is installed on the emission mesh with a configuration of holes that repeats the configuration of the holes in the support grid, and the electron beam is a superposition of electron beamlets formed by separate emission structures, the plasma boundary of which is also stabilized by a fine-structure metal mesh. Under the experimental conditions, the selection of electrons from the emission plasma leads to an increase in the voltage in the interelectrode gap between the cathode and the hollow anode of the plasma emitter, whose “voltage-addition” depends on the conditions of generation of the emission plasma (pressure and type of working gas, the ratio of the anode area of the discharge to the emission area), the area of the emission structures and the cell size of the used emission grid.

Arc-Induced Long Period Gratings from Standard to Polarization-Maintaining and Photonic Crystal Fibers.

In this work, we report about our recent results concerning the fabrication of Long Period Grating (LPG) sensors in several optical fibers, through the Electric Arc Discharge (EAD) technique. In particular, the following silica fibers with both different dopants and geometrical structures are considered: standard Ge-doped, photosensitive B/Ge codoped, P-doped, pure-silica core with F-doped cladding, Panda type Polarization-maintaining, and Hollow core Photonic crystal fiber. An adaptive platform was developed and the appropriate “recipe” was identified for each fiber, in terms of both arc discharge parameters and setup arrangement, for manufacturing LPGs with strong and narrow attenuation bands, low insertion losses, and short length. As the fabricated devices have appealing features from the application point of view, the sensitivity characteristics towards changes in different external perturbations (i.e., surrounding refractive index, temperature, and strain) are investigated and compared, highlighting the effects of different fiber composition and structure.

Electric arc in three-phase metallurgical furnaces

The theoretical and practical assumptions relative to the studies of electric arcs in steel-melting furnaces presented in journal Electrometallurgiya in 2011–2012 are subjected to a critical analysis. Based on classical concepts and the author experiments, the concept is presented regarding to the phases of the state and parameters of arc discharge in the ac electromagnetic field of a three-phase system. Industrial methods of eliminating the injurious effect of flash arc on furnace lining and the furnace efficiency are considered.

Fabrication of CNT Nano-Strands as a Schottky Transistor Platform

In this study, high voltage arc discharge technique is used for direct fabrication of carbon nanotube strands for schottky interconnects to study prototype carbon nanotube field effect transistors. The CNT samples are grown between graphite electrodes mounted on PCB templates in 5 mm gap using pure methane at different flow rate 0.2-1 standard litter per minute under atmospheric conditions. This report discusses the synthesis detail of nano-CNT strands, effect of electrical parameters of arc discharge and growth process. The structure of the grown carbon strands is explored in macro regime by high resolution optical microscope and also by scan electron microscopy technique for structural morphological analysis. The technique has a promising technology to grow unidirectional carbon nanomaterials which is employed on Schottky transistor fabrication.

Angular Distribution of Ions in a Vacuum Arc Plasma With Single-Element and Composite Cathodes

The angular distribution of the different cathode materials and gaseous ion flow from vacuum arc plasma is investigated. A metal-vapor-vacuum-arc-type ion source and a time-of-flight mass spectrometer were used. The experiments were performed using a range of different cathode materials, including C, Al, Zn, Cu, Ti, Co, Cr, W, Pb, <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{Cu}_{0.7}\hbox{Cr}_{0.3}$</tex></formula> , <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$\hbox{W}_{0.4}\hbox{Co}_{0.17}\hbox{C}_{0.43}$</tex></formula> , and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$ \hbox{Zn}_{0.4}\hbox{Pb}_{0.6}$</tex></formula> , over a range of vacuum arc discharge parameters. It was shown that, for all materials, the fraction of singly charged ions on the axis of the system is much less than that of multiply charged ions, but at the edges, the fraction of single-charged ions is greater than that of multiply charged ions; for composite cathodes consisting of light and heavy materials, there were substantially less light atoms on the axis than heavy atoms, while the opposite situation prevailed at the edges, but for cathodes with similar mass, the angular distributions of the materials were very close to each other. The velocities of ions of different materials in the composite cathode were different, but light ions had a higher velocity than those in a pure cathode plasma. With admission of gas, the angular distribution of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{Ar}^{+}$</tex></formula> became more isotropic with increasing pressure, while the metal ion distributions changed only minimally.

Numerical modeling of arc plasma generator for chemical laser applications

The results of the numerical modeling of arc discharge phenomenon relevant to hydrogen fluoride/deuterium fluoride (HF/DF) laser applications are given. The overall mechanics of arc discharge phenomena on the basis of numerical modeling employing the commercial code COMSOL is discussed. The equations for a 2D axisymmetric, weakly compressible, laminar flow with heat transfer and the coupled hydrodynamic and electromagnetic equations are solved using the SIMPLE algorithm. The variations in the material properties, temperature, and velocity due to the generated arc are studied. A comparison of the results obtained with those from the studies available in the literature validates the computational data. Since each designed plasma arc tunnel is unique in itself and specific in application, this would enable one to alter arc discharge parameters to optimize a specific laser.

Size-controlled synthesis and gas sensing application of tungsten oxide nanostructuresproduced by arc discharge

Several different synthetic methods have been developed to fabricate tungsten oxide (WO3) nanostructures, but most of them require exotic reagents or are unsuitablefor mass production. In this paper, we present a systematic investigationdemonstrating that arc discharge is a fast and inexpensive synthesis methodwhich can be used to produce high quality tungsten oxide nanostructures forNO2 gas sensing measurements. The as-synthesizedWO3 nanostructures are characterized by x-ray diffraction (XRD), scanning electron microscopy(SEM), transmission electron microscopy (TEM), finger-print Raman spectroscopy and protoninduced x-ray emission (PIXE). The analysis shows that spheroidal-shaped monoclinicWO3 crystal nanostructures were produced with an average diameter of 30 nm (range 10–100 nm) atan arc discharge current of 110 A and 300 Torr oxygen partial pressure. It is found that themorphology is controlled by the arc discharge parameters of current and oxygen partial pressure,e.g. a high arc discharge current combined with a low oxygen partial pressure results in smallWO3 nanostructures with improved conductivity. Sensors produced from theWO3 nanostructures showa strong response to NO2 gas at 325 °C. The ability to tune the morphology of theWO3 nanostructures makes this method ideal for the fabrication of gas sensing materials.

In Situ Temperature Measurement of an Optical Fiber Submitted to Electric Arc Discharges

Type S thermocouples were assembled in situ by applying high intensity electric arc discharges to the contact junction of two platinum (Pt) and Pt-10% rhodium (Pt-10% Rh) wires, inserted on a silica capillary. The electrically insulated thermocouples built in this way were afterwards employed to estimate the temperature of an optical fiber subjected to arc discharges. For typical values of the arc discharge parameters used to arc-induce long-period fiber gratings (electric current I=9 mA and arc duration t=1 s), a capillary peak temperature value of 1420/spl deg/C/spl plusmn/40/spl deg/C was obtained by extrapolation of the experimental data for the limit situation of having a thermocouple with negligible diameter. The temperature profiles in the capillary and in an optical fiber were calculated based on a heat transfer model implemented by a finite element algorithm and fitted to the experimental temperature distribution in the Pt and Pt-10% Rh wires. The correspondent peak temperatures computed for the capillary and for the fiber were 1450/spl deg/C and 1320/spl deg/C, respectively. A good agreement between the capillary temperature values determined graphically and numerically was obtained.

Effect of hydrogen concentration in argon-hydrogen mixtures on parameters of electric arc in gas-vortex plasmatrons for diamond coating synthesis

Abstract Experiments have been performed to investigate the influence of hydrogen concentration in argon-hydrogen mixtures on arc discharge parameters of a gas-vortex plasmatron with gas-dynamic fixing of the arc length for synthesizing diamond coatings (DC) at different argon flow rates. A phenomenological explanation is offered to account for the dependence of the arc voltage drop on hydrogen concentration in the argon-hydrogen mixture for fixed arc current and argon flow rate values. It is shown that increasing the argon flow rate at a constant hydrogen flow rate increases the specific enthalpy and the temperature of hydrogen. An experimental method of determining the optimum hydrogen concentration in the argon-hydrogen mixture of the arc discharge used for DC synthesis at different arc current values is proposed.

Pulse-frequency, high-intensity ion beams based on a vacuum arc

The production and investigation of pulse-frequency, high-intensity ion beams based on a vacuum arc are examined. The influence of arc discharge parameters, accelerating voltage, residual gas pressure, pulse repetition rate, and geometric dimensions of the accelerator on the ion generation efficiency is analyzed.