Electrical Discharge Parameters Research Articles

Ionization of copper in gas and gasless modes of continuous high-power magnetron sputtering

The results of studies of magnetron sputtering of copper at discharge currents from 2 to 15 A in a 76 mm diameter planar magnetron are presented. In addition to the standard gas mode at an argon pressure of 0.12 Pa, a gasless mode was also implemented in which no argon was supplied to the vacuum chamber and the base pressure was 1·10−3 Pa. The stable gasless mode is realized at a discharge current higher than 8 A. The electrical discharge parameters as well as the copper sputtering rate, the ion current density on the substrate and the degree of ionization of the sputtered target material were measured and compared for the two modes mentioned. The plasma composition was also measured by optical spectrometry. The experimental data were used to calculate the density and composition of the neutral and ion fluxes to the substrate. It is shown that the gasless mode provides a higher ion current density on the probe and a higher degree of ionization of the sputtered copper compared to the gas mode at the same discharge current. The degree of ionization of the sputtered material reaches 14–15 % in gasless mode, whereas in gas mode it varies from 2 to 13 % depending on the discharge current.

Driving voltage frequency and electrode material effects on electromagnetic radiation of the surface dielectric barrier discharge in the air

The electrical discharges are, among others, accompanied by the emission of electromagnetic waves of various frequencies. We studied this emission for the surface dielectric barrier discharge in the air. We used the discharge with one strip-driven electrode and a sinusoidal driving voltage of frequencies 5 and 10 kHz. From the spectra of emitted waves in the frequency band up to 3 GHz, we found that this type of discharge emits the radiation of frequencies below 500 MHz. In this frequency band, we focused on the effect of the driving voltage frequency and driven electrode material on the spectra of these waves. It was found that emitted radiation is distributed in several packages of frequencies, and an increase in the driving voltage frequency or voltage increases the power level of emitted radiation. Compared with the radiation spectrum of the discharge with an aluminium-driven electrode in the spectrum of the discharge with the copper-driven electrode, new peaks of various power levels and the shift of certain radiation frequencies to lower values appear. To understand the underlying mechanism of the discharge electromagnetic waves emission, we focused on the correlation between the electric component of emitted EMWs and the discharge electrical parameters as a function of time and discharge voltage.Graphical abstract

Memory effect and statistical characterization of pulsed vacuum microdischarge breakdowns between palladium electrodes from 500 nm up to [formula omitted

The understanding of microgaps breakdown phenomena at controlled laboratory conditions represents an important prerequisite in the development of future micro-plasma technologies. The present work is focused on the observation of the electrical discharge parameters of the pulsed vacuum breakdown between palladium electrodes. The quasi-homogeneity of the generated fields was achieved using a plane-to-sphere geometry of the electrodes separated from 0.5 to 10μm. The first part of the study covers the conditioning process of the electrodes, including a comparison of the pair-virgin and single-virgin electrode configurations. A detailed statistical analysis of the discharge parameters, such as the breakdown voltage, the duration and the energy released during a pulse, and minimal power for maintaining the discharge is provided for different gap configurations for a voltage ramp speed of 107 kV/s. The analysis with respect to breakdown voltage yielded the observation of the memory effect between subsequent breakdowns.

Integrated physicochemical processes to tackle high-COD wastewater from pharmaceutical industry

Wastewater decontamination in pharmaceuticals is crucial to prevent environmental and health risks from API residues and other contaminants. Advanced oxidation processes (AOPs) combined with cavitational treatments offer effective solutions. Challenges include designing reactors on a large scale and monitoring the effectiveness and synergies of the hybrid technology. In the present work, pilot-scale treatment of a real high COD (485 g/L) pharmaceutical wastewater (PW) was investigated using hydrodynamic cavitation (HC) operated individually at 330 L/h or in combination with oxidants and electrical discharge (ED) with cold plasma (15 kV and 48 kHz). The first approach consisted of PW cavitational treatment alone of 7 L of 1:100 diluted PW at a HC-induced pressure of 60 bar and a flow rate of 330 L/h. However, this strategy did not provide satisfactory results for COD (∼15% less), and only when HC treatment was extended to more than 30 min in a recirculation mode, encouraging results were obtained (∼45% COD reduction). Consequently, a hybrid approach combining HC with ED-cold plasma was chosen to treat this high-COD PW. Aiming to establish an efficient flow-through hybrid process, after optimising all cavitation and electrical discharge parameters (45 bar HC pressure and 10 kHz ED frequency), the best COD abatement of ∼50 % was recorded with a 1:50 diluted PW. However, a subsequent adsorption step over activated carbon was required to achieve an almost quantitative COD reduction (95%+). Our integrated physicochemical process proved to be extremely efficient in treating high-COD industrial wastewater and resulted in a remarkable reduction of the COD value. In addition, the residual surfactants content in the PW were also drastically reduced (98%+) when a small amount of oxidants was added in the hybrid HC/ED treatment.

Acceleration of metal plates by hybridization of electrical and chemical energy for potential application in high-velocity impact welding

Vaporizing foil actuator welding is employed to connect dissimilar metals by utilizing the energy of an electrical explosion as the driving force for flyer plate acceleration. Herein, the electrical and chemical energies of explosives were combined to increase flyer plate velocity. A metal foil or wire mesh was used as an actuator, and a small amount of explosives was placed on the foil. Uniform acceleration of the flyer plate on the actuator was recorded using a high-speed video camera. The electrical energy applied to the actuator was measured synchronously by filming. The explosion of chemical explosives was successfully initiated owing to the electrical explosion of the actuator. In all experiments, the combination of the electrical explosion and chemical reaction improved the acceleration of the samples, facilitating higher velocities. The impact of the actuator type (mesh or foil) and the electric discharge parameters on the performance was studied. While foil actuators were more efficient in experiments on electric explosions alone, mesh actuators were superior when the chemical explosive was added. Explosions of the mesh actuator could initiate low density pentaerythritol tetranitrate (PETN) (the space-filling rate of PETN was approximately 30%). An explosive force of 0.3 g of PETN was converted into a driving force, imparting the flying plate with a velocity greater than 210 m/s. Electrical energy consumption for PETN initiation may be assumed to have an insignificant impact on flyer plate acceleration. In future, the proposed method may be used to connect heavier and thicker materials without expensive high-performance capacitors.

Control of the Energy Impact of Electric Discharges in a Liquid Phase

This paper describes the scheme and algorithm for controlling a laboratory setup that result in low uncertainty and high convergence with respect to the characteristics of electric discharges under the conditions of variable parameters of a reaction medium. The article presents current and voltage oscillograms when processing hydrocarbon raw materials. Methods for calculating the energy impact of electrical discharge are described. A comparison is made between the parameters of electric discharge with current pulse limitations and those without current pulse duration limitations. The proposed approach to controlling the characteristics of electric discharges provides the same parameters of nonthermal nonequilibrium plasma and, as a result, a regular composition of the products of plasma pyrolysis of hydrocarbon raw materials.

Microsecond Discharge Produced in Aqueous Solution for Pollutant Cr(VI) Reduction

This paper presents a detailed analysis of underwater electrical discharge parameters in the treatment of chromium (VI) used as a model pollutant to analyze the reduction process by plasma liquid interaction (PLI). Pin-to-pin microsecond discharges were performed in an aqueous Cr(VI) solution and the processes were characterized using electrical measurements, optical imaging and UV-Vis absorption measurements for [Cr(VI)] estimation. For the first time, the total reduction of Cr(VI) was successfully achieved by PLI process and a maximum energy yield of 4.7 × 10−4 g/kJ was obtained. Parametric studies on electrode geometry, applied voltage, electrodes gap and pulse duration are presented in detail. Finally, an analysis of the process is proposed by comparing our results of the energy yield calculation based on the injected energy with those of the literature and by providing an estimation of the global energy efficiency of the process.

In situ plasma cleaning of large-aperture optical components in ICF

The organic contamination damage of large-aperture optical components limits laser energy improvement of inertial confinement fusion (ICF). In situ cleaning of large-aperture optical components via low-pressure plasma is expected to remove organic contaminants from the optical surface. Herein, low-pressure air plasma equipment was proposed and used on surfaces of SiO2 sol–gel antireflection (AR) films in situ by conducting experiments. Its electrical discharge parameters were investigated and optimized during plasma cleaning. Plasma diffusion characteristics and homogeneity in large-aperture windows were analyzed by optical emission spectroscopy. Dramatic degradation in the optical properties of components was observed after organic contamination for 5 h. Transmittance, laser-induced damage threshold and surface morphology observation results demonstrated that low-pressure air plasma removed the organic contaminants from the surface of sol–gel AR films without causing damage and metal contamination. After plasma cleaning, the hydrophilicity of the films increased significantly due to the increase in the polar components of surface free energy. The mechanism of plasma cleaning organic contaminants was confirmed by x-ray photoelectron spectroscopy measurements. These salient results provide a new alternative method for removing organic contaminants in situ from large-aperture optical components and a foundation for improving the energy output of the ICF system.

High energy ion beams from the plasma focus

Instability development in the pinch induces a locally enhanced electric field that accelerates the charged particles to extraordinary high energies. Rapid discharge is the singular state of the ion source confirming high plasma impedance. High energy ion beam is correlated to the electrical discharge parameters and consequently the ion acceleration potential is directly related to the mean ion energy. Multi−MeV ions have been measured by magnetic spectrometry and nuclear activation yield-ratio to obtain the ion energy spectra and critically analyze the ion spectrum. A set of magnetic lens arranged in an optimized coil configuration results in medical grade radioactivity of 0.5GBq for a low energy plasma focus. High energy proton beams enables evaluating the sensitivity of link-board components and the error structure identification, with a significant probability of 0.1perproton.

Application of the Monte Carlo Method for the Determination of Physical Parameters of an Electrical Discharge

The aim of this paper is to use of the Monte Carlo Method to try to reproduce an electrical discharge in the oxygen gas; by following the random histories of free electrons and using the sampling laws, we can determine some electrical discharge parameters. Additionally we use the simulation results to verify the electrical breakdown criteria under an homogenous field and for small distances; and the obtained results are compared with those of the literature.

Electric signals measured during plasma thin-film etching and their connection to the electron concentration and the properties of the treated surface

The electric characteristics of a discharge are usually changed when a thin film is deposited on or etched from a discharge electrode or a substrate. The electric characteristics include the plasma potential, discharge voltage and discharge current, including higher harmonic frequencies of these quantities. This fact can be used for the monitoring of various plasma processes, but the mechanism by which the thin film influences the electric characteristics of the discharge has not been fully clarified. Our study of diamond-like carbon (DLC) film etching verified that variations of electric discharge parameters are caused by variations of electron concentration, which is caused by a difference in the electron emission yield between the DLC film and its substrate.

Characteristics of pulsed nanosecond discharge excited by compact solid-state pulse forming line at atmospheric pressure air

Non-equilibrium plasma is a promising technology for the generation of ozone and removal of exhausted fuel gases. However, applications of non-equilibrium plasma are restricted by energy utilization efficiency in many industry fields. Discharge excited by nanosecond pulsed power is regarded as one of the most efficient methods. In this study, a compact five stages stacked Blumlein pulse forming line and photoconductive semiconductor switches-based power source was introduced to generate pulsed plasma. This compact source could achieve over 50 kV with 10.1 ns pulse width and 4.8 ns pulse rising time. Coaxial cylindrical reactor was employed to generate a pulsed streamer discharge driven by the nanosecond pulsed source in atmospheric pressure air. Electrical parameters of the streamer discharge have been obtained in this study, the instantaneous power dissipation exceeds 8 MW and the average energy consumption of each pulse exceeds 56 mJ. Experiments of high speed photography have been conducted to observe the evolution process. It can be found that streamer heads start from the central wire electrode and then head to the grounded cylinder electrode in all radial direction of the coaxial electrode. Triple wire-to-cylinder electrodes discharge shows that all the three coaxial discharges develop synchronously and symmetrically, which shows that is capable of generating large volume non-equilibrium diffusive streamer discharge plasma.

About a new method to enhance the productivity of die sinking EDM

In order to control the EDM inter-electrode gap, the regulation is usually done indirectly by measuring the ignition delay or the average gap voltage, and the axes positions of the machine are adjusted accordingly.The machine efficiency strongly depends on the performance of this gap width controller.The problem in the procedure described above, lies in the comparably slow response time of the machine mechanics, in the tens of millisecond range, with respect to the discharge frequency, which is in the kHz range. The machine mechanics cannot follow it, therefore the performance of the machine is affected in terms of material removal rate, electrode wear, and surface quality.However, adapting the electrical discharge parameters can be typically 1000 times faster than moving the machine axis.This paper shows how it is possible, by adapting in real time the ignition voltage of every pulse to the gap width, to realize a sort of electronic servo system. Additional generator parameters are adjusted for every pulse as a function of the gap width, such the pulse interval etc. Moreover, the mechanically coupled servo system, and the electronic one complement each other.Experimental results show a remarkable increase of the discharge frequency and consequently of the material removal, without penalizing the other technological results, i.e. the inter-electrode gap, the workpiece roughness, the tool electrode wear.

Hole size effect on microhollow cathode discharge in air

In this work the values of main electrical parameters of the microhollow cathode discharge in atmospheric air (peak discharge current, discharge ignition voltage) depending on the diameter of the hole in the cathode were obtained. It was experimentally found that at currents up to 2 mA, the discharge operated in a self-pulsing mode. According to the experimental results it was concluded that the value of the discharge ignition voltage at average discharge current exceeding 2 mA didn’t depend on the hole diameter.

Alumo Matrix Composite Materials for Electro Spark Deposition on Carbon Steel

The article presents the research results on the problem of the influence of the electric spark discharge parameters and electrode alloys, based on metal matrix materials, used for electro spark deposition (ESD) on the physicochemical and operational characteristics of the coating layer. Experimental dependences of the cathode weight gain, erosion resistance of the anode materials, mass transfer coefficient, wear resistance of the coating, and their mathematical expressions with a reliability criterion of at least R2> 0.9044, are obtained. It is established that, after steel 45 sample has been treated by ESD with metal-matrix materials, the hardness of its surface increases 6 times on the average and the wear resistance – 2 times. The best values of wear resistance at all the modes under investigation have been obtained for the anode material NiO-Zr-TiO2-Al. Data series of cathode weight gain (ƩΔc), erosion resistance of anode materials (ƩΔа), mass transfer coefficient Кmt, coating wear resistance after ESD (Ʃcwr), coating formation efficiency (γcfe), ESD energy efficiency (γeef), are also obtained. These data can be recommended for achieving the required parameters of the ESD on steels using metal-matrix materials.

DAMAGE OF THE AIRCRAFT STRUCTURAL SYSTEM BY LIGHTING WITH RAIN PRECIPITATION ON ITS SURFACE

When an aircraft is struck by lightning damage of external structural elements is primarily caused by mechanical electrical impact of discharge on the aircraft, which results in the formation of dents on the skin, bends of panel elements (there have been cases of bending turbofan blades) and other deformations. Firstly, the mechanism of such lightning effect is caused by the action of ponderomotive forces generated by the interaction of the current in the lightning channel with currents flowing through the metal structures of the aircraft. Secondly, the shockwave of lightning has a physical impact on the elements of construction. The presence of condensation (moisture, ice) on the surface of the aircraft can significantly increase the damage of fuselage skin resulting from the electromechanical impact of lightning, which was confirmed by the results of the experimental research conducted at the Chair of Physics of the Moscow State Technical University of Civil Aviation. The water depth (as far as it is known, thunderstorm in most cases is accompanied by rain precipitation) can be large enough especially on the ground during parking and taxiing, as well as at takeoff operation and landing. Sheet samples of aluminum alloy skin D16AT with electrical discharge parameters (current amplitude 50–60 kA, duration of the first half-wave 30 microseconds) which were relatively equal to average parameters of natural lightning strike were tested. With water depth of not over 8 mm the indentations up to 2 mm deep and 30 mm in diameter were formed on samples up to 1,5 mm thick, with a sample thickness of 0,8 mm – over 10 mm in depth and up to 60–70 mm in diameter. Educated estimates indicated that presence of water increases the electrodynamic pressure on the skin several times. Firstly, having in consideration the elastic component such deformation can bring a danger to control mechanisms and surfaces located proximately under the skin when subjected to lightning strike. Secondly, electromechanical pressure amplification coupled with the striking acoustic wave generated by lightning can result in supercritical pressures in the mounting hardware of the skin. All of this should be taken into account both at the design stage of the aircraft and during aircraft operation including in particular post-flight inspection of the aircraft struck by lightning.

Ni and Cu oxide supported γ-Al2O3 packed DBD plasma reactor for CO2 activation

The direct activation of undiluted CO2 is carried out in a co-axial dielectric barrier discharge (DBD) reactor. The variation of the electrical discharge parameters and their influence on CO2 decomposition is investigated with the integration of 15 % MO/γ-Al2O3 (M = Ni, Cu) catalyst in the discharge zone. The electrical discharge is found to shift from the filamentary to a combination of surface and micro filamentary discharge on catalyst integration to NTP and also leads to the higher conversion of CO2 than DBD alone. The highest conversion of CO2 (15.7 %) with the energy efficiency of 1.597 mmol/kJ is achieved under CuO/γ-Al2O3 integrated NTP system, whereas the maximum of carbon balance (94.4 %) reaches with 4% CeO2 addition to CuO/Al2O3 catalyst. The oxygen vacancy of the catalyst plays a vital role in improving the performance, especially, the oxygen buffer property of CeO2 facilitates the recombination reaction and contributes to obtaining the highest carbon balance.

Simplified Spark Pulser for Nanoparticles Generation

This article studies the possibility to design high-voltage pulser to sustain spark discharges in dielectric liquid using cheap and simple design. A spark pulser based on a zero-voltage switch oscillating circuit is used to power a high-voltage transformer. Sparks are ignited between copper electrodes in deionized water. The influence of input voltage and electrode gap on voltage and delay before breakdown, deposited charge, and energy is discussed. The effect of a spark gap device is also studied. Parameters of electric discharge are used to determine the capacitance and inductance of generator, through modeling of the equivalent electrical circuit. The utilization of the pulser in nanoparticles synthesis is evaluated by estimating the electrode erosion rate. In addition, the cavitation bubble generated by the spark is used to determine the pressure of the medium in which the spark and nanoparticles formation occur. Results show that the operation is similar to other setups.

Improving the Geiger Muller Counter Characteristics by Optimizing the Anode and Cathode Radius Dimensions

This article considers the influence of the anode (r <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</sub> ) and cathode (r <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</sub> ) radius dimensions in the Geiger Muller counter chamber on its characteristics such as efficiency, measurement uncertainty, dead time, slope, plateau length, and aging. The article is of a theoretical and experimental nature. In the theoretical part of the article, the expression for the dependence of the electrical discharge parameters of a cylindrical electrode system is derived from various radius dimensions of the anode and cathode. For this purpose, the enlargement law of the probability was applied. The experimental part of the work was performed on the models of the Geiger Muller's chamber of different radius dimensions of the anode and cathode. The chamber models (and insulation gas) were made to maintain the geometrical similarity of the commercially applicable chamber. In the first experimental part of this article, the effect of radioactive radiation was simulated with a fast pulse voltage, while real radioactive elements were used in the second experimental part. The testing has shown that the synergy of the stochastic volume effect of the breakdown voltage of the Ruffer-Kuilling mechanism and the corona of the plasma can significantly improve all tested characteristics.

Electrical modeling of dielectric barrier discharge considering surface charge on the plasma modified material**Project supported by the National Key R&D Program of China (Grant No. 2018YFB0904400), the National Natural Science Foundation of China (Grant No. 51977187), the “Science and Technology Innovation 2025” Key Project of Ningbo City, China (Grant No. 2018B10019), the Natural Science Foundation of Zhejiang Province, China (Grant

We present the variations of electrical parameters of dielectric barrier discharge (DBD) when the DBD generator is used for the material modification, whereas the relevant physical mechanism is also elaborated. An equivalent circuit model is applied for a DBD generator working in a filament discharging mode, considering the addition of epoxy resin (EP) as the plasma modified material. The electrical parameters are calculated through the circuit model. The surface conductivity, surface potential decay, trap distributions and surface charge distributions on the EP surface before and after plasma treatments were measured and calculated. It is found that the coverage area of micro-discharge channels on the EP surface is increased with the discharging time under the same applied AC voltage. The results indicate that the plasma modified material could influence the ignition of new filaments in return during the modification process. Moreover, the surface conductivity and density of shallow traps with low trap energy of the EP samples increase after the plasma treatment. The surface charge distributions indicate that the improved surface properties accelerate the movement and redistribution of charge carriers on the EP surface. The variable electrical parameters of discharge are attributed to the redistribution of deposited surface charge on the plasma modified EP sample surface.