High-current Pulsed Discharge Research Articles

Low-pressure high-current magnetron discharge with electron injection: From self-sputtering with multiply charged metal ions to non-sputtering with “pure” gas ions

We report our experimental investigations of the effect on the ion composition, including the ion mass-to-charge composition, of electron injection into the plasma of a high-current pulsed magnetron discharge in the ultra-low operating pressure range. We show that changing the magnetron discharge voltage by injecting additional electrons with adjustable current allows implementation of two operating modes: one with a plasma in which metal ions dominate (including multiply charged ions for certain target materials with low sputtering yield), and the other a magnetron non-sputtering mode with plasma of only gaseous ions.

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.

Spectral diagnosis of underwater microsecond high-current pulsed discharge plasma

Underwater microsecond high-current pulsed discharge can generate powerful shock waves and a significant number of active ions, offering a wide range of applications. To analyse the characteristics of plasma channel formed by the discharge, this study established a comprehensive test platform and conducted spectral diagnosis for underwater high-current pulsed discharge. Considering the randomness of the pulsed arc discharge, the voltage and current waveforms under different discharge cases were measured, and the images and emission spectra of the plasma channel were obtained. The origin of the continuous emission of the initial spectra was analysed. A spectral fitting algorithm was proposed, which could separate the spectral lines into line emission of Hα and continuous background, and correct the self-absorption. The time-varying characteristics of electron density were obtained under three typical discharge cases, the possible errors caused by baseline shift were considered, and the influencing factors of line broadening were analysed. Under the test conditions of this study, the electron density of plasma channel was in the order of 1024–1025 m−3.

Visualization of the vortex structure formation of a long-lived afterglow arising in a symmetrical pulsed discharge

A visualization of the emerging toroidal vortex in the long-lived afterglow of a high-current symmetrical pulse discharge with an electrolyte anode has been carried out. The visualization of the emerging vortex flow was carried out using the laser knife method using a powerful 10 W laser, which formed a flat divergent beam, which was reflected from dust particles in the atmosphere. For greater contrast, water vapor was let in into the region of the discharge and the emerging afterglow, which moved synchronously with the emerging afterglow vortex. The laser beam reflected from small water vapor droplets made it possible to visualize the gas flow, which was then filmed with a high-speed video camera. The presented data clearly show that the emerging afterglows are able to retain their volume for a long time precisely due to the formation of a vortex structure.

Influence of a laser intensity on EUV brightness and ion speed from a laser-assisted discharge-produced plasma

Laser-assisted discharge-produced plasma (LDP) is one of the ways to generate extreme ultraviolet (EUV) light used in the semiconductor manufacturing processes. This light source uses a pulsed laser and a high-current pulsed electrical discharge to make a high-temperature and high-density tin plasma. One of two rotating disk electrodes, of which surfaces are coated by liquid tin (Sn), is irradiated by the laser to produce tin plasma. The plasma propagates from one electrode (cathode) to the other (anode) and ignites an electrical breakdown between the electrodes. The low-inductance circuit connected to the electrodes provides a current of approximately 15 kA and 150 ns to the tin plasma. The plasma implodes due to its own magnetic pressure, and EUV radiation is emitted from the resultant hot and dense plasma. High-speed ions are also emitted from the plasma and limit the lifetime of the mirror used to collect the EUV light. We need to maximize the light emission and minimize the ion emission. The role of the laser is essential in the LDP EUV source not only to ignite the discharge but also to condition the initial plasma. It influences EUV energy, EUV brightness, and emitted ion speed distribution of the plasma. The experiment suggested that laser intensity higher than 25 GW/cm2 produced high EUV brightness and low emitted ion speed.

Low-pressure high-current pulsed magnetron discharge with electron injection from a vacuum arc plasma emitter

We report our investigations on a planar (Ø 125 mm) high-current (up to 50 А) pulsed (100–400 μs) magnetron discharge with injection and acceleration of auxiliary electrons into the cathode layer. The injected electrons were from the plasma of a pulsed (300 μs) vacuum-arc discharge with current amplitude 10–60 A. The magnetron targets were Cu and Zn, and the operating gas was argon. The use of a gasless vacuum-arc electron emitter leads to further decrease in the minimum operating pressure of the high-current form of magnetron discharge, down to 0.18 mTorr (0.024 Pa). We present here the experimental results and a numerical model of the evolution of the ion mass-to-charge composition of the magnetron plasma as the operating pressure decrease to its ultimate lower limit.

Dynamics of Heat Fluxes in a Channel Area Heated by a Pulsed High-Current Discharge

Dynamics of Heat Fluxes in a Channel Area Heated by a Pulsed High-Current Discharge

Influence of flash ignition mechanism of high-current pulsed xenon discharge on the optical degradation of the quartz shell in the UV region of the spectrum

Influence of flash ignition mechanism of high-current pulsed xenon discharge on the optical degradation of the quartz shell in the UV region of the spectrum

Pulsed high-current discharge in water: adiabatic model of expanding plasma channel and acoustic wave

This paper presents the results of a theoretical and experimental study of the use of a pulsed discharge in water to obtain a strong acoustic wave in a liquid medium. A discharge with a current amplitude of 10 kA, a duration of 400 ns, and an amplitude pulsed power of 280 MW in water at atmospheric pressure created an expanding acoustic wave with an amplitude of more than 100 MPa. To describe the formation of the discharge channel, an isothermal plasma model has been developed, which made it possible to calculate both the expansion dynamics of a high-current channel and the strong acoustic wave generated by it. Our calculations show that the number density of plasma in the channel reaches 1020 cm–3, while the degree of water vapor ionization is about 10%, and the channel wall extends with a velocity of 500 m s−1. The calculations for the acoustic wave are in good agreement with measurements.

Analysis of the bubble-pulsation process of underwater high current pulsed discharge

The bubble of underwater high current pulsed discharge forms after the pre-breakdown process, and the change in electrical loop parameters will affect its pulsation characteristics. The relationship between loop electrical parameters and the bubble-pulsation process is unclear, and its influence on the acoustic characteristics of the bubble-pulsation is not apparent. In order to quantitatively analyze the bubble-pulsation characteristics, a comprehensive experimental platform of underwater high current pulsed discharge is built. Under different loop electrical parameters, with the help of experimental data of electrical signals and optical images, the variation characteristics of the bubble-pulsation period and energy are analyzed. The acoustic characteristics of the bubble-pulsation process are analyzed, and the correctness of acoustic characteristic analysis is verified by experimental results. The comparison between experimental and theoretical data shows that the analysis of bubble-pulsation period and energy is correct. The bubble-pulsation characteristics can be predicted utilizing the deposition energy of the plasma channel. The results provide a basis for the quantitative analysis of the bubble-pulsation characteristics and strengthen the connection between the three underwater high current pulsed discharge processes.

A Refined Mathematical Model of Physical Processes in a Conductor at a High-Current Pulse Discharge

A novel mathematical model describing physical processes during the flow of an aperiodic pulse current with amplitude of 100 kA along a conductor with a circular cross-section is proposed and investigated. It is shown how a short-term electric discharge of an aperiodic shape affects the distribution of the current density in the cross-section of the conductor, causing its nonuniform heating and the appearance of significant thermal forces as well as mechanical stresses and strains. Based on the developed mathematical model, the relation-ship between electromagnetic, thermal and mechanical phenomena is shown, allowing a deeper understanding of the multiphysics processes taking place. The maximum values of the current density are calculated, which on the surface of the conductor reach values of 47 kA/mm2, while the temperature rise of a copper conductor with a diameter of 2.44 mm is no more than 80ºC at high temperature gradients, which causes the appearance of thermal stresses that have value (40–50)% of the value of the short-term strength limit of electrical copper. Utilization of this model allows to more accurately determine the required conductor cross-section based on the characteristics of electromagnetic, thermal and mechanical pro-cesses. It is shown that the simplified model (the condition for the uniform distribution of the current over the cross-section) gives significantly underestimated values of temperatures and does not take into account temperature deformations.

Numerical simulation of high-current pulsed arc discharge in air

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

High-current arc discharge in air

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

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

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

Calculation of Electrohydraulic Shockwaves Based on Improved Arc Impedance Model

The intensity of the shockwave generated by the high-current pulse discharge in the liquid is mainly determined by the deposited energy during the accelerated expansion stage of the arc plasma channel. Under the same discharge condition, there is randomness in the shape of the arc channel. Generally, longer arc channels have larger impedance, which can obtain more energy and generate stronger shockwaves. In this article, a comprehensive test platform for high-current pulse discharge in liquid was established; the voltage, current, and far-field shockwaves were measured; and the development images of the arc channel were taken. Considering the influence of temperature, channel expansion, and radiant energy, a calculation method of electrohydraulic shockwaves based on the improved arc impedance model was established. The initial values and parameters of the model were selected by comparison with the test results to ensure their accuracy. The arc channel current, time-varying resistance, deposition energy, and far-field shockwaves were calculated and compared with the test results to verify the rationality of the model. The calculation of electrohydraulic shockwaves based on the improved arc impedance model can provide theoretical guidance for optimizing the industrial application of shockwaves.

Generation of Plasma with Increased Ionization Degree in a Pulsed High-Current Low-Pressure Hollow Cathode Discharge

The paper presents the results of research of the processes of generation of pulsed beam-plasma formations in a high-current non-self-sustained glow discharge with a hollow cathode at low (0.025–0.25 Pa) pressures. In the hollow cathode volume of 0.34 m3, the glow discharge pulsed currents up to 800 A were obtained at injected electron currents up to 150 A, discharge burning voltages up to 400 V, and a pulse duration of 1 ms. The plasma with a density of about 1012 cm-3 was formed with ionization degree up to 16%. It has been shown that the electron free path length λC between the Coulomb interactions in the pressure range 0.025–0.05 Pa is by a factor of about 3.5 less than the electron free path length λe when interacting with neutrals at high (10–15%) degree of plasma ionization. The measured saturation electron current density on the single electric probe was 3.7 (0.025 Pa), 5 (0.05 Pa), and 6.7 A/cm2 (0.25 Pa). Relatively homogeneous beam-plasma formations generated in the glow discharge are promising for the formation of intensive pulsed electron beams of large cross section.

Using a fiber optic sensor for registration of pulsed plasma discharge current

The problem of increasing the accuracy of recording the pulse shape of a rapidly changing current of a powerful plasma emitter under conditions of powerful electromagnetic interference is considered. To register high-current pulsed discharges, it is proposed to use a polarimetric fiber-optic current sensor based on a Spun-type fiber. Using the indicated current sensor, a technique for recording high-current pulsed discharges of a plasma emitter in the mode of time profiling of the current pulse of two high-voltage capacitive storage devices with a total energy of up to 1800 kJ is realized. The discharge chamber, power supply circuits, and the formation of a plasma discharge are described. The design and principle of operation of a prototype of a two-pass polarimetric fiberoptic sensor with a Spun-type fiber and a Faraday compensator of mutual optical anisotropy are presented. The general scheme of current measurements, the sensor calibration scheme is presented, and the experience of using a prototype sensor for measuring high-power pulse currents is described. The features of the preliminary calibration of the sensor are discussed. The results of measuring the current by optical and traditional recording methods based on the Rogowski coil and Hall sensors are compared with each other, and a noticeable increase in the accuracy of reproducing the current pulse shape by the optical recording method is noted. Possible options for upgrading a fiber-optic sensor to expand the range of current recording are considered.

Magic Clusters PtMg2,3 H5 - Facilitated by Local σ-Aromaticity.

The concept of local aromaticity has been successfully utilized in understanding the stability of certain atomic clusters. However, all the skeleton atoms in these clusters are covered by at least one local aromatic feature, collectively making the multiple local aromaticities coexist globally. Herein we show the robustness of local aromaticity as a tool for the discovery of novel magic clusters: not all of the skeleton atoms need to be covered by an aromatic feature to make the cluster magic. In this study, the PtMg2,3 H5 - cluster anions are generated by a unique high-current pulsed discharge ion source and found to be magic numbers using mass spectrometry. Photoelectron spectroscopy and calculations confirm that only the PtH4 2- kernels in these clusters are locally aromatic. Based on these results, we propose that local aromaticity can be gainfully utilized as a new potential magic rule in the search for magic numbers.

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.

Разработка и исследование макета низкочастотного источника питания сильноточного импульсного магнетронного разряда

Разработка и исследование макета низкочастотного источника питания сильноточного импульсного магнетронного разряда