Pulsed Power Source Research Articles

Influence of Detonation Spraying Parameters on the Microstructure and Mechanical Properties of Hydroxyapatite Coatings.

The process of osteointegration depends significantly on the surface roughness, structure, chemical composition, and mechanical characteristics of the coating. In this regard, an important direction in the development of medical materials is the development of new techniques of surface modification and the creation of bioactive ceramic coatings. Calcium-phosphate materials based on hydroxyapatite have been proposed as bioactive ceramic coatings on titanium implants for the effective acceleration of bone tissue healing. To obtain bioactive ceramic coatings, pulse power sources are best suited, namely detonation spraying, in which the energy of the explosion of gas mixtures is used as a source of pulse action. The pulse mode of operation in the detonation spraying method is preferable for the formation of bioactive ceramic coatings. It provides a high velocity of hydroxyapatite particles, which promotes their effective fixation on the titanium substrate, while minimizing the heating of the material. This approach preserves the substrate structure and improves the coating adhesion. Four different types of coatings with varying O2/C2H2 molar ratios, ranging from 2.6 to 3.7, were obtained using detonation spraying. Powders and obtained coatings of hydroxyapatite were studied by Raman spectroscopy and XRD structural analysis. The results of XRD phase analysis showed the partial conversion of the hydroxyapatite phase to the α-tricalcium phosphate (α-TCP) phase during the detonation spraying process. The results obtained by Raman spectroscopy indicate that hydroxyapatite is the main phase in coatings. All hydroxyapatite-based coatings exhibited hydrophobic properties, which was confirmed by contact-angle values above 90° in wettability tests, characteristic of hydrophobic surfaces. The adhesive strength of the coatings was measured by the scratch test method. Tribological tests were conducted using the ball-on-disk method under both dry conditions and in Ringer's solution. This approach enabled the evaluation of wear resistance and friction coefficient of the coatings in different environments, simulating both lubrication-free conditions and those resembling physiological environments.

Thermal management and heat transfer enhancement of electronic devices using integrative phase change material (PCM) and triply periodic minimal surface (TPMS) heat sinks

This study focuses on the thermal management of electronic components using phase change materials (PCM) with triply periodic minimal surface (TPMS) structures. Three PCM-TPMS heat sinks (PCM-Gyroid, PCM-IWP, and PCM-Primitive) are examined, compared to pure PCM heat sinks. The heat sinks are evaluated under pulsed power sources with passive and active cooling. The effect of varying TPMS relative densities (10 %, 20 %, and 30 %) is also analyzed. The results indicate that PCM-TPMS heat sinks significantly accelerate the melting interfaces of PCM and provide improved heat transfer paths. They effectively scatter and reduce the base temperature of electronic components, with average values of 61.9 °C and 34.9 °C, compared to higher temperatures for pure PCM heat sinks under passive and active cooling, respectively. Increasing the relative density of TPMS structures from 10 % to 30 % leads to a slight improvement in base temperature reduction for the different TPMS structures. Among the three TPMS configurations, the PCM-Gyroid heat sinks are found to be the most effective in reducing base temperatures compared to PCM-IWP and PCM-Primitive heat sinks. Additionally, the use of PCM-TPMS significantly enhances the reliability and durability of electronic components by mitigating thermal cycling. Overall, the study demonstrates the potential of PCM-TPMS heat sinks in improving the thermal management and performance of electronic components.

Analysis of pulsed direct current reactive magnetron sputtering on a silicon target

Reactive sputtering is a very useful technique, particularly, for producing inhomogeneous interference filters, where the refractive index changes smoothly during deposition. In such a context, precise control of deposition parameters is crucial for replicating the desired optical properties. This study employed a pulsed DC power source to investigate the influence of a duty cycle on target poisoning, sputtering plasma characteristics, electric signals, and optical and morphological properties of synthesized films. Reactive pulsed DC magnetron sputtering was characterized by analyzing the behavior of plasma emission via optical emission spectroscopy and voltage-current signals, while modulating parameters such as the oxygen content within the vacuum chamber. A set of thin films was coated on glass substrates under different system conditions. These films underwent characterization employing spectroscopic ellipsometry to ascertain their optical constants, atomic force microscopy for surface morphology analysis, and x-ray diffraction for the determination of crystalline structures. The results indicate that longer duty cycles required higher oxygen levels to poison the target. Additionally, a detailed analysis of electrical signals revealed nonsquare waveforms, whose characteristics were influenced by both the duty cycle and the oxygen content within the sputtering chamber, resulting in higher effective voltages during the on-time of the voltage pulse. Grown films via reactive pulsed DC magnetron sputtering were also compared to films grown via conventional DC magnetron sputtering at equivalent conditions of target poisoning.

Research on Solid-State Linear Transformer Driver Power Source Driving Atmospheric Pressure Plasma Jet Treatment of Epoxy Resin

The Solid-State Linear Transformer Driver (SSLTD) is a nanosecond pulse power source characterized by its fast rise time and adjustable output waveform. It can generate uniform and stable atmospheric plasma jets, which is suitable for material surface modification. In this study, a 15-stage SSLTD was designed and assembled, which can produce a stable nanosecond pulse voltage up to 15 times the amplitude of the charging voltage at high frequencies, with a rise time of approximately 10 ns. This device can be used to generate stable atmospheric pressure Ar plasma jets with an electron density in the range of 1015~1016 cm−3 and gas temperatures close to room temperature. After the modification treatment by the plasma jets, the content of the C=O groups on the surface of the epoxy resin significantly increased in the wavelength range of 1720~1740 cm−1, and its flashover resistance was noticeably enhanced. The optimal comprehensive modification effect was achieved at a charging voltage of 600 V, pulse width of 50 ns, and pulse frequency in the range of 800~1000 Hz.

Pulse power supply for plasma aerodynamic actuators

The reduction of local heat load on the structural elements of aircraft or spacecraft vehicles due to the shock wave/boundary layer interaction can be successfully controlled in the future using a system of plasma actuators. The efficiency of plasma aerodynamic actuators operation is directly related to a power source. It determines a covered plasma area, an air flow speed and a thrust the actuator creates. The paper deals with the operation of a high-voltage source of sawtooth pulses with high efficiency for controlling plasma actuators. The pulse power source can be easily scaled for different nonlinear capacitive loads.

Comparative analysis of disinfection effectiveness of Helium CAP jet, sodium hypochlorite and QMix in Enterococcus faecalis infected root canals

In this work, a new geometry Helium Cold Atmospheric-pressure Plasma (CAP) jet operated using bi-polar pulsed power source is reported. Its effectiveness in disinfecting E. faecalis infected root canals is evaluated and compared to that of 5.25% NaOCl and QMix at various time intervals. Before treatment, the jet has been characterized electrically and accordingly optimized for different operating parameters. Kruskal–Wallis Rank Sum and Wilcoxon tests are performed to analyse the difference among all the treatment groups. The CAP jet has shown maximum antibacterial efficiency at 10 min of exposure. CAP Jet, NaOCl, and QMix treatment achieved maximum percentage reductions of 90.8%, 99.99% and 96%, respectively. However, NaOCl and QMix have several disadvantages. It is predicted that the controlled exposure of CAP jet can be used as root canal disinfectant and best optimized further as a non-intrusive method.

Transformative impact of atmospheric cold plasma on mung bean seeds: Unveiling surface characteristics, physicochemical alterations, and enhanced germination potential

This work investigates the impact of a new geometry Atmospheric Cold-Plasma (ACP) system on mung bean (Vigna radiata) seed germination and seedling growth. Plasma is produced using a bipolar pulse power source, providing superior control of the generated species. A substantial increase in germination rates (86.67%–91.67%) and optimal seedling growth after 40 s of treatment is reported. The functional and morphological features have shown improvements. Plasma treatment significantly increases the specific surface area (7.695 m2/g) and total pore volume (0.007 cc/g) of the seeds compared to the control (2.214 m2/g and 0.001 cc/g, respectively), suggesting potential enhancements in water absorption and nutrient exchange. Radicle growth stimulation is also observed without alterations in the seed’s chemical structure. These findings highlight the potential of the ACP system for enhancing mung bean sprout germination and seedling development, which is helpful for agriculture applications.

HighNESS conceptual design report: Volume I

The European Spallation Source, currently under construction in Lund, Sweden, is a multidisciplinary international laboratory. Once completed to full specifications, it will operate the world’s most powerful pulsed neutron source. Supported by a 3 million Euro Research and Innovation Action within the EU Horizon 2020 program, a design study (HighNESS) has been completed to develop a second neutron source located below the spallation target. Compared to the first source, designed for high cold and thermal brightness, the new source has been optimized to deliver higher intensity, and a shift to longer wavelengths in the spectral regions of cold (CN, 2–20 Å), very cold (VCN, 10–120 Å), and ultracold (UCN, >500 Å) neutrons. The second source comprises a large liquid deuterium moderator designed to produce CN and support secondary VCN and UCN sources. Various options have been explored in the proposed designs, aiming for world-leading performance in neutronics. These designs will enable the development of several new instrument concepts and facilitate the implementation of a high-sensitivity neutron-antineutron oscillation experiment (NNBAR). This document serves as the Conceptual Design Report for the HighNESS project, representing its final deliverable.

Nanosecond repetitively pulsed plasmas with MHz bursts for CO2 dissociation

A novel pulsed power source capable of nanosecond pulses with burst frequencies up to 1 MHz is employed to create atmospheric pressure pulsed plasma in pure CO2 gas. The short bursts contain up to four nanosecond pulses. The CO2 conversion and corresponding energy efficiency are measured ex-situ with Fourier-transform infrared absorption spectroscopy. Trends in the absorption line profile of in-situ quantum cascade laser infrared absorption spectroscopy indicate an elevated vibrational temperature of CO2 with an increasing number of pulses per burst. The key result of this paper is that the dissociation energy efficiency is higher when operating the plasma in burst mode. Furthermore, a larger number of pulses in a burst is associated with a further increase of the dissociation efficiency. The highest efficiency measured is (17.7±0.3) % for single pulses spaced 2 ms apart, and (20.0±0.3) % for bursts of three pulses, with an in-burst frequency of 1 MHz and bursts spaced 4 ms apart.

Process parameters optimization for red globe grapes to enhance shelf-life using non-equilibrium cold plasma jet

In this work, a non-equilibrium cold plasma jet (NECPJ) operated by a bi-polar pulse power source was designed and developed, and its impact on red globe grapes (Vitis vinifera) was analyzed for shelf-life enhancement. A total of 17 separate experiments were conducted using a Box-Behnken design to identify the optimum plasma process parameters, i.e., applied voltage, gas flow rate, and treatment time. Food quality parameters such as pH, total suspended solids (TSS), weight loss, total phenol and flavonoid content, vitamin C, contact angle, and firmness were studied. Field emission scanning electron microscopy (FESEM) images were also taken to see the effect of NECPJ treatment on grape surfaces and E. coli bacteria. The results showed that the linear, quadratic, and interaction effects of all three process parameters were statistically significant (p < 0.001, p < 0.01). Accordingly, the optimized plasma process parameters were identified as applied voltage 3.36 kV, gas flow rate 2.87 SLPM, and treatment time 1 min. A shelf-life study of twenty-eight days was done with and without plasma treatment. It was found that NECPJ-treated grapes had a higher shelf-life. The treated grapes contained higher levels of vitamin C, firmness, red grape color index, and total soluble solids than controls. It is inferred that NECPJ can help reduce red globe grape deterioration and maintain quality during post-harvest storage.

The Influence of Potassium Hexafluorophosphate on the Morphology and Anticorrosive Properties of Conversion Coatings Formed on the AM50 Magnesium Alloy by Plasma Electrolytic Oxidation.

In this study, conversion coatings were produced on the AM50 magnesium alloy by a plasma electrolytic oxidation (PEO) process in alkaline-silicate electrolyte with the addition of potassium hexafluorophosphate, using a unipolar pulse power source. The coating microstructure and its composition were determined using scanning electron microscopy (SEM) and an X-ray photoelectron spectroscopy (XPS). The corrosion resistance of the conversion coatings was evaluated by means of potentiodynamic polarization tests (PDP) and electrochemical impedance spectroscopy (EIS) in a dilute Harrison solution (DHS). It has been found that the properties (microstructure, composition, and coating thickness) of the obtained layer and, therefore, their anticorrosive resistance strongly depend on the electrolyte composition. The best anticorrosive properties were observed in the layers obtained in the presence of 2.5 g/L KPF6. It was found that the conversion coating produced with the addition of hexafluorophosphate is characterized by a different morphology (sponge-like) and better anticorrosion properties, in comparison to the coating obtained with the addition of fluoride and orthophosphate salts commonly used in PEO synthesis. The sponge-like structure, which is similar to bone structure in combination with the presence of phosphates in the layer, can increase the biocompatibility and the possibility of self-healing of this coating. However, neither Mg(PF6)2, nor any other compounds containing PF6-, have been found in the layers produced.

Enhanced energy storage performance in samarium and hafnium co-doped silver niobate ceramics

Improving energy storage density and efficiency of antiferroelectric materials could promote their use within energy storage field, particularly in the context of pulsed power sources. In this study, Sm and Hf co-doped silver niobate (AgNbO3; AN) ceramics were prepared using traditional solid-state method. Comprehensive analysis of crystal structure, microstructure, defects, absorbance, and energy storage performance of the material was conducted. Results reveal that co-doping increased the concentration of cation vacancies and band gap, decreased the M1–M2 and M2–M3 phase transition temperatures, and enhanced the antiferroelectric phase stability and energy storage performance. The (Ag0.955Sm0.015)(Nb0.95Hf0.05)O3 ceramic exhibited energy storage density of 5.35 J/cm3 and energy storage efficiency of 73% at electric field (E) of 295 kV/cm, demonstrating significant improvement. The (Ag0.955Sm0.015)(Nb0.95Hf0.05)O3 ceramic exhibited excellent thermal stability (<5% in the range of 25 °C-125 °C) and frequency stability (<3% in the range of 1–100 Hz under E = 290 kV/cm). Additionally, the (Ag0.955Sm0.015)(Nb0.95Hf0.05)O3 ceramic exhibited ultrahigh discharge speed (∼18 μs) and high discharge energy density (4.9 J/cm3). These advantages make these ceramics promising materials for energy storage applications.

A paradigm-shift self-powered optical sensing system enabled by the rotation driven instantaneous discharging triboelectric nanogenerator (RDID-TENG)

Simultaneously achieving laser sensing and communication in a self-powered and wireless manner benefits a great variety of applications especially for the places with limited electrical supply, such as inhabited islands, etc. Regarded as a promising technology, triboelectric nanogenerators (TENGs) harvest mechanical energies with the environmental motion information revealed. However, until now, few TENG-triggered laser sensing and communication systems have been reported since the current required by the laser is several number orders higher than that of TENGs featuring high impedance and low current. This work reports a revolutionary paradigm using the tailored TENG to drive a laser to achieve environmental sensing and wireless communication in the meanwhile. Unlike conventional TENGs transporting the charge continuously during the friction, the developed rotation driven instantaneous discharging TENG (RDID-TENG) releases the whole accumulated charge by the triboelectric layer in extremely short time (i.e. lower than 500 μs), yielding a periodic and ultrahigh instantaneous current, which is 1000 times higher than that of regular rotational TENGs, making it an excellent pulsed electrical power source to drive the laser. The mechanical to electrical to optical signal conversion was achieved employing such a self-powered sensing system, where both rotational speed and medium contamination information can be extracted from the optical signal. This study proposes a new strategy to regulate the charge transportation of TENGs showing its effectiveness in demonstrated environmental online monitoring.

The HighNESS Project at the European Spallation Source: Current Status and Future Perspectives

The European Spallation Source (ESS), presently under construction in Lund, Sweden, is a multidisciplinary international laboratory that, once completed at full specifications, will operate the world’s most powerful pulsed neutron source. Supported by a 3 M Euro Research and Innovation Action within the European Union Horizon 2020 program, a design study (HighNESS) is now underway to develop a second neutron source located below the spallation target. Compared to the first source, which is located above the spallation target and designed for high cold and thermal brightness, the new source is being optimized to deliver higher intensity and a shift to longer wavelengths in the spectral regions of cold neutrons (CNs) (2 to 20 Å), very cold neutrons (VCNs) (10 to 120 Å), and ultracold neutrons (UCNs) ( > 500 Å). The second source consists of a large liquid deuterium moderator to deliver CNs and serve secondary VCN and UCN sources, for which different options are under study. These new sources will boost several areas of condensed matter research and will provide unique opportunities in fundamental physics. The HighNESS project is now entering its last year, and we are working toward the Conceptual Design Report of the ESS upgrade. In this paper, results obtained in the first 2 years, ongoing developments, and future perspectives are described.

Electrohydraulic Yutkin effect and electrospark discharges in liquids

Electrospark discharges in liquids are the subject of numerous studies, as they are a source of powerful wave pulses that can be used in various technological processes. One of the first researchers of this phenomenon was L.O. Yutkin, who substantiated and investigated the electrohydraulic effect (EHE). This effect allows to transform electrical energy into mechanical energy of powerful shock waves, which opens up great opportunities for increasing the efficiency of various technologies. The purpose of the study is to analyze the history of the study of electric spark discharges in liquids, the contribution of L.O. Yutkin to the development of the theory and practical application of the EHE, and to highlight the advantages of wave treatments based on this effect. In the course of the study, scientific papers and experimental data obtained in the study of electrospark discharges in liquids and the electrohydraulic effect were analyzed. The theoretical foundations of these phenomena were considered, as well as practical applications of EHE in various industries. The electrohydraulic effect (EHE), discovered by L.O. Yutkin, is a unique phenomenon that allows converting electrical energy into mechanical energy of powerful shock waves. This is achieved by generating an electric discharge in a liquid, which leads to the formation of a plasma channel and the subsequent occurrence of a shock wave. The main advantage of wave treatments based on EHE is the ability to introduce large amounts of energy into the medium, which allows to increase the efficiency of numerous technological processes. The electrohydraulic Yutkin effect remains an inexhaustible source for the creation of advanced technologies that are already widely used in many industries

Development and Test of 500 kV Repetitive Pulsed Power Source for HPM Application

A compact peaking capacitor-based 500 kV, 10 kA, 100 Hz repetition rate pulsed power source has been designed and developed for high-power microwave applications. This system utilizes a 500 kV, 1.9 nF peaking capacitor to deliver the nanosecond pulse with a peak current of 10 kA. An eight-stage bipolar Marx generator (MG) with 35 kV charging voltage is used for driving this peaking capacitor. The design was carried out by an analytical approach and confirmed by simulation for the MG with and without peaking capacitors using PSpice software. The simulated results were compared to study the enhancement of voltage pulse using a peaking capacitor. The system was developed and tested experimentally with and without a peaking capacitor with different load impedances. The experimental results show the merits of peaking capacitor implementation. The system is suitable for driving HPM load at a high repetition rate with less input energy than similar systems.

Enhancement of underwater shock wave by coupling electrical explosion and al-powder-suspension combustion: Facing advanced reservoir stimulation technology

The development of fossil energy requires eco-friendly and high-efficient approaches, especially in contemporarily low-carbon scenarios. Using the high-power pulsed discharge to induce fractures has drawn increasingly academic and industrial attention in reservoir stimulation. Therein, the electrical wire explosion is commonly adopted as the pulsed discharge load to transfer electrical energy to mechanical one (shock wave and plasma bubble) efficiently. To strengthen mechanical loadings, a discharge capsule with a metallic wire inside Al-powder suspension has been designed and tested. Experiments were performed with a μs-timescale pulsed power source with stored energy from 150 to 750 J, and the electrical explosion were diagnosed via high-speed photography, electrophysical, and mechanical measurements. The experiment shows that there is an optimal concentration of Al-powder suspension in order to obtain the maximum peak pressure of shock wave for a given discharge condition. Too high or low concentrations of the aluminum powder will cause a lower peak pressure. This paper shows that at the stored energy of 500 J, when the concentration of Al-powder suspension is 20 g/L, the peak pressure can reach 4.81 ± 0.27 MPa, which is 2.01 times as large as the shock wave generated by the electrical explosion under the same conditions in pure water. Through the electrophysical measurement, it is found that the aluminum powder almost does not affect the phase transition of the wire. However, in the subsequent plasma formation, the gaseous reaction products make the discharge channel more complex and in a higher pressure density state, which is shown by the increase of channel resistance. Through the backlit images taken by the high-speed camera, it is obvious that two discrete strong shock waves can be seen in the Al-powder-suspension environment.

Generalized plasma focus problem and its application to space propulsion

Space propulsion is unique among many proposed applications of the dense plasma focus in being critically dependent on the availability of a scaling theory that is well-grounded in physics, in conformity with existing experimental knowledge and applicable to experimentally untested configurations. This paper derives such a first-principles-based scaling theory and illustrates its application to a novel space propulsion concept, where the plasma focus sheath is employed as a power density amplifying mechanism to transport electric energy from a capacitive storage to a current-driven fusion load. For this purpose, a Generalized Plasma Focus problem is introduced and formulated. It concerns a finite, axisymmetric plasma, driven through a neutral gas at supersonic speed over distances much larger than its typical gradient scale length by its azimuthal magnetic field while remaining connected with its pulse power source through suitable boundaries. The Gratton-Vargas equation is rederived from the scaling properties of the equations governing plasma dynamics and solved for algebraically defined initial (insulator) and boundary (anode) surfaces. Scaling relations for a new space propulsion concept are derived. This consists of a modified plasma focus with a tapered anode that transports current from a pulsed power source to a consumable portion of the anode in the form of a hypodermic needle tube continuously extruded along the axis of the device. When the tube is filled with deuterium, the device may serve as a small-scale version of magnetized liner inertial fusion (MAGLIF) that could avoid failure of neutron yield scaling in a conventional plasma focus.

Telluric Currents Generated by Solar Flare Radiation: Physical Model and Numerical Estimations

The current studies of solar-terrestrial relations and possible impact of space weather on the seismic activity are based on statistical analysis without detailed consideration of possible physical mechanism that results in fuzzy and contradictory conclusions. We propose to consider a hypothesis of electromagnetic earthquake triggering by a sharp rise of telluric currents in lithosphere including crust faults due to interaction of solar flare X-ray radiation with ionosphere-atmosphere-lithosphere system resulted in a rise of telluric currents in the crust faults. This hypothesis is based on field and laboratory experiments carried out in Russia within the last forty years and clearly demonstrated a possibility of earthquake triggering by electric current injected into the fault. We developed a mathematical model and computer code for numerical estimations of telluric currents generated by solar flare radiations. The obtained numerical results demonstrate that solar flares can cause variations in the density of telluric currents in the crust faults, comparable to the current densities generated in the Earth’s crust by artificial pulsed power sources capable to trigger earthquakes. Consequently, the triggering of seismic events is possible not only by artificial sources of electric current, but also by ionospheric disturbances caused by strong solar flares.

Plasma spectroscopy of electric spark discharge between silver granules immersed in water

This work is devoted to optical emission spectroscopy of plasma of underwater electric discharge, which is used for the synthesis of silver nanoparticles. The main aim of this work is to investigate the possibility and validity of using plasma optical emission spectroscopy to determine its main physical characteristics, such as excitation temperature, electron density, the degree of ionization, etc. The specially developed pulse power source was used to initiate a discharge between silver granules immersed into the deionized water. Typical values of voltage vary from 40 to 200 V, the current is up to 150 A, and pulse frequency is in the range of 0.2–2 kHz. Applied to electrodes, the voltage caused a current flow along the chain of closely arranged granules in the stochastic switching mode. Special attention is paid to methods of spectrum treatment of underwater discharge plasma between silver granules. The method of Boltzmann plots and the method of relative intensities on the basis of both atomic and ionic silver spectral lines are used in order to determine the excitation temperature. The spectral lines, which were investigated and treated in detail, were used. Exposed to the Stark mechanism of spectral line broadening, the spectral profile of Hα spectral line is used to determine the electron density. The degree of ionization of the studied plasma was calculated using the obtained values of the electron density and temperature.