Plasma Stream Research Articles

EXPERIMENTAL STUDIES OF PLASMA-SURFACE INTERACTIONS DURING INCLINED QSPA PLASMA IMPACTS ON Sn-FILLED CPS

A 3D-printed tungsten Sn Capillary Porous Structure (CPS) sample was exposed to oblique high-power plasma in the QSPA facility. The experiment aimed to analyze the damage to a liquid metal prototype, a potential component of the divertor in fusion tokamaks. Observations of plasma-surface interactions revealed particle ejection from the exposed target, which depended on the energy density of the incoming plasma stream. The leading edge of the CPS sample was identified as the primary source of the ejected particles. A reduction in mass loss rate of the plasma-treated sample over the course of the experimental series was demonstrated. The W substrate of the CPS target did not sustain significant damage. A comparative analysis of the damage to Sn-CPS and castellated W samples exposed to inclined and normal plasma streams under conditions simulating transients in a fusion reactor was also performed.

Behavior of Tungsten Coated with Boron Carbide Exposed to Intense Plasma Streams

Behavior of Tungsten Coated with Boron Carbide Exposed to Intense Plasma Streams

The effect of energetic electrons in lunar ionosphere on the streaming plasma instability around moon

The effect of energetic electrons in lunar ionosphere on the streaming plasma instability around moon

Assessment of the effectiveness of atmospheric plasma on the removal of selected pharmaceuticals from water

Plasma, next to solids, liquids and gases, is considered the fourth state of matter, occurring in the ground state or in the excited state, having a neutral charge. Its scope of application is wide and constantly expanding. The conducted research aimed to determine the impact of atmospheric plasma for removing selected pharmaceuticals: diclofenac (DFC), sulfamethoxazole (SMX), trimethoprim (TMP), carbamazepine (CBZ) and caffeine (CAF) from water on a laboratory scale. The concentration of the tested pharmaceuticals was 20 mg/L. The analyzed samples were exposed to a continuous stream of cold plasma. The contact time of the sample with the plasma stream ranged from seconds to minutes - depending on the tested pharmaceutical. By examining the degree of reduction of selected pharmaceutical substances before and after the atmospheric plasma treatment process, the samples were subjected to high-performance liquid chromatography analysis. The removal efficiency of individual pharmaceuticals reached up to 98 %. The conducted research confirms the great application potential of using atmospheric plasma as a tool for the elimination of individual pharmaceutical compounds. Cold plasma can be used as a potential tool in water purification and wastewater treatment. Based on the effects of free radical oxidation, UV radiation and pyrolysis, we can eliminate dangerous micropollutants in a more economical and effective way.

Experiment Evaluation on the Porosity of Plasma Coating from Ceramic Al2O3 – TiO2 Using the Metallography

Background: The objective of this paper is an experimental investigation of the metallographic porosity of plasma coating using standard materials from the ceramic system Al2O3-TiO2 on the substrate of steel SS400 at laboratory scale Lab at the Research Institute of Mechanical Engineering. Contribution: The main contribution of the research is the evaluation of the porosity of the coating under the influence of the main technological parameters since the porosity plays a significant role in the performance of the working surface using the built-in Image Pro-Analyzer software in the Axiovert 25 MAT microscope. Method: The spraying material is Al2O3-TiO2 powder. The input parameters are: spraying distance (Lp; current of plasma stream (Ip); powder feed flow (Gp and spraying rate (Vp). Results: The findings show that the average porosity of the Al2O3-TiO2 plasma coating is inversely decreasing in the increasing direction of the distance: spray in the range Lp = 100–200 mm, increase proportional to the increase of the current plasma flow rate in the range Ip = 400–600 A, provided that the powder feed flow Gp = 1.7 kg/h and the spraying rate Vp = 50 mm/min. Conclusion: The degree of influence of the three main technological parameters (Lp, Ip, and Gp) in the survey limit domain may be due to the selected Lp spray distance within the relatively wide recommended range of the plasma spraying equipment supplier. It is recommended to conduct the experimental planning of the L27 type to localize the optimum area.

Fundamental difference between the mechanisms of electrostatic field screening in dense and thoroughly collisionless plasmas

When an external electric field appears in a homogeneous plasma, ions move into regions where their electrostatic energy is lower. Simultaneously, forces arise that counteract this effect, causing the plasma to reach equilibrium when the field disappears completely. In collisional plasma, the resulting charge inhomogeneities decrease both Coulomb energy and entropy. Randomly induced diffusion flows tend to hinder their growth, minimizing free energy at any point. Accordingly, in the Debye–Hückel theory, the external field strength decreases exponentially with distance within the plasma. In a collisionless plasma, an antiscreening mechanism operates differently. Each ion moves in a self-consistent field along distinct trajectories, following classical dynamics laws. An external field bends these trajectories, bringing ions into regions where their Coulomb energy is lower. The antiscreening mechanism occurs when ions accelerate into potential wells, increasing the distances between them along their trajectories and decreasing their number densities along these paths. The law of energy conservation for any single ion governs this principally nonlocal process, and the dependence of field strength on distance is not necessarily exponential. This paper demonstrates that the Debye–Hückel theory should not be used to describe the charge density distribution within an unrestricted stream of collisionless plasma, such as the solar wind. It also analyzes non-exponential solutions of the Poisson equation for plasma sheaths above flat surfaces, from which such a flow takes off and on which it falls, obtained in quadratures.

Free-burning arc discharge simulation: The self-induced magnetic field analysis and its effect on arc plasma characteristics

Free-burning arc discharges play important roles in physical processes such as cutting, welding, arc furnaces, and switchgear. Therefore, in this paper, a combination of node-based and edge-based finite-element methods with the finite-volume scheme is developed to investigate the dynamics of these arc discharges. Considering the significant effect of self-induced magnetic fields on the dynamics of the thermal plasma arcs, accurate analysis of these magnetic fields is essential, especially for 3D geometries describing realistic conditions. Accordingly, the edge-based finite-element module is utilized to study the Ampere law in its vector form for estimating the vector potential and the corresponding magnetic field. Furthermore, the current conservation equation is solved using the node-based finite-element technique. The fluid dynamics are also investigated with the well-known finite-volume method. This hybrid model gives more accurate magnetic fields and Lorentz forces. Electromagnetic forces create high-speed streams of thermal plasma and increase the pressure in the near regions of the electrodes. As a result, the pressure and velocity profiles are closer to the predicted results. In addition, the fluid flow changes the temperature distribution in a way that agrees with experimental measurements.

Multi-source connectivity as the driver of solar wind variability in the heliosphere

The ambient solar wind that fills the heliosphere originates from multiple sources in the solar corona and is highly structured. It is often described as high-speed, relatively homogeneous, plasma streams from coronal holes and slow-speed, highly variable, streams whose source regions are under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify solar wind sources and understand what drives the complexity seen in the heliosphere. By combining magnetic field modelling and spectroscopic techniques with high-resolution observations and measurements, we show that the solar wind variability detected in situ by Solar Orbiter in March 2022 is driven by spatio-temporal changes in the magnetic connectivity to multiple sources in the solar atmosphere. The magnetic field footpoints connected to the spacecraft moved from the boundaries of a coronal hole to one active region (12961) and then across to another region (12957). This is reflected in the in situ measurements, which show the transition from fast to highly Alfvénic then to slow solar wind that is disrupted by the arrival of a coronal mass ejection. Our results describe solar wind variability at 0.5 au but are applicable to near-Earth observatories.

Smart integration of cold plasma stream and surface discharge with ns laser ablation for composite nanomaterial.

In this paper, smart integration of cold dielectric barrier discharge (DBD) plasma in various geometrical arrangements with laser ablation at atmospheric pressure for nanomaterial was described. A composite Co:ZnO target was ablated in an airflow by a nanosecond (ns) laser (wavelength: 1064 nm, pulse duration: 30 ns) using fluence of 5 J-cm-2 at a repetition rate of 10 Hz. The nanomaterial produced under vertical and oblique plasma streams, surface discharge and gas flow, were compared. Utilization surface discharge markedly improved the material adhesion by altering surface intrinsic behavior, inducing anticipated surface energy activation, chemical changes, and the formation of a densely packed solid structure. Under all conditions, the material consistently retained its crystalline nature, elemental composition, and ultraviolet emission characteristics. These preliminary findings hold promise for additional research, suggesting avenues for making complex materials in a flexible environment. Such new advancements could facilitate applications in the biomedical, catalysis, pharmaceutical, and surgical device domains.

The Effects of Induction Plasma Spheroidization on the Properties of Yttrium-Stabilized Zirconia Powders and the Performance of Corresponding Thermal Barrier Coatings for Gas Turbine Engine Applications

To modify the structure of thermal barrier coatings and improve their high-temperature resistance, induction plasma spheroidization (IPS) technology was applied to regulate the structure of YSZ powders in this study. The surface morphology, particle size distribution, phase composition, and internal microstructure of the conventional agglomerated and spheroidized powders were characterized using scanning electron microscopy and focused ion beam analysis methods. The results showed that the microstructure of the powders presented uneven evolution in the induction plasma stream. Due to the existence of the temperature gradient along the radial direction of the powders, the IPS powders consisted of outer dense shells and internal porous cores. The mechanical property of such shell–core structure was analyzed by using the finite elemental simulation method. In addition, coatings were prepared using the IPS powders and the agglomerated powders. The IPS coating showed improved water-cooling thermal cycling resistance compared to the conventional coating.

Studies on the spatial evolution of pulsed helium plasma

AbstractThe high‐density transient plasma, streaming from a pulsed plasma accelerator (PPA), was diagnosed with a Triple Langmuir probe (TLP) for spatial mapping of the stream in terms of plasma density and temperature. A contour plot for density and temperature shows a distinct form of a highly dense island of plasma with varied plasma temperatures. The formation of such highly dense islands can be correlated with the formation of distinct plasma structures, as observed in astrophysical plasmas and fusion plasma. The results of TLP were supported by the intensity variation derived from signals of a photodetector system. The plasma stream imaged with high‐speed video camera also showed the density fluctuation inside the plasma stream. The estimated maximum density and temperature were ∼7.2 × 1020 m−3 and ∼28 eV, respectively.

3D Multi‐Fluid MHD Simulation of the Early Time Behavior and Cross‐Field Propagation of an Artificial Plasma Cloud in the Bottom Side Ionosphere

AbstractThe relative motion of an artificial plasma stream in an ambient plasma background transverse to the geomagnetic field produces a polarization current and an drift in the direction of the injected photoionized neutral cloud. The polarization current couples the ion cloud momentum to the ambient plasma causing the stream to brake or “skid” before coming to rest. A multi‐fluid five‐moment resistive magnetohydrodynamic (MHD) model has been previously developed and is used in this study to simulate an artificial barium cloud released at 8 km/s in the lower ionosphere transverse to the magnetic field. The MHD model’s governing equations are used to derive 2D analytical solutions to the equations of motion that capture oscillatory behavior relating the cloud ion cyclotron frequency, artificial and ambient plasma density, initial release velocity, and photoionization rate. The analytical solutions are compared to the MHD results for time t < 1 s and previous 1D momentum coupling models. It is shown that motion in the cloud release direction is consistent with previous models while motion in the polarization direction is consistent with numerical results.

Influence of AR injection on shielding layer properties and surface protection from transient high heat loads under the QSPA plasma exposures

The paper presents experimental studies of a shielding plasma layer formation in front of a tungsten surface exposed with hydrogen plasma in the QSPA-M test-bed facility under the conditions of additional seeding of argon (Ar) along the target surface into the zone of plasma-surface interaction. A pulsed gas injector on the base of a fast electromagnetic valve has been developed for the local injection of Ar. The injector is capable of generating a homogeneous argon gas flow with a maximum concentration above n Ar = 6 × 1023 m−3 and a pulse duration of 0.5 ms. It is shown that the increase in the argon gas density in front of the surface leads to an essential decrease (in 1.5–2 times) in the energy load delivered to the target surface. In the presence of a strong magnetic field (up to 1 T), both the thickness of the shielding layer and the fraction of energy dissipated by the shield increase further. Even for moderate energy densities of the QSPA plasma streams in the experiments with Ar gas injection, less than 40% of the impacting plasma load is absorbed by the tungsten surface. The results demonstrate that this additional shielding attributed to the formation of a dense Ar plasma layer in front of the exposed W surface would be favourable for the divertor armour performance, causing the decreasing erosion of plasma-facing components in the course of transient events in a fusion reactor.

Magnetic flutter effect on validated edge turbulence simulations

Small magnetic fluctuations ( B1/B0∼10−4 ) are intrinsically present in a magnetic confinement plasma due to turbulent currents. While the perpendicular transport of particles and heat is typically dominated by fluctuations of the electric field, the parallel stream of plasma is affected by fluttering magnetic field lines. In particular through electrons, this indirectly impacts the turbulence dynamics. Even in low beta conditions, we find that E × B turbulent transport can be reduced by more than a factor 2 when magnetic flutter is included in our validated edge turbulence simulations of L-mode ASDEX Upgrade. The primary reason for this is the stabilization of drift-Alfvén-waves, which reduces the phase shifts of density and temperature fluctuations with respect to potential fluctuations. This stabilization can be qualitatively explained by linear analytical theory and appreciably reinforced by the flutter nonlinearity. As a secondary effect, the steeper temperature gradients and thus higher η i increase the impact of the ion-temperature-gradient mode on overall turbulent transport. With increasing beta, the stabilizing effect on E × B turbulence increases, balancing the destabilization by induction, until direct electromagnetic perpendicular transport is triggered. We conclude that including flutter is crucial for predictive edge turbulence simulations.

Low-Temperature Plasma Techniques in Biomedical Applications and Therapeutics: An Overview.

Plasma, the fourth fundamental state of matter, comprises charged species and electrons, and it is a fascinating medium that is spread over the entire visible universe. In addition to that, plasma can be generated artificially under appropriate laboratory techniques. Artificially generated thermal or hot plasma has applications in heavy and electronic industries; however, the non-thermal (cold atmospheric or low temperature) plasma finds its applications mainly in biomedicals and therapeutics. One of the important characteristics of LTP is that the constituent particles in the plasma stream can often maintain an overall temperature of nearly room temperature, even though the thermal parameters of the free electrons go up to 1 to 10 keV. The presence of reactive chemical species at ambient temperature and atmospheric pressure makes LTP a bio-tolerant tool in biomedical applications with many advantages over conventional techniques. This review presents some of the important biomedical applications of cold-atmospheric plasma (CAP) or low-temperature plasma (LTP) in modern medicine, showcasing its effect in antimicrobial therapy, cancer treatment, drug/gene delivery, tissue engineering, implant modifications, interaction with biomolecules, etc., and overviews some present challenges in the field of plasma medicine.

Determining the possibility of using cold plasma for the oxidation of atmospheric nitrogen into nitrogen oxides and the influence of activating substances on the process

The process of oxidation of molecular nitrogen by high-energy oxidants, such as nitric acid vapor, products of the thermolysis of nitric acid, and hydrogen peroxide, in a cold plasma stream was studied. To implement the process of obtaining nitric acid from atmospheric air using reproductive technology (Zakharov's method), the design of a reactor for obtaining nitrogen oxides by direct oxidation of nitrogen in a cold plasma stream is proposed. At the same time, it was proposed to use the effect of obtaining nitrogen oxides in an air mixture with nitric acid vapors (the Karavaev effect) and during the thermal decomposition of hydrogen peroxide with atmospheric nitrogen (the Nagiev effect). The effectiveness of the use of cold plasma for the oxidation of atmospheric nitrogen was established, which is confirmed by the obtained dependences. It is shown that the amount of nitrogen oxides that are formed depends on the efficiency of the formation of a stable flow of OH- radicals in the plasma flow. It was also found that the amount of nitrogen oxides depends on the parameters of the plasma generator, the composition of the liquid used in the burner, and the amount of air supplied. The effect of nitric acid, hydrogen peroxide, and alcohols as activators of atmospheric nitrogen oxidation in a high-energy field was revealed. It was determined that when comparing three activator substances, which are able to form OH- radicals during their decomposition, it is hydrogen peroxide that is the most promising activator substance for carrying out the process of atmospheric nitrogen oxidation in the plasma flow. The amount of nitrogen oxides formed in the cold plasma region is almost independent of the flow rate of the reaction mixture through the reactor and remains almost unchanged in a wide range of changes in flow rates from 30 to 3000 l/h

Solitary and periodic wave solutions of the unstable nonlinear Schrödinger’s equation

Solving partial differential equations has always been one of the significant mathematical tools for modeling applied phenomena in various fields. In this paper, our main motivation is to find the traveling wave solutions of unstable nonlinear Schrödinger equation (UNLSE) which describes the two layer baroclinic instability, and two lossless symmetric stream plasma instability, and also disturbance of time period in both stable and unstable media. The methods which are used to endure these solutions are extended rational sine-cosine/sinh-cosh. New solutions are constructed in the different forms such as hyperbolic and trigonometric. The achieved results present that proposed techniques are consequential for exploring several types of nonlinear partial differential equations (NLPDEs) in applied sciences and solutions are presented in the form of novel periodic, dark, bright, and periodically bright solitons. These methods are highly effective, robust, and provide an alternative approach for establishing new soliton solutions for various types of partial differential equations (PDEs) used in mathematical physics.

EFFECT OF TRANSIENT LAYERS ON PLASMA ENERGY TRANSFER TO DIFFERENT SURFACES UNDER QSPA EXPOSURES

The plasma energy transfer to plasma-facing materials, as well as the energy and particles exhaust, needs to be extensively studied for the implementation of the next-step fusion reactor project. Analysis of plasma-surface interaction features has been performed using QSPA exposures of reference plasma-facing materials. The parameters of the plasma streams imitated conditions of transient events in a fusion reactor. The influence of an external magnetic field on the energy balance during the plasma-surface interaction is also discussed.

Explosion and Dynamic Transparency of Low-Density Structured Polymeric Targets Irradiated by a Long-Pulse KrF Laser

The hydrodynamics of plasma formed in the interaction of 100 ns UV KrF laser pulses with foam targets with volume densities from 5 to 500 mg/cm3 was studied. Initial and dynamic transmittance at 248 nm wavelength were measured. At intensities of about 1012 W/cm2, the propagation rates of radiation through foam targets reached 80 km/s, while plasma stream velocities from both the front and rear sides of targets were approximately the same, ~ 75 km/s, which confirms a volumetric absorption of radiation within the target thickness and the explosive nature of the plasma formation and expansion.

Turbulence dynamics and flow speeds in the inner solar corona: results from radio-sounding experiments by the Akatsuki spacecraft

ABSTRACT The solar inner corona is a region that plays a critical role in energizing the solar wind and propelling it to supersonic and supra-Alfvénic velocities. Despite its importance, this region remains poorly understood because of being least explored due to observational limitations. The coronal radio-sounding technique in this context becomes useful as it helps in providing information in parts of this least explored region. To shed light on the dynamics of the solar wind in the inner corona, we conducted a study using data obtained from coronal radio-sounding experiments carried out by the Akatsuki spacecraft during the 2021 Venus-solar conjunction event. By analysing X-band radio signals recorded at two ground stations (Indian Deep Space Network in Bangalore and Usuda Deep Space Center in Japan), we investigated plasma turbulence characteristics and estimated flow speed measurements based on isotropic quasi-static turbulence models. Our analysis revealed that the speed of the solar wind in the inner corona (at heliocentric distances from 5 to 13 solar radii), ranging from 220 to 550 km s−1, was higher than the expected average flow speeds in this region. By integrating our radio-sounding results with extreme ultraviolet (EUV) images of the solar disc, we gained a unique perspective on the properties and energization of high-velocity plasma streams originating from coronal holes. We tracked the evolution of fast solar wind streams emanating from an extended coronal hole as they propagated to increasing heliocentric distances. Our study provides unique insights into the least-explored inner coronal region by corroborating radio-sounding results with EUV observations of the corona.