Plasma

20 pages, 9396 KiB

Open AccessArticle

Characterization of the Plasma Generated by a Compact Theta Pinch

by Sagi Turiel, Alexander Gribov, Daniel Maler and Yakov E. Krasik

Plasma 2024, 7(4), 978-997; https://doi.org/10.3390/plasma7040053 - 20 Dec 2024

Viewed by 569

Theta Pinch is one of the promising methods for the generation of hot and dense plasma. In this paper, we describe the results of experimental research on a small-scale Theta Pinch created with Helium or Hydrogen plasmas. Different plasma diagnostics, namely, optical, microwave [...] Read more.

Theta Pinch is one of the promising methods for the generation of hot and dense plasma. In this paper, we describe the results of experimental research on a small-scale Theta Pinch created with Helium or Hydrogen plasmas. Different plasma diagnostics, namely, optical, microwave cut-off, laser interferometry, visible spectroscopy, Thomson scattering, and Laser-Induced Fluorescence were used to characterize the time- and space-resolved evolution of the plasma parameters, and the specific features of these diagnostic results obtained are discussed. The measured plasma density and the electron and ion temperature evolution, obtained by these various diagnostic tools, agree to a satisfactory level. These methods will be applied for studies of the parameters of the plasma in the device that is being developed by the nT-Tao company towards fusion energy. Full article

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39 pages, 4052 KiB

Open AccessArticle

Evaluation of a New Kind of Z-Pinch-Based Space Propulsion Engine: Theoretical Foundations and Design of a Proof-of-Concept Experiment

by S. K. H. Auluck, R. Verma and R. S. Rawat

Plasma 2024, 7(4), 939-977; https://doi.org/10.3390/plasma7040052 - 19 Dec 2024

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Abstract

This paper explores a recently proposed scalable z-pinch-based space propulsion engine in greater detail. This concept involves 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 [...] Read more.

This paper explores a recently proposed scalable z-pinch-based space propulsion engine in greater detail. This concept involves 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”. This tube is filled with a gas at a high pressure and also optionally with an axial magnetic field. The current enters the metal tube through its contact with the anode and returns to the cathode via the plasma sliding over its outer wall. The resulting rapid electrical explosion of the metal tube partially transfers current to a snowplough shock in the fill gas. Both the metal plasma and the fill gas form axisymmetric converging shells. Their interaction forms a hot and dense plasma of the fill gas surrounded by the metal plasma. Its ejection along the axis provides the impulse needed for propulsion. In a nonnuclear version, the fill gas could be xenon or hydrogen. Its unique energy density scaling could potentially lead to a neutron-deficient nuclear fusion drive based on the proton-boron avalanche fusion reaction by lining the tube with solid decaborane. In order to explore the inherent potential of this idea as a scalable space propulsion engine, this paper discusses its theoretical foundations and outlines the first iteration of a conceptual engineering design study for a proof-of-concept experiment based on the UNU-ICTP Plasma Focus facility at the Nanyang Technological University, Singapore. Full article

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19 pages, 4353 KiB

Open AccessArticle

Effect of Cathode Cooling in Three-Dimensional Simulations of an Atmospheric Pressure Glow Discharge

by Valentin Boutrouche and Juan Pablo Trelles

Plasma 2024, 7(4), 920-938; https://doi.org/10.3390/plasma7040051 - 29 Nov 2024

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Abstract

The Atmospheric Pressure Glow Discharge (APGD) is a relatively simple and versatile plasma source used in a wide range of applications. Active cooling of the cathode can effectively mitigate instabilities, leading to glow-to-arc transitions. This study investigates the effect of varying the degree [...] Read more.

The Atmospheric Pressure Glow Discharge (APGD) is a relatively simple and versatile plasma source used in a wide range of applications. Active cooling of the cathode can effectively mitigate instabilities, leading to glow-to-arc transitions. This study investigates the effect of varying the degree of cathode cooling in APGD with a planar cathode in helium. The plasma flow model incorporates mass conservation, chemical species transport, momentum conservation, conservation of thermal energy of heavy species and of electrons, and electrostatics. The model is applied to time-dependent simulations through a three-dimensional computational domain describing the whole discharge, without geometric symmetry or steady-state assumptions. Simulations of an experimentally characterized APGD explore the effects of electric current and cathode cooling—ranging from thermally insulated to extreme convective cooling. Results show the formation of an annular region with high electric field over the cathode surface under conditions of high current and low cooling. Full article

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16 pages, 2963 KiB

Open AccessArticle

A Mechanism for Slow Electrostatic Solitary Waves in the Earth’s Plasma Sheet

by Gurbax Singh Lakhina and Satyavir Singh

Plasma 2024, 7(4), 904-919; https://doi.org/10.3390/plasma7040050 - 27 Nov 2024

Viewed by 1056

Abstract

An analysis of the Magnetospheric Multiscale (MMS) spacecraft data shows the presence of slow electrostatic solitary waves (SESWs) in the Earth’s plasma sheet, which have been interpreted as slow electron holes (SEHs). An alternative mechanism based on slow ion-acoustic solitons is proposed for [...] Read more.

An analysis of the Magnetospheric Multiscale (MMS) spacecraft data shows the presence of slow electrostatic solitary waves (SESWs) in the Earth’s plasma sheet, which have been interpreted as slow electron holes (SEHs). An alternative mechanism based on slow ion-acoustic solitons is proposed for these SESWs. The SESWs are observed in the region where double humped ion distributions and hot electrons co-exist. Our theoretical model considers the plasma in the SESW region to consist of hot electrons with a vortex distribution, core Maxwellian protons drifting parallel to the magnetic field, B and beam protons drifting anti-parallel to B. Parallel propagating nonlinear ion-acoustic waves are studied using the Sagdeev pseudopotential technique. The analysis yields four types of modes, namely, two slow ion-acoustic (SIA1 and SIA2) solitons and two fast ion-acoustic (FIA1 and FIA2) solitons. All solitons have positive potentials. Except the FIA1 solitons which propagate parallel to B; the other three types propagate anti-parallel to B. Good agreement is found between the amplitudes of electrostatic potential, the electric field, the widths and speed of SIA1 and SIA2 solitons, and the observed properties of SESWs by the MMS spacecraft. Full article

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13 pages, 4072 KiB

Open AccessArticle

Electrochemical Reactions at the Boundary Areas Between Cold Atmospheric Pressure Plasma, Air, and Water

by Jamiah Thomas and Alexander G. Volkov

Plasma 2024, 7(4), 891-903; https://doi.org/10.3390/plasma7040049 - 25 Nov 2024

Cited by 1 | Viewed by 716

Abstract

A cold atmospheric-pressure He-plasma jet (CAPPJ) interacts with air and water, producing reactive oxygen and nitrogen species (RONS), including biologically active ions, radicals, and molecules such as NO_x, H₂O₂, HNO₃, HNO₂, and O [...] Read more.

A cold atmospheric-pressure He-plasma jet (CAPPJ) interacts with air and water, producing reactive oxygen and nitrogen species (RONS), including biologically active ions, radicals, and molecules such as NO_x, H₂O₂, HNO₃, HNO₂, and O₃. These compounds can activate interfacial redox processes in biological tissues. The CAPPJ can oxidize N₂ to HNO₃ and water to H₂O₂ at the interface between plasma and water. It can also induce the oxidation of water-soluble redox compounds in various organisms and in vitro. This includes salicylic acid, hydroquinone, and mixtures of antioxidants such as L (+)-ascorbic acid sodium salt with NADPH. It can react with redox indicators, such as ferroin, in a three-phase system consisting of air, CAPPJ, and water. Without reducing agents in the water, the CAPPJ will oxidize the water and decrease the pH of the solution. When antioxidants such as ascorbate, 1,4-hydroquinone, or NADPH are present in the aqueous phase, the CAPPJ oxidizes these substances first and then oxidizes water to H₂O₂. The multielectron mechanisms of the redox reactions in the plasma-air/water interfacial area are discussed and analyzed. Full article

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14 pages, 4583 KiB

Open AccessArticle

Gliding Arc/Glow Discharge for CO₂ Conversion: The Role of Discharge Configuration and Gas Channel Thickness

by Svetlana Lazarova, Tsvetelina Paunska, Veselin Vasilev, Khristo Tarnev, Snejana Iordanova and Stanimir Kolev

Plasma 2024, 7(4), 877-890; https://doi.org/10.3390/plasma7040048 - 21 Nov 2024

Viewed by 783

Abstract

This work investigates CO₂ conversion using atmospheric pressure low-current gliding discharges (GD). The following three modifications are studied: classic GD; magnetically accelerated GD (MAGD); and magnetically retarded GD (MRGD). In the latter two, permanent magnets produce a magnetic field that either accelerates [...] Read more.

This work investigates CO₂ conversion using atmospheric pressure low-current gliding discharges (GD). The following three modifications are studied: classic GD; magnetically accelerated GD (MAGD); and magnetically retarded GD (MRGD). In the latter two, permanent magnets produce a magnetic field that either accelerates or retards the discharge downstream. The gas flow is confined between quartz plates and the electrodes, with varying channel thicknesses. The magnetic configurations improve the performance compared to the classic GD, with up to 30% higher energy efficiency and up to a 50% higher conversion rate. The highest conversion rate is 11–12% with 10% energy efficiency, while the highest efficiency is 40% with 5% conversion, achieved with MRGD and MAGD at channel thicknesses of 2 mm and 3 mm. Full article

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10 pages, 3000 KiB

Open AccessArticle

Polymerization of Sodium 4-Styrenesulfonate Inside Filter Paper via Dielectric Barrier Discharge Plasma

by Samira Amiri Khoshkar Vandani, Lian Farhadian, Alex Pennycuick and Hai-Feng Ji

Plasma 2024, 7(4), 867-876; https://doi.org/10.3390/plasma7040047 - 11 Nov 2024

Viewed by 1142

Abstract

This work explores the polymerization of sodium 4-styrenesulfonate (NaSS) inside filter paper using dielectric barrier discharge (DBD) plasma and its application in the environmental field. The plasma-based technique, performed under mild conditions, solves common problems associated with conventional polymerization inside porous materials. The [...] Read more.

This work explores the polymerization of sodium 4-styrenesulfonate (NaSS) inside filter paper using dielectric barrier discharge (DBD) plasma and its application in the environmental field. The plasma-based technique, performed under mild conditions, solves common problems associated with conventional polymerization inside porous materials. The polymerization process was monitored using Fourier-transform infrared (FTIR) spectroscopy, which confirmed the consumption of double bonds, particularly in NaSS samples containing the optimal concentration of crosslinker divinyl benzene (DVB) (0.25% wt). Our work demonstrates the effectiveness and promise of DBD plasma as a substitute polymerization approach, especially for those in porous materials. Full article

(This article belongs to the Special Issue Dielectric Barrier Discharges 2024)

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9 pages, 6638 KiB

Open AccessArticle

The Influence of the Ionic Core on Structural and Thermodynamic Properties of Dense Plasmas

by Tomiris Ismagambetova, Mukhit Muratov and Maratbek Gabdullin

Plasma 2024, 7(4), 858-866; https://doi.org/10.3390/plasma7040046 - 31 Oct 2024

Viewed by 804

Abstract

In this paper, a new ion–ion screened potential was numerically calculated, which takes into account the ion core effect, i.e., the influence of strongly bound electrons. The pseudopotential model describing the shielding of ion cores and the screening using the density response function [...] Read more.

In this paper, a new ion–ion screened potential was numerically calculated, which takes into account the ion core effect, i.e., the influence of strongly bound electrons. The pseudopotential model describing the shielding of ion cores and the screening using the density response function in the long wavelength approximation were used. To study the influence of this ion core effect on dense plasma’s structural and thermodynamic properties, the integral Ornstein–Zernike equation was solved in the hypernetted chain approximation. Our results show that the ion core has a significant impact on ionic radial distribution functions and thermodynamic properties when compared to the results obtained for the Yukawa potential, which does not take the ion core into account. Increasing the steepness of the core edge or decreasing the depth of the minimum leads to more pronounced screening due to bound electrons. Full article

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16 pages, 1608 KiB

Open AccessArticle

Control-Oriented Free-Boundary Equilibrium Solver for Tokamaks

by Xiao Song, Brian Leard, Zibo Wang, Sai Tej Paruchuri, Tariq Rafiq and Eugenio Schuster

Plasma 2024, 7(4), 842-857; https://doi.org/10.3390/plasma7040045 - 23 Oct 2024

Viewed by 840

Abstract

A free-boundary equilibrium solver for an axisymmetric tokamak geometry was developed based on the finite difference method and Picard iteration in a rectangular computational area. The solver can run either in forward mode, where external coil currents are prescribed until the converged magnetic [...] Read more.

A free-boundary equilibrium solver for an axisymmetric tokamak geometry was developed based on the finite difference method and Picard iteration in a rectangular computational area. The solver can run either in forward mode, where external coil currents are prescribed until the converged magnetic flux function

ψ (R, Z)

map is achieved, or in inverse mode, where the desired plasma boundary, with or without an X-point, is prescribed to determine the required coil currents. The equilibrium solutions are made consistent with prescribed plasma parameters, such as the total plasma current, poloidal beta, or safety factor at a specified flux surface. To verify the mathematical correctness and accuracy of the solver, the solution obtained using this numerical solver was compared with that from an analytic fixed-boundary equilibrium solver based on the EAST geometry. Additionally, the proposed solver was benchmarked against another numerical solver based on the finite-element and Newton-iteration methods in a triangular-based mesh. Finally, the proposed solver was compared with equilibrium reconstruction results in DIII-D experiments. Full article

(This article belongs to the Special Issue New Insights into Plasma Theory, Modeling and Predictive Simulations)

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16 pages, 3663 KiB

Open AccessArticle

Energy Efficiency of Plasma Jets: Electrical Modeling Based on Experimental Results

by Achraf Hani, Karim Saber, Alyen Abahazem and Nofel Merbahi

Plasma 2024, 7(4), 826-841; https://doi.org/10.3390/plasma7040044 - 23 Oct 2024

Viewed by 992

Abstract

This paper focuses on the determination of and improvement in the energy efficiency of plasma jets. To achieve this goal, an equivalent electrical model of a discharge reactor was developed, incorporating variable electrical parameters. The evolution of these parameters was determined by a [...] Read more.

This paper focuses on the determination of and improvement in the energy efficiency of plasma jets. To achieve this goal, an equivalent electrical model of a discharge reactor was developed, incorporating variable electrical parameters. The evolution of these parameters was determined by a mathematical identification method based on the recursive least squares algorithm (RLSA). The good agreement between the measured currents and those calculated using our electrical circuit, as well as the significant shapes of the estimated parameters, confirmed the accuracy of the parameter estimation method. This allowed us to use these parameters to determine the energy delivered to the reactor and that used during the discharge. This made our reactor controllable at the energy level. Thus, the ratio between these two energies allowed us to calculate the energy efficiency of plasma jets at each discharge instant. We also studied the effect of the applied voltage on efficiency. We found that efficiency was increased from 75% to 90% by increasing the voltage from 6 kV to 8 kV. All the results found in this work were interpreted and compared with the discharge behavior. This proposed model will help us to choose the right operating conditions to reach the maximum efficiency. Full article

(This article belongs to the Special Issue New Insights into Plasma Theory, Modeling and Predictive Simulations)

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10 pages, 5511 KiB

Open AccessArticle

Polishing Ceramic Samples with Fast Argon Atoms at Different Angles of Their Incidence on the Sample Surface

by Sergey N. Grigoriev, Alexander S. Metel, Marina A. Volosova, Enver S. Mustafaev and Yury A. Melnik

Plasma 2024, 7(4), 816-825; https://doi.org/10.3390/plasma7040043 - 17 Oct 2024

Viewed by 970

Abstract

Mechanical polishing of a product makes it possible to decrease the roughness of its surface to Ra = 0.001 µm by rubbing it with a fine abrasive contained in a fabric or other soft material. This method takes too much time and is [...] Read more.

Mechanical polishing of a product makes it possible to decrease the roughness of its surface to Ra = 0.001 µm by rubbing it with a fine abrasive contained in a fabric or other soft material. This method takes too much time and is associated with abrasive particles and microscopic scratches remaining after the processing. As such, a non-contact treatment with plasma and accelerated particles has been chosen in the present work to study polishing of ceramic samples. The small angular divergence of fast argon atoms made it possible to obtain the dependence of the sample roughness on the angle α of the atom’s incidence on its surface. It was found that the roughness weakly depends on the angle α, if not exceeding the threshold value α_o ~ 50°, and rapidly decreases with increasing α > α_o. Polishing with fast argon atoms leads to a noticeable decrease in friction of ceramic samples. Full article

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23 pages, 43715 KiB

Open AccessReview

Formation of Fine Structures in Incompressible Hall Magnetohydrodynamic Turbulence Simulations

by Hideaki Miura

Plasma 2024, 7(4), 793-815; https://doi.org/10.3390/plasma7040042 - 11 Oct 2024

Viewed by 990

Abstract

Hall magnetohydrodynamic simulations are often carried out to study the subjects of instabilities and turbulence of space and nuclear fusion plasmas in which sub-ion-scale effects are important. Hall effects on a structure formation at a small scale in homogeneous and isotropic turbulence are [...] Read more.

Hall magnetohydrodynamic simulations are often carried out to study the subjects of instabilities and turbulence of space and nuclear fusion plasmas in which sub-ion-scale effects are important. Hall effects on a structure formation at a small scale in homogeneous and isotropic turbulence are reviewed together with a simple comparison to a (non-Hall) MHD turbulence simulation. A comparison between MHD and Hall MHD simulations highlights a fine structure in Hall MHD turbulence. This enhancement of the fine structures by the Hall term can be understood in relation to the whistler waves at the sub-ion scale. The generation and enhancement of fine-scale sheet, filamentary, or tubular structures do not necessarily contradict one another. Full article

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Plasma, Volume 7, Issue 4 (December 2024) – 12 articles

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