Plasma

13 pages, 8049 KB

Open AccessArticle

Carbon Dioxide Conversion in a Portable Atmospheric Microwave Plasma with High Energy Efficiency

by Songlin Liu, Lianjun Shi, Guilan Liu and Wei Xiao

Plasma 2026, 9(3), 31; https://doi.org/10.3390/plasma9030031 - 7 Aug 2026

The conversion of carbon dioxide (CO₂) driven by microwave plasma has garnered extensive attention due to its capability to recycle carbon resources and mitigate the greenhouse effect. However, the existing microwave plasma technologies suffer from cumbersome system setups and relatively low [...] Read more.

The conversion of carbon dioxide (CO₂) driven by microwave plasma has garnered extensive attention due to its capability to recycle carbon resources and mitigate the greenhouse effect. However, the existing microwave plasma technologies suffer from cumbersome system setups and relatively low energy efficiency. This work investigates CO₂ conversion using a portable atmospheric microwave plasma source, which requires low plasma-generating power. When the working gas is a mixture of CO₂ and Ar, the minimum plasma-generating power required for the proposed portable microwave plasma source is only 50 W. A Fourier transform infrared spectrometer is used to quantify both the CO₂ and CO concentrations, and the C₂ Swan bands in the plasma are measured to determine the gas temperature. The maximum CO₂ conversion rate is approximately 12.7%. Furthermore, the maximum energy efficiency reaches 87.9%, which exceeds that of most state-of-the-art atmospheric microwave plasma configurations. Owing to its simplicity of operation, portability, and high energy efficiency, this method is well-suited for distributed CO₂ conversion systems. Full article

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17 pages, 467 KB

Open AccessArticle

Wave-Breaking Limits of Arbitrary-Amplitude Nonlinear Periodic Electrostatic Waves in a Relativistically Degenerate Electronegative Plasma

by Abdulaziz H. Alharbi and Ibrahem S. Elkamash

Plasma 2026, 9(3), 30; https://doi.org/10.3390/plasma9030030 - 7 Aug 2026

Abstract

Arbitrary-amplitude nonlinear periodic electrostatic waves and the wave-breaking limit are considered in a one-dimensional relativistic electronegative plasma consisting of positive ions, negative ions, and a relativistically degenerate electron-fluid background. A cold, inertial fluid description is adopted for the ions, while the electrons are [...] Read more.

Arbitrary-amplitude nonlinear periodic electrostatic waves and the wave-breaking limit are considered in a one-dimensional relativistic electronegative plasma consisting of positive ions, negative ions, and a relativistically degenerate electron-fluid background. A cold, inertial fluid description is adopted for the ions, while the electrons are described by a relativistic Fermi–Dirac equation of state, which provides the required restoring physics through degeneracy rather than ordinary thermal pressure. After transforming to a travelling coordinate system, we reduce the general multicomponent plasma dynamical system to a pseudopotential energy form with a constant of motion. We then determine the allowed potential range, the associated asymmetric pseudopotentials, and the wave-breaking electric field for both linear and nonlinear waves on each of the two admissible branches. We find that arbitrary-amplitude nonlinear periodic waves are intrinsically asymmetric and that the maximum field strength is set by the effective charge-density boundary of each plasma species along the field direction. Parametric analysis suggests that the critical minimum field strength required for nonlinear wave formation may be controlled by increasing either the negative-ion mass ratio, the wave propagation speed, or the negative-ion concentration; however, each of these changes produces a distinct modification of the pseudopotential geometry. This illustrates that relativistic and interspecies effects are not merely responsible for quantitative deviations from the non-relativistic and single-species cases, but instead completely reshape the nonlinear phase space governing the persistence, deformation, and breaking of periodic electrostatic waves. Full article

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19 pages, 863 KB

Open AccessArticle

Transition from the Space-Charge-Limited Regime to the Inverse Sheath Regime in a Thermionic Emissive Probe

by Rut Morales Crespo, Encarnación Muñoz Serrano and María Simón Lora

Plasma 2026, 9(3), 29; https://doi.org/10.3390/plasma9030029 - 6 Aug 2026

Abstract

This article analyses the transition from the space-charge-limited (SCL) regime to the inverse sheath regime of a thermionic emissive probe, considering ionisation and collisions as presheath mechanisms. We show that, before the fully developed inverse sheath mode is reached, an intermediate regime appears, [...] Read more.

This article analyses the transition from the space-charge-limited (SCL) regime to the inverse sheath regime of a thermionic emissive probe, considering ionisation and collisions as presheath mechanisms. We show that, before the fully developed inverse sheath mode is reached, an intermediate regime appears, characterised by the formation of a virtual cathode structure with ion confinement and probe potentials above the plasma potential. The inverse sheath mode is reached when the minimum potential of the virtual cathode reaches the plasma potential. At this point, a monotonic sheath potential profile above the plasma potential is produced, together with a flat, non-accelerating presheath. The findings of this work can help optimise the performance of emissive probes in plasma diagnostics and control plasma–surface interactions in devices such as fusion reactors and electric propulsion systems, thereby mitigating sputtering and material erosion. Full article

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10 pages, 1053 KB

Open AccessArticle

Bi-Maxwellian Characterization of Energetic Electron Populations in Diffuse Aurora

by Odutayo R. Rufai and Ayooluwa O. Odufowora

Plasma 2026, 9(3), 28; https://doi.org/10.3390/plasma9030028 - 6 Aug 2026

Abstract

We examine energetic electron distributions in the region of the diffuse aurora using a two-dimensional bi-Maxwellian model, applied to electron flux data at a single geomagnetic equator (L = 6.5). Electron flux is analyzed as a function of energy and pitch angle and [...] Read more.

We examine energetic electron distributions in the region of the diffuse aurora using a two-dimensional bi-Maxwellian model, applied to electron flux data at a single geomagnetic equator (L = 6.5). Electron flux is analyzed as a function of energy and pitch angle and transformed into velocity space to reconstruct the distribution function. An unweighted log-space least-squares fit of the bi-Maxwellian model to the reconstructed distribution yields a reduced residual measure of

χ_{v}^{2} = 1.000053

, a mean absolute residual of

| Δ \log_{10} f | = 0.0469

dex, an anisotropy factor,

A_{T} = 0.9886 \pm 0.0016

, and no statistically significant bulk drift. These results show that, at this location, the bi-Maxwellian model reproduces the observed velocity-space structure with good quantitative accuracy and reveals a quasi-isotropic, near-equilibrium electron population. Full article

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22 pages, 14375 KB

Open AccessArticle

Feed Gas Composition and Humidity Shape Reactive Species Signatures in a Clinical Cold Plasma Jet

by Lingyun Yu, Alice Martinet, Linus Hübner, Lars Boeckmann, Steffen Emmert and Sander Bekeschus

Plasma 2026, 9(3), 27; https://doi.org/10.3390/plasma9030027 - 31 Jul 2026

Abstract

Reactive oxygen and nitrogen species (RONS) generated by medical gas plasmas are considered major mediators of plasma-induced biological effects. This includes the atmospheric pressure argon plasma jet kINPen routinely used in clinical applications. The jet’s biomedical action has been shown to be tailored [...] Read more.

Reactive oxygen and nitrogen species (RONS) generated by medical gas plasmas are considered major mediators of plasma-induced biological effects. This includes the atmospheric pressure argon plasma jet kINPen routinely used in clinical applications. The jet’s biomedical action has been shown to be tailored by modifying its feed gas. However, a systematic comparison of how feed gas composition and humidity shape plasma chemistry remains lacking, which would shift application-specific plasma chemistries from guessing to designing. In this study, we systematically investigated, compared, and statistically related 65 individual feed gas conditions of the kINPen argon plasma jet by increasing O₂, N₂, and combined O₂ + N₂ admixtures under dry and humidified conditions. Plasma gas phases were assessed using optical emission spectroscopy and reactive species produced in liquid via hydrogen peroxide, nitrite, and nitrate quantification. O₂-containing admixtures generally reduced overall plasma emission and liquid-phase RONS accumulation, whereas N₂-containing admixtures preferentially enhanced nitrogen-associated emission features. Water vapor addition via the admixture gas stream acted as an important secondary tuning parameter, exerting the strongest effects under combined O₂ + N₂ conditions. Multivariate analyses confirmed clear separation of chemistry profiles according to feed gas composition and humidity, while correlation and regression analyses identified several condition-dependent relationships between gas-phase emissions and liquid-phase reaction products. These data provide a comprehensive characterization of kINPen plasma chemistry under controlled feed gas modification and establish a reference framework for tailoring plasma-derived reactive species profiles in future plasma biology and medicine studies. Full article

(This article belongs to the Special Issue Processes in Atmospheric-Pressure Plasmas—2nd Edition)

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14 pages, 16217 KB

Open AccessArticle

Technological Capabilities of Hollow Cathode Glow Discharge

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

Plasma 2026, 9(3), 26; https://doi.org/10.3390/plasma9030026 - 9 Jul 2026

Abstract

Expanding the operating pressure range of hollow cathode glow discharge to the region of 0.01–0.1 Pa makes it possible to use the discharge plasma in a number of technological processes that were previously not feasible, because pressure always exceeded p = 1 Pa. [...] Read more.

Expanding the operating pressure range of hollow cathode glow discharge to the region of 0.01–0.1 Pa makes it possible to use the discharge plasma in a number of technological processes that were previously not feasible, because pressure always exceeded p = 1 Pa. Implantation of nitrogen ions by means of application of 40 kV pulses to a steel workpiece immersed in plasma at p < 0.1 Pa allows production of a 40 µm thick surface layer with hardness of 13 GPa exceeding by 6.5 times the hardness of the bulk and a decrease in the processing time by an order of magnitude. Nitriding a steel workpiece at p = 0.1 Pa allows a substantial increase in the nitriding rate. The use of a titanium workpiece as a discharge anode with surface area not exceeding a critical value allows it to melt due to heating to the melting point of 1670 °C by electrons accelerated in the positive anode fall of potential. Full article

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17 pages, 13453 KB

Open AccessArticle

Effects of Plasma Treatment of Reinforcing Fibers on the Weathering Stability and Fatigue Behavior of Carbon Fiber Composites After Impact

by Henrik Wollner, Stanislawa Hausmann and Gisela Ohms

Plasma 2026, 9(3), 25; https://doi.org/10.3390/plasma9030025 - 6 Jul 2026

Abstract

Carbon fiber reinforced epoxy resin composites were manufactured using the vacuum infusion technique. Composite samples were subjected to impact and then exposed to various weathering conditions. Static and dynamic mechanical tests were performed to evaluate the effect of an additional process step, a [...] Read more.

Carbon fiber reinforced epoxy resin composites were manufactured using the vacuum infusion technique. Composite samples were subjected to impact and then exposed to various weathering conditions. Static and dynamic mechanical tests were performed to evaluate the effect of an additional process step, a plasma treatment of the carbon fiber fabric, before the composite is manufactured. Scanning electron microscopy and thermal analysis were used to get further information on the degree of damage after weathering. Treating the reinforcing carbon fibers with air plasma resulted in improved strength values and fatigue behavior of the epoxy resin composite. This performance enhancement persisted even after low-energy mechanical stress and subsequent weathering. Full article

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123 pages, 21293 KB

Open AccessReview

Low-Current High-Voltage Vortex-Stabilized Pulsed Arc Atmospheric-Pressure Plasma Jets: Processes and Processing

by Dariusz Korzec, Florian Hoppenthaler and Simona Lerach

Plasma 2026, 9(3), 24; https://doi.org/10.3390/plasma9030024 - 1 Jul 2026

Abstract

Among numerous atmospheric-pressure plasma jets (APPJs), high industrial acceptability has been reached for the ones based on high-voltage, low-current, vortex-stabilized arc, typically operated with kHz DC-pulses. This review explores the interrelations between the “process” in a chemical–physical sense and “process”, or to better [...] Read more.

Among numerous atmospheric-pressure plasma jets (APPJs), high industrial acceptability has been reached for the ones based on high-voltage, low-current, vortex-stabilized arc, typically operated with kHz DC-pulses. This review explores the interrelations between the “process” in a chemical–physical sense and “process”, or to better differentiate, “processing” in the sense of technological treatment, with respect to such APPJs. The mutual dependence of the processing requirements (e.g., high processing speed, compatibility with robotic processing, low total cost of ownership, reliability, and long service intervals) and the physical and chemical processes in the plasma jet are analyzed. The focus is on the hybrid character of the produced plasma, comprising a non-equilibrium arc and a diffuse plasma. Different operation modes of the gliding arc discharge (GAD) are discussed. The reviewed chemical processes are the generation of reactive oxygen–nitrogen species (RONS), oxidation and reduction reactions, and interactions with vapors, solids, and liquids. The considered processing examples are established applications, such as surface activation, cleaning, oxide reduction, film removal, and coating, as well as emerging applications for sterilization and plasma-activated water (PAW) production. Full article

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20 pages, 13088 KB

Open AccessArticle

Formation of Electric Potential Dips and Peaks by Electron-Ion Two-Stream Instability in a Plasma Chamber with an Electron Emitter LaB₆ as the Cathode

by Lou-Chuang Lee, Kun-Han Lee, Hau-Kun Jhuang and Dong-Dong Ni

Plasma 2026, 9(3), 23; https://doi.org/10.3390/plasma9030023 - 1 Jul 2026

Abstract

This paper presents a conducting-channel model aimed at elucidating the generation of high-energy particles within a plasma chamber. Initially, the chamber is charged with neutral hydrogen gas at a density of approximately ~3.3 × 10²²/m³, equivalent to 1 torr [...] Read more.

This paper presents a conducting-channel model aimed at elucidating the generation of high-energy particles within a plasma chamber. Initially, the chamber is charged with neutral hydrogen gas at a density of approximately ~3.3 × 10²²/m³, equivalent to 1 torr at 300 K under ideal gas conditions. A Townsend discharge (dark discharge), driven by an externally imposed electric potential (500–1000 V) across the cathode and anode, is utilized to induce partial ionization of the hydrogen gas. Once a stable conducting channel with a high conductivity is established, a low electric potential (e.g., 100–500 V) is introduced to sustain the current in the conducting channel. Our investigation then delves into the impact of a high-emissivity cathode, such as lanthanum hexaboride (LaB6), on an arc discharge. We develop a theoretical model of the conducting channel that may emerge under these conditions. As the cathode surface heats, thermionic electrons form a localized layer of negative charge density outside the cathode, leading to an electric potential dip. Our multi-fluid simulations reveal the emergence of an electron-ion two-stream instability owing to the high-density electron layer, leading to the appearance of multiple potential peaks and dips, each measuring several to tens of kV. We delineate a set of conditions conducive to the formation of these potential peaks and dips within the conducting channel. Our proposed scenario furnishes a framework for elucidating electron and ion acceleration within a weakly ionized plasma chamber. Full article

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18 pages, 3192 KB

Open AccessEditor’s ChoiceArticle

Study on Arc Characteristics and Structural Optimization of a 550 kV Environmentally Friendly Gas Circuit Breaker

by Nian Tang, Hanyue Zhao and Dongwei Sun

Plasma 2026, 9(2), 22; https://doi.org/10.3390/plasma9020022 - 22 Jun 2026

Abstract

With increasingly stringent restrictions on SF₆ greenhouse gas emissions, C₄F₇N-based gas mixtures have attracted considerable attention as promising alternatives for high-voltage circuit breakers; however, their relatively weaker arc-quenching capability poses significant challenges for interruption chamber design at high [...] Read more.

With increasingly stringent restrictions on SF₆ greenhouse gas emissions, C₄F₇N-based gas mixtures have attracted considerable attention as promising alternatives for high-voltage circuit breakers; however, their relatively weaker arc-quenching capability poses significant challenges for interruption chamber design at high voltage levels. In this study, a 3.5% C₄F₇N/83.5% CO₂/13% O₂ gas mixture was used as the arc-extinguishing medium in a 550 kV environmentally friendly gas circuit breaker. Based on a magnetohydrodynamic (MHD) model considering PTFE nozzle ablation effects, systematic optimization studies were conducted on key structural parameters of the puffer-type interruption chamber, including the exhaust hole diameter, nozzle throat diameter and length, arcing contact diameter, and downstream expansion angle. Simulations under arcing times of 9.9 ms and 11.4 ms were performed to evaluate chamber pressure, axial temperature, extinction peak voltage, and post-arc conductance characteristics. The results indicate that extending the nozzle throat straight section to 70 mm, enlarging the exhaust hole, and increasing the moving contact radius can effectively enhance pressure buildup, reduce arc-core temperature, and improve dielectric recovery capability. Under the 11.4 ms arcing condition, the optimized structure achieved an extinction peak voltage of 6972.4 V and a G200 value of 0.731 ms, demonstrating substantially improved interruption performance. These findings reveal the synergistic relationship between arcing time and structural parameters and provide theoretical guidance for the engineering design of environmentally friendly high-voltage gas circuit breakers. Full article

(This article belongs to the Topic Advanced Electromagnetic Modeling and Simulation for Multidisciplinary Engineering Systems)

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15 pages, 4127 KB

Open AccessArticle

Effects of Non-Thermal Electrons and Non-Extensive Positrons on Dust-Ion-Acoustic Solitary Waves in an Unmagnetized Plasma

by Satyendra Nath Barman and Kingkar Talukdar

Plasma 2026, 9(2), 21; https://doi.org/10.3390/plasma9020021 - 10 Jun 2026

Abstract

In this study, we investigated the existence and properties of solitons in an unmagnetized plasma composed of positive ions, negative ions, negatively charged dust grains, non-thermal electrons and non-extensive positrons. We have conducted our study on this complex plasma model because it moves [...] Read more.

In this study, we investigated the existence and properties of solitons in an unmagnetized plasma composed of positive ions, negative ions, negatively charged dust grains, non-thermal electrons and non-extensive positrons. We have conducted our study on this complex plasma model because it moves away from simplistic and idealized plasma models. Also, a study of solitons has not previously been conducted on this complex plasma model. Through the Sagdeev potential method, we have derived the energy integral and investigated the variation in the Sagdeev potential for different values of the parameters that are involved in our plasma model. We have found that the non-thermal parameter (β) and the non-extensive parameter (q) significantly influence the features of the solitons. The features of the solitons are also found to be influenced by the Mach number (M), the negative-ion-to-positive-ion mass ratio (

Ω

), the positron-to-positive-ion density ratio (δ_p), the electron-to-positron temperature ratio (σ_p), the dust charge density ratio (δ_d) and the negative-ion-to-positive-ion density ratio (δ_). The results from our study can be useful in investigating plasma in astrophysical environments, such as cometary tails and interstellar clouds. Full article

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23 pages, 9716 KB

Open AccessArticle

Influence of Different Catalysts on Ammonia Synthesis Performance in Coaxial DBD Plasma

by Fangcheng Qiu, Xin Zhang, Shuai Jiang, Huilin Zhou, Lin Wang, Yufeng Song, Jian Huang, Xin Zheng, Ronghai Liu and Xuekai Pei

Plasma 2026, 9(2), 20; https://doi.org/10.3390/plasma9020020 - 4 Jun 2026

Abstract

In the renewable energy-driven “green electricity–green hydrogen–green ammonia” pathway, the development of low-temperature and low-energy-consumption ammonia synthesis technologies is of great significance. In this work, a plasma-catalytic ammonia synthesis system was established using a coaxial dielectric barrier discharge (DBD) reactor. The effects of [...] Read more.

In the renewable energy-driven “green electricity–green hydrogen–green ammonia” pathway, the development of low-temperature and low-energy-consumption ammonia synthesis technologies is of great significance. In this work, a plasma-catalytic ammonia synthesis system was established using a coaxial dielectric barrier discharge (DBD) reactor. The effects of different catalysts, including Ag, Cu, γ-Al₂O₃, BaTiO₃ and Co/BaTiO₃, Ni/BaTiO₃ on ammonia synthesis performance were systematically investigated. The reaction process was analyzed using voltage–current waveforms, Lissajous figures, and optical emission spectroscopy (OES). The results show that different catalytic systems have a significant influence on ammonia synthesis performance, with the promotional effect ranked as follows: Ni/BaTiO₃ > Co/BaTiO₃ > BaTiO₃ > Ag > γ-Al₂O₃ > Cu. Among them, Ni/BaTiO₃ exhibited the best performance. Under the conditions of N₂:H₂ = 1:1 and a gas flow rate of 2.5 L/min, the NH₃ synthesis rate reached 259.48 μmol/min, and the maximum energy efficiency reached 1.40 g-NH₃/kWh. Catalyst characterization results indicate that the BaTiO₃ support maintained a stable crystal structure, while the loaded metal species were highly dispersed and uniformly distributed on the support surface, which is beneficial for the adsorption and conversion of reactive species on the catalyst surface. Discharge characteristic analysis shows that the introduction of BaTiO₃ enhanced the local electric field and improved the uniformity of micro-discharges, while the further incorporation of metal active components strengthened the micro-discharge behavior. OES results reveal that the intensities of characteristic emission lines, such as NH, N₂⁺, and Hα, were significantly enhanced in the Ni/BaTiO₃ system, facilitating the formation and conversion of NH_x intermediates. The superior performance of Ni/BaTiO₃ is attributed to the coupling between BaTiO₃-induced dielectric enhancement and Ni-promoted surface hydrogenation and NH₃ desorption. This work provides mechanistic insight into catalyst-dependent DBD plasma-catalytic ammonia synthesis and offers an experimental basis for the further optimization of plasma-based ammonia production. Full article

(This article belongs to the Special Issue Recent Advances of Dielectric Barrier Discharges, 2nd Edition)

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14 pages, 1606 KB

Open AccessArticle

Characteristics of Microsecond-Pulse Source for Atmospheric Pressure Helium Plasma Jet

by Chen Ma, Li Yao, Jialu Liu and Feng He

Plasma 2026, 9(2), 19; https://doi.org/10.3390/plasma9020019 - 2 Jun 2026

Abstract

In this work, based on a half-bridge circuit and pulse transformer, a miniaturized and low-cost microsecond high-voltage pulsed power supply for the atmospheric pressure plasma jet (APPJ) is designed. Because of the low bus voltage of the half-bridge circuit, low-voltage switches can be [...] Read more.

In this work, based on a half-bridge circuit and pulse transformer, a miniaturized and low-cost microsecond high-voltage pulsed power supply for the atmospheric pressure plasma jet (APPJ) is designed. Because of the low bus voltage of the half-bridge circuit, low-voltage switches can be chosen by the power supply. The characteristics of the output high voltage of the power supply are studied. The experimental results show that uni-polar and bi-polar pulses can be generated by the power supply. The high-voltage pulses have good consistency at different frequencies, and the amplitude of the high-voltage pulse varies approximately linearly with the bus voltage. A needle-ring plasma jet device was driven by the uni-polar pulse of this supply, and the single discharge current pulse can be obtained at the rising edge and falling edge of the high-voltage pulse, respectively. The effects of voltage pulse on APPJ and the characteristics of jet are also investigated. The results show that the plasma jet is only formed at the rising edge of the voltage pulse. The jet length is almost unaffected by the pulse frequency, whereas the normalized intensity of most species increases with frequency linearly. Full article

(This article belongs to the Special Issue Processes in Atmospheric-Pressure Plasmas—2nd Edition)

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11 pages, 1015 KB

Open AccessArticle

Deep Learning-Based Reconstruction of Particle Beam Energy Spectra from Attenuation Curve Data

by Vasily Kozhevnikov, Andrey Kozyrev, Dmitry Sorokin, Victor Tarasenko, Dmitry Beloplotov, Eugene Baksht and Mikhail Lomaev

Plasma 2026, 9(2), 18; https://doi.org/10.3390/plasma9020018 - 2 Jun 2026

Abstract

This paper introduces a deep learning-based methodology for reconstructing particle beam energy spectra from experimental attenuation curves. This task involves solving a classic ill-posed inverse problem for a Fredholm integral equation of the first kind. Unlike traditional Arsenin–Tikhonov regularization, the proposed framework utilizes [...] Read more.

This paper introduces a deep learning-based methodology for reconstructing particle beam energy spectra from experimental attenuation curves. This task involves solving a classic ill-posed inverse problem for a Fredholm integral equation of the first kind. Unlike traditional Arsenin–Tikhonov regularization, the proposed framework utilizes two coupled neural networks for spectrum approximation and adaptive kernel correction. This approach explicitly accounts for measurement uncertainties in the experimental data. As a mesh-free technique, it operates directly on raw sparse experimental datasets without preprocessing. Validation using data from subnanosecond electron beams in gas-filled and vacuum diodes demonstrates that the method successfully resolves non-trivial two-peak spectral structures. In particular, it reliably identifies populations of “anomalous” high-energy electrons that are often obscured by classical regularization artifacts. Full article

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

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15 pages, 2675 KB

Open AccessEditor’s ChoiceArticle

The Anti-Inflammatory Activity of No-Ozone Cold Plasma Can Be Delivered Through a Conductive Metal Needle on TNFα-Treated C2C12 Mice Muscle Cells In Vitro

by Jeong-Hae Choi, Seung-Ah Park, Hyun-Young Lee, Wonkyu Hong, Jaehong Kim, Jin-Woo Hong and Gyoo-Cheon Kim

Plasma 2026, 9(2), 17; https://doi.org/10.3390/plasma9020017 - 26 May 2026

Abstract

Recently, an anti-inflammatory effect of no-ozone cold plasma (NCP) has been reported, but the direct use of NCP for treating muscle inflammation is very difficult since NCP is a form of gas. In this study, we tested whether the anti-inflammatory effect of the [...] Read more.

Recently, an anti-inflammatory effect of no-ozone cold plasma (NCP) has been reported, but the direct use of NCP for treating muscle inflammation is very difficult since NCP is a form of gas. In this study, we tested whether the anti-inflammatory effect of the NCP could be delivered through conductive metal needles to reduce muscle inflammation. C2C12 mouse muscle cells were treated with TNFα to induce muscle inflammation and then treated with NCP and a conductive metal needle separately or in combination. The effects of NCP and a needle were monitored by performing RT-PCR and Western blot analysis. As a result, NCP effectively suppressed the TNFα-mediated expression of the TNFα, IL1β, and FasL genes, but this effect weakened as the distance between the cells and the NCP increased. On the other hand, treatment of cells with a plasma-needle (PN) had an anti-inflammatory effect regardless of distance, and the anti-inflammatory effect of the PN was maintained under conditions where the gas flow of NCP was not delivered to the cells. It is believed that the PN-mediated activation of media plays a pivotal role in the anti-inflammatory effect of the PN. Finally, this study also showed that electroacupuncture can inhibit TNFα-induced inflammatory gene expression in a manner like a PN. Taken together, the results of this study demonstrate that the anti-inflammatory effect of NCP can be delivered through metal needles, suggesting that PN may be useful for treating inflammatory muscle pain. Full article

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14 pages, 2434 KB

Open AccessArticle

Study on the Key Influence Factors of Interrupting Characteristics of C₄F₇N Gas Mixture Self-Blast Circuit Breaker

by Ke Wang, Yuying Shi, Bochen Li, Yiheng Zhang, Suoyun Yang and Xianping Zhao

Plasma 2026, 9(2), 16; https://doi.org/10.3390/plasma9020016 - 20 May 2026

Abstract

High-voltage self-blast circuit breakers feature complex gas flow field dynamics during the arc interruption process due to the multiple gas chambers and valves in the interrupter. The structure of key interrupter components and the characteristics of the operating mechanism significantly influence the gas [...] Read more.

High-voltage self-blast circuit breakers feature complex gas flow field dynamics during the arc interruption process due to the multiple gas chambers and valves in the interrupter. The structure of key interrupter components and the characteristics of the operating mechanism significantly influence the gas flow field behavior, thereby affecting the breaking performance. The C₄F₇N gas mixture is currently the most promising alternative to SF₆. However, the influence mechanisms of various factors on its breaking performance remain unclear, which limits the design of C₄F₇N-based self-blast interrupter chambers. This paper investigates the impact of nozzle throat length and mechanism stroke on the breaking performance of a 126 kV double-motion self-blast circuit breaker prototype by establishing a magnetohydrodynamic (MHD) arc model for C₄F₇N gas mixtures. The results indicate that a longer throat length can enhance the pressure-buildup capability in the expansion chamber to some extent, but its effect on short arcing times is limited, whereas it has a more pronounced influence on medium and long arcing times. However, it also impedes arc energy dissipation, potentially reducing the breaking capability for short and medium arcing times while improving performance for long arcing times. A larger mechanism stroke not only ensures a greater contact gap at current zero for long arcing times but also accelerates the gas flow velocity between the contacts, facilitating arc energy dissipation and enhancing the thermal interruption performance. Full article

(This article belongs to the Topic Advanced Electromagnetic Modeling and Simulation for Multidisciplinary Engineering Systems)

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31 pages, 3749 KB

Open AccessEditor’s ChoiceReview

Design Considerations for Low-Temperature Plasma Production in Air Using Pulsed Dielectric Barrier Discharges: A Review

by Luutzen Franciscus Ate Wymenga, Jan van Turnhout, Mohamad Ghaffarian Niasar, Henk van Zeijl, Willem Dirk van Driel and Guoqi Zhang

Plasma 2026, 9(2), 15; https://doi.org/10.3390/plasma9020015 - 14 May 2026

Cited by 1

Abstract

Low-temperature atmospheric plasma (LTP) is widely used in industrial processes, such as disinfection, surface modification and wastewater treatment. The dielectric barrier discharge (DBD) is regarded as one of the most robust and reliable methods for generating LTP in ambient air. Compared to conventional [...] Read more.

Low-temperature atmospheric plasma (LTP) is widely used in industrial processes, such as disinfection, surface modification and wastewater treatment. The dielectric barrier discharge (DBD) is regarded as one of the most robust and reliable methods for generating LTP in ambient air. Compared to conventional AC excitation, pulsed powering offers several advantages (i.e., lower energy use and heat production). The present trend is to use short and fast pulses (in the nano- and picosecond range). In this review, the key design parameters of a DBD (barrier thickness, relative permittivity and gap distance) are discussed. Material-specific phenomena like surface charging and degradation are analyzed. The complex interactions between the pulse source and DBD are examined. By mapping the interdependencies, this review aims to support the rational design and optimization of pulsed DBD systems, and to facilitate their broader industrial use. Full article

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24 pages, 4051 KB

Open AccessArticle

Magnetic Confinement Effects in a Hybrid DC–RF Internal-Antenna Inductively Coupled Plasma: Spatial Diagnostics and Semi-Empirical Modelling

by Mahmood Nasser

Plasma 2026, 9(2), 14; https://doi.org/10.3390/plasma9020014 - 8 May 2026

Abstract

A hybrid DC–RF inductively coupled plasma (ICP) driven by a single-turn internal antenna was experimentally investigated to quantify magnetic confinement effects in low-pressure argon discharges. Superposition of a dc current on the RF antenna generated an azimuthal magnetic field that modified electron transport [...] Read more.

A hybrid DC–RF inductively coupled plasma (ICP) driven by a single-turn internal antenna was experimentally investigated to quantify magnetic confinement effects in low-pressure argon discharges. Superposition of a dc current on the RF antenna generated an azimuthal magnetic field that modified electron transport and reduced cross-field diffusion in the near-antenna region. Spatially resolved measurements of plasma density, electron temperature, plasma potential, and magnetic-field components were obtained using Langmuir, emissive, and B-dot probes. Increasing the dc current enhanced electron confinement and increased the plasma density by up to an order of magnitude at low RF power, together with improved radial and axial uniformity. A semi-empirical diffusion model incorporating electron-temperature-dependent ambipolar transport reproduced the measured ion-density distributions, ni(R,Z), within ±15%. The results support the interpretation that the discharge behaviour is governed by the coupled effects of localized magnetic confinement and inductive power deposition, and show that hybrid DC–RF excitation provides an effective route to denser and more spatially extended plasmas under low-pressure conditions. Full article

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15 pages, 6137 KB

Open AccessArticle

Experimental Investigation of Arc Characteristics Between Piezoelectrically Actuated Contacts in Air, Vacuum, and Nitrogen

by Mohmmad Al-Dweikat, Moath Bani Fayyad, Hana Rababah and Qirong Wu

Plasma 2026, 9(2), 13; https://doi.org/10.3390/plasma9020013 - 8 May 2026

Abstract

Piezoelectric actuators enable ultra-fast switching due to their microsecond-scale response and high acceleration capability. This study experimentally investigates arc behavior in air, vacuum, and nitrogen using round and flat contacts driven by an amplified piezoelectric actuator. Unlike prior work focused mainly on actuation [...] Read more.

Piezoelectric actuators enable ultra-fast switching due to their microsecond-scale response and high acceleration capability. This study experimentally investigates arc behavior in air, vacuum, and nitrogen using round and flat contacts driven by an amplified piezoelectric actuator. Unlike prior work focused mainly on actuation dynamics, this study provides a multi-medium comparison and investigates the coupled effects of drive operating time and contact geometry on arc characteristics. Arc tests were conducted using a capacitor discharge platform, with synchronized electrical measurements and high-speed imaging. In air (140 V, 350 A), arc voltage increased with rise time, reaching 800 V, 840 V, and 1080 V at 0.5 ms, 1 ms, and 2 ms, respectively, while shorter rise times reduced arc duration but promoted reignition. In vacuum (140–200 V), arc voltage stabilized at 80–90 V, with longer rise times extending arc duration; round contacts exhibited faster voltage rise and higher peaks. In nitrogen (140–200 V), higher voltages were obtained at shorter rise times, reaching 2680 V, 2600 V, and 2320 V at 0.5 ms, 1 ms, and 2 ms, respectively, with reduced arc duration. Across all media, round contacts consistently produced higher arc voltages than flat contacts. These results demonstrate that drive dynamics and contact geometry critically influence arc voltage and duration, providing practical guidelines for the design of high-speed piezoelectric-based switching devices. Full article

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