Plasma

To explore the potential of plasma technology in regulating seed germination, this study compared the effects of direct treatment with needle-plate electrodes using DC and pulse power supplies, and indirect treatment with plasma-activated water on the growth characteristics of Bromus inermis seeds. By comparing different pulse power parameters, including voltage, pulse width, frequency, and duration, it was found that treatments at 15 kV, 2500 ns, 6 kHz, and 10 min significantly increased the surface hydrophilicity and germination performance of the seeds. The best conditions for DC power supply were 15 kV and 10 min. Indirect treatment with plasma-activated water (15 kV, 10 min) effectively broke the seed dormancy by regulating active nitrogen oxygen particle components, increasing the germination percentage by 50%. Analysis of antioxidant enzyme activity showed that in seedlings the activities of superoxide dismutase (SOD) and peroxidase (POD) increased by 75% and 21%, respectively, after treatment, revealing the mechanism of oxidative stress response induced by plasma. This study provides theoretical and technical references for the application of plasma technology in enhancing seed vitality and agricultural practices. Full article

When a gas is overvolted at or near atmospheric pressure, it results in a streamer discharge formation. Electrode geometries exert significant impact on the electrical breakdown of gases by altering the spatial profile of the electric field. In many applications the efficient generation of radicals is critical and is determined by the characteristics of the streamer discharge. We examine the effect of electrode geometry on the streamer characteristics and the production of radicals. This is performed for three different electrode geometries: plane–plane, pin–plane, and pin–pin. A two-dimensional rotationally symmetric fluid model is used for the streamer discharge simulation in the hydrogen/air gas mixture. The spatial profile of electron density and the electric field for point electrodes show significant differences when compared to plane electrodes. However, the efficiency of radical generation shows similar trends for the electrode configurations studied. We also present the results of spatial electrical energy density distribution which in turn determines spatial excited species distribution. These results can inform the design of specific applications. Full article

We present an experimentally validated, engineering-oriented framework for the design and operation of pin-to-water (PTW) atmospheric discharges to produce hydrogen peroxide (H₂O₂) on demand. Motivated by industrial needs for safe, point-of-use oxidant supply, we combine time-resolved diagnostics (FTIR, OES), liquid-phase analysis (ion chromatography, pH, conductivity), and coupled plasma-chemistry/fluid simulations to link plasma state to aqueous H₂O₂ yield. Under the tested conditions (14.3 kHz, 0.2 kW; electrode to quartz wall distance 12–14 mm; coolant setpoints 0–40 °C), H₂O₂ concentration follows a reproducible non-monotonic trajectory: rapid accumulation during the early treatment (typical peak at ~15–25 min), followed by decline with continued operation. The decline coincides with a robust vibrational-temperature (T_vib) threshold near ~4900 K measured from N₂ emission, and with concurrent NO_X accumulation and bulk acidification. Global chemistry modeling and Fluent flow fields reproduce the observed trend and show that both vibrational excitation (kinetics) and convective transport (mass/heat transfer) determine the productive time window. Based on these results, we formulate practical design rules—electrode gap (power density), discharge current control, thermal/flow management, water quality, and OES-based T_vib monitoring with an automated stop rule—that maximize H₂O₂ yield while avoiding NO_X-dominated suppression. The study provides a clear path for transforming mechanistic plasma insights into deployable, industrial H₂O₂ generator designs. Full article

The win–win situation of dye degradation and nitrogen fixation in wastewater using non-thermal plasma (NTP) were investigated in this study. Specifically, the feasibility of utilizing plasma-treated dye-contaminated wastewater for seed germination and plant growth was explored. Crystal Violet (CV) and Rhodamine B (RhB) dyes were used as model pollutants, while Sorghum bicolor (great millet) seeds were used to assess germination rates and plant growth responses. In untreated wastewater containing CV and RhB, approximately 45% of seeds germinated after three days, but no significant stem or root growth was observed after 11 days. Plasma treatment significantly enhanced dye degradation, with efficiency improving as treatment time and input power increased. After 16 min of plasma treatment at 1.3 ± 0.2 W input power, about 99% degradation efficiency was achieved for both CV (0.0122 mM) and RhB (0.0104 mM). This degradation was primarily driven by reactive oxygen and nitrogen species (RONS) generated by plasma discharge. When sorghum seeds were germinated using plasma-treated wastewater, the germination rate increased to 65% after three days—20% higher than with untreated wastewater. Furthermore, after 11 days, the average stem length reached 9 cm, while the average root length extended to 7 cm. These findings highlight NTP as a promising and sustainable method for degrading textile industry pollutants while simultaneously enhancing crop productivity through the reuse of treated wastewater. Full article

We present three dimensional particle-in-cell simulations of current-voltage characteristics of the hemispherical Langmuir probe (LAP), onboard the China Seismo-Electromagnetic Satellite (CSES). Using realistic plasma parameters and background magnetic fields obtained from the International Reference Ionosphere (IRI) and International Geomagnetic Reference Field (IGRF) models, we simulate probe–plasma interactions at three locations: the equatorial region and two magnetically conjugate mid-latitude sites: Millstone Hill (Northern Hemisphere) and Rothera (Southern Hemisphere). The simulations, performed using the PTetra PIC code, incorporate realistic LAP geometry and spacecraft motion in the ionospheric plasma. Simulated current voltage characteristics or I–V curves are compared against in-situ LAP measurements from CSES Orbit-026610, with Pearson’s correlation coefficients used to assess agreement. Our findings indicate how plasma temperature, density, and magnetization affect sheath structure and probe floating potential. The study highlights the significance of kinetic modeling in enhancing diagnostic accuracy, particularly in variable sheath regimes where classic analytical models such as the Orbital-Motion-Limited (OML) theory may be inadequate. Full article

The removal of defective surface layers can substantially improve the quality of various products. It can be carried out using beams of accelerated ions or fast argon atoms. However, it is difficult to process the inner surface of narrow channels. In the present work, a narrow beam of fast argon atoms is used to sputter and polish the inner surface of drawing dies with 5.7 mm wide working channels. Due to the high angle of incidence to the channel walls, sputtering with fast argon atoms decreased their roughness to Ra ~ 0.004 µm. Full article

Plasma arcs generated by lightning strikes are prone to tripping distribution lines, especially 10 kV lines. To reduce the lightning-induced tripping rate of 10 kV distribution lines and ensure the safe operation of power systems, this paper proposes a same-level double-fracture lightning protection device containing the electronegative gas trifluoroiodomethane (CF₃I). A mathematical model of the gas arc-extinguishing process is established based on magnetohydrodynamics. Meanwhile, the mechanism of CF₃I in the arc-extinguishing process is analyzed according to its physical and chemical properties, and the arc-extinguishing process is simulated using COMSOL Multiphysics 6.0. The results show that (1) the arc-extinguishing effect is optimal when the horizontal distance of the compression pipeline of the device is 9 mm; (2) under the action of power frequency currents with different initial phases of π/2 and 0, the arc-extinguishing device can extinguish the arc within 800 $\mathsf{\mu }\mathrm{s}$ without re-ignition; and (3) in the arc-extinguishing process involving CF₃I, the arc can be extinguished within 710 $\mathsf{\mu }\mathrm{s}$, which is 11.2% quicker than that without CF₃I. Meanwhile, CF₃I can effectively reduce the arc temperature at the initial stage of arc extinguishing, avoiding damage caused by excessive internal compression of the device. Full article

A system-level study of a NO_x abatement process by means of non-thermal plasma (NTP) generated with dielectric barrier discharges (DBDs) is the framework of this article. With the goal of system improvement, the kinetic reaction simulation software ZdPlaskin is considered to select the most favorable operating conditions in order to optimize NO_x abatement (deNO_x). A parametric exploration of the performance, through variations in operating conditions (temperature, power injection pattern, and input gas mixture composition), requires highly numerous simulations; thus, the shortest possible computation times with robust results are of significant interest. As such, an analysis and filtering method is proposed and detailed to build a minimized chemical kinetic reaction set, allowing us to reliably analyze the impact of the selected operating conditions for the DBD reactor on treatment performance. Full article

Time- and space-resolved radiation emitted by the plasma produced by a 0.8 ns duration at full width half maximum, ~600 MW maximum power microwave (~9.6 GHz) pulse traversing a hydrogen-, helium-, or air-filled circular waveguide, is studied. Gas ionization by microwaves is an old subject but the regime investigated in the present experimental research, of very high-power microwaves and very short pulses using modern diagnostic tools, is new and follows a series of new studies performed so far only in our laboratory, revealing non-linear phenomena never observed before. In the present research, plasma radiation is observed along a slit made in a circular waveguide wall by either an intensified fast frame camera or a streak camera. Using calibrated input and output couplers, the transmission and reflection coefficients of the high-power microwaves were determined over a broad range of gas pressures, 0.1 kPa < P < 90 kPa. It was found that the intensity of the plasma light emission increases significantly after the high-power microwave pulse has left the waveguide. Depending on pressure, the radiation is either uniform along the slit, while the front of the emitted light follows the microwave pulse at a velocity close to its group velocity, or it remains in the vicinity of the input window, indicating that the plasma density is above critical density. It was also found that the radial distribution of radiation depends on pressure. At pressures <10 kPa, when the electron oscillatory energy reaches 20 keV close to the waveguide axis, light emission forms faster near the waveguide walls, where the ionization rate is maximal. Otherwise, when pressure is >80 kPa, light emission is most intense on the axis where the electron oscillatory energy is ~100 eV and the ionization rate is maximal. We also studied the UV radiation from the plasma, the duration of which was found to be longer than the duration of visible light emission. This indicates the existence of energetic electrons for tens of ns after the high-power microwave pulse has left the observation region. Considering that the emitted light intensity depends on the plasma density and temperature, the observed data may be used for a comparison with the results of collisional radiative models if the electron time and spatial energy distribution is known. Full article

The study evaluates the efficacy of an image-guided CAP treatment method with a plasma device capable of rapid biofilm removal from chicken tissue. The plasma treatment operating configuration includes a gas mixture of Argon and H₂O at a flowrate of 1.5 lpm. An X-Y stage was used to move the chicken sample below the stationary plasma scalpel at a speed of 0.1 mm/s. The discharge voltage and current were maintained between 3.2 and 3.7 kV (AC 20 kHz), and at 3 mA, respectively. The electrode gap and sample distance were set to 0.6 mm and 4 mm. This configuration facilitated effective biofilm removal, as confirmed by CFU analysis and 3D microscopic analysis showing a >99% reduction in biofilm post treatment with an etch rate of 2.2–5.8 µm/s and an impact width of up to 300 µm. The plasma scalpel electrode temperature reached 94.7 °C, while the targeted biofilm area was heated to 36.3 °C, suggesting non-thermal biofilm disruption. Three-dimensional microscopic analysis revealed biofilm thickness on chicken tissues ranging from 20 to 180 µm, comparable to biofilm loads on mammalian tissues. In conclusion, the study highlights the potential of CAP devices as a promising solution for biofilm debridement. Full article

Theoretical studies have indicated that borophene is a promising two-dimensional material characterized by remarkable chemical, mechanical, and electrical properties. Nonetheless, its practical applications in areas such as catalysis and gas sensing are hindered by the limited density of reactive sites in its pristine form. To address this limitation, the present study explores the controlled fluorination of borophene nanoflakes as a strategy to modify their surface chemistry and enhance the availability of active sites. Furthermore, it is anticipated that surface fluorination will improve hydrophobicity, which is crucial for reducing humidity-related interference in sensing applications. In this study, we report the successful functionalization of borophene nanoflakes with fluorine using a plasma arc discharge technique for the first time. Borophene nanolayers were synthesized via a sonochemical-assisted exfoliation method, yielding nanosheets with an average lateral dimension of approximately 100 nm. The fluorinated samples were characterized using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM). A systematic investigation of plasma exposure durations demonstrated that fluorine was effectively introduced as a dopant while maintaining the crystallinity of the borophene lattice. Full article

The Multi-Mode Model (MMM) is a physics-based anomalous transport model integrated into TRANSP for predicting electron and ion thermal transport, electron and impurity particle transport, and toroidal and poloidal momentum transport. While MMM provides valuable predictive capabilities, its computational cost, although manageable for standard simulations, is too high for real-time control applications. MMMnet, a neural network-based surrogate model, is developed to address this challenge by significantly reducing computation time while maintaining high accuracy. Trained on TRANSP simulations of DIII-D discharges, MMMnet incorporates an updated version of MMM (9.0.10) with enhanced physics, including isotopic effects, plasma shaping via effective magnetic shear, unified correlation lengths for ion-scale modes, and a new physics-based model for the electromagnetic electron temperature gradient mode. A key advancement is MMMnet’s ability to predict all six transport coefficients, providing a comprehensive representation of plasma transport dynamics. MMMnet achieves a two-order-of-magnitude speed improvement while maintaining strong correlation with MMM diffusivities, making it well-suited for real-time tokamak control and scenario optimization. Full article

The Thomas–Fermi model and its quantum and exchange corrections with mathematic manipulations and numerical approaches are primarily investigated. The reduced ideal electron chemical potential is adopted as the initial value for the iterative solution of the Thomas–Fermi model. A new transformation for the quantum and exchange equations is proposed to apply the boundary conditions easily. Both the Thomas–Fermi equation and correction equations are solved with the Runge–Kutta algorithm. The mathematical difficulties in controlling the computing accuracy of the equations containing the Fermi–Dirac integral are settled. The equation of state, based on the Thomas–Fermi model with its quantum and exchange corrections, is constructed and compared with relevant data. Full article

In this article, we present an overview of our investigations on the formation and behavior of space charge structures in an argon discharge plasma on gridded and smooth spherical hollow electrodes with and without orifices. Four experiments are described, in which we have used the following: (1) one spherical gridded sphere with one orifice, (2) one hollow smooth stainless steel sphere with two opposing orifices, (3) two smooth polished stainless steel spherical electrodes without orifices, (4) two smooth polished stainless steel spherical electrodes with opposing orifices. The experiments were conducted at the University of Innsbruck in a stainless steel cylindrical chamber (the former Innsbruck DP machine—IDP), and at the Alexandru Ioan Cuza University of Iaşi (Romania) in a Pyrex Vacuum Chamber (PCH). As diagnostics, we have used mainly optical emission spectroscopy to determine electron temperature and density. Full article

The mechanisms by which rotation influences zonal flows (ZFs) in plasma are incompletely understood, presenting a significant challenge in the study of plasma dynamics. This research addresses this gap by investigating the role of non-inertial effects—specifically centrifugal and Coriolis forces—on Geodesic Acoustic Modes (GAMs) and ZFs in rotating tokamak plasmas. While previous studies have linked centrifugal convection to plasma toroidal rotation, they often overlook the Coriolis effects or inconsistently incorporate non-inertial terms into magneto-hydrodynamic (MHD) equations. In this work, we derive self-consistent drift-ordered two-fluid equations from the collisional Vlasov equation in a non-inertial frame, and we modify the Hermes cold ion code to simulate the impact of rotation on GAMs and ZFs. Our simulations reveal that toroidal rotation enhances ZF amplitude and GAM frequency, with Coriolis convection playing a critical role in GAM propagation and the global structure of ZFs. Analysis of simulation outcomes indicates that centrifugal drift drives parallel velocity growth, while Coriolis drift facilitates radial propagation of GAMs. This work may provide valuable insights into momentum transport and flow shear dynamics in tokamaks, with implications for turbulence suppression and confinement optimization. Full article

Some of the popular and successful atmospheric pressure fuel/air plasma-assisted combustion methods use repetitive ns pulsed discharges and dielectric-barrier discharges. The transient phase in such discharges is dominated by transport under strong space charge from ionization fronts, which is best characterized by the streamer model. The role of the nonthermal plasma in such discharges is to produce radicals, which accelerates the chemical conversion reaction leading to temperature rise and ignition. Therefore, the characterization of the streamer and its energy partitioning is essential to develop a predictive model. We examine the important characteristics of streamers that influence combustion and develop some macroscopic parameters. Our results show that the radicals’ production efficiency at an applied field is nearly independent of time and the radical density generated depends only on the electrical energy density coupled to the plasma. We compare the results of the streamer model to the zero-dimensional uniform field Townsend-like discharge, and our results show a significant difference. The results concerning the influence of energy density and repetition rate on the ignition of a hydrogen/air fuel mixture are presented. Full article

Reactive oxygen–nitrogen species (RONS) production in a Peltier-cooled hybrid dielectric barrier discharge (HDBD) reactor operated with humid air is characterized. Fourier-transform infrared spectroscopy (FTIR) is used to determine the RONS in the HDBD-produced gases. The presence of molecules ${\mathrm{O}}_3$, ${\mathrm{NO}}_2$, ${\mathrm{N}}_2$O, ${\mathrm{N}}_2{\mathrm{O}}_5$, and ${\mathrm{HNO}}_3$ is evaluated. The influence of HDBD reactor operation parameters on the FTIR result is discussed. The strongest influence of Peltier cooling on RONS chemistry is reached at conditions related to a high specific energy input (SEI): high voltage and duty cycle of plasma width modulation (PWM), and low gas flow. Both PWM and Peltier cooling can achieve a change in the chemistry from oxygen-based to nitrogen-based. ${\mathrm{N}}_2{\mathrm{O}}_5$ and ${\mathrm{HNO}}_3$ are detected at a low humidity of 7% in the reactor input air but not at humidity exceeding 90%. In addition to the FTIR analysis, the plasma-activated water (PAW) is investigated. PAW is produced by bubbling the HDBD plasma gas through 12.5 mL of distilled water in a closed-loop circulation at a high SEI. Despite the absence of ${\mathrm{N}}_2{\mathrm{O}}_5$ and ${\mathrm{HNO}}_3$ in the gas phase, the acidity of the PAW is increased. The pH value decreases on average by 0.12 per minute. Full article

In this study, particle-in-cell (PIC) simulation was used to validate a conceptual design for a quasi-spherical, net power, hydrogen-plus-boron-11-fueled fusion reactor incorporating high-temperature superconducting (HTS) magnets. By burning a fully thermalized plasma, our proposed MET6 reactor uses the principles of the 1980 magneto-electrostatic trap design of Yushmanov to improve the classic Polywell design. Because the input power consumed by the reactor will barely balance the waste bremsstrahlung radiation, future research must focus on reducing the bremsstrahlung losses to reach practical net power levels. The first step to reducing bremsstrahlung, explored in this paper, is to tune the reactor parameters to reduce the energies of trapped electrons. We assume the quality factor Q can be approximated as the ratio of fusion power output divided by bremsstrahlung power loss. Thus, assuming the particles’ power loss is negligible compared to bremsstrahlung power loss, the resulting quality factor is estimated to be Q ≈ 1.3. Full article

Non-thermal plasma (NTP)-assisted material synthesis and surface modification provide a promising approach in various applications, particularly in wastewater treatment. In this study, we reported the synthesis of photocatalytic zinc oxide (ZnO) from zinc hydroxide (Zn(OH)₂) utilizing NTP discharge generated by dielectric barrier discharge (DBD). The results demonstrated that the 40 min plasma treatment at 200 °C (ZnO-P) with a voltage of 20 kV significantly improved the material’s physicochemical properties compared to conventional calcination at 600 °C (ZnO-600). ZnO-P exhibited better crystallinity, a significantly reduced particle size of 41 nm, and a narrower band gap of 3.1 eV compared to ZnO-600. Photocatalytic performance was evaluated through crystal violet degradation, where ZnO-P achieved an 60% degradation rate after 90 min of UV exposure, whereas ZnO-600 exhibited only a 50% degradation rate under identical conditions. These findings underscore the effectiveness of NTP synthesis in enhancing the surface properties of ZnO, leading to superior photocatalytic performance. Full article