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Titanium tetrachloride (TiCl4) is a well-known source of titanium (Ti) for the formation of titanium nitride (TiN) barrier material in the semiconductor interconnection process; however, the reaction of by-products with airborne molecules can cause unexpected pump trips and equipment breakdown from the by-product powder build-up. Plasma scrubbers are used to decompose by-products, but hydrogen chloride (HCl) and nitrogen oxides are produced during and after the process. The process mechanisms change when the temperature and applied power of the heat source change. In this paper, we study the influence of the reactor temperature and applied power to the heat source on the decomposition capacity of TiCl4 in a plasma pretreatment system (PPS). We examine the effect of the temperature and heat source power to understand the reaction mechanisms for the composition and decomposition of gaseous species with chemical reactions through simultaneous methods. We analyzed the system with computational fluid dynamics (CFD) and chemical kinetic simulation to investigate the changes of the system mechanism. Subsequently, we achieved results for the correlation between the temperature of the reactor, power applied to the heat source, composition and decomposition of species, and chemical reaction mechanisms. [ABSTRACT FROM AUTHOR]

We study kink oscillations of the system of two parallel magnetic tubes in the presence of plasma cooling. We assume that the characteristic cooling time is much larger than the characteristic time of kink oscillations. Using the ratio of two characteristic times as a small parameter, we derive the expression for the adiabatic invariant, which is a quantity that remains constant during the cooling process. Then, we study in detail a particular case where the plasma densities in the two tubes are the same, the plasma temperature outside of the tube does not change, and the plasma temperature inside the tubes decreases exponentially. We found that cooling causes the increase of the oscillation frequencies and amplitudes. These results are the generalization of similar results previously obtained for a single magnetic tube. We compared the efficiency of amplification of kink oscillations caused by cooling in counteracting the damping of oscillations due to resonant absorption in two models of coronal magnetic loops: monolithic and consisting of two parallel filaments. [ABSTRACT FROM AUTHOR]

Explosive phenomena are known to trigger a wealth of shocks in warm plasma environments, including the solar chromosphere and molecular clouds where the medium consists of both ionized and neutral species. Partial ionization is critical in determining the behaviour of shocks, since the ions and neutrals locally decouple, allowing for substructure to exist within the shock. Accurately modelling partially ionized shocks requires careful treatment of the ionized and neutral species, and their interactions. Here we study a partially ionized switch-off slow-mode shock using a multilevel hydrogen model with both collisional and radiative ionization and recombination rates that are implemented into the two-fluid (P I P) code, and study physical parameters that are typical of the solar chromosphere. The multilevel hydrogen model differs significantly from magnetohydrodynamic (MHD) solutions due to the macroscopic thermal energy loss during collisional ionization. In particular, the plasma temperature both post-shock and within the finite-width is significantly cooler that the post-shock MHD temperature. Furthermore, in the mid to lower chromosphere, shocks feature far greater compression than their single-fluid MHD analogues. The decreased temperature and increased compression reveal the importance of non-equilibrium ionized in the thermal evolution of shocks in partially ionized media. Since partially ionized shocks are not accurately described by the Rankine-Hugoniot shock jump conditions, it may be incorrect to use these to infer properties of lower atmospheric shocks. [ABSTRACT FROM AUTHOR]

We propose an extended hydrodynamical model for plasmas, based on the moments of the electron distribution function which satisfies the Fokker–Planck–Landau (FPL) transport equation. The equations for the moments can be obtained by multiplying the FPL equation by the corresponding weight functions and integrating over the velocity space. The moments are decomposed in their convective and non–convective parts and closure relations for the fluxes and production terms can be obtained by using the maximum entropy distribution function, which depends on Lagrangian multipliers. These latter can be expressed in terms of the state variables by imposing the constraints that the maximum entropy distribution function reproduces the moments chosen as state variables. In particular, we will concentrate on the 13-moment system. As a first application, we treat the case of the relaxation towards equilibrium of a homogeneous plasma with a temperature anisotropy, showing that the results are in good agreement with those obtained by means of the Kogan solution of the kinetic equation. [ABSTRACT FROM AUTHOR]

In current semiconductor manufacturing, limited raw trace data pertaining to defective wafers make fault detection (FD) assignments extremely difficult due to the data imbalance in wafer classification. To mitigate, this paper proposes using a variational autoencoder (VAE) as a data augmentation strategy for resolving data imbalance of temporal raw trace data. A VAE with few defective samples is first trained. By means of extracting the latent variables that characterize the distribution of the defective samples, we make use of the statistical randomness of the latent variables to generate synthesized defective samples via the decoder scheme in the trained VAE. Two data representations and VAE modeling strategies, concatenation of multiple and individual raw trace data as the input of the VAE during the training stage, are investigated. A real-data plasma enhanced chemical vapor deposition (PECVD) process having only few defective samples is used to illustrate the performance enhancement to wafer classification arising from the proposed data augmentation framework. Based on the computational comparisons between noted classification models, the proposed generative VAE model via the individual strategy enables the adaptive boosting (AdaBoost) classifier to achieve perfect performances in every metrics if the 80% and 100% over-sampling ratios are adopted. [ABSTRACT FROM AUTHOR]

We expose and quantify the inaccuracies of plasma bulk parameters derived from the calculation of velocity moments of noisy in-situ plasma observations. First, we simulate typical solar wind proton plasma observations, obtained by a typical top-hat electrostatic analyzer instrument. We add background noise to the simulated observations and analyze them by applying standard methods to derive the plasma density, speed, and temperature. We then compare the analysis results with the parameters we use to simulate the observations in the first place, in order to quantify the inaccuracies in the calculated plasma parameters as functions of the noise level in the observations. We find that even noise levels that are smaller than 1% of the signal peak, lead to significant inaccuracies in some plasma parameters. The plasma temperature suffers the biggest inaccuracies and the plasma speed the smallest. Our results highlight the importance of removing noise from observations when calculating the moments of the constructed plasma distributions. We finally, evaluate one simple method to remove uniform background noise automatically from measurements, which is useful for future on-board analyses. [ABSTRACT FROM AUTHOR]

Observations suggest that coherent radio emission from pulsars is excited in a dense pulsar plasma by curvature radiation from charge bunches. Numerous studies propose that these charge bunches are relativistic charge solitons that are solutions of the non-linear Schrödinger equation (NLSE) with a group velocity dispersion (G), cubic non-linearity (q), and non-linear Landau damping (s). The formation of stable solitons crucially depends on the parameters G, q , and s as well as the particle distribution function (DF). In this work, we use realistic pulsar plasma parameters obtained from observational constraints to explore the parameter space of NLSE for two representative DFs of particles' momenta: Lorentzian (long-tailed) and Gaussian (short-tailed). The choice of DFs critically affects the value of | s / q |, which, in turn, determines whether solitons can form. Numerical simulations show that well-formed solitons are obtained only for small values of | s / q | ≲ 0.1, while for moderate and higher values of | s / q | ≳ 0.5 soliton formation is suppressed. Small values for | s / q | ∼ 0.1 are readily obtained for long-tailed DF for a wide range of plasma temperatures. On the other hand, short-tailed DF provides these values only for some narrow range of plasma parameters. Thus, the presence of a prominent high-energy tail in the particle DF favours soliton formation for a wide range of plasma parameters. Besides pair plasma, we also include an iron ion component and find that they make a negligible contribution in either modifying the NLSE coefficients or contributing to charge separation. [ABSTRACT FROM AUTHOR]

Silicone rubber (SR) is widely used in external insulation. However, the utilization of either high-temperature vulcanized (HTV) SR or liquid SR (LSR) remains controversial in China because of their differences in tracking and erosion resistance and aging resistance due to various amounts of nonreinforcing fillers. Here, the tracking and erosion behaviors of HTV and LSR during the inclined plane test (IPT) are captured and compared for a detailed comprehension of the difference between the two materials. The results revealed that LSR was easily carbonized and formed electrical tracks initially. Then, the carbonization slowed because of developing a protective ceramic layer. The relatively stable ceramic layer resulted in less frequent rapid erosion but increased the average arc burning time. An energy balance model of dry-band arcing (DBA) was established to evaluate DBA’s energy dissipation and absorption. Then, the emission spectra of DBA were collected to analyze the arc temperature and resistance more accurately. The energy input from the system is dissipated primarily through heating and evaporation of the liquid film, with radiant energy only accounting for a minuscule fraction. In different erosion states, the power absorbed by the surface of samples is different. LSR shows an average absorption power of 19.9 W in the initial carbonization state, which is higher than that of HTV (16.5 W). The average absorption power in the fast erosion state is the same for both samples at about 30 W. The absorption power at 20–25 W is considered the threshold range of relatively stable erosion. [ABSTRACT FROM AUTHOR]

A numerical simulation model was developed and employed in elemental composition determination and characterization of meteor plasma physical parameters, particularly the plasma excitation temperature and electron density, by fitting the model parameters to the emission spectrum of a bright Leonid bolide recorded in the visible spectral range. Novel model introduced in this study involves self-absorption and enables parallel optimization of tens of the parameters. We also discuss that the observed bolide spectrum is strongly dependent on observation geometry. [ABSTRACT FROM AUTHOR]

A method for radio frequency oxygen (O2) plasma-assisted treatment of indium zinc oxide (IZO) films with a multistacked architecture fabricated by a low-temperature (200 °C) solution process is investigated. We demonstrate that radio frequency O2 plasma-assisted posttreatment technology can improve the mobility and stability of IZO thin-film transistors (TFTs). The activity layers were formed by spin coating and subsequently thermally annealed at a low temperature of 200 °C, followed by O2-plasma posttreatment process, to form the O2 triggered multistacked architecture. The TFT devices plasma-treated for 3 min exhibit improved electrical characteristics, with a mobility of 7.09 ± 0.24 cm2/Vs, an ON OFF ratio of (1.21 ± 1.22) $\times 10^{{6}}$ , a threshold voltage of $-0.22\,\,\pm \,\,0.35$ V, and a subthreshold swing of 0.34 ± 0.02 V/dec. The improved results offered by the O2 plasma treatment led to a higher mobility and ON/ OFF ratio compared to sample device without this process. The successful fabrication of radio frequency O2 triggered multistacked architecture-based IZO TFTs showing the practical potential of high-performance low-temperature solution-processed preparation technology and radio frequency O2 plasma-assisted treatment for electrical device application. [ABSTRACT FROM AUTHOR]

This work reports hydrogen (H2) formation using methane nitrogen gas mixture as a feed stream in a rotating gliding arc (RGA) reactor. The H2 formation in the RGA was quantified by experimental studies, and the results were validated by simulating plasma chemical kinetics using the Chemical Workbench software. The simulation was performed for an experimental condition, where methane (1%) and nitrogen (99%) gas mixture was fed to an RGA at 5, 10, 25, and 40 lpm. For these flow rates, the simulation predicted 1417, 802, 299, and 67 ppm of H2, respectively. Also, the results show that at these flow rates, the reduced electric field (E/N) of the discharge was 78, 83, 92, and 101 Td and the gas temperature was 3800, 4108, 4590, and 4975 K respectively. The simulation result was in reasonable agreement with the experimental data, which shows 1276, 717, 213, and 61 ppm of H2 in the product gas, respectively, at 5, 10, 25, and 40 lpm. This work marks the first step toward process optimization through the simulation approach. [ABSTRACT FROM AUTHOR]

Cancer is a devastating and life-threatening disease. It is the second leading cause of death worldwide after heart diseases. While science has significantly advanced to improve the treatment outcome and quality of life in cancer patients, there are still many issues with the current therapies, such as toxicity and the development of resistance to treatment. Among the novel tools to overcome these limitations is nonthermal plasma (NTP) and its treatment regimens. Recent progress in NTP devices with ion temperatures close to room temperature demonstrated significant potential in cancer therapy. NTP devices provide a unique combination of reactive oxygen species (ROS), reactive nitrogen species (RNS), photons, and electric fields that exhibit desirable properties of triggering cell death pathways, selectively for cancer cells. While in principle NTP is nonnecrotic and gentle to the tissue, but reactive oxygen and nitrogen species (RONS)-triggered tumor cell death exhibited to have pro-immunogenic properties. Many in vitro and in vivo experiments have demonstrated antitumor effects of direct NTP, synergistic applications of NTP with anticancer drugs/treatments, and plasma-conditioned medium (PCM) applications against a variety of cancer cells. The latest results and findings in this field are the subject of this review along with a brief lay-reader-explanation of cancer and immunology. In this review, initially, we give an overview of the literature that deals with studies on the use of NTP for cancer treatment. Subsequently, we present typical results from that literature to illustrate the advances of NTP in oncology. Finally, we discuss some challenges and future scopes offered by NTP for cancer treatment. [ABSTRACT FROM AUTHOR]

Divertor is one of the key plasma-facing components (PFCs) for Experimental Advanced Superconducting Tokamak (EAST) since they play important roles in resisting the energetic particle irradiation and huge heat deposition from the core plasma as well as efficaciously dispelling such energy load. Tungsten is used as the plasma-facing material for PFCs due to the excellent properties. During the thermal analysis and the high heat flux test of the PFCs, the heat absorption coefficient is an important parameter that directly affects the availability and reliability of the design structure. Previous studies have shown that there is a large deviation in the measured heat absorption coefficient of tungsten. Therefore, it is very important to accurately measure the heat absorption coefficient of tungsten. In this article, the heat absorption coefficient of tungsten was tested by the e-beam device of the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP). In this test, 36 sets of inlet and outlet water temperature data were obtained by changing the water flow rate and the incident heat flux. The heat absorption coefficient of tungsten was calculated by the theoretical calculation using water calorimetry. The results indicate that the heat absorption coefficient of tungsten is stable at ~0.54, which can be used as a reference for the engineering design of PFCs of the upgraded EAST lower divertor. All test parameters for EAST will provide important reference and guidance to the next-generation fusion facility China Fusion Engineering Test Reactor (CFETR). [ABSTRACT FROM AUTHOR]

To achieve high and uniform phosphorus (P) dopant concentration (more than $1\times 10^{{20}}$ cm−3) near the germanium (Ge) surface, H2 plasma treatment and modified plasma-assisted delta doping (MPADD) process are proposed and investigated. Sufficient vacancies are formed on the Ge surface using H2 plasma treatment. Consequently, P and vacancies are uniformly included inside during Ge growth through the MPADD process. After the annealing, phosphorus-vacancy-oxygen (PVO) clusters with the lowest binding energy are formed. Therefore, the migration activation energy increases, and the dopant diffusion into the substrate is reduced. As a result, the surface P dopant concentration ($4\times 10^{{21}}$ cm−3) improves, and a uniform P concentration of approximately 5 nm is from the Ge surface. These results show that the MPADD process enables a uniform and high surface doping concentration of recently promising Ge materials and compensates for the disadvantages of conventional delta doping, such as long process time and the need for an ultra-high vacuum system. [ABSTRACT FROM AUTHOR]

It is hard to realize the high microwave absorption property and the low operating temperature in a gas discharge plasma simultaneously, due to the electron number density, and electron neutral collision frequency physically needed for the former is a typical severe heating scenario for the latter. In this article, the phase change process is proposed to be introduced into the controlled area of the discharge plasma system to increase collision frequency and decrease the discharging electrode temperature at the same time. An ac high-voltage power-driven quasi-periodic array of the phase change fluid discharge (PCFD) device is investigated. The most apparent tendency of the PCFD plasma is the improved diffusivity and uniformity. At the same time, the temperature of the electrode and its vicinity, where the phase change material is reserved, is lower than the ambient temperature. Compared with the controlled discharge state of the low gaseous pressure dielectric barrier discharge (L-DBD) plasma without phase change process, the absorption attenuation in the $X$ -band is enhanced in all tested polarization angles, which driving strategy could control. Analyses show that the increased microwave absorption, frequency shift, and bandwidth broadening mainly result from the phase change process and its influences on the plasma discharge. [ABSTRACT FROM AUTHOR]

Simulations on the number density and the temperature distribution of the plasma produced by the electron beam are taken by the fluid model with the lattice Boltzmann method (LBM), for which impact ionization is the major mechanism for plasma generation. The simulation results show that the electron number density of the plasma reaches the maximum value exceeding 1016 m−3 at 3-cm downstream the exit of the electron beam on the incident direction under atmospheric pressure when the electron energy is 80 keV. The gas temperature rises due to the heating effect of the electron beam, and the temperature profile is similar to a balloon. The gas flow and background pressure are two important factors that affect the plasma distribution. It is found that the plasma area will expand or compress along the background gas moving direction, and the plasma range is inversely proportional to the background gas pressure. [ABSTRACT FROM AUTHOR]

Plasma gas injection as one of the non-thermal plasma (NTP) technologies has a free-standing gas-phase plasma reactor outside the polluted target and can efficiently degrade contaminants by injecting plasma gas containing a large number of reactive species. This approach has been utilized in various fields of pollutants treatment, because of its structural advantage of indirect contact between pollutants and electrodes and its ability to produce strong oxidizing species. This article first expounds on the principle of the plasma gas injection and then progresses to a discussion of its application for pollutants degradation, mainly focusing on the treatment effect and degradation mechanisms. It is believed that plasma gas injection is considered to be a very practical, clean, efficient, and environmentally friendly method for pollution control. [ABSTRACT FROM AUTHOR]

To reveal the characteristic parameters and the evolutionary rules of plasma and light flash radiation produced by aluminum powder/polytetrafluoroethylene (Al/PTFE) projectile hypervelocity impacting on 2A12 thin aluminum plate, the Al/PTFE projectile was obtained by the improved sintering process of the sample, which is based on the process of the traditional Al/PTFE (mass percentage ratio of aluminum powder and PTFE is 26.5%/73.5%). The dynamic compressive strength of the sample was characterized by the self-constructed split Hopkinson pressure bar (SHPB) system. Meanwhile, the experiments, enhanced Al/PTFE projectile (mass 0.22 g, size $5\times5$ mm) impacting on 2A12 aluminum targets with the thicknesses of 2 and 3 mm at different impact speeds (1.95–2.45 km/s), have been performed using a two-stage light gas gun loading system combining with a high-speed camera acquisition system, a transient fiber pyrometer measurement system, and a plasma characteristic parameter diagnostic system. The electron temperature, electron density of plasma, and the radiant temperature (in the range of visible light wavelength) of light flash have been experimentally studied. The results show that the dynamic compressive strength of the Al/PTFE specimen with rapid cooling was significantly improved at the strain rate of 4000 s−1 comparing with the traditional Al/PTFE projectile (the dynamic compressive strength was 32–44 MPa), which can reach more than 100 MPa. The maximum electron temperature, electron density, and visible light radiant temperature produced by the hypervelocity impact increase with an increase in impact velocities and target thicknesses, respectively. [ABSTRACT FROM AUTHOR]

We report the deposition of nanocrystalline graph- itic films on Cu foil in a roll-to-roll (R2R) plasma-enhanced chemical vapor deposition (PECVD) system. The influence of discharge modes on the graphitic film synthesis is studied in radio frequency (RF) capacitively coupled Ar/H2/CH4 plasma. First, electrical and spectroscopic characterizations supported with modeling are carried out to study the properties of hybrid and gamma modes in Ar plasma at an excitation frequency of 80 kHz. A hybrid mode, which exhibits both alpha and gamma characteristics, exists at 950 Pa for Ar plasma at powers up to 1100 W. However, Ar plasma transitions at 1380 Pa from hybrid to gamma mode when the power is greater than 750 W. Second, the quality of the nanocrystalline graphitic films, which is assessed with Raman spectroscopy, is correlated with the characteristics of hybrid and gamma modes in Ar/H2/CH4 plasma. The hybrid mode in Ar/H2/CH4 plasma has relatively less ion bombardment. However, the gamma mode in Ar/H2/CH4 plasma provides abundant intermediate carbon species and heats the Cu substrate directly to around 1193 K. Hence, thin films of nanocrystalline graphite with different qualities can be produced at a web feed rate of 30 mm/min without supplemental heating by adjusting the discharge modes. [ABSTRACT FROM AUTHOR]

In this article, the role of the positrons shock waves generation in weakly relativistic laser-created plasma is investigated. The plasma considered is generated on the rear face of a target, irradiated by a high intensity short pulse laser, in the framework of target normal sheath acceleration (TNSA) mechanism. This plasma is composed of Boltzmann distributed positrons, hot and cold super-thermal electrons, and dynamic ions. Kinematic viscosity among the plasma constituents has been also considered. With the purpose of studying the behavior of nonlinear ion acoustic shock waves (IASHWs), the reductive perturbation method (RPM) has been employed and Korteweg-de Vries Burgers equation has been derived. It was observed that different plasma parameters (namely, electrons super-thermality, number of positrons, ion temperature, kinematic viscosity, etc.) have a real impact on the propagation of IASHWs. As electron–positron plasmas with ion possessing relativistic velocities are often detected in laboratory experiments, astrophysical, and space environments, the present work will help to explain the different types of collective processes and instabilities in regions where e-p-i plasmas can exist. [ABSTRACT FROM AUTHOR]

The article analyzes two concepts of conduction in a low-density plasma opening switch: based on the formation of a bipolar space charge layer subject to unlimited cathode emissivity (bipolar model) and of a unipolar ion layer due to electron motion off the cathode under an electric field induced by magnetic field penetration into the plasma (unipolar model). A comparison of unipolar-model expressions with widely known experimental data shows that the conduction current behaves strictly as $I_{c} \propto n^{1/2}$ at any plasma bridge length in the range of plasma densities from $\sim 10^{11}$ to $\sim 10^{14}$ cm−3 and current rise rates from ~0.3 to $\sim 4$ kA/ns. Holding the conduction current constant at any bridge length $l$ requires that $nl^{2}$ be constant. As the magnetic field rise rate is varied, the conduction current follows: $I_{c} \propto \dot {B}^{1/2}$. These results differ radically from what is predicted by the bipolar model. Also presented in the article are arguments of why the axial current channel width varies nonmonotonically during a pulse and estimates of the electron temperature at different plasma densities and field rise rates. [ABSTRACT FROM AUTHOR]

Nonequilibrium plasmas have been extensively investigated for polymer surface treatments in industrial applications. Plasma treatments can change the properties, such as electrical, chemical, tribological, biological, optical, and mechanical, which are easy to scale up to industrial applications. These can be extended to electronic industry. Consequently, light-emitting diode (LED) package was processed using Ar plasma at various flow rates and times. Thermal transient analysis showed reduced total thermal resistance ($R_{{\text {th}}}$) and reduced rise in junction temperature ($T_{J}$) for Ar plasma processed LED compared to the bare LED package data. Among the process parameters considered, 20-sccm flow of Ar gas exhibited better performance with respect to processing times. A noticeable reduction in $T_{J}$ value was recorded ($\Delta T_{J} = 49.2\,\,^{\circ }\text{C}$) for Ar plasma processed LED from that of bare LED. Surface modification through cross linking was assumed by the Ar plasma process and supported to enhance the heat transfer through the modified surface of silicone encapsulation of the LED. In addition, the surface smoothness of silicone was induced by Ar plasma and helped to exhibit efficient heat transfer via convection. Based on the observed results, the Ar plasma process would be an effective postprocessing method for LED package to improve the performance as well as lifetime. [ABSTRACT FROM AUTHOR]

This study explores the degradation of the reactive Remazol Blue RR (RBRR) as a model textile effluent upon its exposure to non-thermal atmospheric pressure plasma. An extensive comparative study of different combinations of the following plasma/solution treatment environments was conducted: 1) Ar plasma jet (Ar-PJ) alone; 2) Ar/O2 and Ar/N2 plasmas; 3) Ar plasma with O2 or N2 injected (INJ) in the bulk of the Ar plasma afterglow; and 4) Ar plasma with O2 or N2 bubbling (BB) in the RBRR solution. In all conditions, plasma treatment was carried out at a fixed applied voltage of 31 kV and treatment time of 10 min. The degradation efficiency of RBRR in the different plasma-treated solutions was evaluated using UV–visible spectroscopy. Optical emission spectroscopy (OES) was used to examine the generation of excited species in plasma during the degradation processes. Moreover, the concentration of plasma-induced reactive hydroxyl radicals (OH•) and hydrogen peroxide (H2O2) was determined spectroscopically. To further corroborate the results, the pH, conductivity, and total organic carbon (TOC) of the plasma-treated RBRR solutions were assessed. Overall, the results showed that the highest degradation efficiency (45%) was obtained upon exposure of RBRR aqueous solution to Ar plasma with N2 bubbling in the solution. The non-toxic nature of all plasma-treated solutions was confirmed by non-inhibition of bacterial growth (Escherichia coli and Staphylococcus aureus). Overall, plasma treatment in general and Ar plasma accompanied with N2 bubbling in particular constitute an eco-friendly and very promising techniques to degrade/decolorize textile effluent. [ABSTRACT FROM AUTHOR]

Bifurcation analysis and dynamical system studies are carried out to find the stability regime and chaotic scenario in electron acoustic waves in relativistic degenerate plasma. We have obtained the quantum hydrodynamic model and obtain the Korteweg–de Vries equation describing the nature and characteristics of solitary structures. The amplitude modulated envelop soliton formation due to external perturbations has been studied by analyzing the nonlinear Schrodinger equation. Further to study the stability factors and the parametric range for such stability, the dynamical system is studied and bifurcation analysis has been carried out. The chaotic behavior of the system is studied through largest Lyapunov exponent (LLE). This work will find application in theoretically predicting the stable modes in many solar plasma and stellar plasma applications and in laser plasma in future. [ABSTRACT FROM AUTHOR]

This article provides the description of a qualitative physical model of the boron nitride nanotubes (BNNTs) formation in plasma. This model combines understanding not only chemistry of the process, which is well known, but also gas dynamics, heat and mass transfer, and interactions in a complicated multiphase swirling and highly reactive flow of solids, gases, and plasma. The model offers a concept for predicting and controlling phenomena of the BNNTs formation. It is universal and could be applied not only for boron and N2 plasma but also for a wide variety of solids and plasma gases. It will help to navigate research and focus their efforts on collecting and analyzing numerical data for statistical analysis, further development of a quantitative model, and design and production of new nanomaterials with targeted properties. Inductively coupled or radio frequency plasma sources are selected as the best candidates for providing chemically pure plasma due to their electrodeless design and virtually unlimited service time on different gases and blends and from vacuum to bar pressure. [ABSTRACT FROM AUTHOR]

The analysis of the possibilities of using the cross-flow plasma-fuel nozzle for supporting stable combustion of gaseous fuel in a combustion chamber of the contact-type gas turbine engine with steam injection is presented. Experimental studies of the plasma-fuel nozzle were carried out, which proved the stability of its operation in a wide range of changes in the flow rates of plasma feedstock air. Indicators of the efficiency of the thermal scheme of the contact-type gas turbine engine as well as the characteristics of a low-emission combustion chamber with plasma assistance are obtained. [ABSTRACT FROM AUTHOR]

Previously, we reported an optimization algorithm based on a plasma diagnostic model for optical emission spectroscopic (OES) measurements. In this study, we improved the algorithm. In the improved algorithm, the dependence of unimodality of reduced population density on electron temperature, electron density, and electron energy distribution function (EEDF) was discussed. Furthermore, electron temperature, electron density, and EEDF of 10 Pa argon inductively coupled plasma were diagnosed to experimentally evaluate the proposed algorithm. The diagnosis results were compared with those of the line-pair method and excitation temperature conversion method. The reduced population density distribution, which was calculated under the condition of the result of the proposed method, was in good agreement with the experimental result by OES measurement, thereby demonstrating the reliability of our proposed method. [ABSTRACT FROM AUTHOR]

The authors report the results of design and experimental investigation of a high flow and high concentration NOx production system based on a radio frequency (RF) plasma torch for a variety of applications. Unique gas dynamics of the first stage avoids plasma disturbance by feeding quenching gas and enables NO oxidation into NO2 with a total NOx yield over 6% by mass. The developed system is tunable for NOx concentration, scalable for higher flow, applicable for various technological processes, flexible for using different plasma gases and quenching media, including gases, liquids, and solids. [ABSTRACT FROM AUTHOR]

In this work, we used the semi-Lagrangian method and the Vlasov code to study the instabilities in a quantum plasma with 1-D temperature anisotropy. Taking the Fermi–Dirac type of distribution function (DF) and using the semi-Lagrangian Vlasov code, we studied the gradual evolution of density and kinetic energy in a degenerate plasma with quantum effects. In this collisionless plasma, adiabatic compression will be along the direction of wave propagation and will lead to temperature anisotropy of the electron distribution that varies along the direction of wave propagation. The findings will find application for dense plasma at finite temperature as in laser-produced plasmas, fusion plasma, as well as solar plasmas. [ABSTRACT FROM AUTHOR]

Runaway Electrons (REs) generated during plasma disruptions in fusion grade tokamaks have the potential to severely damage the plasma-facing components. Designing optimal plasma discharge scenarios for RE suppression in future experiments requires interpretative modeling of current experiments. Multiple experiments have been carried out on ADITYA-U tokamak to design optimal plasma discharge scenarios for RE avoidance and suppression. In this article, we have numerically studied two representative pairs of ADITYA-U plasma discharges. In the first pair of discharges, plasma density was increased by gas puffs during the flap-top phase which is shown to suppress RE generation. In the second pair of the representative discharges, the effect of a lower ratio of peak electric field during breakdown to the pre-fill pressure is shown on RE generation. We simulate these plasma discharges using the PREDICT code to study the dynamics of Res. The results are consistent with the experimental Hard X-Ray diagnostic observations for both the pair of representative discharges. Additionally, the lowest RE-current is obtained in the discharges with a low ratio of the peak electric field during breakdown to the pre-fill pressure and high plasma density during the flap-top phase due to gas puffs. The suppression of REs is demonstrated by showing the effect of increasing plasma density on the separatrix in momentum space between thermal electrons and REs. [ABSTRACT FROM AUTHOR]

Helium plasma stream is generated in a coaxial plasma accelerator by applying a high-power pulse derived from a 200-kJ pulsed power system (PPS). The present work aims at measuring the plasma temperature and density of helium plasma produced in a pulsed plasma accelerator (PPA). The plasma is characterized using a triple Langmuir probe (TLP) while translating it along axial direction precisely from 8 to 40 cm inside the plasma stream away from the electrode end. By varying experimental conditions, the plasma temperature and density are measured to be approximately 33 eV and 5 $\times $ 1020 m−3, respectively, and it is observed that the value of parameters decreases with the increase in the axial distance. [ABSTRACT FROM AUTHOR]

A multicomponent degenerate quantum plasma comprising nondegenerate warm light ion species, inertial heavy-ion species, and relativistically degenerate electrons are considered to study the large-amplitude degenerate pressure-driven nucleus–acoustic solitary waves (NASWs). Sagdeev’s pseudopotential approach has been adopted for the energy balance equation of large-amplitude NASWs, and the Mach number domain $({M_{l} \le M\le M_{h}})$ is determined numerically in various plasma parameters. It is seen that only compressive (positive pulse) solitary waves can exist in the present plasma system. The effect of different plasma parameters such as the ratio of light-ion species to heavy-ion species number density ($f$), degenerate electron density ($k$), relativistic factor ($\gamma$), temperature ratio ($\sigma$), and Mach number ($M$) on the characteristic of solitary waves is studied. The corresponding phase trajectory is also drawn for the solitons in the existence domain of the Mach number. Our result may be helpful to understand the basic characteristics of nonlinear solitary waves propagating in an astrophysical object such as white dwarfs and neutrons stars. [ABSTRACT FROM AUTHOR]

This article reports results of the design and experimental investigation of a high-flow and high-concentration NOx production system based on a radio-frequency plasma torch for a variety of applications. The system includes a commercial APT-100 plasma torch with plume power from 25 to 35 kW, a double-stage quenching reactor with “fast” first stage and “slow” second stage, measuring unit, and auxiliary systems. The first stage allows quenching by any gas, such as air, air-based blends, and the products of recirculation. [ABSTRACT FROM AUTHOR]

The plasma torch is the key component of the thermal plasma-assisted material processing system. Particularly, direct current (dc) nontransferred arc plasma torch is widely used in high-temperature material processing applications. The characteristics of the thermal plasma jet emanating from the plasma torch depend on many factors, including arc current, type of plasma forming gas, gas flow rates, gas injection configuration, torch geometry, and so on. This experimental study focuses on the comparison between the effects of CO2 and air on the arc voltage, electrothermal efficiency, and specific enthalpy of the plasma torch operated at the atmospheric pressure. For this purpose, a low-power dc plasma torch consisting of a rod-type thoriated tungsten cathode and the copper anode was customized. CO2 and air were used as the plasma forming gases along with a feeble amount of argon (15 lpm). The plasma torch was operated over a wide range of current (100–175 A) with fixed gas flow rates. The $I$ – $V$ characteristics and the electrothermal efficiency of the plasma torch were measured, and results were compared. The maximum electrothermal efficiency and specific enthalpy of the plasma torch when operated with CO2 were reported as 70% and 1900 KJ/Kg, respectively, which is higher than the same torch operated with air as the plasma forming gas. The electron number density and electron temperature of the air and CO2 plasma jet were measured by optical emission spectroscopy (OES). The calculated electron number density and electron temperature of the plasma jet with CO2 were $2.89\times 10\,\,^{\mathrm{ 16}}$ cm−3 and 8598 K, respectively, which is higher than air plasma jet. It was found that CO2 has a stronger influence than air on the arc voltage fluctuation, electrothermal efficiency, and operating regime of the plasma torch. [ABSTRACT FROM AUTHOR]

A semiconductor p-n junction diode with heavy doping under consideration is kept in forward biased condition. These are oppositely propagating electron and hole currents. These two streams interact among themselves and result in recombination, which supplies additional energy to the system. Such thermal energy creates additional electrical fluctuations, which exists long after the interaction has taken place. We have carried out an analytical investigation with numerical techniques as well as carried out a simulation of the wave–wave interaction in semiconductor junction diodes. In terms of signal transmission and operation of semiconductor device, such a theoretical study is important. [ABSTRACT FROM AUTHOR]

In the work, we study the formation of electron acoustic Korteweg–de Vries (KdV) solitons and their gradual nonlinear evolution into a peregrine soliton (PS) in a dense plasma at finite temperature with quantum effects. The plasma under consideration has temperature anisotropy along the direction of wave propagation. Such an anisotropy is due to the initial disturbance incorporated in the system or due to the lack of homogeneity of field quantities. We have studied both the linear and nonlinear characteristics of their dispersion relation. By employing reductive perturbation technique, we have obtained the KdV equation and studied the characteristics of the solitary structures. The effect of external forcing term which leads to self-interaction among different parts of the system and the gradual conversion of the waveform into Peregrine breather mode is analytically studied. Finally, we study the dynamical properties of the system and its dependence on plasma parameters. This theoretical study will help in predicting possible characteristics in laser plasma interaction and beam plasma experiments in which there are instances of temperature anisotropy. [ABSTRACT FROM AUTHOR]

In this work, the effect of Ar plasma at the S/D contact in a low temperature (200°) fabricated ALD ZnO thin-film transistors (TFTs) for contact resistance reduction is systematically studied. With an optimized Ar plasma process time, the contact resistance is significantly reduced by >50% from 170 to $84 {\sf \Omega }/\mu \text{m}$. This reduction is attributed to the oxygen vacancies modulating the effective contact barrier height, as elucidated by detailed AFM and XPS analysis. Consequently, the effective field-effect mobility ($\mu _{\textit {FE}}$) of the TFT is increased by 50% to 39.2 cm2/Vs. The $\mu _{\textit {FE}}$ of the developed TFT is one of the highest reported thus far using ALD process at the lowest temperature. The advances achieved in this work provide valuable insight into the defect’s regulation mechanism of ZnO-metal contact and its effect on the TFTs performance. This approach paves a pathway to further develop ZnO TFTs in applications in high-speed computational circuitries. [ABSTRACT FROM AUTHOR]

In this article, we investigate the influence of external discharge conditions on plasma parameters in the plasma discharge chamber of the radome configuration. We designed a conformal cavity and then used the multiphysics simulation software COMSOL to establish a 2-D axisymmetric model for discharge simulation research. In the study, we found that the changes in coil power and pressure have a noticeable effect on the distribution of plasma parameters. First, the maximum electron density, electric potential, and electron temperature are obtained by changing the power of the coil in a certain pressure argon environment. Then, under the condition of constant coil power, the discharge characteristics of plasma are studied by changing the gas pressure in the cavity. The results show that the change of coil power has a significant impact on the parameter distribution of plasma discharge. The greater the coil power, the greater the electron density, and the more concentrated the distribution. At the same time, the potential induced in the heating zone and the corresponding electron temperature decreased after the reaction stabilized. The increase of gas pressure significantly increases the peak value of electron density and changes the parameter distribution of discharge. However, when the argon pressure exceeds a certain threshold, it will no longer have a significant effect on the distribution of discharge parameters. The general conclusion is that the increase of power and argon pressure plays an essential role in improving the electron density distribution. This conclusion has guiding significance for exploring the law of plasma parameter distribution on electromagnetic scattering characteristics. [ABSTRACT FROM AUTHOR]

Based on the plasma-modified model and photoionization optimization model, this article constructs a low temperature and subatmospheric pressure air surface dielectric barrier discharge (SDBD) model with 37 plasma chemical reactions composed of 18 particles. Through the model, the characteristics of air SDBD at low temperature and subatmospheric pressure are studied. Under a dc voltage of 12 kV, with the propagation of the streamer, the parameters, such as electron density, $\text{N}_{2}^{+}$ density, N2(C) density, $\text{O}_{2}^{-}$ density, electron temperature, space charge density, electric field, and photoionization rate, show a downward trend at an altitude of 11 000 m but always maintain N2(C) density > electron density > $\text{N}_{2}^{+}$ density > $\text{O}_{2}^{-}$ density. In addition, the propagation velocity of streamer along the surface is positively correlated with altitude. Electron, $\text{N}_{2}^{+}$ , N2(C), and $\text{O}_{2}^{-}$ density are negatively correlated with altitude. Photoionization rate is positively correlated with the altitude in the streamer development stage. In the streamer propagation stage, except for the sudden drop at the altitude of 11 000 m, it is basically consistent at other altitudes. [ABSTRACT FROM AUTHOR]

The spatial confinement effect on the laser-induced plasma parameters and surface modifications of iron (Fe) has been investigated. The Fe plasma has been generated under ultrahigh vacuum (UHV) condition by employing Nd: YAG (532 nm, 6 ns) laser at different laser irradiances ranging from 3.3 to 10 GWcm $^{-2}$. Two important Fe plasma parameters, i.e., electron temperature ranging from 13 to 27 eV and electron number density ranging from $1.92\times 10^{15}$ cm $^{-3}$ to $4.60\times 10^{15}$ cm $^{-3}$ , are evaluated by employing Langmuir probe (LP) as diagnostic technique. The probe was placed at a distance of 1 cm from target. Both plasma parameters are found to be influenced by laser irradiances and spatial confinement. They increase with the increase in laser irradiances both in the presence and absence of metallic blockers. However, it is revealed that the values of both plasma parameters are slightly higher in the presence of blocker as compared to blocker-free case. The percentage increase in electron temperature varies from 10% to 15%, whereas percentage increase in electron density varies from 11% to 25%. These percentage increase in the values of Fe plasma parameters exceeds the limits of experimental errors (±2). Therefore, the role of spatial confinement via metallic blocker for the enhancement of plasma parameters is confirmed and is attributed to the reflection of shockwaves from the blocker. The surface modifications of laser irradiated Fe have been explored by scanning electron microscopy (SEM). Various features, such as ripples, ridges, and cones, have been observed on the surfaces of ablated Fe. More pronounced, organized, and fine structures are grown on the Fe surface in the presence of blocker at lower irradiances than the blocker-free case due to spatial confinement effect. The growth of ripples is attributed to Kelvin–Helmholtz instabilities. PACS: 61.80.Ba, 52.50. −b, 52.50.Jm, 52.50.Lp, 52.35.Tc, 35 52.38., 52.38.Dx. [ABSTRACT FROM AUTHOR]

We present a numerical study disclosing non-linear effects and hysteresis loops for a swept bias Langmuir probe. A full kinetic particle in cell (PIC) model has been used to study the temporal sheath effects and the probe current. Langmuir probes are normally operated at low frequencies, since a “close to steady state” condition is required to characterize the plasma. However, during operations above frequencies normally used, capacitive and non-linear resistive effects are being unveiled. We demonstrate how ion and electron density and temperature change properties of the probe-plasma system. We also show that a swept Langmuir probe exhibits essential properties described as the “fingerprint of memristors” and how a Langmuir probe can be identified as a transversal memristor. Understanding non-linear processes might enable new ways to operate Langmuir probes with higher sampling rates and better accuracy. [ABSTRACT FROM AUTHOR]

We report the improvement of ferroelectric (FE) amorphous InGaZnO4(a-IGZO) thin film transistors (TFT) by Ar/O2 plasma treatment and subsequent thermal annealing. The a-IGZO (In2O3:Ga2O3:ZnO = 1:1:1) and HZO (Hf:Zr = 1:1) layers were deposited by DC sputtering and spray coating, respectively. The Ar/O2 plasma exposure for 10s and thermal annealing at 300°C for 15 min on the a-IGZO/HfZrO(HZO) improves the field effect mobility from 18.6 to 20.0 cm2V−1S−1, subthreshold swing from 345 to 125 mV/decade, memory window from 0.45 V to 1.0 V, and polarization from $7 ~\mu \text{C}$ /cm2 to $9 ~\mu \text{C}$ /cm2. The improvement is mainly due to the reduction of oxygen vacancies at the a-IGZO/HZO interface by Ar/O2 plasma exposure and subsequent annealing. [ABSTRACT FROM AUTHOR]

We prove that a nonequilibrium inhomogeneous giant gas discharge is realized in the heliosphere with huge values of the parameter $E/N$ , which determines the temperature of electrons. This quasi-stationary discharge determines the main parameters of the weak solar wind (SW) in the heliosphere. In connection with the development of space technologies and the human spacewalk, the problem of the nature of the SW is acute. The study of the interference of gravitational and electrical potentials at the earth’s surface began with the work of William Gilbert 1600. Such polarization effects–the interference of Coulomb and gravitational forces–have not been studied well enough even in the heliosphere. Our article is devoted to this problem. The Pannekoek–Rosselan–Eddington model does not consider the important role of highly energetic running (away from the Sun) electrons and, accordingly, the duality of electron fluxes in the heliosphere (from the Sun and to the Sun) According to an alternative model formulated by us, highly energetic (escaping from the positively charged Sun) electrons leave the Sun and the heliosphere, and weakly energetic ones, unable to leave the Coulomb potential well (hole–the positively charged Sun and the heliosphere–return to the positively charged Sun. The weak difference between the opposite currents of highly energetic (escaping from the Sun) electrons and weakly energetic (returning to the Sun) electrons is compensated by the current of positive ions and protons from the Su–SW. These dynamic processes maintain a quasi-constant effective dynamic charge of the Sun and the entire heliosphere all the way to the earth’s orbit. At the same time, quasi-neutrality (see discussion in the following) in the Sun and heliosphere is well performed up to 10−36. According to experiments and analytical calculations based on our model: 1) the plasma in the corona is nonequilibrium; 2) the maximum electron temperature is $T_{e}$ 1–2 million degree; 3) $T_{e}$ grows from 1000 km away from the Sun (see discussion in the following); and 4) the role of highly energetic electrons escaping from the plasma leads to a significant increase in the effective: solar charge and electric fields in the heliosphere in relation to the Pannekoek–Rosselan–Eddington model. This is due to the absence of a compensation layer that screens the effective charge of the Sun It is not formed due to the escape of highly energetic electrons (as in a conventional gas discharge) from the entire heliosphere with high temperatures exceeding the temperature of the Sun’s surface. Thus, the process of escape of highly energetic electrons forms the internal EMF of the entire heliosphere. Interference of gravitational and Coulomb potentials in the entire heliosphere is considered, and it is being manifested in generation of two opposite flows of particles: 1) that are neutral or with a small charge (to the Sun) and 2) in the form of high-energy electrons (escaping from the positively charged Sun) and an SW with positively charged ions with Z/M $\ge0.107$ (from the positively charged Sun). The calculated values of the registered ion parameters in the SW were compared with experimental observations. Reasons for generating the ring current in inhomogeneous heliosphere and inapplicability of the Debye theory in describing processes in the SW (plasma with current) are considered. [ABSTRACT FROM AUTHOR]

In this study, voltage distribution and surface dielectric barrier discharge (DBD) of a microplasma discharge device (MDD) were modeled in 2-D domain using finite-element analysis (FEA). Initially, the voltage distribution across comb-, H-tree-, and honeycomb-structured MDD was analyzed. Then, the cross section of an MDD consisting of a polyimide-based dielectric sandwiched between two copper electrodes was used for modeling the microplasma discharge characteristics in an argon environment. A sinusoidal voltage was applied to one of the copper electrodes while the other electrode was grounded. The spatial distributions of electron temperature (ET) across the electrodes for varying input voltages were simulated to demonstrate the importance of breakdown voltage. A detailed analysis on the effect of varying electrode and dielectric barrier thicknesses on electron density and ET was also performed to understand the importance of optimizing device configurations for microplasma discharge. Moreover, MDD was also simulated in varying ambient temperature and pressure conditions to evaluate their effect on ET and density across the electrodes. The results from these simulations provide a better understanding of parameters such as varying input voltage, electrode, and dielectric thickness on ET and electron density. This enables us to optimize design parameters for fabricating MDDs and the operating conditions for effective sterilization applications. [ABSTRACT FROM AUTHOR]

Here, we study time- and spatially resolved heterogeneous plasma catalysis chemical looping reactions using in situ laser diagnostics in a novel parallel plate dielectric barrier discharge (DBD) plasma reactor at atmospheric pressure and temperatures: 473 and 673 K. A chemical looping material, 50:50 by mass mixture of lanthanum–nickel-based perovskite (La0.9Ce0.1NiO3) and CeO2, was placed directly in non-equilibrium DBD plasma. Optical diagnostic techniques used include high-speed imaging (i.e., ns gate width), N2 optical emission spectroscopy (OES) at 337 nm, and Rayleigh scattering (RS). During the reduction step, a mixture of CH4, CO2, and N2 flow was used, and during the oxidation step, the airflow was used. During the reduction step, the average temperatures measured at the furnace setpoint temperature of 473 and 673 K were 580 and 800 K, respectively. For the oxidation step, the average temperatures measured were 520 and 830 K, respectively. There was good agreement in average temperatures measured by RS and N2 OES. The 2-D RS imaging showed lower temperatures near the catalyst during the reduction step and higher temperatures during the oxidation step. Although corona discharges were observed over chemical looping materials in high-speed images, RS temperature measurements showed non-equilibrium plasma chemistry over the materials. [ABSTRACT FROM AUTHOR]

The degradation of chemical warfare agent (CWA) sarin using plate-to-plate and plate-to-pin electrode structure dielectric barrier discharges (DBDs) was studied in this work. The discharge characteristics, optical emission, decomposition efficiency, and decomposition products in the above apparatus were well investigated. With initial pure sarin of $20 ~\mu \text{L}$ , the decomposition amount per unit time and decomposition efficiency were obtained to be $14.68 \times 10^{-3}$ mg/s and $0.25 ~\mu \text{g}$ /J, for plate-to-plate DBD, and $9.16 \times 10^{-3}$ mg/s and $0.167 ~\mu \text{g}$ /J, for plate-to-pin DBD, respectively. The decomposition products containing isopropyl methylphosphoric acid (IMPA), methylphosphoric acid (MPA), fluoro(methyl)phosphinic acid (MPFA), di-isopropyl methane phosphate (DIMP), and phosphoric acid (PA) were observed in both DBD devices, with MPA and PA as the final products. The production level of PA was highest among all the products in plate-to-plate DBD. However, in plate-to-pin DBD, the concentration of PA and MPA were at the same level. The different decomposition efficiency between two DBD devices were mainly ascribed to the different input energy and their configuration. Our results confirmed that plate-to-plate DBD was a high-efficiency decomposition technology for sarin decomposition. [ABSTRACT FROM AUTHOR]

This article presents a detailed study on the basic features of bifurcation of dust ion acoustic (DIA) traveling waves in a dusty plasma comprising warm adiabatic ions, nonextensive electrons, and arbitrarily charged dust particles. A reduced dynamical system is obtained for plasma waves’ evolution, and the global dynamics of local bifurcation of waves’ motion are determined on the equilibrium points’ dust concentrations’ plane with respect to all possible plasma parametric combinations. The stability and phase portrait analysis indicate a sudden emergence of nonlinear periodic and solitary waves for critical values of negative (positive) dust concentration. At these critical values, waves’ dynamics exhibit a transcritical bifurcation with half-stable fixed points which support new spike-like traveling waves. The analytical and numerical solutions reveal that the decay rate of this localized structure is much slower than ordinary solitary waves that decay exponentially fast. Furthermore, the existence domain of bifurcation parameters and transitions between modes are found for different values of nonextensive electrons and arbitrarily charged dust concentrations. Our results could be applicable to different space and astrophysical plasma systems, particularly in earth atmosphere. [ABSTRACT FROM AUTHOR]

This contribution presents the results of a study of the germination rate and growth parameters of wheat seeds after atmospheric pressure surface coplanar dielectric barrier discharge (DBD) plasma treatment. The germination rate and biometric parameters such as the root, shoot length, mass of the seedlings, and the $\alpha $ -amylase enzyme activity were studied at different plasma exposure time. The seed coat surface wettability and morphology were determined by apparent contact angle measurement and scanning electron microscope (SEM) analysis. Seed surface disinfection and the presence of filamentous fungi have also been investigated at different discharge parameters. It is shown that the optimal plasma treatment duration for increasing the growth parameters and enhancing the enzymatic activity is 5–15 s. It was found that the longer plasma exposure requires complete sterilization of the seed surface from pathogens, compared to the optimal treatment time for high germination. Based on the obtained results, the possible mechanisms of the positive effect of plasma treatment on the enhanced germination of wheat seeds are discussed. [ABSTRACT FROM AUTHOR]

Reentry vehicles used to be enveloped by weakly ionized plasmas. These plasmas could yield communication blackout, which is considered as a serious threat to reentry vehicles. In the recent couple of decades, the terahertz (THz) communication is considered to be a potential approach to mitigate the communication blackout. On the other hand, the electron density distribution surrounding a reentry vehicle is inhomogeneous. The dense and inhomogeneous free electron could make an impact on the THz onboard antenna. The present study investigated the radiation performance of a 0.14-THz phase array antenna in weakly ionized plasma layers. The present study shows that the antenna gain, lobe width, and the lobe direction are influenced by weakly ionized plasma. Further study showed that the antenna gain and the lobe width are impacted by both electron density and electron collision frequency. However, the lobe direction is influenced by the electron density only. The mechanics of such phenomena are analyzed. In addition, a concept of approach to compensate the worsened antenna performance with the beamforming technology is proposed. The simulation results showed that the approach compensates the shifted lobe direction well. Also, it helps improve the antenna gain in the expected direction. [ABSTRACT FROM AUTHOR]

The Langmuir probe (LP) is generally accepted as an effective and relatively simple in situ space plasma instrument (plasma density, electron temperature, and spacecraft potential). As LPs transition to small spacecraft, their implementation encounters new technical challenges. For example, a negative charge is induced on the spacecraft while positively biasing an LP due to the small surface area ratios (spacecraft surface area to probe surface area ≪ 1000). This results in a varying spacecraft potential that degrades the accuracy of electron temperature and electron density measurements, reducing the LP’s effectiveness as a diagnostic tool. To mitigate the effects of this spacecraft charging, the twin-probe method (TPM) was developed. The TPM corrects LP measurements with tracked spacecraft potentials, measured by a separate high-impedance probe. By accounting for the changes in the spacecraft potential, the LP sweeps can be reconstructed to provide more accurate measurements of the ambient plasma’s properties. Here, we detail the TPM and present laboratory experiments that study its effectiveness and summarize constraints. Through these experiments, we found that it is possible to correct for spacecraft charging effects that can cause deviations in temperature and density as large as 20% and 136%, respectively. Furthermore, we will demonstrate a clear correlation between area ratio, spacecraft charging, and the negative impact on temperature and density measurement accuracy. [ABSTRACT FROM AUTHOR]