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We study the bactericidal efficacy of surface dielectric barrier discharge low-temperature plasma treatments, powered by nanosecond high voltage pulses. We achieve ∼ 4-log reduction in Escherichia coli population, after 10 min treatments, at a distance of 1.5 cm from the plasma surface. To investigate the reactive oxygen and nitrogen species (RONS) responsible for the bactericidal effect, we employ in-situ fourier transform infrared (FTIR) spectroscopy to measure a selection of relevant species, such as O 3 , NO 2 , N 2 O and N 2 O 5 . The measurements are taken under various relative humidity conditions to replicate the bacteria treatment environment. While RONS originating from nitrogen chemistry are detected, nitric oxide (NO), a pivotal molecule in nitrate production, is absent due to the sensitivity limitations of FTIR detection. To overcome this limitation, we employ laser induced fluorescence utilizing a picosecond-pulsed laser to measure the kinetics of NO produced by the plasma. Our results show that the NO concentration is smaller than 1 ppm and primarily localized near the plasma surface, with concentrations increasing proportionally with relative humidity. Notably, at a distance of 1.5 cm from the plasma surface, at which the E. coli is treated, the concentration of NO falls below 50 ppb. Although NO is pivotal in generating secondary reactive species within the plasma, our results suggest that it does not directly contribute to the bacteria inactivation process. Instead, other molecules, such as O 3 , NO 2 , and N 2 O, which are found in higher concentrations, may be responsible for the bactericidal properties observed in indirect plasma treatments. [ABSTRACT FROM AUTHOR]

Previous studies on discharge dynamics have primarily focused on the generation and migration of the charged particles and neglecting the influence of neutral excited-state particles. In this study, an integrated approach combining experiment and simulation was used to investigate the effect of neutral excited particles on discharge development. Firstly, partial discharge was induced by applying voltage to a pin-plate electrode in a darkroom environment and the emission spectrum of discharge was captured using an ultra-sensitive spectrometer. Then the formation mechanism of the main neutral excited particles in air corona discharge was analyzed based on the principle of quantum optics, and the collision cross-section data of the non-local thermodynamic equilibrium (NLTE) plasma chemical model for air was updated accordingly. Simulations revealed the process of electron pulses initiates the electron avalanche, which leads to dielectric breakdown. Results indicated that overvoltage can lead to the formation of electron avalanches at defect sites, which is capable of causing dielectric breakdown within the nanosecond time scale. The competitive mechanism of the excitation reactions to ionization reactions results in the dissipation of free electrons’ energy, effectively suppressing the development of electron avalanches and preventing electrical breakdown.

The paper collects and discusses the results obtained in the theoretical investigation of cold plasmas by using a state-to-state self-consistent kinetic approach, coupling chemistry and free electron kinetics. Examples are selected, not only to review the most recent advancements made in updating and extending the chemical model, but also to highlight the role played in all these systems by excited states, either vibrational or electronic, in affecting the plasma evolution in the discharge and in the post-discharge phases in different discharge configurations. The response of the kinetic simulation to the accuracy of the dynamical data describing the collisional processes, to the theoretical scheme adopted for the vibrational levels of molecules, and to the inclusion of the relevant dissociation channels, is discussed also in the light of the comparison with experiments for model validation.

This article presents an analytical study of the shift/splitting of the rovibrational energy levels of diatomic polar molecules under the elliptically-polarized laser field. First, there are derived general formulas for the matrix elements of the energy shift operator between arbitrary rovibrational states. Then there are provided, as an example, explicit analytical results for the energy shifts/splitting of the rotational level J-2 and illustrate them. Based on the derived analytical results, there is proposed a new method for the spectroscopic diagnostic of the parameters of the elliptically-polarized laser field inside low-temperature plasmas. [ABSTRACT FROM AUTHOR]

The breathing mode is an instability typical of Hall thrusters, which is characterized by oscillations of the discharge current with amplitude of the order of its mean value and frequency in the 5–30 kHz range. The strong link between this instability and the ionization processes is generally recognized. If, on one hand, 1D simulations have shown to be able to reproduce the breathing mode, on the other hand 0D models fell short in recovering self sustained oscillations, making it hard to identify the core physical mechanism governing their formation. In this work an original 0D model is presented and characterized by means of linear stability analysis and direct numerical integration. The electric field is allowed to vary in response to variations of the neutral density, acting on the ionization rate via the electron temperature and the ion dynamics. It is shown that the model is able to reproduce self-sustained oscillations with the typical characteristics of the breathing mode, even when fluctuations of the electron temperature are neglected. The stability of the model is strictly determined by the rigidity with which variations of neutral density reflect into variations of electron mobility.

Breathing mode is an ionization instability which is observed ubiquitously in the operation of Hall thrusters. It is recognized as a relatively low frequency (10–30 kHz) longitudinal oscillation of the discharge current and the plasma parameters. Although breathing instability is widely studied in the literature, the conditions for its origin are not fully understood. In this work we investigate the mechanisms responsible for the origin of the breathing mode in Hall thrusters by using a numerical model, allowing us to highlight the importance of electron mobility fluctuations for the onset and self-sustenance of the instability. Our one-dimensional, fully fluid model of the thruster channel is calibrated against the measured discharge current signal for a 5 kW-class Hall thruster operating in a condition where breathing mode is fully developed. The corresponding steady, unstable configuration (base state) is numerically computed by applying the Selective Frequency Damping (SFD) method. Then, a series of numerical tests is performed to show the existence of a feedback loop involving fluctuations around the base state of the neutral density, electron mobility, and electric field. We show that oscillations of the electron mobility are mainly caused by variations of the neutral density and are in phase with them; this, in turn, induces oscillations of the electric field, which are in phase opposition. The electric field acts simultaneously on the electron temperature and on the ion dynamics, promoting the depletion and replenishment of neutrals in the chamber.

Developing a low‐cost depyrogenation process is vital in extending the medical applicability of polymers that can be used in medicine. We present an overview of the plasma‐based depyrogenation literature and address the need to develop a nonthermal plasma‐based depyrogenation process for delicate materials such as chitosan. We present a low‐cost plasma apparatus to treat chitosan powder in hermetically sealed bags. We decouple the experiments into two parts: depyrogenation experiments for dried standard endotoxin on glass slides and analysis of chitosan modifications through Fourier‐transform infrared spectroscopy. We demonstrate depyrogenation efficacy with up to a 4‐log reduction in endotoxin levels and discuss minor changes observed in plasma‐treated chitosan. [ABSTRACT FROM AUTHOR]

Plasma cleaning of extreme ultra-violet (EUV) optics for the semiconductor industry requires atomic-level precision. Low-energy ions and neutrals can be highly beneficial for this purpose. However, ion energies in many industrial capacitively or inductively coupled plasmas may be too high for atomic precision processing so that ions can cause sputtering and re-deposition of materials and produce vacuum system contamination. We discuss two sources that create low-energy ions: a capacitively coupled (CCP) plasma source operating at several tens of MHz and an electron beam gas ionization source. The goal here is to minimize the contamination by limiting the ion impact energy to a few tens of electron-volts. Ion energy and flux measurements on a grounded surface are characterized with a compact retarding field ion spectrometer. Plasma-induced contamination is quantified using X-ray photo-electron spectroscopy (XPS). Low ion energy plasma sources introducing little surface contamination may be interesting for cleaning and accelerated testing in EUV lithography (EUVL)-related research and for cleaning of front-end optical mirrors in fusion reactor diagnostics. [ABSTRACT FROM AUTHOR]

The long-standing problem of plasma diffusion across a magnetic field (B-field) is reviewed, with emphasis on lowerature linear devices of finite length with the magnetic field aligned along an axis of symmetry. In these partially ionized plasmas, cross-field transport is dominated by ion-neutral collisions and can be treated simply with fluid equations. Nonetheless, electron confinement is complicated by sheath effects at the endplates, and these must be accounted for to get agreement with experiment.

We report results from a one-dimensional, numerical simulation of a capacitively coupled H e / O 2 admixture plasma, operated at pressure varying from 1.5 to 7.5 Torr and over a range of molecular oxygen admixtures ( H e + 0.1 % O 2 – H e + 10 % O 2 ). This study is used to investigate the effect of the gas pressure and the addition of small fractions of molecular oxygen on some important species production which have been extensively used for various biomedical applications and several new plasma technologies. The species densities have been presented, and the dominant key production processes have been identified. At a fixed ( H e + 1 % O 2 ) admixture, the electron density decreases with increasing pressure, and the densities of negative ions are relatively high at high pressures and decrease for the positive ions. However, the atomic O, the molecular metastable O 2 (v) , singlet-delta O 2 (a 1 Δ g) and singlet-sigma O 2 (b 1 Σ g +) states are found to be the dominant species and their densities are weakly dependent on the gas pressure. At a fixed pressure, as the O 2 admixture increases, the electron impact with O 2 molecules becomes higher, and consequently, the electron generation decreases considerably. The formation of O, O 2 (v) , O 2 (a 1 Δ g) and O 2 (a 1 Δ g) increases until it reaches a peak at 4 % O 2 and then falls significantly with increasing O 2 admixture. However, the atomic metastable O (1 D) and H e ∗ are less important and they decrease rapidly due to collisional quenching or Penning ionization. The ozone O 3 formation is optimal at 4 % O 2 . The positive and negative atomic and molecular ions are also relatively less important, and they decrease sharply with increasing O 2 admixture due to ion-ion and ion-molecule neutralization. The addition of oxygen resulted in a decrease in all plasma species due to the electronegativity property of oxygen. These results are in fairly good agreement with some experimental observations and allow for a better understanding of the main physicochemical mechanisms taking place in H e / O 2 plasmas admixtures. [ABSTRACT FROM AUTHOR]

The long-standing problem of plasma diffusion across a magnetic field (B-field) is reviewed, with emphasis on lowerature linear devices of finite length with the magnetic field aligned along an axis of symmetry. In these partially ionized plasmas, cross-field transport is dominated by ion-neutral collisions and can be treated simply with fluid equations. Nonetheless, electron confinement is complicated by sheath effects at the endplates, and these must be accounted for to get agreement with experiment.

The transformations of the electron energy distribution (EEDF), their concentration, and plasma space potential along the discharge gap between the hollow rectangular cathode and the mesh anode were experimentally studied. The discharge was 3 cm long, with a cross-section of 10 cm2. A new version of measurements with several single probes with the formation of current-voltage characteristics (IVC) in the probe circuit was proposed with the simultaneous application of voltages in the form of a combination of periodic and noise signals. The proportions of the signals were varied for different sections of the current-voltage characteristics. Measurements along the central axis of the discharge were taken. The dynamic range of the EEDF was not less than 4 orders of magnitude at the electron concentrations of 2–13 × 1010 cm−3, which exceeds the best known achievements. Measurements for discharge in helium at reduced pressures of 1–1.2 mbar and currents of 150–400 mA showed that the EEDFs differ from Maxwell ones, with an excess of fast electrons in the region of 10–20 eV at medium energies 4–6 eV. The fraction of fast electrons decreased in regions closer to the anode, which is associated with the nonlocality of the mechanism of the spectrum formation of free electrons. EEDFs transformations led to the space dependence of electron drift velocities on the plasma area. The dependence of the voltage drop across the cathode on the gas pressure and discharge current was noted. [ABSTRACT FROM AUTHOR]

This study investigated the use of glutathione as a marker to establish a correlation between plasma parameters and the resultant liquid chemistry from two distinct sources to predefined biological outcomes. Two different plasma sources were operated at parameters that resulted in similar biological responses: cell viability, mitochondrial activity, and the cell surface display of calreticulin. Specific glutathione modifications appeared to be associated with biological responses elicited by plasma. These modifications were more pronounced with increased treatment time for the European Cooperation in Science and Technology Reference Microplasma Jet (COST-Jet) and increased frequency for the dielectric barrier discharge and were correlated with more potent biological responses. No correlations were found when cells or glutathione were exposed to exogenously added long-lived species alone. This implied that short-lived species and other plasma components were required for the induction of cellular responses, as well as glutathione modifications. These results showed that comparisons of medical plasma sources could not rely on measurements of long-lived chemical species; rather, modifications of biomolecules (such as glutathione) might be better predictors of cellular responses to plasma exposure. [ABSTRACT FROM AUTHOR]

In similar discharges, the physical characteristics of the plasma in one gap are proportional to those in the others. The similarities of the gas discharge enable scaling discharge features, particularly useful for those scales for which experimental studies are not feasible. In this paper, the history of the similarity theory is revisited, and recent studies of the similarities of low-temperature plasma discharges, including scaling laws for the gas breakdown and steady-state discharges, are reported according to both experiments and numerical simulations. The validity of similarity laws is evaluated from low- to high-pressure discharge regimes, and violations of similarity laws are discussed when the nonlinear processes cannot be ignored, especially in the high-pressure regime. The impact factors, including the nonlinear processes and the scaling factors, for the similarity laws are also discussed. Several applications of the similarity law are explored for the related plasma physics issues. [ABSTRACT FROM AUTHOR]

The aim of this experiment is to enhance selected species in atmospheric pressure plasma jet (APPJ) that might be helpful for the wound healing purpose and to test the performance using basic diagnosis in plasma-treated liquid. A homemade APPJ device is driven by sinusoidal voltage with a excitation frequency of 25 kHz. Argon with admixture of small percentage of nitrogen, oxygen, and water vapor was selected to be carrier gas as the main sources of reactive species. Discharge power consumption is calculated by two approaches. Reactive oxygen species and reactive nitrogen species in the excited states are characterized by optical emission spectroscopy (OES). Excitation temperature $T_{\mathrm {exc}}$ in argon plasmas is calculated to estimate the electron energy distribution. The results show that argon plasmas with small addition of nitrogen and oxygen in this jet configuration are more efficient to generate desired reactive species in terms of OES diagnosis and liquid acidification. Moreover, the distinct efficiency of liquid acidification between direct and indirect plasma treatment of liquid has also been observed. [ABSTRACT FROM AUTHOR]

Electronegativity of CO2 and CO in dc plasma discharge was investigated employing the Allan–Boyd–Reynolds (ABR), the current balance (CB), the orbital motion limited (OML), and the floating potential (FP) methods by taking advantage of the positive ion number density using the recorded $I$ – $V$ curves. Electron energy distribution functions were evaluated, and electron number density and temperature were obtained. Electron temperature and number density were also obtained for both gases, employing the exponentially rising electron current. Results obtained for positive and negative ions were found to be compatible for ABR, CB, and OML for each gas with the FP method to be more than one order of magnitude higher for both gases. Electronegativity of the CO2 and CO was deduced using the measured data for electron and negative ion number densities, with the FP method at about one order of magnitude higher than those for the remaining methods. [ABSTRACT FROM AUTHOR]

The influence of the finite plasma resistance between the Langmuir probe and the reference electrode on the results of measurements of the characteristics of low-temperature plasma: the plasma potential, the average electron energy, the electron concentration, and the electron energy distribution function is analyzed. Specific calculations were made for glow discharge conditions supported by a hollow cathode in helium at a pressure of several millibars. • A study was made on the influence of the finite plasma resistance on the results of Langmuir probe measurements of the plasma characteristics. • The correction of the EEDF leads to a shift in the position of the maximum of the function to the region of lower energies. • Correction leads to an insignificant increase in the electron concentration, about 10%. [ABSTRACT FROM AUTHOR]

This study investigated the use of glutathione as a marker to establish a correlation between plasma parameters and the resultant liquid chemistry from two distinct sources to predefined biological outcomes. Two different plasma sources were operated at parameters that resulted in similar biological responses: cell viability, mitochondrial activity, and the cell surface display of calreticulin. Specific glutathione modifications appeared to be associated with biological responses elicited by plasma. These modifications were more pronounced with increased treatment time for the European Cooperation in Science and Technology Reference Microplasma Jet (COST-Jet) and increased frequency for the dielectric barrier discharge and were correlated with more potent biological responses. No correlations were found when cells or glutathione were exposed to exogenously added long-lived species alone. This implied that short-lived species and other plasma components were required for the induction of cellular responses, as well as glutathione modifications. These results showed that comparisons of medical plasma sources could not rely on measurements of long-lived chemical species; rather, modifications of biomolecules (such as glutathione) might be better predictors of cellular responses to plasma exposure.

Carbon nanostructures (CNs) are amongst the most promising biorecognition nanomaterials due to their unprecedented optical, electrical and structural properties. As such, CNs may be harnessed to tackle the detrimental public health and socio-economic adversities associated with neurodegenerative diseases (NDs). In particular, CNs may be tailored for a specific determination of biomarkers indicative of NDs. However, the realization of such a biosensor represents a significant technological challenge in the uniform fabrication of CNs with outstanding qualities in order to facilitate a highly-sensitive detection of biomarkers suspended in complex biological environments. Notably, the versatility of plasma-based techniques for the synthesis and surface modification of CNs may be embraced to optimize the biorecognition performance and capabilities. This review surveys the recent advances in CN-based biosensors, and highlights the benefits of plasma-processing techniques to enable, enhance, and tailor the performance and optimize the fabrication of CNs, towards the construction of biosensors with unparalleled performance for the early diagnosis of NDs, via a plethora of energy-efficient, environmentally-benign, and inexpensive approaches.

A multichannel scheme and a technique for measuring the parameters of electrons in a discharge plasma in a hollow cathode with several Langmuir probes in different regions of the plasma simultaneously are developed. In the experimentally implemented system, the current-voltage characteristics (IVCs) of the probes are formed by combinations of noise and periodic voltage waveforms, which ensures a high dynamic range and accuracy of the measurement results. In different regions of the plasma space, the electron energy distribution functions (EEDFs), average energies < E >, plasma potentials U p , and electron concentrations N e are determined simultaneously. The capabilities of the system are demonstrated for various probe locations. It is shown that in order to obtain consistent data, special processing (cleaning) of the probes is required, the states of which change with time. Methods of electronic and ionic cleaning and their combinations have been studied. If the probes are located in a plane equidistant from the cathode and anode at distances between them comparable to the transverse dimensions of the plasma, the EEDF shape and the N e value are approximately preserved, but the potential value U p changes. • The developed multichannel system (based on three single Langmuir probes) with I–V characteristic shaping by a noise signal makes it possible to provide high accuracy in determining the electronic plasma parameters. • A combination of cleaning methods for Langmuir probes (using electron and ion current) is optimal. • The plasma potential along the open side of the hollow rectangular cathode differs by 0.4 V at a distance of less than 1 mm. • Determining the electron concentration from the electron saturation current gives a ∼10% lower value compared to the determination by integrating of the second derivative of the IVC. [ABSTRACT FROM AUTHOR]

Electron energy probability functions (eepfs) have been measured along the axis of low pressure plasma expanding in a magnetic nozzle. The eepf at the maximum magnetic field of the nozzle shows a depleted tail commencing at an energy corresponding to the measured potential drop in the magnetic nozzle. The eepfs measured along the axis demonstrate that the potential and kinetic energies of the electrons are conserved and confirm the non-local collisionless kinetics of the electron dynamics.

Carbon nanostructures (CNs) are amongst the most promising biorecognition nanomaterials due to their unprecedented optical, electrical and structural properties. As such, CNs may be harnessed to tackle the detrimental public health and socio-economic adversities associated with neurodegenerative diseases (NDs). In particular, CNs may be tailored for a specific determination of biomarkers indicative of NDs. However, the realization of such a biosensor represents a significant technological challenge in the uniform fabrication of CNs with outstanding qualities in order to facilitate a highly-sensitive detection of biomarkers suspended in complex biological environments. Notably, the versatility of plasma-based techniques for the synthesis and surface modification of CNs may be embraced to optimize the biorecognition performance and capabilities. This review surveys the recent advances in CN-based biosensors, and highlights the benefits of plasma-processing techniques to enable, enhance, and tailor the performance and optimize the fabrication of CNs, towards the construction of biosensors with unparalleled performance for the early diagnosis of NDs, via a plethora of energy-efficient, environmentally-benign, and inexpensive approaches. [ABSTRACT FROM AUTHOR]

This paper presents the development of a model framework for plasma-biofilm and plasma-tissue interactions that can link molecular simulation of plasma chemistry to functions at a cell population level or a tissue level. This is aided with a reactive penetration model for mass transfer of highly transient plasma species across the gas-liquid boundary and a panel of electrical and thermal thresholds considering pain sensation, protein denaturation and lethal electric currents. Application of this model reveals a number of previously little known findings, for example the penetration of plasma chemistry into highly hydrated biofilms is about 10-20 μm deep for low-power He-O plasma and this is closely correlated to the penetration of liquid-phase plasma chemistry dominated by O, HO, and HO or O, HO, and O. Optimization by manipulating liquid-phase chemistry is expected to improve the penetration depth to 40-50 μm. For direct plasma treatment of skin tissues at radio frequencies, the key tolerance issue is thermal injuries even with a tissue temperature <50 °C and these can lead to induction of pain and protein denaturation at a small discharge density of 8-15 mA/cm over few tens of seconds. These and other results presented offer opportunities to improve plasma-biofilm and plasma-tissue interactions. The model framework reported may be further extended and can be used to non-biomedical applications of low-temperature plasmas. [ABSTRACT FROM AUTHOR]

This article concerns a new field covered by low-temperature plasmas at atmospheric pressure for medical treatments. This is based on the very attractive possibility to tune and design plasmas as possible pharmaceutical products using selectively some active species (charged particles, radicals, atomic and molecular agents, UV radiations) and even electric fields self-generated by the plasma. The delivery of active species occurs at the gaseous level. This means that there is no need for a carrier medium, and the treatment of living tissue or surface is optimal because plasmas can penetrate small pores, spread over rough surfaces, and reach both prokaryotic and eukaryotic cells. The present article gives first a review on the main low-temperature plasma setups potentially usable for medical treatments with an emphasis on the setups as, for instance, plasma jets developed in our laboratory. Then, the present article gives a review of the current state of the art of such plasmas as pharmaceutical products or therapeutic tools in medicine with a light on a selection of forefront researches particularly in the field of chronic wounds, blood coagulation, and cancer treatment. [ABSTRACT FROM AUTHOR]

Abstract: The use of polyvinylidene fluoride (PVDF) membrane as a support substrate layer for making a polyamide thin-film composite (TFC) has been hindered by the hydrophobic nature of PVDF. In this study, low temperature plasmas were used to treat a commercial PVDF membrane in order to improve its hydrophilicity and make it suitable for fabrication of a polyamide–polyvinylidene fluoride thin-film composite (PA-PVDF) membrane. The plasma treatment used oxygen, methane, or their 1:1 mixture gas to produce glow discharge for treatment and surface modification of the PVDF membrane. The membrane surfaces were characterized using water contact angle measurements, X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (FE SEM). Pure water permeability and salt rejection tests were performed to evaluate the performance of the resulting PA-PVDF. Our experimental results indicated that plasma treatment of PVDF membrane could significantly reduce its water contact angle and thus produce a hydrophilic surface that could be then used as the support substrate layer for the fabrication of TFC membrane through interfacial polymerization. Our experimental results also demonstrated that PA-PVDF membrane supports not only demonstrated higher pure water permeability, but also higher salt rejections than those of TFC membrane with polysulfone as the support. [Copyright &y& Elsevier]

Abstract: A custom-designed inductively coupled plasma (ICP)-assisted radio-frequency magnetron sputtering deposition system has been employed to synthesize aluminium-doped zinc oxide (ZnO:Al) nanofilms on glass substrates at room temperature. The effects of film thickness and ZnO target (partially covered by Al chips) power on the structural, electrical and optical properties of the ZnO:Al nanofilms are studied. A high growth rate (∼41nm/min), low electrical sheet resistance (as low as 30Ω/□) and high optical transparency (>80%) over the visible spectrum has been achieved at a film thickness of ∼615nm and ZnO target power of 150W. The synthesis of ZnO:Al nanofilms at room temperature and with high growth rates is attributed to the unique features of the ICP-assisted radio-frequency magnetron sputtering deposition approach. The results are relevant to the development of photovoltaic thin-film solar cells and flat panel displays. [Copyright &y& Elsevier]

Abstract: Xenon calibrated two photon absorption laser induced fluorescence (TALIF) is used to measure absolute atomic oxygen concentrations in air, methane–air, and ethylene–air non-equilibrium plasmas, as a function of time after initiation of a single 25ns discharge pulse. Peak mole fraction in air at 60torr is ∼0.5×10−4, with decay occurring on a time scale of ∼2ms. Peak mole fraction in a stoichiometric methane–air mixture is found to be approximately equal to that in pure air, but the rate of decay is found to be faster by a factor of approximately two to three. In Φ =0.5 ethylene–air, peak atomic oxygen concentration is reduced by a factor of approximately four, relative to air, and the rate of decay increased by approximately two orders of magnitude due to the greatly increased rate of reaction of atomic oxygen with ethylene, as compared to methane, at room temperature. Discharge kinetic modeling calculations, using both GRI Mech 3.0 and a more recent model of Wang et al., are shown to provide good overall agreement with all of the experimental data, as well as suggesting key processes of O atom generation and decay. [Copyright &y& Elsevier]

Abstract: This article introduces a deterministic approach to using low-temperature, thermally non-equilibrium plasmas to synthesize delicate low-dimensional nanostructures of a small number of atoms on plasma exposed surfaces. This approach is based on a set of plasma-related strategies to control elementary surface processes, an area traditionally covered by surface science. Major issues related to balanced delivery and consumption of building units, appropriate choice of process conditions, and account of plasma-related electric fields, electric charges and polarization effects are identified and discussed in the quantum dot nanoarray context. Examples of a suitable plasma-aided nanofabrication facility and specific effects of a plasma-based environment on self-organized growth of size- and position-uniform nanodot arrays are shown. These results suggest a very positive outlook for using low-temperature plasma-based nanotools in high-precision nanofabrication of self-assembled nanostructures and elements of nanodevices, one of the areas of continuously rising demand from academia and industry. [Copyright &y& Elsevier]

In this paper, important laboratory experiments in closed-cycle magneto-hydrodynamic (MHD) generator plasmas are discussed. The following aspects are treated: electron temperature elevation and nonequilibrium ionization, fluctuatioas and nonuniformity, streamers as the nonlinear appearance of ionization instability, inlet relaxation, and fully ionized seed as a concept to suppress ionization instability. Conclusions are presented on electrical transport parameters in nonuniform plasmas, streamer fine structure, streamer velocity, streamer initiation in relation to inlet relaxation, and the fully ionized seed concept. [ABSTRACT FROM AUTHOR]

• We study the isothermal two-fluid (electron + ion) equations coupled to Poisson's equation for low-temperature plasmas. • The scheme captures the dynamics where the electron inertia is not negligible and space charge regions such as plasma sheaths. • The scheme preserves the asymptotic regime where the plasma is quasi-neutral with massless electrons. • It does not require resolving the Debye length, the plasma frequency nor the electron sound waves. • It improves dramatically the computational efficiency compared to explicit discretizations. We present a novel numerical scheme for the efficient and accurate solution of the isothermal two-fluid (electron + ion) equations coupled to Poisson's equation for low-temperature plasmas at low-pressure. The model considers electrons and ions as separate fluids, comprising the electron inertia and space charge regions. The discretization of this system with standard explicit schemes is constrained by very restrictive time steps and cell sizes related to the resolution of the Debye length, electron plasma frequency, and electron sound waves. Both sheath and electron inertia are fundamental to fully explain the physics in low-pressure and low-temperature plasmas. However, most of the phenomena of interest for fluid models occur at speeds much slower than the electron thermal speed and are quasi-neutral, except in small charged regions. A numerical method that is able to simulate efficiently and accurately all these regimes is a challenge due to the multiscale character of the problem. In this work, we present a scheme based on the Lagrange-projection operator splitting that preserves the asymptotic regime where the plasma is quasi-neutral with massless electrons. As a result, the quasi-neutral regime is treated without the need of an implicit solver nor the resolution of the Debye length and electron plasma frequency. Additionally, the scheme proves to accurately represent the dynamics of the electrons both at low speeds and when the electron speed is comparable to the thermal speed. In addition, a well-balanced treatment of the ion source terms is proposed in order to tackle problems where the ion temperature is very low compared to the electron temperature. The scheme significantly improves the accuracy both in the quasi-neutral limit and in the presence of plasma sheaths when the Debye length is resolved. In order to assess the performance of the scheme in low-temperature plasmas conditions, we propose two specifically designed test-cases: a quasi-neutral two-stream periodic perturbation with analytical solution and a low-temperature discharge that includes sheaths. The numerical strategy, its accuracy, and computational efficiency are assessed on these two discriminating configurations. [ABSTRACT FROM AUTHOR]

Тhe newly developed electronic set-up for working with Langmuir probes was used in measurements of the properties of the electronic component in the discharge with a hollow rectangular cathode. For the formation of current-voltage characteristics for the first time, it was proposed to use noise voltage signals in combination with traditional sawtooth or sinusoidal ones. The noise voltage can be applied to obtain the electron energy distribution functions (EEDF) both in the whole energy range and for its selected energy intervals. This improves the accuracy and reproducibility of measurements of distributions at the finite frequency band of the equipment. Measurements of the electron energy distributions, concentrations, mean energies, and plasma potentials were carried out with spatial resolution for the discharge in helium and its mixtures with water molecules and other rare gases which are of interest for optical actinometry. The EEDF dynamic is of not less (3–3.5) orders range All parameters are substantially inhomogeneous. An increase in He pressure (1–4) Torr leads to a drop in the plasma potential throughout the space and at the same time increases its gradient. The typical EEDF is of the two-peak shape. This correlates with the redistribution of electrons from the low-energy region to the high-energy region, which is apparently due to the nonlocality of the processes of the formation of distributions in an inhomogeneous electric field. The additives of molecules prevent such energy transfer. [ABSTRACT FROM AUTHOR]