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Radiation sources are promising for thermophysical studies, thermal and thermal strength tests of materials and structural elements subjected to high-temperature heating. Of the existing types of radiation sources, tubular radiation sources play a special role, making it possible to create test installations for heating large-sized fragments and full-scale aircraft structures by assembling them into multi-chamber heating units. For these purposes, incandescent radiation sources and high-current gas-discharge radiation sources can be used. Experimental data on the characteristics of the most common radiation sources are presented, on the basis of which heating installations have been created in relation to thermal tests of aerospace engineering structures. [ABSTRACT FROM AUTHOR]

Karl George Emeléus (1901–1989) was educated at Cambridge and after a short period at King's College, London, he spent the remainder of his career as lecturer (1929–33) and then professor (1933–66) of physics at Queen's University, Belfast. At Queen's, he set the direction of experimental research in gas discharge and plasmas for a generation and oversaw the growth of the department. He also acted as a spokesman for physics in Northern Ireland and was involved in public responses to concerns about the use of nuclear weapons and nuclear energy in the late 1940s and 50s. This paper summarises Emeléus's life and work and sets it in the context of physics at Queen's University in the mid-twentieth century. [ABSTRACT FROM AUTHOR]

Recently, two completely different types of lasers—a fiber laser and a gas-discharge laser—were combined into a single device by demonstrating 2.03 µm laser generation in He-Xe plasma that was produced by a microwave discharge directly inside a hollow-core fiber. This new type of laser—a gas-discharge fiber laser—provides excellent opportunities to greatly enrich the wavelength range of the operation of fiber lasers. In this work, we investigate a He-Kr gas mixture as an active medium of this new type of laser. As a result, a He-Kr gas-discharge fiber laser is demonstrated for the first time. The laser was pumped by a microwave discharge in a He:Kr (40:1) mixture that was filled into a revolver fiber with the hollow-core diameter of 130 µm. The total gas pressure was about 100 torr. With broadband mirrors of the laser resonator, generation was observed simultaneously at wavelengths of 2190 and 2523 nm. The output power of the He-Kr gas-discharge fiber laser was about 1 mW. [ABSTRACT FROM AUTHOR]

The main objective of this study is to demonstrate the active influence on the location of the bow shock wave, as well as on the parameters of an aerodynamic body, of a gas discharge organized near the frontal surface, between the body and the bow shock wave. The research is carried out using both experimental and numerical methods at the freestream Mach number M = 6.8. The working gas is xenon. It is shown that the location of the steady bow shock wave, along with the current and power of the discharge, is associated with the change in the adiabatic index of the plasma created by the discharge, which, in turn, is determined by plasma parameters such as the degrees of nonequilibrium and the degree of ionization. It is shown that the adiabatic index with the power supplied to the impact zone in the range of 30–120 kW can both increase and decrease in the range of 1.25–1.288. A study of the discharge-created plasma zone is conducted, and the correspondence between the gas discharge current and power and the average parameters in the plasma zone created by the discharge are presented. A good agreement between the numerical and experimental data is shown. The results obtained can be useful in the development of control systems for high-speed flows based not only on the effects of heating but also on the impact of plasma parameters. [ABSTRACT FROM AUTHOR]

The study presents and analyzes the experimental results of geological and geomorphological observations in some marine areas with active gas emission from bottom sediments. The study was carried out using an instrumental complex of geophysical sonar equipment, which included a subbottom profiler and side scan bathymetric sonar that uses an interferometric method for measuring depths in the field of view. The results confirm the possibility of using the complex to classify the seabed morphology and control the processes of gas unloading. The use of sonar equipment for remote seabed mapping during satellite observations can be used to interpret the results of satellite remote sensing of the atmosphere. [ABSTRACT FROM AUTHOR]

In the present work, analyses have been performed to determine spectroscopic parameters, including transition probabilities, and relative line strengths of discharge-produced xenon plasma. We present the transition probabilities of twenty-three emission lines originating from the 5p56p →5p56s transition array of neutral xenon covering the wavelength range from 450 to 1100 nm using a xenon-filled hollow cathode discharge lamp. The experimental absolute transition probabilities have been measured by combining the reported lifetimes of upper levels with the integrated spectral intensities of xenon transitions. The results agree well with the reported data in the NIST database, where available. The theoretical line strengths for all spectral transitions originating from the 5p56p→5p56s transition array have been calculated in the LS, LK, jj, and jck coupling schemes using the 3j, 6j, and 9j symbol relations. Furthermore, the normalized experimental line strengths have also been measured and compared with theoretical line strengths, which confirm that the jj and jck coupling scheme is more appropriate for the level designation of xenon. [ABSTRACT FROM AUTHOR]

The paper presents a novel method for obtaining cobalt ferrites with a spinel type structure under the action of a nonequilibrium atmospheric pressure gas-discharge plasma in air on a mixture of solid iron and cobalt hydroxonitrates. The data of energy dispersive X-ray spectroscopy and X-ray phase analysis showed that the synthesized powders have a complex phase and chemical composition, which depends on the Fe:Co molar ratio in the initial salts. The best result in terms of yield of cobalt ferrite is obtained with Fe:Co = 2:1. The resulting material contains 86 wt% Fe2CoO4, also 13.5 wt% Fe2O3 and 0.5 wt% Fe3O4. At other ratios, Co3O4 is also formed. According to dynamic light scattering data, the obtained powders consist of two characteristic fractions. The main fraction (94%) is represented by particles 105 ± 4 nm in size. And the other fraction (6%) consists of particles 18 ± 4 nm in size. The resulting materials have magnetic properties. So, for powders obtained from salts with Fe:Co = 2:1 the coercive force was 490 Oe. The saturation magnetization was 52 emu/g, and the remnant magnetization was 22 emu/g. [ABSTRACT FROM AUTHOR]

This paper deals with experimental studies of ionization waves igniting the breakdown in long discharge tubes in neon at low pressures. Ionization waves were produced by rectangular voltage pulses applied to the high-voltage electrode of the discharge tube. Our research focused on concentration measurements of neon excited atoms at the metastable 1s5(3P2) level after the ionization wave passage and the breakdown termination. We also found the characteristic decay times of these states and the most significant elementary processes responsible for metastable atom deactivation.

Plasma technology has undeniably revolutionized industrial processes in recent decades. Atmospheric pressure plasma (APP) has emerged as a prominent and widely applicable tool in various scientific disciplines. Notably, plasma-assisted flow control has become a subject of intense interest, particularly applying surface dielectric barrier discharge (SDBD) plasma actuators for aerodynamic flow control. In this study, a two-dimensional model of the SDBD plasma actuator is developed using the COMSOL Multiphysics program, incorporating air gas discharge reactions with N2/O2/Ar gases in specific ratios (0.78, 0.21, 0.01). The investigation focuses on the impact of dielectric materials (mica, silica glass, quartz, and polytetrafluoroethylene (PTFE)) on plasma characteristics and body force within the plasma actuator under constant input parameters. Moreover, the study explores how variable pressure (760, 660, and 560 torr) in different applications influences plasma properties, ultimately affecting the magnitude of the body force in the plasma actuator. These findings contribute to optimizing plasma technology for flow control applications and enhance industrial efficiency and performance. [ABSTRACT FROM AUTHOR]

A numerical simulation of an intense thermionic emission of electrons from the cathode into the air medium in an electrode system has been performed with regard for the possible changes in the voltage across the electrodes and in the electronic work function of the cathode. Spatial distributions of the electrons, the electron energy, the ions, the electric-field strength, and the concentration of the atomic oxygen in the air medium were constructed with the use of a simplified set of kinetic reactions. A possibility of using the thermionic emission of electrons from a cathode for the cooling of the members of flying vehicles with the aim to proof them against heat loads was demonstrated. The numerical calculations have shown that the thermionic emission of electrons from the cathode in a system of electrodes with no protective resistor at a high pressure does not provide a cooling of the system. [ABSTRACT FROM AUTHOR]

A novel discharge reactor was designed, utilizing the transient passage of liquid droplets between the electrode pairs to trigger a gas discharge. The reactor was employed to investigate the degradation of carbon disulfide (CS_2) exhaust gas, and the study examined the effects of various parameters including input energy, droplet dropping frequency, gas flow rate, oxygen concentration, and solution composition on the degradation process. The results demonstrated the effective removal and degradation of CS_2 gas from the gas stream using the droplet-triggered gas discharge reactor. During the gas discharges, the droplets absorbed the gas-phase reaction products, thereby promoting the degradation of CS_2. Optimal CS_2 removal was achieved with a droplet dropping frequency of 0.5~1 drop/s. The removal rate decreased with slower frequencies, while higher frequencies led to increased energy consumption. Among the same conditions, the lowest CS_2 removal rate was observed when deionized water was used as the absorbent droplet, followed by a 5% aqueous sodium sulfate solution. The highest removal rate was achieved with a 5% sodium hydroxide solution. The gas-phase products of the CS_2 degradation reaction mainly consisted of SO_2, CO_2, and a small amount of intermediate product COS, while the liquid-phase products were sulfate ions. Furthermore, the degradation mechanism was analyzed.

The main objective of this study is to demonstrate the active influence on the location of the bow shock wave, as well as on the parameters of an aerodynamic body, of a gas discharge organized near the frontal surface, between the body and the bow shock wave. The research is carried out using both experimental and numerical methods at the freestream Mach number M = 6.8. The working gas is xenon. It is shown that the location of the steady bow shock wave, along with the current and power of the discharge, is associated with the change in the adiabatic index of the plasma created by the discharge, which, in turn, is determined by plasma parameters such as the degrees of nonequilibrium and the degree of ionization. It is shown that the adiabatic index with the power supplied to the impact zone in the range of 30–120 kW can both increase and decrease in the range of 1.25–1.288. A study of the discharge-created plasma zone is conducted, and the correspondence between the gas discharge current and power and the average parameters in the plasma zone created by the discharge are presented. A good agreement between the numerical and experimental data is shown. The results obtained can be useful in the development of control systems for high-speed flows based not only on the effects of heating but also on the impact of plasma parameters.

Recently, two completely different types of lasers—a fiber laser and a gas-discharge laser—were combined into a single device by demonstrating 2.03 µm laser generation in He-Xe plasma that was produced by a microwave discharge directly inside a hollow-core fiber. This new type of laser—a gas-discharge fiber laser—provides excellent opportunities to greatly enrich the wavelength range of the operation of fiber lasers. In this work, we investigate a He-Kr gas mixture as an active medium of this new type of laser. As a result, a He-Kr gas-discharge fiber laser is demonstrated for the first time. The laser was pumped by a microwave discharge in a He:Kr (40:1) mixture that was filled into a revolver fiber with the hollow-core diameter of 130 µm. The total gas pressure was about 100 torr. With broadband mirrors of the laser resonator, generation was observed simultaneously at wavelengths of 2190 and 2523 nm. The output power of the He-Kr gas-discharge fiber laser was about 1 mW.

A study of the switching process of a short (1 mm) gas gap initiated by a spark discharge along the dielectric surface was carried out by the metho d of shadowgraphy with nanosecond time resolution. The presence of a shock wave propagating from the cathode spot and signs of intermediate accumulation of the invested energy in the form of excitation energy of gas molecules or turbulent gas flow were detected. [ABSTRACT FROM AUTHOR]

Abstract—The study of the effect of the initial conditions on the features of the formation and development of the anodic ionization wave between two electrodes with a tip–plane gap geometry in argon at atmospheric pressure is performed on the basis of a two-dimensional axisymmetric drift-diffusion model. [ABSTRACT FROM AUTHOR]

The active Brownian motion of single dust particles in a three-dimensional DC discharge trap under the action of laser radiation is experimentally studied. Spherical particles of melamine formaldehyde (MF), part of the surface of which had a copper coating (Janus particle) are used in the experiment. Two-dimensional and three-dimensional analysis methods for root-mean-square displacements are compared. The mean kinetic energy of motion of dust particles at different laser irradiation intensities is determined. The energy balance of dust particles and the influence of their rotation on the nature of the motion are estimated. [ABSTRACT FROM AUTHOR]

Antioxidant cytoprotective properties of mexidol have been studied under the influence of argon and helium gas-discharge cold plasma of atmospheric pressure on Paramecium caudatum cell culture. It has been shown that mexidol exhibits strong antioxidant properties and practically completely eliminates the negative effects of oxidative stress, retaining almost 100% of the initial number of cells. The data obtained demonstrate a wide range of behavioral responses of cells of Paramecium caudatum, which confirms their practical value as model objects for pharmacological and toxicological studies, and the use of gas-discharge cold plasma makes it possible to exclude the direct oxidative effect of hydrogen peroxide (the standard model of oxidative stress) on the studied drugs and to increase the reliability of toxicological studies. [ABSTRACT FROM AUTHOR]

The article presents the results of the theoretical study of the plasma density axial distribution in a stationary gas discharge sustained by the eigen dipolar wave that propagates in a long cylindrical plasma-metal structure. The discharge structure consists of a column of magnetized non-uniform plasma placed in the metal waveguide of variable radius. The study of the gas discharge is carried out within the framework of the electrodynamic model, in which the main attention is paid to the electrodynamic part of the model. To describe the processes that take place in plasma, the model equations are used. The influence of the metal waveguide inhomogeneity along the structure and the plasma density radial non-uniformity on the phase characteristics of the dipolar wave, its spatial attenuation, the field components radial distribution, the axial distribution of the plasma density sustained by this mode are determined. It is also analysed the condition for the discharge stability and find the regions, where dipolar mode can sustain the stable discharge. The obtained results can be useful for various technological applications.

We consider the prospect of development a point-like source of vacuum ultraviolet radiation based on a plasma discharge sustained by terahertz radiation from Novosibirsk free electron laser. [ABSTRACT FROM AUTHOR]

The process of copper nanostructure formation on a silicon dioxide substrate was simulated using the molecular dynamics method. The process parameters corresponded to the conditions in a low-pressure gas-discharge plasma. The relationship between the nanostructure formation rate and the main plasma parameters was determined. [ABSTRACT FROM AUTHOR]

A model for calculating the surface tension coefficient of a spherical cloud of charged microparticles in a plasma is proposed. The coefficients of the surface tension of Coulomb spheres obtained in a low-pressure glow discharge in neon at a temperature of 77 K for particles with a diameter of 4 μm and a temperature of 295 K for particles with a diameter of 2 μm are calculated. The potential energy of microparticles on the surface of a sphere is determined. In the calculations, a hydrodynamic model of a positive column with charged microparticles is used. The obtained values of the surface tension coefficient are compared with the data obtained by other authors for ball lightnings. A hypothesis is proposed for the formation of Coulomb spheres in the Earth's atmosphere. [ABSTRACT FROM AUTHOR]

Dielectric barrier discharge (DBD) plasma is used for various applications. DBD is also one of the most efficient and low-cost methods for active fluid flow control. In this study, a detailed physical model of DBD in atmospheric pressure at 1 kV DC voltage is developed with COMSOL Multiphysics software. Argon gas is also used as a background gas and electrodes are assumed to be copper. Plasma parameters such as electron and ion density, electric field, potential, and temperature for different gap distances of electrodes (1.0 mm, 0.9 mm, 0.8 mm) and different dielectric type (Quartz, Silica Glass, Mica). The results of the simulation show that the longitudinal distance of the grounded electrodes to the power electrodes has a direct influence on parameters such as electron temperature, and electron and ion density which are the main factors of fluid flow control. These parameters have the maximum value when Mica is used as a dielectric and the lowest value when Silica Glass is utilized. [ABSTRACT FROM AUTHOR]

A gas-discharge fiber laser based on a hollow-core fiber is created for the first time. The core diameter is 130 µm. Microwave radiation with a frequency of 2.45 GHz is used as a pump. As an active medium, a He : Ar : Xe gas mixture in the ratio of 100 : 10 : 1 is used. The total gas pressure in the fiber core is 130 Torr. At the output of the fiber cavity formed by broadband mirrors, lasing on xenon atoms at the wavelength of 2027 nm is observed. The result obtained opens new prospects for developing gas-discharge fiber lasers combining advantages of both fiber and gas-discharge lasers, and have potential application in various fields of science and engineering. [ABSTRACT FROM AUTHOR]

Experimentally, under laboratory conditions in the nitrogen acoustic plasma in the region of the forbidden lines at 654.81 and 658.36 nm, a spectral emission line of high intensity was obtained (up to 17 stronger than the neighboring lines of the first positive system of nitrogen). The results were obtained both in pure low-pressure nitrogen acoustic plasma (several hundreds of Pa) and various mixtures containing nitrogen, including the CO2 : N2 : He = 1 : 1 : 8 mixture. The results obtained are explained by the acoustic plasma state of the discharge and an analog of Rahman scattering, which remove some of the quantum mechanical prohibitions. The possible influence of the Coriolis force is also considered. [ABSTRACT FROM AUTHOR]

Shortly after Röntgen's publication about a new kind of rays, a dispute about priority claims began. Röntgen was not the first researcher to produce X-rays nor the first to take X-ray images. An analysis of the history of cathode ray research in the 19th century reveals ample evidence that researchers before Röntgen had already produced X-rays, albeit without knowing this. Most of them, for their part, did not claim any priority, some did so rather casually. The German-Hungarian physicist Philipp Lenard, a co-founder of German Physics, considered himself a “true discoverer”. It remains to be said, however, that he, like many others before him, failed to recognize the character of the new radiation. It was Wilhelm Conrad Röntgen, with his three scientific publications on X-rays, who laid the foundations for their physical clarification and paved the way for the success story of their application in a variety of fields that continues to this day.

Optical emission from gas molecules is considered an excellent solution to gas detection because of its fairly high sensitivity and selectivity. However, its further development is constrained by its large size, high energy consumption, and security risks. Herein, a self‐powered gas sensing solution is proposed by taking advantage of the optical emission of triboelectric discharge (TD). Based on the triboelectric effect, the high output voltage of ≈kV can lead to producing optical emissions through gas discharges, including emission spectra and discharge images, which are affected by gas species and pressure. By means of machine learning, the optical emission signals process the ability to recognize 60 gas atmospheres simultaneously, with an accuracy of 97.67%. With the assistance of the mobile phone or closed‐circuit television, a self‐powered gas sensing system based on TD may serve as a portable detecting device and a vital component of the Internet of Things system. [ABSTRACT FROM AUTHOR]

Shortly after Röntgen's publication about a new kind of rays, a dispute about priority claims began. Röntgen was not the first researcher to produce X-rays nor the first to take X-ray images. An analysis of the history of cathode ray research in the 19th century reveals ample evidence that researchers before Röntgen had already produced X-rays, albeit without knowing this. Most of them, for their part, did not claim any priority, some did so rather casually. The German-Hungarian physicist Philipp Lenard, a co-founder of German Physics, considered himself a "true discoverer". It remains to be said, however, that he, like many others before him, failed to recognize the character of the new radiation. It was Wilhelm Conrad Röntgen, with his three scientific publications on X-rays, who laid the foundations for their physical clarification and paved the way for the success story of their application in a variety of fields that continues to this day. [ABSTRACT FROM AUTHOR]

The main purpose of this article is to study the features of the structure and spectral brightness characteristics of pulsed emitting discharges of the magneto plasma compressor type in dense gases over a wide range of energy–power parameters. A numerical simulation of plasma dynamic magneto plasma compressor discharge in gases is carried out. Different quasi-stationary regimes have been studied and the main characteristics have been estimated. [ABSTRACT FROM AUTHOR]

The perfluoronitrile C4F7N is considered a promising SF6-alternative in high-voltage gas-insulated apparatus, thanks to its high dielectric strength and low global warming potential. However, a complete and consistent set of electron-neutral collision cross-sections of C4F7N is still lacking, which hinders relevant plasma modeling. In this contribution, the available electron-neutral collision cross-sections of C4F7N are first compiled and assessed. The initial cross-sections are adjusted iteratively by the electron swarm method to determine a complete and self-consistent cross-section set of C4F7N for the first time. The set is validated by a systematic comparison of electron swarm parameters between Boltzmann equation analysis and experimental measurements in pure C4F7N as well as C4F7N/N2 and C4F7N/Ar mixtures. The proposed cross-section set of C4F7N will be made available to the community in the LXCat database. It will be of particular importance for applications with an emphasis on the discharge mechanisms of this novel gas. [ABSTRACT FROM AUTHOR]

In the design of MV AC and DC spacers, the predominant factors are surface and interface conditions. Design is generally carried out on specifications and standards which are based on long-term experience and lab testing. However, the diffusion of power electronics with a trend to increase electric field, switching frequency, and rise time to achieve higher power density calls for an innovative, global approach to optimized insulation system design. A new methodology, based on field simulation, discharge modeling, and partial discharge inception measurements, called the three-leg approach, can form the basis to optimize insulation design for any type of supply voltage waveform. This paper focuses on the influence of the type of electrode on the inception and phenomenology of surface discharges and, as a consequence, on the interpretation of the results used for application of the three-leg approach. It is demonstrated that a typical electrode system used for insulating material testing can generate both gas and surface discharges at the triple point, when the electrodes have a smooth profile that is used to avoid corona or flashover. Hence, testing partial discharge may not provide a straightforward indication of the surface discharge inception and, thus, be partially misleading for insulation design. Another takeover is that such analysis must benefit from PD testing tools endowed with analytics able to provide automatic identification of the type of defect generating PD, i.e., internal, surface, and corona, since design and remedy actions can be taken, and adequate insulating materials developed, only knowing the type of source generating PD. Hence, testing partial discharge may not provide a straightforward indication of surface discharge inception and, thus, be partially misleading for insulation design. In addition to the importance of the three-leg approach to favor reliable and optimized design of insulation systems, there is a clear need to have a PD testing tool endowed with analytics. It should preferably be able to provide automatic identification of the type of defect generating PD, i.e., internal, surface, and corona. [ABSTRACT FROM AUTHOR]

The first observation of possible transient luminous events (TLEs) on Jupiter was reported recently. Whereas initiation of elves on Jupiter has been theoretically studied before, the possibility of sprite streamer inception on Jupiter has not been investigated yet. Here we critically review the literature concerned with TLEs on Jupiter. Subsequently, we report on development of a numerical model for modeling of magnetized streamers in presence of Jupiter's strong magnetic field. The model utilizes the knowledge provided by recent observations of Jupiter's lightning and magnetic field by the Juno spacecraft. It is demonstrated that sprite streamer inception under realistic atmospheric conditions on Jupiter is possible. Plain Language Summary: Transient luminous events are large scale (thousands of cubic kilometers) gas discharges produced at low air densities at high altitudes in the Earth's atmosphere. These events are driven by intense lightning discharges in underlying thunderstorms at tropospheric altitudes. Recently the first observation of lightning‐related transient luminous events in Jupiter's ionosphere was reported. Considering Jupiter's conditions, we present here the first modeling of filamentary plasma structures called streamers that are known to produce the brightest optical emissions among different types of transient luminous events in the Earth's atmosphere. In contrast the streamer plasma in Jupiter's atmosphere is strongly magnetized. Key Points: Inception of sprite streamers under realistic atmospheric conditions on Jupiter is possibleDue to Jupiter's strong magnetic field at altitudes where possible transient luminous events emerge, the gas discharge plasma is magnetizedContribution of H2 photoionization due to extreme ultraviolet emissions from atomic helium to streamer propagation is negligible [ABSTRACT FROM AUTHOR]

We propose a low-density discharge plasma model that takes into account the impact of oxygen admixture in typical conditions of complex (dusty) plasmas. Numerical simulations based on this model show that the concentration of negative ions turns out to be very high, and they play an important role in the overall kinetics in this particular range of plasma conditions. The ambipolar diffusion electric field drags these negative ions into the center of the plasma. The density of negative ions is high enough to push the negatively charged dust component out of the center, both by weakening the radial electric field and by increasing the thermophoretic force. This phenomenon was observed in the published experiment and qualitatively supports the proposed model. Additionally, the proposed model allows an alternative explanation of the experiment. [ABSTRACT FROM AUTHOR]

This study was devoted to the development of novel devices and a methodology intended for generating ultrasonic waves in an air medium by using atmospheric pressure gas discharge. In the proposed electrode system, the discharge process was accompanied by the generation of acoustic waves on the emitter surface and, consequently, in the ambient air. The gas discharge emitter vibrations were analyzed by applying the technique of Scanning Laser Doppler Vibrometry (SLDV). It was shown that the magnitude of displacements matched the corresponding characteristics of classical piezoelectric and magnetostrictive transducers. The use of the Fast Fourier transform procedure supplied amplitude–frequency spectra of vibrations generated by the gas discharge emitter. The amplitude–frequency spectrum analysis showed that the proposed emitter was able to generate acoustic waves in the air with frequencies from 50 Hz to 100 kHz, and such a device can be used for the nondestructive testing (NDT) of materials. The results of the statistical analysis of vibration displacements in the repetitive pulsed mode were discussed. A non-stable characteristic of the vibration displacement of the emitter membrane was demonstrated. The parameters of such instability were associated with the features of gas discharge processes. In the experiments, the proposed gas discharge emitter was used in combination with SLDV for inspecting carbon-fiber-reinforced polymer composites. The experiments demonstrated the possibility of using an air-coupled gas discharge transmitter to generate acoustic waves in NDT applications. [ABSTRACT FROM AUTHOR]

It has been experimentally shown that an increase in the intensity of a standing sound wave in the discharge tube results in a decrease in the gas temperature on the axis of the positive column of the argon discharge and an increase in the gas temperature on the tube wall because of the occurrence of vortex motion in the field of the sound wave. In this case, the radial temperature gradient decreases along the radius of the positive column. [ABSTRACT FROM AUTHOR]

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This work focuses on the study of the corona discharge breakdown in groove gap waveguides (GGWs) and inductive bandpass filters (BPFs) based on this technology. With the main aim of improving the peak power handling capability (PPHC), the location of the maximum normalized electric field strength $(|{\hat {E}}_{\text {MAX}}|)$ as a function of the geometrical parameters is analyzed. First, the research deals with wave-guiding structures, comparing the distribution of the transverse electric TE10-like mode of a GGW to that of an equivalent rectangular waveguide (RW). Next, a design strategy based on the adjustment of the geometrical dimensions of the bed of nails is proposed, thus achieving a considerable reduction of $|{\hat {E}}_{\text {MAX}}|$ . The second part of this paper aims for vertically polarized GGW BPFs, where the inductive irises become the most critical part of the component. By a simple modification of their dimensions, a second design criterion is suggested for improving the PPHC. Finally, several Ku-band BPFs centered at 14 GHz and 16 GHz have been manufactured and experimentally verified at the European High-Power Radiofrequency Space Laboratory. This measurement campaign shows peak power thresholds up to 1.09 kW and 3.59 kW at 600 mbar for the non- and full-optimized GGW BPFs, respectively, thereby demonstrating a PPHC enhancement up to 5.16 dB in the high-pressure range when both strategies, proposed in this work, are used.

The results of experimental and computational studies of the pulsed periodic microsecond diffuse discharge excited in the air flow under atmospheric pressure in a sharply heterogeneous interval are described. It is shown that effective synthesis of nitric oxide is ensured in such a discharge. A model of the production of nitrogen oxides in the late stage of discharge has been developed, which takes into account the main plasmachemical reactions and gasdynamics. Simulation shows the combined effect of plasmachemical and gasdynamics processes on the spatiotemporal characteristics of the discharge, which determinethe generation of nitric oxide among others. The values of the main parameters of the discharge are determined, and satisfactory agreement between the calculated and experimental data is shown. [ABSTRACT FROM AUTHOR]

The object of research is the processes of the emergence and glow of a discharge around biological structures in a pulsed electric field. Such processes have found use in the method of gas discharge visualization. In medical diagnostics, the general state of human health is assessed by the characteristics of gas-discharge images of fingers. One of the most problematic areas of the correctness of medical diagnostics is the dependence of the visual components of the image on the electrical characteristics of the discharge and the physical and chemical characteristics of the surrounding environment. In the course of the study, methods of modeling the electric discharge current circuit and electrical properties of biostructures were used. The proposed solution allows taking into account: the amplitude of the impulse voltage of the discharge, the frequency of the impulses, the duration and intensity of the impulses, the polarity, which act as additional diagnostic parameters of the gas-discharge visualization process. Physical processes are considered, and a model of a chain of gas discharge around a biological object in a pulsed electric field is proposed. It is shown that the occurrence of a discharge and the characteristics of the glow depend on the amplitude, duration, frequency, and polarity of the pulse voltage. These additional parameters determine the correctness of further visual diagnostics. Their quantitative measurement and the possibility of objective comparison should be attributed to the advantages of registering the proposed parameters of gas discharge visualization. The specified properties of these parameters provide an additional opportunity to digitally describe the condition of the object under study, and subsequently to automate diagnostics. The structural diagrams of the device for conducting research using the method of gas discharge visualization, the high-voltage impulse voltage generator unit for the hardware consideration of additional gas discharge parameters and their connection with medical and biological indicators have been developed. The use of the method and means of gas discharge visualization to assess the functional state of the flight crew in the pre- and post-flight period requires the development of special equipment. The proposed technical solutions require experimental verification. Comparative studies of diagnostic conclusions by the method of gas-discharge visualization with traditional medical diagnostics are necessary. [ABSTRACT FROM AUTHOR]

In this work, we present an experimental and theoretical study of a cylindrical atmospheric pressure dielectric barrier discharge (DBD) operating in the filamentary mode. An analytical model that takes into account the nonuniformity of the charge distributions on the dielectrics was developed. Using the model, it is possible to estimate important characteristics of a DBD device, like breakdown voltage, mean power consumption, and circuital parameters, directly from the geometry and physical characteristics of the device. The model also helps to understand and quantify some aspects of the behavior of the DBD discharge, like the decrease of breakdown voltage as the amplitude of the applied voltage increases, and how the fraction of area of dielectric covered with deposited charge determines the device performance. The theory was tested with experiments performed with a DBD operated in atmospheric air, with voltages from 14 to 22 kV peak to peak, and a frequency of 10 kHz. [ABSTRACT FROM AUTHOR]

Predicting the insulation performance of SF6 substitute gases through gas molecular structures has been a popular topic worldwide. There is a lack of research on the relationship between the critical reduced electric field and molecular structure under low pressure. The critical reduced electric field intensity and boiling temperature (BT) of gas are used as inputs to extract the important molecular structure parameters (MSPs) of gas at low pressure by using the maximum information coefficient (MIC) method. Through multivariate nonlinear fitting, the structure–activity relationship model of important MSPs of gas is established. The model is verified by the critical reduction strength and MSPs of C4F7N, CF3SO2F, and SF6 gases. The results show that the model has reliable predictive ability. In this study, the micro mechanism of gas discharge under low pressure and a dc electric field is revealed at the molecular level, and the insulation performance of gas is quantitatively predicted, providing a reference for the analysis of SF6 replacement gas performance. [ABSTRACT FROM AUTHOR]

Plasma created in focused beams of electromagnetic waves in the terahertz frequency range is a fairly new object in gas discharge physics. The specified range, located between the microwave and infrared regions of the spectrum of electromagnetic waves, is currently being actively developed. However, until recently, the study of discharge phenomena in it was practically inaccessible. Recent advances in its development are associated primarily with the creation of powerful sources of terahertz radiationâ€"gyrotrons and free electron lasers. This article presents an overview of the latest results of studies of a gaseous terahertz discharge: gas breakdown, discharge propagation, features of the discharge glow, and prospects for a gaseous terahertz discharge as a point source of UV radiation. [ABSTRACT FROM AUTHOR]

The study designs a type of plasma antenna array with four quartz fluorescent lamps, which can be classified into linear polarization and circular polarization (CP). The antenna arrays are designed into a self-phase-shifting cross shape, and the kHz alternating current power supplies are adopted in the proposed antenna arrays. Experimental results show that the cross vibrator antenna can realize not only impedance and pattern reconstruction, but also the polarization transformation. Moreover, the horizontal polarization, vertical polarization, and CP can be mutually transformed into each other by changing the vibrator operation mode. It is noted that we can easily transform the left-hand circular polarization and right-hand circular polarization into each other via modifying vibrator length and plasma density. Compared with a conventional metal antenna with the same shape, polarization conversion can be realized in an easier yet faster way via the help of self-phase-shifting plasma antenna array. [ABSTRACT FROM AUTHOR]

This letter studies the peak power handling capability (PPHC) in groove gap waveguide filters based on horizontally polarized resonators. Moreover, a modification of the resonant cavity is proposed, where the central pins of the original structure are replaced by a rounded metal block. As a result of this change, the TE101-like mode can still be excited, but the maximum electric field strength is shifted to the center of the cavity, which leads to a higher PPHC. The main advantages of the original structure are maintained, and greater robustness in the manufacturing process is achieved. Next, some guidelines for the design of the coupling windows and the dimensions of the blocks are shown to minimize the electric field strength and, consequently, maximize the PPHC. Finally, two third-order bandpass filters (with pins and with blocks) centered at 16 GHz have been manufactured and tested in a measurement campaign, where a PPHC enhancement of 8.7 dB at high pressures is achieved for the novel solution presented in this work. [ABSTRACT FROM AUTHOR]

For the development of negative streamer, a one dimension simulation is presented when a negative electric field is applied at atmospheric pressure to a 4 mm gap in nitrogen. At applied electric fields of 55, 60, 65 and 70 kV/cm, streamer parameters were studied at various time intervals. The aim of this paper is to determine the minimum electric field that must be applied for stable propagation of negative streamer discharge in nitrogen gas. As functions of position and time, the calculations provide detailed electron and ion density predictions, electric fields and density of space charges. The time interval was with a nanosecond resolution. Using 8000 element mesh to resolve the characteristics of the streamer, spatial resolution over the separation of electrodes 4 mm was obtained. The results were obtained by solving the equation of continuity for electrons and ions and the Poisson equation solution. [ABSTRACT FROM AUTHOR]

On the basis of the Monte Carlo method and the many particles dynamics, the ionization and drift characteristics of electrons in a constant field drifting in helium with a certain amount of iron vapor are calculated. The main attention is paid to the study of the influence of iron vapor concentration on the characteristics of escaping electrons. The formulation of the problem involves the death of electrons on the wall and the balance between the birth of ionization and leaving the escape mode (whiz). The obtained results indicate a sharp change in the ionization characteristics when an easily ionizable additive in the form of iron vapor is added to helium. Starting with a fraction of a percent of the concentration of iron atoms in helium, due to the strong ionization of iron atoms, there is a strong change in the electron distribution function, which leads to a significant increase in the frequency of ionization and a non-monotonic dependence of the number of escaping electrons on the concentration of iron vapors.