Discharge Emission Research Articles

X-ray emission from a nanosecond-pulse discharge in an inhomogeneous electric field at atmospheric pressure

This paper describes experimental studies of the dependence of the X-ray intensity on the anode material in nanosecond high-voltage discharges. The discharges were generated by two nanosecond-pulse generators in atmospheric air with a highly inhomogeneous electric field by a tube-plate gap. The output pulse of the first generator (repetitive pulse generator) has a rise time of about 15 ns and a full width at half maximum of 30–40 ns. The output of the second generator (single pulse generator) has a rise time of about 0.3 ns and a full width at half maximum of 1 ns. The electrical characteristics and the X-ray emission of nanosecond-pulse discharge in atmospheric air are studied by the measurement of voltage-current waveforms, discharge images, X-ray count and dose. Our experimental results showed that the anode material rarely affects electrical characteristics, but it can significantly affect the X-ray density. Comparing the density of X-rays, it was shown that the highest x-rays density occurred in the diffuse discharge in repetitive pulse mode, then the spark discharge with a small air gap, and then the corona discharge with a large air gap, in which the X-ray density was the lowest. Therefore, it could be confirmed that the bremsstrahlung at the anode contributes to the X-ray emission from nanosecond-pulse discharges.

Surface charge accumulation and discharge development in diffuse and filamentary barrier discharges operating in He, N2 and mixtures

A new discharge cell configuration was developed which allows the joint investigation of important volume and surface processes of the barrier discharge (BD) operation. In particular, the spatio-temporal and spectrally resolved discharge emission in the volume was studied together with the temporally resolved formation of surface charges on a dielectric BSO crystal. This was possible by the application of the cross-correlation spectroscopy and the electro-optic Pockels effect for surface charge measurement, respectively. Surface charges play an important role for the re-ignition of BDs. In pure nitrogen and helium, the diffuse Townsend-like discharge mode was studied, characterized by an emission maximum near the anode. Small admixtures of nitrogen to helium resulted in the filamentary discharge operation. Under these conditions, the importance of the so-called memory effect has been verified.The lateral extent of the discharge spots in the filamentary mode differs significantly for the positive and negative charges. Both can be approximated by Gaussian profiles. The deposited surface charges are in good agreement with the transferred charge of subsequent discharge breakdowns.

Watershed-based riverine discharge loads and emission factor of perfluorinated surfactants in Korean peninsula

Long-range transport of and exposure to perfluorinated substances (PFSs) strongly depend on their emission mode. In the present study, watershed-based riverine discharge loads and emission factors are estimated for perfluorooctanoate (PFOA), perfluorononanoate (PFNA), perfluorohexylsulfonate (PFHxS), and perfluorooctylsulfonate (PFOS) by using spatially distributed data of chemical concentrations together with water flows and a geographic information system (GIS). Average per capita emissions (emission factor, μg capita−1d−1) are 75 for PFOA, 36 for PFNA, 17 for PFHxS, and 43 for PFOS, which are several times lower than the estimates for Japan and the European continent. A relatively uniform distribution is observed for PFHxS and PFOS emission factors, while elevated values of PFOA and PFNA predominate in one of eight river basins. This may indicate the leading contribution of diffusive sources (e.g. nonpoint source) for PFHxS and PFOS versus the presence of localized point sources for PFOA and PFNA. The lower–upper bound of total riverine loads discharged annually from the Korean peninsula are in the range of 0.53–1.3tons for PFOA, 0.09–0.60tons for PFNA, 0.07–0.29tons for PFHxS, and 0.19–0.73tons for PFOS, accounting for <1% of global annual emissions. Furthermore, these riverine discharge loads are significantly greater than the discharge loads from a wastewater treatment plant, indicating the necessity of further study of nonpoint sources.

Numerical simulation for production of O and N radicals in an atmospheric-pressure streamer discharge

A streamer discharge model is developed to analyse the characteristics of a pulsed positive streamer discharge in point-to-plane electrodes filled with oxygen–nitrogen mixed gas at room temperature and atmospheric pressure. In this paper we study the mechanisms of O and N radical production in an atmospheric-pressure streamer discharge. To confirm the validity of the simulation model, the discharge emission of light and the discharge current are compared with experimental data at several voltages in gas mixtures with 2–20% oxygen concentrations. The calculated streak picture and the axial distribution of streamer luminous intensity are in good agreement with our previous experimental results. After demonstrating the reliability of the model, we performed a numerical study on radical production by the streamer discharge. The experimentally obtained axial distributions of oxygen radical production in O2(20%)/N2 and nitrogen radical production in O2(2%)/N2 are successfully reproduced in our simulation. For the production of nitrogen radicals, two-step dissociation through the vibrationally excited states is predominant.

VUV Enhanced XeF2 Fluorination of Polymer Surfaces

Exposure of polyethylene and polystyrene to xenon difluoride (XeF2) in the presence of vacuum ultraviolet (VUV) irradiation emitted from O2,N2, Ar, Kr and Xe electrical discharges gives rise to surface fluorination. The extent of reaction is found to be governed by the synergistic effect between the VUV absorption characteristics of the XeF2 feed gas and the polymer substrate. Polystyrene in combination with krypton electrical discharge emission lines yields the most fluorinated surface.

OH density measurement by time-resolved broad band absorption spectroscopy in an Ar–H2O dielectric barrier discharge

We report results of a novel time-resolved broad-band absorption spectroscopy experiment for OH density measurement applied to a pulsed dielectric barrier discharge in Ar/H2O mixtures. The measurement is aimed at the calibration of our previous OH LIF measurements in the same discharge. The apparatus is simple and cheap, being based on a UV LED light source and a non-intensified, non-cooled, gateable linear CCD array as a detector. The set-up is capable of ruling out both medium/long-term drifts of the UV source and of the discharge, and discharge emission from the measurement. Performances of the set-up are discussed, together with possible improvements for its use as a standalone technique.

Effect of voltage and capacitance in nanosecond pulse discharge enhanced laser-induced breakdown spectroscopy

The laser ablation fast pulse discharge plasma spectroscopy (LA-FPDPS) technique has demonstrated its validity to enhance the optical emission of laser-induced plasma. It has the potential to improve the performance of traditional LIBS measurement. Very recently, LA-FPDPS with a nanosecond pulse discharge circuit has been developed, which has a better capability to enhance the optical emission intensity of laser plasma compared with that using a microsecond pulse discharge circuit. In this paper, the effect of the discharge capacitance and discharge voltage on the optical emission of soil plasma generated by LA-FPDPS with a nanosecond pulse discharge circuit is evaluated in detail. In addition, the stability of the time delay between the laser firing and discharge, and between the discharge and optical emission, has been carefully investigated.

Plasma diagnostics of barrier-torch discharge in argon flow in a capillary by cross-correlation spectroscopy

The radiation kinetics of the plasma of barrier-torch disrcharge in argon flow in a capillary has been studied by cross-correlation spectroscopy. It was established that the discharge emission spectrum consists of peaks of electronically excited states of argon, bands of hydroxyl radicals, and a second positive system of nitrogen. An analysis of the spatio-temporal distributions of emission intensity for the selected spectral indicators showed that the causes of the torch are ionization waves that extend through the capillary from the electrode system with a speed of 105 m/s and project up to 3–4 mm. It was established that the formation of electronically excited molecules of nitrogen N2(C3Πu) in the torch of discharge occurs mainly on the reaction between metastable electronically excited atoms of argon and molecules of nitrogen in the electronic ground state.

Micromorphology and histochemical traits of staminal osmophores in Asphodelus aestivus Brot. flower

The conducted studies pertained to micromorphology of the surface of epidermis cells and histological traits of staminal filaments of &lt;i&gt;Asphodelus aestivus&lt;/i&gt; Brot. flowers. The structure of the filaments was analyzed in a light microscope (LM) using various histochemical techniques. The morphology of the surface of the epidermis of filaments was observed in scanning electron microscope (SEM). Filaments &lt;i&gt;Asphodelus aestivus&lt;/i&gt; accrete together with the basal part of the abaxial surface with the leaves of perianth. Their lower, wider, and flattened part surrounds the ovary. The epidermis of the staminal osmophores creates papilliose cells and unicellular hairs of various sizes. In the uppermost part of these structures, round marks in the cuticle layer after the emission of discharge were observed with the SEM. The outside, convex wall of the isodiametric cells of the epidermis, papillae and hairs was significantly thicker from the remaining walls. It was covered with cuticle of different ornamentation. The cells that created papillae and hairs had a large, centrally located vacuole and a thin layer of cytoplasm with numerous small vacuoles as well as large, often lobed nuclei. In the protoplasts of these cells the presence of plastids and lipid droplets was noted. During the time of secretion of elicitor between the wall and cuticle of the epidermis cells, convex bubbles were formed, in which the secreted substance was accumulated. At the end of secretion, on the surface of papillae, hairs and other cells of the epidermis, irregularly protruding cuticle was observed. It was noted that the composition of staminal osmophores in the flowers of &lt;i&gt;Asphodelus aestivus&lt;/i&gt; includes papillae, hairs and cells of the epidermis that do not form papillae.

Effects of Controlled and Mid-gathering Irrigation Mode of Paddy Rice on the Pollutants Emission and Reduction

The experiment was carried out in Nanjing Vegetables (Flowers) Scientific Institute with 4 kinds of irrigation and drainage treatments, rice field discharge, nitrogen concentration and total nitrogen emissions in drainage water were studied during the rice growth period. The results showed that discharge in controlled and mid-gathering irrigation reduced by 23.8% -27.7% compared with the other three treatments, It also showed that the total emissions of pollutants in drainage discharge reduced significantly, of which the reduction of NH4+-N reached by 29.1-33.3% and NO3--N reached by 34.3% -51.3% compared with the other three treatments. The results indicated that controlled and mid-gathering irrigation had good environmental effects through accumulating rainfall, achieving the effect of water and fertilizer conservation and reducing pollutant emissions.

Monochromatization effect kinetic model for Penning gas mixtures emission mechanisms

The monochromatization effect (M-effect), which consists in the reduction of an electronegative-electropositive gas mixtures discharge emission spectrum to only a few or a single line, was largely explained in our previous published papers together with their generation mechanisms, namely the polar ion-ion recombination and the energy resonance condition. This paper presents a kinetic model for the M-effect based on the radiative and collisional processes which appear between 1s_2, 1s_3, 1s_4 and 1s_5 Paschen levels, in Penning gas mixtures, where this effect was observed to be the most powerful.

Effect of Emitters' Discharge and Operation Pressure on some Evaluation Parameters of Drip Irrigation System

A field experiment was achieved at Al-Saqlawia Discreet / Al-anbar Province to study the effect of operation pressure and emitters' discharge on each of discharge variations, uniformity coefficient, and emission uniformity. Turbo type of emitters was chosen with two designed discharges , namely; 4 and 8 L.hr ˉ ¹. While the irrigation system was operated with three operation pressures , namely; 30, 40 and 50 Kpa. Actual discharge of emitters was measured, which discharge rates, discharge variation, uniformity coefficient and emission uniformity were calculated. The results showed that 50 Kpa operation pressure gave a nearest values for design discharge of emitters reached to 3.94 and 7.88L.hr ˉ ¹. Also, uniformity coefficient, emission uniformity and discharge variation values were the best values 96.77, 95.69, 9.64% and 96.21, 95.81, 9.58% which used, respectively.

Dynamics of HiPIMS Discharge Operated in Oxygen

We report on time- and species-resolved plasma imaging analysis of high-power impulse magnetron sputtering discharge operated above a Cr target in pure oxygen. It was found that the discharge emission is dominated by oxygen species. No metal-dominated sputtering has been detected, in contrast to the discharges in Ar, N2, and N2/Ar mixtures investigated previously.

Effects of Voltage–Current Characteristics on the Discharge Images in an Arc Reformer

Effects of voltage-current characteristics on the discharge and optical emission images are investigated in an arc reformer driven by two kinds of power supplies with different operational regimes. The results indicate that the voltage-current characteristics greatly influence not only the discharge image but also the plasma chemistry. High-voltage low-current operation attains a longer plasma jet and thus higher CH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> and CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> conversions than high-current low-voltage operation, particularly in the low-power regime.

Pulsed Discharge in Helium and Nitrogen Bubbles in Humate Solution

In this paper, we show images of pulsed discharges in helium and nitrogen bubbles in humate solution. The characteristics of the pulsed discharges in the solution depend on the gas atoms and molecules, the configuration of bubbles in the solution, and the gap length between the bubbles. The colors of the discharge emitted from helium and nitrogen bubbles were red and purple, respectively. In contrast, the color of the discharge emitted between bubbles is white, regardless of the kind of the gas in the bubbles. White discharge emission is radiated from the arc discharge generated between bubbles.

Time-Resolved PLIF Imaging of OH Radicals in the Afterglow of Nanosecond Pulsed Discharge in Combustible Mixtures

A time-resolved planar laser-induced fluorescence (PLIF) imaging technique has been used to investigate the spatial distribution of OH radical dynamics in the afterglow of a pulsed nanosecond discharge. Experiments were carried out using a lean methane/air mixture, at temperatures of 300 K and 500 K and at atmospheric pressure. The nanosecond pulsed discharge was formed in a pin-to-pin electrode system. Time-resolved PLIF imaging indicated uniform OH radical dynamics along the discharge channel. Comparison of OH radical emission dynamics with discharge emission dynamics from excited nitrogen revealed a close similarity in spatial distribution and allowed to clarify the mechanisms of atomic oxygen formation.

Light emission phenomena in dechlorination process of polychlorinated biphenyls by irradiating microwave

In recent years, an effective processing for PCBs (polychlorinated biphenyls) diluted in insulating oil has been developed, which can render PCBs harmless by their dechlorination using microwave of 2.45 GHz. The authors discovered optical emission of electrical discharge during the processing. To clarify how the emission is involved in the decomposition of PCBs, the emission spectra are two-dimensionally observed with interference filters. The observation reveals the generation of excited hydrogen atoms and ultraviolet photons, both of which accelerate the PCBs dechlorination, and suggests the presence of the electric-field effect of microwave other than its heat effect.

Effect of Electron Density on Extreme Ultraviolet Output of a Z-Pinch Xe Discharge Produced Plasma Source

The extreme ultraviolet (EUV) source has many applications, including EUV lithography, EUV diagnostics, and so on. Numerous research groups have developed many EUV light sources and studied their characteristics. In this paper, we measured the temporal EUV emission of a Xe discharge produced plasma (DPP) EUV source and later, attempted to clarify the relationship between electron density evolution and EUV emission. The maximum EUV emission occurred at the optimum electron density of about 1019 cm-3. A preliminarily discussion of the relationship between EUV radiation and electron density evolution based on these experimental results is presented.

Dark phase effect in the evolution of the positive column of a glow discharge in nitrogen

The characteristics of the initial stage of the formation of the positive column of a glow discharge in nitrogen at reduced pressures are studied experimentally and numerically. A dip in the plasma emission intensity in the initial stage of the discharge (the so-called “dark phase”) is observed experimentally at the positive polarity of the high-voltage electrode (the cathode is grounded). The dark phase is preceded by an ionization wave (IW). When the anode is grounded, neither an IW nor a dip in the discharge emission intensity are observed. A theoretical model capable of describing the discharge development under the actual experimental conditions is constructed. It is shown that the dark phase effect may be caused by the high electron density (above the steady-state one) produced in the gas during the passage of the IW across the discharge gap. This mechanism of the dark phase formation differs from the mechanism proposed earlier to explain a similar effect in noble gases. Additional experiments carried out with pure argon, helium, and helium with a nitrogen admixture have shown that, in the case of a grounded cathode, gas breakdown is also accompanied by the passage of an IW, whereas in the case of a grounded anode, no IW is observed; however, the dark phase is present in both cases. It is shown using computer simulations that, in nitrogen (in contrast to noble gases), the mechanism resulting in the dark phase effect does not operate in the absence of an IW.

Development and Application of Eco-Friendly Concrete

Concrete is the most popular construction material. In its lifetime, natural resources such as limestone and aggregate are consumed. Meanwhile, emission of air pollutants and discharge of waste concrete in large quantities are of great concern. However, in recent years, high performance concrete and new types of concretes have been developed to decrease the environmental burden in its lifespan or in production phase, to utilize a substantial amount of recycled industrial waste, and to improve local environment. These eco-friendly concretes are classified into environmental protection type such as high performance concrete and recycled concrete, and environmental creation type such as porous concrete used for planting and air-purifying concrete with TiO2coating. This paper introduces the concept of eco-friendly concrete and summarizes present technologies and application.