Arc Emission Research Articles

Characteristics of an AC rotating gliding arc discharge in NH3 and air atmospheres

Plasmas have emerged as a promising technology for the utilization of NH3 as a carbon-free fuel for direct plasmas-assisted combustion and hydrogen production. This study aims to explore the electrical and optical emission characteristics of the rotating gliding arc (RGA) discharge in NH3 and air swirling flows over a wide range of nominal power inputs. The electrical characteristics were measured using voltage–current probes, while a spectrometer was employed to assess the spectral characteristics. Additionally, a synchronized high-speed camera equipped with a dual-scope objective was utilized to capture transient phenomena of the arc in the optical emission spectrum. Both the spark-type and glow-type discharges were observed in RGA. Interestingly, the spark-type discharge frequency exhibited a non-monotonic variation with increasing nominal power inputs for both NH3 and air, while the glow-type discharge frequency displayed a monotonous upward trend. Regarding the spectral emission characteristics in NH3, a dramatic transition of the arc emission spectrum from Hα to NH2* was observed as nominal power inputs increased. The Hα and NH2* emissions that are dominated in the spark-type and glow-type discharges, respectively, and the intensity ratio of Hα and NH2* emission shows evident correlations with discharge current and electric field strength. In summary, this study represents the first investigation into the electrical and spectral characteristics of RGA in NH3.

Observation of the dynamic evolution process of vacuum arc microscopic particles based on the emission spectrum principle

The distribution of microscopic particles directly affects the recovery of the post arc insulating medium and determines whether the fault current can be interrupted. Based on the principle of vacuum arc emission spectrum, a high-speed spectrum observation platform was built to study the distribution of microscopic particles during the arc burning, and the axial and radial spectral line intensity and density distributions of atoms and ions under different current amplitudes were obtained. The results show that the CuI spectral line intensity has two peaks near the cathode and anode, while in the arc column it is relatively low. The peak of the CuI spectral line intensity near the electrode is caused by electrode evaporation. The peak duration of the CuI spectral line intensity near the cathode is always longer than that near the anode. The CuII spectral line intensity is lower, appears later and disappears earlier, which in the arc column increased obviously, compared with CuI. The CuII density near the cathode is higher than that near the anode, and the CuII density in the arc column is higher than in the two electrodes, which is similar to the axial distribution of electron density. The radial distribution curve of CuI and CuII density is similar to the radial distribution curve of spectral line intensity, and displays the characteristics of a high center and low edge in the radial direction of the arc gap. The difference is that the width of the atomic spectral line is larger than that of the corresponding ionic spectral line, the distribution curve of the ionic spectral line is smooth and symmetrical, and the radial attenuation rate of the CuII density is larger than that of the corresponding CuI. This reflects the ionization of atoms and the effect of magnetic fields. The radial and axial distribution of the particle density is opposite to that of the excitation temperature. Electrode emission will first affect the atom formation.

Studying the effect of the argon flow introduced into the arc discharge in the atomic-emission spectrometry of powdered samples using the spillage-injection method

Atomic emission spectral analysis of a powder sample by the method of spillage-injection into the plasma of an arc discharge burning in air is accompanied by the formation of cyanide, nitride and oxide compounds which form molecular bands in the spectrum thus impeding measuring the intensity of the analytical lines of the elements to be determined. Feeding an argon flow into the arc discharge can reduce the amount of spectral interference and increase the plasma temperature, which promotes more a complete evaporation of the analyzed sample injected into the arc discharge and, accordingly, increases the degree of ionization of the elements and the intensity of ion spectral lines. The aim of the study was to develop a device for argon introduction into the arc discharge zone and simultaneous sample delivery by a spillage-injection method, as well as to study the effect of argon consumption on arc discharge parameters and emission spectra of powder samples. The argon input device (up to 2.25 L/min) is developed on the basis on glass funnels, the geometric dimensions of which are selected with the goal of gaining the maximum intensity of spectral lines and reduced intensity of molecular bands at the minimal argon consumption. The study carried out on a «Grand Potok» spectrometer demonstrated that with an increase in argon consumption, the intensity of SiO molecular bands decreases, the plasma temperature increases by 350 – 540 K, and the intensity of ion and atomic lines with the ionization energy above 8 eV increases by more than 4.7 and 2.9 times, respectively. The developed device can be used in analysis of geological materials to improve the metrological characteristics of the results of atomic emission spectral analysis.

Control of emission diffraction angles and laser threshold in mixed-order sampled distributed feedback laser with organic gain media

The control of laser emission angles in laser devices is essential for many optoelectronic and photonic applications such as optical sensing and displays. In this context, we studied the light diffraction pattern of laser beams in a one-dimensional sampled distributed feedback resonator having organic gain media. The gratings consist of the repetition of supercells having a mixed-order sampled grating in which 1st-order gratings surround a 2nd-order grating. The experimental results showed that the diffraction angles of the laser beams are quite diverse depending on the supercell structures. We demonstrate that the interval of the diffraction angle (θ) of the laser beams is inversely proportional to the length of the supercell experimentally and theoretically. By tuning the length of supercells as well as the length of 1st-order and 2nd-order regions, the interval θ was tuned from 0.1° to 43° with the different arc emission patterns. With the reduction of θ, i.e., the longer 1st-order region, a significant decrease in the laser threshold was obtained, resulting in the lowest lasing threshold of 2.5 ± 0.1 μJ/cm2 with ∼3.5 ns of a long pulse width excitation source.

Research on the Characteristics of the Pantograph Arc and Analyzing its Influence on the ILS

In this article, a radiation model is proposed to estimate the emission of the pantograph arc. An improved least-square regression analysis method is given for studying the pantograph arc characteristics at various sites on electrified railways and at various train speeds. The radiation model and the improved least-square method were both validated using the test data. The impact of arc on the airport instrument landing system (ILS) was investigated using electromagnetic wave propagation theory and the signal-to-noise ratio requirement of the ILS. We deduced the position limit of the articulated neutral section (ANS) and verified it through experiments. This research provides a theoretical foundation and technological methodology for civil aviation and high-speed railway electromagnetic compatibility studies as well as helps for airport site selection and high-speed railway route planning.

A direct dc arc emission spectrometry determination of chlorine impurities in nuclear grade graphite

In the present study, the direct current arc atomic emission spectrometry (dc arc AES) method was proposed for direct determination of chlorine impurities in nuclear-grade graphites and graphite foils in the range of 1‐–100 ppm in order to meet nuclear power industry requirements. The procedure is based on near-infrared (NIR) AES approach for determination of non-metal impurities, contrary to the most common vacuum ultraviolet AES approach. Carbon dc arc in argon atmosphere was used as radiation source. This radiation source employs standard extra high purity 6 mm diameter standard shaped graphite electrodes and standard vertical spectroanalytic stand, but employs several improvements as well: special protective fused quartz tube, and specially built fiber optic refocuser. Registration of spectra was performed via a novel compact tunable spectrometer with linear complementary metal oxide semiconductor array (CMOS) detector. As the work in near-infrared spectral range is hampered by spectral interference factors, measures were taken to counter them. Due to specifics of the radiation source, the excitability of chlorine was studied both in air and argon in presence of carbon, as well as in its absence. Artificial standards for calibration of the spectrometer were prepared by mixing extra high purity NaCl and graphite powder and evaluated by two independent approaches: indirectly by dc arc AES determination of Na, and directly by water extraction and photometrical determination of Cl. The characteristics of evaporation and excitation in dc arc of chlorine from both standards and real nuclear graphite samples were studied due to the differences in the nature of chlorine source in them. The detection limit of was determined 0.8 μg/g. The whole cycle of measurement, including sample preparation is about 10 min.

Parallel and independent true random bitstreams from optical emission spectra of atmospheric microplasma arc discharge

AbstractIn this study, we propose the possibility of generating several parallel and independent random bitstreams from the time‐varying optical emission spectra of an atmospheric pressure air microplasma system. This is achieved by splitting the plasma arc emission into discrete wavelengths using an optical spectrometer and then monitoring the fluctuating intensities of each wavelength as an independent time series. As a proof of concept, we considered eight wavelengths centered at 377.8, 389.1, 425.8, 591.4, 630.5, 673.0, 714.2, and 776.4 nm corresponding to atomic emissions lines from species either from the surrounding atmospheric air gap or from the electrodes' materials. NIST SP 800‐22 statistical randomness tests and other statistical estimates (auto‐ and cross‐correlation analysis and binary vector similarity measures) are subsequently applied to the binarized data, and the obtained results confirm the possibility of generating several parallel and independent random bitstreams from the microplasma system. The data throughput is, however, relatively low with the optical setup we used, which can be improved using faster spectrometry.

Measuring the melt pool size in a wire arc additive manufacturing process using a high dynamic range two-colored pyrometric camera

Control of the melt pool size is necessary to achieve more homogenous material properties in wire arc additive manufacturing (WAAM). The melt pool size can be measured by camera imaging or temperature field measurement. The paper aims to investigate the feasibility of using a high dynamic range two-colored pyrometric camera (Pyrocam) for melt pool size measurement in a gas metal arc welding–based WAAM process. A set of band-pass filters is identified using spectroscopy analysis to reduce the optical arc emission while the melt pool remains visible. The fusion line is identified in temperature field images, the melt pool size is measured by an automated algorithm, and the results are compared with high-speed camera images. A possible correlation between melt pool size and the grain size is examined.

Discovery of a 30-degree-long ultraviolet arc in Ursa Major

Our view of the interstellar medium of the Milky Way and the universe beyond is affected by the structure of the local environment in the solar neighborhood. We present the discovery of a 30-degree-long arc of ultraviolet emission with a thickness of only a few arcminutes: the Ursa Major arc. This consists of several arclets seen in the near- and far-ultraviolet bands of the GALEX satellite. A two degree section of the arc was first detected in the Hα optical spectral line in 1997; additional sections were seen in the optical by the team of amateur astronomers included in this work. This direction of the sky is known for very low hydrogen column density and dust extinction; many deep fields for extragalactic and cosmological investigations lie in this direction. Diffuse ultraviolet and optical interstellar emission are often attributed to scattering of light by interstellar dust. The lack of correlation between the Ursa Major arc and thermal dust emission observed with the Planck satellite, however, suggests that other emission mechanisms must be at play. We discuss the origin of the Ursa Major arc as the result of an interstellar shock in the solar neighborhood.

Study on welding phenomena observation method based on arc and moltenpool light emission characteristics in visible and infrared wavelength region

Study on welding phenomena observation method based on arc and moltenpool light emission characteristics in visible and infrared wavelength region

Experimental Investigation on the Arc Characteristics and Arc Quenching Capabilities of C5F10O-CO2 Mixtures

C5F10O-CO2 mixtures are possible alternatives to SF6 - which has a high global warming potential - as the interruption medium in gas circuit breakers. This paper experimentally studies the arcing characteristics of C5F10O-CO2 mixture, with an experimental model with viewing windows, and measures the arc voltage, current and emission spectrum. The arc evolution process is captured with a high speed camera through an inspection window. The two-dimensional distribution of arc is obtained and analyzed by the inverse transformation of Abel. The results show that, the C5F10O-CO2 mixture arc is more volatile than SF6 gas, and adding C5F10O into CO2 improves the stability of the arc, and significantly reduces the arc temperature.

Study on welding phenomena observation method based on arc and molten pool light emission characteristics in visible and infrared wavelength region – development of image sensing technology for in-process welding monitoring technology

ABSTRACT Arc welding is important technology for manufacturing that is directly linked to quality and productivity. Especially GMAW with Ar or CO2 shielding gas is widely used in various industries because of its high productivity. To achieve high quality and productivity, in-process welding quality control technology will be required. In this study, the authors study the welding phenomena observing technology for online detection of welding defects by using image sensing method. By selecting the transmission wavelength of band-path filter 1320 nm, which is in the wavelength range where the brightness of arc light is weak and the brightness of molten pool light is high, welding phenomena just near arc and molten pool can be observed clearly.

Application of arc emission spectrometry and portable X-ray fluorescence spectrometry to rapid risk assessment of heavy metals in agricultural soils

Ecological risk assessment of soil is commonly performed by determining heavy metals (HMs) through conventional laboratory analysis, which is cost-, time- and labor-consuming, especially in large-scale agricultural soils. Therefore, appropriate cheaper and faster analytical methods of comparable accuracy are urgently required. In this study, rapid analyses of HMs were performed via Portable X-ray fluorescence (PXRF) spectrometry and arc emission spectrometry (AES) in agricultural soils from a representative greenhouse vegetable area on the east bank of Dianchi Lake in Kunming City, Yunnan Province, southwest of China. Here AES was specifically used as a replacement of PXRF for measuring Cd in soil because the measurement limit of PXRF for Cd is usually higher than the normal content of Cd in agricultural soils. The performances of rapid analysis and conventional laboratory analysis were compared and evaluated, and ecological risk was assessed with the Nemerow composite pollution index for classifying HM contamination grades and Kriging interpolation for mapping spatial variation. Results showed that the PXRF and AES were applicable and accurate with the relative standard deviation (RSD) and the relative percent difference (RPD) for HMs being within 20%. Significant positive correlations were found between the rapid analysis results and conventional laboratory analysis results for both certified reference materials and collected soil samples. The classification of soil HM contamination grades and their spatial patterns were similar between the rapid analysis and laboratory analysis. Overall, results of the rapid analysis were almost identical to those of conventional laboratory analysis. Therefore, rapid HM analysis using PXRF and AES is effective and economic for accurately assessing ecological risk of agricultural soils in greenhouses.

Dc arc emission analysis of rare earth metals and their oxides with sorption preconcentration of impurities

The analytical capabilities of arc atomic emission determination of As, Bi, Sb, Cu, Te in rare earth metals (REM) and their oxides after preparatory group concentration using S,N-containing heterochain polymer sorbent are studied on a high-resolution spectrometer “Grand- Extra” (“WMC-Optoelectron-ics” company, Russia). Sorption kinetics and dependence of the degree of the impurity extraction on the solution acidity are analyzed to specify conditions of sorption concentration. To optimize the procedure of arc atomic emission determination of As, Bi, Sb, Cu, and Te various schemes of their sorption preconcentration and subsequent processing of the resulted concentrate with the addition of a collector at different stages of the sorption process have been considered. Graphite powder is used as a collector in analysis of rare earth oxides due to universality and relative simplicity of the emission spectrum. Conditions of analysis and parameters of the spectrometer that affect the analytical signal (mass and composition of the sample, shape and size of the electrodes, current intensity and generator operation mode, interelectrode spacing, wavelengths of the analytical lines) are chosen. The evaporation curves of the determinable impurities were studied and the exposure time of As, Bi, Sb, Cu, and Te in the resulted sorption concentrate was determined. Correctness of the obtained results was evaluated using standard samples of the composition and in comparisons between methods. The results of the study are used to develop a method of arc chemical-atomic emission analysis of yttrium, gadolinium, neodymium, europium, scandium and their oxides in a concentration range of n x (10-2 - 10-5) wt.%.

Flame : A flexible data reduction pipeline for near-infrared and optical spectroscopy

We present flame, a pipeline for reducing spectroscopic observations obtained with multi-slit near-infrared and optical instruments. Because of its flexible design, flame can be easily applied to data obtained with a wide variety of spectrographs. The flexibility is due to a modular architecture, which allows changes and customizations to the pipeline, and relegates the instrument-specific parts to a single module. At the core of the data reduction is the transformation from observed pixel coordinates (x, y) to rectified coordinates (lambda, gamma). This transformation consists in the polynomial functions lambda(x,y) and gamma(x,y) that are derived from arc or sky emission lines and slit edge tracing, respectively. The use of 2D transformations allows one to wavelength calibrate and rectify the data using just one interpolation step. Furthermore, the gamma(x,y) transformation includes also the spatial misalignment between frames, which can be measured from a reference star observed simultaneously with the science targets. The misalignment can then be fully corrected during the rectification, without having to further resample the data. Sky subtraction can be performed via nodding and/or modeling of the sky spectrum; the combination of the two methods typically yields the best results. We illustrate the pipeline by showing examples of data reduction for a near-infrared instrument (LUCI at the Large Binocular Telescope) and an optical one (LRIS at the Keck telescope).

Experimental study on ignition characteristics of kerosene–air mixtures in V-shaped burner with DC plasma jet igniter

In this paper, we investigate the effects of DC plasma jet igniter on ignition characteristics of the kerosene–air mixtures in V-shaped burner. The primary principles of DC plasma igniter design have been put forward to prolong the igniter life and improve ignition performance. The main characteristic of plasma igniter is that the anode arc root is fixed at anode nozzle outside surface other than the anode inner surface in conventional design. The electric characteristics of the plasma jet igniter including voltage–current characteristics, the arc column propagation, emission spectrum and anode arc root movement in a quiescent environment are investigated with high speed CCD together with a recording of the voltage and current. The entire ignition process of the plasma jet igniter is recorded by high speed CCD and the ignition delay times of the kerosene–air mixtures defined by the interval between the onset of the plasma igniter and the establishment of a stable flame are measured with two photomultipliers with one of 10 mm band pass filter centered at 780 mm (the plasma igniter emission spectrum of OI) and the other of 10 mm band pass filter centered at 430 mm (direct flame emission of CH(A2Δ→X2Π)). Results show that the plasma igniter works in a restrike mode and the anode spot movement is irregular. The plasma igniter jet contains abundance active particles inferred from the emission spectrum. The ignition delay times increase at first and then decrease with the increase of excess air coefficient ranging from 0.91 to 6.38. The delay times increase quickly when the mixtures are extremely lean or rich.

Identifying the 630 nm auroral arc emission height: A comparison of the triangulation, FAC profile, and electron density methods

AbstractWe present a comprehensive survey of 630 nm (red‐line) emission discrete auroral arcs using the newly deployed Redline Emission Geospace Observatory. In this study we discuss the need for observations of 630 nm aurora and issues with the large‐altitude range of the red‐line aurora. We compare field‐aligned currents (FACs) measured by the Swarm constellation of satellites with the location of 10 red‐line (630 nm) auroral arcs observed by all‐sky imagers (ASIs) and find that a characteristic emission height of 200 km applied to the ASI maps gives optimal agreement between the two observations. We also compare the new FAC method against the traditional triangulation method using pairs of all‐sky imagers (ASIs), and against electron density profiles obtained from the Resolute Bay Incoherent Scatter Radar‐Canadian radar, both of which are consistent with a characteristic emission height of 200 km.

Study of the AC arc discharge characteristics over polluted insulation surface using optical emission spectroscopy

Flashover of contaminated insulators is one of the major problems for the power distribution. Laboratory experiments have shown that the arc characteristics have great influences on the study of flashover performance of contaminated insulators. In order to investigate the characteristics of AC arc discharge on the polluted insulation surface, an experimental system was designed. The emission spectroscopy of arc discharge was obtained by a CCD spectrometer, and lithium chloride was added in the artificial pollution to introduce lithium as the indicator element in the analysis of arc emission spectroscopy. Arc temperature was obtained by employing the relative line intensities method, and the electron density was determined by analyzing the Stark-broadening values of the profiles. It was indicated that the temperature of partial arc increased with the leakage current value, but electron density of partial arc barely changes with leakage current. Special attention was paid to the influence of gas pressure on the characteristics of partial arc. It was found that both the arc temperature and the electron density of the arc channel increased with pressure in the case of same leakage current.

Analysis of Arc Emission Spectra of Stainless Steel Electric Arc Furnace Slag Affected by Fluctuating Arc Voltage

Control of chromium oxidation in the electric arc furnace (EAF) is a significant problem in stainless steel production due to variations of the chemical compositions in the EAF charge. One potential method to control chromium oxidation is to analyze the emission spectrum of the electric arc in order to find indicators of rising chromium content in slag. The purpose of this study was to determine if slag composition can be gained by utilizing electric arc emission spectra in the laboratory environment, despite electric arc voltage fluctuations and varying slag composition. The purpose of inducing voltage fluctuation was to simulate changes in the industrial EAF process. The slag samples were obtained from Outokumpu Stainless Oy Tornio Works, and three different arc currents were used. The correlation analysis showed that the emission spectra offer numerous peak ratios with high correlations to the X-ray fluorescence-measured slag CrO(x)/FeO(x) and MnO/SiO2 ratios. These ratios are useful in determining if the reduction agents have been depleted in the EAF. The results suggest that analysis of laboratory-scale electric arc emission spectra is suitable for indicating the high CrO(x) or MnO content of the slag despite the arc fluctuations. Reliable analysis of other slag components was not successful.

XMM–Newton observations of the Galactic Centre Region – II. The soft-thermal emission

We have extended our earlier study (Heard & Warwick 2013, Paper I) of the X-ray emission emanating from the central 100 pc x 100 pc region of our Galaxy to an investigation of several features prominent in the soft X-ray (2-4.5 keV) band. We focus on three specific structures: a putative bipolar outflow from the vicinity of Sgr A*; a high surface brightness region located roughly 12 arcmin to the north-east of Sgr A*; and a lower surface-brightness extended loop feature seen to the south of Sgr A*. We show that all three structures are thermal in nature and have similar temperatures (kT ~ 1 keV). The inferred X-ray luminosities lie in the range (2 - 10) x 10^34 erg s^-1. In the case of the bipolar feature we suggest that the hot plasma is produced by the shock-heating of the winds from massive stars within the Central Cluster, possibly collimated by the Circumnuclear Disc. Alternatively the outflow may be driven by outbursts on Sgr A*, which follow tidal disruption events occurring at a rate of roughly 1 every 4000 yr. The north-east enhancement is centred on a candidate PWN which has a relatively hard non-thermal X-ray spectrum. We suggest that the coincident soft-thermal emission traces the core of a new thermal-composite supernova remnant, designated as SNR G0.13-0.12. There is no clear evidence for an associated radio shell but such a feature may be masked by the bright emission of the nearby Radio Arc and other filamentary structures. SNR G0.13-0.12 is very likely interacting with the nearby molecular cloud, G0.11-0.11, and linked to the Fermi source, 2FGL J1746.4-2851c. Finally we explore a previous suggestion that the elliptically-shaped X-ray loop to the south of Sgr A*, of maximum extent ~45 pc, represents the shell of a superbubble located in the GC region. Although plausible, the interpretation of this feature in terms a coherent physical structure awaits confirmation.