Discharge Emission Research Articles

Effects of plasma emission on optical properties of phosphor layers in surface-type alternate current plasma display panel

This study uses helium and xenon gas mixture discharges to determine the effects of helium plasma emission on the characteristics of the visible emission from the stimulation of the red, green, and blue (RGB) phosphor layers in a surface-type alternate current plasma display panel. With a mixture of less than 2% xenon to helium, it was found that the luminance of the RGB phosphor layers decreases with a decrease in the helium plasma emission intensity. However, with a mixture of above 2% xenon to helium, the luminance of the RGB phosphor layers increases regardless of a decrease in the helium plasma emission intensity. Furthermore, the color purity of the RGB phosphor layers improves as the helium plasma emission intensity decreases. Accordingly, it can be concluded that the optical properties of the phosphor layers, including color purity and luminance, depend on the helium plasma discharge emission as well as the visible emission from the stimulation of the phosphor layers.

Spatial structure of emission from an electrode microwave discharge in hydrogen

The structure of electrode microwave (2.45 GHz) discharges in hydrogen with electrodes of various shapes and sizes at pressures of 1–8 torr and incident powers of 2–150 W is studied. It is found that the discharges exhibit a common feature that is independent of the antenna-electrode design: near the electrode surface, there is a thin bright sheath surrounded by a less bright, sharply bounded region, which is usually shaped like a sphere. It is suggested that the structure observed arises because the microwave field maintaining the discharge is strongly nonuniform. Near the electrode, there exists a thin dense plasma sheath with a high electron density gradient. A strong dependence of the electron-impact excitation coefficient on the electric field makes the effect even more pronounced. As the electron density decreases due to dissociative recombination, the microwave field gradient decreases and the discharge emission intensity tends to a nearly constant value. Presumably, in the boundary region of the discharge, there exists a surface wave, which increases the emission intensity at the periphery of the discharge.

Development and characterization of chlorine-selective pulsed discharge emission detector for gas chromatography

A novel chlorine-selective pulsed discharge emission detector (Cl-PDED) for gas chromatography has been developed based on a reaction of krypton with chlorine and a unique design of the detector. A krypton ion produced in the krypton-doped helium pulsed discharge reacts with chlorinated compounds within the pulsed discharge to produce an excited species of KrCl* which emits at 221∼222 nm. The reaction has the following advantages in respect to the detection of chlorinated compounds: (1) the reaction is an ion–molecule reaction that is 100–1000 times faster than a reaction of neutrals, which greatly enhances the sensitivity; (2) the KrCl* emission wavelength is far separated from interfering C emissions at 193. and 247.3 nm; (3) the KrCl* emission is transparent to air and can be recorded without a helium purge of the monochromator. The detector itself has been designed to have the following features: (1) the detector has a microvolume of the pulsed discharge region, ca. 0.35 μl, which increases the discharge power density to enhance the sensitivity; (2) this microvolume detector allows the use of a low flow-rate of ∼5 ml/min, which enhances the sensitivity by the lower dilution of the column effluent; (3) the pulsed discharge is sufficiently narrow to replace the monochromator entrance slit, which gives much greater light gathering power; (4) the discharge electrodes are protected with a helium purge to prevent carbon deposition on the electrodes. This new Cl-PDED is the most sensitive chlorine-selective detector with a minimum detectability of ∼50 fg Cl/s. The selectivity to carbon is 1000. There are no significant carbon emission lines in the KrCl* emission wavelength region, but the carbon continuum interference (stray light) limits the selectivity. The selectivity could be increased if a double monochromator were used to diminish the stray light. The detector linear range is over three orders of magnitude from 40 fg Cl to ∼130 pg Cl, and the dynamic range is ∼4 orders of magnitude. The relative standard deviation of the elemental response to chlorinated compounds is about 5%.

Pulsed discharge emission detector: an element-selective detector for gas chromatography

An element-specific pulsed discharge emission detector (PDED) has been coupled directly with a vacuum UV monochromator so that vacuum UV atomic emissions from Cl, Br, I and S can be observed. The observed sensitivities for the elements are in the range of mid to high pg/s, but can be lowered by direct absorption of the radiation using a vacuum UV radiation photomultiplier tube. A helium pulsed discharge photoionization detector (He-PDPID) was run simultaneously in parallel with the PDED. The chromatograms recorded with the two detectors had similar peak shapes, suggesting that there is no peak tailing in the PDED. The ratio of the detector responses PDED/He-PDPID can be used for qualitative identification of the Cl-, Br-, I- or S-containing compounds.

Applications using the chlorine-selective pulsed discharge emission detector

The use of the chlorine-selective pulsed discharge emission detector (Cl-PDED) for the GC analyses of EPA mixtures 502, 612, 624, organochlorine pesticides, and polychlorinated biphenyls has been demonstrated. The Cl-PDED is the most sensitive chlorine-selective detector with a minimum detectability of 50 fg Cl/s. A constant response/pg Cl was observed for these mixtures regardless of the number of Cl atoms/molecule and structure of the compound to which the Cl atoms are attached. The analysis of standard samples of polychlorinated biphenyls using the Cl-PDED have sensitivities comparable to those of the electron-capture detector; however, the predictable response/pg Cl from the Cl-PDED is preferred over the extremely variable response from the electron capture detector.

Characterization of chlorinated compounds using a dual chlorine-selective pulsed discharge emission detector–helium-pulsed discharge photoionization detector system

The Cl-selective pulsed discharge emission detector (Cl-PDED) response is dependent only upon the Cl content, irrespective of the molecular structures of the compounds. This provides a simple, fast quantitative method of analysis for chlorinated compounds. The response of the helium-pulsed discharge photoionization detector (He-PDPID) is a function of the molecular structure and the number of photoionizable electrons using the He 2 band at 13.5–17.5 eV. The ratio of the responses of the two detectors is independent of concentration and can be used to characterize the Cl-containing compounds along with the retention time, or the ratio can be used as evidence for coelution. The dual Cl-PDED–He-PDPID detector system is a useful tool for peak identification. The effect of coeluting hydrocarbons on the Cl-PDED response was evaluated by spiking a gasoline sample with US Environmental Protection Agency mixture 502. All Cl-PDED responses were greater than 90% of the response in the absence of the hydrocarbons.

大気圧バリア放電におけるコロナ‐グロー混在状態の定量評価

Corona-glow mixed conditions of an atmospheric-pressure barrier discharge in air and nitrogen gases were estimated quantitatively. To quantify the discharge conditions, electrostatic patterns remained on the barrier electrode surface. The patterns, called dust-figures, were produced by a color toner. The complexity of the electrostatic pattern was defined by (outline)2/area. Effective discharge power and discharge emission were estimated using Q-V Lissajous' method and an image intensifier, respectively. The difference between discharge conditions in air and nitrogen could be distinguished using the complexity and the area of the electrostatic pattern on the barrier electrode surface. The difference in discharge conditions with varied discharge gaps was also estimated quantitatively. Further, in the region of complexity from 0 to 20k, it seems that the corona-glow mixed conditions can be defined quantitatively. The quantification method for discharge conditions established in this work is extremely useful in improving the electrode composition, the material for the barrier layer, the frequency and shape of the driving voltage, etc. in an atmospheric-pressure barrier discharge system.

Investigations of the effect of hydrogen in an argon glow discharge

Clear evidence of the effects caused by hydrogen, introduced in different forms in an analytical glow discharge source (GDS) operated with argon, is presented for the different matrix elements copper, stainless steel, titanium, aluminium and silicon. When hydrogen is present even in small quantities in argon, not only are there significant changes in the emission line intensities of most elements (analyte and plasma species), but also new spectral features, such as emission bands of new compounds (hydrides of sputtered sample constituents) and a continuous background in the range ~220–440 nm. Moreover, the discharge current (the dependent parameter in our experiments) decreases with increasing hydrogen concentration. Different modes of hydrogen introduction, externally in gaseous form or sputtered as a sample constituent, cause very similar effects in terms of discharge current, line intensity (of analyte and plasma gas) and emission continua, which implies similar changes in the discharge processes in the two cases. The excitation of the hydrogen continuum appears to quench the population of the argon metastables (11.55 and 11.72 eV) and, consequently, other elementary processes in the plasma in which the argon metastables take part, but to a different extent for each analyte.

Cathode fall-dominated Ar discharge: Transient and steady-state experiments

The time-dependent transition of an Ar discharge from a low-current diffuse or Townsend discharge to a moderately high-current diffuse or abnormal discharge is investigated. We measure the current, voltage, and optical emission transients after a high-voltage pulse is superimposed on the direct current voltage of the low-current discharge. Emission transients are obtained near the cathode, at the end of the steady-state cathode fall, and near the anode. Spatial scans of absolute optical emission at the 750 and 811 nm lines are taken during the development of the cathode fall. These data show the initial growth of current and emission while the electric field is essentially uniform; the early minimum in emission near the anode marking the collapse of the electric field; the motion toward the cathode of the peak of emission; the drop in the discharge voltage, current, and emission during the approach to the steady-state; and the spatial distribution of emission from the steady-state discharge. Measurements are for pressure times electrode separations from 0.5 to 2 Torr cm and steady-state current densities of 500–100 μA/cm2, respectively. The initial rate of rise of the discharge voltage is roughly 100 V/μs and the times required to reach steady state are about 10 μs.

Spontaneous Ultraviolet Emission from233Uranium/T229horiumSamples

The spontaneous ultraviolet luminescence reported [G. M. Irwin and K. H. Kim, Phys. Rev. Lett. 79, 990 (1997); D. S. Richardson et al., ibid. 80, 3206 (1998)] from ${}^{233}\mathrm{uranium}$ compounds and ascribed to an ultraviolet gamma-ray emission from the metastable ${}^{229}\mathrm{thorium}$ daughter is actually ${\mathrm{N}}_{2}$ discharge emission induced in the air surrounding the sample by the sample radioactivity. The UV spectrum from high elemental and isotopic purity ${}^{233}{\mathrm{UO}}_{3}$ reported here also exhibits a line at 391.3 nm that does not appear to be due to electric discharge ${\mathrm{N}}_{2}$ emission.

The X-ray emission from vacuum discharge micro fragments at comparatively low applied voltages

The temporal evolution of X-ray emission of laser-induced discharges was investigated by means of a picosecond X-ray streak camera. Point-like structures with a divergence of order 10/sup -7/ and thin hot layers of intense X-ray radiation with life time from 30 ps to 1.5 ns in spectral range 100 eV-10 keV have been found in a comparatively low voltage vacuum discharge (U=150 V-2.7 kV) initiated by picosecond laser beam. Computer simulation shows that such X-ray generation is connected with a matter transition into extreme states when in local microvolumes of dense current carrying plasma the pressures can exceed values of 5 Mbar and the specific internal energies /spl epsi//spl ges/1 MJ/g.

MERCURY SEPARATION AND IMMOBILIZATION USING SELF-ASSEMBLED MONOLAYERS ON MESOPOROUS SUPPORTS (SAMMS)

ABSTRACT Mercury (Hg) is one of the most toxic metals found in the environment. The purpose of this study was to investigate the performance of an innovative technology, self-assembled monolayers on mesoporous supports (SAMMS), in separating and immobilizing Hg from aqueous solutions. The high surface area of the mesoporous silica and the covalent binding between the thiol (-SH) group in SAMMS and Hg in solution provide SAMMS with distinctive advantages over existing technologies. The results show that (i) the Hg removal is kinetically quite rapid, (ii) the sorption data follow Langmuir isotherms, (iii) the maximum sorption capacity could be up to 613 mg of Hg per gram of SAMMS, (iv) SAMMS was able to reduce Hg concentrations to below the national pollution discharge emission standard level (12 ppt), (v) the Hg-laden SAMMS was stable in aqueous solution at 70°C, and (vi) the Hg-laden SAMMS was able to pass TCLP (Toxicity Characterization Leaching Procedure) tests of the U.S. Environmental Protection Agency. The results, therefore, suggest that SAMMS has a strong potential to be used for the removal and immobilization of Hg and that the Hg-laden SAMMS is suitable for long-term disposal.

MERCURY SEPARATION AND IMMOBILIZATION USING SELF-ASSEMBLED MONOLAYERS ON MESOPOROUS SUPPORTS (SAMMS)

ABSTRACT Mercury (Hg) is one of the most toxic metals found in the environment. The purpose of this study was to investigate the performance of an innovative technology, self-assembled monolayers on mesoporous supports (SAMMS), in separating and immobilizing Hg from aqueous solutions. The high surface area of the mesoporous silica and the covalent binding between the thiol (-SH) group in SAMMS and Hg in solution provide SAMMS with distinctive advantages over existing technologies. The results show that (i) the Hg removal is kinetically quite rapid, (ii) the sorption data follow Langmuir isotherms, (iii) the maximum sorption capacity could be up to 613 mg of Hg per gram of SAMMS, (iv) SAMMS was able to reduce Hg concentrations to below the national pollution discharge emission standard level (12 ppt), (v) the Hg-laden SAMMS was stable in aqueous solution at 70°C, and (vi) the Hg-laden SAMMS was able to pass TCLP (Toxicity Characterization Leaching Procedure) tests of the U.S. Environmental Protection Agenc...

流動層中でのニッケルのホウ化処理

Bonding is useful in surface hardening nickel (Ni) in many surface treatments. Although Ni boronized by powder-pack bonding with amorphous boron and by gas bonding with BCl3 has been reported, few reports cover bonding in a fluidized bed. We analyzed the treated layer using X-ray diffraction (XRD), glancing incidence X-ray diffraction, glow discharge emission spectrometry (GDS), and electron probe microanalyzer (EPMA). High-temperature microhardness and friction and wear characteristics of boronized Ni were studied, with the following results:(1) Bonding Ni at a high temperature over a long time in a fluidized bed showed flaking of the treated layer due to Ni siliconization.(2) The Knoop hardness was 1300HK for the sample boronized 7.2ks at 1073K. The boride layer was about 25μm thick and consisted mainly of Ni2B and Ni3B.(3) The high-temperature microhardness of boronized Ni is higher than that of untreated Ni below about 800K.(4) Friction properties and wear resistance to SUJ2 and SUS304 were improved by Ni bonding.

The X-ray radiation from vacuum discharges at comparatively low applied voltages

The temporal evolution of X-ray emission of laser-induced discharges was investigated by means of a picosecond X-ray streak camera. Point-like structures with small divergence (of order 8 × 10 −6) and thin hot layers of intense X-ray radiation with life-time from 30 ps to 1.5 ns in a spectral range 100 eV – 10 keV have been found for the first time in a comparatively low voltage vacuum discharge ( U ≈ 150 V−2.7 kV) initiated by a picosecond laser beam. The radiation of laser-induced breakdown was investigated just after breakdown as well as with a long delay time (up to 20 ns) relative to the ignition point by the laser beam in order to eliminate the X-ray radiation coming from the laser-produced plasma.

Radiometric characterization of xenon positive column discharges

We use both experimental diagnostics and computational modelling to characterize the electrical properties and vacuum ultraviolet emission of positive column discharges in both pure xenon and mixtures of xenon with other rare gases. Discharge conditions include xenon pressures of 10-100 mTorr at room temperature, discharge currents of 100-500 mA and positive column diameters of 1.1-5 cm. Our primary interest is the efficient generation of large quantities of ultraviolet radiation for use in fluorescent light sources. We therefore focus on the total output of atomic xenon resonance radiation at 147 nm, reported in units of watts of 147 nm radiation per unit length of positive column, and also the efficiency by which electrical input power is converted into 147 nm radiation. Over the range of discharge conditions considered, we observe outputs in excess of of discharge length and efficiencies in excess of 80%, but we also find that there is a strong tradeoff between efficiency and output, and that these two figures of merit cannot be simultaneously maximized. A change in the behaviour of the discharge is observed to occur near 25 mTorr in 2.2 cm diameter tubes and is attributed to the transition from a discharge sustained by multistep electron-impact ionization to one sustained by single-step electron-impact ionization.

Plasma polymerization of fluoromethanes

Methane and fluoromethanes (CHnF4−n, 1 ≤ n ≤ 3) were subjected to an rf glow discharge plasma. All the fluoromethanes (including methane) polymerized in the plasma and formed thin films. The deposition rate of the fluoromethanes depended on their monomer structure: CH2F2, of which the F/H ratio is unity, showed the greatest deposition rate. The elimination of H and F atoms as H—F was found to be a key factor for the polymerization of fluoromethanes. The chemical composition of the polymerized film, measured with X-ray photoelectron spectroscopy and glow discharge emission spectroscopy, was also found to be strongly dependent on monomer structure. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2043–2050, 1998

Effect of thermocatalytic breakdown of gasoline on the operating efficiency of spark-ignition engines

The authors of the present work have undertaken an attempt to reduce the emission of harmful atmospheric discharges by chemical recovery of the exhaust gas heat ; this program required the development of a method for organizing the feed of spark ignition engines operating on low-octane straight-run gasolines.

Fundamental studies of electrolyte-as-cathode glow discharge-atomic emission spectrometry for the determination of trace metals in flowing water

The fundamental characteristics and analytical performance were investigated of a new glow discharge emission source (GDES) for the determination of trace metals in flowing water. The application of an atmospheric glow discharge in argon gas between an electrolyte solution cathode and a platinum rod anode led to the development of a stable discharge. The intensity of the lines was found to depend strongly on the acidity of the water, the current and the discharge gap. The spectrum emitted from the tap water contained the basic atomic lines of the dissolved metals and OH band peaks, but no emission lines of argon from the discharge gas. The strong emission lines for an element and no emission lines from the discharge gas in the electrolyte-as-cathode glow discharge (ELCAD) were different from those in a solid-as-cathode discharge, suggesting a different excitation mechanism. Sub-parts-per-million detection limits of Al, Cd, Cr, Cu, Mn, Pb and Hg were obtained. The continuous-flow sample system demonstrates the possibility to develop a device for the continuous analysis of water and waste water solutions.

Cylindrical glow-discharge-pumped excimer lamps

The results of investigations of the emission of glow discharges in mixtures of inert gases and halogens in cylindrical tubes of various dimensions are presented. Glow-discharge-pumped XeCl* and KrCl* excimer lamps with a homogeneous spatial distribution of the radiation and powers up to 100 W are created. It is shown that the high efficiency of excimer lamps of this type is achieved as a result of the effective formation of exciplexes in a harpoon reaction and the slow rate of their quenching in the glow-discharge plasma at low pressures of the working mixture.