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Sample records for radiofrequency glow discharge

  1. Electric field development in γ-mode radiofrequency atmospheric pressure glow discharge in helium

    NASA Astrophysics Data System (ADS)

    Navrátil, Zdeněk; Josepson, Raavo; Cvetanović, Nikola; Obradović, Bratislav; Dvořák, Pavel

    2016-06-01

    Time development of electric field strength during radio-frequency sheath formation was measured using Stark polarization spectroscopy in a helium γ-mode radio-frequency (RF, 13.56 MHz) atmospheric pressure glow discharge at high current density (3 A cm-2). A method of time-correlated single photon counting was applied to record the temporal development of spectral profile of He I 492.2 nm line with a sub-nanosecond temporal resolution. By fitting the measured profile of the line with a combination of pseudo-Voigt profiles for forbidden (2 1P-4 1F) and allowed (2 1P-4 1D) helium lines, instantaneous electric fields up to 32 kV cm-1 were measured in the RF sheath. The measured electric field is in agreement with the spatially averaged value of 40 kV cm-1 estimated from homogeneous charge density RF sheath model. The observed rectangular waveform of the electric field time development is attributed to increased sheath conductivity by the strong electron avalanches occurring in the γ-mode sheath at high current densities.

  2. Radio-frequency powered glow discharge device and method with high voltage interface

    DOEpatents

    Duckworth, D.C.; Marcus, R.K.; Donohue, D.L.; Lewis, T.A.

    1994-06-28

    A high voltage accelerating potential, which is supplied by a high voltage direct current power supply, is applied to the electrically conducting interior wall of an RF powered glow discharge cell. The RF power supply desirably is electrically grounded, and the conductor carrying the RF power to the sample held by the probe is desirably shielded completely excepting only the conductor's terminal point of contact with the sample. The high voltage DC accelerating potential is not supplied to the sample. A high voltage capacitance is electrically connected in series between the sample on the one hand and the RF power supply and an impedance matching network on the other hand. The high voltage capacitance isolates the high DC voltage from the RF electronics, while the RF potential is passed across the high voltage capacitance to the plasma. An inductor protects at least the RF power supply, and desirably the impedance matching network as well, from a short that might occur across the high voltage capacitance. The discharge cell and the probe which holds the sample are configured and disposed to prevent the probe's components, which are maintained at ground potential, from bridging between the relatively low vacuum region in communication with the glow discharge maintained within the cell on the one hand, and the relatively high vacuum region surrounding the probe and cell on the other hand. The probe and cell also are configured and disposed to prevent the probe's components from electrically shorting the cell's components. 11 figures.

  3. Radio-frequency powered glow discharge device and method with high voltage interface

    DOEpatents

    Duckworth, Douglas C.; Marcus, R. Kenneth; Donohue, David L.; Lewis, Trousdale A.

    1994-01-01

    A high voltage accelerating potential, which is supplied by a high voltage direct current power supply, is applied to the electrically conducting interior wall of an RF powered glow discharge cell. The RF power supply desirably is electrically grounded, and the conductor carrying the RF power to the sample held by the probe is desirably shielded completely excepting only the conductor's terminal point of contact with the sample. The high voltage DC accelerating potential is not supplied to the sample. A high voltage capacitance is electrically connected in series between the sample on the one hand and the RF power supply and an impedance matching network on the other hand. The high voltage capacitance isolates the high DC voltage from the RF electronics, while the RF potential is passed across the high voltage capacitance to the plasma. An inductor protects at least the RF power supply, and desirably the impedance matching network as well, from a short that might occur across the high voltage capacitance. The discharge cell and the probe which holds the sample are configured and disposed to prevent the probe's components, which are maintained at ground potential, from bridging between the relatively low vacuum region in communication with the glow discharge maintained within the cell on the one hand, and the relatively high vacuum region surrounding the probe and cell on the other hand. The probe and cell also are configured and disposed to prevent the probe's components from electrically shorting the cell's components.

  4. Glow discharge detector

    DOEpatents

    Koo, Jackson C.; Yu, Conrad M.

    2002-01-01

    A highly sensitive electronic ion cell for the measurement of trace elements in He carrier gas which involves glow discharge. A constant wave (CW) glow discharge detector which is controlled through a biased resistor, can detect the change of electron density caused by impurities in the He carrier gas by many orders of magnitude larger than that caused by direct ionization or electron capture. The glow discharge detector utilizes a floating pseudo-electrode to form a probe in or near the plasma. By using this probe, the large variation of electron density due to trace amounts of impurities can be directly measured.

  5. Characterization of thin film tandem solar cells by radiofrequency pulsed glow discharge - Time of flight mass spectrometry.

    PubMed

    Fernandez, Beatriz; Lobo, Lara; Reininghaus, Nies; Pereiro, Rosario; Sanz-Medel, Alfredo

    2017-04-01

    Beside low production costs and the use of nontoxic and abundant raw materials, silicon based thin-film solar cells have the advantage to be built up as multi junction devices like tandem or triple junction solar cells. Silicon thin film modules made of tandem cells with hydrogenated amorphous silicon (a-Si:H) top cell and microcrystalline (μc) Si:H bottom cell are available on the market. In this work, the analytical potential of state-of-the art radiofrequency (rf) pulsed glow discharge (PGD) time of flight mass spectrometry (TOFMS) commercial instrumentation is investigated for depth profiling analysis of tandem-junctions solar cells on 2mm thick glass substrate with 1µm thick ZnO:Al. Depth profile characterization of two thin film tandem photovoltaic devices was compared using millisecond and sub-millisecond rf-PGD regimes, as well as the so-called "low mass mode" available in the commercial instrument used. Two procedures for sample preparation, namely using flat or rough cell substrates, were compared and the distribution of dopant elements (phosphorous, boron and germanium) was investigated in both cases. Experimental results obtained by rf-PGD-TOFMS as well as electrical measurements of the samples showed that a worse depth resolution of dopant elements in the silicon layers (e.g. distribution of boron in a thicker region that suggests a diffusion of this dopant in the coating of the sample) found using a rough sample substrate was related to a higher power conversion efficiency.

  6. Stable glow discharge detector

    DOEpatents

    Koo, Jackson C.; Yu, Conrad M.

    2004-05-18

    A highly sensitive electronic ion cell for the measurement of trace elements in He carrier gas which involves glow discharge. A constant wave (CW) stable glow discharge detector which is controlled through a biased resistor, can detect the change of electron density caused by impurities in the He carrier gas by many orders of magnitude larger than that caused by direct ionization or electron capture. The stable glow discharge detector utilizes a floating pseudo-electrode to form a probe in or near the plasma and a solid rod electrode. By using this probe, the large variation of electron density due to trace amounts of impurities can be directly measured. The solid rod electrode provides greater stability and thus easier alignment.

  7. Surface oxide net charge of a titanium alloy: comparison between effects of treatment with heat or radiofrequency plasma glow discharge.

    PubMed

    MacDonald, Daniel E; Rapuano, Bruce E; Schniepp, Hannes C

    2011-01-01

    In the current study, we have compared the effects of heat and radiofrequency plasma glow discharge (RFGD) treatment of a Ti6Al4V alloy on the physico-chemical properties of the alloy's surface oxide. Titanium alloy (Ti6Al4V) disks were passivated alone, heated to 600 °C, or RFGD plasma treated in pure oxygen. RFGD treatment did not alter the roughness, topography, elemental composition or thickness of the alloy's surface oxide layer. In contrast, heat treatment altered oxide topography by creating a pattern of oxide elevations approximately 50-100 nm in diameter. These nanostructures exhibited a three-fold increase in roughness compared to untreated surfaces when RMS roughness was calculated after applying a spatial high-pass filter with a 200 nm-cutoff wavelength. Heat treatment also produced a surface enrichment in aluminum and vanadium oxides. Both RFGD and heat treatment produced similar increases in oxide wettability. Atomic force microscopy (AFM) measurements of metal surface oxide net charge signified by a long-range force of attraction to or repulsion from a (negatively charged) silicon nitride AFM probe were also obtained for all three experimental groups. Force measurements showed that the RFGD-treated Ti6Al4V samples demonstrated a higher net positive surface charge at pH values below 6 and a higher net negative surface charge at physiological pH (pH values between 7 and 8) compared to control and heat-treated samples. These findings suggest that RFGD treatment of metallic implant materials can be used to study the role of negatively charged surface oxide functional groups in protein bioactivity, osteogenic cell behavior and osseointegration independently of oxide topography.

  8. Heat and radiofrequency plasma glow discharge pretreatment of a titanium alloy: evidence [corrected] for enhanced osteoinductive properties.

    PubMed

    Rapuano, Bruce E; Singh, Herman; Boskey, Adele L; Doty, Stephen B; MacDonald, Daniel E

    2013-08-01

    It is believed that orthopedic and implant longevity can be improved by optimizing fixation, or direct bone-implant contact, through the stimulation of new bone formation around the implant. The purpose of this study was to determine whether heat (600°C) or radiofrequency plasma glow discharge (RFGD) pretreatment of Ti6Al4V stimulated calcium-phosphate mineral formation in cultures of attached MC3T3 osteoprogenitor cells with or without a fibronectin coating. Calcium-phosphate mineral was analyzed by flame atomic absorption spectrophotometry, scanning electron microscopy (SEM)/electron dispersive X-ray microanalysis (EDAX) and Fourier transformed infrared spectroscopy (FTIR). RFGD and heat pretreatments produced a general pattern of increased total soluble calcium levels, although the effect of heat pretreatment was greater than that of RFGD. SEM/EDAX showed the presence of calcium-and phosphorus-containing particles on untreated and treated disks that were more numerous on fibronectin-coated disks. These particles were observed earliest (1 week) on RFGD-pretreated surfaces. FTIR analyses showed that the heat pretreatment produced a general pattern of increased levels of apatite mineral at 2-4 weeks; a greater effect was observed for fibronectin-coated disks compared to uncoated disks. The observed findings suggest that heat pretreatment of Ti6Al4V increased the total mass of the mineral formed in MC3T3 osteoprogenitor cell cultures more than RFGD while the latter pretreatment hastened the early deposition of mineral. These findings help to support the hypothesis that the pretreatments enhance the osteoinductive properties of the alloy.

  9. Powerful glow discharge excilamp

    DOEpatents

    Tarasenko, Victor F.; Panchenko, Aleksey N.; Skakun, Victor S.; Sosnin, Edward A.; Wang, Francis T.; Myers, Booth R.; Adamson, Martyn G.

    2002-01-01

    A powerful glow discharge lamp comprising two coaxial tubes, the outer tube being optically transparent, with a cathode and anode placed at opposite ends of the tubes, the space between the tubes being filled with working gas. The electrodes are made as cylindrical tumblers placed in line to one other in such a way that one end of the cathode is inserted into the inner tube, one end of the anode coaxially covers the end of the outer tube, the inner tube penetrating and extending through the anode. The increased electrodes' surface area increases glow discharge electron current and, correspondingly, average radiation power of discharge plasma. The inner tube contains at least one cooling liquid tube placed along the axis of the inner tube along the entire lamp length to provide cathode cooling. The anode has a circumferential heat extracting radiator which removes heat from the anode. The invention is related to lighting engineering and can be applied for realization of photostimulated processes under the action of powerful radiation in required spectral range.

  10. Isotope dilution mass spectrometry for quantitative elemental analysis of powdered samples by radiofrequency pulsed glow discharge time of flight mass spectrometry.

    PubMed

    Alvarez-Toral, Aitor; Fernandez, Beatriz; Malherbe, Julien; Claverie, Fanny; Molloy, John L; Pereiro, Rosario; Sanz-Medel, Alfredo

    2013-10-15

    In recent years particular effort is being devoted to the development of pulsed glow discharges (PGDs) for mass spectrometry because this powering operation mode could offer important ionization analytical advantages. However, the capabilities of radiofrequency (RF) PGD coupled to a time of flight mass spectrometry (ToFMS) for accurate isotope ratio measurements have not been demonstrated yet. This work is focused on investigating different time positions along the pulse profile for the accurate measurement of isotope ratios. As a result, a method has been developed for the direct and simultaneous multielement determination of trace elements in powdered geological samples by RF-PGD-ToFMS in combination with isotope dilution mass spectrometry (IDMS) as an absolute measurement method directly traceable to the International System of Units. Optimized operating conditions were 70 W of applied radiofrequency power, 250 Pa of pressure, 2 ms of pulse width and 4 ms of pulse period, being argon the plasma gas used. To homogeneously distribute the added isotopically-enriched standards, lithium borate fusion of powdered solid samples was used as sample preparation approach. In this way, Cu, Zn, Ba and Pb were successfully determined by RF-PGD-ToF(IDMS) in two NIST Standard Reference Materials (SRM 2586 and SRM 2780) representing two different matrices of geological interest (soil and rock samples). Cu, Zn, Ba and Pb concentrations determined by RF-PGD-ToF(IDMS) were well in agreement with the certified values at 95% confidence interval and precisions below 12% relative standard deviation were observed for three independent analyses. Elemental concentrations investigated were in the range of 81-5770 mg/kg, demonstrating the potential of RF-PGD-ToF(IDMS) for a sensitive, accurate and robust analysis of powdered samples.

  11. Constricted glow discharge plasma source

    DOEpatents

    Anders, Andre; Anders, Simone; Dickinson, Michael; Rubin, Michael; Newman, Nathan

    2000-01-01

    A constricted glow discharge chamber and method are disclosed. The polarity and geometry of the constricted glow discharge plasma source is set so that the contamination and energy of the ions discharged from the source are minimized. The several sources can be mounted in parallel and in series to provide a sustained ultra low source of ions in a plasma with contamination below practical detection limits. The source is suitable for applying films of nitrides such as gallium nitride and oxides such as tungsten oxide and for enriching other substances in material surfaces such as oxygen and water vapor, which are difficult process as plasma in any known devices and methods. The source can also be used to assist the deposition of films such as metal films by providing low-energy ions such as argon ions.

  12. Characterization of helium/argon working gas systems in a radiofrequency glow discharge atomic emission source. Part I: Optical emission, sputtering and electrical characteristics

    NASA Astrophysics Data System (ADS)

    Christopher, Steven J.; Hartenstein, Matthew L.; Marcus, R. Kenneth; Belkin, Mikhail; Caruso, Joseph A.

    1998-08-01

    Studies are performed to determine the influence of discharge gas composition (helium/argon working gas mixtures) on the analyte emission signal intensities, sputtering rates, and DC-bias characteristics of an analytical radiofrequency glow discharge atomic emission spectroscopy (RF-GD-AES) source. As the partial pressure of He is increased from 0 to 15 torr, increased emission intensity is observed for a range of bulk and trace elements in NIST 1250 SRM (low alloy steel), regardless of the base pressure of Ar in the source (5 and 9 torr). In contrast to increases in analyte emission intensity of up to 300%, counterindicative decreases in the sputtering rates on the order of about 30-50% are observed. The magnitude of these effects depends on both the partial pressure of helium introduced to the source and the total pressure of the He and Ar gases. Use of relative emission yield (REY) to normalize changes in emission intensity to sputtering rates indicates that excitation efficiencies increase under these conditions. Increases in average electron energy and temperature appear to control this response. Decreases in both analyte emission intensities and sputter rates occur with increasing He partial pressure when the total pressure in the cell remains fixed (11 torr in these studies). Emission yields for the fixed pressure, mixed gas plasmas decrease as the partial pressure of He (He/Ar ratio) in the RF-GD source increases. In this case, decreases in electron number densities appear to dictate the lower REYs. Measurement of DC-bias values at the sample surface provide understanding with respect to the observed changes in sputtering rates as well as suggest the origins of changes in plasma electron energetics. Use of a diamond stylus profilometer provides both the quantitative sputter rate information as well as qualitative insights into the use of mixed gas plasmas for enhanced depth profiling capabilities. The analyte emission characteristics of these mixed gas

  13. Shockwave Interactions with Argon Glow Discharges

    DTIC Science & Technology

    2006-03-01

    SHOCKWAVE INTERACTIONS WITH ARGON GLOW DISCHARGES THESIS Nicholas S. Siefert, Lieutenant, USAF AFIT/GAP/ENP/06-18 DEPARTMENT OF THE AIR FORCE AIR...the United States Government. AFIT/GAP/ENP/06-18 SHOCKWAVE INTERACTIONS WITH ARGON GLOW DISCHARGES THESIS Presented to the Faculty Department of...APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED AFIT/GAP/ENP/06-18 SHOCKWAVE INTERACTIONS WITH ARGON GLOW DISCHARGES Nicholas S. Siefert, BS

  14. Atmospheric sampling glow discharge ionization source

    DOEpatents

    McLuckey, S.A.; Glish, G.L.

    1989-07-18

    An atmospheric sampling glow discharge ionization source that can be used in combination with an analytical instrument which operates at high vacuum, such as a mass spectrometer. The atmospheric sampling glow discharge ionization source comprises a chamber with at least one pair of electrodes disposed therein, an inlet for a gaseous sample to be analyzed and an outlet communicating with an analyzer which operates at subatmospheric pressure. The ionization chamber is maintained at a pressure below atmospheric pressure, and a voltage difference is applied across the electrodes to induce a glow discharge between the electrodes, so that molecules passing through the inlet are ionized by the glow discharge and directed into the analyzer. The ionization source accepts the sample under atmospheric pressure conditions and processes it directly into the high vacuum instrument, bridging the pressure gap and drawing off unwanted atmospheric gases. The invention also includes a method for analyzing a gaseous sample using the glow discharge ionization source described above. 3 figs.

  15. Characterization of helium/argon working gas systems in a radiofrequency glow discharge atomic emission source. Part II: Langmuir probe and emission intensity studies for Al, Cu and Macor samples

    NASA Astrophysics Data System (ADS)

    Belkin, Mikhail; Caruso, Joseph A.; Christopher, Steven J.; Marcus, R. Kenneth

    1998-08-01

    The application of a tuned Langmuir probe is extended to the measurement of the charged particle characteristics (electron and ion number density, average electron energy and electron temperature) in an analytical radiofrequency glow discharge (RF-GD) in helium. The effects of discharge operating conditions, such as RF power and pressure, on the charged particle characteristics for conducting (aluminum) and nonconducting (Macor) samples are studied. The differences in plasma characteristics between argon and helium working gases are discussed. Langmuir probe measurements are also performed in an argon/helium mixture. Variations of the emission intensities of sputtered analytes (copper and aluminum) are investigated when helium is introduced into an argon RF glow discharge plasma. It is recognized that, although the number of sample atoms in the plasma gradually decreases due to reduced sputtering, the emission intensities of various Al(I) and Cu(I) lines increase with helium addition. Measured electron and ion number densities also decrease with helium addition, whereas the average electron energy and electron temperature increase, accounting for the enhancement of emission intensities.

  16. UV Sustained Glow Discharge Opening Switch.

    DTIC Science & Technology

    1985-06-01

    the program were to undertake a theoretical and experimental investigation into the physics of UV sustained glow discharge opening switches with high...experimental investigation to develop scaling rules for the UV -sustained glow discharge, particularly for, but not restricted to, opening switch ...time is likely due to light emission from the flashboard substrate surface . As described in section 4.3, this long UV decay time severly restricts switch

  17. Sound wave propagation through glow discharge plasma

    NASA Astrophysics Data System (ADS)

    Stepaniuk, Vadim P.

    This work investigates the use of glow discharge plasma for acoustic wave manipulation. The broader goal is the suppression of aerodynamic noise using atmospheric glow discharge plasma as a sound barrier. Part of the effort was devoted to the development of a system for the generation of a large volume stable DC glow discharge in air both at atmospheric and at reduced pressures. The single tone sound wave propagation through the plasma was systematically studied. Attenuation of the acoustic wave passing through the glow discharge was measured for a range of experimental conditions including different discharge currents, electrode configurations, air pressures and sound frequencies including audible sound and ultrasound. Sound attenuation by glow discharge plasma as high as -28 dB was recorded in the experiments. Two types of possible mechanisms were considered that can potentially cause the observed sound attenuation. One is a global mechanism and the other is a local mechanism. The global mechanism considered is based on the reflection and refraction of acoustic wave due to the gas temperature gradients that form around the plasma. The local mechanism, on the other hand, is essentially the interaction of the acoustic wave with the plasma as it propagates inside the discharge and it can be viewed as a feedback system. Detailed temperature measurements, using laser-induced Rayleigh scattering technique, were carried out in the glow discharge plasma in order to evaluate the role of global mechanism in the observed attenuation. These measurements were made for a range of conditions in the atmospheric glow discharge. Theoretical analysis of the sound attenuation was carried out to identify the physical mechanism for the observed sound attenuation by plasma. It was demonstrated that the global mechanism is the dominant mechanism of sound attenuation. As a result of this study, the potentials and limitations of the plasma noise suppression technology were determined and

  18. Stability of atmospheric pressure glow discharges

    NASA Astrophysics Data System (ADS)

    Chirokov, Alexandre V.

    There has been a considerable interest in non-thermal atmospheric pressure discharges over the past decade due to increased number of industrial applications. Although non-thermal atmospheric pressure discharges have been intensively studied for the past century the clear physical picture of these discharges is far from being complete. Spontaneous transition of non-thermal atmospheric pressure discharges to thermal discharge and discharge filamentation are among least understood plasma phenomena. The discharge stability and reliable control of plasma parameters are highly desirable for numerous applications. This study focuses on stability of atmospheric pressure glow discharges with respect to filamentation and arcing. Atmospheric pressure glow discharge (APG) is the newest and the most promising addition to the family of non-thermal atmospheric pressure discharges. However this discharge is very susceptible to thermal instability which causes arcing, loss of uniformity and significant damage to electrodes. Suppression of thermal instability and effective control of discharge parameters is critical for industrial applications. A model was developed to understand transition to arc in atmospheric pressure glow discharges. APG discharges that operate in pure helium and in helium with addition of oxygen and nitrogen were considered in these studies. Simulation results indicate that arcing is the result of sheath breakdown rather than thermal instability. It was shown that although sheath breakdown is always followed by overheating the transition to arc in atmospheric glow discharges is not a result of thermal instability. In second part of this research interaction between plasma filaments in dielectric barrier discharges has been studied. This interaction is responsible for the formation of microdischarge patterns reminiscent of two-dimensional crystals. Depending on the application, microdischarge patterns may have a significant influence on DBD performance

  19. Is the negative glow plasma of a direct current glow discharge negatively charged?

    SciTech Connect

    Bogdanov, E. A.; Saifutdinov, A. I.; Demidov, V. I.; Kudryavtsev, A. A.

    2015-02-15

    A classic problem in gas discharge physics is discussed: what is the sign of charge density in the negative glow region of a glow discharge? It is shown that traditional interpretations in text-books on gas discharge physics that states a negative charge of the negative glow plasma are based on analogies with a simple one-dimensional model of discharge. Because the real glow discharges with a positive column are always two-dimensional, the transversal (radial) term in divergence with the electric field can provide a non-monotonic axial profile of charge density in the plasma, while maintaining a positive sign. The numerical calculation of glow discharge is presented, showing a positive space charge in the negative glow under conditions, where a one-dimensional model of the discharge would predict a negative space charge.

  20. Glow discharge based device for solving mazes

    SciTech Connect

    Dubinov, Alexander E. Mironenko, Maxim S.; Selemir, Victor D.; Maksimov, Artem N.; Pylayev, Nikolay A.

    2014-09-15

    A glow discharge based device for solving mazes has been designed and tested. The device consists of a gas discharge chamber and maze-transformer of radial-azimuth type. It allows changing of the maze pattern in a short period of time (within several minutes). The device has been tested with low pressure air. Once switched on, a glow discharge has been shown to find the shortest way through the maze from the very first attempt, even if there is a section with potential barrier for electrons on the way. It has been found that ionization waves (striations) can be excited in the maze along the length of the plasma channel. The dependancy of discharge voltage on the length of the optimal path through the maze has been measured. A reduction in discharge voltage with one or two potential barriers present has been found and explained. The dependency of the magnitude of discharge ignition voltage on the length of the optimal path through the maze has been measured. The reduction of the ignition voltage with the presence of one or two potential barriers has been observed and explained.

  1. Heat transfer in a longitudinal glow discharge

    NASA Astrophysics Data System (ADS)

    Yunusov, R. F.

    2017-01-01

    This article is devoted to the experimental study of heat transfer in a longitudinal glow discharge. The discharge was ignited in the discharge chamber (DC), consisting of a glass tube 10 mm in diameter and two electrodes. Copper electrodes were placed in the side branches, so that the average distance between them was 9 cm. The discharge pressure was varied in the range of P = (2.5 – 8.5) kPa. The air flow rate was varied from zero to G = 0.06 g / s. Current was varied in the range of I = (30-80) mA. Current-voltage characteristics of the discharge had falling form, and the voltage was varied in the range of U = (1-2) kV. The temperature of neutral particles in the plasma glow discharge was measured by six thermocouples, which were insertedon radius of DC. The aim of the article was to compare achieved experiment data with theoretical studies: recombination and diffusion plasma models.

  2. Influence of dust particles on glow discharge

    NASA Astrophysics Data System (ADS)

    Polyakov, D. N.; Shumova, V. V.; Vasilyak, L. M.; Fortov, V. E.

    2010-11-01

    The gas discharge-dust particle interaction for a dc discharge in air with micron-sized particles is investigated. The plasma of the dc column is described in the frame of diffusion approximation combined with the orbital motion limited approximation for ion and electron flow on the dust component surface. The problem is solved for dust particles of 2 μm radius, embedded in a uniform glow discharge column with a diameter of 16 mm at air pressure 0.5 torr, discharge current 0.5-3 mA and particle concentration up to 105 cm-3. The current-voltage characteristics as an easy-to-observe measure of the nonlocal dust influence on the total amount of charge carriers in the discharge, as well as the radial distributions of plasma components in the dc discharge, are calculated for different dust concentrations and discharge currents. The results are compared with recently published experimental data. The presence of dust particles leads to an increase of the longitudinal electric field due to additional loss of ions and electrons. A decrease of the radial electric field within the dust cloud under the action of dust particles results in an essential change of the electron concentration profile, down to the appearance of the local minimum at the axis of the discharge.

  3. Tailoring Surface Properties of Polymeric Separators for Lithium-Ion Batteries by 13.56 MHz Radio-Frequency Plasma Glow Discharge

    NASA Astrophysics Data System (ADS)

    Liang, Chia-Han; Juang, Ruey-Shin; Tsai, Ching-Yuan; Huang, Chun

    2013-11-01

    The hydrophilic surface modification of the polymeric separator is achieved by low-pressure 13.56 MHz radio-frequency Ar and He gas plasma treatments. The changes in surface hydrophilicity and surface free energy were examined by static contact angle analysis. The static water contact angle of the plasma-modified polymeric separator particularly decreased with the increase in treatment time. An obvious increase in the surface energy of polymeric separators owing to the crosslinking by activated species of inert gases effect of monatomic-gas-plasma treatments was also observed. Optical emission spectroscopy was carried out to analyze the chemical species generated after Ar and He gas plasma treatments. The variations in the surface morphology and chemical structure of the polymeric separators were confirmed by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS) measurements. XPS analysis showed significantly higher surface concentrations of oxygen functional groups for monatomic-gas-plasma-modified polymeric separator surfaces than for the unmodified polymeric separator surface. The experimental results show the important role of chemical species in the interaction between Ar and He gas plasmas and the polymeric separator surface, which can be controlled by surface modification to tailor the hydrophilicity of the polymeric separator.

  4. Plasma sterilization using the RF glow discharge

    NASA Astrophysics Data System (ADS)

    Yang, Liqing; Chen, Jierong; Gao, Junling; Guo, Yafei

    2009-08-01

    In the present work, glow discharge oxygen plasma was used to sterilize the Pseudomonas aeruginosa on the polyethylene terephthalate (PET) sheets. In a self-designed plasma reaction equipment, active species (electron, ion, radical, UV light, etc.) were separated effectively, and the discharge area, afterglow area and remote area were plotted out in the plasma field. Before and after plasma treatment the cell morphology was studied by scanning electron microscopy (SEM). The results showed that after treatment of 30 s the germicidal effect is 4.26, 3. 84, 2.61, respectively in the three areas on the following conditions: discharge power was 40 W and gas flux was 20 cm 3/min. SEM results revealed the cell morphology before and after plasma treatment. The walls or cell membrane cracking was testified by determining the content of protein using coomassie light blue technique. The results from electron spin resonance spectroscopy (ESR) and double Langmuir electron probe showed that electron, ion and oxygen free radical played important roles in sterilization in the discharge area, but only oxygen radicals acted to sterilize the bacteria in the afterglow area and the remote area.

  5. Advances in the Remote Glow Discharge Experiment

    NASA Astrophysics Data System (ADS)

    Dominguez, Arturo; Zwicker, A.; Rusaits, L.; McNulty, M.; Sosa, Carl

    2014-10-01

    The Remote Glow Discharge Experiment (RGDX) is a DC discharge plasma with variable pressure, end-plate voltage and externally applied axial magnetic field. While the experiment is located at PPPL, a webcam displays the live video online. The parameters (voltage, magnetic field and pressure) can be controlled remotely in real-time by opening a URL which shows the streaming video, as well as a set of Labview controls. The RGDX is designed as an outreach tool that uses the attractive nature of a plasma in order to reach a wide audience and extend the presence of plasma physics and fusion around the world. In March 2014, the RGDX was made publically available and, as of early July, it has had approximately 3500 unique visits from 107 countries and almost all 50 US states. We present recent upgrades, including the ability to remotely control the distance between the electrodes. These changes give users the capability of measuring Paschen's Law remotely and provides a comprehensive introduction to plasma physics to those that do not have access to the necessary equipment.

  6. Glow discharge techniques for conditioning high vacuum systems

    SciTech Connect

    Dylla, H.F.

    1988-03-01

    A review is given of glow discharge techniques which are useful for conditioning vacuum vessels for high vacuum applications. Substantial development of glow discharge techniques has been done for the purpose of in-situ conditioning of the large ultrahigh vacuum systems for particle accelerators and magnetic fusion devices. In these applications the glow discharge treatments remove impurities from vessel surfaces in order to minimize particle-induced desorption coefficients. Cleaning mechanisms involve a mixture of sputtering and ion- (or neutral) induced desorption effects depending on the gas mixture (ArO/sub 2/ vs. H/sub 2/) and excitation method (DC, RF, and ECR). The author will review the methodology of glow discharge conditioning, diagnostic measurements provided by residual gas and surface composition analysis, and applications to vessel conditioning and materials processing. 76 refs., 16 figs.

  7. Simulation of nonstationary phenomena in atmospheric-pressure glow discharge

    NASA Astrophysics Data System (ADS)

    Korolev, Yu. D.; Frants, O. B.; Nekhoroshev, V. O.; Suslov, A. I.; Kas'yanov, V. S.; Shemyakin, I. A.; Bolotov, A. V.

    2016-06-01

    Nonstationary processes in atmospheric-pressure glow discharge manifest themselves in spontaneous transitions from the normal glow discharge into a spark. In the experiments, both so-called completed transitions in which a highly conductive constricted channel arises and incomplete transitions accompanied by the formation of a diffuse channel are observed. A model of the positive column of a discharge in air is elaborated that allows one to interpret specific features of the discharge both in the stationary stage and during its transition into a spark and makes it possible to calculate the characteristic oscillatory current waveforms for completed transitions into a spark and aperiodic ones for incomplete transitions. The calculated parameters of the positive column in the glow discharge mode agree well with experiment. Data on the densities of the most abundant species generated in the discharge (such as atomic oxygen, metastable nitrogen molecules, ozone, nitrogen oxides, and negative oxygen ions) are presented.

  8. The radiofrequency magnetic dipole discharge

    NASA Astrophysics Data System (ADS)

    Martines, E.; Zuin, M.; Marcante, M.; Cavazzana, R.; Fassina, A.; Spolaore, M.

    2016-05-01

    This paper describes a novel and simple concept of plasma source, which is able to produce a radiofrequency magnetized discharge with minimal power requirements. The source is based on the magnetron concept and uses a permanent magnet as an active electrode. The dipolar field produced by the magnet confines the electrons, which cause further ionization, thus producing a toroidally shaped plasma in the equatorial region around the electrode. A plasma can be ignited with such scheme with power levels as low as 5 W. Paschen curves have been built for four different working gases, showing that in Helium or Neon, plasma breakdown is easily obtained also at atmospheric pressure. The plasma properties have been measured using a balanced Langmuir probe, showing that the electron temperature is around 3-4 eV and higher in the cathode proximity. Plasma densities of the order of 1016 m-3 have been obtained, with a good positive scaling with applied power. Overall, the electron pressure appears to be strongly correlated with the magnetic field magnitude in the measurement point.

  9. Adherence of Candida albicans to glow-discharge modified acrylic denture base polymers.

    PubMed

    Yildirim, M S; Hasanreisoglu, U; Hasirci, N; Sultan, N

    2005-07-01

    An important aetiologic factor in the pathogenesis of denture-induced stomatitis, is the presence of numerous yeasts, usually Candida albicans, on the fitting surfaces of dentures. In the present study, effect of glow-discharge plasma, a technique applied to increase surface wettability of acrylic resins, on candidial adherence was evaluated. The durability of glow-discharge modification with saliva coating was also evaluated. Samples including control and experimental groups were prepared by using heat compression mould technique. To create a hydrophobicity gradient, experimental groups were exposed to a radiofrequency glow discharge in an O2 atmosphere under different discharge powers. To characterize the wetting properties, an expression of surface hydrophobicity, contact angle measurements were performed by the sessile drop method. The organism used was C. albicans (ATTC10321). Acrylic samples were coated with unstimulated whole saliva collected from a healthy man. The fungal suspension was poured on saliva-inoculated samples and incubated at 37 degrees for 2 h. The samples were then fixed with glutaraldehyde and Gram stained. Adhered candidial cells were examined by light microscope. Diffuse Reflectance FTIR (DRIFT) and scanning electron-microscope examinations were also performed to evaluate the surface composition and roughness of the test groups. Glow-discharge plasma was found to be an effective means of increasing surface wettability even with salivary pellicle. Amounts of candida cells adhered were significantly higher in all the plasma treated surfaces than the unmodified control group (P < 0.001). It was concluded that improving the surface wettability of acrylic resins by glow-discharge plasma in O2 atmosphere increased the adherence of the C. albicans.

  10. Extension of spatiotemporal chaos in glow discharge-semiconductor systems

    SciTech Connect

    Akhmet, Marat Fen, Mehmet Onur; Rafatov, Ismail

    2014-12-15

    Generation of chaos in response systems is discovered numerically through specially designed unidirectional coupling of two glow discharge-semiconductor systems. By utilizing the auxiliary system approach, [H. D. I. Abarbanel, N. F. Rulkov, and M. M. Sushchik, Phys. Rev. E 53, 4528–4535 (1996)] it is verified that the phenomenon is not a chaos synchronization. Simulations demonstrate various aspects of the chaos appearance in both drive and response systems. Chaotic control is through the external circuit equation and governs the electrical potential on the boundary. The expandability of the theory to collectives of glow discharge systems is discussed, and this increases the potential of applications of the results. Moreover, the research completes the previous discussion of the chaos appearance in a glow discharge-semiconductor system [D. D. Šijačić U. Ebert, and I. Rafatov, Phys. Rev. E 70, 056220 (2004).].

  11. Extension of spatiotemporal chaos in glow discharge-semiconductor systems.

    PubMed

    Akhmet, Marat; Rafatov, Ismail; Fen, Mehmet Onur

    2014-12-01

    Generation of chaos in response systems is discovered numerically through specially designed unidirectional coupling of two glow discharge-semiconductor systems. By utilizing the auxiliary system approach, [H. D. I. Abarbanel, N. F. Rulkov, and M. M. Sushchik, Phys. Rev. E 53, 4528-4535 (1996)] it is verified that the phenomenon is not a chaos synchronization. Simulations demonstrate various aspects of the chaos appearance in both drive and response systems. Chaotic control is through the external circuit equation and governs the electrical potential on the boundary. The expandability of the theory to collectives of glow discharge systems is discussed, and this increases the potential of applications of the results. Moreover, the research completes the previous discussion of the chaos appearance in a glow discharge-semiconductor system [D. D. Šijačić U. Ebert, and I. Rafatov, Phys. Rev. E 70, 056220 (2004).].

  12. Organic thin film deposition in atmospheric pressure glow discharge

    SciTech Connect

    Okazaki, S.; Kogoma, M.; Yokoyama, T.; Kodama, M.; Nomiyama, H.; Ichinohe, K.

    1996-01-01

    The stabilization of a homogeneous glow discharge at atmospheric pressure has been studied since 1987. On flat surfaces, various plasma surface treatments and film depositions at atmospheric pressure have been examined. A practical application of the atmospheric pressure glow plasma on inner surfaces of flexible polyvinyl chloride tubes was tested for thin film deposition of polytetrafluoroethylene. Deposited film surfaces were characterized by ESCA and FT-IR/ATR measurements. Also SEM observation was done for platelet adhesion on the plasma treated polyvinyl chloride surface. These results showed remarkable enhancement in the inhibition to platelet adhesion on the inner surface of PVC tube, and homogeneous organic film deposition was confirmed. The deposition mechanism of polytetrafluoroethylene film in atmospheric pressure glow plasma is the same as the mechanism of film formation in the low pressure glow plasma, except for radical formation source. {copyright} {ital 1996 American Institute of Physics.}

  13. Synchronization between two coupled direct current glow discharge plasma sources

    SciTech Connect

    Chaubey, Neeraj; Mukherjee, S.; Sen, A.; Sekar Iyengar, A. N.

    2015-02-15

    Experimental results on the nonlinear dynamics of two coupled glow discharge plasma sources are presented. A variety of nonlinear phenomena including frequency synchronization and frequency pulling are observed as the coupling strength is varied. Numerical solutions of a model representation of the experiment consisting of two coupled asymmetric Van der Pol type equations are found to be in good agreement with the observed results.

  14. Mechanism of boriding from pastes in a glow discharge

    SciTech Connect

    Isakov, S.A.; Al'tshuler, S.A.

    1987-09-01

    The authors investigate the boridation of steel 45 from the standpoint of the glow-discharge dissociation of a borax paste and the plasma arc spraying of the resulting boron into the steel. The effects of process parameters on the impregnation of boron into the steel and its phase behavior in the boridation process are discussed.

  15. Immobilization of proteins on glow discharge treated polymers

    NASA Astrophysics Data System (ADS)

    Kiaei, D.; Safranj, A.; Chen, J. P.; Johnston, A. B.; Zavala, F.; Deelder, A.; Castelino, J. B.; Markovic, V.; Hoffman, A. S.

    Certain glow discharge-treated surfaces have been shown to enhance retention of adsorbed proteins. On the basis of this phenomenon, we have investigated the possibility of immobilizing (a) albumin for developing thromboresistant and non-fouling surfaces, (b) antibodies for immuno-diagnostic assays and (c) enzymes for various biosensors and industrial bioprocesses. Albumin retention was highest on surfaces treated with tetrafluoroethylene (TFE) compared to untreated surfaces or other glow discharge treatments studied. Preadsorption of albumin on TFE-treated surfaces resulted in low fibrinogen adsorption and platelet adhesion. IgG retention was also highest on TFE-treated surfaces. The lower detection limits of both malaria antigen and circulating anodic antigen of the schistosomiasis worm were enhanced following glow discharge treatment of the assay plates with TFE. Both TFE and tetrachloroethylene (TCE) glow discharge treated surfaces showed high retention of adsorbed horseradish peroxidase (HRP). However, the retained specific activity of HRP after adsorption on TCE-treated surfaces was remarkably higher than on TFE-treated surfaces.

  16. Degradation of Organics in a Glow Discharge Under Martian Conditions

    NASA Technical Reports Server (NTRS)

    Hintze, P. E.; Calle, L. M.; Calle, C. I.; Buhler, C. R.; Trigwell, S.; Starnes, J. W.; Schuerger, A. C.

    2006-01-01

    The primary objective of this project is to understand the consequences of glow electrical discharges on the chemistry and biology of Mars. The possibility was raised some time ago that the absence of organic material and carbonaceous matter in the Martian soil samples studied by the VikinG Landers might be due in part to an intrinsic atmospheric mechanism such as glow discharge. The high probability for dust interactions during Martian dust storms and dust devils, combined with the cold, dry climate of Mars most likely results in airborne dust that is highly charged. Such high electrostatic potentials generated during dust storms on Earth are not permitted in the low-pressure CO2 environment on Mars; therefore electrostatic energy released in the form of glow discharges is a highly likely phenomenon. Since glow discharge methods are used for cleaning and sterilizing surfaces throughout industry, the idea that dust in the Martian atmosphere undergoes a cleaning action many times over geologic time scales appears to be a plausible one.

  17. Low-pressure glow discharge with a hollow cathode

    NASA Astrophysics Data System (ADS)

    Lisovskiy, Valeriy; Bogodielnyi, Illia

    2011-10-01

    We measured the breakdown curves of a dc glow discharge with hollow cathode and flat electrodes in the gap between the electrodes L = 100 mm. At low gas pressure, the left branches of the breakdown curves for the hollow cathode and the flat electrodes are identical. At high gas pressures, the right branch of the breakdown curve of the discharge with a hollow cathode is close to the breakdown curve for the distance between the plane electrodes, equal to the gap between the edge of the plates of the hollow cathode and flat anode. Current-voltage characteristics of the hollow cathode discharge were measured. At low gas pressure discharge is in the high-voltage (electron beam) form with ascending CVC. In the gas pressure range p > 0.1 Torr the discharge first burns in the glow mode. At higher current the discharge goes into the hollow cathode mode, filling the space between the plates, and it has an almost vertical CVC. The transition from a glow discharge mode into a hollow one possesses a hysteresis. At gas pressures p ~ 1 Torr the hollow cathode effect disappears, since the thickness of the cathode layer is small compared with the gap between the plates of the cathode.

  18. Effect of glow discharge air plasma on grain crops seed

    SciTech Connect

    Dubinov, A.E.; Lazarenko, E.M.; Selemir, V.D.

    2000-02-01

    Oat and barley seeds have been exposed to both continuous and pulsed glow discharge plasmas in air to investigate the effects on germination and sprout growth. Statistical analysis was used to evaluate the effect of plasma exposure on the percentage germination and length of sprout growth. A stimulating effect of plasma exposure was found together with a strong dependence on whether continuous or pulsed discharges were used.

  19. Dual-frequency glow discharges in atmospheric helium

    SciTech Connect

    Huang, Xiaojiang; Guo, Ying; Dai, Lu; Zhang, Jing; Shi, J. J.

    2015-10-15

    In this paper, the dual-frequency (DF) glow discharges in atmospheric helium were experimented by electrical and optical measurements in terms of current voltage characteristics and optical emission intensity. It is shown that the waveforms of applied voltages or discharge currents are the results of low frequency (LF) waveforms added to high frequency (HF) waveforms. The HF mainly influences discharge currents, and the LF mainly influences applied voltages. The gas temperatures of DF discharges are mainly affected by HF power rather than LF power.

  20. NSTX Filament Preionization and Glow Discharge Cleaning Systems

    SciTech Connect

    Kugel, H. W.; Blanchard, W.; D'Amico, G.; Gernhardt, R.; Provost, T.

    1999-11-01

    Initial NSTX GDC experiments were performed with one moveable anode and a biased filament preionization system that allowed D2 and He Glow Discharge breakdowns at the actual operating pressure, voltage and current. The biased filament system was also operated continuously during ohmic operations, and used to reduce volt-sec consumption for February 1999 plasma discharges up to 280 KA. An upgraded system has been installed with 2 fixed wall anodes and 3 biased filaments; 2 on the mid-plane and one in the divertor region; all separately controllable remotely using a PLC system. Recent applications include assisting in preionization for 800 KA plasma discharges.

  1. The Use of DC Glow Discharges as Undergraduate Educational Tools

    SciTech Connect

    Stephanie A. Wissel and Andrew Zwicker, Jerry Ross, and Sophia Gershman

    2012-10-09

    Plasmas have a beguiling way of getting students excited and interested in physics. We argue that plasmas can and should be incorporated into the undergraduate curriculum as both demonstrations and advanced investigations of electromagnetism and quantum effects. Our device, based on a direct current (DC) glow discharge tube, allows for a number of experiments into topics such as electrical breakdown, spectroscopy, magnetism, and electron temperature.

  2. Simulations of Direct Current Glow Discharges in Supersonic Air Flow

    NASA Astrophysics Data System (ADS)

    Mahadevan, Shankar; Raja, Laxminarayan

    2008-10-01

    In recent years, there have been a significant number of computational and experimental studies investigating the application of plasma discharges as actuators for high speed flow control. The relative importance of the actuation mechanisms: volumetric heating and electrostatic forcing can be established by developing self-consistent models of the plasma and bulk supersonic flow. To simulate the plasma discharge in a supersonic air stream, a fluid model of the glow discharge is coupled with a compressible Navier-Stokes solver in a self-consistent manner. Source terms for the momentum and energy equations are calculated from the plasma model and input into the Navier-Stokes solver. In turn, the pressure, gas temperature and velocity fields from the Navier-Stokes solution are fed back into the plasma model. The results include plasma species number density contour maps in the absence and presence of Mach 3 supersonic flow, and the corresponding effect of the glow discharge on gas dynamic properties such as the gas pressure and temperature. We also examine the effect of increasing the discharge voltage on the structure of the discharge and its corresponding effect on the supersonic flow.

  3. Dust particle radial confinement in a dc glow discharge.

    PubMed

    Sukhinin, G I; Fedoseev, A V; Antipov, S N; Petrov, O F; Fortov, V E

    2013-01-01

    A self-consistent nonlocal model of the positive column of a dc glow discharge with dust particles is presented. Radial distributions of plasma parameters and the dust component in an axially homogeneous glow discharge are considered. The model is based on the solution of a nonlocal Boltzmann equation for the electron energy distribution function, drift-diffusion equations for ions, and the Poisson equation for a self-consistent electric field. The radial distribution of dust particle density in a dust cloud was fixed as a given steplike function or was chosen according to an equilibrium Boltzmann distribution. The balance of electron and ion production in argon ionization by an electron impact and their losses on the dust particle surface and on the discharge tube walls is taken into account. The interrelation of discharge plasma and the dust cloud is studied in a self-consistent way, and the radial distributions of the discharge plasma and dust particle parameters are obtained. It is shown that the influence of the dust cloud on the discharge plasma has a nonlocal behavior, e.g., density and charge distributions in the dust cloud substantially depend on the plasma parameters outside the dust cloud. As a result of a self-consistent evolution of plasma parameters to equilibrium steady-state conditions, ionization and recombination rates become equal to each other, electron and ion radial fluxes become equal to zero, and the radial component of electric field is expelled from the dust cloud.

  4. The One Atmosphere Glow Discharge in Air: Phenomenology and Applications

    NASA Astrophysics Data System (ADS)

    Ben Gadri, Rami; Sherman, Daniel M.; Chen, Zhiyu; Karakaya, Fuat; Reece Roth, J.

    1999-10-01

    The existence of an atmospheric pressure RF glow plasma with the characteristics of a classical low pressure DC glow discharge has been experimentally and theoretically demonstrated [1, 2]. At the UTK Plasma Sciences Laboratory, the One Atmosphere Uniform Glow Discharge Plasma (OAUGDP) in air has been applied to a wide range of plasma processing applications. The technology is simple, technically attractive, and suitable for online treatment of webs and 3-dimensional workpieces. A parallel plate reactor and a Remote Exposure Reactor (RER) have been developed for direct plasma immersion and remote exposure, respectively. The RER is based on generating active species capable of sterilization and surface treatment in a uniform surface layer of the OAUGDP on planar panels [3], and convecting the active species to a remote chamber where the workpiece is located. A related surface plasma has been developed for indoor air filtration systems. In addition, the surface plasma on flat panels modified the boundary layer in wind tunnel tests to produce electrohydrodynamic (EHD) flow effects that can be used to increase or decrease aerodynamic drag [3]. [1] Massines et al., J. Appl. Phys., Vol. 83, N 6, pp 2950-2957, Mar. 1998. [2] J. R. Roth, "Industrial Plasma Engineering" Vol. I: Principles. Inst. Phys. Pub., Bristol and philadelphia, ISBN 0-7503-0318-2, 1995. [3] Roth et al., AIAA Paper 98-0328, 36th AIAA Meeting, Reno NV, 1998, Jan. 12-15.

  5. On electron bunching and stratification of glow discharges

    SciTech Connect

    Golubovskii, Yuri B.; Kolobov, Vladimir I.; Nekuchaev, Vladimir O.

    2013-10-15

    Plasma stratification and excitation of ionization waves is one of the fundamental problems in gas discharge physics. Significant progress in this field is associated with the name of Lev Tsendin. He advocated the need for the kinetic approach to this problem contrary to the traditional hydrodynamic approach, introduced the idea of electron bunching in spatially periodic electric fields, and developed a theory of kinetic resonances for analysis of moving striations in rare gases. The present paper shows how Tsendin's ideas have been further developed and applied for understanding the nature of the well-known S-, P-, and R-striations observed in glow discharges of inert gases at low pressures and currents. We review numerical solutions of a Fokker-Planck kinetic equation in spatially periodic electric fields under the effects of elastic and inelastic collisions of electrons with atoms. We illustrate the formation of kinetic resonances at specific field periods for different shapes of injected Electron Distribution Functions (EDF). Computer simulations illustrate how self-organization of the EDFs occurs under nonlocal conditions and how Gaussian-like peaks moving along resonance trajectories are formed in a certain range of discharge conditions. The calculated EDFs agree well with the experimentally measured EDFs for the S, P, and R striations in noble gases. We discuss how kinetic resonances affect dispersion characteristics of moving striations and mention some non-linear effects associated with glow discharge stratification. We propose further studies of stratification phenomena combining physical kinetics and non-linear physics.

  6. Modelling of tokamak glow discharge cleaning I: physical principles

    NASA Astrophysics Data System (ADS)

    Hagelaar, G. J. M.; Kogut, D.; Douai, D.; Pitts, R. A.

    2015-02-01

    Glow discharge cleaning (GDC) is a common technique for the conditioning of tokamak vessel walls in order to improve plasma performance and will be one of the primary conditioning techniques in ITER. The GDC discharge is a dc low-temperature plasma discharge, operated in the absence of the toroidal magnetic field, between one or more anodes inserted into the vessel, and the entire vessel wall serving as a cathode. This paper presents a self-consistent 2D model of the GDC discharge with the aim of improving fundamental understanding and predicting the wall ion current density distribution in ITER. The model combines a standard fluid model of the quasineutral plasma bulk with non-standard fluid equations for the fast electrons accelerated by the cathode sheath, based on transport coefficients and rate coefficients deduced from a Monte Carlo simulation. Examples of model results are shown in order to illustrate the general principles of the GDC discharge and the influence of the model input parameters. An important insight gained from this work is that the GDC discharge operates basically as a hollow-cathode discharge: the plasma is sustained mainly by ionization by secondary electrons emitted from the cathode, accelerated ballistically through a thin cathode sheath, penetrating the plasma as a fast electron beam, and trapped by the cathode fall surrounding the plasma on all sides. The electric field distribution inside the plasma, which determines the ion flux distribution on the vessel walls, is controlled by low-energy plasma bulk electrons. The relatively small surface area of the anode leads to the formation of an anode glow affecting the plasma uniformity. Comparisons with experimental data and predictions for ITER are presented in a companion paper.

  7. Glow discharges with electrostatic confinement of fast electrons

    NASA Astrophysics Data System (ADS)

    Kolobov, V. I.; Metel, A. S.

    2015-06-01

    This review presents a unified treatment of glow discharges with electrostatic confinement of fast electrons. These discharges include hollow cathode discharges, wire and cage discharges, reflect discharges with brush and multirod cathodes, and discharges in crossed electric and magnetic fields. Fast electrons bouncing inside electrostatic traps provide efficient ionization of gas at very low gas pressures. The electrostatic trap effect (ETE) was first observed by Paschen in hollow cathode discharges almost a century ago. The key parameters that define fundamental characteristics of ETE discharges are the ionization length λN, the penetration range, Λ, and the diffusion length λ of the fast electrons, and two universal geometric parameters of the traps: effective width a and length L. Peculiarities of electron kinetics and ion collection mechanism explain experimental observations for different trap geometries. The ETE is observed only at Λ > a, when the penetration range of the γ-electrons emitted by the cathode exceeds the trap width. In the optimal pressure range, when λN > a, and Λ < L, the cathode potential fall Uc is independent of gas pressure p. With increasing current, Uc tends to its upper limit W/eβγ, where β is the percentage of ions arriving at the cathode and W is the gas ionization cost. In the low-pressure range, Λ > L, Uc rises from hundreds to thousands of volts. The sign of the anode potential fall, Ua, depends on the anode surface Sa and its position. When Sa is large compared to a critical value S*, Ua is negative and small. At Sa < S*, the value of Ua becomes positive and rises up to 0.5-1 kV with decreasing p ultimately causing discharge extinction. Scaling laws indicate common physics between vacuum discharges and atmospheric pressure micro-discharges. We discuss peculiarities of electron kinetics under different conditions using semi-analytical models. Recent experimental results and applications of glow

  8. Glow Discharge Optical Spectroscopy of Ion Implanted Gallium Arsenide.

    DTIC Science & Technology

    1979-12-01

    a depth profile. Obj ect ives Work on this thesis is a part of the continuing research by thca Air Force Avionics Laboratory. Three specific objec...AD- A *" 413 AIR FORCE INST OF YENf WRIGNT-PATTIRSO APB ON /I GLOV OICHARK OPTICAL SPECTROSCOPY OK SON ZNPLANTID "eLL Up AN-fTC (U) MC 79 S PUWrWTI...8217S THESIS,_ (,/AFIT/GE/EE/79D-2 ~ ~ a t u Approved for public release; distribution unlimited. AFIT/GE/EE/79D-29 GLOW DISCHARGE OPTICAL SPECTROSCOPY

  9. Radial Distributions of Dusty Plasma Parameters in a Glow Discharge

    SciTech Connect

    Fedoseev, A. V.; Sukhinin, G. I.

    2011-11-29

    A self-consistent model for radial distributions of dusty plasma parameters in a DC glow discharge based on the non-local Boltzmann equation for EEDF, the drift-diffusion equation for ions, and the Poisson equation for self-consistent electric field is presented. The results show that for the case of high dust particles density when the recombination of electrons and ions exceeds the ionization near the tube axis, radial electron and ion fluxes change their direction toward the center of the tube, and the radial electric field is reversed.

  10. Reproducing continuous radio blackout using glow discharge plasma

    SciTech Connect

    Xie, Kai; Li, Xiaoping; Liu, Donglin; Shao, Mingxu; Zhang, Hanlu

    2013-10-15

    A novel plasma generator is described that offers large-scale, continuous, non-magnetized plasma with a 30-cm-diameter hollow structure, which provides a path for an electromagnetic wave. The plasma is excited by a low-pressure glow discharge, with varying electron densities ranging from 10{sup 9} to 2.5 × 10{sup 11} cm{sup −3}. An electromagnetic wave propagation experiment reproduced a continuous radio blackout in UHF-, L-, and S-bands. The results are consistent with theoretical expectations. The proposed method is suitable in simulating a plasma sheath, and in researching communications, navigation, electromagnetic mitigations, and antenna compensation in plasma sheaths.

  11. Inception of Snapover and Gas Induced Glow Discharges

    NASA Technical Reports Server (NTRS)

    Galofaro, J. T.; Vayner, B. V.; Degroot, W. A.; Ferguson, D. C.; Thomson, C. D.; Dennison, J. R.; Davies, R. E.

    2000-01-01

    Ground based experiments of the snapover phenomenon were conducted in the large vertical simulation chamber at the Glenn Research Center (GRC) Plasma Interaction Facility (PIF). Two Penning sources provided both argon and xenon plasmas for the experiments. The sources were used to simulate a variety of ionospheric densities pertaining to a spacecraft in a Low Earth Orbital (LEO) environment. Secondary electron emission is believed responsible for dielectric surface charging, and all subsequent snapover phenomena observed. Voltage sweeps of conductor potentials versus collected current were recorded in order to examine the specific charging history of each sample. The average time constant for sample charging was estimated between 25 and 50 seconds for all samples. It appears that current drops off by approximately a factor of 3 over the charging time of the sample. All samples charged in the forward and reverse bias directions, demonstrated hysteresis. Current jumps were only observed in the forward or positive swept voltage direction. There is large dispersion in tile critical snapover potential when repeating sweeps on any one sample. The current ratio for the first snapover region jumps between 2 and 4.6 times, with a standard deviation less than 1.6. Two of the samples showed even larger current ratios. It is believed the second large snapover region is due to sample outgassing. Under certain preset conditions, namely at the higher neutral gas background pressures, a perceptible blue-green glow was observed around the conductor. The glow is believed to be a result of secondary electrons undergoing collisions with an expelled tenuous cloud of gas, that is outgassed from the sample. Spectroscopic measurements of the glow discharge were made in an attempt to identify specific lines contributing to the observed glow.

  12. Means of introducing an analyte into liquid sampling atmospheric pressure glow discharge

    DOEpatents

    Marcus, R. Kenneth; Quarles, Jr., Charles Derrick; Russo, Richard E.; Koppenaal, David W.; Barinaga, Charles J.; Carado, Anthony J.

    2017-01-03

    A liquid sampling, atmospheric pressure, glow discharge (LS-APGD) device as well as systems that incorporate the device and methods for using the device and systems are described. The LS-APGD includes a hollow capillary for delivering an electrolyte solution to a glow discharge space. The device also includes a counter electrode in the form of a second hollow capillary that can deliver the analyte into the glow discharge space. A voltage across the electrolyte solution and the counter electrode creates the microplasma within the glow discharge space that interacts with the analyte to move it to a higher energy state (vaporization, excitation, and/or ionization of the analyte).

  13. Endotoxin removal by radio frequency gas plasma (glow discharge)

    NASA Astrophysics Data System (ADS)

    Poon, Angela

    2011-12-01

    Contaminants remaining on implantable medical devices, even following sterilization, include dangerous fever-causing residues of the outer lipopolysaccharide-rich membranes of Gram-negative bacteria such as the common gut microorganism E. coli. The conventional method for endotoxin removal is by Food & Drug Administration (FDA)-recommended dry-heat depyrogenation at 250°C for at least 45 minutes, an excessively time-consuming high-temperature technique not suitable for low-melting or heat-distortable biomaterials. This investigation evaluated the mechanism by which E. coli endotoxin contamination can be eliminated from surfaces during ambient temperature single 3-minute to cumulative 15-minute exposures to radio-frequency glow discharge (RFGD)-generated residual room air plasmas activated at 0.1-0.2 torr in a 35MHz electrodeless chamber. The main analytical technique for retained pyrogenic bio-activity was the Kinetic Chromogenic Limulus Amebocyte Lysate (LAL) Assay, sufficiently sensitive to document compliance with FDA-required Endotoxin Unit (EU) titers less than 20 EU per medical device by optical detection of enzymatic color development corresponding to < 0.5 EU/ml in sterile water extracts of each device. The main analytical technique for identification of chemical compositions, amounts, and changes during sequential reference Endotoxin additions and subsequent RFGD-treatment removals from infrared (IR)-transparent germanium (Ge) prisms was Multiple Attenuated Internal Reflection (MAIR) infrared spectroscopy sensitive to even monolayer amounts of retained bio-contaminant. KimaxRTM 60 mm x 15 mm and 50mm x 15mm laboratory glass dishes and germanium internal reflection prisms were inoculated with E. coli bacterial endotoxin water suspensions at increments of 0.005, 0.05, 0.5, and 5 EU, and characterized by MAIR-IR spectroscopy of the dried residues on the Ge prisms and LAL Assay of sterile water extracts from both glass and Ge specimens. The Ge prism MAIR

  14. Boundary Effect of Planar Glow Dielectric Barrier Discharge and Its Influence on the Discharge Structure

    NASA Astrophysics Data System (ADS)

    Xu, Shaowei; Li, Lulu; Ouyang, Jiting

    2015-05-01

    The dielectric barrier discharge (DBD) in the glow regime in neon has been investigated by experiment and two-dimensional (2D) fluid modeling. The discharge was carried out in a planar DBD system with segmented-electrodes driven by square-wave voltage. The results show that the glow DBD originates in the center of the electrode and expands outward to the electrode edge during each half cycle of the voltage, forming a radial structure. The discharge decays firstly in the inner area but sustains longer in the edge area, showing a reversed discharge area. The discharge cannot completely cover the entire electrode surface, but remains a border of non- or weak discharge. The fluid modeling shows a similar result in agreement with the experiments. The simulations indicate that the electric field in the edge area is distorted due to the boundary effect so that the electric field and charge distribution are different from that in the inner part. The distorted field reduces the longitudinal component near the edge and causes the local field to be lower than that in the center, and hence makes the discharge behindhand. It also induces a transverse field that makes the discharge extend radially outward to the edge. The boundary effect plays an important role in the glow DBD structure. supported by National Natural Science Foundation of China (No. 11175017)

  15. Demonstration of Separation Control Using Glow-Discharge Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Hultgren, Lennart S.; Ashpis, David E.

    2003-01-01

    Active flow control of boundary-layer separation using glow-discharge plasma actuators is studied experimentally. Separation is induced on a flat plate installed in a closed-circuit wind tunnel by a shaped insert on the opposite wall. The flow conditions represent flow over the suction surface of a modem low-pressure-turbine airfoil. The Reynolds number, based on wetted plate length and nominal exit velocity, is varied from 50,000 to 300,000, covering cruise to takeoff conditions. Low (0.2%) and high (2.5%) free-stream turbulence intensities are set using passive grids. A spanwise-oriented phased-plasma-array actuator, fabricated on a printed circuit board, is surface-flush-mounted upstream of the separation point and can provide forcing in a wide frequency range. Static surface pressure measurements and hot-wire anemometry of the base and controlled flows are performed and indicate that the glow-discharge plasma actuator is an effective device for separation control.

  16. Demonstration of Separation Delay with Glow-Discharge Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Hultgren, Lennart S.; Ashpis, David E.

    2004-01-01

    Active flow control of boundary-layer separation using glow-discharge plasma actuators is studied experimentally. Separation is induced on a flat plate installed in a closed-circuit wind tunnel by a shaped insert on the opposite wall. The flow conditions represent flow over the suction surface of a modern low-pressure-turbine airfoil. The Reynolds number, based on wetted plate length and nominal exit velocity, is varied from 50,000 to 300,000, covering cruise to takeoff conditions. Low (0.2 percent) and high (2.5 percent) free-stream turbulence intensities are set using passive grids. A spanwise-oriented phased-plasma-array actuator, fabricated on a printed circuit board, is surface-flush-mounted upstream of the separation point and can provide forcing in a wide frequency range. Static surface pressure measurements and hot-wire anemometry of the base and controlled flows are performed and indicate that the glow-discharge plasma actuator is an effective device for separation control.

  17. Flush-mounted probe diagnostics for argon glow discharge plasma

    SciTech Connect

    Xu, Liang Cao, Jinxiang; Liu, Yu; Wang, Jian; Du, Yinchang; Zheng, Zhe; Zhang, Xiao; Wang, Pi; Zhang, Jin; Li, Xiao; Qin, Yongqiang; Zhao, Liang

    2014-09-15

    A comparison is made between plasma parameters measured by a flush-mounted probe (FP) and a cylindrical probe (CP) in argon glow discharge plasma. Parameters compared include the space potential, the plasma density, and the effective electron temperature. It is found that the ion density determined by the FP agrees well with the electron density determined by the CP in the quasi-neutral plasma to better than 10%. Moreover, the space potential and effective electron temperature calculated from electron energy distribution function measured by the FP is consistent with that measured by the CP over the operated discharge current and pressure ranges. These results present the FP can be used as a reliable diagnostic tool in the stable laboratory plasma and also be anticipated to be applied in other complicated plasmas, such as tokamaks, the region of boundary-layer, and so on.

  18. Flush-mounted probe diagnostics for argon glow discharge plasma.

    PubMed

    Xu, Liang; Cao, Jinxiang; Liu, Yu; Wang, Jian; Du, Yinchang; Zheng, Zhe; Zhang, Xiao; Wang, Pi; Zhang, Jin; Li, Xiao; Qin, Yongqiang; Zhao, Liang

    2014-09-01

    A comparison is made between plasma parameters measured by a flush-mounted probe (FP) and a cylindrical probe (CP) in argon glow discharge plasma. Parameters compared include the space potential, the plasma density, and the effective electron temperature. It is found that the ion density determined by the FP agrees well with the electron density determined by the CP in the quasi-neutral plasma to better than 10%. Moreover, the space potential and effective electron temperature calculated from electron energy distribution function measured by the FP is consistent with that measured by the CP over the operated discharge current and pressure ranges. These results present the FP can be used as a reliable diagnostic tool in the stable laboratory plasma and also be anticipated to be applied in other complicated plasmas, such as tokamaks, the region of boundary-layer, and so on.

  19. Emergence and consequences of lateral sample heterogeneity in glow discharge spectrometry

    NASA Astrophysics Data System (ADS)

    Storey, Andrew P.; Ray, Steven J.; Hoffmann, Volker; Voronov, Maxim; Engelhard, Carsten; Buscher, Wolfgang; Hieftje, Gary M.

    2016-12-01

    Conventional glow discharge emission or mass spectrometry requires the assumption that the surface of the sample is homogeneous. However, recent developments in glow discharge imaging appear to offer an opportunity to obtain three-dimensional concentration maps, in which this assumption is no longer necessary. Here, experiments, models, and a summary of earlier work are combined to examine the sputtering behavior of elemental and morphological heterogeneities in a sample. The theoretical model reveals gaps in current knowledge of glow discharge sputtering of heterogeneous samples, particularly indicating that heterogeneity in the sample leads to roughened crater bottoms and how additional morphology can evolve. Additionally, a three-dimensional profiling microscope is used to characterize the effects of surface inclusions on the sputtering process in a DC glow discharge in a reduced-pressure argon environment. Findings have important implications for bulk analysis, depth-profiling, and elemental surface mapping with glow discharge spectrometry.

  20. Mineralization of aqueous pentachlorophenolate by anodic contact glow discharge electrolysis.

    PubMed

    Yang, Haiming; Tezuka, Meguru

    2011-01-01

    Exhaustive mineralization of pentachlorophenolate ion (PCP) in phosphate buffer was carried out using anodic contact glow discharge electrolysis (CGDE), in which plasma was sustained between the electrolyte and anode. During CGDE, PCP degraded smoothly. The amount of total organic carbon decreased significantly, indicating the eventual conversion of the carbon atoms of benzene nucleus to inorganic carbons. Furthermore, chlorine atoms in PCP were liberated as chloride ions. As a primary intermediate product, 2,3,5,6-tetrachloro-1,4-benzoquinone was detected, and oxalate and formate as byproducts were also found. It was revealed that disappearance of PCP obeyed first-order kinetics. The reaction rate was generally unaffected by both O2 and inert gases in the cell, although it decreased by raising initial pH of solution. In addition, a plausible reaction pathway involving hydroxyl radical was proposed.

  1. Mass dependency of turbulent parameters in stationary glow discharge plasmas

    SciTech Connect

    Titus, J. B.; Alexander, A. B.; Wiggins, D. L.; Johnson, J. A. III

    2013-05-15

    A direct current glow discharge tube is used to determine how mass changes the effects of certain turbulence characteristics in a weakly ionized gas. Helium, neon, argon, and krypton plasmas were created, and an axial magnetic field, varied from 0.0 to 550.0 Gauss, was used to enhance mass dependent properties of turbulence. From the power spectra of light emission variations associated with velocity fluctuations, determination of mass dependency on turbulent characteristic unstable modes, energy associated with turbulence, and the rate at which energy is transferred from scale to scale are measured. The magnetic field strength is found to be too weak to overcome particle diffusion to the walls to affect the turbulence in all four types of plasmas, though mass dependency is still detected. Though the total energy and the rate at which the energy moves between scales are mass invariant, the amplitude of the instability modes that characterize each plasma are dependent on mass.

  2. High-pressure dc glow discharges in hollow diamond cathodes

    NASA Astrophysics Data System (ADS)

    Truscott, B. S.; Turner, C.; May, P. W.

    2016-04-01

    We report the generation and characterization of dc helium microdischarges at several times atmospheric pressure in monolithic diamond hollow-cathode devices having cavity diameters on the order of 100 μm. I-V characteristics indicated operation in the glow discharge regime even at nearly 10 atm, while spectroscopic measurements of the N2 C3Πu  →  B3Πg emission returned rotational temperatures always around 420 K, with a pressure-dependent vibrational population distribution. The variation of breakdown voltage with pressure closely followed Paschen’s law, but with offsets in both axes that we tentatively ascribe to strong diffusive loss and a partial thermalization of electron energies under the high pressures considered here.

  3. Self-pulsing in a low-current hollow cathode discharge: From Townsend to glow discharge

    SciTech Connect

    Qin, Yu; Xie, Kan; Zhang, Yu; Ouyang, Jiting

    2016-02-15

    We investigate the self-pulsing phenomenon of a low current cavity discharge in a cylindrical hollow cathode in pure argon. The waveforms of pulsed current and voltage are measured, and the time-averaged and time-resolved images of hollow cathode discharge are recorded by using high-speed intensified charge coupled device camera. The results show that the self-pulsing is a mode transition between low-current stage of Townsend discharge and high-current stage of glow discharge. During the self-pulsing, the current rising time relates to the dissipation of space charges, and the decay time relates to the reconstruction of the virtual anode by the accumulation of positive ions. Whether or not space charges can form and keep the virtual anode is responsible for the discharge mode and hence plays an important role in the self-pulsing phenomenon in low current hollow cathode discharge.

  4. Experimental studies of breakdown characteristics in pulse-modulated radio-frequency atmospheric discharge

    NASA Astrophysics Data System (ADS)

    Huo, W. G.; Zhang, X.; Gu, J. L.; Ding, Z. F.

    2016-12-01

    The influences of the pulse off-time on the breakdown voltage of the first pulse and the stable pulse discharge (having repeatedly undergone a process of ignition, maintenance, and extinction) are experimentally investigated in a pulse-modulated radio-frequency atmospheric pressure argon discharge. The experimental results show that the first pulse discharge breakdown voltage decreases, but the stable pulse discharge breakdown voltage increases with increasing the pulse off-time. In a large region of the pulse off-time, the luminescence property of the initial breakdown stage is studied using a high speed camera. The captured images at different pulse off-times demonstrate that the gas breakdown exhibits five key characteristics: single-point random breakdown, multi-point random breakdown, stable uniform breakdown, stable glow mixed with pattern breakdown, and stable nonuniform pattern breakdown. The physical reasons for these results are discussed.

  5. Influence of oxygen traces on an atmospheric-pressure radio-frequency capacitive argon plasma discharge

    SciTech Connect

    Li Shouzhe; Wu Qi; Yan Wen; Wang Dezhen; Uhm, Han S.

    2011-10-15

    An atmospheric-pressure capacitive discharge source driven by radio-frequency power supply at 13.56 MHz has been developed experimentally that is capable of producing a homogeneous and cold glow discharge in O{sub 2}/Ar. With respect to the influence of oxygen component when diluted into argon plasma discharge on the discharge characteristics, the measurements of the electrical parameters (impedance, phase angle, resistance, and reactance) are made systematically and the densities of the metastable and resonant state of argon are determined by means of optical emission spectroscopy (OES). It is shown that the admixture of oxygen into argon plasma not only changes the electric characteristics but also alters the optical emission spectra greatly due to strong interaction between the oxygen content and the argon in the plasma environment.

  6. Modeling of asymmetric pulsed phenomena in dielectric-barrier atmospheric-pressure glow discharges

    SciTech Connect

    Ha Yan; Wang Huijuan; Wang Xiaofei

    2012-01-15

    Asymmetric current pulses in dielectric-barrier atmospheric-pressure glow discharges are investigated by a self-consistent, one-dimensional fluid model. It is found that the glow mode and Townsend mode can coexist in the asymmetric discharge even though the gas gap is rather large. The reason for this phenomenon is that the residual space charge plays the role of anode and reduces the gap width, resulting in the formation of a Townsend discharge.

  7. Use of Atmospheric Glow Discharge Plasma to Modify Spaceport Materials

    NASA Technical Reports Server (NTRS)

    Trigwell, S.; Shuerger, A. C.; Buhler, C. R.; Calle, C. J.

    2006-01-01

    Numerous materials used in spaceport operations require stringent evaluation before they can be utilized. It is critical for insulative polymeric materials that any surface charge be dissipated as rapidly as possible to avoid Electrostatic Discharges (ESD) that could present a danger. All materials must pass the Kennedy Space Center (KSC) standard electrostatic test [1]; however several materials that are considered favorable for Space Shuttle and International Space Station use have failed. Moreover, to minimize contamination of Mars spacecraft, spacecraft are assembled under cleanroom conditions and specific cleaning and sterilizing procedures are required for all materials. However, surface characteristics of these materials may allow microbes to survive by protecting them from sterilization and cleaning techniques. In this study, an Atmospheric Pressure Glow Discharge Plasma (APGD) [2] was used to modify the surface of several materials. This allowed the materials surface to be modified in terms of hydrophilicity, roughness, and conductivity without affecting the bulk properties. The objectives of this study were to alter the surface properties of polymers for improved electrostatic dissipation characteristics, and to determine whether the consequent surface modification on spaceport materials enhanced or diminished microbial survival.

  8. Killing Microorganisms with the One Atmosphere Uniform Glow Discharge Plasma

    NASA Astrophysics Data System (ADS)

    South, Suzanne; Kelly-Wintenberg, Kimberly; Montie, T. C.; Reece Roth, J.; Sherman, Daniel; Morrison, Jim; Chen, Zhiyu; Karakaya, Fuat

    2000-10-01

    There is an urgent need for the development of new technologies for sterilization and decontamination in the fields of healthcare and industrial and food processing that are safe, cost-effective, broad-spectrum, and not deleterious to samples. One technology that meets these criteria is the One Atmosphere Uniform Glow Discharge Plasma (OAUGDP). The OAUGDP operates in air and produces uniform plasma without filamentary discharges at room temperature, making this technology advantageous for sterilization of heat sensitive materials. The OAUGDP operates in a frequency band determined by the ion trapping mechanisms provided that, for air, the electric field is above 8.5kV/cm. The OAUGDP efficiently generates plasma reactive oxygen species (ROS) including atomic oxygen and oxygen free radicals without the requirement of a vacuum system. We have demonstrated the efficacy of the OAUGDP in killing microorganisms including bacteria, yeast, viruses, and spores in seconds to minutes on a variety of surfaces such as glass, films and fabrics, stainless steel, paper, and agar.

  9. Efficiency of surface cleaning by a glow discharge for plasma spraying coating

    NASA Astrophysics Data System (ADS)

    Kadyrmetov, A. M.; Kashapov, N. F.; Sharifullin, S. N.; Saifutdinov, A. I.; Fadeev, S. A.

    2016-06-01

    The article presents the results of experimental studies of the quality of cleaning steel surfaces by a glow discharge for plasma spraying. Shows the results of measurements of the angle of surface wetting and bond strength of the plasma coating to the surface treated. The dependence of the influence of the glow discharge power, chamber pressure, distance between the electrodes and the processing time of the surface on cleaning efficiency. Optimal fields of factors is found. It is shown increase joint strength coating and base by 30-80% as a result of cleaning the substrate surface by a glow discharge plasma spraying.

  10. Aqueous organic dye discoloration induced by contact glow discharge electrolysis.

    PubMed

    Wang, Lei

    2009-11-15

    In this study, effects of applied voltage, types of electrolytes, initial substrate concentration, radical scavengers and iron salts on the aqueous polar brilliant B (PBB) discoloration induced by contact glow discharge electrolysis (CGDE) were examined. Experimental results showed that the PBB discoloration proceeded faster in chloride solution than in phosphate or sulfate solutions. Increasing the applied voltage from 450V to 550V did not enhance the discoloration when the applied current was kept constant. Addition of a small amount of hydroxyl scavengers (methanol) to the solution decreased the discoloration, whereas addition of a large amount of methanol increased the discoloration. During the treatment, TOC of the solution smoothly decreased whereas COD of the solution gradually increased due to the production of H(2)O(2) in the liquid phase. Iron salts enhanced the discoloration significantly due to the additional Fenton reaction. Higher initial PBB concentration resulted in lower color removal efficiency, indicating that the PBB discoloration by CGDE did not observe the first-order reaction kinetics in inert electrolytic solutions.

  11. Glow-Discharge Production of Oxygen from the Martian Atmosphere

    NASA Astrophysics Data System (ADS)

    Hughes, Caleb; Outlaw, Ronald

    One of the most crucial aspects of any mission to Mars is a continual supply of oxygen for astronaut respiration on site. The most popular approach to this problem favors in-situ oxygen production on Mars, utilizing the CO2 Martian atmosphere. However, this requires a large energy budget. NASA's current plans for Mars include sending a system called MOXIE, which produces oxygen through solid oxide electrolysis at high temperatures. An alternative approach utilizes the 6 Torr Martian atmosphere to provide a continual source of oxygen by breaking down the molecule into CO and O using a glow-discharge. After dissociation, a thin film Agmembrane uniquely permeates the atomic oxygen which then recombines to O2 on the downstream side, where it is subsequently stored. By taking advantage of recent advances in thin film technology to reduce the thickness of the film to many orders of magnitude less than used in the initial study, a corresponding increase in O2 flux can be realized. The Ag thin film requires the support of a porous ceramic substructure. With this system, it is shown that this method produces a viable energy efficient alternative to MOXIE.

  12. Synthesis of Single-Walled Carbon Nanotubes in a Glow Discharge Fine Particle Plasma

    SciTech Connect

    Imazato, N.; Imano, M.; Hayashi, Y.

    2008-09-07

    Carbon fine particles were synthesized being negatively charged and confined in a glow discharge plasma. The deposited fine particles were analyzed by Raman spectroscopy and transmission electron microscopy (TEM) and were confirmed to include single-walled carbon nanotubes.

  13. Binary and ternary gas mixtures for use in glow discharge closing switches

    DOEpatents

    Hunter, Scott R.; Christophorou, Loucas G.

    1990-01-01

    Highly efficient binary and ternary gas mixtures for use in diffuse glow discharge closing switches are disclosed. The binary mixtures are combinations of helium or neon and selected perfluorides. The ternary mixtures are combinations of helium, neon, or argon, a selected perfluoride, and a small amount of gas that exhibits enhanced ionization characteristics. These mixtures are shown to be the optimum choices for use in diffuse glow discharge closing switches by virtue of the combined physio-electric properties of the mixture components.

  14. Effect of volume and surface charges on discharge structure of glow dielectric barrier discharge

    NASA Astrophysics Data System (ADS)

    Xu, Shao-Wei; He, Feng; Wang, Yu; Li, Lulu; Ouyang, Ji-Ting

    2013-08-01

    The effect of volume and surface charges on the structure of glow dielectric barrier discharge (DBD) has been investigated numerically by using two-dimensional (2D) fluid modeling. The local increase of volume or surface charges induces a kind of activation-inhibition effect, which enhances the local volume discharge and inhibits the discharge in neighborhoods, resulting in non-uniform discharge. The activation-inhibition effect due to the non-uniform volume and/or surface charges depends on the non-uniformity itself and the applied voltage. The activation-inhibition of non-uniform charges has different effects on the volume charges and the accumulated surface charges. The distribution of remaining free charges (seed electrons) in volume at the beginning of voltage pulse plays a key role for the glow DBD structure, resulting in a patterned DBD, when the seed electrons are non-uniform at higher frequency and moderate voltage or uniform DBD, when the seed electrons are uniform at lower frequency or high voltage. The distribution of surface charges is not the determining factor but a result of the formed DBD structure.

  15. Note: Rapid reduction of graphene oxide paper by glow discharge plasma

    SciTech Connect

    Bo, Zheng; Qian, Jiajing; Duan, Liangping; Qiu, Kunzan Yan, Jianhua; Cen, Kefa; Han, Zhao Jun; Ostrikov, Kostya

    2015-05-15

    This note reports on a novel method for the rapid reduction of graphene oxide (GO) paper using a glow discharge plasma reactor. Glow discharge is produced and sustained between two parallel-plate graphite electrodes at a pressure of 240 mTorr. By exposing GO paper at the junction of negative-glow and Faraday-dark area for 4 min, the oxygen-containing groups can be effectively removed (C/O ratio increases from 2.6 to 7.9), while the material integrality and flexibility are kept well. Electrochemical measurements demonstrate that the as-obtained reduced GO paper can be potentially used for supercapacitor application.

  16. A large gap of radio frequency dielectric barrier atmospheric pressure glow discharge

    SciTech Connect

    Li, B.; Chen, Q.; Liu, Z. W.

    2010-01-25

    A large gap was acquired between electrodes (up to 5.5 mm) of Ar atmospheric pressure glow discharge in radio frequency dielectric barrier discharge (rf-DBD). The discharge of Ar plasma was characterized by I-V curve and Lissajous plot, and the effective power of the discharge was calculated based on the measured Lissajous plot and found to be higher than 90% of the input power. To gain a thorough understanding of the mechanism, the rf-DBD with a single dielectric barrier layer operating in gamma mode glow discharge of N{sub 2} plasma was diagnosed in spatial resolution through optical emission spectroscopy. It was concluded that secondary electron emission might be responsible for the sustainable glow discharge in the large gap rf-DBD plasma.

  17. Modeling plasma glow discharges in Air near a Mach 3 bow shock with KRONOS

    NASA Astrophysics Data System (ADS)

    Rassou, Sebastien; Labaune, Julien; Packan, Denis; Elias, Paul-Quentin

    2016-09-01

    In this work, plasma glow discharge in Air is modeled near a Mach 3 bow shock. Numerical simulations are performed using the coupling KRONOS which have been developed at ONERA. The flow field is modeled using the code CFD: CEDRE from ONERA and the electrical and plasma part by the EDF open-source code CODE_SATURNE. The plasma kinetic modeling consists on a two-term Boltzmann equation solver and a chemical reaction solver depending of the electric field. The coupling KRONOS is fully parallelized and run on ONERA supercomputers. The shock wave is formed by the propagation of a supersonic flow (M = 3) through a truncated conical model mounted with a central spike. Depending on the spike's voltage value, corona, glow or arc regime could be obtained in a steady flow. The parameters for the supersonic flow and the spike configurations are chosen to be in glow discharge regime and to reproduce the experimental setup. In our simulations, 12 species and 80 reactions (ionization, electronic or vibrational excitation, attachment etc ...) are considered to properly model the glow discharge and the afterglow. In a stationary flow, glow discharge is observed only at the upstream of the shock wave near the high voltage spike. Behind the bow shock, in the afterglow, negative ions are provided by electrons attachment with O2. The negative ions flow convection ensures the electrical conduction and the establishment of the glow discharge.

  18. Nonlinear dynamics modulation in a neon glow discharge plasma

    NASA Astrophysics Data System (ADS)

    Miller, Paul M.

    In dynamics modulation, two modes in a driven neon glow discharge alternate as the dominant mode as their response to the driving force alternates between spatiotemporal and temporal periodic pulling. This phenomenon was first noted by Koepke, Weltmann, and Selcher (Bull. Am. Phys. Soc. 40, 1716 (1995)), who saw two limited but representative cases and proposed a mechanism (Phys. Rev. E 62, 2773 (2000)) by which it occurs. The intent of this dissertation is to document experimentally and test the dynamics modulation mechanism they proposed. Using a new extension of a previous mathematical treatment of periodic pulling, the resulting experimental data are used to verify the predicted mechanism. A numerical model is also presented that reproduces the signature of dynamics modulation and further supports the validity of the mechanism. For two pairs of mode frequencies, three complete data series as driving frequency is increased are presented. Each of these data series shows the progression of the system from pure spatiotemporal behavior, through dynamics modulation, and ending at entrainment in the upper mode. Ionization wave modes are examined using time series recorded using a photodiode with a narrow band filter that selectively passes the primary neon spectral line at 640 nm. The system was periodically driven using a narrow-band ring dye laser tuned to a wavelength near the metastable neon transition at 588.35 nm. The amplitude of the driving force was decreased (increased) by tuning the laser away from (nearer to) the center of the neon line, while the driving frequency was controlled by an acousto-optic modulator chopping the laser beam at the desired frequency. Arnol'd tongue boundaries identifying the edges of frequency entrainment regions in the driving amplitude-driving frequency plane were established for four different discharge currents. The (upward) dynamics modulation behavior seen by Koepke, Weltmann, and Selcher was reproduced and additional data

  19. Optical emission spectroscopy of glow, Townsend-like and radiofrequency DBDs in an Ar/NH3 mixture

    NASA Astrophysics Data System (ADS)

    Bazinette, R.; Paillol, J.; Massines, F.

    2015-10-01

    Three homogeneous DBD modes have been observed in argon ammonia Penning mixture. The transition from glow to Townsend-like to radiofrequency modes happens when the frequency increases from 50 kHz and 9.6 MHz. The aim of this paper is to characterize these modes based on the study of optical emission spectra. The transition from glow mode to Townsend-like mode is characterized by stronger argon emissions associated to higher energetic electrons. The radio-frequency mode is characterized by a continuum in the UV-vis range. This continuum is attributed to bremsstrahlung emission. Its presence is explained by a high density of less energetic electrons which is consistent with a decrease of argon emissions and an increase of the NH 336 nm system associated with electrons of low energy.

  20. Detrapping of tungsten nanoparticles in a direct-current argon glow discharge

    SciTech Connect

    Couëdel, L. Kumar, K. Kishor; Arnas, C.

    2014-12-15

    Nanoparticles are grown from the sputtering of a tungsten cathode in a direct current argon glow discharge. Laser light scattering of a vertical laser sheet going through the plasma reveals that the dust particle cloud is compressed and pushed towards the anode during the discharge. Scanning electron microscopy images of substrates exposed to the plasma for given durations show that dust particles are continuously falling down on the anode during the discharge. These observations are explained by the fact that the electrostatic force at the negative glow-anode sheath boundary cannot balance the ion drag, gravity, and thermophoresis forces for particles of more than a few tens of nanometres in diameter.

  1. Non-Thermal Equilibrium Atmospheric Pressure Glow-Like Discharge Plasma Jet

    NASA Astrophysics Data System (ADS)

    Chang, Zhengshi; Yao, Congwei; Zhang, Guanjun

    2016-01-01

    Non-thermal equilibrium atmospheric pressure plasma jet (APPJ) is a cold plasma source that promises various innovative applications, and the uniform APPJ is more favored. Glow discharge is one of the most effective methods to obtain the uniform discharge. Compared with the glow dielectric barrier discharge (DBD) in atmospheric pressure, pure helium APPJ shows partial characteristics of both the glow discharge and the streamer. In this paper, considering the influence of the Penning effect, the electrical and optical properties of He APPJ and Ar/NH3 APPJ were researched. A word “Glow-like APPJ” is used to characterize the uniformity of APPJ, and it was obtained that the basic characteristics of the glow-like APPJ are driven by the kHz AC high voltage. The results can provide a support for generating uniform APPJ, and lay a foundation for its applications. supported by National Natural Science Foundation of China (Nos. 51307133, 51125029, 51221005) and the Fundamental Research Funds for the Central Universities of China (Nos. xjj2012132, xkjc2013004)

  2. Requirements of the glow discharge techniques to the fundamentals - an exemplary approach.

    PubMed

    Broekaert, J A

    1996-07-01

    The importance of gaining knowledge on the fundamental processes in glow discharges in the field of the signal generation, the sputtering phenomena taking place in the case of solids and the analyte breakdown in the excitation of gases is treated. For gaining more knowledge on the plasma processes diagnostics including temperature and electron number density as well as gas and analyte atom and ion densities are required. For the sputtering process, it is shown at the hand of measurements with gas-jet enhanced sputtering and magnetically enhanced sputtering that selective sputtering may occur and that the influence of the analyte loading of the glow discharge plasma needs further study. For the case of the introduction of gaseous samples, the analyte distribution as well as the break-down mechanisms and kinetics in the case of molecular species ask for further study as shown by experiments with gas-sampling glow discharges.

  3. Observation and interpretation of energy efficient, diffuse direct current glow discharge at atmospheric pressure

    SciTech Connect

    Tang, Jie Jiang, Weiman; Wang, Yishan; Zhao, Wei; Li, Jing; Duan, Yixiang

    2015-08-24

    A diffuse direct-current glow discharge was realized with low energy consumption and high energy utilization efficiency at atmospheric pressure. The formation of diffuse discharge was demonstrated by examining and comparing the electrical properties and optical emissions of plasmas. In combination with theoretical derivation and calculation, we draw guidelines that appearance of nitrogen ions at low electron density is crucial to enhance the ambipolar diffusion for the expansion of discharge channel and the increasing ambipolar diffusion near the cathode plays a key role in the onset of diffuse discharge. An individual-discharge-channel expansion model is proposed to explain the diffuse discharge formation.

  4. Binary and ternary gas mixtures for use in glow discharge closing switches

    DOEpatents

    Hunter, S.R.; Christophorou, L.G.

    1988-04-27

    Highly efficient binary and ternary gas mixtures for use in diffuse glow discharge closing switches are disclosed. The binary mixtures are combinations of helium or neon and selected perfluorides. The ternary mixtures are combinations of helium, neon, or argon, a selected perfluoride, and a small amount of gas that exhibits enhanced ionization characteristics. These mixtures are shown to be the optimum choices for use in diffuse glow discharge closing switches by virtue if the combines physio-electric properties of the mixture components. 9 figs.

  5. Characteristics of liquid flow induced by atmospheric-pressure DC glow discharge in contact with liquid

    NASA Astrophysics Data System (ADS)

    Tochikubo, Fumiyoshi; Aoki, Takuya; Shirai, Naoki; Uchida, Satoshi

    2017-04-01

    In this work, we investigated the characteristics of liquid flow induced by atmospheric-pressure dc glow discharge in contact with a liquid. The spatiotemporal development of liquid flow was visualized by the schlieren method, and the temperature distribution was measured using microencapsulated thermotropic liquid crystal particles dispersed in a liquid. We confirmed the appearance of specific downward liquid flow immediately below the dc glow discharge. The characteristics of downward liquid flow were reproduced by fluid simulation considering a downward driving force at the plasma–liquid interface. Our results suggest that the probable driving force for the downward liquid flow was the momentum transfer of charged species at the liquid surface.

  6. Binary and ternary gas mixtures with temperature enhanced diffuse glow discharge characteristics for use in closing switches

    DOEpatents

    Christophorou, L.G.; Hunter, S.R.

    1988-06-28

    An improvement to the gas mixture used in diffuse glow discharge closing switches is disclosed which includes binary and ternary gas mixtures which are formulated to exhibit decreasing electron attachment with increasing temperature. This increases the efficiency of the conductance of the glow discharge and further inhibits the formation of an arc. 11 figs.

  7. Binary and ternary gas mixtures with temperature enhanced diffuse glow discharge characteristics for use in closing switches

    DOEpatents

    Christophorou, Loucas G.; Hunter, Scott R.

    1990-01-01

    An improvement to the gas mixture used in diffuse glow discharge closing switches is disclosed which includes binary and ternary gas mixtures which are formulated to exhibit decreasing electron attachment with increasing temperature. This increases the efficiency of the conductance of the glow discharge and further inhibits the formation of an arc.

  8. Binary and ternary gas mixtures with temperature enhanced diffuse glow discharge characteristics for use in closing switches

    DOEpatents

    Christophorou, L.G.; Hunter, S.R.

    1990-06-26

    An improvement to the gas mixture used in diffuse glow discharge closing switches is disclosed which includes binary and ternary gas mixtures which are formulated to exhibit decreasing electron attachment with increasing temperature. This increases the efficiency of the conductance of the glow discharge and further inhibits the formation of an arc. 11 figs.

  9. Formation and characteristics of patterns in atmospheric-pressure radio-frequency dielectric barrier discharge plasma

    NASA Astrophysics Data System (ADS)

    Yang, Lizhen; Liu, Zhongwei; Mao, Zhiguo; Li, Sen; Chen, Qiang

    2017-01-01

    The patterns in radio-frequency dielectric barrier discharge (RF DBD) are studied at atmospheric pressure of argon (Ar) or helium (He) mixed with nitrogen (N2) gas. When a small amount of N2 is mixed with He or Ar gas, discharge patterns are formed. In a N2/He gas mixture, besides the filament discharge that forms patterns, a glow background discharge is also observed, whereas only the filament discharge forms patterns in a N2/Ar gas mixture. The resolution of the hexagonal pattern as a function of applied power and gas flow rate is then explored. On the basis of spatial-temporal images taken using an intensified charge-coupled device (ICCD), we find that there is no interleaving of two transient hexagon sublattices in N2/Ar or N2/He plasma in RF DBD patterns, which are totally different from those in which surface charges dominated in the mid-frequency DBD plasma. This supports our hypothesis that the bulk charges dominate the pattern formation in RF DBD.

  10. Removal of floating dust in glow discharge using plasma jet

    SciTech Connect

    Ticos, C. M.; Jepu, I.; Lungu, C. P.; Chiru, P.; Zaroschi, V.; Lungu, A. M.

    2010-07-05

    Dust can be an inconvenient source of impurities in plasma processing reactors and in many cases it can cause damage to the plasma-treated surfaces. A technique for dust expulsion out of the trapping region in plasma is presented here, based on the wind force exerted on dust particles by a pulsed plasma jet. Its applicability is demonstrated by removing floating dust in the sheath of parallel-plate capacitive radio-frequency plasma.

  11. Plasma Processing with a One Atmosphere Uniform Glow Discharge Plasma (OAUGDP)

    NASA Astrophysics Data System (ADS)

    Reece Roth, J.

    2000-10-01

    The vast majority of all industrial plasma processing is conducted with glow discharges at pressures below 10 torr. This has limited applications to high value workpieces as a result of the large capital cost of vacuum systems and the production constraints of batch processing. It has long been recognized that glow discharges would play a much larger industrial role if they could be operated at one atmosphere. The One Atmosphere Uniform Glow Discharge Plasma (OAUGDP) has been developed at the University of Tennessee Plasma Sciences Laboratory. The OAUGDP is non-thermal RF plasma with the time-resolved characteristics of a classical low pressure DC normal glow discharge. An interdisciplinary team was formed to conduct exploratory investigations of the physics and applications of the OAUGDP. This team includes collaborators from the UTK Textiles and Nonwovens Development Center (TANDEC) and the Departments of Electrical and Computer Engineering, Microbiology, Food Science and Technology, and Mechanical and Aerospace Engineering and Engineering Science. Exploratory tests were conducted on a variety of potential plasma processing and other applications. These include the use of OAUGDP to sterilize medical and dental equipment and air filters; diesel soot removal; plasma aerodynamic effects; electrohydrodynamic (EDH) flow control of the neutral working gas; increasing the surface energy of materials; increasing the wettability and wickability of fabrics; and plasma deposition and directional etching. A general overview of these topics will be presented.

  12. High explosives vapor detection by atmospheric sampling glow discharge ionization/tandem mass spectrometry

    SciTech Connect

    McLuckey, S.A.; Goeringer, D.E.; Asano, K.G.

    1996-02-01

    The combination of atmospheric sampling glow discharge ionization with tandem mass spectrometry for the detection of traces of high explosives is described. Particular emphasis is placed on use of the quadrupole ion trap as the type of tandem mass spectrometer. Atmospheric sampling glow discharge provides a simple, rugged, and efficient means for anion formation while the quadrupole ion trap provides for efficient tandem mass spectrometry. Mass selective ion accumulation and non-specific ion activation methods can be used to overcome deleterious effects arising from ion/ion interactions. Such interactions constitute the major potential technical barrier to the use of the ion trap for real-time monitoring of targeted compounds in uncontrolled and highly variable matrices. Tailored waveforms can be used to effect both mass selective ion accumulation and ion activation. Concatenated tailored waveforms allow for both functions in a single experiment thereby providing the capability for monitoring several targeted species simultaneously. The combination of atmospheric sampling glow discharge ionization with a state-of-the-art analytical quadrupole ion trap is a highly sensitive and specific detector for traces of high explosives. The combination is also small and inexpensive relative to virtually any other form of tandem mass spectrometry. The science and technology underlying the glow discharge/ion trap combination is sufficiently mature to form the basis for an engineering effort to make the detector portable. 85 refs.

  13. Nanosecond Glow and Spark Discharges in Ambient Air and in Water Vapor

    NASA Astrophysics Data System (ADS)

    Laux, Christophe; Rusterholtz, Diane; Sainct, Florent; Xu, Da; Lacoste, Deanna; Stancu, Gabi; Pai, David

    2013-09-01

    Nanosecond repetitively pulsed (NRP) discharges are one of the most energy efficient ways to produce active species in atmospheric pressure gases. In both air and water vapor, three discharge regimes can be obtained: 1) corona, with light emission just around the anode, 2) glow, corresponding to a diffuse nonequilibrium plasma, and 3) spark, characterized by higher temperatures and higher active species densities. The glow regime was initially obtained in air preheated at 2000 K. Based on a model defining the transition between glow and spark, we recently succeeded in obtaining a stable glow in ambient air at 300 K, using a judicious combination of electrode geometry, pulse duration, pulse frequency, and applied voltage. We will present these results and describe the characteristics of the discharge obtained in room air. The spark regime was also studied. NRP sparks induce ultrafast gas heating (about 1000 K in 20 ns) and high oxygen dissociation (up to 50% dissociation of O2) . This phenomenon can be explained by a two-step process involving the excitation of molecular nitrogen followed by exothermic dissociative quenching of molecular oxygen. The characteristics of NRP discharges in water vapor will also be discussed. This work is supported by the ANR PREPA program (grant number ANR-09-BLAN-0043).

  14. An efficient model to simulate stable glow corona discharges and their transition into streamers

    NASA Astrophysics Data System (ADS)

    Liu, Lipeng; Becerra, Marley

    2017-03-01

    A computationally efficient model to evaluate stable glow corona discharges and their transition into streamers is proposed. The simplified physical model referred to as the SPM is based on the classic hydrodynamic model of charge particles and a quasi-steady state approximation for electrons. The solution follows a two-step segregated procedure, which solves sequentially the stationary continuity equation for electrons and then time-dependent continuity equations for ions. The validity of using the SPM to simulate glow corona discharges and their transition into streamers is demonstrated by performing comparisons with a fully coupled physical model (FPM) and with experimental data available in the literature for air under atmospheric conditions. It is shown that the SPM can obtain estimates similar to those calculated with the FPM and those measured in experiments but using significantly less computation time. Since the proposed model simulates efficiently the ionization layer without prior knowledge of the surface electric field or the discharge current, it is a computationally efficient alternative to calculations of glow corona discharges based on Kaptzov’s approximation (KAM). The model can also be employed to efficiently calculate the conditions for the transition of glow corona into streamers, overcoming the limitations of KAM to provide such estimates.

  15. Evidence for large-area superemission into a high-current glow discharge

    NASA Astrophysics Data System (ADS)

    Hartmann, W.; Dominic, V.; Kirkman, G. F.; Gundersen, M. A.

    1988-10-01

    This letter presents evidence for large-area (≊1 cm2) cathode superemission (˜10 000 A/cm2) into a high-current glow discharge in a pseudospark or back lighted thyratron switch. Cathodes studied with a scannning electron microscope following operation at 6-8 kA, ≊1 μs pulse length, and 105 pulses in a low-pressure H2 discharge show evidence of melting of a thin surface layer within a radius of ˜4 mm, indicating that the discharge is a superdense glow with a cross-sectional area of the order of 1 cm2, rather than an arc. Further supporting evidence is provided by streak camera data. An ion beam present during the avalanche phase of the discharge is responsible for heating the cathode surface resulting in a significant field-enhanced thermionic emission.

  16. Polarity functions' characterization and the mechanism of starch modification by DC glow discharge plasma.

    PubMed

    Khorram, S; Zakerhamidi, M S; Karimzadeh, Z

    2015-01-01

    The wheat starch was investigated, before and after exposure to the argon and oxygen glow discharge plasma, without any added chemical reagents, using a novel media polarity functions method. The mechanisms of modification of starch in plasma discharge irradiation were explained using some methods such as; NMR, IR spectroscopy, Kamlet-Abboud-Taft polarity functions (specific and nonspecific interaction) of modified starch. The starch modification, by plasma treatment, shows valuable changes with plasma gas and relative ionized or active species. Characterizations indicate that argon glow discharge plasma increases crosslink in C-2 site of starch. Also, oxygen plasma discharge irradiation tends to oxidize the OH group in C-6 site of carbonyl group. Furthermore, the reported mechanisms show the highest efficiency, because of the stereo-chemical orientation of active sites of starch and plasma potential of wall in plasma media.

  17. Study of the Generation of Intense Pulsed Electron Beams Using Glow Discharges

    DTIC Science & Technology

    1988-02-01

    166 side the discharge chamber. The coil inside diameter is 5 mixture. The electronic component of the glow discharge .167 cm. It was placed coaxial...electron production in 188 of B. Wernsman and the skillful machining by J. Davis. gasesby fast helium (0.133-1.0 MeV): I. Experimental." Phys. Rev...current sure of 10 - Torr. Helium was continuously introduced in- is collected by the acceleration grid. and the pulse of electron side the electron gun

  18. Nonlocal control of electron temperature in short direct current glow discharge plasma

    SciTech Connect

    Demidov, V. I.; Kudryavtsev, A. A.; Stepanova, O. M.; Kurlyandskaya, I. P.

    2014-09-15

    To demonstrate controlling the electron temperature in nonlocal plasma, experiments have been performed on a short (without positive column) dc glow discharge with a cold cathode by applying different voltages to the conducting discharge wall. The experiments have been performed for low-pressure noble gas discharges. The applied voltage can modify trapping the energetic electrons emitted from the cathode sheath and arising from the atomic and molecular processes in the plasma within the device volume. This phenomenon results in the energetic electrons heating the slow plasma electrons, which consequently modifies the electron temperature. Furthermore, a numerical model of the discharge has demonstrated the electron temperature modification for the above case.

  19. Analysis of radiofrequency discharges in plasma

    DOEpatents

    Kumar, Devendra; McGlynn, Sean P.

    1992-01-01

    Separation of laser optogalvanic signals in plasma into two components: (1) an ionization rate change component, and (2) a photoacoustic mediated component. This separation of components may be performed even when the two components overlap in time, by measuring time-resolved laser optogalvanic signals in an rf discharge plasma as the rf frequency is varied near the electrical resonance peak of the plasma and associated driving/detecting circuits. A novel spectrometer may be constructed to make these measurements. Such a spectrometer would be useful in better understanding and controlling such processes as plasma etching and plasma deposition.

  20. Analysis of radiofrequency discharges in plasma

    DOEpatents

    Kumar, D.; McGlynn, S.P.

    1992-08-04

    Separation of laser optogalvanic signals in plasma into two components: (1) an ionization rate change component, and (2) a photoacoustic mediated component. This separation of components may be performed even when the two components overlap in time, by measuring time-resolved laser optogalvanic signals in an rf discharge plasma as the rf frequency is varied near the electrical resonance peak of the plasma and associated driving/detecting circuits. A novel spectrometer may be constructed to make these measurements. Such a spectrometer would be useful in better understanding and controlling such processes as plasma etching and plasma deposition. 15 figs.

  1. Plasma mixing glow discharge device for analytical applications

    DOEpatents

    Pinnaduwage, L.A.

    1999-04-20

    An instrument for analyzing a sample has an enclosure that forms a chamber containing an anode which divides the chamber into a discharge region and an analysis region. A gas inlet and outlet are provided to introduce and exhaust a rare gas into the discharge region. A cathode within the discharge region has a plurality of pins projecting in a geometric pattern toward the anode for exciting the gas and producing a plasma discharge between the cathode and the anode. Low energy electrons (e.g. <0.5 eV) pass into the analysis region through an aperture. The sample to be analyzed is placed into the analysis region and bombarded by the metastable rare gas atoms and the low energy electrons extracted into from the discharge region. A mass or optical spectrometer can be coupled to a port of the analysis region to analyze the resulting ions and light emission. 3 figs.

  2. Attenuation of single-tone ultrasound by an atmospheric glow discharge plasma barrier

    SciTech Connect

    Stepaniuk, Vadim P.; Ioppolo, Tindaro; Oetuegen, M. Volkan; Sheverev, Valery A.

    2010-09-15

    Propagation of 143 kHz ultrasound through an atmospheric pressure glow discharge in air was studied experimentally. The plasma was a continuous dc discharge formed by a multipin electrode system. Distributions of the gas temperature were also obtained in and around the plasma using laser-induced Rayleigh scattering technique. Results show significant attenuation of the ultrasound by the glow discharge plasma barrier (up to -24 dB). The results indicate that sound attenuation does not depend on the thickness of the plasma and attenuation is caused primarily by reflection of the sound waves from the plasma due to the sharp gas temperatures gradients that form at the plasma boundary. These gradients can be as high as 80 K/mm.

  3. Atmospheric pressure glow discharge deposition of thermo-sensitive poly (N-isopropylacrylamide)

    NASA Astrophysics Data System (ADS)

    Shao, M.; Tang, X. L.; Wen, D.; Chen, Y.; Qiu, G.

    2013-12-01

    In this paper, a self-made atmospheric pressure dielectric barrier discharge reactor on intermediate frequency is brought forward and developed, which is equipped with power supply of 1-20 KHz, and the working gas is argon. The experimental results show that is a very stable and uniform atmospheric pressure glow discharge (APGD). Through a series of experiments, the waveforms of single pulse and multi-pulse glow discharge were both obtained. The voltage amplitude, discharge gap and dielectric material are studied, and the conditions of multi-pulse glow discharge are discussed as well. The novel methods of depositing poly (N-isopropylacrylamide) (PNIPAAm) coatings on the surface of glass slides and PS petri dish are provided by atmospheric pressure plasma polymerization. PNIPAAm can be obtained by plasma polymerization of N-isopropylacrylamide using the self-made equipment of atmospheric pressure plasma vapor treatment. The samples were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and water contact angle. SEM analysis has revealed that the PNIPAAm coatings were formed on the surface of the smooth glass slides. Further evaluation by using XPS, it has shown the presence of PNIPAAm. The wettability can be significantly modified by changing of the temperatures at above and below of the lower critical solution temperature (LCST) from the data of the contact angle test. These results have advantage for further application on the thermo-sensitive textile materials.

  4. Numerical simulation of a direct current glow discharge in atmospheric pressure helium

    NASA Astrophysics Data System (ADS)

    Yin, Zeng-Qian; Wang, Yan; Zhang, Pan-Pan; Zhang, Qi; Li, Xue-Chen

    2016-12-01

    Characteristics of a direct current (DC) discharge in atmospheric pressure helium are numerically investigated based on a one-dimensional fluid model. The results indicate that the discharge does not reach its steady state till it takes a period of time. Moreover, the required time increases and the current density of the steady state decreases with increasing the gap width. Through analyzing the spatial distributions of the electron density, the ion density and the electric field at different discharge moments, it is found that the DC discharge starts with a Townsend regime, then transits to a glow regime. In addition, the discharge operates in a normal glow mode or an abnormal glow one under different parameters, such as the gap width, the ballast resistors, and the secondary electron emission coefficients, judged by its voltage-current characteristics. Project supported by the National Natural Science Foundation of China (Grant Nos. 11575050 and 10805013), the Midwest Universities Comprehensive Strength Promotion Project, the Natural Science Foundation of Hebei Province, China (Grant Nos. A2016201042 and A2015201092), and the Research Foundation of Education Bureau of Hebei Province, China (Grant No. LJRC011).

  5. Growth of arc in high-pressure, pulsed glow discharge by gas density depletion

    NASA Astrophysics Data System (ADS)

    Imada, Go; Yatsui, Kiyoshi; Masuda, Wataru

    2000-10-01

    Effects of gas density depletion on arc formation of high-pressure, pulsed glow discharge have been investigated by eliminating the other factors which may affect the discharge stability, such as shock waves, residual ions, electrode heating, and discharge products. The gas density depletion has been simulated by utilizing a subsonic gas flow between the curved electrodes combined with a convergent nozzle and a divergent diffuser. A comparison has been made on the discharge in the aerodynamically created gas density depletion with the second discharge in the double-pulse discharge within a stable gas. We have found that the large gas density depletion, Δρ/ρ0˜-3.6% corresponding to a pulse repetition rate (PRR) of ˜50 Hz, tends to cause an arc-like filament or an arc without the shocks, ions, electrode heating, and products. However, the second discharge in the double-pulse discharge becomes an arc in much smaller gas density depletion (Δρ/ρ0˜-1.2% corresponding to PRR ˜3 Hz). Therefore, the collapse of high-pressure, pulsed glow discharge is most likely caused by some factor other than the gas density depletion.

  6. Ultrasonic nebulization atmospheric pressure glow discharge - Preliminary study

    NASA Astrophysics Data System (ADS)

    Greda, Krzysztof; Jamroz, Piotr; Pohl, Pawel

    2016-07-01

    Atmospheric pressure glow microdischarge (μAPGD) generated between a small-sized He nozzle jet anode and a flowing liquid cathode was coupled with ultrasonic nebulization (USN) for analytical optical emission spectrometry (OES). The spatial distributions of the emitted spectra from the novel coupled USN-μAPGD system and the conventional μAPGD system were compared. In the μAPGD, the maxima of the intensity distribution profiles of the atomic emission lines Ca, Cd, In, K, Li, Mg, Mn, Na and Sr were observed in the near cathode region, whereas, in the case of the USN-μAPGD, they were shifted towards the anode. In the novel system, the intensities of the analytical lines of the studied metals were boosted from several to 35 times. As compared to the conventional μAPGD-OES with the introduction of analytes through the sputtering and/or the electrospray-like nebulization of the flowing liquid cathode solution, the proposed method with the USN introduction of analytes in the form of a dry aerosol provides improved detectability of the studied metals. The detection limits of metals achieved with the USN-μAPGD-OES method were in the range from 0.08 μg L- 1 for Li to 52 μg L- 1 for Mn.

  7. A study of the glow discharge characteristics of contact electrodes at atmospheric pressure in air

    SciTech Connect

    Liu, Wenzheng Sun, Guangliang Li, Chuanhui; Zhang, Rongrong

    2014-04-15

    Electric field distributions and discharge properties of rod-rod contact electrodes were studied under the condition of DBD for the steady generation of atmospheric pressure glow discharge plasma (APGD) in air. We found that under the effect of the initial electrons generated in a nanometer-scale gap, the rod-rod cross-contact electrodes yielded APGD plasma in air. Regarding the rod-rod cross-contact electrodes, increasing the working voltage expanded the strong electric field area of the gas gap so that both discharge area and discharge power increased, and the increase in the number of contact points kept the initial discharge voltage unchanged and caused an increase in the plasma discharge area and discharge power. A mesh-like structure of cross-contact electrodes was designed and used to generate more APGD plasma, suggesting high applicability.

  8. Sub-microsecond pulsed atmospheric glow discharges with and without dielectric barrier

    SciTech Connect

    Song Shutong; Guo Ying; Zhang Jie; Zhang Jing; Shi, J. J.; Choe, Wonho

    2012-12-15

    The discharge characteristics and mechanism of glow discharges in atmospheric pressure helium excited by repetitive voltage pulses with and without dielectric barriers are numerically studied using a one-dimensional self-consistent fluid model. The waveforms of discharge current density show that one discharge event occurs during the voltage pulse with bare electrodes and two distinct discharge events happen at the rising and falling phases of voltage pulse with dielectric barrier electrodes, respectively. The spatial profiles of electron and electric field at the time instant of discharge current peak reveal that the electrons are trapped in the plasma bulk with bare electrodes, while the electrons are accumulated in the region between the sheath and plasma bulk with dielectric barrier electrodes. Furthermore, the spatio-temporal evolution of electron density and mean electron energy clearly demonstrate the dynamics of discharge ignition, especially the temporal evolution of sheath above the instantaneous cathode.

  9. Determination of the plasma parameters of a glow discharge in long tubes

    NASA Astrophysics Data System (ADS)

    Kiselev, A. S.; Kostrin, D. K.; Lisenkov, A. A.; Smirnov, E. A.

    2017-01-01

    In this work experimental current-voltage characteristics of a glow discharge occurring in long tubes for a wide range of discharge conditions (pressure, diameter of the discharge tube, nature of the gas) were obtained. On the basis of the current-voltage characteristics was calculated the longitudinal potential gradient in the positive column. With the help of the developed computer program was calculated the electron temperature for discharge conditions corresponding to the experiment. The technique is based on the use of the balance equations of ionization in gas discharges occurring in long narrow tubes, and provides the possibility for calculation of the discharge plasma parameters, both in pure gases and in multicomponent mixtures. Based on the experimental values of the longitudinal potential gradient in the positive column and the calculated values of the electron temperature was calculated the dependence of accommodation coefficient for the electrons from the discharge conditions. The compliance between the experimental and reference data was obtained.

  10. Effect of a floating circular aperture on a dc glow discharge dusty plasma

    NASA Astrophysics Data System (ADS)

    Heinrich, Jonathon R.; Kim, Su-Hyun; Merlino, Robert L.

    2009-11-01

    We have investigated novel effects observed when a floating aperture, either 6 mm or 8 mm in diameter, is placed 1-2 cm in front of an anode disk (4 cm diameter) that is used to form a dc glow discharge dusty plasma. Dust is incorporated into the anode glow plasma from a tray located below the anode which contained kaolin powder. The glow discharge traps particles with an average size of 1 micron. When the aperture is placed in front of the disk, well-defined pear-shaped or spherical dust clouds are formed, depending on the diameter of the aperture and its distance from the anode. The dust interacts with the aperture through the potential structure associated with the floating (negative) plate in which the aperture is located. The dust cloud is imaged using a CCD camera and a thin sheet of 532 nm laser light. Some of the effects observed include: outwardly expanding spherical dust acoustic waves and shocks, dust rotation around a void formed at the aperture, and a dust/discharge instability in which the discharge is periodically quenched and reignited while the dust cloud expands and contracts, with the dust retaining a residual charge.

  11. Electric-field-vector measurement in a glow discharge

    SciTech Connect

    Ganguly, B.N.; Garscadden, A.

    1985-10-01

    The magnetic quantum number selection rule implies that radiation that is linearly polarized perpendicular to the electric field will not excite ..delta..m = 0 transitions. This phenomenon in Stark spectra has been used to determine the electric field vector in a positive column dc discharge in helium. The technique is applicable to both linear and nonlinear Stark effects.

  12. Comparative Study of Electric Field Measurement in Glow Discharges using Laser Optogalvanic Spectroscopy

    SciTech Connect

    Hussain, Shahid; Saleem, M.; Baig, M. A.

    2008-10-22

    The net electric field inside low-pressure glow discharges has been measured using laser optogalvanic spectroscopy of 1s2s {sup 1}S{sub 0}{yields}np{sup 1}P{sub 1} Rydberg series of atomic helium. Three different types of discharges, an inductively coupled RF discharge cell operating at 4 MHz, a homemade DC discharge cell and a commercial see-through hollow cathode lamp have been used for these studies. The Rydberg series terminates earlier in the high electric field discharge as compared to that in the low electric field discharge. The net electric field also produces shift and broadens the observed spectral lines especially in the high lying Rydberg transitions. The electric field has been determined from the series termination and also from the energy shift of the observed transitions.

  13. Plasma Treatment of Polyethylene Powder Particles in Hollow Cathode Glow Discharge

    SciTech Connect

    Wolter, Matthias; Quitzau, Meike; Bornholdt, Sven; Kersten, Holger

    2008-09-07

    Polyethylen (PE) is widely used in the production of foils, insulators, packaging materials, plastic bottles etc. Untreated PE is hydrophobic due to its unpolar surface. Therefore, it is hard to print or glue PE and the surface has to be modified before converting.In the present experiments a hollow cathode glow discharge is used as plasma source which is mounted in a spiral conveyor in order to ensure a combines transport of PE powder particles. With this set-up a homogeneous surface treatment of the powder is possible while passing the glow discharge. The plasma treatment causes a remarkable enhancement of the hydrophilicity of the PE powder which can be verified by contact angle measurements and X-ray photoelectron spectroscopy.

  14. Analysis Of The Different Zones Of Glow Discharge Of Ethyl Alcohol (C2H6O)

    NASA Astrophysics Data System (ADS)

    Torres, C.; Reyes, P. G.; Mulia, J.; Castillo, F.; Martínez, H.

    2014-05-01

    The aim of this work is to explore the emission spectroscopy of ethyl alcohol in some regions, also is determine the result elements of the glow discharge, the spectrums were observed in a range of 200 at 1100 nm in the different zones inside of the tube at different distances of 20 and 30 cm. The elements are: in anode region C6H5 (483.02nm), CHO (519.56nm) and H2 (560.47nm), in the positive column CO2+ (315.52 y 337.00nm), O+ (357.48nm), CH+ (380.61nm) and CO+ (399.73nm); in the cathode region we observed O+ (391.19nm), CHOCHO (428.00nm), CO+ (471.12nm) and H2 (656.52nm). C6H5, CHO y H2 species occurring in all regions analyzed varying the glow discharge emission intensity.

  15. Boundary Layer Flow Control with a One Atmosphere Uniform Glow Discharge Surface Plasma

    NASA Technical Reports Server (NTRS)

    Roth, J. Reece; Sherman, Daniel M.; Wilkinson, Stephen P.

    1998-01-01

    Low speed wind tunnel data have been acquired for planar panels covered by a uniform, glow-discharge surface plasma in atmospheric pressure air known as the One Atmosphere Uniform Glow Discharge Plasma (OAUGDP). Streamwise and spanwise arrays of flush, plasma-generating surface electrodes have been studied in laminar, transitional, and fully turbulent boundary layer flow. Plasma between symmetric streamwise electrode strips caused large increases in panel drag, whereas asymmetric spanwise electrode configurations produced a significant thrust. Smoke wire flow visualization and mean velocity diagnostics show the primary cause of the phenomena to be a combination of mass transport and vortical structures induced by strong paraelectric ElectroHydroDynamic (EHD) body forces on the flow.

  16. Isotope effects on desorption kinetics of hydrogen isotopes implanted into stainless steel by glow discharge

    SciTech Connect

    Matsuyama, M.; Kondo, M.; Noda, N.; Tanaka, M.; Nishimura, K.

    2015-03-15

    In a fusion device the control of fuel particles implies to know the desorption rate of hydrogen isotopes by the plasma-facing materials. In this paper desorption kinetics of hydrogen isotopes implanted into type 316L stainless steel by glow discharge have been studied by experiment and numerical calculation. The temperature of a maximum desorption rate depends on glow discharge time and heating rate. Desorption spectra observed under various experimental conditions have been successfully reproduced by numerical simulations that are based on a diffusion-limited process. It is suggested, therefore, that desorption rate of a hydrogen isotope implanted into the stainless steel is limited by a diffusion process of hydrogen isotope atoms in bulk. Furthermore, small isotope effects were observed for the diffusion process of hydrogen isotope atoms. (authors)

  17. Dust structurization observed in a dc glow discharge dusty plasma

    NASA Astrophysics Data System (ADS)

    Heinrich, Jonathon R.; Kim, Su-Hyun; Merlino, Robert L.

    2010-11-01

    Dusty plasmas, which are inherently open systems which require an ionization source to replenish the plasma absorbed on the grains, tend to exhibit self-organization. Various structures have been observed in dusty plasmas such as dust crystals, voids, and vortices. Due to the presence of drifting ions in dc discharge plasmas, spontaneously excited dust acoustic waves are also a common occurrence. By adjusting the discharge parameters we have observed a new phenomenon in dusty plasmas -- the spontaneous formation of three-dimensional stationary dust density structures. These structures appear as an ordered pattern consisting of alternating regions of high and low dust density arranged in a nested bowl-type configuration The stationary structure evolves from dust density waves that slow down as their wavelength decreases and eventually stop moving when the wavelength reaches some minimum size.

  18. Positive column of the glow discharge in argon

    NASA Astrophysics Data System (ADS)

    Lisovskiy, Valeriy; Artushenko, Ekaterina; Yegorenkov, Vladimir

    2015-09-01

    We report the measurements we performed of the reduced electric field strength E / p in the positive column in the range of the gas pressure and tube radius product of 0.01 discharge in noble gases. We consider the case of a balance between the rate of charged particle production due to direct ionization of gas molecules through electron impact and their escape to the discharge tube walls. Simple expressions for the reduced electric field E / p in the positive column in argon are obtained. The second model consists in considering the production and loss of charged particles and metastable atoms and obtaining a simple equation for the reduced electric field E / p depending on the discharge current density, gas pressure and tube radius. These models furnish a good description of experimental data in the whole range of pR values studied. and Scientific Center of Physical Technologies, Svobody Sq.6, Kharkov, 61022, Ukraine.

  19. Dynamic of the Dust Structures under Magnetic Field Effect in DC Glow Discharges

    SciTech Connect

    Vasiliev, M. M.; D'yachkov, L. G.; Antipov, S. N.; Petrov, O. F.; Fortov, V. E.

    2008-09-07

    In this work, we investigate dust structures in the striation of DC glow discharges under magnetic field actions. The dependence of rotation frequency of dusty plasma structures as a function of the magnetic field was investigated. For various magnetic fields kinetic temperatures of the dust particles, diffusion coefficients, and effective coupling coefficient {gamma}* have been determined. Obtained results are analyzed and compared with theoretical predictions.

  20. Isotope ratio measurements by secondary ion mass spectrometry (SIMS) and glow discharge mass spectrometry (GDMS)

    NASA Astrophysics Data System (ADS)

    Betti, Maria

    2005-04-01

    The basic principles of secondary ion mass spectrometry and glow discharge mass spectrometry have been shortly revisited. The applications of both techniques as exploited for the isotope ratio measurements in several matrices have been reviewed. Emphasis has been given to research fields in expansions such as solar system studies, medicine, biology, environment and nuclear forensic. The characteristics of the two techniques are discussed in terms of sensitivity and methodology of quantification. Considerations on the different detection possibilities in SIMS are also presented.

  1. Surface Modification of Commercial Low-Carbon Steel using Glow Discharge Nitrogen Plasma and its Characterization

    NASA Astrophysics Data System (ADS)

    Srikanth, S.; Saravanan, P.; Joseph, Alphonsa; Ravi, K.

    2013-09-01

    Plasma nitriding under glow discharge nitrogen plasma has been undertaken on laboratory scale for surface engineering of commercial low carbon steels. The treatment has been shown to confer exceptional improvement in surface properties, viz., hardness and corrosion resistance. The results have been discussed in light of microstructural changes occurring on steel surface and its interior as a result of Fickian nitrogen diffusion and correlated with influences of nitriding-temperature and alloying elements (Mn, Nb, and Si) in steel.

  2. Atmospheric sampling glow discharge ionizataion and triple quadrupole tandem mass spectrometry for explosives vapor detection

    SciTech Connect

    McLuckey, S.A.; Goeringer, D.E.; Asano, K.G.; Hart, K.J.; Glish, G.L.; Grant, B.C.; Chambers, D.M.

    1993-08-01

    The detection and identification of trace vapors of hidden high explosives is an excellent example of a targeted analysis problem. It is desirable to push to ever lower levels the quantity or concentration of explosives material that provides an analytical signal, while at the same time discriminating against all other uninteresting material. The detection system must therefore combine high sensitivity with high specificity. This report describes the philosophy behind the use of atmospheric sampling glow discharge ionization, which is a sensitive, rugged, and convenient means for forming anions from explosives molecules, with tandem mass spectrometry, which provides unparalleled specificity in the identification of explosives-related ions. Forms of tandem mass spectrometry are compared and contrasted to provide a summary of the characteristics to be expected from an explosives detector employing mass spectrometry/mass spectrometry. The instrument developed for the FAA, an atmospheric sampling glow discharge/triple quadrupole mass spectrometer, is described in detail with particular emphasis on the ion source/spectrometer interface and on the capabilities of the spectrometer. Performance characteristics of the system are also described as they pertain to explosives of interest including a description of an automated procedure for the detection and identification of specific explosives. A comparison of various tandem mass spectrometers mated with atmospheric sampling glow discharge is then described and preliminary studies with a vapor preconcentration system provided by the FAA will be described.

  3. Mechanism behind self-sustained oscillations in direct current glow discharges and dusty plasmas

    SciTech Connect

    Cho, Sung Nae

    2013-04-15

    An alternative explanation to the mechanism behind self-sustained oscillations of ions in direct current (DC) glow discharges is provided. Such description is distinguished from the one provided by the fluid models, where oscillations are attributed to the positive feedback mechanism associated with photoionization of particles and photoemission of electrons from the cathode. Here, oscillations arise as consequence of interaction between an ion and the surface charges induced by it at the bounding electrodes. Such mechanism provides an elegant explanation to why self-sustained oscillations occur only in the negative resistance region of the voltage-current characteristic curve in the DC glow discharges. Furthermore, this alternative description provides an elegant explanation to the formation of plasma fireballs in the laboratory plasma. It has been found that oscillation frequencies increase with ion's surface charge density, but at the rate which is significantly slower than it does with the electric field. The presented mechanism also describes self-sustained oscillations of ions in dusty plasmas, which demonstrates that self-sustained oscillations in dusty plasmas and DC glow discharges involve common physical processes.

  4. Wavelength Scanning with a Tilting Interference Filter for Glow-Discharge Elemental Imaging.

    PubMed

    Storey, Andrew P; Ray, Steven J; Hoffmann, Volker; Voronov, Maxim; Engelhard, Carsten; Buscher, Wolfgang; Hieftje, Gary M

    2016-11-21

    Glow discharges have long been used for depth profiling and bulk analysis of solid samples. In addition, over the past decade, several methods of obtaining lateral surface elemental distributions have been introduced, each with its own strengths and weaknesses. Challenges for each of these techniques are acceptable optical throughput and added instrumental complexity. Here, these problems are addressed with a tilting-filter instrument. A pulsed glow discharge is coupled to an optical system comprising an adjustable-angle tilting filter, collimating and imaging lenses, and a gated, intensified charge-coupled device (CCD) camera, which together provide surface elemental mapping of solid samples. The tilting-filter spectrometer is instrumentally simpler, produces less image distortion, and achieves higher optical throughput than a monochromator-based instrument, but has a much more limited tunable spectral range and poorer spectral resolution. As a result, the tilting-filter spectrometer is limited to single-element or two-element determinations, and only when the target spectral lines fall within an appropriate spectral range and can be spectrally discerned. Spectral interferences that result from heterogeneous impurities can be flagged and overcome by observing the spatially resolved signal response across the available tunable spectral range. The instrument has been characterized and evaluated for the spatially resolved analysis of glow-discharge emission from selected but representative samples.

  5. Dusty Plasma in He-Ar Glow Discharge

    SciTech Connect

    Maiorov, S. A.; Ramazanov, T. S.; Dzhumagulova, K. N.; Dosbolayev, M. K.; Jumabekov, A. N.

    2008-09-07

    The paper reports on the first experiments with plasma-dust formations in dc gas discharge plasma for He-Ar mixture. It is shown that under the conventional conditions of the experiments with dusty structures in plasma, the choice of light and heavy gases for the mixture suppresses electron heating in electric field and results in a supersonic jet with high Mach numbers. Distribution functions for drifting ions in the gas mixture are calculated for various mixture concentrations, electric field strengths and gas pressures.

  6. Non-linear macro evolution of a dc driven micro atmospheric glow discharge

    SciTech Connect

    Xu, S. F.; Zhong, X. X.

    2015-10-15

    We studied the macro evolution of the micro atmospheric glow discharge generated between a micro argon jet into ambient air and static water. The micro discharge behaves similarly to a complex ecosystem. Non-linear behaviors are found for the micro discharge when the water acts as a cathode, different from the discharge when water behaves as an anode. Groups of snapshots of the micro discharge formed at different discharge currents are captured by an intensified charge-coupled device with controlled exposure time, and each group consisted of 256 images taken in succession. Edge detection methods are used to identify the water surface and then the total brightness is defined by adding up the signal counts over the area of the micro discharge. Motions of the water surface at different discharge currents show that the water surface lowers increasingly rapidly when the water acts as a cathode. In contrast, the water surface lowers at a constant speed when the water behaves as an anode. The light curves are similar to logistic growth curves, suggesting that a self-inhibition process occurs in the micro discharge. Meanwhile, the total brightness increases linearly during the same time when the water acts as an anode. Discharge-water interactions cause the micro discharge to evolve. The charged particle bomb process is probably responsible for the different behaviors of the micro discharges when the water acts as cathode and anode.

  7. Non-linear macro evolution of a dc driven micro atmospheric glow discharge

    NASA Astrophysics Data System (ADS)

    Xu, S. F.; Zhong, X. X.

    2015-10-01

    We studied the macro evolution of the micro atmospheric glow discharge generated between a micro argon jet into ambient air and static water. The micro discharge behaves similarly to a complex ecosystem. Non-linear behaviors are found for the micro discharge when the water acts as a cathode, different from the discharge when water behaves as an anode. Groups of snapshots of the micro discharge formed at different discharge currents are captured by an intensified charge-coupled device with controlled exposure time, and each group consisted of 256 images taken in succession. Edge detection methods are used to identify the water surface and then the total brightness is defined by adding up the signal counts over the area of the micro discharge. Motions of the water surface at different discharge currents show that the water surface lowers increasingly rapidly when the water acts as a cathode. In contrast, the water surface lowers at a constant speed when the water behaves as an anode. The light curves are similar to logistic growth curves, suggesting that a self-inhibition process occurs in the micro discharge. Meanwhile, the total brightness increases linearly during the same time when the water acts as an anode. Discharge-water interactions cause the micro discharge to evolve. The charged particle bomb process is probably responsible for the different behaviors of the micro discharges when the water acts as cathode and anode.

  8. Charging of dust grains in a nonequilibrium plasma of a stratified glow discharge

    NASA Astrophysics Data System (ADS)

    Sukhinin, G. I.; Fedoseev, A. V.

    2007-12-01

    A theoretical model is presented that describes the charging of dust grains in the positive plasma column of a stratified glow dc discharge in argon. A one-dimensional self-consistent model is used to obtain axial profiles of the electric field, as well as the electron energy distribution function along the axis of the discharge tube. Radial profiles of the electric field are determined in the ambipolar diffusion approximation. It is assumed that, in the radial direction, the electron distribution function depends only on the total electron energy. Two-dimensional distributions of the discharge plasma parameters are calculated and used to determine the potential and charge of a test dust grain at a certain point within the discharge and the electrostatic forces acting on it. It is shown that the grain charge distribution depends strongly on the nonequilibrium electron distribution function and on the nonuniform distribution of the electric field in a stratified glow discharge. A discussion is presented on the suspension of dust grains, the separation of grains by size in the discharge striations, and a possible mechanism for the onset of vortex dust motion at the edge of a dust cloud.

  9. Dynamic model based on voltage transfer curve for pattern formation in dielectric barrier glow discharge

    SciTech Connect

    Li, Ben; He, Feng; Ouyang, Jiting; Duan, Xiaoxi

    2015-12-15

    Simulation work is very important for understanding the formation of self-organized discharge patterns. Previous works have witnessed different models derived from other systems for simulation of discharge pattern, but most of these models are complicated and time-consuming. In this paper, we introduce a convenient phenomenological dynamic model based on the basic dynamic process of glow discharge and the voltage transfer curve (VTC) to study the dielectric barrier glow discharge (DBGD) pattern. VTC is an important characteristic of DBGD, which plots the change of wall voltage after a discharge as a function of the initial total gap voltage. In the modeling, the combined effect of the discharge conditions is included in VTC, and the activation-inhibition effect is expressed by a spatial interaction term. Besides, the model reduces the dimensionality of the system by just considering the integration effect of current flow. All these greatly facilitate the construction of this model. Numerical simulations turn out to be in good accordance with our previous fluid modeling and experimental result.

  10. The Gaseous Electronics Conference radio-frequency reference cell: A defined parallel-plate radio-frequency system for experimental and theoretical studies of plasma-processing discharges

    SciTech Connect

    Hargis, P.J. Jr.; Greenberg, K.E.; Miller, P.A.; Gerardo, J.B.; Torczynski, J.R.; Riley, M.E.; Hebner, G.A. ); Roberts, J.R.; Olthoff, J.K.; Whetstone, J.R.; Van Brunt, R.J.; Sobolewski, M.A. ); Anderson, H.M.; Splichal, M.P.; Mock, J.L. ); Bletzinger, P.; Garscadden, A. ); Gottscho, R.A. ); Selwyn, G.; Dalvie, M.; Heidenreich, J.E. ); Butterbaugh, J.W. ); Brake, M.L.; Passow, M.L.; Pender,

    1994-01-01

    A reference cell'' for generating radio-frequency (rf) glow discharges in gases at a frequency of 13.56 MHz is described. The reference cell provides an experimental platform for comparing plasma measurements carried out in a common reactor geometry by different experimental groups, thereby enhancing the transfer of knowledge and insight gained in rf discharge studies. The results of performing ostensibly identical measurements on six of these cells in five different laboratories are analyzed and discussed. Measurements were made of plasma voltage and current characteristics for discharges in pure argon at specified values of applied voltages, gas pressures, and gas flow rates. Data are presented on relevant electrical quantities derived from Fourier analysis of the voltage and current wave forms. Amplitudes, phase shifts, self-bias voltages, and power dissipation were measured. Each of the cells was characterized in terms of its measured internal reactive components. Comparing results from different cells provides an indication of the degree of precision needed to define the electrical configuration and operating parameters in order to achieve identical performance at various laboratories. The results show, for example, that the external circuit, including the reactive components of the rf power source, can significantly influence the discharge. Results obtained in reference cells with identical rf power sources demonstrate that considerable progress has been made in developing a phenomenological understanding of the conditions needed to obtain reproducible discharge conditions in independent reference cells.

  11. On the mechanism of pattern formation in glow dielectric barrier discharge

    SciTech Connect

    Qiao, Yajun; Li, Ben; Ouyang, Jiting

    2016-01-15

    The formation mechanism of pattern in glow dielectric barrier discharge is investigated by two-dimensional fluid modeling. Experimental results are shown for comparison. The simulation results show that the non-uniform distribution of space charges makes the discharge be enhanced in the high-density region but weakened in its neighborhood, which is considered as an activation-inhibition effect. This effect shows through during a current pulse (one discharge event) but also in a certain period of time after discharge that determines a driving frequency range for the non-uniformity of space charges to be enhanced. The effects of applied voltage, surface charge, electrode boundary, and external field are also discussed. All these factors affect the formation of dielectric-barrier-discharge pattern by changing the distribution or the dynamics of space charges and hence the activation-inhibition effect of non-uniform space charges.

  12. Submillimeter-Wave Observations of C_3N^- in AN Extended Negative Glow Discharge

    NASA Astrophysics Data System (ADS)

    Amano, T.

    2009-06-01

    Extended negative glow and hollow anode discharges are found to be good sources of negative ions, such as CN^-, C_2H^-, and C_4H^-, for observations of pure rotational lines in the submillimeter-wave region. Thaddeus et al. detected C_3N^- in a glow discharge in HC_3N diluted in Ar buffer gas, and its rotational lines up to 378 GHz (J=39-38) were measured. In the present investigation, this anion has been observed in an extended negative glow discharge in a gas mixture of C_2N_2 (˜ 2 mTorr) and C_2H_2 (˜ 3 mTorr) in Ar buffer gas of ˜ 15 mTorr at the cell wall temperature of 230 K. The optimum discharge current was 2-4 mA with 250 Gauss longitudinal magnetic field. The rotational lines of up to J=51-50 in the 495 GHz region have been measured, and the improved rotational and centrifugal distortion constants are obtained. In the discharge optimum for production of C_3N^-, neither CN nor C_3N was detected with a similar signal accumulation time used for observations of the anion. However, this reaction has been found to be an excellent source for HC_3N, and the dominant formation mechanism of C_3N^- is likely to be the dissociative electron attachment to HC_3N. The radiative association of C_3N with electrons seems to be unlikely at least for the extended negative glow discharge. Apparently HC_3N is synthesized by a fast neutral and neutral reaction (C_2{H}_2 + CN → HC_3{N} + {H} It is interesting to see that an isomer, HCCNC, is also detected in the discharge, although the number density of this species is found to be about two orders of magnitude smaller than that of HC_3N. Another isomer, HNCCC, has also been observed with much weaker signal intensity. This species might have been produced by the dissociative recombination reaction of HC_3NH^+ with electrons, although the detection of this cation has not been successful in this type of discharge. T. Amano, J. Chem. Phys., 129, 244305 (2008). P. Thaddeus et al.,Astrophys. J., 677,1132-1139 (2008) K. Graupner

  13. Potential Industrial Applications of the One Atmosphere Uniform Glow Discharge Plasma (OAUGDP) Operating in Ambient Air

    NASA Astrophysics Data System (ADS)

    Reece Roth, J.

    2004-11-01

    The majority of industrial plasma processing with glow discharges has been conducted at pressures below 10 torr. This tends to limit applications to high value workpieces as a result of the high capital cost of vacuum systems and the production constraints of batch processing. It has long been recognized that glow discharge plasmas would play a much larger industrial role if they could be generated at one atmosphere. The One Atmosphere Uniform Glow Discharge Plasma (OAUGDP), developed at the University of Tennessee's Plasma Sciences Laboratory, is a non-thermal RF plasma operating on displacement currents with the time-resolved characteristics of a classical low pressure DC normal glow discharge. As a glow discharge, the OAUGDP operates with maximum electrical efficiency at the Stoletow point, where the energy input per ion-electron pair is a minimum [1, 2]. Several interdisciplinary teams have investigated potential applications of the OAUGDP. These teams included collaborators from the UTK Textiles and Nonwovens Development Center (TANDEC), and the Departments of Electrical and Computer Engineering, Microbiology, and Food Science and Technology, as well as the NASA Langley Research Center. The potential applications of the OAUGDP have all been at one atmosphere and room temperature, using air as the working gas. These applications include sterilizing medical and dental equipment; sterilizable air filters to deal with the "sick building syndrome"; removal of soot from Diesel engine exhaust; subsonic plasma aerodynamic effects, including flow re-attachment to airfoils and boundary layer modification; electrohydrodynamic (EDH) flow control of working gases; increasing the surface energy of materials; improving the adhesion of paints and electroplated layers: improving the wettability and wickability of fabrics; stripping of photoresist; and plasma deposition and directional etching of potential microelectronic relevance. [1] J. R. Roth, Industrial Plasma Engineering

  14. Numerical modeling of a glow discharge through a supersonic bow shock in air

    NASA Astrophysics Data System (ADS)

    Rassou, S.; Packan, D.; Elias, P.-Q.; Tholin, F.; Chemartin, L.; Labaune, J.

    2017-03-01

    The interaction between a glow discharge and the bow shock of a Mach 3 air flow around a truncated conical model with a central spike is modeled, and comparison is made with prior experimental results. The KRONOS workflow for plasma modeling in flow fields, which has recently been developed at ONERA, was used for the modeling. Based on the quasi-neutral approximation, it couples hypersonic and reactive flow fields with electron chemistry, including the effect of non-Maxwellian electron energy distribution function. The model used for the discharge involves 12 species and 82 reactions, including ionization, electronic and vibrational excitation, and attachment. The simulations reproduce the main features of the discharge observed experimentally well, in particular, the very recognizable topology of the discharge. It was found from the simulations that behind the bow shock, in the afterglow, the negative ion flow ensures the electrical conduction and the establishment of the glow discharge. The influence of kinetic rates on the voltage-current characteristics is discussed.

  15. Validation and Verification of Two Particle-In-Cells Codes for a Glow Discharge

    NASA Astrophysics Data System (ADS)

    Carlsson, Johan; Khrabrov, Alexander V.; Kaganovich, Igor D.; Sommerer, Timothy

    2016-10-01

    The two particle-in-cell codes EDIPIC and LSP were benchmarked and validated for a parallel-plate glow discharge in helium, in which the axial electric field had been carefully measured. Both particle-in-cell codes reproduce very well cathode fall and negative glow regions of the discharge, including formation of high density plasma with very low-energy electrons in negative glow. A detailed code comparison was performed for several synthetic cases of electron-beam injection into helium gas and showed that the codes are in excellent agreement for ionization rate, as well as for elastic and excitation collisions with isotropic scattering pattern. However, electron velocity distribution is anisotropic in the cathode fall, and therefore, a more accurate model of anisotropic scattering in elastic and ionization cross sections needs to be taken into account. In the process of validation several issues with both codes were fixed, including necessity to use modern random generators in both codes, and choose efficient numerical model from EDIPIC for secondary electron emission and circuit model in LSP. This Research was supported by US Department of Energy.

  16. Validation and Verification of Two Particle-In-Cells Codes for a Glow Discharge

    NASA Astrophysics Data System (ADS)

    Khrabrov, Alexander; Carlsson, Johan; Kaganovich, Igor; Sommerer, Timothy

    2016-09-01

    Two PIC codes, a research code EDIPIC and a commercial LSP, were benchmarked and validated for a parallel-plate glow discharge in helium, in which the axial electric field profile had been carefully mapped in experiment. Both codes reproduce very well the cathode fall and the negative glow regions of the discharge, including formation of high density plasma with very low-energy (0.1 eV) electrons in the negative glow. A detailed comparison was performed for several synthetic cases of electron-beam injection into helium gas and showed that the codes are in excellent agreement for ionization rate, as well as for collisional transport if isotropic scattering was assumed. However, the electron velocity distribution is anisotropic in the cathode fall; hence an adequate model of anisotropic scattering in elastic/inelastic collisions needs to be adopted. Because of the experimental uncertainty for the emission yield, it is tuned to make the cathode current computed by each code match the experimental values. The resulting computed electric fields are in excellent agreement with each other and within about 10% of the experimental value. In the process of validation, several issues with each of the codes were noted and addressed, including the necessity to use quality random number generators, and, for the commercial code, updating the field solver, the secondary electron emission, and the external circuit algorithms.

  17. Transitions between corona, glow, and spark regimes of nanosecond repetitively pulsed discharges in air at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Pai, David Z.; Lacoste, Deanna A.; Laux, Christophe O.

    2010-05-01

    In atmospheric pressure air preheated from 300 to 1000 K, the nanosecond repetitively pulsed (NRP) method has been used to generate corona, glow, and spark discharges. Experiments have been performed to determine the parameter space (applied voltage, pulse repetition frequency, ambient gas temperature, and interelectrode gap distance) of each discharge regime. In particular, the experimental conditions necessary for the glow regime of NRP discharges have been determined, with the notable result that there exists a minimum and maximum gap distance for its existence at a given ambient gas temperature. The minimum gap distance increases with decreasing gas temperature, whereas the maximum does not vary appreciably. To explain the experimental results, an analytical model is developed to explain the corona-to-glow (C-G) and glow-to-spark (G-S) transitions. The C-G transition is analyzed in terms of the avalanche-to-streamer transition and the breakdown field during the conduction phase following the establishment of a conducting channel across the discharge gap. The G-S transition is determined by the thermal ionization instability, and we show analytically that this transition occurs at a certain reduced electric field for the NRP discharges studied here. This model shows that the electrode geometry plays an important role in the existence of the NRP glow regime at a given gas temperature. We derive a criterion for the existence of the NRP glow regime as a function of the ambient gas temperature, pulse repetition frequency, electrode radius of curvature, and interelectrode gap distance.

  18. Tailoring surface properties of polyethylene separator by low pressure 13.56 MHz RF oxygen plasma glow discharge

    NASA Astrophysics Data System (ADS)

    Li, Chun; Liang, Chia-Han; Huang, Chun

    2016-01-01

    Low-pressure plasma surface modification in a radio-frequency capacitively coupled glow discharge of oxygen gas was carried out to induce polar functional groups onto polyethylene membrane separator surfaces to enhance its hydrophilicity. The surface changes in surface free energy were monitored by static contact angle measurement. A significant increase in the surface energy of polyethylene membrane separators caused by the oxygen gas plasma modifications was observed. The static water contact angle of the plasma-modified membrane separator significantly decreased with the increase in treatment duration and plasma power. An obvious increase in the surface energy of the membrane separators owing to the oxidative effect of oxygen-gas-plasma modifications was also observed. Optical emission spectroscopy was carried out to analyze the chemical species generated by oxygen gas plasma surface modification. The variations in the surface morphology and chemical structure of the separators were confirmed by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS). XPS showed significantly higher surface concentrations of oxygen functional groups in the oxygen-gas-plasma-modified polymeric separator surfaces than in the unmodified polymeric separator surface. The experimental results show the important role of chemical species in the interaction between oxygen gas plasmas and the separator surface, which can be controlled by surface modification to tailor the hydrophilicity of the separator.

  19. Quantitative depth profiling in glow discharge spectroscopies - A new deconvolution technique to separate effects of an uneven erosion crater shape.

    PubMed

    Prässler, F; Hoffmann, V; Schumann, J; Wetzig, K

    1996-07-01

    An algorithm is presented as a concept for the quantification in direct current and radiofrequency glow discharge (GD) modes for GD optical emission spectroscopy. The algorithm is divided into excitation and sputtering part and thus it is possible to distinguish between the different excitation processes and to consider equivalent sputtering crater formations in both modes. Intensity-time profiles are affected corresponding to the method by several effects. One important effect is that sputtering occurs at a single time in different depths because of curved crater bottoms, this is usually called crater effect. The main purpose is to introduce an iterative deconvolution technique which for the quantification numerically takes into account the curved sputtering crater bottom. Input data for the deconvolution technique are the calibrated mass-time profile, the partial densities of the sample constituents and the measured final shape of the sputtering crater. Using a relatively simple model for ion sputtering the deconvolution technique improves iteratively the calculated layer structure by means of information on crater formation. The mathematical handling is illustrated for the quantification of a depth profile of a multilayer sample of ten 100 nm layers. The resulting concentration-depth profile reflects excellently the real elemental distribution of the multilayer system.

  20. On the physical processes ruling an atmospheric pressure air glow discharge operating in an intermediate current regime

    SciTech Connect

    Prevosto, L. Mancinelli, B.; Chamorro, J. C.; Cejas, E.; Kelly, H.

    2015-02-15

    Low-frequency (100 Hz), intermediate-current (50 to 200 mA) glow discharges were experimentally investigated in atmospheric pressure air between blunt copper electrodes. Voltage–current characteristics and images of the discharge for different inter-electrode distances are reported. A cathode-fall voltage close to 360 V and a current density at the cathode surface of about 11 A/cm{sup 2}, both independent of the discharge current, were found. The visible emissive structure of the discharge resembles to that of a typical low-pressure glow, thus suggesting a glow-like electric field distribution in the discharge. A kinetic model for the discharge ionization processes is also presented with the aim of identifying the main physical processes ruling the discharge behavior. The numerical results indicate the presence of a non-equilibrium plasma with rather high gas temperature (above 4000 K) leading to the production of components such as NO, O, and N which are usually absent in low-current glows. Hence, the ionization by electron-impact is replaced by associative ionization, which is independent of the reduced electric field. This leads to a negative current-voltage characteristic curve, in spite of the glow-like features of the discharge. On the other hand, several estimations show that the discharge seems to be stabilized by heat conduction; being thermally stable due to its reduced size. All the quoted results indicate that although this discharge regime might be considered to be close to an arc, it is still a glow discharge as demonstrated by its overall properties, supported also by the presence of thermal non-equilibrium.

  1. Direct determination of Cu by liquid cathode glow discharge-atomic emission spectrometry

    NASA Astrophysics Data System (ADS)

    Lu, Quanfang; Yang, Shuxiu; Sun, Duixiong; Zheng, Jidong; Li, Yun; Yu, Jie; Su, Maogen

    2016-11-01

    In this study, a novel liquid cathode glow discharge-atomic emission spectrometry was developed for the direct determination of Cu in aqueous solutions, in which the glow discharge plasma was produced in the solution between the needle-like Pt cathode and the electrolyte around it. The effects of discharge voltage, solution pH, and the ionic surfactant cetyltrimethylammonium chloride (CTAC) on emission intensities were investigated. The limit of detection (LOD) of Cu was compared with those measured by closed-type electrolyte cathode discharge-atomic emission spectrometry (ELCAD-AES). The results showed that the optimal operation conditions are voltage of 135 V, a pH of 1, and addition of 0.15% CTAC. CTAC can enhance the emission intensity and lower the LOD of Cu I. The net intensity of atomic emission lines of Cu I at 324.8 nm with 0.15% CTAC improved by 1.5 fold, and the LODs of the Cu at 135 V with 0.15% CTAC and without CTAC are 0.019 and 0.234 mg L- 1, respectively. The analytical capability of Cu in this study is comparable to the closed-type ELCAD-AES, and it satisfied the recommended levels of Cu in the WHO standards for drinking-water quality. This technique can be effectively used for on-line monitoring of metal ions in aqueous samples.

  2. Evolution of Multiple Double Layer in Glow discharge and its inherent Properties

    NASA Astrophysics Data System (ADS)

    Alex, Prince; A, Saravanan; Sinha, Suraj

    2016-10-01

    Formation and evolution of multiple anodic double layers (MADLs) were experimentally studied in glow discharge plasma. The boundary condition for the existence of MADL was identified in terms of threshold bias and ambient working pressure. The MADL formation is accompanied by an explosive growth in anode current and consequent current-voltage characteristics follows a hysteresis loop. The analysis yield that stable MADLs is only observed when the control voltage V2 is between a certain critical values (Vq > νte MADL completely transforms to an intense high current carrying unstable anode glow. The floating potential analysis carried out using three axially positioned electrostatic probes shows a bipolar signature of DL with as the control parameter is varied. The floating potential analysis also shows that hysteresis arises due to the difference in magnitude of electric field required to align the space charges in the DL sheet at the control voltage changes forward and backward. The effect of pressure on MADL indicates that the MADL structure advances towards anode surface as the pressure is increases. The power dumped (W) in the MADL is estimated to decrease with increase in pressure while the same increase in the anode glow.

  3. Non-local Effects in a Stratified Glow Discharge With Dusty Particles

    SciTech Connect

    Sukhinin, G. I.; Fedoseev, A. V.; Ramazanov, T. S.; Amangaliyeva, R. Zh.; Dosbolayev, M. K.; Jumabekov, A. N.

    2008-09-07

    The work is aimed to describe non-local effects in the positive column of a low pressure stratified DC glow discharge in argon with dusty particles in a vertical cylindrical discharge tube. The numerical calculations of plasma parameters in the axis of the discharge tube were performed with the help of hybrid model based on the solution of non-local Boltzmann equation for EEDF. Distributions of optical emission from striations were measured experimentally. It is shown that in a stratified positive column the EEDF is not Maxwellian and even non-monotonous. Also, the effect of displacing of optical emission distribution relative to the electric field is shown both by numerical simulation and experimental measurements.

  4. Cathodic contact glow discharge electrolysis: its origin and non-faradaic chemical effects

    NASA Astrophysics Data System (ADS)

    Gupta, Susanta K. Sen; Singh, Rajshree

    2017-01-01

    Normal electrolysis (NE), at sufficiently high voltages, breaks down and undergoes a transition to a phenomenon called contact glow discharge electrolysis (CGDE) in which a sheath of glow discharge plasma encapsulates one of the electrodes, the anode or the cathode. The chemical effects of CGDE are highly non-faradaic e.g. a mixture of H2 and H2O2 plus O2 each in excess of the Faraday law value is liberated at the glow discharge plasma electrode from an aqueous electrolyte solution. Studies of cathodic CGDE, particularly its origin and chemical effects, in comparison to those of anodic CGDE have received significantly less attention and have not been studied in detail. The present paper is an attempt towards elucidation of the mechanisms of the growth of cathodic CGDE during NE and its non-faradaic chemical effects. The findings of the study have led to the inference that emission of secondary electrons from the metal cathode with sufficient kinetic energies, vaporization of the electrolyte solvent in the vicinity of the cathode surface induced by Joule heating and the onset of hydrodynamic instabilities in local vaporization contribute to the generation of the plasma at the cathode during NE. The findings have further shown that non-faradaic yields of CGDE at the cathode originate from energy transfer processes in two reaction zones: a plasma phase reaction zone around the cathode which accounts for ~75% of the yields, and a liquid phase reaction zone near the plasma-catholyte solution interface accounting for the remaining ~25% of the yields.

  5. Experimental verification of dynamics modulation in a periodically-driven neon glow discharge plasma

    NASA Astrophysics Data System (ADS)

    Miller, P. M.; Koepke, M. E.; Gunell, H.

    2010-11-01

    Two ionization wave modes in a driven neon glow discharge alternate as the dominant mode as their response to the driving force alternates between spatiotemporal and temporal periodic pulling. This phenomenon, termed dynamics modulation, was first noted by Koepke, Weltmann, and Selcher [1], who saw two limited but representative cases and proposed a mechanism [2] by which it occurs. Dynamics modulation is reproduced experimentally in a neon glow discharge plasma. The system is periodically driven near a non-dominant mode using a narrow-band ring dye laser tuned to a wavelength near the metastable neon transition at 588.35 nm. A spatially-fixed photodiode with a narrow band filter that selectively passes the primary neon spectral line at 640 nm is used to acquire the time series of luminosity oscillations. These experimental data are used to verify the proposed mechanism and explore the resulting implications for spontaneous unidirectional mode transitions that occur with a change in discharge current.[4pt] [1] M. E. Koepke, K.-D. Weltmann, and C. A. Selcher, Bull. Am. Phys. Soc. 40, 1716 (1995).[0pt] [2] K. -D. Weltmann, M. E. Koepke, and C. A. Selcher, Phys. Rev. E 62, 2773, (2000).

  6. Child-Langmuir law applicability for a cathode sheath description of glow discharge in hydrogen

    NASA Astrophysics Data System (ADS)

    Lisovskiy, V. A.; Artushenko, K. P.; Yegorenkov, V. D.

    2016-08-01

    The present paper reveals that the Child-Langmuir law version with the constant ion mobility has to be applied for the cathode sheath description of the glow discharge in hydrogen. Using the analytical model we demonstrate that even in a high electric field the constant mobility law version rather than that for the constant ion mean free path has to hold in the case of impeded charge exchange and the dominant effect of polarization forces on the ion motion through the cathode sheath.

  7. Analysis of green fluorescent protein bioluminescence in vivo and in vitro using a glow discharge

    NASA Astrophysics Data System (ADS)

    Hernández, L.; Mandujano, L. A.; Cuevas, J.; Reyes, P. G.; Osorio-González, D.

    2015-03-01

    The discovery of fluorescent proteins has been a revolution in cell biology and related sciences because of their many applications, mainly emphasizing their use as cellular markers. The green fluorescent protein (GFP) is one of the most used as it requires no cofactors to generate fluorescence and retains this property into any organism when it is expressed by recombinant DNA techniques, which is a great advantage. In this work, we analyze the emission spectra of recombinant green fluorescent protein in vivo and in vitro exposed to a glow discharge plasma of nitrogen in order to relate electron temperature to fluorescence intensity.

  8. Surface oxygen micropatterns on glow discharge polymer targets by photo irradiation

    DOE PAGES

    Reynolds, Hannah; Baxamusa, Salmaan; Haan, Steven W.; ...

    2016-02-24

    Recent simulations predict surface oxygen may be a significant source of disruptive perturbations in the implosion process of glow-discharge polymers (GDP) ablators at the National Ignition Facility. GDP material held in ambient atmospheric conditions showed an increase in mass when stored in light transparent containers, which suggests that photo exposure is a driving force for oxygen absorption. To investigate if surface oxygen is a contributing factor of disruptive perturbations during implosion, we developed a method to imprint a periodic micropattern of oxygen on the surface of GDP and used it to fabricate a flat sample for empirical testing.

  9. Auxiliary glow discharge in the trigger unit of a hollow-cathode thyratron

    NASA Astrophysics Data System (ADS)

    Korolev, Yu. D.; Landl, N. V.; Geyman, V. G.; Frants, O. B.; Shemyakin, I. A.; Nekhoroshev, V. O.

    2016-08-01

    Results from studies of a low-current glow discharge with a hollow cathode are presented. A specific feature of the discharge conditions was that a highly emissive tablet containing cesium carbonate was placed in the cathode cavity. In the absence of a tablet, the discharge ignition voltage was typically ≥3.5 kV, while the burning voltage was in the range of 500-600 V. The use of the tablet made it possible to decrease the ignition voltage to 280 V and maintain the discharge burning voltage at a level of about 130 V. A model of the current sustainment in a hollow-cathode discharge is proposed. Instead of the conventional secondary emission yield, the model uses a generalized emission yield that takes into account not only ion bombardment of the cathode, but also the emission current from an external source. The model is used to interpret the observed current-voltage characteristics. The results of calculations agree well with the experimental data. It is shown that, in some discharge modes, the external emission current from the cathode can reach 25% of the total discharge current.

  10. Glow Discharge Emission Spectra in Air with Liquid Electrode Based on Distilled Water

    NASA Astrophysics Data System (ADS)

    Chuchman, M. P.; Mesarosz, L. V.; Shuaibov, A. K.; Kiris, V. V.; Tarasenko, N. V.

    2016-11-01

    The results of spectroscopic studies of a glow discharge plasma at atmospheric pressure in air with an electrode based on distilled water are presented. The parametric effects affecting the discharge emission are analyzed. The dependence of the emission intensity of the various discharge components and their spatial localization in the discharge gap on the current strength is explained by change in the discharge geometry and the conditions of oxidation with increase of the current. It is shown that the composition of the gas mixture in the electrode gap changes with increase of the discharge current from nitrogen-rich (12-19 mA) to rich in water vapor and its dissociation products (19-24 mA). At higher currents, the gas mixture is also rich in the products of plasma chemical reactions and nitric oxide in particular. The redistribution of the radiation intensity of the molecules of nitrogen and its oxide with increase of the current occurs mainly in the cathode region (at the plasma-fluid boundary), where the formation of oxides is improved as a result of increase in the amount of vaporized solution and in the effectiveness of oxidation reactions with increase of the water temperature and discharge current.

  11. Time-of-Flight Mass Spectrometry with a Pulsed Glow Discharge Ionization Source.

    PubMed

    Steiner, R E; Lewis, C L; King, F L

    1997-05-01

    The pulsed glow discharge (GD) plasma source exhibits several characteristics that make it ideally suited for use with time-of-flight mass spectrometry (TOFMS). TOFMS uniquely affords the ability to monitor a narrow temporal window for a time-varying process such as ion formation in the pulsed glow discharge plasma. Pulsed GD-TOFMS exhibited distinct advantages for the direct determination of trace elements in solid state samples. Initially, the pulse-powered GD-TOFMS system used for these investigations exhibited poor resolution. In an effort to improve resolution, a slit was introduced to narrow the ion beam orthogonally entering the extraction region of the TOFMS. In an effort to determine optimal operating conditions, the influence of slit width on TOF performance was investigated. In the course of this study, the slit width was found to influence isotope ratio accuracy as well as resolution. A slit width of 1.0 mm was determined to provide the best compromise between resolution and isotope ratio accuracy. Pulsed GD-TOFMS affords improved sensitivity and selectivity because Penning ionization is enhanced during the time period immediately following the termination of the discharge power. Ions sampled by an extraction pulse applied after power termination also yield a mass spectrum that is free of contributions arising from electron-ionized interferences. This advantage arises because only ions generated via the Penning ionization mechanism persist after the termination of discharge power. Sampling in the "afterpeak" time regime eliminates the saturation of the detector arising from discharge support gas ion signal.

  12. Characterization of the large area plane-symmetric low-pressure DC glow discharge

    NASA Astrophysics Data System (ADS)

    Avtaeva, S.; Gorokhovsky, V.; Myers, S.; Robertson, S.; Shunko, E.; Zembower, Z.

    2016-10-01

    Electron density and temperature as well as nitrogen dissociation degree in the low-pressure (10-50 mTorr) large area plane-symmetric DC glow discharge in Ar-N2 mixtures are studied by probes and spectral methods. Electron density measured by a hairpin probe is in good agreement with that derived from the intensity ratio of the N2 2nd positive system bands IC , 1 - 3/IC , 0 - 2 and from the intensity ratio of argon ions and atom lines IArII/IArI, while Langmuir probe data provides slightly higher values of electron density. Electron density in the low-pressure DC glow discharge varies with the discharge conditions in the limits of 108-1010 cm- 3. The concept of electron temperature can be used in low-pressure glow discharges with reservations. The intensity ratio of (0-0) vibrational bands of N2 1st negative and 2nd positive systems I391.4/I337.1 exhibits the electron temperature of 1.5-2.5 eV when argon fraction in the mixture is higher than nitrogen fraction and this ratio quickly increases with nitrogen fraction up to 10 eV in pure nitrogen. The electron temperature calculated from Langmuir probe I-V characteristics assuming a Maxwellian EEDF, gives Te 0.3-0.4 eV. In-depth analysis of the EEDF using the second derivative of Langmuir probe I-V characteristics shows that in a low-pressure glow discharge the EEDF is non-Maxwellian. The EEDF has two populations of electrons: the main background non-Maxwellian population of ;cold; electrons with the mean electron energy of 0.3-0.4 eV and the small Maxwellian population of ;hot; electrons with the mean electron energy of 1.0-2.5 eV. Estimations show that with electron temperature lower than 1 eV the rate of the direct electron impact ionization of N2 is low and the main mechanism of N2 ionization becomes most likely Penning and associative ionization. In this case, assumptions of the intensity ratio IN2+ , 391/IN2 , 337 method are violated. In the glow discharge, N2 dissociation degree reaches about 7% with the argon

  13. Laser-induced optogalvanic signal oscillations in miniature neon glow discharge plasma.

    PubMed

    Saini, V K

    2013-06-20

    Laser-induced optogalvanic (OG) signal oscillations detected in miniature neon glow discharge plasma are investigated using a discharge equivalent-circuit model. The damped oscillations in OG signal are generated when a pulsed dye laser is tuned to a specific neon transition (1s5→2p2) at 588.2 nm under the discharge conditions where dynamic resistance changes its sign. Penning ionization via quasi-resonant energy transfer collisions between neon gas atoms in metastable state and sputtered electrode atoms in ground state is discussed to explain the negative differential resistance properties of discharge plasma that are attributed to oscillations in the OG signal. The experimentally observed results are simulated by analyzing the behavior of an equivalent discharge-OG circuit. Good agreement between theoretically calculated and experimental results is observed. It is found that discharge plasma is more sensitive and less stable in close vicinity to dynamic resistance sign inversion, which can be useful for weak-optical-transition OG detection.

  14. Transmission characteristics of microwave in a glow-discharge dusty plasma

    NASA Astrophysics Data System (ADS)

    Jia, Jieshu; Yuan, Chengxun; Gao, Ruilin; Liu, Sha; Yue, Feng; Wang, Ying; Zhou, Zhong-Xiang; Wu, Jian; Li, Hui

    2016-07-01

    In this study, the propagation characteristics of electromagnetic wave in a glow discharge plasma with dust particles are experimentally investigated. A helium alternating current glow discharge plasmas have been successfully generated. Measurements of the plasma parameters using Langmuir probes, in the absence of dust particles, provide plasma densities (ne) of 1017 m-3 and electron temperatures (Te) ranging from 2 to 4 eV. Dusty plasmas are made by adding 30 nm radius aluminum oxide (Al2O3) particles into the helium plasma. The density of the dust particle (nd) in the device is about 1011-1012 m-3. The propagation characteristics of electromagnetic waves are determined by a vector network analyzer with 4-6 GHz antennas. An apparent attenuation by the dust is observed, and the measured attenuation data are approximately in accordance with the theoretical calculations. The effects of gas pressure and input power on the propagation are also investigated. Results show that the transmission attenuation increases with the gas pressure and input power, the charged dust particles play a significant role in the microwave attenuation.

  15. Borax as flux on sintering of iron Ancor Steel 1000® under glow discharge

    NASA Astrophysics Data System (ADS)

    Ariza Suarez, H. G.; Sarmiento Santos, A.; Ortiz Otálora, C. A.

    2016-02-01

    This work studies the flux effect of borax (di sodium tetraborate decahydrate) on sintering of iron Ancor Steel 1000® in abnormal glow discharge. The incidence of the percentage by weight of borax and the sintering temperature in the process were observed. Samples of powder metallurgical iron were prepared with proportions of 0.50%, 2.0%, 4.0% and 6.0% by weight of borax using the procedures of powder metallurgy. The samples were sintered at 800 and 1100°C for 30min, by glow discharge at low pressure in a reducing atmosphere composed of 20% H2+80% Ar. The samples in compact green-state were analyzed by TGA-DSC to determine the fusion process and mass loss during sintering. The analysis of microhardness and density, shows that at a sintering temperature of 800°C the sample density decreases and the sample microhardness increases with respect to sintered samples without borax. Sintered samples were analysed by DRX showing the absence of precipitates.

  16. Surface modification of corneal contact lens with phosphoryl choline by glow discharge.

    PubMed

    Sunny, M C; Sharma, C P

    1991-01-01

    Polymers like poly(methylmethacrylate) (PMMA) and poly(2-hydroxyethylmethacrylate) (PHEMA) are widely used in the development of hard and soft contact lenses. Cell adhesion and deposition of chemicals such as calcium, lipoproteins and mucin on the lens surface cause visual acuity which is the main problem in extended uses of contact ocular lenses. In order to minimise the cell adhesion and other type of depositions, a method of surface modification of lens involving the use of phosphoryl choline, a phospholipid and the glow discharge technique has been described. The power variation of the lenses after modification has been checked using Topcon lensometer. The possible power changes of the modified samples due to the exposure to the normal light in the laboratory, darkness, ultraviolet (U.V.) light or saline have been investigated by taking the visible and ultra violet spectra using Beckman spectrophotometer. Surface energy variations after modifications of the samples have been checked by sessile drop water contact angle measurements. Glow discharge treatment increases the hydrophilicity of the samples. It seems, the modifications do not affect the power of hard contact lens significantly. It is also observed that the exposure of samples to the normal light in the laboratory, darkness, U.V. light or saline make no significant change in the visible and ultraviolet spectra of the samples before and after modification.

  17. Influences of impedance matching network on pulse-modulated radio frequency atmospheric pressure glow discharges

    SciTech Connect

    Huo, W. G.; Xu, K.; Sun, B.; Ding, Z. F.

    2012-08-15

    Pulse-modulated RF atmospheric pressure glow discharges (APDGs) were investigated in recent years to reduce the thermal accumulation and extend the operation region of the stable alpha glow mode. Different pulse-modulated voltage and current waveforms were acquired in previous experiments, but no attention was paid to the interpretation. We investigated this issue and associated phenomenon via positive and negative feedback effects derived from varying the series capacitor in the inversely L-shaped matching network used in our pulse-modulated RF APGD source. The evolutions of pulse-modulated RF waveforms were found to be associated with the feedback region and the pulsed plasma absorbed RF power. In the positive feedback region, pulse-modulated RF APGDs are relatively stable. In the negative feedback region, wide spikes as well as undershoots occur in RF voltage and current waveforms and the plasma absorbed RF power. In case of a high RF power discharge with a low modulation frequency, the pulse-modulated RF APGD is extinguished and re-ignited due to the enhanced undershoot during the initial pulse phase. The pulse-modulated RF APGD can transit from positive to negative feedback region in a range of series capacitance. Experimental results are discussed by the aid of equivalent circuit, negative and positive feedback effects.

  18. Decomposition of toluene in a steady-state atmospheric-pressure glow discharge

    NASA Astrophysics Data System (ADS)

    Trushkin, A. N.; Grushin, M. E.; Kochetov, I. V.; Trushkin, N. I.; Akishev, Yu. S.

    2013-02-01

    Results are presented from experimental studies of decomposition of toluene (C6H5CH3) in a polluted air flow by means of a steady-state atmospheric pressure glow discharge at different water vapor contents in the working gas. The experimental results on the degree of C6H5CH3 removal are compared with the results of computer simulations conducted in the framework of the developed kinetic model of plasma chemical decomposition of toluene in the N2: O2: H2O gas mixture. A substantial influence of the gas flow humidity on toluene decomposition in the atmospheric pressure glow discharge is demonstrated. The main mechanisms of the influence of humidity on C6H5CH3 decomposition are determined. The existence of two stages in the process of toluene removal, which differ in their duration and the intensity of plasma chemical decomposition of C6H5CH3 is established. Based on the results of computer simulations, the composition of the products of plasma chemical reactions at the output of the reactor is analyzed as a function of the specific energy deposition and gas flow humidity. The existence of a catalytic cycle in which hydroxyl radical OH acts a catalyst and which substantially accelerates the recombination of oxygen atoms and suppression of ozone generation when the plasma-forming gas contains water vapor is established.

  19. Irradiation of silver and agar/silver nanoparticles with argon, oxygen glow discharge plasma, and mercury lamp.

    PubMed

    Ahmad, Mahmoud M; Abdel-Wahab, Essam A; El-Maaref, A A; Rawway, Mohammed; Shaaban, Essam R

    2014-01-01

    The irradiation effect of argon, oxygen glow discharge plasma, and mercury lamp on silver and agar/silver nanoparticle samples is studied. The irradiation time dependence of the synthesized silver and agar/silver nanoparticle absorption spectra and their antibacterial effect are studied and compared. In the agar/silver nanoparticle sample, as the irradiation time of argon glow discharge plasma or mercury lamp increases, the peak intensity and the full width at half maximum, FWHM, of the surface plasmon resonance absorption band is increased, however a decrease of the peak intensity with oxygen glow plasma has been observed. In the silver nanoparticle sample, as the irradiation time of argon, oxygen glow discharge plasma or mercury lamp increases, the peak intensity of the surface plasmon resonance absorption band is increased, however, there is no significant change in the FWHM of the surface plasmon resonance absorption band. The SEM results for both samples showed nanoparticle formation with mean size about 50 nm and 40 nm respectively. Throughout the irradiation time with the argon, oxygen glow discharge plasma or mercury lamp, the antibacterial activity of several kinds of Gram-positive and Gram-negative bacteria has been examined.

  20. Effects of traces of molecular gases (hydrogen, nitrogen) in glow discharges in noble gases

    NASA Astrophysics Data System (ADS)

    Steers, E. B. M.; Smid, P.; Hoffmann, V.

    2008-07-01

    The "Grimm" type of low pressure glow discharge source, introduced some forty years ago, has proved to be a versatile analytical source. A flat sample is used as the cathode and placed about 0.2mm away from the end of a hollow tubular anode leading to an obstructed discharge. When the source was first developed, it was used for the direct analysis of solid metallic samples by optical emission spectroscopy (OES), normally with argon as the plasma gas; it was soon found that, using suitable electrical parameters, the cathode material was sputtered uniformly from a circular crater of diameter equal to that of the tubular anode, so that the technique could be used for compositional depth profile analysis (CDPA). Over the years the capability and applications of the technique have steadily increased. The use of rf powered discharges now permits the analysis of non-conducting layers and samples; improved instrumental design now allows CDPA of ever thinner layers (e.g. resolution of layers 5 nm thick in multilayer stacks is possible). For the original bulk material application, pre-sputtering could be used to remove any surface contamination but for CDPA, analysis must start immediately the discharge is ignited, so that any surface contamination can introduce molecular gases into the plasma gas and have significant analytical consequences, especially for very thin layers; in addition, many types of samples now analysed contain molecular gases as components (either as occluded gas, or e.g. as a nitride or oxide), and this gas enters the discharge when the sample is sputtered. It is therefore important to investigate the effect of such foreign gases on the discharge, in particular on the spectral intensities and hence the analytical results. The presentation will concentrate mainly on the effect of hydrogen in argon discharges, in the concentration range 0-2 % v/v but other gas mixtures (e.g. Ar/N_2, Ne/H_2) will be considered for comparison. In general, the introduction of

  1. Double flush-mounted probe diagnostics and data analysis technique for argon glow discharge plasma.

    PubMed

    Yu, Pengcheng; Liu, Yu; Cao, Jinxiang; Xu, Liang; Zhang, Xiao; Zhang, Zhongkai; Wang, Pi

    2017-01-01

    In this work, a double flush-mounted probe for measuring plasma parameters was designed and fabricated. The method to determine the plasma density and electron temperature using a floating double flush-mounted probe was characterized. To validate this method, the measurement results in an argon glow discharge plasma, including the electron density and temperature measurements, were compared with those obtained using a single probe and a double probe. Results indicate that the electron density measured using the double flush-mounted probe agrees well with those measured using other probes; the effective electron temperature values are also consistent within the admissible error range. These results suggest that the double flush-mounted probe can be used for accurate measurements at low pressure DC plasma discharges and also can be applied to other complex plasmas such as tokamaks, in the boundary-layer region without a reference electrode.

  2. Investigation and quantification of nonlinearity using surrogate data in a glow discharge plasma

    SciTech Connect

    Saha, Debajyoti Shaw, Pankaj Kumar; Ghosh, Sabuj; Janaki, M. S.; Sekar Iyengar, A. N.

    2015-02-15

    Detection of nonlinearity has been carried out in periodic and aperiodic floating potential fluctuations of DC glow discharge plasma by generating surrogate data using iterative amplitude adjusted Fourier transform method. We introduce “delay vector variance” analysis (DVV) for the first time, which allows reliable detection of nonlinearity and provides some easy to interpret diagram conveying information about the nature of the experimental floating potential fluctuations (FPF). The method of false nearest neighbourhood is deployed on the FPF's to find a good embedding so as to be acquainted with the precise knowledge of m, which is desirable for carrying out DVV analysis. The emergence of nonlinearity with increase in discharge voltage has been ensured by taking into consideration the total energy present in different band of frequencies excited due to nonlinear processes. Rejection of null hypothesis has been verified by performing the rank test method that confirms the presence of nonlinearity quantitatively.

  3. Degradation of methyl tert-butyl ether (MTBE) in water by glow discharge plasma.

    PubMed

    Tong, Shaoping; Ni, Yanyan; Shen, Chensi; Wen, Yuezhong; Jiang, Xuanzhen

    2011-01-01

    This study evaluated the ability of the glow discharge plasma (GDP) technique to degrade methyl tert-butyl ether (MTBE) in an aqueous solution. The results showed that a large amount of hydrogen peroxide and highly active *OH free radicals were produced during the treatment. Various experimental parameters including discharge current, initial MTBE concentration and initial pH played significant roles on MTBE degradation. In addition, Fe2+ had a catalytic effect on the degradation of MTBE, which is potentially attributable to the reaction between Fe3+ and the hydrated electron. It was also confirmed that GDP was comparable to electrocatalytic oxidation and high-density plasma and more efficient than photocatalytic degradation techniques. These results suggest that GDP may become a competitive MTBE wastewater treatment technology.

  4. Double flush-mounted probe diagnostics and data analysis technique for argon glow discharge plasma

    NASA Astrophysics Data System (ADS)

    Yu, Pengcheng; Liu, Yu; Cao, Jinxiang; Xu, Liang; Zhang, Xiao; Zhang, Zhongkai; Wang, Pi

    2017-01-01

    In this work, a double flush-mounted probe for measuring plasma parameters was designed and fabricated. The method to determine the plasma density and electron temperature using a floating double flush-mounted probe was characterized. To validate this method, the measurement results in an argon glow discharge plasma, including the electron density and temperature measurements, were compared with those obtained using a single probe and a double probe. Results indicate that the electron density measured using the double flush-mounted probe agrees well with those measured using other probes; the effective electron temperature values are also consistent within the admissible error range. These results suggest that the double flush-mounted probe can be used for accurate measurements at low pressure DC plasma discharges and also can be applied to other complex plasmas such as tokamaks, in the boundary-layer region without a reference electrode.

  5. Experimental observation of phase-flip transitions in two inductively coupled glow discharge plasmas

    NASA Astrophysics Data System (ADS)

    Chaubey, Neeraj; Mukherjee, S.; Sen, A.; Iyengar, A. N. Sekar

    2016-12-01

    We report an experimental observation of a phase-flip transition in the frequency synchronization of two dc glow discharge plasma sources that are coupled in a noninvasive fashion. When the fundamental oscillation frequency of the potential fluctuations of one of the sources is progressively increased, by raising its discharge voltage, a frequency pulling regime is observed, followed by a synchronized regime that shows a frequency jump phenomenon. The jump is associated with a phase-flip transition that takes the synchronized state from an in-phase to an antiphase state. When the process is reversed, the transition takes place at a different frequency, thereby exhibiting a hysteresis effect. A heuristic model, consisting of two van der Pol oscillators that are coupled to each other through a dynamic common medium, eminently captures the essential features of our experimental observations.

  6. Modelling cathode spots in glow discharges in the cathode boundary layer geometry

    NASA Astrophysics Data System (ADS)

    Bieniek, M. S.; Almeida, P. G. C.; Benilov, M. S.

    2016-03-01

    Self-organized patterns of cathode spots in glow discharges are computed in the cathode boundary layer geometry, which is the one employed in most of the experiments reported in the literature. The model comprises conservation and transport equations of electrons and a single ion species, written in the drift-diffusion and local-field approximations, and Poisson’s equation. Multiple solutions existing for the same value of the discharge current and describing modes with different configurations of cathode spots are computed by means of a stationary solver. The computed solutions are compared to their counterparts for plane-parallel electrodes, and experiments. All of the computed spot patterns have been observed in the experiment.

  7. DC negative corona discharge in atmospheric pressure helium: transition from the corona to the ‘normal’ glow regime

    NASA Astrophysics Data System (ADS)

    Hasan, Nusair; Antao, Dion S.; Farouk, Bakhtier

    2014-06-01

    Direct current (dc) negative corona discharges in atmospheric pressure helium are simulated via detailed numerical modeling. Simulations are conducted to characterize the discharges in atmospheric helium for a pin plate electrode configuration. A self-consistent two-dimensional hybrid model is developed to simulate the discharges and the model predictions are validated with experimental measurements. The discharge model considered consists of momentum and energy conservation equations for a multi-component (electrons, ions, excited species and neutrals) gas mixture, conservation equations for each component of the mixture and state relations. A drift-diffusion approximation for the electron and the ion fluxes is used. A model for the external circuit driving the discharge is also considered and solved along with the discharge model. Many of the key features of a negative corona discharge, namely non-linear current-voltage characteristics, spatially flat cathode current density and glow-like discharge in the high current regime are displayed in the predictions. A transition to the ‘normal’ glow discharge from the corona discharge regime is also observed. The transition is identified from the calculated current-voltage characteristic curve and is characterized by the radial growth of the negative glow and the engulfment of the cathode wire.

  8. Fabrication of dense non-circular nanomagnetic device arrays using self-limiting low-energy glow-discharge processing.

    PubMed

    Zheng, Zhen; Chang, Long; Nekrashevich, Ivan; Ruchhoeft, Paul; Khizroev, Sakhrat; Litvinov, Dmitri

    2013-01-01

    We describe a low-energy glow-discharge process using reactive ion etching system that enables non-circular device patterns, such as squares or hexagons, to be formed from a precursor array of uniform circular openings in polymethyl methacrylate, PMMA, defined by electron beam lithography. This technique is of a particular interest for bit-patterned magnetic recording medium fabrication, where close packed square magnetic bits may improve its recording performance. The process and results of generating close packed square patterns by self-limiting low-energy glow-discharge are investigated. Dense magnetic arrays formed by electrochemical deposition of nickel over self-limiting formed molds are demonstrated.

  9. Achieving ultrahigh vacuum in an unbaked chamber with glow discharge conditioning

    NASA Astrophysics Data System (ADS)

    Khan, Ziauddin; Semwal, Pratibha; Dhanani, Kalpesh R.; Raval, Dilip C.; Pradhan, Subrata

    2017-01-01

    Glow discharge conditioning (GDC) has long been accepted as one of the basic wall conditioning techniques for achieving ultrahigh vacuum in an unbaked chamber. As a part of this fundamental experimental study, a test chamber has been fabricated from stainless steel 304 L with its inner surface electropolished on which a detailed investigation has been carried out. Both helium and hydrogen gases have been employed as discharge cleaning medium. The discharge cleaning was carried out at 0.1 A / m 2 current density with working pressure maintained at 1.0 × 10 -2 mbar. It was experimentally observed that the pump-down time to attain the base pressure 10 -8 mbar was reduced by 62% compared to the unbaked chamber being pumped to this ultimate vacuum. The results were similar irrespective of whether the discharge cleaning medium is either hydrogen or helium. It was also experimentally established that a better ultimate vacuum could be achieved as compared to theoretically calculated ultimate vacuum with the help of discharge cleaning.

  10. Validation and benchmarking of two particle-in-cell codes for a glow discharge

    NASA Astrophysics Data System (ADS)

    Carlsson, Johan; Khrabrov, Alexander; Kaganovich, Igor; Sommerer, Timothy; Keating, David

    2017-01-01

    The two particle-in-cell codes EDIPIC and LSP are benchmarked and validated for a parallel-plate glow discharge in helium, in which the axial electric field had been carefully measured, primarily to investigate and improve the fidelity of their collision models. The scattering anisotropy of electron-impact ionization, as well as the value of the secondary-electron emission yield, are not well known in this case. The experimental uncertainty for the emission yield corresponds to a factor of two variation in the cathode current. If the emission yield is tuned to make the cathode current computed by each code match the experiment, the computed electric fields are in excellent agreement with each other, and within about 10% of the experimental value. The non-monotonic variation of the width of the cathode fall with the applied voltage seen in the experiment is reproduced by both codes. The electron temperature in the negative glow is within experimental error bars for both codes, but the density of slow trapped electrons is underestimated. A more detailed code comparison done for several synthetic cases of electron-beam injection into helium gas shows that the codes are in excellent agreement for ionization rate, as well as for elastic and excitation collisions with isotropic scattering pattern. The remaining significant discrepancies between the two codes are due to differences in their electron binary-collision models, and for anisotropic scattering due to elastic and excitation collisions.

  11. Study of a contracted glow in low-frequency plasma-jet discharges operating with argon

    SciTech Connect

    Minotti, F.; Giuliani, L.; Xaubet, M.; Grondona, D.

    2015-11-15

    In this work, we present an experimental and theoretical study of a low frequency, atmospheric plasma-jet discharge in argon. The discharge has the characteristics of a contracted glow with a current channel of submillimeter diameter and a relatively high voltage cathode layer. In order to interpret the measurements, we consider the separate modeling of each region of the discharge: main channel and cathode layer, which must then be properly matched together. The main current channel was modeled, extending a previous work, as similar to an arc in which joule heating is balanced by lateral heat conduction, without thermal equilibrium between electrons and heavy species. The cathode layer model, on the other hand, includes the emission of secondary electrons by ion impact and by additional mechanisms, of which we considered emission due to collision of atoms excited at metastable levels, and field-enhanced thermionic emission (Schottky effect). The comparison of model and experiment indicates that the discharge can be effectively sustained in its contracted form by the secondary electrons emitted by collision of excited argon atoms, whereas thermionic emission is by far insufficient to provide the necessary electrons.

  12. Development and fundamental investigation of Laser Ablation Glow Discharge Time-Of-Flight Mass Spectrometry (LA-GD-TOFMS)

    NASA Astrophysics Data System (ADS)

    Tarik, Mohamed; Lotito, Giovanni; Whitby, James A.; Koch, Joachim; Fuhrer, Katrin; Gonin, Marc; Michler, Johann; Bolli, Jean-Luc; Günther, Detlef

    2009-03-01

    Glow Discharge (GD) spectroscopy is a well known and accepted technique for the bulk and surface composition analysis, while laser ablation (LA) provides analysis with high spatial-resolution analysis in LIBS (laser-induced breakdown spectroscopy) or when coupled to inductively coupled plasma spectrometry (ICP-OES or ICP-MS). This work concerns the construction of a Laser Ablation Glow Discharge Time-Of-Flight Mass Spectrometry (LA-GD-TOFMS) instrument to study the analytical capabilities resulting from the interaction of a laser-generated sample plume with a pulsed glow discharge. Two ablation configurations were studied in detail. In a first approach, the laser-generated plume was introduced directly into the GD, while the second approach generated the plume inside the GD. The ablated material was introduced at different times with respect to the discharge pulse in order to exploit the efficient ionization in the GD plasma. For both LA-GD configurations, direct ablation into the afterglow of the pulsed glow discharge leads to an ion signal enhancement of up to a factor of 7, as compared to the ablation process alone under the same experimental conditions. The LA-GD enhancement was found to occur exclusively in the GD afterglow, with a maximum ablation S/N occurring in a few hundred microseconds after the termination of the glow discharge. The duration of the enhanced signal is about two milliseconds. Both the laser pulse energy and the position of the ablation plume (with respect to the sampling orifice) were found to affect the amount of mass entering the afterglow region and consequently, the enhancement factor of ionization.

  13. Anodization of aluminum and silicon in plasma of a non-self-sustained glow discharge

    SciTech Connect

    Burachevsky, Yu. A. Burdovitsin, V. A.; Oks, E. M.

    2011-12-15

    The results of anodization of aluminum and silicon in an oxygen plasma are presented. The plasma was generated by a non-self-sustained glow discharge with a hollow cathode excited by an electron beam at the oxygen pressure of 20 Pa. The density of the current flowing through the anodized specimen did not exceed 1.5 mA/cm{sup 2}, and its temperature was 200-250 Degree-Sign C. Continuous Al{sub 2}O{sub 3} and SiO{sub 2} films were formed on the aluminum and silicon surfaces. The growth rate of the oxide layers was 150-200 nm/h for Al{sub 2}O{sub 3} and 400-800 nm/h for SiO{sub 2}.

  14. Xe isotopic fractionation in a cathodeless glow discharge. [for carbonaceous meteoritic composition studies

    NASA Technical Reports Server (NTRS)

    Bernatowicz, T. J.; Fahey, A. J.

    1986-01-01

    Results are reported on the isotopic composition of Xe processed in cathodeless glow discharges in rarefied air at pressures of 20-40 microns Hg, in the presence of activated charcoal and in empty pyrex containers. Residual gas phase Xe and trapped Xe were found to be fractionated, with the trapped Xe fractionated up to 1 percent per amu. A model is presented for the fractionating process in which Xe ions are simultaneously implanted and sputtered from substrate material, with a mass dependence favoring retention of the heavy isotopes in the substrate. Results of the investigation show that plasma synthesis of carbonaceous material is unnecessary for producing Xe fractionations, and that the fractionations observed in previous synthesis experiments are probably due to implantation of ions into the synthesized material.

  15. Improved ion implant fluence uniformity in hydrogen enhanced glow discharge plasma immersion ion implantation into silicon

    SciTech Connect

    Luo, J.; Li, L. H. E-mail: paul.chu@cityu.edu.hk; Liu, H. T.; Xu, Y.; Zuo, X. J.; Zhu, P. Z.; Ma, Y. F.; Yu, K. M.; Fu, Ricky K. Y.; Chu, Paul K. E-mail: paul.chu@cityu.edu.hk

    2014-06-15

    Enhanced glow discharge plasma immersion ion implantation does not require an external plasma source but ion focusing affects the lateral ion fluence uniformity, thereby hampering its use in high-fluence hydrogen ion implantation for thin film transfer and fabrication of silicon-on-insulator. Insertion of a metal ring between the sample stage and glass chamber improves the ion uniformity and reduces the ion fluence non-uniformity as the cathode voltage is raised. Two-dimensional multiple-grid particle-in-cell simulation confirms that the variation of electric field inside the chamber leads to mitigation of the ion focusing phenomenon and the results are corroborated experimentally by hydrogen forward scattering.

  16. Observation of dust torus with poloidal rotation in direct current glow discharge plasma

    SciTech Connect

    Kaur, Manjit Bose, Sayak; Chattopadhyay, P. K. Sharma, Devendra; Ghosh, J.; Saxena, Y. C.

    2015-03-15

    Observation of dust cloud rotation in parallel-plate DC glow discharge plasma is reported here. The experiments are carried out at high pressures (∼130 Pa) with a metallic ring placed on the lower electrode (cathode). The dust cloud rotates poloidally in the vertical plane near the cathode surface. This structure is continuous toroidally. Absence of magnetic field rules out the possibility of E × B induced ion flow as the cause of dust rotation. The dust rotational structures exist even with water cooled cathode. Therefore, temperature gradient driven mechanisms, such as thermophoretic force, thermal creep flow, and free convection cannot be causing the observed dust rotation. Langmuir probe measurement reveals the existence of a sharp density gradient near the location of the rotating dust cloud. The gradient in the density, giving rise to a gradient in the ion drag force, has been identified as the principal cause behind the rotation of dust particles.

  17. Analysis of glow discharges for understanding the process of film formation

    NASA Technical Reports Server (NTRS)

    Venugopalan, M.; Avni, R.

    1984-01-01

    The physical and chemical processes which occur during the formation of different types of films in a variety of glow discharge plasmas are discussed. Emphasis is placed on plasma diagnostic experiments using spectroscopic methods, probe analysis, mass spectrometric sampling and magnetic resonance techniques which are well suited to investigate the neutral and ionized gas phase species as well as some aspects of plasma surface interactions. The results on metallic, semi-conducting and insulating films are reviewed in conjunction with proposed models and the problem encountered under film deposition conditions. It is concluded that the understanding of film deposition process requires additional experimental information on plasma surface interactions of free radicals and the synergetic effects where photon, electron and ion bombardment change the reactivity of the incident radical with the surface.

  18. In-situ reactive of x-ray optics by glow discharge

    SciTech Connect

    Johnson, E.D.; Garrett, R.F.

    1987-01-01

    We have developed a method of in-situ reactive glow discharge cleaning of x-ray optical surfaces which is capable of complete removal of carbon contamination. Our work is the first to successfully clean an entire optical system in-situ and characterize its performance at short wavelengths (as low as 10 /angstrom/). The apparatus required is quite simple and can easily be fitted to most existing UHV (ultra high vacuum) mirror boxes of monochromators. The advantages of this technique over previously available methods include dramatic improvements in instrument performance and reductions in down time since the whole process typically takes a few days. This paper will briefly describe our results and detail the experimental considerations for application of the technique on different monochromator geometries. Possible improvements and extensions of the technique are also discussed.

  19. Effect of glow discharge sintering in the properties of a composite material fabricated by powder metallurgy

    NASA Astrophysics Data System (ADS)

    Cardenas, A.; Pineda, Y.; Sarmiento Santos, A.; Vera, E.

    2016-02-01

    Composite samples of 316 stainless steel and SiC were produced by powder metallurgy. Starting materials were mixed in different proportions and compacted to 700MPa. Sintering stage was performed by abnormal glow discharge plasma with direct current in an inert atmosphere of argon. The process was conducted at a temperature of 1200°C±5°C with a heating rate of 100°C/min. This work shows, the effectiveness of plasma sintering process to generate the first contacts between particles and to reduce vacancies. This fact is confirmed by comparing green and sintered density of the material. The results of porosity show a decrease after plasma sintering. Wear tests showed the wear mechanisms, noting that at higher SiC contents, the wear resistance decreases due to poor matrix-reinforcement interaction and by the porosity presence which causes matrix-reinforcement sliding.

  20. PREPARATION OF CU-DOPED GLOW DISCHARGE POLYMER COATINGS FOR ICF APPLICATIONS

    SciTech Connect

    NIKROO,A; CASTILLO,E; HILL,D.W; GREENWOOD,A.L.

    2003-06-01

    OAK-B135 Copper doped polymer shells can provide a very useful diagnostic for fast ignition experiments currently being performed at various laboratories around the world. The low concentration copper dopant acts as an efficient x-ray source providing information on the physics of fast ignition. They have developed copper doped glow discharge (GDP) coatings suitable for such purposes. Copper acetylacetonate (CuAcAC), a solid at room temperature, was used in a heated jacket as the dopant source. They used this technique to fabricate thin ({approx} 5-7 {micro}m) GDP shells doped with {approx} 1 at% copper through the depolymerizable mandrel process for fast ignition experiments. The details of the experimental set up and the range and limitations of the technique are discussed.

  1. Account of nonlocal ionization by fast electrons in the fluid models of a direct current glow discharge

    SciTech Connect

    Rafatov, I.; Bogdanov, E. A.; Kudryavtsev, A. A.

    2012-09-15

    We developed and tested a simple hybrid model for a glow discharge, which incorporates nonlocal ionization by fast electrons into the 'simple' and 'extended' fluid frameworks. Calculations have been performed for an argon gas. Comparison with the experimental data as well as with the hybrid (particle) and fluid modelling results demonstated good applicability of the proposed model.

  2. Anomalous Broadening of Balmer H{sub {alpha}} Line in Aluminum and Copper Hollow Cathode Glow Discharges

    SciTech Connect

    Sisovic, N. M.; Majstorovic, G. Lj.; Konjevic, N.

    2008-10-22

    The presented results are concerned with the shape of Balmer alpha line emitted from a low pressure DC glow discharge with aluminum (Al) and copper (Cu) hollow cathode (HC) in pure H{sub 2} and Ar-H{sub 2} gas mixture. The analysis indicates that the line profile represents a convolution of Gaussian profiles resulting from different collision excitation processes.

  3. Modelling the interaction between the plasma and the neutral gas in a pulsed glow discharge in nitrogen

    SciTech Connect

    Guiberteau, E.; Bonhomme, G.; Zoheir, C.

    1995-12-31

    We present here the first results obtained from the modelling of a pulsed glow discharge in nitrogen, taking into account the heat transfer to the neutral gas. The aim of modelling is to optimize the plasma process in a nitriding reactor. The iron sample to be nitrided forms the cathode of the glow discharge at low pressure (100 to 200 Pa). The reactor uses two disks of diameter 50 mm as electrodes with a 40 mm gap. It works in a pulsed regime (cycle period varies from 10 to 100 ms) with a discharge duration which can be varied from 0.5 to 10 ms. Experimental studies have been carried out using emission spectroscopy resolved in space (1 mm) and time (1 {mu}s), under various discharge and post-discharge durations. These studies have shown the important effect of energy transfer from the discharge to the neutral gas. In fact this transfer produces an expansion of the negative glow observed when the post-discharge duration is decreased. A realistic modelling should thus be performed bearing in mind that the neutral gas behaves not as a thermostat. Consequently the thermal and hydrodynamic evolution of the neutral gas must be considered in the whole modelling.

  4. Nonlinear time-series analysis of current signal in cathodic contact glow discharge electrolysis

    NASA Astrophysics Data System (ADS)

    Allagui, Anis; Rojas, Andrea Espinel; Bonny, Talal; Elwakil, Ahmed S.; Abdelkareem, Mohammad Ali

    2016-05-01

    In the standard two-electrode configuration employed in electrolytic process, when the control dc voltage is brought to a critical value, the system undergoes a transition from conventional electrolysis to contact glow discharge electrolysis (CGDE), which has also been referred to as liquid-submerged micro-plasma, glow discharge plasma electrolysis, electrode effect, electrolytic plasma, etc. The light-emitting process is associated with the development of an irregular and erratic current time-series which has been arbitrarily labelled as "random," and thus dissuaded further research in this direction. Here, we examine the current time-series signals measured in cathodic CGDE configuration in a concentrated KOH solution at different dc bias voltages greater than the critical voltage. We show that the signals are, in fact, not random according to the NIST SP. 800-22 test suite definition. We also demonstrate that post-processing low-pass filtered sequences requires less time than the native as-measured sequences, suggesting a superposition of low frequency chaotic fluctuations and high frequency behaviors (which may be produced by more than one possible source of entropy). Using an array of nonlinear time-series analyses for dynamical systems, i.e., the computation of largest Lyapunov exponents and correlation dimensions, and re-construction of phase portraits, we found that low-pass filtered datasets undergo a transition from quasi-periodic to chaotic to quasi-hyper-chaotic behavior, and back again to chaos when the voltage controlling-parameter is increased. The high frequency part of the signals is discussed in terms of highly nonlinear turbulent motion developed around the working electrode.

  5. Dusty plasma microparticle cloud control and rapid electrostatic mutual-repulsion expansion in a DC glow discharge

    NASA Astrophysics Data System (ADS)

    Gillman, Eric; Amatucci, Bill

    2016-10-01

    Microparticles in plasma discharges rapidly charge up, typically collecting a net negative charge due to the relatively high mobility of electrons compared to ions. Electrostatic forces can be utilized to control charged microparticle behavior and motion in a plasma discharge. In these experiments a metal wire loop is supplied with an electric potential that can be controlled independently from the DC plasma glow discharge electrodes. By varying the voltage on the wire loop, we can attract, trap, manipulate, suspend, and/or repel microparticles that originate from the DC glow discharge. Experiments studied the properties of electrostatic self-repulsion of a cloud of charged microparticles. By pulsing the plasma and controlling wire loop potential, a cloud of trapped microparticles is released and allowed to rapidly expand. A simple force balance simulation code is used as a model to compare and benchmark actual experimental results. This work was supported by the Naval Research Laboratory base program.

  6. Electrical double layers at shock fronts in glow discharges and afterglows

    SciTech Connect

    Siefert, Nicholas S.

    2010-12-15

    This paper examines the propagation of spark-generated shockwaves (1.0glow discharges and their afterglow. Diagnostic methods were employed and expanded in order to capture the dynamics of the shock front in these weakly-ionized, nonmagnetized, collisional plasmas. We used a microwave hairpin resonator to measure the electron number density, and, for all cases, we measured an increase in the electron number density at the shock front. By comparing the increase in electron number density at the shock front in the active discharge and in the afterglow, we conclude that electrons with a temperature much greater than room temperature can be compressed at the shock front. The ratio of electron number density before and after the shock front can be approximately predicted using the Rankine-Hugoniot relationship. The large gradient in electron density, and hence a large gradient in the flux of charged species, created a region of space-charge separation, i.e., a double layer, at the shock front. The double layer balances the flux of charged particles on both sides of the shock front. The double layer voltage drop was measured in the current-carrying discharge using floating probes and compared with previous models. As well, we measured argon 1s{sup 5} metastable-state density and demonstrate that metastable-state neutral species can be compressed across a shock front and approximately predicted using the Rankine-Hugoniot relationship.

  7. Plasma characteristics of argon glow discharge produced by AC power supply operating at low frequencies

    NASA Astrophysics Data System (ADS)

    Kongpiboolkid, Watcharapon; Mongkolnavin, Rattachat

    2015-04-01

    Non-thermal properties of Argon glow discharge operating with various operating pressures were measured and presented in this work. The Argon plasma is produced by a parallel conducting electrodes coupling with a high voltage AC power supply. The power supply can generate high AC voltage at various frequencies. The frequencies for the operation are in the range of a few kHz. The system is capable of generating electric field between the two metal electrodes discharge system. The characteristics of plasma produced were measured by optical emission spectroscopy (OES) technique where electron temperature (Te) and electron number density (ne) can be determined by line intensity ratio method. The value of electron number density was then determined from the Saha-Eggert equation. Our results show that the electron number density of the discharge obtained is of the order of 10-17 - 10-18 m-3 where the electron temperature is between 1.00-2.00 eV for various operating frequencies used which are in good agreement with similar results published earlier.

  8. Mixed mode oscillations in presence of inverted fireball in an excitable DC glow discharge magnetized plasma

    NASA Astrophysics Data System (ADS)

    Mitra, Vramori; Prakash, N. Hari; Solomon, Infant; Megalingam, Mariammal; Sekar Iyengar, A. N.; Marwan, Norbert; Kurths, Jürgen; Sarma, Arun; Sarma, Bornali

    2017-02-01

    The typical phenomena of mixed mode oscillations and their associated nonlinear behaviors have been investigated in collisionless magnetized plasma oscillations in a DC glow discharge plasma system. Plasma is produced between a cylindrical mesh grid and a constricted anode. A spherical mesh grid of 80% optical transparency is kept inside a cylindrical grid to produce an inverted fireball. Three Langmuir probes are kept in the ambient plasma to measure the floating potential fluctuations at different positions of the chamber. It has been observed that under certain conditions of discharge voltages and magnetic fields, the mixed mode oscillation phenomena (MMOs) appears, and it shows a sequential alteration with the variation of the magnetic fields and probe positions. Low frequency instability has been observed consistently in various experimental conditions. The mechanisms of the low frequency instabilities along with the origin of the MMOs have been qualitatively explained. Extensive linear and nonlinear analysis using techniques such as fast Fourier transform, recurrence quantification analysis, and the well-known statistical computing, skewness, and kurtosis are carried out to explore the complex dynamics of the MMO appearing in the plasma oscillations under various discharge conditions and external magnetic fields.

  9. Array of surface-confined glow discharges in atmospheric pressure helium: Modes and dynamics

    SciTech Connect

    Li, D.; Liu, D. X. E-mail: mglin5g@gmail.com; Nie, Q. Y.; Li, H. P.; Chen, H. L.; Kong, M. G. E-mail: mglin5g@gmail.com

    2014-05-19

    Array of atmospheric pressure surface discharges confined by a two-dimensional hexagon electrode mesh is studied for its discharge modes and temporal evolution so as to a theoretical underpinning to their growing applications in medicine, aerodynamic control, and environmental remediation. Helium plasma surface-confined by one hexagon-shaped rim electrode is shown to evolve from a Townsend mode to a normal and abnormal glow mode, and its evolution develops from the rim electrodes as six individual microdischarges merging in the middle of the hexagon mesh element. Within one hexagon element, microdischarges remain largely static with the mesh electrode being the instantaneous cathode, but move towards the hexagon center when the electrode is the instantaneous anode. On the entire array electrode surface, plasma ignition is found to beat an unspecific hexagon element and then spreads to ignite surrounding hexagon elements. The spreading of microdischarges is in the form of an expanding circle at a speed of about 3 × 10{sup 4} m/s, and their quenching starts in the location of the initial plasma ignition. Plasma modes influence how input electrical power is used to generate and accelerate electrons and as such the reaction chemistry, whereas plasma dynamics are central to understand and control plasma instabilities. The present study provides an important aspect of plasma physics of the atmospheric surface-confined discharge array and a theoretical underpinning to its future technological innovation.

  10. Phenol degradation by a nonpulsed diaphragm glow discharge in an aqueous solution.

    PubMed

    Liu, Yong Jun; Jiang, Xuan Zhen

    2005-11-01

    In the present study, a nonpulsed direct current diaphragm glow discharge process was developed for the first time for phenol degradation in an aqueous solution. The discharge was generated in a small hole in a dielectric diaphragm interposed between two submersed graphite electrodes. The experimental results revealed that supplied voltage, initial pH, iron salts, and radical scavengers impact the phenol degradation significantly. Enhancing the applied voltage, lowering the solution pH, and adding appropriate amounts of Fe2+ or Fe3+ to the solution were found to be favorable for phenol degradation. Carbonate ions or n-butanol in the solution can decelerate the phenol removal. When the treatment time is increased, the pH value of the solution decreased, leading to an increase in the phenol decomposition. It was revealed by high performance liquid chromatography and ionic chromatography that the main intermediates of phenol decomposition are hydroquinone, pyrocatechol, p-benzoquinone and organic acids. In comparison with the high-voltage corona discharge plasma in distilled water, this process offers simple technology, higher energy efficiency, easier scaleup, and easier applicability to salt-containing wastewater with no electrode erosion and electromagnetic radiation.

  11. Plasma characteristics of argon glow discharge produced by AC power supply operating at low frequencies

    SciTech Connect

    Kongpiboolkid, Watcharapon; Mongkolnavin, Rattachat

    2015-04-24

    Non-thermal properties of Argon glow discharge operating with various operating pressures were measured and presented in this work. The Argon plasma is produced by a parallel conducting electrodes coupling with a high voltage AC power supply. The power supply can generate high AC voltage at various frequencies. The frequencies for the operation are in the range of a few kHz. The system is capable of generating electric field between the two metal electrodes discharge system. The characteristics of plasma produced were measured by optical emission spectroscopy (OES) technique where electron temperature (T{sub e}) and electron number density (n{sub e}) can be determined by line intensity ratio method. The value of electron number density was then determined from the Saha-Eggert equation. Our results show that the electron number density of the discharge obtained is of the order of 10{sup −17} − 10{sup −18} m{sup −3} where the electron temperature is between 1.00−2.00 eV for various operating frequencies used which are in good agreement with similar results published earlier.

  12. Enhancing of the glow discharge stability in chamber with cathode sections coated by a discontinuous dielectric coating

    NASA Astrophysics Data System (ADS)

    Galeev, I. G.; Asadullin, T. Ya

    2016-01-01

    A method of increasing stability of the glow discharge in a gas flow is implemented by reducing the effective current density at the cathode. In this method the current redistributes at the partitioned cathode using the change in the area of the working surface of each section by applying a discontinuous dielectric coating so that it reaches the distribution of the maximum sustainable current discharge across the working surface of each cathode section.

  13. [Investigation on the Spectral Characteristics of a Plasma Jet in Atmospheric Argon Glow Discharge].

    PubMed

    Li, Xue-chen; Zhang, Chun-yan; Li, Ji-yuan; Bao, Wen-ting

    2015-12-01

    Plasma jet is a kind of important plasma source at atmospheric pressure. In recent years, it becomes an important hot topic in the field of low temperature plasma. In this paper, using a tungsten needle and a tungsten wire mesh, a direct-current excited jet is developed to operate in argon at atmospheric pressure. In the atmospheric pressure argon, the plasma jet can produce a stable plasma plume. By using the method of emission spectroscopy, the parameters of the plasma plume are investigated. The discharge emits dazzling white light from the area between the tungsten needle electrode and the wire mesh electrode. A plasma plume with a flame shape appears outside the tungsten wire mesh electrode. For a constant value of voltage (U = 13.5 kV), the length of the plasma plume increases with the gas flow rate. For a constant value of the gas flow rate(10 L · min⁻¹), the length of the plasma plume increases with the voltage. The voltage is inversely proportional to the current under the constant gas flow rate. In other words, the voltage decreases with the discharge current, which indicates that a glow discharge is formed in the plasma jet. Optical emission spectrum in 300 to 800 nm is collected from the direct-current excited plasma jet. By Boltzmann plot method, the excited electron temperature of the plasma plume is investigated as a function of the applied voltage or the gas flow rate. Results show that the excited electron temperature increases with decreasing applied voltage under the constant gas flow. Moreover, it increases with decreasing the gas flow under the constant voltage. Based on the discharge theory, these experimental phenomena are explained qualitatively. These results are of great importance to the development of atmospheric pressure uniform discharge plasma source and its application in industrial field.

  14. Study of nonlinear oscillations in a glow discharge plasma using empirical mode decomposition and Hilbert Huang transform

    SciTech Connect

    Wharton, A. M.; Sekar Iyengar, A. N.; Janaki, M. S.

    2013-02-15

    Hilbert Huang transform (HHT) based time series analysis was carried out on nonlinear floating potential fluctuations obtained from hollow cathode glow discharge plasma in the presence of anode glow. HHT was used to obtain contour plots and the presence of nonlinearity was studied. Frequency shift with time, which is a typical nonlinear behaviour, was detected from the contour plots. Various plasma parameters were measured and the concepts of correlation coefficients and the physical contribution of each intrinsic mode function have been discussed. Physically important quantities such as instantaneous energy and their uses in studying physical phenomena such as intermittency and non-stationary data have also been discussed.

  15. Role of cathode identity in liquid chromatography particle beam glow discharge mass spectrometry

    NASA Astrophysics Data System (ADS)

    Krishna, M. V. Balarama; Marcus, R. K.

    2008-06-01

    A detailed evaluation of the role of cathode identity on the analytical and spectral characteristics of various organic, organometallic and metal analytes using liquid chromatography-particle beam/glow discharge mass spectrometry (LC-PB/GDMS) has been carried out. A d.c. discharge, operating with argon as the support gas, was used throughout this work. In this study, Cu which has a relatively high sputtering rate, Ni which has moderate sputtering rate and Ta which has very low sputtering rate, are taken as cathode materials to study the ionization, fragmentation, and analytical characteristics of organic (caffeine, epigallocatechin gallate, peptide as representative compounds), organometallic (selenomethionine, triethyl lead chloride as representative compounds) and metal (Fe, La, Cs and Pb) species. A range of discharge gas pressures (26.6-106.4 Pa) and currents (0.2-1.5 mA) were investigated with the test cathodes to determine their influence on the spectral composition and overall analytical response for the various test species. Calibration plots were obtained for all of the species for each of the three cathodes to determine the respective limits of detection. Relative detection limits in the range of 0.02 to 15 ng mL - 1 (0.002-1.5 ng, absolute) for the test species were found to be in the order of Cu > Ni > Ta; which follows the order of the sputtering characteristics of the respective cathodes. These studies rendered information about the respective discharge parameters' role in choosing the most appropriate cathode identity in PB-GDMS for application in the areas of organic, organometallic and inorganic species analysis.

  16. Time and space resolved electron impact excitation rates in an RF glow discharge

    NASA Astrophysics Data System (ADS)

    Murnick, Daniel E.; Li, Yuan

    1992-02-01

    Research on rf glow discharge plasmas was carried out to better understand the fundamental physics and chemistry of important aspects of plasma deposition and etching. A standard reference system for rf plasma processing research was utilized. Power, voltage and current waveforms were monitored and time and space resolved measurements were made using plasma induced emission (PIE). Nanosecond time resolution for PIE greatly expanded the utility of these plasma diagnostics over previous studies. Measurements were carried out with a prototype rf model discharge, atomic argon, concentrating on the important 4s levels 11.5 eV above the ground state and the manifold of p levels coupled to these states by strong dipole transitions. Extensive analysis and computer modeling was carried out to reproduce the experimental data obtained and to test assumptions often used for this model system. Models of electron excitation waves were stringently tested and evaluated. The research concentrated on studying details of excitation waveforms as a function of pressure and rf power. Information on electron energy distribution functions were derived from the experimental results. New experimental techniques to enhance time and space resolution were developed.

  17. Control of plasma properties in a short direct-current glow discharge with active boundaries

    SciTech Connect

    Adams, S. F.; Demidov, V. I.; Bogdanov, E. A.; Kudryavtsev, A. A.; Koepke, M. E.; Kurlyandskaya, I. P.

    2016-02-15

    To demonstrate controlling electron/metastable density ratio and electron temperature by applying negative voltages to the active (conducting) discharge wall in a low-pressure plasma with nonlocal electron energy distribution function, modeling has been performed in a short (lacking the positive-column region) direct-current glow discharge with a cold cathode. The applied negative voltage can modify the trapping of the low-energy part of the energetic electrons that are emitted from the cathode sheath and that arise from the atomic and molecular processes in the plasma within the device volume. These electrons are responsible for heating the slow, thermal electrons, while production of slow electrons (ions) and metastable atoms is mostly due to the energetic electrons with higher energies. Increasing electron temperature results in increasing decay rate of slow, thermal electrons (ions), while decay rate of metastable atoms and production rates of slow electrons (ions) and metastable atoms practically are unchanged. The result is in the variation of electron/metastable density ratio and electron temperature with the variation of the wall negative voltage.

  18. Studies on gas breakdown in pulsed radio frequency atmospheric pressure glow discharges

    SciTech Connect

    Huo, W. G.; Jian, S. J.; Yao, J.; Ding, Z. F.

    2014-05-15

    In pulsed RF atmospheric pressure glow discharges, the gas breakdown judged by the rapid drop in the amplitude of the pulsed RF voltage is no longer universally true. The steep increment of the plasma-absorbed RF power is proposed to determine the gas breakdown. The averaged plasma-absorbed RF power over a pulse period is used to evaluate effects of the preceding pulsed RF discharge on the breakdown voltage of the following one, finding that the breakdown voltage decreases with the increment in the averaged plasma-absorbed RF power under constant pulse duty ratio. Effects of the pulse off-time on the breakdown voltage and the breakdown delay time are also studied. The obtained dependence of the breakdown voltage on the pulse off-time is indicative of the transitional plasma diffusion processes in the afterglow. The breakdown voltage varies rapidly as the plasma diffuses fast in the region of moderate pulse off-time. The contribution of nitrogen atom recombination at the alumina surface is demonstrated in the prolonged memory effect on the breakdown delay time vs. the pulse off-time and experimentally validated by introducing a trace amount of nitrogen into argon at short and long pulse off-times.

  19. Abnormal glow discharge as a variable capacitor for tunable RF systems

    NASA Astrophysics Data System (ADS)

    Macheret, Sergey; Semnani, Abbas; Peroulis, Dimitrios

    2016-09-01

    For frequency-tunable resonators and filters in high-power applications, conventional semiconductor devices are easily damaged, while mechanically-tunable systems are bulky and slow. In this regard, weakly ionized plasmas can offer an attractive solution. In this work, an LC resonator circuit where a commercial gas discharge tube (GDT) serves as a variable capacitor was studied experimentally and theoretically. The experiments show continuous decrease of the resonant frequency by up to 50 percent with increase in the DC current through the GDT. Analysis of the current-voltage characteristic and the breakdown parameters, combined with lumped-parameter equivalent-circuit RF simulations, allowed us to determine the gas pressure, the electrode coating material and the secondary emission coefficient, and to achieve a very good agreement between the calculated and measured transmittance values. The analysis reveals that reduction in the cathode sheath thickness with increase in the DC current in the abnormal glow discharge regime is the key factor responsible for the experimentally observed tunability.

  20. Atmospheric Pressure Glow Discharge for Point-of-Use Water Treatment

    NASA Astrophysics Data System (ADS)

    Lindsay, Alexander; Byrns, Brandon; Shannon, Steven; Knappe, Detlef

    2012-10-01

    Treatment of biological and chemical contaminants is an area of growing global interest where atmospheric pressure plasmas can make a significant contribution. Addressing key challenges of volume processing and operational cost, a large volume 162 MHz coaxial air-plasma source has been developed.footnotetextByrns (2012) J. Phys. D: Appl. Phys. 45 (2012) 195204 Because of VHF ballasting effects, the electric discharge is maintained at a steady glow, allowing formation of critical non-equilibrium chemistry. High densities, ne = 10^11-10^12, have been recorded. The atmospheric nature of the device permits straightforward and efficient treatment of water samples. [H^+] concentrations in 150 milliliter tap water samples have been shown to increase by 10^5 after five minutes of discharge exposure. Recent literature has demonstrated that increasing acidity is strongly correlated with a solution's ability to deactivate microbial contaminants.footnotetextTraylor (2011) J. Phys. D: Appl. Phys. 44 (2011) 472001 The work presented here will explore the impact of treatment gas, system configuration, and power density on water disinfection and PFC abatement. An array of plasma diagnostics, including OES and electrical measurements, are combined with post-process water analysis, including GC-MS and QT analysis of coliform and E.coli bacteria. Development of volume processing atmospheric plasma disinfection methods offers promise for point-of-use treatments in developing areas of the world, potentially supplementing or replacing supply and weather-dependent disinfection methods.

  1. A comparative study on continuous and pulsed RF argon capacitive glow discharges at low pressure by fluid modeling

    NASA Astrophysics Data System (ADS)

    Liu, Ruiqiang; Liu, Yue; Jia, Wenzhu; Zhou, Yanwen

    2017-01-01

    Based on the plasma fluid theory and using the drift-diffusion approximation, a mathematical model for continuous and pulsed radial frequency (RF) argon capacitive glow discharges at low pressure is established. The model is solved by a finite difference method and the numerical results are reported. Based on the systematic analysis of the results, plasma characteristics of the continuous and pulsed RF discharges are comparatively investigated. It is shown that, under the same condition for the peak value of the driving potential, the cycle-averaged electron density, the current density, and other essential physical quantities in the continuous RF discharge are higher than those from the pulsed RF discharge. On the other hand, similar plasma characteristics are obtained with two types of discharges, by assuming the same deposited power. Consequently, higher driving potential is needed in pulsed discharges in order to maintain the same effective plasma current. Furthermore, it is shown that, in the bulk plasma region, the peak value of the bipolar electric field from the continuous RF discharge is greater than that from the pulsed RF discharge. In the sheath region, the ionization rate has the shape of double-peaking and the explanation is given. Because the plasma input power depends on the driving potential and the plasma current phase, the phase differences between the driving potential and the plasma current are compared between the continuous and the pulsed RF discharges. It is found that this phase difference is smaller in the pulsed RF discharge compared to that of the continuous RF discharge. This means that the input energy coupling in the pulsed RF discharge is less efficient than the continuous counterpart. This comparative study, carried out also under other conditions, thus can provide instructive ideas in applications using the continuous and pulsed RF capacitive glow discharges.

  2. Enhancing DC Glow Discharge Tube Museuum Displays using a Theremin Controlled Helmholtz Coil to Demonstrate Magnetic Confinement

    NASA Astrophysics Data System (ADS)

    Siu, Theodore; Wissel, Stephanie; Guttadora, Larry; Liao, Susan; Zwicker, Andrew

    2010-11-01

    Since their discovery in the mid 1800's, DC glow discharge apparatuses have commonly been used for spectral analysis, the demonstration of the Frank-Hertz experiment, and to study plasma breakdown voltages following from the Paschen Curve. A DC glow discharge tube museum display was outfitted with a Helmholtz Coil electromagnet in order to demonstrate magnetic confinement for a science museum display. A device commonly known as a ``theremin'' was designed and built in order to externally control the Helmholtz Coil current and the plasma current. Originally a musical instrument, a theremin has two variable capacitors connected to two radio frequency oscillators which determine pitch and volume. Using a theremin to control current and ``play'' the plasma adds appeal and durability by providing a new innovative means of interacting with a museum exhibit. Educationally, students can use the display to not only learn about plasma properties but also electronic properties of the human body.

  3. Phthalate degradation by glow discharge plasma enhanced with pyrite in aqueous solution.

    PubMed

    Shen, Chensi; Wu, Shaoshuai; Chen, Hui; Rashid, Sadia; Wen, Yuezhong

    2016-09-01

    In order to prevent health risk from potential exposures to phthalates, a glow discharge plasma (GDP) process was applied for phthalate degradation in aqueous solution. The results revealed that the phthalate derivatives 4-hydroxyphthalic acid, 4-methylphthalic acid and 4-tert-butylphthalic anhydride could be degraded efficiently in GDP process (498 V, 0.2 A) with high removal efficiencies of over 99% in 60 minutes. Additionally, pyrite as a promising heterogeneous iron source in the Fenton reaction was found to be favorable for GDP process. The phthalate degradation reaction could be significantly enhanced by the continuous formation of •OH and the inhibition of the quenching reaction in the pyrite Fenton system due to the constant dissolution of Fe(II) from pyrite surface. Meanwhile, the initial pH value showed little impact on the degradation of phthalates and the energy efficiency of GDP system for phthalate degradation ranged between 0.280 × 10(-9) and 1.210 × 10(-9) mol/J, which is similar to the GDP system with phenol, bisphenol A and methyl tert-butyl ether as the substrates. Further, the X-ray diffraction and scanning electron microscopy with energy dispersive X-ray spectroscopy analyses indicated that the pyrite was relatively stable in GDP system and there was no obvious polymeric compound formed on the catalyst surface. Overall, this GDP process offers high removal efficiency, simple technology, considerable energy efficiency and the applicability to salt-containing phthalate wastewater.

  4. Chemical corrosion by chlorides on ancient-like bronzes and treatment by hydrogen glow discharge plasma

    NASA Astrophysics Data System (ADS)

    Papadopoulou, O.; Novakovic, J.; Vassiliou, P.; Filippaki, E.; Bassiakos, Y.

    2013-12-01

    Three representative ancient-like bronzes are employed for the chemical synthesis of Cu2(OH)3Cl rich patinas in order to study the influence of the alloying elements in the evolution of the chloride attack and to further conduct stabilization treatment via Hydrogen Glow Discharge Plasma (HGDP) at low temperature and pressure. The corrosion behavior of specimens having Sn and Pb as main alloying elements is governed by a decuprification mechanism and by the formation of Sn-Pb-O enriched barrier layers. In the case of the Zn containing alloy, dezincification is more pronounced at the corrosion initial stages, and copper species predominate the corrosion products evolution. A three-hour HGDP treatment leads to Cu+ production and metallic Cu, Sn, Zn, and Pb redeposition, as a result of metal cation reduction. This process is accompanied by partial removal of Cl species, O diminution, and change in coloration. The further increase of the Cl/O atomic ratio measured on the post-treated surfaces leads to the formation of nantokite and thus to the conclusion that the stabilization of objects with extensive Cl attack is not feasible by HGDP without preliminary chemical treatment.

  5. Contact glow discharge electrolysis: its origin, plasma diagnostics and non-faradaic chemical effects

    NASA Astrophysics Data System (ADS)

    Gupta, Susanta K. Sen

    2015-12-01

    Contact glow discharge electrolysis (CGDE) also termed plasma electrolysis is a novel electrolysis where a stable sheath of light emitting plasma develops around an electrode immersed well inside a relatively high-conductivity liquid electrolyte during normal electrolysis (NE) at several hundred volts. The phenomenon may develop in dc-, pulsed dc-, ac- as well as RF-driven electrolyses. The chemical effects of CGDE are remarkably non-faradaic in respect to the nature of the products as well as their yields. The article traces comprehensively the progress made in studies of CGDE in aqueous and non-aqueous solutions since 1844 and reviews the developments in the understanding of its origin, light emission, plasma state and non-faradaic effects leading to the elucidation of detailed mechanism of the origin of CGDE on the basis of the onset of hydrodynamic instabilities in local vaporization of the solvent near the working electrode during NE, and that of highly non-faradaic effects of CGDE based on a model of two reaction zones located within the electrode plasma and at the plasma-liquid interface producing solvent derived radicals at high local concentrations. Keeping in view the recent surge of interest in varied applications of CGDE, the article is appended with highlights of these applications across synthetic chemistry, waste water treatment, electrosurgical devices, nanoparticle fabrications, surface engineering and micro-machining.

  6. Destruction of 4-phenolsulfonic acid in water by anodic contact glow discharge electrolysis.

    PubMed

    Yang, Haiming; An, Baigang; Wang, Shaoyan; Li, Lixiang; Jin, Wenjie; Li, Lihua

    2013-06-01

    Destruction of 4-phenolsulfonic acid (4-PSA) in water was carried out using anodic contact glow discharge electrolysis. Accompanying the decay of 4-PSA, the amount of total organic carbon (TOC) in water correspondingly decreased, while the sulfonate group of 4-PSA was released as sulfate ion. Oxalate and formate were obtained as minor by-products. Additionally, phenol, 1,4-hydroquinone, hydroxyquinol and 1,4-benzoquinone were detected as primary intermediates in the initial stages of decomposition of 4-PSA. A reaction pathway involving successive attacks of hydroxyl and hydrogen radicals was assumed on the basis of the observed products and kinetics. It was revealed that the decay of both 4-PSA and TOC obeyed a first-order rate law. The effects of different Fe ions and initial concentrations of 4-PSA on the degradation rate were investigated. It was found that the presence of Fe ions could increase the degradation rate of 4-PSA, while initial concentrations lower than 80 mmol/L had no significant effect on kinetic behaviour. The disappearance rate of 4-PSA was significantly affected by pH.

  7. Effects of rf power on chemical composition and surface roughness of glow discharge polymer films

    NASA Astrophysics Data System (ADS)

    Zhang, Ling; He, Xiaoshan; Chen, Guo; Wang, Tao; Tang, Yongjian; He, Zhibing

    2016-03-01

    The glow discharge polymer (GDP) films for laser fusion targets were successfully fabricated by plasma enhanced chemical vapor deposition (PECVD) at different radio frequency (rf) powers. The films were deposited using trans-2-butene (T2B) mixed with hydrogen as gas sources. The composition and state of plasma were diagnosed by quadrupole mass spectrometer (QMS) and Langmuir probe during the deposition process. The composition, surface morphology and roughness were investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and white-light interferometer (WLI), respectively. Based on these observation and analyses, the growth mechanism of defects in GDP films were studied. The results show that, at low rf power, there is a larger probability for secondary polymerization and formation of multi-carbon C-H species in the plasma. In this case, the surface of GDP film turns to be cauliflower-like. With the increase of rf power, the degree of ionization is high, the relative concentration of smaller-mass hydrocarbon species increases, while the relative concentration of larger-mass hydrocarbon species decreases. At higher rf power, the energy of smaller-mass species are high and the etching effects are strong correspondingly. The GDP film's surface roughness shows a trend of decrease firstly and then increase with the increasing rf power. At rf power of 30 W, the surface root-mean-square roughness (Rq) drops to the lowest value of 12.8 nm, and no ;void; defect was observed.

  8. Application of Glow Discharge Plasma to Alter Surface Properties of Materials

    NASA Technical Reports Server (NTRS)

    Trigwell, Steve; Buhler, Charles R.; Calle, Carlos I.

    2005-01-01

    Some polymer materials that are considered important for spaceport operations are rendered noncompliant when subjected to the Kennedy Space Center (KSC) Standard electrostatic testing. These materials operate in stringent environmental conditions, such as high humidity. Treating materials that fail electrostatic testing and altering their surface properties so that they become compliant would result in considerable cost savings. Significant improvement in electrostatic dissipation of Saf-T-Vu PVC after treatment with air Atmospheric Plasma Glow Discharge (APGD) was observed and the material now passed the KSC electrostatic test. The O:C ratio on the surface, as monitored by X-ray Photoelectron Spectroscopy, increased from 0.165 tO 0.275 indicating enhanced oxidation, and surface contact angle measurements decreased from 107.5 to 72.6 showing increased hydrophilicity that accounted for the increased conductivity. Monitoring of the aging showed that the materials hydrophobic recovery resulted in it failing the electrostatic test 30 hours after treatment. This was probably due to the out-diffusion of the added Zn, Ba, and Cd salt stabilizers detected on the surface and/or diffusion of low molecular weight oligomers. On going work includes improving the long term hydrophilicity by optimizing the APGD process with different gas mixtures. Treatment of other spaceport materials is also presented.

  9. Femtosecond laser ablation particle introduction to a liquid sampling-atmospheric pressure glow discharge ionization source

    SciTech Connect

    Carado, Anthony J.; Quarles, C. Derrick; Duffin, Andrew M.; Barinaga, Charles J.; Russo, Richard E.; Marcus, R. Kenneth; Eiden, Gregory C.; Koppenaal, David W.

    2012-01-01

    This work describes the use of a compact, liquid sampling – atmospheric pressure glow discharge (LS-APGD) ionization source to ionize metal particles within a laser ablation aerosol. Mass analysis was performed with a Thermo Scientific Exactive Mass Spectrometer which utilizes an orbitrap mass analyzer capable of producing mass resolution exceeding M/ΔM > 160,000. The LS-APGD source generates a low-power plasma between the surface of an electrolytic solution flowing at several µl min-1 through a fused silica capillary and a counter electrode consisting of a stainless steel capillary employed to deliver the laser ablation particles into the plasma. Sample particles of approximately 100 nm were generated with an Applied Spectra femtosecond laser located remotely and transported through 25 meters of polyurethane tubing by means of argon carrier gas. Samples consisted of an oxygen free copper shard, a disk of solder, and a one-cent U.S. coin. Analyte signal onset was readily detectable relative to the background signal produced by the carrier gas alone. The high mass resolution capability of the orbitrap mass spectrometer was demonstrated on the solder sample with resolution exceeding 90,000 for Pb and 160,000 for Cu. In addition, results from a laser ablation depth-profiling experiment of a one cent coin revealed retention of the relative locations of the ~10 µm copper cladding and zinc rich bulk layers.

  10. Pulsed laser ablation of borax target in vacuum and hydrogen DC glow discharges

    NASA Astrophysics Data System (ADS)

    Kale, A. N.; Miotello, A.; Mosaner, P.

    2006-09-01

    The aim of our experiment was to produce a material with B sbnd H bonds for applications in hydrogen storage and generation. By using KrF excimer laser ( λ = 248 nm) ablation of borax (Na 2B 4O 7) target, thin films were deposited on KBr and silicon substrates. Ablation was performed both in vacuum and in hydrogen atmosphere. DC glow discharge technique was utilized to enhance hydrogen gas ionization. Experiments were performed using laser fluence from 5 to 20 J/cm 2. Films were deposited under gas pressure of 1 × 10 -5 to 5 × 10 -2 mbar and substrate temperatures of 130-450 °C. Scanning electron microscopy analysis of films showed presence of circular particulates. Film thickness, roughness and particulates number increased with increase in laser fluence. Energy dispersive X-ray spectroscopy analysis shows that sodium content in the particulates is higher than in the target. This effect is discussed in terms of atomic arrangements (both at surface and bulk) in systems where ionic and covalent bonds are present and by looking at the increased surface/bulk ratio of the particulates with respect to the deposited films. The Fourier transform infrared spectroscopy measurements showed presence of B sbnd O stretching and B sbnd O sbnd B bending bonds. Possible reasons for absence of B sbnd H bonds are attributed to binding enthalpy of the competing molecules.

  11. Application of Radio Frequency Glow Discharge Sputtering for Nanoindentation Sample Preparation

    NASA Astrophysics Data System (ADS)

    Sekido, N.; Ohmura, T.; Tsuzaki, K.

    2017-03-01

    The applicability of radio frequency glow discharge (rf-GD) sputtering to the surface finishing of nanoindentation specimens was examined for pure Al, Cu, and Ni. Comparisons were made between specimens that had been subjected to the following surface finishing: (1) rf-GD sputtering, (2) electropolishing, and (3) mechanical polishing with 0.25 µm of diamond suspension. It was suggested from the nanoindentation behavior and the quality of electron backscattered diffraction patterns that residual damage on the surface of the rf-GD sputtered samples was as small as that of electropolished samples, while some damages remained on the surface of the mechanically polished samples. The areal roughness within a 1-μm square of the rf-GD sputtered surface was comparable to that of the mechanically polished surface and slightly larger than that of the electropolished surface. Nonetheless, the difference of the roughness within the range of this study has no practical impact upon nanohardness and elastic modulus evaluation. Pop-in events occurred in the electropolished and rf-GD sputtered specimens, but not in the mechanically polished samples. The critical load for pop-in to occur was slightly smaller in rf-GD sputtered sample than in electropolished samples.

  12. Nitrogen Plasma Ion Implantation of Al and Ti alloys in the High Voltage Glow Discharge Mode

    NASA Astrophysics Data System (ADS)

    Oliveira, R. M.; Ueda, M.; Rossi, J. O.; Reuther, H.; Lepienski, C. M.; Beloto, A. F.

    2006-11-01

    Enhanced surface properties can be attained for aluminum and its alloys (mechanical and tribological) and Ti6Al4V (mainly tribological) by Plasma Immersion Ion Implantation (PIII) technique. The main problem here, more severe for Al case, is the rapid oxygen contamination even in low O partial pressure. High energy nitrogen ions during PIII are demanded for this situation, in order to enable the ions to pass through the formed oxide layer. We have developed a PIII system that can operate at energies in excess of 50keV, using a Stacked Blumlein (SB) pulser which can nominally provide up to 100 kV pulses. Initially, we are using this system in the High Voltage Glow Discharge (HVGD) mode, to implant nitrogen ions into Al5052 alloy with energies in the range of 30 to 50keV, with 1.5μs duration pulses at a repetition rate of 100Hz. AES, pin-on-disc, nanoindentation measurements are under way but x-ray diffraction results already indicated abundant formation of AlN in the surface for Al5052 treated with this HVGD mode. Our major aim in this PIII experiment is to achieve this difficult to produce stable and highly reliable AlN rich surface layer with high hardness, high corrosion resistance and very low wear rate.

  13. Nitrogen Plasma Ion Implantation of Al and Ti alloys in the High Voltage Glow Discharge Mode

    SciTech Connect

    Oliveira, R. M.; Ueda, M.; Rossi, J. O.; Reuther, H.; Lepienski, C. M.; Beloto, A. F.

    2006-11-13

    Enhanced surface properties can be attained for aluminum and its alloys (mechanical and tribological) and Ti6Al4V (mainly tribological) by Plasma Immersion Ion Implantation (PIII) technique. The main problem here, more severe for Al case, is the rapid oxygen contamination even in low O partial pressure. High energy nitrogen ions during PIII are demanded for this situation, in order to enable the ions to pass through the formed oxide layer. We have developed a PIII system that can operate at energies in excess of 50keV, using a Stacked Blumlein (SB) pulser which can nominally provide up to 100 kV pulses. Initially, we are using this system in the High Voltage Glow Discharge (HVGD) mode, to implant nitrogen ions into Al5052 alloy with energies in the range of 30 to 50keV, with 1.5{mu}s duration pulses at a repetition rate of 100Hz. AES, pin-on-disc, nanoindentation measurements are under way but x-ray diffraction results already indicated abundant formation of AlN in the surface for Al5052 treated with this HVGD mode. Our major aim in this PIII experiment is to achieve this difficult to produce stable and highly reliable AlN rich surface layer with high hardness, high corrosion resistance and very low wear rate.

  14. Application of Radio Frequency Glow Discharge Sputtering for Nanoindentation Sample Preparation

    NASA Astrophysics Data System (ADS)

    Sekido, N.; Ohmura, T.; Tsuzaki, K.

    2017-02-01

    The applicability of radio frequency glow discharge (rf-GD) sputtering to the surface finishing of nanoindentation specimens was examined for pure Al, Cu, and Ni. Comparisons were made between specimens that had been subjected to the following surface finishing: (1) rf-GD sputtering, (2) electropolishing, and (3) mechanical polishing with 0.25 µm of diamond suspension. It was suggested from the nanoindentation behavior and the quality of electron backscattered diffraction patterns that residual damage on the surface of the rf-GD sputtered samples was as small as that of electropolished samples, while some damages remained on the surface of the mechanically polished samples. The areal roughness within a 1-μm square of the rf-GD sputtered surface was comparable to that of the mechanically polished surface and slightly larger than that of the electropolished surface. Nonetheless, the difference of the roughness within the range of this study has no practical impact upon nanohardness and elastic modulus evaluation. Pop-in events occurred in the electropolished and rf-GD sputtered specimens, but not in the mechanically polished samples. The critical load for pop-in to occur was slightly smaller in rf-GD sputtered sample than in electropolished samples.

  15. Liquid-phase reactions induced by atmospheric pressure glow discharge with liquid electrode

    NASA Astrophysics Data System (ADS)

    Tochikubo, Fumiyoshi; Shirai, Naoki; Uchida, Satoshi

    2014-12-01

    We experimentally investigated some of the initial reactions in a liquid induced by electron or positive-ion irradiation from an atmospheric-pressure dc glow discharge in contact with the liquid. We used an H-shaped glass reactor to observe the effects of electron irradiation and positive-ion irradiation on the liquid-phase reaction separately and simultaneously. Aqueous solutions of NaCl, AgNO3, HAuCl4, and FeCl2 are used as the electrolyte. Solutions of AgNO3 and HAuCl4 are used for the generation of Ag and Au nanoparticles, respectively. Solution of FeCl2 is used for the generation of ferromagnetic particles. Experimental results showed that electron irradiation of the liquid surface generates OH- in water and that positive-ion irradiation of the liquid surface generates H+ in water even without the dissolution of gas-phase nitrogen oxide. A possible reaction process is qualitatively discussed. We also showed that the control of reductive and oxidative environment in the liquid is possible not only by the gas composition for the plasma generation but also by the liquid composition.

  16. Investigation of multifractal nature of floating potential fluctuations obtained from a dc glow discharge magnetized plasma

    NASA Astrophysics Data System (ADS)

    Shaw, Pankaj Kumar; Saha, Debajyoti; Ghosh, Sabuj; Janaki, M. S.; Iyengar, A. N. Sekar

    2017-03-01

    In this paper, multifractal detrended fluctuation analysis (MF-DFA) has been used to analyze the floating potential fluctuations obtained with a Langmuir probe from a dc glow discharge magnetized plasma device. The generalized Hurst exponents (h(q)) , local fluctuation function (Fq(s)) , the Rényi exponents (τ(q)) and the multifractal spectrum F(α) have been calculated by applying the MF-DFA method. The result of the MF-DFA shows the multifractal nature of these fluctuations. We have investigated the influence of magnetic field on the multifractal nature of the fluctuations and it is seen that degree of multifractality is reduced with the increase in the magnetic field strength. The values of h(q) have been restricted between 0.7 and 1 for the magnetized fluctuations. This result is evidence of the existence of long-range correlations in the fluctuations. Furthermore, we employed shuffle and surrogate approaches to analyze the origins of multifractality. Comparing the MF-DFA results for the data set to those for shuffled and surrogate series, we have found that its multifractal nature is due to the existence of significant long-term correlation.

  17. Measuring glow discharge polymerization coating rates with a quartz crystal monitor

    NASA Astrophysics Data System (ADS)

    Ostrowski, E. T.; Schoff, M.; Greenwood, A.; Castillo, E.; Ravelo, N.

    2016-10-01

    Glow discharge polymerization (GDP) is a well-established method for fabricating the thin-walled polymer shells of targets used in laser-driven inertial confinement fusion. The GDP coating rate is slow, maxing out at approximately 0.5 μm/hr, and varies in time and with changes in system parameters. A quartz crystal monitor (QCM) was installed into a GDP coating apparatus in order to measure the coating rate and thickness in situ by relating shifts in quartz oscillation frequency to changes in mass on the quartz crystal's surface, namely the GDP coating. Further investigation of the quartz crystal surface, post-GDP treatment, revealed that coating thickness was also radially dependent. Subsequent modelling of the thickness and coating rate was performed. The QCM was able to measure and quantify the effects of various system parameters on the GDP coating rate such that optimal coating conditions could be suggested to minimize coating times. Work supported by the US Department of Energy under the Science Undergraduate Laboratory Internship (SULI) program and NA0001808.

  18. Sterilization of Materials with a One Atmosphere Uniform Glow Discharge Plasma.*

    NASA Astrophysics Data System (ADS)

    Ku, Yongmin; Brickman, C.; Tosh, K.; Kelly-Wintenberg, K.; Montie, T. C.; Tsai, P.; Wadsworth, L.; Roth, J. Reece

    1996-11-01

    The relatively recent development of the One Atmosphere Uniform Glow Discharge Plasma sterilization technique at the UTK Plasma Science Laboratory has produced initial results which indicate that the technique may have commercial potential. We have shown that active species in a OAUGDP can be applied to the sterilization of fabrics, films, solid materials, and microbiological culture media. With a OAUGDP, we can eliminate the vacuum system which enforces batch processing and requires a continuous input of electrical power. With a OAUGDP, the exposure time is as little as 15 seconds. Sterilization of microorganisms with a kill ratio of 10E6 or higher, can be achieved with minimal unwanted byproducts and at less expense, compared to such conventional sterilization methods as autoclaving, ethylene oxide, or low pressure plasma treatment. This paper discusses the sterilization mechanisms of this new technique, and compares its advantages and disadvantages with other widely used techniques. ^1 Department of Microbiology, UTK ^2 UTK Textiles and Nonwovens Development Center (TANDEC) Research supported in part by the UTK Textiles and Nonwovens Development Center and UTK Center for Materials Processing.

  19. The use of matrix-specific calibrations for oxygen in analytical glow discharge spectrometry.

    PubMed

    Gonzalez-Gago, Cristina; Smid, Petr; Hofmann, Thomas; Venzago, Cornel; Hoffmann, Volker; Gruner, Wolfgang

    2014-11-01

    The performance of glow discharge optical emission spectroscopy and mass spectrometry for oxygen determination is investigated using a set of new conductive samples containing oxygen in the percent range in three different matrices (Al, Mg, and Cu) prepared by a sintering process. The sputtering rate corrected calibrations obtained at standard conditions for the 4 mm anode (700 V, 20 mA) in GD-OES are matrix independent for Mg and Al but not for Cu. The importance of a "blue shifted" line of oxygen at 130.22 nm (first reported by Köster) for quantitative analyses by GD-OES is confirmed. Matrix-specific calibrations for oxygen in GD-MS are presented. Two source concepts-fast flow (ELEMENT GD) and low gas flow (VG9000)-are evaluated obtaining higher sensitivity with the static flow source. Additional experiments using Ar-He mixtures or μs pulsed GD are carried out in ELEMENT GD aiming to improve the oxygen sensitivity.

  20. Aspects of the practical application of titanium alloys after low temperature nitriding glow discharge in hydrogen- free -gas media

    NASA Astrophysics Data System (ADS)

    Mashovets, N. S.; Pastukh, I. M.; Voloshko, S. M.

    2017-01-01

    X-ray diffraction analysis, X-ray photoelectron spectroscopy, and Electron Auger-spectroscopy investigation of phase transformation on the surface of the VT8 titanium alloy after a low temperature hydrogen-free nitriding in a glow discharge. Operational characteristics of titanium alloys defined physical-mechanical characteristics of the surface and their phase composition, which depend on the process parameters of nitriding. Surface modification of titanium alloys were carried out by low-temperature nitriding in a glow discharge in hydrogen-free environment. The main advantage of this method lies in the absence of hydrogen embrittlement and complete environmental safety process. Application of the glow discharge can not only speed up the process by the order of the diffusion surface saturation with nitrogen, but also significantly alters the kinetics of the process and quality of the nitrided layer, in particular its physio-mechanical properties and phase composition. For research purposes, the standards from an α + β alloy Ti-Al6-Cr2-Mo2,5 (VT8) were used. Research into the phase composition was performed by X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Stratified analysis by AES was conducted by etching the surface of the samples' argon ion beam with diameters of 1.5 mm with an energy of 3000 eV and a current density of 400 mA/cm2. The above material shows the promise of the technology of low-temperature hydrogen-nitriding by glow discharge. This greatly expands the range of practical applications of titanium alloys. In addition, changing the technological mode allows you to manage a wide range of modified phase composition of the surface layer and as a result - to form the surface of titanium parts, taking into account the conditions of the subsequent operation.

  1. Experiment planning, mathematical modelling, and nonlinear optimization of the ion-nitriding process in a glow-discharge plasma

    SciTech Connect

    Petros, O.; Kuhn, S.; Popa, G.

    1982-06-01

    A new, efficient method for investigating and optimizing the ion-nitriding process in a glow-discharge plasma is proposed and worked out in detail for the mass kinetics of Rp-3 steel. This method, which is based on the concepts of experiment planning, mathematical modelling, and nonlinear optimization, is quite general and potentially applicable to a wide class of technological and other processes depending on several parameters.

  2. Signal Enhancement with Stacked Magnets for High-Resolution Radio Frequency Glow Discharge Mass Spectrometry.

    PubMed

    Wei, Juan; Dong, Jiangli; Zhuo, Shangjun; Qian, Rong; Fang, Yuanxing; Chen, Qiao; Patel, Ekbal

    2017-01-17

    A method for signal enhancement utilizing stacked magnets was introduced into high-resolution radio frequency glow discharge-mass spectrometry (rf-GD-MS) for significantly improved analysis of inorganic materials. Compared to the block magnet, the stacked magnets method was able to achieve 50-59% signal enhancement for typical elements in Y2O3, BSO, and BTN samples. The results indicated that signal was enhanced as the increase of discharge pressure from 1.3 to 8.0 mPa, the increase of rf-power from 10 to 50 W with a frequency of 13.56 MHz, the decrease of sample thickness, and the increase of number of stacked magnets. The possible mechanism for the signal enhancement was further probed using the software "Mechanical APDL (ANSYS) 14.0". It was found that the distinct oscillated magnetic field distribution from the stacked magnets was responsible for signal enhancement, which could extend the movement trajectories of electrons and increase the collisions between the electrons and neutral particles to increase the ionization efficiency. Two NIST samples were used for the validation of the method, and the results suggested that relative errors were within 13% and detection limit for six transverse stacked magnets could reach as low as 0.0082 μg g(-1). Additionally, the stability of the method was also studied. RSD within 15% of the elements in three nonconducting samples could be obtained during the sputtering process. Together, the results showed that the signal enhancement method with stacked magnets could offer great promises in providing a sensitive, stable, and facile solution for analyzing the nonconducting materials.

  3. Emission spectroscopic study on gas-gas interactions in glow discharge plasmas using several binary gas mixtures.

    PubMed

    Wagatsuma, Kazuaki

    2010-01-01

    Emission spectra of constituent gas species from glow discharge plasmas using argon-helium, krypton-helium, argon-krypton, and krypton-argon gas mixtures were analyzed to elucidate collisional energy transfer between these gas species occurring in the plasma. In the argon-helium mixed gas plasma, the enhancement or quenching of particular Ar II lines was observed when helium was added to an argon-matrix glow discharge plasma, meaning that a redistribution in the population among the excited levels could be induced through argon-helium collisions. On the other hand, the krypton-helium plasma showed little change in the emission intensities of Kr II lines when helium was added to a krypton-matrix glow discharge plasma, meaning that energy exchanges between krypton and helium excited species occur inactively. These phenomena are principally because the excitation energy as well as the spin multiplicity between collision partners follow both the energy resonance conditions and the spin conservation rule in collisions of the second kind in the argon-helium system, but not in the krypton-helium system. In the argon-krypton and krypton-argon mixed gas plasmas, significant intensity changes of particular Ar II or Kr II lines could not be found; therefore, there were no dominant channels for energy exchanges between argon and krypton species in the mixed gas plasmas.

  4. Physical mechanisms of self-organization and formation of current patterns in gas discharges of the Townsend and glow types

    SciTech Connect

    Raizer, Yu. P.; Mokrov, M. S.

    2013-10-15

    The paper discusses current filamentation and formation of current structures (in particular, hexagonal current patterns) in discharges of the Townsend and glow types. The aim of the paper, which is in part a review, is to reveal basic reasons for formation of current patterns in different cases, namely, in dielectric barrier discharge, discharge with semiconductor cathode, and micro-discharge between metallic electrodes. Pursuing this goal, we give a very brief review of observations and discuss only those theoretical, computational, and experimental papers that shed light on the physical mechanisms involved. The mechanisms are under weak currents—the thermal expansion of the gas as a result of Joule heating; under enhanced currents—the electric field and ionization rate redistribution induced by space charge. Both mechanisms lead to instability of the homogeneous discharges. In addition, we present new results of numerical simulations of observed short-living current filaments which are chaotic in space and time.

  5. Transport Equations Resolution By N-BEE Anti-Dissipative Scheme In 2D Model Of Low Pressure Glow Discharge

    SciTech Connect

    Kraloua, B.; Hennad, A.

    2008-09-23

    The aim of this paper is to determine electric and physical properties by 2D modelling of glow discharge low pressure in continuous regime maintained by term constant source. This electric discharge is confined in reactor plan-parallel geometry. This reactor is filled by Argon monatomic gas. Our continuum model the order two is composed the first three moments the Boltzmann's equations coupled with Poisson's equation by self consistent method. These transport equations are discretized by the finite volumes method. The equations system is resolved by a new technique, it is about the N-BEE explicit scheme using the time splitting method.

  6. Layer-like Structure of Radio-Frequency Discharge with Dust Particles

    SciTech Connect

    Kravchenko, O. Y.; Vakulenko, A. V.; Lisitchenko, T. Y.; Levada, G. I.

    2008-09-07

    In this paper we are carried out the computer simulation of the dust particles dynamics in the radio frequency discharges at the microgravity conditions using PIC/MCC method for electrons and ions and hydrodynamics model for dust particles. The moving of dust particles is governed by the electrostatic force, ion and neutral drag forces, which are averaged over period of RF discharge. The obtained results show that dust particles form layers with sharp boundaries in the discharge chamber that is response on the instability of the radio-frequency discharge.

  7. Enhanced tissue integration of implantable electrodes for sensing, and stimulation, via radio frequency glow discharge

    NASA Astrophysics Data System (ADS)

    O'Connor, Laurie M.

    Biopotential electrodes are conductive materials that convert electronic currents to or from ionic currents for sensing, and stimulating specific tissue sites for medical applications. Implanted electrodes become "walled off" by the foreign body tissue reactions producing poorly attached scar capsules dominated by surrounding dense collagenous lamellae and source fibroblasts which are electrically resistive. The conductive interstitial fluid that is typical between an electrode and the resistive capsule allows spurious current paths. The insulating layer increases the distance between the electrode and the target sites and poor attachment often results in electrode migration within the host tissue. This investigation tested the hypothesis that surface-energy modulation of electrodes, via Radio Frequency Glow Discharge Treatment (RFGDT), can improve the performance of tissue-implantable electrodes by reducing the foreign body tissue reaction and enhancing interfacial bonding between the tissue and electrode material. Previously published findings were reproduced in a pilot study of explanted reference grade medical-grade methyl silicone (PDMS) and commercially pure titanium (cpTi) materials and their tissue capsules from 30-day subcutaneous exposures in Balb/C mice. The low-critical surface tension PDMS produced thick, dense, poorly attached scar capsules while the higher-surface-energy commercially pure titanium (cpTi) produced more cellular and strongly attached tissue layers difficult to delaminate from the biomaterial. For the main body of work, cpTi, capacitor-grade Tantalum (Ta), and synthetic heart valve-quality Pyrolytic Carbon (PyC) were evaluated, representative of potential high-surface-energy implant electrode materials. Their surface characteristics were determined as-manufactured and after Radio Frequency Glow Discharge Treatment (RFGDT) by Critical Surface Tension (CST) measurement, Scanning Electron Microscopy (SEM), Energy Dispersive X

  8. ULTRAVIOLET INDUCED MOTION OF A FLUORESCENT DUST CLOUD IN AN ARGON DIRECT CURRENT GLOW DISCHARGE PLASMA

    SciTech Connect

    Hvasta, M.G.; and Zwicker, A.

    2008-01-01

    Dusty plasmas consist of electrons, ions, neutrals and nm-μm sized particles commonly referred to as dust. In man-made plasmas this dust may represent impurities in a tokamak or plasma etching processing. In astrophysical plasmas this dust forms structures such as planetary rings and comet tails. To study dusty plasma dynamics an experiment was designed in which a 3:1 silica (<5 μm diameter) and fl uorescent dust mixture was added to an argon DC glow discharge plasma and exposed to UV radiation. This fl uorescent lighting technique offers an advantage over laser scattering (which only allows two-dimensional slices of the cloud to be observed) and is simpler than scanning mirror techniques or particle image velocimetry. Under typical parameters (P=150 mTorr, V anode= 100 V, Vcathode= -400 V, Itotal < 2mA) when the cloud is exposed to the UV light (100W, λ = 365 nm) the mixture fl uoresces, moves ~2mm towards the light source and begins rotating in a clockwise manner (as seen from the cathode). By calibrating a UV lamp and adjusting the relative intensity of the UV with a variable transformer it was found that both translational and rotational velocities are a function of UV intensity. Additionally, it was determined that bulk cloud rotation is not seen when the dust tray is not grounded while bulk translation is. This ongoing experiment represents a novel way to control contamination in man-made plasmas and a path to a better understanding of UV-bathed plasma systems in space..

  9. Glow Discharge Plasma Demonstrated for Separation Control in the Low-Pressure Turbine

    NASA Technical Reports Server (NTRS)

    Ashpis, David e.; Hultgren, Lennart S.

    2004-01-01

    Flow separation in the low-pressure turbine (LPT) is a major barrier that limits further improvements of aerodynamic designs of turbine airfoils. The separation is responsible for performance degradation, and it prevents the design of highly loaded airfoils. The separation can be delayed, reduced, or eliminated completely if flow control techniques are used. Successful flow control technology will enable breakthrough improvements in gas turbine performance and design. The focus of this research project was the development and experimental demonstration of active separation control using glow discharge plasma (GDP) actuators in flow conditions simulating the LPT. The separation delay was shown to be successful, laying the foundation for further development of the technologies to practical application in the LPT. In a fluid mechanics context, the term "flow control" means a technology by which a very small input results in a very large effect on the flow. In this project, the interest is to eliminate or delay flow separation on LPT airfoils by using an active flow control approach, in which disturbances are dynamically inserted into the flow, they interact with the flow, and they delay separation. The disturbances can be inserted using a localized, externally powered, actuating device, examples are acoustic, pneumatic, or mechanical devices that generate vibrations, flow oscillations, or pulses. A variety of flow control devices have been demonstrated in recent years in the context of the external aerodynamics of aircraft wings and airframes, where the incoming flow is quiescent or of a very low turbulence level. However, the flow conditions in the LPT are significantly different because there are high levels of disturbances in the incoming flow that are characterized by high free-stream turbulence intensity. In addition, the Reynolds number, which characterizes the viscous forces in the flow and is related to the flow speed, is very low in the LPT passages.

  10. Protein destruction by a helium atmospheric pressure glow discharge: Capability and mechanisms

    SciTech Connect

    Deng, X. T.; Shi, J. J.; Kong, M. G.

    2007-04-01

    Biological sterilization represents one of the most exciting applications of atmospheric pressure glow discharges (APGD). Despite the fact that surgical instruments are contaminated by both microorganisms and proteinaceous matters, sterilization effects of APGD have so far been studied almost exclusively for microbial inactivation. This work presents the results of a detailed investigation of the capability of a helium-oxygen APGD to inactivate proteins deposited on stainless-steel surfaces. Using a laser-induced fluorescence technique for surface protein measurement, a maximum protein reduction of 4.5 logs is achieved by varying the amount of the oxygen admixture into the background helium gas. This corresponds to a minimum surface protein of 0.36 femtomole/mm{sup 2}. It is found that plasma reduction of surface-borne protein is through protein destruction and degradation, and that its typically biphasic reduction kinetics is influenced largely by the thickness profile of the surface protein. Also presented is a complementary study of possible APGD protein inactivation mechanisms. By interplaying the protein inactivation kinetics with optical emission spectroscopy, it is shown that the main protein-destructing agents are excited atomic oxygen (via the 777 and 844 nm emission channels) and excited nitride oxide (via the 226, 236, and 246 nm emission channels). It is also demonstrated that the most effective protein reduction is achieved possibly through a synergistic effect between atomic oxygen and nitride oxide. This study is a useful step toward a full confirmation of the efficacy of APGD as a sterilization technology for surgical instruments contaminated by prion proteins.

  11. Liquid sampling-atmospheric pressure glow discharge as a secondary excitation source: Assessment of plasma characteristics

    NASA Astrophysics Data System (ADS)

    Manard, Benjamin T.; Gonzalez, Jhanis J.; Sarkar, Arnab; Dong, Meirong; Chirinos, Jose; Mao, Xianglei; Russo, Richard E.; Marcus, R. Kenneth

    The liquid sampling-atmospheric pressure glow discharge (LS-APGD) has been assessed as a secondary excitation source with a parametric evaluation regarding carrier gas flow rate, applied current, and electrode distance. With this parametric evaluation, plasma optical emission was monitored in order to obtain a fundamental understanding with regards to rotational temperature (Trot), excitation temperature (Texc), electron number density (ne), and plasma robustness. Incentive for these studies is not only for a greater overall fundamental knowledge of the APGD, but also in instrumenting a secondary excitation/ionization source following laser ablation (LA). Rotational temperatures were determined through experimentally fitting of the N2 and OH molecular emission bands while atomic excitation temperatures were calculated using a Boltzmann distribution of He and Mg atomic lines. The rotational and excitation temperatures were determined to be ~ 1000 K and ~ 2700 K respectively. Electron number density was calculated to be on the order of ~ 3 × 1015 cm- 3 utilizing Stark broadening effects of the Hα line of the Balmer series and a He I transition. In addition, those diagnostics were performed introducing magnesium (by solution feed and laser ablation) into the plasma in order to determine any perturbation under heavy matrix sampling. The so-called plasma robustness factor, derived by monitoring Mg II/Mg I emission ratios, is also employed as a reflection of potential perturbations in microplasma energetics across the various operation conditions and sample loadings. While truly a miniaturized source (< 1 mm3 volume), the LS-APGD is shown to be quite robust with plasma characteristics and temperatures being unaffected upon introduction of metal species, whether by liquid or laser ablation sample introduction.

  12. Protein destruction by a helium atmospheric pressure glow discharge: Capability and mechanisms

    NASA Astrophysics Data System (ADS)

    Deng, X. T.; Shi, J. J.; Kong, M. G.

    2007-04-01

    Biological sterilization represents one of the most exciting applications of atmospheric pressure glow discharges (APGD). Despite the fact that surgical instruments are contaminated by both microorganisms and proteinaceous matters, sterilization effects of APGD have so far been studied almost exclusively for microbial inactivation. This work presents the results of a detailed investigation of the capability of a helium-oxygen APGD to inactivate proteins deposited on stainless-steel surfaces. Using a laser-induced fluorescence technique for surface protein measurement, a maximum protein reduction of 4.5 logs is achieved by varying the amount of the oxygen admixture into the background helium gas. This corresponds to a minimum surface protein of 0.36 femtomole/mm2. It is found that plasma reduction of surface-borne protein is through protein destruction and degradation, and that its typically biphasic reduction kinetics is influenced largely by the thickness profile of the surface protein. Also presented is a complementary study of possible APGD protein inactivation mechanisms. By interplaying the protein inactivation kinetics with optical emission spectroscopy, it is shown that the main protein-destructing agents are excited atomic oxygen (via the 777 and 844 nm emission channels) and excited nitride oxide (via the 226, 236, and 246 nm emission channels). It is also demonstrated that the most effective protein reduction is achieved possibly through a synergistic effect between atomic oxygen and nitride oxide. This study is a useful step toward a full confirmation of the efficacy of APGD as a sterilization technology for surgical instruments contaminated by prion proteins.

  13. Surface oxygen micropatterns on glow discharge polymer targets by photo irradiation

    NASA Astrophysics Data System (ADS)

    Reynolds, Hannah; Baxamusa, Salmaan; Haan, Steven W.; Fitzsimmons, Paul; Carlson, Lane; Farrell, Mike; Nikroo, Abbas; Watson, Brian J.

    2016-02-01

    Recent simulations predict surface oxygen may be a significant source of disruptive perturbations in the implosion process of glow-discharge polymers (GDP) ablators at the National Ignition Facility. GDP material held in ambient atmospheric conditions showed an increase in mass when stored in light transparent containers, which suggests that photo exposure is a driving force for oxygen absorption. To investigate if surface oxygen is a contributing factor of disruptive perturbations during implosion, a method to imprint a periodic micropattern of oxygen on the surface of GDP was developed and used to fabricate a flat sample for empirical testing. Photo exposure using collimated blue light was used to generate micropatterns of surface oxygen on the GDP material. The periodic oxygen micropattern was confirmed by secondary ion mass spectrometry (SIMS) and energy dispersive spectroscopy. A SIMS depth profile showed the atomic percent of oxygen ranged from 8 at. % near the surface to 1 at. % at a depth of 2 μm in a sample exposed for 4 min. The molecular interactions formed between the GDP and oxygen molecules were characterized using Fourier transform infrared resonance (FTIR), which showed the formation of hydroxyl (O-H) and carbonyl (C=O) bonds. The FTIR enabled the oxygen mass uptake as a function of photo exposure time to be quantified (resolved to typically 0.05 at. % oxygen). This experimental protocol was then applied to produce a GDP flat part with a periodic 75 μm wavelength micropattern of photo exposed (oxygen rich) and masked (oxygen deficient) regions. The micropatterned GDP ablators developed in this work are being used to assess the effect of surface oxygen on disruptive perturbations during the inertial confinement fusion implosion process.

  14. Applicability of the Child-Langmuir laws versions for describing the glow discharge cathode sheath in CO2

    NASA Astrophysics Data System (ADS)

    Lisovskiy, Valeriy; Krol, Hennadii; Osmayev, Ruslan; Yegorenkov, Vladimir

    2016-09-01

    This work is devoted to the determination of the law that may be applicable to the description of the cathode sheath in CO2. To this end three versions of the Child-Langmuir law have been considered - a collision free one (for the ions moving through a cathode sheath without collisions with gas molecules) as well as two collision- related versions- one for a constant mean free path of positive ions and one for a constant mobility of positive ions. The current-voltage characteristics and the cathode sheath thickness of the glow discharge in carbon oxide have been simultaneously measured in the pressure range from 0.05 to 1 Torr and with the discharge current values up to 80 mA. The inter-electrode distance has been chosen such that the discharge consists only of the cathode sheath and a small portion of the negative glow, i.e. the experiments have been performed in short tubes. In this case the voltage drop across the cathode sheath is equal approximately to the voltage drop across the electrodes. In the whole range of the discharge conditions we have studied the cathode sheath characteristics are found to obey correctly only to the Child-Langmuir law version with a constant ion mobility. The reason for this phenomenon may be related with a significant conversion of carbon dioxide molecules.

  15. Cathode fall thickness of abnormal glow discharges between parallel-plane electrodes in different radii at low pressure

    SciTech Connect

    Fu, Yangyang; Luo, Haiyun; Zou, Xiaobing; Wang, Xinxin

    2015-02-15

    In order to investigate the influence of electrode radius on the characteristics of cathode fall thickness, experiments of low-pressure (20 Pa ≤ p ≤ 30 Pa) abnormal glow discharge were carried out between parallel-plane electrodes in different radii keeping gap distance unchanged. Axial distributions of light intensity were obtained from the discharge images captured using a Charge Coupled Device camera. The assumption that the position of the negative glow peak coincides with the edge of cathode fall layer was verified based on a two-dimensional model, and the cathode fall thicknesses, d{sub c}, were calculated from the axial distributions of light intensity. It was observed that the position of peak emission shifts closer to the cathode as current or pressure grows. The dependence of cathode fall thickness on the gas pressure and normalized current J/p{sup 2} was presented, and it was found that for discharges between electrodes in large radius the curves of pd{sub c} against J/p{sup 2} were superimposed on each other, however, this phenomenon will not hold for discharges between the smaller electrodes. The reason for this phenomenon is that the transverse diffusions of charged particles are not the same in two gaps between electrodes with different radii.

  16. Linear and Nonlinear Dust Acoustic Waves, Shocks and Stationary Structures in a dc-Glow-Discharge Dusty Plasma

    NASA Astrophysics Data System (ADS)

    Merlino, Robert

    2011-10-01

    In 1990, Rao, Shukla, and Yu (Planet. Space Sci. 38, 543) predicted the existence of the dust acoustic (DA) wave, a low-frequency (~ few Hz), compressional dust density wave that propagates through a dusty plasma at a phase speed ~ several cm/s. The DA wave was first observed by Chu et. al., (J. Phys. D: Appl. Phys. 27, 296, 1994) in an rf-produced dusty plasma, and by Barkan et. al., (Barkan et. al. Phys. Plasmas 2, 2161, 1995) who obtained video images of the DA wave trains using light scattering from a dust suspension confined in an anodic glow discharge plasma formed within a Q machine plasma. The dispersion relation for DAWs was measured by Thompson et. al., (Phys. Plasmas 4, 2331, 1997) in a dc glow discharge dusty plasma by modulating the discharge current at a set frequency. DAWs have been investigated by many groups both in weakly-coupled and strongly-coupled dusty plasmas (E. Thomas, Jr., Contrib. Plasma Phys. 49, 316, 2009). In most experiments where DA waves are present, the wave amplitude is relatively high, indicating that they are nonlinear. In this talk, results of our recent experiments on DAWs will be presented. The following experiments, performed in a dc glow-discharge dusty plasma will be described: (1) Observations of spontaneously excited nonlinear, cylindrical DAWs, which exhibit confluence of waves propagating at different speeds. (2) Investigations of self-steepening DAWs that develop into DA shocks with thicknesses comparable to the interparticle separation (Heinrich et. al., Phys. Rev. Lett. 103, 115001, 2009). (3) Measurements of the linear growth rates of DAWs excited in merging dust clouds. (4) The formation of stationary, stable dust density structures appearing as non-propagating DAWs (Heinrich et. al., Phys. Rev. E, in press, 2011). This work was performed in collaboration with S. H. Kim, J. R. Heinrich, and J. K. Meyer. Work supported by DOE Grant No. DE-FG01-04ER54795

  17. Characteristics of radio-frequency atmospheric pressure dielectric-barrier discharge with dielectric electrodes

    SciTech Connect

    Hussain, S. E-mail: shussainuos@yahoo.com; Qazi, H. I. A.; Badar, M. A.

    2014-03-15

    An experimental investigation to characterize the properties and highlight the benefits of atmospheric pressure radio-frequency dielectric-barrier discharge (rf DBD) with dielectric electrodes fabricated by anodizing aluminium substrate is presented. The current-voltage characteristics and millisecond images are used to distinguish the α and γ modes. This atmospheric rf DBD is observed to retain the discharge volume without constriction in γ mode. Optical emission spectroscopy demonstrates that the large discharge current leads to more abundant reactive species in this plasma source.

  18. Hysteresis in amplitudes of self-excited oscillations for co-axial electrode-geometry DC glow discharge plasma

    SciTech Connect

    Kumar, R.; Narayanan, R.; Prasad, Awadhesh

    2014-12-15

    Hysteresis in amplitudes of the self-excited oscillations of the floating potential and discharge current is observed in an unmagnetized co-axial electrode-geometry DC glow discharge plasma system. The nonlinearities of these oscillations are studied using standard dynamical analysis tools. The characterization revealed the transition of low-amplitude high-frequency period-n oscillations to a large amplitude low frequency period-1 oscillations through a chaotic intermediate route. The transition of the low amplitude, high frequency period-n oscillations to chaotic type is observed to be linked to the dynamical change in the plasma system, i.e., after a negative differential resistance (NDR) region, whereas the transition from chaotic to period-1 is observed to be linked to a discharge current threshold.

  19. Glow discharge electrolysis plasma initiated preparation of temperature/pH dual sensitivity reed hemicellulose-based hydrogels.

    PubMed

    Zhang, Wenming; Zhu, Sha; Bai, Yunping; Xi, Ning; Wang, Shaoyang; Bian, Yang; Li, Xiaowei; Zhang, Yucang

    2015-05-20

    The temperature/pH dual sensitivity reed hemicellulose-based hydrogels have been prepared through glow discharge electrolysis plasma (GDEP). The effect of different discharge voltages on the temperature and pH response performance of reed hemicellulose-based hydrogels was inspected, and the formation mechanism, deswelling behaviors of reed hemicellulose-based hydrogels were also discussed. At the same time, infrared spectroscopy (FT-IR), scanning differential thermal analysis (DSC) and scanning electron microscope (SEM) were adopted to characterize the structure, phase transformation behaviors and microstructure of hydrogels. It turned out to be that all reed hemicellulose-based hydrogels had a double sensitivity to temperature and pH, and their phase transition temperatures were all approximately 33 °C, as well as the deswelling dynamics met the first model. In addition, the hydrogel (TPRH-3), under discharge voltage 600 V, was more sensitive to temperature and pH and had higher deswelling ratio.

  20. Hysteresis in amplitudes of self-excited oscillations for co-axial electrode-geometry DC glow discharge plasma

    NASA Astrophysics Data System (ADS)

    Kumar, R.; Narayanan, R.; Prasad, Awadhesh

    2014-12-01

    Hysteresis in amplitudes of the self-excited oscillations of the floating potential and discharge current is observed in an unmagnetized co-axial electrode-geometry DC glow discharge plasma system. The nonlinearities of these oscillations are studied using standard dynamical analysis tools. The characterization revealed the transition of low-amplitude high-frequency period-n oscillations to a large amplitude low frequency period-1 oscillations through a chaotic intermediate route. The transition of the low amplitude, high frequency period-n oscillations to chaotic type is observed to be linked to the dynamical change in the plasma system, i.e., after a negative differential resistance (NDR) region, whereas the transition from chaotic to period-1 is observed to be linked to a discharge current threshold.

  1. Radiofrequency Glow Discharges Used for Optical Emission Spectroscopy: An Experimental and Analytical Approach

    DTIC Science & Technology

    2003-07-20

    Centre de Physique des Plasmas et Applications de Toulouse, Universit: Paul Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex, France 1. Introduction...millimeters from the sample 0 surface, 2.6 mm, and has a rather high density. 0ൈ rAcknowledgements: The authors would like to thank .o L.C. Pitchford

  2. Numerical study on the gas heating mechanism in pulse-modulated radio-frequency glow discharge

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Yu, Xiao-Li; Wang, De-Zhen

    2017-03-01

    Not Available Project supported by the National Natural Science Foundation of China (Granted Nos. 11405022 and 11475040) and Dalian High Level Talent Innovation Support Plan, China (Grant No. 2015R050).

  3. Investigation of Meltblown Microfiber and Electrospun Nanofiber Fabrics Treated with a One Atmosphere Uniform Glow Discharge Plasma (OAUGDP)

    NASA Astrophysics Data System (ADS)

    Chen, Weiwei; Reece Roth, J.; Tsai, Peter P.-Y.

    2003-10-01

    Nanofiber webs are made by the electrospinning (ES) process [1], which uses the repulsive electrostatic force to spin fibers from a polymer solution or melt at room temperature and low energy input. We have developed apparatus at the UT Textiles and Nonwovens Development Center (TANDEC) to produce fabrics with fiber diameters of tens of nanometers. This paper will report data on the distribution function of nanofiber diameters that were taken from digitized SEM images of the electrospun materials. It is also found in the tensile tests that the strength of the electrospun nanofiber fabrics is up to ten times that of the coarser meltblown material. The one atmosphere uniform glow discharge plasma (OAUGDP) developed at the UT Plasma Sciences Laboratory generates a normal glow electrical discharge at one atmosphere. This plasma has been used to treat meltblown and electrospun fabrics, with a resulting increase in surface energy [1]. We recently found that the surface energy of meltblown Nylon could be increased to 70 dynes/cm by five seconds of OAUGDP exposure, and was durable at this level for six months. Our results also show that Nylon and PU nanofiber fabrics can be exposed to the OAUGDP for treatment without significant damage for up to 10 seconds [1], a duration sufficient to produce important effects, including durable wettability. We will describe our progress in improving the properties of nanofiber fabrics using a variety of latest developments in OAUGDP reactor technology, including a new porous electrode that injects gases other than air to generate different active species for plasma treatment. [1] Tsai P. P.-Y., Chen W., Li X. and Roth J.R.: "Improving the Properties of Protective Clothing by Exposing Nanofiber Webs to a One Atmospheric Uniform Glow Discharge Plasma (OAUGDP)", National Science Foundation (NSF) Grantee¡¯s Workshop and Conference, Birmingham, Alabama, Jan. 6-9, 2003.

  4. Two-dimensional hybrid Monte Carlo–fluid modelling of dc glow discharges: Comparison with fluid models, reliability, and accuracy

    SciTech Connect

    Eylenceoğlu, E.; Rafatov, I.; Kudryavtsev, A. A.

    2015-01-15

    Two-dimensional hybrid Monte Carlo–fluid numerical code is developed and applied to model the dc glow discharge. The model is based on the separation of electrons into two parts: the low energetic (slow) and high energetic (fast) electron groups. Ions and slow electrons are described within the fluid model using the drift-diffusion approximation for particle fluxes. Fast electrons, represented by suitable number of super particles emitted from the cathode, are responsible for ionization processes in the discharge volume, which are simulated by the Monte Carlo collision method. Electrostatic field is obtained from the solution of Poisson equation. The test calculations were carried out for an argon plasma. Main properties of the glow discharge are considered. Current-voltage curves, electric field reversal phenomenon, and the vortex current formation are developed and discussed. The results are compared to those obtained from the simple and extended fluid models. Contrary to reports in the literature, the analysis does not reveal significant advantages of existing hybrid methods over the extended fluid model.

  5. Ab initio and experimental studies of glow-discharge polymer used in laser mégajoule capsules

    NASA Astrophysics Data System (ADS)

    Colin-Lalu, P.; Recoules, V.; Salin, G.; Huser, G.

    2017-01-01

    The equations of state tables used in Inertial Confinement Fusion Capsule design tools are highly dependent on the cold curve in the multimegabar pressure range. Original ab initio molecular dynamic simulations were performed to get accurate cold curves of glow-discharge polymer (GDP) plastics. Furthermore the effect of oxygen absorption by GDP structure is studied on the cold curve, as well as its impact on the Hugoniot curves. Results are compared with the Hugoniot experimental data obtained in a recent experiment at the LULI2000 laser facility in France. This study leads to improve the equation of states knowledge of ablator materials, which is of primary importance for NIF and LMJ experiments.

  6. Ab initio and experimental studies of glow-discharge polymer used in Laser MégaJoule capsules

    NASA Astrophysics Data System (ADS)

    Colin-Lalu, Pierre; Huser, Gaël; Recoules, Vanina; Salin, Gwenael; CEA DAM DIF Team

    2015-06-01

    Equations of state tables used in Initial Confinement Fusion capsule design tools are highly dependent on the cold curve in the multimegabar range. Original ab-initio molecular dynamic simulations were performed to get accurate cold curves of glow-discharge polymer (GDP) plastics. Furthermore the effect of oxygen absorption by GDP structure is studied on the cold curve, as well as its impact on the Hugoniot curves. Results are compared with Hugoniot experimental data obtained in a recent experiment at the LULI2000 laser facility in France. This study leads to improve equation of states knowledge of ablator materials, which is of primary importance for NIF and LMJ experiments.

  7. Radiofrequency antenna for suppression of parasitic discharges in a helicon plasma thruster experiment.

    PubMed

    Takahashi, Kazunori

    2012-08-01

    A radiofrequency (rf) antenna for helicon plasma thruster experiments is developed and tested using a permanent magnets helicon plasma source immersed in a vacuum chamber. A magnetic nozzle is provided by permanent magnets arrays and an argon plasma is produced by a 13.56 MHz radiofrequency helicon-wave or inductively-coupled discharge. A parasitic discharge outside the source tube is successfully suppressed by covering the rf antenna with a ceramic ring and a grounded shield; a decrease in the ion saturation current of a Langmuir probe located outside the source tube is observed and the ion saturation current on axis increases simultaneously, compared with the case of a standard uncovered rf antenna. It is also demonstrated that the covered antenna can yield stable operation of the source.

  8. Existence of solutions for electron balance problem in the stationary radio-frequency induction discharges

    NASA Astrophysics Data System (ADS)

    Zheltukhin, V. S.; Solovyev, S. I.; Solovyev, P. S.; Chebakova, V. Yu

    2016-11-01

    A sufficient condition for the existence of a minimal eigenvalue corresponding to a positive eigenfunction of an eigenvalue problem with nonlinear dependence on the parameter for a second order ordinary differential equation is established. The initial problem is approximated by the finite element method. Error estimates for the approximate minimal eigenvalue and corresponding positive eigenfunction are derived. Problems of this form arise in modelling the plasma of a radio-frequency discharge at reduced pressure.

  9. Modeling the chemical kinetics of high-pressure glow discharges in mixtures of helium with real air

    NASA Astrophysics Data System (ADS)

    Stalder, K. R.; Vidmar, R. J.; Nersisyan, G.; Graham, W. G.

    2006-05-01

    Atmospheric and near-atmospheric pressure glow discharges generated in both pure helium and helium-air mixtures have been studied using a plasma chemistry code originally developed for simulations of electron-beam-produced air plasmas. Comparisons are made with experimental data obtained from high-pressure glow discharges in helium-air mixtures developed by applying sinusoidal voltage wave forms between two parallel planar metallic electrodes covered by glass plates, with frequencies ranging from 10 to 50 kHz and electric field strengths up to 5 kV/cm. The code simulates the plasma chemistry following periodic pulsations of ionization in prescribed E/N environments. Many of the rate constants depend on gas temperature, electron temperature, and E/N. In helium plasmas with small amounts (~850 ppm) of air added, rapid conversion of atomic helium ions to molecular helium ions dominate the positive ion kinetics and these species are strongly modulated while the radical species are not. The charged and neutral species concentrations at atmospheric pressure with air impurity levels up to 10 000 ppm are predicted. The negative ion densities are very small but increase as the air impurity level is raised, which indicates that in helium-based systems operated in open air the concentration of negative ions would be significant. If water vapor at typical humidity levels is present as one of the impurities, hydrated cluster ions eventually comprise a significant fraction of the charged species.

  10. Proton transfer mass spectrometry at 11 hPa with a circular glow discharge: Sensitivities and applications

    NASA Astrophysics Data System (ADS)

    Hanson, D. R.; Koppes, M.; Stoffers, A.; Harsdorf, R.; Edelen, K.

    2009-04-01

    The design and testing of a circular glow discharge ion source on a custom built proton transfer mass spectrometer are described. Also, issues important for quantitative measurements of volatile organic compounds using this instrument were investigated. Detailed calibration procedures based on gravimetry are presented, and representative outdoor air data are shown. Calibrations yield a good sensitivity, up to a few Hz/pptv for some compounds, and the detection limit (S/N = 3) is ~100 pptv or better for methanol, acetaldehyde and acetone (5 s sampling time with a 5 s zero). Detection limits are much lower for most other compounds due to high sensitivity and low background. For ions with m/z > ~90 the background signals are very low and species that appear efficiently at these m/z can be detected at the 10 pptv level in a few seconds. Ion breakup processes for alcohols show that a major product ion of mono-functional alcohols is at 57 u, presumably C4H9+. Oxalic acid is an interesting case in that a major product ion appears on an even mass, 46 u, presumably CO2H2+. The circular glow discharge source is easy to construct and deploy in proton transfer mass spectrometry studies at ~11 hPa. Continuous use of the system over time periods of many days and stable operation over time periods of months to years between disassembly and cleaning demonstrates its robustness.

  11. Determination of trace elements in high purity alumina powder by helium enhanced direct current glow discharge mass spectrometry

    NASA Astrophysics Data System (ADS)

    Jung, Sehoon; Kim, Sunhye; Hinrichs, Joachim

    2016-08-01

    Trace impurities in high purity alumina powder were determined by fast flow direct current glow discharge mass spectrometry (GD-MS). The non-conductive samples were prepared with high purity graphite powder and used as a sample binder and as a secondary cathode. To improve the sensitivity of the GD-MS analysis, helium was introduced as an additional glow discharge gas to argon plasma. The quantification results of the GD-MS measurement were calculated by external calibration with matrix matched certified reference materials. The GD-MS results for the determination of Na, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn and Ga in the alumina samples agreed well with the certified values of a reference material and the results of chemical analysis using wet sample digestion with inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). The GD-MS analysis is a rapid analysis technique to determine trace elements in non-conductive alumina to below mg·kg- 1 levels.

  12. Lithium-fluoride flashover ion source cleaned with a glow discharge and irradiated with vacuum-ultraviolet radiation

    SciTech Connect

    Burns, E.J.T.; Woodworth, J.R.; Bieg, K.W.; Mehlhorn, T.A.; Stygar, W.A.; Sweeney, M.A.

    1988-01-01

    We have studied methods of varying the ion species generated by a lithium-fluoride overcoated anode in a 0.5-MV magnetically insulated ion diode. We found that cleaning the anode surface with a 13.6-MHz rf glow discharge or illuminating the anode with a pulsed soft x-ray, vacuum-ultraviolet (XUV) radiation source just before the accelerator pulse significantly altered the ion species of the ion beam produced by the diode. The glow-discharge plasma removed adsorbates (carbon, hydrogen, and oxygen) from the surface of the LiF flashover source. The ions seen were lithium and hydrogen. Unfortunately, the diode impedance with a lithium-fluoride anode was high and the ion efficiency was low; however, XUV irradiation of the surface dramatically lowered the impedance by desorbing neutrals from the ion source via photon-stimulated desorption. Current densities of ten times the Child--Langmuir space-charge limit were achieved under XUV irradiation. In particular, ion currents increased by over a factor of 3 when 12 mJ/cm/sup 2/ of XUV radiation was used. However, with XUV irradiation the largest fraction of ions were fluorine, oxygen, carbon, and hydrogen, not lithium.

  13. Diagnostics of Rotational Temperature and Mean Electron Energy Distribution of DC Glow Discharge Using Spectral Image Processing

    NASA Astrophysics Data System (ADS)

    Shimizu, Daisuke; Sasamoto, Ryo; Matsumoto, Takao; Izawa, Yasuji; Nishijima, Kiyoto

    2014-10-01

    The non-thermal plasma has been used in various application fields of manufacturing industry such as surface reforming, plasma etching, deposited film forming. The gas temperature and electron energy in non-thermal plasma play a key role of production of active species. Therefore, it is essential to understand the properties of non-thermal plasma for effective plasma applications. In this study, the two-dimensional rotational temperature and mean electron energy distribution of DC glow discharge plasma under various air pressures were observed using spectral image processing. Rotational temperature distribution was estimated from the emission intensity ratio of head and tail of 2nd positive system band of N2 (0, 2). On the other hand, mean electron energy was estimated from the emission intensity ratio of 2nd positive system band of N2 (0, 2) and 1st negative system band of N2+ (0, 0). The each spectral images were taken by an ICCD camera with narrow band-path filters respectively. As a result, the dependences of rotational temperature and mean electron energy distribution in DC glow discharge on ambient air pressure were clearly observed using spectral image processing.

  14. Development of a DC Glow Discharge Exhibit for the Demonstration of Plasma Behavior in a Magnetic Field

    NASA Astrophysics Data System (ADS)

    Bruder, Daniel

    2010-11-01

    The DC Glow Discharge Exhibit is intended to demonstrate the effects a magnetic field produces on a plasma in a vacuum chamber. The display, which will be featured as a part of The Liberty Science Center's ``Energy Quest Exhibition,'' consists of a DC glow discharge tube and information panels to educate the general public on plasma and its relation to fusion energy. Wall posters and an information booklet will offer brief descriptions of fusion-based science and technology, and will portray plasma's role in the development of fusion as a viable source of energy. The display features a horse-shoe magnet on a movable track, allowing viewers to witness the effects of a magnetic field upon a plasma. The plasma is created from air within a vacuum averaging between 100-200 mTorr. Signage within the casing describes the hardware components. The display is pending delivery to The Liberty Science Center, and will replace a similar, older exhibit presently at the museum.

  15. Effect of hydrogen ratio on plasma parameters of N{sub 2}-H{sub 2} gas mixture glow discharge

    SciTech Connect

    El-Brulsy, R. A.; Abd Al-Halim, M. A.; Abu-Hashem, A.; Rashed, U. M.; Hassouba, M. A.

    2012-05-15

    A dc plane glow discharge in a nitrogen-hydrogen (N{sub 2}-H{sub 2}) gas mixture has been operated at discharge currents of 10 and 20 mA. The electron energy distribution function (EEDF) at different hydrogen concentrations is measured. A Maxwellian EEDF is found in the positive column region, while in both cathode fall and negative glow regions, a non-Maxwellian one is observed. Langmuir electric probes are used at different axial positions, gas pressures, and hydrogen concentrations to measure the electron temperature and plasma density. The electron temperature is found to increase with increasing H{sub 2} concentration and decrease with increasing both the axial distance from the cathode and the mixture pressure. At first, with increasing distance from the cathode, the ion density decreases, while the electron density increases; then, as the anode is further approached, they remain nearly constant. At different H{sub 2} concentrations, the electron and ion densities decrease with increasing the mixture pressure. Both the electron and ion densities slightly decrease with increasing H{sub 2} concentration.

  16. Inactivation of Microcystis aeruginosa by DC glow discharge plasma: Impacts on cell integrity, pigment contents and microcystins degradation.

    PubMed

    Zhang, Hong; Yang, Linfang; Yu, Zengliang; Huang, Qing

    2014-03-15

    We proposed a method to inactivate M. aeruginosa by using discharge plasma taking at the gas-solution interface supplied by DC power. Multiple analysis techniques including fluorescence excitation-emission matrix (EEM) and flow cytometry (FCM) were used to reveal the inactivation mechanism of M. aeruginosa. The photosynthetic pigment contents including phycocyanin, chlorophyll and metabolites were examined quantitatively. The DC glow discharge plasma caused an increased level of reactive oxygen species (ROS), and the damage of M. aeruginosa cells are mainly attributed to the oxidative stress including OH attack and H2O2 oxidation. Our findings demonstrate that plasma oxidation is a promising technology for inactivation of M. aeruginosa cells with simultaneous removal of microcystins and so it may lead us to a new route to efficient treatment of cyanobacterial blooms.

  17. Isotope exchange experiments on TEXTOR and TORE SUPRA using Ion Cyclotron Wall Conditioning and Glow Discharge Conditioning

    NASA Astrophysics Data System (ADS)

    Wauters, T.; Douai, D.; Lyssoivan, A.; Philipps, V.; Brémond, S.; Freisinger, M.; Kreter, A.; Lombard, G.; Marchuk, O.; Mollard, P.; Paul, M. K.; Pegourié, B.; Reimer, H.; Sergienko, G.; Tsitrone, E.; Vervier, M.; Van Wassenhove, G.; Wünderlich, D.; Van Schoor, M.; Van Oost, G.

    2011-08-01

    This contribution reports on isotope exchange studies with both Ion Cyclotron Wall Conditioning (ICWC) and Glow Discharge Conditioning (GDC) in TEXTOR and TORE SUPRA. The discharges have been carried out in H2, D2 (ICWC and GDC) and He/H2 mixtures (ICWC). The higher reionization probability in ICWC compared to GDC, following from the 3 to 4 orders of magnitude higher electron density, leads to a lower pumping efficiency of wall desorbed species. GDC has in this analysis (5-10) times higher removal rates of wall desorbed species than ICWC, although the wall release rate is 10 times higher in ICWC. Also the measured high retention during ICWC can be understood as an effect of the high reionization probability. The use of short RF pulses (∼1 s) followed by a larger pumping time significantly improves the ratio of implanted over recovered particles, without severely lowering the total amount of removed particles.

  18. On line vapor generation of osmium based on solution cathode glow discharge for the determination by ICP-OES.

    PubMed

    Zhu, Zhenli; Huang, Chunying; He, Qian; Xiao, Qing; Liu, Zhifu; Zhang, Suicheng; Hu, Shenghong

    2013-03-15

    A novel plasma induced vapor generation method is proposed to determine osmium in solutions. Without any chemical oxidizing agents, osmium ion can be readily converted to volatile osmium tetraoxide vapor in the solution cathode glow discharge (SCGD) system. The generated osmium vapor is then transported to inductively coupled plasma for determination by optical emission spectrometry. The influences of background electrolyte, carrier gas flow rate, sample flow rate, ICP power and discharge current were investigated. The analytical performances of this proposed technique were evaluated under optimized conditions. The detection limit of Os was calculated to be 0.51 ng mL(-1). The reproducibility, expressed as the relative standard deviation (n=11) of a 2.0 μg mL(-1) standard solution, was 1.9%. This SCGD induced vapor generation is sensitive and simple, oxidation reagents free, providing an alternative analytical method for measuring Os in geological or environmental water samples.

  19. Numerical simulation of an oxygen-fed wire-to-cylinder negative corona discharge in the glow regime

    NASA Astrophysics Data System (ADS)

    Yanallah, K.; Pontiga, F.; Castellanos, A.

    2011-02-01

    Negative glow corona discharge in flowing oxygen has been numerically simulated for a wire-to-cylinder electrode geometry. The corona discharge is modelled using a fluid approximation. The radial and axial distributions of charged and neutral species are obtained by solving the corresponding continuity equations, which include the relevant plasma-chemical kinetics. Continuity equations are coupled with Poisson's equation and the energy conservation equation, since the reaction rate constants may depend on the electric field and temperature. The experimental values of the current-voltage characteristic are used as input data into the numerical calculations. The role played by different reactions and chemical species is analysed, and the effect of electrical and geometrical parameters on ozone generation is investigated. The reliability of the numerical model is verified by the reasonable agreement between the numerical predictions of ozone concentration and the experimental measurements.

  20. Modeling of small scale radio-frequency inductive discharges for electric propulsion applications

    NASA Astrophysics Data System (ADS)

    Mistoco, Valerie F. M.

    This work is motivated by the increasing interest in small-scale radio-frequency ion thrusters for micro- and nanosatellite applications, in particular for stationkeeping. This specific type of thruster relies on an inductive discharge to produce positive ions that are accelerated by an external electric field in order to produce thrust. Analyzing the particle dynamics within the discharge vessel is critical for determining the performance of these thrusters, particularly as scaling down the size and thrust level of ion thrusters remains a major challenge. Until now the application of this type of propulsion system has been limited to large satellites and space platforms. The approach taken in this work was, first, to perform a simple analysis of the inductive discharge using a transformer model. However, the dimensions of the thruster and the pressure ranges at which it operates called for a different approach than those used in larger thrusters and reactors as the collisional domain and non-locality effects differ significantly. After estimating the non-locality effects by calculating the non-locality parameter, a kinetic description of the discharge was developed. From the input power, mass flow rate, and the properties of the gas used in the discharge, the density numbers, temperatures of the particles, and thrust are calculated. Simulation values are compared with experimental values obtained with the Miniature Radio-frequency Ion Thruster being developed at The Pennsylvania State University. The approach employed to model this small scale inductive discharge can be summarized as follows. First, conditions of operation and the various plasma parameters of the discharge were derived. Then, a one-dimensional kinetic model of an inductive discharge, using a Maxwellian electron distribution, was built. Results from this model were validated on data available in the literature. Finally, from the beam current derived from the 1-D model, using a two-grid ion optics

  1. Influence of Parameters of the Glow Discharge on Change of Structure and the Isotope Composition of the Cathode Materials

    NASA Astrophysics Data System (ADS)

    Savvatimova, I. B.; Gavritenkov, D. V.

    Results of examinations of changes in structure, element, and isotope composition of cathodes after the glow discharge exposure in hydrogen, deuterium, argon, and xenon are submitted. The voltage of the discharge was less than 1000 V and the current was 5-150 mA. Samples before and after ions bombardment in the glow discharge were explored by the methods of mass spectrometry: the secondary ions (SIMS), the secondary ions with additional ionization of neutral sprayed particles (SNMS), spark (SMS), and thermo-ionization (TIMS), and also methods of energy dispersion X-ray spectral analysis (EDX). The alpha-, beta-, gamma- emission, and gamma- spectrometry for radioactive uranium specimens were also carried out before and after experiments in the glow discharge. Changes in structure, isotope, and element composition of the cathode samples depend on current density, integrated ions flow (fluence of ions), kind of irradiating ions and other experimental conditions. Attempts are made to estimate qualitatively and quantitatively the role of each of the parameters on intensity of the observed changes in cathode composition. It is shown that the maximum changes in structure, chemical and isotope composition of the cathode material occur in "hot points," such as craters from microexplosions, phase segregations, blisters and other new formations. Various methods of the analysis revealed that the basic elements Mg, O, Si, Al, and Ca with quantities up to per cents and more were prevailing in these zones and not found out before experiment. The greatest changes of the isotope relations were observed for iron, calcium, silicon, chromium after experiments with pulsing current. EDX method finds out the elements missing in the samples before experiment such as cadmium, strontium, tin. The isotopes with mass number 59 (Co 100%), 55 (Mn 100%), 45 (Sc 100%) are also not found in initial samples and background measurement by TIMS method. Results of changes in the element and isotope

  2. Generation of uniform low-temperature plasma in a pulsed non-self-sustained glow discharge with a large-area hollow cathode

    NASA Astrophysics Data System (ADS)

    Akhmadeev, Yu. H.; Denisov, V. V.; Koval, N. N.; Kovalsky, S. S.; Lopatin, I. V.; Schanin, P. M.; Yakovlev, V. V.

    2017-01-01

    Generation of plasma in a pulsed non-self-sustained glow discharge with a hollow cathode with an area of ≥2 m2 at gas pressures of 0.4-1 Pa was studied experimentally. At an auxiliary arc-discharge current of 100 A and a main discharge voltage of 240 V, a pulse-periodic glow discharge with a current amplitude of 370 A, pulse duration of 340 μs, and repetition rate of 1 kHz was obtained. The possibility of creating a uniform gas-discharge plasma with a density of up to 1012 cm-3 and an electron temperature of 1 eV in a volume of >0.2 m3 was demonstrated. Such plasma can be efficiently used to treat material surfaces and generate pulsed ion beams with a current density of up to 15 mA/cm2.

  3. Structural properties of nitrogenated amorphous carbon films: Influence of deposition temperature and radiofrequency discharge power

    SciTech Connect

    Lazar, G.; Bouchet-Fabre, B.; Zellama, K.; Clin, M.; Ballutaud, D.; Godet, C.

    2008-10-01

    The structural properties of nitrogenated amorphous carbon deposited by radiofrequency magnetron sputtering of graphite in pure N{sub 2} plasma are investigated as a function of the substrate temperature and radiofrequency discharge power. The film composition is derived from x-ray photoemission spectroscopy, nuclear reaction analysis and elastic recoil detection measurements and the film microstructure is discussed using infrared, Raman, x-ray photoemission and near edge x-ray absorption fine structure spectroscopic results. At low deposition temperature and low radiofrequency power, the films are soft, porous, and easily contaminated with water vapor and other atmospheric components. The concentration of nitrogen in the films is very large for low deposition temperatures ({approx}33.6 at. % N at 150 deg. C) but decreases strongly when the synthesis temperature increases ({approx}15 at. % N at 450 deg. C). With increasing deposition temperature and discharge power values, the main observed effects in amorphous carbon nitride alloys are a loss of nitrogen atoms, a smaller hydrogen and oxygen contamination related to the film densification, an increased order of the aromatic sp{sup 2} phase, and a strong change in the nitrogen distribution within the carbon matrix. Structural changes are well correlated with modifications of the optical and transport properties.

  4. Production of Excess Heat, Impurity Elements and Unnatural Isotopic Ratios in High-Current Glow Discharge Experiments

    NASA Astrophysics Data System (ADS)

    Karabut, A. B.

    2005-12-01

    Results recorded for excess heat measurements in experiments with a high-current glow discharge in D2, Xe and Kr, using previously deuterated Pd and Ti cathode samples, are presented. Excess power up to 10-15 W (and efficiency up to 150%) was recorded for the experiments with a Pd cathode samples in a D2 discharge. Excess power up to 5 W (and efficiency up to 150%) was recorded for previously deuterated Pd cathode samples in Xe and Kr discharges. Excess heat was not observed in similar experiments using pure Pd cathode samples in Xe and Kr discharges. The production of impurity nuclides (7Li, 13C, 15N, 20Ne, 29Si, 44Ca, 48Ca, 56Fe, 57Fe, 59Co, 64Zn, 66Zn, 75As, 107Ag, 109Ag, 110Cg, 111Cg, 112Cg, 114Cg, and 115In) at a rate of up to 1013 atoms/s was recorded. Soft x-ray radiation from the solid-state cathode (with an intensity up to 0.01 Gy/s) was recorded for discharge experiments carried out in H2, D2, Ar, Xe, Kr. X-ray radiation was observed as bursts (up to 106 photons in a burst and up to 105 bursts a second) during the discharge and within 100 ms after turning off the discharge current. The x-ray radiation data showed that excited energy levels having the lifetime up to 100 ms, and more, and an energy of 1.2-1.8 keV, exist in the solid medium. Possible mechanisms for producing the excess heat, and products of nuclear transmutation reactions, in the solid medium with such excited energy levels is considered.

  5. Static current-voltage characteristics for radio-frequency induction discharge

    SciTech Connect

    Budyansky, A.; Zykov, A.

    1995-12-31

    The aim of this work was to obtain experimentally such characteristic of Radio-Frequency Induction Discharge (RFID) that can play the role of its current-voltage characteristic (CVC) and to explain the nature of current and voltage jumps arising in RF coils at exciting of discharge. Experiments were made in quartz 5.5, 11, 20 cm diam tubes with outer RF coil at pressures 10--100 mTorr, at frequency 13.56 MHz and discharge power to 500 W. In case of outer coil as analogue of discharge voltage it`s convenient to use the value of the RF voltage U{sub R}, induced around outer perimeter of discharge tube. It is evident that current and voltage jumps arising at exciting of discharge are due to low output resistance of standard generators and negative slope of initial part of CVC. Three sets of such dependencies for different pressures were obtained for each diameter of tubes. The influence of different metal electrodes placed into discharge volume on CVC`s shape has been studied also. Experimental results can explain the behavior of HFI discharge as a load of RF generator and give data for calculation of RF circuit.

  6. Canard and mixed mode oscillations in an excitable glow discharge plasma in the presence of inhomogeneous magnetic field

    SciTech Connect

    Shaw, Pankaj Kumar Sekar Iyengar, A. N.

    2015-12-15

    We report on the experimental observation of canard orbit and mixed mode oscillations (MMOs) in an excitable glow discharge plasma induced by an external magnetic field perturbation using a bar magnet. At a small value of magnetic field, small amplitude quasiperiodic oscillations were excited, and with the increase in the magnetic field, large amplitude oscillations were excited. Analyzing the experimental results, it seems that the magnetic field could be playing the role of noise for such nonlinear phenomena. It is observed that the noise level increases with the increase in magnetic field strength. The experimental results have also been corroborated by a numerical simulation using a FitzHugh-Nagumo like macroscopic model derived from the basic plasma equations and phenomenology, where the noise has been included to represent the internal plasma noise. This macroscopic model shows MMO in the vicinity of the canard point when an external noise is added.

  7. Submillimeter-wave rotational spectra of DNC in highly excited vibrational states observed in an extended negative glow discharge

    NASA Astrophysics Data System (ADS)

    Amano, T.

    2011-05-01

    Rotational transitions of DNC have been observed in the submillimeter-wave region in an extended negative glow discharge in a gas mixture of CD 4 and N 2. The dissociative recombination reaction of DCND + with electrons is thought to be a dominant channel to produce DNC in highly excited vibrational states. The vibrational temperature for the ν3 vibrational mode is found to be about 4000 K, and the rotational lines in levels up to (0 0 8) are observed. The rotational and centrifugal distortion constants are determined for these states along with those for the (1 0 0) state. The measurement accuracy is high enough to determine some higher order vibration-rotation interaction constants.

  8. Impurity Studies of Cd(0.8)Zn(0.2)Te Crystals Using Photoluminescence and Glow Discharge Mass Spectroscopy

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Lehoczky, Sandor L.; Scripa, Rosalie N.

    2005-01-01

    Cd(1-x)Zn(x)Te semiconductor crystal is a highly promising material for room temperature x- and gamma-ray detector applications because of its high resistivity, long carrier lifetime, and relatively high hole and electron mobilities. This paper reports the investigation of the impurities in several Cd(1-x)Zn(x)Te (x = 0.20) crystals grown using the vertical Bridgman method under a Cd overpressure. The impurity concentrations were measured using glow discharge mass spectroscopy (GDMS). The energy states of the impurities were studied using photoluminescence (PL) spectroscopy at liquid helium temperature. The PL spectra showed a series of sharp high energy lines which are associated with free excitons and excitons bound to impurities as donors and acceptors in the crystals. The impurities also contributed to donor-acceptor pair recombination. The correlation between the GDMS and PL results will be reported.

  9. Evaluation of the stiffness and friction of Ti6Al4V ELI treated by glow discharge nitriding

    NASA Astrophysics Data System (ADS)

    Tavera, J. R.; Peña Ballesteros, D. Y.; Estupiñán Duran, H. A.

    2016-02-01

    In this study, an evaluation of the elastic-plastic surface hardening on Ti6Al4V ELI titanium nitride films obtained by glow discharge method was carried out by nanoindentation tests according to the standard ISO 14577. The nanotribological properties (metal-metal) were also evaluated using the pin-on-disc system Ti6Al4V surface deposition ELI with nitrogen, obtaining a correlation between the coefficient of friction of Ti6Al4V ELI treated by PVD and the Young's modulus of the respective substrate modified by PVD. To characterize the substrate for the characterization tests, scanning electron microscopy, atomic force microscopy and X-ray diffraction and contact angle were carried out. The results demonstrated that the substrates nitrided improved mechanical and tribological properties, hardness, Young's modulus and coefficient of friction, making the alloy Ti6Al4V ELI support axial loads in tension and compression.

  10. The role of oxygen in analytical glow discharges: GD-OES and GD-ToF-MS studies

    NASA Astrophysics Data System (ADS)

    Mushtaq, Sohail; Pickering, Juliet C.; Steers, Edward B. M.; Horvath, Peter; Whitby, James A.; Michler, Johann

    2010-11-01

    The influence of up to 0.8 % O2 on the Ar plasma in a dc analytical glow discharge was studied on Fe, Ti, Cu and Au samples using time of flight mass spectrometry and high resolution optical Fourier transform spectrometry. All positive ion signals decreased gradually by 2 to 3 orders of magnitude with increasing O2. In addition, a sudden 100-fold drop of the ion signals also occurred for Fe and Ti samples at 0.1 % and 0.05 % O2 concentrations, respectively. Optical emission spectra of Fe I, Fe II, Ti I and Ti II in Ar/O2 plasmas also showed a sudden drop of intensity at the same concentrations. This was accompanied by a 20-fold drop in sputter rate for Fe and Ti, whereas the sputter rate changed less for Cu and only slightly for Au. The role of surface and gas-phase processes will be discussed in the presentation.

  11. Final Report DE-FG02-00ER54583: "Physics of Atmospheric Pressure Glow Discharges" and "Nanoparticle Nucleation and Dynamics in Low-Pressure Plasmas"

    SciTech Connect

    Uwe Kortshagen; Joachim Heberlein; Steven L. Girshick

    2009-06-01

    This project was funded over two periods of three years each, with an additional year of no-cost extension. Research in the first funding period focused on the physics of uniform atmospheric pressure glow discharges, the second funding period was devoted to the study of the dynamics of nanometer-sized particles in plasmas.

  12. Influence of Operating Parameters on Surface Properties of RF Glow Discharge Oxygen Plasma Treated TiO2/PET Film for Biomedical Application

    EPA Science Inventory

    Thin transparent titania (TiO2) films were coated on the surface of flexible poly (ethylene terephthalate) (PET) surface using standard sol gel techniques. The TiO2/PET thin film surfaces were further modified by exposing the films to a RF glow discharge oxygen plasma. The exposu...

  13. The effect of frequency on atmospheric pressure glow discharge in a pin-to-plate gap sustained by a resonant power supply

    NASA Astrophysics Data System (ADS)

    Wang, Yong Sheng; Ding, Wei Dong; Wang, Ya Nan; Wang, Jia Chen; Li, Fang; Fan, Chuan

    2016-06-01

    More and more researchers have been attracted to the research of atmospheric pressure glow discharge (APGD) because of its great prospect in numerous industrial applications. Nevertheless, almost all of the industrial applications are based on achievement of stable, large-volume, and uniform APGD. In a previous study, stable filamentary APGD was obtained by applying a resonant power supply between pin-to-plate electrodes which could limit the peak value of discharge current to supress the glow-to-arc transition through a series-wound resonance principle. The filamentary APGD is centimeter-level in the length but only several millimeters in diameter. Therefore, in order to obtain large-volume and uniform APGD, it is significant to study how to diffuse filamentary APGD in radial direction. With the increasing resonant frequency of alternating current discharge, excited particles (mainly including energetic electrons and trapped ions left from the previous half-cycle discharge) in the electrodes gap increase, which benefits obtaining stable self-sustaining APGD. In this paper, mechanism and law of the influence of resonant frequency on the diffusion of filamentary APGD in ambient air were studied. By comparing the photos of discharge plasma and waveforms of the discharge voltage and current, it is found that the volume of the glow discharge plasma enlarges as the resonant frequency of the power supply increases. It is very significant and anticipating to study how to obtain stable, large-volume, and uniform APGD in ambient air by the resonant power supply.

  14. An oscillator circuit to produce a radio-frequency discharge and application to metastable helium saturated absorption spectroscopy

    SciTech Connect

    Moron, F.; Hoendervanger, A. L.; Bonneau, M.; Bouton, Q.; Aspect, A.; Boiron, D.; Clement, D.; Westbrook, C. I.

    2012-04-15

    We present a rf gas discharge apparatus which provides an atomic frequency reference for laser manipulation of metastable helium. We discuss the biasing and operation of a Colpitts oscillator in which the discharge coil is part of the oscillator circuit. Radiofrequency radiation is reduced by placing the entire oscillator in a metal enclosure.

  15. Generation of Volatile Cadmium and Zinc Species Based on Solution Anode Glow Discharge Induced Plasma Electrochemical Processes.

    PubMed

    Liu, Xing; Liu, Zhifu; Zhu, Zhenli; He, Dong; Yao, Siqi; Zheng, Hongtao; Hu, Shenghong

    2017-02-27

    In this study, a novel high efficiency vapor generation strategy was proposed on the basis of solution anode glow discharge for the determination of Cd and Zn by atomic fluorescence spectrometry. In this approach, a glow discharge microplasma was acted as a gaseous cathode to initiate the plasma electrochemical vapor generation of Cd and Zn. Cadmium/zinc ions could be converted into molecular species efficiently at the plasma-liquid interface from a supporting electrolyte (HCl, pH = 3.2). It was found that the overall efficiency of the plasma electrochemical vapor generation (PEVG) system was much higher than the conventional electrochemical hydride generation (EcHG) and HCl-KBH4 system. With no requirement for other reducing reagents, this new approach enabled us to detect Cd and Zn with detection limits as low as 0.003 μg L(-1) for Cd and 0.3 μg L(-1) for Zn. Good repeatability (relative standard deviation (RSD), n = 5) was 2.4% for Cd (0.1 μg L(-1)) and 1.7% for Zn (10 μg L(-1)) standard. The accuracy of the proposed method was successfully validated through analysis of cadmium in reference material of stream sediment (GBW07311), soil (GBW07401), rice (GBW10045), and zinc in a simulated water sample (GSB 07-1184-2000). Replacing a metal electrode with a plasma offers the advantage of eliminating potential interactions between the species in liquid and the electrode, which solves the issues associated with electrode encountered in conventional EcHG. The ability to initiate electrochemical vapor generation reactions at the plasma-liquid interface opens a new approach for chemical vapor generation based on interactions between plasma gas-phase electrons and solutions.

  16. Experimental evidence of intermittent chaos in a glow discharge plasma without external forcing and its numerical modelling

    SciTech Connect

    Ghosh, S. Kumar Shaw, Pankaj; Sekar Iyengar, A. N.; Janaki, M. S.; Saha, Debajyoti; Michael Wharton, Alpha

    2014-03-15

    Intermittent chaos was observed in a glow discharge plasma as the system evolved from regular type of relaxation oscillations (of larger amplitude) to an irregular type of oscillations (of smaller amplitude) as the discharge voltage was increased. Floating potential fluctuations were analyzed by different statistical and spectral methods. Features like a gradual change in the normal variance of the interpeak time intervals, a dip in the skewness, and a hump in the kurtosis with variation in the control parameter have been seen, which are strongly indicative of intermittent behavior in the system. Detailed analysis also suggests that the intrinsic noise level in the experiment increases with the increasing discharge voltage. An attempt has been made to model the experimental observations by a second order nonlinear ordinary differential equation derived from the fluid equations for an unmagnetized plasma. Though the experiment had no external forcing, it was conjectured that the intrinsic noise in the experiment could be playing a vital role in the dynamics of the system. Hence, a constant bias and noise as forcing terms were included in the model. Results from the theoretical model are in close qualitative agreement with the experimental results.

  17. Degradation of bisphenol A and formation of hydrogen peroxide induced by glow discharge plasma in aqueous solutions.

    PubMed

    Wang, Lei; Jiang, Xuanzhen; Liu, Yongjun

    2008-06-15

    Degradation of bisphenol A (BPA) and simultaneous formation of hydrogen peroxide induced by glow discharge plasma in contact with aqueous solution were investigated. Experimental results indicated that the BPA degradation rate was higher in sodium chloride solution than that in sodium sulfate or phosphate solutions. However, the formation rates of hydrogen peroxide were on the opposite case. Both the BPA removal and the hydrogen peroxide production rates decreased in the presence of hydroxyl radical scavengers, indicating that hydroxyl radicals are the most probable oxidants responsible for BPA degradation and the precursors of hydrogen peroxide. Ferric ion showed better catalytic effect than that of ferrous ion, suggesting that the ferric ion was reduced by the intermediates formed during BPA degradation, which was confirmed by following the production of ferrous ion in the system. TOC of the solution gradually reduced with discharge time; however, without catalysts, the solution COD increased with discharge time and sharply decreased in the presence of iron salts. The major intermediate products were identified by LC/MS and the possible degradation mechanism was discussed.

  18. Spatially resolved measurements to improve analytical performance of solution-cathode glow discharge optical-emission spectrometry

    NASA Astrophysics Data System (ADS)

    Schwartz, Andrew J.; Ray, Steven J.; Chan, George C.-Y.; Hieftje, Gary M.

    2016-11-01

    Past studies of the solution-cathode glow discharge (SCGD) revealed that elemental and molecular emission are not spatially homogenous throughout the source, but rather conform to specific zones within the discharge. Exploiting this inhomogeneity can lead to improved analytical performance if emission is collected only from regions of the discharge where analyte species emit strongly and background emission (from continuum, elemental and/or molecular sources) is lower. Effects of this form of spatial discrimination on the analytical performance of SCGD optical emission spectrometry (OES) have been investigated with an imaging spectrograph for fourteen atomic lines, with emphasis on detection limits and precision. Vertical profiles of the emission intensity, signal-to-background ratio, and signal-to-noise ratio were collected and used to determine the optimal region to view the SCGD on a per-element basis. With optimized spatial filtering, detection limits ranged from 0.09-360 ppb, a 1.4-13.6 fold improvement over those obtained when emission is collected from the full vertical profile (1.1-840 ppb), with a 4.2-fold average improvement. Precision was found to be unaffected by spatial filtering, ranging from 0.5-2.6% relative standard deviation (RSD) for all elements investigated, closely comparable to the 0.4-2.4% RSD observed when no spatial filtering is used. Spatial profiles also appear useful for identifying optimal line pairs for internal standardization and for flagging the presence of matrix interferences in SCGD-OES.

  19. FAST TRACK COMMUNICATION: Contrasting characteristics of sub-microsecond pulsed atmospheric air and atmospheric pressure helium-oxygen glow discharges

    NASA Astrophysics Data System (ADS)

    Walsh, J. L.; Liu, D. X.; Iza, F.; Rong, M. Z.; Kong, M. G.

    2010-01-01

    Glow discharges in air are often considered to be the ultimate low-temperature atmospheric pressure plasmas for numerous chamber-free applications. This is due to the ubiquitous presence of air and the perceived abundance of reactive oxygen and nitrogen species in air plasmas. In this paper, sub-microsecond pulsed atmospheric air plasmas are shown to produce a low concentration of excited oxygen atoms but an abundance of excited nitrogen species, UV photons and ozone molecules. This contrasts sharply with the efficient production of excited oxygen atoms in comparable helium-oxygen discharges. Relevant reaction chemistry analysed with a global model suggests that collisional excitation of O2 by helium metastables is significantly more efficient than electron dissociative excitation of O2, electron excitation of O and ion-ion recombination. These results suggest different practical uses of the two oxygen-containing atmospheric discharges, with air plasmas being well suited for nitrogen and UV based chemistry and He-O2 plasmas for excited atomic oxygen based chemistry.

  20. Numerical simulation of capacitively-coupled, radio-frequency plasma discharges

    NASA Astrophysics Data System (ADS)

    Hammond, Edward Percy, IV

    This research develops a novel, non-dissipative discretization for the drift-diffusion expression of electron flux in capacitively-coupled, radio-frequency plasma discharges. The new discretization is more robust and accurate than commonly used numerical techniques when applied to the solution of the plasma fluid equations. On a relatively coarse grid, the method provides results within a few percent of the grid-converged solution. Low-order upwinding, a common method for discretization of the electron flux; introduces significant robustness. However, on the same coarse grid, the plasma density can differ from the grid-converged result by nearly a factor of two. Another popular discretization of the electron flux is the Scharfetter-Gummel method. Although it is accurate on coarse grids, it is more expensive computationally due to its non-linear nature, and it introduces an additional approximation. It neglects the electron temperature gradient in the flux expression; this can affect the plasma density as much as 20%. A formal method for accelerating the solution towards the periodic, steady-state solution in one and multiple dimensions is also described. Direct integration of the governing equations in time will lead to the harmonic steady-state, but this may require tens or hundreds of thousands of radio-frequency periods when the plasma discharge contains significant neutral species that develop on a time-scale much longer than a radio-frequency period. In contrast, the acceleration scheme can reach the periodic steady-state in a few hundred to a few thousand radio-frequency periods. Previous efforts that used formal acceleration schemes were limited to one dimension. Finally, a fluid model of an argon plasma is developed and compared to experimental data at conditions relevant to low-pressure, capacitively-coupled plasma discharges. The computed results agree reasonably well with the experiments both quantitatively and qualitatively. This model is then used to

  1. Radio-Frequency Downstream Plasma Production by Surface-Wave in a Very High-Permittivity Material Discharge Tube

    NASA Astrophysics Data System (ADS)

    Fujiwara, Kazuya; Endo, Masakatsu; Ikeda, Yasushi; Suzuki, Tsutomu; Yanagisawa, Michihiko; Shindo, Haruo

    2005-03-01

    A novel method of radio-frequency surface-wave plasma production is proposed, with a particular interest in use of a very high permittivity material discharge tube. A discharge tube of TiCa-TiMg composite, which has the permittivity of 140, is employed to produce SF6 plasma by the 13.56 MHz radio-frequency power. The axial distribution of optical emission lines of fluorine shows a rapid decay, more than 5 times faster than that in quartz tube. This is because the speed of the surface-wave is reduced in a condition of very high permittivity. It is concluded that the method is innovative in use of radio-frequency power to produce downstream plasma with a very high permittivity discharge tube.

  2. Pulsed radio-frequency discharge inductively coupled plasma mass spectrometry for oxide analysis

    NASA Astrophysics Data System (ADS)

    Li, Weifeng; Yin, Zhibin; Hang, Wei; Li, Bin; Huang, Benli

    2016-08-01

    A direct solid sampling technique has been developed based on a pulsed radio-frequency discharge (RFD) in mixture of N2 and Ar environment at atmospheric pressure. With an averaged input power of 65 W, a crater with the diameter of 80 μm and depth of 50 μm can be formed on sample surface after discharge for 1 min, suggesting the feasibility of the pulsed RFD for sampling nonconductive solids. Combined with inductively coupled plasma mass spectrometry (ICPMS), this technique allows to measure elemental composition of solids directly with relative standard deviation (RSD) of ~ 20%. Capability of quantitative analysis was demonstrated by the use of soil standards and artificial standards. Good calibration linearity and limits of detection (LODs) in range of 10- 8-10- 9 g/g were achieved for most elements.

  3. Modification of hydrophobic acrylic intraocular lens with poly(ethylene glycol) by atmospheric pressure glow discharge: A facile approach

    NASA Astrophysics Data System (ADS)

    Lin, Lin; Wang, Yao; Huang, Xiao-Dan; Xu, Zhi-Kang; Yao, Ke

    2010-10-01

    To improve the anterior surface biocompatibility of hydrophobic acrylic intraocular lens (IOL) in a convenient and continuous way, poly(ethylene glycol)s (PEGs) were immobilized by atmospheric pressure glow discharge (APGD) treatment using argon as the discharge gas. The hydrophilicity and chemical changes on the IOL surface were characterized by static water contact angle and X-ray photoelectron spectroscopy to confirm the covalent binding of PEG. The morphology of the IOL surface was observed under field emission scanning electron microscopy and atomic force microscopy. The surface biocompatibility was evaluated by adhesion experiments with platelets, macrophages, and lens epithelial cells (LECs) in vitro. The results revealed that the anterior surface of the PEG-grafted IOL displayed significantly and permanently improved hydrophilicity. Cell repellency was observed, especially in the PEG-modified IOL group, which resisted the attachment of platelets, macrophages and LECs. Moreover, the spread and growth of cells were suppressed, which may be attributed to the steric stabilization force and chain mobility effect of the modified PEG. All of these results indicated that hydrophobic acrylic IOLs can be hydrophilic modified by PEG through APGD treatment in a convenient and continuous manner which will provide advantages for further industrial applications.

  4. Effect of DC glow discharge plasma treatment on PET/TiO(2) thin film surfaces for enhancement of bioactivity.

    PubMed

    Navaneetha Pandiyaraj, K; Selvarajan, V; Rhee, Young Ha; Kim, Hyoung Woo; Pavese, Matteo

    2010-08-01

    In this paper, the surfaces of PET/TiO(2) thin film were modified by DC glow discharge plasma as a function of discharge potentials for improving the bioactivity. The hydrophilicity of the plasma-treated PET/TiO(2) film was measured by contact angle measurement and the surface energy was estimated by using Fowkes method. The structural and chemical composition of the plasma-treated PET/TiO(2) was analysed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Immersion in a simulated body solution (SBF) solution was used to evaluate the bioactivity of the plasma-treated PET/TiO(2) samples in vitro. It was found that the plasma treatment modified the surfaces both in chemical composition and crystallinity which makes surface of the PET/TiO(2) to become more hydrophilic compared with untreated one. Analytical and microstructural investigations of SBF results, showed considerable higher rates of apatite formation on the plasma-treated PET/TiO(2) compared to the untreated films.

  5. Signal enhancement in solution-cathode glow discharge — optical emission spectrometry via low molecular weight organic compounds

    NASA Astrophysics Data System (ADS)

    Doroski, Todd A.; Webb, Michael R.

    2013-10-01

    HCOOH, CH3COOH, and CH3CH2OH were used as chemical modifiers in a solution-cathode glow discharge. Emission was measured directly from the discharge, without a gas-liquid separator or a secondary excitation source. Emission from Ag, Se, Pb, and Hg was strongly enhanced, and the detection limits (DL) for these elements were improved by up to an order of magnitude using a combination of HCOOH and HNO3 compared to using HNO3 alone. The DL was measured for Mg (1 μg/L), Fe (10 μg/L), Ni (6 μg/L), Cu (6 μg/L), Pb (1 μg/L), Ag (0.1 μg/L), Se (300 μg/L), and Hg (2 μg/L). Coefficients of determination (R2) were between 0.9986 and 0.9999. A voltage of 1 kV was used, which produced a current of approximately 70 mA.

  6. Evaluation of a pulsed glow discharge time-of-flight mass spectrometer as a detector for gas chromatography and the influence of the glow discharge source parameters on the information volume in chemical speciation analysis.

    PubMed

    Fliegel, Daniel; Fuhrer, Katrin; Gonin, Marc; Günther, Detlef

    2006-09-01

    The figures of merit of a pulsed glow discharge time-of-flight mass spectrometer (GD-TOFMS) as a detector for gas chromatography (GC) analysis were evaluated. The mass resolution for the GD-TOFMS was determined on FWHM in the high mass range (208Pb+) as high as 5,500. Precision of 400 subsequent analyses was calculated on 63Cu+ to be better than 1% RSD with no significant drift over the time of the analysis. Isotope precision based on the 63Cu+/65Cu+ ratio over 400 analyses was 1.5% RSD. The limits of detection for gaseous analytes (toluene in methanol as solvent) were determined to be as low as several hundred ppb or several hundred pg absolute without using any pre-concentration technique. Furthermore, the different GD source parameters like capillary distance, cathode-anode spacing, and GD source pressure with regards to the accessible elemental, structural, and molecular information were evaluated. It was demonstrated that each of these parameters has severe influence on the ratio of elemental, structural, and parent molecular information in chemical speciation analysis.

  7. Separation of Radio-Frequency Sources and Localization of Partial Discharges in Noisy Environments

    PubMed Central

    Robles, Guillermo; Fresno, José Manuel; Martínez-Tarifa, Juan Manuel

    2015-01-01

    The detection of partial discharges (PD) can help in early-warning detection systems to protect critical assets in power systems. The radio-frequency emission of these events can be measured with antennas even when the equipment is in service which reduces dramatically the maintenance costs and favours the implementation of condition-based monitoring systems. The drawback of these type of measurements is the difficulty of having a reference signal to study the events in a classical phase-resolved partial discharge pattern (PRPD). Therefore, in open-air substations and overhead lines where interferences from radio and TV broadcasting and mobile communications are important sources of noise and other pulsed interferences from rectifiers or inverters can be present, it is difficult to identify whether there is partial discharges activity or not. This paper proposes a robust method to separate the events captured with the antennas, identify which of them are partial discharges and localize the piece of equipment that is having problems. The separation is done with power ratio (PR) maps based on the spectral characteristics of the signal and the identification of the type of event is done localizing the source with an array of four antennas. Several classical methods to calculate the time differences of arrival (TDOA) of the emission to the antennas have been tested, and the localization is done using particle swarm optimization (PSO) to minimize a distance function. PMID:25923935

  8. Separation of radio-frequency sources and localization of partial discharges in noisy environments.

    PubMed

    Robles, Guillermo; Fresno, José Manuel; Martínez-Tarifa, Juan Manuel

    2015-04-27

    The detection of partial discharges (PD) can help in early-warning detection systems to protect critical assets in power systems. The radio-frequency emission of these events can be measured with antennas even when the equipment is in service which reduces dramatically the maintenance costs and favours the implementation of condition-based monitoring systems. The drawback of these type of measurements is the difficulty of having a reference signal to study the events in a classical phase-resolved partial discharge pattern (PRPD). Therefore, in open-air substations and overhead lines where interferences from radio and TV broadcasting and mobile communications are important sources of noise and other pulsed interferences from rectifiers or inverters can be present, it is difficult to identify whether there is partial discharges activity or not. This paper proposes a robust method to separate the events captured with the antennas, identify which of them are partial discharges and localize the piece of equipment that is having problems. The separation is done with power ratio (PR) maps based on the spectral characteristics of the signal and the identification of the type of event is done localizing the source with an array of four antennas. Several classical methods to calculate the time differences of arrival (TDOA) of the emission to the antennas have been tested, and the localization is done using particle swarm optimization (PSO) to minimize a distance function.

  9. Radio frequency glow discharge source with integrated voltage and current probes used for sputtering rate and emission yield measurements at insulating samples.

    PubMed

    Wilken, L; Hoffmann, V; Wetzig, K

    2005-10-01

    Radio frequency glow discharge optical emission spectroscopy (RF-GD-OES) is routinely used for the chemical analysis of solid samples. Two independent electrical signals from the discharge are required for quantification. When sputtering insulating samples, the voltage over the discharge is not directly measurable. The coupling capacity of the sample is required in order to calculate the discharge voltage. A procedure is outlined where the coupling capacity is determined using an electrical measurement without discharge. The calculated time-dependent discharge voltage and current are evaluated using a plasma equivalent circuit. An insulating sample is sputtered at constant cathode voltage and current. The emission yield for an aluminium line is comparable to that of conducting reference material.

  10. Absolute Spatially- and Temporally-Resolved Optical Emission Measurements of rf Glow Discharges in Argon

    PubMed Central

    Djurović, S.; Roberts, J. R.; Sobolewski, M. A.; Olthoff, J. K.

    1993-01-01

    Spatially- and temporally-resolved measurements of optical emission intensities are presented from rf discharges in argon over a wide range of pressures (6.7 to 133 Pa) and applied rf voltages (75 to 200 V). Results of measurements of emission intensities are presented for both an atomic transition (Ar I, 750.4 nm) and an ionic transition (Ar II, 434.8 nm). The absolute scale of these optical emissions has been determined by comparison with the optical emission from a calibrated standard lamp. All measurements were made in a well-defined rf reactor. They provide detailed characterization of local time-resolved plasma conditions suitable for the comparison with results from other experiments and theoretical models. These measurements represent a new level of detail in diagnostic measurements of rf plasmas, and provide insight into the electron transport properties of rf discharges. PMID:28053464

  11. Distribution of Electric Field across Shock Structure Propagating through a DC Glow Discharge

    NASA Astrophysics Data System (ADS)

    Popovic, S.; Vuskovic, L.

    1998-10-01

    A number of experiments confirmed the existence of double electric layer (DEL) due to ambipolar diffusion of electrons and ions in the shock front propagating through partially ionized gas. It was used to visualize shock shapes with an electric discharge transverse to the flow. Charge separation generated local electric field that interacted with the electric field of the discharge, to slow down the electron drift, and resulted in a decrease of luminosity along shock front. DEL effect was used to demonstrate a "bow shock generator." Voltage difference between upstream and downstream region of partially ionized gas depended on shock strength manifested in electron temperature and number density gradients. These two gradients did not necessarily coincide, and more than one DEL could be associated with the shock. Based on these facts, we derived reduced electric field distributions in a planar and oblique shock structure. We also determined the parameters and stability criteria for the regions of enhanced degree of ionization associated with DEL.

  12. Opto-galvanic effect on degenerate magnetic states of sputtered atoms in a glow discharge

    NASA Astrophysics Data System (ADS)

    Zhechev, D.; Steflekova, V.

    2014-12-01

    The opto-galvanic response of some degenerate states of sputtered atoms to linearly- and circularly polarize light is studied. On the same optical transition both time-resolved- and amplitude opto-galvanic signals are found depending on the polarizations of light absorbed. The latter induces galvanic responses differing in opto-galvanic efficiency, time-evolution and sensitivity to discharge current and laser power. The differences are ascribed to the rate constants of the decay processes, characterizing aligned and oriented atoms.

  13. Progress on the development of a 2-D PIC/Monte Carlo model of glow discharges

    NASA Astrophysics Data System (ADS)

    Greene, A. E.; Faehl, R. J.; Keinigs, R. K.; Oliphant, T. A., Jr.; Shanahan, W. R.

    There are several computational approaches that have been and are being implemented for the investigation of plasma processing discharges. One-dimensional electrostatic PIC calculations have proven useful in modeling the bulk properties of discharges far from the edges and have yielded good agreement with experiment for ion distributions in the sheath region. The value of PIC methods is that they follow the evolution of an N-body system unconstrained by equilibrium requirements. Gaseous discharges are in general far from equilibrium. Electrons in the bulk region and ions in the sheath can have energies greatly exceeding the neutral gas temperature and can be distributed in a highly non-Maxwellian fashion. One dimensional models are incapable of treating flow and transport of reactants in reactors properly. Geometrical features are also neglected. Modeling the more recently developed high density reactors, such as the Hitachi ECRH source, requires at least two-dimensional and possibly three-dimensional electromagnetic models. Therefore, at Los Alamos we have chosen to address these problems with the MERLIN code. In this paper we will discuss our progress toward developing this code. We will describe, briefly the physics that we are including in this model. We will discuss a test problem that is being used to exercise most of the new features that have recently been added to MERLIN. Finally, we will discuss our future efforts.

  14. Dust particle circulation and vortices in a dc glow discharge dusty plasma

    NASA Astrophysics Data System (ADS)

    Kish, Ayden; Thomas, Edward

    2016-10-01

    Complex, or dusty, plasmas introduce a new charged species - dust grains of up to a few microns in diameter - to the dynamics of a background plasma discharge. While the size of these dust grains allow us to observe many plasma phenomena macroscopically, their presence also results in the generation of other processes that are unique to dusty plasmas. This presentation reports the observations of a recent study of toroidally-shaped dust clouds in a direct-current Argon plasma discharge. These dusty plasma clouds are formed by placing a conducting ring on a lower electrode while generating the plasma using an upper, biased electrode. Dust particles become suspended in the plasma between the two electrodes and, under the correct pressure and discharge conditions, the toroidally-shaped cloud is formed. This work reports on a variety of experimental configurations used to generate the clouds, measurements of particle flow and rotation using particle image velocimetry (PIV), and initial characterization of the plasma conditions that lead to the formation of these structures. Auburn University Undergraduate Research Fellowship and U.S. Department of Energy Grant Number DE-SC0010485.

  15. Generation of multiple toroidal dust vortices by a non-monotonic density gradient in a direct current glow discharge plasma

    SciTech Connect

    Kaur, Manjit Bose, Sayak; Chattopadhyay, P. K.; Sharma, D.; Ghosh, J.; Saxena, Y. C.; Thomas, Edward

    2015-09-15

    Observation of two well-separated dust vortices in an unmagnetized parallel plate DC glow discharge plasma is reported in this paper. A non-monotonic radial density profile, achieved by an especially designed cathode structure using a concentric metallic disk and ring of different radii, is observed to produce double dust tori between cathode and anode. PIV analysis of the still images of the double tori shows oppositely rotating dust structures between the central disk and the ring. Langmuir probe measurements of background plasma shows a non-uniform plasma density profile between the disk and the ring. Location and sense of rotation of the dust vortices coincides with the location and direction of the radial gradient in the ion drag force caused by the radial density gradient. The experimentally observed dust vorticity matches well with the calculated one using hydrodynamic formulations with shear in ion drag dominating over the dust charge gradient. These results corroborate that a radial gradient in the ion drag force directed towards cathode is the principal cause of dust rotation.

  16. Shock compression of glow discharge polymer (GDP): density functional theory (DFT) simulations and experiments on Sandia's Z-machine

    NASA Astrophysics Data System (ADS)

    Mattsson, Thomas R.; Cochrane, K. R.; Ao, T.; Lemke, R. W.; Flicker, D. G.; Schoff, M. E.; Blue, B. E.; Hamel, S.; Herrmann, M. C.

    2015-11-01

    Glow discharge polymer (GDP) is used extensively as capsule/ablation material in inertial confinement fusion (ICF) capsules. Accurate knowledge of the equation of state (EOS) under shock and release is particularly important for high-fidelity design, analysis, and optimization of ICF experiments since the capsule material is subject to several converging shocks as well as release towards the cryogenic fuel. We performed Density Functional Theory (DFT) based quantum molecular dynamics (QMD) simulations, to gain knowledge of the behavior of GDP - including the effect of changes in chemical composition. The shock pressures calculated from DFT are compared experimental data taken on magnetically launched flyer plate impact experiments on at Sandia's Z-machine. Large GDP samples were grown in a planar geometry to improve the sample quality and maintained in a nitrogen atmosphere following manufacturing, thus allowing for a direct comparison to the DFT/QMD simulations. Sandia National Laboratories is a multi program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's NNSA under contract DE-AC04-94AL85000.

  17. Shock compression of glow discharge polymer (GDP): density functional theory (DFT) simulations and experiments on Sandia's Z-machine

    NASA Astrophysics Data System (ADS)

    Cochrane, K. R.; Ao, T.; Hamel, S.; Lemke, R. W.; Schoff, M. E.; Blue, B. E.; Herrmann, M. C.; Mattsson, T. R.

    2015-06-01

    Glow discharge polymer (GDP) is used extensively in inertial confinement fusion (ICF) capsules. Accurate knowledge of the equation of state (EOS) under shock and release is particularly important for high-fidelity design and analysis of ICF experiments since the capsule material is subject to several converging shocks as well as release towards the cryogenic fuel. We performed Density Functional Theory (DFT) based molecular dynamics simulations, to gain knowledge of the behavior of GDP - for example regarding the role of chemical dissociation during shock compression, we find that the dissociation regime along the Hugoniot extends from 50 GPa to 250 GPa. The shock pressures calculated from DFT are compared to experimental data taken on magnetically launched flyer plate impact experiments at Sandia's Z-machine. Large GDP samples were grown in a planar geometry to improve the sample quality and maintained in a nitrogen atmosphere following manufacturing, thus allowing for a direct comparison to the simulations. Sandia National Laboratories is a multi program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's NNSA under Contract DE-AC04-94AL85000

  18. Synthesis of AuPd alloyed nanoparticles via room-temperature electron reduction with argon glow discharge as electron source

    NASA Astrophysics Data System (ADS)

    Yang, Manman; Wang, Zongyuan; Wang, Wei; Liu, Chang-jun

    2014-08-01

    Argon glow discharge has been employed as a cheap, environmentally friendly, and convenient electron source for simultaneous reduction of HAuCl4 and PdCl2 on the anodic aluminum oxide (AAO) substrate. The thermal imaging confirms that the synthesis is operated at room temperature. The reduction is conducted with a short time (30 min) under the pressure of approximately 100 Pa. This room-temperature electron reduction operates in a dry way and requires neither hydrogen nor extra heating nor chemical reducing agent. The analyses using X-ray photoelectron spectroscopy (XPS) confirm all the metallic ions have been reduced. The characterization with X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) shows that AuPd alloyed nanoparticles are formed. There also exist some highly dispersed Au and Pd monometallic particles that cannot be detected by XRD and transmission electron microscopy (TEM) because of their small particle sizes. The observed AuPd alloyed nanoparticles are spherical with an average size of 14 nm. No core-shell structure can be observed. The room-temperature electron reduction can be operated in a larger scale. It is an easy way for the synthesis of AuPd alloyed nanoparticles.

  19. Synthesis of AuPd alloyed nanoparticles via room-temperature electron reduction with argon glow discharge as electron source.

    PubMed

    Yang, Manman; Wang, Zongyuan; Wang, Wei; Liu, Chang-Jun

    2014-01-01

    Argon glow discharge has been employed as a cheap, environmentally friendly, and convenient electron source for simultaneous reduction of HAuCl4 and PdCl2 on the anodic aluminum oxide (AAO) substrate. The thermal imaging confirms that the synthesis is operated at room temperature. The reduction is conducted with a short time (30 min) under the pressure of approximately 100 Pa. This room-temperature electron reduction operates in a dry way and requires neither hydrogen nor extra heating nor chemical reducing agent. The analyses using X-ray photoelectron spectroscopy (XPS) confirm all the metallic ions have been reduced. The characterization with X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) shows that AuPd alloyed nanoparticles are formed. There also exist some highly dispersed Au and Pd monometallic particles that cannot be detected by XRD and transmission electron microscopy (TEM) because of their small particle sizes. The observed AuPd alloyed nanoparticles are spherical with an average size of 14 nm. No core-shell structure can be observed. The room-temperature electron reduction can be operated in a larger scale. It is an easy way for the synthesis of AuPd alloyed nanoparticles.

  20. Synthesis of AuPd alloyed nanoparticles via room-temperature electron reduction with argon glow discharge as electron source

    PubMed Central

    2014-01-01

    Argon glow discharge has been employed as a cheap, environmentally friendly, and convenient electron source for simultaneous reduction of HAuCl4 and PdCl2 on the anodic aluminum oxide (AAO) substrate. The thermal imaging confirms that the synthesis is operated at room temperature. The reduction is conducted with a short time (30 min) under the pressure of approximately 100 Pa. This room-temperature electron reduction operates in a dry way and requires neither hydrogen nor extra heating nor chemical reducing agent. The analyses using X-ray photoelectron spectroscopy (XPS) confirm all the metallic ions have been reduced. The characterization with X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) shows that AuPd alloyed nanoparticles are formed. There also exist some highly dispersed Au and Pd monometallic particles that cannot be detected by XRD and transmission electron microscopy (TEM) because of their small particle sizes. The observed AuPd alloyed nanoparticles are spherical with an average size of 14 nm. No core-shell structure can be observed. The room-temperature electron reduction can be operated in a larger scale. It is an easy way for the synthesis of AuPd alloyed nanoparticles. PMID:25177221

  1. Atmospheric pressure glow discharge generated in nitrogen-methane gas mixture: PTR-MS analyzes of the exhaust gas

    NASA Astrophysics Data System (ADS)

    Torokova, Lucie; Mazankova, Vera; Krcma, Frantisek; Mason, Nigel J.; Matejcik, Stefan

    2015-07-01

    This paper reports the results of an extensive study of with the in situ mass spectrometry analysis of gaseous phase species produced by an atmospheric plasma glow discharge in N2-CH4 gas mixtures (with methane concentrations ranging from 1% to 4%). The products are studied using proton-transfer-reaction mass spectrometry (PTR-MS). HCN and CH3CN are identified as the main gaseous products. Hydrazine, methanimine, methyldiazene, ethylamine, cyclohexadiene, pyrazineacetylene, ethylene, propyne and propene are identified as minor compounds. All the detected compounds and their relative abundances are determined with respect to the experimental conditions (gas composition and applied power). The same molecules were observed by the Cassini-Huygens probe in Titan's atmosphere (which has same N2-CH4 gas mixtures). Such, experiments show that the formation of such complex organics in atmospheres containing C, N and H, like that of Titan, could be a source of prebiotic molecules. Contribution to the topical issue "The 14th International Symposium on High Pressure Low Temperature Plasma Chemistry (HAKONE XIV)", edited by Nicolas Gherardi, Ronny Brandenburg and Lars Stollenwark

  2. Impact of low-pressure glow-discharge-pulsed plasma polymerization on properties of polyaniline thin films

    NASA Astrophysics Data System (ADS)

    Jatratkar, Aviraj A.; Yadav, Jyotiprakash B.; Deshmukh, R. R.; Barshilia, Harish C.; Puri, Vijaya; Puri, R. K.

    2016-12-01

    This study reports on polyaniline thin films deposited on a glass substrate using a low-pressure glow-discharge-pulsed plasma polymerization method. The polyaniline thin film obtained by pulsed plasma polymerization has been successfully demonstrated as an optical waveguide with a transmission loss of 3.93 dB cm-1, and has the potential to be employed in integrated optics. An attempt has been made to investigate the effect of plasma OFF-time on the structural, optical as well as surface properties of polyaniline thin film. The plasma ON-time has been kept constant and the plasma OFF-time has been varied throughout the work. The plasma OFF-time strongly influenced the properties of the polyaniline thin film, and a nanostructured and compact surface was revealed in the morphological studies. The plasma OFF-time was found to enhance film thickness, roughness, refractive index and optical transmission loss, whereas it reduced the optical band gap of the polyaniline thin films. Retention in the aromatic structure was confirmed by FTIR results. Optical studies revealed a π-π* electronic transition at about 317 nm as well as the formation of a branched structure. As compared with continuous wave plasma, pulsed plasma polymerization shows better properties. Pulsed plasma polymerization reduced the roughness of the film from 1.2 nm to 0.42 nm and the optical transmission loss from 6.56 dB cm-1 to 3.39 dB cm-1.

  3. Separation of sources in radiofrequency measurements of partial discharges using time-power ratio maps.

    PubMed

    Albarracin, R; Robles, G; Martinez-Tarifa, J M; Ardila-Rey, J

    2015-09-01

    Partial discharges measurement is one of the most useful tools for condition monitoring of high-voltage (HV) equipment. These phenomena can be measured on-line in radiofrequency (RF) with sensors such as the Vivaldi antenna, used in this paper, which improves the signal-to-noise ratio by rejecting FM and low-frequency TV bands. Additionally, the power ratios (PR), a signal-processing technique based on the power distribution of the incoming signals in frequency bands, are used to characterize different sources of PD and electromagnetic noise (EMN). The calculation of the time length of the pulses is introduced to separate signals where the PR alone do not give a conclusive solution. Thus, if several EM sources could be previously calibrated, it is possible to detect pulses corresponding to PD activity.

  4. Effect of resonance in external radio-frequency circuit on very high frequency plasma discharge

    SciTech Connect

    Rauf, Shahid; Chen Zhigang; Collins, Ken

    2010-05-15

    A fully electromagnetic plasma model for an asymmetric capacitively coupled plasma discharge is used to understand the interaction between the external radio-frequency (rf) distributed circuit and the plasma. The plasma is excited using a 150 MHz rf source connected to the top electrode, the bottom electrode is connected to a shorted transmission line, and the electrodes are separated from the chamber walls through dielectric rings. Under typical conditions, the electron density peaks in the center of the plasma chamber due to the standing electromagnetic wave and the rf current from the top electrode primarily returns through the bottom electrode. When the electrical length of the bottom transmission line is adjusted such that it presents a large (open-circuit) impedance at the plasma chamber interface, the rf return current shifts from the bottom electrode to the chamber wall. As a consequence, the peak in electron density also moves from the center of the chamber toward its outer periphery.

  5. Comparison in the analytical performance between krypton and argon glow discharge plasmas as the excitation source for atomic emission spectrometry.

    PubMed

    Wagatsuma, Kazuaki

    2009-04-01

    The emission characteristics of ionic lines of nickel, cobalt, and vanadium were investigated when argon or krypton was employed as the plasma gas in glow discharge optical emission spectrometry. A dc Grimm-style lamp was employed as the excitation source. Detection limits of the ionic lines in each iron-matrix alloy sample were compared between the krypton and the argon plasmas. Particular intense ionic lines were observed in the emission spectra as a function of the discharge gas (krypton or argon), such as the Co II 258.033 nm for krypton and the Co II 231.707 nm for argon. The explanation for this is that collisions with the plasma gases dominantly populate particular excited levels of cobalt ion, which can receive the internal energy from each gas ion selectively, for example, the 3d(7)4p (3)G(5) (6.0201 eV) for krypton and the 3d(7)4p (3)G(4) (8.0779 eV) for argon. In the determination of nickel as well as cobalt in iron-matrix samples, more sensitive ionic lines could be found in the krypton plasma rather than the argon plasma. Detection limits in the krypton plasma were 0.0039 mass% Ni for the Ni II 230.299-nm line and 0.002 mass% Co for the Co II 258.033-nm line. However, in the determination of vanadium, the argon plasma had better analytical performance, giving a detection limit of 0.0023 mass% V for the V II 309.310-nm line.

  6. Optical emission diagnostics of electron cyclotron resonance and glow discharge plasmas for a-Si:H and a-SiC:H film depositions

    NASA Technical Reports Server (NTRS)

    Yang, C. L.; Shing, Y. H.; Allevato, C. E.

    1988-01-01

    It is demonstrated that the steady-state and kinetic characteristics of ECR (electron cyclotron resonance) and RF glow discharge plasmas can be readily monitored by OES (optical emission spectroscopy) in real time during a-Si:H and a-SiC:H film depositions using an OMA detection system. The ECR and RF glow discharge plasmas used for a-Si:H and a-SiC:H film depositions were studied by monitoring the emission of SiH(asterisk), H(asterisk), H(asterisk)2, and CH(asterisk) excited states. The OES of the ECR plasma shows a strong emission at 434 nm from H(asterisk), which is not detectable in the glow discharge plasma. Steady-state OES studies have established preliminary correlations between SiH(asterisk) and CH(asterisk) emission intensities and the film deposition rate. Transient OES spectra of SiH4 and CH4 plasmas have shown different kinetics in SiH(asterisk) and CH(asterisk) emission intensities. Transient studies of the SiH(asterisk) emission intensity have indicated that additional mechanisms for producing the SiH(asterisk) species become evident in hydrogen-diluted silane plasmas.

  7. Water dissociation in a radio-frequency electromagnetic field with ex situ electrodes—modelling of discharge initiation

    NASA Astrophysics Data System (ADS)

    Schneider, Jens; Holzer, Frank; Rabe, Carsten; Häupl, Tilmann; Kopinke, Frank-Dieter; Roland, Ulf

    2013-04-01

    Applying a new experimental design with a capillary glass reactor and plate electrodes outside of the reactor allowed the initiation of discharges in aqueous electrolytes under the influence of a radio-frequency (RF) electromagnetic field. This study focused on the mechanism leading to the initiation of such discharges in the restriction of a glass tube. The light emission correlated with discharges was analysed with optical emission spectroscopy. Electrons with energies between 20 and 45 eV were responsible for the dissociation of water molecules into (excited) OH, H and O radicals. Current-voltage characteristics were measured before and under discharge conditions. Modelling of the experimental setup and simulation of electrical field strength distribution support the hypothesis of the origin of discharges in general and experimental findings such as ring-shaped discharges and a minimum solution conductivity of about 1 S m-1 required for discharge initiation with RF voltages of 2 kV.

  8. Penning Ionization Electron Spectroscopy in Glow Discharge: A New Dimension for Gas Chromatography Detectors

    NASA Technical Reports Server (NTRS)

    Sheverev, V. A.; Khromov, N. A.; Kojiro, D. R.; Fonda, Mark (Technical Monitor)

    2002-01-01

    Admixtures to helium of 100 ppm and 5 ppm of nitrogen, and 100 ppm and 10 ppm of carbon monoxide were identified and measured in the helium discharge afterglow using an electrical probe placed into the plasma. For nitrogen and carbon monoxide gases, the measured electron energy spectra display distinct characteristic peaks (fingerprints). Location of the peaks on the energy scale is determined by the ionization energies of the analyte molecules. Nitrogen and carbon monoxide fingerprints were also observed in a binary mixture of these gases in helium, and the relative concentration analytes has been predicted. The technically simple and durable method is considered a good candidate for a number of analytical applications, and in particular, in GC and for analytical flight instrumentation.

  9. Complementary low energy ion scattering and X-ray photoelectron spectroscopy characterization of polystyrene submitted to N 2/H 2 glow discharge

    NASA Astrophysics Data System (ADS)

    Bonatto, F.; Rovani, S.; Kaufmann, I. R.; Soares, G. V.; Baumvol, I. J. R.; Krug, C.

    2012-02-01

    Low energy ion scattering (LEIS) and X-ray photoelectron spectroscopy (XPS) were used to access the elemental composition and chemical bonding characteristics of polystyrene (PS) surfaces sequentially treated by corona and glow discharge (plasma) processing in N 2/H 2 ambient. The latter has shown activity as suppressor of pathogenic Staphylococcus epidermidis biofilms. LEIS indicated that oxygen from the corona discharge process is progressively replaced by nitrogen at the PS surface. XPS shows C dbnd N and N sbnd C dbnd O chemical groups as significant inhibitors of bacterial adhesion, suggesting application in medical devices.

  10. Cyclic powder formation during pulsed injection of hexamethyldisiloxane in an axially asymmetric radiofrequency argon discharge

    SciTech Connect

    Despax, B.; Makasheva, K.; Caquineau, H.

    2012-11-01

    A new approach of periodic production of dusty plasma consisting of pulsed injection of hexamethyldisiloxane (HMDSO) in argon axially asymmetric radiofrequency (RF) discharge was investigated in this work. The range of plasma operating conditions in which this dusty plasma can exist was closely examined. The obtained results clearly show that a net periodicity in the formation/disappearance of dust particles in the plasma can be maintained on a very large scale of discharge duration. The significance of discharge axial asymmetry to the dust particles behaviour in the plasma is revealed by the development of an asymmetric in shape void shifted towards the powered RF electrode. The key role of the reactive gas and its pulsed injection on each stage of the oscillating process of formation/disappearance of dust particles is disclosed by optical and electrical measurements. It is shown that the period of dusty plasma formation/disappearance is inversely related to the HMDSO injection time. Moreover, the impact of time injection over short period (5 s) is examined. It indicates the conflicting role played by the HMDSO on the reduction of dusty plasma during the reactive gas injection and the reappearance of particles in the plasma during the time off. The electronegative behavior of the plasma in the presence of negatively charged particles seems to explain the energetic modifications in the discharge. A frequency analysis of the floating potential reveals all these cyclic processes. Particularly, in the 10-200 Hz frequency range, the presence and the evolution of dust particles in the plasma over one generation can be observed.

  11. Analytical model of atmospheric pressure, helium/trace gas radio-frequency capacitive Penning discharges

    NASA Astrophysics Data System (ADS)

    Lieberman, M. A.

    2015-04-01

    Atmospheric and near-atmospheric pressure, helium/trace gas radio-frequency capacitive discharges have wide applications. An analytic equilibrium solution is developed based on a homogeneous, current-driven discharge model that includes sheath and electron multiplication effects and contains two electron populations. A simplified chemistry is used with four unknown densities: hot electrons, warm electrons, positive ions and metastables. The dominant electron-ion pair production is Penning ionization, and the dominant ion losses are to the walls. The equilibrium particle balances are used to determine a single ionization balance equation for the warm electron temperature, which is solved, both approximately within the α- and γ-modes, and exactly by conventional root-finding techniques. All other discharge parameters are found, the extinction and α-γ transitions are determined, and a similarity law is given, in which the equilibrium for a short gap at high pressure can be rescaled to a longer gap at lower pressure. Within the α-mode, we find the scaling of the discharge parameters with current density, frequency, gas density and gap width. The analytic results are compared to hybrid and particle-in-cell (PIC) results for He/0.1%N2, and to hybrid results for He/0.1%H2O. For nitrogen, a full reaction set is used for the hybrid calculations and a simplified reaction set for the PIC simulations. For the chemically complex water trace gas, a set of 209 reactions among 43 species is used. The analytic results are found to be in reasonably good agreement with the more elaborate hybrid and PIC calculations.

  12. Boundary-Layer Separation Control under Low-Pressure Turbine Airfoil Conditions using Glow-Discharge Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Hultgren, Lennart S.; Ashpis, David E.

    2003-01-01

    transition. Gad-el-Hak provides a review of various techniques for flow control in general and Volino discusses recent studies on separation control under low-pressure-turbine conditions utilizing passive as well as active devices. As pointed out by Volino, passive devices optimized for separation control at low Reynolds numbers tend to increase losses at high Reynolds numbers, Active devices have the attractive feature that they can be utilized only in operational regimes where they are needed and when turned off would not affect the flow. The focus in the present paper is an experimental Separation is induced on a flat plate installed in a closed-circuit wind tunnel by a shaped insert on the opposite wall. The flow conditions represent flow over the suction surface of a modem low-pressure-turbine airfoil ('Pak-B'). The Reynolds number, based on wetted plate length and nominal exit velocity, is varied from 50,000 to 300,000, covering cruise to takeoff conditions. Low (0.2%) and high (2.5%) Gee-stream turbulence intensities are set using passive grids. A spanwise-oriented phased-plasma-array actuator, fabricated on a printed circuit board, is surface- flush-mounted upstream of the separation point and can provide forcing in a wide frequency range. Static surface pressure measurements and hot-wire anemometry of the base and controlled flows are performed and indicate that the glow-discharge plasma actuator is an effective device for separation control. of active separation control using glow discharge plasma actuators.

  13. Radio-frequency excitation of harmonic microwave radiation from a Penning reflex discharge

    SciTech Connect

    Tate, J.P.; Wharton, C.B. )

    1993-04-01

    Experimental results on multiple-harmonic emission at 8.8 GHz from a Penning reflex discharge (PRD) are reported. Observations of the frequency spectra of microwave emission showed copius harmonic generation of frequencies having two completely different origins: (1) spontaneously excited high harmonics of the electron cyclotron frequency and (2) high harmonics of the frequency of an injected signal independent of the magnetic field strength, a phenomenon reported here for the first time. For spontaneous harmonic emission there was a current threshold, whose magnitude depended on gas pressure and magnetic field strength. When a signal was injected, however, high harmonics (up to the 18th) could be seen at discharge currents well below this threshold value. Comparisons between the two types of radiation are made and discussion of possible mechanisms is provided. It is concluded that the coupling efficiency of the radio-frequency (rf)-excited emission is dependent on the relationship between the rf drive frequency and the electron cyclotron frequency. Finite Larmor radius effects may also influence this coupling. The plasma sheath size will also be a factor in the transfer of energy from the probe to the bulk plasma. Results which seek to elucidate these effects are presented.

  14. Analysis of uncompensated Langmuir probe characteristics in radio-frequency discharges revisited

    SciTech Connect

    Oksuz, L.; Soberon, F.; Ellingboe, A.R.

    2006-01-01

    Measurements of the electron temperature, plasma density, and floating and plasma potentials with Langmuir probes in radio-frequency discharges often represent a challenge due to rf oscillations of the plasma potential. These oscillations distort the probe characteristic, resulting in wrong estimates of the plasma parameters. Both active and passive rf compensation methods have previously been used to eliminate rf fluctuation effects on the electron current drawn by an electrostatic probe. These effects on an uncompensated probe have been theoretically and experimentally studied by Garscadden and Emeleus [Proc. Phys. Soc. London 79, 535 (1962)], Boschi and Magistrelli [Nuovo Cimento 29, 487 (1963)], and Crawford [J. Appl. Phys. 34, 1897 (1963)]. They have shown theoretically that, assuming a Maxwellian distribution and sinusoidal plasma-potential oscillation, the electron temperature can be deduced directly from an uncompensated Langmuir probe trace, by taking the natural logarithm of the electron current. It is the purpose of this paper to bring back the attention onto this result, which shows that under certain discharge conditions it is not necessary to build any rf compensation in a Langmuir probe system. Here we present and reference experimental data found on the literature which support this result. Also computational data are presented.

  15. Uniform surface growth of copper oxide nanowires in radiofrequency plasma discharge and limiting factors

    SciTech Connect

    Filipič, Gregor; Mozetič, Miran; Cvelbar, Uroš; Baranov, Oleg; Ostrikov, Kostya

    2014-11-15

    The uniform growth of copper oxide nanowires on the top of copper plate has been investigated during the exposure to radiofrequency plasma discharge in respect to plasma properties and its localization. The copper samples of 10 mm radius and 1 mm in thickness were exposed to argon-oxygen plasma created at discharge power of 150 W. After 10 min, almost uniform growth of nanowires was achieved over large surface. There were significant distortions in nanowire length and shape near the edges. Based on the experimental results, we developed a theoretical model, which took into account a balance in heat released at the flow of the current to the nanowire and rejected from the nanowire. This model established a dependence of the maximal length of the nanowire at dependence on the plasma parameters, where the limiting factor for nanowire growth and distortions in distribution are ballistic effects of ions and their local fluxes. In contrast, the plasma heating by potential interactions of species has very little influence on the length and smaller deviations in flux are allowed for uniformity of growth.

  16. Production of a biofunctional titanium surface using plasma electrolytic oxidation and glow-discharge plasma for biomedical applications.

    PubMed

    Beline, Thamara; Marques, Isabella da Silva Vieira; Matos, Adaias O; Ogawa, Erika S; Ricomini-Filho, Antônio P; Rangel, Elidiane C; da Cruz, Nilson Cristino; Sukotjo, Cortino; Mathew, Mathew T; Landers, Richard; Consani, Rafael L X; Mesquita, Marcelo Ferraz; Barão, Valentim Adelino Ricardo

    2016-03-16

    In this study, the authors tested the hypotheses that plasma electrolytic oxidation (PEO) and glow-discharge plasma (GDP) would improve the electrochemical, physical, chemical, and mechanical properties of commercially pure titanium (cpTi), and that blood protein adsorption on plasma-treated surfaces would increase. Machined and sandblasted surfaces were used as controls. Standard electrochemical tests were conducted in artificial saliva (pHs of 3.0, 6.5, and 9.0) and simulated body fluid. Surfaces were characterized by scanning electron microscopy, energy-dispersive spectroscopy, x-ray photoelectron spectroscopy, atomic force microscopy, x-ray diffraction, profilometry, Vickers microhardness, and surface energy. For biological assay, the adsorption of blood serum proteins (i.e., albumin, fibrinogen, and fibronectin) was tested. Higher values of polarization resistance and lower values of capacitance were noted for the PEO and GDP groups (p < 0.05). Acidic artificial saliva reduced the corrosion resistance of cpTi (p < 0.05). PEO and GDP treatments improved the surface properties by enrichment of the surface chemistry with bioactive elements and increased surface energy. PEO produced a porous oxide layer (5-μm thickness), while GDP created a very thin oxide layer (0.76-μm thickness). For the PEO group, the authors noted rutile and anatase crystalline structures that may be responsible for the corrosion barrier improvement and increased microhardness values. Plasma treatments were able to enhance the surface properties and electrochemical stability of titanium, while increasing protein adsorption levels.

  17. Selective fibronectin adsorption against albumin and enhanced stem cell attachment on helium atmospheric pressure glow discharge treated titanium

    NASA Astrophysics Data System (ADS)

    Han, Inho; Vagaska, Barbora; Joo Park, Bong; Lee, Mi Hee; Jin Lee, Seung; Park, Jong-Chul

    2011-06-01

    Successful tissue integration of implanted medical devices depends on appropriate initial cellular response. In this study, the effect of helium atmospheric pressure glow discharge (He-APGD) treatment of titanium on selective protein adsorption and the initial attachment processes and focal adhesion formation of osteoprogenitor cells and stem cells were examined. Titanium disks were treated in a self-designed He-APGD system. Initial attachment of MC3T3-E1 mouse pre-osteoblasts and human mesenchymal stem cells (MSCs) was evaluated by MTT assay and plasma membrane staining followed by morphometric analysis. Fibronectin adsorption was investigated by Enzyme-Linked ImmunoSorbant Assay. MSCs cell attachment to treated and non-treated titanium disks coated with different proteins was verified also in serum-free culture. Organization of actin cytoskeleton and focal adhesions was evaluated microscopically. He-APGD treatment effectively modified the titanium surfaces by creating a super-hydrophilic surface, which promoted selectively higher adsorption of fibronectin, a protein of critical importance for cell/biomaterial interaction. In two different types of cells, the He-APGD treatment enhanced the number of attaching cells as well as their attachment area. Moreover, cells had higher organization of actin cytoskeleton and focal adhesions. Faster acceptance of the material by the progenitor cells in the early phases of tissue integration after the implantation may significantly reduce the overall healing time; therefore, titanium treatment with He-APGD seems to be an effective method of surface modification of titanium for improving its tissue inductive properties.

  18. Development of a test methodology for determining the efficacy of One Atmosphere Uniform Glow Discharge Plasma against airborne contaminants

    NASA Astrophysics Data System (ADS)

    Domitrovic, Ronald Edward

    A method of analysis is developed for an atmospheric plasma reactor in a ducted air stream with the intent of enabling parametric analysis for the multi-variable problem. Industrial uses for atmospheric plasma are numerous and in this case, a particular type of plasma known as "One Atmosphere Uniform Glow Discharge Plasma" (OAUGDP(TM)) was studied for its chemistry generation abilities and its microorganism efficacy properties. The system of an OAUGDP reactor positioned in an air duct of fully-developed turbulent flow is constructed of nineteen pertinent variables and dimensional analysis is applied according to the Buckingham Pi method, yielding fourteen dimensionless variable groups. Important Pi groups are identified, namely those relating electrical power input to chemical generation and microorganism efficacy and experimental data is gathered and presented. Ozone is measured as a representative chemical and generation rates are presented in terms of airflow Reynolds number, geometry of the reactor electrodes and power input to the reactor. A universal generation curve is developed for a parallel electrode reactor in which ozone generation rates can be determined from the known Reynolds number, electrode diameter to electrode gap ratio and plasma power to air flow power ratio. It is shown that ozone generation follows a bell shaped curve with increasing rates of production at a low ratio of plasma power to flow power, reaching a maximum and then decreasing to nearly zero at sufficiently high values of plasma power to flow power ratio. A principal area of development for OAUGDP and other atmospheric plasmas is for their use in destroying microorganisms, both on surfaces and in air streams. The ducted OAUGDP system was experimentally tested for efficacy against Bacillus atrophaeus endospores and results are presented in terms of the Reynolds number, the dimensionless plasma exposure time and the plasma power to airflow power ratio. Higher Reynolds numbers require

  19. A photon counting dynamic digital lock-in amplifier for background suppression in glow discharge atomic emission spectrometry

    NASA Astrophysics Data System (ADS)

    Gökmen, Ali; Ulgen, Ahmet; Yalçin, Şerife

    1996-01-01

    A photon counting dynamic digital lock-in amplifier, (PC-DDLIA), has been developed for the suppression of Ar lines in glow discharge lamp atomic emission spectrometry, (GDL-AES). The experimental set-up consists of a Grimm-type GDL, a prism-type scanning monochromator, photon counting electronics, an Apple Ile computer with an interface card and a computer controllable high voltage power supply. The photon counting electronics are designed to convert the photon pulses to logic pulses. A discriminator is used to reject pulses below a threshold level. The high voltage power supply is modulated with a square waveform generated from DAC and photon pulses are counted synchronously by the timer/counter chip, versatile interface adaptor (VIA-6522) on the interface card of computer. The data are analyzed in two steps. In the "learn mode", the GDL is modulated with a square waveform between 370 and 670 V and two spectra consisting of only Ar lines are obtained in a spectral window between 287.1 and 290.0 nm. A new modulation waveform is computed from these spectra which yields two overlapped spectra when the PC-DDLIA is scanned over the same spectral window. In the "analysis mode" of data acquisition, a target material with the analyte element(s) in it is used and the spectrometer is scanned with a dynamically varying rectangular waveform over the same spectral window. The net spectrum consists of pure atomic lines free from any Ar lines. The detection limit for the determination of Si (288.2 nm) in the presence of interfering Ar lines (288.1 and 288.4 nm) is found to be 0.083%, whereas suppression of Ar lines over the same spectral window lowers the detection limit to 0.013%.

  20. Etching of UO2 in NF3 RF Plasma Glow Discharge

    SciTech Connect

    Veilleux, John M.

    1999-08-01

    A series of room temperature, low pressure (10.8 to 40 Pa), low power (25 to 210 W) RF plasma glow discharge experiments with UO2 were conducted to demonstrate that plasma treatment is a viable method for decontaminating UO2 from stainless steel substrates. Experiments were conducted using NF3 gas to decontaminate depleted uranium dioxide from stainless-steel substrates. Depleted UO2 samples each containing 129.4 Bq were prepared from 100 microliter solutions of uranyl nitrate hexahydrate solution. The amorphous UO2 in the samples had a relatively low density of 4.8 gm/cm3. Counting of the depleted UO2 on the substrate following plasma immersion was performed using liquid scintillation counting with alpha/beta discrimination due to the presence of confounding beta emitting daughter products, 234Th and 234Pa. The alpha emission peak from each sample was integrated using a gaussian and first order polynomial fit to improve quantification. The uncertainties in the experimental measurement of the etched material were estimated at about ± 2%. Results demonstrated that UO2 can be completely removed from stainless-steel substrates after several minutes processing at under 200 W. At 180 W and 32.7 Pa gas pressure, over 99% of all UO2 in the samples was removed in just 17 minutes. The initial etch rate in the experiments ranged from 0.2 to 7.4 μm/min. Etching increased with the plasma absorbed power and feed gas pressure in the range of 10.8 to 40 Pa. A different pressure effect on UO2 etching was also noted below 50 W in which etching increased up to a maximum pressure, ~23 Pa, then decreased with further increases in pressure.

  1. Current sheet Formation in a Conical Theta Pinch Faraday Accelerator with Radio-Frequency Assisted Discharge

    NASA Technical Reports Server (NTRS)

    Hallock, Ashley K.; Choueiri, Edgar Y.; Polzin, Kurt A.

    2007-01-01

    The inductive formation of current sheets in a conical theta pinch FARAD (Faraday Accelerator with Radio-frequency Assisted Discharge) thruster is investigated experimentally with time-integrated photography. The goal is to help in understanding the mechanisms and conditions controlling the strength and extent of the current sheet, which are two indices important for FARAD as a propulsion concept. The profiles of these two indices along the inside walls of the conical acceleration coil are assumed to be related to the profiles of the strength and extent of the luminosity pattern derived from photographs of the discharge. The variations of these profiles as a function of uniform back-fill neutral pressure (with no background magnetic field and all parameters held constant) provided the first clues on the nature and qualitative dependencies of current sheet formation. It was found that there is an optimal pressure for which both indices reach a maximum and that the rate of change in these indices with pressure differs on either side of this optimal pressure. This allowed the inference that current sheet formation follows a Townsend-like breakdown mechanism modified by the existence of a finite pressure-dependent radio-frequency-generated electron density background. The observation that the effective location of the luminosity pattern favors the exit-half of the conical coil is explained as the result of the tendency of the inductive discharge circuit to operate near its minimal self-inductance. Movement of the peak in the luminosity pattern towards the upstream side of the cone with increasing pressure is believed to result from the need of the circuit to compensate for the increase in background plasma resistivity due to increasing pressure.

  2. Plasma processing of ? in a hydrogen/oxygen radio-frequency discharge

    NASA Astrophysics Data System (ADS)

    Turcicová, H.; Perina, V.; Vacík, J.; Cervená, J.; Zemek, J.; Zelezný, V.; Arend, H.

    1998-05-01

    Monocrystalline 0022-3727/31/9/004/img10 was processed in a radio-frequency (27.12 MHz) discharge in hydrogen and subsequently in oxygen and the composition of the thus produced surface layers evaluated. The hydrogen plasma treatment caused a heavy blackening of the sample due to chemical reduction. At low 0022-3727/31/9/004/img11 pressures (0022-3727/31/9/004/img12 Torr) the niobate structure on the sample surface was completely destroyed; only niobium and its oxides remained on the surface. At higher pressures (0022-3727/31/9/004/img13 Torr) the niobate structure was preserved. Hydrogenation of the surface layer was found which persisted up to 5000022-3727/31/9/004/img14C. Subsequent treatment in an oxygen plasma under similar processing conditions brought about the restoration of the transparency of the sample. The following methods were used for the modified surface structure analysis: neutron depth profiling, Rutherford backscattering, x-ray photoelectron spectroscopy and VIS and IR spectrometry.

  3. Mission Assessment of the Faraday Accelerator with Radio-frequency Assisted Discharge (FARAD)

    NASA Technical Reports Server (NTRS)

    Dankanich, John W.; Polzin, Kurt A.

    2008-01-01

    Pulsed inductive thrusters have typically been considered for future, high-power, missions requiring nuclear electric propulsion. These high-power systems, while promising equivalent or improved performance over state-of-the-art propulsion systems, presently have no planned missions for which they are well suited. The ability to efficiently operate an inductive thruster at lower energy and power levels may provide inductive thrusters near term applicability and mission pull. The Faraday Accelerator with Radio-frequency Assisted Discharge concept demonstrated potential for a high-efficiency, low-energy pulsed inductive thruster. The added benefits of energy recapture and/or pulse compression are shown to enhance the performance of the pulsed inductive propulsion system, yielding a system that con compete with and potentially outperform current state-of-the-art electric propulsion technologies. These enhancements lead to mission-level benefits associated with the use of a pulsed inductive thruster. Analyses of low-power near to mid-term missions and higher power far-term missions are undertaken to compare the performance of pulsed inductive thrusters with that delivered by state-of-the-art and development-level electric propulsion systems.

  4. Incorporation of the electron energy equation into the hybrid Monte Carlo - fluid model for glow discharge: the applicability and reliability of the model

    NASA Astrophysics Data System (ADS)

    Eylenceoglu, Ender; Rafatov, Ismail; Kudryavtsev, Anatoly

    2016-09-01

    A modification of the conventional hybrid Monte Carlo - fluid model for glow discharge, which incorporates the electron energy equation, is considered. In the proposed model electrons are separated into two groups, namely, high energetic fast and low energetic slow (bulk) electrons. Density profiles of ions, slow electrons, and meta-stable particles are determined from the solution of corresponding continuity equations. Fast electrons, which are responsible for ionization and excitation events in the discharge, are simulated by the Monte-Carlo method. The temperature profile for slow electrons is obtained from the solution of the energy balance equation. The transport (mobility and diffusion) coefficients as well as the reaction rates for slow electrons are determined as functions of the electron temperature. Test calculations are carried out for the direct current glow discharge in argon within two-dimensional geometry. Comparison of the computed results with those obtained from the conventional fluid and hybrid models and the experimental data is done, the applicability and reliability of the proposed model is studied in details.

  5. Synthesis of nano ZnO thin film on Al foil by rf glow discharge plasma and its effect on E. coli and P. aeruginosa

    NASA Astrophysics Data System (ADS)

    Panigrahi, Jagannath; Nayak, Bijan B.; Behera, Debadhyan; Subudhi, Umakanta; Acharya, Bhabani S.

    2012-09-01

    Nano ZnO thin films were deposited on thin Al foils by a rf glow discharge plasma method in which sublimed zinc acetate vapor (precursor) reacted with oxygen plasma inside a low-pressure reactor. The films were microstructurally characterized using XRD, TEM, FESEM, optical reflectance and micro-Raman spectroscopy methods. In view of the good scope of ZnO coating in food packaging, the antibacterial activity in the ZnO thin films was studied by exposing the films to E. coli and P. aeruginosa for up to 8 h. Bacterial cell inhibition of up to 98-99 % was observed in the thin films.

  6. Ion and neutral energy flux distributions to the cathode in glow discharges in Ar/Ne and Xe/Ne mixtures

    NASA Astrophysics Data System (ADS)

    Capdeville, H.; Pédoussat, C.; Pitchford, L. C.

    2002-02-01

    The work presented in the article is a study of the heavy particle (ion and neutral) energy flux distributions to the cathode in conditions typical of discharges used for luminous signs for advertising ("neon" signs). The purpose of this work is to evaluate the effect of the gas mixture on the sputtering of the cathode. We have combined two models for this study: a hybrid model of the electrical properties of the cathode region of a glow discharge and a Monte Carlo simulation of the heavy particle trajectories. Using known sputtering yields for Ne, Ar, and Xe on iron cathodes, we estimate the sputtered atom flux for mixtures of Ar/Ne and Xe/Ne as a function of the percent neon in the mixture.

  7. Determination of major nonmetallic impurities in magnesium by glow discharge mass spectrometry with a fast flow source using sintered and pressed powder samples.

    PubMed

    Plotnikov, Alexei; Pfeifer, Jens; Richter, Silke; Kipphardt, Heinrich; Hoffmann, Volker

    2014-11-01

    Fast flow glow discharge mass spectrometry with a Grimm-type ion source providing a high sputter rate was used for the determination of major nonmetallic impurities in magnesium. The analytical signal was found to be strongly influenced by the electrical discharge parameters. For calibration by standard addition, synthetic standard samples were produced in two different ways-namely, by pressing and by sintering doped metal powders. The observed sensitivity of the calibration curves was shown to depend on the particle size of the powder. For the magnesium powders, the mass fractions of oxygen, nitrogen, boron, and silicon were determined to be about 0.01 kg·kg(-1) (relative standard deviation approximately 10-20 %), 2,700 mg·kg(-1), 150 mg·kg(-1), and 300 mg·kg(-1), respectively.

  8. Glowing Veggies.

    ERIC Educational Resources Information Center

    Scharlin, Pirketta; And Others

    1996-01-01

    Extends the work of Weimer and Battino in electrical conductivity demonstrations creating "glowing" vegetables (see article this issue) to other vegetables and the spectra generated by other elements other than the sodium in pickle brines. Describes a study on the effect of concentration and voltage on glow intensity. (MKR)

  9. [Effect of radio frequency discharge plasma on surface properties and biocompatibility of polycaprolactone matrices].

    PubMed

    Bolbasov, E N; Antonova, L V; Matveeva, V G; Novikov, V A; Shesterikov, E V; Bogomolova, N L; Golovkin, A S; Tverdohlebov, S I; Barbarash, O L; Barbarash, L S

    2016-01-01

    Surface modification of bioresorbable polymer material (polycaprolactone, PCL) with abnormal glow discharge, initiated during radio-frequency magnetron sputtering of a hydroxyapatite target was investigated. Plasma treatment resulted in an increase of surface roughness of PCL, crystallite size, the surface free energy and hydrophilicity. Increased treatment time (30, 60, 150 seconds) provoked the polymer surface saturation with the sputtering target ions (calcium, phosphorus). The assessment of plasma exposure of PCL surface on bone marrow multipotent mesenchymal stromal cells behavior (BM MSCs) has been performed. Modification of the polymer surface with the abnormal glow discharge stimulated adhesion and subsequent proliferation of BM MSCs; thus, maximum values were achieved with the surface treatment for 60 s. This type of plasma modification did not affect cell viability (apoptosis, necrosis). Thus, the surface modification with abnormal glow discharge, initiated during radio-frequency magnetron sputtering of a hydroxyapatite target, appear to be a promising method of surface modification of bioresorbable polymer material (PCL) for tissue engineering.

  10. Study on the effect of hydrogen addition on the variation of plasma parameters of argon-oxygen magnetron glow discharge for synthesis of TiO2 films

    NASA Astrophysics Data System (ADS)

    Saikia, Partha; Saikia, Bipul Kumar; Bhuyan, Heman

    2016-04-01

    We report the effect of hydrogen addition on plasma parameters of argon-oxygen magnetron glow discharge plasma in the synthesis of H-doped TiO2 films. The parameters of the hydrogen-added Ar/O2 plasma influence the properties and the structural phases of the deposited TiO2 film. Therefore, the variation of plasma parameters such as electron temperature (Te), electron density (ne), ion density (ni), degree of ionization of Ar and degree of dissociation of H2 as a function of hydrogen content in the discharge is studied. Langmuir probe and Optical emission spectroscopy are used to characterize the plasma. On the basis of the different reactions in the gas phase of the magnetron discharge, the variation of plasma parameters and sputtering rate are explained. It is observed that the electron and heavy ion density decline with gradual addition of hydrogen in the discharge. Hydrogen addition significantly changes the degree of ionization of Ar which influences the structural phases of the TiO2 film.

  11. Characterization of argon direct-current glow discharge with a longitudinal electric field applied at ambient air

    PubMed Central

    Jiang, Weiman; Tang, Jie; Wang, Yishan; Zhao, Wei; Duan, Yixiang

    2014-01-01

    A direct-current-driven plasma jet is developed by applying a longitudinal electric field on the flowing argon at ambient air. This plasma shows a torch shape with its cross-section increased from the anode to the cathode. Comparison with its counterparts indicates that the gas flow plays a key role in variation of the plasma structure and contributes much to enlarging the plasma volume. It is also found that the circular hollow metal base promotes generation of plasma with a high-power volume density in a limited space. The optical emission spectroscopy (OES) diagnosis indicates that the plasma comprises many reactive species, such as OH, O, excited N2, and Ar metastables. Examination of the rotational and vibrational temperature indicates that the plasma is under nonequilibrium condition and the excited species OH(A 2Σ+), O(5P), and N2(C 3Πu) are partly generated by energy transfer from argon metastables. The spatially resolved OES of plasma reveals that the negative glow, Faraday dark space, and positive column are distributed across the gas gap. The absence of the anode glow is attributed to the fact that many electrons in the vicinity of the anode follow ions into the positive column due to the ambipolar diffusion in the flowing gas. PMID:25205176

  12. Measurement of the equation of state and of the index of refraction of an amorphous glow discharge polymer up to 45 GPa

    NASA Astrophysics Data System (ADS)

    Plisson, Thomas; Colin-Lalu, Pierre; Huser, Gael; Loubeyre, Paul

    2016-08-01

    We present an experimental determination of the ambient temperature equation of state, P ( ρ / ρ 0 , 293 K ) , up to 45 GPa, of the glow discharge polymer (GDP) used as a confining capsule for the fusible deuterium-tritium mixture in inertial confinement fusion experiments. An original method has been implemented to measure both the compression factor and the refractive index versus pressure. The data are obtained in a diamond anvil cell with two sample chambers of equal thickness containing, respectively, the GDP and a NaCl reference. This experimental equation of state is compared to numerical first principles simulations. Deviations are ascribed to the difficulty to simulate the detailed atomic structure of the polymer under moderate pressure.

  13. Degradation of Remazol Red in batik dye waste water by contact glow discharge electrolysis method using NaOH and NaCl electrolytes

    NASA Astrophysics Data System (ADS)

    Saksono, Nelson; Putri, Dita Amelia; Suminar, Dian Ratna

    2017-03-01

    Contact Glow Discharge Electrolysis (CGDE) method is one of Plasma Electrolysis technology which has been approved to degrade organic waste water because it is very productive in producing hydroxyl radical. This study aims to degrade Remazol Red by CGDE method and evaluate important parameters that have influent in degradation process of Remazol Red in Batik dye waste water in batch system. The kind of electrolyte (acid and base) and the addition of metal ion such as Fe2+ have affected Remazol Red degradation percentage. Ultraviolet-Visible (UV-Vis) absorption spectra were used to monitor the degradation process. The result of study showed that percentage degradation was 99.97% which obtained by using NaCl 0.02 M with addition Fe2+ 20 ppm, applied voltage 700 volt, anode depth 0.5 cm, initial concentration of Remazol Red 250 ppm and the temperature of solutions was maintained 50-60 ˚C.

  14. Application of contact glow discharge electrolysis method for degradation of batik dye waste Remazol Red by the addition of Fe2+ ion

    NASA Astrophysics Data System (ADS)

    Saksono, Nelson; Puspita, Indah; Sukreni, Tulus

    2017-03-01

    Contact Glow Discharge Electrolysis (CGDE) has been shown to degrade much weight organic compounds such as dyes because the production of hydroxil radical (•OH) is excess. This research aims to degrade batik dye waste Remazol Red, using CGDE method with the addition of Fe2+ ion. The addition of iron salt compounds has proven to increase process efficiency. Dye degradation is known by measure its absorbances with Spectrophotometer UV-Vis. The result of study showed that percentage degradation was 99.92% in 20 minutes which obtained by using Na2SO4 0.01 M, with addition FeSO4 0,1 gram, applied voltage 860 volt, and 1 wolfram anode 5 mm depth.

  15. Processing materials inside an atmospheric-pressure radiofrequency nonthermal plasma discharge

    DOEpatents

    Selwyn, Gary S.; Henins, Ivars; Park, Jaeyoung; Herrmann, Hans W.

    2006-04-11

    Apparatus for the processing of materials involving placing a material either placed between an radio-frequency electrode and a ground electrode, or which is itself one of the electrodes. This is done in atmospheric pressure conditions. The apparatus effectively etches or cleans substrates, such as silicon wafers, or provides cleaning of spools and drums, and uses a gas containing an inert gas and a chemically reactive gas.

  16. Radio-frequency capacitive discharge with non-flow-type and droplet-jet electrolytic electrodes

    SciTech Connect

    Gaisin, A. F.; Abdullin, I. Sh.; Basyrov, R. Sh.; Khaziev, R. M.; Samitova, G. T.; Shakirova, E. F.

    2014-12-15

    Results are presented from experimental studies of the shape, structure, and spectral characteristics of an RF capacitive discharge operating between a droplet-jet electrolytic electrode and an electrolytic cell in air at pressures of P = 10{sup 3}–10{sup 5} Pa, as well as of a discharge burning between a copper rod and the surface of non-flow electrolyte at atmospheric pressure. It is found that, at voltages of U ≥ 3500 V, the multichannel discharge burning between the rod and the electrolyte (saturated solution of NaCl in technical water) surface transforms into a torch discharge. Specific features of the burning of a discharge with a droplet electrolytic electrode are investigated. Different forms of discharges burning on the surface of a copper tube and an electrolyte jet are revealed.

  17. On the influence of metastable states and the behavior of the EEDF in the characterization of the negative glow of a N2-Ar discharge by OES

    NASA Astrophysics Data System (ADS)

    L, Isola; M, López; J, Gómez B.; V, Guerra

    2014-05-01

    Optical emission spectroscopy (OES) is an essential diagnostic technique in many plasma systems, such as those used for surface treatments or fabrication of thin films. Despite the simplicity of application of OES, its interpretation is not straightforward. In particular, it requires the use of models, which due to the complexity and variety of discharge conditions, have not yet been fully understood [1]-[3]. In addition, Langmuir probes have been widely used to characterize plasmas. They allow the measurement of several parameters of interest, such as the electron density and temperature, as well as the determination of the electron energy distribution function (EEDF) by numerical derivation of the characteristic V - I [4] or by probe-current modulation [5]. In this work, some second positive system bands in the negative glow of an Ar-N2 plasma at a pressure of 2.5 Torr were investigated both by OES and Langmuir probes, for different mixture concentrations. The main purpose of this study was to verify how metastable states and the behavior of the EEDF may influence the interpretation of OES data.

  18. The Influence of CO2 Admixtures on the Product Composition in a Nitrogen-Methane Atmospheric Glow Discharge Used as a Prebiotic Atmosphere Mimic.

    PubMed

    Mazankova, V; Torokova, L; Krcma, F; Mason, N J; Matejcik, S

    2016-11-01

    This work extends our previous experimental studies of the chemistry of Titan's atmosphere by atmospheric glow discharge. The Titan's atmosphere seems to be similarly to early Earth atmospheric composition. The exploration of Titan atmosphere was initiated by the exciting results of the Cassini-Huygens mission and obtained results increased the interest about prebiotic atmospheres. Present work is devoted to the role of CO2 in the prebiotic atmosphere chemistry. Most of the laboratory studies of such atmosphere were focused on the chemistry of N2 + CH4 mixtures. The present work is devoted to the study of the oxygenated volatile species in prebiotic atmosphere, specifically CO2 reactivity. CO2 was introduced to the standard N2 + CH4 mixture at different mixing ratio up to 5 % CH4 and 3 % CO2. The reaction products were characterized by FTIR spectroscopy. This work shows that CO2 modifies the composition of the gas phase with the detection of oxygenated compounds: CO and others oxides. There is a strong influence of CO2 on increasing concentration other products as cyanide (HCN) and ammonia (NH3).

  19. Determination of Hg(2+) by on-line separation and pre-concentration with atmospheric-pressure solution-cathode glow discharge atomic emission spectrometry.

    PubMed

    Li, Qing; Zhang, Zhen; Wang, Zheng

    2014-10-03

    A simple and sensitive method to determine Hg(2+) was developed by combining solution-cathode glow discharge atomic emission spectrometry (SCGD-AES) with flow injection (FI) based on on-line solid-phase extraction (SPE). We synthesized l-cysteine-modified mesoporous silica and packed it in an SPE microcolumn, which was experimentally determined to possess a good mercury adsorption capacity. An enrichment factor of 42 was achieved under optimized Hg(2+) elution conditions, namely, an FI flow rate of 2.0 mL min(-1) and an eluent comprised of 10% thiourea in 0.2 mol L(-1) HNO3. The detection limit of FI-SCGD-AES was determined to be 0.75 μg L(-1), and the precision of the 11 replicate Hg(2+) measurements was 0.86% at a concentration of 100 μg L(-1). The proposed method was validated by determining Hg(2+) in certified reference materials such as human hair (GBW09101b) and stream sediment (GBW07310).

  20. Magnetic and structural properties of CaMn0.9Mo0.1O3 perovskite synthesized in abnormal glow discharge

    NASA Astrophysics Data System (ADS)

    Sarmiento Santos, Armando; Parra Vargas, Carlos Arturo; Supelano García, Ivan

    2015-09-01

    In this work we use the abnormal glow discharge (AGD) to produce the CaMn0.9Mo0.1O3 perovskite through decarbonize, calcination and sintering steps. Structural characterization was carry out by Rietveld refinement of X-ray diffraction on samples after sintering step. The magnetic properties was analysed through magnetization curves as a function of temperature for applied magnetic fields in the range of 20 Oe to 20 kOe by the ZFC-FC method and magnetization curves in function of the applied field at 50 K and 300 K temperatures. The CaMn0.9Mo0.1O3 perovskite was also produced by conventional method in resistive furnace and its behaviour was compared with those of the plasma synthesized. The X-ray analysis reveals that the samples produced by both methods crystalized in a Pnma structure, the lattice parameters change and one second phase appears when the AGD is applied in the last production steps. The magnetization measurements allow analysing the behaviour of the sample at low temperatures and comparing the magnetic transitions in the samples produced by both methods; these are influenced according to production method employed. The results shows that the use of AGD is an alternative method to produce ceramic materials, which reduced ostensibly the production time and allow to obtain similar magnetic and structural properties with respect to conventional method.

  1. Tuneable microsecond-pulsed glow discharge design for the simultaneous acquisition of elemental and molecular chemical information using a time-of-flight mass spectrometer.

    PubMed

    Solà-Vázquez, Auristela; Martín, Antonio; Costa-Fernández, José M; Pereiro, Rosario; Sanz-Medel, Alfredo

    2009-04-01

    A microsecond-pulsed direct current glow discharge (GD) was interfaced and synchronized to a time-of-flight mass spectrometer MS(TOF) for time-gated generation and detection of elemental, structural, and molecular ions. In this way, sequential collection of the mass spectra at different temporal regimes occurring during the GD pulse cycle is allowed. The capabilities of this setup were explored using bromochloromethane as model analyte. A simple GD chamber, developed in our laboratory and characterized by a low plasma volume minimizing dilution of the sample but showing great robustness to the entrance of organic compounds in the microsecond-pulsed plasma, has been used. An exhaustive analytical characterization of the GD-MS(TOF) prototype has been performed. Calibration curves for bromochloromethane observed at the different time regimes of the GD pulse cycle (that is, for elemental, fragment, and molecular ions from the analyte) showed very good linearity for the measurement of the different involved ions, with precisions in the range of 7-13% (relative standard deviation). Actual detection limits obtained for bromochloromethane were in the range of 1-3 microg/L for elements monitoring in the GD pulse "prepeak", in the range of 11-13 microg/L when monitoring analyte fragments in the plateau, and about 238 microg/L when measuring the molecular peak in the afterpeak regime.

  2. Oxynitrided Surface Layer Produced On Ti6Al4V Titanium Alloy Under Low Temperature Glow Discharge Conditions For Medical Applications

    SciTech Connect

    Wierzchon, T.; Ossowski, M.; Borowski, T.; Morgiel, J.; Czarnowska, E.

    2011-01-17

    In spite that titanium oxides increase biocompatibility of titanium implants but their functional life is limited due to the problems arising from brittles and metalosis. Therefore technology, that allow to produce composite surface layer with controlled microstructure, chemical and phase composition and surface morphology on titanium alloy and eliminates the oxides disadvantages has been existing till now is searched. The requirements of titanium and its alloys implants can be fulfill by the low-temperature glow discharge assisted oxynitriding.The paper describes the surface layer of TiO{sub 2}+TiN+Ti{sub 2}N+{alpha}Ti(N) type produced at temperature 680 deg. C that preserves mechanical properties of titanium alloy Ti6Al4V. Characteristics of produced diffusion multi-phase surface layers in range of phase composition, microstructure (SEM, TEM, XRD) and its properties, such as frictional wear resistance are presented. The biological properties in dependency to the applied sterilization method are also analyzed.Properties of produced surface layers are discussed with reference to titanium alloy. The obtained data show that produced surface layers improves titanium alloy properties both frictional wear and biological. Preliminary in vitro examinations show good biocompatibility and antithrombogenic properties.

  3. Measurement of the DC Stark shift for visible NeI lines and electric field distribution in the cathode sheath of an abnormal glow discharge

    NASA Astrophysics Data System (ADS)

    Ivanović, N. V.; Šišović, N. M.; Spasojević, Dj; Konjević, N.

    2017-03-01

    We present the results of an experimental study of the DC Stark shift for seven visible NeI lines in the plane cathode sheath region of an abnormal glow discharge operated in neon with a small admixture of hydrogen. The electric field (up to 13.4 kV cm‑1) in the cathode sheath region is measured from the π-polarized profile of the H alpha line of hydrogen using the Stark polarization spectroscopy technique. Within the realized range of the electric field, the NeI lines exhibit a quadratic Stark effect. The values of coefficients, correlating Stark shift and electric field strength, were determined, enabling their future use for unknown electric field strength measurements. Among the studied lines, so far only the Stark effect analysis of the NeI 511.367 nm line has been reported, in which case our results are in good agreement with the best fit formula proposed by Jäger and Windholz (1984 Phys. Scr. 29 344) for one out of three Stark components detected under our experimental conditions.

  4. The Influence of CO2 Admixtures on the Product Composition in a Nitrogen-Methane Atmospheric Glow Discharge Used as a Prebiotic Atmosphere Mimic

    NASA Astrophysics Data System (ADS)

    Mazankova, V.; Torokova, L.; Krcma, F.; Mason, N. J.; Matejcik, S.

    2016-11-01

    This work extends our previous experimental studies of the chemistry of Titan's atmosphere by atmospheric glow discharge. The Titan's atmosphere seems to be similarly to early Earth atmospheric composition. The exploration of Titan atmosphere was initiated by the exciting results of the Cassini-Huygens mission and obtained results increased the interest about prebiotic atmospheres. Present work is devoted to the role of CO2 in the prebiotic atmosphere chemistry. Most of the laboratory studies of such atmosphere were focused on the chemistry of N2 + CH4 mixtures. The present work is devoted to the study of the oxygenated volatile species in prebiotic atmosphere, specifically CO2 reactivity. CO2 was introduced to the standard N2 + CH4 mixture at different mixing ratio up to 5 % CH4 and 3 % CO2. The reaction products were characterized by FTIR spectroscopy. This work shows that CO2 modifies the composition of the gas phase with the detection of oxygenated compounds: CO and others oxides. There is a strong influence of CO2 on increasing concentration other products as cyanide (HCN) and ammonia (NH3).

  5. Spectroscopic Investigations of Glow Discharges and the Emissions of Nonmetallic Elements in the Argon Inductively Coupled Plasma.

    NASA Astrophysics Data System (ADS)

    Phillips, Hugh Alan

    1988-12-01

    Spectroscopic investigations have been carried out on hollow cathode discharges adapted from laser technology for use as a spectroscopic light source and the argon inductively coupled plasma (ICP) as an excitation source for nonmetal emission. High and low voltage aluminum and copper hollow cathode discharges were studied as a source of ionic and resonant atomic metal emission. The high voltage versions achieve strongly positive current-voltage behavior through utilization of the obstructed discharge phenomenon. The current-pressure-intensity-voltage relationships for low and high voltage copper hollow cathode discharges were studied with the inert gases He, Ne, Ar, Kr, and Xe. The intensity for copper resonant atomic emission with the fill gases Ar, Kr, and Xe improved relative to neon in the high voltage lamp when compared to the low voltage lamp. Absorption measurements through the cathode bore show the ground state atom density to increase with the atomic weight of the fill gas at any given level of intensity, at the fill gas pressure yielding highest resonant atomic copper emission. The estimated ion/atom intensity ratio is increased with fill gases which have metastable or ionization energies greater than the excitation energy of the ion transition. A copper hollow cathode lamp incorporating a short positive column discharge in front of the cathode opening was investigated for its lineshape as measured spectroscopically and by its atomic absorption sensitivity. Incorporation of this positive column allowed higher intensities to be obtained at the same line quality as a commercial hollow cathode lamp. An enlarged cathode volume also improves the lineshape at a given intensity. Inductively coupled plasma spectra for the elements C, O, N, Cl, P, S, and Br were obtained in the vacuum ultraviolet utilizing a vacuum polychromator and SWR film. The detection limit for injected O_2 and N _2 detected electronically by the VUV emissions is 1.3 and 0.9 micrograms

  6. Influence of operating parameters on surface properties of RF glow discharge oxygen plasma treated TiO₂/PET film for biomedical application.

    PubMed

    Pandiyaraj, K Navaneetha; Deshmukh, R R; Mahendiran, R; Su, Pi-G; Yassitepe, Emre; Shah, Ismat; Perni, Stefano; Prokopovich, Polina; Nadagouda, Mallikarjuna N

    2014-03-01

    In this paper, a thin transparent titania (TiO2) film was coated on the surface of flexible poly(ethylene terephthalate) (PET) film using the sol-gel method. The surface properties of the obtained TiO2/PET film were further improved by RF glow discharge oxygen plasma as a function of exposure time and discharge power. The changes in hydrophilicity of TiO2/PET films were analyzed by contact angle measurements and surface energy. The influence of plasma on the surface of the TiO2/PET films was analyzed by atomic force microscopy (AFM) as well as the change in chemical state and composition that were investigated by X-ray photo electron spectroscopy (XPS). The cytotoxicity of the TiO2/PET films was analyzed using human osteoblast cells and the bacterial eradication behaviors of TiO2/PET films were also evaluated against Staphylococcus bacteria. It was found that the surface roughness and incorporation of oxygen containing polar functional groups of the plasma treated TiO2/PET films increased substantially as compared to the untreated one. Moreover the increased concentration of Ti(3+) on the surface of plasma treated TiO2/PET films was due to the transformation of chemical states (Ti(4+)→Ti(3+)). These morphological and chemical changes are responsible for enhanced hydrophilicity of the TiO2/PET films. Furthermore, the plasma treated TiO2/PET film exhibited no citotoxicity against osteoblast cells and antibacterial activity against Staphylococcus bacteria which can find application in manufacturing of biomedical devices.

  7. Isotope ratio characteristics and sensitivity for uranium determinations using a liquid sampling-atmospheric pressure glow discharge ion source coupled to an Orbitrap mass analyzer

    SciTech Connect

    Hoegg, Edward D.; Barinaga, Charles J.; Hager, George J.; Hart, Garret L.; Koppenaal, David W.; Marcus, R. Kenneth

    2016-01-01

    Abstract The continued development of the liquid sampling-atmospheric pressure glow discharge (LS-APGD) microplasma as an ion source for diverse, elemental/isotopic analysis applications continues. To this end, characterization of the capabilities in performing precise and accurate isotope ratio (IR) determinations is essential. Based on past experience with the Thermo Exactive Orbitrap mass analyzer, the LS-APGD was interfaced with this instrument for these tests. While the Orbitrap platform has demonstrated excellent mass resolution and accuracy in “organic” mass spectrometry (MS) applications, work using an Orbitrap for IR analysis is very sparse. These efforts build off previous work in this coupling, where the importance of a few of the LS-APGD discharge parameters and Orbitrap data acquisition methods on IR precision and accuracy were probed. Presented here are the results of a study that evaluated the analytical precision for natural uranium sample (assumed 235U/238U = 0.0072) determinations. The instrumental parameters evaluated include the number of microscans and scans making up a data acquisition set, uranium concentration/signal level, sample make-up, and Fourier transform digitization window. Ultimately, a precision of 0.41% relative standard deviation (RSD) can be achieved for a single determination, with a reproducibility of 1.63 %RSD over 10 separate analytical measurements. A preliminary study of matrix effects on IR measurements of U is presented, highlighting the importance of pre-mass selection before injection into the Orbitrap. The analytical system sensitivity is suggested with the ability to produce a calibration function having an R2 value of >0.99 over a range of 4 orders of magnitude of concentration (~1 – 1000 ng mL-1). These efforts demonstrate the very promising pairing of the LS-APGD ionization source and the Orbitrap, pointing as well to definitive paths forward to better utilize both components in high quality isotope ratio

  8. Factors related to sinus rhythm at discharge after radiofrequency ablation of permanent atrial fibrillation in patients undergoing mitral valve surgery.

    PubMed

    Rostagno, Carlo; Gelsomino, Sandro; Capecchi, Irene; Rossi, Alessandra; Montesi, Gian Franco; Stefàno, Pier Luigi

    2016-04-01

    Late recovery of sinus rhythm is unusual in patients with permanent AF treated by (radiofrequency) RF maze procedure during mitral valve surgery. Identification of clinical and instrumental preoperative factors predictive of early success of RF ablation in patients with permanent AF undergoing mitral valve surgery may improve selection of subjects to obtain long-term results. Hundred and thirty consecutive patients with permanent AF and mitral valve disease underwent modified RF maze procedure during concomitant mitral valve surgery. Rheumatic valve disease (61 pts) and mitral valve prolapse (41 pts) were the more common aetiology of valve abnormalities. Mitral valve replacement was performed in 54 % of patients and mitral valve repair in the remaining 46 %. Four patients died after surgery. At discharge, 87 patients (69 %) were in sinus rhythm (group 1) and 43 patients in AF persisted (group 2). At an average 24-month follow-up, sinus rhythm was present in 67 % of patients, and 33 % were in atrial fibrillation. In this period, late recovery of sinus rhythm was observed only in five patients, while eight discharged in sinus rhythm developed again atrial fibrillation. Among preoperative parameters at univariate analysis female sex, atrial fibrillation >24 months, left atrial diameter >54 mm, left atrial area >24 cm(2), rheumatic valve disease and NYHA class were associated with persistence of AF. At Cox regression multivariate analysis, increased left atrial area (OR 1.07 per unit increase-95 % CI 1.01-1.131) and rheumatic aetiology of valve disease (OR 4.52, 95 % CI 1.65-12.4) were associated with persistence of AF at hospital discharge. Persistence of AF after RF ablation in patients undergoing mitral valve surgery is related to aetiology, e.g. rheumatic valve disease, and to increasing left atrial diameter. Due to low rate of late recovery of sinus rhythm, indication to RF ablation associated with MV surgery should be carefully considered in patients with large

  9. Enhancement of hydrophobicity and tensile strength of muga silk fiber by radiofrequency Ar plasma discharge

    NASA Astrophysics Data System (ADS)

    Gogoi, D.; Choudhury, A. J.; Chutia, J.; Pal, A. R.; Dass, N. N.; Devi, D.; Patil, D. S.

    2011-10-01

    The hydrophobicity and tensile strength of muga silk fiber are investigated using radiofrequency (RF) Ar plasma treatment at various RF powers (10-30 W) and treatment times (5-20 min). The Ar plasma is characterized using self-compensated Langmuir and emissive probe. The ion energy is observed to play an important role in determining the tensile strength and hydrophobicity of the plasma treated fibers. The chemical compositions of the fibers are observed to be affected by the increase in RF power rather than treatment time. XPS study reveals that the ions that are impinging on the substrates are mainly responsible for the cleavage of peptide bond and side chain of amino acid groups at the surface of the fibers. The observed properties (tensile strength and hydrophobicity) of the treated fibers are found to be dependent on their variation in atomic concentration and functional composition at the surfaces. All the treated muga fibers exhibit almost similar thermal behavior as compared to the virgin one. At RF power of 10 W and treatment time range of 5-20 min, the treated fibers exhibit properties similar to that of the virgin one. Higher RF power (30 W) and the increase in treatment time deteriorate the properties of the fibers due to incorporation of more surface roughness caused by sufficiently high energetic ion bombardment. The properties of the plasma treated fibers are attempted to correlate with the XPS analysis and their surface morphologies.

  10. Common Gamma-ray Glows above Thunderclouds

    NASA Astrophysics Data System (ADS)

    Kelley, Nicole; Smith, David; Dwyer, Joseph; Hazelton, Bryna; Grefenstette, Brian; Lowell, Alex; Splitt, Michael; Lazarus, Steven; Rassoul, Hamid

    2013-04-01

    Gamma-ray glows are continuous, long duration gamma- and x-ray emission seen coming from thunderclouds. The Airborne for Energetic Lightning Emissions (ADELE) observed 12 gamma-ray glows during its summer 2009 flight campaign over the areas of Colorado and Florida in the United States. For these glows we shall present their spectra, relationship to lightning activity and how their duration and size changes as a function of distance. Gamma-ray glows follow the relativistic runaway electron avalanche (RREA) spectrum and have been previously measured from the ground and inside the cloud. ADELE measured most glows as it flew above the screening layer of the cloud. During the brightest glow on August 21, 2009, we can show that we are flying directly into a downward facing relativistic runaway avalanche, indicative of flying between the upper positive and negative screening layer of the cloud. In order to explain the brightness of this glow, RREA with an electric field approaching the limit for relativistic feedback must be occurring. Using all 12 glows, we show that lightning activity diminishes during the onset of the glow. Using this along with the fact that glows occur as the field approaches the level necessary for feedback, we attempt to distinguish between two possibilities: that glows are evidence that RREA with feedback, rather than lightning, is sometimes the primary channel for discharging the cloud, or else that the overall discharging is still controlled by lightning, with glows simply appearing during times when a subsidence of lightning allows the field to rise above the threshold for RREA.

  11. Spatially extended void-free dusty plasmas in a laboratory radio-frequency discharge

    SciTech Connect

    Schmidt, C.; Arp, O.; Piel, A.

    2011-01-15

    Laboratory experiments with thermophoretic levitation of dust are described that aim at the closure of a central dust-free void region. A careful study of the void structure as a function of the discharge and levitation parameters leads to the discovery of an extended parameter region where stable void-free equilibria are found. The void closure is effected by a novel mechanism that involves a self-organized change in the discharge topology, in which the dust cloud becomes surrounded by a toroidal region of plasma production. In this geometry ions are found to stream radially inwards instead of outwards as in clouds with a central void. This change in ion flow is proved by a reversal of the propagation direction of dust-density waves.

  12. Hybrid simulations of solenoidal radio-frequency inductively coupled hydrogen discharges at low pressures

    NASA Astrophysics Data System (ADS)

    Yang, Wei; Li, Hong; Gao, Fei; Wang, You-Nian

    2016-12-01

    In this article, we have described a radio-frequency (RF) inductively coupled H2 plasma using a hybrid computational model, incorporating the Maxwell equations and the linear part of the electron Boltzmann equation into global model equations. This report focuses on the effects of RF frequency, gas pressure, and coil current on the spatial profiles of the induced electric field and plasma absorption power density. The plasma parameters, i.e., plasma density, electron temperature, density of negative ion, electronegativity, densities of neutral species, and dissociation degree of H2, as a function of absorption power, are evaluated at different gas pressures. The simulation results show that the utilization efficiency of the RF source characterized by the coupling efficiency of the RF electric field and power to the plasma can be significantly improved at the low RF frequency, gas pressure, and coil current, due to a low plasma density in these cases. The densities of vibrational states of H2 first rapidly increase with increasing absorption power and then tend to saturate. This is because the rapidly increased dissociation degree of H2 with increasing absorption power somewhat suppresses the increase of the vibrational states of H2, thus inhibiting the increase of the H-. The effects of absorption power on the utilization efficiency of the RF source and the production of the vibrational states of H2 should be considered when setting a value of the coil current. To validate the model simulations, the calculated electron density and temperature are compared with experimental measurements, and a reasonable agreement is achieved.

  13. Solution of the problem of interaction between capacitive coupled radio-frequency discharge and a sample

    NASA Astrophysics Data System (ADS)

    Chebakova, V. Ju; Gaisin, A. F.; Zheltukhin, V. S.

    2016-11-01

    The numerical study of interaction between the capacitive coupled radio frequency (CCRF) discharge and materials is performed. A nonlinear problem, which includes initialboundary value problems for electron, ion, neutral atom, metastable atom, gas temperature and Poisson's equation is solved. A harmonic voltage on the loaded electrodes and Ohm's law for the sample is assumed. A results of calculations of the model problem at pressure p=760 Torr, frequency of generator f=13.76 MHz in local approximation are presented.

  14. Microwave induced plasma discharge in multi-cell superconducting radio-frequency cavity.

    PubMed

    Ahmed, Shahid; Mammosser, John D

    2015-07-01

    A R&D effort for in situ cleaning of 1.5 GHz Superconducting Radio Frequency (SRF) cavities at room temperature using the plasma processing technique has been initiated at Jefferson Lab. This is a step toward the cleaning of cryomodules installed in the Continuous Electron Beam Accelerator Facility (CEBAF). For this purpose, we have developed an understanding of plasma discharge in a 5-cell CEBAF-type SRF cavity having configurations similar to those in the main accelerator. The focus of this study involves the detailed investigations of developing a plasma discharge inside the cavity volume and avoids the breakdown condition in the vicinity of the ceramic RF window. A plasma discharge of the gas mixture Ar-O2 (90%:10%) can be established inside the cavity volume by the excitation of a resonant 4π/5 TM010-mode driven by a klystron. The absence of any external magnetic field for generating the plasma is suitable for cleaning cavities installed in a complex cryomodule assembly. The procedures developed in these experimental investigations can be applied to any complex cavity structure. Details of these experimental measurements and the observations are discussed in the paper.

  15. Microwave induced plasma discharge in multi-cell superconducting radio-frequency cavity

    SciTech Connect

    Ahmed, Shahid; Mammosser, John D.

    2015-07-15

    A R&D effort for in situ cleaning of 1.5 GHz Superconducting Radio Frequency (SRF) cavities at room temperature using the plasma processing technique has been initiated at Jefferson Lab. This is a step toward the cleaning of cryomodules installed in the Continuous Electron Beam Accelerator Facility (CEBAF). For this purpose, we have developed an understanding of plasma discharge in a 5-cell CEBAF-type SRF cavity having configurations similar to those in the main accelerator. The focus of this study involves the detailed investigations of developing a plasma discharge inside the cavity volume and avoids the breakdown condition in the vicinity of the ceramic RF window. A plasma discharge of the gas mixture Ar–O{sub 2} (90%:10%) can be established inside the cavity volume by the excitation of a resonant 4π/5 TM{sub 010}-mode driven by a klystron. The absence of any external magnetic field for generating the plasma is suitable for cleaning cavities installed in a complex cryomodule assembly. The procedures developed in these experimental investigations can be applied to any complex cavity structure. Details of these experimental measurements and the observations are discussed in the paper.

  16. Cleaning of inner vacuum surfaces in the Uragan-3M facility by radio-frequency discharges

    SciTech Connect

    Lozin, A. V. Moiseenko, V. E.; Grigor’eva, L. I.; Kozulya, M. M.; Kulaga, A. E.; Lysoivan, A. I.; Mironov, Yu. K.; Pavlichenko, R. O.; Romanov, V. S.; Chernyshenko, V. Ya.; Chechkin, V. V.; Collaboration: Uragan-3M Team

    2013-08-15

    A method for cleaning vacuum surfaces by a low-temperature (T{sub e} ∼ 10 eV) relatively dense (n{sub e} ≈ 10{sup 12} cm{sup −3}) plasma of an RF discharge was developed and successfully applied at the Uragan-3M torsatron. The convenience of the method is that it can be implemented with the same antenna system and RF generators that are used to produce and heat the plasma in the operating mode and does not require retuning the frequencies of the antennas and RF generators. The RF discharge has a high efficiency from the standpoint of cleaning vacuum surfaces. After performing a series of cleanings by the low-temperature RF discharge plasma (about 20000 pulses), (i) the intensity of the CIII impurity line was substantially reduced, (ii) a quasi-steady operating mode with a duration of up to 50 ms, a plasma density of n{sub e} ≈ 10{sup 12} cm{sup −3}, and an electron temperature of up to T{sub e} ∼ 1 keV was achieved, and (iii) mass spectrometric analysis of the residual gas in the chamber indicated a significant reduction in the impurity content.

  17. Preliminary Figures of Merit for Isotope Ratio Measurements: The Liquid Sampling-Atmospheric Pressure Glow Discharge Microplasma Ionization Source Coupled to an Orbitrap Mass Analyzer.

    PubMed

    Hoegg, Edward D; Barinaga, Charles J; Hager, George J; Hart, Garret L; Koppenaal, David W; Marcus, R Kenneth

    2016-08-01

    In order to meet a growing need for fieldable mass spectrometer systems for precise elemental and isotopic analyses, the liquid sampling-atmospheric pressure glow discharge (LS-APGD) has a number of very promising characteristics. One key set of attributes that await validation deals with the performance characteristics relative to isotope ratio precision and accuracy. Owing to its availability and prior experience with this research team, the initial evaluation of isotope ratio (IR) performance was performed on a Thermo Scientific Exactive Orbitrap instrument. While the mass accuracy and resolution performance for Orbitrap analyzers are well-documented, no detailed evaluations of the IR performance have been published. Efforts described here involve two variables: the inherent IR precision and accuracy delivered by the LS-APGD microplasma and the inherent IR measurement qualities of Orbitrap analyzers. Important to the IR performance, the various operating parameters of the Orbitrap sampling interface, high-energy collisional dissociation (HCD) stage, and ion injection/data acquisition have been evaluated. The IR performance for a range of other elements, including natural, depleted, and enriched uranium isotopes was determined. In all cases, the precision and accuracy are degraded when measuring low abundance (<0.1% isotope fractions). In the best case, IR precision on the order of 0.1% RSD can be achieved, with values of 1%-3% RSD observed for low-abundance species. The results suggest that the LS-APGD is a promising candidate for field deployable MS analysis and that the high resolving powers of the Orbitrap may be complemented with a here-to-fore unknown capacity to deliver high-precision IRs. Graphical Abstract ᅟ.

  18. Preliminary Figures of Merit for Isotope Ratio Measurements: The Liquid Sampling-Atmospheric Pressure Glow Discharge Microplasma Ionization Source Coupled to an Orbitrap Mass Analyzer

    SciTech Connect

    Hoegg, Edward D.; Barinaga, Charles J.; Hager, George J.; Hart, Garret L.; Koppenaal, David W.; Marcus, R. Kenneth

    2016-04-14

    ABSTRACT In order to meet a growing need for fieldable mass spectrometer systems for precise elemental and isotopic analyses, the liquid sampling-atmospheric pressure glow discharge (LS-APGD) has a number of very promising characteristics. One key set of attributes that await validation deals with the performance characteristics relative to isotope ratio precision and accuracy. Due to its availability and prior experience with this research team, the initial evaluation of isotope ratio (IR) performance was performed on a Thermo Scientific Exactive Orbitrap instrument. While the mass accuracy and resolution performance for orbitrap analyzers are very well documented, no detailed evaluations of the IR performance have been published. Efforts described here involve two variables: the inherent IR precision and accuracy delivered by the LSAPGD microplasma and the inherent IR measurement qualities of orbitrap analyzers. Important to the IR performance, the various operating parameters of the orbitrap sampling interface, HCD dissociation stage, and ion injection/data acquisition have been evaluated. The IR performance for a range of other elements, including natural, depleted, and enriched uranium isotopes was determined. In all cases the precision and accuracy are degraded when measuring low abundance (<0.1% isotope fractions). In the best case, IR precision on the order of 0.1 %RSD can be achieved, with values of 1-3 %RSD observed for low-abundance species. The results suggest that the LSAPGD is a very good candidate for field deployable MS analysis and that the high resolving powers of the orbitrap may be complemented with a here-to-fore unknown capacity to deliver high-precision isotope ratios.

  19. Preliminary Figures of Merit for Isotope Ratio Measurements: The Liquid Sampling-Atmospheric Pressure Glow Discharge Microplasma Ionization Source Coupled to an Orbitrap Mass Analyzer

    NASA Astrophysics Data System (ADS)

    Hoegg, Edward D.; Barinaga, Charles J.; Hager, George J.; Hart, Garret L.; Koppenaal, David W.; Marcus, R. Kenneth

    2016-08-01

    In order to meet a growing need for fieldable mass spectrometer systems for precise elemental and isotopic analyses, the liquid sampling-atmospheric pressure glow discharge (LS-APGD) has a number of very promising characteristics. One key set of attributes that await validation deals with the performance characteristics relative to isotope ratio precision and accuracy. Owing to its availability and prior experience with this research team, the initial evaluation of isotope ratio (IR) performance was performed on a Thermo Scientific Exactive Orbitrap instrument. While the mass accuracy and resolution performance for Orbitrap analyzers are well-documented, no detailed evaluations of the IR performance have been published. Efforts described here involve two variables: the inherent IR precision and accuracy delivered by the LS-APGD microplasma and the inherent IR measurement qualities of Orbitrap analyzers. Important to the IR performance, the various operating parameters of the Orbitrap sampling interface, high-energy collisional dissociation (HCD) stage, and ion injection/data acquisition have been evaluated. The IR performance for a range of other elements, including natural, depleted, and enriched uranium isotopes was determined. In all cases, the precision and accuracy are degraded when measuring low abundance (<0.1% isotope fractions). In the best case, IR precision on the order of 0.1% RSD can be achieved, with values of 1%-3% RSD observed for low-abundance species. The results suggest that the LS-APGD is a promising candidate for field deployable MS analysis and that the high resolving powers of the Orbitrap may be complemented with a here-to-fore unknown capacity to deliver high-precision IRs.

  20. Particle model analyses of N{sub 2}O dilution with He on electrical characteristics of radio-frequency discharges

    SciTech Connect

    Younis, G.; Yousfi, M.; Despax, B.

    2009-05-01

    The electrical characteristics (voltage, electric field, charged particle densities, dissipated power, particle energy, etc.) are analyzed in the case of low pressure (0.5 and 1 Torr) radio-frequency (rf) discharges in nitrous oxide (N{sub 2}O)/Helium (He) mixtures. An optimized and validated particle model has been used for these analyses in the case of gradual dilutions of N{sub 2}O with He buffer gas. A specific care is carried on the power density evolution and variation which show a complex behavior as a function of He proportion (up to 85%). These analyses are based on a microscopic approach enabling one to show the contribution of the different inelastic processes mainly between electrons and respectively N{sub 2}O and He gases. This approach enables also one to show the discharge region (the positive column or the plasma region) where the power is preferentially dissipated. The power density variation is found to be mainly proportional to the electron density variation. The latter is dependent on the different processes occurring between the charged particles [i.e., electrons, negative ions (O{sup -} and NO{sup -}), and positive ions (N{sub 2}O{sup +} and He{sup +})] and the neutral gas mixture (N{sub 2}O and He). Furthermore, the particle model shows the role of the electron-He collisions on the variation in the electron energy and distribution. This allows more particularly explaining the effects of N{sub 2}O dilution with He on the dissipated power variation in terms of creation and loss of electrons through collision processes.

  1. Determination of ionic and neutral components of argon-methyl methacrylate radiofrequency discharge plasma by mass spectrometry

    SciTech Connect

    Shcheglov, A.N.; Vasilets, V.N.; Ponomarev, A.N.

    1995-09-01

    Positive ions and neutral species formed in the plasma of a radiofrequency discharge in an argonmethyl methacrylate (MMA) mixture at 5.28 MHz, discharge power 12 - 130 W, pressure 10 - 100 Pa, and 0.5 - 10% MMA content of the gas mixture were investigated by mass spectrometry. Over 30 different ionic species were identified in the plasma under various experimental conditions. The most abundant plasma ions were as follows (the m/e values are given in parentheses): CH{sub 3}{sup +} (15), C{sub 2}H{sub 2}{sup +} (26), C{sub 2}H{sub 3}{sup +} (27), C{sub 2}H{sub 4}{sup +}, CO{sup +} (28), C{sub 2}H{sub 5}{sup +}, C{sub 2}H{sub 5}{sup +}, HCO{sup +} (29), C{sub 3}H{sub 3}{sup +} (39), Ar{sup +} (40), C{sub 3}H{sub 5}{sup +} (41), COOCH{sub 3}{sup +} (101). At the MMA concentrations studied, Ar{sup +} was the principal ionic component of the plasma. Among the neutral plasma components, 28 compounds were identified, including C{sub 1}-C{sub 6} hydrocarbons, H{sub 2},H{sub 2}O, CO, HCOH, CH{sub 3}OH, CO{sub 2}, CH{sub 3}COCH{sub 3}, and C{sub 3}H{sub 7}COH. The experimental data suggest that both electron-impact-induced dissociation and ion-molecule reactions involving Ar{sup +}MMA mixture.

  2. Current Sheet Formation in a Conical Theta Pinch Faraday Accelerator with Radio-frequency Assisted Discharge

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A.; Hallock, Ashley K.; Choueiri, Edgar Y.

    2008-01-01

    Data from an inductive conical theta pinch accelerator are presented to gain insight into the process of inductive current sheet formation in the presence of a preionized background gas produced by a steady-state RF-discharge. The presence of a preionized plasma has been previously shown to allow for current sheet formation at lower discharge voltages and energies than those found in other pulsed inductive accelerator concepts, leading to greater accelerator efficiencies at lower power levels. Time-resolved magnetic probe measurements are obtained for different background pressures and pulse energies to characterize the effects of these parameters on current sheet formation. Indices are defined that describe time-resolved current sheet characteristics, such as the total current owing in the current sheet, the time-integrated total current ('strength'), and current sheet velocity. It is found that for a given electric field strength, maximums in total current, strength, and velocity occur for one particular background pressure. At other pressures, these current sheet indices are considerably smaller. The trends observed in these indices are explained in terms of the principles behind Townsend breakdown that lead to a dependence on the ratio of the electric field to the background pressure. Time-integrated photographic data are also obtained at the same experimental conditions, and qualitatively they compare quite favorably with the time-resolved magnetic field data.

  3. Criteria of radio-frequency ring-shaped hollow cathode discharge using H{sub 2} and Ar gases for plasma processing

    SciTech Connect

    Ohtsu, Yasunori; Kawasaki, Yujiro

    2013-01-21

    In order to achieve high-density capacitively coupled plasma, a radio-frequency (RF) ring-shaped hollow cathode discharge has been developed as a candidate for processing plasma sources. The plasma density in the hollow cathode discharge reaches a high magnitude of 10{sup 10}-10{sup 11} cm{sup -3}. The RF ring-shaped hollow cathode discharge depends on the pressure and mass of the working gas. Criteria required for producing a RF ring-shaped hollow cathode discharge have been investigated for various gas pressures using H{sub 2} and Ar gases for high-density plasma production. The results reveal that the criteria for the occurrence of the hollow cathode effect are that the trench width should be approximately equal to the sum of the electron-neutral mean free paths and twice the sheath thickness of the RF powered electrode.

  4. Oxygen depth profiling by resonant backscattering and glow discharge optical emission spectroscopy of Ti-6Al-4V alloy oxidized by ion implantation and plasma based treatment

    NASA Astrophysics Data System (ADS)

    Nsengiyumva, S.; Topic, M.; Pichon, L.; Comrie, C. M.; Mtshali, C.

    2016-10-01

    Oxygen depth profiling by means of 16O(α,α)16O backscattering and glow discharge optical emission spectroscopy (GDOES) was investigated in two different sets of Ti-6Al-4V samples. The first set was made of Ti-6Al-4V samples implanted at room temperature and 550 °C with 50 and 150 keV O+ ions at fluences ranging from 1.5 × 1017 to 6.0 × 1017 ions/cm2. The second set consisted of Ti-6Al-4V samples treated at 550 °C for 7 h and 24 h under low pressure (8 Pa) oxygen, eventually with RF plasma activation. These results are part of a wider investigation on Ti-6Al-4V motivated by recent publications which have shown that an oxide layer can enhance hydrogen absorption and can then promote Ti-6Al-4V alloys as efficient hydrogen storage materials. The results obtained by the two characterization techniques were compared and discussed, enabling to adjust the dependence to the oxygen concentration of the sputtering rates to be used in the time-to-depth transformation required in GDOES analysis. Considering the low thickness of oxidized alloy, usual procedures employed in GDOES depth calculation were indeed not adapted. Once calibrated thanks to the resonant RBS, GDOES can then be easily employed as fast characterization of oxidized and/or hydrogenated surface of Ti-6Al-4V. The obtained results show that the oxygen content into the surface oxidized layer slightly increases in samples implanted at higher fluence and higher temperature. However the overall oxidized layer thickness (<200 nm) remains within the projected ion depth range and is not significantly increased by thermal diffusion at 550 °C. Taken into account the initial oxide layer, the incorporated oxygen quantity mainly corresponds to the implanted fluence but it can be slightly higher with 550 °C implantation, indicating a slight additional oxidation by residual oxygen or surface contamination. The oxygen penetrations and contents in samples oxidized by thermally activated diffusion treatments were more

  5. A study of plasma reaction mechanisms and kinetics in glow discharges of methyl methacrylate and related precursors using in situ FTIR spectroscopy

    NASA Astrophysics Data System (ADS)

    Pan, Yu-Chi Vickie

    In order to understand plasma deposition processes, it is important to have a knowledge of the plasma gas-phase reactions. In this project, in situ Fourier Transform Infrared Spectroscopy (FTIR) was utilized to study the plasma gas-phase chemistry in a capacitively coupled glow discharge. Gas-phase measurements of a number of organic plasmas were performed. The precursors include methyl methacrylate (MMA), methyl crotonate, methyl isobutyrate, ethyl methacrylate, vinyl acetate, isopropanol, methanol, tetramethyl cyclobutanedione and formaldehyde. However, MMA was studied most extensively. In addition to the gas-phase study, plasma polymerized films were also characterized. A number of dissociation products were detected by FTIR in the plasmas. Calibration curves of these products and some monomers were prepared to determine the species concentrations and gas-phase composition. Plasma reaction kinetics were studied in closed systems to determine parameters such as dissociation pathway efficiencies, monomer decomposition rate coefficients, and intermediate species decomposition rate coefficients. The study shows that there are two major electron-impact induced dissociation pathways in MMA plasmas: the C-O bond cleavage reaction and decarboxylations. The C-O bond cleavage reaction accounts for approximately half of the MMA dissociation, and neutral formaldehyde and dimethyl ketene (DMK) molecules are produced via intramolecular rearrangement. Decarboxylation reactions produce CO, COsb2 and a number of radicals that subsequently stabilize to form neutral molecules, such as propylene, allene and methanol. These intermediate species then further dissociate in the plasma to small hydrocarbons (methane, acetylene and ethylene), CO, COsb2 and Hsb2. The reaction mechanisms in the plasmas of other alpha ,beta-unsaturated esters and vinyl acetate were found to be similar to the MMA mechanisms. However, the saturated ester (methyl isobutyrate) and isopropanol plasmas were found

  6. Rapid analysis of pesticide residues in drinking water samples by dispersive solid-phase extraction based on multiwalled carbon nanotubes and pulse glow discharge ion source ion mobility spectrometry.

    PubMed

    Zou, Nan; Gu, Kejia; Liu, Shaowen; Hou, Yanbing; Zhang, Jialei; Xu, Xiang; Li, Xuesheng; Pan, Canping

    2016-03-01

    An analytical method based on dispersive solid-phase extraction with a multiwalled carbon nanotubes sorbent coupled with positive pulse glow discharge ion mobility spectrometry was developed for analysis of 30 pesticide residues in drinking water samples. Reduced ion mobilities and the mass-mobility correlation of 30 pesticides were measured. The pesticides were divided into five groups to verify the separation capability of pulse glow discharge in mobility spectrometry. The extraction conditions such as desorption solvent, ionic strength, conditions of adsorption and desorption, the amounts of multiwalled carbon nanotubes, and solution pH were optimized. The enrichment factors of pesticides were 5.4- to 48.7-fold (theoretical enrichment factor was 50-fold). The detection limits of pesticides were 0.01∼0.77 μg/kg. The linear range was 0.005-0.2 mg/L for pesticide standard solutions, with determination coefficients from 0.9616 to 0.9999. The method was applied for the analysis of practical and spiked drinking water samples. All results were confirmed by high-performance liquid chromatography with tandem mass spectrometry. The proposed method was proven to be a commendably rapid screening qualitative and semiquantitative technique for the analysis of pesticide residues in drinking water samples on site.

  7. Comparison of pulse glow discharge-ion mobility spectrometry and liquid chromatography with tandem mass spectrometry based on multiplug filtration cleanup for the analysis of tricaine mesylate residues in fish and water.

    PubMed

    Zou, Nan; Chen, Ronghua; Qin, Yuhong; Song, Shuangyu; Tang, Xinglin; Pan, Canping

    2016-09-01

    Analytical methods based on multiplug filtration cleanup coupled with pulse glow discharge-ion mobility spectrometry and liquid chromatography tandem mass spectrometry were developed for the analysis of tricaine mesylate residue in fish and fish-raising water samples. A silica fiber holder and an appropriate new interface were designed to make the direct introduction of the fiber into the pulse glow discharge-ion mobility spectrometry introduction mechanism. The multiplug filtration cleanup method with adsorption mixtures was optimized for the determination of tricaine mesylate in fish samples. Good linear relationships were obtained by the two methods. For fish samples, limits of detection were 6 and 0.6 μg/kg by ion mobility spectrometry and liquid chromatography with tandem mass spectrometry, respectively. The matrix effect of the established liquid chromatography tandem mass spectrometry method was negligible for fish samples but that of the ion mobility spectrometry method was not. The two methods were compared. The ion mobility spectrometry system could be used a rapid screening tool on site with the advantage of rapidity, simplicity, and portability, and the liquid chromatography tandem mass spectrometry system could be used for validation in laboratory conditions with the advantage of lower limit of detection, stability, and precision.

  8. Formation and behaviour of dust particle clouds in a radio-frequency discharge: results in the laboratory and under microgravity conditions

    NASA Astrophysics Data System (ADS)

    Mikikian, M.; Boufendi, L.; Bouchoule, A.; Thomas, H. M.; Morfill, G. E.; Nefedov, A. P.; Fortov, V. E.; PKE-Nefedov Team

    2003-03-01

    In this paper we report the first observation on submicron dust particle clouds grown in a radio-frequency sputtering discharge under microgravity conditions. These results have been obtained in the PKE-Nefedov (Plasma Kristall Experiment) chamber in the framework of a French-German-Russian programme. A dust-free region, usually called the `void', is observed in the laboratory and under microgravity conditions even with submicron particles. In this region, successive generations of particles can be grown, leading to the coexistence of particles with various sizes. Each generation of particles constitutes a cloud separated from the others by a definite sheath. Dynamics of these clouds have been investigated showing vortex-like motions or independent behaviour of small heaps of particles, emphasizing both attractive and repulsive effects between dust clouds. As these particles drastically influence the plasma properties, the growth kinetics is followed through the evolution of the discharge current.

  9. Measurements of helium 23S metastable atom density in low-pressure glow discharge plasmas by self-absorption spectroscopy of HeI 23S-23P transition

    NASA Astrophysics Data System (ADS)

    Shikama, Taiichi; Ogane, Shuhei; Ishii, Hidekazu; Iida, Yohei; Hasuo, Masahiro

    2014-08-01

    The helium 23S metastable atom densities are experimentally evaluated by self-absorption spectroscopy of the HeI 23S-23P transition spectra in two kinds of cylindrical glow discharge plasmas, which have different radii and are operated under different pressures of 300 and 20 Pa. The spectra are measured by using an interference spectroscopy system with a wavelength resolution of about 60 pm, and the relative intensities of the fine structure transitions are analyzed. It is found that the method is in principle applicable to plasmas with the pressure up to about the atmospheric pressure and electron density on the order of up to 1022 m-3. For a plasma with an absorption length of 10 mm and a spatially uniform temperature of 300 K, the method is sensitive to the metastable atom density roughly from 1016 to 1019 m-3.

  10. Boundary Values of Some Glow Plasmas

    NASA Astrophysics Data System (ADS)

    Lartigue, Juan; Sánchez, Beatriz; Cisneros, Guadalupe

    2004-04-01

    Paschen curves are widely used to show the relationship between breakdown voltage and the (pressure × gap) product in DC discharge plasmas. A recent paper proposes the use of pressure instead of product since the former gives explicit information about the mean free path. We have applied this criterion to determine the boundary values of three glow plasmas, i.e., the voltage corresponding both to the start and extinction of the glow stage, at a constant pressure. The procedure was tried on helium, argon, and air, there resulting two curves for each of the gases. We have called them the ignition and the extinction curves. We have not found any glow outside the shown pressure limits. So, the plotted pressure and voltage values represent the domain of existence for each of the three glow plasmas. The diagnosis performed lead to glow plasma parameters (such as the Debye length) that match well to those in the literature. A probable relationship between the minimum pressure for glow and the breakdown product is mentioned.

  11. Coupling of multi-walled carbon nanotubes/polydimethylsiloxane coated stir bar sorptive extraction with pulse glow discharge-ion mobility spectrometry for analysis of triazine herbicides in water and soil samples.

    PubMed

    Zou, Nan; Yuan, Chunhao; Liu, Shaowen; Han, Yongtao; Li, Yanjie; Zhang, Jialei; Xu, Xiang; Li, Xuesheng; Pan, Canping

    2016-07-29

    An analytical method based on stir bar sorptive extraction (SBSE) coupled with pulse glow discharge-ion mobility spectrometry (PGD-IMS) was developed for analysis of three triazine pesticide residues in water and soil samples. An injection port with sealing device and stir bars hold device were designed and constructed to directly position the SBSE fiber including the extracted samples into the heating device, making desorption and detection of analytes proceeded simultaneously. The extraction conditions such as SBSE solid phase material, extraction time, extraction temperature, pH value and salt concentration were optimized. Mixture of MWCNTs-COOH and PDMS were shown to be effective in enriching the triazines. The LODs and LOQs of three triazines were found to be 0.006-0.015μgkg(-1) and 0.02-0.05μgkg(-1), and the linear range was 0.05-10μgL(-1) with determination coefficients from 0.9987 to 0.9993. The SBSE-PGD-IMS method was environmentally friendly without organic solvent consumption in the entire experimental procedures, and it was demonstrated to be a commendable rapid analysis technique for analysis of triazine pesticide residues in environmental samples on site. The proposed method was applied for the analysis of real ground water, surface water and soil samples.

  12. Spectral Analysis and Metastable Absorption Measurements of High Pressure Capacitively and Inductively Coupled Radio-Frequency Argon-Helium Discharges

    DTIC Science & Technology

    2013-06-01

    University published a paper that showed that the excited states of the noble gases can be used to form an analogous laser system to the DPAL. Dr...Another method for studying the population of a certain excited state is Tunable Diode Laser Absorption Spectroscopy (TDLAS). This method uses a laser ...four level lasers in a myriad of different transitions. The drawback is in the complicated kinetics of the excited states in the discharge and the

  13. Effects of impedance matching network on the discharge mode transitions in a radio-frequency inductively coupled plasma

    SciTech Connect

    Ding, Z. F.; Yuan, G. Y.; Gao, W.; Sun, J. C.

    2008-06-15

    In inductively coupled plasma sources, discharge transitions from electrostatic mode (E mode) to electromagnetic mode (H mode) and from H mode to E mode occur. In previous studies, only a few works paid attention to the effects of the impedance matching network. Cunge et al. [Plasma Sources Sci. Technol. 8, 576 (1999)] investigated the E-H and H-E mode transitions under two different impedance matching situations, but no physical mechanism or interpretation was presented. This issue is remained to be systematically and quantitatively investigated, and the underlying mechanism to be unveiled. In this paper, the effects of the impedance matching network were experimentally studied in electropositive argon gas by varying the series capacitance in an inversely L-shaped matching network. The positive and negative feedback regions are established according to the effect of varying the series capacitance on the output power of the rf power supply. It was found that under the same experimental parameters, the discharge mode transitions are apt to be discontinuous and continuous in the positive and negative feedback regions, respectively. In addition, the critical coil rf current (or applied power) at the mode transition, the hysteretic loop width, and the difference in applied power during the discharge mode transition vary with the series capacitance. The critical coil rf current at the E-H mode transition is not always higher than that at the H-E mode transition.

  14. High-Temperature Annealing by Subatmospheric-Pressure Radio-Frequency Capacitively Coupled Plasma

    NASA Astrophysics Data System (ADS)

    Miyake, Masatoshi; Yokogawa, Ken'etsu

    2012-08-01

    High-temperature annealing was performed by a novel annealing system using subatmospheric-pressure radio-frequency capacitively coupled plasma (SAP-CCP). The heating characteristics and stability of discharge were studied. An electrode temperature of 1900 °C was obtained with a stable and uniform glow-like discharge. Also, the characteristics of annealing were investigated using silicon wafers implanted with boron ions accelerated by 5 kV at doses of 2.0×1015 cm-2. The sheet resistance decreased with increasing annealing temperature in the same manner as in conventional rapid thermal annealing. As a result, a sheet resistance of 86 Ω/sq was successfully achieved at an electrode temperature of 1080 °C without any surface roughness.

  15. Comparison of pilot and industrial scale atmospheric pressure glow discharge systems including a novel electro-acoustic technique for process monitoring

    NASA Astrophysics Data System (ADS)

    Tynan, J.; Law, V. J.; Ward, P.; Hynes, A. M.; Cullen, J.; Byrne, G.; Daniels, S.; Dowling, D. P.

    2010-02-01

    A comparison of a pilot and industrial scale atmospheric pressure polymer processing plasma system has been carried out using process-monitoring diagnostic tools during treatment of amorphous polyethylene terephthalate. These systems have been compared using optical emission spectroscopy (OES), photodiode (PD) analysis and multi-variate analysis of the applied electrical and emitted electro-acoustic signals to facilitate scale up operations from the pilot to the industrial scale system. The voltage, current, electro-acoustic intensity and frequency of the plasma systems were found to change systematically with an increase in applied plasma power and addition of oxygen (O2) into a helium (He) plasma. The plasma drive frequency was pulled by the plasma reactance from approximately 26 to 16 kHz on the pilot system and from approximately 36 to 32 kHz on the industrial system, for an increase in applied plasma power and addition of O2. The OES analysis revealed a number of peaks associated with nitrogen (N2) species between 250 and 450 nm due to the presence of air within the He plasma. Temporally resolved analysis of the discharge emission carried out using a PD showed an increase in the number of discharge events per power cycle with an increase in power and a decrease in emission intensity for addition of O2 into the He plasma for both the pilot and industrial scale systems. Using these diagnostic tools both plasma stability and run to run variations were assessed. A visual analysis of the 1.2 m wide plasma was also carried out where a more homogeneous plasma was observed at higher powers.

  16. Influence of Discharge Parameters on Tuned Substrate Self-Bias in an Radio-Frequency Inductively Coupled Plasma

    NASA Astrophysics Data System (ADS)

    Ding, Zhenfeng; Sun, Jingchao; Wang, Younian

    2005-12-01

    The tuned substrate self-bias in an rf inductively coupled plasma source is controlled by means of varying the impedance of an external LC network inserted between the substrate and the ground. The influencing parameters such as the substrate axial position, different coupling coils and inserted resistance are experimentally studied. To get a better understanding of the experimental results, the axial distributions of the plasma density, electron temperature and plasma potential are measured with an rf compensated Langmuir probe; the coil rf peak-to-peak voltage is measured with a high voltage probe. As in the case of changing discharge power, it is found that continuity, instability and bi-stability of the tuned substrate bias can be obtained by means of changing the substrate axial position in the plasma source or the inserted resistance. Additionally, continuity can not transit directly into bi-stability, but evolves via instability. The inductance of the coupling coil has a substantial effect on the magnitude and the property of the tuned substrate bias.

  17. Determination of elemental constituents in different matrix materials and flow injection studies by the electrolyte cathode glow discharge technique with a new design

    SciTech Connect

    Shekhar, R.; Karunasagar, D.; Ranjit, M.; Arunachalam, J.

    2009-10-15

    An open-to-air type electrolyte cathode discharge (ELCAD) has been developed with a new design. The present configuration leads to a stable plasma even at low flow rates (0.96 mL/min). Plasma fluctuations arising from the variations in the gap between solid anode and liquid cathode were eliminated by providing a V-groove to the liquid glass-capillary. Cathode (ground) connection is given to the solution at the V-groove itself. Interfaced to atomic emission spectrometry (AES), its analytical performance is evaluated. The optimized molarity of the solution is 0.2 M. The analytical response curves for Ca, Cu, Cd, Pb, Hg, Fe, and Zn demonstrated good linearity. The limit of detections of Ca, Cu, Cd, Pb, Hg, Fe, and Zn are determined to be 17, 11, 5, 45, 15, 28, and 3 ng mL{sup -1}. At an integration time of 0.3 s, the relative standard deviation (RSD) values of the acid blank solutions are found to be less than 10% for the elements Ca, Cu, Cd, Hg, Fe, and Zn and 18% for Pb. The method is applied for the determination of the elemental constituents in different matrix materials such as tuna fish (IAEA-350), oyster tissue (NIST SRM 1566a), and coal fly ash (CFA SRM 1633b). The obtained results are in good agreement with the certified values. The accuracy is found to be between 7% and 0.6% for major to trace levels of constituent elements and the precision between 11% and 0.6%. For the injection of 100 {mu} L of 200 ng mL{sup -1} mercury solution at the flow rate of 0.8 mL/min, the flow injection studies resulted in the relative standard deviation (RSD) of 8%, concentration detection limit of 10 ng/mL, and mass detection limit of 1 ng for mercury.

  18. Assignment of purity to primary metal calibrants using pin-cell VG 9000 glow discharge mass spectrometry: a primary method with direct traceability to the SI international system of units?

    NASA Astrophysics Data System (ADS)

    Sturgeon, R. E.; Methven, B.; Willie, S. N.; Grinberg, P.

    2014-10-01

    A measurement model based on the use of a pin-cell glow discharge source coupled to a VG 9000 sector field mass spectrometer (GD-MS) for the assignment of purity of high-purity metals, i.e., mass fraction of metal matrix, w(M), is presented. A mass balance approach to the calculation requires the determination and summation of impurity mass fractions of all extraneous elements present, including non-metals and gases. It is posited that a primary method of measurement can be devised to yield direct traceability of results to the SI. The major source of uncertainty in the traceability chain stems from the need to adjust the initially estimated quantity values of each impurity element by a relative sensitivity factor ‘influence quantity’ (RSF_{M}^{e} ) , derived from ab initio calculations, and validated through comparison with those derived through use of Certified Reference Materials. It is argued that the method is sufficiently well understood that a measurement equation can be formulated for which all parameters are measured in terms of SI units; that all contributions to uncertainty of measurement can be quantitatively evaluated, underpinning the metrological traceability; and that the performance of GD-MS in CCQM key and pilot comparisons of trace elements in complex metal matrices is in conformance with claimed capabilities. The applicability of the approach to metals in the 3N to 7N range of purity shows that fit-for-purpose relative expanded uncertainties of 0.5% to 0.000 05% can be conservatively achieved for w(M). Presentation of various instrument calibration scenarios vis-à-vis impact on SI traceability of results is also undertaken with a view to eliciting further discussion of this concept within the metrological community.

  19. Radiofrequency Neurotomy

    MedlinePlus

    ... 24 hours after your procedure. Avoid using a heating pad on the injection sites. Avoid baths for ... Smith AD, et al. Cervical radiofrequency neurotomy reduces central hyperexcitability and improves neck movement in individuals with ...

  20. Peakfitter — an integrated Excel-based Visual Basic program for processing multiple skewed and shifting Gaussian-like spectral peaks simultaneously: application to radio frequency glow discharge ion trap mass spectrometry

    NASA Astrophysics Data System (ADS)

    Eanes, Ritchie C.; Marcus, R. Kenneth

    2000-04-01

    This article is an electronic publication in Spectrochimica Acta Electronica (SAE), a section of Spectrochimica Acta Part B (SAB). The hardcopy text is accompanied by an electronic archive, stored on the SAE homepage at (http://www.elsevier.nl/locate/sabe). The archive contains program and data files. The main article discusses the scientific spectroscopic and instrumental aspects of the subject and explains the purpose of the program and data files. The work deals with a Microsoft Excel Visual Basic program, Peakfitter, which can process multiple Gaussian-shaped spectral peaks quickly and easily. The program employs Microsoft Excel Solver to process any Gaussian-like spectra that can be opened in Microsoft Excel 97. Up to three peaks in one to 225 spectra, each containing up to 2000 data points can be processed per data file to give background corrected peak areas for both raw data and its associated fit data as calculated by the trapezoidal method or by simple successive addition of channel intensities across each peak. Concurrently output also includes fit peak heights for Gaussian-shaped spectral peaks. Use of other statistical distributions such as the Lorentzian model requires only slight modification to a template file. Hence, Peakfitter was actually written as two application programs, 'Gaussfitter' and 'Lorenfitter' to accommodate spectra of Gaussian or Lorentzian character, respectively. Written initially to process data from a radio frequency glow discharge ion trap mass spectrometer (rf-GD/ITMS), the program is useful for processing sequentially acquired spectra, which have a limited number of data points across each peak. The user may examine and manipulate program variables in cases where the raw data is skewed with respect to the fit data. An assessment of Peakfitter is given using rf-GD/ITMS elemental analysis and ion-molecule reaction data. Peakfitter's (i.e. 'Gaussfitter's) utility in processing rf-GD/ITMS spectra is characterized by a slight

  1. Modification of carbon fabrics by radio-frequency capacitive discharge at low pressure to regulate mechanical properties of carbon fiber reinforced plastics based on it

    NASA Astrophysics Data System (ADS)

    Garifullin, A. R.; Krasina, I. V.; Skidchenko, E. A.; Shaekhov, M. F.; Tikhonova, N. V.

    2017-01-01

    To increase the values of mechanical properties of carbon fiber (CF) composite materials used in sports equipment production the method of radio-frequency capacitive (RFC) low-pressure plasma treatment in air was proposed. Previously it was found that this type of modification allows to effectively regulate the surface properties of fibers of different nature. This treatment method differs from the traditional ones by efficiency and environmental friendliness as it does not require the use of aggressive, environmentally hazardous chemicals. In this paper it was established that RFC low-pressure air plasma treatment of carbon fabrics enhances the interlaminar shear strength (ILSS) of carbon fiber reinforced plastic (CFRP). As a result of experimental studies of CF by Fourier Transform Infrared (FTIR) spectroscopy method it was proved that after radio-frequency capacitive plasma treatment at low pressure in air the oxygen-containing functional groups is grafted on the surface. These groups improve adhesion at the interface “matrix-fiber”.

  2. Synthesis and characterization of SiC:H ultrafine powder generated in an argon-silane-methane low-pressure radio-frequency discharge

    NASA Astrophysics Data System (ADS)

    Vivet, F.; Bouchoule, A.; Boufendi, L.

    1998-06-01

    The peculiarity of dusty plasma reactors offers a convenient way to obtain processed particles at submicronic levels, with successive layers of different materials grown by using pulsed gas flows, and different plasma chemistries in succession. This concept is applied to the synthesis of silicon carbide (SiC) particles. In this paper two significant situations are reported showing that particles can be synthesized with different properties by varying the process parameters (gas-flow handling, radio-frequency power level). These properties include broad or narrow size dispersion, almost crystalline or amorphous structure, and widely varying Si/C stoichiometry. Monosized particles with high specific surfaces have been obtained by a two-step growth process by using limited radio-frequency power.

  3. Cold starting of fluorescent lamps - part II: experiments on glow times and electrode damaging

    NASA Astrophysics Data System (ADS)

    Langer, Reinhard; Paul, Irina; Hilscher, Achim; Horn, Siegfried; Tidecks, Reinhard

    2017-01-01

    In the present work we present experiments on cold start and the resulting electrode damaging (reducing lamp life) of AC driven fluorescent lamps. The crucial parameter is the glow time, determined from time resolved measurements of lamp voltage and current. The relation between the energy consumed during glow phase and the glow time is studied. It turns out that there is no common threshold of energy until the glow-to-arc transition takes place, but strong energy input into the lamp yields short glow times. The transient behaviour from the glow to the arc regime is investigated and the stable operation points of the arc discharge are determined, yielding an arc discharge voltage-current characteristics of the lamp type investigated. The electrode damage is investigated as a function of the open source voltage and the ballast resistance. Subsequent cold starts lead to an increase of the glow time due to electrode damaging, i.e., the electrode damage accumulates. Different regeneration procedures and their effectiveness are compared. Regeneration burning turns out to be more effective than heating up the electrode. A criterion for avoiding high electrode damage is obtained, indicating that the average power during glow time should exceed 20 W.

  4. Study of short atmospheric pressure dc glow microdischarge in air

    NASA Astrophysics Data System (ADS)

    Kudryavtsev, Anatoly; Bogdanov, Eugene; Chirtsov, Alexander; Emelin, Sergey

    2011-10-01

    The results of experiments and simulations of short (without positive column) atmospheric pressure dc glow discharge in air are presented. We used metal steel electrodes with a gap of 5-100 microns. The experimental voltage-current characteristic's (VAC) have a constant or slightly increasing form at low gap. The most stable microdischarges were burning with a flat cathode and rounded anode, when the length of the discharge is automatically established near the minimum of the Paschen curve by changing their binding on the anode. In this case microdischarge was stable and it had growing VAC. For simulations we used 2D fluid model with kinetic description of electrons. We solved the balance equations for the vibrationally- and the electronically-excited states of a nitrogen and oxygen molecules; nitrogen and oxygen atoms; ozone molecule; and different nitrogen and oxygen ions with different plasmochemical reactions between them. Simulations predicted the main regions of the dc glow discharges including cathode and anode sheath and plasma of negative glow, Faraday dark space and transition region. Gas heating plays an important role in shaping the discharge profiles. The results of experiments and simulations of short (without positive column) atmospheric pressure dc glow discharge in air are presented. We used metal steel electrodes with a gap of 5-100 microns. The experimental voltage-current characteristic's (VAC) have a constant or slightly increasing form at low gap. The most stable microdischarges were burning with a flat cathode and rounded anode, when the length of the discharge is automatically established near the minimum of the Paschen curve by changing their binding on the anode. In this case microdischarge was stable and it had growing VAC. For simulations we used 2D fluid model with kinetic description of electrons. We solved the balance equations for the vibrationally- and the electronically-excited states of a nitrogen and oxygen molecules; nitrogen

  5. Comparing investigation of pattern formation in glow and streamer DBD

    NASA Astrophysics Data System (ADS)

    Li, Ben; Ouyang, Jiting

    2016-11-01

    In this paper, we investigate the behaviors of patterns in dielectric barrier discharge (DBD) in glow and streamer regimes under different operating conditions (driving frequency and voltage) and external electric/magnetic field to explore the similarity and difference of pattern formation. It is found that patterns in both glow and streamer DBDs can be homogenized by decreasing the driving frequency to a low level. But filamentary streamers can still appear at low frequency when the voltage is much higher. With an additional lateral electric field, patterns in both regimes can be homogenized. However, an axial magnetic field makes the glow DBD homogeneous, while the streamer DBD decreases in filamentary size. In both regimes, dynamics and distribution of the space charges, rather than the surface charges, play the predominant role in the formation of DBD patterns. But the surface charges may also play an important role in pattern formation, especially in streamer DBD.

  6. Discharge regime of non-ambipolarity with a self-induced steady-state magnetic field in plasma sources with localized radio-frequency power deposition

    SciTech Connect

    Shivarova, A. Lishev, St.; Todorov, D.; Paunska, Ts.

    2015-10-15

    Involving the idea for the Biermann effect known from space physics as well as recent discussions on non-ambipolarity of the electron and ion fluxes in low-pressure discharges, the study builds the discharge pattern in a source with localized RF power deposition outside the region of high electron density. A vortex dc current flowing in an RF discharge and a steady-state magnetic field induced by this current govern the discharge behavior. Owing to a shift in the positions of the electron-density and plasma-potential maxima, the dc current is driven with the purpose of keeping the conservativity of the dc field in the discharge. The results present the spatial structure of a discharge in a regime of non-ambipolarity of the electron and ion fluxes, including its modifications by the magnetic field.

  7. Detection of particles of less than 5 nm in diameter formed in an argon-silane capacitively coupled radio-frequency discharge

    NASA Astrophysics Data System (ADS)

    Boufendi, L.; Gaudin, J.; Huet, S.; Viera, G.; Dudemaine, M.

    2001-12-01

    A method for the detection of dust particles occurring in silane-argon gas mixture plasmas is presented. It is based on the spectral analysis of the radio-frequency current. The amplitudes of the fundamental (13.56 MHz) and second harmonics (40.68 MHz) are very sensitive to the presence of the earlier nanoparticles when their size is in the range of 2-3 nm even if their influence on the capacitive character of the impedance is negligible. This method is nonperturbative, with a temporal resolution in the microsecond range, very easy to implement, and can thus be used for industrial reactors.

  8. The theory of positive glow corona

    NASA Astrophysics Data System (ADS)

    Morrow, R.

    1997-11-01

    A theory for the current and light pulses of positive glow corona from a point in air is presented; this phenomenon was first observed as an apparently continuous glow by Michael Faraday. Results are obtained, in concentric sphere geometry, for air at atmospheric pressure, by solving the continuity equations for electrons, positive ions, negative ions and metastable oxygen molecules, coupled with Poisson's equation. A series of `saw-toothed' current pulses of period about 0022-3727/30/22/008/img1 is predicted with a DC current level. Accompanying the current peaks are discrete pulses of light 30 ns wide. Successive `shells' of positive ions, from successive current pulses, carry 96% of the mean current. The mean current - voltage relationship has the classic square-law form. The seed electrons required for successive pulses are detached from negative ions by metastable oxygen molecules. Photo-ionization is crucial for the discharge at the anode and for the formation of negative ions throughout the gap. The pulse frequency varies with applied voltage and is found to be approximately proportional to the positive-ion mobility. The surface electric field at the central electrode remains close to Peek's onset field. The origin of onset streamers is explained and sub-microsecond voltage pulses are found to produce streamers. The results for concentric-cylinder electrodes are described briefly.

  9. Simulation of nanoparticle coagulation in radio-frequency C2H2/Ar microdischarges

    NASA Astrophysics Data System (ADS)

    Xiang-Mei, Liu; Qi-Nan, Li; Rui, Li

    2016-06-01

    The nanoparticle coagulation is investigated by using a couple of fluid models and aerosol dynamics model in argon with a 5% molecular acetylene admixture rf microdischarges, with the total input gas flow rate of 400 sccm. It co-exists with a homogeneous, secondary electron-dominated low temperature γ-mode glow discharges. The heat transfer equation and flow equation for neutral gas are taken into account. We mainly focused on investigations of the nanoparticle properties in atmospheric pressure microdischarges, and discussed the influences of pressure, electrode spacing, and applied voltage on the plasma density and nanoparticle density profiles. The results show that the characteristics of microdischarges are quite different from those of low pressure radio-frequency discharges. First, the nanoparticle density in the bulk plasma in microdischarges is much larger than that of low pressure discharges. Second, the nanoparticle density of 10 nm experiences an exponential increase as soon as the applied voltage increases, especially in the presheath. Finally, as the electrode spacing increases, the nanoparticle density decreased instead of increasing. Project supported by the Natural Science Foundation of Heilongjiang Province, China (Grant Nos. A2015011 and A2015010), the Postdoctoral Scientific Research Development Fund of Heilongjiang Province, China (Grant No. LBH-Q14159), the Program for Young Teachers Scientific Research in Qiqihar University (Grant No. 2014k-Z11), the National Natural Science Foundation of China (Grant No. 11404180), and the University Nursing Program for Yong Scholars with Creative Talents in Heilongjiang Province, China (Grant No. UNPYSCT-2015095).

  10. The Effects of Lamp Spectral Distribution on Sky Glow over Observatories

    NASA Astrophysics Data System (ADS)

    Luginbuhl, C. B.; Boley, P. A.; Davis, D. R.; Duriscoe, D. M.

    2015-03-01

    Using a wavelength-generalized version of the Garstang (1991) model, we evaluate overhead sky glow as a function of distance up to 300 km, from a variety of lamp types, including common gas discharge lamps and several types of LED lamps. We conclude for both professional, and especially cultural (visual), astronomy, that low-pressure sodium and narrow-spectrum amber LED lamps cause much less sky glow than all broad-spectrum sources.

  11. Low-pressure hydrogen discharge maintenance in a large-size plasma source with localized high radio-frequency power deposition

    SciTech Connect

    Todorov, D.; Shivarova, A. Paunska, Ts.; Tarnev, Kh.

    2015-03-15

    The development of the two-dimensional fluid-plasma model of a low-pressure hydrogen discharge, presented in the study, is regarding description of the plasma maintenance in a discharge vessel with the configuration of the SPIDER source. The SPIDER source, planned for the neutral-beam-injection plasma-heating system of ITER, is with localized high RF power deposition to its eight drivers (cylindrical-coil inductive discharges) and a large-area second chamber, common for all the drivers. The continuity equations for the charged particles (electrons and the three types of positive ions) and for the neutral species (atoms and molecules), their momentum equations, the energy balance equations for electrons, atoms and molecules and the Poisson equations are involved in the discharge description. In addition to the local processes in the plasma volume, the surface processes of particle reflection and conversion on the walls as well as for a heat exchange with the walls are included in the model. The analysis of the results stresses on the role of the fluxes (particle and energy fluxes) in the formation of the discharge structure. The conclusion is that the discharge behavior is completely obeyed to non-locality. The latter is displayed by: (i) maximum values of plasma parameters (charged particle densities and temperatures of the neutral species) outside the region of the RF power deposition, (ii) shifted maxima of the electron density and temperature, of the plasma potential and of the electron production, (iii) an electron flux, with a vortex structure, strongly exceeding the total ion flux which gives evidence of a discharge regime of non-ambipolarity and (iv) a spatial distribution of the densities of the neutral species resulting from their fluxes.

  12. Low-pressure hydrogen discharge maintenance in a large-size plasma source with localized high radio-frequency power deposition

    NASA Astrophysics Data System (ADS)

    Todorov, D.; Shivarova, A.; Paunska, Ts.; Tarnev, Kh.

    2015-03-01

    The development of the two-dimensional fluid-plasma model of a low-pressure hydrogen discharge, presented in the study, is regarding description of the plasma maintenance in a discharge vessel with the configuration of the SPIDER source. The SPIDER source, planned for the neutral-beam-injection plasma-heating system of ITER, is with localized high RF power deposition to its eight drivers (cylindrical-coil inductive discharges) and a large-area second chamber, common for all the drivers. The continuity equations for the charged particles (electrons and the three types of positive ions) and for the neutral species (atoms and molecules), their momentum equations, the energy balance equations for electrons, atoms and molecules and the Poisson equations are involved in the discharge description. In addition to the local processes in the plasma volume, the surface processes of particle reflection and conversion on the walls as well as for a heat exchange with the walls are included in the model. The analysis of the results stresses on the role of the fluxes (particle and energy fluxes) in the formation of the discharge structure. The conclusion is that the discharge behavior is completely obeyed to non-locality. The latter is displayed by: (i) maximum values of plasma parameters (charged particle densities and temperatures of the neutral species) outside the region of the RF power deposition, (ii) shifted maxima of the electron density and temperature, of the plasma potential and of the electron production, (iii) an electron flux, with a vortex structure, strongly exceeding the total ion flux which gives evidence of a discharge regime of non-ambipolarity and (iv) a spatial distribution of the densities of the neutral species resulting from their fluxes.

  13. Influence of the temporal variations of plasma composition on the cyclic formation of dust in hexamethyldisiloxane-argon radiofrequency discharges: Analysis by time-resolved mass spectrometry

    NASA Astrophysics Data System (ADS)

    Despax, B.; Gaboriau, F.; Caquineau, H.; Makasheva, K.

    2016-10-01

    Cyclic formation of dust nanoparticles in hexamethyldisiloxane (HMDSO, Si2O(CH3)6)-argon RF discharge with pulsed injection of HMDSO was studied using time-resolved mass spectrometry (MS) and optical emission spectroscopy (OES). A large amount of C2H2, considered as promoter of dust nucleation in hydrocarbon plasmas, was found as a by-product of HMDSO fragmentation. Although no negative ions were detected the presence of C2H2 in the HMDSO-Ar discharge supports the hypothesis of a dust growth mechanism based on negative ions being trapped in the plasma. It was found that at the beginning of each cycle of dust formation during α -γ' transition, the discharge sustaining process is accompanied by a strong consumption of the HMDSO main by-products: HMDSO-15, CH4 and C2H2. At the end of the cycle, corresponding to the progressive disappearance of dust, the discharge switches back to its initial conditions. The beginning of the inverse transition, i.e. γ'-α , is most likely correlated to the growing void in the dust cloud and dust disappearance. In presence of dust nanoparticles, Ar+ and ArH+ dominate the ion population and consequently the discharge maintenance. When the dust particles gradually disappear, the discharge is rather controlled by Si2O(CH3)5+ ions. Moreover, the increased amount of such heavy ions reveals clearly their important income in the dust repelling process due to the drag force on the large sized dust even at short time scale during the injection time of HMDSO. Atomic-H production increases during the transition from dusty plasma to HMDSO-rich plasma with no dust and its role is associated to a delay in the dust nucleation stage.

  14. Second Workshop on Spacecraft Glow

    NASA Technical Reports Server (NTRS)

    Waite, J. H., Jr. (Editor); Moorehead, T. W. (Editor)

    1985-01-01

    Various aspects of space glow were considered. Results of a workshop held on May 6 to 7, 1985, at the Space Science Laboratory of NASA/Marshall Space Flight Center, Huntsville, Alabama are presented. The topics of discussion are divided as follows: (1) in situ observations; (2) theoretical calculations; (3) laboratory measurements; and (4) future experiments.

  15. Radiofrequency Ablation of Liver Tumors

    MedlinePlus

    ... Site Index A-Z Radiofrequency Ablation (RFA) of Liver Tumors Radiofrequency ablation (RFA) is a treatment that ... of Liver Tumors? What is Radiofrequency Ablation of Liver Tumors? Radiofrequency ablation, sometimes referred to as RFA, ...

  16. Radio-frequency wave enhanced runaway production rate

    SciTech Connect

    Chan, V.S.; McClain, F.W.

    1983-06-01

    Enhancement of runaway electron production (over that of an Ohmic discharge) can be achieved by the addition of radio-frequency waves. This effect is studied analytically and numerically using a two-dimensional Fokker--Planck quasilinear equation.

  17. Positive Streamers and Glows in Air and Exhaust Gases

    NASA Astrophysics Data System (ADS)

    Morrow, R.

    1998-10-01

    Theoretical and experimental studies have been made of the effects of sub-microsecond voltage pulses on the plasma chemistry of real flue gases in a test cell. Chemical analysis shows that, for real flue gases, the pulsed system can remove up to 90 % of NO, and 30 % of SO_2, if a residence time of ~ 30s is used. We also find that (i) water vapour is essential to the removal of SO_2, but not for the removal of NO or NO_2; and (ii) that small quantities of N_2O are produced. The removal of SO2 is primarily due to reactions with OH radicals from water vapour, producing sulphuric acid, whereas nitrogen oxides are reduced by N atoms. When a positive voltage is abruptly applied to a point in air at atmospheric pressure, positive streamers are produced. A theory is presented for the development of the first such streamer by solving the continuity equations for electrons, positive ions and negative ions, including the effects of ionisation, attachment, recombination, electron diffusion, and photoionisation, simultaneously with Poisson's equation. With an applied voltage of 20 kV across a 50 mm gap, the streamer does not reach the cathode. When the voltage is sustained in the presence of free electrons, the electric field at the anode starts to recover until positive glow pulses develop at the anode. The presence of the positive glow corona precludes any further streamer formation; this limits the number of chemical reactions stimulated by the discharge because the positive glow is confined close to the anode. Thus, a limit is set for the voltage pulse width. A theory is also presented for the current and light pulses of positive glow corona from a point in air; results are obtained by solving the continuity equations, described above, in concentric sphere geometry. A series of ``saw--toothed'' current pulses of period ~ 1 μs are predicted with a dc current level. Accompanying the current peaks are discrete 30 ns wide pulses of light. It is found that if, in the presence

  18. Spectral characteristics of Shuttle glow

    NASA Technical Reports Server (NTRS)

    Viereck, R. A.; Mende, S. B.; Murad, E.; Swenson, G. R.; Pike, C. P.; Culbertson, F. L.; Springer, R. C.

    1992-01-01

    The glowing cloud near the ram surfaces of the Space Shuttle was observed with a hand-held, intensified spectrograph operated by the astronauts from the aft-flight-deck of the Space Shuttle. The spectral measurements were made between 400 and 800 nm with a resolution of 3 nm. Analysis of the spectral response of the instrument and the transmission of the Shuttle window was performed on orbit using earth-airglow OH Meinel bands. This analysis resulted in a correction of the Shuttle glow intensity in the spectral region between 700 and 800 nm. The data presented in this report is in better agreement with laboratory measurements of the NO2 continuum.

  19. Characteristics of short dc glow microdischarges in atmospheric pressure air

    NASA Astrophysics Data System (ADS)

    Kudryavtsev, Anatoly

    2013-09-01

    The main reason that high pressure current-carrying plasmas tend to be unstable is various instability (primarily thermal) of the positive column (PC). So a promising approach is to use short (without PC) discharges that have growing voltage-current characteristic (VAC). These discharges are ignited near the minimum of the Paschen breakdown curve Lmin and it usually have a gap pL <10-20 cm Torr when a distinct PC is absent. In this report the most stable microdischarges were burning with a flat cathode and rounded (or thin rod) anode, which located to a distance less than Lmin when the microdischarge ``choose'' their length itself, so that to match the stable work near Lmin by changing their binding on the anode. For simulations we used 2D hybrid model. Simulations predicted the main regions of the dc glow discharges including cathode and anode sheath and plasma of negative glow, Faraday dark space and transition region, in which the electric field is distributed no uniformly and plasma is nonlocal. Gas heating plays an important role in shaping the discharge profiles. Work supported by FZP and SPbSU.

  20. Spacecraft ram glow and surface temperature

    NASA Technical Reports Server (NTRS)

    Swenson, G. R.; Mende, S. B.; Llewellyn, E. J.

    1987-01-01

    Space shuttle glow intensity measurements show large differences when the data from different missions are compared. In particular, on the 41-G mission the space shuttle ram glow was observed to display an unusually low intensity. Subsequent investigation of this measurement and earlier measurements suggest that there was a significant difference in temperature of the glow producing ram surfaces. The highly insulating properties coupled with the high emissivity of the shuttle tile results in surfaces that cool quickly when exposed to deep space on the night side of the orbit. The increased glow intensity is consistent with the hypothesis that the glow is emitted from excited NO2. The excited NO2 is likely formed through three body recombination (OI + NO + M = NO2*) where ramming of OI interacts with weakly surface bound NO. The NO is formed from atmospheric OI and NI which is scavenged by the spacecraft moving through the atmosphere. It is postulated that the colder surfaces retain a thicker layer of NO thereby increasing the probability of the reaction. It has been found from the glow intensity/temperature data that the bond energy of the surface bound precursor, leading to the chemical recombination producing the glow, is approximately 0.14 eV. A thermal analysis of material samples of STS-8 was made and the postulated temperature change of individual material samples prior to the time of glow measurements above respective samples are consistent with the thermal effect on glow found for the orbiter surface.

  1. Scaled-Up Nonequilibrium Air Plasmas Generated by DC and Pulsed Discharges

    DTIC Science & Technology

    2010-09-08

    scalability of nonequilibrium plasmas produced by electrical discharges in atmospheric pressure air. Both DC and repetitively pulsed discharges ...Key results demonstrate that both DC glow discharge and pulsed transient spark generate air plasmas of required parameters. Glow discharge is easier...Corona discharge as a temperature probe was developed to diagnose the microwave torch preheated air. A new concept of the DC-driven pulsed

  2. Simulation Study of an Extended Density DC Glow Toroidal Plasma Source

    SciTech Connect

    Granda-Gutierrez, E. E.; Piedad-Beneitez, A. de la; Lopez-Callejas, R.; Godoy-Cabrera, O. G.; Benitez-Read, J. S.; Pacheco-Sotelo, J. O.; Pena-Eguiluz, R.; Mercado-Cabrera, A.; Valencia A, R.; Barocio, S. R.

    2006-12-04

    Conventional wisdom assigns the DC glow discharge regime to plasma currents below {approx}500 mA values, beyond which the discharge falls into the anomalous glow and the turbulent arc regimes. However, we have found evidence that, during toroidal discharges, this barrier can be ostensibly extended up to 800 mA. Thus, a computer simulation has been applied to the evolution of the main electrical characteristics of such a glow discharge plasma in a toroidal vessel in order to design and construct a respective voltage/current controlled source. This should be able to generate a DC plasma in the glow regime with which currents in the range 10-3-100 A can be experimented and 109-1010 cm-3 plasma densities can be achieved to PIII optimization purposes. The plasma is modelled as a voltage-controlled current source able to be turned on whenever the breakdown voltage is reached across the gap between the anode and the vessel wall. The simulation outcome fits well our experimental measurements showing that the plasma current obeys power laws that are dependent on the power current and other control variables such as the gas pressure.

  3. Investigation of atmospheric pressure glow microdischarge between flat cathode and needle anode in helium and argon

    NASA Astrophysics Data System (ADS)

    Astafiev, Alexander; Belyaev, Vladimir; Zamchii, Roman; Kudryavtsev, Anatoly; Stepanova, Olga; Chen, Zhaoquan

    2016-09-01

    DC atmospheric-pressure glow microdischarge was generated between a flat cathode and needle anode with a diameter of 100 μm in a special chamber with helium or argon. Dependences of discharge parameters on an interelectrode gap was investigated with an original experimental setup based on a movable arm on the hinge joint which allowed changing the gap with a step of 5 μm. The gap was varied from 5 to 700 μm. Discharge current was 1-21 mA. Such discharge cell has a very low interelectrode capacitance and provides increasing the stability of the discharge against arc formation (transition to RC oscillations mode) at low currents of 1 mA. A weak dependence of discharge voltage across the gap was revealed in helium at 100-250 μm between the electrodes (normal discharge). In contrast to this, glow microdischarge in argon has a descending current-voltage characteristic and unstable nature. The discharge voltage depending on the gap changes significantly slower than in helium. According to our estimations, the strength of electrical field of positive glow in argon is 5 times lower than in helium. Saint Petersburg State University (Grant No. 0.37.218.2016).

  4. APEX reveals glowing stellar nurseries

    NASA Astrophysics Data System (ADS)

    2008-11-01

    Illustrating the power of submillimetre-wavelength astronomy, an APEX image reveals how an expanding bubble of ionised gas about ten light-years across is causing the surrounding material to collapse into dense clumps that are the birthplaces of new stars. Submillimetre light is the key to revealing some of the coldest material in the Universe, such as these cold, dense clouds. Glowing Stellar Nurseries ESO PR Photo 40/08 Glowing Stellar Nurseries The region, called RCW120, is about 4200 light years from Earth, towards the constellation of Scorpius. A hot, massive star in its centre is emitting huge amounts of ultraviolet radiation, which ionises the surrounding gas, stripping the electrons from hydrogen atoms and producing the characteristic red glow of so-called H-alpha emission. As this ionised region expands into space, the associated shock wave sweeps up a layer of the surrounding cold interstellar gas and cosmic dust. This layer becomes unstable and collapses under its own gravity into dense clumps, forming cold, dense clouds of hydrogen where new stars are born. However, as the clouds are still very cold, with temperatures of around -250˚ Celsius, their faint heat glow can only be seen at submillimetre wavelengths. Submillimetre light is therefore vital in studying the earliest stages of the birth and life of stars. The submillimetre-wavelength data were taken with the LABOCA camera on the 12-m Atacama Pathfinder Experiment (APEX) telescope, located on the 5000 m high plateau of Chajnantor in the Chilean Atacama desert. Thanks to LABOCA's high sensitivity, astronomers were able to detect clumps of cold gas four times fainter than previously possible. Since the brightness of the clumps is a measure of their mass, this also means that astronomers can now study the formation of less massive stars than they could before. The plateau of Chajnantor is also where ESO, together with international partners, is building a next generation submillimetre telescope, ALMA

  5. Glow Sticks: Spectra and Color Mixing

    ERIC Educational Resources Information Center

    Birriel, Jennifer; Birriel, Ignacio

    2014-01-01

    Glow sticks are a popular Halloween staple familiar to most of our students. The production of light via a chemical reaction is called "chemiluminescence," and glow sticks are often used as demonstrations and experiments in the chemistry classroom to study reaction rates as a function of temperature. A black light can be used to…

  6. LiNbO 3 exposed to radio-frequency plasma

    NASA Astrophysics Data System (ADS)

    Turcicova, H.; Vacik, J.; Cervena, J.; Perina, V.; Polcarova, M.; Bradler, J.; Zelezny, V.; Zemek, J.

    1998-05-01

    Radio-frequency (27.12 MHz) glow discharge in H 2 and O, have been used for surface modification of LiNbO 3 wafers. The properties of plasma modified surface layers were dependent on the gas pressure and radio frequency (RF) input power. At pressures below 1 Torr of H 2 and input powers of 1-10 W/cm 3 , a low-resistance layer was created with a sheet resistivity of 2.6 mΩ cm. At pressures of several Torrs, an Li density drop up to a depth of 1 μm appeared, accompanied by OH - radical formation. The sample processing in oxygen plasma was aimed at restoring light transparency of the samples, which was lost during hydrogen processing. The restoration is attainable in a short time and at much lower sample temperature than under thermal bleaching. Processing under certain plasma parameters decreased the density of point defects in the material. The methods used for characterizing the plasma-modified layers were neutron depth profiling (NDP) and Rutherford backscattering (RBS), X-ray induced photoelectron spectroscopy (XPS), X-ray diffraction, visible and infrared transmission and reflection spectroscopy. The paper summarizes the results of a four year study and suggests possible applications of the findings.

  7. Analysis of double-probe characteristics in low-frequency gas discharges and its improvement

    SciTech Connect

    Liu, DongLin Li, XiaoPing; Xie, Kai; Liu, ZhiWei; Shao, MingXu

    2015-01-15

    The double-probe has been used successfully in radio-frequency discharges. However, in low-frequency discharges, the double-probe I-V curve is so much seriously distorted by the strong plasma potential fluctuations that the I-V curve may lead to a large estimate error of plasma parameters. To suppress the distortion, we investigate the double-probe characteristics in low-frequency gas discharge based on an equivalent circuit model, taking both the plasma sheath and probe circuit into account. We discovered that there are two primary interferences to the I-V curve distortion: the voltage fluctuation between two probe tips caused by the filter difference voltage and the current peak at the negative edge of the plasma potential. Consequently, we propose a modified passive filter to reduce the two types of interference simultaneously. Experiments are conducted in a glow-discharge plasma (f = 30 kHz) to test the performance of the improved double probe. The results show that the electron density error is reduced from more than 100% to less than 10%. The proposed improved method is also suitable in cases where intensive potential fluctuations exist.

  8. Radiofrequency plasma antenna generated by femtosecond laser filaments in air

    SciTech Connect

    Brelet, Y.; Houard, A.; Point, G.; Prade, B.; Carbonnel, J.; Andre, Y.-B.; Mysyrowicz, A.; Arantchouk, L.; Pellet, M.

    2012-12-24

    We demonstrate tunable radiofrequency emission from a meter-long linear plasma column produced in air at atmospheric pressure. A short-lived plasma column is initially produced by femtosecond filamentation and subsequently converted into a long-lived discharge column by application of an external high voltage field. Radiofrequency excitation is fed to the plasma by induction and detected remotely as electromagnetic radiation by a classical antenna.

  9. Plasma in a Pulsed Discharge Environment

    NASA Technical Reports Server (NTRS)

    Remy, J.; Bienier, L.; Salama, F.

    2005-01-01

    The plasma generated in a pulsed slit discharge nozzle is used to form molecular ions in an astrophysically relevant environment. The plasma has been characterized as a glow discharge in the abnormal regime. Laboratory studies help understand the formation processes of polycyclic aromatic hydrocarbon (PAH) ions that are thought to be the source of the ubiquitous unidentified infrared bands.

  10. Glow plasma trigger for electron cyclotron resonance ion sources.

    PubMed

    Vodopianov, A V; Golubev, S V; Izotov, I V; Nikolaev, A G; Oks, E M; Savkin, K P; Yushkov, G Yu

    2010-02-01

    Electron cyclotron resonance ion sources (ECRISs) are particularly useful for nuclear, atomic, and high energy physics, as unique high current generators of multicharged ion beams. Plasmas of gas discharges in an open magnetic trap heated by pulsed (100 micros and longer) high power (100 kW and higher) high-frequency (greater than 37.5 GHz) microwaves of gyrotrons is promising in the field of research in the development of electron cyclotron resonance sources for high charge state ion beams. Reaching high ion charge states requires a decrease in gas pressure in the magnetic trap, but this method leads to increases in time, in which the microwave discharge develops. The gas breakdown and microwave discharge duration becomes greater than or equal to the microwave pulse duration when the pressure is decreased. This makes reaching the critical plasma density initiate an electron cyclotron resonance (ECR) discharge during pulse of microwave gyrotron radiation with gas pressure lower than a certain threshold. In order to reduce losses of microwave power, it is necessary to shorten the time of development of the ECR discharge. For fast triggering of ECR discharge under low pressure in an ECRIS, we initially propose to fill the magnetic trap with the plasmas of auxiliary pulsed discharges in crossed ExB fields. The glow plasma trigger of ECR based on a Penning or magnetron discharge has made it possible not only to fill the trap with plasma with density of 10(12) cm(-3), required for a rapid increase in plasma density and finally for ECR discharge ignition, but also to initially heat the plasma electrons to T(e) approximately = 20 eV.

  11. Infrared spectral measurement of space shuttle glow

    SciTech Connect

    Ahmadijian, M.

    1992-01-01

    Infrared spectral measurements of the space shuttle glow were successfully conducted during the STS-39 space shuttle mission. Analysis indicates that NO, NO[sup +], OH, and CO are among the molecules associated with the infrared glow phenomenon. During orbiter thruster firings the glow intensities in the infrared are enhanced by factors of 10x to 100x with significant changes in spectral distribution. These measurements were obtained with the Spacecraft Kinetic Infrared Test (SKIRT) payload which included a cryogenic infrared circular variable filter (CVF) spectrometer (0.6 [mu]m to 5.4 [mu]) and a number of infrared, visible, and ultraviolet radiometers (0.2 [mu]m to 5.4 [mu]m and 9.9 [mu]m to 10.4 [mu]m). In addition, glow measurements were unsuccessfully attempted with the Cryogenic Infrared Radiance Instrumentation for Shuttle (CIRRIS-1A) with its 2.5 [mu]m to 25 [mu]m Fourier transform interferometer. SKIRT CVF obtained over 14,000 spectra of quiescent shuttle glow, thruster enhanced shuttle glow, upper atmosphere airglow, aurora, orbiter environment, and deep space non-glow backgrounds during its eight day mission. The SKIRT radiometers operated almost continuously throughout the mission to provide a detailed history of the IR/VIS/UV optical environment associated with the operation of large spacecraft structures in low earth orbit. This dissertation will primarily address those measurements conducted by the SKIRT spectrometer as they relate to space shuttle glow in the infrared. The STS-39 Space Shuttle Discovery was launched from the NASA Kennedy Space Center on 28 April 1991 into a 57 degree inclination circular orbit at an altitude of 260 km.

  12. Vehicle glow measurements on the space shuttle

    NASA Technical Reports Server (NTRS)

    Mende, S. B.; Swenson, G. R.

    1985-01-01

    From the combined data set of glow observations on shuttle flight STS-3, STS-4, STS-5, STS-8, STS-9, 41-E, and 41-G some of the properties of the shuttle glow are discussed. Comparison of the STS-3 and STS-5 (240 and 305 km altitude, respectively) photographs shows that the intensity of the glow is about a factor of 3.5 brighter on the low-altitude (STS-3) flight. In an experiment to observe the dependence of the intensity on the ram angle, the angle of incidence between the spacecraft surface normal and the velocity vector, the Orbiter was purposely rotated about the x axis on the STS-5 mission. For a relatively large angle between the velocity vector and the surface normal there is an appreciable glow, provided the surface is not shadowed by some other spacecraft structure. As the angle becomes less the glow intensifies. Material samples were also exposed in the ram direction during nightside orbits and the glow surrounding the samples was photographed.

  13. Relativistic feedback models of terrestrial gamma-ray flashes and gamma-ray glows

    NASA Astrophysics Data System (ADS)

    Dwyer, J. R.

    2015-12-01

    Relativistic feedback discharges, also known as dark lightning, are capable of explaining many of the observed properties of terrestrial gamma-ray flashes (TGFs) and gamma-ray glows, both created within thunderstorms. During relativistic feedback discharges, the generation of energetic electrons is self-sustained via the production of backward propagating positrons and back-scattered x-rays, resulting in very larges fluxes of energetic radiation. In addition, ionization produces large electric currents that generate LF/VLF radio emissions and eventually discharge the electric field, terminating the gamma-ray production. In this presentation, new relativistic feedback model results will be presented and compared to recent observations.

  14. Investigation of Sheath Phenomena in Electronegative Glow Discharges.

    DTIC Science & Technology

    1985-04-01

    G L DUKE APR 85 UNCLASSIFIED AFWAL-TR-42099 F/G 28/3 Ni. - Mr. • -. r ° • 1 . • . . . . .. . . . ’ . . r .-’ : .:- ;- ...,:,, . ,- 1.2.0 1111111125 M...Final Report for Period July 1980 - September 1984 *Approved for public release; distribution unlimited. r .- TIC DEC 7 1985 AERO PROPULSION...LABORATORY E3 *.. AIR FORCE WRIGHT AERONAUTICAL LABORATORIES AERONAIJTICAL SYSTEMS DIVISION WRIGHT-PATTERSON AIR FORCE BASE, OHIO 45433 .---- . - .- ’ r . t .v

  15. Investigation of Sheath Phenomena in Electronegative Glow Discharges.

    DTIC Science & Technology

    1983-12-01

    300 spatial steps. It required less than 52k of memory to load and run. Parameters used in the numerical calculations are described in Appendix C. 111...202K of memory to load and run. Run times were typically 5-10sec per field iteration on a CDC 6600 computer. More recently Segur, et al. (ref 79) coupled...figure convergence in E(d). The code required 216K of memory to load and run. The majority of this space was taken up by the 220 x 201 array

  16. Electric discharge during electrosurgery

    PubMed Central

    Shashurin, Alexey; Scott, David; Zhuang, Taisen; Canady, Jerome; Beilis, Isak I.; Keidar, Michael

    2015-01-01

    Electric discharge utilized for electrosurgery is studied by means of a recently developed method for the diagnostics of small-size atmospheric plasma objects based on Rayleigh scattering of microwaves on the plasma volume. Evolution of the plasma parameters in the near-electrode sheaths and in the positive column is measured and analyzed. It is found that the electrosurgical system produces a glow discharge of alternating current with strongly contracted positive column with current densities reaching 103 A/cm2. The plasma electron density and electrical conductivities in the channel were found be 1016 cm−3 and (1-2) Ohm−1cm−1, respectively. The discharge interrupts every instance when the discharge-driving AC voltage crosses zero and re-ignites again every next half-wave at the moment when the instant voltage exceeds the breakdown threshold. PMID:25880721

  17. Io Glowing in the Dark

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Volcanic hot spots and auroral emissions glow on the darkside of Jupiter's moon Io in the image at left. The image was taken by the camera onboard NASA's Galileo spacecraft on 29 June, 1996 UT while Io was in Jupiter's shadow. It is the best and highest-resolution image ever acquired of hot spots or auroral features on Io. The mosaic at right of 1979 Voyager images is shown with an identical scale and projection to identify the locations of the hot spots seen in the Galileo image. The grid marks are at 30 degree intervals of latitude and longitude. North is to the top.

    In the nighttime Galileo image, small red ovals and perhaps some small green areas are from volcanic hot spots with temperatures of more than about 700 kelvin (about 1000 degrees Fahrenheit). Greenish areas seen near the limb, or edge of the moon, are probably the result of auroral or airglow emissions of neutral oxygen or sulfur atoms in volcanic plumes and in Io's patchy atmosphere. The image was taken from a range of 1,035,000 kilometers (about 643,000 miles).

    The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

  18. Reversal of radial glow distribution in helicon plasma induced by reversed magnetic field

    NASA Astrophysics Data System (ADS)

    Y, Wang; G, Zhao; C, Niu; Z, W. Liu; J, T. Ouyang; Q, Chen

    2017-02-01

    In this work, the reversal of radial glow distribution induced by reversed magnetic field is reported. Based on the Boswell antenna which is symmetric and insensitive to the magnetic field direction, it seems such a phenomenon in theory appears impossible. However, according to the diagnostic of the helicon waves by magnetic probe, it is found that the direction of magnetic field significantly affects the propagation characteristic of helicon waves, i.e., the interchange of the helicon waves at the upper and the lower half of tube was caused by reversing the direction of magnetic field. It is suggested that the variation of helicon wave against the direction of magnetic field causes the reversed radial glow distribution. The appearance of the traveling wave does not only improve the discharge strength, but also determines the transition of the discharge mode.

  19. Sprite beads and glows arising from the attachment instability in streamer channels

    NASA Astrophysics Data System (ADS)

    Luque, A.; Stenbaek-Nielsen, H. C.; McHarg, M. G.; Haaland, R. K.

    2016-03-01

    The complex dynamics of a sprite discharge are not limited to the propagation of streamers. After the passage of a streamer head, the ionized channel established in its wake develops intricate luminous patterns that evolve on timescales from 1 up to 100 ms. To investigate these patterns, conventionally called beads and glows, we present high-speed recordings of their onset and decay; our main observation here is that in many cases distant points within a channel decay at the same rate despite considerable differences in the underlying air density. We then show that the properties of beads and glows, including this synchronized decay, are explained by the tendency of electric current within a streamer channel to converge to an uniform value and by an attachment instability of electric discharges in air. However, we also discuss the uncertainty about the chemical reactions that affect the electron density during the sprite decay.

  20. A high resolution ultraviolet Shuttle glow spectrograph

    NASA Technical Reports Server (NTRS)

    Carruthers, George R.

    1993-01-01

    The High Resolution Shuttle Glow Spectrograph-B (HRSGS-B) is a small payload being developed by the Naval Research Laboratory. It is intended for study of shuttle surface glow in the 180-400 nm near- and middle-ultraviolet wavelength range, with a spectral resolution of 0.2 nm. It will search for, among other possible features, the band systems of excited NO which result from surface-catalyzed combination of N and O. It may also detect O2 Hertzberg bands and N2 Vegard-Kaplan bands resulting from surface recombination. This wavelength range also includes possible N2+ and OH emissions. The HRSGS-B will be housed in a Get Away Special canister, mounted in the shuttle orbiter payload bay, and will observe the glow on the tail of the orbiter.

  1. A GLOWING POOL OF LIGHT

    NASA Technical Reports Server (NTRS)

    2002-01-01

    NGC 3132 is a striking example of a planetary nebula. This expanding cloud of gas, surrounding a dying star, is known to amateur astronomers in the southern hemisphere as the 'Eight-Burst' or the 'Southern Ring' Nebula. The name 'planetary nebula' refers only to the round shape that many of these objects show when examined through a small visual telescope. In reality, these nebulae have little or nothing to do with planets, but are instead huge shells of gas ejected by stars as they near the ends of their lifetimes. NGC 3132 is nearly half a light year in diameter, and at a distance of about 2000 light years is one of the nearer known planetary nebulae. The gases are expanding away from the central star at a speed of 9 miles per second. This image, captured by NASA's Hubble Space Telescope, clearly shows two stars near the center of the nebula, a bright white one, and an adjacent, fainter companion to its upper right. (A third, unrelated star lies near the edge of the nebula.) The faint partner is actually the star that has ejected the nebula. This star is now smaller than our own Sun, but extremely hot. The flood of ultraviolet radiation from its surface makes the surrounding gases glow through fluorescence. The brighter star is in an earlier stage of stellar evolution, but in the future it will probably eject its own planetary nebula. In the Heritage Team's rendition of the Hubble image, the colors were chosen to represent the temperature of the gases. Blue represents the hottest gas, which is confined to the inner region of the nebula. Red represents the coolest gas, at the outer edge. The Hubble image also reveals a host of filaments, including one long one that resembles a waistband, made out of dust particles which have condensed out of the expanding gases. The dust particles are rich in elements such as carbon. Eons from now, these particles may be incorporated into new stars and planets when they form from interstellar gas and dust. Our own Sun may eject a

  2. Influence of driving frequency on discharge modes in a dielectric-barrier discharge with multiple current pulses

    SciTech Connect

    Jiang, Weiman; Tang, Jie; Wang, Yishan; Zhao, Wei; Duan, Yixiang

    2013-07-15

    A one-dimensional self-consistent fluid model was employed to investigate the effect of the driving frequency on the discharge modes in atmospheric-pressure argon discharge with multiple current pulses. The discharge mode was discussed in detail not only at current peaks but also between two adjacent peaks. The simulation results show that different transitions between the Townsend and glow modes during the discharge take place with the driving frequency increased. A complicated transition from the Townsend mode, through glow, Townsend, and glow, and finally back to the Townsend one is found in the discharge with the driving frequency of 8 kHz. There is a tendency of transition from the Townsend to glow mode for the discharge both at the current peaks and troughs with the increasing frequency. The discharge in the half period can all along operate in the glow mode with the driving frequency high enough. This is resulted from the preservation of more electrons in the gas gap and acquisition of more electron energy from the swiftly varying electric field with the increase in driving frequency. Comparison of the spatial and temporal evolutions of the electron density at different driving frequencies indicates that the increment of the driving frequency allows the plasma chemistry to be enhanced. This electrical characteristic is important for the applications, such as surface treatment and biomedical sterilization.

  3. Qualitative gas temperature distribution in positive DC glow corona using spectral image processing in atmospheric air

    NASA Astrophysics Data System (ADS)

    Matsumoto, Takao; Inada, Yoichi; Shimizu, Daisuke; Izawa, Yasuji; Nishijima, Kiyoto

    2015-01-01

    An experimental method of determining a qualitative two-dimensional image of the gas temperature in stationary atmospheric nonthermal plasma by spectral image processing was presented. In the experiment, a steady-state glow corona discharge was generated by applying a positive DC voltage to a rod-plane electrode in synthetic air. The changes in the gas temperature distribution due to the amplitude of applied voltage and the ambient gas pressure were investigated. Spectral images of a positive DC glow corona were taken using a gated ICCD camera with ultranarrow band-pass filters, corresponding to the head and tail of a N2 second positive system band (0-2). The qualitative gas temperature was obtained from the emission intensity ratio between the head and tail of the N2 second positive system band (0-2). From the results, we confirmed that the gas temperature and its distribution of a positive DC glow corona increased with increasing applied voltage. In particular, just before the sparkover voltage, a distinctly high temperature region was formed in the positive DC glow at the tip of the rod electrode. In addition, the gas temperature decreased and its distribution spread diffusely with decreasing ambient gas pressure.

  4. Columnar discharge mode between parallel dielectric barrier electrodes in atmospheric pressure helium

    SciTech Connect

    Hao, Yanpeng; Zheng, Bin; Liu, Yaoge

    2014-01-15

    Using a fast-gated intensified charge-coupled device, end- and side-view photographs were taken of columnar discharge between parallel dielectric barrier electrodes in atmospheric pressure helium. Based on three-dimensional images generated from end-view photographs, the number of discharge columns increased, whereas the diameter of each column decreased as the applied voltage was increased. Side-view photographs indicate that columnar discharges exhibited a mode transition ranging from Townsend to glow discharges generated by the same discharge physics as atmospheric pressure glow discharge.

  5. Interaction between pulsed discharge and radio frequency discharge burst at atmospheric pressure

    SciTech Connect

    Zhang, Jie; Guo, Ying; Shi, Yuncheng; Zhang, Jing; Shi, J. J.

    2015-08-15

    The atmospheric pressure glow discharges (APGD) with dual excitations in terms of pulsed voltage and pulse-modulation radio frequency (rf) power are studied experimentally between two parallel plates electrodes. Pulse-modulation applied in rf APGD temporally separates the discharge into repetitive discharge bursts, between which the high voltage pulses are introduced to ignite sub-microsecond pulsed discharge. The discharge characteristics and spatio-temporal evolution are investigated by means of current voltage characteristics and time resolved imaging, which suggests that the introduced pulsed discharge assists the ignition of rf discharge burst and reduces the maintain voltage of rf discharge burst. Furtherly, the time instant of pulsed discharge between rf discharge bursts is manipulated to study the ignition dynamics of rf discharge burst.

  6. The Electrostatic Environments of Mars: Atmospheric Discharges

    NASA Technical Reports Server (NTRS)

    Calle, Carlos I.; Mackey, Paul J.; Johansen, Michael R.; Hogue, Michael D.; Phillips, James, III; Cox, Rachel E.

    2016-01-01

    The electrostatic environment on Mars is controlled by its ever present atmospheric dust. Dust devils and dust storms tribocharge this dust. Theoretical studies predict that lightning and/or glow discharges should be present on Mars, but none have been directly observed. Experiments are planned to shed light on this issue.

  7. Radiofrequency Ablation of Cancer

    SciTech Connect

    Friedman, Marc; Mikityansky, Igor; Kam, Anthony; Libutti, Steven K.; Walther, McClellan M.; Neeman, Ziv; Locklin, Julia K.; Wood, Bradford J.

    2004-09-15

    Radiofrequency ablation (RFA) has been used for over 18 years for treatment of nerve-related chronic pain and cardiac arrhythmias. In the last 10 years, technical developments have increased ablation volumes in a controllable, versatile, and relatively inexpensive manner. The host of clinical applications for RFA have similarly expanded. Current RFA equipment, techniques, applications, results, complications, and research avenues for local tumor ablation are summarized.

  8. NASA CONNECT: 'Glow with the Flow'

    NASA Technical Reports Server (NTRS)

    1999-01-01

    'Geometry and Algebra: Glow with the Flow' is the second of five programs in the 2000-2001 NASA CONNECT series. Produced by NASA Langley Research Center's Office of Education, NASA CONNECT is an award-winning series of instructional programs designed to enhance the teaching of math, science and technology in grades 5-8. NASA CONNECT establishes teh 'connection' between the mathematics, science, and tehcnology concepts taught in the classroom and NASA research. NASA CONNECT is FREE and the programs in the series are in the public domain. Visit our web site adn register http://connect.larc.nasa.gov In 'Geometry and Algebra: Glow with the Flow', students will learn about the force of drag and how NASA engineers use models and glowing paints to see how air flows over vehicles in a wind tunnel. Students will also discover how the blended wing body(BWB), a concept super jumbo jet that resembles a flying wing, will affect air travelers of the future. Students will observe NASA engineers using geometry and algebra when they measure and design models to be tested in wind tunnels. By conducting classroom and on-line activities, students will make connections between NASA research and the mathematics, science and technology they learn in their classroom.

  9. Formation of a spark discharge in an inhomogeneous electric field with current limitation by a large ballast Resistance

    SciTech Connect

    Baldanov, B. B.

    2016-01-15

    Results of studies of a spark discharge initiated in argon in a point–plane electrode gap with limitation of the discharge current by a large ballast resistance are presented. It is shown that the current flowing through the plasma channel of such a low-current spark has the form of periodic pulses. It is experimentally demonstrated that, when a low-current spark transforms into a constricted glow discharge, current pulses disappear, the spatial structure of the cathode glow changes abruptly, and a brightly glowing positive plasma column forms in the gap.

  10. The role of helium metastable states in radio-frequency driven helium-oxygen atmospheric pressure plasma jets: measurement and numerical simulation

    NASA Astrophysics Data System (ADS)

    Niemi, K.; Waskoenig, J.; Sadeghi, N.; Gans, T.; O'Connell, D.

    2011-10-01

    Absolute densities of metastable He(23S1) atoms were measured line-of-sight integrated along the discharge channel of a capacitively coupled radio-frequency driven atmospheric pressure plasma jet operated in technologically relevant helium-oxygen mixtures by tunable diode-laser absorption spectroscopy. The dependences of the He(23S1) density in the homogeneous-glow-like α-mode plasma with oxygen admixtures up to 1% were investigated. The results are compared with a one-dimensional numerical simulation, which includes a semi-kinetical treatment of the pronounced electron dynamics and the complex plasma chemistry (in total 20 species and 184 reactions). Very good agreement between measurement and simulation is found. The main formation mechanisms for metastable helium atoms are identified and analyzed, including their pronounced spatio-temporal dynamics. Penning ionization through helium metastables is found to be significant for plasma sustainment, while it is revealed that helium metastables are not an important energy carrying species into the jet effluent and therefore will not play a direct role in remote surface treatments.

  11. Micro glow plasma for localized nanostructural modification of carbon nanotube forest

    NASA Astrophysics Data System (ADS)

    Sarwar, Mirza Saquib us; Xiao, Zhiming; Saleh, Tanveer; Nojeh, Alireza; Takahata, Kenichi

    2016-08-01

    This paper reports the localized selective treatment of vertically aligned carbon nanotubes, or CNT forests, for radial size modification of the nanotubes through a micro-scale glow plasma established on the material. An atmospheric-pressure DC glow plasma is shown to be stably sustained on the surface of the CNT forest in argon using micromachined tungsten electrodes with diameters down to 100 μm. Experiments reveal thinning or thickening of the nanotubes under the micro glow depending on the process conditions including discharge current and process time. These thinning and thickening effects in the treated nanotubes are measured to be up to ˜30% and ˜300% in their diameter, respectively, under the tested conditions. The elemental and Raman analyses suggest that the treated region of the CNT forest is pure carbon and maintains a degree of crystallinity. The local plasma treatment process investigated may allow modification of material characteristics in different domains for targeted regions or patterns, potentially aiding custom design of micro-electro-mechanical systems and other emerging devices enabled by the CNT forest.

  12. Spatiotemporally resolved characteristics of a gliding arc discharge in a turbulent air flow at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Zhu, Jiajian; Gao, Jinlong; Ehn, Andreas; Aldén, Marcus; Larsson, Anders; Kusano, Yukihiro; Li, Zhongshan

    2017-01-01

    A gliding arc discharge was generated in a turbulent air flow at atmospheric pressure driven by a 35 kHz alternating current (AC) electric power. The spatiotemporally resolved characteristics of the gliding arc discharge, including glow-type discharges, spark-type discharges, short-cutting events and transitions among the different types of discharges, were investigated using simultaneously optical and electrical diagnostics. The glow-type discharge shows sinusoidal-like voltage and current waveforms with a peak current of hundreds of milliamperes. The frequency of the emission intensity variation of the glow-type discharge is the same as that of the electronic power dissipated in the plasma column. The glow-type discharge can transfer into a spark discharge characterized by a sharp peak current of several amperes and a sudden increase of the brightness in the plasma column. Transitions can also be found to take place from spark-type discharges to glow-type discharges. Short-cutting events were often observed as the intermediate states formed during the spark-glow transition. Three different types of short-cutting events have been observed to generate new current paths between two plasma channel segments, and between two electrodes, as well as between the channel segment and the electrodes, respectively. The short-cut upper part of the plasma column that was found to have no current passing through can be detected several hundreds of microseconds after the short-cutting event. The voltage recovery rate, the period of AC voltage-driving signal, the flow rates and the rated input powers were found to play an important role in affecting the transitions among the different types of discharges.

  13. Gallbladder removal - laparoscopic - discharge

    MedlinePlus

    Cholecystectomy laparoscopic - discharge; Cholelithiasis - laparoscopic discharge; Biliary calculus - laparoscopic discharge; Gallstones - laparoscopic discharge; Cholecystitis - laparoscopic discharge

  14. The Glowing Eye of NGC 6751

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Astronomers using NASA's Hubble Space Telescope have obtained images of the strikingly unusual planetary nebula, NGC 6751. Glowing in the constellation Aquila like a giant eye, the nebula is a cloud of gas ejected several thousand years ago from the hot star visible in its center. The Hubble observations were obtained in 1998 with the Wide Field and Planetary Camera 2 (WFPC2) by a team of astronomers led by Arsen Hajian of the U.S. Naval Observatory in Washington, DC. The Hubble Heritage team, working at the Space Telescope Science Institute in Baltimore, has prepared this color rendition by combining the Hajian team's WFPC2 images taken through three different color filters that isolate nebular gases of different temperatures. The nebula shows several remarkable and poorly understood features. Blue regions mark the hottest glowing gas, which forms a roughly circular ring around the central stellar remnant. Orange and red show the locations of cooler gas. The cool gas tends to lie in long streamers pointing away from the central star, and in a surrounding, tattered-looking ring at the outer edge of the nebula. The origin of these cooler clouds within the nebula is still uncertain, but the streamers are clear evidence that their shapes are affected by radiation and stellar winds from the hot star at the center.

  15. Acting green elicits a literal warm glow

    NASA Astrophysics Data System (ADS)

    Taufik, Danny; Bolderdijk, Jan Willem; Steg, Linda

    2015-01-01

    Environmental policies are often based on the assumption that people only act environmentally friendly if some extrinsic reward is implicated, usually money. We argue that people might also be motivated by intrinsic rewards: doing the right thing (such as acting environmentally friendly) elicits psychological rewards in the form of positive feelings, a phenomenon known as warm glow. Given the fact that people's psychological state may affect their thermal state, we expected that this warm glow could express itself quite literally: people who act environmentally friendly may perceive the temperature to be higher. In two studies, we found that people who learned they acted environmentally friendly perceived a higher temperature than people who learned they acted environmentally unfriendly. The underlying psychological mechanism pertains to the self-concept: learning you acted environmentally friendly signals to yourself that you are a good person. Together, our studies show that acting environmentally friendly can be psychologically rewarding, suggesting that appealing to intrinsic rewards can be an alternative way to encourage pro-environmental actions.

  16. GLOW: The Goddard Lidar Observatory for Winds

    NASA Technical Reports Server (NTRS)

    Gentry, Bruce M.; Chen, Huailin; Li, Steven X.; Einaudi, Franco (Technical Monitor)

    2000-01-01

    GLOW (Goddard Lidar Observatory for Winds) is a mobile Doppler lidar system which uses direct detection Doppler lidar techniques to measure wind profiles from the surface into the lower stratosphere. The system is contained in a modified van to allow deployment in field operations. The lidar system uses a Nd:YAG laser transmitter to measure winds using either aerosol backscatter at 1064 nm or molecular backscatter at 355 nm. The receiver telescope is a 45 cm Dall-Kirkham which is fiber coupled to separate Doppler receivers, one optimized for the aerosol backscatter wind measurement and another optimized for the molecular backscatter wind measurement. The receivers are implementations of the 'double edge' technique and use high spectral resolution Fabry-Perot etalons to measure the Doppler shift. A 45 cm aperture azimuth-over-elevation scanner is mounted on the roof of the van to allow full sky access and a variety of scanning options. GLOW is intended to be used as a deployable field system for studying atmospheric dynamics and transport and can also serve as a testbed to evaluate candidate technologies developed for use in future spaceborne systems. In addition, it can be used for calibration/validation activities following launch of spaceborne wind lidar systems. A description of the mobile system is presented along with the examples of lidar wind profiles obtained with the system.

  17. GLOW- The Goddard Lidar Observatory for Winds

    NASA Technical Reports Server (NTRS)

    Gentry, Bruce M.; Chen, Huailin; Li, Steven X.

    2000-01-01

    GLOW (Goddard Lidar Observatory for Winds) is a mobile Doppler lidar system which uses direct detection Doppler lidar techniques to measure wind profiles from the surface into the lower stratosphere. The system is contained in a modified van to allow deployment in field operations. The lidar system uses a Nd:YAG laser transmitter to measure winds using either aerosol backscatter at 1064 nm or molecular backscatter at 355 nm. The receiver telescope is a 45 cm Dall-Kirkham which is fiber coupled to separate Doppler receivers, one optimized for the aerosol backscatter wind measurement and another optimized for the molecular backscatter wind measurement. The receivers are implementations of the 'double edge' technique and use high spectral resolution Fabry-Perot etalons to measure the Doppler shift. A 45 cm aperture azimuth-over-elevation scanner is mounted on the roof of the van to allow full sky access and a variety of scanning options. GLOW is intended to be used as a deployable field system for studying atmospheric dynamics and transport and can also serve as a testbed to evaluate candidate technologies developed for use in future spaceborne systems. In addition, it can be used for calibration/validation activities following launch of spaceborne wind lidar systems. A description of the mobile system is presented along with the examples of lidar wind profiles obtained with the system.

  18. Superconductive radiofrequency window assembly

    DOEpatents

    Phillips, H.L.; Elliott, T.S.

    1998-05-19

    The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The SRF window assembly has a superconducting metal-ceramic design. The SRF window assembly comprises a superconducting frame, a ceramic plate having a superconducting metallized area, and a superconducting eyelet for sealing plate into frame. The plate is brazed to eyelet which is then electron beam welded to frame. A method for providing a ceramic object mounted in a metal member to withstand cryogenic temperatures is also provided. The method involves a new metallization process for coating a selected area of a ceramic object with a thin film of a superconducting material. Finally, a method for assembling an electron beam accelerator cavity utilizing the SRF window assembly is provided. The procedure is carried out within an ultra clean room to minimize exposure to particulates which adversely affect the performance of the cavity within the electron beam accelerator. 11 figs.

  19. Superconducting radiofrequency window assembly

    DOEpatents

    Phillips, H.L.; Elliott, T.S.

    1997-03-11

    The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The srf window assembly has a superconducting metal-ceramic design. The srf window assembly comprises a superconducting frame, a ceramic plate having a superconducting metallized area, and a superconducting eyelet for sealing plate into frame. The plate is brazed to eyelet which is then electron beam welded to frame. A method for providing a ceramic object mounted in a metal member to withstand cryogenic temperatures is also provided. The method involves a new metallization process for coating a selected area of a ceramic object with a thin film of a superconducting material. Finally, a method for assembling an electron beam accelerator cavity utilizing the srf window assembly is provided. The procedure is carried out within an ultra clean room to minimize exposure to particulates which adversely affect the performance of the cavity within the electron beam accelerator. 11 figs.

  20. Radiofrequency attenuator and method

    DOEpatents

    Warner, Benjamin P.; McCleskey, T. Mark; Burrell, Anthony K.; Agrawal, Anoop; Hall, Simon B.

    2009-11-10

    Radiofrequency attenuator and method. The attenuator includes a pair of transparent windows. A chamber between the windows is filled with molten salt. Preferred molten salts include quarternary ammonium cations and fluorine-containing anions such as tetrafluoroborate (BF.sub.4.sup.-), hexafluorophosphate (PF.sub.6.sup.-), hexafluoroarsenate (AsF.sub.6.sup.-), trifluoromethylsulfonate (CF.sub.3SO.sub.3.sup.-), bis(trifluoromethylsulfonyl)imide ((CF.sub.3SO.sub.2).sub.2N.sup.-), bis(perfluoroethylsulfonyl)imide ((CF.sub.3CF.sub.2SO.sub.2).sub.2N.sup.-) and tris(trifluoromethylsulfonyl)methide ((CF.sub.3SO.sub.2).sub.3 C.sup.-). Radicals or radical cations may be added to or electrochemically generated in the molten salt to enhance the RF attenuation.

  1. Radiofrequency attenuator and method

    DOEpatents

    Warner, Benjamin P.; McCleskey, T. Mark; Burrell, Anthony K.; Agrawal, Anoop; Hall, Simon B.

    2009-01-20

    Radiofrequency attenuator and method. The attenuator includes a pair of transparent windows. A chamber between the windows is filled with molten salt. Preferred molten salts include quarternary ammonium cations and fluorine-containing anions such as tetrafluoroborate (BF.sub.4.sup.-), hexafluorophosphate (PF.sub.6.sup.-), hexafluoroarsenate (AsF.sub.6.sup.-), trifluoromethylsulfonate (CF.sub.3SO.sub.3.sup.-), bis(trifluoromethylsulfonyl)imide ((CF.sub.3SO.sub.2).sub.2N.sup.-), bis(perfluoroethylsulfonyl)imide ((CF.sub.3CF.sub.2SO.sub.2).sub.2N.sup.-) and tris(trifluoromethylsulfonyl)methide ((CF.sub.3SO.sub.2).sub.3C.sup.-). Radicals or radical cations may be added to or electrochemically generated in the molten salt to enhance the RF attenuation.

  2. Pancreatitis - discharge

    MedlinePlus

    Chronic pancreatitis - discharge; Pancreatitis - chronic - discharge; Pancreatic insufficiency - discharge; Acute pancreatitis - discharge ... fluids through an intravenous (IV) tube in your vein and nutrition through a feeding tube or IV. ...

  3. Nanosecond Repetitively Pulsed Discharges in Air at Atmospheric Pressure -- Experiment and Theory of Regime Transitions

    NASA Astrophysics Data System (ADS)

    Pai, David; Lacoste, Deanna; Laux, Christophe

    2009-10-01

    In atmospheric pressure air preheated from 300 to 1000 K, the Nanosecond Repetitively Pulsed (NRP) method has been used to generate corona, glow, and spark discharges. Experiments have been performed to determine the parameter space (applied voltage, pulse repetition frequency, ambient gas temperature, and inter-electrode gap distance) of each discharge regime. Notably, there is a minimum gap distance for the existence of the glow regime that increases with decreasing gas temperature. A theory is developed to describe the Corona-to-Glow (C-G) and Glow-to-Spark (G-S) transitions for NRP discharges. The C-G transition is shown to depend on the Avalanche-to-Streamer Transition (AST) as well as the electric field strength in the positive column. The G-S transition is due to the thermal ionization instability. The minimum gap distance for the existence of the glow regime can be understood by considering that the applied voltage of the AST must be lower than that of the thermal ionization instability. This is a previously unknown criterion for generating glow discharges, as it does not correspond to the Paschen minimum or to the Meek-Raether criterion.

  4. Capillary underwater discharges in repetitive pulse regime

    NASA Astrophysics Data System (ADS)

    de Baerdemaeker, F.; Monte, M.; Leys, C.

    2004-03-01

    In this study a capillary underwater discharge, that is sustained with AC (50 Hz) voltages up to 7.5 kV, is investigated. In a capillary discharge scheme, the current is, at some point along its path between two submerged electrodes, flowing through a narrow elongated bore in a dielectric material. When the current density is sufficiently high, local boiling and subsequent vapour breakdown results in the formation of a plasma within this capillary. At the same time the capillary emits an intense jet of vapour bubbles. Time-dependent electrical current, voltage and light emission curves are recorded for discharges in solutions of NaCl in distilled water and reveal different discharge regimes, depending on the conductivity and the excitation voltage, ranging from repetitive microsecond discharge pulses to a quasi-continuous discharge with a glow-like voltage-current characteristic.

  5. Space vehicle glow measurements on STS 41-D

    NASA Technical Reports Server (NTRS)

    Mende, S. B.; Swenson, G. R.; Clifton, K. S.; Gause, R.; Leger, L.; Garriott, O. K.

    1985-01-01

    A flight experiment using a hand-held, image-intensified spectrographic camera was performed on mission 41-D. The instrument enabled the photographic documentation of the position of the spectral slit on the image to be subjected to spectrographic analysis. Because of this instrument feature, the spectrum of the glow on the Shuttle tail pod could be clearly separated from spectrum of the scattered light from the Orbiter. From the measurements it is clear that the spectrum of the glow is a continuum in the passband of the instrument between 4200 A and 8000 A. The measured spectral resolution of the instrument was 35 A. The scattered light from the Orbiter surfaces distinctly show the components of the earth's airglow at 5577 A and 7620 A. On the same flight material samples were also carried by the Orbiter attached to the Remote Manipulating System arm. These samples were representative of the material overcoatings used on the space telescope. The altitude of the 41-D flight was 290 km, instead of the 220 km which was originally planned for this experiment. The signal to noise ratio in the material glow discrimination experiment was quite low. This made it difficult to draw strong conclusions regarding the glow propensity of the materials. Nevertheless it was clear that polyethylene produces a very weak glow, while most black overcoating materials produce significant glow. MgF2 was also found to produce a relatively intense glow.

  6. Probiotic bacteria induce a 'glow of health'.

    PubMed

    Levkovich, Tatiana; Poutahidis, Theofilos; Smillie, Christopher; Varian, Bernard J; Ibrahim, Yassin M; Lakritz, Jessica R; Alm, Eric J; Erdman, Susan E

    2013-01-01

    Radiant skin and hair are universally recognized as indications of good health. However, this 'glow of health' display remains poorly understood. We found that feeding of probiotic bacteria to aged mice induced integumentary changes mimicking peak health and reproductive fitness characteristic of much younger animals. Eating probiotic yogurt triggered epithelial follicular anagen-phase shift with sebocytogenesis resulting in thick lustrous fur due to a bacteria-triggered interleukin-10-dependent mechanism. Aged male animals eating probiotics exhibited increased subcuticular folliculogenesis, when compared with matched controls, yielding luxuriant fur only in probiotic-fed subjects. Female animals displayed probiotic-induced hyperacidity coinciding with shinier hair, a feature that also aligns with fertility in human females. Together these data provide insights into mammalian evolution and novel strategies for integumentary health.

  7. Electric discharge for treatment of trace contaminants

    NASA Technical Reports Server (NTRS)

    Flamm, D. L.; Wydeven, T. J. (Inventor)

    1978-01-01

    A radio frequency glow discharge reactor is described for removing trace oxidizable contaminants from an oxygen bearing atmosphere. The reaction chamber is defined by an inner metal electrode facing a dielectric backed by an outer conductive electrode. In one embodiment, a conductive liquid forms the conductor of an outer electrode and cools the dielectric. A resonator coupled to a variable radio frequency source generates the high voltages for creating a glow discharge in the chamber at a predetermined pressure whereby the trace contaminants are oxidized into a few simple non-toxic products that may be easily recovered. The corresponding process for removal of trace contaminants from an oxygen-bearing atmosphere with high efficiency independent of the concentration level is also disclosed.

  8. Relativistic electron avalanches as a thunderstorm discharge competing with lightning

    NASA Astrophysics Data System (ADS)

    Kelley, Nicole A.; Smith, David M.; Dwyer, Joseph R.; Splitt, Michael; Lazarus, Steven; Martinez-McKinney, Forest; Hazelton, Bryna; Grefenstette, Brian; Lowell, Alexander; Rassoul, Hamid K.

    2015-08-01

    Gamma-ray `glows' are long duration (seconds to tens of minutes) X-ray and gamma-ray emission coming from thunderclouds. Measurements suggest the presence of relativistic runaway electron avalanches (RREA), the same process underlying terrestrial gamma-ray flashes. Here we demonstrate that glows are relatively a common phenomena near the tops of thunderstorms, when compared with events such as terrestrial gamma-ray flashes. Examining the strongest glow measured by the airborne detector for energetic emissions, we show that this glow is measured near the end of a downward RREA, consistent with occurring between the upper positive charge layer and the negative screening layer above it. The glow discharges the upper positive layer by >=9.6 mA, strong enough to be an important charging mechanism of the storm. For this glow, the gamma-ray flux observed is close to the value at which relativistic feedback processes become important, with an avalanche multiplication factor of 4,500.

  9. Relativistic electron avalanches as a thunderstorm discharge competing with lightning.

    PubMed

    Kelley, Nicole A; Smith, David M; Dwyer, Joseph R; Splitt, Michael; Lazarus, Steven; Martinez-McKinney, Forest; Hazelton, Bryna; Grefenstette, Brian; Lowell, Alexander; Rassoul, Hamid K

    2015-08-12

    Gamma-ray 'glows' are long duration (seconds to tens of minutes) X-ray and gamma-ray emission coming from thunderclouds. Measurements suggest the presence of relativistic runaway electron avalanches (RREA), the same process underlying terrestrial gamma-ray flashes. Here we demonstrate that glows are relatively a common phenomena near the tops of thunderstorms, when compared with events such as terrestrial gamma-ray flashes. Examining the strongest glow measured by the airborne detector for energetic emissions, we show that this glow is measured near the end of a downward RREA, consistent with occurring between the upper positive charge layer and the negative screening layer above it. The glow discharges the upper positive layer by ≥9.6 mA, strong enough to be an important charging mechanism of the storm. For this glow, the gamma-ray flux observed is close to the value at which relativistic feedback processes become important, with an avalanche multiplication factor of 4,500.

  10. Atmospheric-pressure glow plasma synthesis of plasmonic and photoluminescent zinc oxide nanocrystals

    NASA Astrophysics Data System (ADS)

    Bilik, N.; Greenberg, B. L.; Yang, J.; Aydil, E. S.; Kortshagen, U. R.

    2016-06-01

    In this paper, we present a large-volume (non-micro) atmospheric pressure glow plasma capable of rapid, large-scale zinc oxide nanocrystal synthesis and deposition (up to 400 μg/min), whereas in the majority of the literature, nanoparticles are synthesized using micro-scale or filamentary plasmas. The reactor is an RF dielectric barrier discharge with a non-uniform gap spacing. This design encourages pre-ionization during the plasma breakdown, making the discharge uniform over a large volume. The produced zinc oxide nanocrystals typically have diameters ranging from 4 to 15 nm and exhibit photoluminescence at ≈550 nm and localized surface plasmon resonance at ≈1900 cm-1 due to oxygen vacancies. The particle size can be tuned to a degree by varying the gas temperature and the precursor mixing ratio.

  11. Modeling High Pressure Micro Hollow Cathode Discharges

    DTIC Science & Technology

    2007-11-02

    calculations in glow discharge in argon and neon . A Monte Carlo simulation of the ions and Grant 033083 – Final report 7 the fast neutrals generated...in high pressure xenon or in rare gas mixtures containing xenon are of interest in the context of UV and VUV generation. Numerical experiments on...The shape of the calculated characteristic is similar to those measured by Schoenbach et al1 in argon and by Moselhy and Schoenbach9 in xenon . There

  12. Formation of carbon nanoparticle using Ar+CH4 high pressure nanosecond discharges

    NASA Astrophysics Data System (ADS)

    Koga, K.; Dong, X.; Iwashita, S.; Czarnetzki, U.; Shiratani, M.

    2014-06-01

    We have studied formation of carbon nanoparticles using Ar+CH4 high pressure nanosecond discharge non-thermal plasmas. Transition pressure from uniform glow discharges to filamentary ones was clarified to obtain conditions under which uniform glow discharges are sustained. We have produced nanoparticles using the glow discharges, and then we have collected nanoparticles on the grounded electrode by the filtered vacuum collection method. Size distribution analysis reveals that the CH4 concentration is an important parameter in controlling nanoparticle growth. We have also studied film deposition on the powered electrode and the grounded electrode. The deposition rate on the powered electrode is 7 times higher than that on the grounded electrode. Optical emission observations suggest that radical generation rate near the powered electrode is twice higher than that near the grounded electrode, leading to high deposition rate on the powered electrode.

  13. Experimental analysis on the nonlinear behavior of DC barrier discharge plasmas

    NASA Astrophysics Data System (ADS)

    Dogan, Mansuroglu; Ilker Umit, Uzun-Kaymak

    2017-01-01

    Nonlinear behavior of glow discharge plasmas is experimentally investigated. The glow is generated between a barrier semiconductor electrode, Chromium doped namely Gallium Arsenide (GaAs:Cr), as a cathode and an Indium-Tin Oxide (ITO) coated glass electrode as an anode, in reverse bias. The planar nature of electrodes provides symmetry in spatial geometry. The discharge behaves oscillatory in the time domain, with single and sometimes multi-periodicities in plasma current and voltage characteristics. In this paper, harmonic frequency generation and transition to chaotic behavior is investigated. The observed current-voltage characteristics of the discharge are discussed in detail.

  14. Glow phenomenon surrounding the vertical stabilizer and OMS pods

    NASA Technical Reports Server (NTRS)

    1994-01-01

    This 35mm frame, photographed as the Space Shuttle Columbia was orbiting Earth during a 'night' pass, documents the glow phenomenon surrounding the vertical stabilizer and the Orbital Maneuvering System (OMS) pods of the spacecraft.

  15. Vehicle/Atmosphere Interaction Glows: Far Ultraviolet, Visible, and Infrared

    NASA Technical Reports Server (NTRS)

    Swenson, G.

    1999-01-01

    Spacecraft glow information has been gathered from a number of spacecraft including Atmospheric and Dynamic satellites, and Space Shuttles (numerous flights) with dedicated pallet flow observations on STS-39 (DOD) and STS-62 (NASA). In addition, a larger number of laboratory experiments with low energy oxygen beam studies have made important contributions to glow understanding. The following report provides information on three engineering models developed for spacecraft glow including the far ultraviolet to ultraviolet (1400-4000 A), and infrared (0.9-40 microns) spectral regions. The models include effects resulting from atmospheric density/altitude, spacecraft temperature, spacecraft material, and ram angle. Glow brightness would be predicted as a function of distance from surfaces for all wavelengths.

  16. Superconductive radiofrequency window assembly

    DOEpatents

    Phillips, Harry Lawrence; Elliott, Thomas S.

    1998-01-01

    The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The srf window assembly (20) has a superconducting metal-ceramic design. The srf window assembly (20) comprises a superconducting frame (30), a ceramic plate (40) having a superconducting metallized area, and a superconducting eyelet (50) for sealing plate (40) into frame (30). The plate (40) is brazed to eyelet (50) which is then electron beam welded to frame (30). A method for providing a ceramic object mounted in a metal member to withstand cryogenic temperatures is also provided. The method involves a new metallization process for coating a selected area of a ceramic object with a thin film of a superconducting material. Finally, a method for assembling an electron beam accelerator cavity utilizing the srf window assembly is provided. The procedure is carried out within an ultra clean room to minimize exposure to particulates which adversely affect the performance of the cavity within the electron beam accelerator.

  17. Superconducting radiofrequency window assembly

    DOEpatents

    Phillips, Harry L.; Elliott, Thomas S.

    1997-01-01

    The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The srf window assembly (20) has a superconducting metal-ceramic design. The srf window assembly (20) comprises a superconducting frame (30), a ceramic plate (40) having a superconducting metallized area, and a superconducting eyelet (50) for sealing plate (40) into frame (30). The plate (40) is brazed to eyelet (50) which is then electron beam welded to frame (30). A method for providing a ceramic object mounted in a metal member to withstand cryogenic temperatures is also provided. The method involves a new metallization process for coating a selected area of a ceramic object with a thin film of a superconducting material. Finally, a method for assembling an electron beam accelerator cavity utilizing the srf window assembly is provided. The procedure is carried out within an ultra clean room to minimize exposure to particulates which adversely affect the performance of the cavity within the electron beam accelerator.

  18. Measurement of radiofrequency fields

    SciTech Connect

    Leonowich, J.A.

    1992-05-01

    We are literally surrounded by radiofrequency (RFR) and microwave radiation, from both natural and man-made sources. The identification and control of man-made sources of RFR has become a high priority of radiation safety professionals in recent years. For the purposes of this paper, we will consider RFR to cover the frequencies from 3 kHz to 300 MHz, and microwaves from 300 MHz to 300 GHz, and will use the term RFR interchangeably to describe both. Electromagnetic radiation and field below 3 kHz is considered Extremely Low Frequency (ELF) and will not be discussed in this paper. Unlike x- and gamma radiation, RFR is non-ionizing. The energy of any RFR photon is insufficient to produce ionizations in matter. The measurement and control of RFR hazards is therefore fundamentally different from ionizing radiation. The purpose of this paper is to acquaint the reader with the fundamental issues involved in measuring and safely using RFR fields. 23 refs.

  19. Glow-to-arc transition in plasma-assisted combustion at 100 MPa

    NASA Astrophysics Data System (ADS)

    Larsson, A.; Andreasson, S.

    2015-04-01

    Electric energy can be added to the combustion of solid propellants in a gun in order to augment and to control parts of the internal ballistic cycle of the launch of a projectile. The pressure in the chamber and bore during launch is typically several hundred megapascal and the electric energy must be delivered to the flame at such a pressure level. To increase the understanding of the interaction between a flame and an electrical discharge at elevated pressure, experiments have been performed at 100 MPa in a combustion chamber where electric current has been conducted through the flame of a solid propellant. Pressure, voltage and current have been measured. The measured signals have been analysed and interpreted. The sequence of events has been interpreted as an initial formation of a glow-like discharge in the flame followed by a discharge mode transition to a filamentary arc discharge. The transition is shown to be dependent on the flame conductivity. For the test propellant used (Nzk5230 doped with 5% potassium nitrate), the flame conductivity is calculated to be 0.84 S m-1 and the discharge mode transition is found to occur after a dissipation of 0.2-0.4 kJ, or 11-22 kJ m-1 of electric energy, at an electric power of 0.1-0.5 MW.

  20. tgcd: An R package for analyzing thermoluminescence glow curves

    NASA Astrophysics Data System (ADS)

    Peng, Jun; Dong, ZhiBao; Han, FengQing

    Thermoluminescence (TL) glow curves are widely used in dosimetric studies. Many commercial and free-distributed programs are used to deconvolute TL glow curves. This study introduces an open-source R package tgcd to conduct TL glow curve analysis, such as kinetic parameter estimation, glow peak simulation, and peak shape analysis. TL glow curves can be deconvoluted according to the general-order empirical expression or the semi-analytical expression derived from the one trap-one recombination center (OTOR) model based on the Lambert W function by using a modified Levenberg-Marquardt algorithm from which any of the parameters can be constrained or fixed. The package provides an interactive environment to initialize parameters and offers an automated "trial-and-error" protocol to obtain optimal fit results. First-order, second-order, and general-order glow peaks (curves) are simulated according to a number of simple kinetic models. The package was developed using a combination of Fortran and R programming languages to improve efficiency and flexibility.

  1. Thermoluminescence glow curve analysis of natural onyx from Turkey.

    PubMed

    Dogan, Tamer; Toktamış, Hüseyin; Yüksel, Mehmet; Topaksu, Mustafa; Yazici, A Necmeddin

    2015-02-01

    In this study, the thermoluminesce (TL) properties of natural onyx were determined after β-irradiation ((90)Sr/(90)Y) at room temperature. The effect of the additive dose and variable heating rate for TL glow peaks of the sample were investigated. Computerized glow curve deconvolution (CGCD) methods were used to determine the number of peaks and kinetic parameters related to the TL glow peaks in natural onyx from Turkey. It was also determined kinetic parameters of onyx by means of the variable heating rate (VHR) method. The sample was exposed to β-irradiation between 2.4 Gy and 2.457 kGy. The CGCD methods showed that the glow curve of sample is the superposition of at least six first order components which were ascribed as P1-P6. The dose responses of some peaks have similar patterns and they follow linearity. The effect of heating rates on the response of dosimetric glow peaks of sample was studied. The maximum TL peak intensities of glow curve are decreasing with increasing heating rate and maximum TL peak intensities at 1 °C/s drops to 20% of the initial value when the sample is read at 6 °C/s.

  2. Two-dimensional simulation of spatiotemporal generation of dielectric barrier columnar discharges in atmospheric helium

    SciTech Connect

    Huang, Zhiming; Hao, Yanpeng; Yang, Lin; Han, Yongxia; Li, Licheng

    2015-12-15

    A two-dimensional (2D) fluid model is presented to investigate the spatiotemporal generation and dynamic mechanics of dielectric barrier columnar discharges in atmospheric helium. The model was examined with discharge currents measured in experiments and images taken by an intensified charge couple device camera. Based on the model, a columnar discharge was simulated for several cycles after being ignited. The discharge could be regarded as an initial unstable stage for the first three and a half cycles, then a steady state for the following cycles. In the initial stage, the discharge evolves from a uniform pattern into a columnar one. The calculated equipotential lines, 2D radial electric field, and electron density distributions at the edge of uniform discharges show the radial electric field accounts for the shrinking discharge area and the formation of discharge columns in the end. The columnar glow discharges and the Townsend discharges beyond the columns could coexist in the initial stage, and a Townsend discharge might develop into a new glow column in the next half-cycle. The radial electric field surrounding a glow discharge column has an inhibiting effect on the ionization in the peripheral area.

  3. Light modulated electron beam driven radiofrequency emitter

    DOEpatents

    Wilson, M.T.; Tallerico, P.J.

    1979-10-10

    The disclosure relates to a light modulated electron beam-driven radiofrequency emitter. Pulses of light impinge on a photoemissive device which generates an electron beam having the pulse characteristics of the light. The electron beam is accelerated through a radiofrequency resonator which produces radiofrequency emission in accordance with the electron, hence, the light pulses.

  4. Lung surgery - discharge

    MedlinePlus

    Thoracotomy - discharge; Lung tissue removal - discharge; Pneumonectomy - discharge; Lobectomy - discharge; Lung biopsy - discharge; Thoracoscopy - discharge; Video-assisted thoracoscopic surgery - discharge; VATS - ...

  5. Radiofrequency fields and teratogenesis.

    PubMed

    Heynick, Louis N; Merritt, James H

    2003-01-01

    Experimental studies that sought teratologic effects or developmental abnormalities from exposure to radiofrequency electromagnetic fields (RFEMF) in the range 3 kHz-300 GHz are critically reviewed for their possible consequences on human health. Those studies were conducted on beetles, birds, rodents, and nonhuman primates. Collectively, those experimental studies indicate that teratologic effects can occur only from exposure levels that cause biologically detrimental increases in body temperature. No reliable experimental evidence was found for nonthermal teratologic effects; rodents, mouse fetuses, and perinatal mice are more susceptible to such effects than rats. The primary confirmed effect in rats at high RFEMF levels was initial weight deficits in fetuses and neonates that decreased with infant growth. More generally from findings with pregnant mammals, exposures at RFEMF levels far higher than those permitted under the IEEE human exposure guidelines are necessary to reach or exceed cited experimental thresholds for maternal temperature increases. Some results indicated that the levels necessary to cause such effects in pregnant mammals could exceed those lethal to the dams. In a behavioral study of squirrel monkeys, no effects were observed on usual dam-offspring interactions or EEGs, but unexpected deaths of a number of offspring had occurred. However, this finding was not confirmed in a study solely on infant death using a larger number of subjects for greater statistical validity. Also reviewed were epidemiologic studies of various human populations considered to have been chronically exposed to environmental levels of RFEMF. Early studies on the incidence of congenital anomalies yielded no credible evidence that chronic exposure of pregnant women or of fathers exposed to RFEMF from nearby sources at levels below those guidelines would cause any anomalies in their offspring. The findings of studies on pregnancy outcomes of female physiotherapists

  6. Temporally, spatially, and spectrally resolved barrier discharge produced in trapped helium gas at atmospheric pressure

    SciTech Connect

    Chiper, Alina Silvia; Popa, Gheorghe

    2013-06-07

    Experimental study was made on induced effects by trapped helium gas in the pulsed positive dielectric barrier discharge (DBD) operating in symmetrical electrode configuration at atmospheric pressure. Using fast photography technique and electrical measurements, the differences in the discharge regimes between the stationary and the flowing helium are investigated. It was shown experimentally that the trapped gas atmosphere (TGA) has notable impact on the barrier discharge regime compared with the influence of the flowing gas atmosphere. According to our experimental results, the DBD discharge produced in trapped helium gas can be categorized as a multi-glow (pseudo-glow) discharge, each discharge working in the sub-normal glow regime. This conclusion is made by considering the duration of current pulse (few {mu}s), their maximum values (tens of mA), the presence of negative slope on the voltage-current characteristic, and the spatio-temporal evolution of the most representative excited species in the discharge gap. The paper focuses on the space-time distribution of the active species with a view to better understand the pseudo-glow discharge mechanism. The physical basis for these effects was suggested. A transition to filamentary discharge is suppressed in TGA mode due to the formation of supplementary source of seed electrons by surface processes (by desorption of electrons due to vibrationally excited nitrogen molecules, originated from barriers surfaces) rather than volume processes (by enhanced Penning ionisation). Finally, we show that the pseudo-glow discharge can be generated by working gas trapping only; maintaining unchanged all the electrical and constructive parameters.

  7. a Radio-Frequency

    NASA Astrophysics Data System (ADS)

    Foo, Thomas Kwok-Fah

    Radio-frequency (RF) inhomogeneity encountered in magnetic resonance (MR) imaging poses a significant impediment to obtaining images of the highest diagnostic quality. This inhomogeneity arises from the conductivity effect, which attenuates the RF field with increasing depth, and the permittivity effect. The latter is the dominant effect at 1.5 Tesla (64 MHz), and contributes to standing waves within the body. A theoretical model has been developed which describes these effects for an infinitely long right circularly cylindrical object inside a concentric RF coil and RF shield. This model assumes that the RF field propagates as a travelling wave in the z direction, along the long axis of the cylinder. The resulting solutions adequately predict the field distribution for RF coils which have both a finite wavelength and an infinite wavelength in z. This corresponds to high-pass and low-pass birdcage resonators, respectively, that are in general used in MR imaging. Standing wave models are easily obtained from the superposition of solutions of two travelling waves in opposite directions. The results of this model indicate that the axial propagation constant k_{z} is a strong function of the dielectric present in the coil -to-shield space. The field distribution in the axial plane can be represented by the Bessel function J_1(k _{rho}r), where k _sp{rho}{2} = k^2-k_sp{z}{2} . By varying the dielectric material occupying the coil-to-shield space, an optimum value of k _{z} can be obtained for a particular coil and shield configuration which minimizes the amplitude variations in the axial plane. Experimental verification of the theoretical model has been obtained. These measurements were performed on a non-resonant, travelling wave test coil with a saline phantom as a load simulating the body. The measured field profiles in the axial plane agree with the predicted values, establishing the validity of the theoretical model. As expected, optimal RF homogeneity was obtained

  8. High-Energy Radiation from Thunderstorms with ADELE: TGFs, Steps, and Glows

    NASA Technical Reports Server (NTRS)

    Smith, David M.; Kelley, Nicole; Martinez-McKinney, Forest; Zhang, Zi Yan; Hazelton, Bryna; Grefenstette, Brian; Splitt, Michael; Lazarus, Steven; Ulrich, William; Levine, Steven; Dwyer, Joseph; Schaal, Meagan; Saleh, Ziad; Cramer, Eric; Rassoul, Hamid; Cummer, Steven; Lu, Gaopeng; Shao, Xuan-Min; Ho, Cheng; Blakeslee, Richard

    2011-01-01

    The biggest challenge in the study of high-energy processes in thunderstorms is getting a detector to the vicinity of the electrically active regions of a storm. The Airborne Detector for Energetic Lightning Emissions (ADELE) has been used to detect gamma rays from aircraft above storms and from a storm-chasing van on the ground. In August 2009, ADELE flew above Florida storms in a Gulfstream V jet, detecting the first terrestrial gamma-ray flash (TGF) seen from a plane and continuous glows of high-energy emission above thunderclouds. The presence of these glows suggests that a gradual process of relativistic runaway and feedback may help limit the total amount of charging in thunderstorms, in contrast to the traditional view that only lightning discharges compete with the charging process. The upper limits on TGF emission from intracloud and cloud-to-ground lightning from the ADELE flights demonstrated conclusively that a TGF of the sort seen from space is not associated with most lightning and not necessary to trigger it. In August 2010, observations from a van detected stepped-leader x-ray emission from at least four lightning strikes in ten days of operations. This mode of operation is therefore promising for future observations of the stepping process, although a more varied suite of instrumentation, in particular a flash-distance detector, would be useful. We will report on these results and on future possibilities for ADELE campaigns.

  9. Helicon plasma thruster discharge model

    SciTech Connect

    Lafleur, T.

    2014-04-15

    By considering particle, momentum, and energy balance equations, we develop a semi-empirical quasi one-dimensional analytical discharge model of radio-frequency and helicon plasma thrusters. The model, which includes both the upstream plasma source region as well as the downstream diverging magnetic nozzle region, is compared with experimental measurements and confirms current performance levels. Analysis of the discharge model identifies plasma power losses on the radial and back wall of the thruster as the major performance reduction factors. These losses serve as sinks for the input power which do not contribute to the thrust, and which reduce the maximum plasma density and hence propellant utilization. With significant radial plasma losses eliminated, the discharge model (with argon) predicts specific impulses in excess of 3000 s, propellant utilizations above 90%, and thruster efficiencies of about 30%.

  10. Analysis of Thermoluminescence Glow Curves Using Derivatives of Different Orders.

    PubMed

    Karmakar, Mahua; Bhattacharyya, S; Sarkar, A; Mazumdar, P S; Singh, S D

    2017-01-16

    The suitability of the second derivative method for locating component peaks in complex thermoluminescence (TL) glow curves has been investigated in this work by considering both numerically simulated and experimental TL peaks. This technique is useful to acquire knowledge of the number of component peaks in a complex TL curve which in turn serves as a basic information before applying the deconvolution technique to the glow curve. To check the consistency of the results so obtained, we have also applied the first derivative technique to TL glow curves. It is well-known that kinetic order formalism fails for saturated TL peaks with heavy retrapping. Such peaks are usually broad and, to the best of our knowledge, have not yet been observed experimentally. The present derivative technique has been used to detect whether such broad peaks are truly single or not by considering a number of numerically simulated saturated glow curves with heavy retrapping where the conventional peak shape method fails. In all the cases considered here, the second derivative technique proves to be a potential candidate for estimating the number of peaks and their respective locations in a complex TL glow curve.

  11. Experimental research of radio-frequency ion thruster

    NASA Astrophysics Data System (ADS)

    Antropov, N. N.; Akhmetzhanov, R. V.; Bogatyy, A. V.; Grishin, R. A.; Kozhevnikov, V. V.; Plokhikh, A. P.; Popov, G. A.; Khartov, S. A.

    2016-12-01

    The article is devoted to the research of low-power (300 W) radio-frequency ion thruster designed at the Moscow Aviation Institute. The main results of experimental research of the thruster using the testfacility power supplies and the power processing unit of their own design are presented. The dependence of the working fluid ionization cost on its mass flow rate at the constant ion beam current was investigated experimentally. The influence of the shape and material of the discharge chamber on the integral characteristics of the thruster was studied. The recommendations on the optimization of the thruster primary performance were developed based on the results of experimental studies.

  12. Investigation of planar barrier discharges for coherent nonlinear structures

    NASA Astrophysics Data System (ADS)

    Uzun-Kaymak, I. U.

    2017-02-01

    Nonlinear pattern formations are ubiquitous in nature. One of the analogous configurations in laboratory experiments to such nonlinear systems is the current filament formations observed in glow plasmas. These filaments can generate oscillatory fluctuations in glow, which are also observed in voltage and current measurements. Specifically, semiconductor-gas discharges are known to breed these types of current filaments naturally. The plasma discharge is initiated by applying a DC high voltage to electrodes while they are immersed in nitrogen gas at partial atmospheric pressure. Observed discharge behaves oscillatory in time. Harmonic frequency generation and coherency levels among these modes are investigated. Parametric scans are performed to study the transition to chaotic behavior. Observed results are discussed in detail.

  13. Radical prostatectomy - discharge

    MedlinePlus

    ... prostatectomy - discharge; Laparoscopic radical prostatectomy - discharge; LRP - discharge; Robotic-assisted laparoscopic prostatectomy - discharge ; RALP - discharge; Pelvic lymphadenectomy - discharge; Prostate cancer - prostatectomy

  14. Data requirements for verification of ram glow chemistry

    NASA Technical Reports Server (NTRS)

    Swenson, G. R.; Mende, S. B.

    1985-01-01

    A set of questions is posed regarding the surface chemistry producing the ram glow on the space shuttle. The questions surround verification of the chemical cycle involved in the physical processes leading to the glow. The questions, and a matrix of measurements required for most answers, are presented. The measurements include knowledge of the flux composition to and from a ram surface as well as spectroscopic signatures from the U to visible to IR. A pallet set of experiments proposed to accomplish the measurements is discussed. An interim experiment involving an available infrared instrument to be operated from the shuttle Orbiter cabin is also be discussed.

  15. Influence of dust particles on ionization and excitation in neon dc discharge

    NASA Astrophysics Data System (ADS)

    Shumova, V. V.; Polyakov, D. N.; Vasilyak, L. M.

    2015-11-01

    The influence of dust particles on the concentration of metastable neon atoms and ionization was investigated using the developed drift/diffusion model for plasma of positive column of glow discharge. The detailed de-excitation in neon was considered. In addition to usual plasma losses in dusty plasmas, the quenching of metastable atoms on dust particle surface was considered. The strong influence of dust particles on the ionization rate and concentration of metastable neon atoms in a positive column of glow discharge is shown to result from the change in the longitudinal electric field strength.

  16. Wire chamber radiation detector with discharge control

    DOEpatents

    Perez-Mendez, Victor; Mulera, Terrence A.

    1984-01-01

    A wire chamber radiation detector (11) has spaced apart parallel electrodes (16) and grids (17, 18, 19) defining an ignition region (21) in which charged particles (12) or other ionizing radiations initiate brief localized avalanche discharges (93) and defining an adjacent memory region (22) in which sustained glow discharges (94) are initiated by the primary discharges (93). Conductors (29, 32) of the grids (18, 19) at each side of the memory section (22) extend in orthogonal directions enabling readout of the X-Y coordinates of locations at which charged particles (12) were detected by sequentially transmitting pulses to the conductors (29) of one grid (18) while detecting transmissions of the pulses to the orthogonal conductors (36) of the other grid (19) through glow discharges (94). One of the grids (19) bounding the memory region (22) is defined by an array of conductive elements (32) each of which is connected to the associated readout conductor (36) through a separate resistance (37). The wire chamber (11) avoids ambiguities and imprecisions in the readout of coordinates when large numbers of simultaneous or near simultaneous charged particles (12) have been detected. Down time between detection periods and the generation of radio frequency noise are also reduced.

  17. Vaginal Discharge

    MedlinePlus

    ... also be on the lookout for symptoms of yeast infections, bacterial vaginosis and trichomoniasis, 3 infections that ... cause changes in your vaginal discharge.Signs of yeast infectionsWhite, cottage cheese-like dischargeSwelling and pain around ...

  18. Validating the Goldstein-Wehner Law for the Stratified Positive Column of DC Discharge in an Undergraduate Laboratory

    ERIC Educational Resources Information Center

    Lisovskiy, V. A.; Koval, V. A.; Artushenko, E. P.; Yegorenkov, V. D.

    2012-01-01

    In this paper we suggest a simple technique for validating the Goldstein-Wehner law for a stratified positive column of dc glow discharge while studying the properties of gas discharges in an undergraduate laboratory. To accomplish this a simple device with a pre-vacuum mechanical pump, dc source and gas pressure gauge is required. Experiments may…

  19. Water purification by electrical discharges

    NASA Astrophysics Data System (ADS)

    Arif Malik, Muhammad; Ghaffar, Abdul; Akbar Malik, Salman

    2001-02-01

    There is a continuing need for the development of effective, cheap and environmentally friendly processes for the disinfection and degradation of organic pollutants from water. Ozonation processes are now replacing conventional chlorination processes because ozone is a stronger oxidizing agent and a more effective disinfectant without any side effects. However, the fact that the cost of ozonation processes is higher than chlorination processes is their main disadvantage. In this paper recent developments targeted to make ozonation processes cheaper by improving the efficiency of ozone generation, for example, by incorporation of catalytic packing in the ozone generator, better dispersion of ozone in water and faster conversion of dissolved ozone to free radicals are described. The synthesis of ozone in electrical discharges is discussed. Furthermore, the generation and plasma chemical reactions of several chemically active species, such as H2O2, Obullet, OHbullet, HO2bullet, O3*, N2*, e-, O2-, O-, O2+, etc, which are produced in the electrical discharges are described. Most of these species are stronger oxidizers than ozone. Therefore, water treatment by direct electrical discharges may provide a means to utilize these species in addition to ozone. Much research and development activity has been devoted to achieve these targets in the recent past. An overview of these techniques and important developments that have taken place in this area are discussed. In particular, pulsed corona discharge, dielectric barrier discharge and contact glow discharge electrolysis techniques are being studied for the purpose of cleaning water. The units based on electrical discharges in water or close to the water level are being tested at industrial-scale water treatment plants.}

  20. SkyGlowNet as a Vehicle for STEM Education

    NASA Astrophysics Data System (ADS)

    Flurchick, K. M.; Craine, E. R.; Culver, R. B.; Deal, S.; Foster, C.

    2013-06-01

    SkyGlowNet is an emerging network of internet-enabled sky brightness meters (iSBM) that continuously record and log sky brightness at the zenith of each network node site. Also logged are time and weather information. These data are polled at a user-defined frequency, typically about every 45 seconds. The data are uploaded to the SkyGlowNet website, initially to a proprietary area where the data for each institution are embargoed for one or two semesters as students conduct research projects with their data. When released from embargo, the data are moved to another area where they can be accessed by all SkyGlowNet participants. Some of the data are periodically released to a public area on the website. In this presentation we describe the data formats and provide examples of both data content and the structure of the website. Early data from two nodes in the SkyGlowNet have been characterized, both quantitatively and qualitatively, by undergraduate students at NCAT. A summary of their work is presented here. These analyses are of utility in helping those new to looking at these data to understand how to interpret them. In particular, we demonstrate differences between effects on light at night and sky brightness due to astronomical cycles, atmospheric phenomena, and artificial lighting. Quantitative characterization of the data includes statistical analyses of parsed segments of the temporal data stream. An attempt is made to relate statistical metrics to specific types of phenomena.

  1. Process of commutation of a vacuum electric-discharge gap by laser plasma

    SciTech Connect

    Davydov, S. G. Dolgov, A. N.; Kozlovskaya, T. I.; Revazov, V. O.; Seleznev, V. P.; Yakubov, R. Kh.

    2016-01-15

    The temporal parameters of a process of vacuum gap commutation under exposure to a nanosecond pulse of laser radiation incident on the cathode has been studied depending on the radiation energy. Based on the experiment data, it is suggested that a glow discharge is initially ignited in electrode erosion products under exposure to the laser pulse, which due to development of the ionization-overheating instability undergoes the contraction of current channel and transits to an arc discharge. With the radiation energy exceeding a threshold value, the radiation (incident on the cathode) accelerates directly the instability development and the glow discharge transition to the arc discharge due to the radiation absorption in the discharge plasma.

  2. [Study of plasma temperature measurements for oxygen discharge].

    PubMed

    Li, Liu-Cheng; Wang, Zeng-Qiang; Li, Gu-Fu; Duo, Li-Ping

    2011-10-01

    A radio-frequency discharge setup was constructed by two shell-shaped copper electrodes and a 30 cm long pyrex glass tube (i. d. = 1.65 cm) to examine the gas temperature of oxygen plasma in electric discharge oxygen iodine laser. The discharge was supplied by a 500 watt, 13.56 MHz radio-frequency power. The gas pressure in the discharge cavity was 1 330 Pa. The temperature of oxygen discharge plasma was measured by using the P branch of O2 (b, v = 0) rotational emission spectrum. Two methods were used to deduce the oxygen gas temperature. They are Boltzman plotting method and computer simulating spectrum method, respectively. Gauss fitting method was used to distinguish spectrum peaks for lower resolution spectrum. The spectrum peak area was used to characterize the optical emission intensity. The gas temperature of oxygen discharge plasma was obtained by Boltzmann plotting method. Alternatively, the optical emission spectrum was simulated by computer modeling with spectrometer slit function which was obtained by He-Ne laser. Consequently, the gas temperature of oxygen plasma was obtained by comparing the computer simulating spectrum and the experimentally observed spectrum according to the least square fitting rule. The measurement results with the two methods agree well. It was concluded that the simple optical technique can be used conveniently in the temperature diagnostics of oxygen radio-frequency discharge plasma.

  3. Anti-reflux surgery - discharge

    MedlinePlus

    ... fundoplication - discharge; Toupet fundoplication - discharge; Thal fundoplication - discharge; Hiatal hernia repair - discharge; Endoluminal fundoplication - discharge; GERD - fundoplication discharge; ...

  4. Bone marrow transplant - discharge

    MedlinePlus

    Transplant - bone marrow - discharge; Stem cell transplant - discharge; Hematopoietic stem cell transplant - discharge; Reduced intensity; Non-myeloablative transplant - discharge; Mini transplant - discharge; Allogenic bone marrow transplant - ...

  5. Predicting nurses' acceptance of radiofrequency identification technology.

    PubMed

    Norten, Adam

    2012-10-01

    The technology of radiofrequency identification allows for the scanning of radiofrequency identification-tagged objects and individuals without line-of-sight requirements. Healthcare organizations use radiofrequency identification to ensure the health and safety of patients and medical personnel and to uncover inefficiencies. Although the successful implementation of a system incorporating radiofrequency identification technologies requires acceptance and use of the technology, some nurses using radiofrequency identification in hospitals feel like "Big Brother" is watching them. This predictive study used a theoretical model assessing the effect of five independent variables: privacy concerns, attitudes, subjective norms, controllability, and self-efficacy, on a dependent variable, nurses' behavioral intention to use radiofrequency identification. A Web-based questionnaire containing previously validated questions was answered by 106 US RNs. Multiple linear regression showed that all constructs together accounted for 60% of the variance in nurses' intention to use radiofrequency identification. Of the predictors in the model, attitudes provided the largest unique contribution when the other predictors in the model were held constant; subjective norms also provided a unique contribution. Privacy concerns, controllability, and self-efficacy did not provide a significant contribution to nurses' behavioral intention to use radiofrequency identification.

  6. Carbonaceous Particles Production in a Sputtering Discharge

    SciTech Connect

    Dominique, Claire; Sant, Marco; Arnas, Cecile

    2005-10-31

    Spherical dust particles have been produced in argon glow discharge by sputtering of a graphite cathode. Their size varies from 40 to 200 nm depending on the distance between the two electrodes and the largest ones have a cauliflower shape. Simulations giving the evolution of the energy distribution of sputtered carbon atoms suggest a mechanism of growth by carbon vapour condensation. The chemical composition and structure of particles have been investigated by infrared spectroscopy and appear to be a complex arrangement of the carbon atoms and hetero-atoms.

  7. Radio-Frequency Strain Monitor

    NASA Technical Reports Server (NTRS)

    Heyman, Joseph S.; Rogowski, Robert S.; Holben, Milford S., Jr.

    1988-01-01

    Radio-frequency (RF) strain monitor developed to measure lengths of objects. RF waveguide or cable bonded to structure monitored. Propagation of RF signal along waveguide results in phase shift proportional to length of path traveled. Impedance mismatches placed in RF cable at nodes of structure. Records mismatches and detects overall length of line and lengths of intervals between nodes. Used to detect changes in elements of large structure with single cable. Monitor has potential for many applications, including monitoring stability of such large structures as aircraft, bridges, and buildings in Earthquake zones.

  8. Laser Navigation for Radiofrequency Ablation

    SciTech Connect

    Varro, Zoltan; Locklin, Julia K. Wood, Bradford J.

    2004-09-15

    A 45-year-old male with renal cell carcinoma secondary to von-Hippel Lindau (VHL) disease presented for radiofrequency ablation (RFA) of kidney tumors. Due to his prior history of several partial nephrectomies and limited renal reserve, RFA was chosen because of its relatively nephron-sparing nature. A laser guidance device was used to help guide probe placement in an attempt to reduce procedure time and improve targeting accuracy. The device was successful at guiding needle placement, as both tumors were located with a single pass. Follow-up CT scan confirmed accurate needle placement, showing an area of coagulation necrosis covering the previously seen tumor.

  9. Radiofrequency Ablation for Liver Cancer.

    PubMed

    Jacobs, Amy

    2015-01-01

    Interventional ablative technologies aided by imaging techniques such as ultrasonography, computed tomography, and magnetic resonance imaging have been crucial in managing patients with primary liver cancer and liver metastases over the past 20 years. Several ablative technologies have been used to treat liver cancer; however, radiofrequency ablation (RFA) has emerged as the most common ablative therapy for hepatic lesions, both in the United States and globally. RFA is the treatment of choice for patients who cannot have surgical resection of the liver. This article focuses on the role of imaging in RFA treatment of primary and metastatic hepatic lesions.

  10. Spectral identification/elimination of molecular species in spacecraft glow

    NASA Technical Reports Server (NTRS)

    Green, B. D.; Marinelli, W. J.; Rawlins, W. T.

    1985-01-01

    Computer models of molecular electronic and vibrational emission intensities were developed. Known radiative emission rates (Einstein coefficients) permit the determination of relative excited state densities from spectral intensities. These codes were applied to the published spectra of glow above shuttle surface and to the Spacelab 1 results of Torr and Torr. The theoretical high-resolution spectra were convolved with the appropriate instrumental slit functions to allow accurate comparison with data. The published spacelab spectrum is complex but N2+ Meinel emission can be clearly identified in the ram spectrum. M2 First Positive emission does not correlate well with observed features, nor does the CN Red System. Spectral overlay comparisons are presented. The spectrum of glow above shuttle surfaces, in contrast to the ISO data, is not highly structured. Diatomic molecular emission was matched to the observed spectral shape. Source excitation mechanisms such as (oxygen atom)-(surface species) reaction product chemiluminescence, surface recombination, or resonance fluorescent re-emission will be discussed for each tentative assignment. These assignments are the necessary first analytical step toward mechanism identification. Different glow mechanisms will occur above surfaces under different orbital conditions.

  11. Spectral identification/elimination of molecular species in spacecraft glow

    NASA Astrophysics Data System (ADS)

    Green, B. D.; Marinelli, W. J.; Rawlins, W. T.

    1985-09-01

    Computer models of molecular electronic and vibrational emission intensities were developed. Known radiative emission rates (Einstein coefficients) permit the determination of relative excited state densities from spectral intensities. These codes were applied to the published spectra of glow above shuttle surface and to the Spacelab 1 results of Torr and Torr. The theoretical high-resolution spectra were convolved with the appropriate instrumental slit functions to allow accurate comparison with data. The published spacelab spectrum is complex but N2+ Meinel emission can be clearly identified in the ram spectrum. M2 First Positive emission does not correlate well with observed features, nor does the CN Red System. Spectral overlay comparisons are presented. The spectrum of glow above shuttle surfaces, in contrast to the ISO data, is not highly structured. Diatomic molecular emission was matched to the observed spectral shape. Source excitation mechanisms such as (oxygen atom)-(surface species) reaction product chemiluminescence, surface recombination, or resonance fluorescent re-emission will be discussed for each tentative assignment. These assignments are the necessary first analytical step toward mechanism identification. Different glow mechanisms will occur above surfaces under different orbital conditions.

  12. Analysis of thermoluminescent glow peaks of zoisite under beta irradiations

    SciTech Connect

    Ccallata, Henry Javier; Watanabe, Shigueo

    2010-08-04

    In this study, the thermoluminescence (TL) properties of natural crystal of zoisite were investigated after beta ({sup 90}Sr) irradiation at room temperature (RT). Zoisite, of chemical formula Ca{sub 2}Al{sub 3}(SiO{sub 4})(Si{sub 2}O{sub 7})O(OH), is found in Minas Gerais State, Brazil as natural mineral of silicate, member of the epidote group. The glow curve of a natural sample submitted to a heat treatment at 600 deg. C is composed of two broad peaks, centered at about 110-130 deg. C and another one at about 205-210 deg. C. A heating rate of 4 deg. C s{sup -1} was used in the temperature range from RT to 300 deg. C. The additive dose, T{sub m}-T{sub STOP} thermal cleaning, initial rise, variable heating rate and computerized glow curve deconvolution methods have shown that the glow curve is a superposition of six peaks at 100, 130, 155, 175, 200 and 230 deg. C. The trapping parameters for the individual peaks have been calculated. The TL dose response of 130 and 200 deg. C peaks has a linear response. Zoisite is a candidate for a TL dosimeter because of its high sensitivity.

  13. Space shuttle Ram glow: Implication of NO2 recombination continuum

    NASA Astrophysics Data System (ADS)

    Swenson, G. R.; Mende, S. B.; Clifton, S.

    1985-09-01

    The ram glow data gathered to data from imaging experiments on space shuttle suggest the glow is a continuum (within 34 angstrom resolution); the continuum shape is such that the peak is near 7000 angstroms decreasing to the blue and red, and the average molecular travel leading to emission after leaving the surface is 20 cm (assuming isotropic scattering from the surface). Emission continuum is rare in molecular systems but the measured spectrum does resemble the laboratory spectrum of NO2 (B) recombination continuum. The thickness of the observed emission is consistent with the NO2 hypothesis given an exit velocity of approx. 2.5 km/sec (1.3 eV) which leaves approx. 3.7 eV of ramming OI energy available for unbonding the recombined NO2 from the surface. The NO2 is formed in a 3-body recombination of OI + NO + m = NO2 + m where OI originates from the atmosphere and NO is chemically formed on the surface from atmospheric NI and OI. The spacecraft surface then acts as the n for the reaction: Evidence exists from orbital mass spectrometer data that the NO and NO2 chemistry described in this process does occur on surfaces of spectrometer orifices in orbit. Surface temperature effects are likely a factor in the NO sticking efficiency and, therefore, glow intensities.

  14. Triggering Excimer Lasers by Photoionization from Corona Discharges

    NASA Astrophysics Data System (ADS)

    Xiong, Zhongmin; Duffey, Thomas; Brown, Daniel; Kushner, Mark

    2009-10-01

    High repetition rate ArF (192 nm) excimer lasers are used for photolithography sources in microelectronics fabrication. In highly attaching gas mixtures, preionization is critical to obtaining stable, reproducible glow discharges. Photoionization from a separate corona discharge is one technique for preionization which triggers the subsequent electron avalanche between the main electrodes. Photoionization triggering of an ArF excimer laser sustained in multi-atmosphere Ne/Ar/F2/Xe gas mixtures has been investigated using a 2-dimensional plasma hydrodynamics model including radiation transport. Continuity equations for charged and neutral species, and Poisson's equation are solved coincident with the electron temperature with transport coefficients obtained from solutions of Boltzmann's equation. Photoionizing radiation is produced by a surface discharge which propagates along a corona-bar located adjacent to the discharge electrodes. The consequences of pulse power waveform, corona bar location, capacitance and gas mixture on uniformity, symmetry and gain of the avalanche discharge will be discussed.

  15. Septoplasty - discharge

    MedlinePlus

    ... this page: //medlineplus.gov/ency/patientinstructions/000246.htm Septoplasty - discharge To use the sharing features on this page, please enable JavaScript. Septoplasty is surgery to correct any problems in the ...

  16. Osteomyelitis - discharge

    MedlinePlus

    ... this page: //medlineplus.gov/ency/patientinstructions/000297.htm Osteomyelitis - discharge To use the sharing features on this page, please enable JavaScript. You have osteomyelitis , a bone infection caused by bacteria or other ...

  17. Cirrhosis - discharge

    MedlinePlus

    ... this page: //medlineplus.gov/ency/patientinstructions/000290.htm Cirrhosis - discharge To use the sharing features on this page, please enable JavaScript. You have cirrhosis of the liver. Scar tissue forms and your ...

  18. Detailed kinetic study of the thermoluminescence glow curve of synthetic quartz.

    PubMed

    Kitis, G; Pagonis, V; Carty, H; Tatsis, E

    2002-01-01

    A detailed kinetic analysis has been performed of the thermoluminescence (TL) glow curve of high purity synthetic quartz. The kinetic parameters of the glow peak at 110 degrees C were evaluated for doses ranging from 0.1 Gy to 100 Gy using glow curve deconvolution (GCD), initial rise, variable heating ratc and phosphorescence decay methods. All the methods gave results that agree within the experimental errors.

  19. Radiofrequency Ablation: A Nursing Perspective

    PubMed Central

    Locklin, Julia K.; Wood, Bradford J.

    2008-01-01

    Radiofrequency ablation (RFA) has emerged as a safe and predictable technology for treating certain patients with cancer who otherwise have few treatment options. Nurses need to be familiar with all phases of the RFA procedure to create an optimal environment for patients. This article offers a brief review of the RFA procedure and nurses' responsibilities in caring for these patients. Before RFA, nurses should focus on patient education and aggressive hydration. During the procedure, nurses can prevent injury by placing grounding pads appropriately, monitoring vital signs, and medicating patients as needed. After RFA, nurses should assess the skin puncture site, provide adequate pain relief, and, again, hydrate patients. Nurses who care appropriately for RFA recipients may help to improve patient outcomes and make an otherwise frightening procedure more comfortable. PMID:15973845

  20. Desulfurization of Ni-based super alloys by combined heating and glow discharge

    SciTech Connect

    Outlaw, R.A.; Rezaie-Serej, S.; Allen, W.P.; Latanision, R.M.

    1996-04-15

    The service lifetime of blades and vanes in aircraft gas turbines can be influenced by the degradation of the interface of the Ni-based superalloy and the overlying aluminide coating during cyclic oxidation. Advanced superalloys and coatings rely on formation of a thin and continuous Al{sub 2}O{sub 3} film to protect the base alloy from further oxidative attack at temperatures above 980 C. In order that the Al{sub 2}O{sub 3} scale be protective, it must remain adherent to the underlying alloy under thermal cycling conditions. Recent experimental work indicates that the interfacial binding between Ni and the overlying Al{sub 2}O{sub 3} scale is initially strong, but has also been shown that segregation of indigenous sulfur to the metal/oxide interface induces premature scale spallation, apparently through a reduction in the interfacial adhesive strength with a concomitant reduction in component lifetime. Removal of the sulfur is the best solution to this problem.