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Sample records for low-pressure plasma discharges

  1. Relatively high plasma density in low pressure inductive discharges

    SciTech Connect

    Kang, Hyun-Ju; Kim, Yu-Sin; Chung, Chin-Wook

    2015-09-15

    Electron energy probability functions (EEPFs) were measured in a low pressure argon inductive discharge. As radio frequency (RF) power increases, discharge mode is changed from E-mode (capacitively coupled) to H-mode (inductively coupled) and the EEPFs evolve from a bi-Maxwellian distribution to a Maxwellian distribution. It is found that the plasma densities at low RF powers (<30 W) are much higher than the density predicted from the slope of the densities at high powers. Because high portion of high energy electrons of the bi-Maxwellian distribution lowers the collisional energy loss and low electron temperature of low energy electrons reduces particle loss rate at low powers. Therefore, the energy loss of plasma decreases and electron densities become higher at low powers.

  2. Features of plasma glow in low pressure terahertz gas discharge

    SciTech Connect

    Bratman, V. L.; Golubev, S. V.; Izotov, I. V.; Kalynov, Yu. K.; Koldanov, V. A.; Razin, S. V.; Litvak, A. G.; Sidorov, A. V.; Skalyga, V. A.; Zorin, V. G.

    2013-12-15

    Investigations of the low pressure (1–100 Torr) gas discharge in the powerful (1 kW) quasi-optical terahertz (0.55 THz) wave beams were made. An intense afterglow was observed after the end of gyrotron terahertz radiation pulse. Afterglow duration significantly exceeded radiation pulse length (8 μs). This phenomenon could be explained by the strong dependence of the collisional-radiative recombination rate (that is supposed to be the most likely mechanism of electron losses from the low pressure terahertz gas discharge) on electron temperature.

  3. Features of plasma glow in low pressure terahertz gas discharge

    NASA Astrophysics Data System (ADS)

    Bratman, V. L.; Golubev, S. V.; Izotov, I. V.; Kalynov, Yu. K.; Koldanov, V. A.; Litvak, A. G.; Razin, S. V.; Sidorov, A. V.; Skalyga, V. A.; Zorin, V. G.

    2013-12-01

    Investigations of the low pressure (1-100 Torr) gas discharge in the powerful (1 kW) quasi-optical terahertz (0.55 THz) wave beams were made. An intense afterglow was observed after the end of gyrotron terahertz radiation pulse. Afterglow duration significantly exceeded radiation pulse length (8 μs). This phenomenon could be explained by the strong dependence of the collisional-radiative recombination rate (that is supposed to be the most likely mechanism of electron losses from the low pressure terahertz gas discharge) on electron temperature.

  4. Two-Dimensional Plasma Density Distributions in Low-Pressure Gas Discharges

    SciTech Connect

    Berlin, E.V.; Dvinin, S.A.; Mikheev, V.V.; Omarov, M.O.; Sviridkina, V. S.

    2004-12-15

    The plasma density distribution in a two-dimensional nonuniform positive column of a low-pressure gas discharge is studied in the hydrodynamic approximation with allowance for ion inertia. Exact solutions are derived for discharges in a rectangular and a cylindrical chamber. Asymptotic solutions near the coordinate origin and near the critical surface are considered. It is shown that, for potential plasma flows, the flow velocity component normal to the plasma boundary is equal to the ion acoustic velocity. The results obtained can be used to analyze the processes occurring in low-pressure plasmochemical reactors.

  5. Observation of Quartz Cathode-Luminescence in a Low Pressure Plasma Discharge

    NASA Technical Reports Server (NTRS)

    Foster, John E.

    2004-01-01

    Intense, steady-state cathode-luminescence has been observed from exposure of quartz powder to a low pressure rf-excited argon plasma discharge. The emission spectra (400 to 850 nm) associated with the powder luminescence were documented as a function of bias voltage using a spectrometer. The emission was broad-band, essentially washing out the line spectra features of the argon plasma discharge.

  6. Growth Enhancement of Radish Sprouts Induced by Low Pressure O2 Radio Frequency Discharge Plasma Irradiation

    NASA Astrophysics Data System (ADS)

    Kitazaki, Satoshi; Koga, Kazunori; Shiratani, Masaharu; Hayashi, Nobuya

    2012-01-01

    We studied growth enhancement of radish sprouts (Raphanus sativus L.) induced by low pressure O2 radio frequency (RF) discharge plasma irradiation. The average length of radish sprouts cultivated for 7 days after O2 plasma irradiation is 30-60% greater than that without irradiation. O2 plasma irradiation does not affect seed germination. The experimental results reveal that oxygen related radicals strongly enhance growth, whereas ions and photons do not.

  7. Low pressure plasma discharges for the sterilization and decontamination of surfaces

    NASA Astrophysics Data System (ADS)

    Rossi, F.; Kylián, O.; Rauscher, H.; Hasiwa, M.; Gilliland, D.

    2009-11-01

    The mechanisms of sterilization and decontamination of surfaces are compared in direct and post discharge plasma treatments in two low-pressure reactors, microwave and inductively coupled plasma. It is shown that the removal of various biomolecules, such as proteins, pyrogens or peptides, can be obtained at high rates and low temperatures in the inductively coupled plasma (ICP) by using Ar/O2 mixtures. Similar efficiency is obtained for bacterial spores. Analysis of the discharge conditions illustrates the role of ion bombardment associated with O radicals, leading to a fast etching of organic matter. By contrast, the conditions obtained in the post discharge lead to much lower etching rates but also to a chemical modification of pyrogens, leading to their de-activation. The advantages of the two processes are discussed for the application to the practical case of decontamination of medical devices and reduction of hospital infections, illustrating the advantages and drawbacks of the two approaches.

  8. Enhancement of emission currents in plasma electron sources based on a low-pressure arc discharge

    NASA Astrophysics Data System (ADS)

    Koval, T. V.; Devyatkov, V. N.; Hung, Nguyen Bao

    2015-11-01

    The paper reports on a theoretical and experimental study of the discharge plasma generation with an enhanced electron emission current in a plasma electron source based on a low-pressure arc discharge with a grid-stabilized plasma emission boundary. The source operates at a pressure in the working chamber of p = 0.02-0.05 Pa (Ar), accelerating voltage of up to Ua = 10 kV, and longitudinal magnetic field for electron beam transport of up to Bz = 0.1 T. The experiments show that in the mode of electron emission from the plasma, the voltage Ud between the cathode and grid electrode changes its sign. The numerical simulation demonstrates that the plasma potential and voltage Ud depend on the electric field penetrating from the acceleration gap into the discharge region through the grid meshes, and on the discharge current, gas pressure, geometric transparency of the grid, and gas kind. It is shown that the main mechanisms responsible for the increase in the discharge current and electron emission current from the plasma are associated with secondary ion-electron emission from the emission electrode and with positive feedback between the region of cathode plasma generation and the channel of electron beam transport.

  9. An expression for the h l factor in low-pressure electronegative plasma discharges

    NASA Astrophysics Data System (ADS)

    Chabert, P.

    2016-04-01

    The positive ion flux exiting a low-pressure plasma discharge is a crucial quantity in global (volume-averaged) models. In discharges containing only electrons and positive ions (electropositive discharges), it is common to write this flux {Γ\\text{wall}}={{h}\\text{l}}{{n}\\text{i0}}{{u}\\text{B}} , where {{n}\\text{i0}} is the central positive ion density, {{u}\\text{B}} is the positive ion fluid speed at the sheath edge (the Bohm speed), and {{h}\\text{l}} is the positive ion edge-to-centre density ratio. There are well established formulae for {{h}\\text{l}} in electropositive discharges, but for discharges containing negative ions (electronegative discharges), the analysis is more complicated. The purpose of this paper is to propose a formula for the {{h}\\text{l}} factor in low-pressure electronegative discharges. We use the numerical solution of fluid equations with Boltzmann negative ions, including Poisson’s equation, as a guide to derive an analytical expression that can easily be incorporated in global models. The parameter space in which the derived expression is valid is discussed at the end of the paper.

  10. [Experimental study on closed plasma discharging under low pressure and spectroscopic diagnosis].

    PubMed

    Lin, Min; Xu, Hao-jun; Su, Chen; Liang, Hua

    2014-06-01

    Closed plasma can overcome difficulties of maintaining plasma and excessive energy consumption in open environment. For plasma stealth technology, a closed plasma generator was designed. Using microsecond pulse generator and argon as working gas, discharge experiments were carried out under low pressure environment. The emission spectrum of Ar at different position in discharge chamber was measured. By using collisional-radiative modal (CRM), the distribution of plasma parameters was studied. At a given electron temperature and density with specified discharge parameters, corresponding population distribution could be obtained by CRM. By comparing the line ratio of argon 2p levels acquired from CRM with the line ratio from spectrum measured, the plasma parameters were confirmed after obtaining the minimum difference value. Using the line ratio of argon 2p9 to 2p1 from CRM while the range of electron density was 1-5 eV, the calculating error was analyzed. The results reveal that, the electron density of the closed plasma reaches a magnitude of 10(11) cm(-3) and shows a gradient distribution with small variational amplitude, and the distribution is beneficial to the application of plasma stealth. PMID:25358170

  11. Energetic Ion Beam Production by a Low-Pressure Plasma Focus Discharge

    SciTech Connect

    Lim, L. K.; Yap, S. L.; Wong, C. S.

    2011-03-30

    Energetic ion beam emissions in a 3 kJ Mather type plasma focus operating at low-pressure regime are investigated. Deuterium gas is used and the discharge is operated in a low-pressure regime of below 1 mbar. Formation of the current sheath during the breakdown phase at the back wall is assisted by a set delayed trigger pulse. Energetic and intense ion beams with good reproducibility have been obtained for the operating pressure ranging from 0.05 mbar to 0.5 mbar. Deuteron beam is determined by time resolved measurement by making use of three biased ion collectors placed at the end on direction. The average energies of deuteron beams are resolved by using time-of flight method. Correlation between the ion emissions and the current sheath dynamics is also discussed.

  12. Particle modelling of magnetically confined oxygen plasma in low pressure radio frequency discharge

    SciTech Connect

    Benyoucef, Djilali; Yousfi, Mohammed

    2015-01-15

    The main objective of this paper is the modelling and simulation of a radio frequency (RF) discharge in oxygen at low pressure and at room temperature, including the effect of crossed electric and magnetic fields for generation and confinement of oxygen plasma. The particle model takes into account one axial dimension along the electric field axis and three velocity components during the Monte Carlo treatment of the collisions between charged particles and background gas. The simulation by this developed code allows us not only to determine the electrodynamics characteristics of the RF discharge, but also to obtain kinetics and energetic description of reactive oxygen plasma at low pressure. These information are very important for the control of the deep reactive-ion etching technology of the silicon to manufacture capacitors with high density and for the deposition thick insulating films or thick metal to manufacture micro-coils. The simulation conditions are as follows: RF peak voltage of 200 V, frequency of 13.56 MHz, crossed magnetic field varying from 0 to 50 Gauss, and oxygen pressure of 13.8 Pa. In the presence of magnetic field, the results show an increase of the plasma density, a decrease of the electron mean energy, and also a reduction of the ratio between electron density and positive ion density. Finally in order to validate, the results are successfully compared with measurements already carried out in the literature. The conditions of comparison are from 100 to 300 V of the peak voltage at 13.56 MHz under a pressure of 13.8 Pa and a gap distance of 2.5 cm.

  13. Glow Discharge Plasma Active Control of Separation at Low Pressure Turbine Conditions.

    NASA Astrophysics Data System (ADS)

    Hultgren, Lennart S.; Ashpis, David E.

    2002-11-01

    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%) and high (2.5%) free-stream turbulence intensities are set using passive grids. The base flow includes closed separation bubbles and non-reattaching separated flow, and is thoroughly documented using single-wire constant-temperature anemometry and static surface pressure measurements. 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 controlled flow are performed and indicate that the glow-discharge plasma actuator is an effective device for separation control.

  14. Pulsed Discharge Effects on Bacteria Inactivation in Low-Pressure Radio-Frequency Oxygen Plasma

    NASA Astrophysics Data System (ADS)

    Vicoveanu, Dragos; Ohtsu, Yasunori; Fujita, Hiroharu

    2008-02-01

    The sporicidal effects of low-pressure radio frequency (RF) discharges in oxygen, produced by the application of continuous and pulsed RF power, were evaluated. For all cases, the survival curves showed a biphasic evolution. The maximum efficiency for bacteria sterilization was obtained when the RF power was injected in the continuous wave mode, while in the pulsed mode the lowest treatment temperature was ensured. The inactivation rates were calculated from the microorganism survival curves and their dependencies on the pulse characteristics (i.e., pulse frequency and duty cycle) were compared with those of the plasma parameters. The results indicated that the inactivation rate corresponding to the first phase of the survival curves is related to the time-averaged intensity of the light emission by the excited neutral atoms in the pulsed plasma, whereas the inactivation rate calculated from the second slope of the survival curves and the time-averaged plasma density have similar behaviors, when the pulse parameters were modified.

  15. CH2Cl2 thin film formation on low-pressure DC plasma discharge

    NASA Astrophysics Data System (ADS)

    Martinez, H.; Flores, O.; Campillo, B.; Gomez, A.; Salazar-Flores, L.; Poveda, J. C.

    2012-08-01

    Low-pressure DC plasma discharges sustained in a glow discharge of CH2Cl2 are studied. The plasma conditions were: 1.0 Torr, 20 W and 12 l/min. The electron temperature and ion density were estimated to be 5.47±0.27 eV and (1.57±0.06)×1016 m-3, using a double Langmuir probe. The diagnostic of the species was made by optical emission spectroscopy using a spectrometer. The main species identified were at 339.61, 358.60 and 377.96 nm for C2(c'1Πg-b1Πu); at 392.50 nm for C3('Πu-' ? ); at 431.42 nm for CH(A2Δ-X2Π); at 778.28 nm for Cl; at 657.80 nm for C+; at 471.90 and 487.30 nm for H2; at 380.61 nm for CH+(A'Π-X'Σ) and at 317.73 nm for HCl+(A2Σ-X2Π). Special attention was given to the behavior of material deposited on the electrode and the time discharge dependence was also investigated. The material deposited was analyzed with the aid of a scanning electron microscope (SEM) and Fourier transform infrared spectroscopy. The SEM observation shows an increment in the particle size which is in agreement with the observation of less bands in the infrared spectra.

  16. Production and Study of Titan's Aerosols Analogues with A RF Low Pressure Plasma Discharge

    NASA Astrophysics Data System (ADS)

    Szopa, C.; Cernogora, G.; Correia, J. J.; Boufendi, L.; Jolly, A.

    2005-10-01

    The atmosphere of Titan, the biggest satellite of Saturn, contains aerosols produced by the organic chemistry induced by the photochemistry of N2 and CH4, the major gaseous atmospheric compounds. In spite of their importance for the properties of the Titan's atmosphere, and for organic chemistry, only few direct information are available about them because of the limitations of the observational techniques, and their processes of formation and growth are not understood. In order to bring answers to these questions, we developed a new type of laboratory simulation to produce analogues of Titan's aerosols (known as tholins) with a low pressure Radio Frequency plasma discharge. The main originality of this experiment (named PAMPRE) comes from its ability to produce particles in volume, as they are maintained in levitation by electrostatic forces compensating gravity, whereas the other experiments produce tholins on the reactors walls or a substrate. We initiated our investigations by a study of the properties of the produced particles as a function of the plasma operating conditions (i.e. amount of CH4 in N2, injected RF power, pressure, and gas flow). We here present the results of this study.

  17. Features of the Sterilization by VUV/UV Irradiation of Low-Pressure Discharge Plasma

    NASA Astrophysics Data System (ADS)

    Tsiolko, Vyacheslav V.

    The review is devoted to peculiarities of sterilization of items by VUV/UV ­radiation of the discharge plasma both in case of the items immersed into the ­discharge plasma ("direct plasma" treatment), and in case of flowing afterglow plasma ("remote plasma" treatment). The issues of influence of such factors as UV irradiation spectrum, substrate temperature on the UV sterilization efficiency are also considered.

  18. 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.

  19. Thermal equilibrium in gas-discharge plasma of low pressure mercury lamp

    NASA Astrophysics Data System (ADS)

    Gorbunkov, V. I.; Solomonov, V. I.

    2015-12-01

    A study was conducted emission spectra germicidal low pressure mercury lamp at currents 100-306 mA located in a closed opaque cavity. It is shown that the lamps located in the cavity with perfectly reflecting and absorbing internal surfaces, in the emission resonance line of mercury is dominant at λr = 253.65 nm. The same pattern is observed in the tube placed in a cavity with diffusely reflecting surface at a low current of about 100 mA. However the picture of spectrum changes at higher discharge current. The spectrum of the lamp with arc discharge at a current of 306 mA contains the maxima of the spectral lines. Its intensities are approximately described by Planck's radiation law at the temperature of 9270 +/- 230 K. The mechanisms of establish thermal equilibrium are discussed.

  20. Studies on hydrogen plasma and dust charging in low-pressure filament discharge

    SciTech Connect

    Kakati, B. Kalita, D.; Kausik, S. S.; Saikia, B. K.; Bandyopadhyay, M.

    2014-08-15

    The effect of working gas pressure and dust charging on electron energy probability function has been studied for hydrogen plasma in a multi-dipole dusty plasma device. A cylindrical Langmuir probe is used to evaluate the plasma parameters and electron energy probability function (EEPF) for different working pressures. For lower energy range (below 10 eV), the EEPF follows a bi-Maxwellian shape at very low pressure (6 × 10{sup −5} mbar), while elevating the working pressure up to ∼2 × 10{sup −3} mbar, the shape of the EEPF transforms into a single Maxwellian. Some dip structures are observed at high energy range (ε > 10 eV) in the EEPF of hydrogen plasma at all the working conditions. In presence of dust particles, it is observed that the shape of the EEPF changes due to the redistribution of the high and low-energy electron populations. Finally, the effect of working pressure on charge accumulation on dust particles is studied with the help of a Faraday cup and electrometer. From the observations, a strong influence of working pressure on plasma parameters, EEPF and dust charging is observed.

  1. Magnetic Ignition of Pulsed Gas Discharges in Air of Low Pressure in a Coaxial Plasma Gun

    NASA Technical Reports Server (NTRS)

    Thom, Karlheinz; Norwood, Joseph, Jr.

    1961-01-01

    The effect of an axial magnetic field on the breakdown voltage of a coaxial system of electrodes has been investigated by earlier workers. For low values of gas pressure times electrode spacing, the breakdown voltage is decreased by the application of the magnetic field. The electron cyclotron radius now assumes the role held by the mean free path in nonmagnetic discharges and the breakdown voltage becomes a function of the magnetic flux density. In this paper the dependence of the formative time lag as a function of the magnetic flux density is established and the feasibility of using a magnetic field for igniting high-voltage, high-current discharges is shown through theory and experiment. With a 36 microfarad capacitor bank charged to 48,000 volts, a peak current of 1.3 x 10( exp 6) amperes in a coaxial type of plasma gun was achieved with a current rise time of only 2 microseconds.

  2. Characteristics and plasma parameters of a short-wavelength low-pressure discharge lamp

    NASA Astrophysics Data System (ADS)

    Shuaibov, A. K.; Shevera, I. V.; Malinina, A. A.

    2008-10-01

    We have studied the working optical characteristics and electron kinetic coefficients of a short-wavelength, electric discharge exciplex-halogen UV-VUV lamp employing a mixture of argon and chlorine with a total pressure of P = 0.5 10 kPa. The lamp operates on a system of broadened electron-vibrational bands of ArCl (175 nm) and chlorine (200, 258 nm) molecules, which overlap to form a continuum in the spectral range of 160 260 nm. It is established that the optimum mixtures are those with p(Ar) - p(Cl2) = (2 4)-(0.15 0.30) kPa. The average output power of the short-wavelength radiation is 1 2 W at an efficiency of ˜5%. The electron energy distribution functions (EDFs) and the discharge plasma parameters have been calculated by solving the Boltzmann equation for a gas mixture with the experimentally determined optimum composition in the range of E/ P values from 1 to 200 V/(cm Torr), where E is the electric field strength and P is the total gas pressure. Using the obtained EDFs, the electron transport characteristics, specific discharge power losses for the main elementary processes, and rate constants of electron processes are determined.

  3. Plasma discharge in N2 + CH4 at low pressures - Experimental results and applications to Titan

    NASA Technical Reports Server (NTRS)

    Thompson, W. Reid; Henry, Todd J.; Schwartz, Joel M.; Khare, B. N.; Sagan, Carl

    1991-01-01

    Results are reported from laboratory continuous-flow plasma-discharge experiments designed to simulate the formation of hydrocarbons and nitriles from N2 and CH4 in the atmosphere of Titan. Gas-chromatography and mass-spectrometry data were obtained in experiments lasting up to 100 h at temperature 295 K and pressure 17 or 0.24 mbar, modeling (1) cosmic-ray-induced processes in the Titan troposphere and (2) processes related to stratospheric aurorae excited by energetic electrons and ions from the Saturn magnetosphere, respectively. The results are presented in extensive tables and graphs, and the 0.24-mbar yields are incorporated into an eddy-mixing model to give stratospheric column abundances and mole fractions in good agreement with Voyager IRIS observations.

  4. 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.

  5. Structure and properties of commercially pure titanium nitrided in the plasma of a low-pressure gas discharge produced by a PINK plasma generator

    NASA Astrophysics Data System (ADS)

    Ivanov, Yu F.; Akhmadeev, Yu H.; Lopatin, I. V.; Petrikova, E. A.; Krysina, V.; Koval, N. N.

    2015-11-01

    The paper analyzes the surface structure and properties of commercially pure VT1-0 titanium nitrided in the plasma of a low-pressure gas discharge produced by a PINK plasma generator. The analysis demonstrates that the friction coefficient of the nitrided material decreases more than four times and its wear resistance and microhardness increases more than eight and three times, respectively. The physical mechanisms responsible for the enhancement of strength and tribological properties of the material are discussed.

  6. On the effect of ion-neutral collisions on dust grain screening in a low-pressure gas discharge plasma

    NASA Astrophysics Data System (ADS)

    Semenov, I. L.; Zagorodny, A. G.; Krivtsun, I. V.

    2012-04-01

    The effect of ion-neutral collisions on charging of micrometer-sized dust grains immersed in a low-pressure argon discharge plasma is studied on the basis of the Vlasov-Bhatnagar-Gross-Krook kinetic equations. The equations are solved numerically using the method described in our previous work [I. L. Semenov et al., Phys. Plasmas 18, 103707 (2011)]. A modified version of the numerical method is proposed to reduce the required computational time. Numerical calculations are carried out for typical plasma parameters used in laboratory investigations of dusty plasma. On the basis of the obtained results, the influence of collisions on the ion flux and grain charge is analyzed. A comparison of our results with those obtained using different analytical models proposed earlier is presented. In addition, applicability of simple kinetic models describing the influence of collisions on the electric potential around a dust grain [S. A. Khrapak et al., Phys. Rev. Lett. 100, 225003 (2008); A. G. Zagorodny et al. Ukr. J. Phys. 54, 1089 (2009)] is examined. The influence of ion-neutral collisions on the distribution of plasma macroparameters near the grain surface is also demonstrated.

  7. Plasma discharge in N2 + CH4 at low pressures: experimental results and applications to Titan.

    PubMed

    Thompson, W R; Henry, T J; Schwartz, J M; Khare, B N; Sagan, C

    1991-01-01

    We report the yields of gaseous hydrocarbons and nitriles produced in a continuous flow, low-dose, cold plasma discharge excited in a 10% CH4, 90% N2 atmosphere at 295 K and pressures p of 17 and 0.24 mbar, and use the results to compute expected abundances of minor constituents in Titan's atmosphere. These experiments are, by design, relevant to the atmospheric chemistry induced by cosmic rays in Titan's troposphere and (at the lower pressure) to chemistry initiated by Saturnian magnetospheric electrons and other charged particle sources which excite stratospheric aurorae. At p = 17 mbar, 59 gaseous species including 27 nitriles are detected in overall yield 4.0 (C + N) atoms incorporated into products per 100 eV (heV). At p = 0.24 mbar, 19 species are detected, including six nitriles and three other unidentified N-bearing compounds; the yield is 0.79 (C + N)/heV, a mild decrease with pressure. The types of molecules formed change more markedly, with high degrees of multiple bonding at 0.24 mbar prevailing over more H-saturated molecules at 17 mbar. The molecules and yields at 0.24 mbar bear a striking resemblance to the minor constituents found in Titan's atmosphere, all of which are abundant products in the laboratory experiment. Using the altitude-integrated flux of charged particle energy deposition at Titan, the laboratory yields at p = 0.24 mb, and a simple eddy mixing model, we compute absolute stratospheric column abundances and mole fractions. These are found to be in very good agreement with the Voyager IRIS observations. Except for the primarily photochemical products, C2H6 and C3H8, the match is much better than that obtained by photochemical-kinetic models, demonstrating that properly designed laboratory experiments are directly applicable to modeling radiation-chemical processes in planetary atmospheres. On the basis of this agreement we expect CH3-C triple bond N (ethanenitrile = acetonitrile) CH2=CH-CH=CH2 (1,3-butadiene), CH2=C=CH2 (1,2-propadiene

  8. Gas and plasma dynamics of RF discharge jet of low pressure in a vacuum chamber with flat electrodes and inside tube, influence of RF discharge on the steel surface parameters

    NASA Astrophysics Data System (ADS)

    Khristoliubova, V. I.; Kashapov, N. F.; Shaekhov, M. F.

    2016-06-01

    Researches results of the characteristics of the RF discharge jet of low pressure and the discharge influence on the surface modification of high speed and structural steels are introduced in the article. Gas dynamics, power and energy parameters of the RF low pressure discharge flow in the discharge chamber and the electrode gap are studied in the presence of the materials. Plasma flow rate, discharge power, the concentration of electrons, the density of RF power, the ion current density, and the energy of the ions bombarding the surface materials are considered for the definition of basic properties crucial for the process of surface modification of materials as they were put in the plasma jet. The influence of the workpiece and effect of products complex configuration on the RF discharge jet of low pressure is defined. The correlation of the input parameters of the plasma unit on the characteristics of the discharge is established.

  9. The physical nature of the phenomenon of positive column plasma constriction in low-pressure noble gas direct current discharges

    SciTech Connect

    Kurbatov, P. F.

    2014-02-15

    The essence of the positive-column plasma constriction for static (the diffusion mode) and dynamic ionization equilibrium (the stratificated and constricted modes) is analyzed. Two physical parameters, namely, the effective ionization rate of gas atoms and the ambipolar diffusion coefficient of electrons and ions, determine the transverse distribution of discharge species and affect the current states of plasma. Transverse constriction of the positive column takes place as the gas ionization level (discharge current) and pressure increase. The stratified mode (including the constricted one) is observed between the two adjacent types of self-sustained discharge phases when they coexist together at the same time or in the same place as a coherent binary mixture. In the case, a occurrence of the discharge phase with more high electron density presently involve a great decrease in the cross-section of the current channel for d.c. discharges. Additional physical factors, such as cataphoresis and electrophoresis phenomena and spatial gas density inhomogeneity correlated with a circulatory flow in d.c. discharges, are mainly responsible for the current hysteresis and partially constricted discharge.

  10. Dissociation degree of nitrogen molecule in low-pressure microwave-discharge nitrogen plasma with various rare-gas admixtures

    NASA Astrophysics Data System (ADS)

    Kuwano, Kei; Nezu, Atsushi; Matsuura, Haruaki; Akatsuka, Hiroshi

    2016-08-01

    The dissociation degree of nitrogen molecules is examined in a microwave discharge nitrogen–rare gas mixture plasma with a total discharge pressure of 1 Torr, by actinometry measurement. Although the spectral line from the excited nitrogen atoms is overlapped by the band spectrum of the N2 first positive system (1PS), the subtraction of the 1PS spectrum fitted theoretically can successfully extract the atomic nitrogen line, which enables actinometry measurement. The nitrogen dissociation degree decreases with increasing mixture ratio of Ar to Kr, whereas it increases with He, which is attributed to the variations in the electron temperature and density. When we dilute the nitrogen with neon, however, we find an anomalous increase in the nitrogen dissociation degree by several orders of magnitude even at a downstream region in the discharge tube. The reason for the dissociation enhancement upon adding neon is discussed in terms of atomic and molecular processes in the plasma.

  11. 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.

  12. 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.

  13. Diagnostics of low-pressure hydrogen discharge created in a 13.56 MHz RF plasma reactor

    NASA Astrophysics Data System (ADS)

    Krištof, J.; Annušová, A.; Anguš, M.; Veis, P.; Yang, X.; Angot, T.; Roubin, P.; Cartry, G.

    2016-07-01

    A 13.56 MHz RF discharge in hydrogen was studied within the pressure range of 1–10 Pa, and at a power range of 400–1000 W. The electron energy distribution function and electron density were measured by a Langmuir probe. The gas temperature was determined by the Fulcher-α system in pure H2, and by the second positive system of nitrogen using N2 as the probing gas. The gas temperature was constant and equal to 450 ± 50 K in the capacitively coupled plasma (CCP) mode, and it increased with pressure and power in the inductively coupled plasma (ICP) mode. Also, the vibrational temperature of the ground state of hydrogen molecules was determined to be around 3100 and 2000 ± 500 K in the ICP and CCP mode, respectively. The concentration of atomic hydrogen was determined by means of actinometry, either by using Ar (5%) as the probing gas, or by using H2 as the actinometer in pure hydrogen (Q1 rotational line of Fulcher-α system). The concentration of hydrogen density increased with pressure in both modes, but with a dissociation degree slightly higher in the ICP mode (a factor 2).

  14. "Politically-Incorrect" Electron Behavior in Low Pressure RF Discharges

    NASA Astrophysics Data System (ADS)

    Godyak, Valery; Kolobov, Vladimir

    1996-10-01

    The main interaction of plasma electrons with electromagnetic fields for bounded plasma of an rf discharge occurs in the vicinity of its boundaries (in the rf sheath of a capacitive rf discharge and in the skin layer of an inductive one). On the other hand, due to plasma inhomogeneity, a dc ambipolar field is always present in the bounded plasma. in low pressure discharges the ambipolar potential well captures low energy electrons within the discharge center while high energy electrons freely overcome the ambipolar potential and reach the plasma boundaries where heating takes place. Being segregated in space, low energy electrons are discriminated from participation in the heating process. When Coulomb interaction between low and high energy electron groups is weak, their temperatures appear to be essentially different ( a low energy peak on the EEDF). In this presentation we present theoretical and experimental evidence of such an apartheid in the low and high energy electron populations of the EEDF in rf discharge and we outline discharge conditions where such abnormal EEDF behavior is possible.

  15. Spatial distribution of the electron component parameters in the nitrogen plasma of a low-pressure electrode microwave Discharge

    NASA Astrophysics Data System (ADS)

    Lebedev, Yu. A.; Krashevskaya, G. V.; Gogoleva, M. A.

    2016-01-01

    Spatial distributions of charged particle concentration, electron temperature, and DC potential in an electrode microwave discharge in nitrogen at a pressure of 1 Torr have been measured using the double electric probe method. It has been shown that, near the electrode/antenna, the charged particle concentration exceeds a critical value. The concentration and heterogeneity of the discharge increase with increasing microwave power.

  16. Efficiency of plasma density control with dc discharge and magnetic field for different surface types in low pressure hypersonic flow

    NASA Astrophysics Data System (ADS)

    Schweigert, Irina

    2013-09-01

    Recently the problem of communication blackout during reentrant flight still remains unsolved. The spacecrafts enter the upper atmospheric layers with a hypersonic speed and the shock heated air around them becomes weakly ionized. The gas ionization behind the shock front is associative in nature and occurs through chemical reactions between fragments of molecules. The formation of a plasma layer near the surfaces of spacecraft causes serious problems related to the blocking of communication channels with the Earth and other spacecrafts. A promising way of restoring the radio communications is the application of electrical and magnetic fields for controlling the plasma layer parameters. Nevertheless the flux of electrons and ions on the surface charges it that essentially decrease the effect of electro-magnetic control of local plasma density. In Ref. it is shown that there is the way to remove the surface charge using the lateral diode string structures. Based on two dimensional kinetic Particle in cell Monte Carlo collision simulations, we study the possibility of local control the plasma layer parameters near a flat surface of two different types. The gas velocity distribution is set with a model profile. We apply DC voltage up to 4 kV and magnetic field B up to 200 G.

  17. Ion optical effects in a low pressure rf plasma

    SciTech Connect

    Oechsner, Hans; Paulus, Hubert

    2013-11-15

    Ion optical effects in low pressure gas discharges are introduced as a novel input into low pressure plasma technology. They are based on appropriate geometrical plasma confinements which enable a control of the shape of internal density and potential distributions and, hence, the ion motion in the plasma bulk. Such effects are exemplified for an electron cyclotron wave resonance plasma in Ar at 1–5 × 10{sup −3} millibars. The geometry of the plasma chamber is modified by a conical and a cylindrical insert. Computer simulations display spherical plasma density contours to be formed around the conical confinement. This effects an increase of the ratio of the ion currents into the conical and the cylindrical inserts which depends on the fourth power of the plasma electron temperature. A quantitative understanding of this behavior is presented. As another essential result, the shape of the internal plasma contours is found to be independent of the pressure controlled plasma parameters.

  18. Low pressure glow discharge in a system with hollow electrode at floating potential

    NASA Astrophysics Data System (ADS)

    Babinov, N. A.

    2016-01-01

    This article describes the research of the low pressure gas discharge in a system with hollow electrode at the floating potential. The main characteristic features of the discharge distinguishing it from the glow discharge with hollow cathode are described. The studied type of discharge has good perspective to use in the plasma emission systems allowing to reach high current efficiency of the ion sources.

  19. Properties of microwave plasma torch operating at a low pressure

    SciTech Connect

    Cho, Soon C.; Uhm, Han S.; Hong, Yong C.; Kim, Jae H.

    2008-10-15

    A microwave plasma torch system is attached to a low-pressure chamber in this study. The electric field induced in a quartz discharge tube by microwave radiation breaks down the gas at a sufficiently low pressure, igniting the plasma, which is continuously sustained by the microwave radiation. The plasma profile at a very low pressure is shown to be asymmetric with higher density on the incoming side of the microwaves. The gas temperature at the bright spot of the torch plasma measured via the optical emission from hydroxide radicals is shown to increase drastically upon high-pressure operation as the microwave power increases. The electron density at the torch flame is measured by recording the Stark broadening of the hydrogen Balmer beta line. The plasma density increases as the microwave power increases. The typical argon plasma density of a plasma torch powered at 500 W under a pressure of 150 Torr is on the order of 10{sup 14}/cm{sup 3}. The electron temperature in the argon torch plasma was estimated to be 1.5 eV, thereby effectively exciting the molecules in the torch gas. Disintegration of nitrogen fluoride (NF{sub 3}) indicates that a microwave plasma torch operating at a low pressure can efficiently generate an abundant amount of chemical radicals.

  20. Nonlinear dynamical behavior of thermionic low pressure discharges. I. Simulation

    NASA Astrophysics Data System (ADS)

    Greiner, F.; Klinger, T.; Piel, A.

    1995-06-01

    The discharge modes of a thermionic low pressure discharge (p<1Pa) are investigated with the one-dimensional particle-in-cell simulation codes PDP1 and XPDP1 [C. K. Birdsall, IEEE Trans. Plasma Sci. 19, 65 (1991)]. The simulation results provide a model approach for stable discharge modes, hysteresis, and for nonlinear relaxation-oscillations. During this potential-relaxation instability, nonlinear structures, e.g. electron holes and double layers, are observed. A Pierce-Buneman-mode is suggested as a trigger mechanism for the onset of the instability. The detailed oscillation process can be subdivided into three distinct phases: expansion phase, double layer phase, and relaxation phase. This allows one to explain the parameter dependencies of the oscillation frequency. For a periodically driven discharge, mode-locking in a period-2 state is found and explained by the model. The mode-locking phenomenon is studied systematically. The results of the simulations are well confirmed by experimental observations presented in Part II of this paper [T. Klinger et al., Phys. Plasmas 2, 1822 (1995)].

  1. Nonlinear dynamical behavior of thermionic low pressure discharges. I. Simulation

    SciTech Connect

    Greiner, F.; Klinger, T.; Piel, A.

    1995-06-01

    The discharge modes of a thermionic low pressure discharge ({ital p}{lt}1Pa) are investigated with the one-dimensional particle-in-cell simulation codes PDP1 and XPDP1 [C. K. Birdsall, IEEE Trans. Plasma Sci. {bold 19}, 65 (1991)]. The simulation results provide a model approach for stable discharge modes, hysteresis, and for nonlinear relaxation-oscillations. During this potential-relaxation instability, nonlinear structures, e.g. electron holes and double layers, are observed. A Pierce--Buneman-mode is suggested as a trigger mechanism for the onset of the instability. The detailed oscillation process can be subdivided into three distinct phases: expansion phase, double layer phase, and relaxation phase. This allows one to explain the parameter dependencies of the oscillation frequency. For a periodically driven discharge, mode-locking in a period-2 state is found and explained by the model. The mode-locking phenomenon is studied systematically. The results of the simulations are well confirmed by experimental observations presented in Part II of this paper [T. Klinger {ital et} {ital al}., Phys. Plasmas {bold 2}, 1822 (1995)]. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  2. A DSMC Study of Low Pressure Argon Discharge

    NASA Technical Reports Server (NTRS)

    Hash, David B.; Meyyappan, Meyya; Arnold, James O. (Technical Monitor)

    1997-01-01

    Work toward a self-consistent plasma simulation using the DSMC (Direct Simulation Monte Carlo) method for examination of the flowfields of low-pressure high density plasma reactors is presented. Presently, DSMC simulations for these applications involve either treating the electrons as a fluid or imposing experimentally determined values for the electron number density profile. In either approach, the electrons themselves are not physically simulated. Self-consistent plasma DSMC simulations have been conducted for aerospace applications but at a severe computational cost due in part to the scalar architectures on which the codes were employed. The present work attempts to conduct such simulations at a more reasonable cost using a plasma version of the object-oriented parallel Cornell DSMC code, MONACO, on an IBM SP-2. Due to availability of experimental data, the GEC reference cell is chosen to conduct preliminary investigations. An argon discharge is chosen to conduct preliminary investigations. An argon discharge is examined thus affording a simple chemistry set with eight gas-phase reactions and five species: Ar, Ar(+), Ar(*), Ar(sub 2), and e where Ar(*) is a metastable.

  3. Ozone kinetics in low-pressure discharges

    NASA Astrophysics Data System (ADS)

    Guerra, Vasco; Marinov, Daniil; Guaitella, Olivier; Rousseau, Antoine

    2012-10-01

    Ozone kinetics is quite well established at atmospheric pressure, due to the importance of ozone in atmospheric chemistry and to the development of industrial ozone reactors. However, as the pressure is decreased and the dominant three-body reactions lose importance, the main mechanisms involved in the creation and destruction of ozone are still surrounded by important uncertainties. In this work we develop a self-consistent model for a pulsed discharge and its afterglow operating in a Pyrex reactor with inner radius 1 cm, at pressures in the range 1-5 Torr and discharge currents of 40-120 mA. The model couples the electron Boltzmann equation with a system of equations for the time evolution of the heavy particles. The calculations are compared with time-dependent measurements of ozone and atomic oxygen. Parametric studies are performed in order to clarify the role of vibrationally excited ozone in the overall kinetics and to establish the conditions where ozone production on the surface may become important. It is shown that vibrationally excited ozone does play a significant role, by increasing the time constants of ozone formation. Moreover, an upper limit for the ozone formation at the wall in these conditions is set at 10(-4).

  4. Properties of a low-pressure inductive RF discharge I: Experiment

    SciTech Connect

    Aleksandrov, A. F.; Vavilin, K. V.; Kral'kina, E. A.; Pavlov, V. B.; Rukhadze, A. A.

    2007-09-15

    Results are presented from experimental studies of low-pressure inductive RF discharges (including those with a capacitive component) employed in plasma technology. It is shown that both the RF power absorbed in the plasma and the electron density depend nonmonotonically on the external magnetic field. Discharge disruptions occurring at critical values of the magnetic field and the spatial redistribution and hysteresis of the plasma parameters were observed when varying the magnetic field and RF generator power. The parameters of the plasma of low-pressure (0.5-5 mTorr) inductive RF discharges were investigated, and the discharge properties related to the redistribution of the RF generator power between the plasma and the discharge external circuit were revealed. The experiments were performed with both conventional unmagnetized inductive plasma sources and plasma sources with a magnetic field.

  5. Influence of the oxygen concentration on the formation of crystalline phases of TiO2 during the low-pressure arc-discharge plasma synthesis

    NASA Astrophysics Data System (ADS)

    Ushakov, A. V.; Karpov, I. V.; Lepeshev, A. A.

    2016-02-01

    The synthesis of titanium dioxide (TiO2) nanoparticles with different percentage of anatase and rutile phases is investigated. The synthesis is performed by controlling the oxygen percentage in the gas mixture in the plasmachemical evaporation-condensation process employing a low-pressure arc discharge. In all our experiments, the pressure in the plasmachemical reactor and the average size of particles remain constant and are 60 Pa and 6 nm, respectively. The crystal structure of synthesized TiO2 is studied using X-ray diffraction; the morphology of the particles is analyzed employing transmission electron microscopy. Using X-ray phase analysis, it is established that the concentration of the TiO2 anatase phase decreases upon a decrease in the oxygen concentration in the gas mixture. It is shown that the TiO2 anatase phase is more efficient for photocatalytic decomposition of methylene blue than the rutile phase.

  6. 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.

  7. Kinetic Effects in Low Pressure Capacitively Coupled Plasmas

    NASA Astrophysics Data System (ADS)

    Likhanskii, Alexandre; Roark, Christine; Stoltz, Peter

    2011-10-01

    We present results of particle-in-cell/Monte Carlo collision simulations of kinetic effects in low pressure capacitively coupled plasma discharge. In particular, we examine discharges of various gases (including Ar, Xe, and others) in the pressure range of 10s of mT and the frequency range of 10s of MHz. We track the formation of high energy electrons (e.g., at the ionization threshold or greater) as a marker for enhanced ionization, and look at the effects of elastic and inelastic collisions on the formation of these high energy electron bunches. We show results for 2D and 3D simulations where we include density gradient effects, and results for plasma chemistry effects on the bulk electron energy distribution function and the ion energy distribution function at a plasma surface interface. We discuss the role of the bunches on electron heating in the plasma bulk and on their presence on how electron heating is treated in fluid simulations of plasma sources.

  8. Self-Consistent Simulations of Inductively Coupled Discharges at Very Low Pressures Using a FFT Method for Calculating the Non-local Electron Conductivity for the General Case of a Non-Uniform Plasma

    NASA Astrophysics Data System (ADS)

    Polomarov, Oleg; Theodosiou, Constantine; Kaganovich, Igor

    2003-10-01

    A self-consistent system of equations for the kinetic description of non-local, non-uniform, nearly collisionless plasmas of low-pressure discharges is presented. The system consists of a non-local conductivity operator, and a kinetic equation for the electron distribution function (EEDF) averaged over fast electron bounce motions. A Fast Fourier Transform (FFT) method was applied to speed up the numerical simulations. The importance of accounting for the non-uniform plasma density profile in computing the current density profile and the EEDF is demonstrated. Effects of plasma non-uniformity on electron heating in rf electric field have also been studied. An enhancement of the electron heating due to the bounce resonance between the electron bounce motion and the rf electric field has been observed. Additional information on the subject is posted in http://www.pppl.gov/pub_report/2003/PPPL-3814-abs.html and in http://arxiv.org/abs/physics/0211009

  9. Electron heating in low pressure capacitive discharges revisited

    SciTech Connect

    Kawamura, E.; Lieberman, M. A.; Lichtenberg, A. J.

    2014-12-15

    The electrons in capacitively coupled plasmas (CCPs) absorb energy via ohmic heating due to electron-neutral collisions and stochastic heating due to momentum transfer from high voltage moving sheaths. We use Particle-in-Cell (PIC) simulations to explore these heating mechanisms and to compare the PIC results with available theories on ohmic and stochastic heating. The PIC results for ohmic heating show good agreement with the ohmic heating calculation of Lafleur et al. [Phys. Plasmas 20, 124503 (2013)]. The PIC results for stochastic heating in low pressure CCPs with collisionless sheaths show good agreement with the stochastic heating model of Kaganovich et al. [IEEE Trans. Plasma Sci. 34, 696 (2006)], which revises the hard wall asymptotic model of Lieberman [IEEE Trans. Plasma Sci. 16, 638 (1988)] by taking current continuity and bulk oscillation into account.

  10. Nitrogen incorporation in saturated aliphatic C6-C8 hydrocarbons and ethanol in low-pressure nitrogen plasma generated by a hollow cathode discharge ion source.

    PubMed

    Usmanov, Dilshadbek T; Chen, Lee Chuin; Hiraoka, Kenzo; Wada, Hiroshi; Nonami, Hiroshi; Yamabe, Shinichi

    2016-06-01

    Ion/molecule reactions of saturated hydrocarbons (n-hexane, cyclohexane, n-heptane, n-octane and isooctane) in 28-Torr N2 plasma generated by a hollow cathode discharge ion source were investigated using an Orbitrap mass spectrometer. It was found that the ions with [M+14](+) were observed as the major ions (M: sample molecule). The exact mass analysis revealed that the ions are nitrogenated molecules, [M+N](+) formed by the reactions of N3 (+) with M. The reaction, N3 (+) + M → [M+N](+) + N2 , were examined by the density functional theory calculations. It was found that N3 (+) abstracts the H atom from hydrocarbon molecules leading to the formation of protonated imines in the forms of R'R″CNH2 (+) (i.e. C-H bond nitrogenation). This result is in accord with the fact that elimination of NH3 is the major channel for MS/MS of [M+N](+) . That is, nitrogen is incorporated in the C-H bonds of saturated hydrocarbons. No nitrogenation was observed for benzene and acetone, which was ascribed to the formation of stable charge-transfer complexes benzene⋅⋅⋅⋅N3 (+) and acetone⋅⋅⋅⋅N3 (+) revealed by density functional theory calculations. Copyright © 2016 John Wiley & Sons, Ltd. PMID:27270868

  11. Low-pressure hydrogen plasmas explored using a global model

    NASA Astrophysics Data System (ADS)

    Samuell, Cameron M.; Corr, Cormac S.

    2016-02-01

    Low-pressure hydrogen plasmas have found applications in a variety of technology areas including fusion, neutral beam injection and material processing applications. To better understand these discharges, a global model is developed to predict the behaviour of electrons, ground-state atomic and molecular hydrogen, three positive ion species (H+, \\text{H}2+ , and \\text{H}3+ ), a single negative ion species (H-), and fourteen vibrationally excited states of molecular hydrogen ({{\\text{H}}2}≤ft(\\upsilon =1\\right. -14)). The model is validated by comparison with experimental results from a planar inductively coupled GEC reference cell and subsequently applied to the MAGPIE linear helicon reactor. The MAGPIE reactor is investigated for a range of pressures from 1 to 100 mTorr and powers up to 5 kW. With increasing power between 50 W and 5 kW at 10 mTorr the density of all charged species increases as well as the dissociative fraction while the electron temperature remains almost constant at around 3 eV. For gas pressures from 1-100 mTorr at an input power of 1 kW, the electron density remains almost constant, the electron temperature and dissociative fraction decreases, while \\text{H}3+ density increases in density and also dominates amongst ion species. Across these power and pressure scans, electronegativity remains approximately constant at around 2.5%. The power and pressure determines the dominant ion species in the plasma with \\text{H}3+ observed to dominate at high pressures and low powers whereas H+ tends to be dominant at low pressures and high powers. A sensitivity analysis is used to demonstrate how experimental parameters (power, pressure, reactor wall material, geometry etc) influence individual species’ density as well as the electron temperature. Physical reactor changes including the length, radius and wall recombination coefficient are found to have the largest influence on outputs obtained from the model.

  12. Longitudinal discharge pumped low-pressure XeCl laser

    SciTech Connect

    Fedorov, A I

    2013-10-31

    We have studied output parameters of a XeCl and a N{sub 2} laser pumped by a longitudinal discharge with automatic spark UV preionisation. The output parameters of a low-pressure (30 Torr) XeCl laser operating with Ar, Ne and He as buffer gases or with no buffer gas have been optimised for the first time. The laser generated 5-ns FWHM pulses with an average power of 0.5 mW and output energy of 0.15 mJ. Under longitudinal discharge pumping, an output energy per unit volume of 1.8 J L{sup -1} atm{sup -1} was reached using helium as a buffer gas. With argon-containing and buffer-free mixtures, it was 1.5 J L{sup -1} atm{sup -1}. The N{sub 2} laser generated 2.5-ns FWHM pulses with an average power of 0.35 mW and output energy of 0.05 mJ. (lasers)

  13. In situ CF3 Detection in Low Pressure Inductive Discharges by Fourier Transform Infrared Spectroscopy

    NASA Technical Reports Server (NTRS)

    Kim, J. S.; Cappelli, M. A.; Sharma, S. P.; Arnold, J. O. (Technical Monitor)

    1998-01-01

    The detection of CF(x) (x=1-3) radicals in low pressure discharges using source gases such as CF4 and CHF3 is of importance to the understanding of their chemical structure and relevance in plasma based etching processes. These radicals are known to contribute to the formation of fluorocarbon polymer films, which affect the selectivity and anisotropy of etching. In this study, we present preliminary results of the quantitative measurement of trifluoromethyl radicals, CF3, in low pressure discharges. The discharge studied here is an inductively (transformer) coupled plasma (ICP) source in the GEC reference cell, operating on pure CF4 at pressures ranging from 10 - 100 mTorr, This plasma source generates higher electron number densities at lower operating pressures than obtainable with the parallel-plate capacitively coupled version of the GEC reference cell. Also, this expanded operating regime is more relevant to new generations of industrial plasma reactors being used by the microelectronics industry. Fourier transform infrared (FTIR) spectroscopy is employed to observe the absorption band of CF3 radicals in the electronic ground state X2Al in the region of 1233-1270/cm. The spectrometer is equipped with a high sensitivity HgCdTe (MCT) detector and has a fixed resolution of 0.125/cm. The CF3 concentrations are measured for a range of operating pressures and discharge power levels.

  14. Effect of Coulomb scattering on low-pressure high-density electronegative discharges.

    PubMed

    Kawamura, E; Birdsall, C K

    2005-02-01

    For electronegative plasmas with low gas pressure and high ion densities, we expect Coulomb collisions between positive and negative ions to dominate over collisions between ions and neutrals. We incorporated Nanbu's cumulative small-angle collision method [K. Nanbu, Phys. Rev. E, 55, 4642 (1997)] into our one-dimensional three-velocity-component particle-in-cell code PDP1 in order to study the effect of Coulomb collisions on low pressure high density electronegative discharges. Nanbu's method treats a succession of small-angle binary collisions as a single binary collision with a large scattering angle, which is far faster than treating each individual small-angle collision. We find that Coulomb collisions between positive and negative ions in low-pressure high-density electronegative discharges significantly modify the negative ion flux, density, and kinetic energy profiles. PMID:15783425

  15. Effect of Coulomb scattering on low-pressure high-density electronegative discharges

    SciTech Connect

    Kawamura, E.; Birdsall, C.K.

    2005-02-01

    For electronegative plasmas with low gas pressure and high ion densities, we expect Coulomb collisions between positive and negative ions to dominate over collisions between ions and neutrals. We incorporated Nanbu's cumulative small-angle collision method [K. Nanbu, Phys. Rev. E, 55, 4642 (1997)] into our one-dimensional three-velocity-component particle-in-cell code PDP1 in order to study the effect of Coulomb collisions on low pressure high density electronegative discharges. Nanbu's method treats a succession of small-angle binary collisions as a single binary collision with a large scattering angle, which is far faster than treating each individual small-angle collision. We find that Coulomb collisions between positive and negative ions in low-pressure high-density electronegative discharges significantly modify the negative ion flux, density, and kinetic energy profiles.

  16. Seed disinfection effect of atmospheric pressure plasma and low pressure plasma on Rhizoctonia solani.

    PubMed

    Nishioka, Terumi; Takai, Yuichiro; Kawaradani, Mitsuo; Okada, Kiyotsugu; Tanimoto, Hideo; Misawa, Tatsuya; Kusakari, Shinichi

    2014-01-01

    Gas plasma generated and applied under two different systems, atmospheric pressure plasma and low pressure plasma, was used to investigate the inactivation efficacy on the seedborne pathogenic fungus, Rhizoctonia solani, which had been artificially introduced to brassicaceous seeds. Treatment with atmospheric plasma for 10 min markedly reduced the R. solani survival rate from 100% to 3% but delayed seed germination. The low pressure plasma treatment reduced the fungal survival rate from 83% to 1.7% after 10 min and the inactivation effect was dependent on the treatment time. The seed germination rate after treatment with the low pressure plasma was not significantly different from that of untreated seeds. The air temperature around the seeds in the low pressure system was lower than that of the atmospheric system. These results suggested that gas plasma treatment under low pressure could be effective in disinfecting the seeds without damaging them. PMID:24975415

  17. Breakdown and dc discharge in low-pressure water vapour

    NASA Astrophysics Data System (ADS)

    Sivoš, J.; Škoro, N.; Marić, D.; Malović, G.; Petrović, Z. Lj

    2015-10-01

    In this paper we report studies of basic properties of breakdown, low-current Townsend discharge and high-current discharge regimes in water vapour. Paschen curves and the corresponding distributions of emission intensities at low current were recorded in the range of pd (pressure x electrode gap) from 0.1 to 10 Torrcm covering the region of Paschen minimum. From the experimental profiles we obtained effective ionization coefficient of water vapour for the E/N range 650 Td-7 kTd and fitted the results by using the extended Townsend analytical formula. Using the obtained ionization coefficient, we calculated the effective yield of secondary electrons from the copper cathode. Results of the measurements of Volt-Ampere characteristics in water vapour were presented together with the images of the axial structure of the discharge in a wide range of discharge currents for two pd values. Recorded profiles showed development of the spatial structure of the discharge in different operating regimes. We were able to identify conditions where processes induced by heavy particles, probably fast hydrogen atoms, are dominant in inducing emission from the discharge. Finally, standard scaling laws were tested for low current and glow discharges in water vapour.

  18. Optical emission spectroscopy for simultaneous measurement of plasma electron density and temperature in a low-pressure microwave induced plasma

    SciTech Connect

    Konjevic, N.; Jovicevic, S.; Ivkovic, M.

    2009-10-15

    The simple optical emission spectroscopy technique for diagnostics of low pressure microwave induced plasma (MIP) in hydrogen or in MIP seeded with hydrogen is described and tested. This technique uses the Boltzmann plot of relative line intensities along Balmer spectral series in conjunction with the criterion for partial local thermodynamic equilibrium for low electron density (N{sub e}) plasma diagnostics. The proposed technique is tested in a low pressure MIP discharge for simultaneous determination of electron density N{sub e} (10{sup 17}-10{sup 18} m{sup -3}) and temperature T{sub e}.

  19. Numerical study of effect of secondary electron emission on discharge characteristics in low pressure capacitive RF argon discharge

    SciTech Connect

    Liu, Qian; Liu, Yue Samir, Tagra; Ma, Zhaoshuai

    2014-08-15

    Based on the drift and diffusion approximation theory, a 1D fluid model on capacitively coupled RF argon glow discharge at low pressure is established to study the effect of secondary electron emission (SEE) on the discharge characteristics. The model is numerically solved by using a finite difference method and the numerical results are obtained. The numerical results indicate that when the SEE coefficient is larger, the plasma density is higher and the time of reaching steady state is longer. It is also found that the cycle-averaged electric field, electric potential, and electron temperature change a little as the SEE coefficient is increased. Moreover, the discharge characteristics in some nonequilibrium discharge processes with different SEE coefficients have been compared. The analysis shows that when the SEE coefficient is varied from 0.01 to 0.3, the cycle-averaged electron net power absorption, electron heating rate, thermal convective term, electron energy dissipation, and ionization all have different degrees of growth. While the electron energy dissipation and ionization are quite special, there appear two peaks near each sheath region in the discharge with a relatively larger SEE coefficient. In this case, the discharge is certainly operated in a hybrid α-γ-mode.

  20. Low-pressure indium-halide discharges for fluorescent illumination applications

    NASA Astrophysics Data System (ADS)

    Hayashi, Daiyu; Hilbig, Rainer; Körber, Achim; Schwan, Stefan; Scholl, Robert; Boerger, Martin; Huppertz, Maria

    2010-02-01

    Low-pressure gas discharges of molecular radiators were studied for fluorescent lighting applications with a goal of reducing the energy loss due to the large Stokes shift in phosphors of conventional mercury-based fluorescent lamp technology. Indium halides (InCl, InBr, and InI) were chosen as the molecular radiators that generate ultraviolet to blue light emissions. The electrical characteristics and optical emission intensities were measured in discharges containing gaseous indium halides (InCl, InBr, and InI) as molecular radiators. The low-pressure discharges in indium halide vapor showed potential as a highly efficient gas discharge system for fluorescent lighting application.

  1. Production of a low-pressure processing plasma with ion beam injection for thin-film preparation

    NASA Astrophysics Data System (ADS)

    Fujita, Hiroharu; Yagura, Shinya

    1988-06-01

    A low-pressure processing plasma production with an ion beam injection is presented by applying microwave and rf discharges in a low-pressure gas for thin-film preparation. Electrostatic ion energy analyzer and emissive probe techniques are used in the plasma of a nonreactive gas to get plasma characteristics. The measurement reveals that an energy of ion beam injected into a reactor is controllable by adjusting a bias potential applied between the two plasmas, and electric fields at the steady state are affected by a configuration of a magnetic field applied for an enhancement of a microwave plasma production.

  2. Atomic Processes and Diagnostics of Low Pressure Krypton Plasma

    NASA Astrophysics Data System (ADS)

    Srivastava, Rajesh; Goyal, Dipti; Gangwar, Reetesh; Stafford, Luc

    2015-03-01

    Optical emission spectroscopy along with suitable collisional-radiative (CR) model is used in plasma diagnostics. Importance of reliable cross-sections for various atomic processes is shown for low pressure argon plasma. In the present work, radially-averaged Kr emission lines from the 2pi --> 1sj were recorded as a function of pressure from 1 to 50mTorr. We have developed a CR model using our fine-structure relativistic-distorted wave cross sections. The various processes considered are electron-impact excitation, ionization and their reverse processes. The required rate coefficients have been calculated from these cross-sections assuming Maxwellian energy distribution. Electron temperature obtained from the CR model is found to be in good agreement with the probe measurements. Work is supported by IAEA Vienna, DAE-BRNS Mumbai and CSIR, New Delhi.

  3. Landau Damping and Anomalous Skin Effect in Low-pressure Gas Discharges: Self-consistent Treatment of Collisionless Heating

    SciTech Connect

    Igor D. Kaganovich; Oleg V. Polomarov; Constantine E. Theodosiou

    2004-01-30

    In low-pressure discharges, where the electron mean free path is larger or comparable with the discharge length, the electron dynamics is essentially nonlocal. Moreover, the electron energy distribution function (EEDF) deviates considerably from a Maxwellian. Therefore, an accurate kinetic description of the low-pressure discharges requires knowledge of the nonlocal conductivity operator and calculation of the non-Maxwellian EEDF. The previous treatments made use of simplifying assumptions: a uniform density profile and a Maxwellian EEDF. In the present study a self-consistent system of equations for the kinetic description of nonlocal, nonuniform, nearly collisionless plasmas of low-pressure discharges is reported. It consists of the nonlocal conductivity operator and the averaged kinetic equation for calculation of the non-Maxwellian EEDF. This system was applied to the calculation of collisionless heating in capacitively and inductively coupled plasmas. In particular, the importance of accounting for the nonuniform plasma density profile for computing the current density profile and the EEDF is demonstrated. The enhancement of collisionless heating due to the bounce resonance between the electron motion in the potential well and the external radio-frequency electric field is investigated. It is shown that a nonlinear and self-consistent treatment is necessary for the correct description of collisionless heating.

  4. Low pressure arc discharge lamp apparatus with magnetic field generating means

    DOEpatents

    Grossman, M.W.; George, W.A.; Maya, J.

    1987-10-06

    A low-pressure arc discharge apparatus having a magnetic field generating means for increasing the output of a discharge lamp is disclosed. The magnetic field generating means, which in one embodiment includes a plurality of permanent magnets, is disposed along the lamp for applying a constant transverse magnetic field over at least a portion of the positive discharge column produced in the arc discharge lamp operating at an ambient temperature greater than about 25 C. 3 figs.

  5. Low pressure arc discharge lamp apparatus with magnetic field generating means

    SciTech Connect

    Grossman, Mark W.; George, William A.; Maya, Jakob

    1987-01-01

    A low-pressure arc discharge apparatus having a magnetic field generating means for increasing the output of a discharge lamp is disclosed. The magnetic field generating means, which in one embodiment includes a plurality of permanent magnets, is disposed along the lamp for applying a constant transverse magnetic field over at least a portion of the positive discharge column produced in the arc discharge lamp operating at an ambient temperature greater than about 25.degree. C.

  6. Low Pressure Experimental Simulation of Electrical Discharges Above and Inside a Cloud

    NASA Technical Reports Server (NTRS)

    Jarzembski, Maurice A.; Srivastava, Vandana

    1996-01-01

    A low pressure laboratory experiment to generate sporadic electrical discharges in either a particulate dielectric or air, representing a competing path of preferred electrical breakdown, was investigated. At high pressures, discharges occurred inside the dielectric particulate; at low pressures, discharges occurred outside the dielectric particulate; at a transition pressure regime, which depends on conductivity of the dielectric particulate, discharges were simultaneously generated in both particulate dielectric and air. Unique use of a particulate dielectric was critical for sporadic discharges at lower pressures which were not identical in character to discharges without the particulate dielectric. Application of these experimental results to the field of atmospheric electricity and simulation of the above-cloud type discharges that have recently been documented, called jets and sprites, are discussed.

  7. Low pressure plasma diagnostics by cars and other techniques

    SciTech Connect

    Hata, N. )

    1989-01-01

    Within the past several years, intensive research activities relating amorphous-silicon technology have stimulated plasma-chemical-vapor-deposition (plasma-CVD) diagnostics by laser-spectroscopic techniques. Among them, coherent anti-Stokes Raman spectroscopy (CARS) has attracted much attention because of its great success in combustion diagnostics, and has been employed for low-pressure-plasma studies. Gas-phase species such as SiH{sub 4}, H{sub 2}, Si{sub 2}H{sub 6}, SiH{sub 2}, and GeH{sub 4} have been detected, time dependences of their concentration and spatial profiles of their concentration and rotational temperature have been determined, and the gas-phase mechanisms have been discussed. This talk will employ those results as examples, and discuss (1) the potential of CARS for gas-phase analysis in CVD (including (i) what species are monitored, (ii) what information is obtained, and (iii) what are the advantages and limitations), and (2) some other diagnostic techniques that provide additional information for better understandings of CVD mechanisms.

  8. Highly ionized physical vapor deposition plasma source working at very low pressure

    SciTech Connect

    Stranak, V.; Herrendorf, A.-P.; Drache, S.; Hippler, R.; Cada, M.; Hubicka, Z.; Tichy, M.

    2012-04-02

    Highly ionized discharge for physical vapor deposition at very low pressure is presented in the paper. The discharge is generated by electron cyclotron wave resonance (ECWR) which assists with ignition of high power impulse magnetron sputtering (HiPIMS) discharge. The magnetron gun (with Ti target) was built into the single-turn coil RF electrode of the ECWR facility. ECWR assistance provides pre-ionization effect which allows significant reduction of pressure during HiPIMS operation down to p = 0.05 Pa; this is nearly more than an order of magnitude lower than at typical pressure ranges of HiPIMS discharges. We can confirm that nearly all sputtered particles are ionized (only Ti{sup +} and Ti{sup ++} peaks are observed in the mass scan spectra). This corresponds well with high plasma density n{sub e} {approx} 10{sup 18} m{sup -3}, measured during the HiPIMS pulse.

  9. Highly ionized physical vapor deposition plasma source working at very low pressure

    NASA Astrophysics Data System (ADS)

    Stranak, V.; Herrendorf, A.-P.; Drache, S.; Cada, M.; Hubicka, Z.; Tichy, M.; Hippler, R.

    2012-04-01

    Highly ionized discharge for physical vapor deposition at very low pressure is presented in the paper. The discharge is generated by electron cyclotron wave resonance (ECWR) which assists with ignition of high power impulse magnetron sputtering (HiPIMS) discharge. The magnetron gun (with Ti target) was built into the single-turn coil RF electrode of the ECWR facility. ECWR assistance provides pre-ionization effect which allows significant reduction of pressure during HiPIMS operation down to p = 0.05 Pa; this is nearly more than an order of magnitude lower than at typical pressure ranges of HiPIMS discharges. We can confirm that nearly all sputtered particles are ionized (only Ti+ and Ti++ peaks are observed in the mass scan spectra). This corresponds well with high plasma density ne ˜ 1018 m-3, measured during the HiPIMS pulse.

  10. Influence of emitter temperature on the energy deposition in a low-pressure plasma

    NASA Astrophysics Data System (ADS)

    Levko, Dmitry; Raja, Laxminarayan L.

    2016-03-01

    The influence of emitter temperature on the energy deposition into low-pressure plasma is studied by the self-consistent one-dimensional Particle-in-Cell Monte Carlo Collisions model. Depending on the emitter temperature, different modes of discharge operation are obtained. The mode type depends on the plasma frequency and does not depend on the ratio between the densities of beam and plasma electrons. Namely, plasma is stable when the plasma frequency is small. For this plasma, the energy transfer from emitted electrons to plasma electrons is inefficient. The increase in the plasma frequency results first in the excitation of two-stream electron instability. However, since the thermal velocity of plasma electrons is smaller than the electrostatic wave velocity, the resonant wave-particle interaction is inefficient for the energy deposition into the plasma. Further increase in the plasma frequency leads to the distortion of beam of emitted electrons. Then, the electrostatic wave generated due to two-stream instability decays into multiple slower waves. Phase velocities of these waves are comparable with the thermal velocity of plasma electrons which makes possible the resonant wave-particle interaction. This results in the efficient energy deposition from emitted electrons into the plasma.

  11. Modeling electronegative plasma discharge

    SciTech Connect

    Lichtenberg, A.J.; Lieberman, M.A.

    1995-12-31

    Macroscopic analytic models for a three-component electronegative gas discharge are developed. Assuming the negative ions to be in Boltzmann equilibrium, a positive ion ambipolar diffusion equation is derived. The discharge consists of an electronegative core and electropositive edges. The electron density in the core is nearly uniform, allowing a parabolic approximation to the plasma profile to be employed. The resulting equilibrium equations are solved analytically and matched to a constant mobility transport model of an electropositive edge plasma. The solutions are compared to a simulation of a parallel-plane r.f. driven oxygen plasma for p = 50 mTorr and n{sub eo}= 2.4 x 10{sup 15} m{sup -3}. The ratio {alpha}{sub o} of central negative ion density to electron density, and the electron temperature T{sub e}, found in the simulation, are in reasonable agreement with the values calculated from the model. The model is extended to: (1) low pressures, where a variable mobility model is used in the electropositive edge region; and (2) high {alpha}{sub o} in which the edge region disappears. The inclusion of a second positive ion species, which can be very important in describing electronegative discharges used for materials processing, is a possible extension of the model.

  12. Negative-ion yield in low-pressure radio frequency discharges in hydrogen: Particle modeling and vibrational kinetics

    SciTech Connect

    Diomede, P.; Longo, S.; Capitelli, M.

    2006-03-15

    A theoretical study of the complex interplay between the vibrational kinetics and the plasma dynamics in low-pressure hydrogen plasmas produced by radio frequency discharges is performed. The study is realized by means of a one-dimensional particle model with five species (e, H{sup +}, H{sub 2}{sup +}, H{sub 3}{sup +}, and H{sup -}) while the vibrational/dissociation kinetics is based on a continuum model and the two are self-consistently coupled. In particular, we analyze the influence of pressure.

  13. Compilation of cross sections for kinetic models of low pressure hydrogen discharges

    NASA Astrophysics Data System (ADS)

    Phelps, A. V.

    2011-10-01

    We report an initial compilation of cross sections that have been used to model,the collisional kinetics of low-pressure discharges in H2. Processes that are considered include electron momentum transfer, excitation, and ionization collisions with H2; momentum transfer, Hα excitation, ionization, and charged pair formation in collisions of H+, H2+,H3+,H, H2,and H- with H2; collisions of electrons, H+, H2+,H3+,H, H2, and H- with graphite and Cu surfaces resulting in secondary electrons, particle reflection, and negative ion formation. For each major category, the compilation includes a section reviewing data sources. The recommendations are expressed as analytic formulas expected to be good to +/- 10 % . This compilation is expected to be refined from time to time. As part of the Plasma Data Exchange Project, the compilation will be made available at http://www.lxcat.laplace.univ-tlse.fr/ and/or http://www.icecat.laplace.univ-tlse.fr/. We report an initial compilation of cross sections that have been used to model,the collisional kinetics of low-pressure discharges in H2. Processes that are considered include electron momentum transfer, excitation, and ionization collisions with H2; momentum transfer, Hα excitation, ionization, and charged pair formation in collisions of H+, H2+,H3+,H, H2,and H- with H2; collisions of electrons, H+, H2+,H3+,H, H2, and H- with graphite and Cu surfaces resulting in secondary electrons, particle reflection, and negative ion formation. For each major category, the compilation includes a section reviewing data sources. The recommendations are expressed as analytic formulas expected to be good to +/- 10 % . This compilation is expected to be refined from time to time. As part of the Plasma Data Exchange Project, the compilation will be made available at http://www.lxcat.laplace.univ-tlse.fr/ and/or http://www.icecat.laplace.univ-tlse.fr/. A. V. Phelps, Phys. Rev. E 79, 066401 (2009).

  14. Self-Consistent System of Equations for a Kinetic Description of the Low-Pressure Discharges Accounting for the Nonlocal and Collisionless Electron Dynamics

    SciTech Connect

    Igor D. Kaganovich; Oleg Polomarov

    2003-05-19

    In low-pressure discharges, when the electron mean free path is larger or comparable with the discharge length, the electron dynamics is essentially non-local. Moreover, the electron energy distribution function (EEDF) deviates considerably from a Maxwellian. Therefore, an accurate kinetic description of the low-pressure discharges requires knowledge of the non-local conductivity operator and calculation of the non-Maxwellian EEDF. The previous treatments made use of simplifying assumptions: a uniform density profile and a Maxwellian EEDF. In the present study a self-consistent system of equations for the kinetic description of nonlocal, non-uniform, nearly collisionless plasmas of low-pressure discharges is derived. It consists of the nonlocal conductivity operator and the averaged kinetic equation for calculation of the non-Maxwellian EEDF. The importance of accounting for the non-uniform plasma density profile on both the current density profile and the EEDF is demonstrated.

  15. Analysis based on global model of nitrogen plasma produced by pulsed microwave at low pressure

    SciTech Connect

    Qiu, Feng; Yan, Eryan Meng, Fanbao; Ma, Hongge; Liu, Minghai

    2015-07-15

    This paper analyzes certain evolution processes in nitrogen plasmas discharged using pulsed microwaves at low pressure. Comparing the results obtained from the global model incorporating diffusion and the microwave transmission method, the temporal variation of the electron density is analyzed. With a discharge pressure of 300 Pa, the results obtained from experiments and the global model calculation show that when the discharge begins the electron density in the plasma rises quickly, to a level above the critical density corresponding to the discharge microwave frequency, but falls slowly when the discharge microwave pulse is turned off. The results from the global model also show that the electron temperature increases rapidly to a peak, then decays after the electron density reaches the critical density, and finally decreases quickly to room temperature when the discharge microwave pulse is turned off. In the global model, the electron density increases because the high electron temperature induces a high ionization rate. The decay of the electron density mainly comes from diffusion effect.

  16. Three-electrode low pressure discharge apparatus and method for uniform ionization of gaseous media

    DOEpatents

    McLellan, Edward J.

    1983-01-01

    Uniform, transverse electrical discharges are produced in gaseous media without the necessity of switching the main discharge voltage with an external device which carries the entire discharge current. A three-electrode low pressure discharge tube is charged across its anode (1) and cathode (2) to below breakdown voltage using a dc voltage source (3). An array of resistors (4) or capacitors can be made to discharge to the wire screen anode by means of a low energy high voltage pulse circuit (5) producing sufficient preionization in the region between the anode and cathode to initiate and control the main discharge. The invention has been demonstrated to be useful as a CO.sub.2 laser oscillator and pulse-smoother. It can be reliably operated in the sealed-off mode.

  17. Transport of low pressure electronegative SF6 plasma through a localized magnetic filter

    NASA Astrophysics Data System (ADS)

    Levko, D.; Garrigues, L.; Hagelaar, G. J. M.

    2014-08-01

    The generation of an ion-ion plasma where only few electrons are present in the discharge could be appropriated in the context of ion plasma source applications. We present in this paper results obtained with a one-dimensional fluid model in the context of low pressure electronegative SF6 plasma. Without magnetic field, results show that the electron density is still large in the discharge. With a localized magnetic filter, where the magnetic field strength is such that the transport of the electrons is affected while the transport of ion species remains unmagnetized, we show that a region with a negative-positive ion plasma is found downstream the magnetic filter. The negative ions are produced in the filter due to the decrease of electron temperature. We also find conditions when the plasma sheath near the biased electrode collapses and the negative ion extraction from the plasma becomes possible. In addition, the influence of E × B electron transport on the one-dimensional model results is discussed.

  18. Transport of low pressure electronegative SF{sub 6} plasma through a localized magnetic filter

    SciTech Connect

    Levko, D.; Garrigues, L.; Hagelaar, G. J. M.

    2014-08-15

    The generation of an ion-ion plasma where only few electrons are present in the discharge could be appropriated in the context of ion plasma source applications. We present in this paper results obtained with a one-dimensional fluid model in the context of low pressure electronegative SF{sub 6} plasma. Without magnetic field, results show that the electron density is still large in the discharge. With a localized magnetic filter, where the magnetic field strength is such that the transport of the electrons is affected while the transport of ion species remains unmagnetized, we show that a region with a negative–positive ion plasma is found downstream the magnetic filter. The negative ions are produced in the filter due to the decrease of electron temperature. We also find conditions when the plasma sheath near the biased electrode collapses and the negative ion extraction from the plasma becomes possible. In addition, the influence of E × B electron transport on the one-dimensional model results is discussed.

  19. Dust particle dynamics in low-pressure plasma reactor

    SciTech Connect

    Davoudabadi, M.; Mashayek, F.

    2006-10-15

    In this paper, the structure of a rf plasma glow discharge in a parallel-plate geometry is revisited through a numerical solution of the well-known local field approximation model equations. The dynamics of a dust particle injected into the plasma is elaborated in a Lagrangian framework by solving the particle equations for its motion and charge. Different ion drag expressions are considered. For particles of three different sizes, magnitudes of various forces such as gravity, electricity, and ion drag acting on a stationary particle are compared to each other. Particle potential energy, together with its possible wells, is demonstrated for each case. Taking into account the neutral drag force, damping oscillations and final locations of the particles, depending on their initial injection position (top or bottom), are captured. The transient characteristic of the charging process of smaller particles with respect to their motion time scale is discussed. The effect of inclusion of ion thermal energy in the calculation of drag force on the motion of the particle is illustrated.

  20. Kinetic interpretation of resonance phenomena in low pressure capacitively coupled radio frequency plasmas

    NASA Astrophysics Data System (ADS)

    Wilczek, Sebastian; Trieschmann, Jan; Eremin, Denis; Brinkmann, Ralf Peter; Schulze, Julian; Schuengel, Edmund; Derzsi, Aranka; Korolov, Ihor; Hartmann, Peter; Donkó, Zoltán; Mussenbrock, Thomas

    2016-06-01

    Low pressure capacitive radio frequency (RF) plasmas are often described by equivalent circuit models based on fluid approaches that predict the self-excitation of resonances, e.g., high frequency oscillations of the total current in asymmetric discharges, but do not provide a kinetic interpretation of these effects. In fact, they leave important questions open: How is current continuity ensured in the presence of energetic electron beams generated by the expanding sheaths that lead to a local enhancement of the conduction current propagating through the bulk? How do the beam electrons interact with cold bulk electrons? What is the kinetic origin of resonance phenomena? Based on kinetic simulations, we find that the energetic beam electrons interact with cold bulk electrons (modulated on a timescale of the inverse local electron plasma frequency) via a time dependent electric field outside the sheaths. This electric field is caused by the electron beam itself, which leaves behind a positive space charge, that attracts cold bulk electrons towards the expanding sheath. The resulting displacement current ensures current continuity by locally compensating the enhancement of the conduction current. The backflow of cold electrons and their interaction with the nonlinear plasma sheath cause the generation of multiple electron beams during one phase of sheath expansion and contribute to a strongly non-sinusoidal RF current. These kinetic mechanisms are the basis for a fundamental understanding of the electron power absorption dynamics and resonance phenomena in such plasmas, which are found to occur in discharges of different symmetries including perfectly symmetric plasmas.

  1. Visible and near-ultraviolet spectra of low-pressure rare-gas microwave discharges

    NASA Technical Reports Server (NTRS)

    Campbell, J. P.; Spisz, E. W.; Bowman, R. L.

    1971-01-01

    The spectral emission characteristics of three commercial low pressure rare gas discharge lamps wire obtained in the near ultraviolet and visible wavelength range. All three lamps show a definite continuum over the entire wavelength range from 0.185 to 0.6 micrometers. Considerable line emission is superimposed on much of the continuum for wavelengths greater than 0.35 micrometers. These sources were used to make transmittance measurements on quartz samples in the near ultraviolet wavelength range.

  2. Destruction of methane in low-pressure, electrodeless radio frequency plasma on quartz walls

    NASA Astrophysics Data System (ADS)

    Mozetic, Miran; Vesel, Alenka; Alegre, Daniel; Tabares, Francisco L.

    2011-09-01

    The destruction of methane in a low pressure, electrodeless radiofrequency discharge was studied by mass spectrometry. Plasmas were created in a quartz tube with the inner diameter of 3.6 cm. A coil with 6 turns was fixed onto the tube and connected to radio frequency (RF) generator via a matching network. Methane flows between 1.16 and 3.30 mbar.l/s and various RF powers up to 1200 W were used. Depending on gas flow and RF power, the discharge was either in E or H mode. The evolution of different hydrocarbon species versus discharge power was measured systematically by a differentially pumped mass spectrometer. No carbon deposit on the quartz walls was seen during the scans. The results showed that the destruction of methane depended on the flow rate as well as the discharge power and was accomplished already in the E mode. Well-pronounced maxima in the formation of both ethane and acetylene were observed at low gas flow rates. The observed products from radical recombination evolved with plasma conditions, and their contribution to the global carbon balance strongly decreased at high power-per-particle density. The functionality of secondary hydrocarbon formation with respect to the experimental parameters has been analyzed and a simple kinetic model is proposed in order to account for the observed trends.

  3. Decomposition Characteristics of an Artificial Biogas in a Low-Pressure DC Glow Discharge

    NASA Astrophysics Data System (ADS)

    Itoh, Yasuhiro; Oshita, Takamasa; Satoh, Kohki; Itoh, Hidenori

    The decomposition characteristics of an artificial biogas, which is a mixture of CH4, CO2 and H2S, using a low pressure DC glow discharge have been investigated. It is found that H2, CO, C2H2, H2O, CS2 and COS are produced from the artificial biogas in the glow discharge. About 65 % of hydrogen atoms in CH4 are converted into H2 at the input energy of 800 J, at which CH4 is completely decomposed, and the decomposition characteristics of the artificial biogas has little dependency on H2S additive. Farther, H2S has a tendency to be decomposed earlier than the other components of the artificial biogas. When the glow discharge is generated in the artificial biogas with H2S, some of carbon atoms are found to deposit on electrodes and the wall of a discharge chamber.

  4. Simulation of low-pressure inductively coupled plasmas: Non-local effects and pulsed power operation

    NASA Astrophysics Data System (ADS)

    Ramamurthi, Badri

    For modeling of low-pressure Inductively Coupled Plasma (ICP) discharges, a number of approaches have been proposed with varying degree of complexity. A self-consistent 1-D model was developed in this work to study the effects of non-local electron conductivity on power absorption and plasma density profiles in a planar inductively coupled argon discharge at low pressures (< 10 mTorr). The self-consistent kinetic description of the discharge included three modules: (1) an EEDF module to compute a non-Maxwellian EEDF, (2) a non-local electron conductivity module which predicted current distribution in the plasma as an integral over the electric field and solved Maxwell's equations to find the self-consistent electric field as well as the non-local power deposition profile and (3) a Heavy Species Transport (HST) module which solved for the ion and metastable atom density and velocity. Results from the full model were then compared with those obtained by using a local conductivity model (Ohm's law) for the RF current. For 10 mTorr, the EEDF was found to be almost Maxwellian with electron temperature ˜ 3 V. As a result, the plasma density profiles obtained from the local and non-local cases were almost identical for the same total power. Interestingly, a similar result was obtained even for a pressure of 1 mTorr where the EEDF was non-Maxwellian. This suggests that as far as species density and flux are concerned, local conductivity models, with lesser computational expense, can be employed even in the non-local regime. Comparisons between simulation and experiment for RF field and current density showed better agreement for non-local model compared with local model. A two-dimensional (r,z) continuum model was then developed to study the spatio-temporal dynamics of a pulsed power (square-wave modulated) discharge in argon (electropositive) and chlorine (electronegative) sustained in an inductively coupled plasma (ICP) reactor with a planar coil. The self

  5. Advanced Research on the Electrode Area of a Low Pressure Hg-Ar Discharge Lamp

    NASA Astrophysics Data System (ADS)

    Shi, Jianou

    The phenomenon of electrical discharge in low pressure Hg-Ar vapor has been under continuous investigation since it was first discovered. Because much work has been done in the positive column, it is, therefore, that the electrode area of the lamp is the main focus of this thesis. To simulate the interface phenomena on a electrode surface, samples, with optically smooth tungsten-barium interfaces were fired in a high vacuum furnace at different temperatures. Measurements were made using surface characterization techniques. It is found that no Ba_3WO _6 is formed on the surface as previously reported in the powder mixing experiments, and the interface consists mainly of BaWO_4. It was discovered in the early 1950's that vaporization of the barium from the cathode in a fluorescent lamp could be reduced tremendously with the addition of 5% of ZrO _2 to the coating mix. However, the reason for this is poorly understood. A possible explanation has been found, and number of tests have been completed to simulate the formation of BaZO_3 under different lamp operating conditions. The measurements and simulation of barium atom and ion number densities are presented. Barium emitted from the electrode surface has a strong interaction with the local plasma. The number density distributions depend mainly on the discharge conditions. A Monte Carlo computer simulation for the barium ion number density is described and the results from the simulation compared to the experimental results obtained by absorption method. It is clear that the ion distribution and phosphor contamination in the electrode area are two closely related issues. XPS is used to measure the chemical composition on the phosphor surface of the lamp. A discussion of calibration methods and the possible compounds forming on the phosphors is then presented. A number of questions have been raised concerning the safety of the lamp and its affects on health related to radiation generated in the electrode area. Typically

  6. Effect of confining wall potential on charged collimated dust beam in low-pressure plasma

    SciTech Connect

    Kausik, S. S.; Kakati, B.; Saikia, B. K.

    2013-05-15

    The effect of confining wall potential on charged collimated dust beam in low-pressure plasma has been studied in a dusty plasma experimental setup by applying electrostatic field to each channel of a multicusp magnetic cage. Argon plasma is produced by hot cathode discharge method at a pressure of 5×10{sup −4} millibars and is confined by a full line cusped magnetic field confinement system. Silver dust grains are produced by gas-evaporation technique and move upward in the form of a collimated dust beam due to differential pressure maintained between the dust and plasma chambers. The charged grains in the beam after coming out from the plasma column enter into the diagnostic chamber and are deflected by a dc field applied across a pair of deflector plates at different confining potentials. Both from the amount of deflection and the floating potential, the number of charges collected by the dust grains is calculated. Furthermore, the collimated dust beam strikes the Faraday cup, which is placed above the deflector plates, and the current (∼pA) so produced is measured by an electrometer at different confining potentials. The experimental results demonstrate the significant effect of confining wall potential on charging of dust grains.

  7. Plasma diagnostics of low pressure high power impulse magnetron sputtering assisted by electron cyclotron wave resonance plasma

    SciTech Connect

    Stranak, Vitezslav; Herrendorf, Ann-Pierra; Drache, Steffen; Bogdanowicz, Robert; Hippler, Rainer; Cada, Martin; Hubicka, Zdenek; Tichy, Milan

    2012-11-01

    This paper reports on an investigation of the hybrid pulsed sputtering source based on the combination of electron cyclotron wave resonance (ECWR) inductively coupled plasma and high power impulse magnetron sputtering (HiPIMS) of a Ti target. The plasma source, operated in an Ar atmosphere at a very low pressure of 0.03 Pa, provides plasma where the major fraction of sputtered particles is ionized. It was found that ECWR assistance increases the electron temperature during the HiPIMS pulse. The discharge current and electron density can achieve their stable maximum 10 {mu}s after the onset of the HiPIMS pulse. Further, a high concentration of double charged Ti{sup ++} with energies of up to 160 eV was detected. All of these facts were verified experimentally by time-resolved emission spectroscopy, retarding field analyzer measurement, Langmuir probe, and energy-resolved mass spectrometry.

  8. Biological and Agricultural Studies on Application of Discharge Plasma and Electromagnetic Fields 2.Sterilization by Electrical Discharges and Plasmas

    NASA Astrophysics Data System (ADS)

    Watanabe, Takayuki

    The use of electrical discharges and plasmas for sterilization is reviewed. Plasmas generated by a silent discharge, a pulse discharge, and a radio frequency discharge under atmospheric pressure have been used for sterilization. Furthermore, a microwave plasma, a radio frequency plasma, and a low temperature plasma with hydrogen peroxide under low pressure conditions have been also used for sterilization. Sterilization results from injury caused by the discharge current, and from the reaction of species affected by the discharge. A silent discharge with air or oxygen is most effective for the sterilization. Nitrogen discharge also has a significant effect, however, argon discharge does not have a significant effect.

  9. Characterization of low-pressure microwave and radio frequency discharges in oxygen applying optical emission spectroscopy and multipole resonance probe

    NASA Astrophysics Data System (ADS)

    Steves, Simon; Styrnoll, Tim; Mitschker, Felix; Bienholz, Stefan; Nikita, Bibinov; Awakowicz, Peter

    2013-11-01

    Optical emission spectroscopy (OES) and multipole resonance probe (MRP) are adopted to characterize low-pressure microwave (MW) and radio frequency (RF) discharges in oxygen. In this context, both discharges are usually applied for the deposition of permeation barrier SiOx films on plastic foils or the inner surface of plastic bottles. For technological reasons the MW excitation is modulated and a continuous wave (cw) RF bias is used. The RF voltage produces a stationary low-density plasma, whereas the high-density MW discharge is pulsed. For the optimization of deposition process and the quality of the deposited barrier films, plasma conditions are characterized using OES and MRP. To simplify the comparison of applied diagnostics, both MW and RF discharges are studied separately in cw mode. The OES and MRP diagnostic methods complement each other and provide reliable information about electron density and electron temperature. In the MW case, electron density amounts to ne = (1.25 ± 0.26) × 1017 m-3, and kTe to 1.93 ± 0.20 eV, in the RF case ne = (6.8 ± 1.8)×1015 m-3 and kTe = 2.6 ± 0.35 eV. The corresponding gas temperatures are 760±40 K and 440±20 K.

  10. The importance of ions in low pressure PECVD plasmas

    NASA Astrophysics Data System (ADS)

    Michelmore, Andrew; Whittle, Jason; Short, Robert

    2015-02-01

    Plasma enhanced chemical vapour deposition (PECVD) can be used to fabricate surfaces with a wide range of physical and chemical properties and are used in a variety of applications. Despite this, the mechanisms by which PECVD films grow are not well understood. Moreover, the species which contribute to film growth can be considered quite differently depending on the process. Particularly for functionalized plasma polymer films, the growth mechanisms are considered with respect to the chemistry of the depositing species, ignoring the physics of plasmas. Here we analyse the role ions play in the deposition of three common classes of depositing plasmas, and how these closely related fields treat ions very differently.

  11. Influence of Forbidden Processes on Similarity Law in Argon Glow Discharge at Low Pressure

    NASA Astrophysics Data System (ADS)

    Fu, Yang-Yang; Luo, Hai-Yun; Zou, Xiao-Bing; Wang, Xin-Xin

    2014-07-01

    The similarity law of gas discharge is not always valid due to the occurrence of some elementary processes, such as the stepwise ionization process, which are defined as the forbidden processes. To research the influence of forbidden processes on the similarity law, physical parameters (i.e., the electric field, electron density, electron temperature) in similar gaps are investigated based on the fluid model of gas discharge. The products of gas pressure p and dimensions are kept to be constant in similar gaps and the discharge model is solved with and without the forbidden processes, respectively. Discharges in similar gaps are identified as glow discharges and the typical similarity relations all are investigated. The results show that the forbidden processes cause significant deviations of similarity relations from the theoretical ones and the deviations are enlarged as the scaled-down factor k increases. If the forbidden processes are excluded from the model, the similarity law will be valid in argon glow discharge at low pressure.

  12. Low Pressure High Density Plasma Development on a Small Helicon Plasma Experiment (HPX)*

    NASA Astrophysics Data System (ADS)

    James, R. W.; Allen, L. A.; Paolino, R. N.; Thayer, N.; Romano, B.; Stutzman, B. S.; Welicka, C.; Coast Guard Plasma Lab Team

    2011-10-01

    Small helicon plasmas have been employed in various capacities from industry to spacecraft propulsion. At the Coast Guard Academy Plasma Lab (CGAPL), a small Helicon Plasma Experiment (HPX) is being developed to utilize the reputed high densities (1013 cm-3 and higher) at low pressure (.01 T), in high temperature and density diagnostic development for future laboratory investigations. HPX is designed to operate at these high densities and pressure to create repeatedly stable Capacitively Coupled Plasma (CCP) and Inductively Coupled Plasma (ICP) plasmas induced by an RF frequency in the 10 to 70 MHz range. Progress on the development of the RF coupling system, and qualitative observations from the optical and electric diagnostics are to be reported.

  13. Chemistry in low-pressure cold plasmas: ions of astrophysical interest

    NASA Astrophysics Data System (ADS)

    Carrasco, E.; Jiménez-Redondo, M.; Tanarro, I.; Herrero, V. J.

    2012-12-01

    The ionic chemistry of various hydrogen mixtures (H2/N2, H2/O2, and H2/air) has been studied in low-pressure hollow cathode discharges. The major ions identified in the different discharges (H_3^+ , N2H+, H3O+ and NH_4^+ ) have been also found in astronomical observations or predicted in astrochemical models. The relative stability of the protonated ions in the various mixtures has been investigated in detail. In discharges of H2 with small amounts of N2, O2 and air, appreciable amounts of NH3 and H2O were formed at the reactor walls. The preponderance of the protonated ions in these plasmas was found to be largely dictated by the proton affinity of their respective molecular precursors. Even for small amounts of water and ammonia, proton transfer reactions tend to concentrate the positive charge in H3O+ and, especially, in NH_4^+ ions. These results support the predictions of some astrochemical models indicating that these ions could be dominant in warm astronomical environments where H2O and NH3 molecules evaporate from dust grain mantels.

  14. Characterization and modelling of low-pressure rf discharges at 2-500 MHz for miniature alkali vapour dielectric barrier discharge lamps

    NASA Astrophysics Data System (ADS)

    Venkatraman, Vinu; Pétremand, Yves; de Rooij, Nico; Shea, Herbert

    2012-12-01

    Low-pressure dielectric barrier discharge (DBD) alkali vapour lamps are of particular interest for portable atomic clocks because they (1) could enable low-power operation, (2) generate the precise required wavelength, (3) are planar simplifying chip-level integration and (4) use external electrodes, which increases the lifetime. Given the stringent requirements on lamps for atomic clocks, it is important to identify the parameters that can be optimized to meet these performance requirements (size, power consumption, stability, reliability). We report on the electrical and optical characteristics of dielectric barrier plasma discharges observed in two configurations: (1) in a vacuum chamber over a wide low-pressure range (2-100 mbar) for three different buffer gases (He, Ar, N2) driven at different frequencies between 2 and 500 MHz and (2) on microfabricated hermetically sealed Rb vapour cells filled with 30 and 70 mbar of Ar. We discuss the optimum conditions for a low-power and stable operation of a Rb vapour DBD lamp, aimed at chip-scale atomic clocks. We also present the electrical modelling of the discharge parameters to understand the power distribution mechanisms and the input power to discharge power coupling efficiency.

  15. Kinetic theory of the positive column of a low-pressure discharge in a transverse magnetic field

    SciTech Connect

    Londer, Ya. I.; Ul'yanov, K. N.

    2011-10-15

    The influence of a transverse magnetic field on the characteristics of the positive column of a planar low-pressure discharge is studied theoretically. The motion of magnetized electrons is described in the framework of a continuous-medium model, while the ion motion in the ambipolar electric field is described by means of a kinetic equation. Using mathematical transformations, the problem is reduced to a secondorder ordinary differential equation, from which the spatial distribution of the potential is found in an analytic form. The spatial distributions of the plasma density, mean plasma velocity, and electric potential are calculated, the ion velocity distribution function at the plasma boundary is found, and the electron energy as a function of the magnetic field is determined. It is shown that, as the magnetic field rises, the electron energy increases, the distributions of the plasma density and mean plasma velocity become asymmetric, the maximum of the plasma density is displaced in the direction of the Ampere force, and the ion flux in this direction becomes substantially larger than the counter-directed ion flux.

  16. E-H mode transition in low-pressure inductively coupled nitrogen-argon and oxygen-argon plasmas

    NASA Astrophysics Data System (ADS)

    Lee, Young Wook; Lee, Hye Lan; Chung, T. H.

    2011-06-01

    This work investigates the characteristics of the E-H mode transition in low-pressure inductively coupled N2-Ar and O2-Ar discharges using rf-compensated Langmuir probe measurements and optical emission spectroscopy (OES). As the ICP power increases, the emission intensities from plasma species, the electron density, the electron temperature, and the plasma potential exhibit sudden changes. The Ar content in the gas mixture and total gas pressure have been varied in an attempt to fully characterize the plasma parameters. With these control parameters varying, the changes of the transition threshold power and the electron energy distribution function (EEDF) are explored. In N2-Ar and O2-Ar discharges at low-pressures of several millitorr, the transition thresholds are observed to decrease with Ar content and pressure. It is observed that in N2-Ar plasmas during the transition, the shape of the EEDF changes from an unusual distribution with a flat hole near the electron energy of 3 eV in the E mode to a Maxwellian distribution in the H mode. However, in O2 -Ar plasmas, the EEDFs in the E mode at low Ar contents show roughly bi-Maxwellian distributions, while the EEDFs in the H mode are observed to be nearly Maxwellian. In the E and H modes of O2-Ar discharges, the dissociation fraction of O2 molecules is estimated using optical emission actinometry. During the E-H mode transition, the dissociation fraction of molecules is also enhanced.

  17. Polymerization and surface modification by low pressure plasma technique

    NASA Astrophysics Data System (ADS)

    Tsafack, M.-J.; Hochart, F.; Levalois-Grützmacher, J.

    2004-06-01

    A durable water repellent, stain resistant or flame retardant character can be conferred to polyacrylonitrile (PAN) textiles by using the plasma induced graft polymerization technique. The monomers used are perfluoroalkylacrylate, (meth)acrylate phosphates, and phosphonates which are well known to be effective for the waterproofing and the fireproofing of polymeric substrates, respectively.

  18. Study of flow fields induced by surface dielectric barrier discharge actuator in low-pressure air

    SciTech Connect

    Che, Xueke E-mail: st@mail.iee.ac.cn; Nie, Wansheng; Tian, Xihui; Hou, Zhiyong; He, Haobo; Zhou, Penghui; Zhou, Siyin; Yang, Chao; Shao, Tao E-mail: st@mail.iee.ac.cn

    2014-04-15

    Surface dielectric barrier discharge (SDBD) is a promising method for a flow control. Flow fields induced by a SDBD actuator driven by the ac voltage in static air at low pressures varying from 1.0 to 27.7 kPa are measured by the particle image velocimetry method. The influence of the applied ac voltage frequency and magnitude on the induced flow fields is studied. The results show that three different classes of flow fields (wall jet flow field, complex flow field, and vortex-shape flow field) can be induced by the SDBD actuator in the low-pressure air. Among them, the wall jet flow field is the same as the tangential jet at atmospheric pressure, which is, together with the vertical jet, the complex flow field. The vortex-shape flow field is composed of one vertical jet which points towards the wall and two opposite tangential jets. The complex and the vortex-shape flow fields can be transformed to the wall jet flow field when the applied ac voltage frequency and magnitude are changed. It is found that the discharge power consumption increases initially, decreases, and then increases again at the same applied ac voltage magnitude when the air pressure decreases. The tangential velocity of the wall jet flow field increases when the air pressure decreases. It is however opposite for the complex flow field. The variation of the applied ac voltage frequency influences differently three different flow fields. When the applied ac voltage magnitude increases at the same applied ac voltage frequency, the maximal jet velocity increases, while the power efficiency increases only initially and then decreases again. The discharge power shows either linear or exponential dependences on the applied ac voltage magnitude.

  19. Low-pressure water-cooled inductively coupled plasma torch

    DOEpatents

    Seliskar, Carl J.; Warner, David K.

    1988-12-27

    An inductively coupled plasma torch is provided which comprises an inner tube, including a sample injection port to which the sample to be tested is supplied and comprising an enlarged central portion in which the plasma flame is confined; an outer tube surrounding the inner tube and containing water therein for cooling the inner tube, the outer tube including a water inlet port to which water is supplied and a water outlet port spaced from the water inlet port and from which water is removed after flowing through the outer tube; and an r.f. induction coil for inducing the plasma in the gas passing into the tube through the sample injection port. The sample injection port comprises a capillary tube including a reduced diameter orifice, projecting into the lower end of the inner tube. The water inlet is located at the lower end of the outer tube and the r.f. heating coil is disposed around the outer tube above and adjacent to the water inlet.

  20. Low-pressure water-cooled inductively coupled plasma torch

    DOEpatents

    Seliskar, C.J.; Warner, D.K.

    1984-02-16

    An inductively coupled plasma torch is provided which comprises an inner tube, including a sample injection port to which the sample to be tested is supplied and comprising an enlarged central portion in which the plasma flame is confined; an outer tube surrounding the inner tube and containing water therein for cooling the inner tube, the outer tube including a water inlet port to which water is supplied and a water outlet port spaced from the water inlet port and from which water is removed after flowing through the outer tube; and an rf induction coil for inducing the plasma in the gas passing into the tube through the sample injection port. The sample injection port comprises a capillary tube including a reduced diameter orifice, projecting into the lower end of the inner tube. The water inlet is located at the lower end of the outer tube and the rf heating coil is disposed around the outer tube above and adjacent to the water inlet.

  1. 2D fluid-analytical simulation of electromagnetic effects in low pressure, high frequency electronegative capacitive discharges

    NASA Astrophysics Data System (ADS)

    Kawamura, E.; Lichtenberg, A. J.; Lieberman, M. A.; Marakhtanov, A. M.

    2016-06-01

    A fast 2D axisymmetric fluid-analytical multifrequency capacitively coupled plasma (CCP) reactor code is used to study center high nonuniformity in a low pressure electronegative chlorine discharge. In the code, a time-independent Helmholtz wave equation is used to solve for the capacitive fields in the linearized frequency domain. This eliminates the time dependence from the electromagnetic (EM) solve, greatly speeding up the simulations at the cost of neglecting higher harmonics. However, since the code allows up to three driving frequencies, we can add the two most important harmonics to the CCP simulations as the second and third input frequencies. The amplitude and phase of these harmonics are estimated by using a recently developed 1D radial nonlinear transmission line (TL) model of a highly asymmetric cylindrical discharge (Lieberman et al 2015 Plasma Sources Sci. Technol. 24 055011). We find that at higher applied frequencies, the higher harmonics contribute significantly to the center high nonuniformity due to their shorter plasma wavelengths.

  2. Efficient modification of the surface properties of interconnected porous hydroxyapatite by low-pressure low-frequency plasma treatment to promote its biological performance

    NASA Astrophysics Data System (ADS)

    Lee, Dae-Sung; Moriguchi, Yu; Myoui, Akira; Yoshikawa, Hideki; Hamaguchi, Satoshi

    2012-09-01

    Dielectric barrier discharge plasma treatment at low pressure is found to significantly improve the biological performance of artificial bones made of interconnected porous calcium hydroxyapatite (IP-CHA). One of the essential parameters associated with their biological performance is hydrophilicity of their exterior surfaces as well as surfaces of inner pores. It is found that plasma treatment at low pressures is highly effective in making the inner pore surfaces more hydrophilic. Preliminary in vivo experiments of plasma-treated IP-CHA artificial bones in rats have shown fast formation of blood vessels in their inner pores, implying the increase in osteoconductivity due to the plasma treatment.

  3. The effects of plasma inhomogeneity on the nanoparticle coating in a low pressure plasma reactor

    SciTech Connect

    Pourali, N.; Foroutan, G.

    2015-10-15

    A self-consistent model is used to study the surface coating of a collection of charged nanoparticles trapped in the sheath region of a low pressure plasma reactor. The model consists of multi-fluid plasma sheath module, including nanoparticle dynamics, as well as the surface deposition and particle heating modules. The simulation results show that the mean particle radius increases with time and the nanoparticle size distribution is broadened. The mean radius is a linear function of time, while the variance exhibits a quadratic dependence. The broadening in size distribution is attributed to the spatial inhomogeneity of the deposition rate which in turn depends on the plasma inhomogeneity. The spatial inhomogeneity of the ions has strong impact on the broadening of the size distribution, as the ions contribute both in the nanoparticle charging and in direct film deposition. The distribution width also increases with increasing of the pressure, gas temperature, and the ambient temperature gradient.

  4. An improved process for high nutrition of germinated brown rice production: Low-pressure plasma.

    PubMed

    Chen, Hua Han; Chang, Hung Chia; Chen, Yu Kuo; Hung, Chien Lun; Lin, Su Yi; Chen, Yi Sheng

    2016-01-15

    Brown rice was exposed to low-pressure plasma ranging from 1 to 3kV for 10min. Treatment of brown rice in low-pressure plasma increases the germination percentage, seedling length, and water uptake in laboratory germination tests. Of the various treatments, 3-kV plasma exposure for 10min yielded the best results. In germinating brown rice, α-amylase activity was significantly higher in treated groups than in controls. The higher enzyme activity in plasma-treated brown rice likely triggers the rapid germination and earlier vigor of the seedlings. Low-pressure plasma also increased gamma-aminobutyric acid (GABA) levels from ∼19 to ∼28mg/100g. In addition, a marked increase in the antioxidant activity of brown rice was observed with plasma treatments compared to controls. The main finding of this study indicates that low-pressure plasma is effective at enhancing the growth and GABA accumulation of germinated brown rice, which can supply high nutrition to consumer. PMID:26258710

  5. Sensitive Measurement of Trace Mercury Using Low Pressure Laser-Induced Plasma

    NASA Astrophysics Data System (ADS)

    Wang, Zhenzhen; Deguchi, Yoshihiro; Kuwahara, Masakazu; Zhang, Xiaobo; Yan, Junjie; Liu, Jiping

    2013-11-01

    The emission of trace heavy metals, such as mercury (Hg), from power plants and other industries is a severe environmental problem concerning the public health. The laser-induced plasma technique was employed to measure Hg under various conditions, which reveals several merits of this method at low pressure. The main interferences of laser-induced breakdown spectroscopy (LIBS), which include the black-body-like emission from plasma itself and coexisting molecular and atomic emissions, decreased significantly using low pressure laser-induced plasma. Under low pressure conditions, Hg signal was rather clear without serious influence even if there is no delay time from the laser irradiation, which means the gated detection device is not necessary. This method featured the detection limit of 0.3 ppm at pressure 700 Pa. Additionally, the feasible of this method in real applications was demonstrated by measuring Hg in combustion gas which performed preferable results.

  6. Progress in Development of Low Pressure High Density Plasmas on a Small Helicon Plasma Experiment (HPX)

    NASA Astrophysics Data System (ADS)

    James, Royce; Lopez, M.; Nolan, S.; Page, E. L.; Schlank, C.; Sherman, J.; Stutzman, B. S.; Zuniga, J.

    2012-10-01

    At the Coast Guard Academy Plasma Lab (CGAPL), a small Helicon Plasma Experiment (HPX) is being developed to utilize the reputed high densities (10^13 cm-3 and higher) at low pressure (.01 T) [1], for eventual high temperature and density diagnostic development in future laboratory investigations. HPX is designed to create repeatedly stable plasmas induced by an RF frequency in the 10 to 70 MHz range and employs an electromagnet to provide the external energy in the plasma's magnetic field to transition from the H-Mode to the Helicon Mode. An acceleration coil, currently under construction, will place the plasma in the vacuum chamber for optical and particle probing. With the initial construction phase complete and first plasmas attained, HPX is constructing triple and mach particle probes, magnetic probes, and a single point 300 W Thompson Scattering system backed by a 32-channel DAQ system capable 12 bits of sampling precision at 2 MS/s for plasma property investigations. Progress on the development of the RF coupling system, magnetic coils, and qualitative observations from the optical and electric diagnostics are to be reported. [4pt] [1] K. Toki, et al., Thin Solid Films 506-507 (2005).

  7. Understanding of the importance of the spore coat structure and pigmentation in the Bacillus subtilis spore resistance to low-pressure plasma sterilization

    NASA Astrophysics Data System (ADS)

    Raguse, Marina; Fiebrandt, Marcel; Denis, Benjamin; Stapelmann, Katharina; Eichenberger, Patrick; Driks, Adam; Eaton, Peter; Awakowicz, Peter; Moeller, Ralf

    2016-07-01

    Low-pressure plasmas have been evaluated for their potential in biomedical and defense purposes. The sterilizing effect of plasma can be attributed to several active agents, including (V)UV radiation, charged particles, radical species, neutral and excited atoms and molecules, and the electric field. Spores of Bacillus subtilis were used as a bioindicator and a genetic model system to study the sporicidal effects of low-pressure plasma decontamination. Wild-type spores, spores lacking the major protective coat layers (inner, outer, and crust), pigmentation-deficient spores or spore impaired in encasement (a late step in coat assembly) were systematically tested for their resistance to low-pressure argon, hydrogen, and oxygen plasmas with and without admixtures. We demonstrate that low-pressure plasma discharges of argon and oxygen discharges cause significant physical damage to spore surface structures as visualized by atomic force microscopy. Spore resistance to low-pressure plasma was primarily dependent on the presence of the inner, and outer spore coat layers as well as spore encasement, with minor or less importance of the crust and spore pigmentation, whereas spore inactivation itself was strongly influenced by the gas composition and operational settings.

  8. Characterization of Dust-Plasma Interactions In Non-Thermal Plasmas Under Low Pressure and the Atmospheric Pressure

    NASA Astrophysics Data System (ADS)

    Bilik, Narula

    This dissertation research focuses on the experimental characterization of dust-plasma interactions at both low and atmospheric pressure. Its goal is to fill the knowledge gaps in (1) the fundamental research of low pressure dusty plasma electrons, which mainly relied on models with few experimental results; and (2) the nanoparticle synthesis process in atmospheric pressure uniform glow plasmas (APGDs), which is largely unexplored in spite of the economical advantage of APGDs in nanotechnology. The low pressure part of the dissertation research involves the development of a complete diagnostic process for an argon-siline capacitively-coupled RF plasma. The central part of the diagnostic process is the Langmuir probe measurement of the electron energy probability function (EEPF) in a dusty plasma, which has never been measured before. This is because the dust particles in the plasma cause severe probe surface contamination and consequently distort the measurement. This problem is solved by adding a solenoid-actuated shield structure to the Langmuir probe, which physically protects the Langmuir probe from the dust particle deposition to ensure reliable EEPF measurements. The dusty plasma EEPFs are characterized by lower electron density and higher electron temperature accompanied by a drop in the low energy electron population. The Langmuir probe measurement is complemented with other characterizations including the capacitive probe measurement, power measurement, and dust particle collection. The complete diagnostic process then gives a set of local plasma parameters as well as the details of the dust-electron interactions reflected in the EEPFs. This set of data serves as input for an analytical model of nanoparticle charging to yield the time evolution of nanoparticle size and charge in the dusty plasma. The atmospheric pressure part of the dissertation focuses on the design and development of an APGD for zinc oxide nanocrystal synthesis. One of the main

  9. Progress on Development of Low Pressure High Density Plasmas on the Helicon Plasma Experiment (HPX)

    NASA Astrophysics Data System (ADS)

    James, R. W.; Duke-Tinson, O.; Nolan, S.; Page, E. J.; Lopez, M.; Karama, J.; Paolino, R. N.; Schlank, C.; Sherman, J.; Stutzman, B. S.; Crilly, P. B.

    2013-10-01

    At the Coast Guard Academy Plasma Lab (CGAPL), a small Helicon Plasma Experiment (HPX) is being developed to utilize the reputed high densities (1013 cm-3 and higher) at low pressure (.01 T), for eventual high temperature and density diagnostic development in future laboratory investigations. HPX is designed to create repeatedly stable plasmas induced by an RF frequency in the 10 to 70 MHz range. We employ a 400 to 1000 Gauss electromagnet that promotes energy conservation in the plasma via external energy production in the magnetic field facilitated by decreased inertial effects, in order to reach the Helicon Mode. With the initial construction phase complete and repeatable plasmas attained, HPX is constructing triple and mach particle probes, magnetic probes, and a single point 300 W Thompson Scattering system backed by a 32-channel Data Acquisition (DAQ) system capable 12 bits of sampling precision at 2 MS/s for HPX plasma property investigations. Progress on the development of the RF coupling system, Helicon Mode development, magnetic coils, and observations from the optical, particle, and electromagnetic scattering diagnostics will be reported. Supported by U.S. DEPS Grant [HEL-JTO] PRWJFY12.

  10. Study of the low-pressure plasma effect on polypropylene nonwovens

    SciTech Connect

    Lopez, R.; Pascual, M.; Calvo, O.

    2010-06-02

    In this work we have used low-pressure plasma with a gas based on methane and oxygen mixture to improve wettability and durability of a PP nonwoven fabrics. The obtained results show good durability with the use of methane-oxygen plasma mixture gas. The effects of the plasma are similar to a plasmapolymerization process but in this case we obtain hydrophilic properties with high durability. The surface does not suffer important changes and the roughness of the material remains constant.

  11. "Virtual IED sensor" at an rf-biased electrode in low-pressure plasma

    NASA Astrophysics Data System (ADS)

    Bogdanova, M. A.; Lopaev, D. V.; Zyryanov, S. M.; Rakhimov, A. T.

    2016-07-01

    Energy distribution and the flux of the ions coming on a surface are considered as the key-parameters in anisotropic plasma etching. Since direct ion energy distribution (IED) measurements at the treated surface during plasma processing are often hardly possible, there is an opportunity for virtual ones. This work is devoted to the possibility of such indirect IED and ion flux measurements at an rf-biased electrode in low-pressure rf plasma by using a "virtual IED sensor" which represents "in-situ" IED calculations on the absolute scale in accordance with a plasma sheath model containing a set of measurable external parameters. The "virtual IED sensor" should also involve some external calibration procedure. Applicability and accuracy of the "virtual IED sensor" are validated for a dual-frequency reactive ion etching (RIE) inductively coupled plasma (ICP) reactor with a capacitively coupled rf-biased electrode. The validation is carried out for heavy (Ar) and light (H2) gases under different discharge conditions (different ICP powers, rf-bias frequencies, and voltages). An EQP mass-spectrometer and an rf-compensated Langmuir probe (LP) are used to characterize plasma, while an rf-compensated retarded field energy analyzer (RFEA) is applied to measure IED and ion flux at the rf-biased electrode. Besides, the pulsed selfbias method is used as an external calibration procedure for ion flux estimating at the rf-biased electrode. It is shown that pulsed selfbias method allows calibrating the IED absolute scale quite accurately. It is also shown that the "virtual IED sensor" based on the simplest collisionless sheath model allows reproducing well enough the experimental IEDs at the pressures when the sheath thickness s is less than the ion mean free path λi (s < λi). At higher pressure (when s > λi), the difference between calculated and experimental IEDs due to ion collisions in the sheath is observed in the low energy range. The effect of electron impact ionization

  12. Investigation of the DSMC Approach for Ion/neutral Species in Modeling Low Pressure Plasma Reactor

    SciTech Connect

    Deng Hao; Li, Z.; Levin, D.; Gochberg, L.

    2011-05-20

    Low pressure plasma reactors are important tools for ionized metal physical vapor deposition (IMPVD), a semiconductor plasma processing technology that is increasingly being applied to deposit Cu seed layers on semiconductor surfaces of trenches and vias with the high aspect ratio (e.g., >5:1). A large fraction of ionized atoms produced by the IMPVD process leads to an anisotropic deposition flux towards the substrate, a feature which is critical for attaining a void-free and uniform fill. Modeling such devices is challenging due to their high plasma density, reactive environment, but low gas pressure. A modular code developed by the Computational Optical and Discharge Physics Group, the Hybrid Plasma Equipment Model (HPEM), has been successfully applied to the numerical investigations of IMPVD by modeling a hollow cathode magnetron (HCM) device. However, as the development of semiconductor devices progresses towards the lower pressure regime (e.g., <5 mTorr), the breakdown of the continuum assumption limits the application of the fluid model in HPEM and suggests the incorporation of the kinetic method, such as the direct simulation Monte Carlo (DSMC), in the plasma simulation.The DSMC method, which solves the Boltzmann equation of transport, has been successfully applied in modeling micro-fluidic flows in MEMS devices with low Reynolds numbers, a feature shared with the HCM. Modeling of the basic physical and chemical processes for ion/neutral species in plasma have been developed and implemented in DSMC, which include ion particle motion due to the Lorentz force, electron impact reactions, charge exchange reactions, and charge recombination at the surface. The heating of neutrals due to collisions with ions and the heating of ions due to the electrostatic field will be shown to be captured by the DSMC simulations. In this work, DSMC calculations were coupled with the modules from HPEM so that the plasma can be self-consistently solved. Differences in the Ar

  13. Physical and chemical properties of low-pressure argon-chlorine dielectric barrier discharge

    NASA Astrophysics Data System (ADS)

    Barjasteh, Azadeh; Eslami, Esmaeil

    2016-03-01

    The influence of adding chlorine on the characteristics of a dielectric barrier discharge in Argon is investigated on the basis of a one-dimensional fluid model. The spatio-temporal characteristics of the discharge are obtained by applying a sinusoidal voltage with a frequency and amplitude of 7 kHz and 350 V, respectively. The study shows that the discharge has a homogeneous feature across the electrodes and has only one current pulse per half cycle of the applied voltage. The calculated electric field and electric potential as well as species number densities indicated that the discharge is in glow mode, and adding chlorine as electronegative gas up to 50% does not change its mode. It is observed that the most abundant negative species are C l - ions even in low additive chlorine. As a result, the maximum of plasma electronegativity takes place at 30% amounts of chlorine additive. The study of plasma radiations on the discharge gap shows that the main spontaneous emissions are observed at the wavelengths of 128.5 nm and 258 nm due to de-excitation of A r C l * and C l2 * molecules, respectively. Between different Ar/Cl2 mixtures, 0.99 A r - 0.01 C l 2 has the nearly uniform radiation in the positive column region.

  14. Progress on Development of Low Pressure High Density Plasmas on the Helicon Plasma Experiment (HPX)

    NASA Astrophysics Data System (ADS)

    James, Royce; Azzari, Phillip; Duke-Tinson, Omar; Frank, John; Karama, Jackson; Hopson, Jordan; Paolino, Richard; Sandri, Eva; Sherman, Justin; Wright, Erin; Turk, Jeremy

    2015-11-01

    The small Helicon Plasma Experiment (HPX) at the Coast Guard Academy Plasma Lab (CGAPL), continues to progress toward utilizing the reputed high densities (1013 cm-3 and higher) at low pressure (.01 T) [1] of helicons, for eventual high temperature and density diagnostic development in future laboratory investigations. HPX is designed to create repeatedly stable plasmas (~ 20 - 30 ns) induced by an RF frequency in the 10 to 70 MHz range. HPX is constructing RF field corrected Langmuir probe raw data will be collected and used to measure the plasma's density, temperature, and potentially the structure and behavior during experiments. Our 2.5 J YAG laser Thomson Scattering system backed by a 32-channel Data Acquisition (DAQ) system is capable 12 bits of sampling precision at 2 MS/s for HPX plasma property investigations. Progress on the development of the RF coupling system, Helicon Mode development, magnetic coils, and observations from the Thomson Scattering, particle, and electromagnetic scattering diagnostics will be reported. Supported by U.S. DEPS Grant [HEL-JTO] PRWJFY15.

  15. Development of Low Pressure High Density Plasmas on the Helicon Plasma Experiment (HPX)

    NASA Astrophysics Data System (ADS)

    James, Royce; Azzari, Phillip; Crilly, Paul; Duke-Tinson, Omar; Karama, Jackson; Paolino, Richard; Schlank, Carter; Sherman, Justin

    2014-10-01

    The small Helicon Plasma Experiment (HPX) at the Coast Guard Academy Plasma Lab (CGAPL), continues to progress toward utilizing the reputed high densities (10 cm-3 and higher) at low pressure (.01 T) of helicons, for eventual high temperature and density diagnostic development in future laboratory investigations. HPX is designed to create repeatedly stable plasmas induced by an RF frequency in the 10 to 70 MHz range. We employ a 400 to 1000 Gauss electromagnet that promotes energy conservation in the plasma via external energy production in the magnetic field facilitated by decreased inertial effects, in order to reach the Helicon Mode. HPX is completing construction of triple and mach particle probes, magnetic probes, and is designing a single point 300 W Thompson Scattering system backed by a 32-channel Data Acquisition (DAQ) system capable 12 bits of sampling precision at 2 MS/s for HPX plasma property investigations. Progress on the development of the RF coupling system, Helicon Mode development, magnetic coils, and observations from the optical, particle, and electromagnetic scattering diagnostics will be reported. Supported by U.S. DEPS Grant [HEL-JTO] PRWJFY13.

  16. 2D laser-collision induced fluorescence in low-pressure argon discharges

    SciTech Connect

    Barnat, E. V.; Weatherford, B. R.

    2015-09-25

    Development and application of laser-collision induced fluorescence (LCIF) diagnostic technique is presented for the use of interrogating argon plasma discharges. Key atomic states of argon utilized for the LCIF method are identified. A simplified two-state collisional radiative model is then used to establish scaling relations between the LCIF, electron density, and reduced electric fields (E/N). The procedure used to generate, detect and calibrate the LCIF in controlled plasma environments is discussed in detail. LCIF emanating from an argon discharge is then presented for electron densities spanning 109 e cm–3 to 1012 e cm–3 and reduced electric fields spanning 0.1 Td to 40 Td. Lastly, application of the LCIF technique for measuring the spatial distribution of both electron densities and reduced electric field is demonstrated.

  17. 2D laser-collision induced fluorescence in low-pressure argon discharges

    DOE PAGESBeta

    Barnat, E. V.; Weatherford, B. R.

    2015-09-25

    Development and application of laser-collision induced fluorescence (LCIF) diagnostic technique is presented for the use of interrogating argon plasma discharges. Key atomic states of argon utilized for the LCIF method are identified. A simplified two-state collisional radiative model is then used to establish scaling relations between the LCIF, electron density, and reduced electric fields (E/N). The procedure used to generate, detect and calibrate the LCIF in controlled plasma environments is discussed in detail. LCIF emanating from an argon discharge is then presented for electron densities spanning 109 e cm–3 to 1012 e cm–3 and reduced electric fields spanning 0.1 Tdmore » to 40 Td. Lastly, application of the LCIF technique for measuring the spatial distribution of both electron densities and reduced electric field is demonstrated.« less

  18. Experimental investigations of driving frequency effect in low-pressure capacitively coupled oxygen discharges

    SciTech Connect

    Liu, Jia; Liu, Yong-Xin; Liu, Gang-Hu; Gao, Fei; Wang, You-Nian

    2015-04-14

    The effect of driving frequency on the electron density is investigated in low-pressure capacitively coupled oxygen plasmas by utilizing a floating hairpin probe. The power absorbed by the plasma is investigated and it is found that the power lost in the matching network can reach 50% or higher under certain conditions. The effect of driving frequency on the electron density is studied from two aspects, i.e., constant absorbed power and electrode voltage. In the former case, the electron density increases with the driving frequency increasing from 13.56 to 40.68 MHz and slightly changes depending on the gas pressures with the frequency further increasing to 100 MHz. In the latter case, the electron density rapidly increases when the driving frequency increases from 13.56 to 40.68 MHz, and then decreases with the frequency further increasing to 100 MHz. The electron series resonance is observed at 40.68 MHz and can be attributed to the higher electron density. And the standing wave effect also plays an important role in increasing electron density at 100 MHz and 2.6 Pa.

  19. Experimental investigations of driving frequency effect in low-pressure capacitively coupled oxygen discharges

    NASA Astrophysics Data System (ADS)

    Liu, Jia; Liu, Yong-Xin; Liu, Gang-Hu; Gao, Fei; Wang, You-Nian

    2015-04-01

    The effect of driving frequency on the electron density is investigated in low-pressure capacitively coupled oxygen plasmas by utilizing a floating hairpin probe. The power absorbed by the plasma is investigated and it is found that the power lost in the matching network can reach 50% or higher under certain conditions. The effect of driving frequency on the electron density is studied from two aspects, i.e., constant absorbed power and electrode voltage. In the former case, the electron density increases with the driving frequency increasing from 13.56 to 40.68 MHz and slightly changes depending on the gas pressures with the frequency further increasing to 100 MHz. In the latter case, the electron density rapidly increases when the driving frequency increases from 13.56 to 40.68 MHz, and then decreases with the frequency further increasing to 100 MHz. The electron series resonance is observed at 40.68 MHz and can be attributed to the higher electron density. And the standing wave effect also plays an important role in increasing electron density at 100 MHz and 2.6 Pa.

  20. Low-pressure sustainment of surface-wave microwave plasma with modified microwave coupler

    NASA Astrophysics Data System (ADS)

    Sasai, Kensuke; Suzuki, Haruka; Toyoda, Hirotaka

    2016-01-01

    Sustainment of long-scale surface-wave plasma (SWP) at pressures below 1 Pa is investigated for the application of the SWP as an assisting plasma source for roll-to-roll sputter deposition. A modified microwave coupler (MMC) for easier surface-wave propagation is proposed, on the basis of the concept of the power direction alignment of the slot antenna and surface-wave propagation. The superiority of the MMC-SWP over conventional SWPs is shown at a sustainment pressure as low as 0.6 Pa and an electron density as high as 3 × 1017 m-3. A polymer film is treated with the MMC-SWP at a low pressure of 0.6 Pa, and surface modification at a low pressure is proved using Ar plasma. These results show the availability of the MMC-SWP as the surface treatment plasma source that is compatible with sputter deposition in the same processing chamber.

  1. Life modeling of atmospheric and low pressure plasma-sprayed thermal-barrier coating

    NASA Technical Reports Server (NTRS)

    Miller, R. A.; Argarwal, P.; Duderstadt, E. C.

    1984-01-01

    The cycles-to-failure vs cycle duration data for three different thermal barrier coating systems, which consist of atmospheric pressure plasma-sprayed ZrO2-8 percent Y2O3 over similarly deposited or low pressure plasma sprayed Ni-base alloys, are presently analyzed by means of the Miller (1980) oxidation-based life model. Specimens were tested at 1100 C for heating cycle lengths of 1, 6, and 20 h, yielding results supporting the model's value.

  2. Modelling Of Generation And Growth Of Nanoparticles In Low-Pressure Plasmas

    SciTech Connect

    Gordiets, B. F.

    2008-09-07

    Theoretical kinetic models of generation and growth of clusters and nanoparticles in low-pressure plasma are briefly rewired. The relatively simple kinetic model is discussed more detail. Simple formulas and equations are given for monomer density; cluster dimension distribution; critical cluster dimension; rate of particle production; particle density and average dimension as well as plasma characteristics. The analytical formula is also obtained for the time delay of the measured LIPEE signal in the 'Laser Induced Particle Explosive Evaporation' experimental method.

  3. E-H mode transition in low-pressure inductively coupled nitrogen-argon and oxygen-argon plasmas

    SciTech Connect

    Lee, Young Wook; Lee, Hye Lan; Chung, T. H.

    2011-06-01

    This work investigates the characteristics of the E-H mode transition in low-pressure inductively coupled N{sub 2}-Ar and O{sub 2}-Ar discharges using rf-compensated Langmuir probe measurements and optical emission spectroscopy (OES). As the ICP power increases, the emission intensities from plasma species, the electron density, the electron temperature, and the plasma potential exhibit sudden changes. The Ar content in the gas mixture and total gas pressure have been varied in an attempt to fully characterize the plasma parameters. With these control parameters varying, the changes of the transition threshold power and the electron energy distribution function (EEDF) are explored. In N{sub 2}-Ar and O{sub 2}-Ar discharges at low-pressures of several millitorr, the transition thresholds are observed to decrease with Ar content and pressure. It is observed that in N{sub 2}-Ar plasmas during the transition, the shape of the EEDF changes from an unusual distribution with a flat hole near the electron energy of 3 eV in the E mode to a Maxwellian distribution in the H mode. However, in O{sub 2} -Ar plasmas, the EEDFs in the E mode at low Ar contents show roughly bi-Maxwellian distributions, while the EEDFs in the H mode are observed to be nearly Maxwellian. In the E and H modes of O{sub 2}-Ar discharges, the dissociation fraction of O{sub 2} molecules is estimated using optical emission actinometry. During the E-H mode transition, the dissociation fraction of molecules is also enhanced.

  4. Mass spectrometry of positive ions in capacitively coupled low pressure RF discharges in oxygen with water impurities

    NASA Astrophysics Data System (ADS)

    Stefanović, Ilija; Stojanović, Vladimir; Boulmer-Leborgne, Chantal; Lecas, Thomas; Kovacevic, Eva; Berndt, Johannes

    2016-07-01

    A capacitively coupled RF oxygen discharge is studied by means of mass spectroscopy. Mass spectra of neutral and positive species are measured in the mid plane between the electrodes at different distances between plasma and mass-spectrometer orifice. In the case of positive ions, as expected, the largest flux originates from \\text{O}2+ . However, a significant number of impurities are detected, especially for low input powers and larger distances. The most abundant positive ions (besides \\text{O}2+ ) are \\text{N}{{\\text{O}}+}, \\text{NO}2+ , {{\\text{H}}+}≤ft({{\\text{H}}2}\\text{O}\\right) , and {{\\text{H}}+}{{≤ft({{\\text{H}}2}\\text{O}\\right)}2} . In particular, for the case of hydrated hydronium ions {{\\text{H}}+}{{≤ft({{\\text{H}}2}\\text{O}\\right)}n} (n  =  1, 2) a surprisingly large flux (for low pressure plasma conditions) is detected. Another interesting fact concerns the {{\\text{H}}2}{{\\text{O}}+} ions. Despite the relatively high ammount of water impurities {{\\text{H}}2}{{\\text{O}}+} ions are present only in traces. The reaction mechanisms leading to the production of the observed ions, especially the hydrated hydronium ions are discussed.

  5. Generation of ion-acoustic waves in an inductively coupled, low-pressure discharge lamp

    SciTech Connect

    Camparo, J. C.; Klimcak, C. M.

    2006-04-15

    For a number of years it has been known that the alkali rf-discharge lamps used in atomic clocks can exhibit large amplitude intensity oscillations. These oscillations arise from ion-acoustic plasma waves and have typically been associated with erratic clock behavior. Though large amplitude ion-acoustic plasma waves are clearly deleterious for atomic clock operation, it does not follow that small amplitude oscillations have no utility. Here, we demonstrate two easily implemented methods for generating small amplitude ion-acoustic plasma waves in alkali rf-discharge lamps. Furthermore, we demonstrate that the frequency of these waves is proportional to the square root of the rf power driving the lamp and therefore that their examination can provide an easily accessible parameter for monitoring and controlling the lamp's plasma conditions. This has important consequences for precise timekeeping, since the atomic ground-state hyperfine transition, which is the heart of the atomic clock signal, can be significantly perturbed by changes in the lamp's output via the ac-Stark shift.

  6. Linear electromagnetic excitation of an asymmetric low pressure capacitive discharge with unequal sheath widths

    NASA Astrophysics Data System (ADS)

    Lieberman, M. A.; Lichtenberg, A. J.; Kawamura, E.; Chabert, P.

    2016-01-01

    It is well-known that standing waves having radially center-high radio frequency (rf) voltage profiles exist in high frequency capacitive discharges. In this work, we determine the symmetric and antisymmetric radially propagating waves in a cylindrical capacitive discharge that is asymmetrically driven at the lower electrode by an rf voltage source. The discharge is modeled as a uniform bulk plasma which at lower frequencies has a thicker sheath at the smaller area powered electrode and a thinner sheath at the larger area grounded electrode. These are self-consistently determined at a specified density using the Child law to calculate sheath widths and the electron power balance to calculate the rf voltage. The fields and the system resonant frequencies are determined. The center-to-edge voltage ratio on the powered electrode is calculated versus frequency, and central highs are found near the resonances. The results are compared with simulations in a similar geometry using a two-dimensional hybrid fluid-analytical code, giving mainly a reasonable agreement. The analytic model may be useful for finding good operating frequencies for a given discharge geometry and power.

  7. Experimental observation of standing wave effect in low-pressure very-high-frequency capacitive discharges

    SciTech Connect

    Liu, Yong-Xin; Gao, Fei; Liu, Jia; Wang, You-Nian

    2014-07-28

    Radial uniformity measurements of plasma density were carried out by using a floating double probe in a cylindrical (21 cm in electrode diameter) capacitive discharge reactor driven over a wide range of frequencies (27–220 MHz). At low rf power, a multiple-node structure of standing wave effect was observed at 130 MHz. The secondary density peak caused by the standing wave effect became pronounced and shifts toward the axis as the driving frequency further to increase, indicative of a much more shortened standing-wave wavelength. With increasing rf power, the secondary density peak shift toward the radial edge, namely, the standing-wave wavelength was increased, in good qualitative agreement with the previous theory and simulation results. At higher pressures and high frequencies, the rf power was primarily deposited at the periphery of the electrode, due to the fact that the waves were strongly damped as they propagated from the discharge edge into the center.

  8. Elongated dust clouds in a uniform DC positive column of low pressure gas discharge

    NASA Astrophysics Data System (ADS)

    Usachev, A. D.; Zobnin, A. V.; Petrov, O. F.; Fortov, V. E.; Thoma, M. H.; Pustylnik, M. Y.; Fink, M. A.; Morfill, G. E.

    2016-06-01

    Experimental investigations of the formation of elongated dust clouds and their influence on the plasma glow intensity of the uniform direct current (DC) positive column (PC) have been performed under microgravity conditions. For the axial stabilization of the dust cloud position a polarity switching DC gas discharge with a switching frequency of 250 Hz was used. During the experiment, a spontaneous division of one elongated dust cloud into two smaller steady state dust clouds has been observed. Quantitative data on the dust cloud shape, size and dust number density distribution were obtained. Axial and radial distributions of plasma emission within the 585.2 nm and 703.2 nm neon spectral lines were measured over the whole discharge volume. It has been found that both spectral line intensities at the dust cloud region grew 1.7 times with respect to the undisturbed positive column region; in this the 585.2 nm line intensity increased by 10% compared to the 703.2 nm line intensity. For a semi-quantitative explanation of the observed phenomena the Schottky approach based on the equation of diffusion was used. The model reasonably explains the observed glow enhancement as an increasing of the ionization rate in the discharge with dust cloud, which compensates ion-electron recombination on the dust grain surfaces. In this, the ionization rate increases due to the growing of the DC axial electric field, and the glow grows directly proportional to the electric field. It is shown that the fundamental condition of the radial stability of the dusty plasma cloud is equal to the ionization and recombination rates within the cloud volume that is possible only when the electron density is constant and the radial electric field is absent within the dust cloud.

  9. Nonlinear standing wave excitation by series resonance-enhanced harmonics in low pressure capacitive discharges

    NASA Astrophysics Data System (ADS)

    Lieberman, M. A.; Lichtenberg, A. J.; Kawamura, Emi; Marakhtanov, A. M.

    2015-09-01

    It is well known that standing waves having radially center-high rf voltage profiles exist in high frequency capacitive discharges. It is also known that in radially uniform discharges, the capacitive sheath nonlinearities excite strong nonlinear series resonance harmonics that enhance the electron power deposition. In this work, we consider the coupling of the series resonance-enhanced harmonics to the standing waves. A one-dimensional, asymmetric radial transmission line model is developed incorporating the wave and nonlinear sheath physics and a self-consistent dc potential. The resulting coupled pde equation set is solved numerically to determine the discharge voltages and currents. A 10 mT argon base case is chosen with plasma density 2 ×1016 m-3, gap width 2 cm and conducting electrode radius 15 cm, driven by a high frequency 500 V source with source resistance 0.5 ohms. We find that nearby resonances lead to an enhanced ratio of 4.5 of the electron power per unit area on axis, compared to the average. The radial dependence of electron power with frequency shows significant variations, with the central enhancement and sharpness of the spatial resonances depending in a complicated way on the harmonic structure. Work supported by DOE Fusion Energy Science Contract DE-SC000193 and by a gift from the Lam Research Corporation.

  10. Does asymmetric charge transfer play an important role as an ionization mode in low power-low pressure glow discharge mass spectrometry?

    NASA Astrophysics Data System (ADS)

    Mushtaq, S.; Steers, E. B. M.; Churchill, G.; Barnhart, D.; Hoffmann, V.; Pickering, J. C.; Putyera, K.

    2016-04-01

    We report results of comprehensive studies using the Nu Instruments Astrum high-resolution glow discharge mass spectrometer (GD-MS) and optical emission spectrometry (OES) to investigate the relative importance of discharge mechanisms, such as Penning ionization (PI) and asymmetric charge transfer (ACT), at low-power/low-pressure discharge conditions. Comparison of the ratios of the ion signals of each constituent element to that of the plasma gas shows that for oxygen, the ratio in krypton is more than ten times higher than in argon (oxygen ground state ions are produced by Kr-ACT). For many elements, the ratios are very similar but that for tungsten is higher with krypton, while for iron, the reverse holds. These effects are linked to the arrangement of ionic energy levels of the elements concerned and the resulting relative importance of ACT and PI. The GD-MS and GD-OES results have shown that the ACT process can play an important role as the ionization mode in low-power/low-pressure discharges. However, OES results have shown that the magnitude of change in spectral intensities of elements studied are dependent on the discharge conditions.

  11. Measurement of vibrational populations in low-pressure hydrogen plasma by coherent anti-Stokes Raman scattering

    NASA Astrophysics Data System (ADS)

    Pealat, M.; Taran, J. P. E.; Taillet, J.; Bacal, M.; Bruneteau, A. M.

    1981-04-01

    Vibrational populations in a low-pressure H2 plasma have been measured by coherent anti-Stokes Raman scattering (CARS). The plasma generator is described, and some particulars of the optical arrangement are given. The CARS system is a commercial spectrometer, whose original optical system has been slightly modified for this study, by eliminating the Polarex arrangement for the YAG laser oscillator and by adding a YAG amplifier stage. This has resulted in improved beam quality and enhanced peak power. For an electron density of 2 x 10 to the 11th cm to the 0.001 and a total pressure of 0.13 m bar, the rotational temperature was found to be 475 K. The populations of the vibrational states v equals 0, 1, and 2 have also been measured. Their distribution is non-Boltzmann. The influence of pressure and discharge parameters is discussed.

  12. Utilization of Low-Pressure Plasma to Inactivate Bacterial Spores on Stainless Steel Screws

    PubMed Central

    Stapelmann, Katharina; Fiebrandt, Marcel; Raguse, Marina; Awakowicz, Peter; Reitz, Günther

    2013-01-01

    Abstract A special focus area of planetary protection is the monitoring, control, and reduction of microbial contaminations that are detected on spacecraft components and hardware during and after assembly. In this study, wild-type spores of Bacillus pumilus SAFR-032 (a persistent spacecraft assembly facility isolate) and the laboratory model organism B. subtilis 168 were used to study the effects of low-pressure plasma, with hydrogen alone and in combination with oxygen and evaporated hydrogen peroxide as a process gas, on spore survival, which was determined by a colony formation assay. Spores of B. pumilus SAFR-032 and B. subtilis 168 were deposited with an aseptic technique onto the surface of stainless steel screws to simulate a spore-contaminated spacecraft hardware component, and were subsequently exposed to different plasmas and hydrogen peroxide conditions in a very high frequency capacitively coupled plasma reactor (VHF-CCP) to reduce the spore burden. Spores of the spacecraft isolate B. pumilus SAFR-032 were significantly more resistant to plasma treatment than spores of B. subtilis 168. The use of low-pressure plasma with an additional treatment of evaporated hydrogen peroxide also led to an enhanced spore inactivation that surpassed either single treatment when applied alone, which indicates the potential application of this method as a fast and suitable way to reduce spore-contaminated spacecraft hardware components for planetary protection purposes. Key Words: Bacillus spores—Contamination—Spacecraft hardware—Plasma sterilization—Planetary protection. Astrobiology 13, 597–606. PMID:23768085

  13. Diagnostics of plasma-biological surface interactions in low pressure and atmospheric pressure plasmas

    NASA Astrophysics Data System (ADS)

    Ishikawa, Kenji; Hori, Masaru

    2014-08-01

    Mechanisms of plasma-surface interaction are required to understand in order to control the reactions precisely. Recent progress in atmospheric pressure plasma provides to apply as a tool of sterilization of contaminated foodstuffs. To use the plasma with safety and optimization, the real time in situ detection of free radicals - in particular dangling bonds by using the electron-spin-resonance (ESR) technique has been developed because the free radical plays important roles for dominantly biological reactions. First, the kinetic analysis of free radicals on biological specimens such as fungal spores of Penicillium digitatum interacted with atomic oxygen generated plasma electric discharge. We have obtained information that the in situ real time ESR signal from the spores was observed and assignable to semiquinone radical with a g-value of around 2.004 and a line width of approximately 5G. The decay of the signal was correlated with a link to the inactivation of the fungal spore. Second, we have studied to detect chemical modification of edible meat after the irradiation. Using matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF-MS) and ESR, signals give qualification results for chemical changes on edible liver meat. The in situ real-time measurements have proven to be a useful method to elucidate plasma-induced surface reactions on biological specimens.

  14. Direct current-self-sustained non-ambipolar plasma at low pressure

    SciTech Connect

    Chen, Zhiying; Chen, Lee; Funk, Merritt

    2013-12-16

    For decades, non-ambipolar diffusion has been observed and studied in laboratory plasmas that contain a double layer. However, self-sustained non-ambipolar plasma has yet to be demonstrated. This article reports the method and results for achieving such a condition at low pressure, with a wide power range (as low as 6 W). The findings reveal that to achieve self-sustained non-ambipolar plasma, both the balance between electron and ion heating and the space-potential gradient are critical. The plasma reactor developed in this work has potential applications that include microelectronic surface processing and space propulsion, via space-charge-neutral plasma-beam thruster, when operated in the high power regime.

  15. Low-pressure microwave plasma nucleation and deposition of diamond films

    NASA Technical Reports Server (NTRS)

    Shing, Y. H.; Pool, F. S.; Rich, D. H.

    1992-01-01

    Low-pressure microwave plasma nucleation and deposition of diamond films were investigated in the pressure range 10-mtorr to 10 torr, at substrate temperatures 400-750 C and with CH4 and O2 concentrations in H2 plasma of 2-15 percent and 2-10 percent, respectively. The experiments were performed in a microwave plasma system consisting of a microwave plasma chamber, a downstream deposition chamber, and an RF induction heated sample stage. Scanning electron microscopy of diamond films deposited at 600 C with 5 percent CH4 and 5 percent O2 in H2 plasmas showed high-quality well faceted crystallites of 1/2 micron size. Cathodoluminescence measurements of these films showed very few nitrogen impurities and no detectable silicon impurities.

  16. The multipole resonance probe: A concept for simultaneous determination of plasma density, electron temperature, and collision rate in low-pressure plasmas

    SciTech Connect

    Lapke, M.; Mussenbrock, T.; Brinkmann, R. P.

    2008-08-04

    A diagnostic concept is presented which enables the simultaneous determination of plasma density, electron temperature, and collision rate in low-pressure gas discharges. The proposed method utilizes a radio-frequency driven probe of particular spherical design which is immersed in the plasma to excite a family of spatially bounded surface resonances. An analysis of the measured absorption spectrum S({omega}) of the probe provides information on the distribution of the plasma in its vicinity, from which the values of the plasma parameters can be inferred. In its simplest realization, the probe consists of two dielectrically shielded, conducting hemispheres, which are symmetrically driven by an radio-frequency source, and the excited resonances can be classified as multipole fields, which allows an analytical evaluation of the measured signal. The proposed method is robust, calibration free, economical, and can be used for ideal and reactive plasmas alike.

  17. Kinetic model and spectroscopic measurement of NO (A, B, C) states in low-pressure N2-O2 microwave discharge

    NASA Astrophysics Data System (ADS)

    Tan, Hao; Nezu, Atsushi; Akatsuka, Hiroshi

    2015-09-01

    A self-consistent kinetic model is developed to study the atomic and molecular processes in the microwave discharge plasma of N2-O2 mixtures. We focus on the NO A 2Σ+, B 2Π, and C 2Π states in the mixture discharge. We find good agreement between the calculated and experimental NO A 2Σ+ densities. On the other hand, the radiation bands from the NO B 2Π and C 2Π states are observed only when the oxygen partial pressure is less than 3%. We discuss the de-excitation processes for the NO B 2Π and C 2Π states in this low-pressure plasma. We also propose that the de-excitation processes involve collision with O2 X 3Σ \\text{g} - for these levels, which can explain the observed spectral disappearance.

  18. Nonlinear standing wave excitation by series resonance-enhanced harmonics in low pressure capacitive discharges

    NASA Astrophysics Data System (ADS)

    Lieberman, M. A.; Lichtenberg, A. J.; Kawamura, E.; Marakhtanov, A. M.

    2015-10-01

    It is well-known that standing waves having radially center-high rf voltage profiles exist in high frequency capacitive discharges. It is also known that in radially uniform discharges, the capacitive sheath nonlinearities excite strong nonlinear series resonance harmonics that enhance the electron power deposition. In this work, we consider the coupling of the series resonance-enhanced harmonics to the standing waves. A one-dimensional, asymmetric radial transmission line model is developed incorporating the wave and nonlinear sheath physics and a self-consistent dc potential, for both conducting and insulating electrode surfaces. The resulting coupled pde equation set is solved numerically to determine the discharge voltages and currents. A 10 mTorr argon plasma is chosen with density 2× {{10}16} m-3, gap width 2 cm and conducting electrode radius 15 cm, driven by a 500 V rf source with resistance 0.5 Ω . We examine a set of frequencies from near 30 MHz up to frequencies more than three times as high. For most frequencies, no harmonics correspond exactly with the series or spatial resonances, which is the generic situation. Nevertheless, nearby resonances lead to a significantly enhanced ratio of the electron power per unit area on axis, compared to the average. Nearly similar results are found for insulating electrodes. Strong effects are seen for varying source resistance: high (50 Ω ) resistance damps out most of the harmonic activity, while zero source resistance leads to a non-steady discharge with bias voltage relaxation oscillations. Stronger harmonic effects are seen for an increased radius of 30 cm, as lower harmonics become spatially resonant at lower frequencies. The radial dependence of electron power with frequency showed significant variations, with the central enhancement and sharpness of the spatial resonances depending in a complicated way on the amplitudes of the nearby series resonance current harmonics and the phase relations among

  19. 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.

  20. Characteristics of Ceramic Coatings Made by Thin Film Low Pressure Plasma Spraying (LPPS-TF)

    NASA Astrophysics Data System (ADS)

    Hospach, Andreas; Mauer, Georg; Vaßen, Robert; Stöver, Detlev

    2012-06-01

    The thin film low pressure plasma spray process (LPPS-TF) has been developed with the aim of efficient depositing uniform and thin coatings with large area coverage by plasma spraying. At high power input (~150 kW) and very low pressure (~100 Pa) the plasma jet properties change considerably and it is even possible to evaporate the powder feedstock material providing advanced microstructures of the deposits. This relatively new technique bridges the gap between conventional plasma spraying and physical vapor deposition. In addition, the resulting microstructures are unique and can hardly be obtained by other processes. In this paper, microstructures made by LPPS-TF are shown and the columnar layer growth by vapor deposition is demonstrated. In addition to the ceramic materials TiO2, Al2O3 or MgAl2O4, the focus of the research was placed on partially yttria-stabilized zirconia. Variations of the microstructures are shown and discussed concerning potential coating applications.

  1. Hydrogen negative-ion surface production on diamond materials in low-pressure H2 plasmas

    NASA Astrophysics Data System (ADS)

    Cartry, Gilles; Achkasov, Kostiantyn; Pardanaud, Cédric; Layet, Jean-Marc; Simonin, Alain; Gicquel, Alix; PIIM Collaboration; IRFM Collaboration; LSPM Collaboration

    2014-10-01

    Negative-ion sources producing H-current density of ~200 A/m2 are required for the heating of the fusion plasma of the international project ITER. The only up-to-date solution to reach such a high H-negative-ion current is the use of cesium (Cs). Deposition of Cs on the negative-ion source walls lowers the material work function and allows for high electron-capture efficiency by incident particles and thus, high negative ion yields. However, severe drawbacks to the use of Cs have been identified and its elimination from the fusion negative-ion sources would be highly valuable. Volume production is not efficient enough at low-pressure to reach the high current required. Therefore, we are working on alternative solutions to produce high yield of H-negative-ions on surfaces in Cs-free H2 plasmas. In this communication, we will detail the methodology employed to study negative-ion surface production. In particular we will describe how the negative-ions are extracted from the plasma, and how we can obtain information on surface production mechanisms from the measurement of the H-energy distribution functions. We will present some results obtained on diamond surfaces and show that diamond is a promising candidate as a negative-ion enhancer material in low-pressure H2 plasmas. EFDA, FR-FCM, ANR, PACA are acknowledged for their support.

  2. Sterilization of dental bacteria in a N2text{-O2} microwaves post-discharge, at low pressure: influence of temperature

    NASA Astrophysics Data System (ADS)

    Villeger, S.; Ricard, A.; Sixou, M.

    2004-06-01

    Recently, plasmas have been largely studied to develop a new cold and safe sterilization process. The plasma efficiency on bacteria destruction has been proved at low or near atmospheric pressure. In our investigation we used a N{2}-O{2} post discharge at low pressure, where the experimental conditions allowing the optimal production of active species have been determined: 100 Watt, 1 Ln.min-1, 5 Torr. By exposing E. coli to these plasma conditions, it is demonstrated a synergy of N and O active atoms on substrate temperature: a reduction of 6 log was achieved after a treatment time of 20 minutes at 80 °C and of 12 log after 5 minutes at 120 °C.

  3. A 2-D Self-Consistent DSMC Model for Chemically Reacting Low Pressure Plasma Reactors

    SciTech Connect

    Bartel, Timothy J.; Economou, Demetre; Johannes, Justine E.

    1999-06-17

    This paper will focus on the methodology of using a 2D plasma Direct Simulation Monte Carlo technique to simulate the species transport in an inductively coupled, low pressure, chemically reacting plasma system. The pressure in these systems is typically less than 20 mtorr with plasma densities of approximately 10{sup 17} {number_sign}/m{sup 3} and an ionization level of only 0.1%. This low ionization level tightly couples the neutral, ion, and electron chemistries and interactions in a system where the flow is subsonic. We present our strategy and compare simulation results to experimental data for Cl{sub 2} in a Gaseous Electronics Conference (GEC) reference cell modified with an inductive coil.

  4. Decay of a low-pressure oxygen magnetized and unmagnetized plasma

    SciTech Connect

    Levko, Dmitry

    2014-09-14

    Extraction of negative ions from electronegative plasmas is one of the key issues addressed during the study of these plasmas. One of the widely used methods is the turn off of the electron heating power. This results in the escape of electrons from the plasma and results in the formation of almost pure ion-ion plasma. In the latter case, the plasma sheath collapses, which enables the extraction of negative ions from the plasma. Another method is the application of a large magnetic field to the plasma. If the electrons become magnetized and trapped near the center of discharge chamber, the plasma sheaths near the walls collapse. This also enables the negative ion extraction from the plasma even during the power-on stage. The aim of the present paper is the comparison of these two methods.

  5. Diagnostics of surface wave driven low pressure plasmas based on indium monoiodide-argon system

    NASA Astrophysics Data System (ADS)

    Ögün, C. M.; Kaiser, C.; Kling, R.; Heering, W.

    2015-06-01

    Indium monoiodide is proposed as a suitable alternative to hazardous mercury, i.e. the emitting component inside the compact fluorescent lamps (CFL), with comparable luminous efficacy. Indium monoiodide-argon low pressure lamps are electrodelessly driven with surface waves, which are launched and coupled into the lamp by the ‘surfatron’, a microwave coupler optimized for an efficient operation at a frequency of 2.45 GHz. A non intrusive diagnostic method based on spatially resolved optical emission spectroscopy is employed to characterize the plasma parameters. The line emission coefficients of the plasma are derived by means of Abel’s inversion from the measured spectral radiance data. The characteristic plasma parameters, e.g. electron temperature and density are determined by comparing the experimentally obtained line emission coefficients with simulated ones from a collisional-radiative model. Additionally, a method to determine the absolute plasma efficiency via irradiance measurements without any goniometric setup is presented. In this way, the relationship between the plasma efficiency and the plasma parameters can be investigated systematically for different operating configurations, e.g. electrical input power, buffer gas pressure and cold spot temperature. The performance of indium monoiodide-argon plasma is compared with that of conventional CFLs.

  6. Controlling VUV photon fluxes in low-pressure inductively coupled plasmas

    NASA Astrophysics Data System (ADS)

    Tian, Peng; Kushner, Mark J.

    2015-06-01

    Low-pressure (a few to hundreds of millitorrs) inductively coupled plasmas (ICPs), as typically used in microelectronics fabrication, often produce vacuum-ultraviolet (VUV) photon fluxes onto surfaces comparable to or exceeding the magnitude of ion fluxes. These VUV photon fluxes are desirable in applications such as sterilization of medical equipment but are unwanted in many materials fabrication processes due to damage to the devices by the high-energy photons. Under specific conditions, VUV fluxes may stimulate etching or synergistically combine with ion fluxes to modify polymeric materials. In this regard, it is desirable to control the magnitude of VUV fluxes or the ratio of VUV fluxes to those of other reactive species, such as ions, or to discretely control the VUV spectrum. In this paper, we discuss results from a computational investigation of VUV fluxes from low-pressure ICPs sustained in rare gas mixtures. The control of VUV fluxes through the use of pressure, pulsed power, and gas mixture is discussed. We found that the ratio, β, of VUV photon to ion fluxes onto surfaces generally increases with increasing pressure. When using pulsed plasmas, the instantaneous value of β can vary by a factor of 4 or more during the pulse cycle due to the VUV flux more closely following the pulsed power.

  7. Microwave air plasmas in capillaries at low pressure I. Self-consistent modeling

    NASA Astrophysics Data System (ADS)

    Coche, P.; Guerra, V.; Alves, L. L.

    2016-06-01

    This work presents the self-consistent modeling of micro-plasmas generated in dry air using microwaves (2.45 GHz excitation frequency), within capillaries (<1 mm inner radius) at low pressure (300 Pa). The model couples the system of rate balance equations for the most relevant neutral and charged species of the plasma to the homogeneous electron Boltzmann equation. The maintenance electric field is self-consistently calculated adopting a transport theory for low to intermediate pressures, taking into account the presence of O‑ ions in addition to several positive ions, the dominant species being O{}2+ , NO+ and O+ . The low-pressure small-radius conditions considered yield very-intense reduced electric fields (∼600–1500 Td), coherent with species losses controlled by transport and wall recombination, and kinetic mechanisms strongly dependent on electron-impact collisions. The charged-particle transport losses are strongly influenced by the presence of the negative ion, despite its low-density (∼10% of the electron density). For electron densities in the range (1–≤ft. 4\\right)× {{10}12} cm‑3, the system exhibits high dissociation degrees for O2 (∼20–70%, depending on the working conditions, in contrast with the  ∼0.1% dissociation obtained for N2), a high concentration of O2(a) (∼1014 cm‑3) and NO(X) (5× {{10}14} cm‑3) and low ozone production (<{{10}-3}% ).

  8. A Simple Ion Flux Estimation in a Low Pressure R.F. Plasma (13.56MHz)

    NASA Astrophysics Data System (ADS)

    Grenier, I.; Massereau, V.; Celerier, A.; Machet, J.

    1997-04-01

    A new application of the sputtering rate measurement is given in this paper. In fact, by measuring the sputtering rate of different materials fixed on the radio frequency (r.f.) biased electrode, it is possible to determine easily ion flux that falls onto this biased electrode. This study is realized in a low pressure (0.4 Pa) argon planar r.f. discharge system (13.56 MHz). This sputtering method is interesting to have informations about the deposition process in physical vapour deposition. In order to demonstrate the validity of this method, experiments have been carried out in two reactors, each one with different geometrical parameters and the results obtained have been compared and confirmed using the Child-Langmuir law. The ion flux increases as a function of the incident r.f power (0 300 W). The values obtained range from 10^{18} to 10^{19} ions m^{-2} s^{-1}. These results in an argon plasma are applied to estimate incident ion flux in a nitrogen atmosphere. Finally, we show that it is possible to evaluate the incident ion flux by measuring the sputtering rate when the plasma is densified using either an auxiliary hot cathode discharge or an additional magnetic field. These experimental cases correspond respectively to r.f. triode ion plating or r.f. magnetron sputtering.

  9. Formation processes of nanometer sized particles in low pressure Ar/CH{sub 4} rf plasmas

    SciTech Connect

    Beckers, J.; Vacaresse, G. D. G. J.; Stoffels, W. W.

    2008-09-07

    In this paper, formation and growth processes of nanometer and micrometer sized dust particles in low pressure Ar/CH{sub 4} rf (13.56 MHz) plasmas are investigated as function of temperature in the range 25-100 deg. C. During experiments the pressure was typically 0.8 mbar and the forward power to the plasma was {approx}70 Watt. Measuring the fundamental voltage, current and phase angle together with their harmonics (up to the fourth) gives a good method to monitor the creation and growth of these dust particles in time. Furthermore, laser light scattering measurements are performed to give information about the dust particle density. It has been shown that dust particle formation in these conditions depends greatly on temperature.

  10. Low-pressure electrical discharge experiment to simulate high-altitude lightning above thunderclouds

    NASA Technical Reports Server (NTRS)

    Jarzembski, M. A.; Srivastava, V.

    1995-01-01

    Recently, extremely interesting high-altitude cloud-ionosphere electrical discharges, like lightning above thunderstorms, have been observed from NASA's space shuttle missions and during airborne and ground-based experiments. To understand these discharges, a new experiment was conceived to simulate a thundercloud in a vacuum chamber using a dielectric in particulate form into which electrodes were inserted to create charge centers analogous to those in an electrified cloud. To represent the ionosphere, a conducting medium (metallic plate) was introduced at the top of the chamber. It was found that for different pressures between approximately 1 and 300 mb, corresponding to various upper atmospheric altitudes, different discharges occurred above the simulated thundercloud, and these bore a remarkable similarity to the observed atmospheric phenomena. At pressures greater than 300 mb, these discharges were rare and only discharges within the simulated thundercloud were observed. Use of a particulate dielectric was critical for the successful simulation of the high-altitude lightning.

  11. Controlling Ion and UV/VUV Photon Fluxes in Pulsed Low Pressure Plasmas for Materials Processing

    NASA Astrophysics Data System (ADS)

    Tian, Peng; Kushner, Mark J.

    2012-10-01

    UV/VUV photon fluxes in plasma materials processing have a variety of effects ranging from damaging to synergistic. To optimize these processes, it is desirable to have separate control over the fluxes of ions and photons, or at least be able to control their relative fluxes or overlap in time. Pulsed plasmas may provide such control as the rates at which ion and photon fluxes respond to the pulse power deposition are different. Results from a computational investigation of pulsed plasmas will be discussed to determine methods to control the ratio of ion to photon fluxes. Simulations were performed using a 2-dimensional plasma hydrodynamics model which addresses radiation transport using a Monte Carlo Simulation. Radiation transport is frequency resolved using partial-frequency-redistribution algorithms. Results for low pressure (10s of mTorr) inductively and capacitively coupled plasmas in Ar/Cl2 mixtures will be discussed while varying duty cycle, reactor geometry, gas mixture and pressure. We found that the time averaged ratio of VUV photon-to-ion fluxes in ICPs can be controlled with duty cycle of the pulsed power. Even with radiation trapping, photon fluxes tend to follow the power pulse whereas due to their finite response times, fluxes of ions tend to average the power pulse. Due to the overshoot in electron temperature that occurs at the start of low-duty-cycle pulses, disproportionately large photon fluxes (compared to ion fluxes) can be generated.

  12. A large-volume microwave plasma source based on parallel rectangular waveguides at low pressures

    NASA Astrophysics Data System (ADS)

    Zhang, Qing; Zhang, Guixin; Wang, Shumin; Wang, Liming

    2011-02-01

    A large-volume microwave plasma with good stability, uniformity and high density is directly generated and sustained. A microwave cavity is assembled by upper and lower metal plates and two adjacently parallel rectangular waveguides with axial slots regularly positioned on their inner wide side. Microwave energy is coupled into the plasma chamber shaped by quartz glass to enclose the space of working gas at low pressures. The geometrical properties of the source and the existing modes of the electric field are determined and optimized by a numerical simulation without a plasma. The calculated field patterns are in agreement with the observed experimental results. Argon, helium, nitrogen and air are used to produce a plasma for pressures ranging from 1000 to 2000 Pa and microwave powers above 800 W. The electron density is measured with a Mach-Zehnder interferometer to be on the order of 1014 cm-3 and the electron temperature is obtained using atomic emission spectrometry to be in the range 2222-2264 K at a pressure of 2000 Pa at different microwave powers. It can be seen from the interferograms at different microwave powers that the distribution of the plasma electron density is stable and uniform.

  13. Negative ion density in magnetically confined low-pressure argon-acetylene plasmas using laser-induced photodetachment

    NASA Astrophysics Data System (ADS)

    Margot, Joelle; Al Makdessi, Georges; Hamdan, Ahmad; Clergereaux, Richard

    2015-09-01

    In plasmas generated in reactive gases such as silane and acetylene, dust particles can spontaneously form provided the residence time of the precursors is large enough for allowing volume interactions to dominate over surface interactions. In discharges at intermediate pressure (e.g. 100 mTorr), anions are considered to be the most likely precursors to dust particles formation. In the present work, we examine the negative ion density in very low pressure conditions, namely 1-10 mTorr. For this purpose, we investigate magnetized dusty plasmas produced in argon-acetylene mixtures in which dust particles have been observed. The negative ion density is measured using a laser photodetachment technique. It is is observed to increase with the magnetic field intensity and to slightly decrease with increasing C2H2 percentage in argon. In addition, it decreases with increasing gas pressure. The photodetachment cross section deduced from the photodetachment signal as a function of laser energy is found to be significantly higher than the value expected for the C2H- ion, which may be explained by the presence in the plasma of negatively charged dust particles.

  14. Nanostructure protein repellant amphiphilic copolymer coatings with optimized surface energy by Inductively Excited Low Pressure Plasma.

    PubMed

    Bhatt, Sudhir; Pulpytel, Jérome; Ceccone, Giacomo; Lisboa, Patricia; Rossi, François; Kumar, Virendra; Arefi-Khonsari, Farzaneh

    2011-12-01

    Statistically designed amphiphilic copolymer coatings were deposited onto Thermanox, Si wafer, and quartz crystal microbalance (QCM) substrates via Plasma Enhanced Chemical Vapor Deposition of 1H,1H,2H,2H-perfluorodecyl acrylate and diethylene glycol vinyl ether in an Inductively Excited Low Pressure Plasma reactor. Plasma deposited amphiphilic coatings were characterized by Field Emission Scanning Electron Microscopy, X-ray Photoelectron Spectroscopy, Atomic Force Microscopy, and Water Contact Angle techniques. The surface energy of the coatings can be adjusted between 12 and 70 mJ/m(2). The roughness of the coatings can be tailored depending on the plasma mode used. A very smooth coating was deposited with a CW (continuous wave) power, whereas a rougher surface with R(a) in the range of 2 to 12 nm was deposited with the PW (pulsed wave) mode. The nanometer scale roughness of amphiphilic PFDA-co-DEGVE coatings was found to be in the range of the size of the two proteins namely BSA and lysozyme used to examine for the antifouling properties of the surfaces. The results show that the statistically designed surfaces, presenting a surface energy around 25 mJ/m(2), present no adhesion with respect to both proteins measured by QCM. PMID:22029599

  15. Amine Enrichment of Thin-Film Composite Membranes via Low Pressure Plasma Polymerization for Antimicrobial Adhesion.

    PubMed

    Reis, Rackel; Dumée, Ludovic F; He, Li; She, Fenghua; Orbell, John D; Winther-Jensen, Bjorn; Duke, Mikel C

    2015-07-15

    Thin-film composite membranes, primarily based on poly(amide) (PA) semipermeable materials, are nowadays the dominant technology used in pressure driven water desalination systems. Despite offering superior water permeation and salt selectivity, their surface properties, such as their charge and roughness, cannot be extensively tuned due to the intrinsic fabrication process of the membranes by interfacial polymerization. The alteration of these properties would lead to a better control of the materials surface zeta potential, which is critical to finely tune selectivity and enhance the membrane materials stability when exposed to complex industrial waste streams. Low pressure plasma was employed to introduce amine functionalities onto the PA surface of commercially available thin-film composite (TFC) membranes. Morphological changes after plasma polymerization were analyzed by SEM and AFM, and average surface roughness decreased by 29%. Amine enrichment provided isoelectric point changes from pH 3.7 to 5.2 for 5 to 15 min of plasma polymerization time. Synchrotron FTIR mappings of the amine-modified surface indicated the addition of a discrete 60 nm film to the PA layer. Furthermore, metal affinity was confirmed by the enhanced binding of silver to the modified surface, supported by an increased antimicrobial functionality with demonstrable elimination of E. coli growth. Essential salt rejection was shown minimally compromised for faster polymerization processes. Plasma polymerization is therefore a viable route to producing functional amine enriched thin-film composite PA membrane surfaces. PMID:26083007

  16. Vapors and Droplets Mixture Deposition of Metallic Coatings by Very Low Pressure Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Vautherin, B.; Planche, M.-P.; Bolot, R.; Quet, A.; Bianchi, L.; Montavon, G.

    2014-04-01

    In recent years, the very low pressure plasma-spraying (VLPPS) process has been intensely developed and implemented to manufacture thin, dense and finely structured ceramic coatings for various applications, such as Y2O3 for diffusion barriers, among other examples. This paper aims at presenting developments carried out on metallic coatings. Aluminum was chosen as a demonstrative material due to its "moderate" vaporization enthalpy (i.e., 38.23 KJ cm-3) compared to the one of copper (i.e., 55.33 KJ cm-3), cobalt (i.e., 75.03 KJ cm-3), or even tantalum (i.e., 87.18 KJ cm-3). The objective of this work is primarily to better understand the behavior of a solid precursor injected into the plasma jet leading to the formation of vapors and to better control the factors affecting the coating structure. Nearly dense aluminum coatings were successfully deposited by VLPPS at 100 Pa with an intermediate power plasma torch (i.e., Sulzer Metco F4 type gun with maximum power of 45 kW). Optical emission spectroscopy (OES) was implemented to study and analyze the vapor behavior into the plasma jet. Simplified CFD modeling allowed better understanding of some of the thermo-physical mechanisms. The effect of powder-size distribution, substrate temperature and spray distance were studied. The phase composition and microstructural features of the coatings were characterized by XRD and SEM. Moreover, Vickers microhardness measurements were implemented.

  17. Very low pressure plasma sprayed yttria-stabilized zirconia coating using a low-energy plasma gun

    NASA Astrophysics Data System (ADS)

    Zhu, Lin; Zhang, Nannan; Bolot, Rodolphe; Planche, Marie-Pierre; Liao, Hanlin; Coddet, Christian

    2011-12-01

    In the present study, a more economical low-energy plasma source was used to perform a very low pressure plasma-spray (VLPPS) process. The plasma-jet properties were analyzed by means of optical emission spectroscopy (OES). Moreover, yttria-stabilized zirconia coating (YSZ) was elaborated by a F100 low-power plasma gun under working pressure of 1 mbar, and the substrate specimens were partially shadowed by a baffle-plate during plasma spraying for obtaining different coating microstructures. Based on the SEM observation, a column-like grain coating was deposited by pure vapor deposition at the shadowed region, whereas, in the unshadowed region, the coating exhibited a binary microstructure which was formed by a mixed deposition of melted particles and evaporated particles. The mechanical properties of the coating were also well under investigation.

  18. Development of compact high voltage switched mode power supply for microwave plasma sources supply for low pressure plasma

    NASA Astrophysics Data System (ADS)

    Kerdtongmee, P.; Srinoum, D.; Nisoa, M.

    2011-08-01

    Although microwave induced plasmas are well known as high efficiency plasma sources, their uses in laboratories are limited since the microwave power systems are complicated and expensive. The output power of commercially available low-cost microwave ovens is fixed and discontinuous resulting from the high voltage doubler topology of the magnetron tube power supply. In this paper, a high voltage switched mode power supply of forward topology has been developed for continuous microwave power radiation. The forward converter can generate a no-load high voltage output maximum of 7 kV. When driving the magnetron tube, the microwave output power could be varied from 0 to 35 W while the high voltage output level was constantly regulated at -3.4 kV. A microwave induced plasma system was setup to investigate the plasma produced. A low pressure argon plasma was produced with only 2 W over a wide range of pressures.

  19. Treatment Characteristics of Second Order Structure of Proteins Using Low-Pressure Oxygen RF Plasma

    NASA Astrophysics Data System (ADS)

    Hayashi, Nobuya; Nakahigashi, Akari; Kawaguchi, Ryutaro; Goto, Masaaki

    2010-10-01

    Removal of proteins from the surface of medical equipments is attempted using oxygen plasma produced by RF discharge. FTIR spectra indicate that the bonding of C-H and N-H in the casein protein is reduced after irradiation of oxygen plasma. Also, the second order structure of a protein such as α-helix and β-sheet are modified by the oxygen plasma. Complete removal of casein protein with the concentration of 0.016 mg/cm2 that is equivalent to remnants on the medical equipment requires two hours avoiding the damage to medical equipments.

  20. Treatment Characteristics of Second Order Structure of Proteins Using Low-Pressure Oxygen RF Plasma

    SciTech Connect

    Hayashi, Nobuya; Nakahigashi, Akari; Kawaguchi, Ryutaro; Goto, Masaaki

    2010-10-13

    Removal of proteins from the surface of medical equipments is attempted using oxygen plasma produced by RF discharge. FTIR spectra indicate that the bonding of C-H and N-H in the casein protein is reduced after irradiation of oxygen plasma. Also, the second order structure of a protein such as {alpha}-helix and {beta}-sheet are modified by the oxygen plasma. Complete removal of casein protein with the concentration of 0.016 mg/cm{sup 2} that is equivalent to remnants on the medical equipment requires two hours avoiding the damage to medical equipments.

  1. Dynamics of cathode spots in low-pressure arc plasma removing oxide layer on steel surfaces

    NASA Astrophysics Data System (ADS)

    Tang, Z. L.; Yang, K.; Liu, H. X.; Zhang, Y. C.; Li, H.; Zhu, X. D.

    2016-03-01

    The dynamics of cathode spots has been investigated in low-pressure arc plasma for removing oxide layer on low carbon steel surfaces. The motion of cathode spots was observed with a high speed camera, and the arc voltage was analyzed by fast Fourier transform. The spots move on clean steel surface as a random walk, and the low-frequency components dominated the voltage waveform. However, the spots on steel surfaces with oxide layer tend to burn on the rim of the eroded area formed in the previous arcing, and the low-frequency components decrease correspondingly. The "color" of the colored random noise for arc voltage varies from the approximate brown noise for clean steel surface to pink noise for thick oxide layer, where the edge effect of boundary is considered to play a significant role.

  2. Low Pressure Plasma Sprayed Overlay Coatings for GRCop-84 Combustion Chamber Liners for Reusable Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Barrett, C.; Ghosn, L. J.; Lerch, B.; Robinson,; Thorn, G.

    2005-01-01

    An advanced Cu-8(at.%)Cr-4%Nb alloy developed at NASA's Glenn Research Center, and designated as GRCop-84, is currently being considered for use as combustor chamber liners and nozzle ramps in NASA s future generations of reusable launch vehicles (RLVs). However, past experience has shown that unprotected copper alloys undergo an environmental attack called "blanching" in rocket engines using liquid hydrogen as fuel and liquid oxygen as the oxidizer. Potential for sulfidation attack of the liners in hydrocarbon-fueled engines is also of concern. Protective overlay coatings alloys are being developed for GRCop-84. The development of this coatings technology has involved a combination of modeling, coatings development and characterization, and process optimization. Coatings have been low pressure plasma sprayed on GRCop-84 substrates of various geometries and shapes. Microstructural, mechanical property data and thermophysical results on the coated substrates are presented and discussed.

  3. Instability of a Low-Pressure Hollow-Cathode Discharge in a Magnetic Field

    SciTech Connect

    Oks, E.M.; Anders, A.; Brown, I.G.; Soloshenko, I.A.; Shchedrin, A.I.

    2005-11-15

    Mechanisms responsible for current oscillations at the ion branch of the probe characteristic are investigated experimentally and theoretically. A comparison between experiment and theory shows that the oscillations in a hollow-cathode discharge in a longitudinal magnetic field are most likely related to the onset of helical instabili0008.

  4. Investigation of post-discharge processes in nitrogen at low pressure

    NASA Astrophysics Data System (ADS)

    Pejovic, Momcilo M.; Nesic, Nikola T.; Pejovic, Milic M.; Brajovic, Dragan V.; Denic, Ivana V.

    2012-12-01

    The processes which are a consequence of neutral active particles presence in post-discharge nitrogen-filled tube at 13.3 mbar pressure have been analyzed. The analysis has been performed based on the experimental data of electrical breakdown time delay as a function of afterglow period τ . The most significant parameters such as applied voltage, discharge current, time, and exposure to radiation have been varied. It has been shown that the increase in applied voltage and discharge time, as well as exposure to UV radiation, leads to the decrease of the mean value of electrical breakdown time delay t¯d. This decrease occurs for τ >70 ms, when N(S4) atoms play a dominant role in breakdown initiation. The increase in discharge current leads to the decrease of t ¯d values for τ ≤70 ms, when positive ions dominantly induce breakdown. The most important reactions which lead to formation of positive ions and neutral active particles are also presented in the paper.

  5. Investigation of post-discharge processes in nitrogen at low pressure

    SciTech Connect

    Pejovic, Momcilo M.; Nesic, Nikola T.; Pejovic, Milic M.; Denic, Ivana V.; Brajovic, Dragan V.

    2012-12-15

    The processes which are a consequence of neutral active particles presence in post-discharge nitrogen-filled tube at 13.3 mbar pressure have been analyzed. The analysis has been performed based on the experimental data of electrical breakdown time delay as a function of afterglow period {tau}. The most significant parameters such as applied voltage, discharge current, time, and exposure to radiation have been varied. It has been shown that the increase in applied voltage and discharge time, as well as exposure to UV radiation, leads to the decrease of the mean value of electrical breakdown time delay t{sub d}. This decrease occurs for {tau}>70 ms, when N({sup 4}S) atoms play a dominant role in breakdown initiation. The increase in discharge current leads to the decrease of t{sub d} values for {tau}{<=}70 ms, when positive ions dominantly induce breakdown. The most important reactions which lead to formation of positive ions and neutral active particles are also presented in the paper.

  6. Simulation study of nanoparticle coating in a low pressure plasma reactor

    SciTech Connect

    Pourali, N.; Foroutan, G.

    2015-02-15

    A self-consistent combination of plasma fluid model, nanoparticle heating model, and surface deposition model is used to investigate the coating of nanosize particles by amorphous carbon layers in a low pressure plasma reactor. The numerical results show that, owing to the net heat release in the surface reactions, the particle temperature increases and its equilibrium value remains always 50 K above the background gas temperature. The deposition rate decreases with increasing of the particle temperature and the corresponding time scale is of the order of 10 ms. The deposition rate is also strongly affected by the change in plasma parameters. When the electron temperature is increased, the deposition rate first increases due to the enhanced ion and radical generation, shows a maximum and then declines as the particle temperature rises above the gas temperature. An enhancement in the background gas pressure and/or temperature leads to a reduction in the deposition rate, which can be explained in terms of the enhanced etching by atomic hydrogen and particle heating by the background gas.

  7. Crater effects on H and D emission from laser induced low-pressure helium plasma

    SciTech Connect

    Pardede, Marincan; Lie, Tjung Jie; Kurniawan, Koo Hendrik; Maruyama, Tadashi; Kagawa, Kiichiro; Tjia, May On

    2009-09-15

    An experimental study has been performed on the effects of crater depth on the hydrogen and deuterium emission intensities measured from laser plasmas generated in low-pressure helium ambient gas from zircaloy-4 samples doped with different H and D impurity concentrations as well as a standard brass sample for comparison. The results show that aside from emission of the host atom, the emission intensities of other ablated atoms of significantly smaller masses as well as that of the He atom generally exhibit relatively rapid initial decline with increasing crater depth. This trend was found to have its origin in the decreasing laser power density arriving at the crater bottom and thereby weakened the shock wave generated in the crater. As the crater deepened, the declining trend of the intensity appeared to level off as a result of compensation of the decreasing laser power density by the enhanced plasma confinement at increasing crater depth. Meanwhile, the result also reveals the significant contribution of the He-assisted excitation process to the doped hydrogen and deuterium emission intensities, leading to similar crater-depth dependent variation patterns in contrast to that associated with the surface water, with growing dominance of this common feature at the later stage of the plasma expansion. Therefore, a carefully chosen set of gate delay and gate width which are properly adapted to the crater-depth dependent behavior of the emission intensity may produce the desired intrinsic emission data for quantitative depth profiling of H impurity trapped inside the zircaloy wall.

  8. Experimental Investigation on Electromagnetic Attenuation by Low Pressure Radio-Frequency Plasma for Cavity Structure

    NASA Astrophysics Data System (ADS)

    He, Xiang; Zhang, Yachun; Chen, Jianping; Chen, Yudong; Zeng, Xiaojun; Yao, Hong; Tang, Chunmei

    2016-01-01

    This paper reports on an experiment designed to test electromagnetic (EM) attenuation by radio-frequency (RF) plasma for cavity structures. A plasma reactor, in the shape of a hollow cylinder, filled with argon gas at low pressure, driven by a RF power source, was produced by wave-transmitting material. The detailed attenuations of EM waves were investigated under different conditions: the incident frequency is 1-4 GHz, the RF power supply is 13.56 MHz and 1.6-3 kW, and the argon pressure is 75-200 Pa. The experimental results indicate that 5-15 dB return loss can be obtained. From a first estimation, the electron density in the experiment is approximately (1.5-2.2) × 1016 m-3 and the collision frequency is about 11-30 GHz. The return loss of EM waves was calculated using a finite-difference time-domain (FDTD) method and it was found that it has a similar development with measurement. It can be confirmed that RF plasma is useful in the stealth of cavity structures such as jet-engine inlet. supported by National Natural Science Foundation of China (No. 51107033) and the Fundamental Research Funds for the Central Universities of China (No. 2013B33614)

  9. Vibrational kinetics in Cl2 and O2 low-pressure inductively-coupled plasmas

    NASA Astrophysics Data System (ADS)

    Booth, Jean-Paul; Foucher, Mickael; Marinov, Daniil; Chabert, Pascal; Annusova, Anna; Guerra, Vasco; Agarwal, Ankur; Rauf, Shahid

    2015-09-01

    Low energy electron interactions with molecules via resonances can cause vibrational excitation (affecting chemical kinetics), electron energy loss and modification of the EEDF. However, with the exception of N2 and H2 plasmas, very little attention has been paid to this subject. We have implemented a novel high-sensitivity ultra-broadband UV absorption bench, allowing spectra to be recorded with noise as low as 2×10-5 over a 250 nm wavelength range, and recording of complete vibronic bands. We applied this to radiofrequency inductively-coupled plasmas in low pressure (5-50 mTorr) pure O2 and pure Cl2. In O2 plasmas we surprisingly observe highly vibrationally excited O2 (v'' up to 18) via B-X Schumann-Runge bands. Cl2 molecules show a broad UV absorption spectrum in the region 250-400 nm, with distinctly different absorption spectra for vibrationally excited molecules. However, only a small fraction of the Cl2 molecules were observed in vibrationally excited states and the vibrational temperature is close to equilibrium with the local gas translational temperature (up to 1000 K), in contrast to O2. We are currently working on global models with vibrational kinetics to explain these results. Work supported by LABEX Plas@par (ANR-11-IDEX-0004-02), and Applied Materials.

  10. Solid oxide fuel cell electrolytes produced via very low pressure suspension plasma spray and electrophoretic deposition

    NASA Astrophysics Data System (ADS)

    Fleetwood, James D.

    Solid oxide fuel cells (SOFCs) are a promising element of comprehensive energy policies due to their direct mechanism for converting the oxidization of fuel, such as hydrogen, into electrical energy. Both very low pressure plasma spray and electrophoretic deposition allow working with high melting temperature SOFC suspension based feedstock on complex surfaces, such as in non-planar SOFC designs. Dense, thin electrolytes of ideal composition for SOFCs can be fabricated with each of these processes, while compositional control is achieved with dissolved dopant compounds that are incorporated into the coating during deposition. In the work reported, sub-micron 8 mole % Y2O3-ZrO2 (YSZ) and gadolinia-doped ceria (GDC), powders, including those in suspension with scandium-nitrate dopants, were deposited on NiO-YSZ anodes, via very low pressure suspension plasma spray (VLPSPS) at Sandia National Laboratories' Thermal Spray Research Laboratory and electrophoretic deposition (EPD) at Purdue University. Plasma spray was carried out in a chamber held at 320 - 1300 Pa, with the plasma composed of argon, hydrogen, and helium. EPD was characterized utilizing constant current deposition at 10 mm electrode separation, with deposits sintered from 1300 -- 1500 °C for 2 hours. The role of suspension constituents in EPD was analyzed based on a parametric study of powder loading, powder specific surface area, polyvinyl butyral (PVB) content, polyethyleneimine (PEI) content, and acetic acid content. Increasing PVB content and reduction of particle specific surface area were found to eliminate the formation of cracks when drying. PEI and acetic acid content were used to control suspension stability and the adhesion of deposits. Additionally, EPD was used to fabricate YSZ/GDC bilayer electrolyte systems. The resultant YSZ electrolytes were 2-27 microns thick and up to 97% dense. Electrolyte performance as part of a SOFC system with screen printed LSCF cathodes was evaluated with peak

  11. Growth dynamics of copper oxide nanowires in plasma at low pressures

    SciTech Connect

    Filipič, Gregor; Mozetič, Miran; Cvelbar, Uroš; Baranov, Oleg

    2015-01-28

    The growth time dynamics of the copper oxide nanowires (NWs) in radiofrequency plasma discharge were investigated. Grounded copper samples were treated in argon-oxygen plasma with the discharge power of 150 W for sequenced times up to 20 min. After the treatment, the samples were analysed with scanning electron microscopy and image processing to obtain the length and aspect ratio of the NWs. A growth mode with the saturation was observed in dependence to NW length, where the maximal length of 5 μm was achieved in 20 min. However, the best NW aspect ratio had maximum of about 40 after 10 min of plasma treatment. To describe and understand nanowire growth mechanism, a theoretical model was developed and it is in agreement with the experiment. The model results indicate that different densities of the ion current to the side and top area of NW modify the NW growth in height and width. The NW growth is enhanced by presence of ions, and thus this implies that it can be controlled by discharge power. This explains much faster growth of copper oxide nanowires in plasma environment compared to prolonged thermal treatments.

  12. Ozone kinetics in low-pressure discharges: vibrationally excited ozone and molecule formation on surfaces

    NASA Astrophysics Data System (ADS)

    Marinov, Daniil; Guerra, Vasco; Guaitella, Olivier; Booth, Jean-Paul; Rousseau, Antoine

    2013-10-01

    A combined experimental and modeling investigation of the ozone kinetics in the afterglow of pulsed direct current discharges in oxygen is carried out. The discharge is generated in a cylindrical silica tube of radius 1 cm, with short pulse durations between 0.5 and 2 ms, pressures in the range 1-5 Torr and discharge currents ˜40-120 mA. Time-resolved absolute concentrations of ground-state atoms and ozone molecules were measured simultaneously in situ, by two-photon absorption laser-induced fluorescence and ultraviolet absorption, respectively. The experiments were complemented by a self-consistent model developed to interpret the results and, in particular, to evaluate the roles of vibrationally excited ozone and of ozone formation on surfaces. It is found that vibrationally excited ozone, O_3^{*} , plays an important role in the ozone kinetics, leading to a decrease in the ozone concentration and an increase in its formation time. In turn, the kinetics of O_3^{*} is strongly coupled with those of atomic oxygen and O2(a 1Δg) metastables. Ozone formation at the wall does not contribute significantly to the total ozone production under the present conditions. Upper limits for the effective heterogeneous recombination probability of O atoms into ozone are established.

  13. 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.

  14. Generation of neutrons in a nanosecond low-pressure discharge in deuterium

    NASA Astrophysics Data System (ADS)

    Lomaev, M. I.; Nechaev, B. A.; Padalko, V. N.; Dudkin, G. N.; Sorokin, D. A.; Tarasenko, V. F.; Shuvalov, E. N.

    2015-04-01

    The neutron yield is measured in a high-voltage Townsend discharge in deuterium with a hollow cylinder made of tungsten or steel used as a polarizing anode of electrons. A flat metallic plate covered by a layer of deuterated zirconium is applied as a grounded cathode. The highest yield of neutrons in the reaction 2H(d,n)3He, ˜1.2 × 104 neutrons per pulse, is observed in the case of the tungsten anode at a deuterium pressure on the order of 100 Pa. The pulsed neutron flux duration estimated with data obtained from a scintillation detector is roughly equal to 1.5 ns.

  15. Homogeneous reactions of hydrocarbons, silane, and chlorosilanes in radiofrequency plasmas at low pressures

    NASA Technical Reports Server (NTRS)

    Avni, R.; Carmi, U.; Inspektor, A.; Rosenthal, I.

    1984-01-01

    The ion-molecule and radical-molecule mechanisms are responsible for the dissociation of hydrocarbon, silane, and chlorosilane monomers and the formation of polymerized species, respectively, in an RF plasma discharge. In a plasma containing a mixture of monomer and argon the rate-determining step for both dissociation and polymerization is governed by an ion-molecule type of interaction. Adding hydrogen or ammonia to the monomer-argon mixture transforms the rate-determining step from an ion-molecule interaction to a radical-molecule interaction for both monomer dissociation and polymerization.

  16. Polydiagnostic calibration performed on a low pressure surface wave sustained argon plasma

    NASA Astrophysics Data System (ADS)

    de Vries, N.; Palomares, J. M.; Iordanova, E. I.; van Veldhuizen, E. M.; van der Mullen, J. J. A. M.

    2008-10-01

    The electron density and electron temperature of a low pressure surface wave sustained argon plasma have been determined using passive and active (laser) spectroscopic methods simultaneously. In this way the validity of the various techniques is established while the plasma properties are determined more precisely. The electron density, ne, is determined with Thomson scattering (TS), absolute continuum measurements, Stark broadening and an extrapolation of the atomic state distribution function (ASDF). The electron temperature, Te, is obtained using TS and absolute line intensity (ALI) measurements combined with a collisional-radiative (CR) model for argon. At an argon pressure of 15 mbar, the ne values obtained with TS and Stark broadening agree with each other within the error bars and are equal to (4 ± 0.5) × 1019 m-3, whereas the ne value (2 ± 0.5) × 1019 m-3 obtained from the continuum is about 30% lower. This suggests that the used formula and cross-section values for the continuum method have to be reconsidered. The electron density determined by means of extrapolation of the ASDF to the continuum is too high (~1020 m-3). This is most probably related to the fact that the plasma is strongly ionizing so that the extrapolation method is not justified. At 15 mbar, the Te values obtained with TS are equal to 13 400 ± 1100 K while the ALI/CR-model yields an electron temperature that is about 10% lower. It can be concluded that the passive results are in good or fair agreement with the active results. Therefore, the calibrated passive methods can be applied to other plasmas in a similar regime for which active diagnostic techniques cannot be used.

  17. Inactivation of Pathogenic Bacteria on Seeds by Active Oxygen Species Generated in Low-Pressure Plasma

    NASA Astrophysics Data System (ADS)

    Ono, Reoto; Uchida, Shohei; Hayashi, Nobuya; Kosaka, Rina; Soeda, Yasutaka

    2015-09-01

    The inactivation of bacteria on seeds by active oxygen species generated by a low-pressure oxygen plasma is investigated. Species of active oxygen contributing to the inactivation of bacteria are attempted to be identified. Cylindrical stainless chamber with the internal volume of 17 L is used and RF antenna is set inside the chamber. The oxygen gas pressure is 20-100 Pa. RF power of 13.56 MHz is supplied to RF antenna and CCP is generated. After irradiation, bacteria are extracted from seeds and cultivated on nutrient agars. The number of colonies on these agars is counted after 48 h incubation. The number of bacteria on seeds decreases to less than 10-3 after plasma irradiation for 45 min comparing with that of control. The tendency of the reduction rate of bacteria on seeds has positive correlation with that of the light emission intensity of the singlet excited oxygen molecule as the oxygen gas pressure is varied. It is supposed that the singlet excited oxygen molecule would be one of the major factors for the inactivation of bacteria on seeds.

  18. Characterization of Yttria-Stabilized Zirconia Coatings Deposited by Low-Pressure Plasma Spraying

    NASA Astrophysics Data System (ADS)

    He, Peng-jiang; Yin, Shuo; Song, Chen; Lapostolle, Frédéric; Liao, Han-lin

    2016-02-01

    The research presented here aimed to apply plasma spraying at a low pressure of 100 Pa for fabricating the columnar structure or dense coatings. These coatings with different structures were elaborated from the vapor condensation and molten droplets, respectively, using the agglomerated YSZ powders and a relatively low power commercial F4-VB torch. It was shown that the crystallite size of coating deposited from the vapor condensation at a spraying distance of 200 mm was reduced to 17.1 nm from 43.7 nm of the feedstock. Observations indicated that a thin columnar structured coating was produced out of the line of sight of projection. In the line of sight of projection, the hybrid structured coating was obtained. The relatively dense coating was fabricated using a specifically designed extended nozzle. Investigations by means of optical emission spectroscopy were performed to analyze the nature of the plasma jet with YSZ powders. The Vickers microhardness was also conducted. It was found that the relatively dense coating showed a higher value in comparison to the hybrid structure coating, up to 1273 ± 56 Hv100g.

  19. Effects Of Pressure And Power On The Ionic Saturation Current And Self-Bias Voltage In A RF Discharge 13.56 MHz Of (SF{sub 6}, O{sub 2}) At Low Pressure

    SciTech Connect

    Alim, M. M.; Zekara, M.; Henni, L.; Tadjine, R.; Lahmar, E.; Henda, K.

    2008-09-23

    In the present work, we are interested in RF plasma discharge for surface texturing in solar cells application. We then present the results of the electrical characterization of plasma reactor at low pressure (<1 Torr) in (SF{sub 6},O{sub 2}) gases mixtures at 13.56 MHz. We've particularly followed the self-bias voltage (V{sub DC}) and the density of ionic current saturation (J{sub s}) depending in various parameters of the discharge as pressure and power.

  20. Plasma species dynamics in a laser produced carbon plasma expanding in low pressure neutral gas background

    NASA Astrophysics Data System (ADS)

    Ruiz, H. M.; Guzmán, F.; Favre, M.; Bhuyan, H.; Chuaqui, H.; Wyndham, E.

    2012-06-01

    We present time and space resolved spectroscopic observations of a laser produced carbon plasma, in an argon background. An Nd:YAG laser pulse, 370 mJ, 3.5 ns, at 1.06 μm, with a fluence of 6.8 J/cm2, is used to produce a plasma from a solid graphite target, at a base pressure of 0.5 mTorr, and with 80 mTorr Argon background. The spectral emission in the visible is recorded with 15 ns time resolution. 20 ns time resolution plasma imagining, filtered at characteristic carbon species emission wavelengths, is used to study the dynamics of the expanding plasma. Two different fronts with ionic or molecular compositions are seen to detach from de laser target plasma.

  1. Experimental and numerical investigations of electron density in low-pressure dual-frequency capacitively coupled oxygen discharges

    SciTech Connect

    Liu, Jia; Wen, De-Qi; Liu, Yong-Xin; Gao, Fei; Lu, Wen-Qi; Wang, You-Nian

    2013-11-15

    The electron density is measured in low-pressure dual-frequency (2/60 MHz) capacitively coupled oxygen discharges by utilizing a floating hairpin probe. The dependence of electron density at the discharge center on the high frequency (HF) power, low frequency (LF) power, and gas pressure are investigated in detail. A (1D) particle-in-cell/Monte Carlo method is developed to calculate the time-averaged electron density at the discharge center and the simulation results are compared with the experimental ones, and general agreements are achieved. With increasing HF power, the electron density linearly increases. The electron density exhibits different changes with the LF power at different HF powers. At low HF powers (e.g., 30 W in our experiment), the electron density increases with increasing LF power while the electron density decreases with increasing LF power at relatively high HF powers (e.g., 120 W in our experiment). With increasing gas pressure the electron density first increases rapidly to reach a maximum value and then decreases slowly due to the combined effect of the production process by the ionization and the loss processes including the surface and volume losses.

  2. Modeling positive ion current to a planar probe in low-pressure electronegative discharges

    SciTech Connect

    Chung, T. H.

    2009-06-15

    A fluid model is utilized to describe the plasma-sheath boundary for a negatively biased planar probe immersed in electronegative plasmas. The model equations are solved on the scale of the electron Debye length and calculate the spatial distributions of electric potential, velocity, and density of positive ions in front of the probe. The position of sheath edge, the positive ion velocity at sheath edge (the Bohm velocity), and the positive ion flux collected by the probe are determined and compared with analytic (or scaling) formulas. Effects of control parameters on the Bohm velocity, the sheath thickness, and on the positive ion flux are investigated. A larger thermal motion of negative ions causes the Bohm velocity to increase, the sheath to increase, and the positive ion flux collected by the probe to increase. An increase in collision causes the Bohm velocity to decrease and the sheath to decrease resulting in a decrease in the positive ion flux. An increase in electronegativity causes both the Bohm velocity and the sheath thickness to decrease, resulting in an increase in the positive ion flux. As the value of the non-neutrality parameter q increases, the Bohm velocity and the sheath thickness are found to decrease, and the positive ion flux collected by the probe increases. The behavior of the positive ion flux entering the sheath is discussed as functions of control parameters. A careful comparison of theoretical positive ion flux with the experimental flux can allow us to obtain the electronegativity, the plasma ionization rate (q), and the collision parameter ({delta})

  3. Progress on Development of Low Pressure High Density Plasmas on the Helicon Plasma Experiment (HPX)

    NASA Astrophysics Data System (ADS)

    Azzari, Phillip; Hopson, Jordan; Crilly, Paul; Duke-Tinson, Omar; Karama, Jackson; Paolino, Richard; Sandri, Eva; Sherman, Justin; Wright, Erin; Frank, John; Turk, Jeremy

    2015-11-01

    HPX Plasmas are created by imparting directed energy into a Pyrex tube preloaded with Ar gas at fill pressures on the order of 104 mTorr utilizing an RF power supply and matching box that can deliver about 250 W of power in the 20 MHz to 100 MHz frequency range. It has been demonstrated that a uniform magnetic field in lower energy level plasmas can facilitate a decrease in inertial effects, which promotes energy conservation within the plasma to provide the necessary external energy in the plasma's magnetic field required to reach the Helicon Mode. This uniform magnetic field will be created by a set of electromagnets capable of producing 1000 gauss. These electromagnets, provided by Princeton Plasma Physics Laboratory will facilitate W-mode production. After reaching the Helicon Mode, the plasma must be forced along the Pyrex tube by an acceleration coil in order to come in contact with several diagnostic probes and to be propelled into a viewing port so Thompson Scattering can be conducted. The progress on the development of the acceleration coil and electromagnets will be presented. Supported by U.S. DEPS Grant [HEL-JTO] PRWJFY15.

  4. Anomalous memory effect in the breakdown of low-pressure argon in a long discharge tube

    SciTech Connect

    Meshchanov, A. V.; Korshunov, A. N.; Ionikh, Yu. Z.; Dyatko, N. A.

    2015-08-15

    The characteristics of breakdown of argon in a long tube (with a gap length of 75 cm and diameter of 2.8 cm) at pressures of 1 and 5 Torr and stationary discharge currents of 5–40 mA were studied experimentally. The breakdown was initiated by paired positive voltage pulses with a rise rate of ∼10{sup 8}–10{sup 9} V/s and duration of ∼1–10 ms. The time interval between pairs was varied in the range of Τ ∼ 0.1–1 s, and that between pulses in a pair was varied from τ = 0.4 ms to ≈Τ/2. The aim of this work was to detect and study the so-called “anomalous memory effect” earlier observed in breakdown in nitrogen. The effect consists in the dynamic breakdown voltage in the second pulse in a pair being higher than in the first pulse (in contrast to the “normal” memory effect, in which the relation between the breakdown voltages is opposite). It is found that this effect is observed when the time interval between pairs of pulses is such that the first pulse in a pair is in the range of the normal memory effect of the preceding pair (under the given conditions, Τ ≈ 0.1–0.4 s). In this case, at τ ∼ 10 ms, the breakdown voltage of the second pulse is higher than the reduced breakdown voltage of the first pulse. Optical observations of the ionization wave preceding breakdown in a long tube show that, in the range of the anomalous memory effect and at smaller values of τ, no ionization wave is detected before breakdown in the second pulse. A qualitative interpretation of the experimental results is given.

  5. Microwave ECR plasma electron flood for low pressure wafer charge neutralization

    SciTech Connect

    Vanderberg, Bo; Nakatsugawa, Tomoya; Divergilio, William

    2012-11-06

    Modern ion implanters typically use dc arc discharge Plasma Electron Floods (PEFs) to neutralize wafer charge. The arc discharge requires using at least some refractory metal hardware, e.g. a thermionically emitting filament, which can be undesirable in applications where no metallic contamination is critical. rf discharge PEFs have been proposed to mitigate contamination risks but the gas flows required can result in high process chamber pressures. Axcelis has developed a microwave electron cyclotron resonance (ECR) PEF to provide refractory metals contamination-free wafer neutralization with low gas flow requirement. Our PEF uses a custom, reentrant cusp magnet field providing ECR and superior electron confinement. Stable PEF operation with extraction slits sized for 300 mm wafers can be attained at Xe gas flows lower than 0.2 sccm. Electron extraction currents can be as high as 20 mA at absorbed microwave powers < 70 W. On Axcelis' new medium current implanter, plasma generation has proven robust against pressure transients caused by, for example, photoresist outgassing by high power ion beams. Charge monitor and floating potential measurements along the wafer surface corroborate adequate wafer charge neutralization for low energy, high current ion beams.

  6. Effects of the nozzle design on the properties of plasma jet and formation of YSZ coatings under low pressure conditions

    NASA Astrophysics Data System (ADS)

    Sun, Chengqi; Gao, Yang; Yang, Deming; Fu, Yingqing

    2016-06-01

    How to control the quality of the coatings has become a major problem during the plasma spraying. Because nozzle contour has a great influence on the characteristic of the plasma jet, two kinds of plasma torches equipped with a standard cylindrical nozzle and a converging-diverging nozzle are designed for low pressure plasma spraying(LPPS) and very low pressure plasma spraying(VLPPS). Yttria stabilized zirconia(YSZ) coatings are obtained in the reducing pressure environment. The properties of the plasma jet without or with powder injection are analyzed by optical emission spectroscopy, and the electron temperature is calculated based on the ratio of the relative intensity of two Ar I spectral lines. The results show that some of the YSZ powder can be vaporized in the low pressure enlarged plasma jet, and the long anode nozzle may improve the characteristics of the plasma jet. The coatings deposited by LPPS are mainly composed of the equiaxed grains and while the unmelted powder particles and large scalar pores appear in the coatings made by VLPPS. The long anode nozzle could improve the melting of the powders and deposition efficiency, and enhance the coatings' hardness. At the same time, the long anode nozzle could lead to a decrease in the overspray phenomenon. Through the comparison of the two different size's nozzle, the long anode is much more suitable for making the YSZ coatings.

  7. A computational analysis of the vibrational levels of molecular oxygen in low-pressure stationary and transient radio-frequency oxygen plasma

    NASA Astrophysics Data System (ADS)

    Kemaneci, Efe; Booth, Jean-Paul; Chabert, Pascal; van Dijk, Jan; Mussenbrock, Thomas; Brinkmann, Ralf Peter

    2016-04-01

    Vibrational levels of molecular oxygen, O2(v  <  42), are investigated in continuous and pulse-modulated low-pressure radio-frequency oxygen plasma with a global modelling approach. The model is benchmarked against a variety of pressure-, power- and time-resolved measurements of several inductive and asymmetric capacitive discharges available in the literature, and a good agreement is obtained. The sensitivity of the model with respect to the vibrational kinetics, the wall reactions and the spatial inhomogeneity of the charged particles are presented. The simulations without the vibrational levels are also shown for the sake of comparison.

  8. Deuterium analysis in zircaloy using ps laser-induced low pressure plasma

    SciTech Connect

    Marpaung, Alion Mangasi; Lie, Zener Sukra; Niki, Hideaki; Kagawa, Kiichiro; Fukumoto, Ken-ichi; Ramli, Muliadi; Abdulmadjid, Syahrun Nur; Idris, Nasrullah; Hedwig, Rinda; Tjia, May On; Pardede, Marincan; Suliyanti, Maria Margaretha; Jobiliong, Eric; Kurniawan, Koo Hendrik

    2011-09-15

    An experimental study on picosecond laser induced plasma spectroscopy of a zircaloy sample with low-pressure surrounding helium gas has been carried out to demonstrate its potential applicability to three-dimensional quantitative micro-analysis of deuterium impurities in zircaloy. This was achieved by adopting the optimal experimental condition ascertained in this study, which is specified as 7 mJ laser energy, 1.3 kPa helium pressure, and 50 {mu}s measurement window, and which was found to result in consistent D emission enhancement. Employing these operational parameters, a linear calibration line exhibiting a zero intercept was obtained from zircaloy-4 samples doped with various concentrations of D impurity, regarded as surrogates for H impurity. An additional measurement also yielded a detection limit of about 10 {mu}g/g for D impurity, well below the acceptable threshold of damaging H concentration in zircaloy. Each of these measurements was found to produce a crater size of only 25 {mu}m in diameter, promising its application for performing less-destructive measurements. The result of this study has thus paved the way for conducting a further experiment with hydrogen-doped zircaloy samples and the further technical development of a three-dimensional quantitative micro-analysis of detrimental hydrogen impurity in zircaloy vessels used in nuclear power plants.

  9. Quantitative deuterium analysis of titanium samples in ultraviolet laser-induced low-pressure helium plasma.

    PubMed

    Abdulmadjid, Syahrun Nur; Lie, Zener Sukra; Niki, Hideaki; Pardede, Marincan; Hedwig, Rinda; Lie, Tjung Jie; Jobiliong, Eric; Kurniawan, Koo Hendrik; Fukumoto, Ken-Ichi; Kagawa, Kiichiro; Tjia, May On

    2010-04-01

    An experimental study of ultraviolet (UV) laser-induced plasma spectroscopy (LIPS) on Ti samples with low-pressure surrounding He gas has been carried out to demonstrate its applicability to quantitative micro-analysis of deuterium impurities in titanium without the spectral interference from the ubiquitous surface water. This was achieved by adopting the optimal experimental condition ascertained in this study, which is specified by 5 mJ laser energy, 10 Torr helium pressure, and 1-50 mus measurement window, which resulted in consistent D emission enhancement and effective elimination of spectral interference from surface water. As a result, a linear calibration line exhibiting a zero intercept was obtained from Ti samples doped with various D impurity concentrations. An additional measurement also yielded a detection limit of about 40 ppm for D impurity, well below the acceptable threshold of damaging H concentration in Ti and its alloys. Each of these measurements was found to produce a crater size of only 25 mum in diameter, and they may therefore qualify as nondestructive measurements. The result of this study has therefore paved the way for conducting further experiments with hydrogen-doped Ti samples and the technical implementation of quantitative micro-analysis of detrimental hydrogen impurity in Ti metal and its alloys, which is the ultimate goal of this study. PMID:20412619

  10. Deuterium analysis in zircaloy using ps laser-induced low pressure plasma

    NASA Astrophysics Data System (ADS)

    Marpaung, Alion Mangasi; Lie, Zener Sukra; Niki, Hideaki; Kagawa, Kiichiro; Fukumoto, Ken-ichi; Ramli, Muliadi; Abdulmadjid, Syahrun Nur; Idris, Nasrullah; Hedwig, Rinda; Tjia, May On; Pardede, Marincan; Suliyanti, Maria Margaretha; Jobiliong, Eric; Kurniawan, Koo Hendrik

    2011-09-01

    An experimental study on picosecond laser induced plasma spectroscopy of a zircaloy sample with low-pressure surrounding helium gas has been carried out to demonstrate its potential applicability to three-dimensional quantitative micro-analysis of deuterium impurities in zircaloy. This was achieved by adopting the optimal experimental condition ascertained in this study, which is specified as 7 mJ laser energy, 1.3 kPa helium pressure, and 50 μs measurement window, and which was found to result in consistent D emission enhancement. Employing these operational parameters, a linear calibration line exhibiting a zero intercept was obtained from zircaloy-4 samples doped with various concentrations of D impurity, regarded as surrogates for H impurity. An additional measurement also yielded a detection limit of about 10 μg/g for D impurity, well below the acceptable threshold of damaging H concentration in zircaloy. Each of these measurements was found to produce a crater size of only 25 μm in diameter, promising its application for performing less-destructive measurements. The result of this study has thus paved the way for conducting a further experiment with hydrogen-doped zircaloy samples and the further technical development of a three-dimensional quantitative micro-analysis of detrimental hydrogen impurity in zircaloy vessels used in nuclear power plants.

  11. Quantification of the VUV radiation in low pressure hydrogen and nitrogen plasmas

    NASA Astrophysics Data System (ADS)

    Fantz, U.; Briefi, S.; Rauner, D.; Wünderlich, D.

    2016-08-01

    Hydrogen and nitrogen containing discharges emit intense radiation in a broad wavelength region in the VUV. The measured radiant power of individual molecular transitions and atomic lines between 117 nm and 280 nm are compared to those obtained in the visible spectral range and moreover to the RF power supplied to the ICP discharge. In hydrogen plasmas driven at 540 W of RF power up to 110 W are radiated in the VUV, whereas less than 2 W is emitted in the VIS. In nitrogen plasmas the power level of about 25 W is emitted both in the VUV and in the VIS. In hydrogen–nitrogen mixtures, the NH radiation increases the VUV amount. The analysis of molecular and atomic hydrogen emission supported by a collisional radiative model allowed determining plasma parameters and particle densities and thus particle fluxes. A comparison of the fluxes showed that the photon fluxes determined from the measured emission are similar to the ion fluxes, whereas the atomic hydrogen fluxes are by far dominant. Photon fluxes up to 5  ×  1020 m‑2 s‑1 are obtained, demonstrating that the VUV radiation should not be neglected in surface modifications processes, whereas the radiant power converted to VUV photons is to be considered in power balances. Varying the admixture of nitrogen to hydrogen offers a possibility to tune photon fluxes in the respective wavelength intervals.

  12. Particle energy distributions and metastable atoms in transient low pressure interpulse microwave plasma

    NASA Astrophysics Data System (ADS)

    Pandey, Shail; Nath Patel, Dudh; Ram Baitha, Anuj; Bhattacharjee, Sudeep

    2015-12-01

    The electron energies and its distribution function are measured in non-equilibrium transient pulsed microwave plasmas in the interpulse regime using a retarding field electron energy analyzer. The plasmas are driven to different initial conditions by varying the electromagnetic (EM) wave pulse duration, peak power, or the wave frequency. Two cases of wave excitation are investigated: (i) short-pulse (pulse duration, t w ~ 1 μs), high-power (~60 kW) waves of 9.45 GHz and (ii) medium-pulse (t w ~ 20 μs), and moderate power waves of ~3 kW at 2.45 GHz. It is found that high-power, short-duration pulses lead to a significantly different electron energy probability function (EEPF) in the interpulse phase—a Maxwellian with a bump on the tail, although the average energy per pulse (~60 mJ) is maintained the same in the two modes of wave excitation. Electrons with energies  >250 eV are found to exist in the discharge in the both cases. Another subset of experiments is performed to delineate the effect of the wave frequency and the peak power on EEPF. A traveling wave tube (TWT) amplifier based microwave source for generating pulsed plasma (t w  =  230 μs) in a wide frequency range (6-18 GHz) is employed for this purpose. Further experiments on measurements of metastable density using optical emission spectroscopy and ion energy analyzer have been carried out. By tailoring the EEPF of the transient plasma and metastable densities, new applications in plasma processing, chemistry and biology can be realized in the interpulse phase of the discharge.

  13. Solid oxide fuel cell electrolytes produced by a combination of suspension plasma spray and very low pressure plasma spray.

    SciTech Connect

    Slamovich, Elliot; Fleetwood, James; McCloskey, James F.; Hall, Aaron Christopher; Trice, Rodney Wayne

    2010-07-01

    Plasma spray coating techniques allow unique control of electrolyte microstructures and properties as well as facilitating deposition on complex surfaces. This can enable significantly improved solid oxide fuel cells (SOFCs), including non-planar designs. SOFCs are promising because they directly convert the oxidization of fuel into electrical energy. However, electrolytes deposited using conventional plasma spray are porous and often greater than 50 microns thick. One solution to form dense, thin electrolytes of ideal composition for SOFCs is to combine suspension plasma spray (SPS) with very low pressure plasma spray (VLPPS). Increased compositional control is achieved due to dissolved dopant compounds in the suspension that are incorporated into the coating during plasma spraying. Thus, it is possible to change the chemistry of the feed stock during deposition. In the work reported, suspensions of sub-micron diameter 8 mol.% Y2O3-ZrO2 (YSZ) powders were sprayed on NiO-YSZ anodes at Sandia National Laboratories (SNL) Thermal Spray Research Laboratory (TSRL). These coatings were compared to the same suspensions doped with scandium nitrate at 3 to 8 mol%. The pressure in the chamber was 2.4 torr and the plasma was formed from a combination of argon and hydrogen gases. The resultant electrolytes were well adhered to the anode substrates and were approximately 10 microns thick. The microstructure of the resultant electrolytes will be reported as well as the electrolyte performance as part of a SOFC system via potentiodynamic testing and impedance spectroscopy.

  14. Spectral intensity of the N2 emission in argon low-pressure arc discharges for lighting purposes

    NASA Astrophysics Data System (ADS)

    Friedl, R.; Fantz, U.

    2012-04-01

    Nitrogen is discussed as an alternative to hazardous mercury in lamps for general lighting. Molecular nitrogen bands emit in both the near-UV (the second positive system C3Πu → B3Πg) and the visible spectral range (the first positive system B3Πg → A3Σ+u), which reduces conversion losses. To analyse the potential of nitrogen, low-pressure arc discharges in an argon background were characterized by means of optical emission spectroscopy. The spectral intensity of the molecular nitrogen emission rises with increasing nitrogen content in the discharge and shows a maximum around 4 mbar of absolute pressure. With regard to the application as a light source, radiation efficiencies were determined, which are around 5% at maximum. In order to identify the main population processes a collisional radiative model for the nitrogen-argon system was established which reveals the high relevance of heavy-particle collisions due to a pressure of a few mbar. The decisive excitation reactions for the state N2 C3Πu are the well-known processes of energy pooling between metastable nitrogen molecules and energy transfer from metastable argon atoms. For the state N2 B3Πg the main population channels are collision-induced crossings within the nitrogen states, where the collision partner can be either a nitrogen molecule or an argon atom, and the quenching collisions with argon.

  15. Effect of low-pressure cold plasma on surface microflora of meat and quality attributes.

    PubMed

    Ulbin-Figlewicz, Natalia; Brychcy, Ewa; Jarmoluk, Andrzej

    2015-02-01

    The aim of this study was to investigate the effect of cold plasma treatment on the inactivation of microorganisms on meat surface and its influence on colour of meat and pH value. Nitrogen, argon and helium plasma were generated by high voltage discharge in a vacuum chamber (final 0.8 MPa) with exposure times of 5 and 10 min. Total number of microorganisms, psychrotrophs and number of yeast and mould were determined using plate method. Instrumental evaluation of colour parameters L* a* b* was performed by colorimeter Minolta Cr 400. Psychrotroph bacteria counts and total number of microorganisms exposed to helium and argon plasma for 10 min were reduced about 3 log cfu/cm(2) and 2 log cfu/cm(2), respectively. Increasing reductions of yeasts and moulds were also obtained and were about 3 cfu/cm(2) (helium) and 2,6 cfu/cm(2) (argon). The usage of nitrogen plasma has not resulted in any significant reduction of counts of psychrotrophs and total. number of microorganisms. Yeasts and moulds were little affected by nitrogen plasma and their numbers decrease about 1 log cfu/cm(2.) after 10 min of treatment. No significant differences in colour parameters and pH value after cold plasma treatment were observed. These results demonstrated that cold plasma has antimicrobial activity and could be a promising method of biodecontamination, but further investigations focusing on meat quality have to be determinate. PMID:25694745

  16. Thermal Shock Properties of Yttria-Stabilized Zirconia Coatings Deposited Using Low-Energy Very Low Pressure Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Zhu, Lin; Zhang, Nannan; Bolot, Rodolphe; Liao, Hanlin; Coddet, Christian

    2015-08-01

    Yttria-stabilized zirconia (YSZ) coatings have been frequently used as a thermal protective layer on the metal or alloy component surfaces. In the present study, ZrO2-7%Y2O3 thermal barrier coatings (TBCs) were successfully deposited by DC (direct current) plasma spray process under very low pressure conditions (less than 1 mbar) using low-energy plasma guns F4-VB and F100. The experiments were performed to evaluate the thermal shock resistance of different TBC specimens which were heated to 1373 K at a high-temperature cycling furnace and held for 0.5 h, followed by air cooling at room temperature for 0.2 h. For comparison, a corresponding atmospheric plasma spray (APS) counterpart was also elaborated to carry out the similar experiments. The results indicated that the very low pressure plasma spray (VLPPS) coatings displayed better thermal shock resistance. Moreover, the failure mechanism of the coatings was elucidated.

  17. 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.

  18. Plasma instabilities in electronegative inductive discharges

    NASA Astrophysics Data System (ADS)

    Marakhtanov, Alexei Mikhail

    Plasma instabilities have been observed in low-pressure inductive discharges, in the transition between low density capacitive mode and high density inductive mode of the discharge when attaching gases such as SF6 and Ar/SF 6 mixtures are used. Oscillations of charged particles, plasma potential and light emitted from the plasma with the frequencies from a few hertz to tens of kilohertz are seen for gas pressures between 1 and 100 mTorr and the discharge power in the range of 75--1200 W. The region of instability increases as the plasma becomes more electronegative and the frequency of plasma oscillations increases as the power, pressure, and gas flow rate increase. The instability frequencies may also depend on the settings of a matching network. A volume-averaged (global) model of the instability has been developed, for a discharge containing time varying densities of electrons, positive ions, and negative ions, and time invariant excited states and neutral densities. The particle and energy balance equations are integrated to produce the dynamical behavior. As pressure or power is varied to cross a threshold, the instability goes through a series of oscillatory states to large scale relaxation oscillations between higher and lower density states. The model qualitatively agrees with experimental observations, and also shows a significant influence of the matching network. A stability analysis of an electronegative discharge has been performed, using a Hurwitz criterion, for a system of linearized particle and power balance differential equations. Capacitive coupling plays a crucial role in the instability process. A variable electrostatic (Faraday) shield has been used to control the capacitive coupling from the excitation coil to the plasma. The plasma instability disappears when the shielded area exceeds 65% of the total area of the coil. The global model of instability gives a slightly higher value of 85% for instability suppression with the same discharge

  19. Kinetic studies of NO formation in pulsed air-like low-pressure dc plasmas

    NASA Astrophysics Data System (ADS)

    Hübner, M.; Gortschakow, S.; Guaitella, O.; Marinov, D.; Rousseau, A.; Röpcke, J.; Loffhagen, D.

    2016-06-01

    The kinetics of the formation of NO in pulsed air-like dc plasmas at a pressure of 1.33 mbar and mean currents between 50 and 150 mA of discharge pulses with 5 ms duration has been investigated both experimentally and by self-consistent numerical modelling. Using time-resolved quantum cascade laser absorption spectroscopy, the densities of NO, NO2 and N2O have been measured in synthetic air as well as in air with 0.8% of NO2 and N2O, respectively. The temporal evolution of the NO density shows four distinct phases during the plasma pulse and the early afterglow in the three gas mixtures that were used. In particular, a steep density increase during the ignition phase and after termination of the discharge current pulse has been detected. The NO concentration has been found to reach a constant value of 0.57× {{10}14}~\\text{molecules}~\\text{c}{{\\text{m}}-3} , 1.05× {{10}14}~\\text{molecules}~\\text{c}{{\\text{m}}-3} , and 1.3× {{10}14}~\\text{molecules}~\\text{c}{{\\text{m}}-3} for mean plasma currents of 50 mA, 100 mA and 150 mA, respectively, in the afterglow. The measured densities of NO2 and N2O in the respective mixture decrease exponentially during the plasma pulse and remain almost constant in the afterglow, especially where the admixture of NO2 has a remarkable impact on the NO production during the ignition. The numerical results of the coupled solution of a set of rate equations for the various heavy particles and the time-dependent Boltzmann equation of the electrons agree quite well with the experimental findings for the different air-like plasmas. The main reaction processes have been analysed on the basis of the model calculations and the remaining differences between the experiment and modelling especially during the afterglow are discussed.

  20. Effect of excited nitrogen atoms on inactivation of spore-forming microorganisms in low pressure N2/O2 surface-wave plasma

    NASA Astrophysics Data System (ADS)

    Yang, Xiaoli; Chang, Xijiang; Tei, Reitou; Nagatsu, Masaaki

    2016-06-01

    Using a vacuum ultraviolet (VUV) absorption spectroscopy with a compact low pressure plasma light source, the absolute nitrogen atom density was measured to study its role in the spore inactivation with low pressure N2/O2 gas mixture surface-wave plasmas (SWPs). Self-absorption effect of the resonance emission lines of nitrogen atoms near 120 nm was minimized by optimizing its discharge conditions of the plasma light source. Experimental results showed that excited nitrogen atom densities monotonically decreased with the decrease of N2 gas percentage in N2/O2 gas mixture SWPs, concomitantly with similar decrease of VUV/UV emission intensities of nitrogen atoms and molecules. In the pure N2 gas SWPs, it was confirmed that a dominant lethal factor was VUV/UV emission generated by N2 plasma, while spore etching occurred via physical and chemical interactions with nitrogen species. With an addition of O2 gas, significant spore etching by excited oxygen atoms made it much easier for the VUV/UV photons emitted by nitrogen atoms, N2 and NO molecules to penetrate through the etched spore coats to the core and cause the fatal DNA damage of the microorganisms. As a result, more rapid inactivation was achieved in the middle region of N2/O2 gas mixture ratio, such as 30–80% O2 gas addition, in the present N2/O2 gas mixture SWPs.

  1. Effect of low-pressure plasma treatment on the color and oxidative stability of raw pork during refrigerated storage.

    PubMed

    Ulbin-Figlewicz, Natalia; Jarmoluk, Andrzej

    2016-06-01

    The effect of low-pressure plasma on quality attributes of meat is an important aspect, which must be considered before application in food. The aim of this study was to determine the color, fatty acid composition, lipid oxidation expressed as thiobarbituric acid reactive substances and total antioxidant capacity of raw pork samples exposed to helium low-pressure plasma treatment (20 kPa) for 0, 2, 5, and 10 min during the storage period. The thiobarbituric acid reactive substance concentrations of all plasma-treated samples during storage were in the range from 0.26 to 0.61 mg malondialdehyde/kg. Exposure time caused significant changes only in total color difference, hue angle, and chroma after 10 min of treatment. Ferric reducing ability of plasma values of meat samples decreased from 1.93 to 1.40 mmol Trolox Eq/kg after 14 days of storage. The storage period significantly affected proportion of polyunsaturated fatty acids, with an increase about 3% after 14 days of refrigeration storage while the content of saturated fatty acids was at the same level. Helium low-pressure plasma does not induce oxidative processes. Application of this decontamination technique while maintaining product quality is possible in food industry. PMID:26223879

  2. Columnar-Structured Thermal Barrier Coatings (TBCs) by Thin Film Low-Pressure Plasma Spraying (LPPS-TF)

    NASA Astrophysics Data System (ADS)

    Hospach, Andreas; Mauer, Georg; Vaßen, Robert; Stöver, Detlev

    2011-01-01

    The very low-pressure plasma Spray (VLPPS) process has been developed with the aim of depositing uniform and thin coatings with coverage of a large area by plasma spraying. At typical pressures of 100-200 Pa, the characteristics of the plasma jet change compared to conventional low-pressure plasma-spraying processes (LPPS) operating at 5-20 kPa. The combination of plasma spraying at low pressures with enhanced electrical input power has led to the development of the LPPS-TF process (TF = thin film). At appropriate parameters, it is possible to evaporate the powder feedstock material providing advanced microstructures of the deposits. This technique offers new possibilities for the manufacturing of thermal barrier coatings (TBCs). Besides the material composition, the microstructure is an important key to reduce thermal conductivity and to increase strain tolerance. In this regard, columnar microstructures deposited from the vapor phase show considerable advantages. Therefore, physical vapor deposition by electron beam evaporation (EB-PVD) is applied to achieve such columnar-structured TBCs. However, the deposition rate is low, and the line-of-sight nature of the process involves specific restrictions. In this article, the deposition of TBCs by the LPPS-TF process is shown. How the evaporation of the feedstock powder could be improved and to what extent the deposition rates could be increased were investigated.

  3. The glow discharge inception and post-discharge relaxation of charged and neutral active particles in synthetic air at low pressure

    NASA Astrophysics Data System (ADS)

    Jovanović, A. P.; Marković, V. Lj; Stamenković, S. N.; Stankov, M. N.

    2015-11-01

    The study of dc glow discharge inception and post-discharge relaxation of charged and neutral active particles in synthetic air at low pressure is presented. The breakdown time delay dependence as a function of relaxation time \\overline{{{t}\\text{d}}}(τ ) (the memory curve) is measured and modelled from milliseconds to the saturation region determined by the cosmic rays and natural radioactivity level. Due to fast conversion \\text{N}2++{{\\text{O}}2}\\to {{\\text{N}}2}+\\text{O}2+ , relaxation of dc discharge in synthetic air in the time interval from one to about ninety milliseconds is dominated by the diffusion decay of molecular oxygen {{O}}_2^ + ions. The change of regimes, from ambipolar to the free diffusion limit, is investigated and the variation of effective diffusion coefficients is determined. The late relaxation is explained by the kinetics of nitrogen atoms, recombining on the surfaces of gas discharge tube and stainless steel electrodes and relevant surface recombination coefficients are determined.

  4. Surface chemistry and optical property of TiO{sub 2} thin films treated by low-pressure plasma

    SciTech Connect

    Dhayal, Marshal Jun, Jin; Gu, Hal Bon; Hee Park, Kyung

    2007-10-15

    The low temperature RF plasma treatment was used to control the surface chemistry and optical property of TiO{sub 2} thin films deposited by RF magnetron sputtering with a very good uniformity at 300 deg. C substrate heating temperature. The XRD pattern indicates the crystalline structure of the film could be associated to amorphous structure of TiO{sub 2} in thin film. The plasma treatment of TiO{sub 2} film can increase the proportion of Ti{sup 3+} in Ti2p and decrease in carbon atoms as alcohol/ether group in C1s at the surface. The optical transmittance of the film was enhanced by 50% after the plasma treatment. The surface structure and morphology remain the same for untreated and low-pressure plasma-treated films. Therefore, increase in the optical transmission could be due to change in surface chemistry and surface cleaning by plasma treatment. - Graphical abstract: The surface chemistry and surface states of TiO{sub 2} films was modified using low-pressure RF plasma treatment. The surface roughness and crystalline structure remain unchanged for low-pressure plasma-treated films. There was an increase in the Ti{sup 3+} surface states of Ti2p at the surface and this can be useful to increase the photocatalytic activities of TiO{sub 2} films. The proportion of carbon atoms as carboxyl group in C1s was also increased after plasma treatment. All the plasma-treated films show a higher optical transmittance when untreated and it was increased when the power was increased. The increase in the optical transmission could be due to surface cleaning of films by plasma treatment and possibly due to change in the surface chemistry.

  5. 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%.

  6. Helicon plasma thruster discharge model

    NASA Astrophysics Data System (ADS)

    Lafleur, T.

    2014-04-01

    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%.

  7. Abatement characteristics of N2O in low-pressure plasma reactor

    NASA Astrophysics Data System (ADS)

    Hur, M.; Lee, J. O.; Lee, J. Y.; Kang, W. S.; Song, Y.-H.

    2016-02-01

    The abatement characteristics of N2O were investigated in a plasma reactor positioned in front of a vacuum pump. Fourier transform infrared (FTIR) spectroscopy was used for evaluating the destruction and removal efficiency (DRE) and the identification of byproducts. The concentration of NO x (NO and NO2) was quantified by using an NO x analyzer. The DRE of N2O was enhanced by increasing the power or decreasing the N2O flow rate. A higher pressure yields a higher DRE of N2O and a lower concentration of NO x in the destroyed N2O. For understanding this phenomenon, the discharge characteristics were analyzed by using optical emission spectroscopy (OES). The spatial distribution of emission spectra from the discharge in a mixture of N2O and Ar gases was measured by varying the pressure. The mechanisms underlying the pressure effect on the N2O DRE and NO x concentration are discussed in terms of the electron density and the concentration of O radicals.

  8. Inactivation factors of spore-forming bacteria using low-pressure microwave plasmas in an N2 and O2 gas mixture

    NASA Astrophysics Data System (ADS)

    Singh, M. K.; Ogino, A.; Nagatsu, M.

    2009-11-01

    In this study, we investigated the inactivation characteristics of Geobacillus stearothermophilus spores under different plasma exposure conditions using low-pressure microwave plasma in nitrogen, oxygen and an air-simulated (N2:O2=4:1) gas mixture. The microwave-excited surface-wave plasma discharges were produced at low pressure by a large volume device. The directly plasma-exposed spores, up to 106 populations, were successfully inactivated within 15, 10 and 5 min of surface-wave plasma treatment using nitrogen, oxygen and an air-simulated gas mixture, respectively, as working gases within the temperature of 75 °C. The contribution of different inactivation factors was evaluated by placing different filters (e.g. a LiF plate, a quartz plate and a Tyvek® sheet) as indirect exposure of spores to the plasma. It was observed that optical emissions (including vacuum UV (VUV)/UV) play an important role in the inactivation process. To further evaluate the effect of VUV/UV photons, we placed an evacuated isolated chamber, inside which spores were set, into the main plasma chamber. The experimental results show that the inactivation time by VUV/UV photons alone, without working gas in the immediate vicinity of the spores, is longer than that with working gas. This suggests that the VUV/UV emission is responsible not only for direct UV inactivation of spores but also for generation of reactive neutral species by photoexcitation. The scanning electron microscopy images revealed significant changes in the morphology of directly plasma-exposed spores but no change in the spores irradiated by VUV/UV photons only.

  9. Experimental investigation of supersonic low pressure air plasma flows obtained with different arc-jet operating conditions

    SciTech Connect

    Lago, Viviana; Ndiaye, Abdoul-Aziz

    2012-11-27

    A stationary arc-jet plasma flow at low pressure is used to simulate some properties of the gas flow surrounding a vehicle during its entry into celestial body's atmospheres. This paper presents an experimental study concerning plasmas simulating a re-entry into our planet. Optical measurements have been carried out for several operating plasma conditions in the free stream, and in the shock layer formed in front of a flat cylindrical plate, placed in the plasma jet. The analysis of the spectral radiation enabled the identification of the emitting species, the determination of the rotational and vibrational temperatures in the free-stream and in the shock layer and the determination of the distance of the shock to the flat plate face. Some plasma fluid parameters like, stagnation pressure, specific enthalpy and heat flux have been determined experimentally along the plasma-jet axis.

  10. Experimental investigation of supersonic low pressure air plasma flows obtained with different arc-jet operating conditions

    NASA Astrophysics Data System (ADS)

    Lago, Viviana; Ndiaye, Abdoul-Aziz

    2012-11-01

    A stationary arc-jet plasma flow at low pressure is used to simulate some properties of the gas flow surrounding a vehicle during its entry into celestial body's atmospheres. This paper presents an experimental study concerning plasmas simulating a re-entry into our planet. Optical measurements have been carried out for several operating plasma conditions in the free stream, and in the shock layer formed in front of a flat cylindrical plate, placed in the plasma jet. The analysis of the spectral radiation enabled the identification of the emitting species, the determination of the rotational and vibrational temperatures in the free-stream and in the shock layer and the determination of the distance of the shock to the flat plate face. Some plasma fluid parameters like, stagnation pressure, specific enthalpy and heat flux have been determined experimentally along the plasma-jet axis.

  11. Plasma Discharge Process in a Pulsed Diaphragm Discharge System

    NASA Astrophysics Data System (ADS)

    Duan, Jianjin; Hu, Jue; Zhang, Chao; Wen, Yuanbin; Meng, Yuedong; Zhang, Chengxu

    2014-12-01

    As one of the most important steps in wastewater treatment, limited study on plasma discharge process is a key challenge in the development of plasma applications. In this study, we focus on the plasma discharge process of a pulsed diaphragm discharge system. According to the analysis, the pulsed diaphragm discharge proceeds in seven stages: (1) Joule heating and heat exchange stage; (2) nucleated site formation; (3) plasma generation (initiation of the breakdown stage); (4) avalanche growth and plasma expansion; (5) plasma contraction; (6) termination of the plasma discharge; and (7) heat exchange stage. From this analysis, a critical voltage criterion for breakdown is obtained. We anticipate this finding will provide guidance for a better application of plasma discharges, especially diaphragm plasma discharges.

  12. Competitive Low Pressure Oxygen Plasma Interactions with Different= Carbon-Carbon Double Bonds

    NASA Astrophysics Data System (ADS)

    Patiño, P.; Sifontes, A.; Gambús, G.

    1999-10-01

    Recently we have shown advances from reactions of O(^3P) with both, l ong-chain hydrocarbons and refinery residuum. The oxidation products of t he process, a mixture of alcohols, epoxides and carbonyl compounds, might have potential properties as additives in formulating fuels. This work s hows the results of the interactions of an oxygen plasma with double bond s, both olefin and aromatic, in the same compound. The reactions have bee n carried out by making the plasma, created by a high voltage glow discha rge, reach the low vapor pressure surface of liquid 4-phenyl-1-butene. Th is (3 mL) was cooled down to -45 ^oC in a glass reactor, applied power was 24 W, at an oxygen pressure of 20 Pa. Products were analyzed by IR, N MR and mass spectroscopies. Conversions were studied as a function of the reaction time, this ranging from 5 to 120 minutes. At short times the O( ^3P) atoms produced in the discharge only reacted with the alkene fra ction of the hydrocarbon, 4-phenyl-1,2-epoxibutane (52%) and 4-phenyl-bu tanal (48%) being the products. Reactions on the benzene ring were obser ved from about 30 minutes on, the corresponding phenols having being prod uced at ratios ortho:para:meta :: 4:1:0.7. At 120 minutes, the ol efin have been completely oxidized and a low fraction of the non-equivale nt two methylene groups have reacted to produce alcohols and ketones.

  13. 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.

  14. Three-electrode low pressure discharge apparatus and method for uniform ionization of gaseous media. [CO/sub 2/ laser oscillator and pulse smoother

    DOEpatents

    McLellan, E.J.

    1980-10-17

    Uniform, transverse electrical discharges are produced in gaseous media without the necessity of switching the main discharge voltage with an external device which carries the entire discharge current. A three-electrode low pressure discharge tube is charged across its anode and cathode to below breakdown voltage using a dc voltage source. An array of resistors or capacitors can be made to discharge to the wire screen anode by means of a low energy high voltage pulse circuit producing sufficient preionization in the region between the anode and cathode to initiate and control the main discharge. The invention has been demonstrated to be useful as a CO/sub 2/ laser oscillator and pulse-smoother. It can be reliably operated in the sealed-off mode.

  15. Effect of plasma gas for spectrometric analysis of tin and zinc using low-pressure laser-induced plasma

    NASA Astrophysics Data System (ADS)

    Naeem, Tariq Mahmood; Matsuta, Hideyuki; Wagatsuma, Kazuaki

    2003-05-01

    The emission characteristics of tramp elements such as Sn and Zn in low-pressure laser-induced plasma have been examined with reference to change of the surrounding gas (Ar, Ne and He). From the pressure dependence of the intensity of Sn I 326.23-nm, Sn II 335.22-nm, Zn I 213.86-nm and Zn II 210.00-nm emission lines, it was found that Sn and Zn atoms could be excited by the collision between surrounding gas species and ablated atoms with large kinetic energy by laser irradiation. Besides the collisional excitation, resonance charge-transfer collision between Zn atoms and Ne ions proved to be effective in the selective excitation of Zn II 206.42-nm and 210.00-nm emission lines, because the emission intensity of these lines was strongly enhanced in Ne atmosphere, and the sum of the excitation energy of these lines and the ionization potential of Zn is very close to the ground-state energy of Ne ions.

  16. Quantitative and sensitive analysis of CN molecules using laser induced low pressure He plasma

    NASA Astrophysics Data System (ADS)

    Pardede, Marincan; Hedwig, Rinda; Abdulmadjid, Syahrun Nur; Lahna, Kurnia; Idris, Nasrullah; Jobiliong, Eric; Suyanto, Hery; Marpaung, Alion Mangasi; Suliyanti, Maria Margaretha; Ramli, Muliadi; Tjia, May On; Lie, Tjung Jie; Lie, Zener Sukra; Kurniawan, Davy Putra; Kurniawan, Koo Hendrik; Kagawa, Kiichiro

    2015-03-01

    We report the results of experimental study on CN 388.3 nm and C I 247.8 nm emission characteristics using 40 mJ laser irradiation with He and N2 ambient gases. The results obtained with N2 ambient gas show undesirable interference effect between the native CN emission and the emission of CN molecules arising from the recombination of native C ablated from the sample with the N dissociated from the ambient gas. This problem is overcome by the use of He ambient gas at low pressure of 2 kPa, which also offers the additional advantages of cleaner and stronger emission lines. The result of applying this favorable experimental condition to emission spectrochemical measurement of milk sample having various protein concentrations is shown to yield a close to linear calibration curve with near zero extrapolated intercept. Additionally, a low detection limit of 5 μg/g is found in this experiment, making it potentially applicable for quantitative and sensitive CN analysis. The visibility of laser induced breakdown spectroscopy with low pressure He gas is also demonstrated by the result of its application to spectrochemical analysis of fossil samples. Furthermore, with the use of CO2 ambient gas at 600 Pa mimicking the Mars atmosphere, this technique also shows promising applications to exploration in Mars.

  17. Quantitative and sensitive analysis of CN molecules using laser induced low pressure He plasma

    SciTech Connect

    Pardede, Marincan; Hedwig, Rinda; Abdulmadjid, Syahrun Nur; Lahna, Kurnia; Idris, Nasrullah; Ramli, Muliadi; Jobiliong, Eric; Suyanto, Hery; Marpaung, Alion Mangasi; Suliyanti, Maria Margaretha; Tjia, May On

    2015-03-21

    We report the results of experimental study on CN 388.3 nm and C I 247.8 nm emission characteristics using 40 mJ laser irradiation with He and N{sub 2} ambient gases. The results obtained with N{sub 2} ambient gas show undesirable interference effect between the native CN emission and the emission of CN molecules arising from the recombination of native C ablated from the sample with the N dissociated from the ambient gas. This problem is overcome by the use of He ambient gas at low pressure of 2 kPa, which also offers the additional advantages of cleaner and stronger emission lines. The result of applying this favorable experimental condition to emission spectrochemical measurement of milk sample having various protein concentrations is shown to yield a close to linear calibration curve with near zero extrapolated intercept. Additionally, a low detection limit of 5 μg/g is found in this experiment, making it potentially applicable for quantitative and sensitive CN analysis. The visibility of laser induced breakdown spectroscopy with low pressure He gas is also demonstrated by the result of its application to spectrochemical analysis of fossil samples. Furthermore, with the use of CO{sub 2} ambient gas at 600 Pa mimicking the Mars atmosphere, this technique also shows promising applications to exploration in Mars.

  18. Synthesis of highly transparent ultrananocrystalline diamond films from a low-pressure, low-temperature focused microwave plasma jet

    PubMed Central

    2012-01-01

    This paper describes a new low-temperature process underlying the synthesis of highly transparent ultrananocrystalline diamond [UNCD] films by low-pressure and unheated microwave plasma jet-enhanced chemical vapor deposition with Ar-1%CH4-10%H2 gas chemistry. The unique low-pressure/low-temperature [LPLT] plasma jet-enhanced growth even with added H2 and unheated substrates yields UNCD films similar to those prepared by plasma-enhanced growth without addition of H2 and heating procedure. This is due to the focused plasma jet which effectively compensated for the sluggish kinetics associated with LPLT growth. The effects of pressure on UNCD film synthesis from the microwave plasma jet were systematically investigated. The results indicated that the substrate temperature, grain size, surface roughness, and sp3 carbon content in the films decreased with decreasing pressure. The reason is due to the great reduction of Hα emission to lower the etching of sp2 carbon phase, resulting from the increase of mean free path with decreasing pressure. We have demonstrated that the transition from nanocrystalline (80 nm) to ultrananocrystalline (3 to 5 nm) diamond films grown via microwave Ar-1%CH4-10%H2 plasma jets could be controlled by changing the pressure from 100 to 30 Torr. The 250-nm-thick UNCD film was synthesized on glass substrates (glass transition temperature [Tg] 557°C) using the unique LPLT (30 Torr/460°C) microwave plasma jet, which produced UNCD films with a high sp3 carbon content (95.65%) and offered high optical transmittance (approximately 86% at 700 nm). PMID:22260391

  19. Ion energy distributions and the density of CH3 radicals in a low pressure inductively coupled CH4/H2 plasma used for nanocrystalline diamond deposition

    NASA Astrophysics Data System (ADS)

    Okada, Katsuyuki; Komatsu, Shojiro; Matsumoto, Seiichiro

    2003-11-01

    Ion energy distributions (IEDs) and the density of CH3 radicals (n) in a 13.56 MHz radio frequency (rf) low pressure inductively coupled CH4/H2 plasma used for nanocrystalline diamond deposition have been investigated with a quadrupole mass spectrometer. The energy distributions of positive ions were measured in a CH4/H2 plasma with 50 mTorr of the gas pressure at 500 W of the plasma input power, and were compared with those of an Ar plasma. We have found that the IEDs of Ar+, CH4+, and C2H5+ have a nearly monoenergetic peak, and a hump due to a small degree of capacitive coupling. The plasma potentials obtained from the peaks are consistent with the previously reported values measured with a Langmuir probe. On the other hand, the IEDs of H+, H2+, and H3+ have a clear asymmetric double peak due to the modulation of rf driven glow discharge. The n monotonously increases with increasing pressure. The n indicates that CH3 radicals are main precursors for the growth of nanocrystalline diamond. The estimated sticking coefficient of the CH3 radical is comparable with the reported value.

  20. Study of metallic powder behavior in very low pressure plasma spraying (VLPPS) — Application to the manufacturing of titanium–aluminum coatings

    SciTech Connect

    Vautherin, B.; Planche, M.-P.; Montavon, G.; Lapostolle, F.; Quet, A.; Bianchi, L.

    2015-08-28

    In this study, metallic materials made of aluminum and titanium were manufactured implementing very low pressure plasma spraying (VLPPS). Aluminum was selected at first as a demonstrative material due to its rather low vaporization enthalpy (i.e., 381.9 kJ·mol⁻¹). Developments were then carried out with titanium which exhibits a higher vaporization enthalpy (i.e., 563.6 kJ·mol⁻¹). Optical emission spectroscopy (OES) was implemented to analyze the behavior of each solid precursor (metallic powders) when it is injected into the plasma jet under very low pressure (i.e., in the 150 Pa range). Besides, aluminum, titanium and titanium–aluminum coatings were deposited in the same conditions implementing a stick-cathode plasma torch operated at 50 kW, maximum power. Coating phase compositions were identified by X-Ray Diffraction (XRD). Coating elementary compositions were quantified by Glow Discharge Optical Emission Spectroscopy (GDOES) and Energy Dispersive Spectroscopy (EDS) analyses. The coating structures were observed by Scanning Electron Microscopy (SEM). The coating void content was determined by Ultra-Small Angle X-ray Scattering (USAXS). The coatings exhibit a two-scale structure corresponding to condensed vapors (smaller scale) and solidified areas (larger scale). Titanium–aluminum sprayed coatings, with various Ti/Al atomic ratios, are constituted of three phases: metastable α-Ti, Al and metastable α₂-Ti₃Al. This latter is formed at elevated temperature in the plasma flow, before being condensed. Its rather small fraction, impeded by the rather small amount of vaporized Ti, does not allow modifying however the coating hardness.

  1. Gemini: A hybrid plasma modelling capability for low pressure systems. User`s manual - V.1.7

    SciTech Connect

    Johannes, J.; Bartel, T.; Sears, D.; Payne, J.

    1996-10-01

    Gemini is the coupling of Icarus, the Sandia National Laboratories (SNL) 2-D Direct Simulation Monte Carlo (DMSC) code, to MPRES, the University of Houston 2-D finite element plasma reactor code. Thus, Gemini is not a stand alone code. The primary application of Gemini is the simulation of inductively coupled plasma reactors that operate at low pressures (< 10mtorr) where continuum formulations of the transport equations begin to break down. Plasma parameters (electron density (ne), electron temperature (Te) and electrostatic fields (Er and Ez)) are computed in MPRES and interpolated onto the DSMC grid. This allows transport of the neutrals and ions to be performed using the DSMC method while including electron impact reactions and field transport effects. A sample calculation including appropriate input files is given.

  2. Low-pressure plasma enhanced immobilization of chitosan on low-density polyethylene for bio-medical applications

    NASA Astrophysics Data System (ADS)

    Pandiyaraj, K. Navaneetha; Ferraria, Ana Maria; Rego, Ana Maria Botelho do; Deshmukh, Rajendra. R.; Su, Pi-Guey; Halleluyah Mercy, Jr.; Halim, Ahmad Sukari

    2015-02-01

    With the aim of improving blood compatibility of low density polyethylene (LDPE) films, an effective low-pressure plasma technology was employed to functionalize the LDPE film surfaces through in-situ grafting of acrylic acid (AAc). Subsequently, the molecules of poly(ethylene glycol) (PEG) and chitosan (CHI) were immobilized on the surface of grafted LDPE films. The unmodified and modified LDPE films were analyzed using various characterization techniques such as contact angle, atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR) and X-ray photo electron spectroscopy (XPS) to understand the changes in surface properties such as hydrophilicity, surface topography and chemical composition, respectively. Furthermore, LDPE films have been subjected to an ageing process to determine the durability of the plasma assisted surface modification. The blood compatibility of the surface modified LDPE films was confirmed by in vitro tests. It was found that surface modified LDPE films show better hydrophilic behavior compared with the unmodified one. FTIR and XPS results confirm the successful immobilization of CHI on the surface of LDPE films. LDPE films showed marked morphological changes after grafting of AAc, PEG and CHI which were confirmed through AFM imaging. The in vitro blood compatibility tests have clearly demonstrated that CHI immobilized LDPE films exhibit remarkable anti thrombogenic nature compared with other modified films. Surface modified LDPE films through low-pressure plasma technique could be adequate for biomedical implants such as artificial skin substrates, urethral catheters or cardiac stents, among others.

  3. Low-pressure, high-density, and supersonic plasma flow generated by a helicon magnetoplasmadynamic thruster

    NASA Astrophysics Data System (ADS)

    Takahashi, Kazunori; Komuro, Atsushi; Ando, Akira

    2014-11-01

    A high density magnetoplasmadynamic (MPD) plasma under a magnetic nozzle is produced with a low gas flow rate of argon by combining helicon and MPD plasma sources, where a cathode and an anode are located upstream and downstream of the helicon source, respectively. Once the high density helicon plasma is produced in the source tube, a pulsed current of a few kA is triggered between the cathode and anode. A plasma density above 1020 m-3 and a supersonic plasma flow (Mach number of ˜1.8) are obtained at ˜10 cm downstream of the source exit. As the thrust efficiency estimated from the measured plasma parameters is much higher than that of the simple MPD thruster, the helicon MPD thruster being proposed and tested potentially provides more efficient high-power plasma thruster.

  4. Comments on "Sensitive analysis of carbon, chromium and silicon in steel using picosecond laser induced low pressure helium plasma"

    NASA Astrophysics Data System (ADS)

    Zaytsev, Sergey M.; Popov, Andrey M.; Zorov, Nikita B.; Labutin, Timur A.

    2016-04-01

    In the paper "Sensitive analysis of carbon, chromium and silicon in steel using picosecond laser induced low pressure helium plasma" by Syahrun Nur Abdulmadjid, Nasrullah Idris, Marincan Pardede, Eric Jobiliong, Rinda Hedwig, Zener Sukra Lie, Hery Suyanto, May On Tjia, Koo Hendrik Kurniawan and Kiichiro Kagawa [Spectrochim. Acta Part B 114 (2015) 1-6], the authors presented experimental study to demonstrate the sensitive detection of C, Cr and Si in low-alloy steels under low pressure He atmosphere. Although the use of only UV-VIS spectral range for determination of these elements seems to be a beneficial, the point that needs to be commented is the result of carbon determination with the use of C I 247.856 nm line. Thermodynamic modeling based on the NIST and R. Kurucz data for the different excitation conditions in plasma demonstrates that it is hardly possible to distinguish any carbon signal due to significantly intensive iron line Fe II 247.857 nm. Authors are kindly requested to re-consider this part of their study.

  5. Excitation of ion rarefaction waves in a low pressure plasma by applying a short high negative voltage pulse

    SciTech Connect

    Kar, S.; Mukherjee, S.; Saxena, Y. C.

    2011-05-15

    The ion rarefaction response to a high negative voltage pulse (U{sub 0} >> kT{sub e}/e) applied to a metal plate immersed in a low pressure argon plasma, for time duration lower than ion plasma period, is experimentally examined. In the present experiment the pulse duration is kept intermediate between the ion and electron plasma response times. Such a pulse duration is chosen so that ions are collectively undisturbed and, according to general understanding, no force is given to ions. Hence no ion rarefaction wave should be excited. But contrary to the general understanding, excitation of a rarefaction wave is observed. The results indicate that the speed of the rarefaction waves for various conditions (like plasma density, applied pulse magnitude, and pulse duration) is supersonic. After a distance from the exciter (biased plate), typically three-fourth of the exciter diameter, the rarefaction waves are turned into ion acoustic waves. The experimental results indicate that even though the bias durations are shorter than the ion plasma period, if the bias magnitude is large enough, some collective plasma behavior can still be excited.

  6. Creation of a conductive surface layer on polypropylene samples by low-pressure plasma treatments

    NASA Astrophysics Data System (ADS)

    Coen, M. Collaud; Groening, P.; Dietler, G.; Schlapbach, L.

    1995-06-01

    Polypropylene (PP) samples were treated in an electron cyclotron resonance plasma with several gases and under different treatment conditions (pressure, treatment time, rf potential). The surfaces were chemically characterized in situ by x-ray photoelectron spectroscopy (XPS). Changes in the electrical resistance of the surface layer were analyzed by four points measurements. Noble gas plasma treatments led to a great decrease (ten orders of magnitude) of the resistance, whereas reactive gas plasma treatments induced no modification of the resistance. Taking into account that the treated layer corresponds to the ion penetration depth, an estimation gives 0.1 Ω cm for the bulk resistivity of He plasma treated PP. For noble gases, this value depends on the plasma gas and on the ion kinetic energy. The resistance decrease is explained by a dehydrogenation and an increase of carbon-carbon bonds. During reactive gas plasma treatments, the incorporation of new chemical species prevents this graphitization. Correlations of the resistance with XPS measurements and comparisons with literature on high energetic ion treatments allow a better understanding of the effects of the plasma treatment.

  7. 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.

  8. An Assessment of the Residual Stresses in Low Pressure Plasma Sprayed Coatings on an Advanced Copper Alloy

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Ghosn, L. J.; Agarwal, A.; Lachtrupp, T. P.

    2002-01-01

    Modeling studies were conducted on low pressure plasma sprayed (LPPS) NiAl top coat applied to an advanced Cu-8(at.%)Cr-4%Nb alloy (GRCop-84) substrate using Ni as a bond coat. A thermal analysis suggested that the NiAl and Ni top and bond coats, respectively, would provide adequate thermal protection to the GRCop-84 substrate in a rocket engine operating under high heat flux conditions. Residual stress measurements were conducted at different depths from the free surface on coated and uncoated GRCop-84 specimens by x-ray diffraction. These data are compared with theoretically estimated values assessed by a finite element analysis simulating the development of these stresses as the coated substrate cools down from the plasma spraying temperature to room temperature.

  9. Modelling of NO destruction in a low-pressure reactor by an Ar plasma jet: species abundances in the reactor

    NASA Astrophysics Data System (ADS)

    Kutasi, Kinga

    2011-03-01

    The destruction of NO molecules by an Ar plasma jet in a low-pressure (0.2 Torr) reactor is investigated by means of a 3D hydrodynamic model. The density distribution of species created through molecular kinetics triggered by the collision of Ar+ with NO is calculated, showing that in the case of the most abundant species a quasi-homogeneous density distribution builds up in a large part of the reactor. The conversion of NO into stable O2 and N2 molecules is followed under different plasma jet conditions and NO gas flows, and the effect of N2 addition on NO destruction is studied. It is shown that in the present system the reproduction of NO molecules on the surface through surface-assisted recombination of N and O atoms becomes impossible due to the fast disappearance of N atoms in the jet's inlet vicinity.

  10. Thermalization of electrons in decaying extreme ultraviolet photons induced low pressure argon plasma

    NASA Astrophysics Data System (ADS)

    Beckers, J.; van der Horst, R. M.; Osorio, E. A.; Kroesen, G. M. W.; Banine, V. Y.

    2016-06-01

    We monitored—in the pressure range: 0.5–15 Pa—the electron temperature in decaying plasmas induced in argon gas by pulsed irradiation with extreme ultraviolet (EUV) photons with wavelengths closely around 13.5 nm. For this purpose, temporal measurements of the space-averaged and electric field weighted electron density after pulsed EUV irradiation are combined with an ambipolar diffusion model of the plasma. Results demonstrate that electrons are thermalized to room temperature before the plasma has fully expanded to the chamber walls for pressures of 3 Pa and higher. At pressures below 3 Pa, the electron temperature was found to be up to 0.1 eV above room temperature which is explained by the fact that plasma expansion is too quick for the electrons to fully thermalize. The comparison between plasma expansion duration towards a surface, plasma decay at a surface and time needed for thermalization and cooling of electrons is essential for designers of EUV lithography tools and EUV sources since the temperature of electrons dictates many fundamental physical processes.

  11. Effects of N2-O2 Gas Mixture Ratio on Microorganism Inactivation in Low-Pressure Surface Wave Plasma

    NASA Astrophysics Data System (ADS)

    Zhao, Ying; Ogino, Akihisa; Nagatsu, Masaaki

    2011-08-01

    In this study, the effect of N2/O2 gas mixture ratio on low-pressure surface wave plasma inactivation of spore-forming bacteria was investigated. It was experimentally confirmed from the quadrupole mass spectrometry measurements that the spores were etched by atomic oxygen via converting the hydrogen atoms constituting microorganisms into H2O and the carbon into CO2. On the basis of results of plasma diagnostics by optical emission spectroscopy and the results of inactivation efficiency by colony-forming units and scanning electron microscope, we found that although there is the highest ultraviolet (UV) emission intensity in pure N2 plasma and the highest etching efficiency in 90% O2/10% N2 plasma, the inactivation rate of microorganisms was not so efficient. The best inactivation result was obtained in 30-80% O2 gas mixture ratios after 60 s plasma irradiation. The present results indicated that more efficient inactivation is achieved by the synergetic effects between atomic oxygen etching and the vacuum ultraviolet (VUV)/UV emission by combining both effects via optimizing N2/O2 gas mixture ratio.

  12. Investigations of chemical erosion of carbon materials in hydrogen and deuterium low pressure plasmas

    NASA Astrophysics Data System (ADS)

    Starke, P.; Fantz, U.; Balden, M.

    2005-03-01

    Investigations on chemical erosion of pure and carbide-doped graphite materials were carried out in inductively coupled RF plasmas containing hydrogen, deuterium or a mixture of both in helium. For extrapolations of erosion yields to future fusion devices the relevant particle fluxes have to be known precisely. This was done by several diagnostic techniques. In particular the ion fluxes are determined by an energy mass analyzer. An isotope effect of the ion composition is measured resulting in an enhanced erosion of graphite in deuterium plasmas. Since in fusion plasmas a mixture of deuterium and tritium will interact with the surface, a mixture of hydrogen and deuterium on graphite was investigated as well. In order to reduce erosion yields doping of carbon is under discussion. Therefore, fluence dependent erosion yields of several W-, Ti-, V- and Zr-doped graphite materials are measured and compared with pure graphite.

  13. Momentum transfer interaction of a laser-produced plasma with a low-pressure background.

    NASA Technical Reports Server (NTRS)

    Koopman, D. W.

    1972-01-01

    The expansion of a laser-produced metallic plasma into a photoionized hydrogen background has been experimentally studied. Langmuir probe and microwave diagnostics have detected an interaction front which decelerates with a dependence on background density and time consistent with a momentum coupling between the laser plasma and the ionized fraction of the background. An ion percursor has also been observed. Calculations of scattering cross sections indicate that multiple-encounter Coulomb scattering will dominate collisional momentum transfer. The leading edge of the laser plasma contains multiply charged ions of charge state z greater than or equal to 5, and collisional effects appear adequate to explain the principal features of the momentum coupling. The ion precursor may have a collisionless origin.

  14. Phenomenology of plasma engine cathodes at high current rates and low pressures

    NASA Technical Reports Server (NTRS)

    Huegel, H.; Kruelle, G.

    1984-01-01

    The effects of low surrounding pressures on cathodes of arc jet engines with electromagnetic acceleration are investigated for pressure and current energies of 20 to 100 Torr. and 400 to 1000 A. Experiments with 50 mm long and 8 mm diameter tungsten-thorium cathode in a coaxial gas flow show that pre-heating of the cathode reduces the duration of the instable arc discharge and thus material loss. The use of lighter gases also reduces instability effects, as well as the use of increased pressures and a massive gas influx.

  15. Direct Simulation Monte Carlo Simulations of Low Pressure Semiconductor Plasma Processing

    SciTech Connect

    Gochberg, L. A.; Ozawa, T.; Deng, H.; Levin, D. A.

    2008-12-31

    The two widely used plasma deposition tools for semiconductor processing are Ionized Metal Physical Vapor Deposition (IMPVD) of metals using either planar or hollow cathode magnetrons (HCM), and inductively-coupled plasma (ICP) deposition of dielectrics in High Density Plasma Chemical Vapor Deposition (HDP-CVD) reactors. In these systems, the injected neutral gas flows are generally in the transonic to supersonic flow regime. The Hybrid Plasma Equipment Model (HPEM) has been developed and is strategically and beneficially applied to the design of these tools and their processes. For the most part, the model uses continuum-based techniques, and thus, as pressures decrease below 10 mTorr, the continuum approaches in the model become questionable. Modifications have been previously made to the HPEM to significantly improve its accuracy in this pressure regime. In particular, the Ion Monte Carlo Simulation (IMCS) was added, wherein a Monte Carlo simulation is used to obtain ion and neutral velocity distributions in much the same way as in direct simulation Monte Carlo (DSMC). As a further refinement, this work presents the first steps towards the adaptation of full DSMC calculations to replace part of the flow module within the HPEM. Six species (Ar, Cu, Ar*, Cu*, Ar{sup +}, and Cu{sup +}) are modeled in DSMC. To couple SMILE as a module to the HPEM, source functions for species, momentum and energy from plasma sources will be provided by the HPEM. The DSMC module will then compute a quasi-converged flow field that will provide neutral and ion species densities, momenta and temperatures. In this work, the HPEM results for a hollow cathode magnetron (HCM) IMPVD process using the Boltzmann distribution are compared with DSMC results using portions of those HPEM computations as an initial condition.

  16. A study of the influence of Hg(6(3)P2) population in a low-pressure discharge on mercury ion emission at 194.2 nm

    NASA Technical Reports Server (NTRS)

    Maleki, L.; Blasenheim, B. J.; Janik, G. R.

    1990-01-01

    A low-pressure mercury-argon discharge, similar to the type existing in the mercury lamp for the trapped-ion standard, is probed with a new technique of laser spectroscopy to determine the influence of the Hg(6 3P(sub 2)) population on discharge emission. The discharge is excited with inductively coupled rf power. Variations in the intensity of emission lines in the discharge were examined as lambda = 546.1 nm light from a continuous wave (CW) laser excited the Hg(6 3P(sub 2)) to (7 3S (sub 1)) transition. The spectrum of the discharge viewed in the region of laser irradiation showed increased emission in lambda = 546.1, 435.8, 404.7, 253.7, and 194.2 nm lines. Other lines in Hg I exhibited a decrease in emission. When the discharge was viewed outside the region of laser irradiation, all lines exhibited an increased emission. Based on these results, it is concluded that the dominant mechanism for the excitation of higher lying levels of mercury is the the electron-impact excitation via the 3P(sub 2) level. The depopulation of this metastable is also responsible for the observed increase in the electron temperature when the laser irradiates the discharge. It is also concluded that the 3P(sub 2) metastable level of mercury does not play a significant role in the excitation of the 3P(sub 1/2) level of mercury ion.

  17. Correction factors for saturation effects in white light and laser absorption spectroscopy for application to low pressure plasmas

    SciTech Connect

    Briefi, S.; Wimmer, C.; Fantz, U.

    2012-05-15

    In white light absorption spectroscopy, the broadening of the absorption signal due to the apparatus profile of the spectrometer may lead to an underestimation of the determined density as one measures an apparent optical depth. This is in particular true for high optical depth where saturation effects of the transmitted intensity occur. Provided that the line profile of the absorption line is known, the apparent optical depth effect can be accounted for by introducing a correction factor. The impact of the saturation and the approach of considering the effect are demonstrated for argon and indium lines in low pressure plasmas where correction factors of one order of magnitude or even higher are reached very easily. For the indium line, the hyperfine splitting has been taken into account. In laser absorption, the line profile is resolved. However, the weak but rather broad background emission of the laser diode can cause a saturation signal at the photo diode resulting also in an underestimation of the density obtained from the analysis. It is shown that this can be taken into account by fitting the theoretical line profile to the measured absorption signal which yields also a correction factor. The method is introduced and demonstrated at the example of the cesium resonance line including the hyperfine splitting. Typical correction factors around two are obtained for the cesium ground state density at conditions of a low pressure negative hydrogen ion source in which cesium is evaporated to enhance the negative ion production.

  18. Ionization dynamics in the laser plasma in a low pressure gas target

    NASA Astrophysics Data System (ADS)

    Demidov, R. A.; Kalmykov, S. G.; Mozharov, A. M.; Petrenko, M. V.; Sasin, M. E.

    2012-11-01

    In Xe-laser-plasma short-wave-radiation sources, the laser-energy-to-EUV conversion efficiency (CE) turns out to be substantially lower than theoretical expectations. An estimation made in the present work is evidence of what a long period of the primary ionization, lasting up to a moment when high- Z ions appear to emit short-wave photons, can be considered as a main cause for the low CE values. During that period the plasma remains low-ionized and absorbs weakly the laser energy. Data deduced from laser light absorption measurements confirm the estimation above. A preionization of the gas target with the UV excimer laser pulse is proposed as a method to accelerate the ionization process.

  19. Effects of oxygen radicals in low-pressure surface-wave plasma on sterilization

    SciTech Connect

    Nagatsu, Masaaki; Terashita, Fumie; Nonaka, Hiroyuki; Xu, Lei; Nagata, Toshi; Koide, Yukio

    2005-05-23

    The effects of oxygen radicals on sterilization were studied using a 2.45 GHz surface-wave oxygen plasma. A population of 1.5x10{sup 6} Bacillus stearothermophilus spores was irradiated for 3 min or more with oxygen plasma, generated at pressures between 6 and 14 Pa. The decimal reduction value (D value), a measure of the effectiveness of sterilization, was determined to be about 15-25 s. Using only oxygen radicals, excluding all charged particles, the 1.5x10{sup 6} spores were sterilized with a D value of 30-45 s after 5 min or more of irradiation. On scanning electron microscopy, the length and width of the spores changed significantly due to chemical etching by oxygen radicals.

  20. Effects of oxygen radicals in low-pressure surface-wave plasma on sterilization

    NASA Astrophysics Data System (ADS)

    Nagatsu, Masaaki; Terashita, Fumie; Nonaka, Hiroyuki; Xu, Lei; Nagata, Toshi; Koide, Yukio

    2005-05-01

    The effects of oxygen radicals on sterilization were studied using a 2.45GHz surface-wave oxygen plasma. A population of 1.5×106 Bacillus stearothermophilus spores was irradiated for 3min or more with oxygen plasma, generated at pressures between 6 and 14Pa. The decimal reduction value (D value), a measure of the effectiveness of sterilization, was determined to be about 15-25s. Using only oxygen radicals, excluding all charged particles, the 1.5×106 spores were sterilized with a D value of 30-45s after 5min or more of irradiation. On scanning electron microscopy, the length and width of the spores changed significantly due to chemical etching by oxygen radicals.

  1. Computational study on reliability of sheath width measurement by the cutoff probe in low pressure plasmas

    NASA Astrophysics Data System (ADS)

    Kim, D.-W.; You, S.-J.; Kim, J.-H.; Seong, D.-J.; Chang, H.-Y.; Oh, W.-Y.

    2015-11-01

    Recently, the technique for measurement of the sheath width by using the cutoff probe and its equivalent circuit model was proposed and conducted experimentally. In this study, we investigate the reliability of this technique based on the computational simulation. The simulation of three-dimensional Finite-Difference Time-Domain reproduces the transmission spectrum of the cutoff probe with an input parameter of sheath width. We measure the sheath width by using the circuit model and calculate the discrepancy between them under various input plasma densities and sheath widths. The results show the acceptable discrepancy under all of the conditions we studied (the largest discrepancy is about 45%). This indicates that the technique for measurement of sheath width around the floating tip of cutoff probe is robust and reliable. A shorter version of this contribution is due to be published in PoS at: 1st EPS conference on Plasma Diagnostics

  2. Numerical Simulations of Flow Separation Control in Low-Pressure Turbines using Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Suzen, Y. B.; Huang, P. G.; Ashpis, D. E.

    2007-01-01

    A recently introduced phenomenological model to simulate flow control applications using plasma actuators has been further developed and improved in order to expand its use to complicated actuator geometries. The new modeling approach eliminates the requirement of an empirical charge density distribution shape by using the embedded electrode as a source for the charge density. The resulting model is validated against a flat plate experiment with quiescent environment. The modeling approach incorporates the effect of the plasma actuators on the external flow into Navier Stokes computations as a body force vector which is obtained as a product of the net charge density and the electric field. The model solves the Maxwell equation to obtain the electric field due to the applied AC voltage at the electrodes and an additional equation for the charge density distribution representing the plasma density. The new modeling approach solves the charge density equation in the computational domain assuming the embedded electrode as a source therefore automatically generating a charge density distribution on the surface exposed to the flow similar to that observed in the experiments without explicitly specifying an empirical distribution. The model is validated against a flat plate experiment with quiescent environment.

  3. Portable rotating discharge plasma device

    NASA Astrophysics Data System (ADS)

    Dwyer, B. L.; Brooks, N. H.; Lee, R. L.

    2011-10-01

    We constructed two devices for the purpose of educational demonstration: a rotating tube containing media of two densities to demonstrate axial confinement and a similar device that uses pressure variation to convert a long plasma glow discharge into a long straight arc. In the first device, the buoyant force is countered by the centripetal force, which confines less dense materials to the center of the column. Similarly, a plasma arc heats the gas through which it passes, creating a hot gaseous bubble that is less dense than the surrounding medium. Rotating its containment envelope stabilizes this gas bubble in an analogous manner to an air bubble in a rotating tube of water. In addition to stabilization, the rotating discharge also exhibits a decrease in buoyancy-driven convection currents. This limits the power loss to the walls, which decreases the field strength requirement for maintaining the arc. These devices demonstrate principles of electrodynamics, plasma physics, and fluid mechanics. They are portable and safe for classroom use. Work supported by US DOE under DE-FC02-04ER54698 and the National Undergraduate Fellowship in Fusion Science and Engineering.

  4. Low pressure R.F. plasma reactions in light hydrocarbons. Ethylene and acetylene

    NASA Astrophysics Data System (ADS)

    Canepa, Pietro; Castello, Gianrico; Nicchia, Mario; Munari, Stelio

    The results obtained in the plasmolysis of ethylene and acetylene in an inductively coupled radiofrequency glow discharge are reported. A static system at a constant initial pressure of 0.5 torr and input power of 50 W was used; the gaseous and polymeric products were evaluated and compared with previous data on ethane plasmolysis and other available literature data. The decomposition products of ethylene were similar to those obtained during the plasmolysis of ethane, with a different distribution and a smaller initial increase of the total pressure. The total pressure of acetylene quickly decreased to near zero value at small specific energy, due to rapid polymerization. No gaseous products were detected, except hydrogen and traces of diacetylene.

  5. Microstructure and Oxidation Resistance of NiCoCrAlYTa Coating by Low Pressure Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Liang, X.-H.; Zhou, K. S.; Liu, M.; Hong, R. J.; Deng, C. G.; Luo, S.; Chen, Z. K.

    The NiCoCrAlYTa coating was prepared on Ni-based single crystal super-alloys by low pressure plasma spraying (LPPS). The phases and microstructures for the coatings were characterized by X-ray diffraction and scanning electron microscopy, and the fracture toughness and micro-hardness for both coatings and substrate were also investigated. The relationship between coating properties and oxidation was analyzed. The result shows that elementary distribution of NiCoCrAlYTa coatings, which consists of γ-Ni, β-NiAl, γ'-Ni3Al, and CrCoTa phases, is much homogeneous. The composition changes with depth from the surface to substrate for the coatings. The micro-hardness of coatings is 350.8 HV0.3 and fracture toughness is 2.73 MPa m1/2. The oxidation resistance of coatings excelled than Ni-based single crystal super-alloys.

  6. Analysis of the low-pressure plasma pretreated polymer surface in terms of acid-base approach

    NASA Astrophysics Data System (ADS)

    Kraus, Eduard; Orf, Lukas; Baudrit, Benjamin; Heidemeyer, Peter; Bastian, Martin; Bonenberger, Ramona; Starostina, Irina; Stoyanov, Oleg

    2016-05-01

    We demonstrate the use of a modern wetting method for determining the acid-base properties of treated polymer surfaces for different plastics and adhesives. The effect of the surface treatment with low pressure plasma was evaluated from the viewpoint of acid-base approach with plastics polyoxymethylene (POM) and polyetheretherketone (PEEK). The correlations between the acid-base properties and the identified mechanical tensile strengths of adhesive bonded joints were evaluated and discussed. In the investigated range the determination coefficients for POM and PEEK were calculated to R2 = 0.93 and R2 = 0.97, respectively. These relatively high determination coefficients showed a good correlation between the mechanical strength and the acidity parameter ΔDshort for use in bonding technology for surface pretreatment of polymers with LPP.

  7. High T(c) superconducting films of Y-Ba-Cu oxides prepared by low-pressure plasma spraying

    NASA Astrophysics Data System (ADS)

    Tachikawa, K.; Watanabe, I.; Kosuge, S.; Kabasawa, M.; Suzuki, T.

    1988-03-01

    A low-pressure plasma spraying technique for depositing high T(c) Y-Ba-Cu-O thick films has been developed. Films with a thickness range of 20-100 microns have been prepared by using Y(0.3)Ba(0.7)CuO(x) powders. After post-annealing in oxygen for 1 h at 950 C, the flims, which were deposited on a nimonic alloy substrate heated at 650 C during spraying, exhibited a zero resistance temperature of 90.6 K, with a transition width (90-10 percent) of 2 K and a critical current density (77 K, 0 T) of 690 A/sq cm.

  8. Measurement of effective sheath width around cutoff probe in low-pressure plasmas

    SciTech Connect

    Kim, D. W.; Oh, W. Y.; You, S. J. Kim, J. H.; Chang, H. Y.

    2014-05-15

    Previous studies indicated that the measurement results of microwave probes can be improved by applying the adequate sheath width to their measurement models, and consequently the sheath width around the microwave probe tips has become very important information for microwave probe diagnostics. In this paper, we propose a method for measuring the argon plasma sheath width around the cutoff probe tips by applying the circuit model to the cutoff probe phase spectrum. The measured sheath width of the cutoff probe was found to be in good agreement with the floated sheath width calculated from the Child-Langmuir sheath law. The physical reasons for a discrepancy between the two measurements are also discussed.

  9. Measurement of effective sheath width around cutoff probe in low-pressure plasmas

    NASA Astrophysics Data System (ADS)

    Kim, D. W.; You, S. J.; Kim, J. H.; Chang, H. Y.; Oh, W. Y.

    2014-05-01

    Previous studies indicated that the measurement results of microwave probes can be improved by applying the adequate sheath width to their measurement models, and consequently the sheath width around the microwave probe tips has become very important information for microwave probe diagnostics. In this paper, we propose a method for measuring the argon plasma sheath width around the cutoff probe tips by applying the circuit model to the cutoff probe phase spectrum. The measured sheath width of the cutoff probe was found to be in good agreement with the floated sheath width calculated from the Child-Langmuir sheath law. The physical reasons for a discrepancy between the two measurements are also discussed.

  10. Modelling electron transport in magnetized low-temperature discharge plasmas

    NASA Astrophysics Data System (ADS)

    Hagelaar, G. J. M.

    2007-02-01

    Magnetic fields are sometimes used to confine the plasma in low-pressure low-temperature gas discharges, for example in magnetron discharges, Hall-effect-thruster discharges, electron-cyclotron-resonance discharges and helicon discharges. We discuss how these magnetized discharges can be modelled by two-dimensional self-consistent models based on electron fluid equations. The magnetized electron flux is described by an anisotropic drift diffusion equation, where the electron mobility is much smaller perpendicular to the magnetic field than parallel to it. The electric potential is calculated either from Poisson's equation or from the electron equations, assuming quasineutrality. Although these models involve many assumptions, they are appropriate to study the main effects of the magnetic field on the charged particle transport and space charge electric fields in realistic two-dimensional discharge configurations. We demonstrate by new results that these models reproduce known phenomena such as the establishment of the Boltzmann relation along magnetic field lines, the penetration of perpendicular applied electric fields into the plasma bulk and the decrease in magnetic confinement by short-circuit wall currents. We also present an original method to prevent numerical errors arising from the extreme anisotropy of the electron mobility, which tend to invalidate model results from standard numerical methods.

  11. Low-pressure barrier discharge ion source using air as a carrier gas and its application to the analysis of drugs and explosives.

    PubMed

    Usmanov, Dilshadbek T; Yu, Zhan; Chen, Lee Chuin; Hiraoka, Kenzo; Yamabe, Shinichi

    2016-02-01

    In this work, a low-pressure air dielectric-barrier discharge (DBD) ion source using a capillary with the inner diameter of 0.115 and 12 mm long applicable to miniaturized mass spectrometers was developed. The analytes, trinitrotoluene (TNT), 1,3,5-trinitroperhydro-1,3,5-triazine (RDX), 1,3,5,7-tetranitroperhydro-1,3,5,7-tetrazocine (HMX), pentaerythritol tetranitrate (PETN), nitroglycerine (NG), hexamethylene triperoxide diamine (HMTD), caffeine, cocaine and morphine, introduced through the capillary, were ionized by a low-pressure air DBD. The ion source pressures were changed by using various sizes of the ion sampling orifice. The signal intensities of those analytes showed marked pressure dependence. TNT was detected with higher sensitivity at lower pressure but vice versa for other analytes. For all analytes, a marked signal enhancement was observed when a grounded cylindrical mesh electrode was installed in the DBD ion source. Among nine analytes, RDX, HMX, NG and PETN could be detected as cluster ions [analyte + NO3 ](-) even at low pressure and high temperature up to 180 °C. The detection indicates that these cluster ions are stable enough to survive under present experimental conditions. The unexpectedly high stabilities of these cluster ions were verified by density functional theory calculation. PMID:26889929

  12. Double layers and other phenomena in low-pressure plasma columns generated by ultra-violet light

    NASA Astrophysics Data System (ADS)

    Valentini, H.-B.; Kaiser, D.

    2015-12-01

    Low-pressure steady-state plasmas are analysed by means of a two-fluid model in both plane and cylindrical geometries. The charged particles are generated by UV illumination. Both a Gaussian and a one-step profile of the ionization are taken into account. Numerical results reveal various types of solutions depending on the ionization profile and the collisionality. The first state arises if the ionization spreads from the centre over a great part of the plasma. It has an almost quasineutral plasma core and a positively charged boundary sheath. The curvature of the number density of the charge particles is negative, except the boundary sheath. The second state occurs if the ionization is mainly localized in the vicinity of the centre and the collisionality is below a threshold. A slightly positive plasma core is surrounded by a double layer there where the ionization falls off steeply. Between the double layer and the boundary sheath a broad zone can exist where the plasma is nearly quasi-neutral and the electric field is small. Within the double layer the ion drift speed attains the Bohm velocity in collisionless plasmas, it is smaller in collisional cases. In a broad domain, the curvature of the number density of the charged particles can be positive. This is a feature of the so-called contracted columns. The transition between both the states occurs abruptly under collisonless conditions and becomes smooth as the collisionality increases. The minimum of the space charge density can become positive in this case. Several layers are possible, as well. Using the Gaussian profile analytical criteria can be given for a few of the mentioned phenomena. Probably, ionization profiles prescribed by photons allow to understand the origin of the contracted column more completely than up to now.

  13. Double layers and other phenomena in low-pressure plasma columns generated by ultra-violet light

    SciTech Connect

    Valentini, H.-B.; Kaiser, D.

    2015-12-15

    Low-pressure steady-state plasmas are analysed by means of a two-fluid model in both plane and cylindrical geometries. The charged particles are generated by UV illumination. Both a Gaussian and a one-step profile of the ionization are taken into account. Numerical results reveal various types of solutions depending on the ionization profile and the collisionality. The first state arises if the ionization spreads from the centre over a great part of the plasma. It has an almost quasineutral plasma core and a positively charged boundary sheath. The curvature of the number density of the charge particles is negative, except the boundary sheath. The second state occurs if the ionization is mainly localized in the vicinity of the centre and the collisionality is below a threshold. A slightly positive plasma core is surrounded by a double layer there where the ionization falls off steeply. Between the double layer and the boundary sheath a broad zone can exist where the plasma is nearly quasi-neutral and the electric field is small. Within the double layer the ion drift speed attains the Bohm velocity in collisionless plasmas, it is smaller in collisional cases. In a broad domain, the curvature of the number density of the charged particles can be positive. This is a feature of the so-called contracted columns. The transition between both the states occurs abruptly under collisonless conditions and becomes smooth as the collisionality increases. The minimum of the space charge density can become positive in this case. Several layers are possible, as well. Using the Gaussian profile analytical criteria can be given for a few of the mentioned phenomena. Probably, ionization profiles prescribed by photons allow to understand the origin of the contracted column more completely than up to now.

  14. Electron energy distribution functions in low-pressure oxygen plasma columns sustained by propagating surface waves

    SciTech Connect

    Stafford, L.; Margot, J.; Moisan, M.; Khare, R.; Donnelly, V. M.

    2009-01-12

    Electron energy distribution functions (EEDFs) were measured in a 50 mTorr oxygen plasma column sustained by propagating surface waves. Trace-rare-gas-optical-emission spectroscopy was used to derive EEDFs by selecting lines to extract ''electron temperature''(T{sub e}) corresponding to either lower energy electrons that excite high-lying levels through stepwise excitation via metastable states or higher energy electrons that excite emission directly from the ground state. Lower energy T{sub e}'s decreased from 8 to 5.5 eV with distance from the wave launcher, while T{sub e}{approx_equal}6 eV for higher energy electrons and T{sub e}>20 eV for a high-energy tail. Mechanisms for such EEDFs are discussed.

  15. High pressure laser plasma studies. [energy pathways in He-Ar gas mixtures at low pressure

    NASA Technical Reports Server (NTRS)

    Wells, W. E.

    1980-01-01

    The operation of a nuclear pumped laser, operating at a wavelength of 1.79 micron m on the 3d(1/2-4p(3/2) transition in argon with helium-3 as the majority gas is discussed. The energy pathways in He-Ar gas were investigated by observing the effects of varying partial pressures on the emissions of levels lying above the 4p level in argon during a pulsed afterglow. An attempt is made to determine the population mechanisms of the 3d level in pure argon by observing emission from the same transition in a high pressure plasma excited by a high energy electron beam. Both collisional radiative and dissociative recombination are discussed.

  16. Elemental analysis of bead samples using a laser-induced plasma at low pressure

    NASA Astrophysics Data System (ADS)

    Lie, Tjung Jie; Kurniawan, Koo Hendrik; Kurniawan, Davy P.; Pardede, Marincan; Suliyanti, Maria Margaretha; Khumaeni, Ali; Natiq, Shouny A.; Abdulmadjid, Syahrun Nur; Lee, Yong Inn; Kagawa, Kiichiro; Idris, Nasrullah; Tjia, May On

    2006-01-01

    An Nd:YAG laser (1064 nm, 8 ns, 30 mJ) was focused on various types of fresh, fossilized white coral and giant shell samples, including samples of imitation shell and marble. Such samples are extremely important as material for preparing prayer beads that are extensively used in the Buddhist faith. The aim of this research was to develop a non-destructive method to distinguish original beads from their imitations by means of spectral measurements of the carbon, hydrogen, sodium and magnesium emission intensities and by measuring the hardness of the sample using the ratio between Ca (II) 396.8 nm and Ca (I) 422.6 nm. Based on these measurements, original fresh coral beads can be distinguished from any imitation made from hard wood. The same technique was also effective in distinguishing beads made of shell from its imitation. A spectral analysis of bead was also performed on a fossilized white coral sample and the result can be used to distinguish to some extent the fossilized white coral beads from any imitation made from marble. It was also found that the plasma plume should be generated at low ambient pressure to significantly improve the hydrogen and carbon emission intensity and also to avoid energy loss inside the crater during laser irradiation at atmospheric pressure. The results of this study confirm that operating the laser-induced plasma spectroscopy at reduced ambient pressure offers distinct advantage for bead analysis over the conventional laser-induced breakdown spectroscopy (LIBS) technique operated at atmospheric pressure.

  17. Investigation of effect of excitation frequency on electron energy distribution functions in low pressure radio frequency bounded plasmas

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, Sudeep; Lafleur, Trevor; Charles, Christine; Boswell, Rod

    2011-07-01

    Particle in cell (PIC) simulations are employed to investigate the effect of excitation frequency ω on electron energy distribution functions (EEDFs) in a low pressure radio frequency (rf) discharge. The discharge is maintained over a length of 0.10 m, bounded by two infinite parallel plates, with the coherent heating field localized at the center of the discharge over a distance of 0.05 m and applied perpendicularly along the y and z directions. On varying the excitation frequency f (=ω/2π) in the range 0.01-50 MHz, it is observed that for f ≤ 5 MHz the EEDF shows a trend toward a convex (Druyvesteyn-like) distribution. For f > 5 MHz, the distribution resembles more like a Maxwellian with the familiar break energy visible in most of the distributions. A prominent "hot tail" is observed at f ≥ 20 MHz and the temperature of the tail is seen to decrease with further increase in frequency (e.g., at 30 MHz and 50 MHz). The mechanism for the generation of the "hot tail" is considered to be due to preferential transit time heating of energetic electrons as a function of ω, in the antenna heating field. There exists an optimum frequency for which high energy electrons are maximally heated. The occurrence of the Druyvesteyn-like distributions at lower ω may be explained by a balance between the heating of the electrons in the effective electric field and elastic cooling due to electron neutral collision frequency νen; the transition being dictated by ω ˜ 2πνen.

  18. Electron series resonance plasma discharges: Unmagnetized and magnetized

    NASA Astrophysics Data System (ADS)

    Qiu, Weiguang

    2001-08-01

    This thesis explores high frequency electron series resonance in unmagnetized and magnetized bounded plasmas. Special interest is focused on low temperature plasmas in planar systems as such are useful for material processing and fusion devices. Chapter 1, Chapter 2 and Chapter 3 describe simulation studies of unmagnetized electron series resonance (ESR) sustained discharges with comparisons to theory and experiment. These plasmas have many desirable characteristics. The input resistance is small and the drive voltage and current are in phase. The drive voltage is small (˜Te) and the time average plasma potential is low (˜10Te). A strong kinetic phase space bunching process is shown to provide electrons of sufficient energy for ionization, which allows discharge operation at low neutral pressure and low electron temperatures. At low pressure, the ion flux to the wall has a narrow angular spread about the normal and the ion bombarding energy distribution has a sharp peak at the plasma potential. Scaling laws at fixed pressure nr∝w3RF ,s¯∝w -1RF are shown to hold when RF frequency is varied smoothly ("chirping") demonstrating continuous density control. Research on magnetized electron series resonance (MESR) discharges is described in Chapter 4, Chapter 5 and Chapter 6. The resonant frequency is derived from cold plasma theory and shows two resonant modes. Simulations verify these modes to be the natural oscillatory frequencies of weakly magnetized plasmas in a planar plasma diode. A global model is established for magnetized resonant discharges. The interrelations among the plasma parameters and the drive terms are formulated for both resonant modes. The initiation of a MESR discharge and its steady state properties are discussed and compared to the unmagnetized case. Weak lock-on of MESR frequency to the drive frequency is observed in simulation. Similar V - I characteristics as those in ESR are found both in theory and in simulation. Different from the ESR

  19. Global model analysis of negative ion generation in low-pressure inductively coupled hydrogen plasmas with bi-Maxwellian electron energy distributions

    SciTech Connect

    Huh, Sung-Ryul; Kim, Nam-Kyun; Jung, Bong-Ki; Chung, Kyoung-Jae; Hwang, Yong-Seok; Kim, Gon-Ho

    2015-03-15

    A global model was developed to investigate the densities of negative ions and the other species in a low-pressure inductively coupled hydrogen plasma with a bi-Maxwellian electron energy distribution. Compared to a Maxwellian plasma, bi-Maxwellian plasmas have higher populations of low-energy electrons and highly vibrationally excited hydrogen molecules that are generated efficiently by high-energy electrons. This leads to a higher reaction rate of the dissociative electron attachment responsible for negative ion production. The model indicated that the bi-Maxwellian electron energy distribution at low pressures is favorable for the creation of negative ions. In addition, the electron temperature, electron density, and negative ion density calculated using the model were compared with the experimental data. In the low-pressure regime, the model results of the bi-Maxwellian electron energy distributions agreed well quantitatively with the experimental measurements, unlike those of the assumed Maxwellian electron energy distributions that had discrepancies.

  20. Documentation and Control of Flow Separation on a Low Pressure Turbine Linear Cascade of Pak-B Blades Using Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Corke, Thomas c.; Thomas, FLint, O.; Huang, Junhui

    2007-01-01

    This work involved the documentation and control of flow separation that occurs over low pressure turbine (LPT) blades at low Reynolds numbers. A specially constructed linear cascade was utilized to study the flow field over a generic LPT cascade consisting of Pratt & Whitney "Pak-B" shaped blades. Flow visualization, surface pressure measurements, LDV measurements, and hot-wire anemometry were conducted to examine the flow fields with and without separation control. Experimental conditions were chosen to give a range of chord Reynolds numbers (based on axial chord and inlet velocity) from 10,000 to 100,000, and a range of freestream turbulence intensities from u'/U(infinity) = 0.08 to 2.85 percent. The blade pressure distributions were measured and used to identify the region of separation that depends on Reynolds number and the turbulence intensity. Separation control was performed using dielectric barrier discharge (DBD) plasma actuators. Both steady and unsteady actuation were implemented and found to work well. The comparison between the steady and unsteady actuators showed that the unsteady actuators worked better than the steady ones. For the steady actuators, it was found that the separated region is significantly reduced. For the unsteady actuators, where the signal was pulsed, the separation was eliminated. The total pressure losses (a low Reynolds number) was reduced by approximately a factor of two. It was also found that lowest plasma duty cycle (10 percent in this work) was as effective as the highest plasma duty cycle (50 percent in this work). The mechanisms of the steady and unsteady plasma actuators were studied. It was suggested by the experimental results that the mechanism for the steady actuators is turbulence tripping, while the mechanism for the unsteady actuators is to generate a train of spanwise structures that promote mixing.

  1. End-boundary sheath potential, electron and ion energy distribution in the low-pressure non-ambipolar electron plasma

    NASA Astrophysics Data System (ADS)

    Chen, Lee; Chen, Zhiying; Funk, Merritt

    2013-12-01

    The end-boundary floating-surface sheath potential, electron and ion energy distribution functions (EEDf, IEDf) in the low-pressure non-ambipolar electron plasma (NEP) are investigated. The NEP is heated by an electron beam extracted from an inductively coupled electron-source plasma (ICP) through a dielectric injector by an accelerator located inside the NEP. This plasma's EEDf has a Maxwellian bulk followed by a broad energy continuum connecting to the most energetic group with energies around the beam energy. The NEP pressure is 1-3 mTorr of N2 and the ICP pressure is 5-15 mTorr of Ar. The accelerator is biased positively from 80 to 600 V and the ICP power range is 200-300 W. The NEP EEDf and IEDf are determined using a retarding field energy analyser. The EEDf and IEDf are measured at various NEP pressures, ICP pressures and powers as a function of accelerator voltage. The accelerator current and sheath potential are also measured. The IEDf reveals mono-energetic ions with adjustable energy and it is proportionally controlled by the sheath potential. The NEP end-boundary floating surface is bombarded by a mono-energetic, space-charge-neutral plasma beam. When the injected energetic electron beam is adequately damped by the NEP, the sheath potential is linearly controlled at almost a 1 : 1 ratio by the accelerator voltage. If the NEP parameters cannot damp the electron beam sufficiently, leaving an excess amount of electron-beam power deposited on the floating surface, the sheath potential will collapse and become unresponsive to the accelerator voltage.

  2. Influence of the excited states on the electron-energy distribution function in low-pressure microwave argon plasmas

    SciTech Connect

    Yanguas-Gil, A.; Cotrino, J.; Gonzalez-Elipe, A.R.

    2005-07-01

    In this work the influence of the excited states on the electron-energy distribution function has been determined for an argon microwave discharge at low pressure. A collisional-radiative model of argon has been developed taking into account the most recent experimental and theoretical values of argon-electron-impact excitation cross sections. The model has been solved along with the electron Boltzmann equation in order to study the influence of the inelastic collisions from the argon excited states on the electron-energy distribution function. Results show that under certain conditions the excited states can play an important role in determining the shape of the distribution function and the mean kinetic energy of the electrons, deplecting the high-energy tail due to inelastic processes from the excited states, especially from the 4s excited configuration. It has been found that from the populations of the excited states an excitation temperature can be defined. This excitation temperature, which can be experimentally determined by optical emission spectroscopy, is lower than the electron kinetic temperature obtained from the electron-energy distribution function.

  3. Low Pressure Radio-Frequency Oxygen Plasma Induced Oxidation of Titanium – Surface Characteristics and Biological Effects

    PubMed Central

    Tseng, Wan-Yu; Hsu, Sheng-Hao; Huang, Chieh-Hsiun; Tu, Yu-Chieh; Tseng, Shao-Chin; Chen, Hsuen-Li; Chen, Min-Huey; Su, Wei-Fang; Lin, Li-Deh

    2013-01-01

    Objective This research was designed to investigate the effects of low pressure radio-frequency (RF) oxygen plasma treatment (OPT) on the surface of commercially pure titanium (CP-Ti) and Ti6Al4V. Surface topography, elemental composition, water contact angle, cell viability, and cell morphology were surveyed to evaluate the biocompatibility of titanium samples with different lengths of OP treating time. Materials and Methods CP-Ti and Ti6Al4V discs were both classified into 4 groups: untreated, treated with OP generated by using oxygen (99.98%) for 5, 10, and 30 min, respectively. After OPT on CP-Ti and Ti6Al4V samples, scanning probe microscopy, X-ray photoelectron spectrometry (XPS), and contact angle tests were conducted to determine the surface topography, elemental composition and hydrophilicity, respectively. The change of surface morphology was further studied using sputtered titanium on silicon wafers. 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay and F-actin immunofluorescence stain were performed to investigate the viability and spreading behavior of cultivated MG-63 cells on the samples. Results The surface roughness was most prominent after 5 min OPT in both CP-Ti and Ti6Al4V, and the surface morphology of sputtered Ti sharpened after the 5 min treatment. From the XPS results, the intensity of Ti°, Ti2+, and Ti3+ of the samples’ surface decreased indicating the oxidation of titanium after OPT. The water contact angles of both CP-Ti and Ti6Al4V were increased after 5 min OPT. The results of MTT assay demonstrated MG-63 cells proliferated best on the 5 min OP treated titanium sample. The F-actin immunofluorescence stain revealed the cultivated cell number of 5 min treated CP-Ti/Ti6Al4V was greater than other groups and most of the cultivated cells were spindle-shaped. Conclusions Low pressure RF oxygen plasma modified both the composition and the morphology of titanium samples’ surface. The CP-Ti/Ti6Al4V treated with 5 min

  4. 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.

  5. Plasma discharge self-cleaning filtration system

    DOEpatents

    Cho, Young I.; Fridman, Alexander; Gutsol, Alexander F.; Yang, Yong

    2014-07-22

    The present invention is directed to a novel method for cleaning a filter surface using a plasma discharge self-cleaning filtration system. The method involves utilizing plasma discharges to induce short electric pulses of nanoseconds duration at high voltages. These electrical pulses generate strong Shockwaves that disintegrate and dislodge particulate matter located on the surface of the filter.

  6. 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.

  7. High temperature tensile and creep behaviour of low pressure plasma-sprayed Ni-Co-Cr-Al-Y coating alloy

    NASA Technical Reports Server (NTRS)

    Hebsur, M. G.; Miner, R. V.

    1986-01-01

    The high temperature tensile and creep behavior of low pressure plasma-sprayed plates of a typical Ni-Co-Cr-Al-Y alloy has been studied. From room temperature to 800 K, the Ni-Co-Cr-Al-Y alloy studied has nearly a constant low ductility and a high strength. At higher temperatures, it becomes weak and highly ductile. At and above 1123 K, the behavior is highly dependent on strain rate and exhibits classic superplastic characteristics with a high ductility at intermediate strain rates and a strain rate sensitivity of about 0.5. At either higher or lower strain rates, the ductility decreases and the strain rate sensitivities are about 0.2. In the superplastic deformation range, the activation energy for creep is 120 + or - 20 kJ/mol, suggesting a diffusion-aided grain boundary sliding mechanism. Outside the superplastic range, the activation energy for creep is calculated to be 290 + or - 20 kJ/mol.

  8. Thermal barrier coating life and isothermal oxidation of low-pressure plasma-sprayed bond coat alloys

    NASA Technical Reports Server (NTRS)

    Brindley, W. J.; Miller, R. A.

    1990-01-01

    The paper investigates the isothermal oxidation kinetics of Ni-35Cr-6Al-0.95Y, Ni-18Cr-12Al-0.3Y, and Ni-16Cr-6Al-0.3Y low-pressure plasma-sprayed bond coat alloys and examines the effect of these alloys on the thermal barrier coating (TBC) cyclic life. TBC life was examined by cycling substrates coated with the different bond coats and a ZrO2-7 wt pct Y2O3 TBC in an air-rich burner rig flame between 1150 C and room temperature. The oxidation kinetics of the three bond coat alloys was examined by isothermal oxidation of monolithic NJiCrAlY coupons at 1083 C. The Ni-35Cr-6Al-0.95Y alloy exhibits comparatively high isothermal oxidation weight gains and provides the longest TBC life, whereas the Ni-16Cr-6Al-0.3Y alloy had the lowest weight gains and provided the shortest TBC life. The results show that, although bond coat oxidation is known to have a strong detrimental effect on TBC life, it is not the only bond coat factor that determines TBC life.

  9. Correlation Between the Population of Active Species in Low Pressure Plasmas and Their Reactions with Organic Compounds

    NASA Astrophysics Data System (ADS)

    Patiño, Pedro

    The oxidation of four alkanes, two olefins and twelve aromatic compounds in the liquid phase with either high voltage or radio frequency glow discharges has been studied. The results of the liquid-plasma interactions of this work considerably differ from those in homogeneous gas phase. Neither fragmentation products in the traps nor polymers on the reactor walls have been detected. The selectivity of product formation is far superior to plasma oxidations in gas phase, making these techniques attractive for preparative chemistry. Total conversion, i.e., mass transformed against initial mass of substrate, has been studied as a function of the temperature of the liquid and the oxygen flow rate in the reactor. Optical emission spectroscopy has been utilized to detect and monitor the active species in the plasma. At the conditions for maximum oxidation no evidence of O_2(^1Delta_g) has been observed. A correlation between the behavior of the O(^3P) population in the discharge and the reactivity of the different compounds, as a function of the oxygen flow rate in the reactor, is presented.

  10. Self-excited nonlinear plasma series resonance oscillations in geometrically symmetric capacitively coupled radio frequency discharges

    SciTech Connect

    Donko, Z.; Schulze, J.; Czarnetzki, U.; Luggenhoelscher, D.

    2009-03-30

    At low pressures, nonlinear self-excited plasma series resonance (PSR) oscillations are known to drastically enhance electron heating in geometrically asymmetric capacitively coupled radio frequency discharges by nonlinear electron resonance heating (NERH). Here we demonstrate via particle-in-cell simulations that high-frequency PSR oscillations can also be excited in geometrically symmetric discharges if the driving voltage waveform makes the discharge electrically asymmetric. This can be achieved by a dual-frequency (f+2f) excitation, when PSR oscillations and NERH are turned on and off depending on the electrical discharge asymmetry, controlled by the phase difference of the driving frequencies.

  11. Surface effects on the diagnostic of carbon/nitrogen low-pressure plasmas studied by differentially pumped mass spectrometry.

    PubMed

    Alegre, Daniel; Ferreira, Jose A; Tabarés, Francisco L

    2014-05-01

    In this work, the characterization of the species produced in reactive plasmas by differentially pumped mass spectrometry is addressed. A H2/CH4/N2 mixture (90 : 5 : 5) was fed into a direct current glow discharge and analysed by conventional and cryo-trap assisted mass spectrometry. The gaseous mixture was chosen because of its particular relevance in the inhibition of tritium-rich carbon film deposition in fusion plasmas (scavenger technique) and in the deposition of amorphous hydrogenated carbon films by plasma-assisted chemical vapour deposition. Important changes in the composition of the detected species upon surface modification of the reactor walls (stainless steel or covered by an amorphous hydrogenated carbon layer) or in the way they are sampled (length and spatial configuration of the stainless steel duct) were detected. They are analysed in terms of radical formation and recombination on the reactor walls or into the sampling duct, thus providing some insight into the underlying chemistry. In general, when the reactor walls are covered by an amorphous hydrogenated carbon layer, more hydrocarbons are produced, but the radical production is lower and seem to be less reactive than in stainless steel. Also, two sources of oxygen contamination in the plasma have been identified, from the native oxide layer in stainless steel and from unintended water contamination in the chamber, which modify considerably the detected species. PMID:24809896

  12. Plasma variables and tribological properties of coatings in low pressure (0.1 - 10.0 torr) plasma systems

    NASA Technical Reports Server (NTRS)

    Avni, R.; Spalvins, T.

    1984-01-01

    A detailed treatment is presented of the dialog known as plasma surface interactions (PSI) with respect to the coating process and its tribological behavior. Adsorption, morphological changes, defect formation, sputtering, chemical etching, and secondary electron emission are all discussed as promoting and enhancing the surface chemistry, thus influencing the tribological properties of the deposited flux. Phenomenological correlations of rate of deposition, flux composition, microhardness, and wear with the plasma layer variables give an insight to the formation of chemical bonding between the deposited flux and the substrate surface.

  13. Ion bombardment effects in low-pressure plasmas: In situ spectroscopic ellipsometry and Monte-Carlo simulation study

    NASA Astrophysics Data System (ADS)

    Amassian, Aram

    Plasma-enhanced chemical vapor deposition (PECVD) is a very versatile, yet highly complex process which has attracted the attention of the optical coatings community for its ability to synthesize thin film materials with a wide and continuous range of optical properties. In this work, we investigate the effects of ion-surface interactions in the case of hyperthermal ions (100 to 103 eV) accelerated at the RF-biased electrode of a PECVD reactor, in order to better understand their effect beneath the substrate surface, on growing films, and on interface formation. We apply in situ real-time spectroscopic ellipsometry (RTSE): (1) to monitor modifications at the surface of model c-Si(001) substrates exposed to low-pressure O2 plasma at the RF-powered electrode as a function of substrate bias voltage (VB), (2) to determine interface broadening during the initial stages of TiO 2 deposition on SiO2, and (3) to monitor the Ar plasma treatment of the interface between porous and dense Si3N4 films, and its effect on the growth of multilayer dense/porous stacks. The first part of this thesis focuses on the modifications of a c-Si substrate resulting from an exposure to an O2 plasma at the RF-powered electrode by using ex situ variable angle spectroscopic ellipsometry (VASE). The study demonstrates the presence of significant sub-surface modifications, giving rise to a top layer oxide (SiO 2) and an interfacial damage layer on c-Si(001). The depth of modifications was found to scale with ˜|VB|½ , increasing from ˜3.4 nm up to ˜9.6 nm for V B ranging between -60 and -600 V after 10 minutes of plasma exposure. Static Monte-Carlo TRIM simulations confirmed that the modifications and scaling can be explained on the basis of depth-dependent O transport by ion implantation. In the second part of this work, we studied the dynamical effects of plasma-surface interactions by using in situ RTSE in combination with TRIDYN (a dynamical version of TRIM) simulations. TRIDYN simulations

  14. Plasma quiescence in a reflex discharge

    SciTech Connect

    Jerde, L.; Friedman, S.; Carr, W.; Seidl, M.

    1980-02-01

    A thermionic cathode reflex discharge and the plasma it produces are studied. It is found that extremely quiescent plasmas can be produced when the electron-loss rate due to classical diffusion is equal to the ion-loss rate. Particle and power balances for the quiescent plasma are obtained, and the average electron energy loss per ion produced is determined.

  15. Inactivation of Gram-Negative Bacteria by Low-Pressure RF Remote Plasma Excited in N2-O2 Mixture and SF6 Gases

    PubMed Central

    Al-Mariri, Ayman; Saloum, Saker; Mrad, Omar; Swied, Ghayath; Alkhaled, Bashar

    2013-01-01

    The role of low-pressure RF plasma in the inactivation of Escherichia coli O157, Klebsiella pneumoniae, Proteus mirabilis, and Enterobacter sakazakii using N2-O2 and SF6 gases was assessed. 1×109 colony-forming units (CFUs) of each bacterial isolate were placed on three polymer foils. The effects of pressure, power, distance from the source, and exposure time to plasma gases were optimized. The best conditions to inactivate the four bacteria were a 91%N2-9%O2 mixture and a 30-minute exposure time. SF6 gas was more efficient for all the tested isolates in as much as the treatment time was reduced to only three minutes. Therefore, low-pressure plasma could be used to sterilize heat and/or moisture-sensitive medical instruments. PMID:24293788

  16. Study of pulsed neon-xenon VUV radiating low pressure plasmas for mercury free fluorescent sign optimization

    NASA Astrophysics Data System (ADS)

    Robert, E.; Point, S.; Dozias, S.; Viladrosa, R.; Pouvesle, J. M.

    2010-04-01

    This work deals with the study and optimization of mercury free fluorescent discharge tubes for publicity lighting applications. The experimental set-up allows for time resolved spectroscopy from 110 up to 900 nm, photometric characterization in a large volume integrating sphere and the current and voltage measurement of microsecond duration signals delivered by lab-developed pulsed drivers. The glow and afterglow radiative process analysis indicates that the best performance measured with the pulsed excitation of rare gas plasma, in comparison with the conventional ac excitation, essentially originates from the efficient plasma relaxation during the afterglow at the benefit of the vacuum ultraviolet (VUV) resonance line radiated at 146.9 nm for xenon. The fit of the VUV time resolved experimental measurements, with the results issued from a simplified kinetic model of neon-xenon plasmas, evidences the crucial role of production of molecular ions during the glow phase and of their radiative recombination during the afterglow. The pulse duration and the gas mixture pressure appear as two experimental parameters whose influence, studied over an extended range, has been demonstrated to bring about a significant sign performance enhancement. There exists an optimum pulse duration range, which results in the appearance of limited stepwise excitation and ionization processes, favourable for an intense afterglow VUV production. The pressure dependence study shows that the best performance for pulsed excitation is obtained in Ne/Xe (100/1) mixtures around 50 mbar, at the difference of an ac driven Ne/Xe plasma for which the best conditions were reported to be of a few millibars. This pressure increase results both in the VUV and sign light output enhancement and the successful continuous operation of pulsed mercury free signs for time as long as 4000 h with neither electrode erosion, nor glass or phosphor degradation nor chromatic coordinate variation. For the green

  17. One-dimensional time-dependent fluid model of a very high density low-pressure inductively coupled plasma

    SciTech Connect

    Chaplin, Vernon H.; Bellan, Paul M.

    2015-12-28

    A time-dependent two-fluid model has been developed to understand axial variations in the plasma parameters in a very high density (peak ne~ > 5x1019 m–3) argon inductively coupled discharge in a long 1.1 cm radius tube. The model equations are written in 1D, with radial losses to the tube walls accounted for by the inclusion of effective particle and energy sink terms. The ambipolar diffusion equation and electron energy equation are solved to find the electron density ne(z,t) and temperature Te(z,t), and the populations of the neutral argon 4s metastable, 4s resonant, and 4p excited state manifolds are calculated in order to determine the stepwise ionization rate and calculate radiative energy losses. The model has been validated through comparisons with Langmuir probe ion saturation current measurements; close agreement between the simulated and measured axial plasma density profiles and the initial density rise rate at each location was obtained at pAr = 30-60 mTorr. Lastly, we present detailed results from calculations at 60 mTorr, including the time-dependent electron temperature, excited state populations, and energy budget within and downstream of the radiofrequency (RF) antenna.

  18. One-dimensional time-dependent fluid model of a very high density low-pressure inductively coupled plasma

    NASA Astrophysics Data System (ADS)

    Chaplin, Vernon H.; Bellan, Paul M.

    2015-12-01

    A time-dependent two-fluid model has been developed to understand axial variations in the plasma parameters in a very high density (peak ne≳ 5 ×1019 m-3 ) argon inductively coupled discharge in a long 1.1 cm radius tube. The model equations are written in 1D with radial losses to the tube walls accounted for by the inclusion of effective particle and energy sink terms. The ambipolar diffusion equation and electron energy equation are solved to find the electron density ne(z ,t ) and temperature Te(z ,t ) , and the populations of the neutral argon 4s metastable, 4s resonant, and 4p excited state manifolds are calculated to determine the stepwise ionization rate and calculate radiative energy losses. The model has been validated through comparisons with Langmuir probe ion saturation current measurements; close agreement between the simulated and measured axial plasma density profiles and the initial density rise rate at each location was obtained at pA r=30 -60 mTorr . We present detailed results from calculations at 60 mTorr, including the time-dependent electron temperature, excited state populations, and energy budget within and downstream of the radiofrequency antenna.

  19. One-dimensional time-dependent fluid model of a very high density low-pressure inductively coupled plasma

    DOE PAGESBeta

    Chaplin, Vernon H.; Bellan, Paul M.

    2015-12-28

    A time-dependent two-fluid model has been developed to understand axial variations in the plasma parameters in a very high density (peak ne~ > 5x1019 m–3) argon inductively coupled discharge in a long 1.1 cm radius tube. The model equations are written in 1D, with radial losses to the tube walls accounted for by the inclusion of effective particle and energy sink terms. The ambipolar diffusion equation and electron energy equation are solved to find the electron density ne(z,t) and temperature Te(z,t), and the populations of the neutral argon 4s metastable, 4s resonant, and 4p excited state manifolds are calculated inmore » order to determine the stepwise ionization rate and calculate radiative energy losses. The model has been validated through comparisons with Langmuir probe ion saturation current measurements; close agreement between the simulated and measured axial plasma density profiles and the initial density rise rate at each location was obtained at pAr = 30-60 mTorr. Lastly, we present detailed results from calculations at 60 mTorr, including the time-dependent electron temperature, excited state populations, and energy budget within and downstream of the radiofrequency (RF) antenna.« less

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. A parametric study of the destruction efficiency of Bacillus spores in low pressure oxygen-based plasmas.

    PubMed

    Hury, S; Vidal, D R; Desor, F; Pelletier, J; Lagarde, T

    1998-06-01

    The destruction of Bacillus spores in oxygen-based plasmas sustained in the millitorr pressure range has been studied as functions of various biological and plasma parameters, namely Bacillus species, surface concentration of spores, treatment temperature, and gas composition. In an oxygen plasma, Bacillus stearothermophilus appears less plasma-resistant than the other spores tested. Oxygen, H2O2 and chiefly CO2 plasmas are clearly shown to be much more efficient in destroying Bacillus subtilis spores than pure argon plasma. The bacterial surface concentration on the spore carriers and the treatment temperature also lead to significant variations in the destruction efficiency of spores when using CO2 plasma. PMID:9717311

  5. Gas-discharge plasma sources for nonlocal plasma technology

    SciTech Connect

    Demidov, V. I.; DeJoseph, C. A. Jr.; Simonov, V. Ya.

    2007-11-12

    Nonlocal plasma technology is based on the effect of self-trapping of fast electrons in the plasma volume [V. I. Demidov, C. A. DeJoseph, Jr., and A. A. Kudryavtsev, Phys. Rev. Lett. 95, 215002 (2006)]. This effect can be achieved by changing the ratio of fast electron flux to ion flux incident on the plasma boundaries. This in turn leads to a significant change in plasma properties and therefore can be useful for technological applications. A gas-discharge device which demonstrates control of the plasma properties by this method is described.

  6. Measurements of time average series resonance effect in capacitively coupled radio frequency discharge plasma

    SciTech Connect

    Bora, B.; Bhuyan, H.; Favre, M.; Wyndham, E.; Chuaqui, H.; Kakati, M.

    2011-10-15

    Self-excited plasma series resonance is observed in low pressure capacitvely coupled radio frequency discharges as high-frequency oscillations superimposed on the normal radio frequency current. This high-frequency contribution to the radio frequency current is generated by a series resonance between the capacitive sheath and the inductive and resistive bulk plasma. In this report, we present an experimental method to measure the plasma series resonance in a capacitively coupled radio frequency argon plasma by modifying the homogeneous discharge model. The homogeneous discharge model is modified by introducing a correction factor to the plasma resistance. Plasma parameters are also calculated by considering the plasma series resonances effect. Experimental measurements show that the self-excitation of the plasma series resonance, which arises in capacitive discharge due to the nonlinear interaction of plasma bulk and sheath, significantly enhances both the Ohmic and stochastic heating. The experimentally measured total dissipation, which is the sum of the Ohmic and stochastic heating, is found to increase significantly with decreasing pressure.

  7. Langmuir probe measurements of weakly collisional electropositive RF discharge plasmas

    NASA Astrophysics Data System (ADS)

    Bryant, Paul; Dyson, Anthony; Allen, John E.

    2001-05-01

    We report on Langmuir probe measurements of low-pressure (0.1-20 Pa) electropositive plasmas in an RF discharge at 13.56 MHz. From the probe I-V characteristic it is found that the electron density inferred from the ion current in the ion saturation region using radial motion (Allen, Boyd and Reynolds, ABR) theory can be up to one-half that obtained directly from the electron current at the plasma potential. The reduction in the ion current is attributed to orbital motion (OM) of the ions and also to a small number of ion-neutral collisions in the presheath. We show that if a sufficiently large probe is chosen so as to minimize the OM effects then the collisional theory developed by Shih and Levi (1971) can be used to give an appropriate correction factor over a narrow pressure range. The corrected electron density is found to agree with the knee current value to typically 10% for Ar, N2 and Kr plasmas.

  8. Improving plasma actuator performance at low pressure, and an analysis of the pointing capabilities of cubeSats using Plasmonic Force Propulsion (PFP) thrusters

    NASA Astrophysics Data System (ADS)

    Friz, Paul Daniel

    This thesis details the work done on two unrelated projects, plasma actuators, an aerodynamic flow control device, and Plasmonic Force Propulsion (PFP) thrusters, a space propulsion system for small satellites. The first half of the thesis is a paper published in the International Journal of Flow Control on plasma actuators. In this paper the thrust and power consumption of plasma actuators with varying geometries was studied at varying pressure. It was found that actuators with longer buried electrodes produce the most thrust over all and that they substantially improved thrust at low pressure. In particular actuators with 75 mm buried electrodes produced 26% more thrust overall and 34% more thrust at low pressure than the standard 15 mm design. The second half details work done modeling small satellite attitude and reaction control systems in order to compare the use of Plasmonic Force Propulsion thrusters with other state of the art reaction control systems. The model uses bang bang control algorithms and assumes the worst case scenario solar radiation pressure is the only disturbing force. It was found that the estimated 50-500 nN of thrust produced by PFP thrusters would allow the spacecraft which use them extremely high pointing and positioning accuracies (<10-9 degrees and 3 pm). PFP thrusters still face many developmental challenges such as increasing specific impulse which require more research, however, they have great potential to be an enabling technology for future NASA missions such as the Laser Interferometer Space Antenna, and The Stellar Imager.

  9. Feasibility of atomic layer etching of polymer material based on sequential O{sub 2} exposure and Ar low-pressure plasma-etching

    SciTech Connect

    Vogli, Evelina; Metzler, Dominik; Oehrlein, Gottlieb S.

    2013-06-24

    We describe controlled, self-limited etching of a polystyrene polymer using a composite etching cycle consisting of sequential deposition of a thin reactive layer from precursors produced from a polymer-coated electrode within the etching chamber, modification using O{sub 2} exposure, and subsequent low-pressure Ar plasma etching, which removes the oxygen-modified deposited reactive layer along with Almost-Equal-To 0.1 nm unmodified polymer. Deposition prevents net etching of the unmodified polymer during the etching step and enables self-limited etch rates of 0.1 nm/cycle.

  10. Glow discharge plasma deposition of thin films

    DOEpatents

    Weakliem, Herbert A.; Vossen, Jr., John L.

    1984-05-29

    A glow discharge plasma reactor for deposition of thin films from a reactive RF glow discharge is provided with a screen positioned between the walls of the chamber and the cathode to confine the glow discharge region to within the region defined by the screen and the cathode. A substrate for receiving deposition material from a reactive gas is positioned outside the screened region. The screen is electrically connected to the system ground to thereby serve as the anode of the system. The energy of the reactive gas species is reduced as they diffuse through the screen to the substrate. Reactive gas is conducted directly into the glow discharge region through a centrally positioned distribution head to reduce contamination effects otherwise caused by secondary reaction products and impurities deposited on the reactor walls.

  11. How does a probe inserted into the discharge influence the plasma structure?

    NASA Astrophysics Data System (ADS)

    Yordanov, D.; Lishev, St.; Shivarova, A.

    2016-05-01

    Shielding the bias applied to the probe by the sheath formed around it and determination of parameters of unperturbed plasmas are in the basis of the probe diagnostics. The results from a two-dimensional model of a discharge with a probe inserted in it show that the probe influences the spatial distribution of the plasma parameters in the entire discharge. The increase (although slight) in the electron temperature, due to the increased losses of charged particles on the additional wall in the discharge (mainly the probe holder), leads to redistribution of the plasma density and plasma potential, as shown by the results obtained at the floating potential of the probe. The deviations due to the bias applied to the probe tip are stronger in the ion saturation region of the probe characteristics. The pattern of the spatial redistribution of the plasma parameters advances together with the movement of the probe deeper in the discharge. Although probe sheaths and probe characteristics resulting from the model are shown, the study does not aim at discussions on the theories for determination of the plasma density from the ion saturation current. Regardless of the modifications in the plasma behavior in the entire discharge, the deviations of the plasma parameters at the position of the probe tip and, respectively, the uncertainty which should be added as an error when the accuracy of the probe diagnostics is estimated do not exceed 10%. Consequently, the electron density and temperature obtained, respectively, at the position of the plasma potential on the probe characteristics and from its transition region are in reasonable agreement with the results from the model of the discharge without a probe. Being in the scope of research on a source of negative hydrogen ions with the design of a matrix of small radius inductive discharges, the model is specified for a low-pressure hydrogen discharge sustained in a small-radius tube.

  12. Low-pressure plasma columns sustained by traveling electromagnetic surface waves in the dipolar (m=1) mode

    NASA Astrophysics Data System (ADS)

    Benova, E.; Zhelyazkov, I.; Ghanashev, I.

    1992-01-01

    An extension of a theoretical study of a plasma column surrounded by vacuum and sustained by an electromagnetic surface wave in the dipolar mode [E. Benova, I. Ghanashev, and I. Zhelyazkov, J. Plasma Phys. 45, 137 (1991)] is presented. Following the same formalism the plasma column and the wave characteristics have been calculated taking into account the presence of a dielectric container in order to improve the agreement between theory and experiment.

  13. Pulse-discharge plasmas for plasma-accelerator applications

    SciTech Connect

    Clayton, C. E.; Joshi, C.; Lopes, N. C.

    2012-12-21

    For particle-beam-driven plasma wakefield accelerators, a long and fully-ionized plasma is desirable. We describe an experiment at UCLA to develop a prototype of such plasma using a pulsed-current discharge. Scaling of the plasma density with glass-tube diameter and with discharge-circuit parameters is currently underway. We have found that 4 Torr of Argon can be fully ionized to a density of about 1.3 Multiplication-Sign 10{sup 17} cm{sup -3} when the current density in the 1 inch diameter, 1.2 meter-long tube is around 2 kA/cm{sup 2}, at least at one point along the discharge. The homogeneity of the plasma density in the longitudinal direction is crucial to prevent slippage of the driven plasma structures with the particles. Equally important are the transverse gradients since any dipole asymmetry in the transverse direction can lead to 'steering' of the particle beam. The longitudinal and transverse gradients may be a function of time into the discharge, the shape of the electrodes, the tube size, and the fractional ionization for a given fill pressure. These issues are currently under investigation.

  14. A hybrid model for low pressure inductively coupled plasmas combining a fluid model for electrons with a plasma-potential-dependent energy distribution and a fluid-Monte Carlo model for ions

    NASA Astrophysics Data System (ADS)

    Mouchtouris, S.; Kokkoris, G.

    2016-04-01

    A hybrid plasma model is utilized for the simulation of inductively coupled plasmas (ICPs). It consists of a plasma fluid model coupling fluid with Maxwell’s equations and a Monte Carlo (MC) particle tracing model utilized for the calculation of the ion mobility in high electrostatic fields (sheaths). The model is applied to low pressure Argon plasma in the gaseous electronics conference (GEC) reference cell. Following measurements of electron energy distribution function (EEDF) in low pressure ICPs, a three-temperature EEDF is considered; it is formulated with a generalized equation and depends on the local plasma potential. The use of a predefined formula for the EEDF entails a low computational cost: All parameters affected by the EEDF are calculated as functions of the plasma potential and the mean electron energy once and before the solution of the model. The model results are validated by a comparison with spatially resolved (on axial and radial distance) measurements of electron density, electron temperature, and plasma potential. Both the calculation of the ion mobility by the MC model and the consideration of the three-temperature EEDF are critical for the accuracy of the model results. The very good agreement of the model results with the measurements and the low computational cost in combination with the flexibility of the code utilized for the numerical solution manifest the potential of the hybrid plasma model for the simulation of low pressure ICPs.

  15. Numerical simulations of electrical asymmetry effect on electronegative plasmas in capacitively coupled rf discharge

    NASA Astrophysics Data System (ADS)

    Zhang, Quan-Zhi; Jiang, Wei; Hou, Lu-Jing; Wang, You-Nian

    2011-01-01

    Recently a so-called electrical asymmetry effect (EAE), which could achieve high-degree separate control of ion flux and energy in dual-frequency capacitively coupled radio-frequency (CCRF) discharges, was discovered theoretically by Heil et al. [J. Phys. D: Appl. Phys. 41, 165202 (2008)] and was confirmed by experiments and theory/numerical simulations later on for electropositive argon discharges. In this work simulations based on particle-in-cell/Monte Carlo collision are performed to study the EAE on electronegative oxygen plasmas in geometrically symmetric CCRF discharges. Dual frequency discharges operating at 13.56 and 27.12 MHz are simulated for different pressures and the results are compared with those of electropositive argon discharges at the same conditions. It is found that in general the EAE on oxygen discharges has similar behavior as on argon discharge: The self-bias voltage η increases monotonically and almost linearly with the increase in the phase angle θ between the two driving voltages in the range 0<θ<90°, and the maximum ion energy varies by a factor of 3 by adjusting θ. However, the ion flux varies with θ by ±12% for low pressure and by ±15% for higher pressure, due primarily to an enhanced plasma series resonance, which then leads to dramatic changes in plasma density, power absorption and consequently the electronegativity. This may place a limitation for achieving separate control of ion energy and flux for electronegative plasma via the EAE.

  16. Numerical simulations of electrical asymmetry effect on electronegative plasmas in capacitively coupled rf discharge

    SciTech Connect

    Zhang Quanzhi; Jiang Wei; Wang Younian; Hou Lujing

    2011-01-01

    Recently a so-called electrical asymmetry effect (EAE), which could achieve high-degree separate control of ion flux and energy in dual-frequency capacitively coupled radio-frequency (CCRF) discharges, was discovered theoretically by Heil et al. [J. Phys. D: Appl. Phys. 41, 165202 (2008)] and was confirmed by experiments and theory/numerical simulations later on for electropositive argon discharges. In this work simulations based on particle-in-cell/Monte Carlo collision are performed to study the EAE on electronegative oxygen plasmas in geometrically symmetric CCRF discharges. Dual frequency discharges operating at 13.56 and 27.12 MHz are simulated for different pressures and the results are compared with those of electropositive argon discharges at the same conditions. It is found that in general the EAE on oxygen discharges has similar behavior as on argon discharge: The self-bias voltage {eta} increases monotonically and almost linearly with the increase in the phase angle {theta} between the two driving voltages in the range 0<{theta}<90 deg. , and the maximum ion energy varies by a factor of 3 by adjusting {theta}. However, the ion flux varies with {theta} by {+-}12% for low pressure and by {+-}15% for higher pressure, due primarily to an enhanced plasma series resonance, which then leads to dramatic changes in plasma density, power absorption and consequently the electronegativity. This may place a limitation for achieving separate control of ion energy and flux for electronegative plasma via the EAE.

  17. Novel Giant-Size Plasmas Produced by Microwave Discharge with Slot Antenna Array

    NASA Astrophysics Data System (ADS)

    Sugai, H.; Nojiri, Y.; Takasu, K.; Ishijima, T.; Stamate, E.

    2004-09-01

    There is a growing need for giant-scale high-density plasma sources for manufacturing a meter-size flat panel display and for surface modification of large-area various materials. Capacitive discharges at frequencies in VHF range have been studied to meet this demand, however standing wave effect and edge effect significantly degrade the plasma uniformity. Here, we present a new technology for generation of large-area flat high-density plasma based on surface wave excitation at 2.45 GHz. A critical challenge to avoid huge atmospheric pressure acting on a microwave window was dodged by fully filling a waveguide, which is directly inserted in a low-pressure discharge vessel. The second challenge is a discharge antenna construction to attain the plasma uniformity over meter-scale. This issue was solved by a careful design of slot antenna array. Surface waves propagating along the dielectric-plasma interface were investigated in FDT simulation. A surface wave mode was observed in plasma by a movable antenna, indicating the mode number predicted in the simulation. In a discharge vessel, 1 m long and 0.3 m wide, we obtained the plasma density of 5x10@super11@ cm@super-3@ with 10 and 50 mTorr Ar. Three-dimensional profiles of plasma density in different conditions measured by a Langmuir probe will be presented.

  18. Numerical simulation of atomic nitrogen formation in plasma of glow discharge in nitrogen-argon mixture

    NASA Astrophysics Data System (ADS)

    Khomich, V. A.; Ryabtsev, A. V.; Didyk, E. G.; Zhovtyansky, V. A.; Nazarenko, V. G.

    2010-10-01

    We consider the problem of determining the content of atomic nitrogen as an active component responsible for the efficiency of metal surface modification in plasma of stationary low-pressure glow discharge in nitrogen-argon mixture (widely used in this technology). The influence of the gas mixture composition on the rate constant of molecular nitrogen dissociation, which determines the atomic nitrogen production, has been calculated, The parameters of plasma have been experimentally determined using the method of double probes. The electron energy distribution function is found by numerically integrating the Boltzmann equation in a two-term approximation for the molecular nitrogen-argon mixture.

  19. Plasma foundation in a pseudospark discharge

    SciTech Connect

    Choi, P.; Chauqui, H. ); Lunney, J. ); Reichle, R. ); Mittag, K. ); Davies, A.J. )

    1989-10-01

    This paper reports that unique features associated with the hollow cathode recess in a pseudospark discharge have been identified from streak camera observations. A plasma is observed to form in a highly localized region immediately behind the cathode aperture prior to gas breakdown in the main discharge volume. The point-like plasma expands from an initial diameter of below 0.3 to 3 mm, the size of the cathode aperture, in about 20 ns, at which time the main discharge is formed starting from the axis. Numerical modeling based on swarm parameters has been carried out to investigate the plasma formation in the hollow cathode region. Results show that a combination of varying ionization rates due to the field geometry and differing mobilities of electrons and ions leads to the formation of a highly localized space-charge field on axis behind the hollow cathode. This space-charge field in turn brings about the rapid formation of a highly localized, high density of charge carriers behind the cathode aperture. The authors suggest that this point-like formation of a plasma source is the phenomenon observed in the streak camera observation of the hollow cathode region.

  20. Final Report for Award DE-FG02-99ER54554 Kinetics of Electron Fluxes in Low-Pressure Nonthermal Plasmas

    SciTech Connect

    Uwe Kortshagen

    2004-12-13

    This grant has focused on the study of several aspects of electron kinetics in low pressure plasmas. Entirely new effects arise from the fact that the electron kinetics is governed by non-local effects, in which the electron distribution function is not equilibrium with the local electric field but is governed by spatial transport effects. In this grant, we were able to demonstrate several previously un-studied effects which are a direct result of the nonlocal transport. These are: (1) The existence of a ''convective cell' in electron phase space. The phenomenon was observed and studied in CW plasma conditions. (2) The occurrence of non-collisional cooling of electrons through an effect known as ''diffusive cooling''.

  1. Film analysis employing subtarget effect using 355 nm Nd-YAG laser-induced plasma at low pressure

    NASA Astrophysics Data System (ADS)

    Hedwig, Rinda; Budi, Wahyu Setia; Abdulmadjid, Syahrun Nur; Pardede, Marincan; Suliyanti, Maria Margaretha; Lie, Tjung Jie; Kurniawan, Davy Putra; Kurniawan, Koo Hendrik; Kagawa, Kiichiro; Tjia, May On

    2006-12-01

    The applicability of spectrochemical analysis for liquid and powder samples of minute amount in the form of thin film was investigated using ultraviolet Nd-YAG laser (355 nm) and low-pressure ambient air. A variety of organic samples such as commercial black ink usually used for stamp pad, ginseng extract, human blood, liquid milk and ginseng powder was prepared as film deposited on the surface of an appropriate hard substrate such as copper plate or glass slide. It was demonstrated that in all cases studied, good quality spectra were obtained with very low background and free from undesirable contamination by the substrate elements, featuring ppm or even sub-ppm sensitivity and worthy of application for quantitative analysis of organic samples. The proper preparation of the films was found to be crucial in achieving the high quality spectra. It was further shown that much inferior results were obtained when the atmospheric-pressure (101 kPa) operating condition of laser-induced breakdown spectroscopy or the fundamental wavelength of the Nd-YAG laser was employed due to the excessive or improper laser ablation process.

  2. An experimental study on sub-cooled flow boiling CHF of R134a at low pressure condition with atmospheric pressure (AP) plasma assisted surface modification

    SciTech Connect

    Kim, Seung Jun; Zou, Ling; Jones, Barclay G.

    2015-02-01

    In this study, sub-cooled flow boiling critical heat flux tests at low pressure were conducted in a rectangular flow channel with one uniformly heated surface, using simulant fluid R-134a as coolant. The experiments were conducted under the following conditions: (1) inlet pressure (P) of 400-800 kPa, (2) mass flux (G) of 124-248 kg/m2s, (3) inlet sub-cooling enthalpy (ΔHi) of 12~ 26 kJ/kg. Parametric trends of macroscopic system parameters (G, P, Hi) were examined by changing inlet conditions. Those trends were found to be generally consistent with previous understandings of CHF behavior at low pressure condition (i.e. reduced pressure less than 0.2). A fluid-to-fluid scaling model was utilized to convert the test data obtained with the simulant fluid (R-134a) into the prototypical fluid (water). The comparison between the converted CHF of equivalent water and CHF look-up table with same operation conditions were conducted, which showed good agreement. Furthermore, the effect of surface wettability on CHF was also investigated by applying atmospheric pressure plasma (AP-Plasma) treatment to modify the surface characteristic. With AP-Plasma treatment, the change of microscopic surface characteristic was measured in terms of static contact angle. The static contact angle was reduced from 80° on original non-treated surface to 15° on treated surface. An enhancement of 18% on CHF values under flow boiling conditions were observed on AP-Plasma treated surfaces compared to those on non-treated heating surfaces.

  3. Particle-in-cell simulations of multi-MeV pulsed X-ray induced air plasmas at low pressures

    NASA Astrophysics Data System (ADS)

    Ribière, M.; Cessenat, O.; d'Almeida, T.; de Gaufridy de Dortan, F.; Maulois, M.; Delbos, C.; Garrigues, A.; Azaïs, B.

    2016-03-01

    A full kinetic modelling of the charge particles dynamics generated upon the irradiation of an air-filled cavity by a multi-MeV pulsed x-ray is performed. From the calculated radiative source generated by the ASTERIX generator, we calculated the electromagnetic fields generated by x-ray induced air plasmas in a metallic cavity at different pressures. Simulations are carried out based on a Particle-In-Cell interpolation method which uses 3D Maxwell-Vlasov calculations of the constitutive charged species densities of air plasmas at different pressures at equilibrium. The resulting electromagnetic fields within the cavity are calculated for different electron densities up to 4 × 1010 cm-3. For each air pressure, we show electronic plasma waves formation followed by Landau damping. As electron density increases, the calculations exhibit space-charged neutralization and return current formation.

  4. Pulsed-ultraviolet laser Raman diagnostics of plasma processing discharges

    SciTech Connect

    Hargis P.J. Jr.; Greenberg, K.E.

    1988-11-07

    Spontaneous Raman spectroscopy with pulsed-ultraviolet laser excitation of the Stokes vibrational Raman lines was used to measure the percent dissociation of nitrogen and sulfur hexafluoride in low-pressure radio refrequency discharges of the type used for processing semiconductor materials. Measurements of the percent dissociation of sulfur hexafluoride, at pressures between 200 and 600 mTorr, show a strong pressure dependence which is consistent with recombination playing an important role in sulfur hexafluoride discharge kinetics.

  5. An investigation of environmental influence on the creep behavior of a low pressure plasma sprayed NiCoCrAlY alloy

    NASA Technical Reports Server (NTRS)

    Hebsur, M. G.; Miner, R. V.

    1985-01-01

    Low pressure sprayed MCrAlY overlay coatings are currently being used on advanced single crystal superalloy blades for gas turbine engines. Many studies were made on the influence of coatings on the mechanical properties of superalloys in oxidizing or hot-corroding environments, but very few on the properties of the bulk coating alloy itself. The creep behavior of a typical NiCoCrAlY alloyd (PWA 276) was studied in air and vacuum. The as-received low pressure plasma sprayed NiCoCrAlY plates were heat treated for 4 h at 1080 C followed by 32 h at 870 C, the heat treatment applied to coated superalloy parts. Standard creep specimens 12.7 mm long and 3.2 mm in diameter were then machined. Constant load creep-rupture tests were performed in air and vacuum at 650, 850, and 1050 C and various initial stresses. In addition, some specimens were preoxidized at 1050 C for 100 h prior to testing. Results are briefly discussed.

  6. A proposal for dust-ion-acoustic soliton excitation in a discharge plasma

    SciTech Connect

    Abbasi, H.; Pajouh, H. Hakimi

    2009-03-15

    Nonlinear dynamics of disintegration process of a localized perturbation into dust-ion-acoustic (DIA) solitons is studied. The present paper is a theoretical attempt to propose and model the experimental DIA soliton excitation [Y. Nakamura and A. Sarma, Phys. Plasmas 8, 3921 (2001)] in the presence of both superthermal and trapped electrons. The proposal is designed for low-pressure electrical gas discharges that are in nonequilibrium state. In the discharge plasmas, the electron temperature is usually much greater than ion temperature. Thus, the electron distribution function (DF) that in low-pressure discharges is generally non-Maxwellian has to be modeled. For this purpose, the generalized Lorentzian ({kappa})-DF is used to simulate the electron DF. The formalism is derived near the ion-plasma frequency. In this range of frequency, the ion dynamics is considerable and the DIA solitons are the outcome of the disintegration process. Electron trapping is included in the model as the result of positive polarity of the initial potential. A Gaussian initial perturbation is used to model the localized perturbation. It is shown that a slowly varying dynamics of the order of ion motions causes an initial Gaussian perturbation to be, adiabatically, disintegrated to a number of DIA solitons. The disintegration attributes and influence of both trapped and superthermal electrons on this process, are studied.

  7. Numerical investigation of the film uniformity during the surface coating of charged nanoparticles in a low pressure plasma reactor

    NASA Astrophysics Data System (ADS)

    Pourali, N.; Foroutan, G.

    2016-07-01

    The uniformity of film deposition on charged nanoparticles, trapped near the sheath of a capacitively coupled plasma reactor, is studied by numerical simulation of the multi-fluid plasma equations, surface deposition processes, and nanoparticle heating effects. It is found that the anisotropy in the ion flux onto the powered electrode may be hold responsible for the film nonuniformity. The nonuniformity increases with increasing of the particle radius, although small particles lose sphericity faster than the large particles. Because of the electron temperature dependence of the deposition rate and the incident ion flux, higher electron temperatures lead to more nonuniform film deposition. However, the uniformity is improved and the sphericity is restored by the increase in the background gas pressure and/or temperature.

  8. Poly(dimethyl siloxane) surface modification by low pressure plasma to improve its characteristics towards biomedical applications.

    PubMed

    Pinto, S; Alves, P; Matos, C M; Santos, A C; Rodrigues, L R; Teixeira, J A; Gil, M H

    2010-11-01

    Poly(dimethyl siloxane) elastomer, (PDMS) is widely used as a biomaterial. However, PDMS is very hydrophobic and easily colonized by several bacteria and yeasts. Consequently, surface modification has been used to improve its wettability and reduce bacterial adhesion. The aim of this work was to modify the PDMS surface in order to improve its hydrophilicity and bacterial cell repulsion to be used as a biomaterial. Plasma was used to activate the PDMS surface and sequentially promote the attachment of a synthetic surfactant, Pluronic F-68, or a polymer, Poly(ethylene glycol) methyl methacrylate, PEGMA. Bare PDMS, PDMS argon plasma activated, PDMS coated with Pluronic F-68 and PEGMA-grafted PDMS were characterized by contact angle measurements, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The influence of the surface modifications on blood compatibility of the materials was evaluated by thrombosis and haemolysis assays. The cytotoxicity of these materials was tested for mouse macrophages. After modification, AFM results suggest the presence of a distinct layer at the surface and by the contact angle measures it was observed an increase of hydrophilicity. XPS analysis indicates an increase of the oxygen content at the surface as a result of the modification. All the studied materials revealed no toxicity and were found to be non-haemolytic or in some cases slightly haemolytic. Therefore, plasma was found to be an effective technique for the PDMS surface modification. PMID:20638249

  9. Fundamental Study on Filter Effect of Confronting Divergent Magnetic Fields Applied to a Low-Pressure Inductively Coupled Plasma

    NASA Astrophysics Data System (ADS)

    Sugawara, Hirotake

    2015-09-01

    Function of confronting divergent magnetic fields (CDMFs) applied to an inductively coupled plasma called the X-point plasma was investigated. The plasma is driven by a planar spiral rf antenna on the top of a cylindrical chamber. The CDMFs are induced by two coaxial coils with dc currents of opposite directions, and have cusps on their separatrix plane and a magnetic null point at its center. Electron motion in H2 at 1 Pa under the CDMFs was simulated using a Monte Carlo method. Electrons released form the chamber ceiling were captured in the upper region of the chamber by magnetic flux lines running between the ceiling and side wall. However, some of them diffused downward across the separatrix in two ways: passage through the weak magnetic field around the center, and displacement of electron gyrocenters from the upper region to the lower region due to scattering by gas molecules near the outer part of the separatrix. While the former was unselective about electron energy, the latter tended to occur for high-energy electrons with long gyroradii. This position-dependent selectivity in electron passage across the separatrix indicates applicability of the CDMFs as a magnetic filter or shutter. Work supported by JSPS KAKENHI Grant Number 25400528.

  10. Kinetic modeling of evolution of 3 + 1:Resonance enhanced multiphoton ionization plasma in argon at low pressures

    SciTech Connect

    Tholeti, Siva Sashank; Alexeenko, Alina A.; Shneider, Mikhail N.

    2014-06-15

    We present numerical kinetic modeling of generation and evolution of the plasma produced as a result of resonance enhanced multiphoton ionization (REMPI) in Argon gas. The particle-in-cell/Monte Carlo collision (PIC/MCC) simulations capture non-equilibrium effects in REMPI plasma expansion by considering the major collisional processes at the microscopic level: elastic scattering, electron impact ionization, ion charge exchange, and recombination and quenching for metastable excited atoms. The conditions in one-dimensional (1D) and two-dimensional (2D) formulations correspond to known experiments in Argon at a pressure of 5 Torr. The 1D PIC/MCC calculations are compared with the published results of local drift-diffusion model, obtained for the same conditions. It is shown that the PIC/MCC and diffusion-drift models are in qualitative and in reasonable quantitative agreement during the ambipolar expansion stage, whereas significant non-equilibrium exists during the first few 10 s of nanoseconds. 2D effects are important in the REMPI plasma expansion. The 2D PIC/MCC calculations produce significantly lower peak electron densities as compared to 1D and show a better agreement with experimentally measured microwave radiation scattering.

  11. Radiative heat transfer in plasma of pulsed high pressure caesium discharge

    NASA Astrophysics Data System (ADS)

    Lapshin, V. F.

    2016-01-01

    Two-temperature many component gas dynamic model is used for the analysis of features of radiative heat transfer in pulsed high pressure caesium discharge plasma. It is shown that at a sufficiently high pressure the radial optical thickness of arc column is close to unit (τR (λ) ∼ 1) in most part of spectrum. In this case radiative heat transfer has not local character. In these conditions the photons which are emitted in any point of plasma volume are absorbed in other point remote from an emission point on considerable distance. As a result, the most part of the electric energy put in the discharge mainly near its axis is almost instantly redistributed on all volume of discharge column. In such discharge radial profiles of temperature are smooth. In case of low pressure, when discharge plasma is optically transparent for own radiation in the most part of a spectrum (τR(λ) << 1), the emission of radiation without reabsorption takes place. Radiative heat transfer in plasma has local character and profiles of temperature have considerable gradient.

  12. Fundamental study on filter effect of confronting divergent magnetic fields applied to low-pressure inductively coupled plasmas

    NASA Astrophysics Data System (ADS)

    Sugawara, Hirotake; Ogino, So

    2016-07-01

    The electron motion under confronting divergent magnetic fields (CDMFs) applied to inductively coupled plasmas was simulated using a Monte Carlo method. The CDMFs induced by two coaxial dc coils confined electrons in one side of the separatrix of the CDMFs. However, electrons diffused across the separatrix mainly in two ways. One was the displacement of their gyrocenters due to scattering near the outer part of the separatrix. This process tended to occur for high-energy electrons with correspondingly large gyroradii. The other was passage through the weak magnetic field around the center. This process was allowed for low-energy electrons. The position-dependent selectivity about the electron energy was pointed out as a seed property for applications of the separatrix as a magnetic filter or shutter. The mechanism by which the functions of the separatrix emerge was explained from a viewpoint of electron motion under the CDMFs.

  13. Spectral signature of the beam plasma discharge

    NASA Technical Reports Server (NTRS)

    Hallinan, T. J.; Deehr, C. S.; Hoch, E.; Viereck, R.; Bernstein, W.; Konradi, A.

    1988-01-01

    The effect of the beam current on the spectrum of a beam plasma discharge (BPD) in N2 at 50, 100, or 400 microtorr is investigated experimentally in the 2.6-m chamber described by Bernstein et al. (1983). The results are presented graphically and discussed in detail. An increase in the ratio of first positive N2 emissions to first negative N2(+) emissions at BPD onset is shown to disappear at currents above the BPD threshold and is attributed to a large population of suprathermal electrons.

  14. Silane injection in a high-density low-pressure plasma system and its influence on the deposition kinetics and material properties of SiO{sub 2}

    SciTech Connect

    Botha, R.; Haj Ibrahim, B.; Bulkin, P.; Drevillon, B.

    2008-09-15

    High-rate, low temperature deposition is an essential requirement for industrial fabrication technology to be suitable for the deposition of optical and protective coatings. High-density, low-pressure plasmas have received significant attention for such applications due to their ability to create large and controllable ion fluxes onto the substrate. In this study, the high-rate deposition of silica films from a silane and oxygen gas mixture in a high-density plasma system based on a matrix distributed electron cyclotron resonance (MDECR) plasma source is investigated using directional jet injection of undiluted silane. The influence of process parameters such as the microwave power, radio frequency biasing of the substrate holder, and gas flows on the OH content of the oxide films is studied using phase-modulated spectroscopic ellipsometry (SE), Fourier transform infrared (FTIR) spectroscopy, and transmission measurements. The results of the measurements, taken at various points across the wafer, show a decrease in the thickness-normalized OH concentration in the areas of higher deposition rates. The corresponding gas phase composition is investigated using optical emission spectroscopy and compared to the FTIR, transmission and SE measurement results in order to validate our findings and ultimately optimize the deposition process. It is found that the primary silane flux onto the surface, which depends on the positioning of the jet injection point and gas flow rate, plays an important role not only on the deposition rate but also on the OH content of the films. The authors conclude that high-density plasma deposition systems such as the MDECR plasma enhanced chemical vapor deposition system cannot be considered as well mixed for gases with dissociation products that have high sticking coefficients, contrary to the accepted paradigm.

  15. Modelling of RF Discharge in Argon Plasma

    SciTech Connect

    Jelinek, P.; Virostko, P.; Hubicka, Z.; Bartos, P.

    2007-12-26

    An one-dimensional hybrid model of RF discharge in low-temperature argon plasma is presented in our paper. The hybrid model consists of two parts--particle model which simulates fast electrons while fluid model simulates slow electrons and positive argon ions. In the particle model the positions and velocities of fast electrons are calculated by means of deterministic Verlet algorithm while the collision processes are treated by the stochastic way. For the solution of fluid equations, for slow electrons and positive argon ions, the Scharfetter-Gummel exponential algorithm was used. Typical results of our calculations presented in this paper are total RF current and RF voltage waveforms on the planar substrate immersed into argon plasma. The next results which can be found here are the ion, electron and displacement current waveforms on the substrate. Especially, the knowledge of waveform of the ion current is very important for experimental physicists during the deposition of thin films.

  16. Surface loss probability of atomic hydrogen for different electrode cover materials investigated in H₂-Ar low-pressure plasmas

    SciTech Connect

    Sode, M. Schwarz-Selinger, T.; Jacob, W.; Kersten, H.

    2014-07-07

    In an inductively coupled H₂-Ar plasma at a total pressure of 1.5 Pa, the influence of the electrode cover material on selected line intensities of H, H₂, and Ar are determined by optical emission spectroscopy and actinometry for the electrode cover materials stainless steel, copper, tungsten, Macor{sup ®}, and aluminum. Hydrogen dissociation degrees for the considered conditions are determined experimentally from the measured emission intensity ratios. The surface loss probability β{sub H} of atomic hydrogen is correlated with the measured line intensities, and β{sub H} values are determined for the considered materials. Without the knowledge of the atomic hydrogen temperature, β{sub H} cannot be determined exactly. However, ratios of β{sub H} values for different surface materials are in first order approximation independent of the atomic hydrogen temperature. Our results show that β{sub H} of copper is equal to the value of stainless steel, β{sub H} of Macor{sup ®} and tungsten is about 2 times smaller and β{sub H} of aluminum about 5 times smaller compared with stainless steel. The latter ratio is in reasonable agreement with literature. The influence of the atomic hydrogen temperature T{sub H} on the absolute value is thoroughly discussed. For our assumption of T{sub H}=600 K, we determine a β{sub H} for stainless steel of 0.39±0.13.

  17. Emission characteristics and parameters of gas-discharge plasma in mixtures of heavy inert gases with chlorine

    NASA Astrophysics Data System (ADS)

    Shuaibov, A. K.; Malinin, A. N.

    2009-04-01

    The ultraviolet (UV) radiation from longitudinal glow-discharge plasma in three- and four-component mixtures of argon, krypton, and xenon with chlorine has been investigated. The total radiation of Ar, Kr, and Xe monochlorides and chlorine molecules in the spectral range 170-310 nm has been optimized with respect to the composition and the pressure of gas mixtures, as well as the discharge current. The mean output power, the electric power of discharge, and the efficiency of a broadband low-pressure exciplex halogen lamp have been determined. Parameters of the glow discharge in Ar-Kr-Cl2 and Kr-Xe-Cl2 mixtures have been simulated numerically. The electron energy distribution functions have been determined through the solution of the Boltzmann kinetic equation. These functions have been used to calculate the plasma parameters, namely, electron transfer characteristics, specific losses of discharge power for electronic processes, and ionization and attachment coefficients.

  18. Extended dielectric relaxation scheme for fluid transport simulations of high density plasma discharges

    NASA Astrophysics Data System (ADS)

    Kwon, Deuk-Chul; Song, Mi-Young; Yoon, Jung-Sik

    2014-10-01

    It is well known that the dielectric relaxation scheme (DRS) can efficiently overcome the limitation on the simulation time step for fluid transport simulations of high density plasma discharges. By imitating a realistic and physical shielding process of electric field perturbation, the DRS overcomes the dielectric limitation on time step. However, the electric field was obtained with assuming the drift-diffusion approximation. Although the drift-diffusion expressions are good approximations for both the electrons and ions at high pressure, the inertial term cannot be neglected in the ion momentum equation for low pressure. Therefore, in this work, we developed the extended DRS by introducing an effective electric field. To compare the extended DRS with the previous method, two-dimensional fluid simulations for inductively coupled plasma discharges were performed. This work was supported by the Industrial Strategic Technology Development Program (10041637, Development of Dry Etch System for 10 nm class SADP Process) funded by the Ministry of Knowledge Economy (MKE, Korea).

  19. Radical and ion molecule mechanisms in the polymerization of hydrocarbons and chlorosilanes in RF plasmas at low pressures ( 1.0 torr)

    NASA Technical Reports Server (NTRS)

    Avni, R.; Carmi, U.; Inspektor, A.; Rosenthal, I.

    1984-01-01

    The ion-molecule and the radical-molecule mechanisms are responsible for the dissociation of hydrocarbons, and chlorosilane monomers and the formation of polymerized species, respectively, in the plasma state of a RF discharge. In the plasma, of a mixture of monomer with Ar, the rate determining step for both dissociation and polymerization is governed by an ion-molecular type interaction. Additions of H2 or NH3 to the monomer Ar(+) mixture transforms the rate determining step from an ion-molecular interaction to a radical-molecule type interaction for both monomer dissociation and polymerization processes.

  20. Self-energized plasma compressor. [for compressing plasma discharged from coaxial plasma generator

    NASA Technical Reports Server (NTRS)

    Shriver, E. L.; Igenbergs, E. B. (Inventor)

    1974-01-01

    The self-energized plasma compressor is described which compresses plasma discharged from a coaxial plasma generator. The device includes a helically shaped coil which is coaxially aligned with the center axis of the coaxial plasma generator. The plasma generator creates a current through the helical coil which, in turn, generates a time varying magnetic field that creates a force which acts radially upon the plasma. The coaxial plasma generator and helical coil move the plasma under high pressure and temperature to the narrow end of the coil. Positioned adjacent to the narrow end of the coil are beads which are engaged by the plasma to be accelerated to hypervelocities for simulating meteoroids.

  1. Modification of surface properties of polyethylene by Ar plasma discharge

    NASA Astrophysics Data System (ADS)

    Švorčík, V.; Kotál, V.; Slepička, P.; Bláhová, O.; Špírková, M.; Sajdl, P.; Hnatowicz, V.

    2006-03-01

    Polyethylene (PE) surface was modified by Ar plasma discharge. The changes of surface morphology and surface wettability (characterized by contact angle) were followed using AFM microscopy and standard goniometry, respectively. The changes of chemical structure of PE polymeric chain were characterized by FTIR and XPS techniques. A nanoindenter was used to study mechanical properties (microhardness, elasticity module and microscratch test) of modified PE. After exposition to the plasma discharge a fast decline of the contact angle is observed. The decline depends on the discharge power and the time elapsed from the plasma exposition. FTIR and XPS measurements indicate an oxidation of degraded polymeric chains and creation of hydroxyl, carbonyl, ether, ester and carboxyl groups. Surface morphology of modified PE depends on the plasma discharge power and exposure time. Maximum microhardness and elastic module, observed on PE specimens exposed to plasma discharge for 240 s, may be connected with PE crosslinking initiated by plasma discharge.

  2. Autonomous Method and System for Minimizing the Magnitude of Plasma Discharge Current Oscillations in a Hall Effect Plasma Device

    NASA Technical Reports Server (NTRS)

    Hruby, Vladimir (Inventor); Demmons, Nathaniel (Inventor); Ehrbar, Eric (Inventor); Pote, Bruce (Inventor); Rosenblad, Nathan (Inventor)

    2014-01-01

    An autonomous method for minimizing the magnitude of plasma discharge current oscillations in a Hall effect plasma device includes iteratively measuring plasma discharge current oscillations of the plasma device and iteratively adjusting the magnet current delivered to the plasma device in response to measured plasma discharge current oscillations to reduce the magnitude of the plasma discharge current oscillations.

  3. Usefulness of Magnetic Neutral Loop Discharge Plasma in Plasma Processing

    NASA Astrophysics Data System (ADS)

    Tsuboi, Hideo; Itoh, Masahiro; Tanabe, Masafumi; Hayashi, Toshio; Uchida, Taijiro

    1995-05-01

    Usefulness in plasma processing is demonstrated for a plasma produced in a closed magnetic neutral loop, which consists of zero magnetic field points connected continuously. A preliminary experiment was carried out to show the advantage of magnetic neutral loop discharge (NLD) plasma in sputter etching processing of SiO2/Si wafer in the lower Ar gas pressure range. The experiment shows that a high-density plasma was obtained for Ar gas lower than 0.1 Pa and the sputter etching rate is 3 times higher than that for the usual inductively coupled plasma (ICP). In a large-loop case, the sputter etching profile obtained has a peak at a radius along the azimuthal direction. This implies that a uniform etching profile could be realized by controlling the radius of the neutral loop during process operation. The NLD plasma current induced with an rf primary one-turn antenna coil reaches up to one-third of that of the primary.

  4. Excitation mechanisms in 1 mJ picosecond laser induced low pressure He plasma and the resulting spectral quality enhancement

    SciTech Connect

    Idris, Nasrullah; Lahna, Kurnia; Abdulmadjid, Syahrun Nur; Ramli, Muliadi; Suyanto, Hery; Marpaung, Alion Mangasi; Pardede, Marincan; Jobiliong, Eric; Hedwig, Rinda; Lie, Zener Sukra; Lie, Tjung Jie; Kurniawan, Koo Hendrik; Tjia, May On

    2015-06-14

    We report in this paper the results of an experimental study on the spectral and dynamical characteristics of plasma emission induced by 1 mJ picoseconds (ps) Nd-YAG laser using spatially resolved imaging and time resolved measurement of the emission intensities of copper sample. This study has provided the experimental evidence concerning the dynamical characteristics of the excitation mechanisms in various stages of the plasma formation, which largely consolidate the basic scenarios of excitation processes commonly accepted so far. However, it is also clearly shown that the duration of the shock wave excitation process induced by ps laser pulses is much shorter than those observed in laser induced breakdown spectroscopy employing nanosecond laser at higher output energy. This allows the detection of atomic emission due exclusively to He assisted excitation in low pressure He plasma by proper gating of the detection time. Furthermore, the triplet excited state associated with He I 587.6 nm is shown to be the one most likely involved in the process responsible for the excellent spectral quality as evidenced by its application to spectrochemical analysis of a number of samples. The use of very low energy laser pulses also leads to minimal destructive effect marked by the resulted craters of merely about 10 μm diameter and only 10 nm deep. It is especially noteworthy that the excellent emission spectrum of deuterium detected from D-doped titanium sample is free of spectral interference from the undesirable ubiquitous water molecules without a precleaning procedure as applied previously and yielding an impressive detection limit of less than 10 μg/g. Finally, the result of this study also shows a promising application to depth profiling of impurity distribution in the sample investigated.

  5. Enhancement of laser-induced breakdown spectroscopy (LIBS) Detection limit using a low-pressure and short-pulse laser-induced plasma process.

    PubMed

    Wang, Zhen Zhen; Deguchi, Yoshihiro; Kuwahara, Masakazu; Yan, Jun Jie; Liu, Ji Ping

    2013-11-01

    Laser-induced breakdown spectroscopy (LIBS) technology is an appealing technique compared with many other types of elemental analysis because of the fast response, high sensitivity, real-time, and noncontact features. One of the challenging targets of LIBS is the enhancement of the detection limit. In this study, the detection limit of gas-phase LIBS analysis has been improved by controlling the pressure and laser pulse width. In order to verify this method, low-pressure gas plasma was induced using nanosecond and picosecond lasers. The method was applied to the detection of Hg. The emission intensity ratio of the Hg atom to NO (IHg/INO) was analyzed to evaluate the LIBS detection limit because the NO emission (interference signal) was formed during the plasma generation and cooling process of N2 and O2 in the air. It was demonstrated that the enhancement of IHg/INO arose by decreasing the pressure to a few kilopascals, and the IHg/INO of the picosecond breakdown was always much higher than that of the nanosecond breakdown at low buffer gas pressure. Enhancement of IHg/INO increased more than 10 times at 700 Pa using picosecond laser with 35 ps pulse width. The detection limit was enhanced to 0.03 ppm (parts per million). We also saw that the spectra from the center and edge parts of plasma showed different features. Comparing the central spectra with the edge spectra, IHg/INO of the edge spectra was higher than that of the central spectra using the picosecond laser breakdown process. PMID:24160875

  6. Novel approach to produce polymerized hydrocarbon coatings using dielectric barrier controlled atmospheric pressure glow discharge plasma

    NASA Astrophysics Data System (ADS)

    Mishra, K. K.; Khardekar, R. K.; Singh, Rashmi; Pant, H. C.

    2002-09-01

    Conventionally, low-pressure (<1 Torr) electrical discharges are used for material processing and thin-film deposition. These schemes suffer mainly due to the high cost of equipment and the complexity of operations. The atmospheric pressure glow discharge plasma is developed using a threaded styled electrode in different configurations, and these reactors are used to produce plasma polymerized coatings, required on plane substrates as self-supporting films to obtain membranes for blocking holes in cavities, and on microballoon targets, which are used as fuel containers for inertial confinement fusion, to avoid DT gas permeation. Helium gas is used as the supporting gas for formation and stabilization of atmospheric pressure glow discharge plasma reactors. Ethylene and acetylene gases are used as monomers to produce plasma polymerized hydrocarbon films. These films are characterized using scanning electron microscopy. Plasma polymerized coatings of thickness 100 nm-10 μm with a smooth surface finish (rms<100 nm) are deposited successfully. The surface finish is further improved using a postdischarge configuration. Preliminary results are very encouraging but further progress is to be made in this area. We are also planning to extend this technique for C:H coating of microballoons, which are used as fuel containers in inertial confinement fusion.

  7. Excitation Energy Transfer of Metastable Krypton Atoms in Kr-He-Xe Low Pressure Glow Discharge for Mercury-Free Lighting

    NASA Astrophysics Data System (ADS)

    Hwang, Hyeon Seok; Baik, Hong Koo; Park, Ki Wan; Song, Kie Moon; Jong Lee, Se

    2010-08-01

    The discharge of the gas mixture Kr-He-Xe was investigated as a source of vacuum ultraviolet for lighting purposes. The discharge characteristics of the Xe-He-Kr gas mixture were enhanced in comparison to those of Xe and a Xe-He gas mixture. The experimental results were evaluated by the infrared radiation from the positive column. The amount of infrared radiation under optimum conditions displayed higher efficiency than that of the He-Xe gas mixture, which results in the improved efficacy of lamp. This result was due to the emission properties that were improved by the potential energy transferred from the excited Kr to the Xe.

  8. Influence of dust-particle concentration on gas-discharge plasma

    SciTech Connect

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

    2010-01-15

    A self-consistent kinetic model of a low-pressure dc glow discharge with dust particles based on Boltzmann equation for the electron energy distribution function is presented. The ions and electrons production in ionizing processes as well as their recombination on the dust-particle surface and on the discharge tube wall were taken into account. The influence of dust-particle concentration N{sub d} on gas discharge and dust particles parameters was investigated. It is shown that the increase of N{sub d} leads to the increase of an averaged electric field and ion density, and to the decrease of a dust-particle charge and electron density in the dusty cloud. The results were obtained in a wide region of different discharge and dusty plasma parameters: dust particles density 10{sup 2}-10{sup 8} cm{sup -3}, discharge current density 10{sup -1}-10{sup 1} mA/cm{sup 2}, and dust particles radius 1, 2, and 5 mum. The scaling laws for dust-particle surface potential and electric filed dependencies on dust-particle density, particle radius and discharge currents were revealed. It is shown that the absorption of electrons and ions on the dust particles surface does not lead to the electron energy distribution function depletion due to a self-consistent adjustment of dust particles and discharge parameters.

  9. The effect of the operation modes of a gas discharge low-pressure amalgam lamp on the intensity of generation of 185 nm UV vacuum radiation

    SciTech Connect

    Vasilyak, L. M.; Drozdov, L. A. Kostyuchenko, S. V.; Sokolov, D. V.; Kudryavtsev, N. N.; Sobur, D. A.

    2011-12-15

    The effect of the discharge current, mercury vapor pressure, and the inert gas pressure on the intensity and efficiency of the 185 nm line generation are considered. The spectra of the UV radiation (vacuum ultraviolet) transmission by protective coatings from the oxides of rare earth metals and aluminum are investigated.

  10. Correlations between plasma variables and the deposition process of Si films from chlorosilanes in low pressure RF plasma of argon and hydrogen

    NASA Technical Reports Server (NTRS)

    Avni, R.; Carmi, U.; Grill, A.; Manory, R.; Grossman, E.

    1984-01-01

    The dissociation of chlorosilanes to silicon and its deposition on a solid substrate in a RF plasma of mixtures of argon and hydrogen were investigated as a function of the macrovariables of the plasma. The dissociation mechanism of chlorosilanes and HCl as well as the formation of Si in the plasma state were studied by sampling the plasma with a quadrupole mass spectrometer. Macrovariables such as pressure, net RF power input and locations in the plasma reactor strongly influence the kinetics of dissociation. The deposition process of microcrystalline silicon films and its chlorine contamination were correlated to the dissociation mechanism of chlorosilanes and HCl.

  11. Properties of corona discharge plasma near metal surface

    NASA Astrophysics Data System (ADS)

    Lavrinenko, M.; Biktashev, E.; Kirko, D.

    2016-01-01

    Properties of corona discharge near metallic surface were researched. Electrical oscillations in discharge plasma of 1 kHz - 100 MHz rate were registered. Spectrum of electrical oscillations in this range was obtained. Possible plasma waves for observed electronic oscillations explanation are discussed.

  12. Absorption spectroscopy measurements of argon metastable and resonant atom density in atmospheric pressure Ar-He surface-wave plasmas using a low pressure lamp

    SciTech Connect

    Munoz, J.; Margot, J.; Calzada, M. D.

    2012-01-15

    The densities of metastable and resonant atom were measured in atmospheric pressure Ar-He surface-wave plasmas. Measurements were performed using an absorption spectroscopy method taking into account the Voigt profiles of the plasma lines. The density values of the argon {sup 3}P{sub 2}, {sup 3}P{sub 0} (metastable atoms) and {sup 3}P{sub 1} (resonant atoms) levels measured in pure argon discharges are in good agreement with those reported in the literature. A drastic decrease of metastable and resonant densities is observed when introducing helium in amounts as low as 2%. The influence of electron density and gas temperature on the population mechanisms (direct electron excitation from the ground state and dissociative recombination) of metastable and resonant atoms is discussed using a simplified theoretical model.

  13. Measurements of Nitric Oxide in a Plasma Generated by a Variable-Width, Constant Energy Discharge

    NASA Astrophysics Data System (ADS)

    Burnette, David; Adamovich, Igor; Lempert, Walter; Non-equilibrium Thermodynamics Laboratory Team

    2014-10-01

    A diffuse plasma filament within a low pressure sphere gap was generated using a high voltage, solid state switch. For a constant pressure and overvoltage, the peak current and voltage drop were altered by a change in the ballast resistor while a simultaneous adjustment to the variable pulse width was used to maintain a constant pulse energy. The discharge parameters were chosen to result in a quasi-steady state discharge with near constant current and very little change in size and uniformity for each condition studied. The absolute density and temporal evolution of nitric oxide (NO) was measured via laser-induced fluorescence for each condition. The effect of the pulse characteristics and estimated E/N on the formation of NO are discussed.

  14. Operation of Ferroelectric Plasma Sources in a Gas Discharge Mode

    SciTech Connect

    A. Dunaevsky; N.J. Fisch

    2004-03-08

    Ferroelectric plasma sources in vacuum are known as sources of ablative plasma, formed due to surface discharge. In this paper, observations of a gas discharge mode of operation of the ferroelectric plasma sources (FPS) are reported. The gas discharge appears at pressures between approximately 20 and approximately 80 Torr. At pressures of 1-20 Torr, there is a transition from vacuum surface discharge to the gas discharge, when both modes coexist and the surface discharges sustain the gas discharge. At pressures between 20 and 80 Torr, the surface discharges are suppressed, and FPS operate in pure gas discharge mode, with the formation of almost uniform plasma along the entire surface of the ceramics between strips. The density of the expanding plasma is estimated to be about 1013 cm-3 at a distance of 5.5 mm from the surface. The power consumption of the discharge is comparatively low, making it useful for various applications. This paper also presents direct measurements of the yield of secondary electron emission from ferroelectric ceramics, which, at low energies of primary electrons, is high and dependent on the polarization of the ferroelectric material

  15. Simulation of DBD plasma actuators, and nanoparticle-plasma interactions in argon-hydrogen CCP RF discharges

    NASA Astrophysics Data System (ADS)

    Mamunuru, Meenakshi

    The focus of this work is modeling and simulation of low temperature plasma discharges (LTPs). The first part of the thesis consists of the study of dielectric barrier (DBD) plasma actuators. Use of DBD plasma actuators on airfoil surfaces is a promising method for increasing airfoil efficiency. Actuators produce a surface discharge that causes time averaged thrust in the neutral gas. The thrust modifies the boundary layer properties of the flow and prevents the occurrence of separation bubbles. In simulating the working of an actuator, the focus is on the spatial characteristics of the thrust produced by the discharge over very short time and space scales. The results provide an understanding of the causes of thrust, and the basic principles behind the actuator operation. The second part of this work focusses on low pressure plasma discharges used for silicon nanoparticle synthesis. When reactive semiconductor precursor gases are passed through capacitively coupled plasma (CCP) radio frequency (RF) reactors, nano sized particles are formed. When the reactors are operated at high enough powers, a very high fraction of the nanoparticles are crystallized in the chamber. Nanoparticle crystallization in plasma is a very complex process and not yet fully understood. It can be inferred from experiments that bulk and surface processes initiated due to energetic ion impaction of the nanoparticles are responsible for reordering of silicon atoms, causing crystallization. Therefore, study of plasma-particle interactions is the first step towards understanding how particles are crystallized. The specific focus of this work is to investigate the experimental evidence that hydrogen gas presence in argon discharges used for silicon nanocrystal synthesis, leads to a superior quality of nanocrystals. Influence of hydrogen gas on plasma composition and discharge characteristics is studied. Via Monte Carlo simulation, distribution of ion energy impacting particles surface is studied

  16. Characterization of a low-pressure chlorine plasma column sustained by propagating surface waves using phase-sensitive microwave interferometry and trace-rare-gas optical emission spectroscopy

    SciTech Connect

    Mattei, S.; Boudreault, O.; Stafford, L.; Khare, R.; Donnelly, V. M.

    2011-06-01

    Phase-sensitive microwave interferometry and trace-rare-gas optical emission spectroscopy were used to measure the line-integrated electron density, n{sub e}, and electron temperature, T{sub e}, in a high-density chlorine plasma sustained in a quartz discharge tube (inner diameter = 6 mm) by an electromagnetic surface wave at 2.45 GHz. For pressures in the 0.1-1 Torr range, n{sub e} decreased nearly linearly along the tube's z-axis down to the critical density for surface wave propagation, where the plasma decayed abruptly. At lower pressures (< 50 mTorr), however, the plasma extended well beyond this critical point, after which n{sub e} decreased quasiexponentially toward the end of the plasma column. The length of this expansion region increased with decreasing pressure, going from {approx}8 cm at 5 mTorr to {approx}1 cm at 50 mTorr. T{sub e} was nearly independent of the axial position in the main plasma region and strongly decreased in the expansion region at lower pressures. The Cl{sub 2} percent dissociation, {tau}{sub D}, obtained from the calibrated Cl{sub 2} (306 nm)-to-Xe (828 nm) emission ratio, displayed behavior similar to that of n{sub e} and T{sub e}. For example, at 5 mTorr, {tau}{sub D} was close to 100% near the wave launcher and {approx}70% at 0.5 cm from the end of the plasma column.

  17. 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.

  18. 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.

  19. Energy and matter flows in a plasma focus discharge

    NASA Astrophysics Data System (ADS)

    Vikhrev, V. V.; Suslin, S. V.

    2016-01-01

    The Plasma Focus is a type of z-pinch that is widely used for both basic research and applied tasks, e.g., as materials modification or research on intense plasma flows. Although the basic mechanisms of z-pinch compression are well-known, many of the processes that occur in the plasma focus have received less attention. This article is devoted to the study of plasma jets and some of its consequences in plasma focus discharges.

  20. Numerical investigation of the effect of driving voltage pulse shapes on the characteristics of low-pressure argon dielectric barrier discharge

    SciTech Connect

    Eslami, E. Barjasteh, A.; Morshedian, N.

    2015-06-15

    In this work, we numerically compare the effect of a sinusoidal, triangular, and rectangular pulsed voltage profile on the calculated particle production, electric current, and gas voltage in a dielectric barrier discharge. The total argon gas pressure of 400 Pa, the distance between dielectrics of 5 mm, the dielectric thickness of 0.7 mm, and the temperature of T = 300 K were considered as input parameters. The different driving voltage pulse shapes (triangular, rectangular, and sinusoidal) are considered as applied voltage with a frequency of 7 kHz and an amplitude of 700 V peak to peak. It is shown that applying a rectangular voltage, as compared with a sinusoidal or triangle voltage, increases the current peak, while the peak width is decreased. Higher current density is related to high production of charged particles, which leads to the generation of some highly active species, such as Ar* (4s level), and Ar** (4p level) in the gap.

  1. Spectroscopic and microscopic studies of self-assembled nc-Si/a-SiC thin films grown by low pressure high density spontaneous plasma processing.

    PubMed

    Das, Debajyoti; Kar, Debjit

    2014-12-14

    In view of suitable applications in the window layer of nc-Si p-i-n solar cells in superstrate configuration, the growth of nc-Si/a-SiC composite films was studied, considering the trade-off relation between individual characteristics of its a-SiC component to provide a wide optical-gap and electrically conducting nc-Si component to simultaneously retain enough crystalline linkages to facilitate proper crystallization to the i-nc-Si absorber-layer during its subsequent growth. Self-assembled nc-Si/a-SiC thin films were spontaneously grown by low-pressure planar inductively coupled plasma CVD, operating in electromagnetic mode, providing high atomic-H density. Spectroscopic simulations of ellipsometry and Raman data, and systematic chemical and structural analysis by XPS, TEM, SEM and AFM were performed. Corresponding to optimized inclusion of C essentially incorporated as Si-C bonds in the network, the optical-gap of the a-SiC component widened, void fraction including the incubation layer thickness reduced. While the bulk crystallinity decreased only marginally, Si-ncs diminished in size with narrower distribution and increased number density. With enhanced C-incorporation, formation of C-C bonds in abundance deteriorates the Si continuous bonding network and persuades growth of an amorphous dominated silicon-carbon heterostructure containing high-density tiny Si-ncs. Stimulated nanocrystallization identified in the Si-network, induced by a limited amount of carbon incorporation, makes the material most suitable for applications in nc-Si solar cells. The novelty of the present work is to enable spontaneous growth of self-assembled superior quality nc-Si/a-SiC thin films and simultaneous spectroscopic simulation-based optimization of properties for utilization in devices. PMID:25342429

  2. Sterilization characteristics of dental instruments using oxygen plasma produced by narrow gap RF discharge

    NASA Astrophysics Data System (ADS)

    Sakai, Yasuhiro; Liu, Zhen; Goto, Masaaki; Hayashi, Nobuya

    2016-07-01

    Sterilization characteristics and material compatibility of low-pressure RF oxygen plasma sterilization method for dental instruments are investigated. Regarding the characteristics of the plasma sterilizer for dental instruments, it is small and can rapidly sterilize owing to a narrow gap discharge. Sterilization of vial-type biological indicators is achieved for the shortest treatment period of 40 min at an RF power of 80 W at a temperature of 70 °C. At a temperature lower than 60 °C, a sterilization period of 90 min is required using a water-cooled electrode. No surface modifications of dental instruments such as chemical composition and deterioration of fine crystals of a diamond bar were observed under a scanning electron microscope.

  3. Indirect determination of the electric field in plasma discharges using laser-induced fluorescence spectroscopy

    SciTech Connect

    Vaudolon, J. Mazouffre, S.

    2014-09-15

    The evaluation of electric fields is of prime interest for the description of plasma characteristics. In this work, different methods for determining the electric field profile in low-pressure discharges using one- and two-dimensional Laser-Induced Fluorescence (LIF) measurements are presented and discussed. The energy conservation, fluid, and kinetic approaches appear to be well-suited for the electric field evaluation in this region of the plasma flow. However, the numerical complexity of a two-dimensional kinetic model is penalizing due to the limited signal-to-noise ratio that can be achieved, making the computation of the electric field subject to large error bars. The ionization contribution which appears in the fluid model makes it unattractive on an experimental viewpoint. The energy conservation and 1D1V kinetic approaches should therefore be preferred for the determination of the electric field when LIF data are used.

  4. Effect of neutral gas heating on the wave magnetic fields of a low pressure 13.56 MHz planar coil inductively coupled argon discharge

    SciTech Connect

    Jayapalan, Kanesh K. Chin, Oi-Hoong

    2014-04-15

    The axial and radial magnetic field profiles in a 13.56 MHz (radio frequency) laboratory 6 turn planar coil inductively coupled plasma reactor are simulated with the consideration of the effect of neutral gas heating. Spatially resolved electron densities, electron temperatures, and neutral gas temperatures were obtained for simulation using empirically fitted electron density and electron temperature and heuristically determined neutral gas temperature. Comparison between simulated results and measured fields indicates that neutral gas heating plays an important role in determining the skin depth of the magnetic fields.

  5. High efficiency ionizer using a hollow cathode discharge plasma

    SciTech Connect

    Alessi, J.G.; Prelec, K.

    1984-01-01

    A proposal for an ionizer using a hollow cathode discharge plasma is described. Ionization is via the very high current density electron beam component in the plasma, as well as from charge exchange with plasma ions. Extraction of a He/sup +/ current corresponding to approximately 50% of the incoming atomic beam flux should be possible.

  6. Stabilizing effect of plasma discharge on bubbling fluidized granular bed

    NASA Astrophysics Data System (ADS)

    Hu, Mao-Bin; Dang, Sai-Chao; Ma, Qiang; Xia, Wei-Dong

    2015-07-01

    Fluidized beds have been widely used for processing granular materials. In this paper, we study the effect of plasma on the fluidization behavior of a bubbling fluidized bed with an atmospheric pressure plasma discharger. Experiment results show that the bubbling fluidized bed is stabilized with the discharge of plasma. When the discharge current reaches a minimum stabilization current Cms, air bubbles in the bed will disappear and the surface fluctuation is completely suppressed. A simplified model is proposed to consider the effect of electric Coulomb force generated by the plasma. It is found that the Coulomb force will propel the particles to move towards the void area, so that the bubbling fluidized bed is stabilized with a high enough plasma discharge. Project supported by the National Natural Science Foundation of China (Grant Nos. 11035005 and 11034010).

  7. Achieving an intense enough maintenance electric field in a low-pressure discharge sustained by a microwave field under ambipolar diffusion regime such that periodic parametric instabilities are generated

    NASA Astrophysics Data System (ADS)

    Moisan, M.; Nowakowska, H.

    2015-11-01

    The intensity of the maintenance electric field of a given discharge is one of its internal parameters. Under ambipolar diffusion conditions, it is almost exclusively set by particle losses, which are related to the dimensions of the discharge vessel and to the gas pressure, and ultimately are determined by the electron energy distribution function. For instance, raising the density of microwave power absorbed in a discharge tube essentially increases the electron density without much increasing the amplitude of the maintenance E-field. To raise the intensity of this E-field in such a case, one needs to reduce the volume into which electromagnetic power is absorbed relative to the diffusion volume, i.e. the volume within which electrons transfer their power through collisions with heavy particles. To show this point, we consider a power balance based on the power lost per electron through collisions with heavy particles, θ L, to the power absorbed (over a period of the microwave field) per electron in the discharge, θ A. The power θ A, which depends on E02 , the square of the amplitude (intensity) of the maintenance electric field, adjusts to compensate for the power lost θ L. The analysis presented is achieved for a particular microwave discharge configuration that is known to provide an intense E 0-field, which means x  ⩾  λ De, where x is the oscillation amplitude of electrons in the E 0-field and λ De the electron Debye length. Such a condition allows one to observe periodic parametric instabilities at, or close to, the electron-plasma frequency f pe and at their corresponding ion-plasma frequency f pi, these oscillations being caused by the simultaneous propagation of an electron-plasma wave and an ion-plasma wave in the discharge as a result of an applied ‘pump’ power, which also sustains the discharge. A 2D hydrodynamic calculation of the specific plasma discharge system is performed, which yields the value of the x/λ De ratio in

  8. Control of plasma properties in capacitively coupled oxygen discharges via the electrical asymmetry effect

    NASA Astrophysics Data System (ADS)

    Schüngel, E.; Zhang, Q.-Z.; Iwashita, S.; Schulze, J.; Hou, L.-J.; Wang, Y.-N.; Czarnetzki, U.

    2011-07-01

    Using a combined experimental, numerical and analytical approach, we investigate the control of plasma properties via the electrical asymmetry effect (EAE) in a capacitively coupled oxygen discharge. In particular, we present the first experimental investigation of the EAE in electronegative discharges. A dual-frequency voltage source of 13.56 MHz and 27.12 MHz is applied to the powered electrode and the discharge symmetry is controlled by adjusting the phase angle θ between the two harmonics. It is found that the bulk position and density profiles of positive ions, negative ions, and electrons have a clear dependence on θ, while the peak densities and the electronegativity stay rather constant, largely due to the fact that the time-averaged power absorption by electrons is almost independent of θ. This indicates that the ion flux towards the powered electrode remains almost constant. Meanwhile, the dc self-bias and, consequently, the sheath widths and potential profile can be effectively tuned by varying θ. This enables a flexible control of the ion bombarding energy at the electrode. Therefore, our work proves the effectiveness of the EAE to realize separate control of ion flux and ion energy in electronegative discharges. At low pressure, the strength of resonance oscillations, which are found in the current of asymmetric discharges, can be controlled with θ.

  9. 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

  10. Discharge conditions for CW and pulse-modulated surface-wave plasmas in low-temperature sterilization

    NASA Astrophysics Data System (ADS)

    Xu, L.; Terashita, F.; Nonaka, H.; Ogino, A.; Nagata, T.; Koide, Y.; Nanko, S.; Kurawaki, I.; Nagatsu, M.

    2006-01-01

    The discharge conditions required for low-temperature plasma sterilization were investigated using low-pressure surface-wave plasma (SWP). The discharge conditions for both continuous wave (CW) and pulse-modulated SWPs in low-temperature sterilization of Geobacillus stearothermophilus with a population of 1.5 × 106 and 3.0 × 106 were studied by varying the microwave input power from 500 W to 3 kW, and the effective plasma treatment time from 40 to 300 s. Results showed that sterilization was possible in a shorter treatment time using a higher microwave power for both CW and pulse-modulated SWPs. Pulse-modulated SWPs gave effective sterilization at a temperature roughly 10 to 20 °C below that of CW SWPs under the same average microwave power.

  11. Direct current dielectric barrier assistant discharge to get homogeneous plasma in capacitive coupled discharge

    SciTech Connect

    Du, Yinchang; Li, Yangfang; Cao, Jinxiang; Liu, Yu; Wang, Jian; Zheng, Zhe

    2014-06-15

    In this paper, we propose a method to get more homogeneous plasma in the geometrically asymmetric capacitive coupled plasma (CCP) discharge. The dielectric barrier discharge (DBD) is used for the auxiliary discharge system to improve the homogeneity of the geometrically asymmetric CCP discharge. The single Langmuir probe measurement shows that the DBD can increase the electron density in the low density volume, where the DBD electrodes are mounted, when the pressure is higher than 5 Pa. By this manner, we are able to improve the homogeneity of the plasma production and increase the overall density in the target volume. At last, the finite element simulation results show that the DC bias, applied to the DBD electrodes, can increase the homogeneity of the electron density in the CCP discharge. The simulation results show a good agreement with the experiment results.

  12. Multifunctional bulk plasma source based on discharge with electron injection

    SciTech Connect

    Klimov, A. S.; Medovnik, A. V.; Tyunkov, A. V.; Savkin, K. P.; Shandrikov, M. V.; Vizir, A. V.

    2013-01-15

    A bulk plasma source, based on a high-current dc glow discharge with electron injection, is described. Electron injection and some special design features of the plasma arc emitter provide a plasma source with very long periods between maintenance down-times and a long overall lifetime. The source uses a sectioned sputter-electrode array with six individual sputter targets, each of which can be independently biased. This discharge assembly configuration provides multifunctional operation, including plasma generation from different gases (argon, nitrogen, oxygen, acetylene) and deposition of composite metal nitride and oxide coatings.

  13. Enhanced Discharge Performance in a Ring Cusp Plasma Source

    NASA Technical Reports Server (NTRS)

    Foster, John E.; Patterson, Michael J.

    2000-01-01

    There is a need for a lightweight, low power ion thruster for space science missions. Such an ion thruster is under development at NASA Glenn Research Center. In an effort to better understand the discharge performance of this thruster, a thruster discharge chamber with an anode containing electrically isolated electrodes at the cusps was fabricated and tested. Characteristics of this ring cusp ion discharge were measured without ion beam extraction. Discharge current was measured at collection electrodes located at the magnetic cusps and at the anode body itself. Discharge performance and plasma properties were measured as a function of power, which was varied between 20 and 50 W. It was found that ion production costs decreased by as much as 20 percent when the two most downstream cusp electrodes were allowed to float. Floating the electrodes did not give rise to a significant increase in discharge power even though the plasma density increased markedly. The improved performance is attributed to enhanced electron containment.

  14. Magnetic tearing of plasma discharges due to nonuniform resistivity

    NASA Technical Reports Server (NTRS)

    Hassam, A. B.

    1988-01-01

    The rearrangement of current in a plasma discharge in response to resistivity nonuniformities within a magnetic surface is studied. It is shown that macroscopic magnetic islands develop about those surfaces where the nonuniformity is aligned with the magnetic field. If the nonuniformity and the field are not aligned anywhere, there is no current rearrangement; instead, relatively large plasma flows are set up. Such resistivity inhomogeneities can obtain in solar coronal loops and, in some circumstances, in tokamak discharges.

  15. Electrical isolation of RF plasma discharges

    SciTech Connect

    Miller, P.A.; Anderson, H.; Splichal, M.P.

    1992-12-01

    Plasmas excited by radio-frequency (rf) power have nonlinear impedance characteristics. This causes the plasma state to depend on the nature of the circuitry that supplies electrical power to the plasma. This dependency occurs because the harmonics of the drive frequency, which are generated by the plasma nonlinearity, interact with the impedance of the external circuitry at the harmonic frequencies. The authors describe the use of a low-pass rf filter in the power feed to the plasma in the GEC RF Reference Cell. The filter successfully isolates the plasma and eliminates its sensitivity to changes in the rf generator, cable plant, and matching network.

  16. [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. PMID:22250527

  17. Plasma Acceleration from RF Discharge in Dielectric Capillary

    SciTech Connect

    A. Dunaevsky; Y. Raitses; N. J. Fisch

    2005-08-09

    Plasma acceleration from rf discharge in dielectric capillary was demonstrated. Observed plasma flow had ion energies of approximately 100 eV and electron energies of approximately 20 eV. The discharge was powered by a MHz-range rf generator and fed by Ar. Experimental results indicate possible validity of assumptions about formation of a potential difference at the open end of the capillary and presence of hot electron fraction in the capillary discharge. Simplicity and small dimensions of the source are attractive for micro-propulsion applications.

  18. Plasma Flow During RF Discharges in VASIMR

    NASA Technical Reports Server (NTRS)

    Jacobson, V. T.; Chang Diaz, F. R.; Squire, J. P.; Ilin, A. V.; Bengtson, R. D.; Carter, M. D.; Goulding, R. H.

    1999-01-01

    The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) plasma source consists of a helical antenna, driven at frequencies of 4 to 19 MHz with powers up to 1 kW, in a magnetic field up to 3 kG. Helium is the current test gas, and future experiments with hydrogen are planned. Plasma density and temperature profiles were measured by a reciprocating Langmuir probe, and plasma flow profiles were measured with a reciprocating Mach probe. Both probes were located about 0.5 m downstream from the helical antenna. The plasma source operated in capacitive and inductive modes in addition to a helicon mode. During capacitive and inductive modes, densities were low and plasma flow was < 0.5 Cs. When the plasma operated in a helicon mode, the densities measured downstream from the source were higher [10(exp 12) / cubic cm ] and plasma flow along the magnetic field was of the order Mach 1. Details of the measurements will be shown.

  19. Enhanced magnetic ionization in hydrogen reflex discharge plasma source

    SciTech Connect

    Toader, E.I.; Covlea, V.N.

    2005-03-01

    The effect of enhanced magnetic ionization on the external and internal parameters of a high-density, low pressure reflex plasma source operating in hydrogen is studied. The Langmuir probe method and Druyvesteyn procedure coupled with suitable software are used to measure the internal parameters. The bulk plasma region is free of an electric field and presents a high degree of uniformity. The electron energy distribution function is bi-Maxwellian with a dip/shoulder structure around 5.5 eV, independent of external parameters and radial position. Due to the enhanced hollow cathode effect by the magnetic trapping of electrons, the electron density n{sub e} is as high as 10{sup 18} m{sup -3}, and the electron temperature T{sub e} is as low as a few tens of an electron volt, for dissipated energy of tens of Watts. The bulk plasma density scales with the dissipated power.

  20. 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.

  1. Rotational CARS Temperature Measurements in Nanosecond Pulse Discharge Plasmas

    NASA Astrophysics Data System (ADS)

    Zuzeek, Yvette; Takashima, Keisuke; Adamovich, Igor; Lempert, Walter

    2009-10-01

    Time-resolved and spatially resolved temperatures in repetitively pulsed nanosecond discharges in air and ethylene-air mixtures have been measured by purely rotational Coherent Anti-Stokes Raman Specroscopy (CARS). The experiments have been done in a capacitively coupled plane-to-plane discharge and in an atmospheric pressure near-surface Dielectric Barrier Discharge (DBD), both powered by repetitive nanosecond duration voltage pulses. Gated ICCD camera images demonstrated that the capacitively coupled discharge plasma remains diffuse and stable, with no sign of arc filaments. Comparison of the experimental results with plasma chemical kinetic modeling calculations shows good agreement. The results demonstrate that the rate of heating in the fuel-air plasma is significantly more rapid compared to the one in the air plasma. Kinetic model analysis shows that this occurs due to exothermic reactions of fuel with radical species generated in the plasma, such as O atoms. The present results provide additional insight into kinetics of hydrocarbon fuel oxidation in low-temperature plasmas and into the mechanism of localized heating of air flows by nanosecond DBD discharges.

  2. An investigation of Ar metastable state density in low pressure dual-frequency capacitively coupled argon and argon-diluted plasmas

    SciTech Connect

    Liu, Wen-Yao; Xu, Yong Peng, Fei; Guo, Qian; Li, Xiao-Song; Zhu, Ai-Min; Liu, Yong-Xin; Wang, You-Nian

    2015-01-14

    An tunable diode laser absorption spectroscopy has been used to determine the Ar*({sup 3}P{sub 2}) and Ar*({sup 3}P{sub 0}) metastable atoms densities in dual-frequency capacitively coupled plasmas. The effects of different control parameters, such as high-frequency power, gas pressure and content of Ar, on the densities of two metastable atoms and electron density were discussed in single-frequency and dual-frequency Ar discharges, respectively. Particularly, the effects of the pressure on the axial profile of the electron and Ar metastable state densities were also discussed. Furthermore, a simple rate model was employed and its results were compared with experiments to analyze the main production and loss processes of Ar metastable states. It is found that Ar metastable state is mainly produced by electron impact excitation from the ground state, and decayed by diffusion and collision quenching with electrons and neutral molecules. Besides, the addition of CF{sub 4} was found to significantly increase the metastable destruction rate by the CF{sub 4} quenching, especially for large CF{sub 4} content and high pressure, it becomes the dominant depopulation process.

  3. Long-pulse plasma discharge on the Large Helical Device

    NASA Astrophysics Data System (ADS)

    Kumazawa, R.; Mutoh, T.; Saito, K.; Seki, T.; Nakamura, Y.; Kubo, S.; Shimozuma, T.; Yoshimura, Y.; Igami, H.; Ohkubo, K.; Takeiri, Y.; Oka, Y.; Tsumori, K.; Osakabe, M.; Ikeda, K.; Nagaoka, K.; Kaneko, O.; Miyazawa, J.; Morita, S.; Narihara, K.; Shoji, M.; Masuzaki, S.; Kobayashi, M.; Ogawa, H.; Goto, M.; Morisaki, T.; Peterson, B. J.; Sato, K.; Tokuzawa, T.; Ashikawa, N.; Nishimura, K.; Funaba, H.; Chikaraishi, H.; Watari, T.; Watanabe, T.; Sakamoto, M.; Ichimura, M.; Takase, Y.; Notake, T.; Takeuchi, N.; Torii, Y.; Shimpo, F.; Nomura, G.; Takahashi, C.; Yokota, M.; Kato, A.; Zhao, Y.; Kwak, J. G.; Yoon, J. S.; Yamada, H.; Kawahata, K.; Ohyabu, N.; Ida, K.; Nagayama, Y.; Noda, N.; Komori, A.; Sudo, S.; Motojima, O.; LHD experiment Group

    2006-03-01

    A long-pulse plasma discharge of more than 30 min duration was achieved on the Large Helical Device (LHD). A plasma of ne = 0.8 × 1019 m-3 and Ti0 = 2.0 keV was sustained with PICH = 0.52 MW, PECH = 0.1 MW and averaged PNBI = 0.067 MW. The total injected heating energy was 1.3 GJ. One of the keys to the success of the experiment was a dispersion of the local plasma heat load to divertors, accomplished by sweeping the magnetic axis inward and outward. Causes limiting the long pulse plasma discharge are discussed. An ion impurity penetration limited further long-pulse discharge in the 8th experimental campaign (2004).

  4. Design of a Microwave Assisted Discharge Inductive Plasma Accelerator

    NASA Technical Reports Server (NTRS)

    Hallock, Ashley K.; Polzin, Kurt A.

    2010-01-01

    A new plasma accelerator concept that employs electrodeless plasma preionization and pulsed inductive acceleration is presented. Preionization is achieved through an electron cyclotron resonance discharge that produces a weakly-ionized plasma at the face of a conical theta pinch-shaped inductive coil. The presence of the preionized plasma allows for current sheet formation at lower discharge voltages than those found in other pulsed inductive accelerators. The location of an electron cyclotron resonance discharge can be controlled through the design of the applied magnetic field in the thruster. A finite-element model of the magnetic field was used as a design tool, allowing for the implementation of an arrangement of permanent magnets that yields a small volume of preionized propellant at the coil face. This allows for current sheet formation at the face of the inductive coil, minimizing the initial inductance of the pulse circuit and maximizing the potential efficiency of the new accelerator.

  5. Negative ion source with hollow cathode discharge plasma

    DOEpatents

    Hershcovitch, Ady; Prelec, Krsto

    1983-01-01

    A negative ion source of the type where negative ions are formed by bombarding a low-work-function surface with positive ions and neutral particles from a plasma, wherein a highly ionized plasma is injected into an anode space containing the low-work-function surface. The plasma is formed by hollow cathode discharge and injected into the anode space along the magnetic field lines. Preferably, the negative ion source is of the magnetron type.

  6. Negative ion source with hollow cathode discharge plasma

    DOEpatents

    Hershcovitch, A.; Prelec, K.

    1980-12-12

    A negative ion source of the type where negative ions are formed by bombarding a low-work-function surface with positive ions and neutral particles from a plasma, wherein a highly ionized plasma is injected into an anode space containing the low-work-function surface is described. The plasma is formed by hollow cathode discharge and injected into the anode space along the magnetic field lines. Preferably, the negative ion source is of the magnetron type.

  7. Low pressure characteristics of the multipole resonance probe

    NASA Astrophysics Data System (ADS)

    Brinkmann, Ralf Peter; Oberrath, Jens

    2014-10-01

    The term ``Active plasma resonance spectroscopy'' (APRS) denotes a class of related techniques which utilize, for diagnostic purposes, the natural ability of plasmas to resonate on or near the electron plasma frequency ωpe. The basic idea dates back to the early days of discharge physics but has recently found renewed interest as an approach to industry-compatible plasma diagnostics: A radio frequent signal (in the GHz range) is coupled into the plasma via an antenna or probe, the spectral response is recorded (with the same or another antenna or probe), and a mathematical model is used to determine plasma parameters like the electron density or the electron temperature. When the method is applied to low pressure plasmas (of a few Pa and lower), kinetic effects must be accounted for in the mathematical model. This contribution studies a particular realization of the APRS scheme, the geometrically and electrically symmetric Multipole Resonance Probe (MRP). It is shown that the resonances of the MRP exhibit a residual damping in the limit p --> 0 which cannot be explained by Ohmic dissipation but only by kinetic effects. Supported by the German Federal Ministry of Education and Research (BMBF) in the framework of the PluTO project.

  8. Plasma Structure and Behavior of Miniature Ring-Cusp Discharges

    NASA Astrophysics Data System (ADS)

    Mao, Hann-Shin

    Miniature ring-cusp ion thrusters provide a unique blend of high efficiencies and millinewton level thrust for future spacecraft. These thrusters are attractive as a primary propulsion for small satellites that require a high delta V, and as a secondary propulsion for larger spacecraft that require precision formation flying, disturbance rejection, or attitude control. To ensure desirable performance throughout the life of such missions, an advancement in the understanding of the plasma structure and behavior of miniature ring-cusp discharges is required. A research model was fabricated to provide a simplified experimental test bed for the analysis of the plasma discharge chamber of a miniature ion thruster. The plasma source allowed for spatially resolved measurements with a Langmuir probe along a meridian plane. Probe measurements yielded plasma density, electron temperature, and plasma potential data. The magnetic field strength was varied along with the discharge current to determine the plasma behavior under various conditions. The structure of the plasma properties were found to be independent of the discharge power under the proper scaling. It was concluded that weaker magnetic fields can improve the overall performance for ion thruster operation. To further analyze the experimental measurements, a framework was developed based on the magnetic field. A flux aligned coordinate system was developed to decouple the perpendicular and parallel plasma motion with respect to the magnetic field. This was done using the stream function and magnetic scalar potential. Magnetic formulae provided intuition on the field profiles dependence on magnet dimensions. The flux aligned coordinate system showed that the plasma was isopycnic along constant stream function values. This was used to develop an empirical relation suitable for estimating the spatial behavior and to determine the plasma volume and loss areas. The plasma geometry estimates were applied to a control volume

  9. On the Structure of the Two-Dimensional Spatially Periodic Inner Transition Layers in a Gas-Discharge Plasma

    SciTech Connect

    Voronov, A.Ya.

    2005-07-01

    We investigate the structure of the spatially periodic inner boundary layers in the plasma of a positive glow-discharge column produced in a long cylindrical tube with an electropositive gas inside. Asymptotic methods, namely, the method of boundary functions, are used to analyze the initial mathematical model. We consider the formation of contrast burst-type structures. We have found all principal terms of the boundary-layer asymptotics of the solution. The results obtained are compared with the available probe measurements of basic physical parameters of ionization waves (strata) in neon at low pressures.

  10. The low-pressure sodium lamp

    SciTech Connect

    Hooker, J.D.

    1997-12-31

    For many years before the introduction of the sodium vapor lamp, scientists had been aware of the remarkably high luminous efficacy of the sodium discharge. However, many technical problems had to be overcome before these lamps could be marketed. The first commercial low pressure sodium lamps were introduced in the early 1930s and to this day they remain the most efficient light sources available. The high efficacy is due partly to the fact that these lamps emit nearly monochromatic yellow light, which is very close to the peak sensitivity of the human eye. Sodium lamps have come a long way since their introduction, and efficacies are now approaching 200 lumens per watt. Despite increasing competition from other types of discharge lamp, low pressure sodium lamps of the SOX type find widespread use in road and security lighting, particularly in Great Britain and many other parts of Europe. This paper reviews the operation and development of the low pressure sodium lamp, and shows what makes it different from the many other types of discharge lamp available.

  11. Energy coupling to the plasma in repetitive nanosecond pulse discharges

    SciTech Connect

    Adamovich, Igor V.; Nishihara, Munetake; Choi, Inchul; Uddi, Mruthunjaya; Lempert, Walter R.

    2009-11-15

    A new analytic quasi-one-dimensional model of energy coupling to nanosecond pulse discharge plasmas in plane-to-plane geometry has been developed. The use of a one-dimensional approach is based on images of repetitively pulsed nanosecond discharge plasmas in dry air demonstrating that the plasma remains diffuse and uniform on a nanosecond time scale over a wide range of pressures. The model provides analytic expressions for the time-dependent electric field and electron density in the plasma, electric field in the sheath, sheath boundary location, and coupled pulse energy. The analytic model predictions are in very good agreement with numerical calculations. The model demonstrates that (i) the energy coupled to the plasma during an individual nanosecond discharge pulse is controlled primarily by the capacitance of the dielectric layers and by the breakdown voltage and (ii) the pulse energy coupled to the plasma during a burst of nanosecond pulses decreases as a function of the pulse number in the burst. This occurs primarily because of plasma temperature rise and resultant reduction in breakdown voltage, such that the coupled pulse energy varies approximately proportionally to the number density. Analytic expression for coupled pulse energy scaling has been incorporated into the air plasma chemistry model, validated previously by comparing with atomic oxygen number density measurements in nanosecond pulse discharges. The results of kinetic modeling using the modified air plasma chemistry model are compared with time-resolved temperature measurements in a repetitively pulsed nanosecond discharge in air, by emission spectroscopy, and purely rotational coherent anti-Stokes Raman spectroscopy showing good agreement.

  12. Energy coupling to the plasma in repetitive nanosecond pulse discharges

    NASA Astrophysics Data System (ADS)

    Adamovich, Igor V.; Nishihara, Munetake; Choi, Inchul; Uddi, Mruthunjaya; Lempert, Walter R.

    2009-11-01

    A new analytic quasi-one-dimensional model of energy coupling to nanosecond pulse discharge plasmas in plane-to-plane geometry has been developed. The use of a one-dimensional approach is based on images of repetitively pulsed nanosecond discharge plasmas in dry air demonstrating that the plasma remains diffuse and uniform on a nanosecond time scale over a wide range of pressures. The model provides analytic expressions for the time-dependent electric field and electron density in the plasma, electric field in the sheath, sheath boundary location, and coupled pulse energy. The analytic model predictions are in very good agreement with numerical calculations. The model demonstrates that (i) the energy coupled to the plasma during an individual nanosecond discharge pulse is controlled primarily by the capacitance of the dielectric layers and by the breakdown voltage and (ii) the pulse energy coupled to the plasma during a burst of nanosecond pulses decreases as a function of the pulse number in the burst. This occurs primarily because of plasma temperature rise and resultant reduction in breakdown voltage, such that the coupled pulse energy varies approximately proportionally to the number density. Analytic expression for coupled pulse energy scaling has been incorporated into the air plasma chemistry model, validated previously by comparing with atomic oxygen number density measurements in nanosecond pulse discharges. The results of kinetic modeling using the modified air plasma chemistry model are compared with time-resolved temperature measurements in a repetitively pulsed nanosecond discharge in air, by emission spectroscopy, and purely rotational coherent anti-Stokes Raman spectroscopy showing good agreement.

  13. Plasma discharge characteristics in compact SF6 radio-frequency plasma source for plasma etching application

    NASA Astrophysics Data System (ADS)

    Motomura, Taisei; Takahashi, Kazunori; Kasashima, Yuji; Uesugi, Fumihiko; Ando, Akira

    2015-09-01

    In order to create a compact plasma etching reactor, plasma discharge characteristics in compact SF6 radio-frequency (RF) plasma source which has a chamber diameter of 40 mm have been studied. Convergent magnetic field configuration produced by a solenoid coil and a permanent magnet located behind substrate is employed for efficient plasma transport downstream of plasma source. A discharge characteristics with the changes in relative emission intensity of fluorine atom of FI at 703.7 nm in compact SF6 plasma source are discussed: the dependence of relative emission intensity on the magnetic field strength, the RF input power, and the mass flow rate of the SF6 gas. The relative emission intensity was significantly increased when the RF input power is ~150 W. We present the fundamental etching performance (especially etching rate) of compact plasma source, and then the etching rate of 0.1-1.0 μm/min was obtained under the condition of a RF input power of 50-200 W, a mass flow rate of SF6 of 5.5 sccm and a bias RF power of 20 W. The results of test etching will be shown in presentation.

  14. Plasma instability in fast spherical discharge induced by a preionization

    SciTech Connect

    Antsiferov, P. S.; Dorokhin, L. A.

    2015-04-07

    As it was shown earlier, fast discharge (dI/dt ∼ 10{sup 12 }A/s and I{sub max} ≈ 40 kA) in a spherical cavity (Al{sub 2}O{sub 3}, inner diameter 11 mm, 4 mm apertures for the current supply) filled with working gas (Ar and Xe, pressure 80 Pa), results in the formation of a plasma with the form close to spherical. The physical mechanism can be the cumulation of a convergent shock wave, which was originated near the inner surface of the discharge cavity. It was also shown for the cylindrical fast discharge that the preionization influences the dynamics of the cylindrical convergent shock wave, its evolutions becomes faster. The present work is devoted to the study of the influence of the preionization on the plasma formation in the fast discharge with spherical geometry (Ar, 80 Pa). The inductive storage with plasma erosion opening switch was used as a current driver. The spatial structure of the discharge plasma was studied by means of a pin-hole camera with the microchannel plate (MCP) detector with time gate of 5 ns. The extreme ultra violet spectra were studied by means of the grazing incidence spectrometer with the same MCP detector with time gate of 20 ns. Beside the expected effects (reduction of the spherical plasma formation time and some increase of the electron temperature), the preionization of the discharge by the current 500 A results also in the development of the plasma instabilities and destruction of the compact plasma ball in several tens of nanoseconds. Possible mechanism of the instability is discussed.

  15. Plasma instability in fast spherical discharge induced by a preionization

    NASA Astrophysics Data System (ADS)

    Antsiferov, P. S.; Dorokhin, L. A.

    2015-04-01

    As it was shown earlier, fast discharge (dI/dt ˜ 1012 A/s and Imax ≈ 40 kA) in a spherical cavity (Al2O3, inner diameter 11 mm, 4 mm apertures for the current supply) filled with working gas (Ar and Xe, pressure 80 Pa), results in the formation of a plasma with the form close to spherical. The physical mechanism can be the cumulation of a convergent shock wave, which was originated near the inner surface of the discharge cavity. It was also shown for the cylindrical fast discharge that the preionization influences the dynamics of the cylindrical convergent shock wave, its evolutions becomes faster. The present work is devoted to the study of the influence of the preionization on the plasma formation in the fast discharge with spherical geometry (Ar, 80 Pa). The inductive storage with plasma erosion opening switch was used as a current driver. The spatial structure of the discharge plasma was studied by means of a pin-hole camera with the microchannel plate (MCP) detector with time gate of 5 ns. The extreme ultra violet spectra were studied by means of the grazing incidence spectrometer with the same MCP detector with time gate of 20 ns. Beside the expected effects (reduction of the spherical plasma formation time and some increase of the electron temperature), the preionization of the discharge by the current 500 A results also in the development of the plasma instabilities and destruction of the compact plasma ball in several tens of nanoseconds. Possible mechanism of the instability is discussed.

  16. Removing of Mixed Coatings by Plasma Discharges

    NASA Astrophysics Data System (ADS)

    Vassallo, E.; Caniello, R.; Deambrosis, S.; Dellasega, D.; Ghezzi, F.; Laguardia, L.; Miorin, E.; Passoni, M.

    2013-08-01

    Next generation tokamaks offer the possibility of highly efficient energy generation from the fusion reaction of hydrogen isotopes. In tokamak operation, the core plasma interaction with the wall materials could produce tiles erosion. Redeposition of the eroded materials (C-W-Be) leads to an increase in the allowable tritium load if the coatings are not periodically removed. Amongst removal methods, plasma based techniques employing Ar, H2 gas have been investigated. Plasma cleaning has been carried out on hydrogenated carbon and carbon-tungsten coatings. It has been shown that at a RF power density of 1.3 W/cm2 (pressure of 1 Pa), the plasma cleaning was effective in removing the coatings. Details of further work in this research activity will be presented.

  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. Characterization of microwave discharge plasmas for surface processing

    NASA Astrophysics Data System (ADS)

    Nikolic, Milka

    We have developed several diagnostic techniques to characterize two types of microwave (MW) discharge plasmas: a supersonic flowing argon MW discharge maintained in a cylindrical quartz cavity at frequency ƒ = 2.45 GHz and a pulse repetitive MW discharge in air at ƒ = 9.5 GHz. Low temperature MW discharges have been proven to posses attractive properties for plasma cleaning and etching of niobium surfaces of superconductive radio frequency (SRF) cavities. Plasma based surface modification technologies offer a promising alternative for etching and cleaning of SRF cavities. These technologies are low cost, environmentally friendly and easily controllable, and present a possible alternative to currently used acid based wet technologies, such as buffered chemical polishing (BCP), or electrochemical polishing (EP). In fact, weakly ionized. non-equilibrium, and low temperature gas discharges represent a powerful tool for surface processing due to the strong chemical reactivity of plasma radicals. Therefore, characterizing these discharges by applying non-perturbing, in situ measurement techniques is of vital importance. Optical emission spectroscopy has been employed to analyze the molecular structure and evaluate rotational and vibrational temperatures in these discharges. The internal plasma structure was studied by applying a tomographic numerical method based on the two-dimensional Radon formula. An automated optical measurement system has been developed for reconstruction of local plasma parameters. It was found that excited argon states are concentrated near the tube walls, thus confirming the assumption that the post discharge plasma is dominantly sustained by a travelling surface wave. Employing a laser induced fluorescence technique in combination with the time synchronization device allowed us to obtain time-resolved population densities of some excited atomic levels in argon. We have developed a technique for absolute measurements of electron density based

  19. 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.

  20. On the self-excitation mechanisms of plasma series resonance oscillations in single- and multi-frequency capacitive discharges

    SciTech Connect

    Schüngel, Edmund; Brandt, Steven; Schulze, Julian; Korolov, Ihor; Derzsi, Aranka; Donkó, Zoltán

    2015-04-15

    The self-excitation of plasma series resonance (PSR) oscillations is a prominent feature in the current of low pressure capacitive radio frequency discharges. This resonance leads to high frequency oscillations of the charge in the sheaths and enhances electron heating. Up to now, the phenomenon has only been observed in asymmetric discharges. There, the nonlinearity in the voltage balance, which is necessary for the self-excitation of resonance oscillations with frequencies above the applied frequencies, is caused predominantly by the quadratic contribution to the charge-voltage relation of the plasma sheaths. Using Particle In Cell/Monte Carlo collision simulations of single- and multi-frequency capacitive discharges and an equivalent circuit model, we demonstrate that other mechanisms, such as a cubic contribution to the charge-voltage relation of the plasma sheaths and the time dependent bulk electron plasma frequency, can cause the self-excitation of PSR oscillations, as well. These mechanisms have been neglected in previous models, but are important for the theoretical description of the current in symmetric or weakly asymmetric discharges.

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

    NASA Astrophysics Data System (ADS)

    Demidov, Vladimir; Adams, Steven; Bogdanov, Yevgeny; Koepke, Mark; Kudryavtsev, Anatoly; Kurlyandskaya, Iya

    2015-11-01

    To demonstrate controlling electron and 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 (without positive column) dc glow discharge with a cold cathode. The applied negative voltage can modify trapping the low-energy part of the energetic electrons emitted from the cathode sheath and arising from the atomic and molecular processes in the plasma within the device volume. Those electrons are responsible for heating the slow, thermal electrons, while production of slow electrons (ions) and metastable atoms is mostly due to energetic electrons with higher energies. Increasing electron temperature results in increasing decay rate of slow, thermal electrons, while decay rate of metastable atoms and production rates of slow electrons and metastable atoms practically are unchanged. The result is in variation of electron and metastable density ratio and electron temperature with variation of the wall negative voltage. A part of this research was performed, while one of the authors (VID) held a National Research Council Research Associateship Award at AFRL. The work was also partially supported by SPbGU (Grant No. 11.38.658.2013) and ITMO University (Grant No. 713577).

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    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.

  3. Characteristics of 2-heptanone decomposition using nanosecond pulsed discharge plasma

    NASA Astrophysics Data System (ADS)

    Nakase, Yuki; Fukuchi, Yuichi; Wang, Douyan; Namihira, Takao; Akiyama, Hidenori; Kumamoto University Collaboration

    2015-09-01

    Volatile organic compounds (VOC) evaporate at room temperature. VOCs typically consist of toluene, benzene and ethyl acetate, which are used in cosmetics, dry cleaning products and paints. Exposure to elevated levels of VOCs may cause headaches, dizziness and irritation to the eyes, nose, and throat; they may also cause environmental problems such as air pollution, acid rain and photochemical smog. As such, they require prompt removal. Nanosecond pulsed discharge is a kind of non-thermal plasma consisting of a streamer discharge. Several advantages of nanosecond pulsed discharge plasma have been demonstrated by studies of our research group, including low heat loss, highly energetic electron generation, and the production of highly active radicals. These advantages have shown ns pulsed discharge plasma capable of higher energy efficiency for processes, such as air purification, wastewater treatment and ozone generation. In this research, nanosecond pulsed discharge plasma was employed to treat 2-heptanone, which is a volatile organic compound type and presents several harmful effects. Characteristics of treatment dependent on applied voltage, gas flow rate and input energy density were investigated. Furthermore, byproducts generated by treatment were also investigated.

  4. Temporal modulation of plasma species in atmospheric dielectric barrier discharges

    SciTech Connect

    Yang, Aijun; Wang, Xiaohua E-mail: mzrong@mail.xjtu.edu.cn; Liu, Dingxin; Rong, Mingzhe E-mail: mzrong@mail.xjtu.edu.cn; Kong, Michael G.

    2014-07-15

    The atmospheric pressure dielectric barrier discharge in helium is a pulsed discharge in nature and the moment of maximum species densities is almost consistent with peak discharge current density. In this paper, a one-dimensional fluid model is used to investigate the temporal structure of plasma species in an atmospheric He-N{sub 2} dielectric barrier discharge (DBD). It is demonstrated that there exist microsecond delays of the moments of the maximum electron and ion densities from the peak of discharge current density. These time delays are caused by a competition between the electron impact and Penning ionizations, modulated by the N{sub 2} level in the plasma-forming gas. Besides, significant electron wall losses lead to the DBD being more positively charged and, with a distinct temporal separation in the peak electron and cation densities, the plasma is characterized with repetitive bursts of net positive charges. The temporal details of ionic and reactive plasma species may provide a new idea for some biological processes.

  5. Characteristics of dielectric barrier discharge plasmas in atmospheric humid air

    NASA Astrophysics Data System (ADS)

    Fukuda, Y.; Fukui, K.; Iwami, R.; Matsuoka, Y.; Kikuchi, Y.; Fukumoto, N.; Nagata, M.

    2012-10-01

    Atmospheric pressure plasmas have a great advantage for industrial applications such as surface modifications, sterilization and film preparation. In particular, reactive plasmas including OH radicals can be generated in humid air. On the other hand, it is known that dielectric barrier discharge (DBD) plasmas in air are strongly affected by humidity. In this study, a twisted pair sample is used as a DBD electrode. The twisted pair consists of two enameled wires, and it is installed in a climate chamber to control ambient temperature and humidity. Repetitive impulse voltage pulses were applied to the twisted pair to produce DBD plasmas. Light emission, electromagnetic wave and current pulses were used to detect discharge activities. The discharge inception voltage (DIV) is basically determined by Paschen curve in air, however, the DIV was decreased by increasing the humidity. In addition, it was found that there were largely scattered data of DIV at the low humidity condition. After the pre-discharges, the DIV reached to the steady state value. On the other hand, there was no scattering of the observed DIV at the high humidity condition. Measurements of surface potential of the sample after the discharge show these behaviors could be explained by surface charge accumulation on the enameled wire. It is noted that there was no fluctuation in the DIV data in the case of unipolar voltage pulse.

  6. Dynamics of plasma evolution in a nanosecond underwater discharge

    NASA Astrophysics Data System (ADS)

    Marinov, Ilya; Starikovskaia, Svetlana; Rousseau, Antoine

    2014-06-01

    A positive discharge in water is generated by applying a 30 ns high-voltage (HV) pulse on a micrometre scale electrode. The applied voltage ranges from 6 to 15 kV and a fast plasma propagating mode is launched with a velocity of up to 60 km s-1. Time-resolved shadowgraphy and spectroscopy are performed to monitor the time evolution of the discharge structure and of the plasma emission spectra. By analysing the dynamics of the shock front velocity and the lateral expansion of the plasma channel, it is possible to estimate the pressure at the ignition of the plasma by two independent methods: very good agreement is found at 6 kV giving initial pressures of 0.4 GPa and 0.3 GPa, respectively. At 15 kV, only the shock front velocity method is applicable under our experimental conditions, giving an estimate of the initial pressure of 5.8 GPa. Such high initial pressures show that, under a nanosecond HV pulse, the plasma is ignited directly in the dense phase. Emission spectra show a strong continuum emission as well as a broad Balmer α line with a strong red shift, with an estimate of the initial plasma density of 1.3 × 1026 m-3. The relaxation of discharge pressure and plasma density is studied under a series of six successive pulses.

  7. Glow discharge plasma treatment for surface cleaning and modification of metallic biomaterials.

    PubMed

    Aronsson, B O; Lausmaa, J; Kasemo, B

    1997-04-01

    Glow discharge plasma treatment is a frequently used method for cleaning, preparation, and modification of biomaterial and implant surfaces. The merits of such treatments are, however, strongly dependent on the process parameters. In the present work the possibilities, limitations, and risks of plasma treatment for surface preparation of metallic materials are investigated experimentally using titanium as a model system, and also discussed in more general terms. Samples were treated by different low-pressure direct current plasmas and analyzed using Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS), atomic force microscopy, scanning electron microscopy, and light microscopy. The plasma system is a home-built, ultra-high vacuum-compatible system that allows sample introduction via a load-lock, and precise control of pressure, gas composition and flow rate, etc. This system allows uniform treatment of cylindrical and screw-shaped samples. With appropriate plasma parameters, argon plasma remove all chemical traces from former treatments (adsorbed contaminants and other impurities, and native oxide layers), in effect producing cleaner and more well-controlled surfaces than with conventional preparation methods. Removal (sputtering) rates up to 30 nm/min are possible. However, when inappropriate plasma parameters are used, the result may be increased contamination and formation of unintentional or undesired surface layers (e.g., carbides and nitrides). Plasma-cleaned surfaces provide a clean and reproducible starting condition for further plasma treatments to form well-controlled surface layers. Oxidation in pure O2 (thermally or in oxygen plasmas) results in uniform and stoichiometric TiO2 surface oxide layers of reproducible composition and thicknesses in the range 0.5-150 nm, as revealed by AES and XPS analyses. Titanium nitride layers were prepared by using N2 plasmas. While mild plasma treatments leave the surface microstructure unaffected

  8. 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.

  9. Plasma mixing glow discharge device for analytical applications

    DOEpatents

    Pinnaduwage, Lal A.

    1999-01-01

    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.

  10. A numerical study of the sodium vapor discharge plasma

    SciTech Connect

    Ben Ahmed, R.; Araoud, Z.; Charrada, K.

    2011-06-15

    In this article we will discuss, in detail, the results obtained for a simple geometry of discharge (two-dimensional stationary or one-dimensional non stationary). It aims to give an idea about the discharge properties that emerge from the interaction of various physical processes. By using a variation of the fundamental parameters, we can show the capacity of the model to reproduce all the macroscopic properties of plasma discharge in sodium vapor. The validation of the model will be discussed and some comparisons with the existing experimental data will be presented.

  11. Formation of nanostructures in a plasma focus discharge

    SciTech Connect

    Krauz, V. I.; Khimchenko, L. N.; Myalton, V. V.; Vinogradov, V. P.; Vinogradova, Yu. V.; Gureev, V. M.; Koidan, V. S.; Smirnov, V. P.; Fortov, V. E.

    2013-04-15

    A new method for creating nanostructures in a plasma focus discharge is proposed. It is shown that the material of a micron-size dust target produced at the discharge axis efficiently evaporates and is then involved in the pinching process. After the pinch decays, the plasma expands with the thermal velocity and the evaporated dust material is deposited on the collectors in the form of fractal particles or nanoclusters organized into various structures. Such structures have a well-developed surface, which is important for various technological applications.

  12. Influence of annular magnet on discharge characteristics in enhanced glow discharge plasma immersion ion implantation

    SciTech Connect

    Li Liuhe; Wang Zhuo; Lu Qiuyuan; Fu, Ricky K. Y.; Chu, Paul K.; Pang Enjing; Dun Dandan; He Fushun; Li Fen

    2011-01-10

    A permanent annular magnet positioned at the grounded anode alters the discharge characteristics in enhanced glow discharge plasma immersion ion implantation (EGD-PIII). The nonuniform magnetic field increases the electron path length and confines electron motion due to the magnetic mirror effect and electron-neutral collisions thus occur more frequently. The plasma potential and ion density measured by a Langmuir probe corroborate that ionization is improved near the grounded anode. This hybrid magnetic field EGD-PIII method is suitable for implantation of gases with low ionization rates.

  13. N2O Decomposed by Discharge Plasma with Catalysts

    NASA Astrophysics Data System (ADS)

    Hu, Hui; Huang, Hao; Xu, Jie; Yang, Qi; Tao, Gongkai

    2015-12-01

    A great deal of attention has been focused on discharge plasma as it can rapidly decompose N2O without additives, which is not only a kind of greenhouse gas but also a kind of damages to the ozone layer. The thermal equilibrium plasma is chosen to combine with catalysts to decompose N2O, and its characteristics are analyzed in the present paper. The results indicate that NO and NO2 were formed besides N2 and O2 during N2O decomposition when N2O was treated merely by discharge plasma. Concentration of NO declined greatly when the discharge plasma was combined with catalysts. Results of Raman spectra analysis on CeO2, Ce0.75Zr0.25O2 and Ce0.5Zr0.5O2 imply that the products selectivity has been obviously improved in discharge plasma decomposing N2O because of the existence of massive oxygen vacancies over the composite oxide catalysts. supported by National Natural Science Foundation of China (No. 50677026) and the Applied Basic Research Program of Wuhan, China (No. 2015060101010068)

  14. Observation and numerical analysis of plasma parameters in a capillary discharge-produced plasma channel waveguide

    SciTech Connect

    Terauchi, Hiromitsu; Bobrova, Nadezhda; Sasorov, Pavel; Kikuchi, Takashi; Sasaki, Toru; Higashiguchi, Takeshi; Yugami, Noboru; Kodama, Ryosuke

    2011-03-01

    We observed the parameters of the discharge-produced plasma in cylindrical capillary. Plasma parameters of the waveguide were investigated by use of both a Normarski laser interferometer and a hydrogen plasma line spectrum. A space-averaged maximum temperature of 3.3 eV with electron densities of the order of 10{sup 17} cm{sup -3} was observed at a discharge time of 150 ns and a maximum discharge current of 200 A. One-dimensional dissipative magnetohydrodynamic (MHD) code was used to analyze the discharge dynamics in the gas-filled capillary discharge waveguide for high-intensity laser pulses. Simulations were performed for the conditions of the experiment. We compared the temporal behavior of the electron temperature and the radial electron density profiles, measured in the experiment with the results of the numerical simulations. They occurred to be in a good agreement. An ultrashort, intense laser pulse was guided by use of this plasma channel.

  15. Plasma Dynamics of Capillary Discharges for the BELLA project

    NASA Astrophysics Data System (ADS)

    Stoltz, Peter; Hakim, Ammar; Loverich, John; Fillmore, David; Johnson, Jeffrey; Geddes, Cameron; Esarey, Eric; Mittelberger, Daniel; Bulanov, Stepan; Gonsalves, Anthony; Leemans, Wim

    2010-11-01

    Capillary discharges to form a meter-scale plasma waveguide are important for 10 GeV scale laser plasma accelerator experiments on the BELLA laser in progress at Lawrence Berkeley National Laboratory. We present simulation results of capillary plasma properties, including radial density and temperature profiles, using the Nautilus code. An effect known to play a dominant role is the transfer of heat from the plasma to the capillary wall. We present benchmark results for heat transfer modeling with Nautilus in the regime of interest to capillary discharges. We also discuss the relative importance of diffusion, Ohm's law, and applied solenoidal fields on the radial profiles needed for experiments. For instance, some previous models estimate applied solenoidal fields could increase on-axis temperatures by roughly a factor of two, and we compare with these estimates. Finally, we compare radial profile results with other simulation results and with recent measurements made at LBNL.

  16. Optical emission spectroscopy observations of fast pulsed capillary discharge plasmas

    NASA Astrophysics Data System (ADS)

    Avaria, G.; Ruiz, M.; Guzmán, F.; Favre, M.; Wyndham, E. S.; Chuaqui, H.; Bhuyan, H.

    2014-05-01

    We present time resolved optical emission spectroscopic (OES) observations of a low energy, pulsed capillary discharage (PCD). The optical emission from the capillary plasma and plasma jets emitted from the capillary volume was recorded with with a SpectraPro 275 spectrograph, fitted with a MCP gated OMA system, with 15 ns time resolution. The discharge was operated with different gases, including argon, nitrogen, hydrogen and methane, in a repetitive pulsed discharge mode at 10-50 Hz, with, 10-12 kV pulses applied at the cathode side. The time evolution of the electron density was measured using Stark broadening of the Hβ line. Several features of the capillary plasma dynamics, such as ionization growth, wall effects and plasma jet evolution, are inferred from the time evolution of the optical emission.

  17. Evolution of a vortex in glow discharge plasma

    SciTech Connect

    Soukhomlinov, V.S.; Sheverev, V.A.; Oetuegen, M.V.

    2005-05-01

    The evolution of a vortex in glow discharge plasma is studied analytically. Specifically, the mechanism of local energy deposition into the flow by the plasma is considered and its effect on the structure of an inviscid vortex is analyzed. The vortex is modeled by a set of Euler's equations while the energy transferred by the plasma into the gas is represented by Rayleigh mechanism. In this mechanism, the amount of heat addition is a function of local gas density. The analysis indicates that the plasma can have a considerable effect on the structure of a vortex. The inviscid calculations show that in a uniform discharge, a 1 cm vortex dies out in a fraction of a second.

  18. 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.

  19. Mode transition of a Hall thruster discharge plasma

    SciTech Connect

    Hara, Kentaro Sekerak, Michael J. Boyd, Iain D.; Gallimore, Alec D.

    2014-05-28

    A Hall thruster is a cross-field plasma device used for spacecraft propulsion. An important unresolved issue in the development of Hall thrusters concerns the effect of discharge oscillations in the range of 10–30 kHz on their performance. The use of a high speed Langmuir probe system and ultra-fast imaging of the discharge plasma of a Hall thruster suggests that the discharge oscillation mode, often called the breathing mode, is strongly correlated to an axial global ionization mode. Stabilization of the global oscillation mode is achieved as the magnetic field is increased and azimuthally rotating spokes are observed. A hybrid-direct kinetic simulation that takes into account the transport of electronically excited atoms is used to model the discharge plasma of a Hall thruster. The predicted mode transition agrees with experiments in terms of the mean discharge current, the amplitude of discharge current oscillation, and the breathing mode frequency. It is observed that the stabilization of the global oscillation mode is associated with reduced electron transport that suppresses the ionization process inside the channel. As the Joule heating balances the other loss terms including the effects of wall loss and inelastic collisions, the ionization oscillation is damped, and the discharge oscillation stabilizes. A wide range of the stable operation is supported by the formation of a space charge saturated sheath that stabilizes the electron axial drift and balances the Joule heating as the magnetic field increases. Finally, it is indicated from the numerical results that there is a strong correlation between the emitted light intensity and the discharge current.

  20. Mode transition of a Hall thruster discharge plasma

    NASA Astrophysics Data System (ADS)

    Hara, Kentaro; Sekerak, Michael J.; Boyd, Iain D.; Gallimore, Alec D.

    2014-05-01

    A Hall thruster is a cross-field plasma device used for spacecraft propulsion. An important unresolved issue in the development of Hall thrusters concerns the effect of discharge oscillations in the range of 10-30 kHz on their performance. The use of a high speed Langmuir probe system and ultra-fast imaging of the discharge plasma of a Hall thruster suggests that the discharge oscillation mode, often called the breathing mode, is strongly correlated to an axial global ionization mode. Stabilization of the global oscillation mode is achieved as the magnetic field is increased and azimuthally rotating spokes are observed. A hybrid-direct kinetic simulation that takes into account the transport of electronically excited atoms is used to model the discharge plasma of a Hall thruster. The predicted mode transition agrees with experiments in terms of the mean discharge current, the amplitude of discharge current oscillation, and the breathing mode frequency. It is observed that the stabilization of the global oscillation mode is associated with reduced electron transport that suppresses the ionization process inside the channel. As the Joule heating balances the other loss terms including the effects of wall loss and inelastic collisions, the ionization oscillation is damped, and the discharge oscillation stabilizes. A wide range of the stable operation is supported by the formation of a space charge saturated sheath that stabilizes the electron axial drift and balances the Joule heating as the magnetic field increases. Finally, it is indicated from the numerical results that there is a strong correlation between the emitted light intensity and the discharge current.

  1. Energetic Photons From Transient Plasma Discharges

    SciTech Connect

    Robert, E.; Cachoncinlle, C.; Dozias, S.; Khacef, A.; Majeri, N.; Romero, E.; Point, S.; Viladrosa, R.; Pouvesle, J. M.

    2008-09-23

    An overview of the plasma based sources of energetic photons, ranging from UV to hard X-rays, developed in GREMI is proposed. Each source principle is shortly described and applications of these specially designed sources are documented. The possibility of producing energetic photons over a very broad wavelength domain, together with the versatility of the mode of operations allow for a very large range of applications. The matching of the photon energy, the pulse repetition rate, the short duration, of a few nanosecond, of photon pulses offer for instance unique possibility for fast dynamic study, low Z element spray characterization, X-ray fluorescence of dense targets, lithography issues, and UV VUV radiating plasma optimization.

  2. Destruction of Bacterial Biofilms Using Gas Discharge Plasma

    NASA Astrophysics Data System (ADS)

    Abramzon, Nina

    2005-03-01

    Biofilms are bacterial communities embedded in an exopolysaccharidic matrix with a complex architectural structure. Bacteria in biofilms show different properties from those in free life thus, conventional methods of killing bacteria are often ineffective with biofilms. The use of plasmas potentially offers an alternative to conventional sterilization methods since plasmas contain a mixture of charged particles, chemically reactive species, and UV radiation. 4 and 7 day-old biofilms were produced using two bacterial species: Rhizobium gallicum and Chromobacterium violaceum. Gas discharge plasma was produced by using an AtomfloTM reactor (Surfx Technologies) and bacterial biofilms were exposed to it for different periods of time. Our results show that a 10-minute plasma treatment was able to kill 100% of the cells in most cases. Optical emission spectroscopy was used to study plasma composition which is then correlated with the effectiveness of killing. These results indicate the potentiality of plasma as an alternative sterilization method. Supported by CSuperb.

  3. Two-dimensional plasma photonic crystals in dielectric barrier discharge

    SciTech Connect

    Fan Weili; Dong Lifang; Zhang Xinchun

    2010-11-15

    A series of two-dimensional plasma photonic crystals have been obtained by filaments' self-organization in atmospheric dielectric barrier discharge with two water electrodes, which undergo the transition from square to square superlattice and finally to the hexagon. The spatio-temporal behaviors of the plasma photonic crystals in nanosecond scale have been studied by optical method, which show that the plasma photonic crystal is actually an integration of different transient sublattices. The photonic band diagrams of the transverse electric (TE) mode and transverse magnetic mode for each sublattice of these plasma photonic crystals have been investigated theoretically. A wide complete band gap is formed in the hexagonal plasma photonic crystal with the TE mode. The changes of the band edge frequencies and the band gap widths in the evolvement of different structures are studied. A kind of tunable plasma photonic crystal which can be controlled both in space and time is suggested.

  4. Sterilization of Turmeric by Atmospheric Pressure Dielectric Barrier Discharge Plasma

    NASA Astrophysics Data System (ADS)

    Setareh, Salarieh; Davoud, Dorranian

    2013-11-01

    In this study atmospheric pressure dielectric barrier discharge (DBD) plasma has been employed for sterilizing dry turmeric powders. A 6 kV, 6 kHz frequency generator was used to generate plasma with Ar, Ar/O2, He, and He/O2 gases between the 5 mm gap of two quartz covered electrodes. The complete sterilization time of samples due to plasma treatment was measured. The most important contaminant of turmeric is bacillus subtilis. The results show that the shortest sterilization time of 15 min is achieved by exposing the samples to Ar/O2 plasma. Survival curves of samples are exponential functions of time and the addition of oxygen to plasma leads to a significant increase of the absolute value of time constant of the curves. Magnitudes of protein and DNA in treated samples were increased to a similar value for all samples. Taste, color, and solubility of samples were not changed after the plasma treatment.

  5. Low-pressure plasma-etching of bulk polymer materials using gas mixture of CF{sub 4} and O{sub 2}

    SciTech Connect

    Nabesawa, Hirofumi; Hiruma, Takaharu; Seki, Minoru; Hitobo, Takeshi; Wakabayashi, Suguru; Asaji, Toyohisa; Abe, Takashi

    2013-11-15

    In this study, we have proposed a low-pressure reactive ion etching of bulk polymer materials with a gas mixture of CF{sub 4} and O{sub 2}, and have achieved precise fabrication of poly(methyl methacrylate) (PMMA) and perfluoroalkoxy (PFA) bulk polymer plates with high-aspect-ratio and narrow gap array structures, such as, pillar, frustum, or cone, on a nano/micro scale. The effects of the etching conditions on the shape and size of each pillar were evaluated by changing etching duration and the size/material of etching mask. The fabricated PMMA array structures indicate possibilities of optical waveguide and nanofiber array. PFA cone array structures showed super-hydrophobicity without any chemical treatments. Also, polystyrene-coated silica spheres were used as an etching mask for the pillar array structure formation to control the gap between pillars.

  6. Study on Glow Discharge Plasma Used in Polyester Surface Modification

    NASA Astrophysics Data System (ADS)

    Liu, Wenzheng; Lei, Xiao; Zhao, Qiang

    2016-01-01

    To achieve an atmospheric pressure glow discharge (APGD) in air and modify the surface of polyester thread using plasma, the electric field distribution and discharge characteristics under different conditions were studied. We found that the region with a strong electric field, which was formed in a tiny gap between two electrodes constituting a line-line contact electrode structure, provided the initial electron for the entire discharge process. Thus, the discharge voltage was reduced. The dielectric barrier of the line-line contact electrodes can inhibit the generation of secondary electrons. Thus, the transient current pulse discharge was reduced significantly, and an APGD in air was achieved. We designed double layer line-line contact electrodes, which can generate the APGD on the surface of a material under treatment directly. A noticeable change in the surface morphology of polyester fiber was visualized with the aid of a scanning electron microscope (SEM). Two electrode structures - the multi-row line-line and double-helix line-line contact electrodes - were designed. A large area of the APGD plasma with flat and curved surfaces can be formed in air using these contact electrodes. This can improve the efficiency of surface treatment and is significant for the application of the APGD plasma in industries.

  7. 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.

  8. Experimental investigations of silicon tetrafluoride decomposition in ECR discharge plasma.

    PubMed

    Vodopyanov, A V; Golubev, S V; Mansfeld, D A; Sennikov, P G; Drozdov, Yu N

    2011-06-01

    The results of first experiments on the investigation of plasma of electron cyclotron resonance (ECR) discharge, sustained by CW radiation of technological gyrotron with frequency 24 GHz are considered. The parameters of nitrogen plasma of ECR discharge in magnetic field up to 1 T were investigated by Langmuir probe in the pressure range 10(-4)-10(-2) mbar under different values of microwave power. Depending on gas pressure and power of microwave radiation, the typical temperature and density of electrons could attain values of 1-5 eV and 10(11)-10(12) cm(-3), respectively. The prospects for using of ECR discharge for plasma chemical decomposition of silicon tetrafluoride (SiF(4)) have been experimentally demonstrated. Plasma was created from SiF(4) and hydrogen (H(2)) gas mixture and heated by microwave radiation in ECR conditions. Using the method of mass-spectrometry analysis of the gas at the outlet from the reactor and the weighting method, the content of the resultants of SiF(4) decomposition as a function of process parameters was investigated. It was shown that SiF(4) decomposition degree strongly depends on the microwave power, gas pressure in the reactor, gas flow rates, and can attain the value of 50%. The possible applications of PECVD method based on ECR discharge for production of isotopically pure elements with high deposition rate are discussed. PMID:21721687

  9. Experimental investigations of silicon tetrafluoride decomposition in ECR discharge plasma

    SciTech Connect

    Vodopyanov, A. V.; Golubev, S. V.; Mansfeld, D. A.; Sennikov, P. G.; Drozdov, Yu. N.

    2011-06-15

    The results of first experiments on the investigation of plasma of electron cyclotron resonance (ECR) discharge, sustained by CW radiation of technological gyrotron with frequency 24 GHz are considered. The parameters of nitrogen plasma of ECR discharge in magnetic field up to 1 T were investigated by Langmuir probe in the pressure range 10{sup -4}-10{sup -2} mbar under different values of microwave power. Depending on gas pressure and power of microwave radiation, the typical temperature and density of electrons could attain values of 1-5 eV and 10{sup 11}-10{sup 12} cm{sup -3}, respectively. The prospects for using of ECR discharge for plasma chemical decomposition of silicon tetrafluoride (SiF{sub 4}) have been experimentally demonstrated. Plasma was created from SiF{sub 4} and hydrogen (H{sub 2}) gas mixture and heated by microwave radiation in ECR conditions. Using the method of mass-spectrometry analysis of the gas at the outlet from the reactor and the weighting method, the content of the resultants of SiF{sub 4} decomposition as a function of process parameters was investigated. It was shown that SiF{sub 4} decomposition degree strongly depends on the microwave power, gas pressure in the reactor, gas flow rates, and can attain the value of 50%. The possible applications of PECVD method based on ECR discharge for production of isotopically pure elements with high deposition rate are discussed.

  10. 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.

  11. Nonsputtering impulse magnetron discharge

    SciTech Connect

    Khodachenko, G. V.; Mozgrin, D. V.; Fetisov, I. K.; Stepanova, T. V.

    2012-01-15

    Experiments with quasi-steady high-current discharges in crossed E Multiplication-Sign B fields in various gases (Ar, N{sub 2}, H{sub 2}, and SF{sub 6}) and gas mixtures (Ar/SF{sub 6} and Ar/O{sub 2}) at pressures from 10{sup -3} to 5 Torr in discharge systems with different configurations of electric and magnetic fields revealed a specific type of stable low-voltage discharge that does not transform into an arc. This type of discharge came to be known as a high-current diffuse discharge and, later, a nonsputtering impulse magnetron discharge. This paper presents results from experimental studies of the plasma parameters (the electron temperature, the plasma density, and the temperature of ions and atoms of the plasma-forming gas) of a high-current low-pressure diffuse discharge in crossed E Multiplication-Sign B fields.

  12. A capillary discharge plasma source of intense VUV radiation

    SciTech Connect

    Sobel'man, Igor I; Shevelko, A P; Yakushev, O F; Knight, L V; Turley, R S

    2003-01-31

    The results of investigation of a capillary discharge plasma, used as a source of intense VUV radiation and soft X-rays, are presented. The plasma was generated during the discharge of low-inductance condensers in a gas-filled ceramic capillary. Intense line radiation was observed in a broad spectral range (30-400 A) in various gases (CO{sub 2}, Ne, Ar, Kr, Xe). The absolute radiation yield for the xenon discharge was {approx}5 mJ (2{pi} sr){sup -1} pulse{sup -1} within a spectral band of width 9 A at 135 A. Such a radiation source can be used for various practical applications, such as EUV projection lithography, microscopy of biological objects in a 'water window', reflectometry, etc. (special issue devoted to the 80th anniversary of academician n g basov's birth)

  13. ICRF Heated Long-Pulse Plasma Discharges in LHD

    NASA Astrophysics Data System (ADS)

    Kumazawa, R.; Seki, T.; Mutoh, T.; Saito, K.; Watari, T.; Nakamura, Y.; Sakamoto, M.; Watanabe, T.; Kubo, S.; Shimozuma, T.; Yoshimura, Y.; Igami, H.; Takeiri, Y.; Oka, Y.; Tsumori, K.; Osakabe, M.; Ikeda, K.; Nagaoka, K.; Kaneko, O.; Miyazawa, J.; Morita, S.; Narihara, K.; Shoji, M.; Masuzaki, S.; Goto, M.; Morisaki, T.; Peterson, B. J.; Sato, K.; Tokuzawa, T.; Ashikawa, N.; Nishimura, K.; Funaba, H.; Chikaraishi, H.; Notake, T.; Torii, Y.; Okada, H.; Ichimura, M.; Higaki, H.; Takase, Y.; Kasahara, H.; Shimpo, F.; Nomura, G.; Takahashi, C.; Yokota, M.; Kato, A.; Zhao, Yanping; Yoon, J. S.; Kwak, J. G.; Yamada, H.; Kawahata, K.; Ohyabu, N.; Ida, K.; Nagayama, Y.; Noda, N.; Komori, A.; Sudo, S.; Motojima, O.; LHD Experimental Group

    2006-01-01

    A long-pulse plasma discharge for more than 30 min. was achieved on the Large Helical Device (LHD). A plasma of ne = 0.8× 1019 m-3 and Ti0 = 2.0 keV was sustained with PICH = 0.52 MW, PECH = 0.1 MW and averaged PNBI = 0.067 MW. Total injected heating energy was 1.3 GJ, which was a quarter of the prepared RF heating energy. One of the keys to the success of the experiment was a dispersion of the local plasma heat load to divertors, accomplished by shifting the magnetic axis inward and outward.

  14. 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.

  15. Instability of plasma plume of micro-hollow cathode discharge

    SciTech Connect

    Levko, D.; Bliokh, Y. P.; Gurovich, V. Tz.; Krasik, Ya. E.

    2015-11-15

    The micro-hollow cathode gas discharge driven by thermionic emission is studied using the two-dimensional particle-in-cell Monte Carlo collisions simulation. The electron current is extracted from the plasma plume penetrating into the keeper–anode space through a small keeper orifice from the cathode-keeper space. The results of simulations and a simplified analytical model showed that the plasma density and extracted current can exhibit deep modulation in the range of frequencies of tens of MHz. This modulation appears when the space-charge limited current between the plume boundary and the anode exceeds the plasma thermal electron current through the orifice.

  16. Effect of the radio frequency discharge on the dust charging process in a weakly collisional and fully ionized plasma

    SciTech Connect

    Motie, Iman; Bokaeeyan, Mahyar

    2015-02-15

    A close analysis of dust charging process in the presence of radio frequency (RF) discharge on low pressure and fully ionized plasma for both weak and strong discharge's electric field is considered. When the electromagnetic waves pass throughout fully ionized plasma, the collision frequency of the plasma is derived. Moreover, the disturbed distribution function of plasma particles in the presence of the RF discharge is obtained. In this article, by using the Krook model, we separate the distribution function in two parts, the Maxwellian part and the perturbed part. The perturbed part of distribution can make an extra current, so-called the accretion rate of electron (or ion) current, towards a dust particle as a function of the average electron-ion collision frequency. It is proven that when the potential of dust grains increases, the accretion rate of electron current experiences an exponential reduction. Furthermore, the accretion rate of electron current for a strong electric field is relatively smaller than that for a weak electric field. The reasons are elaborated.

  17. Theoretical modeling of pulse discharge cycle in dielectric barrier discharge plasma actuator

    NASA Astrophysics Data System (ADS)

    Sato, Shintaro; Ohnishi, Naofumi

    2016-07-01

    Simple models based on two-dimensional simulations are proposed to estimate intervals of periodically observed current pulses with a positive-going voltage in a dielectric barrier discharge plasma actuator. There are two distinct peaks in one streamer discharge; one is related to the formation of an ion cloud and the other is related to a filamentary discharge that is identified as a streamer. Simulation results show that the intervals of the current pulses depend on the slope of the applied voltage. For the ion-cloud formation phase, we model the time evolution of electron number density at the exposed electrode with ionization frequency. For the ion-cloud expansion phase, a positive ion cylinder model is proposed to estimate the electric field generated by surface charge on the dielectric. These models well reproduce the discharge intervals obtained in the numerical simulations.

  18. Self-consistent discharge growing model of helicon plasma

    NASA Astrophysics Data System (ADS)

    Isayama, Shogo; Hada, Tohru; Shinohara, Shunjiro; Tanikawa, Takao

    2015-11-01

    Helicon plasma is a high-density and low-temperature plasma generated by the electromagnetic (Helicon) wave excited in the plasma. It is thought to be useful for various applications including electric thrusters. Physics of helicon plasma production involves such fundamental processes as the wave propagation (dispersion relation), collisional and non-collisional wave damping, plasma heating, ionization/recombination of neutral particles, and modification of the dispersion relation by newly ionized plasma. There remain a number of unsolved physical issues such as, how the Helicon and the TG modes influence the plasma density, electron temperature and their spatial profiles. While the Helicon mode is absorbed in the bulk plasma, the TG mode is mostly absorbed near the edge of the plasma. The local power deposition in the helicon plasma is mostly balanced by collisional loss. This local power balance can give rise to the inhomogeneous electron temperature profile that leads to time evolution of density profile and dispersion relation. In our study, we construct a self-consistent model of the discharge evolution that includes the wave excitation, electron heat transfer, and diffusion of charged particles.

  19. Thomson scattering diagnostics of atmospheric pressure plasmas - Pulsed filament discharges and plasma jets

    NASA Astrophysics Data System (ADS)

    Tomita, Kentaro

    2015-09-01

    Recently, non-thermal atmospheric-pressure plasmas have received much attention. Because the characteristics of the plasmas are governed by free electrons, measurements of the electron density (ne) and electron temperature (Te) are a prerequisite for understanding plasma behavior. To contribute to the understanding of non-thermal atmospheric-pressure plasmas, we have been developing a laser Thomson scattering (LTS) technique as a diagnostic method for measuring ne and Te of two types of plasmas; a pulsed-filament discharge and He flow plasma jet. The pulsed filament discharge has a short current width (a few tens of ns) and a small size. In order to apply LTS to such plasmas, reproducibility of time and space of the plasmas were improved using a high-speed semiconductor switch. Spatiotemporal evolutions of ne and Te of a main discharge have been obtained. Now we try to apply LTS at a time of primary streamer. Regarding to the He flow plasma jet, the discharge was generated with He gas flow with N2/O2(20%) or N2 shielding gas. It was confirmed that the ne at the center of the plasma with N2/O2 shielding gas was around 50% higher than that with the N2 shielding gas. In collaboration with Keiichiro Urabe, The University of Tokyo; Naoki Shirai, Tokyo Metropolitan University; Safwat Hassaballa, Al-Azhar University; Nima Bolouki, Munehiro Yoneda, Takahiro Shimizu, Yuta Sato, and Kiichiro Uchino, Kyushu University.

  20. Modeling of inductively coupled plasma SF{sub 6}/O{sub 2}/Ar plasma discharge: Effect of O{sub 2} on the plasma kinetic properties

    SciTech Connect

    Pateau, Amand; Rhallabi, Ahmed Fernandez, Marie-Claude; Boufnichel, Mohamed; Roqueta, Fabrice

    2014-03-15

    A global model has been developed for low-pressure, inductively coupled plasma (ICP) SF{sub 6}/O{sub 2}/Ar mixtures. This model is based on a set of mass balance equations for all the considered species, coupled with the discharge power balance equation and the charge neutrality condition. The present study is an extension of the kinetic global model previously developed for SF{sub 6}/Ar ICP plasma discharges [Lallement et al., Plasma Sources Sci. Technol. 18, 025001 (2009)]. It is focused on the study of the impact of the O{sub 2} addition to the SF{sub 6}/Ar gas mixture on the plasma kinetic properties. The simulation results show that the electron density increases with the %O{sub 2}, which is due to the decrease of the plasma electronegativity, while the electron temperature is almost constant in our pressure range. The density evolutions of atomic fluorine and oxygen versus %O{sub 2} have been analyzed. Those atomic radicals play an important role in the silicon etching process. The atomic fluorine density increases from 0 up to 40% O{sub 2} where it reaches a maximum. This is due to the enhancement of the SF{sub 6} dissociation processes and the production of fluorine through the reactions between SF{sub x} and O. This trend is experimentally confirmed. On the other hand, the simulation results show that O(3p) is the preponderant atomic oxygen. Its density increases with %O{sub 2} until reaching a maximum at almost 40% O{sub 2}. Over this value, its diminution with O{sub 2}% can be justified by the high increase in the loss frequency of O(3p) by electronic impact in comparison to its production frequency by electronic impact with O{sub 2}.

  1. PlasmaPIC: A tool for modeling low-temperature plasma discharges

    NASA Astrophysics Data System (ADS)

    Muehlich, Nina Sarah; Becker, Michael; Henrich, Robert; Heiliger, Christian

    2015-09-01

    PlasmaPIC is a three-dimensional particle in cell (PIC) code. It consists of an electrostatic part for modeling dc and rf-ccp discharges as well as an electrodynamic part for modeling inductively coupled discharges. The three-dimensional description enables the modeling of discharges in arbitrary geometries without limitations to any symmetry. These geometries can be easily imported from common CAD tools. A main feature of PlasmaPIC is the ability of an excellent massive parallelization of the computation, which scales linearly up to a few hundred cpu cores. This is achieved by using a multigrid algorithm for the field solver as well as an effective load balancing of the particles. Moreover, PlasmaPIC includes the interaction of the neutral gas and the plasma discharge. Because the neutral gas and the plasma simulation are acting on different time scales we perform the simulation of both separately in a self-consistent treatment, whereas the neutral gas distribution is calculated using the direct simulation Monte Carlo method (DSMC). The merge of these features turns PlasmaPIC into a powerful simulation tool for a wide range of plasma discharges and introduces a new way of understanding and optimizing low-temperature plasma applications. This work has been supported by the ``Bundesministerium fuer Wirtschaft und Energie.'' Grant 50RS1507.

  2. Grassroots Advancement Plasma Physics: The Creation of a Dc Glow Discharge Tube for a high school classroom

    NASA Astrophysics Data System (ADS)

    Onumah, Henrietta; Sheth, Niraj; Gershman, Sophia; Post Zwicker, Andrew

    2002-11-01

    The objective of the project is to create a safe, affordable, portable, computer interactive, and multifunctional DC glow discharge tube for use in a typical high school physics classroom. Our goal is to use this device not only to capture and cerate interest in plasma physics but as a tool to engage students in an active exploration of a variety of physics topics. We present the design, operation and labs created with our discharge tube. We are creating a selection of labs ranging from current/voltage relationships to spectroscopy that can be done on our setup. We have evaluated the vacuum chamber material- glass vs. plastic, our electrode spacing- a fixed vs. variable, external electronics with an emphasis on the power supply, safety and ease of use. Our design is an accessible 6 inch long tube with an inner diameter of 2 inches, which attains low pressure of about 20- 40 mTorr and is computer interactive.

  3. Doppler spectroscopy on plasma discharges produced in Proto-MPEX

    NASA Astrophysics Data System (ADS)

    Dhaliwal, Runpal; Biewer, Theodore; Klepper, Chris; Martin, Elijah; Rapp, Juergen

    2015-11-01

    The Prototype Material Plasma Exposure eXperiment (Proto-MPEX) is a linear machine that produces pulsed plasma discharges, and is intended to study plasma-material interactions in conditions similar to those found in future fusion reactors. A high-resolution McPherson Czerny-Turner visible range spectrometer has been installed to study the behavior of ions in the plasma. Together with a Princeton Instruments EMCCD camera and an external trigger box, this system provides excellent spectral and temporal resolution for viewing the emission spectra of the discharges. Around 100 lines of sight have been established for use by this and other diagnostics in the lab. Initial data from recent experiments validate the utility of this setup. Analysis of spectral lines in helium and deuterium plasmas yields valuable information regarding the temperature and density of plasma ions at various locations in the machine as the various RF heating sources are implemented. Differentiating the thermal width of lines from other sources of broadening is an ongoing process. In addition to He I lines, data indicates the presence of the He II line at 468.5 nm, which corresponds to emission from singly ionized atoms at higher temperatures.

  4. Design of a plasma discharge circuit for particle wakefield acceleration

    NASA Astrophysics Data System (ADS)

    Anania, M. P.; Chiadroni, E.; Cianchi, A.; Di Giovenale, D.; Ferrario, M.; Flora, F.; Gallerano, G. P.; Ghigo, A.; Marocchino, A.; Massimo, F.; Mostacci, A.; Mezi, L.; Musumeci, P.; Serio, M.

    2014-03-01

    Plasma wakefield acceleration is the most promising acceleration technique known nowadays, able to provide very high accelerating fields (10-100 GV m-1), enabling acceleration of electrons to GeV energy in few centimetres. However, the quality of the electron bunches accelerated with this technique is still not comparable with that of conventional accelerators; radiofrequency-based accelerators, in fact, are limited in the accelerating field (10-100 MV m-1) requiring therefore kilometric distances to reach the GeV energies, but can provide very bright electron bunches. Combining high brightness electron bunches from conventional accelerators and high accelerating fields reachable with plasmas could be a good compromise allowing to further accelerate high brightness electron bunches coming from LINAC while preserving electron beam quality. Following the idea of plasma wave resonant excitation driven by a train of short bunches, we have started to study the requirements in terms of plasma for SPARC-LAB [1,2]. In particular, here we focus on the ionization process; we show a simplified model to study the evolution of plasma induced by discharge, very useful to design the discharge circuit able to fully ionize the gas and bring the plasma at the needed temperature and density.

  5. Numerical analysis of plasma evolution on dielectric barrier discharge plasma actuator

    SciTech Connect

    Nishida, Hiroyuki; Abe, Takashi

    2011-07-01

    Time evolution of the discharge plasma in the dielectric barrier discharge (DBD) plasma actuator was simulated by the simple fluid model in which the electron and single positive ion species were considered. The characteristics of the discharge plasma evolution were investigated in detail, and the following results were obtained. When the positive-going voltage is applied, the streamer discharge is formed periodically. The periodically formed streamer expands from the exposed electrode, and its length becomes longer than the previous one. Periodic breakdown of the gas and step-by-step plasma expansion are also observed during the negative-going voltage; however, the streamer is not formed and the breakdown frequency is much higher. The simulation results with a triangular applied voltage waveform show the same characteristics as observed in the experiment; large discharge current spikes are observed during both the positive- and negative-going voltage phase, and the plasma in the negative-going voltage phase expands more smoothly than that in the positive phase because of its higher breakdown frequency. It was shown that even the simple numerical model could provide valuable insights into the physics of DBD plasma actuator; this indicates that the positive ions and electrons play a prominent role in determining the general characteristics of the plasma evolution.

  6. Spectroscopic investigation of the NO C 2Π de-excitation process by collision with O2 X 3Σg- in a low-pressure N2-O2 mixture microwave discharge

    NASA Astrophysics Data System (ADS)

    Tan, Hao; Nezu, Atsushi; Akatsuka, Hiroshi

    2016-01-01

    We use a spectroscopic method to diagnose the microwave discharge plasma of N2-O2 mixtures. We succeed in observing NO δ-band radiation peaks when the oxygen partial pressure is smaller than 3%. In order to quantitatively investigate the de-excitation processes of the NO C 2Π excited state, we improve our self-consistent kinetic model to include some of the main excited states of NO molecules. In providing our numerical results, we discuss a reasonable NO C 2Π de-population process by that involves collision with the O2 X 3Σg- state molecule, which leads to the disappearance of δ-band radiation. We propose an indirect proof that this de-population process results in an increase in the vibrational temperature of NO A 2Σ+.

  7. MHD Simulation of the Inverse Pinch Plasma Discharge

    SciTech Connect

    Esaulov, A; Bauer, B; Lindemuth, I; Makhin, V; Presura, R; Ryutov, D

    2004-07-01

    A wall confined plasma in an inverse pinch configuration holds potential as a plasma target for Magnetized Target Fusion (MTF) as well as the simple geometry to study wall-confined plasma. An experiment is planned to study the inverse pinch configuration using the Nevada Terawatt Facility (NTF) at the University of Nevada, Reno (UNR). The dynamics of the discharge formation have been analyzed using analytic models and numerical methods. Strong heating occurs by thermalization of directed energy when an outward moving current sheet (the inverse pinch effect) collides with the outer wall of the experimental chamber. Two dimensional MHD simulations show Rayleigh-Taylor and Richtmyer-Meshkov -like modes of instability, as expected because of the shock acceleration during plasma formation phase. The instabilities are not disruptive, but give rise to a mild level of turbulence. The conclusion from this work is that an interesting experiment relevant to wall confinement for MTF could be done using existing equipment at UNR.

  8. Simulation Tool for Dielectric Barrier Discharge Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Likhanskii, Alexander

    2014-01-01

    Traditional approaches for active flow separation control using dielectric barrier discharge (DBD) plasma actuators are limited to relatively low speed flows and atmospheric conditions. This results in low feasibility of the DBDs for aerospace applications. For active flow control at turbine blades, fixed wings, and rotary wings and on hypersonic vehicles, DBD plasma actuators must perform at a wide range of conditions, including rarified flows and combustion mixtures. An efficient, comprehensive, physically based DBD simulation tool can optimize DBD plasma actuators for different operation conditions. Researchers are developing a DBD plasma actuator simulation tool for a wide range of ambient gas pressures. The tool will treat DBD using either kinetic, fluid, or hybrid models, depending on the DBD operational condition.

  9. Diagnostics of Argon Inductively Coupled Plasma and Dielectric Barrier Discharge Plasma by Optical Emission Spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Jia-liang; Yu, Shi-ji; Ma, Teng-cai; Deng, Xin-lu

    2001-08-01

    An experimental setup was built up to carry out radio frequency (RF) inductively coupled plasma (ICP) and dielectric barrier discharge (DBD), and to depict the optical emission spectra (OES) of the discharges. OES from argon ICP and DBD plasmas in visible and near ultraviolet region were measured. For argon ICP, the higher RF power input (higher than 500 W for our machine), the higher degree of argon plasma ionization. But that doesn't mean a higher mean electron energy. With the increase in the power input, the mean electron energy increases slightly, whereas the density of electron increases apparently. Or, the contrary, argon DBD discharge behaves in the manner of a pulsed DC discharge on optical emission spectroscopy and V-I characteristics. DBD current is composed of a series of pulses equally spaced in temporal domain. The kinetics of DBD emission strength is mainly governed by the frequency of the current pulse.

  10. Particle based plasma simulation for an ion engine discharge chamber

    NASA Astrophysics Data System (ADS)

    Mahalingam, Sudhakar

    Design of the next generation of ion engines can benefit from detailed computer simulations of the plasma in the discharge chamber. In this work a complete particle based approach has been taken to model the discharge chamber plasma. This is the first time that simplifying continuum assumptions on the particle motion have not been made in a discharge chamber model. Because of the long mean free paths of the particles in the discharge chamber continuum models are questionable. The PIC-MCC model developed in this work tracks following particles: neutrals, singly charged ions, doubly charged ions, secondary electrons, and primary electrons. The trajectories of these particles are determined using the Newton-Lorentz's equation of motion including the effects of magnetic and electric fields. Particle collisions are determined using an MCC statistical technique. A large number of collision processes and particle wall interactions are included in the model. The magnetic fields produced by the permanent magnets are determined using Maxwell's equations. The electric fields are determined using an approximate input electric field coupled with a dynamic determination of the electric fields caused by the charged particles. In this work inclusion of the dynamic electric field calculation is made possible by using an inflated plasma permittivity value in the Poisson solver. This allows dynamic electric field calculation with minimal computational requirements in terms of both computer memory and run time. In addition, a number of other numerical procedures such as parallel processing have been implemented to shorten the computational time. The primary results are those modeling the discharge chamber of NASA's NSTAR ion engine at its full operating power. Convergence of numerical results such as total number of particles inside the discharge chamber, average energy of the plasma particles, discharge current, beam current and beam efficiency are obtained. Steady state results for

  11. Mass spectrometric study on inactivation mechanism of spore-forming bacteria by low-pressure surface-wave excited oxygen plasma

    SciTech Connect

    Zhao Ying; Ogino, Akihisa; Nagatsu, Masaaki

    2011-05-09

    In this letter, the etching phenomena of the spore-forming bacteria by oxygen plasma were investigated by using quadrupole mass spectrometry. The etching by-products of H{sub 2}O and CO{sub 2} were obviously detected during the oxygen plasma irradiation by the multiple ion detection measurement. Inactivation of roughly 10{sup 6} spores population was achieved under almost the same reduced spore shapes for three different incident microwave powers. It is considered from the present results that the oxygen radical etching could cause damage to the germinant receptors located in the inner membrane inevitable for germination of spores, without any damage of the DNA in the cores.

  12. Mass spectrometric study on inactivation mechanism of spore-forming bacteria by low-pressure surface-wave excited oxygen plasma

    NASA Astrophysics Data System (ADS)

    Zhao, Ying; Ogino, Akihisa; Nagatsu, Masaaki

    2011-05-01

    In this letter, the etching phenomena of the spore-forming bacteria by oxygen plasma were investigated by using quadrupole mass spectrometry. The etching by-products of H2O and CO2 were obviously detected during the oxygen plasma irradiation by the multiple ion detection measurement. Inactivation of roughly 106 spores population was achieved under almost the same reduced spore shapes for three different incident microwave powers. It is considered from the present results that the oxygen radical etching could cause damage to the germinant receptors located in the inner membrane inevitable for germination of spores, without any damage of the DNA in the cores.

  13. Numerical description of discharge characteristics of the plasma needle

    SciTech Connect

    Brok, W.J.M.; Bowden, M.D.; Dijk, J. van; Mullen, J.J.A.M. van der; Kroesen, G.M.W.

    2005-07-01

    The plasma needle is a small atmospheric, nonthermal, radio-frequency discharge, generated at the tip of a needle, which can be used for localized disinfection of biological tissues. Although several experiments have characterized various qualities of the plasma needle, discharge characteristics and electrical properties are still not well known. In order to provide initial estimates on electrical properties and quantities such as particle densities, we employed a two-dimensional, time-dependent fluid model to describe the plasma needle. In this model the balance equation is solved in the drift-diffusion approach for various species and the electron energy, as well as Poisson's equation. We found that the plasma production occurs in the sheath region and results in a steady flux of reactive species outwards. Even at small (<0.1%) admixtures of N{sub 2} to the He background, N{sub 2}{sup +} is the dominant ion. The electron density is typically 10{sup 11} cm{sup -3} and the dissipated power is in the order of 10 mW. These results are consistent with the experimental data available and can give direction to the practical development of the plasma needle.

  14. Suprathermal electrons produced by beam-plasma-discharge

    NASA Technical Reports Server (NTRS)

    Sharp, W. E.

    1982-01-01

    Experiments conducted with a low energy plasma lens, HARP, in the electron beam of the large vacuum chamber at Johnson Space Center indicate that an enhanced population of 50 to 300 volt electrons appear when the beam goes into the Beam-Plasma Discharge (BPD) mode. Below the BPD instability the electron distribution appears to be characterized as non-energized single particle scattering and energy loss. At 100 cm from the beam core in the BPD mode the fluxes parallel to the beam are reduced by a factor of 20 with respect to the fluxes at 25 cm. Some evidence for isotropy near the beam core is presented.

  15. Plasma physics issues in gas discharge laser development

    SciTech Connect

    Garscadden, A. ); Kushner, M.J.; Eden, J.G. . Dept. of Electrical and Computer Engineering)

    1991-12-01

    In this paper an account is given of the interplay between partially ionized plasma physics and the development of gas discharge lasers. Gas discharge excitation has provided a wide array of laser devices extending from the soft X-ray region to the far infrared. The scaling of gas discharge lasers in power and energy also covers many orders of magnitude. The particular features of three regimes are discussed: short wavelength lasers (deep UV to soft X-ray); visible and near UV lasers; and infrared molecular gas lasers. The current status (Fall 1990) of these areas is reviewed, and an assessment is made of future research topics that are perceived to be important.

  16. Effects of discharge voltage waveform on the discharge characteristics in a helium atmospheric plasma jet

    SciTech Connect

    Uchida, Giichiro Takenaka, Kosuke; Setsuhara, Yuichi

    2015-04-21

    We present here an analysis of the discharge characteristics of a He plasma jet operating under three different types of applied voltage waveform: (a) a μs-pulse voltage waveform with a slow voltage rise time, (b) ns-pulse, and (c) rectangular voltage waveforms with fast voltage rise time. Optical emission measurements show that the application of a voltage with a fast voltage rise time induces rapid discharge growth and, consequently, produces an abundance of energetic electrons, which in turn leads to high optical emission from the O atoms. We also estimate the optical emission efficiency of the O atom (η{sub o}), which corresponds roughly to the production efficiency of the reactive O species. η{sub o} increases with increasing applied voltage, and the highest value of η{sub o} is obtained in the shortest pulse discharge, which was ignited by a ns-pulse voltage waveform with a fast voltage rise time and short pulse width.

  17. Production Of Multi-magnetron Plasma By Using Polyphase Ac Glow Discharge In An Improved Multi-pole Magnetic Field

    NASA Astrophysics Data System (ADS)

    Matsumoto, Kazunori; Motoki, Kentaro; Miyamoto, Masahiro; Uetani, Yasuhiro

    1998-10-01

    Effects of an improved multi-pole magnetic field on a plasma production generated by a polyphase ac glow discharge with multiple electrodes have been investigated. Conventional configuration of the multi-pole magnetic filed has been modified to suppress plasma losses at both ends of the chamber due to ExB drift motion. The modified multi-pole magnetic field has enabled us to produce a multiple magnetron-plasma at a considerably low pressure less than mTorr. The low temperature plasma has been widely used as the fine processing technology of a dry etching and as the thin film formation technology of a sputtering coating. Large-scale plasmas which can be generated at a low gas-pressure have been desired for more wider dry etching and greater sputter coating. The purpose of this study is to develop a large-scale and low-cost plasma generator by using a polyphase ac power source with the low frequency. In this session, we will present the experimental result as to a multiple magnetron-plasma generated in the modified twenty-four poles magnetic field by using the twenty-four-phase ac power source with the commercial electric power frequency of 60Hz. The ac power is supplied to twenty-four electrodes which are fixed to the water-cooled chamber-wall through sheet insulators so that the electrodes can be cooled indirectly.

  18. End-boundary sheath potential, Langmuir waves, electron and ion energy distribution in the low pressure DC powered Non-ambipolar Electron Plasma

    NASA Astrophysics Data System (ADS)

    Chen, Lee; Chen, Zhiying; Funk, Merritt

    2013-09-01

    The non-ambipolar electron plasma (NEP) is heated by electron beam extracted from the electron-source Ar plasma through a dielectric injector by an accelerator located inside NEP. NEP pressure is in the 1-3mTorr range of N2 and its accelerator voltage varied from VA = + 80 to VA = + 600V. The non-ambipolar beam-current injected into NEP is in the range of 10s Acm-2 and it heats NEP through beam-plasma instabilities. Its EED f has a Maxwellian bulk followed by a broad energy-continuum connecting to the most energetic group with energies above the beam-energy. The remnant of the injected electron-beam power terminates at the NEP end-boundary floating-surface setting up sheath potentials from VS = 80 to VS = 580V in response to the applied values of VA. The floating-surface is bombarded by a space-charge neutral plasma-beam whose IED f is near mono-energetic. When the injected electron-beam power is adequately damped by NEP, its end-boundary floating-surface VS can be linearly controlled at almost 1:1 ratio by VA. NEP does not have an electron-free sheath; its ``sheath'' is a widen presheath that consists of a thermal presheath followed by an ``anisotropic'' presheath, leading up to the end-boundary floating-surface. Its ion-current of the plasma-beam is much higher than what a conventional thermal presheath can supply. If the NEP parameters cannot damp the electron beam power sufficiently, VS will collapse and becomes irresponsive to VA.

  19. Study of organic pollutants oxidation by atmospheric plasma discharge

    NASA Astrophysics Data System (ADS)

    Gumuchian, Diane; Cavadias, Simeon; Duten, Xavier; Tatoulian, Michael; da Costa, Patrick; Ognier, Stephanie

    2013-09-01

    Ozonation is one of the usual steps in water treatment processes. However, some organic molecules (acetic acid) cannot be decomposed during ozonation. In that context, we are developing an Advanced Oxidation Process based on the use of a needle plate discharge at atmospheric pressure. The process is a reactor with a plasma discharge between a high voltage electrode and the solution in controlled atmosphere. Characterizations of the plasma obtained in different atmospheres were carried out (Optical Emission Spectroscopy, iCCD camera observations, etc). The efficiency of the process was evaluated by the percentage of degradation of the model-pollutant, measured by liquid chromatography analysis. Treatments in nitrogen lead to the formation of NOx species that decrease the efficiency of the process. Indeed, NOx lead to the consumption of actives species created. Treatments in argon are the most efficient. Two hypotheses are considered: (i) metastable argon participates to the degradation of acetic acid or to the formation of radicals (ii) discharges in argon lead to the formation of many streamers of low energy that increase the interface plasma/solution.

  20. Design of a Microwave Assisted Discharge Inductive Plasma Accelerator

    NASA Technical Reports Server (NTRS)

    Hallock, Ashley K.; Polzin, Kurt A.

    2010-01-01

    The design and construction of a thruster that employs electrodeless plasma preionization and pulsed inductive acceleration is described. Preionization is achieved through an electron cyclotron resonance discharge that produces a weakly-ionized plasma at the face of a conical theta pinch-shaped inductive coil. The presence of the preionized plasma allows for current sheet formation at lower discharge voltages than those employed in other pulsed inductive accelerators that do not employ preionization. The location of the electron cyclotron resonance discharge is controlled through the design of the applied magnetic field in the thruster. Finite element analysis shows that there is an arrangement of permanent magnets that yields a small volume of resonant magnetic field at the coil face. Preionization in the resonant zone leads to current sheet formation at the coil face, which minimizes the initial inductance of the pulse circuit and maximizes the potential electrical efficiency of the accelerator. A magnet assembly was constructed around an inductive coil to provide structural support to the selected arrangement of neodymium magnets. Measured values of the resulting magnetic field compare favorably with the finite element model.

  1. Carbon deposition on metallic surfaces studied by RF plasma discharge

    NASA Astrophysics Data System (ADS)

    Cairns, J. A.; Coad, J. P.; Richards, E. W. T.; Stenhouse, I. A.

    1980-12-01

    The accumulation of carbonaceous deposits on surfaces exposed to gases containing hydrocarbons or carbon monoxide, such as the stainless steel fuel pins in an advanced gas-cooled nuclear reactor, is investigated by means of an RF plasma discharge system. Specimens of the 20/25/Nb steel used for the fuel pins and of copper were subjected to an RF plasma discharge of a CO/CH4 gas mixture, and the amounts and compositions of the deposits formed were determined. The steel is observed to acquire a significant deposit of carbon after 4 h in the discharge, while the copper remained essentially clean. When the steel is coated with a silica layer, however, it is also found to remain clean throughout its exposure, while nearby uncoated steel specimens were contaminated. Spectroscopic examination of the light emitted from the plasma in the vicinity of the specimens indicates that the carbonaceous deposition is induced largely by the catalytic activity of the steel surface itself, and that deposition can be prevented by the use of suitable coatings.

  2. Chemical waste disposal in space by plasma discharge

    NASA Technical Reports Server (NTRS)

    Baird, James K.

    1991-01-01

    An inductively coupled plasma discharge apparatus operating at 13.56 MHz and with electrical power up to 2.5 kW was constructed. The efficiency of this device to destroy various gases expected to be carried aboard the Space Station was tested. By expressing the efficiency of the device in terms of G-value (the number of molecules decomposed per 100 eV of energy absorbed), the results are compared with known efficiencies of ionizing radiation to destroy these same gases. In the case of ammonia, it was found that in the inductively coupled device, the destruction efficiency, G(-NH3) varied from 6.0 to 32.0 molecules/100 eV, depending on conditions. It was also found that capacitatively coupled discharges were less efficient in destroying NH2 than the inductively coupled discharge. In the case NH2 destruction, it was found that the G(-NH3) was a qualitative guide to the efficiencies of plasmas. The plasma device was also used to destroy nitrous oxide and methane. It is shown how the G-value for the destruction of any gas can be computed theoretically from a knowledge of the electron velocity distribution, the various electron molecule scattering cross sections, and the rate constants for the reactions of secondary species.

  3. Volume Diffuse Dielectric Barrier Discharge Plasma Produced by Nanosecond High Voltage Pulse in Airflow

    NASA Astrophysics Data System (ADS)

    Qi, Haicheng; Gao, Wei; Fan, Zhihui; Liu, Yidi; Ren, Chunsheng

    2016-05-01

    Volume diffuse dielectric barrier discharge (DBD) plasma is produced in subsonic airflow by nanosecond high-voltage pulse power supply with a plate-to-plate discharge cell at 6 mm air gap length. The discharge images, optical emission spectra (OES), the applied voltage and current waveforms of the discharge at the changed airflow rates are obtained. When airflow rate is increased, the transition of the discharge mode and the variations of discharge intensity, breakdown characteristics and the temperature of the discharge plasma are investigated. The results show that the discharge becomes more diffuse, discharge intensity is decreased accompanied by the increased breakdown voltage and time lag, and the temperature of the discharge plasma reduces when airflow of small velocity is introduced into the discharge gap. These phenomena are because that the airflow changes the spatial distribution of the heat and the space charge in the discharge gap. supported by National Natural Science Foundation of China (No. 51437002)

  4. Dielectric barrier discharge plasma actuator for flow control

    NASA Astrophysics Data System (ADS)

    Opaits, Dmitry Florievich

    Electrohydrodynamic (EHD) and magnetohydrodynamic phenomena are being widely studied for aerodynamic applications. The major effects of these phenomena are heating of the gas, body force generation, and enthalpy addition or extraction, [1, 2, 3]. In particular, asymmetric dielectric barrier discharge (DBD) plasma actuators are known to be effective EHD device in aerodynamic control, [4, 5]. Experiments have demonstrated their effectiveness in separation control, acoustic noise reduction, and other aeronautic applications. In contrast to conventional DBD actuators driven by sinusoidal voltages, we proposed and used a voltage profile consisting of nanosecond pulses superimposed on dc bias voltage. This produces what is essentially a non-self-sustained discharge: the plasma is generated by repetitive short pulses, and the pushing of the gas occurs primarily due to the bias voltage. The advantage of this non-self-sustained discharge is that the parameters of ionizing pulses and the driving bias voltage can be varied independently, which adds flexibility to control and optimization of the actuators performance. Experimental studies were conducted of a flow induced in a quiescent room air by a single DBD actuator. A new approach for non-intrusive diagnostics of plasma actuator induced flows in quiescent gas was proposed, consisting of three elements coupled together: the Schlieren technique, burst mode of plasma actuator operation, and 2-D numerical fluid modeling. During the experiments, it was found that DBD performance is severely limited by surface charge accumulation on the dielectric. Several ways to mitigate the surface charge were found: using a reversing DC bias potential, three-electrode configuration, slightly conductive dielectrics, and semi conductive coatings. Force balance measurements proved the effectiveness of the suggested configurations and advantages of the new voltage profile (pulses+bias) over the traditional sinusoidal one at relatively low

  5. Etching of UO{sub 2} in NF{sub 3} RF Plasma Glow Discharge

    SciTech Connect

    John M. Veilleux

    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 UO{sub 2} were conducted to demonstrate that plasma treatment is a viable method for decontaminating UO{sub 2} from stainless steel substrates. Experiments were conducted using NF{sub 3} gas to decontaminate depleted uranium dioxide from stainless-steel substrates. Depleted UO{sub 2} samples each containing 129.4 Bq were prepared from 100 microliter solutions of uranyl nitrate hexahydrate solution. The amorphous UO{sub 2} in the samples had a relatively low density of 4.8 gm/cm{sub 3}. Counting of the depleted UO{sub 2} 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, {sup 234}Th and {sup 234}Pa. 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 UO{sub 2} 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 UO{sub 2} in the samples was removed in just 17 minutes. The initial etch rate in the experiments ranged from 0.2 to 7.4 {micro}m/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 UO{sub 2} etching was also noted below 50 W in which etching increased up to a maximum pressure, {approximately}23 Pa, then decreased with further increases in pressure.

  6. Cyclic evolution of the electron temperature and density in dusty low-pressure radio frequency plasmas with pulsed injection of hexamethyldisiloxane

    SciTech Connect

    Garofano, V.; Stafford, L. E-mail: kremena.makasheva@laplace.univ-tlse.fr; Despax, B.; Clergereaux, R.; Makasheva, K. E-mail: kremena.makasheva@laplace.univ-tlse.fr

    2015-11-02

    Optical emission spectroscopy was used to analyze the very-low-frequency cyclic evolution of the electron energy and density caused by repetitive formation and loss of dust nanoparticles in argon plasmas with pulsed injection of hexamethyldisiloxane (HMDSO, [CH{sub 3}]{sub 6}Si{sub 2}O). After elaborating a Boltzmann diagram for Ar high-lying levels and a collisional-radiative model for Ar 2p (Paschen notation) states, temperatures characterizing the low- and high-energy parts of the electron population were calculated. Relative electron densities were also estimated from relative line emission intensities. Both temperatures increase when the dust occupation increases, and then decrease when dust is lost. The opposite trend was observed for the electron density. Such cyclic behaviors of the electron energy and electron density in the HMDSO-containing plasmas are in good agreement with the evolution processes in dusty plasmas, in which the formation of negative ions followed by an electron attachment on the surfaces of the nanoparticles is a critical phenomenon driving dust growth.

  7. Spectroscopic diagnostics of low-pressure inductively coupled Kr plasma using a collisional–radiative model with fully relativistic cross sections

    NASA Astrophysics Data System (ADS)

    Gangwar, Reetesh K.; Dipti; Srivastava, Rajesh; Stafford, Luc

    2016-06-01

    A collisional–radiative (C–R) model for krypton plasma using fully relativistic distorted-wave cross sections for electron excitations was developed. The model was applied to the characterization of inductively coupled Kr plasma with cylindrical geometry over the pressure regime 1–50 mTorr. Radially averaged emission intensities from transitions of Kr (4p55p  →  4p55s) in the range 500–900 nm were recorded at 17 cm from the planar RF-driven coil, with the plasma operated in the inductive regime (H mode). The measured emission intensities were then fitted by varying the electron density, n e, and electron temperature, T e, in the C–R model. At both low and high pressures, variations of the electron density by over two orders of magnitude had only a minor role on the relative emission intensities. On the other hand, T e values deduced from the comparison between experiment and model decreased from 6.7 to 2.6 eV as pressure increased from 1 to 50 mTorr. These results are found to be in good agreement with the effective electron temperature determined from Langmuir probe measurements and the predictions of a model based on the particle balance equation of charged particles.

  8. Study of DC discharge plasma polymerization kinetics, film properties and applications and initial study of silica powder surface modification by RF plasma polymerization

    NASA Astrophysics Data System (ADS)

    Guo, Sheyu

    1998-09-01

    In this work, two kinds of plasma polymerization for surface modification are discussed. In part-I, DC plasma polymerization is investigated for film properties, film growth mechanism and film application. The monomers heaxamethyldisiloxane (HMDSO) and pyrrole were selected to study the deposition rates change with discharge parameters such as pressure, flow rate, power, discharge current density. Structures and properties of film deposited at extreme conditions (high power/low pressure or low power/high pressure) were studied with FT-IR, SEM, TOF-SIMS, AIM, surface energy measurement and tribology test. This work also investigated DC plasma polymerization kinetics by combining plasma parameters with film deposited rate at different conditions. Both single and double Langmuir probes were used to measure the plasma parameters in pulsed power and continuous discharges. Plasma density and electron temperature are reported. A DC plasma polymerization kinetic model is Proposed based on the experimental data and a best-fit mathematical method. DC plasma polymerization application was the other object of this study. Cold-rolled steel and copper were coated with pyrrole and HMDSO, respectively. Corrosion rate were obtained from electrochemical polarization methods, and tests in humidity chamber directly. Various monomers were used to change the substrate surface energy. Hydrophilic and hydrophobic surface were achieved respectively by different monomers. A water-soluble film was obtained with acrylic acid in mild plasma conditions. In part-II, a initial study of powder surface modification has been done. The aim of this work was to investigate the possibility of changing powder surface properties with plasma-polymerized coatings. RF inductive plasma was used as a source to excite plasma polymerization for powder treatment. Plasma-polymerized pyrrole films were deposited on silica surface. Several techniques such as SEM, EDX, TOF-SIMS, FT-IF, DSC&TGA, and surface energy

  9. Focusing of plasma flow in an E cross B discharge

    NASA Astrophysics Data System (ADS)

    Griswold, Martin; Raitses, Yevgeny; Fisch, Nathaniel J.

    2010-11-01

    ExB discharges can be used to accelerate ions in a quasi-neutral plasma. Large ion fluxes can be produced in this way because there is no space charge limitation, however difficulty in specifying the electric field distribution results in large flow divergence [1]. Recent work has identified new methods to control the flow divergence [2,3]. We present the results of new techniques that are designed to further reduce the divergence. [4pt] [1] A.I. Morozov and V.V. Savelyev, Reviews of Plasma Physics vol. 21, B. B. Kadomtsev and V. D. Shafranov, Eds. New York: Consultants Bureau, 2000. [2] Y. Raitses, L.A. Dorf, A.A. Litvak, and N.J. Fisch, Journal of Applied Physics 88 (2000) 1263. [3] A. Smirnov, Y. Raitses, and N.J. Fisch, IEEE Transactions on Plasma Science 36 (2008) 1998.

  10. Kinetic instabilities in a mirror-confined ECR discharge plasma

    NASA Astrophysics Data System (ADS)

    Mansfeld, Dmitry; Viktorov, Mikhail; Vodopyanov, Alexander; Golubev, Sergey

    2015-11-01

    Kinetic instabilities of nonequilibrium plasma heated by powerful radiation of gyrotron in electron cyclotron resonance conditions and confined in a mirror magnetic trap are reported. Instabilities are manifested as the generation of short pulses of electromagnetic radiation accompanied by precipitation of hot electrons from magnetic trap. Measuring electromagnetic field with high temporal resolution allowed to observe various dynamic spectra of electromagnetic radiation related to at least five types of kinetic instabilities. The opportunity to recreate different conditions for excitation and amplification of waves in plasma in a single ECR discharge pulse has been demonstrated. This report may be of interest in the context of a laboratory modeling of nonstationary wave-particle interaction processes in nonequilibrium space plasma since the observed phenomena have much in common with similar processes occurring in the magnetosphere of the Earth, planets, and in solar coronal loops. Work was supported by Russian Foundation for Basic Research # 15-32-20770.

  11. 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.

  12. Plasma core reactor simulations using RF uranium seeded argon discharges

    NASA Technical Reports Server (NTRS)

    Roman, W. C.

    1975-01-01

    An experimental investigation was conducted using the United Technologies Research Center (UTRC) 80 kW and 1.2 MW RF induction heater systems to aid in developing the technology necessary for designing a self-critical fissioning uranium plasma core reactor (PCR). A nonfissioning, steady-state RF-heated argon plasma seeded with pure uranium hexafluoride (UF6) was used. An overall objective was to achieve maximum confinement of uranium vapor within the plasma while simultaneously minimizing the uranium compound wall deposition. Exploratory tests were conducted using the 80 kW RF induction heater with the test chamber at approximately atmospheric pressure and discharge power levels on the order of 10 kW. Four different test chamber flow configurations were tested to permit selection of the configuration offering the best confinement characteristics for subsequent tests at higher pressure and power in the 1.2 MW RF induction heater facility.

  13. RF wave observations in beam-plasma discharge

    NASA Technical Reports Server (NTRS)

    Bernstein, W.

    1986-01-01

    The Beam Plasma Discharge (BPD) was produced in the large vacuum chamber at Johnson Space Center (20 x 30 m) using an energetic electron beam of moderately high perveance. A more complete expression of the threshold current I sub c taking into account the pitch angle injection dependence is given. Ambient plasma density inferred from wave measurements under various beam conditions are reported. Maximum frequency of the excited RF band behaves differently than the frequency of the peak amplitude. The latter shows signs of parabolic saturation consistent with the light data. Beam plasma state (pre-BPD or BPD) does not affect the pitch angle dependence. Unexpected strong modulation of the RF spectrum at half odd integer of the electron cyclotron frequency (n + 1/2)f sub ce is reported (5 n 10). Another new feature, the presence of wave emission around 3/2 f sub ce for I sub b is approximate I sub c is reported.

  14. Dielectric barrier discharge plasma induced degradation of aqueous atrazine.

    PubMed

    Feng, Jingwei; Jiang, Lin; Zhu, Dan; Su, Kuizu; Zhao, Dayong; Zhang, Jibiao; Zheng, Zheng

    2016-05-01

    Degradation of herbicide atrazine in aqueous solution was investigated using a plate type dielectric barrier discharge (DBD) plasma reactor. DBD plasma was generated at the gas-liquid interface of the formed water film. At discharge time of 14 min, atrazine was degradated effectively with a degradation rate of 99 % at the discharge power of 200 W. The experimental data fitted well with first-order kinetics and the energy efficiency for 90 % degradation of atrazine (G value) was calculated, obtaining a rate constant of 0.35 min(-1) and a G value of 1.27 × 10(-10) mol J(-1) (98.76 mg kW(-1) h(-1)) at a discharge power of 200 W, respectively. The addition of Fe(2+) increased the rate constant and G value dramatically, and a significant decrease of the rate constant and G value was observed with the addition of radical scavengers (tert-butyl alcohol, isopropyl alcohol, or Na2CO3). The generated aqueous O3 and H2O2 were determined, which promoted the degradation of herbicide atrazine. Dechlorination was observed and the experimentally detected Cl(-) was 1.52 mg L(-1) at a discharge time of 14 min. The degradation intermediates of atrazine were detected by means of liquid chromatography-mass spectrometry; dechlorination, hydroxylation, dealkylation, and alkyl oxidation processes were involved in the degradation pathways of atrazine. PMID:26832879

  15. Velocimetry of cathode particles in a magnetoplasmadynamic thruster discharge plasma.

    PubMed

    Walker, J; Langendorf, S; Walker, M; Polzin, K; Kimberlin, A

    2015-07-01

    With high-speed imaging, it is possible to directly observe the time-evolution of the macroscopic behavior of the discharge plasma in a magnetoplasmadynamic thruster (MPDT). By utilizing direct high-speed imaging capable of capturing many images over the course of a single discharge, the velocity of the cathode erosion particles can be measured, opening the possibility of a novel, noninvasive technique for discharge plasma flow field velocimetry. In this work, an 8 kA argon MPDT discharge is imaged at 26 173 fps utilizing a 0.9 neutral density filter. The camera is aligned with thruster centerline 4 m downstream of the thruster exit plane. By tracking visible particles appearing in the multiple images, the particle motion in the radial and azimuthal directions is directly imaged. Through the use of traditional techniques in digital particle image velocimetry, the cathode particles emanating from the discharge are measured to have a mean radial velocity of 44.6 ± 6.0 m/s with a 95% confidence interval and a statistically insignificant azimuthal velocity. The setup and analysis employed permits measurement of the particle velocity in orthogonal direction to the image sensor plane using a single camera. By combining a background removal subtraction technique and knowledge of the optical focal plane, the estimated mean axial velocity of the particles is 1.59 km/s. This investigation ends with a discussion of important factors to consider for future MPDT high-speed imaging particle velocimetry, such as frame-rate, image size, spatial resolution, optics, and data handling selections. PMID:26233389

  16. Velocimetry of cathode particles in a magnetoplasmadynamic thruster discharge plasma

    NASA Astrophysics Data System (ADS)

    Walker, J.; Langendorf, S.; Walker, M.; Polzin, K.; Kimberlin, A.

    2015-07-01

    With high-speed imaging, it is possible to directly observe the time-evolution of the macroscopic behavior of the discharge plasma in a magnetoplasmadynamic thruster (MPDT). By utilizing direct high-speed imaging capable of capturing many images over the course of a single discharge, the velocity of the cathode erosion particles can be measured, opening the possibility of a novel, noninvasive technique for discharge plasma flow field velocimetry. In this work, an 8 kA argon MPDT discharge is imaged at 26 173 fps utilizing a 0.9 neutral density filter. The camera is aligned with thruster centerline 4 m downstream of the thruster exit plane. By tracking visible particles appearing in the multiple images, the particle motion in the radial and azimuthal directions is directly imaged. Through the use of traditional techniques in digital particle image velocimetry, the cathode particles emanating from the discharge are measured to have a mean radial velocity of 44.6 ± 6.0 m/s with a 95% confidence interval and a statistically insignificant azimuthal velocity. The setup and analysis employed permits measurement of the particle velocity in orthogonal direction to the image sensor plane using a single camera. By combining a background removal subtraction technique and knowledge of the optical focal plane, the estimated mean axial velocity of the particles is 1.59 km/s. This investigation ends with a discussion of important factors to consider for future MPDT high-speed imaging particle velocimetry, such as frame-rate, image size, spatial resolution, optics, and data handling selections.

  17. Effects of ionic liquid electrode on pulse discharge plasmas in the wide range of gas pressures

    SciTech Connect

    Chen Qiang; Hatakeyama, Rikizo; Kaneko, Toshiro

    2010-11-15

    Gas-liquid interfacial pulse discharge plasmas are generated in the wide range of gas pressures, where an ionic liquid is used as the liquid electrode. By analyzing the characteristics of discharge voltage and current, the discharge mechanisms at low and high pressures are found to be dominated by secondary electron emission and first Townsend ionization, respectively. Therefore, the discharge properties at low and high pressures are mainly determined by the cathode material and the discharge gas type, respectively. Furthermore, the plasma properties are investigated by a double Langmuir probe. The density of the positive pulse plasma is found to be much smaller than that of the negative pulse plasma, although the discharge voltage and current of the negative and positive pulse plasmas are of the same order of magnitude. The positive pulse discharge plasma is considered to quickly diffuse onto the chamber wall from the radially central region due to its high plasma potential compared with that in the peripheral region.

  18. Formation and emission characteristics of CN molecules in laser induced low pressure He plasma and its applications to N analysis in coal and fossilization study.

    PubMed

    Lahna, Kurnia; Idroes, Rinaldi; Idris, Nasrullah; Abdulmadjid, Syahrun Nur; Kurniawan, Koo Hendrik; Tjia, May On; Pardede, Marincan; Kagawa, Kiichiro

    2016-03-01

    Presented in this paper are the results of an experimental study on the laser induced plasma emission of a number of CN free samples (urea, sucrose) with 40 mJ pulse energy using He and N₂ ambient gases. It is shown that the CN emission has its exclusive sources in the molecules produced as the result of chemical bonding either between the ablated C and N ions in the He plasma or between the ablated C and dissociated N from the N₂ ambient gas. The emission intensities in both cases are found to have the highest values at the low gas pressure of 2 kPa. The emission in He gas is shown to exhibit the typical characteristics related to a shockwave generated excitation mechanism. The experiments using He ambient gas further demonstrate the feasible laser-induced breakdown spectroscopy application to quantitative and sensitive N analysis of coal and promising application for practical in situ carbon dating of fossils. PMID:26974637

  19. Analysis on electromagnetic characteristics and military application of non-magnetized discharge plasma

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Wang, Jiachun; Miao, Lei; Li, Zhigang

    2015-11-01

    Firstly, the dispersion equation of a plane electromagnetic wave in homogeneous and non-magnetized discharge plasma was established. According to the different frequency of electromagnetic wave and plasma parameters, the characteristics were discussed when the plasma interacted with electromagnetic waves. Then the gas discharge approach was put forward according to characteristics of plasma generated by different methods and their advantages and disadvantages. The possibility of using non-magnetized discharge plasma for the military purpose was analyzed. In the end, the principle and characteristics of the application of the non-magnetized discharge plasma were studied in the fields of stealth and protection against strong electromagnetic pulse.

  20. ROS/RNS Production in Water Using Various Discharge Plasma

    NASA Astrophysics Data System (ADS)

    Takahashi, Kazuhiro; Satoh, Kohki; Itoh, Hidenori; Kawaguchi, Hideki; Timoshkin, Igor; Given, Martin; MacGregor, Scott

    2015-09-01

    A pulsed discharge, a DC corona discharge and an atmospheric pressure plasma jet are generated above water, the off-gas of a packed-bed dielectric barrier discharge (PB-DBD) is sparged into water, and then reactive oxygen species and reactive nitrogen species in the water are investigated. H2O2, NO3- and a trace of NO2- are produced in the water after the plasma exposure. H2O2 concentration decreases when NO3- concentration increases, so that this is likely that OH radical to produce H2O2 by OH + OH -->H2O2 is consumed in the NO3- production by NO2 + OH --> HNO3 --> NO3-+ H+ (in water). Since no species is detected in water by the sparging of the PB-DBD off-gas containing more than 1000 ppm of O3, O3 does not contribute to produce H2O2 in water. Further, only NO3- is produced by the sparging of the off-gas containing N2O5 and HNO3. This leads that H2O2 and NO2- can be produced by short-lifetime species in plasma. In this work, the highest generation efficiency of H2O2 and NO2- are respectively 3,820 μg/Wh and 830 μg/Wh by the pulsed-plasma exposure, and that of NO3- is 2,530 μg/Wh by the off-gas sparging of the PB-DBD.

  1. Plasma Parameter of a Capillary Discharge-Produced Plasma Channel to Guide an Ultrashort Laser Pulse

    SciTech Connect

    Higashiguchi, Takeshi; Terauchi, Hiromitsu; Bai, Jin-xiang; Yugami, Noboru

    2009-01-22

    We have observed the optical guiding of a 100-fs laser pulse with the laser intensity in the range of 10{sup 16} W/cm{sup 2} using a 1.5-cm long capillary discharge-produced plasma channel for compact electron acceleration applications. The optical pulse propagation using the plasma channel is achieved with the electron densities of 10{sup 17}-10{sup 18} cm{sup -3} and the electron temperatures of 0.5-4 eV at a discharge time delay of around 150 ns and a discharge current of 500 A with a pulse duration of 100-150 ns. An energy spectrum of the accelerated electrons from a laser-plasma acceleration scheme showed a peak at 1.3 MeV with a maximum energy tail of 1.6 MeV.

  2. Low-energy BO and BO 2 emission from H 2BO 3 sputtered in a low-pressure high-frequency SNMS plasma

    NASA Astrophysics Data System (ADS)

    Jenett, Holger; Ai, Xingtao; Hodoroaba, Vasile-Dan; Iga, Ione; Mu Tao, Lee

    1999-07-01

    Background corrected secondary neutral energy spectra derived from Cu powder pellets with H 3BO 3, MgO, Al 2O 3, TiO 2, Y 2O 3 and ZrO 2, show energy distributions being more or less typical for collision cascades in the cases of the metal ions M +, of O + at energies >5 eV above the ion generation potential, and of the molecules Cu 2+, AlO +, TiO +, YO + and ZrO +, whereas the larger parts of the energy distributions of BO +and BO 2+exhibit a similar shape as the Ar +plasma gas ions. From this, and from the background of the low decomposition and melting temperatures of H 3BO 3 and B 2O 3, respectively, we conclude that the detected BO and BO 2 molecules have been emitted with thermal energies in processes implying lower energies than collision cascades. Evidence was found that the same holds for HBO 2 and H 2BO 2. In order to obtain relative correction factors for MO + molecular ion intensities, electron impact ionization cross sections have been calculated for the light MO molecules using the binary-encounter Bethe (BEB) formula, and for the respective metal M atoms by means of the semiempirical Lotz formula. For the heavy MO molecules YO and ZrO, cross sections have been estimated using the Thomson formula. The comparison of corrected relative MO/M and M/Cu intensities yields evidence that thermal (H)BO x emission amounts to the same order of magnitude as B emission from collision cascades, and that this situation is comparable to the high yield of MO molecules emitted in collision cascades from oxides with high M masses. Since the normal energy window of an HF-plasma secondary neutral mass spectrometer does not accept particles with originally thermal energies, it is concluded that these findings are relevant for quantification.

  3. Study on electrolytic plasma discharging behavior and its influence on the plasma electrolytic oxidation coatings

    NASA Astrophysics Data System (ADS)

    Hussein, Riyad Omran

    In this study, aluminum oxide was deposited on a pure aluminum substrate to produce hard ceramic coatings using a Plasma Electrolytic Oxidation (PEO) process. The process utilized DC, unipolar pulsed DC in the frequency range (0.2 KHz -- 20 KHz) and bipolar pulsed DC current modes. The effects of process parameters (i.e., electrolyte concentration, current density and treatment time) on the plasma discharge behavior during the PEO treatment were investigated using optical emission spectroscopy (OES) in the visible and near ultraviolet (NUV) band (285 nm -- 900 nm). The emission spectra were recorded and plasma temperature profile versus processing time was constructed using the line intensity ratios method. Scanning Electron Microscopy (SEM) with energy dispersive x-ray analysis (EDS) was used to study the coating microstructure. It was found that the plasma discharge behavior significantly influenced the microstructure and the morphology of the oxide coatings. The main effect came from the strongest discharges which were initiated at the interface between the substrate and the coating. Through manipulation of process parameters to control or reduce the strongest discharge, the density and quality of the coating layers could be modified. This work demonstrated that by adjusting the ratio of the positive to negative pulse currents as well as their timing in order to eliminate the strongest discharges, the quality of the coatings was considerably improved.

  4. Plasma chemistry in CO2 dielectric barrier discharges

    NASA Astrophysics Data System (ADS)

    Brehmer, F.; Welzel, S.; van de Sanden, M. C. M.; Engeln, R.

    2013-09-01

    Plasma-assisted gas phase conversion in non-thermal environments is increasingly being considered as promising technology for fuel production from CO2 and hydrogen containing sources. Particularly the rate-limiting activation of CO2 is suggested to be tackled in plasmas at (sub-)atmospheric pressure conditions without the admixture of carrier gases. Therefore CO2 dielectric barrier discharges were studied to assess conversion yields and reaction mechanisms. The CO2 discharges were resonantly excited at around 100 kHz in a flow-tube lab-scale reactor designed to facilitate time-resolved in-situ optical emission and infrared laser absorption spectroscopy. Complementary analysis of the gas phase constituents using ex-situ FT-IR spectroscopy and a thorough electrical characterisation were carried out. The CO conversion yields were typically below 5% and hence in-line with similar studies. The energy efficiency can be uniformly described for different external plasma parameters (e.g. flow rate, power input, excitation frequency) as function of the specific energy input. Special attention was paid to the non-negligible formation of by-products such as O3 and O2 which suggests an inefficient recycling of atomic oxygen in secondary CO2 dissociation reactions.

  5. 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.

  6. An investigation of an underwater steam plasma discharge as alternative to air plasmas for water purification

    NASA Astrophysics Data System (ADS)

    Gucker, Sarah N.; Foster, John E.; Garcia, Maria C.

    2015-10-01

    An underwater steam plasma discharge, in which water itself is the ionizing media, is investigated as a means to introduce advanced oxidation species into contaminated water for the purpose of water purification. The steam discharge avoids the acidification observed with air discharges and also avoids the need for a feed gas, simplifying the system. Steam discharge operation did not result in a pH changes in the processing of water or simulated wastewater, with the actual pH remaining roughly constant during processing. Simulated wastewater has been shown to continue to decompose significantly after steam treatment, suggesting the presence of long-lived plasma produced radicals. During steam discharge operation, nitrate production is limited, and nitrite production was found to be below the detection threshold of (roughly 0.2 mg L-1). The discharge was operated over a broad range of deposited power levels, ranging from approximately 30 W to 300 W. Hydrogen peroxide production was found to scale with increasing power. Additionally, the hydrogen peroxide production efficiency of the discharge was found to be higher than many of the rates reported in the literature to date.

  7. Computational Simulation of Nanosecond Pulsed Discharge for Plasma Assisted Ignition

    NASA Astrophysics Data System (ADS)

    Takana, H.; Adamovich, I. V.; Nishiyama, H.

    2014-11-01

    Detailed two dimensional numerical simulations of a nanosecond pulsed pin-to-pin discharge in a lean methane/air mixture were conducted under 10 atm and 600 K for plasma assisted combustion in internal combustion engines. It was clarified from this study that the produced radicals were locally higher in the vicinity of electrodes, and high density radicals are more widely distributed on the anode side rather than the cathode side which the streamer is propagating toward. The electron energy partition has been clarified during a single pulse. Total electron energy increases with fuel equivalent ratio under the same applied voltage. Pronounced enhancement of ignition delay has been shown by nanosecond pulsed discharge.

  8. Mixing Layer Excitation by Dielectric Barrier Discharge Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Ely, Richard; Little, Jesse

    2012-11-01

    The response of a mixing layer with velocity ratio 0.28 to perturbations near the high-speed side (U2=11 m/s, ReL = 0.26 × 106) of its origin from dielectric barrier discharge plasma actuators is studied experimentally. Both alternating current (ac) and nanosecond (ns) pulse driven plasma are investigated in an effort to clarify the mechanisms associated with each technique as well as the more general physics associated with flow control via momentum-based versus thermal actuation. Ac-DBD plasma actuators, which function through electrohydrodynamic effects, are found to generate an increase in mixing layer momentum thickness that is strongly dependent on forcing frequency. Results are qualitatively similar to previous archival literature on the topic employing oscillating flaps. Ns-DBD plasma, which is believed to function through thermal effects, has no measureable influence on the mixing layer profile at similar forcing conditions. In the context of previous archival literature, these results suggest different physical mechanisms govern active control via ac- and ns-DBD plasma actuation and more generally, momentum versus thermal perturbations. Further investigation of these phenomena will be provided through variation of the boundary/mixing layer properties and forcing parameters in the context of spatially and temporally resolved experimental data. Supported by: AFOSR and Raytheon Missile Systems.

  9. [Study on Chemical Kinetic Effect of Dielectric Barrier Discharge Plasma].

    PubMed

    Zrang, Peng; Hong, Yan-ji; Shen, Shuang-yan; Ding, Xiao-yu; Ma, Di

    2015-03-01

    To reveal the mechanism of plasma (assisted the ignition process of methane/air further, schematic of dielectric barrier discharge plasma system with atmospheric air was designed and set up, the emission spectrum of dielectric barrier discharge plasma with atmospheric air was measured, and the active particles produced by the interaction of dielectric barrier discharge plasma with atmospheric air were analyzed with the spectrum technology, the ignition model and calculation methods of sensitivity analysis and reaction path analysis were given, effects of NO and O3 on the ignition delay time were simulated, and the chemical kinetics mechanism of NO and O3 assisted ignition was revealed via sensitivity analysis and reaction path analysis. The results show that main excited particles of N2 and O3 are generated via effect of plasma on the atmospheric air, which are converted into active particles of NO(ξ) and O3 in the end, the life of which are longer than any other active particles, effects of plasma on the ignition is simplified as effects of NO(ξ) and O3 on the ignition; NO and O3 could reduce the ignition delay time significantly, but the amplitude decrease with increase of the initial temperature, this is because the rate of ignition is decided by the oxidation rate of CH3, the oxidized pathway of CH3 is R155 and R156 for auto-ignition and their rates are slower when temperature is low, so the ignition delay time of methane/air is longer; NO could reduce the ignition delay time significantly because of the oxidized pathway of CH3 is changed to R327 CH3O2 + NO = CH3O + NO2, R328 CH3 + NO2 = CH3O + NO for NO(ξ) (assisted ignition process from R155 and R156 for auto-ignition; and the chemical kinetic effect is the dominating factor of O3 on the ignition and which change the reaction path. PMID:26117883

  10. Abatement of CF{sub 4} and CHF{sub 3} byproducts using low-pressure plasmas generated by annular-shaped electrodes

    SciTech Connect

    Hur, Min; Lee, Jae O. K.; Hoon Song, Young; Yoo, Hoon A.

    2012-03-15

    Three different driving schemes are tested for a plasma reactor designed to abate the greenhouse gases emitted by the semiconductor industry. The reactor and electrodes all have a concentric annular shape, which allows them to be easily connected to pre-existing pipelines without any disturbance to the exhaust stream. The destruction and removal efficiencies are measured for CF{sub 4} by varying the O{sub 2}/CF{sub 4} ratio and pressure. The influences of adding O{sub 2} and H{sub 2}O to the byproducts of the CHF{sub 3} abatement process are investigated by analyzing the spectra resulting from Fourier transform infrared spectroscopy measurements. Based on the experimental results we suggest an appropriate combination of driving scheme and reactant gas species for efficient and economical abatement of a mixture of CHF{sub 3} and CF{sub 4}. Then, the optimal flow rate of the reactant gas is presented. Finally, the reduction rates for global warming emissions are estimated to demonstrate the feasibility of using our device for abatement of greenhouse gases emitted by the semiconductor industry.

  11. Low Temperature Plasma Nitriding Of Stainless Steel In N_2/H_2/Ar LFICP Discharges

    NASA Astrophysics Data System (ADS)

    Xu, S.; Luo, W.; Jiang, N.; Ostrikov, K. N.

    2001-10-01

    A low frequency, high density, inductively coupled plasma (LF ICP) source has been developed and used for nitriding of AISI stainless steels. A series of experiments has been conducted in a low temperature (320-400^circC), low pressure N_2/H_2/Ar gas mixture discharges. The results show that the nitriding process is very fast, ~ 45μm/hr for AISI 304 and ~ 90μm/hr for AIS410, even at a low nitriding temperature. After nitriding, the micro hardness of the nitrided layer is increased by a factor of 7 and the free corrosion potential is also improved. The pin-on-disc measurement indicates that the wear resistance improved more than 10 times. The microstructure and composition of the nitrided surface layers characterised using scanning electron microscopy/energy dispersive x-ray diffraction and x-ray diffraction reveal that the nitrided layer has crystalline structure with various phases. The distribution of the nitrogen content varies sharply: high in the nitrided layer and almost zero elsewhere. The content of Cr, however, remains constant over the entire substrate/nitrided layer.

  12. Nanosecond time-resolved microscopic spectroscopy for diagnostics of an atmospheric-pressure discharge plasma formed in aqueous solution

    NASA Astrophysics Data System (ADS)

    Banno, Motohiro; Kanno, Kenta; Someya, Yuu; Yui, Hiroharu

    2015-06-01

    Glow discharge plasma formed in solution under atmospheric pressure has been expected to provide reaction fields with characteristic physical and chemical properties owing to the frequent collisions and reactions of reactive particles inside and the rapid quenching of the products by the surrounding cold solutions. In particular, when an aqueous solution is utilized as the surrounding solution, the atmospheric-pressure in-solution glow (ASG) plasma contains hydrogen and hydroxyl radicals showing large activities for reduction and oxidation, respectively. In addition, because the ASG plasma is formed under atmospheric pressure, the collision frequencies between the particles contained in the plasma are higher than those in other plasmas ordinarily formed under low pressure. This feature should result in rapid energy redistribution among particles contained in the plasma. In the present study, time-resolved optical emission spectroscopy with nanosecond time resolution was applied for the diagnostics of the ASG plasma with chemical species selectivity. The time-resolved measurements revealed that the temporal evolutions of the temperatures of blackbody, hydrogen radical, and hydroxyl radical contained in the ASG plasma consist of two stages: initial rise within 0.15 µs (rising stage) and fluctuation around certain values for about 1 µs (fluctuating stage). In the time region corresponding to the rising stage, the electron number density is about ten times larger than the value temporally averaged during the plasma emission. The initial rise should result from frequent collisions between charged particles accelerated by the applied voltage and unexcited particles. In the fluctuating stage, the electron number density strongly correlates with the increase in the radical temperatures. It is concluded that the electron number density, rather than the electron temperature, is a key parameter determining the temperatures of reactive species in the ASG plasma.

  13. Ion flux onto conducting and isolated surfaces in the beam-plasma discharge: Computer simulation

    SciTech Connect

    Klykov, I. L.; Shustin, E. G.; Tarakanov, V. P.

    2010-12-15

    A physical model which allows the use of the program code KARAT for simulating the quasisteady state of the beam-plasma discharge with plasma regeneration from a neutral gas is developed. The results of simulation of the modes of discharge at different potentials at the discharge collector are reported. The results obtained for isolated and grounded ion collectors are compared.

  14. Ion flux onto conducting and isolated surfaces in the beam-plasma discharge: Computer simulation

    NASA Astrophysics Data System (ADS)

    Klykov, I. L.; Shustin, E. G.; Tarakanov, V. P.

    2010-12-01

    A physical model which allows the use of the program code KARAT for simulating the quasisteady state of the beam-plasma discharge with plasma regeneration from a neutral gas is developed. The results of simulation of the modes of discharge at different potentials at the discharge collector are reported. The results obtained for isolated and grounded ion collectors are compared.

  15. Nanosecond Nd-YAG laser induced plasma emission characteristics in low pressure CO2 ambient gas for spectrochemical application on Mars

    NASA Astrophysics Data System (ADS)

    Lie, Zener Sukra; Pardede, Marincan; Tjia, May On; Kurniawan, Koo Hendrik; Kagawa, Kiichiro

    2015-08-01

    An experimental study is conducted on the possibility and viability of performing spectrochemical analysis of carbon and other elements in trace amount in Mars, in particular, the clean detection of C, which is indispensible for tracking the sign of life in Mars. For this study, a nanosecond Nd-YAG laser is employed to generate plasma emission from a pure copper target in CO2 ambient gas of reduced pressure simulating the atmospheric condition of Mars. It is shown that the same shock wave excitation mechanism also works this case while exhibiting remarkably long cooling stage. The highest Cu emission intensities induced by 4 mJ laser ablation energy is attained in 600 Pa CO2 ambient gas. Meanwhile the considerably weaker carbon emission from the CO2 gas appears relatively featureless over the entire range of pressure variation, posing a serious problem for sensitive trace analysis of C contained in a solid sample. Our time resolved intensity measurement nevertheless reveals earlier appearance of C emission from the CO2 gas with a limited duration from 50 ns to 400 ns after the laser irradiation, well before the initial appearance of the long lasting C emission from the solid target at about 1 μs, due to the different C-releasing processes from their different host materials. The unwanted C emission from the ambient gas can thus be eliminated from the detected spectrum by a proper time gated detection window. The excellent spectra of carbon, aluminum, calcium, sodium, hydrogen, and oxygen obtained from an agate sample are presented to further demonstrate and verify merit of this special time gated LIBS using CO2 ambient gas and suggesting its viability for broad ranging in-situ applications in Mars.

  16. Nanosecond Nd-YAG laser induced plasma emission characteristics in low pressure CO{sub 2} ambient gas for spectrochemical application on Mars

    SciTech Connect

    Lie, Zener Sukra; Kurniawan, Koo Hendrik; Tjia, May On; Kagawa, Kiichiro

    2015-08-28

    An experimental study is conducted on the possibility and viability of performing spectrochemical analysis of carbon and other elements in trace amount in Mars, in particular, the clean detection of C, which is indispensible for tracking the sign of life in Mars. For this study, a nanosecond Nd-YAG laser is employed to generate plasma emission from a pure copper target in CO{sub 2} ambient gas of reduced pressure simulating the atmospheric condition of Mars. It is shown that the same shock wave excitation mechanism also works this case while exhibiting remarkably long cooling stage. The highest Cu emission intensities induced by 4 mJ laser ablation energy is attained in 600 Pa CO{sub 2} ambient gas. Meanwhile the considerably weaker carbon emission from the CO{sub 2} gas appears relatively featureless over the entire range of pressure variation, posing a serious problem for sensitive trace analysis of C contained in a solid sample. Our time resolved intensity measurement nevertheless reveals earlier appearance of C emission from the CO{sub 2} gas with a limited duration from 50 ns to 400 ns after the laser irradiation, well before the initial appearance of the long lasting C emission from the solid target at about 1 μs, due to the different C-releasing processes from their different host materials. The unwanted C emission from the ambient gas can thus be eliminated from the detected spectrum by a proper time gated detection window. The excellent spectra of carbon, aluminum, calcium, sodium, hydrogen, and oxygen obtained from an agate sample are presented to further demonstrate and verify merit of this special time gated LIBS using CO{sub 2} ambient gas and suggesting its viability for broad ranging in-situ applications in Mars.

  17. Role of Plasma Discharge in Division of Prostatic Tissue

    NASA Astrophysics Data System (ADS)

    Ward, Arlen; Almgren, Carl; Yu, Zeng-Qi; Sartor, Joe; Collins, George

    2009-10-01

    During the treatment of benign prostatic hyperplasia electrical energy is used to separate prostatic tissue and remove it as a urinary obstruction. This surgical procedure is often performed in a saline environment, and current paths change as the tissue and fluid are heated. This study shows that a plasma discharge at the electrode is necessary to provide the current densities necessary to vaporize portions of the prostatic tissue in order to facilitate removal. This behavior is predicted in finite element simulations, and verified with color schlieren imaging and ex vivo bovine prostate tests.

  18. 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.

  19. Coagulation of Dust Particles in Argon Plasma of RF Discharge

    SciTech Connect

    Mankelevich, Yu. A.; Olevanov, M. A.; Pal, A. F.; Rakhimova, T. V.; Ryabinkin, A. N.; Serov, A. O.; Filippov, A. V.

    2008-09-07

    The experiments on coagulation of poly-disperse particles with various size distributions injected into the argon plasma of the magnetron radio-frequency discharge are discussed. The experiments were carried out under the conditions similar to those using dusty plasma for technology applications. Within the created theory the threshold behavior of the coagulation process was explained for the first time, the estimation of the critical particle size for onset of a fast coagulation was made, and the analytical calculation of the coagulation rate of dust particles was performed. The proposed coagulation mechanism makes it possible to describe the typical features of coagulation processes observed in experiments and to explain the effects of attraction and coalescence of highly negatively charged microns size particles.

  20. Performance of capillary discharge guided laser plasma wakefieldaccelerator

    SciTech Connect

    Nakamura, Kei; Esarey, Eric; Geddes, Cameron G.R.; Gonsalves,Anthony J.; Leemans, Wim P.; Panasenko, Dmitriy; Schroeder, Carl B.; Toth, Csaba; Hooker, S.M.

    2007-06-25

    A GeV-class laser-driven plasma-based wakefield acceleratorhas been realized at the Lawrence Berkeley National Laboratory (LBNL).The device consists of the 40TW high repetition rate Ti:sapphire LOASISlaser system at LBNL and a gas-filled capillary discharge waveguidedeveloped at Oxford University. The operation of the capillary dischargeguided laser plasma wakefield accelerator with a capillaryof 225 mu mdiameter and 33 mm in length was analyzed in detail. The input intensitydependence suggests that excessive self-injection causes increased beamloading leading to broadband lower energy electron beam generation. Thetrigger versus laser arrival timing dependence suggests that the plasmachannel parameters can be tuned to reduce beam divergence.

  1. Instability of dusty particle system in gas-discharge plasma

    SciTech Connect

    Filinov, V.S.; Petrov, O.F.; Fortov, V.E.; Molotkov, V.I.

    2005-10-31

    An effective anisotropic potential is proposed for the interaction between dust particles in a gas-discharge plasma. In addition to the Coulomb repulsion this potential takes into account attraction due to the spatial positive plasma charge originating from focusing of the ionic fluxes by dusty particles. The time evolution of the dust particle kinetic and potential energies from random initial configurations have been investigated by the Brownian dynamics method. Results of our simulation showed that the attraction between dusty particles can be the main physical reason of formation and decay of classical bound dust particle pairs and many particle complexes with low potential energy, while the kinetic energy (temperature) of unbound dust particles and particle oscillating in bound complexes may increase on three order as observed in experiments.

  2. A Multicell Converter Model of DBD Plasma Discharges

    SciTech Connect

    Flores-Fuentes, A. A.; Piedad-Beneitez, A. de la; Pena-Eguiluz, R.; Mercado-Cabrera, A.; Valencia A, R.; Barocio, S. R.; Lopez-Callejas, R.; Godoy-Cabrera, O. G.; Benitez-Read, J. S.; Pacheco-Sotelo, J. O.

    2006-12-04

    A compact Matlab model of plasma discharges in a DBD reactor consisting of two parallel electrode plates with a small gap and a thin dielectric sheet between them is reported. Its DBD plasma is modelled as a voltage controlled current-source switched on when the voltage across the gap exceeds the breakdown voltage. A three cell voltage-source inverter, configured in half-bridge, has been used as a power supply. This configuration has an excellent performance when operating as an open-loop. The distribution of total energy between a large number of low power converters proofs to be advantageous, allowing an efficient high power drive. Simulation results show that the current source and its output current tend to follow an exponential behaviour. A phenomenological characteristic of the voltage-current behaviour of DBD is then described by power laws with different voltage exponent function values.

  3. Electric plasma discharge combustion synthesis of chlorine dioxide

    SciTech Connect

    Dotson, R. L.; Geren, G. W.

    1984-09-18

    A process for the production of chlorine dioxide comprises feeding an inert gas to a reaction zone and applying an electrical discharge to the inert gas to produce a high temperature plasma. Chlorine gas and oxygen gas are supplied simultaneously to the reaction zone and reacted in the plasma to produce a gaseous mixture comprised of chlorine dioxide, chlorine, oxygen and inert gas, the molar ratio of oxygen to chlorine in the reaction zone being at least about 2.5;1. The gaseous mixture is recovered from the reaction zone. Chlorine dioxide, which may be recovered as a gas or reacted to produce an alkali metal chlorite, is employed as a bleaching agent and a water treatment agent.

  4. Fluorination of polymethylmethaacrylate with tetrafluoroethane using DC glow discharge plasma

    NASA Astrophysics Data System (ADS)

    Guruvenket, S.; Iyer, Ganjigunte R. S.; Shestakova, Larisa; Morgen, Per; Larsen, N. B.; Mohan Rao, G.

    2008-07-01

    Fluorination of polymer surfaces has technological applications in various fields such as microelectronics, biomaterials, textile, packing, etc. In this study PMMA surfaces were fluorinated using DC glow discharge plasma. Tetrafluoroethane was used as the fluorinating agent. On the fluorinated PMMA surface, static water contact angle, surface energy, optical transmittance (UV-vis), XPS and AFM analyses were carried out. After the fluorination PMMA surface becomes hydrophobic with water contact angle of 107° without losing optical transparency. Surface energy of fluorine plasma-treated PMMA decreased from 35 mJ/cm 2 to 21.2 mJ/cm 2. RMS roughness of the fluorinated surface was 4.01 nm and XPS studies revealed the formation of C-CF x and CF 3 groups on the PMMA surface.

  5. Prediction of plasma rotation and neoclassical toroidal viscosity in KSTAR discharges based on plasma fluid formulation

    NASA Astrophysics Data System (ADS)

    Bae, Cheonho; Stacey, Weston

    2015-11-01

    Braginskii's flow rate of strain tensor formalism, as extended first to low collisional plasmas in axisymmetric circular toroidal flux surface geometry, then to elongated axisymmetric flux surface geometry, has recently been extended to 3-D non-axisymmetric toroidal flux surface geometry. In toroidally non-axisymmetric plasmas, the leading order neoclassical parallel viscosity terms in the flow rate of strain tensor do not vanish to cause flux surface averaged toroidal angular momentum damping and eventually slow down the plasma rotation. The formalism of Ref. 5 provides a means to systematically evaluate the ``neoclassical toroidal viscosity (NTV)'' in curvilinear plasma geometry based on the plasma fluid equations. As the first step of its application, a practical formalism for circular plasmas, given in the appendix of Ref. 5, will be applied to KSTAR discharges to predict the rotation and NTV, which can also be compared with actual rotation measurements to numerically validate the NTV damping effects.

  6. Dielectric Barrier Discharge Plasma Actuator for Flow Control

    NASA Technical Reports Server (NTRS)

    Opaits, Dmitry, F.

    2012-01-01

    This report is Part II of the final report of NASA Cooperative Agreement contract no. NNX07AC02A. It includes a Ph.D. dissertation. The period of performance was January 1, 2007 to December 31, 2010. Part I of the final report is the overview published as NASA/CR-2012- 217654. Asymmetric dielectric barrier discharge (DBD) plasma actuators driven by nanosecond pulses superimposed on dc bias voltage are studied experimentally. This produces non-self-sustained discharge: the plasma is generated by repetitive short pulses, and the pushing of the gas occurs primarily due to the bias voltage. The parameters of ionizing pulses and the driving bias voltage can be varied independently, which adds flexibility to control and optimization of the actuators performance. The approach consisted of three elements coupled together: the Schlieren technique, burst mode of plasma actuator operation, and 2-D numerical fluid modeling. During the experiments, it was found that DBD performance is severely limited by surface charge accumulation on the dielectric. Several ways to mitigate the surface charge were found: using a reversing DC bias potential, three-electrode configuration, slightly conductive dielectrics, and semi conductive coatings. Force balance measurements proved the effectiveness of the suggested configurations and advantages of the new voltage profile (pulses+bias) over the traditional sinusoidal one at relatively low voltages. In view of practical applications certain questions have been also addressed, such as electrodynamic effects which accompany scaling of the actuators to real size models, and environmental effects of ozone production by the plasma actuators.

  7. Anomalous electron mobility in a coaxial Hall discharge plasma.

    PubMed

    Meezan, N B; Hargus, W A; Cappelli, M A

    2001-02-01

    A comprehensive analysis of measurements supporting the presence of anomalous cross-field electron mobility in Hall plasma accelerators is presented. Nonintrusive laser-induced fluorescence measurements of neutral xenon and ionized xenon velocities, and various electrostatic probe diagnostic measurements are used to locally determine the effective electron Hall parameter inside the accelerator channel. These values are then compared to the classical (collision-driven) Hall parameters expected for a quiescent magnetized plasma. The results indicate that in the vicinity of the anode, where there are fewer plasma instabilities, the electron-transport mechanism is likely elastic collisions with the background neutral xenon. However, we find that in the vicinity of the discharge channel exit, where the magnetic field is the strongest and where there are intense fluctuations in the plasma properties, the inferred Hall parameter departs from the classical value, and is close to the Bohm value of (omega(ce)tau)(eff) approximately 16. These results are used to support a simple model for the Hall parameter that is based on the scalar addition of the electron collision frequencies (elastic collision induced plus fluctuation induced), as proposed by Boeuf and Garrigues [J. Appl. Phys. 84, 3541 (1998)]. The results also draw attention to the possible role of fluctuations in enhancing electron transport in regions where the electrons are highly magnetized. PMID:11308588

  8. Degradation of pentachlorophenol in soil by pulsed corona discharge plasma.

    PubMed

    Wang, Tie Cheng; Lu, Na; Li, Jie; Wu, Yan

    2010-08-15

    The remediation of pentachlorophenol (PCP) contaminated soil using pulsed corona discharge plasma was reported in this study. The effect of practical run parameters such as peak pulse voltage, pulse frequency, gas atmospheres (air, O(2), Ar and N(2)), air flow rate and pollution time on PCP degradation was investigated, and the intermediate products were also studied. The results indicated that PCP degradation efficiency increased with an increase in peak pulse voltage or pulse frequency, due to the enhancement of energy input. There existed a maximal PCP degradation efficiency with the change of air flow rate. PCP degradation efficiencies under oxygen and air atmospheres were achieved 92% and 77% after 45 min of discharge treatment at 14.0 kV, respectively, which were only 19% and 8% under argon and nitrogen atmospheres, respectively. O(3) played an important role in PCP degradation. However, other processes also contributed to PCP degradation, such as N, N(2)(+), N(+) and OH. The pollution time evidenced slight influence on PCP degradation. The main intermediate products produced during the treatment process were identified as tetrachlorocatechol, tetrachlorohydroquinone, acetic acid, formic acid and oxalic acid by HPLC/MS and ion chromatography. This study is expected to provide reference for the application of pulsed corona discharge in soil remediation. PMID:20452725

  9. Plasma Effects on Electrostatic Chuck Characteristics on Capacitive RF Discharge

    NASA Astrophysics Data System (ADS)

    Shim, Gyu Il; Yamauchi, Takeshi; Sugai, Hideo

    Johnsen-Rahbek electrostatic chuck (ESC) is installed on the cathode side of a capacitive RF discharge, and the ESC voltage-current (V-I) characteristic is measured under various conditions. First, the reference V-I curve is obtained for a grounded aluminum (Al) wafer without discharge. The observed nonlinear characteristic is attributed to the field emission of electrons at irregular contacting surfaces. When the discharge is turned on with an electrically floating wafer, the V-I curve shifts from the reference curve toward the negative direction along the chuck voltage axis. The amount of shifted chuck voltage coincides with the self-bias DC voltage induced on the wafer. This plasma effect on the V-I characteristics can be explained well in terms of the effective chuck voltage, taking into account the self-bias. On the other hand, the replacement of the Al wafer with a silicon (Si) wafer leads to a considerable reduction in the chuck current. When a thin Al foil is inserted between the Si wafer and the aluminum nitride (AlN) spacer layer, the chuck current recovers upto the reference value, suggesting that the Johnsen-Rahbek effect is extremely sensitive to the electrical and mechanical properties of the contacting interface.

  10. Laser Thomson Scattering Diagnostics of Pulsed Filamentary Discharge Plasmas

    NASA Astrophysics Data System (ADS)

    Bolouki, Nima

    2012-10-01

    Laser Thomson scattering (LTS) has been applied to measure spatiotemporal evolution of electron density and electron temperature in a pulsed filamentary discharge. The light source of LTS is the second harmonics Nd:YAG laser with a energy of 8 mJ. Also a triple grating spectrometer (TGS) having high rejection rate for stray light is used to measure LTS spectra. In our experimental conditions, non-thermal and non-equilibrium micro-plasmas are generated at round atmospheric pressure. Moreover, the electrode set in this experiment is consisted of a needle electrode and a hemispherical electrode with an inter-electrode gap of 0.5 mm. The total electric charge that flows through the discharge channel vary from 20 nC to 850 nC by changing capacitance in electrical circuit. We could show that the total charge variation leads to increase in electron density from 10^22 m-3 to 10^23 m-3. However, the electron temperature remains almost constant at the main discharge. In order to investigate the streamer phase, we changed the gap up to 16mm, and then performed the LTS method to measure the electron density and electron temperature.

  11. Improvement of the discharge efficiency in plasma displays

    NASA Astrophysics Data System (ADS)

    Oversluizen, G.; Klein, M.; de Zwart, S.; van Heusden, S.; Dekker, T.

    2002-02-01

    The dependence of the efficacy of an alternating current surface-discharge plasma display panel on the gas pressure is investigated for several Xe-Ne gas mixtures. In monochrome green 4 in. test panels the efficacy trends and emission spectra are examined for increasing gas pressure and/or Xe concentration. The measured panel efficacy and emission characteristics are compared with the results of a numerical discharge model. It is found that the discharge efficiency for the cell geometry used in present-day commercial products can be increased significantly by using a larger Xe partial pressure. An increase of the electron heating efficiency and of the Xe excitation efficiency contribute about equally to the efficacy increase. The contribution of the increasing Xe dimer radiation fraction to the efficacy improvement is relatively small. These findings are applied in a 4 in. color test display with a design that resembles the one used in present-day commercial products and contains a gas mixture of 13.5% Xe in Ne at 800 hPa. For realistic operating conditions an efficacy of 3.8 lm/W at a white luminance of 2010 cd/m2 is obtained. Furthermore, the panel chromaticity improves for increasing Xe partial pressure due to decreasing Ne emission.

  12. Plasma acceleration from radio-frequency discharge in dielectric capillary

    SciTech Connect

    Dunaevsky, A.; Raitses, Y.; Fisch, N.J.

    2006-06-19

    A capacitive rf discharge was demonstrated in a dielectric capillary for generation of quasineutral plasma flow with energies of several tens of eV. A potential gradient at the open end of the capillary and high-temperature electrons in the capillary discharge promote the ion acceleration. The plasma flow was generated from a ceramic capillary with inner diameter of {approx}0.8 mm and a length of {approx}10 mm, at a gas flow rate of 2-10 SCCM (SCCM denotes cubic centimeter per minute at STP) and input power of 15-20 W. The ion energy spectrum consists of high-energy accelerated ions and a low-energy tail formed due to ionization in the acceleration region. The relatively wide plume angle of {approx}65 deg. indicates that the acceleration region is placed outside the capillary and has a convex shape. Estimated total efficiency at 2 SCCM Xe flow rate and 15 W input power reaches 2%-3%. This approach may be attractive for micropropulsion applications due to its simplicity, low weight and small dimensions of the source, and the absence of a cathode neutralizer.

  13. Time resolved EUV spectra from Zpinching capillary discharge plasma

    NASA Astrophysics Data System (ADS)

    Jancarek, Alexandr; Nevrkla, Michal; Nawaz, Fahad

    2015-09-01

    We developed symmetrically charged driver to obtain high voltage, high current Z-pinching capillary discharge. Plasma is created by up to 70 kA, 29 ns risetime current pulse passing through a 5 mm inner diameter, 224 mm long capillary filled with gas to initial pressure in the range of 1 kPa. Due to the low inductance design of the driver, the pinch is observable directly from the measured current curve. Time-integrated and time-resolved spectra of discharge plasma radiation are recorded together with the capillary current and analyzed. The most encouraging spectra were captured in the wavelength range 8.3 ÷ 14 nm. This spectral region contains nitrogen Balmer series lines including potentially lasing NVII 2 - 3 transition. Spectral lines are identified in the NIST database using the FLY kinetic code. The line of 13.38 nm wavelength, transition NVII 2 - 3, was observed in gated, and also in time-integrated spectra for currents >60 kA. This work has been supported by the Ministry of Education, Youth and Sports of the Czech Republic grants LG13029.

  14. Reasonable structure for the discharge type plasma source. [In Pulsed Plasma Thruster

    SciTech Connect

    An, S.M.

    1987-01-01

    Experiments conducted with a magnetoplasma thruster in which plasma production and acceleration were treated separately indicate that different plasma source geometries have the most direct effect on energy conversion efficiency. An analysis of cup and tube type constraining structures shows the cup type to incur the greatest losses. It is noted that a parallel rail-type open structure such as that employed by the Chinese MDT-2A thruster leads to substantial discharge process dispersion. It is emphasized that the type and performance characteristics of a plasma source have a critical influence on thruster behavior. 5 references.

  15. FAST TRACK COMMUNICATION: Effects of Penning ionization on the discharge patterns of atmospheric pressure plasma jets

    NASA Astrophysics Data System (ADS)

    Li, Qing; Zhu, Wen-Chao; Zhu, Xi-Ming; Pu, Yi-Kang

    2010-09-01

    Atmospheric pressure plasma jets, generated in a coaxial dielectric barrier discharge configuration, have been investigated with different flowing gases. Discharge patterns in different tube regions were compared in the flowing gases of helium, neon and krypton. To explain the difference of these discharge patterns, a theoretical analysis is presented to reveal the possible basic processes. A comparison of experimental and theoretical results identifies that Penning ionization is mainly responsible for the discharge patterns of helium and neon plasma jets.

  16. Influence of voltage pulse width on the discharge characteristics in an atmospheric dielectric-barrier-discharge plasma jet

    NASA Astrophysics Data System (ADS)

    Uchida, Giichiro; Takenaka, Kosuke; Setsuhara, Yuichi

    2016-01-01

    We present here the analysis of the discharge characteristics of a He dielectric-barrier-discharge (DBD) plasma jet operated in the voltage duty ratio of 20 to 80% under the condition of driving voltage frequency 5 kHz. Discharge strength is sensitive to the voltage pulse width, and the pulse width of 70 µs, which corresponds to the duty ratio of 35%, leads to high O optical emission intensity. We also performed time-resolved optical emission measurements in a transient pulse discharge driven by various voltage duty ratios. Two distinct pulse discharges are observed in the rising and falling periods of the positive rectangular voltage, and the first and second discharges have a peak intensity of optical emission at different duty ratio. The observations indicate that an adequate voltage pulse width could ignite a strong discharge both in the rising and falling period of applied voltage, which could produce a large amount of reactive excited O atoms.

  17. Simulation Tool for Dielectric Barrier Discharge Plasma Actuators at Atmospheric and Sub-Atmospheric Pressures: SBIR Phase I Final Report

    NASA Technical Reports Server (NTRS)

    Likhanskii, Alexandre

    2012-01-01

    This report is the final report of a SBIR Phase I project. It is identical to the final report submitted, after some proprietary information of administrative nature has been removed. The development of a numerical simulation tool for dielectric barrier discharge (DBD) plasma actuator is reported. The objectives of the project were to analyze and predict DBD operation at wide range of ambient gas pressures. It overcomes the limitations of traditional DBD codes which are limited to low-speed applications and have weak prediction capabilities. The software tool allows DBD actuator analysis and prediction for subsonic to hypersonic flow regime. The simulation tool is based on the VORPAL code developed by Tech-X Corporation. VORPAL's capability of modeling DBD plasma actuator at low pressures (0.1 to 10 torr) using kinetic plasma modeling approach, and at moderate to atmospheric pressures (1 to 10 atm) using hydrodynamic plasma modeling approach, were demonstrated. In addition, results of experiments with pulsed+bias DBD configuration that were performed for validation purposes are reported.

  18. Long range temporal correlation in the chaotic oscillations of a dc glow discharge plasma

    SciTech Connect

    Lahiri, S.; Roychowdhury, D.

    2012-08-15

    Long range temporal correlations in the fluctuations of the plasma floating potentials (measured using a Langmuir probe) are investigated in a dc glow discharge plasma. Keeping the neutral pressure constant, the discharge voltage was varied and at the formation of the plasma, quasi periodic oscillations were excited and on further increase of the discharge voltage they became chaotic (irregular) beyond a threshold voltage. We compared the Lyapunov exponent with the Hurst exponent obtained from R/S statistics which showed an opposite behaviour at the transition point. These results are perhaps new since we have not come across such comparative analysis for chaotic oscillations in a glow discharge plasma before.

  19. MERCURY OXIDIZATION IN NON-THERMAL PLASMA BARRIER DISCHARGE SYSTEM

    SciTech Connect

    V.K. Mathur

    2003-02-01

    In the past decade, the emission of toxic elements from human activities has become a matter of great public concern. Hg, As, Se and Cd typically volatilize during a combustion process and are not easily caught with conventional air pollution control techniques. In addition, there is no pollution prevention technique available now or likely be available in the foreseeable future that can prevent the emission of these trace elements. These trace elements pose additional scientific challenge as they are present at only ppb levels in large gas streams. Mercury, in particular, has attracted significant attention due to its high volatility, toxicity and potential threat to human health. In the present research work, a non-thermal plasma dielectric barrier discharge technique has been used to oxidize Hg{sup 0}(g) to HgO. The basic premise of this approach is that Hg{sup 0} in vapor form cannot be easily removed in an absorption tower whereas HgO as a particulate is amiable to water scrubbing. The work presented in this report consists of three steps: (1) setting-up of an experimental apparatus to generate mercury vapors at a constant rate and modifying the existing non-thermal plasma reactor system, (2) solving the analytical challenge for measuring mercury vapor concentration at ppb level, and (3) conducting experiments on mercury oxidation under plasma conditions to establish proof of concept.

  20. Ion Exchange Resin and Clay Vitrification by Plasma Discharges

    NASA Astrophysics Data System (ADS)

    Díaz A., Laura V.; Pacheco S., Joel O.; Pacheco P., Marquidia; Monroy G., Fabiola; Emeterio H., Miguel; Ramos F., Fidel

    2006-12-01

    The lack of treatment of a low and intermediate level radioactive waste (LILRW) lead us to propose a vitrification process based on a plasma discharge; this technique incorporates LILRW into a matrix glass composed of ceramic clays material. The Mexican Institute of Nuclear Research (ININ), uses an ion exchange resin IRN 150 (styrene-divinilbence copolymer) in the TRIGA MARK III nuclear reactor. The principal objective of this resin is to absorb particles containing heavy metals and low-level radioactive particles. Once the IRN 150 resin filter capacity has been exceeded, it should be replaced and treated as LILRW. In this work, a transferred plasma system was realized to vitrify this resin taking advantage of its high power density, enthalpy and chemical reactivity as well as its rapid quenching and high operation temperatures. In order to characterize the morphological structure of these clay samples, Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and Thermogravimetric analysis (TGA) techniques were applied before and after the plasma treatment.