Science.gov

Sample records for nif plasma electrode

  1. Pulsed Power Aspects of the NIF Plasma Electrode Pockels Cell

    SciTech Connect

    Arnold, P A; Ollis, C W; Hinz, A F; Barbosa, F; Fulkerson, E S

    2005-06-09

    The Plasma Electrode Pockels Cell (PEPC) embodies technology essential to the National Ignition Facility (NIF). Together with a thin-film polarizer, PEPC functions as an optical switch for the main amplifier cavity, allowing optical pulses to be trapped, and then released, and enabling NIF to take advantage of the attendant gain and cost-savings. Details of the genesis, development, and prototyping of the PEPC are well documented. After moving from its laboratory setting to the NIF facility, PEPC--via its performance during the two-year NIF Early Light (NEL) campaign and its ongoing operation during facility build-out--has proven to be a fully functional system. When complete, NIF will accommodate 192 beams, capable of delivering 1.8 MJ to a fusion target. Forty-eight Plasma Electrode Pockels--driven by nearly 300 high-power, high-voltage pulse generators--will support this complement of beams. As deployed, PEPC is a complex association of state-of-the-art optics; low-voltage and high-voltage electronics; and mechanical, gas, and vacuum subsystems--all under computer control. In this paper, we briefly describe each of these elements, but focus on the pulse power aspects of the PEPC system.

  2. Plasma Electrode Pockels Cells for the Beamlet and NIF lasers

    SciTech Connect

    Rhodes, M.A.; Woods, B.; DeYoreo, J.; Atherton, J.

    1994-05-01

    We describe Plasma Electrode Pockels Cells (PEPC) for the Beamlet laser and the proposed National Ignition Facility (NIF) laser. These PEPCs, together with passive polarizers, function as large aperture (> 35 {times} 35 cm{sup 2}) optical switches enabling the design of high-energy (> 5 kJ), multipass laser amplifiers. In a PEPC, plasma discharges form on both sides of a thin (1 cm) electro-optic crystal (KDP). These plasma discharges produce highly conductive and transparent electrodes that facilitate rapid (< 100 ns) and uniform charging of the KDP up to the half-wave voltage (17 kV) and back to zero volts. We discuss the operating principles, design, and optical performance of the Beamlet PEPC and briefly discuss our plans to extend PEPC technology for the NIF.

  3. Plasma Electrode Pockels Cells for the Beamlet and NIF lasers

    SciTech Connect

    Rhodes, M.A.; Woods, B.; De Yoreo, J.; Atherton, J.

    1994-11-01

    The authors describe Plasma Electrode Pockels Cells (PEPC) for the Beamlet laser and the proposed National Ignition Facility (NIF) laser. These PEPCs, together with passive polarizers, function as large aperture (>35 x 35 cm{sup 2}) optical switches enabling the design of high-energy (>5 kJ), multipass laser amplifiers. In a PEPC, plasma discharges form on both sides of a thin (1 cm) electro-optic crystal (KDP). These plasma discharges produce highly conductive and transparent electrodes that facilitate rapid (<100 ns) and uniform charging of the KDP up to the half-wave voltage (17 kV) and back to zero volts. The authors discuss the operating principles, design, and optical performance of the Beamlet PEPC and briefly discuss their plans to extend PEPC technology for the NIF.

  4. DEVELOPMENT OF SOLID-STATE DRIVERS FOR THE NIF PLASMA ELECTRODE POCKELS CELL

    SciTech Connect

    Barbosa, F; Arnold, P A; McHale, G B; James, G; Brown, G; Cook, E G; Hickman, B C

    2008-05-14

    Large aperture Plasma Electrode Pockels Cells (PEPC) are an enabling technology in the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory. The Pockels cell allows the NIF laser to take advantage of multipass amplifier architecture, thus reducing costs and physical size of the facility. Each Pockels cell comprises four 40-cm x 40-cm apertures arranged in a 4 x 1 array. The combination of the Pockels cell and a thin-film polarizer, configured in a 4 x 1 array, form an optical switch that is key to achieving multi-pass operation. Solid-state Plasma Pulse Generators (PPGs) and high current high voltage solid-state Switch Pulse Generators (SPGs) have been developed for use in the PEPC. The solid-state plasma pulse generators initiate and maintain plasma within the cells; each pulser is capable of delivering 60J of energy to each plasma channel. Deployment of the solid-state PPGs has been completed in NIF. The MOSFET-switched SPG is capable of delivering a requisite fast rise time, 17kV flattop pulse to the cells nonlinear crystals. A complete software and hardware control system has been developed and is currently being tested for use on the solid-state SPGs. Also a transmission line modeling, development, and testing effort is in process, in support of NIFs Advanced Radiographic Capabilities (ARC). Work is scheduled for completion by the end of the calendar year.

  5. A HIGH CURRENT, HIGH VOLTAGE SOLID-STATE PULSE GENERATOR FOR THE NIF PLASMA ELECTRODE POCKELS CELL

    SciTech Connect

    Arnold, P A; Barbosa, F; Cook, E G; Hickman, B C; Akana, G L; Brooksby, C A

    2007-07-27

    A high current, high voltage, all solid-state pulse modulator has been developed for use in the Plasma Electrode Pockels Cell (PEPC) subsystem in the National Ignition Facility. The MOSFET-switched pulse generator, designed to be a more capable plug-in replacement for the thyratron-switched units currently deployed in NIF, offers unprecedented capabilities including burst-mode operation, pulse width agility and a steady-state pulse repetition frequency exceeding 1 Hz. Capable of delivering requisite fast risetime, 17 kV flattop pulses into a 6 {Omega} load, the pulser employs a modular architecture characteristic of the inductive adder technology, pioneered at LLNL for use in acceleration applications, which keeps primary voltages low (and well within the capabilities of existing FET technology), reduces fabrication costs and is amenable to rapid assembly and quick field repairs.

  6. Modeling laser-plasma interactions in NIF vacuum hohlraums

    NASA Astrophysics Data System (ADS)

    Williams, E. A.; Hinkel, D. E.; Still, C. H.; Langdon, A. B.; Olson, R. E.; Kline, J.

    2009-11-01

    In preparation for the NIF ignition campaign, a series of experiments are underway firing 96 and 192 beams of the NIF laser into empty gold hohlraums. The primary purpose of these experiments is to qualify the DANTE filtered x-ray diode radiation temerature diagnostic. We plan to have backscatter diagnostics available, giving us an opportunity to test our LPI modeling on the NIF scale. In addition to scaling with energy, we test the use of a gold-boron coating on the hohlraum wall to reduce SBS via increased ion Landau damping of the ion-acoustic waves. We use Lasnex to simulate the hydrodynamic evolution of the hohlraum plasma. Steady state gains were computed using our diagnostic NEWLIP. These were used to suggest appropriate backscatter simulations to be performed with pF3D, a massivel parallel code that couples paraxial light propagation with fluid models of the stimulated plasma ansd ion waves evolving on a background plasma. We describe the results of these simulations, pre- and post-shot, and compare them with experimental results.

  7. Simulating NIF laser-plasma interaction with multiple SRS frequencies

    SciTech Connect

    Still, C H; Hinkel, D E; Langdon, A B; Palastro, J P; Williams, E A

    2009-10-05

    Understanding the energetics of a NIF ignition hohlraum is important to achieving ignition. Laser-plasma interactions (LPI) can reduce the radiation drive if backscatter occurs, and can also affect the hohlraum energetics by modifying the laser beam energy deposition which in turn can alter the implosion symmetry. The addition of a second SRS frequency to the modeling code pF3d can capture physics which would otherwise have been omitted. In the case of a wide or bi-modal SRS spectrum, this physics can be important. We discuss the modifications to the pF3d computational model, and exhibit its effect in a NIF ignition-relevant LPI simulation.

  8. First Laser-Plasma Interaction and Hohlraum Experiments on NIF

    SciTech Connect

    Dewald, E L; Glenzer, S H; Landen, O L; Suter, L J; Jones, O S; Schein, J; Froula, D; Divol, L; Campbell, K; Schneider, M S; McDonald, J W; Niemann, C; Mackinnon, A J

    2005-06-17

    Recently the first hohlraum experiments have been performed at the National Ignition Facility (NIF) in support of indirect drive Inertial Confinement Fusion (ICF) designs. The effects of laser beam smoothing by spectral dispersion (SSD) and polarization smoothing (PS) on the beam propagation in long scale gas-filled pipes has been studied at plasma scales as found in indirect drive gas filled ignition hohlraum designs. The long scale gas-filled target experiments have shown propagation over 7 mm of dense plasma without filamentation and beam break up when using full laser smoothing. Vacuum hohlraums have been irradiated with laser powers up to 6 TW, 1-9 ns pulse lengths and energies up to 17 kJ to activate several diagnostics, to study the hohlraum radiation temperature scaling with the laser power and hohlraum size, and to make contact with hohlraum experiments performed at the NOVA and Omega laser facilities. Subsequently, novel long laser pulse hohlraum experiments have tested models of hohlraum plasma filling and long pulse hohlraum radiation production. The validity of the plasma filling assessment in analytical models and in LASNEX calculations has been proven for the first time. The comparison of these results with modeling will be discussed.

  9. Plasma jet electrode has longer operating life

    NASA Technical Reports Server (NTRS)

    Gracey, C. M.

    1967-01-01

    Water-cooled, silver-infiltrated tungsten electrode has twice the operating lifetime of the pure tungsten electrode used in plasma jet generators. This electrode reduces the erosion rate, ensures excellent heat transfer, and reduces thermal stresses.

  10. AN UPDATE ON NIF PULSED POWER

    SciTech Connect

    Arnold, P A; James, G F; Petersen, D E; Pendleton, D L; McHale, G B; Barbosa, F; Runtal, A S; Stratton, P L

    2009-06-22

    The National Ignition Facility (NIF) is a 192-beam laser fusion driver operating at Lawrence Livermore National Laboratory. NIF relies on three large-scale pulsed power systems to achieve its goals: the Power Conditioning Unit (PCU), which provides flashlamp excitation for the laser's injection system; the Power Conditioning System (PCS), which provides the multi-megajoule pulsed excitation required to drive flashlamps in the laser's optical amplifiers; and the Plasma Electrode Pockels Cell (PEPC), which enables NIF to take advantage of a fourpass main amplifier. Years of production, installation, and commissioning of the three NIF pulsed power systems are now complete. Seven-day-per-week operation of the laser has commenced, with the three pulsed power systems providing routine support of laser operations. We present the details of the status and operational experience associated with the three systems along with a projection of the future for NIF pulsed power.

  11. Laser-plasma interactions in NIF-scale plasmas (HLP5 and HLP6)

    SciTech Connect

    MacGowan, B.; Berger, R.; Fernandez, J.

    1996-06-01

    The understanding of laser-plasma interactions in ignition-scale inertial confinement fusion (ICF) hohlraum targets is important for the success of the proposed National Ignition Facility (NIF). The success of an indirect-drive ICF ignition experiment depends on the ability to predict and control the history and spatial distribution of the x-radiation produced by the laser beams that are absorbed by the inside of the hohlraum wall. Only by controlling the symmetry of this x-ray drive is it possible to obtain the implosion symmetry in the fusion pellet necessary for ignition. The larger hohlraums and longer time scales required for ignition-scale targets result in the presence of several millimeters of plasma (electron density n{sub e} {approximately} 0.1 n{sub c} {approximately} 10{sup 21} cm{sup {minus}3}), through which the 3{omega} (351-nm) laser beams must propagate before they are absorbed at the hohlraum wall. Hydrodynamic simulations show this plasma to be very uniform [density-gradient scalelength L{sub n} = n{sub e}(dn{sub e}/dx){sup {minus}1}{approximately} 2mm] and to exhibit low velocity gradients [velocity-gradient scale-length L{sub v} = c{sub s}(dv/dx){sup {minus}1} > 6 mm].

  12. Magnetron cathodes in plasma electrode Pockels cells

    DOEpatents

    Rhodes, M.A.

    1995-04-25

    Magnetron cathodes, which produce high current discharges, form greatly improved plasma electrodes on each side of an electro-optic crystal. The plasma electrode has a low pressure gas region on both sides of the crystal. When the gas is ionized, e.g., by a glow discharge in the low pressure gas, the plasma formed is a good conductor. The gas electrode acts as a highly uniform conducting electrode. Since the plasma is transparent to a high energy laser beam passing through the crystal, the plasma is transparent. A crystal exposed from two sides to such a plasma can be charged up uniformly to any desired voltage. A typical configuration utilizes helium at 50 millitorr operating pressure and 2 kA discharge current. The magnetron cathode produces a more uniform plasma and allows a reduced operating pressure which leads to lower plasma resistivity and a more uniform charge on the crystal. 5 figs.

  13. Magnetron cathodes in plasma electrode pockels cells

    DOEpatents

    Rhodes, Mark A.

    1995-01-01

    Magnetron cathodes, which produce high current discharges, form greatly improved plasma electrodes on each side of an electro-optic crystal. The plasma electrode has a low pressure gas region on both sides of the crystal. When the gas is ionized, e.g., by a glow discharge in the low pressure gas, the plasma formed is a good conductor. The gas electrode acts as a highly uniform conducting electrode. Since the plasma is transparent to a high energy laser beam passing through the crystal, the plasma is transparent. A crystal exposed from two sides to such a plasma can be charged up uniformly to any desired voltage. A typical configuration utilizes helium at 50 millitorr operating. pressure and 2 kA discharge current. The magnetron cathode produces a more uniform plasma and allows a reduced operating pressure which leads to lower plasma resistivity and a more uniform charge on the crystal.

  14. PLASMA ELECTRODE POCKELS CELL SUBSYSTEM PERFORMANCE IN THE NATIONAL IGNITION FACILITY

    SciTech Connect

    Barbosa, F; Arnold, P; Hinz, A; Zacharias, R; Ollis, C; Fulkerson, E; Mchale, B; Runtal, A; Bishop, C

    2007-07-27

    The Plasma Electrode Pockels Cell (PEPC) subsystem is a key component of the National Ignition Facility, enabling the laser to employ an efficient four-pass main amplifier architecture. PEPC relies on a pulsed power technology to initiate and maintain plasma within the cells and to provide the necessary high voltage bias to the cells nonlinear crystals. Ultimately, nearly 300 high-voltage, high-current pulse generators will be deployed in the NIF in support of PEPC. Production of solid-state plasma pulse generators and thyratron-switched pulse generators is now complete, with the majority of the hardware deployed in the facility. An entire cluster (one-fourth of a complete NIF) has been commissioned and is operating on a routine basis, supporting laser shot operations. Another cluster has been deployed, awaiting final commissioning. Activation and commissioning of new hardware continues to progress in parallel, driving toward a goal of completing the PEPC subsystem in late 2007.

  15. Plasma torch with liquid metal electrodes

    SciTech Connect

    Predtechenskii, M.R.; Tukhto, O.M.

    2006-03-15

    In order to eliminate the negative effect of erosion processes on electrodes in arc plasma generators, a new scheme of arc discharge was proposed in which the surface of a molten metal acts as electrodes. A plasma reactor was designed on the basis of this concept. The electrophysical characteristics of such a discharge in steam and air as plasma gases were studied. Experiments on destruction of toxic polychlorinated biphenyls and steam coal gasification were performed.

  16. Electrode assemblies, plasma apparatuses and systems including electrode assemblies, and methods for generating plasma

    DOEpatents

    Kong, Peter C; Grandy, Jon D; Detering, Brent A; Zuck, Larry D

    2013-09-17

    Electrode assemblies for plasma reactors include a structure or device for constraining an arc endpoint to a selected area or region on an electrode. In some embodiments, the structure or device may comprise one or more insulating members covering a portion of an electrode. In additional embodiments, the structure or device may provide a magnetic field configured to control a location of an arc endpoint on the electrode. Plasma generating modules, apparatus, and systems include such electrode assemblies. Methods for generating a plasma include covering at least a portion of a surface of an electrode with an electrically insulating member to constrain a location of an arc endpoint on the electrode. Additional methods for generating a plasma include generating a magnetic field to constrain a location of an arc endpoint on an electrode.

  17. Diagnosing Te of NIF plasmas using the isoelectronic ratios of microdot tracer elements

    NASA Astrophysics Data System (ADS)

    Barrios, M. A.; Regan, S. P.; Fournier, K. B.; Schneider, M. B.; Liedahl, D. A.; Kemp, G. E.; Moody, J. D.; Brown, G. V.; Chen, H.; Landen, O.; Bradley, D.; Jones, O.; Epstein, R.; LLNL Collaboration; LLE Collaboration

    2014-10-01

    Experiments planned on NIF will diagnose the electron temperature (Te) of the hohlraum in the vicinity of the laser entrance hole (LEH) using x-ray spectroscopy. A microdot consisting of Ti and Cr will be coated on the surface of a CH implosion capsule and centered on the symmetry axis of the hohlraum. As the microdot is ablated it is ionized by the hohlraum plasma and flows into the LEH region. The experimental plan to use the isoelectronic line ratio technique to diagnose Te of the hohlraum plasma near the LEH will be presented. Exploratory experiments at NIF tested the Te sensitivity of the technique by recording time resolved K-shell emission of direct-drive spherical targets coated with a CrNiZn alloy. Application of the isoelectronic technique to the coronal plasma of these targets will be presented. This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344.

  18. Effect of a floating electrode on a plasma jet

    SciTech Connect

    Hu, J. T.; Wang, J. G.; Liu, X. Y.; Liu, D. W.; Lu, X. P.; Shi, J. J.; Ostrikov, K.

    2013-08-15

    Two kinds of floating electrode, floating dielectric barrier covered electrode (FDBCE) and floating pin electrode (FPE), which can enhance the performance of plasma jet are reported. The intense discharge between the floating electrode and power electrode decreased the voltage to trigger the plasma jet substantially. The transition of plasma bullet from ring shape to disk shape in the high helium concentration region happened when the floating electrode was totally inside the powered ring electrode. The enhanced electric field between propagating plasma bullet and ground electrode is the reason for this transition. The double plasma bullets happened when part of the FDBCE was outside the powered ring electrode, which is attributed to the structure and surface charge of FDBCE. As part of the FPE was outside the powered ring electrode, the return stroke resulted in a single intensified plasma channel between FPE and ground electrode.

  19. Tailored ion energy distributions on plasma electrodes

    SciTech Connect

    Economou, Demetre J.

    2013-09-15

    As microelectronic device features continue to shrink approaching atomic dimensions, control of the ion energy distribution on the substrate during plasma etching and deposition becomes increasingly critical. The ion energy should be high enough to drive ion-assisted etching, but not too high to cause substrate damage or loss of selectivity. In many cases, a nearly monoenergetic ion energy distribution (IED) is desired to achieve highly selective etching. In this work, the author briefly reviews: (1) the fundamentals of development of the ion energy distribution in the sheath and (2) methods to control the IED on plasma electrodes. Such methods include the application of “tailored” voltage waveforms on an electrode in continuous wave plasmas, or the application of synchronous bias on a “boundary electrode” during a specified time window in the afterglow of pulsed plasmas.

  20. Control of laser-ablation plasma potential with external electrodes

    SciTech Connect

    Isono, Fumika Nakajima, Mitsuo; Hasegawa, Jun; Kawamura, Tohru; Horioka, Kazuhiko

    2015-08-15

    The potential of a laser-ablation plasma was controlled stably up to +2 kV by using external ring electrodes. A stable electron sheath was formed between the plasma and the external electrodes by placing the ring electrodes away from the boundary of the drifting plasma. The plasma kept the potential for a few μs regardless of the flux change of the ablation plasma. We also found that the plasma potential changed with the expansion angle of the plasma from the target. By changing the distance between the plasma boundary and the external electrodes, we succeeded in controlling the potential of laser-ablation plasma.

  1. Characterizing Hohlraum Plasma Conditions at the National Ignition Facility (NIF) Using X-ray Spectroscopy

    NASA Astrophysics Data System (ADS)

    Barrios, Maria Alejandra

    2015-11-01

    Improved hohlraums will have a significant impact on increasing the likelihood of indirect drive ignition at the NIF. In indirect-drive Inertial Confinement Fusion (ICF), a high-Z hohlraum converts laser power into a tailored x-ray flux that drives the implosion of a spherical capsule filled with D-T fuel. The x-radiation drive to capsule coupling sets the velocity, adiabat, and symmetry of the implosion. Previous experiments in gas-filled hohlraums determined that the laser-hohlraum energy coupling is 20-25% less than modeled, therefore identifying energy loss mechanisms that reduce the efficacy of the hohlraum drive is central to improving implosion performance. Characterizing the plasma conditions, particularly the plasma electron temperature (Te) , is critical to understanding mechanism that affect the energy coupling such as the laser plasma interactions (LPI), hohlraum x-ray conversion efficiency, and dynamic drive symmetry. The first Te measurements inside a NIF hohlraum, presented here, were achieved using K-shell X-ray spectroscopy of an Mn-Co tracer dot. The dot is deposited on a thin-walled CH capsule, centered on the hohlraum symmetry axis below the laser entrance hole (LEH) of a bottom-truncated hohlraum. The hohlraum x-ray drive ablates the dot and causes it to flow upward, towards the LEH, entering the hot laser deposition region. An absolutely calibrated streaked spectrometer with a line of sight into the LEH records the temporal history of the Mn and Co X-ray emission. The measured (interstage) Lyα/ Heα line ratios for Co and Mn and the Mn-Heα/Co-Heα isoelectronic line ratio are used to infer the local plasma Te from the atomic physics code SCRAM. Time resovled x-ray images perpendicular to the hohlraum axis record the dot expansion and trajectory into the LEH region. The temporal evolution of the measured Te and dot trajectory are compared with simulations from radiation-hydrodynamic codes. This work was performed under the auspices of the U

  2. The heating of plasma focus electrodes

    NASA Astrophysics Data System (ADS)

    Angeli, E.; Frignani, M.; Mannucci, S.; Rocchi, F.; Sumini, M.; Tartari, A.

    2006-02-01

    Plasma focus (PF) technology development today is strictly related to the possibility of a high frequency repetitive working regime. One of the more relevant obstacles to this goal is the heating of structural components due to direct interaction with plasma. In this paper, temperature decay measurements of the inner electrode of a 7 kJ Mather type PF are presented. Data from several series of shots at different bank energies are analysed and compared with theoretical and numerical models. Two possible scale laws are derived from the experimental data to correlate thermal deposition with bank energy. It is found that a fraction of about 10% of total energy is released to the inner electrode. Finally, after some considerations about the cooling and heating mechanisms, an analysis on maximum temperature sustained by materials is presented.

  3. Deployment, Commissioning and Operation of Plasma Electrode Pockels Cells in the National Ignition Facility

    SciTech Connect

    Arnold, P A; Ollis, C W; Hinz, A; Robb, C; Primdahl, K A; Watson, J J; O'Brien, M D; Funkhouser, W G; Biltoft, P J; Shelton, R T; Tapley, W C; DeHope, W J

    2003-12-01

    Large aperture Plasma Electrode Pockels Cells (PEPCs) are an enabling technology in the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory. The Pockels cells allow the NIF laser to take advantage of multipass main amplifier architecture, thus reducing costs and physical size of the facility. Each Pockels cell comprises four 40-cm x 40-cm apertures arranged in a 4 x 1 array. The combination of the Pockels cell and a thin-film polarizer, also configured in a 4 x 1 array, forms an optical switch that is key to achieving the required multi-pass operation. The operation of the PEPC is a follows: Before the arrival of the laser pulse, optically transparent, low-density helium plasmas are initiated to serve as electrodes for the KDP crystals mounted in the Pockels cell. During beam propagation through the main laser cavity a longitudinal electric field is impressed on the electro-optic crystals. The polarization of the propagating beams is rotated by 90{sup o} on each of two passes, thereby allowing the beam to be trapped in the main laser amplifier cavity for a total of four passes before being switched out into the cavity spatial filter. The physics aspects of the PEPC are well documented. Consequently, this paper will emphasize the PEPC subsystem in the context of its role and relevance within the broader NIF laser system, provide a view of the complexity of the subsystem and give an overview of PEPC's interactions with other elements of NIF, including interfaces to the Beamline Infrastructure, the NIF Timing Subsystem, and the Integrated Computer Control System (ICCS); along with dependence on the Optics Production, Transport and Handling (T&H), and Assembly, Integration and Refurbishment (AIR) and Operations organizations. Further, we will discuss implementation details related to the functional blocks and individual components that comprise PEPC, with particular emphasis on the unique constraints placed on the elements and the attendant

  4. Deployment, commissioning, and operation of plasma electrode Pockels cells in the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Arnold, Phillip A.; Ollis, Craig W.; Hinz, Andrew F.; Robb, Calvin L.; Primdahl, Keith A.; Watson, Jayson J.; O'Brien, Michael D.; Funkhouser, William G.; Biltoft, Peter J.; Shelton, Randy T.; Tapley, William C.; DeHope, William J.

    2004-05-01

    Large aperture Plasma Electrode Pockels Cells (PEPCs) are an enabling technology in the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory. The Pockels cells allow the NIF laser to take advantage of multipass main amplifier architecture, thus reducing costs and physical size of the facility. Each Pockels cell comprises four 40-cm x 40-cm apertures arranged in a 4x1 array. The combination of the Pockels cell and a thin-film polarizer, also configured in a 4x1 array, forms an optical switch that is key to achieving the required multi-pass operation. The operation of the PEPC is a follows: Before the arrival of the laser pulse, optically transparent, low-density helium plasmas are initiated to serve as electrodes for the KDP crystals mounted in the Pockels cell. During beam propagation through the main laser cavity a longitudinal electric field is impressed on the electro-optic crystals. The polarization of the propagating beams is rotated by 90° on each of two passes, thereby allowing the beam to be trapped in the main laser amplifier cavity for a total of four passes before being switched out into the cavity spatial filter. The physics aspects of the PEPC are well documented. Consequently, this paper will emphasize the PEPC subsystem in the context of its role and relevance within the broader NIF laser system, provide a view of the complexity of the subsystem and give an overview of PEPC's interactions with other elements of NIF, including interfaces to the Beamline Infrastructure, the NIF Timing Subsystem, and the Integrated Computer Control System (ICCS); along with dependence on the Optics Production, Transport and Handling (T&H), and Assembly, Integration and Refurbishment (AIR) and Operations organizations. Further, we will discuss implementation details related to the functional blocks and individual components that comprise PEPC, with particular emphasis on the unique constraints placed on the elements and the attendant

  5. Simulation of laser-driven, ablated plasma flows in collisionless shock experiments on OMEGA and the NIF

    NASA Astrophysics Data System (ADS)

    Grosskopf, M. J.; Drake, R. P.; Kuranz, C. C.; Rutter, E. M.; Ross, J. S.; Kugland, N. L.; Plechaty, C.; Remington, B. A.; Spitkovsky, A.; Gargate, L.; Gregori, G.; Bell, A.; Murphy, C. D.; Meinecke, J.; Reville, B.; Sakawa, Y.; Kuramitsu, Y.; Takabe, H.; Froula, D. H.; Fiksel, G.; Miniati, F.; Koenig, M.; Ravasio, A.; Liang, E.; Fu, W.; Woolsey, N.; Park, H.-S.

    2013-03-01

    Experiments investigating the physics of interpenetrating, collisionless, ablated plasma flows have become an important area of research in the high-energy-density field. In order to evaluate the feasibility of designing experiments that will generate a collisionless shock mediated by the Weibel instability on the National Ignition Facility (NIF) laser, computer simulations using the Center for Radiative Shock Hydrodynamics (CRASH) radiation-hydrodynamics model have been carried out. This paper reports assessment of whether the experiment can reach the required scale size while maintaining the low interflow collisionality necessary for the collisionless shock to form. Comparison of simulation results with data from Omega experiments shows the ability of the CRASH code to model these ablated systems. The combined results indicate that experiments on the NIF are capable of reaching the regimes necessary for the formation of a collisionless shock in a laboratory experiment.

  6. Model of the influence of magnetic fields on a plasma electrode Pockels cell

    SciTech Connect

    Boley, C.D.; Rhodes, M.A.

    1996-10-01

    We describe a model which gives the effects of magnetic fields on a plasma electrode Pockels cell. The fields arise from the return currents to the cathode as well as from neighboring devices such as amplifier flashlamps. In effect, electrons are treated as a static, planar fluid moving under the influence of magnetic fields, the electric field of the discharge, electron pressure gradients, and electron-atom elastic collisions. This leads to a closed two- dimensional equation for the electron density, which is solved subject to appropriate boundary collisions. The model is applied to four cases-. the baseline NIF configuration with magnetic fields due to balanced return currents; a case with unbalanced return currents; the reverser configuration containing an external field parallel to the main plasma current; and a configuration with a field perpendicular to both the current and the optical direction.

  7. Ablation of NIF Targets and Diagnostic Components by High Power Lasers and X-Rays from High Temperature Plasmas

    SciTech Connect

    Eder, D.C; Anderson, A.T.; Braun, D.G; Tobin, M.T.

    2000-04-19

    The National Ignition Facility (NIF) will consist of 192 laser beams that have a total energy of up to 1.8 MJ in the 3rd harmonic ({lambda} = 0.35 {micro}m) with the amount of 2nd harmonic and fundamental light depending on the pulse shape. Material near best focus of the 3rd harmonic light will be vaporized/ablated very rapidly, with a significant fraction of the laser energy converted into plasma x rays. Additional plasma x rays can come from imploding/igniting capsule inside Inertial Confinement Fusion (ICF) hohlraums. Material from outer portions of the target, diagnostic components, first-wall material, and optical components, are ablated by the plasma x rays. Material out to a radius of order 3 cm from target center is also exposed to a significant flux of 2nd harmonic and fundamental laser light. Ablation can accelerate the remaining material to high velocities if it has been fragmented or melted. In addition, the high velocity debris wind of the initially vaporized material pushes on the fragments/droplets and increases their velocity. The high velocity shrapnel fragments/droplets can damage the fused silica shields protecting the final optics in NIF. We discuss modeling efforts to calculate vaporization/ablation, x-ray generation, shrapnel production, and ways to mitigate damage to the shields.

  8. Three electrode atmospheric pressure plasma jet in helium flow

    NASA Astrophysics Data System (ADS)

    Maletic, Dejan; Puac, Nevena; Malovic, Gordana; Petrovic, Zoran Lj.

    2015-09-01

    Plasma jets are widely used in various types of applications and lately more and more in the field of plasma medicine. However, it is not only their applicability that distinguishes them from other atmospheric plasma sources, but also the behavior of the plasma. It was shown that plasma plume is not continuous, but discrete set of plasma packages. Here we present iCCD images and current voltage characteristics of a three electrode plasma jet. Our plasma jet has a simple design with body made of glass tube and two transparent electrodes wrapped around it. The additional third metal tip electrode was positioned at 10 and 25 mm in front of the jet nozzle and connected to the same potential as the powered electrode. Power transmitted to the plasma was from 0.5 W to 4.0 W and the helium flow rate was kept constant at 4 slm. For the 10 mm configuration plasma is ignited on the metal tip in the whole period of the excitation signal and in the positive half cycle plasma ``bullet'' is propagating beyond the metal tip. In contrast to that, for the 25 mm configuration at the tip electrode plasma can be seen only in the minimum and maximum of the excitation signal, and there is no plasma ``bullet'' formation. This research has been supported by the Ministry of Education, Science and Technological Development, Republic of Serbia, under projects ON171037 and III41011.

  9. Design of microplasma electrodes for plasma-on-chip devices

    NASA Astrophysics Data System (ADS)

    Chang, Chun-Yao; Sasaki, Minoru; Kumagai, Shinya; Wang, Gou-Jen

    2016-04-01

    Plasma-on-chip (POC) devices have been developed to achieve plasma treatment of individual cells. However, the microcathode of a POC can be easily damaged during plasma firing. In this study, microplasma electrodes for POC devices were designed to enhance the lifetime of plasma electrodes while maintaining their microplasma characteristics. An electrode comprising a 20 nm-thick titanium layer and a 200 nm-thick gold layer on a silicon substrate was fabricated by photolithography and evaporation. Experimental results illustrated that a microelectrode with a blunt-ended cathode and a flat anode can extend the firing lifetime by as much as 30 times that of a double-tip electrode. We also fabricated a 220 nm-thick pure titanium electrode to further extend the lifetime of the electrode. Experimental results showed that the pure titanium electrode can further extend the lifetime 60 fold when compared with an Au / Ti hybrid electrode. However, the voltage requirement for the pure titanium electrode is only 20 V higher than that for the Au/Ti electrode. The pure titanium microelectrode proposed in this study possesses several advantages such as low cost, simple fabrication, and high biocompatibility. Hence, it is highly feasible for POC applications.

  10. Effects of wall electrodes on Hall effect thruster plasma

    SciTech Connect

    Langendorf, S. Walker, M.; Xu, K.

    2015-02-15

    This paper investigates the physical mechanisms that cause beneficial and detrimental performance effect observed to date in Hall effect thrusters with wall electrodes. It is determined that the wall electrode sheath can reduce ion losses to the wall if positioned near the anode (outside the dense region of the plasma) such that an ion-repelling sheath is able to form. The ability of the wall electrode to form an ion-repelling sheath is inversely proportional to the current drawn—if the wall electrode becomes the dominant sink for the thruster discharge current, increases in wall electrode bias result in increased local plasma potential rather than an ion-repelling sheath. A single-fluid electron flow model gives results that mimic the observed potential structures and the current-sharing fractions between the anode and wall electrodes, showing that potential gradients in the presheath and bulk plasma come at the expense of current draw to the wall electrodes. Secondary electron emission from the wall electrodes (or lack thereof) is inferred to have a larger effect if the electrodes are positioned near the exit plane than if positioned near the anode, due to the difference in energy deposition from the plasma.

  11. Effects of wall electrodes on Hall effect thruster plasma

    NASA Astrophysics Data System (ADS)

    Langendorf, S.; Xu, K.; Walker, M.

    2015-02-01

    This paper investigates the physical mechanisms that cause beneficial and detrimental performance effect observed to date in Hall effect thrusters with wall electrodes. It is determined that the wall electrode sheath can reduce ion losses to the wall if positioned near the anode (outside the dense region of the plasma) such that an ion-repelling sheath is able to form. The ability of the wall electrode to form an ion-repelling sheath is inversely proportional to the current drawn—if the wall electrode becomes the dominant sink for the thruster discharge current, increases in wall electrode bias result in increased local plasma potential rather than an ion-repelling sheath. A single-fluid electron flow model gives results that mimic the observed potential structures and the current-sharing fractions between the anode and wall electrodes, showing that potential gradients in the presheath and bulk plasma come at the expense of current draw to the wall electrodes. Secondary electron emission from the wall electrodes (or lack thereof) is inferred to have a larger effect if the electrodes are positioned near the exit plane than if positioned near the anode, due to the difference in energy deposition from the plasma.

  12. Study of the near-electrode processes in quasi-steady plasma accelerators with impenetrable electrodes

    NASA Astrophysics Data System (ADS)

    Kozlov, A. N.

    2012-01-01

    Near-electrode processes in a coaxial plasma accelerator with equipotential impenetrable electrodes are simulated using a two-dimensional (generally, time-dependent) two-fluid MHD model with allowance for the Hall effect and the plasma conductivity tensor. The simulations confirm the theoretically predicted mechanism of the so-called "crisis of current" caused by the Hall effect. The simulation results are compared with available experimental data. The influence of both the method of plasma supply to the channel and an additional longitudinal magnetic field on the development of near-electrode instabilities preceding the crisis of current is studied.

  13. Nuclear Physics using NIF

    SciTech Connect

    Bernstein, L A; Bleuel, D L; Caggiano, J A; Cerjan, C; Gostic, J; Hatarik, R; Hartouni, E; Hoffman, R D; Sayre, D; Schneider, D G; Shaughnessy, D; Stoeffl, W; Yeamans, C; Greife, U; Larson, R; Hudson, M; Herrmann, H; Kim, Y H; Young, C S; Mack, J; Wilson, D; Batha, S; Hoffman, N; Langenbrunner, J; Evans, S

    2011-09-28

    The National Ignition Facility (NIF) is the world's premier inertial confinement fusion facility designed to achieve sustained thermonuclear burn (ignition) through the compression of hydrogen isotopic fuels to densities in excess of 10{sup 3} g/cm{sup 3} and temperatures in excess of 100 MK. These plasma conditions are very similar to those found in the cores of Asymptotic Giant Branch (AGB) stars where the s-process takes place, but with a neutron fluence per year 10{sup 4} times greater than a star. These conditions make NIF an excellent laboratory to measure s-process (n,{gamma}) cross sections in a stellar-like plasma for the first time. Starting in Fall 2009, NIF has been operating regularly with 2-4 shots being performed weekly. These experiments have allowed the first in situ calibration of the detectors and diagnostics needed to measure neutron capture, including solid debris collection and prompt {gamma}-ray detection. In this paper I will describe the NIF facility and capsule environment and present two approaches for measuring s-process neutron capture cross sections using NIF.

  14. NIF facts

    SciTech Connect

    Carpenter, J; Warner, B

    2000-09-08

    The National Ignition Facility (NIF) will use the world's largest laser to compress and heat BB-sized capsules of fusion fuel to thermo-nuclear ignition. NIF experiments will produce temperatures and densities like those in the Sun or in an exploding nuclear weapon. The experiments will help scientists sustain confidence in the nuclear weapon stockpile without nuclear tests as a unique element of the DOE'S Stockpile Stewardship Program and will produce additional benefits in basic science and fusion energy.

  15. Measurements of Plasma Potential Distribution in Segmented Electrode Hall Thruster

    SciTech Connect

    Y. Raitses; D. Staack; N.J. Fisch

    2001-10-16

    Use of a segmented electrode placed at the Hall thruster exit can substantially reduce the voltage potential drop in the fringing magnetic field outside the thruster channel. In this paper, we investigate the dependence of this effect on thruster operating conditions and segmented electrode configuration. A fast movable emissive probe is used to measure plasma potential in a 1 kW laboratory Hall thruster with semented electrodes made of a graphite material. Relatively small probe-induced perturbations of the thruster discharge in the vicinity of the thruster exit allow a reasonable comparison of the measured results for different thruster configurations. It is shown that the plasma potential distribution is almost not sensitive to changes of the electrode potential, but depends on the magnetic field distribution and the electrode placement.

  16. Generation of solution plasma over a large electrode surface area

    NASA Astrophysics Data System (ADS)

    Saito, Genki; Nakasugi, Yuki; Akiyama, Tomohiro

    2015-07-01

    Solution plasma has been used in a variety of fields such as nanomaterials synthesis, the degradation of harmful substances, and solution analysis. However, as existing methods are ineffective in generating plasma over a large surface area, this study investigated the contact glow discharge electrolysis, in which the plasma was generated on the electrode surface. To clarify the condition of plasma generation, the effect of electrolyte concentration and temperature on plasma formation was studied. The electrical energy needed for plasma generation is higher than that needed to sustain a plasma, and when the electrolyte temperature was increased from 32 to 90 °C at 0.01 M NaOH solution, the electric power density for vapor formation decreased from 2005 to 774 W/cm2. From these results, we determined that pre-warming of the electrolyte is quite effective in generating plasma at lower power density. In addition, lower electrolyte concentrations required higher power density for vapor formation owing to lower solution conductivity. On the basis these results, a method for large-area and flat-plate plasma generation is proposed in which an initial small area of plasma generation is extended. When used with a plate electrode, a concentration of current to the edge of the plate meant that plasma could be formed by covering the edge of the electrode plate.

  17. Effects of Segmented Electrode in Hall Current Plasma Thrusters

    SciTech Connect

    Y. Raitses; M. Keidar; D. Staack; N.J. Fisch

    2001-12-03

    Segmented electrodes with a low secondary electron emission are shown to alter significantly plasma flow in the ceramic channel of the Hall thruster. The location of the axial acceleration region relative to the magnetic field can be moved. The radial potential distribution can also be altered near the channel walls. A hydrodynamic model shows that these effects are consistent with a lower secondary electron emission of the segmented electrode as compared to ceramic channel walls.

  18. Whistler wings from moving electrodes in a magnetized laboratory plasma

    SciTech Connect

    Urrutia, J.M.; Stenzel, R.L. )

    1989-05-01

    In a large laboratory plasma the current pattern set up by moving electrodes has been measured. It is observed that the current flow oblique to the magnetic field {rvec B}{sub o} at an angle given by the electrode speed across {rvec B}{sub o} and the current penetration along {rvec B}{sub o} which is controlled by whistler waves. The current pattern, characterized as whistler wings, occurs irrespective of whether the electrodes collect electrons/ions or emit fast electron beams. These results are relevant to active experiments in space involving electrodynamic tethers, beam injections and large space stations.

  19. Calculations for NIF first quad gas-filled hohlraum experiments testing beryllium microstructure growth and laser plasma interaction physics

    SciTech Connect

    Goldman, S. R.; Fernández, J. C.; Hoffman, N. M.; Kindel, J. M.; Langdon, A. Bruce

    2004-01-01

    The first quad of the NIF provides four nearly collinear f/20 laser beams, which can be treated as a single f/8 beam of maximum energy 16 kJ. We are designing experiments on halfraums in which the composite beam is focused in the plane of the (single) halfraum laser entry hole (LEH) with its symmetry axis collinear with the halfiaum symmetry axis. For most of the calculations, the halfraum diameter is 1.6mm, the LEH is 1.2mm, and axial length is 3.0mm. The incident laser power consists of an early foot followed by a final peak. Peak radiation temperatures for this relatively narrow hohlraum are greater than for wider hohlraums of the same length. Plasma conditions within the halfraum are calculated with Lasnex using azimuthally symmetric, (r,z) geometry, taking into account a polyimide membrane which contains the fill gas (CH{sub 2}) within the halfraum. Estimates for microstructure growth due to the volume crystalline structure within a beryllium slab mounted in the halfraum sidewall are obtained by a post-processor, which applies plasma conditions within the halfraum to an ablatively accelerated, two-dimensional beryllium slab. We present a detailed simulation of the hohlraum conditions resulting from a laser spot of diameter 500 {mu}m, with peak intensity at 3.5 x 10{sup 15} W/cm{sup 2}, a comparison with a simulation with the same power-time profile at an intensity about 1/4 as great, and a comparison with a simulation with more detailed attention to hydro coupling between the gold and gas-fill regions of the hohlraum. We are currently attempting to model the consequences of possible beam filamentation during the pulse.

  20. Surface Plasma Source Electrode Activation by Surface Impurities

    SciTech Connect

    Dudnikov, Vadim; Han, Baoxi; Johnson, Rolland P.; Murray Jr, S N; Pennisi, Terry R; Santana, Manuel; Stockli, Martin P; Welton, Robert F

    2011-01-01

    In experiments with RF saddle antenna surface plasma sources (SPS), the efficiency of H- ion generation was increased by up to a factor of 5 by long time plasma electrode activation, without adding Cs from Cs supply, by heating the collar to high temperature using hot air flow and plasma discharge. Without cracking or heating the cesium ampoule, but likely with Cs recovery from impurities, the achieved energy efficiency was comparable to that of conventionally cesiated SNS RF sources with an external or internal Cs supply. In the experiments, perfect cesiation was produced (without additional Cs supply) by the collection and trapping of traces of remnant cesium compounds from SPS surfaces.

  1. Surface Plasma Source Electrode Activation by Surface Impurities

    SciTech Connect

    Dudnikov, Vadim; Johnson, Rolland P.; Han, B.; Murray, S. N.; Pennisi, T. R.; Santana, M.; Stockli, Martin P.; Welton, R. F.

    2011-09-26

    In experiments with RF saddle antenna surface plasma sources (SPS), the efficiency of H{sup -} ion generation was increased by up to a factor of 5 by plasma electrode 'activation', without supplying additional Cs, by heating the collar to high temperature for several hours using hot air flow and plasma discharge. Without cracking or heating the cesium ampoule, but likely with Cs recovery from impurities, the achieved energy efficiency was comparable to that of conventionally cesiated SNS RF sources with an external or internal Cs supply. In the experiments, optimum cesiation was produced (without additional Cs) by the collection and trapping of traces of remnant cesium compounds from SPS surfaces. Such activation by accumulation of impurities on electrode surfaces can be a reason for H{sup -} emission enhancement in other so-called 'volume' negative ion sources.

  2. Nanosecond plasma-mediated electrosurgery with elongated electrodes

    NASA Astrophysics Data System (ADS)

    Vankov, Alexander; Palanker, Daniel

    2007-06-01

    Progress in interventional medicine is associated with the development of more delicate and less invasive surgical procedures, which requires more precise and less traumatic, yet affordable, surgical instruments. Previously we reported on the development of the pulsed electron avalanche knife for dissection of soft tissue in liquid media using the 100 ns plasma-mediated electric discharges applied via a 25 μm disk microelectrode. Cavitation bubbles accompanying explosive vaporization of the liquid medium in front of such a pointed electrode produced a series of craters that did not always merge into a continuous cut. In addition, this approach of surface ablation provided a limited depth of cutting. Application of an elongated electrode capable of cutting with its edge rather than just with its pointed apex faces a problem of nonuniformity of the electric field on a nonspherical electrode. In this article we explore dynamics of the plasma-mediated nanosecond discharges in liquid medium in positive and negative polarities and describe the geometry of an electrode that provides a sufficiently uniform electric field along an extended edge of a surgical probe. A highly enhanced and uniform electric field was obtained on very sharp (2.5 μm) exposed edges of a planar electrode insulated on its flat sides. Uniform ionization and simultaneous vaporization was obtained along the whole edge of such a blade with 100 ns pulses at 4-6 kV. A continuous cutting rate of 1 mm/s in the retina and in soft membranes was achieved at a pulse repetition rate of 100 Hz. The collateral damage zone at the edges of incision did not exceed 80 μm. Negative polarity was found advantageous due to the lower rate of electrode erosion and due to better spatial confinement of the plasma-mediated discharge in liquid.

  3. Nanopillar ITO electrodes via argon plasma etching

    SciTech Connect

    Van Dijken, Jaron G.; Brett, Michael J.

    2012-07-15

    The authors demonstrate the formation of vertically aligned indium tin oxide (ITO) nanopillars by exposing planar ITO films to Ar plasma, the conditions of which determine the size, spacing, and aspect ratio of the pillars. Annealing in air and forming gas is used to recover and optimize the optical transmittance and electrical conductivity of the nanopillar films. The final product is an ITO film whose superior optical transmittance and strong electrical conductivity combine with its robust columnar morphology and processing scalability to make it suitable for use in highly absorbing organic solar cells.

  4. Grid-Sphere Electrodes for Contact with Ionospheric Plasma

    NASA Technical Reports Server (NTRS)

    Stone, Nobie H.; Poe, Garrett D.

    2010-01-01

    Grid-sphere electrodes have been proposed for use on the positively biased end of electrodynamic space tethers. A grid-sphere electrode is fabricated by embedding a wire mesh in a thin film from which a spherical balloon is formed. The grid-sphere electrode would be deployed from compact stowage by inflating the balloon in space. The thin-film material used to inflate the balloon is formulated to vaporize when exposed to the space environment. This would leave the bare metallic spherical grid electrode attached to the tether, which would present a small cross-sectional area (essentially, the geometric wire shadow area only) to incident neutral atoms and molecules. Most of the neutral particles, which produce dynamic drag when they impact a surface, would pass unimpeded through the open grid spaces. However, partly as a result of buildup of a space charge inside the grid-sphere, and partially, the result of magnetic field effects, the electrode would act almost like a solid surface with respect to the flux of electrons. The net result would be that grid-sphere electrodes would introduce minimal aerodynamic drag, yet have effective electrical-contact surface areas large enough to collect multiampere currents from the ionospheric plasma that are needed for operation of electrodynamic tethers. The vaporizable-balloon concept could also be applied to the deployment of large radio antennas in outer space.

  5. Nuclear science research with dynamic high energy density plasmas at NIF

    NASA Astrophysics Data System (ADS)

    Shaughnessy, D. A.; Gharibyan, N.; Moody, K. J.; Despotopulos, J. D.; Grant, P. M.; Yeamans, C. B.; Berzak Hopkins, L.; Cerjan, C. J.; Schneider, D. H. G.; Faye, S.

    2016-05-01

    Nuclear reaction measurements are performed at the National Ignition Facility in a high energy density plasma environment by adding target materials to the outside of the hohlraum thermo-mechanical package on an indirect-drive exploding pusher shot. Materials are activated with 14.1-MeV neutrons and the post-shot debris is collected via the Solid Radiochemistry diagnostic, which consists of metal discs fielded 50 cm from target chamber center. The discs are removed post-shot and analyzed via radiation counting and mass spectrometry. Results from a shot using Nd and Tm foils as targets are presented, which indicate enhanced collection of the debris in the line of sight of a given collector. The capsule performance was not diminished due to the extra material. This provides a platform for future measurements of nuclear reaction data through the use of experimental packages mounted external to the hohlraum.

  6. Currents between tethered electrodes in a magnetized laboratory plasma

    NASA Technical Reports Server (NTRS)

    Stenzel, R. L.; Urrutia, J. M.

    1989-01-01

    Laboratory experiments on important plasma physics issues of electrodynamic tethers were performed. These included current propagation, formation of wave wings, limits of current collection, nonlinear effects and instabilities, charging phenomena, and characteristics of transmission lines in plasmas. The experiments were conducted in a large afterglow plasma. The current system was established with a small electron-emitting hot cathode tethered to an electron-collecting anode, both movable across the magnetic field and energized by potential difference up to V approx.=100 T(sub e). The total current density in space and time was obtained from complete measurements of the perturbed magnetic field. The fast spacecraft motion was reproduced in the laboratory by moving the tethered electrodes in small increments, applying delayed current pulses, and reconstructing the net field by a linear superposition of locally emitted wavelets. With this technique, the small-amplitude dc current pattern is shown to form whistler wings at each electrode instead of the generally accepted Alfven wings. For the beam electrode, the whistler wing separates from the field-aligned beam which carries no net current. Large amplitude return currents to a stationary anode generate current-driven microinstabilities, parallel electric fields, ion depletions, current disruptions and time-varying electrode charging. At appropriately high potentials and neutral densities, excess neutrals are ionized near the anode. The anode sheath emits high-frequency electron transit-time oscillations at the sheath-plasma resonance. The beam generates Langmuir turbulence, ion sound turbulence, electron heating, space charge fields, and Hall currents. An insulated, perfectly conducting transmission line embedded in the plasma becomes lossy due to excitation of whistler waves and magnetic field diffusion effects. The implications of the laboratory observations on electrodynamic tethers in space are discussed.

  7. Controlled particle transport in a plasma chamber with striped electrode

    SciTech Connect

    Jiang Ke; Li Yangfang; Shimizu, T.; Konopka, U.; Thomas, H. M.; Morfill, G. E.

    2009-12-15

    The controlled transport of micrometer size dust particles in a parallel-plate radio frequency discharge has been investigated. The lower stainless steel electrode consisted of 100 independently controllable electrical metal stripes. The voltage signals on these stripes were modulated, causing traveling plasma sheath distortions. Because the particles trapped in local potential wells moved according to the direction of the distortion, the transport velocity could be actively controlled by adjusting frequencies and phase shifts of the applied periodic voltage signals. To investigate the detailed principle of this transport, molecular dynamic simulations was performed to reproduce the observations with the plasma background conditions calculated by separated particle-in-cell simulations for the experimental parameters. The findings will help develop novel technologies for investigating large-scale complex plasma systems and techniques for achieving clean environments in plasma processing reactors.

  8. A Performance Comparison of Pulsed Plasma Thruster Electrode Configurations

    NASA Technical Reports Server (NTRS)

    Arrington, Lynn A.; Haag, Tom W.; Pencil, Eric J.; Meckel, Nicole J.

    1997-01-01

    Pulsed plasma thrusters are currently planned on two small satellite missions and proposed for a third. In these missions, the pulsed plasma thruster's unique characteristics will be used variously to provide propulsive attitude control, orbit raising, translation, and precision positioning. Pulsed plasma thrusters are attractive for small satellite applications because they are essentially stand alone devices which eliminate the need for toxic and/or distributed propellant systems. Pulsed plasma thrusters also operate at low power and over a wide power range without loss of performance. As part of the technical development required for the noted missions, an experimental program to optimize performance with respect to electrode configuration was undertaken. One of the planned missions will use pulsed plasma thrusters for orbit raising requiring relatively high thrust and previously tested configurations did not provide this. Also, higher capacitor energies were tested than previously tried for this mission. Multiple configurations were tested and a final configuration was selected for flight hardware development. This paper describes the results of the electrode optimization in detail.

  9. National NIF Diagnostic Program Interim Management Plan

    SciTech Connect

    Warner, B

    2002-04-25

    The National Ignition Facility (NIF) has the mission of supporting Stockpile Stewardship and Basic Science research in high-energy-density plasmas. To execute those missions, the facility must provide diagnostic instrumentation capable of observing and resolving in time events and radiation emissions characteristic of the plasmas of interest. The diagnostic instrumentation must conform to high standards of operability and reliability within the NIF environment. These exacting standards, together with the facility mission of supporting a diverse user base, has led to the need for a central organization charged with delivering diagnostic capability to the NIF. The National NIF Diagnostics Program (NNDP) has been set up under the aegis of the NIF Director to provide that organization authority and accountability to the wide user community for NIF. The funds necessary to perform the work of developing diagnostics for NIF will be allocated from the National NIF Diagnostics Program to the participating laboratories and organizations. The participating laboratories and organizations will design, build, and commission the diagnostics for NIF. Restricted availability of funding has had an adverse impact, unforeseen at the time of the original decision to projectize NIF Core Diagnostics Systems and Cryogenic Target Handing Systems, on the planning and initiation of these efforts. The purpose of this document is to provide an interim project management plan describing the organizational structure and management processes currently in place for NIF Core Diagnostics Systems. Preparation of a Program Execution Plan for NIF Core Diagnostics Systems has been initiated and a current draft is provided as Attachment 1 to this document. The National NIF Diagnostics Program Interim Management Plan provides a summary of primary design criteria and functional requirements, current organizational structure, tracking and reporting procedures, and current planning estimates of project scope

  10. Field-enhanced electrodes for additive-injection non-thermal plasma (NTP) processor

    DOEpatents

    Rosocha, Louis A.; Ferreri, Vincent; Kim, Yongho

    2009-04-21

    The present invention comprises a field enhanced electrode package for use in a non-thermal plasma processor. The field enhanced electrode package includes a high voltage electrode and a field-enhancing electrode with a dielectric material layer disposed in-between the high voltage electrode and the field-enhancing electrode. The field-enhancing electrode features at least one raised section that includes at least one injection hole that allows plasma discharge streamers to occur primarily within an injected additive gas.

  11. Ultrafast-Contactless Flash Sintering using Plasma Electrodes

    NASA Astrophysics Data System (ADS)

    Saunders, Theo; Grasso, Salvatore; Reece, Michael J.

    2016-06-01

    This paper presents a novel derivative of flash sintering, in which contactless flash sintering (CFS) is achieved using plasma electrodes. In this setup, electrical contact with the sample to be sintered is made by two arc plasma electrodes, one on either side, allowing current to pass through the sample. This opens up the possibility of continuous throughput flash sintering. Preheating, a usual precondition for flash sintering, is provided by the arc electrodes which heat the sample to 1400 °C. The best results were produced with pre-compacted samples (bars 1.8 mm thick) of pure B4C (discharge time 2s, current 4A) and SiC:B4C 50 wt% (3s at 6A), which were fully consolidated under a heating rate approaching 20000 °C/min. For the composite a cylindrical volume of 14 mm3 was sintered to full density with limited grain growth.

  12. Ultrafast-Contactless Flash Sintering using Plasma Electrodes.

    PubMed

    Saunders, Theo; Grasso, Salvatore; Reece, Michael J

    2016-01-01

    This paper presents a novel derivative of flash sintering, in which contactless flash sintering (CFS) is achieved using plasma electrodes. In this setup, electrical contact with the sample to be sintered is made by two arc plasma electrodes, one on either side, allowing current to pass through the sample. This opens up the possibility of continuous throughput flash sintering. Preheating, a usual precondition for flash sintering, is provided by the arc electrodes which heat the sample to 1400 °C. The best results were produced with pre-compacted samples (bars 1.8 mm thick) of pure B4C (discharge time 2s, current 4A) and SiC:B4C 50 wt% (3s at 6A), which were fully consolidated under a heating rate approaching 20000 °C/min. For the composite a cylindrical volume of 14 mm(3) was sintered to full density with limited grain growth. PMID:27273255

  13. Ultrafast-Contactless Flash Sintering using Plasma Electrodes

    PubMed Central

    Saunders, Theo; Grasso, Salvatore; Reece, Michael J.

    2016-01-01

    This paper presents a novel derivative of flash sintering, in which contactless flash sintering (CFS) is achieved using plasma electrodes. In this setup, electrical contact with the sample to be sintered is made by two arc plasma electrodes, one on either side, allowing current to pass through the sample. This opens up the possibility of continuous throughput flash sintering. Preheating, a usual precondition for flash sintering, is provided by the arc electrodes which heat the sample to 1400 °C. The best results were produced with pre-compacted samples (bars 1.8 mm thick) of pure B4C (discharge time 2s, current 4A) and SiC:B4C 50 wt% (3s at 6A), which were fully consolidated under a heating rate approaching 20000 °C/min. For the composite a cylindrical volume of 14 mm3 was sintered to full density with limited grain growth. PMID:27273255

  14. Material for electrodes of low temperature plasma generators

    DOEpatents

    Caplan, Malcolm; Vinogradov, Sergel Evge'evich; Ribin, Valeri Vasil'evich; Shekalov, Valentin Ivanovich; Rutberg, Philip Grigor'evich; Safronov, Alexi Anatol'evich; Shiryaev, Vasili Nikolaevich

    2010-03-02

    Material for electrodes of low temperature plasma generators. The material contains a porous metal matrix impregnated with a material emitting electrons. The material uses a mixture of copper and iron powders as a porous metal matrix and a Group IIIB metal component such as Y.sub.2O.sub.3 is used as a material emitting electrons at, for example, the proportion of the components, mass %: iron:3-30; Y.sub.2O.sub.3:0.05-1; copper: the remainder. Copper provides a high level of heat conduction and electric conductance, iron decreases intensity of copper evaporation in the process of plasma creation providing increased strength and lifetime, Y.sub.2O.sub.3 provides decreasing of electronic work function and stability of arc burning. The material can be used for producing the electrodes of low temperature AC plasma generators used for destruction of liquid organic wastes, medical wastes, municipal wastes as well as for decontamination of low level radioactive waste, the destruction of chemical weapons, warfare toxic agents, etc.

  15. Material for electrodes of low temperature plasma generators

    DOEpatents

    Caplan, Malcolm; Vinogradov, Sergel Evge'evich; Ribin, Valeri Vasil'evich; Shekalov, Valentin Ivanovich; Rutberg, Philip Grigor'evich; Safronov, Alexi Anatol'evich

    2008-12-09

    Material for electrodes of low temperature plasma generators. The material contains a porous metal matrix impregnated with a material emitting electrons. The material uses a mixture of copper and iron powders as a porous metal matrix and a Group IIIB metal component such as Y.sub.2O.sub.3 is used as a material emitting electrons at, for example, the proportion of the components, mass %: iron: 3-30; Y.sub.2O.sub.3:0.05-1; copper: the remainder. Copper provides a high level of heat conduction and electric conductance, iron decreases intensity of copper evaporation in the process of plasma creation providing increased strength and lifetime, Y.sub.2O.sub.3 provides decreasing of electronic work function and stability of arc burning. The material can be used for producing the electrodes of low temperature AC plasma generators used for destruction of liquid organic wastes, medical wastes, and municipal wastes as well as for decontamination of low level radioactive waste, the destruction of chemical weapons, warfare toxic agents, etc.

  16. High-contrast plasma-electrode Pockels cell

    SciTech Connect

    Kruschwitz, B. E.; Kelly, J. H.; Shoup, M. J. III; Waxer, L. J.; Cost, E. C.; Green, E. T.; Hoyt, Z. M.; Taniguchi, J.; Walker, T. W

    2007-03-10

    A plasma-electrode Pockels cell (PEPC) has been developed for use on the OMEGA extended performance (EP)laser system that can be used in a high-contrast optical switch, as required for isolation of the system from retroreflected pulses. Contrast ratios reliably exceeded 500:1 locally everywhere in the clear aperture. The key to achieving this improvement was the use of circular windows simply supported on compliant O rings, which is shown to produce very low stress-induced birefringence despite vacuum loading. Reliable operation was achieved operating at a relatively high operating pressure, low operating pressures being found to be strongly correlated to occurrences of local loss of plasma density.

  17. Plasma Characterization of Hall Thruster with Active and Passive Segmented Electrodes

    SciTech Connect

    Raitses, Y.; Staack, D.; Fisch, N.J.

    2002-09-04

    Non-emissive electrodes and ceramic spacers placed along the Hall thruster channel are shown to affect the plasma potential distribution and the thruster operation. These effects are associated with physical properties of the electrode material and depend on the electrode configuration, geometry and the magnetic field distribution. An emissive segmented electrode was able to maintain thruster operation by supplying an additional electron flux to sustain the plasma discharge between the anode and cathode neutralizer. These results indicate the possibility of new configurations for segmented electrode Hall thruster.

  18. Performance analysis of charge plasma based dual electrode tunnel FET

    NASA Astrophysics Data System (ADS)

    Anand, Sunny; Intekhab Amin, S.; Sarin, R. K.

    2016-05-01

    This paper proposes the charge plasma based dual electrode doping-less tunnel FET (DEDLTFET). The paper compares the device performance of the conventional doping-less TFET (DLTFET) and doped TFET (DGTFET). DEDLTEFT gives the superior results with high ON state current (ION ∼ 0.56 mA/μm), ION/IOFF ratio ∼ 9.12 × 1013 and an average subthreshold swing (AV-SS ∼ 48 mV/dec). The variation of different device parameters such as channel length, gate oxide material, gate oxide thickness, silicon thickness, gate work function and temperature variation are done and compared with DLTFET and DGTFET. Through the extensive analysis it is found that DEDLTFET shows the better performance than the other two devices, which gives the indication for an excellent future in low power applications.

  19. Voltage distribution over capacitively coupled plasma electrode for atmospheric-pressure plasma generation

    PubMed Central

    2013-01-01

    When capacitively coupled plasma (CCP) is used to generate large-area plasma, the standing wave effect becomes significant, which results in the hindering of the uniform plasma process such as in a plasma etcher or plasma chemical vapor deposition. In this study, the transmission line modeling method is applied to calculate the voltage distribution over atmospheric-pressure CCP electrodes with the size of 1 m × 0.2 m. The measured plasma impedance in our previous study was used in the present calculation. The results of the calculations clearly showed the effects of excitation frequency and the impedance of the plasma on the form of the voltage distribution caused by the standing wave effect. In the case of 150 MHz frequency, the standing wave effect causes a drastic change in the voltage distribution via plasma ignition; however, the change is small for 13.56 MHz. It was also clarified that the power application position is important for obtaining a uniform voltage distribution. PMID:23634893

  20. On Power Measurements of Single-Electrode Low-Power Ar Plasma Jets

    NASA Astrophysics Data System (ADS)

    Prysiazhnyi, Vadym; Ricci, Alonso H. C.; Kostov, Konstantin G.

    2016-06-01

    A study of electrical properties, methodology, and precision of power measurement was made on two types of Ar plasma jets, a single-strip-electrode plasma jet and a single-rod-electrode plasma jet. The dynamics of current peaks, methods for determining discharge power, and power measurement precision (especially important for applications in plasma medicine) are discussed for each type of plasma jet. Lower error in power calculation was obtained when the plasma jet did not touch the substrate, as well as more repetitive dynamics of the current peaks. Averaging high number of periods (over 500) when calculating the power by the Lissajous figure technique led to decrease of the experimental error.

  1. Removal characteristics of plasma chemical vaporization machining with a pipe electrode for optical fabrication

    SciTech Connect

    Takino, Hideo; Yamamura, Kazuya; Sano, Yasuhisa; Mori, Yuzo

    2010-08-10

    Plasma chemical vaporization machining (CVM) is a high-precision chemical shaping method using rf plasma generated in the proximity of an electrode in an atmospheric environment. The purpose of the present study is to clarify the removal characteristics of plasma CVM using a pipe electrode. Polished fused silica plates were processed by plasma CVM, polishing, and precision grinding under various conditions. The removal rate of plasma CVM was about 4 to 1100 times faster than that of polishing, and the maximum removal rate was almost equal to that of precision grinding. The roughness of the resultant surfaces was almost the same as that of the polished surfaces.

  2. Influence of finite geometrical asymmetry of the electrodes in capacitively coupled radio frequency plasma

    SciTech Connect

    Bora, B. Soto, L.

    2014-08-15

    Capacitively coupled radio frequency (CCRF) plasmas are widely studied in last decades due to the versatile applicability of energetic ions, chemically active species, radicals, and also energetic neutral species in many material processing fields including microelectronics, aerospace, and biology. A dc self-bias is known to generate naturally in geometrically asymmetric CCRF plasma because of the difference in electrode sizes known as geometrical asymmetry of the electrodes in order to compensate electron and ion flux to each electrode within one rf period. The plasma series resonance effect is also come into play due to the geometrical asymmetry and excited several harmonics of the fundamental in low pressure CCRF plasma. In this work, a 13.56 MHz CCRF plasma is studied on the based on the nonlinear global model of asymmetric CCRF discharge to understand the influences of finite geometrical asymmetry of the electrodes in terms of generation of dc self-bias and plasma heating. The nonlinear global model on asymmetric discharge has been modified by considering the sheath at the grounded electrode to taking account the finite geometrical asymmetry of the electrodes. The ion density inside both the sheaths has been taken into account by incorporating the steady-state fluid equations for ions considering that the applied rf frequency is higher than the typical ion plasma frequency. Details results on the influences of geometrical asymmetry on the generation of dc self-bias and plasma heating are discussed.

  3. Reproducibility of NIF hohlraum measurements

    NASA Astrophysics Data System (ADS)

    Moody, J. D.; Ralph, J. E.; Turnbull, D. P.; Casey, D. T.; Albert, F.; Bachmann, B. L.; Doeppner, T.; Divol, L.; Grim, G. P.; Hoover, M.; Landen, O. L.; MacGowan, B. J.; Michel, P. A.; Moore, A. S.; Pino, J. E.; Schneider, M. B.; Tipton, R. E.; Smalyuk, V. A.; Strozzi, D. J.; Widmann, K.; Hohenberger, M.

    2015-11-01

    The strategy of experimentally ``tuning'' the implosion in a NIF hohlraum ignition target towards increasing hot-spot pressure, areal density of compressed fuel, and neutron yield relies on a level of experimental reproducibility. We examine the reproducibility of experimental measurements for a collection of 15 identical NIF hohlraum experiments. The measurements include incident laser power, backscattered optical power, x-ray measurements, hot-electron fraction and energy, and target characteristics. We use exact statistics to set 1-sigma confidence levels on the variations in each of the measurements. Of particular interest is the backscatter and laser-induced hot-spot locations on the hohlraum wall. Hohlraum implosion designs typically include variability specifications [S. W. Haan et al., Phys. Plasmas 18, 051001 (2011)]. We describe our findings and compare with the specifications. This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

  4. The nifU, nifS and nifV gene products are required for activity of all three nitrogenases of Azotobacter vinelandii.

    PubMed

    Kennedy, C; Dean, D

    1992-02-01

    Strains with mutations in 23 of the 30 genes and open reading frames in the major nif gene cluster of A. vinelandii were tested for ability to grow on N-free medium with molybdenum (Nif phenotype), with vanadium (Vnf phenotype), or with neither metal present (Anf phenotype). As reported previously, nifE, nifN, nifU, nifS and nifV mutants were Nif- (failed to grow on molybdenum) while nifM mutants were Nif-, Vnf- and Anf-. nifV, nifS, and nifU mutants were found to be unable to grow on medium with or without vanadium, i.e. were Vnf- Anf-. Therefore neither vnf nor anf analogoues of nifU, nifS, nifV or nifM are expected to be present in A. vinelandii. PMID:1538703

  5. Immobilization of biorecognition molecules on O2 plasma-functionalized SWCNT electrodes for biosensors

    NASA Astrophysics Data System (ADS)

    Jin, Joon-Hyung; Kim, Joon Hyub; Lee, Jun-Yong; Min, Nam Ki

    2012-11-01

    Biointerfaces capable of biological recognition and specificity are very important for the development of carbon nanotube based biosensors. Here, we explore experimentally the effects of O2 plasma treatment on the biomolecule immobilization properties of single-walled carbon nanotube (SWCNT) electrodes for electrochemical biosensing. The SWCNT film was integrated into an electrochemical three-electrode system on a glass substrate and then treated with an O2 plasma to improve its electrochemical response. Glucose oxidases, antibodies, and deoxyribonucleic acids (DNAs) were covalently immobilized on the plasma-functionalized (pf) SWCNT working electrodes, and the electrochemical and bioelectrocatalytic properties of three biomolecular assemblies generated on the pf-SWCNT electrodes were investigated using cyclic voltammetry, square-wave voltammetry, and chronoamperometry. The pf-SWCNT films were found to provide electrochemical biosensing electrodes having high electroactivity and sensitivity for detecting glucoses, antigens, and DNA molecules.

  6. Radial profile of plasma potential with various biased electrode ring configurations in a toroidal plasma

    SciTech Connect

    Chaube, N.R.; Jain, K.K.

    1996-07-01

    An experimental study on behavior of radial profile of the floating potential with different biased electrode ring configurations has been carried out in a currentless magnetized toroidal plasma. Radial profile of the floating potential has been measured by biasing single ring of various sizes and two rings. It is observed that floating potential profile of a well shaped with controllable depth, hill-cum-well shaped, and almost flat positive potential can be obtained. Results on parameter dependence studies of floating potential on the bias voltage, magnetic field, and gas pressure are presented. {copyright} {ital 1996 American Institute of Physics.}

  7. in situ plasma removal of surface contaminants from ion trap electrodes

    SciTech Connect

    Haltli, Raymond A.

    2015-04-01

    This research resulted in a construction and implementation of an in situ plasma discharge to remove surface contaminants from electrodes in an ion trapping experimental system is presented with results.

  8. The effect of electrode material on the motion of a plasma piston in rail accelerators

    NASA Astrophysics Data System (ADS)

    Bobashev, S. V.; Zhukov, B. G.; Kurakin, R. O.; Ponyaev, S. A.; Reznikov, B. I.

    2015-10-01

    The acceleration of a plasma piston in the channels of rail accelerators with copper and graphite electrodes is studied experimentally. It is found that the plasma velocity is reduced by 15-20% (at equal discharge currents) when graphite electrodes are used instead of copper ones. This may be attributed to an increase in the erosion graphite mass that is drawn into motion by the plasma piston. It is concluded based on the interpretation of the obtained data that the current flow in the channels of rail accelerators is governed at high plasma speeds by the processes of thermoautoelectron emission.

  9. Spectroscopy peculiarities of thermal plasma of electric arc discharge between electrodes with Zn admixtures

    NASA Astrophysics Data System (ADS)

    Semenyshyn, R. V.; Veklich, A. N.; Babich, I. L.; Boretskij, V. F.

    2014-10-01

    Plasma of the free burning electric arc between Ag-SnO2-ZnO composite electrodes as well as brass electrodes were investigated. The plasma temperature distributions were obtained by Boltzmann plot method involving Cu I, Ag I or Zn I spectral line emissions. The electron density distributions were obtained from the width and from absolute intensity of spectral lines. The laser absorption spectroscopy was used for measurement of copper atom concentration in plasma. Plasma equilibrium composition was calculated using two independent groups of experimental values (temperature and copper atom concentration, temperature and electron density). It was found that plasma of the free burning electric arc between brass electrodes is in local thermodynamical equilibrium. The experimental verification of the spectroscopic data of Zn I spectral lines was carried out.

  10. OH density optimization in atmospheric-pressure plasma jet by using multiple ring electrodes

    NASA Astrophysics Data System (ADS)

    Yue, Y.; Pei, X.; Lu, X.

    2016-01-01

    OH radical is one of the important reactive species generated by non-equilibrium atmospheric-pressure plasma jets, which is believed to play an important role in plasma medicine applications such as cancer therapy, wound healing and sterilization. In this study, a method to increase OH density is proposed. By using multiple pairs of ring electrodes, we generate 3-5 times more OH radicals than in the common device which uses only one high-voltage ring electrode. Discharge imaging shows that the plasma plume with only one ring electrode is longer and its emission intensity is higher than those with multiple pairs of ring electrodes. Further studies indicate that the distribution of OH radicals is significantly influenced by the gas flow rate. At higher gas flow rates, the OH peak concentration is detected further away from the nozzle, and the position of the peak OH concentration correlates with the product of the gas flow velocity and the pulse duration. As observed from the emission spectra, multiple electrodes only enhance the plasma inside the tube rather than the plasma plume in the surrounding air. These results suggest that the OH radicals are mainly generated inside the tube and then delivered to the outer plasma plume region by the gas flow.

  11. Decomposition of methyl orange using pulsed discharge plasma at atmospheric pressure: Effect of different electrodes

    NASA Astrophysics Data System (ADS)

    Hayashi, Yui; Wahyudiono; Machmudah, Siti; Takada, Noriharu; Kanda, Hideki; Sasaki, Koichi; Goto, Motonobu

    2014-01-01

    One of the new technologies for water treatment is the pulsed discharge plasma method, which utilizes high voltage pulses with a fast rise time and a very short duration. In this study, under argon atmosphere at 313 K, the decoloration of methyl orange was conducted with copper (Cu) and stainless steel #304 (SUS-304) as electrodes in the batch reactor. The performance of pulse discharge plasma generation was observed using an intensified charge coupled device (ICCD) camera. The results show that the intermediate compounds from the degradation of methyl orange consist primarily of aromatic compounds containing nitrogen functional groups. At the same number of plasma discharge times, the percentage conversion of methyl orange with Cu as the electrode is higher than that with SUS as the electrode. However, the percentage degradation of methyl orange is over 90% in both cases when the number of plasma discharge times was 20000.

  12. Numerical analysis on plasma characteristics of high power plasma torch of hollow electrode type for waste treatment

    SciTech Connect

    Hur, M.; Kang, K.D.; Hong, S.H.

    1997-12-31

    In this study, the plasma characteristics of a high power nontransferred plasma torch with hollow electrodes are investigated in the atmospheric condition by analyzing the distributions of plasma temperature, velocity and current density. Typical assumptions of steady state, axisymmetry, local thermodynamic equilibrium (LTE) and optically thin plasma are adopted in a two-dimensional magnetohydrodynamic (MHD) modeling of thermal plasma with a special treatment of arc spot positions. A control volume method and the modified SIMPLER algorithm are used for solving the governing equations numerically, i.e., conservation equations of mass, momentum, and energy along with the equations describing the {Kappa}-{var_epsilon} model for turbulence and the current continuity for arc discharge. The distributions of plasma temperature, velocity, and current density are calculated in various operation conditions such as gas species, gas flowrate, input current, and electrode geometry. The calculated results of plasma characteristics in various operations can be useful to determine the design parameters of the high power plasma torch of hollow electrode type for incinerating the hospital and municipal solid wastes.

  13. Electrode Erosion in Pulsed Arc for Generating Air Meso-Plasma Jet under Atmospheric Pressure

    NASA Astrophysics Data System (ADS)

    Shiki, Hajime; Motoki, Junpei; Takikawa, Hirofumi; Sakakibara, Tateki; Nishimura, Yoshimi; Hishida, Shigeji; Okawa, Takashi; Ootsuka, Takeshi

    Various materials of the rod electrode were examined in pulsed arc of PEN-Jet (Plasma ENergized-Jet) with working gas of air, which can be used for the surface treatment under atmospheric pressure. The erosion of the rod electrode was measured and it surface was observed. The amount of erosion and surface appearance were found to be different for the materials, input power and energizing time. Tungsten (W) rod electrode was oxidized immediately after starting the discharge and tungsten oxide (WO3) powder was generated over the side surface of electrode tip. This powder contaminated the treating surface. Copper (Cu) rod electrode was also oxidized immediately and CuO/Cu2O multi-layer was formed on the electrode surface. However, the erosion of Cu electrode was quite small. Platinum (Pt) and iridium (20 wt%)-contained-platinum (Pt-Ir) rod electrode were not oxidized and their erosions were significantly small. This indicated that they could be employed for keeping the constant electrode-gap and processing the surface treatment without contamination due to electrode erosion.

  14. Hydrodynamic simulations of long-scale-length plasmas for two-plasmon-decay planar-target experiments on the NIF

    NASA Astrophysics Data System (ADS)

    Solodov, A. A.; Rosenberg, M. J.; Myatt, J. F.; Epstein, R.; Regan, S. P.; Seka, W.; Shaw, J.; Hohenberger, M.; Bates, J. W.; Moody, J. D.; Ralph, J. E.; Turnbull, D. P.; Barrios, M. A.

    2016-05-01

    The two-plasmon-decay (TPD) instability can be detrimental for direct-drive inertial confinement fusion because it generates high-energy electrons that can preheat the target, thereby reducing target performance. Hydrodynamic simulations to design a new experimental platform to investigate TPD and other laser-plasma instabilities relevant to direct-drive-ignition implosions at the National Ignition Facility are presented. The proposed experiments utilize planar plastic targets with an embedded Mo layer to characterize generation of hot electrons through Mo Kα fluorescence and hard x-ray emission. Different laser-irradiation geometries approximate conditions near both the equator and the pole of a polar-direct-drive implosion.

  15. In situ plasma removal of surface contaminants from ion trap electrodes

    SciTech Connect

    Haltli, Raymond A.

    2015-05-01

    In this thesis, the construction and implementation of an in situ plasma discharge designed to remove surface contaminants from electrodes in an ion trapping experimental system is presented with results. In recent years, many advances have been made in using ion traps for quantum information processing. All of the criteria defined by DiVincenzo for using ion traps for implementing a quantum computer have been individually demonstrated, and in particular surface traps provide a scalable platform for ions. In order to be used for quantum algorithms, trapped ions need to be cooled to their motional (quantum mechanical) ground state. One of the hurdles in integrating surface ion traps for a quantum computer is minimizing electric field noise, which causes the ion to heat out of its motional ground state and which increases with smaller ion-to-electrode distances realized with surface traps. Surface contamination of trap electrodes is speculated to be the primary source of electric field noise. The main goal achieved by this work was to implement an in situ surface cleaning solution for surface electrode ion traps, which would not modify the ion trap electrode surface metal. Care was taken in applying the RF power in order to localize a plasma near the trap electrodes. A method for characterizing the energy of the plasma ions arriving at the ion trap surface is presented and results for plasma ion energies are shown. Finally, a method for quantifying the effectiveness of plasma cleaning of trap electrodes, using the surface analysis technique of X-ray photoelectron spectroscopy for measuring the amount and kind of surface contaminants, is described. A significant advantage of the trap electrode surface cleaning method presented here is the minimal changes necessary for implementation on a working ion trap experimental system.

  16. Size dependent transitions induced by an electron collecting electrode near the plasma potential

    NASA Astrophysics Data System (ADS)

    Barnat, Edward; Laity, George; Hopkins, Matt; Baalrud, Scott

    2014-10-01

    As the size of a positively biased electrode increases, the nature of the interface formed between the electrode and the host plasma undergoes a transition from an electron-rich structure (electron sheath) to an intermediate structure containing both ion and electron rich regions (double layer) and ultimately forms an electron-depleted structure (ion sheath). In this study, measurements are performed to further test how the key scaling relationship relating the area of the electrode to that of the area of the vessel containing the plasma discharge impacts this transition. This was accomplished using a segmented disk electrode in which individual segments were individually biased to change the effective surface area of the anode. Measurements on bulk plasma parameters such as the collected current density, plasma potential, electron density, electron temperature and optical emission are made as both the size and the bias placed on the electrode are varied. Size dependent transitions in the voltage dependence of the plasma parameters are identified in both argon and helium discharges and are compared to the interface transitions predicted by global current balance. This work was supported by the Office of Fusion Energy Science at the U.S. Department of Energy under Contract DE-AC04-94SL85000.

  17. Three-electrode plasma reactor for the removal of toxic gases

    NASA Astrophysics Data System (ADS)

    Gallego, J. L.; Giuliani, L.; Grondona, D.; Minotti, F.

    2015-03-01

    Electrical and spectroscopic measurement for the characterization of a novel three- electrode plasma reactor for the treatment of toxic gases is presented. The three-electrode discharge consists in a dielectric barrier discharge (DBD) combined with a corona discharge (CD). The DBD is generated by applying an alternating high voltage signal between two circular aluminium plate electrodes attached to opposite sides of a disk made of dielectric material. The CD is generated applying a continuous negative high voltage to an external cylindrical mesh electrode, coaxial with the DBD electrode system. The gap between the edge of the DBD system and the mesh electrode is approximately 20 mm wide. Up to five DBD electrode systems can be connected in parallel inside the reactor, axially separated from each other by 30 mm. The electrical characterization consisted in the measurement of the current between the DBD system and the external mesh, and the voltages of the electrodes. In order to understand the dynamics of the streamers, a theoretical determination of the laplacian electric field generated by the biased electrodes was done. Optical emission spectroscopy was performed in the range of wavelengths 280-480 nm, containing the typical spectral bands 2nd positive and 1st negative systems of molecular nitrogen.

  18. Detection of high tritium activity on the central titanium electrode of a plasma focus device

    SciTech Connect

    Rout, R.K.; Spinivasan, M.; Shyam, A.; Chitra, V. )

    1991-03-01

    In this paper a 2-kJ Mather plasma focus device is used to deuterate the top end surface (or tip) of its central titanium electrode to investigate the occurrence of anomalous nuclear reactions in the context of the cold fusion phenomenon. The tip of the central titanium electrode is found to develop at least a few tens of microcuries of tritium after several plasma focus discharges. Neither the tritium impurity level in the deuterium gas used in the experiment nor the tritium branch of the d-d reactions that are known to occur in plasma focus devices can account for such activity in the electrode. Anomalous nuclear reactions in the deuterated titanium lattice appear to be the most probable source of this high activity.

  19. Large-scale plasma patterning of transparent graphene electrode on flexible substrates.

    PubMed

    Kim, Ji Hye; Ko, Euna; Hwang, Joonki; Pham, Xuan-Hung; Lee, Joo Heon; Lee, Sung Hwan; Tran, Van-Khue; Kim, Jong-Ho; Park, Jin-Goo; Choo, Jaebum; Han, Kwi Nam; Seong, Gi Hun

    2015-03-10

    Graphene, a two-dimensional carbon material, has attracted significant interest for applications in flexible electronics as an alternative transparent electrode to indium tin oxide. However, it still remains a challenge to develop a simple, reproducible, and controllable fabrication technique for producing homogeneous large-scale graphene films and creating uniform patterns with desired shapes at defined positions. Here, we present a simple route to scalable fabrication of flexible transparent graphene electrodes using an oxygen plasma etching technique in a capacitively coupled plasma (CCP) system. Ascorbic acid-assisted chemical reduction enables the large-scale production of graphene with solution-based processability. Oxygen plasma in the CCP system facilitates the reproducible patterning of graphene electrodes, which allows controllable feature sizes and shapes on flexible plastic substrates. The resulting graphene electrode exhibits a high conductivity of 80 S cm(-1) and a transparency of 76% and retains excellent flexibility upon hard bending at an angle of ±175° and after repeated bending cycles. A simple LED circuit integrated on the patterned graphene film demonstrates the feasibility of graphene electrodes for use in flexible transparent electrodes. PMID:25692852

  20. Optimization of hollow cathode discharge electrode for damage free remote plasma removal process for semiconductor manufacturing

    NASA Astrophysics Data System (ADS)

    Cho, Tae S.; Han, Qing; Yang, Dongqing; Park, Soonam; Lubomirsky, Dima; Venkataraman, Shankar

    2016-05-01

    Cone-shaped hollow cathode electrode configuration for a damage free remote plasma removal process has been optimized for given pressures based on Paschen characteristic curves, voltage-current characteristics and time-resolved discharge observations as well as oxide film removal performances. Remote plasmas have been generated in two types of cone-shaped electrodes with mixtures of He, NF3, and NH3 for pressure range of 1-30 Torr. Paschen characteristic curves and voltage-current (V-I) characteristics define an operating pressure for low breakdown voltage and the hollow cathode effect to minimize the particles. Sinusoidal voltage waveform and asymmetry electrode configuration alternate the glow discharge and hollow cathode discharge modes in a cycle. The current and infrared emission intensity from the glow discharge increases together for both cone-shaped electrodes with increasing pressure, whereas the hollow cathode discharge plasma emits strong infrared only when pD condition is satisfied. For the wide cone electrode configuration, high voltage operation at higher pressure results in particle contamination on the processed wafer by high energy ion bombardment. Operating at optimum pressure for a given electrode configuration shows faster oxide etch rate with better uniformity over a whole 300 mm wafer.

  1. The differing behavior of electrosurgical devices made of various electrode materials operating under plasma conditions

    NASA Astrophysics Data System (ADS)

    Stalder, K. R.; Ryan, T. P.; Gaspredes, J.; Woloszko, J.

    2015-03-01

    Coblation® is an electrosurgical technology which employs electrically-excited electrodes in the presence of saline solution to produce a localized and ionized plasma that can cut, ablate, and otherwise treat tissues for many different surgical needs. To improve our understanding of how Coblation plasmas develop from devices made from different electrode materials we describe several experiments designed to elucidate material effects. Initial experiments studied simple, noncommercial cylindrical electrode test devices operating in buffered isotonic saline without applied suction. The applied RF voltage, approximately 300 V RMS, was sufficient to form glow discharges around the active electrodes. The devices exhibited significantly different operating characteristics, which we ascribe to the differing oxidation tendencies and other physical properties of the electrode materials. Parameters measured include RMS voltage and current, instantaneous voltage and current, temporally-resolved light emission and optical emission spectra, and electrode mass-loss measurements. We correlate these measured properties with some of the bulk characteristics of the electrode materials such as work functions, standard reduction potentials and sputter yields.

  2. 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.

  3. Excitation of electrostatic plasma waves using a dielectric covered metallic electrode

    SciTech Connect

    Kar, S.; Mukherjee, S.

    2011-11-15

    Plasma response to high positive and negative voltage pulses is studied using pulsed capacitive excitation in a uniform and unmagnetized plasma. The positive or negative voltage pulse is applied to a metallic electrode, covered by a dielectric (Kapton) film, immersed in a low pressure argon plasma. The pulse magnitude is much greater than the electron temperature (U{sub 0} >> kT{sub e}/e). Experiments are carried out for different plasma parameters, to find how the plasma perturbations propagate for various applied pulse widths in comparison to ion plasma period ( f{sub i}{sup -1}). Plasma perturbations are studied by varying the thickness of the dielectric. For positive pulse bias, depending on the dielectric thickness, excitation of solitary electron holes, or solitary ion holes are observed. For negative pulse bias, varying the dielectric thicknesses, only ion rarefaction waves are excited.

  4. NIF injection laser system

    NASA Astrophysics Data System (ADS)

    Wisoff, Peter J.; Bowers, Mark W.; Erbert, Gaylen V.; Browning, Donald F.; Jedlovec, Donald R.

    2004-05-01

    The National Ignition Facility (NIF) is a high-power, 192-beam laser facility being built at the Lawrence Livermore National Laboratory. The 192 laser beams that will converge on the target at the output of the NIF laser system originate from a low power fiber laser in the Master Oscillator Room (MOR). The MOR is responsible for generating the single pulse that seeds the entire NIF laser system. This single pulse is phase-modulated to add bandwidth, and then amplified and split into 48 separate beam lines all in single-mode polarizing fiber. Before leaving the MOR, each of the 48 output pulses are temporally sculpted into high contrast shapes using Arbitrary Waveform Generators (AWG). Each output pulse is then carried by optical fiber to the Preamplifier Module (PAM) where it is amplified to the multi-joule level using a diode-pumped regenerative amplifier and a multi-pass, flashlamp-pumped rod amplifier. Inside the PAM, the beam is spatially shaped to pre-compensate for the spatial gain profile in the main laser amplifiers. The output from the PAM is sampled by a diagnostic package called the Input Sensor Package (ISP) and then split into four beams in the Preamplifier Beam Transport System (PABTS). Each of these four beams is injected into one of NIF's 192 beam lines. The combination of the MOR, PAM, ISP and PABTS constitute the Injection Laser System (ILS) for NIF. This system has proven its flexibility of providing a wide variety of pulse shapes and energies during the first experiments utilizing four beam lines of NIF.

  5. Electrocatalytically Active Nickel-Based Electrode Coatings Formed by Atmospheric and Suspension Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Aghasibeig, M.; Mousavi, M.; Ben Ettouill, F.; Moreau, C.; Wuthrich, R.; Dolatabadi, A.

    2014-01-01

    Ni-based electrode coatings with enhanced surface areas, for hydrogen production, were developed using atmospheric plasma spray (APS) and suspension plasma spray (SPS) processes. The results revealed a larger electrochemical active surface area for the coatings produced by SPS compared to those produced by APS process. SEM micrographs showed that the surface microstructure of the sample with the largest surface area was composed of a large number of small cauliflower-like aggregates with an average diameter of 10 μm.

  6. Method of forming a plasma sprayed interconnection layer on an electrode of an electrochemical cell

    DOEpatents

    Spengler, Charles J.; Folser, George R.; Vora, Shailesh D.; Kuo, Lewis; Richards, Von L.

    1995-01-01

    A dense, substantially gas-tight, electrically conductive interconnection layer is formed on an air electrode structure of an electrochemical cell by (A) providing an electrode surface; (B) forming on a selected portion of the electrode surface, a layer of doped LaCrO.sub.3 particles doped with an element selected from Ca, Sr, Ba, Mg, Co, Ni, Al and mixtures thereof by plasma spraying doped LaCrO.sub.3 powder, preferably compensated with chromium as Cr.sub.2 O.sub.3 and/or dopant element, preferably by plasma arc spraying; and, (C) heating the doped and compensated LaCrO.sub.3 layer to about 1100.degree. C. to 1300.degree. C. to provide a dense, substantially gas-tight, substantially hydration-free, electrically conductive interconnection material bonded to the electrode surface. A solid electrolyte layer can be applied to the unselected portion of the air electrode, and a fuel electrode can be applied to the solid electrolyte, to provide an electrochemical cell.

  7. Method of forming a plasma sprayed interconnection layer on an electrode of an electrochemical cell

    DOEpatents

    Spengler, C.J.; Folser, G.R.; Vora, S.D.; Kuo, L.; Richards, V.L.

    1995-06-20

    A dense, substantially gas-tight, electrically conductive interconnection layer is formed on an air electrode structure of an electrochemical cell by (A) providing an electrode surface; (B) forming on a selected portion of the electrode surface, a layer of doped LaCrO{sub 3} particles doped with an element selected from Ca, Sr, Ba, Mg, Co, Ni, Al and mixtures thereof by plasma spraying doped LaCrO{sub 3} powder, preferably compensated with chromium as Cr{sub 2}O{sub 3} and/or dopant element, preferably by plasma arc spraying; and, (C) heating the doped and compensated LaCrO{sub 3} layer to about 1100 C to 1300 C to provide a dense, substantially gas-tight, substantially hydration-free, electrically conductive interconnection material bonded to the electrode surface. A solid electrolyte layer can be applied to the unselected portion of the air electrode, and a fuel electrode can be applied to the solid electrolyte, to provide an electrochemical cell. 6 figs.

  8. A unified model of coupled arc plasma and weld pool for double electrodes TIG welding

    NASA Astrophysics Data System (ADS)

    Wang, Xinxin; Fan, Ding; Huang, Jiankang; Huang, Yong

    2014-07-01

    A three-dimensional model containing tungsten electrodes, arc plasma and a weld pool is presented for double electrodes tungsten inert gas welding. The model is validated by available experimental data. The distributions of temperature, velocity and pressure of the coupled arc plasma are investigated. The current density, heat flux and shear stress over the weld pool are highlighted. The weld pool dynamic is described by taking into account buoyance, Lorentz force, surface tension and plasma drag force. The turbulent effect in the weld pool is also considered. It is found that the temperature and velocity distributions of the coupled arc are not rotationally symmetrical. A similar property is also shown by the arc pressure, current density and heat flux at the anode surface. The surface tension gradient is much larger than the plasma drag force and dominates the convective pattern in the weld pool, thus determining the weld penetration. The anodic heat flux and plasma drag force, as well as the surface tension gradient over the weld pool, determine the weld shape and size. In addition, provided the welding current through one electrode increases and that through the other decreases, keeping the total current unchanged, the coupled arc behaviour and weld pool dynamic change significantly, while the weld shape and size show little change. The results demonstrate the necessity of a unified model in the study of the arc plasma and weld pool.

  9. Currents between tethered electrodes in a magnetized laboratory plasma

    NASA Technical Reports Server (NTRS)

    Stenzel, R. L.; Urrutia, J. M.

    1990-01-01

    This paper describes the experimental setup and measurement techniques used to investigate currents between tethered electodes in a magnetized laboratory plasma. Experimental results include information on current propagation, the formation of wave wings, the limits of current collection, nonlinear effects and instabilities, charging phenomena, and the characteristics of transmission lines in plasma. The results were found to support certain predictions on tethers in space (e.g., the MHD far zone or the motional emf) while contradicting others (e.g., distant current closure), and revealed such new phenomena as current disruptions, current-neutralized beams, and wing spread.

  10. Numerical Studies of Electrode Plasma Formation and Expansion in High Power Charged Particle Beam Diodes

    NASA Astrophysics Data System (ADS)

    Rittersdorf, I. M.; Swanekamp, S. B.; Richardson, A. S.; Allen, R. J.; Schumer, J. W.

    2014-10-01

    High-power diodes that generate intense electron beams are useful in many applications, such as producing x-rays for flash radiography and nuclear weapon effects simulations. Desorption and ionization of gases from electrodes can form a plasma during operation. Expansion of this plasma into the gap leads to a short circuit, which limits the radiation production. It is difficult for particle-in-cell codes to model the surface physics or the subsequent expansion of the plasma. NRL is beginning a multi-year research effort to study such plasmas. This paper will summarize the relevant literature on plasma formation in high-power diodes with a goal of developing dynamic models that describe the formation and expansion of these plasmas that are suitable for PIC codes. This work was supported by the NRL Basic and Applied Research Program.

  11. Charge trapping induced by plasma in alumina electrode surface investigated by thermoluminescence and optically stimulated luminescence

    SciTech Connect

    Ambrico, P. F.; Ambrico, M.; Schiavulli, L.; Ligonzo, T.; Augelli, V.

    2009-02-02

    The plasma of a dielectric barrier discharge can fill traps in the alumina that cover the electrode. Trap energies and lifetimes are estimated by thermoluminescence and optically stimulated luminescence. Comparison with similar results for traps created by other radiation sources clarifies the mechanisms regulating this effect. Alumina's trap energies are approximately 1 eV, and the traps remain active for several days after plasma exposure. These results could be important to keep dielectric barrier discharge plasmas uniform since a trapped charge can be an electron reservoir.

  12. Effects of atmospheric air plasma treatment of graphite and carbon felt electrodes on the anodic current from Shewanella attached cells.

    PubMed

    Epifanio, Monica; Inguva, Saikumar; Kitching, Michael; Mosnier, Jean-Paul; Marsili, Enrico

    2015-12-01

    The attachment of electrochemically active microorganisms (EAM) on an electrode is determined by both the chemistry and topography of the electrode surface. Pre-treatment of the electrode surface by atmospheric air plasma introduces hydrophilic functional groups, thereby increasing cell attachment and electroactivity in short-term experiments. In this study, we use graphite and carbon felt electrodes to grow the model EAM Shewanella loihica PV-4 at oxidative potential (0.2 V vs. Ag/AgCl). Cell attachment and electroactivity are measured through electrodynamic methods. Atmospheric air plasma pre-treatment increases cell attachment and current output at graphite electrodes by 25%, while it improves the electroactivity of the carbon felt electrodes by 450%. Air plasma pre-treatment decreased the coulombic efficiency on both carbon felt and graphite electrodes by 60% and 80%, respectively. Microbially produced flavins adsorb preferentially at the graphite electrode, and air plasma pre-treatment results in lower flavin adsorption at both graphite and carbon felt electrodes. Results show that air plasma pre-treatment is a feasible option to increase current output in bioelectrochemical systems. PMID:25862431

  13. Pulse power requirements for large aperture optical switches based on plasma electrode Pockels cells

    SciTech Connect

    Rhodes, M.A.; Taylor, J.

    1992-06-01

    We discuss very large-aperture optical switches (greater than 30 [times] 30 cm) as an enabling technology for inertial confinement fusion drivers based on multipass laser amplifiers. Large-scale laser fusion drivers such as the Nova laser have been based on single-pass amplifier designs in part because of the unavailability of a suitable large-aperture switch. We are developing an optical switch based on a Pockels cell employing plasma-electrodes. A plasma-electrode Pockels cell (PEPC) is a longitudinal-mode Pockels cell in which a plasma discharge is formed on each side of an electro-optic crystal (typically KDP or deuterated KDP, often designated KD*P). The plasmas formed on either side of the crystal act as transparent electrodes for a switching-pulse and are intended to allow uniform charging of the entire crystal. The switching-pulse is a nominally rectangular high-voltage pulse equal to the half-wave voltage V[sub x] ( 8 kV for KD*P or 17 kV for KDP) and is applied across the crystal via the plasma-electrodes. When the crystal is charged to V[sub x], the polarization of an incoming, linearly polarized, laser beam is rotated by 90[degree]. When used in conjunction with an appropriate, passive polarizer, an optical switch is thus realized. A switch with a clear aperture of 37 [times] 37 cm is now in construction for the Beamlet laser which will serve as a test bed for this switch as well as other technologies required for an advanced NOVA laser design. In this paper, we discuss the unique power electronics requirements of PEPC optical switches.

  14. Pulse power requirements for large aperture optical switches based on plasma electrode Pockels cells

    SciTech Connect

    Rhodes, M.A.; Taylor, J.

    1992-06-01

    We discuss very large-aperture optical switches (greater than 30 {times} 30 cm) as an enabling technology for inertial confinement fusion drivers based on multipass laser amplifiers. Large-scale laser fusion drivers such as the Nova laser have been based on single-pass amplifier designs in part because of the unavailability of a suitable large-aperture switch. We are developing an optical switch based on a Pockels cell employing plasma-electrodes. A plasma-electrode Pockels cell (PEPC) is a longitudinal-mode Pockels cell in which a plasma discharge is formed on each side of an electro-optic crystal (typically KDP or deuterated KDP, often designated KD*P). The plasmas formed on either side of the crystal act as transparent electrodes for a switching-pulse and are intended to allow uniform charging of the entire crystal. The switching-pulse is a nominally rectangular high-voltage pulse equal to the half-wave voltage V{sub x} ( 8 kV for KD*P or 17 kV for KDP) and is applied across the crystal via the plasma-electrodes. When the crystal is charged to V{sub x}, the polarization of an incoming, linearly polarized, laser beam is rotated by 90{degree}. When used in conjunction with an appropriate, passive polarizer, an optical switch is thus realized. A switch with a clear aperture of 37 {times} 37 cm is now in construction for the Beamlet laser which will serve as a test bed for this switch as well as other technologies required for an advanced NOVA laser design. In this paper, we discuss the unique power electronics requirements of PEPC optical switches.

  15. Evaluation of materials proposed for the construction of the plasma electrode Pockels cell (PEPC) on beamlet

    SciTech Connect

    Roberts, D.; Robb, C.; DeYoreo, J.; Atherton, J.

    1992-11-01

    The proposed upgrade of the NOVA laser system at Lawrence Livermore National Laboratory employs a multipass architecture that requires an optical switch to emit the laser light at the appropriate fluence. This Pockels cell-based optical switch does not use traditional ring or thin-film electrodes because of the large aperture and high fluence of the laser system. Rather, it uses a plasma electrode Pockels cell with a KD*P crystal as the electro-optical medium. A discharge plasma is formed on each side of the electro-optic crystal and high voltage is applied across the crystal through the plasma electrode to initiate optical switching. In October 1991 we began evaluating materials suggested for the large aperture plasma electrode optical switch. Previous experiments suggested that switching performance could be significantly affected by the deterioration of cell materials. The final prototype switch tested used polyethylene for the switch body, Mykroy for the mid-plane and a silicone vulcanite to encapsulate the KD*P crystal. The encapsulant easily compensated for the effect of assembling the optical switch and we measured no strain-induced birefringence in the crystal after encapsulation. Oxygen was eventually added to the plasma to react with the sputtered carbon from the cathode and produce a gaseous effluent. As an added benefit, the production of ozone absorbed most of the ultra violet radiation affecting the encapsulant. All the materials tested decomposed and produced volatiles, although we have seen no change in the damage threshold of exposed optical surfaces tested to date. The following is an evaluation of the recommended materials for major cell components using published manufacturers data, experimental results from our Material Evaluation Apparatus, and outgassing performance and sputtering data produced at the Laboratory`s Vacuum Process Lab.

  16. Fluoride determination in plasma by ion selective electrodes: a simplified method for the clinical laboratory.

    PubMed

    Fuchs, C; Dorn, D; Fuchs, C A; Henning, H V; McIntosh, C; Scheler, F; Stennart, M

    1975-04-16

    A potentiometric method for the determination of fluoride (F-) in serum and plasma is proposed; it is based on a combination of the single-known-addition method and the electrode slope-by-dilution method. This procedure provides reliable results in extremely low measuring ranges down to 2.5 mug/l, where the electrode slope deviates markedly from Nernstian behaviour. In this method no electrode calibration is required and only one standard is necessary. 1 ml of plasma is sufficient for one analysis. Apart from a 5% enrichment of all samples with a concentrated total ionic strength adjustment buffer, no further preparation of the sample is required. The simplicity of the various pipetting and analytical steps, and also of the evaluation of the readings, may render this method highly suitable for the clinical laboratory. Investigations into the accuracy and precision of the method produced satisfactory results. The recovery in plasma amounted to 99.7%, even in the low measuring ranges. The discrimination capacity of the method amounts to 0.1 mug/l. With the apparatus and experimental procedures described, 18 plasma analyses per day can be performed even at low F- concentrations with which longer electrode stabilization periods are required. Storage of the plasma samples frozen at --20 degrees C for up to 8 weeks exerts no effect on the F- concentration. Problems of sample contamination and other disturbances are discussed. Determinations of normal values in 20 test subjects resulted in a mean value of 10.4 plus or minus 4.01 mug/l (Mean plus or minus S.D.). The modal value amounted to 9.5 mug/l, and the range was between 5.9 and 18.8 mug/l. The F- content of the drinking water supplied to this group of persons amounted to 180 mug/l. The importance of the method has been illustrated using a clinico-nephrological study as an example. PMID:236104

  17. Sheath expansion and plasma dynamics in the presence of electrode evaporation: Application to a vacuum circuit breaker

    SciTech Connect

    Sarrailh, P.; Garrigues, L.; Hagelaar, G. J. M.; Boeuf, J. P.; Sandolache, G.; Rowe, S.

    2009-09-01

    During the postarc dielectric recovery phase in a vacuum circuit breaker, a cathode sheath forms and expels the plasma from the electrode gap. The success or failure of current breaking depends on how efficiently the plasma is expelled from the electrode gap. The sheath expansion in the postarc phase can be compared to sheath expansion in plasma immersion ion implantation except that collisions between charged particles and atoms generated by electrode evaporation may become important in a vacuum circuit breaker. In this paper, we show that electrode evaporation plays a significant role in the dynamics of the sheath expansion in this context not only because charged particle transport is no longer collisionless but also because the neutral flow due to evaporation and temperature gradients may push the plasma toward one of the electrodes. Using a hybrid model of the nonequilibrium postarc plasma and cathode sheath coupled with a direct simulation Monte Carlo method to describe collisions between heavy species, we present a parametric study of the sheath and plasma dynamics and of the time needed for the sheath to expel the plasma from the gap for different values of plasma density and electrode temperatures at the beginning of the postarc phase. This work constitutes a preliminary step toward understanding and quantifying the risk of current breaking failure of a vacuum arc.

  18. SOLUTION NEBULIZATION OF AQUEOUS SAMPLES INTO THE TUBULAR-ELECTRODE TORCH CAPACITATIVELY-COUPLED MICROWAVE PLASMA (JOURNAL VERSION)

    EPA Science Inventory

    The work shows the feasibility of using nebulization for introduction of aqueous samples into the tubular-torch capacitatively-coupled microwave plasma (CMP). Previously, solid electrodes were used with this type of plasma, in which analyte carrier and plasma support gases are pr...

  19. Research on 2x1 plasma electrode electro-optical switch with large aperture

    NASA Astrophysics Data System (ADS)

    Zhang, Xiong Jun; Zheng, Kui Xing; Feng, B.; Wu, D. S.; Lu, J. P.; Tian, X. L.; Jin, F.; Sui, Zhan; Wei, Xiaofeng; Zhang, Xiaomin

    2005-01-01

    In conceptual design of the prototype for SG-III facility, a full aperture electro-optical switch was placed between the cavity mirror and the main amplifier to isolate the reflected beams. The beam on the cavity mirror is 240mm×240mm square. Pockells cells of conversional design with coaxial ring electrodes can not scale to such large square aperture. In the 1980s, a plasma electrode Pockels cell (PEPC) concept was invented at LLNL. It uses transparent plasma electrode formed through gas discharge as the electrodes to apply the voltage across switching crystal to rotate the polarization of a transmitted laser beam. And it can be scaled to large aperture with thin crystal. So the switch which would be used in SG-III is based on this technology. The technical integration line as a prototype of SG-III laser is actually a 4×2 beam bundle. And the full aperture optical switch is mechanically designed four apertures as a removable unit, and electrically two 2×1 PEPC putting together. So we built a 2×1 PEPC to develop the technology first. The 2×1 PEPC is a sandwich structure made of an insulating mid plane between a pair of plasma chambers. The frame of both plasma chambers are machining in duralumin. Each chamber is installed with a planar magnetic cathode and four segments spherical anodes made from stainless steel. The cathode and anode are insulated from the housing with a special shell made from plastic, and plasma is insulated from the housing by an 80-μm-thick anodic coating on the duralumin. The two plasma chambers are separated by a mid plane of glass frame with two square holes. The two holes are filled by two electro-optical crystals with a 240-mm square aperture. With the optimized operating pressure and the electrical parameters, a very good homogeneity and low resistivity plasma electrode is obtained. Finally we tested its switching performance to simulate the case that it will be used in the SG-III prototype facility. It works with a quarter wave

  20. Calibration Facilities for NIF

    SciTech Connect

    Perry, T.S.

    2000-06-15

    The calibration facilities will be dynamic and will change to meet the needs of experiments. Small sources, such as the Manson Source should be available to everyone at any time. Carrying out experiments at Omega is providing ample opportunity for practice in pre-shot preparation. Hopefully, the needs that are demonstrated in these experiments will assure the development of (or keep in service) facilities at each of the laboratories that will be essential for in-house preparation for experiments at NIF.

  1. A study of the glow discharge plasma jet of the novel Hamburger-electrode

    NASA Astrophysics Data System (ADS)

    Liu, Wenzheng; Ma, Chuanlong; Yang, Xiao; Cui, Weisheng; Chen, Xiuyang

    2016-08-01

    To generate atmospheric pressure glow discharge plasma jets (APGDPJs), a novel Hamburger-electrode was proposed. Through the study on electric field distributions, flow field distributions, and characteristics of the discharge and jet, we found that adopting the mode of dielectric barrier discharge with non-uniform thickness of dielectric, it was easy to form the strong electric field areas which were conducive to generate discharge and electric field distributions with large electric field intensity in the narrow gap and weak electric field intensity in the wide gap that were not inclined to form a filament discharge. Using the structure of evenly distributed inner electrodes, it was easy to weaken the pressure of strong electric field areas and form flow field distributions which is beneficial for taking out the high density charged particles and generating APGDPJs. Stable APGDPJs in nitrogen with 3.5 mm in diameter and 9 mm in length were formed by using the novel Hamburger-electrode.

  2. Generation of Atmospheric Pressure Plasma by Repetitive Nanosecond Pulses in Air Using Water Electrodes

    NASA Astrophysics Data System (ADS)

    Shao, Tao; Yu, Yang; Zhang, Cheng; Jiang, Hui; Yan, Ping; Zhou, Yuanxiang

    2011-12-01

    Dielectric barrier discharge (DBD) excitated by pulsed power is a promising method for producing nonthermal plasma at atmospheric pressure. Discharge characteristic in a DBD with salt water as electrodes by a home-made unipolar nanosecond-pulse power source is presented in this paper. The generator is capable of providing repetitive pulses with the voltage up to 30 kV and duration of 70 ns at a 300 Ω resistive load. Applied voltage and discharge current are measured under various experimental conditions. The DBD created between two liquid electrodes shows that the discharge is homogeneous and diffuse in the whole discharge regime. Spectra diagnosis is conducted by an optical emission spectroscopy. The air plasma has strong emission from nitrogen species below 400 nm, notably the nitrogen second positive system.

  3. "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

  4. Evaluation of microwave plasma sintering for the fabrication of dye sensitized solar cell (DSSC) electrodes.

    PubMed

    Dembele, A; Rahman, M; MacElroy, J M D; Dowling, D P

    2012-06-01

    Dye-sensitized solar cells (DSSCs) have demonstrated considerable potential due to their solar energy conversion efficiency and their fabrication from relatively low cost materials. Titanium dioxide (TiO2) nanoparticles are widely used in the fabrication of the DSSC electrodes. There is a considerable energy requirement however required for the sintering of the TiO2 particles during the fabrication of the mesoporous electrodes. This study investigates the use of microwave (MW) plasma treatments as a rapid, energy efficient processing technique for the sintering of the metal oxide particles. A comparison is made with conventional furnace treatments for the sintering of TiO2 nanoparticles (Degussa P25), deposited onto fluorine doped tin oxide (FTO) coated glass substrates. Subsequent to the TiO2 sintering, ruthenium based dye (N719) adsorption studies were carried out for coatings heated using both sintering techniques. Based on UV/Vis absorption spectra measurements of 5 mins plasma and 30 mins furnace sintering, it was observed that both sintering techniques exhibited similar levels of dye adsorption. A decrease in the level of dye adsorption was observed for the TiO2 coatings sintered for longer periods (up to 10 mins in this study). This change with longer plasma treatment times was associated with rutile grain growth and a decrease in surface roughness, possibly due to a densification of the mesoporous structure. The effect of TiO2 coating plasma treatment times on the conversion efficiency of the dye sensitised electrodes was also evaluated. Plasma treatments of 5 mins were found to yield the highest conversion efficiency of 6.4%. PMID:22905529

  5. Atmospheric pressure plasma polymerization using double grounded electrodes with He/Ar mixture

    SciTech Connect

    Kim, Dong Ha; Kim, Hyun-Jin; Park, Choon-Sang; Tae, Heung-Sik; Shin, Bhum Jae; Seo, Jeong Hyun

    2015-09-15

    In this study, we have proposed the double grounded atmospheric pressure plasma jet (2G-APPJ) device to individually control the plasmas in both fragmentation (or active) and recombination (or passive) regions with a mixture of He and Ar gases to deposit organic thin films on glass or Si substrates. Plasma polymerization of acetone has been successfully deposited using a highly energetic and high-density 2G-APPJ and confirmed by scanning electron microscopy (SEM). Plasma composition was measured by optical emission spectroscopy (OES). In addition to a large number of Ar and He spectra lines, we observed some spectra of C{sub 2} and CH species for fragmentation and N{sub 2} (second positive band) species for recombination. The experimental results confirm that the Ar gas is identified as a key factor for facilitating fragmentation of acetone, whereas the He gas helps the plume of plasma reach the substrate on the 2{sup nd} grounded electrode during the plasma polymerization process. The high quality plasma polymerized thin films and nanoparticles can be obtained by the proposed 2G-APPJ device using dual gases.

  6. Neutron monitoring and electrode calorimetry experiments in the HIP-1 Hot Ion Plasma

    NASA Technical Reports Server (NTRS)

    Reinmann, J. J.; Layman, R. W.

    1977-01-01

    Results are presented for two diagnostic procedures on HIP-1: neutron diagnostics to determine where neutrons originated within the plasma discharge chamber and electrode calorimetry to measure the steady-state power absorbed by the two anodes and cathodes. Results are also reported for a hot-ion plasma formed with a continuous-cathode rod, one that spans the full length of the test section, in place of the two hollow cathodes. The outboard neutron source strength increased relative to that at the midplane when (1) the cathode tips were moved farther outboard, (2) the anode diameters were increased, and (3) one of the anodes was removed. The distribution of neutron sources within the plasma discharge chamber was insensitive to the division of current between the two cathodes. For the continuous cathode, increasing the discharge current increased the midplane neutron source strength relative to the outboard source strength. Each cathode absorbed from 12 to 15 percent of the input power regardless of the division of current between the cathodes. The anodes absorbed from 20 to 40 percent of the input power. The division of power absorption between the anodes varied with plasma operating conditions and electrode placement.

  7. Missed targets prompt NIF reshuffle

    NASA Astrophysics Data System (ADS)

    Cartlidge, Edwin

    2013-06-01

    The Lawrence Livermore National Laboratory in California has appointed a new director for its 3.5bn National Ignition Facility (NIF). Jeffrey Atherton, a chemical engineer who has worked at NIF for 20 years, took up the post on 1 May and will take on some of the responsibilities previously held by the facility's existing boss Edward Moses.

  8. NIF small mirror mount

    SciTech Connect

    McCarville, T

    1999-07-01

    A number of small mirror mounts have been identified that meet the stringent stability, wave front, and cleanliness standards of the NIF. These requirements are similar to those required in other performance critical optical design applications. Future design teams would conserve time and effort if recognized standards were established for mirror mount design and performance characteristics. Standards for stability, physical features, wave front distortion, and cleanliness would simplify the qualification process considerably. At this point such standards are not difficult to define, as the technical support work has been performed repeatedly by mirror mount consumers and suppliers.

  9. Development of AC-driven liquid electrode plasma for sensitive detection of metals

    NASA Astrophysics Data System (ADS)

    Van Khoai, Do; Miyahara, Hidekazu; Yamamoto, Tamotsu; Trong Tue, Phan; Okino, Akitoshi; Takamura, Yuzuru

    2016-02-01

    A novel liquid electrode plasma (LEP) driven by AC, which is used as an excitation source for elemental analysis, has been developed for the first time. The conditions such as chip layout and flow rate were found to produce the plasma in the channel. The mechanism of AC LEP generation was determined. AC LEP could be sustained in the resin channel with no severe damage on the channel. The emission spectra of electrolyte, lead and cadmium solution were obtained and compared with those generated by DC LEP. AC LEP was developed for the quantitative determination of lead and cadmium with limits of detection of 75.0 µg/L (ppb) and 4.5 µg/L (ppb), respectively. The novel plasma source is promising for on-chip combination and integration because it could be maintained at low flow rates on a resin-based platform.

  10. Polar-Drive--Ignition Experimental Plan on the NIF

    NASA Astrophysics Data System (ADS)

    Meyerhofer, D. D.; Froula, D. H.; Goncharov, V. N.; Igumenshchev, I. V.; Loucks, S. J.; McKenty, P. W.; McCrory, R. L.; Radha, P. B.; Sangster, T. C.

    2012-10-01

    The University of Rochester's Laboratory for Laser Energetics has proposed a multi-campaign series of experiments on the National Ignition Facility (NIF)footnotetext E. I. Moses et al., Phys. Plasmas 16, 041006 (2009). to develop polar-drive ignition.footnotetext S. Skupsky et al., Phys. Plasmas 11, 2763 (2004). Polar drive is predicted to couple significantly more energy to the compressed core than the baseline indirect-drive approach. This presentation provides an overview of the plan to achieve polar-drive ignition on the NIF and describes the initial experiments that can be performed without changes in the NIF infrastructure. The first proposed experiments will assess the symmetry of moderate convergence ratio, polar-driven capsule implosions. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302.

  11. Improvement of efficiency and viability in plasma gene transfection by plasma minimization and optimization electrode configuration

    NASA Astrophysics Data System (ADS)

    Jinno, Masafumi; Tachibana, Kunihide; Motomura, Hideki; Saeki, Noboru; Satoh, Susumu

    2016-07-01

    Plasma gene transfection is expected as a safe and useful method of gene transfection. However, in this method, there is difficulty in keeping both high transfection efficiency and less cell damage simultaneously. The authors have evaluated transfection efficiency and cell viability using four different plasma sources, such as arc discharge, plasma jet, dielectric barrier discharge (DBD), and microplasma. A high transfection efficiency was achieved by discharge forms in which the electric current flows via the cells. This suggested that an electric current plays an important role in plasma gene transfection. The total volume of gas flow must be small or zero and the area in which the cells are directly irradiated by plasma must be small in order to achieve a higher cell viability. The microplasma that satisfies these conditions achieved both the highest transfection efficiency and the highest cell viability simultaneously.

  12. Calculation of the velocity of a plasma flow in the nozzle exit section of a coaxial-electrode Hall accelerator

    NASA Astrophysics Data System (ADS)

    Anoshko, I. A.; Ermachenko, V. S.

    2006-05-01

    The velocity of a plasma jet in the nozzle exit section and the pressure in the discharge zone of a coaxial-electrode Hall accelerator have been calculated on the basis of the experimentally measured enthalpy, temperature, and electron concentration near the indicated section within the framework of a model of the magnetic hydrodynamics of a plasma flow.

  13. Numerical analysis of a hollow electrode plasma torch with a reversed polarity discharge for radioactive waste treatment

    NASA Astrophysics Data System (ADS)

    Park, Seung-Chul; Kim, Dong-Uk; Kim, Min-Ho; Seo, Jun-Ho; Yang, O.-Bong

    2013-11-01

    In this study, a numerical analysis is carried out in order to investigate the effects of the electrode configuration and the operation conditions on the arc flow structure and the performance of a hollow electrode plasma torch with a reversed polarity discharge. From the numerical results, a swirl injection of plasma gas and a hollowed cathode with a convergent entrance are found to help control the recirculation directions of backflows and the attachment position of the anode spot in the rear electrode. For example, the anode spot is observed to be moved to the central point of the blocked side in the rear electrode (the anode) when the plasma-forming gases are injected with a swirl. This attachment point is predicted to act as a stable anode spot for the transferred operation of the hollow electrode plasma torch with a reversed polarity discharge. In addition, the torch performance is analyzed for operation variables, such as the arc current and the gas flow rates. Similar to that of a conventional hollow electrode plasma torch, the scale-up of input power is accompanied by increases in the arc current and the gas flow rate while increasing the arc current brings about a deterioration in the torch efficiency, which is defined as the ratio of the exit enthalpy to the input power. On the other hand, the temperature profiles at the torch's exit plane show relatively negligible differences for various arc currents and gas flow rates due to the cathode spot being close to the torch exit. Based on these features, we expect the hollow electrode plasma torch with a reversed polarity discharge to be a promising tool for treating radioactive wastes in a single step, both as a non-transferred-type plasma incinerator for combustibles and as a transferred-type arc-melter for non-combustibles.

  14. Operating conditions for the generation of stable anode spot plasma in front of a positively biased electrode.

    PubMed

    Park, Yeong-Shin; Lee, Yuna; Dang, Jeong-Jeung; Chung, Kyoung-Jae; Hwang, Y S

    2014-02-01

    Stability of an anode spot plasma, which is an additional high density plasma generated in front of a positively biased electrode immersed in ambient plasma, is a critical issue for its utilization to various types of ion sources. In this study, operating conditions for the generation of stable anode spot plasmas are experimentally investigated. Diagnostics of the bias current flowing into the positively biased electrode and the properties of ambient plasma reveal that unstable nature of the anode spot is deeply associated with the reduction of double layer potential between the anode spot plasma and the ambient plasma. It is found that stability of the anode spot plasma can be improved with increasing the ionization rate in ambient plasma so as to compensate the loss of electrons across the double layer or with enlarging the area of the biased electrode to prevent electron accumulation inside the anode spot. The results obtained from the present study give the guideline for operating conditions of anode spot plasmas as an ion source with high brightness. PMID:24593431

  15. Parametric Study of Plasma Torch Operation Using a MHD Model Coupling the Arc and Electrodes

    NASA Astrophysics Data System (ADS)

    Alaya, M.; Chazelas, C.; Vardelle, A.

    2016-01-01

    Coupling of the electromagnetic and heat transfer phenomena in a non-transferred arc plasma torch is generally based on a current density profile and a temperature imposed on the cathode surface. However, it is not possible to observe the current density profile experimentally and so the computations are grounded on an estimation of current distribution at cathode tip. To eliminate this boundary condition and be able to predict the arc dynamics in the plasma torch, the cathode was included in the computational domain, the arc current was imposed on the rear surface of the cathode, and the electromagnetism and energy conservation equations for the fluid and the electrode were coupled and solved. The solution of this system of equations was implemented in a CFD computer code to model various plasma torch operating conditions. The model predictions for various arc currents were consistent and indicated that such a model could be applied with confidence to plasma torches of different geometries, such as cascaded-anode plasma torches.

  16. Plasma meniscus and extraction electrode studies of the ISIS H{sup -} ion source

    SciTech Connect

    Lawrie, S. R.; Faircloth, D. C.; Letchford, A. P.; Gabor, C.; Pozimski, J. K.

    2010-02-15

    In order to reduce the emittance and increase the transported beam current from the ISIS Penning-type H{sup -} ion source, improvements to the extraction system are required. This ion source is currently being commissioned on the front end test stand at the Rutherford Appleton Laboratory, which demands higher extraction energies, higher beam currents, and smaller emittances. To facilitate this, the present geometry requires optimization. This paper details the experimental and simulation studies performed of the plasma meniscus and the possible electrode geometry modifications needed to extract the highest quality beam.

  17. Backscatter measurements for NIF ignition targets (invited)

    SciTech Connect

    Moody, J. D.; Datte, P.; Krauter, K.; Bond, E.; Michel, P. A.; Glenzer, S. H.; Divol, L.; Suter, L.; Meezan, N.; MacGowan, B. J.; Hibbard, R.; London, R.; Kilkenny, J.; Wallace, R.; Knittel, K.; Frieders, G.; Golick, B.; Ross, G.; Widmann, K.; Jackson, J.; and others

    2010-10-15

    Backscattered light via laser-plasma instabilities has been measured in early NIF hohlraum experiments on two beam quads using a suite of detectors. A full aperture backscatter system and near backscatter imager (NBI) instrument separately measure the stimulated Brillouin and stimulated Raman scattered light. Both instruments work in conjunction to determine the total backscattered power to an accuracy of {approx}15%. In order to achieve the power accuracy we have added time-resolution to the NBI for the first time. This capability provides a temporally resolved spatial image of the backscatter which can be viewed as a movie.

  18. Backscatter measurements for NIF ignition targets (invited).

    PubMed

    Moody, J D; Datte, P; Krauter, K; Bond, E; Michel, P A; Glenzer, S H; Divol, L; Niemann, C; Suter, L; Meezan, N; MacGowan, B J; Hibbard, R; London, R; Kilkenny, J; Wallace, R; Kline, J L; Knittel, K; Frieders, G; Golick, B; Ross, G; Widmann, K; Jackson, J; Vernon, S; Clancy, T

    2010-10-01

    Backscattered light via laser-plasma instabilities has been measured in early NIF hohlraum experiments on two beam quads using a suite of detectors. A full aperture backscatter system and near backscatter imager (NBI) instrument separately measure the stimulated Brillouin and stimulated Raman scattered light. Both instruments work in conjunction to determine the total backscattered power to an accuracy of ∼15%. In order to achieve the power accuracy we have added time-resolution to the NBI for the first time. This capability provides a temporally resolved spatial image of the backscatter which can be viewed as a movie. PMID:21033953

  19. NIF Ambient Vibration Measurements

    SciTech Connect

    Noble, C.R.; Hoehler, M.S., S.C. Sommer

    1999-11-29

    LLNL has an ongoing research and development project that includes developing data acquisition systems with remote wireless communication for monitoring the vibrations of large civil engineering structures. In order to establish the capability of performing remote sensing over an extended period of time, the researchers needed to apply this technology to a real structure. The construction of the National Ignition Facility provided an opportunity to test the data acquisition system on a large structure to monitor whether the facility is remaining within the strict ambient vibration guidelines. This document will briefly discuss the NIF ambient vibration requirements and summarize the vibration measurements performed during the Spring and Summer of 1999. In addition, a brief description of the sensors and the data acquisition systems will be provided in Appendix B.

  20. How NIF Works

    ScienceCinema

    None

    2010-09-01

    The National Ignition Facility, located at Lawrence Livermore National Laboratory, is the world's largest laser system... 192 huge laser beams in a massive building, all focused down at the last moment at a 2 millimeter ball containing frozen hydrogen gas. The goal is to achieve fusion... getting more energy out than was used to create it. It's never been done before under controlled conditions, just in nuclear weapons and in stars. We expect to do it within the next 2-3 years. The purpose is threefold: to create an almost limitless supply of safe, carbon-free, proliferation-free electricity; examine new regimes of astrophysics as well as basic science; and study the inner-workings of the U.S. stockpile of nuclear weapons to ensure they remain safe, secure and reliable without the need for underground testing. More information about NIF can be found at:

  1. NIF symmetry capsule modeling

    NASA Astrophysics Data System (ADS)

    Weber, S. V.; Casey, D. T.; Pino, J. E.; Rowley, D. P.; Smalyuk, V. A.; Spears, B. K.; Tipton, R. E.

    2013-10-01

    NIF CH ablator symmetry capsules are filled with hydrogen or helium gas. SymCaps have more moderate convergence ratios ~ 15 as opposed to ~ 35 for ignition capsules with DT ice layers, and better agreement has been achieved between simulations and experimental data. We will present modeling of capsules with CD layers and tritium fill, for which we are able to match the dependence of DT yield on recession distance of the CD layer from the gas. We can also match the performance of CH capsules with D3 He fill. The simulations include surface roughness, drive asymmetry, a mock-up of modulation introduced by the tent holding the capsule, and an empirical prescription for ablator-gas atomic mix. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  2. How NIF Works

    SciTech Connect

    2009-07-30

    The National Ignition Facility, located at Lawrence Livermore National Laboratory, is the world's largest laser system... 192 huge laser beams in a massive building, all focused down at the last moment at a 2 millimeter ball containing frozen hydrogen gas. The goal is to achieve fusion... getting more energy out than was used to create it. It's never been done before under controlled conditions, just in nuclear weapons and in stars. We expect to do it within the next 2-3 years. The purpose is threefold: to create an almost limitless supply of safe, carbon-free, proliferation-free electricity; examine new regimes of astrophysics as well as basic science; and study the inner-workings of the U.S. stockpile of nuclear weapons to ensure they remain safe, secure and reliable without the need for underground testing. More information about NIF can be found at:

  3. Dynamics of flows, fluctuations, and global instability under electrode biasing in a linear plasma device

    NASA Astrophysics Data System (ADS)

    Desjardins, T. R.; Gilmore, M.

    2016-05-01

    Grid biasing is utilized in a large-scale helicon plasma to modify an existing instability. It is shown both experimentally and with a linear stability analysis to be a hybrid drift-Kelvin-Helmholtz mode. At low magnetic field strengths, coherent fluctuations are present, while at high magnetic field strengths, the plasma is broad-band turbulent. Grid biasing is used to drive the once-coherent fluctuations to a broad-band turbulent state, as well as to suppress them. There is a corresponding change in the flow shear. When a high positive bias (10Te) is applied to the grid electrode, a large-scale ( n ˜/n ≈50 % ) is excited. This mode has been identified as the potential relaxation instability.

  4. 02-NIF Dedication: Edward Moses

    ScienceCinema

    Edward Moses

    2010-09-01

    The National Ignition Facility, the world's largest laser system, was dedicated at a ceremony on May 29, 2009 at Lawrence Livermore National Laboratory. These are the remarks by NIF Director Edward Moses.

  5. 02-NIF Dedication: Edward Moses

    SciTech Connect

    Edward Moses

    2009-07-02

    The National Ignition Facility, the world's largest laser system, was dedicated at a ceremony on May 29, 2009 at Lawrence Livermore National Laboratory. These are the remarks by NIF Director Edward Moses.

  6. Metastable helium atom density in a single electrode atmospheric plasma jet during sample treatment

    NASA Astrophysics Data System (ADS)

    Zaplotnik, R.; Bišćan, M.; Popović, D.; Mozetič, M.; Milošević, S.

    2016-06-01

    The metastable He atoms play an important role in atmospheric pressure plasma jet (APPJ) chemistry processes and in the plasma generation. This work presents cavity ring-down spectroscopy (CRDS) investigation of metastable helium atom (2{{3}}{{S}1} ) densities in a single electrode APPJ during sample treatment. A spatially resolved density distribution of a free jet (without sample) was measured at a He flow rate of 2 slm. The maximum measured density of a free jet was around 7× {{10}11} cm‑3. With the insertion of a sample the densities increased up to 10 times. Helium metastable atoms, in a single electrode helium APPJ (2 slm, ≈2.5 kV, pulsed DC, 10 kHz repetition rate), decayed exponentially with a mean lifetime of 0.27+/- 0.03 μs. Eight different samples of the same sizes but different conductivities were used to investigate the influence of a sample material on the He metastable densities. The correlation between sample conductivities and metastable He densities above the sample surface was found. Metastable He density can also be further increased with decreasing sample distance, increasing conductive sample surface area and by increasing He flow.

  7. Hollow electrode enhanced radio frequency glow plasma and its application to the chemical vapor deposition of microcrystalline silicon

    SciTech Connect

    Tabuchi, Toshihiro; Mizukami, Hiroyuki; Takashiri, Masayuki

    2004-09-01

    A hollow electrode enhanced radio frequency (rf) glow plasma excitation technique and its application to the chemical vapor deposition of microcrystalline silicon films have been studied. In this technique, the reactor has two types of hollow structure. One is a hollow counterelectrode, and the other serves as both a hollow counterelectrode and a hollow rf electrode. The application of these discharge types to semiconductor processing is studied in the case of plasma enhanced chemical vapor deposition of hydrogenated microcrystalline silicon thin films. High crystallinity, photosensitivity and a maximum deposition rate of 6.0 nm/s can all be achieved at plasma excitation frequency of 13.56 MHz and substrate temperature of 300 deg. C. Properties of these plasmas are investigated by observing the plasma emission pattern, optical emission spectrum analysis and electrical parameters of the rf electrode. It is found that the plasma technique using both types of hollow discharge not only results in higher intensity of SiH{sup *} and H{alpha} but also in much smaller self-bias voltage of the rf electrode. Faster processing of device grade hydrogenated microcrystalline silicon films can also be achieved under lower rf power compared to use of the hollow counterelectrode technique alone.

  8. SOLVING THE STAND-OFF PROBLEM FOR MAGNETIZED TARGET FUSION: PLASMA STREAMS AS DISPOSABLE ELECTRODES, PLUS A LOCAL SPHERICAL BLANKET

    SciTech Connect

    Ryutov, D D; Thio, Y F

    2006-03-21

    In a fusion reactor based on the Magnetized Target Fusion approach, the permanent power supply has to deliver currents up to a few mega-amperes to the target dropped into the reaction chamber. All the structures situated around the target will be destroyed after every pulse and have to be replaced at a frequency of 1 to 10 Hz. In this paper, an approach based on the use of spherical blanket surrounding the target, and pulsed plasma electrodes connecting the target to the power supply, is discussed. A brief physic analysis of the processes associated with creation of plasma electrodes is discussed.

  9. Enthalpy probe measurements and three-dimensional modelling on air plasma jets generated by a non-transferred plasma torch with hollow electrodes

    NASA Astrophysics Data System (ADS)

    Kim, Keun Su; Park, Jin Myung; Choi, Sooseok; Kim, Jongin; Hong, Sang Hee

    2008-03-01

    Thermal flow characteristics of air plasma jets generated by a non-transferred plasma torch with hollow electrodes are experimentally and numerically investigated in order to provide more reliable scientific and technical information, which has been insufficient for their practical applications to material and environmental industries. In this work, a thermal plasma torch of hollow electrode type is first designed and fabricated, and similarity criteria for predicting operational conditions for the scale-up to high-power torches are derived from the arc voltage characteristics measured with various operating and geometry conditions of the torch. The thermal flow characteristics of air plasma jets ejected from the torch are measured by enthalpy probe diagnostics and turn out to have relatively low temperatures of around 3000-7000 K, but show features of other unique properties, such as high energy flux, broad high temperature region and long plasma jet with moderate axial velocity, which are promising for their applications to material syntheses and hazardous waste treatments. Such high enthalpy at a relatively low temperature of air thermal plasma compared with the argon one is due to the high thermal energy residing in the vibrational and rotational states and oxygen dissociation, besides the translational states in monatomic gases such as argon. It is expected that this high specific enthalpy of the air plasma will enable material and environmental industries to treat a large amount of precursors and waste materials effectively at a lower temperature for a longer residence time by the low plasma velocity. It is also found from the measurements that the turbulence intensity influenced by the size of the electrode diameter has a significant effect on the axial and radial profiles of plasma jet properties and that a longer plasma jet is more readily achievable with a larger electrode diameter reducing the turbulence intensity in the external region of the torch. In

  10. Fine structure of modal focusing effect in a three dimensional plasma-sheath-lens formed by disk electrodes

    SciTech Connect

    Stamate, Eugen; Yamaguchi, Masahito

    2015-08-31

    Modal and discrete focusing effects associated with three-dimensional plasma-sheath-lenses show promising potential for applications in ion beam extraction, mass spectrometry, plasma diagnostics and for basic studies of plasma sheath. The ion focusing properties can be adjusted by controlling the geometrical structure of the plasma-sheath-lens and plasma parameters. The positive and negative ion kinetics within the plasma-sheath-lens are investigated both experimentally and theoretically and a modal focusing ring is identified on the surface of disk electrodes. The focusing ring is very sensitive to the sheath thickness and can be used to monitor very small changes in plasma parameters. Three dimensional simulations are found to be in very good agreement with experiments.

  11. Virtual Cathodes near small electrodes biased near the plasma potential and its effects on Langmuir probes

    NASA Astrophysics Data System (ADS)

    Yip, Chi-Shung; Hershkowitz, Noah; Severn, Greg

    2015-09-01

    Movable small (3cm x 3.8cm) plates biased near the plasma potential are immersed in a filament discharge in a multi-dipole chamber. The plates are small (Aplate /Achamber < (me/Mi)1/2 such that an electron sheath is possible. Plasma potential and IVDF's near the plate are measured, and virtual cathodes, a double layer consists of an ion sheath and an electron sheath, was found to form. Ion velocities are determined by Laser-Induced Florescence, the electron temperature and electron density are measured by a planar Langmuir probe and the plasma potential is measured by an emissive probe. Effects of the virtual cathode on Langmuir probe I-V characteristics were predicted through estimating the current collection of an electrode in the presence of the virtual cathode, and was experimentally investigated by comparing I-V characteristics of the small plate and a 0.6cm diameter Langmuir probe. This work is supported by U.S. DOE under the Grant and Contract No. DE-FG02-97ER54437.

  12. NOx removal using a wet type plasma reactor based on a three-electrode device

    NASA Astrophysics Data System (ADS)

    Jolibois, J.; Takashima, K.; Mizuno, A.

    2011-06-01

    In this paper, a wet type plasma reactor based on a three electrode device is investigated experimentally in order to remove NO and NOx at low flow rate. First, a comparison of cleaning performances of gas exhaust has been performed when the surface discharge operates in DBD or SD modes. From these previous results, the second part of study has consisted to improve the electrochemical conversion of the wet type plasma reactor by adding a coil between the AC HV power supply and the surface discharge. The parametric study has been performed with 100 ppm of NO content in gas flow at room temperature and atmospheric pressure for a flow rate of 1 L/min. For each electrical parameter tested, an electric characterization and measurement of NOx content via FT-IR has been conducted. The results highlight a better cleaning of gas exhaust when the surface discharge operates in DBD mode. Moreover, the presence of solution promotes the arc transition when the operating mode is SD, resulting a reliability reduction of plasma device. In addition, the measurements show that the insertion of coil in the electrical circuit improves the NOx removal at a given power consumption for the DBD operating mode.

  13. Spatially-Selective Membrane Permeabilization Induced by Cell-Solution Electrode Atmospheric Pressure Plasma Irradiation

    NASA Astrophysics Data System (ADS)

    Sasaki, Shota; Hokari, Yutaro; Kanzaki, Makoto; Kaneko, Toshiro

    2015-09-01

    Gene transfection, which is the process of deliberately introducing nucleic acids into cells, is expected to play an important role in medical treatment because the process is necessary for gene therapy and creation of induced pluripotent stem (iPS) cells. However, the conventional transfection methods have some problems, so we focus attention on promising transfection methods by atmospheric pressure plasma (APP). We have previously reported that the cell membrane permeability, which is closely related with gene transfection, is improved using a cell-solution electrode for generating He-APP. He-APP is irradiated to the solution containing the adherent cells and delivery materials such as fluorescent dyes (YOYO-1) and plasmid DNA (GFP). In case of YOYO-1 delivery, more than 80% of cells can be transferred only in the plasma-irradiated area and the spatially-selective membrane permeabilization is realized by the plasma irradiation. In addition, it is confirmed that plasmid DNA is transfected and the GFP genes are expressed using same APP irradiation system with no obvious cellular damage.

  14. Quantification of ethanol in plasma by electrochemical detection with an unmodified screen printed carbon electrode

    PubMed Central

    Tian, Gang; Zhang, Xiao-Qing; Zhu, Ming-Song; Zhang, Zhong; Shi, Zheng-Hu; Ding, Min

    2016-01-01

    Simple, rapid and accurate detection of ethanol concentration in blood is very crucial in the diagnosis and management of potential acute ethanol intoxication patients. A novel electrochemical detection method was developed for the quantification of ethanol in human plasma with disposable unmodified screen-printed carbon electrode (SPCE) without sample preparation procedure. Ethanol was detected indirectly by the reaction product of ethanol dehydrogenase (ADH) and cofactor nicotinamide adenine dinucleotide (NAD+). Method validation indicated good quantitation precisions with intra-day and inter-day relative standard deviations of ≤9.4% and 8.0%, respectively. Ethanol concentration in plasma is linear ranging from 0.10 to 3.20 mg/mL, and the detection limit is 40.0 μg/mL (S/N > 3). The method shows satisfactory correlation with the reference method of headspace gas chromatography in twenty human plasma samples (correlation coefficient 0.9311). The proposed method could be applied to diagnose acute ethanol toxicity or ethanol-related death. PMID:27006081

  15. Method of forming a leak proof plasma sprayed interconnection layer on an electrode of an electrochemical cell

    DOEpatents

    Kuo, L.J.H.; Vora, S.D.

    1995-02-21

    A dense, substantially gas-tight, electrically conductive interconnection layer is formed on an electrode structure of an electrochemical cell by: (A) providing an electrode structure; (B) forming on a selected portion of the electrode surface, an interconnection layer having the general formula La{sub 1{minus}x}M{sub x}Cr{sub 1{minus}y}N{sub y}O{sub 3}, where M is a dopant selected from the group of Ca, Sr, Ba, and mixtures thereof, and where N is a dopant selected from the group of Mg, Co, Ni, Al, and mixtures thereof, and where x and y are each independently about 0.075--0.25, by thermally spraying, preferably plasma arc spraying, a flux added interconnection spray powder, preferably agglomerated, the flux added powder comprising flux particles, preferably including dopant, preferably (CaO){sub 12}(Al{sub 2}O{sub 3}){sub 7} flux particles including Ca and Al dopant, and LaCrO{sub 3} interconnection particles, preferably undoped LaCrO{sub 3}, to form a dense and substantially gas-tight interconnection material bonded to the electrode structure by a single plasma spraying step; and (C) heat treating the interconnection layer at from about 1,200 to 1,350 C to further densify and heal the micro-cracks and macro-cracks of the thermally sprayed interconnection layer. The result is a substantially gas-tight, highly doped, electrically conductive interconnection material bonded to the electrode structure. The electrode structure can be an air electrode, and a solid electrolyte layer can be applied to the unselected portion of the air electrode, and further a fuel electrode can be applied to the solid electrolyte, to form an electrochemical cell for generation of electrical power. 4 figs.

  16. Method of forming a leak proof plasma sprayed interconnection layer on an electrode of an electrochemical cell

    DOEpatents

    Kuo, Lewis J. H.; Vora, Shailesh D.

    1995-01-01

    A dense, substantially gas-tight, electrically conductive interconnection layer is formed on an electrode structure of an electrochemical cell by: (A) providing an electrode structure; (B) forming on a selected portion of the electrode surface, an interconnection layer having the general formula La.sub.1-x M.sub.x Cr.sub.1-y N.sub.y O.sub.3, where M is a dopant selected from the group of Ca, Sr, Ba, and mixtures thereof, and where N is a dopant selected from the group of Mg, Co, Ni, Al, and mixtures thereof, and where x and y are each independently about 0.075-0.25, by thermally spraying, preferably plasma arc spraying, a flux added interconnection spray powder, preferably agglomerated, the flux added powder comprising flux particles, preferably including dopant, preferably (CaO).sub.12. (Al.sub.2 O.sub.3).sub.7 flux particles including Ca and Al dopant, and LaCrO.sub.3 interconnection particles, preferably undoped LaCrO.sub.3, to form a dense and substantially gas-tight interconnection material bonded to the electrode structure by a single plasma spraying step; and, (C) heat treating the interconnection layer at from about 1200.degree. to 1350.degree. C. to further densify and heal the micro-cracks and macro-cracks of the thermally sprayed interconnection layer. The result is a substantially gas-tight, highly doped, electrically conductive interconnection material bonded to the electrode structure. The electrode structure can be an air electrode, and a solid electrolyte layer can be applied to the unselected portion of the air electrode, and further a fuel electrode can be applied to the solid electrolyte, to form an electrochemical cell for generation of electrical power.

  17. Sequences of nifX, nifW, nifZ, nifB and two ORF in the Frankia nitrogen fixation gene cluster.

    PubMed

    Harriott, O T; Hosted, T J; Benson, D R

    1995-08-01

    The actinomycete Frankia alni fixes N2 in root nodules of several non-leguminous plants. It is one of the few known N2-fixing members of the high-GC Gram+ lineage of prokaryotes. Thus, we have undertaken a study of its nitrogen fixation gene (nif) organization to compare with that of the more extensively characterized proteobacteria. A cosmid (pFN1) containing the nif region of Fa CpI1 was isolated from a cosmid library using the nifHDK genes of Fa CpI1 as a probe. A 4.5-kb BamHI fragment that mapped downstream from the previously characterized nifHDK genes was cloned and sequenced. Based on nt and aa sequence similarities to nif from other N2-fixing bacteria, eight ORF were identified and designated nifX, orf3, orf1, nifW, nifZ, nifB, orf2 and nifU. A region that hybridized to Rhizobium meliloti and Klebsiella pneumoniae nifA did not appear to contain a nifA-like gene. We have revised the map of the Fa nif region to reflect current information. PMID:7642138

  18. Thorium-Free Versus Thoriated Plasma Gun Electrodes: Statistical Evaluation of Coating Properties

    NASA Astrophysics Data System (ADS)

    Colmenares-Angulo, Jose; Molz, Ronald; Hawley, David; Seshadri, Ramachandran Chidambaram

    2016-04-01

    Industries throughout the world today have an increased awareness of environmental, health, and safety issues. This, together with recent Nuclear Regulatory Commission changes concerning source material (e.g., thorium) has added complexity in the supply chain of thoriated tungsten commonly used in plasma spray gun spares. In the interest of a safer and more sustainable work environment, Oerlikon Metco has developed thorium-free material solutions proven to have longer service life than conventional thoriated spares. This work reports on the effect, if any, caused by tungsten compositional changes and extended service life in coating properties. Microstructure, coating efficiency parameters, hardness, particle state, in situ coating stress, and ex situ modulus are evaluated over the service life duration of the nozzle, comparing coatings with thoriated and non-thoriated nozzles and electrodes with the same spray parameters.

  19. All-vanadium redox flow batteries with graphite felt electrodes treated by atmospheric pressure plasma jets

    NASA Astrophysics Data System (ADS)

    Chen, Jian-Zhang; Liao, Wei-Yang; Hsieh, Wen-Yen; Hsu, Cheng-Che; Chen, Yong-Song

    2015-01-01

    Graphite felts modified with atmospheric pressure plasma jets (APPJs) are applied as electrodes in an all-vanadium redox flow battery (VRFB). APPJ flow penetrates deeply into the graphite felt, improving significantly the wettability of the graphite felt inside out and, thereby, enhancing graphite fiber-electrolyte contact during battery operation. The energy efficiency of a VRFB was improved from 62% (untreated) to 76% (APPJ-treated with the scan mode) at a current density of 80 mA cm-2, an improvement of 22%. The efficiency improvement is attributed to the oxygen-containing groups and nitrogen doping introduced by N2 APPJs on the fiber surfaces of graphite felt, both of which enhance electrochemical reactivity.

  20. Dynamics of Fluctuations, Flows and Global Stability Under Electrode Biasing in a Linear Plasma Device

    NASA Astrophysics Data System (ADS)

    Desjardins, Tiffany

    2015-11-01

    Various bias electrodes have been inserted into the Helicon-Cathode (HelCat) device at the University of New Mexico, in order to affect intrinsic drift-wave turbulence and flows. The goal of the experiments was to suppress and effect the intrinsic turbulence and with detailed measurements, understand the changes that occur during biasing. The drift-mode in HelCat varies from coherent at low magnetic field (<1kG) to broad-band turbulent at high magnetic fields (>1kG). The first electrode consists of 6 concentric rings set in a ceramic substrate; these rings act as a boundary condition, sitting at the end of the plasma column 2-m away from the source. A negative bias has been found to have no effect on the fluctuations, but a positive bias (Vr>5Te) is required in order to suppress the drift-mode. Two molybdenum grids can also be inserted into the plasma and sit close to the source. Floating or grounding a grid results in suppressing the drift-mode of the system. A negative bias (>-5Te) is found to return the drift-mode, and it is possible to drive a once coherent mode into a broad-band turbulent one. From a bias voltage of -5Teplasma is found to be quiescent. A positive bias greater the 5Te is found to excite a new mode, which is identified as a parallel-driven Kelvin-Helmholtz mode. At high positive bias, Vg>10Te, a new large-scale global mode is excited. This mode exhibits fluctuations in the ion saturation current, as well as in the potential, with a magnitude >50%. This mode has been identified as the potential relaxation instability (PRI). In order to better understand the modes and changes observed in the plasma, a linear stability code, LSS, was employed. As well, a 1D3V-PIC code utilizing Braginskii's equations was also utilized to understand the high-bias instability.

  1. Progress towards polar-drive ignition for the NIF

    NASA Astrophysics Data System (ADS)

    McCrory, R. L.; Betti, R.; Boehly, T. R.; Casey, D. T.; Collins, T. J. B.; Craxton, R. S.; Delettrez, J. A.; Edgell, D. H.; Epstein, R.; Frenje, J. A.; Froula, D. H.; Gatu-Johnson, M.; Glebov, V. Yu.; Goncharov, V. N.; Harding, D. R.; Hohenberger, M.; Hu, S. X.; Igumenshchev, I. V.; Kessler, T. J.; Knauer, J. P.; Li, C. K.; Marozas, J. A.; Marshall, F. J.; McKenty, P. W.; Meyerhofer, D. D.; Michel, D. T.; Myatt, J. F.; Nilson, P. M.; Padalino, S. J.; Petrasso, R. D.; Radha, P. B.; Regan, S. P.; Sangster, T. C.; Séguin, F. H.; Seka, W.; Short, R. W.; Shvydky, A.; Skupsky, S.; Soures, J. M.; Stoeckl, C.; Theobald, W.; Yaakobi, B.; Zuegel, J. D.

    2013-11-01

    The University of Rochester's Laboratory for Laser Energetics (LLE) performs direct-drive inertial confinement fusion (ICF) research. LLE's Omega Laser Facility is used to study direct-drive ICF ignition concepts, developing an understanding of the underlying physics that feeds into the design of ignition targets for the National Ignition Facility (NIF). The baseline symmetric-illumination, direct-drive-ignition target design consists of a 1.5 MJ multiple-picket laser pulse that generates four shock waves (similar to the NIF baseline indirect-drive design) and is predicted to produce a one-dimensional (1D) gain of 48. LLE has developed the polar-drive (PD) illumination concept (for NIF beams in the x-ray-drive configuration) to allow the pursuit of direct-drive ignition without significant reconfiguration of the beam paths on the NIF. Some less-invasive changes in the NIF infrastructure will be required, including new phase plates, polarization rotators, and a PD-specific beam-smoothing front end. A suite of PD ignition designs with implosion velocities from 3.5 to 4.3 × 107 cm s-1 are predicted to have significant 2D gains (Collins et al 2012 Bull. Am. Phys. Soc. 57 155). Verification of the physics basis of these simulations is a major thrust of direct-drive implosion experiments on both OMEGA and the NIF. Many physics issues are being examined with symmetric beam irradiation on OMEGA, varying the implosion parameters over a wide region of design space. Cryogenic deuterium-tritium target experiments with symmetric irradiation have produced areal densities of ˜0.3 g cm-2, ion temperatures over 3 keV, and neutron yields in excess of 20% of the ‘clean’ 1D predicted value. The inferred Lawson criterion figure of merit (Betti R. et al 2010 Phys. Plasmas 17 058102) has increased from 1.7 atm s (IAEA 2010) to 2.6 atm s.

  2. Modeling of gas flow in the cylindrical channels of high-voltage plasma torches with rod electrodes

    NASA Astrophysics Data System (ADS)

    Borovskoy, A. M.; Popov, S. D.; Surov, A. V.

    2013-08-01

    The article is devoted to the calculation of gas dynamic parameters of gas flow in various areas of low-temperature plasma generator, therefore, target area's grid was built for the simulation of plasma gas flow in channels of studied high-voltage AC plasma torches and calculations of three-dimensional gas flow was made using GAMBIT and FLUENT soft-ware and Spalart-Allmares turbulence model, air flow was simulated in the tangential feed's areas, in the cylindrical channel, in the tapering nozzle chamber and in the mixing chamber of plasma torches and outside (in the environment); thus, 3D-modelling of the cold plasma-forming gas flow was performed in cylindrical channels of studied high-voltage AC plasma torches with rod electrodes for the first time.

  3. Collection of Solid Debris on NIF for Radiochemical Diagnostics and Measurements

    SciTech Connect

    Shaughnessy, D A

    2009-02-23

    A system for collecting solid, post-explosion debris samples from the NIF chamber and their subsequent radiochemical analysis is currently under development. If the debris that condenses out of the plasma can be collected and analyzed, the number and type of nuclear reactions that occurred in the capsule material can be determined. this has applications both for radiochemical diagnostics of NIF capsule performance as well as radiochemical measurements relevant to basic science and stockpile stewardship. Several design prototypes have been studied and a prioritized list of radiochemical measurements that could be performed on NIF is under development based on interactions with capsule design, fabrication, and WCI design divisions.

  4. Plans for Double Shell Experiments on NIF

    NASA Astrophysics Data System (ADS)

    Montgomery, D. S.; Daughton, W. S.; Gunderson, M. A.; Simakov, A. N.; Wilson, D. C.; Watt, R. G.; Kline, J. L.; Hayes, A. C.; Herrmann, H. W.; Boswell, M.; Danly, C. R.; Merrill, F. E.; Batha, S. H.; Amendt, P. A.; Milovich, J. L.; Robey, H. F.

    2015-11-01

    Double-shells are an alternative approach to achieving indirect drive ignition. These targets consist of a low-Z ablatively-driven outer shell that impacts a high-Z inner shell filled with DT fuel. In contrast to single-shell designs, double-shell targets burn the fuel via volume ignition, albeit with a lower gain. While double-shell capsules are complicated to fabricate, their design includes several beneficial metrics such as a low convergence pusher (C.R. < 10), low implosion speed (~ 250 km/s), a simple few-ns laser drive in a vacuum hohlraum, less sensitivity to hohlraum asymmetries, and low expected laser-plasma instabilities. We present preliminary double-shell capsule designs for NIF using a cryogenic gas DT fill which are optimized for yield and minimized for fall-line mix. Challenges will be discussed, as well as uncertainties and trade-offs in the physics issues compared to single-shells. A development path for double-shell experiments on NIF will be presented. Work performed under the auspices of DOE by LANL under contract DE-AC52-06NA25396.

  5. Improvement of Dielectric Barrier Discharge Plasma Reactor for Ozone Generation by Electrode Shape

    NASA Astrophysics Data System (ADS)

    Shimizu, Masaki; Sato, Tohru; Kato, Shoji; Mukaigawa, Seiji; Takaki, Koichi; Fujiwara, Tamiya

    An effect of electrode shape on ozone generation in dielectric barrier discharge reactor is described in this article. Three different shape electrodes were employed as ground electrodes. A plane electrode is 6 cm in width, and 20 cm in length. A trench electrode has large number of knife-edge rails. A multipoint electrode has large number of four-sided pyramid projections on the plane. A high voltage plane electrode is covered with 0.5 mm thickness alumina layer worked as dielectric barrier. The experimental results show that the breakdown for the multipoint electrode occurs at 7.0 kVpp. This value is lower than 8.4 kVpp that is the breakdown voltage of the plane electrode. The ozone yield increases from 80 g/kWh to 130 g/kWh by changing the electrode shape from the plane to the multipoint. The ozone generation efficiency decreased with increase of the ozone concentration.

  6. Design, fabrication, and characterization of a 2.3 kJ plasma focus of negative inner electrode

    SciTech Connect

    Mathuthu, M.; Zengeni, T.G.; Gholap, A.V.

    1997-03-01

    The design, fabrication, and characterization of a 2.3 kJ plasma focus device with negative inner electrode are discussed. The purpose of the design was to initiate research in and study of plasma dynamics, nuclear reactions, and neutron emission mechanisms at the university. Also the device will be used to teach and demonstrate plasma phenomena at the postgraduate level and to perform experiments with inverted polarity to examine different operating regimes with nonstandard gases. It is hoped that in the long run the research work will help find a solution to the polarity riddle of plasma focus devices. When the system was operated with spectrographic argon as the filling gas, the best focus was obtained at a pressure range of 0.1{endash}1.25 Torr. With nitrogen as the filling gas, the best focus was obtained at pressures between 0.1 and 1.25 Torr. Air gave the best focus at a pressure range of 0.5{endash}1.5 Torr. The observed good focus action is attributed to the small inner electrode length (this reduces the amount of anode material ablated into the current sheath) and tapering of the inner electrode. Positive {ital z}-directed electrons contribute to the temperature and further ionization of the plasma gas during focusing. The performance of the device compares quite well with other known devices. {copyright} {ital 1997 American Institute of Physics.}

  7. Determination of salbutamol in human plasma and urine by high-performance liquid chromatography with a coulometric electrode array system.

    PubMed

    Zhang, X Z; Gan, Y R; Zhao, F N

    2004-01-01

    A method is developed to determine salbutamol in human plasma and urine using high-performance liquid chromatography (HPLC) with a coulometric electrode array system, based on the electrochemical behavior of salbutamol at graphite electrode. The mobile phase component A is 30 mM sodium dihydroxy phosphate-30 mM triethylamine and is adjusted to pH 6.0 with 20% phosphate acid. The mobile phase component B is methanol. The optimized mobile phase composition was A and B in the proportion of 90:10 (v/v). Paracetamol is selected as the external standard. The human plasma and urine samples are pretreated using solid-phase extraction cartridges (Sep-Pak Silica), and the eluting solution is monitored by the coulometric electrode array system. The electrode potentials are set at 300, 400, 550, and 650 mV, respectively. Calibration curves show good linearity, and the recovery of salbutamol proves to be constant and unaffected by the concentration of the drug. This method, developed using HPLC-electrochemical detection, is reproducible and sensitive enough for the determination of salbutamol in human plasma and urine. PMID:15189600

  8. NIF featured on BBC "Horizon"

    ScienceCinema

    Brian Cox

    2010-09-01

    The National Ignition Facility, the world's largest laser system, located at Lawrence Livermore National Laboratory, was featured in the BBC broadcast "Horizon" hosted by physicist Brian Cox. Here is the NIF portion of the program, which was entitled "Can We Make A Star On Earth?" This video is used with the express permission of the BBC.

  9. NIF Project Management System Description

    SciTech Connect

    Wolfe, C.R.

    1997-08-01

    This document has been prepared for two purposes: 1. To demonstrate compliance with the project management requirements of DOE Order 430. 1, Life-Cycle Asset Management (LCAM). 2. To summarize in one place the approved Project documents which, taken as a whole, describe the NIF Project Management System.

  10. NIF featured on BBC "Horizon"

    SciTech Connect

    Brian Cox

    2010-01-12

    The National Ignition Facility, the world's largest laser system, located at Lawrence Livermore National Laboratory, was featured in the BBC broadcast "Horizon" hosted by physicist Brian Cox. Here is the NIF portion of the program, which was entitled "Can We Make A Star On Earth?" This video is used with the express permission of the BBC.

  11. Post-plasma treatment of a carbon nanowall for use as a counter electrode in a dye-sensitized solar cell

    NASA Astrophysics Data System (ADS)

    Jung, Yong Ho; Choi, Won Seok; Hong, Byungyou

    2014-08-01

    This research investigates plasma-treated carbon nanowalls (CNW) for use as counter electrodes in dye-sensitized solar cells (DSSCs). The CNWs were synthesized on a fluorine-tin-oxide (FTO) glass substrate via microwave plasma-enhanced chemical vapor-deposition (PECVD) using CH4 gas. Then, post-plasma treatments were performed on the CNWs in different plasma environments (using O2, H2 and N2 gas) under the same conditions, after which DSSCs were fabricated using the plasma-treated CNWs as counter electrodes. Scanning electron microscopy (SEM) was performed to obtain cross-sectional and planar images of the CNWs, and Raman spectroscopy was used to analyze the structural characteristics of the post-plasma-treated synthesized CNWs. The energy conversion efficiency was then used to analyze the effect of using the plasma-treated CNWs as counter electrodes in the DSSCs. The DSSC for which the as-deposited CNW was used as a counter electrode showed an energy conversion efficiency of 1.64%, and the DSSC with the H2 postplasma-treated CNW counter electrode showed an energy conversion efficiency of 2.23%. Thus, the DSSC with the H2-treated electrode presented a 36% higher efficiency than the DSSC with the as-deposited CNW electrode.

  12. NIF Laser Line Replaceable Units (LRUs)

    SciTech Connect

    Larson, D W

    2003-12-19

    The National Ignition Facility (NIF) is designed with its high value optical systems in cassettes called Line Replaceable Units (LRUs). Virtually all of the NIF's active components are assembled in one of the {approx}4000 electrical and optical LRUs that serve between two and eight of NIF's 192 laser beam lines. Many of these LRUs are optomechanical assemblies that are roughly the size of a telephone booth. The primary design challenges for this hardware include meeting stringent mechanical precision, stability and cleanliness requirements. Pre-production units of each LRU type have been fielded on the first bundle of NIF and used to demonstrate that NIF meets its performance objectives. This presentation provides an overview of the NIF LRUs, their design and production plans for building out the remaining NIF bundles.

  13. DNA sequence and genetic analysis of the Rhodobacter capsulatus nifENX gene region: homology between NifX and NifB suggests involvement of NifX in processing of the iron-molybdenum cofactor.

    PubMed

    Moreno-Vivian, C; Schmehl, M; Masepohl, B; Arnold, W; Klipp, W

    1989-04-01

    Rhodobacter capsulatus genes homologous to Klebsiella pneumoniae nifE, nifN and nifX were identified by DNA sequence analysis of a 4282 bp fragment of nif region A. Four open reading frames coding for a 51,188 (NifE), a 49,459 (NifN), a 17,459 (NifX) and a 17,472 (ORF4) dalton protein were detected. A typical NifA activated consensus promoter and two imperfect putative NifA binding sites were located in the 377 bp sequence in front of the nifE coding region. Comparison of the deduced amino acid sequences of R. capsulatus NifE and NifN revealed homologies not only to analogous gene products of other organisms but also to the alpha and beta subunits of the nitrogenase iron-molybdenum protein. In addition, the R. capsulatus nifE and nifN proteins shared considerable homology with each other. The map position of nifX downstream of nifEN corresponded in R. capsulatus and K. pneumoniae and the deduced molecular weights of both proteins were nearly identical. Nevertheless, R. capsulatus NifX was more related to the C-terminal end of NifY from K. pneumoniae than to NifX. A small domain of approximately 33 amino acid residues showing the highest degree of homology between NifY and NifX was also present in all nifB proteins analyzed so far. This homology indicated an evolutionary relationship of nifX, nifY and nifB and also suggested that NifX and NifY might play a role in maturation and/or stability of the iron-molybdenum cofactor. The open reading frame (ORF4) downstream of nifX in R. capsulatus is also present in Azotobacter vinelandii but not in K. pneumoniae.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2747620

  14. DC non-thermal atmospheric-pressure plasma jet generated using a syringe needle electrode

    NASA Astrophysics Data System (ADS)

    Matra, Khanit

    2016-07-01

    Non-thermal plasma jet was generated by applying a dc source voltage between the syringe needle anode with flowing Argon gas and a planar or a hollow copper cathode in an atmospheric-pressure environment. The two operating discharge modes, which were self-pulsing and a continuous discharge mode, these were mainly controlled by the limitations of the current flowing in the discharge circuit. A ballast resistor was an important factor in affecting the limitations of the operating discharge mode. The gas breakdown was initially generated in the self-pulsing discharge mode at the source voltage of 1.2 kV. This was slightly higher than the breakdown voltage at the experimental condition of 1 lpm of Argon and a 1 mm electrode gap distance. The peak self-pulsing discharge currents were up to 15–20 A with a self-pulsing frequency in the range of 10–20 kHz. The continuous discharge mode could be observed at the higher source voltage with the continuous discharge current within the range of a few milliamperes.

  15. Numerically controlled atmospheric-pressure plasma sacrificial oxidation using electrode arrays for improving silicon-on-insulator layer uniformity

    NASA Astrophysics Data System (ADS)

    Takei, Hiroyasu; Yoshinaga, Keinosuke; Matsuyama, Satoshi; Yamauchi, Kazuto; Sano, Yasuhisa

    2015-01-01

    Silicon-on-insulator (SOI) wafers are important semiconductor substrates in high-performance devices. In accordance with device miniaturization requirements, ultrathin and highly uniform top silicon layers (SOI layers) are required. A novel method involving numerically controlled (NC) atmospheric-pressure plasma sacrificial oxidation using an electrode array system was developed for the effective fabrication of an ultrathin SOI layer with extremely high uniformity. Spatial resolution and oxidation properties are the key factors controlling ultraprecision machining. The controllability of plasma oxidation and the oxidation properties of the resulting experimental electrode array system were examined. The results demonstrated that the method improved the thickness uniformity of the SOI layer over one-sixth of the area of an 8-in. wafer area.

  16. Investigation Of Plasma Discharges Within Maja-PF Device Operated With Tungsten Inserts In The Central Electrode

    SciTech Connect

    Malinowski, K.; Skladnik-Sadowska, E.; Jakubowski, L.; Sadowski, M. J.; Ladygina, M.

    2008-03-19

    The paper presents results of recent experimental studies with a MAJA-PF plasma-focus facility, as carried out for two different configurations of the end-plate of the central electrode. The main aim was to investigate an influence of the shape and material of the electrode end-plate on the formation and structure of the plasma column as well as to record and identify spectral lines of tungsten. The first version of the end-plate was made of Cu, while the second one had an insert made of a Cu-W alloy. Optical spectra were recorded by means of a Mechelle 900 spectrometer, operated with some delay in relation to a current peculiarity and with exposition times varied from 200 ns to 10 {mu}s. For shots with the Cu electrode spectral lines of deuterium (working gas) and carbon ions were recorded, but tungsten lines were not identified. It was estimated that the electron concentration changed from (8 divide 10)x10{sup 17} cm{sup -3} to about 2x10{sup 17} cm{sup -3} in 5 {mu}s after the current dip. In experiments with the second electrode version, among numerous spectral lines there were identified distinct WI and WII lines. Estimates of the tungsten ion concentration were impossible because of close positions of other lines. Diagrams of changes in the electron density are of importance for applications of DPM streams.

  17. Disruption avoidance in the SINP-Tokamak by means of electrode-biasing at the plasma edge

    SciTech Connect

    Basu, Debjyoti; Pal, Rabindranath; Ghosh, Joydeep; Chattopadhyay, Prabal K.

    2013-05-15

    Control of plasma disruption by a biased edge electrode is reported in SINP-Tokamak. The features that characterize a plasma disruption are reduced with increasing bias potential. The disruption can be completely suppressed with the concomitant stabilization of observed MHD modes that are allegedly precursors of the disruption. An m = 3/n = 1 tearing mode, which apparently causes disruption can be stabilized when a negative biasing potential is applied near the edge. These changes in the disruptive behavior with edge biasing are hypothesized to be due to changes in the current density profile.

  18. Discharge characteristics of an atmospheric-pressure argon plasma column generated with a single-electrode configuration

    SciTech Connect

    Li Shouzhe; Huang Wentong; Zhang Jialiang; Wang Dezhen

    2009-07-15

    An atmospheric-pressure argon discharge plasma column is generated by making use of a single-electrode configuration with the power supply operating at a frequency of 45 kHz. It is observed that corona, glowlike plume, and filamentary discharges evolve individually with increasing applied voltage. It is in the filamentary state with average electron density of order 10{sup 12} cm{sup -3} that plasma column grows up in the tube with increasing applied voltage. Its discharge characteristics are determined by measuring electrical parameters (voltage, conduction current, and average absorbed power) and optical emission spectroscopy.

  19. Evaluation and Optimization of Electrode Configuration of Multi-Channel Corona Discharge Plasma for Dye-Containing Wastewater Treatment

    NASA Astrophysics Data System (ADS)

    Ren, Jingyu; Wang, Tiecheng; Qu, Guangzhou; Liang, Dongli; Hu, Shibin

    2015-12-01

    A discharge plasma reactor with a point-to-plane structure was widely studied experimentally in wastewater treatment. In order to improve the utilization efficiency of active species and the energy efficiency of this kind of discharge plasma reactor during wastewater treatment, the electrode configuration of the point-to-plane corona discharge reactor was studied by evaluating the effects of discharge spacing and adjacent point distance on discharge power and discharge energy density, and then dye-containing wastewater decoloration experiments were conducted on the basis of the optimum electrode configuration. The experimental results of the discharge characteristics showed that high discharge power and discharge energy density were achieved when the ratio of discharge spacing to adjacent point distance (d/s) was 0.5. Reactive Brilliant Blue (RBB) wastewater treatment experiments presented that the highest RBB decoloration efficiency was observed at d/s of 0.5, which was consistent with the result obtained in the discharge characteristics experiments. In addition, the biodegradability of RBB wastewater was enhanced greatly after discharge plasma treatment under the optimum electrode configuration. RBB degradation processes were analyzed by GC-MS and IC, and the possible mechanism for RBB decoloration was also discussed. supported by China's Postdoctoral Science Foundation (No. 2014M562460), the Initiative Funding Programs for Doctoral Research of Northwest A&F University (No. 2013BSJJ121), and National Natural Science Foundation of China (No. 21107085)

  20. Status of the NIF Project

    SciTech Connect

    Moses, E

    2007-04-30

    Ground was broken for the National Ignition Facility, a stadium-sized complex, in 1997. When complete, the project will contain a 192-beam, 1.8-megajoule, 500-terawatt laser system adjoining a 10-meter-diameter target chamber with room for nearly 100 experimental diagnostics. NIF's beams will compress and heat small capsules containing a mixture of hydrogen isotopes of deuterium and tritium. These targets will undergo nuclear fusion, producing more energy than the energy in the laser pulse and achieving scientific breakeven. NIF experiments will allow scientists to study physical processes at temperatures approaching 100 million degrees Kelvin and 100 billion times atmospheric pressure--conditions that exist naturally only in the interior of stars and in nuclear weapon detonations.

  1. NIF Title III engineering plan

    SciTech Connect

    Deis, G

    1998-06-01

    The purpose of this document is to define the work that must be accomplished by the NIF Project during Title III Engineering. This definition is intended to be sufficiently detailed to provide a framework for yearly planning, to clearly identify the specific deliverables so that the Project teams can focus on them, and to provide a common set of objectives and processes across the Project. This plan has been preceded by similar documents for Title I and Title II design and complements the Site Management Plan, the Project Control Manual, the Quality Assurance Program Plan, the RM Parsons NIF Title III Configuration Control Plan, the Integrated Project Schedule, the Preliminary Safety Analysis Report, the Configuration Management Plan, and the Transition Plan.

  2. Posttranscriptional control of Klebsiella pneumoniae nif mRNA stability by the nifL product.

    PubMed Central

    Collins, J J; Roberts, G P; Brill, W J

    1986-01-01

    Posttranscriptional control of nif mRNA stability was demonstrated by functional and chemical analyses, using specific probes for four nif transcripts. In the wild type, nif transcripts (except nifLA) were stable during derepression, with half-lives of approximately 30 min. They were dramatically destabilized by O2 or elevated temperature (41 degrees C) and to a lesser extent by NH4+. In contrast, the nifLA message was not particularly stable, and posttranscriptional control was not evident. In NifL- strains, both forms of analysis indicated that the nifL product was involved in nif mRNA destabilization in the presence of O2 and NH4+. PMID:2428807

  3. Characterization of Pb(Zr, Ti)O3 thin films fabricated by plasma enhanced chemical vapor deposition on Ir-based electrodes

    NASA Astrophysics Data System (ADS)

    Lee, Hee-Chul; Lee, Won-Jong

    2002-11-01

    Structural and electrical characteristics of Pb(Zr, Ti)O3 (PZT) ferroelectric thin films deposited on various Ir-based electrodes (Ir, IrO2, and Pt/IrO2) using electron cyclotron resonance plasma enhanced chemical vapor deposition were investigated. On the Ir electrode, stoichiometric PZT films with pure perovskite phase could be obtained over a very wide range of processing conditions. However, PZT films prepared on the IrO2 electrode contain a large amount of PbOx phases and exhibited high Pb-excess composition. The deposition characteristics were dependent on the behavior of PbO molecules on the electrode surface. The PZT thin film capacitors prepared on the Ir bottom electrode showed different electrical properties depending on top electrode materials. The PZT capacitors with Ir, IrO2, and Pt top electrodes showed good leakage current characteristics, whereas those with the Ru top electrode showed a very high leakage current density. The PZT capacitor exhibited the best fatigue endurance with an IrO2 top electrode. An Ir top electrode provided better fatigue endurance than a Pt top electrode. The PZT capacitor with an Ir-based electrode is thought to be attractive for the application to ferroelectric random access memory devices because of its wide processing window for a high-quality ferroelectric film and good polarization, fatigue, and leakage current characteristics.

  4. National Ignition Facility (NIF) operations procedures plan

    SciTech Connect

    Mantrom, D.

    1998-05-06

    The purpose of this Operations Procedures Plan is to establish a standard procedure which outlines how NIF Operations procedures will be developed (i.e , written, edited, reviewed, approved, published, revised) and accessed by the NIF Operations staff who must use procedures in order to accomplish their tasks. In addition, this Plan is designed to provide a guide to the NIF Project staff to assist them in planning and writing procedures. Also, resource and scheduling information is provided.

  5. Assembling and Installing LRUs for NIF

    SciTech Connect

    Bonanno, R E

    2003-12-31

    Within the 192 National Ignition Facility (NIF) beamlines, there are over 7000 large (40 x 40 cm) optical components, including laser glass, mirrors, lenses, and polarizers. These optics are held in large opto-mechanical assemblies called line-replaceable units (LRUs). Each LRU has strict specifications with respect to cleanliness, alignment, and wavefront so that once activated, each NIF beamline will meet its performance requirements. NIF LRUs are assembled, tested, and refurbished in on-site cleanroom facilities. The assembled LRUs weigh up to 1800 kilograms, and are about the size of a phone booth. They are transported in portable clean canisters and inserted into the NIF beampath using robotic transporters. This plug and play design allows LRUs to be easily removed from the beampath for maintenance or upgrades. Commissioning of the first NIF quad, an activity known as NIF Early Light (NEL), has validated LRU designs and architecture, as well as demonstrated that LRUs can be assembled and installed as designed. Furthermore, it has served to develop key processes and tools forming the foundation for NIF s long-term LRU production and maintenance strategy. As we look forward to building out the rest of NIF, the challenge lies in scaling up the production rate while maintaining quality, implementing process improvements, and fully leveraging the learning and experience gained from NEL. This paper provides an overview of the facilities, equipment and processes used to assemble and install LRUs in NIF.

  6. Experimental investigation of cathode spots and plasma jets behavior subjected to two kinds of axial magnetic field electrodes

    NASA Astrophysics Data System (ADS)

    Wang, Lijun; Deng, Jie; Zhou, Xin; Jia, Shenli; Qian, Zhonghao; Shi, Zongqian

    2016-04-01

    In this paper, cathode spot plasma jet (CSPJ) rotation and cathode spots behavior subjected to two kinds of large diameter axial magnetic field (AMF) electrode (cup-shaped and coil-shaped) are studied and analyzed based on experiments. The influence of gap distances on the CSPJ rotational behavior is analyzed. Experimental results show that CSPJ rotational phenomena extensively exist in the vacuum interrupters, and CSPJ rotational direction is along the direction of composite magnetic field (mainly the combination of the axial and azimuthal components). For coil-shaped and cup-shaped AMF electrodes, the rotational or inclination phenomena before the current peak value are much more significant than that after current peak value (for the same arc current), which is related to the larger ratio of azimuthal magnetic field Bt and AMF Bz (Bt/Bz). With the increase of the gap distance, the AMF strength decreases, when the arc current is kept as constant, the azimuthal magnetic field is kept invariable, the ratio between azimuthal magnetic field and AMF is increased, which results in the increase of rotational effect. For cathode spots motion, compared with cup-shaped electrode, coil-shaped electrode has the inverse AMF direction. The Robson drift direction of cathode spots of coil-shaped electrode is opposite to that of cup-shaped electrode. With the increase of gap distance, the Robson angle is decreased, which is associated with the reduced AMF strength. Erosion imprints of anode and cathode are also related to the CSPJ rotational phenomena and cathode spots behavior. The noise of arc voltage in the initial arcing stage is related to the weaker AMF.

  7. 13.56 MHz radio frequency plasma properties on hemispheric electrodes and diamond-like carbon films deposition on three-dimensional polyurethane diaphragms

    SciTech Connect

    Ohgoe, Yasuharu; Hirakuri, Kenji K.

    2004-09-01

    The characteristics of the radio frequency (rf) plasma that could hold an entire hemispheric polyurethane diaphragm generated using the hemispheric-type electrode were investigated. The plasma states were measured using Langmuir probe. Although the common rf plasma chemical vapor deposition technique using planar electrodes makes it difficult to apply uniform plasma to three-dimensional structures, the hemispheric-type electrode process could uniformly hold a hemispheric polyurethane diaphragm at self-bias voltage. As a result, this process could uniformly keep the ion sheath on the diaphragm. In case of using this process for diamond-like carbon (DLC) film deposition, the DLC film was deposited uniformly on the diaphragm at approximately 300 nm. Besides electron temperatures and electron number of densities were similar to the behavior of common rf plasma. This means that the characteristics of plasma are kept in the same states even if the plasma form is controlled using such a hemispheric-type electrode. Based on these results, this hemispheric-type electrode process was observed to be quite applicable to three-dimensional insulator structures.

  8. Stark broadening measurement of the electron density in an atmospheric pressure argon plasma jet with double-power electrodes

    SciTech Connect

    Qian Muyang; Ren Chunsheng; Wang Dezhen; Zhang Jialiang; Wei Guodong

    2010-03-15

    Characteristics of a double-power electrode dielectric barrier discharge of an argon plasma jet generated at the atmospheric pressure are investigated in this paper. Time-averaged optical emission spectroscopy is used to measure the plasma parameters, of which the excitation electron temperature is determined by the Boltzmann's plot method whereas the gas temperature is estimated using a fiber thermometer. Furthermore, the Stark broadening of the hydrogen Balmer H{sub {beta}} line is applied to measure the electron density, and the simultaneous presence of comparable Doppler, van der Waals, and instrumental broadenings is discussed. Besides, properties of the jet discharge are also studied by electrical diagnosis. It has been found that the electron densities in this argon plasma jet are on the order of 10{sup 14} cm{sup -3}, and the excitation temperature, gas temperature, and electron density increase with the applied voltage. On the other hand, these parameters are inversely proportional to the argon gas flow rate.

  9. The effect of oxygen plasma ashing on the resistance of TiN bottom electrode for phase change memory

    NASA Astrophysics Data System (ADS)

    Dan, Gao; Bo, Liu; Ying, Li; Zhitang, Song; Wanchun, Ren; Juntao, Li; Zhen, Xu; Shilong, Lü; Nanfei, Zhu; Jiadong, Ren; Yipeng, Zhan; Hanming, Wu; Songlin, Feng

    2015-05-01

    Phase change memory (PCM) has been regarded as a promising candidate for the next generation of nonvolatile memory. To decrease the power required to reset the PCM cell, titanium nitride (TiN) is preferred to be used as the bottom electrode of PCM due to its low thermal and suitable electrical conductivity. However, during the manufacture of PCM cell in 40 nm process node, abnormally high and discrete distribution of the resistance of TiN bottom electrode was found, which might be induced by the surface oxidation of TiN bottom electrode during the photoresist ashing process by oxygen plasma. In this work, we have studied the oxidation of TiN and found that with the increasing oxygen plasma ashing time, the thickness of the TiO2 layer became thicker and the state of the TiO2 layer changed from amorphous to crystalline, respectively. The resistance of TiN electrode contact chain with 4-5 nm TiO2 layer was confirmed to be almost three-orders of magnitude higher than that of pure TiN electrode, which led to the failure issue of PCM cell. We efficiently removed the oxidation TiO2 layer by a chemical mechanical polishing (CMP) process, and we eventually recovered the resistance of TiN bottom electrode from 1 × 105 Ω/via back to 6 × 102 Ω/via and successfully achieved a uniform resistance distribution of the TiN bottom electrode. Project supported by the National Key Basic Research Program of China (Nos. 2010CB934300, 2013CBA01900, 2011CBA00607, 2011CB932804), the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDA09020402), the National Integrate Circuit Research Program of China (No. 2009ZX02023-003), the National Natural Science Foundation of China (Nos. 61176122, 61106001, 61261160500, 61376006), and the Science and Technology Council of Shanghai (Nos. 12nm0503701, 13DZ2295700, 12QA1403900, 13ZR1447200).

  10. Generation of large-scale, barrier-free diffuse plasmas in air at atmospheric pressure using array wire electrodes and nanosecond high-voltage pulses

    SciTech Connect

    Teng, Yun; Li, Lee Liu, Yun-Long; Liu, Lun; Liu, Minghai

    2014-10-15

    This paper introduces a method to generate large-scale diffuse plasmas by using a repetition nanosecond pulse generator and a parallel array wire-electrode configuration. We investigated barrier-free diffuse plasmas produced in the open air in parallel and cross-parallel array line-line electrode configurations. We found that, when the distance between the wire-electrode pair is small, the discharges were almost extinguished. Also, glow-like diffuse plasmas with little discharge weakening were obtained in an appropriate range of line-line distances and with a cathode-grounding cross-electrode configuration. As an example, we produced a large-scale, stable diffuse plasma with volumes as large as 18 × 15 × 15 cm{sup 3}, and this discharge region can be further expanded. Additionally, using optical and electrical measurements, we showed that the electron temperature was higher than the gas temperature, which was almost the same as room temperature. Also, an array of electrode configuration with more wire electrodes had helped to prevent the transition from diffuse discharge to arc discharge. Comparing the current waveforms of configurations with 1 cell and 9 cells, we found that adding cells significantly increased the conduction current and the electrical energy delivered in the electrode gaps.

  11. Generation of large-scale, barrier-free diffuse plasmas in air at atmospheric pressure using array wire electrodes and nanosecond high-voltage pulses

    NASA Astrophysics Data System (ADS)

    Teng, Yun; Li, Lee; Liu, Yun-Long; Liu, Lun; Liu, Minghai

    2014-10-01

    This paper introduces a method to generate large-scale diffuse plasmas by using a repetition nanosecond pulse generator and a parallel array wire-electrode configuration. We investigated barrier-free diffuse plasmas produced in the open air in parallel and cross-parallel array line-line electrode configurations. We found that, when the distance between the wire-electrode pair is small, the discharges were almost extinguished. Also, glow-like diffuse plasmas with little discharge weakening were obtained in an appropriate range of line-line distances and with a cathode-grounding cross-electrode configuration. As an example, we produced a large-scale, stable diffuse plasma with volumes as large as 18 × 15 × 15 cm3, and this discharge region can be further expanded. Additionally, using optical and electrical measurements, we showed that the electron temperature was higher than the gas temperature, which was almost the same as room temperature. Also, an array of electrode configuration with more wire electrodes had helped to prevent the transition from diffuse discharge to arc discharge. Comparing the current waveforms of configurations with 1 cell and 9 cells, we found that adding cells significantly increased the conduction current and the electrical energy delivered in the electrode gaps.

  12. Three-dimensional modeling of a negative ion source with a magnetic filter: impact of biasing the plasma electrode on the plasma asymmetry

    NASA Astrophysics Data System (ADS)

    Fubiani, G.; Boeuf, J. P.

    2015-10-01

    The effect on the plasma characteristics of biasing positively the plasma electrode (PE) in negative ion sources with a magnetic filter is analysed using a 3D particle-in-cell model with Monte-Carlo collisions (PIC-MCC). We specialize to the one driver (i.e. one inductively coupled radio-frequency discharge) BATMAN negative ion source and the 4-drivers (large volume) ELISE device. Both are ITER prototype high power tandem-type negative ion sources developed for the neutral beam injector (NBI) system. The plasma is generated in the driver and diffuses inside the second chamber which is magnetized. Asymmetric plasma profiles originate from the formation of an electric field transverse to the electron current flowing through the magnetic filter (Hall effect). The model shows that the importance of the asymmetry increases with the PE bias potential, i.e. with the electron flow from the driver to the extraction region and depends on the shape of the magnetic filter field. We find that although the plasma density and potential profiles may be more or less asymmetric depending on the filter field configuration, the electron current to the plasma grid is always strongly asymmetric.

  13. Studying Nuclear Astrophysics at NIF

    SciTech Connect

    Boyd, R; Bernstein, L; Brune, C

    2009-07-01

    The National Ignition Facility's primary goal is to generate fusion energy. But the starlike conditions that it creates will also enable NIF scientists to study astrophysically important nuclear reactions. When scientists at the stadium-sized National Ignition Facility attempt to initiate fusion next year, 192 powerful lasers will direct 1.2 MJ of light energy toward a two-mm-diameter pellet of deuterium ({sup 2}H, or D) and tritium ({sup 3}H, or T). Some of that material will be gaseous, but most will be in a frozen shell. The idea is to initiate 'inertial confinement fusion', in which the two hydrogen isotopes fuse to produce helium-4, a neutron, and 17.6 MeV of energy. The light energy will be delivered to the inside walls of a hohlraum, a heavy-metal, centimeter-sized cylinder that houses the pellet. The container's heated walls will produce x rays that impinge on the pellet and ablate its outer surface. The exiting particles push inward on the pellet and compresses the DT fuel. Ultimately a hot spot develops at the pellet's center, where fusion produces {sup 4}He nuclei that have sufficient energy to propagate outward, trigger successive reactions, and finally react the frozen shell. Ignition should last several tens of picoseconds and generate more than 10 MJ of energy and roughly 10{sup 19} neutrons. The temperature will exceed 10{sup 8} K and fuel will be compressed to a density of several hundred g/cm{sup 3}, both considerably greater than at the center of the Sun. The figure shows a cutaway view of NIF. The extreme conditions that will be produced there simulate those in nuclear weapons and inside stars. For that reason, the facility is an important part of the US stockpile stewardship program, designed to assess the nation's aging nuclear stockpile without doing nuclear tests. In this Quick Study we consider a third application of NIF - using the extraordinary conditions it will produce to perform experiments in basic science. We will focus on

  14. Open reading frame 5 (ORF5), encoding a ferredoxinlike protein, and nifQ are cotranscribed with nifE, nifN, nifX, and ORF4 in Rhodobacter capsulatus.

    PubMed

    Moreno-Vivian, C; Hennecke, S; Pühler, A; Klipp, W

    1989-05-01

    DNA sequence analysis of a 1,600-base-pair fragment located downstream of nifENX in nif region A of Rhodobacter capsulatus revealed two additional open reading frames (ORFs): ORF5, encoding a ferredoxinlike protein, and nifQ. The ferredoxinlike gene product contained two cysteine motifs, typical of ferredoxins coordinating two 4Fe-4S clusters, but the distance between these two motifs was unusual for low-molecular-weight ferredoxins. The R. capsulatus nifQ gene product shared a high degree of homology with Klebsiella pneumoniae and Azotobacter vinelandii NifQ, including a typical cysteine motif located in the C-terminal part. nifQ insertion mutants and also an ORF5-nifQ double deletion mutant showed normal diazotrophic growth only in the presence of high concentrations of molybdate. This demonstrated that the gene encoding the ferredoxinlike protein is not essential for nitrogen fixation. No NifA-activated consensus promoter could be found in the intergenic region between nifENX-ORF4 and ORF5-nifQ. Analyses of a nifQ-lacZYA fusion revealed that transcription of nifQ was initiated at a promoter in front of nifE. In contrast to other nitrogen-fixing organisms, R. capsulatus nifE, nifN, nifX, ORF4, ORF5, and nifQ were organized in one transcriptional unit. PMID:2708314

  15. Open reading frame 5 (ORF5), encoding a ferredoxinlike protein, and nifQ are cotranscribed with nifE, nifN, nifX, and ORF4 in Rhodobacter capsulatus.

    PubMed Central

    Moreno-Vivian, C; Hennecke, S; Pühler, A; Klipp, W

    1989-01-01

    DNA sequence analysis of a 1,600-base-pair fragment located downstream of nifENX in nif region A of Rhodobacter capsulatus revealed two additional open reading frames (ORFs): ORF5, encoding a ferredoxinlike protein, and nifQ. The ferredoxinlike gene product contained two cysteine motifs, typical of ferredoxins coordinating two 4Fe-4S clusters, but the distance between these two motifs was unusual for low-molecular-weight ferredoxins. The R. capsulatus nifQ gene product shared a high degree of homology with Klebsiella pneumoniae and Azotobacter vinelandii NifQ, including a typical cysteine motif located in the C-terminal part. nifQ insertion mutants and also an ORF5-nifQ double deletion mutant showed normal diazotrophic growth only in the presence of high concentrations of molybdate. This demonstrated that the gene encoding the ferredoxinlike protein is not essential for nitrogen fixation. No NifA-activated consensus promoter could be found in the intergenic region between nifENX-ORF4 and ORF5-nifQ. Analyses of a nifQ-lacZYA fusion revealed that transcription of nifQ was initiated at a promoter in front of nifE. In contrast to other nitrogen-fixing organisms, R. capsulatus nifE, nifN, nifX, ORF4, ORF5, and nifQ were organized in one transcriptional unit. PMID:2708314

  16. NIF Integrated Computer Controls System Description

    SciTech Connect

    VanArsdall, P.

    1998-01-26

    This System Description introduces the NIF Integrated Computer Control System (ICCS). The architecture is sufficiently abstract to allow the construction of many similar applications from a common framework. As discussed below, over twenty software applications derived from the framework comprise the NIF control system. This document lays the essential foundation for understanding the ICCS architecture. The NIF design effort is motivated by the magnitude of the task. Figure 1 shows a cut-away rendition of the coliseum-sized facility. The NIF requires integration of about 40,000 atypical control points, must be highly automated and robust, and will operate continuously around the clock. The control system coordinates several experimental cycles concurrently, each at different stages of completion. Furthermore, facilities such as the NIF represent major capital investments that will be operated, maintained, and upgraded for decades. The computers, control subsystems, and functionality must be relatively easy to extend or replace periodically with newer technology.

  17. Measurements and simulations of ion energy distributions at rf-biased substrate electrodes in high density plasma reactors

    NASA Astrophysics Data System (ADS)

    Edelberg, Erik Andrew

    In plasma etching and deposition processes, the energy distribution of ions incident onto the substrate strongly affects the surface reactions and film deposition and etching rates. A compact floating retarding-field ion energy analyzer and the accompanying electronics have been designed and built to measure the energy distribution of ions bombarding radio frequency (rf) biased electrodes in high-density, inductively coupled plasma (ICP) reactors. The analyzer was designed to be able to operate in the presence of several hundred volts of rf-bias and in the harsh conditions encountered in commercial high density plasma reactors. The operation and capabilities of the energy analyzer are demonstrated through ion energy distribution measurements conducted on a rf-biased electrostatic chuck in a high-density transformer coupled plasma (TCP) reactor. A Langmuir probe is used in conjunction with the ion energy analyzer to verify the accuracy of the analyzer measurements. The effects of plasma power, rf-bias power, gas composition, and ion mass on the ion energy distributions are demonstrated through Ar, Ne, Ar/Ne, O 2 and CF4/O2 discharges. In the operating range studied, the average ion energy increases linearly with increasing rf-bias while the ion flux remains constant indicating that independent control of ion flux and energy is achieved in the TCP reactor. Bimodal ion energy distributions resulting from ion energy modulation in the sheath were observed and multiple peaks in the IEDs measured in gas mixtures were identified as ions with different masses falling through the sheath. The magnitude and frequency of the rf-bias power applied to the substrate electrode determines the spatiotemporal variations of the sheath potentials and hence the energy distribution of the ions impinging upon the substrate. A self-consistent dynamic model of the sheath, capable of predicting ion energy distributions (IEDs) impinging on a rf-biased electrode, was developed. The model

  18. Laboratory astrophysical collisionless shock experiments on Omega and NIF

    NASA Astrophysics Data System (ADS)

    Park, Hye-Sook; Ross, J. S.; Huntington, C. M.; Fiuza, F.; Ryutov, D.; Casey, D.; Drake, R. P.; Fiksel, G.; Froula, D.; Gregori, G.; Kugland, N. L.; Kuranz, C.; Levy, M. C.; Li, C. K.; Meinecke, J.; Morita, T.; Petrasso, R.; Plechaty, C.; Remington, B.; Sakawa, Y.; Spitkovsky, A.; Takabe, H.; Zylstra, A. B.

    2016-03-01

    We are performing scaled astrophysics experiments on Omega and on NIF. Laser driven counter-streaming interpenetrating supersonic plasma flows can be studied to understand astrophysical electromagnetic plasma phenomena in a controlled laboratory setting. In our Omega experiments, the counter-streaming flow plasma state is measured using Thomson scattering diagnostics, demonstrating the plasma flows are indeed super-sonic and in the collisionless regime. We observe a surprising additional electron and ion heating from ion drag force in the double flow experiments that are attributed to the ion drag force and electrostatic instabilities. [1] A proton probe is used to image the electric and magnetic fields. We observe unexpected large, stable and reproducible electromagnetic field structures that arise in the counter-streaming flows [2]. The Biermann battery magnetic field generated near the target plane, advected along the flows, and recompressed near the midplane explains the cause of such self-organizing field structures [3]. A D3He implosion proton probe image showed very clear filamentary structures; three-dimensional Particle-In-Cell simulations and simulated proton radiography images indicate that these filamentary structures are generated by Weibel instabilities and that the magnetization level (ratio of magnetic energy over kinetic energy in the system) is ∼0.01 [4]. These findings have very high astrophysical relevance and significant implications. We expect to observe true collisionless shock formation when we use >100 kJ laser energy on NIF.

  19. Acetylene-argon plasmas measured at a biased substrate electrode for diamond-like carbon deposition: I. Mass spectrometry

    NASA Astrophysics Data System (ADS)

    Baby, A.; Mahony, C. M. O.; Maguire, P. D.

    2011-02-01

    We report, for the first time, quadrupole mass spectrometry of neutral and positive ionic hydrocarbon species measured at the rf-biased substrate electrode of an inductively coupled plasma for acetylene rich C2H2 : Ar mixtures under various bias, frequency and pressure conditions. It has been observed that, irrespective of initial gas mixture, the resultant plasma is dominated by argon neutrals and ions. This is attributed to highly efficient conversion of acetylene to C2H due to the enhanced electron density compared with a standard capacitive plasma where the acetylene (neutral and ion) species remain dominant. This conversion may be crucial to film formation via inert rather than hydrocarbon ion bombardment. In addition, the transient formation of CH4 from acetylene has been discovered using IR absorption spectroscopy with time constants similar to observed pressure variations. Rate coefficients and rates for many of the reaction mechanisms, calculated using measured electron energy distribution functions and species densities, are given. These results have important application in plasma models and growth studies for hydrogenated amorphous or diamond-like carbon film deposition. Film growth under similar plasma conditions is reported in an associated paper along with ion energy distributions for important growth species. .

  20. Spatial and Temporal Properties of Radiation for Various Electrode Configurations in Arrays of Glass Microchannel Plasma Devices

    NASA Astrophysics Data System (ADS)

    Sung, S. H.; Lee, H. C.; Berger, A. G.; Park, S.-J.; Eden, J. G.

    2009-10-01

    Asymmetric and symmetric structures of microchannel plasma devices having different channel width of 50 -- 200 μm are fabricated on 0.4 mm thick sodalime glass substrate. The aspect ratio -- channel length to width -- has been obtained up to 500. All microplasmas are stable and well confined for several gas pressures of 200 -- 700 Torr, and gas mixtures including ambient air. The examination for spatially-resolved emission shows the tendency that peak intensity increases with increasing pressure. The peak emission intensity for 100 μm wide channel plasmas is doubled while increasing pressure from 200 to 600 Torr, but it also depends on geometrical factors. The temporal radiation in 300 -- 800 nm for various pressures also shows different feature when the microdischarge is driven by AC source. It will be reported that the effect of electrode configuration on the properties of microplasmas.

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

    SciTech Connect

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

    2014-12-15

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

  2. The smooth transition from field emission to a self-sustained plasma in microscale electrode gaps at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Bilici, Mihai A.; Haase, John R.; Boyle, Calvin R.; Go, David B.; Sankaran, R. Mohan

    2016-06-01

    We report on the existence of a smooth transition from field emission to a self-sustained plasma in microscale electrode geometries at atmospheric pressure. This behavior, which is not found at macroscopic scales or low pressures, arises from the unique combination of large electric fields that are created in microscale dimensions to produce field-emitted electrons and the high pressures that lead to collisional ionization of the gas. Using a tip-to-plane electrode geometry, currents less than 10 μA are measured at onset voltages of ˜200 V for gaps less than 5 μm, and analysis of the current-voltage (I-V) relationship is found to follow Fowler-Nordheim behavior, confirming field emission. As the applied voltage is increased, gas breakdown occurs smoothly, initially resulting in the formation of a weak, partial-like glow and then a self-sustained glow discharge. Remarkably, this transition is essentially reversible, as no significant hysteresis is observed during forward and reverse voltage sweeps. In contrast, at larger electrode gaps, no field emission current is measured and gas breakdown occurs abruptly at higher voltages of ˜400 V, absent of any smooth transition from the pre-breakdown condition and is characterized only by glow discharge formation.

  3. FANTM, the First Article NIF Test Module

    SciTech Connect

    HAMMON,JUD; HARJES,HENRY C.; MOORE,WILLIAM B. S.; SMITH,DAVID L.; WILSON,J. MICHAEL

    1999-11-30

    Designing and developing the 1.7 to 2.1-MJ Power Conditioning System (PCS), that will power the flashlamps of the main and power amplifiers for the National Ignition Facility (NIF) lasers, is one of several responsibilities assumed by Sandia National Labs (SNL) in support of the NIF Project. Maxwell Physics International has been a partner in this process. The NIF is currently being constructed at Lawrence Livermore National Labs (LLNL). The test facility that has evolved over the last three years to satisfy the project requirements is called FANTM, for the First Article NIF Test Module. It was built at SNL and operated for about 17,000 shots to demonstrate component performance expectations over the lifetime of NIF. A few modules similar to the one shown in Fig. 1 will be used initially in the amplifier test phase of the project. The final full NIF system will require at least 192 of them in four capacitor bays. This paper briefly summarizes the final design of the FANTM facility and compares its performance with the predictions of circuit simulations for both normal operation and fault-mode response. Applying both the measured and modeled power pulse waveforms as input to a physics-based, semi-empirical amplifier gain code indicates that the 20-capacitor PCS can satisfy the NIF requirement for an average gain coefficient of 5.00 %/cm and can exceed 5.20 %/cm with 24 capacitors.

  4. Activation of the Klebsiella pneumoniae nifU promoter: identification of multiple and overlapping upstream NifA binding sites.

    PubMed Central

    Cannon, W V; Kreutzer, R; Kent, H M; Morett, E; Buck, M

    1990-01-01

    The Klebsiella pneumoniae nifU promoter is positively controlled by the NifA protein and requires a form of RNA polymerase holoenzyme containing the rpoN encoded sigma factor, sigma 54. Occupancy of the K. pneumoniae nifU promoter by NifA was examined using in vivo dimethyl sulphate footprinting. Three binding sites for NifA (Upstream Activator Sequences, UASs 1, 2 and 3) located at -125, -116 and -72 were identified which conform to the UAS consensus sequence TGT-N10-ACA. An additional NifA binding site was identified at position -90. The UASs located at -125 (UAS1) and -116 (UAS2) overlap and do not appear to bind NifA as independent sites. They may represent a NifA binding site interacting with two NifA dimers. UAS3 is located at -72, and abuts a binding site for integration host factor (IHF) and is not normally highly occupied by NifA. In the absence of IHF UAS3 showed increased occupancy by NifA. Mutational and footprinting analysis of the three UASs indicates (1) IHF and NifA can compete for binding and that this competition influences the level of expression from the nifU promoter (2) that UAS2 is a principle sequence of the UAS 1,2 region required for activation and (3) that none of the NifA binding sites interacts with NifA independently. In vivo KMnO4 footprinting demonstrated that NifA catalyses open complex formation at the nifU promoter. IHF was required for maximal expression from the nifU and nifH promoters in Escherichia coli, and for the establishment of a Nif+ phenotype in E. coli from the nif plasmid pRD1. Images PMID:2186362

  5. Plasma Sprayed Si Nano Composite Powders for Negative Electrode of Lithium Ion Batteries

    NASA Astrophysics Data System (ADS)

    Kaga, Mashiro; Hideshima, Tasuku; Kambara, Makoto

    The electrochemical performance of the Si nano composite powders produced by PS-PVD was analyzed with Li counter electrode. The PS-PVD powders have showed an improved capacity compared to the raw mg-Si as negative electrode. Furthermore composite powders produced with CH4 addition showed higher specific gravimetric capacities per Si active materials of 1200 mAh/g, compared to 1024 mAh/g for the powders without C, suggesting the effectiveness of C coating on to the primary nano-Si and SiC particle inclusion for reinforcement of the active materials.

  6. Understanding the stagnation and burn of implosions on NIF

    NASA Astrophysics Data System (ADS)

    Kilkenny, J. D.; Caggiano, J. A.; Hatarik, R.; Knauer, J. P.; Sayre, D. B.; Spears, B. K.; Weber, S. V.; Yeamans, C. B.; Cerjan, C. J.; Divol, L.; Eckart, M. J.; Glebov, V. Yu; Herrmann, H. W.; Le Pape, S.; Munro, D. H.; Grim, G. P.; Jones, O. S.; Berzak-Hopkins, L.; Gatu-Johnson, M.; Mackinnon, A. J.; Meezan, N. B.; Casey, D. T.; Frenje, J. A.; Mcnaney, J. M.; Petrasso, R.; Rinderknecht, H.; Stoeffl, W.; Zylstra, A. B.

    2016-03-01

    An improved the set of nuclear diagnostics on NIF measures the properties of the stagnation plasma of implosions, including the drift velocity, areal density (ρr) anisotropy and carbon ρr of the compressed core. Two types of deuterium-tritium (DT) gas filled targets are imploded by shaped x-ray pulses, producing stagnated and burning DT cores of radial convergence (Cr) ∼ 5 or ∼20. Comparison with two-dimensional modeling with inner and outer surface mix shows good agreement with nuclear measurements.

  7. Electrochemical Characterization of O2 Plasma Functionalized Multi-Walled Carbon Nanotube Electrode for Legionella pneumophila DNA Sensor

    NASA Astrophysics Data System (ADS)

    Park, Eun Jin; Lee, Jun-Yong; Hyup Kim, Jun; Kug Kim, Sun; Lee, Cheol Jin; Min, Nam Ki

    2010-08-01

    An electrochemical DNA sensor for Legionella pneumophila detection was constructed using O2 plasma functionalized multi-walled carbon nanotube (MWCNT) film as a working electrode (WE). The cyclic voltammetry (CV) results revealed that the electrocatalytic activity of plasma functionalized MWCNT (pf-MWCNT) significantly changed depending on O2 plasma treatment time due to some oxygen containing functional groups on the pf-MWCNT surface. Scanning electron microscope (SEM) images and X-ray photoelectron spectroscopy (XPS) spectra were also presented the changes of their surface morphologies and oxygen composition before and after plasma treatment. From a comparison study, it was found that the pf-MWCNT WEs had higher electrocatalytic activity and more capability of probe DNA immobilization: therefore, electrochemical signal changes by probe DNA immobilization and hybridization on pf-MWCNT WEs were larger than on Au WEs. The pf-MWCNT based DNA sensor was able to detect a concentration range of 10 pM-100 nM of target DNA to detect L. pneumophila.

  8. Plans for Ignition Experiments on NIF

    SciTech Connect

    Moses, E

    2007-07-27

    The National Ignition Facility (NIF) is a 192-beam Nd-glass laser facility presently under construction at Lawrence Livermore National Laboratory (LLNL) in support of inertial confinement fusion (ICF) and high-energy-density (HED) science. NIF will produce 1.8 MJ, 500 TW of ultraviolet light, making it the world's largest and most powerful laser system. NIF will be the world's preeminent facility for the study of matter at extreme temperatures and densities and for producing and developing ICF. The ignition studies will be the next important step in developing inertial fusion energy.

  9. Genetic analysis of nif regulatory genes by utilizing the yeast two-hybrid system detected formation of a NifL-NifA complex that is implicated in regulated expression of nif genes.

    PubMed

    Lei, S; Pulakat, L; Gavini, N

    1999-10-01

    In diazotrophic organisms, nitrogenase synthesis and activity are tightly regulated. Two genes, nifL and nifA, are implicated as playing a major role in this regulation. NifA is a transcriptional activator, and its activity is inhibited by NifL in response to availability of excess fixed nitrogen and high O(2) tension. It was postulated that NifL binds to NifA to inhibit NifA-mediated transcriptional activation of nif genes. Mutational analysis combined with transcriptional activation studies clearly is in agreement with the proposal that NifL interacts with NifA. However, several attempts to identify NifA-NifL interactions by using methods such as coimmunoprecipitations and chemical cross-linking experiments failed to detect direct interactions between these proteins. Here we have taken a genetic approach, the use of a yeast two-hybrid protein-protein interaction assay system, to investigate NifL interaction with NifA. A DNA fragment corresponding to the kinase-like domain of nifL was PCR amplified and was used to generate translation fusions with the DNA binding domain and the DNA activation domain of the yeast transcriptional activator GAL4 in yeast two-hybrid vectors. Similarly, a DNA fragment corresponding to the catalytic domain of nifA was PCR amplified and used to generate translation fusions with the DNA-binding domain and the DNA-activation domain of GAL4 in yeast two-hybrid vectors. After introducing appropriate plasmid combinations in yeast cells, the existance of direct interaction between NifA and NifL was analyzed with the MATCHMAKER yeast two-hybrid system by testing for the expression of lacZ and his3 genes. These analyses showed that the kinase-like domain of NifL directly interacts with the catalytic domain of NifA. PMID:10515947

  10. Enhanced NIF neutron activation diagnostics

    SciTech Connect

    Yeamans, C. B.; Bleuel, D. L.; Bernstein, L. A.

    2012-10-15

    The NIF neutron activation diagnostic suite relies on removable activation samples, leading to operational inefficiencies and a fundamental lower limit on the half-life of the activated product that can be observed. A neutron diagnostic system measuring activation of permanently installed samples could remove these limitations and significantly enhance overall neutron diagnostic capabilities. The physics and engineering aspects of two proposed systems are considered: one measuring the {sup 89}Zr/{sup 89m}Zr isomer ratio in the existing Zr activation medium and the other using potassium zirconate as the activation medium. Both proposed systems could improve the signal-to-noise ratio of the current system by at least a factor of 5 and would allow independent measurement of fusion core velocity and fuel areal density.

  11. Charged-particle spectroscopy for diagnosing shock {rho}R and strength in NIF implosions

    SciTech Connect

    Zylstra, A. B.; Frenje, J. A.; Seguin, F. H.; Rosenberg, M. J.; Rinderknecht, H. G.; Johnson, M. Gatu; Casey, D. T.; Sinenian, N.; Manuel, M. J.-E.; Waugh, C. J.; Sio, H. W.; Li, C. K.; Petrasso, R. D.; Friedrich, S.; Knittel, K.; Bionta, R.; McKernan, M.; Callahan, D.; Collins, G. W.; Dewald, E.; and others

    2012-10-15

    The compact Wedge Range Filter (WRF) proton spectrometer was developed for OMEGA and transferred to the National Ignition Facility (NIF) as a National Ignition Campaign diagnostic. The WRF measures the spectrum of protons from D-{sup 3}He reactions in tuning-campaign implosions containing D and {sup 3}He gas; in this work we report on the first proton spectroscopy measurement on the NIF using WRFs. The energy downshift of the 14.7-MeV proton is directly related to the total {rho}R through the plasma stopping power. Additionally, the shock proton yield is measured, which is a metric of the final merged shock strength.

  12. 12-NIF Dedication: Concluding remarks and video

    ScienceCinema

    Edward Moses

    2010-09-01

    The National Ignition Facility, the world's largest laser system, was dedicated at a ceremony on May 29, 2009 at Lawrence Livermore National Laboratory. These are the concluding remarks by NIF Director Edward Moses, and a brief video presentation.

  13. 12-NIF Dedication: Concluding remarks and video

    SciTech Connect

    Edward Moses

    2009-07-02

    The National Ignition Facility, the world's largest laser system, was dedicated at a ceremony on May 29, 2009 at Lawrence Livermore National Laboratory. These are the concluding remarks by NIF Director Edward Moses, and a brief video presentation.

  14. Alternate Alpha Induced Reactions for NIF Radiochemistry

    SciTech Connect

    Shaughnessy, D A; Moody, K J; Bernstein, L A

    2010-02-26

    Radiochemical analysis of NIF capsule residues has been identified as a potential diagnostic of NIF capsule performance. In particular, alpha-induced nuclear reactions that occur on tracer elements added to the NIF capsule have been shown through simulation to be a very sensitive diagnostic for mix. The short range of the alpha particles makes them representative of the hot spot where they are created through the fusion of deuterium and tritium. Reactions on elements doped into the innermost part of the capsule ablator would therefore be sensitive to material that had mixed into the hot spot. Radiochemical determinations of activated detector elements may perhaps be the only true measure of mix that occurs in a NIF capsule, particularly in cases when the capsule fails.

  15. Debris shield survivability and lifetimes for NIF

    SciTech Connect

    Davis, S; Duewer, T; Eder, D; Ertel, J; Horton, R; Latkowski, Brereton, S; MacGowan, B; Thomas, I; Tobin, M; Zaka, F

    1999-09-01

    The survivability and performance of the NIF debris shields on the National Ignition Facility are a key factor for the successful conduct and affordable operation of the facility. Estimates of debris shield lifetime in the presence of target emissions indicate severely shortened lifetimes. We have tested a new coating design that improves debris shield cleaning. A combination of modeling and continuous data collection on NIF is described/recommended to allow cost effective debris shield operation.

  16. Thermal recovery of the NIF amplifiers

    NASA Astrophysics Data System (ADS)

    Sutton, Steven B.; Erlandson, A. E.; London, Richard A.; Manes, Kenneth R.; Marshall, Christopher D.; Petty, Charles S.; Pierce, R.; Smith, Larry K.; Zapata, Luis E.; Beullier, J.; Bicrel, B.

    1999-07-01

    With approximately 99 percent of the electrical energy supplied to the NIF appearing as heat in the amplifiers, thermal recovery of the NIF system is a major consideration in the design process. The NIF shot rate is one shot every 8 hours, with a goal of 4 hours between shots. This necessitates that thermal recovery take place in no more than 7 hours, with a goal of 3 hours for the accelerated shot rate. Residual optical distortions, which restrict the shot rate, are grouped into two discrete categories: (1) distortions associated with residual temperature gradients in the laser slabs, and (2) distortions associated with buoyantly driven convective currents in the amplifier cavity and beam-tube regions. Thermal recovery of the amplifiers is achieved by cooling the flashlamps and blastshields with a heat deposited in the slabs and edge claddings. Advanced concepts, such as the use of slightly chilled gas to accelerate some aspects of recovery, are addressed. To quantify recovery rates of the amplifiers, experiments and numerical models are used to measure and calculate the temperatures and optical distortions in NIF-like amplifier elements. The calculation results are benchmarked against AMPLAB temperature measurements, thus allowing a quantitative prediction of NIF thermal recovery. These results indicate that the NIF requirement of 7 hour thermal recovery can be achieved with chilled temperature cooling gas. It is further shown that residual temperature gradient driven distortions in the slabs reach an acceptable level, after 4 hours of thermal recovery.

  17. Regulation of nitrogen fixation in Klebsiella pneumoniae and Azotobacter vinelandii: NifL, transducing two environmental signals to the nif transcriptional activator NifA.

    PubMed

    Schmitz, Ruth A; Klopprogge, Kai; Grabbe, Roman

    2002-05-01

    The enzymatic reduction of molecular nitrogen to ammonia requires high amounts of energy, and the presence of oxygen causes the catalyzing nitrogenase complex to be irreversible inactivated. Thus nitrogen-fixing microorganisms tightly control both the synthesis and activity of nitrogenase to avoid the unnecessary consumption of energy. In the free-living diazotrophs Klebsiella pneumoniae and Azotobacter vinelandii, products of the nitrogen fixation nifLA operon regulate transcription of the other nifoperons. NifA activates transcription of nif genes by the alternative form of RNA-polymerase, sigma54-holoenzyme; NifL modulates the activity of the transcriptional activator NifA in response to the presence of combined nitrogen and molecular oxygen. The translationally-coupled synthesis of the two regulatory proteins, in addition to evidence from studies of NifL/NifA complex formation, imply that the inhibition of NifA activity by NifL occurs via direct protein-protein interaction in vivo. The inhibitory function of the negative regulator NifL appears to lie in the C-terminal domain, whereas the N-terminal domain binds FAD as a redox-sensitive cofactor, which is required for signal transduction of the internal oxygen status. Recently it was shown, that NifL acts as a redox-sensitive regulatory protein, which modulates NifA activity in response to the redox-state of its FAD cofactor, and allows NifA activity only in the absence of oxygen. In K. pneumoniae, the primary oxygen sensor appears to be Fnr (fumarate nitrate reduction regulator), which is presumed to transduce the signal of anaerobiosis towards NifL by activating the transcription of gene(s) whose product(s) function to relieve NifL inhibition through reduction of the FAD cofactor. In contrast, the reduction of A. vinelandii-NifL appears to occur unspecifically in response to the availability of reducing equivalents in the cell. Nitrogen status of the cells is transduced towards the NifL/NifA regulatory system

  18. Multi-electrodes Atmospheric Pressure Plasma Jet Aiming Bio-applications

    NASA Astrophysics Data System (ADS)

    Han, Jeon G.; Sahu, B. B.; Shin, K. S.; Lee, J. S.; Hori, M.

    2015-09-01

    For the recent advancement in the field of plasma medicine, there is growing demand for the atmospheric-pressure plasma (APP) jet sources with desired plasma characteristics. In this study, a stable non-thermal low-voltage APP jet device was designed and developed for optical and electrical characterizations. The jet was operated at very low frequency in the range 10-40 KHz, which enabled the generation of low power (~ 7W) plasma with a plasma column diameter of about 5 mm. The jet has a visible radial diameter of approximately 10 mm. Optical emission spectroscopy was used as a diagnostic tool to investigate the generation of plasmas and radical species. Discharge parameters are also measured to evaluate the different operating conditions. The gas temperature measured at the substrate location varies from 300 to 315 K for different gases where the electrical input power ranged from 1 to 7 W. The highly reactive species like OH, O, N2, N2 + and along with the trace of NO are characterized with respect to the different gas flow rate of Ar/He/O2/N2, applied voltages, duty cycles and frequencies to evaluate the capability of the APP jet for future bio-applications.

  19. Characterization of plasma ion source utilizing anode spot with positively biased electrode for stable and high-current ion beam extraction

    SciTech Connect

    Park, Yeong-Shin; Lee, Yuna; Chung, Kyoung-Jae; Hwang, Y. S.

    2011-12-15

    The operating conditions of a rf plasma ion source utilizing a positively biased electrode have been investigated to develop a stably operating, high-current ion source. Ion beam characteristics such as currents and energies are measured and compared with bias currents by varying the bias voltages on the electrode immersed in the ambient rf plasma. Current-voltage curves of the bias electrode and photographs confirm that a small and dense plasma, so-called anode spot, is formed near an extraction aperture and plays a key role to enhance the performance of the plasma ion source. The ion beam currents from the anode spot are observed to be maximized at the optimum bias voltage near the knee of the characteristic current-voltage curve of the anode spot. Increased potential barrier to obstruct beam extraction is the reason for the reduction of the ion beam current in spite of the increased bias current indicating the density of the anode spot. The optimum bias voltage is measured to be lower at higher operating pressure, which is favorable for stable operation without severe sputtering damage on the electrode. The ion beam current can be further enhanced by increasing the power for the ambient plasma without increasing the bias voltage. In the same manner, noble gases with higher atomic number as a feedstock gas are preferable for extracting higher beam current more stably. Therefore, performance of the plasma ion source with a positively biased electrode can be enhanced by controlling the operating conditions of the anode spot in various manners.

  20. 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.

  1. Enhanced methylene blue oxidative removal by copper electrode-based plasma irradiation with the addition of hydrogen peroxide.

    PubMed

    Son, Guntae; Kim, Do-Hyung; Lee, Jung Seok; Lee, Hongshin

    2016-08-01

    Submerged plasma irradiation (SPI)-based advanced oxidation processes have been studied for the oxidation of recalcitrant organic compounds because of their various physical and chemical properties. However, SPI technologies still have a few drawbacks such as relatively low efficiency for wastewater treatment and high energy consumption. In order to overcome these drawbacks, in this study, we proposed the combination of SPI and the Cu(II)-catalyzed Fenton-like system. The removal of methylene blue (MB) by the SPI system was significantly enhanced upon the addition of H2O2. The pseudo-first-order rate constants of MB removal increased with the increase of applied voltage. In addition, the optimum H2O2 dose and initial solution pH were 100 mM and 9, respectively. The reactive oxidants responsible for MB removal in copper electrode-based SPI/H2O2 systems are likely to be hydroxyl radicals (OH) or cupryl ion (Cu(III)), wherein Cu(III) is especially important. Furthermore, the copper electrode-based SPI/H2O2 system is a novel advanced oxidation process capable of oxidizing water recalcitrant and toxic organic pollutants at neutral pH. PMID:27236847

  2. Effect of plasma treatments to graphite nanofibers supports on electrochemical behaviors of metal catalyst electrodes.

    PubMed

    Lee, Hochun; Jung, Yongju; Kim, Seok

    2012-02-01

    In the present work, we had studied the graphite nanofibers as catalyst supports after a plasma treatment for studying the effect of surface modification. By controlling the plasma intensity, a surface functional group concentration was changed. The nanoparticle size, loading efficiency, and catalytic activity were studied, after Pt-Ru deposition by a chemical reduction. Pt-Ru catalysts deposited on the plasma-treated GNFs showed the smaller size, 3.58 nm than the pristine GNFs. The catalyst loading contents were enhanced with plasma power and duration time increase, meaning an enhanced catalyst deposition efficiency. Accordingly, cyclic voltammetry result showed that the specific current density was increased proportionally till 200 W and then the value was decreased. Enhanced activity of 40 (mA mg(-1)-catalyst) was accomplished at 200 W and 180 sec duration time. Consequently, it was found that the improved electroactivity was originated from the change of size or morphology of catalysts by controlling the plasma intensity. PMID:22629990

  3. Focus on NIF May 2001

    SciTech Connect

    Warner, B

    2001-05-01

    The National Ignition Facility, a stadium-size, 192-beam laser, is an essential tool for maintaining the safety and reliability of our nuclear weapons, harnessing fusion energy for future generations, and unlocking the origins of the universe. In the FY2001 Energy and Water Appropriations Act (FPN00-48), Congress appropriated $199.1 million for the continued construction of NIF. Immediately, $130 million became available. After March 31, 2001, $69.1 million was to be made available only after Department of Energy certification to Congress regarding six specific points: (1) recommend an appropriate path forward for the project; (2) certify that all established project and scientific milestones are on schedule and cost; (3) conduct 1st and 2nd quarter project reviews in FY01 and determine the project is on schedule and cost; (4) study alternatives to a 192-beam ignition facility for the stockpile stewardship program (SSP); (5) implement an integrated cost-schedule earned-value project control system; and (6) create a five-year budget plan for the SSP.

  4. Oxygen sensitivity of the nifLA promoter of Klebsiella pneumoniae

    SciTech Connect

    Kong, Q.T.; Wu, Q.L.; Ma, Z.F.; Shen, S.C.

    1986-05-01

    Oxygen sensitivity of the nifLA promoter of Klebsiella pneumoniae has been demonstrated. Studies on the oxygen regulation of nifB-lacZ and nifH-lacZ fusions in the presence of the nifLA operon, which contains either an intact or a deleted nifL gene, indicate that possible both the nifL promoter and the nifL product are responsible for nif repression by oxygen.

  5. Bipolar plasma vaporization using plasma-cutting and plasma-loop electrodes versus cold-knife transurethral incision for the treatment of posterior urethral stricture: a prospective, randomized study

    PubMed Central

    Cai, Wansong; Chen, Zhiyuan; Wen, Liping; Jiang, Xiangxin; Liu, Xiuheng

    2016-01-01

    OBJECTIVE: Evaluate the efficiency and safety of bipolar plasma vaporization using plasma-cutting and plasma-loop electrodes for the treatment of posterior urethral stricture. Compare the outcomes following bipolar plasma vaporization with conventional cold-knife urethrotomy. METHODS: A randomized trial was performed to compare patient outcomes from the bipolar and cold-knife groups. All patients were assessed at 6 and 12 months postoperatively via urethrography and uroflowmetry. At the end of the first postoperative year, ureteroscopy was performed to evaluate the efficacy of the procedure. The mean follow-up time was 13.9 months (range: 12 to 21 months). If re-stenosis was not identified by both urethrography and ureteroscopy, the procedure was considered “successful”. RESULTS: Fifty-three male patients with posterior urethral strictures were selected and randomly divided into two groups: bipolar group (n=27) or cold-knife group (n=26). Patients in the bipolar group experienced a shorter operative time compared to the cold-knife group (23.45±7.64 hours vs 33.45±5.45 hours, respectively). The 12-month postoperative Qmax was faster in the bipolar group than in the cold-knife group (15.54±2.78 ml/sec vs 18.25±2.12 ml/sec, respectively). In the bipolar group, the recurrence-free rate was 81.5% at a mean follow-up time of 13.9 months. In the cold-knife group, the recurrence-free rate was 53.8%. CONCLUSIONS: The application of bipolar plasma-cutting and plasma-loop electrodes for the management of urethral stricture disease is a safe and reliable method that minimizes the morbidity of urethral stricture resection. The advantages include a lower recurrence rate and shorter operative time compared to the cold-knife technique. PMID:26872076

  6. Plasma accelerator

    DOEpatents

    Wang, Zhehui; Barnes, Cris W.

    2002-01-01

    There has been invented an apparatus for acceleration of a plasma having coaxially positioned, constant diameter, cylindrical electrodes which are modified to converge (for a positive polarity inner electrode and a negatively charged outer electrode) at the plasma output end of the annulus between the electrodes to achieve improved particle flux per unit of power.

  7. Fine-structure mapping and complementation analysis of nif (nitrogen fixation) genes in Klebsiella pneumoniae.

    PubMed Central

    MacNeil, T; MacNeil, D; Roberts, G P; Supiano, M A; Brill, W J

    1978-01-01

    Four hundred and eighty-nine independent Nif- strains containing 260 point, 130 millimicron-induced, and 99 deletion mutations in nif in the Klebsiella pneumoniae chromosome were isolated. Three hundred and ninety insertion and point mutations were mapped with millimicron-induced deletions carried on 44 plasmids derived from pTM4010, a recombinant R factor containing the his-nif region of K. pneumoniae. The 99 chromosomal deletions in the nif region were mapped with 69 derivatives of pTM4010 carrying insertion and point mutations in nif. Complementation analysis between 84 derivatives of pTM4010 carrying nif mutations and Rec- derivatives of the 390 Nif- mutants identified 14 genes. The nif mutations were ordered into 49 deletion groups with a gene order of his...nifQBALFMVSNEKDHJ. Complementation analysis of millimicron-induced, amber, frameshift, and deletion mutations indicates there are five polycistronic and two monocistronic operons: nifQ nifB, nifA nifL, nifF, nifM nifV nifS, nifN nifE, nifK nifD nifH, and nifJ. Transcription is from right to left in all polycistronic operons. PMID:361693

  8. Challenges to develop nitrogen-fixing cereals by direct nif-gene transfer.

    PubMed

    Curatti, Leonardo; Rubio, Luis M

    2014-08-01

    Some regions of the developing world suffer low cereal production yields due to low fertilizer inputs, among other factors. Biological N2 fixation, catalyzed by the prokaryotic enzyme nitrogenase, is an alternative to the use of synthetic N fertilizers. The molybdenum nitrogenase is an O2-labile metalloenzyme composed of the NifDK and NifH proteins, which biosyntheses require a number of nif gene products. A challenging strategy to increase cereal crop productivity in a scenario of low N fertilization is the direct transfer of nif genes into cereals. The sensitivity of nitrogenase to O2 and the apparent complexity of nitrogenase biosynthesis are the main barriers identified so far. Expression of active NifH requires the products of nifM, nifH, and possibly nifU and nifS, whereas active NifDK requires the products of nifH, nifD, nifK, nifB, nifE, nifN, and possibly nifU, nifS, nifQ, nifV, nafY, nifW and nifZ. Plastids and mitochondria are potential subcellular locations for nitrogenase. Both could provide the ATP and electrons required for nitrogenase to function but they differ in their internal O2 levels and their ability to incorporate ammonium into amino acids. PMID:25017168

  9. NIF ICCS network design and loading analysis

    SciTech Connect

    Tietbohl, G; Bryant, R

    1998-02-20

    The National Ignition Facility (NIF) is housed within a large facility about the size of two football fields. The Integrated Computer Control System (ICCS) is distributed throughout this facility and requires the integration of about 40,000 control points and over 500 video sources. This integration is provided by approximately 700 control computers distributed throughout the NIF facility and a network that provides the communication infrastructure. A main control room houses a set of seven computer consoles providing operator access and control of the various distributed front-end processors (FEPs). There are also remote workstations distributed within the facility that allow provide operator console functions while personnel are testing and troubleshooting throughout the facility. The operator workstations communicate with the FEPs which implement the localized control and monitoring functions. There are different types of FEPs for the various subsystems being controlled. This report describes the design of the NIF ICCS network and how it meets the traffic loads that will are expected and the requirements of the Sub-System Design Requirements (SSDR's). This document supersedes the earlier reports entitled Analysis of the National Ignition Facility Network, dated November 6, 1996 and The National Ignition Facility Digital Video and Control Network, dated July 9, 1996. For an overview of the ICCS, refer to the document NIF Integrated Computer Controls System Description (NIF-3738).

  10. Measurement of Electron Density and Ion Collision Frequency with Dual Assisted Grounded Electrode DBD in Atmospheric Pressure Helium Plasma Jet

    NASA Astrophysics Data System (ADS)

    Zhou, Qiujiao; Qi, Bing; Huang, Jianjun; Pan, Lizhu; Liu, Ying

    2016-04-01

    The properties of a helium atmospheric-pressure plasma jet (APPJ) are diagnosed with a dual assisted grounded electrode dielectric barrier discharge device. In the glow discharge, we captured the current waveforms at the positions of the three grounded rings. From the current waveforms, the time delay between the adjacent positions of the rings is employed to calculate the plasma bullet velocity of the helium APPJ. Moreover, the electron density is deduced from a model combining with the time delay and current intensity, which is about 1011 cm‑3. In addition, The ion-neutral particles collision frequency in the radial direction is calculated from the current phase difference between two rings, which is on the order of 107 Hz. The results are helpful for understanding the basic properties of APPJs. supported by National Natural Science Foundation of China (No. 11105093), the Technological Project of Shenzhen, China (No. JC201005280485A), and the Planned S&T Program of Shenzhen, China (No. JC201105170703A)

  11. NIF Project Quality Assurance Program Plan Revision E

    SciTech Connect

    Dun, C; Brereton, S; Yatabe, J; Moses, E I

    2001-06-01

    The National Ignition Facility (NIF) is a key constituent of the Department Energy's (DOE's) Stockpile Stewardship Program. The NIF will use inertial confinement fusion (ICF) to produce ignition and energy gain in ICF targets and will perform weapons physics, weapons effects, and high-energy-density experiments in support of national security and civilian objectives. The primary mission of the NIF Project is the design and construction of the facility and equipment, acceptance testing, and activation. To accomplish this mission, the LLNL Director created the NIF Programs Directorate, and within that Directorate, the NIF Project Office to organize and manage the Project. The NIF Project Office establishes this QA Program to ensure its success. This QA Program Plan (QAPP) defines and describes the program--the management system--for specifying, achieving, and assuring the quality of all NIF Project work consistent with the policies of LLNL and the NIF Programs Directorate.

  12. Deposition of solid oxide fuel cell electrodes by solution precursor plasma spray

    NASA Astrophysics Data System (ADS)

    Wang, Youliang

    Porous La1-xSrxMnO3 (LSM) perovskite cathodes and Yttria Stabilized Zirconia (YSZ)-Nickel (Ni) anodes were successfully deposited by direct current arc solution precursor plasma spray (DC-SPPS), in which a solution precursor of the product material was injected into DC plasma jet. The deposition mechanisms, such as the changes in the solution precursor with the increase of temperature and the evolution of the droplet as it moved along the plasma jet, as well as the impact of the synthesized particles onto the substrate, were investigated. The effects of processing parameters on the microstructure and phase composition of the fabricated LSM cathode and Ni-YSZ anode were examined systematically using TGA/TDA, XRD and SEM. Coating deposition efficiencies and porosities as a function of processing parameters were analyzed by statistical experimental design techniques, based on which the deposition processes were optimized. In addition, the hardness and electrical resistance of the fabricated coatings were measured. From the theoretical and experimental analyses conducted, a comprehensive description of the DC-SPPS process was developed. The precursor solution droplets undergo breakup; solvent evaporation and precursor salt precipitation and crystallization; precursor salt melting and decomposition; nucleation and growth of particles of the product phase; agglomeration, sintering, and perhaps melting of these particles; and impact onto the substrate. The breakup of droplets can only occur in the short period of time after the droplets are injected into the plasma jet. Agglomeration of droplets or particles may occur at any point along the plasma plume. This work has clearly established: (a) the critical importance of droplet breakup and the agglomeration of precursors or synthesized particles in-flight in the plasma jet in determining the structure of the deposited coating, and (b) the basis of the low deposition efficiencies obtained in DC-SPPS. The microstructure and

  13. Control of work function of indium tin oxide: A surface treatment by atmospheric-pressure plasma layer on fabric-type electrodes

    NASA Astrophysics Data System (ADS)

    Ueda, Yoshihiko; Abe, Junichi; Murata, Hideyuki; Gotoh, Yasuhito; Sakai, Osamu

    2014-01-01

    The surface electronic properties of metal oxides, which affect the performances of layered electronic devices, are controlled by non-thermal atmospheric-pressure plasmas generated using a fabric-type electrode and gas flow induced through this plasma layer. We specify a method to control the work function of indium tin oxide (ITO) films by this plasma, in which such reactive species as oxidant radicals are generated. These oxidants are spatially transported in the gas flow to the ITO surface and increase the ITO’s work function, as verified in our experimental results. To examine the effects of the increased work function in a specific electronic device, we treat the surface of an ITO electrode in an organic light-emitting diode and observe the enhancement of the light-emitting efficiency.

  14. Plasma Sputter-type Ion Source with Wire Electrodes for Low-energy Gallium Ion Extraction

    SciTech Connect

    Vasquez, M. Jr.; Kasuya, T.; Wada, M.; Maeno, S.; Miyamoto, N.

    2011-01-07

    Low-energy ions of gallium (Ga) and argon (Ar) were extracted from a plasma sputter-type ion source system that utilized a tungsten (W) wire extractor geometry. The 90% transparent W wire extractor configuration had shown that the system was capable of producing an ion beam with the energy as low as 10 eV in a dc filament discharge and 50 eV in a radio frequency (rf) excited system. In the present investigation, Ar plasma was sustained in an ion source chamber through an inductively coupled 13.56 MHz rf power source. Negatively biased liquid Ga target suspended on a W reservoir was sputtered and postionized prior to extraction. Mass spectral analyses revealed a strong dependence of the Ga{sup +} current on the induced target bias.

  15. Preliminary investigation of power flow and electrode phenomena in a multi-megawatt coaxial plasma thruster

    NASA Technical Reports Server (NTRS)

    Schoenberg, Kurt; Gerwin, Richard; Henins, Ivars; Mayo, Robert; Scheuer, Jay; Nurden, Glen

    1993-01-01

    This paper summarizes preliminary experimental and theoretical research that was directed towards the study of quasisteady-state power flow in a large, un-optimized, multi-megawatt coaxial plasma thruster. The report addresses large coaxial thruster operation and includes evaluation and interpretation of the experimental results with a view to the development of efficient, steady-state megawatt-class magnetoplasmadynamic (MPD) thrusters.

  16. STATUS OF THE NIF POWER CONDITIONING SYSTEM

    SciTech Connect

    Arnold, P; Hulsey, S; Ullery, G; Petersen, D; Pendleton, D; Ollis, C; Newton, M

    2007-07-26

    The NIF Power Conditioning System provides the pulsed excitation required to drive flashlamps in the laser's optical amplifiers. Modular in design, each of the 192 Main Energy Storage Modules (MESMs) storage up to 2.2 MJ of electrical energy in its capacitor bank before delivering the energy to 20 pairs of flashlamps in a 400 {micro}s pulse (10% power points). The peak current of each MESM discharge is 0.5 MA. Production, installation, commissioning and operation of the NIF Power Conditioning continue to progress rapidly, with the goals of completing accelerated production in late 2007 and finishing commissioning by early 2008, all the while maintaining an aggressive operations schedule. To date, more than 80% of the required modules have been assembled, shipped and installed in the facility, representing more that 240 MJ of stored energy available for driving NIF flashlamps. The MESMs have displayed outstanding reliability during daily, multiple-shift operations.

  17. NIF Ignition Target 3D Point Design

    SciTech Connect

    Jones, O; Marinak, M; Milovich, J; Callahan, D

    2008-11-05

    We have developed an input file for running 3D NIF hohlraums that is optimized such that it can be run in 1-2 days on parallel computers. We have incorporated increasing levels of automation into the 3D input file: (1) Configuration controlled input files; (2) Common file for 2D and 3D, different types of capsules (symcap, etc.); and (3) Can obtain target dimensions, laser pulse, and diagnostics settings automatically from NIF Campaign Management Tool. Using 3D Hydra calculations to investigate different problems: (1) Intrinsic 3D asymmetry; (2) Tolerance to nonideal 3D effects (e.g. laser power balance, pointing errors); and (3) Synthetic diagnostics.

  18. Configuring NIF for direct drive experiments

    SciTech Connect

    Eimerl, D.; Rothenberg, J.; Key, M.

    1995-07-11

    The National Ignition Facility (NIF) is a proposed 1.8 MJ laser facility for carrying out experiments in inertial confinement fusion, currently designed for indirect drive experiments. The direct drive approach is being pursued at the 30 kJ Omega facility at the University of Rochester. In this paper we discuss the modifications to the NIF laser that would be required for both indirect and direct drive experiments. A primary concern is the additional cost of adding direct drive capability to the facility.

  19. NIF PEPC Mechanical Test Stand Safety Note

    SciTech Connect

    Trent, J W

    1998-05-21

    The NIF PEPC Mechanical Test Stand is to be used in the building 432. Building 432 is being used to test components and processes for NIF. The test stand is to be bolted to the floor. The test stand provides a platform from which the PEPC kinematic repeatability and vibrational characteristics of the PEPC LRU can be tested. The test stand will allow user access to the LRU to install instrumentation and to make adjustments to the kinematics. The mechanical test stand is designed to hold the 1700 lb. PEPC LRU.

  20. Preliminary investigation of power flow and electrode phenomena in a multi-megawatt coaxial plasma thruster

    NASA Technical Reports Server (NTRS)

    Schoenberg, Kurt F.; Gerwin, Richard A.; Henins, Ivars; Mayo, Robert; Scheuer, Jay; Wurden, Glen

    1992-01-01

    The present report on preliminary results of theoretical and experimental investigations of power flow in a large, unoptimized, multimegawatt coaxial thruster evaluates the significance of these data for the development of efficient, megawatt-class magnetoplasmadynamic (MPD) thrusters. The good agreement obtained between thruster operational performance and model predictions suggests that ideal MHD processes, including those of a magnetic nozzle, play an important role in coaxial plasma thruster dynamics at power levels relevant to advanced space propulsion. An optimized magnetic nozzle design would aid the development of efficient, multimegawatt MPD thrusters.

  1. Preliminary investigation of power flow and electrode phenomena in a multi-megawatt coaxial plasma thruster

    SciTech Connect

    Schoenberg, K.F.; Gerwin, R.A.; Henins, I.; Mayo, R.; Scheuer, J.; Wurden, G. North Carolina State University, Raleigh )

    1992-07-01

    The present report on preliminary results of theoretical and experimental investigations of power flow in a large, unoptimized, multimegawatt coaxial thruster evaluates the significance of these data for the development of efficient, megawatt-class magnetoplasmadynamic (MPD) thrusters. The good agreement obtained between thruster operational performance and model predictions suggests that ideal MHD processes, including those of a magnetic nozzle, play an important role in coaxial plasma thruster dynamics at power levels relevant to advanced space propulsion. An optimized magnetic nozzle design would aid the development of efficient, multimegawatt MPD thrusters. 10 refs.

  2. Physical and genetic map of the major nif gene cluster from Azotobacter vinelandii.

    PubMed

    Jacobson, M R; Brigle, K E; Bennett, L T; Setterquist, R A; Wilson, M S; Cash, V L; Beynon, J; Newton, W E; Dean, D R

    1989-02-01

    Determination of a 28,793-base-pair DNA sequence of a region from the Azotobacter vinelandii genome that includes and flanks the nitrogenase structural gene region was completed. This information was used to revise the previously proposed organization of the major nif cluster. The major nif cluster from A. vinelandii encodes 15 nif-specific genes whose products bear significant structural identity to the corresponding nif-specific gene products from Klebsiella pneumoniae. These genes include nifH, nifD, nifK, nifT, nifY, nifE, nifN, nifX, nifU, nifS, nifV, nifW, nifZ, nifM, and nifF. Although there are significant spatial differences, the identified A. vinelandii nif-specific genes have the same sequential arrangement as the corresponding nif-specific genes from K. pneumoniae. Twelve other potential genes whose expression could be subject to nif-specific regulation were also found interspersed among the identified nif-specific genes. These potential genes do not encode products that are structurally related to the identified nif-specific gene products. Eleven potential nif-specific promoters were identified within the major nif cluster, and nine of these are preceded by an appropriate upstream activator sequence. A + T-rich regions were identified between 8 of the 11 proposed nif promoter sequences and their upstream activator sequences. Site-directed deletion-and-insertion mutagenesis was used to establish a genetic map of the major nif cluster. PMID:2644218

  3. Physical and genetic map of the major nif gene cluster from Azotobacter vinelandii.

    PubMed Central

    Jacobson, M R; Brigle, K E; Bennett, L T; Setterquist, R A; Wilson, M S; Cash, V L; Beynon, J; Newton, W E; Dean, D R

    1989-01-01

    Determination of a 28,793-base-pair DNA sequence of a region from the Azotobacter vinelandii genome that includes and flanks the nitrogenase structural gene region was completed. This information was used to revise the previously proposed organization of the major nif cluster. The major nif cluster from A. vinelandii encodes 15 nif-specific genes whose products bear significant structural identity to the corresponding nif-specific gene products from Klebsiella pneumoniae. These genes include nifH, nifD, nifK, nifT, nifY, nifE, nifN, nifX, nifU, nifS, nifV, nifW, nifZ, nifM, and nifF. Although there are significant spatial differences, the identified A. vinelandii nif-specific genes have the same sequential arrangement as the corresponding nif-specific genes from K. pneumoniae. Twelve other potential genes whose expression could be subject to nif-specific regulation were also found interspersed among the identified nif-specific genes. These potential genes do not encode products that are structurally related to the identified nif-specific gene products. Eleven potential nif-specific promoters were identified within the major nif cluster, and nine of these are preceded by an appropriate upstream activator sequence. A + T-rich regions were identified between 8 of the 11 proposed nif promoter sequences and their upstream activator sequences. Site-directed deletion-and-insertion mutagenesis was used to establish a genetic map of the major nif cluster. PMID:2644218

  4. The C-terminal domain of NifL is sufficient to inhibit NifA activity.

    PubMed Central

    Narberhaus, F; Lee, H S; Schmitz, R A; He, L; Kustu, S

    1995-01-01

    In Klebsiella pneumoniae, transcription of all nif (nitrogen fixation) operons except the regulatory nifLA operon itself is regulated by the proteins NifA and NifL. NifA, an enhancer-binding protein, activates transcription by RNA polymerase containing the alternative sigma factor sigma 54. The central catalytic domain of NifA is sufficient for transcriptional activation, which can occur from solution. In vivo, NifL antagonizes the action of NifA in the presence of molecular oxygen or combined nitrogen. Inhibition has also been shown in vitro, but it was not responsive to environmental signals. Assuming a two-domain structure of NifL, we localized inhibition by NifL to its carboxy (C)-terminal domain, which is more soluble than the intact protein. The first line of evidence for this is that internal deletions of NifL containing an intact C-terminal domain were able to inhibit transcriptional activation by NifA in a coupled transcription-translation system. The second line of evidence is that the isolated C-terminal domain of NifL (assayed as a fusion to the soluble maltose-binding protein [MBP]) was sufficient to inhibit transcriptional activation by the central domain of NifA in a purified transcription system. The final line of evidence is that an MBP fusion to the C-terminal domain of NifL inhibited transcriptional activation by NifA in vivo. On the basis of these data, we postulate that the inhibitory function of NifL lies in its C-terminal domain and hence infer that this domain is responsible for interaction with NifA. Gel filtration experiments with MBP-NifL fusion derivatives lacking portions of the N- or C-terminal domain of the protein revealed that the C-terminal domain is the most soluble part of NifL. Up to 50% of two MBP-NifL truncations containing only the C-terminal domain appeared to be in a defined dimeric state. PMID:7665487

  5. First NIF ARC target shot results

    NASA Astrophysics Data System (ADS)

    Chen, Hui; di Nicola, P.; Hermann, M.; Kalantar, D.; Martinez, D.; Tommasini, R.; NIF ARC Team

    2015-11-01

    The commissioning of the Advanced Radiographic Capability (ARC) laser system in the National Ignition Facility (NIF) is currently in progress. ARC laser is designed to ultimately provide eight beamlets with pulse duration adjustable from 1 to 50 ps, and energies up to 1.7 kJ per beamlet. ARC will add critical capability for the NIF facility for creating precision x-ray backlighters needed for many current NIF ICF and HED experiments. ARC can also produce MeV electrons and protons for new science experiment on NIF. In the initial set of experiments, 4 of the 8 beamlets are being commissioned up to 1 kJ per beam at 30 ps pulse length using foil and wire targets. X-ray energy distribution, spot size and pulse duration are measured using various diagnostics. This talk will describe the shot setup and results. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  6. Nucleotide sequence and genetic analysis of the Rhodobacter capsulatus ORF6-nifUI SVW gene region: possible role of NifW in homocitrate processing.

    PubMed

    Masepohl, B; Angermüller, S; Hennecke, S; Hübner, P; Moreno-Vivian, C; Klipp, W

    1993-04-01

    DNA sequence analysis of a 3494-bp HindIII-BclI fragment of the Rhodobacter capsulatus nif region A revealed genes that are homologous to ORF6, nifU, nifS, nifV and nifW from Azotobacter vinelandii and Klebsiella pneumoniae. R. capsulatus nifU, which is present in two copies, encodes a novel type of NifU protein. The deduced amino acid sequences of NifUI and NifUII share homology only with the C-terminal domain of NifU from A. vinelandii and K. pneumoniae. In contrast to nifA and nifB, which are almost perfectly duplicated, the predicted amino acid sequences of the two NifU proteins showed only 39% sequence identity. Expression of the ORF6-nifUISVW operon, which is preceded by a putative sigma 54-dependent promoter, required the function of NifA and the nif-specific rpoN gene product encoded by nifR4. Analysis of defined insertion and deletion mutants demonstrated that only nifS was absolutely essential for nitrogen fixation in R. capsulatus. Strains carrying mutations in nifV were capable of very slow diazotrophic growth, whereas ORF6, nifUI and nifW mutants as well as a nifUI/nifUII double mutant exhibited a Nif+ phenotype. Interestingly, R. capsulatus nifV mutants were able to reduce acetylene not only to ethylene but also to ethane under conditions preventing the expression of the alternative nitrogenase system. Homocitrate added to the growth medium repressed ethane formation and cured the NifV phenotype in R. capsulatus. Higher concentrations of homocitrate were necessary to complement the NifV phenotype of a polar nifV mutant (NifV-NifW-), indicating a possible role of NifW either in homocitrate transport or in the incorporation of this compound into the iron-molybdenum cofactor of nitrogenase. PMID:8492805

  7. Improvement of luminous efficacy in plasma display panels by a counter-type electrode configuration with a large gap

    NASA Astrophysics Data System (ADS)

    Hur, Min; Kim, Jae Rok; Yi, Jeong Doo; Cho, Yoon Hyoung; Song, Su Bin; Park, Jun Yong; Lee, Han Yong

    2006-06-01

    The discharge characteristics of plasma display panel with coplanar and counter-type electrode configurations are compared using the numerical modeling and experiment with respect to real and macrocells, respectively. Numerical analysis shows that the ultraviolet (UV) efficiency and driving voltage of counter type at a gap distance of 230 μm are located at similar levels to those of coplanar type at a gap distance of 60 μm. The UV efficiency for counter type is enhanced with the rise of xenon fraction and gap distance, between which the large gap operation is more advantageous to high UV efficiency. The measured temporal evolution of infrared emission reveals that the cathode layer plays an important role in forming the discharge current after the gas breakdown. It is found from the time-averaged visible and infrared emissions for the counter type that as the gap distance becomes larger, the positive column region increases but the sheath regime remains almost unchanged. On the other hand, the variation of gap distance gives a little influence on the average discharge current at the same applied voltage. The UV efficiency is thus greatly improved with the gap distance. When the gap becomes double, the UV efficiency is improved by 75%, which is well agreed with the results predicted in the numerical modeling.

  8. Sensitive high-performance liquid chromatographic method for profiling phytoestrogens using coulometric electrode array detection: application to plasma analysis.

    PubMed

    Nurmi, T; Adlercreutz, H

    1999-10-01

    An HPLC method for profiling 13 phytoestrogens and their metabolites using coulometric electrode array detection was developed. Sensitivity of the method was slightly less than that of our GC-MS method, but significantly higher compared to the HPLC methods using diode-array or UV detection. Detection limits varied from 3.4 (secoisolariciresinol) to 40.3 (genistin) pg on column. Signal linearities ranged from the detection limits to 61 ng on column. Resolution values for the peak pairs varied from 1.1 (O-desmethylangolensin-anhydrosecoisolariciresinol) to 16 (daidzin-genistin). Intra- and interassay retention time variations were negligible and detector response variation was eliminated by frequent calibration. Chromatographic method was applied to plasma analyses and 6 of the 13 compounds were detected. Method accuracy for those six analytes varied from 69% (enterodiol) to 118% (genistein). Intraassay precision CVs ranged from 1.5% (enterolactone, 12.4 nmol/liter) to 14% (genistein, 245 nmol/liter) and interassay precision CVs ranged from 9.9% (daidzein, 67.4 nmol/liter) to 44% (enterodiol, 1.20 nmol/liter). PMID:10527503

  9. Functional expression of the FeMo-cofactor-specific biosynthetic genes nifEN as a NifE-N fusion protein synthesizing unit in Azotobacter vinelandii.

    PubMed

    Suh, Man Hee; Pulakat, Lakshmi; Gavini, Nara

    2002-11-29

    The nifEN encodes an E2N2 tetrameric metalloprotein complex that serves as scaffold for assembly of the FeMo cofactor of nitrogenase. In most diazotrophs, the NifE and NifN are translated as separate polypeptides and then assembled into tetrameric E2N2 complex. However, in Anabaena variabilis which has two nif clusters that encode two different NifEN complexes, the NifEN2 is encoded by a single nifE-N like gene, which has high homology to the NifE at amino-terminus and to the NifN at the carboxy-terminus. These observations implied that a metalloprotein like NifEN can accommodate large variations in their amino acid composition and also in the way they are synthesized (as two separate proteins or as a single protein) and yet remain functional. In Azotobacter vinelandii NifE and NifN are synthesized separately. To test whether NifEN could retain its functionality when encoded by a single gene, we generated a translational fusion of the nifE and nifN genes of A. vinelandii that could encode a large NifE-N fusion protein. When expressed in the nifEN-minus strain of A. vinelandii, the nifE-N gene fusion could complement the NifEN function. Western blot analysis by using polyclonal NifEN antibodies revealed that the complementing nifEN product is a large NifE-N fusion protein unit. The fact that the gene fusion of nifE-N specifies a functional NifE-N fusion protein reflects that these metalloproteins can accommodate a wide range of flexibility in their gene organization, structure, and assembly. PMID:12437975

  10. The DNA-binding domain of the transcriptional activator protein NifA resides in its carboxy terminus, recognises the upstream activator sequences of nif promoters and can be separated from the positive control function of NifA.

    PubMed Central

    Morett, E; Cannon, W; Buck, M

    1988-01-01

    The positive control protein NifA activates transcription of nitrogen fixation promoters in Klebsiella pneumoniae. NifA is believed to bind to specific sites, the upstream activator sequences (UAS's), of the nif promoters which it activates. We have now shown by mutation of the carboxy terminus of NifA that this is the DNA-binding domain and that the DNA-binding and positive activator functions of NifA can be separated. Mutational analysis of the nifH UAS and in vivo methylation protection analysis of the interaction of NifA with the nifH promoter demonstrates that the UAS is recognised by the carboxy terminus of NifA. The UAS's of K. pneumoniae nif promoters are also required for activation by the Rhizobium meliloti NifA indicating that this activator also possesses DNA-binding activity. Images PMID:3062575

  11. Rutile-structured TiO{sub 2} deposited by plasma enhanced atomic layer deposition using tetrakis(dimethylamino)titanium precursor on in-situ oxidized Ru electrode

    SciTech Connect

    Pointet, John; Gonon, Patrice; Latu-Romain, Lawrence; Bsiesy, Ahmad Vallée, Christophe

    2014-01-15

    In this work, tetrakis(dimethylamino)titanium precursor as well as in-situ oxidized ruthenium bottom electrode were used to grow rutile-structured titanium dioxide thin layers by plasma enhanced atomic layer deposition. Metal–insulator–metal capacitors have been elaborated in order to study the electrical properties of the device. It is shown that this process leads to devices exhibiting excellent results in terms of dielectric constant and leakage current.

  12. Purification and in vitro activities of the native nitrogen fixation control proteins NifA and NifL.

    PubMed

    Austin, S; Buck, M; Cannon, W; Eydmann, T; Dixon, R

    1994-06-01

    The prokaryotic enhancer-binding protein NifA stimulates transcription at a distance by binding to sequences upstream of nitrogen fixation (nif) promoters and catalyzing the formation of open promoter complexes by RNA polymerase containing the alternative sigma factor, sigma 54. The activity of NifA in vivo is modulated by the negative regulatory protein NifL in response to environmental oxygen and fixed nitrogen. To date, a detailed biochemical analysis of these proteins from the model diazotroph Klebsiella pneumoniae has been hindered by their insolubility. We have now purified NifA and NifL from Azotobacter vinelandii in their native form. NifA is competent in specific DNA binding, transcriptional activation, and response to negative regulation by NifL in vitro. In contrast to the conserved mechanism of phosphotransfer demonstrated by other two-component regulatory systems, our results support a model in which NifL regulates the activity of NifA via a protein-protein steric block interaction rather than a catalytic modification of NifA. PMID:8206822

  13. Evaluation of 2 portable ion-selective electrode meters for determining whole blood, plasma, urine, milk, and abomasal fluid potassium concentrations in dairy cattle.

    PubMed

    Megahed, A A; Hiew, M W H; Grünberg, W; Constable, P D

    2016-09-01

    Two low-cost ion-selective electrode (ISE) handheld meters (CARDY C-131, LAQUAtwin B-731; Horiba Ltd., Albany, NY) have recently become available for measuring the potassium concentration ([K(+)]) in biological fluids. The primary objective of this study was to characterize the analytical performance of the ISE meters in measuring [K(+)] in bovine whole blood, plasma, urine, milk, and abomasal fluid. We completed 6 method comparison studies using 369 whole blood and plasma samples from 106 healthy periparturient Holstein-Friesian cows, 138 plasma samples from 27 periparturient Holstein-Friesian cows, 92 milk samples and 204 urine samples from 16 lactating Holstein-Friesian cows, and 94 abomasal fluid samples from 6 male Holstein-Friesian calves. Deming regression and Bland-Altman plots were used to characterize meter performance against reference methods (indirect ISE, Hitachi 911 and 917; inductively coupled plasma-optical emission spectroscopy). The CARDY ISE meter applied directly in plasma measured [K(+)] as being 7.3% lower than the indirect ISE reference method, consistent with the recommended adjustment of +7.5% when indirect ISE methods are used to analyze plasma. The LAQUAtwin ISE meter run in direct mode measured fat-free milk [K(+)] as being 3.6% lower than the indirect ISE reference method, consistent with a herd milk protein percentage of 3.4%. The LAQUAtwin ISE meter accurately measured abomasal fluid [K(+)] compared to the indirect ISE reference method. The LAQUAtwin ISE meter accurately measured urine [K(+)] compared to the indirect ISE reference method, but the median measured value for urine [K(+)] was 83% of the true value measured by inductively coupled plasma-optical emission spectroscopy. We conclude that the CARDY and LAQUAtwin ISE meters are practical, low-cost, rapid, accurate point-of-care instruments suitable for measuring [K(+)] in whole blood, plasma, milk, and abomasal fluid samples from cattle. Ion-selective electrode methodology is

  14. The effects of total gas pressure and Xe partial pressure on the properties of plasma display panels with two-opposite-electrode cells

    NASA Astrophysics Data System (ADS)

    Ok, Jung-Woo; Lee, Byoung-Seob; Choi, Seyong; Won, Mi-Sook; Kim, Dong-Hyun; Lee, Hae June; Lee, Ho-Jun

    2014-04-01

    The effects of total pressure and Xe partial pressure on the characteristics of an alternating-current plasma display panel with a two-opposite-electrode discharge cell configuration and a three-electrode surface-discharge cell configuration were investigated in terms of the following electro-optical properties: breakdown voltage, sustain voltage, wall charge transfer curve, infrared emission characteristics, luminance and luminous efficacy. Despite the longer discharge gap length, the results of the experiment and three-dimensional plasma simulation indicated that the opposite-discharge configuration has a significantly lower breakdown voltage than the surface-discharge configuration. Furthermore, the ratio of the increase in the breakdown voltage for the opposite-discharge configuration to the incremental Xe partial pressure was found to be smaller than that of the surface-discharge configuration. Because of its low driving voltage and possible use of high-Xe partial pressure, the opposite-discharge mode exhibited a higher luminous efficacy compared with the surface-discharge mode. These results indicated that the two-opposite-electrode discharge cell configuration has a cost reduction potential in electronics as well as high efficacy for plasma displays.

  15. Biochemical and genetic analysis of the nifUSVWZM cluster from Azotobacter vinelandii.

    PubMed

    Jacobson, M R; Cash, V L; Weiss, M C; Laird, N F; Newton, W E; Dean, D R

    1989-10-01

    Azotobacter vinelandii genes contained within the major nif-cluster and designated orf6, nifU, nifS, nifV, orf7, orf8, nifW, nifZ, nifM, and orf9 are organized into at least two overlapping transcriptional units. Nitrogenase derepressed crude extracts of Azotobacter vinelandii mutant strains having individual deletions located within nifU, nifS, nifV, nifW, nifZ, or nifM were examined for nitrogenase component protein activities. The results of these experiments indicated that, in A. vinelandii, the nifU, nifS and nifM gene products are required for the full activation or the catalytic stability of the nitrogenase Fe protein. Deletion of the nifV gene resulted in lower MoFe protein activity, probably resulting from the accumulation of an altered FeMo-cofactor. The nifW and nifZ gene products were required for the full activation or catalytic stability of the MoFe protein. Deletion of nifZ alone or nifM alone did not appear to affect FeMo-cofactor biosynthesis. However, deletion of both nifZ and nifM eleminated either FeMo-cofactor biosynthesis or the insertion of FeMo-cofactor into the apo-MoFe protein. Other genes contained within the nifUSVWZM gene cluster (orf6, orf7, orf8, and orf9) were not required for Mo-dependent diazotrophic growth. PMID:2615765

  16. Effect of NLTE emissivity models on NIF ignition hohlraum power requirements

    NASA Astrophysics Data System (ADS)

    Suter, L.; Hansen, S.; Rosen, M.; Springer, P.; Callahan, D.

    2008-11-01

    It's well known that the NLTE atomic physics model can significantly affect the power requirements and plasma conditions in ignition hohlraums. This is because the emissivity(Te,ne) is a significant factor in determining the time dependent coronal temperature of the hot blow-off plasma filling ignition hohlraums which, in turn, determines the total energy stored in that coronal plasma at any instant. In this talk we present best estimates of NLTE emissivity using the SCRAM model, including the range of uncertainty, and compare them with the emissivity of the model used to design NIF ignition hohlraums and set the NIF pulse shape. We then present pulse shapes derived from hohlraum simulations using an atomic physics model that approximates the SCRAM emissivities. We discuss the differences in coronal energetics and show how this affects the pulse shape and decreases the peak power requirement. Finally, we present design simulations of potential NIF-commissioning scaling experiments that could distinguish among emissivity models. Prepared by LLNL under Contract DE-AC52-07NA27344.

  17. Status of NIF mirror technologies for completion of the NIF facility

    SciTech Connect

    Stolz, C J

    2008-08-07

    The 1600 mirrors required for the National Ignition Facility (NIF) are now coated with the last optics currently being installed. The combined surface area of the NIF mirrors is almost 450 square meters, roughly 3.4 times greater than the surface area of the two Keck primary mirrors. Additionally, the power handling specification of NIF mirrors is 19 orders of magnitude greater than that of the Keck mirrors. The NIF laser will be at least 40x greater energy than the previous LLNL fusion laser called NOVA. To manufacture these mirrors, a number of new technologies (electrolytic in-situ dressing, ion figuring, source stabilization) were used that were not available for previous fusion laser optics. Post deposition technologies designed to increase laser resistance (off-line laser conditioning, solarization, air knives) have also been utilized. This paper summarizes the differences in technologies used to manufacture NIF mirrors from those used for previous fusion lasers and examines potential future technologies that would enable higher fluence operations and extend lifetimes.

  18. Design of the NIF Cryogenic Target System

    SciTech Connect

    Gibson, C; Baltz, J; Malsbury, T; Atkinson, D; Brugmann, V; Coffield, F; Edwards, O; Haid, B; Locke, S; Shiromizu, S; Skulina, K

    2008-06-10

    The United States Department of Energy has embarked on a campaign to conduct credible fusion ignition experiments on the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory in 2010. The target assembly specified for this campaign requires the formation of a deuterium/tritium (DT) fuel ice layer in a 2 mm diameter capsule at the center of a 9 mm long by 5 mm diameter cylinder, called a hohlraum. The ice layer must be formed and maintained at temperatures below 20 K. At laser shot time, the target is positioned at the center of the NIF target chamber, aligned to the laser beams and held stable to less than 7 {micro}m rms. We have completed the final design of the Cryogenic Target System and are integrating the devices necessary to create, characterize and position the cryogenic target for ignition experiments. These designs, with supporting analysis and prototype test results, will be presented.

  19. NIF Power Conditioning System Testing at LLNL

    SciTech Connect

    Fulkerson, E S; Newton, M; Hulsey, s; Hammon, J; Moore, W

    2001-06-05

    The National Ignition Facility (NIF) is now under construction at the Lawrence Livermore National Laboratory (LLNL). The Power Conditioning System (PCS) for NIF, when completed will consist of a 192 nearly identical 2 megajoule capacitor storage banks driving 7680 two meter long flashlamps. A fully integrated single-module test facility was completed in August of 2000 at LLNL. The purpose to the Test Facility is to conduct Reliability and Maintainability (RAM) testing of a true ''First Article'' system (built to the final drawing package as opposed to a prototype). The test facility can be fired once every ten minutes with a total peak output current of 580kA with a pulse width of 400us. To date over 4000 full power shots have been conducted at this facility.

  20. Neutron Activation of NIF Final Optics Assemblies

    SciTech Connect

    Sitaraman, S; Dauffy, L; Khater, H; Brereton, S

    2009-09-29

    Analyses were performed to characterize the radiation field in the vicinity of the Final Optics Assemblies (FOAs) at the National Ignition Facility (NIF) due to neutron activation following Deuterium-Deuterium (DD), Tritium-Hydrogen-Deuterium (THD), and Deuterium-Tritium (DT) shots associated with different phases of the NIF operations. The activation of the structural components of the FOAs produces one of the larger sources of gamma radiation and is a key factor in determining the stay out time between shots to ensure worker protection. This study provides estimates of effective dose rates in the vicinity of a single FOA and concludes that the DD and THD targets produce acceptable dose rates within 10 minutes following a shot while about 6-days of stay out time is suggested following DT shots. Studies are ongoing to determine the combined effects of multiple FOAs and other components present in the Target Bay on stay-out time and worker dose.

  1. Comparative study of two- and three-dimensional modeling on arc discharge phenomena inside a thermal plasma torch with hollow electrodes

    SciTech Connect

    Kim, Keun Su; Park, Jin Myung; Choi, Sooseok; Kim, Jongin; Hong, Sang Hee

    2008-02-15

    A comparative study between two- and three-dimensional (2D and 3D) modeling is carried out on arc discharge phenomena inside a thermal plasma torch with hollow electrodes, in order to evaluate the effects of arc root configuration characterized by either 2D annular or 3D highly localized attachment on the electrode surface. For this purpose, a more precise 3D transient model has been developed by taking account of 3D arc current distribution and arc root rotation. The 3D simulation results apparently reveal that the 3D arc root attachment brings about the inherent 3D and turbulence nature of plasma fields inside the torch. It is also found that the constricted arc column near the vortex chamber plays an important role in heating and acceleration of injected arc gases by concentrating arc currents on the axis of the hollow electrodes. The inherent 3D nature of arc discharge is well preserved inside the cathode region, while these 3D features slowly diminish behind the vortex chamber where the turbulent flow begins to be developed in the anode region. Based on the present simulation results, it is noted that the mixing effects of the strong turbulent flow on the heat and mass transfer are mainly responsible for the gradual relaxation of the 3D structures of plasma fields into the 2D axisymmetric ones that eventually appear in the anode region near the torch exit. From a detailed comparison of the 3D results with the 2D ones, the arc root configuration seems to have a significant effect on the heat transfer to the electrode surfaces interacting with the turbulent plasma flow. That is, in the 2D simulation based on an axisymmetric stationary model, the turbulence phenomena are fairly underestimated and the amount of heat transferred to the cold anode wall is calculated to be smaller than that obtained in the 3D simulation. For the validation of the numerical simulations, calculated plasma temperatures and axial velocities are compared with experimentally measured ones

  2. Beam control and laser characterization for NIF

    SciTech Connect

    Boege, S. J., LLNL

    1998-06-10

    The demanding energy, power, pulse shape, focusability, pointing, and availability requirements placed on the 192 National Ignition Facility (NIF) beams lead to the need for an automatic operation capability that is well beyond that of previous inertial confinement fusion (ICF) lasers. Alignment, diagnostic, and wavefront correction subsystems are integrated in an approach that, by permitting maximal sharing of instrumentation between subsystems, meets performance requirements at a reasonable cost.

  3. Design Calculations For NIF Convergent Ablator Experiments

    SciTech Connect

    Olson, R E; Hicks, D G; Meezan, N B; Callahan, D A; Landen, O L; Jones, O S; Langer, S H; Kline, J L; Wilson, D C; Rinderknecht, H; Zylstra, A; Petrasso, R D

    2011-10-25

    The NIF convergent ablation tuning effort is underway. In the early experiments, we have discovered that the design code simulations over-predict the capsule implosion velocity and shock flash rhor, but under-predict the hohlraum x-ray flux measurements. The apparent inconsistency between the x-ray flux and radiography data implies that there are important unexplained aspects of the hohlraum and/or capsule behavior.

  4. 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.

  5. Fielding the NIF Cryogenic Ignition Target

    SciTech Connect

    Malsbury, T; Haid, B; Gibson, C; Atkinson, D; Skulina, K; Klingmann, J; Atherton, J; Mapoles, E; Kozioziemski, B; Dzenitis, E

    2008-02-28

    The United States Department of Energy has embarked on a campaign to conduct credible fusion ignition experiments on the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory in 2010. The target assembly specified for this campaign requires the formation of a deuterium/tritium (DT) fuel ice layer on the inside of a 2 millimeter diameter capsule positioned at the center of a 9 millimeter long by 5 millimeter diameter cylinder, called a hohlraum. The ice layer requires micrometer level accuracy and must be formed and maintained at temperatures below 19 K. At NIF shot time, the target must be positioned at the center of the NIF 10 meter diameter target chamber, aligned to the laser beam lines and held stable to less than 7 micrometers rms. We have completed the final design and are integrating the systems necessary to create, characterize and field the cryogenic target for ignition experiments. These designs, with emphasis on the challenges of fielding a precision cryogenic positioning system will be presented.

  6. Gamma Reaction History for the NIF

    SciTech Connect

    Herrmann, H W; Evans, S C; Kim, Y; Mack, J M; Young, C S; Cox, B C; Frogget, B C; Kaufman, M I; Malone, R M; Tunnell, T W; Stoeffl, W; Horsfield, C J

    2009-06-05

    Bang time and reaction history measurements are fundamental components of diagnosing ICF implosions and will be essential contributors to diagnosing attempts at ignition on the National Ignition Facility (NIF). Fusion gammas provide a direct measure of fusion interaction rate without being compromised by Doppler spreading. Gamma-based gas Cherenkov detectors that convert fusion gamma rays to optical Cherenkov photons for collection by fast recording systems have been developed and fielded at Omega. These systems have established their usefulness in illuminating ICF physics in several experimental campaigns. Bang time precision better than 25 ps has been demonstrated, well below the 50 ps accuracy requirement defined by the NIF System Design Requirements. A staged approach of implementing Gamma Reaction History (GRH) diagnostics on the NIF has been initiated. In the early stage, multiple detectors located close to target chamber center (at 2 and 6 m) and coupled to photomultiplier tubes are geared toward the loweryield THD campaign. In the later stage, streak camera–coupled instruments will be used for improved temporal resolution at the higher yields expected from the DT ignition campaign. Multiple detectors will allow for increased dynamic range and gamma energy spectral information.

  7. X-Ray Diffraction on NIF

    SciTech Connect

    Eggert, J H; Wark, J

    2012-02-15

    The National Ignition Facility (NIF) is currently a 192 beam, 1.6 MJ laser. NIF Ramp-Compression Experiments have already made the relevant exo-planet pressure range from 1 to 50 Mbar accessible. We Proposed to Study Carbon Phases by X-Ray Diffraction on NIF. Just a few years ago, ultra-high pressure phase diagrams for materials were very 'simple'. New experiments and theories point out surprising and decidedly complex behavior at the highest pressures considered. High pressures phases of aluminum are also predicted to be complex. Recent metadynamics survey of carbon proposed a dynamic pathway among multiple phases. We need to develop diagnostics and techniques to explore this new regime of highly compressed matter science. X-Ray Diffraction - Understand the phase diagram/EOS/strength/texture of materials to 10's of Mbar. Strategy and physics goals: (1) Powder diffraction; (2) Begin with diamond; (3) Continue with metals etc.; (4) Explore phase diagrams; (5) Develop liquid diffraction; and (6) Reduce background/improve resolution.

  8. NIF Target Assembly Metrology Methodology and Results

    SciTech Connect

    Alger, E. T.; Kroll, J.; Dzenitis, E. G.; Montesanti, R.; Hughes, J.; Swisher, M.; Taylor, J.; Segraves, K.; Lord, D. M.; Reynolds, J.; Castro, C.; Edwards, G.

    2011-01-01

    During our inertial confinement fusion (ICF) experiments at the National Ignition Facility (NIF) we require cryogenic targets at the 1-cm scale to be fabricated, assembled, and metrologized to micron-level tolerances. During assembly of these ICF targets, there are physical dimensmetrology is completed using optical coordinate measurement machines that provide repeatable measurements with micron precision, while also allowing in-process data collection for absolute accuracy in assembly. To date, 51 targets have been assembled and metrologized, and 34 targets have been successfully fielded on NIF relying on these metrology data. In the near future, ignition experiments on NIF will require tighter tolerances and more demanding target assembly and metrology capability. Metrology methods, calculations, and uncertainty estimates will be discussed. Target diagnostic port alignment, target position, and capsule location results will be reviewed for the 2009 Energetics Campaign. The information is presented via control charts showing the effect of process improvements that were made during target production. Certain parameters, including capsule position, met the 2009 campaign specifications but will have much tighter requirements in the future. Finally, in order to meet these new requirements assembly process changes and metrology capability upgrades will be necessary.

  9. NIF Laboratory Astrophysics Experiments Investigating The Effects Of A Radiative Shock On Hydrodynamic Instabilities

    NASA Astrophysics Data System (ADS)

    Kuranz, Carolyn; Drake, R. P.; Park, H. S.; Remington, B. A.; Huntington, C. M.; Doss, F. W.; Krauland, C. M.; Harding, E. C.; Grosskopf, M. J.; Marion, D. C.; Myra, E.; Fryxell, B.; Kalantar, D. H.; Keane, C. J.; Kilkenny, J. D.; Robey, H. F.; Maddox, B. R.; Miles, A. R.; Wallace, R. J.; May, M. J.; Kline, J. L.; Kyrala, G. A.; Plewa, T.; Wheeler, J. C.; Arnett, W. D.; Giraldez, E.; Nikroo, A.

    2010-05-01

    This paper will describe ongoing laboratory astrophysics experiments at the National Ignition Facility (NIF) relevant to the complex radiation hydrodynamics that occurs in red supergiant, and core-collapse supernovae. Experiments on NIF can deliver 300 eV radiative heating that can be utilized uniquely access the regime in which radiation affects the development of hydrodynamic instabilities within an evolving object. This is relevant to the dynamics that occur during the core-collapse explosions of red supergiant stars. These stars have dense circumstellar plasma, producing a strongly radiative shock whose radiation interacts with the hydrodynamic structures produced by instabilities during the explosion. While published astrophysical simulations have not included complex, multidimensional radiation hydrodynamics, such effects are very physical and expected to affect the evolution of early stages of astrophycal objects described above. This presentation will include a summary of the two test shots that we have performed on NIF, including a 0.7 scale, gas-filled hohlraum test shot, and a description of the integrated physics shots scheduled at the facility. This work is funded by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas under grant number DE-FG52-09NA29548 , the Lawrence Livermore National Security, LLC, under Contract No. DE-AC52-07NA27344 and Predictive Sciences Academic Alliances Program in NNSA-ASC via grant DEFC52- 08NA28616.

  10. NIF Laboratory Astrophysics Experiments Investigating The Effects Of A Radiative Shock On Hydrodynamic Instabilities

    NASA Astrophysics Data System (ADS)

    Kuranz, Carolyn C.; Drake, R. P.; Huntington, C. M.; Klein, S. R.; Trantham, M. R.; Park, H. S.; Remington, B. A.; Miles, A. R.; Raman, K.; Kline, J. L.; Plewa, T.

    2012-05-01

    This paper will describe ongoing laboratory astrophysics experiments at the National Ignition Facility (NIF) relevant to the complex radiation hydrodynamics that occurs in red supergiant, and core-collapse supernovae. Experiments on NIF can deliver 300 eV radiative heating that can be utilized uniquely access the regime in which radiation affects the development of hydrodynamic instabilities within an evolving object. This is relevant to the dynamics that occur during the core-collapse explosions of red supergiant stars. These stars have dense circumstellar plasma, producing a strongly radiative shock whose radiation interacts with the hydrodynamic structures produced by instabilities during the explosion. While published astrophysical simulations have not included complex, multidimensional radiation hydrodynamics, such effects are very physical and expected to affect the evolution of early stages of astrophysical objects described above. This presentation will include a summary of the two test shots that we have performed on NIF, including a 0.7 scale, gas-filled hohlraum test shot, and a description of the integrated physics shots scheduled at the facility. This work is funded by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas under grant number DE-FG52-09NA29548 , the Lawrence Livermore National Security, LLC, under Contract No. DE-AC52-07NA27344 and Predictive Sciences Academic Alliances Program in NNSA-ASC via grant DEFC52- 08NA28616.

  11. Beryllium ignition target design for indirect drive NIF experiments

    NASA Astrophysics Data System (ADS)

    Simakov, A. N.; Wilson, D. C.; Yi, S. A.; Kline, J. L.; Salmonson, J. D.; Clark, D. S.; Milovich, J. L.; Marinak, M. M.

    2016-03-01

    Beryllium (Be) ablator offers multiple advantages over carbon based ablators for indirectly driven NIF ICF ignition targets. These are higher mass ablation rate, ablation pressure and ablation velocity, lower capsule albedo, and higher thermal conductivity at cryogenic temperatures. Such advantages can be used to improve the target robustness and performance. While previous NIF Be target designs exist, they were obtained a long time ago and do not incorporate the latest improved physical understanding and models based upon NIF experiments. Herein, we propose a new NIF Be ignition target design at 1.45 MJ, 430 TW that takes all this knowledge into account.

  12. Transparent electrode for optical switch

    DOEpatents

    Goldhar, Julius; Henesian, Mark A.

    1986-01-01

    A low pressure gas electrode utilizing ionized gas in a glow discharge regime forms a transparent electrode for electro-optical switches. The transparent electrode comprises a low pressure gas region on both sides of the crystal. When the gas is ionized, e.g., by a glow discharge in the low pressure gas, the plasma formed is a good conductor. The gas electrode acts as a highly uniform conducting electrode. Since the plasma is transparent to a high energy laser beam passing through the crystal, the electrode is a transparent electrode. A crystal exposed from two sides to such a plasma can be charged up uniformly to any desired voltage. The plasma can be created either by the main high voltage pulser used to charge up the crystal or by auxiliary discharges or external sources of ionization. A typical configuration utilizes 10 torr argon in the discharge region adjacent to each crystal face.

  13. The use of a dynamic hydrogen electrode as an electrochemical tool to evaluate plasma activated carbon as electrocatalyst support for direct methanol fuel cell

    SciTech Connect

    Carmo, Marcelo Roepke, Thorsten; Scheiba, Frieder; Roth, Christina; Moeller, Stephan; Fuess, Hartmut; Poco, Joao G.R.; Linardi, Marcelo

    2009-01-08

    The objectives of this study were to functionalize the carbon black surface by chemically introducing oxygenated groups using plasma technology. This should enable a better interaction of the carbon support with the metallic catalyst nanoparticles, hindering posterior support particle agglomeration and preventing loss of active surface. PtRu/C nanoparticles were anchored on the carbon supports by the impregnation method and direct reduction with hydrazine. Physical characterization of the materials was carried out using energy dispersive X-ray analysis and transmission electron microscopy. The screen printing technique was used to produce membrane electrode assemblies for single cell tests in methanol/air (DMFC). Tests were carried out using the dynamic hydrogen electrode as an electrochemical tool to evaluate the anode and cathode behavior separately.

  14. Work function tuning of plasma-enhanced atomic layer deposited WC{sub x}N{sub y} electrodes for metal/oxide/semiconductor devices

    SciTech Connect

    Zonensain, Oren; Fadida, Sivan; Eizenberg, Moshe; Fisher, Ilanit; Gao, Juwen; Chattopadhyay, Kaushik; Harm, Greg; Mountsier, Tom; Danek, Michal

    2015-02-23

    One of the main challenges facing the integration of metals as gate electrodes in advanced MOS devices is control over the Fermi level position at the metal/dielectric interface. In this study, we demonstrate the ability to tune the effective work function (EWF) of W-based electrodes by process modifications of the atomic layer deposited (ALD) films. Tungsten carbo-nitrides (WC{sub x}N{sub y}) films were deposited via plasma-enhanced and/or thermal ALD processes using organometallic precursors. The process modifications enabled us to control the stoichiometry of the WC{sub x}N{sub y} films. Deposition in hydrogen plasma (without nitrogen based reactant) resulted in a stoichiometry of WC{sub 0.4} with primarily W-C chemical bonding, as determined by x-ray photoelectron spectroscopy. These films yielded a relatively low EWF of 4.2 ± 0.1 eV. The introduction of nitrogen based reactant to the plasma or the thermal ALD deposition resulted in a stoichiometry of WC{sub 0.1}N{sub 0.6–0.8} with predominantly W-N chemical bonding. These films produced a high EWF of 4.7 ± 0.1 eV.

  15. The amino-terminal GAF domain of Azotobacter vinelandii NifA binds 2-oxoglutarate to resist inhibition by NifL under nitrogen-limiting conditions.

    PubMed

    Little, Richard; Dixon, Ray

    2003-08-01

    The expression of genes required for the synthesis of molybdenum nitrogenase in Azotobacter vinelandii is controlled by the NifL-NifA transcriptional regulatory complex in response to nitrogen, carbon, and redox status. Activation of nif gene expression by the transcriptional activator NifA is inhibited by direct protein-protein interaction with NifL under conditions unfavorable for nitrogen fixation. We have recently shown that the NifL-NifA system responds directly to physiological concentrations of 2-oxoglutarate, resulting in relief of NifA activity from inhibition by NifL under conditions when fixed nitrogen is limiting. The inhibitory activity of NifL is restored under conditions of excess combined nitrogen through the binding of the signal transduction protein Av GlnK to the carboxyl-terminal domain of NifL. The amino-terminal domain of NifA comprises a GAF domain implicated in the regulatory response to NifL. A truncated form of NifA lacking this domain is not responsive to 2-oxoglutarate in the presence of NifL, suggesting that the GAF domain is required for the response to this ligand. Using isothermal titration calorimetry, we demonstrate stoichiometric binding of 2-oxoglutarate to both the isolated GAF domain and the full-length A. vinelandii NifA protein with a dissociation constant of approximately 60 microm. Limited proteolysis experiments indicate that the binding of 2-oxoglutarate increases the susceptibility of the GAF domain to trypsin digestion and also prevents NifL from protecting these cleavage sites. However, protection by NifL is restored when the non-modified (non-uridylylated) form of Av GlnK is also present. Our results suggest that the binding of 2-oxoglutarate to the GAF domain of NifA may induce a conformational change that prevents inhibition by NifL under conditions when fixed nitrogen is limiting. PMID:12759352

  16. Results from neutron imaging of ICF experiments at NIF

    NASA Astrophysics Data System (ADS)

    Merrill, F. E.; Danly, C. R.; Fittinghoff, D. N.; Grim, G. P.; Guler, N.; Volegov, P. L.; Wilde, C. H.

    2016-03-01

    In 2011 a neutron imaging diagnostic was commissioned at the National Ignition Facility (NIF). This new system has been used to collect neutron images to measure the size and shape of the burning DT plasma and the surrounding fuel assembly. The imaging technique uses a pinhole neutron aperture placed between the neutron source and a neutron detector. The detection system measures the two-dimensional distribution of neutrons passing through the pinhole. This diagnostic collects two images at two times. The long flight path for this diagnostic, 28 m, results in a chromatic separation of the neutrons, allowing the independently timed images to measure the source distribution for two neutron energies. Typically one image measures the distribution of the 14 MeV neutrons, and the other image measures the distribution of the 6-12 MeV neutrons. The combination of these two images has provided data on the size and shape of the burning plasma within the compressed capsule, as well as a measure of the quantity and spatial distribution of the cold fuel surrounding this core. Images have been collected for the majority of the experiments performed as part of the ignition campaign. Results from this data have been used to estimate a burn-averaged fuel assembly as well as providing performance metrics to gauge progress towards ignition. This data set and our interpretation are presented.

  17. Single-pulse driven, large-aperture 2×1 array plasma-electrodes optical switch for SG-II upgrading facility

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Wu, Dengsheng; Zheng, Jiangang; Zheng, Kuixing; Zhu, Qihua; Zhang, Xiongjun

    2014-12-01

    We demonstrate the design and performance of an optical switch that has been constructed for the SG-II upgrading facility. The device is a longitudinal, potassium di-hydrogen phosphate (KDP), 360 mm×360 mm aperture, and 2×1 array electro-optical switch driven by a 20 kV output switching-voltage pulse generator through two plasma electrodes produced at the rise edge of the switching-voltage pulse. The results show that the temporal responses and the spatial performance of the optical switch fulfill the operation requirements of the SG-II upgrading facility.

  18. NifB and NifEN protein levels are regulated by ClpX2 under nitrogen fixation conditions in Azotobacter vinelandii.

    PubMed

    Martínez-Noël, Giselle; Curatti, Leonardo; Hernandez, Jose A; Rubio, Luis M

    2011-03-01

    The major part of biological nitrogen fixation is catalysed by the molybdenum nitrogenase that carries at its active site the iron and molybdenum cofactor (FeMo-co). The nitrogen fixation (nif) genes required for the biosynthesis of FeMo-co are derepressed in the absence of a source of fixed nitrogen. The nifB gene product is remarkable because it assembles NifB-co, a complex cluster proposed to comprise a [6Fe-9S-X] cluster, from simpler [Fe-S] clusters common to other metabolic pathways. NifB-co is a common intermediate of the biosyntheses of the cofactors present in the molybdenum, vanadium and iron nitrogenases. In this work, the expression of the Azotobacter vinelandii nifB gene was uncoupled from its natural nif regulation to show that NifB protein levels are lower in cells growing diazotrophically than in cells growing at the expense of ammonium. A. vinelandii carries a duplicated copy of the ATPase component of the ubiquitous ClpXP protease (ClpX2), which is induced under nitrogen fixing conditions. Inactivation of clpX2 resulted in the accumulation of NifB and NifEN and a defect in diazotrophic growth, especially when iron was in short supply. Mutations in nifE, nifN and nifX or in nifA also affected NifB accumulation, suggesting that NifB susceptibility to degradation might vary during its catalytic cycle. PMID:21231969

  19. NifX and NifEN exchange NifB cofactor and the VK-cluster, a newly isolated intermediate of the iron-molybdenum cofactor biosynthetic pathway.

    PubMed

    Hernandez, Jose A; Igarashi, Robert Y; Soboh, Basem; Curatti, Leonardo; Dean, Dennis R; Ludden, Paul W; Rubio, Luis M

    2007-01-01

    The iron-molybdenum cofactor of nitrogenase (FeMo-co) is synthesized in a multistep process catalysed by several Nif proteins and is finally inserted into a pre-synthesized apo-dinitrogenase to generate mature dinitrogenase protein. The NifEN complex serves as scaffold for some steps of this synthesis, while NifX belongs to a family of small proteins that bind either FeMo-co precursors or FeMo-co during cofactor synthesis. In this work, the binding of FeMo-co precursors and their transfer between purified Azotobacter vinelandii NifX and NifEN proteins was studied to shed light on the role of NifX on FeMo-co synthesis. Purified NifX binds NifB cofactor (NifB-co), a precursor to FeMo-co, with high affinity and is able to transfer it to the NifEN complex. In addition, NifEN and NifX exchange another [Fe-S] cluster that serves as a FeMo-co precursor, and we have designated it as the VK-cluster. In contrast to NifB-co, the VK-cluster is electronic paramagnetic resonance (EPR)-active in the reduced and the oxidized states. The NifX/VK-cluster complex is unable to support in vitro FeMo-co synthesis in the absence of NifEN because further processing of the VK-cluster into FeMo-co requires the simultaneous activities of NifEN and NifH. Our in vitro studies suggest that the role of NifX in vivo is to serve as transient reservoir of FeMo-co precursors and thus help control their flux during FeMo-co synthesis. PMID:17163967

  20. Polarimetry of uncoupled light on the NIF

    SciTech Connect

    Turnbull, D. Moody, J. D.; Michel, P.; Ralph, J. E.; Divol, L.

    2014-11-15

    Polarimetry has been added to the full aperture backscatter diagnostic on the NIF. Wollaston prisms are used to sample a small region of a beam's backscatter, effectively separating it into two linear polarizations, one of which is parallel to the incident beam. A time-averaged measurement of each polarization is obtained by imaging the separated spots off of a scatter plate. Results have improved understanding of crossed beam energy transfer, glint, and sidescatter, and motivated plans to upgrade to a time-resolved polarimeter measuring the full Stokes vector.

  1. Fast Ignition Transport Simulations for NIF

    SciTech Connect

    Strozzi, D J; Grote, D P; Tabak, M; Cohen, B I; Town, R P; Kemp, A J

    2009-10-05

    This paper shows work at Lawrence Livermore National Lab (LLNL) devoted to modeling the propagation of, and heating by, a relativistic electron beam in a idealized dense fuel assembly for fast ignition. The implicit particle-in-cell (PIC) code LSP is used. Experiments planned on the National Ignition Facility (NIF) in the next few years using the Advanced Radiography Capability (ARC) short-pulse laser motivate this work. We demonstrate significant improvement in the heating of dense fuel due to magnetic forces, increased beam collimation, and insertion of a finite-radius carbon region between the beam excitation and fuel regions.

  2. Achieving and maintaining cleanliness in NIF amplifiers

    SciTech Connect

    Burnham, A. K.; Horvath, J. A.; Letts, S. A.; Menapace, J. A.; Stowers, I. F.

    1998-07-28

    Cleanliness measurements made on AMPLAB prototype National Ignition Facility (NIF) laser amplifiers during assembly, cassette transfer, and amplifier operation are summarized. These measurements include particle counts from surface cleanliness assessments using filter swipe techniques and from airborne particle monitoring. Results are compared with similar measurements made on the Beamlet and Nova lasers and in flashlamp test fixtures. Observations of Class 100,000 aerosols after flashlamp firings are discussed. Comparisons are made between typical damage densities on laser amplifier optics from Novette, NOVA, Beamlet, and AMPLAB.

  3. Breakthrough at NIF 'unlikely' in 2010

    NASA Astrophysics Data System (ADS)

    Harris, Margaret

    2010-05-01

    Hopes of reaching a milestone in fusion research by the end of 2010 have dimmed following a US government report that plays down the chances of an early breakthrough and sharply criticizes management of the 4bn National Ignition Facility (NIF). In the report, officials from the Government Accountability Office (GAO) state that ignition - fusion's "break-even" point - is "unlikely" to occur at the laser-fusion lab this year and that "significant scientific and technical challenges" could delay or even prevent the facility from achieving ignition by 2012.

  4. Kinetic Modeling of Divertor Plasma

    NASA Astrophysics Data System (ADS)

    Ishiguro, Seiji; Hasegawa, Hiroki; Pianpanit, Theerasarn

    2015-11-01

    Particle-in-Cell (PIC) simulation with the Monte Carlo collisions and the cumulative scattering angle coulomb collision can present kinetic dynamics of divertor plasmas. We are developing two types of PIC codes. The first one is the three dimensional bounded PIC code where three dimensional kinetic dynamics of blob is studied and current flow structures related to sheath formation are unveiled. The second one is the one spatial three velocity space dimensional (1D3V) PIC code with the Monte Carlo collisions where formation of detach plasma is studied. First target of our research is to construct self-consistent full kinetic simulation modeling of the linear divertor simulation experiments. This work is performed with the support and under the auspices of NIFS Collaboration Research program (NIFS15KNSS059, NIFS14KNXN279, and NIFS13KNSS038) and the Research Cooperation Program on Hierarchy and Holism in Natural Science at NINS.

  5. Regulation of nif gene expression in Enterobacter agglomerans: nucleotide sequence of the nifLA operon and influence of temperature and ammonium on its transcription.

    PubMed

    Siddavattam, D; Steibl, H D; Kreutzer, R; Klingmüller, W

    1995-12-20

    The nucleotide sequence of a plasmid-borne 3.9 kb XhoI-SmaI fragment comprising the 3'-region of the nifM gene, the nifL and nifA genes and the 5'-region of nifB gene of Enterobacter agglomerans was determined. The genes were identified by their homology to the corresponding nif genes of Klebsiella pneumoniae. A typical sigma 54-dependent promoter and a consensus NtrC-binding motif were identified upstream of nifL. The predicted amino acid sequence of NifL showed close similarities to NifL of K. pneumoniae and Azotobacter vinelandii. However, no histidine residue was found to correspond to histidine-304 of A. vinelandii NifL, which had been proposed to be required for the repressor activity of NifL. The NifA sequence with a putative DNA binding motif (Q(x3) A(x3) G(x5)I) and an ATP binding site in the C-terminal and central domains, respectively, resembles that of other known NifA proteins. The function of the nifL and nifA genes was demonstrated in vivo using a binary plasmid system by their ability to activate a nifH promoter-lacZ fusion at different temperatures and concentrations of NH4+. Maximal promoter activity occurred at 25 degrees C, and it appears that the sensitivity of NifA to elevated temperatures is independent of NifL. The expression of nifL inhibited promoter activity in the presence of NifA when the initial NH4+ concentration in the medium exceeded 4 mM. PMID:8544828

  6. Graphene-NiO nanohybrid prepared by dry plasma reduction as a low-cost counter electrode material for dye-sensitized solar cells.

    PubMed

    Dao, Van-Duong; Larina, Liudmila L; Jung, Kwang-Deog; Lee, Joong-Kee; Choi, Ho-Suk

    2014-01-01

    NiO nanoparticles (NPs) were hybridized on the surface of reduced graphene oxide (RGO) by dry plasma reduction (DPR) at atmospheric pressure without any toxic chemicals and at a low temperature. NiO-NPs of 0.5-3 nm size, with a typical size of 1.5 nm, were uniformly hybridized on the surface of RGO. An XPS analysis and the Raman spectra also revealed the repair of some structural damage on the basal plane of the graphene. The material when applied to the counter electrode (CE) of dye-sensitized solar cells (DSCs) exhibited a power conversion efficiency of 7.42% (± 0.10%), which is comparable to a conventional Pt-sputtered CE (8.18% (± 0.08%)). This material outperformed CEs produced using NiO-NPs (1.53% (± 0.15%)), GO (4.48% (± 0.12%)) and RGO (5.18% (± 0.11)) due to its high electrochemical catalytic activity and high conductivity. The charge transfer resistance for NiO-NP-RGO was as low as 1.93 Ω cm(2), while those of a NiO-NP-immobilized electrode and a GO-coated electrode were 44.39 Ω cm(2) and 12.19 Ω cm(2), respectively, due to a synergistic effect. PMID:24217311

  7. Surface potential distribution and airflow performance of different air-exposed electrode plasma actuators at different alternating current/direct current voltages

    SciTech Connect

    Yang, Liang; Yan, Hui-Jie; Qi, Xiao-Hua; Hua, Yue; Ren, Chun-Sheng

    2015-04-15

    Asymmetric surface dielectric barrier discharge (SDBD) plasma actuators have been intensely studied for a number of years due to their potential applications for aerodynamic control. In this paper, four types of actuators with different configurations of exposed electrode are proposed. The SDBD actuators investigated are driven by dual-power supply, referred to as a fixed AC high voltage and an adjustable DC bias. The effects of the electrode structures on the dielectric surface potential distribution, the electric wind velocity, and the mean thrust production are studied, and the dominative factors of airflow acceleration behavior are revealed. The results have shown that the actions of the SDBD actuator are mainly dependent on the geometry of the exposed electrode. Besides, the surface potential distribution can effectively affect the airflow acceleration behavior. With the application of an appropriate additional DC bias, the surface potential will be modified. As a result, the performance of the electric wind produced by a single SDBD can be significantly improved. In addition, the work also illustrates that the actuators with more negative surface potential present better mechanical performance.

  8. Plasma characteristics of single- and dual-electrode ion source systems utilized in low-energy ion extraction

    SciTech Connect

    Vasquez, M. R.; Tokumura, S.; Kasuya, T.; Wada, M.

    2014-02-15

    Discharge characteristics in the upstream as well as in the downstream regions of a 50-eV positive ion beam were measured along the beam axis. Single- and dual-electrode configurations made of 0.1-mm diameter tungsten wires were tested. By varying the upstream discharge parameters, the shape of the sheath edge around the extractors, which can either be “planar” or “cylindrical,” can be controlled. The sheath eventually affected the simultaneous extraction of ions and neutralizing electrons. The dual-electrode configuration at the lower discharge current, revealed a homogeneous discharge downstream. At this condition, the edge of the sheath can be inferred to be “planar” which allowed the uniform extraction and propagation of low-energy ions at longer distances. The dual-electrode configuration was capable of transmitting low-energy ions up to 70 mm downstream.

  9. High-performance liquid chromatographic method with amperometric detection employing boron-doped diamond electrode for the determination of sildenafil, vardenafil and their main metabolites in plasma.

    PubMed

    Bartošová, Zdenka; Jirovský, David; Horna, Aleš

    2011-11-01

    A simple, fast and sensitive HPLC method with electrochemical detection employing boron-doped diamond electrode (BDD) for the determination of sildenafil (Viagra™), vardenafil (Levitra™) and their main metabolites, N-desmethyl sildenafil and N-desethyl vardenafil in human plasma is presented. The assay involved drug extraction by tert-butyl methyl ether and isocratic reversed-phase liquid chromatography with amperometric detection. Complete separation of all analytes was achieved within 12 min. The mobile phase consisted of 20mM sodium dihydrogen phosphate with 40 mM sodium perchlorate/acetonitrile (70:30, v/v), pH 3.5. The electrode working potential was +1520 mV (vs. Pd/H(2)). Calibration curves were linear over the concentration range of 10-400 ng mL(-1). Phloretin was used as an internal standard. The limits of detection (LOD) and quantification (LOQ) for the studied analytes were within the range of 2-4 ng mL(-1) and 7.0-13.4 ng mL(-1), respectively. The developed method was applied to human plasma samples spiked with analytes at therapeutic concentrations. The study confirms the method's suitability for both pharmacokinetic studies and therapeutic monitoring. PMID:21943935

  10. Design Calculations for NIF Convergent Ablator Experiments

    NASA Astrophysics Data System (ADS)

    Olson, R. E.; Callahan, D. A.; Hicks, D. G.; Landen, O. L.; Langer, S. H.; Meezan, N. B.; Spears, B. K.; Widmann, K.; Kline, J. L.; Wilson, D. C.; Petrasso, R. D.; Leeper, R. J.

    2010-11-01

    Design calculations for NIF convergent ablator experiments will be described. The convergent ablator experiments measure the implosion trajectory, velocity, and ablation rate of an x-ray driven capsule and are a important component of the U. S. National Ignition Campaign at NIF. The design calculations are post-processed to provide simulations of the key diagnostics -- 1) Dante measurements of hohlraum x-ray flux and spectrum, 2) streaked radiographs of the imploding ablator shell, 3) wedge range filter measurements of D-He3 proton output spectra, and 4) GXD measurements of the imploded core. The simulated diagnostics will be compared to the experimental measurements to provide an assessment of the accuracy of the design code predictions of hohlraum radiation temperature, capsule ablation rate, implosion velocity, shock flash areal density, and x-ray bang time. Post-shot versions of the design calculations are used to enhance the understanding of the experimental measurements and will assist in choosing parameters for subsequent shots and the path towards optimal ignition capsule tuning. *SNL, LLNL, and LANL are operated under US DOE contracts DE-AC04-94AL85000. DE-AC52-07NA27344, and DE-AC04-94AL85000.

  11. Design calculations for NIF convergent ablator experiments.

    SciTech Connect

    Callahan, Debra; Leeper, Ramon Joe; Spears, B. K.; Zylstra, A.; Seguin, F.; Landen, Otto L.; Petrasso, R. D.; Rinderknecht, H.; Kline, J. L.; Frenje, J.; Wilson, D. C.; Langer, S. H.; Widmann, K.; Meezan, Nathan B.; Hicks, Damien G.; Olson, Richard Edward

    2010-11-01

    Design calculations for NIF convergent ablator experiments will be described. The convergent ablator experiments measure the implosion trajectory, velocity, and ablation rate of an x-ray driven capsule and are a important component of the U. S. National Ignition Campaign at NIF. The design calculations are post-processed to provide simulations of the key diagnostics: (1) Dante measurements of hohlraum x-ray flux and spectrum, (2) streaked radiographs of the imploding ablator shell, (3) wedge range filter measurements of D-He3 proton output spectra, and (4) GXD measurements of the imploded core. The simulated diagnostics will be compared to the experimental measurements to provide an assessment of the accuracy of the design code predictions of hohlraum radiation temperature, capsule ablation rate, implosion velocity, shock flash areal density, and x-ray bang time. Post-shot versions of the design calculations are used to enhance the understanding of the experimental measurements and will assist in choosing parameters for subsequent shots and the path towards optimal ignition capsule tuning.

  12. Automated Test System for NIF Flashlamps

    SciTech Connect

    da Silva, T; Creely, P; Hammon, J; Shaw, R; Boyle, R T; Fulkerson, E S

    2001-06-05

    This paper describes design and operation of the flashlamp test system, used to evaluate the primary laser flashlamps on the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory (LLNL) in Livermore, California. The tester delivers repetitive high voltage pulses to a series pair of flashlamps at levels closely simulating those encountered in normal operation. Each lamp pair is subjected to a pre-ionization and main pulse shot sequence, with two minute intervals between shots. This capability allows the manufacturer to test and evaluate the flashlamps for infant mortality and longevity before delivery to NIF. All operations are under computer control with fully automated test and data acquisition capabilities requiring minimal operator input. The system is designed to operate continuously. Typical pre-ionization and main pulse outputs are: (1) Pre-ionization Pulse--V{sub chg} = 27kV, I{sub peak} = 3kA, E = 2.4kJ; Pulse Width--(10%-90%) - 200us; Main Pulse--V{sub chg} = 23kV, I{sub peak} - 24kA, E - 78.6kJ; and Pulse Width--(10%-90%) - 350us.

  13. First-principles study of the change in the electronic properties of NiF2 by the introduction of oxygen

    NASA Astrophysics Data System (ADS)

    Kim, Yongseon; Kim, Subin; Choi, Sujin

    2013-12-01

    NiF2 is investigated as a conversion-reaction-based positive electrode material in applications to lithium ion batteries. Despite high discharge capacity, slow reaction kinetics due to poor electrical conductivity is a general drawback of the conversion reaction. The electronic features of NiF2 were investigated using the DV-Xα molecular orbital method in this study. The effects of oxygen doping on the bonding characteristics and electrical conductivity were examined in particular. An analysis of the bond overlap population and spatial distribution of electrons showed that the Ni-O bond has a more covalent nature than the Ni-F bond, and doping of oxygen increases the covalent characteristics of Ni-F bond. New energy levels were generated in the band gap region through an interaction between the Ni3d and O2p orbitals with the introduction of oxygen. The electrical conductivity of NiF2 is expected to be increased by the substitution of fluorine by oxygen owing to the higher covalent character and the formation of new energy levels.

  14. Electrical and structural characterization of plasma polymerized polyaniline/TiO2 heterostructure diode: a comparative study of single and bilayer TiO2 thin film electrode.

    PubMed

    Ameen, Sadia; Akhtar, M Shaheer; Kimi, Young Soon; Yang, O-Bong; Shin, Hyung-Shik

    2011-04-01

    A heterostructure was fabricated using p-type plasma polymerized polyaniline (PANI) and n-type (single and bilayer) titanium dioxide (TiO2) thin film on FTO glass. The deposition of single and bilayer TiO2 thin film on FTO substrate was achieved through doctor blade followed by dip coating technique before subjected to plasma enhanced polymerization. To fabricate p-n heterostructure, a plasma polymerization of aniline was conducted using RF plasma at 13.5 MHz and at the power of 120 W on the single and bilayer TiO2 thin film electrodes. The morphological, optical and the structural characterizations revealed the formation of p-n heterostructures between PANI and TiO2 thin film. The PANI/bilayer TiO2 heterostructure showed the improved current-voltage (I-V) characteristics due to the substantial deposition of PANI molecules into the bilayer TiO2 thin film which provided good conducting pathway and reduced the degree of excitons recombination. The change of linear I-V behavior of PANI/TiO2 heterostructure to non linear behavior with top Pt contact layer confirmed the formation of Schottky contact at the interfaces of Pt layer and PANI/TiO2 thin film layers. PMID:21776701

  15. Fabrication of electrodes with ultralow platinum loading by RF plasma processing of self-assembled arrays of Au@Pt nanoparticles

    NASA Astrophysics Data System (ADS)

    Banerjee, Ipshita; Kumaran, V.; Santhanam, Venugopal

    2016-07-01

    Conductive, carbon-free, electrocatalytically active, nanostructured electrodes with ultra-low platinum loading were fabricated using self-assembly of octadecanethiol-coated Au@Pt nanoparticles followed by RF plasma treatment. Bilayer arrays of Au@Pt nanoparticles with platinum loadings of 0.50, 1.04, 1.44, and 1.75 μg cm‑2 (corresponding to 0.5, 1, 1.5 and 2 atomic layer coverage of platinum on nominally 5 nm gold core) were subjected to RF argon plasma treatment for various durations and their electrical conductivity, morphological evolution, and electrocatalytic activity characterized. Samples with monolayer and above platinum coverages exhibit maximum electrochemically active surface areas values of ∼100 m2/gpt and specific activities that are ∼4× to 6× of a reference platinum nanoparticle bilayer array. The underlying gold core influences the structural evolution of the samples upon RF plasma treatment and leads to the formation of highly active Pt(110) facets on the surface at an optimal plasma treatment duration, which also corresponds to the onset of a sharp decline in lateral sheet resistance. The sample having a two atom thick platinum coating has the highest total mass activity of 48 ± 3 m2/g(pt+au), corresponding to 44% Pt atom utilization, while also exhibiting enhanced CO tolerance as well as high methanol oxidation reaction and oxygen reduction reaction activity.

  16. Fabrication of electrodes with ultralow platinum loading by RF plasma processing of self-assembled arrays of Au@Pt nanoparticles.

    PubMed

    Banerjee, Ipshita; Kumaran, V; Santhanam, Venugopal

    2016-07-29

    Conductive, carbon-free, electrocatalytically active, nanostructured electrodes with ultra-low platinum loading were fabricated using self-assembly of octadecanethiol-coated Au@Pt nanoparticles followed by RF plasma treatment. Bilayer arrays of Au@Pt nanoparticles with platinum loadings of 0.50, 1.04, 1.44, and 1.75 μg cm(-2) (corresponding to 0.5, 1, 1.5 and 2 atomic layer coverage of platinum on nominally 5 nm gold core) were subjected to RF argon plasma treatment for various durations and their electrical conductivity, morphological evolution, and electrocatalytic activity characterized. Samples with monolayer and above platinum coverages exhibit maximum electrochemically active surface areas values of ∼100 m(2)/gpt and specific activities that are ∼4× to 6× of a reference platinum nanoparticle bilayer array. The underlying gold core influences the structural evolution of the samples upon RF plasma treatment and leads to the formation of highly active Pt(110) facets on the surface at an optimal plasma treatment duration, which also corresponds to the onset of a sharp decline in lateral sheet resistance. The sample having a two atom thick platinum coating has the highest total mass activity of 48 ± 3 m(2)/g(pt+au), corresponding to 44% Pt atom utilization, while also exhibiting enhanced CO tolerance as well as high methanol oxidation reaction and oxygen reduction reaction activity. PMID:27302373

  17. The National Ignition Facility (NIF) as a User Facility

    NASA Astrophysics Data System (ADS)

    Keane, Christopher; NIF Team

    2013-10-01

    The National Ignition Facility (NIF) has made significant progress towards operation as a user facility. Through June 2013, NIF conducted over 1200 experiments in support of ICF, HED science, and development of facility capabilities. The NIF laser has met or achieved all specifications and a wide variety of diagnostic and target fabrication capabilities are in place. A NIF User Group and associated Executive Board have been formed. Two User Group meetings have been conducted since formation of the User Group. NIF experiments in fundamental science have provided important new results. NIF ramp compression experiments have been conducted using diamond and iron, with EOS results obtained at pressures up to approximately 50 Mbar and 8 Mbar, respectively. Initial experiments in supernova hydrodynamics, the fundamental physics of the Rayleigh-Taylor instability, and equation of state in the Gbar pressure regime have also been conducted. This presentation will discuss the fundamental science program at NIF, including the proposal solicitation and scientific review processes and other aspects of user facility operation. This work was performed under the auspices of the Lawrence Livermore National Security, LLC, (LLNS) under Contract No. DE-AC52-07NA27344.

  18. National NIF Diagnostic Program Fiscal Year 2002 Second Quarter Report

    SciTech Connect

    MacGowan, B

    2002-04-01

    Since October 2001 the development of the facility diagnostics for NIF has been funded by the NIF Director through the National NIF Diagnostic Program (NNDP). The current emphasis of the NNDP is on diagnostics for the early NIF quad scheduled to be available for experiment commissioning in FY03. During the past six months the NNDP has set in place processes for funding diagnostics, developing requirements for diagnostics, design reviews and monthly status reporting. Those processes are described in an interim management plan for diagnostics (''National NIF Diagnostic Program Interim Plan'', NIF-0081315, April 2002) and a draft Program Execution Plan (''Program Execution Plan for the National NlF Diagnostic Program'', NIF-0072083, October 2001) and documents cited therein. Work has been funded at Lawrence Livermore National Laboratory (LLNL), Los Alamos National Laboratory (LANL), Naval Research Laboratory (NRL), Sandia National Laboratories (SNL), Bechtel Nevada at Los Alamos and Santa Barbara. There are no major technical risks with the early diagnostics. The main concerns relate to integration of the diagnostics into the facility, all such issues are being worked. This report is organized to show the schedule and budget status and a summary of Change Control Board actions for the past six months. The following sections then provide short descriptions of the status of each diagnostic. Where design reviews or requirements documents are cited, the documents are available on the Diagnostics file server or on request.

  19. Effects of N2O Plasma Annealing on the Characteristics of Tantalum Oxide Thin Films Deposited on TaN/Ta Electrode

    NASA Astrophysics Data System (ADS)

    Liu, Tzu-Ping; Huang, Ya-Huang; Chang, Chich-Shang; Wu, Tai-Bor

    2002-12-01

    The effects of N2O plasma annealing on the structural and leakage current characteristics of amorphous and crystallized TaOx thin films deposited on a TaN/Ta bottom electrode by chemical vapor deposition at 350°C were investigated. An interfacial Ta(O,N) layer was formed following the oxidation of the TaN electrode after plasma annealing the TaOx films of ˜25 nm thickness, which decreased the effective capacitance of the thin film capacitors, and the Ta(O,N) layer grew with increasing annealing time or temperature. The growth of the Ta(O,N) layer up to a thickness of 38 nm followed a linear oxidation law with an activation energy of ˜0.74 eV for the annealing of the amorphous TaOx films in a temperature range of 300°C-450°C. However, an activation energy of ˜1.18 eV was found for the linear oxidation of TaN within an oxidation thickness of 22 nm, and then, the oxidation switched to a parabolic process with an activation energy of ˜0.8 eV for annealing the crystallized TaOx films. The current-voltage (I-V) relation of the TaOx films was asymmetric with respect to the biasing polarity, and the leakage current decreased with increasing annealing time or temperature due to the formation and growth of a Ta(ON) layer. Barrier heights of 1.08 and 0.74 eV were evaluated from the temperature dependence of the I-V characteristics for the Schottky emission in the amorphous and crystalline 50-nm-thick TaOx films annealed in N2O plasma at 350°C for 10 min, respectively.

  20. Use of Lubricants in the NIF

    SciTech Connect

    Gourdin, W; Biltoft, P

    2006-07-06

    There are two principal concerns that govern the use of lubricants in NIF: (1) Airborne molecular contaminants (AMCs)--AMCs are known to seriously degrade the performance of sol-gel coated optics. AMCs are produced by the slow outgassing of residues (non-volatile residues or ''NVRs'') of high molecular weight compounds left on surfaces. Lubricants, particularly hydrocarbon lubricants, are a primary source of such NVRs. (2) Particulates--Particulates that accumulate on optical surfaces can cause permanent physical damage when exposed to high energy density laser light. Lubricant residues exposed to high energy density light will pyrolyze or decompose and produce carbon particulates. The NIF Approved Materials Database lists several lubricants that have been tested for use in NIF environments. Many of these lubricants were tested according to MELs 99-006 (oven outgassing test) or 99-007 (vacuum outgassing test). In these tests, the change in percent transmission of light through a sol-gel coated optic placed next to the sample under evaluation is used as the diagnostic. Samples that cause less than 0.1% change in optical transmission are deemed suitable for use inside beam enclosures. This testing, however, addresses only the concern associated with AMCs. To assess the issue of particle generation, a flashlamp or ''aerosol'' test is used. In this test a sample with residues is subjected to intense light from the main amplifier flashlamps. The number density of particles per unit volume is measure after each flash. A measurement of an average of fewer than 1000 particles >0.5{micro}m in diameter produced per square foot of exposed surface per flash for each of the last ten flashes in a series of 60 flashes of light is deemed to be acceptable for polymers. A measurement of an average of fewer than 100 particles >0.5{micro}m in diameter produced per square foot of exposed surface per flash for each of the last ten flashes in a series of 60 flashes of light is deemed to

  1. Genetic analysis on the NifW by utilizing the yeast two-hybrid system revealed that the NifW of Azotobacter vinelandii interacts with the NifZ to form higher-order complexes.

    PubMed

    Lee, S H; Pulakat, L; Parker, K C; Gavini, N

    1998-03-17

    Nitrogenase is a complex metalloenzyme composed of two separately purified proteins designated the Fe-protein and the MoFe-protein. Apart from these two proteins, a number of accessory proteins are essential for the maturation and assembly of nitrogenase. Even though experimental evidence suggests that these accessory proteins are required for nitrogenase activity, the exact roles played by many of these proteins in the functions of nitrogenase are unclear. Our studies were directed to understand the role of two nif accessory proteins, the NifW and the NifZ in the biological nitrogen fixation. To accomplish this, we have utilized a genetic method, the Yeast based Two-Hybrid protein-protein interaction assay. This analysis showed that the NifW could interact with itself to make a multimeric complex. In contrast, the NifZ could not interact with itself. However, the NifZ could interact with the NifW. Previously it was shown that mutating either the NifW or the NifZ have similar effects on the activity of nitrogenase. This observation indicated that both these proteins may exert their regulation on the nitrogenase by a common pathway. Furthermore, it was suggested that the NifW plays a role in the oxygen-protection of the MoFe-protein by direct physical interaction. Our observation that the NifW can interact with itself as well as with the NifZ, suggests that the NifW and the NifZ may form a higher order complex and such a complex may be needed to exert the effects of the NifW or the NifZ on the nitrogenase activity. PMID:9514861

  2. Science on high-energy lasers: From today to the NIF

    SciTech Connect

    Lee, R.W.; Petrasso, R.; Falcone, R.W.

    1995-01-01

    This document presents both a concise definition of the current capabilities of high energy lasers and a description of capabilities of the NIF (National Ignition Facility). Five scientific areas are discussed (Astrophysics, Hydrodynamics, Material Properties, Plasma Physics, Radiation Sources, and Radiative Properties). In these five areas we project a picture of the future based on investigations that are being carried on today. Even with this very conservative approach we find that the development of new higher energy lasers will make many extremely exciting areas accessible to us.

  3. Site-directed mutagenesis of the Klebsiella pneumoniae nifL and nifH promoters and in vivo analysis of promoter activity.

    PubMed Central

    Buck, M; Khan, H; Dixon, R

    1985-01-01

    The role of conserved nucleotides in nitrogen-fixation promoter function has been examined using both oligonucleotide and chemical mutagenesis to introduce base changes in the Klebsiella pneumoniae nifL and nifH promoters. Among ten mutations analysed, including six spontaneous mutations, base changes at -12, -13, -14, and -26, located in previously identified conserved sequences, perturbed the activity of the promoters, demonstrating that these sequences are required for transcription. Not all base changes produced similar strong promoter down phenotypes when the nifL and nifH promoters were compared: activation of the nifH promoter by the nifA gene product was less sensitive to base changes in conserved nucleotides than was activation of the equivalently altered nifL promoter by the nifA or ntrC products. We have found that the nifH promoter can be weakly activated by the ntrC product; this activation shows the same down response to base changes seen with ntrC activation of the nifL promoter. We present evidence that the efficient activation of the nifH promoter by nifA (but not ntrC) can be attributed to specific upstream sequences present in the nifH promoter. PMID:3906564

  4. The NIF Ignition Program: Progress And Planning

    SciTech Connect

    Hammel, B A

    2006-06-12

    The first experimental campaign for ignition, beginning in 2010 after NIF construction and commissioning are completed, will include experiments to measure and optimize key laser and target conditions necessary for ignition. These ''tuning campaigns'' will precede the first ignition shots. Ignition requires acceptable target performance in several key areas: Energetics, Symmetry, Shock timing, and Capsule Hydrodynamics. Detailed planning and simulations for ''tuning campaigns'' in each of these areas is currently underway, as part of the National Ignition Campaign (NIC) Program. Tuning and diagnostic methods are being developed and tested on present facilities, including the Omega laser at the Laboratory for Energetics (LLE), the Z facility at Sandia National Laboratories (SNL), and the Trident laser at Los Alamos National Laboratory (LANL).

  5. Performance of the NIF prototype beamlet

    SciTech Connect

    Van Wonterghem, B.M.; Murray, J.R.; Speck, D.R.; Campbell, J.H.

    1994-07-20

    Beamlet is a full scale single beam prototype laser system, built to demonstrate the laser technology and performance of the 192 beam National Ignition Facility (NIF) fusion laser driver. Both laser systems apply multipass amplifier architectures. By passing the beam four times through the large aperture amplifier sections, the small signal gain during the first few passes is used efficiently to reduce expensive staged amplifier chains. The beamlet prototype laser integrates results of development programs for large aperture components: large aperture optical switch, polarizers, 2 x 2 multisegment amplifiers and new pulse generation and pre-amplification techniques. The authors report on performance test results of the recently completed 1 {omega}-laser section of Beamlet.

  6. Transport Simulations for Fast Ignition on NIF

    SciTech Connect

    Strozzi, D J; Tabak, M; Grote, D P; Cohen, B I; Shay, H D; Town, R J; Kemp, A J; Key, M

    2009-10-26

    We are designing a full hydro-scale cone-guided, indirect-drive FI coupling experiment, for NIF, with the ARC-FIDO short-pulse laser. Current rad-hydro designs with limited fuel jetting into cone tip are not yet adequate for ignition. Designs are improving. Electron beam transport simulations (implicit-PIC LSP) show: (1) Magnetic fields and smaller angular spreads increase coupling to ignition-relevant 'hot spot' (20 um radius); (2) Plastic CD (for a warm target) produces somewhat better coupling than pure D (cryogenic target) due to enhanced resistive B fields; and (3) The optimal T{sub hot} for this target is {approx} 1 MeV; coupling falls by 3x as T{sub hot} rises to 4 MeV.

  7. Target Diagnostics Supports NIF's Path to Ignition

    SciTech Connect

    Shelton, R

    2011-12-07

    The physics requirements derived from the National Ignition Facility (NIF) experimental campaigns are leading to a wide variety of target diagnostics. Software development for the control and analysis of these diagnostics is included in the NIF Integrated Computer Control System, Diagnostic Control System and Data Visualization. These projects implement the configuration, controls, data analysis and visual representation of most of these diagnostics. To date, over 40 target diagnostics have been developed to support NIF experiments. In 2011 diagnostics were developed or enhanced to measure Ignition performance in a high neutron yield environment. Performance is optimized around four key variables: Adiabat (a) which is the strength and timing of four shocks delivered to the target, Velocity (V) of the imploding target, Mix (M) is the uniformity of the burn, and the Shape (S) of the imploding Deuterium Tritium (DT) hot spot. The diagnostics used to measure each of these parameters is shown in figure 1. Adiabat is measured using the Velocity Interferometer System for Any Reflector (VISAR) diagnostic consisting of three streak cameras. To provide for more accurate adiabat measurements the VISAR streak cameras were enhanced in FY11 with a ten comb fiducial signal controller to allow for post shot correction of the streak camera sweep non-linearity. Mix is measured by the Neutron Time of Flight (NTOF) and Radiochemical Analysis of Gaseous Samples (RAGS) diagnostics. To accommodate high neutron yield shots, NTOF diagnostic controls are being modified to use Mach Zehnder interferometer signals to allow the digitizers to be moved from near the target chamber to the neutron shielded diagnostic mezzanine. In December 2011 the first phase of RAGS diagnostic commissioning will be completed. This diagnostic will analyze the tracers that are added to NIF target capsules that undergo nuclear reactions during the shot. These gases are collected and purified for nuclear counting by

  8. Final report for NIF chamber dynamics studies

    SciTech Connect

    Burnham, A; Peterson, P F; Scott, J M

    1998-09-01

    The National Ignition Facility (NIF), a 1.8 MJ, 192 laser beam facility, will have anticipated fusion yields of up to 20 MJ from D-T pellets encased in a gold hohlraum target. The energy emitted from the target in the form of x rays, neutrons, target debris kinetic energy, and target shrapnel will be contained in a 5 m. radius spherical target chamber. various diagnostics will be stationed around the target at varying distances from the target. During each shot, the target will emit x rays that will vaporize nearby target facing surfaces including those of the diagnostics, the target positioner, and other chamber structures. This ablated vapor will be transported throughout the chamber, and will eventually condense and deposit on surfaces in the chamber, including the final optics debris shields. The research at the University of California at Berkeley relates primarily to the NIF chamber dynamics. The key design issues are the ablation of the chamber structures, transport of the vapor through the chamber and the condensation or deposition processes of those vaporized materials. An understanding of these processes is essential in developing a concept for protecting the fina optics debris shields from an excessive coating (> 10 A) of target debris and ablated material, thereby prolonging their lifetime between change-outs. At Berkeley, we have studied the physical issues of the ablation process and the effects of varying materials, the condensation process of the vaporized material, and design schemes that can lower the threat posed to the debris shields by these processes. The work or portions of the work completed this year have been published in several papers and a dissertation [l-5].

  9. Measurements and Simulations of the Energy Distributions of Ions Bombarding Radio-frequency Biased Electrodes in an Inductively Coupled Plasma Reactor

    NASA Astrophysics Data System (ADS)

    Edelberg, Erik A.; Perry, Andrew; Benjamin, Neil; Aydil, Eray S.

    1998-10-01

    A compact retarding field ion energy analyzer has been designed and built to measure the energy distribution of ions bombarding the surface of radio frequency (rf) biased electrodes in high-density plasma reactors. Specifically, the analyzer was installed in the rf biased electrostatic chuck of a high-density, transformer-coupled plasma (TCP) reactor. The effects of TCP power, rf bias power, pressure, and gas composition on the measured ion energy distributions are demonstrated through Ar, Ne, Ar/Ne, O2 and CF4/O2 discharges. To complement the experimental results, a numerical sheath model that predicts the spatio-temporal variations of the potential across the sheath in a high density plasma has been developed. The energy distribution of ions bombarding the rf biased surface is then calculated using Monte Carlo simulations of the ion trajectories. Bimodal ion energy distributions resulting from ion energy modulation in the sheath were observed and simulated. Multiple peaks in the IEDs measured in gas mixtures were identified as signatures of ions with different masses falling through the sheath. The simulations predict both the energy separation of the bimodal IEDs as well as the ratio of the peak heights as measured by the ion energy analyzer.

  10. Identification, sequencing and structural analysis of a nifA-like gene of Acetobacter diazotrophicus.

    PubMed

    Teixeira, K R; Morgan, T; Meletzus, D; Galler, R; Baldani, J I; Kennedy, C

    1999-01-01

    A recombinant plasmid, pAD101, containing a DNA fragment of Acetobacter diazotrophicus strain PAL5 was isolated by its ability to restore Nif+ phenotype to a nifA- ntrC- double mutant of Azotobacter vinelandii. Hybridization with the nifA genes of Azospirillum brasilense located the nifA gene more precisely to specific fragments of pAD101. DNA sequencing of appropriate subclones of pAD101 revealed that the nifA gene was adjacent to the nifB gene in A. diazotrophicus, and the 5' end of the nifB gene was located downstream of the nitrogenase MoFe subunit gene, nifK. The deduced aminoacid sequence of A. diazotrophicus nifA and nifB gene were most similar to the NifA and NifB proteins of Azorhizobium caulinodans and Rhodobacter capsulatus, respectively. In addition, nucleotide sequences upstream of the A. diazotrophicus nifA-encoding region indicate features similar to those in the A. caulinodans nifA promoter region involved in O2 and fixed N regulation of nifA expression. PMID:10530336

  11. Iron is required to relieve inhibitory effects on NifL on transcriptional activation by NifA in Klebsiella pneumoniae.

    PubMed

    Schmitz, R A; He, L; Kustu, S

    1996-08-01

    In Klebsiella pneumoniae, products of the nitrogen fixation nifLA operon regulate transcription of the other nif operons. NifA activates transcription by sigma54-holoenzyme. In vivo, NifL antagonizes the action of NifA under aerobic conditions or in the presence of combined nitrogen. In contrast to a previous report, we show that depletion of iron (Fe) from the growth medium with the chelating agent o-phenanthroline (20 microM) mimics aerobiosis or combined nitrogen in giving rise to inhibition of NifA activity even under anaerobic, nitrogen-limiting conditions. Adding back Fe in only twofold molar excess over phenanthroline restores NifA activity, whereas adding other metals fails to do so. By using strains that lack NifL, we showed that NifA activity itself does not require Fe and is not directly affected by phenanthroline. Hence, Fe is required to relieve the inhibition of NifA activity by NifL in vivo. Despite the Fe requirement in vivo, we have found no evidence that NifL contains Fe or an iron-sulfur (Fe-S) cluster. Determination of the molecular mass of an inhibitory form of NifL overproduced under aerobic conditions indicated that it was not posttranslationally modified. When NifL was synthesized in vitro, it inhibited transcriptional activation by NifA even when it was synthesized under anaerobic conditions in the presence of a high Fe concentration or of superoxide dismutase, which is known to protect some Fe-S clusters. Moreover, overproduction of superoxide dismutase in vivo did not relieve NifL, inhibition under aerobic conditions, and attempts to relieve NifL inhibition in vitro by reconstituting Fe-S clusters with the NifS enzyme (Azotobacter vinelandii) were unsuccessful. Since we obtained no evidence that Fe acts directly on NifL or NifA, we postulate that an additional Fe-containing protein, not yet identified, may be required to relieve NifL inhibition under anaerobic, nitrogen-limiting conditions. PMID:8755900

  12. Inertial Confinement Fusion and the National Ignition Facility (NIF)

    SciTech Connect

    Ross, P.

    2012-08-29

    Inertial confinement fusion (ICF) seeks to provide sustainable fusion energy by compressing frozen deuterium and tritium fuel to extremely high densities. The advantages of fusion vs. fission are discussed, including total energy per reaction and energy per nucleon. The Lawson Criterion, defining the requirements for ignition, is derived and explained. Different confinement methods and their implications are discussed. The feasibility of creating a power plant using ICF is analyzed using realistic and feasible numbers. The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory is shown as a significant step forward toward making a fusion power plant based on ICF. NIF is the world’s largest laser, delivering 1.8 MJ of energy, with a peak power greater than 500 TW. NIF is actively striving toward the goal of fusion energy. Other uses for NIF are discussed.

  13. Role of the NIF in the development of ICF applications

    SciTech Connect

    Hogan, W.

    1998-04-23

    The National Ignition Facility (NIF) is a 1.8 MJ (at 351 nm), 192 beam laser facility being built at the Lawrence Livermore National Laboratory (LLNL) to achieve inertial fusion ignition in the laboratory. The NIF Project is being designed and built by a team from LLNL, Los Alamos National Laboratory, Sandia National Laboratory, and the University of Rochester. When completed in 2003, it will be a multipurpose facility that will be used for many applications in national security, energy, and the basic sciences. In addition to the National Security Mission, these applications include, for example, electric power generation, space propulsion, and study of basic astrophysical phenomena in the laboratory. Such applications receive benefit both through the state- of-the-art technology developments necessary to build NIF and through specific experiments that will be performed on NIF.

  14. Observation of radio frequency ring-shaped hollow cathode discharge plasma with MgO and Al electrodes for plasma processing

    SciTech Connect

    Ohtsu, Yasunori Matsumoto, Naoki

    2014-05-15

    Various high-density plasma sources have been proposed for plasma processing. Especially, the hollow cathode discharge is one of the powerful ones. In this work, radio-frequency (RF) driven ring-shaped hollow cathode discharges with high secondary-electron emission have been investigated, using an aluminum (Al) cathode, coated or not with magnesium oxide (MgO). The thickness of MgO thin film is approximately 200 nm. The RF discharge voltage for the coated cathode is almost the same as that for the uncoated one, in a wide range of Ar gas pressure, from 5.3 to 53.2 Pa. The results reveal that the plasma density has a peak at an Ar gas pressure of 10.6 Pa for both cathodes. The plasma density for the coated cathode is about 1.5–3 times higher than that for the uncoated one, at various gas pressures. To the contrary, the electron temperature for the coated cathode is lower than temperature obtained with the uncoated cathode, at various gas pressures. Radial profiles of electron saturation current, which is proportional to plasma flux, are also examined for a wide range of gas pressure. Radial profiles of electron temperature at various axial positions are almost uniform for both cathodes so that the diffusion process due to density gradient is dominant for plasma transport. The secondary electrons emitted from the coated cathode contribute to the improvement of the plasma flux radial profile obtained using the uncoated cathode.

  15. Modulation of NifA activity by PII in Azospirillum brasilense: evidence for a regulatory role of the NifA N-terminal domain.

    PubMed Central

    Arsene, F; Kaminski, P A; Elmerich, C

    1996-01-01

    Azospirillum brasilense NifA, which is synthesized under all physiological conditions, exists in an active or inactive from depending on the availability of ammonia. The activity also depends on the presence of PII, as NifA is inactive in a glnB mutant. To investigate further the mechanism that regulates NifA activity, several deletions of the nifA coding sequence covering the amino-terminal domain of NifA were constructed. The ability of these truncated NifA proteins to activate the nifH promoter in the absence or presence of ammonia was assayed in A. brasilense wild-type and mutant strains. Our results suggest that the N-terminal domain is not essential for NifA activity. This domain plays an inhibitory role which prevents NifA activity in the presence of ammonia. The truncated proteins were also able to restore nif gene expression to a glnB mutant, suggesting that PII is required to activate NifA by preventing the inhibitory effect of its N-terminal domain under conditions of nitrogen fixation. Low levels of nitrogenase activity in the presence of ammonia were also observed when the truncated gene was introduced into a strain devoid of the ADP-ribosylation control of nitrogenase. We propose a model for the regulation of NifA activity in A. brasilense. PMID:8759845

  16. NIF Projects Controls and Information Systems Software Quality Assurance Plan

    SciTech Connect

    Fishler, B

    2011-03-18

    Quality achievement for the National Ignition Facility (NIF) and the National Ignition Campaign (NIC) is the responsibility of the NIF Projects line organization as described in the NIF and Photon Science Directorate Quality Assurance Plan (NIF QA Plan). This Software Quality Assurance Plan (SQAP) is subordinate to the NIF QA Plan and establishes quality assurance (QA) activities for the software subsystems within Controls and Information Systems (CIS). This SQAP implements an activity level software quality assurance plan for NIF Projects as required by the LLNL Institutional Software Quality Assurance Program (ISQAP). Planned QA activities help achieve, assess, and maintain appropriate quality of software developed and/or acquired for control systems, shot data systems, laser performance modeling systems, business applications, industrial control and safety systems, and information technology systems. The objective of this SQAP is to ensure that appropriate controls are developed and implemented for management planning, work execution, and quality assessment of the CIS organization's software activities. The CIS line organization places special QA emphasis on rigorous configuration control, change management, testing, and issue tracking to help achieve its quality goals.

  17. NIF Optical Materials and Fabrication Technologies: An Overview

    SciTech Connect

    Campbell, J H; Hawley-Fedder, R; Stolz, C J; Menapace, J A; Borden, M R; Whitman, P; Yu, J; Runkel, M; Riley, M; Feit, M; Hackel, R

    2004-02-23

    The high-energy/high-power section of the NIF laser system contains 7360 meter-scale optics. Advanced optical materials and fabrication technologies needed to manufacture the NIF optics have been developed and put into production at key vendor sites. Production rates are up to 20 times faster and per-optic costs 5 times lower than could be achieved prior to the NIF. In addition, the optics manufactured for NIF are better than specification giving laser performance better than the design. A suite of custom metrology tools have been designed, built and installed at the vendor sites to verify compliance with NIF optical specifications. A brief description of the NIF optical wavefront specifications for the glass and crystal optics is presented. The wavefront specifications span a continuous range of spatial scale-lengths from 10 {micro}m to 0.5 m (full aperture). We have continued our multi-year research effort to improve the lifetime (i.e. damage resistance) of bulk optical materials, finished optical surfaces and multi-layer dielectric coatings. New methods for post-processing the completed optic to improve the damage resistance have been developed and made operational. This includes laser conditioning of coatings, glass surfaces and bulk KDP and DKDP and well as raster and full aperture defect mapping systems. Research on damage mechanisms continues to drive the development of even better optical materials.

  18. Effect of electrode spacing on the density distributions of electrons, ions, and metastable and radical molecules in SiH{sub 4}/NH{sub 3}/N{sub 2}/He capacitively coupled plasmas

    SciTech Connect

    Kim, Ho Jun; Yang, Wonkyun; Joo, Junghoon

    2015-07-28

    Semiconductor fabrication often requires the deposition of hydrogenated silicon nitride (SiN{sub x}H{sub y}) film using SiH{sub 4}/NH{sub 3}/N{sub 2}/He capacitively coupled plasma (CCP) discharge. As analysis of the discharge geometry is essential to understanding CCP deposition, the effect of electrode spacing on the two-dimensional distributions of electrons, ions, and metastable and radical molecules was analyzed numerically using a fluid model. The simulation shows that the spatial variations in the ionization rates near the sheath become more obvious as the electrode spacing increases. In addition, as molecule-molecule gas-phase reactions are significantly affected by the local residence time, large electrode spacings are associated with significant volumetric losses for positive ions. Consequently, an increase of the electrode spacing leads axial density profiles of ions to change from bell shaped to double humped. However, NH{sub 4}{sup +} persistently maintains a bell-shaped axial density profile regardless of the degree of electrode spacing. We set the mole fraction of NH{sub 3} to only 1% of the total flow at the inlet, but NH{sub 4}{sup +} is the most abundant positive ion at the large electrode spacings. As the gas flow can transport the radicals around the space between the electrodes, we found that radical density distribution shifts toward the grounded electrode. The shift becomes pronounced as the electrode spacing increases. Finally, to validate our model, we compared the calculated deposition rate profile with the experimental data obtained along the wafer radius. According to our numerical results, the SiN{sub x}H{sub y} deposition rate decreases by approximately 16% when the electrode spacing increases from 9 to 20 mm.

  19. Structural and Phylogenetic Analysis of Rhodobacter capsulatus NifF: Uncovering General Features of Nitrogen-fixation (nif)-Flavodoxins

    PubMed Central

    Pérez-Dorado, Inmaculada; Bortolotti, Ana; Cortez, Néstor; Hermoso, Juan A.

    2013-01-01

    Analysis of the crystal structure of NifF from Rhodobacter capsulatus and its homologues reported so far reflects the existence of unique structural features in nif flavodoxins: a leucine at the re face of the isoalloxazine, an eight-residue insertion at the C-terminus of the 50’s loop and a remarkable difference in the electrostatic potential surface with respect to non-nif flavodoxins. A phylogenetic study on 64 sequences from 52 bacterial species revealed four clusters, including different functional prototypes, correlating the previously defined as “short-chain” with the firmicutes flavodoxins and the “long-chain” with gram-negative species. The comparison of Rhodobacter NifF structure with other bacterial flavodoxin prototypes discloses the concurrence of specific features of these functional electron donors to nitrogenase. PMID:23303276

  20. Gated photocathode design for the P510 electron tube used in the National Ignition Facility (NIF) optical streak cameras

    NASA Astrophysics Data System (ADS)

    Datte, P.; James, G.; Celliers, P.; Kalantar, D.; Vergel de Dios, G.

    2015-08-01

    The optical streak cameras currently used at the National Ignition Facility (NIF) implement the P510 electron tube from Photonis1. The existing high voltage electronics provide DC bias voltages to the cathode, slot, and focusing electrodes. The sweep deflection plates are driven by a ramp voltage. This configuration has been very successful for the majority of measurements required at NIF. New experiments require that the photocathode be gated or blanked to reduce the effects of undesirable scattered light competing with low light level experimental data. The required ~2500V gate voltage is applied between the photocathode and the slot electrode in response to an external trigger to allow the electrons to flow. Otherwise the slot electrode is held approximately 100 Volts more negative than the potential of the photocathode, preventing electron flow. This article reviews the implementation and performance of the gating circuit that applies an electronic gate to the photocathode with a nominal 50ns rise and fall time, and a pulse width between 50ns and 2000ns.

  1. Sequencing and complementation analysis of the nifUSV genes from Azospirillum brasilense.

    PubMed

    Frazzon, J; Schrank, I S

    1998-02-15

    The functionality of nitrogenase in diazotrophic bacteria is dependent upon nif genes other than the structural nifH, D, and K genes which encode the enzyme subunit proteins. Such genes are involved in the activation of nif gene expression, maturation of subunit proteins, cofactor biosynthesis, and electron transport. In this work, approximately 5500 base pairs located within the major nif gene cluster of Azospirillum brasilense Sp7 have been sequenced. The deduced open reading frames were compared to the nif gene products of Azotobacter vinelandii and other diazotrophs. This analysis indicates the presence of five ORFs encoding ORF2, nifU, nifS, nifV, and ORF4 in the same sequential organization as found in other organisms. Consensus sigma 54 and NifA binding sites are present in the putative promoter region upstream of ORF2 in the A. brasilense sequence. The nifV gene of A. brasilense but not nifU or nifS complemented corresponding mutants strains of A. vinelandii. PMID:9503607

  2. Electrochemically modulated separation, concentration, and detection of plutonium using an anodized glassy carbon electrode and inductively coupled plasma mass spectrometry.

    PubMed

    Clark, William J; Park, Sea H; Bostick, Debra A; Duckworth, Douglas C; Van Berkel, Gary J

    2006-12-15

    Plutonium is shown to be retained on anodized glassy carbon (GC) electrodes at potentials positive of +0.7 V (vs Ag/AgCl reference) and released upon potential shifts to values negative of +0.3 V. This phenomenon has been exploited for the separation, concentration, and detection of plutonium by the coupling an electrochemical flow cell on-line with an ICPMS system. The electrochemically controlled deposition and analysis of Pu improves detection limits by analyte preconcentration and by matrix and isobaric ion elimination. Information related to the parametric optimization of the technique and hypotheses regarding the mechanism of electrochemical accumulation of Pu are reported. The most likely accumulation scenario involves complexation of Pu(IV) species, produced under a controlled potential, with anions retained in the anodization film that develops during the activation of the GC electrode. The release mechanism is believed to result from the reduction of Pu(IV) in the anion complex to Pu(III), which has a lower tendency to form complexes. PMID:17165850

  3. Electrochemically Modulated Separation, Concentration, and Detection of Plutonium Using an Anodized Glassy Carbon Electrode and Inductively Coupled Plasma Mass Spectrometry

    SciTech Connect

    Clark, William J.; Park, Sea H.; Bostick, Debra A.; Duckworth, Doug C.; Van Berkel, Gary J.

    2006-12-15

    Plutonium is shown to be retained on anodized glassy carbon (GC) electrodes at potentials positive of +0.7 V (vs. Ag/AgCl reference) and released upon potential shifts to values negative of +0.3 V. This phenomenon has been exploited for the separation, concentration, and detection of plutonium by the coupling an electrochemical flow cell online with an ICP-MS system. The electrochemically-controlled deposition and analysis of Pu improves detection limits by analyte preconcentration and by matrix and isobaric ion elimination. Information related to the parametric optimization of the technique and hypotheses regarding the mechanism of electrochemical accumulation of Pu are reported. The most likely accumulation scenario involves complexation of Pu (IV) species, produced under a controlled potential, with anions retained in the anodization film that develops during the activation of the GC electrode. The release mechanism is believed to result from the reduction of Pu(IV) in the anion complex to Pu (III), which has a lower tendency to form complexes.

  4. Electron donation to the flavoprotein NifL, a redox-sensing transcriptional regulator.

    PubMed

    Macheroux, P; Hill, S; Austin, S; Eydmann, T; Jones, T; Kim, S O; Poole, R; Dixon, R

    1998-06-01

    Transcriptional control of the nitrogen fixation (nif) genes in response to oxygen in Azotobacter vinelandii is mediated by nitrogen fixation regulatory protein L (NifL), a regulatory flavoprotein that modulates the activity of the transcriptional activator nitrogen fixation regulatory protein A (NifA). CD spectra of purified NifL indicate that FAD is bound to NifL in an asymmetric environment and the protein is predominantly alpha-helical. The redox potential of NifL is -226 mV at pH 8 as determined by the enzymic reduction of NifL by xanthine oxidase/xanthine in the presence of appropriate mediators. The reduction of NifL by xanthine oxidase prevented NifL from acting as an inhibitor of NifA. In the absence of electron mediators NifL could also be reduced by Escherichia coli flavohaemoprotein (Hmp) with NADH as reductant. Hmp contains a globin-like domain with haem B as prosthetic group and an FAD-containing oxidoreductase module. The carboxyferrohaem form of Hmp was competent to reduce NifL, suggesting that electron donation to NifL originates from the flavin in Hmp rather than by direct electron transfer from the haem. Spinach ferredoxin:NAD(P) oxidoreductase, which adopts a folding similar to the FAD- and NAD-binding domains of Hmp, also reduced NifL with NADH as reductant. Re-oxidation of NifL occurs rapidly in the presence of air, raising the possibility that NifL might sense intracellular oxygen. We propose a physiological redox cycle in which the oxidation of NifL by oxygen and hence the activation of its inhibitory properties occurs rapidly, in contrast with the switch from the active to the reduced form of NifL, which occurs more slowly. PMID:9601070

  5. Nucleotide sequence and genetic analysis of the Azotobacter chroococcum nifUSVWZM gene cluster, including a new gene (nifP) which encodes a serine acetyltransferase.

    PubMed

    Evans, D J; Jones, R; Woodley, P R; Wilborn, J R; Robson, R L

    1991-09-01

    Nucleotide sequence was obtained for a region of 7,099 bp spanning the nifU, nifS, nifV, nifW, nifZ, and nifM genes from Azotobacter chroococcum. Chromosomal mutations constructed at several sites within the locus confirmed a requirement for this region for expression of the molybdenum nitrogenase in this organism. The genes are tightly clustered and ordered as in Klebsiella pneumoniae except for two additional open reading frames (ORFs) between nifV and nifW. The arrangement of genes in A. chroococcum closely matches that described for Azotobacter vinelandii. The polypeptide encoded by ORF4 immediately downstream from nifV is 41% identical over 186 amino acids to the product of the cysE gene from Escherichia coli, which encodes serine acetyltransferase (SAT), a key enzyme in cysteine biosynthesis. Plasmids which potentially express ORF4 complemented E. coli JM39, a cysteine auxotroph which lacks SAT. SAT activity was detected in crude extracts of one such complemented strain. A strain of A. chroococcum carrying a chromosomal disruption of ORF4 grew normally with ammonium as the N source but more slowly than the parental strain when N2 was the sole N source. These data suggest that ORF4 encodes a nif-specific SAT required for optimizing expression of nitrogenase activity. ORF4 was assigned the name nifP. nifP may be required to boost rates of synthesis or intracellular concentrations of cysteine or methionine. Sequence identity between nifV and leuA gene products suggests that nifV may catalyze a condensation reaction analogous to that carried out by isopropylmalate synthase (LEUA) but in which acetyl coenzyme and alpha-ketoglutarate are substrates for the formation of homocitrate, the proposed product of NIFV activity. PMID:1885524

  6. Nucleotide sequence and genetic analysis of the Azotobacter chroococcum nifUSVWZM gene cluster, including a new gene (nifP) which encodes a serine acetyltransferase.

    PubMed Central

    Evans, D J; Jones, R; Woodley, P R; Wilborn, J R; Robson, R L

    1991-01-01

    Nucleotide sequence was obtained for a region of 7,099 bp spanning the nifU, nifS, nifV, nifW, nifZ, and nifM genes from Azotobacter chroococcum. Chromosomal mutations constructed at several sites within the locus confirmed a requirement for this region for expression of the molybdenum nitrogenase in this organism. The genes are tightly clustered and ordered as in Klebsiella pneumoniae except for two additional open reading frames (ORFs) between nifV and nifW. The arrangement of genes in A. chroococcum closely matches that described for Azotobacter vinelandii. The polypeptide encoded by ORF4 immediately downstream from nifV is 41% identical over 186 amino acids to the product of the cysE gene from Escherichia coli, which encodes serine acetyltransferase (SAT), a key enzyme in cysteine biosynthesis. Plasmids which potentially express ORF4 complemented E. coli JM39, a cysteine auxotroph which lacks SAT. SAT activity was detected in crude extracts of one such complemented strain. A strain of A. chroococcum carrying a chromosomal disruption of ORF4 grew normally with ammonium as the N source but more slowly than the parental strain when N2 was the sole N source. These data suggest that ORF4 encodes a nif-specific SAT required for optimizing expression of nitrogenase activity. ORF4 was assigned the name nifP. nifP may be required to boost rates of synthesis or intracellular concentrations of cysteine or methionine. Sequence identity between nifV and leuA gene products suggests that nifV may catalyze a condensation reaction analogous to that carried out by isopropylmalate synthase (LEUA) but in which acetyl coenzyme and alpha-ketoglutarate are substrates for the formation of homocitrate, the proposed product of NIFV activity. PMID:1885524

  7. Comparison of Raman Scattering Measurements and Modeling in NIF Ignition Experiments

    SciTech Connect

    Strozzi, D J; Hinkel, D E; Williams, E A; Town, R J; Michel, P A; Divol, L; Berger, R L; Moody, J D

    2011-11-04

    Recent NIF indirect-drive experiments have shown significant Raman scattering from the inner beams. NIF data has motivated improvements to rad-hydro modeling, leading to the 'high flux model' [M. D. Rosen et al., HEDP 7, 180 (2011)]. Cross-beam energy transfer [P. A. Michel et al., Phys. Plasmas 17, 056305 (2010] in the laser entrance hole is an important tool for achieving round implosions, and is uniformly distributed across the laser spot in rad-hydro simulations (but not necessarily in experiments). We find the Raman linear gain spectra computed with these plasma conditions agree well in time-dependent peak wavelength with the measured data, especially when overlapping laser-beam intensities are used. More detailed, spatially non-uniform modeling of the cross-beam transfer has been performed. The resulting gains better follow the time history of the measured backscatter. We shall present the impact of spatially non-uniform energy transfer on SRS gain. This metric is valid when amplification is in a linear regime, and so we shall also present an assessment of whether electron trapping in Langmuir waves can play a role in these shots.

  8. Rydberg gas theory of a glow discharge plasma: II. Electrode kinetics (probe theory) and the thermal rate constant for Symmetrical charge transfer involving Rydberg atoms of Ar.

    PubMed

    Mason, Rod S

    2010-04-21

    A steady state chemical kinetic model is developed to describe the conduction of electrical current between two probes, of relatively large surface area, immersed in a fast flowing plasma by the mechanism of charge transfer through a gas of Rydberg atoms. It correctly predicts the shape of current-voltage profiles which are similar to those of Langmuir, or floating double probe measurements. The difference is that the plateau current at the probe reflects the transport limited ion current at the cathodic electrode, even when the probe is being scanned in the anodic region. The sharp gradient leading up to the plateau of the I-V curve is associated with the field dependence of the efficiency of Rydberg atom ionisation, not the electron temperature. This approach gives a good qualitative explanation of experimental behaviour over a wide range of probe bias voltages and includes the occurrence of electron impact ionisation at the anode. It also gives a value for the thermal rate coefficient of symmetrical charge transfer between Rydberg atoms of Ar (8.2 x 10(-7) molecule(-1) cm(3) s(-1), at 313 K; plasma density approximately = 10(10) atoms cm(-3), total pressure = 2.7 mbar). PMID:20358036

  9. Computational Aided-Molecular Imprinted Polymer Design for Solid Phase Extraction of Metaproterenol from Plasma and Determination by Voltammetry Using Modified Carbon Nanotube Electrode

    PubMed Central

    Ahmadi, Farhad; Karamian, Ehsan

    2014-01-01

    A molecular imprinted polymer (MIP) was computationally designed and synthesized for the selective extraction of metaproterenol (MTP), from human plasma. In this regards semi empirical MP3 and mechanical quantum (DFT) calculations were used to find a suitable functional monomers. On the basis of computational and experimental results, acrylic acid (AA) and DMSO:MeOH (90:10 %V/V) were found to be the best choices of functional monomer and polymerization solvents, respectively. This polymer was then used as a selective sorbent to develop a molecularly imprinted solid-phase extraction (MISPE) procedure followed by differential pulse voltammetry by using modified carbon nanotube electrode. The analysis was performed in phosphate buffer, pH 7.0. Peak currents were measured at +0.67 V versus Ag/AgCl. The linear calibration range was 0.026–8.0 μg mL-1 with a limit of detection 0.01 μg mL-1. The relative standard deviation at 0.5 μg mL-1 was 4.76% (n=5). The mean recoveries of 5 μg mL-1 MTP from plasma was 92.2% (n=5). The data of MISPE-DPV were compared with the MISPE-HPLC-UV. Although, the MISPE-DPV was more sensitive but both techniques have similar accuracy and precision. PMID:25237337

  10. Electrode modifications to lower electrode impedance and improve neural signal recording sensitivity

    NASA Astrophysics Data System (ADS)

    Chung, T.; Wang, J. Q.; Wang, J.; Cao, B.; Li, Y.; Pang, S. W.

    2015-10-01

    Objective. Although electrode size should be miniaturized to provide higher selectivity for neural signal recording and to avoid tissue damage, small sized electrodes induce high impedance, which decreases recording quality. In this work, the electrode surface was modified to increase the effective surface area to lower the electrode impedance and to improve the neural signal detection quality by optimizing plasma conditions. Approach. A tetrafluoromethane (CF4) plasma was used to increase the effective surface area of gold electrode sites of polyimide-based neural probes. In vitro electrode impedance and in vivo neural signal recording and stimulation were characterized. Main results. For 15 μm diameter (dia.) electrode size, the average surface roughness could be increased from 1.7 to 22 nm after plasma treatment, and the electrode impedance was decreased by 98%. Averaged background noise power in the range of 1 to 1000 Hz was decreased to -106 dB after the 30 μm dia. electrodes were plasma modified—lower than the noise level of -86 dB without plasma treatment. Neural probes with plasma-modified electrode sites of 15 and 30 μm dia. were implanted to the anterior cingulate cortex (ACC) region for acute recording of spontaneous and electrical evoked local field potential (LFP) of neural signals. Spontaneous LFP recorded in vivo by the plasma-modified electrodes of 30 μm dia. was two times higher compared to electrodes without treatment. For a stimulation current of 400 μA, electrically evoked LFP recorded by the plasma-modified electrodes was seven times higher than those without plasma exposure. Significance. A controllable technology was developed to increase the effective surface area of electrodes using a CF4 plasma. Plasma-modified electrodes improved the quality of the neural probe recording and more sensitive to record spontaneous and evoked LFP in the ACC region.

  11. Multiple Experimental Platform Consistency at NIF

    NASA Astrophysics Data System (ADS)

    Benedetti, L. R.; Barrios, M. A.; Bradley, D. K.; Eder, D. C.; Khan, S. F.; Izumi, N.; Jones, O. S.; Ma, T.; Nagel, S. R.; Peterson, J. L.; Rygg, J. R.; Spears, B. K.; Town, R. P.

    2013-10-01

    ICF experiments at NIF utilize several platforms to assess different metrics of implosion quality. In addition to the point design-a target capsule of DT ice inside a thin plastic ablator-notable platforms include: (i) Symmetry Capsules(SymCaps), mass-adjusted CH capsules filled with DT gas for similar hydrodynamic performance without the need for a DT crystal; (ii) D:3He filled SymCaps, designed for low neutron yield implosions to accommodate a variety of x-ray and optical diagnostics; and (iii) Convergent Ablators, SymCaps coupled with x-radiography to assess in-flight velocity and symmetry of the implosion over ~1 ns before stagnation and burn. These platforms are expected to be good surrogates for one another, and their hohlraum and implosion performance variations have been simulated in detail. By comparing results of similar experiments, we isolate platform-specific variations. We focus on the symmetry, convergence, and timing of x-ray emission as observed in each platform as this can be used to infer stagnation pressure and temperature. This work performed under the auspices of the U.S. Dept. of Energy by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-640865.

  12. Preliminary report: NIF laser bundle review

    SciTech Connect

    Tietbohl, G.L.; Larson, D.W.; Erlandson, A.C.

    1995-08-31

    As requested in the guidance memo {sup 1}, this committe determined whether there are compelling reasons to recommend a change from the NIF CDR baseline laser. The baseline bundle design based on a tradeoff between cost and technical risk, which is replicated four times to create the required 192 beams. The baseline amplifier design uses bottom loading 1{times}4 slab and flashlamp cassettes for amplifier maintenance and large vacuum enclosures (2.5m high {times} 7m wide in cross-section for each of the two spatial filters in each of the four bundles. The laser beams are arranged in two laser bays configured in a u-shape around the target area. The entire bundle review effort was performed in a very short time (six weeks) and with limited resources (15 personnel part-time). This should be compared to the effort that produced the CDR design (12 months, 50 to 100 personnel). This committee considered three alternate bundle configurations (2{times}2, 4{times}2, and 4{times}4 bundles), and evaluated each bundle against the baseline design using the seven requested issues in the guidance memo: Cost; schedule; performance risk; maintainability/operability; hardware failure cost exposure; activation; and design flexibility. The issues were reviewed to identify differences between each alternate bundle configuration and the baseline.

  13. Cleanliness validation of NIF small optics

    NASA Astrophysics Data System (ADS)

    Chow, Robert; Bickel, Robert C.; Ertel, John; Pryatel, James; Loomis, Gary E.; Stowers, Irving F.; Taylor, John R.

    2002-09-01

    The National Ignition Facility will be the highest energy laser in the world when completed. Many small optics (less than or equal to 14" in diameter) have stringent transport efficiency and some have very high laser fluence requirements. For optics to sustain high spectral efficiencies and survive high fluences for a 30-year operation, these optics have cleanliness requirements to assure optimal laser system performance. These optical components have insufficient surface areas to validate the particulate and organic contamination requirements by methods used for mechanical parts. Also, the common validation techniques require some sort of surface contact which is not compatible with handling of laser optics. This presentation describes alternate cleanliness validation methods developed for the NIF small optical components. An organic validation procedure was devised based on the spectral transmission sensitivity to contamination layers on coated and uncoated fused silica windows. Optics were scanned in the near infrared before and after an application of a specific amount of organic contamination onto the surface. Changes in transmission correlated to organic contamination levels and used to determine non-volatile organic contamination optics. A validation method for particulate contamination was demonstrated on a large window, showing that acceptable cleanliness levels could be achieved after a wet-wipe and inspection with a high intensity light. The method is similar to that used to inspect the surface quality of optical components.

  14. Advances in NIF Shock Timing Experiments

    NASA Astrophysics Data System (ADS)

    Robey, Harry

    2012-10-01

    Experiments are underway to tune the shock timing of capsule implosions on the National Ignition Facility (NIF). These experiments use a modified cryogenic hohlraum geometry designed to precisely match the performance of ignition hohlraums. The targets employ a re-entrant Au cone to provide optical access to multiple shocks as they propagate in the liquid deuterium-filled capsule interior. The strength and timing of all four shocks is diagnosed with VISAR (Velocity Interferometer System for Any Reflector). Experiments are now routinely conducted in a mirrored keyhole geometry, which allows for simultaneous diagnosis of the shock timing at both the hohlraum pole and equator. Further modifications are being made to improve the surrogacy to ignition hohlraums by replacing the standard liquid deuterium (D2) capsule fill with a deuterium-tritium (DT) ice layer. These experiments will remove any possible surrogacy difference between D2 and DT as well as incorporate the physics of shock release from the ice layer, which is absent in current experiments. Experimental results and comparisons with numerical simulation are presented.

  15. Cleanliness Validation of NIF Small Optics

    SciTech Connect

    Chow, R; Bickel, R; Ertel, J; Pryatel, J; Loomis, G; Stowers, I; Taylor, J R

    2002-05-07

    The National Ignition Facility will be the highest energy laser in the world when completed. Many small optics ({le} 14 inches in diameter) have stringent transport efficiency and some have very high laser fluence requirements. For optics to sustain high spectral efficiencies and survive high fluences for a 30-year operation, these optics have cleanliness requirements to assure optimal laser system performance. These optical components have insufficient surface areas to validate the particulate and organic contamination requirements by methods used for mechanical parts. Also, the common validation techniques require some sort of surface contact which is not compatible with handling of laser optics. This presentation describes alternate cleanliness validation methods developed for the NIF small optical components. An organic validation procedure was devised based on the spectral transmission sensitivity to contamination layers on coated and uncoated fused silica windows. Optics were scanned in the near infrared before and after an application of a specific amount of organic contamination onto the surface. Changes in transmission correlated to organic contamination levels and used to determine non-volatile organic contamination optics. A validation method for particulate contamination was demonstrated on a large window, showing that acceptable cleanliness levels could be achieved after a wet-wipe and inspection with a high intensity light. The method is similar to that used to inspect the surface quality of optical components.

  16. NIF Sub-scale Platform Development

    NASA Astrophysics Data System (ADS)

    Town, R. P. J.; Albert, F.; Benedetti, L. R.; Bradley, D. K.; Celliers, P. M.; Dewald, E. L.; Divol, L.; Eder, D. E.; Hall, G. N.; Jones, O. S.; Le Pape, S.; MacGowan, B. J.; Milovich, J. L.; Moody, J. D.; Pak, A.; Ralph, J.; Robey, H. F.; Rygg, J. R.; Schneider, M. B.; Strozzi, D. J.

    2014-10-01

    In order to increase the shot rate on the National Ignition Facility (NIF) a smaller, lower-energy, room-temperature experimental capability has been designed. The goal of the sub-scale design was to reduce the energy requirement to 900 kJ. The starting point for the sub-scale design was a layered plastic capsule in a full scale (575) gold hohlraum that was driven by a four shock, low adiabat, 1.8 MJ, 420 TW, 21-ns long laser pulse. Simple scaling arguments showed that scaling the capsule and hohlraum dimensions to 80% of full scale should meet the energy requirements. The capability includes sub-scale versions of the ignition-scale re-emit, keyhole, symmetry, backlit, and hydro-growth radiography platforms. An experimental campaign to commission these platforms was performed. This talk will review the design and results of these commissioning experiments. This work performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344.

  17. Sequence and structural organization of a nif A-like gene and part of a nifB-like gene of Herbaspirillum seropedicae strain Z78.

    PubMed

    Souza, E M; Funayama, S; Rigo, L U; Yates, M G; Pedrosa, F O

    1991-07-01

    The deduced amino acid sequence derived from the sequence of a fragment of DNA from the free-living diazotroph Herbaspirillum seropedicae was aligned to the homologous protein sequences encoded by the nifA genes from Azorhizobium caulinodans, Rhizobium leguminosarum, Rhizobium meliloti and Klebsiella pneumoniae. High similarity was found in the central domain and in the C-terminal region. The H. seropedicae putative NifA sequence was also found to contain an interdomain linker similar to that conserved among rhizobial NifA proteins, but not K. pneumoniae or Azotobacter vinelandii. Analysis of the regulatory sequences found 5' from nifA indicated that the expression of this gene in H. seropedicae is likely to be controlled by NifA, NtrC and RpoN, as judged by the presence of specific NifA- and NtrC-binding sites and characteristic -24/-12 promoters. Possible additional regulatory features included an 'anaerobox' and a site for integration host factor. The N-terminus of another open reading frame was found 3' from nifA and tentatively identified as nifB by amino acid sequence comparison. The putative nifB promoter sequence suggests that expression of H. seropedicae nifB may be activated by NifA and dependent on RpoN. PMID:1840608

  18. Role of GlnK in NifL-mediated regulation of NifA activity in Azotobacter vinelandii.

    PubMed

    Rudnick, Paul; Kunz, Christopher; Gunatilaka, Malkanthi K; Hines, Eric R; Kennedy, Christina

    2002-02-01

    In several diazotrophic species of Proteobacteria, P(II) signal transduction proteins have been implicated in the regulation of nitrogen fixation in response to NH(4)(+) by several mechanisms. In Azotobacter vinelandii, expression of nifA, encoding the nif-specific activator, is constitutive, and thus, regulation of NifA activity by the flavoprotein NifL appears to be the primary level of nitrogen control. In vitro and genetic evidence suggests that the nitrogen response involves the P(II)-like GlnK protein and GlnD (uridylyltransferase/uridylyl-removing enzyme), which reversibly uridylylates GlnK in response to nitrogen limitation. Here, the roles of GlnK and GlnK-UMP in A. vinelandii were studied to determine whether the Nif (-) phenotype of glnD strains was due to an inability to modify GlnK, an effort previously hampered because glnK is an essential gene in this organism. A glnKY51F mutation, encoding an unuridylylatable form of the protein, was stable only in a strain in which glutamine synthetase activity is not inhibited by NH(4)(+), suggesting that GlnK-UMP is required to signal adenylyltransferase/adenylyl-removing enzyme-mediated deadenylylation. glnKY51F strains were significantly impaired for diazotrophic growth and expression of a nifH-lacZ fusion. NifL interacted with GlnK and GlnKY51F in a yeast two-hybrid system. Together, these data are consistent with those obtained from in vitro experiments (Little et al., EMBO J., 19:6041-6050, 2000) and support a model for regulation of NifA activity in which unmodified GlnK stimulates NifL inhibition and uridylylation of GlnK in response to nitrogen limitation prevents this function. This model is distinct from one proposed for the related bacterium Klebsiella pneumoniae, in which unmodified GlnK relieves NifL inhibition instead of stimulating it. PMID:11790752

  19. An MPP hydrocode to study laser-plasma interactions

    SciTech Connect

    Berger, R L; Langdon, A B; Langer, S H; Still, C H; Suter, L J; Williams E A

    1998-10-01

    Because of the increased size and power inherent in a laser-AGEX on NIF, laser-plasma interactions (LPI) observed in NOVA AGEX play an increasingly important role. The process by which filamentation and stimulated backscatter grow is complex. Furthermore, there is a competition among the instabilities so that lessening one can increase another. Therefore, simulating them is an integral part to successful experiments on NIF. In this paper, we present a massively parallel hydrocode to simulate laser-plasma interactions in NIF-relevant AGEX regimes.

  20. NtrC is required for control of Klebsiella pneumoniae NifL activity.

    PubMed Central

    He, L; Soupene, E; Kustu, S

    1997-01-01

    In response to molecular oxygen and/or fixed nitrogen, the product of the Klebsiella pneumoniae nitrogen fixation L (nifL) gene inhibits NifA-mediated transcriptional activation. Nitrogen regulation of NifL function occurs at two levels: transcription of the nifLA operon is regulated by the general Ntr system, and the activity of NifL is controlled by an unknown mechanism. We have studied the regulation of NifL activity in Escherichia coli and Salmonella typhimurium by monitoring its inhibition of NifA-mediated expression of a K. pneumoniae phi(nifH'-'lacZ) fusion. The activity of the NifL protein transcribed from the tac promoter is regulated well in response to changes of oxygen and/or nitrogen status, indicating that no nif- or K. pneumoniae-specific product is required. Unexpectedly, strains carrying ntrC (glnG) null alleles failed to release NifL inhibition, despite the fact that synthesis of NifL was no longer under Ntr control. Additional evidence indicated that it is indeed the transcriptional activation capacity of NtrC, rather than its repression capacity, that is needed, and hence it is a plausible hypothesis that NtrC activates transcription of a gene(s) whose product(s) in turn functions to relieve NifL inhibition under nitrogen-limiting conditions. PMID:9393710

  1. Regulation of nitrogen fixation in Klebsiella pneumoniae: isolation and characterization of strains with nif-lac fusions.

    PubMed Central

    MacNeil, D; Zhu, J; Brill, W J

    1981-01-01

    Strains with lac fused to each of the seven nif operons were isolated by two different methods. Repressing conditions prevented expression of all nif operons, whereas derepressing conditions led to the expression of all nif operons. No differences in Nif regulation were observed between Escherichia coli and Klebsiella pneumoniae with the same nif-lac fusions. Most derivatives of nif-lac fusion strains selected on lactose and NH4+ contained nif operator mutations. Some derivative contained deletions, which establishes that the direction of transcription of all seven nif operons is toward his Images PMID:7007318

  2. Evaulation of B{sub 4}C as an ablator material for NIF capsules. Revision 1

    SciTech Connect

    Burnham, A.K.; Alford, C.S.; Makowiecki, D.M.; Dittrich, T.R.; Wallace, R.J.; Honea, E.C.; King, C.M.; Steinman, D.

    1997-03-26

    Boron carbide (B{sub 4}C) is examined as a potential fuel container and ablator for implosion capsules on the National Ignition Facility (NIF). A capsule of pure B{sub 4}C encasing a layer of solid DT implodes stably and ignites with anticipated NIF x-ray drives, producing 18 MJ of energy. Thin films of B{sub 4}C were found to be resistant to oxidation and modestly transmitting in the infrared (IR), possibly enabling IR fuel characterization and enhancement for thin permeation barriers but not for full-thickness capsules. Polystyrene mandrels 0.5 mm in diameter were successfully coated with 0.15-2.0 micrometers of B{sub 4}C. Thickness estimated from optical density agreed well with those measured by scanning electron microscopy (SEM). The B{sub 4}C microstructure was columnar but finer than for Be made at the same conditions. B{sub 4}C is a very strong material, with a fiber tensile strength capable of holding NIF fill pressures at room temperature, but it is also very brittle, and microscopic flaws or grain structure may limit the noncryogenic fill pressure. Argon (Ar) permeation rates were measured for a few capsules that had been further coated with 5 micrometers of plasma polymer. The B{sub 4}C coatings tended to crack under tensile load. Some shells filled more slowly than they leaked, suggesting that the cracks open and close under opposite pressure loading. As observed earlier for Ti coatings, 0.15-micrometer layers of B{sub 4}C had better gas retention properties than 2-micrometer layers, possibly because of fewer cracks. Permeation and fill strength issues for capsules with a full ablator thickness of B{sub 4}C are unresolved. 21 refs., 6 figs.

  3. NIF conventional facilities construction health and safety plan

    SciTech Connect

    Benjamin, D W

    1998-05-14

    The purpose of this Plan is to outline the minimum health and safety requirements to which all participating Lawrence Livermore National Laboratory (LLNL) and non-LLNL employees (excluding National Ignition Facility [NIF] specific contractors and subcontractors covered under the construction subcontract packages (e.g., CSP-9)-see Construction Safety Program for the National Ignition Facility [CSP] Section I.B. ''NIF Construction Contractors and Subcontractors'' for specifics) shall adhere to for preventing job-related injuries and illnesses during Conventional Facilities construction activities at the NIF Project. For the purpose of this Plan, the term ''LLNL and non-LLNL employees'' includes LLNL employees, LLNL Plant Operations staff and their contractors, supplemental labor, contract labor, labor-only contractors, vendors, DOE representatives, personnel matrixed/assigned from other National Laboratories, participating guests, and others such as visitors, students, consultants etc., performing on-site work or services in support of the NIF Project. Based upon an activity level determination explained in Section 1.2.18, in this document, these organizations or individuals may be required by site management to prepare their own NIF site-specific safety plan. LLNL employees will normally not be expected to prepare a site-specific safety plan. This Plan also outlines job-specific exposures and construction site safety activities with which LLNL and non-LLNL employees shall comply.

  4. National Ignition Facility (NIF) Control Network Design and Analysis

    SciTech Connect

    Bryant, R M; Carey, R W; Claybourn, R V; Pavel, G; Schaefer, W J

    2001-10-19

    The control network for the National Ignition Facility (NIF) is designed to meet the needs for common object request broker architecture (CORBA) inter-process communication, multicast video transport, device triggering, and general TCP/IP communication within the NIF facility. The network will interconnect approximately 650 systems, including the embedded controllers, front-end processors (FEPs), supervisory systems, and centralized servers involved in operation of the NIF. All systems are networked with Ethernet to serve the majority of communication needs, and asynchronous transfer mode (ATM) is used to transport multicast video and synchronization triggers. CORBA software infra-structure provides location-independent communication services over TCP/IP between the application processes in the 15 supervisory and 300 FEP systems. Video images sampled from 500 video cameras at a 10-Hz frame rate will be multicast using direct ATM Application Programming Interface (API) communication from video FEPs to any selected operator console. The Ethernet and ATM control networks are used to broadcast two types of device triggers for last-second functions in a large number of FEPs, thus eliminating the need for a separate infrastructure for these functions. Analysis, design, modeling, and testing of the NIF network has been performed to provide confidence that the network design will meet NIF control requirements.

  5. MHD Electrode and wall constructions

    DOEpatents

    Way, Stewart; Lempert, Joseph

    1984-01-01

    Electrode and wall constructions for the walls of a channel transmitting the hot plasma in a magnetohydrodynamic generator. The electrodes and walls are made of a plurality of similar modules which are spaced from one another along the channel. The electrodes can be metallic or ceramic, and each module includes one or more electrodes which are exposed to the plasma and a metallic cooling bar which is spaced from the plasma and which has passages through which a cooling fluid flows to remove heat transmitted from the electrode to the cooling bar. Each electrode module is spaced from and electrically insulated from each adjacent module while interconnected by the cooling fluid which serially flows among selected modules. A wall module includes an electrically insulating ceramic body exposed to the plasma and affixed, preferably by mechanical clips or by brazing, to a metallic cooling bar spaced from the plasma and having cooling fluid passages. Each wall module is, similar to the electrode modules, electrically insulated from the adjacent modules and serially interconnected to other modules by the cooling fluid.

  6. Production of composite Si nanoparticles by plasma spraying PVD and CH4 annealing for negative electrodes of lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Ohta, Ryoshi; Ohta, Yutaro; Tashiro, Toru; Kambara, Makoto

    2015-09-01

    Si is a promising candidate as anode of next generation high density Li ion batteries. This material, however, needs to be nanostructured, nanoparticles and C coating of active material, to cope with huge volume change and associated rapid capacity decay. Si nanoparticles with 20-40 nm have been successfully produced by plasma spraying PVD and also Si-C core-shell composite particles by adding CH4 during processing. The battery performance has been improved with these nanopowders as anode, especially with the C coated Si particles. However, SiC that is inactive in battery reaction forms inevitably at high temperature during plasma spraying PVD and reduces the capacity density. In this work, therefore, post CH4 annealing was attempted to form Si-C nanocomposite particles while suppressing formation of SiC. The primary Si nanoparticles were unchanged in size after annealing and were coated with the finer carbonous particles that formed after CH4 infiltration through pores between nanoparticles. The batteries using annealed powders with C/Si molar ratio of 0.3 have shown two-fold capacity retention increase after 50 cycles with no capacity reduction associated with SiC formation as compared to the powders without C. This work was partly supported by the Funding Program for Next Generation World-Leading Researchers (NEXT Program) of Japan.

  7. Auxins upregulate nif and fix genes.

    PubMed

    Bianco, Carmen; Defez, Roberto

    2010-10-01

    In a recent publication we analyzed the global effects triggered by IAA overproduction in S. meliloti RD64 under free-living conditions by comparing the gene expression pattern of wild type 1021 with that of RD64 and 1021 treated with IAA and other four chemically or functionally related molecules. Among the genes differentially expressed in RD64 and IAA-treated 1021 cells we found two genes of pho operon, phoT and phoC. Based on this finding we examined the mechanisms for mineral P solubilization in RD64 and the potential ability of this strain to improve Medicago growth under P-starved conditions. Here, we further analyze the expression profiles obtained in microarray analysis and evaluate the specificity and the extent of overlap between all treatments. Venn diagrams indicated that IAA- and 2,4-D-regulated genes were closely related. Furthermore, most differentially expressed genes from pSymA were induced in 1021 cells treated with 2,4-D, ICA, IND and Trp as compared to the untreated 1021 cells. RT-PCR analysis was employed to analyze the differential expression patterns of nitrogen fixation genes under free-living and symbiotic conditions. Under symbiotic condition, the relative expression levels of nif and fix genes were significantly induced in Mt- RD64 plants and in Mt-1021 plants treated with IAA and 2,4-D whereas they were unchanged or repressed in Mt-1021 plants treated with the other selected compounds when compared to the untreated Mt-1021 plants. PMID:20930554

  8. Timing shifts due to NIF beam repointing

    SciTech Connect

    Koch, J

    2007-08-15

    Repointing a NIF beam to hit a target position off target chamber center (TCC) will introduce a timing shift due to changes in the light pathlength. This shift could be important for target experiment requirements even for targets placed at TCC, since beam timing test shots will place beams up to 15 mm off TCC in order to spatially separate them on foil targets. In particular, timing errors due to beam repointing need to be considered against the 30 ps RMS timing requirement. Since the repointing process will keep the beam passing through a fixed point in the final optics assembly (the conversion crystal) by tip/tilt adjustments of two turning mirrors (LM5 and LM7), the problem naturally divides into two parts: Timing offsets past the conversion crystal due to target positioning changes, and timing offsets behind the fixed point on the conversion crystal due to turning mirror adjustments. Timing offsets past the conversion crystal can be significant, but are trivial to calculate exactly; however, an exact calculation of timing offsets behind the fixed point on the conversion crystal would require a three-dimensional optomechanical raytrace model to be developed for every beamline, and this would be difficult and expensive. In this memo, I estimate the magnitude of timing offsets due to pathlength changes behind the conversion crystal by analysis of a worst-case model. I conclude that these timing offsets are insignificant compared with the current allocation in the 30 ps RMS timing requirement, and that more detailed raytrace modeling of individual beams is not necessary.

  9. Clostridium pasteurianum W5 synthesizes two NifH-related polypeptides under nitrogen-fixing conditions.

    PubMed

    Kasap, Murat; Chen, Jiann-Shin

    2005-07-01

    Previous studies identified five nifH-like genes (nifH2 through nifH6) in Clostridium pasteurianum (strain W5), where the nifH1 gene encodes the nitrogenase iron protein. Transcripts of these nifH genes, with the exception of nifH3, were detected in molybdenum-sufficient nitrogen-fixing cells. However, the size of the transcripts, the level of transcription and the presence of polypeptides encoded by the nifH-like genes were not reported. The nifH2 and nifH6 genes were extremely similar, as they seemed to differ by only two bases in a span of 2481 bp, one in the coding region and another in the upstream region. Re-examination of the DNA sequences revealed that the coding region of nifH2 and nifH6 was identical, whereas the difference in the upstream region was confirmed. Results from the authors' ongoing study of the nif genes of single-colony isolates of C. pasteurianum suggest that the nifH6 designation should be eliminated. Here the size of mRNA from nifH2 and the detection of the NifH2 polypeptide in nitrogen-fixing cells of C. pasteurianum are reported. Northern blot analysis of periodically collected nitrogen-fixing cells showed that the nifH1 and nifH2 mRNAs were present throughout growth. Addition of ammonium acetate repressed the transcription of both these genes similarly. Using an antiserum raised against NifH of Azotobacter vinelandii, two NifH-related bands were detected by Western blot analysis after electrophoretic separation of proteins in extracts of nitrogen-fixing C. pasteurianum cells. After separation of proteins by preparative SDS-PAGE, the NifH polypeptides were characterized by MALDI-TOF-MS (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry) and by ES-MS/MS (electrospray tandem mass spectrometry) analyses. The results confirmed the presence of NifH2, in addition to NifH1, in nitrogen-fixing C. pasteurianum cells. PMID:16000725

  10. Improved plasma accelerator

    NASA Technical Reports Server (NTRS)

    Cheng, D. Y.

    1971-01-01

    Converging, coaxial accelerator electrode configuration operates in vacuum as plasma gun. Plasma forms by periodic injections of high pressure gas that is ionized by electrical discharges. Deflagration mode of discharge provides acceleration, and converging contours of plasma gun provide focusing.

  11. Modelling NifH2 protein of Clostridium pasteurianum reveals clues about its physiological function.

    PubMed

    Kasap, Murat

    2006-11-01

    Clostridium pasteurianum is an anaerobic free-living nitrogen fixer. As a unique feature, the organism contains five extra nifH-like genes in addition to nifH1. Detailed analysis with respect to the structure and function of the nifH-like gene products is missing due to the lack of information about the presence of their translation products in the cell. Recent work indicates that the nifH2 gene is transcribed and translated into a polypeptide of expected size in nitrogen-fixing cells of C. pasteurianum and is regulated both at the transcriptional and translational levels. However, the current data do not reveal the physiological function of the NifH2 protein. In this study, we have used computer tools and the NifH1 of C. pasteurianum as the template to predict a possible tertiary structure and assign a putative function for NifH2 protein. A comparison of the structures of the NifH1 and modelled NifH2 revealed similarities in the polypeptide conformations for both monomers. Analysis of the properties of nucleotide binding, dimer interacting and cluster containing regions did not reveal major differences between NifH1 and modelled NifH2, although minor differences were observed. Rigid docking results revealed the possibility of formation of a NifH1-NifH2 heterodimer as well as formation of a NifH2 homodimer. We, therefore, propose that NifH2 can form a dimer with NifH1, albeit less efficiently and may function as a regulatory Fe-protein. PMID:16495101

  12. Penetrating radiation impact on NIF final optic components

    SciTech Connect

    Marshall, C.D.; Speth, J.A.; DeLoach, L.D.; Payne, S.A.

    1996-10-15

    Goal of the National Ignition Facility (NIF) is to achieve thermonuclear ignition in a laboratory environment in inertial confinement fusion (ICF). This will enable NIF to service the DOE stockpile stewardship management program, inertial fusion energy goals, and advance scientific frontiers. All of these applications will make use of the extreme conditions that the facility will create in the target chamber. In the case of a prospected 20 MJ yield scenario, NIF will produce 10{sup 19} neutrons with DT fusion 14 MeV energy per neutron. There will also be high-energy x rays as well as solid, liquid, and gaseous target debris produced either directly or indirectly by the inertial confinement fusion process. A critical design issue is the protection of the final optical components as well as sophisticated target diagnostics in such a harsh environment.

  13. Target technologies for indirect drive ignition on the NIF

    SciTech Connect

    Bernat, T P

    1999-09-09

    X-ray driven ignition targets for the NIF will include fuel capsule materials different from those used up to now in ICF experiments. They will contain cryogenic fuel layers, and will be enclosed in cryogenic hohlraums. These hohlraums must provide the thermal environment required to shape the fuel layers, and must be supported by cryogenic equipment in the NIF target chamber. The methods for filling and delivering the targets to the NIF chamber will combine high-temperature diffusion with cryogenic transport. A program is in place in the US to design and develop the ignition targets, and the cryogenic support and fill systems needed to field them. This program includes participation from Lawrence Livermore National Laboratory, Los Alamos National Laboratory, and General Atomics.

  14. Electrode compositions

    DOEpatents

    Block, J.; Fan, X.

    1998-10-27

    An electrode composition is described for use as an electrode in a non-aqueous battery system. The electrode composition contains an electrically active powder in a solid polymer and, as a dispersant, a C{sub 8}-C{sub 15} alkyl capped oligomer of a hexanoic acid that is electrochemically inert at 2.5--4.5 volts.

  15. Electrode compositions

    DOEpatents

    Block, Jacob; Fan, Xiyun

    1998-01-01

    An electrode composition for use as an electrode in a non-aqueous battery system. The electrode composition contains an electrically active powder in a solid polymer and, as a dispersant, a C.sub.8 -C.sub.15 alkyl capped oligomer of a hexanoic acid that is electrochemically inert at 2.5-4.5 volts.

  16. Functional Bradyrhizobium japonicum NifA expression under a hybrid nptII-nifH promoter in E. coli and Acetobacter diazotrophicus SRT4.

    PubMed

    Menéndez, C; Selman-Housein, G; Arrieta, J G; Coego, A; Hernández, L

    1998-01-01

    A hybrid promoter consisting of the in tandem fusion of the Tn5 nptII and the Klebsiella pneumoniae nifH promoters was constructed to study the functionality of the nif genes transcriptional activator NifA from Bradyrhizobium japonicum in two different host bacteria. beta-galactosidase experiments in E. coli revealed that the hybrid nptII-nifH promoter can behave as a constitutive or a NifA-inducible promoter depending on the aeration conditions. Expression of the B. japonicum NifA from the hybrid nptII-nifH promoter (plasmid pBPF204) induced "in trans" lacZ transcription from the Azotobacter chroococcum nifH promoter in E. coli and A. diazotrophicus cells grown at low pO2. Similarly, the plasmid pBPF204 increased nitrogenase activity in A. diazotrophicus cells grown under microaerobic conditions. Based on these results, we suggest that the B. japonicum NifA could function as an efficient O2-sensitive transcriptional activator of nif genes in genetically distant diazotrophic bacteria. PMID:10932742

  17. Peptidyl-prolyl cis/trans isomerase-independent functional NifH mutant of Azotobacter vinelandii.

    PubMed

    Gavini, Nara; Tungtur, Sudheer; Pulakat, Lakshmi

    2006-08-01

    Peptidyl-prolyl cis/trans isomerases (PPIases) play a pivotal role in catalyzing the correct folding of many prokaryotic and eukaryotic proteins that are implicated in a variety of biological functions, ranging from cell cycle regulation to bacterial infection. The nif accessory protein NifM, which is essential for the biogenesis of a functional NifH component of nitrogenase, is a PPIase. To understand the nature of the molecular signature that defines the NifM dependence of NifH, we screened a library of nifH mutants in the nitrogen-fixing bacterium Azotobacter vinelandii for mutants that acquired NifM independence. Here, we report that NifH can acquire NifM independence when the conserved Pro258 located in the C-terminal region of NifH, which wraps around the other subunit in the NifH dimer, is replaced by serine. PMID:16885471

  18. Preparation of NIF Scale Poly ((alpha)-METHYLSTYRENE) Mandrels

    SciTech Connect

    Takagi, M; Cook, R; McQuillan, B; Elsner, F; Stephens, R; Nikroo, A; Paguio, S

    2002-06-07

    All planned National Ignition Facility (NIF) capsule targets except machined beryllium require a plastic mandrel upon which the ablator is applied. This mandrel must at least meet if not exceed the symmetry and surface finish requirements of the final capsule. The mandrels are produced by a two-step process. In the first step a thin-walled poly({alpha}-methylstyrene)(P{alpha}MS) shell is produced using microencapsulation techniques. This shell is overcoated with 10 to 15 {micro}m of glow discharge polymer (GDP) and then pyrolyzed at 300 C. This pyrolysis causes the P{alpha}MS to depolymerize to gas phase monomer that diffuses away through the more thermally stable plasma polymer shell, which retains all the symmetry of the original P{alpha}MS shell. Thus our challenge has been to produce 2-mm-diameter P{alpha}MS shells to serve as these initial ''decomposable'' mandrels that meet or exceed the current NIF design specifications. The basic microencapsulation process used in producing P{alpha}MS mandrels involves using a droplet generator to produce a water droplet (Wl) encapsulated by a fluorobenzene solution of P{alpha}MS (O), this compound droplet being suspended in a stirred aqueous bath (W2). Historically this bath has contained poly(vinyl alcohol) (PVA, 88% hydrolyzed, mol. wt. {approx}25,000 g/mol) to prevent agglomeration of the initially fluid compound droplets. As the compound droplets are stirred in the bath, the fluorobenzene solvent slowly dissipates leaving a solid P{alpha}MS shell. The internal water is subsequently removed by low temperature drying. We found using these techniques that 2-mm shells could easily be produced, however their low mode sphericity did not meet design specifications. In our last published report we detailed how replacement of the PVA with poly(acrylic acid) (PAA) resulted in a major improvement in sphericity due to a greatly increased interfacial tension between the bath and the compound droplet, relative to the use of PVA as

  19. Expression from the nifB promoter of Azotobacter vinelandii can be activated by NifA, VnfA, or AnfA transcriptional activators.

    PubMed Central

    Drummond, M; Walmsley, J; Kennedy, C

    1996-01-01

    In Azotobacter vinelandii, nifB is required for the activity of all three nitrogenases. Expression of a nifB-lacZ fusion was examined to determine which regulatory gene products are important for nifB expression and how its transcription is regulated in response to metals. In all conditions, expression in A. vinelandii was eliminated by an rpoN mutation, confirming the absolute requirement for sigma N. In the wild type, nifB-lacZ expression was approximately twofold higher in cells grown with Mo than without. Expression was negligible in a nifA mutant grown with Mo but was much higher in Mo-free medium, suggesting that in these conditions, another sigma N-dependent activator was responsible for nifB expression, possibly VnfA, AnfA, or NtrC. Although expression of the nifB-lacZ fusion in A. vinelandii vnfA, anfA, and ntrC mutants was little different from that in the wild type, nifB transcription could be activated by NifA, VnfA, or a truncated form of AnfA in Escherichia coli. The two potential NifA binding sites centered at -87 and -129 bp upstream of the transcription start site each overlapped a VnfA recognition sequence, motifs also found in Azotobacter chroococcum in two exactly conserved regions. Deletion analysis showed that both regions are important for nifB expression. Activation of the full-length promoter by AnfA was impaired by overexpressing the DNA-binding domain of NifA, suggesting that binding of NifA and AnfA can be competitive. PMID:8550514

  20. National Ignition Facility (NIF) FY2015 Facility Use Plan

    SciTech Connect

    Folta, P.; Wisoff, Jeff

    2014-12-18

    Major features of the FY2015 NIF Use Plan include: • Performing a record number of layered DT experiments with 28 planned compared with 15 in FY2014. Executing the first plutonium experiments on the NIF in support of the Science Campaigns. • Over 300 targets shots, a 57% increase compared to FY14. This is a stretch goal defined in the 120-Day Study document, and relies upon the success of many shot-rate improvement actions, as well as on the distribution of shot type selected by the users. While the Plan is consistent with this goal, the increased proportion of layered DT experiments described above reduces the margin against this goal. • Commissioning of initial ARC capability, which will support both SSP-HED and SSPICF programs. • Increase in days allocated to Discovery Science to a level that supports an ongoing program for academic use of NIF and an annual solicitation for new proposals. • Six Facility Maintenance and Reconfiguration (FM&R) periods totaling 30 days dedicated to major facility maintenance and modifications. • Utilization of the NIF Facility Advisory Schedule Committee (FASC) to provide stakeholder review and feedback on the NIF schedule. The Use Plan assumes a total FY2015 LLNL NIF Operations funding in MTE 10.7 of $229.465M and in MTE 10.3 of 47.0M. This Use Plan will be revised in the event of significant changes to the FY2015 funding or if NNSA provides FY2016 budget guidance significantly reduced compared to FY2015.

  1. Solid expellant plasma generator

    NASA Technical Reports Server (NTRS)

    Stone, Nobie H. (Inventor); Poe, Garrett D. (Inventor); Rood, Robert (Inventor)

    2010-01-01

    An improved solid expellant plasma generator has been developed. The plasma generator includes a support housing, an electrode rod located in the central portion of the housing, and a mass of solid expellant material that surrounds the electrode rod within the support housing. The electrode rod and the solid expellant material are made of separate materials that are selected so that the electrode and the solid expellant material decompose at the same rate when the plasma generator is ignited. This maintains a point of discharge of the plasma at the interface between the electrode and the solid expellant material.

  2. Laser/x-ray coupling in the first NIF beryllium implosions

    NASA Astrophysics Data System (ADS)

    Wilson, D. C.; Kline, J. L.; Yi, S. A.; Simakov, A. N.; Olson, R. E.; Kyrala, G. A.; Perry, T. S.; Batha, S.; Callahan, D. A.; Dewald, E. L.; Jones, O.; Hinkel, D. E.; Hurricane, O. A.; Izumi, N.; Macphee, A. G.; Milovich, J. L.; Ralph, J. E.; Rygg, J. R.; Schneider, M. B.; Strozzi, D. J.; Thomas, C. A.; Tommasini, R.

    2015-11-01

    The x-ray flux driving a capsule is currently overestimated in standard Hydra high-flux model (Rosen et al., HEDP 7,180 (2011)) calculations of gas-filled hohlraums. Jones et al. (Phys. Plasmas,19,056315 (2012)) introduced time dependent multipliers to reduce the laser drive and achieve an appropriate radiation drive on NIF capsules. Using shock velocities from VISAR capsule experiments, symmetry capsule implosion times with truncated laser pulses, and time dependent DANTE X-ray flux measurements from 1D and 2D convergent ablator implosions, we derived a set of time dependent flux multipliers for the first NIF cryogenically layered beryllium capsule implosion. The similarity between these multipliers for both plastic and beryllium capsules suggests that they are primarily correcting for improper modeling of the hohlraum physics, with possibly some residual contribution from capsule modeling deficiencies. Using Lasnex we have adjusted hohlraum physics and resolution in an attempt to model these implosions without drive multipliers. This work was funded by the US Department of Energy.

  3. The effect of laser pulse shape variations on the adiabat of NIF capsule implosions

    NASA Astrophysics Data System (ADS)

    Robey, H. F.; MacGowan, B. J.; Landen, O. L.; LaFortune, K. N.; Widmayer, C.; Celliers, P. M.; Moody, J. D.; Ross, J. S.; Ralph, J.; LePape, S.; Berzak Hopkins, L. F.; Spears, B. K.; Haan, S. W.; Clark, D.; Lindl, J. D.; Edwards, M. J.

    2013-05-01

    Indirectly driven capsule implosions on the National Ignition Facility (NIF) [Moses et al., Phys. Plasmas 16, 041006 (2009)] are being performed with the goal of compressing a layer of cryogenic deuterium-tritium (DT) fuel to a sufficiently high areal density (ρR) to sustain the self-propagating burn wave that is required for fusion power gain greater than unity. These implosions are driven with a temporally shaped laser pulse that is carefully tailored to keep the DT fuel on a low adiabat (ratio of fuel pressure to the Fermi degenerate pressure). In this report, the impact of variations in the laser pulse shape (both intentionally and unintentionally imposed) on the in-flight implosion adiabat is examined by comparing the measured shot-to-shot variations in ρR from a large ensemble of DT-layered ignition target implosions on NIF spanning a two-year period. A strong sensitivity to variations in the early-time, low-power foot of the laser pulse is observed. It is shown that very small deviations (˜0.1% of the total pulse energy) in the first 2 ns of the laser pulse can decrease the measured ρR by 50%.

  4. The effect of laser pulse shape variations on the adiabat of NIF capsule implosions

    SciTech Connect

    Robey, H. F.; MacGowan, B. J.; Landen, O. L.; LaFortune, K. N.; Widmayer, C.; Celliers, P. M.; Moody, J. D.; Ross, J. S.; Ralph, J.; LePape, S.; Berzak Hopkins, L. F.; Spears, B. K.; Haan, S. W.; Clark, D.; Lindl, J. D.; Edwards, M. J.

    2013-05-15

    Indirectly driven capsule implosions on the National Ignition Facility (NIF) [Moses et al., Phys. Plasmas 16, 041006 (2009)] are being performed with the goal of compressing a layer of cryogenic deuterium-tritium (DT) fuel to a sufficiently high areal density (ρR) to sustain the self-propagating burn wave that is required for fusion power gain greater than unity. These implosions are driven with a temporally shaped laser pulse that is carefully tailored to keep the DT fuel on a low adiabat (ratio of fuel pressure to the Fermi degenerate pressure). In this report, the impact of variations in the laser pulse shape (both intentionally and unintentionally imposed) on the in-flight implosion adiabat is examined by comparing the measured shot-to-shot variations in ρR from a large ensemble of DT-layered ignition target implosions on NIF spanning a two-year period. A strong sensitivity to variations in the early-time, low-power foot of the laser pulse is observed. It is shown that very small deviations (∼0.1% of the total pulse energy) in the first 2 ns of the laser pulse can decrease the measured ρR by 50%.

  5. Pleiades Experiments on the NIF: Phase II-C

    SciTech Connect

    Benstead, James; Morton, John; Guymer, Thomas; Garbett, Warren; Stevenson, Mark; Moore, Alastair; Kline, John; Schmidt, Derek; Perry, Ted; Lanier, Nick; Workman, Jonathan

    2015-06-08

    Pleiades was a radiation transport campaign fielded at the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory (LLNL) between 2011 and 2014. The primary goals of the campaign were to develop and characterise a reproducible ~350eV x-ray drive and to constrain a number of material data properties required to successfully model the propagation of radiation through two low-density foam materials. A further goal involved the development and qualification of diagnostics for future radiation transport experiments at NIF. Pleiades was a collaborative campaign involving teams from both AWE and the Los Alamos National Laboratory (LANL).

  6. Magnetohydrodynamic electrode

    DOEpatents

    Boquist, Carl W.; Marchant, David D.

    1978-01-01

    A ceramic-metal composite suitable for use in a high-temperature environment consists of a refractory ceramic matrix containing 10 to 50 volume percent of a continuous high-temperature metal reinforcement. In a specific application of the composite, as an electrode in a magnetohydrodynamic generator, the one surface of the electrode which contacts the MHD fluid may have a layer of varying thickness of nonreinforced refractory ceramic for electrode temperature control. The side walls of the electrode may be coated with a refractory ceramic insulator. Also described is an electrode-insulator system for a MHD channel.

  7. 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.

  8. Working Electrodes

    NASA Astrophysics Data System (ADS)

    Komorsky-Lovrić, Šebojka

    In electrochemistry an electrode is an electronic conductor in contact with an ionic conductor. The electronic conductor can be a metal, or a semiconductor, or a mixed electronic and ionic conductor. The ionic conductor is usually an electrolyte solution; however, solid electrolytes and ionic melts can be used as well. The term "electrode" is also used in a technical sense, meaning the electronic conductor only. If not specified otherwise, this meaning of the term "electrode" is the subject of the present chapter. In the simplest case the electrode is a metallic conductor immersed in an electrolyte solution. At the surface of the electrode, dissolved electroactive ions change their charges by exchanging one or more electrons with the conductor. In this electrochemical reaction both the reduced and oxidized ions remain in solution, while the conductor is chemically inert and serves only as a source and sink of electrons. The technical term "electrode" usually also includes all mechanical parts supporting the conductor (e.g., a rotating disk electrode or a static mercury drop electrode). Furthermore, it includes all chemical and physical modifications of the conductor, or its surface (e.g., a mercury film electrode, an enzyme electrode, and a carbon paste electrode). However, this term does not cover the electrolyte solution and the ionic part of a double layer at the electrode/solution interface. Ion-selective electrodes, which are used in potentiometry, will not be considered in this chapter. Theoretical and practical aspects of electrodes are covered in various books and reviews [1-9].

  9. Identification and characterization of functional homologs of nitrogenase cofactor biosynthesis protein NifB from methanogens

    PubMed Central

    Fay, Aaron W.; Wiig, Jared A.; Lee, Chi Chung; Hu, Yilin

    2015-01-01

    Nitrogenase biosynthesis protein NifB catalyzes the radical S-adenosyl-L-methionine (SAM)-dependent insertion of carbide into the M cluster, the cofactor of the molybdenum nitrogenase from Azotobacter vinelandii. Here, we report the identification and characterization of two naturally “truncated” homologs of NifB from Methanosarcina acetivorans (NifBMa) and Methanobacterium thermoautotrophicum (NifBMt), which contain a SAM-binding domain at the N terminus but lack a domain toward the C terminus that shares homology with NifX, an accessory protein in M cluster biosynthesis. NifBMa and NifBMt are monomeric proteins containing a SAM-binding [Fe4S4] cluster (designated the SAM cluster) and a [Fe4S4]-like cluster pair (designated the K cluster) that can be processed into an [Fe8S9] precursor to the M cluster (designated the L cluster). Further, the K clusters in NifBMa and NifBMt can be converted to L clusters upon addition of SAM, which corresponds to their ability to heterologously donate L clusters to the biosynthetic machinery of A. vinelandii for further maturation into the M clusters. Perhaps even more excitingly, NifBMa and NifBMt can catalyze the removal of methyl group from SAM and the abstraction of hydrogen from this methyl group by 5′-deoxyadenosyl radical that initiates the radical-based incorporation of methyl-derived carbide into the M cluster. The successful identification of NifBMa and NifBMt as functional homologs of NifB not only enabled classification of a new subset of radical SAM methyltransferases that specialize in complex metallocluster assembly, but also provided a new tool for further characterization of the distinctive, NifB-catalyzed methyl transfer and conversion to an iron-bound carbide. PMID:26627238

  10. NifU and NifS are required for the maturation of nitrogenase and cannot replace the function of isc-gene products in Azotobacter vinelandii.

    PubMed

    Johnson, D C; Dos Santos, P C; Dean, D R

    2005-02-01

    In recent years, it has become evident that [Fe-S] proteins, such as hydrogenase, nitrogenase and aconitase, require a complex machinery to assemble and insert their associated [Fe-S] clusters. So far, three different types of [Fe-S] cluster biosynthetic systems have been identified and these have been designated nif, isc and suf. In the present work, we show that the nif-specific [Fe-S] cluster biosynthetic system from Azotobacter vinelandii, which is required for nitrogenase maturation, cannot functionally replace the isc [Fe-S] cluster system used for the maturation of other [Fe-S] proteins, such as aconitase. The results indicate that, in certain cases, [Fe-S] cluster biosynthetic machineries have evolved to perform only specialized functions. PMID:15667274

  11. Techniques of Electrode Fabrication

    NASA Astrophysics Data System (ADS)

    Guo, Liang; Li, Xinyong; Chen, Guohua

    Electrochemical applications using many kinds of electrode materials as an advanced oxidation/reduction technique have been a focus of research by a number of groups during the last two decades. The electrochemical approach has been adopted successfully to develop various environmental applications, mainly including water and wastewater treatment, aqueous system monitoring, and solid surface analysis. In this chapter, a number of methods for the fabrication of film-structured electrode materials were selectively reviewed. Firstly, the thermal decomposition method is briefly described, followed by introducing chemical vapor deposition (CVD) strategy. Especially, much attention was focused on introducing the methods to produce diamond novel film electrode owing to its unique physical and chemical properties. The principle and influence factors of hot filament CVD and plasma enhanced CVD preparation were interpreted by refereeing recent reports. Finally, recent developments that address electro-oxidation/reduction issues and novel electrodes such as nano-electrode and boron-doped diamond electrode (BDD) are presented in the overview.

  12. NIF ICCS Test Controller for Automated & Manual Testing

    SciTech Connect

    Zielinski, J S

    2007-10-03

    The National Ignition Facility (NIF) Integrated Computer Control System (ICCS) is a large (1.5 MSLOC), hierarchical, distributed system that controls all aspects of the NIF laser [1]. The ICCS team delivers software updates to the NIF facility throughout the year to support shot operations and commissioning activities. In 2006, there were 48 releases of ICCS: 29 full releases, 19 patches. To ensure the quality of each delivery, thousands of manual and automated tests are performed using the ICCS Test Controller test infrastructure. The TestController system provides test inventory management, test planning, automated test execution and manual test logging, release testing summaries and test results search, all through a web browser interface. Automated tests include command line based frameworks server tests and Graphical User Interface (GUI) based Java tests. Manual tests are presented as a checklist-style web form to be completed by the tester. The results of all tests, automated and manual, are kept in a common repository that provides data to dynamic status reports. As part of the 3-stage ICCS release testing strategy, the TestController system helps plan, evaluate and track the readiness of each release to the NIF facility.

  13. Correlation of Test Data from Some NIF Small Optical Components

    SciTech Connect

    Chow, R; McBurney, M; Eickelberg, W K; Williams, W H; Thomas, M D

    2001-06-12

    The NIF injection laser system requires over 8000 precision optical components. Two special requirements for such optics are wavefront and laser damage threshold. Wavefront gradient is an important specification on the NIF ILS optics. The gradient affects the spot size and, in the second order, the contrast ratio of the laser beam. Wavefront errors are specified in terms of peak-to-valley, rms, and rms gradient, with filtering requirements. Typical values are lambda/8 PV, lambda/30 rms, and lambda/30/cm rms gradient determined after filtering for spatial periods greater than 2 mm. One objective of this study is to determine whether commercial software supplied with common phase measuring interferometers can filter, perform the gradient analysis, and produce numbers comparable to that by CVOS, the LLNL wavefront analysis application. Laser survivability of optics is another important specification for the operational longevity of the laser system. Another objective of this study is to find alternate laser damage test facilities. The addition of non-NIF testing would allow coating suppliers to optimize their processes according to their test plans and NIF integrators to validate the coatings from their sub-tiered suppliers. The maximum level required for anti-reflective, 45-degree high reflector, and polarizer coatings are 20, 30, and 5 J/cm{sup 2} (1064 nm, 3 ns pulse-width), respectively. The damage threshold correlation between a common set of samples tested by LLNL and a commercial test service is given.

  14. The National Ignition Facility (NIF) wavefront control system

    SciTech Connect

    Van Atta, L; Bliss, E; Bruns, D; Feldman, M; Grey, A; Henesian, M; J; Koch, J; LaFiandra, C; Lawson; Sacks, R; Salmon, T; Toeppen, J; Winters, S; Woods, B; Zacharias, R

    1998-08-17

    A wavefront control system will be employed on NIF to correct beam aberrations that otherwise would limit the minimum target focal spot size. For most applications, NIF requires a focal spot that is a few times the diffraction limit. Sources of aberrations that must be corrected include prompt pump-induced distortions in the laser slabs, thermal distortions in the laser slabs from previous shots, manufacturing figure errors in the optics, beam off-axis effects, gas density variations, and gravity, mounting, and coating- induced optic distortions. The NIF Wavefront Control System consists of five subsystems: 1) a deformable mirror, 2) a wavefront sensor, 3) a computer controller, 4) a wavefront reference system, and 5) a system of fast actuators to allow the wavefront control system to operate to within one second of the laser shot. The system includes the capability for in situ calibrations and operates in closed loop prior to the shot. Shot wavefront data is recorded. This paper describes the function, realization, and performance of each wavefront control subsystem. Subsystem performance will be characterized by computer models and by test results. The focal spot improvement in the NIF laser system effected by the wavefront control system will be characterized through computer models.

  15. Dynamics of molecular clouds: observations, simulations, and NIF experiments

    NASA Astrophysics Data System (ADS)

    Kane, Jave O.; Martinez, David A.; Pound, Marc W.; Heeter, Robert F.; Casner, Alexis; Mancini, Roberto C.

    2015-02-01

    For over fifteen years astronomers at the University of Maryland and theorists and experimentalists at LLNL have investigated the origin and dynamics of the famous Pillars of the Eagle Nebula, and similar parsec-scale structures at the boundaries of HII regions in molecular hydrogen clouds. Eagle Nebula was selected as one of the National Ignition Facility (NIF) Science programs, and has been awarded four NIF shots to study the cometary model of pillar formation. These experiments require a long-duration drive, 30 ns or longer, to drive deeply nonlinear ablative hydrodynamics. The NIF shots will feature a new long-duration x-ray source prototyped at the Omega EP laser, in which multiple hohlraums are driven with UV light in series for 10 ns each and reradiate the energy as an extended x-ray pulse. The new source will be used to illuminate a science package with directional radiation mimicking a cluster of stars. The scaled Omega EP shots tested whether a multi-hohlraum concept is viable — whether earlier time hohlraums would degrade later time hohlraums by preheat or by ejecting ablated plumes that would deflect the later beams. The Omega EP shots illuminated three 2.8 mm long by 1.4 mm diameter Cu hohlraums for 10 ns each with 4.3 kJ per hohlraum. At NIF each hohlraum will be 4 mm long by 3 mm in diameter and will be driven with 80 kJ per hohlraum.

  16. Tamping effects and confinement time in NIF experiments

    NASA Astrophysics Data System (ADS)

    Wang, Y. M.; Cheng, B.; Kwan, T. J. T.; Merrill, F.; Cerjan, C.; Batha, S. H.

    2015-11-01

    Tamper is expected to play an important role in inertial confinement fusion capsule experiments performed at the National Ignition Facility (NIF). It is expected to increase the confinement time of thermonuclear burning (TN) in the hot spot. In this work, we study the dependence of the capsule performance with respect to the density ratio of the pusher to the hot fuel at the cold-hot interface numerically through LASNEX simulations in one-dimension. Our study shows that the dependence of the capsule performance (neutron yield) with respect to the square root of the density ratio is not linear: the sharper the interface, the higher the tamping effect and neutron yields. Our analysis indicates that the tamping factor in both NIC and NIF experiments has not been appreciable and the tamping factor on yield is less than 1.1. Thus, the tamping factor has not yet played a significant role in the current NIF ignition design. Furthermore, the confinement time in NIF experiments will be discussed. (LA-UR-15-25596).

  17. Target diagnostic system for the National Ignition Facility (NIF)

    SciTech Connect

    Leeper, R.J.; Chandler, G.A.; Cooper, G.W.; Derzon, M.S.

    1996-07-01

    A review of recent progress on the design of a diagnostic system proposed for ignition target experiments on the National Ignition Facility (NIF) will be presented. This diagnostic package contains an extensive suite of optical, x-ray, gamma-ray, and neutron diagnostics that enable measurements of the performance of both direct and indirect driven NIF targets. The philosophy used in designing all of the diagnostics in the set has emphasized redundant and independent measurement of fundamental physical quantities relevant to the operation of the NIF target. A unique feature of these diagnostics is that they are being designed to be capable of operating, in the high radiation, EMP, and debris backgrounds expected on the NIF facility. The diagnostic system proposed can be categorized into three broad areas: laser characterization, hohlraum characterization, and capsule performance diagnostics. The operating principles of a representative instrument from each class of diagnostic employed in this package will be summarized and illustrated with data obtained in recent prototype diagnostic tests.

  18. Design for manufacturability evaluation: Composite NIF Pockel Cell body

    SciTech Connect

    Jensen, W.A.; Spellman, G.P.

    1994-04-01

    A survey of composite materials and processes for the NIF Optical Switch Body is described. Mechanical and physical criterion set upon the part are used as guidelines for the selection of materials and processes for manufacturing. Benefits, costs, and risks associated with selected processes, as well as a recommendation for prototype fabrication is presented.

  19. NIF Rugby High Foot Campaign from the design side

    NASA Astrophysics Data System (ADS)

    Leidinger, J.-P.; Callahan, D. A.; Berzak-Hopkins, L. F.; Ralph, J. E.; Amendt, P.; Hinkel, D. E.; Michel, P.; Moody, J. D.; Ross, J. S.; Rygg, J. R.; Celliers, P.; Clouët, J.-F.; Dewald, E. L.; Kaiser, P.; Khan, S.; Kritcher, A. L.; Liberatore, S.; Marion, D.; Masson-Laborde, P.-E.; Milovich, J. L.; Morice, O.; Pak, A. E.; Poujade, O.; Strozzi, D.; Hurricane, O. A.

    2016-05-01

    The NIF Rugby High Foot campaign results, with 8 shots to date, are compared with the 2D FCI2 design simulations. A special emphasis is placed on the predictive features and on those areas where some work is still required to achieve the best possible modelling of these MJ-class experiments.

  20. NIF Large Optics Metrology Software: Description and Algorithms

    SciTech Connect

    Williams, W H

    2002-10-15

    Several software packages have been developed for use by NIF large optics vendors during production of NIF optics. These packages allow specific comparison of the interferometer measurements done on optics against the wavefront requirements for those optics, as given on relevant drawings. This document outlines the various packages, and their specific applications, and describes in some detail the calculational algorithms used. It is intended as the primary reference document for the codes (aside from the source codes themselves). In order to ensure good laser beam quality, NIF requires that all large optics be measured with an interferometer to monitor how that optic will affect beam wavefront quality and focusability. Various specifications for transmitted wavefront (TWF) and reflected wavefront (RWF) for the full-aperture parts, and for various sub-apertures, are given on the large optics drawings. For reference, a summary of the various specifications for the NIF large optics is given in Figure 1. Each large optic in production will be measured against some of these specifications. Other specifications will be monitored in a 'process validation' fashion by measuring a representative sample of parts to assure the process is yielding parts which pass specification. This document will focus on the specifications requiring measurements on every part. This document will not go into detail concerning the procedures and limitations of the measurements themselves.

  1. Role of conserved cysteine residues in Herbaspirillum seropedicae NifA activity.

    PubMed

    Oliveira, Marco A S; Baura, Valter A; Aquino, Bruno; Huergo, Luciano F; Kadowaki, Marco A S; Chubatsu, Leda S; Souza, Emanuel M; Dixon, Ray; Pedrosa, Fábio O; Wassem, Roseli; Monteiro, Rose A

    2009-01-01

    Herbaspirillum seropedicae is an endophytic diazotrophic bacterium that associates with economically important crops. NifA protein, the transcriptional activator of nif genes in H. seropedicae, binds to nif promoters and, together with RNA polymerase-sigma(54) holoenzyme, catalyzes the formation of open complexes to allow transcription initiation. The activity of H. seropedicae NifA is controlled by ammonium and oxygen levels, but the mechanisms of such control are unknown. Oxygen sensitivity is attributed to a conserved motif of cysteine residues in NifA that spans the central AAA+ domain and the interdomain linker that connects the AAA+ domain to the C-terminal DNA binding domain. Here we mutagenized this conserved motif of cysteines and assayed the activity of mutant proteins in vivo. We also purified the mutant variants of NifA and tested their capacity to bind to the nifB promoter region. Chimeric proteins between H. seropedicae NifA, an oxygen-sensitive protein, and Azotobacter vinelandii NifA, an oxygen-tolerant protein, were constructed and showed that the oxygen response is conferred by the central AAA+ and C-terminal DNA binding domains of H. seropedicae NifA. We conclude that the conserved cysteine motif is essential for NifA activity, although single cysteine-to-serine mutants are still competent at binding DNA. PMID:19573596

  2. Cloning, characterization, and regulation of nifF from Rhodobacter capsulatus.

    PubMed

    Gennaro, G; Hübner, P; Sandmeier, U; Yakunin, A F; Hallenbeck, P C

    1996-07-01

    The Rhodobacter capsulatus nifF gene and upstream sequence were cloned by using a probe based on the N-terminal sequence of NifF. nifF was found to not be contained in the previously described nif regions I, II, and III. Comparison of the deduced amino acid sequence showed that it is highly similar to NifF from Azotobacter vinelandii and NifF from Klebsiella pneumoniae. Analysis of translational fusions demonstrated that the regulation of transcription was the same as previously reported at the protein level. Insertional mutagen esis showed that NifF contributes significantly to nitrogenase activity under normal nitrogen-fixing conditions and that it is absolutely required for nitrogen fixation under iron limitation. PMID:8682802

  3. Multi-Megajoule NIF: Ushering In a New Era in High Energy Density Science

    SciTech Connect

    Keane, C; Moses, E I

    2008-04-30

    This paper describes the status of the stadium-sized National Ignition Facility (NIF), the world's largest laser system and first operational multi-megajoule laser. The 192-beam NIF, located at Lawrence Livermore National Laboratory (LLNL), is 96% complete and scheduled for completion in March 2009. The NIF laser will produce nanosecond laser pulses with energies up to approximately 4 MJ in the infrared (laser wavelength = 1.053-{micro}m) and 2MJ in the ultraviolet (laser wavelength = 0.35-{micro}m). With these energies NIF will access conditions of pressure and temperature not previously available on earth, allowing it to conduct experiments in support of the nation's national security, energy, and fundamental science goals. First ignition experiments at NIF are scheduled for FY2010. This paper will provide an overview of the NIF laser and the ignition, energy, and fundamental science activities at NIF.

  4. Liquid electrode

    DOEpatents

    Ekechukwu, Amy A.

    1994-01-01

    A dropping electrolyte electrode for use in electrochemical analysis of non-polar sample solutions, such as benzene or cyclohexane. The liquid electrode, preferably an aqueous salt solution immiscible in the sample solution, is introduced into the solution in dropwise fashion from a capillary. The electrolyte is introduced at a known rate, thus, the droplets each have the same volume and surface area. The electrode is used in making standard electrochemical measurements in order to determine properties of non-polar sample solutions.

  5. In vitro biosynthesis of iron-molybdenum cofactor and maturation of the nif-encoded apodinitrogenase. Effect of substitution for NifH with site-specifically altered forms of NifH.

    PubMed

    Rangaraj, P; Ryle, M J; Lanzilotta, W N; Ludden, P W; Shah, V K

    1999-07-01

    NifH has three different roles in the nitrogenase enzyme system. Apart from serving as the physiological electron donor to dinitrogenase, NifH is involved in iron-molybdenum cofactor (FeMo-co) biosynthesis and in maturation of the FeMo-co-deficient form of apodinitrogenase to a FeMo-co-activable form (apodinitrogenase maturation). The exact roles of NifH in these processes are not well understood. In the present study, the features of NifH required for the aforementioned processes have been investigated by the use of site-specifically altered forms of the enzyme. The ability of six altered forms of NifH inactive in substrate reduction (K15R, D39N, D43N, L127Delta, D129E, and F135Y) to function in in vitro FeMo-co synthesis and apodinitrogenase maturation reactions was investigated. We report that the ability of NifH to bind and not hydrolyze MgATP is required for it to function in these processes. We also present evidence that the ability of NifH to function in these processes is not dictated by the properties known to be required for its function in electron transfer to dinitrogenase. Evidence toward the existence of separate, overlapping sites on NifH for each of its functions (substrate reduction, FeMo-co biosynthesis, and apodinitrogenase maturation) is presented. PMID:10391920

  6. The role of heterologous nifAc product in the regulation of nif expression in Agrobacterium tumefaciens.

    PubMed

    Zhang, J; Zhang, J

    1997-01-01

    The plasmids pCK5, pCK3, pSZ36, and pSZ23-CA, which carried constitutive nifAc gene of Azotobacter chroococcum and Klebsiella pneumoniae were transferred into A. tumefaciens C58/pGV3850 with triparental mating. The growth rate of these transconjugants was similar to the wild type. Nitrogenase synthesis was demonstrated by Western blotting, in the presence of 10 mmol/L NH4+, and the nitrogenase activity was restored to 73%, 24%, 11%, and 62%, respectively. The results showed that the regulative gene of nitrogen fixation in A. chroococcum and K. pneumoniae played a regulative role for the expression of A. tumefaciens nitrogen fixation gene. Among them, the role of A. chroococcum nifAc gene was the strongest, the fusion plasmid pSZ23-CA which carried nifA-ntrC gene of K. pneumoniae was stronger, and the nifAc gene of K. pneumoniae was weak. PMID:9376504

  7. Reaction-in-Flight Neutrons and the Stopping Power in Cryogenic NIF Capsules

    NASA Astrophysics Data System (ADS)

    Hayes, Anna

    2014-10-01

    Recent experiments in cryogenic DT capsules at the National Ignition Facility (NIF) observed high-energy reaction-in-flight (RIF) neutrons via threshold (>15 MeV) neutron reactions on thulium foils. This represents the first measurements of RIF neutrons in inertial confinement fusion plasmas. RIF neutrons are produced by a two-step process. In the first step, a primary 14.1 MeV DT neutron knocks a triton or deuteron up to a spectrum of energies from 0 to more than 10 MeV. In the second step, the energetic knocked-on ion undergoes a DT reaction with a thermal ion, producing a neutron above the primary 14 MeV peak. Transport and energy loss of the knock-on ions inducing the RIF reactions directly affect the RIF production rate, and RIF measurements can be used to determine the stopping power for charged particles in the plasma. Here we present the formalism for extracting the stopping power from the measured RIF signals. We find that the stopping power extracted from these measurements is consistent with a strongly coupled quantum degenerate plasma for the high-density cold fuel surrounding the hotspot of the compressed capsule. These RIF measurements represent the first determination of stopping powers in strongly coupled plasmas.

  8. Role of Escherichia coli nitrogen regulatory genes in the nitrogen response of the Azotobacter vinelandii NifL-NifA complex.

    PubMed

    Reyes-Ramirez, F; Little, R; Dixon, R

    2001-05-01

    The redox-sensing flavoprotein NifL inhibits the activity of the nitrogen fixation (nif)-specific transcriptional activator NifA in Azotobacter vinelandii in response to molecular oxygen and fixed nitrogen. Although the mechanism whereby the A. vinelandii NifL-NifA system responds to fixed nitrogen in vivo is unknown, the glnK gene, which encodes a PII-like signal transduction protein, has been implicated in nitrogen control. However, the precise function of A. vinelandii glnK in this response is difficult to establish because of the essential nature of this gene. We have shown previously that A. vinelandii NifL is able to respond to fixed nitrogen to control NifA activity when expressed in Escherichia coli. In this study, we investigated the role of the E. coli PII-like signal transduction proteins in nitrogen control of the A. vinelandii NifL-NifA regulatory system in vivo. In contrast to recent findings with Klebsiella pneumoniae NifL, our results indicate that neither the E. coli PII nor GlnK protein is required to relieve inhibition by A. vinelandii NifL under nitrogen-limiting conditions. Moreover, disruption of both the E. coli glnB and ntrC genes resulted in a complete loss of nitrogen regulation of NifA activity by NifL. We observe that glnB ntrC and glnB glnK ntrC mutant strains accumulate high levels of intracellular 2-oxoglutarate under conditions of nitrogen excess. These findings are in accord with our recent in vitro observations (R. Little, F. Reyes-Ramirez, Y. Zhang, W. Van Heeswijk, and R. Dixon, EMBO J. 19:6041-6050, 2000) and suggest a model in which nitrogen control of the A. vinelandii NifL-NifA system is achieved through the response to the level of 2-oxoglutarate and an interaction with PII-like proteins under conditions of nitrogen excess. PMID:11325935

  9. 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.

  10. Excretion of ammonium by a nifL mutant of Azotobacter vinelandii fixing nitrogen.

    PubMed Central

    Bali, A; Blanco, G; Hill, S; Kennedy, C

    1992-01-01

    A mutation in the gene upstream of nifA in Azotobacter vinelandii was introduced into the chromosome to replace the corresponding wild-type region. The resulting mutant, MV376, produced nitrogenase constitutively in the presence of 15 mM ammonium. When introduced into a nifH-lacZ fusion strain, the mutation permitted beta-galactosidase production in the presence of ammonium. The gene upstream of nifA is therefore designated nifL because of its similarity to the Klebsiella pneumoniae nifL gene in proximity to nifA, in mutant phenotype, and in amino acid sequence of the gene product. The A. vinelandii nifL mutant MV376 excreted significant quantities of ammonium (approximately 10 mM) during diazotrophic growth. In contrast, ammonium excretion during diazotrophy was much lower in a K. pneumoniae nifL deletion mutant (maximum, 0.15 mM) but significantly higher than in NifL+ K. pneumoniae. The expression of the A. vinelandii nifA gene, unlike that of K. pneumoniae, was not repressed by ammonium. PMID:1622243

  11. The basis of ammonium release in nifL mutants of Azotobacter vinelandii.

    PubMed

    Brewin, B; Woodley, P; Drummond, M

    1999-12-01

    In Azotobacter vinelandii, nitrogen fixation is regulated at the transcriptional level by an unusual two-component system encoded by nifLA. Certain mutations in nifL result in the bacterium releasing large quantities of ammonium into the medium, and earlier work suggested that this occurs by a mechanism that does not involve NifA, the activator of nif gene transcription. We have investigated a number of possible alternative mechanisms and find no evidence for their involvement in ammonium release. Enhancement of NifA-mediated transcription, on the other hand, by either elimination of nifL or overexpression of nifA, resulted in ammonium release, correlating with enhanced levels of nifH mRNA, raised levels of nitrogenase and acetylene-reducing activity, and increased concentrations of intracellular ammonium. Up to 35 mM ammonium can accumulate in the medium. Where measured, intracellular levels exceeded extracellular levels, indicating that rather than being actively transported, ammonium is lost from the cell passively, possibly by reversal of an NH(4)(+) uptake system. The data also indicate that in the wild type the bulk of NifA is inactivated by NifL during steady-state growth on dinitrogen. PMID:10572141

  12. A Comprehensive Evaluation of PCR Primers to Amplify the nifH Gene of Nitrogenase

    PubMed Central

    Gaby, John Christian; Buckley, Daniel H.

    2012-01-01

    The nifH gene is the most widely sequenced marker gene used to identify nitrogen-fixing Bacteria and Archaea. Numerous PCR primers have been designed to amplify nifH, but a comprehensive evaluation of nifH PCR primers has not been performed. We performed an in silico analysis of the specificity and coverage of 51 universal and 35 group-specific nifH primers by using an aligned database of 23,847 nifH sequences. We found that there are 15 universal nifH primers that target 90% or more of nitrogen fixers, but that there are also 23 nifH primers that target less than 50% of nifH sequences. The nifH primers we evaluated vary in their phylogenetic bias and their ability to recover sequences from commonly sampled environments. In addition, many of these primers will amplify genes that do not mediate nitrogen fixation, and thus it would be advisable for researchers to screen their sequencing results for the presence of non-target genes before analysis. Universal primers that performed well in silico were tested empirically with soil samples and with genomic DNA from a phylogenetically diverse set of nitrogen-fixing strains. This analysis will be of great utility to those engaged in molecular analysis of nifH genes from isolates and environmental samples. PMID:22848735

  13. Excretion of ammonium by a nifL mutant of Azotobacter vinelandii fixing nitrogen.

    PubMed

    Bali, A; Blanco, G; Hill, S; Kennedy, C

    1992-05-01

    A mutation in the gene upstream of nifA in Azotobacter vinelandii was introduced into the chromosome to replace the corresponding wild-type region. The resulting mutant, MV376, produced nitrogenase constitutively in the presence of 15 mM ammonium. When introduced into a nifH-lacZ fusion strain, the mutation permitted beta-galactosidase production in the presence of ammonium. The gene upstream of nifA is therefore designated nifL because of its similarity to the Klebsiella pneumoniae nifL gene in proximity to nifA, in mutant phenotype, and in amino acid sequence of the gene product. The A. vinelandii nifL mutant MV376 excreted significant quantities of ammonium (approximately 10 mM) during diazotrophic growth. In contrast, ammonium excretion during diazotrophy was much lower in a K. pneumoniae nifL deletion mutant (maximum, 0.15 mM) but significantly higher than in NifL+ K. pneumoniae. The expression of the A. vinelandii nifA gene, unlike that of K. pneumoniae, was not repressed by ammonium. PMID:1622243

  14. The Basis of Ammonium Release in nifL Mutants of Azotobacter vinelandii

    PubMed Central

    Brewin, Brett; Woodley, Paul; Drummond, Martin

    1999-01-01

    In Azotobacter vinelandii, nitrogen fixation is regulated at the transcriptional level by an unusual two-component system encoded by nifLA. Certain mutations in nifL result in the bacterium releasing large quantities of ammonium into the medium, and earlier work suggested that this occurs by a mechanism that does not involve NifA, the activator of nif gene transcription. We have investigated a number of possible alternative mechanisms and find no evidence for their involvement in ammonium release. Enhancement of NifA-mediated transcription, on the other hand, by either elimination of nifL or overexpression of nifA, resulted in ammonium release, correlating with enhanced levels of nifH mRNA, raised levels of nitrogenase and acetylene-reducing activity, and increased concentrations of intracellular ammonium. Up to 35 mM ammonium can accumulate in the medium. Where measured, intracellular levels exceeded extracellular levels, indicating that rather than being actively transported, ammonium is lost from the cell passively, possibly by reversal of an NH4+ uptake system. The data also indicate that in the wild type the bulk of NifA is inactivated by NifL during steady-state growth on dinitrogen. PMID:10572141

  15. PLASMA GENERATOR

    DOEpatents

    Wilcox, J.M.; Baker, W.R.

    1963-09-17

    This invention is a magnetohydrodynamic device for generating a highly ionized ion-electron plasma at a region remote from electrodes and structural members, thus avoiding contamination of the plasma. The apparatus utilizes a closed, gas-filled, cylindrical housing in which an axially directed magnetic field is provided. At one end of the housing, a short cylindrical electrode is disposed coaxially around a short axial inner electrode. A radial electrical discharge is caused to occur between the inner and outer electrodes, creating a rotating hydromagnetic ionization wave that propagates aiong the magnetic field lines toward the opposite end of the housing. A shorting switch connected between the electrodes prevents the wave from striking the opposite end of the housing. (AEC)

  16. PLASMA DEVICE

    DOEpatents

    Baker, W.R.; Brathenahl, A.; Furth, H.P.

    1962-04-10

    A device for producing a confined high temperature plasma is described. In the device the concave inner surface of an outer annular electrode is disposed concentrically about and facing the convex outer face of an inner annular electrode across which electrodes a high potential is applied to produce an electric field there between. Means is provided to create a magnetic field perpendicular to the electric field and a gas is supplied at reduced pressure in the area therebetween. Upon application of the high potential, the gas between the electrodes is ionized, heated, and under the influence of the electric and magnetic fields there is produced a rotating annular plasma disk. The ionized plasma has high dielectric constant properties. The device is useful as a fast discharge rate capacitor, in controlled thermonuclear research, and other high temperature gas applications. (AEC)

  17. The NIF Integrated Timimg System-Design and Performance

    SciTech Connect

    Lerche, R A; Coutts, G W; Lagin, L J; Nyholm, R A; Stever, R D; Wiedwald, J D; Sewall, N R; Larkin, J; Stein, S; Martin, R

    2001-10-18

    The National Ignition Facility (NIF) will contain the world's most powerful laser. NIF requires more than 1500 precisely timed trigger pulses to control the timing of laser and diagnostic equipment. The Integrated Timing System applies new concepts to generate and deliver triggers at preprogrammed times to equipment throughout the laser and target areas of the facility. Trigger pulses during the last 2 seconds of a shot cycle are required to have a jitter of less than 20 ps (rms) and a wander of less than 100 ps (max). Also, Timing System allows simultaneous, independent use by multiple clients by partitioning the system hardware into subsets that are controlled via independent software keys. The hardware necessary to implement the Integrated Timing System is commercially available.

  18. GIGABAR MATERIAL PROPERTIES EXPERIMENTS ON NIF AND OMEGA

    SciTech Connect

    Swift, D C; Hawreliak, J A; Braun, D; Kritcher, A; Glenzer, S; Collins, G W; Rothman, S D; Chapman, D; Rose, S

    2011-08-04

    The unprecedented laser capabilities of the National Ignition Facility (NIF) make it possible for the first time to countenance laboratory-scale experiments in which gigabar pressures can be applied to a reasonable volume of material, and sustained long enough for percent level equation of state measurements to be made. We describe the design for planned experiments at the NIF, using a hohlraum drive to induce a spherically-converging shock in samples of different materials. Convergence effects increase the shock pressure to several gigabars over a radius of over 100 microns. The shock speed and compression will be measured radiographically over a range of pressures using an x-ray streak camera. In some cases, we will use doped layers to allow a radiographic measurement of particle velocity.

  19. Orchestrating Shots for the National Ignition Facililty (NIF)

    SciTech Connect

    Mathisen, D G; Bettenhausen, R C; Beeler, R G; Bowers, G A; Carey, R W; Casavant, D D; Cline, B D; Demaret, R D; Domyancic, D M; Elko, S D; Fisher, J M; Krammen, J E; Lagin, L J; Ludwigsen, A P; Patterson, R W; Sanchez, R J; Stout, E A

    2005-05-12

    The National Ignition Facility (NIF), currently under construction at the Lawrence Livermore National Laboratory, is a stadium-sized facility containing a 192-beam, 1.8 Megajoule, 500-Terawatt, ultra-violet laser system together with a 10-meter diameter target chamber with room for nearly 100 experimental diagnostics. When completed, NIF will be the world's largest and most energetic laser experimental system, providing an international center to study inertial confinement fusion and physics of matter at extreme densities and pressures. The NIF is operated by the Integrated Computer Control System (ICCS), which is a layered architecture of over 700 lower-level front-end processors attached to nearly 60,000 control points and coordinated by higher-level supervisory subsystems in the main control room. A shot automation framework has been developed and deployed during the past year to orchestrate and automate shots performed at the NIF using the ICCS. The Shot Automation framework is designed to automate 4-8 hour shot sequences, that includes deriving shot goals from an experiment definition, set up of the laser and diagnostics, automatic alignment of laser beams, and a countdown to charge and fire the lasers. These sequences consist of set of preparatory verification shots, leading to amplified system shots followed by post-shot analysis and archiving. The framework provides for a flexible, model-based work-flow execution, driven by scripted automation called macro steps. The shot director software is the orchestrating component of a very flexible automation layer which allows us to define, coordinate and reuse simpler automation sequences. This software provides a restricted set of shot life cycle state transitions to 26 collaboration supervisors that automate 8-laser beams (bundle) and a common set of shared resources. Each collaboration supervisor commands approximately 10 subsystem shot supervisors that perform automated control and status verification

  20. The NIF 4.5-m nTOF Detectors

    SciTech Connect

    Moran, M J; Bond, E J; Clancy, T J; Eckart, M J; Khater, H Y; Glebov, V Y

    2012-05-07

    The first several campaigns of laser fusion experiments at the National Ignition Facility (NIF) included a family of high-sensitivity scintillator/photodetector neutron-time-of-flight (nTOF) detectors for measuring DD and DT neutron yields. The detectors provided consistent neutron yield benchmarks from below 1E9 (DD) to nearly 1E15 (DT). The detectors demonstrated DT yield measurement precisions better than 5%, but the absolute accuracy relies on cross calibration with independent measurements of absolute neutron yield. The 4.5-m nTOF data have provided a useful testbed for testing improvements in nTOF data processing, especially with respect to improving the accuracies of the detector impulse response functions. The resulting improvements in data analysis methods have produced more accurate results. In summary, results from the NIF 4.5-m nTOF detectors have provided consistent measurements of DD and DT neutron yields from laser-fusion implosions.

  1. In-Situ Diffraction on the National Ignition Facility (NIF)

    NASA Astrophysics Data System (ADS)

    Eggert, Jon; Braun, Dave; Rygg, Ryan; Lazicki, Amy; Fratanduono, Dayne; Smith, Ray; Coppari, Federica; Kraus, Rick; Swift, Damian; McNaney, Jim; Ping, Yuan; Blobaum, Kerri; Wilson, Mike; Ahmed, Marium; Collins, Gilbert; Arsenlis, Tom; LLNL-Shock Physics Group Team

    2015-06-01

    Ramp compression experiments have opened a path toward the measurement of extreme states of compression for solid-state materials on lasers, pulsed power, and gas guns. While most experiments have measured wave profiles as an integrated probe of the material state, there is a trend toward making direct measurements of the material state in situ using diffraction, phase-contrast imaging, EXAFS, and XANES. This past year we succeeded in obtaining high-quality diffraction on the NIF using the TARget Diffraction In Situ (TARDIS) diagnostic. I will present some of our NIF results on lead and tantalum, including the prospects for determining not only structure, density, and stress, but also temperature and grain size in these experiments. I will close with future plans for further improving TARDIS.

  2. Liquid electrode

    DOEpatents

    Ekechukwu, A.A.

    1994-07-05

    A dropping electrolyte electrode is described for use in electrochemical analysis of non-polar sample solutions, such as benzene or cyclohexane. The liquid electrode, preferably an aqueous salt solution immiscible in the sample solution, is introduced into the solution in dropwise fashion from a capillary. The electrolyte is introduced at a known rate, thus, the droplets each have the same volume and surface area. The electrode is used in making standard electrochemical measurements in order to determine properties of non-polar sample solutions. 2 figures.

  3. 6-cyanopurine, a color indicator useful for isolating mutations in the nif (nitrogen fixation) genes of Klebsiella pneumoniae.

    PubMed Central

    MacNeil, D; Brill, W J

    1978-01-01

    6-Cyanopurine (6-CP) can be used as a color indicator for certain classes of nif (N2 fixation) mutations in Klebsiella pneumoniae. Under N2-fixing conditions, Nif+ colonies and most Nif- colonies are purple on media containing 6-CP. Twenty-two Nif- mutants with altered color on medium containing 6-CP were isolated. All white mutants contained mutations in the regulatory genes, nifAA-nifL. Mutants which were more darkly colored than the wild type had mutations distributed among six nif genes. Medium with 6-CP was used to isolate Nif- mutants with deletions internal to the nif genes, and 6-CP was used to identify strains depressed for nitrogenase synthesis in the presence of NH4+. PMID:361692

  4. The structure of the Laser Entrance Hole in NIF Ignition gas-filled hohlraums

    NASA Astrophysics Data System (ADS)

    Schneider, M. B.; Doeppner, T.; Thomas, C. A.; Widmann, K.; MacLaren, S. A.; Meezan, N. B.; Bell, P. M.; Benedetti, L. R.; Bradley, D. K.; Callahan, D. A.; Eder, D.; Hammer, J. H.; Hinkel, D. E.; Jones, O. S.; Michel, P.; Milovich, J. L.; Moody, J. D.; Moore, A. J.; Park, H. S.; Ralph, J. E.; Regan, S. E.; Strozzi, D. J.; Town, R. P.

    2014-10-01

    At the National Ignition Facility (NIF), the energy from 192 laser beams is converted to an x-ray drive in a gas-filled hohlraum. The drive heats and implodes a fuel capsule. The laser beams enter the hohlraum via laser entrance holes (LEHs) at each end. The LEH size decreases as heated plasma from the LEH material blows radially inward but this is largely balanced by hot plasma in the laser deposition region pushing radially outward. Compared to models, the LEH size is larger than predicted. In addition, the plasma in the LEH region is hotter than predicted. Instead of being at the radiation temperature of about 300 eV, it is at an electron temperature of 1 to a few keV. The experimental measurements for this conclusion are discussed. Data on the LEH as a function of laser pulse shape, gas fill, and energy transfer are presented. This work performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  5. NiF2 Cathodes For Rechargeable Na Batteries

    NASA Technical Reports Server (NTRS)

    Bugga, Ratnakumar V.; Distefano, Salvador; Halpert, Gerald

    1992-01-01

    Use of NiF2 cathodes in medium-to-high-temperature rechargeable sodium batteries increases energy and power densities by 25 to 30 percent without detracting from potential advantage of safety this type of sodium battery offers over sodium batteries having sulfur cathodes. High-energy-density sodium batteries with metal fluoride cathodes used in electric vehicles and for leveling loads on powerlines.

  6. NIF unconverted light and its influence on DANTE measurements

    SciTech Connect

    Girard, Frederic; Suter, Larry; Landen, Otto; Munro, Dave; Regan, Sean; Kline, John

    2009-06-15

    NIF laser facility produces 1053 nm light and a fundamental requirement for NIF is to give up to 1.8 MJ of 351 nm light for target physics experiments. The 351 nm light is provided by frequency tripling the 1053 nm light in nonlinear crystals in the final optics assembly, just before the laser light enters the target chamber. Since this tripling process is not 100% efficient, unconverted light from the conversion process also enters the chamber. This unconverted light does not directly hit the target but it can strike target support structures at average intensities of few TW/cm{sup 2} where it can generate unwanted, background soft x-rays that are measured by the soft x-ray diagnostic DANTE installed on the NIF target chamber. This diagnostic quantifies the x-radiation intensity inside the hohlraum by measuring the x-ray flux coming from the target's laser entrance hole. Due to its centimeter wide field of view, it integrates x-ray emission from both the flux exiting a hohlraum laser entrance hole and from the target support structure irradiated by residual 1{omega} and 2{omega} unconverted light. This work gives quantitative evaluations of the unconverted light for the first time and the effects on DANTE measurements for the future NIF tuning experiment called ''Shock timing.'' Emission spectra are significantly modified leading to an overestimation of radiative temperature during the foot of the laser pulse since background x-rays are predominant in first two DANTE channel measurements. Mitigations of these effects by coating silicon paddle with plastic, using a smaller collimator to reduce DANTE field of view or eliminating DANTE channels in the analysis have been investigated.

  7. High-Pressure, Solid-State Experiments for NIF

    SciTech Connect

    Remington, B; Belak, J; Colvin, J; Edwards, J; Kalantar, D; Lasinski, B; Pollaine, S; Shay, H; Weber, S; Wolfer, B

    2001-02-15

    In this report, we summarize our plan for using NIF for measuring solid-state deformation physics at very high pressures, P >> 1 Mbar. There are several key uncertainties, the strength and phase being two of them. The deformation mechanisms at high pressure and high strain rate are also uncertain. The state, as well as strength, of a material that has first been melted, then dynamically refrozen by high-pressure compression is very uncertain. There is no single facility that can address all of these issues at all parameter regimes of interest. Rather, a coordinated plan involving multiple laboratories and universities and multiple facilities will ultimately be needed. We present here our first thoughts for the NIF component of this effort. In Sec. I, we motivate the physics of this regime, and point out the uncertainties, then describe in Sec. II the development work that we have done over the last 5 years in this area. In Sec. III, we describe several NIF designs we have developed to probe solid-state deformation physics at very high pressures.

  8. Damage mechanisms avoided or managed for NIF large optics

    DOE PAGESBeta

    Manes, K. R.; Spaeth, M. L.; Adams, J. J.; Bowers, M. W.; Bude, J. D.; Carr, C. W.; Conder, A. D.; DiNicola, J. M. G.; Dixit, S. N.; Feigenbaum, E.; et al

    2016-02-09

    After every other failure mode has been considered, in the end, the high-performance limit of all lasers is set by optical damage. The demands of inertial confinement fusion (ICF) pushed lasers designed as ICF drivers into this limit from their very earliest days. The first ICF lasers were small, and their pulses were short. Their goal was to provide as much power to the target as possible. Typically, they faced damage due to high intensity on their optics. As requests for higher laser energy, longer pulse lengths, and better symmetry appeared, new kinds of damage also emerged, some of themmore » anticipated and others unexpected. This paper will discuss the various types of damage to large optics that had to be considered, avoided to the extent possible, or otherwise managed as the National Ignition Facility (NIF) laser was designed, fabricated, and brought into operation. Furthermore, it has been possible for NIF to meet its requirements because of the experience gained in previous ICF systems and because NIF designers have continued to be able to avoid or manage new damage situations as they have appeared.« less

  9. Beryllium Ignition Targets for Indirect Drive NIF Experiments

    NASA Astrophysics Data System (ADS)

    Simakov, A. N.; Wilson, D. C.; Yi, S. A.; Kline, J. L.; Salmonson, J. D.; Clark, D. S.; Milovich, J. L.; Marinak, M. M.; Callahan, D. A.

    2013-10-01

    Current NIF plastic capsules are under-performing, and alternate ablators are being investigated. Beryllium presents an attractive option, since it has lower opacity and therefore higher ablation rate, pressure, and velocity. Previous NIF Be designs assumed significantly better hohlraum performance than recently observed (e.g., 7.5 vs. 15-17% of back-scattered power and 1.0 vs. 0.85 main pulse's power multipliers) and employed less accurate atomic configuration models than currently used (XSN vs. DCA), and thus an updated design is required. We present a new, Rev. 6 Be ignition target design that employs the full NIF capacity (1.8 MJ, 520 TW) and uses a standard 5.75 mm gold hohlraum with 1.5 mg/cm3 of helium gas fill. The 1051 μm capsule features 180 μm of layered copper-doped (with the maximum of 3 atom-%) Be ablator and 90 μm of cryogenic deuterium-tritium fuel. The peak implosion velocity of 367 μm/ns results in 4.1 keV of no-burn ion temperature, 1.6 and 1.9 g/cm2 of fuel and total areal densities, respectively, and 20.6 MJ of fusion yield. The capsule demonstrates robust performance with surface/interface roughnesses up to 1.6 times larger that Rev. 3 specs. Work supported by the US Department of Energy.

  10. Disposable blast shields for use on NIF imaging diagnostics

    NASA Astrophysics Data System (ADS)

    Smith, Cal A.; Wang, Karen M.; Masters, Nathan

    2015-08-01

    The NIFs 192 lasers can deliver 2 MJ of energy to Target Chamber Center (TCC) to produce environments not available in any other experimental laboratory. The NIFs ability to deliver such intense energy to a small volume causes harsh consequences to experimental equipment and supporting diagnostics such as holhraums, support packages, target positioners, diagnostic equipment, and laser optics. Of these, the hohlraum and support packages are typically quickly vaporized and transformed into an expanding shell of high-hypersonic gases referred to as debris wind. During an experimental event such as fusion implosion, the target diagnostic components used to measure key observables in the experiment are subjected to extreme pressures and impact shocks due to incident debris wind loading. As diagnostics are positioned closer to TCC, the diagnostic pinhole stacks and other components along the diagnostic structure become more likely to be at or above the yield strength of the materials commonly used. In particular, the pinhole stack components and data recording instruments behind the pinholes are the most costly to replace. Thus, a conceptual configuration for a pinhole shield is proposed, analyzed, and tested with the intent of mitigating damage to the pinhole stack and imaging equipment and allowing immediate re-use of this diagnostic equipment. This pinhole shield would be a replaceable window that can be replaced quickly by inserting and removing it before and after each experimental laser shot, which will allow NIF to benefit from significant material and labor costs.

  11. Calibration results for first NIF Kirkpatrick-Baez microscope

    NASA Astrophysics Data System (ADS)

    Brejnholt, Nicolai F.; Ayers, Jay J.; McCarville, Thomas J.; Pardini, Tom; Pickworth, Louisa A.; Bradley, David K.; Decker, Todd A.; Hau-Riege, Stefan P.; Hill, Randal M.; Pivovaroff, Michael J.; Soufli, Regina; Vogel, Julia K.; Walton, Chris C.

    2015-09-01

    The Lawrence Livermore National Laboratory (LLNL) has been developing a novel X-ray imager for the National Ignition Facility (NIF) utilizing Kirkpatrick-Baez (KB) mirror geometry. A fully assembled mirror pack contains four KB optic pairs featuring cylindrical mirrors with custom-designed multilayer coatings. Multiple interchangeable mirror packs have been commissioned for various experimental campaigns, with high spatial resolution (< 5 μm) at the center of the field of view and 12× magnification. Tight tolerances on the grazing angles of the X-ray mirrors require precision alignment and assembly of each component via a coordinate measuring machine, and a comprehensive off-line calibration of the four KB channels at X-ray wavelengths. The main goals of the calibration campaign are to measure the performance of the multilayer, validate the assembly procedure by measuring the as-built spatial resolution and determine the best object to mirror pack distance (drive depth) of the microscope for fielding at NIF. We report on the results of this effort on the first fully assembled NIF KB X-ray imager.

  12. Sequence and molecular analysis of the nifL gene of Azotobacter vinelandii.

    PubMed

    Blanco, G; Drummond, M; Woodley, P; Kennedy, C

    1993-08-01

    In both Klebsiella pneumoniae and Azotobacter vinelandii the nifL gene, which encodes a negative regulator of nitrogen fixation, lies immediately upstream of nifA. We have sequenced the A. vinelandii nifL gene and found that it is more homologous in its C-terminal domain to the histidine protein kinases (HPKs) than is K. pneumoniae NifL. In particular A. vinelandii NifL contains a conserved histidine at a position shown to be phosphorylated in other systems. Both NifL proteins are homologous in their N-termini to a part of the Halobacterium halobium bat gene product; Bat is involved in regulation of bacterio-opsin, the expression of which is oxygen sensitive. The same region showed homology to the haem-binding N-terminal domain of the Rhizobium meliloti fixL gene product, an oxygen-sensing protein. Like K. pneumoniae NifL, A. vinelandii NifL is shown here to prevent expression of nif genes in the presence of NH+4 or oxygen. The sequences found homologous in the C-terminal regions of NifL, FixL and Bat might therefore be involved in oxygen binding or sensing. An in-frame deletion mutation in the nifL coding region resulted in loss of repression by NH+4 and the mutant excreted high amounts of ammonia during nitrogen fixation, thus confirming a phenotype reported earlier for an insertion mutation. In addition, nifLA are cotranscribed in A. vinelandii as in K. pneumoniae, but expression from the A. vinelandii promoter requires neither RpoN nor NtrC. PMID:8231815

  13. Segmented electrode hall thruster with reduced plume

    DOEpatents

    Fisch, Nathaniel J.; Raitses, Yevgeny

    2004-08-17

    An apparatus and method for thrusting plasma, utilizing a Hall thruster with segmented electrodes along the channel, which make the acceleration region as localized as possible. Also disclosed are methods of arranging the electrodes so as to minimize erosion and arcing. Also disclosed are methods of arranging the electrodes so as to produce a substantial reduction in plume divergence. The use of electrodes made of emissive material will reduce the radial potential drop within the channel, further decreasing the plume divergence. Also disclosed is a method of arranging and powering these electrodes so as to provide variable mode operation.

  14. Inflight Properties of NIF Ignition Capsules Inferred from Convergent Ablator Experiments

    NASA Astrophysics Data System (ADS)

    Meezan, Nathan

    2012-10-01

    Convergent ablator (ConA) experiments on the National Ignition Facility (NIF) are indirect drive implosions that study the inflight dynamics of an imploding capsule. Side-on, back-lit radiography provides data used by the National Ignition Campaign to infer time-dependent properties of the capsule ablator, including its center of mass radius, velocity, unablated mass, shell thickness, and peak density. Previously, CallahanfootnotetextD. A. Callahan et al., Phys. Plasmas 19, 056305 (2012) and Hicks reported ConA experiments demonstrating velocities approaching those required for ignition. Here, we present the findings from a full year of NIF ConA experiments where we have shot more than 20 targets at energies greater than 1 MJ to study the inflight dynamics of ignition-like implosions. These include: *Studies of ablator center of mass motion vs. time, suggesting that the drive history differs substantially from that predicted by standard modeling *Pulse shape scalings studying the dynamics of a ``fifth shock'' that can significantly increase the entropy of the DT fuel in an ignition implosion. *Performance of different ablators, including CH ablators with graded Si doping, CH ablators with uniform Si doping, and other ablators. *ConA experiments using capsules with cryogenic ice layers, demonstrating that gas-filled capsules are adequate surrogates for DT layered implosions. *Studies of thicker capsules shot at powers and energies surpassing 500 TW and 1.8 MJ as we work to meet the ignition implosion velocity requirement in the presence of hydrodynamic instabilities. Finally, we describe insights into hydrodynamic instabilities that we have gained through this large database, from variations in capsule performance (neutron yield and Tion) as well as from the impact of mix on observed late-time ablator properties.

  15. Analysis of a Direct-Drive Ignition Capsule Designed for the NIF

    NASA Astrophysics Data System (ADS)

    McKenty, P. W.

    2000-10-01

    The current direct-drive ignition capsule design planned by the University of Rochester's Laboratory for Laser Energetics to be fielded on the National Ignition Facility (NIF) will be reviewed in this paper. The direct-drive requirements to establish a propagating thermonuclear burn on the NIF will be discussed in terms of the constraints on laser-irradiation uniformity and target surface roughness. The ignition design(C. P. Verdon, Bull. Am. Phys. Soc. 38), 2010 (1993).^,(S. E. Bodner et al.), Phys. Plasmas 5, 1901 (1998). consists of a cryogenic DT shell ( ~350 μm thick and ~3 mm in diameter) contained within a very thin ( ~2-μm) CH shell. To maintain stability during the implosion, the target is placed on an isentrope approximately three times that of Fermi-degenerate DT (α = 3). One-dimensional hydrodynamic studies using LILAC show that the ignition design is robust to uncertainties in laser power history and fuel composition. The two-dimensional hydrodynamics code ORCHID is used to examine the target performance under the influence of the main sources of nonuniformity: laser imprint, power imbalance, and inner- and outer-target-surface roughness. Results from these studies indicate that the reduction in target gain from all sources of nonuniformity can be described in terms of a single parameter related to the resultant inner-surface deformation at the end of the acceleration stage of the implosion. This parameter is constructed from a spectral decomposition of the surface deformation by giving different weights to the long and short wavelengths of nonuniformity. The physical reason for the difference in weighting is discussed in terms of the mechanisms for ignition failure. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460.

  16. Nucleotide sequence of the nifH gene coding for nitrogen reductase in the acetic acid bacterium Acetobacter diazotrophicus.

    PubMed

    Franke, I H; Fegan, M; Hayward, A C; Sly, L I

    1998-01-01

    The nifH gene sequence of the nitrogen-fixing bacterium Acetobacter diazotrophicus was determined with the use of the polymerase chain reaction and universal degenerate oligonucleotide primers. The gene shows highest pair-wise similarity to the nifH gene of Azospirillum brasilense. The phylogenetic relationships of the nifH gene sequences were compared with those inferred from 16S rRNA gene sequences. Knowledge of the sequence of the nifH gene contributes to the growing database of nifH gene sequences, and will allow the detection of Acet. diazotrophicus from environmental samples with nifH gene-based primers. PMID:9489028

  17. Producing KDP and DKDP crystals for the NIF laser

    SciTech Connect

    Atherton, L J; Burnham, A K; Combs, R C; Couture, S A; De Yoreo, J J; Hawley-Fedder, R A; Montesant, R C; Robey, H F; Runkel, M; Staggs, M; Wegner, P J; Yan, M; Zaitseva, N P

    1999-09-02

    The cost and physics requirements of the NIF have established two important roles for potassium dihydrogen phosphate (KDP) crystals. 1. To extract more laser energy per unit of flashlamp light and laser glass, the NIF has adopted a multipass architecture as shown in Figure 1. Light is injected in the transport spatial filter, first traverses the power amplifiers, and then is directed to main amplifiers, where it makes four passes before being redirected through the power amplifiers towards the target. To enable the multipass of the main amplifiers, a KDP-containing Pockels cell rotates the polarization of the beam to make it either transmit through or reflect off a polarizer held at Brewster's angle within the main laser cavity. If transmitted, the light reflects off a mirror and makes another pass through the cavity. If reflected, it proceeds through the power amplifier to the target. the original seed crystal as the pyramid faces grow. Unfortunately, this pyramidal growth is very slow, and it takes about two years to grow a crystal to NIF size. To provide more programmatic flexibility and reduce costs in the long run, we have developed an alternative technology commonly called rapid growth. Through a combination of higher temperatures and higher supersaturation of the growth solution, a NIF-size boule can be grown in 1 to 2 months from a small ''point'' seed. However, growing boules of adequate size is not sufficient. Care must be taken to prevent inclusions of growth solution and incorporation of atomically substituted 2. Implosions for ICF work far better at shorter wavelengths due to less generation of hot electrons, which preheat the fuel and make it harder to compress. Compromising between optic lifetime and implosion efficiency, both Nova and the NIF operate at a tripled frequency of the 1053-nm fundamental frequency of a neodymium glass laser. This tripling is accomplished by two crystals, one made of KDP and one made of deuterated KDP (DKDP). The first

  18. Ternary gas plasma welding torch

    NASA Technical Reports Server (NTRS)

    Rybicki, Daniel J. (Inventor); Mcgee, William F. (Inventor); Waldron, Douglas J. (Inventor)

    1995-01-01

    A plasma arc welding torch is discussed. A first plasma gas is directed through the body of the welding torch and out of the body across the tip of a welding electrode disposed at the forward end of the body. A second plasma gas is disposed for flow through a longitudinal bore in the electrode. The second plasma gas enters one end of the electrode and exits the electrode at the tip thereof for co-acting with the electric welding arc to produce the desired weld. A shield gas is directed through the torch body and circulates around the head of the torch adjacent to the electrode tip.

  19. Summary of Disposable Debris Shields (DDS) Analysis for Development of Solid Debris Collection at NIF

    SciTech Connect

    Shaughnessy, D A; Moody, K J; Grant, P M; Lewis, L A; Hutcheon, I D; Lindvall, R; Gostic, J M

    2011-11-20

    through the use of a part meant to be replaced regularly. The solid angle covered by one of the shields is roughly 10{sup -4} of 4{pi}. If several shields were analyzed at once, it would increase the solid angle of the collection area accordingly. The glass shields consist of ammonia hardened silica with a sol gel coating and kapton tape around the edge. The square sheets are 14-inch on each side. The original shields were 1 mm thick, but it was determined that a thicker shield (3.3 mm) was more effective in preventing debris from reaching the FOA. The Solid Radchem group received two sets of DDS as part of our evaluation of the potential use of the DDS as solid debris collectors. The first set consisted of two 3.3 mm shields, one each from the top and bottom of the chamber (the '3mm set'). The second set consisted of four 1mm shields, one from the top of the chamber and the other three from the bottom (the 'IFSA set'). For each set, the shields were cut into smaller subsamples, which were then imaged using scanning electron microscopy (SEM) followed by chemical leaching and mass spectrometry. The purpose was to evaluate both the quantity and identity of the debris that was present on the DDS surfaces, and to determine if any of the capsule debris was reaching the chamber walls. In addition, potential enhancement due to gravity in the chamber was evaluated by directly comparing shields fielded in the top and bottom of the chamber. Based on the results, the use of the DDS as debris collectors would be evaluated. The results from both sets were presented to the DDS Working Group. The slides are attached to this document. The 3mm set results are presented first, followed by the results from the IFSA set. In both cases it was determined that a small fraction of the overall debris field was collected on the DDS. This means that the debris that is formed during a NIF shot is condensing out of the plasma and depositing on surfaces closer to the target chamber center, or else it

  20. Plasma sweeper. [Patents

    DOEpatents

    Motley, R.W.; Glanz, J.

    1982-10-25

    A device is described for coupling RF power (a plasma sweeper) from RF power introducing means to a plasma having a magnetic field associated therewith comprises at least one electrode positioned near the plasma and near the RF power introducing means. Means are described for generating a static electric field at the electrode directed into the plasma and having a component substantially perpendicular to the plasma magnetic field such that a non-zero vector cross-product of the electric and magnetic fields exerts a force on the plasma causing the plasma to drift.

  1. Cloning, DNA sequencing, and characterization of a nifD-homologous gene from the archaeon Methanosarcina barkeri 227 which resembles nifD1 from the eubacterium Clostridium pasteurianum.

    PubMed Central

    Chien, Y T; Zinder, S H

    1994-01-01

    L. Sibold, M. Henriquet, O. Possot, and J.-P. Aubert (Res. Microbiol. 142:5-12, 1991) cloned and sequenced two nifH-homologous open reading frames (ORFs) from Methanosarcina barkeri 227. Phylogenetic analysis of the deduced amino acid sequences of the nifH ORFs from M. barkeri showed that nifH1 clusters with nifH genes from alternative nitrogenases, while nifH2 clusters with nifH1 from the gram-positive eubacterium Clostridium pasteurianum. The N-terminal sequence of the purified nitrogenase component 2 (the nifH gene product) from M. barkeri was identical with that predicted for nifH2, and dot blot analysis of RNA transcripts indicated that nifH2 (and nifDK2) was expressed in M. barkeri when grown diazotrophically in Mo-containing medium. To obtain nifD2 from M. barkeri, a 4.7-kbp BamHI fragment of M. barkeri DNA was cloned which contained at least five ORFs, including nifH2, ORF105, and ORF125 (previously described by Sibold et al.), as well as nifD2 and part of nifK2. ORFnifD2 is 1,596 bp long and encodes 532 amino acid residues, while the nifK2 fragment is 135 bp long. The deduced amino acid sequences for nifD2 and the nifK2 fragment from M. barkeri cluster most closely with the corresponding nifDK1 gene products from C. pasteurianum. The predicted M. barkeri nifD2 product contains a 50-amino acid insert near the C terminus which has previously been found only in the clostridial nifD1 product. Previous biochemical and sequencing evidence indicates that the C. pasteurianum nitrogenase is the most divergent of known eubacterial Mo-nitrogenases, most likely representing a distinct nif gene family, which now also contains M. barkeri as a member. The similarity between the methanogen and clostridial nif sequences is especially intriguing in light of the recent findings of sequence similarities between gene products from archaea and from low-G+C gram-positive eubacteria for glutamate dehydrogenase, glutamine synthetase I, and heat shock protein 70. It is not clear

  2. Temporal patterns of nitrogenase gene (nifH) expression in the oligotrophic North Pacific Ocean.

    PubMed

    Church, Matthew J; Short, Cindy M; Jenkins, Bethany D; Karl, David M; Zehr, Jonathan P

    2005-09-01

    Dinitrogen (N(2))-fixing microorganisms (diazotrophs) play important roles in ocean biogeochemistry and plankton productivity. In this study, we examined the presence and expression of specific planktonic nitrogenase genes (nifH) in the upper ocean (0 to 175 m) at Station ALOHA in the oligotrophic North Pacific Ocean. Clone libraries constructed from reverse-transcribed PCR-amplified mRNA revealed six unique phylotypes. Five of the nifH phylotypes grouped with sequences from unicellular and filamentous cyanobacteria, and one of the phylotypes clustered with gamma-proteobacteria. The cyanobacterial nifH phylotypes retrieved included two sequence types that phylogenetically grouped with unicellular cyanobacteria (termed groups A and B), several sequences closely related (97 to 99%) to Trichodesmium spp. and Katagnymene spiralis, and two previously unreported phylotypes clustering with heterocyst-forming nifH cyanobacteria. Temporal patterns of nifH expression were evaluated using reverse-transcribed quantitative PCR amplification of nifH gene transcripts. The filamentous and presumed unicellular group A cyanobacterial phylotypes exhibited elevated nifH transcription during the day, while members of the group B (closely related to Crocosphaera watsonii) unicellular phylotype displayed greater nifH transcription at night. In situ nifH expression by all of the cyanobacterial phylotypes exhibited pronounced diel periodicity. The gamma-proteobacterial phylotype had low transcript abundance and did not exhibit a clear diurnal periodicity in nifH expression. The temporal separation of nifH expression by the various phylotypes suggests that open ocean diazotrophic cyanobacteria have unique in situ physiological responses to daily fluctuations of light in the upper ocean. PMID:16151126

  3. Cermet electrode

    DOEpatents

    Maskalick, Nicholas J.

    1988-08-30

    Disclosed is a cermet electrode consisting of metal particles of nickel, cobalt, iron, or alloys or mixtures thereof immobilized by zirconia stabilized in cubic form which contains discrete deposits of about 0.1 to about 5% by weight of praseodymium, dysprosium, terbium, or a mixture thereof. The solid oxide electrode can be made by covering a substrate with particles of nickel, cobalt, iron, or mixtures thereof, growing a stabilized zirconia solid oxide skeleton around the particles thereby immobilizing them, contacting the skeleton with a compound of praseodymium, dysprosium, terbium, or a mixture thereof, and heating the skeleton to a temperature of at least 500.degree. C. The electrode can also be made by preparing a slurry of nickel, cobalt, iron, or mixture and a compound of praseodymium, dysprosium, terbium, or a mixture thereof, depositing the slurry on a substrate, heating the slurry to dryness, and growing a stabilized zirconia skeleton around the metal particles.

  4. Magnetohydrodynamic electrode

    DOEpatents

    Marchant, David D.; Killpatrick, Don H.

    1978-01-01

    An electrode capable of withstanding high temperatures and suitable for use as a current collector in the channel of a magnetohydrodynamic (MHD) generator consists of a sintered powdered metal base portion, the upper surface of the base being coated with a first layer of nickel aluminide, an intermediate layer of a mixture of nickel aluminide - refractory ceramic on the first layer and a third or outer layer of a refractory ceramic material on the intermediate layer. The sintered powdered metal base resists spalling by the ceramic coatings and permits greater electrode compliance to thermal shock. The density of the powdered metal base can be varied to allow optimization of the thermal conductivity of the electrode and prevent excess heat loss from the channel.

  5. Photoelectrochemical electrodes

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Rembaum, A. (Inventor)

    1983-01-01

    The surface of a moderate band gap semiconductor such as p-type molybdenum sulfide is modified to contain an adherent film of charge mediating ionene polymer containing an electroactive unit such as bipyridimium. Electron transport between the electrode and the mediator film is favorable and photocorrosion and recombination processes are suppressed. Incorporation of particles of catalyst such as platinum within the film provides a reduction in overvoltage. The polymer film is readily deposited on the electrode surface and can be rendered stable by ionic or addition crosslinking. Catalyst can be predispersed in the polymer film or a salt can be impregnated into the film and reduced therein.

  6. Identification of a NifL-like protein in a diazotroph of the beta-subgroup of the Proteobacteria, Azoarcus sp. strain BH72.

    PubMed

    Egener, Tanja; Sarkar, Abhijit; Martin, Dietmar E; Reinhold-Hurek, Barbara

    2002-10-01

    NifA, the transcriptional activator of nitrogenase (nif) genes, has up to now been described to be regulated in its activity via the sensor NifL only for members of the gamma-subgroup of the PROTEOBACTERIA: This paper reports a functionally similar NifL-like protein outside this group in Azoarcus sp. strain BH72, a diazotrophic grass endophyte belonging to the beta-subgroup of the PROTEOBACTERIA: Its structural genes for nitrogenase (nifHDK) are regulated in response to combined nitrogen and O(2) and expressed endophytically inside rice roots. In order to characterize nitrogen-regulatory genes, an Azoarcus sp. BH72 genomic library was used to select cosmids that complemented a nifA mutation in Azotobacter vinelandii. Sequence analysis of the 3.4 kb genomic region complementing nifA showed two ORFs with sequence identities of 44% to NifL and 61% to NifA of Azotobacter vinelandii. According to Northern blot and reverse transcriptase PCR analysis, the nifLA transcript was more abundant at low combined nitrogen and O(2) levels, results which were corroborated by GUS (beta-glucuronidase) assays using a transcriptional nifL::gusA fusion. N(2) fixation was abolished in a NifLA(-) and a NifA(-) mutant, wild-type fixation being restored by nifLA in trans. The NifLA(-) mutant also failed to activate nifH::gus expression, indicating that NifA is the obligate transcriptional activator for nifHDK. A nifL mutant was diazotrophic and did not show repression of nifH::gusA by ammonium or O(2), suggesting that NifL of Azoarcus sp. strain BH72 has a similar role in inactivating NifA in response to O(2) and combined nitrogen as NifL in bacteria of the gamma-PROTEOBACTERIA: PMID:12368454

  7. Predicting bulk damage in NIF triple harmonic generators

    SciTech Connect

    De Yoreo, J; Runkel, M; Williams, W

    1998-09-18

    Recently reported experiments have investigated the statistics of laser damage in KDP and KD*P. Automated damage tests have allowed cumulative failure and damage probability distributions to be constructed. Large area tests have investigated the feasibility of on-line laser conditioning and damage evolution for tripler harmonic generation (THG) crystals on the National Ignition Facility (NIF). These tests have shown that there is a nonzero probability of damage at NIF redline fluence (14.3 J/cm2, 351 nm, 3 ns) and that the damage pinpoint density evolves exponentially with fluence. In this paper, the results of these tests are used in conjunction with model spatial profiles of the NIP beam to predict the level of damage created in the THG crystal. A probabilistic calculation based on the overlap of the beam fluence and damage probabiity distribution shows that the overall damage probability is less than 3% for well-conditioned, high quality KDP/KD*P crystals of conventional or rapid growth. The number density of generated pinpoints has been calculated by mapping the damage evolution curves onto the NlF model profile. This shows that the number of damage pinpoints generated in high fluence portions of the NIF beam will be low for well-conditioned THG crystals. In contrast, unconditioned triplers of the same material will exhibit an increase in pinpoint density of greater than 20x. To test the validity of these calculations a 37 cm, conventionally grown KD*P tripler from the Beamlet laser was scatter mapped for bulk damage. The tripler had been exposed to NE-like fluences during its operational lifetime on Beamlet and exhibited very low levels of bulk pinpoint damage, essentially supporting the predictions based on tests and modeling.

  8. The OMEGA Gas Sampling System and Radiochemical Diagnostics for NIF

    NASA Astrophysics Data System (ADS)

    Stoyer, Mark; Sangster, Craig; Hudson, Bryant; Lougheed, Ron; Freeman, Charlie; Schwartz, Brook-Eden; Olsen, Michele

    2000-10-01

    Radiochemical diagnostics for the National Ignition Facility (NIF) will address important issues such as shell rho-R, mix and charged particle production in ignition and near-ignition capsules. Development of key tools for these diagnostics has been progressing on NOVA and OMEGA laser systems. A limitation of the sample collection techniques currently being used is the solid angle for collection of post-shot debris, which is maximally about 1collections at NOVA. Because of the large standoff for NIF (5 m), the solid angle subtended would be expected to be much less without development of expandable foil collection schemes. Many reaction products from charged particle reactions are noble gases. A gas sampling system for obtaining radiochemical samples following OMEGA shots is currently being assembled at LLNL. Results of benchtop tests with such a system will be discussed. A primary goal is to demonstrate reproducible collection efficiencies for this new technical capability of near 100Secondary goals include measuring collection efficiencies for certain reaction processes and to test the collection scheme for other low energy reaction products. Should high collection efficiencies be demonstrated, test reactions of 18O(alpha,n)21Ne and 79Br(p,n)79Kr will be investigated at OMEGA as mix-diagnostics for NIF. Note that it may be possible to use the 18O or Br already in most capsules, circumventing some target development issues. The gas sampling system will be designed in such a way as to not preclude the addition of carrier gas to the target chamber following an experiment for "flushing" of other, perhaps non-gaseous, reaction products.

  9. Status Update: Modeling Energy Balance in NIF Hohlraums

    SciTech Connect

    Jones, O. S.

    2015-07-22

    We have developed a standardized methodology to model hohlraum drive in NIF experiments. We compare simulation results to experiments by 1) comparing hohlraum xray fluxes and 2) comparing capsule metrics, such as bang times. Long-pulse, high gas-fill hohlraums require a 20-28% reduction in simulated drive and inclusion of ~15% backscatter to match experiment through (1) and (2). Short-pulse, low fill or near-vacuum hohlraums require a 10% reduction in simulated drive to match experiment through (2); no reduction through (1). Ongoing work focuses on physical model modifications to improve these matches.

  10. Status of cryogenic layering for NIF ignition targets

    SciTech Connect

    Moody, J D; Kozioziemski, B J; Mapoles, E R; Sater, J D; Dewald, E L; Koch, J A; Izumi, N; Chernov, A; Salmonson, J; Montesanti, R C; Atherton, L J; Burmann, J A; Pipes, J W; Stefanescu, D; Salari, K; Weisgrabber, T; Reynolds, J; Castro, C; Klingmann, J; Dzenitis, B

    2008-10-20

    Recent advances in cryogenic layering include improved surface roughness characterization of many layers formed using 'slow-cool' and 'rapid-cool' protocols. At 0.25 K below the melt, slow-cooled layers meet the NIF smoothness requirement. However, at 1.5 K below the melt grain-boundary misalignments dominate the layer roughness and cause it to exceed the smoothness specification. Rapid-cool of the layer to 1.5 K below the melt shows promise for meeting the ignition requirements. Much of the current research effort is aimed at characterizing the onset of roughness during rapid cooling and determining the scale of the resulting roughness.

  11. Probing matter at extreme Gbar pressures at the NIF

    SciTech Connect

    Kritcher, A. L.; Doeppner, T.; Swift, D.; Hawreliak, J.; Collins, G.; Nilsen, J.; Bachmann, B.; Dewald, E.; Strozzi, D.; Felker, S.; Landen, O. L.; Jones, O.; Thomas, C.; Hammer, J.; Keane, C.; Lee, H. J.; Glenzer, S. H.; Rothman, S.; Chapman, D.; Kraus, D.; Neumayer, P.; Falcone, R. W.

    2013-12-04

    Here we describe a platform to measure the material properties, specifically the equation of state and electron temperature, at pressures of 100 Mbar to a Gbar at the National Ignition Facility (NIF). In our experiments we launch spherically convergent shock waves into solid CH, CD, or diamond samples using a hohlraum radiation drive, in an indirect drive laser geometry. X-ray radiography is applied to measure the shock speed and infer the mass density profile, enabling determination of the material pressure and Hugoniot equation of state. X-ray scattering is applied to measure the electron temperature through probing of the electron velocity distribution via Doppler broadening.

  12. Nucleotide sequence of nifD from Frankia alni strain ArI3: phylogenetic inferences.

    PubMed

    Normand, P; Gouy, M; Cournoyer, B; Simonet, P

    1992-05-01

    The complete nucleotide sequence of the nifD gene encoding the alpha subunit of component I of nitrogenase from Frankia alni strain ArI3 was determined. The coding region is 1,458 bp in length and encodes a polypeptide of 486 residues with a predicted molecular weight of 53,500. Phylogenetic inferences with 12 complete published nifD sequences were drawn using a variety of approaches. Frankia nifD clusters with proteobacteria rather than with Clostridium pasteurianum, the other Gram-positive bacterium studied. Extant eubacterial nif genes seem to have at least three distinct evolutionary origins as a result of ancient gene duplications. Within the Gram-positive bacterial phylum, functional nif genes descend from different duplicates. PMID:1584016

  13. The National Ignition Facility (NIF) and the issue of nonproliferation. Final study

    SciTech Connect

    1995-12-19

    NIF, the next step proposed by DOE in a progression of Inertial Confinement Fusion (ICF) facilities, is expected to reach the goal of ICF capsule ignition in the laboratory. This report is in response to a request of a Congressman that DOE resolve the question of whether NIF will aid or hinder U.S. nonproliferation efforts. Both technical and policy aspects are addressed, and public participation was part of the decision process. Since the technical proliferation concerns at NIF are manageable and can be made acceptable, and NIF can contribute positively to U.S. arms control and nonproliferation policy goals, it is concluded that NIF supports the nuclear nonproliferation objectives of the United States.

  14. A concept to collect neutron and x-ray images on the same line of sight at NIF

    SciTech Connect

    Merrill, F. E. Danly, C. R.; Grim, G. P.; Volegov, P. L.; Wilde, C. H.; Izumi, N.; Jedlovec, D.; Fittinghoff, D. N.; Pak, A.; Park, H.-S.

    2014-11-15

    Neutron and x-ray images are collected at the National Ignition Facility (NIF) to measure the size and shape of inertial confinement fusion implosions. The x-ray images provide a measure of the size and shape of the hot region of the deuterium-tritium fuel while the neutron images provide a measure of the size and shape of the burning plasma. Although these two types of images are collected simultaneously, they are not collected along the same line of sight (LOS). One 14 MeV neutron image is collected on the NIF equator, and two x-ray images are collected along the polar axis and nearly perpendicular to the neutron imaging line of sight on the equator. Both measurements use pinhole apertures to form the images, but existing x-ray imaging provides time-resolved measurements while the neutron images are time-integrated. Detailed comparisons of the x-ray and neutron images can provide information on the fuel assembly, but these studies have been limited because the implosions are not azimuthally symmetric and the images are collected along different LOS. We have developed a conceptual design of a time-integrated x-ray imaging system that could be added to the existing neutron imaging LOS. This new system would allow these detailed studies, providing important information on the fuel assembly of future implosions. Here we present this conceptual design and the expected performance characteristics.

  15. A concept to collect neutron and x-ray images on the same line of sight at NIF.

    PubMed

    Merrill, F E; Danly, C R; Izumi, N; Jedlovec, D; Fittinghoff, D N; Grim, G P; Pak, A; Park, H-S; Volegov, P L; Wilde, C H

    2014-11-01

    Neutron and x-ray images are collected at the National Ignition Facility (NIF) to measure the size and shape of inertial confinement fusion implosions. The x-ray images provide a measure of the size and shape of the hot region of the deuterium-tritium fuel while the neutron images provide a measure of the size and shape of the burning plasma. Although these two types of images are collected simultaneously, they are not collected along the same line of sight (LOS). One 14 MeV neutron image is collected on the NIF equator, and two x-ray images are collected along the polar axis and nearly perpendicular to the neutron imaging line of sight on the equator. Both measurements use pinhole apertures to form the images, but existing x-ray imaging provides time-resolved measurements while the neutron images are time-integrated. Detailed comparisons of the x-ray and neutron images can provide information on the fuel assembly, but these studies have been limited because the implosions are not azimuthally symmetric and the images are collected along different LOS. We have developed a conceptual design of a time-integrated x-ray imaging system that could be added to the existing neutron imaging LOS. This new system would allow these detailed studies, providing important information on the fuel assembly of future implosions. Here we present this conceptual design and the expected performance characteristics. PMID:25430360

  16. Investigation of the possibility of gamma-ray diagnostic imaging of target compression at NIF

    PubMed Central

    Lemieux, Daniel A.; Baudet, Camille; Grim, Gary P.; Barber, H. Bradford; Miller, Brian W.; Fasje, David; Furenlid, Lars R.

    2013-01-01

    The National Ignition Facility at Lawrence Livermore National Laboratory is the world’s leading facility to study the physics of igniting plasmas. Plasmas of hot deuterium and tritium, undergo d(t,n)α reactions that produce a 14.1 MeV neutron and 3.5 MeV a particle, in the center of mass. As these neutrons pass through the materials surrounding the hot core, they may undergo subsequent (n,x) reactions. For example, 12C(n,n’γ)12C reactions occur in remnant debris from the polymer ablator resulting in a significant fluence of 4.44 MeV gamma-rays. Imaging of these gammas will enable the determination of the volumetric size and symmetry of the ablation; large size and high asymmetry is expected to correlate with poor compression and lower fusion yield. Results from a gamma-ray imaging system are expected to be complimentary to a neutron imaging diagnostic system already in place at the NIF. This paper describes initial efforts to design a gamma-ray imaging system for the NIF using the existing neutron imaging system as a baseline for study. Due to the cross-section and expected range of ablator areal densities, the gamma flux should be approximately 10−3 of the neutron flux. For this reason, care must be taken to maximize the efficiency of the gamma-ray imaging system because it will be gamma starved. As with the neutron imager, use of pinholes and/or coded apertures are anticipated. Along with aperture and detector design, the selection of an appropriate scintillator is discussed. The volume of energy deposition of the interacting 4.44 MeV gamma-rays is a critical parameter limiting the imaging system spatial resolution. The volume of energy deposition is simulated with GEANT4, and plans to measure the volume of energy deposition experimentally are described. Results of tests on a pixellated LYSO scintillator are also presented. PMID:23420688

  17. Investigation of the possibility of gamma-ray diagnostic imaging of target compression at NIF.

    PubMed

    Lemieux, Daniel A; Baudet, Camille; Grim, Gary P; Barber, H Bradford; Miller, Brian W; Fasje, David; Furenlid, Lars R

    2011-09-23

    The National Ignition Facility at Lawrence Livermore National Laboratory is the world's leading facility to study the physics of igniting plasmas. Plasmas of hot deuterium and tritium, undergo d(t,n)α reactions that produce a 14.1 MeV neutron and 3.5 MeV a particle, in the center of mass. As these neutrons pass through the materials surrounding the hot core, they may undergo subsequent (n,x) reactions. For example, (12)C(n,n'γ)(12)C reactions occur in remnant debris from the polymer ablator resulting in a significant fluence of 4.44 MeV gamma-rays. Imaging of these gammas will enable the determination of the volumetric size and symmetry of the ablation; large size and high asymmetry is expected to correlate with poor compression and lower fusion yield. Results from a gamma-ray imaging system are expected to be complimentary to a neutron imaging diagnostic system already in place at the NIF. This paper describes initial efforts to design a gamma-ray imaging system for the NIF using the existing neutron imaging system as a baseline for study. Due to the cross-section and expected range of ablator areal densities, the gamma flux should be approximately 10(-3) of the neutron flux. For this reason, care must be taken to maximize the efficiency of the gamma-ray imaging system because it will be gamma starved. As with the neutron imager, use of pinholes and/or coded apertures are anticipated. Along with aperture and detector design, the selection of an appropriate scintillator is discussed. The volume of energy deposition of the interacting 4.44 MeV gamma-rays is a critical parameter limiting the imaging system spatial resolution. The volume of energy deposition is simulated with GEANT4, and plans to measure the volume of energy deposition experimentally are described. Results of tests on a pixellated LYSO scintillator are also presented. PMID:23420688

  18. Science of NIF scale capsule development (activities for FY97)

    SciTech Connect

    Hamilton, K.E.; Buckley, S.R.; Cook, R.R.

    1997-11-12

    The focus of this work is the production of 2-mm P{alpha}MS mandrels by microencapsulation for use as National Ignition Facility (NIF) laser targets. It is our findings thus far that the processing techniques used previously for the 0.5-mm and 1.0-mm targets are no longer useful for preparation of the larger targets for a few fundamental reasons. The driving force for sphericity (from the minimization of interracial energy) decreases as the radius of curvature increases. Simultaneously, the mechanical robustness /stability of the water-oil-water emulsion droplets decreases as the droplet size increases. The impact of these physical conditions and the possibilities of circumventing these limitations have been examined while attempting to meet the NIF shell power spectrum criteria. Identifying the key parameters in the transition (solidification) from a w-o-w droplet to a solid polymer shell has been understood implicitly to be the paramount goal. It is believed through the knowledge gained that it will be possible to minimize the deleterious forces and maximize shell sphericity. At this point it is believed that properties intrinsic to the polymer (i.e., P{alpha}MS) such as its solution behavior and evolution of film stresses control the overall shell sphericity.

  19. Quality Control, Testing and Deployment Results in NIF ICCS

    NASA Astrophysics Data System (ADS)

    Woodruff, John

    The strategy used to develop the NIF Integrated Computer Control System (ICCS) calls for incremental cycles of construction and formal test to deliver a total of 1 million lines of code. Each incremental release takes four to six months to implement specific functionality and culminates when offline tests conducted in the ICCS Integration and Test Facility verify functional, performance, and interface requirements. Tests are then repeated on line to confirm integrated operation in dedicated laser laboratories or ultimately in the NIF. Test incidents along with other change requests are recorded and tracked to closure by the software change control board (SCCB). Annual independent audits advise management on software process improvements. Extensive experience has been gained by integrating controls in the prototype laser preamplifier laboratory. The control system installed in the preamplifier lab contains five of the ten planned supervisory subsystems and seven of sixteen planned front-end processors (FEPs). Beam alignment, timing, diagnosis and laser pulse amplification up to 20 joules was tested through an automated series of shots. Other laboratories have provided integrated testing of six additional FEPs. Process measurements including earned-value, product size, and defect densities provide software project controls and generate confidence that the control system will be successfully deployed.

  20. Diagnosing Turbulent Shear in HED Experiments on NIF

    NASA Astrophysics Data System (ADS)

    Flippo, K. A.; Kline, J. L.; Doss, F. W.; Perry, T. S.; Devolder, B.; Murphy, T. J.; Merritt, E. C.; Tregillis, I. A.; Loomis, E. N.; Schmidt, D.; Capelli, D.; Regan, S. P.; Barrios, M. A.; Huntington, C. M.; MacLaren, S. A.

    2014-10-01

    We report on experiments planned for and performed at the NIF to investigate turbulent mix in and HED régime using a platform scaled from the Omega laser facility. We are investigating turbulence-driven mix from the shear induced Kelvin-Helmholtz instability, like those experienced in an ICF capsule with instabilities present. Two shocks are generated at either end of cylinder, inside CH foams act as a light fluid and the evolution of an Al tracer layer heavy fluid in the center plane is observed using the Big Area Backlighter (BABL), an especially large area backlighter developed for this project. Simulations of the BABL were carried out to optimize spatial profile. Another backlighter, the Long Duration Backlighter (LDBL) a variation of the BABL has also been developed and shot on NIF. The LDBL has been tuned spatially and temporally to emit x-rays in a very flat profile over a 7 ns time frame. Comparison of this data with simulations using the Besnard-Harlow-Rauenzahn (BHR) model is used. BHR is intended for turbulent transport in fluids with large density variations and has the ability to improve our predictive capability of mix in ICF experiments. Los Alamos National Laboratory is operated by the Los Alamos National Security, LLC for the National Nuclear Security Administration of the U.S. Department of Energy under Contract DE-AC52-06NA25396.

  1. Optimization of experimental designs by incorporating NIF facility impacts

    NASA Astrophysics Data System (ADS)

    Eder, D. C.; Whitman, P. K.; Koniges, A. E.; Anderson, R. W.; Wang, P.; Gunney, B. T.; Parham, T. G.; Koerner, J. G.; Dixit, S. N.; Suratwala, T. I.; Blue, B. E.; Hansen, J. F.; Tobin, M. T.; Robey, H. F.; Spaeth, M. L.; MacGowan, B. J.

    2006-06-01

    For experimental campaigns on the National Ignition Facility (NIF) to be successful, they must obtain useful data without causing unacceptable impact on the facility. Of particular concern is excessive damage to optics and diagnostic components. There are 192 fused silica main debris shields (MDS) exposed to the potentially hostile target chamber environment on each shot. Damage in these optics results either from the interaction of laser light with contamination and pre-existing imperfections on the optic surface or from the impact of shrapnel fragments. Mitigation of this second damage source is possible by identifying shrapnel sources and shielding optics from them. It was recently demonstrated that the addition of 1.1-mm thick borosilicate disposable debris shields (DDS) blocks the majority of debris and shrapnel fragments from reaching the relatively expensive MDS's. However, DDS's cannot stop large, fast moving fragments. We have experimentally demonstrated one shrapnel mitigation technique showing that it is possible to direct fast moving fragments by changing the source orientation, in this case a Ta pinhole array. Another mitigation method is to change the source material to one that produces smaller fragments. Simulations and validating experiments are necessary to determine which fragments can penetrate or break 1-3 mm thick DDS's. Three-dimensional modeling of complex target-diagnostic configurations is necessary to predict the size, velocity, and spatial distribution of shrapnel fragments. The tools we are developing will be used to assure that all NIF experimental campaigns meet the requirements on allowed level of debris and shrapnel generation.

  2. Imaging VISAR diagnostic for the National Ignition Facility (NIF)

    SciTech Connect

    Malone, R M; Bower, J R; Bradley, D K; Capelle, G A; Celeste, J R; Celliers, P M; Collins, G W; Eckart, M J; Eggert, J H; Frogget, B C; Guyton, R L; Hicks, D G; Kaufman, M I; MacGowan, B J; Montelongo, S; Ng, E W; Robinson, R B; Tunnell, T W; Watts, P W; Zapata, P G

    2004-08-30

    The National Ignition Facility (NIF) requires diagnostics to analyze high-energy density physics experiments. A VISAR (Velocity Interferometry System for Any Reflector) diagnostic has been designed to measure shock velocities, shock breakout times, and shock emission of targets with sizes from 1 to 5 mm. An 8-inch-diameter fused silica triplet lens collects light at f/3 inside the 30-foot-diameter vacuum chamber. The optical relay sends the image out an equatorial port, through a 2-inch-thick vacuum window, and into two interferometers. A 60-kW VISAR probe laser operates at 659.5 nm with variable pulse width. Special coatings on the mirrors and cutoff filters are used to reject the NIF drive laser wavelengths and to pass a band of wavelengths for VISAR, passive shock breakout light, or thermal imaging light (bypassing the interferometers). The first triplet can be no closer than 500 mm from the target chamber center and is protected from debris by a blast window that is replaced after every event. The front end of the optical relay can be temporarily removed from the equatorial port, allowing other experimenters to use that port. A unique resolution pattern has been designed to validate the VISAR diagnostic before each use. All optical lenses are on kinematic mounts so that the pointing accuracy of the optical axis can be checked. Seven CCD cameras monitor the diagnostic alignment.

  3. Development and Testing of the NIF Prototype Module

    SciTech Connect

    Adcock, J.; Harjes, C.; Mowrer, G.; Wilson, M.

    1999-06-25

    The NIF Power Conditioning System (PCS) is required to deliver -68 kJ to each of the 3840 flashlamp pairs in the NIF laser in a current pulse with a peak of -500 kA and rise time of- 150 µs. The PCS will consist of 192 modules each of which drive 20 lamp-pairs. Each module will basically be a 6 rnF capacitor bank with a nominal charge voltage of 23.5 kV which is switched by a single pressurized air gas switch to 20 RG-220 cables that are connected to individual lamp loads. In addition each module will have a number of subsystems including; a lamp pre-ionization system, power supplies, isolation circuits, trigger systems, safety dump systems, gas system, and an embedded control system. A module will also include components whose primary function is to limit fault currents and thus minimize collateral damage in faults. In the Prototype Development and Testing effort at Sandia National Laboratories all of these were integrated into a single system and proper fimctionality was demonstrated. Extensive testing was done at nominal operating levels into resistive dummy loads and some testing in fault modes was also done. A description of the system and a summary of testing is given in this paper.

  4. Alpha Heating and TN Burn in NIF Experiments

    NASA Astrophysics Data System (ADS)

    Cheng, Baolian; Kwan, Thomas; Wang, Yi-Ming; Merrill, Frank; Cerjan, Charlie; Batha, Steven

    2015-11-01

    Sustainable TN burn requires alpha-particle energy deposition in the hot fuel. Recently, we developed an analytic model to estimate the neutron yield generated by the alpha-particle energy deposited in the hot spot, in terms of the measured total neutron yield, the adiabat of the cold fuel and the peak implosion kinetic energy of the pusher. Our alpha heating model has been applied to a number of inertial confinement fusion capsule experiments performed at the National Ignition Facility (NIF). Our model predictions are consistent with the post-shot calibrated code simulations and experimental data. We have also studied the uncertainty and sensitivities of alpha heating on various physics parameters, such as the adiabat of cold fuel, total neutron yield and peak implosion velocity. Our analysis demonstrates that the alpha particle heating was appreciable in only high-foot experiments. Based on our work, we will discuss paths and parameters to reach ignition at NIF (LA-UR-15-25507). This work was performed under the auspices of the U.S. Department of Energy by the Los Alamos National Laboratory under Contract No. W-7405-ENG-36.

  5. Analysis of NIF experiments with the minimal energy implosion model

    SciTech Connect

    Cheng, B. Kwan, T. J. T.; Wang, Y. M.; Merrill, F. E.; Batha, S. H.; Cerjan, C. J.

    2015-08-15

    We apply a recently developed analytical model of implosion and thermonuclear burn to fusion capsule experiments performed at the National Ignition Facility that used low-foot and high-foot laser pulse formats. Our theoretical predictions are consistent with the experimental data. Our studies, together with neutron image analysis, reveal that the adiabats of the cold fuel in both low-foot and high-foot experiments are similar. That is, the cold deuterium-tritium shells in those experiments are all in a high adiabat state at the time of peak implosion velocity. The major difference between low-foot and high-foot capsule experiments is the growth of the shock-induced instabilities developed at the material interfaces which lead to fuel mixing with ablator material. Furthermore, we have compared the NIF capsules performance with the ignition criteria and analyzed the alpha particle heating in the NIF experiments. Our analysis shows that alpha heating was appreciable only in the high-foot experiments.

  6. Analysis of NIF experiments with the minimal energy implosion model

    NASA Astrophysics Data System (ADS)

    Cheng, B.; Kwan, T. J. T.; Wang, Y. M.; Merrill, F. E.; Cerjan, C. J.; Batha, S. H.

    2015-08-01

    We apply a recently developed analytical model of implosion and thermonuclear burn to fusion capsule experiments performed at the National Ignition Facility that used low-foot and high-foot laser pulse formats. Our theoretical predictions are consistent with the experimental data. Our studies, together with neutron image analysis, reveal that the adiabats of the cold fuel in both low-foot and high-foot experiments are similar. That is, the cold deuterium-tritium shells in those experiments are all in a high adiabat state at the time of peak implosion velocity. The major difference between low-foot and high-foot capsule experiments is the growth of the shock-induced instabilities developed at the material interfaces which lead to fuel mixing with ablator material. Furthermore, we have compared the NIF capsules performance with the ignition criteria and analyzed the alpha particle heating in the NIF experiments. Our analysis shows that alpha heating was appreciable only in the high-foot experiments.

  7. NIF Anti-Reflective Coating Solutions: Preparation, Procedures and Specifications

    SciTech Connect

    Suratwala, T; Carman, L; Thomas, I

    2003-07-01

    The following document contains a detailed description of the preparation procedures for the antireflective coating solutions used for NIF optics. This memo includes preparation procedures for the coating solutions (sections 2.0-4.0), specifications and vendor information of the raw materials used and on all equipment used (section 5.0), and QA specifications (section 6.0) and procedures (section 7.0) to determine quality and repeatability of all the coating solutions. There are different five coating solutions that will be used to coat NIF optics. These solutions are listed below: (1) Colloidal silica (3%) in ethanol (2) Colloidal silica (2%) in sec-butanol (3) Colloidal silica (9%) in sec-butanol (deammoniated) (4) HMDS treated silica (10%) in decane (5) GR650 (3.3%) in ethanol/sec-butanol The names listed above are to be considered the official name for the solution. They will be referred to by these names in the remainder of this document. Table 1 gives a summary of all the optics to be coated including: (1) the surface to be coated; (2) the type of solution to be used; (3) the coating method (meniscus, dip, or spin coating) to be used; (4) the type of coating (broadband, 1?, 2?, 3?) to be made; (5) number of optics to be coated; and (6) the type of post processing required (if any). Table 2 gives a summary of the batch compositions and measured properties of all five of these solutions.

  8. A comprehensive aligned nifH gene database: a multipurpose tool for studies of nitrogen-fixing bacteria

    PubMed Central

    Gaby, John Christian; Buckley, Daniel H.

    2014-01-01

    We describe a nitrogenase gene sequence database that facilitates analysis of the evolution and ecology of nitrogen-fixing organisms. The database contains 32 954 aligned nitrogenase nifH sequences linked to phylogenetic trees and associated sequence metadata. The database includes 185 linked multigene entries including full-length nifH, nifD, nifK and 16S ribosomal RNA (rRNA) gene sequences. Evolutionary analyses enabled by the multigene entries support an ancient horizontal transfer of nitrogenase genes between Archaea and Bacteria and provide evidence that nifH has a different history of horizontal gene transfer from the nifDK enzyme core. Further analyses show that lineages in nitrogenase cluster I and cluster III have different rates of substitution within nifD, suggesting that nifD is under different selection pressure in these two lineages. Finally, we find that that the genetic divergence of nifH and 16S rRNA genes does not correlate well at sequence dissimilarity values used commonly to define microbial species, as stains having <3% sequence dissimilarity in their 16S rRNA genes can have up to 23% dissimilarity in nifH. The nifH database has a number of uses including phylogenetic and evolutionary analyses, the design and assessment of primers/probes and the evaluation of nitrogenase sequence diversity. Database URL: http://www.css.cornell.edu/faculty/buckley/nifh.htm PMID:24501396

  9. Federated Access to Heterogeneous Information Resources in the Neuroscience Information Framework (NIF)

    PubMed Central

    Gupta, Amarnath; Bug, William; Marenco, Luis; Qian, Xufei; Condit, Christopher; Rangarajan, Arun; Müller, Hans Michael; Miller, Perry L.; Sanders, Brian; Grethe, Jeffrey S.; Astakhov, Vadim; Shepherd, Gordon; Sternberg, Paul W.; Martone, Maryann E.

    2009-01-01

    The overarching goal of the NIF (Neuroscience Information Framework) project is to be a one-stop-shop for Neuroscience. This paper provides a technical overview of how the system is designed. The technical goal of the first version of the NIF system was to develop an information system that a neuroscientist can use to locate relevant information from a wide variety of information sources by simple keyword queries. Although the user would provide only keywords to retrieve information, the NIF system is designed to treat them as concepts whose meanings are interpreted by the system. Thus, a search for term should find a record containing synonyms of the term. The system is targeted to find information from web pages, publications, databases, web sites built upon databases, XML documents and any other modality in which such information may be published. We have designed a system to achieve this functionality. A central element in the system is an ontology called NIFSTD (for NIF Standard) constructed by amalgamating a number of known and newly developed ontologies. NIFSTD is used by our ontology management module, called OntoQuest to perform ontology-based search over data sources. The NIF architecture currently provides three different mechanisms for searching heterogeneous data sources including relational databases, web sites, XML documents and full text of publications. Version 1.0 of the NIF system is currently in beta test and may be accessed through http://nif.nih.gov. PMID:18958629

  10. Kinetics of Nif gene expression in a nitrogen-fixing bacterium.

    PubMed

    Poza-Carrión, César; Jiménez-Vicente, Emilio; Navarro-Rodríguez, Mónica; Echavarri-Erasun, Carlos; Rubio, Luis M

    2014-02-01

    Nitrogen fixation is a tightly regulated trait. Switching from N2 fixation-repressing conditions to the N2-fixing state is carefully controlled in diazotrophic bacteria mainly because of the high energy demand that it imposes. By using quantitative real-time PCR and quantitative immunoblotting, we show here how nitrogen fixation (nif) gene expression develops in Azotobacter vinelandii upon derepression. Transient expression of the transcriptional activator-encoding gene, nifA, was followed by subsequent, longer-duration waves of expression of the nitrogenase biosynthetic and structural genes. Importantly, expression timing, expression levels, and NifA dependence varied greatly among the nif operons. Moreover, the exact concentrations of Nif proteins and their changes over time were determined for the first time. Nif protein concentrations were exquisitely balanced, with FeMo cofactor biosynthetic proteins accumulating at levels 50- to 100-fold lower than those of the structural proteins. Mutants lacking nitrogenase structural genes or impaired in FeMo cofactor biosynthesis showed overenhanced responses to derepression that were proportional to the degree of nitrogenase activity impairment, consistent with the existence of at least two negative-feedback regulatory mechanisms. The first such mechanism responded to the levels of fixed nitrogen, whereas the second mechanism appeared to respond to the levels of the mature NifDK component. Altogether, these findings provide a framework to engineer N2 fixation in nondiazotrophs. PMID:24244007

  11. Cloning, expression, purification, crystallization and preliminary crystallographic analysis of NifH1 from Methanocaldococcus jannaschii.

    PubMed

    Wu, Hao; Yuan, Ye; Ma, Jinming; Gao, Yongxiang

    2011-05-01

    Nitrogen fixation is catalyzed by the nitrogenase complex in Azotobacter, which is composed of dinitrogenase and dinitrogenase reductase. Dinitrogenase is an α(2)β(2) heterotetramer of the proteins NifD and NifK. Dinitrogenase reductase is a homodimer of the protein NifH. The expression of NifD/K and NifH nitrogenase homologues (named NflD/K and NflH for Nif-like D and H, respectively) has been detected in the non-nitrogen-fixing hyperthermophilic methanogen Methanocaldococcus jannaschii. Solving the structure of MjNifH1 may help in better understanding its function and may supply some clues to understanding the evolution of nitrogenase. The full-length protein with an additional His(6) tag at the C-terminus was expressed, purified and crystallized by the hanging-drop vapour-diffusion method at 287 K. An X-ray diffraction data set was collected to a resolution of 3.3 Å. The crystal belonged to space group P4(1)32, with unit-cell parameters a = b = c = 139.45 Å, and was estimated to contain one protein molecule per asymmetric unit. PMID:21543862

  12. Kinetics of nif Gene Expression in a Nitrogen-Fixing Bacterium

    PubMed Central

    Poza-Carrión, César; Jiménez-Vicente, Emilio; Navarro-Rodríguez, Mónica; Echavarri-Erasun, Carlos

    2014-01-01

    Nitrogen fixation is a tightly regulated trait. Switching from N2 fixation-repressing conditions to the N2-fixing state is carefully controlled in diazotrophic bacteria mainly because of the high energy demand that it imposes. By using quantitative real-time PCR and quantitative immunoblotting, we show here how nitrogen fixation (nif) gene expression develops in Azotobacter vinelandii upon derepression. Transient expression of the transcriptional activator-encoding gene, nifA, was followed by subsequent, longer-duration waves of expression of the nitrogenase biosynthetic and structural genes. Importantly, expression timing, expression levels, and NifA dependence varied greatly among the nif operons. Moreover, the exact concentrations of Nif proteins and their changes over time were determined for the first time. Nif protein concentrations were exquisitely balanced, with FeMo cofactor biosynthetic proteins accumulating at levels 50- to 100-fold lower than those of the structural proteins. Mutants lacking nitrogenase structural genes or impaired in FeMo cofactor biosynthesis showed overenhanced responses to derepression that were proportional to the degree of nitrogenase activity impairment, consistent with the existence of at least two negative-feedback regulatory mechanisms. The first such mechanism responded to the levels of fixed nitrogen, whereas the second mechanism appeared to respond to the levels of the mature NifDK component. Altogether, these findings provide a framework to engineer N2 fixation in nondiazotrophs. PMID:24244007

  13. Federated access to heterogeneous information resources in the Neuroscience Information Framework (NIF).

    PubMed

    Gupta, Amarnath; Bug, William; Marenco, Luis; Qian, Xufei; Condit, Christopher; Rangarajan, Arun; Müller, Hans Michael; Miller, Perry L; Sanders, Brian; Grethe, Jeffrey S; Astakhov, Vadim; Shepherd, Gordon; Sternberg, Paul W; Martone, Maryann E

    2008-09-01

    The overarching goal of the NIF (Neuroscience Information Framework) project is to be a one-stop-shop for Neuroscience. This paper provides a technical overview of how the system is designed. The technical goal of the first version of the NIF system was to develop an information system that a neuroscientist can use to locate relevant information from a wide variety of information sources by simple keyword queries. Although the user would provide only keywords to retrieve information, the NIF system is designed to treat them as concepts whose meanings are interpreted by the system. Thus, a search for term should find a record containing synonyms of the term. The system is targeted to find information from web pages, publications, databases, web sites built upon databases, XML documents and any other modality in which such information may be published. We have designed a system to achieve this functionality. A central element in the system is an ontology called NIFSTD (for NIF Standard) constructed by amalgamating a number of known and newly developed ontologies. NIFSTD is used by our ontology management module, called OntoQuest to perform ontology-based search over data sources. The NIF architecture currently provides three different mechanisms for searching heterogeneous data sources including relational databases, web sites, XML documents and full text of publications. Version 1.0 of the NIF system is currently in beta test and may be accessed through http://nif.nih.gov. PMID:18958629

  14. Requirement of NifX and other nif proteins for in vitro biosynthesis of the iron-molybdenum cofactor of nitrogenase.

    PubMed

    Shah, V K; Rangaraj, P; Chatterjee, R; Allen, R M; Roll, J T; Roberts, G P; Ludden, P W

    1999-05-01

    The iron-molybdenum cofactor (FeMo-co) of nitrogenase contains molybdenum, iron, sulfur, and homocitrate in a ratio of 1:7:9:1. In vitro synthesis of FeMo-co has been established, and the reaction requires an ATP-regenerating system, dithionite, molybdate, homocitrate, and at least NifB-co (the metabolic product of NifB), NifNE, and dinitrogenase reductase (NifH). The typical in vitro FeMo-co synthesis reaction involves mixing extracts from two different mutant strains of Azotobacter vinelandii defective in the biosynthesis of cofactor or an extract of a mutant strain complemented with the purified missing component. Surprisingly, the in vitro synthesis of FeMo-co with only purified components failed to generate significant FeMo-co, suggesting the requirement for one or more other components. Complementation of these assays with extracts of various mutant strains demonstrated that NifX has a role in synthesis of FeMo-co. In vitro synthesis of FeMo-co with purified components is stimulated approximately threefold by purified NifX. Complementation of these assays with extracts of A. vinelandii DJ42. 48 (DeltanifENX DeltavnfE) results in a 12- to 15-fold stimulation of in vitro FeMo-co synthesis activity. These data also demonstrate that apart from the NifX some other component(s) is required for the cofactor synthesis. The in vitro synthesis of FeMo-co with purified components has allowed the detection, purification, and identification of an additional component(s) required for the synthesis of cofactor. PMID:10217770

  15. Laser{endash}plasma interactions in ignition-scale hohlraum plasmas

    SciTech Connect

    MacGowan, B.J.; Afeyan, B.B.; Back, C.A.; Berger, R.L.; Bonnaud, G.; Casanova, M.; Cohen, B.I.; Desenne, D.E.; DuBois, D.F.; Dulieu, A.G.; Estabrook, K.G.; Fernandez, J.C.; Glenzer, S.H.; Hinkel, D.E.; Kaiser, T.B.; Kalantar, D.H.; Kauffman, R.L.; Kirkwood, R.K.; Kruer, W.L.; Langdon, A.B.; Lasinski, B.F.; Montgomery, D.S.; Moody, J.D.; Munro, D.H.; Powers, L.V.; Rose, H.A.; Rousseaux, C.; Turner, R.E.; Wilde, B.H.; Wilks, S.C.; Williams, E.A.

    1996-05-01

    Scattering of laser light by stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) is a concern for indirect drive inertial confinement fusion (ICF). The hohlraum designs for the National Ignition Facility (NIF) raise particular concerns due to the large scale and homogeneity of the plasmas within them. Experiments at Nova have studied laser{endash}plasma interactions within large scale length plasmas that mimic many of the characteristics of the NIF hohlraum plasmas. Filamentation and scattering of laser light by SBS and SRS have been investigated as a function of beam smoothing and plasma conditions. Narrowly collimated SRS backscatter has been observed from low density, low-{ital Z}, plasmas, which are representative of the plasma filling most of the NIF hohlraum. SBS backscatter is found to occur in the high-{ital Z} plasma of gold ablated from the wall. Both SBS and SRS are observed to be at acceptable levels in experiments using smoothing by spectral dispersion (SSD). {copyright} {ital 1996 American Institute of Physics.}

  16. NIF Programs Directorate: Integrated Safety Management System Implementation Plan October 2000

    SciTech Connect

    Fischer, L

    2001-09-17

    Lawrence Livermore National Laboratory (LLNL) has developed a work structure that serves to ensure work is performed safely and in compliance with applicable environment, safety, and health (ES&H) requirements. Safety begins and ends with the worker ''on the floor'' conducting the work activity. The primary focus of the NIF Programs Integrated Safety Management System (ISMS) is to provide the worker with a sound work environment, necessary resources to perform the job, and adequate procedures and controls to ensure the work is performed safely. It is to this end that the ES&H roles, responsibilities, and authorities are developed and practiced. NIF Programs recognizes and understands the Department of Energy (DOE)/University of California (UC) Contract requirements for ISMS at LLNL and the opportunities and values of the system. NIF Programs understands and supports the DOE Integrated Safety Management (ISM) objective, guiding principles, core functions, and the institutional requirements contained in the LLNL ISMS Description document. NIF Programs is committed to implementing and utilizing ISMS in all of its programs, operations, facilities, and activities and to continuing to assess its successful implementation and use. NIF Programs ISMS has been developed consistent with the requirements of the ''LLNL Integrated Safety Management System Description'' document and specific ISMS implementation needs of NIF Programs. The purpose of this document is to define for NIF Programs' workers and communicate to both senior LLNL management and DOE how and where NIF Programs satisfies the institutional ISM requirements. This document consists of: (1) A NIF Programs document hierarchy that illustrates the flow of ES&H requirements from the directorate level to the worker. (2) A roles, responsibilities, and authorities section for ES&H management chain positions, (3) An ISM implementation matrix that references specific implementing documents for each of the ISM core

  17. Diagnosing implosion velocity and ablator dynamics at NIF (u)

    SciTech Connect

    Hayes, Anna; Grim, Gary; Jungnam, Jerry; Bradley, Paul; Rundberg, Bob; Wilhelmy, Jerry; Wilson, Doug

    2009-07-09

    An enhanced understanding of the unique physics probed in a burning NIP capsule is important for both nuclear weapons physics and thermonuclear ignition. In this talk we introduce a new diagnostic idea, designed to measure dynamic aspects of the capsule implosion that are not currently accessible. The current set of diagnostics for the NIF experiments includes reaction history (a time resolved measure of the d + t burn), neutron time-of-flight and spectrometry and spatial imaging of the neutron production and scattering. Although valuable, this abbreviated set of diagnostics cannot determine key dynamical properties of the implosion, such as implosion velocity (v{sub impl}) and ablator thickness. To surpass the present limits of {approx} 10{sup 15} d+t reactions, it will be necessary to increase significantly the implosion energy delivered to the DT fuel by finely tuning the balance between the remaining (imploding) ablator mass and velocity. If too much mass remains, the implosion velocity will be too slow, and the subsecpwnt PdV work will not be sufficient to overcome cooling via conduction and radiation. If too little mass remains, hydrodynamic instabilities will occur, resulting in unpredictable and degraded performance. Detailed calculations suggest the ablator must reach an implosion velocity of 3-4 x 10{sup 7} cm/sec and an areal density of {rho}{Delta}R {approx}200 mg/cm{sup 2} in order to achieve ignition. The authors present a new scheme to measure these important quantities using neutron reactions on the ablator material. During the burn, the ablator is moving relative to the 14.1 MeV d+t neutrons that are traversing the capsule. The resulting neutron-ablator Doppler shift causes a few unique nuclear reactions to become sensitive detectors of the ablator velocity at peak burn time. The 'point-design' capsule at the NIF will be based on a {sup 9}Be ablator, and the {sup 9}Be(n,p){sup 9}Li reaction has an energy threshold of 14.2 MeV, making it the ideal

  18. 3D Simulations of the ``Keyhole'' Hohlraum for Shock Timing on NIF

    NASA Astrophysics Data System (ADS)

    Robey, H. F.; Marinak, M. M.; Munro, D. H.; Jones, O. S.

    2007-11-01

    Ignition implosions planned for the National Ignition Facility (NIF) require a pulse shape with a carefully designed series of steps, which launch a series of shocks through the ablator and DT fuel. The relative timing of these shocks must be tuned to better than +/- 100ps to maintain the DT fuel on a sufficiently low adiabat. To meet these requirements, pre-ignition tuning experiments using a modified hohlraum geometry are being planned. This modified geometry, known as the ``keyhole'' hohlraum, adds a re-entrant gold cone, which passes through the hohlraum and capsule walls, to provide an optical line-of-sight to directly measure the shocks as they break out of the ablator. In order to assess the surrogacy of this modified geometry, 3D simulations using HYDRA [1] have been performed. The drive conditions and the resulting effect on shock timing in the keyhole hohlraum will be compared with the corresponding results for the standard ignition hohlraum. [1] M.M. Marinak, et al., Phys. Plasmas 8, 2275 (2001).

  19. Experimental Results of High Pressure and High Strain Rate Tantalum Flow Stress on Omega and NIF

    NASA Astrophysics Data System (ADS)

    Park, Hye-Sook; Arsenlis, A.; Barton, N.; Benedetti, L.; Huntington, C.; McNaney, J.; Orlikowski, D.; Prisbrey, S.; Remington, B.; Rudd, R.; Swift, D.; Weber, S.; Wehrenberg, C.; Comley, A.

    2015-11-01

    Understanding the high pressure, high strain rate plastic deformation dynamics of materials is an area of research of high interest to planetary formation dynamics, meteor impact dynamics, and inertial confinement fusion designs. Developing predictive theoretical and computational descriptions of such systems, however, has been a difficult undertaking. We have performed many experiments on Omega, LCLS and NIF to test Ta strength models at high pressures (~ up to 4 Mbar), high strain rates (~ 107 s-1) and high strains (>30%) under ramped compression conditions using Rayleigh-Taylor and Richtmyer-Meshkov instability properties. These experiments use plasma drive to ramp compress the sample to higher pressure without shock-melting. We also studied lattice level strength mechanisms under shocked compression using a diffraction-based technique. Our studies show that the strength mechanisms from macro to micro scales are different from the traditional strength model predictions and that they are loading path dependent. We will report the experimental results. Work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA273.

  20. The Evolution of the Gold Bubble in NIF Ignition Gas-Filled Hohlraums

    NASA Astrophysics Data System (ADS)

    Schneider, Marilyn; MacLaren, Steve; Widmann, Klaus; Meezan, Nathan; Hammer, James; Bell, Perry; Benedetti, Robin; Bradley, David; Callahan, Deborah; Dewald, Eduard; Doeppner, Tilo; Hinkel, Denise; Jones, Oggie; Landen, O. L.; Michel, Pierre; Milovich, Jose; Moody, John; Moore, Alastair

    2015-11-01

    At the National Ignition Facility (NIF), the energy from 192 laser beams is converted to an x-ray drive in a gas-filled gold hohlraum. The x-ray drive heats and implodes a fuel capsule. The ViewFactor platform uses a truncated hohlraum to measure the x-ray drive from the capsule point-of-view. This platform also affords excellent diagnostic views of the hohlraum interior, in particular, of the region in which the outer beams deposit their energy (the ``gold bubble'') Time-resolved and time-integrated images in the hard x-ray range (>3 keV) reveal an 8-fold symmetry in the gold bubble. The Au plasma in the bubble from the eight 50 degree quads expands faster than that from the interleaved 44.5 degree quads. The variation in this structure with laser intensity, with pulse shape and cross beam energy transfer, and comparison to models, will be discussed. This work performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  1. Characterizing high energy spectra of NIF ignition Hohlraums using a differentially filtered high energy multipinhole x-ray imager.

    PubMed

    Park, Hye-Sook; Dewald, E D; Glenzer, S; Kalantar, D H; Kilkenny, J D; MacGowan, B J; Maddox, B R; Milovich, J L; Prasad, R R; Remington, B A; Robey, H F; Thomas, C A

    2010-10-01

    Understanding hot electron distributions generated inside Hohlraums is important to the national ignition campaign for controlling implosion symmetry and sources of preheat. While direct imaging of hot electrons is difficult, their spatial distribution and spectrum can be deduced by detecting high energy x-rays generated as they interact with target materials. We used an array of 18 pinholes with four independent filter combinations to image entire Hohlraums with a magnification of 0.87× during the Hohlraum energetics campaign on NIF. Comparing our results with Hohlraum simulations indicates that the characteristic 10-40 keV hot electrons are mainly generated from backscattered laser-plasma interactions rather than from Hohlraum hydrodynamics. PMID:21034047

  2. Characterizing high energy spectra of NIF ignition Hohlraums using a differentially filtered high energy multipinhole x-ray imager

    SciTech Connect

    Park, Hye-Sook; Dewald, E. D.; Glenzer, S.; Kalantar, D. H.; Kilkenny, J. D.; MacGowan, B. J.; Maddox, B. R.; Milovich, J. L.; Prasad, R. R.; Remington, B. A.; Robey, H. F.; Thomas, C. A.

    2010-10-15

    Understanding hot electron distributions generated inside Hohlraums is important to the national ignition campaign for controlling implosion symmetry and sources of preheat. While direct imaging of hot electrons is difficult, their spatial distribution and spectrum can be deduced by detecting high energy x-rays generated as they interact with target materials. We used an array of 18 pinholes with four independent filter combinations to image entire Hohlraums with a magnification of 0.87x during the Hohlraum energetics campaign on NIF. Comparing our results with Hohlraum simulations indicates that the characteristic 10-40 keV hot electrons are mainly generated from backscattered laser-plasma interactions rather than from Hohlraum hydrodynamics.

  3. Characterizing high energy spectra of NIF ignition hohlraums using a differentially filtered high energy multi-pinhole X-ray imager

    SciTech Connect

    Park, H; Dewald, E D; Glenzer, S; Kalantar, D H; Kilkenny, J D; MacGowan, B J; Maddox, B R; Milovich, J L; Prasad, R R; Remington, B A; Thomas, C A

    2010-05-11

    Understanding hot electron distributions generated inside hohlraums is important to the ignition campaign for controlling implosion symmetry and sources of preheat. While direct imaging of hot electrons is difficult, their spatial distribution and spectrum can be deduced by detecting high energy x-rays generated as they interact with the target materials. We used an array of 18 pinholes, with four independent filter combinations, to image entire hohlraums with a magnification of 0.87x during the hohlraum energetics campaign on NIF. Comparing our results with hohlraum simulations indicates that the characteristic 30 keV hot electrons are mainly generated from backscattered laser plasma interactions rather than from hohlraum hydrodynamics.

  4. Reaction-in-Flight Neutrons as a Probe of Hydrodynamical Mixing at NIF

    NASA Astrophysics Data System (ADS)

    Hayes, Anna; Grim, Gary; Jungman, Jerry

    2009-10-01

    At the National Ignition Facility (NIF) reaction-in-flight (RIF) neutrons above the main 14 MeV peak make up about 0.5% of the neutrons production. In this talk we present calculations that show the sensitivity of the RIF neutron production to hydrodynamical mixing of the outer shell of the NIF capsule into the main dt fuel. This mixing generally quenches the dt burn and could be a serious mode of ignition failure. These calculations suggest that a time-of-flight measurement or radiochemical measurement of the RIF neutrons could be used as a robust indicator of the degree o mix taking place in an imploded NIF capsule.

  5. Dependence of beam emittance on plasma electrode temperature and rf-power, and filter-field tuning with center-gapped rod-filter magnets in J-PARC rf-driven H- ion source

    NASA Astrophysics Data System (ADS)

    Ueno, A.; Koizumi, I.; Ohkoshi, K.; Ikegami, K.; Takagi, A.; Yamazaki, S.; Oguri, H.

    2014-02-01

    The prototype rf-driven H- ion-source with a nickel plated oxygen-free-copper (OFC) plasma chamber, which satisfies the Japan Proton Accelerator Research Complex (J-PARC) 2nd stage requirements of a H- ion beam current of 60 mA within normalized emittances of 1.5 π mm mrad both horizontally and vertically, a flat top beam duty factor of 1.25% (500 μs × 25 Hz) and a life-time of more than 50 days, was reported at the 3rd international symposium on negative ions, beams, and sources (NIBS2012). The experimental results of the J-PARC ion source with a plasma chamber made of stainless-steel, instead of nickel plated OFC used in the prototype source, are presented in this paper. By comparing these two sources, the following two important results were acquired. One was that the about 20% lower emittance was produced by the rather low plasma electrode (PE) temperature (TPE) of about 120 °C compared with the typically used TPE of about 200 °C to maximize the beam current for the plasma with the abundant cesium (Cs). The other was that by using the rod-filter magnets with a gap at each center and tuning the gap-lengths, the filter-field was optimized and the rf-power necessary to produce the J-PARC required H- ion beam current was reduced typically 18%. The lower rf-power also decreases the emittances.

  6. Dependence of beam emittance on plasma electrode temperature and rf-power, and filter-field tuning with center-gapped rod-filter magnets in J-PARC rf-driven H{sup −} ion source

    SciTech Connect

    Ueno, A. Koizumi, I.; Ohkoshi, K.; Ikegami, K.; Takagi, A.; Yamazaki, S.; Oguri, H.

    2014-02-15

    The prototype rf-driven H{sup −} ion-source with a nickel plated oxygen-free-copper (OFC) plasma chamber, which satisfies the Japan Proton Accelerator Research Complex (J-PARC) 2nd stage requirements of a H{sup −} ion beam current of 60 mA within normalized emittances of 1.5 π mm mrad both horizontally and vertically, a flat top beam duty factor of 1.25% (500 μs × 25 Hz) and a life-time of more than 50 days, was reported at the 3rd international symposium on negative ions, beams, and sources (NIBS2012). The experimental results of the J-PARC ion source with a plasma chamber made of stainless-steel, instead of nickel plated OFC used in the prototype source, are presented in this paper. By comparing these two sources, the following two important results were acquired. One was that the about 20% lower emittance was produced by the rather low plasma electrode (PE) temperature (T{sub PE}) of about 120 °C compared with the typically used T{sub PE} of about 200 °C to maximize the beam current for the plasma with the abundant cesium (Cs). The other was that by using the rod-filter magnets with a gap at each center and tuning the gap-lengths, the filter-field was optimized and the rf-power necessary to produce the J-PARC required H{sup −} ion beam current was reduced typically 18%. The lower rf-power also decreases the emittances.

  7. Initial NIF Shock Timing Experiments: Comparison with Simulation

    NASA Astrophysics Data System (ADS)

    Robey, H. F.; Celliers, P. M.; Boehly, T. R.; Datte, P. S.; Bowers, M. W.; Olson, R. E.; Munro, D. H.; Milovich, J. L.; Jones, O. S.; Nikroo, A.; Kroll, J. J.; Horner, J. B.; Hamza, A. V.; Bhandarkar, S. D.; Giraldez, E.; Castro, C.; Gibson, C. R.; Eggert, J. H.; Smith, R. F.; Park, H.-S.; Young, B. K.; Hsing, W. W.; Landen, O. L.; Meyerhofer, D. D.

    2010-11-01

    Initial experiments are underway to demonstrate the techniques required to tune the shock timing of capsule implosions on the National Ignition Facility (NIF). These experiments use a modified cryogenic hohlraum geometry designed to precisely match the performance of ignition hohlraums. The targets employ a re-entrant Au cone to provide optical access to the shocks as they propagate in the liquid deuterium-filled capsule interior. The strength and timing of the shocks is diagnosed with VISAR (Velocity Interferometer System for Any Reflector) and DANTE. The results of these measurements will be used to set the precision pulse shape for ignition capsule implosions to follow. Experimental results and comparisons with numerical simulation are presented.

  8. Probing matter at extreme Gbar pressures at the NIF

    DOE PAGESBeta

    Kritcher, A. L.; Doeppner, T.; Swift, D.; Hawreliak, J.; Collins, G.; Nilsen, J.; Bachmann, B.; Dewald, E.; Strozzi, D.; Felker, S.; et al

    2013-12-04

    Here we describe a platform to measure the material properties, specifically the equation of state and electron temperature, at pressures of 100 Mbar to a Gbar at the National Ignition Facility (NIF). In our experiments we launch spherically convergent shock waves into solid CH, CD, or diamond samples using a hohlraum radiation drive, in an indirect drive laser geometry. X-ray radiography is applied to measure the shock speed and infer the mass density profile, enabling determination of the material pressure and Hugoniot equation of state. X-ray scattering is applied to measure the electron temperature through probing of the electron velocitymore » distribution via Doppler broadening.« less

  9. Detection of Off-normal Images for NIF Automatic Alignment

    SciTech Connect

    Candy, J V; Awwal, A S; McClay, W A; Ferguson, S W; Burkhart, S C

    2005-07-11

    One of the major purposes of National Ignition Facility at Lawrence Livermore National Laboratory is to accurately focus 192 high energy laser beams on a nanoscale (mm) fusion target at the precise location and time. The automatic alignment system developed for NIF is used to align the beams in order to achieve the required focusing effect. However, if a distorted image is inadvertently created by a faulty camera shutter or some other opto-mechanical malfunction, the resulting image termed ''off-normal'' must be detected and rejected before further alignment processing occurs. Thus the off-normal processor acts as a preprocessor to automatic alignment image processing. In this work, we discuss the development of an ''off-normal'' pre-processor capable of rapidly detecting the off-normal images and performing the rejection. Wide variety of off-normal images for each loop is used to develop the criterion for rejections accurately.

  10. NIF-0096141-OA Prop Simulations of NEL PBRS Measurements

    SciTech Connect

    Widmayer, C; Manes, K

    2003-02-21

    Portable Back Reflection Sensor, PBRS, (NEL only) and Quad Back Reflection Sensor, QBRS, time delay reflectometer traces are among the most useful diagnostics of NIF laser status available. NEL PBRS measurements show several signals reaching the detector for each shot. The time delay between signals suggests that the largest of these is due to energy at the spatial filter pinhole planes leaking into adjacent pinholes and traveling back upstream to the PBRS. Prop simulations agree with current PBRS measurements to within 50%. This suggests that pinhole leakage is the dominant source of energy at the PBRS. However, the simulations predict that the energy leakage is proportional to beam output energy, while the PBRS measurements increase more slowly (''saturate''). Further refinement of the model or the measurement may be necessary to resolve this discrepancy.

  11. Hohlraum Drive and Asymmetry in High Foot Implosions on NIF

    NASA Astrophysics Data System (ADS)

    Callahan, D.; Hurricane, O.; Casey, D.; Dewald, E.; Dittrich, T.; Doeppner, T.; Haan, S.; Hinkel, D.; Berzak Hopkins, L.; Jones, O.; Kritcher, A.; Lepape, S.; Ma, T.; Macphee, A.; Milovich, J.; Pak, A.; Park, H.-S.; Patel, P.; Ralph, J.; Robey, H.; Ross, S.; Salmonson, J.; Spears, B.; Springer, P.; Tommasini, R.

    2015-11-01

    The strategy in the high foot campaign on NIF has been to take reasonably small steps away from a working design, which means that we have a very rich database to understand both capsule and hohlraum performance. Over the course of the campaign, we have changed the laser power and energy, used both gold and depleted uranium hohlraums, and varied the thickness of the ablator. Each of these changes has an impact on the hohlraum drive and drive asymmetry, as measured by the implosion shape. In this talk, we will discuss what we have learned about hohlraum performance and residual kinetic energy resulting from drive asymmetry in the high foot database. Work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA273.

  12. Hard x-ray spectrometers for NIF (abstract)

    NASA Astrophysics Data System (ADS)

    Seely, John; Holland, Glenn; Brown, Charles; Deslattes, Richard; Hudson, Lawrence; Bell, Perry; Miller, Michael; Back, Christina

    2001-01-01

    A National Ignition Facility (NIF) core diagnostic instrument has been designed and will be fabricated to record x-ray spectra in the 1.2-20 keV energy range. The high-energy electronic x-ray instrument has four reflection crystals with overlapping coverage of 1.2-10.9 keV and one transmission crystal covering 8.6-20 keV. The spectral resolving power varies from approximately 1000 at low energies to 315 at 20 keV. The spectrum produced by each crystal is recorded by a modified commercial dental x-ray charge coupled device (CCD) detector. The scintillators on the CCD detectors are optimized for the energy ranges. A one-channel x-ray spectrometer, using one transmission crystal covering 12-60 keV, will be fabricated for the OMEGA laser facility. The transmission crystal spectrometers are based on instruments originally designed at National Institute for Standards and Technology for the purpose of characterizing the x-ray flux from medical radiography sources. Utilizing one of those instruments and a commercial dental x-ray CCD detector, x-ray images were recorded using a single pulse from a laboratory x-ray source with a peak charging voltage of 200 kV. A resolving power of 300 was demonstrated by recording on film the Kα1 and Kα2 characteristic x-ray lines near 17 keV from a molybdenum anode. The continuum radiation from a tungsten anode was recorded in the 20-50 keV energy range. The transmission crystal spectrometer has sufficient spectral resolution and sensitivity to record the line and continuum radiation from high-Z targets irradiated by the NIF laser and the OMEGA laser.

  13. Pure ion current collection in ion sensitive probe measurement with a metal mesh guard electrode for evaluation of ion temperature in magnetized plasma

    NASA Astrophysics Data System (ADS)

    Hsieh, Tung-Yuan; Kawamori, Eiichirou; Nishida, Yasushi

    2013-02-01

    This paper presents a new design of ion sensitive probe (ISP) that enables collection of pure ion current for accurate measurement of the perpendicular ion temperature in magnetized plasmas. The new type of ISP resolves a longstanding issue widely observed in ISP type measurements, namely, that the current-voltage characteristic is smeared by an unexpected electron current in the standard ISP model. The new ISP is equipped with a fine scale metal mesh on the sensor entrance to prevent electrons from flowing to the sensor, a phenomenon considered to be caused by the space-charge effect. The new ISP successfully measured the ion temperature of electron cyclotron resonance plasmas.

  14. Sol-gel deposition and plasma treatment of intrinsic, aluminum-doped, and gallium-doped zinc oxide thin films as transparent conductive electrodes

    NASA Astrophysics Data System (ADS)

    Zhu, Zhaozhao; Mankowski, Trent; Balakrishnan, Kaushik; Shikoh, Ali Sehpar; Touati, Farid; Benammar, Mohieddine A.; Mansuripur, Masud; Falco, Charles M.

    2015-09-01

    Zinc oxide and aluminum/gallium-doped zinc oxide thin films were deposited via sol-gel spin-coating technique. Employing plasma treatment as alternative to post thermal annealing, we found that the morphologies of these thin films have changed and the sheet resistances have been significantly enhanced. These plasma-treated thin films also show very good optical properties, with transmittance above 90% averaged over the visible wavelength range. Our best aluminum/gallium-doped zinc oxide thin films exhibit sheet resistances (Rs) of ~ 200 Ω/sq and ~ 150 Ω/sq, respectively.

  15. Pure ion current collection in ion sensitive probe measurement with a metal mesh guard electrode for evaluation of ion temperature in magnetized plasma

    SciTech Connect

    Hsieh, Tung-Yuan; Kawamori, Eiichirou; Nishida, Yasushi

    2013-02-15

    This paper presents a new design of ion sensitive probe (ISP) that enables collection of pure ion current for accurate measurement of the perpendicular ion temperature in magnetized plasmas. The new type of ISP resolves a longstanding issue widely observed in ISP type measurements, namely, that the current-voltage characteristic is smeared by an unexpected electron current in the standard ISP model. The new ISP is equipped with a fine scale metal mesh on the sensor entrance to prevent electrons from flowing to the sensor, a phenomenon considered to be caused by the space-charge effect. The new ISP successfully measured the ion temperature of electron cyclotron resonance plasmas.

  16. Single drop solution electrode glow discharge for plasma assisted-chemical vapor generation: sensitive detection of zinc and cadmium in limited amounts of samples.

    PubMed

    Li, Zhi-ang; Tan, Qing; Hou, Xiandeng; Xu, Kailai; Zheng, Chengbin

    2014-12-16

    A simple and sensitive approach is proposed and evaluated for determination of ultratrace Zn and Cd in limited amounts of samples or tens of cells based on a novel single drop (5-20 μL) solution electrode glow discharge assisted-chemical vapor generation technique. Volatile species of Zn and Cd were immediately generated and separated from the liquid phase for transporting to atomic fluorescence or atomic mass spectrometric detectors for their determination only using hydrogen when the glow discharge was ignited between the surface of a liquid drop and the tip of a tungsten electrode. Limits of detection are better than 0.01 μg L(-1) (0.2 pg) for Cd and 0.1 μg L(-1) (2 pg) for Zn, respectively, and comparable or better than the previously reported results due to only a 20 μL sampling volume required, which makes the proposed technique convenient for the determination of Zn and Cd in limited amounts of samples or even only tens of cells. The proposed method not only retains the advantages of conventional chemical vapor generation but also provides several unique advantages, including better sensitivity, lower sample and power consumption, higher chemical vapor generation efficiencies and simpler setup, as well as greener analytical chemistry. The utility of this technique was demonstrated by the determination of ultratrace Cd and Zn in several single human hair samples, Certified Reference Materials GBW07601a (human hair powder) and paramecium cells. PMID:25409265

  17. Expression of the nifBfdxNnifOQ region of Azotobacter vinelandii and its role in nitrogenase activity.

    PubMed Central

    Rodríguez-Quiñones, F; Bosch, R; Imperial, J

    1993-01-01

    The nifBQ transcriptional unit of Azotobacter vinelandii has been previously shown to be required for activity of the three nitrogenase systems, Mo nitrogenase, V nitrogenase, and Fe nitrogenase, present in this organism. We studied regulation of expression and the role of the nifBQ region by means of translational beta-galactosidase fusions to each of the five open reading frames: nifB, orf2 (fdxN), orf3 (nifO), nifQ, and orf5. Expression of the first three open reading frames was observed under all three diazotrophic conditions; expression of orf5 was never observed. Genes nifB and fdxN were expressed at similar levels. With Mo, expression of nifO and nifQ was approximately 20- and approximately 400-fold lower than that of fdxN, respectively. Without Mo, expression of nifB dropped three- to fourfold and that of nifQ dropped to the detection limit. However, expression of nifO increased threefold. The products of nifB, fdxN, nifO, and nifQ have been visualized in A. vinelandii as beta-galactosidase fusion proteins with the expected molecular masses. The NifB- fusion lacked activity for any of the three nitrogenase systems and showed an iron-molybdenum cofactor-deficient phenotype in the presence of Mo. The FdxN- mutation resulted in reduced nitrogenase activities, especially when V was present. Dinitrogenase activity in extracts was similarly affected, suggesting a role of FdxN in iron-molybdenum cofactor synthesis. The NifO(-)-producing mutation did not affect any of the nitrogenases under standard diazotrophic conditions. The NifQ(-)-producing mutation resulted in an increased (approximately 1,000-fold) Mo requirement for Mo nitrogenase activity, a phenotype already observed with Klebsiella pneumoniae. No effect of the NifQ(-)-producing mutation on V or Fe nitrogenase was found; this is consistent with its very low expression under those conditions. Mutations in orf5 had no effect on nitrogenase activity. Images PMID:8491713

  18. Optomechanical considerations for the VISAR diagnostic at the National Ignition Facility (NIF)

    NASA Astrophysics Data System (ADS)

    Kaufman, Morris I.; Celeste, John R.; Frogget, Brent C.; Lee, Tony L.; MacGowan, Brian J.; Malone, Robert M.; Ng, Edmund W.; Tunnell, Tom W.; Watts, Phillip W.

    2006-08-01

    The National Ignition Facility (NIF) requires optical diagnostics for measuring shock velocities in shock physics experiments. The velocity interferometer for any reflector measures shock velocities at a location remote to the NIF target chamber. Our team designed two systems, one for a polar port orientation, and the other to accommodate two equatorial ports. The polar-oriented design requires a 48-m optical relay to move the light from inside the target chamber to a separately housed measurement and laser illumination station. The currently operational equatorial design requires a much shorter relay of 21 m. Both designs posed significant optomechanical challenges due to the long optical path length, large quantity of optical elements, and stringent NIF requirements. System design had to tightly control the use of lubricants and materials, especially those inside the vacuum chamber; tolerate earthquakes and radiation; and consider numerous other tolerance, alignment, and steering adjustment issues. To ensure compliance with NIF performance requirements, we conducted a finite element analysis.

  19. Progress on Converting a NIF Quad to Eight, Petawatt Beams for Advanced Radiography

    SciTech Connect

    Crane, J K

    2009-10-19

    We are converting a quad of NIF beamlines into eight, short-pulse (1-50 ps), petawatt-class beams for advanced radiography and fast ignition experiments. This paper describes progress toward completing this project.

  20. Optomechanical considerations for the VISAR diagnostic at the National Ignition Facility (NIF)

    SciTech Connect

    Kaufman, Morris I.; Celeste, John R.; Frogget, Brent C.; Lee, Tony L.; GacGowan, Brian J.; Malone, Robert M.; Ng, Edmund W.; Tunnell, Tom W.; Watts, Phillip W.

    2006-09-01

    The National Ignition Facility (NIF) requires optical diagnostics for measuring shock velocities in shock physics experiments. The velocity interferometer for any reflector measures shock velocities at a location remote to the NIF target chamber. Our team designed two systems, one for a polar port orientation, and the other to accommodate two equatorial ports. The polar-oriented design requires a 48-m optical relay to move the light from inside the target chamber to a separately housed measurement and laser illumination station. The currently operational equatorial design requires a much shorter relay of 21 m. Both designs posed significant optomechanical challenges due to the long optical path length, large quantity of optical elements, and stringent NIF requirements. System design had to tightly control the use of lubricants and materials, especially those inside the vacuum chamber; tolerate earthquakes and radiation; and consider numerous other tolerance, alignment, and steering adjustment issues. To ensure compliance with NIF performance requirements, we conducted a finite element analysis.

  1. Progress on converting a NIF quad to eight, petawatt beams for advanced radiography

    NASA Astrophysics Data System (ADS)

    Crane, J. K.; Tietbohl, G.; Arnold, P.; Bliss, E. S.; Boley, C.; Britten, G.; Brunton, G.; Clark, W.; Dawson, J. W.; Fochs, S.; Hackel, R.; Haefner, C.; Halpin, J.; Heebner, J.; Henesian, M.; Hermann, M.; Hernandez, J.; Kanz, V.; McHale, B.; McLeod, J. B.; Nguyen, H.; Phan, H.; Rushford, M.; Shaw, B.; Shverdin, M.; Sigurdsson, R.; Speck, R.; Stolz, C.; Trummer, D.; Wolfe, J.; Wong, J. N.; Siders, G. C.; Barty, C. P. J.

    2010-08-01

    We are converting a quad of NIF beamlines into eight, short-pulse (1-50 ps), petawatt-class beams for advanced radiography and fast ignition experiments. This paper describes progress toward completing this project.

  2. Facilitization of the National Ignition Facility (NIF) for radiation sciences experiments

    SciTech Connect

    Davis, J.F.

    1995-12-15

    This report will provide a summary report of work performed under Subcontract B324681 from November 1 through December 14, 1995 and covers work relevant to Subtasks 1-11. The work performed under this contract was presented and reviewed at the NIF Radiation Sciences Users Group meeting held on November 29-30. Present where senior representatives from the NIF Project, the DOE Office of the NIF, the DOE ICF program, and the Defense Nuclear Agency. This report is divided into seven sections, not including the Introduction to include; Potential Test Capability, Operational Scenarios, Facilitization Issues, Security Issues, Performance/Cost/Risk Considerations, a Summary of Requested Modifications to the NIF and finally, Conclusions. Within each section will be a short narrative and a copy of the view graph presentation.

  3. COATING AND MANDREL EFFECTS ON FABRICATION OF GLOW DISCHARGE POLYMER NIF SCALE INDIRECT DRIVE CAPSULES

    SciTech Connect

    NIKROO,A; PONTELANDOLFO,JM; CASTILLO,ER

    2002-04-01

    OAK A271 COATING AND MANDREL EFFECTS ON FABRICATION OF GLOW DISCHARGE POLYMER NIF SCALE INDIRECT DRIVE CAPSULES. Targets for the National Ignition Facility (NIF) need to be about 200 {micro}m thick and 2 mm in diameter. These dimensions are well beyond those currently fabricated on a routine basis. They have investigated fabrication of near NIF scale targets using the depolymerizable mandrel technique. Poly-alpha-methylstyrene (PAMS) mandrels, about 2 mm in diameter, of varying qualities were coated with as much as 125 {micro}m of glow discharge polymer (GDP). The surface finish of the final shells was examined using a variety of techniques. A clear dependence of the modal spectrum of final GDP shell on the quality of the initial PAMS mandrels was observed. isolated features were found to be the greatest cause for a shell not meeting the NIF standard.

  4. sensor electrodes

    NASA Astrophysics Data System (ADS)

    Zhang, Zhiqiang; Ma, Congcong; He, Lian; Zhu, Shijin; Hao, Xiaodong; Xie, Wanyi; Zhang, Wei; Zhang, Yuxin

    2014-11-01

    In this work, an ultrafast and facile method is developed to synthesize Au(I)-dodecanethiolate nanotubes (Au(I)NTs) with the assistance of glycyl-glycyl-glycine (G-G-G). Transmission electron microscopy (TEM) images reveal that the as-prepared Au(I)NTs can be obtained in a 2-h reaction instead of a previous 24-h reaction and are uniform with a hollow structure and smooth surface by virtue of the G-G-G peptide tubular template. According to structural analysis, a possible preparative mechanism is proposed that the G-G-G peptide could help to curl into tube-like morphology in alkaline situation spontaneously to accelerate the formation of Au(I)NTs. Meanwhile, PVDF-stabilized Au(I)NT-modified glassy carbon electrodes present their promising potential for Hg2+ detection.

  5. Effect of point mutations on Herbaspirillum seropedicae NifA activity

    PubMed Central

    Aquino, B.; Stefanello, A.A.; Oliveira, M.A.S.; Pedrosa, F.O.; Souza, E.M.; Monteiro, R.A.; Chubatsu, L.S.

    2015-01-01

    NifA is the transcriptional activator of the nif genes in Proteobacteria. It is usually regulated by nitrogen and oxygen, allowing biological nitrogen fixation to occur under appropriate conditions. NifA proteins have a typical three-domain structure, including a regulatory N-terminal GAF domain, which is involved in control by fixed nitrogen and not strictly required for activity, a catalytic AAA+ central domain, which catalyzes open complex formation, and a C-terminal domain involved in DNA-binding. In Herbaspirillum seropedicae, a β-proteobacterium capable of colonizing Graminae of agricultural importance, NifA regulation by ammonium involves its N-terminal GAF domain and the signal transduction protein GlnK. When the GAF domain is removed, the protein can still activate nif genes transcription; however, ammonium regulation is lost. In this work, we generated eight constructs resulting in point mutations in H. seropedicae NifA and analyzed their effect on nifH transcription in Escherichia coli and H. seropedicae. Mutations K22V, T160E, M161V, L172R, and A215D resulted in inactive proteins. Mutations Q216I and S220I produced partially active proteins with activity control similar to wild-type NifA. However, mutation G25E, located in the GAF domain, resulted in an active protein that did not require GlnK for activity and was partially sensitive to ammonium. This suggested that G25E may affect the negative interaction between the N-terminal GAF domain and the catalytic central domain under high ammonium concentrations, thus rendering the protein constitutively active, or that G25E could lead to a conformational change comparable with that when GlnK interacts with the GAF domain. PMID:26176311

  6. Antagonism of CD11b with Neutrophil Inhibitory Factor (NIF) Inhibits Vascular Lesions in Diabetic Retinopathy

    PubMed Central

    Veenstra, Alexander A.; Tang, Jie; Kern, Timothy S.

    2013-01-01

    Leukocytes and proteins that govern leukocyte adhesion to endothelial cells play a causal role in retinal abnormalities characteristic of the early stages of diabetic retinopathy, including diabetes-induced degeneration of retinal capillaries. Leukocyte integrin αmβ2 (CD11b/CD18, MAC1), a protein mediating adhesion, has been shown to mediate damage to endothelial cells by activated leukocytes in vitro. We hypothesized that Neutrophil Inhibitory Factor (NIF), a selective antagonist of integrin αmβ2, would inhibit the diabetes-induced degeneration of retinal capillaries by inhibiting the excessive interaction between leukocytes and retinal endothelial cells in diabetes. Wild type animals and transgenic animals expressing NIF were made diabetic with streptozotocin and assessed for diabetes-induced retinal vascular abnormalities and leukocyte activation. To assess if the leukocyte blocking therapy compromised the immune system, animals were challenged with bacteria. Retinal superoxide production, leukostasis and leukocyte superoxide production were increased in wild type mice diabetic for 10 weeks, as was the ability of leukocytes isolated from diabetic animals to kill retinal endothelial cells in vitro. Retinal capillary degeneration was significantly increased in wild type mice diabetic 40 weeks. In contrast, mice expressing NIF did not develop any of these abnormalities, with the exception that non-diabetic and diabetic mice expressing NIF generated greater amounts of superoxide than did similar mice not expressing NIF. Importantly, NIF did not significantly impair the ability of mice to clear an opportunistic bacterial challenge, suggesting that NIF did not compromise immune surveillance. We conclude that antagonism of CD11b (integrin αmβ2) by NIF is sufficient to inhibit early stages of diabetic retinopathy, while not compromising the basic immune response. PMID:24205223

  7. Advances in Inertial Confinement Fusion at the National Ignition Facility (NIF)

    SciTech Connect

    Moses, E

    2009-10-15

    The 192-beam National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory (LLNL) in Livermore, CA, is now operational and conducting experiments. NIF, the flagship facility of the U.S. Inertial Confinement Fusion (ICF) Program, will achieve high-energy-density conditions never previously obtained in the laboratory - temperatures over 100 million K, densities of 1,000 g/cm3, and pressures exceeding 100 billion atmospheres. Such conditions exist naturally only in the interiors of the stars and during thermonuclear burn. Demonstration of ignition and thermonuclear burn in the laboratory is a major NIF goal. To date, the NIF laser has demonstrated all pulse shape, beam quality, energy, and other specifications required to meet the ignition challenge. On March 10, 2009, the NIF laser delivered 1.1 MJ of ultraviolet laser energy to target chamber center, approximately 30 times more energy than any previous facility. The ignition program at NIF is the National Ignition Campaign (NIC), a national collaboration for ignition experimentation with participation from General Atomics, LLNL, Los Alamos National Laboratory (LANL), Sandia National Laboratories (SNL), and the University of Rochester Laboratory for Laser Energetics (LLE). The achievement of ignition at NIF will demonstrate the scientific feasibility of ICF and focus worldwide attention on fusion as a viable energy option. A particular energy concept under investigation is the LIFE (Laser Inertial Fusion Energy) scheme. The LIFE engine is inherently safe, minimizes proliferation concerns associated with the nuclear fuel cycle, and can provide a sustainable carbon-free energy generation solution in the 21st century. This talk will describe NIF and its potential as a user facility and an experimental platform for high-energy-density science, NIC, and the LIFE approach for clean, sustainable energy.

  8. 3D Simulations of the NIF Indirect Drive Ignition Target Design

    SciTech Connect

    Jones, O S; Milovich, J L; Callahan, D A; Edwards, M J; Landen, O L; Salmonson, J D; Clark, D S; Haan, S W; Marinak, M M; Patel, M V; Langer, S H; Sepke, S M; Springer, P T; Hatchett, S P

    2010-01-05

    The radiation hydrodynamics code Hydra is used to quantify the sensitivity of different NIF ignition point designs to several 3D effects. Each of the 48 NIF quads is included in the calculations and is allowed to have different power. With this model they studied the effect on imploded core symmetry of discrete laser spots (as opposed to idealized azimuthally-averaged rings) and random variations in laser power.

  9. Comparison between single- and dual-electrode ion source systems for low-energy ion transport

    SciTech Connect

    Vasquez, M. Jr.; Tokumura, S.; Kasuya, T.; Maeno, S.; Wada, M.

    2012-11-06

    Extraction of ions with energies below 100 eV has been demonstrated using a hot-cathode multi-cusp ion source equipped with extraction electrodes made of thin wires. Two electrode geometries, a single-electrode system, and a dual-electrode system were built and tested. The single-electrode configuration showed high ion beam current densities at shorter distances from the electrode but exhibited rapid attenuation as the distance from the electrode increased. Beam angular spread measurements showed similar beam divergence for both electrode configurations at low plasma densities. At high plasma densities and low extraction potentials, the single-electrode system showed the angular spread twice as large as that of the dual-electrode system. Energy distribution analyses showed a broader energy spread for ion beams extracted from a single-electrode set-up.

  10. Low-voltage pulsed plasma discharges inside water using a bubble self-generating parallel plate electrode with a porous ceramic

    NASA Astrophysics Data System (ADS)

    Muradia, Sonia; Nagatsu, Masaaki

    2013-04-01

    Characteristics of pulsed bubbles discharges in water were investigated using parallel punched plate electrodes with a porous thin ceramic plate inserted between two metal plates. The micro-bubbles were generated just beneath the porous ceramic plate by flowing gas through it. The transition from spiky dielectric barrier discharges to pulsed glow discharges enables efficient bubble discharges at a relatively low voltage of 1.8 ˜ 4.0 kV of the 5 kHz square-waves with a pulse-width of about 750 ns. With 80% Ar and 20% O2 mixture gas at 4.0 kV, the 50 mg/l Indigo Carmine aqueous solution was efficiently decolorized within about 3 min.

  11. Abundance and genetic diversity of nifH gene sequences in anthropogenically affected Brazilian mangrove sediments.

    PubMed

    Dias, Armando Cavalcante Franco; Pereira e Silva, Michele de Cassia; Cotta, Simone Raposo; Dini-Andreote, Francisco; Soares, Fábio Lino; Salles, Joana Falcão; Azevedo, João Lúcio; van Elsas, Jan Dirk; Andreote, Fernando Dini

    2012-11-01

    Although mangroves represent ecosystems of global importance, the genetic diversity and abundance of functional genes that are key to their functioning scarcely have been explored. Here, we present a survey based on the nifH gene across transects of sediments of two mangrove systems located along the coast line of São Paulo state (Brazil) which differed by degree of disturbance, i.e., an oil-spill-affected and an unaffected mangrove. The diazotrophic communities were assessed by denaturing gradient gel electrophoresis (DGGE), quantitative PCR (qPCR), and clone libraries. The nifH gene abundance was similar across the two mangrove sediment systems, as evidenced by qPCR. However, the nifH-based PCR-DGGE profiles revealed clear differences between the mangroves. Moreover, shifts in the nifH gene diversities were noted along the land-sea transect within the previously oiled mangrove. The nifH gene diversity depicted the presence of nitrogen-fixing bacteria affiliated with a wide range of taxa, encompassing members of the Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Firmicutes, and also a group of anaerobic sulfate-reducing bacteria. We also detected a unique mangrove-specific cluster of sequences denoted Mgv-nifH. Our results indicate that nitrogen-fixing bacterial guilds can be partially endemic to mangroves, and these communities are modulated by oil contamination, which has important implications for conservation strategies. PMID:22941088

  12. Abundance and Genetic Diversity of nifH Gene Sequences in Anthropogenically Affected Brazilian Mangrove Sediments

    PubMed Central

    Dias, Armando Cavalcante Franco; Pereira e Silva, Michele de Cassia; Cotta, Simone Raposo; Dini-Andreote, Francisco; Soares, Fábio Lino; Salles, Joana Falcão; Azevedo, João Lúcio; van Elsas, Jan Dirk

    2012-01-01

    Although mangroves represent ecosystems of global importance, the genetic diversity and abundance of functional genes that are key to their functioning scarcely have been explored. Here, we present a survey based on the nifH gene across transects of sediments of two mangrove systems located along the coast line of São Paulo state (Brazil) which differed by degree of disturbance, i.e., an oil-spill-affected and an unaffected mangrove. The diazotrophic communities were assessed by denaturing gradient gel electrophoresis (DGGE), quantitative PCR (qPCR), and clone libraries. The nifH gene abundance was similar across the two mangrove sediment systems, as evidenced by qPCR. However, the nifH-based PCR-DGGE profiles revealed clear differences between the mangroves. Moreover, shifts in the nifH gene diversities were noted along the land-sea transect within the previously oiled mangrove. The nifH gene diversity depicted the presence of nitrogen-fixing bacteria affiliated with a wide range of taxa, encompassing members of the Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Firmicutes, and also a group of anaerobic sulfate-reducing bacteria. We also detected a unique mangrove-specific cluster of sequences denoted Mgv-nifH. Our results indicate that nitrogen-fixing bacterial guilds can be partially endemic to mangroves, and these communities are modulated by oil contamination, which has important implications for conservation strategies. PMID:22941088

  13. Hot-spot mix in ignition-scale implosions on the NIF

    SciTech Connect

    Regan, S. P.; Epstein, R.; McCrory, R. L.; Meyerhofer, D. D.; Sangster, T. C.; Hammel, B. A.; Suter, L. J.; Ralph, J.; Scott, H.; Barrios, M. A.; Bradley, D. K.; Callahan, D. A.; Cerjan, C.; Collins, G. W.; Dixit, S. N.; Doeppner, T.; Edwards, M. J.; Farley, D. R.; Glenn, S.; Glenzer, S. H.; and others

    2012-05-15

    Ignition of an inertial confinement fusion (ICF) target depends on the formation of a central hot spot with sufficient temperature and areal density. Radiative and conductive losses from the hot spot can be enhanced by hydrodynamic instabilities. The concentric spherical layers of current National Ignition Facility (NIF) ignition targets consist of a plastic ablator surrounding a thin shell of cryogenic thermonuclear fuel (i.e., hydrogen isotopes), with fuel vapor filling the interior volume [S. W. Haan et al., Phys. Plasmas 18, 051001 (2011)]. The Rev. 5 ablator is doped with Ge to minimize preheat of the ablator closest to the DT ice caused by Au M-band emission from the hohlraum x-ray drive [D. S. Clark et al., Phys. Plasmas 17, 052703 (2010)]. Richtmyer-Meshkov and Rayleigh-Taylor hydrodynamic instabilities seeded by high-mode () ablator-surface perturbations can cause Ge-doped ablator to mix into the interior of the shell at the end of the acceleration phase [B. A. Hammel et al., Phys. Plasmas 18, 056310 (2011)]. As the shell decelerates, it compresses the fuel vapor, forming a hot spot. K-shell line emission from the ionized Ge that has penetrated into the hot spot provides an experimental signature of hot-spot mix. The Ge emission from tritium-hydrogen-deuterium (THD) and deuterium-tritium (DT) cryogenic targets and gas-filled plastic-shell capsules, which replace the THD layer with a mass-equivalent CH layer, was examined. The inferred amount of hot-spot-mix mass, estimated from the Ge K-shell line brightness using a detailed atomic physics code [J. J. MacFarlane et al., High Energy Density Phys. 3, 181 (2006)], is typically below the 75-ng allowance for hot-spot mix [S. W. Haan et al., Phys. Plasmas 18, 051001 (2011)]. Predictions of a simple mix model, based on linear growth of the measured surface-mass modulations, are consistent with the experimental results.

  14. Identification and functional characterization of NifA variants that are independent of GlnB activation in the photosynthetic bacterium Rhodospirillum rubrum.

    PubMed

    Zou, Xiaoxiao; Zhu, Yu; Pohlmann, Edward L; Li, Jilun; Zhang, Yaoping; Roberts, Gary P

    2008-09-01

    The activity of NifA, the transcriptional activator of the nitrogen fixation (nif) gene, is tightly regulated in response to ammonium and oxygen. However, the mechanisms for the regulation of NifA activity are quite different among various nitrogen-fixing bacteria. Unlike the well-studied NifL-NifA regulatory systems in Klebsiella pneumoniae and Azotobacter vinelandii, in Rhodospirillum rubrum NifA is activated by a direct protein-protein interaction with the uridylylated form of GlnB, which in turn causes a conformational change in NifA. We report the identification of several substitutions in the N-terminal GAF domain of R. rubrum NifA that allow NifA to be activated in the absence of GlnB. Presumably these substitutions cause conformational changes in NifA necessary for activation, without interaction with GlnB. We also found that wild-type NifA can be activated in a GlnB-independent manner under certain growth conditions, suggesting that some other effector(s) can also activate NifA. An attempt to use Tn5 mutagenesis to obtain mutants that altered the pool of these presumptive effector(s) failed, though much rarer spontaneous mutations in nifA were detected. This suggests that the necessary alteration of the pool of effector(s) for NifA activation cannot be obtained by knockout mutations. PMID:18757802

  15. resterilizable electrode for electrosurgery

    NASA Technical Reports Server (NTRS)

    Engstrom, E. R.; Houge, J. C.

    1979-01-01

    Required properties of flexibility, electrical conductivity, tensile strength, and tear resistance of electrosurgical electrodes is retained through utilization of flexible-polymer/conductive particle composites for electrodes.

  16. The N-terminal and C-terminal portions of NifV are encoded by two different genes in Clostridium pasteurianum.

    PubMed

    Wang, S Z; Dean, D R; Chen, J S; Johnson, J L

    1991-05-01

    The nifV gene products from Azotobacter vinelandii and Klebsiella pneumoniae share a high level of primary sequence identity and are proposed to catalyze the synthesis of homocitrate. While searching for potential nif (nitrogen fixation) genes within the genomic region located downstream from the nifN-B gene of Clostridium pasteurianum, we observed two open reading frames (ORFs) whose deduced amino acid sequences exhibit nonoverlapping sequence identity to different portions of the nifV gene products from A. vinelandii and K. pneumoniae. Conserved regions were located between the C-terminal 195 amino acid residues of the first ORF and the C-terminal portion of the nifV gene product and between the entire sequence of the second ORF (269 amino acid residues) and the N-terminal portion of the nifV gene product. We therefore designated the first ORF nifV omega and the second ORF nifV alpha. The deduced amino acid sequences of nifV omega and nifV alpha were also found to have sequence similarity when compared with the primary sequence of the leuA gene product from Salmonella typhimurium, which encodes alpha-isopropylmalate synthase. Marker rescue experiments were performed by recombining nifV omega and nifV alpha from C. pasteurianum, singly and in combination, into the genome of an A. vinelandii mutant strain which has an insertion and a deletion mutation located within its nifV gene. A NifV+ phenotype was obtained only when both the C. pasteurianum nifV omega and nifV alpha genes were introduced into the chromosome of this mutant strain. These results suggest that the nifV omega and nifV alpha genes encode separate domains, both of which are required for homocitrate synthesis in C. pasteurianum. PMID:2022611

  17. Controlling electrode gap during vacuum arc remelting at low melting current

    DOEpatents

    Williamson, Rodney L.; Zanner, Frank J.; Grose, Stephen M.

    1997-01-01

    An apparatus and method for controlling electrode gap in a vacuum arc remelting furnace, particularly at low melting currents. Spectrographic analysis is performed of the metal vapor plasma, from which estimates of electrode gap are derived.

  18. Controlling electrode gap during vacuum arc remelting at low melting current

    DOEpatents

    Williamson, R.L.; Zanner, F.J.; Grose, S.M.

    1997-04-15

    An apparatus and method are disclosed for controlling electrode gap in a vacuum arc remelting furnace, particularly at low melting currents. Spectrographic analysis is performed of the metal vapor plasma, from which estimates of electrode gap are derived. 5 figs.

  19. Identification of a positive transcription regulatory element within the coding region of the nifLA operon in Azotobacter vinelandii.

    PubMed

    Mitra, Ranjana; Das, Hirendra K; Dixit, Aparna

    2005-07-01

    Nitrogen fixation in Azotobacter vinelandii is regulated by the nifLA operon. NifA activates the transcription of nif genes, while NifL antagonizes the transcriptional activator NifA in response to fixed nitrogen and molecular oxygen levels. However, transcriptional regulation of the nifLA operon of A. vinelandii itself is not fully understood. Using the S1 nuclease assay, we mapped the transcription start site of the nifLA operon, showing it to be similar to the sigma54-dependent promoters. We also identified a positive cis-acting regulatory element (+134 to +790) of the nifLA operon within the coding region of the nifL gene of A. vinelandii. Deletion of this element results in complete loss of promoter activity. Several protein factors bind to this region, and the specific binding sites have been mapped by DNase I foot printing. Two of these sites, namely dR1 (+134 to +204) and dR2 (+745 to +765), are involved in regulating the nifLA promoter activity. The absence of NtrC-like binding sites in the upstream region of the nifLA operon in A. vinelandii makes the identification of these downstream elements a highly significant finding. The interaction of the promoter with the proteins binding to the dR2 region spanning +745 to +765 appears to be dependent on the face of the helix as introduction of 4 bases just before this region completely disrupts promoter activity. Thus, the positive regulatory element present within the BglII-BglII fragment may play, in part; an important role in nifLA regulation in A. vinelandii. PMID:16000781

  20. The National Ignition Facility (NIF) and the National Ignition Campaign (NIC)

    SciTech Connect

    Moses, E

    2009-09-17

    The National Ignition Facility (NIF), the world's largest and most powerful laser system for inertial confinement fusion (ICF) and experiments studying high-energy-density (HED) science, is now operational at Lawrence Livermore National Laboratory (LLNL). NIF construction was certified by the Department of Energy as complete on March 27, 2009. NIF, a 192-beam Nd:glass laser facility, will ultimately produce 1.8-MJ, 500-TW of 351-nm third-harmonic, ultraviolet light. On March 10, 2009, total 192-beam energy of 1.1 MJ was demonstrated; this is approximately 30 times more energy than ever produced in an ICF laser system. The principal goal of NIF is to achieve ignition of a deuterium-tritium (DT) fuel capsule and provide access to HED physics regimes needed for experiments related to national security, fusion energy and broader frontier scientific exploration. NIF experiments in support of indirect-drive ignition began in August 2009. These first experiments represent the next phase of the National Ignition Campaign (NIC). The NIC is a national effort to achieve fusion ignition and is coordinated through a detailed execution plan that includes the science, technology, and equipment. Equipment required for ignition experiments includes diagnostics, a cryogenic target manipulator, and user optics. Participants in this effort include LLNL, General Atomics (GA), Los Alamos National Laboratory (LANL), Sandia National Laboratory (SNL), and the University of Rochester Laboratory for Energetics (LLE). The primary goal for NIC is to have all of the equipment operational, integrated into the facility, and ready to begin a credible ignition campaign in 2010. With NIF now operational, the long-sought goal of achieving self-sustained nuclear fusion and energy gain in the laboratory is much closer to realization. Successful demonstration of ignition and net energy gain on NIF will be a major step towards demonstrating the feasibility of Inertial Fusion Energy (IFE) and will likely

  1. The Azorhizobium caulinodans nifA gene: identification of upstream-activating sequences including a new element, the 'anaerobox'.

    PubMed Central

    Nees, D W; Stein, P A; Ludwig, R A

    1988-01-01

    From nucleotide sequencing analyses, the A. caulinodans nifA gene seems to be under dual control by the Ntr (in response to available N) and Fnr (in response to available O2) transcriptional activation/repression systems. Because it fixes N2 in two contexts, the Ntr system might regulate A. caulinodans nif gene expression ex planta, while the Fnr system might similarly regulate in planta. As nifA upstream-activating elements, we have identified: (i) a gpNifA binding site allowing autogenous nifA regulation, (ii) an Ntr-dependent transcription start, presumably the target of gpNifA activation, and (iii) an "anaerobox" tetradecameric nucleotide sequence that is precisely conserved among O2 regulated enteric bacterial genes controlled by the gpFnr transcriptional activator. Because it is precisely positioned upstream of enteric bacterial transcriptional starts, the "anaerobox" sequence may constitute the gpFnr DNA binding site. If so, then a second, Ntr-independent nifA transcription start may exist. We have also deduced the A. caulinodans nifA open reading frame and have compared the gene product (gpNifA) with those of other N2-fixing organisms. These proteins exhibit strongly conserved motifs: (i) sites conserved among ATP-binding proteins, (ii) an interdomain linker region, and (iii) a C-terminal alpha-helix-turn-alpha-helix DNA binding site. PMID:3186446

  2. Sputter-deposited Be ablators for NIF target capsules

    SciTech Connect

    McEachern, R.; Clford, C.; Cook, R.; Makowiecki, E.; Wallace, R.

    1997-03-26

    We have performed a series of preliminary experiments to determine whether sputter deposition of doped Be is a practical route to producing NIF target capsules with Be ablators. Films ranging in thickness from 7 to {approximately} 120 {micro}m have been deposited on spherical polymer mandrels using a bounce pan to ensure uniform coating. With no voltage bias applied to the pan, relatively porous coatings were formed that were highly permeable to hydrogen. The surface finish of these films ranged from {approximately}250 nm rms for 13-{micro}m-thick films to a minimum of {approximately}75 nm rms for an 80-{micro}m-thick film. Application of a voltage bias was found to significantly modify the film morphology. At a bias of 120 V, 7-{micro}m-thick films with a dense, fine-grained microstructure were produced. These capsules had a reflective surface with a 50 nm rms roughness. Finally, to demonstrate the ability to produce a graded dopant profile, a coating was produced in which the concentration of added Cu was varied from 2.5 atom % at the beginning to zero after 40 {micro}m of deposition.

  3. The Ignition Physics Campaign on NIF: Status and Progress

    NASA Astrophysics Data System (ADS)

    Edwards, M. J.; Ignition Team

    2016-03-01

    We have made significant progress in ICF implosion performance on NIF since the 2011 IFSA. Employing a 3-shock, high adiabat CH (“High-Foot”) design, total neutron yields have increased 10-fold to 6.3 x1015 (a yield of ∼ 17 kJ, which is greater than the energy invested in the DT fuel ∼ 12kJ). At that level, the yield from alpha self-heating is essentially equivalent to the compression yield, indicating that we are close to the alpha self-heating regime. Low adiabat, 4-shock High Density Carbon (HDC) capsules have been imploded in conventional gas-filled hohlraums, and employing a 6 ns, 2-shock pulse, HDC capsules were imploded in near-vacuum hohlraums with overall coupling ∼ 98%. Both the 4- and 2-shock HDC capsules had very low mix and high yield over simulated performance. Rugby holraums have demonstrated uniform x-ray drive with minimal Cross Beam Energy Transfer (CBET), and we have made good progress in measuring and modelling growth of ablation front hydro instabilities.

  4. Post Shot Simulations of NIF Convergent Ablator Experiments

    NASA Astrophysics Data System (ADS)

    Olson, R. E.; Meezan, N. B.; Hicks, D. G.; Landen, O. L.; Dewald, E. L.; Jones, O. S.; Langer, S. H.; Callahan, D. A.; Petrasso, R. D.; Zylstra, A. B.

    2012-10-01

    Post shot simulations of NIF convergent ablator experiments will be described. The experiments use a streaked radiograph of a backlit capsule implosion to measure the trajectory, velocity, remaining mass, and ablator rhoR and are an important component of the U. S. National Ignition Campaign. The integrated (capsule-in-hohlraum) post shot simulations use measured target parameters, measured laser input powers, measured time-resolved backscatter, and calculated cross-beam power transfer. The integrated calculations are post-processed to provide simulations of the key diagnostics, including: 1) Dante measurements of the hohlraum x-ray flux and spectrum; 2) streaked radiographs of the imploding ablator shell; 3) wedge range filter measurements of D-He3 proton output spectra; and 4) GXD images of the imploded core. The simulated diagnostics are compared to the experimental measurements to provide an assessment of the accuracy of the design code, to enhance understanding of the experiments, and to assist in choosing parameters for subsequent steps in the path towards optimal ignition capsule tuning.

  5. Robotic System for Precision Assembly of NIF Ignition Targets

    SciTech Connect

    Montesanti, R C; Seugling, R M; Klingmann, J L; Dzenitis, E G; Alger, E T; Miller, G L; Kent, R A; Castro, C; Reynolds, J L; Carrillo, M A

    2008-08-27

    This paper provides an overview of the design and testing of a robotic system developed for assembling the inertial confinement fusion ignition targets (depicted in Figures 1 and 2) that will be fielded on the National Ignition Facility (NIF) laser [1]. The system, referred to as the Final Assembly Machine and shown in Figure 3, consists of six groups of stacked axes that allow manipulating millimeter-sized components with submicron precision, integrated with an optical coordinate measuring machine (OCMM) that provides in-situ metrology. Nineteen motorized axes and ten manual axes are used to control the position and orientation of five objects that are predominantly assembled together in a cubic centimeter work zone. An operator-in-the-loop provides top-level control of the system, making it more similar to a surgical robot than to a programmed computer-controlled machine tool. The operator is provided visual feedback by the vision system of the OCMM, and tactile feedback by force and torque sensors embedded in the tooling that holds the major components being assembled. The vision system is augmented with auxiliary mirrors providing multiple viewing directions, and is used to guide the approach and alignment of the components, and to measure the relative position and orientation of the components. The force and torque sensors are used to guide the final approach, alignment, and mating of the components that are designed to slip-fit together, and to monitor that mating while adhesively bonding those components and attaching the target base.

  6. Hugoniot measurements at near Gbar pressures at the NIF

    NASA Astrophysics Data System (ADS)

    Kritcher, Andrea; Swift, Damian; Doeppner, Tilo; Collins, Gilbert; Bachmann, Benjamin; Nilsen, Joe; Chapman, Dave; Correa, Alfredo; Sterne, Phil; Benedict, Lorin; Gaffney, Jim; Kraus, Dominik; Falcone, Roger; Glenzer, Siegfried; Rothman, Steve

    2015-11-01

    Laboratory measurements of the Equation of State (EOS) of matter at high pressure are of great importance in the understanding and accurate modeling of matter at extreme conditions. For example, at hundreds of Mbars - Gbar pressures atomic shell effects may come into play, which can change the predicted compressibility at given pressure due to pressure and temperature ionization. In this work we present measurements of the strong shock hugoniot, at pressures up to 720 Mbar for CH and 630 Mbar for High Density Carbon (HDC, or diamond) at the National Ignition Facility (NIF). Spherically convergent shocks are launched into solid CH or diamond samples, using a hohlraum radiation drive. X-ray radiography is applied to measure the shock speed and infer the mass density profile, enabling determining of the shock pressure and Hugoniot equation of state. This work was performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48. Supported by LDRD 08-ERI-003.

  7. Hot spot conditions achieved in DT implosions on the NIF

    NASA Astrophysics Data System (ADS)

    Patel, P. K.; Callahan, D. A.; Cerjan, C.; Clark, D. S.; Dittrich, T. R.; Doeppner, T.; Edwards, M. J.; Haan, S.; Hinkel, D. E.; Berzak Hopkins, L. F.; Hurricane, O. A.; Kritcher, A. L.; Lindl, J. D.; Ma, T.; Macphee, A. G.; Pak, A. E.; Park, H. S.; Robey, H. F.; Salmonson, J. D.; Spears, B.; Springer, P. T.; Izumi, N.; Khan, S.

    2014-10-01

    We describe a 1D model that uses experimentally measured data to derive the thermodynamic conditions at stagnation of the hot spot, dense fuel, and ablator, in deuterium-tritium (DT) layered implosions on the National Ignition Facility (NIF). Neutron measurements--spectrally, spatially and temporally resolved--are used to infer the hot spot burn-averaged pressure, density, areal density, ion temperature, volume, and internal energy. X-ray spectral measurements are used to infer electron temperature, radiative energy loss, and the presence of ablator mix in the hot spot. In addition, we can calculate the fraction of alpha-particle energy trapped in the hot spot and, hence, estimate the degree of self-heating. Recent DT layered implosions using the high-foot design [Hurricane et al., Nature 506, 343 (2014)] have achieved areal densities and temperatures in the hot spot whereby a significant fraction of the internal energy at stagnation can be attributed to alpha-particle self-heating. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  8. Thin Shell Model for NIF capsule stagnation studies

    NASA Astrophysics Data System (ADS)

    Hammer, J. H.; Buchoff, M.; Brandon, S.; Field, J. E.; Gaffney, J.; Kritcher, A.; Nora, R. C.; Peterson, J. L.; Spears, B.; Springer, P. T.

    2015-11-01

    We adapt the thin shell model of Ott et al. to asymmetric ICF capsule implosions on NIF. Through much of an implosion, the shell aspect ratio is large so the thin shell approximation is well satisfied. Asymmetric pressure drive is applied using an analytic form for ablation pressure as a function of the x-ray flux, as well as time-dependent 3D drive asymmetry from hohlraum calculations. Since deviations from a sphere are small through peak velocity, we linearize the equations, decompose them by spherical harmonics and solve ODE's for the coefficients. The model gives the shell position, velocity and areal mass variations at the time of peak velocity, near 250 microns radius. The variables are used to initialize 3D rad-hydro calculations with the HYDRA and ARES codes. At link time the cold fuel shell and ablator are each characterized by a density, adiabat and mass. The thickness, position and velocity of each point are taken from the thin shell model. The interior of the shell is filled with a uniform gas density and temperature consistent with the 3/2PV energy found from 1D rad-hydro calculations. 3D linked simulations compare favorably with integrated simulations of the entire implosion. Through generating synthetic diagnostic data, the model offers a method for quickly testing hypothetical sources of asymmetry and comparing with experiment. Prepared by LLNL under Contract DE-AC52-07NA27344.

  9. Ultrasonic Testing of NIF Amplifier FAU Top Plates

    SciTech Connect

    Chinn, D J; Huber, R D; Haskins, J J; Rodriguez, J A; Souza, P R; Le, T V

    2002-05-07

    A key component in the National Ignition Facility (NIF) laser optic system is the amplifier frame assembly unit (FAU). The cast aluminum top plate that supports the FAU is required to withstand loads that would occur during an earthquake with a recurrence period of 1000 years. The stringent seismic requirements placed on the FAU top plate induced a study of the cast aluminum material used in the top plate. Ultrasonic testing was used to aid in characterizing the aluminum material used in the plates. This report documents the work performed using contact ultrasonic testing to characterize the FAU top plate material. The ultrasonic work reported here had 3 objectives: (1) inspect the plate material before cyclic testing conducted at the Pacific Earthquake Engineering Research Center (PEER); (2) determine the overall quality of individual plates; and (3) detect large defects in critical areas of individual plates. Section III, ''Pre-cyclic test inspection'', describes work performed in support of Objective 1. Section IV, ''Ultrasonic field measurements'', describes work performed in support of Objectives 2 and 3.

  10. 3D studies of the NIF symmetry tuning targets

    NASA Astrophysics Data System (ADS)

    Milovich, J.; Jones, O.; Edwards, M.; Weber, S.; Dewald, E.; Landen, O.; Marinak, M.

    2009-11-01

    Minimizing radiation drive asymmetries is necessary for a successful ignition campaign. Since the ignition capsule symmetry is most sensitive to the foot (first 2 ns) and the peak of the laser pulse, two different targets will be fielded on the NIF: re-emit and symmetry capsules (Sym-Caps). The first measures the incoming flux asymmetries during the foot by observing the re-radiated flux of a high-Z ball in place of the ignition capsule. The Sym-Caps resemble the ignition target with the frozen DT layer replaced by an equivalent mass of ablator material, thus preserving the hydrodynamic implosion properties. By measuring the x-ray self-emission near peak compression the ignition capsule core shape can be tuned. Simulations with 2D radiation-hydrodynamic simulations codes omit 3D effects in the hohlraum such as diagnostic holes, capsule roughness, shot-to-shot variations caused by laser beam power imbalances and pointing errors. We study these effects by performing 3D simulations using HYDRA and found that tuning the laser pulse using a finite number of shots is not substantially compromised.

  11. A Retrieval System for Radioactive Target Materials at the NIF

    NASA Astrophysics Data System (ADS)

    Krieger, M.; Shibata, K.; Fallica, J.; Henchen, R.; Pogozelski, E.; Padalino, S.; Sangster, T. C.; Suny Collaboration; Laboratory Collaboration

    2011-10-01

    Currently, solid radioactive material collection from the NIF target chamber is performed via the DIM. The retrieval process takes several hours to complete. To decrease this time for short lived radioisotopes, the Target Materials Retrieval System (TMRS) is being designed to move a radioactive sample from the target chamber to the counting station in less than 50 seconds, using a closed-loop helium filled RaPToRS system. The TMRS consists of three components: the retrieval apparatus, RaPToRS and the counting station. Starting at 0.5 meters from TCC, the sample will move from the vacuum chamber, travel through 60 meters of 10 centimeter diameter RaPToRS tubes, reaching speeds of 10 m/s. The sample will then arrive at the counting station, where it be robotically placed in front of a gamma ray detector. The use of helium will decrease background gamma radiation produced by activated N2 normally found in a pressurized air system. This work was supported in part by the US Department of Energy through the LLE.

  12. Design study for a diverging supernova explosion experiment on NIF

    NASA Astrophysics Data System (ADS)

    Flaig, Markus; Plewa, Tomasz; Keiter, Paul; Grosskopf, Michael; Kuranz, Carolyn; Drake, Paul; Park, Hye-Sook

    2013-10-01

    We report on design simulations of a spherically-diverging, multi-interface, supernova-relevant Rayleigh-Taylor experiment (DivSNRT) to be carried out at the National Ignition Facility (NIF). The simulations are performed in two and three dimensions using the block-adaptive, multi-group radiative diffusion hydrodynamics code CRASH and the FLASH-based MHD code Proteus. In the present study, we concentrate mainly on a planar variant of the experiment. We assess the sensitivity of the Rayleigh-Taylor instability growth on numerical discretization, variations in the laser drive energy and the manufacturing noise at the material interfaces. We find that a simple buoyancy-drag model accurately predicts the mixed-layer width obtained in the simulations. We use synthetic radiographs to optimize the diagnostic system and the experimental setup. Finally, we perform a series of exploratory MHD simulations and investigate the self-generation of magnetic fields and their role in the system evolution. Supported by the DOE grant DE-SC0008823.

  13. The Defect Induced Mix Experiment (DIME) for NIF

    SciTech Connect

    Schmitt, Mark J; Bradley, Paul A; Cobble, James A; Hakel, Peter; Hsu, Scott C; Krasheninnikova, Natalia S; Kyrala, George A; Murphy, Thomas J; Obrey, Kimberly A; Shah, Rahul C; Tregillis, Ian L

    2012-06-18

    LANL will perform two Defect Induced Mix Experiment (DIME) implosion campaigns on NIF in July and September, 2012. This presentation describes the goals for these shots and the experimental configuration and diagnostic set up to collect the appropriate data. The first two-shot campaign will focus on executing polar direct drive (PDD) implosions of plastic CH capsules filled with deuterium gas. Gas filling will be performed through a fill tube at target chamber center. A vanadium backligher foil will provide x-rays to radiograph the last half of the implosion to compare the implosion trajectory with modeling predictions. An equatorial groove in one of the capsules will be present to determine its effect on implosion dynamics. The second DIME campaign will commission and use a spectral imager (MMI) to examine the evolution of thin capsule layers doped with either Ge or Ga at 1.85%. Spectral line emission from these layers will quantify the mix width at the inner shell radius and near an equatorial groove feature.

  14. Nucleoprotein complex formation by the enhancer binding protein nifA.

    PubMed

    Wang, X Y; Kolb, A; Cannon, W; Buck, M

    1997-09-01

    The nitrogen fixation protein NifA is a member of the protein family activating transcription by the alternative eubacterial sigmaN (sigma54) RNA polymerase holoenzyme. Binding sites for NifA, upstream activator sequences (UASs), are remotely located. Interaction between holoenzyme bound in a closed promoter complex and NiFA is facilitated by bending of the intervening DNA by integration host factor (IHF). We have examined NifA contact with the Klebsiella pneumoniae nifH promoter UAS in the presence and absence of holoenzyme and IHF. Footprints with UV light were made on 5-BrdU-substituted DNA and DNase I and laser UV footprints on conventional DNA templates. Results establish that the consensus thymidine residues of the UAS motif 5'-TGT are in close proximity to NifA. Reactivity suggests that each UAS thymidine is not structurally equivalent. Titration of NifA binding to the UAS in the presence or absence of the closed promoter complex indicates that the interaction of NifA with the UAS is not strongly co-operative with holoenzyme or IHF, a result supportive of an activation mechanism not reliant upon simple recruitment of factors to the promoter. Laser footprints demonstrated that holoenzyme suppressed reactivity of promoter consensus -14, -15 and -16 T residues, indicating close contact. Binding of holoenzyme resulted in a specific increase in 5-BrdU reactivity at -9 within the holoenzyme binding site, likely reflecting DNA distortion. Enhanced -9 reactivity required sigmaNN-terminal sequences that are necessary for activation. Since T-9 is melted in open complexes the closed complex appears poised for melting. Open promoter complex formation was accompanied by a distinct change in laser footprint signal at -11, consistent with the view that nucleation of strand separation occurs within or close to the -12 promoter element. PMID:9254707

  15. Fluid model of the sheath in front of a floating electrode immersed in a magnetized plasma with oblique magnetic field: Some comments on ion source terms and ion temperature effects

    NASA Astrophysics Data System (ADS)

    Gyergyek, T.; Kovačič, J.

    2015-04-01

    A one-dimensional fluid model of the magnetized plasma-wall transition region in front of a floating electrode immersed in a magnetized plasma with oblique magnetic field is presented. The Boltzmann relation is assumed for the electrons, while the positive ions obey the ion continuity and momentum exchange equation. The ions are assumed to be isothermal. By comparison with a two-fluid model, it is shown that assuming the Boltzmann relation for the electrons implies that there is no creation or annihilation of the electrons. Consequently, there should not be any creation and annihilation of the positive ions either. The models that assume the Boltzmann relation for the electrons and a non-zero ion source term at the same time are therefore inconsistent, but such models have nevertheless been used extensively by many authors. So, in this work, an extensive comparison of the results obtained using the zero source term on one hand and three different non-zero source terms on the other hand is made. Four different ion source terms are considered in total: the zero source term and three different non-zero ion source terms. When the zero source term is used, the model becomes very sensitive to the boundary conditions, and in some cases, the solutions exhibit large amplitude oscillations. If any of the three non-zero ion source terms is used, those problems are eliminated, but also the consistency of the model is broken. The model equations are solved numerically in the entire magnetized plasma-wall transition region. For zero ion temperature, the model can be solved even if a very small ion velocity is selected as a boundary condition. For finite ion temperature, the system of equations becomes stiff, unless the ion velocity at the boundary is increased slightly above the ion thermal velocity. A simple method how to find a solution with a very small ion velocity at the boundary also for finite ion temperature in the entire magnetized plasma-wall transition region is

  16. Dynamics of ion bombardment-induced modifications of Si(001) at the radio-frequency-biased electrode in low-pressure oxygen plasmas: In situ spectroscopic ellipsometry and Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Amassian, A.; Svec, M.; Desjardins, P.; Martinu, L.

    2006-09-01

    Low-pressure O2 plasma exposures were performed on c-Si(001) at a radio frequency (rf)-powered electrode in the presence of substrate self-biasing (VB) from VB=-60to-600V, in order to evaluate ion-surface interactions at the growth surface under ion bombardment conditions suitable for the fabrication of high quality optical coatings. The plasma-surface interactions were monitored in situ using real-time spectroscopic ellipsometry (RTSE), which reveals time- and ion-fluence-resolved information about depth-dependent modifications, such as damage and oxidation below the c-Si substrate surface. RTSE analysis indicates almost immediate damage formation (≪1s ) to a depth of a few nanometers below the surface after exposure to a low oxygen ion fluence (˜5×1014Ocm-2). Oxide growth is detected at intermediate fluence (˜1015-1016Ocm-2) and is attributed to O subplantation (shallow implantation); it forms near the surface of the target on top of an O-deficient interfacial damage layer (DL). Both layers experience a self-limiting growth behavior at high fluence (>1017cm-2) as oxide and DL thicknesses reach bias-dependent steady-state values, determined by the maximum ion penetration depth, which increases from ˜3.6to9.5nm for VB=-60to-600V. The in situ experimental study was complemented by Monte Carlo TRIDYN simulations based on the binary collision approximation, which were modified to calculate dynamic changes in the composition of a target exposed to a broad-energy ion source (rf plasma source) at high fluence. Simulation results are found to agree exceptionally well with experiment. In addition, they reveal that the 1.2-3.5-nm-thick DL formed in the steady-state regime is a result of (1) damage formation due to the presence of a small number of high energy O+ ions in the plasma environment, capable of penetrating and damaging up to 3nm deeper than the majority ion population (O2+), and (2) because of important surface motion resulting from oxidation

  17. Fluid model of the sheath in front of a floating electrode immersed in a magnetized plasma with oblique magnetic field: Some comments on ion source terms and ion temperature effects

    SciTech Connect

    Gyergyek, T.; Kovačič, J.

    2015-04-15

    A one-dimensional fluid model of the magnetized plasma-wall transition region in front of a floating electrode immersed in a magnetized plasma with oblique magnetic field is presented. The Boltzmann relation is assumed for the electrons, while the positive ions obey the ion continuity and momentum exchange equation. The ions are assumed to be isothermal. By comparison with a two-fluid model, it is shown that assuming the Boltzmann relation for the electrons implies that there is no creation or annihilation of the electrons. Consequently, there should not be any creation and annihilation of the positive ions either. The models that assume the Boltzmann relation for the electrons and a non-zero ion source term at the same time are therefore inconsistent, but such models have nevertheless been used extensively by many authors. So, in this work, an extensive comparison of the results obtained using the zero source term on one hand and three different non-zero source terms on the other hand is made. Four different ion source terms are considered in total: the zero source term and three different non-zero ion source terms. When the zero source term is used, the model becomes very sensitive to the boundary conditions, and in some cases, the solutions exhibit large amplitude oscillations. If any of the three non-zero ion source terms is used, those problems are eliminated, but also the consistency of the model is broken. The model equations are solved numerically in the entire magnetized plasma-wall transition region. For zero ion temperature, the model can be solved even if a very small ion velocity is selected as a boundary condition. For finite ion temperature, the system of equations becomes stiff, unless the ion velocity at the boundary is increased slightly above the ion thermal velocity. A simple method how to find a solution with a very small ion velocity at the boundary also for finite ion temperature in the entire magnetized plasma-wall transition region is

  18. Bioanalysis with Potentiometric Membrane Electrodes.

    ERIC Educational Resources Information Center

    Rechnitz, G. A.

    1982-01-01

    Discusses major themes and interrelationships common to bioselective potentiometric membrane electrodes including the nature of bioselective electrodes, applications, and future prospects. Includes tables on traditional ion-selective membrane electrodes, nontraditional electrodes, and typical biocatalytic potentiometric electrodes. (Author/JN)

  19. Ion-Selective Electrodes.

    ERIC Educational Resources Information Center

    Arnold, Mark A.; Meyerhoff, Mark E.

    1984-01-01

    Literature on ion-selective electrodes (ISEs) is reviewed in seven sections: books, conferences, reviews; potentiometric membrane electrodes; glass and solid-state membrane electrodes; liquid and polymer membrane ISEs; coated wire electrodes, ion-selective field effect transistors, and microelectrodes; gas sensors and selective bioelectrode…

  20. Fundamental electrode kinetics

    NASA Technical Reports Server (NTRS)

    Elder, J. P.

    1968-01-01

    Report presents the fundamentals of electrode kinetics and the methods used in evaluating the characteristic parameters of rapid-charge transfer processes at electrode-electrolyte interfaces. The concept of electrode kinetics is outlined, followed by the principles underlying the experimental techniques for the investigation of electrode kinetics.