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Sample records for high confinement influence

  1. Dynamic testing of concrete under high confined pressure. Influence of saturation ratio and aggregate size

    NASA Astrophysics Data System (ADS)

    Forquin, P.; Piotrowska, E.; Gary, G.

    2015-09-01

    Concrete structures can be exposed to intense pressure loadings such as projectile-impact or detonation near a concrete structural element. To investigate the mechanical behaviour of concrete under high confining pressure, dynamic quasi-oedometric compression tests have been performed with a large diameter (80 mm) Split Hopkinson Pressure Bar apparatus. The concrete sample is placed within a steel confining ring and compressed along its axial direction. Hydrostatic pressures as high as 800 MPa and axial strain of about - 10% are reached during the tests. In the present work, experiments have been conducted on two types of concrete: MB50 microconcrete with a maximum grain size of 2 mm and R30A7 ordinary concrete of maximum grain size about 8 mm. Both concretes are tested in dry or saturated conditions. According to these dynamic experiments it is noted that grain size has a small influence whereas water content has a strong effect on the confined behaviour of concrete.

  2. Thermostating highly confined fluids.

    PubMed

    Bernardi, Stefano; Todd, B D; Searles, Debra J

    2010-06-28

    In this work we show how different use of thermostating devices and modeling of walls influence the mechanical and dynamical properties of confined nanofluids. We consider a two dimensional fluid undergoing Couette flow using nonequilibrium molecular dynamics simulations. Because the system is highly inhomogeneous, the density shows strong fluctuations across the channel. We compare the dynamics produced by applying a thermostating device directly to the fluid with that obtained when the wall is thermostated, considering also the effects of using rigid walls. This comparison involves an analysis of the chaoticity of the fluid and evaluation of mechanical properties across the channel. We look at two thermostating devices with either rigid or vibrating atomic walls and compare them with a system only thermostated by conduction through vibrating atomic walls. Sensitive changes are observed in the xy component of the pressure tensor, streaming velocity, and density across the pore and the Lyapunov localization of the fluid. We also find that the fluid slip can be significantly reduced by rigid walls. Our results suggest caution in interpreting the results of systems in which fluid atoms are thermostated and/or wall atoms are constrained to be rigid, such as, for example, water inside carbon nanotubes. PMID:20590213

  3. Influence of confinement on thermodiffusion

    NASA Astrophysics Data System (ADS)

    Hannaoui, Rachid; Galliero, Guillaume; Hoang, Hai; Boned, Christian

    2013-09-01

    This work focuses on a possible influence of a nanoporous medium on the thermodiffusion of a fluid "isotopic" mixture. To do so, we performed molecular dynamics simulations of confined Lennard-Jones binary equimolar mixtures using grand-canonical like and non-equilibrium approaches in sub- and super-critical conditions. The study was conducted in atomistic slit pore of three adsorbent natures for various widths (from 5 to 35 times the size of a molecule). The simulation results indicate that for all thermodynamic conditions and whatever the pore characteristics, the confinement has a negligible effect on the thermal diffusion factor/Soret coefficient. However, when considered separately, the mass diffusion and thermodiffusion coefficients have been found to be largely influenced by the pore characteristics. These two coefficients decrease noticeably when adsorption is stronger and pore width smaller, a behavior that is consistent with a simple hydrodynamic explanation.

  4. CONFINEMENT OF HIGH TEMPERATURE PLASMA

    DOEpatents

    Koenig, H.R.

    1963-05-01

    The confinement of a high temperature plasma in a stellarator in which the magnetic confinement has tended to shift the plasma from the center of the curved, U-shaped end loops is described. Magnetic means are provided for counteracting this tendency of the plasma to be shifted away from the center of the end loops, and in one embodiment this magnetic means is a longitudinally extending magnetic field such as is provided by two sets of parallel conductors bent to follow the U-shaped curvature of the end loops and energized oppositely on the inside and outside of this curvature. (AEC)

  5. Effects of high sound speed confiners on ANFO detonations

    NASA Astrophysics Data System (ADS)

    Kiyanda, Charles; Jackson, Scott; Short, Mark

    2011-06-01

    The interaction between high explosive (HE) detonations and high sound speed confiners, where the confiner sound speed exceeds the HE's detonation speed, has not been thoroughly studied. The subsonic nature of the flow in the confiner allows stress waves to travel ahead of the main detonation front and influence the upstream HE state. The interaction between the detonation wave and the confiner is also no longer a local interaction, so that the confiner thickness now plays a significant role in the detonation dynamics. We report here on larger scale experiments in which a mixture of ammonium nitrate and fuel oil (ANFO) is detonated in aluminium confiners with varying charge diameter and confiner thickness. The results of these large-scale experiments are compared with previous large-scale ANFO experiments in cardboard, as well as smaller-scale aluminium confined ANFO experiments, to characterize the effects of confiner thickness.

  6. Influence of the radial profile of the electric potential on the confinement of a high-{beta} two-component plasma in a gas-dynamic trap

    SciTech Connect

    Soldatkina, E. I.; Bagryansky, P. A.; Solomakhin, A. L.

    2008-04-15

    One of the most important problems to be studied in the gas-dynamic trap (GDT) facility is the investigation of MHD stability and cross-field transport in a plasma with a relatively high value of {beta} = {pi}p/B{sup 2}. Recent experiments demonstrated that the radial electric field produced in the plasma by using radial limiters and coaxial end plasma collectors improves plasma stability in axisymmetric magnetic mirror systems without applying special MHD stabilizers. The experimental data presented in this work show that stable plasma confinement can be achieved by producing a radial potential drop across a narrow region near the plasma boundary. Creating radial electric fields of strength 15-40 V/cm causes a shear plasma flow, thereby substantially increasing the plasma confinement time. When all the radial electrodes were grounded, the confinement was unstable and the plasma confinement time was much shorter than the characteristic time of plasma outflow through the magnetic mirrors. Measurements of cross-field plasma fluxes with the use of a specially designed combined probe show that, in confinement modes with differential plasma rotation, transverse particle losses are negligibly small as compared to longitudinal ones and thus can be ignored. It is also shown that, when the GDT plasma is in electric contact with the radial limiters and end collectors, the growth rate of interchange instability decreases considerably; such a contact, however, does not ensure complete MHD stability when the electrodes are at the same potential.

  7. The Influence of Electric Field and Confinement on Cell Motility

    PubMed Central

    Huang, Yu-Ja; Samorajski, Justin; Kreimer, Rachel; Searson, Peter C.

    2013-01-01

    The ability of cells to sense and respond to endogenous electric fields is important in processes such as wound healing, development, and nerve regeneration. In cell culture, many epithelial and endothelial cell types respond to an electric field of magnitude similar to endogenous electric fields by moving preferentially either parallel or antiparallel to the field vector, a process known as galvanotaxis. Here we report on the influence of dc electric field and confinement on the motility of fibroblast cells using a chip-based platform. From analysis of cell paths we show that the influence of electric field on motility is much more complex than simply imposing a directional bias towards the cathode or anode. The cell velocity, directedness, as well as the parallel and perpendicular components of the segments along the cell path are dependent on the magnitude of the electric field. Forces in the directions perpendicular and parallel to the electric field are in competition with one another in a voltage-dependent manner, which ultimately govern the trajectories of the cells in the presence of an electric field. To further investigate the effects of cell reorientation in the presence of a field, cells are confined within microchannels to physically prohibit the alignment seen in 2D environment. Interestingly, we found that confinement results in an increase in cell velocity both in the absence and presence of an electric field compared to migration in 2D. PMID:23555674

  8. Confinement of hydrogen at high pressure in carbon nanotubes

    DOEpatents

    Lassila, David H.; Bonner, Brian P.

    2011-12-13

    A high pressure hydrogen confinement apparatus according to one embodiment includes carbon nanotubes capped at one or both ends thereof with a hydrogen-permeable membrane to enable the high pressure confinement of hydrogen and release of the hydrogen therethrough. A hydrogen confinement apparatus according to another embodiment includes an array of multi-walled carbon nanotubes each having first and second ends, the second ends being capped with palladium (Pd) to enable the high pressure confinement of hydrogen and release of the hydrogen therethrough as a function of palladium temperature, wherein the array of carbon nanotubes is capable of storing hydrogen gas at a pressure of at least 1 GPa for greater than 24 hours. Additional apparatuses and methods are also presented.

  9. High-Energy Electron Confinement in a Magnetic Cusp Configuration

    NASA Astrophysics Data System (ADS)

    Park, Jaeyoung; Krall, Nicholas A.; Sieck, Paul E.; Offermann, Dustin T.; Skillicorn, Michael; Sanchez, Andrew; Davis, Kevin; Alderson, Eric; Lapenta, Giovanni

    2015-04-01

    We report experimental results validating the concept that plasma confinement is enhanced in a magnetic cusp configuration when β (plasma pressure/magnetic field pressure) is of order unity. This enhancement is required for a fusion power reactor based on cusp confinement to be feasible. The magnetic cusp configuration possesses a critical advantage: the plasma is stable to large scale perturbations. However, early work indicated that plasma loss rates in a reactor based on a cusp configuration were too large for net power production. Grad and others theorized that at high β a sharp boundary would form between the plasma and the magnetic field, leading to substantially smaller loss rates. While not able to confirm the details of Grad's work, the current experiment does validate, for the first time, the conjecture that confinement is substantially improved at high β . This represents critical progress toward an understanding of the plasma dynamics in a high-β cusp system. We hope that these results will stimulate a renewed interest in the cusp configuration as a fusion confinement candidate. In addition, the enhanced high-energy electron confinement resolves a key impediment to progress of the Polywell fusion concept, which combines a high-β cusp configuration with electrostatic fusion for a compact, power-producing nuclear fusion reactor.

  10. Impurity confinement and transport in high confinement regimes without edge localized modes on DIII-D

    SciTech Connect

    Grierson, B. A. Nazikian, R. M.; Solomon, W. M.; Burrell, K. H.; Garofalo, A. M.; Belli, E. A.; Staebler, G. M.; Evans, T. E.; Smith, S. P.; Chrobak, C.; Fenstermacher, M. E.; McKee, G. R.; Orlov, D. M.; Chrystal, C.

    2015-05-15

    Impurity transport in the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] is investigated in stationary high confinement (H-mode) regimes without edge localized modes (ELMs). In plasmas maintained by resonant magnetic perturbation (RMP), ELM-suppression, and QH-mode, the confinement time of fluorine (Z = 9) is equivalent to that in ELMing discharges with 40 Hz ELMs. For selected discharges with impurity injection, the impurity particle confinement time compared to the energy confinement time is in the range of τ{sub p}/τ{sub e}≈2−3. In QH-mode operation, the impurity confinement time is shown to be smaller for intense, coherent magnetic, and density fluctuations of the edge harmonic oscillation than weaker fluctuations. Transport coefficients are derived from the time evolution of the impurity density profile and compared to neoclassical and turbulent transport models NEO and TGLF. Neoclassical transport of fluorine is found to be small compared to the experimental values. In the ELMing and RMP ELM-suppressed plasma, the impurity transport is affected by the presence of tearing modes. For radii larger than the mode radius, the TGLF diffusion coefficient is smaller than the experimental value by a factor of 2–3, while the convective velocity is within error estimates. Low levels of diffusion are observed for radii smaller than the tearing mode radius. In the QH-mode plasma investigated, the TGLF diffusion coefficient is higher inside of ρ=0.4 and lower outside of 0.4 than the experiment, and the TGLF convective velocity is more negative by a factor of approximately 1.7.

  11. Velocity alignment leads to high persistence in confined cells.

    PubMed

    Camley, Brian A; Rappel, Wouter-Jan

    2014-06-01

    Many cell types display random motility on two-dimensional substrates but crawl persistently in a single direction when confined in a microchannel or on an adhesive micropattern. Does this imply that the motility mechanism of confined cells is fundamentally different from that of unconfined cells? We argue that both free- and confined-cell migration may be described by a generic model of cells as "velocity-aligning" active Brownian particles previously proposed to solve a completely separate problem in collective cell migration. Our model can be mapped to a diffusive escape over a barrier and analytically solved to determine the cell's orientation distribution and repolarization rate. In quasi-one-dimensional confinement, velocity-aligning cells maintain their direction for times that can be exponentially larger than their persistence time in the absence of confinement. Our results suggest an important connection between single- and collective-cell migration: high persistence in confined cells corresponds with fast alignment of velocity to cell-cell forces. PMID:25019812

  12. High beta and confinement studies of TFTR

    SciTech Connect

    Navratil, G.A.; Bhattacharjee, A.; Iacono, R.; Mauel, M.E.; Sabbagh, S.A. ); Kesner, J. )

    1993-01-01

    The project discussed in this report are: Enhanced High Poloidal Beta Operation in TFTR with Deuterium Pellet Injection; Approaching High Q by Utilizing High [beta][sub p] Operation in TFTR; Advanced Tokamak Regime Experiment, and Second Regime Studies at large Major Radius High [beta][sub p] Plasmas. Analysis of the data taken during these experiments as well as continuing analysis of earlier data led to a number important results described in publications in the past year including two invited presentations at the 1992 American Physical Society Division of Plasma Physics Meeting in Seattle an oral presentation at the 1992 IAEA Meeting in Wuertzburg, Germany, and a Physical Review Letter. These results included extending the high 11/2 regime to 1.2 MA current and neutron production rates to more than 3 [times] 10[sup 16] sec[sup [minus

  13. Simulation of transition dynamics to high confinement in fusion plasmas

    NASA Astrophysics Data System (ADS)

    Nielsen, A. H.; Xu, G. S.; Madsen, J.; Naulin, V.; Juul Rasmussen, J.; Wan, B. N.

    2015-12-01

    The transition dynamics from the low (L) to the high (H) confinement mode in magnetically confined plasmas is investigated using a first-principles four-field fluid model. Numerical results are in agreement with measurements from the Experimental Advanced Superconducting Tokamak - EAST. Particularly, the slow transition with an intermediate dithering phase is well reproduced at proper parameters. The model recovers the power threshold for the L-H transition as well as the decrease in power threshold switching from single to double null configuration observed experimentally. The results are highly relevant for developing predictive models of the transition, essential for understanding and optimizing future fusion power reactors.

  14. Diffusion NMR of Fluids Confined to Mesopores under High Pressures

    NASA Astrophysics Data System (ADS)

    Zeigermann, Philipp; Dvoyashkin, Muslim; Gläser, Roger; Valiullin, Rustem

    2011-03-01

    Supercritical fluids are extensively used in various chemical applications including processes involving porous solids. The knowledge of their transport in bulk as well as under spatial confinements is critical for modeling and optimizing chemical reactions. In this contribution, we describe a high-pressure cell designed for pulsed field gradient NMR studies of diffusion of supercritical solvents in mesoporous materials. Some preliminary results on diffusion properties of ethane in bulk phase and confined to pores of mesoporous silicon obtained in a broad range of pressures below and above the critical temperature are reported.

  15. Transitions Out of High-Confinement Mode to Lower Confinement Regimes in Tokamaks

    NASA Astrophysics Data System (ADS)

    Eldon, David

    A high-resolution edge Thomson Scattering (TS) system was developed and installed on the DIII-D tokamak, and was then used to study the back transition from High Confinement (H-mode) to Low Confinement (L-mode) in DIII-D. The transient event seen to initiate some back transition sequences is superficially similar to a large type-I ELM, which is described by the linear ideal MHD theory of peeling-ballooning modes. Detailed edge pedestal profile evolution studies during the back transition show that the plasma does not exceed this linear stability limit during the back transition, indicating that the transient is not a type-I ELM event. The E x B shearing rate oE x B and turbulence decorrelation rate oT were then compared before the H-L sequence. The results show that the back transition sequence begins while oE x B is still well above oT, indicating that the sequences observed in these experiments are not triggered by the collapse of the E x B shear layer. Further investigation is made to characterize a coherent density fluctuation whose behavior is linked to back transition sequences. Strategies for avoiding the transient are tested and a reliable method for producing a "soft'' back transition is identified. Such cases are compared to the class of "hard'' transitions in which the pedestal pressure gradient rapidly relaxes.

  16. Optical nonlinearities in high-confinement silicon carbide waveguides.

    PubMed

    Cardenas, Jaime; Yu, Mengjie; Okawachi, Yoshitomo; Poitras, Carl B; Lau, Ryan K W; Dutt, Avik; Gaeta, Alexander L; Lipson, Michal

    2015-09-01

    We demonstrate strong nonlinearities of n2=8.6±1.1×10(-15)  cm2 W(-1) in single-crystal silicon carbide (SiC) at a wavelength of 2360 nm. We use a high-confinement SiC waveguide fabricated based on a high-temperature smart-cut process. PMID:26368731

  17. The Radioelectric effect in doped superlattices under the influence of confined phonon

    NASA Astrophysics Data System (ADS)

    Quang Bau, Nguyen; Thu Hang, Dao; Long, Do Tuan

    2016-06-01

    The Radioelectric effect in doped superlattices under the influence of confined phonon has been theoretically studied. The analytical expression for the Radioelectric field is obtained by quantum kinetic equation method. The theoretical expression shows that the Radioelectric field in doped superlattices depends on the frequencies and amplitudes of the laser and the linearly polarized electromagnetic wave, the period of the superlattices and especially the quantum number m characterizing the phonon confinement. Numerical calculation is also applied for GaAs:Si/GaAs:Be doped superlattices. It is found that the Radioelectric field is different from that in the normal bulk semiconductor as well as two-dimensional systems in case of unconfined phonon and in case of confined phonon when the contribution of confined potential of doped superlattices and confined phonon is remarkable. The Radioelectric field has multiple resonance peaks and increases as the increasing of quantum number m.

  18. High-performance inertial confinement fusion target implosions on OMEGA

    SciTech Connect

    Meyerhofer, D. D.; 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; Fletcher, K A; Frenje, J A; Glebov, Y Yu; Goncharov, V N; Harding, D R; Hu, S X; Igumenshchev, I V; Knauer, J P; Li, C K; Marozas, J A; Marshall, F J; McKenty, P W; Nilson, P M; Padalino, S P; Petrasso, R D; Radha, P B; Regan, S P; Sangster, T C; Seguin, F H; Seka, W; Short, R W; Shvarts, D; Skupsky, S; Soures, J M; Stoeckl, C; Theobald, W; Yaakobi, B

    2011-04-18

    The Omega Laser Facility is used to study inertial confinement fusion (ICF) concepts. This paper describes progress in direct-drive central hot-spot (CHS) ICF, shock ignition (SI) and fast ignition (FI) since the 2008 IAEA FEC conference. CHS cryogenic deuterium-tritium (DT) target implosions on OMEGA have produced the highest DT areal densities yet measured in ICF implosions (~300 mg cm{sup -2}). Integrated FI experiments have shown a significant increase in neutron yield caused by an appropriately timed high-intensity, high-energy laser pulse.

  19. Measurements of uranium mass confined in high density plasmas

    NASA Technical Reports Server (NTRS)

    Stoeffler, R. C.

    1976-01-01

    An X-ray absorption method for measuring the amount of uranium confined in high density, rf-heated uranium plasmas is described. A comparison of measured absorption of 8 keV X-rays with absorption calculated using Beer Law indicated that the method could be used to measure uranium densities from 3 times 10 to the 16th power atoms/cu cm to 5 times 10 to the 18th power atoms/cu cm. Tests were conducted to measure the density of uranium in an rf-heated argon plasma with UF6 infection and with the power to maintain the discharge supplied by a 1.2 MW rf induction heater facility. The uranium density was measured as the flow rate through the test chamber was varied. A maximum uranium density of 3.85 times 10 to the 17th power atoms/cu cm was measured.

  20. Influence of Homopolymers on the Microdomain Behavior of Block Copolymers in 2D Confinement

    NASA Astrophysics Data System (ADS)

    Kim, Youngkeol; Hwang, Sungyoul; Yu, Guiduk; Char, Kookheon

    Constraints imposed by nanometer scale confinement lead to changes in bulk equilibrium behavior of block copolymers (BCPs). Cylindrical pores with diameters corresponding to the length equivalent of several copolymer chains have been employed to investigate the influence of two-dimensional confinement on the behavior of BCPs. In this study, we expand the scope to homopolymer-BCP binary blends. Given fraction of homopolymers, the phase behavior of blends is dependent on molecular weight (Mw) of homopolymers. Lamella- and cylinder-forming poly(styrene-b-butadiene) (PS-b-PBD) and PS homopolymers (hPS) were drawn into the pores of anodized aluminum oxide (AAO) membranes in the melt by capillary forces. Based on the detailed observation of the morphologies within porous columns, we analyzed the structural transition of BCPs induced by the presence of hPS and confinement. The effect of hPS on the micro-domain of BCPs is greatly accentuated in nanoscale confinement compared to the bulk state due to the entropic loss of polymer chains. Pore diameters of AAO and Mw of the PS-b-PBD are also controlled so as to examine the effects of confinement on the phase transition of PS-b-PBD/hPS blends.

  1. Influence of the confining pressure on precursory and rupture processes of Westerly granite.

    NASA Astrophysics Data System (ADS)

    Passelegue, Francois; Nicolas, Aurelien; Madonna, Claudio; Schubnel, Alexandre

    2016-04-01

    In the shallow crust, brittle deformation mechanisms lead to damage and rupture of rocks. These mechanisms are generally described by non-linear stress relations and decrease of the elastic moduli due to microcrak opening and sliding. However, failure mode depends on confining pressure and ranges from axial splitting to shear localization. Here we report experiments on Westerly granite samples deformed under controlled upper crustal stress conditions in the laboratory. Experiments were conducted under triaxial loading (σ1>σ2=σ3) at confining pressures (σ3) ranging from 2 to 50 MPa (similar to upper crustal stress conditions) and at constant axial strain rate 10-5/s. Usual a dual gain system, a high frequency acoustic monitoring array recorded particles acceleration during macroscopic rupture of the intact specimen and premonitory background microseismicity. Secondly, acoustic sensors were used in an active way to measure the evolution of elastic wave velocities. In addition, we used an amplified strain gage to record the dynamic stress change during the dynamic rupture. Our preliminary results show that increasing confining pressure leads to the transition between axial cracks opening to shear localization. This result is supported by the moment tensor solutions of acoustic emissions and CT scan imaging of the post mortem sample. In addition, we systematically observe an exponential increase of the premonitory activity up to the shear failure of the sample. While the intensity of this precursory activity increase with the confining pressure in term of energy, the crack density leading to the failure of the sample is independent of the confinement. We show that the dynamic rupture occurs in only few microseconds, suggesting a rupture speed close to the shear wave velocity. In addition, the ratio between the stress drop and the peak of stress increases with the confinement. This result suggest that the weakening of faulting increases with the confinement. Finally

  2. Mixing Diagnostics in Confined, High-Speed Droplet Collisions

    NASA Astrophysics Data System (ADS)

    Carroll, Brian; Hidrovo, Carlos

    2012-11-01

    Fast mixing remains a major challenge in droplet-based microfluidics. The low Reynolds number operating regime of most mixing devices signifies orderly flows that are devoid of any inertial characteristics. To increase droplet mixing rates, a novel technique is under development that uses a high Reynolds number gaseous phase for droplet generation and transport and promotes mixing through binary droplet collisions at velocities near 1m/s. Limitations in existing mixing diagnostic methodologies has persuaded cultivation of a new technique for measuring droplet collision mixing in confined microchannels. The technique employs single fluorophore laser-induced fluorescence, custom image processing, and meaningful statistical analysis for monitoring and quantifying mixing in high-speed droplet collisions. Mixing progress is revealed through two statistics that separate the roles of convective rearrangement and molecular diffusion during the mixing process. The end result is a viewing window into the rich dynamics of droplet collisions with spatial and temporal resolutions of 1 μm and 25 μs, respectively. Experimental results obtained across a decade of Reynolds and Peclet numbers reveal a direct link between droplet mixing time and the collision convective timescale. This work provides valuable insight into the emerging field of two-phase gas-liquid microfluidics and opens the door to fundamental research possibilities not offered by traditional oil-based architectures.

  3. High efficiency ICF driver employing magnetically confined plasma rings

    SciTech Connect

    Meeker, D.J.; Hammer, J.H.; Hartman, C.W.

    1985-03-04

    We discuss the possibility of achieving energy, power and power density necessary for ICF by magnetically accelerating plasma confined by a compact torus (CT) field configuration. The CT, which consists of a dipole (poloidal) field and imbedded toroidal field formed by force-free, plasma current, is compressed and accelerated between coaxial electrodes by B/sub THETA/ fields as in a coaxial railgun. Compression and acceleration over several meters by a 9.4 MJ capacitor bank is predicted to give a 5.7 cm radius, 0.001 gm CT 5 MJ kinetic energy (10/sup 7/ m/sec). Transport and focussing several meters by a disposable lithium pipe across the containment vessel is predicted to bring 4.8 MJ into the pellet region in 0.5 cm/sup 2/ area in 0.3 ns. The high efficiency (approx.50%) and high energy delivery of the CT accelerator could lead to low cost, few hundred MW power plants that are economically viable.

  4. Fault gouge rheology under confined, high-velocity conditions

    NASA Astrophysics Data System (ADS)

    Reches, Z.; Madden, A. S.; Chen, X.

    2012-12-01

    We recently developed the experimental capability to investigate the shear properties of fine-grain gouge under confined conditions and high-velocity. The experimental system includes a rotary apparatus that can apply large displacements of tens of meters, slip velocity of 0.001- 2.0 m/s, and normal stress of 35 MPa (Reches and Lockner, 2010). The key new component is a Confined ROtary Cell (CROC) that can shear a gouge layer either dry or under pore-pressure. The pore pressure is controlled by two syringe pumps. CROC includes a ring-shape gouge chamber of 62.5 mm inner diameter, 81.25 mm outer diameter, and up to 3 mm thick gouge sample. The lower, rotating part of CROC contains the sample chamber, and the upper, stationary part includes the loading, hollow cylinder and setting for temperature, and dilation measurements, and pore-pressure control. Each side of the gouge chamber has two pairs of industrial, spring-energized, self-lubricating, teflon-graphite seals, built for particle media and can work at temperature up to 250 ded C. The space between each of the two sets of seals is pressurized by nitrogen. This design generates 'zero-differential pressure' on the inner seal (which is in contact with the gouge powder), and prevents gouge leaks. For the preliminary dry experiments, we used ~2.0 mm thick layers of room-dry kaolinite powder. Total displacements were on the order of meters and normal stress up to 4 MPa. The initial shear was accommodated by multiple internal slip surfaces within the kaolinite layer accommodated as oriented Riedel shear structures. Later, the shear was localized within a thin, plate-parallel Y-surface. The kaolinite layer was compacted at a quasi-asymptotic rate, and displayed a steady-state friction coefficient of ~ 0.5 with no clear dependence on slip velocity up to 0.15 m/s. Further experiments with loose quartz sand (grain size ~ 125 micron) included both dry runs and pore-pressure (distilled water) controlled runs. The sand was

  5. Confinement physics for thermal, neutral, high-charge-state plasmas in nested-well solenoidal traps.

    PubMed

    Dolliver, D D; Ordonez, C A

    1999-06-01

    A theoretical study is presented which indicates that it is possible to confine a neutral plasma using static electric and solenoidal magnetic fields. The plasma consists of equal temperature electrons and highly stripped ions. The solenoidal magnetic field provides radial confinement, while the electric field, which produces an axial nested-well potential profile, provides axial confinement. A self-consistent, multidimensional numerical solution for the electric potential is obtained, and a fully kinetic theoretical treatment on axial transport is used to determine an axial confinement time scale. The effect on confinement of the presence of a radial electric field is explored with the use of ion trajectory calculations. A thermal, neutral, high-charge-state plasma confined in a nested-well trap opens new possibilities for fundamental studies on plasma recombination and cross-field transport processes under highly controlled conditions. PMID:11969700

  6. Polymer segregation under confinement: Influences of macromolecular crowding and the interaction between the polymer and crowders

    NASA Astrophysics Data System (ADS)

    Chen, Yuhao; Yu, Wancheng; Wang, Jiajun; Luo, Kaifu

    2015-10-01

    Entropy driven polymer segregation in confinements as a model for chromosome separation in bacteria has attracted wide attention; however, the effects of macromolecular crowding and the interaction between the binding protein and the newly replicated DNA on the segregation dynamics are not clear. Using Langevin dynamics simulations, we investigate the influences of crowders and the attractive interaction between the polymer and a small number of crowders on segregation of two overlapping polymers under a cylindrical confinement. We find that the segregation time increases with increasing the volume fraction of crowders due to the slower chain diffusion in crowded environments. For a fixed volume fraction of crowders, the segregation time decreases with increasing the size of crowders. Moreover, the attractive interaction between the polymer and a small number of crowders can significantly facilitate the chain segregation. These results are important for understanding the chromosome segregation in living cells.

  7. Evolution from surface-influenced to bulk-like dynamics in nanoscopically confined water.

    PubMed

    Romero-Vargas Castrillón, Santiago; Giovambattista, Nicolás; Aksay, Ilhan A; Debenedetti, Pablo G

    2009-06-11

    We use molecular dynamics simulations to study the influence of confinement on the dynamics of a nanoscopic water film at T = 300 K and rho = 1.0 g cm(-3). We consider two infinite hydrophilic (beta-cristobalite) silica surfaces separated by distances between 0.6 and 5.0 nm. The width of the region characterized by surface-dominated slowing down of water rotational dynamics is approximately 0.5 nm, while the corresponding width for translational dynamics is approximately 1.0 nm. The different extent of perturbation undergone by the in-plane dynamic properties is evidence of rotational-translational decoupling. The local in-plane rotational relaxation time and translational diffusion coefficient collapse onto confinement-independent "master" profiles as long as the separation d >or= 1.0 nm. Long-time tails in the perpendicular component of the dipole moment autocorrelation function are indicative of anisotropic behavior in the rotational relaxation. PMID:19449830

  8. Influence of crystallization-induced amorphous phase confinement on α- and β-relaxation molecular mobility in parylene F

    NASA Astrophysics Data System (ADS)

    Diaham, S.; Bechara, M.; Locatelli, M.-L.; Lebey, T.

    2011-09-01

    The molecular mobility of cooperative segmental (α-process) and local (β-process) motions in semicrystalline fluorinated parylene (PA-F) films has been studied using broadband dielectric spectroscopy in a wide temperature range. Particularly, the α-relaxation is, for the first time in a semicrystalline polymer, probed well above the glass transition temperature (˜10Tg) based on the PA-F strong difference between Tg and the crystallization temperature (Tc ˜ 16Tg). The influence of the amorphous phase confinement on the chain dynamics, induced by increasing crystallinity, is also explored. Thus, in the range of Tg, the α-relaxation is described by two crossover Vogel-Fulcher-Tamman characteristics, and the high temperature one presents an exacerbated low fragility. The space confinement of the amorphous regions, as characterized by x-ray diffraction, shows an important mobility restriction of both the α- and β-relaxations. The β-process, which has been related to CF2 group local motions, does not present a modification of its activation energy (Ea ˜ 30.8 kJ mol-1) with confinement, showing that it happens in the pure amorphous regions. The dielectric strength analysis of each process, through the Onsager-Kirkwood-Fröhlich (OKF) theory, has demonstrated that a rigid amorphous phase is strongly involved in the very high temperature range well above Tg. In the range around Tg, a peculiar behavior of the low temperature α-relaxation dielectric strength is reported, in agreement with the OKF temperature decreasing dependency that has been related to cooperative rearranging regions in the pure amorphous phase. The disappearance of the α-relaxation with the amorphous phase confinement leads to a transformation from 2D to 3D crystallite arrangements of the PA-F chains in correlation with the formation of spherulitic structures.

  9. Capillary effects in a confined smectic phase of hard spherocylinders: influence of particle elongation.

    PubMed

    de Las Heras, D; Velasco, E; Mederos, L

    2006-07-01

    A system of hard rods confined into a pore with slit geometry (two parallel planar substrates) is studied theoretically in the regime of high packing fraction. In this regime the bulk system exhibits a nematic phase as well as a smectic-A (spatially layered) phase. When the system is confined, strong commensuration effects between the layer spacing and the pore width bring about a rich phenomenology, with a phase diagram showing layering and capillary transitions. The latter include capillary smectization transitions whereby a confined smectic phase occurs at conditions of saturation different from those of the corresponding bulk fluid. These transitions are seen to be intimately connected with layering transitions involving discontinuous changes in the number of layers inside the pore. This rich phenomenology is obtained by use of a sophisticated density-functional, Onsager-theory-based approach, especially suited to deal with strongly inhomogeneous fluids. The theory allows for a unified description of ordering and phase behavior of the fluid in confined geometry, and permits us to correlate the above behavior with the wetting properties of the fluid on a single substrate. PMID:16907113

  10. Impurity accumulation in plasma regimes with high energy confinement

    NASA Astrophysics Data System (ADS)

    Ran, L. B.; Roberts, D. E.; Yang, H. R.; Dodel, G.; Gentle, K.; Von Goeler, S.; Holzhauer, E.; Hübner, K.; Keilhacker, M.; Korotkov, A.; Luce, T. C.; Miura, Y.; Tsois, N.; Würz, H.; Fussmann, G.; Hofmann, J.; Janeschitz, G.; Krieger, K.; Müller, E. R.; Nolte, R.; Röhr, H.; Steuer, K. H.; Becker, G.; Bomba, B.; Bruhns, H.; Büchl, K.; Carlson, A.; Eberhagen, A.; Fahrbach, H.-U.; Gehre, O.; Gernhardt, J.; Giannone, L.; Von Gierke, G.; Glock, E.; Gruber, O.; Haas, G.; Herrmann, H.; Kaesdorf, S.; Karger, F.; Kaufmann, M.; Klüber, O.; Kornherr, M.; Lackner, K.; Lang, R.; Lee, P.; Lisitano, G.; Mast, F.; Mayer, H. M.; McCormick, K.; Meisel, D.; Mertens, V.; Murmann, H.; Neuhauser, J.; Niedermeyer, H.; Noterdaeme, J. M.; Poschenrieder, W.; Preis, R.; Rapp, H.; Rudyj, A.; Sandmann, W.; Schneider, F.; Schnider, U.; Siller, G.; Simmet, E.; Speth, E.; Söldner, F.; Stäbler, A.; Steinmetz, K.; Stroth, U.; Vollmer, O.; Zasche, D.

    1989-04-01

    Investigations of impurity accumulation phenomena in ASDEX are reviewed. There are four different operating regimes where pronounced accumulation is observed and these regimes are also characterized by improved energy confinement. In particular, medium-Z metallic ions are involved in accumulation processes whereas low-Z ions appear almost unaffected. The rapid accumulation observed in the case of metallic ions may be explained by neoclassical inward drifts if we assume that the anomalous diffusion is sufficiently suppressed, some indication of this being found from laser blow-off studies. The present results, however, can only be partly explained by neoclassical theory, according to which accumulation of low-Z impurities should also occur. The temporal behaviour of accumulation and the retarding effect of proton dilution for collision dominated transport are also discussed. Finally, we conclude that the full benefits of improved energy confinement can be achieved only if the impurity influxes are kept to a sufficiently low level. Expressed in terms of concentrations under low confinement conditions we have to postulate, for ASDEX, concentrations ≲ 10 -4 for metals and ≲ 2% for all light impurities.

  11. Influence of Aging and Environment on Nanoparticle Chemistry: Implication to Confinement Effects in Nanoceria

    SciTech Connect

    Kuchibhatla, Satyanarayana V N T; Karakoti, Ajay S.; Baer, Donald R.; Samudrala, Saritha; Engelhard, Mark H.; Amonette, James E.; Thevuthasan, Suntharampillai; Seal, Sudipta

    2012-07-05

    The oxidation state switching of cerium in cerium oxide nanoparticles is studied in detail. The influence of synthesis medium, aging time and local environment on the oxidation state switching, between +3 and + 4, is analyzed by tracking the absorption edge using UV-Visible spectroscopy. It is observed that by tuning the local environment, the chemistry of the nanoparticles could be altered. These time dependent, environmentally induced changes likely contribute to inconsistencies in the literature regarding quantum-confinement effects for ceria nanoparticles. The results in this article indicate that there is a need to carry out comprehensive analysis of nanoparticles while considering the influence of synthesis and processing conditions, aging time and local environment.

  12. Stability analysis of confined V-shaped flames in high-velocity streams.

    PubMed

    El-Rabii, Hazem; Joulin, Guy; Kazakov, Kirill A

    2010-06-01

    The problem of linear stability of confined V-shaped flames with arbitrary gas expansion is addressed. Using the on-shell description of flame dynamics, a general equation governing propagation of disturbances of an anchored flame is obtained. This equation is solved analytically for V-flames anchored in high-velocity channel streams. It is demonstrated that dynamics of the flame disturbances in this case is controlled by the memory effects associated with vorticity generated by the perturbed flame. The perturbation growth rate spectrum is determined, and explicit analytical expressions for the eigenfunctions are given. It is found that the piecewise linear V structure is unstable for all values of the gas expansion coefficient. Despite the linearity of the basic pattern, however, evolutions of the V-flame disturbances are completely different from those found for freely propagating planar flames or open anchored flames. The obtained results reveal strong influence of the basic flow and the channel walls on the stability properties of confined V-flames. PMID:20866527

  13. Laboratory tests to study the influence of rock stress confinement on the performances of TBM discs in tunnels

    NASA Astrophysics Data System (ADS)

    Innaurato, N.; Oggeri, C.; Oreste, P.; Vinai, R.

    2011-06-01

    To clarify some aspects of rock destruction with a disc acting on a high confined tunnel face, a series of tests were carried out to examine fracture mechanisms under an indenter that simulates the tunnel boring machine (TBM) tool action, in the presence of an adjacent groove, when a state of stress (lateral confinement) is imposed on a rock sample. These tests proved the importance of carefully establishing the optimal distance of grooves produced by discs acting on a confined surface, and the value (as a mere order of magnitude) of the increase of the thrust to produce the initiation of chip formation, as long as the confinement pressure becomes greater.

  14. Influence of the confinement on laser-induced dry etching at the rear side of fused silica

    NASA Astrophysics Data System (ADS)

    Pan, Yunxiang; Ehrhardt, Martin; Lorenz, Pierre; Han, Bing; Hopp, Bela; Vass, Csaba; Ni, Xiaowu; Zimmer, Klaus

    2016-04-01

    Laser-induced etching at the rear side of transparent material enables high-quality machining results. However, the mechanism is still not completely recognized which would allow further optimization. Therefore, multi-pulsed laser-induced backside dry etching with different thick photoresist films was studied experimentally for air (MP-LIBDE) and water confinements (cMP-LIBDE). The water confinement causes differences in photoresist ablation morphology and etching rate in dependence on laser fluence, film thickness and pulse number. Owing to the water confinement, the extent of photoresist film spallation and the etching rate slope difference in low and high fluence ranges are reduced. In particular, the etching rate of cMP-LIBDE keeps constant with different film thicknesses in contrast to MP-LIBDE. Two effects that are related to the water confinement, mechanical confinement and heat transfer alterations, are analysed and discussed in relation to the differences between MP-LIBDE and cMP-LIBDE.

  15. PCF Based Sensor with High Sensitivity, High Birefringence and Low Confinement Losses for Liquid Analyte Sensing Applications

    PubMed Central

    Ademgil, Huseyin; Haxha, Shyqyri

    2015-01-01

    In this paper, we report a design of high sensitivity Photonic Crystal Fiber (PCF) sensor with high birefringence and low confinement losses for liquid analyte sensing applications. The proposed PCF structures are designed with supplementary elliptical air holes in the core region vertically-shaped V-PCF and horizontally-shaped H-PCF. The full vectorial Finite Element Method (FEM) simulations performed to examine the sensitivity, the confinement losses, the effective refractive index and the modal birefringence features of the proposed elliptical air hole PCF structures. We show that the proposed PCF structures exhibit high relative sensitivity, high birefringence and low confinement losses simultaneously for various analytes. PMID:26694408

  16. Polarization of emission from non-polar III-nitride quantum wells: the influence of confinement

    NASA Astrophysics Data System (ADS)

    Arora, Ashish; Ghosh, Sandip

    2014-01-01

    Taking M-plane oriented GaN quantum wells (QW) as an example, it is shown that the finite out-of-plane crystal momentum arising from quantum confinement modifies valence band mixing in a way that can significantly alter the emission polarization properties of strained non-polar oriented wurtzite group III-nitride QWs. For certain values of strain, the emission polarization direction can rotate by 90° either within the QW plane, or from being out-of-plane to being in-plane which is desirable for light emission applications. The study based on a k · p type perturbation theory simultaneously accounts for the influence of anisotropic in-plane strain which arises in such QWs and also affects the optical polarization properties. An important practical implication of these results is that M-plane oriented AlxGa1-xN QWs under anisotropic in-plane tensile strain can work as efficient ultra-violet light emitters, unlike bulk AlxGa1-xN films with identical composition and strain. After including the influence of the out-of-plane crystal momentum, the emission polarization criterion allows for larger concentration of Al in such QW active layers if the well width is kept sufficiently small. These results are also applicable to A-plane oriented QWs.

  17. High-Performance of Gas Hydrates in Confined Nanospace for Reversible CH4 /CO2 Storage.

    PubMed

    Casco, Mirian E; Jordá, José L; Rey, Fernando; Fauth, François; Martinez-Escandell, Manuel; Rodríguez-Reinoso, Francisco; Ramos-Fernández, Enrique V; Silvestre-Albero, Joaquín

    2016-07-11

    The molecular exchange of CH4 for CO2 in gas hydrates grown in confined nanospace has been evaluated for the first time using activated carbons as a host structure. The nano-confinement effects taking place inside the carbon cavities and the exceptional physicochemical properties of the carbon structure allows us to accelerate the formation and decomposition process of the gas hydrates from the conventional timescale of hours/days in artificial bulk systems to minutes in confined nanospace. The CH4 /CO2 exchange process is fully reversible with high efficiency at practical temperature and pressure conditions. Furthermore, these activated carbons can be envisaged as promising materials for long-distance natural gas and CO2 transportation because of the combination of a high storage capacity, a high reversibility, and most important, with extremely fast kinetics for gas hydrate formation and release. PMID:27273454

  18. Device for plasma confinement and heating by high currents and nonclassical plasma transport properties

    DOEpatents

    Coppi, B.; Montgomery, D.B.

    1973-12-11

    A toroidal plasma containment device having means for inducing high total plasma currents and current densities and at the same time emhanced plasma heating, strong magnetic confinement, high energy density containment, magnetic modulation, microwaveinduced heating, and diagnostic accessibility is described. (Official Gazette)

  19. Confinement of high-energy trapped particles in tokamaks

    SciTech Connect

    Goldston, R.J.; White, R.B.; Boozer, A.H.

    1981-08-31

    The banana orbits of high-energy trapped particles in tokamaks are found to diffuse rapidly in the radial direction if the toroidal ripple exceeds a low critical value. During this diffusion the energy, the magnetic moment, and the value of the magnetic field strength at the banana tips are conserved.

  20. Confinement of high energy trapped particles in tokamaks

    SciTech Connect

    Goldston, R.J.; White, R.B.; Boozer, A.H.

    1981-04-01

    The banana orbits of high energy trapped particles in tokamaks are found to diffuse rapidly in the radial direction if the toroidal ripple exceeds a low critical value. During this diffusion the energy, the magnetic moment, and the value of the magnetic field strength at the banana tips are conserved.

  1. Phase behaviour and correlations of parallel hard squares: from highly confined to bulk systems

    NASA Astrophysics Data System (ADS)

    González-Pinto, Miguel; Martínez-Ratón, Yuri; Varga, Szabolcs; Gurin, Peter; Velasco, Enrique

    2016-06-01

    We study a fluid of two-dimensional parallel hard squares in bulk and under confinement in channels, with the aim of evaluating the performance of fundamental-measure theory (FMT). To this purpose, we first analyse the phase behaviour of the bulk system using FMT and Percus–Yevick (PY) theory, and compare the results with molecular dynamics and Monte Carlo simulations. In a second step, we study the confined system and check the results against those obtained from the transfer matrix method and from our own Monte Carlo simulations. Squares are confined to channels with parallel walls at angles of 0° or 45° relative to the diagonals of the parallel hard squares, respectively, which allows for an assessment of the effect of the external-potential symmetry on the fluid structural properties. In general FMT overestimates bulk correlations, predicting the existence of a columnar phase (absent in simulations) prior to crystallization. The equation of state predicted by FMT compares well with simulations, although the PY approach with the virial route is better in some range of packing fractions. The FMT is highly accurate for the structure and correlations of the confined fluid due to the dimensional crossover property fulfilled by the theory. Both density profiles and equations of state of the confined system are accurately predicted by the theory. The highly non-uniform pair correlations inside the channel are also very well described by FMT.

  2. Phase behaviour and correlations of parallel hard squares: from highly confined to bulk systems.

    PubMed

    González-Pinto, Miguel; Martínez-Ratón, Yuri; Varga, Szabolcs; Gurin, Peter; Velasco, Enrique

    2016-06-22

    We study a fluid of two-dimensional parallel hard squares in bulk and under confinement in channels, with the aim of evaluating the performance of fundamental-measure theory (FMT). To this purpose, we first analyse the phase behaviour of the bulk system using FMT and Percus-Yevick (PY) theory, and compare the results with molecular dynamics and Monte Carlo simulations. In a second step, we study the confined system and check the results against those obtained from the transfer matrix method and from our own Monte Carlo simulations. Squares are confined to channels with parallel walls at angles of 0° or 45° relative to the diagonals of the parallel hard squares, respectively, which allows for an assessment of the effect of the external-potential symmetry on the fluid structural properties. In general FMT overestimates bulk correlations, predicting the existence of a columnar phase (absent in simulations) prior to crystallization. The equation of state predicted by FMT compares well with simulations, although the PY approach with the virial route is better in some range of packing fractions. The FMT is highly accurate for the structure and correlations of the confined fluid due to the dimensional crossover property fulfilled by the theory. Both density profiles and equations of state of the confined system are accurately predicted by the theory. The highly non-uniform pair correlations inside the channel are also very well described by FMT. PMID:27115832

  3. Influence of pore size on the Knight shift in liquid tin and mercury in a confined geometry

    NASA Astrophysics Data System (ADS)

    Tien, Cheng; Charnaya, E. V.; Lee, M. K.; Kumzerov, Yu A.

    2007-03-01

    119Sn and 199Hg NMR studies were carried out for metallic tin and mercury embedded in synthetic opals and porous glasses. The Knight shift for confined liquid tin and mercury was found to decrease monotonically with decreasing pore size, evidence for the reduction of electron susceptibility. Size-induced alterations in the Knight shift were more pronounced for confined mercury than for tin. The influence of pore filling on the NMR line shape and Knight shift was observed for tin within opal. The reasons for the decreasing Knight shift for liquid metals in a confined geometry are discussed. Correlations between the alteration in the Knight shift and atomic number are shown, the changes in fractional values of the Knight shift remaining almost identical.

  4. High convergence, indirect drive inertial confinement fusion experiments at Nova

    SciTech Connect

    Lerche, R.A.; Cable, M.D.; Hatchett, S.P.

    1995-06-02

    High convergence, indirect drive implosion experiments have been done at the Nova Laser Facility. The targets were deuterium and deuterium/tritium filled, glass microballoons driven symmetrically by x rays produced in a surrounding uranium hohlraum. Implosions achieved convergence ratios of 24:1 with fuel densities of 19 g/cm{sup 3}; this is equivalent to the range required for the hot spot of ignition scale capsules. The implosions used a shaped drive and were well characterized by a variety of laser and target measurements. The primary measurement was the fuel density using the secondary neutron technique (neutrons from the reaction {sup 2}H({sup 3}H,n){sup 4}He in initially pure deuterium fuel). Laser measurements include power, energy and pointing. Simultaneous measurement of neutron yield, fusion reaction rate, and x-ray images provide additional information about the implosion process. Computer models are in good agreement with measured results.

  5. Simulation of Microdamage in Ceramics Deformed under High Confinement

    NASA Astrophysics Data System (ADS)

    Zhang, Dongmei; Feng, Ruqiang

    2004-06-01

    A polycrystalline ceramic may display high strength under dynamic compression but fails catastrophically during load reversal to tension. One plausible mechanism is that heterogeneous plasticity in some of the crystals under compression induces microdamage during load reversal. To examine this possibility quantitatively, we developed a computational method, in which the polycrystalline microstructure is realistically simulated using Voronoi crystals having grain boundary layer. Both anisotropic elasticity and plastic slip in limited crystallographic planes are considered in crystal modeling. The grain boundary material is treated as an isotropic glassy solid, which has pressure-dependent shear strength under compression and fractures in Mode I when the threshold is reached. The structural and material models have been implemented into ABAQUS/Explicit code. Model simulations have been performed to analyze the intragranular microplasticity, intergranular microdamage, and their interactions in polycrystalline α-6H silicon carbide subjected to dynamic unaxial-strain compression and then load reversal to tension. It is found that microplasticity is more favorable than intergranular shear damage during compression. However, both the microplasticity-induced heterogeneity and the grain boundary damage affect strongly microcracking during load reversal, which leads to fragmentation or spallation depending on the level of compression. The significance of these findings is discussed.

  6. Metallic tin quantum sheets confined in graphene toward high-efficiency carbon dioxide electroreduction.

    PubMed

    Lei, Fengcai; Liu, Wei; Sun, Yongfu; Xu, Jiaqi; Liu, Katong; Liang, Liang; Yao, Tao; Pan, Bicai; Wei, Shiqiang; Xie, Yi

    2016-01-01

    Ultrathin metal layers can be highly active carbon dioxide electroreduction catalysts, but may also be prone to oxidation. Here we construct a model of graphene confined ultrathin layers of highly reactive metals, taking the synthetic highly reactive tin quantum sheets confined in graphene as an example. The higher electrochemical active area ensures 9 times larger carbon dioxide adsorption capacity relative to bulk tin, while the highly-conductive graphene favours rate-determining electron transfer from carbon dioxide to its radical anion. The lowered tin-tin coordination numbers, revealed by X-ray absorption fine structure spectroscopy, enable tin quantum sheets confined in graphene to efficiently stabilize the carbon dioxide radical anion, verified by 0.13 volts lowered potential of hydroxyl ion adsorption compared with bulk tin. Hence, the tin quantum sheets confined in graphene show enhanced electrocatalytic activity and stability. This work may provide a promising lead for designing efficient and robust catalysts for electrolytic fuel synthesis. PMID:27585984

  7. Sequential Indentation Tests to Investigate the Influence of Confining Stress on Rock Breakage by Tunnel Boring Machine Cutter in a Biaxial State

    NASA Astrophysics Data System (ADS)

    Liu, Jie; Cao, Ping; Han, Dongya

    2016-04-01

    The influence of confining stress on rock breakage by a tunnel boring machine cutter was investigated by conducting sequential indentation tests in a biaxial state. Combined with morphology measurements of breaking grooves and an analysis of surface and internal crack propagation between nicks, the effects of maximum confining stress and minimum stress on indentation efficiency, crack propagation and chip formation were investigated. Indentation tests and morphology measurements show that increasing a maximum confining stress will result in increased consumed energy in indentations, enlarged groove volumes and promoted indentation efficiency when the corresponding minimum confining stress is fixed. The energy consumed in indentations will increase with increase in minimum confining stress, however, because of the decreased groove volumes as the minimum confining stress increases, the efficiency will decrease. Observations of surface crack propagation show that more intensive fractures will be induced as the maximum confining stress increases, whereas the opposite occurs for an increase of minimum confining stress. An observation of the middle section, cracks and chips shows that as the maximum confining stress increases, chips tend to form in deeper parts when the minimum confining stress is fixed, whereas they tend to formed in shallower parts as the minimum confining stress increases when the maximum confining stress is fixed.

  8. Observation of sub-detonative responses in confined high density HMX-based PBXs

    NASA Astrophysics Data System (ADS)

    Cumming, Andrew; Wood, Andrew; Steward, Paul; Ottley, Philip; Gould, Peter; Lewtas, Ian

    2015-06-01

    This paper describes experiments and modelling aimed at understanding the behaviour of highly loaded (90%-95%) pressed HMX-based PBXs, when subjected to shock compression and ignition by means of distinct mechanical and thermal insults under confinement. In order to separate the role of the stimuli, a test has been designed where a metal impactor is propelled at test samples using a well characterised propellant over a range of velocities to produce various levels of mechanical damage. The impactor is then heated using a characterised pyrotechnic composition which ignites the mechanically damaged explosive. Tubes have been designed to examine the effect of confinement at burst pressures of 218.5MPa and 120MPa. The high confinement tubes employ polycarbonate windows and the low confinement tubes are manufactured from polycarbonate blocks to allow the reaction of the energetic material to be captured using high-speed video. Tests carried out using these tubes have given a good insight into the processes occurring. Modelling runs have predicted an oscillating compressive wave in the explosive and considerable damage at either end of the explosive column. The latter leads to potential deconsolidation once the donor charge has burnt out allowing increased burning and violence.

  9. The influence of the stagnation zone on the fluid dynamics at the nozzle exit of a confined and submerged impinging jet

    NASA Astrophysics Data System (ADS)

    Jeffers, Nicholas; Stafford, Jason; Conway, Ciaran; Punch, Jeff; Walsh, Edmond

    2016-02-01

    Low profile impinging jets provide a means to achieve high heat transfer coefficients while occupying a small quantity of space. Consequently, they are found in many engineering applications such as electronics cooling, annealing of metals, food processing, and others. This paper investigates the influence of the stagnation zone fluid dynamics on the nozzle exit flow condition of a low profile, submerged, and confined impinging water jet. The jet was geometrically constrained to a round, 16-mm diameter, square-edged nozzle at a jet exit to target surface spacing ( H/ D) that varied between 0.25 < {{ H}{/}{ D}} < 8.75. The influence of turbulent flow regimes is the main focus of this paper; however, laminar flow data are also presented between 1350 < Re < 17{,}300. A custom measurement facility was designed and commissioned to utilise particle image velocimetry in order to quantitatively measure the fluid dynamics both before and after the jet exits its nozzle. The velocity profiles are normalised with the mean velocity across the nozzle exit, and turbulence statistics are also presented. The primary objective of this paper is to present accurate flow profiles across the nozzle exit of an impinging jet confined to a low H/ D, with a view to guide the boundary conditions chosen for numerical simulations confined to similar constraints. The results revealed in this paper suggest that the fluid dynamics in the stagnation zone strongly influences the nozzle exit velocity profile at confinement heights between 0 < {{ H}{/}{ D}} < 1. This is of particular relevance with regard to the choice of inlet boundary conditions in numerical models, and it was found that it is necessary to model a jet tube length {{ L}{/}{ D}} > 0.5—where D is the inner diameter of the jet—in order to minimise modelling uncertainty.

  10. String tension scaling in high-temperature confined SU(N) gauge theories

    SciTech Connect

    Meisinger, Peter N.; Ogilvie, Michael C.

    2010-01-15

    SU(N) gauge theories, extended with adjoint fermions having periodic boundary conditions, are confining at high temperature for sufficiently light fermion mass m. In the high-temperature confining region, the one-loop effective potential for Polyakov loops has a Z(N)-symmetric confining minimum. String tensions associated with Polyakov loops are calculable in perturbation theory, and display a novel scaling behavior in which higher representations have smaller string tensions than the fundamental representation. In the magnetic sector, the Polyakov loop plays a role similar to a Higgs field, leading to an apparent breaking of SU(N) to U(1){sup N-1}. This in turn yields a dual effective theory where magnetic monopoles give rise to string tensions for spatial Wilson loops. The spatial string tensions arise semiclassically from kink solutions of the dual system. We prove that the spatial string tensions {sigma}{sub k}{sup (s)} associated with each N-ality k are constrained by a rigorous upper bound. This bound is saturated for N=2 and 3, but is insufficient to determine the spatial string tension scaling law for N{>=}4. Lattice simulations indicate that the high-temperature confining region is smoothly connected to the confining region of low-temperature pure SU(N) gauge theory. However, our results show that the string tension scaling behavior of the low-temperature region does not hold for the electric sector in the high-temperature region, and may not hold in the magnetic sector. The predicted change in the behavior of the electric sector should be readily distinguishable in lattice simulations.

  11. The Influence of Silica Nanoparticles on Ionic Liquid Behavior: A Clear Difference between Adsorption and Confinement

    PubMed Central

    Wang, Yaxing; Li, Cheng; Guo, Xiaojing; Wu, Guozhong

    2013-01-01

    The phase behaviors of ionic liquids (ILs) confined in nanospace and adsorbed on outer surface of nanoparticles are expected to be different from those of the bulk. Anomalous phase behaviors of room temperature ionic liquid tributylhexadecylphosphonium bromide (P44416Br) confined in ordered mesoporous silica nanoparticles with average pore size 3.7 nm and adsorbed on outer surface of the same silica nanoparticles were reported. It was revealed that the melting points (Tm) of confined and adsorbed ILs depressed significantly in comparison with the bulk one. The Tm depressions for confined and adsorbed ILs are 8 °C and 14 °C, respectively. For comparison with the phase behavior of confined P44416Br, 1-butyl-3-methylimidazolium bromide (BmimBr) was entrapped within silica nanopores, we observed an enhancement of 50 °C in Tm under otherwise similar conditions. The XRD analysis indicates the formation of crystalline-like phase under confinement, in contrast to the amorphous phase in adsorbed IL. It was confirmed that the behavior of IL has clear difference. Moreover, the complex π-π stacking and H-bonding do not exist in the newly proposed phosphonium-based IL in comparison with the widely studied imidazolium-based IL. The opposite change in melting point of P44416Br@SiO2 and BmimBr@SiO2 indicates that the cationic species plays an important role in the variation of melting point. PMID:24145752

  12. Superwettability-Induced Confined Reaction toward High-Performance Flexible Electrodes.

    PubMed

    Xiong, Weiwei; Liu, Hongliang; Zhou, Yahong; Ding, Yi; Zhang, Xiqi; Jiang, Lei

    2016-05-18

    To find a general strategy to realize confinement of the conductive layer for high-performance flexible electrodes, with improved interfacial adhesion and high conductivity, is of important scientific significance. In this work, superwettability-induced confined reaction is used to fabricate high-performance flexible Ag/polymer electrodes, showing significantly improved silver conversion efficiency and interfacial adhesion. The as-prepared flexible electrodes by superhydrophilic polymeric surface under oil are highly conductive with an order of magnitude higher than the Ag/polymer electrodes obtained from original polymeric surface. The high conductivity achieved via superhydrophilic confinement is ascribed to the fact that the superhydrophilic polymeric surface can enhance the reaction rate of silver deposition and reduce the size of silver nanoparticles to achieve the densest packing. This new approach will provide a simple method to fabricate flexible and highly conductive Ag/polymer electrodes with excellent adhesion between the conductive layer and the substrate, and can be extended to other metal/polymeric electrodes or alloy/polymeric electrodes. PMID:27115913

  13. Holocene river dynamics in Northland, New Zealand: The influence of valley floor confinement on floodplain development

    NASA Astrophysics Data System (ADS)

    Richardson, J. M.; Fuller, I. C.; Holt, K. A.; Litchfield, N. J.; Macklin, M. G.

    2013-11-01

    Valley floor mapping, sedimentology, and 14C-dating have been used to reconstruct the fluvial history at eight floodplain sites spread throughout Northland, a region removed from the main areas of tectonic and volcanic activity in New Zealand. We present a probability-based record of Holocene river behaviour for Northland using 14C-dated Holocene fluvial deposits and compare this with independent palaeoclimate proxy records from the North Island. Holocene floodplain evolution and fluvial behaviour have been conditioned by the degree of valley-floor confinement. In the most and least confined valley settings, Holocene floodplain evolution has involved the development of a single floodplain surface. At partly confined sites, the river terrace and floodplain geomorphology are more complex. Region-wide progressive floodplain alluviation through the mid to late Holocene and a period of increased river activity between 3500 and 2800 cal. YBP in response to climatically driven increases in sediment supply was followed by a period of valley floor incision and terrace formation beginning after 1900 cal. YBP. In partly confined valley settings, this was followed by the aggradation of a lower Holocene floodplain surface, with rapid rates of vertical accretion in response to post-settlement catchment disturbance. The results of this study indicate that valley floor confinement has played a major role in controlling Northland Holocene river floodplain development, producing a continuum of floodplain and river terrace landforms in response to climatically and anthropogenically driven variations in sediment flux.

  14. Influence of the nanoparticles agglomeration state in the quantum-confinement effects: Experimental evidences

    SciTech Connect

    Lorite, I.; Romero, J. J.; Fernandez, J. F.

    2015-03-15

    The agglomeration state facilitates particle-particle interaction which produces important effects in the phonon confinement effects at the nanoscale. A partial phonon transmission between close nanoparticles yields a lower momentum conservation relaxation than in a single isolated nanoparticle. It means a larger red shift and broadening of the Raman modes than the expected ones for Raman quantum confinement effects. This particle-particle interaction can drive to error when Raman responses are used to estimate the size of the nanoscaled materials. In this work different corrections are suggested to overtake this source of error.

  15. Design of Topas photonic bandgap fiber with high birefringence and low confinement loss

    NASA Astrophysics Data System (ADS)

    Wang, Doudou; Wang, Lili

    2010-09-01

    A highly birefringent hollow-core photonic bandgap fiber based on Topas cyclic olefin copolymer is designed. The rhombic hollow-core with rounded corners is formed by omitting four central air holes of the cladding structure. The guided modes, birefringence and confinement loss of the fiber are investigated by using the full-vector finite element method. A high phase birefringence of the order of 10 -3, a group birefringence of the order of 10 -2 and confinement loss less than 0.1 dB/km are obtained at the central wavelength (1.55 μm) range of the bandgap for fiber with seven rings of air holes in the cladding region.

  16. High pressure induced phase transition and superdiffusion in anomalous fluid confined in flexible nanopores

    SciTech Connect

    Bordin, José Rafael; Krott, Leandro B. Barbosa, Marcia C.

    2014-10-14

    The behavior of a confined spherical symmetric anomalous fluid under high external pressure was studied with Molecular Dynamics simulations. The fluid is modeled by a core-softened potential with two characteristic length scales, which in bulk reproduces the dynamical, thermodynamical, and structural anomalous behavior observed for water and other anomalous fluids. Our findings show that this system has a superdiffusion regime for sufficient high pressure and low temperature. As well, our results indicate that this superdiffusive regime is strongly related with the fluid structural properties and the superdiffusion to diffusion transition is a first order phase transition. We show how the simulation time and statistics are important to obtain the correct dynamical behavior of the confined fluid. Our results are discussed on the basis of the two length scales.

  17. Energy Confinement of High-Density Pellet-Fueled Plasmas in the Alcator C Tokamak

    NASA Astrophysics Data System (ADS)

    Greenwald, M.; Gwinn, D.; Milora, S.; Parker, J.; Parker, R.; Wolfe, S.; Besen, M.; Camacho, F.; Fairfax, S.; Fiore, C.; Foord, M.; Gandy, R.; Gomez, C.; Granetz, R.; Labombard, B.; Lipschultz, B.; Lloyd, B.; Marmar, E.; McCool, S.; Pappas, D.; Petrasso, R.; Pribyl, P.; Rice, J.; Schuresko, D.; Takase, Y.; Terry, J.; Watterson, R.

    1984-07-01

    A series of pellet-fueling experiments has been carried out on the Alcator C tokamak. High-speed hydrogen pellets penetrate to within a few centimeters of the magnetic axis, raise the plasma density, and produce peaked density profiles. Energy confinement is observed to increase over similar discharges fueled only by gas puffing. In this manner record values of electron density, plasma pressure, and Lawson number (n τ) have been achieved.

  18. Observation of a high-confinement regime in a tokamak plasma with ion cyclotron resonance heating

    NASA Astrophysics Data System (ADS)

    Steinmetz, K.; Noterdaeme, J.-M.; Wagner, F.; Wesner, F.; Bäumler, J.; Becker, G.; Bosch, H. S.; Brambilla, M.; Braun, F.; Brocken, H.; Eberhagen, A.; Fritsch, R.; Fussmann, G.; Gehre, O.; Gernhardt, J.; v. Gierke, G.; Glock, E.; Gruber, O.; Haas, G.; Hofmann, J.; Hofmeister, F.; Izvozchikov, A.; Janeschitz, G.; Karger, F.; Keilhacker, M.; Klüber, O.; Kornherr, M.; Lackner, K.; Lisitano, G.; van Mark, E.; Mast, F.; Mayer, H. M.; McCormick, K.; Meisel, D.; Mertens, V.; Müller, E. R.; Murmann, H.; Niedermeyer, H.; Poschenrieder, W.; Puri, S.; Rapp, H.; Röhr, H.; Ryter, F.; Schmitter, K.-H.; Schneider, F.; Setzensack, C.; Siller, G.; Smeulders, P.; Söldner, F.; Speth, E.; Steuer, K.-H.; Vollmer, O.; Wedler, H.; Zasche, D.

    1987-01-01

    The H mode in ion cyclotron-resonance-heated plasmas has been investigated with and without additional neutral beam injection. Ion cyclotron-resonance heating can cause the transition into a high-confinement regime (H mode) in combination with beam heating. The H mode, however, has also been realized-for the first time-with ion cyclotron-resonance heating alone in the D (H)-hydrogen minority scheme at an absorbed rf power of 1.1 MW.

  19. High-Beta, Improved Confinement Reversed-Field Pinch Plasmas at High Density

    SciTech Connect

    Wyman, M.; Chapman, B. E.; Ahn, J. W.; Almagri, A.; Anderson, J.; Bonomo, F.; Brower, D. L.; Combs, Stephen Kirk; Craig, D.; Hartog, D. J. Den; Deng, B.; Ding, W. X.; Ebrahimi, F.; Ennis, D.; Fiksel, G.; Foust, Charles R; Franz, P.; Goetz, J.; O'Connell, R,; Oliva, S.; Prager, S. C.; Reusch, J. A.; Sarff, J. S.; Stephens, H. D.; Yates, T.

    2008-01-01

    In Madison Symmetric Torus Dexter et al., Fusion Technol. 19, 131 1991 discharges where improved confinement is brought about by modification of the current profile, pellet injection has quadrupled the density, reaching ne=41019 m 3. Without pellet injection, the achievable density in improved confinement discharges had been limited by edge-resonant tearing instability. With pellet injection, the total beta has been increased to 26%, and the energy confinement time is comparable to that at low density. Pressure-driven local interchange and global tearing are predicted to be linearly unstable. Interchange has not yet been observed experimentally, but there is possible evidence of pressure-driven tearing, an instability usually driven by the current gradient in the reversed-field pinch.

  20. High-{beta}, improved confinement reversed-field pinch plasmas at high density

    SciTech Connect

    Wyman, M. D.; Chapman, B. E.; Ahn, J. W.; Almagri, A. F.; Anderson, J. K.; Den Hartog, D. J.; Ebrahimi, F.; Ennis, D. A.; Fiksel, G.; Gangadhara, S.; Goetz, J. A.; O'Connell, R.; Oliva, S. P.; Prager, S. C.; Reusch, J. A.; Sarff, J. S.; Stephens, H. D.; Bonomo, F.; Franz, P.; Brower, D. L.

    2008-01-15

    In Madison Symmetric Torus [Dexter et al., Fusion Technol. 19, 131 (1991)] discharges where improved confinement is brought about by modification of the current profile, pellet injection has quadrupled the density, reaching n{sub e}=4x10{sup 19} m{sup -3}. Without pellet injection, the achievable density in improved confinement discharges had been limited by edge-resonant tearing instability. With pellet injection, the total beta has been increased to 26%, and the energy confinement time is comparable to that at low density. Pressure-driven local interchange and global tearing are predicted to be linearly unstable. Interchange has not yet been observed experimentally, but there is possible evidence of pressure-driven tearing, an instability usually driven by the current gradient in the reversed-field pinch.

  1. Influence of channel position on sample confinement in two-dimensional planar microfluidic devices.

    PubMed

    Lerch, Margaret A; Hoffman, Michelle D; Jacobson, Stephen C

    2008-02-01

    We report enhanced sample confinement on microfluidic devices using a combination of electrokinetic flow from adjacent control channels and electric field shaping with an array of channels perpendicular to the sample stream. The basic device design consisted of a single first dimension (1D) channel, intersecting an array of 32 or 96 parallel second dimension (2D) channels. To minimize sample dispersion and leakage into the parallel channels as the sample traversed the sample transfer region, control channels were placed to the left and right of the 1D and waste channels. The electrokinetic flow from the control channels confined the sample stream and acted as a buffer between the sample stream and the 2D channels. To further enhance sample confinement, the electric field was shaped parallel to the sample stream by placing the channel array in close proximity to the sample transfer region. Using COMSOL Multiphysics, initial work focused on simulating the electric fields and fluid flows in various device geometries, and the results guided device design. Following the design phase, we fabricated devices with 40, 80, and 120 microm wide control channels and evaluated the sample stream width as a function of the electric field strength ratio in the control and 1D channels (E(C)/E(1D)). For the 32 channel design, the 40 and 80 microm wide control channels produced the most effective sample confinement with stream widths as narrow as 75 microm, and for the 96 channel design, all three control channel widths generated comparable sample stream widths. Comparison of the 32 and 96 channel designs showed sample confinement scaled easily with the length of the sample transfer region. PMID:18231672

  2. High-density plasma production with potential confinement in the GAMMA 10 tandem mirror

    NASA Astrophysics Data System (ADS)

    Ichimura, M.; Cho, T.; Hirata, M.; Hojo, H.; Ishii, K.; Itakura, A.; Katanuma, I.; Kohagura, J.; Nakashima, Y.; Saito, T.; Tamano, T.; Tanaka, S.; Tatematsu, Y.; Yatsu, K.; Yoshikawa, M.

    2001-05-01

    The improvement of potential confinement was attained in the GAMMA 10 tandem mirror [Phys. Rev. Lett. 55, 939 (1985); Proceedings of the 13th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Washington, 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. 2, p. 539] by axisymmetrization of heating systems for the plasma production, heating, and potential formation. A significant increase of the density and diamagnetism by the potential confinement was observed. In the previous experiment, it was difficult to increase the central cell density higher than 2.7×1018m-3. One of the possible mechanisms is the density clamping due to the eigenmode formation of the ion-cyclotron-range of frequency (ICRF) waves in the axial direction. With high harmonic ICRF waves (RF3), the experiments to overcome this problem have been performed. In preliminary experiments with RF3 and NBI the maximum density of 4×1018m-3 was attained.

  3. Observation of sub-detonative responses in confined high density HMX-based PBXs

    NASA Astrophysics Data System (ADS)

    Cook, Malcolm; Wood, Andrew; Ottley, Philip; Cheese, Phil

    2013-06-01

    This paper describes experiments and modelling aimed at understanding the behaviour of highly loaded (90%-95%) pressed HMX-based PBX compositions, when subjected to shock compression and ignition, by means of a propellant donor charge, under confinement. Such tests are routinely carried out in the UK on new formulations to determine their burn to violent reaction characteristics. The Bullseye propellant donor charge has been characterised in terms of pressure and temperature output. A range of tubes have been designed to examine the contribution of tube material properties (steel versus aluminium, 218.5 MPa) and to examine the effect of reduced confinement (120 MPa). For the reduced confinement scenario polycarbonate as well as steel and aluminium vessels have been designed which allow the reaction of the energetic material to be captured using high-speed video. In particular, tests carried out in the polycarbonate tubes have given a good insight of the processes occurring. Preliminary hydrocode modelling runs predicted an oscillating compressive wave in the explosive and considerable damage at either end of the explosive column. The latter leads to potential deconsolidation once the donor charge has burnt out allowing increased burning and violence. This work was undertaken as part of the MOD funded UK-Energetics research programme.

  4. Observation of sub-detonation response in confined high density HMX based PBXs

    NASA Astrophysics Data System (ADS)

    Cook, M. D.; Wood, A. D.; Ottley, P. R.; Cheese, P. J.

    2014-05-01

    This paper describes experiments and modelling aimed at understanding the behaviour of highly loaded (90%-95%) pressed HMX-based PBX compositions, when subjected to shock compression and ignition, by means of a propellant donor charge, under confinement. Such tests are routinely carried out in the UK on new formulations to determine their burn to violent reaction characteristics. The Bullseye propellant donor charge has been characterised in terms of pressure and temperature output. A range of tubes have been designed to examine the contribution of tube material properties (steel versus aluminium, 218.5 MPa) and to examine the effect of reduced confinement (120 MPa). For the reduced confinement scenario polycarbonate as well as steel and aluminium vessels have been designed which allow the reaction of the energetic material to be captured using a Phantom high-speed camera. In particular, tests carried out in the polycarbonate tubes have given a good insight of the processes occurring. Preliminary hydrocode modelling runs predicted an oscillating compressive wave in the explosive and considerable damage at either end of the explosive column. The latter leads to potential deconsolidation once the donor charge has burnt out allowing increased burning and violence.

  5. New steady-state quiescent high-confinement plasma in an experimental advanced superconducting tokamak.

    PubMed

    Hu, J S; Sun, Z; Guo, H Y; Li, J G; Wan, B N; Wang, H Q; Ding, S Y; Xu, G S; Liang, Y F; Mansfield, D K; Maingi, R; Zou, X L; Wang, L; Ren, J; Zuo, G Z; Zhang, L; Duan, Y M; Shi, T H; Hu, L Q

    2015-02-01

    A critical challenge facing the basic long-pulse high-confinement operation scenario (H mode) for ITER is to control a magnetohydrodynamic (MHD) instability, known as the edge localized mode (ELM), which leads to cyclical high peak heat and particle fluxes at the plasma facing components. A breakthrough is made in the Experimental Advanced Superconducting Tokamak in achieving a new steady-state H mode without the presence of ELMs for a duration exceeding hundreds of energy confinement times, by using a novel technique of continuous real-time injection of a lithium (Li) aerosol into the edge plasma. The steady-state ELM-free H mode is accompanied by a strong edge coherent MHD mode (ECM) at a frequency of 35-40 kHz with a poloidal wavelength of 10.2 cm in the ion diamagnetic drift direction, providing continuous heat and particle exhaust, thus preventing the transient heat deposition on plasma facing components and impurity accumulation in the confined plasma. It is truly remarkable that Li injection appears to promote the growth of the ECM, owing to the increase in Li concentration and hence collisionality at the edge, as predicted by GYRO simulations. This new steady-state ELM-free H-mode regime, enabled by real-time Li injection, may open a new avenue for next-step fusion development. PMID:25699449

  6. Dielectric confinement influenced screened Coulomb potential for a semiconductor quantum wire

    NASA Astrophysics Data System (ADS)

    Aharonyan, K. H.; Margaryan, N. B.

    2016-01-01

    A formalism of the Thomas-Fermi method has been applied for studying the screening effect due to quasi-one-dimensional electron gas in a semiconductor cylindrical quantum wire embedded in the barrier environment. With taking into account of strongly low dielectric properties of the barrier material, an applicability of the quantum wire effective interaction potential of the confined charge carriers has been revealed. Both screened quasi- one-dimensional interaction potential and effective screening length analytical expressions are derived in the first time. It is shown that in the long wavelength moderate limit dielectric confinement effect enhances strength of the screening potential depending on the both radius of the wire and effective screening length, whereas in the long wavelength strong limit the screening potential solely is determined by barrier environment dielectric properties.

  7. Bubble confinement in flow boiling of FC-72 in a ''rectangular'' microchannel of high aspect ratio

    SciTech Connect

    Barber, Jacqueline; Brutin, David; Tadrist, Lounes; Sefiane, Khellil

    2010-11-15

    Boiling in microchannels remains elusive due to the lack of full understanding of the mechanisms involved. A powerful tool in achieving better comprehension of the mechanisms is detailed imaging and analysis of the two-phase flow at a fundamental level. Boiling is induced in a single microchannel geometry (hydraulic diameter 727 {mu}m), using a refrigerant FC-72, to investigate the effect of channel confinement on bubble growth. A transparent, metallic, conductive deposit has been developed on the exterior of the rectangular microchannel, allowing simultaneous uniform heating and visualisation to be achieved. The data presented in this paper is for a particular case with a uniform heat flux applied to the microchannel and inlet liquid mass flowrate held constant. In conjunction with obtaining high-speed images and videos, sensitive pressure sensors are used to record the pressure drop across the microchannel over time. Bubble nucleation and growth, as well as periodic slug flow, are observed in the microchannel test section. The periodic pressure fluctuations evidenced across the microchannel are caused by the bubble dynamics and instances of vapour blockage during confined bubble growth in the channel. The variation of the aspect ratio and the interface velocities of the growing vapour slug over time, are all observed and analysed. We follow visually the nucleation and subsequent both 'free' and 'confined' growth of a vapour bubble during flow boiling of FC-72 in a microchannel, from analysis of our results, images and video sequences with the corresponding pressure data obtained. (author)

  8. High temperatures in inertial confinement fusion radiation cavities heated with 0. 35 [mu]m light

    SciTech Connect

    Kauffman, R.L.; Suter, L.J.; Darrow, C.B.; Kilkenny, J.D.; Kornblum, H.N.; Montgomery, D.S.; Phillion, D.W.; Rosen, M.D.; Theissen, A.R.; Wallace, R.J.; Ze, F. )

    1994-10-24

    We have demonstrated efficient coupling of 0.35 [mu]m laser light for radiation production in inertial confinement fusion (ICF) cavity targets. Temperatures of 270 eV are measured in cavities used for implosions and 300 eV in smaller cavities, significantly extending the temperature range attained in the laboratory to those required for high-gain indirect drive ICF. High-contrast, shaped drive pulses required for implosion experiments have also been demonstrated for the first time. Low levels of scattered light and fast electrons are observed, indicating that plasma instability production is not significant.

  9. Production and study of high-beta plasma confined by a superconducting dipole magnet

    SciTech Connect

    Garnier, D.T.; Hansen, A.; Mauel, M.E.; Ortiz, E.; Boxer, A.C.; Ellsworth, J.; Karim, I.; Kesner, J.; Mahar, S.; Roach, A.

    2006-05-15

    The Levitated Dipole Experiment (LDX) [J. Kesner et al., in Fusion Energy 1998, 1165 (1999)] is a new research facility that is exploring the confinement and stability of plasma created within the dipole field produced by a strong superconducting magnet. Unlike other configurations in which stability depends on curvature and magnetic shear, magnetohydrodynamic stability of a dipole derives from plasma compressibility. Theoretically, the dipole magnetic geometry can stabilize a centrally peaked plasma pressure that exceeds the local magnetic pressure ({beta}>1), and the absence of magnetic shear allows particle and energy confinement to decouple. In initial experiments, long-pulse, quasi-steady-state microwave discharges lasting more than 10 s have been produced that are consistent with equilibria having peak beta values of 20%. Detailed measurements have been made of discharge evolution, plasma dynamics and instability, and the roles of gas fueling, microwave power deposition profiles, and plasma boundary shape. In these initial experiments, the high-field superconducting floating coil was supported by three thin supports. The plasma is created by multifrequency electron cyclotron resonance heating at 2.45 and 6.4 GHz, and a population of energetic electrons, with mean energies above 50 keV, dominates the plasma pressure. Creation of high-pressure, high-beta plasma is possible only when intense hot electron interchange instabilities are stabilized by sufficiently high background plasma density. A dramatic transition from a low-density, low-beta regime to a more quiescent, high-beta regime is observed when the plasma fueling rate and confinement time become sufficiently large.

  10. First Observation of the High Field Side Sawtooth Crash and Heat Transfer during Driven Reconnection Processes in Magnetically Confined Plasmas

    SciTech Connect

    Park, HK; Luhmann, NC; Donne, AJH; Classen, IGJ; Domier, CW; Mazzucato, E; Munsat, T; van de Pol, MJ; Xia, Z

    2005-12-01

    High resolution (temporal and spatial), two-dimensional images of electron temperature fluctuations during sawtooth oscillations were employed to study driven reconnection processes in magnetically confined toroidal plasmas. The combination of kink and local pressure driven instabilities leads to an "X-point" reconnection process that is localized in the toroidal and poloidal planes. The reconnection is not always confined to the magnetic surfaces with minimum energy. The heat transport process from the core is demonstrated to be highly collective rather than stochastic.

  11. Single molecule tracking fluorescence microscopy in mitochondria reveals highly dynamic but confined movement of Tom40

    PubMed Central

    Kuzmenko, Anton; Tankov, Stoyan; English, Brian P.; Tarassov, Ivan; Tenson, Tanel; Kamenski, Piotr; Elf, Johan; Hauryliuk, Vasili

    2011-01-01

    Tom40 is an integral protein of the mitochondrial outer membrane, which as the central component of the Translocase of the Outer Membrane (TOM) complex forms a channel for protein import. We characterize the diffusion properties of individual Tom40 molecules fused to the photoconvertable fluorescent protein Dendra2 with millisecond temporal resolution. By imaging individual Tom40 molecules in intact isolated yeast mitochondria using photoactivated localization microscopy with sub-diffraction limited spatial precision, we demonstrate that Tom40 movement in the outer mitochondrial membrane is highly dynamic but confined in nature, suggesting anchoring of the TOM complex as a whole. PMID:22355710

  12. Single molecule tracking fluorescence microscopy in mitochondria reveals highly dynamic but confined movement of Tom40

    NASA Astrophysics Data System (ADS)

    Kuzmenko, Anton; Tankov, Stoyan; English, Brian P.; Tarassov, Ivan; Tenson, Tanel; Kamenski, Piotr; Elf, Johan; Hauryliuk, Vasili

    2011-12-01

    Tom40 is an integral protein of the mitochondrial outer membrane, which as the central component of the Translocase of the Outer Membrane (TOM) complex forms a channel for protein import. We characterize the diffusion properties of individual Tom40 molecules fused to the photoconvertable fluorescent protein Dendra2 with millisecond temporal resolution. By imaging individual Tom40 molecules in intact isolated yeast mitochondria using photoactivated localization microscopy with sub-diffraction limited spatial precision, we demonstrate that Tom40 movement in the outer mitochondrial membrane is highly dynamic but confined in nature, suggesting anchoring of the TOM complex as a whole.

  13. Design of high-perveance confined-flow guns for periodic-permanent-magnet-focused tubes

    NASA Technical Reports Server (NTRS)

    Stankiewicz, N.

    1979-01-01

    An approach to the design of high perveance, low compression guns is described in which confinement is used to stabilize the beam for subsequent periodic-permanent-magnet focusing. The computed results for two cases are presented. A magnetic boundary value problem was solved for the scalar potential from which the axial magnetic field was computed. A solution was found by iterating between Poisson's equation and the electron trajectory calculations. Magnetic field values were varied in magnitude until a laminar beam with minimum scalloping was produced.

  14. Indirect-drive inertial confinement fusion using highly supersonic, radiatively cooled, plasma slugs.

    PubMed

    Chittenden, J P; Dunne, M; Zepf, M; Lebedev, S V; Ciardi, A; Bland, S N

    2002-06-10

    We present a new approach to indirect-drive inertial confinement fusion which makes use of highly supersonic, radiatively cooled, slugs of plasma to energize a hohlraum. 2D resistive magnetohydrodynamic simulations of slug formation in shaped liner Z-pinch implosions are presented along with 2D-radiation-hydrodynamic simulations of the slug impacting a converter foil and 3D-view-factor simulations of a double-ended hohlraum. Results for the Z facility at Sandia National Laboratory indicate that two synchronous slugs of 250 kJ kinetic energy could be produced, resulting in a capsule surface temperature of approximately 225 eV. PMID:12059369

  15. Influence of the added mass effect and boundary conditions on the dynamic response of submerged and confined structures

    NASA Astrophysics Data System (ADS)

    Valentín, D.; Presas, A.; Egusquiza, E.; Valero, C.

    2014-03-01

    The dynamic response of submerged and confined disk-like structures is of interest in the flied of hydraulic machinery, especially in hydraulic turbine runners. This response is difficult to be estimated with accuracy due to the strong influence of the boundary conditions. Small radial gaps as well as short axial distances to rigid surfaces greatly modify the dynamic response because the fact of the added mass and damping effects. Moreover, the effect of the shaft coupling is also important for certain mode-shapes of the structure. In the present study, the influence of the added mass effect and boundary conditions on the dynamic behavior of a submerged disk attached to a shaft is evaluated through experimental tests and structural- acoustic coupling numerical simulations. For the experimentation, a test rig has been developed. It consists of a confined disk attached to a shaft inside a cylindrical container full of water. The disk can be fixed at different axial positions along the shaft. Piezoelectric patches are used to excite the disk and the response is measured with submersible accelerometers. For each configuration tested, the natural frequencies of the disk and the shaft are studied. Numerical results have been compared with experimental results.

  16. Influence of surface scattering on the thermal properties of spatially confined GaN nanofilm

    NASA Astrophysics Data System (ADS)

    Hou, Yang; Zhu, Lin-Li

    2016-08-01

    Gallium nitride (GaN), the notable representative of third generation semiconductors, has been widely applied to optoelectronic and microelectronic devices due to its excellent physical and chemical properties. In this paper, we investigate the surface scattering effect on the thermal properties of GaN nanofilms. The contribution of surface scattering to phonon transport is involved in solving a Boltzmann transport equation (BTE). The confined phonon properties of GaN nanofilms are calculated based on the elastic model. The theoretical results show that the surface scattering effect can modify the cross-plane phonon thermal conductivity of GaN nanostructures completely, resulting in the significant change of size effect on the conductivity in GaN nanofilm. Compared with the quantum confinement effect, the surface scattering leads to the order-of-magnitude reduction of the cross-plane thermal conductivity in GaN nanofilm. This work could be helpful for controlling the thermal properties of GaN nanostructures in nanoelectronic devices through surface engineering. Project supported by the National Natural Science Foundation of China (Grant Nos. 11302189 and 11321202) and the Doctoral Fund of Ministry of Education of China (Grant No. 20130101120175).

  17. Hydraulic head response of a confined aquifer influenced by river stage fluctuations and mechanical loading

    NASA Astrophysics Data System (ADS)

    Pacheco, F. A. L.; Fallico, C.

    2015-12-01

    The response to river stage fluctuation of a drilled well penetrating a confined aquifer was simulated using a stream-aquifer interaction algorithm. Because the confined aquifer is overlaid by a water table aquifer, the algorithm was coupled with formulae used to correct the heads for mechanical loading. The coupling of stream-aquifer interaction and mechanical loading models was tried for the first time in this study. The test site was a drilled well installed on the Montalto Uffugo aquifer located at the Calabria University groundwater test field (Calabria region, south of Italy). This aquifer comprises a 44 m-thick sand bank bounded on bottom and top by clay layers and covered by a 7 m-thick sandy conglomerate, being adjacent to the Mavigliano River. Overall, the head changes caused by a river stage raise represented a contribution of 49.3-57.8% to the total head, while mechanical loading accounted for the remaining 50.7-32.2%. The loading was triggered by a sequence of short-spaced rainfall events lasting for a total of 167 days, which caused recharge to the unconfined aquifer thickening the water column by some 3.1 m.

  18. Impurity Particle Transport in High Confinement Regimes Without ELMs on DIII-D

    NASA Astrophysics Data System (ADS)

    Grierson, B. A.

    2014-10-01

    Recent experiments on DIII-D using trace levels of fluorine gas injection have shown that high confinement regimes without ELMs can achieve rapid transport of impurity ions. Much attention has recently been given to regimes with H-mode energy confinement without edge-localized modes (ELMs), accessed either through Resonant Magnetic Perturbations (RMPs) or MHD such as edge harmonic oscillations or quasi-coherent edge oscillations. Experiments on DIII-D have used gas puffing of trace levels of fluorine to introduce this fully-stripped, non-intrinsic and non-recycling impurity that can be easily measured with charge-exchange recombination spectroscopy. Trace fluorine is used because the time-history of the fluorine density profile permits direct extraction of the confinement time, particle diffusivity and convective velocity without relying on atomic modeling or assumptions about the source recycling. Results indicate impurity accumulation is more pronounced in RMP ELM suppressed plasmas with a pure n = 3 spectrum compared with mixed n = 1 and n = 3 RMP fields with reduced number of control coils. In cases where strong central carbon impurity accumulation occurs, trace fluorine analysis reveals a strong inward impurity pinch. Conversely, in plasmas with weak central carbon accumulation, the fluorine pinch is significantly lower. These measurements of impurity influx are consistent with TGLF modeling of the ELM-suppressed phase of the discharge revealing that strong impurity influx occurs when the ratio V/D is between -1 to -3. In this work, the dependencies of impurity transport on local driving gradients will be presented, and the means of increasing the impurity diffusion to recover high purity plasmas will be discussed providing a basis for achieving low-dilution, stationary ELM-free operation in ITER and future devices. Supported by the US DOE under DE-AC0-09CH11466 and DE-FC02-05ER54698.

  19. Electrofreezing of confined water.

    PubMed

    Zangi, Ronen; Mark, Alan E

    2004-04-15

    We report results from molecular dynamics simulations of the freezing transition of TIP5P water molecules confined between two parallel plates under the influence of a homogeneous external electric field, with magnitude of 5 V/nm, along the lateral direction. For water confined to a thickness of a trilayer we find two different phases of ice at a temperature of T=280 K. The transformation between the two, proton-ordered, ice phases is found to be a strong first-order transition. The low-density ice phase is built from hexagonal rings parallel to the confining walls and corresponds to the structure of cubic ice. The high-density ice phase has an in-plane rhombic symmetry of the oxygen atoms and larger distortion of hydrogen bond angles. The short-range order of the two ice phases is the same as the local structure of the two bilayer phases of liquid water found recently in the absence of an electric field [J. Chem. Phys. 119, 1694 (2003)]. These high- and low-density phases of water differ in local ordering at the level of the second shell of nearest neighbors. The results reported in this paper, show a close similarity between the local structure of the liquid phase and the short-range order of the corresponding solid phase. This similarity might be enhanced in water due to the deep attractive well characterizing hydrogen bond interactions. We also investigate the low-density ice phase confined to a thickness of 4, 5, and 8 molecular layers under the influence of an electric field at T=300 K. In general, we find that the degree of ordering decreases as the distance between the two confining walls increases. PMID:15267616

  20. Reinforced Conductive Confinement of Sulfur for Robust and High-Performance Lithium-Sulfur Batteries.

    PubMed

    Lai, Chao; Wu, Zhenzhen; Gu, Xingxing; Wang, Chao; Xi, Kai; Kumar, R Vasant; Zhang, Shanqing

    2015-11-01

    Sulfur is an attractive cathode material in energy storage devices due to its high theoretical capacity of 1672 mAh g(-1). However, practical application of lithium-sulfur (Li-S) batteries can be achieved only when the major barriers, including the shuttling effect of polysulfides (Li2Sx, x = 3-8), significant volume change (∼80%), and the resultant rapid deterioration of electrodes, are tackled. Here, we propose an "inside-out" synthesis strategy by mimicking the structure of the pomegranate fruit to achieve conductive confinement of sulfur to address these issues. In the proposed pomegranate-like structure, sulfur and carbon nanotubes composite is encapsulated by the in situ formed amorphous carbon network, which allows the regeneration of electroactive material sulfur and the confinement of the sulfur as well as the lithium polysulfide within the electrical conductive carbon network. Consequently, a highly robust sulfur cathode is obtained, delivering remarkable performance in a Li-S battery. The obtained composite cathode shows a reversible capacity of 691 mAh g(-1) after 200 cycles with impressive cycle stability at the current density of 1600 mA g(-1). PMID:26470838

  1. Highly confined low-loss plasmons in graphene-boron nitride heterostructures

    NASA Astrophysics Data System (ADS)

    Woessner, Achim; Lundeberg, Mark B.; Gao, Yuanda; Principi, Alessandro; Alonso-González, Pablo; Carrega, Matteo; Watanabe, Kenji; Taniguchi, Takashi; Vignale, Giovanni; Polini, Marco; Hone, James; Hillenbrand, Rainer; Koppens, Frank H. L.

    2015-04-01

    Graphene plasmons were predicted to possess simultaneous ultrastrong field confinement and very low damping, enabling new classes of devices for deep-subwavelength metamaterials, single-photon nonlinearities, extraordinarily strong light-matter interactions and nano-optoelectronic switches. Although all of these great prospects require low damping, thus far strong plasmon damping has been observed, with both impurity scattering and many-body effects in graphene proposed as possible explanations. With the advent of van der Waals heterostructures, new methods have been developed to integrate graphene with other atomically flat materials. In this Article we exploit near-field microscopy to image propagating plasmons in high-quality graphene encapsulated between two films of hexagonal boron nitride (h-BN). We determine the dispersion and plasmon damping in real space. We find unprecedentedly low plasmon damping combined with strong field confinement and confirm the high uniformity of this plasmonic medium. The main damping channels are attributed to intrinsic thermal phonons in the graphene and dielectric losses in the h-BN. The observation and in-depth understanding of low plasmon damping is the key to the development of graphene nanophotonic and nano-optoelectronic devices.

  2. Nonlinear gyrokinetic simulations of the I-mode high confinement regime and comparisons with experiment

    SciTech Connect

    White, A. E. Howard, N. T.; Creely, A. J.; Chilenski, M. A.; Greenwald, M.; Hubbard, A. E.; Hughes, J. W.; Marmar, E.; Rice, J. E.; Sierchio, J. M.; Sung, C.; Walk, J. R.; Whyte, D. G.; Mikkelsen, D. R.; Edlund, E. M.; Kung, C.; Holland, C.; Candy, J.; Petty, C. C.; Reinke, M. L.; and others

    2015-05-15

    For the first time, nonlinear gyrokinetic simulations of I-mode plasmas are performed and compared with experiment. I-mode is a high confinement regime, featuring energy confinement similar to H-mode, but without enhanced particle and impurity particle confinement [D. G. Whyte et al., Nucl. Fusion 50, 105005 (2010)]. As a consequence of the separation between heat and particle transport, I-mode exhibits several favorable characteristics compared to H-mode. The nonlinear gyrokinetic code GYRO [J. Candy and R. E. Waltz, J Comput. Phys. 186, 545 (2003)] is used to explore the effects of E × B shear and profile stiffness in I-mode and compare with L-mode. The nonlinear GYRO simulations show that I-mode core ion temperature and electron temperature profiles are more stiff than L-mode core plasmas. Scans of the input E × B shear in GYRO simulations show that E × B shearing of turbulence is a stronger effect in the core of I-mode than L-mode. The nonlinear simulations match the observed reductions in long wavelength density fluctuation levels across the L-I transition but underestimate the reduction of long wavelength electron temperature fluctuation levels. The comparisons between experiment and gyrokinetic simulations for I-mode suggest that increased E × B shearing of turbulence combined with increased profile stiffness are responsible for the reductions in core turbulence observed in the experiment, and that I-mode resembles H-mode plasmas more than L-mode plasmas with regards to marginal stability and temperature profile stiffness.

  3. Nonlinear gyrokinetic simulations of the I-mode high confinement regime and comparisons with experimenta)

    NASA Astrophysics Data System (ADS)

    White, A. E.; Howard, N. T.; Creely, A. J.; Chilenski, M. A.; Greenwald, M.; Hubbard, A. E.; Hughes, J. W.; Marmar, E.; Rice, J. E.; Sierchio, J. M.; Sung, C.; Walk, J. R.; Whyte, D. G.; Mikkelsen, D. R.; Edlund, E. M.; Kung, C.; Holland, C.; Candy, J.; Petty, C. C.; Reinke, M. L.; Theiler, C.

    2015-05-01

    For the first time, nonlinear gyrokinetic simulations of I-mode plasmas are performed and compared with experiment. I-mode is a high confinement regime, featuring energy confinement similar to H-mode, but without enhanced particle and impurity particle confinement [D. G. Whyte et al., Nucl. Fusion 50, 105005 (2010)]. As a consequence of the separation between heat and particle transport, I-mode exhibits several favorable characteristics compared to H-mode. The nonlinear gyrokinetic code GYRO [J. Candy and R. E. Waltz, J Comput. Phys. 186, 545 (2003)] is used to explore the effects of E × B shear and profile stiffness in I-mode and compare with L-mode. The nonlinear GYRO simulations show that I-mode core ion temperature and electron temperature profiles are more stiff than L-mode core plasmas. Scans of the input E × B shear in GYRO simulations show that E × B shearing of turbulence is a stronger effect in the core of I-mode than L-mode. The nonlinear simulations match the observed reductions in long wavelength density fluctuation levels across the L-I transition but underestimate the reduction of long wavelength electron temperature fluctuation levels. The comparisons between experiment and gyrokinetic simulations for I-mode suggest that increased E × B shearing of turbulence combined with increased profile stiffness are responsible for the reductions in core turbulence observed in the experiment, and that I-mode resembles H-mode plasmas more than L-mode plasmas with regards to marginal stability and temperature profile stiffness.

  4. Influence of the interface on the optical activity of confined glucose films.

    PubMed

    Emile, Olivier; Emile, Janine; Ghoufi, Aziz

    2016-09-01

    We report on the time evolution of the optical activity of a thinning liquid film containing glucose, and confined between two glass slides. This dynamics strongly depends on the presence of surfactant molecules. With sodium dodecyl sulfate (SDS), we evidence favorable interactions of sugar molecules with the sulfate group. As previously observed for a freely suspended soap film in the air (see Emile et al., 2013), this corresponds to an anchoring of glucose molecules at the interface. For glucose alone, we also highlight a molecular rearrangement that is not instantaneous and occurs after several minutes. This interfacial organization leads to an unusual giant optical activity that is different with or without SDS. Molecular simulations confirm the anchoring of the glucose molecules at the glass/liquid interface, and show a different molecular orientation in each case. PMID:27254252

  5. Thin Shell, High Velocity Inertial Confinement Fusion Implosions on the National Ignition Facility

    SciTech Connect

    Ma, T.; Hurricane, O. A.; Callahan, D. A.; Barrios, M. A.; Casey, D. T.; Dewald, E. L.; Dittrich, T. R.; Doppner, T.; Haan, S. W.; Hinkel, D. E.; Berzak Hopkins, L. F.; Le Pape, S.; MacPhee, A. G.; Pak, A.; Park, H. S.; Patel, P. K.; Remington, B. A.; Robey, H. F.; Salmonson, J. D.; Springer, P. T.; Tommasini, R.; Benedetti, L. R.; Bionta, R.; Bond, E.; Bradley, D. K.; Caggiano, J.; Celliers, P.; Cerjan, C. J.; Church, J. A.; Dixit, S.; Dylla-Spears, R.; Edgell, D.; Edwards, M. J.; Field, J.; Fittinghoff, D. N.; Frenje, J. A.; Gatu Johnson, M.; Grim, G.; Guler, N.; Hatarik, R.; Herrmann, H. W.; Hsing, W. W.; Izumi, N.; Jones, O. S.; Khan, S. F.; Kilkenny, J. D.; Knauer, J.; Kohut, T.; Kozioziemski, B.; Kritcher, A.; Kyrala, G.; Landen, O. L.; MacGowan, B. J.; Mackinnon, A. J.; Meezan, N. B.; Merrill, F. E.; Moody, J. D.; Nagel, S. R.; Nikroo, A.; Parham, T.; Ralph, J. E.; Rosen, M. D.; Rygg, J. R.; Sater, J.; Sayre, D.; Schneider, M. B.; Shaughnessy, D.; Spears, B. K.; Town, R.P. J.; Volegov, P. L.; Wan, A.; Widmann, K.; Wilde, C. H.; Yeamans, C.

    2015-04-06

    Experiments have recently been conducted at the National Ignition Facility utilizing inertial confinement fusion capsule ablators that are 175 and 165 μm in thickness, 10% and 15% thinner, respectively, than the nominal thickness capsule used throughout the high foot and most of the National Ignition Campaign. These three-shock, high-adiabat, high-foot implosions have demonstrated good performance, with higher velocity and better symmetry control at lower laser powers and energies than their nominal thickness ablator counterparts. Little to no hydrodynamic mix into the DT hot spot has been observed despite the higher velocities and reduced depth for possible instability feedthrough. Earlier results have shown good repeatability, with up to 1/2 the neutron yield coming from α-particle self-heating.

  6. Thin shell, high velocity inertial confinement fusion implosions on the national ignition facility.

    PubMed

    Ma, T; Hurricane, O A; Callahan, D A; Barrios, M A; Casey, D T; Dewald, E L; Dittrich, T R; Döppner, T; Haan, S W; Hinkel, D E; Berzak Hopkins, L F; Le Pape, S; MacPhee, A G; Pak, A; Park, H-S; Patel, P K; Remington, B A; Robey, H F; Salmonson, J D; Springer, P T; Tommasini, R; Benedetti, L R; Bionta, R; Bond, E; Bradley, D K; Caggiano, J; Celliers, P; Cerjan, C J; Church, J A; Dixit, S; Dylla-Spears, R; Edgell, D; Edwards, M J; Field, J; Fittinghoff, D N; Frenje, J A; Gatu Johnson, M; Grim, G; Guler, N; Hatarik, R; Herrmann, H W; Hsing, W W; Izumi, N; Jones, O S; Khan, S F; Kilkenny, J D; Knauer, J; Kohut, T; Kozioziemski, B; Kritcher, A; Kyrala, G; Landen, O L; MacGowan, B J; Mackinnon, A J; Meezan, N B; Merrill, F E; Moody, J D; Nagel, S R; Nikroo, A; Parham, T; Ralph, J E; Rosen, M D; Rygg, J R; Sater, J; Sayre, D; Schneider, M B; Shaughnessy, D; Spears, B K; Town, R P J; Volegov, P L; Wan, A; Widmann, K; Wilde, C H; Yeamans, C

    2015-04-10

    Experiments have recently been conducted at the National Ignition Facility utilizing inertial confinement fusion capsule ablators that are 175 and 165  μm in thickness, 10% and 15% thinner, respectively, than the nominal thickness capsule used throughout the high foot and most of the National Ignition Campaign. These three-shock, high-adiabat, high-foot implosions have demonstrated good performance, with higher velocity and better symmetry control at lower laser powers and energies than their nominal thickness ablator counterparts. Little to no hydrodynamic mix into the DT hot spot has been observed despite the higher velocities and reduced depth for possible instability feedthrough. Early results have shown good repeatability, with up to 1/2 the neutron yield coming from α-particle self-heating. PMID:25910132

  7. Thin Shell, High Velocity Inertial Confinement Fusion Implosions on the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Ma, T.; Hurricane, O. A.; Callahan, D. A.; Barrios, M. A.; Casey, D. T.; Dewald, E. L.; Dittrich, T. R.; Döppner, T.; Haan, S. W.; Hinkel, D. E.; Berzak Hopkins, L. F.; Le Pape, S.; MacPhee, A. G.; Pak, A.; Park, H.-S.; Patel, P. K.; Remington, B. A.; Robey, H. F.; Salmonson, J. D.; Springer, P. T.; Tommasini, R.; Benedetti, L. R.; Bionta, R.; Bond, E.; Bradley, D. K.; Caggiano, J.; Celliers, P.; Cerjan, C. J.; Church, J. A.; Dixit, S.; Dylla-Spears, R.; Edgell, D.; Edwards, M. J.; Field, J.; Fittinghoff, D. N.; Frenje, J. A.; Gatu Johnson, M.; Grim, G.; Guler, N.; Hatarik, R.; Herrmann, H. W.; Hsing, W. W.; Izumi, N.; Jones, O. S.; Khan, S. F.; Kilkenny, J. D.; Knauer, J.; Kohut, T.; Kozioziemski, B.; Kritcher, A.; Kyrala, G.; Landen, O. L.; MacGowan, B. J.; Mackinnon, A. J.; Meezan, N. B.; Merrill, F. E.; Moody, J. D.; Nagel, S. R.; Nikroo, A.; Parham, T.; Ralph, J. E.; Rosen, M. D.; Rygg, J. R.; Sater, J.; Sayre, D.; Schneider, M. B.; Shaughnessy, D.; Spears, B. K.; Town, R. P. J.; Volegov, P. L.; Wan, A.; Widmann, K.; Wilde, C. H.; Yeamans, C.

    2015-04-01

    Experiments have recently been conducted at the National Ignition Facility utilizing inertial confinement fusion capsule ablators that are 175 and 165 μ m in thickness, 10% and 15% thinner, respectively, than the nominal thickness capsule used throughout the high foot and most of the National Ignition Campaign. These three-shock, high-adiabat, high-foot implosions have demonstrated good performance, with higher velocity and better symmetry control at lower laser powers and energies than their nominal thickness ablator counterparts. Little to no hydrodynamic mix into the DT hot spot has been observed despite the higher velocities and reduced depth for possible instability feedthrough. Early results have shown good repeatability, with up to 1 /2 the neutron yield coming from α -particle self-heating.

  8. Enhancement of high harmonic generation by confining electron motion in plasmonic nanostrutures.

    PubMed

    Ciappina, M F; Aćimović, Srdjan S; Shaaran, T; Biegert, J; Quidant, R; Lewenstein, M

    2012-11-19

    We study high-order harmonic generation (HHG) resulting from the illumination of plasmonic nanostructures with a short laser pulse of long wavelength. We demonstrate that both the confinement of the electron motion and the inhomogeneous character of the laser electric field play an important role in the HHG process and lead to a significant increase of the harmonic cutoff. In particular, in bow-tie nanostructures with small gaps, electron trajectories with large excursion amplitudes experience significant confinement and their contribution is essentially suppressed. In order to understand and characterize this feature, we combine the numerical solution of the time-dependent Schrödinger equation (TDSE) with the electric fields obtained from 3D finite element simulations. We employ time-frequency analysis to extract more detailed information from the TDSE results and classical tools to explain the extended harmonic spectra. The spatial inhomogeneity of the laser electric field modifies substantially the electron trajectories and contributes also to cutoff increase. PMID:23187480

  9. Onset of hydrodynamic mix in high-velocity, highly compressed inertial confinement fusion implosions.

    PubMed

    Ma, T; Patel, P K; Izumi, N; Springer, P T; Key, M H; Atherton, L J; Benedetti, L R; Bradley, D K; Callahan, D A; Celliers, P M; Cerjan, C J; Clark, D S; Dewald, E L; Dixit, S N; Döppner, T; Edgell, D H; Epstein, R; Glenn, S; Grim, G; Haan, S W; Hammel, B A; Hicks, D; Hsing, W W; Jones, O S; Khan, S F; Kilkenny, J D; Kline, J L; Kyrala, G A; Landen, O L; Le Pape, S; MacGowan, B J; Mackinnon, A J; MacPhee, A G; Meezan, N B; Moody, J D; Pak, A; Parham, T; Park, H-S; Ralph, J E; Regan, S P; Remington, B A; Robey, H F; Ross, J S; Spears, B K; Smalyuk, V; Suter, L J; Tommasini, R; Town, R P; Weber, S V; Lindl, J D; Edwards, M J; Glenzer, S H; Moses, E I

    2013-08-23

    Deuterium-tritium inertial confinement fusion implosion experiments on the National Ignition Facility have demonstrated yields ranging from 0.8 to 7×10(14), and record fuel areal densities of 0.7 to 1.3 g/cm2. These implosions use hohlraums irradiated with shaped laser pulses of 1.5-1.9 MJ energy. The laser peak power and duration at peak power were varied, as were the capsule ablator dopant concentrations and shell thicknesses. We quantify the level of hydrodynamic instability mix of the ablator into the hot spot from the measured elevated absolute x-ray emission of the hot spot. We observe that DT neutron yield and ion temperature decrease abruptly as the hot spot mix mass increases above several hundred ng. The comparison with radiation-hydrodynamic modeling indicates that low mode asymmetries and increased ablator surface perturbations may be responsible for the current performance. PMID:24010449

  10. Shock ignition: a new approach to high gain inertial confinement fusion on the national ignition facility.

    PubMed

    Perkins, L J; Betti, R; LaFortune, K N; Williams, W H

    2009-07-24

    Shock ignition, an alternative concept for igniting thermonuclear fuel, is explored as a new approach to high gain, inertial confinement fusion targets for the National Ignition Facility (NIF). Results indicate thermonuclear yields of approximately 120-250 MJ may be possible with laser drive energies of 1-1.6 MJ, while gains of approximately 50 may still be achievable at only approximately 0.2 MJ drive energy. The scaling of NIF energy gain with laser energy is found to be G approximately 126E (MJ);{0.510}. This offers the potential for high-gain targets that may lead to smaller, more economic fusion power reactors and a cheaper fusion energy development path. PMID:19659364

  11. A long-pulse high-confinement plasma regime in the Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Li, J.; Guo, H. Y.; Wan, B. N.; Gong, X. Z.; Liang, Y. F.; Xu, G. S.; Gan, K. F.; Hu, J. S.; Wang, H. Q.; Wang, L.; Zeng, L.; Zhao, Y. P.; Denner, P.; Jackson, G. L.; Loarte, A.; Maingi, R.; Menard, J. E.; Rack, M.; Zou, X. L.

    2013-12-01

    High-performance and long-pulse operation is a crucial goal of current magnetic fusion research. Here, we demonstrate a high-confinement plasma regime known as an H-mode with a record pulse length of over 30s in the Experimental Advanced Superconducting Tokamak sustained by lower hybrid wave current drive (LHCD) with advanced lithium wall conditioning. We find that LHCD provides a flexible boundary control for a ubiquitous edge instability in H-mode plasmas known as an edge-localized mode, which leads to a marked reduction in the heat load on the vessel wall compared with standard edge-localized modes. LHCD also induces edge plasma ergodization that broadens the heat deposition footprint. The heat transport caused by this ergodization can be actively controlled by regulating the edge plasma conditions. This potentially offers a new means for heat-flux control, which is a key issue for next-step fusion development.

  12. Experimental evaluation of connectivity influence on dispersivity under confined and unconfined radial convergent flow conditions

    NASA Astrophysics Data System (ADS)

    Guzzi, Silvia; Molinari, Antonio; Fallico, Carmine; Pedretti, Daniele

    2014-05-01

    Heterogeneity and connectivity have a significant impact on the fate and transport of contaminants due to the occurrence of formations with largest permeability than the surrounding geological materials, which can originate preferential pathways in groundwater system. These issues are usually addressed by tracer tests and a radial convergent (RC) flow setting is typically selected for convenience but more complicated for model interpretation than uniform flow transport. An experimental investigation was performed using RC tracer tests in a 3D intermediate scale physical model to illustrate the role of connected features on the estimation of dispersivity using the classical Sauty solution and the method of moments, under confined and unconfined aquifer conditions. The physical model consists of 26 piezometers located at difference distances from a constant-discharge central pumping well. The box is filled with gravel channels embedded in a sandy matrix and organized in different layers. Materials have been well characterized before and after the test. For the confined configuration, a silt layer was placed above the previous layers. Tracer tests were performed using potassium iodide solutions with concentration of 3•10-3 M and under a constant pumping flow rate of 0.05 L/s. To mimic a pulse injection in each piezometer we used syringes and pipes, whereas a probe allowed continuous measuring of tracer concentration. Average velocity and longitudinal dispersion coefficient were defined from the first and second central moment of the observed breakthrough curves for each piezometer (integrated over the outflow boundary of the domain) and using the classical curve matching from the Sauty's solution at different Péclet numbers. Results reveal in some cases that estimates of hydrodynamic parameters from the Sauty solution and the method of moments seem to be different. This is related to the different basic assumptions of the two methods applied, and especially because

  13. Influence of surface property on the crystallization of hentetracontane under nanoscopic cylindrical confinement.

    PubMed

    Kim, Bong Seock; Jeong, Young Gyu; Shin, Kyusoon

    2013-05-16

    The crystallization behavior and the orientation of linear alkane hentetracontane (C41) confined in cylindrical nanoporous alumina templates with different surface energies were investigated by nonisothermal crystallization and X-ray diffraction. The surface of pristine nanoporous alumina was modified to have low surface energy by grafting with polydimethylsiloxane. In the pristine nanoporous alumina, C41 crystallized at two crystallization temperature ranges, lower than bulk, and exhibited the decreased Avrami exponents. C41 in the surface-modified nanoporous alumina showed the inhibition of crystallization at higher temperature range among the two crystallization temperature ranges but the enhancement of crystallization at much lower temperature ranges than in the pristine nanoporous alumina. It was clearly shown that those variations of crystallization behavior imply the surface effect on crystallization. The crystal orientation was also affected by surface-modification of the alumina template. The a-axis of orthorhombic C41 crystals in the pristine nanoporous alumina was preferentially oriented parallel to the pore axis, while b- and c-axes were perpendicular to the pore axis. C41 crystals in the surface-modified nanoporous alumina showed two types of orientation. One was identical to that in the pristine nanoporous alumina, and the other was the orientation that the crystals were tilted with respect to the c-axis as the (110) plane parallel to the pore axis. PMID:23586535

  14. Quantum Confinement Induced Oscillatory Electric Field on a Stepped Pb(111) Film and Its Influence on Surface Reactivity

    SciTech Connect

    Liu, Xiaojie; Wang, Cai-Zhuang; Hupalo, Myron; Lin, Hai-Quing; Ho, Kai-Ming; Tringides, Michael C.

    2014-01-06

    When the thickness of ultrathin metal films approaches the nanometer scale comparable to the coherence length of the electrons, significant effects on the structure stability and the electronic properties of the metal films emerge due to electron confinement and quantization of the allowed electronic states in the direction perpendicular to the film. Using first-principles calculations, we showed that such quantum size effects can induce oscillatory electrostatic potential and thus alternating electric field on the surface of the wedge-shaped Pb(111) films. The alternating electric field has significant influence on surface reactivity, leading to selective even- or odd-layer adsorption preference depending on the charge state of the adatoms, consistent with the odd-layer preference of higher Mg coverage on wedge-shaped Pb(111) films, as observed in experiment.

  15. High-speed 850 nm oxide-confined VCSELs for DATACOM applications

    NASA Astrophysics Data System (ADS)

    Mutig, Alex; Blokhin, Sergey; Nadtochiy, Alexey M.; Fiol, Gerrit; Lott, James A.; Shchukin, Vitaly A.; Ledenstov, Nikolai N.; Bimberg, Dieter

    2010-02-01

    Vertical cavity surface emitting lasers (VCSELs) are low cost and reliable light sources for high-speed local area and storage area network (LAN/SAN) optical fiber data communication systems and short-reach computer interconnects. The continuing rapid increase of serial transmission data rates driven by multi-core microprocessor's bandwidth upgrades cannot be sustained via conventional copper-based links as bit rates move beyond 10 Gbit/s and distances greater than 1 m. The intrinsic limitation of copper at high single-channel data rates facilitates the need to transition to optical fiberbased links at ever shorter distances. For LAN/SAN applications the 850 nm wavelength is standard. This same wavelength is also the standard for several other evolving short-reach application areas including Fibre Channel, CEI, USB, InfiniBand, and HDMI optical link systems. Herein we present our recent results on 850 nm oxide-confined VCSELs operating at data bit rates up to 40 Gbit/s. The low operational current density in the range of ~10 kA/cm2 ensures viable device reliability and long-term stability based on well-known industry certification specifications. Key VCSEL device parameters including the relaxation resonance frequency, damping, and parasitic cut-off frequency are determined for VCSELs with oxide-confined apertures of various diameters. We find that a parasitic cut-off frequency of 24-28 GHz limits the VCSEL's high speed operation at the highest optical modulation rates. We believe that with some effort the device parasitics can be further reduced such that current modulated VCSELs can be realized with larger than 30 GHz optical modulation bandwidth and reliable and practical operation beyond 40 Gbit/s.

  16. The influence of electron confinement, quantum size effects, and film morphology on the dispersion and the damping of plasmonic modes in Ag and Au thin films

    NASA Astrophysics Data System (ADS)

    Politano, Antonio; Chiarello, Gennaro

    2015-05-01

    Plasmons are collective longitudinal modes of charge fluctuation in metal samples excited by an external electric field. Surface plasmons (SPs) are waves that propagate along the surface of a conductor. SPs find applications in magneto-optic data storage, optics, microscopy, and catalysis. The investigation of SPs in silver and gold is relevant as these materials are extensively used in plasmonics. The theoretical approach for calculating plasmon modes in noble metals is complicated by the existence of localized d electrons near the Fermi level. Nevertheless, recent calculations based on linear response theory and time-dependent local density approximation adequately describe the dispersion and damping of SPs in noble metals. Furthermore, in thin films the electronic response is influenced by electron quantum confinement. Confined electrons modify the dynamical screening processes at the film/substrate interface by introducing novel properties with potential applications. The presence of quantum well states in the Ag and Au overlayer affects both the dispersion relation of SP frequency and the damping processes of the SP. Recent calculations indicate the emergence of acoustic surface plasmons (ASP) in Ag thin films exhibiting quantum well states. The slope of the dispersion of ASP decreases with film thickness. High-resolution electron energy loss spectroscopy (HREELS) is the main experimental technique for investigating collective electronic excitations, with adequate resolution in both the energy and momentum domains to investigate surface modes. Herein we review on recent progress of research on collective electronic excitations in Ag and Au films deposited on single-crystal substrates.

  17. A highly efficient neutron time-of-flight detector for inertial confinement fusion experiments

    NASA Astrophysics Data System (ADS)

    Izumi, N.; Yamaguchi, K.; Yamagajo, T.; Nakano, T.; Kasai, T.; Urano, T.; Azechi, H.; Nakai, S.; Iida, T.

    1999-01-01

    We have developed the highly efficient neutron detector system MANDALA for the inertial-confinement-fusion experiment. The MANDALA system consists of 842 elements plastic scintillation detectors and data acquisition electronics. The detection level is the yield of 1.2×105 for 2.5 MeV and 1×105 for 14.1 MeV neutrons (with 100 detected hits). We have calibrated the intrinsic detection efficiencies of the detector elements using a neutron generator facility. Timing calibration and integrity test of the system were also carried out with a 60Co γ ray source. MANDALA system was applied to the implosion experiments at the GEKKO XII laser facility. The integrity test was carried out by implosion experiments.

  18. Observations of PAN and its confinement in the Asian Monsoon Anticyclone in high spatial resolution

    NASA Astrophysics Data System (ADS)

    Ungermann, Joern; Ploeger, Felix; Spang, Reinhold; Riese, Martin

    2016-04-01

    This talk presents a set of observations by the CRyogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) infrared limb sounder on the SPAS platform in low-earth orbit. The spatially highly resolved trace gas measurements of six days in August 1997 allow a close look on the confinement of air masses within the Asian Summer Monsoon (ASM) anticyclone. Peroxyacetyl nitrate (PAN) is a secondary pollutant without sources in the stratosphere and acts as a tropospheric tracer. In combination with ozone as a stratospheric tracer, an eddy-shedding event of the ASM could be observed. The measured PAN volume mixing ratios (VMR) correlate well with potential vorticity (PV) derived from ECMWF ERA-Interim model data. Computing the gradient of PAN over PV on isentropes reveals that PAN VMR exhibit the strongest decrease at each isentrope for an increasing value of PV, which may be used to identify the extent of the ASM on that isentrope. CRISTA measurements also provide the temperature of measured air parcels and thus allow to derive the location of the thermal tropopause. We find that the thermal tropopause coincides with the border of the positive PAN anomaly both horizontally and vertically within the ASM anticyclone. In contrast, the shed eddy exhibits enhanced PAN VMRs for 1 to 2 km above the thermal tropopause. The amount of mixing may also be characterised by projecting the derived air parcels into tracer-tracer space using PAN and ozone as tropospheric and stratospheric tracer, respectively. This reveals that the anticyclone contains few mixed parcels in contrast to the region between the anticyclone and the shed eddy. This implies that while the anticyclone confines polluted air masses well, eddy shedding provides a very rapid horizontal transport pathway of Asian pollution into the extratropical lowermost stratosphere with a time scale of only a few days.

  19. Observations of PAN and its confinement in the Asian summer monsoon anticyclone in high spatial resolution

    NASA Astrophysics Data System (ADS)

    Ungermann, Jörn; Ern, Mandfred; Kaufmann, Martin; Müller, Rolf; Spang, Reinhold; Ploeger, Felix; Vogel, Bärbel; Riese, Martin

    2016-07-01

    This paper presents an analysis of trace gases in the Asian summer monsoon (ASM) region on the basis of observations by the CRISTA infrared limb sounder taken in low-earth orbit in August 1997. The spatially highly resolved measurements of peroxyacetyl nitrate (PAN) and O3 allow a detailed analysis of an eddy-shedding event of the ASM anticyclone. We identify enhanced PAN volume mixing ratios (VMRs) within the main anticyclone and within the eddy, which are suitable as a tracer for polluted air originating in India and China. Plotting the retrieved PAN VMRs against potential vorticity (PV) and potential temperature reveals that the PV value at which the PAN VMRs exhibit the strongest decrease with respect to PV increases with potential temperature. These PV values might be used to identify the extent of the ASM. Using temperature values also derived from CRISTA measurements, we also computed the location of the thermal tropopause according to the WMO criterion and find that it confines the PAN anomaly vertically within the main ASM anticyclone. In contrast, the shed eddy exhibits enhanced PAN VMRs for 1 to 2 km above the thermal tropopause. Using the relationship between PAN as a tropospheric tracer and O3 as a stratospheric tracer to identify mixed air parcels, we further found the anticyclone to contain few such air parcels, whereas the region between the anticyclone and the eddy as well as the eddy itself contains many mixed air parcels. In combination, this implies that while the anticyclone confines polluted air masses well, eddy shedding provides a very rapid horizontal transport pathway of Asian pollution into the extratropical lowermost stratosphere with a timescale of only a few days.

  20. Highly Active Nanoreactors: Patchlike or Thick Ni Coating on Pt Nanoparticles Based on Confined Catalysis.

    PubMed

    Qi, Xinhong; Li, Xiangcun; Chen, Bo; Lu, Huilan; Wang, Le; He, Gaohong

    2016-01-27

    Catalyst-containing nanoreactors have attracted considerable attention for specific applications. Here, we initially report preparation of PtNi@SiO2 hollow microspheres based on confined catalysis. The previous encapsulation of dispersed Pt nanoparticles (NPs) in hollow silica microspheres ensures the formation of Pt@Ni coreshell NPs inside the silica porous shell. Thus, the Pt NPs not only catalyze the reduction of Ni ions but also direct Ni deposition on the Pt cores to obtain Pt@Ni core-shell catalyst. It is worthy to point out that this synthetic approach helps to form a patchlike or thick Ni coating on Pt cores by controlling the penetration time of Ni ions from the bulk solution into the SiO2 microspheres (0.5, 1, 2, or 4 h). Notably, the Pt@Ni core-shell NPs with a patch-like Ni layer on Pt cores (0.5 and 1 h) show a higher H2 generation rate of 1221-1475 H2 mL min(-1) g(-1)cat than the Pt@Ni NPs with a thick Ni layer (2 and 4 h, 920-1183 H2 mL min(-1) g(-1)cat), and much higher than that of pure Pt NPs (224 H2 mL min(-1) g(-1)cat). In addition, the catalyst possesses good stability and recyclability for H2 generation. The Pt@Ni core-shell NPs confined inside silica nanocapsules, with well-defined compositions and morphologies, high H2 generation rate, and recyclability, should be an ideal catalyst for specific applications in liquid phase reaction. PMID:26725500

  1. Linear and nonlinear characterization of low-stress high-confinement silicon-rich nitride waveguides.

    PubMed

    Krückel, Clemens J; Fülöp, Attila; Klintberg, Thomas; Bengtsson, Jörgen; Andrekson, Peter A; Torres-Company, Víctor

    2015-10-01

    In this paper we introduce a low-stress silicon enriched nitride platform that has potential for nonlinear and highly integrated optics. The manufacturing process of this platform is CMOS compatible and the increased silicon content allows tensile stress reduction and crack free layer growth of 700 nm. Additional benefits of the silicon enriched nitride is a measured nonlinear Kerr coefficient n(2) of 1.4·10(-18) m(2)/W (5 times higher than stoichiometric silicon nitride) and a refractive index of 2.1 at 1550 nm that enables high optical field confinement allowing high intensity nonlinear optics and light guidance even with small bending radii. We analyze the waveguide loss (∼1 dB/cm) in a spectrally resolved fashion and include scattering loss simulations based on waveguide surface roughness measurements. Detailed simulations show the possibility for fine dispersion and nonlinear engineering. In nonlinear experiments we present continuous-wave wavelength conversion and demonstrate that the material does not show nonlinear absorption effects. Finally, we demonstrate microfabrication of resonators with high Q-factors (∼10(5)). PMID:26480096

  2. Regime of Improved Confinement and High Beta in Neutral-Beam-Heated Divertor Discharges of the ASDEX Tokamak

    NASA Astrophysics Data System (ADS)

    Wagner, F.; Becker, G.; Behringer, K.; Campbell, D.; Eberhagen, A.; Engelhardt, W.; Fussmann, G.; Gehre, O.; Gernhardt, J.; Gierke, G. V.; Haas, G.; Huang, M.; Karger, F.; Keilhacker, M.; Klüber, O.; Kornherr, M.; Lackner, K.; Lisitano, G.; Lister, G. G.; Mayer, H. M.; Meisel, D.; Müller, E. R.; Murmann, H.; Niedermeyer, H.; Poschenrieder, W.; Rapp, H.; Röhr, H.; Schneider, F.; Siller, G.; Speth, E.; Stäbler, A.; Steuer, K. H.; Venus, G.; Vollmer, O.; Yü, Z.

    1982-11-01

    A new operational regime has been observed in neutral-injection-heated ASDEX divertor discharges. This regime is characterized by high βp values comparable to the aspect ratio A (βp<=0.65A) and by confinement times close to those of Ohmic discharges. The high-βp regime develops at an injection power >=1.9 MW, a mean density n¯e>=3×1013 cm-3, and a q(a) value >=2.6. Beyond these limits or in discharges with material limiter, low βp values and reduced particle and energy confinement times are obtained compared to the Ohmic heating phase.

  3. Highly confined, enhanced surface fluorescence imaging with two-dimensional silver nanoparticle sheets

    SciTech Connect

    Usukura, Eiji; Shinohara, Shuhei; Okamoto, Koichi; Tamada, Kaoru; Lim, Jaehoon; Char, Kookheon

    2014-03-24

    A method of obtaining highly confined, enhanced surface fluorescence imaging is proposed using two-dimensional (2D) silver nanoparticle (AgMy) sheets. This technique is based on the localized surface plasmon resonance excited homogeneously on a 2D silver nanoparticle sheet. The AgMy sheets are fabricated at the air–water interface by self-assembly and transferred onto hydrophobic glass substrates. These sheets can enhance the fluorescence only when the excitation wavelength overlaps with the plasmon resonance wavelength. To confirm the validity of this technique, two separate test experiments are performed. One is the epifluorescence microscope imaging of a quantum dot 2D sheet on the AgMy 2D sheet with a SiO{sub 2} spacer layer, where the fluorescence is maximized with the 20 nm SiO{sub 2} layer, determined by the Förster resonance energy transfer distances. The second experiment is the imaging of a single fluorescence bead with a total internal reflection fluorescent microscope. We confirmed that the AgMy sheet provides a 4-fold increase in fluorescence with a 160-nm spatial resolution at 30 ms/frame snapshot. The AgMy sheet will be a powerful tool for high sensitivity and high-resolution real time bioimaging at nanointerfaces.

  4. Recent advances in long-pulse high-confinement plasma operations in Experimental Advanced Superconducting Tokamak

    SciTech Connect

    Guo, H. Y.; Li, J.; Wan, B. N. Gong, X. Z.; Xu, G. S.; Zhang, X. D.; Ding, S. Y.; Gan, K. F.; Hu, J. S.; Hu, L. Q.; Liu, S. C.; Qian, J. P.; Sun, Y. W.; Wang, H. Q.; Wang, L.; Xia, T. Y.; Xiao, B. J.; Zeng, L.; Zhao, Y. P.; and others

    2014-05-15

    A long-pulse high confinement plasma regime known as H-mode is achieved in the Experimental Advanced Superconducting Tokamak (EAST) with a record duration over 30 s, sustained by Lower Hybrid wave Current Drive (LHCD) with advanced lithium wall conditioning and divertor pumping. This long-pulse H-mode plasma regime is characterized by the co-existence of a small Magneto-Hydrodynamic (MHD) instability, i.e., Edge Localized Modes (ELMs) and a continuous quasi-coherent MHD mode at the edge. We find that LHCD provides an intrinsic boundary control for ELMs, leading to a dramatic reduction in the transient power load on the vessel wall, compared to the standard Type I ELMs. LHCD also induces edge plasma ergodization, broadening heat deposition footprints, and the heat transport caused by ergodization can be actively controlled by regulating edge plasma conditions, thus providing a new means for stationary heat flux control. In addition, advanced tokamak scenarios have been newly developed for high-performance long-pulse plasma operations in the next EAST experimental campaign.

  5. Traction and nonequilibrium phase behavior of confined sheared liquids at high pressure

    NASA Astrophysics Data System (ADS)

    Gattinoni, Chiara; Heyes, David M.; Lorenz, Christian D.; Dini, Daniele

    2013-11-01

    Nonequilibrium molecular dynamics simulations of confined model liquids under pressure and sheared by the relative sliding of the boundary walls have been carried out. The relationship between the time-dependent traction coefficient, μ(t), and the state of internal structure of the film is followed from commencement of shear for various control parameters, such as applied load, global shear rate, and solid-liquid atom interaction parameters. Phase diagrams, velocity and temperature profiles, and traction coefficient diagrams are analyzed for pure Lennard-Jones (LJ) liquids and a binary LJ mixture. A single component LJ liquid is found to form semicrystalline arrangements with high-traction coefficients, and stick-slip behavior is observed for high pressures and low-shear velocities, which is shown to involve periodic deformation and stress release of the wall atoms and slip in the solid-liquid boundary region. A binary mixture, which discourages crystallization, gives a more classical tribological response with the larger atoms preferentially adsorbing commensurate with the wall. The results obtained are analyzed in the context of tribology: the binary mixture behaves like a typical lubricant, whereas the monatomic system behaves like a traction fluid. It is discussed how this type of simulation can give insights on the tribological behavior of realistic systems.

  6. Performance of large-aperture optical switches for high-energy inertial-confinement fusion lasers

    SciTech Connect

    Rhodes, M.A.; Woods, B.; DeYoreo, J.J.; Roberts, D.; Atherton, L.J.

    1995-08-20

    We describe the design and performance of large-aperture ({lt}30 cm {times} 30 cm) optical switches that have demonstrated, for the first time to our knowledge, active switching of a high-energy ({lt}5 kJ) optical pulse in an inertial-confinement fusion laser. These optical switches, which consist of a plasma-electrode Pockels cell (PEPC) and a passive polarizer, permit the design of efficient, multipass laser amplifiers. In a PEPC, plasma discharges on the faces of a thin (1-cm) electro-optic crystal (KDP or KD{bold |}P) act as highly conductive and transparent electrodes. These plasma electrodes facilitate rapid ({lt}100 ns) and uniform charging of the crystal to the half-wave voltage and discharging back to 0 V. We discuss the operating principles, design, optical performance, and technical issues of a 32 cm {times} 32 cm prototype PEPC with both KDP and KD{bold |}P crystals, and a 37 cm {times} 37 cm PEPC with a KDP crystal for the Beamlet laser. This PEPC recently switched a 6-kJ, 3-ns pulse in a four-pass cavity.

  7. Rotational dynamics of confined C60 from near-infrared Raman studies under high pressure

    SciTech Connect

    Zou, Y.; Liu, B.; Wang, L.; Liu, D.; Yu, S.; Wang, P.; Wang, T.; Yao, M.; Li, Q.; Zou, B.; Cui, T.; Zou, G.; Wagberg, T.; Sundqvist, B.; Mao, H.-K.

    2009-12-29

    Peapods present a model system for studying the properties of dimensionally constrained crystal structures, whose dynamical properties are very important. We have recently studied the rotational dynamics of C60 molecules confined inside single walled carbon nanotube (SWNT) by analyzing the intermediate frequency mode lattice vibrations using near-infrared Raman spectroscopy. The rotation of C60 was tuned to a known state by applying high pressure, at which condition C60 first forms dimers at low pressure and then forms a single-chain, nonrotating, polymer structure at high pressure. In the latter state the molecules form chains with a 2-fold symmetry. We propose that the C60 molecules in SWNT exhibit an unusual type of ratcheted rotation due to the interaction between C60 and SWNT in the “hexagon orientation,” and the characteristic vibrations of ratcheted rotation becomes more obvious with decreasing temperature.

  8. A high efficiency I. C. F. driver employing magnetically confined plasma rings

    SciTech Connect

    Meeker, D.J.; Hammer, J.M.; Hartman, C.W.

    1985-07-01

    We discuss the possibility of achieving energy, power and power density necessary for ICF by magnetically accelerating plasma confined by a compact torus (CT) field configuration. The CT, which consists of a dipole (poloidal) field and imbedded toroidal field formed by force-free, plasma current, is compressed and accelerated between coaxial electrodes by Btheta fields as in a coaxial railgun. Compression and accleration over several meters by a 9.4 MJ capacitor bank is predicted to give a 5.7 cm radius, 0.001 gm CT 5 MJ kinetic energy (10/sup 7/ m/sec). Transport and focusing several meters by a disposable lithium pipe across the containment vessel is predicted to bring 4.8 MJ into the pellet region in 0.5 cm/sup 2/ area in 0.3 ns. The high efficiency ( about 50%) and high energy delivery of the CT accelerator could lead to low cost, few hundred MW power plants that are economically viable.

  9. Recent advances in long-pulse high-confinement plasma operations in Experimental Advanced Superconducting Tokamaka)

    NASA Astrophysics Data System (ADS)

    Guo, H. Y.; Li, J.; Wan, B. N.; Gong, X. Z.; Liang, Y. F.; Xu, G. S.; Zhang, X. D.; Ding, S. Y.; Gan, K. F.; Hu, J. S.; Hu, L. Q.; Liu, S. C.; Qian, J. P.; Sun, Y. W.; Wang, H. Q.; Wang, L.; Xia, T. Y.; Xiao, B. J.; Zeng, L.; Zhao, Y. P.; Denner, P.; Ferron, J. R.; Garofalo, A. M.; Holcomb, C. T.; Hyatt, A. W.; Jackson, G. L.; Loarte, A.; Maingi, R.; Menard, J. E.; Rack, M.; Solomon, W. M.; Xu, X. Q.; Van Zeeland, M.; Zou, X. L.

    2014-05-01

    A long-pulse high confinement plasma regime known as H-mode is achieved in the Experimental Advanced Superconducting Tokamak (EAST) with a record duration over 30 s, sustained by Lower Hybrid wave Current Drive (LHCD) with advanced lithium wall conditioning and divertor pumping. This long-pulse H-mode plasma regime is characterized by the co-existence of a small Magneto-Hydrodynamic (MHD) instability, i.e., Edge Localized Modes (ELMs) and a continuous quasi-coherent MHD mode at the edge. We find that LHCD provides an intrinsic boundary control for ELMs, leading to a dramatic reduction in the transient power load on the vessel wall, compared to the standard Type I ELMs. LHCD also induces edge plasma ergodization, broadening heat deposition footprints, and the heat transport caused by ergodization can be actively controlled by regulating edge plasma conditions, thus providing a new means for stationary heat flux control. In addition, advanced tokamak scenarios have been newly developed for high-performance long-pulse plasma operations in the next EAST experimental campaign.

  10. Programmable high voltage power supply with regulation confined to the high voltage section

    NASA Technical Reports Server (NTRS)

    Castell, Karen D. (Inventor); Ruitberg, Arthur P. (Inventor)

    1994-01-01

    A high voltage power supply in a dc-dc converter configuration includes a pre-regulator which filters and regulates the dc input and drives an oscillator which applies, in turn, a low voltage ac signal to the low side of a step-up high voltage transformer. The high voltage side of the transformer drives a voltage multiplier which provides a stepped up dc voltage to an output filter. The output voltage is sensed by a feedback network which then controls a regulator. Both the input and output of the regulator are on the high voltage side, avoiding isolation problems. The regulator furnishes a portion of the drive to the voltage multiplier, avoiding having a regulator in series with the load with its attendant, relatively high power losses. This power supply is highly regulated, has low power consumption, a low parts count and may be manufactured at low cost. The power supply has a programmability feature that allows for the selection of a large range of output voltages.

  11. Public Data Set: High Confinement Mode and Edge Localized Mode Characteristics in a Near-Unity Aspect Ratio Tokamak

    DOE Data Explorer

    Thome, Kathreen E. [University of Wisconsin-Madison] (ORCID:0000000248013922); Bongard, Michael W. [University of Wisconsin-Madison] (ORCID:0000000231609746); Barr, Jayson L. [University of Wisconsin-Madison] (ORCID:0000000177685931); Bodner, Grant M. [University of Wisconsin-Madison] (ORCID:0000000324979172); Burke, Marcus G. [University of Wisconsin-Madison] (ORCID:0000000176193724); Fonck, Raymond J. [University of Wisconsin-Madison] (ORCID:0000000294386762); Kriete, David M. [University of Wisconsin-Madison] (ORCID:0000000236572911); Perry, Justin M. [University of Wisconsin-Madison] (ORCID:0000000171228609); Schlossberg, David J. [University of Wisconsin-Madison] (ORCID:0000000287139448)

    2016-04-27

    This data set contains openly-documented, machine readable digital research data corresponding to figures published in K.E. Thome et al., 'High Confinement Mode and Edge Localized Mode Characteristics in a Near-Unity Aspect Ratio Tokamak,' Phys. Rev. Lett. 116, 175001 (2016).

  12. Does the spatial confinement influence the electric properties and cooperative effects of the hydrogen bonded systems? HCN chains as a case study

    NASA Astrophysics Data System (ADS)

    Roztoczyńska, Agnieszka; Kozłowska, Justyna; Lipkowski, Paweł; Bartkowiak, Wojciech

    2014-07-01

    In this Letter the impact of orbital compression on the energetic and electric properties as well as cooperative effects in the hydrogen bonded systems was investigated. The model (HCN)n chains, with n = 2-5, were chosen as a case study. The effect of spatial restriction was modeled by the harmonic oscillator potential. Moreover, changes in the structural parameters in the presence of model confining potential were also analyzed. All calculations were performed using the MP2 method. The obtained results demonstrated inter alia that the spatial confinement significantly influences the analyzed properties.

  13. High-adiabat high-foot inertial confinement fusion implosion experiments on the national ignition facility.

    PubMed

    Park, H-S; Hurricane, O A; Callahan, D A; Casey, D T; Dewald, E L; Dittrich, T R; Döppner, T; Hinkel, D E; Berzak Hopkins, L F; Le Pape, S; Ma, T; Patel, P K; Remington, B A; Robey, H F; Salmonson, J D; Kline, J L

    2014-02-01

    This Letter reports on a series of high-adiabat implosions of cryogenic layered deuterium-tritium (DT) capsules indirectly driven by a "high-foot" laser drive pulse at the National Ignition Facility. High-foot implosions have high ablation velocities and large density gradient scale lengths and are more resistant to ablation-front Rayleigh-Taylor instability induced mixing of ablator material into the DT hot spot. Indeed, the observed hot spot mix in these implosions was low and the measured neutron yields were typically 50% (or higher) of the yields predicted by simulation. On one high performing shot (N130812), 1.7 MJ of laser energy at a peak power of 350 TW was used to obtain a peak hohlraum radiation temperature of ∼300  eV. The resulting experimental neutron yield was (2.4±0.05)×10(15) DT, the fuel ρR was (0.86±0.063)  g/cm2, and the measured Tion was (4.2±0.16)  keV, corresponding to 8 kJ of fusion yield, with ∼1/3 of the yield caused by self-heating of the fuel by α particles emitted in the initial reactions. The generalized Lawson criteria, an ignition metric, was 0.43 and the neutron yield was ∼70% of the value predicted by simulations that include α-particle self-heating. PMID:24580603

  14. Progress in laboratory high gain ICF (inertial confinement fusion): Prospects for the future

    SciTech Connect

    Storm, E.; Lindl, J.D.; Campbell, E.M.; Bernat, T.P.; Coleman, L.W.; Emmett, J.L.; Hogan, W.J.; Hunt, J.T.; Krupke, W.F.; Lowdermilk, W.H.

    1988-01-01

    Inertial confinement fusion (ICF), a thermonuclear reaction in a small (/approximately/5 mm diameter) fuel capsule filled with a few milligrams of deuterium and tritium, has been the subject of very fruitful experimentation since the early 1970's. High gain ICF is now on the threshold of practical applications. With a Laboratory Microfusion Facility (LMF), these applications will have major implications for national defense, basic and applied science, and power production. With a driver capable of delivering about 10 MJ in a 10-ns pulse at an intensity of /approximately/3 /times/ 10/sup 14/ W/cm/sup 2/, an appropriately configured cryogenic capsule could be compressed to a density of about 200 g/cm/sup 3/ and a temperature of 3--5 keV. Under these conditions, up to 10 mg of DT could be ignited, and with a burn efficiency of about 30%, release up to 1000 MJ of fusion energy, an energy gain of about 100. A thousand megajoules is equivalent to about one quarter ton of TNT, or about 7 gallons of oil--an amount of energy tractable under laboratory conditions and potentially very useful for a variety of applications. 61 refs., 33 figs.

  15. Ideal magnetohydrodynamic stability of the tokamak high-confinement-mode edge region

    NASA Astrophysics Data System (ADS)

    Wilson, H. R.; Connor, J. W.; Field, A. R.; Fielding, S. J.; Miller, R. L.; Lao, L. L.; Ferron, J. R.; Turnbull, A. D.

    1999-05-01

    The ideal magnetohydrodynamic (MHD) stability of the tokamak edge is analyzed, with particular emphasis on radially localized instabilities; it is proposed that these are responsible for edge pressure gradient limits and edge localized modes (ELMS). Data and stability calculations from DIII-D [to appear in Proceedings of the 16th International Conference on Fusion Energy, Yokohama (International Atomic Energy Agency, Vienna, 1998), Paper No. IAEA-F1-CN-69/EX8/1] tokamak equilibria indicate that two types of instability are important: the ballooning mode (driven by pressure gradient) and the peeling mode (driven by current density). The characteristics of these instabilities, and their coupling, are described based on a circular cross-section, large aspect ratio model of the tokamak equilibrium. In addition, preliminary results are presented from an edge MHD stability code which is being developed to analyze general geometry tokamak equilibria; an interpretation of the density threshold to access the high-confinement-mode (H-mode), observed on COMPASS-D [Plasma Phys. Controlled Fusion 38, 1091 (1996)] is provided by these results. Experiments on DIII-D and the stability calculations indicate how to control ELMs by plasma shaping.

  16. Mitigating laser imprint in direct-drive inertial confinement fusion implosions with high-Z dopants.

    PubMed

    Hu, S X; Fiksel, G; Goncharov, V N; Skupsky, S; Meyerhofer, D D; Smalyuk, V A

    2012-05-11

    Nonuniformities seeded by both long- and short-wavelength laser perturbations can grow via Rayleigh-Taylor (RT) instability in direct-drive inertial confinement fusion, leading to performance reduction in low-adiabat implosions. To mitigate the effect of laser imprinting on target performance, spherical RT experiments have been performed on OMEGA using Si- or Ge-doped plastic targets in a cone-in-shell configuration. Compared to a pure plastic target, radiation preheating from these high-Z dopants (Si/Ge) increases the ablation velocity and the standoff distance between the ablation front and laser-deposition region, thereby reducing both the imprinting efficiency and the RT growth rate. Experiments showed a factor of 2-3 reduction in the laser-imprinting efficiency and a reduced RT growth rate, leading to significant (3-5 times) reduction in the σ(rms) of shell ρR modulation for Si- or Ge-doped targets. These features are reproduced by radiation-hydrodynamics simulations using the two-dimensional hydrocode DRACO. PMID:23003051

  17. High-resolution Electrical Resistivity Tomography monitoring of a tracer test in a confined aquifer

    NASA Astrophysics Data System (ADS)

    Wilkinson, P. B.; Meldrum, P. I.; Kuras, O.; Chambers, J. E.; Holyoake, S. J.; Ogilvy, R. D.

    2010-04-01

    A permanent geoelectrical subsurface imaging system has been installed at a contaminated land site to monitor changes in groundwater quality after the completion of a remediation programme. Since the resistivities of earth materials are sensitive to the presence of contaminants and their break-down products, 4-dimensional resistivity imaging can act as a surrogate monitoring technology for tracking and visualising changes in contaminant concentrations at much higher spatial and temporal resolution than manual intrusive investigations. The test site, a municipal car park built on a former gasworks, had been polluted by a range of polycyclic aromatic hydrocarbons and dissolved phase contaminants. It was designated statutory contaminated land under Part IIA of the UK Environmental Protection Act due to the risk of polluting an underlying minor aquifer. Resistivity monitoring zones were established on the boundaries of the site by installing vertical electrode arrays in purpose-drilled boreholes. After a year of monitoring data had been collected, a tracer test was performed to investigate groundwater flow velocity and to demonstrate rapid volumetric monitoring of natural attenuation processes. A saline tracer was injected into the confined aquifer, and its motion and evolution were visualised directly in high-resolution tomographic images in near real-time. Breakthrough curves were calculated from independent resistivity measurements, and the estimated seepage velocities from the monitoring images and the breakthrough curves were found to be in good agreement with each other and with estimates based on the piezometric gradient and assumed material parameters.

  18. Phase Dynamics Criterion for Fast Relaxation of High-Confinement-Mode Plasmas

    NASA Astrophysics Data System (ADS)

    Xi, P. W.; Xu, X. Q.; Diamond, P. H.

    2014-02-01

    We derive a new nonlinear criterion for the occurrence of fast relaxation (crash) events at the edge of high-confinement-mode plasmas. These fast relaxation events called ELMs (edge-localized modes) evolve from ideal magnetohydrodynamics (MHD) instabilities, but the crash is not due only to linear physics. We show that for an ELM crash to occur, the coherence time of the relative phase between potential and pressure perturbations must be long enough to allow growth to large amplitude. This phase coherence time is determined by both linear and nonlinear dynamics. An ELM crash requires that the instability growth rate exceed a critical value, i.e., γ >γc, where γc is set by 1/τc and τc is the phase coherence time. For 0<γ <γc, MHD turbulence develops and drives enhanced turbulent transport. The results indicate that the shape of the growth rate spectrum γ(n) is important to whether the result is a crash or turbulence. We demonstrate that ELMs can be mitigated by reducing the phase coherence time without changing linear instability. These findings also offer an explanation of the occurrence of ELM-free H-mode regimes.

  19. The ''ring killer'' experiment: Electron confinement in the ELMO Bumpy Torus without the influence of hot-electron rings

    SciTech Connect

    Hillis, D.L.; Wilgen, J.B.; Cobble, J.A.; Davis, W.A.; Hiroe, S.; Rasmussen, D.A.; Richards, R.K.; Uckan, T.; Jaeger, E.F.; Hankins, O.E.

    1986-11-01

    The ELMO Bumpy Torus (EBT) (Plasma Physics and Controlled Nuclear Fusion Research (IAEA, Vienna, 1975), Vol. II, p. 141) normally has an energetic electron ring in each of its 24 mirror sectors. The original intention of using this hot-electron population was to provide an average local minimum in the magnetic field (through its diamagnetism) to stabilize the simple interchange and flute modes, which otherwise are theoretically inherent in a closed-field-line bumpy torus. To study the confinement properties of a bumpy torus without the influence of hot-electron rings, a water-cooled stainless steel limiter in each mirror sector was extended into the plasma to the ring location; this eliminated the hot-electron ring population. These limiters were aptly named ''ring killers.'' Electron temperature, density, space potential, and plasma fluctuations have been measured during the ring killer experiment and are compared to standard EBT operation. The results of these experiments indicate that the hot-electron rings in EBT do enhance the core plasma properties of EBT and do, in fact, reduce plasma fluctuations; however, these improvements are not large in magnitude. These measurements and recent theoretical models suggest that simple interchange/flute modes are stabilized, or fluctuation levels reduced, well before that condition is obtained for average minimum-B stabilization. Several possible mechanisms for this stabilization are discussed.

  20. Electron confinement in a bumpy torus without the influence of hot-electron rings: ''Ring killer'' experiment

    SciTech Connect

    Hillis, D.L.; Wilgen, J.B.; Cobble, J.A.; Davis, W.A.; Hiroe, S.; Rasmussen, D.A.; Richards, R.K.; Uckan, T.; Jaeger, E.F.; Hankins, O.E.

    1985-09-01

    The ELMO Bumpy Torus (EBT) (Plasma Physics and Controlled Nuclear Fusion (IAEA, Vienna, 1975), Vol. II, p. 141) normally has an energetic electron ring in each of its 24 mirror sectors. The original intention of using this hot-electron population was to provide an average local minimum in the magnetic field (through its diamagnetism) to stabilize the simple interchange and flute modes, which otherwise are theoretically inherent in a closed-field-line bumpy torus. To study the confinement properties of a bumpy torus without the influence of hot-electron rings, a water-cooled stainless steel limiter in each mirror sector was extended into the plasma to the ring location; this eliminated the hot-electron ring population. These limiters were aptly named ''ring killers.'' Electron temperature, density, space potential, and plasma fluctuations have been measured during the ring killer experiment and are compared to standard EBT operation. The results of these experiments indicate that the hot-electron rings in EBT do enhance the core plasma properties of EBT and do, in fact, reduce plasma fluctuations; however, these improvements are not large in magnitude. These measurements and recent theoretical models suggest that simple interchange/flute modes are stabilized, or fluctuation levels reduced, well before that condition is obtained for average minimum-B stabilization.

  1. Economics of fertility in high-yielding dairy cows on confined TMR systems.

    PubMed

    Cabrera, V E

    2014-05-01

    The objective of this review paper was to summarise the latest findings in dairy cattle reproductive economics with an emphasis on high yielding, confined total mixed ration systems. The economic gain increases as the reproductive efficiency improves. These increments follow the law of diminishing returns, but are still positive even at high reproductive performance. Reproductive improvement results in higher milk productivity and, therefore, higher milk income over feed cost, more calf sales and lower culling and breeding expenses. Most high-yielding herds in the United States use a combination of timed artificial insemination (TAI) and oestrous detection (OD) reproductive programme. The ratio of achievable pregnancies between OD and TAI determines the economic value difference between both and their combinations. Nonetheless, complex interactions between reproductive programme, herd relative milk yield, and type of reproductive programme are reported. For example, higher herd relative milk yield would favour programme relying more on TAI. In addition, improved reproductive efficiency produces extra replacements. The availability of additional replacements could allow more aggressive culling policies (e.g. less services for non-pregnant cows) to balance on-farm supply and demand of replacements. Balancing heifer replacement availability in an efficient reproductive programme brings additional economic benefits. New technologies such as the use of earlier chemical tests for pregnancy diagnosis could be economically effective depending on the goals and characteristics of the farm. Opportunities for individual cow reproductive management within defined reproductive programme exist. These decisions would be based on economic metrics derived from the value of a cow such as the value of a new pregnancy, the cost of a pregnancy loss, or the cost of an extra day open. PMID:24679357

  2. Dynamics of Confined Flexible and Unentangled Polymer Melts in Highly Adsorbing Cylindrical Pores

    SciTech Connect

    Carrillo, Jan-Michael Y; Sumpter, Bobby G

    2014-01-01

    Inspired by the recent neutron spin echo experiments (NSE) designed to address the dynamic phenomena in polymer melts that are induced by interactions with a confining surface, we performed coarse-grained molecular dynamics simulations to replicate the experimental results in order to provide new molecular insight for the observations. The results show excellent agreement in the values obtained for the normalized coherent single chain dynamic structure factor, S(Q;Dt)/S(Q;0) , between experiments and simulations. The simulations indicate that using different chain molecular weights that are used to achieve scattering contrast results in the uneven distribution of scatterers in the radial direction because lower molecular weight chains prefer to adsorb in the confining surface. In the bulk configuration, both simulations and experiments confirm that the polymer chains follow Rouse dynamics. However, under confinement, the Rouse modes are suppressed. The mean-squared radius of gyration, R2g, and the average relative shape anisotropy k2 of the conformation of the polymer chains indicate a pancake-like conformation near the surface and a bulk-like conformation near the center of the confining cylinder. Direct visualization of the polymers in the simulation confirm the pancake-like conformation of the adsorbed chains and the presence of trains, loops and tails in the region between the adsorbed chains and the chains not in contact with the surface. Despite the presence of these different conformations, the average form factor of the confined chains still follows the Debye function which describes linear ideal chains, which is in agreement with small angle neutron scattering (SANS) experiments. The experimentally inaccessible mean squared displacement of the confined monomers, calculated as a function of radial distance from the pore surface, was obtained in the simulations. The simulation shows a gradual increase of the MSD from the adsorbed, but mobile layer, to that

  3. High-speed repetitive pellet injector for plasma fueling of magnetic confinement fusion devices

    SciTech Connect

    Combs, S.K.; Baylor, L.R.; Foust, C.R.

    1993-11-01

    The projected fueling requirements of future magnetic confinement devices for controlled thermonuclear research [e.g., the International Thermonuclear Experimental Reactor (ITER)] indicate that a flexible plasma fueling capability is required. This includes a mix of traditional gas puffing and low- and high-velocity deuterium-tritium pellets. Conventional pellet injectors (based on light gas guns or centrifugal accelerators) can reliably provide frozen hydrogen pellets (1- to 6-mm-diam sizes tested) up to {approximately}1.3-km/s velocity at the appropriate pellet fueling rates (1 to 10 Hz or greater). For long-pulse operation in a higher velocity regime (>2 km/s), an experiment in collaboration between Oak Ridge National Laboratory (ORNL) and ENEA Frascati is under way. This activity will be carried out in the framework of a collaborative agreement between the US Department of Energy and European Atomic Energy Community -- ENEA Association. In this experiment, an existing ORNL hydrogen extruder (equipped with a pellet chambering mechanism/gun barrel assembly) and a Frascati two-stage light gas gun driver have been combined on a test facility at ORNL. Initial testing has been carried out with single deuterium pellets accelerated up to 2.05 km/s with the two-stage driver; in addition, some preliminary repetitive testing (to commission the diagnostics) was performed at reduced speeds, including sequences at 0.5 to 1 Hz and 10 to 30 pellets. The primary objective of this study is to demonstrate repetitive operation (up to {approximately}1 Hz) with speeds in the 2- to 3-km/s range. In addition, the strength of extruded hydrogen ice as opposed to that produced in situ by direct condensation in pipe guns can be investigated. The equipment and initial experimental results are described.

  4. The Smith Cloud: High-Velocity Accretion and Dark Matter Confinement

    NASA Astrophysics Data System (ADS)

    Nichols, M.; Bland-Hawthorn, J.

    2009-12-01

    The Smith Cloud is a massive system of metal-poor neutral and ionized gas (M gas gsim 2 × 106 M sun) that is presently moving at high velocity (V GSR≈ 300 km s-1) with respect to the Galaxy at a distance of 12 kpc from the Sun. The kinematics of the cloud's cometary tail indicates that the gas is in the process of accretion onto the Galaxy, as first discussed by Lockman et al. Here, we re-investigate the cloud's orbit by considering the possibility that the cloud is confined by a dark matter halo. This is required for the cloud to survive its passage through the Galactic corona. We consider three possible models for the dark matter halo (Navarro-Frenk-White (NFW), Einasto, and Burkert) including the effects of tidal disruption and ram pressure stripping during the cloud's infall onto and passage through the Galactic disk. For the NFW and Einasto dark matter models, we are able to determine reasonable initial conditions for the Smith Cloud, although this is only marginally possible with the Burkert model. For all three models, the progenitor had an initial (gas+dark matter) mass that was an order-of-magnitude higher than inferred today. In agreement with Lockman et al., the cloud appears to have punched through the disk ≈70 Myr ago. For our most successful models, the baryon-to-dark matter ratio is fairly constant during an orbital period but drops by a factor of 2-5 after transiting the disk. The cloud appears to have only marginally survived its transit and is unlikely to retain its integrity during the next transit ≈ 30 Myr from now.

  5. Collisions between Dark Matter Confined High Velocity Clouds and Magnetized Galactic Disks: The Smith Cloud

    NASA Astrophysics Data System (ADS)

    Galyardt, Jason; Shelton, Robin L.

    2016-01-01

    The Galaxy’s population of High Velocity Clouds (HVCs) may include a subpopulation that is confined by dark matter minihalos and falling toward the Galactic disk. We present the first magnetohydrodynamic simulational study of dark-matter-dominated HVCs colliding with a weakly magnetized galactic disk. Our HVCs have baryonic masses of 5 × 106M⊙ and dark matter minihalo masses of 0, 3 × 108, or 1 × 109 M⊙. They are modeled on the Smith Cloud, which is said to have collided with the disk 70 Myr ago. We find that, in all cases, the cloud’s collision with the galactic disk creates a hole in the disk, completely disperses the cloud, and forms a bubble-shaped structure on the far side of the disk. In contrast, when present, the dark matter minihalo continues unimpeded along its trajectory. Later, as the minihalo passes through the bubble structure and galactic halo, it accretes up to 6.0 × 105 M⊙ in baryonic material, depending on the strengths of the magnetic field and minihalo gravity. These simulations suggest that if the Smith Cloud is associated with a dark matter minihalo and collided with the Galactic disk, the minihalo has accreted the observed gas. However, if the Smith Cloud is dark-matter-free, it is on its first approach toward the disk. These simulations also suggest that the dark matter is most concentrated either at the head of the cloud or near the cloud, depending upon the strength of the magnetic field, a point that could inform indirect dark matter searches.

  6. A case study of the carbon footprint of milk from high-performing confinement and grass-based dairy farms.

    PubMed

    O'Brien, D; Capper, J L; Garnsworthy, P C; Grainger, C; Shalloo, L

    2014-03-01

    Life-cycle assessment (LCA) is the preferred methodology to assess carbon footprint per unit of milk. The objective of this case study was to apply an LCA method to compare carbon footprints of high-performance confinement and grass-based dairy farms. Physical performance data from research herds were used to quantify carbon footprints of a high-performance Irish grass-based dairy system and a top-performing United Kingdom (UK) confinement dairy system. For the US confinement dairy system, data from the top 5% of herds of a national database were used. Life-cycle assessment was applied using the same dairy farm greenhouse gas (GHG) model for all dairy systems. The model estimated all on- and off-farm GHG sources associated with dairy production until milk is sold from the farm in kilograms of carbon dioxide equivalents (CO2-eq) and allocated emissions between milk and meat. The carbon footprint of milk was calculated by expressing GHG emissions attributed to milk per tonne of energy-corrected milk (ECM). The comparison showed that when GHG emissions were only attributed to milk, the carbon footprint of milk from the Irish grass-based system (837 kg of CO2-eq/t of ECM) was 5% lower than the UK confinement system (884 kg of CO2-eq/t of ECM) and 7% lower than the US confinement system (898 kg of CO2-eq/t of ECM). However, without grassland carbon sequestration, the grass-based and confinement dairy systems had similar carbon footprints per tonne of ECM. Emission algorithms and allocation of GHG emissions between milk and meat also affected the relative difference and order of dairy system carbon footprints. For instance, depending on the method chosen to allocate emissions between milk and meat, the relative difference between the carbon footprints of grass-based and confinement dairy systems varied by 3 to 22%. This indicates that further harmonization of several aspects of the LCA methodology is required to compare carbon footprints of contrasting dairy systems. In

  7. Development of a Binary Mixture Gas Composition Instrument for Use in a Confined High Temperature Environment

    NASA Astrophysics Data System (ADS)

    Cadell, Seth R.

    , or used to measure the purity of the coolant itself. This work details the efforts conducted to develop such an instrument. While the concept of designing a capacitance sensor to measure a gas mixture is not unique, the application of using a capacitance sensor within a nuclear reactor is a new application. This application requires the development of an instrument that will survive a high temperature nuclear reactor environment and operate at a sensitivity not found in current applications. To prove this technique, instrument prototypes were built and tested in confined environments and at high temperatures. This work discusses the proof of concept testing and outlines an application in the High Temperature Test Facility to increase the operational understanding of the instrument. This work is the first step toward the ultimate outcome of this work, which is to provide a new tool to the gas reactor community allowing real-time measurements of coolant properties within the core.

  8. The influence of toroidal Alfvén modes on the confinement of fast particles in the Globus-M spherical tokamak

    NASA Astrophysics Data System (ADS)

    Petrov, Yu. V.; Bakharev, N. N.; Gusev, V. K.; Minaev, V. B.; Kornev, V. A.; Mel'nik, A. D.; Patrov, M. I.; Sakharov, N. V.; Tolstyakov, S. Yu.; Kurskiev, G. S.; Chernyshev, F. V.; Shchegolev, P. B.

    2014-12-01

    Neutral beam injection into the Globus-M spherical tokamak at the early stage of discharge leads to the development of instabilities in a frequency range of 50-200 kHz, which have been identified as toroidal Alfvén eigenmodes (TAEs) [1]. The influence of these modes on the confinement of fast particles has been studied with the aid of a neutral particle analyzer (NPA) and a neutron detector. The isotope effect was studied using hydrogen and deuterium both in the injected beam and in the target plasma. A correlation analysis of signals from magnetic probes showed that the observed modes in most cases contain a single harmonic with toroidal number n = 1. Upon the injection of deuterium into deuterium plasma, the development of TAEs led to a decrease in the neutron flux by 25%, whereas the fluxes of high-energy recharge atoms decreased by 75%. After the injection of hydrogen, a decrease in the flux measured by NPA did not exceed 25%.

  9. Detailed high-resolution three-dimensional simulations of OMEGA separated reactants inertial confinement fusion experiments

    NASA Astrophysics Data System (ADS)

    Haines, Brian M.; Grim, Gary P.; Fincke, James R.; Shah, Rahul C.; Forrest, Chad J.; Silverstein, Kevin; Marshall, Frederic J.; Boswell, Melissa; Fowler, Malcolm M.; Gore, Robert A.; Hayes-Sterbenz, Anna C.; Jungman, Gerard; Klein, Andreas; Rundberg, Robert S.; Steinkamp, Michael J.; Wilhelmy, Jerry B.

    2016-07-01

    We present results from the comparison of high-resolution three-dimensional (3D) simulations with data from the implosions of inertial confinement fusion capsules with separated reactants performed on the OMEGA laser facility. Each capsule, referred to as a "CD Mixcap," is filled with tritium and has a polystyrene (CH) shell with a deuterated polystyrene (CD) layer whose burial depth is varied. In these implosions, fusion reactions between deuterium and tritium ions can occur only in the presence of atomic mix between the gas fill and shell material. The simulations feature accurate models for all known experimental asymmetries and do not employ any adjustable parameters to improve agreement with experimental data. Simulations are performed with the RAGE radiation-hydrodynamics code using an Implicit Large Eddy Simulation (ILES) strategy for the hydrodynamics. We obtain good agreement with the experimental data, including the DT/TT neutron yield ratios used to diagnose mix, for all burial depths of the deuterated shell layer. Additionally, simulations demonstrate good agreement with converged simulations employing explicit models for plasma diffusion and viscosity, suggesting that the implicit sub-grid model used in ILES is sufficient to model these processes in these experiments. In our simulations, mixing is driven by short-wavelength asymmetries and longer-wavelength features are responsible for developing flows that transport mixed material towards the center of the hot spot. Mix material transported by this process is responsible for most of the mix (DT) yield even for the capsule with a CD layer adjacent to the tritium fuel. Consistent with our previous results, mix does not play a significant role in TT neutron yield degradation; instead, this is dominated by the displacement of fuel from the center of the implosion due to the development of turbulent instabilities seeded by long-wavelength asymmetries. Through these processes, the long

  10. High-field penning-malmberg trap: confinement properties and use in positron accumulation

    SciTech Connect

    Hartley, J.H.

    1997-09-01

    This dissertation reports on the development of the 60 kG cryogenic positron trap at Lawrence Livermore National Laboratory, and compares the trap`s confinement properties with other nonneutral plasma devices. The device is designed for the accumulation of up to 2{times}10{sup 9} positrons from a linear-accelerator source. This positron plasma could then be used in Bhabha scattering experiments. Initial efforts at time-of-flight accumulation of positrons from the accelerator show rapid ({approximately}100 ms) deconfinement, inconsistent with the long electron lifetimes. Several possible deconfinement mechanisms have been explored, including annihilation on residual gas, injection heating, rf noise from the accelerator, magnet field curvature, and stray fields. Detailed studies of electron confinement demonstrate that the empirical scaling law used to design the trap cannot be extrapolated into the parameter regime of this device. Several possible methods for overcoming these limitations are presented.

  11. Graphene/Si-quantum-dot heterojunction diodes showing high photosensitivity compatible with quantum confinement effect.

    PubMed

    Shin, Dong Hee; Kim, Sung; Kim, Jong Min; Jang, Chan Wook; Kim, Ju Hwan; Lee, Kyeong Won; Kim, Jungkil; Oh, Si Duck; Lee, Dae Hun; Kang, Soo Seok; Kim, Chang Oh; Choi, Suk-Ho; Kim, Kyung Joong

    2015-04-24

    Graphene/Si quantum dot (QD) heterojunction diodes are reported for the first time. The photoresponse, very sensitive to variations in the size of the QDs as well as in the doping concentration of graphene and consistent with the quantum-confinement effect, is remarkably enhanced in the near-ultraviolet range compared to commercially available bulk-Si photodetectors. The photoresponse proves to be dominated by the carriertunneling mechanism. PMID:25776865

  12. Breaking the acoustic diffraction limit via nonlinear effect and thermal confinement for potential deep-tissue high-resolution imaging

    PubMed Central

    Yuan, Baohong; Pei, Yanbo; Kandukuri, Jayanth

    2013-01-01

    Our recently developed ultrasound-switchable fluorescence (USF) imaging technique showed that it was feasible to conduct high-resolution fluorescence imaging in a centimeter-deep turbid medium. Because the spatial resolution of this technique highly depends on the ultrasound-induced temperature focal size (UTFS), minimization of UTFS becomes important for further improving the spatial resolution USF technique. In this study, we found that UTFS can be significantly reduced below the diffraction-limited acoustic intensity focal size via nonlinear acoustic effects and thermal confinement by appropriately controlling ultrasound power and exposure time, which can be potentially used for deep-tissue high-resolution imaging. PMID:23479498

  13. Indoor Confined Feedlots.

    PubMed

    Grooms, Daniel L; Kroll, Lee Anne K

    2015-07-01

    Indoor confined feedlots offer advantages that make them desirable in northern climates where high rainfall and snowfall occur. These facilities increase the risk of certain health risks, including lameness and tail injuries. Closed confinement can also facilitate the rapid spread of infectious disease. Veterinarians can help to manage these health risks by implementing management practices to reduce their occurrence. PMID:26139194

  14. Geometric conductive filament confinement by nanotips for resistive switching of HfO2-RRAM devices with high performance

    PubMed Central

    Niu, Gang; Calka, Pauline; Auf der Maur, Matthias; Santoni, Francesco; Guha, Subhajit; Fraschke, Mirko; Hamoumou, Philippe; Gautier, Brice; Perez, Eduardo; Walczyk, Christian; Wenger, Christian; Di Carlo, Aldo; Alff, Lambert; Schroeder, Thomas

    2016-01-01

    Filament-type HfO2-based RRAM has been considered as one of the most promising candidates for future non-volatile memories. Further improvement of the stability, particularly at the “OFF” state, of such devices is mainly hindered by resistance variation induced by the uncontrolled oxygen vacancies distribution and filament growth in HfO2 films. We report highly stable endurance of TiN/Ti/HfO2/Si-tip RRAM devices using a CMOS compatible nanotip method. Simulations indicate that the nanotip bottom electrode provides a local confinement for the electrical field and ionic current density; thus a nano-confinement for the oxygen vacancy distribution and nano-filament location is created by this approach. Conductive atomic force microscopy measurements confirm that the filaments form only on the nanotip region. Resistance switching by using pulses shows highly stable endurance for both ON and OFF modes, thanks to the geometric confinement of the conductive path and filament only above the nanotip. This nano-engineering approach opens a new pathway to realize forming-free RRAM devices with improved stability and reliability. PMID:27181525

  15. First-order transition in confined water between high-density liquid and low-density amorphous phases.

    PubMed

    Koga, K; Tanaka, H; Zeng, X C

    2000-11-30

    Supercooled water and amorphous ice have a rich metastable phase behaviour. In addition to transitions between high- and low-density amorphous solids, and between high- and low-density liquids, a fragile-to-strong liquid transition has recently been proposed, and supported by evidence from the behaviour of deeply supercooled bilayer water confined in hydrophilic slit pores. Here we report evidence from molecular dynamics simulations for another type of first-order phase transition--a liquid-to-bilayer amorphous transition--above the freezing temperature of bulk water at atmospheric pressure. This transition occurs only when water is confined in a hydrophobic slit pore with a width of less than one nanometre. On cooling, the confined water, which has an imperfect random hydrogen-bonded network, transforms into a bilayer amorphous phase with a perfect network (owing to the formation of various hydrogen-bonded polygons) but no long-range order. The transition shares some characteristics with those observed in tetrahedrally coordinated substances such as liquid silicon, liquid carbon and liquid phosphorus. PMID:11117739

  16. Geometric conductive filament confinement by nanotips for resistive switching of HfO2-RRAM devices with high performance

    NASA Astrophysics Data System (ADS)

    Niu, Gang; Calka, Pauline; Auf der Maur, Matthias; Santoni, Francesco; Guha, Subhajit; Fraschke, Mirko; Hamoumou, Philippe; Gautier, Brice; Perez, Eduardo; Walczyk, Christian; Wenger, Christian; di Carlo, Aldo; Alff, Lambert; Schroeder, Thomas

    2016-05-01

    Filament-type HfO2-based RRAM has been considered as one of the most promising candidates for future non-volatile memories. Further improvement of the stability, particularly at the “OFF” state, of such devices is mainly hindered by resistance variation induced by the uncontrolled oxygen vacancies distribution and filament growth in HfO2 films. We report highly stable endurance of TiN/Ti/HfO2/Si-tip RRAM devices using a CMOS compatible nanotip method. Simulations indicate that the nanotip bottom electrode provides a local confinement for the electrical field and ionic current density; thus a nano-confinement for the oxygen vacancy distribution and nano-filament location is created by this approach. Conductive atomic force microscopy measurements confirm that the filaments form only on the nanotip region. Resistance switching by using pulses shows highly stable endurance for both ON and OFF modes, thanks to the geometric confinement of the conductive path and filament only above the nanotip. This nano-engineering approach opens a new pathway to realize forming-free RRAM devices with improved stability and reliability.

  17. Graphene-Analogues Boron Nitride Nanosheets Confining Ionic Liquids: A High-Performance Quasi-Liquid Solid Electrolyte.

    PubMed

    Li, Mingtao; Zhu, Wenshuai; Zhang, Pengfei; Chao, Yanhong; He, Qian; Yang, Bolun; Li, Huaming; Borisevich, Albinab; Dai, Sheng

    2016-07-01

    Solid electrolytes are one of the most promising electrolyte systems for safe lithium batteries, but the low ionic conductivity of these electrolytes seriously hinders the development of efficient lithium batteries. Here, a novel class of graphene-analogues boron nitride (g-BN) nanosheets confining an ultrahigh concentration of ionic liquids (ILs) in an interlayer and out-of-layer chamber to give rise to a quasi-liquid solid electrolyte (QLSE) is reported. The electron-insulated g-BN nanosheet host with a large specific surface area can confine ILs as much as 10 times of the host's weight to afford high ionic conductivity (3.85 × 10(-3) S cm(-1) at 25 °C, even 2.32 × 10(-4) S cm(-1) at -20 °C), which is close to that of the corresponding bulk IL electrolytes. The high ionic conductivity of QLSE is attributed to the enormous absorption for ILs and the confining effect of g-BN to form the ordered lithium ion transport channels in an interlayer and out-of-layer of g-BN. Furthermore, the electrolyte displays outstanding electrochemical properties and battery performance. In principle, this work enables a wider tunability, further opening up a new field for the fabrication of the next-generation QLSE based on layered nanomaterials in energy conversion devices. PMID:27225944

  18. Geometric conductive filament confinement by nanotips for resistive switching of HfO2-RRAM devices with high performance.

    PubMed

    Niu, Gang; Calka, Pauline; Auf der Maur, Matthias; Santoni, Francesco; Guha, Subhajit; Fraschke, Mirko; Hamoumou, Philippe; Gautier, Brice; Perez, Eduardo; Walczyk, Christian; Wenger, Christian; Di Carlo, Aldo; Alff, Lambert; Schroeder, Thomas

    2016-01-01

    Filament-type HfO2-based RRAM has been considered as one of the most promising candidates for future non-volatile memories. Further improvement of the stability, particularly at the "OFF" state, of such devices is mainly hindered by resistance variation induced by the uncontrolled oxygen vacancies distribution and filament growth in HfO2 films. We report highly stable endurance of TiN/Ti/HfO2/Si-tip RRAM devices using a CMOS compatible nanotip method. Simulations indicate that the nanotip bottom electrode provides a local confinement for the electrical field and ionic current density; thus a nano-confinement for the oxygen vacancy distribution and nano-filament location is created by this approach. Conductive atomic force microscopy measurements confirm that the filaments form only on the nanotip region. Resistance switching by using pulses shows highly stable endurance for both ON and OFF modes, thanks to the geometric confinement of the conductive path and filament only above the nanotip. This nano-engineering approach opens a new pathway to realize forming-free RRAM devices with improved stability and reliability. PMID:27181525

  19. Factors Influencing High School Students' Career Aspirations

    ERIC Educational Resources Information Center

    Tang, Mei; Pan, Wei; Newmeyer, Mark D.

    2008-01-01

    This article explores the factors influencing high school students' career aspirations with a study analyzing 141 high school students. The Social Cognitive Career Development Model was utilized to examine the interactive relationships among learning experiences, career self-efficacy, outcome expectations, career interests, and career choices. The…

  20. Formation of high-{beta} plasma and stable confinement of toroidal electron plasma in Ring Trap 1

    SciTech Connect

    Saitoh, H.; Yoshida, Z.; Morikawa, J.; Furukawa, M.; Yano, Y.; Kawai, Y.; Kobayashi, M.; Vogel, G.; Mikami, H.

    2011-05-15

    Formation of high-{beta} electron cyclotron resonance heating plasma and stable confinement of pure electron plasma have been realized in the Ring Trap 1 device, a magnetospheric configuration generated by a levitated dipole field magnet. The effects of coil levitation resulted in drastic improvements of the confinement properties, and the maximum local {beta} value has exceeded 70%. Hot electrons are major component of electron populations, and its particle confinement time is 0.5 s. Plasma has a peaked density profile in strong field region [H. Saitoh et al., 23rd IAEA Fusion Energy Conference EXC/9-4Rb (2010)]. In pure electron plasma experiment, inward particle diffusion is realized, and electrons are stably trapped for more than 300 s. When the plasma is in turbulent state during beam injection, plasma flow has a shear, which activates the diocotron (Kelvin-Helmholtz) instability. The canonical angular momentum of the particle is not conserved in this phase, realizing the radial diffusion of charged particles across closed magnetic surfaces. [Z. Yoshida et al., Phys Rev. Lett. 104, 235004 (2010); H. Saitoh et al., Phys. Plasmas 17, 112111 (2010).].

  1. Investigation of the influence of divertor recycling on global plasma confinement in JET ITER-like wall

    NASA Astrophysics Data System (ADS)

    Tamain, P.; Joffrin, E.; Bufferand, H.; Järvinen, A.; Brezinsek, S.; Ciraolo, G.; Delabie, E.; Frassinetti, L.; Giroud, C.; Groth, M.; Lipschultz, B.; Lomas, P.; Marsen, S.; Menmuir, S.; Oberkofler, M.; Stamp, M.; Wiesen, S.; JET EFDA contributors

    2015-08-01

    The impact of the divertor geometry on global plasma confinement in type I ELMy H-mode has been investigated in the JET tokamak equipped with ITER-Like Wall. Discharges have been performed in which the position of the strike-points was changed while keeping the bulk plasma equilibrium essentially unchanged. Large variations of the global plasma confinement have been observed, the H98 factor changing from typically 0.7 when the outer strike-point is on the vertical or horizontal targets to 0.9 when it is located in the pump duct entrance. Profiles are mainly impacted in the pedestal but core gradient lengths, especially for the density, are also modified. Although substantial differences are observed in the divertor conditions, none seem to correlate directly with the confinement. Modelling with the EDGE2D-EIRENE and SOLEDGE2D-EIRENE transport codes exhibits differences in the energy losses due to neutrals inside the separatrix, but orders of magnitude are too low to explain simply the impact on the confinement.

  2. The influence of hydrodynamic interactions on protein dynamics in confined and crowded spaces—assessment in simple models

    NASA Astrophysics Data System (ADS)

    Wojciechowski, Michał; Szymczak, Piotr; Cieplak, Marek

    2010-12-01

    We consider several systems that are confined within a softly repulsive sphere. The first one is a model protein, crambin, which is described by a structure-based coarse grained model. We demonstrate that the folding process is accelerated by the hydrodynamic interactions (HI) in a way that depends on the radius of the sphere. The tighter the encompassing sphere, the smaller the effect, independent of the nature of the starting conformations. The second system is a protein surrounded by protein-like softly repulsive spheres that make the confined space crowded. In this case, the HI shorten the folding times in a way which depends on the degree of crowdedness only weakly. The third system is a collection of spheres that are meant to represent molecules. We show that confinement increases association times. We also observe that the HI either facilitate or obstruct association of two spheres depending on the crowding conditions. The dependence of the association time on crowdedness in the confining sphere is qualitatively distinct from that derived by Wieczorek and Zielenkiewicz for a cube with the periodic boundary conditions.

  3. The influence of hydrodynamic interactions on protein dynamics in confined and crowded spaces-assessment in simple models.

    PubMed

    Wojciechowski, Michał; Szymczak, Piotr; Cieplak, Marek

    2010-01-01

    We consider several systems that are confined within a softly repulsive sphere. The first one is a model protein, crambin, which is described by a structure-based coarse grained model. We demonstrate that the folding process is accelerated by the hydrodynamic interactions (HI) in a way that depends on the radius of the sphere. The tighter the encompassing sphere, the smaller the effect, independent of the nature of the starting conformations. The second system is a protein surrounded by protein-like softly repulsive spheres that make the confined space crowded. In this case, the HI shorten the folding times in a way which depends on the degree of crowdedness only weakly. The third system is a collection of spheres that are meant to represent molecules. We show that confinement increases association times. We also observe that the HI either facilitate or obstruct association of two spheres depending on the crowding conditions. The dependence of the association time on crowdedness in the confining sphere is qualitatively distinct from that derived by Wieczorek and Zielenkiewicz for a cube with the periodic boundary conditions. PMID:21119219

  4. Size control, quantum confinement, and oxidation kinetics of silicon nanocrystals synthesized at a high rate by expanding thermal plasma

    SciTech Connect

    Han, Lihao E-mail: A.H.M.Smets@tudelft.nl; Zeman, Miro; Smets, Arno H. M. E-mail: A.H.M.Smets@tudelft.nl

    2015-05-25

    The growth mechanism of silicon nanocrystals (Si NCs) synthesized at a high rate by means of expanding thermal plasma chemical vapor deposition technique are studied in this letter. A bimodal Gaussian size distribution is revealed from the high-resolution transmission electron microscopy images, and routes to reduce the unwanted large Si NCs are discussed. Photoluminescence and Raman spectroscopies are employed to study the size-dependent quantum confinement effect, from which the average diameters of the small Si NCs are determined. The surface oxidation kinetics of Si NCs are studied using Fourier transform infrared spectroscopy and the importance of post-deposition passivation treatments of hydrogenated crystalline silicon surfaces are demonstrated.

  5. High Confinement Mode and Edge Localized Mode Characteristics in a Near-Unity Aspect Ratio Tokamak

    NASA Astrophysics Data System (ADS)

    Thome, K. E.; Bongard, M. W.; Barr, J. L.; Bodner, G. M.; Burke, M. G.; Fonck, R. J.; Kriete, D. M.; Perry, J. M.; Schlossberg, D. J.

    2016-04-01

    Tokamak experiments at near-unity aspect ratio A ≲1.2 offer new insights into the self-organized H -mode plasma confinement regime. In contrast to conventional A ˜3 plasmas, the L -H power threshold PL H is ˜15 × higher than scaling predictions, and it is insensitive to magnetic topology, consistent with modeling. Edge localized mode (ELM) instabilities shift to lower toroidal mode numbers as A decreases. These ultralow-A operations enable heretofore inaccessible Jedge(R ,t ) measurements through an ELM that show a complex multimodal collapse and the ejection of a current-carrying filament.

  6. High Confinement Mode and Edge Localized Mode Characteristics in a Near-Unity Aspect Ratio Tokamak.

    PubMed

    Thome, K E; Bongard, M W; Barr, J L; Bodner, G M; Burke, M G; Fonck, R J; Kriete, D M; Perry, J M; Schlossberg, D J

    2016-04-29

    Tokamak experiments at near-unity aspect ratio A≲1.2 offer new insights into the self-organized H-mode plasma confinement regime. In contrast to conventional A∼3 plasmas, the L-H power threshold P_{LH} is ∼15× higher than scaling predictions, and it is insensitive to magnetic topology, consistent with modeling. Edge localized mode (ELM) instabilities shift to lower toroidal mode numbers as A decreases. These ultralow-A operations enable heretofore inaccessible J_{edge}(R,t) measurements through an ELM that show a complex multimodal collapse and the ejection of a current-carrying filament. PMID:27176526

  7. High confinement mode and edge localized mode characteristics in a near-unity aspect ratio tokamak

    DOE PAGESBeta

    Thome, Kathreen E.; Bongard, Michael W.; Barr, Jayson L.; Bodner, Grant M.; Burke, Marcus G.; Fonck, Raymond J.; Kriete, David M.; Perry, Justin M.; Schlossberg, David J.

    2016-04-27

    Tokamak experiments at near-unity aspect ratio A ≲ 1.2 offer new insights into the self-organized H-mode plasma confinement regime. In contrast to conventional A ~ 3 plasmas, the L–H power threshold PLH is ~15× higher than scaling predictions, and it is insensitive to magnetic topology, consistent with modeling. Edge localized mode (ELM) instabilities shift to lower toroidal mode numbers as A decreases. Furthermore, these ultralow-A operations enable heretofore inaccessible Jedge(R,t) measurements through an ELM that show a complex multimodal collapse and the ejection of a current-carrying filament.

  8. Discovery of Bragg confined hybrid modes with high Q factor in a hollow dielectric resonator

    NASA Astrophysics Data System (ADS)

    le Floch, Jean-Michel; Tobar, Michael E.; Mouneyrac, David; Cros, Dominique; Krupka, Jerzy

    2007-10-01

    The authors report on observation of Bragg confined mode in a hollow cylindrical dielectric cavity. A resonance was observed at 13.4GHz with an unloaded Q factor of order 2×105, which is more than a factor of 6 above the dielectric loss limit. Previously, such modes have only been realized from pure transverse electric modes with no azimuthal variations and only the Eϕ component. From rigorous numeric simulations, it is shown that the mode is a hybrid mode with nonzero azimuthal variations and with dominant Er and Eϕ electric field components and Hz magnetic field component.

  9. Equilibrium drives of the low and high field side n = 2 plasma response and impact on global confinement

    DOE PAGESBeta

    Paz-Soldan, C.; Logan, N. C.; Haskey, S. R.; Nazikian, R.; Strait, E. J.; Chen, X.; Ferraro, N. M.; King, J. D.; Lyons, B. C.; Park, J. -K.

    2016-03-31

    The nature of the multi-modal n=2 plasma response and its impact on global confinement is studied as a function of the axisymmetric equilibrium pressure, edge safety factor, collisionality, and L-versus H-mode conditions. Varying the relative phase (ΔΦUL) between upper and lower in-vessel coils demonstrates that different n=2 poloidal spectra preferentially excite different plasma responses. These different plasma response modes are preferentially detected on the tokamak high-field side (HFS) or low-field side (LFS) midplanes, have different radial extents, couple differently to the resonant surfaces, and have variable impacts on edge stability and global confinement. In all equilibrium conditions studied, the observedmore » confinement degradation shares the same ΔΦUL dependence as the coupling to the resonant surfaces given by both ideal (IPEC) and resistive (MARS-F) MHD computation. Varying the edge safety factor shifts the equilibrium field-line pitch and thus the ΔΦUL dependence of both the global confinement and the n=2 magnetic response. As edge safety factor is varied, modeling finds that the HFS response (but not the LFS response), the resonant surface coupling, and the edge displacements near the X-point all share the same ΔΦUL dependence. The LFS response magnitude is strongly sensitive to the core pressure and is insensitive to the collisionality and edge safety factor. This indicates that the LFS measurements are primarily sensitive to a pressure-driven kink-ballooning mode that couples to the core plasma. MHD modeling accurately reproduces these (and indeed all) LFS experimental trends and supports this interpretation. In contrast to the LFS, the HFS magnetic response and correlated global confinement impact is unchanged with plasma pressure, but is strongly reduced in high collisionality conditions in both H- and L-mode. This experimentally suggests the bootstrap current drives the HFS response through the kink-peeling mode drive, though

  10. Hard x-ray backlighters for high resolution Compton radiography of Inertial Confinement Fusion targets

    NASA Astrophysics Data System (ADS)

    Tommasini, R.; Macphee, A.; Hey, D.; Ma, T.; Chen, C.; Izumi, N.; MacKinnon, A.; Hatchett, S. P.; Koch, J. A.; Springer, P.; Landen, O. L.

    2008-11-01

    Radiographs of the final stages of imploding DT fuel in inertial confinement fusion experiments will be extremely valuable for checking the convergence, areal density and areal density uniformity of the fuel. For x-rays with energies between 30 and 200 keV, the main opacity will be due to Compton scattering. Here we present the demonstration of 75-200 keV point backlighter sources generated by gold targets irradiated by picosecond laser pulses. In experiments performed at the Titan laser facility at Lawrence Livermore National Laboratory, we measured the source size and the Bremsstrahlung spectrum, as a function of laser intensity and pulse length, from by 5e17-5e18 W/cm^2 using 2-40 ps pulses. We achieved 1D and 2D source sizes of 10 μm, and conversion efficiencies exceeding 1e-3 J/J into x-ray photons with energies in the 100-200 keV spectral range. These sources meet the requirements for radiographing the fuel in inertial confinement fusion implosions at both OMEGA and the National Ignition Facility (NIF) whose experimental designs will also be discussed.

  11. High-Energy Cosmic Ray Self-Confinement Close to Extra-Galactic Sources

    NASA Astrophysics Data System (ADS)

    Blasi, Pasquale; Amato, Elena; D'Angelo, Marta

    2015-09-01

    The ultrahigh-energy cosmic rays observed on the Earth are most likely accelerated in extra-Galactic sources. For the typical luminosities invoked for such sources, the electric current associated to the flux of cosmic rays that leave them is large. The associated plasma instabilities create magnetic fluctuations that can efficiently scatter particles. We argue that this phenomenon forces cosmic rays to be self-confined in the source proximity for energies E confined close to their sources for energies E

  12. High-Energy Cosmic Ray Self-Confinement Close to Extra-Galactic Sources.

    PubMed

    Blasi, Pasquale; Amato, Elena; D'Angelo, Marta

    2015-09-18

    The ultrahigh-energy cosmic rays observed on the Earth are most likely accelerated in extra-Galactic sources. For the typical luminosities invoked for such sources, the electric current associated to the flux of cosmic rays that leave them is large. The associated plasma instabilities create magnetic fluctuations that can efficiently scatter particles. We argue that this phenomenon forces cosmic rays to be self-confined in the source proximity for energies Econfined close to their sources for energies E

  13. Measurement of RF electric field in high- β plasma using a Pockels detector in magnetosphere plasma confinement device RT-1

    NASA Astrophysics Data System (ADS)

    Mushiake, Toshiki; Nishiura, M.; Yoshida, Z.; Yano, Y.; Kawazura, Y.; Saitoh, H.; Yamasaki, M.; Kashyap, A.; Takahashi, N.; Nakatsuka, M.; Fukuyama, Atsushi

    2015-11-01

    The magnetosphere plasma confinement device RT-1 generates a dipole magnetic field that can confine high- β plasma by using a levitated superconducting coil. So far it is reported that high temperature electrons (up to 50keV) exist and that the local electron βe value exceeds more than 100%. However, the ion β value βi remains low in the present high- β state. To realize a high-βi state, we have started Ion Cyclotron Heating (ICH) experiments. For efficient ICH in a dipole topology, it is important to measure RF electric fields and characterize the propagation of RF waves in plasmas. On this viewpoint, we started direct measurement of local RF electric fields in RT-1 with a Pockels sensor system. A non-linear optical crystal in the Pockels sensor produces birefringence in an ambient electric field. The refractive index change of the birefringence is proportional to the applied electric field strength, which can be used to measure local electric fields. RF electric field distribution radiated from an ICH antenna was measured inside RT-1 in air, and was compared with numerical results calculated by TASK code. Results on the measurement of electric field distribution in high- β plasma and evaluation of the absorbed RF power into ions will be reported. Supported by JSPS KAKENHI Grant Numbers 23224014.

  14. Magneto-optical absorption in semiconducting spherical quantum dots: Influence of the dot-size, confining potential, and magnetic field

    SciTech Connect

    Kushwaha, Manvir S.

    2014-12-15

    Semiconducting quantum dots – more fancifully dubbed artificial atoms – are quasi-zero dimensional, tiny, man-made systems with charge carriers completely confined in all three dimensions. The scientific quest behind the synthesis of quantum dots is to create and control future electronic and optical nanostructures engineered through tailoring size, shape, and composition. The complete confinement – or the lack of any degree of freedom for the electrons (and/or holes) – in quantum dots limits the exploration of spatially localized elementary excitations such as plasmons to direct rather than reciprocal space. Here we embark on a thorough investigation of the magneto-optical absorption in semiconducting spherical quantum dots characterized by a confining harmonic potential and an applied magnetic field in the symmetric gauge. This is done within the framework of Bohm-Pines’ random-phase approximation that enables us to derive and discuss the full Dyson equation that takes proper account of the Coulomb interactions. As an application of our theoretical strategy, we compute various single-particle and many-particle phenomena such as the Fock-Darwin spectrum; Fermi energy; magneto-optical transitions; probability distribution; and the magneto-optical absorption in the quantum dots. It is observed that the role of an applied magnetic field on the absorption spectrum is comparable to that of a confining potential. Increasing (decreasing) the strength of the magnetic field or the confining potential is found to be analogous to shrinking (expanding) the size of the quantum dots: resulting into a blue (red) shift in the absorption spectrum. The Fermi energy diminishes with both increasing magnetic-field and dot-size; and exhibits saw-tooth-like oscillations at large values of field or dot-size. Unlike laterally confined quantum dots, both (upper and lower) magneto-optical transitions survive even in the extreme instances. However, the intra-Landau level

  15. Magneto-optical absorption in semiconducting spherical quantum dots: Influence of the dot-size, confining potential, and magnetic field

    NASA Astrophysics Data System (ADS)

    Kushwaha, Manvir S.

    2014-12-01

    Semiconducting quantum dots - more fancifully dubbed artificial atoms - are quasi-zero dimensional, tiny, man-made systems with charge carriers completely confined in all three dimensions. The scientific quest behind the synthesis of quantum dots is to create and control future electronic and optical nanostructures engineered through tailoring size, shape, and composition. The complete confinement - or the lack of any degree of freedom for the electrons (and/or holes) - in quantum dots limits the exploration of spatially localized elementary excitations such as plasmons to direct rather than reciprocal space. Here we embark on a thorough investigation of the magneto-optical absorption in semiconducting spherical quantum dots characterized by a confining harmonic potential and an applied magnetic field in the symmetric gauge. This is done within the framework of Bohm-Pines' random-phase approximation that enables us to derive and discuss the full Dyson equation that takes proper account of the Coulomb interactions. As an application of our theoretical strategy, we compute various single-particle and many-particle phenomena such as the Fock-Darwin spectrum; Fermi energy; magneto-optical transitions; probability distribution; and the magneto-optical absorption in the quantum dots. It is observed that the role of an applied magnetic field on the absorption spectrum is comparable to that of a confining potential. Increasing (decreasing) the strength of the magnetic field or the confining potential is found to be analogous to shrinking (expanding) the size of the quantum dots: resulting into a blue (red) shift in the absorption spectrum. The Fermi energy diminishes with both increasing magnetic-field and dot-size; and exhibits saw-tooth-like oscillations at large values of field or dot-size. Unlike laterally confined quantum dots, both (upper and lower) magneto-optical transitions survive even in the extreme instances. However, the intra-Landau level transitions are seen

  16. E-H mode transition of a high-power inductively coupled plasma torch at atmospheric pressure with a metallic confinement tube

    NASA Astrophysics Data System (ADS)

    Altenberend, Jochen; Chichignoud, Guy; Delannoy, Yves

    2012-08-01

    Inductively coupled plasma torches need high ignition voltages for the E-H mode transition and are therefore difficult to operate. In order to reduce the ignition voltage of an RF plasma torch with a metallic confinement tube the E-H mode transition was studied. A Tesla coil was used to create a spark discharge and the E-H mode transition of the plasma was then filmed using a high-speed camera. The electrical potential of the metallic confinement tube was measured using a high-voltage probe. It was found that an arc between the grounded injector and the metallic confinement tube is maintained by the electric field (E-mode). The transition to H-mode occurred at high magnetic fields when the arc formed a loop. The ignition voltage could be reduced by connecting the metallic confinement tube with a capacitor to the RF generator.

  17. Exploring the potential high energy locations and intensities in confined work spaces of waveguide dimensions

    NASA Astrophysics Data System (ADS)

    Rodriguez, Ricardo; Lewis, Winston G.

    2014-07-01

    review visits the likelihood for potential energy build-up due to RF propagation in confined spaces that are of waveguide design but with larger dimensions. Such confined spaces include silos, tanks, pipes, manholes, air-condition ducts, tunnels, wells, engine rooms and operator rooms on board vessels. In these confined spaces waves reflect off of the walls and combine constructively or destructively with incident waves producing reinforcement or cancellation respectively. Where there is reinforcement, the intensity of the wave for a particular distance in accordance with the standard, may exceed the exposure limit for this distance from the source thereby exposing the worker to larger intensities than the accepted limit and presenting a potential health and safety threat.

  18. Experimental study of magnetically confined hollow electron beams in the Tevatron as collimators for intense high-energy hadron beams

    SciTech Connect

    Stancari, G.; Annala, G.; Shiltsev, V.; Still, D.; Valishev, A.; Vorobiev, L.; /Fermilab

    2011-03-01

    Magnetically confined hollow electron beams for controlled halo removal in high-energy colliders such as the Tevatron or the LHC may extend traditional collimation systems beyond the intensity limits imposed by tolerable losses. They may also improve collimation performance by suppressing loss spikes due to beam jitter and by increasing capture efficiency. A hollow electron gun was designed and tested at Fermilab for this purpose. It was installed in one of the Tevatron electron lenses in the summer of 2010. We present the results of the first experimental tests of the hollow-beam collimation concept on 980-GeV antiproton bunches in the Tevatron.

  19. The influence of topology on the free energy and metric properties of ring polymer confined in a slit

    NASA Astrophysics Data System (ADS)

    Sun, Zhao-Yan; Li, Bing; An, Li-Jia; Wang, Zhen-Gang

    2014-03-01

    An off-lattice model with no excluded volume is used to study the effect of topological constraint on the free energy and metric properties of ring polymer confined in a slit with height d. The topological state is conserved by forbidding bond crossing. This model was applied to ring polymers with chain length up to N =103 . Umbrella sampling and weighted histogram analysis method (WHAM) are used to calculate the free energy and the radius of gyration. In the strong confinement limit, free energy of linear chain in our model scales as d-2 and the in-plane radius of gyration R| | is independent of confinement, which agrees with the theoretical prediction very well. However, unlike the linear chain, the scaling behavior of ring polymer shows a different trend. This abnormal scaling behavior is thought to be caused by the topological constraint: the knotting probability of ring polymer increases with decreasing the slit height, and in this case, ring polymer is forced to expand itself to conserve its topological unknotted state. This work is subsidized by the National Basic Research Program of China (973 Program, 2012CB821500), and supported by the National Natural Science Foundation of China (21222407, 21074137, 50930001) programs.

  20. Second Harmonic Generation and Confined Acoustic Phonons in HighlyExcited Semiconductor Nanocrystals

    SciTech Connect

    Son, Dong Hee; Wittenberg, Joshua S.; Banin, Uri; Alivisatos, A.Paul

    2006-03-30

    The photo-induced enhancement of second harmonic generation, and the effect of nanocrystal shape and pump intensity on confined acoustic phonons in semiconductor nanocrystals, has been investigated with time-resolved scattering and absorption measurements. The second harmonic signal showed a sublinear increase of the second order susceptibility with respect to the pump pulse energy, indicating a reduction of the effective one-electron second-order nonlinearity with increasing electron-hole density in the nanocrystals. The coherent acoustic phonons in spherical and rod-shaped semiconductor nanocrystals were detected in a time-resolved absorption measurement. Both nanocrystal morphologies exhibited oscillatory modulation of the absorption cross section, the frequency of which corresponded to their coherent radial breathing modes. The amplitude of the oscillation also increased with the level of photoexcitation, suggesting an increase in the amplitude of the lattice displacement as well.

  1. Spatially confined catalysis-enhanced high-temperature carbon dioxide electrolysis.

    PubMed

    Yang, Liming; Xue, Xingjian; Xie, Kui

    2015-05-01

    In this study, a potential ilmenite cathode material Ni0.9TiO3 is designed for efficient CO2 electrolysis in an oxide-ion-conducting solid-oxide electrolyzer. Spatially confined catalysis has been successfully achieved to substantially improve cathode activity by in situ growth of catalytically active nickel nanoparticles on a ceramic skeleton. The combined analysis of XRD, SEM, EDS, XPS, TGA and Raman results together confirm that the growth of nickel catalyst is completely reversible in redox cycles. The n-type electrical properties of cathodes are systematically investigated and correlated to electrochemical performance. Efficient CO2 electrolysis with a Faraday efficiency above 90% has been demonstrated with Ni0.9TiO3 in contrast to 60% for a TiO2 cathode at 800 °C. PMID:25864375

  2. Carrier dynamics in highly quantum-confined, colloidal indium antimonide nanocrystals.

    PubMed

    Chang, Angela Y; Liu, Wenyong; Talapin, Dmitri V; Schaller, Richard D

    2014-08-26

    Nanometer-sized particles of indium antimonide (InSb) offer opportunities in areas such as solar energy conversion and single photon sources. Here, we measure electron-hole pair dynamics, spectra, and absorption cross sections of strongly quantum-confined colloidal InSb nanocrystal quantum dots using femtosecond transient absorption. For all samples, we observe a bleach feature that develops on ultrafast time scales, which notably moves to lower energy during the first several picoseconds following excitation. We associate this unusual red shift, which becomes larger for larger particles and more distinct at lower sample temperatures, with hot exciton cooling through states that we suggest arise from energetically proximal conduction band levels. From controlled optical excitation intensities, we determine biexciton lifetimes, which range from 2 to 20 ps for the studied 3-6 nm diameter particle sizes. PMID:25106893

  3. Reported Pain During Labour – A Qualitative Study of Influencing Factors among Parturient During Confinement in Private or Government Hospital

    PubMed Central

    Ravishankar, M.; Hemanthkumar, V.R.

    2016-01-01

    Introduction Labour pain is distressing and it produces undue side effects both to the mother and the baby. The incidence is high in developing countries like India where the awareness about labour analgesia is still lacking. Aim It is to find out the incidence of labour pain and the influence of various described factors on pain with a comparison between patients admitted in a government set up with a private set up in a south Indian semi-urban area. Materials and Methods Two hundred continuous uneventful normal deliveries each in a Government (group G) and a private hospital (group P) were enrolled for the study. The reported pain during labour was noted 6-7 hours after delivery by interacting with the patient. The factors like age of the mother, sex and weight of the baby, literacy, socioeconomic status, the use of oxytocics and analgesia were evaluated. Results The incidence of severe pain was more in group G (43.5%) than group P (12%). There was no analgesic intervention in 68.5% in group G while it was 13.5% (27/200) in group P. Even among these 27 patients who did not receive analgesics, only three parturients reported severe pain. Even administration of analgesics in a Government set up did not decrease pain to a significant extent. There were richer and more literate patients in group P. Booked cases were less in group G. Logistic regression analyses to find out factors which influenced pain in either group was used. Gravida, analgesic intervention and admission in a Govt. hospital influenced the pain experience of the parturient. There was minimal antenatal preparation in both the groups. There were no post partum complications. Conclusion Mothers suffered from labour pain to a significant extent and there is an urgent need for awareness about labour analgesia. Primigravida, admission in a Govt. set up and analgesic interventions were the factors which influenced pain than others. Patients admitted in Govt. hospitals suffered more pain with less analgesic

  4. Confined Porous Graphene/SnOx Frameworks within Polyaniline-Derived Carbon as Highly Stable Lithium-Ion Battery Anodes.

    PubMed

    Zhou, Dan; Song, Wei-Li; Li, Xiaogang; Fan, Li-Zhen

    2016-06-01

    Tin oxides are promising anode materials for their high theoretical capacities in rechargeable lithium-ion batteries (LIBs). However, poor stability usually limits the practical application owing to the large volume variation during the cycling process. Herein, a novel carbon confined porous graphene/SnOx framework was designed using a silica template assisted nanocasting method followed by a polyaniline-derived carbon coating process. In this process, silica served as a template to anchor SnOx nanoparticles on porous framework and polyaniline was used as the carbon source for coating on the porous graphene/SnOx framework. The synthesized carbon confined porous graphene/SnOx frameworks demonstrate substantially improved rate capacities and enhanced cycling stability as the anode materials in LIBs, showing a high reversible capacity of 907 mAh g(-1) after 100 cycles at 100 mA g(-1) and 555 mAh g(-1) after 400 cycles at 1000 mA g(-1). The remarkably improved electrochemical performance could be assigned to the unique porous architecture, which effectively solves the drawbacks of SnOx including poor electrical conductivity and undesirable volume expansion during cycling process. Consequently, such design concept for promoting SnOx performance could provide a novel stage for improving anode stability in LIBs. PMID:27169479

  5. Sulfur nanocrystals confined in carbon nanotube network as a binder-free electrode for high-performance lithium sulfur batteries.

    PubMed

    Sun, Li; Li, Mengya; Jiang, Ying; Kong, Weibang; Jiang, Kaili; Wang, Jiaping; Fan, Shoushan

    2014-07-01

    A binder-free nano sulfur-carbon nanotube composite material featured by clusters of sulfur nanocrystals anchored across the superaligned carbon nanotube (SACNT) matrix is fabricated via a facile solution-based method. The conductive SACNT matrix not only avoids self-aggregation and ensures dispersive distribution of the sulfur nanocrystals but also offers three-dimensional continuous electron pathway, provides sufficient porosity in the matrix to benefit electrolyte infiltration, confines the sulfur/polysulfides, and accommodates the volume variations of sulfur during cycling. The nanosized sulfur particles shorten lithium ion diffusion path, and the confinement of sulfur particles in the SACNT network guarantees the stability of structure and electrochemical performance of the composite. The nano S-SACNT composite cathode delivers an initial discharge capacity of 1071 mAh g(-1), a peak capacity of 1088 mAh g(-1), and capacity retention of 85% after 100 cycles with high Coulombic efficiency (∼100%) at 1 C. Moreover, at high current rates the nano S-SACNT composite displays impressive capacities of 1006 mAh g(-1) at 2 C, 960 mAh g(-1) at 5 C, and 879 mAh g(-1) at 10 C. PMID:24884659

  6. Phase-controlled synthesis of α-NiS nanoparticles confined in carbon nanorods for High Performance Supercapacitors

    NASA Astrophysics Data System (ADS)

    Sun, Chencheng; Ma, Mingze; Yang, Jun; Zhang, Yufei; Chen, Peng; Huang, Wei; Dong, Xiaochen

    2014-11-01

    A facile and phase-controlled synthesis of α-NiS nanoparticles (NPs) embedded in carbon nanorods (CRs) is reported by in-situ sulfurating the preformed Ni/CRs. The nanopore confinement by the carbon matrix is essential for the formation of α-NiS and preventing its transition to β-phase, which is in strong contrast to large aggregated β-NiS particles grown freely without the confinement of CRs. When used as electrochemical electrode, the hybrid electrochemical charge storage of the ultrasmall α-NiS nanoparticels dispersed in CRs is benefit for the high capacitor (1092, 946, 835, 740 F g-1 at current densities of 1, 2, 5, 10 A g-1, respectively.). While the high electrochemical stability (approximately 100% retention of specific capacitance after 2000 charge/discharge cycles) is attributed to the supercapacitor-battery electrode, which makes synergistic effect of capacitor (CRs) and battery (NiS NPs) components rather than a merely additive composite. This work not only suggests a general approach for phase-controlled synthesis of nickel sulfide but also opens the door to the rational design and fabrication of novel nickel-based/carbon hybrid supercapacitor-battery electrode materials.

  7. Phase-controlled synthesis of α-NiS nanoparticles confined in carbon nanorods for high performance supercapacitors.

    PubMed

    Sun, Chencheng; Ma, Mingze; Yang, Jun; Zhang, Yufei; Chen, Peng; Huang, Wei; Dong, Xiaochen

    2014-01-01

    A facile and phase-controlled synthesis of α-NiS nanoparticles (NPs) embedded in carbon nanorods (CRs) is reported by in-situ sulfurating the preformed Ni/CRs. The nanopore confinement by the carbon matrix is essential for the formation of α-NiS and preventing its transition to β-phase, which is in strong contrast to large aggregated β-NiS particles grown freely without the confinement of CRs. When used as electrochemical electrode, the hybrid electrochemical charge storage of the ultrasmall α-NiS nanoparticels dispersed in CRs is benefit for the high capacitor (1092, 946, 835, 740 F g(-1) at current densities of 1, 2, 5, 10 A g(-1), respectively.). While the high electrochemical stability (approximately 100% retention of specific capacitance after 2000 charge/discharge cycles) is attributed to the supercapacitor-battery electrode, which makes synergistic effect of capacitor (CRs) and battery (NiS NPs) components rather than a merely additive composite. This work not only suggests a general approach for phase-controlled synthesis of nickel sulfide but also opens the door to the rational design and fabrication of novel nickel-based/carbon hybrid supercapacitor-battery electrode materials. PMID:25394517

  8. Phase-controlled synthesis of α-NiS nanoparticles confined in carbon nanorods for High Performance Supercapacitors

    PubMed Central

    Sun, Chencheng; Ma, Mingze; Yang, Jun; Zhang, Yufei; Chen, Peng; Huang, Wei; Dong, Xiaochen

    2014-01-01

    A facile and phase-controlled synthesis of α-NiS nanoparticles (NPs) embedded in carbon nanorods (CRs) is reported by in-situ sulfurating the preformed Ni/CRs. The nanopore confinement by the carbon matrix is essential for the formation of α-NiS and preventing its transition to β-phase, which is in strong contrast to large aggregated β-NiS particles grown freely without the confinement of CRs. When used as electrochemical electrode, the hybrid electrochemical charge storage of the ultrasmall α-NiS nanoparticels dispersed in CRs is benefit for the high capacitor (1092, 946, 835, 740 F g−1 at current densities of 1, 2, 5, 10 A g−1, respectively.). While the high electrochemical stability (approximately 100% retention of specific capacitance after 2000 charge/discharge cycles) is attributed to the supercapacitor-battery electrode, which makes synergistic effect of capacitor (CRs) and battery (NiS NPs) components rather than a merely additive composite. This work not only suggests a general approach for phase-controlled synthesis of nickel sulfide but also opens the door to the rational design and fabrication of novel nickel-based/carbon hybrid supercapacitor-battery electrode materials. PMID:25394517

  9. High-power ultralow-noise semiconductor external cavity lasers based on low-confinement optical waveguide gain media

    NASA Astrophysics Data System (ADS)

    Juodawlkis, Paul W.; Loh, William; O'Donnell, Frederick J.; Brattain, Michael A.; Plant, Jason J.

    2010-02-01

    For the past several years, we have been developing a new class of high-power, low-noise semiconductor optical gain medium based on the slab-coupled optical waveguide (SCOW) concept. The key characteristics of the SCOW design are (i) large (> 5 x 5 μm), symmetric, fundamental-transverse-mode operation attained through a combination of coupledmode filtering and low index-contrast, (ii) very low optical confinement factor (Γ ~ 0.3-0.5%), and (iii) low excessoptical loss (αi ~ 0.5 cm-1). The large transverse mode and low confinement factor enables SCOW lasers (SCOWLs) and amplifiers (SCOWAs) having Watt-class output power. The low confinement factor also dictates that the waveguide length be very large (0.5-1 cm) to achieve useful gain, which provides the benefits of small ohmic and thermal resistance. In this paper, we review the operating principles and performance of the SCOW gain medium, and detail its use in 1550-nm single-frequency SCOW external cavity lasers (SCOWECLs). The SCOWECL consists of a doublepass, curved-channel InGaAlAs quantum-well SCOWA and a narrowband (2.5 GHz) fiber Bragg grating (FBG) external cavity. We investigate the impact of the cavity Q on SCOWECL performance by varying the FBG reflectivity. We show that a bench-top SCOWECL having a FBG reflectivity of R = 10% (R = 20%) has a maximum output power of 450 mW (400 mW), linewidth of 52 kHz (28 kHz), and RIN at 2-MHz offset frequency of -155 dB/Hz (-165 dB/Hz).

  10. Influence of confinement in controlled-pore glass on the layer spacing of smectic- A liquid crystals

    NASA Astrophysics Data System (ADS)

    Cordoyiannis, George; Zidanšek, Aleksander; Lahajnar, Gojmir; Kutnjak, Zdravko; Amenitsch, Heinz; Nounesis, George; Kralj, Samo

    2009-05-01

    A detailed x-ray scattering study has been performed in the temperature range of the smectic- A phase for the liquid crystal compounds dodecylcyanobiphenyl (12CB) and octylcyanobiphenyl (8CB) confined in different controlled-pore glasses (CPGs) characterized by their average void radius R . On decreasing the temperature in bulk samples the layer thickness is increasing for 12CB and decreasing for 8CB, respectively. In nontreated CPG samples the layers dilate significantly with respect to the bulk liquid crystal. In order to explain the layer thickness behavior on varying temperature and R , one has to take into account molecular details of the liquid crystalline samples as well as memory effects.

  11. Misinformation can influence memory for recently experienced, highly stressful events.

    PubMed

    Morgan, C A; Southwick, Steven; Steffian, George; Hazlett, Gary A; Loftus, Elizabeth F

    2013-01-01

    A large body of research has demonstrated that exposure to misinformation can lead to distortions in human memory for genuinely experienced objects or people. The current study examined whether misinformation could affect memory for a recently experienced, personally relevant, highly stressful event. In the present study we assessed the impact of misinformation on memory in over 800 military personnel confined in the stressful, mock POW camp phase of Survival School training. Misinformation introduced after the negatively affected memory for the details of the event (such as the presence of glasses or weapons), and also affected the accuracy of identification of an aggressive interrogator. In some conditions more than half of the subjects exposed to a misleading photograph falsely identified a different individual as their interrogator after the interrogation was over. These findings demonstrate that memories for stressful events are highly vulnerable to modification by exposure to misinformation, even in individuals whose level of training and experience might be thought to render them relatively immune to such influences. PMID:23219699

  12. Simulation of High Re Boundary Layer Flows on Uniform Grids Using Immersed Boundaries with Vorticity Confinement

    NASA Astrophysics Data System (ADS)

    Chitta, Subhashini; Steinhoff, John

    2015-11-01

    This paper describes the use of Vorticity Confinement (VC) to efficiently treat complex blunt bodies with thin shed vortex sheets and attached boundary layers. Because these flows involve turbulence in the vortical regions, there is currently no ab initio method to treat them on current or foreseeable computers. In fact, in spite of years of turbulence modeling efforts (such as LES or RANS), serious flaws in aerodynamic design involving vortex shedding may still be left undetected until the expensive prototype or production stage. Our basic premise is that, for a class of real-world problems requiring simulating ensembles of flow conditions for overall accuracy, conventional turbulence models suffer cost constraints. For these reasons, VC is used to rapidly simulate many operating conditions, as is often done in expensive testing programs for flying prototypes, and in realistic simulations. To achieve dramatically lower computational cost, VC treats the entire flow in a uniform, coarse grid with solid surfaces ``immersed'' in the grid so that they can be quickly generated for many configurations with no requirement for adaptive or conforming fine grids. Also, the VC method has the efficiency of panel methods, but the generality and ease of use of Euler equation methods. We would like to thank Dr. Frank Caradonna for his suggestions and support.

  13. Reversible optical switching of highly confined phonon-polaritons with an ultrathin phase-change material

    NASA Astrophysics Data System (ADS)

    Li, Peining; Yang, Xiaosheng; Maß, Tobias W. W.; Hanss, Julian; Lewin, Martin; Michel, Ann-Katrin U.; Wuttig, Matthias; Taubner, Thomas

    2016-08-01

    Surface phonon-polaritons (SPhPs), collective excitations of photons coupled with phonons in polar crystals, enable strong light-matter interaction and numerous infrared nanophotonic applications. However, as the lattice vibrations are determined by the crystal structure, the dynamical control of SPhPs remains challenging. Here, we realize the all-optical, non-volatile, and reversible switching of SPhPs by controlling the structural phase of a phase-change material (PCM) employed as a switchable dielectric environment. We experimentally demonstrate optical switching of an ultrathin PCM film (down to 7 nm, <λ/1,200) with single laser pulses and detect ultra-confined SPhPs (polariton wavevector kp > 70k0, k0 = 2π/λ) in quartz. Our proof of concept allows the preparation of all-dielectric, rewritable SPhP resonators without the need for complex fabrication methods. With optimized materials and parallelized optical addressing we foresee application potential for switchable infrared nanophotonic elements, for example, imaging elements such as superlenses and hyperlenses, as well as reconfigurable metasurfaces and sensors.

  14. Influence of substrate interaction and confinement on electric-field-induced transition in symmetric block-copolymer thin films.

    PubMed

    Mukherjee, Arnab; Mukherjee, Rajdip; Ankit, Kumar; Bhattacharya, Avisor; Nestler, Britta

    2016-03-01

    In the present work, we study morphologies arising due to competing substrate interaction, electric field, and confinement effects on a symmetric diblock copolymer. We employ a coarse-grained nonlocal Cahn-Hilliard phenomenological model taking into account the appropriate contributions of substrate interaction and electrostatic field. The proposed model couples the Ohta-Kawasaki functional with Maxwell equation of electrostatics, thus alleviating the need for any approximate solution used in previous studies. We calculate the phase diagram in electric-field-substrate strength space for different film thicknesses. In addition to identifying the presence of parallel, perpendicular, and mixed lamellae phases similar to analytical calculations, we also find a region in the phase diagram where hybrid morphologies (combination of two phases) coexist. These hybrid morphologies arise either solely due to substrate affinity and confinement or are induced due to the applied electric field. The dependence of the critical fields for transition between the various phases on substrate strength, film thickness, and dielectric contrast is discussed. Some preliminary 3D results are also presented to corroborate the presence of hybrid morphologies. PMID:27078402

  15. Influence of substrate interaction and confinement on electric-field-induced transition in symmetric block-copolymer thin films

    NASA Astrophysics Data System (ADS)

    Mukherjee, Arnab; Mukherjee, Rajdip; Ankit, Kumar; Bhattacharya, Avisor; Nestler, Britta

    2016-03-01

    In the present work, we study morphologies arising due to competing substrate interaction, electric field, and confinement effects on a symmetric diblock copolymer. We employ a coarse-grained nonlocal Cahn-Hilliard phenomenological model taking into account the appropriate contributions of substrate interaction and electrostatic field. The proposed model couples the Ohta-Kawasaki functional with Maxwell equation of electrostatics, thus alleviating the need for any approximate solution used in previous studies. We calculate the phase diagram in electric-field-substrate strength space for different film thicknesses. In addition to identifying the presence of parallel, perpendicular, and mixed lamellae phases similar to analytical calculations, we also find a region in the phase diagram where hybrid morphologies (combination of two phases) coexist. These hybrid morphologies arise either solely due to substrate affinity and confinement or are induced due to the applied electric field. The dependence of the critical fields for transition between the various phases on substrate strength, film thickness, and dielectric contrast is discussed. Some preliminary 3D results are also presented to corroborate the presence of hybrid morphologies.

  16. Experimental observations of detonation in ammonium-nitrate-fuel-oil (ANFO) surrounded by a high-sound speed, shockless, aluminum confiner

    SciTech Connect

    Jackson, Scott I; Klyanda, Charles B; Short, Mark

    2010-01-01

    Detonations in explosive mixtures of ammonium-nitrate-fuel-oil (ANFO) confined by aluminum allow for transport of detonation energy ahead of the detonation front due to the aluminum sound speed exceeding the detonation velocity. The net effect of this energy transport on the detonation is unclear. It could enhance the detonation by precompressing the explosive near the wall. Alternatively, it could desensitize the explosive by crushing porosity required for shock initiation or destroying confinement ahead of the detonation. As these phenomena are not well understood, most numerical explosive models are unable to account for them. But with slowly detonating, non-ideal high explosive (NIHE) systems becoming increasing prevalent, proper understanding and prediction of the performance of these metal-confined NIHE systems is desirable. Experiments are discussed that measured the effect of this ANFO detonation energy transported upstream of the front by an aluminum confining tube. Detonation velocity, detonation front curvature, and aluminum response are recorded as a function of confiner wall thickness and length. Front curvature profiles display detonation acceleration near the confining surface, which is attributed to energy transported upstream modifying the flow. Average detonation velocities were seen to increase with increasing confiner thickness due to the additional inertial confinement of the reaction zone flow. Significant radial sidewall tube motion was observed immediately ahead of the detonation. Axial motion was also detected which interfered with the front curvature measurements in some cases. It was concluded that the confiner was able to transport energy ahead of the detonation and that this transport has a definite effect on the detonation.

  17. A simple structure of all circular-air-holes photonic crystal fiber for achieving high birefringence and low confinement loss

    NASA Astrophysics Data System (ADS)

    Chou Chau, Yuan-Fong; Lim, Chee Ming; Yoong, Voo Nyuk; Syafi'ie Idris, Muhammad Nur

    2015-12-01

    We propose a simple structure of photonic crystal fibers (PCFs) with high birefringence and low confinement loss based on one rectangular centric ring of smaller circular air holes (CAHs) in the fiber core, and three rings of larger CAHs in the fiber cladding. This simple geometry (using all CAHs with two different air hole sizes) is capable of achieving a flexible control of the birefringence, B = 5.501 × 10-3, and ultra-low confinement loss, 7.30 × 10-5 dB/km, at an excitation wavelength of λ = 1550 nm. The birefringence value is ˜5.0 times greater than that obtained for conventional CAH PCF. This simple structure has the added advantage from the view point of easy fabrication, robustness, and cost. A full-vector finite element method combined with anisotropic perfectly matched layers was used to analyze the various fiber structures. We have analyzed four cases of CAH PCFs, focusing on the core asymmetry design as opposed to the conventional approach of CAHs or elliptical air holes on the cladding and core. The robustness against manufacturing inaccuracies of the proposed structure has also been further investigated in this work.

  18. A simple structure of all circular-air-holes photonic crystal fiber for achieving high birefringence and low confinement loss

    SciTech Connect

    Chou Chau, Yuan-Fong Lim, Chee Ming; Yoong, Voo Nyuk; Syafi'ie Idris, Muhammad Nur

    2015-12-28

    We propose a simple structure of photonic crystal fibers (PCFs) with high birefringence and low confinement loss based on one rectangular centric ring of smaller circular air holes (CAHs) in the fiber core, and three rings of larger CAHs in the fiber cladding. This simple geometry (using all CAHs with two different air hole sizes) is capable of achieving a flexible control of the birefringence, B = 5.501 × 10{sup −3}, and ultra-low confinement loss, 7.30 × 10{sup −5 }dB/km, at an excitation wavelength of λ = 1550 nm. The birefringence value is ∼5.0 times greater than that obtained for conventional CAH PCF. This simple structure has the added advantage from the view point of easy fabrication, robustness, and cost. A full-vector finite element method combined with anisotropic perfectly matched layers was used to analyze the various fiber structures. We have analyzed four cases of CAH PCFs, focusing on the core asymmetry design as opposed to the conventional approach of CAHs or elliptical air holes on the cladding and core. The robustness against manufacturing inaccuracies of the proposed structure has also been further investigated in this work.

  19. Hitherto unknown shear rupture mechanism as a source of instability in intact hard rocks at highly confined compression

    NASA Astrophysics Data System (ADS)

    Tarasov, Boris G.

    2014-05-01

    Today, frictional shear resistance along pre-existing faults is considered to be the lower limit on rock shear strength for confined conditions corresponding to the seismogenic layer. This paper introduces a recently identified shear rupture mechanism providing a paradoxical feature of hard rocks - the possibility of shear rupture propagation through the highly confined intact rock mass at shear stress levels significantly less than frictional strength. In the new mechanism, the rock failure associated with consecutive creation of small slabs (known as ‘domino-blocks') from the intact rock in the rupture tip is driven by a fan-shaped domino structure representing the rupture head. The fan-head combines such unique features as: extremely low shear resistance, self-sustaining stress intensification, and self-unbalancing conditions. Due to this the failure process caused by the mechanism is very dynamic and violent. This makes it impossible to directly observe and study the mechanism and can explain why the mechanism has not been detected before. This paper provides physical motivation for the mechanism, based upon side effects accompanying the failure process. Physical and mathematical models of the mechanism presented in the paper explain unique and paradoxical features of the mechanism. The new shear rupture mechanism allows a novel point of view for understanding the nature of spontaneous failure processes in hard rocks including earthquakes.

  20. High confinement in fusion oriented plasmas with kV-order potential, ion, and electron temperatures with controlled radial turbulent transport in GAMMA 10

    NASA Astrophysics Data System (ADS)

    Cho, Teruji

    2007-11-01

    The tandem mirror system has achieved improved energy confinement times (> 60-90 ms) with radial transport dominating the Pastukhov axial energy confinement time (> 100 ms). This high confinement regime establishes a proof of principle that the combination of electrostatic and magnetic mirror confinement can successfully insulate electrons from thermal ions. ECH controlled hot-layer formation facilitates plasma-rotation profile formation with a radially localized high-vorticity layer. In the vicinity of the layer, a radial transport barrier is formed [1], showing similar properties to ITB in toroidal plasmas. Coaxially nested intense E(r)xB sheared flow [2] in the GAMMA 10 core plasma realizes an upgraded stable regime having (i) > 0.75 keV bulk central electron temperature with (ii) an achievement of larger stored energy for axially potential-confined ions exceeding that (i.e., diamagnetism) for central magnetically confined ions ( 7 keV). The radially sheared flow having peak-on-axis high vorticity guards and improves whole core plasma confinement, and is controlled by (iii) improved 3 kV ion-confining potential due to simultaneous central and plug ECH. X-ray imaging of the suppression of turbulent structures [1-3] will be shown [1,2]. [1] T. Cho et al., Phys. Rev. Lett. 97, 055001 (2006). [2] T. Cho et al., Phys. Rev. Lett. 94, 085002 (2005). [3] J. Pratt and W. Horton, Phys. Plasmas 13, 042513 (2006). Collaborators; W. Horton^1, J. Pratt^1, M. Hirata, J. Kohagura, T. Numakura, H. Hojo, M. Ichimura, A. Itakura, T. Kariya, I. Katanuma, R. Minami, Y. Nakashima, M. Yoshikawa, Y. Miyata, Y. Yamaguchi, T. Imai, V. P. Pastukhov^2, S. Miyoshi, GAMMA 10 Group (^1IFS, Univ. Texas at Austin, ^2Kurchatov Institute, Russia)

  1. High-Capacity Te Anode Confined in Microporous Carbon for Long-Life Na-Ion Batteries.

    PubMed

    Zhang, Juan; Yin, Ya-Xia; Guo, Yu-Guo

    2015-12-23

    Sodium-ion batteries (SIBs) have attracted considerable attention as an alternative energy-storage technology in recent years. Developing advanced sodium storage anode materials with appropriate working potential, high capacity, and good cycling performance is very important. Herein, we demonstrate a nanostructured tellurium@carbon (nano-Te@C) composite by confining nano-Te molecules in the space of carbon micropores as an attractive anode material for SIBs. The nano-Te@C anode presents an appropriate redox potential in the range of 1.05-1.35 V (vs Na(+)/Na), which avoids the Na dendrite problem and achieves a high reversible capacity of 410 mA h g(-1) on the basis of a two-electron redox reaction mechanism. Notably, the nano-Te@C exhibits an admirable long-term cycling stability with a high capacity retention of 90% for 1000 cycles (i.e., ultralow capacity decay of 0.01% per cycle). The excellent electrochemical property of nano-Te@C benefits from the high electroactivity from the nanostructure design and the effective confinement of the microporous carbon host. In addition, a Na-ion full cell by using nano-Te@C as anode and Na2/3Ni1/3Mn2/3O2 as cathode is demonstrated for the first time and exhibits a remarkable capacity retention up to 95% after 150 cycles. The results put new insights for the development of advanced SIBs with long-cycle lifespan. PMID:26618232

  2. Evidence of the existence of the high-density and low-density phases in deeply-cooled confined heavy water under high pressures

    SciTech Connect

    Wang, Zhe; Chen, Sow-Hsin; Liu, Kao-Hsiang; Harriger, Leland; Leão, Juscelino B.

    2014-07-07

    The average density of D{sub 2}O confined in a nanoporous silica matrix (MCM-41-S) is studied with neutron scattering. We find that below ∼210 K, the pressure-temperature plane of the system can be divided into two regions. The average density of the confined D{sub 2}O in the higher-pressure region is about 16% larger than that in the lower-pressure region. These two regions could represent the so-called “low-density liquid” and “high-density liquid” phases. The dividing line of these two regions, which could represent the associated 1st order liquid-liquid transition line, is also determined.

  3. Influence of external pressure and surface energies on the phase evolution of ultrathin blend films under symmetrical confinement

    NASA Astrophysics Data System (ADS)

    Zhang, Zheng; Wang, Zhen; Ding, Yifu

    2014-03-01

    We investigate the phase evolution of an ultrathin (100 nm) PS/PMMA blend film strongly confined between two parallel rigid plates with identical surface energy. The symmetry was achieved by pressurizing a spun-cast PS/PMMA film on a silicon wafer with a native oxide layer against another silicon wafer under a nanoimprinter. During subsequent annealing without pressurization, preferential wetting of a component (PMMA) occurred on both substrates, leading to phase inversion. The correlation wavelength in the final morphologies was reduced in half, compared with non-capped systems. When annealed while maintaining an external pressure, the predominant preferential substrate wetting of PMMA was prevented completely. Acknowledgement is made to NSF and ACS-PRF for financial support.

  4. Slip-localization within confined gouge powder sheared at moderate to high slip-velocity

    NASA Astrophysics Data System (ADS)

    Reches, Zeev; Chen, Xiaofeng; Morgan, Chance; Madden, Andrew

    2015-04-01

    Slip along faults in the upper crust is always associated with comminution and formation of non-cohesive gouge powder that can be lithified to cataclasite. Typically, the fine-grained powders (grain-size < 1 micron) build a 1-10 cm thick inner-core of a fault-zone. The ubiquitous occurrence of gouge powder implies that gouge properties may control the dynamic weakening of faults. Testing these properties is the present objective. We built a Confined ROtary Cell, CROC, with a ring-shape, ~3 mm thick gouge chamber, with 62.5 and 81.2 mm of inner and outer diameters. The sheared powder is sealed by two sets of seals pressurized by nitrogen. In CROC, we can control the pore-pressure and to inject fluids, and to monitor CO2 and H2O concentration; in addition, we monitor the standard mechanical parameters (slip velocity, stresses, dilation, and temperature). We tested six types of granular materials (starting grain-size in microns): Talc (<250), Kasota dolomite (125-250), ooides grains (125-250), San Andreas fault zone powder (< 840), montmorillonite powder (1-2), kaolinite powder and gypsum. The experimental slip-velocity ranged 0.001-1 m/s, slip distances from a few tens of cm to tens of m, effective normal stress up to 6.1 MPa. The central ultra-microscopic (SEM) observation is that almost invariably the slip was localized along principal-slip-zone (PSZ) within the granular layer. Even though the starting material was loose, coarse granular material, the developed PSZ was cohesive, hard, smooth and shining. The PSZ is about 1 micron thick, and built of agglomerated, ultra-fine grains (20-50 nm) that were pulverized from the original granular material. We noted that PSZs of the different tested compositions display similar characteristics in terms of structure, grain size, and roughness. Further, we found striking similarities between PSZ in the granular samples and the PZS that developed along experimental faults made of solid rock that were sheared at similar

  5. Characterization of particle confinement properties in RFX-mod at a high plasma current

    NASA Astrophysics Data System (ADS)

    Auriemma, F.; Lorenzini, R.; Agostini, M.; Carraro, L.; De Masi, G.; Fassina, A.; Gobbin, M.; Martines, E.; Innocente, P.; Scarin, P.; Schneider, W.; Zuin, M.

    2015-04-01

    Transport phenomena affect the performance of fusion devices, reducing heat and particle confinement and consequently leading to a lower fusion triple product and higher fluxes on the plasma facing material. Special attention is devoted in the fusion community to the study of transport mitigation phenomena which lead to the onset of transport barriers in tokamaks, stellarators and reverse field pinch plasmas. The aim of this study is to deepen our understanding of the mechanisms driving transport in the presence of electron internal transport barriers in the RFX-mod single helical axis (SHAx) state (Lorenzini et al 2009 Nature Phys. 5 570). We discuss whether transport in the core can be described within the theory of chaotic transport. Light is also shed on the mechanisms acting at the plasma edge. The particle source is calculated using the 2D Monte-Carlo code NENE, considering the pattern of plasma-wall interaction. In the core region of the SHAx we found that the diffusivity along 90% of the radius is reduced with respect to the standard case: D ˜ 1 m2 s-1 fits well with the density profile, compared with the ˜50 m2 s-1 of a standard plasma. This result confirms a strong mitigation of magnetic chaos, although comparison with the neoclassical diffusivity Dneo ˜ 0.01-0.4 m2 s-1 indicates that transport in the SHAx is still anomalous. The same picture describes well both the particle and energy transport in the plasma core: comparison with the effective thermal diffusivity χeff indicates that the ratio χeff/D ˜ (mi/me)0.5 is consistent with the theory of chaos-dominated transport. The plasma edge is affected by a different mechanism. In the external region (the final 10% of the radius) magnetic chaos is suppressed and the edge diffusivity is likely to be ruled by electrostatic turbulence, in particular a direct link with the presence of pressure coherent structures is found.

  6. THERMAL COOK-OFF EXPERIMENTS OF THE HMX BASED HIGH EXPLOSIVE LX-04 TO CHARACTERIZE VIOLENCE WITH VARYING CONFINEMENT

    SciTech Connect

    Garcia, F; Vandersall, K S; Forbes, J W; Tarver, C M; Greenwood, D

    2005-07-25

    Thermal cook-off experiments were carried out using LX-04 explosive (85% HMX and 15% Viton by weight) with different levels of confinement to characterize the effect of confinement on the reaction violence. These experiments involved heating a porous LX-04 sample in a stainless steel container with varying container end plate thickness and assembly bolt diameter to control overall confinement. As expected, detonation did not occur and reducing the overall confinement lowered the reaction violence. This is consistent with modeling results that predict that a lower confinement will act to lower the cook-off pressure and thus the overall burn rate which lowers the overall violence. These results suggest that controlling the overall system confinement can modify the relative safety in a given scenario.

  7. Long-lived nanosecond spin coherence in high-mobility 2DEGs confined in double and triple quantum wells

    NASA Astrophysics Data System (ADS)

    Ullah, S.; Gusev, G. M.; Bakarov, A. K.; Hernandez, F. G. G.

    2016-06-01

    We investigated the spin coherence of high-mobility two-dimensional electron gases confined in multilayer GaAs quantum wells. The dynamics of the spin polarization was optically studied using pump-probe techniques: time-resolved Kerr rotation and resonant spin amplification. For double and triple quantum wells doped beyond the metal-to-insulator transition, the spin-orbit interaction was tailored by the sample parameters of structural symmetry (Rashba constant), width, and electron density (Dresselhaus linear and cubic constants) which allow us to attain long dephasing times in the nanoseconds range. The determination of the scales, namely, transport scattering time, single-electron scattering time, electron-electron scattering time, and spin polarization decay time further supports the possibility of using n-doped multilayer systems for developing spintronic devices.

  8. Development and characterization of a Z-pinch-driven hohlraum high-yield inertial confinement fusion target concept

    NASA Astrophysics Data System (ADS)

    Cuneo, Michael E.; Vesey, Roger A.; Porter, John L.; Chandler, Gordon A.; Fehl, David L.; Gilliland, Terrance L.; Hanson, David L.; McGurn, John S.; Reynolds, Paul G.; Ruggles, Laurence E.; Seamen, Hans; Spielman, Rick B.; Struve, Ken W.; Stygar, William A.; Simpson, Walter W.; Torres, Jose A.; Wenger, David F.; Hammer, James H.; Rambo, Peter W.; Peterson, Darrell L.; Idzorek, George C.

    2001-05-01

    Initial experiments to study the Z-pinch-driven hohlraum high-yield inertial confinement fusion (ICF) concept of Hammer, Tabak, and Porter [Hammer et al., Phys. Plasmas 6, 2129 (1999)] are described. The relationship between measured pinch power, hohlraum temperature, and secondary hohlraum coupling ("hohlraum energetics") is well understood from zero-dimensional semianalytic, and two-dimensional view factor and radiation magnetohydrodynamics models. These experiments have shown the highest x-ray powers coupled to any Z-pinch-driven secondary hohlraum (26±5 TW), indicating the concept could scale to fusion yields of >200 MJ. A novel, single-sided power feed, double-pinch driven secondary that meets the pinch simultaneity requirements for polar radiation symmetry has also been developed. This source will permit investigation of the pinch power balance and hohlraum geometry requirements for ICF relevant secondary radiation symmetry, leading to a capsule implosion capability on the Z accelerator [Spielman et al., Phys. Plasmas 5, 2105 (1998)].

  9. Low-to-High Confinement Transition Mediated by Turbulence Radial Wave Number Spectral Shift in a Fusion Plasma

    NASA Astrophysics Data System (ADS)

    Xu, G. S.; Wan, B. N.; Wang, H. Q.; Guo, H. Y.; Naulin, V.; Rasmussen, J. Juul; Nielsen, A. H.; Wu, X. Q.; Yan, N.; Chen, L.; Shao, L. M.; Chen, R.; Wang, L.; Zhang, W.

    2016-03-01

    A new model for the low-to-high (L -H ) confinement transition has been developed based on a new paradigm for turbulence suppression by velocity shear [G. M. Staebler et al., Phys. Rev. Lett. 110, 055003 (2013)]. The model indicates that the L -H transition can be mediated by a shift in the radial wave number spectrum of turbulence, as evidenced here, for the first time, by the direct observation of a turbulence radial wave number spectral shift and turbulence structure tilting prior to the L -H transition at tokamak edge by direct probing. This new mechanism does not require a pretransition overshoot in the turbulent Reynolds stress, shunting turbulence energy to zonal flows for turbulence suppression as demonstrated in the experiment.

  10. Low-to-High Confinement Transition Mediated by Turbulence Radial Wave Number Spectral Shift in a Fusion Plasma.

    PubMed

    Xu, G S; Wan, B N; Wang, H Q; Guo, H Y; Naulin, V; Rasmussen, J Juul; Nielsen, A H; Wu, X Q; Yan, N; Chen, L; Shao, L M; Chen, R; Wang, L; Zhang, W

    2016-03-01

    A new model for the low-to-high (L-H) confinement transition has been developed based on a new paradigm for turbulence suppression by velocity shear [G. M. Staebler et al., Phys. Rev. Lett. 110, 055003 (2013)]. The model indicates that the L-H transition can be mediated by a shift in the radial wave number spectrum of turbulence, as evidenced here, for the first time, by the direct observation of a turbulence radial wave number spectral shift and turbulence structure tilting prior to the L-H transition at tokamak edge by direct probing. This new mechanism does not require a pretransition overshoot in the turbulent Reynolds stress, shunting turbulence energy to zonal flows for turbulence suppression as demonstrated in the experiment. PMID:26991181

  11. REVIEW High-power semiconductor separate-confinement double heterostructure lasers

    NASA Astrophysics Data System (ADS)

    Tarasov, I. S.

    2010-10-01

    The review is devoted to high-power semiconductor lasers. Historical reference is presented, physical and technological foundations are considered, and the concept of high-power semiconductor lasers is formulated. Fundamental and technological reasons limiting the optical power of a semiconductor laser are determined. The results of investigations of cw and pulsed high-power semiconductor lasers are presented. Main attention is paid to inspection of the results of experimental studies of single high-power semiconductor lasers. The review is mainly based on the data obtained in the laboratory of semiconductor luminescence and injection emitters at the A.F. Ioffe Physicotechnical Institute.

  12. q Profile evolution and enhanced core confinement of high {beta}{sub p} plasmas in DIII-D

    SciTech Connect

    Stallard, B.W.; Casper, T.A.; Fenstermacher, M.E.

    1994-10-01

    In DIII-D the authors have investigated the long pulse evolution of high poloidal beta ({sub beta}{sub p}), double-null diverted H-mode discharges, which exhibit high bootstrap current fractions attractive for a reactor. At low currents I{sub p}, the current profile evolved over several seconds and the on-axis safety factor (q{sub 0}) increased. When q{sub 0} increased above {approximately}2, the MHD character changed from an m/n = 2/1 to an m/n = 3/1 internal kink mode, where m(n) are poloidal (toroidal) mode numbers, which then disappeared with further increases in q{sub 0}. Coincident with a strong reduction of fluctuations, the authors observed enhanced core confinement, leading to strong density peaking, a further rise in {beta}{sub p}, and a bootstrap current increasing to I{sub boot}/I{sub p} {approx} 0.8, peaked within the core. Ideal MHD calculations showed access to second stability during the density rise. During the enhanced performance phase core particle lifetime ({tau}{sub p}) and global energy lifetime ({tau}{sub E}) increased by factors of 2 and 1.2 respectively. Transport analysis showed that core particle and thermal diffusivities D{sub e} and {chi}{sub eff} approached neoclassical values. During the low current experiments, large losses of fast ions (typically {approximately}50% at 0.4 MA) were observed; at higher currents these losses are much smaller. The authors have also investigated discharges with current rampdown to high {beta}{sub p}. For a 5 to 6 {tau}{sub E} duration following rampdown, enhanced values of {beta}{sub p}, normalized toroidal beta ({beta}{sub N}), and {tau}{sub E} were obtained at high internal inductance ({ell}{sub i}). During both the ramp and the high confinement phases, fast ion losses were low ({approximately}10%). The loss then increased, correlated with an increase in the anisotropy ratio of perpendicular and parallel plasma pressure that suggests a fast ion loss mechanism coupled to the fast ion parallel energy.

  13. Thermal Cook-Off Experiments of the HMX Based High Explosive LX-04 to Characterize Violence with Varying Confinement

    NASA Astrophysics Data System (ADS)

    Garcia, Frank; Forbes, Jerry W.

    2005-07-01

    Thermal cook-off experiments were carried out using LX-04 explosive (85% HMX and 15% Viton by weight) with different levels of confinement to characterize the effect of confinement on the reaction violence. These experiments involved heating a porous LX-04 sample in a stainless steel container with varying container end plate thickness and assembly bolt diameter to control overall confinement. As expected, detonation did not occur and reducing the overall confinement lowered the reaction violence. Modeling was also performed using Ignition and Growth kinetics with reasonable agreement to the experiment. These results suggest that controlling the overall system confinement can modify the relative safety in a given scenario. This work was performed under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

  14. Maximally confined high-speed second-order silicon microdisk switches.

    SciTech Connect

    Young, Ralph Watson; Trotter, Douglas Chandler; Watts, Michael R.

    2008-03-01

    We demonstrate the first high-speed second-order silicon microdisk bandpass switch. The switch, constructed of a pair of 3 {micro}m radii active microdisks possesses {approx}40GHz flat-top passbands, a 4.2THz free-spectral-range, and a 2.4ns switching time.

  15. In Situ Confinement of Ultrasmall Pd Clusters within Nanosized Silicalite-1 Zeolite for Highly Efficient Catalysis of Hydrogen Generation.

    PubMed

    Wang, Ning; Sun, Qiming; Bai, Risheng; Li, Xu; Guo, Guanqi; Yu, Jihong

    2016-06-22

    Well-dispersed and ultrasmall Pd clusters in nanosized silicalite-1 (MFI) zeolite have been prepared under direct hydrothermal conditions using [Pd(NH2CH2CH2NH2)2]Cl2 as precursor. High-resolution scanning transmission electron microscopy studies indicate that the Pd clusters are encapsulated within the intersectional channels of MFI, and the Pd clusters in adjacent channels visually aggregate, forming nanoparticles (NPs) of ∼1.8 nm. The resultant catalysts show an excellent activity and highly efficient H2 generation toward the complete decomposition of formic acid (FA) under mild conditions. Notably, thanks to the further reduced Pd NP size (∼1.5 nm) and the additionally introduced basic sites, the Pd/S-1-in-K catalyst affords turnover frequency values up to 856 h(-1) at 25 °C and 3027 h(-1) at 50 °C. The easy in situ confinement synthesis of metal clusters in zeolites endows the catalysts with superior catalytic activities, excellent recyclability, and high thermal stability, thus opening new perspectives for the practical application of FA as a viable and effective H2 storage material for use in fuel cells. PMID:27248462

  16. High-resolution spectroscopy used to measure inertial confinement fusion neutron spectra on Omega (invited).

    PubMed

    Forrest, C J; Radha, P B; Glebov, V Yu; Goncharov, V N; Knauer, J P; Pruyne, A; Romanofsky, M; Sangster, T C; Shoup, M J; Stoeckl, C; Casey, D T; Gatu-Johnson, M; Gardner, S

    2012-10-01

    The areal density (ρR) of cryogenic DT implosions on Omega is inferred by measuring the spectrum of neutrons that elastically scatter off the dense deuterium (D) and tritium (T) fuel. Neutron time-of-flight (nTOF) techniques are used to measure the energy spectrum with high resolution. High signal-to-background data has been recorded on cryogenic DT implosions using a well-collimated 13.4-m line of sight and an nTOF detector with an advanced liquid scintillator compound. An innovative method to analyze the elastically scattered neutron spectra was developed using well-known cross sections of the DT nuclear reactions. The estimated areal densities are consistent with alternative ρR measurements and 1-D simulations. PMID:23126921

  17. Team dynamics in isolated, confined environments - Saturation divers and high altitude climbers

    NASA Technical Reports Server (NTRS)

    Kanki, Barbara G.; Gregorich, Steven E.

    1992-01-01

    The effects of leadership dynamics and social organization factors on team performance under conditions of high altitude climbing and deep sea diving are studied. Teams of two to four members that know each other well and have a relaxed informal team structure with much sharing of responsibilities are found to do better than military teams with more than four members who do not know each other well and have a formal team structure with highly specialized rules. Professionally guided teams with more than four members, a formally defined team structure, and clearly designated role assignments did better than 'club' teams of more than four members with a fairly informal team structure and little role specialization.

  18. High-resolution spectroscopy used to measure inertial confinement fusion neutron spectra on Omega (invited)

    SciTech Connect

    Forrest, C. J.; Radha, P. B.; Glebov, V. Yu.; Goncharov, V. N.; Knauer, J. P.; Pruyne, A.; Romanofsky, M.; Sangster, T. C.; Shoup, M. J. III; Stoeckl, C.; Casey, D. T.; Gatu-Johnson, M.; Gardner, S.

    2012-10-15

    The areal density ({rho}R) of cryogenic DT implosions on Omega is inferred by measuring the spectrum of neutrons that elastically scatter off the dense deuterium (D) and tritium (T) fuel. Neutron time-of-flight (nTOF) techniques are used to measure the energy spectrum with high resolution. High signal-to-background data has been recorded on cryogenic DT implosions using a well-collimated 13.4-m line of sight and an nTOF detector with an advanced liquid scintillator compound. An innovative method to analyze the elastically scattered neutron spectra was developed using well-known cross sections of the DT nuclear reactions. The estimated areal densities are consistent with alternative {rho}R measurements and 1-D simulations.

  19. HIGH CHARGE EFFECTS IN SILICON DRIFT DETECTORS WITH LATERAL CONFINEMENT OF ELECTRONS.

    SciTech Connect

    CASTOLDI,A.; REHAK,P.

    1995-10-21

    A new drift detector prototype which provides suppression of the lateral diffusion of electrons has been tested as a function of the signal charge up to high charge levels, when electrostatic repulsion is not negligible. The lateral diffusion of the electron cloud has been measured for injected charges up to 2 {center_dot} 10{sup 5} electrons. The maximum number of electrons for which the suppression of the lateral spread is effective is obtained.

  20. Highly Reliable Operation of High-Power InGaAsP/InGaP/AlGaAs 0.8 µ m Separate Confinement Heterostructure Lasers

    NASA Astrophysics Data System (ADS)

    Fukunaga, Toshiaki; Wada, Mitsugu; Asano, Hideki; Hayakawa, Toshiro

    1995-09-01

    We report the high-power and reliable operation of InGaAsP/InGaP/AlGaAs 0.8 µ m separate confinement heterostructure single-quantum-well laser diodes. High output power of 1.8 W is achieved from an anti-reflection- and high-reflection-coated device with stripe width of 50 µ m and cavity length of 1.25 mm. This device has high characteristic temperature of 164 K and low threshold current density of 300 A/cm2. No catastrophic failure in the laser with 0.75 mm cavity length is observed during 1000 h aging test at 50° C under an automatic power control of 500 mW. The effect of cavity length on laser characteristics is also discussed.

  1. Behavior Of A Confined Tension Lap Splice In High-Strength Reinforced Concrete Beams

    NASA Astrophysics Data System (ADS)

    Abdel-Kareem, Ahmed H.; Abousafa, Hala; El-Hadidi, Omaia S.

    2015-09-01

    The results of an experimental program conducted on seventeen simply supported concrete beams to study the effect of transverse reinforcement on the behavior of the lap splice of a steel reinforcement in tension zones in high-strength concrete beams are presented. The parameters included in the experimental program were the concrete compressive strength, the lap splice length, the amount of transverse reinforcement provided within the splice region, and the shape of the transverse reinforcement around the spliced bars. The experimental results showed that the displacement ductility increased and the mode of failure changed from a splitting bond failure to a flexural failure when the amount of the transverse reinforcement in the splice region increased, and the compressive strength increased up to 100 MPa. The presence of the transverse reinforcement around the spliced bars had a pronounced effect on increasing the ultimate load, the ultimate deflection, and the displacement ductility. The prediction of maximum steel stresses for spliced bars using the ACI 318-05 building code was compared with the experimental results. The comparison showed that the effect of the transverse reinforcement around spliced bars has to be considered into the design equations for lap splice length in high-strength concrete beams.

  2. Spatially resolved high resolution x-ray spectroscopy for magnetically confined fusion plasmas (invited)

    SciTech Connect

    Ince-Cushman, A.; Rice, J. E.; Reinke, M. L.; Podpaly, Y.; Marmar, E. S.; Bitter, M.; Hill, K. W.; Scott, S.; Gu, M. F.; Eikenberry, E.; Broennimann, Ch.; Lee, S. G.

    2008-10-15

    The use of high resolution x-ray crystal spectrometers to diagnose fusion plasmas has been limited by the poor spatial localization associated with chord integrated measurements. Taking advantage of a new x-ray imaging spectrometer concept [M. Bitter et al., Rev. Sci. Instrum. 75, 3660 (2004)], and improvements in x-ray detector technology [Ch. Broennimann et al., J. Synchrotron Radiat. 13, 120 (2006)], a spatially resolving high resolution x-ray spectrometer has been built and installed on the Alcator C-Mod tokamak. This instrument utilizes a spherically bent quartz crystal and a set of two dimensional x-ray detectors arranged in the Johann configuration [H. H. Johann, Z. Phys. 69, 185 (1931)] to image the entire plasma cross section with a spatial resolution of about 1 cm. The spectrometer was designed to measure line emission from H-like and He-like argon in the wavelength range 3.7 and 4.0 A with a resolving power of approximately 10 000 at frame rates up to 200 Hz. Using spectral tomographic techniques [I. Condrea, Phys. Plasmas 11, 2427 (2004)] the line integrated spectra can be inverted to infer profiles of impurity emissivity, velocity, and temperature. From these quantities it is then possible to calculate impurity density and electron temperature profiles. An overview of the instrument, analysis techniques, and example profiles are presented.

  3. Youth pathways to placement: the influence of gender, mental health need and trauma on confinement in the juvenile justice system.

    PubMed

    Espinosa, Erin M; Sorensen, Jon R; Lopez, Molly A

    2013-12-01

    Although the juvenile crime rate has generally declined, the involvement of girls in the juvenile justice system has been increasing. Possible explanations for this gender difference include the impact of exposure to trauma and mental health needs on developmental pathways and the resulting influence of youth's involvement in the justice system. This study examined the influence of gender, mental health needs and trauma on the risk of out-of-home placement for juvenile offenders. The sample included youth referred to three urban juvenile probation departments in Texas between January 1, 2007 and December 31, 2008 and who received state-mandated mental health screening (N = 34,222; 30.1 % female). The analysis revealed that, for both genders, elevated scores on the seven factor-analytically derived subscales of a mental health screening instrument (Alcohol and Drug Use, Depressed-Anxious, Somatic Complaints, Suicidal Ideation, Thought Disturbance, and Traumatic Experiences), especially related to past traumatic experiences, influenced how deeply juveniles penetrated the system. The findings suggest that additional research is needed to determine the effectiveness of trauma interventions and the implementation of trauma informed systems for youth involved with the juvenile justice system. PMID:23824982

  4. Comparative analysis of low- and high-swirl confined flames and jets by proper orthogonal and dynamic mode decompositions

    NASA Astrophysics Data System (ADS)

    Markovich, D. M.; Abdurakipov, S. S.; Chikishev, L. M.; Dulin, V. M.; Hanjalić, K.

    2014-06-01

    Low-order coherent structures of non-reacting and combusting low- and high-swirl (swirl rates S = 0.41 and S = 1.0) jet flows in an open-ended cylindrical model combustor have been studied using the proper orthogonal decomposition (POD) and the dynamic mode decomposition (DMD) of high-repetition stereoscopic particle image velocimetry (PIV) velocity measurements. Lean methane-air mixture with the equivalence ratio of 0.6 was chosen for the reacting case as lean flames are generally less stable and more receptive to active control. The nonreacting and reacting flows at the same swirl rates exhibit qualitatively similar overall features characterized by highly turbulent annular jets enveloping the central retarding zone (for S = 0.41) or a recirculating bubble (for S = 1.0). At low swirl the dominant coherent structures appeared in the form of tilted ring vortices, evolving into helices as the swirl rate increases. The high-swirl flows are characterized by a pair of well-organized counter-rotating co-winding helical vortices originating in the inner and outer jet shear layers. Vortex cores were detected in both cases, but at low swirl it was less energetic and not associated with a distinct precession frequency. The core region of the low-swirl flame shows intermittent mild flow reversal without permanent central recirculation zone. The thermal expansion enhances the spreading of the reacting flow, especially at the high swirl number. Here the helices pitch is smaller and some neighbouring vortices merge into vortical sheets that act as shear shield confining the flame within the inner shear layer. Despite the significant effects of combustion on the time-averaged characteristics for the high-swirl, the dynamics of both flows were dominated by the global inviscid helical instability mode with a DMD detected conspicuous frequencies of 223 Hz for the nonreacting jet and 257 Hz for the flame.

  5. New concept for a high-repetition-rate reactor for inertial-confinement fusion

    SciTech Connect

    Monsler, M.J.

    1980-11-01

    A new design concept was developed that has three additional features that are very important in reducing program risk: (1) through a proper choice of the working temperature (400 to 540/sup 0/C) and of the liquid metal (lithium or lead-lithium eutectic alloy), we can select a chamber pressure within the range of 10/sup -1/ to 10/sup -4/ Torr, required for the propagation of either a laser-beam or a heavy-ion-beam driver; (2) presently available ferritic steels can be used for the structural material; and (3) the new concept allows flexibility in irradiaton geometry. Although two-sided irradiation at high f/Nos. seems most attractive from the standpoints of minimizing the number of chamber penetrations and of simplifing the layout of the balance of plant, we must provide for the possibility that target-implosion physics will require a more symmetrical illumination geometry.

  6. High illumination uniformity scheme with 32 beams configuration for direct-drive inertial confinement fusion

    NASA Astrophysics Data System (ADS)

    Li, Li; Gu, Chun; Xu, Lixin; Zhou, Shenlei

    2016-04-01

    The self-adapting algorithms are improved to optimize a beam configuration in the direct drive laser fusion system with the solid state lasers. A configuration of 32 laser beams is proposed for achieving a high uniformity illumination, with a root-mean-square deviation at 10-4 level. In our optimization, the parameters such as beam number, beam arrangement, and beam intensity profile are taken into account. The illumination uniformity robustness versus the parameters such as intensity profile deviations, power imbalance, intensity profile noise, the pointing error, and the target position error is also discussed. In this study, the model is assumed a solid-sphere illumination, and refraction effects of incident light on the corona are not considered. Our results may have a potential application in the design of the direct-drive laser fusion of the Shen Guang-II Upgrading facility (SG-II-U, China).

  7. Abrasion-resistant solgel antireflective films with a high laser-induced damage threshold for inertial confinement fusion

    NASA Astrophysics Data System (ADS)

    Xu, Yao; Zhang, Lei; Wu, Dong; Sun, Yu Han; Huang, Zu Xing; Jiang, Xiao Dong; Wei, Xiao Feng; Li, Zhi Hong; Dong, Bao Zhong; Wu, Zhong Hua

    2005-09-01

    To prepare abrasion-resistant antireflective (AR) films for inertial confinement fusion, four solgel routes have been investigated on polysiloxane-modified and polyvinylalcohol- (PVA-) modified SiO2 sols. As confirmed with a transmissive electron microscope, different fractal structure characteristics of the modified SiO2 particles are disclosed by small-angle x-ray scattering technology. And it is these special fractal characteristics that determine the performance of AR films on the level of internal microstructure. A 29Si magic angle spinning and nuclear magnetic resonance study has been successfully applied in explaining the fractal microstructure and its relation to the laser-induced damage threshold (LIDT) of AR films. The films modified by PVA120000 or acetic acid-catalyzed polysiloxane have higher LIDTs than those films modified by PVA16000 or hydrochloride acid-catalyzed polysiloxane. The films from PVA-modified SiO2 sols have a stronger abrasion resistance but lower antireflection than those films from polysiloxane-modified SiO2 sols. In addition, the films from polysiloxane-modified SiO2 sols can possess high transmittance and high LIDT if the polysiloxane synthesis condition is appropriately chosen, but the abrasion resistance is not as good as that from PVA modification. If strong abrasion resistance is necessary, a possible resolution may be to choose a more appropriate hydrophilic polymer than PVA. If not, polysiloxane-modified silica sol can also work when polysiloxane is synthesized under acetic acid catalysis.

  8. Durable solgel antireflective films with high laser-induced damage thresholds for inertial confinement fusion

    NASA Astrophysics Data System (ADS)

    Xu, Yao; Zhang, Lei; Wu, Dong; Sun, Yu Han; Huang, Zu Xing; Jiang, Xiao Dong; Wei, Xiao Feng; Li, Zhi Hong; Dong, Bao Zhong; Wu, Zhong Hua

    2005-04-01

    We tested the use of two hydrophobic methyl-substituted silane precursors, methyltriethoxysilane and dimethyldiethoxysilane, to synthesize methyl-modified silica sols by a two-step method and a cohydrolysis method to produce durable antireflective films with high laser-induced-damage thresholds (LIDTs). Using small-angle x-ray scattering technology, we obtained details of the microstructure of clusters in sol and found various double fractal structural characteristics in the methyl-modified silica clusters; our findings were confirmed by transmission-electron micrographs. Through a 29Si magic-angle spin nuclear magnetic resonance study of the corresponding xerogels, we determined the double-fractal microstructure, which we then related to the LIDTs of AR films. The distribution configuration of methyls in clusters determined the double-fractal microstructure of clusters and then the LIDTs of AR films. The LIDTs of films produced by the cohydrolysis method (the highest was 38 J/cm2 for 1-ns, 1064-nm laser action) were much higher than those from the two-step method because of the loose netlike clusters in the former configuration. During the 220-day aging, the transmittance of hydrophobic AR film decreased ~0.2%. So it is practicable to prepare durable AR films with higher LIDTs than those of normal AR SiO2 films only by introducing hydrophobic methyls into a Si-O-Si matrix of clusters if an appropriate hydrophobic precursor is chosen.

  9. Dynamic Formation of a Hot Field Reversed Configuration with Improved Confinement by Supersonic Merging of Two Colliding High-β Compact Toroids

    NASA Astrophysics Data System (ADS)

    Binderbauer, M. W.; Guo, H. Y.; Tuszewski, M.; Putvinski, S.; Sevier, L.; Barnes, D.; Rostoker, N.; Anderson, M. G.; Andow, R.; Bonelli, L.; Brandi, F.; Brown, R.; Bui, D. Q.; Bystritskii, V.; Ceccherini, F.; Clary, R.; Cheung, A. H.; Conroy, K. D.; Deng, B. H.; Dettrick, S. A.; Douglass, J. D.; Feng, P.; Galeotti, L.; Garate, E.; Giammanco, F.; Glass, F. J.; Gornostaeva, O.; Gota, H.; Gupta, D.; Gupta, S.; Kinley, J. S.; Knapp, K.; Korepanov, S.; Hollins, M.; Isakov, I.; Jose, V. A.; Li, X. L.; Luo, Y.; Marsili, P.; Mendoza, R.; Meekins, M.; Mok, Y.; Necas, A.; Paganini, E.; Pegoraro, F.; Pousa-Hijos, R.; Primavera, S.; Ruskov, E.; Qerushi, A.; Schmitz, L.; Schroeder, J. H.; Sibley, A.; Smirnov, A.; Song, Y.; Sun, X.; Thompson, M. C.; van Drie, A. D.; Walters, J. K.; Wyman, M. D.

    2010-07-01

    A hot stable field-reversed configuration (FRC) has been produced in the C-2 experiment by colliding and merging two high-β plasmoids preformed by the dynamic version of field-reversed θ-pinch technology. The merging process exhibits the highest poloidal flux amplification obtained in a magnetic confinement system (over tenfold increase). Most of the kinetic energy is converted into thermal energy with total temperature (Ti+Te) exceeding 0.5 keV. The final FRC state exhibits a record FRC lifetime with flux confinement approaching classical values. These findings should have significant implications for fusion research and the physics of magnetic reconnection.

  10. (19) F NMR Spectroscopy as a Highly Sensitive Method for the Direct Monitoring of Confined Crystallization within Nanoporous Materials.

    PubMed

    Nartowski, Karol P; Malhotra, Diksha; Hawarden, Lucy E; Sibik, Juraj; Iuga, Dinu; Zeitler, J Axel; Fábián, László; Khimyak, Yaroslav Z

    2016-07-25

    The introduction of fluorine into the structure of pharmaceuticals has been an effective strategy for tuning their pharmacodynamic properties, with more than 40 new drugs entering the market in the last 15 years. In this context, (19) F NMR spectroscopy can be viewed as a useful method for investigating the host-guest chemistry of pharmaceuticals in nanosized drug-delivery systems. Although the interest in confined crystallization, nanosized devices, and porous catalysts is gradually increasing, understanding of the complex phase behavior of organic molecules confined within nanochambers or nanoreactors is still lacking. Using (19) F magic-angle-spinning NMR spectroscopy, we obtained detailed mechanistic insight into the crystallization of flufenamic acid (FFA) in a confined environment of mesoporous silica materials with different pore diameters (3.2-29 nm), providing direct experimental evidence for the formation of a molecular-liquid-like layer besides crystalline confined FFA form I. PMID:27272008

  11. High birefringent rectangular-lattice photonic crystal fibers with low confinement loss employing different sizes of elliptical air holes in the cladding and the core

    NASA Astrophysics Data System (ADS)

    Liao, Jianfei; Sun, Junqiang

    2012-12-01

    Based on the full-vector finite element method with anisotropic perfectly matched layers, modal birefringence and confinement loss for the fundamental mode in rectangular-lattice photonic crystal fibers with different sizes of elliptical air holes in the cladding and the core are investigated numerically. The results show that the modal birefringence in this proposed photonic crystal fibers can be up to 5.64 × 10-2 at the wavelength of 1.55 μm. Moreover, when the birefringence is higher than 4 × 10-2, the confinement loss of x-polarized mode can be kept less than 0.005 dB/km at 1.55 μm. It means that the tradeoff between the high birefringence and the low confinement loss is overcome.

  12. Accessible passively stored highly spin-polarized D in solid HD, with application to inertially confined fusion

    SciTech Connect

    Alexander, N.B.

    1992-01-01

    Highly spin-polarized D in solid HD was produced in a dilution refrigerator-magnet system under conditions whereby the polarization remains high upon removal of the sample to a 1K, modest field ([approximately]0.1 T) environment. This retained polarization remains for many hours to days. The first intended application of this system is for inertially confined fusion (ICF) experiments with spin-polarized D fuel. The actual (vector) polarization attained thus far is P[sup D] = 38%. The maximum D polarization obtainable with the present refrigerator and magnet (8 mK and 13 T) is 61%. The difference is due to the author's reluctance to wait the full time constants in these demonstration experiments and due to the inability to attain full efficiency in radio-frequency dynamic polarization transfer between D and H, the maximum polarizability of the latter in the system equaling about 85%. It was necessary to develop methods for cold (4 K) sample transfer with engagement and disengagement provisions for the dilution-refrigerator apparatus, a storage-transport cryostat, various sample-preparation and diagnostic apparatus, and an interface to an experimental destination facility. The nature of the fusion experiments required designing and constructing a complex mating system with interchange of cold shrouds to ascertain the sample was always shielded from room temperature black body radiation, and still provide means for positioning the target to within a few microns of the intersection of the high power laser beams. Means of filling plastic target shells to high pressure with the special isotopic composition of HD with H[sub 2]and D[sub 2] impurities, and condensing them at cryogenic temperatures, were also perfected.

  13. Accessible Passively Stored Highly Spin-Polarized Deuterium in Solid Hydrogen Deuterium, with Application to Inertially Confined Fusion

    NASA Astrophysics Data System (ADS)

    Alexander, Neil Brooks

    1992-01-01

    Highly spin-polarized D in solid HD was produced in a dilution refrigerator-magnet system under conditions whereby the polarization remains high upon removal of the sample to a 1K, modest field (~0.1 T) environment. This retained polarization remains for many hours to days, sufficient to allow the polarized material to be transported to distant locations and utilized there. The first intended application of this system is for inertially confined fusion (ICF) experiments with spin-polarized D fuel. The actual (vector) polarization attained thus far is P^{rm D} = 38%. The maximum D polarization obtainable with our present refrigerator and magnet (8 mK and 13 T) is 61%. The difference is due to our reluctance to wait the full time constants in these demonstration experiments and due to the inability to attain full efficiency in radio-frequency dynamic polarization transfer between D and H, the maximum polarizability of the latter in our system equaling about 85%. In addition to implementation of the polarization method, it was also necessary to develop methods for cold (4 K) sample transfer with engagement and disengagement provisions for the dilution-refrigerator apparatus, a storage -transport cryostat, various sample-preparation and diagnostic apparatuses, and an interface to an experimental destination facility, in the present case, the OMEGA fusion chamber at the University of Rochester's Laboratory for Laser Energetics. The nature of the fusion experiments required designing and constructing a complex mating system with interchange of cold shrouds to ascertain the sample was always shielded from room temperature black body radiation, and still provide means for positioning the target to within a few microns of the intersection of the high power laser beams. Means of filling plastic target shells to high pressure (at room temperature) with our special isotopic composition of HD with H_2 and D_2 impurities, and condensing them at cryogenic temperatures, were also

  14. Discovery of Stationary Operation of Quiescent H-mode Plasmas with Net-Zero NBI Torque and High Energy Confinement on DIII-D

    NASA Astrophysics Data System (ADS)

    Burrell, Keith

    2015-11-01

    Experiments this summer in DIII-D have used edge turbulence control to achieve stationary, high confinement operation without Edge Localized Mode (ELM) instabilities and with no external torque input. Eliminating the ELM-induced heat bursts and controlling plasma stability at low rotation represent two of the great challenges for fusion energy. By exploiting edge turbulence in a novel manner, we achieved outstanding tokamak performance, well above the H98 international tokamak energy confinement scaling (H98 =1.25), thus meeting an additional confinement challenge that is usually difficult at low torque. The new regime is triggered in double null plasmas by ramping the injected torque to zero and then maintaining it there. This lowers ExB rotation shear in the plasma edge, allowing low-k, broadband, electromagnetic turbulence to increase. In the H-mode edge, a narrow transport barrier usually grows until MHD instability (a peeling ballooning mode) leads to the ELM heat burst. However, the increased turbulence reduces the pressure gradient, allowing the development of a broader and thus higher transport barrier. A 60% increase in pedestal pressure and 40% increase in energy confinement result. Strong double-null plasma shaping raises the threshold for the ELM instability, allowing the plasma to reach a transport-limited state near but below the explosive ELM stability boundary. The resulting plasmas have burning-plasma-relevant betan =1.6-1.8 and run without the need for extra torque from 3D magnetic fields. To date, stationary conditions have been produced for 2 s or 12 energy confinement times, limited only by external hardware constraints. Stationary operation with improved pedestal conditions is highly significant for future burning plasma devices, since operation without ELMs at low rotation and good confinement is key for fusion energy production. Supported by the US DOE under DE-FC02-04ER54698.

  15. Fabrication of a High-Quality, Porous, Surface-Confined Covalent Organic Framework on a Reactive Metal Surface.

    PubMed

    Larrea, Christian R; Baddeley, Christopher J

    2016-04-01

    A major goal of heterogeneous catalysis is to optimize catalytic selectivity. Selectivity is often limited by the fact that most heterogeneous catalysts possess sites with a range of reactivities, resulting in the formation of unwanted by-products. The construction of surface-confined covalent organic frameworks (sCOFs) on catalytically active surfaces is a desirable strategy, as pores can be tailored to operate as catalytic nanoreactors. Direct modification of reactive surfaces is impractical, because the strong molecule-surface interaction precludes monomer diffusion and formation of extended architectures. Herein, we describe a protocol for the formation of a high-quality sCOF on a Pd-rich surface by first fabricating a porous sCOF through Ullmann coupling on a Au-rich bimetallic surface on Pd(111). Once the sCOF has formed, thermal processing induces a Pd-rich surface while preserving the integrity of the sCOF architecture, as evidenced by scanning tunneling microscopy and titration of Pd sites through CO adsorption. PMID:26773305

  16. Influence of finite size and wetting on nematic and smectic phase behavior of liquid crystal confined to controlled-pore matrices

    NASA Astrophysics Data System (ADS)

    Kutnjak, Zdravko; Kralj, Samo; Lahajnar, Gojmir; Žumer, Slobodan

    2004-11-01

    The high-resolution calorimetric study was carried out on octylcyanobiphenyl liquid crystal (LC) confined to various controlled-pore glass (CPG) matrices with silane-treated surface. The diameter of the voids cross section ranged between 23.7 and 395nm . The results are compared to those obtained previously on CPG voids nontreated with silane. We found a striking similarity between the shifts in the isotropic to nematic and nematic to smectic- A phase transition temperatures as a function of the void radius in which order parameter variations at the LC-void interface play the dominant role. Weaker temperature shifts are observed in silane-treated samples, where surface ordering tendency is larger. In nontreated samples, a finite-size scaling law in the maximum value of the heat capacity at the nematic to smectic- A transition was observed for void diameters larger than 20nm . In silane-treated samples, this behavior is considerably changed by surface wetting interactions.

  17. Abrasion-resistant solgel antireflective films with a high laser-induced damage threshold for inertial confinement fusion

    SciTech Connect

    Xu Yao; Zhang Lei; Wu Dong; Sun Yu Han; Huang Zuxing; Jiang Xiaodong; Wei Xiaofeng; Li Zhihong; Dong Baozhong; Wu Zhonghua

    2005-09-01

    To prepare abrasion-resistant antireflective (AR) films for inertial confinement fusion, four solgel routes have been investigated on polysiloxane-modified and polyvinylalcohol- (PVA-) modified SiO{sub 2} sols. As confirmed with a transmissive electron microscope, different fractal structure characteristics of the modified SiO{sub 2} particles are disclosed by small-angle x-ray scattering technology. And it is these special fractal characteristics that determine the performance of AR films on the level of internal microstructure. A {sup 29}Si magic angle spinning and nuclear magnetic resonance study has been successfully applied in explaining the fractal microstructure and its relation to the laser-induced damage threshold (LIDT) of AR films. The films modified by PVA120000 or acetic acid-catalyzed polysiloxane have higher LIDTs than those films modified by PVA16000 or hydrochloride acid-catalyzed polysiloxane. The films from PVA-modified SiO{sub 2} sols have a stronger abrasion resistance but lower antireflection than those films from polysiloxane-modified SiO{sub 2} sols. In addition, the films from polysiloxane-modified SiO{sub 2} sols can possess high transmittance and high LIDT if the polysiloxane synthesis condition is appropriately chosen, but the abrasion resistance is not as good as that from PVA modification. If strong abrasion resistance is necessary, a possible resolution may be to choose a more appropriate hydrophilic polymer than PVA. If not, polysiloxane-modified silica sol can also work when polysiloxane is synthesized under acetic acid catalysis.

  18. INSTALLATION OF A POST-ACCIDENT CONFINEMENT HIGH-LEVEL RADIATION MONITORING SYSTEM IN THE KOLA NUCLEAR POWER STATION (UNIT 2) IN RUSSIA

    SciTech Connect

    GREENE,G.A.; GUPPY,J.G.

    1998-09-01

    This is the final report on the INSP project entitled, ``Post-Accident Confinement High-Level Radiation Monitoring System'' conducted by BNL under the authorization of Project Work Plan WBS 1.2.2.6 (Attachment 1). This project was initiated in February 1993 to assist the Russians in reducing risks associated with the continued operation of older Soviet-designed nuclear power plants, specifically the Kola VVER-440/230 Unit 2, through improved accident detection capability, specifically by the installation of a dual train high-level radiation detection system in the confinement of Unit 2 of the Kola NPP. The major technical objective of this project was to provide, install and make operational the necessary hardware inside the confinement of the Kola NPP Unit 2 to provide early and reliable warning of the release of radionuclides from the reactor into the confinement air space as an indication of the occurrence of a severe accident at the plant. In addition, it was intended to provide hands-on experience and training to the Russian plant workers in the installation, operation, calibration and maintenance of the equipment in order that they may use the equipment without continued US assistance as an effective measure to improve reactor safety at the plant.

  19. Influence of quantum-confined Stark effect on optical properties within trench defects in InGaN quantum wells with different indium content

    SciTech Connect

    Vaitkevičius, A. Mickevičius, J.; Dobrovolskas, D.; Tamulaitis, G.; Tuna, Ö.; Giesen, C.; Heuken, M.

    2014-06-07

    The trench defects in InGaN/GaN multiple quantum well structures are studied using confocal photoluminescence (PL) spectroscopy and atomic force microscopy. A strong blueshift (up to ∼280 meV) and an intensity increase (by up to a factor of 700) of the emission are demonstrated for regions enclosed by trench loops. The influence of the difference in the well width inside and outside the trench loops observed by transmission electron microscopy, the compositional pulling effect, the strain relaxation inside the loop, and corresponding reduction in the built-in field on the PL band peak position and intensity were estimated. The competition of these effects is mainly governed by the width of the quantum wells in the structure. It is shown that the PL band blueshift observed within the trench defect loops in the InGaN structures with wide quantum wells is mainly caused by the reduction in efficiency of the quantum-confined Stark effect due to strain relaxation.

  20. Influence of colloidal particle transfer on the quality of self-assembling colloidal photonic crystal under confined condition

    NASA Astrophysics Data System (ADS)

    Zhao, Yong-Qiang; Li, Juan; Liu, Qiu-Yan; Dong, Wen-Jun; Chen, Ben-Yong; Li, Chao-Rong

    2015-02-01

    The relationship between colloidal particle transfer and the quality of colloidal photonic crystal (CPC) is investigated by comparing colloidal particle self-assembling under the vertical channel (VC) and horizontal channel (HC) conditions. Both the theoretical analyses and the experimental measurements indicate that crystal quality depends on the stability of mass transfer. For the VC, colloidal particle transfer takes place in a stable laminar flow, which is conducive to forming high-quality crystal. In contrast, it happens in an unstable turbulent flow for the HC. Crystals with cracks and an uneven surface formed under the HC condition can be seen from the images of a field emission scanning electron microscope (SEM) and a three-dimensional (3D) laser scanning microscope (LSM), respectively. Project supported by the National Natural Science Foundation of China (Grant Nos. 91122022 and 51172209) and the Program for Changjiang Scholars and Innovative Research Team in University (PCSIRT), China (Grant No. IRT13097).

  1. The design and simulation of high-voltage Applied-B ion diodes for inertial confinement fusion

    NASA Astrophysics Data System (ADS)

    Slutz, S. A.; Seidel, D. B.; Coats, R. S.

    1987-06-01

    We present the design of the high-voltage (30 MV) Applied-B ion diode that is now being tested on the PBFA-II accelerator at Sandia National Laboratories. This diode design is the first application of a new set of numerical design tools that have been developed over the past several years. Furthermore, this design represents significant departures from previous designs due to much higher voltage and the use of a nonprotonic ion, Li+. The higher voltage increases the magnetic field strength required to insulate the diode from 1 to 2 T of previous diodes to 3-7 T. This represents a very large increase in the magnetic field energy and the magnetic forces exerted on the field-coil structures. Our new design incorporates changes in the field-coil locations to significantly reduce the field energy and the forces on the field-coil structures. The use of nonprotonic ions introduces a new complication in that these ions will be stripped when they penetrate material, i.e., the gas cell membrane. The importance of current neutralization, charge-exchange reactions, and the conservation of canonical angular momentum are discussed in the context of designing light ion diodes suitable as drivers for inertial confinement fusion. We have simulated the performance of this diode design using the electromagnetic particle-in-cell code, magic. We find that the most sensitive point in the power flow is the transition from the self-magnetically insulated transmission line to the applied field region of the diode.

  2. Single- and multi-beam confinement of electromagnetic waves in a photonic crystal open cavity providing rapid heating and high temperatures

    NASA Astrophysics Data System (ADS)

    Yogesh, N.; Yu, Quanqiang; Ouyang, Zhengbiao

    2015-06-01

    Light is the best energy source for heating substances. As an attempt to utilize light energy, we demonstrate the single- and multi-beam confinement of electromagnetic (EM) waves in an open cavity formed by one-dimensional photonic crystals for efficient heat conversion. The multilayer cavity confines electromagnetic waves at near-band-edge frequencies uniquely. We use this confinement to heat substances under normal and oblique incident radiations. We perform electromagnetic thermal co-simulation to demonstrate the functionality of rapid heating under single- and multi-beam excitations of EM waves. The cavity shows a rapid heating rate of 4 °C/s for a nominal input power of 850 W under single-beam excitation. The demonstration of multi-beam (four beams) confinement in the proposed cavity reveals ultra-high temperatures at the rate of 560 °C/s for the input electric field strength of 1000 V/m. The role of strong perturbation in heat conversion task is studied with respect to various substances. Finally, we have demonstrated the heating effect under oblique incidence of weak EM radiations so that the proposed cavity can avail the utilization of natural radiation for better green life. The proposed multilayer cavity is anticipated for laser heating, creation of plasmas and renewable energy sources.

  3. Discovery of stationary operation of quiescent H-mode plasmas with net-zero neutral beam injection torque and high energy confinement on DIII-D

    NASA Astrophysics Data System (ADS)

    Burrell, K. H.; Barada, K.; Chen, X.; Garofalo, A. M.; Groebner, R. J.; Muscatello, C. M.; Osborne, T. H.; Petty, C. C.; Rhodes, T. L.; Snyder, P. B.; Solomon, W. M.; Yan, Z.; Zeng, L.

    2016-05-01

    Recent experiments in DIII-D [J. L. Luxon et al., in Plasma Physics and Controlled Nuclear Fusion Research 1996 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] have led to the discovery of a means of modifying edge turbulence to achieve stationary, high confinement operation without Edge Localized Mode (ELM) instabilities and with no net external torque input. Eliminating the ELM-induced heat bursts and controlling plasma stability at low rotation represent two of the great challenges for fusion energy. By exploiting edge turbulence in a novel manner, we achieved excellent tokamak performance, well above the H98y2 international tokamak energy confinement scaling (H98y2 = 1.25), thus meeting an additional confinement challenge that is usually difficult at low torque. The new regime is triggered in double null plasmas by ramping the injected torque to zero and then maintaining it there. This lowers E × B rotation shear in the plasma edge, allowing low-k, broadband, electromagnetic turbulence to increase. In the H-mode edge, a narrow transport barrier usually grows until MHD instability (a peeling ballooning mode) leads to the ELM heat burst. However, the increased turbulence reduces the pressure gradient, allowing the development of a broader and thus higher transport barrier. A 60% increase in pedestal pressure and 40% increase in energy confinement result. An increase in the E × B shearing rate inside of the edge pedestal is a key factor in the confinement increase. Strong double-null plasma shaping raises the threshold for the ELM instability, allowing the plasma to reach a transport-limited state near but below the explosive ELM stability boundary. The resulting plasmas have burning-plasma-relevant βN = 1.6-1.8 and run without the need for extra torque from 3D magnetic fields. To date, stationary conditions have been produced for 2 s or 12 energy confinement times, limited only by external hardware constraints. Stationary operation with

  4. Factors and Influences on High School Student's Career Choices.

    ERIC Educational Resources Information Center

    Dick, Thomas P.; Rallis, Sharon F.

    1991-01-01

    A survey (n=2213) of high school seniors from nine Rhode Island schools studied their academic and career choices related to science and engineering and the perceived influences on those choices. Gender differences are discussed for the influences of parents, pay, interest, and teachers, with the latter potentially influencing career choices of…

  5. Plasma confinement at JET

    NASA Astrophysics Data System (ADS)

    Nunes, I.; JET Contributors

    2016-01-01

    Operation with a Be/W wall at JET (JET-ILW) has an impact on scenario development and energy confinement with respect to the carbon wall (JET-C). The main differences observed were (1) strong accumulation of W in the plasma core and (2) the need to mitigate the divertor target temperature to avoid W sputtering by Be and other low Z impurities and (3) a decrease of plasma energy confinement. A major difference is observed on the pedestal pressure, namely a reduction of the pedestal temperature which, due to profile stiffness the plasma core temperature is also reduced leading to a degradation of the global confinement. This effect is more pronounced in low β N scenarios. At high β N, the impact of the wall on the plasma energy confinement is mitigated by the weaker plasma energy degradation with power relative to the IPB98(y, 2) scaling calculated empirically for a CFC first wall. The smaller tolerable impurity concentration for tungsten (<10-5) compared to that of carbon requires the use of electron heating methods to prevent W accumulation in the plasma core region as well as gas puffing to avoid W entering the plasma core by ELM flushing and reduction of the W source by decreasing the target temperature. W source and the target temperature can also be controlled by impurity seeding. Nitrogen and Neon have been used and with both gases the reduction of the W source and the target temperature is observed. Whilst more experiments with Neon are necessary to assess its impact on energy confinement, a partial increase of plasma energy confinement is observed with Nitrogen, through the increase of edge temperature. The challenge for scenario development at JET is to extend the pulse length curtailed by its transient behavior (W accumulation or MHD), but more importantly by the divertor target temperature limits. Re-optimisation of the scenarios to mitigate the effect of the change of wall materials maintaining high global energy confinement similar to JET-C is

  6. Experimental Investigation on the Influence of High Pressure and High Temperature on the Mechanical Properties of Deep Reservoir Rocks

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Mishra, Brijes; Heasley, Keith A.

    2015-11-01

    Deep and ultra-deep resources extraction has resulted in the challenge of drilling into high-pressure, high-temperature (HPHT) environments. Drilling challenges at such extreme conditions prompted NETL to develop a specialized ultra-deep drilling simulator (UDS) for investigating drill behavior in such conditions. Using the UDS apparatus, complex laboratory tests were performed on Carthage marble (Warsaw limestone) and Crab Orchard sandstone, which represent the rocks in the basins of the Tuscaloosa trend in southern Louisiana and the Arbuckle play in Oklahoma and North Texas. Additionally, numerical models of the UDS were developed for performing parametric analyses that would be impossible with the UDS alone. Subsequently, it was found that the input properties for these two rock types at such extreme pressure and temperature conditions were unavailable. Therefore, a suite of unconfined compressive strength, indirect tensile strength, and triaxial compression tests ( σ 1 > σ 2 = σ 3) were performed on Carthage marble and Crab Orchard sandstone for investigating their behavior in HPHT environments. The HPHT experiments were performed at confining pressures ranging from atmospheric to 200 MPa, and with temperatures ranging from 25 to 180 °C. The influences of confining pressure and temperature on the mechanical properties of two rocks were investigated.

  7. Confined helium on Lagrange meshes.

    PubMed

    Baye, D; Dohet-Eraly, J

    2015-12-21

    The Lagrange-mesh method has the simplicity of a calculation on a mesh and can have the accuracy of a variational method. It is applied to the study of a confined helium atom. Two types of confinement are considered. Soft confinements by potentials are studied in perimetric coordinates. Hard confinement in impenetrable spherical cavities is studied in a system of rescaled perimetric coordinates varying in [0,1] intervals. Energies and mean values of the distances between electrons and between an electron and the helium nucleus are calculated. A high accuracy of 11 to 15 significant figures is obtained with small computing times. Pressures acting on the confined atom are also computed. For sphere radii smaller than 1, their relative accuracies are better than 10(-10). For larger radii up to 10, they progressively decrease to 10(-3), still improving the best literature results. PMID:25732054

  8. Interplay of explosive thermal reaction dynamics and structural confinement

    NASA Astrophysics Data System (ADS)

    Perry, W. Lee; Zucker, Jonathan; Dickson, Peter M.; Parker, Gary R.; Asay, Blaine W.

    2007-04-01

    Explosives play a significant role in human affairs; however, their behavior in circumstances other than intentional detonation is poorly understood. Accidents may have catastrophic consequences, especially if additional hazardous materials are involved. Abnormal ignition stimuli, such as impact, spark, friction, and heat may lead to a very violent outcome, potentially including detonation. An important factor influencing the behavior subsequent to abnormal ignition is the strength and inertia of the vessel confining the explosive, i.e., the near-field structural/mechanical environment, also known as confinement (inertial or mechanical). However, a comprehensive and quantified understanding of how confinement affects reaction violence does not yet exist. In the research discussed here, we have investigated a wide range of confinement conditions and related the explosive response to the fundamentals of the combustion process in the explosive. In our experiments, a charge of an octahydrotetranitrotetrazine-based plastic bonded explosive (PBX 9501) was loaded into a gun assembly having variable confinement conditions and subjected to a heating profile. The exploding charge breached the confinement and accelerated a projectile down the gun barrel. High bandwidth pressure and volume measurements were made and a first-law analysis was used to obtain enthalpy and power from the raw data. These results were then used to quantify reaction violence. Enthalpy change and power ranged from 0-1.8 kJ and 0-12 MW for 300 mg charges, respectively. Below a confinement strength of 20 MPa, violence was found to decline precipitously with decreasing confinement, while the violence for the heaviest confinement experiments was found to be relatively constant. Both pressure and pressurization rate were found to have critical values to induce and sustain violent reaction.

  9. Influence of particle size and water coverage on the thermodynamic properties of water confined on the surface of SnO2 cassiterite nanoparticles

    SciTech Connect

    Spencer, Elinor; Ross, Dr. Nancy; Parker, Stewart F.; Kolesnikov, Alexander I; Woodfield, Brian; Woodfield, K; Rytting, M; Boerio-Goates, Juliana; Navrotsky, Alexandra

    2011-01-01

    Inelastic neutron scattering (INS) data for SnO2 nanoparticles of three different sizes and varying hydration levels are presented. Data were recorded on five nanoparticle samples that had the following compositions: 2 nm SnO2*0.82H2O, 6 nm SnO2*0.055H2O, 6 nm SnO2*0.095H2O, 20 nm SnO2*0.072H2O, and 20 nm SnO2*0.092H2O. The isochoric heat capacity and vibrational entropy values at 298 K for the water confined on the surface of these nanoparticles were calculated from the vibrational density of states that were extracted from the INS data. This study has shown that the hydration level of the SnO2 nanoparticles influences the thermodynamic properties of the water layers and, most importantly, that there appears to be a critical size limit for SnO2 between 2 and 6 nm below which the particle size also affects these properties and above which it does not. These results have been compared with those for isostructural rutile-TiO2 nanoparticles [TiO2*0.22H2O and TiO2*0.37H2O], which indicated that water on the surface of TiO2 nanoparticles is more tightly bound and experiences a greater degree of restricted motion with respect to water on the surface of SnO2 nanoparticles. This is believed to be a consequence of the difference in chemical composition, and hence surface properties, of these metal oxide nanoparticles.

  10. Graphene/sulfur hybrid nanosheets from a space-confined "sauna" reaction for high-performance lithium-sulfur batteries.

    PubMed

    Fei, Linfeng; Li, Xiaogang; Bi, Wentuan; Zhuo, Zhiwen; Wei, Wenfei; Sun, Li; Lu, Wei; Wu, Xiaojun; Xie, Keyu; Wu, Changzheng; Chan, Helen L W; Wang, Yu

    2015-10-21

    A space-confined "sauna" reaction system is introduced for the simultaneous reduction and functionalization of graphene oxide to unique graphene-sulfur hybrid nanosheets, in which thin layers of amorphous sulfur are tightly anchored on the graphene sheet via strong chemical bonding. Upon being used as the cathode material in lithium-sulfur batteries, the as-synthesized composite shows an excellent electrochemical performance. PMID:26310671

  11. Trophic dynamics influence climate at high latitudes

    NASA Astrophysics Data System (ADS)

    Oksanen, L.; Tuomi, M.; Hoset, K.; Oksanen, T.; Olofsson, J.; Dahlgren, J.; Nordic Center of Excellence-Tundra

    2011-12-01

    Abundance relationships between tall woody plants and low herbaceous plants influence ground albedo. Increasing abundance of erect woody plants on the tundra increase the amount of solar energy converted to heat, thus speeding up global warming. By transplanting vegetation blocks from an island with predatory mammals and gray-sided voles (Myodes rufocanus) to similar habitats on islands with gray-sided voles but no resident predators and to islands with neither voles nor predators, we show that changing trophic dynamics radically change the abundance relationships between woody and herbaceous plants. Impacts of food limited gray-sided voles result to devastation of all erect woody plants, regardless of their palatability, thus differing both quantitatively and qualitatively from the selective impacts of the same species in the presence of predators. The shift from vegetation dominated by erect woody plants to vegetation dominated by herbs or trailing dwarf shrubs also increases ground albedo. The relationship between climate and trophic dynamics is thus no one way street. Rather than responding passively to changes in climate, food webs can also influence climate via their impacts on ground albedo.

  12. The dynamics of short-scale turbulent fluctuations across low-intermediate-high-confinement transition with lower hybrid current drive in the EAST superconducting tokamak

    SciTech Connect

    Cao, G. M.; Li, Y. D.; Zhang, X. D.; Sun, P. J.; Wu, G. J.; Hu, L. Q.

    2015-02-15

    Two different confinement transition discharges, the low-intermediate-high (L-I-H) and the low-intermediate-low (L-I-L) confinement transitions, respectively, have been obtained by lower hybrid current drive with lithium wall conditioning in the EAST superconducting tokamak. The dynamic features of short-scale turbulent fluctuations in the two discharges are investigated by a tangential CO{sub 2} laser collective scattering system. It is found that the great changes of broadband fluctuations in amplitude and structure characteristics are closely related to the choice of the final transition to H-mode. These results could shed light on the understanding of the L-H transition mechanism.

  13. Review of energy confinement and local transport scaling results in neutral-beam-heated tokamaks

    SciTech Connect

    Kaye, S.M.

    1985-05-01

    Over the past several years, tokamak neutral beam injection experiments have evolved from the brute force study of the effects of global discharge characteristics (I/sub p/, anti n/sub e/, P/sub heat/, etc.) on energy confinement to the appreciation that there are effects more subtle, yet controllable, that may influence confinement dramatically. While this evolution from first to second generation experiments is derived from an empirical understanding of low and high energy confinement modes and how to achieve them operationally, the underlying physics is still unknown. Several theories with different physical bases appear to describe the global scaling of the low confinement mode discharges quite well. On the other hand, little agreement has been found between theoretical and experimentally deduced values of local transport coefficients. While it is known operationally how to achieve any one of several types of high confinement mode discharges, here too, the underlying physics of the transport associated with these modes is poorly understood.

  14. 2D Colloidal Wigner crystals in confined geometries

    NASA Astrophysics Data System (ADS)

    Higler, Ruben; Sprakel, Joris

    2015-03-01

    Crystallization of bulk systems has been widely studied using colloids as a model system. However, study into colloidal crystallization in confined geometries has been sparse and little is known about the effects of strong confinement on the dynamics of colloidal crystal. In our research we prepare 2D crystals from charged colloids in an apolar solvent to study crystal dynamics, formation, and structure in circular confinements. These confining geometries are made using softlithography techniques from SU-8. In order to broaden the parameter space we can reach in experiments we employ brownian dynamics simulations to supplement our experimental results. Using single-particle tracking we have subpixel resolution positional information of every particle in the system. We study the vibrational modes of our confined crystals and find well defined modes unique to confined systems, such as a radially symmetric compression (or breathing) mode, a collective rotation mode, and distinct resonance modes. Furthermore, due to the circular nature of our constrictions, defectless crystals are impossible, we find, for sufficiently high area fractions, that the defects order at well defined points at the edge. The effect of this ``defect-localization'' has a clear influence on the vibrational modes.

  15. Social support and depressed mood in isolated and confined environments

    NASA Astrophysics Data System (ADS)

    Palinkas, Lawrence A.; Johnson, Jeffrey C.; Boster, James S.

    2004-05-01

    The influence of isolation and confinement on social support and depressed mood was examined in a study of 235 men and women who spent a year at McMurdo Station in Antarctica, and a study of 77 men and women who spent a year at the Amundson-Scott South Pole Station. Although availability of support remained unchanged, there was a significant decrease in reported satisfaction with support obtained, as well as a significant increase in depressed mood. Satisfaction with support was inversely associated with depressed mood at the beginning and end of isolation and confinement. At the end of winter, this association varied by source of support. High levels of tension-anxiety, depression and anger preceded an increase in advice seeking, but high levels of advice seeking also preceded an increase in tension-anxiety and depression. Results suggest a significant erosion of social support under conditions of prolonged isolation and confinement, leading to an increase in depressed mood.

  16. Tiny Pd@Co core-shell nanoparticles confined inside a metal-organic framework for highly efficient catalysis.

    PubMed

    Chen, Yu-Zhen; Xu, Qiang; Yu, Shu-Hong; Jiang, Hai-Long

    2015-01-01

    A new strategy to pre-incorporate metal precursors followed by their in situ reduction is established to prepare tiny core-shell nanoparticles (NPs) stabilized by a metal-organic framework (MOF). The obtained Pd@Co core-shell NPs of ∼2.5 nm confined in the pores of a mesoporous MOF, MIL-101, exhibit synergistic and superior catalytic performance in hydrolytic dehydrogenation of NH3 BH3 under mild conditions compared to their monometallic and alloy counterparts as well as Pd@Co NPs located on a MOF surface. PMID:25201445

  17. Equilibrium drives of the low and high field side n  =  2 plasma response and impact on global confinement

    NASA Astrophysics Data System (ADS)

    Paz-Soldan, C.; Logan, N. C.; Haskey, S. R.; Nazikian, R.; Strait, E. J.; Chen, X.; Ferraro, N. M.; King, J. D.; Lyons, B. C.; Park, J.-K.

    2016-05-01

    The nature of the multi-modal n  =  2 plasma response and its impact on global confinement is studied as a function of the axisymmetric equilibrium pressure, edge safety factor, collisionality, and L-versus H-mode conditions. Varying the relative phase (Δ {φ\\text{UL}} ) between upper and lower in-vessel coils demonstrates that different n  =  2 poloidal spectra preferentially excite different plasma responses. These different plasma response modes are preferentially detected on the tokamak high-field side (HFS) or low-field side (LFS) midplanes, have different radial extents, couple differently to the resonant surfaces, and have variable impacts on edge stability and global confinement. In all equilibrium conditions studied, the observed confinement degradation shares the same Δ {φ\\text{UL}} dependence as the coupling to the resonant surfaces given by both ideal (IPEC) and resistive (MARS-F) MHD computation. Varying the edge safety factor shifts the equilibrium field-line pitch and thus the Δ {φ\\text{UL}} dependence of both the global confinement and the n  =  2 magnetic response. As edge safety factor is varied, modeling finds that the HFS response (but not the LFS response), the resonant surface coupling, and the edge displacements near the X-point all share the same Δ {φ\\text{UL}} dependence. The LFS response magnitude is strongly sensitive to the core pressure and is insensitive to the collisionality and edge safety factor. This indicates that the LFS measurements are primarily sensitive to a pressure-driven kink-ballooning mode that couples to the core plasma. MHD modeling accurately reproduces these (and indeed all) LFS experimental trends and supports this interpretation. In contrast to the LFS, the HFS magnetic response and correlated global confinement impact is unchanged with plasma pressure, but is strongly reduced in high collisionality conditions in both H- and L-mode. This experimentally suggests the bootstrap

  18. Development of an NDA system for high-level waste from the Chernobyl new safe confinement construction site

    SciTech Connect

    Lee, Sang-yoon; Browne, Michael C; Rael, Carlos D; Carroll, Colin J; Sunshine, Alexander; Novikov, Alexander; Lebedev, Evgeny

    2010-01-01

    In early 2009, preliminary excavation work has begun in preparation for the construction of the New Safe Confinement (NSC) at the Chernobyl Nuclear Power Plant (ChNPP) in Ukraine. The NSC is the structure that will replace the present containment structure and will confine the radioactive remains of the ChNPP Unit-4 reactor for the next 100 years. It is expected that special nuclear material (SNM) that was ejected from the Unit-4 reactor during the accident in 1986 could be uncovered and would therefore need to be safeguarded. ChNPP requested the assistance of the United States Department of Energy/National Nuclear Security Administration (NNSA) with developing a new non-destructive assay (NDA) system that is capable of assaying radioactive debris stored in 55-gallon drums. The design of the system has to be tailored to the unique circumstances and work processes at the NSC construction site and the ChNPP. This paper describes the Chernobyl Drum Assay System (CDAS), the solution devised by Los Alamos National Laboratory, Sonalysts Inc., and the ChNPP, under NNSA's International Safeguards and Engagement Program (INSEP). The neutron counter measures the spontaneous fission neutrons from the {sup 238}U, {sup 240}Pu, {sup 244}Cm in a waste drum and estimates the mass contents of the SNMs in the drum by using of isotopic compositions determined by fuel burnup. The preliminary evaluation on overall measurement uncertainty shows that the system meets design performance requirements imposed by the facility.

  19. De-confinement in small systems: Clustering of color sources in high multiplicity p¯p collisions at s = 1.8TeV

    NASA Astrophysics Data System (ADS)

    Gutay, L. J.; Hirsch, A. S.; Scharenberg, R. P.; Srivastava, B. K.; Pajares, C.

    2015-12-01

    It is shown that de-confinement can be achieved in high multiplicity nonjet p¯p collisions at s = 1.8TeV Fermi National Accelerator Laboratory (FNAL- E735) experiment. Previously, the evidence for de-confinement was demonstrated by the constant freeze out energy density in high multiplicity events. In this paper, we use the same but analyze the transverse momentum spectrum in the framework of the clustering of color sources. This frame work naturally predicts the reduction in the charged particle multiplicity with respect to the value expected from the number of independent strings. The charged particle pseudorapidity densities in the range 7.0 ≤≤ 26.0 are considered. Results are presented for both thermodynamic and transport properties. The initial temperature and energy density are obtained from the data via the color reduction factor F(ξ) and the associated string density parameter ξ. The Bjorken ideal fluid description of the QGP, when modified by the color reduction factor and the trace anomaly Δ is in remarkable agreement with the lattice quantum chromo dynamics (LQCD) simulations. The energy density (ɛ/T4) ˜ 11.5 for ˜ 25.0 is close to the value for 0-10% central events in Au+Au collisions at sNN = 200GeV. The shear viscosity to entropy density ratio (η/s) is ˜0.2 at the transition temperature of 167MeV. The result for the trace anomaly Δ is in excellent agreement with LQCD simulations. These results confirm our earlier observation that the de-confined state of matter was created in high multiplicity events in p¯p collisions at s = 1.8TeV.

  20. QUIESCENT H-MODE, AN ELM-FREE HIGH-CONFINEMENT MODE ON DIII-D WITH POTENTIAL FOR STATIONARY STATE OPERATION

    SciTech Connect

    WEST,WP; BURRELL,KH; deGRASSIE,JS; DOYLE,EJ; GREENFIELD,CM; LASNIER,CJ; SNYDER,PB; ZENG,L

    2003-08-01

    OAK-B135 The quiescent H-mode (QH-mode) is an ELM-free and stationary state mode of operation discovered on DIII-D. This mode achieves H-mode levels of confinement and pedestal pressure while maintaining constant density and radiated power. The elimination of edge localized modes (ELMs) and their large divertor loads while maintaining good confinement and good density control is of interest to next generation tokamaks. This paper reports on the correlations found between selected parameters in a QH-mode database developed from several hundred DIII-D counter injected discharges. Time traces of key plasma parameters from a QH-mode discharge are shown. On DIII-D the negative going plasma current (a) indicates that the beam injection direction is counter to the plasma current direction, a common feature of all QH-modes. The D{sub {alpha}} time behavior (c) shows that soon after high powered beam heating (b) is applied, the discharge makes a transition to ELMing H-mode, then the ELMs disappear, indicating the start of the QH period that lasts for the remainder of the high power beam heating (3.5 s). Previously published work showing density and temperature profiles indicates that long-pulse, high-triangularity QH discharges develop an internal transport barrier in combination with the QH edge barrier. These discharges are known as quiescent, double-barrier discharges (QDB). The H-factor (d) and stored energy (c) rise then saturate at a constant level and the measured axial and minimum safety factors remain above 1.0 for the entire QH duration. During QDB operation the performance of the plasma can be very good, with {beta}{sub N}*H{sub 89L} product reaching 7 for > 10 energy confinement times. These discharges show promise that a stationary state can be achieved.

  1. High-energy X-ray diffuse scattering studies on deformation-induced spatially confined martensitic transformations in multifunctional Ti-24Nb-4Zr-8Sn alloy

    SciTech Connect

    Liu, J. P.; Wang, Y. D.; Hao, Y. L.; Wang, H. L.; Wang, Y.; Nie, Z. H.; Su, R.; Wang, D.; Ren, Y.; Lu, Z. P.; Wang, J. G.; Hui, X. D.; Yang, R.

    2014-12-01

    Two main explanations exist for the deformation mechanisms in Ti-Nb-based gum metals, i.e. the formation of reversible nanodisturbance and reversible stress-induced martensitic transformation. In this work, we used the in situ synchrotron-based high-energy X-ray diffuse-scattering technique to reveal the existence of a specific deformation mechanism, i.e. deformation-induced spatially confined martensitic transformations, in Ti-24Nb-4Zr-8Sn-0.10O single crystals with cubic 13 parent phase, which explains well some anomalous mechanical properties of the alloy such as low elastic modulus and nonlinear superelasticity. Two kinds of nanosized martensites with different crystal structures were found during uniaxial tensile loading along the [11 0](beta) axis at room temperature and 190 K, respectively. The detailed changes in the martensitic phase transformation characteristics and the transformation kinetics were experimentally observed at different temperatures. The domain switch from non-modulated martensite to a modulated one occurred at 190 K, with its physical origin attributed to the heterogeneity of local phonon softening depending on temperature and inhomogeneous composition in the parent phase. An in-depth understanding of the formation of stress-induced spatially confined nanosized martensites with a large gradient in chemical composition may benefit designs of high-strength and high-ductility alloys. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  2. Confinement Vessel Dynamic Analysis

    SciTech Connect

    R. Robert Stevens; Stephen P. Rojas

    1999-08-01

    A series of hydrodynamic and structural analyses of a spherical confinement vessel has been performed. The analyses used a hydrodynamic code to estimate the dynamic blast pressures at the vessel's internal surfaces caused by the detonation of a mass of high explosive, then used those blast pressures as applied loads in an explicit finite element model to simulate the vessel's structural response. Numerous load cases were considered. Particular attention was paid to the bolted port connections and the O-ring pressure seals. The analysis methods and results are discussed, and comparisons to experimental results are made.

  3. Quark confinement in a constituent quark model

    SciTech Connect

    Langfeld, K.; Rho, M.

    1995-07-01

    On the level of an effective quark theory, we define confinement by the absence of quark anti-quark thresholds in correlation function. We then propose a confining Nambu-Jona-Lasinio-type model. The confinement is implemented in analogy to Anderson localization in condensed matter systems. We study the model`s phase structure as well as its behavior under extreme conditions, i.e. high temperature and/or high density.

  4. How ship wave action influences the sediment budget of a nature friendly bank protection in a confined, non-tidal waterway

    NASA Astrophysics Data System (ADS)

    De Roo, S.; Vanhaute, L.; Troch, P.

    2012-04-01

    Failure of the concrete slab revetment resulted in progressive bank erosion along the Lys (Belgium), a confined, non-tidal waterway subject to heavy shipping traffic. In an attempt to reconcile both the technical and environmental requirements related to a river bank, restoration was carried out using a more ecologically sound, 'soft' engineering method. A nature friendly bank protection, consisting of off-bank timber piling in combination with (reed)vegetation in the shallow water zone behind, was installed. As a consequence of this effort towards a more sustainable and ecological design of the waterway, sediment redistribution and transport processes are however altered distinctly. Being a waterway subject to heavy shipping traffic (on monthly average 1700 ship passages), hydrodynamic ship wave action on this open, semi-natural bank protection also induces sediment (re)suspension and acts as a main contributor to sediment transport (in normal weather conditions). In order to identify the relevant transport processes caused by ship-generated wave forcing, a field measurement campaign took place in April 2011. By measuring instantaneous water velocities, suspended sediment concentrations and wave hydrodynamics with a high temporal resolution, the effects on the sediment budget were quantified. It is found that the driving forces for these processes are the ship's speed, its blockage coefficient and the distance of the sailing ship to the timber piling. Bottom shear stresses significantly increase to values up to 10 N/m2 during a ship passage. Being much higher than the critical shear stress of 1.5 N/m2 and lasting for several minutes, the fine as well as coarser fractions of bottom sediment are dislodged and (re)suspended. Wave height also correlates well with the amount of sediment suspension. The best predictor for bank erosion is the velocity at which the displaced water mass hits the river bank. These experimental results indicate a reduced yet continuing

  5. De-Confinement in small systems: Clustering of color sources in high multiplicity p¯p collisions at √s = 1.8 TeV

    NASA Astrophysics Data System (ADS)

    Gutay, L. J.

    2016-07-01

    It is shown that de-confinement can be achieved in high multiplicity non jet p¯p collisions at √s = 1.8 TeV Fermi National Accelerator Laboratory(FNAL- E735) experiment. In this paper we have analyzed the transverse momentum spectrum in the framework of the clustering of color sources. This frame-work naturally predicts the reduction in the charged particle multiplicity with respect to the value expected from the number of independent strings. Results are presented for both thermodynamic and transport properties. The initial temperature and energy density are obtained from the data via the color reduction factor F(ξ) and the associated string density parameter ξ. The results for he trace anomaly Δ and shear viscosity to entropy density ratio(η/s) are presented. These results confirm our earlier observation that the de-confined state of matter was created in high multiplicity events in p¯p collisions at √s = 1.8 TeV.

  6. Reversible optical switching of highly confined phonon-polaritons with an ultrathin phase-change material.

    PubMed

    Li, Peining; Yang, Xiaosheng; Maß, Tobias W W; Hanss, Julian; Lewin, Martin; Michel, Ann-Katrin U; Wuttig, Matthias; Taubner, Thomas

    2016-08-01

    Surface phonon-polaritons (SPhPs), collective excitations of photons coupled with phonons in polar crystals, enable strong light-matter interaction and numerous infrared nanophotonic applications. However, as the lattice vibrations are determined by the crystal structure, the dynamical control of SPhPs remains challenging. Here, we realize the all-optical, non-volatile, and reversible switching of SPhPs by controlling the structural phase of a phase-change material (PCM) employed as a switchable dielectric environment. We experimentally demonstrate optical switching of an ultrathin PCM film (down to 7 nm, <λ/1,200) with single laser pulses and detect ultra-confined SPhPs (polariton wavevector kp > 70k0, k0 = 2π/λ) in quartz. Our proof of concept allows the preparation of all-dielectric, rewritable SPhP resonators without the need for complex fabrication methods. With optimized materials and parallelized optical addressing we foresee application potential for switchable infrared nanophotonic elements, for example, imaging elements such as superlenses and hyperlenses, as well as reconfigurable metasurfaces and sensors. PMID:27213955

  7. Translocation of a Polymer Chain Through a Nanopore Starting From a Confining Nanotube: The Limit of high Peclet Numbers

    NASA Astrophysics Data System (ADS)

    Slater, Gary W.; Sean, David; de Haan, Hendrick

    2015-03-01

    We use Langevin Dynamics simulations to study a scenario where a confining nanotube is used as a way to limit the range of conformations available to a polymer chain prior to driven translocation. We find that the tube not only reduces the variance in translocation times (a useful result for practical applications), but also that the elongated polymer conformations yield longer translocation times (also a useful result) that can be dominated by the post-propagation process when the diameter of the nanotube is smaller than a universal critical value. We adapt the tension propagation theory for this geometry and find agreement with the simulations using a single friction parameter to model the roles of both the nanopore and the crowding. To gain insight into the physical mechanisms behind this effective friction, we systematically remove i) crowding on the trans-side and/or ii) monomer collisions with the membrane containing the nanopore. We find that higher Peclet numbers increase the impact of crowding on the trans side but diminish the impact of the friction between the nanopore and the polymer.

  8. Confined vortex scrubber

    SciTech Connect

    Not Available

    1990-07-01

    The program objective is to demonstrate efficient removal of fine particulates to sufficiently low levels to meet proposed small scale coal combustor emission standards using a cleanup technology appropriate to small scale coal combustors. This to be accomplished using a novel particulate removal device, the Confined Vortex Scrubber (CVS), which consists of a cylindrical vortex chamber with tangential flue gas inlets. The clean gas exit is via vortex finder outlets, one at either end of the tube. Liquid is introduced into the chamber and is confined within the vortex chamber by the centrifugal force generated by the gas flow itself. This confined liquid forms a layer through which the flue gas is then forced to bubble, producing a strong gas/liquid interaction, high inertial separation forces and efficient particulate cleanup. During this quarter a comprehensive series of cleanup experiments have been made for three CVS configurations. The first CVS configuration tested gave very efficient fine particulate removal at the design air mass flow rate (1 MM BUT/hr combustor exhaust flow), but had over 20{double prime}WC pressure drop. The first CVS configuration was then re-designed to produce the same very efficient particulate collection performance at a lower pressure drop. The current CVS configuration produces 99.4 percent cleanup of ultra-fine fly ash at the design air mass flow at a pressure drop of 12 {double prime}WC with a liquid/air flow ratio of 0.31/m{sup 3}. Unlike venturi scrubbers, the collection performance of the CVS is insensitive to dust loading and to liquid/air flow ratio.

  9. High-resolution dielectric study reveals pore-size-dependent orientational order of a discotic liquid crystal confined in tubular nanopores.

    PubMed

    Całus, Sylwia; Kityk, Andriy V; Borowik, Lech; Lefort, Ronan; Morineau, Denis; Krause, Christina; Schönhals, Andreas; Busch, Mark; Huber, Patrick

    2015-07-01

    We report a high-resolution dielectric study on a pyrene-based discotic liquid crystal (DLC) in the bulk state and confined in parallel tubular nanopores of monolithic silica and alumina membranes. The positive dielectric anisotropy of the DLC molecule at low frequencies (in the quasistatic case) allows us to explore the thermotropic collective orientational order. A face-on arrangement of the molecular discs on the pore walls and a corresponding radial arrangement of the molecules is found. In contrast to the bulk, the isotropic-to-columnar transition of the confined DLC is continuous, shifts with decreasing pore diameter to lower temperatures, and exhibits a pronounced hysteresis between cooling and heating. These findings corroborate conclusions from previous neutron and x-ray-scattering experiments as well as optical birefringence measurements. Our study also indicates that the relative simple dielectric technique presented here is a quite efficient method in order to study the thermotropic orientational order of DLC-based nanocomposites. PMID:26274191

  10. A Review of Quantum Confinement

    SciTech Connect

    Connerade, Jean-Patrick

    2009-12-03

    A succinct history of the Confined Atom problem is presented. The hydrogen atom confined to the centre of an impenetrable sphere counts amongst the exactly soluble problems of physics, alongside much more noted exact solutions such as Black Body Radiation and the free Hydrogen atom in absence of any radiation field. It shares with them the disadvantage of being an idealisation, while at the same time encapsulating in a simple way particular aspects of physical reality. The problem was first formulated by Sommerfeld and Welker - henceforth cited as SW - in connection with the behaviour of atoms at very high pressures, and the solution was published on the occasion of Pauli's 60th birthday celebration. At the time, it seemed that there was not much other connection with physical reality beyond a few simple aspects connected to the properties of atoms in solids, for which more appropriate models were soon developed. Thus, confined atoms attracted little attention until the advent of the metallofullerene, which provided the first example of a confined atom with properties quite closely related to those originally considered by SW. Since then, the problem has received much more attention, and many more new features of quantum confinement, quantum compression, the quantum Faraday cage, electronic reorganisation, cavity resonances, etc have been described, which are relevant to real systems. Also, a number of other situations have been uncovered experimentally to which quantum confinement is relevant. Thus, studies of the confined atom are now more numerous, and have been extended both in terms of the models used and the systems to which they can be applied. Connections to thermodynamics are explored through the properties of a confined two-level atom adapted from Einstein's celebrated model, and issues of dynamical screening of electromagnetic radiation by the confining shell are discussed in connection with the Faraday cage produced by a confining conducting shell. The