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Sample records for plasmas confines par

  1. 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

  2. Tandem mirror plasma confinement apparatus

    DOEpatents

    Fowler, T. Kenneth

    1978-11-14

    Apparatus and method for confining a plasma in a center mirror cell by use of two end mirror cells as positively charged end stoppers to minimize leakage of positive particles from the ends of the center mirror cell.

  3. Alternative approaches to plasma confinement

    NASA Technical Reports Server (NTRS)

    Roth, J. R.

    1978-01-01

    The paper discusses 20 plasma confinement schemes each representing an alternative to the tokamak fusion reactor. Attention is given to: (1) tokamak-like devices (TORMAC, Topolotron, and the Extrap concept), (2) stellarator-like devices (Torsatron and twisted-coil stellarators), (3) mirror machines (Astron and reversed-field devices, the 2XII B experiment, laser-heated solenoids, the LITE experiment, the Kaktus-Surmac concept), (4) bumpy tori (hot electron bumpy torus, toroidal minimum-B configurations), (5) electrostatically assisted confinement (electrostatically stuffed cusps and mirrors, electrostatically assisted toroidal confinement), (6) the Migma concept, and (7) wall-confined plasmas. The plasma parameters of the devices are presented and the advantages and disadvantages of each are listed.

  4. Alternative approaches to plasma confinement

    NASA Technical Reports Server (NTRS)

    Roth, J. R.

    1977-01-01

    The potential applications of fusion reactors, the desirable properties of reactors intended for various applications, and the limitations of the Tokamak concept are discussed. The principles and characteristics of 20 distinct alternative confinement concepts are described, each of which may be an alternative to the Tokamak. The devices are classed as Tokamak-like, stellarator-like, mirror machines, bumpy tori, electrostatically assisted, migma concept, and wall-confined plasma.

  5. CORRELATIONS IN CONFINED QUANTUM PLASMAS

    SciTech Connect

    DUFTY J W

    2012-01-11

    This is the final report for the project 'Correlations in Confined Quantum Plasmas', NSF-DOE Partnership Grant DE FG02 07ER54946, 8/1/2007 - 7/30/2010. The research was performed in collaboration with a group at Christian Albrechts University (CAU), Kiel, Germany. That collaboration, almost 15 years old, was formalized during the past four years under this NSF-DOE Partnership Grant to support graduate students at the two institutions and to facilitate frequent exchange visits. The research was focused on exploring the frontiers of charged particle physics evolving from new experimental access to unusual states associated with confinement. Particular attention was paid to combined effects of quantum mechanics and confinement. A suite of analytical and numerical tools tailored to the specific inquiry has been developed and employed

  6. Experimental Achievements on Plasma Confinement and Turbulence

    SciTech Connect

    Fujisawa, A.

    2009-02-19

    This article presents a brief review of the experimental studies on turbulence and resultant transport in toroidal plasmas. The article focuses on two topics, physics of transport barrier and the role of mesoscale structure on plasma confinement, i.e. zonal flows. The two topics show the important roles of the mutual interactions between sheared flows, zonal flows and drift waves for plasma turbulence and transport. The findings can lead us to further generalized concept of the disparate scale interactions which could give a fundamental understanding of the plasma confinement from the first principle.

  7. Microwave Reflectometry for Magnetically Confined Plasmas

    SciTech Connect

    Mazzucato, E.

    1998-02-01

    This paper is about microwave reflectometry -- a radar technique for plasma density measurements using the reflection of electromagnetic waves by a plasma cutoff. Both the theoretical foundations of reflectometry and its practical application to the study of magnetically confined plasmas are reviewed in this paper. In particular, the role of short-scale density fluctuations is discussed at length, both as a unique diagnostic tool for turbulence studies in thermonuclear plasmas and for the deleterious effects that fluctuations may have on the measurement of the average plasma density with microwave reflectometry.

  8. PLASMA HEATING AND CONFINING DEVICE

    DOEpatents

    Baker, W.R.; Bratenahl, Al.; Kunkel, W.B.

    1962-02-13

    ABS> A device is designed for generating, heating, and containing a very pure electrical plasma. Plasma purity is maintained by preventing the hot plasma from contacting insulators, which are a principal source of impurities in prior constructions. An insulator is disposed at each end of a pair of long coaxial cylinders forming an annular chamber therebetween. High voltage is applied between the cylinders and an axial magnetic field is created therethrough. At a middle position on the inner cylinder, a fastopening valve releases a quantity of gas into the chamber, and before the gas can diffuse to the distant insulators, a discharge occurs between the cylinders and plasma is formed in the central region of the chamber away from the insulators. (AEC)

  9. Neoclassical transport in enhanced confinement toroidal plasmas

    SciTech Connect

    Lin, Z.; Tang, W.M.; Lee, W.W.

    1996-11-01

    It has recently been reported that ion thermal transport levels in enhanced confinement tokamak plasmas have been observed to fall below the irreducible minimum level predicted by standard neoclassical theory. This apparent contradiction is resolved in the present analysis by relaxing the basic neoclassical assumption that the ions orbital excursions are much smaller than the local toroidal minor radius and the equilibrium scale lengths of the system.

  10. Confinement Studies in High Temperature Spheromak Plasmas

    SciTech Connect

    Hill, D N; Mclean, H S; Wood, R D; Casper, T A; Cohen, B I; Hooper, E B; LoDestro, L L; Pearlstein, L D; Romero-Talamas, C

    2006-10-23

    Recent results from the SSPX spheromak experiment demonstrate the potential for obtaining good energy confinement (Te > 350eV and radial electron thermal diffusivity comparable to tokamak L-mode values) in a completely self-organized toroidal plasma. A strong decrease in thermal conductivity with temperature is observed and at the highest temperatures, transport is well below that expected from the Rechester-Rosenbluth model. Addition of a new capacitor bank has produced 60% higher magnetic fields and almost tripled the pulse length to 11ms. For plasmas with T{sub e} > 300eV, it becomes feasible to use modest (1.8MW) neutral beam injection (NBI) heating to significantly change the power balance in the core plasma, making it an effective tool for improving transport analysis. We are now developing detailed designs for adding NBI to SSPX and have developed a new module for the CORSICA transport code to compute the correct fast-ion orbits in SSPX so that we can simulate the effect of adding NBI; initial results predict that such heating can raise the electron temperature and total plasma pressure in the core by a factor of two.

  11. Thomson scattering from inertial confinement fusion plasmas

    SciTech Connect

    Glenzer, S.H.; Back, C.A.; Suter, L.J.

    1997-07-08

    Thomson scattering has been developed at the Nova laser facility as a direct and accurate diagnostic to characterize inertial confinement fusion plasmas. Flat disks coated with thin multilayers of gold and beryllium were with one laser beam to produce a two ion species plasma with a controlled amount of both species. Thomson scattering spectra from these plasmas showed two ion acoustic waves belonging to gold and beryllium. The phase velocities of the ion acoustic waves are shown to be a sensitive function of the relative concentrations of the two ion species and are in good agreement with theoretical calculations. These open geometry experiments further show that an accurate measurement of the ion temperature can be derived from the relative damping of the two ion acoustic waves. Subsequent Thomson scattering measurements from methane-filled, ignition-relevant hohlraums apply the theory for two ion species plasmas to obtain the electron and ion temperatures with high accuracy. The experimental data provide a benchmark for two-dimensional hydrodynamic simulations using LASNEX, which is presently in use to predict the performance of future megajoule laser driven hohlraums of the National Ignition Facility (NIF). The data are consistent with modeling using significantly inhibited heat transport at the peak of the drive. Applied to NIF targets, this flux limitation has little effect on x- ray production. The spatial distribution of x-rays is slightly modified but optimal symmetry can be re-established by small changes in power balance or pointing. Furthermore, we find that stagnating plasma regions on the hohlraum axis are well described by the calculations. This result implies that stagnation in gas-filled hohlraums occurs too late to directly affect the capsule implosion in ignition experiments.

  12. Confinement Studies of Auxiliary Heated NSTX Plasmas

    SciTech Connect

    B.P. LeBlanc; M.G. Bell; R.E. Bell; M.L. Bitter; C. Bourdelle; D.A. Gates; S.M. Kaye; R. Maingi; J.E. Menard; D. Mueller; S.F. Paul; A.L. Roquemore; A. Rosenberg1; S.A. Sabbagh; D. Stutman; E.J. Synakowski; V.A. Soukhanovskii; J.R.Wilson; the NSTX Research Team

    2003-05-06

    The confinement of auxiliary heated NSTX discharges is discussed. The energy confinement time in plasmas with either L-mode or H-mode edges is enhanced over the values given by the ITER97L and ITER98Pby(2) scalings, being up to 2-3 times L-mode and 1.5 times H-mode. TRANSP calculations based on the kinetic profile measurements reproduce the magnetics-based determination of stored energy and the measured neutron production rate. Power balance calculations reveal that, in a high power neutral beam heated H-mode discharge, the ion thermal transport is near neoclassical levels, and well below the electron thermal transport, which is the main loss channel. Perturbative impurity injection techniques indicate the particle diffusivity to be slightly above the neoclassical level in discharges with L-mode edge. High-harmonic fast-wave (HHFW) bulk electron heating is described and thermal transport is discussed. Thermal ion transport is found to be above neoclassical level, but thermal electron transport remains the main loss mechanism. Evidences of an electron thermal internal transport barrier obtained with HHFW heating are presented. A description of H-mode discharges obtained during HHFW heating is presented.

  13. Properties of radio-frequency heated argon confined uranium plasmas

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Pure uranium hexafluoride (UF6) was injected into an argon confined, steady state, rf-heated plasma within a fused silica peripheral wall test chamber. Exploratory tests conducted using an 80 kW rf facility and different test chamber flow configurations permitted selection of the configuration demonstrating the best confinement characteristics and minimum uranium compound wall coating. The overall test results demonstrated applicable flow schemes and associated diagnostic techniques were developed for the fluid mechanical confinement and characterization of uranium within an rf plasma discharge when pure UF6 is injected for long test times into an argon-confined, high-temperature, high-pressure, rf-heated plasma.

  14. Theoretical studies on plasma heating and confinement

    SciTech Connect

    Sudan, R.N.

    1993-01-01

    Three principal topics are covered in this final report: Stabilization of low frequency modes of an axisymmetric compact torus plasma confinement system, such as, spheromaks and FRC'S, by a population of large orbit axis encircling energetic ions. Employing an extension of the energy principle' which utilizes a Vlasov description for the energetic 'ion component, it has been demonstrated that short wavelength MHD type modes are stabilized while the long wavelength tilt and precessional modes are marginally stable. The deformation of the equilibrium configuration by the energetic ions results in the stabilization of the tilt mode for spheromaks. Formation of Ion Rings and their coalescence with spheromaks. A two dimensional electromagnetic PIC codes has been developed for the study of ion ring formation and its propagation, deformation and slowing down in a cold plasma. It has been shown that a ring moving at a speed less than the Alfven velocity can merge with a stationary spheromak. Anomalous transport from drift waves in a Tokomak. The Direct Interaction Approximation in used to obtain incremental transport coefficients for particles and heat for drift waves in a Tokomak. It is shown that the transport matrix does not obey Onsager's principle.

  15. Order in very cold confined plasmas

    SciTech Connect

    Schiffer, J.P. |

    1995-12-31

    The study of the structure and dynamic properties of classical systems of charged particles confined by external forces, and cooled to very low internal energies, is the subject of this talk. An infinite system of identical charged particles has been known for some time to form a body-centered cubic lattice and is a simple classical prototype for condensed matter. Recent technical developments in storage rings, ion traps, and laser cooling of ions, have made it possible to produce such systems in the laboratory, though somewhat modified because of their finite size. I would like to discuss what one may expect in such systems and also show some examples of experiments. If we approximate the potential of an ion trap with an isotropic harmonic force F = {minus}Kr then the Hamiltonian for this collection of ions is the same as that for J. J. Thomson`s ``plum pudding`` model of the atom, where electrons were thought of as discrete negative charges imbedded in a larger, positive, uniformly charged sphere. The harmonic force macroscopically is canceled by the average space-charge forces of the plasma-, and this fixes the overall radius of the distribution. What remains, are the residual two-body Coulomb interactions that keep the particles within the volume as nearly equidistant as possible in order to minimize the potential energy. The configurations obtained for the minimum energy of small ionic systems [2] in isotropic confinement are shown in figure 1. Indeed this is an `Exotic Atom` and fits well into the subject of this symposium honoring the 60th birthday of Professor Toshi Yamazaki.

  16. Self-confinement of finite dust clusters in isotropic plasmas.

    PubMed

    Miloshevsky, G V; Hassanein, A

    2012-05-01

    Finite two-dimensional dust clusters are systems of a small number of charged grains. The self-confinement of dust clusters in isotropic plasmas is studied using the particle-in-cell method. The energetically favorable configurations of grains in plasma are found that are due to the kinetic effects of plasma ions and electrons. The self-confinement phenomenon is attributed to the change in the plasma composition within a dust cluster resulting in grain attraction mediated by plasma ions. This is a self-consistent state of a dust cluster in which grain's repulsion is compensated by the reduced charge and floating potential on grains, overlapped ion clouds, and depleted electrons within a cluster. The common potential well is formed trapping dust clusters in the confined state. These results provide both valuable insights and a different perspective to the classical view on the formation of boundary-free dust clusters in isotropic plasmas.

  17. Stellarator approach to toroidal plasma confinement

    SciTech Connect

    Johnson, J.L.

    1981-12-01

    An overview is presented of the development and current status of the stellarator approach to controlled thermonuclear confinement. Recent experimental, theoretical, and systems developments have made this concept a viable option for the evolution of the toroidal confinement program. Some experimental study of specific problems associated with departure from two-dimensional symmetry must be undertaken before the full advantages and opportunities of steady-state, net-current-free operation can be realized.

  18. Heat flow in a gravitationally confined plasma

    NASA Astrophysics Data System (ADS)

    Dorelli, John Charles

    We study the problem of electron heat flow in a gravitationally confined hilly ionized plasma. Our goal is to determine the conditions under which the classical description of electron heat flow-which requires heat to flow down the local temperature gradient-breaks down. We investigate this question from both a macroscopic (fluid theory) and a microscopic (kinetic theory) point of view. We use fluid conservation laws to demonstrate generally that a nearly isotropic non-Maxwellian electron velocity distribution can have a heat flux vector which points up the local temperature gradient. As a specific example, we demonstrate that electron velocity distributions with high energy power law tails in the solar corona can have a heat flux vector which points up a radially directed temperature gradient. We confirm this result by numerically solving the steady state Fokker-Planck equation describing the electron velocity distribution in the presence of a strong gravitational field. Our conclusions can be summarized as follows: (1)It is possible for a nearly isotropic electron velocity distribution with a weak power law tail near the base of the solar corona to have a heat flux which points up a radially directed temperature gradient, (2)The Spitzer-Harm theory does not give an adequate description of electron heat flow in the solar corona for any finite temperature gradient (no matter how small), (3)If the electron velocity distribution function at the base of the corona does not have a non- Maxwellian tail which connects nearly collisionlessly to the high altitude boundary, then the electron phase space density develops a spatial boundary layer near the low altitude boundary of the system. This spatial boundary layer implies large anisotropies in the electron velocity distribution which cannot be described self consistently by the mathematical model employed in this thesis, (4)If the electron velocity distribution functions at the boundaries of the system have nearly

  19. Magnetic confinement of a high-density cylindrical plasma

    SciTech Connect

    Ahedo, Eduardo

    2011-10-15

    The stationary structure of a weakly collisional plasma column, confined by an axial magnetic field and a cylindrical vessel, is studied for the high-density case, when the diamagnetic azimuthal current is large enough to demagnetize partially the plasma. The plasma response is characterized mainly by two dimensionless parameters: the ratios of the electron gyroradius and the electron skin-depth to the plasma radius, and each of them measures the independent influence of the applied magnetic field and the plasma density on the plasma response. The strong magnetic confinement regime, characterized by very small wall losses, is limited to the small gyroradius and large skin-depth ranges. In the high-density case, when the electron skin-depth is smaller than the electron gyroradius, the skin-depth turns out to be the magnetic screening length, so that the bulk of the plasma behaves as unmagnetized.

  20. The Plasma Anvil in Inertial Confinement Fusion

    NASA Astrophysics Data System (ADS)

    Fechner, Walter; Morley, P. D.

    We examine theoretically an inertial confinement fusion (ICF) target consisting of a spherical wedge embedded in a relatively nondeformable "anvil". Questions such as heat loss to the anvil, optimum wedge angle, liner and anvil materials, anvil deformations and deleterious 2-D shock effects on D-T burn and compression symmetry are discussed.

  1. Transport processes in magnetically confined plasmas

    SciTech Connect

    Callen, J.D.

    1991-12-01

    Intensified studies of plasma transport in toroidal plasmas over the past three to five years have progressed through increased understanding in some areas and changed perceptions about the most important issues in other areas. Recent developments are reviewed for six selected topics: edge fluctuations and transport; L-H mode transition; core fluctuations; modern plasma turbulence theory; transient transport; and global scaling. Some of the developments that are highlighted include: the role of a strongly sheared poloidal flow in edge plasma turbulence, transport and the L-H transition; change of focus from {kappa}{perpendicular}{rho}s {approximately} 1 to {kappa}{perpendicular}{rho}s {much_lt} 1 fluctuations in tokamak plasmas; modern Direct-Interaction-Approximation plasma turbulence and hybrid fluid/kinetic theoretical models; and transient transport experiments that are raising fundamental questions about our conceptions of local transport processes in tokamaks. 104 refs., 6 figs.

  2. Transport processes in magnetically confined plasmas

    SciTech Connect

    Callen, J.D.

    1991-12-01

    Intensified studies of plasma transport in toroidal plasmas over the past three to five years have progressed through increased understanding in some areas and changed perceptions about the most important issues in other areas. Recent developments are reviewed for six selected topics: edge fluctuations and transport; L-H mode transition; core fluctuations; modern plasma turbulence theory; transient transport; and global scaling. Some of the developments that are highlighted include: the role of a strongly sheared poloidal flow in edge plasma turbulence, transport and the L-H transition; change of focus from {kappa}{perpendicular}{rho}s {approximately} 1 to {kappa}{perpendicular}{rho}s {much lt} 1 fluctuations in tokamak plasmas; modern Direct-Interaction-Approximation plasma turbulence and hybrid fluid/kinetic theoretical models; and transient transport experiments that are raising fundamental questions about our conceptions of local transport processes in tokamaks. 104 refs., 6 figs.

  3. Laboratory-scale uranium RF plasma confinement experiments

    NASA Technical Reports Server (NTRS)

    Roman, W. C.

    1976-01-01

    An experimental investigation was conducted using 80 kW and 1.2 MW RF induction heater facilities to aid in developing the technology necessary for designing a self-critical fissioning uranium plasma core reactor. Pure uranium hexafluoride (UF6) was injected into argon-confined, steady-state, RF-heated plasmas in different uranium plasma confinement tests to investigate the characteristics of plamas core nuclear reactors. The objectives were: (1) to confine as high a density of uranium vapor as possible within the plasma while simultaneously minimizing the uranium compound wall deposition; (2) to develop and test materials and handling techniques suitable for use with high-temperature, high-pressure gaseous UF6; and (3) to develop complementary diagnostic instrumentation and measurement techniques to characterize the uranium plasma and residue deposited on the test chamber components. In all tests, the plasma was a fluid-mechanically-confined vortex-type contained within a fused-silica cylindrical test chamber. The test chamber peripheral wall was 5.7 cm ID by 10 cm long.

  4. Apparatus for magnetic and electrostatic confinement of plasma

    DOEpatents

    Rostoker, Norman; Binderbauer, Michl

    2006-04-11

    An apparatus and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions they are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.

  5. Apparatus for magnetic and electrostatic confinement of plasma

    DOEpatents

    Rostoker, Norman; Binderbauer, Michl

    2013-06-11

    An apparatus and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions ions are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.

  6. Apparatus for magnetic and electrostatic confinement of plasma

    DOEpatents

    Rostoker, Norman; Binderbauer, Michl

    2006-10-31

    An apparatus and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions they are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.

  7. Apparatus for magnetic and electrostatic confinement of plasma

    DOEpatents

    Rostoker, Norman; Binderbauer, Michl

    2016-07-05

    An apparatus and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions ions are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.

  8. Probing cell migration in confined environments by plasma lithography.

    PubMed

    Junkin, Michael; Wong, Pak Kin

    2011-03-01

    Cellular processes are regulated by various mechanical and physical factors in their local microenvironment such as geometric confinements, cell-substrate interactions, and cell-cell contact. Systematic elucidation of these regulatory mechanisms is crucial for fundamental understanding of cell biology and for rational design of biomedical devices and regenerative medicine. Here, we report a generally applicable plasma lithography technique, which performs selective surface functionalization on large substrate areas, for achieving long-term, stable confinements with length scales from 100 nm to 1 cm toward the investigation of cell-microenvironment interactions. In particular, we applied plasma lithography for cellular confinement of neuroblastomas, myoblasts, endothelial cells, and mammary gland epithelial cells, and examined the motion of mouse embryonic fibroblasts in directionality-confined environments for studying the effect of confinements on migratory behavior. In conjunction with live cell imaging, the distance traveled, velocity, and angular motion of individual cells and collective cell migration behaviors were measured in confined environments with dimensions comparable to a cell. A critical length scale that a cell could conceivably occupy and migrate to was also identified by investigating the behaviors of cells using confined environments with subcellular length scales.

  9. Magnetohydrodynamically generated velocities in confined plasma

    SciTech Connect

    Morales, Jorge A. Bos, Wouter J. T.; Schneider, Kai; Montgomery, David C.

    2015-04-15

    We investigate by numerical simulation the rotational flows in a toroid confining a conducting magnetofluid in which a current is driven by the application of externally supported electric and magnetic fields. The computation involves no microscopic instabilities and is purely magnetohydrodynamic (MHD). We show how the properties and intensity of the rotations are regulated by dimensionless numbers (Lundquist and viscous Lundquist) that contain the resistivity and viscosity of the magnetofluid. At the magnetohydrodynamic level (uniform mass density and incompressible magnetofluids), rotational flows appear in toroidal, driven MHD. The evolution of these flows with the transport coefficients, geometry, and safety factor are described.

  10. Magnetohydrodynamically generated velocities in confined plasma

    NASA Astrophysics Data System (ADS)

    Morales, Jorge A.; Bos, Wouter J. T.; Schneider, Kai; Montgomery, David C.

    2015-04-01

    We investigate by numerical simulation the rotational flows in a toroid confining a conducting magnetofluid in which a current is driven by the application of externally supported electric and magnetic fields. The computation involves no microscopic instabilities and is purely magnetohydrodynamic (MHD). We show how the properties and intensity of the rotations are regulated by dimensionless numbers (Lundquist and viscous Lundquist) that contain the resistivity and viscosity of the magnetofluid. At the magnetohydrodynamic level (uniform mass density and incompressible magnetofluids), rotational flows appear in toroidal, driven MHD. The evolution of these flows with the transport coefficients, geometry, and safety factor are described.

  11. Space charge neutralization in inertial electrostatic confinement plasmas

    SciTech Connect

    Evstatiev, E. G.; Nebel, R. A.; Chacon, L.; Park, J.; Lapenta, G.

    2007-04-15

    A major issue for electron injected inertial electrostatic confinement (IEC) devices is space charge neutralization. A new formalism is developed that will allow this neutralization to occur for both oscillating and steady-state IEC plasmas. Results indicate that there are limits on the amount of compression that can be achieved by oscillating plasmas while simultaneously maintaining space charge neutralization and parabolic background potential. For steady-state plasmas, there are no such limits and space charge neutralization can be achieved even when the plasma becomes quasineutral.

  12. Passive Spectroscopic Diagnostics for Magnetically-confined Fusion Plasmas

    SciTech Connect

    Stratton, B. C.; Biter, M.; Hill, K. W.; Hillis, D. L.; Hogan, J. T.

    2007-07-18

    Spectroscopy of radiation emitted by impurities and hydrogen isotopes plays an important role in the study of magnetically-confined fusion plasmas, both in determining the effects of impurities on plasma behavior and in measurements of plasma parameters such as electron and ion temperatures and densities, particle transport, and particle influx rates. This paper reviews spectroscopic diagnostics of plasma radiation that are excited by collisional processes in the plasma, which are termed 'passive' spectroscopic diagnostics to distinguish them from 'active' spectroscopic diagnostics involving injected particle and laser beams. A brief overview of the ionization balance in hot plasmas and the relevant line and continuum radiation excitation mechanisms is given. Instrumentation in the soft X-ray, vacuum ultraviolet, ultraviolet, visible, and near-infrared regions of the spectrum is described and examples of measurements are given. Paths for further development of these measurements and issues for their implementation in a burning plasma environment are discussed.

  13. Confinement and heating of a deuterium-tritium plasma

    SciTech Connect

    Hawryluk, R.J.; Adler, H.; Alling, P.; Ancher, C.; Anderson, H.; Anderson, J.L.; Ashcroft, D.; Barnes, C.W.; Barnes, G.; Batha, S.; Bell, M.G.; Bell, R.; Bitter, M.; Blanchard, W.; Bretz, N.L.; Budny, R.; Bush, C.E.; Camp, R.; Caorlin, M.; Cauffman, S.; Chang, Z.; Cheng, C.Z.; Collins, J.; Coward, G.; Darrow, D.S.; DeLooper, J.; Duong, H.; Dudek, L.; Durst, R.; Efthimion, P.C.; Ernst, D.; Fisher, R.; Fonck, R.J.; Fredrickson, E.; Fromm, N.; Fu, G.Y.; Furth, H.P.; Gentile, C.; Gorelenkov, N.; Grek, B.; Grisham, L.R.; Hammett, G.; Hanson, G.R.; Heidbrink, W.; Herrmann, H.W.; Hill, K.W.; Hosea, J.; Hsuan, H.; Janos, A.; Jassby, D.L.; Jobes, F.C.; Johnson, D.W.; Johnson, L.C.; Kamperschroer, J.; Kugel, H.; Lam, N.T.; LaMarche, P.H.; Loughlin, M.J.; LeBlanc, B.; Leonard, M.; Levinton, F.M.; Machuzak, J.; Mansfield, D.K.; Martin, A.; Mazzucato, E.; Majeski, R.; Marmar, E.; McChesney, J.; McCormack, B.; McCune, D.C.; McGuire, K.M.; McKee, G.; Meade, D.M.; Medley, S.S.; Mikkelsen, D.R.; Muelle

    1994-05-30

    The Tomamak Fusion Test reactor has performed initial high-power experiments with the plasma fueled with nominally equal densities of deuterium and tritium. Compared to pure deuterium plasmas, the energy stored in the electron and ions increased by [similar to]20%. These increases indicate improvements in confinement associated with the use of tritium and possibly heating of electrons by [alpha] particles created by the D-T fusion reactions.

  14. Magnetic plasma confinement for laser ion source.

    PubMed

    Okamura, M; Adeyemi, A; Kanesue, T; Tamura, J; Kondo, K; Dabrowski, R

    2010-02-01

    A laser ion source (LIS) can easily provide a high current beam. However, it has been difficult to obtain a longer beam pulse while keeping a high current. On occasion, longer beam pulses are required by certain applications. For example, more than 10 micros of beam pulse is required for injecting highly charged beams to a large sized synchrotron. To extend beam pulse width, a solenoid field was applied at the drift space of the LIS at Brookhaven National Laboratory. The solenoid field suppressed the diverging angle of the expanding plasma and the beam pulse was widened. Also, it was observed that the plasma state was conserved after passing through a few hundred gauss of the 480 mm length solenoid field.

  15. MHD-stable plasma confinement in an axisymmetric mirror system

    SciTech Connect

    Stupakov, G.V.

    1988-02-01

    If the magnetic field of a nonparaxial mirror system is chosen appropriately, it is possible to maintain a sharp plasma boundary in an open axisymmetric confinement system in a manner which is stable against flute modes (both global and small-scale). Stability prevails in the ideal MHD approximation without finite-ion-Larmor radius effects.

  16. Plasma confinement apparatus using solenoidal and mirror coils

    DOEpatents

    Fowler, T. Kenneth; Condit, William C.

    1979-01-01

    A plasma confinement apparatus, wherein multiple magnetic mirror cells are linked by magnetic field lines inside of a solenoid with the mirroring regions for adjacent magnetic mirror cells each formed by a separate mirror coil inside of the solenoid. The magnetic mirror cells may be field reversed.

  17. The RFP: Plasma Confinement with a Reversed Twist.

    NASA Astrophysics Data System (ADS)

    Sarff, John S.

    1997-11-01

    The reversed field pinch (RFP) is an axisymmetric plasma torus which, like the better known tokamak, is confined by a magnetic field partly produced by a current within the plasma itself (i.e., a toroidal pinch) and partly by an external solenoidal magnet. But in the RFP, the field produced by the plasma is dominant. This means that the helical magnetic field lines spiral more tightly in the RFP, like a coiled spring bent into a torus. Also, the field lines near the boundary spiral in reverse direction to the field lines nearer the center of the plasma, like nested springs with opposite pitch, giving the plasma its ``reversed field'' name. Most of RFP physics--including that which is related to its fusion reactor potential--traces to these unique magnetic equilibrium features. Since the externally applied field is small, RFP plasmas naturally produce high β >10%, the ratio of plasma thermal pressure to confining magnetic pressure. But the large plasma current provides free energy for small ~1% magnetic fluctuations which, amazingly, regulate much of the RFP's macroscopic behavior, like generation of equilibrium magnetic field through turbulent < tilde v × tilde b > motion (a ``dynamo effect'') and anomalous transport of particles and energy. In fact without the dynamo, the field line pitch reversal after which the RFP is named would not persist. This tutorial aims to introduce the RFP to those less familiar with the concept. A present and future perspective on recent RFP research which has led to significant advances in our understanding of plasmas with strong magnetic turbulence will be emphasized. Initial efforts and future plans to control magnetic turbulence, thereby improving RFP confinement, will be discussed, and examples of RFP physics with general impact, like the relationship of the RFP dynamo to solar and planetary dynamos, will be noted.

  18. Space-charge-based electrostatic plasma confinement involving relaxed plasma species

    SciTech Connect

    Pacheco, J. L.; Ordonez, C. A.; Weathers, D. L.

    2012-10-15

    A numerical study is reported on the equilibrium properties of a surface-emitted or edge-confined non-drifting plasma. A self-consistent finite-differences evaluation of the electrostatic potential is carried out for a non-neutral plasma that follows a Boltzmann density distribution. The non-neutral plasma generates an electrostatic potential that has an extremum at the geometric center. Poisson's equation is solved for different ratios of the non-neutral plasma size to the edge Debye length. The profiles of the electrostatic potential and the plasma density are presented for different values of that ratio. A second plasma species is then introduced for two-plasma-species confinement studies, with one species confined by the space charge of the other, while each species follows a Boltzmann density distribution. An equilibrium in which a neutral region forms is found. An equilibrium is also found in which the two species have equal temperatures and charge states.

  19. 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)

  20. 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.

  1. Negative specific heat of a magnetically self-confined plasma torus

    PubMed Central

    Kiessling, Michael K.-H.; Neukirch, Thomas

    2003-01-01

    It is shown that the thermodynamic maximum-entropy principle predicts negative specific heat for a stationary, magnetically self-confined current-carrying plasma torus. Implications for the magnetic self-confinement of fusion plasma are considered. PMID:12576553

  2. Confinement projections for the Burning Plasma Experiment (BPX)

    SciTech Connect

    Goldston, R.J.; Bateman, G.; Kaye, S.M.; Perkins, F.W.; Pomphrey, N.; Stotler, D.P.; Zarnstorff, M.C. . Plasma Physics Lab.); Houlberg, W.A.; Neilson, G.H. ); Porkolab, M. ); Reidel, K.S. ); Stambaugh, R.D.; Waltz, R.E. )

    1991-01-01

    The mission of the Burning Plasma Experiment (BPX, formerly CIT) is to study the physics of self-heated fusion plasmas (Q = 5 to ignition), and to demonstrate the production of substantial amounts of fusion power (P{sub fus} = 100 to 500 MW). Confinement projections for BPX have been made on the basis of (1) dimensional extrapolation (2) theory-based modeling calibrated to experiment, and (3) statistical scaling from the available empirical data base. The results of all three approaches, discussed in this paper, roughly coincide. We presently view the third approach, statistical scaling, as the most reliable means for projecting the confinement performance of BPX, and especially for assessing the uncertainty in the projection. 11 refs., 2 figs., 1 tab.

  3. Symmetry Constraints on the Dynamics of Magnetically Confined Plasma

    SciTech Connect

    Arter, Wayne

    2009-05-15

    In respect of their symmetry properties, toroidal magnetically confined plasmas have much in common with the Taylor-Couette flow. A symmetry-based analysis (equivalent bifurction theory) has proved very powerful in the analysis of the latter problem. This Letter discusses the applicability of the method to nuclear fusion experiments such as tokamaks and pinches. The likely behavior of the simplest models of rotationally symmetric tokamaks is described, and found to be potentially consistent with observation.

  4. Magnetohydrodynamics equilibrium of a self-confined elliptical plasma ball

    SciTech Connect

    Wu, H. P. O. Box 8730, Beijing 100080 and Institute of Mechanics, Academia Sinica, Beijing, People's Republic of China ); Oakes, M.E. )

    1991-08-01

    A variational principle is applied to the problem of magnetohydrodynamics (MHD) equilibrium of a self-contained elliptical plasma ball, such as elliptical ball lightning. The principle is appropriate for an approximate solution of partial differential equations with arbitrary boundary shape. The method reduces the partial differential equation to a series of ordinary differential equations and is especially valuable for treating boundaries with nonlinear deformations. The calculations conclude that the pressure distribution and the poloidal current are more uniform in an oblate self-confined plasma ball than that of an elongated plasma ball. The ellipticity of the plasma ball is obviously restricted by its internal pressure, magnetic field, and ambient pressure. Qualitative evidence is presented for the absence of sighting of elongated ball lightning.

  5. Implicit Methods for the Magnetohydrodynamic Description of Magnetically Confined Plasmas

    SciTech Connect

    Jardin, S C

    2010-09-28

    Implicit algorithms are essential for predicting the slow growth and saturation of global instabilities in today’s magnetically confined fusion plasma experiments. Present day algorithms for obtaining implicit solutions to the magnetohydrodynamic (MHD) equations for highly magnetized plasma have their roots in algorithms used in the 1960s and 1970s. However, today’s computers and modern linear and non-linear solver techniques make practical much more comprehensive implicit algorithms than were previously possible. Combining these advanced implicit algorithms with highly accurate spatial representations of the vector fields describing the plasma flow and magnetic fields and with improved methods of calculating anisotropic thermal conduction now makes possible simulations of fusion experiments using realistic values of plasma parameters and actual configuration geometry.

  6. Confinement of pure ion plasma in a cylindrical current sheet

    NASA Astrophysics Data System (ADS)

    Paul, Stephen F.; Chao, Edward H.; Davidson, Ronald C.; Phillips, Cynthia K.

    1999-12-01

    A novel method for containing a pure ion plasma at thermonuclear densities and temperatures has been modeled. The method combines the confinement principles of a Penning-Malmberg trap and a pulsed theta-pinch. A conventional Penning trap can confine a uniform-density plasma of about 5×1011cm-3 with a 30-Tesla magnetic field. However, if the axial field is ramped, a much higher local ion density can be obtained. Starting with a 107cm-3 trapped deuterium plasma at the Brillouin limit (B=0.6 Tesla), the field is ramped to 30 Tesla. Because the plasma is comprised of particles of only one sign of charge, transport losses are very low, i.e., the conductivity is high. As a result, the ramped field does not penetrate the plasma and a diamagnetic surface current is generated, with the ions being accelerated to relativistic velocities. To counteract the inward j×B forces from this induced current, additional ions are injected into the plasma along the axis to increase the density (and mutual electrostatic repulsion) of the target plasma. In the absence of the higher magnetic field in the center, the ions drift outward until a balance is established between the outward driving forces (centrifugal, electrostatic, pressure gradient) and the inward j×B force. An equilibrium calculation using a relativistic, 1-D, cold-fluid model shows that a plasma can be trapped in a hollow, 49-cm diameter, 0.2-cm thick cylinder with a density exceeding 4×1014cm-3.

  7. Confinement of Plasma along Shaped Open Magnetic Fields from the Centrifugal Force of Supersonic Plasma Rotation

    SciTech Connect

    Teodorescu, C.; Young, W. C.; Swan, G. W. S.; Ellis, R. F.; Hassam, A. B.; Romero-Talamas, C. A.

    2010-08-20

    Interferometric density measurements in plasmas rotating in shaped, open magnetic fields demonstrate strong confinement of plasma parallel to the magnetic field, with density drops of more than a factor of 10. Taken together with spectroscopic measurements of supersonic ExB rotation of sonic Mach 2, these measurements are in agreement with ideal MHD theory which predicts large parallel pressure drops balanced by centrifugal forces in supersonically rotating plasmas.

  8. Particle confinement of pellet-fuelled tokamak plasma

    NASA Astrophysics Data System (ADS)

    Valovič, M.; Axon, K.; Garzotti, L.; Saarelma, S.; Thyagaraja, A.; Akers, R.; Gurl, C.; Kirk, A.; Lloyd, B.; Maddison, G. P.; Morris, A. W.; Patel, A.; Shibaev, S.; Scannell, R.; Taylor, D.; Walsh, M.; MAST Team

    2008-07-01

    This paper quantifies the particle confinement of pellet-fuelled plasmas as measured in the Mega Ampere Spherical Tokamak. The dataset is restricted mostly to neutral beam heated plasmas in H-mode and to shallow pellets launched from the high-field side. It is shown that the pellet deposition can be explained only by invoking the ∇B drift of the pellet ablatant. The pellet creates a zone with positive density gradient and increased temperature gradient. Simulations show that these changes could increase the level of micro-turbulence and thus enhance further the penetration of pellet-deposited particles towards the core. Post-pellet dynamics of the density profile is characterized by the pellet retention time τpel. It is shown that τpel correlates with the status of the edge transport barrier (L-mode or H-mode) and decreases rapidly for pellet deposition radius rpel approaching the plasma edge. For ELMy H-mode and pellet deposition radius of rpel ≈ 0.8a, the pellet retention time is about 20% of the energy confinement time. The fuelling requirement by the pellets for ITER and the Component Test Facility based on the spherical tokamak is discussed.

  9. Antiproton powered propulsion with magnetically confined plasma engines

    NASA Technical Reports Server (NTRS)

    Lapointe, Michael R.

    1989-01-01

    Matter-antimatter annihilation releases more energy per unit mass than any other method of energy production, making it an attractive energy source for spacecraft propulsion. In the magnetically confined plasma engine, antiproton beams are injected axially into a pulsed magnetic mirror system, where they annihilate with an initially neutral hydrogen gas. The resulting charged annihilation products transfer energy to the hydrogen propellant, which is then exhausted through one end of the pulsed mirror system to provide thrust. The calculated energy transfer efficiencies for a low number density (10(14)/cu cm) hydrogen propellant are insufficient to warrant operating the engine in this mode. Efficiencies are improved using moderate propellant number densities (10(16)/cu cm), but the energy transferred to the plasma in a realistic magnetic mirror system is generally limited to less than 2 percent of the initial proton-antiproton annihilation energy. The energy transfer efficiencies are highest for high number density (10(18)/cu cm) propellants, but plasma temperatures are reduced by excessive radiation losses. Low to moderate thrust over a wide range of specific impulse can be generated with moderate propellant number densities, while higher thrust but lower specific impulse may be generated using high propellant number densities. Significant mass will be required to shield the superconducting magnet coils from the high energy gamma radiation emitted by neutral pion decay. The mass of such a radiation shield may dominate the total engine mass, and could severely diminish the performance of antiproton powered engines which utilize magnetic confinement. The problem is compounded in the antiproton powered plasma engine, where lower energy plasma bremsstrahlung radiation may cause shield surface ablation and degradation.

  10. Confinement of complex plasmas by dielectric walls under microgravity

    SciTech Connect

    Klindworth, M.; Arp, O.; Piel, A.

    2005-10-31

    Dusty plasmas have been confined by glass walls in order to generate void-free particle structures under microgravity conditions. Different types of clouds establish in the cuvette in dependence on the rf power and dc bias applied to the multi-electrode system of the discharge device. The observations can be basically understood when applying standard force models to discharge simulation results. The various dust topologies are proposed to result from a change in the direction of the ion drag - inwards or outwards the cuvette gap.

  11. Finite Time Lyapunov Exponents for magnetically confined plasmas

    NASA Astrophysics Data System (ADS)

    Sugiyama, Linda; Krishnan, Harinarayan

    2012-10-01

    Finite Time Lyapunov Exponents (FTLEs) are applied for the first time to magnetically confined plasmas. The FTLE measures the local divergence or convergence of n-dimensional vector fields. Time-dependent FTLEs are directly related to Lagrangian Coherent Structures, which form the underlying structure of turbulent flows. Modern FTLE methods, developed over the past decade, are evolving rapidly and leading to new practical and theoretical insights into turbulent fluid dynamics. In contrast to fluids, an MHD plasma has two vector fields, the magnetic field and the plasma flow. Accurate methods for computing and visualizing FTLEs for the MHD fields have been developed, based on the VisIt visualization package. They are applied to time slices of a large sawtooth crash in a toroidal plasma, computed by the M3D extended MHD code. The plasma structures for both B and v have unexpected properties that are not brought out by conventional analyses. The sawtooth crash is also found to have well-organized ``flow'' structures in v±B. The FTLE appears to be a sensitive diagnostic for the structure of stochastic magnetic fields. The methods are not restricted to MHD, since they apply to almost any vector field.

  12. 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.

  13. Experiments on Plasma Injection into a Centrifugally Confined System

    NASA Astrophysics Data System (ADS)

    Messer, S.; Bomgardner, R.; Brockington, S.; Case, A.; Witherspoon, F. D.; Uzun-Kaymak, I.; Elton, R.; Young, W.; Teodorescu, C.; Morales, C. H.; Ellis, R. F.

    2009-11-01

    We describe the cross-field injection of plasma into a centrifugally-confined system. Two different types of plasma railgun have been installed on the Maryland Centrifugal Experiment (MCX) in an attempt to drive that plasma's rotation. The initial gun was a coaxial device designed to mitigate the blowby instability. The second one was a MiniRailgun with a rectangular bore oriented so that the MCX magnetic field augments the railgun's internal magnetic field. Tests at HyperV indicate this MiniRailgun reaches much higher densities than the original gun, although muzzle velocity is slightly reduced. We discuss the impact of these guns on MCX for various conditions. Initial results show that even for a 2 kG field, firing the MiniRailgun modifies oscillations of the MCX diamagnetic loops and can impact the core current and voltage. The gun also has a noticeable impact on MCX microwave emissions. These observations suggest plasma enters the MCX system. We also compare diagnostic data collected separately from MCX for these and other guns, focussing primarily on magnetic measurements.

  14. Alpha Heating and Burning Plasmas in Inertial Confinement Fusion

    NASA Astrophysics Data System (ADS)

    Christopherson, A. R.

    2015-11-01

    In inertial confinement fusion, a spherical capsule of cryogenic DT is accelerated inward at a high velocity. Near stagnation, a dense hot spot is formed where the deuterium and tritium ions begin to fuse, creating a 3.5-MeV alpha particle per reaction. These alpha particles deposit energy back into the plasma, thereby increasing the pressure, temperature, and reaction rate. This feedback process is called ``alpha heating,'' and ignition is a direct consequence of this thermal instability. The onset of a burning-plasma regime occurs when the total alpha-particle energy produced exceeds the shell compression work. Using an analytic compressible-shell model for the implosion, it is found that the onset of the burning-plasma regime is a unique function of the neutron yield enhancement caused by alpha particles for any target, direct or indirect drive. This yield enhancement can then be inferred from experimentally measureable quantities, such as the Lawson parameter. From this analysis, the onset of a burning plasma occurs at yields exceeding 50 kJ for implosions at the National Ignition Facility. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and DE-FC02-04ER54789 (Fusion Science Center).

  15. Integrated models for plasma/material interaction during loss of plasma confinement.

    SciTech Connect

    Hassanein, A.

    1998-07-29

    A comprehensive computer package, High Energy Interaction with General Heterogeneous Target Systems (HEIGHTS), has been developed to evaluate the damage incurred on plasma-facing materials during loss of plasma confinement. The HEIGHTS package consists of several integrated computer models that follow the start of a plasma disruption at the scrape-off layer (SOL) through the transport of the eroded debris and splashed target materials to nearby locations as a result of the energy deposited. The package includes new models to study turbulent plasma behavior in the SOL and predicts the plasma parameters and conditions at the divertor plate. Full two-dimensional comprehensive radiation magnetohydrodynamic models are coupled with target thermodynamics and liquid hydrodynamics to evaluate the integrated response of plasma-facing materials. A brief description of the HEIGHTS package and its capabilities are given in this work with emphasis on turbulent plasma behavior in the SOL during disruptions.

  16. Numerical modeling of the transition from low to high confinement in magnetically confined plasma

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    The transition dynamics from low (L) to high (H) mode confinement in magnetically confined plasmas is investigated using a four-field drift fluid model—HESEL (Hot Edge-Sol-Electrostatic). The model includes profile evolution and is solved in a 2D domain at the out-board mid-plane of a tokamak including both open and closed field lines. The results reveal different types of L-H-like transitions in response to ramping up the input power by increasing the ion temperature in the edge region. For a fast rising input power we obtain an abrupt transition, and for a slow rising power we obtain a L-I-H transition with an intermediate I-phase displaying limit-cycle oscillations (LCO). The model recovers the power threshold for the L-H transition, the scaling of the threshold with the density and with the loss-rate in the SOL, indicating a decrease in power threshold when switching from single to double null configuration. The results hold promises for developing full predictive modeling of the L-H transition, which is an essential step in understanding and optimizing fusion devices.

  17. Collective excitations of a spherically confined Yukawa plasma

    SciTech Connect

    Kaehlert, H.; Bonitz, M.

    2011-05-15

    The complete spectrum of eigenmodes of a spherically confined Yukawa plasma is presented, based on first-principle molecular dynamics simulations. These results are compared with a recent fluid theory for the multipole modes of this system [H. Kaehlert and M. Bonitz, Phys. Rev. E 82, 036407 (2010)] and with the exact N-particle eigenmodes in the crystalline phase. Simulations confirm the existence of high-order modes found in cold fluid theory. We investigate the influence of screening, coupling, and friction on the mode spectra in detail. Good agreement between theory and simulation is found for weak to moderate screening and low-order modes. In addition, a number of new modes are observed which are missing in the fluid theory. The relations between the breathing mode in the fluid theory, simulation, and the crystal eigenmode are investigated in further detail.

  18. Antiproton powered propulsion with magnetically confined plasma engines

    NASA Technical Reports Server (NTRS)

    Lapointe, Michael R.

    1989-01-01

    The reaction of the matter-antimatter annihilation, with its specific energy being over 250 times the specific energy released in nuclear fusion, is considered as an energy source for spacecraft propulsion. A concept of a magnetically confined pulsed plasma engine is described. In this concept, antiproton beams are injected axially into a pulsed magnetic mirror system, where they annihilate with an initially neutral hydrogen gas; the resulting charge annihilation products transfer energy to the hydrogen propellant, which is then exhausted through one end of the pulsed mirror system to provide thrust. Numerical simulations were developed to calculate the annihilation rate of antiprotons in hydrogen and to follow the resulting ion, muon, and electron/positron number density evolutions.

  19. Anisotropic confinement effects in a two-dimensional plasma crystal.

    PubMed

    Laut, I; Zhdanov, S K; Räth, C; Thomas, H M; Morfill, G E

    2016-01-01

    The spectral asymmetry of the wave-energy distribution of dust particles during mode-coupling-induced melting, observed for the first time in plasma crystals by Couëdel et al. [Phys. Rev. E 89, 053108 (2014)PLEEE81539-375510.1103/PhysRevE.89.053108], is studied theoretically and by molecular-dynamics simulations. It is shown that an anisotropy of the well confining the microparticles selects the directions of preferred particle motion. The observed differences in intensity of waves of opposed directions are explained by a nonvanishing phonon flux. Anisotropic phonon scattering by defects and Umklapp scattering are proposed as possible reasons for the mean phonon flux. PMID:26871180

  20. Alpha Heating and Burning Plasmas in Inertial Confinement Fusion

    NASA Astrophysics Data System (ADS)

    Betti, R.; Christopherson, A. R.; Bose, A.; Woo, K. M.

    2016-05-01

    Assessing the degree to which fusion alpha particles contribute to the fusion yield is essential to understanding the onset of the thermal runaway process of thermonuclear ignition. It is shown that in inertial confinement fusion, the yield enhancement due to alpha particle heating (before ignition occurs) depends on the generalized Lawson parameter that can be inferred from experimental observables. A universal curve valid for arbitrary laser-fusion targets shows the yield amplification due to alpha heating for a given value of the Lawson parameter. The same theory is used to determine the onset of the burning plasma regime when the alpha heating exceeds the compression work. This result can be used to assess the performance of current ignition experiments at the National Ignition Facility.

  1. Simulating the magnetized liner inertial fusion plasma confinement with smaller-scale experiments [Simulating the MagLIF plasma confinement with smaller-scale experiments

    SciTech Connect

    Ryutov, D. D.; Cuneo, M. E.; Herrmann, M. C.; Sinars, D. B.; Slutz, S. A.

    2012-06-20

    The recently proposed magnetized liner inertial fusion approach to a Z-pinch driven fusion [Slutz et al., Phys. Plasmas17, 056303 (2010)] is based on the use of an axial magnetic field to provide plasma thermal insulation from the walls of the imploding liner. The characteristic plasma transport regimes in the proposed approach cover parameter domains that have not been studied yet in either magnetic confinement or inertial confinement experiments. In this article, an analysis is presented of the scalability of the key physical processes that determine the plasma confinement. The dimensionless scaling parameters are identified and conclusion is drawn that the plasma behavior in scaled-down experiments can correctly represent the full-scale plasma, provided these parameters are approximately the same in two systems. Furthermore, this observation is important in that smaller-scale experiments typically have better diagnostic access and more experiments per year are possible.

  2. Laser-plasma interactions relevant to Inertial Confinement Fusion

    SciTech Connect

    Wharton, K.B.

    1998-11-02

    Research into laser-driven inertial confinement fusion is now entering a critical juncture with the construction of the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL). Many of the remaining unanswered questions concerning NIF involve interactions between lasers and plasmas. With the eventual goal of fusion power in mind, laser-plasma interactions relevant to laser fusion schemes is an important topic in need of further research. This work experimentally addresses some potential shortcuts and pitfalls on the road to laser-driven fusion power. Current plans on NIF have 192 laser beams directed into a small cylindrical cavity which will contain the fusion fuel; to accomplish this the beams must cross in the entrance holes, and this intersection will be in the presence of outward-flowing plasma. To investigate the physics involved, interactions of crossing laser beams in flowing plasmas are investigated with experiments on the Nova laser facility at LLNL. It was found that in a flowing plasma, energy is transferred between two crossing laser beams, and this may have deleterious consequences for energy balance and ignition in NIF. Possible solutions to this problem are presented. A recently-proposed alternative to standard laser-driven fusion, the ''fast ignitor'' concept, is also experimentally addressed in this dissertation. Many of the laser-plasma interactions necessary for the success of the fast ignitor have not previously been explored at the relevant laser intensities. Specifically, the transfer of high-intensity laser energy to electrons at solid-target interfaces is addressed. 20-30% conversion efficiencies into forward-propagated electrons were measured, along with an average electron energy that varied with the type of target material. The directionality of the electrons was also measured, revealing an apparent beaming of the highest energy electrons. This work was extended to various intensities and pulse lengths and a

  3. Why Magnetically Confined Plasmas Rotate and Why it is Important

    NASA Astrophysics Data System (ADS)

    Kaye, Stanley

    2012-03-01

    Rotation in tokamak and spherical tokamak magnetic confinement devices has been found to be critical to enhancing the plasma stability to both the electron and ion gyroradius scale-turbulence as well to magnetohydrodynamic (MHD) modes whose characteristic scales can be of order the device size. Suppression of these modes leads to reduced energy and particle transport losses in these plasmas, thus increasing the potential fusion power production. Rotation can also lead to the avoidance of catastrophic MHD events known as ``disruptions.'' This strong impact of the rotation underscores the importance of developing the knowledge of how rotation is generated in these devices and how the momentum is transported through the plasma. Rotation in these plasmas is generated by a number of different torques, including external momentum input from neutral beam injection, and magnetic torques (toroidal viscosity) resulting from a non-axisymmetric magnetic field structure. One leading theory suggests that rotation can also be self-generated from microturbulence. In this strongly coupled, predator-prey-like system, the plasma can self-organize from a turbulent state to one with directed flow in directions both parallel and perpendicular to the magnetic field. The rotation in the perpendicular direction is often seen to have radial structure and is analogous to the Zonal Flows observed in planetary atmospheres. The self-generated, or intrinsic, rotation that flows mainly along the magnetic field, has been measured on virtually all experimental devices. The theory suggests that the intrinsic torque generating the intrinsic rotation is due to long-wavelength (of order the ion gyroradius) modes, and experimental measurements of intrinsic torque and rotation generally follow the trends predicted by theory. Values of the momentum diffusivity and convective pinch term have been determined from perturbation experiments, and their trends indicate that the same modes that drive intrinsic

  4. Transmission Grating Imaging Spectrometer for Magnetically Confined Fusion Plasmas

    NASA Astrophysics Data System (ADS)

    Blagojevic, B.; Stutman, D.; Vero, R.; Finkenthal, M.; Moos, H. W.

    2001-10-01

    The Johns Hopkins Plasma Spectroscopy Group is developing a transmission grating (TG) based imaging spectrometer for the soft and ultrasoft X-ray (USXR) ranges. The spectrometer will be integrated into a multi-purpose impurity diagnostic package for Magnetically Confined Fusion experiments, which will provide time and space resolved information about radiation losses, Zeff profiles and particle transport. The package will also include 2-D filtered USXR diode arrays and atomic physics and impurity transport computational capability. The spectrometer has a very simple layout, consisting of two collimating and space resolving slits, a TG and a 2-D imaging detector. As detector we are developing phosphor (P45) coated fiber optic plates with CCD and intensified CCD image readout. The performance of a test 5000 l/mm, 2:1 bar to open area ratio TG has been evaluated in the laboratory using a K-alpha Manson source and the emission from a Penning Discharge. The incident and diffracted photon flux was recorded in the 10-300 Å range with a gas flow proportional counter. The measurements show that spectral resolution and efficiency agree well with the predicted values. A device optimized for spectral resolution and higher order suppression will be tested on the CDX-U and NSTX tokamak at Princeton Plasma Physics Laboratory. Work supported by DoE grant No. DE-FG02-86ER52314ATDoE

  5. Transport processes in magnetically confined plasmas in the nonlinear regime

    SciTech Connect

    Sonnino, Giorgio

    2006-06-15

    A field theory approach to transport phenomena in magnetically confined plasmas is presented. The thermodynamic field theory (TFT), previously developed for treating the generic thermodynamic system out of equilibrium, is applied to plasmas physics. Transport phenomena are treated here as the effect of the field linking the thermodynamic forces with their conjugate flows combined with statistical mechanics. In particular, the Classical and the Pfirsch-Schlueter regimes are analyzed by solving the thermodynamic field equations of the TFT in the weak-field approximation. We found that, the TFT does not correct the expressions of the ionic heat fluxes evaluated by the neoclassical theory in these two regimes. On the other hand, the fluxes of matter and electronic energy (heat flow) is further enhanced in the nonlinear Classical and Pfirsch-Schlueter regimes. These results seem to be in line with the experimental observations. The complete set of the electronic and ionic transport equations in the nonlinear Banana regime, is also reported. A paper showing the comparison between our theoretic results and the experimental observations in the JET machine is currently in preparation.

  6. Heavy ion plasma confinement in an RF quadrupole trap

    NASA Technical Reports Server (NTRS)

    Schermann, J.; Major, F. G.

    1971-01-01

    The confinement of an electron free plasma in a pure quadrupole RF electric trap was considered. The ultimate goal was to produce a large density of mercury ions, in order to realize a trapped ion frequency standard using the hyperfine resonance of 199 Hg(+) at 40.7 GHz. An attempt was made to obtain an iodine plasma consisting of equal numbers of positive and negative ions of atomic iodine, the positive iodine ions, being susceptible to charge-exchange with mercury atoms, will produce the desired mercury ions. The experiment showed that the photoproduction of ions pairs in iodine using the necessary UV radiation occurs with a small cross-section, making it difficult to demonstrate the feasibility of space charge neutralization in a quadrupole trap. For this reason it was considered expedient to choose thallium iodide, which has a more favorable absorption spectrum (in the region of 2000 to 2100 A). The results indicate that, although the ionic recombination is a serious limiting factor, a considerable improvement can be obtained in practice for the density of trapped ions, with a considerable advantage in lifetimes for spectroscopic purposes. The ion pair formation by photoionization is briefly reviewed.

  7. Internal Kink Quasi-Mode in Magnetically Confined Toroidal Plasmas

    NASA Astrophysics Data System (ADS)

    Porcelli, F.; Candy, J.; Breizman, B.; Berk, H.

    1997-11-01

    A well-known instability of magnetically confined plasmas, the internal kink mode, is thought to be responsible for sawtooth relaxations and fishbone oscillations in tokamak discharges. The mode structure is dominated by the (n,m)=(1,1) Fourier harmonic, with a radial structure characterized by a rigid displacement of the plasma core region (where the safety factor is below unity). In standard linear magnetohydrodynamic (MHD) theory, an eigenmode can be obtained only under unstable conditions (dwmhd < 0). When dwmhd > 0, the solution in the q=1 layer cannot by asymptotically matched to the outer region, and so an eigenmode does not exist. In the more general case where energetic particles modify the energy functional via an additive term, dw = dwmhd + dwhot, the standard theory still fails to provide a well-behaved mode structure when Re dw > 0. In this work, we show how to obtain a mode structure that is valid in both stable and unstable conditions by solving a real-time initial value problem. This extension of the standard linear theory of internal kinks is especially desirable with regard to the development of nonlinear models of the fishbone instability, which attempt to simulate a full fishbone burst. We refer to the internal kink profile that is obtained under stable conditions as a quasi-mode, in view of the fact that the space and time dependences cannot be separated.

  8. Taming Magnetically Confined Plasmas with RF Waves: A Historical Perspective

    NASA Astrophysics Data System (ADS)

    Porkolab, Miklos

    2009-11-01

    Heating and profile control by RF waves in magnetic fusion experiments has led to the development of a new area of physics, namely wave propagation and absorption in high temperature plasmas in complex magnetic field geometries. In addition, the development of high power microwave sources as well as novel antenna structures capable of handling high RF powers has also been necessary. In this talk I shall summarize the historical progression of relevant results in three frequency regimes, namely the ion cyclotron range of frequencies (ICRF), the electron cyclotron frequency and its harmonics (ECRH), and the lower hybrid frequency range (LHRF). In the ICRF regime breakthrough heating results were obtained in the 1980s in tokamaks with good confinement of energetic ions, such as PLT, TFTR and JET. In the period of late 1970s to mid 1980s the theory of RF current drive (LHCD, ECCD and that of fast wave, or FWCD) was developed. Soon thereafter efficient lower hybrid current drive was demonstrated in tokamak experiments such as Versator II, Alcator--C and PLT, and later JT60-U, Tore-Supra and JET. High harmonic FWCD has been also demonstrated on DIII-D and NSTX. Long pulse multi-MW LHCD experiments are now in preparation on the new superconducting tokamaks EAST (China) and K-STAR (Korea). ECRH results in the 1980s and beyond progressed rapidly with the development of gyrotron sources at the MW level and subsequently efficient heating and current drive was demonstrated on DIII-D, Asdex-U, JT-60U and TCV, including the stabilization of neoclassical tearing modes. Recent gyrotron tube development at the MW level at 170 GHz ensures the availability of ECH and ECCD on ITER. Finally, new results on RF induced transport phenomena have been discovered, such as enhanced plasma rotation and flow drive that hold promise for optimizing ITER performance.

  9. Composite Transport Coefficients and Novel Scalings for Well Confined Plasmas

    NASA Astrophysics Data System (ADS)

    Coppi, B.; Daughton, W.

    1997-11-01

    Starting from an analysis of the transport properties of the plasmas produced by the Alcator C-Mod machine over a rather wide variety of conditions, a novel form of a thermal transport coefficient which reproduces both ohmic and auxiliary heated L-mode discharges [1] has been identified. This coefficient involves the difference of two terms, one representing the normal outward diffusion of thermal energy and the other corresponding to a process reducing the outward flux. There are in fact theoretical arguments [2] in support of a composite transport coefficient based on the symmetry properties of an appropriate transport matrix. The relevant scaling for the energy confinement time is also composed of two terms and the L-mode database including D3D, JET, JT60, PDX, TFTR, FTU, Alcator C-Mod is used to construct a general scaling law that is shown to be more comprehensive and accurate than the standard L-mode scaling, particularly for high field experiments. [1] B. Coppi A. Airoldi, F. Bombarda et al., IAEA Conference, F1-CN-64/BP-14 (1996) [2] B. Coppi and F. Pegoraro, Phys. Fluids B 3 2582 (1991)

  10. Improvement of confinement times of lithium ion and electron plasmas in BX-U

    SciTech Connect

    Himura, H.; Noichi, T.; Nakata, S.; Kawai, S.; Sanpei, A.

    2015-06-29

    Confinements of both electron (e{sup −}) and Lithium ion (Li{sup +}) plasmas in the BX-U machine are improved experimentally. For the e{sup −} plasma, the longest confinement time so far has been ∼ 10 s, which is much longer than the classical electron-electron collision time: τ{sub ee} ∼ 0.6 s. On the other hand, for the Li{sup +} plasma, the longest confinement time has been about 0.5 s, which is still much shorter than the classical ion-ion collision time.

  11. Spectrometry of charged particles from inertial-confinement-fusion plasmas

    NASA Astrophysics Data System (ADS)

    Séguin, F. H.; Frenje, J. A.; Li, C. K.; Hicks, D. G.; Kurebayashi, S.; Rygg, J. R.; Schwartz, B.-E.; Petrasso, R. D.; Roberts, S.; Soures, J. M.; Meyerhofer, D. D.; Sangster, T. C.; Knauer, J. P.; Sorce, C.; Glebov, V. Yu.; Stoeckl, C.; Phillips, T. W.; Leeper, R. J.; Fletcher, K.; Padalino, S.

    2003-02-01

    High-resolution spectrometry of charged particles from inertial-confinement-fusion (ICF) experiments has become an important method of studying plasma conditions in laser-compressed capsules. In experiments at the 60-beam OMEGA laser facility [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)], utilizing capsules with D2, D3He, DT, or DTH fuel in a shell of plastic, glass, or D2 ice, we now routinely make spectral measurements of primary fusion products (p, D, T, 3He, α), secondary fusion products (p), "knock-on" particles (p, D, T) elastically scattered by primary neutrons, and ions from the shell. Use is made of several types of spectrometers that rely on detection and identification of particles with CR-39 nuclear track detectors in conjunction with magnets and/or special ranging filters. CR-39 is especially useful because of its insensitivity to electromagnetic noise and its ability to distinguish the types and energies of individual particles, as illustrated here by detailed calibrations of its response to 0.1-13.8 MeV protons from a Van de Graaff accelerator and to p, D, T, and α from ICF experiments at OMEGA. A description of the spectrometers is accompanied by illustrations of their operating principles using data from OMEGA. Sample results and discussions illustrate the relationship of secondary-proton and knock-on spectra to capsule fuel and shell areal densities and radial compression ratios; the relationship of different primary fusion products to each other and to ion temperatures; the relationship of deviations from spherical symmetry in particle yields and energies to capsule structure; the acceleration of fusion products and the spectra of ions from the shell due to external fields; and other important physical characteristics of the laser-compressed capsules.

  12. Simulating the magnetized liner inertial fusion plasma confinement with smaller-scale experiments

    SciTech Connect

    Ryutov, D. D.; Cuneo, M. E.; Herrmann, M. C.; Sinars, D. B.; Slutz, S. A.

    2012-06-15

    The recently proposed magnetized liner inertial fusion approach to a Z-pinch driven fusion [Slutz et al., Phys. Plasmas 17, 056303 (2010)] is based on the use of an axial magnetic field to provide plasma thermal insulation from the walls of the imploding liner. The characteristic plasma transport regimes in the proposed approach cover parameter domains that have not been studied yet in either magnetic confinement or inertial confinement experiments. In this article, an analysis is presented of the scalability of the key physical processes that determine the plasma confinement. The dimensionless scaling parameters are identified and conclusion is drawn that the plasma behavior in scaled-down experiments can correctly represent the full-scale plasma, provided these parameters are approximately the same in two systems. This observation is important in that smaller-scale experiments typically have better diagnostic access and more experiments per year are possible.

  13. System and method for generating steady state confining current for a toroidal plasma fusion reactor

    DOEpatents

    Bers, Abraham

    1981-01-01

    A system for generating steady state confining current for a toroidal plasma fusion reactor providing steady-state generation of the thermonuclear power. A dense, hot toroidal plasma is initially prepared with a confining magnetic field with toroidal and poloidal components. Continuous wave RF energy is injected into said plasma to estalish a spectrum of traveling waves in the plasma, where the traveling waves have momentum components substantially either all parallel, or all anti-parallel to the confining magnetic field. The injected RF energy is phased to couple to said traveling waves with both a phase velocity component and a wave momentum component in the direction of the plasma traveling wave components. The injected RF energy has a predetermined spectrum selected so that said traveling waves couple to plasma electrons having velocities in a predetermined range .DELTA.. The velocities in the range are substantially greater than the thermal electron velocity of the plasma. In addition, the range is sufficiently broad to produce a raised plateau having width .DELTA. in the plasma electron velocity distribution so that the plateau electrons provide steady-state current to generate a poloidal magnetic field component sufficient for confining the plasma. In steady state operation of the fusion reactor, the fusion power density in the plasma exceeds the power dissipated inthe plasma.

  14. System and method for generating steady state confining current for a toroidal plasma fusion reactor

    DOEpatents

    Fisch, Nathaniel J.

    1981-01-01

    A system for generating steady state confining current for a toroidal plasma fusion reactor providing steady-state generation of the thermonuclear power. A dense, hot toroidal plasma is initially prepared with a confining magnetic field with toroidal and poloidal components. Continuous wave RF energy is injected into said plasma to establish a spectrum of traveling waves in the plasma, where the traveling waves have momentum components substantially either all parallel, or all anti-parallel to the confining magnetic field. The injected RF energy is phased to couple to said traveling waves with both a phase velocity component and a wave momentum component in the direction of the plasma traveling wave components. The injected RF energy has a predetermined spectrum selected so that said traveling waves couple to plasma electrons having velocities in a predetermined range .DELTA.. The velocities in the range are substantially greater than the thermal electron velocity of the plasma. In addition, the range is sufficiently broad to produce a raised plateau having width .DELTA. in the plasma electron velocity distribution so that the plateau electrons provide steady-state current to generate a poloidal magnetic field component sufficient for confining the plasma. In steady state operation of the fusion reactor, the fusion power density in the plasma exceeds the power dissipated in the plasma.

  15. Observation of Centrifugally Driven Interchange Instabilities in a Plasma Confined by a Magnetic Dipole

    SciTech Connect

    Levitt, B.; Maslovsky, D.; Mauel, M.E.

    2005-05-06

    Centrifugally driven interchange instabilities are observed in a laboratory plasma confined by a dipole magnetic field. The instabilities appear when an equatorial mesh is biased to drive a radial current that causes rapid axisymmetric plasma rotation. The observed instabilities are quasicoherent in the laboratory frame of reference; they have global radial mode structures and low azimuthal mode numbers, and they are modified by the presence of energetic, magnetically confined electrons. Results from a self-consistent nonlinear simulation reproduce the measured mode structures.

  16. Debye Layers in Plasmas Generalized to Hadron Confinement of Nuclei and Quark-Gluon-Plasmas

    NASA Astrophysics Data System (ADS)

    Hora, Heinrich; Miley, George H.

    2005-10-01

    . A new theory for the nuclear forces for confining the hadrons in a nucleus has been derived from a generalization of the Debye layer as known from the plasma ablation at laser irradiation where the temperature is substituted by the Fermi energy of the nucleons [1]. The first convincing proof is by using the empirical density of the nucleons defining their Fermi energy to arrive at a Debye length of about 3 fm as measured by Hofstadter for the decay of the nucleon density at the surface of heavy nuclei. This decay is interpreted as Wigner scattering and the Goos-Haenchen effect. With the same steps of substitutions, the surface energy of nuclei is always too small against the nucleon enthalpy to confine the hadrons until the density reaches such high values reproducing the empirical known radii of nuclei. By this way nuclei are possible only until uranium or curium by a Boltzmann equilibrium process explaining the endothermic generation of heavy nuclei in the Universe [2]. At and about six times higher nucleon density, the Fermi statistics changes into its relativistic branch excluding nucleation in neutron stars and explaining the quark-gluon plasma. [1] Edward Teller Lectures, H. Hora and G.H. Miley eds. (Imperial College Press London 2005) p. 103. [2] H. Hora, G.H. Miley, F. Osman, Astrophysics and Space Science, 298, 247 (2005)

  17. Plasma Confinement in Glass Microcavities: Dependence of Plasma Properties on Microcavity Geometry.

    NASA Astrophysics Data System (ADS)

    Sung, S. H.; Berger, A. G.; Kim, J.-Y.; Park, S.-J.; Eden, J. G.

    2007-10-01

    Arrays of glass microcavities having diameters of 50-200 μm and controllable geometries have been successfully fabricated by micropowder blasting techniques. Anisotropic or isotropic microcavities, including cavities with ellipsoidal geometry have been fabricated in large scale arrays with high resolution and various shapes of microcavities were prepared precisely. Arrays having as much as 1000 microcavities were fabricated on 400 μm thick soda lime glasses and a pair of these glasses was aligned and sealed to form a closed microdischarge cell. The cross-sectional microcavity shape in the discharge cell is designed from the calculation of electric field distribution. Powered by electrodes located outside the microcavity with ac frequencies of 20-100 kHz, the stable, uniform discharges and confinement of plasma in entire microcavity was observed at 300-800 Torr of noble gases. From the spatially-resolved measurement of emission from a microcavity, the device has better plasma confinement and increased emission intensity in higher gas pressures. Discharge performance in various gas or gas mixtures and its dependence on microcavity geometry will be discussed.

  18. Magnetic Field Required for Ignition in a Magnetically Confined Plasma in Reactor-Type Conditions

    NASA Astrophysics Data System (ADS)

    Panarella, Emilio

    1996-11-01

    A complete and rigorous analysis will be given of the ignition conditions for a pulsed DT plasma magnetically confined, where the conduction losses are introduced from heat transfer theory, rather than from the empirically defined energy confinement time. It will be shown that the magnetic field required for ignition greatly exceeds any of those presently considered for major machines. It will also be shown that ignition is independent of particle density. On the basis of these results it is argued that ignition is facilitated in an inertially confined plasma, both of the classical type with lasers, or with the Spherical Pinch, or the Magnetized Target Fusion concepts.

  19. Studies of plasma confinement in linear and RACETRACK mirror configurations

    SciTech Connect

    Kuthi, A.; Wong, A.Y.

    1986-06-30

    This report discusses research on the following magnetic mirror configurations: Racetrack; ECRH generated plasmas; RF generated plasmas; potential structures; surface multipole fields, and lamex; hot electron physics; axial loss processes; and RF induced effects.

  20. Influence of scrape-off layer on plasma confinement

    SciTech Connect

    Dolan, Thomas J.

    2011-03-15

    The purpose of this paper is to discuss how plasma phenomena in the scrape-off layer (SOL) can affect the plasma density gradient at the separatrix and hence the plasma behavior inside the separatrix. The parallel flow loss rate and ionization rate in the SOL (related to the electron temperature and neutral gas density) affect the curvature of the electron density profile, which limits the density gradient at the separatrix. This density gradient acts like a boundary condition for plasma inside the separatrix, affecting the ion pressure gradient, radial electric field, and plasma behavior.

  1. Ion confinement and transport in a toroidal plasma with externally imposed radial electric fields

    NASA Technical Reports Server (NTRS)

    Roth, J. R.; Krawczonek, W. M.; Powers, E. J.; Kim, Y. C.; Hong, H. Y.

    1979-01-01

    Strong electric fields were imposed along the minor radius of the toroidal plasma by biasing it with electrodes maintained at kilovolt potentials. Coherent, low-frequency disturbances characteristic of various magnetohydrodynamic instabilities were absent in the high-density, well-confined regime. High, direct-current radial electric fields with magnitudes up to 135 volts per centimeter penetrated inward to at least one-half the plasma radius. When the electric field pointed radially toward, the ion transport was inward against a strong local density gradient; and the plasma density and confinement time were significantly enhanced. The radial transport along the electric field appeared to be consistent with fluctuation-induced transport. With negative electrode polarity the particle confinement was consistent with a balance of two processes: a radial infusion of ions, in those sectors of the plasma not containing electrodes, that resulted from the radially inward fields; and ion losses to the electrodes, each of the which acted as a sink and drew ions out of the plasma. A simple model of particle confinement was proposed in which the particle confinement time is proportional to the plasma volume. The scaling predicted by this model was consistent with experimental measurements.

  2. MAGNETIC END CLOSURES FOR PLASMA CONFINING AND HEATING DEVICES

    DOEpatents

    Post, R.F.

    1963-08-20

    More effective magnetic closure field regions for various open-ended containment magnetic fields used in fusion reactor devices are provided by several spaced, coaxially-aligned solenoids utilized to produce a series of nodal field regions of uniform or, preferably, of incrementally increasing intensity separated by lower intensity regions outwardly from the ends of said containment zone. Plasma sources may also be provided to inject plasma into said lower intensity areas to increase plasma density therein. Plasma may then be transported, by plasma diffusion mechanisms provided by the nodal fields, into the containment field. With correlated plasma densities and nodal field spacings approximating the mean free partl cle collision path length in the zones between the nodal fields, optimum closure effectiveness is obtained. (AEC)

  3. APPARATUS FOR MINIMIZING ENERGY LOSSES FROM MAGNETICALLY CONFINED VOLUMES OF HOT PLASMA

    DOEpatents

    Post, R.F.

    1961-10-01

    An apparatus is described for controlling electron temperature in plasma confined in a Pyrotron magnetic containment field. Basically the device comprises means for directing low temperature electrons to the plasma in controlled quantities to maintain a predetermined optimum equilibrium electron temperature whereat minimum losses of plasma ions due to ambipolar effects and energy damping of the ions due to dynamical friction with the electrons occur. (AEC)

  4. Pure electron plasmas confined for 90 ms in a stellarator without electron sources or internal objects

    SciTech Connect

    Brenner, P. W.; Sunn Pedersen, T.

    2012-05-15

    We report on the creation and up to 90 ms sustainment of pure electron plasmas confined in a stellarator without internal objects. Injection of positrons into such plasmas is expected to lead to the creation of the first electron-positron plasma experiments. These newly created plasmas will also allow a study of pure electron plasmas without the perturbing presence of internal objects. The plasmas were created by thermionic emission of electrons from a heated, biased filament that was retracted in 20 ms. The confinement of these transient plasmas is different from that of steady state plasmas with internal objects and emissive filaments, and is generally shorter, limited by ion buildup. The decay time is increased by lowering the neutral pressure, lowering the electron plasma temperature, or operating with neutrals with high ionization energies (helium). These findings are all consistent with ion accumulation being the cause for the shorter than expected confinement times. The magnetic field strength also moderately increases the decay times. The deleterious effect of ions is not expected to imply a similar deleterious effect when introducing positrons, but it implies that ion accumulation must be avoided also in an electron-positron experiment.

  5. Alpha Heating and Burning Plasmas in Inertial Confinement Fusion.

    PubMed

    Betti, R; Christopherson, A R; Spears, B K; Nora, R; Bose, A; Howard, J; Woo, K M; Edwards, M J; Sanz, J

    2015-06-26

    Estimating the level of alpha heating and determining the onset of the burning plasma regime is essential to finding the path towards thermonuclear ignition. In a burning plasma, the alpha heating exceeds the external input energy to the plasma. Using a simple model of the implosion, it is shown that a general relation can be derived, connecting the burning plasma regime to the yield enhancement due to alpha heating and to experimentally measurable parameters such as the Lawson ignition parameter. A general alpha-heating curve is found, independent of the target and suitable to assess the performance of all laser fusion experiments whether direct or indirect drive. The onset of the burning plasma regime inside the hot spot of current implosions on the National Ignition Facility requires a fusion yield of about 50 kJ. PMID:26197131

  6. Alpha heating and burning plasmas in inertial confinement fusion

    SciTech Connect

    Betti, R.; Christopherson, A. R.; Spears, B. K.; Nora, R.; Bose, A.; Howard, J.; Woo, K. M.; Edwards, M. J.; Sanz, J.

    2015-06-01

    Estimating the level of alpha heating and determining the onset of the burning plasma regime is essential to finding the path towards thermonuclear ignition. In a burning plasma, the alpha heating exceeds the external input energy to the plasma. Using a simple model of the implosion, it is shown that a general relation can be derived, connecting the burning plasma regime to the yield enhancement due to alpha heating and to experimentally measurable parameters such as the Lawson ignition parameter. A general alpha-heating curve is found, independent of the target and suitable to assess the performance of all laser fusion experiments whether direct or indirect drive. The onset of the burning plasma regime inside the hot spot of current implosions on the National Ignition Facility requires a fusion yield of about 50 kJ.

  7. Alpha Heating and Burning Plasmas in Inertial Confinement Fusion

    NASA Astrophysics Data System (ADS)

    Betti, R.; Christopherson, A. R.; Spears, B. K.; Nora, R.; Bose, A.; Howard, J.; Woo, K. M.; Edwards, M. J.; Sanz, J.

    2015-06-01

    Estimating the level of alpha heating and determining the onset of the burning plasma regime is essential to finding the path towards thermonuclear ignition. In a burning plasma, the alpha heating exceeds the external input energy to the plasma. Using a simple model of the implosion, it is shown that a general relation can be derived, connecting the burning plasma regime to the yield enhancement due to alpha heating and to experimentally measurable parameters such as the Lawson ignition parameter. A general alpha-heating curve is found, independent of the target and suitable to assess the performance of all laser fusion experiments whether direct or indirect drive. The onset of the burning plasma regime inside the hot spot of current implosions on the National Ignition Facility requires a fusion yield of about 50 kJ.

  8. Spherical fusion plasma-confinement field of Surmac type

    SciTech Connect

    Wipf, S.L.

    1981-01-01

    The concept of a Surmac confinement field that can be completely closed is presented. The internal conductor is magnetically suspended inside large corrugations of a superconducting spherical shell structure that carries the return current. Presently available superconductor technology using superfluid helium cooling allows fields above 1.5T throughout the wall region. Such a Surmac has potential for the study of advanced fuel cycles.

  9. Simulations of plasma confinement in an antihydrogen trap

    SciTech Connect

    Gomberoff, K.; Fajans, J.; Friedman, A.; Grote, D.; Vay, J.-L.; Wurtele, J.S.

    2007-10-15

    The three-dimensional particle-in-cell (3-D PIC) simulation code WARP is used to study positron confinement in antihydrogen traps. The magnetic geometry is close to that of a UC Berkeley experiment conducted, with electrons, as part of the ALPHA collaboration (W. Bertsche et al., AIP Conf. Proc. 796, 301 (2005)). In order to trap antihydrogen atoms, multipole magnetic fields are added to a conventional Malmberg-Penning trap. These multipole fields must be strong enough to confine the antihydrogen, leading to multipole field strengths at the trap wall comparable to those of the axial magnetic field. Numerical simulations reported here confirm recent experimental measurements of reduced particle confinement when a quadrupole field is added to a Malmberg-Penning trap. It is shown that, for parameters relevant to various antihydrogen experiments, the use of an octupole field significantly reducesthe positron losses seen with a quadrupole field. A unique method for obtaining a 3-D equilibrium of the positrons in the trap with a collisionless PIC code was developed especially for the study of the antihydrogen trap; however, it is of practical use for other traps as well.

  10. Simulations of plasma confinement in an antihydrogen trap

    SciTech Connect

    Gomberoff, K.; Fajans, J.; Friedman, A.; Grote, D.; Vay, J.-L.; Wurtele, J. S.

    2007-10-15

    The three-dimensional particle-in-cell (3-D PIC) simulation code WARP is used to study positron confinement in antihydrogen traps. The magnetic geometry is close to that of a UC Berkeley experiment conducted, with electrons, as part of the ALPHA collaboration [W. Bertsche et al., AIP Conf. Proc. 796, 301 (2005)]. In order to trap antihydrogen atoms, multipole magnetic fields are added to a conventional Malmberg-Penning trap. These multipole fields must be strong enough to confine the antihydrogen, leading to multipole field strengths at the trap wall comparable to those of the axial magnetic field. Numerical simulations reported here confirm recent experimental measurements of reduced particle confinement when a quadrupole field is added to a Malmberg-Penning trap. It is shown that, for parameters relevant to various antihydrogen experiments, the use of an octupole field significantly reduces the positron losses seen with a quadrupole field. A unique method for obtaining a 3-D equilibrium of the positrons in the trap with a collisionless PIC code was developed especially for the study of the antihydrogen trap; however, it is of practical use for other traps as well.

  11. 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.

  12. Complex Plasmas in Narrow Channels: Impact of Confinement on the Local Order

    SciTech Connect

    Klumov, B. A.

    2008-10-15

    Two-dimensional (2D) and three-dimensional (3D) quasi-equilibrium configurations of a complex (dusty) plasma in narrow channels are investigated using the molecular dynamics simulations for various confining potentials (confinements). The dynamics of the microparticles is described within the framework of a Langevin thermostat with allowance for the pair interaction between charged particles, which is described by a screened Coulomb potential (Yukawa potential). Two types of confinement: the parabolic electrostatic potential and hard elastic wall are considered. It is shown that the confinement strongly affects the crystallization and the local order of the microparticles in the system under consideration; in particular, the appearance of a new quasicrystalline phase induced by the hard wall confinement is revealed in 3D case.

  13. Formation of a field reversed configuration for magnetic and electrostatic confinement of plasma

    DOEpatents

    Rostoker, Norman; Binderbauer, Michl

    2003-12-16

    A system and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions they are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.

  14. Magnetic and electrostatic confinement of plasma with tuning of electrostatic field

    DOEpatents

    Rostoker, Norman; Binderbauer, Michl; Qerushi, Artan; Tahsiri, Hooshang

    2006-03-21

    A system and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions they are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.

  15. Magnetic and electrostatic confinement of plasma with tuning of electrostatic field

    DOEpatents

    Rostoker, Norman; Binderbauer, Michl; Qerushi, Artan; Tahsiri, Hooshang

    2006-10-10

    A system and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions they are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.

  16. Magnetic and electrostatic confinement of plasma with tuning of electrostatic field

    DOEpatents

    Rostoker, Norman; Binderbauer, Michl; Qerushi, Artan; Tahsiri, Hooshang

    2008-10-21

    A system and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions they are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.

  17. Formation of a field reversed configuration for magnetic and electrostatic confinement of plasma

    DOEpatents

    Rostoker, Norman; Binderbauer, Michl; Qerushi, Artan; Tahsiri, Hooshang

    2007-02-20

    A system and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions they are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.

  18. Formation of a field reversed configuration for magnetic and electrostatic confinement of plasma

    DOEpatents

    Rostoker, Norman; Binderbauer, Michl; Qerushi, Artan; Tahsiri, Hooshang

    2006-02-07

    A system and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions they are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.

  19. Overview of Spontaneous Frequency Chirping in Confined Plasmas

    NASA Astrophysics Data System (ADS)

    Berk, Herbert

    2012-10-01

    Spontaneous rapid frequency chirping is now a commonly observed phenomenon in plasmas with an energetic particle component. These particles typically induce so called weak instabilities, where they excite background waves that the plasma can support such as shear Alfven waves. The explanation for this phenomenon attributes the frequency chirping to the formation of phase space structures in the form of holes and clumps. Normally a saturated mode, in the presence of background dissipation, would be expected decay after saturation as the background plasma absorbs the energy of the excited wave. However the phase space structures take an alternate route, and move to a regions of phase space that are lower energy states of the energetic particle distribution. Through the wave-resonant particle interaction, this movement is locked to the frequency observed by the wave. This phenomenon implies that alternate mechanisms for plasma relaxation need to be considered for plasma states new marginal stability. It is also possible that these chirping mechanisms can be used to advantage to externally control states of plasma.

  20. Study of intermittent small-scale turbulence in Wendelstein 7-AS plasmas during controlled confinement transitions

    NASA Astrophysics Data System (ADS)

    Basse, N. P.; Zoletnik, S.; Michelsen, P. K.; W7-As Team

    2005-01-01

    Confinement transitions in the Wendelstein 7-AS stellarator [H. Renner et al., Plasma Phys. Controlled Fusion 31, 1579 (1989)] can be induced by varying either the internal plasma current or the external magnetic field. In this paper we report on experiments where closely matched confinement states (good and bad) were constructed using the latter method. Analysis using the former scheme has been reported upon previously [S. Zoletnik et al., Plasma Phys. Controlled Fusion 44, 1581 (2002)]. The electron temperature, along with the major spectral characteristics of magnetic and small-scale electron density fluctuations, changes dramatically at the transition from good to bad confinement. The fluctuation power is intermittent, and core bursts traveling in the electron diamagnetic drift (DD) direction are correlated between the bottom and top of the plasma, especially during degraded confinement. A corresponding top-bottom correlation for the edge ion DD direction turbulence feature was not found. Strong correlations are observed both between the two density fluctuation signals and between magnetic and density fluctuations in bad compared to good confinement. The correlation time of the bursts is of order 100μs, similar to the lifetime observed during edge localized modes.

  1. Study of intermittent small-scale turbulence in Wendelstein 7-AS plasmas during controlled confinement transitions

    SciTech Connect

    Basse, N.P.; Zoletnik, S.; Michelsen, P.K.

    2005-01-01

    Confinement transitions in the Wendelstein 7-AS stellarator [H. Renner et al., Plasma Phys. Controlled Fusion 31, 1579 (1989)] can be induced by varying either the internal plasma current or the external magnetic field. In this paper we report on experiments where closely matched confinement states (good and bad) were constructed using the latter method. Analysis using the former scheme has been reported upon previously [S. Zoletnik et al., Plasma Phys. Controlled Fusion 44, 1581 (2002)]. The electron temperature, along with the major spectral characteristics of magnetic and small-scale electron density fluctuations, changes dramatically at the transition from good to bad confinement. The fluctuation power is intermittent, and core bursts traveling in the electron diamagnetic drift (DD) direction are correlated between the bottom and top of the plasma, especially during degraded confinement. A corresponding top-bottom correlation for the edge ion DD direction turbulence feature was not found. Strong correlations are observed both between the two density fluctuation signals and between magnetic and density fluctuations in bad compared to good confinement. The correlation time of the bursts is of order 100 {mu}s, similar to the lifetime observed during edge localized modes.

  2. 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).].

  3. Convective plasma stability consistent with MHD equilibrium in magnetic confinement systems with a decreasing field

    SciTech Connect

    Tsventoukh, M. M.

    2010-10-15

    A study is made of the convective (interchange, or flute) plasma stability consistent with equilibrium in magnetic confinement systems with a magnetic field decreasing outward and large curvature of magnetic field lines. Algorithms are developed which calculate convective plasma stability from the Kruskal-Oberman kinetic criterion and in which the convective stability is iteratively consistent with MHD equilibrium for a given pressure and a given type of anisotropy in actual magnetic geometry. Vacuum and equilibrium convectively stable configurations in systems with a decreasing, highly curved magnetic field are calculated. It is shown that, in convectively stable equilibrium, the possibility of achieving high plasma pressures in the central region is restricted either by the expansion of the separatrix (when there are large regions of a weak magnetic field) or by the filamentation of the gradient plasma current (when there are small regions of a weak magnetic field, in which case the pressure drops mainly near the separatrix). It is found that, from the standpoint of equilibrium and of the onset of nonpotential ballooning modes, a kinetic description of convective stability yields better plasma confinement parameters in systems with a decreasing, highly curved magnetic field than a simpler MHD model and makes it possible to substantially improve the confinement parameters for a given type of anisotropy. For the Magnetor experimental compact device, the maximum central pressure consistent with equilibrium and stability is calculated to be as high as {beta} {approx} 30%. It is shown that, for the anisotropy of the distribution function that is typical of a background ECR plasma, the limiting pressure gradient is about two times steeper than that for an isotropic plasma. From a practical point of view, the possibility is demonstrated of achieving better confinement parameters of a hot collisionless plasma in systems with a decreasing, highly curved magnetic field

  4. 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.

  5. Characterization of the Horizontal Confinement Produced by a Glass Box in a Complex Plasma

    NASA Astrophysics Data System (ADS)

    Bradshaw, Jace; Douglass, Angela

    2013-10-01

    The majority of plasmas in the visible universe are complex plasmas, consisting of not only electrons, ions, and neutral particles, but also small, usually micron-sized particles called ``dust.'' Recent complex plasma experiments have placed a glass box on the lower electrode of a GEC RF reference cell in order to alter the electric confinement experienced by micrometer-sized particles in the plasma. While this has led to interesting observations, such as vertical chains and Coulomb balls, the nature of the confinement is not well understood. In this experiment, a single melamine formaldehyde dust particle was levitated in the plasma sheath and contained by a glass box. The dust particle was then struck by a laser pulse to perturb the particle from its equilibrium position. The trajectory of the particle was analyzed to determine the nature of the electric potential produced by the walls of the glass box. Trials were run with varying pressures, particle sizes, box sizes, and plasma powers to determine the effect of each parameter on the confinement.

  6. 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.

  7. Enhanced efficiency of laser shock cleaning process by geometrical confinement of laser-induced plasma

    SciTech Connect

    Jang, Deoksuk; Oh, Joon Ho; Kim, Dongsik; Lee, Jong-Myoung

    2009-07-01

    Surface cleaning based on the laser-induced breakdown of gas and subsequent plasma and shock wave generation can remove small particles from solid surfaces. Accordingly, several studies were performed to expand the cleaning capability of the process. In this work, the cleaning process using laser-induced plasma (LIP) under geometrical confinement is analyzed both theoretically and experimentally. Two-dimensional numerical analysis is conducted to examine the behavior of the LIP shock wave under geometrical confinement for several geometries. As a result of the analysis, we propose a simple and practical method to amplify the intensity of laser-induced shock. In the proposed method, a flat quartz plate placed close to the focal point of the laser pulse confines the expansion of the LIP, allowing the plasma to expand only in one direction. As a consequence of the plasma confinement, the intensity of the shock wave produced is increased significantly. Experiments demonstrate that the enhanced shock wave can remove smaller particles from the surface better than the existing process.

  8. Density distribution of a rotating plasma in Tornado magnetic confinement systems

    SciTech Connect

    Kuznetsov, V.M.; Pakhomov, A.B.; Rusakov, A.I.

    1984-12-01

    The density distribution of a rotating plasma in a Tornado magnetic confinement system is calculated under the assumption that the plasma rotates at constant angular velocity throughout the region bounded by the separatrix. The component of the centrifugal inertial force parallel to the magnetic force lines is shown to pinch the plasma toward the equatorial plane of the system. The density distribution depends on the ratio v/T of the plasma drift velocity and temperature. The experimentally measured density distribution can be used to determine v/T and thus to analyze the rotating plasma. If v is known for the rotating plasma then T can be calculated from v, and vice versa.

  9. Study of plasma confinement in ELMO Bumpy Torus with a heavy-ion beam probe

    SciTech Connect

    Bieniosek, F. M.

    1981-01-01

    Plasma confinement in ELMO Bumpy Torus (EBT) is generally strongly dependent on an ambipolar electric field. Spatially resolved measurements of the resulting electric space potential phi/sub sp/ have been made in a single plasma cross section by the heavy-ion beam probe. This diagnostic injects a 4-60-keV beam of (usually) Cs/sup +/ ions into the plasma. Measurement of the energy of Cs/sup 2 +/ secondary ions leaving the plasma gives a continuous monitor of the local space potential. In addition, the total detected Cs/sup 2 +/ ion current is proportional to the product of the local electron density and the ionization rate, which, in turn, is a function of the electron temperature. This signal, nf(T/sub e/), is sensitive to all three electron distributions found in EBT - those of the cold surface plasma, the warm core plasma, and the hot electron ring.

  10. Multi-fluid studies of plasma shocks relevant to inertial confinement fusion

    NASA Astrophysics Data System (ADS)

    Srinivasan, B.; Kagan, G.; Adams, C. S.

    2016-05-01

    Results from inertial confinement fusion (ICF) experiments performed at the Omega laser facility suggest the potential role of kinetic effects in plasmas during implosion. Recent theoretical and numerical work has indicated the importance of diffusion effects in the presence of multiple ion species as well as the importance of ion viscosity. This provides the motivation to adequately develop multi-fluid plasma models capable of capturing kinetic physics including concentration diffusion and ion species separation driven by the ion concentration gradient, the ion pressure gradient, the electron and ion temperature gradients, and the electric field. Benchmarks between the newly developed code and analytical results are presented for multi-fluid plasma shocks.

  11. K-alpha conversion efficiency measurments for x-ray scattering in inertial confinement fusion plasmas

    SciTech Connect

    Kritcher, A L; Neumayer, P; Urry, M K; Robey, H; Niemann, C; Landen, O L; Morse, E; Glenzer, S H

    2006-11-21

    The conversion efficiency of ultra short-pulse laser radiation to K-{alpha} x-rays has been measured for various chlorine-containing targets to be used as x-ray scattering probes of dense plasmas. The spectral and temporal properties of these sources will allow spectrally-resolved x-ray scattering probing with picosecond temporal resolution required for measuring the plasma conditions in inertial confinement fusion experiments. Simulations of x-ray scattering spectra from these plasmas show that fuel capsule density, capsule ablator density, and shock timing information may be inferred.

  12. Tridimensional Burning Structures Associated with Anisotropic Thermal Conductivities in Magnetically Confined and Pulsar Plasmas

    NASA Astrophysics Data System (ADS)

    Cardinali, A.; Coppi, B.; Sonnino, G.

    2015-11-01

    A surprising result of the most recent theory of the thermonuclear instability, which can take place in D-T plasmas close to ignition, is that it can develop with tridimensional structures emerging from an axisymmetric toroidal confinement configurations. These structures are helical filaments (``snakes'') that are localized radially around a given rational magnetic surface. Until now well known analyses of fusion burning processes in magnetically confined plasmas, that include the thermonuclear instability, have been carried out by 1+1/2 D transport codes and, consequently, the onset of tri-dimensional structures has not been investigated. The importance of the electron thermal conductivities anisotropy is pointed out also for the inhomogeneous thermonuclear burning of plasmas on the surface of pulsars and for the formation of the observed bright spots on some of them. Sponsored in part by the U.S. DoE.

  13. Hot-electron plasma formation and confinement in the tandem mirror experiment-upgrade

    SciTech Connect

    Ress, D.B.

    1988-06-01

    The tandem mirror experiment-upgrade (TMX-U) at the Lawrence Livermore National Laboratory (LLNL) is the first experiment to investigate the thermal-barrier tandem-mirror concept. One attractive feature of the tandem magnetic mirror as a commercial power reactor is that the fusion reactions occur in an easily accessible center-cell. On the other hand, complicated end-cells are necessary to provide magnetohydrodynamic (MHD) stability and improved particle confinement of the center-cell plasma. In these end-cells, enhanced confinement is achieved with a particular axial potential profile that is formed with electron-cyclotron range-of-frequency heating (ECRF heating, ECRH). By modifying the loss rates of electrons at spatially distinct locations within the end-cells, the ECRH can tailor the plasma potential profile in the desired fashion. Specifically, the thermal-barrier concept requires generation of a population of energetic electrons near the midplane of each end-cell. To be effective, the transverse (to the magnetic field) spatial structure of the hot-electron plasma must be fairly uniform. In this dissertation we characterize the spatial structure of the ECRH-generated plasma, and determine how the structure builds up in time. Furthermore, the plasma should efficiently absorb the ECRF power, and a large fraction of the electrons must be well confined near the end-cell midplane. Therefore, we also examine in detail the ECRH power balance, determining how the ECRF power is absorbed by the plasma, and the processes through which that power is confined and lost. 43 refs., 69 figs., 6 tabs.

  14. Laboratory studies of kinetic instabilities under double plasma resonance condition in a mirror-confined non-equilibrium plasma

    NASA Astrophysics Data System (ADS)

    Viktorov, Mikhail; Golubev, Sergey; Mansfeld, Dmitry; Vodopyanov, Alexander; Zaitsev, Valery

    2016-04-01

    Plasma instabilities in magnetic traps on the Sun are the sources of powerful broadband radio emission (the so-called type IV bursts) which is interpreted as the excitation of plasma waves by fast electrons in the upper hybrid resonance frequency followed by transformation in electromagnetic waves. In the case of double plasma resonance condition when the frequency of the upper hybrid resonance coincides with one of the electron gyrofrequency harmonics the instability increment of plasma waves is greatly increased. This leads to the appearance of bright narrow-band radio emission near the harmonics of the electron gyrofrequency - the so-called zebra patterns. With the use of non-equilibrium mirror-confined plasma produced by the electron cyclotron resonance (ECR) discharge we provide the possibility to study plasma instabilities under double plasma resonance condition in the laboratory. In the experiment such conditions are fulfilled just after ECR heating switch-off, i.e. in the very beginning of a dense plasma decay phase. The observed instability is accompanied by a pulse-periodic generation of a powerful electromagnetic radiation at a frequency close to the upper hybrid resonance frequency and a second harmonic of the electron gyrofrequency, and synchronous precipitations of fast electrons from the trap ends. It is shown that the observed instability is due to the excitation of plasma waves at a double plasma resonance in decaying plasma of the ECR discharge. Possible manifestations of double plasma resonance effect are not rare in astrophysical plasmas. The phenomenon of zebra pattern is observed not only on the Sun, but in the decametric radiation of the Jupiter, kilometric radiation of the Earth and even in the radio emissions of pulsars. Thus, verification of the effect of double plasma resonance in a laboratory plasma experiments is a very relevant task.

  15. Surface-confined activation of ultra low-k dielectrics in CO2 plasma

    NASA Astrophysics Data System (ADS)

    Sun, Yiting; Krishtab, Mikhail; Mankelevich, Yuri; Zhang, Liping; De Feyter, Steven; Baklanov, Mikhail; Armini, Silvia

    2016-06-01

    An approach allowing surface-confined activation of porous organosilicate based low-k dielectrics is proposed and studied. By examining the plasma damage mechanism of low-k, we came up with an initial idea that the main requirements for the surface-confined modification would be the high reactivity and high recombination rate of the plasma species. Based on this concept, CO2 plasma was selected and benchmarked with several other plasmas. It is demonstrated that a short exposure of organosilicate low-k films to CO2 plasma enables high surface hydrophilicity with limited bulk modification. CO2+ ions predominantly formed in this plasma have high oxidation potential and efficiently remove surface -CH3 groups from low-k. At the same time, the CO2+ ions get easily discharged (deactivated) during their collisions with pore walls and therefore have very limited probability of penetration into the low-k bulk. Low concentration of oxygen radicals is another factor avoiding the bulk damage. The chemical reactions describing the interactions between CO2 plasma and low-k dielectrics are proposed.

  16. Nonlinear competition of turbulent structures and improved confinement in magnetized cylindrical plasmas

    NASA Astrophysics Data System (ADS)

    Sasaki, M.; Kasuya, N.; Itoh, K.; Yagi, M.; Itoh, S.-I.

    2014-11-01

    Nonlinear competition of turbulent structures and their roles in transport are investigated by using three-dimensional simulation code of resistive drift wave turbulence in magnetized cylindrical plasmas. Selective formation of zonal flows and streamers has been obtained by controlling the strength of damping of the zonal flow. In addition, there is an energy path from the drift waves to a flute type structure, which is linearly stable, and it becomes effective just below the stability boundary of the zonal flow. The flute structure directly induces transport effectively, and affects the drift waves and the zonal flow. A large amplitude zonal flow is formed selectively even with existence of the flute structure. The property of the particle confinement is investigated by changing the particle source intensity, which controls the strength of driving of the drift waves. The characteristic of the particle confinement changes according to turbulent states, and an improved confinement regime is obtained in the zonal flow dominant state. Study on cylindrical plasmas reveals the fundamental mechanism of improved confinement in the magnetized plasma with influence of turbulent structural formation.

  17. Traitement par plasma thermique d'une liqueur caustique pour la destruction des cyanures

    NASA Astrophysics Data System (ADS)

    Fortin, Luc

    L'objectif principal de cette recherche est d'evaluer la possibilite de traiter le lixiviat de brasques usees produit par le procede LCL&L (Lixiviation a bas caustique et chaulage) par contact direct avec un jet de plasma thermique. L'utilisation d'un chalumeau au plasma permet d'eliminer les problemes de reaction avec les produits de combustion relies a l'utilisation de chalumeaux conventionnels (e.g. carbonatation du NaOH en Na2CO3). Le fait de se servir de ce type de chalumeau en mode submerge pour le traitement d'une solution liquide constitue l'originalite du projet. Les essais effectues dans le cadre de ce travail experimental sont realises a l'echelle banc d'essai dans un premier temps. Ils visent a determiner le taux de decomposition des cyanures contenus dans le lixiviat sous des conditions de plasma thermique en fonction de differents parametres et a faire la mise a l'echelle d'un reacteur pilote. La puissance electrique fournie au chalumeau, la temperature et la pression d'operation, le point d'addition d'eau, le volume de lixiviat traite et l'addition de peroxyde d'hydrogene (H2O2) comme co-reactif ont tous un impact sur le taux de destruction des cyanures trouve. Sous toutes les conditions etudiees, le reacteur plasma offre un taux de destruction plus rapide qu'un reacteur agite sous pression pour une meme concentration en cyanures. Ainsi, la comparaison de la constante cinetique obtenue pour le reacteur agite avec une constante similaire pour le reacteur plasma (pente du graphique -ln(C/C0) en fonction du temps) est de 0.04x10-3 s-1 vs 0.59x10-3 s-1 a 100°C et de 1.85x10-3 s-1' vs 3x10 -3 s-1s a 170°C. Ces resultats confirment que le plasma joue un role important sur la decomposition des cyanures et qu'il contribue a en augmenter le taux de destruction. Suite aux connaissances acquises sur le banc d'essai, un reacteur pilote est concu. Un chalumeau au plasma d'une puissance de 60 kW-150 kW et fonctionnant avec l'air comme gaz plasmagene y est

  18. Spectroscopic, imaging, and probe diagnostics of laser plasma plumes expanding between confining surfaces

    SciTech Connect

    Yeates, P.; Kennedy, E. T.

    2010-11-15

    Laser plasma plumes were generated in aluminum rectangular cavities of fixed depth (6 mm) and varying height (2.0, 1.5, and 1.0 mm). Space and time resolved visible emission spectroscopy, gated intensified visible imaging, and Langmuir probe diagnostics were utilized to diagnose the evolution of the confined plasma plumes in comparison to freely expanding plasma plume generated from ablation of a planar target. The constrained plasma behavior displayed a multiphase history. Early stage interactions (t<100 ns) resulted in enhanced continuum and line emission, shockwave formation and plasma plume rebound. Later phase, long duration plasma-surface interactions (t>160 ns) resulted in sustained 'decay', i.e., a rapid termination of continuum emission, in concert with decreases in peak electron density (N{sub e}) and plasma temperature (T). This later phase originates from loss mechanisms which bleed the plasma plume of thermal energy and charged particles. These loss mechanisms increase in magnitude as the duration of the plasma-surface interaction increases. The transition from enhancement phase, originating from hydrodynamic containment, and plasma-surface collisions, to decay phase is described and occurs for each cavity at a different point in the space time history.

  19. Improved confinement region without large magnetohydrodynamic activity in TPE-RX reversed-field pinch plasma

    SciTech Connect

    Yambe, Kiyoyuki; Hirano, Yoichi; Sakakita, Hajime; Koguchi, Haruhisa

    2014-11-15

    We found that spontaneous improved confinement was brought about depending on the operating region in the Toroidal Pinch Experiment-Reversed eXperiment (TPE-RX) reversed-field pinch plasma [Y. Yagi et al., Fusion Eng. Des. 45, 421 (1999)]. Gradual decay of the toroidal magnetic field at plasma surface B{sub tw} reversal makes it possible to realize a prolonged discharge, and the poloidal beta value and energy confinement time increase in the latter half of the discharge, where reversal and pinch parameters become shallow and low, respectively. In the latter half of the discharge, the plasma current and volume-averaged toroidal magnetic field 〈B{sub t}〉 increase again, the electron density slowly decays, the electron temperature and soft X-ray radiation intensity increase, and the magnetic fluctuations are markedly reduced. In this period of improved confinement, the value of (〈B{sub t}〉-B{sub tw})/B{sub pw}, where B{sub pw} is the poloidal magnetic field at the plasma surface, stays almost constant, which indicates that the dynamo action occurs without large magnetohydrodynamic activities.

  20. 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.

  1. Confinement effects of magnetic field on two-dimensional hydrogen atom in plasmas

    SciTech Connect

    Bahar, M. K.; Soylu, A.

    2015-05-15

    In this study, for the first time, the Schrödinger equation with more general exponential cosine screened Coulomb (MGECSC) potential is solved numerically in the presence and in the absence of an external magnetic field within two-dimensional formalism using the asymptotic iteration method. The MGECSC potential includes four different potential forms when considering different sets of the parameters in the potential. The plasma screening effects in the weak and strong magnetic field regimes as well as the confinement effects of magnetic field on the two-dimensional hydrogen atom in Debye and quantum plasmas are investigated by solving the corresponding equations. It is found that applying a uniform magnetic field on the hydrogen atom embedded in a plasma leads to change in the profile of the total interaction potential. Thus, confinement effects of magnetic field on hydrogen atom embedded in Debye and quantum plasmas modeled by a MGECSC potential lead to shift bound state energies. This effect would be important to isolate the plasma from the external environment in the experimental applications of plasma physics.

  2. Fast Ion Confinement in High Beta, Steady-State Scenario Plasmas

    NASA Astrophysics Data System (ADS)

    Heidbrink, W. W.; Chen, X.; Ferron, J. R.; van Zeeland, M. A.; Grierson, B. A.; Holcomb, C. T.

    2013-10-01

    Fast-ion confinement is studied for qmin between 1.2-2.8 in plasmas with normalized β > 2 . 6 . Fast-ion D-alpha (FIDA), neutron, and neutral-particle diagnostics measure the confined fast ions. Tearing modes and a ``sea'' of unstable Alfvén eigenmodes (AE) are observed. In preliminary analysis, the degradation in fast-ion confinement increases with qmin ; increased AE activity appears responsible. Predictions of a model that assumes that AE-induced fast-ion transport is stiff are compared with the data. Work supported by the US Department of Energy under SC-G903402, DE-FC-02-04ER54698, DE-AC02-09CH11466, and DE-AC52-07NA27344.

  3. Plasma sweeper to control the coupling of RF power to a magnetically confined plasma

    DOEpatents

    Motley, Robert W.; Glanz, James

    1985-01-01

    A device for coupling RF power (a plasma sweeper) from a phased waveguide array for introducing RF power to a plasma having a magnetic field associated therewith comprises at least one electrode positioned near the plasma and near the phased waveguide array; and a potential source coupled to the electrode for generating a static electric field at the electrode directed into the plasma and having a component substantially perpendicular to the plasma magnetic field such that a non-zero vector cross-product of the electric and magnetic fields exerts a force on the plasma causing the plasma to drift.

  4. Robustness of predator-prey models for confinement regime transitions in fusion plasmas

    SciTech Connect

    Zhu, H.; Chapman, S. C.; Dendy, R. O.

    2013-04-15

    Energy transport and confinement in tokamak fusion plasmas is usually determined by the coupled nonlinear interactions of small-scale drift turbulence and larger scale coherent nonlinear structures, such as zonal flows, together with free energy sources such as temperature gradients. Zero-dimensional models, designed to embody plausible physical narratives for these interactions, can help to identify the origin of enhanced energy confinement and of transitions between confinement regimes. A prime zero-dimensional paradigm is predator-prey or Lotka-Volterra. Here, we extend a successful three-variable (temperature gradient; microturbulence level; one class of coherent structure) model in this genre [M. A. Malkov and P. H. Diamond, Phys. Plasmas 16, 012504 (2009)], by adding a fourth variable representing a second class of coherent structure. This requires a fourth coupled nonlinear ordinary differential equation. We investigate the degree of invariance of the phenomenology generated by the model of Malkov and Diamond, given this additional physics. We study and compare the long-time behaviour of the three-equation and four-equation systems, their evolution towards the final state, and their attractive fixed points and limit cycles. We explore the sensitivity of paths to attractors. It is found that, for example, an attractive fixed point of the three-equation system can become a limit cycle of the four-equation system. Addressing these questions which we together refer to as 'robustness' for convenience is particularly important for models which, as here, generate sharp transitions in the values of system variables which may replicate some key features of confinement transitions. Our results help to establish the robustness of the zero-dimensional model approach to capturing observed confinement phenomenology in tokamak fusion plasmas.

  5. Divertor plasma conditions and neutral dynamics in horizontal and vertical divertor configurations in JET-ILW low confinement mode plasmas

    NASA Astrophysics Data System (ADS)

    Groth, M.; Brezinsek, S.; Belo, P.; Brix, M.; Calabro, G.; Chankin, A.; Clever, M.; Coenen, J. W.; Corrigan, G.; Drewelow, P.; Guillemaut, C.; Harting, D.; Huber, A.; Jachmich, S.; Järvinen, A.; Kruezi, U.; Lawson, K. D.; Lehnen, M.; Maggi, C. F.; Marchetto, C.; Marsen, S.; Maviglia, F.; Meigs, A. G.; Moulton, D.; Silva, C.; Stamp, M. F.; Wiesen, S.

    2015-08-01

    Measurements of the plasma conditions at the low field side target plate in JET ITER-like wall ohmic and low confinement mode plasmas show minor differences in divertor plasma configurations with horizontally and vertically inclined targets. Both the reduction of the electron temperature in the vicinity of the strike points and the rollover of the ion current to the plates follow the same functional dependence on the density at the low field side midplane. Configurations with vertically inclined target plates, however, produce twice as high sub-divertor pressures for the same upstream density. Simulations with the EDGE2D-EIRENE code package predict significantly lower plasma temperatures at the low field side target in vertical than in horizontal target configurations. Including cross-field drifts and imposing a pumping by-pass leak at the low-field side plate can still not recover the experimental observations.

  6. Plasma confinement to enhance the momentum coupling coefficient in ablative laser micro-propulsion: a novel approach

    NASA Astrophysics Data System (ADS)

    Ahmad, Muhammad Raza; Jamil, Yasir; Qaiser Zakaria, M.; Hussain, Tousif; Ahmad, Riaz

    2015-07-01

    We introduce for the first time the novel idea of manipulating the momentum coupling coefficient using plasma confinement and shock wave reflection from the cavity walls. The plasma was confined using cylindrical geometries of various cavity aspect ratios to manipulate the momentum coupling coefficient (C m ). The Nd: YAG laser (532 nm, 5 ns pulse duration) was focused on the ferrite sample surface to produce plasma in a region surrounded by cylindrical cavity walls. The multiple reflections of the shockwaves from the cavity walls confined the laser-induced plasma to the central region of the cavity that subsequently resulted in a significant enhancement of the momentum coupling coefficient values. The plasma shielding effect has also been observed for particular values of laser fluencies and cavity aspect ratios. Compared with the direct ablation, the confined ablation provides an effective way to obtain high C m values.

  7. Banana fluxes in the plateau regime for a nonaxisymmetrically confined plasma

    SciTech Connect

    Balescu, R.; Fantechi, S. )

    1990-09-01

    The banana (or banana-plateau) fluxes, related to the generalized stresses {l angle}{bold B}{center dot}{del}{center dot}{pi}{sup {alpha}({ital n})}{r angle}, {l angle}{bold B}{sub {ital T}}{center dot}{del}{center dot}{pi}{sup {alpha}({ital n})}{r angle} have been determined in the plateau regime, for a plasma confined by a toroidal magnetic field of arbitrary geometry. The complete set of transport coefficients for both the parallel'' (ambipolar) and toroidal'' (nonambipolar) banana fluxes was obtained in the 13-moment (13M) approximation, going beyond the previously known expressions in the nonaxisymmetric case. The main emphasis is laid on the structure of the transport matrix and of its coefficients. It is shown that the Onsager symmetry of this matrix partly breaks down (for the mixed electron--ion coefficients) in a nonaxisymmetrically confined plasma.

  8. Is Onsager symmetry relevant in the transport equations for magnetically confined plasmas

    SciTech Connect

    Balescu, R. )

    1991-03-01

    A global, algebraic view of the transport processes in a magnetically confined plasma is developed. Both the neoclassical (banana) and the anomalous transport matrices are represented in a factorized form, thus separating the roles of the dynamics and of the geometric constraints. The self-adjointness of the collision operator (the sole condition for classical Onsager symmetry) is shown to be a necessary, but not sufficient condition for this symmetry in confined plasmas. The latter results for the banana transport matrix from a delicate relationship between dynamic and geometric components. This structure is not present in the anomalous transport matrix, and the Onsager symmetry is broken in this case. It is stressed that the symmetry breaking does not violate any general principles.

  9. A low energy positron accumulator for the plasma confinement in a compact magnetic mirror trap

    SciTech Connect

    Higaki, Hiroyuki Kaga, Chikato; Nagayasu, Katsushi; Okamoto, Hiromi; Nagata, Yugo; Kanai, Yasuyuki; Yamazaki, Yasunori

    2015-06-29

    A low energy positron accumulator was constructed at RIKEN for the purpose of confining an electron-positron plasma. The use of 5 mCi {sup 22}Na RI source with a standard solid Ne moderator and N{sub 2} buffer gas cooling resulted in a low energy positron yield of ∼ 3 × 10{sup 5} e+/s. So far, 2 × 10{sup 6} positrons have been accumulated in 120s.

  10. 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.

  11. Experimental Observation of a Periodically Oscillating Plasma Sphere in a Gridded Inertial Electrostatic Confinement Device

    SciTech Connect

    Park, J.; Nebel, R.A.; Stange, S.; Murali, S. Krupakar

    2005-07-01

    The periodically oscillating plasma sphere (POPS) [D. C. Barnes and R. A. Nebel, Phys. Plasmas 5, 2498 (1998).] oscillation has been observed in a gridded inertial electrostatic confinement device. In these experiments, ions in the virtual cathode exhibit resonant behavior when driven at the POPS frequency. Excellent agreement between the observed POPS resonance frequency and theoretical predictions has been observed for a wide range of potential well depths and for three different ion species. The results provide the first experimental validation of the POPS concept proposed by Barnes and Nebel [R. A. Nebel and D. C. Barnes, Fusion Technol. 34, 28 (1998).].

  12. Ion flux enhancements and oscillations in spatially confined laser produced aluminum plasmas

    SciTech Connect

    Singh, S. C. Fallon, C.; Hayden, P.; Yeates, P.; Costello, J. T.; Mujawar, M.

    2014-09-15

    Ion signals from laser produced plasmas (LPPs) generated inside aluminum rectangular cavities at a fixed depth d = 2 mm and varying width, x = 1.0, 1.6, and 2.75 mm were obtained by spatially varying the position of a negatively biased Langmuir probe. Damped oscillatory features superimposed on Maxwellian distributed ion signals were observed. Depending on the distance of the probe from the target surface, three to twelve fold enhancements in peak ion density were observed via confinement of the LPP, generated within rectangular cavities of varying width which constrained the plasma plume to near one dimensional expansion in the vertical plane. The effects of lateral spatial confinement on the expansion velocity of the LPP plume front, the temperature, density and expansion velocity of ions, enhancement of ion flux, and ion energy distribution were recorded. The periodic behavior of ion signals was analyzed and found to be related to the electron plasma frequency and electron-ion collision frequency. The effects of confinement and enhancement of various ion parameters and expansion velocities of the LPP ion plume are explained on the basis of shock wave theory.

  13. An empirical scaling law for improved confinement in reversed-field pinch plasmas

    NASA Astrophysics Data System (ADS)

    Yagi, Y.; Koguchi, H.; Hirano, Y.; Sakakita, H.; Frassinetti, L.

    2005-02-01

    A database of the confinement properties of the toroidal pinch experiment (TPE) series reversed-field pinch (RFP) devices was established, and an empirical scaling law for the energy confinement time, τE, was deduced for a consistently selected set of the database (Yagi Y. et al 2003 Nucl. Fusion 43 1787). The scaling for τE [TPE-scaling; \\smash{\\tau _E \\sim a^{1.7} I_p^{0.8} (I_p/N)^{0.3} \\Theta ^{3}} ], in particular, is a power law similar to that predicted on the basis of the tearing modes, as a function of the plasma minor radius (a), plasma current (Ip), and Ip/N, where N is the column density. On the other hand, the TPE-scaling has a strong dependence on the pinch parameter, Θ, namely τE ~ Θ3. Recently, we have investigated the database of the improved confinement in the pulsed poloidal current drive (PPCD). We show that the TPE-scaling agrees well with the improved τE in the PPCD database, because of its strong Θ dependence. Namely, Θ3 is a factor of merit for RFP plasmas. We discuss why this agreement is obtained in spite of the general difference between the underlying transport mechanisms of the standard and PPCD discharges. We also show that this improvement, represented by Θ3, is related to the increase in magnetic shear with Θ.

  14. Ion flux enhancements and oscillations in spatially confined laser produced aluminum plasmas

    NASA Astrophysics Data System (ADS)

    Singh, S. C.; Fallon, C.; Hayden, P.; Mujawar, M.; Yeates, P.; Costello, J. T.

    2014-09-01

    Ion signals from laser produced plasmas (LPPs) generated inside aluminum rectangular cavities at a fixed depth d = 2 mm and varying width, x = 1.0, 1.6, and 2.75 mm were obtained by spatially varying the position of a negatively biased Langmuir probe. Damped oscillatory features superimposed on Maxwellian distributed ion signals were observed. Depending on the distance of the probe from the target surface, three to twelve fold enhancements in peak ion density were observed via confinement of the LPP, generated within rectangular cavities of varying width which constrained the plasma plume to near one dimensional expansion in the vertical plane. The effects of lateral spatial confinement on the expansion velocity of the LPP plume front, the temperature, density and expansion velocity of ions, enhancement of ion flux, and ion energy distribution were recorded. The periodic behavior of ion signals was analyzed and found to be related to the electron plasma frequency and electron-ion collision frequency. The effects of confinement and enhancement of various ion parameters and expansion velocities of the LPP ion plume are explained on the basis of shock wave theory.

  15. Une alternative au cobalt pour la synthese de nanotubes de carbone monoparoi par plasma inductif thermique

    NASA Astrophysics Data System (ADS)

    Carrier, Jean-Francois

    Les nanotubes de carbone de type monoparoi (C-SWNT) sont une classe recente de nanomateriaux qui ont fait leur apparition en 1991. L'interet qu'on leur accorde provient des nombreuses proprietes d'avant-plan qu'ils possedent. Leur resistance mecanique serait des plus rigide, tout comme ils peuvent conduire l'electricite et la chaleur d'une maniere inegalee. Non moins, les C-SWNT promettent de devenir une nouvelle classe de plateforme moleculaire, en servant de site d'attache pour des groupements reactifs. Les promesses de ce type particulier de nanomateriau sont nombreuses, la question aujourd'hui est de comment les realiser. La technologie de synthese par plasma inductif thermique se situe avantageusement pour la qualite de ses produits, sa productivite et les faibles couts d'operation. Par contre, des recherches recentes ont permis de mettre en lumiere des risques d'expositions reliees a l'utilisation du cobalt, comme catalyseur de synthese; son elimination ou bien son remplacement est devenu une preoccupation importante. Quatre recettes alternatives ont ete mises a l'essai afin de trouver une alternative plus securitaire a la recette de base; un melange catalytique ternaire, compose de nickel, de cobalt et d'oxyde d'yttrium. La premiere consiste essentiellement a remplacer la proportion massique de cobalt par du nickel, qui etait deja present dans la recette de base. Les trois options suivantes contiennent de nouveaux catalyseurs, en remplacement au Co, qui sont apparus dans plusieurs recherches scientifiques au courant des dernieres annees: le dioxyde de zircone (ZrO2), dioxyde de manganese (MnO2) et le molybdene (Mo). La methode utilisee consiste a vaporiser la matiere premiere, sous forme solide, dans un reacteur plasma a haute frequence (3 MHz) a paroi refroidi. Apres le passage dans le plasma, le systeme traverse une section dite de "croissance", isolee thermiquement a l'aide de graphite, afin de maintenir une certaine plage de temperature favorable a la

  16. Fueling of magnetically confined plasmas by single- and two-stage repeating pneumatic pellet injectors

    SciTech Connect

    Gouge, M.J.; Combs, S.K.; Foust, C.R.; Milora, S.L.

    1990-01-01

    Advanced plasma fueling systems for magnetic fusion confinement experiments are under development at Oak Ridge National Laboratory (ORNL). The general approach is that of producing and accelerating frozen hydrogenic pellets to speeds in the kilometer-per-second range using single shot and repetitive pneumatic (light-gas gun) pellet injectors. The millimeter-to-centimeter size pellets enter the plasma and continuously ablate because of the plasma electron heat flux, depositing fuel atoms along the pellet trajectory. This fueling method allows direct fueling in the interior of the hot plasma and is more efficient than the alternative method of injecting room temperature fuel gas at the wall of the plasma vacuum chamber. Single-stage pneumatic injectors based on the light-gas gun concept have provided hydrogenic fuel pellets in the speed range of 1--2 km/s in single-shot injector designs. Repetition rates up to 5 Hz have been demonstrated in repetitive injector designs. Future fusion reactor-scale devices may need higher pellet velocities because of the larger plasma size and higher plasma temperatures. Repetitive two-stage pneumatic injectors are under development at ORNL to provide long-pulse plasma fueling in the 3--5 km/s speed range. Recently, a repeating, two-stage light-gas gun achieved repetitive operation at 1 Hz with speeds in the range of 2--3 km/s.

  17. 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.

  18. Turbulence in Toroidally Confined Plasma: Ion - - Gradient-Driven Turbulence; Dynamics of Magnetic Relaxation in Current-Carrying Plasma

    NASA Astrophysics Data System (ADS)

    Lee, Gyung Su.

    This thesis is devoted to two studies of low-frequency turbulence in toroidally confined plasma. Low-frequency turbulence is believed to play an important role in anomalous transport in toroidal confinement devices. The first study pertains the the development of an analytic theory of ion-temperature-gradient-driven turbulence in tokamaks. Energy-conserving, renormalized spectrum equations are derived and solved in order to obtain the spectra of stationary ion-temperature-gradient-driven turbulence. Corrections to mixing-length estimates are calculated explicitly. The resulting anomalous ion thermal diffusivity is derived and is found to be consistent with experimentally-deduced ion thermal diffusivities. The associated electron thermal diffusivity, particle and heat-pinch velocities are also calculated. The effects of impurity gradients on saturated ion-temperature-gradient-driven turbulence are discussed and a related explanation of density profile steepening during Z-mode operation is proposed. The second study is devoted to the role of multiple helicity nonlinear interactions of tearing modes and dynamics of magnetic relaxation in a high-temperature current-carrying plasma. To extend the resistive MHD theory of magnetic fluctuations and dynamo activity observed in the reversed field pinch, the fluid equations for high-temperature regime are derived and basic nonlinear interaction mechanism and the effects of diamagnetic corrections to the MHD turbulence theory are studied for the case of fully developed, densely packed turbulence. Modifications to the MHD dynamo theory and anomalous thermal transport and confinement scaling predictions are examined.

  19. Spectroscopic diagnostics of plume rebound and shockwave dynamics of confined aluminum laser plasma plumes

    SciTech Connect

    Yeates, P.; Kennedy, E. T.

    2011-06-15

    Generation and expansion dynamics of aluminum laser plasma plumes generated between parallel plates of varying separation ({Delta}Z = 2.0, 3.2, 4.0, and 5.6 mm), which confined plume expansion normal to the ablation surface, were diagnosed. Space and time resolved visible emission spectroscopy in the spectral range {lambda} = 355-470 nm and time gated visible imaging were employed to record emission spectra and plume dynamics. Space and time resolved profiles of N{sub e} (the electron density), T{sub e} (the electron temperature), and T{sub ionz} (the ionization temperature) were compared for different positions in the plasma plume. Significant modifications of the profiles of the above parameters were observed for plasma-surface collisions at the inner surface of the front plate, which formed a barrier to the free expansion of the plasma plume generated by the laser light on the surface of the back plate. Shockwave generation at the collision interface resulted in delayed compression of the low-density plasma plume near the inner ablation surface, at late stages in the plasma history. Upon exiting the cavity formed by the two plates, through an aperture in the front plate, the plasma plume underwent a second phase of free expansion.

  20. Microwave remote plasma enhanced-atomic layer deposition system with multicusp confinement chamber

    SciTech Connect

    Dechana, A.; Thamboon, P.; Boonyawan, D.

    2014-10-15

    A microwave remote Plasma Enhanced-Atomic Layer Deposition system with multicusp confinement chamber is established at the Plasma and Beam Physics research facilities, Chiang Mai, Thailand. The system produces highly-reactive plasma species in order to enhance the deposition process of thin films. The addition of the multicusp magnetic fields further improves the plasma density and uniformity in the reaction chamber. Thus, the system is more favorable to temperature-sensitive substrates when heating becomes unwanted. Furthermore, the remote-plasma feature, which is generated via microwave power source, offers tunability of the plasma properties separately from the process. As a result, the system provides high flexibility in choice of materials and design experiments, particularly for low-temperature applications. Performance evaluations of the system were carried on coating experiments of Al{sub 2}O{sub 3} layers onto a silicon wafer. The plasma characteristics in the chamber will be described. The resulted Al{sub 2}O{sub 3} films—analyzed by Rutherford Backscattering Spectrometry in channeling mode and by X-ray Photoelectron Spectroscopy techniques—will be discussed.

  1. Application of spatially resolved high resolution crystal spectrometry to inertial confinement fusion plasmas

    SciTech Connect

    Hill, K. W.; Bitter, M.; Delgado-Aparacio, L.; Pablant, N. A.; Beiersdorfer, P.; Schneider, M.; Widmann, K.; Sanchez del Rio, M.; Zhang, L.

    2012-10-15

    High resolution ({lambda}/{Delta}{lambda}{approx} 10 000) 1D imaging x-ray spectroscopy using a spherically bent crystal and a 2D hybrid pixel array detector is used world wide for Doppler measurements of ion-temperature and plasma flow-velocity profiles in magnetic confinement fusion plasmas. Meter sized plasmas are diagnosed with cm spatial resolution and 10 ms time resolution. This concept can also be used as a diagnostic of small sources, such as inertial confinement fusion plasmas and targets on x-ray light source beam lines, with spatial resolution of micrometers, as demonstrated by laboratory experiments using a 250-{mu}m {sup 55}Fe source, and by ray-tracing calculations. Throughput calculations agree with measurements, and predict detector counts in the range 10{sup -8}-10{sup -6} times source x-rays, depending on crystal reflectivity and spectrometer geometry. Results of the lab demonstrations, application of the technique to the National Ignition Facility (NIF), and predictions of performance on NIF will be presented.

  2. Plasma confinement by magnetic field with convex-concave field lines

    NASA Astrophysics Data System (ADS)

    Tsventoukh, Mikhail M.; Krashevskaya, Galina V.; Prishvitsyn, Alexander S.

    2015-06-01

    It has been found that plasma confinement by the magnetic field of alternating-sign curvature with convex-concave field lines results in a strong stabilizing action against convective (flute-interchange) perturbations. For simple combinations of axisymmetric mirrors and cusps the calculations according to the kinetic stability criterion give strongly, centrally peaked stable plasma pressure profiles instead of shallow ones. For the experimental research of this effect, a compact magnetic confinement device has been modified by adding of the external current coil to fulfil the field-line curvature requirements. The critical convectively-stable plasma pressure profiles calculation in this experimental geometry and the probe measurements of the spatial plasma distribution in the new magnetic configuration of alternating-sign curvature have been performed. The experimental results give some support for a conclusion that there is an increase in the ion saturation current at the region near the minimum of the specific volume min ∫dl/B. This region corresponds to the average minimum in the second adiabatic invariant, and the kinetic description predicts the stable pressure profile peaking here due to reduction of charge separation by particle drift in alternating-sign curvature.

  3. Intense field induced excitation and ionization of an atom confined in a dense quantum plasma

    NASA Astrophysics Data System (ADS)

    Lumb, Shalini; Lumb, Sonia; Munjal, D.; Prasad, V.

    2015-09-01

    Exponential cosine screened Coulomb potential (ECSCP) has been widely used in various branches of physics e.g., solid-state physics, nuclear physics and plasma physics. The atomic photoionization processes under plasma shielding can serve as an efficient tool for study of plasma properties in various environments ranging from nano-scale devices to astrophysical objects. In the present study, ECSCP has been used to characterize a dense quantum plasma and its effect on the spectrum of an atom encaged in a spherical box has been investigated. The work has further been extended to study the response of such a system to a periodic laser field. Photoexcitation and ionization probabilities of the system have been studied as a function of applied laser field parameters using the non-perturbative Floquet technique. As the Floquet method requires exact energy values and oscillator strengths, the spectrum of confined system has been calculated using Bernstein-polynomial method. The variation of energy spectrum and oscillator strengths with screening as well as confinement parameters has also been explored.

  4. Static and dynamic properties of confined, cold ion plasmas: MD (molecular dynamics) simulations

    SciTech Connect

    Schiffer, J.P.

    1989-01-01

    Some four years ago it was suggested that in the new generation of heavy ion accelerator storage rings for multiply charged ions, being planned in Europe, one may well attain internal temperatures that would correspond to very cold plasmas. Since that time, the techniques of electron or laser cooling of such beams has evolved and it may well be possible to reach temperatures corresponding to a plasma coupling parameter {Gamma} >> 100. I was fortunate to have had an opportunity to collaborate during 1986-87 with my former colleague Aneesur Rahman, of Molecular Dynamics fame, and we adapted the MD method to the calculation of the properties of cold confined plasmas. After Rahman's premature death two years ago I have continued the exploration of these systems and would like to summarize the results here. 9 refs., 10 figs.

  5. Autowaves in a dc complex plasma confined behind a de Laval nozzle

    NASA Astrophysics Data System (ADS)

    Fink, M. A.; Zhdanov, S. K.; Schwabe, M.; Thoma, M. H.; Höfner, H.; Thomas, H. M.; Morfill, G. E.

    2013-05-01

    Experiments to explore stability conditions and topology of a dense microparticle cloud supported against gravity by a gas flow were carried out. By using a nozzle-shaped glass insert within the glass tube of a dc discharge plasma chamber a weakly ionized gas flow through a de Laval nozzle was produced. The experiments were performed using neon gas at a pressure of 100 Pa and melamine-formaldehyde particles with a diameter of 3.43 μm. The capturing and stable global confining of the particles behind the nozzle in the plasma were demonstrated. The particles inside the cloud behaved as a single convection cell inhomogeneously structured along the nozzle axis in a tube-like manner. The pulsed acceleration localized in the very head of the cloud mediated by collective plasma-particle interactions and the resulting wave pattern were studied in detail.

  6. Spherical plasma oscillations in a reversed-polarity inertial-electrostatic confinement device

    SciTech Connect

    Tuft, C.; Khachan, J.

    2010-11-15

    A pulsed reversed-polarity inertial-electrostatic confinement device has been investigated experimentally using voltage and spectroscopic diagnostics. Large-amplitude oscillations were observed in the floating potential of the plasma immediately following the initiation of the discharge. It is postulated that the observations were the result of coherent ion oscillations within a harmonic potential well formed by a uniform electron density in the center of the device. A simple model of the system predicts the depth of this transient potential well to be approximately 100 V. Observations of the relative occupation of the third and fourth energy levels of hydrogen in the plasma indicated the formation of a Maxwellian electron energy distribution after 20 {mu}s. The results suggest a promising avenue toward a net fusion power gain by utilizing these oscillations to periodically compress and heat the plasma to thermonuclear densities and energies.

  7. Low beta equilibrium and stability for anisotropic pressure closed field line plasma confinement systems

    SciTech Connect

    Pastukhov, V.P.; Ilgisonis, V.I.; Subbotin, A.A.

    1994-05-01

    General formalism is developed to analyze the equilibrium and stability of low beta anisotropic pressure plasmas confined in closed field line magnetic systems. The formalism allows one to consider rather general magnetic systems with nonuniform axis curvature and longitudinal profiles of toroidal and multipole poloidal field. It also allows having a strong pressure anisotropy corresponding to enhanced plasma pressure in mirror cells of the system. As an example of such a system the authors consider the recently proposed linked mirror neutron source (LMNS). Application of the above formalism to the LMNS analysis confirms most of the preliminary results, however, they obtain a considerable reduction of mirror cell axis curvature and an appreciable ellipticity of plasma cross-section in the mirror cell midplane. They have also optimized the longitudinal pressure and magnetic field distribution.

  8. Dynamic Confinement of ITER Plasma by O-Mode Driver at Electron Cyclotron Frequency Range

    NASA Astrophysics Data System (ADS)

    Stefan, V. Alexander

    2009-05-01

    A low B-field side launched electron cyclotron O-Mode driver leads to the dynamic rf confinement, in addition to rf turbulent heating, of ITER plasma. The scaling law for the local energy confinement time τE is evaluated (τE ˜ 3neTe/2Q, where (3/2) neTe is the local plasma thermal energy density and Q is the local rf turbulent heating rate). The dynamics of unstable dissipative trapped particle modes (DTPM) strongly coupled to Trivelpiece-Gould (T-G) modes is studied for gyrotron frequency 170GHz; power˜24 MW CW; and on-axis B-field ˜ 10T. In the case of dynamic stabilization of DTPM turbulence and for the heavily damped T-G modes, the energy confinement time scales as τE˜(I0)-2, whereby I0(W/m^2) is the O-Mode driver irradiance. R. Prater et. al., Nucl. Fusion 48, No 3 (March 2008). E. P. Velikhov, History of the Russian Tokamak and the Tokamak Thermonuclear Fusion Research Worldwide That Led to ITER (Documentary movie; Stefan Studios Int'l, La Jolla, CA, 2008; E. P. Velikhov, V. Stefan.) M N Rosenbluth, Phys. Scr. T2A 104-109 1982 B. B. Kadomtsev and O. P. Pogutse, Nucl. Fusion 11, 67 (1971).

  9. Confinement effects of shock waves on laser-induced plasma from a graphite target

    SciTech Connect

    Huang, Feiling; Liang, Peipei; Yang, Xu; Cai, Hua; Wu, Jiada; Xu, Ning; Ying, Zhifeng; Sun, Jian

    2015-06-15

    The spatial confinement effects of shock waves on the laser-induced plasma (LIP) from a graphite target in air were studied by probe beam deflection (PBD) measurements and optical emission spectroscopy (OES). A clear relationship between the confinement of the LIP by the shock wave and the effects on the LIP emission was observed, and the underlying mechanisms are discussed. PBD monitoring revealed that the laser-ablation induced shock wave could be well analogized to the shock wave generated by a point explosion and would be reflected by a block. OES measurements indicated that the optical emission of the LIP exhibited significant variations with the block placement. A first enhancement and then a fast decay of CN molecular emission as well as a suppression of carbon atomic emission were observed in the presence of the block. The results revealed that the reflected shock wave spatially confined the expansion of the LIP and compressed the LIP after encountering it, pushing back the species of the LIP and changing the density of the LIP species including luminous carbon atoms and CN molecules. It is suggested that the change of the LIP emission is attributed to the density variation of the LIP species due to the compression of the LIP and the reactions occurring in the plasma.

  10. Observation of energetic electron confinement in a largely stochastic reversed-field pinch plasma

    NASA Astrophysics Data System (ADS)

    Clayton, D. J.; Chapman, B. E.; O'Connell, R.; Almagri, A. F.; Burke, D. R.; Forest, C. B.; Goetz, J. A.; Kaufman, M. C.; Bonomo, F.; Franz, P.; Gobbin, M.; Piovesan, P.

    2010-01-01

    Runaway electrons with energies >100 keV are observed with the appearance of an m =1 magnetic island in the core of otherwise stochastic Madison Symmetric Torus [Dexter et al., Fusion Technol. 19, 131 (1991)] reversed-field-pinch plasmas. The island is associated with the innermost resonant tearing mode, which is usually the largest in the m =1 spectrum. The island appears over a range of mode spectra, from those with a weakly dominant mode to those, referred to as quasi single helicity, with a strongly dominant mode. In a stochastic field, the rate of electron loss increases with electron parallel velocity. Hence, high-energy electrons imply a region of reduced stochasticity. The global energy confinement time is about the same as in plasmas without high-energy electrons or an island in the core. Hence, the region of reduced stochasticity must be localized. Within a numerical reconstruction of the magnetic field topology, high-energy electrons are substantially better confined inside the island, relative to the external region. Therefore, it is deduced that the island provides a region of reduced stochasticity and that the high-energy electrons are generated and well confined within this region.

  11. SCR-1: Design and Construction of a Small Modular Stellarator for Magnetic Confinement of Plasma

    NASA Astrophysics Data System (ADS)

    Barillas, L.; Vargas, V. I.; Alpizar, A.; Asenjo, J.; Carranza, J. M.; Cerdas, F.; Gutiérrez, R.; Monge, J. I.; Mora, J.; Morera, J.; Peraza, H.; Queral, V.; Rojas, C.; Rozen, D.; Saenz, F.; Sánchez, G.; Sandoval, M.; Trimiño, H.; Umaña, J.; Villegas, L. F.

    2014-05-01

    This paper describes briefly the design and construction of a small modular stellarator for magnetic confinement of plasma, called Stellarator of Costa Rica 1, or SCR-1; developed by the Plasma Physics Group of the Instituto Tecnológico de Costa Rica, PlasmaTEC. The SCR-1 is based on the small Spanish stellarator UST_1, created by the engineer Vicente Queral. The SCR-1 will employ stainless steel torus-shaped vacuum vessel with a major radius of 460.33 mm and a cross section radius of 110.25mm. A typical SCR-1 plasma will have an average radius 42.2 mm and a volume of 8 liters (0.01 m3), and an aspect ratio of 5.7. The magnetic resonant field will be 0.0878 T, and a period of 2 (m=2) with a rotational transform of 0.3. The magnetic field will be provided by 12 modular coils, with 8 turns each, with an electrical current of 8704 A per coil (1088 A per turn of each coil). This current will be fed by a bank of cell batteries. The plasma will be heated by ECRH with magnetrons of a total power of 5kW, in the first harmonic at 2.45GHz. The expected electron temperature and density are 15 eV and 1017 m-3 respectively with an estimated confinement time of 7.30 x 10-4 ms. The initial diagnostics on the SCR-1 will consist of a Langmuir probe, a heterodyne microwave interferometer, and a field mapping system. The first plasma of the SCR-1 is expected at the end of 2011.

  12. Method for determining fast-alpha-particle confinement in tokamak plasmas using resonant nuclear reactors

    SciTech Connect

    Cecil, F.E.; Zweben, S.J.; Medley, S.S.

    1986-03-01

    The resonant nuclear reactions D(..cap alpha..,..gamma..)/sup 6/Li, /sup 6/Li(..cap alpha..,..gamma..)/sup 10/B, and /sup 7/Li(..cap alpha..,..gamma..)/sup 11/B are examined as diagnostics of fast-alpha-particle confinement in tokamak plasmas. Gamma rays from these resonant reactions with energies from 2.1 MeV to 9.2 MeV may be used to infer the alpha-particle population between energies of 0.4 MeV and 2.6 MeV. The ratio of these alpha-burnup reactions to the reactions T(D,..gamma..)/sup 5/He and /sup 3/He(D,..gamma..)/sup 5/Li provides a technique for the measurement of alpha confinement.

  13. Cholesterol Modulates CFTR Confinement in the Plasma Membrane of Primary Epithelial Cells

    PubMed Central

    Abu-Arish, Asmahan; Pandzic, Elvis; Goepp, Julie; Matthes, Elizabeth; Hanrahan, John W.; Wiseman, Paul W.

    2015-01-01

    The cystic fibrosis transmembrane conductance regulator (CFTR) is a plasma-membrane anion channel that, when mutated, causes the disease cystic fibrosis. Although CFTR has been detected in a detergent-resistant membrane fraction prepared from airway epithelial cells, suggesting that it may partition into cholesterol-rich membrane microdomains (lipid rafts), its compartmentalization has not been demonstrated in intact cells and the influence of microdomains on CFTR lateral mobility is unknown. We used live-cell imaging, spatial image correlation spectroscopy, and k-space image correlation spectroscopy to examine the aggregation state of CFTR and its dynamics both within and outside microdomains in the plasma membrane of primary human bronchial epithelial cells. These studies were also performed during treatments that augment or deplete membrane cholesterol. We found two populations of CFTR molecules that were distinguishable based on their dynamics at the cell surface. One population showed confinement and had slow dynamics that were highly cholesterol dependent. The other, more abundant population was less confined and diffused more rapidly. Treatments that deplete the membrane of cholesterol caused the confined fraction and average number of CFTR molecules per cluster to decrease. Elevating cholesterol had the opposite effect, increasing channel aggregation and the fraction of channels displaying confinement, consistent with CFTR recruitment into cholesterol-rich microdomains with dimensions below the optical resolution limit. Viral infection caused the nanoscale microdomains to fuse into large platforms and reduced CFTR mobility. To our knowledge, these results provide the first biophysical evidence for multiple CFTR populations and have implications for regulation of their surface expression and channel function. PMID:26153705

  14. First results from a soft-x-ray laser experiment in a confined plasma column

    SciTech Connect

    Suckewer, S; Johnson, L C; Sato, K; Semet, A; Skinner, C H; Voorhees, D

    1982-04-01

    We present a description of the experimental set up and the first results from an experiment designed to achieve lasing action in the soft x-ray region of the spectrum. A 0.5 kJ CO/sub 2/ laser was focused into a target gas, typically CO/sub 2/, and the resulting plasma was confined in a 50 to 90 kG magnetic field. Spectroscopic diagnostics were used to monitor the n = 7 and n = 8 level populations of CVI as well as ultraviolet emission lines of CV and CIII, for different plasma conditions. We present data showing that as the confining magnetic field was increased, the plasma column diameter decreased, the CVI 3434 line intensity (7 ..-->.. 6 transition) increased and its decay time decreased consistent with earlier computer modeling. We also discuss the effect of the low intensity tail, normally present in CO/sub 2/ laser pulses, on the predicted population inversion. Analysis of the experimental data by computer simulation shows the range of expected total gain on the n = 3 to n = 2 transition at 182A in these experiments was G = 0.05 to 0.1 and the possibility for its significant increase.

  15. Excitation of the centrifugally driven interchange instability in a plasma confined by a magnetic dipole

    SciTech Connect

    Levitt, B.; Maslovsky, D.; Mauel, M.E.; Waksman, J.

    2005-05-15

    The centrifugally driven electrostatic interchange instability is excited for the first time in a laboratory magnetoplasma. The plasma is confined by a dipole magnetic field, and the instability is excited when an equatorial mesh is biased to induce a radial current that creates rapid axisymmetric plasma rotation. The observed instabilities appear quasicoherent in the lab frame of reference; they have global radial mode structures and low azimuthal mode numbers, and they are modified by the presence of energetic, magnetically confined electrons. The mode structure is measured using a multiprobe correlation technique as well as a novel 96-point polar imaging diagnostic which measures particle flux along field lines that map to the pole. Interchange instabilities caused by hot electron pressure are simultaneously observed at the hot electron drift frequency. Adjusting the hot electron fraction {alpha} modifies the stability as well as the structures of the centrifugally driven modes. In the presence of larger fractions of energetic electrons, m=1 is observed to be the dominant mode. For faster rotating plasmas containing fewer energetic electrons, m=2 dominates. Results from a self-consistent nonlinear simulation reproduce the measured mode structures in both regimes. The low azimuthal mode numbers seen in the experiment and simulation can also be interpreted with a local, linear dispersion relation of the electrostatic interchange instability. Drift resonant hot electrons give the instability a real frequency, inducing stabilizing ion polarization currents that preferentially suppress high-m modes.

  16. Application of Smoothed Particle MHD (SPMHD) techniques to the simulation of magnetically confined plasma dynamics

    NASA Astrophysics Data System (ADS)

    Vela-Vela, Luis; Sanchez, Raul; Reynolds-Barredo, J. Miguel

    2015-11-01

    Magnetically confined plasmas relevant for fusion scenarios are, to first approximation, well described by ideal and resistive MHD. This includes the description of their equilibrium and stability properties, as well as their medium-to-long term nonlinear evolution under external forcing. In many of these cases, one needs to deal with magnetic topologies that include magnetic islands, stochastic regions or that require the consideration of free-moving boundaries. The present work is part of an on-going effort to develop of a numerical code capable of dealing with these situations by taking advantage of the SPMHD formalism that, although widely used in astrophysical plasmas, is not widespread within the fusion community. SPMHD is a particle (i.e., Lagrangian) method particularly well-suited to deal with complicated boundaries while retaining great parallelization benefits. Here, we will report on the adaptation of the SPMHD equations to the case of magnetically confined plasmas, several benchmarking tests typical for MHD codes, and some preliminary results obtained for more elaborate scenarios. Our results suggest that our new code (EVA) can be very advantageous to deal with problems of current interest for the fusion community, including tokamaks and stellarators.

  17. Particle confinement of pellet-fuelled H-mode plasmas in the Mega Ampere Spherical Tokamak

    NASA Astrophysics Data System (ADS)

    Valovič, M.; Axon, K.; Garzotti, L.; Saarelma, S.; Thyagaraja, A.; Akers, R.; Gurl, C.; Kirk, A.; Lloyd, B.; Maddison, G. P.; Patel, A.; Shibaev, S.; Scannell, R.; Taylor, D.; Walsh, M.; MAST Team

    2008-07-01

    This paper quantifies the particle confinement of pellet-fuelled plasmas in the Mega Ampere Spherical Tokamak (MAST). The dataset is restricted mostly to neutral beam heated plasmas and to shallow pellets launched from the high field side. It is shown that the pellet deposition can be explained only by invoking the ∇B drift of the pellet ablatant. The pellet creates a zone with positive density gradient and increased temperature gradient. Simulations show that these changes could increase the level of micro-turbulence and thus enhance further the penetration of pellet-deposited particles towards the core. Post-pellet dynamics of the density profile is characterised by the pellet retention time τpel. It is shown that τpel correlates with the status of the edge transport barrier (L-mode or H-mode) and decreases rapidly for pellet deposition radius rpel approaching the plasma edge. For ELMy H-mode and ITER-like pellets, rpel ≈ 0.8a, the pellet retention time is about 20% of the energy confinement time. The fuelling requirement by the pellets for ITER is discussed.

  18. Resonant magnetic perturbations of edge-plasmas in toroidal confinement devices

    NASA Astrophysics Data System (ADS)

    Evans, T. E.

    2015-12-01

    Controlling the boundary layer in fusion-grade, high-performance, plasma discharges is essential for the successful development of toroidal magnetic confinement power generating systems. A promising approach for controlling the boundary plasma is based on the use of small, externally applied, edge resonant magnetic perturbation (RMP) fields (δ b\\bot\\text{ext}≈ {{10}-4}\\to {{10}-3}~\\text{T} ). A long-term focus area in tokamak fusion research has been to find methods, involving the use of non-axisymmetric magnetic perturbations to reduce the intense particle and heat fluxes to the wall. Experimental RMP research has progressed from the early pioneering work on tokamaks with material limiters in the 1970s, to present day research in separatrix-limited tokamaks operated in high-confinement mode, which is primarily aimed at the mitigation of the intermittent fluxes due edge localized modes (ELMs). At the same time, theoretical research has evolved from analytical models to numerical simulations, including the full 3D complexities of the problem. Following the first demonstration of ELM suppression in the DIII-D tokamak during 2003, there has been a rapid worldwide growth in theoretical, numerical and experimental edge RMP research resulting in the addition of ELM control coils to the ITER baseline design (Loarte et al 2014 Nucl. Fusion 54 033007). This review provides an overview of edge RMP research including a summary of the early theoretical and numerical background along with recent experimental results on improved particle and energy confinement in tokamaks triggered by edge RMP fields. The topics covered make up the basic elements needed for developing a better understanding of 3D magnetic perturbation physics, which is required in order to utilize the full potential of edge RMP fields in fusion relevant high performance, H-mode, plasmas.

  19. Élimination du bore du silicium par plasma inductif sous champ électrique

    NASA Astrophysics Data System (ADS)

    Combes, R.; Morvan, D.; Picard, G.; Amouroux, J.

    1993-05-01

    We analyzed purification mechanisms of silicon by inductive plasma with a fluoride slag. The aim is to study boron elimination from doped electronic grade silicon in function of the nature of the slag to obtain a photovoltaic grade silicon. The steady began with the calculation and the comparison of the stability diagram of boron compounds in presence of CaF2, BaF2 and MgF2. This study led us to conclude that BaF2 is the better slag for silicon purification. This has been confirmed by experience. In a second time, we made purifications under electric bias to enhance slag efficiency. We noticed that BaF2 is more sensitive to electric bias than other slags. Nous avons analysé le mécanisme de purification du silicium sous plasma inductif en présence d'un laitier fluoré. L'objectif principal est d'étudier l'élimination du bore du silicium électronique dopé en fonction de la nature du fluorure pour obtenir un silicium de qualité photovoltaïque. L'étude a commencé par l'établissement et la comparaison de diagrammes des composés du bore en présence de CaF2, de MgF2 et de BaF2. Nous avons déduit de cette première étude que BaF2 est le meilleur laitier pour la purification du silicium. Ceci a été corroboré par l'expérience. Nous avons ensuite opéré en présence d'un champ électrique dans le but d'améliorer encore l'efficacité des laitiers. Nous avons constaté que BaF2 est plus sensible au champ électrique que les deux autres laitiers utilisés.

  20. Magnetic field generation in Rayleigh-Taylor unstable inertial confinement fusion plasmas.

    PubMed

    Srinivasan, Bhuvana; Dimonte, Guy; Tang, Xian-Zhu

    2012-04-20

    Rayleigh-Taylor instabilities (RTI) in inertial confinement fusion implosions are expected to generate magnetic fields. A Hall-MHD model is used to study the field generation by 2D single-mode and multimode RTI in a stratified two-fluid plasma. Self-generated magnetic fields are predicted and these fields grow as the RTI progresses via the ∇n(e)×∇T(e) term in the generalized Ohm's law. Scaling studies are performed to determine the growth of the self-generated magnetic field as a function of density, acceleration, Atwood number, and perturbation wavelength.

  1. Multiple-beam laser–plasma interactions in inertial confinement fusion

    SciTech Connect

    Myatt, J. F. Zhang, J.; Maximov, A. V.; Short, R. W.; Seka, W.; Edgell, D. H.; Michel, D. T.; Igumenshchev, I. V.; Froula, D. H.; Hinkel, D. E.; Michel, P.; Moody, J. D.

    2014-05-15

    The experimental evidence for multiple-beam laser-plasma instabilities of relevance to laser driven inertial confinement fusion at the ignition scale is reviewed, in both the indirect and direct-drive approaches. The instabilities described are cross-beam energy transfer (in both indirectly driven targets on the NIF and in direct-drive targets), multiple-beam stimulated Raman scattering (for indirect-drive), and multiple-beam two-plasmon decay instability (in direct drive). Advances in theoretical understanding and in the numerical modeling of these multiple beam instabilities are presented.

  2. Basic physics of Alfven instabilities driven by energetic particles in toroidally confined plasmas

    SciTech Connect

    Heidbrink, W. W.

    2008-05-15

    Superthermal energetic particles (EP) often drive shear Alfven waves unstable in magnetically confined plasmas. These instabilities constitute a fascinating nonlinear system where fluid and kinetic nonlinearities can appear on an equal footing. In addition to basic science, Alfven instabilities are of practical importance, as the expulsion of energetic particles can damage the walls of a confinement device. Because of rapid dispersion, shear Alfven waves that are part of the continuous spectrum are rarely destabilized. However, because the index of refraction is periodic in toroidally confined plasmas, gaps appear in the continuous spectrum. At spatial locations where the radial group velocity vanishes, weakly damped discrete modes appear in these gaps. These eigenmodes are of two types. One type is associated with frequency crossings of counterpropagating waves; the toroidal Alfven eigenmode is a prominent example. The second type is associated with an extremum of the continuous spectrum; the reversed shear Alfven eigenmode is an example of this type. In addition to these normal modes of the background plasma, when the energetic particle pressure is very large, energetic particle modes that adopt the frequency of the energetic particle population occur. Alfven instabilities of all three types occur in every toroidal magnetic confinement device with an intense energetic particle population. The energetic particles are most conveniently described by their constants of motion. Resonances occur between the orbital frequencies of the energetic particles and the wave phase velocity. If the wave resonance with the energetic particle population occurs where the gradient with respect to a constant of motion is inverted, the particles transfer energy to the wave, promoting instability. In a tokamak, the spatial gradient drive associated with inversion of the toroidal canonical angular momentum P{sub {zeta}} is most important. Once a mode is driven unstable, a wide variety

  3. Apparatus and method for removing particle species from fusion-plasma-confinement devices

    DOEpatents

    Hamilton, G.W.

    1981-10-26

    In a mirror fusion plasma confinement apparatus, method and apparatus are provided for selectively removing (pumping) trapped low energy (thermal) particle species from the end cell region, without removing the still useful high energy particle species, and without requiring large power input to accomplish the pumping. Perturbation magnets are placed in the thermal barrier region of the end cell region at the turning point characteristic of trapped thermal particles, thus deflecting the thermal particles from their closed trajectory, causing them to drift sufficiently to exit the thermal barrier.

  4. Flute instability in a plasma confined by perfectly reflecting end walls

    SciTech Connect

    Farina, D.; Pozzoli, R.; Ryutov, D. )

    1993-11-01

    The magnetohydrodynamic stability of a low-pressure plasma confined along the magnetic field by the end walls that are perfectly reflecting the impinging particles is considered. It is shown that, if the magnetic field lines do not intersect the walls along the normal, a fast instability can develop. An explicit expression for the growth rate has been derived, and an analogy with the usual flute instability has been traced. The instability can play some role in the scrape-off layers of tokamaks with poloidal limiter.

  5. Study of plasma convection and wall interactions in magnetic confinement systems

    NASA Astrophysics Data System (ADS)

    York, T. M.

    1986-06-01

    The subject contract research effort was initiated in September 1976 with two specific tasks: (1) to study the fundamental physics of confinement of an alternate concept (i.e., theta pinch based) devices; and (2) to study and to develop new diagnostic systems for use on major experiments at other locations in the country. There has been active collaboration with Los Alamos National Laboratory and Lawrence Livermore National Laboratory; there has been proposed collaboration with Princeton Plasma Physics Laboratory, Fusion Research Center at the University of Texas, and General Atomics.

  6. The technology and science of steady-state operation in magnetically confined plasmas

    NASA Astrophysics Data System (ADS)

    Bécoulet, A.; Hoang, G. T.

    2008-12-01

    The steady-state operation of magnetically confined fusion plasmas is considered as one of the 'grand challenges' of future decades, if not the ultimate goal of the research and development activities towards a new source of energy. Reaching such a goal requires the high-level integration of both science and technology aspects of magnetic fusion into self-consistent plasma regimes in fusion-grade devices. On the physics side, the first constraint addresses the magnetic confinement itself which must be made persistent. This means to either rely on intrinsically steady-state configurations, like the stellarator one, or turn the inductively driven tokamak configuration into a fully non-inductive one, through a mix of additional current sources. The low efficiency of the external current drive methods and the necessity to minimize the re-circulating power claim for a current mix strongly weighted by the internal 'pressure driven' bootstrap current, itself strongly sensitive to the heat and particle transport properties of the plasma. A virtuous circle may form as the heat and particle transport properties are themselves sensitive to the current profile conditions. Note that several other factors, e.g. plasma rotation profile, magneto-hydro-dynamics activity, also influence the equilibrium state. In the present tokamak devices, several examples of such 'advanced tokamak' physics research demonstrate the feasibility of steady-state regimes, though with a number of open questions still under investigation. The modelling activity also progresses quite fast in this domain and supports understanding and extrapolation. This high level of physics sophistication of the plasma scenario however needs to be combined with steady-state technological constraints. The technology constraints for steady-state operation are basically twofold: the specific technologies required to reach the steady-state plasma conditions and the generic technologies linked to the long pulse operation of a

  7. Emissive Probe Measurements in a Dual-Frequency-Confined Capacitively-Coupled-Plasma System

    NASA Astrophysics Data System (ADS)

    Linnane, Shane; Ellingboe, Albert R.

    2002-10-01

    Dual frequency confined capacitively coupled plasmas (DFC-CCP) are increasingly used in semiconductor manufacturing for dielectric etching, allowing greater (and independent) control of ion energies and ion flux on the etched substrate. The powered electrode is driven with the summation of 27MHz and 2MHz sinusoidal voltages, while the other electrode is grounded. The electrode areas are similar in size, giving an electrode aspect ratio less than 2. Because of this low aspect ratio, there are large oscillations in the plasma potential. The expectation is for sinusoidal oscillations at the higher driving frequency, due to capacitive sheaths, while a rectified oscillation is expected at the lower driving frequency.(E. Kawamura, V. Vahedi, M. A. Lieberman and C. K. Birdsall, Plasma Sources Sci. Technology. 8 (1999) R45-R64 Work Supported by EURATOM.) Measurements of rf oscillation in the plasma potential taken with a floating emissive probe will be presented. The emissive probe and circuitry allows direct realtime measurement of plasma potential oscillation at both driving frequencies and the harmonics of each, thus allowing measurement of the actual potential on the driven electrode and ion energy incident on grounded electrode.

  8. Plasma viscosity with mass transport in spherical inertial confinement fusion implosion simulations

    SciTech Connect

    Vold, E. L.; Molvig, K.; Joglekar, A. S.; Ortega, M. I.; Moll, R.; Fenn, D.

    2015-11-15

    The effects of viscosity and small-scale atomic-level mixing on plasmas in inertial confinement fusion (ICF) currently represent challenges in ICF research. Many current ICF hydrodynamic codes ignore the effects of viscosity though recent research indicates viscosity and mixing by classical transport processes may have a substantial impact on implosion dynamics. We have implemented a Lagrangian hydrodynamic code in one-dimensional spherical geometry with plasma viscosity and mass transport and including a three temperature model for ions, electrons, and radiation treated in a gray radiation diffusion approximation. The code is used to study ICF implosion differences with and without plasma viscosity and to determine the impacts of viscosity on temperature histories and neutron yield. It was found that plasma viscosity has substantial impacts on ICF shock dynamics characterized by shock burn timing, maximum burn temperatures, convergence ratio, and time history of neutron production rates. Plasma viscosity reduces the need for artificial viscosity to maintain numerical stability in the Lagrangian formulation and also modifies the flux-limiting needed for electron thermal conduction.

  9. Plasma viscosity with mass transport in spherical inertial confinement fusion implosion simulations

    NASA Astrophysics Data System (ADS)

    Vold, E. L.; Joglekar, A. S.; Ortega, M. I.; Moll, R.; Fenn, D.; Molvig, K.

    2015-11-01

    The effects of viscosity and small-scale atomic-level mixing on plasmas in inertial confinement fusion (ICF) currently represent challenges in ICF research. Many current ICF hydrodynamic codes ignore the effects of viscosity though recent research indicates viscosity and mixing by classical transport processes may have a substantial impact on implosion dynamics. We have implemented a Lagrangian hydrodynamic code in one-dimensional spherical geometry with plasma viscosity and mass transport and including a three temperature model for ions, electrons, and radiation treated in a gray radiation diffusion approximation. The code is used to study ICF implosion differences with and without plasma viscosity and to determine the impacts of viscosity on temperature histories and neutron yield. It was found that plasma viscosity has substantial impacts on ICF shock dynamics characterized by shock burn timing, maximum burn temperatures, convergence ratio, and time history of neutron production rates. Plasma viscosity reduces the need for artificial viscosity to maintain numerical stability in the Lagrangian formulation and also modifies the flux-limiting needed for electron thermal conduction.

  10. Stable anisotropic plasma confinement in magnetic configurations with convex-concave field lines

    NASA Astrophysics Data System (ADS)

    Tsventoukh, M. M.

    2014-02-01

    It is shown that a combination of the convex and the concave part of a field line provides a strong stabilizing action against convective (flute-interchange) plasma instability (Tsventoukh 2011 Nucl. Fusion 51 112002). This results in internal peaking of the stable plasma pressure profile that is calculated from the collisionless kinetic stability criterion for any magnetic confinement system with combination of mirrors and cusps. Connection of the convex and concave field line parts results in a reduction of the space charge that drives the unstable E × B motion, as there is an opposite direction of the particle drift in a non-uniform field at convex and concave field lines. The pressure peaking arises at the minimum of the second adiabatic invariant J that takes place at the ‘middle’ of a tandem mirror-cusp transverse cross-section. The position of the minimum in J varies with the particle pitch angle that results in a shift of the peaking position depending on plasma anisotropy. This allows one to improve a stable peaked pressure profile at a convex-concave field by changing the plasma anisotropy over the trap cross-section. Examples of such anisotropic distribution functions are found that give an additional substantial enhancement in the maximal central pressure. Furthermore, the shape of new calculated stable profiles has a wide central plasma layer instead of a narrow peak.

  11. Angular Momentum of Non-axisymmetric Global Modes in Magnetically Confined Plasmas and in Astrophysics*

    NASA Astrophysics Data System (ADS)

    Fei, L.; Coppi, B.

    2008-11-01

    The angular momentum of typical tridimensional modes that can be excited in magnetically confined laboratory plasmas and in astrophysics is evaluated by extending pre-existing theories [1], that are applicable to ``conventional'' waves. For the former case, pressure gradient driven ballooning modes whose frequencies are larger than their growth rates (e.g. given by two-fluid theories) are considered in view of the transport of angular momentum out of the plasma column produced by them. This is one of the processes that can lead to a spontaneous rotation [2], by recoil, of the plasma column. For the latter case tridimensional spiral modes [3] are considered that can be excited in plasma disk structures around compact objects and transport angular momentum radially away from the radius where they co-rotate with the plasma. This allows for mass accretion toward the central object to occur. Two classes of spirals are considered: those that are radially standing and are unstable and those that are convective and oscillatory in the relevant co-rotating frame.*Sponsored in part by the U.S. D.O.E. [1] B. Coppi, M.N. Rosenbluth and R.N. Sudan, Ann. Phys. 55, 2; 207-248 (1969).[2] B. Coppi, Nucl. Fus. 42, 1 (2002).[3]B. Coppi, Paper P1.177, E.P.S. Inter. Conf. (Crete, Greece, 2008).

  12. Scaling of confinement with isotopic content in deuterium and tritium plasmas

    SciTech Connect

    Phillips, C.K.; Scott, S.D.; Bell, M.

    1997-01-01

    The scaling of the electron thermal diffusivity, {chi}{sub e}, with relative gyro radius, {rho}*, has been measured on TFTR by comparing nearly identical ICRF-heated discharges which differ only in hydrogenic isotopic content. Contrary to the gyro-Bohm scaling ({chi}{sub e} {approximately} {chi}{sub B}{rho}*, where {chi}{sub B} is the Bohm diffusivity) observed on DIII-D when {rho}* was varied through a scan of magnetic field strength, {chi}{sub e} is found to scale inversely with {rho}*. Hence, global energy confinement is 8--11% higher in deuterium-tritium plasmas than in deuterium only plasmas, with the higher stored energy attributed almost entirely to the electrons.

  13. Study of Effects of Different Reactions on Plasma Parameters in D-T Magnetic Confinement Fusion

    NASA Astrophysics Data System (ADS)

    Motevalli, S. M.; Fadaei, F.

    2012-09-01

    The consideration of the three main nuclear reactions of the hydrogen isotopes (D(D, n)3He, D(D, p)T and T(D, n)4He) only leads to wrong results for determination of plasma parameters in magnetic confinement fusion reactors. The nuclear reaction 3He(D, p)4He influences the amount of produced tritium since it makes an important contribution to the charged particle energy deposition and to the temperatures. In this paper, we have considered different nuclear reactions of Deuterium-Tritium (D-T) fusion in tokamak reactor. This study has been carried out on the base of the particle and power balance equations in a zero-dimensional model then plasma parameters have been calculated. Finally, the obtained results have been compared with the theoretical results reported by other researchers.

  14. SXR-XUV Diagnostics for Edge and Core of Magnetically Confined Plasmas

    SciTech Connect

    Stutman, Dan

    2014-09-10

    The present report summarizes the results obtained during a one-year extension of DoE grant “SXR-XUV Diagnostics for Edge and Core of Magnetically Confined Plasmas”, at Johns Hopkins University, aimed at completing the development of a new type of magnetic fusion plasma diagnostic, the XUV Transmission Grating Imaging Radiometer (TGIR). The TGIR enables simultaneous spatially and spectrally resolved measurements of the XUV/VUV radiated power from impurities in fusion plasmas, with high speed. The instrument was successfully developed and qualified in the laboratory and in experiments on a tokamak. Its future applications will be diagnostic of the impurity content and transport in the divertor and edge of advanced magnetic fusion experiments, such as NSTX Upgrade.

  15. Ion distribution in the hot spot of an inertial confinement fusion plasma

    NASA Astrophysics Data System (ADS)

    Tang, Xianzhu; Guo, Zehua; Berk, Herb

    2012-10-01

    Maximizing the fusion gain of inertial confinement fusion (ICF) for inertial fusion energy (IFE) applications leads to the standard scenario of central hot spot ignition followed by propagating burn wave through the cold/dense assembled fuel. The fact that the hot spot is surrounded by cold but dense fuel layer introduces subtle plasma physics which requires a kinetic description. Here we perform Fokker-Planck calculations and kinetic PIC simulations for an ICF plasma initially in pressure balance but having large temperature gradient over a narrow transition layer. The loss of the fast ion tail from the hot spot, which is important for fusion reactivity, is quantified by Fokker-Planck models. The role of electron energy transport and the ambipolar electric field is investigated via kinetic simulations and the fluid moment models. The net effect on both hot spot ion temperature and the ion tail distribution, and hence the fusion reactivity, is elucidated.

  16. Sheared-flow induced confinement transition in a linear magnetized plasma

    SciTech Connect

    Zhou, S.; Heidbrink, W. W.; Boehmer, H.; McWilliams, R.; Carter, T. A.; Vincena, S.; Friedman, B.; Schaffner, D.

    2012-01-15

    A magnetized plasma cylinder (12 cm in diameter) is induced by an annular shape obstacle at the Large Plasma Device [W. Gekelman, H. Pfister, Z. Lucky, J. Bamber, D. Leneman, and J. Maggs, Rev. Sci. Instrum. 62, 2875 (1991)]. Sheared azimuthal flow is driven at the edge of the plasma cylinder through edge biasing. Strong fluctuations of density and potential ({delta}n/n{approx}e{delta}{phi}/kT{sub e}{approx}0.5) are observed at the plasma edge, accompanied by a large density gradient (L{sub n}={nabla}lnn{sup -1}{approx}2cm) and shearing rate ({gamma}{approx}300kHz). Edge turbulence and cross-field transport are modified by changing the bias voltage (V{sub bias}) on the obstacle and the axial magnetic field (B{sub z}) strength. In cases with low V{sub bias} and large B{sub z}, improved plasma confinement is observed, along with steeper edge density gradients. The radially sheared flow induced by ExB drift dramatically changes the cross-phase between density and potential fluctuations, which causes the wave-induced particle flux to reverse its direction across the shear layer. In cases with higher bias voltage or smaller B{sub z}, large radial transport and rapid depletion of the central plasma density are observed. Two-dimensional cross-correlation measurement shows that a mode with azimuthal mode number m=1 and large radial correlation length dominates the outward transport in these cases. Linear analysis based on a two-fluid Braginskii model suggests that the fluctuations are driven by both density gradient (drift wave like) and flow shear (Kelvin-Helmholtz like) at the plasma edge.

  17. Distinct turbulence sources and confinement features in the spherical tokamak plasma regime

    DOE PAGES

    Wang, W. X.; Ethier, S.; Ren, Y.; Kaye, S.; Chen, J.; Startsev, E.; Lu, Z.

    2015-10-30

    New turbulence contributions to plasma transport and confinement in the spherical tokamak (ST) regime are identified through nonlinear gyrokinetic simulations. The drift wave Kelvin-Helmholtz (KH) mode characterized by intrinsic mode asymmetry is shown to drive significant ion thermal transport in strongly rotating national spherical torus experiment (NSTX) L-modes. The long wavelength, quasi-coherent dissipative trapped electron mode (TEM) is destabilized in NSTX H-modes despite the presence of strong E x B shear, providing a robust turbulence source dominant over collisionless TEM. Dissipative trapped electron mode (DTEM)-driven transport in the NSTX parametric regime is shown to increase with electron collision frequency, offeringmore » one possible source for the confinement scaling observed in experiments. There exists a turbulence-free regime in the collision-induced collisionless trapped electron mode to DTEM transition for ST plasmas. In conclusion, this predicts a natural access to a minimum transport state in the low collisionality regime that future advanced STs may cover.« less

  18. Distinct turbulence sources and confinement features in the spherical tokamak plasma regime

    SciTech Connect

    Wang, W. X.; Ethier, S.; Ren, Y.; Kaye, S.; Chen, J.; Startsev, E.; Lu, Z.

    2015-10-30

    New turbulence contributions to plasma transport and confinement in the spherical tokamak (ST) regime are identified through nonlinear gyrokinetic simulations. The drift wave Kelvin-Helmholtz (KH) mode characterized by intrinsic mode asymmetry is shown to drive significant ion thermal transport in strongly rotating national spherical torus experiment (NSTX) L-modes. The long wavelength, quasi-coherent dissipative trapped electron mode (TEM) is destabilized in NSTX H-modes despite the presence of strong E x B shear, providing a robust turbulence source dominant over collisionless TEM. Dissipative trapped electron mode (DTEM)-driven transport in the NSTX parametric regime is shown to increase with electron collision frequency, offering one possible source for the confinement scaling observed in experiments. There exists a turbulence-free regime in the collision-induced collisionless trapped electron mode to DTEM transition for ST plasmas. In conclusion, this predicts a natural access to a minimum transport state in the low collisionality regime that future advanced STs may cover.

  19. NBI fast ion confinement in the helical core of MAST hybrid-like plasmas

    NASA Astrophysics Data System (ADS)

    Pfefferlé, D.; Graves, J. P.; Cooper, W. A.; Misev, C.; Chapman, I. T.; Turnyanskiy, M.; Sangaroon, S.

    2014-06-01

    Energetic ions are found to be transported strongly from the core of MAST hybrid-like plasmas during long-lived mode (LLM) magnetohydrodynamic activity. The resulting impact on the neutral beam ion deposition and concurrent current drive is modelled using the guiding-centre approximation in the internal kinked magnetic topology. General coordinate guiding-centre equations are extended for this purpose. It is found that the kinked core spirals around the position of strongest ionization, which remains geometrically centred, so that a large fraction of the population is deposited in the high shear external region where the plasma is almost axisymmetric. Those particles ionized in the low shear region exhibit exotic drift motion due to the strongly non-axisymmetric equilibrium, periodically passing near the magnetic axis and then reflected by the boundary of the kinked equilibrium, which in this respect acts as a confining pinch. Broad agreement is found against experimental measurement of fast ion particle confinement degradation as the MAST LLM amplitude varies.

  20. MAGNETICALLY CONFINED INTERSTELLAR HOT PLASMA IN THE NUCLEAR BULGE OF OUR GALAXY

    SciTech Connect

    Nishiyama, Shogo; Kwon, Jungmi; Tamura, Motohide; Yasui, Kazuki; Nagata, Tetsuya; Yoshikawa, Tatsuhito; Uchiyama, Hideki; Schödel, Rainer; Hatano, Hirofumi; Sato, Shuji; Sugitani, Koji; Suenaga, Takuya

    2013-06-01

    The origin of the Galactic center diffuse X-ray emission (GCDX) is still under intense investigation. In particular, the interpretation of the hot (kT ≈ 7 keV) component of the GCDX, characterized by the strong Fe 6.7 keV line emission, has been contentious. If the hot component originates from a truly diffuse interstellar plasma, not a collection of unresolved point sources, such plasma cannot be gravitationally bound, and its regeneration would require a huge amount of energy. Here, we show that the spatial distribution of the GCDX does not correlate with the number density distribution of an old stellar population traced by near-infrared light, strongly suggesting a significant contribution of the diffuse interstellar plasma. Contributions of the old stellar population to the GCDX are implied to be ∼50% and ∼20% in the nuclear stellar disk (NSD) and nuclear star cluster, respectively. For the NSD, a scale height of 0.°32 ± 0.°02 is obtained for the first time from the stellar number density profiles. We also show the results of the extended near-infrared polarimetric observations in the central 3° × 2° region of our Galaxy, and confirm that the GCDX region is permeated by a large scale, toroidal magnetic field (MF) as previously claimed. Together with observed MF strengths close to energy equipartition, the hot plasma could be magnetically confined, reducing the amount of energy required to sustain it.

  1. The potential role of electric fields and plasma barodiffusion on the inertial confinement fusion databasea)

    NASA Astrophysics Data System (ADS)

    Amendt, Peter; Wilks, S. C.; Bellei, C.; Li, C. K.; Petrasso, R. D.

    2011-05-01

    The generation of strong, self-generated electric fields (GV/m) in direct-drive, inertial-confinement-fusion (ICF) capsules has been reported [Rygg et al., Science 319, 1223 (2008); Li et al., Phys. Rev. Lett. 100, 225001 (2008)]. A candidate explanation for the origin of these fields based on charge separation across a plasma shock front was recently proposed [Amendt et al., Plasma Phys. Controlled Fusion 51 124048 (2009)]. The question arises whether such electric fields in imploding capsules can have observable consequences on target performance. Two well-known anomalies come to mind: (1) an observed ≈2× greater-than-expected deficit of neutrons in an equimolar D3He fuel mixture compared with hydrodynamically equivalent D [Rygg et al., Phys. Plasmas 13, 052702 (2006)] and DT [Herrmann et al., Phys. Plasmas 16, 056312 (2009)] fuels, and (2) a similar shortfall of neutrons when trace amounts of argon are mixed with D in indirect-drive implosions [Lindl et al., Phys. Plasmas 11, 339 (2004)]. A new mechanism based on barodiffusion (or pressure gradient-driven diffusion) in a plasma is proposed that incorporates the presence of shock-generated electric fields to explain the reported anomalies. For implosions performed at the Omega laser facility [Boehly et al., Opt. Commun. 133, 495 (1997)], the (low Mach number) return shock has an appreciable scale length over which the lighter D ions can diffuse away from fuel center. The depletion of D fuel is estimated and found to lead to a corresponding reduction in neutrons, consistent with the anomalies observed in experiments for both argon-doped D fuels and D3He equimolar mixtures. The reverse diffusional flux of the heavier ions toward fuel center also increases the pressure from a concomitant increase in electron number density, resulting in lower stagnation pressures and larger imploded cores in agreement with gated, self-emission, x-ray imaging data.

  2. 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.

  3. Confinement time of electron plasma approaching magnetic pumping transport limit in small aspect ratio C-shaped torus

    NASA Astrophysics Data System (ADS)

    Lachhvani, Lavkesh; Pahari, Sambaran; Goswami, Rajiv; Bajpai, Manu; Yeole, Yogesh; Chattopadhyay, P. K.

    2016-06-01

    A long confinement time of electron plasma, approaching magnetic pumping transport limit, has been observed in SMARTEX-C (a small aspect ratio partial torus with R o / a ˜ 1.59 ). Investigations of the growth rate reveal that they are governed by instabilities like resistive wall destabilization, ion driven instabilities, and electron-neutral collisions. Successful confinement of electron plasmas exceeding > 1 × 10 5 poloidal E → × B → rotations lasting for nearly 2.1 ± 0.1 s is achieved by suppressing these instabilities. The confinement time has been estimated in two ways: (a) from the frequency scaling of the linear diocotron mode launched from sections of the wall that are also used as capacitive probes and (b) by dumping the plasma onto a charge collector at different hold times.

  4. Effects of acute temperature change, confinement and housing on plasma corticosterone in water snakes, Nerodia sipedon (Colubridae: Natricinae).

    PubMed

    Sykes, Kyle Lea; Klukowski, Matthew

    2009-03-01

    Body temperature affects many aspects of reptilian behavior and physiology, but its effect on hormonal secretion has been little studied, especially in snakes. Major objectives of this study were to determine if acute changes in body temperature during confinement influenced plasma corticosterone levels and if initial body temperatures upon capture in the field were related to baseline corticosterone levels in water snakes (Nerodia sipedon). Water snakes were bled upon capture in the field and after one hour of confinement in a cooled, control, or heated incubator. Since little is known about the potential metabolic changes in response to stress in reptiles, plasma triglyceride levels were also measured. Upon completion of the field study, snakes were housed for 5-8 days without food to determine the effect of chronic stress on both corticosterone and triglyceride levels. Plasma corticosterone concentrations were measured using enzyme-linked immunosorbant assay (ELISA) and plasma triglycerides were determined enzymatically. In the field, experimental alterations of body temperature during confinement had no effect on corticosterone levels. Similarly, there was no correlation between initial body temperature and baseline plasma corticosterone concentrations. However, post-confinement corticosterone levels were approximately three-times greater in females than males. Plasma triglyceride levels were not affected by temperature treatment, confinement, or sex. Compared to field values, both baseline and post-confinement corticosterone levels were elevated after the chronic stress of short-term laboratory housing but triglyceride levels decreased. Overall, these results indicate that sex but not body temperature has a major influence on the adrenocortical stress response in Nerodia sipedon.

  5. Fusion reactivity, confinement, and stability of neutral-beam heated plasmas in TFTR and other tokamaks

    SciTech Connect

    Park, Hyeon, K.; Sabbagh, S.A.

    1996-05-01

    The hypothesis that the heating beam fueling profile shape connects the edge condition and improved core confinement and fusion reactivity is extensively studied on TFTR and applied to other tokamaks. The derived absolute scalings based on beam fueling profile shape for the stored energy and neutron yield can be applied to the deuterium discharges at different major radii in TFTR. These include Supershot, High poloidal beta, L-mode, and discharges with a reversed shear (RS) magnetic configuration. These scalings are also applied to deuterium-tritium discharges. The role of plasma parameters, such as plasma current, Isdo2(p), edge safety factor, qsdo5(a), and toroidal field, Bsdo2(T), in the performance and stability of the discharges is explicitly studied. Based on practical and externally controllable plasma parameters, the limitation and optimization of fusion power production of the present TFTR is investigated and a path for a discharge condition with fusion power gain, Q > 1 is suggested based on this study. Similar physics interpretation is provided for beam heated discharges on other major tokamaks.

  6. Particle and momentum confinement in tokamak plasmas with unbalanced neutral beam injection and strong rotation

    SciTech Connect

    Malik, M.A.

    1988-01-01

    There is a self-consistent theory of the effects of neutral beam injection on impurity transport in tokamak plasmas. The theory predicts that co-injection drives impurities outward and that counter-injection enhances the normally inward flow of impurities. The theory was applied to carry out a detailed analysis of the large experimental database from the PLT and the ISX-B tokamaks. The theory was found to generally model the experimental data quite well. It is, therefore, concluded that neutral beam co-injection can drive impurities outward to achieve clean central plasmas and a cool radiating edge. Theoretical predictions for future thermonuclear reactors such as INTOR, TIBER II, and ITER indicated that neutral beam driven flow reversal might be an effective impurity control method if the rate of beam momentum deposited per plasma ion is adequate. The external momentum drag, which is a pivotal concept in impurity flow reversal theory, is correctly predicted by the gyroviscous theory of momentum confinement. The theory was applied to analyze experimental data from the PLT and the PDX tokamaks with exact experimental conditions. The theory was found to be in excellent agreement with experiment over a wide range of parameters. It is, therefore, possible to formulate the impurity transport theory from first principles, without resort to empiricism.

  7. Study of improved confinement by a stepwise increase of the input heating power for tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Asif, Muhammad; Mohamed, Mabruka; Kim, Eun-Jin

    2016-09-01

    This paper is an extension of the brief study by Sarah Douglas et al. [Phys. Plasmas 20 (2013) 114504] where in the study a sinusoidal perturbation of the heating power has been studied. In this paper a stepwise increase of the heating power and its influence on the L-H transition are studied. Using a function, Atanh(t/T) for the transition of input heating power for tokamak plasmas, i.e. the addition of the perturbation, Atanh(t/T), to constant power q0 is shown to promote the confinement, leading to the L-H transition at a lower value of q0, as compared to the case of constant q0 without the Atanh(t/T) perturbation. It is seen that the input heating power Q that consists of constant part q0 in addition to a function Atanh(t/T) provides the L-H transition for relatively small A and much wider range values of 1/T as compared to Sarah Douglas et al. [Phys. Plasmas 20 (2013) 114504].

  8. Topics on the Formation and Stability of Magnetic Mirror Confined Plasmas.

    NASA Astrophysics Data System (ADS)

    Wickham, Michael Gordon

    We have investigated two methods of creating a magnetic mirror confined plasma. The first method used the direct cross-field injection of a potassium plasma into a magnetic mirror, and the second applied ion-cyclotron -resonance heating (ICRH) to a barium Q-machine plasma in a simple axisymmetric mirror field. The latter procedure provided a plasma which was particularly suitable for the investigation of MHD stability and kinetic microstability. In the first method, a beam of potassium plasma of 10('12)cm('-3). density was formed in a continuous magnetoplasmadynamic arc. source. This beam was then injected into a mirror configuration from. a direction transverse to the magnetic field. The self-induced polarization and subsequent E(' )X(' )B drift of the beam allowed the plasma to fill the magnetic mirror. A density of 10('12)cm('-3) was obtained when insulating end plugs were used, a slightly reduced value when the beam was injected into a straight solenoidal field, and a lower limit of 10('11)cm('-3) if the end plugs were made conducting. The temperature of the trapped plasma corresponded to approximately two thirds of the energy in the initial directed motion of the beam. We discuss these results qualitatively in terms of the polarization-drift model of Schmidt. The possible application of this injection technique to the fueling of tandem-mirror end cells is described briefly. The second series of experiments studied a low (beta), high density, collisionless, barium plasma which was energized by the application of ICRH in a simple axisymmetric mirror. The barium ions were thereby heated from an initial perpendicular temperature of 0.2 eV to 3-5 eV. We then measured, with laser induced resonance-fluorescence techniques, the ion velocity distribution under the influence of ICRH. In particular, we examined the temporal evolution of two components of the ion velocity distribution, f(v(,x),t) and f(v(,(VBAR)(VBAR)),t), in a fixed magnetic field configuration. The ion

  9. Oligomers of the ATPase EHD2 confine caveolae to the plasma membrane through association with actin

    PubMed Central

    Stoeber, Miriam; Stoeck, Ina Karen; Hänni, Christine; Bleck, Christopher Karl Ernst; Balistreri, Giuseppe; Helenius, Ari

    2012-01-01

    Caveolae are specialized domains present in the plasma membrane (PM) of most mammalian cell types. They function in signalling, membrane regulation, and endocytosis. We found that the Eps-15 homology domain-containing protein 2 (EHD2, an ATPase) associated with the static population of PM caveolae. Recruitment to the PM involved ATP binding, interaction with anionic lipids, and oligomerization into large complexes (60–75S) via interaction of the EH domains with intrinsic NPF/KPF motifs. Hydrolysis of ATP was essential for binding of EHD2 complexes to caveolae. EHD2 was found to undergo dynamic exchange at caveolae, a process that depended on a functional ATPase cycle. Depletion of EHD2 by siRNA or expression of a dominant-negative mutant dramatically increased the fraction of mobile caveolar vesicles coming from the PM. Overexpression of EHD2, in turn, caused confinement of cholera toxin B in caveolae. The confining role of EHD2 relied on its capacity to link caveolae to actin filaments. Thus, EHD2 likely plays a key role in adjusting the balance between PM functions of stationary caveolae and the role of caveolae as vesicular carriers. PMID:22505029

  10. Oligomers of the ATPase EHD2 confine caveolae to the plasma membrane through association with actin.

    PubMed

    Stoeber, Miriam; Stoeck, Ina Karen; Hänni, Christine; Bleck, Christopher Karl Ernst; Balistreri, Giuseppe; Helenius, Ari

    2012-05-16

    Caveolae are specialized domains present in the plasma membrane (PM) of most mammalian cell types. They function in signalling, membrane regulation, and endocytosis. We found that the Eps-15 homology domain-containing protein 2 (EHD2, an ATPase) associated with the static population of PM caveolae. Recruitment to the PM involved ATP binding, interaction with anionic lipids, and oligomerization into large complexes (60-75S) via interaction of the EH domains with intrinsic NPF/KPF motifs. Hydrolysis of ATP was essential for binding of EHD2 complexes to caveolae. EHD2 was found to undergo dynamic exchange at caveolae, a process that depended on a functional ATPase cycle. Depletion of EHD2 by siRNA or expression of a dominant-negative mutant dramatically increased the fraction of mobile caveolar vesicles coming from the PM. Overexpression of EHD2, in turn, caused confinement of cholera toxin B in caveolae. The confining role of EHD2 relied on its capacity to link caveolae to actin filaments. Thus, EHD2 likely plays a key role in adjusting the balance between PM functions of stationary caveolae and the role of caveolae as vesicular carriers. PMID:22505029

  11. Customizing electron confinement in plasma-assembled Si/AlN nanodots for solar cell applications

    SciTech Connect

    Huang, S. Y.; Xu, S.; Arulsamy, A. Das; Xu, M.; Cvelbar, U.; Mozetic, M.; Ostrikov, K.

    2009-12-15

    Size-uniform Si nanodots (NDs) are synthesized on an AlN buffer layer at low Si(111) substrate temperatures using inductively coupled plasma-assisted magnetron sputtering deposition. High-resolution electron microscopy reveals that the sizes of the Si NDs range from 9 to 30 nm. Room-temperature photoluminescence (PL) spectra indicate that the energy peak shifts from 738 to 778 nm with increasing the ND size. In this system, the quantum confinement effect is fairly strong even for relatively large (up to 25 nm in diameter) NDs, which is promising for the development of the next-generation all-Si tandem solar cells capable of effectively capturing sunlight photons with the energies between 1.7 (infrared: large NDs) and 3.4 eV (ultraviolet: small NDs). The strength of the resulting electron confinement in the Si/AlN ND system is evaluated and justified by analyzing the measured PL spectra using the ionization energy theory approximation.

  12. Inertially confined fusion plasmas dominated by alpha-particle self-heating

    NASA Astrophysics Data System (ADS)

    Hurricane, O. A.; Callahan, D. A.; Casey, D. T.; Dewald, E. L.; Dittrich, T. R.; Döppner, T.; Haan, S.; Hinkel, D. E.; Berzak Hopkins, L. F.; Jones, O.; Kritcher, A. L.; Le Pape, S.; Ma, T.; Macphee, A. G.; Milovich, J. L.; Moody, J.; Pak, A.; Park, H.-S.; Patel, P. K.; Ralph, J. E.; Robey, H. F.; Ross, J. S.; Salmonson, J. D.; Spears, B. K.; Springer, P. T.; Tommasini, R.; Albert, F.; Benedetti, L. R.; Bionta, R.; Bond, E.; Bradley, D. K.; Caggiano, J.; Celliers, P. M.; Cerjan, C.; Church, J. A.; Dylla-Spears, R.; Edgell, D.; Edwards, M. J.; Fittinghoff, D.; Barrios Garcia, M. A.; Hamza, A.; Hatarik, R.; Herrmann, H.; Hohenberger, M.; Hoover, D.; Kline, J. L.; Kyrala, G.; Kozioziemski, B.; Grim, G.; Field, J. E.; Frenje, J.; Izumi, N.; Gatu Johnson, M.; Khan, S. F.; Knauer, J.; Kohut, T.; Landen, O.; Merrill, F.; Michel, P.; Moore, A.; Nagel, S. R.; Nikroo, A.; Parham, T.; Rygg, R. R.; Sayre, D.; Schneider, M.; Shaughnessy, D.; Strozzi, D.; Town, R. P. J.; Turnbull, D.; Volegov, P.; Wan, A.; Widmann, K.; Wilde, C.; Yeamans, C.

    2016-08-01

    Alpha-particle self-heating, the process of deuterium-tritium fusion reaction products depositing their kinetic energy locally within a fusion reaction region and thus increasing the temperature in the reacting region, is essential for achieving ignition in a fusion system. Here, we report new inertial confinement fusion experiments where the alpha-particle heating of the plasma is dominant with the fusion yield produced exceeding the fusion yield from the work done on the fuel (pressure times volume change) by a factor of two or more. These experiments have achieved the highest yield (26 +/- 0.5 kJ) and stagnation pressures (≍220 +/- 40 Gbar) of any facility-based inertial confinement fusion experiments, although they are still short of the pressures required for ignition on the National Ignition Facility (~300-400 Gbar). These experiments put us in a new part of parameter space that has not been extensively studied so far because it lies between the no-alpha-particle-deposition regime and ignition.

  13. Mean and Oscillating Plasma Flows and Turbulence Interactions across the L-H Confinement Transition

    SciTech Connect

    Conway, G. D.; Angioni, C.; Ryter, F.; Sauter, P.; Vicente, J.

    2011-02-11

    A complex interaction between turbulence driven ExB zonal flow oscillations, i.e., geodesic acoustic modes (GAMs), the turbulence, and mean equilibrium flows is observed during the low to high (L-H) plasma confinement mode transition in the ASDEX Upgrade tokamak. Below the L-H threshold at low densities a limit-cycle oscillation forms with competition between the turbulence level and the GAM flow shearing. At higher densities the cycle is diminished, while in the H mode the cycle duration becomes too short to sustain the GAM, which is replaced by large amplitude broadband flow perturbations. Initially GAM amplitude increases as the H-mode transition is approached, but is then suppressed in the H mode by enhanced mean flow shear.

  14. Probing Leader Cells in Endothelial Collective Migration by Plasma Lithography Geometric Confinement

    PubMed Central

    Yang, Yongliang; Jamilpour, Nima; Yao, Baoyin; Dean, Zachary S.; Riahi, Reza; Wong, Pak Kin

    2016-01-01

    When blood vessels are injured, leader cells emerge in the endothelium to heal the wound and restore the vasculature integrity. The characteristics of leader cells during endothelial collective migration under diverse physiological conditions, however, are poorly understood. Here we investigate the regulation and function of endothelial leader cells by plasma lithography geometric confinement generated. Endothelial leader cells display an aggressive phenotype, connect to follower cells via peripheral actin cables and discontinuous adherens junctions, and lead migrating clusters near the leading edge. Time-lapse microscopy, immunostaining, and particle image velocimetry reveal that the density of leader cells and the speed of migrating clusters are tightly regulated in a wide range of geometric patterns. By challenging the cells with converging, diverging and competing patterns, we show that the density of leader cells correlates with the size and coherence of the migrating clusters. Collectively, our data provide evidence that leader cells control endothelial collective migration by regualting the migrating clusters. PMID:26936382

  15. Stability properties and fast ion confinement of hybrid tokamak plasma configurations

    NASA Astrophysics Data System (ADS)

    Graves, J. P.; Brunetti, D.; Pfefferle, D.; Faustin, J. M. P.; Cooper, W. A.; Kleiner, A.; Lanthaler, S.; Patten, H. W.; Raghunathan, M.

    2015-11-01

    In hybrid scenarios with flat q just above unity, extremely fast growing tearing modes are born from toroidal sidebands of the near resonant ideal internal kink mode. New scalings of the growth rate with the magnetic Reynolds number arise from two fluid effects and sheared toroidal flow. Non-linear saturated 1/1 dominant modes obtained from initial value stability calculation agree with the amplitude of the 1/1 component of a 3D VMEC equilibrium calculation. Viable and realistic equilibrium representation of such internal kink modes allow fast ion studies to be accurately established. Calculations of MAST neutral beam ion distributions using the VENUS-LEVIS code show very good agreement of observed impaired core fast ion confinement when long lived modes occur. The 3D ICRH code SCENIC also enables the establishment of minority RF distributions in hybrid plasmas susceptible to saturated near resonant internal kink modes.

  16. Probing Leader Cells in Endothelial Collective Migration by Plasma Lithography Geometric Confinement.

    PubMed

    Yang, Yongliang; Jamilpour, Nima; Yao, Baoyin; Dean, Zachary S; Riahi, Reza; Wong, Pak Kin

    2016-03-03

    When blood vessels are injured, leader cells emerge in the endothelium to heal the wound and restore the vasculature integrity. The characteristics of leader cells during endothelial collective migration under diverse physiological conditions, however, are poorly understood. Here we investigate the regulation and function of endothelial leader cells by plasma lithography geometric confinement generated. Endothelial leader cells display an aggressive phenotype, connect to follower cells via peripheral actin cables and discontinuous adherens junctions, and lead migrating clusters near the leading edge. Time-lapse microscopy, immunostaining, and particle image velocimetry reveal that the density of leader cells and the speed of migrating clusters are tightly regulated in a wide range of geometric patterns. By challenging the cells with converging, diverging and competing patterns, we show that the density of leader cells correlates with the size and coherence of the migrating clusters. Collectively, our data provide evidence that leader cells control endothelial collective migration by regualting the migrating clusters.

  17. Probing Leader Cells in Endothelial Collective Migration by Plasma Lithography Geometric Confinement

    NASA Astrophysics Data System (ADS)

    Yang, Yongliang; Jamilpour, Nima; Yao, Baoyin; Dean, Zachary S.; Riahi, Reza; Wong, Pak Kin

    2016-03-01

    When blood vessels are injured, leader cells emerge in the endothelium to heal the wound and restore the vasculature integrity. The characteristics of leader cells during endothelial collective migration under diverse physiological conditions, however, are poorly understood. Here we investigate the regulation and function of endothelial leader cells by plasma lithography geometric confinement generated. Endothelial leader cells display an aggressive phenotype, connect to follower cells via peripheral actin cables and discontinuous adherens junctions, and lead migrating clusters near the leading edge. Time-lapse microscopy, immunostaining, and particle image velocimetry reveal that the density of leader cells and the speed of migrating clusters are tightly regulated in a wide range of geometric patterns. By challenging the cells with converging, diverging and competing patterns, we show that the density of leader cells correlates with the size and coherence of the migrating clusters. Collectively, our data provide evidence that leader cells control endothelial collective migration by regualting the migrating clusters.

  18. Dust confinement and dust-acoustic waves in weakly magnetized anodic plasmas

    SciTech Connect

    Trottenberg, Thomas; Block, Dietmar; Piel, Alexander

    2006-04-15

    Experiments on dust-acoustic waves (DAW) in a magnetized anodic plasma are presented for the regime of low collisionality. The dust trapping and the self-excited and synchronized DAW dynamics are studied. Based on Langmuir and emissive probe measurements the dust confinement is found to be well described with respect to size, stability, and position of the dust cloud by an effective potential well formed by ion drag and Coulomb forces. Moreover, the measurements indicate the necessity for a kinetic model for the wave dispersion. By means of singular value decomposition the local wavelengths and growth rates of the waves are measured systematically. It is found that the measured mean wave number is well described by kinetic theory, while the theoretical growth rates overestimate the experiments. A novel observation for the DAW is a systematic variation of the wavelength inside the dust cloud.

  19. Quiescent double barrier high-confinement mode plasmas in the DIII-D tokamak

    NASA Astrophysics Data System (ADS)

    Burrell, K. H.; Austin, M. E.; Brennan, D. P.; DeBoo, J. C.; Doyle, E. J.; Fenzi, C.; Fuchs, C.; Gohil, P.; Greenfield, C. M.; Groebner, R. J.; Lao, L. L.; Luce, T. C.; Makowski, M. A.; McKee, G. R.; Moyer, R. A.; Petty, C. C.; Porkolab, M.; Rettig, C. L.; Rhodes, T. L.; Rost, J. C.; Stallard, B. W.; Strait, E. J.; Synakowski, E. J.; Wade, M. R.; Watkins, J. G.; West, W. P.

    2001-05-01

    High-confinement (H-mode) operation is the choice for next-step tokamak devices based either on conventional or advanced tokamak physics. This choice, however, comes at a significant cost for both the conventional and advanced tokamaks because of the effects of edge localized modes (ELMs). ELMs can produce significant erosion in the divertor and can affect the beta limit and reduced core transport regions needed for advanced tokamak operation. Experimental results from DIII-D [J. L. Luxon et al., Plasma Physics and Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] this year have demonstrated a new operating regime, the quiescent H-mode regime, which solves these problems. We have achieved quiescent H-mode operation that is ELM-free and yet has good density and impurity control. In addition, we have demonstrated that an internal transport barrier can be produced and maintained inside the H-mode edge barrier for long periods of time (>3.5 s or >25 energy confinement times τE), yielding a quiescent double barrier regime. By slowly ramping the input power, we have achieved βNH89=7 for up to 5 times the τE of 150 ms. The βNH89 values of 7 substantially exceed the value of 4 routinely achieved in the standard ELMing H mode. The key factors in creating the quiescent H-mode operation are neutral beam injection in the direction opposite to the plasma current (counter injection) plus cryopumping to reduce the density. Density and impurity control in the quiescent H mode is possible because of the presence of an edge magnetohydrodynamic (MHD) oscillation, the edge harmonic oscillation, which enhances the edge particle transport while leaving the energy transport unaffected.

  20. Theoretical studies on plasma heating and confinement. Final report, May 4, 1984--May 13, 1988

    SciTech Connect

    Sudan, R.N.

    1993-01-01

    Three principal topics are covered in this final report: Stabilization of low frequency modes of an axisymmetric compact torus plasma confinement system, such as, spheromaks and FRC`S, by a population of large orbit axis encircling energetic ions. Employing an extension of the `energy principle` which utilizes a Vlasov description for the energetic `ion component, it has been demonstrated that short wavelength MHD type modes are stabilized while the long wavelength tilt and precessional modes are marginally stable. The deformation of the equilibrium configuration by the energetic ions results in the stabilization of the tilt mode for spheromaks. Formation of Ion Rings and their coalescence with spheromaks. A two dimensional electromagnetic PIC codes has been developed for the study of ion ring formation and its propagation, deformation and slowing down in a cold plasma. It has been shown that a ring moving at a speed less than the Alfven velocity can merge with a stationary spheromak. Anomalous transport from drift waves in a Tokomak. The Direct Interaction Approximation in used to obtain incremental transport coefficients for particles and heat for drift waves in a Tokomak. It is shown that the transport matrix does not obey Onsager`s principle.

  1. Introduction to Gyrokinetic Theory with Applications in Magnetic Confinement Research in Plasma Physics

    SciTech Connect

    W.M. Tang

    2005-01-03

    The present lecture provides an introduction to the subject of gyrokinetic theory with applications in the area of magnetic confinement research in plasma physics--the research arena from which this formalism was originally developed. It was presented as a component of the ''Short Course in Kinetic Theory within the Thematic Program in Partial Differential Equations'' held at the Fields Institute for Research in Mathematical Science (24 March 2004). This lecture also discusses the connection between the gyrokinetic formalism and powerful modern numerical simulations. Indeed, simulation, which provides a natural bridge between theory and experiment, is an essential modern tool for understanding complex plasma behavior. Progress has been stimulated in particular by the exponential growth of computer speed along with significant improvements in computer technology. The advances in both particle and fluid simulations of fine-scale turbulence and large-scale dynamics have produced increasingly good agreement between experimental observations and computational modeling. This was enabled by two key factors: (i) innovative advances in analytic and computational methods for developing reduced descriptions of physics phenomena spanning widely disparate temporal and spatial scales and (ii) access to powerful new computational resources.

  2. Identification of new turbulence contributions to plasma transport and confinement in spherical tokamak regime

    DOE PAGES

    Wang, W. X.; Ethier, S.; Ren, Y.; Kaye, S.; Chen, J.; Startsev, E.; Lu, Z.; Li, Z. Q.

    2015-10-15

    Highly distinct features of spherical tokamaks (ST), such as National Spherical Torus eXperiment (NSTX) and NSTX-U, result in a different fusion plasma regime with unique physics properties compared to conventional tokamaks. Nonlinear global gyrokinetic simulations critical for addressing turbulence and transport physics in the ST regime have led to new insights. The drift wave Kelvin-Helmholtz (KH) instability characterized by intrinsic mode asymmetry is identified in strongly rotating NSTX L-mode plasmas. While the strong E x B shear associated with the rotation leads to a reduction in KH/ion temperature gradient turbulence, the remaining fluctuations can produce a significant ion thermal transportmore » that is comparable to the experimental level in the outer core region (with no "transport shortfall"). The other new, important turbulence source identified in NSTX is the dissipative trapped electron mode (DTEM), which is believed to play little role in conventional tokamak regime. Due to the high fraction of trapped electrons, long wavelength DTEMs peaking around kθρs ~ 0.1 are destabilized in NSTX collisionality regime by electron density and temperature gradients achieved there. Surprisingly, the E x B shear stabilization effect on DTEM is remarkably weak, which makes it a major turbulence source in the ST regime dominant over collisionless TEM (CTEM). The latter, on the other hand, is subject to strong collisional and E x B shear suppression in NSTX. DTEM is shown to produce significant particle, energy and toroidal momentum transport, in agreement with experimental levels in NSTX H-modes. Furthermore, DTEM-driven transport in NSTX parametric regime is found to increase with electron collision frequency, providing one possible source for the scaling of confinement time observed in NSTX H-modes. Most interestingly, the existence of a turbulence-free regime in the collision-induced CTEM to DTEM transition, corresponding to a minimum plasma transport in

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

    SciTech Connect

    Benyoucef, Djilali; Yousfi, Mohammed

    2015-01-15

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

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

    NASA Astrophysics Data System (ADS)

    Benyoucef, Djilali; Yousfi, Mohammed

    2015-01-01

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

  5. Identification of new turbulence contributions to plasma transport and confinement in spherical tokamak regime

    SciTech Connect

    Wang, W. X.; Ethier, S.; Ren, Y.; Kaye, S.; Chen, J.; Startsev, E.; Lu, Z.; Li, Z. Q.

    2015-10-15

    Highly distinct features of spherical tokamaks (ST), such as National Spherical Torus eXperiment (NSTX) and NSTX-U, result in a different fusion plasma regime with unique physics properties compared to conventional tokamaks. Nonlinear global gyrokinetic simulations critical for addressing turbulence and transport physics in the ST regime have led to new insights. The drift wave Kelvin-Helmholtz (KH) instability characterized by intrinsic mode asymmetry is identified in strongly rotating NSTX L-mode plasmas. While the strong E x B shear associated with the rotation leads to a reduction in KH/ion temperature gradient turbulence, the remaining fluctuations can produce a significant ion thermal transport that is comparable to the experimental level in the outer core region (with no "transport shortfall"). The other new, important turbulence source identified in NSTX is the dissipative trapped electron mode (DTEM), which is believed to play little role in conventional tokamak regime. Due to the high fraction of trapped electrons, long wavelength DTEMs peaking around kθρs ~ 0.1 are destabilized in NSTX collisionality regime by electron density and temperature gradients achieved there. Surprisingly, the E x B shear stabilization effect on DTEM is remarkably weak, which makes it a major turbulence source in the ST regime dominant over collisionless TEM (CTEM). The latter, on the other hand, is subject to strong collisional and E x B shear suppression in NSTX. DTEM is shown to produce significant particle, energy and toroidal momentum transport, in agreement with experimental levels in NSTX H-modes. Furthermore, DTEM-driven transport in NSTX parametric regime is found to increase with electron collision frequency, providing one possible source for the scaling of confinement time observed in NSTX H-modes. Most interestingly, the existence of a turbulence-free regime in the collision-induced CTEM to DTEM transition, corresponding to a minimum plasma

  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 mitigating effect of magnetic fields on Rayleigh-Taylor unstable inertial confinement fusion plasmas

    SciTech Connect

    Srinivasan, Bhuvana; Tang, Xian-Zhu

    2013-05-15

    Rayleigh-Taylor (RT) instabilities at interfaces of disparate mass densities have long been known to generate magnetic fields during inertial confinement fusion implosions. An externally applied magnetic field can also be efficiently amplified by RT instabilities. The focus here is on magnetic field generation and amplification at the gas-ice interface which is RT unstable during the deceleration phase of the implosion. RT instabilities lead to undesirable mix of hot and cold plasmas which enhances thermal energy loss and tends to produce a more massive warm-spot instead of a hot-spot. Two mechanisms are shown here to mitigate the thermal energy loss from the hot-spot. The first mechanism is the reduction of electron thermal conductivity with interface-aligned magnetic fields. This can occur through self-generated magnetic fields via the Biermann battery effect as well as through externally applied magnetic fields that undergo an exponential growth via the stretch-and-fold magnetohydrodynamic dynamo. Self-generated magnetic fields during RT evolution can result in a factor of 2−10 decrease in the electron thermal conductivity at the gas-ice interface, while externally applied magnetic fields that are compressed to 6–1000 T at the onset of deceleration (corresponding to pre-implosion external fields of 0.06–10 T) could result in a factor of 2–500 reduction in electron thermal conductivity at the gas-ice interface. The second mechanism to mitigate thermal energy loss from the hot-spot is to decrease the interface mixing area between the hot and cold plasmas. This is achieved through large external magnetic fields of 1000 T at the onset of deceleration which damp short-wavelength RT modes and long-wavelength Kelvin-Helmholtz modes thus significantly slowing the RT growth and reducing mix.

  8. The field line map approach for simulations of magnetically confined plasmas

    NASA Astrophysics Data System (ADS)

    Stegmeir, Andreas; Coster, David; Maj, Omar; Hallatschek, Klaus; Lackner, Karl

    2016-01-01

    Predictions of plasma parameters in the edge and scrape-off layer of tokamaks is difficult since most modern tokamaks have a divertor and the associated separatrix causes the usually employed field/flux-aligned coordinates to become singular on the separatrix/X-point. The presented field line map approach avoids such problems as it is based on a cylindrical grid: standard finite-difference methods can be used for the discretisation of perpendicular (w.r.t. magnetic field) operators, and the characteristic flute mode property (k∥ ≪k⊥) of structures is exploited computationally via a field line following discretisation of parallel operators which leads to grid sparsification in the toroidal direction. This paper is devoted to the discretisation of the parallel diffusion operator (the approach taken is very similar to the flux-coordinate independent (FCI) approach which has already been adopted to a hyperbolic problem (Ottaviani, 2011; Hariri, 2013)). Based on the support operator method, schemes are derived which maintain the self-adjointness property of the parallel diffusion operator on the discrete level. These methods have very low numerical perpendicular diffusion compared to a naive discretisation which is a critical issue since magnetically confined plasmas exhibit a very strong anisotropy. Two different versions of the discrete parallel diffusion operator are derived: the first is based on interpolation where the order of interpolation and therefore the numerical diffusion is adjustable; the second is based on integration and is advantageous in cases where the field line map is strongly distorted. The schemes are implemented in the new code GRILLIX, and extensive benchmarks and numerous examples are presented which show the validity of the approach in general and GRILLIX in particular.

  9. Confined trapped-alpha behavior in TFTR deuterium-tritium plasmas

    SciTech Connect

    Medley, S.S.; Budny, R.V.; Redi, M.H.; Roquemore, A.L.; White, R.B.; Duong, H.H.; Fisher, R.K.; Petrov, M.P.; Gorelenkov, N.N.

    1997-10-01

    Confined trapped-alpha energy spectra and differential radial density profiles in TFTR D-T plasmas are obtained with the Pellet Charge-eXchange (PCX) diagnostic which measures high energy (E{sub {alpha}} = 0.5--3.5 MeV), trapped alphas (v{sub {parallel}}/v = - 0.048) at a single time slice ({Delta}t {approximately} 1 msec) with a spatial resolution of {Delta}r {approximately} 5 cm. Tritons produced in D-D plasmas and RF-driven ion tails (H, {sup 3}He or T) were also observed and energetic tritium ion tail measurements will be discussed. PCX alpha and triton energy spectra extending up to their birth energies were measured in the core of MHD-quiescent discharges where the expected classical slowing down and pitch angle scattering effects are not complicated by stochastic ripple diffusion and sawtooth activity. Both the shape of the measured alpha and triton energy distributions and their density ratios are in good agreement with TRANSP predictions, indicating that the PCX measurements are consistent with classical thermalization of the fusion-generated alphas and tritons. From calculations, these results set an upper limit on possible anomalous radial diffusion for trapped alphas of D{sub {alpha}} {le} 0.01 m{sup 2}s{sup {minus}1}. Outside the core, where the trapped alphas are influenced by stochastic ripple diffusion effects, the PCX measurements are consistent with the functional dependence of the Goldston-White-Boozer stochastic ripple threshold on the alpha energy and the q-profile. In the presence of strong sawtooth activity, the PCX diagnostic observes significant redistribution of the alpha signal radial profile wherein alphas are depleted in the core and redistributed to well outside the q = 1 radius, but apparently not beyond the energy-dependent stochastic ripple loss boundary.

  10. APPARATUS FOR TRAPPING ENERGETIC CHARGED PARTICLES AND CONFINING THE RESULTING PLASMA

    DOEpatents

    Gibson, G.; Jordan, W.C.; Lauer, E.J.

    1963-04-01

    The present invention relates to a plasma-confining device and a particle injector therefor, the device utilizing a generally toroidal configuration with magnetic fields specifically tailored to the associated injector. The device minimizes the effects of particle end losses and particle drift to the walls with a relatively simple configuration. More particularly, the magnetic field configuration is created by a continuous array of circular, mirror field coils, disposed side-by- side, in particularly spaced relation, to form an endless, toroidal loop. The resulting magnetic field created therein has the appearance of a bumpy'' torus, from which is derived the name Bumpy Torus.'' One of the aforementioned coils is split transverse to its axis, and injection of particles is accomplished along a plane between the halves of such modified coil. The guiding center of the particles follows a constant magnetic field in the plane for a particular distance within the torus, to move therefrom onto a precessional surface which does not intersect the point of injection. (AEC)

  11. Dynamic materials evaluation by confined plasma ablation and laser-generated shocks

    NASA Astrophysics Data System (ADS)

    Paisley, Dennis L.; Swift, D. C.; Forsman, A. C.; Kyrala, George A.; Johnson, Randall P.; Kopp, Roger A.; Hauer, Allan A.; Wark, Justin S.; Loveridge, A.; Allen, A. M.; Kalantar, Daniel H.

    2000-08-01

    Laser-generated shocks can and have been used to study their effects on single crystal materials during shock compression. While a crystal undergoes shock compression and release, the transient x- ray diffraction (TXD) of the Bragg and Laue signals is indicative of the change in the crystal lattice spacing. The lattice spacing directly relates to the strain in the crystal. From the dynamic lattice data, strain, strain rate, and/or phase change in a material may be determined. Confined ablation plasmas can efficiently launch a flyer plate for direct impact on a target material imparting a well-characterized shock input and generate kilobar to megabar pressure pulses over a wide range of pulse duration (= 20 ns). The laser-launched flyer plates are analogous to those launched by gas guns, but the smaller size provides an experimental method not easily accessible by larger gas gun experiments. With lasers, diagnostic equipment can be easily synchronized to study dynamic material parameters, i.e., single crystal shock dynamics, interfacial bond strengths of thin coatings, grain-interfaces, texture, and high strain rates (106 - 109 sec-1).

  12. Mechanism for magnetic field generation and growth in Rayleigh-Taylor unstable inertial confinement fusion plasmas

    SciTech Connect

    Srinivasan, Bhuvana; Tang Xianzhu

    2012-08-15

    Rayleigh-Taylor instabilities (RTI) in inertial confinement fusion (ICF) implosions are expected to generate magnetic fields at the gas-ice interface and at the ice-ablator interface. The focus here is on the gas-ice interface where the temperature gradient is the largest. A Hall-MHD model is used to study the magnetic field generation and growth for 2-D single-mode and multimode RTI in a stratified two-fluid plasma, the two fluids being ions and electrons. Self-generated magnetic fields are observed and these fields grow as the RTI progresses via the {nabla}n{sub e} Multiplication-Sign {nabla}T{sub e} term in the generalized Ohm's law. Srinivasan et al.[Phys. Rev. Lett. 108, 165002 (2012)] present results of the magnetic field generation and growth, and some scaling studies in 2-dimensions. The results presented here study the mechanism behind the magnetic field generation and growth, which is related to fluid vorticity generation by RTI. The magnetic field wraps around the bubbles and spikes and concentrates in flux bundles at the perturbed gas-ice interface where fluid vorticity is large. Additionally, the results of Srinivasan et al.[Phys. Rev. Lett. 108, 165002 (2012)] are described in greater detail. Additional scaling studies are performed to determine the growth of the self-generated magnetic field as a function of density, acceleration, perturbation wavelength, Atwood number, and ion mass.

  13. Mechanism for magnetic field generation and growth in Rayleigh-Taylor unstable inertial confinement fusion plasmas

    NASA Astrophysics Data System (ADS)

    Srinivasan, Bhuvana; Tang, Xian-Zhu

    2012-08-01

    Rayleigh-Taylor instabilities (RTI) in inertial confinement fusion (ICF) implosions are expected to generate magnetic fields at the gas-ice interface and at the ice-ablator interface. The focus here is on the gas-ice interface where the temperature gradient is the largest. A Hall-MHD model is used to study the magnetic field generation and growth for 2-D single-mode and multimode RTI in a stratified two-fluid plasma, the two fluids being ions and electrons. Self-generated magnetic fields are observed and these fields grow as the RTI progresses via the ∇ne×∇Te term in the generalized Ohm's law. Srinivasan et al. [Phys. Rev. Lett. 108, 165002 (2012)] present results of the magnetic field generation and growth, and some scaling studies in 2-dimensions. The results presented here study the mechanism behind the magnetic field generation and growth, which is related to fluid vorticity generation by RTI. The magnetic field wraps around the bubbles and spikes and concentrates in flux bundles at the perturbed gas-ice interface where fluid vorticity is large. Additionally, the results of Srinivasan et al. [Phys. Rev. Lett. 108, 165002 (2012)] are described in greater detail. Additional scaling studies are performed to determine the growth of the self-generated magnetic field as a function of density, acceleration, perturbation wavelength, Atwood number, and ion mass.

  14. Plasma viscosity with mass transport in spherical inertial confinement fusion implosion simulations

    DOE PAGES

    Vold, Erik Lehman; Joglekar, Archis S.; Ortega, Mario I.; Moll, Ryan; Fenn, Daniel; Molvig, Kim

    2015-11-20

    The effects of viscosity and small-scale atomic-level mixing on plasmas in inertial confinement fusion(ICF) currently represent challenges in ICF research. Many current ICF hydrodynamic codes ignore the effects of viscosity though recent research indicates viscosity and mixing by classical transport processes may have a substantial impact on implosion dynamics. In this paper, we have implemented a Lagrangian hydrodynamic code in one-dimensional spherical geometry with plasmaviscosity and mass transport and including a three temperature model for ions, electrons, and radiation treated in a gray radiation diffusion approximation. The code is used to study ICF implosion differences with and without plasmaviscosity andmore » to determine the impacts of viscosity on temperature histories and neutron yield. It was found that plasmaviscosity has substantial impacts on ICF shock dynamics characterized by shock burn timing, maximum burn temperatures, convergence ratio, and time history of neutron production rates. Finally, plasmaviscosity reduces the need for artificial viscosity to maintain numerical stability in the Lagrangian formulation and also modifies the flux-limiting needed for electron thermal conduction.« less

  15. Plasma viscosity with mass transport in spherical inertial confinement fusion implosion simulations

    SciTech Connect

    Vold, Erik Lehman; Joglekar, Archis S.; Ortega, Mario I.; Moll, Ryan; Fenn, Daniel; Molvig, Kim

    2015-11-20

    The effects of viscosity and small-scale atomic-level mixing on plasmas in inertial confinement fusion(ICF) currently represent challenges in ICF research. Many current ICF hydrodynamic codes ignore the effects of viscosity though recent research indicates viscosity and mixing by classical transport processes may have a substantial impact on implosion dynamics. In this paper, we have implemented a Lagrangian hydrodynamic code in one-dimensional spherical geometry with plasmaviscosity and mass transport and including a three temperature model for ions, electrons, and radiation treated in a gray radiation diffusion approximation. The code is used to study ICF implosion differences with and without plasmaviscosity and to determine the impacts of viscosity on temperature histories and neutron yield. It was found that plasmaviscosity has substantial impacts on ICF shock dynamics characterized by shock burn timing, maximum burn temperatures, convergence ratio, and time history of neutron production rates. Finally, plasmaviscosity reduces the need for artificial viscosity to maintain numerical stability in the Lagrangian formulation and also modifies the flux-limiting needed for electron thermal conduction.

  16. A spectral line survey from 17.5–250 nm of plasmas created in a magnetic confinement device

    NASA Astrophysics Data System (ADS)

    McCarthy, K. J.; Zurro, B.; Hollmann, E. M.; Hernández Sánchez, J.; TJ-II team1, the

    2016-11-01

    Spectral emission lines continue to be a powerful tool for studying astrophysical, process, laser-produced, and magnetically confined plasmas, among others. Hence, numerous spectroscopy-based plasma diagnostics, from the x-ray to the infrared, make use of the relative intensity, width, displacement in wavelength, or temporal evolution of such emission lines emitted by the atoms and ions present in such plasmas. In this work, a spectral line survey, from 17.5–250 nm, is presented for electron cyclotron resonance heated (ECRH) and neutral beam injection (NBI) heated plasmas created and maintained in the TJ-II stellarator, a medium-sized magnetically confined plasma device. In these plasmas, for which hydrogen, deuterium or helium have been used as the working gas, central electron temperatures and densities up to 1 keV and 5 × 1019 m‑3, respectively, are achieved. This work is a compilation of the identified spectral emission lines emitted by the working gas as well by the intrinsic and injected impurity ions in the above wavelength range. For this, spectra were recorded, over the past fifteen years of TJ-II operation, using a 1 m focal length normal incidence spectrometer equipped with a charge-coupled detector at its output focal plane. In total, almost 400 spectral emission lines from eighteen different elements have been identified using a number of atomic line emission databases.

  17. First-principles thermal conductivity of warm-dense deuterium plasmas for inertial confinement fusion applications.

    PubMed

    Hu, S X; Collins, L A; Boehly, T R; Kress, J D; Goncharov, V N; Skupsky, S

    2014-04-01

    Thermal conductivity (κ) of both the ablator materials and deuterium-tritium (DT) fuel plays an important role in understanding and designing inertial confinement fusion (ICF) implosions. The extensively used Spitzer model for thermal conduction in ideal plasmas breaks down for high-density, low-temperature shells that are compressed by shocks and spherical convergence in imploding targets. A variety of thermal-conductivity models have been proposed for ICF hydrodynamic simulations of such coupled and degenerate plasmas. The accuracy of these κ models for DT plasmas has recently been tested against first-principles calculations using the quantum molecular-dynamics (QMD) method; although mainly for high densities (ρ > 100 g/cm3), large discrepancies in κ have been identified for the peak-compression conditions in ICF. To cover the wide range of density-temperature conditions undergone by ICF imploding fuel shells, we have performed QMD calculations of κ for a variety of deuterium densities of ρ = 1.0 to 673.518 g/cm3, at temperatures varying from T = 5 × 103 K to T = 8 × 106 K. The resulting κQMD of deuterium is fitted with a polynomial function of the coupling and degeneracy parameters Γ and θ, which can then be used in hydrodynamic simulation codes. Compared with the "hybrid" Spitzer-Lee-More model currently adopted in our hydrocode lilac, the hydrosimulations using the fitted κQMD have shown up to ∼20% variations in predicting target performance for different ICF implosions on OMEGA and direct-drive-ignition designs for the National Ignition Facility (NIF). The lower the adiabat of an imploding shell, the more variations in predicting target performance using κQMD. Moreover, the use of κQMD also modifies the shock conditions and the density-temperature profiles of the imploding shell at early implosion stage, which predominantly affects the final target performance. This is in contrast to the previous speculation that κQMD changes mainly the

  18. First-principles thermal conductivity of warm-dense deuterium plasmas for inertial confinement fusion applications

    NASA Astrophysics Data System (ADS)

    Hu, S. X.; Collins, L. A.; Boehly, T. R.; Kress, J. D.; Goncharov, V. N.; Skupsky, S.

    2014-04-01

    Thermal conductivity (κ) of both the ablator materials and deuterium-tritium (DT) fuel plays an important role in understanding and designing inertial confinement fusion (ICF) implosions. The extensively used Spitzer model for thermal conduction in ideal plasmas breaks down for high-density, low-temperature shells that are compressed by shocks and spherical convergence in imploding targets. A variety of thermal-conductivity models have been proposed for ICF hydrodynamic simulations of such coupled and degenerate plasmas. The accuracy of these κ models for DT plasmas has recently been tested against first-principles calculations using the quantum molecular-dynamics (QMD) method; although mainly for high densities (ρ > 100 g/cm3), large discrepancies in κ have been identified for the peak-compression conditions in ICF. To cover the wide range of density-temperature conditions undergone by ICF imploding fuel shells, we have performed QMD calculations of κ for a variety of deuterium densities of ρ = 1.0 to 673.518 g/cm3, at temperatures varying from T = 5 × 103 K to T = 8 × 106 K. The resulting κQMD of deuterium is fitted with a polynomial function of the coupling and degeneracy parameters Γ and θ, which can then be used in hydrodynamic simulation codes. Compared with the "hybrid" Spitzer-Lee-More model currently adopted in our hydrocode lilac, the hydrosimulations using the fitted κQMD have shown up to ˜20% variations in predicting target performance for different ICF implosions on OMEGA and direct-drive-ignition designs for the National Ignition Facility (NIF). The lower the adiabat of an imploding shell, the more variations in predicting target performance using κQMD. Moreover, the use of κQMD also modifies the shock conditions and the density-temperature profiles of the imploding shell at early implosion stage, which predominantly affects the final target performance. This is in contrast to the previous speculation that κQMD changes mainly the

  19. Radio Frequency (RF) Trap for Confinement of Antimatter Plasmas Using Rotating Wall Electric Fields

    NASA Technical Reports Server (NTRS)

    Sims, William Herbert, III; Pearson, J. Boise

    2004-01-01

    Perturbations associated with a rotating wall electric field enable the confinement of ions for periods approaching weeks. This steady state confinement is a result of a radio frequency manipulation of the ions. Using state-of-the-art techniques it is shown that radio frequency energy can produce useable manipulation of the ion cloud (matter or antimatter) for use in containment experiments. The current research focuses on the improvement of confinement systems capable of containing and transporting antimatter.

  20. Local regulation of interchange turbulence in a dipole-confined plasma torus using current-collection feedback

    SciTech Connect

    Roberts, T. M. Mauel, M. E. Worstell, M. W.

    2015-05-15

    Turbulence in plasma confined by a magnetic dipole is dominated by interchange fluctuations with complex dynamics and short spatial coherence. We report the first use of local current-collection feedback to modify, amplify, and suppress these fluctuations. The spatial extent of turbulence regulation is limited to a correlation length near the collector. Changing the gain and phase of collection results in power either extracted from or injected into the turbulence. The measured plasma response shows some agreement with calculations of the linear response of global interchange-like MHD and entropy modes to current-collection feedback.

  1. BX-U linear trap for one-way production and confinement of Li+ and e- plasmas

    NASA Astrophysics Data System (ADS)

    Himura, Haruhiko

    2016-03-01

    A modified version of the Penning-Malmberg trap was developed wherein both positive and negative harmonic potential wells were created by using multi-ring electrodes. The sequence of particle injection, particle trapping, and plasma extraction from the potential wells was controlled by a set of switching circuits. All the guns launching charged particles were collected together in one side of the linear trap. Nevertheless, pure electron (e-) and lithium-ion (Li+) plasmas were not only separately produced on the machine axis but also confined simultaneously. Preliminary data show that for B ≈ 0.13 T the e- plasma lasted for 15 s and the Li+ plasma lasted for ~ 4 s.

  2. Characterization of magnetically confined low-pressure plasmas produced by an electromagnetic field in argon-acetylene mixtures

    NASA Astrophysics Data System (ADS)

    Makdessi, G. Al; Margot, J.; Clergereaux, R.

    2016-10-01

    Dust particles formation was investigated in magnetically confined low-pressure plasma produced in argon-acetylene mixtures. The plasma characteristics were measured in order to identify the species involved in the dust particles formation. Their dependence on the operating conditions including magnetic field intensity, acetylene fraction in the gas mixture and operating pressure was examined. In contrast with noble gases, in the presence of acetylene, the electron temperature increases with the magnetic field intensity, indicating additional charged particles losses in the plasma. Indeed, in these conditions, larger hydrocarbon ions are produced leading to the formation of dust particles in the plasma volume. The observed dependence of positive ion mass distribution and density and relative negative ion density on the operating parameters suggests that the dust particles are formed through different pathways, where negative and positive ions are both involved in the nucleation.

  3. Wave excitation by nonlinear coupling among shear Alfvén waves in a mirror-confined plasma

    SciTech Connect

    Ikezoe, R. Ichimura, M.; Okada, T.; Hirata, M.; Yokoyama, T.; Iwamoto, Y.; Sumida, S.; Jang, S.; Takeyama, K.; Yoshikawa, M.; Kohagura, J.; Shima, Y.; Wang, X.

    2015-09-15

    A shear Alfvén wave at slightly below the ion-cyclotron frequency overcomes the ion-cyclotron damping and grows because of the strong anisotropy of the ion temperature in the magnetic mirror configuration, and is called the Alfvén ion-cyclotron (AIC) wave. Density fluctuations caused by the AIC waves and the ion-cyclotron range of frequencies (ICRF) waves used for ion heating have been detected using a reflectometer in a wide radial region of the GAMMA 10 tandem mirror plasma. Various wave-wave couplings are clearly observed in the density fluctuations in the interior of the plasma, but these couplings are not so clear in the magnetic fluctuations at the plasma edge when measured using a pick-up coil. A radial dependence of the nonlinearity is found, particularly in waves with the difference frequencies of the AIC waves; bispectral analysis shows that such wave-wave coupling is significant near the core, but is not so evident at the periphery. In contrast, nonlinear coupling with the low-frequency background turbulence is quite distinct at the periphery. Nonlinear coupling associated with the AIC waves may play a significant role in the beta- and anisotropy-limits of a mirror-confined plasma through decay of the ICRF heating power and degradation of the plasma confinement by nonlinearly generated waves.

  4. 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.

  5. Plasma suPAR levels are associated with mortality, admission time, and Charlson Comorbidity Index in the acutely admitted medical patient: a prospective observational study

    PubMed Central

    2012-01-01

    Introduction Soluble urokinase plasminogen activator receptor (suPAR) is the soluble form of the membrane-bound receptor (uPAR) expressed predominantly on various immune cells. Elevated plasma suPAR concentration is associated with increased mortality in various patient groups, and it is speculated that suPAR is a low-grade inflammation marker reflecting on disease severity. The aim of this prospective observational study was to determine if the plasma concentration of suPAR is associated with admission time, re-admission, disease severity/Charlson Comorbidity Index Score, and mortality. Methods We included 543 patients with various diseases from a Danish Acute Medical Unit during a two month period. A triage unit ensured that only medical patients were admitted to the Acute Medical Unit. SuPAR was measured on plasma samples drawn upon admission. Patients were followed-up for three months after inclusion by their unique civil registry number and using Danish registries to determine admission times, readmissions, International Classification of Diseases, 10th Edition (ICD-10) diagnoses, and mortality. Statistical analysis was used to determine suPAR's association with these endpoints. Results Increased suPAR was significantly associated with 90-day mortality (4.87 ng/ml in survivors versus 7.29 ng/ml in non-survivors, P < 0.0001), higher Charlson Score (P < 0.0001), and longer admission time (P < 0.0001), but not with readmissions. The association with mortality remained when adjusting for age, sex, C-reactive protein (CRP), and Charlson Score. Furthermore, among the various Charlson Score disease groups, suPAR was significantly higher in those with diabetes, cancer, cardiovascular disease, and liver disease compared to those without comorbidities. Conclusions SuPAR is a marker of disease severity, admission time, and risk of mortality in a heterogeneous cohort of patients with a variety of diseases. The independent value of suPAR suggests it could be of value in

  6. Experimental Study of the Effects of Lithium Coated Plasma Facing Components on Energy Confinement Time in the CDX-U Device

    NASA Astrophysics Data System (ADS)

    Spaleta, Jeffrey; Zakharov, Leonid; Majeski, Richard; Kaita, Robert; Gray, Timothy

    2006-10-01

    The first ever measurements of energy confinement time for spherical tokamak plasmas in the presence of lithium coated plasma facing components (PFC's) have been made in the CDX-U device. The energy confinement time, as derived from power balance considerations using parameters calculated from plasma equilibria, was as large as 6 milliseconds for Ohmic plasmas in the presence of both solid and liquid lithium PFC's. This represents a significant improvement over baseline plasmas, which typically had energy confinement times of 1 millisecond or less. The energy confinement for plasmas with lithium PFC's also showed an improvement over that expected from the ITER98(y,1) confinement scaling. The improvement in confinement over this scaling correlates with the observed increase in density ``pump-out'', which is indicative of low wall-recycling. Plasma equilibria were calculated using a modified version of the Equilibrium and Stability Code (ESC), and were constrained by measurements made from a collection of magnetic field diagnostics. The ESC was modified to incorporate the first ever implementation of a novel response function technique for in-situ magnetic field diagnostic calibration that is insensitive to toroidal asymmetries and vessel wall currents.

  7. Generating end plug potentials in tandem mirror plasma confinement by heating thermal particles so as to escape low density end stoppering plasmas

    DOEpatents

    Baldwin, David E.; Logan, B. Grant

    1981-01-01

    The invention provides a method and apparatus for raising the potential of a magnetic mirror cell by pumping charged particles of the opposite sign of the potential desired out of the mirror cell through excitation, with the pumping being done by an externally imposed field at the bounce frequency of the above charged particles. These pumped simple mirror cells then provide end stoppering for a center mirror cell for the tandem mirror plasma confinement apparatus. For the substantially complete pumping case, the end plugs of a tandem mirror can be up to two orders of magnitude lower in density for confining a given center mirror cell plasma than in the case of end plugs without pumping. As a result the decrease in recirculating power required to keep the system going, the technological state of the art required, and the capital cost are all greatly lowered.

  8. Generating end plug potentials in tandem mirror plasma confinement by heating thermal particles so as to escape low density end stoppering plasmas

    DOEpatents

    Baldwin, D.E.; Logan, B.G.

    The invention provides a method and apparatus for raising the potential of a magnetic mirror cell by pumping charged particles of the opposite sign of the potential desired out of the mirror cell through excitation, with the pumping being done by an externally imposed field at the bounce frequence of the above charged particles. These pumped simple mirror cells then provide end stoppering for a center mirror cell for the tandem mirror plasma confinement apparatus. For the substantially complete pumping case, the end plugs of a tandem mirror can be up to two orders of magnitude lower in density for confining a given center mirror cell plasma than in the case of end plugs without pumping. As a result the decrease in recirculating power required to keep the system going, the technical state of the art required, and the capital cost are all greatly lowered.

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

    DOE PAGES

    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. Contribution a l'etude de l'inactivation de micro-organismes par plasma

    NASA Astrophysics Data System (ADS)

    Benhacene-Boudam, Mustafa-Karim

    The present work is a deepening of some specific research aspects concerning medical device sterilization by ionized gases, that were initiated almost ten years ago and pursued since then by the "Sterilization team" of the Groupe de physique des plasmas. Initially, the thesis was directed at spore inactivation by atmospheric-pressure plasmas with the intent of showing that it was possible to reach sterility mainly by the action of UV photons, therefore minimizing damage to materials (in contrast to using chemically reactive species from the plasma) and, at the same time, achieving a greater control of the process through its better understanding. We actually succeeded in demonstrating the possibility of spore inactivation based on the dominant action of UV photons issued from an atmospheric-pressure plasma. However, the low inactivation efficiency and the practical difficulty of the atmospheric-pressure plasma used made us turn to low-pressure post-discharge sterilization systems. To comply with this new goal, we first characterized, essentially through emission spectroscopy, the flowing afterglow of a N2-O2 low-pressure discharge, concentrating on the properties and effects of the early and late post-discharges as far as sterilization is concerned. We demonstrated that the early afterglow is responsible for heavy damage to processed polymers but that it is possible to reduce its influence provided a minimum percentage of O2 is added in the N2-O2 mixture and also by moving away the plasma source from the sterilization chamber entrance. We then studied the combined effects, on the kinetics of spore inactivation, of the species (UV photons, radicals) issued from the plasma and of the heating of the petri dish, using B. atrophaeus spores as reference microorganisms. We clearly proved the existence of synergy between UV photons and heating in inactivating spores, provided UV photons and heating act simultaneously. Whatever the O2% in the mixture, and thus the UV

  11. Refraction-Enhanced X-ray Radiography for Inertial Confinement Fusion and Laser-Produced Plasma Applications

    SciTech Connect

    Koch, J A; Landen, O L; Kozioziemski, B J; Izumi, N; Dewald, E L; Salmonson, J D; Hammel, B A

    2008-08-26

    We explore various laser-produced plasma and inertial-confinement fusion (ICF) applications of phase-contrast x-ray radiography, and we show how the main features of these enhancements can be considered from a geometrical optics perspective as refraction enhancements. This perspective simplifies the analysis, and often permits simple analytical formulae to be derived that predict the enhancements. We explore a raytrace approach to various material interface applications, and we explore a more general example of refractive bending of x-rays by an implosion plasma. We find that refraction-enhanced x-ray radiography of implosions may provide a means to quantify density differences across shock fronts as well as density variations caused by local heating due to high-Z dopants. We also point out that refractive bending by implosions plasmas can blur fine radiograph features, and can also provide misleading contrast information in area-backlit pinhole imaging experiments unless its effects are taken into consideration.

  12. D-T gamma-to-neutron branching ratio determined from inertial confinement fusion plasmas

    SciTech Connect

    Kim, Y.; Mack, J. M.; Herrmann, H. W.; Young, C. S.; Hale, G. M.; Caldwell, S.; Hoffman, N. M.; Evans, S. C.; Sedillo, T. J.; McEvoy, A.; Langenbrunner, J.; Hsu, H. H.; Huff, M. A.; Batha, S.; Horsfield, C. J.; Rubery, M. S.; Garbett, W. J.; Stoeffl, W.; Grafil, E.; Bernstein, L.; and others

    2012-05-15

    A new deuterium-tritium (D-T) fusion gamma-to-neutron branching ratio [{sup 3}H(d,{gamma}){sup 5}He/{sup 3}H(d,n){sup 4}He] value of (4.2 {+-} 2.0) Multiplication-Sign 10{sup -5} was recently reported by this group [Y. Kim et al. Phys. Rev. C (submitted)]. This measurement, conducted at the OMEGA laser facility located at the University of Rochester, was made for the first time using inertial confinement fusion (ICF) plasmas. Neutron-induced backgrounds are significantly reduced in these experiments as compared to traditional beam-target accelerator-based experiments due to the short pulse nature of ICF implosions and the use of gas Cherenkov {gamma}-ray detectors with fast temporal responses and inherent energy thresholds. It is expected that this ICF-based measurement will help resolve the large and long-standing inconsistencies in previously reported accelerator-based values, which vary by a factor of approximately 30. The reported value at ICF conditions was determined by averaging the results of two methods: (1) a direct measurement of ICF D-T {gamma}-ray and neutron emissions using absolutely calibrated detectors and (2) a separate cross-calibration against the better known D-{sup 3}He gamma-to-proton branching ratio [{sup 3}He(d, {gamma}){sup 5}Li/{sup 3}He(d,p){sup 4}He]. Here we include a detailed explanation of these results, and introduce as a corroborative method an in-situ{gamma}-ray detector calibration using neutron-induced {gamma}-rays. Also, by extending the established techniques to two additional series of implosions with significantly different ion temperatures, we test the branching ratio dependence on ion temperature. The data show a D-T branching ratio is nearly constant over the temperature range 2-9 keV. These studies motivate further investigation into the {sup 5}He and {sup 5}Li systems resulting from D-T and D-{sup 3}He fusion, respectively, and result in improved ICF {gamma}-ray reaction history diagnosis at the National Ignition

  13. GPUbased, Microsecond Latency, HectoChannel MIMO Feedback Control of Magnetically Confined Plasmas

    NASA Astrophysics Data System (ADS)

    Rath, Nikolaus

    Feedback control has become a crucial tool in the research on magnetic confinement of plasmas for achieving controlled nuclear fusion. This thesis presents a novel plasma feedback control system that, for the first time, employs a Graphics Processing Unit (GPU) for microsecond-latency, real-time control computations. This novel application area for GPU computing is opened up by a new system architecture that is optimized for low-latency computations on less than kilobyte sized data samples as they occur in typical plasma control algorithms. In contrast to traditional GPU computing approaches that target complex, high-throughput computations with massive amounts of data, the architecture presented in this thesis uses the GPU as the primary processing unit rather than as an auxiliary of the CPU, and data is transferred from A-D/D-A converters directly into GPU memory using peer-to-peer PCI Express transfers. The described design has been implemented in a new, GPU-based control system for the High-Beta Tokamak - Extended Pulse (HBT-EP) device. The system is built from commodity hardware and uses an NVIDIA GeForce GPU and D-TACQ A-D/D-A converters providing a total of 96 input and 64 output channels. The system is able to run with sampling periods down to 4 μs and latencies down to 8 μs. The GPU provides a total processing power of 1.5 x 1012 floating point operations per second. To illustrate the performance and versatility of both the general architecture and concrete implementation, a new control algorithm has been developed. The algorithm is designed for the control of multiple rotating magnetic perturbations in situations where the plasma equilibrium is not known exactly and features an adaptive system model: instead of requiring the rotation frequencies and growth rates embedded in the system model to be set a priori, the adaptive algorithm derives these parameters from the evolution of the perturbation amplitudes themselves. This results in non-linear control

  14. Self-organized criticality and the dynamics of near-marginal turbulent transport in magnetically confined fusion plasmas

    NASA Astrophysics Data System (ADS)

    Sanchez, R.; Newman, D. E.

    2015-12-01

    The high plasma temperatures expected at reactor conditions in magnetic confinement fusion toroidal devices suggest that near-marginal operation could be a reality in future devices and reactors. By near-marginal it is meant that the plasma profiles might wander around the local critical thresholds for the onset of instabilities. Self-organized criticality (SOC) was suggested in the mid 1990s as a more proper paradigm to describe the dynamics of tokamak plasma transport in near-marginal conditions. It advocated that, near marginality, the evolution of mean profiles and fluctuations should be considered simultaneously, in contrast to the more common view of a large separation of scales existing between them. Otherwise, intrinsic features of near-marginal transport would be missed, that are of importance to understand the properties of energy confinement. In the intervening 20 years, the relevance of the idea of SOC for near-marginal transport in fusion plasmas has transitioned from an initial excessive hype to the much more realistic standing of today, which we will attempt to examine critically in this review paper. First, the main theoretical ideas behind SOC will be described. Secondly, how they might relate to the dynamics of near-marginal transport in real magnetically confined plasmas will be discussed. Next, we will review what has been learnt about SOC from various numerical studies and what it has meant for the way in which we do numerical simulation of fusion plasmas today. Then, we will discuss the experimental evidence available from the several experiments that have looked for SOC dynamics in fusion plasmas. Finally, we will conclude by identifying the various problems that still remain open to investigation in this area. Special attention will be given to the discussion of frequent misconceptions and ongoing controversies. The review also contains a description of ongoing efforts that seek effective transport models better suited than traditional

  15. 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.

  16. Observation of High-Field-Side Crash and Heat Transfer during Sawtooth Oscillation in Magnetically Confined Plasmas

    SciTech Connect

    Park, H.K.; Mazzucato, E.; Luhmann, N.C. Jr.; Domier, C.W.; Xia, Z.; Donne, A.J.H.; Classen, I.G.J.; Pol, M.J. van de; Munsat, T.

    2006-05-19

    High resolution (temporal and spatial), two-dimensional images of electron temperature fluctuations during sawtooth oscillations were employed to study the crash process and heat transfer in magnetically confined toroidal plasmas. The combination of kink and local pressure driven instabilities leads to a small poloidally localized puncture in the magnetic surface at both the low and the high field sides of the poloidal plane. This observation closely resembles the 'fingering event' of the ballooning mode model with the high-m mode only predicted at the low field side.

  17. Quasi-analytical method for solving nonlinear differential equations for turbulent self-confined magneto-plasmas

    NASA Astrophysics Data System (ADS)

    Maurier, M.; Hayd, A.; Kaeppeler, H. J.

    1986-09-01

    The mathematical procedures employed in REDUCE/FORTRAN, a hybrid code developed by Hearn (1969 and 1973) and Hayd and Meinke (1980) to compute the dynamics of confined plasmas with simple magnetic-field configurations (Hayd et al., 1982; Kaeppeler, 1982; Kaeppeler et al., 1983) are explained. In REDUCE/FORTRAN, the dispersion relation is derived analytically, Fourier-transformed, and solved numerically, and the solution is then fitted to an analytical formula for further manipulation (including back-transformation). The procedure is demonstrated by solving the Burgers equation with a delta function for the initial conditions, and numerical results are presented in tables and graphs.

  18. Exact solutions of the Grad-Shafranov equation via similarity reduction and applications to magnetically confined plasmas

    NASA Astrophysics Data System (ADS)

    Kaltsas, Dimitrios A.; Throumoulopoulos, George N.

    2016-10-01

    We derive exact solutions of a linear form of the Grad-Shafranov (GS) equation, including incompressible equilibrium flow, using ansatz-based similarity reduction methods. The linearity of the equilibrium equation allows linear combinations of solutions in order to obtain axisymmetric MHD equilibria with closed and nested magnetic surfaces which are favorable for the effective confinement of laboratory plasmas. In addition, employing the same reduction methods we obtain analytical solutions for several non-linear forms of the GS equation. In this context analytic force-free solutions in both linear and nonlinear regimes are also derived.

  19. 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.

  20. Studies of thermal energy confinement scaling in PDX plasmas: D/sup 0/. -->. H/sup +/ limiter discharges

    SciTech Connect

    Kaye, S.M.; Goldston, R.J.; Bell, M.; Bol, K.; Bitter, M.; Fonck, R.; Grek, B.; Hawryluk, R.J.; Johnson, D.; Kaita, R.

    1984-06-01

    Experiments were performed on the PDX tokamak to study plasma heating and ..beta.. scaling with higher power, near-perpendicular neutral beam injection. The data taken during these experiments were analyzed using a time-dependent data interpretation code (TRANSP) to study the transport and thermal confinement scaling over a wide range of plasma parameters. This study focuses on results from experiments with D/sup 0/ injection into H/sup +/ plasmas using graphite rail limiters, a = 40 to 44 cm, R = 143 cm, I/sub p/ = 200 to 480 kA, B/sub T/ = 0.7 to 2.2 T, and typically anti n/sub e/ = 2.5 to 4.2 x 10/sup 13/ cm/sup -3/. The results of this study indicate that for both ohmic and neutral beam heated discharges the energy flow out of the plasma is dominated by anomalous electron losses, attributed to electron thermal conduction. The ion conduction losses are well described to electron thermal conduction. The ion conduction losses are well described by neoclassical theory; however, the total ion loss influences the power balance significantly only at high toroidal fields and high plasma currents.

  1. Caracterisation de nanofilms polymeriques deposes par plasma froid : Stabilite et proprietes mecaniques

    NASA Astrophysics Data System (ADS)

    Barrette, Jeremie

    The current project is inscribed in the research axis on bioactive coatings of Dr. Sophie Lerouge's Laboratoire de Biomatériaux endovasculaires (LBeV). The aim of our work was to extract mechanical properties of a new plasma polymer called L-PPE :N (developed to enhance healing around stent-graft) and determine the effect of various experimental parameters on the stability behavior of our thin films (hundred nanometer thick coatings). Subsidiary to these goals, we also had in mind to test whether usual methods for characterizing polymers and films were applicable on our cold-plasma deposited material. Properties concerned by our endeavor included Young's modulus, hardness, storage and loss modulus, resistance to tearing, ultimate strain and aqueous stability under different temperature and pH for films of varying ratio of gases and thicknesses. Apparatus and work hypothesis used to succeed in our characterization work included, but was not limited to: a quartz crystal dissipative microbalance (QCM-D), a nanoindenter, an ellipsometer, and a tensile testing bench specifically designed for microscopic observation. Hypothesis attached to these methods are that each of these will work as intended for the characterization of our material. Furthermore, we also need to consider the properties of our film as constant throughout its volume (surface-wise for QCM-D analysis and thickness-wise for nanoindentation). QCM-D results allowed us to determine the best compromise of deposition gas ratio R=NH3/C2H4 of L-PPE:N for our biomedical application to be 0.75, from a stability and bioactivity point of view. Starting from that information, we submitted ratio 0.75 films to temperature, thickness and pH essays to make sure they could handle every situation we could need to put them through. Nanoindentation essays have helped us finding reduced modulus and hardness of 8.0 and 0.4 GPa for the 2 µm coating and 10.4 and 0.5 GPa for the 200 nm film

  2. Polymerisation par plasma a pression atmospherique: Caracterisation des depots et leurs applications en biotechnologies

    NASA Astrophysics Data System (ADS)

    Girard-Lauriault, Pierre-Luc

    Nitrogen (N)-containing polymer surfaces are attractive in numerous technological contexts, for example in biomedical applications. Here, we have used an atmospheric-pressure dielectric barrier discharge (DBD) apparatus to deposit novel families of N-rich plasma polymers, designated PP:N, using mixtures of three different hydrocarbon precursors (methane, ethylene, and acetylene) in nitrogen at varying respective gas flow ratios, typically parts per thousand. In preparation for subsequent cell-surface interaction studies, the first part of this research focuses on the chemical mapping of those materials, with specific attention to (semi)- quantitative analyses of functional groups. Well-established and some lesser-known analytical techniques have been combined to provide the best possible chemical and structural characterisations of these three families of PP:N thin films; namely, X-ray photoelectron spectroscopy (XPS), Near-edge X-ray absorption fine structure (NEXAFS), Fourier transform infrared spectroscopy (FTIR), contact angle goniometry (CAG), and elemental analysis (EA). High, "tunable" total nitrogen content was measured by both XPS and EA (between 6% and 25% by EA, or between 10% and 40% by XPS, which cannot detect hydrogen). Chemical derivatisation with 4-trifluoromethylbenzaldehyde (TFBA) enabled measurements of primary amine concentrations, the functionality of greatest bio-technological interest, which were found to account for 5 % to 20 % of the total bound nitrogen. By combining the above-mentioned complementary methods, we were further able to determine the complete chemical formulae, the degrees of unsaturation, and other major chemical functionalities in PP:N film structures. Several of these features are believed to be without precedents in the literature on hydrocarbon plasma polymers, for example measurements of absolute compositions (including hydrogen), and of unsaturation. It was shown that besides amines, nitriles, isonitriles and imines are

  3. Non-Neutral Plasma Confinement In A Cusp-Trap And Possible Application To Anti-Hydrogen Beam Generation

    SciTech Connect

    Mohri, Akihiro; Kanai, Yasuyuki; Nakai, Yoichi; Yamazaki, Yasunori

    2005-10-19

    A new scheme for synthesizing antihydrogen by trapping positrons and antiprotons in a field consisting of a magnetic quadrupole and an electric octupole (cusp -trap) is now under investigation. The total electric field of the octupole with the space charge of a nonneutral plasma composed of particles of the same sign of charge, i.e., positrons or mixture of electrons and antiprotons, is expected to form a potential well for particles of the opposite sign of charge. Particles trapped in the well are mixed with the present dense particles, where positrons and antiprotons will combine to produce antihydrogen atoms. A considerable fraction of antihydrogen atoms in low-field seeking states will be transported outside as a beam.Experiments on electron confinement in the cusp-trap were carried out in a strong magnetic quadrupole (3.8T at the maximum on the axis). The confinement time reached 400s for the trapped electron number N0= 3.6x107. The time decreased with N0 but it was still about 100s for N0= 1.6x108.An electron plasma initially formed around the zero-field point rapidly expanded and settled down onto a quasi-stable state. Cross-sectional density profiles had shapes like a high volcano with a big crater. Analysis of the density profile shows that a potential well for oppositely charged particles (positive ions in this case) is probably formed inside the trapped electrons.

  4. Son of IXION: A Steady State Centrifugally Confined Plasma for Fusion*

    NASA Astrophysics Data System (ADS)

    Hassam, Adil

    1996-11-01

    A magnetic confinement scheme in which the inertial, u.grad(u), forces effect parallel confinement is proposed. The basic geometry is mirror-like as far as the poloidal field goes or, more simply, multipole (FM-1) type. The rotation is toroidal in this geometry. A supersonic rotation can effect complete parallel confinement, with the usual magnetic mirror force rendered irrelevant. The rotation shear, in addition, aids in the suppression of the flute mode. This suppression is not complete which indicates the addition of a toroidal field, at maximum of the order of the poloidal field. We show that at rotation in excess of Mach 3, the parallel particle and heat losses can be minimized to below the Lawson breakeven point. The crossfield transport can be expected to be better than tokamaks on account of the large velocity shear. Other advantages of the scheme are that it is steady state and disruption free. An exploratory experiment that tests equilibrium, parallel detachment, and MHD stability is proposed. The concept resembles earlier (Geneva, 1958) experiments on "homopolar generators" and a mirror configuration called IXION. Ixion, Greek mythological king, was forever strapped to a rotating, flaming wheel. *Work supported by DOE

  5. Experimental study of the effects of lithium coated plasma facing components on energy confinement time in the CDX-U device

    NASA Astrophysics Data System (ADS)

    Spaleta, Jeffrey Dario

    Experimentally constrained equilibrium reconstructions are an important analysis tool used to understand the physics of magnetically confined plasmas. This thesis describes the first ever calculations of equilibrium reconstructions for spherical tokamak plasmas in the presence of lithium coated plasma facing components (PFC's) in the Current Drive eXperiment - Upgrade (CDX-U) device. Equilibria were calculated using a modified version of the Equilibrium and Stability Code (ESC), and were constrained by measurements made from a collection of magnetic field diagnostics. The ESC was modified to incorporate the first ever implementation of a novel response function technique for magnetic field diagnostic calibration. The technique is well suited for situations where the assumption of toroidal symmetry of the magnetic field is invalid, or when wall eddy currents are too large to neglect. Also included is a detailed discussion of the calculation of energy confinement time from power balance arguments, using parameters obtained from equilibrium reconstructions. The energy confinement time, as derived from plasma equilibria, was as large as 6 milliseconds for plasmas in the presence of both solid and liquid lithium PFC's. This represents a significant improvement over baseline plasmas, which typically had energy confinement times of 1 millisecond or less. The energy confinement for plasmas with lithium PFC's also showed an improvement over that expected from the ITER98y1 confinement scaling, which is derived from a database of earlier tokamak results. The improvement in confinement over this scaling correlates with the observed increase in density "pump-out", which is indicative of low wall-recycling. Traditionally, plasma fueling has been dominated by wall-recycling, with 90% or more of the fuel coming from recycling sources instead of externally controlled means, such as gas puffing or pellet injection. Previous lithium wall coating experiments on the Tokamak Fusion Test

  6. Spectroscopic modeling and characterization of a collisionally confined laser-ablated plasma plume.

    PubMed

    Sherrill, M E; Mancini, R C; Bailey, J; Filuk, A; Clark, B; Lake, P; Abdallah, J

    2007-11-01

    Plasma plumes produced by laser ablation are an established method for manufacturing the high quality stoichiometrically complex thin films used for a variety of optical, photoelectric, and superconducting applications. The state and reproducibility of the plasma close to the surface of the irradiated target plays a critical role in producing high quality thin films. Unfortunately, this dense plasma has historically eluded quantifiable characterization. The difficulty in modeling the plume formation arises in the accounting for the small amount of energy deposited into the target when physical properties of these exotic target materials are not known. In this work we obtain the high density state of the plasma plume through the use of an experimental spectroscopic technique and a custom spectroscopic model. In addition to obtaining detailed temperature and density profiles, issues regarding line broadening and opacity for spectroscopic characterization will be addressed for this unique environment.

  7. Excitation of Ion Acoustic Waves in Confined Plasmas with Untrapped Electrons

    NASA Astrophysics Data System (ADS)

    Schamis, Hanna; Dow, Ansel; Carlsson, Johan; Kaganovich, Igor; Khrabrov, Alexander

    2015-11-01

    Various plasma propulsion devices exhibit strong electron emission from the walls either as a result of secondary processes or due to thermionic emission. To understand the electron kinetics in plasmas with strong emission, we have performed simulations using a reduced model with the LSP particle-in-cell code. This model aims to show the instability generated by the electron emission, in the form of ion acoustic waves near the sheath. It also aims to show the instability produced by untrapped electrons that propagate across the plasma, similarly to a beam, and can drive ion acoustic waves in the plasma bulk. This work was made possible by funding from the Department of Energy for the Summer Undergraduate Laboratory Internship (SULI) program. This work is supported by the US DOE Contract No.DE-AC02-09CH11466.

  8. Equilibrium, stability, and estimate of plasma confinement in the L-5 compact torsatron

    SciTech Connect

    Mikhailov, M. I.; Shafranov, V. D.; Drevlyak, M.; Nuehrenberg, J.; Grebenshchikov, S. E.; Kuznetsov, A. B.; Shchepetov, S. V.

    2011-04-15

    Possible parameters of a plasma in a compact torsatron that is to be constructed at the Prokhorov Institute of General Physics, Russian Academy of Sciences (the L-5 project) are discussed. The properties of the original vacuum configuration created by the external coils are described. The equilibrium of a plasma with a free boundary and the stability of local MHD modes are investigated. The effective magnetic field ripples and the structural factor of the bootstrap current in the 1/{nu} regime are calculated, as well as collisionless losses of trapped {alpha}-particles. The dependence of these properties on the relative plasma pressure is examined. It is shown that the maximum possible <{beta}> (the ratio of the gas-kinetic plasma pressure to the magnetic field pressure, averaged over the volume of the plasma column) consistent with equilibrium exceeds 2.0%. The power of the external sources for plasma heating in the anticipated operating modes is estimated using the present-day scalings. The efficiency of different methods for calculating the magnetic fields and, accordingly, the magnetic surfaces created by the external coils is analyzed in the Appendix.

  9. Extreme ultraviolet emission and confinement of tin plasmas in the presence of a magnetic field

    SciTech Connect

    Roy, Amitava E-mail: aroy@barc.gov.in; Murtaza Hassan, Syed; Harilal, Sivanandan S.; Hassanein, Ahmed; Endo, Akira; Mocek, Tomas

    2014-05-15

    We investigated the role of a guiding magnetic field on extreme ultraviolet (EUV) and ion emission from a laser produced Sn plasma for various laser pulse duration and intensity. For producing plasmas, planar slabs of pure Sn were irradiated with 1064 nm, Nd:YAG laser pulses with varying pulse duration (5–15 ns) and intensity. A magnetic trap was fabricated with the use of two neodymium permanent magnets which provided a magnetic field strength ∼0.5 T along the plume expansion direction. Our results indicate that the EUV conversion efficiency do not depend significantly on applied axial magnetic field. Faraday Cup ion analysis of Sn plasma show that the ion flux reduces by a factor of ∼5 with the application of an axial magnetic field. It was found that the plasma plume expand in the lateral direction with peak velocity measured to be ∼1.2 cm/μs and reduced to ∼0.75 cm/μs with the application of an axial magnetic field. The plume expansion features recorded using fast photography in the presence and absence of 0.5 T axial magnetic field are simulated using particle-in-cell code. Our simulation results qualitatively predict the plasma behavior.

  10. Effects of Laser-Plasma Instabilities on Hydro Evolution in Direct-Drive Inertial Confinement Fusion

    NASA Astrophysics Data System (ADS)

    Li, J.; Hu, S. X.; Ren, C.

    2015-11-01

    Laser-plasma instabilities and hydro evolution of coronal plasmas in an OMEGA EP long-scale-length experiment with planar targets are studied with particle-in-cell (PIC) and hydrodynamics simulations. Plasma and laser conditions are first obtained in a DRACO simulation with only inverse-bremsstrahlung absorption. Using these conditions, an OSIRIS simulation is performed to study laser absorption and hot-electron generation caused by laser-plasma instabilities near the quarter-critical region. The obtained PIC information has subsequently been coupled to another DRACO simulation to examine how the laser-plasma instabilities affect the overall hydrodynamics. The results show that the more-realistic laser absorption can increase the electron temperature but only slightly changes the density scale length in the corona. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944, DE-FC02-04ER54789 (Fusion Science Center), and DE-SC0012316.

  11. Effects of Lithium Plasma-Facing Surfaces on Particle Confinement in CDX-U

    NASA Astrophysics Data System (ADS)

    Gray, T.; Soukhanovskii, V.; Maingi, R.

    2005-10-01

    Recent experiments on the CDX-U spherical torus have successfully achieved a significant reduction in recycling with large-area liquid lithium plasma-facing surfaces. The effects of a liquid lithium toroidal limiter and evaporative lithium coatings on overall density and τp^* will be presented. Such conditions have also demonstrated the need to improve plasma fueling. To address this challenge, a supersonic gas injector, based on a Mach 8 Laval nozzle design,[1] has been installed on CDX-U. The fueling efficiency of the nozzle compared to standard gas puffing will be compared. [1] M. Baumgartner, Ph. D. thesis, Princeton University (1997)

  12. Effect of different tritium fractions on some plasma parameters in deuterium-tritium magnetic confinement fusion

    NASA Astrophysics Data System (ADS)

    Motevalli, S. M.; Mohsenpour, T.; Dashtban, N.

    2016-09-01

    Nearly all reactor projects have considered deuterium-tritium (D-T) fusion. The cross section of D-T reaction is larger than those of other fusion reactions, thus it is considered to be a more favorable reaction. The mix of fuel can vary. In this work, a comparison between the effects of different mixture of D-T fuel on the plasma parameters is made. A time dependence calculation of the fusion process is performed using the zero-dimensional model based on a coupled set of particle and energy balance equations in ITER (International Thermonuclear Experimental Reactor). The time evolution of plasma parameters is also analyzed numerically.

  13. Steady-shear-enhanced microdiffusion with multiple time scales of confined, mesoscopic, two-dimensional dusty-plasma liquids.

    PubMed

    Io, Chong-Wai; I, Lin

    2009-09-01

    We experimentally investigate the multitime scale diffusion and the spatiotemporal behaviors of the degrees of enhancement for the longitudinal and the transverse diffusions in a confined mesoscopic quasi-two-dimensional dusty-plasma liquid sheared by two parallel counterpropagating laser beams. The steady external drive directly enhances the longitudinal cooperative hopping, associated with the shear bands that have high shear rate near boundaries. It drastically excites the slow hopping modes to high fluctuation level in the outer band region, accompanied by the enhanced superdiffusion. Through cascaded many-body interaction, the excitation flows from the outer region toward the center region, from the longitudinal modes to the transverse mode, and from the slow hopping modes to the fast caging modes, which are in better contact with the thermal bath. It causes the weaker enhancement of fluctuation level, and diffusion for the center region and the fast modes. The boundary confinement further breaks the system symmetry and enhances anisotropy. It has much stronger effect on the suppression of the transverse hopping modes than the longitudinal hopping mode. The degrees of enhancement of the fluctuations by the shear stress are highly anisotropic for the large amplitude slow modes, especially in the outer region but are more isotropic in the inner band.

  14. 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

  15. Space-charge waves in magnetized and collisional quantum plasma columns confined in carbon nanotubes

    SciTech Connect

    Bagheri, Mehran; Abdikian, Alireza

    2014-04-15

    We study the dispersion relation of electrostatic waves propagating in a column of quantum magnetized collisional plasma embraced completely by a metallic single-walled carbon nanotubes. The analysis is based on the quantum linearized hydrodynamic formalism of collective excitations within the quasi-static approximation. It is shown when the electronic de Broglie's wavelength of the plasma is comparable in the order of magnitude to the radius of the nanotube, the quantum effects are quite meaningful and our model anticipates one acoustical and two optical space-charge waves which are positioned into three propagating bands. With increasing the nanotube radius, the features of the acoustical branch remain unchanged, yet two distinct optical branches are degenerated and the classical behavior is recovered. This study might provide a platform to create new finite transverse cross section quantum magnetized plasmas and to devise nanometer dusty plasmas based on the metallic carbon nanotubes in the absence of either a drift or a thermal electronic velocity and their existence could be experimentally examined.

  16. Design of a toroidal plasma confinement device with a levitated super-conducting internal coil

    SciTech Connect

    Ogawa, Y.; Morikawa, J.; Himura, H.; Kondoh, S.; Yoshida, Z.; Mito, T.; Yanagi, N.; Iwakuma, N.

    1999-12-10

    A toroidal device has been constructed and nonneutral plasma experiments have been intensively promoted, where an internal ring coil with a copper conductor has been employed. We are now designing a toroidal plasma trapping device with a levitated superconducting internal coil, so as to avoid plasma loss through current-lead and support structures of the internal coil. Typical machine parameters are as follows; the major radius of the internal ring coil is 40 cm and the coil current is 500 kA. Concerning to the levitated coil, the high-temperature (high-Tc) super-conducting coil is preferable for plasma experiments, because long pulse and/or high power heating experiments might be available due to the good property for the thermal stability and large heat capacity of the high-Tc super-conducting coil. Our primary candidate is Bi-2223 super-conducting cable. Since the maximum magnetic field strength is around 2 T in our device, the deterioration of the critical current is not so severe up to 40 K. We are now promoting a detailed design of the toroidal device with a high-Tc super-conducting internal coil.

  17. Design of a Toroidal Plasma Confinement Device with a Levitated Super-Conducting Internal Coil

    SciTech Connect

    Y. Ogawa; H. Himura; S. Kondoh; J. Morikawa; Z. Yoshida

    1999-12-31

    A toroidal device has been constructed and nonneutral plasma experiments have been intensively promoted, where an internal ring coil with a copper conductor has been employed. We are now designing a toroidal plasma trapping device with a levitated superconducting internal coil, so as to avoid plasma loss through current-lead and support structures of the internal coil. Typical machine parameters are as follows; the major radius of the internal ring coil is 40 cm and the coil current is 500 kA. Concerning to the levitated coil, the high-temperature (high-Tc) super-conducting coil is preferable for plasma experiments, because long pulse and/or high power heating experiments might be available due to the good property for the thermal stability and large heat capacity of the high-Tc super-conducting coil. Our primary candidate is Bi-2223 super-conducting cable. Since the maximum magnetic field strength is around 2 T in our device, the deterioration of the critical current is not so severe up to 40 K. We are now promoting a detailed design of the toroidal device with a high-Tc super-conducting internal coil.

  18. Perspectives of millimeter-wave collective Thomson scattering of confined alphas in ignited plasmas

    SciTech Connect

    Tartari, U.; Nowak, S.; Ramponi, G.

    1996-11-01

    Collective Thomson scattering on alpha density fluctuations in ignited plasma regimes is investigated with reference to a promising candidate source as the mm-wave gyrotron and a representative ITER-like plasma regime. It is shown that a number of intrinsic limitations characterize each of the equatorial scattering geometries selected as more promising, namely a backscattering geometry at {ital f}{sub 0}=80 GHz and two similar quasiorthogonal geometries at {ital f}{sub 0}=180 GHz. A lack of spatial resolution typical of the former geometry has to be contrasted with a significant limitation in plasma access typical of the remaining geometries. Other relevant differences concern the requirements in terms of gyrotron power, acceptable stray radiation levels, etc. Special emphasis is given in the work to a discussion of ECE noise, on which the feasibility itself of the alpha collective scattering diagnostics at mm-waves largely depends in the plasma regimes considered. {copyright} {ital 1996 American Institute of Physics.}

  19. Transport processes in well confined high temperature plasmas and collective modes in their partially ionized edge region

    NASA Astrophysics Data System (ADS)

    Daughton, William Scott

    1998-12-01

    of conditions, a novel form of a thermal transport coefficient which reproduces both ohmic and auxiliary heated L-mode discharges has been identified. This thermal transport coefficient involves the difference of two terms, one representing the normal outward diffusion of thermal energy and the other corresponding to a process reducing the outward flux. The coefficient includes the constraint of profile consistency. In a series of transport simulations for plasmas produced by the Alcator C-Mod machine, the thermal transport coefficient is shown to reproduce the observed electron temperature profile, stored energy and loop voltage. The relevant scaling for the energy confinement time is also composed of two terms. The L- mode database assembled for the ITER project is used to compare DIII-D, JET, JT60, PDX, TFTR, FTU, and Alcator C- Mod with this analysis. With the exception of PDX, the comparison is substantially better than standard L-mode power law scalings. Based on this analysis, an extrapolation is made for the confinement time of two proposed ignition experiments. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.) (Abstract shortened by UMI.)

  20. Composition of the source region plasma in inertial electrostatic confinement devices

    SciTech Connect

    Boris, D. R.; Emmert, G. A.

    2008-08-15

    The ion species composition in the source region of inertial electrostatic confinement (IEC) devices plays an important role in the atomic and molecular physics processes in the device and in the resulting energy spectrum of the fast ions and the neutron production rate. A zero dimensional rate equation model for the ion species composition in the source region of IEC devices is presented and compared with experimental measurements on the Wisconsin IEC device [J. F. Santarius, G. L. Kulcinski, R. P. Ashley et al., Fusion Sci. Tech. 47, 1238 (2005)]. The ion species composition is measured using an ion acoustic wave diagnostic; the results are in good agreement with the theoretical predictions. Both the theory and the experimental results show that D{sub 3}{sup +} ions are the majority species in the source region.

  1. Radiative power losses from impurities in high-density plasmas confined by high magnetic fields

    NASA Astrophysics Data System (ADS)

    May, Mark Joseph

    1998-07-01

    Quantifying and controlling the radiative power losses from impurities in the tokamak fusion plasma is crucial for obtaining ignition conditions. In the present work, therefore, losses from impurities have been measured in different operating regimes of the Alcator C-Mod Tokamak and the Frascati Tokamak Upgrade (FTU) plasmas. The major radiating intrinsic impurity in both tokamaks was molybdenum sputtered from the armor tiles covering all the plasma facing surfaces. The radiative power losses from the molybdenum ions accounted for [>]80/% of the total radiative power losses in ICRF heated plasmas and ~60/% in ohmically heated plasmas. Molybdenum could radiate as much as several thousand kW with concentrations as high as ~1× 1011/ particles/cm3 or ~0.001 of the plasma (electron) density. The radiative losses were found to increase linearly with increasing ICRF power and to vary weakly with the central electron density of the plasma. The other major intrinsic impurities in Alcator C-Mod Tokamak, carbon and boron, radiated at most ~100 kW from the plasma and had concentrations in ohmically heated plasmas of ~1.7× 10/ particles/cm3 and ~6.3× 1011/ particles/cm3, respectively. At Alcator C-Mod Tokamak, the total radiative power losses were measured with bolometric systems. The contribution to the total radiative losses from each major impurity and the impurity concentrations were determined spectroscopically from the line brightnesses of XUV (soft X-ray and extreme ultraviolet) transitions. The line brightnesses were interpreted via a detailed atomic physics model which included the Multiple Ionization State Transport (MIST) code, the ab initio atomic rates from the Hebrew University-Jerusalem Lawrence Livermore Atomic Code (HULLAC) and a collisional radiative model. At the FTU Tokamak, brightnesses from impurity emission measured with an X-ray crystal spectrometer were interpreted with a similar atomic physics model which included the molybdenum rates from HULLAC

  2. Déformation à l'échelle cristallographique d'alliages à base de nickel mono- et polycristallins par choc laser en mode confiné

    NASA Astrophysics Data System (ADS)

    Forget, P.; Jeandin, M.

    1995-08-01

    The so-called “laser peening” treatment based on laser shock processing has been developed to improve mechanical properties due to work-hardening and formation of residual stresses. When applied to aeronautical Ni-based superalloys, an increase of fatigue resistance is expected. This article deals with deformation resulting from laser shock. The study is centered on the observation of superficial micro-roughness in the impacted zone. Micro-roughness is discussed as resulting from crystallographic changes due to shock process. Various slip phenomena were in particular determined. More generally, superficial heterogeneities in the different parts of the shocked area are discussed in the light of results on release wave propagation and formation of residual stresses. Two Ni-based superalloys, i.e. AM1 single crystal and polycrystalline Inconel718, were used. Le traitement de “grenaillage photonique” par choc laser vise à écrouir un matériau et à y introduire des contraintes résiduelles de compression en vue d'améliorer ses propriétés mécaniques. Dans le cas de superalliages aéronautiques à base de nickel, on attend une augmentation de la tenue en fatigue. On traite ici de la déformation induite par le choc grâce à une étude microstructurale fondée sur l'observation des microreliefs de surface dans la zone traitée. Ceux-ci sont interprétés comme le résultat de l'évolution cristallographique du matériau soumis au choc. Les phénomènes de glissement, sont, en particulier, précisément identifiés. Plus généralement, les hétérogénéités de surface dans les différentes parties de l'impact sont expliquées à la lumière de résultats sur la propagation des ondes de détente de surface et sur la création de contraintes résiduelles. Deux superalliages à base de nickel, l'AM1 monocristallin et l'Inconel 718 polycristallin, ont été étudiés.

  3. High Density Plasma Beam Target Fusion: An Alternative form of Inertial Confinement to Ignition

    NASA Astrophysics Data System (ADS)

    Cheng, Dah Yu

    2005-10-01

    A scaling law has been demonstrated for a plasma gun in a 30 m diameter space chamber. Using a specific combination of delay time between the gas valve opening and operation of a capacitor bank switch, and the capacitor bank's voltage, the deflagration gun (Ref. 1) is capable of producing high kinetic energy and at a high density beam. Using a convergent gun barrel it is possible to compress beam density by a factor of 100. A 10^17/c.c.beam was obtained. If the kinetic energy is at 280 Kev (fusion threshold) Neutron flux up to 5 x 10^19 could be produced in a 1 micro-second period. This represents 500 MJ of energy yield. If the classical fusion energy data were in error by a factor of 100 that still would yield 5 MJ of fusion energy. Results obtained from experiments in the 30 m diameter space chamber have demonstrated such a capability using a 120 KV capacitor bank with 200 KJ of stored energy (Ref. 1). A very small scale experiment has demonstrated a yield of 10^15 neutrons using less than 10 kJ of capacitor energy.References:1. Cheng, D.Y. 1970 Plasma Deflagration and the Properties of a Coaxial Plasma Deflagration Gun. Nuclear Fusion, 10, pp. 305- 317

  4. Non-resonant elastic scattering of low-energy photons by atomic sodium confined in quantum plasmas

    SciTech Connect

    Ghosh, Avijit Ray, Debasis

    2015-03-15

    The non-resonant elastic scattering of low-energy photons by the bound valence electron in the ground state 3s of atomic sodium confined in quantum plasmas is investigated theoretically. The incident photon energy is assumed to be much smaller than the 3s-3p excitation energy. The alkali atom sodium is first formulated as an effective one-electron problem in which the attractive interaction between the valence electron and the atomic ion core is simulated by a spherically symmetric model potential. The Shukla-Eliasson oscillatory exponential cosine screened-Coulomb potential model is then used to mimic the effective two-body (valence-core) interaction within quantum plasmas. Non-relativistic calculations performed within the electric dipole approximation indicate that the non-resonant elastic photon scattering cross-section undergoes a dramatic growth by several orders of magnitude as the quantum wave number increases. A qualitative explanation of this phenomenon is presented. In the absence of the oscillatory cosine screening term, a similar growth is observed at larger values of the quantum wave number. Our computed relevant atomic data are in very good agreement with the experimental as well as the previous theoretical data for the zero-screening (free atom) case, and with the very limited, accurate theoretical results available for the case of exponential screened-Coulomb two-body interaction, without the cosine screening term.

  5. Population inversion and gain measurements for X-ray laser development in magnetically confined plasma column in fiscal year 1984

    NASA Astrophysics Data System (ADS)

    Suckewer, S.

    1985-03-01

    This report covers X-ray laser development in magnetically confined plasmas, as well as in expanding recombining plasma columns using time resolved soft X-ray monochromators. Experiments with both solid and gas targets resulted in gain measurements for hydrogen-like Carbon(6+) (CVI) ions and population inversion measurements for lithium-like Neon(8+) (NeVIII) ions. Our most recent results, involving carbon disc targets in a 90 k Gauss field with a 300 Joule carbon dioxide laser pulse, in which a one-pass gain of kl 6.5 (enhancement of stimulated emission over spontaneous emission about 100) was obtained for CVI 182A are presented. Results of a gain kl = 3.0 (k approx. 7.5/cm) for thick carbon fiber targets are also presented. Population inversions of NeVIII ions as a function of initial gas pressure are also discussed, as well as an overview of the instrumentation, experimental setup, and target configurations used.

  6. The impact of laser plasma interactions on three-dimensional drive symmetry in inertial confinement fusion implosions

    SciTech Connect

    Peterson, J. L. Michel, P.; Thomas, C. A.; Town, R. P. J.

    2014-07-15

    Achieving symmetric hohlraum radiation drive is an important aspect of indirectly driven inertial confinement fusion experiments. However, when experimentally delivered laser powers deviate from ideal conditions, the resultant radiation field can become asymmetric. Two situations in which this may arise are random uncorrelated fluctuations, in as-delivered laser power and laser beams that do not participate in the implosion (either intentionally or unintentionally). Furthermore, laser plasma interactions in the hohlraum obfuscate the connection between laser powers and radiation drive. To study the effect of these situations on drive symmetry, we develop a simplified model for crossed-beam energy transfer, laser backscatter, and plasma absorption that can be used in conjunction with view factor calculations to expediently translate laser powers into three-dimensional capsule flux symmetries. We find that crossed-beam energy transfer can alter both the statistical properties of uncorrelated laser fluctuations and the impact of missing laser beams on radiation symmetry. A method is proposed to mitigate the effects of missing laser beams.

  7. Inertia driven radial breathing and nonlinear relaxation in cylindrically confined pure electron plasma

    SciTech Connect

    Sengupta, M.; Ganesh, R.

    2014-02-15

    The dynamics of cylindrically trapped electron plasma has been investigated using a newly developed 2D Electrostatic PIC code that uses unapproximated, mass-included equations of motion for simulation. Exhaustive simulations, covering the entire range of Brillouin ratio, were performed for uniformly filled circular profiles in rigid rotor equilibrium. The same profiles were then loaded away from equilibrium with an initial value of rigid rotation frequency different from that required for radial force balance. Both these sets of simulations were performed for an initial zero-temperature or cold load of the plasma with no spread in either angular velocity or radial velocity. The evolution of the off-equilibrium initial conditions to a steady state involve radial breathing of the profile that scales in amplitude and algebraic growth with Brillouin fraction. For higher Brillouin fractions, the growth of the breathing mode is followed by complex dynamics of spontaneous hollow density structures, excitation of poloidal modes, leading to a monotonically falling density profile.

  8. Inertia driven radial breathing and nonlinear relaxation in cylindrically confined pure electron plasma

    SciTech Connect

    Sengupta, M.; Ganesh, R.

    2015-06-29

    The dynamics of cylindrically trapped electron plasma has been investigated using a newly developed 2D Electrostatic PIC code that uses unapproximated, mass-included equations of motion for simulation. Exhaustive simulations, covering the entire range of Brillouin ratio, were performed for uniformly filled circular profiles in rigid rotor equilibrium. The same profiles were then loaded away from equilibrium with an initial value of rigid rotation frequency different from that required for radial force balance. Both these sets of simulations were performed for an initial zero-temperature or cold load of the plasma with no spread in either angular velocity or radial velocity. The evolution of the off-equilibrium initial conditions to a steady state involve radial breathing of the profile that scales in amplitude and algebraic growth with Brillouin fraction. For higher Brillouin fractions, the growth of the breathing mode is followed by complex dynamics of spontaneous hollow density structures, excitation of poloidal modes, leading to a monotonically falling density profile.

  9. Time-dependent filamentation and stimulated Brillouin forward scattering in inertial confinement fusion plasmas

    NASA Astrophysics Data System (ADS)

    Schmitt, Andrew J.; Afeyan, Bedros B.

    1998-02-01

    Numerical simulations of the temporal evolution of laser light filamentation and stimulated Brillouin forward scattering (SBFS) in plasmas, under conditions that are relevant to laser fusion, are presented and analyzed. Long term unsteady behavior of filaments is observed to be the norm. Temporal and spatial incoherence due to filamentation and SBFS are impressed upon time-independent incident laser beams. The bandwidth and angular divergence imposed upon the beam increase with the strength of the interaction. In addition, the spectrum of the transmitted light is redshifted by an amount that increases with the interaction strength. Spectral analysis of the transmitted light reveals that SBFS plays a role in the generation of the observed temporal incoherence. Incident beams with some spatial incoherence but no temporal smoothing are compared to those with ab initio temporal beam smoothing (TBS). Under typical conditions, TBS beams will undergo far less angular and spectral spreading and far less SBFS than unsmoothed beams.

  10. Spectroscopic study of molecular-hydrogen processes in a mirror-confined plasma

    SciTech Connect

    Moran, T.G. |

    1995-04-01

    Visible and near-ultraviolet molecular hydrogen emission from the Tara Tandem Mirror central cell plasma was investigated in order to determine molecular densities, ionization rates, and continuum dissociation rates. Measurements of H{sub 2} {ital G}{r_arrow}{ital B} band emission were used to infer spatial density and ionization profiles, maximum densities of 4{times}10{sup 12} cm{sup {minus}3} at the gas injection port, and a total molecular ionization rate of 254 A. Continuum emission in the near ultraviolet was identified as the H{sub 2} dissociative continuum through its wavelength distribution, time behavior, and intensity. Wavelength-integrated continuum emission measurements were used to obtain the dissociation rate associated with the continuum: 6 A. The power expended in molecular ionization, dissociation, and radiation is estimated to be 8.4 kW out of 300 kW of rf power injected.

  11. Abrupt onset of tongue deformation and phase space response of ions in magnetically-confined plasmas

    PubMed Central

    Ida, K.; Kobayashi, T.; Itoh, K.; Yoshinuma, M.; Tokuzawa, T.; Akiyama, T.; Moon, C.; Tsuchiya, H.; Inagaki, S.; Itoh, S.-I.

    2016-01-01

    An abrupt onset of the new tongue-shaped deformation of magnetic surface in magnetized plasmas, which was conjectured in since the 1960s but has not been observed, is experimentally identified just before an abrupt onset of a large-scale collapse event. Two novel properties of the event are identified. First, the transition of symmetry of perturbation (rather than a growth of linearly unstable MHD modes) was found to be a key for the onset of abrupt collapse, i.e., the transition of symmetry gives a new route to the collapse from stable state. Second, as a phase-space response of ions, the distortion from Maxwell-Boltzmann distribution of epithermal ions was observed for the first time. PMID:27796370

  12. Experimental verification of the Boltzmann relation in confined plasmas: Comparison of noble and molecule gases

    SciTech Connect

    Lee, Hyo-Chang; Hwang, Hye-Ju; Kim, Young-Cheol; Kim, June Young; Kim, Dong-Hwan; Chung, Chin-Wook

    2013-03-15

    Experimental verification of the Boltzmann relation is performed in argon and oxygen gas inductively coupled plasmas from the measurements of both the spatial electron currents (as a fluid approach) and the electron energy probability functions (EEPFs, as a kinetic approach). At a low gas pressure of 10 mTorr, the measured electron currents are spatially uniform, and the EEPFs in the total electron energy scale are identical, which indicate that the Boltzmann relation is valid at both the argon and oxygen gases. As the gas pressure increases to 30-40 mTorr, however, the Boltzmann relation is broken in the oxygen gas discharge, while the Boltzmann relation is still valid in the argon gas discharge. This different variation in the oxygen gas discharge is mainly due to the presence of various inelastic collisions in the entire electron energy region, which causes the transition of the electron kinetics from a non-local to a local regime.

  13. Thermo-statistical study of evaporation effects in a non neutral plasma under an imperfect magnetic confinement

    NASA Astrophysics Data System (ADS)

    Ordenes-Huanca, C.; Velazquez, L.

    2016-09-01

    Experimental studies of non-neutral plasmas in magnetic traps undergo, in some degree of affectation, the incidence of evaporation. For example, the existence of a finite threshold energy {{\\varepsilon}c} for the escaping of plasma constituents can be favored by the external electrostatic forces near the grounded conducting walls of a cylindrical Penning trap. In contrast, the conventional statistical mechanics description of these situations is performed assuming the existence of a rigorous thermodynamic equilibrium (Dubin and O’Neil 1999 Rev. Mod. Phys. 71 87), dismissing thus the existence of evaporation effects. We propose in this work a two-dimensional toy model that describes the incidence of evaporation on thermo-statistics of a pure non-neutral plasma (a system composed of a single charge species like an infinitely long electron column). Considering the existing connections between the macroscopic descriptions of pure non-neutral plasmas and astrophysical systems, the treatment of evaporation along a quasi-stationary regime is developed here in analogy to some astrophysical models proposed in the literature. We start from a regularized microcanonical description that only considers those microscopic configurations where particles are trapped inside a confinement region of radius R c , which is implemented introducing a truncation of their velocity spectrum. These arguments lead us to a statistical procedure to predict the quasi-stationary particles distribution n≤ft(\\mathbf{r}\\right) similar to the maximum entropy approach. According to our analysis, the influence of evaporation for a non-zero temperature T crucially depends on the saturation parameter δ ={{r}\\text{B}}/{{R}c} , whose admissible values are located in the interval 0<δ <1 , with r B being the radius of Billouin steady state that appears in the limit T\\to 0 . The theoretical profiles predicted from this model are then compared to the metastable radial density distribution reported by

  14. Gaussian beams for a linearized cold plasma confined in a torus

    NASA Astrophysics Data System (ADS)

    Cardinali, A.; Dobrokhotov, S. Yu.; Klevin, A.; Tirozzi, B.

    2016-04-01

    We consider a system of linear pde describing a cold plasma in a toroidal region in three-dimensional space. This system simulates the passage of a laser beam through the TOKAMAK, it consists of 9 equations for the electric field and the velocities of electrons and ions in a given magnetic field. Asymptotic solutions describing high-frequency Gaussian beams are constructed using the theory of Maslov complex germ in a fairly effective form. The solutions of the system are localized in the neighborhood of the beam passing through the toroidal domain (the camera). The equations for a ray take into account the density of particles in the camera and don't ``feel'' the presence of the magnetic field because of the high frequency of the Gaussian beam; the dependence on the magnetic field is contained in the amplitude of the electric field. Before the TOKAMAK camera the amplitude of the Gaussian beam is the same as in free space, but after the camera the amplitude vector rotates under the influence of the magnetic field. The formula for the angle of rotation is given explicitly. An analytical-numerical algorithm based on the asymptotic solutions is used to analyze the parameters of the magnetic field in the TOKAMAK.

  15. A self-organized criticality model for ion temperature gradient mode driven turbulence in confined plasma

    SciTech Connect

    Isliker, H.; Pisokas, Th.; Vlahos, L.; Strintzi, D.

    2010-08-15

    A new self-organized criticality (SOC) model is introduced in the form of a cellular automaton (CA) for ion temperature gradient (ITG) mode driven turbulence in fusion plasmas. Main characteristics of the model are that it is constructed in terms of the actual physical variable, the ion temperature, and that the temporal evolution of the CA, which necessarily is in the form of rules, mimics actual physical processes as they are considered to be active in the system, i.e., a heating process and a local diffusive process that sets on if a threshold in the normalized ITG R/L{sub T} is exceeded. The model reaches the SOC state and yields ion temperature profiles of exponential shape, which exhibit very high stiffness, in that they basically are independent of the loading pattern applied. This implies that there is anomalous heat transport present in the system, despite the fact that diffusion at the local level is imposed to be of a normal kind. The distributions of the heat fluxes in the system and of the heat out-fluxes are of power-law shape. The basic properties of the model are in good qualitative agreement with experimental results.

  16. LDRD final report on confinement of cluster fusion plasmas with magnetic fields.

    SciTech Connect

    Argo, Jeffrey W.; Kellogg, Jeffrey W.; Headley, Daniel Ignacio; Stoltzfus, Brian Scott; Waugh, Caleb J.; Lewis, Sean M.; Porter, John Larry, Jr.; Wisher, Matthew; Struve, Kenneth William; Savage, Mark Edward; Quevedo, Hernan J.; Bengtson, Roger

    2011-11-01

    Two versions of a current driver for single-turn, single-use 1-cm diameter magnetic field coils have been built and tested at the Sandia National Laboratories for use with cluster fusion experiments at the University of Texas in Austin. These coils are used to provide axial magnetic fields to slow radial loss of electrons from laser-produced deuterium plasmas. Typical peak field strength achievable for the two-capacitor system is 50 T, and 200 T for the ten-capacitor system. Current rise time for both systems is about 1.7 {mu}s, with peak current of 500 kA and 2 MA, respectively. Because the coil must be brought to the laser, the driver needs to be portable and drive currents in vacuum. The drivers are complete but laser-plasma experiments are still in progress. Therefore, in this report, we focus on system design, initial tests, and performance characteristics of the two-capacitor and ten-capacitors systems. The questions of whether a 200 T magnetic field can retard the breakup of a cluster-fusion plasma, and whether this field can enhance neutron production have not yet been answered. However, tools have been developed that will enable producing the magnetic fields needed to answer these questions. These are a two-capacitor, 400-kA system that was delivered to the University of Texas in 2010, and a 2-MA ten-capacitor system delivered this year. The first system allowed initial testing, and the second system will be able to produce the 200 T magnetic fields needed for cluster fusion experiments with a petawatt laser. The prototype 400-kA magnetic field driver system was designed and built to test the design concept for the system, and to verify that a portable driver system could be built that delivers current to a magnetic field coil in vacuum. This system was built copying a design from a fixed-facility, high-field machine at LANL, but made to be portable and to use a Z-machine-like vacuum insulator and vacuum transmission line. This system was sent to the

  17. Rôle de l'hydrogène dans le procédé de purification du silicium par plasma thermique inductif

    NASA Astrophysics Data System (ADS)

    Erin, J.; Morvan, D.; Amouroux, J.

    1993-03-01

    The use of the thermal process for purification of silicon led to a material with the chemical purity required for phototovoltaic applications. In this paper, the various properties of ArH2 plasma mixtures are briefly reviewed and the effect of hydrogen percentage in an argon plasma used for melting and purifying silicon is pointed out. Physico-chemical analysis of the purified silicon showed that hydrogen diffused in the material and could passivate crystal defects by formation of stable chemical bonds such as Si-H. La technique de purification du silicium sous plasma thermique permet d'aboutir à un matériau de pureté chimique requise pour l'industrie photovoltaïque. Dans ce travail, nous soulignerons le rôle de l'hydrogène intervenant dans les propriétés du plasma en rappelant les caractéristiques des plasmas Ar-H2 utilisés pour fondre et purifier le silicium. Les caractéristiques physico-chimiques du silicium purifié montrent que l'hydrogène diffuse dans le matériau et est en mesure de cicatriser les défauts cristallins par formation de liaisons chimiques stables de type Si-H.

  18. The effect of magnetic fields and ablative stabilization on Rayleigh-Taylor unstable inertial confinement fusion plasmas

    NASA Astrophysics Data System (ADS)

    Srinivasan, Bhuvana; Tang, Xian-Zhu

    2013-10-01

    It has long been expected that Rayleigh-Taylor instabilities (RTI) in inertial confinement fusion (ICF) can generate magnetic fields at the gas-ice interface and at the ice-ablator interface during the deceleration phase of target implosion. The focus here is on the gas-ice interface where the temperature gradient is the largest. Nonlinear evolution of RTI leads to undesirable mixing of hot and cold plasmas and enhances target energy loss. RTI is also expected to generate magnetic fields via the Biermann battery effect which mitigate energy loss by decreasing electron thermal conduction at the gas-ice interface. The Hall-magnetohydrodynamics model is used to self-consistently study the generation and growth of magnetic fields in RTI. Externally applied magnetic fields grow due to the MHD dynamo and can result in mix mitigation in addition to significant electron thermal conductivity mitigation. Electron thermal conductivity can cause ablation of the ice into the gas, leading to ablative stabilization of RTI. Mitigation of electron thermal conductivity (and energy loss) in the presence of magnetic fields has a conflicting effect with the ablative stabilization of RTI brought about due to electron thermal conductivity. A study of this conflicting effect will be presented.

  19. Power Coupling of the Rotating Magnetic Field to the Plasma in the Translation, Confinement and Sustainment Experiment

    NASA Astrophysics Data System (ADS)

    Tobin, Stephen; Schrank, Louis; Wurden, Glen; Brooks, Bob; Crawford, Ed; Guo, Houyang; Hoffman, Alan; Lotz, Dan; Slough, John; Votroubek, George

    2000-10-01

    Experimental results utilizing the rotating magnetic field (RMF) current drive system at TCS are presented. The procedure at TCS is to form a hot, FRC (RFTP method); translate it to the confinement chamber; then drive a poloidal current in it with a RMF so that the magnetic flux is sustained. The goal is to sustain the flux so that the lifetime of the FRC becomes limited by particle inventory rather that resistive flux losses, as is presently the case. In addition, the RMF can form FRCs from a pre-ionized gas fill. Experiments to date have been conducted with the following properties: RMF field strengths of about 25 G (1 mWb flux), densities of about 0.5x10^19 m-3, electron temperatures of about 100 eV, and external fields of 150 G. This poster will address the coupling of the RMF power to the plasma, in particular, how this coupling varies with density and RMF properties (field strength, frequency, pulse width and relative phasing).

  20. Confined diffusion of transmembrane proteins and lipids induced by the same actin meshwork lining the plasma membrane.

    PubMed

    Fujiwara, Takahiro K; Iwasawa, Kokoro; Kalay, Ziya; Tsunoyama, Taka A; Watanabe, Yusuke; Umemura, Yasuhiro M; Murakoshi, Hideji; Suzuki, Kenichi G N; Nemoto, Yuri L; Morone, Nobuhiro; Kusumi, Akihiro

    2016-04-01

    The mechanisms by which the diffusion rate in the plasma membrane (PM) is regulated remain unresolved, despite their importance in spatially regulating the reaction rates in the PM. Proposed models include entrapment in nanoscale noncontiguous domains found in PtK2 cells, slow diffusion due to crowding, and actin-induced compartmentalization. Here, by applying single-particle tracking at high time resolutions, mainly to the PtK2-cell PM, we found confined diffusion plus hop movements (termed "hop diffusion") for both a nonraft phospholipid and a transmembrane protein, transferrin receptor, and equal compartment sizes for these two molecules in all five of the cell lines used here (actual sizes were cell dependent), even after treatment with actin-modulating drugs. The cross-section size and the cytoplasmic domain size both affected the hop frequency. Electron tomography identified the actin-based membrane skeleton (MSK) located within 8.8 nm from the PM cytoplasmic surface of PtK2 cells and demonstrated that the MSK mesh size was the same as the compartment size for PM molecular diffusion. The extracellular matrix and extracellular domains of membrane proteins were not involved in hop diffusion. These results support a model of anchored TM-protein pickets lining actin-based MSK as a major mechanism for regulating diffusion.

  1. Confined diffusion of transmembrane proteins and lipids induced by the same actin meshwork lining the plasma membrane

    PubMed Central

    Fujiwara, Takahiro K.; Iwasawa, Kokoro; Kalay, Ziya; Tsunoyama, Taka A.; Watanabe, Yusuke; Umemura, Yasuhiro M.; Murakoshi, Hideji; Suzuki, Kenichi G. N.; Nemoto, Yuri L.; Morone, Nobuhiro; Kusumi, Akihiro

    2016-01-01

    The mechanisms by which the diffusion rate in the plasma membrane (PM) is regulated remain unresolved, despite their importance in spatially regulating the reaction rates in the PM. Proposed models include entrapment in nanoscale noncontiguous domains found in PtK2 cells, slow diffusion due to crowding, and actin-induced compartmentalization. Here, by applying single-particle tracking at high time resolutions, mainly to the PtK2-cell PM, we found confined diffusion plus hop movements (termed “hop diffusion”) for both a nonraft phospholipid and a transmembrane protein, transferrin receptor, and equal compartment sizes for these two molecules in all five of the cell lines used here (actual sizes were cell dependent), even after treatment with actin-modulating drugs. The cross-section size and the cytoplasmic domain size both affected the hop frequency. Electron tomography identified the actin-based membrane skeleton (MSK) located within 8.8 nm from the PM cytoplasmic surface of PtK2 cells and demonstrated that the MSK mesh size was the same as the compartment size for PM molecular diffusion. The extracellular matrix and extracellular domains of membrane proteins were not involved in hop diffusion. These results support a model of anchored TM-protein pickets lining actin-based MSK as a major mechanism for regulating diffusion. PMID:26864625

  2. The roles of electric field shear and Shafranov shift in sustaining high confinement in enhanced reversed shear plasmas on the TFTR tokamak

    SciTech Connect

    Synakowski, E.J.; Beer, M.A.; Batha, S.H.

    1997-02-01

    The relaxation of core transport barriers in TFTR Enhanced Reversed Shear plasmas has been studied by varying the radial electric field using different applied torques from neutral beam injection. Transport rates and fluctuations remain low over a wide range of radial electric field shear, but increase when the local E x B shearing rates are driven below a threshold comparable to the fastest linear growth rates of the dominant instabilities. Shafranov-shift-induced stabilization alone is not able to sustain enhanced confinement.

  3. The geometrical-optics law of reflection for electromagnetic waves in magnetically confined plasmas: Specular reflection of rays at the last closed flux surface

    SciTech Connect

    Bizarro, Joao P. S.

    2010-10-15

    Within the geometrical-optics approximation, it is shown that the reflection of rays describing the propagation of electromagnetic waves in fusion-grade, magnetically confined plasmas and impinging on the last closed flux surface, or plasma surface, is necessarily specular or mirror-like. More precisely, the component of the wave vector tangential to that surface does not change, whereas the component normal to it reverses its sign while keeping its magnitude. The well-known law of reflection, stating that the angle of incidence equals that of reflection, is thus generalized to anisotropic media.

  4. 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

  5. Magnetic Fusion Energy Plasma Interactive and High Heat Flux Components: Volume 5, Technical assessment of critical issues in the steady state operation of fusion confinement devices

    SciTech Connect

    Not Available

    1988-01-01

    Critical issues for the steady state operation of plasma confinement devices exist in both the physics and technology fields of fusion research. Due to the wide range and number of these issues, this technical assessment has focused on the crucial issues associated with the plasma physics and the plasma interactive components. The document provides information on the problem areas that affect the design and operation of a steady state ETR or ITER type confinement device. It discusses both tokamaks and alternative concepts, and provides a survey of existing and planned confinement machines and laboratory facilities that can address the identified issues. A universal definition of steady state operation is difficult to obtain. From a physics point of view, steady state is generally achieved when the time derivatives approach zero and the operation time greatly exceeds the characteristic time constants of the device. Steady state operation for materials depends on whether thermal stress, creep, fatigue, radiation damage, or power removal are being discussed. For erosion issues, the fluence and availability of the machine for continuous operation are important, assuming that transient events such as disruptions do not limit the component lifetimes. The panel suggests, in general terms, that steady state requires plasma operation from 100 to 1000 seconds and an availability of more than a few percent, which is similar to the expectations for an ETR type device. The assessment of critical issues for steady state operation is divided into four sections: physics issues; technology issues; issues in alternative concepts; and devices and laboratory facilities that can address these problems.

  6. Amelioration de l'adhesion de revetements organiques deposes par plasma froid sur polymeres pour applications biomedicales

    NASA Astrophysics Data System (ADS)

    Sbai, Marouan

    Plasma surface modification is commonly used in biomedical field, for example to enhance cell adhesion and growth surrounding the stent covers without affecting its bulk properties. Plasma polymer (PP) deposition used to create thin films rich in functional groups, e.g. primary amines, known to enhance the cellular response and allow grafting of biomolecules especially on stent grafts. Thin film adhesion to stent polymeric cover should be considered especially as they will evolve in a biological environment. The aim of this project is to evaluate the adhesion of PP on polytetrafluoroethylene (PTFE) and polyethyleneterephthalate (PET). Thereafter, an ammonia plasma treatment on PTFE is performed prior to deposition of PP to optimize the PP/PTFE adhesion. PP studied here (referred to as "LP") is prepared from a mixture of ethylene (C2H4) and ammonia (NH3). It is deposited on two supports, PET and PTFE. The interfacial adhesion between the LP coating and the substrate was evaluated by "Peel-test 180 °" according to ASTM F1842. Staining of the surface after peel test followed by an image analysis was performed to determine the percentage of removed coating. Adhesion optimization is done by varying operating plasma parameters such as power, pressure and pretreatment time. Chemical analyses and wettability of LP and pretreated surfaces in dry and wet conditions are characterized by XPS and contact angle measurements, respectively. The adhesion of LP/PET was excellent in a dry environment (<1%), but lower under wet conditions (4+/-6% and 44+/-7% as minimum and maximum values at 5min and 60min of immersion in deionized water, respectively). However, 56% to 75% of the LP is removed from virgin PTFE in a dry and wet environment, respectively; percentages can be substantially reduced by plasma pretreatment (0% and 8+/-3% in air and 30min in deionized water). Almost no delamination was observed with NH3 plasma pretreatment at 15s, 100 mTorr and 50W. N2 plasma pretreatment

  7. Studies of plasma confinement in linear and RACETRACK mirror configurations. Progress report, January 1--October 31, 1986

    SciTech Connect

    Kuthi, A.; Wong, A.Y.

    1986-06-30

    This report discusses research on the following magnetic mirror configurations: Racetrack; ECRH generated plasmas; RF generated plasmas; potential structures; surface multipole fields, and lamex; hot electron physics; axial loss processes; and RF induced effects.

  8. A study of the methods for the production and confinement of high energy plasmas. [injection of dense plasma into long magnetic field

    NASA Technical Reports Server (NTRS)

    Cheng, D. Y.; Wang, P.

    1972-01-01

    The injection of dense plasmas into a B sub z long magnetic field from both ends of the field coil was investigated. Deflagration plasma guns and continuous flow Z-pinch are discussed along with the possibility of a continuous flow Z-pinch fusion reactor. The injection experiments are described with emphasis on the synchronization of the two plasma deflagration guns, the collision of the two plasma beams, and the determination of plasma density.

  9. Absolute measurement of the total ion-drag force on a single plasma-confined microparticle at the void edge under microgravity conditions.

    PubMed

    Beckers, J; Trienekens, D J M; Kroesen, G M W

    2013-11-01

    We present an absolute measurement of the total ion-drag force on one single microparticle at the edge of the dust free region in low pressure complex plasmas: the void. In order to do so, the particle confinement position was monitored as a function of the gas pressure for two particle sizes under normal gravity conditions and under microgravity conditions during parabolic flights. At the border of the void, the ion-drag force on a particle with a radius of 4.90 μm appeared to be (3.6±0.3)×10(-12) N.

  10. On the Uniqueness of Solutions of a Nonlinear Elliptic Problem Arising in the Confinement of a Plasma in a Stellarator Device

    SciTech Connect

    Diaz, J. I.; Galiano, G.; Padial, J. F.

    1999-01-15

    We study the uniqueness of solutions of a semilinear elliptic problem obtained from an inverse formulation when the nonlinear terms of the equation are prescribed in a general class of real functions. The inverse problem arises in the modeling of the magnetic confinement of a plasma in a Stellarator device. The uniqueness proof relies on an L{sup {infinity}} -estimate on the solution of an auxiliary nonlocal problem formulated in terms of the relative rearrangement of a datum with respect to the solution.

  11. Fabrication et analyse de revetements de nitrure de silicium deposes par plasma pour de nouvelles applications optiques

    NASA Astrophysics Data System (ADS)

    Vernhes, Richard

    In the present thesis, innovative methods and strategies are proposed for the plasma-enhanced chemical vapor deposition (PECVD) of thin films in order to tune their physical properties (e.g. optical constants, optical gap, etc.), by relying on the control and understanding of plasma characteristics and plasma-surface interactions rather than on the traditional variation of the gas mixture composition. The following paragraphs summarize the applied methodology and the main results, presented in the form of three articles at the core of this thesis, plus an additional chapter devoted to sensor fabrication and testing. (1) In the first article, we propose a new method of fabricating a-SiNx:H alloys by pulsing the radiofrequency (RF) signal during the PECVD process. Spectroscopic ellipsometric analysis in the UV-VIS-NIR and FIR ranges, atomic force microscopy, and elastic recoil detection reveal strong variations in the optical constants (1.88 ≤ n ≤ 2.75, 10-4 ≤ k ≤ 5 x 10-2 at 550 nm), optical gap (4.01 eV ≥ E 9 ≥ 1.95 eV), microstructural characteristics (1.3 nm ≤ surface roughness ≤ 8.3 nm), and chemical composition (0.47 ≤ x ≤ 1.35) of the coatings as a function of duty cycle. Using solely the control of duty cycle, we fabricate two types of a-SiNx:H-based thin film devices, namely (i) a model Fabry-Perot optical filter deposited on a plastic substrate, and (ii) a superlattice structure displaying a photoluminescence signal four times as large as the reference single layer. (2) In the second article, transparent hydrogenated amorphous silicon nitride coatings are prepared by dual-mode microwave/radiofrequency PECVD. By controlling the effects of plasma density and ion energy on the film growth, it is possible to modify the microstructure of the coatings and hence the refractive index, n. Using this method, we are able to vary n from 1.6 to 2.0 at 550 nm, simply by adjusting the power levels of the radiofrequency and microwave components. (3) In

  12. Local transport in Joint European Tokamak edge-localized, high-confinement mode plasmas with H, D, DT, and T isotopes

    NASA Astrophysics Data System (ADS)

    Budny, R. V.; Ernst, D. R.; Hahm, T. S.; McCune, D. C.; Christiansen, J. P.; Cordey, J. G.; Gowers, C. G.; Guenther, K.; Hawkes, N.; Jarvis, O. N.; Stubberfield, P. M.; Zastrow, K.-D.; Horton, L. D.; Saibene, G.; Sartori, R.; Thomsen, K.; von Hellermann, M. G.

    2000-12-01

    The edge-localized, high-confinement mode regime is of interest for future Tokamak reactors since high performance has been sustained for long durations. Experiments in the Joint European Tokamak [M. Keilhacker et al., Nuclear Fusion 39, 209 (1999)] have studied this regime using scans with the toroidal field and plasma current varied together in H, D, DT, and T isotopes. The local energy transport in more than fifty of these plasmas is analyzed, and empirical scaling relations are derived for energy transport coefficients during quasi-steady state conditions using dimensionless parameters. Neither the Bohm nor gyro-Bohm expressions give the shapes of the profiles. The scalings with β and ν* are in qualitative agreement with Ion Temperature Gradient theory.

  13. Effect of the laser wavelength: A long story of laser-plasma interaction physics for Inertial Confinement Fusion Teller Medal Lecture

    NASA Astrophysics Data System (ADS)

    Labaune, Christine

    2013-11-01

    Laser-driven Inertial Confinement Fusion (ICF) relies on the use of high-energy laser beams to compress and ignite a thermonuclear fuel with the ultimate goal of producing energy. Fusion is the holy grail of energy sources-combining abundant fuel with no greenhouse gas emissions, minimal waste products and a scale that can meet mankind's long-term energy demands. The quality and the efficiency of the coupling of the laser beams with the target are an essential step towards the success of laser fusion. A long-term program on laser-plasma interaction physics has been pursued to understand the propagation and the coupling of laser pulses in plasmas for a wide range of parameters.

  14. Effect of the laser wavelength: A long story of laser-plasma interaction physics for Inertial Confinement Fusion Teller Medal Lecture

    NASA Astrophysics Data System (ADS)

    Labaune, Christine

    2016-10-01

    Laser-driven Inertial Confinement Fusion (ICF) relies on the use of high-energy laser beams to compress and ignite a the1monuclear fuel with the ultimate goal of producing energy. Fusion is the holy grail of energy sources-combining abundant fuel with no greenhouse gas emissions, minimal waste products and a scale that can meet mankind's long-term energy demands. The quality and the efficiency of the coupling of the laser beams with the target are an essential step towards the success of laser fusion. A long-te1m program on laser-plasma interaction physics has been pursued to understand the propagation and the coupling of laser pulses in plasmas for a wide range of parameters.

  15. Changes in core electron temperature fluctuations across the ohmic energy confinement transition in Alcator C-Mod plasmas

    NASA Astrophysics Data System (ADS)

    Sung, C.; White, A. E.; Howard, N. T.; Oi, C. Y.; Rice, J. E.; Gao, C.; Ennever, P.; Porkolab, M.; Parra, F.; Mikkelsen, D.; Ernst, D.; Walk, J.; Hughes, J. W.; Irby, J.; Kasten, C.; Hubbard, A. E.; Greenwald, M. J.; the Alcator C-Mod Team

    2013-08-01

    The first measurements of long wavelength (kyρs < 0.3) electron temperature fluctuations in Alcator C-Mod made with a new correlation electron cyclotron emission diagnostic support a long-standing hypothesis regarding the confinement transition from linear ohmic confinement (LOC) to saturated ohmic confinement (SOC). Electron temperature fluctuations decrease significantly (∼40%) crossing from LOC to SOC, consistent with a change from trapped electron mode (TEM) turbulence domination to ion temperature gradient (ITG) turbulence as the density is increased. Linear stability analysis performed with the GYRO code (Candy and Waltz 2003 J. Comput. Phys. 186 545) shows that TEMs are dominant for long wavelength turbulence in the LOC regime and ITG modes are dominant in the SOC regime at the radial location (ρ ∼ 0.8) where the changes in electron temperature fluctuations are measured. In contrast, deeper in the core (ρ < 0.8), linear stability analysis indicates that ITG modes remain dominant across the LOC/SOC transition. This radial variation suggests that the robust global changes in confinement of energy and momentum occurring across the LOC/SOC transition are correlated to local changes in the dominant turbulent mode near the edge.

  16. Electron Density and Two-Channel Neutron Emission Measurements in Steady-State Spherical Inertial-Electrostatically Confined Plasmas, with Review of the 1-D Kinetic Model

    NASA Technical Reports Server (NTRS)

    Dobson, Chris C.; Hrbud, Ivana

    2004-01-01

    Electron density measurements have been made in steady-state plasmas in a spherical inertial electrostatic confinement (IEC) discharge using microwave interferometry. Plasma cores interior to two cathodes, having diameters of 15 and 23 cm, respectively, were probed over a transverse range of 10 cm with a spatial resolution of about 1.4 cm for buffer gas pressures from 0.2 to 6 Pa in argon and deuterium. The transverse profiles are generally flat, in some cases with eccentric symmetric minima, and give mean densities of from approx. = 0.4 to 7x 10(exp 10)/cu cm, the density generally increasing with the neutral gas pressure. Numerical solutions of the 1-D Poisson equation for EC plasmas are reviewed and energy distribution functions are identified which give flat transverse profiles. These functions are used with the plasma approximation to obtain solutions which also give densities consistent with the measurements, and a double potential well solution is obtained which has minima qualitatively similar to those observed. Explicit consideration is given to the compatibility of the solutions interior and exterior to the cathode, and to grid transparency. Deuterium fusion neutron emission rates were also measured and found to be isotropic, to within the measurement error, over two simultaneous directions. Anisotropy was observed in residual emissions during operation with non-fusing hydrogen-1. The deuterium rates are consistent with predictions from the model.

  17. Direct observation of transition to electron Bernstein waves from electromagnetic mode by three mode-conversion scenarios in the dipole confinement torus plasma

    NASA Astrophysics Data System (ADS)

    Uchijima, K.; Takemoto, T.; Morikawa, J.; Ogawa, Y.

    2015-06-01

    Direct measurement experiments on the mode conversion to the electron Bernstein wave (EBW) have been conducted in dipole confinement torus plasmas for three excitation scenarios; i.e. perpendicular injections of an eXtraordinary mode (X-mode) from the low- and high-magnetic-field sides, and the oblique injection of an Ordinary mode (O-mode) from the low-magnetic-field side. By inserting probe antennas into plasmas, wave propagation has been directly measured. At plasma conditions for the EBW excitation, several characteristics which indicate the mode conversion to the EBWs have been observed; i.e. a short wavelength wave, an electrostatic and longitudinal mode, backward propagation at the upper hybrid resonance (UHR) region. Meanwhile, the wavelengths experimentally observed might be slightly longer than those of theoretical prediction. In the case of the oblique injection of the O-mode, it has been identified that the window of the injection angle for the excitation of the EBW would be quite limited, and the optimum angle seems to be roughly in agreement with theory. These experimental results might support that the electromagnetic waves injected outside of torus plasmas reach to the UHR region and convert wave characteristics to the EBWs for three excitation scenarios.

  18. Cylindrically confined pair-ion-electron and pair-ion plasmas having axial sheared flow and radial gradients

    SciTech Connect

    Batool, Nazia; Saleem, H.

    2013-10-15

    The linear and nonlinear dynamics of pair-ion (PI) and pair-ion-electron plasmas (PIE) have been investigated in a cylindrical geometry with a sheared plasma flow along the axial direction having radial dependence. The coupled linear dispersion relation of low frequency electrostatic waves has been presented taking into account the Guassian profile of density and linear gradient of sheared flow. It is pointed out that the quasi-neutral cold inhomogeneous pure pair ion plasma supports only the obliquely propagating convective cell mode. The linear dispersion relation of this mode has been solved using boundary conditions. The nonlinear structures in the form of vortices formed by different waves have been discussed in PI and PIE plasmas.

  19. Plasma barodiffusion in inertial-confinement-fusion implosions: application to observed yield anomalies in thermonuclear fuel mixtures.

    PubMed

    Amendt, Peter; Landen, O L; Robey, H F; Li, C K; Petrasso, R D

    2010-09-10

    The observation of large, self-generated electric fields (≥10(9)  V/m) in imploding capsules using proton radiography has been reported [C. K. Li, Phys. Rev. Lett. 100, 225001 (2008)]. A model of pressure gradient-driven diffusion in a plasma with self-generated electric fields is developed and applied to reported neutron yield deficits for equimolar D3He [J. R. Rygg, Phys. Plasmas 13, 052702 (2006)] and (DT)3He [H. W. Herrmann, Phys. Plasmas 16, 056312 (2009)] fuel mixtures and Ar-doped deuterium fuels [J. D. Lindl, Phys. Plasmas 11, 339 (2004)]. The observed anomalies are explained as a mild loss of deuterium nuclei near capsule center arising from shock-driven diffusion in the high-field limit.

  20. AINSE Plasma Science and Technology Conference and Elizabeth and Frederick White Workshop on Fundamental Problems in the Physics of Magnetically Confined Plasmas: Conference handbook

    NASA Astrophysics Data System (ADS)

    The handbook contains abstracts of papers and posters presented at the conference. The main topics relate to plasma physics and fusion, plasma processing and uses as well as specific fusion devices and experiments. Eighty-four out of ninety-two presentations were considered to be in the INIS subject scope and have been separately indexed.

  1. Direct asymmetry measurement of temperature and density spatial distributions in inertial confinement fusion plasmas from pinhole space-resolved spectra

    SciTech Connect

    Nagayama, T.; Mancini, R. C.; Florido, R.; Mayes, D.; Tommasini, R.; Koch, J. A.; Delettrez, J. A.; Regan, S. P.; Smalyuk, V. A.

    2014-05-15

    Two-dimensional space-resolved temperature and density images of an inertial confinement fusion (ICF) implosion core have been diagnosed for the first time. Argon-doped, direct-drive ICF experiments were performed at the Omega Laser Facility and a collection of two-dimensional space-resolved spectra were obtained from an array of gated, spectrally resolved pinhole images recorded by a multi-monochromatic x-ray imager. Detailed spectral analysis revealed asymmetries of the core not just in shape and size but in the temperature and density spatial distributions, thus characterizing the core with an unprecedented level of detail.

  2. Mapping the electromagnetic field confinement in the gap of germanium nanoantennas with plasma wavelength of 4.5 micrometers

    NASA Astrophysics Data System (ADS)

    Calandrini, Eugenio; Venanzi, Tommaso; Appugliese, Felice; Badioli, Michela; Giliberti, Valeria; Baldassarre, Leonetta; Biagioni, Paolo; De Angelis, Francesco; Klesse, Wolfgang M.; Scappucci, Giordano; Ortolani, Michele

    2016-09-01

    We study plasmonic nanoantennas for molecular sensing in the mid-infrared made of heavily doped germanium, epitaxially grown with a bottom-up doping process and featuring free carrier density in excess of 1020 cm-3. The dielectric function of the 250 nm thick germanium film is determined, and bow-tie antennas are designed, fabricated, and embedded in a polymer. By using a near-field photoexpansion mapping technique at λ = 5.8 μm, we demonstrate the existence in the antenna gap of an electromagnetic energy density hotspot of diameter below 100 nm and confinement volume 105 times smaller than λ3.

  3. Fusion, magnetic confinement

    SciTech Connect

    Berk, H.L.

    1992-08-06

    An overview is presented of the principles of magnetic confinement of plasmas for the purpose of achieving controlled fusion conditions. Sec. 1 discusses the different nuclear fusion reactions which can be exploited in prospective fusion reactors and explains why special technologies need to be developed for the supply of tritium or {sup 3}He, the probable fuels. In Sec. 2 the Lawson condition, a criterion that is a measure of the quality of confinement relative to achieving fusion conditions, is explained. In Sec. 3 fluid equations are used to describe plasma confinement. Specific confinement configurations are considered. In Sec. 4 the orbits of particle sin magneti and electric fields are discussed. In Sec. 5 stability considerations are discussed. It is noted that confinement systems usually need to satisfy stability constraints imposed by ideal magnetohydrodynamic (MHD) theory. The paper culminates with a summary of experimental progress in magnetic confinement. Present experiments in tokamaks have reached the point that the conditions necessary to achieve fusion are being satisfied.

  4. A novel technique for single-shot energy-resolved 2D x-ray imaging of plasmas relevant for the inertial confinement fusion

    SciTech Connect

    Labate, L.; Koester, P.; Levato, T.; Gizzi, L. A.

    2012-10-15

    A novel x-ray diagnostic of laser-fusion plasmas is described, allowing 2D monochromatic images of hot, dense plasmas to be obtained in any x-ray photon energy range, over a large domain, on a single-shot basis. The device (named energy-encoded pinhole camera) is based upon the use of an array of many pinholes coupled to a large area CCD camera operating in the single-photon mode. The available x-ray spectral domain is only limited by the quantum efficiency of scientific-grade x-ray CCD cameras, thus extending from a few keV up to a few tens of keV. Spectral 2D images of the emitting plasma can be obtained at any x-ray photon energy provided that a sufficient number of photons had been collected at the desired energy. Results from recent inertial confinement fusion related experiments will be reported in order to detail the new diagnostic.

  5. Saturation of the Two-Plasmon Decay Instability in Long-Scale-Length Plasmas Relevant to Direct-Drive Inertial Confinement Fusion

    SciTech Connect

    Froula, D. H.; Yaakobi, B.; Hu, S. X.; Chang, P-Y.; Craxton, R. S.; Edgell, D. H.; Follett, R.; Michel, D. T.; Myatt, J. F.; Seka, W.; Short, R. W.; Solodov, A.; Stoeckl, C.

    2012-04-01

    Measurements of the hot-electron generation by the two-plasmon-decay instability are made in plasmas relevant to direct-drive inertial confinement fusion. Density-scale lengths of 400 {micro}m at n{sub cr}/4 in planar CH targets allowed the two-plasmon-decay instability to be driven to saturation for vacuum intensities above ~3.5 x 10{sup 14} W cm{sup -2}. In the saturated regime, ~1% of the laser energy is converted to hot electrons. The hot-electron temperature is measured to increase rapidly from 25 to 90 keV as the laser beam intensity is increased from 2 to 7 x 10{sup 14} W cm{sup -2}. This increase in the hot-electron temperature is compared with predictions from nonlinear Zakharov models.

  6. Injection of electrons with predominantly perpendicular energy into an area of toroidal field ripple in a tokamak plasma to improve plasma confinement

    DOEpatents

    Ono, Masayuki; Furth, Harold

    1993-01-01

    An electron injection scheme for controlling transport in a tokamak plasma. Electrons with predominantly perpendicular energy are injected into a ripple field region created by a group of localized poloidal field bending magnets. The trapped electrons then grad-B drift vertically toward the plasma interior until they are detrapped, charging the plasma negative. Calculations indicate that the highly perpendicular velocity electrons can remain stable against kinetic instabilities in the regime of interest for tokamak experiments. The penetration distance can be controlled by controlling the "ripple mirror ratio", the energy of the injected electrons, and their v.sub..perp. /v.sub.51 ratio. In this scheme, the poloidal torque due to the injected radial current is taken by the magnets and not by the plasma. Injection is accomplished by the flat cathode containing an ECH cavity to pump electrons to high v.sub..perp..

  7. An experimental investigation of stimulated Brillouin scattering in laser-produced plasmas relevant to inertial confinement fusion

    SciTech Connect

    Bradley, K.S.

    1993-02-11

    Despite the apparent simplicity of controlled fusion, there are many phenomena which have prevented its achievement. One phenomenon is laser-plasma instabilities. An investigation of one such instability, stimulated Brillouin scattering (SBS), is reported here. SBS is a parametric process whereby an electromagnetic wave (the parent wave) decays into another electromagnetic wave and an ion acoustic wave (the daughter waves). SBS impedes controlled fusion since it can scatter much or all of the incident laser light, resulting in poor drive symmetry and inefficient laser-plasma coupling. It is widely believed that SBS becomes convectively unstable--that is, it grows as it traverses the plasma. Though it has yet to be definitively tested, convective theory is often invoked to explain experimental observations, even when one or more of the theory`s assumptions are violated. In contrast, the experiments reported here not only obeyed the assumptions of the theory, but were also conducted in plasmas with peak densities well below quarter-critical density. This prevented other competing or coexisting phenomena from occurring, thereby providing clearly interpretable results. These are the first SBS experiments that were designed to be both a clear test of linear convective theory and pertinent to controlled fusion research. A crucial part of this series of experiments was the development of a new instrument, the Multiple Angle Time Resolving Spectrometer (MATRS). MATRS has the unique capability of both spectrally and temporally resolving absolute levels of scattered light at many angles simultaneously, and is the first of its kind used in laser-plasma experiments. A detailed comparison of the theoretical predictions and the experimental observations is made.

  8. Propagation of shear Alvén waves in two-ion species plasmas confined by a nonuniform magnetic field

    SciTech Connect

    Farmer, W. A.; Morales, G. J.

    2013-08-15

    Ray tracing calculations are performed for shear Alfvén waves in two-ion species plasmas in which the magnetic field varies with position. Three different magnetic topologies of contemporary interest are explored: a linear magnetic mirror, a pure toroidal field, and a tokamak field. The wave frequency is chosen to lie in the upper propagation band, so that reflection at the ion-ion hybrid frequency can occur for waves originally propagating along the magnetic field direction. Calculations are performed for a magnetic well configuration used in recent experiments [S. T. Vincena et al., Geophys. Res. Lett. 38, L11101 (2011) and S. T. Vincena et al., Phys. Plasmas 20, 012111 (2013)] in the Large Plasma Device (LAPD) related to the ion-ion hybrid resonator. It is found that radial spreading cannot explain the relatively low values of the resonator quality factor (Q) measured in those experiments, even when finite ion temperature is considered. This identifies that a damping mechanism is present that is at least an order of magnitude larger than dissipation due to radial energy loss. Calculations are also performed for a magnetic field with pure toroidal geometry, without a poloidal field, as in experiments being planned for the Enormous Toroidal Plasma Device. In this case, the effects of field-line curvature cause radial reflections. A poloidal field is included to explore a tokamak geometry with plasma parameters expected in ITER. When ion temperature is ignored, it is found that the ion-ion hybrid resonator can exist and trap waves for multiples bounces. The effects of finite ion temperature combine with field line curvature to cause the reflection point to move towards the tritium cyclotron frequency when electron temperature is negligible. However, for ITER parameters, it is shown that the electrons must be treated in the adiabatic limit to properly describe resonator phenomena.

  9. 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.

  10. 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.

  11. Magnetic reconnection in plasma under inertial confinement fusion conditions driven by heat flux effects in Ohm's law.

    PubMed

    Joglekar, A S; Thomas, A G R; Fox, W; Bhattacharjee, A

    2014-03-14

    In the interaction of high-power laser beams with solid density plasma there are a number of mechanisms that generate strong magnetic fields. Such fields subsequently inhibit or redirect electron flows, but can themselves be advected by heat fluxes, resulting in complex interplay between thermal transport and magnetic fields. We show that for heating by multiple laser spots reconnection of magnetic field lines can occur, mediated by these heat fluxes, using a fully implicit 2D Vlasov-Fokker-Planck code. Under such conditions, the reconnection rate is dictated by heat flows rather than Alfvènic flows. We find that this mechanism is only relevant in a high β plasma. However, the Hall parameter ωcτei can be large so that thermal transport is strongly modified by these magnetic fields, which can impact longer time scale temperature homogeneity and ion dynamics in the system.

  12. Proton Radiography of Spontaneous Fields, Plasma Flows and Dynamics in X-Ray Driven Inertial-Confinement Fusion Implosions

    NASA Astrophysics Data System (ADS)

    Li, C. K.; Seguin, F. H.; Frenje, J. A.; Rosenberg, M.; Zylstra, A. B.; Rinderknecht, H. G.; Petrasso, R. D.; Amendt, P. A.; Landen, O. L.; Town, R. P. J.; Betti, R.; Knauer, J. P.; Meyerhofer, D. D.; Back, C. A.; Kilkenny, J. D.; Nikroo, A.

    2010-11-01

    Backlighting of x-ray-driven implosions in empty hohlraums with mono-energetic protons on the OMEGA laser facility has allowed a number of important phenomena to be observed. Several critical parameters were determined, including plasma flow, three types of spontaneous electric fields and megaGauss magnetic fields. These results provide insight into important issues in indirect-drive ICF. Even though the cavity is effectively a Faraday cage, the strong, local fields inside the hohlraum can affect laser-plasma instabilities, electron distributions and implosion symmetry. They are of fundamental scientific importance for a range of new experiments at the frontiers of high-energy-density physics. Future experiments designed to characterize the field formation and evolution in low-Z gas fill hohlraums will be discussed.

  13. An Experimental Study of Continuous Plasma Flows Driven by a Confined Arc in a Transverse Magnetic Field

    NASA Technical Reports Server (NTRS)

    Barger, R. L.; Brooks, J. D.; Beasley, W. D.

    1961-01-01

    A crossed-field, continuous-flow plasma accelerator has been built and operated. The highest measured velocity of the flow, which was driven by the interaction of the electric and magnetic fields, was about 500 meters per second. Some of the problems discussed are ion slip, stability and uniformity of the discharge, effect of the magnetic field on electron emission, use of preionization, and electrode contamination.

  14. Approaching to the ideal condition of plasma confinement by applying external resonant fields in IR-T1 tokamak

    NASA Astrophysics Data System (ADS)

    Meshkani, Sakineh; Ghoranneviss, Mahmood; Lafouti, Mansoureh

    2015-06-01

    For understanding the effect of resonant helical magnetic field (RHF) and bias on the edge plasma turbulent transport, the radial and poloidal electric field (Er, EP ), poloidal and toroidal magnetic field (BP, Br ) were detected by the Langmuir probe, magnetic probe and diamagnetic loop. The poloidal, toroidal and radial velocity (VP, Vr, Vt ) can be determined from the electric and magnetic field. In the present work, we have investigated the effect of the magnitude of bias (V bias = 200v, V bias = 320v) on Er, EP, BP, Bt, VP, Vr, Vt . Moreover, we applied RHF with L = 2, L = 3 and L = 2 and 3 and investigate the effect of the helical windings radius on above parameters. Also, the experiment was repeated by applying the positive biasing potentials and RHF's simultaneously. The results show that by applying bias to the plasma at t = 15 msec at r/a = 0.9, Er , BP and Bt increase while EP decreases. The best modification occurs at V bias = 200v. By applying RHF to the plasma, both the electric and magnetic field vary. Er reaches the highest in the presence of RHF with L = 3. The same results are obtained for BP, Bt, VP and Vt . While the inverse results are obtained for EP and Vr . Finally, RHF and bias are applied simultaneously to the plasma. With applied bias with V bias = 200v and RHF with L = 2 and 3, we reach to the ideal circumstance. The same results obtain in the situation with V bias = 320v and RHF with L = 2 and 3.

  15. Neutron Time-of-Flight Measurements of Charged-Particle Energy Loss in Inertial Confinement Fusion Plasmas

    NASA Astrophysics Data System (ADS)

    Sayre, Daniel; Cerjan, Charlie; Berzak Hopkins, Laura; Caggiano, Joseph; Divol, Laurent; Eckart, Mark; Graziani, Frank; Grim, Gary; Hartouni, Ed; Hatarik, Robert; Le Pape, Sebastien; MacKinnon, Andrew; Schneider, Dieter; Sepke, Scott

    2015-11-01

    Neutron time-of-flight measurements of inflight T (d , n) α reactions created during an implosion of a deuterium gas target have been performed at the National Ignition Facility, with order of magnitude improvements in statistics and resolution over past experiments. In the implosion, energetic tritons emitted by thermonuclear fusion within the deuterium plasma produced over 1011 inflight T (d , n) α reactions. The yield and particle spectrum of inflight reactions are sensitive to the triton's energy loss in the plasma, which, in this implosion, consisted of multi-keV temperatures and number densities above 1024 cm-3. Radiation-hydrodynamic simulations of the implosion were adjusted to match the yield and broadening of the D (d , n) 3 He neutron peak. These same simulations give reasonable agreement with the measured T (d , n) α yield and neutron spectrum, and this provides a strong consistency check of the simulated plasma conditions and energy loss model. This research was performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  16. Plasma physics. Proceedings. 7th Latin American Workshop on Plasma Physics (VII LAWPP 97), Caracas (Venezuela), 20 - 31 Jan 1997.

    NASA Astrophysics Data System (ADS)

    Martín, P.; Puerta, J.

    The following topics were dealt with: general plasma theory, plasma confinement, shock waves and instabilities in plasma, plasma spectroscopy, astrophysical and space plasmas, pulse power experiments, plasma processing.

  17. Development of diagnostic and manipulation systems for space-charge dominated electron beams and confined electron plasmas in ELTRAP

    SciTech Connect

    Rome, M.; Cavaliere, F.; Maero, G.; Paroli, B.; Pozzoli, R.; Cavenago, M.; Ikram, M.

    2013-03-19

    Modifications have been implemented in the Penning-Malmberg device ELTRAP aimed at performing studies on the dynamics of space-charge dominated nanosecond electron bunches traveling along the magnetic field. In particular, a Thomson backscattering apparatus has been developed where an infrared (IR) laser pulse collides with the bunched electron beam. The frequency-shifted backscattered radiation, acquired by means of a photomultiplier (PMT), can be exploited to evaluate information on energy, energy spread and density of the bunch. The achievable sensitivity of the diagnostics has been estimated, and valuable information on the main parameters affecting the signal-to-noise (S/N) ratio has been obtained [B. Paroli, F. Cavaliere, M. Cavenago, F. De Luca, M. Ikram, G. Maero, C. Marini, R. Pozzoli, and M. Rome, JINST 7, P01008 (2012)]. A series of upgrades are under way, aimed at increasing the S/N ratio through the use of a new laser for the electron source, the insertion of a stray light shield, and the optimization of the detection electronics. Moreover, electromagnetic simulations relevant to the design and implementation of a microwave heating system are presented. The generation of an electron plasma in ELTRAP by means of a low-power radio frequency (RF) drive in the MHz range applied on one of the trap electrodes and under ultra-high vacuum (UHV) conditions has previously been demonstrated [B. Paroli, F. De Luca, G. Maero, F. Pozzoli, and M. Rome, Plasma Sources Sci. Technol. 19, 045013 (2010)]. The new heating system will allow the extension of the RF studies to the GHz range and in particular the production of a more energetic electron plasma via cyclotron resonant excitation.

  18. Development of diagnostic and manipulation systems for space-charge dominated electron beams and confined electron plasmas in ELTRAP

    NASA Astrophysics Data System (ADS)

    Romé, M.; Cavaliere, F.; Cavenago, M.; Ikram, M.; Maero, G.; Paroli, B.; Pozzoli, R.

    2013-03-01

    Modifications have been implemented in the Penning-Malmberg device ELTRAP aimed at performing studies on the dynamics of space-charge dominated nanosecond electron bunches traveling along the magnetic field. In particular, a Thomson backscattering apparatus has been developed where an infrared (IR) laser pulse collides with the bunched electron beam. The frequency-shifted backscattered radiation, acquired by means of a photomultiplier (PMT), can be exploited to evaluate information on energy, energy spread and density of the bunch. The achievable sensitivity of the diagnostics has been estimated, and valuable information on the main parameters affecting the signal-to-noise (S/N) ratio has been obtained [B. Paroli, F. Cavaliere, M. Cavenago, F. De Luca, M. Ikram, G. Maero, C. Marini, R. Pozzoli, and M. Romé, JINST 7, P01008 (2012)]. A series of upgrades are under way, aimed at increasing the S/N ratio through the use of a new laser for the electron source, the insertion of a stray light shield, and the optimization of the detection electronics. Moreover, electromagnetic simulations relevant to the design and implementation of a microwave heating system are presented. The generation of an electron plasma in ELTRAP by means of a low-power radio frequency (RF) drive in the MHz range applied on one of the trap electrodes and under ultra-high vacuum (UHV) conditions has previously been demonstrated [B. Paroli, F. De Luca, G. Maero, F. Pozzoli, and M. Romé, Plasma Sources Sci. Technol. 19, 045013 (2010)]. The new heating system will allow the extension of the RF studies to the GHz range and in particular the production of a more energetic electron plasma via cyclotron resonant excitation.

  19. Ablation de ZnO par laser UV (193 nm) : nano-agrégats en phase gazeuse

    NASA Astrophysics Data System (ADS)

    Ozerov, I.; Bulgakov, A.; Nelson, D.; Castell, R.; Sentis, M.; Marine, W.

    2003-06-01

    La condensation de nano-agrégats d'oxyde de zinc en phase gazeuse est mise en évidence lors de l'ablation de ZnO massif par laser ArF pulsé. Nous comparons l'évolution spatio-temporelle de la forme du panache d'ablation (plume) de ZnO sous vide et sous atmosphère de gaz de couverture (oxygène et/ou hélium) à partir des images CCD et des résultats issus d'analyses spectroscopiques. L'expansion du plasma et la croissance des nano-clusters sont influencées par l'effet du confinement de la plume dû aux collisions entre les particules ablatées et les molécules de gaz ambiant ainsi que par les réactions chimiques dans le cas de l'oxygène. Le spectre de rayonnement du plasma est constitué principalement par l'émission d'atomes excités de Zn neutre. Nous avons observé la photoluminescence des nano-agrégats en suspension dans le gaz ainsi que leur décomposition par laser ArF.

  20. The mitigating effect of self-generated magnetic field on Rayleigh-Taylor unstable inertial confinement fusion plasmas

    NASA Astrophysics Data System (ADS)

    Srinivasan, Bhuvana

    2012-10-01

    It has long been expected that Rayleigh-Taylor instabilities (RTI) in ICF can generate magnetic fields at the gas-ice interface and at the ice-ablator interface during the deceleration phase of target implosion. The focus here is on the gas-ice interface where the temperature gradient is the largest. Nonlinear evolution of RTI leads to undesirable mixing of hot and cold plasmas and enhances target energy loss. RTI is also expected to generate magnetic fields via the Biermann battery effect, which is related to fluid vorticity generation by RTI. The magnetic field wraps around the bubbles and spikes and concentrates in flux bundles at the perturbed gas-ice interface where fluid vorticity is large. The generated magnetic field can then be further amplified via the MHD dynamo effect. While the planar 2-D simulations only generate out-of-plane magnetic fields, 3-D simulations will result in further amplification of the complex magnetic field structures via the MHD dynamo. This is studied by including a seed in-plane magnetic field in 2-D and examining the resulting magnetic field structure and magnitude. The self-generated out-of-plane magnetic fields depend on ICF parameters via the scaling law, mi√A g/λ where mi is the ion mass, A is the Atwood number, g is the acceleration, and λ is the wavelength. These magnetic fields grow to magnitudes of 10^2-10^3 T for ICF relevant parameter regimes. While this is dynamically insignificant due to the plasma pressure far exceeding the magnetic pressure, it can significantly reduce perpendicular electron thermal conductivity by a factor of 2-10. Such a reduction in thermal conductivity perpendicular to the magnetic field contributes to lowering of radial energy transport in the implosion target.

  1. Conception et caracterisation d'un magnetoplasma produit par une onde de surface pour la pulverisation d'echantillons solides

    NASA Astrophysics Data System (ADS)

    Masse, Louis Philippe

    puissance. Une etude des caracteristiques du plasma seul a revele que le champ magnetique confine si bien le plasma que le maximum de densite electronique se trouve hors axe, plus exactement a la position radiale correspondant au rayon du cylindre dielectrique servant a former l'interface dielectrique-plasma dans la zone source du reacteur. Ce phenomene indique une tres nette superiorite du coefficient de diffusion axial par rapport au coefficient de diffusion radial. Notre reacteur a un potentiel interessant pour l'analyse elementaire de materiaux solides puisque le taux de pulverisation y est eleve et que les especes pulverisees sont aisement excitees et ionisees par le plasma.

  2. Masked-backlighter technique used to simultaneously image x-ray absorption and x-ray emission from an inertial confinement fusion plasma

    SciTech Connect

    Marshall, F. J. Radha, P. B.

    2014-11-15

    A method to simultaneously image both the absorption and the self-emission of an imploding inertial confinement fusion plasma has been demonstrated on the OMEGA Laser System. The technique involves the use of a high-Z backlighter, half of which is covered with a low-Z material, and a high-speed x-ray framing camera aligned to capture images backlit by this masked backlighter. Two strips of the four-strip framing camera record images backlit by the high-Z portion of the backlighter, while the other two strips record images aligned with the low-Z portion of the backlighter. The emission from the low-Z material is effectively eliminated by a high-Z filter positioned in front of the framing camera, limiting the detected backlighter emission to that of the principal emission line of the high-Z material. As a result, half of the images are of self-emission from the plasma and the other half are of self-emission plus the backlighter. The advantage of this technique is that the self-emission simultaneous with backlighter absorption is independently measured from a nearby direction. The absorption occurs only in the high-Z backlit frames and is either spatially separated from the emission or the self-emission is suppressed by filtering, or by using a backlighter much brighter than the self-emission, or by subtraction. The masked-backlighter technique has been used on the OMEGA Laser System to simultaneously measure the emission profiles and the absorption profiles of polar-driven implosions.

  3. Nanocrystalline-Si-dot multi-layers fabrication by chemical vapor deposition with H-plasma surface treatment and evaluation of structure and quantum confinement effects

    SciTech Connect

    Kosemura, Daisuke Mizukami, Yuki; Takei, Munehisa; Numasawa, Yohichiroh; Ogura, Atsushi; Ohshita, Yoshio

    2014-01-15

    100-nm-thick nanocrystalline silicon (nano-Si)-dot multi-layers on a Si substrate were fabricated by the sequential repetition of H-plasma surface treatment, chemical vapor deposition, and surface oxidation, for over 120 times. The diameter of the nano-Si dots was 5–6 nm, as confirmed by both the transmission electron microscopy and X-ray diffraction analysis. The annealing process was important to improve the crystallinity of the nano-Si dot. We investigated quantum confinement effects by Raman spectroscopy and photoluminescence (PL) measurements. Based on the experimental results, we simulated the Raman spectrum using a phenomenological model. Consequently, the strain induced in the nano-Si dots was estimated by comparing the experimental and simulated results. Taking the estimated strain value into consideration, the band gap modulation was measured, and the diameter of the nano-Si dots was calculated to be 5.6 nm by using PL. The relaxation of the q ∼ 0 selection rule model for the nano-Si dots is believed to be important to explain both the phenomena of peak broadening on the low-wavenumber side observed in Raman spectra and the blue shift observed in PL measurements.

  4. X-Ray Modeling of Very Young Early-Type Stars in the Orion Trapezium: Signatures of Magnetically Confined Plasmas and Evolutionary Implications

    NASA Astrophysics Data System (ADS)

    Schulz, N. S.; Canizares, C.; Huenemoerder, D.; Tibbets, K.

    2003-09-01

    The Orion Trapezium is one of the youngest and closest star-forming regions within our Galaxy. With a dynamic age of ~3×105 yr, it harbors a number of very young hot stars, which likely are on the zero-age main sequence (ZAMS). We analyzed high-resolution X-ray spectra in the wavelength range of 1.5-25 Å of three of its X-ray-brightest members (Θ1 Ori A, C, and E) obtained with the High Energy Transmission Grating Spectrometer (HETGS) on board the Chandra X-Ray Observatory. We measured X-ray emission lines, calculated differential emission measure distributions (DEMs), and fitted broadband models to the spectra. The spectra from all three stars are very rich in emission lines, specifically from highly ionized Fe, which includes emission from Fe XVII to Fe XXV ions. A complete line list is included. This is a mere effect of high temperatures rather than an overabundance of Fe, which in fact turns out to be underabundant in all three Trapezium members. Similarly there is a significant underabundance in Ne and O as well, whereas Mg, Si, S, Ar, and Ca appear close to solar. The DEM derived from over 80 emission lines in the spectrum of Θ1 Ori C indicates three peaks located at 7.9, 25, and 66 MK. The emission measure varies over the 15.4 day wind period of the star. For the two phases observed, the low-temperature emission remains stable, while the high-temperature emission shows significant differences. The line widths seem to show a similar bifurcation, where we resolve some of the soft X-ray lines with velocities up to 850 km s-1 (all widths are stated as half-width at half-maximum), whereas the bulk of the lines remain unresolved with a confidence limit of 110 km s-1. The broadband spectra of the other two stars can be fitted with several collisionally ionized plasma model components within a temperature range of 4.3-46.8 MK for Θ1 Ori E and 4.8-42.7 MK for Θ1 Ori A. The high-temperature emissivity contributes over 70% to the total X-ray flux. None of the

  5. Enhancement of confinement in tokamaks

    SciTech Connect

    Furth, H.P.

    1986-05-01

    A plausible interpretation of the experimental evidence is that energy confinement in tokamaks is governed by two separate considerations: (1) the need for resistive MHD kink-stability, which limits the permissible range of current profiles - and therefore normally also the range of temperature profiles; and (2) the presence of strongly anomalous microscopic energy transport near the plasma edge, which calibrates the amplitude of the global temperature profile, thus determining the energy confinement time tau/sub E/. Correspondingly, there are two main paths towards the enhancement of tokamak confinement: (1) Configurational optimization, to increase the MHD-stable energy content of the plasma core, can evidently be pursued by varying the cross-sectional shape of the plasma and/or finding stable radial profiles with central q-values substantially below unity - but crossing from ''first'' to ''second'' stability within the peak-pressure region would have the greatest ultimate potential. (2) Suppression of edge turbulence, so as to improve the heat insulation in the outer plasma shell, can be pursued by various local stabilizing techniques, such as use of a poloidal divertor. The present confinement model and initial TFTR pellet-injection results suggest that the introduction of a super-high-density region within the plasma core should be particularly valuable for enhancing ntau/subE/. In D-T operation, a centrally peaked plasma pressure profile could possibly lend itself to alpha-particle-driven entry into the second-stability regime.

  6. De Par en Par (Wide Open), 1993.

    ERIC Educational Resources Information Center

    De Par en Par, 1993

    1993-01-01

    This document consists of the four issues of the serial "De Par en Par" published during 1993. This serial provides lessons in Spanish for elementary school children. It is written by bilingual education teachers for use in the bilingual classroom. The magazine bases itself on the K-6 curriculum and offers a variety of activities for classroom…

  7. Partial confinement photonic crystal waveguides

    SciTech Connect

    Saini, S.; Hong, C.-Y.; Pfaff, N.; Kimerling, L. C.; Michel, J.

    2008-12-29

    One-dimensional photonic crystal waveguides with an incomplete photonic band gap are modeled and proposed for an integration application that exploits their property of partial angular confinement. Planar apodized photonic crystal structures are deposited by plasma enhanced chemical vapor deposition and characterized by reflectivity as a function of angle and polarization, validating a partial confinement design for light at 850 nm wavelength. Partial confinement identifies an approach for tailoring waveguide properties by the exploitation of conformal film deposition over a substrate with angularly dependent topology. An application for an optoelectronic transceiver is demonstrated.

  8. Understanding and improving confinement in CNT

    NASA Astrophysics Data System (ADS)

    Brenner, Paul; Pedersen, Thomas; Sarasola, Xabier; Durand de Gevigney, Benoit; Traverso, Peter

    2010-11-01

    Confinement studies in the Columbia Non-neutral Torus (CNT) are providing new insights into the physics of pure electron plasmas confined on magnetic surfaces. The confinement of pure electron plasmas has now been measured in the absence of internal objects . These transient plasmas exhibit confinement times that are shorter than expected and have a strong dependence on neutral pressure. Plasmas created by electron emission in one direction have been compared to those created by emission in two directions. The confinement is significantly longer when emitting in only one direction, suggesting that a two-stream instability is present and affects the radial transport rate. Progress on verifying the existence of a two-stream instability will be presented. Experimental results from previously unexplored stellarator configurations, with low shear and large islands will also be shown.

  9. Visualization of Magnetically Confined Plasmas

    SciTech Connect

    J.L.V. Lewandowski

    1999-12-10

    With the rapid developments in experimental and theoretical fusion energy research towards more geometric details, visualization plays an increasingly important role. In this paper we will give an overview of how visualization can be used to compare and contrast some different configurations for future fusion reactors. Specifically we will focus on the stellarator and tokamak concepts. In order to gain understanding of the underlying fundamental differences and similarities these two competing concepts are compared and contrasted by visualizing some key attributes.

  10. Momentum Confinement at Low Torque

    SciTech Connect

    Solomon, W M; Burrell, K H; deGrassie, J S; Budny, R; Groebner, R J; Heidbrink, W W; Kinsey, J E; Kramer, G J; Makowski, M A; Mikkelsen, D; Nazikian, R; Petty, C C; Politzer, P A; Scott, S D; Van Zeeland, M A; Zarnstorff, M C

    2007-06-26

    Momentum confinement was investigated on DIII-D as a function of applied neutral beam torque at constant normalized {beta}{sub N}, by varying the mix of co (parallel to the plasma current) and counter neutral beams. Under balanced neutral beam injection (i.e. zero total torque to the plasma), the plasma maintains a significant rotation in the co-direction. This 'intrinsic' rotation can be modeled as being due to an offset in the applied torque (i.e. an 'anomalous torque'). This anomalous torque appears to have a magnitude comparable to one co-neutral beam source. The presence of such an anomalous torque source must be taken into account to obtain meaningful quantities describing momentum transport, such as the global momentum confinement time and local diffusivities. Studies of the mechanical angular momentum in ELMing H-mode plasmas with elevated q{sub min} show that the momentum confinement time improves as the torque is reduced. In hybrid plasmas, the opposite effect is observed, namely that momentum confinement improves at high torque/rotation. The relative importance of E x B shearing between the two is modeled using GLF23 and may suggest a possible explanation.

  11. System and method of operating toroidal magnetic confinement devices

    DOEpatents

    Chance, M.S.; Jardin, S.C.; Stix, T.H.; Grimm, R.C.; Manickam, J.; Okabayashi, M.

    1984-08-30

    This invention pertains to methods and arrangements for attaining high beta values in plasma confinement devices. More specifically, this invention pertains to methods for accessing the second stability region of operation in toroidal magnetic confinement devices.

  12. Etude de la preparation de poudres et de depots a partir de suspension par plasma inductif: Le cas de l'hydroxyapatite phosphocalcique

    NASA Astrophysics Data System (ADS)

    Bouyer, Etienne

    The work presented in this thesis has been directed to the study and the development of a new thermal spray process now known as the "SPS" (Suspension Plasma Spraying), in which the raw material to be treated is initially a liquid suspension. The SPS process is employed either for the preparation of thick coating or to the production of spherical and dense powders. The principle of SPS is the axial injection of a suspension into the plasma core by gas atomization. The atomization droplets are successively dried, melted and accelerated in the plasma plume. Finally, melt droplets strike a substrate and solidify to build the coating (deposition route) or are solidified in-flight and are then collected from within the reactor (powder route). The SPS process is best achieved with the use of r.f. thermal plasma technology and has been applied to the complex shape forming of ceramic materials: e.g. hydroxyapatite (HA), Ca10(PO4)6(OH) 2. HA, which is a bioceramic used in various biomedical applications such as bone substitute. The original chemical synthesis of the HA is a key step for the control of physical and chemical properties of the HA suspension which in turn are fundamental to the success of the entire SPS process. HA decomposes at elevated temperatures. With proper control of the plasma spraying parameters (i.e. the nature of the plasma gas and its composition, plasma power level, pressure, etc), the in-flight plasma decomposition can be minimized. Moreover it is possible to control the coating texture, its crystallinity and adhesion strength while maintaining high deposition rates (>150 mum/min). The morphology of powders prepared by the SPS technique and the size of resultant powders depends strongly on the atomization parameters of the spray suspension in the plasma. Water promotes the stabilization of HA during the plasma treatment and therefore helps to limit its in-flight decomposition. The SPS process is a potentially powerful technology providing in

  13. Pars Injuries in Athletes.

    PubMed

    Oren, Jonathan H; Gallina, Jason M

    2016-03-01

    Pars injuries are common causes of low back pain in adolescent athletes. Workup traditionally has included lumbar radiographs with oblique views and single-photon emission computed tomography (SPECT). However, recent literature has demonstrated the accuracy of MRI as a diagnostic modality. Acute injuries may be amenable to bracing with the goal of a healed lesion. Most cases of spondylolysis will result in asymptomatic non-union, though pars repair is an option for symptomatic pars defects without spondylolisthesis. PMID:26977552

  14. Stochastic Self-Assembly of ParB Proteins Builds the Bacterial DNA Segregation Apparatus.

    PubMed

    Sanchez, Aurore; Cattoni, Diego I; Walter, Jean-Charles; Rech, Jérôme; Parmeggiani, Andrea; Nollmann, Marcelo; Bouet, Jean-Yves

    2015-08-26

    Many canonical processes in molecular biology rely on the dynamic assembly of higher-order nucleoprotein complexes. In bacteria, the assembly mechanism of ParABS, the nucleoprotein super-complex that actively segregates the bacterial chromosome and many plasmids, remains elusive. We combined super-resolution microscopy, quantitative genome-wide surveys, biochemistry, and mathematical modeling to investigate the assembly of ParB at the centromere-like sequences parS. We found that nearly all ParB molecules are actively confined around parS by a network of synergistic protein-protein and protein-DNA interactions. Interrogation of the empirically determined, high-resolution ParB genomic distribution with modeling suggests that instead of binding only to specific sequences and subsequently spreading, ParB binds stochastically around parS over long distances. We propose a new model for the formation of the ParABS partition complex based on nucleation and caging: ParB forms a dynamic lattice with the DNA around parS. This assembly model and approach to characterizing large-scale, dynamic interactions between macromolecules may be generalizable to many unrelated machineries that self-assemble in superstructures. PMID:27135801

  15. During the Long Way to Mars: Effects of 520 Days of Confinement (Mars500) on the Assessment of Affective Stimuli and Stage Alteration in Mood and Plasma Hormone Levels

    PubMed Central

    Wang, Yue; Jing, Xiaolu; Lv, Ke; Wu, Bin; Bai, Yanqiang; Luo, Yuejia; Chen, Shanguang; Li, Yinghui

    2014-01-01

    For future interplanetary manned spaceflight, mental issues, as well as physiological problems, must inevitably be considered and solved. Mars500 is a high-fidelity ground simulation experiment that involved 520 days of confined isolation for six multinational crewmembers. This experiment provided a good opportunity to perform psycho-physiological and psycho-social researches on such missions. To investigate emotional responses and psychological adaptation over long-term confinement, the International Affective Pictures System (IAPS) was selected as the visual emotional stimuli in this study. Additional data collected and analyzed included the Profile of Mood States (POMS) questionnaire and the levels of four types of plasma hormones: cortisol, 5-hydroxy tryptamine, dopamine, and norepinephrine. The results demonstrated an obvious bias on valence rating for unpleasant stimuli with time (p<0.05), and the correlation between psychological and biochemical data was identified (p<0.05). Overall, we concluded that the confined crew tended to assign positive ratings to negative pictures with time, which might be driven by a defensive system. There was a stage-changing pattern of psychological adaptation of the Mars500 crew, which is similar to the third-quarter phenomenon. PMID:24695321

  16. During the long way to Mars: effects of 520 days of confinement (Mars500) on the assessment of affective stimuli and stage alteration in mood and plasma hormone levels.

    PubMed

    Wang, Yue; Jing, Xiaolu; Lv, Ke; Wu, Bin; Bai, Yanqiang; Luo, Yuejia; Chen, Shanguang; Li, Yinghui

    2014-01-01

    For future interplanetary manned spaceflight, mental issues, as well as physiological problems, must inevitably be considered and solved. Mars500 is a high-fidelity ground simulation experiment that involved 520 days of confined isolation for six multinational crewmembers. This experiment provided a good opportunity to perform psycho-physiological and psycho-social researches on such missions. To investigate emotional responses and psychological adaptation over long-term confinement, the International Affective Pictures System (IAPS) was selected as the visual emotional stimuli in this study. Additional data collected and analyzed included the Profile of Mood States (POMS) questionnaire and the levels of four types of plasma hormones: cortisol, 5-hydroxy tryptamine, dopamine, and norepinephrine. The results demonstrated an obvious bias on valence rating for unpleasant stimuli with time (p<0.05), and the correlation between psychological and biochemical data was identified (p<0.05). Overall, we concluded that the confined crew tended to assign positive ratings to negative pictures with time, which might be driven by a defensive system. There was a stage-changing pattern of psychological adaptation of the Mars500 crew, which is similar to the third-quarter phenomenon.

  17. Nonconsecutive Pars Interarticularis Defects.

    PubMed

    Elgafy, Hossein; Hart, Ryan C; Tanios, Mina

    2015-12-01

    Lumbar spondylolysis is a well-recognized condition occurring in adolescents because of repetitive overuse in sports. Nonconsecutive spondylolysis involving the lumbar spine is rare. In contrast to single-level pars defects that respond well to conservative treatment, there is no consensus about the management of multiple-level pars fractures; a few reports indicated that conservative management is successful, and the majority acknowledged that surgery is often required. The current study presents a rare case of pars fracture involving nonconsecutive segments and discusses the management options. In this case report, we review the patient's history, clinical examination, radiologic findings, and management, as well as the relevant literature. An 18-year-old man presented to the clinic with worsening lower back pain related to nonconsecutive pars fractures at L2 and L5. After 6 months of conservative management, diagnostic computed tomography-guided pars block was used to localize the symptomatic level at L2, which was treated surgically; the L5 asymptomatic pars fracture did not require surgery. At the last follow-up 2 years after surgery, the patient was playing baseball and basketball, and denied any back pain. This article reports a case of rare nonconsecutive pars fractures. Conservative management for at least 6 months is recommended. Successful management depends on the choice of appropriate treatment for each level. Single-photon emission computed tomography scan, and computed tomography-guided pars block are valuable preoperative tools to identify the symptomatic level in such a case. PMID:26665257

  18. Nonconsecutive Pars Interarticularis Defects.

    PubMed

    Elgafy, Hossein; Hart, Ryan C; Tanios, Mina

    2015-12-01

    Lumbar spondylolysis is a well-recognized condition occurring in adolescents because of repetitive overuse in sports. Nonconsecutive spondylolysis involving the lumbar spine is rare. In contrast to single-level pars defects that respond well to conservative treatment, there is no consensus about the management of multiple-level pars fractures; a few reports indicated that conservative management is successful, and the majority acknowledged that surgery is often required. The current study presents a rare case of pars fracture involving nonconsecutive segments and discusses the management options. In this case report, we review the patient's history, clinical examination, radiologic findings, and management, as well as the relevant literature. An 18-year-old man presented to the clinic with worsening lower back pain related to nonconsecutive pars fractures at L2 and L5. After 6 months of conservative management, diagnostic computed tomography-guided pars block was used to localize the symptomatic level at L2, which was treated surgically; the L5 asymptomatic pars fracture did not require surgery. At the last follow-up 2 years after surgery, the patient was playing baseball and basketball, and denied any back pain. This article reports a case of rare nonconsecutive pars fractures. Conservative management for at least 6 months is recommended. Successful management depends on the choice of appropriate treatment for each level. Single-photon emission computed tomography scan, and computed tomography-guided pars block are valuable preoperative tools to identify the symptomatic level in such a case.

  19. Confinement and the safety factor profile

    SciTech Connect

    Batha, S.H.; Levinton, F.M.; Scott, S.D.

    1995-12-01

    The conjecture that the safety factor profile, q(r), controls the improvement in tokamak plasmas from poor confinement in the Low (L-) mode regime to improved confinement in the supershot regime has been tested in two experiments on the Tokamak Fusion Test Reactor (TFTR). First, helium was puffed into the beam-heated phase of a supershot discharge which induced a degradation from supershot to L-mode confinement in about 100 msec, far less than the current relaxation time. The q and shear profiles measured by a motional Stark effect polarimeter showed little change during the confinement degradation. Second, rapid current ramps in supershot plasmas altered the q profile, but were observed not to change significantly the energy confinement. Thus, enhanced confinement in supershot plasmas is not due to a particular q profile which has enhanced stability or transport properties. The discharges making a continuous transition between supershot and L-mode confinement were also used to test the critical-electron-temperature-gradient transport model. It was found that this model could not reproduce the large changes in electron and ion temperature caused by the change in confinement.

  20. Ideal magnetohydrodynamic interchanges in low density plasmas

    SciTech Connect

    Huang Yimin; Goel, Deepak; Hassam, A.B.

    2005-03-01

    The ideal magnetohydrodynamic equations are usually derived under the assumption V{sub A}<plasmas wherein V{sub A} can be comparable to or greater than c. This involves relaxation of the usual charge quasineutrality assumption and the inclusion of electromagnetic momentum on par with plasma momentum. The extended system is applied to interchange instabilities in 'line-tied' slab geometry as well as to centrifugally confined plasmas. It is found that interchange growth rates are reduced by a factor of 1+V{sub A}{sup 2}/c{sup 2}, corresponding to a larger effective mass resulting from the extra electromagnetic momentum. Line tying is unaffected.

  1. Par Pond water balance

    SciTech Connect

    Hiergesell, R.A.; Dixon, K.L.

    1996-06-01

    A water budget for the Par Pond hydrologic system was established in order to estimate the rate of groundwater influx to Par Pond. This estimate will be used in modeling exercises to predict Par Pond reservoir elevation and spillway discharge in the scenario where Savannah River water is no longer pumped and discharged into Par Pond. The principal of conservation of mass was used to develop the water budget, where water inflow was set equal to water outflow. Components of the water budget were identified, and the flux associated with each was determined. The water budget was considered balanced when inflow and outflow summed to zero. The results of this study suggest that Par Pond gains water from the groundwater system in the upper reaches of the reservoir, but looses water to the groundwater system near the dam. The rate of flux of groundwater from the water table aquifer into Par Pond was determined to be 13 cfs. The rate of flux from Par Pond to the water table aquifer near the dam was determined to be 7 cfs.

  2. The Texas Experimental Tokamak: A plasma research facility. A proposal submitted to the Department of Energy in response to Program Notice 95-10: Innovations in toroidal magnetic confinement systems

    SciTech Connect

    1995-06-12

    The Fusion Research Center (FRC) at the University Texas will operate the tokamak TEXT-U and its associated systems for experimental research in basic plasma physics. While the tokamak is not innovative, the research program, diagnostics and planned experiments are. The fusion community will reap the benefits of the success in completing the upgrades (auxiliary heating, divertor, diagnostics, wall conditioning), developing diverted discharges in both double and single null configurations, exploring improved confinement regimes including a limiter H-mode, and developing unique, critical turbulence diagnostics. With these new regimes, the authors are poised to perform the sort of turbulence and transport studies for which the TEXT group has distinguished itself and for which the upgrade was intended. TEXT-U is also a facility for collaborators to perform innovative experiments and develop diagnostics before transferring them to larger machines. The general philosophy is that the understanding of plasma physics must be part of any intelligent fusion program, and that basic experimental research is the most important part of any such program. The emphasis of the proposed research is to provide well-documented plasmas which will be used to suggest and evaluate theories, to explore control techniques, to develop advanced diagnostics and analysis techniques, and to extend current drive techniques. Up to 1 MW of electron cyclotron heating (ECH) will be used not only for heating but as a localized, perturbative tool. Areas of proposed research are: (1) core turbulence and transport; (2) edge turbulence and transport; (3) turbulence analysis; (4) improved confinement; (5) ECH physics; (6) Alfven wave current drive; and (7) diagnostic development.

  3. Electrons Confined with an Axially Symmetric Magnetic Mirror Field

    SciTech Connect

    Higaki, H.; Ito, K.; Kira, K.; Okamoto, H.

    2008-08-08

    Low energy non-neutral electron plasmas were confined with an axially symmetric magnetic mirror field and an electrostatic potential to investigate the basic confinement properties of a simple magnetic mirror trap. As expected the confinement time became longer as a function of the mirror ratio. The axial electrostatic oscillations of a confined electron plasma were also observed. Obtained results suggested an improved scheme to accumulate low energy charged particles with the use of a magnetic mirror field, which would enable the investigation of electron-positron plasmas.

  4. Final Report DOE Grant No. DE-FG03-01ER54617 Computer Modeling of Microturbulence and Macrostability Properties of Magnetically Confined Plasmas

    SciTech Connect

    Jean-Noel Leboeuf

    2004-03-04

    OAK-B135 We have made significant progress during the past grant period in several key areas of the UCLA and national Fusion Theory Program. This impressive body of work includes both fundamental and applied contributions to MHD and turbulence in DIII-D and Electric Tokamak plasmas, and also to Z-pinches, particularly with respect to the effect of flows on these phenomena. We have successfully carried out interpretive and predictive global gyrokinetic particle-in-cell calculations of DIII-D discharges. We have cemented our participation in the gyrokinetic PIC effort of the SciDAC Plasma Microturbulence Project through working membership in the Summit Gyrokinetic PIC Team. We have continued to teach advanced courses at UCLA pertaining to computational plasma physics and to foster interaction with students and junior researchers. We have in fact graduated 2 Ph. D. students during the past grant period. The research carried out during that time has resulted in many publications in the premier plasma physics and fusion energy sciences journals and in several invited oral communications at major conferences such as Sherwood, Transport Task Force (TTF), the annual meetings of the Division of Plasma Physics of the American Physical Society, of the European Physical Society, and the 2002 IAEA Fusion Energy Conference, FEC 2002. Many of these have been authored and co-authored with experimentalists at DIII-D.

  5. Energy confinement in Doublet III with high-Z limiters

    SciTech Connect

    Marcus, F.B.; Adcock, S.J.; Baker, D.R.; Blau, F.P.; Brooks, N.H.; Chase, R.P.; DeBoo, J.C.; Ejima, S.; Fairbanks, E.S.; Fisher, R.K.

    1980-02-01

    This report describes the experimental measurements and data analysis techniques used to evaluate the energy confinement in noncircular plasmas produced in Doublet III. Major aspects of the confinement measurements and analysis techniques are summarized. Machine parameters, diagnostic systems and discharge parameters relavent to the confinement measurements are given. Magnetic analysis techniques used to determine the plasma shape are reviewed. Scaling of the on-axis values of electron temperature, confinement time and Z/sub eff/ with plasma density is presented. Comparison with scaling results from other circular tokamaks is discussed. Numerical and analytic techniques developed for calculating the plasma energy confinement time and self-consistent profiles of density, temperature, current, and flux in non-circular geometries are described. These techniques are applied to the data and used to determine the central and global electron energy confinement time for a typical doublet plasma. Additional aspects of the confinement such as the radial dependence of the electron thermal conductivity and the estimated ion temperature are explored with the aid of a non-circular transport simulation code. The results of the confinement measurements are summarized and discussed. A brief summary of the theoretically expected effects of noncircularity on plasma confinement is included for reference as Appendix I.

  6. Development of a tunable Fabry-Perot etalon-based near-infrared interference spectrometer for measurement of the HeI 2³S-2³P spectral line shape in magnetically confined torus plasmas.

    PubMed

    Ogane, S; Shikama, T; Zushi, H; Hasuo, M

    2015-10-01

    In magnetically confined torus plasmas, the local emission intensity, temperature, and flow velocity of atoms in the inboard and outboard scrape-off layers can be separately measured by a passive emission spectroscopy assisted by observation of the Zeeman splitting in their spectral line shape. To utilize this technique, a near-infrared interference spectrometer optimized for the observation of the helium 2(3)S-2(3)P transition spectral line (wavelength 1083 nm) has been developed. The applicability of the technique to actual torus devices is elucidated by calculating the spectral line shapes expected to be observed in LHD and QUEST (Q-shu University Experiment with Steady State Spherical Tokamak). In addition, the Zeeman effect on the spectral line shape is measured using a glow-discharge tube installed in a superconducting magnet. PMID:26520955

  7. A Particle X-ray Temporal Diagnostic (PXTD) for studies of kinetic, multi-ion effects, and ion-electron equilibration rates in Inertial Confinement Fusion plasmas at OMEGA (invited)

    DOE PAGES

    Sio, H.; Frenje, J. A.; Katz, J.; Stoeckl, C.; Weiner, D.; Bedzyk, M.; Glebov, V.; Sorce, C.; Gatu Johnson, M.; Rinderknecht, H. G.; et al

    2016-09-14

    Here, a Particle X-ray Temporal Diagnostic (PXTD) has been implemented on OMEGA for simultaneous time-resolved measurements of several nuclear products as well as the x-ray continuum produced in High Energy Density Plasmas and Inertial Confinement Fusion implosions. The PXTD removes systematic timing uncertainties typically introduced by using multiple instruments, and it has been used to measure DD, DT, D3He, and T3He reaction histories and the emission history of the x-ray core continuum with relative timing uncertainties within ±10-20 ps. This enables, for the first time, accurate and simultaneous measurements of the x-ray emission histories, nuclear reaction histories, their time differences,more » and measurements of Ti(t) and Te(t) from which an assessment of multiple-ion-fluid effects, kinetic effects during the shock-burn phase, and ion-electron equilibration rates can be made.« less

  8. A Particle X-ray Temporal Diagnostic (PXTD) for studies of kinetic, multi-ion effects, and ion-electron equilibration rates in Inertial Confinement Fusion plasmas at OMEGA (invited)

    NASA Astrophysics Data System (ADS)

    Sio, H.; Frenje, J. A.; Katz, J.; Stoeckl, C.; Weiner, D.; Bedzyk, M.; Glebov, V.; Sorce, C.; Gatu Johnson, M.; Rinderknecht, H. G.; Zylstra, A. B.; Sangster, T. C.; Regan, S. P.; Kwan, T.; Le, A.; Simakov, A. N.; Taitano, W. T.; Chacòn, L.; Keenan, B.; Shah, R.; Sutcliffe, G.; Petrasso, R. D.

    2016-11-01

    A Particle X-ray Temporal Diagnostic (PXTD) has been implemented on OMEGA for simultaneous time-resolved measurements of several nuclear products as well as the x-ray continuum produced in High Energy Density Plasmas and Inertial Confinement Fusion implosions. The PXTD removes systematic timing uncertainties typically introduced by using multiple instruments, and it has been used to measure DD, DT, D3He, and T3He reaction histories and the emission history of the x-ray core continuum with relative timing uncertainties within ±10-20 ps. This enables, for the first time, accurate and simultaneous measurements of the x-ray emission histories, nuclear reaction histories, their time differences, and measurements of Ti(t) and Te(t) from which an assessment of multiple-ion-fluid effects, kinetic effects during the shock-burn phase, and ion-electron equilibration rates can be made.

  9. Development of a tunable Fabry-Perot etalon-based near-infrared interference spectrometer for measurement of the HeI 2{sup 3}S-2{sup 3}P spectral line shape in magnetically confined torus plasmas

    SciTech Connect

    Ogane, S.; Shikama, T. Hasuo, M.; Zushi, H.

    2015-10-15

    In magnetically confined torus plasmas, the local emission intensity, temperature, and flow velocity of atoms in the inboard and outboard scrape-off layers can be separately measured by a passive emission spectroscopy assisted by observation of the Zeeman splitting in their spectral line shape. To utilize this technique, a near-infrared interference spectrometer optimized for the observation of the helium 2{sup 3}S–2{sup 3}P transition spectral line (wavelength 1083 nm) has been developed. The applicability of the technique to actual torus devices is elucidated by calculating the spectral line shapes expected to be observed in LHD and QUEST (Q-shu University Experiment with Steady State Spherical Tokamak). In addition, the Zeeman effect on the spectral line shape is measured using a glow-discharge tube installed in a superconducting magnet.

  10. Development of a tunable Fabry-Perot etalon-based near-infrared interference spectrometer for measurement of the HeI 23S-23P spectral line shape in magnetically confined torus plasmas

    NASA Astrophysics Data System (ADS)

    Ogane, S.; Shikama, T.; Zushi, H.; Hasuo, M.

    2015-10-01

    In magnetically confined torus plasmas, the local emission intensity, temperature, and flow velocity of atoms in the inboard and outboard scrape-off layers can be separately measured by a passive emission spectroscopy assisted by observation of the Zeeman splitting in their spectral line shape. To utilize this technique, a near-infrared interference spectrometer optimized for the observation of the helium 23S-23P transition spectral line (wavelength 1083 nm) has been developed. The applicability of the technique to actual torus devices is elucidated by calculating the spectral line shapes expected to be observed in LHD and QUEST (Q-shu University Experiment with Steady State Spherical Tokamak). In addition, the Zeeman effect on the spectral line shape is measured using a glow-discharge tube installed in a superconducting magnet.

  11. Investigations of the radial propagation of blob-like structure in a non-confined electron cyclotron resonance heated plasma on Q-shu University Experiment with a Steady-State Spherical Tokamak

    SciTech Connect

    Ogata, R.; Liu, H. Q.; Ishiguro, M.; Ikeda, T.; Hanada, K.; Zushi, H.; Nakamura, K.; Fujisawa, A.; Idei, H.; Hasegawa, M.; Kawasaki, S.; Nakashima, H.; Higashijima, A.; Nishino, N.; Collaboration: QUEST Group

    2011-09-15

    A study of radial propagation and electric fields induced by charge separation in blob-like structures has been performed in a non-confined cylindrical electron cyclotron resonance heating plasma on Q-shu University Experiment with a Steady-State Spherical Tokamak using a fast-speed camera and a Langmuir probe. The radial propagation of the blob-like structures is found to be driven by E x B drift. Moreover, these blob-like structures were found to have been accelerated, and the property of the measured radial velocities agrees with the previously proposed model [C. Theiler et al., Phys. Rev. Lett. 103, 065001 (2009)]. Although the dependence of the radial velocity on the connection length of the magnetic field appeared to be different, a plausible explanation based on enhanced short-circuiting of the current path can be proposed.

  12. Spatial confinement effects in laser-induced breakdown spectroscopy

    SciTech Connect

    Shen, X. K.; Sun, J.; Ling, H.; Lu, Y. F.

    2007-08-20

    The spatial confinement effects in laser-induced breakdown of aluminum (Al) targets in air have been investigated both by optical emission spectroscopy and fast photography. A KrF excimer laser was used to produce plasmas from Al targets in air. Al atomic emission lines show an obvious enhancement in the emission intensity when a pair of Al-plate walls were placed to spatially confine the plasma plumes. Images of the Al plasma plumes showed that the plasma plumes evolved into a torus shape and were compressed in the Al walls. The mechanism for the confinement effects was discussed using shock wave theory.

  13. The Physics Basis of ITER Confinement

    SciTech Connect

    Wagner, F.

    2009-02-19

    ITER will be the first fusion reactor and the 50 year old dream of fusion scientists will become reality. The quality of magnetic confinement will decide about the success of ITER, directly in the form of the confinement time and indirectly because it decides about the plasma parameters and the fluxes, which cross the separatrix and have to be handled externally by technical means. This lecture portrays some of the basic principles which govern plasma confinement, uses dimensionless scaling to set the limits for the predictions for ITER, an approach which also shows the limitations of the predictions, and describes briefly the major characteristics and physics behind the H-mode--the preferred confinement regime of ITER.

  14. THE MEASURES PAR PROJECT

    NASA Astrophysics Data System (ADS)

    Frouin, R. J.; Franz, B.

    2009-12-01

    The solar energy available for photosynthesis, known as PAR, controls the growth of phytoplankton and, therefore, regulates the composition and evolution of marine ecosystems. Knowing the spatial and temporal distribution of PAR over the oceans is critical to understanding biogeochemical cycles of carbon, nutrients, and oxygen, and to address important climate and global change issues such as the fate of anthropogenic atmospheric carbon dioxide. In view of this, a 12-year time series of PAR at the ocean surface, starting in September 1997, is being produced by the NASA Ocean Biology Processing Group from SeaWiFS, MODIS-Terra, and MODIS-Aqua data. The product covers the global oceans, with a spatial resolution of about 9.3x9.3 km (equal area grid) and a temporal resolution of one day. PAR is computed as the difference between the 400-700 nm solar flux incident on the top of the atmosphere (known) and reflected back to space by the atmosphere and surface (derived from satellite radiance), taking into account atmospheric absorption (modeled). Knowledge of pixel composition is not required, eliminating the need for cloud screening and arbitrary assumptions about sub-pixel cloudiness. Combining data from satellite sensors with different equatorial crossing times accounts for the diurnal variability of clouds and, therefore, increases accuracy on a daily time scale. The processing system, including routine check of accuracy and control of quality, is designed to operate during the entire lifetime of SeaWiFS and MODIS, and to accommodate future sensors with ocean-color capabilities. Maps of daily, weekly, and monthly PAR obtained from individual sensors are presented, as well as merged products. Accuracy is quantified in comparisons with other satellite estimates, the National Centers for Environmental Prediction reanalysis product, and in-situ measurements from fixed buoys and platforms. The good statistical performance makes the satellite PAR product suitable for large

  15. Confinement of translated field-reversed configurations

    NASA Astrophysics Data System (ADS)

    Tuszewski, M.; Armstrong, W. T.; Chrien, R. E.; Klingner, P. L.; McKenna, K. F.; Rej, D. J.; Sherwood, E. G.; Siemon, R. E.

    1986-03-01

    The confinement properties of translating field-reversed configurations (FRC) in the FRX-C/T device [Phys. Fluids 29, (1986)] are analyzed and compared to previous data without translation and to available theory. Translation dynamics do not appear to appreciably modify the FRC confinement. Some empirical scaling laws with respect to various plasma parameters are extracted from the data. These are qualitatively similar to those obtained in the TRX-1 device [Phys. Fluids 28, 888 (1985)] without translation and with a different formation method. Translation with a static gas fill offers new opportunities such as improved particle confinement or refueling of the FRC particle inventory.

  16. Cortical actin networks induce spatio-temporal confinement of phospholipids in the plasma membrane - a minimally invasive investigation by STED-FCS

    NASA Astrophysics Data System (ADS)

    Andrade, Débora M.; Clausen, Mathias P.; Keller, Jan; Mueller, Veronika; Wu, Congying; Bear, James E.; Hell, Stefan W.; Lagerholm, B. Christoffer; Eggeling, Christian

    2015-06-01

    Important discoveries in the last decades have changed our view of the plasma membrane organisation. Specifically, the cortical cytoskeleton has emerged as a key modulator of the lateral diffusion of membrane proteins. Cytoskeleton-dependent compartmentalised lipid diffusion has been proposed, but this concept remains controversial because this phenomenon has thus far only been observed with artefact-prone probes in combination with a single technique: single particle tracking. In this paper, we report the first direct observation of compartmentalised phospholipid diffusion in the plasma membrane of living cells using a minimally invasive, fluorescent dye labelled lipid analogue. These observations were made using optical STED nanoscopy in combination with fluorescence correlation spectroscopy (STED-FCS), a technique which allows the study of membrane dynamics on a sub-millisecond time-scale and with a spatial resolution of down to 40 nm. Specifically, we find that compartmentalised phospholipid diffusion depends on the cortical actin cytoskeleton, and that this constrained diffusion is directly dependent on the F-actin branching nucleator Arp2/3. These findings provide solid evidence that the Arp2/3-dependent cortical actin cytoskeleton plays a pivotal role in the dynamic organisation of the plasma membrane, potentially regulating fundamental cellular processes.

  17. An ELISA method detecting the active form of suPAR.

    PubMed

    Zhou, Xiaolei; Xu, Mingming; Huang, Hailong; Mazar, Andrew; Iqbal, Zafar; Yuan, Cai; Huang, Mingdong

    2016-11-01

    Urokinase plasminogen activator receptor (uPAR) exists in a number of formats in human plasma, including soluble uPAR (suPAR) and uPAR fragments. We developed an ELISA method to detect specifically the active form suPAR, which binds to its natural ligand uPA. The intra CV and inter CV of this ELISA assay is 8.5% and 9.6% respectively, and the assay can recover 99.74% of added recombinant suPAR from 10% plasma. This assay is quite sensitive, capable of detecting down to 15pg/ml of suPAR, and can measure suPAR concentrations in the range of 0.031-8ng/ml with high linear relationship. Plasma samples from pregnant women were also measured for the active form of suPAR with this assay, giving an averaged level of 1.39ng/ml, slightly higher than the level of pooled plasma from healthy donors (0.96ng/ml). This study demonstrates the feasibility to measure the active form of suPAR, which will likely have value in clinical applications. PMID:27591605

  18. Plasma valve

    DOEpatents

    Hershcovitch, Ady; Sharma, Sushil; Noonan, John; Rotela, Elbio; Khounsary, Ali

    2003-01-01

    A plasma valve includes a confinement channel and primary anode and cathode disposed therein. An ignition cathode is disposed adjacent the primary cathode. Power supplies are joined to the cathodes and anode for rapidly igniting and maintaining a plasma in the channel for preventing leakage of atmospheric pressure through the channel.

  19. Progress of ECRH by EBW in over-dense plasmas and controlling the confinement regime by ECCD with high power launching in LHD

    NASA Astrophysics Data System (ADS)

    Igami, H.; Yoshimura, Y.; Takahashi, H.; Shimozuma, T.; Kubo, S.; Idei, H.; Nishiura, M.; Ogasawara, S.; Makino, R.; Ohdachi, S.; Ida, K.; Yoshinuma, M.; Ido, T.; Shimizu, A.; Tamura, N.; Inagaki, S.; Mutoh, T.

    2012-09-01

    In the large helical device (LHD), fundamental electron cyclotron resonance heating (ECRH) by the electron Bernstein wave (EBW) excited via the ordinary-extraordinary-EBW (O-X-B) mode conversion process was performed with high power (~1MW) launching. Profiles of increase of the electron temperature (Te) and the soft X-ray signals during the power injection suggest power absorption in the core region. Effects of the local modification of the rotational transform l/2π(=1/q) by electron cyclotron current drive (ECCD) on the formation and sustainment of the electron internal transport barrier (e-ITB) was investigated for the first time. Co ECCD raised l/2π close to 0.5 in the core region and caused the flattening of the Te profile. Additional ECRH power is required to form the e-ITB. On the contrary, counter (cntr.) ECCD separates l/2π from 0.5 in the core region and avoids the flattening of the Te profile. The e-ITB can be formed and sustained without additional ECRH. Analysis of the heat pulse transport with use of the modulation ECRH (MECH) shows the good confinement region extends to the l/2π =0.5 rational surface in the case of cntr. ECCD.

  20. Observations of the vacuum ultraviolet and x-ray brightness profiles of Fe, Ni, and Ge in magnetically confined fusion plasmas

    SciTech Connect

    May, M. J.; Finkenthal, M.; Moos, H. W.; Fournier, K. B.; Goldstein, W. H.; Mattioli, M.; Pacella, D.; Mazzitelli, G.; Leigheb, M.; Gabellieri, L.

    2001-09-01

    The spatial brightness profiles of emission lines for the K-like through He-like ionization states of Fe, Ge, and Ni have been measured during a set of experiments in which Fe and Ge were introduced into FTU tokamak plasmas by using the laser blowoff technique. Nickel was an intrinsic impurity observed during these experiments that was sputtered from the inconel limiter. The brightness profiles were measured by spatially scanable, photometrically calibrated vaccum ultraviolet and x-ray spectrometers that covered the 1 to 1700 {angstrom} region. Simulations of these profiles and the time evolution of the laser blowoffs were performed with the MIST transport code using several sets of atomic physics compilations [ADPAK (originally in MIST), Arnaud and Raymond (AR92), Arnaud and Rothenflug (AR85), Mazzotta , and Mattioli (an extension to Mazzotta)]. The goal was to determine which set of available rates could best simulate the measured spatial brightness profiles and the charge state balance in the plasma. The Mazzotta (for Fe and Ni), the Mattioli (for Ge), and the AR92 (for Fe only) rates adequately simulated the He-, Li-, Be-, Na-, Mg-like ionization states. The F- to B-like charge states could not be simulated by these compilations unless the relevant dielectronic rates were multiplied by a factor of 2. The ADPAK rates could not adequately predict any of the charge states of Fe, Ge, or Ni.

  1. Liquid injection plasma deposition method and apparatus

    DOEpatents

    Kong, Peter C.; Watkins, Arthur D.

    1999-01-01

    A liquid injection plasma torch deposition apparatus for depositing material onto a surface of a substrate may comprise a plasma torch for producing a jet of plasma from an outlet nozzle. A plasma confinement tube having an inlet end and an outlet end and a central bore therethrough is aligned with the outlet nozzle of the plasma torch so that the plasma jet is directed into the inlet end of the plasma confinement tube and emerges from the outlet end of the plasma confinement tube. The plasma confinement tube also includes an injection port transverse to the central bore. A liquid injection device connected to the injection port of the plasma confinement tube injects a liquid reactant mixture containing the material to be deposited onto the surface of the substrate through the injection port and into the central bore of the plasma confinement tube.

  2. Liquid injection plasma deposition method and apparatus

    DOEpatents

    Kong, P.C.; Watkins, A.D.

    1999-05-25

    A liquid injection plasma torch deposition apparatus for depositing material onto a surface of a substrate may comprise a plasma torch for producing a jet of plasma from an outlet nozzle. A plasma confinement tube having an inlet end and an outlet end and a central bore therethrough is aligned with the outlet nozzle of the plasma torch so that the plasma jet is directed into the inlet end of the plasma confinement tube and emerges from the outlet end of the plasma confinement tube. The plasma confinement tube also includes an injection port transverse to the central bore. A liquid injection device connected to the injection port of the plasma confinement tube injects a liquid reactant mixture containing the material to be deposited onto the surface of the substrate through the injection port and into the central bore of the plasma confinement tube. 8 figs.

  3. suPAR and Team Nephrology

    PubMed Central

    2014-01-01

    Primary focal segmental glomerulosclerosis (FSGS) accounts for nearly 10 % of patients who require renal replacement therapy. Elevated circulating levels of soluble urokinase receptor (suPAR) have been identified as a biomarker to discriminate primary FSGS from other glomerulopathies. Subsequent reports have questioned the diagnostic utility of this test. In a study in BMC Medicine, Huang et al. demonstrate that urinary soluble urokinase receptor (suPAR) excretion assists in distinguishing primary FSGS from other glomerular diseases, and that high plasma suPAR concentrations are not directly linked to a decline in glomerular filtration rate (GFR). This observation suggests that further investigation of suPAR is warranted in patients with FSGS. It should be interpreted in light of a recent report that B7-1 is expressed in the podocytes of a subset of patients with FSGS, and that blocking this molecule may represent the first successful targeted intervention for this disease. These advances highlight the rapid pace of scientific progress in the field of nephrology. Nephrologists should work together, share resources, and expedite the design of protocols to evaluate these novel biomarkers in a comprehensive and scientifically valid manner. Please see related article http://www.biomedcentral.com/1741-7015/12/81. PMID:24885021

  4. Inertial confinement fusion

    SciTech Connect

    Powers, L.; Condouris, R.; Kotowski, M.; Murphy, P.W.

    1992-01-01

    This issue of the ICF Quarterly contains seven articles that describe recent progress in Lawrence Livermore National Laboratory's ICF program. The Department of Energy recently initiated an effort to design a 1--2 MJ glass laser, the proposed National Ignition Facility (NIF). These articles span various aspects of a program which is aimed at moving forward toward such a facility by continuing to use the Nova laser to gain understanding of NIF-relevant target physics, by developing concepts for an NIF laser driver, and by envisioning a variety of applications for larger ICF facilities. This report discusses research on the following topics: Stimulated Rotational Raman Scattering in Nitrogen; A Maxwell Equation Solver in LASNEX for the Simulation of Moderately Intense Ultrashort Pulse Experiments; Measurements of Radial Heat-Wave Propagation in Laser-Produced Plasmas; Laser-Seeded Modulation Growth on Directly Driven Foils; Stimulated Raman Scattering in Large-Aperture, High-Fluence Frequency-Conversion Crystals; Fission Product Hazard Reduction Using Inertial Fusion Energy; Use of Inertial Confinement Fusion for Nuclear Weapons Effects Simulations.

  5. La pelade par plaques

    PubMed Central

    Spano, Frank; Donovan, Jeff C.

    2015-01-01

    Résumé Objectif Présenter aux médecins de famille des renseignements de base pour faire comprendre l’épidémiologie, la pathogenèse, l’histologie et l’approche clinique au diagnostic de la pelade par plaques. Sources des données Une recension a été effectuée dans PubMed pour trouver des articles pertinents concernant la pathogenèse, le diagnostic et le pronostic de la pelade par plaques. Message principal La pelade par plaques est une forme de perte pileuse auto-immune dont la prévalence durant une vie est d’environ 2 %. Des antécédents personnels ou familiaux de troubles auto-immuns concomitants, comme le vitiligo ou une maladie de la thyroïde, peuvent être observés dans un petit sous-groupe de patients. Le diagnostic peut souvent être posé de manière clinique en se fondant sur la perte de cheveux non cicatricielle et circulaire caractéristique, accompagnée de cheveux en « point d’exclamation » en périphérie chez ceux dont le problème en est aux premiers stades. Le diagnostic des cas plus complexes ou des présentations inhabituelles peut être facilité par une biopsie et un examen histologique. Le pronostic varie largement et de mauvais résultats sont associés à une apparition à un âge précoce, une perte importante, la variante ophiasis, des changements aux ongles, des antécédents familiaux ou des troubles auto-immuns concomitants. Conclusion La pelade par plaques est une forme auto-immune de perte de cheveux périodiquement observée en soins primaires. Les médecins de famille sont bien placés pour identifier la pelade par plaques, déterminer la gravité de la maladie et poser le diagnostic différentiel approprié. De plus, ils sont en mesure de renseigner leurs patients à propos de l’évolution clinique de la maladie ainsi que du pronostic général selon le sous-type de patients.

  6. Numerical Study of Velocity Shear Stabilization of 3D and Theoretical Considerations for Centrifugally Confined Plasmas and Other Interchange-Limited Fusion Concepts

    SciTech Connect

    Hassam, Adil

    2015-09-21

    We studied the feasibility of resonantly driving GAMs in tokamaks. A numerical simulation was carried out and showed the essential features and limitations. It was shown further that GAMs can damp by phase-mixing, from temperature gradients, or nonlinear detuning, thus broadening the resonance. Experimental implications of this were quantified. Theoretical support was provided for the Maryland Centrifugal Experiment, funded in a separate grant by DOE. Plasma diamagnetism from supersonic rotation was established. A theoretical model was built to match the data. Additional support to the experiment in terms of numerical simulation of the interchange turbulence was provided. Spectra from residual turbulence on account of velocity shear suppression were obtained and compared favorably to experiment. A new drift wave, driven solely by the thermal force, was identified.

  7. Fast ion JET diagnostics: confinement and losses

    SciTech Connect

    Kiptily, V. G.; Pinches, S. D.; Sharapov, S. E.; Syme, D. B.; Cecconello, M.; Darrow, D.; Hill, K.; Goloborod'ko, V.; Yavorskij, V.; Johnson, T.; Murari, A.; Reich, M.; Gorini, G.; Zoita, V.

    2008-03-12

    A study of magnetically confined fast ions in tokamaks plays an important role in burning plasma research. To reach ignition and steady burning of a reactor plasma an adequate confinement of energetic ions produced by NBI heating, accelerated with ICRF and born in fusion reactions is essential to provide efficient heating of the bulk plasma. Thus, investigation of the fast ion behaviour is an immediate task for present-day large machines, such as JET, in order to understand the main mechanisms of slowing down, redistribution and losses, and to develop optimal plasma scenarios. Today's JET has an enhanced suite of fast ion diagnostics both of confined and lost ions that enable to significantly contribute to this important area of research. Fast ion populations of p, d, t, {sup 3}He and {sup 4}He, made with ICRF, NBI, and fusion reactions have been investigated in experiments on JET with sophisticated diagnostics in conventional and shear-reversed plasmas, exploring a wide range of effects. This paper will introduce to the JET fast-ion diagnostic techniques and will give an overview of recent observations. A synergy of the unique diagnostic set was utilised in JET, and studies of the response of fast ions to MHD modes (e.g. tornado modes, sawtooth crashes), fast {sup 3}He-ions behaviour in shear-reversed plasmas are impressive examples of that. Some results on fast ion losses in JET experiments with various levels of the toroidal field ripple will be demonstrated.

  8. La pelade par plaques

    PubMed Central

    Spano, Frank; Donovan, Jeff C.

    2015-01-01

    Résumé Objectif Présenter aux médecins de famille des renseignements de base pour faire comprendre les schémas thérapeutiques et les résultats des traitements pour la pelade par plaques, de même que les aider à identifier les patients pour qui une demande de consultation en dermatologie pourrait s’imposer. Sources des données Une recension a été effectuée dans PubMed pour trouver des articles pertinents concernant le traitement de la pelade par plaques. Message principal La pelade par plaques est une forme auto-immune de perte pileuse qui touche à la fois les enfants et les adultes. Même s’il n’y a pas de mortalité associée à la maladie, la morbidité découlant des effets psychologiques de la perte des cheveux peut être dévastatrice. Lorsque la pelade par plaques et le sous-type de la maladie sont identifiés, un schéma thérapeutique approprié peut être amorcé pour aider à arrêter la chute des cheveux et possiblement faire commencer la repousse. Les traitements de première intention sont la triamcinolone intralésionnelle avec des corticostéroïdes topiques ou du minoxidil ou les 2. Les médecins de famille peuvent prescrire ces traitements en toute sécurité et amorcer ces thérapies. Les cas plus avancés ou réfractaires pourraient avoir besoin de diphénylcyclopropénone topique ou d’anthraline topique. On peut traiter la perte de cils avec des analogues de la prostaglandine. Les personnes ayant subi une perte de cheveux abondante peuvent recourir à des options de camouflage ou à des prothèses capillaires. Il est important de surveiller les troubles psychiatriques en raison des effets psychologiques profonds de la perte de cheveux. Conclusion Les médecins de famille verront de nombreux patients qui perdent leurs cheveux. La reconnaissance de la pelade par plaques et la compréhension du processus pathologique sous-jacent permettent d’amorcer un schéma thérapeutique approprié. Les cas plus graves ou r

  9. Discovery of Octahydroindenes as PAR1 Antagonists

    PubMed Central

    2013-01-01

    Octahydroindene was identified as a novel scaffold for protease activated receptor 1 (PAR1) antagonists. Herein, the 2-position (C2) was explored for structure–activity relationship (SAR) studies. Compounds 14, 19, and 23b showed IC50 values of 1.3, 8.6, and 2.7 nM in a PAR1 radioligand binding assay, respectively, and their inhibitory activities on platelet activation were comparable to that of vorapaxar in a platelet rich plasma (PRP) aggregation assay. This series of compounds showed high potency and no significant cytotoxicity; however, the compounds were metabolically unstable in both human and rat liver microsomes. Current research efforts are focused on optimizing the compounds to improve metabolic stability and physicochemical properties as well as potency. PMID:24900604

  10. Progress in toroidal confinement and fusion research

    SciTech Connect

    Furth, H.P.

    1987-10-01

    During the past 30 years, the characteristic T/sub i/n tau/sub E/-value of toroidal-confinement experiments has advanced by more than seven orders of magnitude. Part of this advance has been due to an increase of gross machine parameters. Most of this advance has been due to an increase of gross machine parameters. Most of the advance is associated with improvements in the ''quality of plasma confinement.'' The combined evidence of spherator and tokamak research clarifies the role of magnetic-field geometry in determining confinement and points to the importance of shielding out plasma edge effects. A true physical understanding of anomalous transport remains to be achieved. 39 refs., 11 figs., 1 tab.

  11. Trace Amine-Associated Receptor 1 Localization at the Apical Plasma Membrane Domain of Fisher Rat Thyroid Epithelial Cells Is Confined to Cilia

    PubMed Central

    Szumska, Joanna; Qatato, Maria; Rehders, Maren; Führer, Dagmar; Biebermann, Heike; Grandy, David K.; Köhrle, Josef; Brix, Klaudia

    2015-01-01

    Background The trace amine-associated receptor 1 (Taar1) is one member of the Taar family of G-protein-coupled receptors (GPCR) accepting various biogenic amines as ligands. It has been proposed that Taar1 mediates rapid, membrane-initiated effects of thyronamines, the endogenous decarboxylated and deiodinated relatives of the classical thyroid hormones T4 and T3. Objectives Although the physiological actions of thyronamines in general and 3-iodothyronamine (T1AM) in particular are incompletely understood, studies published to date suggest that synthetic T1AM-activated Taar1 signaling antagonizes thyromimetic effects exerted by T3. However, the location of Taar1 is currently unknown. Methods To fill this gap in our knowledge we employed immunofluorescence microscopy and a polyclonal antibody to detect Taar1 protein expression in thyroid tissue from Fisher rats, wild-type and taar1-deficient mice, and in the polarized FRT cells. Results With this approach we found that Taar1 is expressed in the membranes of subcellular compartments of the secretory pathway and on the apical plasma membrane of FRT cells. Three-dimensional analyses further revealed Taar1 immunoreactivity in cilial extensions of postconfluent FRT cell cultures that had formed follicle-like structures. Conclusions The results suggest Taar1 transport along the secretory pathway and its accumulation in the primary cilium of thyrocytes. These findings are of significance considering the increasing interest in the role of cilia in harboring functional GPCR. We hypothesize that thyronamines can reach and activate Taar1 in thyroid follicular epithelia by acting from within the thyroid follicle lumen, their potential site of synthesis, as part of a nonclassical mechanism of thyroid autoregulation. PMID:26601071

  12. PLASMA ENERGIZATION

    DOEpatents

    Furth, H.P.; Chambers, E.S.

    1962-03-01

    BS>A method is given for ion cyclotron resonance heatthg of a magnetically confined plasma by an applied radio-frequency field. In accordance with the invention, the radiofrequency energy is transferred to the plasma without the usual attendent self-shielding effect of plasma polarlzatlon, whereby the energy transfer is accomplished with superior efficiency. More explicitly, the invention includes means for applying a radio-frequency electric field radially to an end of a plasma column confined in a magnetic mirror field configuration. The radio-frequency field propagates hydromagnetic waves axially through the column with the waves diminishing in an intermediate region of the column at ion cyclotron resonance with the fleld frequency. In such region the wave energy is converted by viscous damping to rotational energy of the plasma ions. (AEC)

  13. Recent results on heating and confinement in TEXTOR

    SciTech Connect

    Vandenplas, P.E.; Koch, R.; Messiaen, A.M.; Finken, K.H.; Ongena, J.; Philipps, V.; Samm, U.; Unterberg, B.; Van Oost, G.; Van Wassenhove, G.; Winter, J.; Dumortier, P.; Durodie, F.; Esser, H.G.; Euringer, H.; Giesen, B.; Hintz, E.; Lochter, M.; Tokar, M.Z.; Wolf, G.H.; Bertschinger, G.; Fuchs, G.; Hillis, D.L.; Hoenen, F.; Huettemann, P.; Koenen, L.; Koslowski, H.R.; Kraemer-Flecken, A.; Mank, G.; Pettiaux, D.

    1995-09-01

    The experiments on plasma heating and confinement in a medium size tokamak are reported. A high neutron production is obtained due to reaching the I-mode of the confinement operation better energy storage and the efficient use of RF reactor systems. (AIP) {copyright} {ital 1996 American Institute of Physics.}

  14. Confinement Aquaculture. Final Report.

    ERIC Educational Resources Information Center

    Delaplaine School District, AR.

    The Delaplaine Agriculture Department Confinement Project, begun in June 1988, conducted a confinement aquaculture program by comparing the growth of channel catfish raised in cages in a pond to channel catfish raised in cages in the Black River, Arkansas. The study developed technology that would decrease costs in the domestication of fish, using…

  15. 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.

  16. Elastic membranes in confinement.

    PubMed

    Bostwick, J B; Miksis, M J; Davis, S H

    2016-07-01

    An elastic membrane stretched between two walls takes a shape defined by its length and the volume of fluid it encloses. Many biological structures, such as cells, mitochondria and coiled DNA, have fine internal structure in which a membrane (or elastic member) is geometrically 'confined' by another object. Here, the two-dimensional shape of an elastic membrane in a 'confining' box is studied by introducing a repulsive confinement pressure that prevents the membrane from intersecting the wall. The stage is set by contrasting confined and unconfined solutions. Continuation methods are then used to compute response diagrams, from which we identify the particular membrane mechanics that generate mitochondria-like shapes. Large confinement pressures yield complex response diagrams with secondary bifurcations and multiple turning points where modal identities may change. Regions in parameter space where such behaviour occurs are then mapped. PMID:27440257

  17. Results from deuterium-tritium tokamak confinement experiments

    SciTech Connect

    Hawryluk, R.J.

    1997-02-01

    Recent scientific and technical progress in magnetic fusion experiments has resulted in the achievement of plasma parameters (density and temperature) which enabled the production of significant bursts of fusion power from deuterium-tritium fuels and the first studies of the physics of burning plasmas. The key scientific issues in the reacting plasma core are plasma confinement, magnetohydrodynamic (MHD) stability, and the confinement and loss of energetic fusion products from the reacting fuel ions. Progress in the development of regimes of operation which have both good confinement and are MHD stable have enabled a broad study of burning plasma physics issues. A review of the technical and scientific results from the deuterium-tritium experiments on the Joint European Torus (JET) and the Tokamak Fusion Test Reactor (TFTR) is given with particular emphasis on alpha-particle physics issues.

  18. Elastic membranes in confinement

    NASA Astrophysics Data System (ADS)

    Bostwick, Joshua; Miksis, Michael; Davis, Stephen

    2014-11-01

    An elastic membrane stretched between two walls takes a shape defined by its length and the volume of fluid it encloses. Many biological structures, such as cells, mitochondria and DNA, have finer internal structure in which a membrane (or elastic member) is geometrically ``confined'' by another object. We study the shape stability of elastic membranes in a ``confining'' box and introduce repulsive van der Waals forces to prevent the membrane from intersecting the wall. We aim to define the parameter space associated with mitochondria-like deformations. We compare the confined to `unconfined' solutions and show how the structure and stability of the membrane shapes changes with the system parameters.

  19. Fueling of magnetic-confinement devices

    SciTech Connect

    Milora, S.L.

    1981-01-01

    A general overview of the fueling of magnetic confinement devices is presented, with particular emphasis on recent experimental results. Various practical fueling mechanisms are considered, such as cold gas inlet (or plasma edge fueling), neutral beam injection, and injection of high speed cryogenic hydrogen pellets. The central role played by charged particle transport and recycle of plasma particles from material surfaces in contact with the plasma is discussed briefly. The various aspects of hydrogen pellet injection are treated in detail, including applications to the production of high purity startup plasmas for stellarators and other devices, refueling of tokamak plasmas, pellet ablation theory, and the technology and performance characteristics of low and high speed pellet injectors.

  20. Nonideal magnetohydrodynamic instabilities and toroidal magnetic confinement

    SciTech Connect

    Furth, H.P.

    1985-05-01

    The marked divergence of experimentally observed plasma instability phenomena from the predictions of ideal magnetohydrodynamics led in the early 1960s to the formulations of finite-resistivity stability theory. Beginning in the 1970s, advanced plasma diagnostics have served to establish a detailed correspondence between the predictions of the finite-resistivity theory and experimental plasma behavior - particularly in the case of the resistive kink mode and the tokamak plasma. Nonlinear resistive-kink phenomena have been found to govern the transport of magnetic flux and plasma energy in the reversed-field pinch. The other predicted finite-resistivity instability modes have been more difficult to identify directly and their implications for toroidal magnetic confinement are still unresolved.

  1. Polymer Crystallization under Confinement

    NASA Astrophysics Data System (ADS)

    Floudas, George

    Recent efforts indicated that polymer crystallization under confinement can be substantially different from the bulk. This can have important technological applications for the design of polymeric nanofibers with tunable mechanical strength, processability and optical clarity. However, the question of how, why and when polymers crystallize under confinement is not fully answered. Important studies of polymer crystallization confined to droplets and within the spherical nanodomains of block copolymers emphasized the interplay between heterogeneous and homogeneous nucleation. Herein we report on recent studies1-5 of polymer crystallization under hard confinement provided by model self-ordered AAO nanopores. Important open questions here are on the type of nucleation (homogeneous vs. heterogeneous), the size of critical nucleus, the crystal orientation and the possibility to control the overall crystallinity. Providing answers to these questions is of technological relevance for the understanding of nanocomposites containing semicrystalline polymers. In collaboration with Y. Suzuki, H. Duran, M. Steinhart, H.-J. Butt.

  2. Bacteria in Confined Spaces

    NASA Astrophysics Data System (ADS)

    Wilking, Connie; Weitz, David

    2010-03-01

    Bacterial cells can display differentiation between several developmental pathways, from planktonic to matrix-producing, depending upon the colony conditions. We study the confinement of bacteria in hydrogels as well as in liquid-liquid double emulsion droplets and observe the growth and morphology of these colonies as a function of time and environment. Our results can give insight into the behavior of bacterial colonies in confined spaces that can have applications in the areas of food science, cosmetics, and medicine.

  3. Confinement of bunched beams

    NASA Astrophysics Data System (ADS)

    Hess, Mark; Chen, Chiping

    2001-05-01

    The non-relativistic motion is analyzed for a highly bunched beam propagating through a perfectly conducting cylindrical pipe confined radially by a constant magnetic field parallel to the conductor axis, using a Green's function technique and Hamiltonian dynamics analysis. It is shown that for the confinement of beams with the same charge per unit length, the maximum value of the effective self-field parameter for a highly bunched beam is significantly lower than the Brillouin density limit for an unbunched beam.

  4. Plasma confinement theory and transport simulation

    NASA Astrophysics Data System (ADS)

    Ross, D. W.

    1989-06-01

    An overview of the program has been given in the contract proposal. The principal objectives are: to provide theoretical interpretation and computer modelling for the TEXT tokamak, and to advance the simulation studies of tokamaks generally, functioning as a National Transport Center. We also carry out equilibrium and stability studies in support of the TEXT upgrade, and work has continued on Alfven waves and MFENET software development. The focus of the program is to lay the groundwork for detailed comparison with experiment of the various transport theories to improve physics understanding and confidence in predictions of future machine behavior. This involves: to collect, in retrievable form, the data from TEXT and other tokamaks; to make the data available through easy-to-use interfaces; to develop criteria for success in fitting models to the data; to maintain the Texas transport code CHAPO and make it available to users; to collect theoretical models and implement them in the transport code; and to carry out simulation studies and evaluate fits to the data. In the following we outline the progress made in fiscal year 1989. Of special note are the proposed participation of our data base project in the ITER program, and a proposed q-profile diagnostic based on our neutral transport studies.

  5. 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.

  6. Platelet activation via PAR4 is involved in the initiation of thrombin generation and in clot elasticity development.

    PubMed

    Vretenbrant, Karin; Ramström, Sofia; Bjerke, Maria; Lindahl, Tomas L

    2007-03-01

    Thrombin is a pivotal enzyme formed in the coagulation cascade and an important and potent platelet activator. The two protease-activated thrombin receptors on human platelets are denoted PAR1 and PAR4. The physiological relevance of PAR4 is still unclear, as both aggregation and secretion can be accomplished by PAR1 activation alone. In the present study we have investigated the role of PARs in platelet activation, blood coagulation, clot elasticity and fibrinolysis. Flow cytometry, free oscillation rheometry and thrombin generation measurements were used to analyze blood or platelet-rich plasma from healthy individuals. Maximum PAR1 activation with the peptide SFLLRN gave fewer fibrinogen-binding platelets with lower mean fluorescent intensity than maximum PAR4 activation with AYPGKF. Inhibition of any of the receptors prolonged clotting times. However, PAR1 is more important for fibrinolysis; inhibition of this receptor prolonged all the steps in the fibrinolytic process. Clot elasticity decreased significantly when the PAR4 receptor was inhibited. In the thrombin generation measurements, PAR4 inhibition delayed the thrombin generation start and peak, but did not affect the total amount of thrombin generated. PAR1 inhibition had no significant impact on thrombin generation. We found that PAR4 is most likely activated by low concentrations of thrombin during the initial phase of thrombin generation and is of importance to the clotting time. Furthermore, we suggest that the PAR4 receptor may have a physiological role in the stabilisation of the coagulum. PMID:17334509

  7. Confinement scaling and ignition in tokamaks

    SciTech Connect

    Perkins, F.W.; Sun, Y.C.

    1985-10-01

    A drift wave turbulence model is used to compute the scaling and magnitude of central electron temperature and confinement time of tokamak plasmas. The results are in accord with experiment. Application to ignition experiments shows that high density (1 to 2) . 10/sup 15/ cm/sup -3/, high field, B/sub T/ > 10 T, but low temperature T approx. 6 keV constitute the optimum path to ignition.

  8. PLASMA DEVICE

    DOEpatents

    Gow, J.D.; Wilcox, J.M.

    1961-12-26

    A device is designed for producing and confining highenergy plasma from which neutrons are generated in copious quantities. A rotating sheath of electrons is established in a radial electric field and axial magnetic field produced within the device. The electron sheath serves as a strong ionizing medium to gas introdueed thereto and also functions as an extremely effective heating mechanism to the resulting plasma. In addition, improved confinement of the plasma is obtained by ring magnetic mirror fields produced at the ends of the device. Such ring mirror fields are defined by the magnetic field lines at the ends of the device diverging radially outward from the axis of the device and thereafter converging at spatial annular surfaces disposed concentrically thereabout. (AFC)

  9. Normal modes of confined cold ionic systems

    SciTech Connect

    Schiffer, J.P.; Dubin, D.H.

    1995-08-01

    The normal modes of a cloud of confined ions forming a strongly-correlated plasma were investigated. The results of molecular-dynamics simulations were compared to predictions of a cold fluid mode. Mode frequencies are observed to shift slightly compared to the cold fluid predictions, and the modes are also observed to damp in time. Simulations also reveal a set of torsional oscillations which have no counterpart in cold fluid theory. The frequency shift, damping, and torsional effects are compared to a model that treats trapped plasmas as a visco-elastic spheroid. It may be possible to measure high-frequency bulk and shear moduli of a strongly-correlated plasma from mode excitation experiments on trapped non-neutral plasmas. An example of the results of the calculation is presented.

  10. Par Pond vegetation status 1996

    SciTech Connect

    Mackey, H.E. Jr.; Riley, R.S.

    1996-12-01

    The water level of Par Pond was lowered approximately 20 feet in mid-1991 in order to protect downstream residents from possible dam failure suggested by subsidence on the downstream slope of the dam and to repair the dam. This lowering exposed both emergent and nonemergent macrophyte beds to drying conditions resulting in extensive losses. A survey of the newly emergent, shoreline aquatic plant communities of Par Pond began in June 1995, three months after the refilling of Par Pond to approximately 200 feet above mean sea level. These surveys continued in July, September, and late October, 1995, and into the early spring and late summer of 1996. Communities similar to the pre-drawdown, Par Pond aquatic plant communities continue to become re-established. Emergent beds of maidencane, lotus, waterlily, watershield, and Pontederia are extensive and well developed. Measures of percent cover, width of beds, and estimates of area of coverage with satellite data indicate regrowth within two years of from 40 to 60% of levels prior to the draw down. Cattail occurrence continued to increase during the summer of 1996, especially in the former warm arm of Par Pond, but large beds common to Par Pond prior to the draw down still have not formed. Lotus has invaded and occupies many of the areas formerly dominated by cattail beds. To track the continued development of macrophytes in Par Pond, future surveys through the summer and early fall of 1997, along with the evaluation of satellite data to map the extent of the macrophyte beds of Par Pond, are planned.

  11. Spherical microwave confinement and ball lightning

    NASA Astrophysics Data System (ADS)

    Robinson, William Richard

    This dissertation presents the results of research done on unconventional energy technologies from 1995 to 2009. The present civilization depends on an infrastructure that was constructed and is maintained almost entirely using concentrated fuels and ores, both of which will run out. Diffuse renewable energy sources rely on this same infrastructure, and hence face the same limitations. I first examined sonoluminescence directed toward fusion, but demonstrated theoretically that this is impossible. I next studied Low Energy Nuclear Reactions and developed methods for improving results, although these have not been implemented. In 2000, I began Spherical Microwave Confinement (SMC), which confines and heats plasma with microwaves in a spherical chamber. The reactor was designed and built to provide the data needed to investigate the possibility of achieving fusion conditions with microwave confinement. A second objective was to attempt to create ball lightning (BL). The reactor featured 20 magnetrons, which were driven by a capacitor bank and operated in a 0.2 s pulse mode at 2.45 GHz. These provided 20 kW to an icosahedral array of 20 antennas. Video of plasmas led to a redesign of the antennas to provide better coupling of the microwaves to the plasma. A second improvement was a grid at the base of the antennas, which provided corona electrons and an electric field to aid quick formation of plasmas. Although fusion conditions were never achieved and ball lightning not observed, experience gained from operating this basic, affordable system has been incorporated in a more sophisticated reactor design intended for future research. This would use magnets that were originally planned. The cusp geometry of the magnetic fields is suitable for electron cyclotron resonance in the same type of closed surface that in existing reactors has generated high-temperature plasmas. Should ball lightning be created, it could be a practical power source with nearly ideal

  12. Field reversed configuration confinement enhancement through edge biasing and neutral beam injection.

    PubMed

    Tuszewski, M; Smirnov, A; Thompson, M C; Korepanov, S; Akhmetov, T; Ivanov, A; Voskoboynikov, R; Schmitz, L; Barnes, D; Binderbauer, M W; Brown, R; Bui, D Q; Clary, R; Conroy, K D; Deng, B H; Dettrick, S A; Douglass, J D; Garate, E; Glass, F J; Gota, H; Guo, H Y; Gupta, D; Gupta, S; Kinley, J S; Knapp, K; Longman, A; Hollins, M; Li, X L; Luo, Y; Mendoza, R; Mok, Y; Necas, A; Primavera, S; Ruskov, E; Schroeder, J H; Sevier, L; Sibley, A; Song, Y; Sun, X; Trask, E; Van Drie, A D; Walters, J K; Wyman, M D

    2012-06-22

    Field reversed configurations (FRCs) with high confinement are obtained in the C-2 device by combining plasma gun edge biasing and neutral beam injection. The plasma gun creates an inward radial electric field that counters the usual FRC spin-up. The n = 2 rotational instability is stabilized without applying quadrupole magnetic fields. The FRCs are nearly axisymmetric, which enables fast ion confinement. The plasma gun also produces E × B shear in the FRC edge layer, which may explain the observed improved particle transport. The FRC confinement times are improved by factors 2 to 4, and the plasma lifetimes are extended from 1 to up to 4 ms.

  13. Field Reversed Configuration Confinement Enhancement through Edge Biasing and Neutral Beam Injection

    NASA Astrophysics Data System (ADS)

    Tuszewski, M.; Smirnov, A.; Thompson, M. C.; Korepanov, S.; Akhmetov, T.; Ivanov, A.; Voskoboynikov, R.; Schmitz, L.; Barnes, D.; Binderbauer, M. W.; Brown, R.; Bui, D. Q.; Clary, R.; Conroy, K. D.; Deng, B. H.; Dettrick, S. A.; Douglass, J. D.; Garate, E.; Glass, F. J.; Gota, H.; Guo, H. Y.; Gupta, D.; Gupta, S.; Kinley, J. S.; Knapp, K.; Longman, A.; Hollins, M.; Li, X. L.; Luo, Y.; Mendoza, R.; Mok, Y.; Necas, A.; Primavera, S.; Ruskov, E.; Schroeder, J. H.; Sevier, L.; Sibley, A.; Song, Y.; Sun, X.; Trask, E.; Van Drie, A. D.; Walters, J. K.; Wyman, M. D.

    2012-06-01

    Field reversed configurations (FRCs) with high confinement are obtained in the C-2 device by combining plasma gun edge biasing and neutral beam injection. The plasma gun creates an inward radial electric field that counters the usual FRC spin-up. The n=2 rotational instability is stabilized without applying quadrupole magnetic fields. The FRCs are nearly axisymmetric, which enables fast ion confinement. The plasma gun also produces E×B shear in the FRC edge layer, which may explain the observed improved particle transport. The FRC confinement times are improved by factors 2 to 4, and the plasma lifetimes are extended from 1 to up to 4 ms.

  14. Field reversed configuration confinement enhancement through edge biasing and neutral beam injection.

    PubMed

    Tuszewski, M; Smirnov, A; Thompson, M C; Korepanov, S; Akhmetov, T; Ivanov, A; Voskoboynikov, R; Schmitz, L; Barnes, D; Binderbauer, M W; Brown, R; Bui, D Q; Clary, R; Conroy, K D; Deng, B H; Dettrick, S A; Douglass, J D; Garate, E; Glass, F J; Gota, H; Guo, H Y; Gupta, D; Gupta, S; Kinley, J S; Knapp, K; Longman, A; Hollins, M; Li, X L; Luo, Y; Mendoza, R; Mok, Y; Necas, A; Primavera, S; Ruskov, E; Schroeder, J H; Sevier, L; Sibley, A; Song, Y; Sun, X; Trask, E; Van Drie, A D; Walters, J K; Wyman, M D

    2012-06-22

    Field reversed configurations (FRCs) with high confinement are obtained in the C-2 device by combining plasma gun edge biasing and neutral beam injection. The plasma gun creates an inward radial electric field that counters the usual FRC spin-up. The n = 2 rotational instability is stabilized without applying quadrupole magnetic fields. The FRCs are nearly axisymmetric, which enables fast ion confinement. The plasma gun also produces E × B shear in the FRC edge layer, which may explain the observed improved particle transport. The FRC confinement times are improved by factors 2 to 4, and the plasma lifetimes are extended from 1 to up to 4 ms. PMID:23004613

  15. 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

  16. Poloidal rotation, density asymmetries and momentum confinement in tokamak experiments

    SciTech Connect

    Stacey, W.M.; Jackson, D.R.

    1992-08-01

    Poloidal rotation speeds and density asymmetries are calculated for the deuterium and dominant carbon (oxygen) impurity ions in discharges in ASDEX, DIII, ISX-B, JET, and TFTR for which {upsilon}{sub {phi}} {approximately} {upsilon}{sub th} for the ions. These poloidal rotation speeds and density asymmetries are used to evaluate the neoclassical gyroviscous model for the momentum confinement time. The rather good agreement with experimental momentum confinement times obtained over this wide range of plasma parameters provides a measure of confidence in the calculated density asymmetries and poloidal rotation, as well as arguing for a neoclassical explanation for momentum confinement in tokamaks.

  17. Confinement and water quality-induced stress in largemouth bass

    SciTech Connect

    Carmichael, G.J.; Tomasso, J.R.; Simco, B.A.; Davis, K.B.

    1984-11-01

    Plasma values of corticosteroids, glucose, chloride, and osmolality were determined in largemouth bass Micropterus salmoides under various environmental conditions. No differences were observed in quiescent fish due to sex, size, time of day, or the types of holding facilities tested (tanks, raceways, ponds). Differences were observed in plasma glucose, chloride, and osmolality values among fish acclimated to 10, 16, and 23 C. Abrupt temperature changes caused elevations in plasma corticosteroid and glucose concentrations and reduced plasma chloride and osmolality. Confinement in a net, for up to 48 hours, caused elevated glucose and corticosteroids and reduced chloride and osmolality values. After 48 hours of confinement, fish required up to 14 days to recover normal plasma characters. Generally, short-term exposure to poor water quality (high concentrations of CO/sub 2/ and NH/sub 3/, and low concentrations of dissolved oxygen) altered plasma corticosteroids and glucose but had little effect on plasma chloride or osmolality. Net confinement plus poor water quality caused additional stress. Plasma glucose and corticosteroid values were good indicators of stress during application of acute stressors whereas chloride and osmolality were useful indicators of long-term stress and patterns of recovery after stressors were removed.

  18. Operational Principles for the Dynamics of the In Vitro ParA-ParB System

    PubMed Central

    Jindal, Lavisha; Emberly, Eldon

    2015-01-01

    In many bacteria the ParA-ParB protein system is responsible for actively segregating DNA during replication. ParB proteins move by interacting with DNA bound ParA-ATP, stimulating their unbinding by catalyzing hydrolysis, that leads to rectified motion due to the creation of a wake of depleted ParA. Recent in vitro experiments have shown that a ParB covered magnetic bead can move with constant speed over a DNA covered substrate that is bound by ParA. It has been suggested that the formation of a gradient in ParA leads to diffusion-ratchet like motion of the ParB bead but how it forms and generates a force is still a matter of exploration. Here we develop a deterministic model for the in vitro ParA-ParB system and show that a ParA gradient can spontaneously form due to any amount of initial spatial noise in bound ParA. The speed of the bead is independent of this noise but depends on the ratio of the range of ParA-ParB force on the bead to that of removal of surface bound ParA by ParB. We find that at a particular ratio the speed attains a maximal value. We also consider ParA rebinding (including cooperativity) and ParA surface diffusion independently as mechanisms for ParA recovery on the surface. Depending on whether the DNA covered surface is undersaturated or saturated with ParA, we find that the bead can accelerate persistently or potentially stall. Our model highlights key requirements of the ParA-ParB driving force that are necessary for directed motion in the in vitro system that may provide insight into the in vivo dynamics of the ParA-ParB system. PMID:26670738

  19. Simulation of Spheromak Evolution and Energy Confinement

    NASA Astrophysics Data System (ADS)

    Cohen, Bruce I.

    2004-11-01

    Electron temperatures near 400 eV were observed transiently in the Los Alamos CTX spheromak experiment.[1] Temperatures of 100-200 eV have been observed in the SSPX spheromak.[2] Understanding the energy confinement in these experiments is a challenging problem. Results from numerical simulations with the NIMROD nonlinear resistive MHD code (at zero or finite plasma pressure) have shown that closed flux surfaces with net current can arise only after electrostatic drive is reduced.[3,4] Computations in the last year have directly investigated the importance of inductive effects on energy confinement including the evolution of the temperature and number density using thermal transport coefficients, electrical resistivity, and Ohmic heating that are appropriate for collisional plasmas. In conditions with sustained coaxial electrostatic drive, the cold edge plasma impedes parallel thermal conduction to the wall, despite the chaotic magnetic topology, allowing the plasma core temperature to reach tens of eVs. When the drive is temporarily removed, relatively symmetric closed flux surfaces form. Magnetic reconnection occurs rapidly in the cold outer plasma, and core temperatures increase toward 100 eV or more. Applying a second current pulse, as in some SSPX discharges,[5] is shown to improve performance by delaying the onset of MHD modes that are resonant in the closed-flux region, and higher current, increased magnetic fields, and larger volumes of closed flux can be achieved. The simulations reveal the sensitivity with respect to symmetry-breaking magnetic fluctuations of the magnetic surfaces and the energy confinement. We present a detailed comparison of results from nonlinear simulations with laboratory measurements from SSPX[5,6] and assess transport mechanisms through computational diagnostics. The simulation results are yielding electron temperatures and other features agreeing well with SSPX observations. [1] T. R. Jarboe, Plasma Phys. Control. Fusion 36, 945

  20. Totally confined explosive welding

    NASA Technical Reports Server (NTRS)

    Bement, L. J. (Inventor)

    1978-01-01

    The undesirable by-products of explosive welding are confined and the association noise is reduced by the use of a simple enclosure into which the explosive is placed and in which the explosion occurs. An infrangible enclosure is removably attached to one of the members to be bonded at the point directly opposite the bond area. An explosive is completely confined within the enclosure at a point in close proximity to the member to be bonded and a detonating means is attached to the explosive. The balance of the enclosure, not occupied by explosive, is filled with a shaped material which directs the explosive pressure toward the bond area. A detonator adaptor controls the expansion of the enclosure by the explosive force so that the enclosure at no point experiences a discontinuity in expansion which causes rupture. The use of the technique is practical in the restricted area of a space station.

  1. Classical confined particles

    NASA Technical Reports Server (NTRS)

    Horzela, Andrzej; Kapuscik, Edward

    1993-01-01

    An alternative picture of classical many body mechanics is proposed. In this picture particles possess individual kinematics but are deprived from individual dynamics. Dynamics exists only for the many particle system as a whole. The theory is complete and allows to determine the trajectories of each particle. It is proposed to use our picture as a classical prototype for a realistic theory of confined particles.

  2. Energy confinement in tokamaks

    SciTech Connect

    Sugihara, M.; Singer, C.

    1986-08-01

    A straightforward generalization is made of the ohmic heating energy confinement scalings of Pfeiffer and Waltz and Blackwell et. al. The resulting model is systematically calibrated to published data from limiter tokamaks with ohmic, electron cyclotron, and neutral beam heating. With considerably fewer explicitly adjustable free parameters, this model appears to give a better fit to the available data for limiter discharges than the combined ohmic/auxiliary heating model of Goldston.

  3. Inertial Confinement fusion targets

    NASA Technical Reports Server (NTRS)

    Hendricks, C. D.

    1982-01-01

    Inertial confinement fusion (ICF) targets are made as simple flat discs, as hollow shells or as complicated multilayer structures. Many techniques were devised for producing the targets. Glass and metal shells are made by using drop and bubble techniques. Solid hydrogen shells are also produced by adapting old methods to the solution of modern problems. Some of these techniques, problems, and solutions are discussed. In addition, the applications of many of the techniques to fabrication of ICF targets is presented.

  4. Freezing in confined geometries

    NASA Technical Reports Server (NTRS)

    Sokol, P. E.; Ma, W. J.; Herwig, K. W.; Snow, W. M.; Wang, Y.; Koplik, Joel; Banavar, Jayanth R.

    1992-01-01

    Results of detailed structural studies, using elastic neutron scattering, of the freezing of liquid O2 and D2 in porous vycor glass, are presented. The experimental studies have been complemented by computer simulations of the dynamics of freezing of a Lennard-Jones liquid in narrow channels bounded by molecular walls. Results point to a new simple physical interpretation of freezing in confined geometries.

  5. Topological confinement and superconductivity

    SciTech Connect

    Al-hassanieh, Dhaled A; Batista, Cristian D

    2008-01-01

    We derive a Kondo Lattice model with a correlated conduction band from a two-band Hubbard Hamiltonian. This mapping allows us to describe the emergence of a robust pairing mechanism in a model that only contains repulsive interactions. The mechanism is due to topological confinement and results from the interplay between antiferromagnetism and delocalization. By using Density-Matrix-Renormalization-Group (DMRG) we demonstrate that this mechanism leads to dominant superconducting correlations in aID-system.

  6. 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.

  7. Heating, Confinement, and Extrapolation to Reactors

    SciTech Connect

    Ongena, J.; Messiaen, A.M

    2004-03-15

    The total amount of heating power coupled to the plasma P{sub tot} and the energy confinement time are determining parameters for realizing the plasma conditions suitable for the reactor. We recall that the ignition condition can be expressed by the following condition on the triple fusion product:NT{tau} = P{sub tot}{tau}{sup 2}/(3 Vol) = 3N{sup 2}T{sup 2}Vol/P{sub tot} > (NT{tau}){sub ignition} (1)with T [approximately equal to] 15 keV where {tau} = E/P{sub tot} is the energy confinement time, E = 3NT Vol for an isothermal plasma with T{sub i} = T{sub e} = T and a plasma volume Vol; N is the plasma density. The value T [approximately equal to] 15 keV corresponds to the minimum value of (NT{tau}){sub ignition} as a function T (see Fig. 1). In the present discussion for the sake of simplicity, we neglect density and temperature profile factors. The heating power in most of the present experiments is given by P{sub tot} = P{sub OH} + P{sub add} where P{sub OH} is the ohmic power and P{sub add} is the additional heating due to neutral beam injection or R.F. heating. At ignition, the additional heating power must come completely from the energetic {alpha} particles produced by the fusion reactions and we must have P{sub tot} = P{sub {alpha}} if we neglect the residual P{sub OH} and the plasma losses by Bremsstrahlung (P{sub Br} [is proportional to] N{sup 2} T{sup 1/2})

  8. Structure of Polymer Chains Confined in Vycor

    NASA Astrophysics Data System (ADS)

    Lal, Jyotsana; Sinha, Sunil K.; Auvray, Loïc

    1997-11-01

    We observe by Small Angle Neutron Scattering the structure of polystyrene chains in semi-dilute solutions confined in a model porous medium, Vycor. The size of the free chains in solution is always larger than the pore diameter, 70 Å. The use of a suitable mixture of hydrogenated and deuterated solvents and polymers enables us to measure directly the form factor of one single chain among the others. The penetration of the chains in the porous medium is almost complete for the concentration (Φ = 20%) and the range of molecular weight (35 000 < M_w < 800 000) used. The radius of gyration of the confined chains is always smaller than the radius of gyration of the free chains in the equivalent bulk solution. Our measurements are in agreement with the theoretical predictions established by Daoud and de Gennes for chains confined in a cylindrical pore when the chains are entangled and laterally squeezed but remain ideal at large scale along the cylinder axis because of the screening of the excluded volume interactions (so-called regime of “semi-dilute cigars”). The values of the partition coefficient of the chains between the porous medium and the free solution and the asymptotic behavior of the structure factors indicate that polystyrene adsorbs onto the bare surface of Vycor. We show that silanizing Vycor suppresses this adsorption. Nous observons par diffusion de neutrons aux petits angles la structure de chaînes de polystyrène en solution semi-diluée confinées dans un milieu poreux modèle, le Vycor. La taille des chaînes en solution à l'état libre est toujours supérieure au diamètre des pores, 70 Å. L'utilisation d'un mélange adéquat de solvants et de polymères hydrogénés et deutérés nous permet de mesurer directement le facteur de forme d'une seule chaîne au milieu des autres. La pénétration des chaînes dans le milieu poreux est presque totale pour la concentration (Φ = 20%) et la gamme de poids moléculaire (35 000 < M_w < 800 000

  9. Plasma engineering for MARS

    SciTech Connect

    Carlson, G.A.; Baldwin, D.E.; Barr, W.L.

    1983-03-24

    The two-year Mirror Advanced Reactor Study (MARS) has resulted in the conceptual design of a commercial, electricity-producing fusion reactor based on tandem mirror confinement. The physics basis for the MARS reactor was developed through work in two highly coupled areas of plasma engineering: magnetics and plasma performance.

  10. 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.

  11. The ''Kinetic Stabilizer'': A Simpler Tandem Mirror Confinement?

    SciTech Connect

    Post, R.F.

    2000-06-15

    In the search for better approaches to magnetic fusion it is important to keep in mind the lessons learned in the 50 years that fusion plasma confinement has been studied. One of the lessons learned is that ''closed'' and ''open'' fusion devices differ fundamentally with respect to an important property of their confinement, as follows: Without known exception closed systems such as the tokamak, the stellarator, or the reversed-field pinch, have been found to have their confinement times limited by non-classical, i.e., turbulence-related, processes, leading to the requirement that such systems must be scaled-up in dimensions to sizes much larger than would be the case in the absence of turbulence. By contrast, from the earliest days of fusion research, it has been demonstrated that open magnetic systems of the mirror variety can achieve confinement times close to that associated with classical, i.e., collisional, processes. While these good results have been obtained in both axially symmetric fields and in non-axisymmetric fields, the clearest cases have been those in which the confining fields are solenoidal and axially symmetric. These observations, i.e., of confinement not enhanced by turbulence, can be traced theoretically to such factors as the absence of parallel currents in the plasma, and to the constraints on particle drifts imposed by the adiabatic invariants governing particle confinement in axisymmetric open systems. In the past the MHD instability of axially symmetric open systems has been seen as a barrier to their use. However, theory predicts MHD-stable confinement is achievable if sufficient plasma is present in the ''good curvature'' regions outside the mirrors. This theory has been confirmed by experiments on the Gas Dynamic Trap mirror-based experiment at Novosibirsk, In this paper a new way of exploiting this stabilizing principle, involving creating a localized ''stabilizer plasma'' outside a mirror, will be discussed. To create this plasma

  12. Confinement Contains Condensates

    SciTech Connect

    Brodsky, Stanley J.; Roberts, Craig D.; Shrock, Robert; Tandy, Peter C.

    2012-03-12

    Dynamical chiral symmetry breaking and its connection to the generation of hadron masses has historically been viewed as a vacuum phenomenon. We argue that confinement makes such a position untenable. If quark-hadron duality is a reality in QCD, then condensates, those quantities that have commonly been viewed as constant empirical mass-scales that fill all spacetime, are instead wholly contained within hadrons; i.e., they are a property of hadrons themselves and expressed, e.g., in their Bethe-Salpeter or light-front wave functions. We explain that this paradigm is consistent with empirical evidence, and incidentally expose misconceptions in a recent Comment.

  13. 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.

  14. Plasma control and utilization

    DOEpatents

    Ensley, Donald L.

    1976-12-28

    A plasma is confined and heated by a microwave field resonant in a cavity excited in a combination of the TE and TM modes while responding to the resonant frequency of the cavity as the plasma dimensions change to maintain operation at resonance. The microwave field is elliptically or circularly polarized as to prevent the electromagnetic confining field from going to zero. A high Q chamber having superconductive walls is employed to minimize wall losses while providing for extraction of thermonuclear energy produced by fusion of nuclei in the plasma.

  15. An Experiment to study sheared magnetofluids and Bernoulli confinement

    NASA Astrophysics Data System (ADS)

    Bengtson, Roger D.; Valanju, P. M.; Mahajan, S. M.; Hazeltine, R. D.; Chatterjee, R.; Queredo, H. J.; Meintanis, Evangelos

    2000-10-01

    Dynamically stable magnetofluid states with strong velocity shear and good Bernoulli confinement result from the relaxation process in which total magnetic and generalized helicities are both conserved [1].Because of the extra invariant these states can sustain a large pressure gradient without requiring the existence of closed flux surfaces. Their investigation bears upon fundamental issues of plasma confinement. We are building a small mirror machine with high radial electric fields to create a rotating, self-organizing, detached toroidal plasma ring. Under some conditions, we expect the plasma to relax through a turbulent process to a nearby megnetofluid state which deponds only on the initial values of the two helicity invariants set by the initial flows and currents. The evolution of the plasma profiles will be measured by magnetic, Langmuir, and Mach probes, spectroscopic techniques, and by interferometry. Initial measurements will be shown. [S. M. Mahajan and Z. Yoshida, Phys. Rev. Lett. 81, 4863 (1998)

  16. Plasma Physics: An Introductory Course

    NASA Astrophysics Data System (ADS)

    Dendy, R. O.

    1995-03-01

    Preface; Introduction R. O. Dendy; 1. Plasma particle dynamics R. J. Hastie; 2. Plasma kinetic theory J. A. Elliott; 3. Waves in plasmas J. P. Doughtery; 4. Magnetohydrodynamics K. I. Hopcraft; 5. Turbulence in fluids and fusion plasmas F. A. Haas; 6. Finite-dimensional dynamics and chaos T. J. Mullin; 7. Computational plasma physics J. W. Eastwood; 8. Tokomak experiments D. C. Robinson and M. R. O'Brien; 9. Magnetospheric plasmas: Part I Basic processes in the solar system D. A. Bryant; Part II Microprocesses R. L. Bingham; 10. Solar plasmas R. A. Hood; 11. Gravitational plasmas J. J. Binney; 12. Laser plasmas A. R. Bell; 13. Industrial plasmas P. C. Johnson; 14. Transport in magnetically confined plasmas T. E. Stringer; 15. Radio-frequency plasma heating R. A. Cairns; 16. Boundary plasmas G. McCracken; 17. How to build a tokomak T. N. Todd; 18. Survey of fusion plasma physics R. S. Pease; Index.

  17. Inertial confinement fusion quarterly report, July--September 1994. Volume 4, Number 4

    SciTech Connect

    Honea, E.

    1994-09-01

    The ICF Quarterly continues with six articles in this issue describing recent developments in the Inertial Confinement Fusion (ICF) Program at Lawrence Livermore National Laboratory. The topics include plasma characterization, production of millimeter scale-length plasmas for studying laser-plasma instabilities, hohlraum physics, three-dimensional hydrodynamic modeling, crystal growth, and laser-beam smoothing.

  18. Par Pond Fish, Water, and Sediment Chemistry

    SciTech Connect

    Paller, M.H.; Wike, L.D.

    1996-06-01

    The objectives of this report are to describe the Par Pond fish community and the impact of the drawdown and refill on the community, describe contaminant levels in Par Pond fish, sediments, and water and indicate how contaminant concentrations and distributions were affected by the drawdown and refill, and predict possible effects of future water level fluctuations in Par Pond.

  19. Directed and persistent movement arises from mechanochemistry of the ParA/ParB system

    NASA Astrophysics Data System (ADS)

    Hu, Longhua; Vecchiarelli, Anthony G.; Mizuuchi, Kiyoshi; Neuman, Keir C.; Liu, Jian

    The segregation of DNA prior to cell division is essential for faithful genetic inheritance. In many bacteria, segregation of the low-copy-number plasmids involves an active partition system composed of ParA ATPase and its stimulator protein ParB. Recent experiments suggest that ParA/ParB system motility is driven by a diffusion-ratchet mechanism in which ParB-coated plasmid both creates and follows a ParA gradient on the nucleoid surface. However, the detailed mechanism of ParA/ParB-mediated directed and persistent movement remains unknown. We develop a theoretical model describing ParA/ParB-mediated motility. We show that the ParA/ParB system can work as a Brownian ratchet, which effectively couples the ATPase-dependent cycling of ParA-nucleoid affinity to the motion of the ParB bound cargo. Paradoxically, the resulting processive motion relies on quenching diffusive plasmid motion through a large number of transient ParA/ParB-mediated tethers to the nucleoid surface. Our work sheds light on a new emergent phenomenon in which non-motor proteins work collectively via mechanochemical coupling to propel cargos -- an ingenious solution shaped by evolution to cope with the lack of processive motor proteins in bacteria.

  20. Immune responses in humans after 60 days of confinement

    NASA Technical Reports Server (NTRS)

    Schmitt, D. A.; Peres, C.; Sonnenfeld, G.; Tkackzuk, J.; Arquier, M.; Mauco, G.; Ohayon, E.

    1995-01-01

    A confinement experiment in a normobaric diving chamber was undertaken to better understand the effect of confinement and isolation on human psychology and physiology. Pre- and postconfinement blood samples were obtained from four test subjects and control donors to analyze immune responses. No modification in the levels of CD2+, CD3+, CD4+, CD8+, CD19+, and CD56+ cells was observed after confinement. Mitogen-induced T-lymphocyte proliferation and interleukin-2 receptor expression were not altered significantly. Whole blood interferon-alpha and gamma-induction and plasma cortisol levels were also unchanged, as was natural killer cell activity. These data suggest that in humans, no specific components of the immune response are affected by a 2-month isolation and confinement of a small group.

  1. Inertial-Electrostatic Confinement (IEC) Fusion for Space Propulsion

    NASA Technical Reports Server (NTRS)

    Nadler, Jon

    1999-01-01

    An Inertial-Electrostatic Confinement (IEC) device was assembled at the Marshall Space Flight Center (MSFC) Propulsion Research Center (PRC) to study the possibility of using EEC technology for deep space propulsion and power. Inertial-Electrostatic Confinement is capable of containing a nuclear fusion plasma in a series of virtual potential wells. These wells would substantially increase plasma confinement, possibly leading towards a high-gain, breakthrough fusion device. A one-foot in diameter IEC vessel was borrowed from the Fusion Studies Laboratory at the University of Illinois@Urbana-Champaign for the summer. This device was used in initial parameterization studies in order to design a larger, actively cooled device for permanent use at the PRC.

  2. Inertial-Electrostatic Confinement (IEC) Fusion For Space Propulsion

    NASA Technical Reports Server (NTRS)

    Nadler, Jon

    1999-01-01

    An Inertial-Electrostatic Confinement (IEC) device was assembled at the Marshall Space Flight Center (MSFC) Propulsion Research Center (PRC) to study the possibility of using IEC technology for deep space propulsion and power. Inertial-Electrostatic Confinement is capable of containing a nuclear fusion plasma in a series of virtual potential wells. These wells would substantially increase plasma confinement, possibly leading towards a high-gain, breakthrough fusion device. A one-foot in diameter IEC vessel was borrowed from the Fusion Studies Laboratory at the University of Illinois @ Urbana-Champaign for the summer. This device was used in initial parameterization studies in order to design a larger, actively cooled device for permanent use at the PRC.

  3. Analysis of the ITER H-mode confinement database

    SciTech Connect

    Schissel, D.P.; Kardaun, O.J.W.F.; Ryter, F.; Stroth, U.

    1993-05-01

    In order to predict the global energy confinement time in the next generation of large tokamaks it is essential to have data from machines of different sizes and operating parameter regimes. This data can also be used to construct dimensionless scalings and thereby attempt to differentiate between Bohm and gyro-Bohm based transport models. Previously, at the request of the ITER project, H-mode global confinement data was assembled from six machines ASDEX, DIII-D, JET, JFT-2M, PBX-M, and PDX into a single database. This collaboration has continued with the initial database being expanded by extending the plasma parameter space as well as by improving the precision of some of the relevant calculated plasma parameters. This paper summarizes work that has been performed on the newest version (ITERH.DB2) of the confinement database.

  4. Analysis of the ITER H-mode confinement database

    NASA Astrophysics Data System (ADS)

    Schissel, D. P.; Kardaun, O.; Ryter, F.; Stroth, U.

    1993-05-01

    In order to predict the global energy confinement time in the next generation of large tokamaks it is essential to have data from machines of different sizes and operating parameter regimes. This data can also be used to construct dimensionless scalings and thereby attempt to differentiate between Bohm and gyro-Bohm based transport models. Previously, at the request of the ITER project, H-mode global confinement data was assembled from six machines, ASDEX, DIII-D, JET, JFT-2M, PBX-M, and PDX, into a single database. This collaboration has continued with the initial database being expanded by extending the plasma parameter space as well as by improving the precision of some of the relevant calculated plasma parameters. This paper summarizes work that has been performed on the newest version (ITERH.DB2) of the confinement database.

  5. Amoeboid motion in confined geometry.

    PubMed

    Wu, Hao; Thiébaud, M; Hu, W-F; Farutin, A; Rafaï, S; Lai, M-C; Peyla, P; Misbah, C

    2015-01-01

    Many eukaryotic cells undergo frequent shape changes (described as amoeboid motion) that enable them to move forward. We investigate the effect of confinement on a minimal model of amoeboid swimmer. A complex picture emerges: (i) The swimmer's nature (i.e., either pusher or puller) can be modified by confinement, thus suggesting that this is not an intrinsic property of the swimmer. This swimming nature transition stems from intricate internal degrees of freedom of membrane deformation. (ii) The swimming speed might increase with increasing confinement before decreasing again for stronger confinements. (iii) A straight amoeoboid swimmer's trajectory in the channel can become unstable, and ample lateral excursions of the swimmer prevail. This happens for both pusher- and puller-type swimmers. For weak confinement, these excursions are symmetric, while they become asymmetric at stronger confinement, whereby the swimmer is located closer to one of the two walls. In this study, we combine numerical and theoretical analyses. PMID:26651631

  6. Amoeboid motion in confined geometry

    NASA Astrophysics Data System (ADS)

    Wu, Hao; Thiébaud, M.; Hu, W.-F.; Farutin, A.; Rafaï, S.; Lai, M.-C.; Peyla, P.; Misbah, C.

    2015-11-01

    Many eukaryotic cells undergo frequent shape changes (described as amoeboid motion) that enable them to move forward. We investigate the effect of confinement on a minimal model of amoeboid swimmer. A complex picture emerges: (i) The swimmer's nature (i.e., either pusher or puller) can be modified by confinement, thus suggesting that this is not an intrinsic property of the swimmer. This swimming nature transition stems from intricate internal degrees of freedom of membrane deformation. (ii) The swimming speed might increase with increasing confinement before decreasing again for stronger confinements. (iii) A straight amoeoboid swimmer's trajectory in the channel can become unstable, and ample lateral excursions of the swimmer prevail. This happens for both pusher- and puller-type swimmers. For weak confinement, these excursions are symmetric, while they become asymmetric at stronger confinement, whereby the swimmer is located closer to one of the two walls. In this study, we combine numerical and theoretical analyses.

  7. Plasma stabilization experiment

    NASA Astrophysics Data System (ADS)

    Sziklas, E. A.; Fader, W. J.; Jong, R. A.; Stufflebeam, J. H.

    1980-07-01

    The plasma stabilization experiment is an effort to enhance stability in a mirror-confined plasma by trapping cold ions with rf fields applied near the mirror throats. Nagoya Type 3 antennas, coupled to a 60 kW rf power supply are mounted in the throats of the UTRC baseball magnet. An external washer gun provides a source of plasma for both streaming and confined plasma tests. Results show a strong stoppering effect on streaming plasmas and a marginal effect on confined plasmas. Theoretical calculations provide an explanation for the experimental observations. The field generates a ponderomotive force acting on the electrons. The resultant improvement in electron confinement changes the ambipolar potential and inhibits the flow of ions through the mirror throat. Criteria are derived for the validity of this trapping concept. The requisite field strengths are significantly lower than those required to trap ions directly. Scaling laws are developed for application of cold ion trapping to large mirror devices containing dense plasmas. The use of slow-wave antenna structures operated at frequencies above the lower hybrid frequency is recommended for these applications.

  8. Computational Knowledge for Toroidal Confinement Physics: Part I

    SciTech Connect

    Chang, C. S.

    2009-02-19

    Basic high level computational knowledge for studying the toroidal confinement physics is discussed. Topics include the primacy hierarchy of simulation quantities in statistical plasma physics, importance of the nonlinear-multiscale self-organization phenomena in a computational study, different types of codes for different applications, and different types of computer architectures for different types of codes.

  9. H-mode confinement and fusion performance in JET

    NASA Astrophysics Data System (ADS)

    Campbell, D. J.; JET Team

    1997-05-01

    JET has conducted extensive experiments in H-mode plasmas focusing on two broad aims. The first, involving the characterization of reactor-relevant aspects of the regime, encompasses the study of steady-state H-modes at plasma currents of up to 6 MA. In these plasmas, energy confinement is typically a factor of 1.8 - 2 greater than predicted by L-mode scalings and local transport varies with the ion Larmor radius, at least for input powers well above the H-mode threshold power. Using nitrogen impurity seeding, a regime has been developed in which good core confinement, with an enhancement of 1.5 relative to L-mode scaling, is combined with radiated power fractions of up to 80%. The second major goal is to optimize fusion power production by exploiting high-confinement ELM-free H-modes, which exhibit energy confinement enhancement factors of three or more relative to L-mode plasmas. In this regime, fusion power quotients $Q_{DT} \\sim 1$Energy confinement scaling and the extrapolation to ITER

    SciTech Connect

    1997-11-01

    The fusion performance of ITER is predicted using three different techniques; statistical analysis of the global energy confinement data, a dimensionless physics parameter similarity method and the full 1-D modeling of the plasma profiles. Although the three methods give overlapping predictions for the performance of ITER, the confidence interval of all of the techniques is still quite wide.

  10. Recent results on heating and confinement in TEXTOR

    SciTech Connect

    Vandenplas, P.E.; Koch, R.; Messiaen, A.M.; Finken, K.H.; Ongena, J.; Philipps, V.; Samm, U.; Unterberg, B.; Oost, G.V.; Wassenhove, G.V.; Winter, J.; Bonheure, G.; Dumortier, P.; Durodie, F.; Esser, H.G.; Euringer, H.; Giesen, B.; Lochter, M.; Tokar, M.Z.; Wolf, G.H.; Bertschinger, G.; Fuchs, G.; Hillis, D.L.; Hoenen, F.; Huettemann, P.; Koenen, L.; Koslowski, H.R.; Kraemer-Flecken, A.; Mank, G.; Pospieszczyk, A.

    1996-02-01

    Experimentation with TEXTOP tokamak using the ICR plasma heating together with an auxiliary heating system involving the neutral beam injection have allowed to extend the improved confinement mode to the high density regime. The third harmonic D heating and a new reactor coating with edge radiative cooling have given a strong increase of the neutron yield. {copyright} {ital 1996 American Institute of Physics.}

  11. Parallel Climate Analysis Toolkit (ParCAT)

    SciTech Connect

    Smith, Brian Edward

    2013-06-30

    The parallel analysis toolkit (ParCAT) provides parallel statistical processing of large climate model simulation datasets. ParCAT provides parallel point-wise average calculations, frequency distributions, sum/differences of two datasets, and difference-of-average and average-of-difference for two datasets for arbitrary subsets of simulation time. ParCAT is a command-line utility that can be easily integrated in scripts or embedded in other application. ParCAT supports CMIP5 post-processed datasets as well as non-CMIP5 post-processed datasets. ParCAT reads and writes standard netCDF files.

  12. Home versus hospital confinement

    PubMed Central

    Barry, C. N.

    1980-01-01

    The case for hospital rather than home delivery has been powerfully argued, especially in and since the Report of the Peel Committee. Nevertheless, evidence of comparison with other countries, notably the Netherlands, suggests the choice is not necessarily simple. Some general practitioner units are now reporting perinatal mortality rates which are consistently lower than those of specialist units, and recent statistical analyses suggest that the presence of more high risk cases in consultant units does not explain this. The only big controlled home-versus-hospital trial did not lead to a significantly lower perinatal mortality rate in the hospital group. The onus of proof now seems to lie with those who advocate 100 per cent hospital confinement. PMID:7373581

  13. Coronal electron confinement by double layers

    SciTech Connect

    Li, T. C.; Drake, J. F.; Swisdak, M.

    2013-12-01

    In observations of flare-heated electrons in the solar corona, a longstanding problem is the unexplained prolonged lifetime of the electrons compared to their transit time across the source. This suggests confinement. Recent particle-in-cell (PIC) simulations, which explored the transport of pre-accelerated hot electrons through ambient cold plasma, showed that the formation of a highly localized electrostatic potential drop, in the form of a double layer (DL), significantly inhibited the transport of hot electrons. The effectiveness of confinement by a DL is linked to the strength of the DL as defined by its potential drop. In this work, we investigate the scaling of the DL strength with the hot electron temperature by PIC simulations and find a linear scaling. We demonstrate that the strength is limited by the formation of parallel shocks. Based on this, we analytically determine the maximum DL strength, and also find a linear scaling with the hot electron temperature. The DL strength obtained from the analytic calculation is comparable to that from the simulations. At the maximum strength, the DL is capable of confining a significant fraction of hot electrons in the source.

  14. Coronal Electron Confinement by Double Layers

    NASA Astrophysics Data System (ADS)

    Li, T. C.; Drake, J. F.; Swisdak, M.

    2013-12-01

    In observations of flare-heated electrons in the solar corona, a longstanding problem is the unexplained prolonged lifetime of the electrons compared to their transit time across the source. This suggests confinement. Recent particle-in-cell (PIC) simulations, which explored the transport of pre-accelerated hot electrons through ambient cold plasma, showed that the formation of a highly localized electrostatic potential drop, in the form of a double layer (DL), significantly inhibited the transport of hot electrons. The effectiveness of confinement by a DL is linked to the strength of the DL as defined by its potential drop. In this work, we investigate the scaling of the DL strength with the hot electron temperature by PIC simulations and find a linear scaling. We demonstrate that the strength is limited by the formation of parallel shocks. Based on this, we analytically determine the maximum DL strength, and also find a linear scaling with the hot electron temperature. The DL strength obtained from the analytic calculation is comparable to that from the simulations. At the maximum strength, the DL is capable of confining a significant fraction of hot electrons in the source.

  15. suPAR: The Molecular Crystal Ball

    PubMed Central

    Thunø, Maria; Macho, Betina; Eugen-Olsen, Jesper

    2009-01-01

    soluble urokinase Plasminogen Activator Receptor (suPAR) levels reflect inflammation and elevated suPAR levels are found in several infectious diseases and cancer. suPAR exists in three forms; suPARI-III, suPARII-III and suPARI which show different properties due to structural differences. Studies suggest that full-length suPAR is a regulator of uPAR/uPA by acting as uPA-scavenger, whereas the cleaved suPARII-III act as a chemotactic agent promoting the immune response via the SRSRY sequence in the linker-region. This review focus on the various suPAR fragments and their involvement in inflammation and pathogenic processes. We focus on the molecular mechanisms of the suPAR fragments and the link to the inflammatory process, as this could lead to medical applications in infectious and pathological conditions. PMID:19893210

  16. Hot electron confinement in a microwave heated spindle cusp

    SciTech Connect

    Prelas, M.A.

    1991-08-01

    The Plasma Research Laboratory at the University of Missouri-Columbia was established with awards from the McDonnel Douglas Foundation, ARMCO, Union Electric, Black and Vetch, Kansas City Power and Light, the National Science Foundation, and DOE. The Plasma Research Lab's major effort is the Missouri Magnetic Mirror (MMM or M{sup 3}) Project. The technical goals of MMM have been (1) Diagnostic Development, (2) Plasma Physics in the Cusp geometry, (3) plasma-wall interactions, (4) impurity effects in a steady-state plasma, and (5) Development of Diagnostics for use in harsh plasma processing environments. The other major goal of MMM has remained providing a facility for hands-on training in experimental plasma physics. The major experimental facility of MMM is the MMM Modified Experiment (M4X). Other research efforts in the Plasma Research Laboratory include small efforts in cold fusion, toroidal magnetic confinement, and inertial confinement and a potentially major effort in direct conversion of nuclear energy.

  17. Hot electron confinement in a microwave heated spindle cusp

    NASA Astrophysics Data System (ADS)

    Prelas, M. A.

    1991-08-01

    The Plasma Research Laboratory at the University of Missouri-Columbia was established with awards from the McDonnell Douglas Foundation, ARMCO, Union Electric, Black and Vetch, Kansas City Power and Light, the National Science Foundation, and DOE. The Plasma Research Lab's major effort is the Missouri Magnetic Mirror (MMM or M(exp 3)) Project. The technical goals of MMM have been (1) Diagnostic Development, (2) Plasma Physics in the Cusp geometry, (3) plasma-wall interactions, (4) impurity effects in a steady-state plasma, and (5) Development of Diagnostics for use in harsh plasma processing environments. The other major goal of MMM has remained providing a facility for hands-on training in experimental plasma physics. The major experimental facility of MMM is the MMM Modified Experiment (M4X). Other research efforts in the Plasma Research Laboratory include small efforts in cold fusion, toroidal magnetic confinement, and inertial confinement and a potentially major effort in direct conversion of nuclear energy.

  18. PLASMA DEVICE

    DOEpatents

    Baker, W.R.; Brathenahl, A.; Furth, H.P.

    1962-04-10

    A device for producing a confined high temperature plasma is described. In the device the concave inner surface of an outer annular electrode is disposed concentrically about and facing the convex outer face of an inner annular electrode across which electrodes a high potential is applied to produce an electric field there between. Means is provided to create a magnetic field perpendicular to the electric field and a gas is supplied at reduced pressure in the area therebetween. Upon application of the high potential, the gas between the electrodes is ionized, heated, and under the influence of the electric and magnetic fields there is produced a rotating annular plasma disk. The ionized plasma has high dielectric constant properties. The device is useful as a fast discharge rate capacitor, in controlled thermonuclear research, and other high temperature gas applications. (AEC)

  19. Global confinement analysis. Final report, May 1, 1992--April 31, 1994

    SciTech Connect

    Riedel, K.S.

    1994-07-22

    A brief description of the task: (1) Analyze confinement databases to development predictions for ITER, and identify and quantify major sources of continement uncertainty. (2) Determine the parametric dependencies of the temperature and density profiles for reactor relevant plasmas.

  1. Thermonuclear ignition in inertial confinement fusion and comparison with magnetic confinement

    SciTech Connect

    Betti, R.; Chang, P. Y.; Anderson, K. S.; Nora, R.; Spears, B. K.; Edwards, J.; Lindl, J. D.; Fatenejad, M.; McCrory, R. L.; Shvarts, D.

    2010-05-15

    The physics of thermonuclear ignition in inertial confinement fusion (ICF) is presented in the familiar frame of a Lawson-type criterion. The product of the plasma pressure and confinement time Ptau for ICF is cast in terms of measurable parameters and its value is estimated for cryogenic implosions. An overall ignition parameter chi including pressure, confinement time, and temperature is derived to complement the product Ptau. A metric for performance assessment should include both chi and Ptau. The ignition parameter and the product Ptau are compared between inertial and magnetic-confinement fusion. It is found that cryogenic implosions on OMEGA[T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] have achieved Ptauapprox1.5 atm s comparable to large tokamaks such as the Joint European Torus [P. H. Rebut and B. E. Keen, Fusion Technol. 11, 13 (1987)] where Ptauapprox1 atm s. Since OMEGA implosions are relatively cold (Tapprox2 keV), their overall ignition parameter chiapprox0.02-0.03 is approx5x lower than in JET (chiapprox0.13), where the average temperature is about 10 keV.

  2. Tgermonuclear Ignition in Inertial Confinement Fusion and Comparison with Magnetic Confinement

    SciTech Connect

    Betti, R.; Chang, P.Y.; Spears, B.K.; Anderson, K.S.; Edwards, J.; Fatenejad, M.; Lindl, J.D.; McCrory, R.L.; Nora, R.; Shvarts, D.

    2010-04-23

    The physics of thermonuclear ignition in inertial confinement fusion (ICF) is presented in the familiar frame of a Lawson-type criterion. The product of the plasma pressure and confinement time Ptau for ICF is cast in terms of measurable parameters and its value is estimated for cryogenic implosions. An overall ignition parameter chi including pressure, confinement time, and temperature is derived to complement the product Ptau. A metric for performance assessment should include both chi and Ptau. The ignition parameter and the product Ptau are compared between inertial and magnetic-confinement fusion. It is found that cryogenic implosions on OMEGA [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] have achieved Ptau ~ 1.5 atm s comparable to large tokamaks such as the Joint European Torus [P. H. Rebut and B. E. Keen, Fusion Technol. 11, 13 (1987)] where Ptau ~ 1 atm s. Since OMEGA implosions are relatively cold (T ~ 2 keV), their overall ignition parameter chi ~ 0.02–0.03 is ~5X lower than in JET (chi ~ 0.13), where the average temperature is about 10 keV.

  3. Directed and persistent movement arises from mechanochemistry of the ParA/ParB system.

    PubMed

    Hu, Longhua; Vecchiarelli, Anthony G; Mizuuchi, Kiyoshi; Neuman, Keir C; Liu, Jian

    2015-12-22

    The segregation of DNA before cell division is essential for faithful genetic inheritance. In many bacteria, segregation of low-copy number plasmids involves an active partition system composed of a nonspecific DNA-binding ATPase, ParA, and its stimulator protein ParB. The ParA/ParB system drives directed and persistent movement of DNA cargo both in vivo and in vitro. Filament-based models akin to actin/microtubule-driven motility were proposed for plasmid segregation mediated by ParA. Recent experiments challenge this view and suggest that ParA/ParB system motility is driven by a diffusion ratchet mechanism in which ParB-coated plasmid both creates and follows a ParA gradient on the nucleoid surface. However, the detailed mechanism of ParA/ParB-mediated directed and persistent movement remains unknown. Here, we develop a theoretical model describing ParA/ParB-mediated motility. We show that the ParA/ParB system can work as a Brownian ratchet, which effectively couples the ATPase-dependent cycling of ParA-nucleoid affinity to the motion of the ParB-bound cargo. Paradoxically, this resulting processive motion relies on quenching diffusive plasmid motion through a large number of transient ParA/ParB-mediated tethers to the nucleoid surface. Our work thus sheds light on an emergent phenomenon in which nonmotor proteins work collectively via mechanochemical coupling to propel cargos-an ingenious solution shaped by evolution to cope with the lack of processive motor proteins in bacteria.

  4. Directed and persistent movement arises from mechanochemistry of the ParA/ParB system

    PubMed Central

    Hu, Longhua; Vecchiarelli, Anthony G.; Mizuuchi, Kiyoshi; Neuman, Keir C.; Liu, Jian

    2015-01-01

    The segregation of DNA before cell division is essential for faithful genetic inheritance. In many bacteria, segregation of low-copy number plasmids involves an active partition system composed of a nonspecific DNA-binding ATPase, ParA, and its stimulator protein ParB. The ParA/ParB system drives directed and persistent movement of DNA cargo both in vivo and in vitro. Filament-based models akin to actin/microtubule-driven motility were proposed for plasmid segregation mediated by ParA. Recent experiments challenge this view and suggest that ParA/ParB system motility is driven by a diffusion ratchet mechanism in which ParB-coated plasmid both creates and follows a ParA gradient on the nucleoid surface. However, the detailed mechanism of ParA/ParB-mediated directed and persistent movement remains unknown. Here, we develop a theoretical model describing ParA/ParB-mediated motility. We show that the ParA/ParB system can work as a Brownian ratchet, which effectively couples the ATPase-dependent cycling of ParA–nucleoid affinity to the motion of the ParB-bound cargo. Paradoxically, this resulting processive motion relies on quenching diffusive plasmid motion through a large number of transient ParA/ParB-mediated tethers to the nucleoid surface. Our work thus sheds light on an emergent phenomenon in which nonmotor proteins work collectively via mechanochemical coupling to propel cargos—an ingenious solution shaped by evolution to cope with the lack of processive motor proteins in bacteria. PMID:26647183

  5. Potential Ecological Effects of Contaminants in the Exposed Par Pond Sediments

    SciTech Connect

    Paller, M.H.; Wike, L.D.

    1996-08-01

    Sediment and small mammal samples were collected from the exposed sediments of Par Pond in early 1995, shortly before the reservoir was refilled after a 4-year drawdown. Sampling was confined to elevations between 58 and 61 meters (190 and 200 feet) above mean sea level, which includes the sediments likely to be exposed if the Par Pond water level is permitted to fluctuate naturally. Both soil and small mammal samples were analyzed for a number of radionuclides and metals. Some of the soil samples were also analyzed for organic contaminants. The objective of the study was to determine if contaminant levels in the Par Pond sediments were high enough to cause deleterious ecological effects.

  6. Working safely in confined spaces

    SciTech Connect

    Bush, C.; Versweyveld, J. )

    1992-08-13

    Working in confined spaces is a delicate balance of the correct equipment, hazard knowledge, proper training, and common sense. Anything less has potentially deadly consequences. The dangerous atmospheric and physical hazards often encountered in confined spaces must be recognized and accounted for. In addition, procedures and practices must conform to Occupational Safety and health Administration (OSHA) confined space regulations. Last year, three men were asphyxiated while surveying beneath a manhole in Boulder, CO. An area newspaper called the deaths the result of a freak accident. Whatever the cause, entering a manhole without first monitoring the air and posting an outside attendant is both extremely dangerous and a violation of safe entry procedures. The National Institute for Health and Occupational Safety (NIOSH) estimates that millions of workers from a wide range of occupations and industries are exposed to confined space hazards every year. Although confined space deaths are not a new phenomenon, only recently has the problem received serious study. Government regulatory agencies are becoming more involved OSHA recently proposed ruling 1910.146, Permit Required Confined Spaces, to mandate safe entry practices and procedures. The ruling requires all employers to develop a specific action plan for confined space entry, including entry procedures, worker training, safety equipment, and emergency action. This first article defines a confined space and examines some common hazards, including toxic, combustible, and oxygen-deficient atmospheres and combustible dusts. A subsequent article will review the use of test instruments, personal protective equipment, worker training, and emergency response.

  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.

  8. Confined Selective Withdrawal

    NASA Astrophysics Data System (ADS)

    Evangelio, Alvaro; Campo-Cortes, Francisco; Gordillo, Jose Manuel

    2014-11-01

    It is well known that the controlled production of monodisperse simple and composite emulsions possesses uncountable applications in medicine, pharmacy, materials science and industry. Here we present both experiments and slender-body theory regarding the generation of simple emulsions using a configuration that we have called Confined Selective Withdrawal, since it is an improved configuration of the classical Selective Withdrawal. We consider two different situations, namely, the cases when the outer flow Reynolds number is high and low, respectively. Several geometrical configurations and a wide range of viscosity ratios are analyzed so that the physics behind the phenomenon can be fully understood. In addition, we present both experiments and theory regarding the generation of composite emulsions. This phenomenon is only feasible when the outer flow Reynolds number is low enough. In this case, we propose a more complex theory which requires the simultaneous resolution of two interfaces in order to predict the shape of the jet and the sizes of the drops formed. The excellent agreement between our slender-body approximation and the experimental evidence fully validates our theories.

  9. Axisymmetric Tandem Mirrors: Stabilization and Confinement Studies

    SciTech Connect

    Post, R F; Fowler, T K; Bulmer, R; Byers, J; Hua, D; Tung, L

    2004-07-15

    The 'Kinetic Stabilizer' has been proposed as a means of MHD stabilizing an axisymmetric tandem mirror system. The K-S concept is based on theoretical studies by Ryutov, confirmed experimentally in the Gas Dynamic Trap experiment in Novosibirsk. In the K-S beams of ions are directed into the end of an 'expander' region outside the outer mirror of a tandem mirror. These ions, slowed, stagnated, and reflected as they move up the magnetic gradient, produce a low-density stabilizing plasma. At the Lawrence Livermore National Laboratory we have been conducting theoretical and computational studies of the K-S Tandem Mirror. These studies have employed a low-beta code written especially to analyze the beam injection/stabilization process, and a new code SYMTRAN (by Hua and Fowler) that solves the coupled radial and axial particle and energy transport in a K-S TM. Also, a 'legacy' MHD stability code, FLORA, has been upgraded and employed to benchmark the injection/stabilization code and to extend its results to high beta values. The FLORA code studies so far have confirmed the effectiveness of the K-S in stabilizing high-beta (40%) plasmas with stabilizer plasmas the peak pressures of which are several orders of magnitude smaller than those of the confined plasma. Also the SYMTRAN code has shown D-T plasma ignition from alpha particle energy deposition in T-M regimes with strong end plugging. Our studies have confirmed the viability of the K-S-T-M concept with respect to MHD stability and radial and axial confinement. We are continuing these studies in order to optimize the parameters and to examine means for the stabilization of possible residual instability modes, such as drift modes and 'trapped-particle' modes. These modes may in principle be controlled by tailoring the stabilizer plasma distribution and/or the radial potential distribution. In the paper the results to date of our studies are summarized and projected to scope out possible fusion-power versions of the K

  10. Protease-activated receptor-1 (PAR1) and PAR2 but not PAR4 mediate relaxations in lower esophageal sphincter.

    PubMed

    Huang, Shih-Che

    2007-07-01

    Protease-activated receptor-1 (PAR1), PAR2 and PAR4 activation can alter the gastrointestinal motility. To investigate effects mediated by PARs in the lower esophageal sphincter, we measured contraction or relaxation of transverse strips from the guinea-pig lower esophageal sphincter caused by PAR1 (TFLLR-NH2 and SFLLRN-NH2), PAR2 (SLIGKV-NH2 and SLIGRL-NH2) and PAR4 peptide agonists (GYPGKF-NH2, GYPGQV-NH2 and AYPGKF-NH2) as well as PAR protease activators (thrombin and trypsin). In resting lower esophageal sphincter strips, TFLLR-NH2 and SFLLRN-NH2 caused moderate concentration-dependent relaxation whereas thrombin did not cause any relaxation or contraction. Furthermore, in carbachol-contracted strips, TFLLR-NH2 and SFLLRN-NH2 caused marked whereas thrombin caused mild concentration-dependent relaxation. These indicate the existence of PAR1 mediating relaxation. Similarly, in resting lower esophageal sphincter strips, trypsin caused moderate concentration-dependent relaxation whereas SLIGRL-NH2 and SLIGKV-NH2 did not cause any relaxation or contraction. In addition, in carbachol-contracted strips, trypsin caused marked whereas SLIGRL-NH2 and SLIGKV-NH2 caused mild concentration-dependent relaxation. These indicate the existence of PAR2 mediating relaxation. The relaxant response of thrombin, TFLLR-NH2, trypsin and SLIGKV-NH2 was insensitive to atropine or tetrodotoxin, suggesting a direct effect. The relaxant response of trypsin was not affected by apamin, charybdotoxin, indomethacin and capsaicin but was attenuated by NG-nitro-L-arginine methyl ester, indicating involvement of NO. FSLLR-NH2, a PAR1 control peptide, and VKGILS-NH2, a PAR2 control peptide, as well as all three PAR4 peptide agonists, GYPGKF-NH2, GYPGQV-NH2 and AYPGKF-NH2, did not cause any relaxation or contraction. Taken together, these results demonstrate that PAR1 and PAR2 but not PAR4 mediate relaxations in the guinea-pig lower esophageal sphincter. PMID:17335921

  11. Tokamak confinement projections and performance goals

    SciTech Connect

    Uckan, N.A.

    1988-01-01

    One key quantity to be determined in the design of burning-plasma devices (CIT, ITER, reactors, etc.) is the level of plasma current (I) required to meet the desired plasma performance goals (ignition, high Q, etc.) and device objectives (fusion power, wall loading, current drive power, etc.). It is shown that these goals and objectives can be expressed in terms of the ''figure-of-merit'' parameter IA/sup alpha//R/sup x/(/approximately/f(LB/sup y/), where A is the aspect ratio, R is the major radius, L(= R, a) is the characteristic length, B is the toroidal magnetic field on axis, and the exponents ..cap alpha.. /approximately/ 1 +- 0.5 and x /approximately/ 0-0.5 (y /approximately/ 1-2) depend on the confinement assumptions and operational limits. To reach ignition or high Q, the main goal is to optimize IA/sup alpha//R/sup x/, subject to other engineering design constraints. In a CIT-like device (with R /approximately/ 2 m, kappa /approximately/ 2, q/sub psi/ greater than or equal to 3), the ignition requirements is I(A/3)/sup alpha/ /approximately/ 9-15 MA for ''enhanced'' L-mode (H-mode) confinement scaling expressions; an ITER-like device (with R /approximately/ 5-6 m, kappa /approximately/ 2, q/sub psi/ greater than or equal to 3) would require I(A/3)/sup alpha/ /approximately/ 15-25 MA. These requirements are embodied in the present CIT (with I /approximately/ 11 MA, A /approximately 3.25) and ITER (with I /approximately/ 18-22, A /approximately/ 3.1-2.6) designs. 12 refs., 1 fig., 3 tabs.

  12. Runaway electrons and magnetic island confinement

    NASA Astrophysics Data System (ADS)

    Boozer, Allen H.

    2016-08-01

    The breakup of magnetic surfaces is a central feature of ITER planning for the avoidance of damage due to runaway electrons. Rapid thermal quenches, which lead to large accelerating voltages, are thought to be due to magnetic surface breakup. Impurity injection to avoid and to mitigate both halo and runaway electron currents utilizes massive gas injection or shattered pellets. The actual deposition is away from the plasma center, and the breakup of magnetic surfaces is thought to spread the effects of the impurities across the plasma cross section. The breakup of magnetic surfaces would prevent runaway electrons from reaching relativistic energies were it not for the persistence of non-intercepting flux tubes. These are tubes of magnetic field lines that do not intercept the walls. In simulations and in magnetic field models, non-intercepting flux tubes are found to persist near the magnetic axis and in the cores of magnetic islands even when a large scale magnetic surface breakup occurs. As long as a few magnetic surfaces reform before all of the non-intercepting flux tubes dissipate, energetic electrons confined and accelerated in these flux tubes can serve as the seed electrons for a transfer of the overall plasma current from thermal to relativistic carriers. The acceleration of electrons is particularly strong because of the sudden changes in the poloidal flux that naturally occur in a rapid magnetic relaxation. The physics of magnetic islands as non-intercepting flux tubes is studied. Expressions are derived for (1) the size of islands required to confine energetic runaway electrons, (2) the accelerating electric field in an island, (3) the increase or reduction in the size of an island by the runaway electron current, (4) the approximate magnitude of the runaway current in an island, and (5) the time scale for the evolution of an island.

  13. Thermal noise in confined fluids.

    PubMed

    Sanghi, T; Aluru, N R

    2014-11-01

    In this work, we discuss a combined memory function equation (MFE) and generalized Langevin equation (GLE) approach (referred to as MFE/GLE formulation) to characterize thermal noise in confined fluids. Our study reveals that for fluids confined inside nanoscale geometries, the correlation time and the time decay of the autocorrelation function of the thermal noise are not significantly different across the confinement. We show that it is the strong cross-correlation of the mean force with the molecular velocity that gives rise to the spatial anisotropy in the velocity-autocorrelation function of the confined fluids. Further, we use the MFE/GLE formulation to extract the thermal force a fluid molecule experiences in a MD simulation. Noise extraction from MD simulation suggests that the frequency distribution of the thermal force is non-Gaussian. Also, the frequency distribution of the thermal force near the confining surface is found to be different in the direction parallel and perpendicular to the confinement. We also use the formulation to compute the noise correlation time of water confined inside a (6,6) carbon-nanotube (CNT). It is observed that inside the (6,6) CNT, in which water arranges itself in a highly concerted single-file arrangement, the correlation time of thermal noise is about an order of magnitude higher than that of bulk water.

  14. Density shocks in confined microswimmers

    NASA Astrophysics Data System (ADS)

    Tsang, Alan Cheng Hou; Kanso, Eva; Biodynamics Team

    2014-11-01

    Motile microorganisms are often subject to different types of boundary confinement in their natural environment, but the effects of confinement on their dynamics are poorly understood. We consider an idealized model of confined microswimmers restricted to move in a two-dimensional Hele-Shaw cell. We then impose two different types of boundary confinement: circular and sidewalls confinement. We study how boundaries trigger the emergence of global modes. In the case of circular confinement, the microswimmers can spontaneously organize themselves into a single vortex state when the radius of the circular boundary is below a certain critical value, reminiscent to what have been observed in recent experiments of bacterial suspensions. In the case of sidewalls confinement in a rectangular channel, the microswimmers form density shock, via interaction with the sidewalls and background flow. We show that, through controlling the strength of background flow, we can manipulate the density shock to form at the back or front of the swimmer clusters or the suppression of the shock which gives rise to a uniform traveling wave of swimmers.

  15. Thermal noise in confined fluids

    NASA Astrophysics Data System (ADS)

    Sanghi, T.; Aluru, N. R.

    2014-11-01

    In this work, we discuss a combined memory function equation (MFE) and generalized Langevin equation (GLE) approach (referred to as MFE/GLE formulation) to characterize thermal noise in confined fluids. Our study reveals that for fluids confined inside nanoscale geometries, the correlation time and the time decay of the autocorrelation function of the thermal noise are not significantly different across the confinement. We show that it is the strong cross-correlation of the mean force with the molecular velocity that gives rise to the spatial anisotropy in the velocity-autocorrelation function of the confined fluids. Further, we use the MFE/GLE formulation to extract the thermal force a fluid molecule experiences in a MD simulation. Noise extraction from MD simulation suggests that the frequency distribution of the thermal force is non-Gaussian. Also, the frequency distribution of the thermal force near the confining surface is found to be different in the direction parallel and perpendicular to the confinement. We also use the formulation to compute the noise correlation time of water confined inside a (6,6) carbon-nanotube (CNT). It is observed that inside the (6,6) CNT, in which water arranges itself in a highly concerted single-file arrangement, the correlation time of thermal noise is about an order of magnitude higher than that of bulk water.

  16. Enhanced coupling of optical energy during liquid-confined metal ablation

    SciTech Connect

    Kang, Hyun Wook; Welch, Ashley J.

    2015-10-21

    Liquid-confined laser ablation was investigated with various metals of indium, aluminum, and nickel. Ablation threshold and rate were characterized in terms of surface deformation, transient acoustic responses, and plasma emissions. The surface condition affected the degree of ablation dynamics due to variations in reflectance. The liquid confinement yielded up to an order of larger ablation crater along with stronger acoustic transients than dry ablation. Enhanced ablation performance resulted possibly from effective coupling of optical energy at the interface during explosive vaporization, plasma confinement, and cavitation. The deposition of a liquid layer can induce more efficient ablation for laser metal processing.

  17. Effects of internal inductance on the energy confinement time by using the solution of equilibrium problem

    NASA Astrophysics Data System (ADS)

    Asif, M.

    2016-06-01

    In this work, dependence of energy confinement time on plasma internal inductance has been studied by using the solution of Grad-Shafranov equation (GSE) for circular cross-section HT-7 tokamak. For this, the Shafranov parameter (asymmetry factor) and poloidal beta were obtained from solution of GSE. Then we can find the dependence of energy confinement time, on plasma internal inductance. It is observed that the maximum energy confinement time is related to the low values of internal inductance (0.7 < li < 0.9).

  18. Regimes of improved confinement and stability in DIII-D obtained through current profile modifications

    SciTech Connect

    Lao, L.L.; Ferron, J.R.; Taylor, T.S.; Chan, V.S.; Osborne, T.H.; Burrell, K.H.; Chu, M.S.; DeBoo, J.C.; Greenfield, C.M.; Groebner, R.J.; Jackson, G.L.; St. John, H.; Strait, E.J.; Thompson, S.J.; Turnbull, A.D.; Doyle, E.J.; Rettig, C.; James, R.; Wroblewski, D.; Lazarus, E.A.; Zohm, H.

    1992-09-01

    Several regimes of improved confinement and stability have been obtained in recent experiments in the DIII-D tokamak by dynamically varying the toroidal current density profile to transiently produce a poloidal magnetic field profile with more favorable confinement and stability properties. A very peaked current density profile with high plasma internal inductance, {ell}{sub i}, is produced either by a rapid change in the plasma poloidal cross section or by a rapid change in the total plasma current. Values of thermal energy confinement times nearly 1.8 times the JET/DIII-D ELM-free H-mode thermal confinement scaling are obtained. The confinement enhancement factor over the ITER89-P L-mode confinement scaling, H, is as high as 3. Normalized toroidal beta, {beta}{sub N}, greater than 6%-m-T/MA and values of the product {beta}{sub N}H greater than 15 have also been obtained. Both the confinement and the maximum achievable {beta} vary with {ell}{sub i} and decrease as the current profile relaxes. For strongly shaped H-mode discharges, in addition to the current density profile peakedness, as measured by {ell}{sub i} other current profile parameters, such as its distribution near the edge region, may also affect the confinement enhancement.

  19. Regimes of improved confinement and stability in DIII-D obtained through current profile modifications

    SciTech Connect

    Lao, L.L.; Ferron, J.R.; Taylor, T.S.; Chan, V.S.; Osborne, T.H.; Burrell, K.H.; Chu, M.S.; DeBoo, J.C.; Greenfield, C.M.; Groebner, R.J.; Jackson, G.L.; St. John, H.; Strait, E.J.; Thompson, S.J.; Turnbull, A.D. ); Doyle, E.J.; Rettig, C. ); James, R.; Wroblewski, D. (Lawrence Livermore National Lab., CA (United Sta

    1992-09-01

    Several regimes of improved confinement and stability have been obtained in recent experiments in the DIII-D tokamak by dynamically varying the toroidal current density profile to transiently produce a poloidal magnetic field profile with more favorable confinement and stability properties. A very peaked current density profile with high plasma internal inductance, [ell][sub i], is produced either by a rapid change in the plasma poloidal cross section or by a rapid change in the total plasma current. Values of thermal energy confinement times nearly 1.8 times the JET/DIII-D ELM-free H-mode thermal confinement scaling are obtained. The confinement enhancement factor over the ITER89-P L-mode confinement scaling, H, is as high as 3. Normalized toroidal beta, [beta][sub N], greater than 6%-m-T/MA and values of the product [beta][sub N]H greater than 15 have also been obtained. Both the confinement and the maximum achievable [beta] vary with [ell][sub i] and decrease as the current profile relaxes. For strongly shaped H-mode discharges, in addition to the current density profile peakedness, as measured by [ell][sub i] other current profile parameters, such as its distribution near the edge region, may also affect the confinement enhancement.

  20. Spatial confinement of muonium atoms

    NASA Astrophysics Data System (ADS)

    Khaw, K. S.; Antognini, A.; Prokscha, T.; Kirch, K.; Liszkay, L.; Salman, Z.; Crivelli, P.

    2016-08-01

    We report the achievement of spatial confinement of muonium atoms (the bound state of a positive muon and an electron). Muonium emitted into a vacuum from mesoporous silica reflects between two SiO2 confining surfaces separated by 1 mm. From the data, one can extract that the reflection probability on the confining surfaces kept at 100 K is about 90% and the reflection process is well described by a cosine law. This technique enables new experiments with this exotic atomic system and is a very important step towards a measurement of the 1 S -2 S transition frequency using continuous-wave laser spectroscopy.

  1. A double-layer based model of ion confinement in electron cyclotron resonance ion source

    SciTech Connect

    Mascali, D. Neri, L.; Celona, L.; Castro, G.; Gammino, S.; Ciavola, G.; Torrisi, G.; Sorbello, G.

    2014-02-15

    The paper proposes a new model of ion confinement in ECRIS, which can be easily generalized to any magnetic configuration characterized by closed magnetic surfaces. Traditionally, ion confinement in B-min configurations is ascribed to a negative potential dip due to superhot electrons, adiabatically confined by the magneto-static field. However, kinetic simulations including RF heating affected by cavity modes structures indicate that high energy electrons populate just a thin slab overlapping the ECR layer, while their density drops down of more than one order of magnitude outside. Ions, instead, diffuse across the electron layer due to their high collisionality. This is the proper physical condition to establish a double-layer (DL) configuration which self-consistently originates a potential barrier; this “barrier” confines the ions inside the plasma core surrounded by the ECR surface. The paper will describe a simplified ion confinement model based on plasma density non-homogeneity and DL formation.

  2. EDITORIAL: Energetic particles in magnetic confinement systems

    NASA Astrophysics Data System (ADS)

    Toi, K.

    2006-10-01

    Energetic alpha particle physics plays an obviously crucial role in burning fusion plasmas. Good confinement of them is required to sustain fusion burn and to avoid damage of the first wall. Because of this importance for nuclear fusion research, Y. Kolesnichenko and the late D. Sigmar initiated a series of IAEA technical (committee) meetings (TCM, since the 8th meeting TM) in order to exchange information on the behaviour of energetic particles in magnetic confinement devices. The role of the TMs has become increasingly important since burning plasma projects such as ITER are in preparation. After every TM, invited speakers are encouraged to publish an adapted and extended version of their contributions to the meeting as an article in a special issue of Nuclear Fusion. An exception was the 8th TM the articles of which were published in a special issue of Plasma Physics and Controlled Fusion (2004 46 S1-118). These special issues attract much interest in the subject. The 9th IAEA TM of this series was held in Takayama, Japan, 9-11 November 2005, and 53 papers including 16 invited talks were presented. A total of 11 papers based on these invited talks are included in this special issue of Nuclear Fusion and are preceded by a conference summary. Experimental results of energetic ion driven global instabilities such as Alfvén eigenmodes (AEs), energetic particle modes (EPMs) and fishbone instabilities were presented from several tokamaks (JET, JT-60U, DIII-D and ASDEX Upgrade), helical/stellarator devices (LHD and CHS) and spherical tori (NSTX and MAST). Experimental studies from JET and T-10 tokamaks on the interaction of ion cyclotron waves with energetic ions and runaway electrons were also presented. Theoretical works on AEs, EPMs and nonlinear phenomena induced by energetic particles were presented and compared with experimental data. Extensive numerical codes have been developed and applied to obtain predictions of energetic particle behaviour in future ITER

  3. Confined explosive joining of tubes

    NASA Technical Reports Server (NTRS)

    Bement, L. J.

    1979-01-01

    Technique uses explosive ribbon to join and seal tubes hermetically while totally confining explosive products, such as smoke, light, and sound. Only click is audible. Process yields joints of the same strengths as parent metal.

  4. Assessing confinement in coastal lagoons.

    PubMed

    Canu, Donata Melaku; Solidoro, Cosimo; Umgiesser, Georg; Cucco, Andrea; Ferrarin, Christian

    2012-11-01

    Measures of transport scale in aquatic systems can contribute to the formulation of definitions of indicators of the system's ecological properties. This paper addresses confinement, a specific transport scale proposed by biological scientists as a parameter that can capture and synthesize the principal properties that determine the spatial structure of biological communities in transitional environments. Currently, there is no direct experimental measure of confinement. In this study, a methodology based on the accumulation rate within a lagoon of a passive tracer of marine origin is proposed, the influences of different factors in the calculation of confinement are analyzed, and general recommendations are derived. In particular, we analyze the spatial and the temporal variability of confinement and its sensitivity to the seasonal variability of climatic forcing, the inputs from rivers and the parameterization of the tidal exchanges. The Lagoon of Venice is used as a case study.

  5. PAR for the Course: A Congruent Pedagogical Approach for a PAR Methods Class

    ERIC Educational Resources Information Center

    Hammond, Joyce D.; Hicks, Maria; Kalman, Rowenn; Miller, Jason

    2005-01-01

    In the past two years, three graduate students and a senior faculty member have co-taught a participatory action research (PAR) course to undergraduate and graduate students. In this article the co-teachers advocate a set of pedagogical principles and practices in a PAR-oriented classroom that establishes congruency with community PAR projects in…

  6. Confined flow of polymer blends.

    PubMed

    Tufano, C; Peters, G W M; Meijer, H E H

    2008-05-01

    The influence of confinement on the steady-state morphology of two different emulsions is investigated. The blends, made from polybutene (PB) in polydimethylsiloxane (PDMS) and polybutadiene (PBD) in PDMS, are sheared between two parallel plates, mostly with a standard gap spacing of 40 microm, in the range of shear rates at which the transition from "bulk" behavior toward "confined" behavior is observed. For both cases, the influence of the concentration was systematically investigated, as well as the shear rate effects on the final steady-state morphology. By decreasing the shear rate, for each blend, the increasing droplets, i.e., increasing confinement for a fixed gap spacing, arrange themselves first into two layers, and when the degree of confinement reaches an even higher value, a single layer of droplets is formed. The ratio between the drop diameters and the gap spacing at which this transition occurs is always lower than 0.5. While decreasing the shear rate, the degree of confinement increases due to drop coalescence. Droplets arrange themselves in superstructures like ordered pearl necklaces and, at the lower shear rates, strings. The aspect ratio and the width of the droplet obtained from optical micrographs are compared to predictions of the single droplet Maffettone-Minale model (MM model(1)). It is found that the theory, meant for unconfined shear flow, is not able to predict the drop deformation when the degree of confinement is above a critical value that depends on the blends considered and the shear rate applied. A recently developed extension of the MM model is reported by Minale (M model(2)) where the effect of the confinement is included by using the Shapira-Haber correction.3 Further extending this M model, by incorporating an effective viscosity as originally proposed by Choi and Showalter,4 we arrive at the mM model that accurately describes the experiments of blends in confined flow. PMID:18348582

  7. Magnetic-confinement fusion

    NASA Astrophysics Data System (ADS)

    Ongena, J.; Koch, R.; Wolf, R.; Zohm, H.

    2016-05-01

    Our modern society requires environmentally friendly solutions for energy production. Energy can be released not only from the fission of heavy nuclei but also from the fusion of light nuclei. Nuclear fusion is an important option for a clean and safe solution for our long-term energy needs. The extremely high temperatures required for the fusion reaction are routinely realized in several magnetic-fusion machines. Since the early 1990s, up to 16 MW of fusion power has been released in pulses of a few seconds, corresponding to a power multiplication close to break-even. Our understanding of the very complex behaviour of a magnetized plasma at temperatures between 150 and 200 million °C surrounded by cold walls has also advanced substantially. This steady progress has resulted in the construction of ITER, a fusion device with a planned fusion power output of 500 MW in pulses of 400 s. ITER should provide answers to remaining important questions on the integration of physics and technology, through a full-size demonstration of a tenfold power multiplication, and on nuclear safety aspects. Here we review the basic physics underlying magnetic fusion: past achievements, present efforts and the prospects for future production of electrical energy. We also discuss questions related to the safety, waste management and decommissioning of a future fusion power plant.

  8. Par Pond vegetation status Summer 1995 -- Summary

    SciTech Connect

    Mackey, H.E. Jr.; Riley, R.S.

    1996-01-01

    The water level of Par Pond was lowered approximately 20 feet in mid-1991 in order to protect downstream residents from possible dam failure suggested by subsidence on the downstream slope of the dam and to repair the dam. This lowering exposed both emergent and nonemergent macrophyte beds to drying conditions resulting in extensive losses. A survey of the newly emergent, shoreline aquatic plant communities of Par Pond began in June 1995, three months after the refilling of Par Pond to approximately 200 feet above mean sea level. These surveys continued in July, September, and late October, 1995. Communities similar to the pre-drawdown, Par Pond aquatic plant communities are becoming re-established. Emergent beds of maidencane, lotus, waterlily, and watershield are extensive and well developed. Cattail occurrence continued to increase during the summer, but large beds common to Par Pond prior to the drawdown have not formed. Estimates from SPOT HRV, remote sensing satellite data indicated that as much as 120 hectares of emergent wetlands vegetation may have been present along the Par Pond shoreline by early October, 1995. To track the continued development of macrophytes in Par Pond, future surveys throughout 1996 and 1997, along with the continued evaluation of satellite data to map the areal extent of the macrophyte beds of Par Pond, are planned.

  9. A matrix metalloprotease-PAR1 system regulates vascular integrity, systemic inflammation and death in sepsis

    PubMed Central

    Tressel, Sarah L; Kaneider, Nicole C; Kasuda, Shogo; Foley, Caitlin; Koukos, Georgios; Austin, Karyn; Agarwal, Anika; Covic, Lidija; Opal, Steven M; Kuliopulos, Athan

    2011-01-01

    Sepsis is a deadly disease characterized by the inability to regulate the inflammatory–coagulation response in which the endothelium plays a key role. The cause of this perturbation remains poorly understood and has hampered the development of effective therapeutics. Matrix metalloproteases (MMPs) are involved in the host response to pathogens, but can also cause uncontrolled tissue damage and contribute to mortality. We found that human sepsis patients had markedly elevated plasma proMMP-1 and active MMP-1 levels, which correlated with death at 7 and 28 days after diagnosis. Likewise, septic mice had increased plasma levels of the MMP-1 ortholog, MMP-1a. We identified mouse MMP-1a as an agonist of protease-activated receptor-1 (PAR1) on endothelial cells. MMP-1a was released from endothelial cells in septic mice. Blockade of MMP-1 activity suppressed endothelial barrier disruption, disseminated intravascular coagulation (DIC), lung vascular permeability as well as the cytokine storm and improved survival, which was lost in PAR1-deficient mice. Infusion of human MMP-1 increased lung vascular permeability in normal wild-type mice but not in PAR1-deficient mice. These findings implicate MMP-1 as an important activator of PAR1 in sepsis and suggest that therapeutics that target MMP1-PAR1 may prove beneficial in the treatment of sepsis. PMID:21591259

  10. Étude des modifications structurales de l'eau confinée dans le gel de silice

    NASA Astrophysics Data System (ADS)

    Fouzri, A.; Dorbez-Sridi, R.; Oumezzine, M.

    2004-11-01

    Les modifications structurales de l'eau confinée dans le gel de silice en poudre en fonction du taux d'hydratation sont étudiées par calorimétrie différentielle à balayage et par diffusion des rayons X. L'analyse thermique par DSC a permis de montrer que pour les faibles taux d'hydratation (≤ 50%) l'eau est complètement confinée dans les pores alors que pour les forts taux d'hydratation (>50%) l'eau se trouve aussi bien dans les pores qu'autour des grains de la silice. L'apparition de la glace cubique lors du refroidissement de l'eau confinée dans le gel de silice prouve que l'interaction eau-silice ne peut être négligée lors de la détermination du signal de l'eau. L'extraction du signal, diffusé uniquement par l'eau confinée, à partir des intensités diffusées par le gel de silice à deux taux d'hydratation distincts, révèle dans les fonctions de corrélation de paire un pic à 3.7Å qui ne peut être attribué qu'à une corrélation oxygène-oxygène inexistante dans l'eau massique et résultant de la déformation du réseau tétraédrique des molécules d'eau sous l'effet du confinement et de la proximité d'une surface.

  11. Dynamics of laser-blow-off induced Li plume in confined geometry

    SciTech Connect

    Kumar, Bhupesh; Singh, R K; Kumar, Ajai

    2013-08-15

    Dynamics of Li plasma plume created by laser-blow-off technique in air ambient is reported. Plasma plume dynamics and its optical emission are investigated in planar and confined geometries using time resolved shadowgraph imaging and optical emission spectroscopy. Significant differences in the plasma characteristics in confined geometry are quantitatively investigated by comparing the plasma parameters (temperature and density) in free expansion and confined geometry configurations. Dynamics and physical parameters of the primary as well as the reflected shock waves (in confined geometry) and their interactions with expanding plasma are briefly addressed. A large enhancement in the emission intensities of Li I 610.3 nm (2p {sup 2}P{sub 1/2,3/2}← 3d {sup 2}P{sub 3/2,5/2}) and 670.8 nm (2s {sup 2}S{sub 1/2}← 2p {sup 2}P{sub 1/2,3/2}) is correlated with the shock wave dynamics in the two geometries. Strong self reversal in the neutral emission infers an increase in the population density of neutrals within the confined plasma plume.

  12. Magnetically confined wind shocks in X-rays - A review

    NASA Astrophysics Data System (ADS)

    ud-Doula, Asif; Nazé, Yaël

    2016-09-01

    A subset (∼ 10%) of massive stars present strong, globally ordered (mostly dipolar) magnetic fields. The trapping and channeling of their stellar winds in closed magnetic loops leads to magnetically confined wind shocks (MCWS), with pre-shock flow speeds that are some fraction of the wind terminal speed. These shocks generate hot plasma, a source of X-rays. In the last decade, several developments took place, notably the determination of the hot plasma properties for a large sample of objects using XMM and Chandra, as well as fully self-consistent MHD modeling and the identification of shock retreat effects in weak winds. Despite a few exceptions, the combination of magnetic confinement, shock retreat and rotation effects seems to be able to account for X-ray emission in massive OB stars. Here we review these new observational and theoretical aspects of this X-ray emission and envisage some perspectives for the next generation of X-ray observatories.

  13. Microinstability-based model for anomalous thermal confinement in tokamaks

    SciTech Connect

    Tang, W.M.

    1986-03-01

    This paper deals with the formulation of microinstability-based thermal transport coefficients (chi/sub j/) for the purpose of modelling anomalous energy confinement properties in tokamak plasmas. Attention is primarily focused on ohmically heated discharges and the associated anomalous electron thermal transport. An appropriate expression for chi/sub e/ is developed which is consistent with reasonable global constraints on the current and electron temperature profiles as well as with the key properties of the kinetic instabilities most likely to be present. Comparisons of confinement scaling trends predicted by this model with the empirical ohmic data base indicate quite favorable agreement. The subject of anomalous ion thermal transport and its implications for high density ohmic discharges and for auxiliary-heated plasmas is also addressed.

  14. ParAB Partition Dynamics in Firmicutes: Nucleoid Bound ParA Captures and Tethers ParB-Plasmid Complexes

    PubMed Central

    Lioy, Virginia S.; Volante, Andrea; Soberón, Nora E.; Lurz, Rudi; Ayora, Silvia; Alonso, Juan C.

    2015-01-01

    In Firmicutes, small homodimeric ParA-like (δ2) and ParB-like (ω2) proteins, in concert with cis-acting plasmid-borne parS and the host chromosome, secure stable plasmid inheritance in a growing bacterial population. This study shows that (ω:YFP)2 binding to parS facilitates plasmid clustering in the cytosol. (δ:GFP)2 requires ATP binding but not hydrolysis to localize onto the cell’s nucleoid as a fluorescent cloud. The interaction of (δ:CFP)2 or δ2 bound to the nucleoid with (ω:YFP)2 foci facilitates plasmid capture, from a very broad distribution, towards the nucleoid and plasmid pairing. parS-bound ω2 promotes redistribution of (δ:GFP)2, leading to the dynamic release of (δ:GFP)2 from the nucleoid, in a process favored by ATP hydrolysis and protein-protein interaction. (δD60A:GFP)2, which binds but cannot hydrolyze ATP, also forms unstable complexes on the nucleoid. In the presence of ω2, (δD60A:GFP)2 accumulates foci or patched structures on the nucleoid. We propose that (δ:GFP)2 binding to different nucleoid regions and to ω2-parS might generate (δ:GFP)2 gradients that could direct plasmid movement. The iterative pairing and unpairing cycles may tether plasmids equidistantly on the nucleoid to ensure faithful plasmid segregation by a mechanism compatible with the diffusion-ratchet mechanism as proposed from in vitro reconstituted systems. PMID:26161642

  15. Density Limits in Toroidal Magnetic Confinement Experiments

    NASA Astrophysics Data System (ADS)

    Greenwald, Martin

    2001-10-01

    The density limit represents one of the fundamental operating boundaries for magnetic confinement devices - one with practical importance to the goal of fusion power. With fusion reactivity maximized at a plasma temperature on the order of 10 keV and a reaction rate scaling as n^2, an optimum density can be calculated which is not guaranteed to be achievable in any given device. Unlike operational limits for plasma current or pressure, the density limit cannot be explained by magneto-hydrodynamics alone. There is general agreement that the proximate cause for the disruptive limit in the tokamak is cooling of the plasma edge and subsequent current profile shrinkage. The edge cooling may be dominated by atomic physics processes or as suggested in recent experiments, by anomalous transport. A similar picture is emerging for the reversed field pinch (RFP), while the limit in stellarators is apparently due to loss of thermal equilibrium from radiation. Empirical scaling laws in which the maximum plasma density is proportional to the average current density have been fairly successful in predicting the limit for subsequent experiments. Surprisingly, the density limits found in tokamaks and RFPs are virtually identical. Currentless stellarators reach similar density limits, though the expression needs to be recast in terms of the rotational transform. While scaling laws have done a reasonable job in describing data from many recent experiments, they can only give hints at the underlying physics. Understanding the mechanism for the density limit is crucial for extrapolating machine performance into untested regimes and so far, a completely satisfactory theory has not emerged. It seems likely that robust, reliable predictions will only come from the development of a first-principles theory backed up by detailed experimental observations. The extensive work already accomplished and reviewed here should provide a solid basis for such development.

  16. Thermodynamics of confined gallium clusters

    NASA Astrophysics Data System (ADS)

    Chandrachud, Prachi

    2015-11-01

    We report the results of ab initio molecular dynamics simulations of Ga13 and Ga17 clusters confined inside carbon nanotubes with different diameters. The cluster-tube interaction is simulated by the Lennard-Jones (LJ) potential. We discuss the geometries, the nature of the bonding and the thermodynamics under confinement. The geometries as well as the isomer spectra of both the clusters are significantly affected. The degree of confinement decides the dimensionality of the clusters. We observe that a number of low-energy isomers appear under moderate confinement while some isomers seen in the free space disappear. Our finite-temperature simulations bring out interesting aspects, namely that the heat capacity curve is flat, even though the ground state is symmetric. Such a flat nature indicates that the phase change is continuous. This effect is due to the restricted phase space available to the system. These observations are supported by the mean square displacement of individual atoms, which are significantly smaller than in free space. The nature of the bonding is found to be approximately jellium-like. Finally we note the relevance of the work to the problem of single file diffusion for the case of the highest confinement.

  17. Semiflexible chains in confined spaces

    NASA Astrophysics Data System (ADS)

    Morrison, Greg; Thirumalai, D.

    2009-01-01

    We develop an analytical method for studying the properties of a noninteracting wormlike chain (WLC) in confined geometries. The mean-field-like theory replaces the rigid constraints of confinement with average constraints, thus allowing us to develop a tractable method for treating a WLC wrapped on the surface of a sphere, and fully encapsulated within it. The efficacy of the theory is established by reproducing the exact correlation functions for a WLC confined to the surface of a sphere. In addition, the coefficients in the free energy are exactly calculated. We also describe the behavior of a surface-confined chain under external tension that is relevant for single molecule experiments on histone-DNA complexes. The force-extension curves display spatial oscillations, and the extension of the chain, whose maximum value is bounded by the sphere diameter, scales as f-1 at large forces, in contrast to the unconfined chain that approaches the contour length as f-1/2 . A WLC encapsulated in a sphere, that is relevant for the study of the viral encapsulation of DNA, can also be treated using the mean-field approach. The predictions of the theory for various correlation functions are in excellent agreement with Langevin simulations. We find that strongly confined chains are highly structured by examining the correlations using a local winding axis. The predicted pressure of the system is in excellent agreement with simulations but, as is known, is significantly lower than the pressures seen for DNA packaged in viral capsids.

  18. Issues in tokamak/stellarator transport and confinement enhancement mechanisms

    SciTech Connect

    Perkins, F.W.

    1990-08-01

    At present, the mechanism for anomalous energy transport in low-{beta} toroidal plasmas -- tokamaks and stellarators -- remains unclear, although transport by turbulent E {times} B velocities associated with nonlinear, fine-scale microinstabilities is a leading candidate. This article discusses basic theoretical concepts of various transport and confinement enhancement mechanisms as well as experimental ramifications which would enable one to distinguish among them and hence identify a dominant transport mechanism. While many of the predictions of fine-scale turbulence are born out by experiment, notable contradictions exist. Projections of ignition margin rest both on the scaling properties of the confinement mechanism and on the criteria for entering enhanced confinement regimes. At present, the greatest uncertainties lie with the basis for scaling confinement enhancement criteria. A series of questions, to be answered by new experimental/theoretical work, is posed to resolve these outstanding contradictions (or refute the fine-scale turbulence model) and to establish confinement enhancement criteria. 73 refs., 4 figs., 5 tabs.

  19. Confinement and heating studies of field-reversed configurations

    NASA Astrophysics Data System (ADS)

    Chrien, Robert E.

    1990-10-01

    Confinement studies of field-reversed configurations (FRCs) have been actively pursued during the past ten years with the larger and longer-lived FRCs produced in the FRX-C and FRX-C/LSM devices. Confinement measurements have included the global FRC quantities and, in some cases, profiles of electron temperature and density. The inferred confinement times and transport coefficients are used for comparison with transport models as well as to find the best operating conditions in the experiment. Global power flow modelling shows that energy confinement during the equilibrium phase is usually dominated by particle losses, with a substantial secondary contribution from electron thermal conduction. Particle losses in present kinetic FRCs are strongly influenced by open field line confinement, which complicates the study of transport mechanisms. The electron thermal conduction is observed to be anomalous, as in other plasma devices. The bulk electrical resistivity is also anomalous and shows no evidence of classical Spitzer scaling. Recently, the resistive anomaly has been shown to correlate with tilt-like magnetic perturbations observed with Mirnov coils. FRC confinement studies have also been extended to a higher temperature regime during magnetic compression heating. In these experiments, translated FRCs are compressed by increasing the external magnetic flux up to a factor of seven on a time scale between the radial Alfven time and the FRC lifetime. Electron and ion temperatures up to 0.4 keV and 1.6 keV, respectively have been obtained. Confinement times scale roughly as r(exp 2) during compression.

  20. Computations in Plasma Physics.

    ERIC Educational Resources Information Center

    Cohen, Bruce I.; Killeen, John

    1983-01-01

    Discusses contributions of computers to research in magnetic and inertial-confinement fusion, charged-particle-beam propogation, and space sciences. Considers use in design/control of laboratory and spacecraft experiments and in data acquisition; and reviews major plasma computational methods and some of the important physics problems they…

  1. Magnetospheric vortex formation: self-organized confinement of charged particles.

    PubMed

    Yoshida, Z; Saitoh, H; Morikawa, J; Yano, Y; Watanabe, S; Ogawa, Y

    2010-06-11

    A magnetospheric configuration gives rise to various peculiar plasma phenomena that pose conundrums to astrophysical studies; at the same time, innovative technologies may draw on the rich physics of magnetospheric plasmas. We have created a "laboratory magnetosphere" with a levitating superconducting ring magnet. Here we show that charged particles (electrons) self-organize a stable vortex, in which particles diffuse inward to steepen the density gradient. The rotating electron cloud is sustained for more than 300 s. Because of its simple geometry and self-organization, this system will have wide applications in confining single- and multispecies charged particles. PMID:20867249

  2. System and method of operating toroidal magnetic confinement devices

    DOEpatents

    Chance, Morrell S.; Jardin, Stephen C.; Stix, Thomas H.; Grimm, deceased, Ray C.; Manickam, Janardhan; Okabayashi, Michio

    1987-01-01

    For toroidal magnetic confinement devices the second region of stability against ballooning modes can be accessed with controlled operation. Under certain modes of operation, the first and second stability regions may be joined together. Accessing the second region of stability is accomplished by forming a bean-shaped plasma and increasing the indentation until a critical value of indentation is reached. A pusher coil, located at the inner-major-radius side of the device, is engaged to form a bean-shaped poloidal cross-section in the plasma.

  3. Beam-ion confinement for different injection geometries

    SciTech Connect

    Heidbrink, W. W.; Murakami, Masanori; Park, Jin Myung; Petty, C C.; Van Zeeland, Michael; Yu, J.H.; Mckee, G. R.

    2009-01-01

    The DIII-D tokamak is equipped with neutral beam sources that inject in four different directions; in addition, the plasma can be moved up or down to compare off-axis with on-axis injection. Fast-ion data for eight different conditions have been obtained: co/counter, near-tangential/near-perpendicular and on-axis/off-axis. Neutron measurements during short beam pulses assess prompt and delayed losses under low-power conditions. As expected, co-injection has fewer losses than counter, tangential fewer than perpendicular and on-axis fewer than off-axis; the differences are greater at low current than at higher current. The helicity of the magnetic field has a weak effect on the overall confinement. Fast-ion D-alpha (FIDA) and neutron measurements diagnose the confinement at higher power. The basic trends are the same as in low-power plasmas but, even in plasmas without long wavelength Alfven modes or other MHD, discrepancies with theory are observed, especially in higher temperature plasmas. At modest temperature, two-dimensional images of the FIDA light are in good agreement with the simulations for both on-axis and off-axis injection. Discrepancies with theory are more pronounced at low fast-ion energy and at high plasma temperature, suggesting that fast-ion transport by microturbulence is responsible for the anomalies.

  4. Comparison of hybrid and baseline ELMy H-mode confinement in JET with the carbon wall

    NASA Astrophysics Data System (ADS)

    Beurskens, M. N. A.; Frassinetti, L.; Challis, C.; Osborne, T.; Snyder, P. B.; Alper, B.; Angioni, C.; Bourdelle, C.; Buratti, P.; Crisanti, F.; Giovannozzi, E.; Giroud, C.; Groebner, R.; Hobirk, J.; Jenkins, I.; Joffrin, E.; Leyland, M. J.; Lomas, P.; Mantica, P.; McDonald, D.; Nunes, I.; Rimini, F.; Saarelma, S.; Voitsekhovitch, I.; de Vries, P.; Zarzoso, D.; Contributors, JET-EFDA

    2013-01-01

    The confinement in JET baseline type I ELMy H-mode plasmas is compared to that in so-called hybrid H-modes in a database study of 112 plasmas in JET with the carbon fibre composite (CFC) wall. The baseline plasmas typically have βN ˜ 1.5-2, H98 ˜ 1, whereas the hybrid plasmas have βN ˜ 2.5-3, H98 < 1.5. The database study contains both low- (δ ˜ 0.2-0.25) and high-triangularity (δ ˜ 0.4) hybrid and baseline H-mode plasmas from the last JET operational campaigns in the CFC wall from the period 2008-2009. Based on a detailed confinement study of the global as well as the pedestal and core confinement, there is no evidence that the hybrid and baseline plasmas form separate confinement groups; it emerges that the transition between the two scenarios is of a gradual kind rather than demonstrating a bifurcation in the confinement. The elevated confinement enhancement factor H98 in the hybrid plasmas may possibly be explained by the density dependence in the τ98 scaling as n0.41 and the fact that the hybrid plasmas operate at low plasma density compared to the baseline ELMy H-mode plasmas. A separate regression on the confinement data in this study shows a reduction in the density dependence as n0.09±0.08. Furthermore, inclusion of the plasma toroidal rotation in the confinement regression provides a scaling with the toroidal Alfvén Mach number as Mach_A^{0.41+/- 0.07} and again a reduced density dependence as n0.15±0.08. The differences in pedestal confinement can be explained on the basis of linear MHD stability through a coupling of the total and pedestal poloidal pressure and the pedestal performance can be improved through plasma shaping as well as high β operation. This has been confirmed in a comparison with the EPED1 predictive pedestal code which shows a good agreement between the predicted and measured pedestal pressure within 20-30% for a wide range of βN ˜ 1.5-3.5. The core profiles show a strong degree of pressure profile consistency. No

  5. Building solids inside nano-space: from confined amorphous through confined solvate to confined 'metastable' polymorph.

    PubMed

    Nartowski, K P; Tedder, J; Braun, D E; Fábián, L; Khimyak, Y Z

    2015-10-14

    The nanocrystallisation of complex molecules inside mesoporous hosts and control over the resulting structure is a significant challenge. To date the largest organic molecule crystallised inside the nano-pores is a known pharmaceutical intermediate - ROY (259.3 g mol(-1)). In this work we demonstrate smart manipulation of the phase of a larger confined pharmaceutical - indomethacin (IMC, 357.8 g mol(-1)), a substance with known conformational flexibility and complex polymorphic behaviour. We show the detailed structural analysis and the control of solid state transformations of encapsulated molecules inside the pores of mesoscopic cellular foam (MCF, pore size ca. 29 nm) and controlled pore glass (CPG, pore size ca. 55 nm). Starting from confined amorphous IMC we drive crystallisation into a confined methanol solvate, which upon vacuum drying leads to the stabilised rare form V of IMC inside the MCF host. In contrast to the pure form, encapsulated form V does not transform into a more stable polymorph upon heating. The size of the constraining pores and the drug concentration within the pores determine whether the amorphous state of the drug is stabilised or it recrystallises into confined nanocrystals. The work presents, in a critical manner, an application of complementary techniques (DSC, PXRD, solid-state NMR, N2 adsorption) to confirm unambiguously the phase transitions under confinement and offers a comprehensive strategy towards the formation and control of nano-crystalline encapsulated organic solids. PMID:26280634

  6. Comparative cactus architecture and par interception

    SciTech Connect

    Geller, G.N.; Nobel, P.S. )

    1987-07-01

    Because CO{sup 2} uptake by cacti can be limited by low levels of photosynthetically active radiation (PAR) and because plant form affects PAR interception, various cactus forms were studied using a computer model, field measurements, and laboratory phototropic studies. Model predictions indicated that CO{sub 2} uptake by individual stems at an equinox was greatest when the stem were vertical, but at the summer and the winter solstice CO{sub 2} uptake was greatest for stems titled 30{degree} away from the equator. Stem tilting depended on form and taxonomic group. Not only can the shape of cacti be affected by PAR, but also shape influences PAR interception and hence CO{sub 2} uptake.

  7. Physical insights of cavity confinement enhancing effect in laser-induced breakdown spectroscopy.

    PubMed

    Fu, Yangting; Hou, Zongyu; Wang, Zhe

    2016-02-01

    Using cavity confinement to enhance the plasma emission has been proved to be an effective way in LIBS technique while no direct visual evidence has been made to illustrate the physical mechanism of this enhancing effect. In this work, both laser-induced plasma plume images and shockwave images were obtained and synchronized for both flat surface case and rectangular cavity case. Phenomena of shockwave reflection, plasma compression by the reflected shockwave and merge of the reflected shockwave into plasma were observed. Plasma emission intensities recorded by ICCD in both cases were compared and the enhancement effect in the cavity case was identified in the comparison. The enhancement effect could be explained as reflected shockwave "compressing" effect, that is, the reflected shockwave would compress the plasma and result in a more condensed plasma core area with higher plasma temperature. Reflected shockwave also possibly contributed to plasma core position stabilization, which indicated the potential of better plasma signal reproducibility for the cavity case. Both plasma emission enhancement and plasma core position stabilization only exist within a certain temporal window, which indicates that the delay time of spectra acquisition is essential while using cavity confinement as a way to improve LIBS performance.

  8. Inertial confinement fusion (ICF) review

    SciTech Connect

    Hammer, D.; Dyson, F.; Fortson, N.; Novick, B.; Panofsky, W.; Rosenbluth, M.; Treiman, S.; York, H.

    1996-03-01

    During its 1996 winter study JASON reviewed the DOE Inertial Confinement Fusion (ICF) program. This included the National Ignition Facility (NIF) and proposed studies. The result of the review was to comment on the role of the ICF program in support of the DOE Science Based Stockpile Stewardship program.

  9. Limiting Spectra from Confining Potentials.

    ERIC Educational Resources Information Center

    Nieto, Michael Martin; Simmons, L. M., Jr.

    1979-01-01

    The author explains that, for confining potentials and large quantum numbers, the bound-state energies rise more rapidly as a function of n the more rapidly the potential rises with distance. However, the spectrum can rise no faster than n squared in the nonrelativistic case, or n in the relativistic case. (Author/GA)

  10. Improved Confinement due to Open Ergodic Field Lines Imposed by the Dynamic Ergodic Divertor in TEXTOR

    NASA Astrophysics Data System (ADS)

    Finken, K. H.; Abdullaev, S. S.; Jakubowski, M. W.; de Bock, M. F. M.; Bozhenkov, S.; Busch, C.; von Hellermann, M.; Jaspers, R.; Kikuchi, Y.; Krämer-Flecken, A.; Lehnen, M.; Schega, D.; Schmitz, O.; Spatschek, K. H.; Unterberg, B.; Wingen, A.; Wolf, R. C.; Zimmermann, O.

    2007-02-01

    The ergodization of the magnetic field lines imposed by the dynamic ergodic diverter (DED) in TEXTOR can lead both to confinement improvement and to confinement deterioration. The cases of substantial improvement are in resonant ways related to particular conditions in which magnetic flux tubes starting at the X points of induced islands are connected with the wall. This opening process is connected with a characteristic modification of the heat deposition pattern at the divertor target plate and leads to a substantial increase and steepening of the core plasma density and pressure. The improvement is tentatively attributed to a modification of the electric potential in the plasma carried by the open field lines. The confinement improvement bases on a spontaneous density built up due to the application of the DED and is primarily a particle confinement improvement.

  11. Inertial Confinement Fusion quarterly report, January--March 1995. Volume 5, No. 2

    SciTech Connect

    1995-09-01

    The ICF quarterly report is published by the Inertial Confinement Fusion Program at the Lawrence Livermore National Laboratory. Topics included this quarter include: the role of the National Ignition Facility in the development of Inertial Confinement Fusion, laser-plasma interactions in large gas-filled hohlraums, evolution of solid-state induction modulators for a heavy-ion recirculator, the National Ignition Facility project, and terminal-level relaxation in Nd-doped laser material.

  12. Proteinase-activated receptor-1 (PAR(1)) and PAR(2) but not PAR(4) mediate contraction in human and guinea-pig gallbladders.

    PubMed

    Lee, M-C; Huang, S-C

    2008-04-01

    Proteinase-activated receptor-1 (PAR(1)) and PAR(2) mediate contraction in the guinea-pig gallbladder. To investigate and compare the effects mediated by PARs in the human gallbladder with those in the guinea-pig gallbladder, we measured contractions of isolated human and guinea-pig gallbladder strips caused by PAR agonists. Results in human were similar to those in guinea-pig gallbladder. The PAR(1) agonists, thrombin, TFLLR-NH2 and SFLLRN-NH2, as well as the PAR(2) agonists, trypsin, SLIGKV-NH2 and SLIGRL-NH2, caused contraction in both human and guinea-pig gallbladders. These indicate the existence of PAR(1) and PAR(2) mediating gallbladder contraction. Furthermore, the existence of PAR(1) and PAR(2) in the human gallbladder was confirmed by reverse transcription-polymerase chain reaction. In contrast, FSLLR-NH2, a PAR(1) control peptide, and VKGILS-NH2, a PAR(2) control peptide, as well as three PAR(4) agonists, GYPGKF-NH2, GYPGQV-NH2 and AYPGKF-NH2, did not cause any contraction or relaxation. The contractile responses to TFLLR-NH2, SFLLRN-NH2 and trypsin in both human and guinea-pig gallbladders were insensitive to atropine and tetrodotoxin, suggesting direct effects. These results demonstrate that, similar to the guinea-pig gallbladder, both PAR(1) and PAR(2) but not PAR(4) mediate muscle contraction in the human gallbladder. PAR(1) and PAR(2) may play important roles in the control of both human and guinea-pig gallbladder motility. PMID:18179608

  13. Proteinase-activated receptor-1 (PAR1) and PAR2 mediate relaxation of guinea pig internal anal sphincter.

    PubMed

    Huang, Shih-Che

    2014-02-10

    Activation of proteinase-activated receptor-1 (PAR1) and PAR2 stimulates contraction of the rat but relaxation of the guinea pig colon. The aim of the present study was to investigate PAR effects on internal anal sphincter (IAS) motility. We measured relaxation of isolated muscle strips from the guinea pig IAS caused by PAR agonists using isometric transducers. Reverse transcription polymerase chain reaction (RT-PCR) was performed to determine the existence of PAR. In the IAS, thrombin and PAR1 peptide agonists TFLLR-NH2 and SFLLRN-NH2 evoked moderate to marked relaxation in a concentration-dependent manner. In addition, trypsin and PAR2 peptide agonists 2-furoyl-LIGRLO-NH2, SLIGRL-NH2 and SLIGKV-NH2 produced relaxation. In contrast, both PAR1 and PAR2 inactive control peptides did not elicit relaxation. Furthermore, the selective PAR1 antagonist vorapaxar and PAR2 antagonist GB 83 specifically inhibited thrombin and trypsin-induced relaxations, respectively. RT-PCR revealed the presence of PAR1 and PAR2 in the IAS. This indicates that PAR1 and PAR2 mediate the IAS relaxation. The relaxant responses of TFLLR-NH2 and trypsin were attenuated by N(omega)-Nitro-L-arginine (L-NNA), indicating involvement of NO. These responses were not affected by tetrodotoxin, implying that the PAR effects are not neurally mediated. On the other hand, PAR4 agonists GYPGKF-NH2, GYPGQV-NH2 and AYPGKF-NH2 did not cause relaxation or contraction, suggesting that PAR4 is not involved in the sphincter motility. Taken together, these results demonstrate that both PAR1 and PAR2 mediate relaxation of the guinea pig IAS through the NO pathway. PAR1 and PAR2 may regulate IAS tone and might be potential therapeutic targets for anal motility disorders. PMID:24631471

  14. Production of field-reversed mirror plasma with a coaxial plasma gun

    DOEpatents

    Hartman, C.W.; Shearer, J.W.

    The use of a coaxial plasma gun to produce a plasma ring which is directed into a magnetic field so as to form a field-reversed plasma confined in a magnetic mirror. Plasma thus produced may be used as a target for subsequent neutral beam injection or other similarly produced and projected plasma rings or for direct fusion energy release in a pulsed mode.

  15. Production of field-reversed mirror plasma with a coaxial plasma gun

    DOEpatents

    Hartman, Charles W.; Shearer, James W.

    1982-01-01

    The use of a coaxial plasma gun to produce a plasma ring which is directed into a magnetic field so as to form a field-reversed plasma confined in a magnetic mirror. Plasma thus produced may be used as a target for subsequent neutral beam injection or other similarly produced and projected plasma rings or for direct fusion energy release in a pulsed mode.

  16. JET confinement studies and their scaling to high βN, ITER scenarios

    NASA Astrophysics Data System (ADS)

    McDonald, D. C.; Laborde, L.; DeBoo, J. C.; Ryter, F.; Brix, M.; Challis, C. D.; de Vries, P.; Giroud, C.; Hobirk, J.; Howell, D.; Joffrin, E.; Luce, T. C.; Mailloux, J.; Pericoli-Ridolfini, V.; Sips, A. C. C.; Thomsen, K.; EFDA Contributors, JET

    2008-12-01

    The ITER hybrid scenario aims to exploit non-inductive current drive to enable burn times in excess of 1000 s. To achieve this, and optimize fusion performance, requires high βN (the plasma pressure normalized to a stability scaling) and energy confinement equal to or greater than that predicted for the baseline scenario. This paper discusses results from the JET candidate hybrid scenario, where βN,MHD <= 3.6 plasmas have been produced. Despite a different initial phase, confinement relevant plasma parameters evolve rapidly towards those of equivalent ELMy H-modes and are well described by IPB98(y, 2). In contrast to previous ELMy H-mode studies, a dedicated β scan experiment in the JET hybrid candidate scenario shows a strong negative dependence of global confinement on βN. Analysis indicates that the core transport remains consistent with weakly dependent electrostatic transport, whilst the edge confinement decreases strongly with increasing βN. By combining global confinement data from ASDEX Upgrade, DIII-D and JET hybrid scenario discharges, a multi-machine database is produced. In contrast to the JET case, confinement in ASDEX Upgrade and DIII-D is shown to be inconsistent with IPB98(y, 2) and alternative dependences are explored.

  17. The Clinical Value of Soluble Urokinase Plasminogen Activator Receptor (suPAR) Levels in Autoimmune Connective Tissue Disorders

    PubMed Central

    Toldi, Gergely; Balog, Attila

    2016-01-01

    The assessment of the general inflammatory condition of patients with autoimmune connective tissue disorders (ACTD) is a major challenge. The use of traditional inflammatory markers including CRP-levels and erythrocyte sedimentation rate (ESR) is limited by several preanalytical factors and their low specificities. Soluble urokinase plasminogen activator receptor (suPAR) is one of the novel candidate markers that is increasingly used in immune mediated disorders. In our studies we compared suPAR levels of patients with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), systemic sclerosis (SSc) and ankylosing spondylitis with those of healthy controls. suPAR provided valuable clinical information on disease activity in RA, SLE and SSc. We identified a subgroup of remitted RA patients, who presented still clinical symptoms of inflammatory activity which correlated to high plasma suPAR (while ESR and CRP were normal). In SLE we established specific suPAR cut-off values that support the discrimination between patients with high and those with moderate SLE activity. In patients with SSc suPAR correlated with objective measures of lung and other complications. In the majority of ACTDs including SLE, SSc or RA, suPAR is seemingly a good biomarker that would provide valuable clinical information. However, before the introduction of this novel parameter in laboratory repertoire important issues should be elucidated. These include the establishment of appropriate and disease specific cutoff values, clarification of interfering preanalytical values and underlying conditions and declaration of age- and gender-specific reference ranges. PMID:27683525

  18. The Clinical Value of Soluble Urokinase Plasminogen Activator Receptor (suPAR) Levels in Autoimmune Connective Tissue Disorders.

    PubMed

    Vasarhelyi, Barna; Toldi, Gergely; Balog, Attila

    2016-04-01

    The assessment of the general inflammatory condition of patients with autoimmune connective tissue disorders (ACTD) is a major challenge. The use of traditional inflammatory markers including CRP-levels and erythrocyte sedimentation rate (ESR) is limited by several preanalytical factors and their low specificities. Soluble urokinase plasminogen activator receptor (suPAR) is one of the novel candidate markers that is increasingly used in immune mediated disorders. In our studies we compared suPAR levels of patients with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), systemic sclerosis (SSc) and ankylosing spondylitis with those of healthy controls. suPAR provided valuable clinical information on disease activity in RA, SLE and SSc. We identified a subgroup of remitted RA patients, who presented still clinical symptoms of inflammatory activity which correlated to high plasma suPAR (while ESR and CRP were normal). In SLE we established specific suPAR cut-off values that support the discrimination between patients with high and those with moderate SLE activity. In patients with SSc suPAR correlated with objective measures of lung and other complications. In the majority of ACTDs including SLE, SSc or RA, suPAR is seemingly a good biomarker that would provide valuable clinical information. However, before the introduction of this novel parameter in laboratory repertoire important issues should be elucidated. These include the establishment of appropriate and disease specific cutoff values, clarification of interfering preanalytical values and underlying conditions and declaration of age- and gender-specific reference ranges. PMID:27683525

  19. Techniques for measuring intercepted and absorbed PAR in corn canopies

    NASA Technical Reports Server (NTRS)

    Gallo, K. P.; Daughtry, C. S. T.

    1984-01-01

    The quantity of radiation potentially available for photosynthesis that is captured by the crop is best described as absorbed photosynthetically active radiation (PAR). Absorbed PAR (APAR) is the difference between descending and ascending fluxes. The four components of APAR were measured above and within two planting densities of corn (Zea mays L.) and several methods of measuring and estimating APAR were examined. A line quantum sensor that spatially averages the photosynthetic photon flux density provided a rapid and portable method of measuring APAR. PAR reflectance from the soil (Typic Argiaquoll) surface decreased from 10% to less than 1% of the incoming PAR as the canopy cover increased. PAR reflectance from the canopy decreased to less than 3% at maximum vegetative cover. Intercepted PAR (1 - transmitted PAR) generally overestimated absorbed PAR by less than 4% throughout most of the growing season. Thus intercepted PAR appears to be a reasonable estimate of absorbed PAR.

  20. Magnetic confinement experiment -- 1: Tokamaks

    SciTech Connect

    Goldston, R.J.

    1994-12-31

    This report reviews presentations made at the 15th IAEA Conference on Plasma Physics and Controlled Nuclear Fusion on experimental tokamak physics, particularly on advances in core plasma physics, divertor and edge physics, heating and current drive, and tokamak concept optimization.