Bulletin of the American Physical Society
2008 APS April Meeting and HEDP/HEDLA Meeting
Volume 53, Number 5
Friday–Tuesday, April 11–15, 2008; St. Louis, Missouri
Session 8HE: HEDP/HEDLA Poster Session (4:05-6:30pm) |
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Sponsoring Units: HEDP HEDLA Chair: Bruce Remington, Lawrence Livermore National Laboratory Room: Hyatt Regency St. Louis Riverfront (formerly Adam's Mark Hotel), Promenade E and Promenade Lobby |
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8HE.00001: From dimensional analysis to Burgan-Feix transformation: a self-similar and unified analysis Emeric Falize, Serge Bouquet Self-Similar Solutions (SSS) play a key role in physics and astrophysics. They give basic information about physical systems and are an essential complement to numerical simulations. Several approaches, based on properties of invariance, exist and provide many classes of solutions compatible with only specific initial conditions (IC). In order to make sure that solutions be compatible with any boundary and/or IC, Burgan and Feix derived a transformation group - which we name the Burgan-Feix Transformation (BFT) - based upon the concept of partial invariance. The BFT leads also to new solutions through more complex analytical calculations. Including IC in the structure of solutions is very appropriate for High-Energy-Density experiments. In this work, we will propose a progressive approach, from dimensional analysis to BFT, providing SSS containing increasing degree of complexity. Moreover, we will present the theory of the BFT with different point of view. [Preview Abstract] |
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8HE.00002: Self-similar evolution, structure and stability of optically thin plasmas: analytical and numerical study Emeric Falize, Berenice Loupias, Serge Bouquet, Claire Michaut, Michel Koenig In this work we will consider, analytically and numerically, the multi-dimensional dynamics (expansion and collapse) of optically thin plasmas. We will present self-similar solutions when the cooling function can be written in power law forms. These solutions are obtained using the Burgan-Feix transformation which consists in a generalized self-similar transformation. We will establish the plasma configurations compatible with cooling flows. It turns out that from a multi-dimensional analysis these solutions apply to jets as well as supernovae remnant dynamics. We compare these results with numerical simulations. Moreover, virial theorem predicts the existence of instability that we will physically identify. Thus, we will present the study of the linear stability of the radial and non-radial evolution and the study of the non-linear regime with numerical simulations. We will discuss the astrophysical implications of these results and their reproduction in laboratory. [Preview Abstract] |
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8HE.00003: Investigation of flute and lower hybrid drift instabilities in application to laboratory astrophysics and Z-pinch experiments V.I. Sotnikov, V. Ivanov, R. Presura, J. Kindel, J.N. Leboeuf, O.G. Onishchenko, B.V. Oliver, T.A. Mehlhorn, C. Deeney In a cylindrical Z-pinch plasma column and in a laser ablated plasma flows interacting with an external magnetic field conditions are favorable for excitation of flute and lower hybrid drift oscillations. Linear analysis of the flute mode instability in a finite beta Z-pinch plasma has demonstrated good agreement between theory and experimental data. Laboratory experiments on the interaction of a plasma flow, produced by laser ablation of a solid target with the inhomogeneous magnetic field demonstrated the presence of strong wave activity in the region of the flow deceleration. Excitation of flute-type modes as well as LHD waves with plasma and magnetic field parameters, corresponding to the ongoing experiments is examined. [Preview Abstract] |
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8HE.00004: Progress toward Kelvin-Helmholtz instabilities in a High-Energy-Density Plasma on the Nike laser E.C. Harding, R.P. Drake, R.S. Gillespie, M.J. Grosskopf, C.M. Huntington, Y. Aglitskiy, J.L. Weaver, A.L. Velikovich, T. Plewa, V.V. Dwarkadas In the realm of high-energy-density (HED) plasmas, there exist three primary hydrodynamic instabilities of concern: Rayleigh-Taylor (RT), Richtmyer-Meshkov (RM), and Kelvin-Helmholtz (KH). Although the RT and the RM instabilities have been readily observed and diagnosed in the laboratory, the KH instability remains relatively unexplored in HED plasmas. Unlike the RT and RM instabilities, the KH instability is driven by a lifting force generated by a strong velocity gradient in a stratified fluid. Understanding the KH instability mechanism in HED plasmas will provide essential insight into oblique shock systems, jets, mass stripping, and detailed RT-spike development. In addition, our KH experiment will help provide the groundwork for future transition to turbulence experiments. We present 2D FLASH simulations and experimental data from our initial attempts to create a pure KH system using the Nike laser at the Naval Research Laboratory. [Preview Abstract] |
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8HE.00005: Structure of solutions of the buoyancy -- drag equation Serge Bouquet, Emeric Falize, Pierre Gandeboeuf, Pierre Pailhori\`es In this paper, the well-known buoyancy-drag equation (BDE) is studied. This equation describes the non linear regime of Rayleigh -- Taylor instabilities and also the structure of the mixing zone where both fluids are present. Analytical solutions of the BDE are derived for time-dependent accelerations, $\gamma $(t), of the form $\gamma $(t) $\sim $ t$^{n}$ where the exponent n can be positive, negative or zero. It is shown, first, that the width, h(t), of the mixing zone behaves like h$_{n}$(t) $\sim $ t$^{n+2}$ and, second, provided the initial conditions satisfy some constraints, the special solution h$_{n}$(t) is an attractor for t going to infinity. On the other hand, the behavior of the asymtotic solutions for $\gamma $(t) $\sim $ t$^{n}$ is examined in terms of the drag coefficient, C$_{d}$, that is present in the drag force (proportional to the square of the derivative dh/dt) in the right hand side of the BDE. Critical values for this coefficient are derived analytically and it is shown that the asymptotic behaviors are strongly dependent on the value of C$_{d}$. These results are also evidenced from numerical simulations achieved with the CLAWPACK numerical package. [Preview Abstract] |
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8HE.00006: Using the Rayleigh-Taylor instability for in situ measurements of thermal conductivity of warm dense matter. Dmitri Ryutov The Rayleigh-Taylor instability of the material with stratified density, temperature, and composition is considered. The variation of composition gives rise to the appearance of modes whose growth rate is directly related to the finite thermal conductivity (D.D. Ryutov, Phys. Plas., v.7 , p. 4797, 2000). It is proposed to use this effect for in situ measurements of thermal conductivity of warm dense matter. Expressions for the growth rate for the general equation of state are derived and the modes that are most convenient for the aforementioned measurements are identified. A desired perturbation can be introduced by machining the package or by using masks during the surface deposition process. To visualize the evolution of the embedded perturbation, higher-Z tracers can be used. A concept of a laser-driven experiment where this approach can be realized is presented. Prepared by LLNL under contract DE-AC52-07NA27344. [Preview Abstract] |
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8HE.00007: Simulation and Analysis of Mixing Layer Evolution in Multi-Mode, Laser-Driven Rayleigh-Taylor Experiments Nathan Hearn, Tomasz Plewa, R. Paul Drake, Carolyn Kuranz Recent experiments at the Omega laser facility have produced data of sufficient quality to investigate structural details of single- and multi-mode Rayleigh-Taylor instability growth. The FLASH hydrodynamics code has been used to model these experiments in two and three dimensions. We present a comparison between the experimental data and raytraced images of the three-dimensional simulations, and we also explore the effects of choosing different adiabatic indexes for our ideal-gas realizations of the two fluids. Finally, we contrast the simulated evolution of single- and double-mode perturbations in terms of their mixing layer growth and mass distributions. In accordance with theoretical expectations, we find that short-wavelength modes show the fastest initial growth, and that the structure of the mixing layer is eventually dominated by the longer modes. [Preview Abstract] |
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8HE.00008: Using Hydrodynamic Codes in Modeling of Multi-Interface Diverging Experiments for NIF Michael Grosskopf, R.P. Drake, C.C. Kuranz, T. Plewa, N. Hearn, C. Meakin, D. Arnett, A.R. Miles, H.F. Robey, J.F. Hansen, B.A. Remington, W. Hsing, M.J. Edwards Using the Omega Laser, researchers studying supernova dynamics have observed the growth of Rayleigh-Taylor instabilities in a high energy density system. The NIF laser hopes to generate the energy needed to expand these experiments to a diverging system. We report scaling simulations to model the interface dynamics of a multilayered, diverging Rayleigh-Taylor experiment for NIF using CALE, a hybrid adaptive Lagrangian-Eulerian code developed at LLNL. Specifically, we looked both qualitatively and quantitatively at the Rayleigh-Taylor growth and multi-interface interactions in mass-scaled systems using different materials. The simulations will assist in the target design process and help choose diagnostics to maximize the information we receive in a particular shot. Simulations are critical for experimental planning, especially for experiments on large-scale facilities. [Preview Abstract] |
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8HE.00009: Richtmyer-Meshkov instability in elastic-plastic media Antonio R. Piriz, Juan J. L\'opez Cela, Naeem A. Tahir, Dieter H. H. Hoffmann Hydrodynamic instabilities are of great importance in the LAPLAS (Laboratory of Planetary Sciences) experiment that is being designed for the study of high energy density states of matter in the framework of the FAIR projectDuring the implosion of the LAPLAS cylindrical target Richtmyer-Meshkov (RM) instability occurs when a shock is launched into a material pusher with elastic and plastic properties that determines the physics of the instability evolution. We have studied the evolution of the interface from which the shock is launched as a consequence of the RM instability. For this we have developed an analytical model and we have performed two-dimensional numerical simulations in order to validate the model. Model and simulations show the asymptotic stability state in which the interface oscillates elastically around a mean value higher than the initial perturbation amplitude. Such a mean value is determined by an initial plastic phase. Applications to the measurement of the yield strength of materials under extreme conditions are foreseen. [Preview Abstract] |
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8HE.00010: Theoretical and numerical studies of Vishniac instability in supernova remnants C\'ecile Cavet, Hung Chinh Nguyen, Claire Michaut, Emeric Falize, Serge Bouquet In this work, the Vishniac instability is first of all theoretically studied in supernova remnants. This instability is sometimes invoked to explain fragmentation of interstellar medium, but its role is not correctly demonstrated. Conditions and assumptions required for the instability growth are detailed and explained. In addition, an experimental feasibility of the Vishniac instability combined with a radiative shock experiment is examined with the high-power laser facility, i.e., LIL (Bordeaux, France). Another part of this study is also to simulate this instability, because we would compare its numerical growth rate with analytical theory which we derived as an extension of the initial approach by Vishniac. To lead this numerical work we have developed an hydrodynamic code (called HYDRO-MUSCL) and we will show new results. [Preview Abstract] |
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8HE.00011: 3D RAGE Simulations of Sapphire Balls Driven by Strong Shocks B.H. Wilde, R.F. Coker, P.A. Rosen, J.M. Foster , P.M. Hartigan, R. Carver , A. Frank , J.F. Hansen , B.E. Blue The goal of our 2007-2008 NLUF experiments at the OMEGA laser facility is to investigate the physics associated with the interaction of strong shocks and jets with clumpy media. These experiments have close analogs with structures observed in a variety of astrophysical flows, including jets from young stars, outflows from planetary nebulae, and extragalactic jets. In these experiments, a multi-mega bar shock is created in a plastic layer by heating a hohlraum to 190 eV temperature with 5 kJ of laser energy. The shock enters a 0.3 g/cc RF foam into which are embedded 500 micron diameter sapphire balls. The shock shears off the ball such that it creates thin two-dimensional sheets of sapphire which subsequently break up and undergo the three-dimensional Widnall instability. The time evolution of the ball/balls is diagnosed with dual-axes point-projection radiography. In this poster, we discuss the results of high-resolution three-dimensional radiation-hydrodynamic simulations with the adaptive-mesh-refinement RAGE code of single and multiple balls. Comparisons with data from our shots will be made. [Preview Abstract] |
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8HE.00012: Fluid Solvers For High-Energy Density Applications: Initial Results Ammar Hakim, John Loverich We have developed a general purpose, parallel, high-performance framework, TxFluids, for the solution of plasma fluid equations. TxFluids works on both structured (hexahedral) and unstructured (mixed tetrahedral and hexahedral) meshes and uses modern high-order and high-resolution schemes to solve the MHD equations formulated as systems of hyperbolic conservation laws. In particular, we have implemented the High-Resolution Wave Propagation Scheme and the Discontinuous Galerkin (DG) Scheme. Both these schemes are particularly suited to plasma physics problems as they are very accurate, fully upwind and also capture shocks. In the absence of shocks the DG scheme in TxFluids is spectrally accurate, i.e. it can be run with arbitrary spatial order specifiable in the input file. This allows us to resolve complex flow features even with coarse meshes and is hence valuable to study turbulence and micro-instabilities. TxFluids allows coupled simulations using different fluid models. Among these, we have presently implemented the resistive-MHD model, the Hall-MHD model and the full two-fluid model. The latter includes electron physics needed to simulate micro-instabilities like the Lower-Hybrid Drift Instability. As an application we present initial results of simulating a Magneto-Inertial Fusion (MIF) concept. Here an aluminum liner is collapsed on a target plasma (a Field-Reversed Configuration) to produce intense magnetic fields and fusion conditions. We present results of the FRC formation, translation and heating due to adiabatic compression. [Preview Abstract] |
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8HE.00013: Laboratory investigation of bow shocks in radiatively cooled plasmas D.J. Ampleford, C.A. Jennings, S.V. Lebedev, G.N. Hall, S.N. Bland, S.C. Bott, F. Suzuki-Vidal, J.B.A. Palmer, J.P. Chittenden, A. Ciardi Magnetized and radiatively cooled shocks are present in many astrophysical systems. The early stage of a wire array z-pinch implosion consists of the steady ablation of material from fine metallic wires. Ablated material is accelerated toward the array axis by the JxB force. This flow is highly supersonic (M$>$5) and becomes super-Afvenic (MA$>$2). Radiative cooling is significant in this flow, and can be controlled by varying the material in the ablated plasma. The introduction of a wire as an obstruction in this steady flow leads to the formation of bow shocks. The magnetic field associated with this obstruction wire can be controlled by varying the current through it. Differences in the shock for different cooling rates and different magnetic fields associated with the obstruction will be discussed. [Preview Abstract] |
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8HE.00014: A Jet Production Experiment using the ASTRA Laser Jonathan Waugh, Erik Brambrink, Chris Gregory, Michel Koenig, Yasuhiro Kuramitsu, Berenice Loupias, Youichi Sakawa, Lucy Wilson, Nigel Woolsey Plasma jets were produced by the ablation of material with an intense short pulse laser from conical and groove shaped impressions in targets. The use of a high repetition rate laser allowed the use of a variety of jet materials, background gases and gas pressures. Plasma jets coming from plastic, Al, Cu and Au targets were observed and propagation of these stagnating plasmas into background He, N2 and Xe gases was studied. Interferometry data is used to infer the time dependent density of the stagnating region and the launch and propagation of shocks into the background gas. Here, the first analysed results from this experiment are presented. [Preview Abstract] |
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8HE.00015: Directed Plasma Flow across Magnetic Field R. Presura, Y. Stepanenko, S. Neff, V.I. Sotnikov The Hall effect plays a significant role in the penetration of plasma flows across magnetic field. For example, its effect may become dominant in the solar wind penetration into the magnetosphere, in the magnetic field advection in wire array z-pinch precursors, or in the arcing of magnetically insulated transmission lines. An experiment performed at the Nevada Terawatt Facility explored the penetration of plasma with large Hall parameter ($\sim $10) across ambient magnetic field. The plasma was produced by ablation with the short pulse high intensity laser Leopard (0.35 ps, 10$^{17}$W/cm$^{2})$ and the magnetic field with the pulsed power generator Zebra (50 T). The expanding plasma assumed a jet configuration and propagated beyond a distance consistent with a diamagnetic bubble model. Without magnetic field, the plasma expansion was close to hemispherical. The ability to produce the plasma and the magnetic field with distinct generators allows a controlled, quasi-continuous variation of the Hall parameter and other plasma parameters making the experiments useful for benchmarking numerical simulations. [Preview Abstract] |
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8HE.00016: Laser-triggered millimeter-scale collimated plasma jets in crossed electric and magnetic fields P. Brady, H. Quevedo, P. Valanju, M. McCormick, R. Bengtson, T. Ditmire We present a laser plasma triggered jet experiment where we produce millimeter-scale collimated outflows from a cylindrically symmetric electrode configuration motivated by astrophysical jet dynamics. The electrode design consists of a grounded plane with a $\sim $1 cm diameter hole and a wire aligned normally to this plane, with its tip placed at the center of the hole. A rapid discharge is formed between the wire and ground plane when a laser pulse hits an aluminum target placed above the electrodes, creating plasma which closes the circuit. The resulting current and corresponding magnetic fields give rise to a plasma jet. The jets were 0.1-0.3 cm wide, about 2 cm in length, had velocities of $\sim $40 km/s and an estimated plasma density of less than 10$^{17}$ cm$^{-3}$. To study the effects of magnetic fields on jet evolution, we have embedded the plasma in axially directed permanent magnetic fields with strength up to 0.4 Tesla. We measured the evolution of the jet over duration of $\sim $1 $\mu $s with nanosecond resolution using a fast ICCD camera and interferometry. Under certain conditions the jets also form helical structures due to kink instabilities and the onset is characterized. We compare the dynamics of the plasma jet with one dimensional MHD codes. [Preview Abstract] |
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8HE.00017: Dense Plasma Injectors for the HyperV Plasma Jets F Douglas Witherspoon, Richard Bomgardner, Andrew Case, Sarah Messer, Samuel Brockington HyperV is developing high velocity dense plasma jets for application to fusion and HEDP. The approach uses symmetric pulsed injection of high density plasma into a coaxial EM accelerator having a cross-section tailored to prevent formation of the blow-by instability. Work to date has focused on injection using ablative plasma sources, such as capillaries and sparkgaps, but injection of pure plasma, such as D and T, or high-Z gases such as Argon, require a different approach. We describe experiments and diagnostic measurements to develop small parallel plate railguns (MiniRailguns) to generate high density plasma pulses for injection into the coax gun. We also present a brief update of latest results from the 112 electrode sparkgap gun and the 64 capillary TwoPi plasma jet merging experiment, both of which have been upgraded with higher energy pulse forming networks to double the mass of ablatively injected plasma. [Preview Abstract] |
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8HE.00018: ABSTRACT WITHDRAWN |
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8HE.00019: Formation of Magnetically Driven Radiatively Cooled Plasma Jets in the Laboratory F. Suzuki-Vidal, S.V. Lebedev, S.N. Bland, J.P. Chittenden, G. Hall, A. Harvey-Thompson, A. Marocchino, C. Ning, A. Ciardi, C. Stehle, A. Frank, E.G. Blackman, S.C. Bott, T. Ray Previous experiments have successfully showed the formation of magnetically driven radiatively cooled plasma jets which are relevant to the launching of astrophysical jets. The jets in these experiments are driven by the pressure of the toroidal magnetic field produced by the MAGPIE generator which leads to the formation of a ``magnetic tower'' structure. This scenario is characterized by the formation of a magnetic ``bubble'' surrounding a collimated plasma jet on axis. A modification of this experimental configuration, in which radial wire array is replaced by radial metallic foil, results in the formation of episodic magnetic tower outflows which emerge periodically on timescales of $\sim $30ns. The subsequent magnetic bubbles propagate with velocities reaching $\sim $300km/s and interacting with previous eruptions leading to the formation of shocks. This research was supported by the European Community's Marie Curie JETSET network (contract MRTN-CT-2004 005592) and the SSAA program of the NNSA (DOE Cooperative Agreement DE-FC03-02NA00057). [Preview Abstract] |
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8HE.00020: Laboratory experiments to study supersonic astrophysical flows interacting with clumpy environments Paula Rosen, J.M. Foster, R.J.R. Williams, B.H. Wilde, R. Coker, P. Hartigan, R. Carver, J. Palmer, B.E. Blue, F. Hansen, C. Sorce, A. Frank A wide variety of objects in the universe drive supersonic outflows through the interstellar medium which is often highly clumpy. These inhomogeneities affect the morphology of the shocks that are generated. The hydrodynamics is difficult to model as the problem is inherently 3D and the clumps are subject to a variety of fluid instabilities as they are accelerated and destroyed by the shock. Over the last two years, we have been carrying out experiments on the Omega laser to address the interaction of a dense-plasma jet with a localized density perturbation. More recently, we have turned our attention to the interaction of a shock wave with a spherical particle. We use a 1.6-mm diameter, 1.2-mm length hohlraum to drive a composite plastic ablator (which includes bromine to prevent M-band radiation from preheating the experiment). The ablator acts as a ``piston'' driving a shock into 0.3 g/cc foam containing a 0.5-mm diameter sapphire sphere. We radiograph along two orthogonal lines of sight, using nickel or zinc pinhole-apertured x-ray backlighters, to study the subsequent hydrodynamics. We present initial experimental results and multi-dimensional simulations of the experiment. [Preview Abstract] |
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8HE.00021: Astrophysical jet experiments with colliding laser-produced plasmas Chris Gregory, Jon Howe, Berenice Loupias, Simon Myers, Margaret Notley, Youichi Sakawa, Akira Oya, Ryosuke Kodama, Michel Keonig, Nigel Woolsey We present the results of experiments in which jets are created through the collision of two laser-produced plasmas. These experiments use a simple `v-foil' target design: two thin foils are placed at an angle of 140 degrees to each other, and irradiated with a high-energy laser. The plasmas from the rear face of these foils collide and drive plasma jets moving with a velocity of $\sim $ 300 km/s. By choosing the foil thickness and material to suit the laser conditions available, it has proven possible to create plasma jets for which the relevant scaling parameters show significant overlap with those of outflows associated with young stellar objects (YSOs). Preliminary results are also shown from experiments to study the effect of an ambient gas on jet propagation. Nominally identical experiments are conducted either in vacuum or in an ambient medium of 5 mbar of nitrogen gas. The gas is seen to increase the jet collimation, and to introduce shock structures at the head of the outflow. [Preview Abstract] |
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8HE.00022: Simulations of the supersonic radiative jet propagation in plasmas Xavier Ribeyre, Philippe Nicolai, Stephane Galera, Vladimir Tikhonchuk The supersonic plasma jets are ubiquitous in astrophysics. We focus our attention on the jets emanated Herbig-Haro objects. They have velocities of a few hundred km/s and extending for a parsec. The interaction of the jets with the surrounding matter produces two structures at the jet head: the bow shock and the Mach disk. The radiative cooling of these shocks affects strongly the jet dynamics. A tool to understand the physics of these jets is the laboratory experiment. The supersonic jet-plasma interaction with surrounding plasma was studied on the PALS laser facility [1]. A collimated high-Z plasma jet with a velocity exceeding 400 km/s was generated and propagated over a few millimeters length. The jet radiative cooling is an important mechanism of jet formation, and propagation similarly to what was shown in the astrophysical context [2]. We study the jet propagation in plasmas and structure of the interaction zone using 2D ALE radiative code CHIC. A comparison between the adiabatic and radiative jets for various relative density ratios is performed. The bow shock and Mach disk evolution and their dependence are studied. A multigroup treatment of the radiative transport makes important differences in the shock structure, compared to the model [2] of radiative losses. [1] Nicola\"i, Ph., 2006 {\it et al.} {\it Phys. of Plasmas} {\bf 13}, 062701 [2] Blondin, J. M. {\it et al.}, 1990 {\it Astr. Phys. J.} {\bf 360}, 370 [Preview Abstract] |
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8HE.00023: Curved Herbi-Haro Jets: Simulations and Experiments Andrea Ciardi, David J. Ampleford, Sergey V. Lebedev, Chantal Stehle Herbig-Haro jets often show some degree of curvature along their path, in many cases produced by the ram pressure of a side-wind. We present simulations of both laboratory and astrophysical curved jets and experimental results from laboratory experiments. We discuss the properties and similarities of the laboratory and astrophysical flow, which show the formation of internal shocks and working surfaces. In particular the results illustrate how the break-up of the bow-shock and clumps in the flow are produced without invoking jet variability; we also discuss how jet rotation reduces the growth of the Rayleigh-Taylor instability in curved jets. [Preview Abstract] |
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8HE.00024: Kelvin-Helmholtz instability in radiative jets: analytical and numerical study Emeric Falize, Frederic Dias, Serge Bouquet, Nicolas Charpentier We study the influence of cooling on the Kelvin-Helmholtz instability in the context of astrophysical and laboratory jets. It is clear that YSO jets spread into interstellar medium and consequently they may develop shear instability. We know that YSO jets are radiative (radiative energy losses) and therefore the cooling can play an important role in the morphologic and dynamic evolution of jets [Blondin et al., ApJ \textbf{360 }370-386 (1990)]. Thus we study the feedback of the radiative process in the development of Kelvin-Helmholtz instability. We derive the dispersion relation in the linear stability and obtain the different stability branches numerically. These results will permit to validate numerical codes in order to study non-linear regimes. [Preview Abstract] |
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8HE.00025: Simulations of high energy density plasma physics and laboratory astrophysics experiments J.P. Chittenden, A. Marocchino, S.V. Lebedev, R.A. Smith, A. Ciardi, C.A. Jennings We show how 3D resistive MHD simulations can be used in the design and interpretation of Laboratory Astrophysics and High Energy Density Plasma Physics experiments at Imperial College, Sandia National Laboratory and Centre d'Etudes de Gramat. Using pulsed power generators to drive conical wire arrays, provides a mechanism of generating radiatively cooled hypersonic jets which model the interaction of jets from young stellar objects with the ISM and the deflection of these jets by side-winds. Radial wire arrays can be used to study magnetically launched jets, the effects of field topology on jet stability and episodic jets. Radial arrays also represent a high intensity compact radiation source, with potential applications to inertial confinement fusion. The collision of a magnetically accelerated foil with a gaseous target can be used to study of shock waves with strong radiative cooling. The interaction of a short pulse laser with cluster media can generate expanding blast waves in high energy density plasmas. Simulations of experiments with two cylindrical expanding blast waves, show the evolution of a complex 3D Mach stem, which can be compared to tomographic experimental data. [Preview Abstract] |
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8HE.00026: Analytical structure of stationary radiative shocks in polars Emeric Falize, Serge Bouquet, Claire Michaut, Cecile Cavet, Michel Koenig, Alessandra Ravasio Radiating shocks are very common in astrophysics. We may find them in accretion objects but also in InterStellar Medium [ISM] (bow shocks, supernova remnants). Moreover, the prediction of the structure of the post-shock zone is crucial to understand the evolution of accreted plasmas and ISM, as well. In this paper, we will present the general analytical solution for the stationary radiating shock problem. After having discussed the fundamental physics of this type of shock and explained their location in Drake diagram with our radiation approximation, we present the analytical solutions of generalized power law cooling functions where we introduce the possibility of local dependence that allows to include phenomena arising in optical thick regimes. We will construct the scaling laws of radiative shocks in polars context and study the possibility to reproduce them in laboratory. [Preview Abstract] |
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8HE.00027: ABSTRACT WITHDRAWN |
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8HE.00028: Design of Jet-Driven, Radiative-Blast-Wave Experiments for Omega EP R. Paul Drake, J.P. Knauer We discuss the design of jet-driven, radiative-blast-wave experiments for the Omega EP (EP) laser facility. In experiments motivated by astrophysics, plasma jets have been produced by a number of research teams on a variety of laser and z-pinch facilities. Among those that have driven a bow shock into an ambient medium, none have yet been fast enough to create strong radiative effects in the ambient medium. This becomes possible on EP because of the large amount of energy available (7.5 kJ in 1 ns or 19.5 kJ in 10 ns) when three EP beams are used to drive the experiment. We describe the design and simulations of such experiments for EP. The basic approach is to shock the jet material and then accelerate it through a collimating hole and into a Xe ambient medium. We identify issues that must be addressed through experimentation or further simulations in order to field successful experiments. [Preview Abstract] |
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8HE.00029: Radiation effects and radiation back reaction in strong and QED-strong pulsed laser fields Igor Sokolov, Stepan Bulanov, Natalia Naumova, John Nees, Victor Yanovsky A particle counter-propagating in strong laser field may experience QED strong field, as long as the energy associated with its motion is sufficiently high. An electric field may be considered to be QED-strong if it exceeds the Schwinger limit: E$>$m$^{2}$c$^{3}$/eh. Counter-propagating electrons can be generated in the course of strong laser pulse interaction with a solid target, so that QED effects become both macroscopic and significant, at high laser intensities. A correlated example exists in close proximity to a pulsar, where a QED-strong electric field may be exerted by relativistic charged particles, gyrating in the strong magnetic field of a neutron star, as the result of the Lorentz transformation of the electromagnetic field. We offer a model which is based on a numerical procedure to solve the Lorentz-Abraham-Dirac equation, with the self-force, in a classical limit, with QED corrections derived from the solution of the Dirac equation, for QED-strong fields. The QED effects are included into a kinetic physical and PIC numerical model via the effective interaction integral, quantitatively accounting for the electron and positron interactions with virtual photons. [Preview Abstract] |
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8HE.00030: Applications of Radiation-Driven Blast Waves at Z T.E. Tierney, R.G. Watt, G.C. Idzorek, C.L. Fryer, D.L. Peterson, R.R. Peterson, H.E. Tierney Radiation-driven blast waves (BWs) occur when the wave speed of an initially diffusive, supersonic radiation wave becomes subsonic and forms a radiographically-visible, hydrodynamic shock wave.~ BWs have been shown to be extremely energy sensitive, a fact we exploit as a calorimetry diagnostic. Experiments that use Sandia's Z-dynamic hohlraum as a quasi-Planckian radiation source often require accurate source energy measurements.~ We have used BWs as a principal diagnostic in experiments of hohlraum energy loss through diagnostic and entrance holes. We also intend to use BWs as a code validation technique for simulating the interaction between radiation-driven BWs sourced by a supernova with a companion star. We discuss experimental designs that use BWs as a diagnostic, and describe the computational and experimental uncertainties associated with BWs. This work was performed under the auspices of the Los Alamos National Laboratory for the U.S. Department of Energy. [Preview Abstract] |
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8HE.00031: Investigation of the evolution of modulated radiative blast waves created by high intensity laser - cluster interaction H.J. Quevedo, I.T. Kim, W. Bang, D.R. Symes, J. Osterhoff, R. Faustlin, M. Maurer, A.C. Bernstein, A.S. Moore, E.T. Gumbrell, A.D. Edens, R.A. Smith, T. Ditmire Radiative blast waves exhibiting instabilities are common and play an important role in astrophysics. Certain aspects of these astrophysical waves can be reproduced in suitably designed laboratory experiments. Previous laboratory experiments have shown that blast waves can be created from intense laser-cluster interactions and the evolution of these waves in high Z cluster gases is radiative, with trajectories that deviate from an adiabatic Sedov-Taylor expansion. With this approach, we have been studying the evolution of hydrodynamic perturbations on cylindrical blast waves in the radiative regime. In our experiment, cylindrical blast waves are generated by high intensity irradiation of an argon cluster jet. The blast waves' spatial profile is modified by initially destroying clusters in specific locations using another laser pulse. This modulation then becomes the seed to study the variation in the perturbations' amplitude. We observe some initial evidence for the oscillatory behavior predicted by the Vishniac model of perturbations on thin shell blast waves. [Preview Abstract] |
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8HE.00032: Laser driven shocks in a large magnetized plasma Christoph Niemann, Carmen Constantin, Andrew Collette, Patrick Pribyl, Shreekrishna Tripathi, Erik Everson, Alexandre Gigliotti, Stephen Vincena, Nathan Kugland, Walter Gekelman, Radu Presura, Stephan Neff, Christopher Plechaty We will present experiments on the interaction of an energetic laser-produced plasma with a large magnetoplasma. Laser intensities in excess of 10$^{12}$ W/cm$^2$ produce an ablating plasma plume with expansion velocities of several 100 km/s. Prior to the laser pulse an ambient plasma with a length of 18 m and a dimater of 50 cm is created at 2x10$^{12}$ cm$^{-3}$ and 5 eV in an axial magnetic field of 600 G (the Large Plasma Device). We observe large amplitude Alfv$\acute{e}$n waves radiated from the laser-produced plasma. [Preview Abstract] |
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8HE.00033: Simulations of Radiative Shock Experiments for Omega F.W. Doss, R.P. Drake, A. Reighard, H.F. Robey, L. Suter Astrophysical systems in which radiation transport across a shock front contributes substantially to the properties and dynamics of the system may be modeled in laboratory experiments under high-energy-density conditions. Recent experiments on the Omega laser facility have launched drive disks of Be into shock tubes of Xe gas at atmospheric pressure to produce radiating shocks, which are then diagnosed for structure and density profile by x-ray pinhole radiography. A series of radiation-hydrodynamics simulations using the code HYDRA have been produced, exploring the predicted results of experiments of this type. The simulations will assist in our target design process and in choosing which experiments should be run to obtain maximum information of interest. This research was sponsored by the NNSA through DOE Research Grants DE-FG52-07NA28058, DE-FG52-04NA0064, and the NNSA Stewardship Science Graduate Fellowship. [Preview Abstract] |
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8HE.00034: ABSTRACT WITHDRAWN |
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8HE.00035: Interplay of electrostatic and electromagnetic instabilities for ultra-intense charged particle beams in a plasma Dmitri Ryutov The physics of ultra-Intense charged particle beams propagating through the plasma is of a significant interest for laboratory astrophysics. Most attention has been directed towards the analysis of electromagnetic filamentation instabilities. On the other hand, there exists a broad class of very powerful electrostatic instabilities, e.g., the Bunemen instability. The author considers in a unified fashion linear theory for both types of instabilities under conditions where there is no magnetic field in an unperturbed state (i.e., the beam current is fully neutralized by the plasma current). The following factors are taken into account: the beam energy and angular spread; plasma non-uniformity; particle collisions in the background plasma. The areas of the parameter domain where one or another instability is prevalent are identified; the results are presented in the form of several easy-to-use diagrams. Prepared by LLNL under contract DE-AC52-07NA27344. [Preview Abstract] |
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8HE.00036: Relativistic Boltzmann equations for the pair plasma in presence of baryon loading Alexey Aksenov, Remo Ruffini, Gregory Vereshchagin In the recent publication we analyzed the role of the direct and the inverse binary and triple interactions in reaching thermal equilibrium in homogeneous isotropic pair plasma, starting from a nonequlibrium state. In the present work we extend the analysis to the case of baryon-loaded plasma. The corresponding timescales for thermalization of electrons, positrons, protons and photons are determined out from the numerical solution of the relativistic Boltzmann equations. We include all exact QED collisional integrals for binary reactions, while for the corresponding radiative variants we reduce reaction rates to the known expressions of kinetic coefficients in the thermal equilibrium. [Preview Abstract] |
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8HE.00037: Pair production in non-uniform electric fields Hagen Kleinert, Remo Ruffini, She-Sheng Xue Treating the production of electron and positron pairs in vacuum by a strong electric field as a quantum tunneling process, we derive in semiclassical approximation the pair production rate for nonuniform fields E(z) pointing the z-direction. In addition, we discuss tunneling processes in which an empty atomic bound state is spontaneously filled with a negative-energy electron creating a positron. The general expression is applied to a confined field, a semi-confined field, and a linearly increasing field. The boundary effects of the confined fields on pair-production rates are explicitly evaluated. Finally, we calculate the rate at which the atomic level of a bare nucleus of finite size and large Z are filled by electrons from the vacuum under positrons emission. [Preview Abstract] |
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8HE.00038: Electron-positron pairs production in an electric potential of massive cores She-Sheng Xue, Remo Ruffini Negative energy states of electrons bounded by a massive core with the charge-mass-radio Q/M and macroscopic radius R$_c$ are discussed. We show that the negative energies of bound states are lower than the negative electron mass-energy (-mc$^2$), and energy-level-crossing occurs. If these bound states are not occupied, electron-positron pair production takes place by quantum tunneling. Electrons fill into these bound states and positrons go to infinity. We explicitly calculate the rate of such pair-production, and compare it with the rates of electron-positron production by the Sauter-Euler-Heisenberg-Schwinger and Hawking processes. [Preview Abstract] |
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8HE.00039: Radiation of electrons in Weibel-generated fields. -- A general case. Mikhail Medvedev Weibel instability turns out to be the a ubiquitous phenomenon in High-Energy Density environments, ranging from astrophysical sources, e.g., gamma-ray bursts, to laboratory experiments involving laser-rpoduced plasmas. Relativistic particles (electrons) radiate in the Weibel-produced magnetic fields in the Jitter regime. Conventionally, in this regime, the particle deflections are considered to be smaller than the relativistic beaming angle of 1/$\gamma$ ($\gamma$ being the Lorentz factor of an emitting particle) and the particle distribution is assumed to be isotropic. This is a relatively idealized situation as far as lab experiments are concerned. We relax both assumptions (i.e., the smallness of the deflection angle and the isotropy of radiating particles) and present the extension of the jitter theory amenable for comparisons with experimental data. [Preview Abstract] |
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8HE.00040: Effects of Shock Instability on Spin and Kick of Proto-Neutron Star in Supernova Cores Wakana Iwakami, Naofumi Ohnishi, Kei Kotake, Shoichi Yamada, Keisuke Sawada We have numerically studied the standing/spherical accretion shock instability (SASI) for a core-collapse supernova. The core-collapse supernova is an explosion of a massive star in the final stage of its evolution. Although this spectacular phenomenon is a key issue for astrophysics, the explosion mechanism has not been understood perfectly. Recently, SASI has widely been noticed since it may play an important role for the explosion mechanism of a core-collapse supernova. In addition to it, the latest studies suggest that SASI may also affect on rotation and kick of a pulsar which is regarded as a neutron star formed by the supernova explosion. The origin of a pulsar spin and kick has been vigorously investigated, but it is still controversial among astrophysicists. We report on the effects of SASI on spin and kick of the proto-neutron star with the results of three-dimensional simulations. [Preview Abstract] |
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8HE.00041: Roles of shock instability interacting with neutrino radiation on supernova explosions Naofumi Ohnishi, Wakana Iwakami, Kenichi Sugai, Kei Kotake, Shoichi Yamada Standing accretion shock instability (SASI) is expected to be a feasible candidate to trigger a core-collapse supernova explosion which has not well understood yet. We have studied this phenomenon with including neutrino heating and realistic EOS and found that SASI may enhance neutrino heating. However, the successful explosion still seems to be difficult without additional excitaion process of the shock instability which may be sustained by acoustic-vortex cycle in the supernova cores. We have performed the simulations with $g$-mode of proto-neutron star that may enhance the SASI growth. Moreover, a new numerical method of neutrino transport for more sophisticated simulations is presented. We discuss also a possible laboratory experiment of SASI. [Preview Abstract] |
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8HE.00042: Non-relativistic collisionless shocks in unmagnetized electron-proton plasmas Tsunehiko Kato, Yasuhiro Kuramitsu, Youichi Sakawa, Hideaki Takabe We show that collisionless shocks with non-relativistic propagation speed can be driven even in unmagnetized electron-proton plasmas by using two-dimensional particle-in-cell simulations. We performed a series of simulations for flow velocities of 0.9c, 0.45c, 0.2c and 0.1c with a reduced proton to electron mass ratio of 20 and observed formation of collisionless shocks in all cases. In these shocks, the Weibel-type instability generates strong magnetic fields within the shock transition layer. The generated magnetic fields provide an effective dissipation mechanism for the upstream plasma which enables the shocks to form without background magnetic fields. Since non-relativistic shocks are frequently driven in weakly magnetized electron-proton plasmas in the universe associated with various astrophysical phenomena (e.g., supernova explosions), this kind of shocks mediated by the Weibel instability can exist in the universe. In addition, thanks to the self-similarity in the basic equations of collisionless plasma, there is a possibility to generate such shocks in a laboratory with high-power laser facilities by scaling the quantities. [Preview Abstract] |
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8HE.00043: Relativistic Jets from Collapsars and its Energy Distribution Akira Mizuta The origin of some of long GRBs is believed to be supernovae. It is difficult to know the properties of progenitors. We perform relativistic hydrodynamic simulations of jet propagation in the collapsar and interstellar medium, using some possible progenitors developed by massive stellar evolution to study the dependence on the progenitor for the emissivity from the jet. The the jet is well collimated in the progenitor, though the injected jet has some opening angles. The internal structure, such as internal shocks, is quite less, if the opening angle is not so small. Though the progenitors which we used in this study have different radius, total mass, mass distribution, etc. the energy distribution of jet in angle does not strongly depend on the properties of the progenitors after the jet break of the progenitor. [Preview Abstract] |
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8HE.00044: On the self-acceleration of fireshell Carlo Bianco, Remo Ruffini, Gregory Vereshchagin, She-Sheng Xue The Fireshell in a Gamma-Ray Burst (GRB) has the most unique feature in the entire field of physics of self-accelerating from a Lorentz gamma factor equal to 1 all the way to 200-300. The hysics of this most extraordinary system is based on the continuous annihilation of electron-positron pairs in an optically thick e$^{+}$e$^{-}$ plasma. The physical reasons for this self-acceleration reanalyzed and the fireshell dynamics is compared with the ``fireball'' solution usually adopted in GRB literature. [Preview Abstract] |
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8HE.00045: Thermalization of the pair plasma and the consequences for Gamma-Ray Bursts Gregory Vereshchagin, Alexey Aksenov, Remo Ruffini We consider initial conditions in the sources of Gamma-Ray Bursts. We show that hot and dense pair plasma, created in the source, relaxes to thermal equilibrium configuration with zero chemical potentials well before it starts to expand driven by the radiative pressure. The relaxation process follows the sequence: pairs, protons, photons, thus the first particles reaching the same temperature are electrons and positrons, while photons join the thermal math latest. We also show that light nuclear elements cannot be synthesized in the fireball. [Preview Abstract] |
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8HE.00046: High Density Plasmas in Black Hole Candidates Ari Brynjolfsson While cosmological observations are progressing exceptionally well, the theoretical interpretation of the observations are becoming ever more difficult. The difficulties are mainly due to two fundamental misconceptions: 1. It is generally believed that most of the redshifts are due to Doppler shifts, while in fact most of them are due to plasma redshifts. 2. It is generally believed that photons have weight in the local system of reference, while photons actually are weightless. Eliminating these misconceptions changes in fundamental ways the cosmological perspective and facilitates explanation of great many phenomena that have been difficult to explain, including the physics of black hole candidates. The overlooked plasma-redshift cross-section gives an explanation of the cosmological redshift without ``big bang,'' ``inflation,'' ``dark energy,'' or ``dark matter.'' It also explains the cosmic microwave background, the X-ray background, and much more. There are no black holes due to the weightlessness of photons. Instead the black hole candidates are engines for conversion of burned out nuclear matter to hot and dense primordial matter, which assures continual renewal of the world. [Preview Abstract] |
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8HE.00047: Static equilibrium configuration of two charges in General Relativity Vladimir Belinski, George Alekseev An asymptotically flat static solution of Einstein-Maxwell equations which describes the field of two Reissner - Nordstrom sources in equilibrium is presented. It is expressed in terms of physical parameters of the sources (their masses, charges and separating distance). Very simple analytical forms were found for the solution as well as for the equilibrium condition which guarantees the absence of any struts on the symmetry axis. This condition shows that the equilibrium is not possible for two black holes or for two naked singularities. However, in the case when one of the sources is a black hole and another one is a naked singularity, the equilibrium is possible at some distance separating the sources. It is interesting that for appropriately chosen parameters even a neutral Schwarzschild black hole can be ``suspended'' freely in the field of a naked singularity which phenomenon is due to the repulsive forces produced by a naked singularity. [Preview Abstract] |
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8HE.00048: On the general theory for construction the static solutions for two charges in General Relativity George Alekseev, Vladimir Belinski In this talk we present a general family of static asymptotically flat solutions for the superposed gravitational and electromagnetic fields of two Reissner-Nordstrom sources with arbitrary parameters: masses, charges and separating distance. The Inverse Scattering Method for Einstein-Maxwell equations for stationary axisymmetric fields is outlined. The family of equilibrium configurations of two Reissner-Nordstrom sources (one of which should be a black hole and another one $\vert $a naked singularity) described in our first talk arises after a restriction of the parameters of the general solution presented here by the equilibrium condition which provides the absence in the solution of conical singularities on the symmetry axis between the sources. [Preview Abstract] |
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8HE.00049: Lines of force in the Alekseev-Belinski solution Marco Pizzi, Armando Paolino Recently Alekseev and Belinski have presented a new exact solution of the Einstein-Maxwell equations which describes two Reissner-Nordstrom (RN) sources in reciprocal equilibrium (no struts nor strings); one source is a naked singularity, the other is a black hole: this is the only possible configuration for separable objects, apart from the well-known Majumdar-Papapetrou case. We studied in some detail the coordinate systems used and the main features of the gravitational and electric fields of this solution. Classically-forbitten equilibria are also allowed by this new solution. In particular we show the plots of the electric force lines in the three qualitatively different equilibrium configurations: equal-signed charges, opposite charges and the case of a naked singularity near a neutral black hole. [Preview Abstract] |
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8HE.00050: On the dyadotorus Christian Cherubini, Andrea Geralico, Jorge Rueda, Remo Ruffini The ``dyadotorus'' is defined as the region around a Kerr-Newman black hole where pair creation by vacuum polarization occurs. This concept extends to the case of stationary geometries the concept of ``dyadosphere'' already introduced in the static case in the Reissner-Nordstrom geometry. The energetics of the dyadotorii, their topology and embedding diagrams are compared and contrasted to the ones of the black hole. [Preview Abstract] |
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8HE.00051: Charged particles in the Reissner-Nordstrom geometry Donato Bini, Andrea Geralico, Remo Ruffini The multiyear problem of a two-body system consisting of a Reissner-Nordstr\"om black hole and a charged massive particle at rest is here solved by an exact perturbative solution of the full Einstein-Maxwell system of equations. The expressions of the metric and of the electromagnetic field, including the effects of the electromagnetically induced gravitational perturbation and of the gravitationally induced electromagnetic perturbation, are presented in closed analytic formulas. Particular attention is given to the analysis of the lines of force of the system formed by the black hole and the naked singularity describing the test particle. The new general relativistic effects leading to an electric Meissner effect are explored. [Preview Abstract] |
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8HE.00052: The electrostatics of naked singularity Andrea Geralico, Donato Bini, Remo Ruffini In order to further explore the physical reasons leading to an equilibrium configuration of a charged naked singularity in the field of the black hole the structure of the naked singularity and its mass energy are examined. Particular attention is given to define the physical achievable, stable equilibrium configurations. [Preview Abstract] |
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8HE.00053: HED physics opportunities on OMEGA/OMEGA EP David Meyerhofer The 60 beam, 30 kJ, OMEGA laser facility has been operating at the University of Rochester for more than a decade. The OMEGA EP laser facility adjacent to it will be completed in Q3FY08. OMEGA EP will consist of four beamlines with NIF-like architecture. Each of the beams will ultimately produce 10 ns 6.5 kJ energy ultraviolet pulses directed into the EP target chamber. Two of the beamlines will also operate as high energy petawatt (HEPW) lasers, with up to 2.6 kJ each in 10 ps IR pulses. The HEPW beams can be injected into either the EP chamber or the existing OMEGA target chamber for integrated experiments. This talk will describe the OMEGA EP project status, HED physics possibilities on the combined system, and opportunities for external user access. The ongoing OMEGA EP Use Planning process will be described. This work was supported by the U.S. D.O.E Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. [Preview Abstract] |
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8HE.00054: High-energy laser experiments on the Large Plasma Device Carmen Constantin, Andrew Collette, Shreekrishna Tripathi, Patrick Pribyl, Erik Everson, Alexandre Gigliotti, Steve Vincena, Nathan Kugland, Radu Presura, Stefan Neff, Christopher Plechaty, Walter Gekelman, Christoph Niemann The interaction of a laser-plasma with a large magnetized plasma was studied with a high-energy laser at the Large Plasma Device. We will compare the magnetohydrodynamic response of the ambient plasma for a variety of plasma blow-off conditions as measured with an array of magnetic pickup and Langmuir probes. [Preview Abstract] |
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8HE.00055: Solid liner on plasma Magnetized Target Fusion physics demonstration T.P. Intrator, G.A. Wurden, P.E. Sieck, W. Waganaar, M. Kostora, J. Degnan, E.L. Ruden, C. Grabowski, M. Domonkos, W. Sommars, M. Frese, R.E. Siemon, T. Awe, A.G. Lynn, M. Gilmore We summarize a Magnetized Target Fusion (MTF) effort, whose primary goal is the first integrated solid liner on plasma physics demonstration at Air Force Research Laboratory (AFRL) in 2008. The compression experiment at AFRL uses an aluminum, flux conserving shell, and a physics experiment at LANL defines the experimental design and diagnostic capabilities. The initial target plasma parameters are 400eV temperature, 3e22m$^{-3}$ density, and lifetime of 10 micro sec. Deformable contact vacuum liner experiments at the AFRL Shiva Star facility have demonstrated a shell kinetic energy of 1.5MJoule which stretches to maintain contact with the electrodes while the body of the liner glides radially inward to implode uniformly. The LANL FRXL experiment has a physics oriented front end with slotted liner, radial access for probes, optical diagnostics, and magnetics. [Preview Abstract] |
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8HE.00056: Diagnostics for heavy ion beam driven Warm-dense-matter experiments. Pavel Ni, Bieniosek Frank, Matthaeus Leitner, William Waldron Intense heavy ion beams are an excellent tool to create large-volume samples of warm-dense-matter (WDM) with fairly uniform physical conditions. An extensive WDM experimental program is scheduled at LBNL where NDCX accelerator is used as a driver for heating metallic targets. This poster will focus on designing and im- plementation of diagnostics for a target. The diagnostics include a fast multi-channel optical pyrometer, absolutely calibrated streak camera- based spectrometer, Doppler-shift laser interferometer (VISAR) and fast gated CCD cameras. This equipment is capable of precise measurement of temperature starting from 2000 K, pressure in kbar region, and ex- pansion velocities up to several km/sec. Temporal resolution of the diagnostic is on a sub-nanosecond time scale. [Preview Abstract] |
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8HE.00057: Ideal Z-Pinch Instabilities Across Fluid Plasma Regimes John Loverich, Ammar Hakim In this paper we model instabilities in high density Z-pinches across fluid plasma regimes. The theory of MHD instabilities in a Z-pinch plasma is well understood, in this paper we look at numerical predictions that extend well beyond MHD to a variety of high energy density fluid models. Currently, researchers at Tech-X are investigating Hall MHD, Two-Fluid and Gyroviscous models of plasma to properly model fast fluid plasma processes that are high density, but where the plasma size approaches the ion magnetization scale length. It is in this regime that electron drift velocities are high relative to the ion acoustic speed and a number of new instabilities begin to emerge that cannot be modeled with traditional MHD theory and where numerical methods are highly desirable for modeling the non-linear effects. Results are presented for Z- pinch simulations using ideal fluid models with comparison to MHD. In time, we hope to model other key effects such as radiation and ionization in addition to developing algorithms for better modeling the vacuum region. [Preview Abstract] |
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8HE.00058: A Web 2.0 Interface to Ion Stopping Power and Other Physics Routines for High Energy Density Physics Applications Peter Stoltz, Seth Veitzer We present a new Web 2.0-based interface to physics routines for High Energy Density Physics applications. These routines include models for ion stopping power, sputtering, secondary electron yields and energies, impact ionization cross sections, and atomic radiated power. The Web 2.0 interface allows users to easily explore the results of the models before using the routines within other codes or to analyze experimental results. We discuss how we used various Web 2.0 tools, including the Python 2.5, Django, and the Yahoo User Interface library. Finally, we demonstrate the interface by showing as an example the stopping power algorithms researchers are currently using within the Hydra code to analyze warm, dense matter experiments underway at the Neutralized Drift Compression Experiment facility at Lawrence Berkeley National Laboratory. [Preview Abstract] |
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8HE.00059: Effects of a Center Wire on Conical Wire Array Z-Pinches David Martinez, Radu Presura, Lucas Wanex, David Ampleford Recent experiments have shown that plasma dynamics of conical wire arrays can help elucidate aspects of z-pinch dynamics [Ampleford et. al. Phys of Plasma 14 102704, (2007)]. At the Nevada Terawatt Facility we investigated the implosion dynamics of conical wire arrays with an additional wire located on the axis of the pinch. These experiments were conducted on Zebra, a 2 TW pulse power device capable of delivering a 1 MA current in 100 ns [Bauer et al AIP Conf. Proc. 409, 153 (1997)]. Normally a conical wire array generates an imploding plasma with an axial velocity component. The additional center wire generates an axial current carrying plasma that serves as a target for the plasma accelerated from the outer wires, leading to the growth of the Kelvin-Helmholtz instability. This poster compares the dynamics and x-ray emission of the traditional and modified conical wire array pinches. In addition, we explore the effect of the center wire by including in the comparison cylindrical wire arrays with and without a center wire. [Preview Abstract] |
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8HE.00060: Penetration of Conductive Plasma Across a Magnetic Field Christopher Plechaty, Sandra Wright, Stephan Neff, Philippe Leblanc, Radu Presura The mechanism which allows a conductive plasma to penetrate through a magnetic field, such as the penetration of the solar wind into the Earth's magnetosphere, is still under debate. Several explanations exist which attempt to explain this phenomenon. Three such explanations are magnetic reconnection (Dungey 1961), a viscous-like interaction (Axford and Hines 1961), and a process called impulsive penetration (Lemaire and Roth 1978, Schmidt 1960). Experiments were performed at the Nevada Terawatt Facility to investigate the interaction of an expanding, conductive plasma with an external magnetic field orientated perpendicular to the expansion direction. In these experiments, the plasma was observed to penetrate the magnetic field due to instabilities which formed on the boundary layer between the plasma and the magnetic field. The experimentally observed penetration mechanism will be compared with those previously listed. Work supported by DOE/NNSA grant DE-FC52-06NA27616. [Preview Abstract] |
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8HE.00061: Laboratory Simulation of Instabilities in the Earth's Magnetotail Sandra Wright, Radu Presura, Stephan Neff, Christopher Plechaty, Philippe Leblanc The solar wind crosses the magnetic field of the earth and mixes with the plasma of terrestrial origin. The fast particles from the solar wind are responsible for satellite damage, communication disruptions and power blackouts on earth. A better understanding of this penetration process is needed in order to be able to accurately predict it. One experiment attempting to accomplish this was performed at the Nevada Terawatt Facility. This utilized the coupling of a short-pulse laser with a pulsed-power generator to study the interaction of a laser produced plasma with an independently produced magnetic field. The magnetic field induced a sheared flow along the boundary of the plasma plume which caused a Kelvin-Helmholtz instability similar to that found in the interaction between the solar wind and the magnetosphere that leads to the penetration of the fast particles. The instability produced in the experiment will be discussed along with its relevance to the solar wind/magnetosphere interaction. [Preview Abstract] |
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8HE.00062: Magnetically accelerated foils for shock wave experiments Stephan Neff, Jessica Ford, David Martinez, Christopher Plechaty, Sandra Wright, Radu Presura The interaction of shock waves with inhomogeneous media is important in many astrophysical problems, e.g. the role of shock compression in star formation. Using scaled experiments with inhomogeneous foam targets makes it possible to study relevant physics in the laboratory, to better understand the mechanisms of shock compression and to benchmark astrophysical simulation codes. Experiments with flyer-generated shock waves have been performed on the Z machine in Sandia. The Zebra accelerator at the Nevada Terawatt Facility (NTF) allows for complementary experiments with high repetition rate. First experiments on Zebra demonstrated flyer acceleration to sufficiently high velocities (around 2 km/s) and that laser shadowgraphy can image sound fronts in transparent targets. Based on this, we designed an optimized setup to improve the flyer parameters (higher speed and mass) to create shock waves in transparent media. Once x-ray backlighting with the Leopard laser at NTF is operational, we will switch to foam targets with parameters relevant for laboratory astrophysics. [Preview Abstract] |
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8HE.00063: Progress in Ion Beam Driven High Energy Density Physics and Heavy Ion Fusion J.J. Barnard, R.H. Cohen, A. Friedman, D.P. Grote, S.M. Lund, L.J. Perkins, W.M. Sharp, B.G. Logan, J. Armijo, F.M. Bieniosek, J.E. Coleman, E. Henestroza, E.P. Lee, M. Leitner, R.M. More, P. Ni, P.K. Roy, P.A. Seidl, J.-L. Vay, W.L. Waldron, A. Zylstra, R.C. Davidson, E.P. Gilson, I. Kaganovich, H. Qin Recently, the U.S. heavy ion fusion science program has made significant experimental and theoretical progress in simultaneous transverse and longitudinal beam compression, ion-beam-driven warm dense matter and direct drive fusion target physics. First experiments combining radial and longitudinal compression of intense ion beams propagating through background plasma resulted in longitudinal compression by factors of over sixty and transverse focusing to focal spot sizes in which space charge effects have been virtually eliminated. These results are enabling ion beam target experiments at LBNL in 2008. We are theoretically investigating the physics of ion beam heated foils and metallic foams and the evolution of these targets. We are assessing how these new techniques apply to low cost modular drivers for inertial fusion energy. [Preview Abstract] |
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8HE.00064: High Energy-Density Plasma Production from Plasma-Filled Rod-Pinch Diodes J.W. Schumer, B.V. Weber, D. Mosher, J.P. Apruzese The Plasma-Filled Rod-Pinch diode (PFRP) concentrates a 100-ns, 500-kA, $>$MeV electron-beam onto the tip of a tapered tungsten rod, generating a High Energy Density Plasma (HEDP). The HEDP (warm dense plasma) is created by deposition of a high-power-density (40 $TW/cm^2$) electron-beam into solid-density tungsten. The diode current and voltage has been shown to be controllably modified between 260 kA and 1.8 MV to 770 kA and 0.45 MV by increasing the initial plasma-fill density. At the time of peak energy density, analytic estimates using a 0-d self-similar MHD model predict a solid-density (20 $g/cm^3$) tungsten plasma with 25 eV temperature, 16 Mbar pressure, and 2.4 $MJ/cm^3$ thermal energy density prior to rapid plasma expansion (after about 10 ns). Temperature and ionization state increase after this time as the rod-tip rapidly expands. This PFRP approach may have advantages for HEDP research. Various applications include high-fluence flash radiography and the study of equation-of-state of materials. Current research results will be presented. [Preview Abstract] |
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8HE.00065: 3D MHD simulations of radial wire arrays C. Jennings, D. Ampleford, A. Ciardi, J. Chittenden, S. Bland, N. Niasse We present 3D resistive MHD simulations evaluating multi-MA radial wire arrays as a potential compact, high intensity source for inertial confinement fusion and laboratory astrophysics. A radial wire array consists of wires running radially outwards from a central electrode, and was first investigated at the 1 MA level on the MAGPIE generator at Imperial College. Originally used as a method of producing magnetic tower laboratory jets relevant to astrophysics[1], they have also shown potential as a high power x-ray source. Able to produce x-ray pulses with a rise time and peak power comparable to cylindrical wire arrays, radial arrays occupy a smaller volume and may consequently be able to access higher power densities. We discuss simulation results reproducing radial array experiments performed on the MAGPIE facility as a means of benchmarking our model. This model is then used to evaluate radial wire arrays in the multi-MA regime for planned experiments on the Saturn generator of Sandia National Laboratories. [1] A. Ciardi et al, Phys. Plasmas 14, 056501 (2007) [Preview Abstract] |
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8HE.00066: Modeling double pulsing of ion beams for HEDP target heating experiments Seth Veitzer, John Barnard, Peter Stoltz, Enrique Henestroza Recent research on direct drive targets using heavy ion beams suggests optimal coupling will occur when the energy of the ions increases over the course of the pulse. In order to experimentally explore issues involving the interaction of the beam with the outflowing blowoff from the target, double pulse experiments have been proposed whereby a first pulse heats a planar target producing an outflow of material, and a second pulse ($\sim10$ ns later) of higher ion energy (and hence larger projected range) interacts with this outflow before reaching and further heating the target. We report here results for simulations of double pulsing experiments using HYDRA for beam and target parameters relevant to the proposed Neutralized Drift Compression Experiment (NDCX) II at LBNL. [Preview Abstract] |
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8HE.00067: K$_{\alpha}$ conversion efficiency from rare gas jets irradiated by ultra short laser pulses Nathan Kugland, Paul Neumayer, Andrew Collette, Carmen Constantin, Eduard Dewald, Tilo Doeppner, Dustin Froula, Frederic Girard, Siegfried Glenzer, Andrea Kritcher, Christoph Niemann The absolute laser conversion efficiency to K$_{\alpha }$-like inner shell x-rays (integrated from K$_{\alpha }$ to K$_{\beta })$ is observed to be an order of magnitude higher in argon gas jets than in solid targets due to enhanced emission from higher ionization stages following ultra short pulse laser irradiation. Excluding the higher ionization stages, the conversion efficiency to near-cold K$_{\alpha }$ is the same in argon gas jets as in solid targets. In krypton gas jets, we present conversion efficiency exclusively into near-cold K$_{\alpha }$ and K$_{\beta }$. This work was performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory, through the Institute for Laser Science and Applications, under contract DE-AC52-07NA27344. [Preview Abstract] |
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8HE.00068: Observations of Improvement in Conversion Efficiency to Laser Accelerated Protons Using Er-Hydride Coated Targets D. Offermann, L. Van Woerkom, R. Freeman, Y. Ping, A.J. Mackinnin, A.G. MacPhee, M.E. Foord, J.J. Sanchez, N. Shen, C.D. Chen Using the Callisto Laser, at LLNL ($8J$, $3\times10^{19}W/cm^2 $) we have compared proton beams originating from contaminant layers on Gold foil targets with beams from Gold targets coated with $ErH_3$. Contaminants were removed using an Ar-Ion etching beam. Data was collected using radiochromic film and a Thomson spectrometer. An improvement of 23\% in conversion efficiency for protons above $3MeV$ was observed due to $ErH_3 $. LSP simulations agree with this result when assumed that carbon ions in contaminants are predominantly He-like, as seen on the Thomson spectrometer. [Preview Abstract] |
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8HE.00069: Isochoric heating from fast electrons using mass limited targets Michel Koenig, Sophie Baton, Perceval Guillou, Patrick Audebert, Ludovic Lecherbourg, Benjamin Barbrel, Serna Bastiani-Ceccotti, Christophe Rousseaux, Laurent Gremillet, Erik Lefevre, Christina Back, Pravesh Patel, Tom Cowan, Jenny Rassuchine Experiments to investigate fast electron transport in thin, mass-limited multilayer targets were performed at the LULI 100 TW laser facility. The targets were composed of V/Cu/Al and varied from 300 to 50 $\mu $m in diameter. They were isochorically heated by a 20 J, 300 ps laser pulse that delivered I$\sim $2x10$^{19}$ W/cm2 to form a warm dense plasma. X-ray emission from the Cu and Al layers was measured using conical and spherical Bragg crystals. Time-resolved K$\alpha $ emission spectra were also obtained using an ultra-fast streak camera indicating a total refluxing of the electrons. The data from targets of different size and/or Cu layer thickness are compared and analyzed to better understand the heating of the target and temperature of the plasma. Temperatures up to several hundred eV have been deduced from detailed spectra analysis. Comparison with PIC simulations will be presented. [Preview Abstract] |
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8HE.00070: Hot Electron Generation in the Micro-Tipped Cone and Wedge Targets Irradiated with Ultra Intense Laser. B.I. Cho, G.M. Dyer, S. Kneip, D.R. Symes, A.C. Bernstein, S. Pikuz, Y. Sentoku, N. Le Galloudec, T.E. Cowan, T. Ditmire By comparing \textit{K$\alpha $} and bremsstrahlung x-rays yields, we have investigated hot electron generation from pyramidal-shaped reentrant micro-structured targets. We focused the THOR laser at the University of Texas at Austin (800nm, 40fs, 600mJ, 2 $\times $ 10$^{19}$ W/cm$^{2}$ ) into these cone and wedge shaped targets with various polarizations. We find that hot electron production is highest in the wedge targets when irradiated with transverse polarization, though \textit{K$\alpha $} is maximized with wedge targets and parallel polarization. These results are explained with particle-in-cell simulations. [Preview Abstract] |
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8HE.00071: Electron transport in the tip of cone targets in high intensity laser-plasma interaction Nathalie Le Galloudec, Emmanuel D'humieres, Byoung-Ick Cho, Jens Osterholz, Yasuhiko Sentoku, Todd Ditmire Cones targets of specific parameters were irradiated with the Thor laser (0.5J, 40fs, 800nm, 7micron focal spot, 3.10$^{19}$W/cm$^2$) at UT Austin. These targets have been diagnosed with a focus on hot electron transport especially in the tip. The results show a 5micron diameter beam exiting the outside tip after about 60 micron propagation in the bulk material of the tip itself. Key elements of the interaction will be presented along with supporting simulations. [Preview Abstract] |
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8HE.00072: High Intensity Laser Coupling to a Cone Geometry for Fast Ignition R.B. Stephens, K.U. Akli, A.J. MacKinnon, M.H. Key, A. MacPhee, Y. Ping, D. Offerman, D. Clark, R.R. Freeman, T. Link, V. Ovchinnikov, L. VanWoerkom, T. Bartal, F. Beg, S. Chawla, R.R. Freman, J.A. King, T. Ma, M.S. Wei, C. Chen, D. Hey, Y. Tsu The short -pulse laser, which ignites a fast ignition target, gains access to the compressed core through a reentrant cone that maintains a clear path through the blow-off plasma. The interaction of the laser with the cone surface is complex due to light and electron focusing by the cone walls. Furthermore, plasma produced by the prepulse can affect the interaction physics and electron transport. We report on experiments to study this, performed using Titan Laser facility (2$\times $10$^{20}$ W cm$^{-2})$. We imaged Cu K$_{\alpha }$ fluorescence in flat foils to show for the first time that the laser-generated electrons from glancing incidence light have no significant forward direction. Fluorescence images from cones support this conclusion, showing the electrons spread essentially randomly up to several hundred microns from a cone tip independent of focus conditions. [Preview Abstract] |
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8HE.00073: Analytical theory for the laser driven TNSA ion acceleration Matteo Passoni, Maurizio Lontano Ions can be effectively accelerated during the interaction of an ultra-intense ultra-short laser pulse irradiating a thin solid target via the so-called Target Normal Sheath Acceleration (TNSA) mechanism. A theoretical model of the quasi-static electric field that is formed at the target surfaces, due to the appearance of a cloud of laser-produced hot electrons, has been developed. The 1-dim Poisson equation has been analytically solved assuming a Maxwell-Boltzmann distribution in the ultrarelativistic limit for those electrons which are bounded in the positive electrostatic potential produced by the excess of ions left in the target. The solution turns out to depend on the maximum energy of the electrons responsible for the acceleration. This model is used to describe the maximum energies and the energy spectra of the ions accelerated in the field, making possible satisfactory comparisons with the most recent experimental and numerical data and predictions of regimes achievable in the future. [Preview Abstract] |
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8HE.00074: Study of Acceleration, Transport and Dephasing of Hot Electrons in Solid Density Plasmas Irradiated with Ultra Intense Laser Pulses B.I. Cho, J. Osterholz, A.C. Bernstein, G.M. Dyer, T. Ditmire We have characterized the transport of hot electrons in solid targets by coherent transition radiation (CTR). CTR was observed from the rear side of aluminum foils irradiated with the THOR laser (800 nm, 40 fs, 600 mJ, 2 $\times $ 10$^{19}$ W/cm$^{2})$ at the University of Texas at Austin. In the experiment, two distinct beams of hot electrons are emitted simultaneously from the target rear side. This observation shows that two different mechanisms, namely resonance absorption and $j \times $ B heating, accelerate the electrons at the target front side. These two distinct beams propagate through aluminum foils with different spatial and temporal characteristics and electron temperatures. The interpretation is confirmed by calculations of the electron acceleration and transport inside the target. [Preview Abstract] |
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8HE.00075: Observation of Two-Beam Coupling between Intersecting Filament-Forming Beams in Air Aaron Bernstein, Matthew McCormick, James Sanders, Todd Ditmire Controlling laser plasma filaments and their propagation is a major step toward their practical use in a variety of applications. Techniques typically rely on modifying beam launch conditions to optimize filament propagation. We present measurements of two-beam coupling between crossed filament-producing beams in ambient laboratory air, which may lead to scalable techniques for extending filament propagation dynamically. In the experiment, two pulses of less than 10 mJ and 80 fs duration were reflected off a 5 m focal length mirror, and made to cross either before, at, or after the filament location. By imaging the beams after the filaments have diffracted, energy transfers of +/-10{\%} were measured. This energy transfer was controllable by a relative delay of +/-20 fs for the compressed pulse case. In addition to beam images, single-shot measurements were made of laser energy and spectra of one of the beams. [Preview Abstract] |
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8HE.00076: Transport of Energy by Ultra-Intense Laser-Generated Electrons in Nail-Wire Targets T. Ma, J.A. King, M.S. Wei, F.N. Beg, K. Akli, R.B. Stephens, S.P. Hatchett, M.H. Key, A.J. Mackinnon, A.G. MacPhee, R.R. Freeman, L. Van Woerkom, J.S. Green, K.L. Lancaster, P.A. Norreys, W. Theobald, R. Mason Understanding the transport of energy by relativistic fast electrons produced in petawatt (10$^{15}$ W) laser matter interactions is one of the key challenges in fast ignition of ICF. A simple and small target (nail-wire) was designed to investigate aspects of this transport. Nail-wire targets were irradiated using the Vulcan Petawatt Laser (0.8 ps, 3x10$^{20}$ W/cm$^{-2})$ at the Rutherford Appleton Laboratory. A Cu K$\alpha $ spherically bent crystal imager, a Highly Ordered Pyrolytic Graphite (HOPG) Spectrometer, and Single Photon Counting CCD were employed to give absolute K$\alpha $ measurements. The penetration of hot electrons via the nail head into the bulk of the wire has been determined from the K$\alpha $ data. XUV images (68 and 256 eV) indicate heating of a thin surface layer of the targets. A comparison of experimental results with the PIC/hybrid simulations using both LSP and e-PLAS will be presented at the meeting. [Preview Abstract] |
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8HE.00077: Quantitative spatial information from K-alpha and XUV imagers in FI-related experiments with cone targets V.M. Ovchinnikov, D.W. Schumacher, L. Van Woerkom, R.R. Freeman The Fast Ignition (FI) concept for Inertial Confinement Fusion (ICF) relies on energetic electrons produced by laser-plasma interaction to deliver their energy into a pre-compressed fuel core. Metallic cones are proposed as a way of protecting the incoming short pulse igniter laser from the compression. Currently cone structures are widely studied to understand their effects on laser coupling to electrons. Typically, K-alpha and XUV two dimensional imaging diagnostics are used to obtain spatially resolved information of fast electron transport and temperature within a target, respectively. Since these images only capture specific emission wavelengths, uncertainties arise as to the physical location of the emission within the target. We developed detailed optical models for these diagnostics to obtain computer-generated images of a cone target as it would appear in the image plane of each diagnostic. Superimposing these images with actual K-alpha and XUV experimental images allowed us to pinpoint the location of emission with respect to the target boundaries. Sufficient knowledge of the target geometry along with the dimensions made it possible to map intensities from a 2D image onto a 3D cone surface thus reconstructing a 3D emission picture. [Preview Abstract] |
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8HE.00078: Laser channeling in mm-scale underdense plasmas of fast ignition targets C. Ren, G. Li, R. Yan, T.-L. Wang, J. Tonge, W.B. Mori In the fast ignition approach to laser fusion, non-linear laser-plasma interactions could cause significant energy loss for an ignition laser in an underdense plasma. One way to avoid this is to use a channeling pulse to create a low-density channel for the ignition pulse. Two dimensional Particle-in-cell simulations show that laser channeling in mm-scale underdense plasmas has many new phenomena that are not present in previous short-scale experiments and simulations, including plasma buildup to $n_c$ in front of the laser, laser hosing/refraction, channel bifurcation, and self-correction and electron heating to relativistic temperatures. The channeling speed is much less than the linear group velocity of the laser. The simulations find that low- intensity channeling pulses are preferred to minimize the required laser energy. The channel is also shown to significantly increase the transmission of an ignition pulse. [Preview Abstract] |
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8HE.00079: The ePLAS code for high-intensity laser-matter interaction studies R.J. Mason, M. Wei, F. Beg, J. King, R. Stephens, J. Fernandez, M. Hegelich The 2-D implicit hybrid simulation code e-PLAS has been developed to study inertial fusion targets undergoing intense short pulse laser illumination over large problem space and time scales. It treats the background target plasma electrons as a collisional Eulerian fluid and the ions as either a fluid or PIC particles-in-cell. Laser deposition near the critical surface converts the local cold electrons into a relativistic PIC component. Self-consistent \textit{E- and B- fields} are computed by the Implicit Moment Method [1,2]. This permits the completion of full interaction simulations in only a few hours of CPU time on a modern PC. Recent application has been made to cone -capped and nail-headed wire targets driven by sub-picosecond laser pulses at 1.06 $\mu $m and up to 4.0 x 10$^{20}$ W/cm$^{2}$, as well as to the focusing of ions driven from the back side of thin foils. Discussion will be given to recent ePLAS improvements in the light absorption physics and fast ion modeling. [1] R. J. Mason, and C. Cranfill, IEEE Trans. Plasma Sci. \textbf{PS-14}, 45 (1986). [2] R. J. Mason, J. Comp. Phys. \textbf{71,} 429 (1987). [Preview Abstract] |
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8HE.00080: Shock Compression of Iron Foils Relevant to Earth Core Conditions with Intense Laser K. Shigemori, Y. Hironaka, T. Kadono, K. Otani, A. Shiroshita, T. Irifune, N. Ozaki, K. MIyanishi, T. Endo, T. Kimura, R. Kodama, T. Sakaiya, T. Kondo, K. Shimizu, J. Wark Shock compression experiments were performed on GEKKO-XII/HIPER laser facility at ILE, Osaka University. Iron foils were irradiated to generate the pressure of Earth core ($\sim $ 350 GPa). We measured shock parameters with optical diagnostics, such as velocity interferometer system for any reflector (VISAR) and spectrally streaked optical pyrometer. We also measured with x-ray diffraction technique for determination of shock compressed crystal structure. Simultaneous measurements of optical diagnostics and x-ray diffraction were done for MgO and diamond crystal foils as well as iron foils. [Preview Abstract] |
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8HE.00081: Laser-shock compression of liquid hydrogen and the interior structure of gas giant planets Takayoshi Sano, Masahiro Ikoma, Keisuke Shigemori, Norimasa Ozaki, Takashi Endo, Yoichiro Hironaka, Yasunori Hori, Akifumi Iwamoto, Toshihiko Kadono, Tomoaki Kimura, Ryosuke Kodama, Kohei Miyanishi, Mitsuo Nakai, Takuo Okuchi, Kazuto Otani, Tatsuhiro Sakaiya, Katsuya Shimizu, Akiyuki Shiroshita, Hideki Takahashi Equation of state for hydrogen under high pressure is a key to understand the interior structure of gas giant planets like Jupiter. Uncertainty in the hydrogen EOS makes it difficult to estimate the mass of a central core in Jupiter, which can be an important clue to determine the formation scenario of our solar system. To obtain a more accurate EOS model, we have started to investigate the primary Hugoniot of liquid hydrogen by using the GEKKO XII laser. We adopt $\alpha$-quartz as a standard material. Shock velocities in quartz and a sample are measured by VISAR. In this paper, we show the current status of our experiment and future plan. [Preview Abstract] |
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8HE.00082: Time-Resolved Third Order Harmonic Generation on Shocked Silicon Crystals D.A. Dalton, W. Grigsby, H. Quevedo, A.C. Bernstein, T. Ditmire We are using nonlinear optical diagnostics to probe the shock-induced melt transition in silicon. Pump-probe shock experiments on [100] Si crystals were carried out using the Ti:Sapphire THOR laser (800 nm, 1 J, 600 ps-chirped, 40 fs-compressed). Two dimensional interferometry was used to map rear surface displacement at discrete times to infer a peak shock pressure. Third order harmonic generation (THG) is used to probe the bulk material's long range order, while a reflectivity diagnostic is used in conjuction with the THG diagnostic to determine it's validity. Preliminary evidence shows the anomalous response that at shock pressures $<$100 kbar ($\sim $elastic limit) the THG signal does not decrease; however, at higher pressures of $\sim $300-400 kbar the THG signal falls dramatically indicating fast crystalline disordering. [Preview Abstract] |
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8HE.00083: Equation of State Measurements of Dense Plasmas Heated by Laser Accelerated MeV Protons Gilliss Dyer, Aaron Bernstein, Byoung-Ick Cho, Will Grigsby, Allen Dalton, Ronnie Shepherd, Yuan Ping, Hui Chen, Klaus Widmann, Jens Ozterhoz, Todd Ditmire Using a fast proton beam generated with an ultra intense laser we have generated and measured the equation of state of solid density plasma at temperatures near 20 eV, a regime in which there have been few previous experimental measurements. The laser accelerated a directional, short pulse of MeV protons, which isochorically heated a solid slab of aluminum. Using two simultaneous, temporally resolved measurements we observed the thermal emission and expansion of the heated foil with picosecond time resolution. With these data we were able to confirm, to within 10{\%}, the SESAME equation-of-state table in this dense plasma region. [Preview Abstract] |
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8HE.00084: Probing the microscopic state of warm dense matter G. Gregori, B. Barbrel, A. Benuzzi-Mounaix, C. Brown, R. Clarke, E. Garcia Saiz, S. Glenzer, F. Khattak, D. Neely, M. Notley, A. Pelka, D. Riley, M. Roth, C. Spindloe, M. Koenig We have performed spectrally and angularly resolved x-ray scattering measurements in solid density plasmas produced by shock compression with a high power laser. The experiments have been performed at the VULCAN laser facility and at the LULI2000 facility. We have investigated warm and dense low-Z materials with particular regards to the regime where electron-ion correlation becomes important (i.e., the hydrodynamic regime). In these experiments, we used a secondary plasma to generate an intense source of x-ray radiation that is then scattered across the sample and observed in a forward scattering geometry and dispersed using a graphite Bragg spectrometer. The shock properties have been monitored with a dual color VISAR and streaked optical pyrometry, as well as with a XUV flat-field spectrometer. The inferred properties of the dense plasma from the scattering data are discussed and detailed comparison with statistical models of strongly coupled plasmas is reported. [Preview Abstract] |
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8HE.00085: Destruction of nanograins by grain-grain collisions Naofumi Ohnishi, Eduardo Bringa, Bruce Remington, George Gilmer, Roger Minich, Yasutaka Yamaguchi, Alexander Tielens Atomistic simulations of grain-grain collisions have been carried out for spherical grains of 1.4 and 4 nm radii with relative velocities of 3.6--6.1 km/s and a number of random impact parameters. Since the initial grains are crystallites without any pre-existing defects, grain shattering due to nucleation of cracks was not observed in our simulations. We find grain fusion in some events, but generally melting occurs due to the small size of grain. The melting leads to nucleation, growth and linkage of voids in the melt, and finally small clusters are produced through a web-like structure. The size distribution does not obey a single power law and can be considered as four different regimes in the cluster size. [Preview Abstract] |
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8HE.00086: Brittle-to-Ductile Spall Transition in Laser Shocked Aluminum Alloys D.A. Dalton, A.C. Bernstein, J.L. Brewer, E.D. Jackson, S. Steuck, W. Grigsby, D. Milathianaki, E.M. Taleff, T. Ditmire We have explored the role material microstructure plays on the spall strength of alloyed aluminum in the high strain rate range of 10$^{6}$ to 10$^{7}$ s$^{-1}$. We performed pump-probe style experiments using the Z-Beamlet Laser at Sandia National Laboratories to drive shocks in thin slabs of recrystallized Al+3 wt. pct. Mg. Velocity interferometry was used to measure the spall strength of the materials, and post-shot target analysis explored the microscopic fracture morphology. Observation of the Al+3 wt. pct. Mg showed evidence of a combination of brittle intergranular and ductile transgranular fracture features. Post-shot target analysis and hydrocode simulations indicate that this mixed mode failure results from spall dynamics occuring on spatial scales on the order of the grain size. [Preview Abstract] |
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8HE.00087: Ab initio simulation of the Helium Hugoniot up to very high temperatures. Gilles Zerah, Stephane Leroux The advent of very high energy lasers will allow probing extreme states of matter, and in particular inducing extremely strong shocks. These new experiments begs for the development of techniques capable of addressing these extreme states of matter using first principle techniques in order to probe our current understanding of physics in these regimes. In this paper, we consider First Principles Molecular Dynamics simulations, which have already shown to be a very powerful tool for dense plasmas simulations. Up to now these simulations were limited to temperatures up to approximately 10eV as a consequence of the very rapid growth of the number of electronic states when solving the Mermin-Kohn-Sham effective Schr\"{o}dinger equation. In this talk, we will present a new technique, based on a direct evaluation of the density matrix, which bypasses the need to compute eigenstates and therefore allow simulation up to very high temperatures (here, up to 100eV). We apply this method to the computation of the Hugoniot curve of cryogenic Helium, and compare our results with Path Integral Monte Carlo simulations and recent experimental data. [Preview Abstract] |
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8HE.00088: Study of the particles kinetic energy enhancement in explosions of atomic argon clusters driven by two-color three pulse intense laser H.J. Quevedo, M. Avila, T. Ditmire A pump-probe experiment was designed to study the particle kinetic energy enhancement in the explosion of large argon clusters driven by high intensity lasers. The nano-plasma model has been effective in explaining laser-cluster interactions and the efficient absorption of laser energy by the cluster through resonant collisional heating. This resonance occurs when the electron density is similar to three times the critical density, enhancing the laser energy absorption by electrons. Previous experiments have shown the existence of this resonance achieving enhancement of the ions kinetic energy for an optimum delay between two laser pulses. In our experiment we attempt to reach the resonant condition two times to achieve extra absorption using a timed sequence of two intense red femtosecond pulses and one frequency double blue. [Preview Abstract] |
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8HE.00089: Intense XUV radiation driven explosions of Xe clusters B. Murphy, K. Hoffmann, A. Belolipetski, A. Bernstein, J. Keto, T. Ditmire, I. Artyukov We have investigated the explosions of large xenon clusters subject to irradiation by high intensity extreme ultraviolet (XUV) light with wavelength near 38 nm. To do this we generated high order harmonics by focusing the output of the 20 TW, 40 fs, 800nm wavelength THOR laser into a jet of argon gas. To select a single harmonic we then employed a Sc/Si short focal length multilayer mirror optimized for the 21st harmonic at 38.1 nm at near normal incidence. This harmonic is focused onto a jet of xenon gas. We characterized the XUV focal spot by scanning a knife edge across an XUV photodiode and determined that our peak XUV intensity was 2x10$^{10}$ Wcm$^{-2}$. Fast ion time-of-flight spectra reveal high ion charge states well above single photon ionization thresholds. These ions exhibit low kinetic energies consistent with hydrodynamic cluster expansion rather than Coulomb explosion. We also measured the electron spectra from these Xe cluster explosions and have observed moderate energy electrons ejected from the clusters. [Preview Abstract] |
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8HE.00090: Experimental evidence and theoretical analysis of photoionized plasma under x-ray radiation produced by intense laser Feilu Wang, Shinsuke Fujioka, Hiroaki Nishimura, Daiji Kato, Yutong Li, Gang Zhao, Jie Zhang, Hideaki Takabe We composed a time-dependent detailed-configuration-accounting atomic model, which solves rate equations for level population distributions including collisional and radiative atomic processes based on the screened hydrogenic model (R. M. More, Handbook of Plasma Physics, vol. 3, Amsterdam: Elsevier Science Publishers, 1991). This model is used to interpret recent photoionization experiment on the large-scale laser system Gekko-XII (Yamanaka et al., 1981, IEEE, J. Quantum Electron. 17, 1639). In this experiment, the nitrogen gas was bathed in a Planckian radiation field of 80eV and was ionized beyond He-like state (open K-shell). It indicates the ionization parameter is around 10 erg cm/s under near steady-state conditions and the reasonable range of the electron temperature is 20-30eV. The comparison of synthetic and experimental spectra shows reasonable agreement and photoionization plays a significant role in this experiment. [Preview Abstract] |
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8HE.00091: Characterization of photoionized SiO2 aerogel plasmas created by radiation fields in gold hohlraum targets Yutong Li, Jie Zhang, Zhengming Sheng, Xin Lu, Quangli Dong The photoionized SiO2 aerogel plasmas generated under a near-Planckian radiation field in gold hohlraum targets irradiated by high power laser pulses are measured by observing the absorption spectra and line emissions in the range between 0.64 and 0.74 nm. The experimental results are simulated by theoretical calculations under local thermodynamic equilibrium (LTE) using a detailed-level-accounting (DLA) model. The contributions of different Si ions to the specific components of the measured absorption spectra are identified. [Preview Abstract] |
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8HE.00092: The atomic number -- charge relation in the nuclear matter in bulk Barbara Patricelli, Michael Rotondo, Remo Ruffini We determine theoretically the atomic number (A)- charge relation in the nuclear matter in bulk with the model recently proposed by Ruffini et al. (2007). We compare this relation with the data of the Periodic Table, finding a very good agreement. Our relation also agrees with the semi-empirical one obtained from the Weizsacker mass formula up to A$\sim $10$^{4}$. For higher values of A our relation has a different behaviour and we interpret this as a result of the penetration of electrons (initially confined in an external shell) inside the core that becomes more and more important by increasing the atomic number; these effects are not taken into account in the semi-empirical mass-formula. [Preview Abstract] |
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8HE.00093: The extended nuclear matter model with smooth transition surface Jorge Rueda, Barbara Patricelli, Michael Rotondo, Remo Ruffini The existence of electric fields close to their critical value E$_{c}$=(m$_{e}$c$^3$)/(e$\hbar )$ has been proved for massive cores of 10$^{7}$ up to 10$^{57}$ nucleons using a distribution of constant nuclear density and a sharp step function at its boundary. We explore the modifications of this effect by considering a smoother density profile with a proton distribution fulfilling a Wood-Saxon dependence. The occurrence of a critical field has been confirmed. We discuss how the location of the maximum of the electric field as well as its magnitude is modified by the smoother distribution. [Preview Abstract] |
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8HE.00094: The relativistic Thomas-Fermi equation for extended nuclear matter Remo Ruffini, Michael Rotondo, She-Sheng Xue The derivation of the dimensionless form of the relativistic Thomas-Fermi equation for extended nuclear matter are described, taking into due account the process of inverse beta decay. The equations of the binding energy of such a configuration are also derived. The analogy and the differences between this treatment and the classical one by Greiner, Migdal, Popov and their schools are presented. [Preview Abstract] |
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8HE.00095: Solutions of the ultra-relativistic Thomas-Fermi equation Michael Rotondo, Remo Ruffini, She-Sheng Xue The general solutions of a massive core at nuclear density are presented both from an analytic and numerical treatment. The analytic solutions generalize the solution introduced by Migdal, Volskerenskii and Popov in the case of heavy nuclei extending their treatment from Z$\sim $10$^{7}$ all the way to Z$\sim $10$^{57}$, corresponding to stellar massive cores. Special attention is given to the energetics of these configurations. It is shown that the solutions obeying the condition of global neutrality are much more bound than the traditional ones adopting the condition of local neutrality. The relevance of these solutions for X-ray busters models is outlined. [Preview Abstract] |
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8HE.00096: Ultra-intense laser driven high-energy K-$\alpha $ sources for high-energy density experiments. Hye-Sook Park When a high-intensity short-pulse laser with the intensity $>$10$^{17}$ W/cm$^{2}$ illuminates a micro target, super-thermal to relativistic hot electrons are created along with the intense magnetic and electric fields. These hot electrons transports through the target material vacating and backfilling of the inner K-shell electrons creating K-$\alpha $ photons. Utilizing this property, we are developing backlighters of energy $>$17 keV that are needed for many high energy density experiments on NIF and Omega-EP. We carried out experiments to demonstrate that high energy 1-D and 2-D radiography are possible using $\mu $-foil ($\sim $5 $\mu $m thin) and $\mu $-wire (10x10x300 $\mu $m long) targets attached to low-Z substrates [1]. We have tested Mo (17 keV), Ag (22 keV), Sm (40 keV) and Au (69 keV) backlighters using the Titan laser at LLNL and utilized them to radiograph laser driven samples. This paper will present our radiography results and K-$\alpha $ source characteristics comparing them with the required signal level for NIF HED experiments. [1] H. S. Park et al., Physics of Plasma, 13, 056309 (2006) [Preview Abstract] |
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8HE.00097: Status of High Energy Density Physics at GSI. Dieter H.H. Hoffmann A detailed understanding of interaction phenomena of intense ion- and laser radiation with matter is important for a large number of applications in different fields of science, from basic research of plasma properties to application in energy science. Energy loss processes of heavy ions in plasma and cold matter are important for the generation of high energy density states in general and especially in the hot dense plasma of an inertial fusion target. Of special interest are phase transitions and the associated time scales when matter passes the warm dense matter regime of the phase diagram at high density but relatively low temperature. We present an overview on recent results and developments of beam plasma, and beam matter interaction processes studied with heavy ion beams from the GSI accelerator facilities. [Preview Abstract] |
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8HE.00098: Direct study of eos mixing laws through an orbital-free-molecular-dynamics point of view Flavien Lambert, Jean-Francois Danel, Luc Kazandjian, Jean Clerouin We have investigated eos mixing rules by an approach coupling consistently molecular dynamics for the nuclei and orbital free density functional theory for the electronic fluid. This framework allowed us to study, without mixing approximation, mixtures in the hot and dense regime -- \textit{ie} a plasma strongly coupled and partially degenerated --, regime relevant for inertial confinement fusion. Several mixtures borrowed from this field have been examined in order to both present the method and check the validity of eos mixing rules commonly used in hydrodynamics simulations. \newline \newline [1] F.~Lambert, J.~Clerouin, J.-F. Danel, L.~Kazandjian, and G.~Zerah. Direct verification of mixing rules in the hot and dense regime. {\em Phys. Rev. E}, 2007. Submitted. \newline [2] F.~Lambert, J.~Clerouin, and S.~Mazevet. Structural and dynamical properties of hot dense matter by a Thomas-Fermi-Dirac molecular dynamics. {\em Europhysics Lett.}, 75(5):681--687, 2006. [Preview Abstract] |
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8HE.00099: Rayleigh -- Taylor instabilities and radiative cooling Serge Bouquet The morphology and filamentary structure of old supernova remnants (SNR) -- see for instance Crab Nebula -- is still an open question. Rayleigh -- Taylor instabilities (RTI) are suspected to play an important role in that structuration, however, as old SNR are optically thin, radiation can freely escape and local overdensifications can be produced. In this paper, we study the properties of media experiencing both RTI and radiative cooling. This work is performed analytically and numerically. In the analytical approach, the equations of the model are linearized and the key equation leading to the dispersion relation is derived. The structure of this key equation is studied and analytical solutions are provided in some special cases. The non linear phase of the radiative Rayleigh -- Taylor instability (RRTI) is examined numerically. It is shown that compared to the pure RTI, RRTI alters the structure of heavy material spikes. The morphology of the mixing zone is also modified and the formation of overdense regions is evidenced. [Preview Abstract] |
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8HE.00100: Scaling laws for radiative and magnetic fluids: pillar of laboratory astrophysics Emeric Falize In this work, we consider the fundamental problem of scaling laws in RMHD. The emergence of powerful facilities (Laser, Pinch devices and Spheromack) allows the study of dynamical evolution of plasmas with radiation and magnetic field. This kind of plasmas is very usual in astrophysical environments and it is very interesting for Astrophysicists to obtain similar plasma in laboratory. We explore regimes [o(v/c) and o(v$^{2}$/c$^{2})$ approximation] with an approach based on Lie groups which leads to a rigorous and systematic method to get scaling laws. We focus on the number of free parameters (in the different regimes) available to determine all the physical quantities related to the target and to the laser, but also on the astrophysical objects that can potentially reproduced in laboratory with nowadays (LULI2000, Omega, GekkoXII, LIL) and future (LMJ, NIF) laser facilities. [Preview Abstract] |
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8HE.00101: Laser-Plasma simulations of Artificial Magnetosphere formed by Giant Coronal Mass Ejections Yuri Zakharov, Arnold Ponomarenko, Konstantin Vchivkov, Wendell Horton, Parrish Brady We study by the laboratory (Laser-Plasmas, LP) and numerical (3D/PIC-code) simulations a resulting state of very strong magnetopause' (MP) compression by CME with effective energy Eo $>$ 10$^{34}$ ergs directed to the Earth. During probable formation of such Artificial Magnetosphere (AM) with the MP stand-off at Rm up to (2-3)R$_{E}$, a lot of catastrophic phenomena in a space and ground networks could occur due to very high curl electric fields induced by world-wide magnetic field's changes with a SC-rate $>$ 50 nT/s. The laboratory models of AM (with Rm $\sim $ 0,1-30 cm) were formed around high-field, 1D and 3D magnetic obstacles, overflowing by LP-blobs with Eo up to kJ and magnetized ions. The shape and internal structure of such large-scale AM at KI-1 facility of Russian team were studied by a set of B-dot magnetic probes, while a main goal of UT' small-AM experiment was to explore a possible shock's generation and relevant electron accelerations. A preliminary results of KI-1 experiments show that the both Rm-size and SC(Eo) of AM could be described by modified Chapman-Ferraro Scaling, while the whole SC-distribution (in equatorial plane) by well-known ``Image Dipole'' model of the Earth magnetosphere. [Preview Abstract] |
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8HE.00102: Particle-in-Cell (PIC) Simulations of Laser Plasma Interactions in Underdense Plasmas F.S. Tsung, J. Fahlen, B.J. Winjum, J. Tonge, W.B. Mori In underdense plasmas, an incident laser can decay into a backward going electromagnetic wave and a forward going plasma wave (backward stimulated Raman scattering, or BSRS), or two counterpropagating plasma waves (2$\omega$p instability). These laser-plasma instabilities (LPI) can potentially reduce ICF yields either by preheating the target (through fast electrons generated by large amplitude plasma waves), or by reflecting the incident laser and thereby reducing the driver energy. We have studied these instabilities self-consistently using the electromagnetic PIC code OSIRIS, as well as with the electrostatic PIC code BEPS1 with external drivers. In this poster, we will present simulation results which address numerous kinetic aspects of these LPI under plasma parameters relevant to the National Ignition Facility (NIF), such as particle trapping due to large amplitude plasma waves, nonlinear frequency shifts which can detune and saturate the three wave interactions, and sideband instabilities resulting from trapped particles. [Preview Abstract] |
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8HE.00103: Fast Ignition with Ultra-High Intensity Lasers J. Tonge, J. May, W.B. Mori, F.S. Tsung, C. Ren, M. Marti, L. Silva Energy transport within overdense plasma with a fast ignition target is explored by examining the interaction of different intensity ignition lasers with a 50 $\mu$m radius target using two-dimensional Particle-In-Cell simulation. In fast ignition schemes the ignition energy must be delivered to a small region ($\sim$20 $\mu$m in radius) of dense plasma within the target in order to create a localized region where fusion occurs. The electron stopping length in the core and the energy spectrum of the ignition electrons determines the depth of this region. This depth is sensitive to the spectrum of the energy flux of fast electrons generated as a function of laser intensity at the critical surface. Coupled with current assumptions of the spectrum of electrons generated by high intensity lasers this limits ignition laser intensity to 5x10$^{19}$ W/cm$^2$. Our simulations show that the peak energy flux of the ignition electrons is significantly lowered as the electrons traverse the collisionless plasma from the critical density surface of the plasma to the high density target core where ignition occurs. This allows higher intensity lasers to be used thus delivering power to a narrower region. In addition we find that a higher percentage of the ignition lasers energy is delivered to the core with the higher intensity laser. [Preview Abstract] |
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8HE.00104: Experimental results to study astrophysical plasma jets using Intense Lasers B. Loupias, E. Falize, C.D. Gregory, D. Seiichi, T. Vinci, J. Waugh, M. Koenig, N.C. Woolsey, N. Osaki, A. Benuzzi-Mounaix, S. Bouquet, C. Michaut, M. Rabec le Goahec, W. Nazarov, S. Pikuz, A. Faenov, Y. Kuramitsu, S. Atzeni, A. Schiavi, Y. Sakawa, H. Takabe, R. Kodama We will present our experimental characterization of a jet generation in vacuum using foam filled cone target and intense laser. The obtained results on shape, time evolution, temperature and density, are in good agreements with 2D simulations. We also compared these measurements with theory and astronomical observations. Further study, with ambient gas, simulating the interstellar medium, to evaluate its effect on the above plasma jet evolution have been performed. We will demonstrate the importance to implement several diagnostics to measure the required parameters to infer the dimensionless astrophysical numbers. [Preview Abstract] |
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8HE.00105: Study of Hot Electron Propagation in Low Density Foams in Ultra Intense Laser Pulse Interaction B. Ramakrishna, P.A. Wilson, K. Quinn, L. Romagnani, M. Borghesi, A. Pipahl, O. Willi, L. Lancia, J. Fuchs, M. Notley, R.J. Clarke Ultrashort bursts of high energy charged particles produced from high intensity laser matter interactions have many potential applications in advanced science and technology areas. A vital application of laser produced MeV electrons is in inertial confinement fusion [1]. Scaling laws for the fast electrons produced during ultrahigh intensity interactions give electron temperatures KBThot $\sim $ Upond $\sim $ 1MeV$\times $ (I$^{2}$/10$^{19}$Wcm$^{2}\mu $m$^{2}) \quad ^{0.5}$, with up to 30{\%} of the laser energy converted into these relativistic electrons. Electric effects may cause a reduction of the range of fast electrons as compared to what is predicted taking into account collisional effects only. These arise from the electric field E generated by charge separation and by inductive effects, as the fast electrons propagate into the target. These electrons carry a current density Jhot of magnitude which can be as large as 10$^{12}$ A/cm$^{2}$. The electric field E depends on the conductivity $\sigma $ of the target material, because a return current balancing the current of fast electron must be set up to maintain quasi-neutrality (i.e. Jhot + J return $\sim $0) and allow propagation [2]. We present here recent results obtained from experiments carried out in the Petawatt laser facility at the Rutherford Appleton Laboratory. [Preview Abstract] |
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