This report discusses topics on hydrodynamics instabilities in inertial confinement: linear analysis of Rayleigh-Taylor instability; ablation-surface instability; bubble rise in late-stage Rayleigh-Taylor instability; and saturation and multimode interactions in ...

This report discusses topics on hydrodynamics instabilities in inertial confinement: linear analysis of Rayleigh-Taylor instability; ablation-surface instability; bubble rise in late-stage Rayleigh-Taylor instability; and saturation and multimode interact...

An extensive series of experiments has been conducted on the Nova laser to measure hydrodynamic instabilities in planar foils accelerated by x-ray ablation. Single mode experiments allow a measurement of the fundamental growth rates from the linear well i...

A laminated ablator is explored as an alternative concept for stabilizing the ablative Rayleigh-Taylor instability which develops in inertial fusion targets. Experiments measuring the growth of the Rayleigh-Taylor instability of laminated planar foils are reported. Consistent with both theory and simulations, a ...

A laminated ablator is explored as an alternative concept for stabilizing the ablative Rayleigh-Taylor instability which develops in inertial fusion targets. Experiments measuring the growth of the Rayleigh-Taylor instability of laminated planar foils are reported. Consistent with both theory and simulations, a ...

An extensive series of experiments has been conducted on the Nova laser to measure hydrodynamic instabilities in planar foils accelerated by x-ray ablation. Single mode experiments allow a measurement of the fundamental growth rates from the linear well into the nonlinear regime. Two-mode foils allow a first direct observation of mode ...

The dynamics of doping transformation fronts in organic semiconductor plasma is studied for application in light-emitting electrochemical cells. We show that new fundamental effects of the plasma dynamics can significantly improve the device performance. We obtain an electrodynamic instability, which distorts the doping fronts and increases the transformation rate ...

Perturbation amplitudes and correlated growth rates of hydrodynamic instabilities in the compressed core of a directly driven inertial confinement fusion capsule are analyzed in planar and spherical geometries, with and without heat conduction. It is found that the maximum Lagrangian perturbation amplitude is always located inside the hot spot and not at ...

... Considerable hydrodynamic disturbance results from the rather ... as influenced by the hydrodynamics of the ... The amount of mass ablated determined ...

Understanding and controlling hydrodynamic instabilities is critical to achieving ignition at National Ignition Facility (NIF). High resolution x-ray radiography of a NIF capsule may be able to measure key aspects of short wavelength instability growth including time dependent areal density variations, the dominant wavelength of ...

The dynamics of doping transformation fronts in organic semiconductor plasma is studied for application in light-emitting electrochemical cells. We show that new fundamental effects of the plasma dynamics can significantly improve the device performance. We obtain an electrodynamic instability, which distorts the doping fronts and increases the transformation rate ...

This paper reviews the All Russian Scientific Research Institute of Experimental Physics open publications on hydrodynamic instability in strong media.

An initial study aimed at elucidating the multidimensional aspects of the hydrodynamic instabilities

... Title : Cusp Shaped Hydrodynamic Instability in a Nematic (Instabilite Hydrodynamique en Forme de Bec dans un Nematique),. ...

As shown elsewhere an ablatively imploded shell is hydrodynamically unstable, the dominant instability being the well known Rayleigh-Taylor instability with growth rate {gamma} = {radical}Akg where k = 2{pi}/{lambda} is the wave number, g is the acceleration and A the Attwood number ({rho}{sub hi} {minus} {rho}{sub ...

The National Ignition Facility (NIF) is capable of creating new and novel high-energy-density (HED) systems relevant to astrophysics. Specifically, a system could be created that studies the effects of a radiative shock on a hydrodynamically unstable interface. These dynamics would be relevant to the early evolution after a core-collapse supernova of a red supergiant star. ...

Time evolution of the ablation front displacement between concave and convex regions of a surface corrugated spherical target was observed by flash x-ray radiography. The results are compared with calculations based on the linearized fluid equation combined with a one-dimensional simulation to describe the ambient fluid motion. In the analysis, perturbation of the fluid is ...

Three similar cryogenic ignition capsule designs for the National Ignition Facility [J. Lindl, Phys. Plasmas {bold 2}, 3933 (1995)] are analyzed to determine surface roughness specifications required to mitigate the growth of hydrodynamic instabilities. These capsule utilize brominated plastic, polyimid and copper-doped beryllium ...

Additional features have been included in the DRACO Lagrangian radiation hydrodynamics code enabling realistic 3D simulation of laser driven ablation, shocks, and fluid instabilities in low-Z plasmas. Since last reported (Fatenejad and Moses, Bull. APS 51, 209(2006).), DRACO now includes 3D laser ray tracing to model laser absorption ...

Large lasers such as Nova allow the possibility of achieving regimes of high energy densities in plasmas of millimeter spatial scales and nanosecond time scales. In those plasmas where thermal conductivity and viscosity do not play a significant role, the hydrodynamic evolution is suitable for benchmarking hydrodynamics modeling in astrophysical codes. ...

The intent of this paper is to review how instability growth is modeled in ICF targets, and to identify the principal issues. Most of the material has been published previously, but is not familiar to a wide audience. Hydrodynamic instabilities are a key ...

Transverse and longitudinal beam compression in neutralizing plasma enable heavy ion beam direct drive in the ablative rocket regime at high rocket efficiency with ion ranges a fraction of the initial ablator thickness for low adiabat implosions. Ions can couple energy into thick fuel capsule ablators at the peak in rocket efficiency ...

... of the propellant ablation under plasma effect based on ... Knudsen layer and the hydrodynamic layer. ... indicate that the ablated mass increases with ...

... beam and target uniformity requirements ... Descriptors : *LASER BEAMS, *ABLATION ... INTERACTIONS, HYDRODYNAMICS, LASERS, INTENSITY ...

Summaries of work completed during this period are included as follows: (1) oscillator for echelon-free 151, (2) construction of laser enclosure, and (3) design of the target area. A short review of the KrF program is also included: (1) effect of 151 on the early-time hydrodynamics of accelerating foils, (2) evaluation of hot-cold fuel mix, (3) effect of 151 upon plasma ...

Target designs are described that are meant to achieve ignition on the National Ignition Facility. Simulations of recent indirect drive cryogenic capsule designs indicate dramatically reduced growth of short wavelength hydrodynamic instabilities, resulting from two changes in the designs. First, better optimization results from systematic mapping of the ...

We report on our investigation of the Rayleigh--Taylor and Kelvin--Helmholtz (KH) instabilities in laser ablatively accelerated targets for a series of single mode perturbations. We find linear growth rates well below classical values and a cutoff in the growth rates for wavelengths less than the foil thickness. However, the striking result is the ...

The presence of hydrodynamic fluid instability at the ablation surface puts constraints on the kinds of targets, surface finish, and energy sources that one can use for thermonuclear micro-implosions. If Taylor-like modes grow at near the classical value, one is limited to low aspect ratio shells and surface finishes of 10-100 A. These ...

Hydrodynamic instability of an accelerating ionization front (IF) is investigated with 2D hydrodynamic simulations, including absorption of incident photoionizing photons, recombination in the HII region, and radiative molecular cooling. When the amplitude of the perturbation is large enough, nonlinear dynamics of the IF triggered by ...

The authors are performing experiments to study hydrodynamic perturbation growth in x-ray driven targets to test models used to analyze the stability of ignition targets. They use cylindrical implosions to directly image perturbation growth and ``feed-through`` to the inner surface in convergent geometry. The implosion trajectories and azimuthal structure of inner and outer ...

We performed electron microscopy studies of targets subjected to the multipulse laser irradiation in the regime characteristic of reactive pulsed laser deposition from bulk Si in low-pressure ammonia. Experimental evidence is provided concerning the expulsion of liquid droplets from the crater that forms on the target surface. In our opinion, the main mechanisms responsible for droplets spraying ...

Perturbations on an ICF capsule ablator surface can seed Rayleigh-Taylor instability, which can lead to ablator material being injected into the hot spot, cooling it by radiation. If sufficient mass is injected, the radiative energy loss can be sufficient to quench ignition. Modal growth factors derived from ...

... Taylor instability in laser ablatively accelerated targets for a fairly wide range of initial conditions. It is shown that the Rayleigh-Taylor growth rate in ...

Supernova 1987A focused attention on the critical role of hydrodynamic instabilities in the evolution of supernovae. To test the modeling of these instabilities we are developing laboratory experiments of hydrodynamic mixing under conditions relevant to s...

During the last year, the principle activities and accomplishments under this contract have been: (1) detailed examination of steady flow model calculations of ablation driven Taylor instability to determine the specific cause of growth rate reductions at short wavelengths; (2) implementation of the ''piggy back'' type, ...

Two-dimensional Lagrangian hydrodynamics simulation techniques were used to study fluid instability in laser fusion pellets. A slab geometry comparison with classical Rayleigh-Taylor theory shows good agreement, as do other slab and spherical test problems over a wide range of accelerations and wavelengths. Isentropic ...

... Based on classical hydrodynamics theories, the axial ... Numerical modeling of hydrodynamic instability of ... the Soret effect), the mass diffusion velocity ...

The hydrodynamics of cylindrical buoyant bubbles (magnetic flux tubes) in an atmosphere is examined.

... functions of the hydrodynamic wave speeds, at ... we need to properly model the evolution of ... Foundations of Radiation Hydrodynamics (Dover, New ...

For the study of hydrodynamic instabilities of a spherical implosion, a very simple Lagrangian-type formulation is proposed, based on the introduction of a potential of transverse displacements, and on the decomposition of disturbances into spherical harm...

The evolution of hydrodynamic instability modes self-excited by harmonically related natural screech

Hydrodynamic instabilities in compressible plasmas play a critical role in the fields of inertial confinement fusion (ICF), astrophysics, and high energy-density physics. We are, investigating hydrodynamic instabilities such as the Rayleigh-Taylor (RT) instability, at high compression at the ...

The 1D performance of laser or X-ray driven targets to study phenomena such as the Richtmyer-Meshkov instability in a single, steady shock, step down in density system has been described by a simple model based on 1D hydrodynamics. It is shown that the distance the interface travels under constant velocity conditions is a multiple of the separation between ...

Analytic solutions are dervied for plasma flows in a spherical laser target, emphasizing the region which lies between the ablation surface and the critical density surface. Electron thermal conductivity dominates the heat transport in this zone. Both classical electron thermal conduction and flux-limited conduction are treated in which the finite electron thermal velocity ...

In the frame of a CEA/US DOE collaboration, convergent experiments have been done on the Nova laser. Numerical simulations with our 2D Lagrangian code FCI2 led the analysis and correctly reproduced the experimental data. From single mode 2D perturbations, ablation front Rayleigh-Taylor instability growth is computed. Moderate and high convergence ratios ...

Gated X-ray images of laser-driven implosions can provide movies of typically 16 frames with {approximately} 80 ps time resolution and 10 {micro}m spatial resolution. Cylindrical implosions allow study of convergent hydrodynamics but with excellent diagnostic access down the axis of the cylinder. This example from a recent cylindrical implosion campaign on the OMEGA laser ...

We examine the scaling of implosion symmetry, ablation pressure, and hydrodynamic efficiency with the wavelength of the laser, using a recent theoretical analysis of ablative laser driven implosions as a tool. Symmetrization by a hot atmosphere is most effective for long wavelength lasers, whereas ablation pressure ...

A series of experiments have been conducted to investigate the dynamic over-pressure stabilization of the ablative Richtmyer-Meshkov (RM) instability in inertial confinement fusion (ICF) targets during the start-up phase of implosion. Theory and hydrodynamic simulations predict that due to localized thermal flux variations modulating ...

We present results from a number of 2D high-resolution hydrodynamical simulations of asteroids striking the atmosphere of Venus. These cover a wide range of impact parameters (velocity, size, and incidence angle), but the focus is on 2-3 km diameter asteroids, as these are responsible for most of the impact craters on Venus. Asteroids in this size range are disintegrated, ...

The Richtmyer-Meshkov instability (RMI) at the ablation front of laser-irradiated planar targets is investigated by two-dimensional numerical hydrodynamics simulations. The linear evolution of perturbations seeded either by surface roughness or target inhomogeneity is studied for perturbation wavelengths in the range 10<=?<=400 ...

Indirectly driven, ablative Rayleigh-Taylor instability growth measurements in Ge-doped plastic foils were studied using face-on and side-on x-ray radiography. Laminated samples consisting of alternating layers of Ge-doped and undoped plastic and homogeneous Ge-doped foils were considered. We show for the first time that hydrodynamics ...

The National Ignition Facility (NIF) technology is designed to drive deuterium-tritium (DT) internal confinement fusion (ICF) targets to ignition using indirect radiation from laser beam energy captured in a hohlraum. Hydrodynamical instabilities at interfaces in the ICF capsule leading to mix between the DT fue l and the ablator shell ...

Both the efficiency of an implosion and the growth rate of hydrodynamic instability increase with the aspect ratio of an implosion. In order to study the physics of implosions with high Rayleigh-Taylor growth factors, we use doped ablators which should minimize x-ray preheat and shell decompression, and hence increase in- flight aspect ...

A new semianalytical model describing the entry and deformation of meteoroids entering planetary atmospheres has been developed and calibrated against numerical simulations performed using the CTH shock-physics computational hydrocode. The model starts with the classical treatment of meteoroid ablation which is modified to include an explicit treatment of energy conservation ...

A new semianalytical model describing the entry and deformation of meteoroids entering planetary atmospheres has been developed and calibrated against numerical simulations performed using the CTH shock-physics computational hydrocode. The model starts with the classical treatment of meteoroid ablation which is modified to include an explicit treatment of energy conservation ...

Lecture notes from class on Advanced Fluid Dynamics of the Environment. Part of a segment on "Rudiments of Hydrodynamic Instability".

Cylindrical experiments were performed on the OMEGA laser at the University of Rochester to study unstable interfaces in single and double shells. For single shells a marker layer of more opaque and higher density material is placed between foam and an outside ablator. The marker is either smooth or with a well defined surface roughness. For double shells an inner cylinder is ...

The performance of NIF target designs is simulated in three dimensions using the HYDRA multiphysics radiation hydrodynamics code. In simulations of a cylindrical NIF hohlraum that include an imploding capsule, the motion of the wall material inside the hohlraum shows a high degree of axisymmetry. Laser radiation is able to propagate through the entrance hole for the required ...

The paper develops the theory of the hydrodynamic stability of an electrolytic cell as a function of

... generated by an interaction between the ... MATHEMATICAL MODELS), STABILITY, OSCILLATION, GRAVITY, INTERACTIONS, HYDRODYNAMICS. ...

The nature of turbulence (and the enhanced transport it provides) is a key element to comprehend the

Megajoule-class hohlraums at the National Ignition Facility (NIF) were used to implode gas-filled (helium/deuterium) plastic shell inertial confinement fusion targets with a buried Ge-doped shell layer offset from the inner gas--shell interface. Hydrodynamic instabilities and jets seeded by isolated shell-surface mass modulations and the gas-fill tube are ...

Experimental measurements of perturbation growth due to the Rayleigh-Taylor (RT) instability at the ablation interface have been used to try to understand the physical processes involved in ablative stabilization. The growth rate calculated from a dispersion relation and values for the acceleration and ablation ...

We present preliminary results from two-dimensional numerical studies of nuclear burning and hydrodynamic instabilities in pair-instability supernova (PSN) performed with the new radiation-hydrodynamics code CASTRO.

The Rayleigh-Taylor (RT) instability, which occurs when a lower-density fluid accelerates a higher-density layer, is common in nature. At an ablation front a sharp reduction in the growth rate of the instability at short wave-lengths can occur, in marked contrast to the classical case where growth rates are highest at the shortest ...

The development of hydrodynamic instabilities at the interface between two fluids of different densities is one of the major limiting factors in the Inertial Confinement Fusion. To study this effect, the incompressible fluid model is widely used for describing the motion near the interface separating the two fluids (see Refs. 1, 2 and references therein). ...

We will present the results of experiments designed to study hydrodynamic instability growth in spherical targets imploded by the 30-kJ OMEGA laser system. Instability growth during the acceleration phase of the implosion can be diagnosed using the burnthrough technique. This method has been shown(D. K. Bradley et al.), Phys. Rev. ...

ICF direct-drive targets perform best when the pressure of the driving pulse is maximized: the targets can then be designed with small aspect ratios that are more hydrodynamically stable. However the drive pressure in direct drive targets is limited by laser plasma instabilities, which must be avoided to limit unwanted preheat of the fusion fuel. In direct ...

An annealing model is extended to treat the vaporization process, and a hydrodynamic model describes the ablated material. We find that dynamic source and ionization effects accelerate the expansion front of the ablated plume with thermal vaporization tem...

An enhanced understanding of the unique physics probed in a burning NIP capsule is important for both nuclear weapons physics and thermonuclear ignition. In this talk we introduce a new diagnostic idea, designed to measure dynamic aspects of the capsule implosion that are not currently accessible. The current set of diagnostics for the NIF experiments includes reaction history (a time resolved ...

This article presents a theory of these instabilities and potential modes of failure caused by them. Discussions are given for the following: small amplitude growth of the outside surface instability; and modes of failure resulting from nonlinear development of the inside surface instability.

Various aspects of hydrodynamics and elastic--plastic flow are introduced for the purpose of defining hydrodynamic terms and explaining what some of the important hydrodynamic concepts are. The first part covers hydrodynamic theory; and discussed fundamental hydrodynamic equations, ...

Within the framework of the quasi-isobaric approximation (low Mach number), a self-consistent stability analysis of ablation fronts in inertial confinement fusion is performed for all the modes with a wavelength larger than the conduction length in the cold material. The validity domain is ranging from short to long wavelength modes, shorter and larger than the total thickness ...

In inertial confinement fusion (ICF) implosions, a spherical shell of cryogenic deuterium and tritium (DT) filled with DT gas is accelerated by direct laser irradiation (direct drive) or x-rays produced by a high-Z enclosure (indirect drive). Hydrodynamic instabilities, growing on the outer shell surface during the acceleration phase, cause the outer ...

The evolution of the Rayleigh-Taylor (RT) instability at an embedded, or classical, interface is examined in a series of experiments at the Nova laserfacility .[reference for Nova] These experiments focused on the transition from the linear to nonlinear regimes for both single- and multimode initialperturbations. The development of a single mode at the embedded interface is ...

Backlighting is extensively used as a diagnostic tool in experiments relative to Inertial Confinement Fusion. Thus, beam and target nonuniformities effects on hydrodynamic instabilities growth and imprinting, shock propagation in solid materials and foil acceleration are studied in planar geometry. Spherical or cylindrical implosions measurements are ...

The effects of Rayleigh-Taylor flow in laser-driven ablation are simulated within the one-dimensional hydrocode LILAC as a diffusive transport process where material constituents are redistributed continuously along with their thermal and mix-motion energy within a growing mix region whose boundaries are obtained from a saturable linear multimode model of the Rayleigh-Taylor ...

Experiments have been conducted with planar foils to study the growth of perturbations due to the Rayleigh-Taylor instability with direct-drive, picket-fence-like pulses on CH ablators. The laser illumination has an intensity of 1.5�10^14:W/cm^2 at 351 nm and has been smoothed with smoothing by spectral dispersion and distributed polarization rotators. ...

... Accession Number : ADA129723. Title : Prospects for Optical Probing of the Rayleigh-Taylor Instability in Ablatively-Accelerated Foil Targets. ...

... produced jets to electromagnetically driven wires in a Z-pinch, and to test various methods suggested for mitigation of the Rayleigh-Taylor instability ...

The onset of instability occasioned by mass concentration gradient in a porous medium is investigated within the realms of hydrodynamic stability. It is established that as the permeability of the medium decreases, the Rayleigh number for onset of instabi...

... We observe large reductions in hydrodynamic instability seeded by laser imprint when certain minimum thickness gold or palladium layers are ...

The success of the inertial confinement fusion program is critically dependent on our ability to accelerate and implode the fuel capsules (targets) with a high degree of symmetry. Distortion of laser fusion targets, primarily by the Rayleigh-Taylor (RT) hydrodynamic instability, is a major obstacle to achieving ignition and high energy gain. ...

Linear theory of the ablative Rayleigh-Taylor instability in anisotropic diffusive materials is presented. This analysis indicates that enhancing diffusion in a plane transverse to the mean longitudinal flow can strongly reduce the growth of the instability. In the context of inertial confinement fusion, it is shown that anisotropic ...

Linear theory of the ablative Rayleigh-Taylor instability in anisotropic diffusive materials is presented. This analysis indicates that enhancing diffusion in a plane transverse to the mean longitudinal flow can strongly reduce the growth of the instability. In the context of inertial confinement fusion, it is shown that anisotropic ...

This paper presents the hydrodynamic efficiency of ablation plasma produced by pulsed ion beam on the basis of the ion beam-target interaction. We used a one-dimensional hydrodynamic fluid compressible to study the physics involved namely an ablation acceleration behavior and analyzed it as a rocketlike model in ...

... developed in the target after the shock ... INSTABILITY, COMPUTERIZED SIMULATION, LASER BEAMS. Subject Categories : LASERS AND MASERS ...

The study has indicated that the aerodynamics of raindrops have a profound effect on their behavior in intense vertical electric fields as regards onset, mechanism, and products of instability.

Lecture notes from class on Advanced Fluid Dynamics of the Environment. Part of a segment on "Rudiments of Hydrodynamic Instability".

Lecture notes from class on Advanced Fluid Dynamics of the Environment. Part of a segment on "Rudiments of Hydrodynamic Instability".

This report contains abstracts on topics in the following areas: parametric instabilities; hohlraum physics; laser plasma physics with short pulses; and rayleigh-taylor instability and hydrodynamics.

Adiabat shaping in inertial confinement fusion (ICF) capsules has been proposed as a method for increasing the stability of ICF implosions without compromising capsule compressibility and one-dimensional yield. The optimal adiabat profile has a maximum on the outer, ablation surface for higher ablative mitigation of the Rayleigh-Taylor (RT) ...

This experiment performed on the OMEGA laser facility, was designed to mimic the hydrodynamic features of an exploding supernova. In the shot, a hemispherical Ge-doped plastic capsule is ablatively driven outward into a low density carbon resorcinol foam (CRF). The initial interface between the plastic capsule and CRF was perturbed with a single mode 2D ...

In inertial confinement fusion (ICF), the possibility of ignition or high energy gain is largely determined by our ability to control the Rayleigh-Taylor (RT) instability growth in the target. The exponentially amplified RT perturbation eigenmodes are formed from all sources of the target and radiation non-uniformity in a process called seeding. This process involves a variety ...

The classical Richtmyer-Meshkov (RM) instability develops when a planar shock wave interacts with a corrugated interface between two different fluids. A larger family of so-called RM-like hydrodynamic interfacial instabilities is discussed. All of these feature a perturbation growth at an interface, which is driven mainly by vorticity, ...

Determining the capsule ablator thickness and peak laser or x-ray drive pressure required to optimize fuel compression is a critical part of ensuring ICF ignition on the NIF. If too little ablator is burned off, the implosion velocity will be too low for adequate final compression; if too much ablator is burned off, the fuel will be ...

Since the advent of SN 1987A considerable progress has been made in our understanding of supernova explosions. It is now realized that they are intrinsically multidimensional in nature due to the various hydrodynamical instabilities which take place at al...

An extended Landau/Levich model of liquid-propellant combustion, one that allows for a local dependence of the burning rate on the (gas) pressure at the liquid/gas interface, exhibits not only the classical hydrodynamic cellular instability attributed to ...

An extended Landau-Levich model of liquid-propellant combustion, one that allows for a local dependence of the burning rate on the (gas) pressure at the liquid-gas interface, exhibits not only the classical hydrodynamic cellular instability attributed to ...

This is the final report of the research completed under the auspices of the Department of Energy grant ''Periodically Structured Multiphase Flows and Hydrodynamic Instabilities in Narrow Capillaries''. The research studies the mobility of train flows of ...

The main characteristics of the linear Darrieus-Landau instability in the laser ablation flow are investigated. The dispersion relation of the instability is found numerically as a solution to an eigenvalue stability problem, taking into account the continuous structure of the flow. The results are compared to the classical ...

The main characteristics of the linear Darrieus-Landau instability in the laser ablation flow are investigated. The dispersion relation of the instability is found numerically as a solution to an eigenvalue stability problem, taking into account the continuous structure of the flow. The results are compared to the classical ...

... that the electron collision frequency in a semiconductor is greater than the hydrodynamic increment of instability in collisionless plasma but less ...

Lecture notes from class on Advanced Fluid Dynamics of the Environment. Part of a segment on "Rudiments of Hydrodynamic Instability".

Lecture notes from class on Advanced Fluid Dynamics of the Environment. Part of a segment on "Rudiments of Hydrodynamic Instability".

... COLLISIONS, *DROPS, *FLAMES, COMBUSTION, COALESCENCE, HYDRODYNAMICS, VAN DER WAALS FORCES, INSTABILITY, LIQUID ...

... Of particular con- cern would be the growth of IG wave produced by the adjustment process due to the presences of hydrodynamic instabilities. ...

A multiple-laboratory campaign is underway to qualify beryllium as a fusion capsule ablator for the National Ignition Facility [Moses and Wuest, Fusion Sci. Technol. 43, 420 (2003)]. Although beryllium has many advantages over other ablator materials, individual crystals of beryllium have anisotropic properties, e.g., sound speed, elastic constants, and ...

Radiation may be useful for reducing laser imprint and Rayleigh-Taylor (RT) growth in direct-drive target pellets. We will discuss the important role of radiation in a proposed direct-drive X-ray preheated target concept(S.Bodner et al., Phys. Plasmas 5,1901(1998)). In this design, a high-Z coating surrounds a thin plastic coat, over a DT-wicked foam and on top of the DT fuel. Radiation effects ...

Dynamic overpressure sets the growth rate of the ablative Richtmyer--Meshkov (RM) instability and the seeds for subsequent growth of perturbations due to the Rayleigh--Taylor instability in directly driven ICF targets. It leads to temporal oscillations of the perturbed ablation front, which have been predicted ...

The authors investigate hydrodynamic instability of accelerating ionization fronts with two dimensional hydrodynamic simulations. When recombination in the ionized region is turned off, Rayleigh-Taylor instability is effective. Perturbation grows up with classical Rayleigh-Taylor growth rate. In the case with ...

A mathematical method for a fully self-consistent treatment of the Rayleigh--Taylor instability is developed by solving the linearized fluid equations as an eigenvalue problem. The method is applied to analyze the instability in stationary ablating plasmas with strong inhomogeneity. A reduction of growth rate compared to the classical ...

The results of the experiments carried out on a laser system are reported. The work is performed in order to investigate the problem of target instability under ablative acceleration and to get direct evidence of Rayleigh-Taylor instabilities. Tri-layer e...

A shock tube investigation of two hydrodynamic issues related to inertial confinement fusion (ICF) is undertaken. ICF is a promising source of energy for the future. There has been a considerable increase in the interest in ICF with the development of the National Ignition Facility (NIF). However, much remains to be investigated before a useful yield is obtained from a fusion ...

Directly driven Rayleigh-Taylor instability growth experiments being performed on NOVA have been simulated using the computer code, LASNEX. Foils with single-wavelength imposed surface perturbations have been driven with a single beam of 0.53 {mu}m light, employing smoothing by spectral dispersion (SSD). In addition to simulating foils with imposed surface perturbations, we ...

Both the efficiency of an implosion and the growth rate of hydrodynamic instability increase with the aspect ratio of an implosion. In order to study the physics of implosions with high Rayleigh-Taylor growth factors, we use doped ablators which should minimize x-ray preheat and shell decompression, and hence increase in-flight aspect ...

The hydrodynamic stability of laser-driven polymer foils and imploding polymer shells is expected to improve when radiative preheat occurs ahead of the ablation front before the target starts to accelerate. This preheat, produced by radiation from various additives in the hot corona, is simulated in one dimension to assess the dependence of the stability ...

In order to synthesis zinc oxide thin films and nanostructures, laser ablation of ZnO target into both vacuum and oxygen atmosphere was performed. The gas effect on the plume dynamics was studied for O{sub 2} pressures varied between 10{sup -2} to 70 mbar. Plasma plume evolution was investigated by ICCD camera fast imaging. The plasma was created by a KrF excimer laser ...

We investigate numerically the hydrodynamic instability of an ionization front (IF) accelerating into a molecular cloud, with imposed initial perturbations of different amplitudes. When the initial amplitude is small, the imposed perturbation is completely stabilized and does not grow. When the initial perturbation amplitude is large enough, roughly the ...

Here reported is our new cryogenic target apparatus for the GEKKO XII HIPER system, which provide a planar foam target filled with liquid deuterium for laser ablation acceleration experiments. In order to achieve the required high density compression for the inertial confinement fusion with deuterium/tritium fuel, preheating of the pusher and fuel itself by fast electrons and ...

This paper is devoted to the study of the deceleration phase of inertial confinement capsules. First the self-similar flow exhibited by Betti et al. [Phys. Plasmas 8, 5257 (2001)] is proved to be an attractor in the sense that arbitrary initial conditions converge towards this solution. The convergence rate depends on the ablation process and heat conductivity and it is shown ...

Single-mode experiments have been conducted on the Nova laser to examine the effect of perturbation shape on ablation front Rayleigh-Taylor growth. The perturbations investigated had the same magnitude wave vector k=(k{sub x}{sup 2}+k{sub y}{sup 2}){sup 1/2} and the same initial amplitude. The shapes corresponded to 2D {lambda}=50 {mu}m, 3D square k{sub x}=k{sub y}, and ...

A theory is worked out for the cyclotron instability of the plasmasphere with a longitudinal inhomogeneity of the magnetic field taken into account. In this case, the instability converts from a hydrodynamic instability into a kinetic instability. The influence of bounce effects on the ...

An analysis of the relations between hydrodynamic instability and the critical heat flux in water cooling systems is presented. It is concluded that hydrodynamic instability results from slug flow, which is precipitated in the bubble flow regime by coalescence of flow-stream bubbles to form vapor slugs. At ...

Cylindrical implosion experiments at the University of Rochester laser facility, OMEGA, were performed to study radiation hydrodynamics and compressible turbulence in convergent geometry. Laser beams were used to directly drive a cylinder with either a gold (AU) or dichloropolystyrene (C6H8CL2) marker layer placed between a solid CH ablator and a foam ...

Cylindrical experiments were performed on the OMEGA laser at the University of Rochester to study unstable interfaces in single and double shells. For single shells a marker layer of more opaque and higher density material is placed between foam and an outside ablator. The marker is either smooth or with a well defined surface roughness. For double shells an inner cylinder is ...

A computational model for the ablation of tooth enamel by ultra-short laser pulses is presented. The role of simulations using this model in designing and understanding laser drilling systems is discussed. Pulses of duration 300 fsec and intensity greater...

Laser irradiation can be utilized to remove (i.e., ablate) material in a controlled manner by a hydrodynamic process, referred to as front surface spallation. In this process, a thin layer next to a free surface is heated to a level (below vaporization) s...

A simulation code for analyzing laser matter interactions is described in the context of short pulse laser ablation of hard tissue. Some experimental results on short pulse laser absorption are presented and used to motivate employing such systems for ablating biological tissues. Results of simulations of hard tissue drilling are given, including ...

The Inertial Confinement Fusion (ICF) Program and the Lawrence Livermore National Laboratory has made substantial progress in understanding the details of the radiation drive and the dynamics of capsules imploded by the Nova laser. A detailed understanding, validated by Nova experiments of the crucial physics for implosions is necessary before a new facility is started. A National Academy of ...

A two stage numerical study of the filamentation of a laser beam in a plasma is presented. The electromagnetic energy propagation is coupled self-consistently with the plasma hydrodynamics, including the heating and ablation processes. Calculations cover ...

... Principal Investigators: DATidman and S. A. Goldstein One-Dimensional Hydrodynamic Model: RF Hubbard Detailed Physics Model: N. K. Winsor ...

... induced fragmentation of kidney stones and gallstones, and (4) modeling of the above surface hydrodynamics, ie, bubble growth and acoustic ...

Jul 15, 2007 ... Fluid Mechanics and Heat Transfer. Used For: ... Includes boundary layers; hydrodynamics; fluidics; mass transfer and ablation cooling. ...

... Fig. 6 Effect of Mass Injection Due ... 2. G. W. Sutton, "The Hydrodynamics and Heat Conduction of a Melting Surface," J. of the Aero/Space Sci., Vol. ...

We present the results of a series of detailed numerical simulations of the Rayleigh-Taylor instability in laser ablatively accelerated targets for a fairly wide range of initial conditions. It is shown that the Rayleigh-Taylor growth rate in an ablative ...

A mode-coupling model is developed to treat the multimode evolution of the ablative Richtmyer-Meshkov (RM) and Landau-Darrieus (LD) instability in the laser imprint of planar targets. Using this mode coupling model, the multimode power spectrum of the RM and LD instability is computed. For the RM instability, ...

The highly nonlinear evolution of the single-mode Rayleigh-Taylor instability (RTI) at the ablation front of an accelerated target is investigated in the parameter range typical of inertial confinement fusion implosions. A new phase of the nonlinear bubble evolution is discovered. After the linear growth phase and a short constant-velocity phase, it is ...

Extensive modeling of proposed National Ignition Facility (NIF) ignition targets has resulted in a variety of targets using different materials in the fuel shell, using driving temperatures which range from 250-300 eV, and requiring energies from < 1 MJ up to the full 1. 8 MJ design capability of NIF. Recent Nova experiments have shown that hohlraum walls composed of a mixture of high-z ...

A computational model for the ablation of tooth enamel by ultra-short laser pulses is presented. The role of simulations using this model in designing and understanding laser drilling systems is discussed. Pulses of duration 300 fsec and intensity greater than 10{sup 12} W/cm{sup 2} are considered. Laser absorption proceeds via multi-photon initiated plasma mechanism. The ...

Inertial Confinement Fusion is an approach to fusion which relies on the inertia of the fuel mass to provide confinement. To achieve conditions under which this confinement is sufficient for efficient thermonuclear burn, high gain ICF targets designed to be imploded directly by laser light. These capsules are generally a spherical shell which is filled with low density DT gas. The shell is ...

and angular momentum'. A&A 139, 378--388. Benz, W.: 1990, `Smoothed Particle Hydrodynamics � A review'. In: J, `Correction and stabilization of smooth particle hydrodynamics methods with applications in metal forming on tension instability of Eulerian and Lagrangian cor� rected smooth particle hydrodynamics ...

Instabilities C54H � Astrophysical Fluid Dynamics 1 Hydrodynamic Instabilities References Fluid Dynamics A large number of the properties of this instabilities can be under- stood in terms= divV 0= #12;Instabilities C54H � Astrophysical Fluid Dynamics 3 where the 0 subscripts refer

Pinch-point instability analysis is used to study the effects of finite temperature on the time-asymptotic pulse shapes of electrostatic and electromagnetic two-stream instabilities. Their absolute or convective instability nature is established over the entire regime from instability threshold at finite ...

The evolution of the Rayleigh-Taylor (RT) instability in a compressible medium was investigated both at an accelerating embedded interface and at the ablation front in a new series of experiments on Nova. The x-ray drive generated in a hohlraum ablatively...

Excimer laser ablation of gold films deposited on a quartz crystal microbalance is investigated. The ablation rate is directly obtained from the frequency shift of the microbalance. The measured single-shot ablation rate is found to be at least two orders of magnitude higher than the numerical predictions based on a surface ...

In this paper, we study the ablation phenomena associated with the operation of a capillary discharge for an electrothermal gun. Electrothermal-chemical (ETC) guns are used for enhancement of ignition and combustion of an energetic propellant. One of the major components of the ETC system is a plasma source based on a capillary discharge. In this paper, a model of the ...

In the regime of normal dispersion and low-frequency detunings (or high powers), four-wave mixing is shown to undergo a hydrodynamic type of instability. Such instability involves the formation of shocks (steep fronts) from smooth initial data that are regularized through the appearance of trains of fast oscillations, which exhibit ...

A fully nonlinear sharp-boundary model of the ablative Rayleigh-Taylor instability is derived and closed in a similar way to the self-consistent closure of the linear theory. It contains the stabilizing effect of ablation and accurately reproduces the results of 2D DRACO simulations. The single-mode saturation amplitude, bubble and ...

A weakly nonlinear model is proposed for the Rayleigh-Taylor instability in presence of ablation and thermal transport. The nonlinear effects for a single-mode disturbance are computed, included the nonlinear correction to the exponential growth of the fundamental modulation. Mode coupling in the spectrum of a multimode disturbance is thoroughly analyzed ...

A weakly nonlinear model is proposed for the Rayleigh-Taylor instability in presence of ablation and thermal transport. The nonlinear effects for a single-mode disturbance are computed, included the nonlinear correction to the exponential growth of the fundamental modulation. Mode coupling in the spectrum of a multimode disturbance is thoroughly analyzed ...

Demonstration of thermonuclear ignition and gain on a laboratory scale is one of science's grand challenges. The National Ignition Facility (NIF) is committed to achieving inertial confinement fusion (ICF) by 2010. Success in this endeavor depends on four elements: the laser driver performance, target design, experimental diagnostics performance, and target fabrication and target ...

The study investigates the problem of Rayleigh-Taylor instabilities in inhomogeneous media, including the effects of thermal conduction and convection. This problem is of significance in connection with the ablative stabilization of fusion targets. (ERA c...

... case (1) to (3) the density gradient near the ablation front is substantially reduced, implying a decrease in the Rayleigh-Taylor instability growth ...

... Accession Number : ADA129774. Title : Experimental Methods for Studying the Rayleigh-Taylor Instability of Ablatively Accelerated Targets. ...

... Abstract : Techniques have been developed to improve the uniformity of the laser focal profile to reduce the ablative Rayleigh Taylor instability, and ...

... Perturbations that seed Rayleigh-Taylor (RT) instability in laser-driven targets ... uniformity (laser imprint, surface ripple) are expected to oscillate. ...

... Abstract : Perturbations that seed Rayleigh-Taylor (RT) instability in laser-driven targets form during the early-time period. ...

... This process redistributes mass in the volume of the target, forming the feedout-generated seed for ablative Rayleigh-Taylor (RT) instability. ...

... The target starts accelerating only after the hydrostatic equilibrium in it has been established by a passage of all shock and rarefaction waves back ...

... ADA138644. Title : A Novel X-Ray Backlighting Method for Rayleigh-Taylor Instability Measurements on Ablatively Driven Targets. ...

Optical/electrical characterization of transient plasmas generated by high-fluence (up to 1 kJ/cm{sup 2}) laser ablation of various targets revealed as a general feature the splitting of the plume in two structures. In order to account for this behavior, a new fractal hydrodynamic model has been developed in a non-differentiable space-time. The model ...

The discussions cover the following areas, code tests and anomalies, comparison with previous work, current understanding of fluid instability in the presence of ablation, and the implications of these results for laser fusion target design. (MOW)

Techniques have been developed to improve the uniformity of the laser focal profile to reduce the ablative Rayleigh Taylor instability, and to suppress the various laser plasma instabilities. There are now three ignition target design concepts that utiliz...

The scientific research objective concerns the phenomena of tornadoes in meteorology, basin drainage in hydrodynamics, plasma confinement in magneto-hydrodynamics. The study is centered on the problems of genesis and stability of these vortices.

The highly nonlinear evolution of the single-mode Rayleigh-Taylor instability (RTI) at the ablation front of an accelerated target is investigated in the parameter range typical of inertial confinement fusion implosions. A new phase of the nonlinear bubble evolution is discovered. After the linear growth phase and a short constant-velocity phase, it is ...

The design of efficient, high-gain capsules for inertial confinement fusion (ICF) and the modeling of supernova implosions and explosions requires a detailed understanding of the consequences of material interpenetration, hydrodynamic instabilities and mi...

Hydrodynamic instability of an accelerating ionization front (IF) is investigated with 2D hydrodynamic simulations, including absorption of incident photoionizing photons, recombination in the Hll region, and radiative molecular cooling. When the amplitud...

There is a great deal of interest in studying the evolution of hydrodynamic phenomena in high energy density plasmas that have transitioned beyond the initial phases of instability into a fully developed turbulent state. Motivation for this study arises b...

In this paper we present an analysis of the theory of the energy deposition of ions in cold materials and hot dense plasmas together with numerical calculations for heavy and light ions of interest to ion-beam fusion. We have used the g-smcapso-smcapsr-smcapsg-smcapso-smcapsn-smcaps computer code of Long, Moritz, and Tahir (which is an extension of the code originally written for protons by Nardi, ...

In this paper we present an analysis of the theory of the energy deposition of ions in cold materials and hot dense plasmas together with numerical calculations for heavy and light ions of interest to ion-beam fusion. We have used the gorgon computer code of Long, Moritz, and Tahir (which is an extension of the code originally written for protons by Nardi, Peleg, and Zinamon) to carry out these ...

An annealing model is extended to treat the vaporization process, and a hydrodynamic model describes the ablated material. We find that dynamic source and ionization effects accelerate the expansion front of the ablated plume with thermal vaporization temperature. The vaporization process and plume propagation in high background gas ...

Ablative acceleration of thin foil targets at low laser irradiance (10 exp 12 to 10 exp 13 W/cm exp 2 ) are studied experimentally and theoretically. Ablative acceleration of foils up to approx. 10 exp 7 cm/sec with good hydrodynamic efficiency (20%) have...

for the in- viscid case [5,6], and the expansion in powers ofe TM is suggested by the expansions for r and q given be- low equation. 17, which have the form ...

Jan 1, 1991 ... Keywords: ASTRONOMICAL MODELS; FLOW STABILITY; HYDRODYNAMICS; SUPERNOVA 1987A; SUPERNOVAE; TAYLOR INSTABILITY; MATHEMATICAL MODELS; ...

We report several limitations and failure modes of the recently expanded Layzer model for hydrodynamic instabilities. The failures occur for large initial amplitudes, for stable accelerations, and for spikes in two-fluid systems.

Lecture notes from class on Advanced Fluid Dynamics of the Environment. Part of a segment on "Rudiments of Hydrodynamic Instability".

Lecture notes from class on Advanced Fluid Dynamics of the Environment. Part of a segment on "Rudiments of Hydrodynamic Instability".

The effect of gravity on the chemical vapor deposition process is described as twofold: it affects the convection in the stationary case, and it creates instabilities. The hydrodynamic theory of chemical vapor deposition process is described. Theoretical ...

This report briefly discusses electrically conducting fluids, Kolmogorov flow, triangular-eddy flow, thin film flow, and core-annular flow. (LSP)

In a laser cutting process, understanding of the hydrodynamics of melt layer is significant, because it is an important factor which controls the final quality. In this work, we observed the hydrodynamics of melt layer on a kerf front in the case of laser cutting of steel with an inert gas. The observation shows that the melt flow on the kerf front ...

Using the approximation of two-fluid hydrodynamics, the matrix element of the three-wave interaction is shown to be nonzero in a hot plasma. (AIP)

A spectral collocation method is used to solve the linearized Euler equations in a duct with shear flow and lined walls in order to identify a possible hydrodynamic instability observed in published experiments. This method is first checked against a reference test case in a cylindrical duct. Then a theoretical test case in a plane bi-dimensional duct with ...

devoted to hydrodynamic instabilities in Nematic Liquid Crystals [1]. A situation of particular interest of ref. [5] have been performed assuming Numerical applications correspond to MBBA, the nematic which for an imaginary nematic which would have the same viscoelastic coefficients as MBBA except for a small

Laser-accelerated targets have been predicted to be subject to the Rayleigh-Taylor hydrodynamic instability. The development of the instability was studied by introducing mass thickness variations in foil targets and observing the development of the targe...

Laser-accelerated targets have been predicted to be subject to the Rayleigh-Taylor hydrodynamic instability. The development of the instability was studied by introducing mass thickness variations in foil targets and observing the development of the targe...

Unstable lateral vibrations caused by hydrodynamic journal bearings, seals or other fluid-mechanical interactions, are the most common types of rotordynamic instabilities in high-speed turbomachinery. Mechanically, high-speed turbomachines are often model...

The evolution of the multimode Rayleigh-Taylor instability of nearly incompressible fluids, with density ratio r = 2, is investigated by means of two-dimensional hydrodynamic simulations. The study focuses on the effect of the initial perturbation on the ...

The purpose of this report is to clarify the conclusions of linear and quasi-linear theories, through which a better understanding of ion acoustic instability is possible. One of the subjects covered is the hydrodynamics derived from the quasi-linear theo...

The use of high-performance computers to simulate hydrodynamic instabilities has resulted in the generation of massive amounts of data. One aspect of the analysis of this data involves the identification and characterization of coherent structures known a...

A theoretical study has been made of the flutter and divergence instabilities of cantilevered flexible hydrofoils in a supercavitating flow condition. A two-dimensional, fluid-loading theory is used to define the unsteady hydrodynamic loads acting along t...

There is theoretical and experimental evidence [1-3] that Rayleigh-Taylor (RT) instability growth is possible in the solid state. In recent Nova laser experiments [4], a target consisting of a CH(Br) ablator with Cu backing having a sinusoidal ripple at the interface was shocked by a shaped indirect drive pulse to ~ 3 Mbar; the observed RT growth was ...

The growing effort in inertial confinement fusion (ICF) research, with the upcoming new MJ class laser facilities, NIF in USA and LMJ in France, and the upgraded MJ z-pinch ZR facility in the USA, makes the appearance of this book by Atzeni and Meyer-ter-Vehn very timely. This book is an excellent introduction for graduate or masters level students and for researchers just entering the field. It ...

Shock waves generated during inertial confinement fusion implosions propagate toward the center of the capsule encountering interfaces between materials with different densities, such as between the ablator and the DT fuel. These interactions are hydrodynamically unstable and the resulting instability causes mixing of the materials at ...

Recent advances in hydrodynamics theory and experiments at the Laboratory for Laser Energetics are described. Particular emphasis is laid on improvements in the implosion stability achieved by shaping the ablator adiabat and on the newly developed designs for fast ignition fuel assembly. The results of two-dimensional simulations and a recent set of ...

We present the results of hydrodynamic simulations of high velocity clouds (HVCs) carried out using FLASH. The simulations self-consistently trace the non-equilibrium ionization evolution of carbon, nitrogen, and oxygen in a realistic HVC geometry, in which a cool dense spherical cloud moves through hot, tenuous halo gas. In our simulations, H I is ablated ...

With an interest in pulsed laser deposition and remote spectroscopy techniques, we explore here the potential of laser pulses temporally tailored on ultrafast time scales to control the expansion and the excitation degree of various ablation products including atomic species and nanoparticulates. Taking advantage of automated pulse-shaping techniques, an adaptive procedure ...

With an interest in pulsed laser deposition and remote spectroscopy techniques, we explore here the potential of laser pulses temporally tailored on ultrafast time scales to control the expansion and the excitation degree of various ablation products including atomic species and nanoparticulates. Taking advantage of automated pulse-shaping techniques, an adaptive procedure ...

Since the advent of SN 1987A considerable progress has been made in our understanding of supernova explosions. It is now realized that they are intrinsically multidimensional in nature due to the various hydrodynamical instabilities which take place at almost all stages of the explosion. These instabilities not only modify the ...

The intent of this paper is to review how instability growth is modeled in ICF targets, and to identify the principal issues. Most of the material has been published previously, but is not familiar to a wide audience. Hydrodynamic instabilities are a key issue in ICF. Along with laser-plasma instabilities, they ...