A first set of shock propagation, laser-plasma interaction, hohlraum energetics and hydrodynamic experiments have been performed using the first 4 beams of the National Ignition Facility (NIF), in support of indirect drive Inertial Confinement Fusion (ICF) and High Energy Density Physics.

The production of supersonic jets of material via the interaction of a strong shock wave with a spatially localized density perturbation is a common feature of inertial confinement fusion and astrophysics. The spatial structure and mass evolution of supersonic jets has previously been investigated in detail [J. M. Foster et. at, Phys. Plasmas 9, 2251 (2002) and B. E. Blue et. at, Phys. Plasmas 12, 056312 (2005)]. In this paper, the results from the first series of hydrodynamic experiments will be presented in which the mass distribution within the jet was quantified. In these experiments, two of the first four beams of NIF are used to drive a 40 Mbar shock wave into millimeter scale aluminum targets backed by 100mg/cc carbon aerogel foam. The remaining beams are delayed in time and are used to provide a point-projection x-ray backlighter source for diagnosing the structure of the jet. Comparisons between data and simulations using several codes are presented.

The first hydrodynamic experiments were performed on the National Ignition Facility. A supersonic jet was formed via the interaction of a laser driven shock ( approximately 40 Mbar) with 2D and 3D density perturbations. The temporal evolution of the jet's spatial scales and ejected mass were measured with point-projection x-ray radiography. Measurements of the large-scale features and mass are in good agreement with 2D and 3D numerical simulations. These experiments provide quantitative data on the evolution of 3D supersonic jets and provide insight into their 3D behavior.

The production of supersonic jets of material via the interaction of a strong shock wave with a spatially localized density perturbation is a common feature of inertial confinement fusion and astrophysics. The behavior of two-dimensional (2D) supersonic jets has previously been investigated in detail [J. M. Foster, B. H. Wilde, P. A. Rosen, T. S. Perry, M. Fell, M. J. Edwards, B. F. Lasinski, R. E. Turner, and M. L. Gittings, Phys. Plasmas 9, 2251 (2002)]. In three dimensions (3D), however, there are new aspects to the behavior of supersonic jets in compressible media. In this paper, the commissioning activities on the National Ignition Facility (NIF) [J. A. Paisner, J. D. Boyes, S. A. Kumpan, W. H. Lowdermilk, and M. Sorem, Laser Focus World 30, 75 (1994)] to enable hydrodynamic experiments will be presented as well as the results from the first series of hydrodynamic experiments. In these experiments, two of the first four beams of NIF are used to drive a 40Mbar shock wave into millimeter scale aluminum targets backed by 100mg∕cc carbon aerogel foam. The remaining beams are delayed in time and are used to provide a point-projection x-ray backlighter source for diagnosing the three-dimensional structure of the jet evolution resulting from a variety of 2D and 3D features. Comparisons between data and simulations using several codes will be presented.

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 wavelengths can occur, in marked contrast to the classical case where growth rates are highest at the shortest wavelengths. Theoretical and numerical investigations of the ablative RT instability are numerous and differ considerably on the level of stabilization expected. Presented here are the results of a series of laser experiments designed to measure the RT dispersion curve for a radiatively driven sample. Aluminum foils with imposed sinusoidal perturbations ranging in wavelength from 10 to 70 μm were ablatively accelerated with a radiation drive generated in a gold cylindrical hohlraum. A strong shock wave compresses the package followed by an ∼2 ns period of roughly constant acceleration and the experiment is diagnosed via face-on radiography. Perturbations with wavelengths ⩾20 μm experienced substantial growth during the acceleration phase while shorter wavelengths showed a sharp drop off in overall growth. These experimental results compared favorably to calculations with a two-dimensional radiation-hydrodynamics code, however, the growth is significantly affected by the rippled shock launched by the drive. Due to the influence of the rippled shock transit phase of the experiment and ambiguities associated with directly extracting the physical amplitude of the perturbations at the ablation front from the simulations, direct comparison to the ablation front RT theory of Betti et al. [Phys. Plasmas 5, 1446 (1998)], was difficult. Instead, a numerical “experiment” was constructed that minimized the influence of the shock and this was compared to the Betti model showing quite good agreement.

We have conducted high-speed jet experiments using the Nova laser facility located at the Lawrence Livermore National Laboratory. The experiments make use of energy deposited in a Nova hohlraum to launch a strong shock down the axis of a cylindrical, millimeter-scale package containing a plastic/foam interface. The passage of the shock, causes a hemispherical indentation at the interface to invert and form a plasma jet. The jet-tip velocity is approximately 60 km s(-1), with a corresponding jet-tip Mach number of about 17. An X-ray backlighter foil and an electronic X-ray framing camera are used to radiograph the flow side-on. Vortical structures are observed, and the development of the jet over time is measured. An additional set of experiments was undertaken to elucidate these structures using a tracer material. Numerical simulations have been performed to provide additional insights into this flow and to permit examination of unmeasured quantities. The experiments include aspects of observed astrophysical jet phenomena, which could prove useful for benchmarking codes.

We report on results of an experimental study of the Richtmyer- Meshkov instability. The growth of the mixing region in the nonlinear regime is measured for a set of cases in which the amplitude and wavelength of the initial perturbation are varied systematically. The experiments are conducted on the Nova laser facility, and use a Nova hohlraum as a driver source to launch a high-Mach-number shock into a miniature shock tube attached to the hohlraum. The shock tube contains brominated plastic and low-density carbon foam as the two working fluids, with a micro-machined, triangular sawtooth interface between them serving as the initial perturbation. The sawtooth perturbation waveform is dominated by a single mode, and the perturbation amplitudes are chosen to expedite transition into the nonlinear phase of the instability. The shock, upon crossing the perturbation at the interface, instigates the Richtmyer- Meshkov instability. The resulting growth of the mixing region is diagnosed radiographically. Quantitative measurements of the temporal growth of the width of the mixing region are made for six different combinations of amplitude and wavelength, building upon previous results which employed a single amplitude/wavelength combination. Data from both experiment and supporting simulations suggest that the nonlinear growth of the mix width admits a logarithmic time dependence. The results also suggest that, properly normalized, the total mixing width grows in a nearly self-similar fashion, with a weak shape dependence.

We review experiments and calculations of the compressible Richtmyer-Meshkov instability from a single-mode, nonlinear initial perturbation. These experiments were performed using the Nova laser. Measurements of the time-evolution of the mixing region were reported previously. We compared the experimental measurements with numerical simulations [1,2]. We found both experiment and simulation to be in good agreement with recent theories for the nonlinear evolution of the instability [3,4]. Experimental results beyond those previously presented provide additional support for the use of two phase flow models to describe the flow in the nonlinear regime. These experiments include measurement of the mixing region at additional times, including times earlier in the evolution of the instability than previously reported. We have also carried out experiments to examine the difference in the evolution of the instability from initial perturbations consisting of circular sawtooth grooves as well as rectilinear sawteeth. Our previous two-dimensional numerical simulations approximated the experimental linear grooves as circular grooves. We reasoned that the difference between the two cases would be small, based on scaling arguments, and limited to a very small region near the centerline. New experimental and numerical results confirm this. Finally, we discuss some additional issues in the derivation of the two-phase flow model used previously in describing the growth of the Richtmyer-Meshkov instability in the nonlinear phase relevant to other work presented at this meeting [5,6].

We present the results from a series of experiments recently completed on the Nova laser studying the growth of the Richtmyer-Meshkov instability from an initially nonlinear perturbation. These are the first experimental measurements of the time-dependent mixing of materials at a shocked interface from a high-amplitude, short-wavelength perturbation in a high Mach number regime. The experiments were simulated using CALE, a two-dimensional arbitrary Lagrangian-Eulerian hydrodynamics code. The calculations correctly captured the measured growth of the mixing zone from the initial applied perturbation. The simulations also permitted consideration of nonideal effects (e.g. post-shock decompression) required to compare the results of calculation and experiment with theory. Both the experiment and calculations were found to be in good agreement with recent theories for the nonlinear evolution of the instability.