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in creator/contributor: "Remington, B. A."

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Development of backlighting sources for a Compton radiography diagnostic of Inertial Confinement Fusion targets

We present scaled demonstrations of backlighter sources, emitting Bremsstrahlung x-rays with photon energies above 75 keV, that we will use to record x-ray Compton radiographic snapshots of cold dense DT fuel in inertial confinement fusion implosions at the National Ignition Facility (NIF). In experiments performed at the Titan laser facility at Lawrence Livermore National Laboratory, we measured the source size and the Bremsstrahlung spectrum as a function of laser intensity and pulse length, … more

Date: May 7, 2008

Creator: Tommasini, R.; MacPhee, A.; Hey, D.; Ma, T.; Chen, C.; Izumi, N. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Structures in Molecular Clouds: Modeling

We attempt to predict the observed morphology, column density and velocity gradient of Pillar II of the Eagle Nebula, using Rayleigh Taylor (RT) models in which growth is seeded by an initial perturbation in density or in shape of the illuminated surface, and cometary models in which structure is arises from a initially spherical cloud with a dense core. Attempting to mitigate suppression of RT growth by recombination, we use a large cylindrical model volume containing the illuminating source a… more

Date: April 20, 2006

Creator: Kane, J. O.; Mizuta, A.; Pound, M. W.; Remington, B. A. & Ryutov, D. D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

High resolution 17 keV to 75 keV backlighters for High Energy Density experiments

We have developed 17 keV to 75 keV 1-dimensional and 2-dimensional high-resolution (< 10 {micro}m) radiography using high-intensity short pulse lasers. High energy K-{alpha} sources are created by fluorescence from hot electrons interacting in the target material after irradiation by lasers with intensity I{sub L} > 10{sup 17} W/cm{sup 2}. We have achieved high resolution point projection 1-dimensional and 2-dimensional radiography using micro-foil and micro-wire targets attached to low-Z… more

Date: February 25, 2008

Creator: Park, H.; Maddox, B. R.; Giraldez, E.; Hatchett, S. P.; Hudson, L.; Izumi, N. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Structures in Molecular Clouds: Modeling

No Description Available.

Date: March 7, 2006

Creator: Kane, J. O.; Ryutov, D. D.; Remington, B. A.; Pound, M. & Mizuta, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Experimental astrophysics with high power lasers and Z pinches

With the advent of high energy density (HED) experimental facilities, such as high-energy lasers and fast Z-pinch, pulsed-power facilities, mm-scale quantities of matter can be placed in extreme states of density, temperature, and/or velocity. This has enabled the emergence of a new class of experimental science, HED laboratory astrophysics, wherein the properties of matter and the processes that occur under extreme astrophysical conditions can be examined in the laboratory. Areas particularly … more

Date: December 10, 2004

Creator: Remington, B. A.; Drake, R. P. & Ryutov, D. D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Formation of Pillars at the Boundaries between HII Regions and Molecular Clouds

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 ratio of the initial amplitude to wavelength is greater than 0.02, portions of the IF temporarily separate from the molecular cloud surface, lo… more

Date: April 20, 2006

Creator: Mizuta, A.; Kane, J. O.; Pound, M. W.; Remington, B. A.; Ryutov, D. D. & Takabe, H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

EXAFS Measurements of Laser-Shocked V and Ti and Crystal Phase Transformation in Ti

Extended X-Ray Absorption Fine Structure (EXAFS), using a laser-imploded target as a source, can yield the properties of laser-shocked metals on a nanosecond time scale. EXAFS measurements of vanadium shocked to {approx}0.4 Mbar yield the compression and temperature in good agreement with hydrodynamic simulations and shock-speed measurements. In laser-shocked titanium at the same pressure, the EXAFS modulation damping is much higher than warranted by the predicted temperature increase. This is … more

Date: March 10, 2004

Creator: Yaakobi, B.; Meyerhofer, D. D.; Boehly, T. R.; Rehr, J. J.; Remington, B. A.; Allen, P. G. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Materials Science at the Extremes of Pressure and Strain Rate

Solid state experiments at very high pressures and strain rates are possible on high power laser facilities, albeit over brief intervals of time and spatial small scales. A new shockless drive has been developed on the Omega laser. VISAR measurements establish the high strain rates, 10{sup 7}-10{sup 8} s{sup -1}. Solid-state strength is inferred using the Rayleigh-Taylor instability as a ''diagnostic''. Temperature and compression in polycrystalline samples can be deduced from EXAFS measurement… more

Date: August 20, 2003

Creator: Remington, B. A.; Cavallo, R. M.; Edwards, M. J.; Lasinski, B. F.; Lorenz, K. T.; Lorenzana, H. E. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Models and theory for precompound angular distributions

We compare angular distributions calculated by folding nucleon- nucleon scattering kernels, using the theory of Feshbach, Kerman and Koonin, and the systematics of Kalbach, with a wide range of data. The data range from (n,xn) at 14 MeV incident energy to (p,xn) at 160 MeV incident energy. The FKK theory works well with one adjustable parameter, the depth of the nucleon-nucleon interaction potential. The systematics work well when normalized to the hybrid model single differential cross section… more

Date: June 6, 1990

Creator: Blann, M.; Pohl, B. A.; Remington, B. A.; Scobel, W.; Trabandt, M.; Byrd, R. C. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

High precision Woelter optic calibration facility

We have developed an off-line facility for very precise characterization of the reflectance and spatial resolution of the grazing incidence Woelter Type 1 x-ray optics used at Nova. The primary component of the facility is a high brightness, ``point`` x-ray source consisting of a focussed DC electron beam incident onto a precision manipulated target/pinhole array. The data are recorded with a selection of detectors. For imaging measurements we use direct exposure x-ray film modules or an x-ray … more

Date: May 2, 1994

Creator: Morales, R. I.; Remington, B. A. & Schwinn, T.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Laboratory characterization of Woelter x-ray optics

We have conducted an extensive series of characterization measurements of a Woe1ter incidence x-ray microscope. The measurements were carried out on 5% sectors of the Woe1ter x-ray optic in a laboratory utilizing a high brightness, ``point`` x-ray source and fall into two categories. (1) Absolute reflectance measurements as a function of x-ray energy were made with Si(Li) detectors to acquire continuum spectra prior to and after reflecting off the Woe1ter optic. (2) Spatial resolution measureme… more

Date: April 1, 1994

Creator: Remington, B. A. & Morales, R. I.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Accessing High Pressure States Relevant to Core Conditions in the Giant Planets

We have designed an experimental technique to use on the National Ignition Facility (NIF) laser to achieve very high pressure (P{sub max} > 10 Mbar = 1000 GPa), dense states of matter at moderate temperatures (kT < 0.5 eV = 6000 K), relevant to the core conditions of the giant planets. A discussion of the conditions in the interiors of the giant planets is given, and an experimental design that can approach those conditions is described.

Date: April 15, 2004

Creator: Remington, B. A.; Cavallo, R. M.; Edwards, M. J.; Ho, D. D.; Lorenz, K. T.; Lorenzana, H. E. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Laser Driven High Pressure, High Strain-Rate Materials Experiments

Laser-based experiments are being developed to study the response of solids under high pressure loading. Diagnostic techniques that have been applied include dynamic x-ray diffraction, VISAR wave profile measurements, and post-shock recovery and analysis. These techniques are presented with some results from shocked Si, Al, and Cu experiments.

Date: June 29, 2001

Creator: Kalantar, D. H.; Allen, A. M.; Gregori, F.; Kad, B.; Kumar, M.; Lorenz, K. T. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Strong stabilization of the Rayleigh-Taylor instability by material strength at Mbar pressures

Experimental results showing significant reductions from classical in the Rayleigh-Taylor (RT) instability growth rate due to high pressure effective lattice viscosity are presented. Using a laser created ramped drive, vanadium samples are compressed and accelerated quasi-isentropically at {approx}1 Mbar pressures, while maintaining the sample in the solid-state. Comparisons with simulations and theory indicate that the high pressure, high strain rate conditions trigger a phonon drag mechanism,… more

Date: November 19, 2009

Creator: Park, H. S.; Lorenz, K. T.; Cavallo, R. M.; Pollaine, S. M.; Prisbrey, S. T.; Rudd, R. E. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

X-ray radiographic imaging of hydrodynamic phenomena in radiation driven materials -- shock propagation, material compression and shear flow. Revision 1

One- and two-dimensional, time resolved x-ray radiographic imaging at high photon energy (5-7 keV) is used to study shock propagation, material motion and compression, and the effects of shear flow in solid density samples which are driven by x-ray ablation with the Nova laser. By backlighting the samples with x-rays and observing the increase in sample areal density due to shock compression, the authors directly measure the trajectory of strong shocks ({approx}40 Mbar) in flight, in solid dens… more

Date: February 1, 1994

Creator: Hammel, B. A.; Kilkenny, J. D.; Munro, D.; Remington, B. A.; Kornblum, H. N.; Perry, T. S. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Design of an electromagnetic accelerator for turbulent hydrodynamic mix studies. Revision 1

An electromagnetic accelerator in the form of a linear electric motor (LEM) has been designed to achieve controlled acceleration profiles of a carriage containing hydrodynamically unstable fluids for the investigation of the development of turbulent mix. Key features of the design include: (1) independent control of acceleration, deceleration and augmentation currents to provide a variety of acceleration-time profiles, (2) a robust support structure to minimized deflection and dampen vibration … more

Date: March 1, 1994

Creator: Susoeff, A. R.; Hawke, R. S.; Morrison, J. J.; Dimonte, G. & Remington, B. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Three-dimensional modeling and analysis of a high energy density Kelvin-Helmholtz experiment

No Description Available.

Date: February 14, 2012

Creator: Raman, K. S.; Hurricane, O. A.; Park, H. S.; Remington, B. A.; Robey, H. & Smalyuk, V. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

RAYLEIGH-TAYLOR STRENGTH EXPERIMENTS OF THE PRESSURE-INDUCED alpha->epsilon->alpha' PHASE TRANSITION IN IRON

We present here the first dynamic Rayleigh-Taylor (RT) strength measurement of a material undergoing solid-solid phase transition. Iron is quasi-isentropically driven across the pressure-induced bcc ({alpha}-Fe) {yields} hcp ({var_epsilon}-Fe) phase transition and the dynamic strength of the {alpha}, {var_epsilon} and reverted {alpha}{prime} phases have been determined via proton radiography of the resulting Rayleigh-Taylor unstable interface between the iron target and high-explosive products.… more

Date: August 10, 2011

Creator: Belof, J. L.; Cavallo, R. M.; Olson, R. T.; King, R. S.; Gray, G. T.; Holtkamp, D. B. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Theory and Simulation of 1D to 3D Plastic Relaxation in Tantalum

No Description Available.

Date: August 2, 2011

Creator: Rudd, R. E.; Comley, A. J.; Hawreliak, J.; Maddox, B. R.; Park, H. S. & Remington, B. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

High Energy K(alpha) Radiography Using High-intensity, Short-pulse Lasers

We have performed experiments using Callisto, the Vulcan 100 TW and the Vulcan Petawatt high intensity lasers to understand the characteristics of high energy, K{alpha} x-ray sources and to implement workable radiography solutions at 20-100 keV. Our measurements show that the K{alpha} size from a simple foil target is larger than 60 {micro}m, far larger than the experiment resolution requirement. The total K{alpha} yield is independent of target thicknesses verifying that refluxing plays a majo… more

Date: November 16, 2005

Creator: Park, H.; Izumi, N.; Key, M. H.; King, J. A.; Koch, J. A.; Landen, O. L. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Similarity Laws for Collisionless Interaction of Superstrong Electromagnetic Fields with a Plasma

Several similarity laws for the collisionless interaction of ultra-intense electromagnetic fields with a plasma of an arbitrary initial shape is presented. Both ultra-relativistic and non-relativistic cases are covered. The ion motion is included. A brief discussion of possible ways of experimental verification of scaling laws is presented. The results can be of interest for experiments and numerical simulations in the areas of particle acceleration, harmonic generation, and Coulomb explosion o… more

Date: October 18, 2005

Creator: Ryutov, D. D. & Remington, B. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A Hypothesis of the Magnetostatic Turbulence and its Implications for Astrophysics

Arguments are presented in favor of a possible existence of a random, force-free magnetic field. Ponderomotive forces in such a field are small, and the evolutionary time is much longer than Alfven crossing time over the vortex scale, whence the suggested term ''magnetostatic''. The presence of this long-lived random magnetic field provides stiffness with respect to large-scale compressional motions. On the other hand, such a field cannot be detected by techniques involving line-of-sight averag… more

Date: February 26, 2007

Creator: Ryutov, D. D. & Remington, B. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Phenomenological Theory of the Photoevaporation Front Instability

The dynamics of photoevaporated molecular clouds is determined by the ablative pressure acting on the ionization front. An important step in the understanding of the ensuing motion is to develop the linear stability theory for the initially flat front. Despite the simplifications introduced by the linearization, the problem remains quite complex and still draws a lot of attention. The complexity is related to the large number of effects that have to be included in the analysis: acceleration of … more

Date: April 10, 2006

Creator: Ryutov, D. D.; Kane, J. O.; Mizuta, A.; Pound, M. W. & Remington, B. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

LSP Calculations of Cone-Wire Experiments

Recent experiments at the Institute of Laser Engineering (ILE) in Japan [1] and at Rutherford Appleton Laboratory (RAL) in the United Kingdom [2] have shown good coupling of short-pulse high-intensity laser light into high-energy electrons channeled down a narrow fiber. Such target configurations are being considered as backlighter targets on the National Ignition Facility (NIF). We will report on LSP calculations of these cone-wire experiments and other candidate target configurations. These c… more

Date: June 13, 2005

Creator: Town, R. J.; Cottrill, L. A.; Key, M. H.; Kruer, W. L.; Langdon, A. B.; Lasinski, B. F. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department