82 results on '"Paul Keiter"'
Search Results
2. Mitigating the Joint Feature in Double Shell Implosion Simulations
- Author
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Irina Sagert, Lindsey Kuettner, T. E. Quintana, T. Morrow, Brian Haines, D. S. Montgomery, Brian M. Patterson, D. J. Stark, Lynne Goodwin, J. P. Sauppe, Steven H. Batha, Paul Keiter, Sasikumar Palaniyappan, Eric Loomis, and R. F. Sacks
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Fusion ,Yield (engineering) ,Materials science ,Shell (structure) ,Implosion ,Perturbation (astronomy) ,Mechanics ,Joint (geology) ,Inertial confinement fusion ,Symmetry (physics) - Abstract
Double shell capsules are an attractive alternative in inertial confinement fusion experiments due to their potential for achieving a low-convergence, robust burn 1 . However, symmetry degradation and accompanying reduced fuel confinement plagues these systems due to the joint between the two hemispheres of the outer shell. The gap widens during irradiation and this perturbation grows and imprints onto the inner shell during the collision. xRAGE Eulerian radiation-hydrodynamic simulations predict significant reductions in deuterium–tritium fusion yields compared to joint-less simulations when the depth of the outer joint is increased. We demonstrate that the technique of plating the insides of the outer gap with gold can mitigate the impact of this feature. Gold-plating in quantities comparable to or exceeding the "missing" outer shell mass shows promise toward restoring both implosion symmetry and yield closer to the joint-less levels 2 . The shape and symmetry retention in the outer and inner shells is captured in high-energy x-ray synthetic radiographs.
- Published
- 2021
3. Assessment of double shell ablator asymmetry sources and shape control [Slides]
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Harry Robey, Paul Keiter, Eric Loomis, and R. F. Sacks
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Physics ,media_common.quotation_subject ,Shell (structure) ,Mechanics ,Asymmetry ,Shape control ,media_common - Published
- 2021
4. Symmetry requirements for double shell capsules with aluminum ablators
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Ryan Sacks, Eric Loomis, Paul Keiter, Elizabeth Merritt, David Montgomery, Joshua Sauppe, Brian Haines, David Stark, Irina Sagert, Harry Robey, III, Sasikumar Palaniyappan, Tana Morrow, Sean Finnegan, John Kline, and Steven Batha
- Published
- 2021
5. Phase contrast imaging of irradiated foils through Talbot Lau X ray Deflectometry on OMEGA EP
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Sean Regan, Christian Stoeckl, S. Muller, Carolyn Kuranz, K Matsuo, Ildar A. Begishev, Raul Melean, J. Zou, V. Bouffetier, F. N. Beg, Chad Mileham, C. Sorce, Dan Stutman, W. Theobald, Sallee Klein, Alexis Casner, Paul Keiter, Matthew Trantham, M Bailly-Grandvaux, R. P. Drake, Jeffrey Fein, Marilyn Schneider, and M. P. Valdivia
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Nuclear magnetic resonance ,Materials science ,Phase-contrast imaging ,X-ray ,Irradiation ,Omega - Published
- 2020
6. CT analysis of double shell targets
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Tana Cardenas, Eric Loomis, Lindsey Kuettner, Abigail Louise Ferris, and Paul Keiter
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Nuclear magnetic resonance ,Materials science ,Shell (structure) ,Ct analysis - Published
- 2020
7. Implementation of a Talbot-Lau x-ray deflectometer diagnostic platform for the OMEGA EP laser
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J. R. Fein, Matthew Trantham, K. Kaiser, Dan Stutman, M. P. Valdivia, J. Zou, Christian Stoeckl, R. P. Drake, S. Muller, Chad Mileham, Paul Keiter, Susan Regan, and C. Sorce
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010302 applied physics ,Materials science ,business.industry ,medicine.medical_treatment ,X-ray ,Moiré pattern ,Grating ,Ablation ,Laser ,01 natural sciences ,Omega ,010305 fluids & plasmas ,law.invention ,Optics ,law ,0103 physical sciences ,Moire deflectometry ,medicine ,business ,Instrumentation ,FOIL method - Abstract
A Talbot-Lau X-ray Deflectometer (TXD) was implemented in the OMEGA EP laser facility to characterize the evolution of an irradiated foil ablation front by mapping electron densities >1022 cm-3 by means of Moire deflectometry. The experiment used a short-pulse laser (30-100 J, 10 ps) and a foil copper target as an x-ray backlighter source. In the first experimental tests performed to benchmark the diagnostic platform, grating survival was demonstrated and x-ray backlighter laser parameters that deliver Moire images were described. The necessary modifications to accurately probe the ablation front through TXD using the EP-TXD diagnostic platform are discussed.
- Published
- 2020
8. Resonant ion heating in a helicon plasma
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Robert Boivin, Earl Scime, Paul Keiter, Matthew M. Balkey, and John Kline
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Physics ,Helicon ,Plasma ,Atomic physics ,Ion - Published
- 2019
9. The design of a photoionization front experiment using the Z-Machine as a driving source and estimated measurements
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M. Springstead, Roberto Mancini, R. P. Drake, Heath LeFevre, Paul Keiter, C.C. Kuranz, Guillaume Loisel, and K. Kelso
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Physics ,Radiation flux ,Attenuation ,Atomic model ,Front (oceanography) ,Flux ,Photoionization ,Condensed Matter Physics ,Reionization ,Line (formation) ,Computational physics - Abstract
Radiation-driven heat fronts are present in the early universe during reionization, the circumstellar medium of supernovae, and in high-energy-density physics experiments. Dedicated experiments to observe and diagnose the behavior of these types of heat fronts can improve our understanding of these phenomena. A simulation study of photoionization fronts using the HELIOS-CR radiation hydrodynamics code provides an experimental design for the Z-Machine at Sandia National Laboratory using a measurement-calibrated input radiation flux to drive the photoionization front. The simulations use detailed atomic physics and non-diffusive radiation transport in 1D to determine an optimal gas pressure of 0.75 atm for an experiment in N gas as well as the effects of increasing the thickness of the window that seals the gas cell. Post-processing of these simulations demonstrates that ratios of atomic rate coefficients place the heat front in a physics regime where photoionization dominates the energy deposition. To see the sensitivity of the simulations to changes in the model and spatial grid, this analysis performed resolution, atomic model detail, and radiation transport angular grid studies showing less than 10% deviation from the nominal model for increased complexity, when possible. An effort to emulate 3D geometric effects on the radiation flux using an artificial attenuation scheme has shown that, even for conservative estimates of the flux, simulations still produce a photoionization front. Estimations of a streaked, visible spectroscopy measurement using SPECT3D showed that line emission measurements are present early in time and that later in time thermal emission should become dominant.
- Published
- 2021
10. Detrimental effects and mitigation of the joint feature in double shell implosion simulations
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Brian M. Patterson, Sasikumar Palaniyappan, D. J. Stark, T. E. Quintana, R. F. Sacks, D. S. Montgomery, Steven H. Batha, Lynne Goodwin, T. Morrow, Irina Sagert, Eric Loomis, Paul Keiter, Brian Haines, Joshua Sauppe, and Lindsey Kuettner
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Physics ,Fusion ,Yield (engineering) ,Phase (waves) ,Shell (structure) ,Implosion ,Mechanics ,Condensed Matter Physics ,01 natural sciences ,Symmetry (physics) ,010305 fluids & plasmas ,0103 physical sciences ,010306 general physics ,Joint (geology) ,Inertial confinement fusion - Abstract
Double shell capsules provide an attractive option in inertial confinement fusion experiments due to their potential for achieving a low-convergence, robust burn. However, these designs suffer from symmetry degradation and accompanying reduced fuel confinement due to the currently necessary joint between the two hemispheres of the outer shell. The gap widens as a result of the excess ablation pressure produced by x rays that penetrate the joint during the drive phase, and this perturbation grows and imprints onto the inner shell during the collision. xRAGE Eulerian radiation-hydrodynamic simulations predict significant reductions in deuterium–tritium fusion yields compared to joint-less simulations when the depth of the outer joint is increased, whereas the performance is less sensitive to the depth of the inner gap. Here we examine the technique of plating the insides of the outer gap with a high-Z material to mitigate the impact of this feature. Gold-plating in quantities comparable to or exceeding the “missing” outer shell mass shows promise toward restoring both implosion symmetry and yield closer to the joint-less levels, and synthetic diagnostics suggest that high-energy x-ray radiographs can capture this shape retention of the inner and outer shells in experiments.
- Published
- 2021
11. Design of laboratory experiments to study radiation-driven implosions
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Y. Frank, M. Fraenkel, J. S. Davis, R. P. Drake, Matthew Trantham, Dov Shvarts, E. Raicher, Robert Vandervort, Paul Keiter, Sallee Klein, Guy Malamud, and James M. Stone
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Physics ,Nuclear and High Energy Physics ,Radiation ,Photon ,010504 meteorology & atmospheric sciences ,Mean free path ,Astrophysics ,01 natural sciences ,Computational physics ,Interstellar medium ,Stars ,0103 physical sciences ,Irradiation ,Current (fluid) ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,0105 earth and related environmental sciences ,Dimensionless quantity - Abstract
The interstellar medium is heterogeneous with dense clouds amid an ambient medium. Radiation from young OB stars asymmetrically irradiate the dense clouds. Bertoldi (1989) developed analytic formulae to describe possible outcomes of these clouds when irradiated by hot, young stars. One of the critical parameters that determines the cloud’s fate is the number of photon mean free paths in the cloud. For the extreme cases where the cloud size is either much greater than or much less than one mean free path, the radiation transport should be well understood. However, as one transitions between these limits, the radiation transport is much more complex and is a challenge to solve with many of the current radiation transport models implemented in codes. We present the design of laboratory experiments that use a thermal source of x-rays to asymmetrically irradiate a low-density plastic foam sphere. The experiment will vary the density and hence the number of mean free paths of the sphere to study the radiation transport in different regimes. We have developed dimensionless parameters to relate the laboratory experiment to the astrophysical system and we show that we can perform the experiment in the same transport regime.
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- 2017
12. Magnetized Disruption of Inertially Confined Plasma Flows
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Patrick Belancourt, Matthew Trantham, B. B. Pollock, Alexander Rasmus, Adam B Sefkow, J. R. Fein, M. J.-E. Manuel, R. P. Drake, Rachel Young, J. Park, C.C. Kuranz, Paul Keiter, A. Hazi, H. Chen, Michael MacDonald, Sallee Klein, and Gerald Williams
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Physics ,Jet (fluid) ,Field (physics) ,General Physics and Astronomy ,Flux ,Plasma ,Mechanics ,01 natural sciences ,Collimated light ,Interferometry ,Electrical resistivity and conductivity ,0103 physical sciences ,Supersonic speed ,010306 general physics - Abstract
The creation and disruption of inertially collimated plasma flows are investigated through experiment, simulation, and analytical modeling. Supersonic plasma jets are generated by laser-irradiated plastic cones and characterized by optical interferometry measurements. Targets are magnetized with a tunable $B$ field with strengths of up to 5 T directed along the axis of jet propagation. These experiments demonstrate a hitherto unobserved phenomenon in the laboratory, the magnetic disruption of inertially confined plasma jets. This occurs due to flux compression on axis during jet formation and can be described using a Lagrangian-cylinder model of plasma evolution implementing finite resistivity. The basic physical mechanisms driving the dynamics of these systems are described by this model and then compared with two-dimensional radiation-magnetohydrodynamic simulations. Experimental, computational, and analytical results discussed herein suggest that contemporary models underestimate the electrical conductivity necessary to drive the amount of flux compression needed to explain observations of jet disruption.
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- 2019
13. Opacity: A window into High Energy Density Plasma Physics
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Pawel Kozlowski, Peter Hakel, Robert Heeter, Christopher J. Fontes, T. S. Perry, James Colgan, Paul Keiter, and Heather Johns
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Physics ,Optics ,Opacity ,business.industry ,Energy density ,Window (computing) ,Plasma ,business - Published
- 2019
14. A platform for x-ray Thomson scattering measurements of radiation hydrodynamics experiments on the NIF
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Patrick Belancourt, Channing Huntington, K. H. Ma, Heath LeFevre, Paul Keiter, Carolyn Kuranz, Tilo Döppner, M. J. MacDonald, and Eric Johnsen
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Materials science ,Thomson scattering ,Scattering ,Astrophysics::High Energy Astrophysical Phenomena ,Energy flux ,Electron ,Thermal conduction ,01 natural sciences ,010305 fluids & plasmas ,Computational physics ,0103 physical sciences ,Electron temperature ,010306 general physics ,National Ignition Facility ,Instrumentation ,Inertial confinement fusion - Abstract
We present an experimental design for a radiation hydrodynamics experiment at the National Ignition Facility that measures the electron temperature of a shocked region using the x-ray Thomson scattering technique. Previous National Ignition Facility experiments indicate a reduction in Rayleigh-Taylor instability growth due to high energy fluxes, compared to the shocked energy flux, from radiation and electron heat conduction. In order to better quantify the effects of these energy fluxes, we modified the previous experiment to allow for non-collective x-ray Thomson scattering to measure the electron temperature. Photometric calculations combined with synthetic scattering spectra demonstrate an estimated noise.
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- 2018
15. Constraining computational modeling of indirect drive double shell capsule implosions using experiments
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Harry Robey, John C. Field, Lindsey Kuettner, Marius Millot, E.N. Loomis, Brian Haines, D. S. Montgomery, Brian M. Patterson, Joshua Sauppe, R. F. Sacks, Doug Wilson, D. J. Stark, T. E. Quintana, Peter M. Celliers, Paul Keiter, T. Morrow, M. S. Rubery, and C. M. Krauland
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Physics ,Computational model ,Shell (structure) ,Mechanics ,Condensed Matter Physics ,01 natural sciences ,Instability ,010305 fluids & plasmas ,Machining ,0103 physical sciences ,Inner shell ,010306 general physics ,National Ignition Facility ,Keyhole - Abstract
Double shell capsule implosions are an alternative approach to achieving alpha heating on the National Ignition Facility. Current machining techniques construct the outer shell as two hemispheres that are glued together, and the deuterium and tritium (DT) liquid inside the inner shell will be injected by a fill tube. These features introduce asymmetries and jetting that may disrupt the confinement of the DT fuel if not carefully controlled. Simulations indicate that in order to achieve high yields in the laboratory, these features as well as susceptibility to the Rayleigh–Taylor instability (RTI) must be mitigated. Due to uncertainties in computational models and the expense of using the best physics models at adequate resolution in three dimensions, our computational modeling must be constrained by experiments. We report on the results of recent hydrogrowth radiography and dual-axis keyhole experiments with double shell targets that have been used to evaluate our modeling of the outer shell joint as well as the impacts of high-energy x-ray preheat that strongly impacts RTI growth. Our simulations show good agreement with the experimental data and inform several important modeling choices.
- Published
- 2021
16. Neural network for 3D inertial confinement fusion shell reconstruction from single radiographs
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Brian M. Patterson, Lindsey Kuettner, D. S. Montgomery, Eric Loomis, John Kline, Zhizhong Han, Jonathan S. Ben-Benjamin, Paul Keiter, Zhehui Wang, Bradley T. Wolfe, and Elizabeth Merritt
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010302 applied physics ,Artificial neural network ,Computer science ,business.industry ,3D reconstruction ,Implosion ,01 natural sciences ,Convolutional neural network ,Synthetic data ,010305 fluids & plasmas ,0103 physical sciences ,Preprocessor ,Computer vision ,Sensitivity (control systems) ,Artificial intelligence ,business ,Instrumentation ,Inertial confinement fusion - Abstract
In inertial confinement fusion (ICF), x-ray radiography is a critical diagnostic for measuring implosion dynamics, which contain rich three-dimensional (3D) information. Traditional methods for reconstructing 3D volumes from 2D radiographs, such as filtered backprojection, require radiographs from at least two different angles or lines of sight (LOS). In ICF experiments, the space for diagnostics is limited, and cameras that can operate on fast timescales are expensive to implement, limiting the number of projections that can be acquired. To improve the imaging quality as a result of this limitation, convolutional neural networks (CNNs) have recently been shown to be capable of producing 3D models from visible light images or medical x-ray images rendered by volumetric computed tomography. We propose a CNN to reconstruct 3D ICF spherical shells from single radiographs. We also examine the sensitivity of the 3D reconstruction to different illumination models using preprocessing techniques such as pseudo-flatfielding. To resolve the issue of the lack of 3D supervision, we show that training the CNN utilizing synthetic radiographs produced by known simulation methods allows for reconstruction of experimental data as long as the experimental data are similar to the synthetic data. We also show that the CNN allows for 3D reconstruction of shells that possess low mode asymmetries. Further comparisons of the 3D reconstructions with direct multiple LOS measurements are justified.
- Published
- 2021
17. Experimental results from magnetized-jet experiments executed at the Jupiter Laser Facility
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Rachel Young, Matthew Trantham, Michael MacDonald, B. B. Pollock, J. Park, J. R. Fein, Paul Keiter, R. P. Drake, Gerald Williams, C.C. Kuranz, Patrick Belancourt, A. Hazi, Sallee Klein, Hui Chen, Mario Manuel, and Alexander Rasmus
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Physics ,Nuclear and High Energy Physics ,Jet (fluid) ,Radiation ,Dense plasma focus ,business.industry ,Solenoid ,Plasma ,equipment and supplies ,Collimated light ,Magnetic field ,Jupiter ,Interferometry ,Optics ,Physics::Accelerator Physics ,Atomic physics ,business ,human activities - Abstract
Recent experiments at the Jupiter Laser Facility investigated magnetization effects on collimated plasma jets. Laser-irradiated plastic-cone-targets produced collimated, millimeter-scale plasma flows as indicated by optical interferometry. Proton radiography of these jets showed no indication of strong, self-generated magnetic fields, suggesting a dominantly hydrodynamic collimating mechanism. Targets were placed in a custom-designed solenoid capable of generating field strengths up to 5 T. Proton radiographs of the well-characterized B-field, without a plasma jet, suggested an external source of trapped electrons that affects proton trajectories. The background magnetic field was aligned with the jet propagation direction, as is the case in many astrophysical systems. Optical interferometry showed that magnetization of the plasma results in disruption of the collimated flow and instead produces a hollow cavity. This result is a topic of ongoing investigation.
- Published
- 2015
18. Preliminary characterization of a laser-generated plasma sheet
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R. P. Drake, J. R. Fein, Sallee Klein, Paul Keiter, J. S. Davis, Guy Malamud, and Matthew Trantham
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Physics ,Nuclear and High Energy Physics ,Radiation ,Binary star ,Plasma sheet ,Cataclysmic variable star ,White dwarf ,Plasma ,Astrophysics ,Mechanics ,Wedge (geometry) ,Blast wave ,Shock (mechanics) - Abstract
We present the results from recent experiments to create a flowing plasma sheet. Two groups of three laser beams with nominally 1.5 kJ of energy per group were focused to separate pointing locations, driving a shock into a wedge target. As the shock breaks out of the wedge, the plasma is focused on center, creating a sheet of plasma. Measurements at 60 ns indicate the plasma sheet has propagated 2825 microns with an average velocity of 49 microns/ns. These experiments follow previous experiments [Krauland et al. 2013], which are aimed at studying similar physics as that found in the hot spot region of cataclysmic variables. Krauland et al. created a flowing plasma, which represents the flowing plasma from the secondary star. This flow interacted with a stationary object, which represented the disk around the white dwarf. A reverse shock is a shock formed when a freely expanding plasma encounters an obstacle. Reverse shocks can be generated by a blast wave propagating through a medium. They can also be found in binary star systems where the flowing gas from a companion star interacts with the accretion disk of the primary star.
- Published
- 2015
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19. Laboratory Photoionization Fronts in Nitrogen Gas: A Numerical Feasibility and Parameter Study
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Kenneth G. Powell, J. S. Davis, Heath LeFevre, B. van der Holst, William J. Gray, Paul Keiter, R. P. Drake, and C. R. Patterson
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Physics ,Front (oceanography) ,Flux ,FOS: Physical sciences ,Astronomy and Astrophysics ,Photoionization ,Electron ,Thermal conduction ,01 natural sciences ,Astrophysics - Astrophysics of Galaxies ,010305 fluids & plasmas ,Computational physics ,Atmospheric radiative transfer codes ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Ionization ,Astrophysics of Galaxies (astro-ph.GA) ,0103 physical sciences ,Diffusion (business) ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
Photoionization fronts play a dominant role in many astrophysical situations, but remain difficult to achieve in a laboratory experiment. We present the results from a computational parameter study evaluating the feasibility of the photoionization experiment presented in the design paper by Drake, R. P., Hazak, G., Keiter, P. A., Davis, J. S., Patterson, C. R., Frank, A., Blackman, E. G., & Busquet, M. 2016, ApJ, 833, 249 in which a photoionization front is generated in a nitrogen medium . The nitrogen gas density and the Planckian radiation temperature of the x-ray source define each simulation. Simulations modeled experiments in which the x-ray flux is generated by a laser-heated gold foil, suitable for experiments using many kJ of laser energy, and experiments in which the flux is generated by a "z-pinch" device, which implodes a cylindrical shell of conducting wires. The models are run using CRASH, our block-adaptive-mesh code for multi-material radiation hydrodynamics. The radiative transfer model uses multi-group, flux-limited diffusion with thirty radiation groups. In addition, electron heat conduction is modeled using a single-group, flux-limited diffusion. In the theory, a photoionization front can exist only when the ratios of the electron recombination rate to the photoionization rate and the electron impact ionization rate to the recombination rate lie in certain ranges. These ratios are computed for several ionization states of nitrogen. Photoionization fronts are found to exist for laser driven models with moderate nitrogen densities ($\sim$10$^{21}$ cm$^{-3}$) and radiation temperatures above 90 eV. For "z-pinch" driven models, lower nitrogen densities are preferred ($, Comment: 22 pages, 14 figures, comments welcome
- Published
- 2018
20. Observations of the Magnetized Disruption of Collimated Plasma Flows
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Michael MacDonald, A. U. Hazi, Pat Belancourt, Carolyn Kuranz, Jackson Williams, Alexander Rasmus, Matt Trantham, Rachel Young, B. B. Pollock, Hui Chen, J. Park, Mario Manuel, Jeff Fein, R. P. Drake, Sallee Klein, and Paul Keiter
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Physics ,Optics ,business.industry ,law ,Astrophysics::High Energy Astrophysical Phenomena ,Plasma ,business ,Laser ,Accretion (astrophysics) ,Collimated light ,law.invention ,Magnetic field - Abstract
The dynamics of magnetized flows is of great interest to the astrophysics community as the formation and long collimation distances of jets in accretion systems are still open questions. In many of these systems, the background magnetic field is parallel to the jet propagation direction. Recent experiments [1] performed at the Jupiter Laser Facility investigated the effects of imposing a background magnetic field aligned with a collimated jet. Plastic cone targets were irradiated by a long-pulse laser as shown schematically in Fig. 1a. When the shock emerges from the backside of the cone, accelerated material accumulates on axis producing a collimated flow. Figure 1b demonstrates the collimation of the plasma without the background field and the disruption of the flow when applying a 5 T field. Experimental results will be discussed in detail with supporting numerical work describing the mechanisms causing the jet disruption.
- Published
- 2017
21. Design of a supernova-relevant Rayleigh–Taylor experiment on the National Ignition Facility. I. Planar target design and diagnostics
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Hye-Sook Park, R. Paul Drake, Carolyn Kuranz, Tomasz Plewa, Markus Flaig, Paul Keiter, and M.J. Grosskopf
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Physics ,Nuclear and High Energy Physics ,Radiation ,Mechanics ,Laser ,Instability ,Shock (mechanics) ,law.invention ,Spherical geometry ,symbols.namesake ,Planar ,law ,symbols ,Rayleigh scattering ,National Ignition Facility ,Mixing (physics) - Abstract
We present a feasability study for a laser-driven shock experiment on the National Ignition Facility (NIF) to study the evolution of the Rayleigh-Taylor instability in the non-linear regime. The experiment is relevant to the problem of material mixing in core-collapse supernovae and is intended to serve as a stepping stone for more realistic Rayleigh–Taylor experiments using spherical geometry. The radiation hydrodynamics simulations described here are done using the CRASH code and include the actual NIF laser drive. It is shown that the simulations are converged with respect to numerical resolution effects. Small-scale imperfections, such as they might be introduced during the process of target fabrication, are found to have negligible impact, provided that their size is smaller than 1 μm. The simulation results are in excellent agreement with a buoyancy-drag model, and the mix layer width is found to increase at higher drive energies.
- Published
- 2014
22. Spatially-resolved X-ray scattering measurements of a planar blast wave
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Katerina Falk, R. P. Drake, E. J. Gamboa, Paul Keiter, D. S. Montgomery, and John F. Benage
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Physics ,Nuclear and High Energy Physics ,Radiation ,Scattering ,Astrophysics::High Energy Astrophysical Phenomena ,Rarefaction ,Plasma ,Warm dense matter ,Computational physics ,Shock (mechanics) ,Wavelength ,Ionization ,Atomic physics ,Blast wave - Abstract
We present X-ray scattering measurements characterizing the spatial temperature and ionization profile of a blast wave driven in a near-solid density foam. Several-keV X-rays scattered from a laser-driven blast wave in a carbon foam. We resolved the scattering in high resolution in space and wavelength to extract the plasma conditions along the propagation direction of the blast wave. We infer temperatures of 20–40 eV and ionizations of 2–4 in the shock and rarefaction regions of the blast wave. This range of measured ionization states allows for a detailed comparison between different models for the bound–free scattering. FLYCHK simulations of the temperature-ionization balance generally agree with the experimental values in the shocked region while consistently underestimating the ionization in the rarefaction.
- Published
- 2014
23. Atomic modeling of photoionization fronts in nitrogen gas
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Carolyn Kuranz, Paul Keiter, William J. Gray, R. P. Drake, J. S. Davis, C. R. Patterson, Kenneth G. Powell, and Heath LeFevre
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FOS: Physical sciences ,chemistry.chemical_element ,Electron ,Photoionization ,Kinetic energy ,01 natural sciences ,010305 fluids & plasmas ,Atmospheric radiative transfer codes ,Ionization ,0103 physical sciences ,Physics::Atomic and Molecular Clusters ,Physics::Atomic Physics ,010306 general physics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Electron ionization ,Physics ,Front (oceanography) ,Condensed Matter Physics ,Astrophysics - Astrophysics of Galaxies ,Nitrogen ,Physics - Plasma Physics ,Plasma Physics (physics.plasm-ph) ,Astrophysics - Solar and Stellar Astrophysics ,chemistry ,Astrophysics of Galaxies (astro-ph.GA) ,Atomic physics - Abstract
Photoionization fronts play a dominant role in many astrophysical environments, but remain difficult to achieve in a laboratory experiment. Recent papers have suggested that experiments using a nitrogen medium held at ten atmospheres of pressure that is irradiated by a source with a radiation temperature of T$_{\rm R}\sim$ 100 eV can produce viable photoionization fronts. We present a suite of one-dimensional numerical simulations using the \helios\ multi-material radiation hydrodynamics code that models these conditions and the formation of a photoionization front. We study the effects of varying the atomic kinetics and radiative transfer model on the hydrodynamics and ionization state of the nitrogen gas, finding that more sophisticated physics, in particular a multi-angle long characteristic radiative transfer model and a collisional-radiative atomics model, dramatically changes the atomic kinetic evolution of the gas. A photoionization front is identified by computing the ratios between the photoionization rate, the electron impact ionization rate, and the total recombination rate. We find that due to the increased electron temperatures found using more advanced physics that photoionization fronts are likely to form in our nominal model. We report results of several parameter studies. In one of these, the nitrogen pressure is fixed at ten atmospheres and varies the source radiation temperature while another fixes the temperature at 100 eV and varied the nitrogen pressure. Lower nitrogen pressures increase the likelihood of generating a photoionization front while varying the peak source temperature has little effect., Comment: 17 pages, 10 figures, accepted to physics of plasmas
- Published
- 2019
24. Experimental study of energy transfer in double shell implosions
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Doug Wilson, Evan Dodd, Eric Loomis, Yuan Ping, Randall B. Randolph, D. S. Montgomery, J. R. Rygg, Joshua Sauppe, Brian M. Patterson, Lindsey Kuettner, M. Schoff, Sasikumar Palaniyappan, William Daughton, John Kline, E. C. Merritt, M. Hoppe, Shahab Khan, Paul Keiter, W. C. Wan, Tana Cardenas, R. F. Sacks, F. Fierro, Peter Amendt, Steven H. Batha, and V. A. Smalyuk
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Physics ,Internal energy ,Shell (structure) ,Implosion ,Mechanics ,Condensed Matter Physics ,Kinetic energy ,01 natural sciences ,010305 fluids & plasmas ,Hohlraum ,0103 physical sciences ,Radiative transfer ,Radiation trapping ,010306 general physics ,Inertial confinement fusion - Abstract
Advances in target fabrication have made double shell capsule implosions a viable platform to study burning fusion plasmas. Central to the double shell capsule is a high-Z (e.g., Au) metal pusher that accesses the volume-burn regime by reducing radiative losses through radiation trapping and compressing a uniform fuel volume at reduced velocities. A double shell implosion relies on a series of energy transfer processes starting from x-ray absorption by the outer shell, followed by transfer of kinetic energy to an inner shell, and finally conversion of kinetic energy to fuel internal energy. We present simulation and experimental results on momentum transfer to different layers in a double shell. We also present the details of the development of the NIF cylindrical hohlraum double shell platform including an imaging shell design with a mid-Z inner shell necessary for imaging the inner shell shape and the trajectory with the current 2DConA platform capability. We examine 1D energy transfer between shell layers using trajectory measurements from a series of surrogate targets; the series builds to a complete double shell layer by layer, isolating the physics of each step of the energy transfer process. The measured energy transfer to the foam cushion and the inner shell suggests that our radiation-hydrodynamics simulations capture most of the relevant collision physics. With a 1 MJ laser drive, the experimental data indicate that 22% ± 3% of the ablator kinetic energy couples into inner shell KE, compared to a 27% ± 2% coupling in our xRAGE simulations. Thus, our xRAGE simulations match experimental energy transfer to ∼5%, without inclusion of higher order 2D and 3D effects.
- Published
- 2019
25. A design of a two-dimensional, supersonic KH experiment on OMEGA-EP
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Carolyn Kuranz, W. C. Wan, Paul Keiter, Y. Elbaz, A. Shimony, R. P. Drake, Dov Shvarts, Guy Malamud, and C. A. Di Stefano
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Shock wave ,Physics ,Nuclear and High Energy Physics ,Radiation ,Single-mode optical fiber ,Mechanics ,Instability ,Vortex ,Theoretical physics ,symbols.namesake ,Mach number ,Experimental system ,symbols ,Supersonic speed ,Scaling - Abstract
An experiment meant to investigate the evolution of single mode Kelvin–Helmholtz (KH) instability in the supersonic regime is presented and theoretically analyzed. This experiment is intended to provide a direct measurement of the two-dimensional vortex evolution so that the high-Mach-number effects can be measured. The proposed design takes advantage of the ability of OMEGA-EP to drive experiments for up to 30 ns to produce steady conditions for KH that endure long enough to observe substantial growth. KH growth for the proposed design has been analyzed using two-dimensional numerical simulations. The results were compared to synthetic temporal KH numerical simulations using non-dimensional scaling in the low and high Mach number regime. The comparisons show that the growth in the high Mach number regime is expected to be suppressed by up to a factor of two. The effects of two-dimensional rarefactions from the lateral boundaries of the experimental system were also investigated. It was found that they introduce no major uncertainties or hazards to the experiment. We produced simulated radiographs, which show that the proposed experimental system will enable observation of the KH structures. An experiment of this kind has not yet been performed, and therefore would serve to validate numerical results and analytical models presented here and in the literature.
- Published
- 2013
26. Experimental considerations to observe two ionizing fronts in systems with a sharp absorption edge
- Author
-
Griffin Cearley, Robert Vandervort, Paul Keiter, Eric Johnsen, and R. Paul Drake
- Subjects
Physics ,Photon ,Opacity ,Astrophysics::High Energy Astrophysical Phenomena ,Plasma ,Radiation ,Photon energy ,01 natural sciences ,010305 fluids & plasmas ,Computational physics ,Shock (mechanics) ,Absorption edge ,0103 physical sciences ,Plasma diagnostics ,010306 general physics ,Instrumentation - Abstract
This paper examines the experimental requirements to observe two shock fronts driven by a single x-ray source in systems with a sharp absorption edge. We consider systems where the peak of the x-ray radiation drive coincides with the K-edge of the carbon, which occurs at a photon energy of 284 eV, causing photons to be deposited in two regions. The low-energy photons (E284 eV) penetrate further and drive the main shock, while the higher-energy photons (E284 eV) are absorbed in the ablated plasma. These higher-energy photons create an ionization front, which then produces a second shock, termed an edge-shock. Using a different radiation-hydrodynamics code and different opacity and equation of state tables, we replicate the previous work and build upon them to explore the conditions required to form the edge shock. We find that having the material K-edge coincide with the spectral domain of the radiation source is necessary but not sufficient on its own to drive the edge-shock.
- Published
- 2018
27. Development of a backlit-multi-pinhole radiography source
- Author
-
Paul Keiter, Matthew Trantham, R. Paul Drake, Robert Vandervort, Sallee Klein, and Chuck Sorce
- Subjects
010302 applied physics ,Materials science ,business.industry ,Radiography ,Substrate (printing) ,Backlight ,01 natural sciences ,Sample (graphics) ,010305 fluids & plasmas ,Optics ,Titanium foil ,0103 physical sciences ,Pinhole (optics) ,Development (differential geometry) ,business ,Instrumentation - Abstract
Backlit-pinhole radiography uses a pinhole placed between an x-ray source and a sample. The backlit-multi-pinhole design uses two pinholes on the same substrate, which are separated by a wall, to create two radiographic images projected along similar axes. The wall, a 100-μm thick titanium foil, prevents x-rays generated near one pinhole from exiting the other pinhole. First results indicate that the multi-pinhole target can create two independent radiographs along similar axes. The images are recorded 2 ns apart. Details of our multi-pinhole design and our first results are discussed.
- Published
- 2018
28. Two laser-driven mix experiments to study reshock and shear
- Author
-
Kirk Flippo, L. Welser-Sherrill, Eric Loomis, Fernando F. Grinstein, Dustin Offermann, Forrest Doss, James R. Fincke, Brian Haines, and Paul Keiter
- Subjects
Nuclear and High Energy Physics ,Radiation ,Materials science ,Turbulence ,Mixing (process engineering) ,Time evolution ,Implosion ,Mechanics ,Compression (physics) ,Laser ,law.invention ,Physics::Fluid Dynamics ,Shear (sheet metal) ,law ,Inertial confinement fusion - Abstract
In an effort to better understand mix in Inertial Confinement Fusion (ICF) implosion cores, a series of laser-driven mix experiments has been designed for the University of Rochester's OMEGA laser. Our objective is to perform experiments to investigate the turbulent mixing at material interfaces when subject to multiple shocks and reshocks or high-speed shear. Ultimately, these experiments are providing detailed quantitative measurements to assist in validation efforts for the BHR-2 mix model, which is implemented in the RAGE hydrodynamics code. The Reshock experiment studies the physical process of shocking and reshocking mix layers. Radiographs are recorded to compile a temporal evolution of the mixing layer and its subsequent reshock, compression, and re-growth phases. The Shear experiment investigates shear-driven growth of a mix layer, and radiography captures the time evolution of the development of turbulent mixing due to shear. Simulations of both the Reshock and Shear experiments using RAGE and the BHR-2 mix model demonstrate good agreement with the mix evolution seen in the experimental data, giving confidence that BHR-2 is capable of simulating the behavior of both compressive and shear-driven turbulent flows.
- Published
- 2013
29. An experimental concept to measure opacities under solar-relevant conditions
- Author
-
Katie Mussack, Sallee Klein, and Paul Keiter
- Subjects
Physics ,Nuclear and High Energy Physics ,Radiation ,Convection zone ,Opacity ,Abundance (ecology) ,Astrophysics ,Measure (mathematics) - Abstract
Recent solar abundance models (Asplund 2009) use a significantly lower abundance for C, N, O compared to models used roughly a decade ago. Although the models used now are much more sophisticated than before, a discrepancy still exists between the abundances in the models and the abundances determined by helioseismic measurements. Agreement can be obtained by ad hoc adjustments to the opacity of high-Z (Z > 2) elements ranging from a few percent in the solar interior to as much as 30 just below the convection zone (CZ). Although many of the opacity models are thought to agree within a few percent, a recent element-by-element study (Blancard 2012) indicates a larger disagreement between models for certain elements. Experimental opacity measurements for these elements in the regimes of interest will provide valuable information to help resolve these discrepancies. We will present an experimental platform designed to measure the opacity of C, N, and O and discuss the achievable parameter regime. We will also briefly discuss how this platform can be extended to include other high-Z elements.
- Published
- 2013
30. Developing High-Temperature Laser-Driven Half Hohlraums for High-Energy-Density Physics Experiments at the National Ignition Facility
- Author
-
M. Stevenson, B. Peterson, Derek Schmidt, Paul Keiter, K. Mussack, A. S. Moore, Nick Lanier, N. Bazin, John J. L. Morton, Christopher E. Hamilton, M. Taccetti, Jonathan Workman, Christopher D. B. Bentley, John Kline, and T. M. Guymer
- Subjects
010302 applied physics ,Physics ,Nuclear and High Energy Physics ,High energy density physics ,Mechanical Engineering ,010401 analytical chemistry ,Radiation ,Laser ,01 natural sciences ,0104 chemical sciences ,law.invention ,Nuclear physics ,Nuclear Energy and Engineering ,law ,Hohlraum ,0103 physical sciences ,General Materials Science ,Supersonic speed ,National Ignition Facility ,Civil and Structural Engineering - Abstract
A high-temperature (>340 eV) half-hohlraum target platform has been developed on the National Ignition Facility (NIF) to enable the study of diffusive supersonic radiation flow in low-density foams...
- Published
- 2013
31. Comparison between Kelvin–Helmholtz instability experiments on OMEGA and simulation results using the CRASH code
- Author
-
R. P. Drake, Michael Grosskopf, Eric Harding, Paul Keiter, Erica M. Rutter, C.C. Kuranz, and Guy Malamud
- Subjects
Physics ,Nuclear and High Energy Physics ,Radiation ,Adaptive mesh refinement ,Perturbation (astronomy) ,chemistry.chemical_element ,Eulerian path ,Crash ,Mechanics ,Omega ,Instability ,symbols.namesake ,Theoretical physics ,chemistry ,symbols ,Radiative transfer ,Beryllium - Abstract
The Center for Radiative Shock Hydrodynamics (CRASH) at the University of Michigan has developed a Eulerian radiation-hydrodynamics code with dynamic adaptive mesh refinement, CRASH, which can model high-energy-density laser-driven experiments. One of these experiments, performed previously on the OMEGA laser facility, was designed to produce and observe the Kelvin–Helmholtz instability. The target design included low-density carbonized-resorcinol-formaldehyde (CRF) foam layered on top of polyamide–imide plastic, with a sinusoidal perturbation on the interface and with the assembled materials encased in beryllium. The results of a series of CRASH simulations of these Kelvin–Helmholtz instability experiments are presented. These simulation results show good agreement both quantitatively and qualitatively with the experimental data.
- Published
- 2013
32. A design of a two-dimensional, multimode RM experiment on OMEGA-EP
- Author
-
Carolyn Kuranz, Guy Malamud, Y. Elbaz, R. P. Drake, Paul Keiter, C. M. Huntington, and C. A. Di Stefano
- Subjects
Physics ,Shock wave ,Nuclear and High Energy Physics ,Radiation ,Multi-mode optical fiber ,Classical mechanics ,Atwood number ,Bubble ,Mode coupling ,Perturbation (astronomy) ,Mechanics ,Instability ,Omega - Abstract
An experiment, meant to investigate the evolution of Richtmyer–Meshkov (RM) instability in the bubble merger regime and at low Atwood number ( A ∼0.3), is proposed and theoretically analyzed. This experiment is intended to provide a direct measurement of the two-dimensional bubble-front shape and spectrum evolution in time, along with the power-law coefficient for bubble-front growth ( θ b ). It is unique in its use of a well-characterized two-dimensional initial perturbation, allowing controlled initiation and growth of the instability. The proposed design assures a significant time scale of steady RM conditions, taking advantage of the long drive (∼30 ns) available on the OMEGA-EP laser facility, along with neither a Rayleigh–Taylor (RT) component nor shock-proximity effects, due to the use of a light to heavy configuration. Multimode RM growth for the proposed configuration has been analyzed using two-dimensional, direct numerical simulations, showing significant mode coupling and convergence to power-law growth of the bubble front. The effects of two-dimensional rarefactions were also investigated, and it was found that they introduce no major uncertainties or hazards to the physics. An experiment of this kind has not yet been performed, and therefore would serve to validate numerical results and analytical models presented in literature.
- Published
- 2013
33. Late-time breakup of laser-driven hydrodynamics experiments
- Author
-
Sallee Klein, Carolyn Kuranz, Paul Keiter, R. P. Drake, C. A. Di Stefano, and D. C. Marion
- Subjects
Physics ,Nuclear and High Energy Physics ,Work (thermodynamics) ,Radiation ,Richtmyer–Meshkov instability ,Turbulence ,Context (language use) ,Mechanics ,Statistical physics ,Breakup ,Instability ,Blast wave ,Mixing (physics) - Abstract
Laser-driven blast waves are frequently used to explore hydrodynamic instability at high energy density. Experiments are designed such that the instability physics occurs in isolation, but secondary processes will eventually develop within the experimental system and affect the physics. At late times, as the blast wave diminishes in strength, these processes increasingly dominate while the instability physics weakens. The resulting dynamics can appear turbulent, and the root cause is not immediately apparent. In this work, we examine the conditions under which a system can begin to exhibit such behavior and, in this context, consider data from an experiment exploring Rayleigh–Taylor hydrodynamic instability, showing significant turbulent-like structure in the material mixing region.
- Published
- 2012
34. Tracking the density evolution in counter-propagating shock waves using imaging X-ray scattering
- Author
-
Siegfried Glenzer, Eric Galtier, R. P. Drake, John F. Benage, K. W. Hill, N. A. Pablant, Roger Falcone, Philip Heimann, Dirk O. Gericke, Paul Keiter, Hae Ja Lee, Dominik Kraus, Bob Nagler, Eduardo Granados, J. Lu, A. Schropp, P. C. Efthimion, Benjamin Tobias, Maxence Gauthier, Michael MacDonald, Katerina Falk, Luke Fletcher, E. J. Gamboa, D. S. Montgomery, J. B. Hastings, and Ulf Zastrau
- Subjects
Shock wave ,Physics ,Technology ,Physics and Astronomy (miscellaneous) ,Scattering ,Forward scatter ,Astrophysics::High Energy Astrophysical Phenomena ,Inelastic scattering ,Tracking (particle physics) ,01 natural sciences ,010305 fluids & plasmas ,Shock waves in astrophysics ,Engineering ,0103 physical sciences ,Physical Sciences ,Quasiparticle ,ddc:530 ,Graphite ,Atomic physics ,010306 general physics ,Applied Physics - Abstract
Applied physics letters 109(3), 031108 (2016). doi:10.1063/1.4959256, We present results from time-resolved X-ray imaging and inelastic scattering on collective excitations. These data are then employed to infer the mass density evolution within laser-driven shock waves. In our experiments, thin carbon foils are first strongly compressed and then driven into a dense state by counter-propagating shock waves. The different measurements agree that the graphite sample is about twofold compressed when the shock waves collide, and a sharp increase in forward scattering indicates disassembly of the sample 1 ns thereafter. We can benchmark hydrodynamics simulations of colliding shock waves by the X-ray scattering methods employed., Published by American Inst. of Physics, Melville, NY
- Published
- 2016
35. Soft X-ray emission from laser-irradiated gold foils
- Author
-
R. P. Drake, Matthew Trantham, E. Raicher, M. Fraenkel, Y. Frank, Paul Keiter, Sallee Klein, Dov Shvarts, and J. S. Davis
- Subjects
Physics ,business.industry ,Astrophysics::High Energy Astrophysical Phenomena ,Monte Carlo method ,Energy flux ,Condensed Matter Physics ,Laser ,01 natural sciences ,Spectral line ,010305 fluids & plasmas ,law.invention ,Photodiode ,Radiation flux ,Optics ,law ,0103 physical sciences ,Irradiation ,010306 general physics ,business ,FOIL method - Abstract
This paper reports measurements of soft-x-ray emission from gold foils irradiated by 6 ns laser pulses, and analysis and simulations of the observations. These foils can be used as x-ray sources to drive a wide range of experiments. A multichannel, photodiode array measured the time-resolved, soft-x-ray emission. A soft-x-ray framing camera imaged the emission in selected energy bands. Foil thicknesses were from 0.5 to 1.5 μm. The imaging data show that the region emitting soft x-rays grows throughout the laser drive, on both the front and rear surfaces. Analysis of the emitted radiation flux from the rear surface, taking the time-dependent spot size into account, showed that the peak effective temperature of 0.5-μm-thick foils is near 88 eV, while that of 0.75-μm-thick foils is near 78 eV. A Monte Carlo method was used to evaluate the component of the uncertainty in the effective temperature introduced by variations in signal voltages and by uncertainty in the size of the emitting spot. This was found to be near ±2 eV in most cases. Simple theoretical considerations explain the main features of the observations. The Florence code, working with atomic physics from sophisticated models, proved able to reproduce the main features of the observed spectra with 1D simulations in which the laser energy flux was adjusted on the basis of the observed lateral spreading of energy.
- Published
- 2018
36. Heat waves and ionization fronts
- Author
-
J. S. Davis, Paul Keiter, and R. P. Drake
- Subjects
Physics ,Shock waves in astrophysics ,Ionization ,Energy density ,Heat wave ,Atomic physics ,Computational physics - Abstract
In the literature regarding the penetration of energy into matter in experiments at high energy density, one often encounters discussions of “Marshak waves”, or of “ionization fronts” or sometimes of “heat waves” or “heat fronts”. Looking a bit deeper, one finds that these terms are used rather inconsistently. In addition, many of the papers refer to connections with similar phenomena in astrophysics, but there is rarely any discussion of how the experiment actually connects with real astrophysical cases.
- Published
- 2015
37. Experiments to Study Radiation Transport in Clumpy Media
- Author
-
J. R. Finke, C.C. Smith, Ted Perry, Paul Keiter, Mark Gunderson, Paula Rosen, John Foster, and M. J. Taylor
- Subjects
Physics ,SIMPLE (dark matter experiment) ,Star formation ,Infrared ,Molecular cloud ,Astronomy ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Star (graph theory) ,Radiation ,Cosmology ,Interstellar medium ,Space and Planetary Science ,Astrophysics::Galaxy Astrophysics - Abstract
Clumpiness of the interstellar medium may play an important role in the transfer of infrared continuum radiation in star forming regions (Boisse, 1990). For example, in homogeneous models, C II emission should be confined to the cloud edge (Viala, 1986). However, in star formation regions (such as M17SW, M17 and W51), it is observed to extend deep into the molecular cloud (Stutzki et al., 1988; Keene et al., 1985). One plausible interpretation of these observations is that, due to their clumpiness, the clouds are penetrated by UV radiation far deeper than expected from simple homogeneous models.
- Published
- 2006
38. Investigation of the hard x-ray background in backlit pinhole imagers
- Author
-
Mario Manuel, J. R. Fein, Jonathan Peebles, Paul Keiter, R. P. Drake, Carolyn Kuranz, James Paul Holloway, and Sallee Klein
- Subjects
Physics ,Spectrometer ,business.industry ,X-ray background ,Bremsstrahlung ,Electron ,Laser ,Collimated light ,law.invention ,Optics ,law ,Pinhole (optics) ,Plasma diagnostics ,business ,Instrumentation - Abstract
Hard x-rays from laser-produced hot electrons (>10 keV) in backlit pinhole imagers can give rise to a background signal that decreases signal dynamic range in radiographs. Consequently, significant uncertainties are introduced to the measured optical depth of imaged plasmas. Past experiments have demonstrated that hard x-rays are produced when hot electrons interact with the high-Z pinhole substrate used to collimate the softer He-α x-ray source. Results are presented from recent experiments performed on the OMEGA-60 laser to further study the production of hard x-rays in the pinhole substrate and how these x-rays contribute to the background signal in radiographs. Radiographic image plates measured hard x-rays from pinhole imagers with Mo, Sn, and Ta pinhole substrates. The variation in background signal between pinhole substrates provides evidence that much of this background comes from x-rays produced in the pinhole substrate itself. A Monte Carlo electron transport code was used to model x-ray production from hot electrons interacting in the pinhole substrate, as well as to model measurements of x-rays from the irradiated side of the targets, recorded by a bremsstrahlung x-ray spectrometer. Inconsistencies in inferred hot electron distributions between the different pinhole substrate materials demonstrate that additional sources of hot electrons beyond those modeled may produce hard x-rays in the pinhole substrate.
- Published
- 2014
39. Construction of a solenoid used on a magnetized plasma experiment
- Author
-
Mario Manuel, R. P. Drake, C.C. Kuranz, S. R. Klein, R.S. Gillespie, B. B. Pollock, Michael Deininger, and Paul Keiter
- Subjects
Physics ,Plasma Gases ,Young stellar object ,Solenoid ,Plasma ,Computational physics ,Magnetic field ,Magnetization ,symbols.namesake ,Nuclear magnetic resonance ,Magnetic Fields ,Electrical equipment ,symbols ,Titan (rocket family) ,Instrumentation - Abstract
Creating magnetized jets in the laboratory is relevant to studying young stellar objects, but generating these types of plasmas within the laboratory setting has proven to be challenging. Here, we present the construction of a solenoid designed to produce an axial magnetic field with strengths in the gap of up to 5 T. This novel design was a compact 75 mm × 63 mm × 88 mm, allowing it to be placed in the Titan target chamber. It was robust, surviving over 50 discharges producing fields ≲ 5 T, reaching a peak magnetic field of 12.5 T.
- Published
- 2014
40. High-Energy-Density Laboratory Astrophysics Studies of Jets and Bow Shocks
- Author
-
John Foster, Alexei Khokhlov, Robert Coker, Paula Rosen, J. P. Knauer, B. H. Wilde, B. E. Blue, R. P. Drake, R. J. R. Williams, Adam Frank, Paul Keiter, and Ted Perry
- Subjects
Physics ,Jet (fluid) ,Astrophysics::High Energy Astrophysical Phenomena ,Reynolds number ,Astronomy and Astrophysics ,Astrophysics ,Plasma ,symbols.namesake ,Space and Planetary Science ,symbols ,Supersonic speed ,Bow shock (aerodynamics) ,Herbig–Haro object ,Axial symmetry ,Dimensionless quantity - Abstract
Large-scale directional outflows of supersonic plasma, also known as ''jets'', are ubiquitous phenomena in astrophysics [1]. The interaction of such jets with surrounding matter often results in spectacular bow shocks, and intense radiation from radio to gamma-ray wavelengths. The traditional approach to understanding such phenomena is through theoretical analysis and numerical simulations. However, such numerical simulations have limited resolution, often assume axial symmetry, do not include all relevant physical processes, and fail to scale correctly in Reynolds number and perhaps other key dimensionless parameters. Additionally, they are frequently not tested by comparison with laboratory experiments. Recent advances in high-energy-density physics using large inertial-confinement-fusion devices now allow controlled laboratory experiments on macroscopic volumes of plasma of direct relevance relevant to astrophysics [2]. In this Letter we report the first results of experiments designed to study the evolution of supersonic plasma jets and the bow shocks they drive into a surrounding medium. Our experiments reveal both regular and highly complex flow patterns in the bow shock, thus opening a new window--complementary to computer simulations--into understanding the nature of three-dimensional astrophysical jets.
- Published
- 2005
41. Development of intense point x-ray sources for backlighting high energy density experiments (invited)
- Author
-
Otto Landen, S. G. Glendinning, S. Sublett, Timothy Pierce, Jonathan Workman, J. P. Knauer, George A. Kyrala, B. E. Blue, Paul Keiter, J. R. Fincke, and Harry Robey
- Subjects
Physics ,business.industry ,X-ray ,Backlight ,Laser ,law.invention ,Optics ,law ,Z-pinch ,Energy density ,Plasma diagnostics ,business ,National Ignition Facility ,Instrumentation ,Laboratory for Laser Energetics - Abstract
High-energy-density (HED) experiments are often diagnosed using x-ray backlighting. Recently, experiments have been designed and fielded that require x-ray backlighting having large fields of view and high x-ray energies. These types of experiments will be even more prevalent on the National Ignition Facility laser. Point backlighting offers the potential to obtain higher-energy x rays using less laser energy while giving a large, uniform field of view (millimeters). We present recent results from Los Alamos National Lab, Lawrence Livermore National Lab, and the University of Rochester’s Laboratory for laser energetics obtained on the OMEGA laser at the University of Rochester on the development of such bright sources. We include discussion of the challenges and successes to date.
- Published
- 2004
42. Target Fabrication: A View from the Users
- Author
-
Dennis L. Paisley, George A. Kyrala, Paul Keiter, C. R. Christensen, Cris W. Barnes, Steven H. Batha, M. M. Balkey, James R. Fincke, Damian Swift, Jonathan Workman, Michael S. Sorem, Nicholas E. Lanier, and James A. Cobble
- Subjects
Nuclear and High Energy Physics ,Fabrication ,business.industry ,High energy density physics ,Computer science ,Mechanical Engineering ,Metrology ,Optics ,Planar ,Nuclear Energy and Engineering ,Hohlraum ,General Materials Science ,Aerospace engineering ,business ,National laboratory ,Inertial confinement fusion ,Representative sampling ,Civil and Structural Engineering - Abstract
Targets are used for a variety of purposes, but ultimately we use them to validate codes that help us predict and understand new phenomena or effects. The sophistication and complexity of High Energy Density Physics (HEDP) and Inertial Confinement Fusion (ICF) targets has increased in time to match the advances made in modeling complex phenomena. The targets have changed from simple hohlraums, spherical geometries, and planar foils, to 3-dimensional geometries that require precision in construction, alignment, and metrology. Furthermore, material properties, such as surface morphologies and volume texture, have significant impact on the behavior of the targets and must be measured and controlled. In the following we will discuss how experimental physicists view targets and the influence that target construction has on interpreting the experimental results. We review a representative sampling of targets fabricated at the Los Alamos National Laboratory that are used in different experiments in support of ICF and HEDP.
- Published
- 2004
43. Ion dynamics in helicon sources
- Author
-
Robert Boivin, Paul Keiter, E. E. Scime, Amy Keesee, Matthew M. Balkey, John Kline, Xuan Sun, M. W. Zintl, C. S. Compton, and R. A. Hardin
- Subjects
Physics ,Helicon ,Plasma heating ,Physics::Plasma Physics ,Particle ,Plasma ,Atomic physics ,Condensed Matter Physics ,Instability ,Resonance (particle physics) ,Electromagnetic radiation ,Ion - Abstract
Recent experiments have demonstrated that phenomena associated with ion dynamics, such as the lower hybrid resonance, play an important role in helicon source operation. In this work, a review of recent ion heating measurements and the role of the slow wave in heating ions at the edge of helicon sources is presented. The relationship between parametrically driven waves and ion heating near the rf antenna in helicon sources is also discussed. Recent measurements of parallel and rotational ion flows in helicon sources are presented and the implications for particle confinement, instability growth, and helicon source operation are reviewed.
- Published
- 2003
44. The time scale for the transition to turbulence in a high Reynolds number, accelerated flow
- Author
-
A. C. Buckingham, Harry Robey, R. P. Drake, Ye Zhou, Paul Keiter, and Bruce Remington
- Subjects
Shock wave ,Physics ,Shock (fluid dynamics) ,Turbulence ,Reynolds number ,Particle-laden flows ,Mechanics ,Condensed Matter Physics ,Physics::Fluid Dynamics ,symbols.namesake ,Mach number ,symbols ,Rayleigh–Taylor instability ,Two-phase flow ,Statistical physics - Abstract
An experiment is described in which an interface between materials of different density is subjected to an acceleration history consisting of a strong shock followed by a period of deceleration. The resulting flow at this interface, initiated by the deposition of strong laser radiation into the initially well characterized solid materials, is unstable to both the Richtmyer–Meshkov (RM) and Rayleigh–Taylor (RT) instabilities. These experiments are of importance in their ability to access a difficult experimental regime characterized by very high energy density (high temperature and pressure) as well as large Reynolds number and Mach number. Such conditions are of interest, for example, in the study of the RM/RT induced mixing that occurs during the explosion of a core-collapse supernova. Under these experimental conditions, the flow is in the plasma state and given enough time will transition to turbulence. By analysis of the experimental data and a corresponding one-dimensional numerical simulation of the...
- Published
- 2003
45. Mitigation of hot electrons from laser-plasma instabilities in high-Z, highly ionized plasmas
- Author
-
Dustin Froula, J. R. Fein, Paul Keiter, James Paul Holloway, Y. Frank, Dan Haberberger, Dov Shvarts, R. P. Drake, E. Raicher, M. Fraenkel, D. H. Edgell, and Matthew Trantham
- Subjects
Physics ,Electron density ,Waves in plasmas ,Plasma ,Electron ,Condensed Matter Physics ,01 natural sciences ,010305 fluids & plasmas ,Two-stream instability ,Physics::Plasma Physics ,Ionization ,0103 physical sciences ,Electromagnetic electron wave ,Landau damping ,Atomic physics ,010306 general physics - Abstract
Hard x-ray measurements are used to infer production of hot electrons in laser-irradiated planar foils of materials ranging from low- to high-Z. The fraction of laser energy converted to hot electrons, fhot, was reduced by a factor of 103 going from low-Z CH to high-Z Au, and hot electron temperatures were reduced from 40 to ∼20 keV. The reduction in fhot correlates with steepening electron density gradient length-scales inferred from plasma refraction measurements. Radiation hydrodynamic simulations predicted electron density profiles in reasonable agreement with those from measurements. Both multi-beam two-plasmon decay (TPD) and multi-beam stimulated Raman scattering (SRS) were predicted to be above threshold with linear threshold parameters that decreased with increasing Z due to steepening length-scales, as well as enhanced laser absorption and increased electron plasma wave collisional and Landau damping. The results add to the evidence that SRS may play a comparable or a greater role relative to TP...
- Published
- 2017
46. An experimental testbed for the study of hydrodynamic issues in supernovae
- Author
-
David Arnett, J. P. Knauer, H. Louis, R. P. Drake, Jave Kane, Harry Robey, Bruce Remington, Paul Keiter, Omar Hurricane, R. J. Wallace, and Dmitri Ryutov
- Subjects
Physics ,Explosive material ,Astrophysics::High Energy Astrophysical Phenomena ,Fluid mechanics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Mechanics ,Astrophysics ,Condensed Matter Physics ,Shock (mechanics) ,Stars ,Supernova ,Binary star ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysical plasma ,Variable star ,Astrophysics::Galaxy Astrophysics - Abstract
More than a decade after the explosion of supernova 1987A, unresolved discrepancies still remain in attempts to numerically simulate the mixing processes initiated by the passage of a very strong shock through the layered structure of the progenitor star. Numerically computed velocities of the radioactive 56Ni and 56Co, produced by shock-induced explosive burning within the silicon layer, for example, are still more than 50% too low as compared with the measured velocities. To resolve such discrepancies between observation and simulation, an experimental testbed has been designed on the Omega Laser for the study of hydrodynamic issues of importance to supernovae (SNe). In this paper, results are presented from a series of scaled laboratory experiments designed to isolate and explore several issues in the hydrodynamics of supernova explosions. The results of the experiments are compared with numerical simulations and are generally found to be in reasonable agreement.
- Published
- 2001
47. DESIGN OF LABORATORY EXPERIMENTS TO STUDY PHOTOIONIZATION FRONTS DRIVEN BY THERMAL SOURCES
- Author
-
J. S. Davis, C. R. Patterson, Adam Frank, Paul Keiter, Michel Busquet, G. Hazak, R. P. Drake, and Eric G. Blackman
- Subjects
Physics ,Radiation flux ,Space and Planetary Science ,Ionization ,0103 physical sciences ,Thermal ,Astronomy and Astrophysics ,Astrophysics ,Photoionization ,010306 general physics ,010303 astronomy & astrophysics ,01 natural sciences ,Computational physics - Published
- 2016
48. Laser experiments to simulate supernova remnants
- Author
-
J. J. Carroll, Eli Michael, Dmitri Ryutov, Timothy B. Smith, Omar Hurricane, Richard McCray, Bruce Remington, R. J. Wallace, S. Gail Glendinning, R. P. Drake, Paul Keiter, and Kent Estabrook
- Subjects
Shock wave ,Physics ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics ,Plasma ,Impulse (physics) ,Condensed Matter Physics ,Laser ,law.invention ,Supernova ,Hohlraum ,law ,Astrophysical plasma ,Stagnation pressure ,Astrophysics::Galaxy Astrophysics - Abstract
An experiment using a large laser facility to simulate young supernova remnants (SNRs) is discussed. By analogy to the SNR, the laboratory system includes dense matter that explodes, expansion and cooling to produce energetic, flowing plasma, and the production of shock waves in lower-density surrounding matter. The scaling to SNRs in general and to SN1987A in particular is reviewed. The methods and results of x-ray radiography, by which the system in diagnosed, are discussed. The data show that the hohlraum used to provide the energy for explosion does so in two ways—first, through its radiation pulse, and second, through an additional impulse that is attributed to stagnation pressure. Attempts to model these dynamics are discussed.
- Published
- 2000
49. Ion temperature anisotropy limitation in high beta plasmas
- Author
-
Matthew M. Balkey, S. Peter Gary, Earl Scime, Robert Boivin, John Kline, Melanie Blackburn, and Paul Keiter
- Subjects
Physics ,Magnetosheath ,Physics::Plasma Physics ,Scattering ,Waves in plasmas ,Beta (plasma physics) ,Physics::Space Physics ,Atomic physics ,Condensed Matter Physics ,Anisotropy ,Ion acoustic wave ,Electromagnetic radiation ,Ion - Abstract
Measurements of parallel and perpendicular ion temperatures in the Large Experiment on Instabilities and Anisotropies (LEIA) space simulation chamber display an inverse correlation between the upper bound on the ion temperature anisotropy and the parallel ion beta (β=8πnkT/B2). Fluctuation measurements indicate the presence of low frequency, transverse, electromagnetic waves with wave numbers and frequencies that are consistent with predictions for Alfven Ion Cyclotron instabilities. These observations are also consistent with in situ spacecraft measurements in the Earth’s magnetosheath and with a theoretical/computational model that predicts that such an upper bound on the ion temperature anisotropy is imposed by scattering from enhanced fluctuations due to growth of the Alfven ion cyclotron instability.
- Published
- 2000
50. Beta-dependent upper bound on ion temperature anisotropy in a laboratory plasma
- Author
-
Earl Scime, John Kline, S. Peter Gary, Robert Boivin, Matthew M. Balkey, and Paul Keiter
- Subjects
Physics ,Magnetosheath ,Physics::Plasma Physics ,Beta (plasma physics) ,Physics::Space Physics ,Atmospheric-pressure plasma ,Plasma diagnostics ,Plasma ,Atomic physics ,Condensed Matter Physics ,Anisotropy ,Ion cyclotron resonance ,Ion - Abstract
Laser induced fluorescence measurements of ion temperatures, parallel and perpendicular to the local magnetic field, in the Large Experiment on Instabilities and Anisotropies space simulation chamber (a steady-state, high beta, argon plasma) display an inverse correlation between the upper bound on the ion temperature anisotropy and the parallel ion beta (β=8πnkT/B2). These observations are consistent with in situ spacecraft measurements in the Earth’s magnetosheath and with a theoretical/computational model that predicts that such an upper bound is imposed by scattering from enhanced fluctuations due to growth of the ion cyclotron anisotropy instability (the Alfven ion cyclotron instability).
- Published
- 2000
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