69 Matching Results

Search Results

Advanced search parameters have been applied.
in creator/contributor: "Key, M.H."  
prev Results: 25 - 48 next
open access

Relativistic Electron Beam Transport and Characteristics in Solid Density Plasmas

Description: The transport of intense relativistic beams in solid density plasma presently is actively being studied in laser laboratories around the world. The correct understanding of the transport enables further application of fast laser driven electrons to a host of interesting uses. Advanced x-ray sources, proton and ion beam generation and plasma heating in fast ignitor fusion all are owed their eventual utility to this transport. We report on measurements of relativistic transport over the whole of … more
Date: August 13, 2003
Creator: Snavely, R. A.; King, J.; Freeman, R. R.; Hatchett, S.; Key, M. H.; Koch, J. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Simulations of Laser Imprint for Nova Experiments and for Ignition Capsules. Revision 1

Description: In direct drive ICF, nonuniformities in laser illumination seed ripples at the ablation front in a process called ``imprint``. These nonuniformities grow during the capsule implosion and, if initially large enough, can penetrate the capsule shell, impede ignition, or degrade burn. Imprint has been simulated for recent experiments performed on the Nova laser at LLNL examining a variety of beam smoothing conditions. Most used laser intensities similar to the early part of an ignition capsule puls… more
Date: December 1, 1996
Creator: Weber, S. V.; Glendinning, S. G.; Kalantar, D. H.; Key, M. H.; Remington, B. A.; Rothenberg, J. L. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Simulations of Laser Imprint for Nova Experiments and for Ignition Capsules

Description: In direct drive ICF, nonuniformities in laser illumination seed ripples at the ablation front in a process called imprint. These non nonuniformities grow during the capsule implosion and, if initially large enough, can penetrate the capsule shell, impede ignition, or degrade burn. Imprint has been simulated for recent experiments performed on the Nova laser at LLNL examining a variety of beam smoothing conditions. Most used laser intensities similar to the early part of an ignition capsule puls… more
Date: November 8, 1996
Creator: Weber, S. V.; Glendinning, S. G.; Kalantar, D. H.; Key, M. H.; Remington, B. A.; Rothenberg, J. E. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Laser plasma diagnostics of dense plasmas

Description: The authors describe several experiments on Nova that use laser-produced plasmas to generate x-rays capable of backlighting dense, cold plasmas (p {approximately} 1--3 gm/cm{sup 3}, kT {approximately} 5--10 eV, and areal density {rho}{ell}{approximately} 0.01--0.05 g/cm{sup 2}). The x-rays used vary over a wide range of h{nu}, from 80 eV (X-ray laser) to 9 keV. This allows probing of plasmas relevant to many hydrodynamic experiments. Typical diagnostics are 100 ps pinhole framing cameras for a … more
Date: July 12, 1995
Creator: Glendinning, S. G.; Amendt, P.; Budil, K. S.; Hammel, B. A.; Kalantar, D. H.; Key, M. H. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Isochoric Heating of Solid-Density Matter with an Ultrafast Proton Beam

Description: A new technique is described for the isochoric heating (i.e., heating at constant volume) of matter to high energy-density plasma states (>10{sup 5} J/g) on a picosecond timescale (10{sup -12} sec). An intense, collimated, ultrashort-pulse beam of protons--generated by a high-intensity laser pulse--is used to isochorically heat a solid density material to a temperature of several eV. The duration of heating is shorter than the timescale for significant hydrodynamic expansion to occur, hence … more
Date: December 22, 2003
Creator: Key, M. H.; Mackinnon, A. J.; Patel, P. K.; Springer, P. T.; Price, D. F.; Allen, M. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Diagnosing hot electron production by short pulse, high intensity lasers using photonuclear reactions

Description: Solid targets irradiated with 10{sup 19} W/cm{sup 2} or greater of 1 {mu}m light in picosecond pulses are found to be radioactive. The strongest activities observed are the result of photonuclear reactions in which an energetic photon excites the nucleus sufficiently to produce particle emission leaving a radioactive daughter. The photoreaction cross sections are known for a wide range of nuclei and provide a quantitative measure of the photon flux produced in the target. Both the delayed daugh… more
Date: June 2, 1998
Creator: Phillips, T. W.; Cable, M. D.; Cowan, T. E.; Hatchett, S. P.; Henry, E. A.; Key, M. H. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Energetic Proton Generation in Ultra-Intense Laser-Solid Interactions

Description: An explanation for the energetic ions observed in the PetaWatt experiments is presented. In solid target experiments with focused intensities exceeding 10{sup 20} W/cm{sup 2}, high-energy electron generation, hard bremsstrahlung, and energetic protons have been observed on the backside of the target. In this report, we attempt to explain the physical process present that will explain the presence of these energetic protons, as well as explain the number, energy, and angular spread of the proton… more
Date: March 1, 2000
Creator: Wilks, S. C.; Langdon, A. B.; Cowan, T. E.; Roth, M.; Singh, M.; Hatchett, S. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Simulations Of Electron Transport For Fast Ignition Using LSP

Description: A crucial issue for the viability of the fast ignition approach to inertial fusion energy is the transport of the ignition pulse energy from the critical surface to the high-density compressed fuel. Experiments have characterized this transport through the interaction of short pulse, high intensity lasers with solid-density targets containing thin K{sub alpha} fluorescence layers. These experiments show a reasonably well-collimated beam, although with a significantly larger radius than the inci… more
Date: May 27, 2004
Creator: Town, R. J.; Chen, C.; Cottrill, L. A.; Key, M. H.; Kruer, W. L.; Langdon, A. B. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

High Energy Electrons, Positrons and Photonuclear Reactions in Petawatt Laser-Solid Experiments

Description: The Petawatt laser at LLNL has opened a new regime of high-energy laser-matter interactions in which the quiver motion of plasma electrons is fully relativistic with energies extending well above the threshold for nuclear processes. We have observed that, in addition to the large flux of several MeV electrons ponderomotively expelled from the ultra-intense laser focus, there is a high energy component of electrons extending to -100 MeV, apparently from relativistic self-focusing and plasma acce… more
Date: September 9, 1999
Creator: Cowan, T. E.; Hunt, A. W.; Johnson, J.; Perry, M. D.; Fountain, W.; Hatchett, S. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Proton Radiography of Laser-Plasma Interactions with Picosecond Time Resolution

Description: Radiography of laser-produced plasmas with MeV protons has the potential to provide new information on plasma conditions in extreme states of matter. Protons with energies up to many hundreds MeV, produced by large scale accelerators have been recently been used to obtain mass density radiographs of the behavior of large samples which have been shocked on microsecond timescales with approximately mm spatial resolution. The recent discovery of laminar proton beams accelerated to multi-MeV energi… more
Date: February 10, 2005
Creator: Mackinnon, A. J.; Patel, P. K.; Town, R. J.; Hatchett, S. P.; Hicks, D.; Phillips, T. H. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Fast Ignition: Physics Progress in the US Fusion Energy Program and Prospects for Achieving Ignition.

Description: Fast ignition (FI) has significant potential advantages for inertial fusion energy and it is therefore being studied as an exploratory concept in the US fusion energy program. FI is based on short pulse isochoric heating of pre-compressed DT by intense beams of laser accelerated MeV electrons or protons. Recent experimental progress in the study of these two heating processes is discussed. The goal is to benchmark new models in order to predict accurately the requirements for full-scale fast ig… more
Date: October 16, 2002
Creator: Key, M. H.; Andersen, C.; Cowan, T.; Fisch, N.; Freeman, R.; Hatchett, S. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Gigagauss Magnetic Field Generation From High Intensity Laser Solid Interactions

Description: Intense laser (>10<sup>21</sup> W/cm2 ) sources using pulse compression techniques in the sub-picosecond time frame have been used to create dynamic electric field strenghs in excess of 100 Megavolts/micron with associated magnetic field strengths in the Gigagauss regime. We have begun a series of experiments using the Petawatt Laser system at LLNL to determine the potential of these sources for a variety of applications. Hot electron spectra from laser-target interactions in Au have been measu… more
Date: October 15, 1998
Creator: Cowan, T.; Moran, M.; Hammer, J.; Hatchett, S.; Hunt, A.; Key, M. H. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Experiment vs. theory on electric inhibition of fast electron penetration of targets

Description: A dominant force of inhibition of fast electrons in normal density matter is due to an axially directed electrostatic field. Fast electrons leave the critical density layer and enter the solid in an assumed relativistic Maxwellian energy distribution. Within a cycle of the solid density plasma frequency, the charge separation is neutralized by a background return current density j{sub b} = en{sub b}v{sub b} equal and opposite to the fast electron current density j{sub f} = en{sub f}v{sub f} [1]… more
Date: June 13, 2005
Creator: Freeman, R. R.; Akli, K. U.; Batani, D.; Baton, S.; Hatchett, S. P.; Hey, D. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Development of a Radiative-Hydrodynamics Testbed Using the Petawatt Laser Facility

Description: Many of the conditions believed to underlie astrophysical phenomena have been difficult to achieve in a laboratory setting. For example, models of supernova remnant evolution rely on a detailed understanding of the propagation of shock waves with gigabar pressures at temperatures of 1 keV or more where radiative effects can be important. Current models of gamma ray bursts posit a relativistically expanding plasma fireball with copious production of electron-positron pairs, a difficult scenario … more
Date: August 27, 1998
Creator: Koch, J. A.; Bell, P. M.; Brown, C.; Budil, K. S.; Estabrook, K. G.; Gold, D. M. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

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

Description: We have developed 17 keV to 75 keV 1-dimensional and 2-dimensional high-resolution (&lt; 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} &gt; 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: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

LSP Calculations of Cone-Wire Experiments

Description: 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: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Exploring the Fast Ignition Approach to Fusion Energy

Description: Probably the most famous equation in physics is Einstein's E=mc{sup 2}, which was contained within his fifth and final paper that was published in 1905. It is this relationship between energy ( E) and mass ( m) that the fusion process exploits to generate energy. When two isotopes of hydrogen (normally Deuterium and Tritium (DT)) fuse they form helium and a neutron. In this process some of the mass of the hydrogen is converted into energy. In the fast ignition approach to fusion a large driver … more
Date: April 18, 2005
Creator: Town, R. J.; Chung, H.; Cottrill, L. A.; Foord, M.; Hatchett, S. P.; Key, M. H. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Nail-like targets for laser plasma interaction experiments

Description: The interaction of ultra-high power picosecond laser pulses with solid targets is of interest both for benchmarking the results of hybrid particle in cell (PIC) codes and also for applications to re-entrant cone guided fast ignition. We describe the construction of novel targets in which copper/titanium wires are formed into 'nail-like' objects by a process of melting and micromachining, so that energy can be reliably coupled to a 24 {micro}m diameter wire. An extreme-ultraviolet image of the i… more
Date: December 18, 2007
Creator: Pasley, J.; Wei, M.; Shipton, E.; Chen, S.; Ma, T.; Beg, F. N. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Electron-Heated Target Temperature Measurements in Petawatt Laser Experiments Based on Extreme Ultraviolet Imaging and Spectroscopy

Description: Three independent methods (XUV spectroscopy, imaging at 68 eV and 256 eV) have been used to measure planar target rear surface plasma temperature due to heating by hot electrons. The hot electrons are produced by ultra-intense laser plasma interactions using the 150 J, 0.5 ps Titan laser. Soft x-ray spectroscopy in the 50-400 eV region and imaging at the 68 eV and 256 eV photon energies were used to determine the rear surface temperature of planar CD targets. Temperatures were found to be in th… more
Date: May 2, 2008
Creator: Ma, T. A.; Beg, F. N.; Macphee, A. G.; Chung, H. K.; Key, M. H.; Mackinnon, A. J. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Temperature sensitivity of Cu K(alpha) imaging efficiency using a spherical Bragg reflecting crystal

Description: The Vulcan laser facility at the Rutherford Appleton Laboratory was used to study the interaction of a 75 J 10 ps, high intensity laser beam with low-mass solid, Cu targets. Two instruments were fielded as diagnostics of the Cu K-shell emission from the targets: A single photon counting CCD spectrometer provided the absolute K{sub {alpha}} yield and a spherically bent Bragg crystal recorded 2D monochromatic images with a spatial resolution of 10 {micro}m. Due to the shifting and broadening of t… more
Date: August 7, 2006
Creator: Akli, K. U.; Key, M. H.; Chung, H. K.; Hansen, S. B.; Freeman, R. R.; Chen, M. H. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
Back to Top of Screen