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in creator/contributor: "Freeman, R. R."

open access

Laser heating of solid matter by light pressure-driven shocks

Heating by irradiation of a solid surface in vacuum with 5 x 10{sup 20} W cm{sup -2}, 0.8 ps, 1.05 {micro}m wavelength laser light is studied by x-ray spectroscopy of the K-shell emission from thin layers of Ni, Mo and V. A surface layer is heated to {approx} 5 keV with an axial temperature gradient of 0.6 {micro}m scale length. Images of Ni Ly{sub {alpha}} show the hot region has a {approx} 25 {micro}m diameter, much smaller than {approx} 70 {micro}m region of K{sub {alpha}} emission. 2D parti… more

Date: May 4, 2007

Creator: Akli, K.; Hansen, S. B.; Kemp, A. J.; Freeman, R. R.; Beg, F. N.; Clark, D. et al.

Item Type: 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

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: Article

Partner: UNT Libraries Government Documents Department

open access

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

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: Article

Partner: UNT Libraries Government Documents Department

open access

Proton Fast Ignition

No Description Available.

Date: January 27, 2005

Creator: Key, M. H.; Freeman, R. R.; Hatchett, S. P.; MacKinnon, A. J.; Patel, P. K.; Snavely, R. A. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

On Point Designs for High Gain Fast Ignition

Fast ignition research has reached the stage where point designs are becoming crucial to the identification of key issues and the development of projects to demonstrate high gain fast ignition. The status of point designs for cone coupled electron fast ignition and some of the issues they highlight are discussed.

Date: September 27, 2007

Creator: Key, M.; Akli, K.; Beg, F.; Betti, R.; Clark, D. S.; Chen, S. N. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Nail-like targets for laser plasma interaction experiments

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: Article

Partner: UNT Libraries Government Documents Department

open access

Hot Electron Generation and Transport Using K(alpha) Emission

We have conducted experiments on both the Vulcan and Titan laser facilities to study hot electron generation and transport in the context of fast ignition. Cu wires attached to Al cones were used to investigate the effect on coupling efficiency of plasma surround and the pre-formed plasma inside the cone. We found that with thin cones 15% of laser energy is coupled to the 40{micro}m diameter wire emulating a 40{micro}m fast ignition spot. Thick cone walls, simulating plasma in fast ignition, re… more

Date: October 15, 2009

Creator: Akli, K. U.; Stephens, R. B.; Key, M. H.; Bartal, T.; Beg, F. N.; Chawla, S. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Development of a Laboratory Extreme-Ultraviolet Lithography Tool

The development of a laboratory EUV lithography tool based on a laser plasma source, a 10x Schwarzchild camera, and a magnetically levitated wafer stage is presented. Interferometric measurements of the camera aberrations are incorporated into physical-optics simulations to estimate the EUV imaging performance of the camera. Experimental results demonstrate the successful matching of five multilayer reflecting surfaces, coated to specification for a wide range of figure and incidence angle requ… more

Date: April 1, 1994

Creator: Tichenor, D. A.; Kubiak, G. D.; Malinowski, M. E.; Stulen, R. H.; Haney, S. J.; Berger, K. W. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Hot Surface Ionic Line Emission and Cold K-Inner Shell Emission From Petawatt-Laser Irradiated Cu Foil Targets

A hot, T{sub e} {approx} 2- to 3-keV surface plasma was observed in the interaction of a 0.7-ps petawatt laser beam with solid copper-foil targets at intensities >10{sup 20} W/cm{sup 2}. Copper K-shell spectra were measured in the range of 8 to 9 keV using a single-photon-counting x-ray CCD camera. In addition to K{sub {alpha}} and K{sub {beta}} inner-shell lines, the emission contained the Cu He{sub {alpha}} and Ly{sub {alpha}} lines, allowing the temperature to be inferred. These lines hav… more

Date: December 13, 2005

Creator: Theobald, W.; Akli, K.; Clarke, R.; Delettrez, J. A.; Freeman, R. R.; Glenzer, S. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Limitation on Pre-pulse Level for Cone-Guided Fast-Ignition ICF

The viability of fast-ignition (FI) inertial confinement fusion hinges on the efficient transfer of laser energy to the compressed fuel via multi-MeV electrons. Pre-formed plasma due to laser pre-pulse strongly influences ultra-intense laser plasma interactions and hot electron generation in the hollow cone of an FI target. We induced a prepulse and consequent preplasma in copper cone targets and measured the energy deposition zone of the main pulse by imaging the emitted K{sub {alpha}} radiati… more

Date: September 1, 2009

Creator: MacPhee, A. G.; Akli, K. U.; Beg, F. N.; Chen, C. D.; Chen, H.; Divol, L. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A Dual Channel X-ray Spectrometer for Fast Ignition Research

A new Dual Channel Highly Ordered Pyrolytic Graphite (DC-HOPG) x-ray spectrometer was developed to study laser-generated electron beam transport. The instrument uses a pair of graphite crystals and has the advantage of simultaneously detecting self emission from low-Z materials in first diffraction order and high-Z materials in second order. The emissions from the target are detected using a pair of parallel imaging plates positioned in a such way that the noise from background is minimized and… more

Date: April 19, 2010

Creator: Akli, K. U.; Patel, P. K.; Van Maren, R.; Stephens, R. B.; Key, M. H.; Higginson, D. P. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Relativistic Electron Beam Transport and Characteristics in Solid Density Plasmas

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: Article

Partner: UNT Libraries Government Documents Department

open access

Overview of recent progress in US fast ignition research

The Fast Ignition Program in the United States has enjoyed increased funding in various forms from the Office of Fusion Energy Sciences of the Department of Energy. The program encompasses experiments on large laser facilities at various world-wide locations, and benefits enormously from collaborations with many international scientists. The program includes exploratory work in cone-target design and implosion dynamics, high electron current transport measurements in normal density materials, d… more

Date: September 28, 2005

Creator: Freeman, R. R.; Akli, K.; Beg, F.; Betti, R.; Chen, S.; Clark, D. J. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

High Energy Electron Transport in Solids

No Description Available.

Date: September 28, 2005

Creator: Snavely, R.; Aglitskii, Y.; Akli, K. U.; Amiranoff, F.; Andersen, C.; Batani, D. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Characterization of Ti K-alpha radiation resulting from interaction of a highly intense laser pulse with a thin titanium foil

A first demonstration has recently been made of radiography of implosions using a nonthermal K{alpha} radiation source generated with a high intensity picosecond laser pulse [1]. Absolute source brightness is important in assessing the potential of this diagnostic and we present here measurements and Monte-Carlo simulations of the brightness of the Ti K{alpha} back-lighter source. The experiment was conducted at the Vulcan laser within the Rutherford Appleton Laboratory (RAL) in the UK. A set o… more

Date: June 13, 2005

Creator: King, J. A.; Key, M. H.; Chen, C. D.; Freeman, R. R.; Phillips, T.; Akli, K. U. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

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

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: Article

Partner: UNT Libraries Government Documents Department