The 1990 National Academy of Science final report of its review of the Inertial Confinement Fusion Program recommended completion of a series of target physics objectives on the 10-beam Nova laser at the Lawrence Livermore National Laboratory as the highest-priority prerequisite for proceeding with construction of an ignition-scale laser facility, now called the National Ignition Facility (NIF). These objectives were chosen to demonstrate that there was sufficient understanding of the physics of ignition targets that the laser requirements for laboratory ignition could be accurately specified. This research on Nova, as well as additional research on the Omega laser at the University of Rochester, is the subject of this review. The objectives of the U.S. indirect-drive target physics program have been to experimentally demonstrate and predictively model hohlraum characteristics, as well as capsule performance in targets that have been scaled in key physics variables from NIF targets. To address the hohlrau...

The physics basis for ignition using indirect-drive targets on the National Ignition Facility

Physics of shock waves and high-temperature hydrodynamic phenomena - Ya.B. Zeldovich and Yu.P. Raizer (translated from the Russian and then edited by Wallace D. Hayes and Ronald F. Probstein); Dover Publications, New York, 2002, 944 pp., $34.

Based on density functional calculations, optimized structures of graphite oxide are found for various coverages by oxygen and hydroxyl groups, as well as their ratio corresponding to the minimum of total energy. The model proposed describes well-known experimental results. In particular, it explains why it is so difficult to reduce the graphite oxide up to pure graphene. Evolution of the electronic structure of graphite oxide with the coverage change is investigated.

Modeling of Graphite Oxide

Accurate x-ray scattering techniques to measure the physical properties of dense plasmas have been developed for applications in high energy density physics. This class of experiments produces short-lived hot dense states of matter with electron densities in the range of solid density and higher where powerful penetrating x-ray sources have become available for probing. Experiments have employed laser-based x-ray sources that provide sufficient photon numbers in narrow bandwidth spectral lines, allowing spectrally resolved x-ray scattering measurements from these plasmas. The backscattering spectrum accesses the noncollective Compton scattering regime which provides accurate diagnostic information on the temperature, density, and ionization state. The forward scattering spectrum has been shown to measure the collective plasmon oscillations. Besides extracting the standard plasma parameters, density and temperature, forward scattering yields new observables such as a direct measure of collisions and quantum effects. Dense matter theory relates scattering spectra with the dielectric function and structure factors that determine the physical properties of matter. Applications to radiation-heated and shock-compressed matter have demonstrated accurate measurements of compression and heating with up to picosecond temporal resolution. The ongoing development of suitable x-ray sources and facilities will enable experiments in a wide range of research areas including inertial confinement fusion,more » radiation hydrodynamics, material science, or laboratory astrophysics.« less

X-ray Thomson scattering in high energy density plasmas

Rayleigh–Taylor and Richtmyer-Meshkov instability induced flow, turbulence, and mixing. II

Initial performance results of the OMEGA laser system

Techniques have been developed to improve the uniformity of the laser focal profile, to reduce the ablative Rayleigh–Taylor instability, and to suppress the various laser–plasma instabilities. There are now three direct-drive ignition target designs that utilize these techniques. An evaluation of these designs is still ongoing. Some of them may achieve the gains above 100 that are necessary for a fusion reactor. Two laser systems have been proposed that may meet all of the requirements for a fusion reactor.

/pdf/direct-drive-laser-fusion-status-and-prospects-yvv2xk86dp.pdf

Direct-drive laser fusion: Status and prospects

The performance of triple-picket deuterium-tritium cryogenic target designs on the OMEGA Laser System [T. R. Boehly, Opt. Commun. 133, 495 (1997)] is reported. These designs facilitate control of shock heating in low-adiabat inertial confinement fusion targets. Areal densities up to 300 mg/cm2 (the highest ever measured in cryogenic deuterium-tritium implosions) are inferred in the experiments with an implosion velocity approximately 3x10(7) cm/s driven at peak laser intensities of 8x10(14) W/cm2. Extension of these designs to ignition on the National Ignition Facility [J. A. Paisner, Laser Focus World 30, 75 (1994)] is presented.

/pdf/demonstration-of-the-highest-deuterium-tritium-areal-density-3c4i43pn8g.pdf

Demonstration of the highest deuterium-tritium areal density using multiple-picket cryogenic designs on OMEGA.

Measurements of smoothing rates for smoothing by spectral dispersion (SSD) of high-power, solid-state laser beams used for inertial confinement fusion (ICF) research are reported. Smoothing rates were obtained from the intensity distributions of equivalent target plane images for laser pulses of varying duration. Simulations of the experimental data with the known properties of the phase plates and the frequency modulators are in good agreement with the experimental data. These results inspire confidence in extrapolating to higher bandwidths and other SSD configurations that may be suitable for ICF experiments and ultimately for direct-drive laser-fusion ignition.

Experimental investigation of smoothing by spectral dispersion

Techniques have been developed to improve the uniformity of the laser focal profile, to reduce the ablative Rayleigh-Taylor instability, and to suppress the various laser-plasma instabilities. There are now three direct-drive ignition target designs that utilize these techniques. Evaluation of these designs is still ongoing. Some of them may achieve the gains above 100 that are necessary for a fusion reactor. Two laser systems have been proposed that may meet all of the requirements for a fusion reactor.

/pdf/direct-drive-laser-fusion-status-and-prospects-zw3dzqbzqa.pdf

W. Seka

Papers

Initial performance results of the OMEGA laser system

Direct-drive laser fusion: Status and prospects

Demonstration of the highest deuterium-tritium areal density using multiple-picket cryogenic designs on OMEGA.

Experimental investigation of smoothing by spectral dispersion

Direct-drive laser fusion: status and prospects