Photon radiation transport is described by the Boltzmann equation. Because this equation is difficult to solve, many different approximate forms have been implemented in computer codes. Several of the most common approximations are reviewed, and test problems illustrate the characteristics of each of the approximations. This document is designed as a tutorial so that code users can make an educated choice about which form of approximate radiation transport to use for their particular simulation.4

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The Z accelerator [R. B. Spielman, W. A. Stygar, J. F. Seamen et al., Proceedings of the 11th International Pulsed Power Conference, Baltimore, MD, 1997, edited by G. Cooperstein and I. Vitkovitsky (IEEE, Piscataway, NJ, 1997), Vol. 1, p. 709] at Sandia National Laboratories delivers ∼20MA load currents to create high magnetic fields (>1000T) and high pressures (megabar to gigabar). In a z-pinch configuration, the magnetic pressure (the Lorentz force) supersonically implodes a plasma created from a cylindrical wire array, which at stagnation typically generates a plasma with energy densities of about 10MJ∕cm3 and temperatures >1keV at 0.1% of solid density. These plasmas produce x-ray energies approaching 2MJ at powers >200TW for inertial confinement fusion (ICF) and high energy density physics (HEDP) experiments. In an alternative configuration, the large magnetic pressure directly drives isentropic compression experiments to pressures >3Mbar and accelerates flyer plates to >30km∕s for equation of state (EOS) experiments at pressures up to 10Mbar in aluminum. Development of multidimensional radiation-magnetohydrodynamic codes, coupled with more accurate material models (e.g., quantum molecular dynamics calculations with density functional theory), has produced synergy between validating the simulations and guiding the experiments. Z is now routinely used to drive ICF capsule implosions (focusing on implosion symmetry and neutron production) and to perform HEDP experiments (including radiation-driven hydrodynamic jets, EOS, phase transitions, strength of materials, and detailed behavior of z-pinch wire-array initiation and implosion). This research is performed in collaboration with many other groups from around the world. A five year project to enhance the capability and precision of Z, to be completed in 2007, will result in x-ray energies of nearly 3MJ at x-ray powers >300TW.