J. R. Albritton

Theory and simulation of stimulated Brillouin scatter excited by nonabsorbed light in laser fusion systems

The noise spectrum from which stimulated Brillouin scatter grows has two sources in laser fusion plasmas; a broadband source due to ion‐acoustic fluctuations, and a line source, usually much larger, which is the nonabsorbed light returning from the plasma critical surface. We give a theoretical description of stimulated Brillouin backscatter when the fluctuation source may be neglected and the scatter grows exclusively from the nonabsorbed light. Gradients of background density, velocity, and temperature are allowed. Theoretical predictions are compared to numerical simulations of scatter for parameters of recent experiments. It is found that stimulated Brillouin scatter can be greatly enhanced by the presence of a critical surface and that it can become an important part of the total energy balance.

Theory and experiment for ultrahigh pressure shock Hugoniots

Abstract Several equation of state models for hot, dense matter are compared with experimental data for the shock Hugoniots of beryllium, aluminum, iron, copper, and molybdenum up to extreme pressures. The best models are in good agreement with experiment and with one another, suggesting that our understanding of dense, partially ionized matter is good.

Relativistic many-body calculations of electric-dipole lifetimes, transition rates, and oscillator strengths for n=3 states in Al-like ions

Abstract Transition rates, oscillator strengths, and line strengths are calculated for electric-dipole (E1) transitions between even-parity 3s3p2, 3s23d, 3p23d, 3d23s, and 3d3 states and odd-parity 3s23p, 3p3, 3s3p3d, and 3d23p states in Al-like ions with the nuclear charges ranging from Z=15 to 100. Relativistic many-body perturbation theory (MBPT), including the Breit interaction, is used to evaluate retarded E1 matrix elements in length and velocity forms. The calculations start from a 1s22s22p6 Dirac–Fock potential. First-order MBPT is used to obtain intermediate coupling coefficients and second-order MBPT is used to calculate transition matrix elements. Contributions from negative-energy states are included in the second-order E1 matrix elements to ensure gauge-independence of transition amplitudes. Transition energies used in the calculation of oscillator strengths and transition rates are from second-order MBPT. Transition rates, line strengths, and oscillator strengths are compared with critically evaluated experimental values and with results from other recent calculations. We present data for selected transitions between 10 of the possible 73 even-parity 3s3p2, 3s23d states and 29 of the possible 75 odd-parity 3s23p, 3p3, and 3s3p3d states in Al-like ions. Trends of the transition rates as functions of Z are illustrated graphically for 220 of the 3220 possible transitions. Lifetimes of the 10 even-parity lower levels and the 27 odd-parity upper levels are given for Z=15–100.

Accurate determination of the charge state distribution in a well characterized highly ionized Au plasma

Abstract The density, temperature and charge state distribution are accurately determined in a highly ionized non-LTE Au sample. Laser heated Au microdots buried in a thin Be foil, reach temperatures of 2 keV and ionize into the M-shell. During expansion, the tamped Au samples remain uniform and in near steady-state ionization equilibrium. The electron temperature is measured with time and space resolved Thomson scattering while the density is determined from time-gated X-ray imaging the expanded Au sample. The charge state distribution is obtained from analysis of emission measurements of Au 5f–3d transition arrays in the wavelength range 3.3–3.9 A, allowing the average charge to be determined to within ∼1% accuracy.

NLTE ionization and energy balance in high-Z laser-plasmas including two-electron transitions

Abstract We describe a new non-LTE statistical atomic kinetics model of plasmas in which the two-electron transitions of auto-ionization and its inverse, resonant-capture, play a dominant role in establishing ionization and energy balance. We show that, compared with a familiar collisional–radiative-equilibrium model which includes only the one-electron bound–bound and bound–free transitions: (1) the two-electron transitions force recombination of the plasma with decreasing density, (2) the two-electron transitions nevertheless further act to greatly increase the radiative emissivity of the plasma, and (3) the relaxation of the two-electron transition driven sysems proceeds much faster.

Dense plasma equation of state model

Abstract Low density models of atoms in plasmas use isolated ion data plus a uniform electron gas correction (usually called continuum lowering) to arrive at new energy levels. When levels pass into the continuum they become resonances—then broaden and diminish in strength. At high plasma densities the energy levels require further correction, and an estimate of the effective level degeneracy is needed. We describe our model of these effects and show results for low temperature gold plasmas in the density range 10 -4 to 10 +3 g⧸cc.

Relativistic many-body calculations of excitation energies and transition rates in ytterbiumlike ions

Excitation energies, oscillator strengths, and transition rates are calculated for

On the distribution of bound levels of ions in dense plasmas: The plasma polarization shift

{(5d}^{2}{+5d6s+6s}^{2})\ensuremath{-}(5d6p+5d5f+6s6p)

Finite density effects in plasmas

electric dipole transitions in Yb-like ions with nuclear charges Z ranging from 72 to 100. Relativistic many-body perturbation theory (RMBPT), including the retarded Breit interaction, is used to evaluate retarded

Nonlocal electron heat transport by not quite Maxwell-Boltzmann distributions.

E1