Oxford Centre for High Energy Density Science (OxCHEDS)

Abstract:

A review is presented here of a number of invited papers presented at the 2008 American Physical Society April meeting [held jointly with High Energy Density Physics/High Energy Density Laboratory Astrophysics (HEDP/HEDLA) Conference] devoted to intense laser-matter interactions. They include new insights gained from wave-kinetic theory into laser-wakefield accelerators and drift wave turbulence interacting with zonal flows in magnetized plasmas; interactions with cluster media for the generation of radiative blast waves; fast electron energy transport in cone-wire targets; numerical investigations into Weibel instability in electron-positron-ion plasmas and the generation of gigabar pressures with thin foil interactions. © 2009 American Institute of Physics.

Abstract:

We present calculations of the free-free XUV opacity of warm, solid-density aluminum at photon energies between the plasma frequency at 15 eV and the L-edge at 73 eV, using both density functional theory combined with molecular dynamics and a semi-analytical model in the RPA framework with the inclusion of local field corrections. As the temperature is increased from room temperature to 10 eV, with the ion and electron temperatures equal, we calculate an increase in the opacity in the range over which the degree of ionization is constant. The effect is less pronounced if only the electron temperature is allowed to increase. The physical significance of these increases is discussed in terms of intense XUV-laser matter interactions on both femtosecond and picosecond time-scales.

Abstract:

We have performed short-pulse x-ray scattering measurements on laser-driven shock-compressed plastic samples in the warm dense matter regime, providing instantaneous snapshots of the system evolution. Time-resolved and angularly resolved scattered spectra sensitive to the correlation effects in the plasma show the appearance of short-range order within a few interionic separations. Comparison with radiation-hydrodynamic simulations indicates that the shocked plastic is compressed with a temperature of a few electron volts. These results are important for the understanding of the thermodynamic behavior of strongly correlated matter for conditions relevant to both laboratory astrophysics and inertial confinement fusion research.