Numerical simulation of laser driven Inertial Confinement Fusion (ICF) related experiments require the use of large multidimensional hydro codes. Though these codes include detailed physics for numerous phenomena, they deal poorly with electron conduction, which is the leading energy transport mechanism of these systems. Electron heat flow is known, since the work of Luciani, Mora, and Virmont (LMV) [Phys. Rev. Lett. 51, 1664 (1983)], to be a nonlocal process, which the local Spitzer–Harm theory, even flux limited, is unable to account for. The present work aims at extending the original formula of LMV to two or three dimensions of space. This multidimensional extension leads to an equivalent transport equation suitable for easy implementation in a two-dimensional radiation-hydrodynamic code. Simulations are presented and compared to Fokker–Planck simulations in one and two dimensions of space.

For the simulation of laser-created plasmas, hydrodynamic codes need an atomic physics package, for both the equation of state and the optical properties, which does not use the hypothesis of local thermodynamical equilibrium (LTE). However, in x-ray laser studies, as well as in indirect drive inertial confinement fusion studies, high-Z materials can be found where radiation trapping can induce a significant departure from the optically thin description. A method is presented in which an existing LTE code can be changed into a non-LTE code with radiation-dependent ionization. This method is numerically simple and its cost, in terms of computing time, is low enough to be used in two-dimensional simulations.

Relativistic electrons are produced, with energies up to 20 MeV, by the interaction of a high-intensity subpicosecond laser pulse (1 mm, 300 fs, 10 19 W͞cm 2 ) with an underdense plasma. Two suprathermal electron populations appear with temperatures of 1 and 3 MeV. In the same conditions, the laser beam transmission is increased up to 20%-30%. We observe both features along with the evidence of laser pulse channeling. A fluid model predicts a strong self-focusing of the pulse. Acceleration in the enhanced laser field seems the most likely mechanism leading to the second electron population.[S0031-9007(97)03893-3]

Radiative shock waves are observed around astronomical objects in a wide variety of environments, for example, they herald the birth of stars and sometimes their death. Such shocks can also be created in the laboratory, for example, by using energetic lasers. In the astronomical case, each observation is unique and almost fixed in time, while shocks produced in the laboratory and by numerical simulations can be reproduced, and investigated in greater detail. The combined study of experimental and computational results, as presented here, becomes a unique and powerful probe to understanding radiative shock physics. Here we show the first experiment on radiative shock performed at the PALS laser facility. The shock is driven by a piston made from plastic and gold in a cell filled with xenon at 0.2 bar. During the first 40 ns of the experiment, we have traced the radiative precursor velocity, that is showing a strong decrease at that stage. Three-dimensional~3D! numerical simulations, including state-of-art opacities, seem to indicate that the slowing down of the precursor is consistent with a radiative loss, induced by a transmission coefficient of about 60% at the walls of the cell. We infer that such 3D radiative effects are governed by the lateral extension of the shock wave, by the value of the opacity, and by the reflection on the walls. Further investigations will be required to quantify the relative importance of each component on the shock properties.