Foams are an important component of various inertial confinement fusion target schemes. The propagation of shock waves in foams is also an important issue for many other laser experiments (e.g., laboratory astrophysics experiments). The usual approach is to assume that the foam can be considered as a homogeneous mixture. Taking into account the effects of foam heterogeneity leads to increased shock velocity and reduced compressibility. Evidence of this effect is obtained using two-dimensional adaptive mesh refinement Eulerian numerical simulations. Nonetheless, for the very low density foams filled with DT ice used in recent direct drive target designs, the homogeneous mixture model provides adequate shock timing, density, and pressure profiles.

In the context of the French Laser Mégajoule (LMJ) fusion research program, direct drive is an alternate to indirect drive to reach ignition and thermonuclear burn. We present recent progress in the direct-drive fusion studies for LMJ. Calculations have shown that the LMJ irradiation uniformity is characterized by long wavelength asymmetries compatible with direct drive requirements. Calculations of the irradiation uniformity in the context of indirect drive beam positioning have been done. We show that non-uniformity can be minimized by repointing the beams. Unfortunately, a time analysis shows that this nonuniformity increases strongly in time above levels usually considered inconsistent for direct drive. Finally, a recent baseline target design is presented and consists of a DT ice shell surrounded by a low-density CH foam wicked with cryogenic DT. This design can potentially reach a gain of 90 with a 1-MJ on-target laser driver. Hydrodynamic stability is increased at the ablation front and the laser–target coupling efficiency achieves 85%.

Ion beam analysis techniques have become very useful for characterization of low k materials. Studies on several ion beam analysis techniques will be discussed. Rutherford Backscattering Spectrometry (RBS) provides a very powerful analytical technique for the thickness and porosity measurements on porous Si0 2 films. Nuclear Reaction Analysis (NRA) techniques for hydrogen and fluorine profiling are very useful to characterize fluorinated polymer and fluorinated oxide films. Examples of low k materials including Si02:F, Parylene-AF and Teflon-AF will be discussed. Fluorine diffusion in to metals and various interface effects between metal and low k materials will be presented.