Two alternative schemes exist to perform Inertial Confinement Fusion (ICF) experiments with lasers. In indirect drive, the target is confined in a gold cavity whose irradiation by the laser beams generates a radiation which causes the implosion of the target. On the contrary, in direct drive, the compression of the target is directly ensured by the lasers. Whether in ICF, or more generally for High Energy Density Physics experiments, it is necessary to master the different aspects of the physics involved. In these experiments, laser beams propagate in plasmas over several millimeters and are affected by many phenomena resulting from the coupling between the laser and the plasma. This coupling is at the origin of mechanisms such as self-focusing, filamentation, deflection and energy transfer between beams or parametric instabilities (Raman, Brillouin) which lead to laser energy losses. Moreover, laser propagation is also influenced by hydrodynamic flows and the resulting instabilities, which are themselves dependent on complex phenomena to model such as electron thermal conduction and plasma interpenetration.

We study theoretically and numerically these different topics, fundamental for ICF, and we investigate various strategies to contain the instabilities through the control of the beams or the plasma.

This work, which leads to the evolution of the design of the targets used, is carried out in conjunction with the realization and interpretation of experiments on lasers in France or abroad.