07 Juin – Thesis defense - Jocelain Trela

14 h Amphi A, Building A29

Effect of hot electron on the hydrodynamic of shocks and implosions for shock ignition.

The shock ignition scheme is a promising alternative approach to the classical ignition schemes in Inertial Confinement Fusion. It relies on the generation of a strong shock at the end of the compression phase in order to allow the ignition of the target at lower implosion velocities. This ignition shock is created using a short, intense laser pulse. Yet, in order to create a shock wave of few hundreds of megabars, the required intensity is high enough so that non-linear mechanisms of absorption lead to the production of suprathermal electrons. The effect of these hot electrons on the hydrodynamic of implosion can be beneficial (increase of the ignition shock pressure) or detrimental (preaheating of the target). A good description of these hot electrons in the hydrodynamic codes used for the design of implosions is therefore necessary. The objective of this thesis is to provide a better understanding of the effect of the hot electrons on the hydrodynamic of implosion and shocks. To do so, results from experiments realized in conditions relevant for shock ignition are compared to hydrodynamic simulations including, or not, packages for the description of hot electrons.
First, a description of the shock ignition principle in absence of hot electrons in given. For this, a semi-analytical 1D planar code, coupling the solutions of hydrodynamic equations of shocks and rarefaction waves to a package describing the propagation of discontinuities, has been developed. This code, together with radiation hydrodynamic simulations realized with LILAC (LLE, University of Rochester, USA), allowed to interpret an experiment realized on OMEGA (LLE, University of Rochester, USA). Afterwards, the effect of the hot electrons on shock hydrodynamic is investigated by analyzing the results from planar geometry experiments realized on PALS (Plasma physics institute of CAS, Czech Republic) and OMEGA EP (LLE, University of Rochester, USA). For these two experiments, the results from the main diagnostics (Streak Optical Pyrometry for PALS and radiography for OMEGA EP) have been reproduced by radiation hydrodynamic simulations realized with CHIC (CELIA, University of Bordeaux, France). In this regard, a post-processing tool for the realization of synthetic radiography from simulation results has been developed. These results have been used for the design of an experiment that will be realized on LMJ-PETAL (CEA-CESTA, France). Finally, the effect of the hot electrons on the hydrodynamic of implosion is evaluated though the analysis of a spherical geometry experiment realized on OMEGA and interpreted with LILAC simulations.

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