Evaluation of density modulations induced by foam structures relevant to inertial confinement fusion applications

In laser direct-drive inertial confinement fusion, foams can be used for laser imprint mitigation or as a matrix to contain liquid deuterium-tritium. One of the key questions is the possible generation of density modulations coming from the foam structure, especially when considering additively manufactured foams. In this work, we report on simulations performed with Excession, a 3D ALE-AMR radiative-hydrodynamic code, by considering a plastic foil covered with a foam layer where the struts and the pores of the foams are meshed directly. The characterization of the shock propagating in the foil reveals significant modulations which patterns can clearly correspond to the initial integrated density profile of the foam. To highlight the importance of the foam structure on the shock characteristic, regular anisotropic structures (logpile foams) and stochastic structures (Voronoi foams) have been considered. We identify two sources of these modulations : the rippled shock propagating in the foam when it reaches the foil, as well as the direct imprint of the foam structure on the foil due to the initial laser propagation through the pores of the foam. This work opens the way to integrated simulations with accurate foam discretization.

This work is supported by the U.S. Department of Energy (DOE), Office of Science, Fusion Energy Sciences, under Award No. DE-SC0024863: IFE-STAR and AWD-00007026: INFUSE.