Observable reduction of the density compression due to shock-generated turbulence in empty foams

The post-shock flow is turbulent when a strong shock wave propagates through a material with a small-scale random non-uniformity, such as a foam or an aerogel. If the turbulence dissipates slowly enough, its generation affects the shock Hugoniot, reducing the large-scale density compression. Hazak et al., PoP 5, 4357 (1998) first detected this undercompression effect in 2D simulations of shock propagation through a deuterium-wetted foam, later confirmed by many numerical and theoretical works. Absolute Hugoniot measurements for CH foams of 100 mg/cc density made by Aglitskiy et al., PoP 25, 032705 (2018) on the Nike KrF laser showed a significantly lower density compression than predicted by SESAME and other tabulated EOS in the shock pressure range 2 to 5 Mbar. This discrepancy may manifest the undercompression caused by the shock-generated turbulence predicted by theory and simulations. We report the design, theoretical predictions, and the first data from a new experimental campaign on Nike aimed at using high-precision Hugoniot measurements for a detailed investigation of the effect of shock-induced turbulence on shock compression in the most promising parameter range: empty DVB foam targets with densities 70 and 100 mg/cm, shock pressures between 1 and 5 Mbar.