Probing Hotspot Conditions in Spherically Shock Compressed Matter

We present results of an approach to experimentally determine the conditions in the center of a CD$_{\mathrm{2}}$ sphere that has been compressed to petapascal pressures by spherically converging shocks. By measuring the hotspot size using penumbral imaging [1], hotspot temperature using two-color spectroscopy [2], the neutron yield from DD nuclear reactions and the x-ray burn width, we infer average hotspot densities of 43 g/cm$^{\mathrm{3}}$ at 1.6 keV temperature. These conditions correspond to pressures of 4.4 petapascal (44 Gbar) in an ideal gas and 3.5 petapascal from independently performed rad.-hydro. simulations. The experimentally determined neutron yield, temperature and density constrain the EOS in a regime that exceeds previously reported pressures obtained in carbon EOS measurements by three orders of magnitude [3]. The results show a path for constraining the EOS of matter at conditions that have been inaccessible with state-of-the-art experimental EOS techniques. [1] B. Bachmann \textit{et al.}, Rev. Sci. Instrum. 85, 11D606 (2014) [2] B. Bachmann \textit{et al}., J. Phys. D: Appl. Phys. 46, 125203 (2013) [3] R. F. Smith \textit{et al.}, Nature 511, 330-333 (2014)