Rayleigh-Taylor experimental results of dynamic Ta material strength at $>$1 Mbar pressure*

We have measured the Rayleigh-Taylor (RT) instability growth rate in Ta using Omega and EP joint laser shots. The Ta sample is maintained in the solid state by a ramped drive using a reservoir-gap-sample configuration, reaching peak pressures $>$ 1 Mbar at strain rates of 10$^{6}$-10$^{8}$ s$^{-1}$. The Ta sample RT growth factors were measured using a 22 keV backlighter driven by the EP petawatt laser. The material strength can greatly suppress the RT instability growth rate via an effective lattice viscosity [1]. In 2D simulations of these experiments, we find that the various analytic constitutive (material strength) models overpredict the Ta growth by factors of $\sim $2 or more, whereas a newly developed multiscale model matches the experimental measurements to within $\sim $30{\%}. This paper will present the details on the experimental results and comparisons with the multi-scale model. Designs that extend this experiment to 5 Mbar on NIF will also be shown [1] J. D. Colvin et al., JAP, 93, 5287 (2003); H.S. Park et al., PRL. 104, 135504 (2010).