Experimental Comparison of Tantalum Material Strength between Single Crystal [100] and [111] Samples at High Pressure and Strain Rates

Experiments were performed using the OMEGA laser to investigate the strength difference between single crystal [100] and [111] Ta samples at high pressure (1 Mbar), and high strain rates (10$^{6}$- 10$^{8}$ s$^{-1})$. To achieve these pressures and strain rates in experiment without melting the sample, a quasi-isentropic drive [1] was employed to drive the growth of pre-imposed sinusoidal perturbations on the surface of the Ta samples, via the Rayleigh-Taylor (RT) instability. By measuring the ripple amplitude using face-on high energy ($\sim$22 KeV) radiography [2], the strength of the Ta sample is inferred from the amount of RT growth observed [1]. Under these experimental conditions, the Ta material strength can be modeled by the Multiscale (MS) model [3], developed at LLNL. The value of the ``Taylor Factor'' (a MS model parameter), is thought to vary for [100] and [111] crystal orientations. To investigate this difference under these conditions, a comparison of the ripple growth was performed on the two samples for the same shot and drive conditions. [1] Park, H.S., \textit{et al}., PRL \textbf{104}, 135504 (2010). [2] Barnes, J. F., \textit{et al}., JAP \textbf{45}, 727, (1974). [3] N. Barton \textit{et al.}, JAP \textbf{109}, 073501 (2011).