Measurements of High Strain Rate Rayleigh-Taylor Growth in Solid Pb at the National Ignition Facility*

We report on recent National Ignition Facility experiments investigating high pressure (~3.5 Mbar), high strain rate (> 10⁶ s^-1) deformation of Pb. Face-on X-ray radiography is used to monitor the growth of pre-formed sinusoidal ripples, which seed Rayleigh-Taylor growth as the driven material flows. Our samples are driven by a ramped pressure wave that is generated by an expanding plasma drive from a low-density foam reservoir that achieves these high pressures while maintaining Pb in the solid state. Pb makes an interesting study case at it transforms from the ambient face-centered-cubic to the body-centered-cubic phase at the conditions in our experiments. Phase transformations are expected to influence material strength and could contribute to the high strength seen in high strain rate Fe using multiple platforms [1-2]. The dynamic strength of Pb is inferred by comparing our data to hydrodynamics simulations that include strength models, including a newly developed Improved-Steinberg-Guinan model for body-centered-cubic Pb [3].

[1] CM Huntington et al., APS SCCM Proc., 2015
[2] Y Ping et al. PRL 111, 065501 (2013)
[3] Robert E. Rudd et al., APS SCCM Proc., 2017.