Dynamic Yield Strength of Single Crystal Tantalum Measured from in-Situ Bragg Diffraction*

Laser driven shock experiments featuring in situ Bragg diffraction were performed at the Omega EP facility on single crystal Tantalum to study the dynamic yield strength and lattice dynamics. Polished tantalum samples were shocked along the [111] direction to peak stresses in the range of $\sim $20-90 GPa and probed using a 22 keV x-ray source foil driven using the Omega EP petawatt beam. Diffraction from (222) and (231) lattice planes was obtained and the patterns recorded on time-integrating image plate detectors using the Lawrence Livermore Diffraction Imager (LLDI). The diffraction profiles were analyzed using the profile synthesis method to infer the detailed strain profile in the shock compressed material. Yield strength inferred from the data is compared with predictions from various rate-independent and rate-dependent models, including the LLNL multi-scale strength model for Ta.