X-ray diffraction techniques for in-situ measurements of the dynamic flow stress of shock compressed Ta

A range of experimental techniques using in-situ x-ray diffraction have been developed to study the dynamic flow stress and underlying deformation of shock compressed samples. Experiments performed at the Omega and Omega EP facilities can generate both a high pressure drive, ranging from 0.3 Mbar up to and beyond the Hugoniot melt line, while simultaneous providing a short, bright x-ray source. Single crystal samples were studied either by Laue diffraction, using a broadband x-ray source created by an imploding CH capsule, or by Bragg diffraction, using a short pulse driven metal foil backlighter. The strength of polycrystalline samples can be determined using a pinhole camera setup and a quasi-monochromatic source. For highly-textured polycrystalline samples, additional strength information can be inferred from the azimuthal position of the texture spots on the Debye ring. Through measurements of the 1D-to-3D relaxation time or changes in the observed texture, information about the deformation mechanics of shock loading can be inferred.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.