X-ray diffraction measurements and pressure determination in nanosecond compression of solids up to 600 GPa

X-ray diffraction measurements under laser-driven dynamic compression now allow us to investigate the atomic structure of matter at TPa pressures and thousands of degree temperatures, with broad implications for condensed matter physics, planetary science, and astronomy. Pressure determination in these experiments often relies on velocimetry measurements coupled with modeling that requires accurate knowledge of the optical and thermomechanical properties of a window material, resulting in significant systematic uncertainty. Here we report on a series of x-ray diffraction experiments on five metals dynamically compressed to 600 GPa. In addition to simultaneously collecting atomic structure information for multiple compressed samples, namely Pt, Ta, Au, W, and Fe, we demonstrate a different approach for pressure determination applicable to x-ray diffraction experiments under quasi-isentropic ramp compression. The method, based on the use of in situ pressure calibrants, is similar to the techniques often adopted in static compression with diamond anvil cells. Focusing on experiments using a diamond window, we discuss challenges and mitigation strategies for the novel approach. Our study provides lattice-level information on five different metals compressed to hundreds of GPa and validation to the currently used methods for pressure determination based on time-resolved measurement of the diamond free-surface velocity, revealing that the use of in situ calibrants enables a factor of four reduction in the pressure uncertainty in these experiments.