Multi-megabar ramp-compression experiments on rhenium

Pure rhenium (Re) metal is often used as a gasket material in static compression experiments with diamond-anvil cells (DAC). For extreme (> 300 GPa) pressure DAC configurations (toroidal, staged, etc.), it can become difficult to employ a separate pressure calibrant material due to sample volume limitations, in which case the Re gasket might serve as a calibrant. While recent computational and static-compression experimental results have refined the equation of state (EOS) for Re, magnetically driven ramped compression experiments at Sandia National Laboratories' Z Machine offer high-accuracy absolute measurements of the solid-phase compressibility to multi-megabar pressures. We present experiments (and analyses thereof) on Re under ramped compression to > 400 GPa, and under ramp-release loading for peak pressures in the range 100-350 GPa; the latter allow estimation of Re's strength (flow stress) at high pressure, significantly improving precision of the bulk compressibility measurement. These strength data may also aid interpretation of DAC data using Re as both gasket and calibrant under non-hydrostatic conditions.