Soft x-ray shock loading and momentum coupling in meteorite and planetary materials

X-ray momentum coupling coefficients, CM, were determined by measuring stress waveforms in planetary materials subjected to impulsive radiation loading from the Sandia National Laboratories Z-machine. Results from the velocity interferometry (VISAR) diagnostic provided limited equation-of-state data as well. Targets were iron and stone meteorites, magnesium rich olivine (dunite) solid and powder (∼5--300 μm), and Si, Al, and Fe calibration targets. All samples were ∼1 mm thick and, except for Si, backed by LiF single-crystal windows. The x-ray spectrum included a combination of thermal radiation (blackbody 170--237 eV) and line emissions from the pinch material (Cu, Ni, Al, or stainless steel). Target fluences 0.4--1.7 kJ/cm2 at intensities 43--260 GW/cm2 produced front surface plasma pressures 2.6--12.4 GPa. Stress waves driven into the samples were attenuating due to the short (∼5 ns) duration of the drive pulse. Attenuating wave impulse is constant allowing accurate CM measurements provided mechanical impedance mismatch between samples and the window are known. Impedance-corrected CM determined from rear-surface motion was 1.9--3.1 x 10-5 s/m for stony meteorites, 2.7 and 0.5 x 10-5 s/m for solid and powdered dunite, 0.8--1.4 x 10-5.