Plasma-driven Z-pinch X-ray loading and momentum coupling in meteorite and planetary materials

X-ray momentum coupling coefficients, C _M, were determined by measuring stress waveforms in planetary materials subjected to impulsive radiation loading from the Sandia National Laboratories Z-machine. Velocity interferometry (VISAR) diagnostics provided equation-of-state data. Targets were iron and stone meteorites, magnesium-rich olivine (dunite) solid and powder (~5-300 μm), and Si, Al, and Fe calibration targets. Samples were ~1-mm thick and, except for Si, backed by LiF single-crystal windows. X-ray spectra combined thermal radiation (blackbody 170-237 eV) and line emissions from pinch materials (Cu, Ni, Al, or stainless steel). Target fluences of 0.4-1.7 kJ/cm² at intensities of 43-260GW/cm² produced plasma pressures of 2.6-12.4 GPa. The short (~5 ns) drive pulses gave rise to attenuating stress waves in the samples. The attenuating wave impulse is constant, allowing accurate C _M measurements from rear-surface motion. C _M was 1.9 - 3.1 × 10^-5 s/m for stony meteorites, 2.7 and 0.5 × 10^-5 s/m for solid and powdered dunite, 0.8 - 1.4 × 10^-5 s/m for iron meteorites, and 0.3, 1.8, and 2.7 × 10^-5 s/m respectively for Si, Fe, and Al calibration targets. Results are consistent with geometric scaling from recent laser hohlraum measurements. CTH hydrocode modeling of X-ray coupling to porous silica corroborated experimental measurements and supported extrapolations to other materials. CTH-modeled C _M for porous materials was low and consistent with experimental results. Analytic modeling (BBAY) of X-ray radiation-induced momentum coupling to selected materials was also performed, often producing higher C _M values than experimental results. Reasons for the higher values include neglect of solid ejecta mechanisms, turbulent mixing of heterogeneous phases, variances in heats of melt/vaporization, sample inhomogeneities, wave interactions at the sample/window boundary, and finite sample/window sizes. The measurements validate application of C _M to (inhomogeneous) planetary materials from high-intensity soft X-ray radiation.