Analysis of Z-pinch shock wave experiments on meteorite and planetary materials

Abstract

Abstract The response of a range of meteorite and planetary materials of astrophysical and planetary science interest to pulsed high-energy-density soft X-ray irradiation from the Sandia National Laboratories Z-pinch accelerator is described. These materials include selected iron and stony meteorites, magnesium-rich olivine (dunite), and Al and Fe calibration materials. In each experiment, the motion of the rear surface of the sample was monitored by velocity interferometry. From the resulting waveform and information about the incident pulse, information about the radiation coupling and the response of the sample to stress waves was deduced. The primary Planckian Z-pinch soft X-ray stagnation emissions have black body equivalent temperatures in the range 170–237 eV, with ∼1–10% K-alpha radiation derived from the pinch material (Cu, Al, Ni or steel). Hohlraum intensities at the stagnation pinch were in the range 84–316 TW/cm 2 on time scales from 3.0 to 8.2 ns, and from 43 to 260 GW/cm 2 at the sample positions 7–14 cm away from the pinch center, assuming an inverse-square radial dependence along a line-of-sight distance. This is analytically estimated to generate target surface radiation pressure of 6.1–12.4 GPa. The very short duration of the loading pulse establishes an attenuating shock wave. Consistent pressure measurements on the calibration targets' rear surfaces suggest a uniform soft X-ray beam on the calibration target surfaces while the (inhomogeneous) natural materials yield Hugoniot pressures with considerable variance, as expected. Thusfar we have not recovered the targets, precluding post-irradiation analysis.