Analysis of shock temperature data for iron

Abstract

Reanalysis of the shock temperatures for iron employing the method of Tan and Ahrens permits reinterpretation of previously reported Fe-Al₂, O₃, and Fe-LiF interface radiance temperatures. The reduced data for iron foils and films in contact with Al₂, O₃, and LiF windows are consistent and indicate that the melting temperatures for iron range from 5300 K at 120 GPa to 7300 K at 240 GPa. This revised analysis indicates that the melting temperatures are-350 K higher than previously reported on the basis of a simpler analysis. Data for the initial density of a series of iron foils indicate a density of 7.87 ± 0.17 g/cm³, which indicates a total absence of porosity. Scanning electron microscope images of the 0.3 to 0.4 μpm thick iron foils used in the experiments indicate no detectable initial porosity. However these films demonstrate a variation in thickness of ∼0.1 μm which induces thermal transients at the iron-window interfaces with durations of ∼4 × 10⁻¹¹ s. These temperature fluctuations would occur more rapidly than the 10⁻⁹ s time resolution of present recording methods.