Multiple thickness Fe foils were ramp compressed over several nanoseconds to pressure conditions relevant to the Earth's core. Using wave-profile analysis, the sound speed and the stress-density response were determined to a peak longitudinal stress of 273 GPa. The measured stress-density states lie between shock compression and 300-K static data, and are consistent with relatively low temperatures being achieved in these experiments. Phase transitions generally display time-dependent material response and generate a growing shock. We demonstrate for the first time that a low-pressure phase transformation (-Fe to -Fe) can be overdriven by an initial steady shock to avoid both the time-dependent response and the growing shock that has previously limited ramp-wave-loading experiments. In addition, the initial steady shock pre-compresses the Fe and allows different thermodynamic compression paths to be explored.
Ramp compression of iron to 273 GPa
Jue Wang, Raymond F. Smith, Jon H. Eggert, Dave G. Braun, Thomas R. Boehly, J. Reed Patterson, Peter M. Celliers, Raymond Jeanloz, Gilbert W. Collins, Thomas S. Duffy; Ramp compression of iron to 273 GPa. J. Appl. Phys. 14 July 2013; 114 (2): 023513. https://doi.org/10.1063/1.4813091
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