Simulating earth core using high energy lasers
Résumé
The melting curve and equation of state of iron and iron alloys at the inner core boundary (330 GPa, about 5000 K) are still unknown. This severally limits current modelling of earth constitution and dynamics. In this paper, recent numerical and experimental studies performed using laser generated isentropic ramp compression on iron and aluminium samples are presented. On the experimental side, direct laser ramp compression was achieved on iron. Time-resolved measurements were compared to hydrodynamic computations accounting for the polymorphic phase transformations. Before studying iron that presents a solid-solid phase transition along the isentropic path, we studied the time evolution of the atomic structure of aluminium using molecular dynamics simulations at the same length and time scales as the experiment. Like many metals, aluminium presents an elasto-plastic phase transition and we studied, using this microscopic approach, the effect of plasticity on the backward integration technique used to extract equation of state information from the experimental VISAR signal.