Extension of picosecond acoustics measurements to extreme temperature

Picosecond acoustics is a laboratory-based time-resolved optical pump-probe technique exploiting time-resolved reflectivity measurements to study the propagation of acoustic echoes in a large variety of samples. Up to now, this technique has been used to determine sound velocities of polycrystalline metals at ambient temperatures up to 150 GPa [e.g. 1,2] and to determine the full elastic tensors of single crystals up to 8 GPa [e.g. 3]. Measurements under simultaneous high-pressure and high-temperature conditions have been performed using resistively heated diamond anvil cell up to 600 K at 10 GPa for the determination of sound velocities, melting curves and thermodynamic properties of liquids [e.g. 4,5]. Extension to higher pressure and temperature conditions, above Mbar and at several thousands K, would offer the possibility of comparing sound velocity and density of planetary materials with reference seismic models. Moreover, the determination of melting curves over an increased range allows constraining the temperature profile of planetary interiors. The prospect of fully exploiting the capabilities of the technique at the extreme pressures and temperatures conditions of planetary interiors called for an upgrade of the picosecond acoustics system installed at the Institut de Mineralogie Physique des Materiaux et Cosmochimie (IMPMC). The coupling of a laser heating system to the picosecond acoustics setup will be presented here. The new potentialities of the technique will be illustrated by our very first sound velocity measurements on laser-heated molybdenum at 30 GPa. References [1] F. Decremps, D. Antonangeli, M. Gauthier, S. Ayrinhac, M. Morand, G. Le Marchand, F. Bergame, J. Philippe, Geophys. Res. Lett. 41, 1459 (2014). [2] E. Edmund, D. Antonangeli, F. Decremps, F. Miozzi, G. Morard, E. Boulard, A.N. Clark, S. Ayrinhac, M. Gauthier, M. Morand, M. Mezouar, J. Gephys. Res. Solid Earth 124, 3436 (2019). [3] F. Decremps, L. Belliard, M. Gauthier, and B. Perrin, Phys. Rev. B 82, 104119 (2010). [4] F. Decremps, S. Ayrinhac, M. Gauthier, D. Antonangeli, M. Morand, Y. Garino, P. Parisiades, Phys. Rev. B 98, 184103 (2018). [5] S. Ayrinhac, V. Naden Robinson, F. Decremps, M. Gauthier, D. Antonangeli, S. Scandolo, M. Morand, Phys. Rev. Materials 4, 113611 (2020).