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Designing quasi-isentropic compression experiment

A series of experiments have been performed in collaboration with the PHYHDEL team on the LULI2000 and LIL laser facilities to quasi-isentropically compress materials up to 10 Mbars, thus to achieve pressure and temperature conditions relevant to planetary interiors. Reaching for the first time that region of the phase diagram is a real challenge and was successfully achieved.

The materials studied were Iron (in the framework of the ANR SECHEL project) and Quartz (in the framework of the ANR PlanetLab project); they are both among the most important materials that compose the planet’s interiors and difficult to study theoretically.
Iron was successfully investigated thanks to the use of a ramp-shaped laser profile, to gently compress the target and avoid pre-heating, which was numerically optimized by the TIPS team with the help of the MULTI rad-hydro. code. The Neutrino software was also used to analyze the experimental data, as well as other existing numerical programs which were slightly improved.

The experimental campaign on Quartz was more challenging since, at low pressures, this material exhibits of phase transitions which may prevent from isentropic compression. The laser profile was thus adapted to allow the target “avoiding” the low pressure phase diagram; for that purpose, a small shock was launched prior to the continuous compression ramp.

Relevant publications

- N. Amdou et al., HEDP 9, 243 (2013)