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Diamond Anvil Cells

Experiments on high-temperature liquids in a laser-heated DAC are relatively difficult due to potential reaction of the sample with the diamond anvils, chemical diffusion and difficulties to keep liquids in the focal spot of the IR heating laser. We need to better understand how a molten sample evolves in the diamond anvil cell as a function of time and composition. Combining fast in situ X-ray diagnostics such as diffraction or absorption is now feasible but characterization studies of LH-DAC recovered samples using focused ion beam (FIB) and further analytical TEM analyses is essential to get a better control on experiments. No systematic study of recovered LH-DAC has been performed so far to understand how melting occurs in LH-DAC and how liquid migrate in the pressure medium. The study of recovered samples and 3D texture of quenched liquids are restricted to very few cases, such as the melting study of peridotite, a good proxy for the Earth’s mantle (e.g. Fiquet et al., 2010).

A laser-heating experiment is a subtle equilibrium between the energy brought to the sample through the diamond anvil by one IR laser, which results in a hot spot, and the loss of energy (and resulting decrease of temperature) which depends on the thermal insulation, the type of pressure transmitting medium, the geometry of the experiment, and the spatial stability of the sample. A clear improvement will arise when the geometry of samples, types and thickness of insulating media will be perfectly controlled at the micron scale. We therefore plan to control starting material geometry through a plasma deposition method (well characterized thickness of insulator and sample, with parallel layers), that will enable us to set up a reproducible procedure for the study of melts under planetary core conditions.

 

© CNRS Photothèque / Cyril Frésillon

Diamond Anvil Cells, IMPMC

Cécile Duflot - 29/02/16

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