Calibration of the diamond anvil Raman pressure gauge to above 500 GPa in a toroidal-DAC.

The diamond anvil Raman phonon frequency shift at the interface with the sample is now currently used as a pressure measurement for laboratory experiments above 100 GPa up to 500 GPa at least. However, the calibration of this spectroscopic pressure measurement is questioned. The aim of this proposal is twofold: 1) Calibrate the Raman diamond pressure gauge up to above 500 GPa by using the XRD and the EoS of two pressure standards, gold and Rhenium. Data have been collected up to 420 GPa so far. 2) Validate the pressure scale using the volume of diamond under hydrostatic pressure up to above 500 GPa. Data have been collected up to 200 GPa so far. The Raman shift of diamond under hydrostatic pressure will be also measured, so to provide the diamond Gruneisen parameter . Toroidal-DACs will be used to reach the 500 GPa range.