The diamond anvil Raman phonon frequency shift at the interface with the sample is now currently used as a pressure measurement above 100 GPa for laboratory experiments. However, this spectroscopic pressure measurement could largely overestimate pressure above 400 GPa. The aim of this proposal is to accurately calibrate the Raman diamond pressure gauge up to 500 GPa. Three calibrants will be selected: Au, Pt and diamond, all embedded in Ne, by relating their XRD volumes to pressure through their EOS. The Raman shift of diamond under hydrostatic pressure, hence the diamond Gruneisen parameter, will also be measured up to 500 GPa. Toroidal-DACs will be used to reach the 500 GPa range.