The knowledge of elastic properties of geo-materials is crucial to determine the mineralogical composition of the Earth's interior. The Brillouin system built at the Helmholtz-Zentrum Potsdam, Deutsches GeoForschungsZentrum allows to determine the sound wave velocities of minerals. This technique exploits Brillouin scattering - the inelastic scattering of laser light by thermally activated vibrations (phonons) in the sample. The frequency shift of the scattered light is related to the sound wave velocity of the sample as a function of pressure, temperature and the crystallographic orientation.
Fig.: Our Brillouin spectroscopy system at GFZ Potsdam is designed to host large experimental setups
We have built, in collaboration with DESY HASYLAB, a new Brillouin spectroscopy system at PETRA III, the third generation synchrotron source in Hamburg. The new systems allows one to combine acoustic velocity measurements and density measurements by x-ray diffraction at the same experimental conditions at the extreme conditions beamline P02.2, next to the Brillouin scattering laboratory.
Fig.: Left: spatial dispersion of acoustic velocity in a (110) plane of spinel (MgAl2O4) at high pressure in the diamond anvil cell (DAC). Center: a photo of the sample in the DAC. Right: X-ray diffraction photo of the sample in the DAC to determine its density at high pressure.