Understanding the physics and chemistry of carbon at the conditions existing in Earth’s deep interior is an important DCO Decadal Goal. Such advances rely on developing comprehensive thermodynamic models of phase stability and physical properties of C-H-O fluid systems and their interactions with other deep phases—models that rely on as-yet-unknown thermodynamic properties of C-bearing materials. An ultrafast laser instrument for in situ measurements, developed with partial DCO support, aims to rapidly determine thermodynamic properties at submicron-length scales to enable measurements in previously unattainable pressure-temperature regimes.
With the DCO funding, the ultrafast laser system was modified for time-resolved measurements of the optical properties and emissivity of materials at high temperatures—leading to measurements of lattice and radiative thermal conductivity of the Earth’s materials at simultaneous conditions of high pressures and temperatures. These cutting-edge measurements led to publications in PNAS and Physics of the Earth and Planetary Interiors. The prototype instrument resides at the Geophysical Laboratory of the Carnegie Institution of Washington and has been used in collaborative research with a number of scientists from institutions including: the Deutsches Elektronen-Synchrotron research center (Germany), University of Edinburg (United Kingdom), the University of Texas at Austin (USA), and the University of Illinois (USA).
Prototype instrument development and improvement is an ongoing process with each achievement paving the way for new advances. In 2015, principal investigator Alex Goncharov started a new collaboration with scientists from the University of Pierre and Marie Curie in Paris, France, including Prof. F. Decremps, an expert in laser ultrasonics. The group has measured sound velocities of H2 and D2 up to 55 GPa in Paris. Next, with support from the Carnegie Institution of Washington, they will establish a laser ultrasonics system at the Geophysical Laboratory in Washington, DC. This additional capability will allow researchers to obtain revolutionary measurements, including the reaction mechanisms and kinetics of abiotic hydrocarbon generation, determination of sound velocities, and measurement of thermal conductivity of fluids under conditions of very high P (100 GPa) and T (4000°K). The science team is finalizing the proposed system’s design, but to continue advancing the instrument’s development and further leverage the DCO investment, Goncharov is submitting instrument proposals to multiple funding sources in the US and China.