Seismo Lab Seminar

Giant lasers such as the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) in California – the world's most energetic laser system – provide enormous amounts of power and energy (kJ to MJ in 1 to 50 ns long pulses) with exquisite control and full suites of advanced diagnostics to recreate in the laboratory the extreme conditions of pressure and temperature that exist deep inside planets and stars.

In this presentation I will provide a very brief overview of Inertial Confinement Fusion (ICF) research. Our LLNL team recently demonstrated that implosions of small pellets of Deuterium-Tritium (DT) can produce more nuclear fusion energy than the laser energy that was used to drive the target—that is a target energy gain G>1 [1]. Because ICF implosions at the NIF use diamond capsules to contain and compress the DT fuel, better understanding the TPa pressure phase diagram of carbon is important to achieve more efficient implosions and higher energy gain.

I will describe laser-driven shock compression experiments at the Omega Laser Facility using velocimetry, pyrometry and x-ray diffraction (XRD) to revise the diamond melting temperature and reveal the evolution of the atomic structure near 1 TPa where a new post-diamond phase of carbon has been predicted to exist.

The versatility of kJ and MJ lasers can also be exploited to perform dynamic compression experiments to recreate planetary relevant extreme conditions. We investigate how the extreme pressures and temperatures typical of planetary interiors and giant impacts modify the physical and chemical properties of constituent materials to provide robust foundations for integrated studies of the physical origin and geochemical evolution of planets and planetary systems.

I will discuss previously published experimental results including the discovery of superionic water ice which could dominate the interior of icy planets [3,4], the demixing of hydrogen and helium at Jovian planet conditions [5] as well as unpublished new results addressing the long standing discrepancy between experiments [6] and theoretical predictions for the shock response and the melting temperature of MgO at giant planet interior conditions.

Prepared by LLNL under Contract DE-AC52-07NA27344.

[1] Zylstra, A., et al., Burning plasma achieved in inertial fusion, Nature 601 542-548 (2022). [2] Abu-Shawareb, H. et al. Physical Review Letters 132, 065102 (2024). [3] Millot, M., et al., Nat. Phys. 14, 297–302 (2018). [4] Millot, M., et al., Nature 569, 251–255 (2019). [5] Brygoo, S., et al., Nature 593, 517–521 (2021). [6] Wicks, J. et al., Science Advances 10, eadk0306 (2024).