Earl O'Bannon | 20-FS-028
The ability to compress highly compressible, low-compressibility-factor (low-Z) materials to pressures exceeding 4.0 megabar (Mbar) is currently limited to dynamic compression platforms and a few isolated conventional diamond anvil cell experiments. During this feasibility study, we tested secondary gasket configurations to contain highly-compressible materials using the Lawrence Livermore National Laboratory-developed toroidal diamond anvil cell (t-DAC).
We tested the new sample chamber configuration using tungsten gaskets that were manufactured with focused ion beam techniques. The secondary gaskets are small and resemble a donut with an outside diameter of 10 micrometers and an inside diameter of 5-6 micrometers. The small dimensions of the secondary gasket make it difficult to mount onto the toroidal diamond anvil, but it is feasible when a micromanipulator is used. We compressed argon in two different experiments, and the secondary tungsten gasket configuration achieved pressures of 0.7 and 1.0 Mbar using synchrotron x-ray diffraction as the diagnostic. In addition, we conducted multi-million atom simulations of the uniaxial loading of tungsten and rhenium at various temperatures and strain rates to investigate the deformation and dislocation generation under uniaxial loading and to better understand if this configuration could support the loads required for ultra-high-pressure conditions.
This project supports the Laboratory's mission research challenge in nuclear weapons science, as well as the Laboratory's high-energy-density science core competency, by maintaining Livermore capabilities at the leading edge of static high-pressure science. This work demonstrated advances in the ability to compress highly compressible materials, expanding the experimental basis for equation-of-state development and providing a platform to validate state-of-the-art models for complex systems like those found in the ice giant planets.