Mapping Pressure Distribution in a Diamond Anvil Cell above 200 GPa*

At the highest pressures, diamond anvil cell experiments are unavoidably nonhydrostatic. The presence of deviatoric stress can, for example, shift the pressure at which structural transitions are found, or even whether they are present at all. Understanding how loading conditions change the degree of pressure inhomogeneity is crucial when comparing and evaluating different works.

In this talk, we will present the results of mapping the pressure distribution within a DAC with 2 micron resolution. We compressed copper foil to pressures above 200 GPa in a neon medium, a mineral oil medium, and in a sample chamber filled entirely with copper. By measuring the pressure throughout the sample space and the gasket we can quantify how different media affect pressure homogeneity and gradients. A key element of our work is that it replicates the conditions of a typical DAC x-ray diffraction measurement over a very wide pressure range, making our conclusions highly informative for the preparation and analysis of future experiments.