Using X-ray free electron lasers to explore extreme states under quasi-static compression

The exceptional brilliance of X-ray free electron lasers (XFELs) combined with quasi-static compression in diamond anvil cells (DACs) has enabled novel time-resolved methods for probing extreme states of matter. Coupling serial X-ray techniques with dynamic drivers for rapidly changing pressure and temperature, these studies offer insight into phase equilibria, chemical reaction kinetics, and geophysical processes. Here, we present the current state-of-the-art XFEL techniques used for DAC research, including serial X-ray heating, pulsed laser heating, and rapid compression. Essential questions for future investigation are also highlighted, regarding the interactions of intense X-rays with samples at high pressure and associated non-equilibrium states.