Laser driven shock compression of Iron at the EuXFEL

The Earth’s inner core presents interesting properties such as seismic velocity anisotropy and a complex internal structure that is still under investigation. Establishing the phase diagram of the relevant iron alloys and, first, of pure iron itself is necessary to improve our understanding of planetary cores.

The iron phase diagram at high pressure and temperature is still discussed despite numerous experimental and simulation studies. Indeed, discrepancies still exist on the melting curve and the existence of a high pressure and high temperature cubic phase is debated. New techniques must be developed to address those issues.

The European X-ray Free Electron Laser (EuXFEL) offers a high brilliance pulsed X-ray beam. The pulses duration is below 50 fs and can be synchronized with the DiPOLE 100-X laser, enabling X-ray diffraction experiments during dynamic compression. This type of experiments was first tested at the EuXFEL in 2023 by an international consortium that was followed by a second experiment in 2024.

Those experiments allow the collection of high-quality in situ X-ray diffraction data and visar measurements of shocked and off-Hugoniot Iron. After establishing procedures for the processing of such data, comparison between results from the two experiments will ensure repeatability. In this presentation, we will show first results including solid phases and melt diffraction patterns collected during those experiments.

This work is the result of experiments performed under the EuXFEL 2740 and 6659 community proposals led by M. McMahon, K. Appel, J. Eggert and G. Morard.