New facilities for high pressure / high temperature experiments on iron alloys at planetary core conditions on the European XFEL

Abstract

The European XFEL is a new X-ray facility installed near Hamburg, Germany, that provides extremely intense X-ray flashes of less than 50 fs (10-12 s) that can be repeated every 220 ns (10-9 s). The facility, coupled with the High Energy Density (HED) instrument, opens new avenues for experiments on iron alloys under planetary core conditions. The instrument can be coupled with diamond anvil cell experiments. In this case, the X-ray flashes of the XFEL are not only used to measure diffraction images in less that 50 fs, but also to heat the samples and gradually increase sample temperatures every 220 ns, reaching several thousands of degrees at pressures well over a megabar in microseconds. During the 3063 community proposal, we hence tested a new method to explore the phase diagrams of iron alloys at planetary core conditions, inducing phase transformations, melting and microstructural changes in conditions and timeframes that could not be reached in previous experimental systems. The instrument is also compatible with laser-driven shock experiments. DiPOLE 100-X is a world-class laser that can deliver up to 100 J (in 1-omega) and 50 J (in 2-omega) over up to 15 ns pulses, with a repetition rate up to 10 Hz. It is now installed at the High-Energy Density (HED) beamline of the European XFEL. By shining DIPOLE pulses into polymers in the back of our samples, we can generate pressure and temperature conditions well over 100 GPa and several thousands of K and using the European XFEL, we can get in-situ X-ray diffraction! The facility was tested in May 2023 during the 2740 community proposal, involving over 100 scientists from over 40 world-wide institutions. In this presentation, I will hence present these new experiments at the European XFEL and preliminary results that can be obtained. These new measurements will require a lot of development and metrology, however, which are actively pursuing at present. Our work is supported by the ERC HotCores (Grant No 101054994) at the université de Lille.