M A T T E R A T E X T R E M E S

S C I E N T I F I C H I G H L I G H T S

1 2 H I G H L I G H T S 2 0 2 2 I

M A T T E R A T E X T R E M E S

Science under extreme conditions is by essence multidisciplinary. Varying the pressure and the temperature enables the exploration of energy landscapes corresponding to a great diversity of fascinating structures and electronic and magnetic states. This edition of the ESRF Highlights is a very good illustration of this.

During 2022, the ambitious refurbishment plans of several key beamlines in the Matter at Extremes group have progressed very well to take full advantage of the outstanding performance of the Extremely Brilliant Source (EBS) and open unique opportunities for the ESRF user community. The high-pressure X-ray diffraction (XRD) beamline ID15B benefits from the installation of high- quality refractive lenses that enable a sub-micron X-ray beam. These focusing devices permit 2D XRD mapping of powders and single crystals in the multi-megabar pressure regime.

The Nuclear Resonance beamline ID18 will continue user operation until August 2023 and then will be transferred to its final location at ID14. The upgraded Nuclear Resonance beamline ID14 is expected to restart user operation in February 2024, providing improved beam size, energy resolution and beam stability. In particular, the hard X-ray spectrograph, an instrument that largely improves the energy resolution from ~0.6 meV to ~100 µeV, and the X-ray nanoscope, which will provide a submicron beam for hyperfine spectroscopy, will be installed on high thermal and mechanical stability experimental hutches. A state- of-the-art laser heating system will be installed at ID14 to explore materials under extreme pressure and temperature conditions.

The X-ray absorption spectroscopy (XAS) beamlines BM23 and ID24-ED have resumed user operation since January and December 2021, respectively. More than 40 user experiments have been carried out at the EXAFS beamline BM23, including four industrial ones, taking full advantage of the new two-pole wiggler EBS X-ray source. The main research areas covered at BM23 are operando chemistry, environmental sciences, planetary interior studies, cultural heritage, materials science and fundamental physics. The upgraded micro-XAS station offers a high-precision, submicron positioning system and a variety of sample environments (cryostat, oven, high-pressure cells, chemical reactor cells and gas system).

The ID24 beamline is composed of a XAS branch (ID24- DCM) equipped with the high-precision ESRF double- crystal monochromator (DCM), and a high-brilliance EDXAS-L branch optimised for fast time-resolved XAS application with time resolution down to 100 picoseconds using an energy dispersive scheme (ID24-ED). Nine user experiments were performed at ID24-ED, including laser- driven dynamic compression sessions that combined the 5ns/50J drive laser and the ID24-ED single-bunch XAS probe, together with a high quality VISAR system.