BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:Science at the European X-ray Free Electron Laser DTSTART:20260409T090000Z DTEND:20260409T100000Z DTSTAMP:20260425T151400Z UID:indico-event-1567@indico.ifj.edu.pl DESCRIPTION:Speakers: Thomas Feurer (EUROPEAN XFEL\, GERMANY)\n\nX-ray Fre e Electron Lasers (XFELs) have greatly enhanced our ability to observe tra nsient nuclear and electronic motions in real time at atomic resolution\, thereby deepening our fundamental understanding of matter across different disciplines. Moreover\, XFELs offer several significant advantages in Hig h Energy Density (HED) science\, which deals with matter under extreme con ditions of temperature and pressure. For instance\, XFELs can probe struct ure and ionization dynamics in warm dense matter\, a regime between solid and plasma states\, investigate material response to ultra-high pressures\ , help refine models of radiation transport at extreme conditions\, and re create and study conditions inside gas giants or white dwarfs.Most XFELs t oday generate pulses that consist of amplified noise\, leading to signific ant shot-to-shot fluctuations. While these pulses exhibit high transverse coherence\, their longitudinal coherence remains very low. In this talk\, I will present two methods for controlling longitudinal coherence and demo nstrate their application in X-ray spectroscopy. Such experiments are made possible only by the resulting exceptional spectral brilliance of XFEL so urces. Specifically\, I will discuss a nuclear clock transition in a speci fic scandium isotope. Because of the Heisenberg uncertainty principle\, t he structure of a molecule fluctuates about its mean geometry\, even in th e ground state. I will show the observation of this fundamental quantum ef fect experimentally\, particularly\, revealing the collective nature of th e structural quantum fluctuations\, by Coulomb Explosion Imaging for compl ex molecules. In detail\, an 11-atom molecule was investigated by inducing its Coulomb explosion with an x-ray free-electron laser. The structural f luctuations manifest themselves in correlated variations of ion momenta ob tained through coincident detection of the atomic fragments from individua l molecules.Lastly\, I will discuss several applications of XFELs in the a rea of high energy density science. For example\, I will present the first experimental evidence of liquid carbon\, formed by shock-compressing grap hite with a high-energy laser and probing it transiently using ultrashort XFEL pulses. Additionally\, I will show the first experimental observation of plasma compression driven by relativistic currents in a cylindrical ge ometry\; this effect was predicted over two decades ago but never confirme d until now. These experiments underscore the transformative impact of XFE Ls on advancing inertial fusion energy research. The European X-Ray Free Electron Laser (EuXFEL)\, located near Hamburg and operated as a non-prof it collaboration of 12 member states\, is one of the world’s most advanc ed scientific research facilities. It provides scientists with extremely b right\, coherent\, and ultrafast X-ray flashes that allow exploration of m atter at atomic length and ultrafast time scales. Since its completion in 2018\, the facility\, with 580 staff members from over 60 countries and mo re than 1’200 users per year\, has produced more than 1’500 scientific publications and >30 PB of data annually.The EuXFEL accelerates up to 27 ’000 electron pulses per second to energies up to 17.5 GeV. These electr on pulses generate soft to hard X-rays in three different undulator system s\, which feed seven operational instruments: FXE\, SPB/SFX\, SCS\, SQS\, SXP\, HED\, and MID\, with an eighth under construction. These instruments support studies ranging from time-resolved crystallography to high-energy -density physics. The EuXFEL’s first operation mode as a free-electron l aser (FEL) uses self-amplified spontaneous emission (SASE)\, but through s elf-seeding\, spectral brightness and coherence can be significantly enhan ced. The most recent further evolution toward coherent laser-like X-ray ra diation\, with appropriate feedback\, marks a key milestone: the realizati on of the first hard X-ray laser oscillator. Several scientific areas will significantly benefit\, for instance nuclear spectroscopy. An especially notable application is the resonant excitation of the potential nuclear cl ock isomer ⁴⁵Sc\, whose ultranarrow 12.4 keV nuclear transition with l inewidth of approximately 1.4 feV promises unprecedented timekeeping preci sion. In the Quantum World section\, the presentation highlighted how EuX FEL enables direct imaging of small quantum systems and molecular dynamics at atomic resolution. Using X-ray-induced Coulomb explosion imaging (CEI) \, researchers can reconstruct molecular structures by measuring the three -dimensional momenta of ions produced when intense X-ray pulses strip elec trons of the constituting atoms. CEI offers equal sensitivity to all atomi c species\, including hydrogen unlike diffraction-based methods. Recent wo rk revealed how ground-state molecules exhibit collective quantum fluctuat ions\, small correlated atomic motions detectable through momentum correla tions.European XFEL also enables unique experiments at conditions that sim ulate the interior conditions of planets and stars\, exploring temperature -pressure regimes from ambient up to multi-terapascal and million-kelvin r anges. Using X-ray diagnostics and laser-based compression\, scientists ca n reproduce environments akin to Earth’s core or the center of the Sun. Research topics include: The phase diagrams of iron and water\, essential for understanding planetary interiors and exoplanet composition. Discovery of superionic ice\, a phase where hydrogen ions move freely within a soli d oxygen lattice\, and the prediction of metallic ice phases at pressures above 1.5 TPa (Nature Communications 2024). Moreover\, experimental insigh ts into diamond formation from hydrocarbons (Nature Astronomy 2024) and th e melting behavior of carbon under extreme compression (Nature 2025). Thes e results deepen our grasp of planetary structures and high-pressure chemi stry. The EuXFEL also contributes to the pursuit of nuclear fusion. Its u ltrafast\, high-brightness X-rays allow researchers to observe fusion dyna mics in real time\, offering data that can guide\, for instance\, the desi gn of more efficient inertial-confinement fusion targets. Current collabor ations aim to quantify energy transfer\, ablator behavior\, and plasma evo lution to move toward viable\, sustainable fusion energy. \nA conceptual electricity budget illustrates the challenge: achieving a gain of 160 requ ires balancing input from lasers (10 % efficiency) and power conversion (4 5 %)\, demanding several hundred megawatts of grid and recirculated energy .European XFEL research spans multiple scientific frontiers:\n* **Astrophy sics**: simulating matter at stellar cores and planetary interiors.* **Che mistry & Biology**: revealing protein and enzyme structures at atomic reso lution\, enabling studies of photosynthesis and artificial energy conversi on.* **Material Science & Technology**: creating and characterizing novel materials with tailored electronic and magnetic properties.* **Quantum Phy sics & Digitalization**: advancing ultrafast control of quantum systems an d data processing methods.\nThe European XFEL stands as a **flagship for E uropean and international science**\, merging cutting-edge accelerator phy sics\, quantum optics\, and high-energy-density research. It opens entirel y new ways to visualize and manipulate matter—from probing the structure of planets and molecules to driving innovations in timekeeping and sustai nable energy. As the facility continues expanding its capabilities and col laborations\, it is poised to play a defining role in understanding the un iverse at its most fundamental scales.\n\nhttps://indico.ifj.edu.pl/event/ 1567/ URL:https://indico.ifj.edu.pl/event/1567/ END:VEVENT END:VCALENDAR