Ultrahigh Resolution X-ray Thomson Scattering Measurements at the European XFEL

Using a novel ultrahigh resolution (Δ E ∼ 0.1eV) setup to measureelectronic features in x-ray Thomson scattering (XRTS) experiments at theEuropean XFEL in Germany, we have studied the collective plasmon excitation inaluminium at ambient conditions, which we can measure very accurately even atlow momentum transfers. As a result, we can resolve previously reporteddiscrepancies between ab initio time-dependent density functional theorysimulations and experimental observations. The demonstrated capability forhigh-resolution XRTS measurements will be a game changer for the diagnosis ofexperiments with matter under extreme densities, temperatures, and pressures,and unlock the full potential of state-of-the-art x-ray free electron laser(XFEL) facilities to study planetary interior conditions, to understandinertial confinement fusion applications, and for material science anddiscovery.