title: Ultra-high-resolution inelastic X-ray scattering at high-repetition-rate self-seeded X-ray free-electron lasers.
abstract: Inelastic X-ray scattering (IXS) is an important tool for studies of equilibrium dynamics in condensed matter. A new spectrometer recently proposed for ultra-high-resolution IXS (UHRIX) has achieved 0.6 meV and 0.25 nm(-1) spectral and momentum-transfer resolutions, respectively. However, further improvements down to 0.1 meV and 0.02 nm(-1) are required to close the gap in energy-momentum space between high- and low-frequency probes. It is shown that this goal can be achieved by further optimizing the X-ray optics and by increasing the spectral flux of the incident X-ray pulses. UHRIX performs best at energies from 5 to 10 keV, where a combination of self-seeding and undulator tapering at the SASE-2 beamline of the European XFEL promises up to a 100-fold increase in average spectral flux compared with nominal SASE pulses at saturation, or three orders of magnitude more than what is possible with storage-ring-based radiation sources. Wave-optics calculations show that about 7 × 10(12) photons s(-1) in a 90 µeV bandwidth can be achieved on the sample. This will provide unique new possibilities for dynamics studies by IXS.
authors.affiliation: National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY 11973, USA.
authors.forename: Oleg
authors.initials: O
authors.lastname: Chubar
authors.affiliation: European X-ray Free-Electron Laser, Albert-Einstein-Ring 19, 22761 Hamburg, Germany.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Geloni
authors.affiliation: Deutsches Elektronen-Synchrotron, 22761 Hamburg, Germany.
authors.forename: Vitali
authors.initials: V
authors.lastname: Kocharyan
authors.affiliation: European X-ray Free-Electron Laser, Albert-Einstein-Ring 19, 22761 Hamburg, Germany.
authors.forename: Anders
authors.initials: A
authors.lastname: Madsen
authors.affiliation: Deutsches Elektronen-Synchrotron, 22761 Hamburg, Germany.
authors.forename: Evgeni
authors.initials: E
authors.lastname: Saldin
authors.affiliation: Deutsches Elektronen-Synchrotron, 22761 Hamburg, Germany.
authors.forename: Svitozar
authors.initials: S
authors.lastname: Serkez
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Shvyd'ko
authors.affiliation: Diamond Light Source Ltd, Didcot OX11 0DE, UK.
authors.forename: John
authors.initials: J
authors.lastname: Sutter
keywords: X-ray free-electron laser; X-ray optics; inelastic X-ray scattering