Novel opportunities for sub-meV 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. We show 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 hundred-fold increase in average spectral flux compared with nominal SASE pulses at saturation, or three orders of magnitude more than possible with storage-ring based radiation sources. Wave-optics propagation shows that about $7\times 10^{12}$~ph/s in a $90$-$\mu$eV bandwidth can be achieved on the sample. This will provide unique new possibilities for dynamics studies by IXS.

17 pages, 14 figures

References in corpus (2)

• Spatiotemporal Response of Crystals in X-ray Bragg Diffraction
• Theory of angular dispersive imaging hard x-ray spectrographs

Cited by in corpus (5)

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• Performance of a cryo-cooled crystal monochromator illuminated by hard X-rays with MHz repetition rate at the European X-ray Free-Electron Laser
• Theory and optical design of x-ray echo spectrometers
• Brillouin-Mandelstam Light Scattering Spectroscopy: Applications in Phononics and Spintronics
• Diamond Channel-Cut Crystals for High-Heat-Load, Beam-Multiplexing, Narrow-Band X-ray Monochromators