Speaker
Description
Momentum-resolved inelastic x-ray scattering (IXS) probes the dynamical structure factor S(Q,ω) in solids, liquids, biological systems, and quantum materials, providing access to phonons, magnons, and charge, orbital, and valence excitations on meV energy scales and nm$^{−1}$ momentum scales. Although IXS is a well-established technique at storage-ring sources, its broader impact is limited by low spectral flux.
Self-seeded and cavity-based x-ray free-electron lasers (XFELs) can deliver spectral flux at least four orders of magnitude higher than storage rings [1]. Echo-type IXS uses broadband dispersive optics with refocusing (“echo”) imaging to decouple energy resolution from instrument bandwidth, enabling scanless measurements of S(Q,ω) over a broad energy-loss range. This approach supports single-shot IXS measurements with meV or sub-meV resolution using broadband incident x-rays [2].
Coupling echo-type IXS with seeded XFELs could increase signal strength by up to 10$^6$ relative to current storage-ring IXS spectrometers, opening new opportunities for high-resolution spectroscopy. We present optical designs for echo-type IXS instruments with a 20 meV single-shot spectral window at 9.83 keV, tailored to CBXFELs, including the system under development at LCLS through a joint ANL-SLAC project [3] and the CBXFEL recently demonstrated at the European XFEL [4].
Funding Agency
Supported by the U.S. DOE Office of Science, Basic Energy Sciences, under Contract No. DE-AC02-06CH11357, using resources of the Advanced Photon Source at Argonne National Laboratory.
Footnotes
[1] Oleg Chubar, et al. J. Synchrotron Radiation 23, (2016) 410
[2] Yuri Shvyd’ko. "X-ray echo spectroscopy". Phys. Rev. Lett., 116 (2016) 080801.
[3] Gable Marcus, et al. ``Cavity-Based Free-Electron Laser Research and Development: A Joint Argonne National Laboratory and SLAC National Laboratory Collaboration'' (FEL2019), doi:10.18429/JACoW-FEL2019-TUD04
[4] Patrick Rauer et al. "Lasing of a cavity-based X-ray source", Nature, 650 (2026) 93.
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