Ultra-high-resolution inelastic X-ray scattering at high-repetition-rate self-seeded X-ray free-electron lasers

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• 作者：Oleg Chubar ; Gianluca Geloni ; Vitali Kocharyan ; Anders Madsen ; Evgeni Saldin ; Svitozar Serkez ; Yuri Shvyd'ko and John Sutter
• 关键词：inelastic X-ray scattering ; X-ray free-electron laser ; X-ray optics
• 刊名：Journal of Synchrotron Radiation
• 出版年：2016
• 出版时间：March 2016
• 年：2016
• 卷：23
• 期：2
• 页码：410-424
• 全文大小：2721K
• ISSN：1600-5775

文摘

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 × 10¹² 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.