Discussion on XFEL Sciences

1. Discussion on XFEL Sciences • XFELO Characteristics High repetition rate (cf. XFEL) → High Flux (2) Long longitudinal coherence length (Full temporal coherence) (3) Ultrafine BW (4) Stability (5) Other: - Tunable, typically over 5% photon energy - Pulse length: 0.1 – 1 ps

2. Possible Scientific Areas to be explored • High resolution spectroscopy • - Inelastic x-ray scattering • - Mössbauerspectroscopy • Highenergy X-ray photoemission spectroscopy • Dynamics and Imaging with Coherent X-rays (CDI, XPCS, speckle analysis) • Dynamics with X-ray Microscopy and Phase Contrast Imaging • Quantum Optics in X-ray regime, Non-linear optics • Any other?

3. IXS with sub-meV Resolution: Opening New Frontiers in the Study of the Dynamics in Disordered Systemsby Giulio Monaco Key word XFELO promises to offer 104 times more intensity than the ESRF and 102 more than the XFEL when used as a CW machine. High resolution IXS experiments with 0.1 meV resolution, Small samples, disordered systems.

4. XFELO for Studying Dynamics with Coherent X-raysby Hyunjung Kim Key word Stability : Traditional XPCS available. Dynamics with Microsecond time scale in 2D, Highly Coherent Flux for Biological Samples, Wide Angle Scattering Measurement, Coherent at High Energy will be useful.

5. IXS and Atto-second Imagingby Yu Gan Key word Collective Excitations, Standing Wave Inelastic X-ray Scattering, Attosecondtime resolution without attosecond pulses – 1000x better resolution than XFEL pump-probe. XFELO provides much higher brilliance (x) to overcome small cross sections of IXS.

6. Hard X-Ray Photoemission (HXPS, HAXPES) with an XFELOby Chuck Fadley Key word More bulk sensitive spectra  a versatile tool for any new material or multilayer nanostructure

7. Structure of Coatomer (COPI) Cage Proteinsby Changwook Lee Key word Beautiful research work by means of structural protein crystallography, however, this work can be done by using general 3rd generation synchrotron sources. We should try to find much more suitable scientific application for protein crystallography by means of XFELO.

8. Time-Resolved Studies with XFELOby HyotcherlIhee Key word For pump-probe X-ray diffraction (scattering), XFELO may be comparable to or even better than XFEL. (as far as a MHz optical laser that provides comparable energy per pulse with a typical 1 kHz femtosecond laser system. But it may be for “soft matter”. ).

9. Bubble Dynamics Studied by X-ray Imagingby Jung Ho Je . Key word Phase contrast imaging, Ultrafast Dynamics, Dynamics of turbulent flow,supersonic flow, water drop skating on air film will be possible. X-ray Imaging for Soft matter

10. Coherent X-ray Diffraction Imaging with Future Light Sourcesby Do Young Noh Key word Anomalous CDI, (2meV resolution with full coherence), High Resolution CDI, pump-probe CDI, BraggCDIat wide angle

11. Mossbauer Science – x-ray quantum optics with nucleiby Jorg Evers Key word Quantum, Non-linear, Nuclear quantum optics, and Control  Largely unexplored field

12. Sub-Angstrom stabilized XFELO for Nuclear Resonance Metrology and Fundamental Physicsby Bernhard Adams Key word Length/time Standard, Precision Probe of Magnetic & Gravitational Fields, Quantum Gravity, and Quantum Decoherence Largely unexplored field

13. Discussion and Perspectives With all the “prominent” characteristics available from XFELO, a “new” group of users can be drawn into the “community”. The characteristics available from “seeded XFEL” should be carefully compared. – “single shot” vs “continuous (?) pulse” (in terms of stability) – advantages of narrow BW with stability and higher rep. rate Any other possible experiments?