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Introduction to XFEL-O and Charges to the Workshop

Introduction to XFEL-O and Charges to the Workshop. Kwang -Je Kim ANL & U of C& POSTECH Workshop on Sciences Outlook and R&D Issues of X-ray FEL Oscillator February 14-15, 2013 POSCO International Center Pohang, Korea. Free Electron Laser Oscillator.

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Introduction to XFEL-O and Charges to the Workshop

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  1. Introduction to XFEL-O and Charges to the Workshop Kwang-Je Kim ANL & U of C& POSTECH Workshop on Sciences Outlook and R&D Issues of X-ray FEL Oscillator February 14-15, 2013 POSCO International Center Pohang, Korea

  2. Free Electron Laser Oscillator • A low-gain device with high Q optical cavity • Optical pulse formed over many electron passes • Difficult for x-rays • Electron beam qualities • High-reflectivity normal incidence mirror Science Outlook and R&D Issues for an XFELO

  3. X-Ray FEL Oscillator (XFEL-O) An FEL oscillator is feasible in hard x-ray region by using Bragg mirrors R. Collela and A. Luccio, 1983; KJK, Y. Shvyd’ko, and S. Reiche, 2008 Tuning is possible with a four mirror configuration R. M.J.Cotterill, (1968) KJK & Y. Shvyd’ko (2009) A super-conducting linac with a photo-cathode gun can drive an XFELO 3 Science Outlook and R&D Issues for an XFELO

  4. Ginger Simulation of XFELO Spectrum After 500 Passes (Two Diamond Crystal Cavity, 50 mm and 200mm, R. Lindberg) Science Outlook and R&D Issues for an XFELO

  5. Temporal and spectral evolution of XFELO R.R. Lindberg, K.-J. Kim, Yu. Shvyd’ko, and W.M. Fawley, Phys. Rev. ST-AB. 14, 010701 (2011) Science Outlook and R&D Issues for an XFELO

  6. An XFELO produces fully coherent, temporal as well as transverse, x-ray pulses Science Outlook and R&D Issues for an XFELO

  7. Example Parameters Electron beam: Energy 6 GeV Bunch charge ~ 25-50 pC low intensity Bunch length (rms)  1 (0.1 ps)  Peak current 20 (100) A Normalized rms emittance 0.2 (0.3) mm-mr, rms energy spread ~ 210-4 Constant bunch rep rate @ ~1 MHz Undulator: Lu= 60 (30) m,lu ~2.0 cm, K=1.0 – 1.5 Optical cavity: 2- or 4- diamond crystals and focusing mirrors Total round trip reflectivity > 85 (50) % XFELO output: 5 keV w 25 keV Bandwidth: Dw/w ~ 1 (5) 10-7; rms pulse length = 500 (80) fs # photons/pulse ~ 1109 Rep rate ~ a few MHz (..) indicates short-pulse mode for relaxed tolerances Science Outlook and R&D Issues for an XFELO 8

  8. XFELO applications High resolution spectroscopy Inelastic x-ray scattering Mössbauerspectroscopy 103/pulse, 109/sec Moessbauergs (14.4 keV, 5 neV BW) X-ray photoemission spectroscopy Bulk-sensitive Fermi surface study with HX-TR-AR PES X-ray imaging with nm resolution Smaller focal spot with the absence of chromatic aberration Other talks in this workshop Science Outlook and R&D Issues for an XFELO

  9. An Ultimate X-Ray FEL Facility • A grand facility employing XFELOs and high-gain XFELs can be envisaged in which an XFELO serves as the seed for a high gain amplifier Science Outlook and R&D Issues for an XFELO

  10. Accelerator Technology Issues • Basic configuration: low emittance gun + SCRF Linac • Gun • LCLS low charge operation demonstrated that the beam quality requirements for single pulse can be met • High rep rate (> MHz) guns have been constructed and are being tested • Cost saving R&D in super-conducting linac • High Q0 (10101011) to save the refrigerator cost • Solid state RF power • One or more recirculation passes could reduce the cost • Use ERL but in accelerating phase Science Outlook and R&D Issues for an XFELO

  11. Accelerator technology: Injector • DC gun for ERL(KEK/JAEA, Cornell) and the low frequency RF gun for NGLS will meet the XFELO requirements C. Papadopoulus, et al., MOPD31 N. Nishimori, et al, WEPD51 Science Outlook and R&D Issues for an XFELO

  12. Science Outlook and R&D Issues for an XFELO

  13. Using ERL loops for additional acceleration: KEK/JAEA project lrf/2 path-length changer 6 (7) GeV 3GeV ERL in the first stage XFEL-O in 2nd stage Science Outlook and R&D Issues for an XFELO

  14. Challenges for X-ray Optical Elements • Diamond is best: high reflectivity and thermo-mechanical properties • Heat load dynamics: Can DEBragg< 1 meV maintained? • Radiation damage issues • Stability of optical elements • Angular <10 nr & position< 3 mm @ 1 kHz BW • Precision stages • Surface qualities • Reflectivity and wavefront distortion • Quality of grazing incidence focusing mirrors Science Outlook and R&D Issues for an XFELO

  15. Reflectivity of TISNCM* Diamond was measured to be >98% at the APS *Technological Institute for Superhard Novel Carbon Materials, Russia Science Outlook and R&D Issues for an XFELO 16

  16. Grazing Incidence, Curved Mirror JTEC Developing a technique combining elastic emission machining (slow) and electrolytic in-process dressing (fast) to fabricate a smooth surface to <nm height error and 0.25 mrad figure error Issue: large difference in the sagital and meridional depths Such mirrors are sought after by “every body” in SR business Other ways of focusing Curved crystal surface, CRL,.. H. Mimura, et. al. RSI 79, 083104, 2008 Science Outlook and R&D Issues for an XFELO

  17. Further opportunities for an XFELO: Extreme temporal coherence length from sub-mm km108 m(spontaneous emission limit)! • The XFEL-O output pulses are copies of the same circulating intra-cavity pulse • The pulse spacing needs to be stable to maintain a good overlap with electron beams: DT < 3 mm • If the pulse spacing T can be controlled far more accurately, DT <0.01l/c, the spectrum of XFELO output becomes a comb • The extreme-stabilized XFEL-O may establish an x-ray-based length standard and have applications in fundamental physics—quantum gravity, wavefunction collapse of mesoscopic system Science Outlook and R&D Issues for an XFELO

  18. Cavity stabilization by tying one of the comb lines to a nuclear resonance line(B.W. Adams and K.-J. Kim, to be published) Find the signal maximum by changing the cavity length ~1 Å and lock to it Science Outlook and R&D Issues for an XFELO

  19. Charge to Workshop • Identify the prospects and importance for sciences that can be done by XFELO • Are there scientific areas not discussed in this workshop? How can we find them? • Identify the technological challenges for constructing an XFELO, in accelerator and in x-ray optics. • Can the challenges be addressed by an R&D program, say, for 5 years? • Comment on the scientific prospects and technological challenges for an extreme-stabilized XFELO Science Outlook and R&D Issues for an XFELO

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