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X-Rays and Materials

X-Rays and Materials. A Vision of the Future. Joachim Stöhr Stanford Synchrotron Radiation Laboratory. The big $$$ Picture: US Gross Domestic Product: $10 Trillion. In $$$$$'s Information technology: 800 Billion Chemical Industry: 400 Billion

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X-Rays and Materials

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  1. X-Rays and Materials A Vision of the Future Joachim Stöhr Stanford Synchrotron Radiation Laboratory

  2. The big $$$ Picture: US Gross Domestic Product: $10 Trillion In $$$$$'s Information technology: 800 Billion Chemical Industry: 400 Billion Semiconductors: 80 Billion Magnetic materials: 25 Billion Pharmaceutical industry: 220 Billion Biotech Industry: 30 Billion Modern materials are complex – studies require sophisticated techniques

  3. Present: Size > 0.1 mm, Speed > 1 nsec Future: Size < 0.1 mm, Speed < 1 nsec Ultrafast Nanoscale Dynamics

  4. Growth of X-Ray Brightness and Magnetic Storage Density

  5. Why X-Rays? - Chemical Sensitivity Core level shifts and Molecular orbital shifts Stöhr et.al

  6. C C Normal Incidence Grazing Incidence C F C O C F Polarization Dependence Normalized Intensity (a.u.) F8 22°C Photon Energy (eV)

  7. Magnetic Spectroscopy and Microscopy

  8. Real Space Imaging X-Rays have come a long way…… 1895 1993

  9. Photoemission Electron Microscopy – PEEM at ALS The Future: PEEM3 PEEM2 on BL 7.3.1.1 PEEM2 PEEM3 nm nm Resolution 50 nm < 5 nm (1% transmission) Transmission 1% 50% @ 50 nm Resolution Relative photon flux 1 20 Relative Flux density 1 >1000 Source / bend EPU (arbitrary) Polarization

  10. 4.0.3 PEEM3 Microscope • total electron yield imaging • no LEEM mode (as in SMART)

  11. Resolution vs Transmission

  12. s s [010] 2m m Spectromicroscopy of Ferromagnets and Antiferromagnets AFM domain structure at surface of NiO substrate FM domain structure inthin Co film on NiO substrate NiO XMLD Co XMCD H. Ohldag, A. Scholl et al., Phys. Rev. Lett. 86(13), 2878 (2001).

  13. Non Resonant X-Ray Scattering Relative Intensity: 1 Relative Intensity: (hn / mc2)2 hn ~ 10 keV, mc2 = 500 keV

  14. Fe metal – L edge Kortright and Kim, Phys. Rev. B 62, 12216 (2000)

  15. 2 e’ e M Resonant Magnetic Soft X-ray Scattering Fe charge magnetic -XMCD ( 1 ) f = e ' × e - i ( e ' ´ e ) × M F F ( 0 ) n n n n where Fn(i) are complex = f1 + i f2 Note: at resonance f1 = 0 Kortright and Kim, Phys. Rev. B 62, 12216 (2000)

  16. scattering vector q (mm-1) scattering vector q (mm-1) 40 40 20 20 0 0 scattering vector q (mm-1) -20 -20 -40 -40 -40 -40 -20 -20 0 0 20 20 40 40 scattering vector q (mm-1) Incoherent vs. Coherent X-Ray Scattering Small Angle Scattering Coherence length larger than domains, but smaller than illuminated area information about domain statistics Speckle Coherence length larger than illuminated area true information about domain structure

  17. Present Pump/Probe Experiments Laser pulse • Pump: Laser • Probe: delayed photon pulse • Vary the delay between laser and x-ray pulses 50 ps 330 ns X-Ray pulse  Can also produce current pulses

  18. Development of High Energy Physics and X-Ray Sources -- From storage rings to linacs -- SR HEP Storage rings Single pass linacs Free electron lasers (FELs) Energy recovery linacs (ERLs) Single pass linear colliders

  19. X-Ray Brightness and Pulse Length • X-ray brightness determined by electron beam brightness • X-ray pulse length determined by electron beam pulse length Storage ring Emittance and bunch length are result of an equilibrium typical numbers: 2 nm rad, 50 psec Linac Normalized emittance is determined by gun Bunch length is determined by compression typical numbers: 0.03 nm rad, 100 fs Linac beam can be much brighter and pulses much shorter – at cost of “jitter”

  20. SASE gives 106 intensity gain • over spontaneous emission • FELs can produce ultrafast • pulses (of order 100 fs) l

  21. LINAC COHERENT LIGHT SOURCE 0 Km 2 Km 3 Km

  22. Concepts of the LCLS: • Based on single pass free electron laser (FEL) • Uses high energy linac (~15 GeV) to provide compressed electron beam to long undulator(s) (~120 m) – 200 fs or less • Based on SASE physics to produce 800-8,000eV (up to 24KeV in 3rd harmonic) radiation - 1012 photon/shot • Analogous in concept to XFEL of TESLA project at DESY • Planned operation starting in 2008

  23. H Condensed Matter: S typical vibrational period is 100 fs Speed of sound is 100 fs / Å - coherent acoustic phonons 90o spin precession time 10 ps for H = 1 Tesla From Molecules to Solids: Ultra-fast Phenomena Note in quantum regime: 1 eV corresponds to fluctuation time of 4 fs Chemistry & Biology: H2OOH + H about 10 fs time depends on mass and size Fundamental atomic and molecular reaction and dissociation processes Fundamental motions of charge and spin on the nanoscale (atomic – 100nm size)

  24. splitter X-Ray Photon Correlation Spectroscopy Using Split Pulse In picoseconds - nanoseconds range: Uses high peak brilliance sample transversely coherent X-ray pulse from LCLS variable delay sum of speckle patterns from prompt and delayed pulses recorded on CCD Analyze contrast as f(delay time) Contrast

  25. Transmission X-ray Microscope Reconstruction from Speckle Intensities Single shot Imaging by Coherent X-Ray Diffraction Phase problem can be solved by “oversampling” speckle image  5 m (different areas) S. Eisebitt, M. Lörgen, J. Lüning, J. Stöhr, W. Eberhardt,E. Fullerton (unpublished)

  26. Spin Block Fluctuations around Critical Temperature Tc Magnetization Temperature t = (T-Tc) / Tc T < Tc T  Tc T > Tc

  27. Structural Studies on Single Particles and Biomolecules Conventional method: x-ray diffraction from crystal Proposed method: diffuse x-ray scattering from single protein molecule Neutze, Wouts, van der Spoel, Weckert, Hajdu Nature 406, 752-757 (2000) Lysozyme Calculated scattering pattern from lysozyme molecule Implementation limited by radiation damage: In crystals limit to damage tolerance is about 200 x-ray photons/Å2 For single protein molecules need about 1010 x-ray photons/Å2 (for 2Å resolution)

  28. X-Ray Diffraction from a Single Molecules A bright idea: Use ultra-short, intense x-ray pulse to produce scattering pattern before molecule explodes Just before LCLS pulse Just after pulse Long after pulse The million dollar question: Can we produce an x-ray pulse that is short enough? intense enough?

  29. Summary X-FELs will deliver: unprecedented brightness and femtosecond pulses Understanding of laser physics and technology well founded FELs promise to be extraordinary scientific tools Applications in many areas: chemistry, biology, plasma physics, atomic physics, condensed matter physics

  30. The End

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