Birth of the X-Ray Laser and a New Era of Science Joachim Stohr http://www-ssrl.slac.stanford.edu/stohr.
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Birth of the X-Ray Laser and a New Era of Science Joachim Stohr http://www-ssrl.slac.stanford.edu/stohr Overview of “Light Sources” J. Ullrich, A. Rudenko, R. Moshammer Ann. Rev. Phys. Chem. 63, 635 (2012) SLAC operates two world class x-ray user facilities LCLS SSRL storage ring electron beam x-ray beam LCLS: the world’s first x-ray free electron laser Injector electron beam 1km linac 14GeV AMO SXR Undulator hall XPP Near-hall: 3 stations XCS x-ray beam CXI Far-hall: 3 stations MEC X-Rays from SSRL X-Ray pulse length determined by electron bunch length Bunch width ~ 100 ps Bunch spacing 2 ns beam line x-ray pulses 100 ps width/pulse 106 x-rays/pulse 500 MHz rate Can make shorter pulses (~ 1ps) at great loss of intensity What is a x-ray free electron laser, anyway? Optical laser X-ray free electron laser 10 fs width/pulse 1012 photons/pulse 120 Hz rate • bound electrons in atoms - transitions between discrete states • amplification through stimulated emission • fixed photon energy around 1 eV • compact size • free electrons in bunch - radiation in periodic H-field • amplification through electron bunch orders in its own radiation (SASE) electron bunch orders in imposed radiation (seeding) • tunable photon energy > 1000 eV • very large size X-Rays can see the invisible --provide static and dynamic information-- “Imaging” Photoemission X-ray absorption X-ray emission Diffraction EXAFS X-ray magnetic dichroism spin pol. photoemission X-FEL Science or The Need for Speed ! The size and speed of things: -- from “structure” to “function” -- The speed of things – the smaller the faster macro molecules molecular groups atoms “electrons” & “spins” the technology gap optical laser pulse Light pulses can be used to capture (or beat) all motion… • Atoms: Speed of sound: 1 nm / 1 ps • Electrons: Fermi velocity: 1 nm / 1 fs • Light: Speed of light: 1 nm / 3 as Three Strategic Science Areas of LCLS Biological structure and function Chemical structure and function drug design, health energy, environment Material structure and function information technology Mn4CaO5 cluster Atoms Atoms/Electrons Atoms/Electrons/Spins Biological Structure: X-Rays are the key tool (courtesy H. Chapman) Cumulative number of structures in the PDB ribosome myosin Structures virus nucleosome antibody transfer RNA actin hemoglobin myoglobin 2011 Year C. Zardecki - PDB C. Abad-Zapatero - Acta Cryst D68 (2012) Femtosecond Protein Nanocrystallography beating the speed of sound with the speed of light Liquid jet atomic structure shape of nanocrystal Nanocrystals (~500nm) contained in water jet - developed at ASU Patterns of single nanocrystals recorded in single, intense and fast <50 fs x-ray shots Atoms move after shot (“speed of sound”) crystal blows up - new crystal for new shot Complete structure from ~1 million shots Chemical structure: Understanding Photosynthesis ( Water Splitting Not Understood ) Fixation ( Carbon Understood ) Has created our atmosphere and ozone layer Only fundamental source of food on earth Has created fossil energy sources (crude oil, coal, gas) Photosystem II: Where Plants Split Water Photosystem II [ ] 1 ms Mn4CaO5 X-ray damage has prevented conclusive structure determination Beat damage with intense, fast pulses Information Technology: Data storage X-Rays have revealed how most advanced magnetic devices switch today 0 200ps 100 nm SSRL LCLS 400ps 600ps 800ps 1 ns Tomorrow’s switching of information “bits” Roadmap for data storage: Magnetic “1” and “0” bits are switched by weak field pulse aided by heat from laser Magnetic “bits” have nanoscale dimensions The dream: magnetic switching by a fast laser pulse All-optical magnetic writing Only works for one material – we do not understand process Need LCLS: nanoscale dimension plus fast timing LCLS is being extended by LCLS-II project Expand capacity and capability New injector plus 1 km linac Two new undulator sources Extended spectral range from 250eV to 18 keV Experimental hall for 6 instruments First light in fall of 2018 Assures international competitiveness (Japan, Germany, Korea, Switzerland)