Synchrotron Radiation: A Future Retrospective Symposium in Honor of Iran Thomas May 2003
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Synchrotron Radiation: A Future Retrospective Symposium in Honor of Iran Thomas May 2003 Sunil K.Sinha UCSD/LANL Where were we in 2003? • Over 8000 users at 4 DOE Light Sources Methods of obtaining structures with X-Rays • Scattering--beam can be large, but measures spatially and time-averaged snapshots of F.T. of instantaneous correlations ( no phase information) • EXAFS/NEXAFS/DAFS ( local order) Protein Crystallography Previous and Current Accomplishments • Structure of Physisorbed and Chemisorbed Layers and 2D Phase Transitions. • Liquid Crystal Phases and Phase Transitions • Structure of Nanowires, Quantum Dots, Magnetic Dot and Hole Arrays. • Structures of Surface Reconstruction, Thin Films, Liquid Surfaces, Confined fluids • Magnetic multilayers and interfaces New types of Charge, Spin and Orbital Ordering and Polarons in Complex Oxides: Manganites, Hi-Tc S/C, etc. Imaging ---limited by size to which we can focus beam down to. Depends on Source Brilliance. Current limit 0.1 microns (Hard X-Rays), 35 nm (Soft X-Rays) Microbeam studies of Residual Strain in Materials • Schematic drawing of an x-ray microbeam experiment. Curved mirrors focus the synchrotron x rays down to a diameter of less than one micron on the sample. The microbeam penetrates each layer of the sample, and an area detector measures the directions of the scattered x rays. Here, the sample consists of a roll-textured nickel substrate covered with two epitaxial films: a buffer layer and a superconductor (YBCO). The detector image provides a grain-by-grain description of the atomic structure, orientation, and strain of each layer. Schematic of a scanning x-ray nanoprobe using zone plate focusing. Example----Element specific Imaging of Cells What is exchange bias? W.H. Meiklejohn, C.P. Bean, Phys Rev., 105, 904(1957). J. Nogués, Ivan K. Schuller, J. of Magn. Magn. Mater., 192, 203 (1999). Small sense current flows through bit • MR=37% • Write at 4mA digit line and 3.2mA bit line current Isolation Transistor “ON” bit line current produces easy axis field digit line current produces hard axis field Isolation Transistor “OFF” “Write Mode” “Read Mode” Random-field, domain state, etc., Super exchange (AF-coupling) Frustrated super exchange (AF-coupling) models+1 -1 -’ve HE +’ve HE HCF HCF 10nm U. Nowak et. al., J. Magn. Magn. and Mater., 240, 243 (2002). A.P. Malozemoff, J. Appl. Phys., 63, 3874 (1988). Phase Contrast Imaging (B.Lai et al./APS) Sample (1-10 mm) can be in air, water, or any low-absorption substance. Detector system f scintillator 0.5 m X-rays f x y z Motion stages Experimental set-up CCD/video Lens x y Wah-Keat Lee et al./ APS QuickTime™ and a Motion JPEG A decompressor are needed to see this picture. X-ray Photoemission Spectroscopy • Energy Bands and Fermi Surfaces of important materials -XPES/SPXPES • Symmetry of S/C Order Parameter and Electron Phonon coupling in Hi-Tc S/C Metal Clusters and Magnetism; From Atoms to Solids (Nora Berrah/ALS) Electrons Mott Scattering Metal Clusters and Magnetism Mott Polarimeter Detection •Measure the spin component parallel to the photon •Electron emitted perpendicularly to the photons, at 45 with respect to the storage ring plane. IXS measures S(q,) to ~2meV resolution (t≤ ps.) • Phonons in Liquids, Glasses, Quantum Crystals, Semiconductors, Metals • Electronic Excitations in metals, Hi-Tc Oxides, Spin-Peierls Chains, Mott Insulators Photon Correlation Spectroscopy coherent beam sample detector X-ray speckle pattern from a static silica aerogel X-Ray Photon Correlation Spectroscopy (XPCS)--measures time scales greater than ms. Dynamics of Colloids, Liquid Surfaces Pump-Probe Expts.---measures response on time scales ns. or greater. J.Stohr, A.Scholl et al./SSR Photoconductive switch Time resolved probe <100 ps resolution Sample Deposition -sputter deposition (CXRO) -e-beam evaporation (PEEM) Conducting wire Waveguide Structure - photo-lithography, lift-off (UCB microlab) Magnetic Cells Patterning -Focused Ion Beam (FIB) etching (NCEM) Current 10 m Substrate: GaAs Ground plane Waveguide: 200 nm Cu GaAs 10 m waveguide H Pattern: 20 nm Co90Fe10 Gradient image Movie H XMCD image 1 m Time X-Ray Waveguides • Capable of focusing hard X-Ray beam down to <50nm • In 1- or 2-D Geophysics and Environmental Science • Diamond Anvil Cell coupled with small bright beams enabled studies of structure (phases).dynamics (Equation of State) of minerals in earth’s mantle and core; new phases of Hydrogen,ice, etc. • Fluorescence Microtomography yielded information on transfer of elements into environment, etc. Ultimate Goal Can we image actual atoms (and maybe electrons) in real space and time? Why go lensless? (Courtesy of Janos Kirz) • A technique for 3D imaging of 0.5 – 20 µm isolated objects • Too thick for EM (0.5 µm is practical upper limit) • Too thick for tomographic X-ray microscopy (depth of focus < 1 µm at 10 nm resolution for soft X-rays even if lenses become available) • Goals <10 nm resolution (3D) in 1 - 10µm size biological specimens (small frozen hydrated cell, organelle; see macromolecular aggregates) Limitation: radiation damage! • 2 nm resolution in less sensitive nanostructures (Inclusions, porosity, clusters, composite nanostructures, aerosols…) eg: molecular sieves, catalysts, crack propagation Image reconstruction from the diffraction pattern •Lenses do it, mirrors do it – but they use the full complex amplitude! •Recording the diffraction intensity leads to the “phase problem”! •Holographers do it – but they mix in a reference wave, need very high resolution detector or similar precision apparatus •Crystallographers do it – but they use MAD, isomorphous replacement, or other tricks (plus the amplification of many repeats) “Oversampling”: Non-crystals: pattern continuous, can do finer sampling of intensity Finer sampling; larger array; smaller transform; “finite support” (area around specimen must be clear!) 5/23/2016 Miao thesis 30 Reconstruction Equations can still not be solved analytically Fienup iterative algorithm Reciprocal space •Positivity of electron density helps! 5/23/2016 Impose diffraction magnitudes Miao thesis Real space Impose finite support 31 DIFFRACTION IMAGING BY J. MIAO ET AL • From Miao, Ishikawa, Johnson, Anderson, Lai, Hodgson PRL Aug 2002 • Diffraction pattern taken at 2 Å wavelength at SPring 8 • Both levels show because the depth of focus is sufficient • SEM image of a 3-D Ni microfabricated object with two levels 1 µm apart • Only top level shows to useful extent 5/23/2016 • 2-D reconstruction with Fienup-type algorithm • Resolution = 8 nm (new record) from Howells 32 MIAO ET AL 3-D RECONSTRUCTIONS • Miao et al 3-D reconstruction of the same object pair • a and b are sections through the image • c is 3-D density • Resolution = 55 nm JCHS 7 Successful reconstruction of image from soft X-ray speckle alone. SEM Image X-ray reconstruction 50 nm diameter Gold Balls on transparent SiN membrane. No “secondary image” was used Approximate object boundary obtained from autocorrelation fn. *How to make an isolated object ? Use AFM to remove unwanted balls. He, Howells, Weierrstall, Spence Chapman, Marchesini et al. Phys Rev B In press. 03, Acta A.59, 143 (2003) . I.K. Robinson et al. gold nanocrystals 7.5 KeV beam at the APS 5/23/2016 PRL 87, 195505 (2001) 35 New apparatus: Diffraction patterns from yeast cells 5/23/2016 D. Shapiro et al., Stony Brook 36 Rapid development of accelerator technology, laser technology, XRay Physics and Scientific Knowledge will usher in a Revolution over the next 2 decades. In the Decades after 2003…. Upgraded Rings,LCLS,LUX,CIRCE,TJFEL XFEL • Brilliances increase by 3-12 orders of magnitude • Femtosecond X-Ray pulses/attosecond pulses • Total transverse coherence • Photon degeneracies go from 0.4 to 1010 •Presented to BESAC 10-Oct-2000 Femtochemistry •Critical Decision 0 approved 13-June 2001 Science Assessment Nanoscale Dynamics in Condensed matter t= t=0 Atomic Physics Aluminum plasma classical plasma Plasma and Warm Dense Matter G =1 G =10 dense plasma G =100 high density matter 10- 4 Program developed by international team of scientists working with accelerator and laser physics communities “the beginning.... not the end” 10-2 1 10 2 10 4 Density (g/cm-3) Structural Studies on Single Particles and Biomolecules FEL Science/Technology • Atomic resolution structures known for few mammalian membrane proteins! • Collect many single molecule diffraction patterns from fast xray pulses, and reconstruct? • Lysozyme explodes in ~50 fsec • R. Neutze et al., Nature 406, 752 (2000) Single molecule imaging? FEL Interaction Electron slips backwards one wavefront per undulator period Undulator Seed Ebeam laser log (power) Saturation Distance Electrons are bunched under the influence of the light that they radiate. The bunch dimensions are characteristic of the wavelength of the light. High-Harmonic Generation Noble Gas Jet (He, Ne, Ar, Kr) 100 J - 1 mJ XUV @ 3 – 30 nm @ 800 nm h = 10-8 - 10-5 Propagation Recombination 0 b Ionization Energy -Wb XUV Laser electric field x High Gain Harmonic Generation Method to reach short wavelength FEL output from longer wavelength input seed laser. Input seed at 0 overlaps electron beam in energy modulator undulator. Modulator is tuned to 0. Electron beam develops energy modulation at 0. Energy modulation is converted to spatial bunching in chicane magnets. 3rd harmonic bunching is optimized in chicane. Electron beam radiates coherently at 3 in long radiator undulator. Radiator is tuned to 3. Cascaded HGHG Output at 30 Output at 90 Final output seeds 2nd stage seeds 3rd stage at 270 Input seed 0 1st stage 2nd stage 3rd stage •Number of stages and harmonic of each to be optimized during study. •Factor of 10 – 30 in wavelength is reasonable without additional acceleration between stages. •Seed longer wavelength (100 – 10 nm) beamlines with ~200 nm harmonic from synchronized Ti:Sapp laser. •Seed shorter wavelength (10 – 0.3 nm) beamlines with HHG pulses. MIT X-ray Laser Concept Main oscillator Seed laser UV Hall Fiber link synchronization Pump laser Seed laser X-ray Hall Pump laser Undulators 100 nm Injector laser 30 nm Undulators 1 nm 10 nm 0.3 nm 0.3 nm SC Linac 1 GeV 2 GeV SC Linac 0.1 nm 4 GeV 10 nm Upgrade: 0.1 nm at 8 GeV 3 nm 1 nm Undulators Seed laser Nanometer Hall Pump laser HISTORY of ADVANCES in ULTRASHORT PULSE DURATION SHORTEST PULSE DURATION 10ps Nd:glass Nd:YAG Dye S-P Dye rotation Nd:YLF Diode 1ps SOLID-STATE REVOLUTION CW Dye vibration Color Center 100fs Cr:LiS(C)AF Er:fiber CPM Dye DYE LASER BREAKTHROUGHS Nd:fiber Cr:forsterite w/Compression 10fs Cr:YAG Ti:sapphire 1fs1965 1970 1975era: 1980 attophysics 1985 1990 1995 2000 “new” YEAR First laser 2005 Vienna Saclay/FOM First passive modelocking 100as atomic unit of time 24 as 10as 1970 1975 1980 1985 YEAR 1990 1995 2000 2005 electronic BREAKING THE fs BARRIER Uncertainty Principle: t need bandwidth !! 100 nm (50 THz) 700 time 750 800 850 900 wavelength (nm) 100 as 5,000 THz !!! Control phases of field e.g. mode-locked Attosecond metrology 950 MEASURING ULTRASHORT PULSES autocorrelation: determine I(t). (x) Criteria: delay line (2), (3) • Prism nonlinear media, e.g. A() PMT • adequate peak power 2 time BS (2) A t t dt NL interferometric techniques: complete determination of E,f. FROG, TAPOLE, SPIDER, etc. These techniques are applicable throughout the visible and near IR and UV. ATTOSECOND SIDEBAND CROSS-CORRELATION e energy HHG HHGphotoionization + fundamental H17 electrons H13 gnd sidebands are XUV+o cross-correlation. scan delay between XUV and o . amplitude or energy modulation. analysis is model dependent. TRAIN of ATTOSECOND PULSES sideband amplitude P. M. Paul et al., Science 292, 1689 (2001) -4 -2 0 delay (fs) 1 TRAIN of ATTOSECOND PULSES P. M. Paul et al., Science 292, 1689 (2001) • analysis shows the formation of a train of 250 as pulses. GENERATION of a ‘SINGLE’ ASEC PULSE M. Hentschel et al., Nature 414, 509 (2001) These enabled: • Creation and Study of Dense Warm Plasmas • Multi-photoionization studies, “Hollow Atoms” • Above Threshold Ionization (ATI) Studies in X-ray regime • Diffraction, EXAFS, PES, Pump-Probe Studies of Clusters. • Photodissociation of molecules • Laser Excited, Aligned or Oriented Atoms • EXAFS,NEXAFS, Photoemission on fs timescales. So (maybe) we will have …. • Completely understood High-Temperature superconductivity and strongly correlated systems. How gaps evolve with time at phase transitions, how inhomogeneous phases evolve, etc. • Understood the relation between exchange bias, magnetotransport and interface properties, understood dynamics of domain switching, spatial and dynamical behavior of spin injection into semiconductors. • Understood Glasses and the Glass Transition • Mapped out energy bands, collective electronic and spin excitations in solids. • Solved the detailed structure of non-crystallizable proteins, and understood the relations between structure, dynamics and function; understood Protein folding. and • Understood in exquisite detail what the atoms do during structural phase transitions,shock wave induced phase changes, pressure-induced amorphization, etc.--strain propagation, bond stretching, bond-breaking, transient structures, melting and recrystallization, etc. • Characterize non-linear excitations in solids • Create, and test theories of warm dense plasmas and • Characterize and make 2D and 3D nanostructures with X-ray nanolithography • Able to exercise quantum control over chemical reactions, excited states of atoms nad molecules • Trap atoms and create BE condensates, “crystals”, etc. on nm lengthscales and study their interactions and study ultrafast perturbations