Introduction to Synchrotron Radiation Frederico Alves Lima International School on Laser-Beam Interactions Centro Nacional de Pesquisa em Energia e Materiais - CNPEM UFRN - Natal, Brazil Laboratório Nacional de Luz Síncrotron - LNLS September 2016 Outline ✓ Tools for structural analysis ✓ History of X-rays ✓ Synchrotron Radiation ✓ LNLS & SIRIUS: Synchrotron Radiation in Brazil Why do we need to study “structure” Structure Dynamics - X-ray crystallography - Laser spectroscopy - electron microscopy - NMR - atomic force microscopy - Time-resolved diffraction & XAS - electron diffraction - Time-resolved PES - X-ray absorption spectroscopy - NMR Manganite: atomic motion coupled by charge and orbital order Graphene Fullerene Layer-selective spin dynamics in Nanotube magnetic multilayers Photosystem II Rotating hydrated Mb molecule What are the length scales involved ? http://www.newgrounds.com/portal/view/525347 The Electromagnetic Spectrum Electromagnetic wave ➟ Light! Orthogonal and alternating electric and magnetic fields that propagate into space. Set of equations describing how electric and magnetic fields are generated and altered by each other and by charges and currents. Maxwell’s equation of electromagnetism James Clerk Maxwell The Electromagnetic Spectrum 700 nm 400 nm X-ray ➟ proper tool to investigate atoms. History of X-rays In the evening of Nov. 8th 1895 Wilhem Röntgen first detected x-rays He found that when running a high-voltage discharge tube enclosed in thick black cardboard which excluded all visible light, in his darkened room, a paper plate covered on one side with barium platinocyanide would fluoresce, even when it was as far as 2 m from the discharge tube. ➟ X-rays! He soon discovered that these ‘x-rays’ also stained photographic plates and latter demonstrated that objects of different thicknesses showed different degrees of transparency. First x-ray photograph of a human hand with a ring… probably from his wife! Synchrotron Radiation We need an extremely bright source of x-rays ➟ Synchrotron F divergence flux brightness Ω F / S ⌦ source area S · Synchrotrons are very bright because the source size and divergence are very small. But why is that? Synchrotron Radiation Accelerated electric charge ➟ electromagnetic radiation In the non-relativistic case, the dominant emission from an electric charge is dipolar. ∆!0 Maxwell’s equation !0 The emitted power and spectrum are proportional do the acceleration, was given by the Larmor formula. Acceleration is usually a function of t, resulting in a certain distribution of the emitted energy. antenna Synchrotron Radiation Decelerated electric charge ➟ Bremsstrahlung radiation (Non-relativistic) charges colliding with a target also emit radiation with a dominant dipolar contribution. X-ray spectrum of a Silver target (anode) as a function of the voltage. Note the different emission lines and also the Bremsstrahlung radiation. X-ray tube Synchrotron Radiation Relativistic limit + acceleration ➟ synchrotron radiation Relativistic electrons can be accelerated by a magnetic F~ = q(E~ + ~v B~ ) field through the Lorentz force ⇥ Emitted radiation cone has an angular opening depending on " 1 the Lorentz factor γ = , that is: ✓ mc2 ⇠ γ ✓ Synchrotron source Synchrotron Radiation: bending magnets Magnetic field used to change the propagation direction of electric charges in movement The critical energy of radiation emitted by bending magnets depends on the energy of the accelerated electrons. Synchrotron Radiation: insertion devices Alternating magnetic poles make electric charges 'wiggle' Wiggler Undulator http://photon-science.desy.de/research/studentsteaching/primers/synchrotron_radiation/index_eng.html Insertion devices in reality How to produce Synchrotron radiation? Synchrotron Radiation Main components: - LINAC: linear accelerator - Booster - Storage ring - Beamlines Where are the synchrotron sources? http://www.lightsources.org/ Synchrotron Radiation: Optics Synchrotron Radiation: stored electrons Stored electrons are in dynamic equilibrium inside the lattice Concrete wall shielding Front-end Bending magnet Insertion device RF cavity restores the energy lost each turn. It also generates a potential well in the storage ring which is responsible for packing the electrons in “bunches”. Synchrotron radiation is intrinsically pulsed Resonant RF cavity Experiments exploiting temporal resolution! X-ray Free-Electron Lasers Resonant condition: The slippage between the electromagnetic wave and a given electron, while the electron advances by one undulator period must be equal to the field wavelength. ➟ ⇥0 2 ⇥rad = 2 (1 + Keff /2) Micro-bunching 2γ Keff =0.934λradBeff SASE - Self Amplified Spontaneous Emission Long undulators are needed as the saturation of the micro-bunching effect is a function of the length. X-ray Free-Electron Lasers The result is a tremendous increase in the peak brilliance! X-ray FEL’s generate laser-like radiation: coherent x-rays and with ultrafast temporal duration (femtosecond pulses!) Ultrafast dynamics Single-molecule diffraction Coherent imaging/scattering Investigation of Small quantum systems Non-linear X-ray Matter under extreme conditions et cetera Completely new science could be done at XFELs! Interaction of X-rays with Matter How does electromagnetic radiation interact with matter? - Scatter - Diffraction - Absorption - … We make use of these phenomena to design experiments that help us to elucidate the properties of matter. - Small/Wide Angle X-ray Scattering - X-ray Diffraction - X-ray Absorption Spectroscopy Structural characterization using x-rays Scattering sample Int q Structural characterization using x-rays Diffraction �istal histidine ligand heme �istal histidine proximal histidine ligand heme proximal histidine http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/bragg.html Structural characterization using x-rays Absorption X-RAYS 0 An x-ray photon is absorbed by an atom ejected an electron, I / I which then propagates in the material using the excess energy. 1 Z 1.4 1.2 1.0 0.8 0.6 Norm. [a.u.]µ(E) 0.4 0.2 7.105 7.110 7.115 7.120 0.0 7.1 7.2 7.3 7.4 7.5 7.6 X-ray energy [keV] Synchrotron Radiation Around the World Brazil has one such light source operating since 1997! CNPEM - LNLS & SIRIUS LNLS: research and development using LNNano: research on nano(materials) synchrotron radiation CTBE: research on ethanol production LNBio: research on biosciences SIRIUS% Synchrotron Radiation LNLS Synchrotron Radiation in Brazil Laboratório Nacional de Luz Síncrotron: LNLS - One out of the 4 labs (LNLS, LNNano, LNBio & CTBE) of the CNPEM - 18 beamlines operating http://lnls.cnpem.br/ LNLS User community Other States São Paulo Other countries In 1997 In 2013 100 proposals 400 proposals 180 users 1200 users 18 beamlines 7 beamlines http://lnls.cnpem.br CNPEM: areas of actuation - Synchrotron Light Source operation and development - Material’s science - Molecular biology - NMR spectroscopy - Mass spectrometry - Electron microscopy & Scanning probe microscopy - Mechanical microfabrication - Chemical synthesis - Engineering (scientific instrumentation) - Bioethanol research - etc Summary ✓ CNPEM is a multi-disciplinary research center with cutting edge equipment and staff ✓ Structure & dynamics are important to determine how materials function ✓ X-rays are suitable to study atomic scale ✓ Synchrotron light ➟ indispensable scientific & technologic tool ✓ To produce SR we need accelerated relativistic charges (e-) ✓ The SR has very special characteristics - Hight brightness - Very collimamated - (Almost) continuum spectrum Thank you.