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Crystallography workshop, Ismailia, Egypt, 2-7 February 2002 - Giuseppe Dalba - University of Trento - Italy. The shorter the wavelength, the greater ...

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ldsegypt2002

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    Giuseppe Dalba Department of Physics, University of Trento - Italy Workshop on Computer Based Crystallographic Teaching Materials Outline

    2. This talk is a primer about Synchrotron Radiation. The educational aspects are preferred to technical topicss and completenessThis talk is a primer about Synchrotron Radiation. The educational aspects are preferred to technical topicss and completeness

    The shorter the wavelength, the greater the resolution for observing small object Electromagnetic Radiation and Structure of matter Synchrotron radiation sources span wide regions of the electromagnetic spectrum

    3. Synchrotron radiation sources span almost the entire electromagnetic spectrumSynchrotron radiation sources span almost the entire electromagnetic spectrum

    Classical mechanism: acceleration of charged particle (for instance, electrons and positrons) Bremsstrahlung: deceleration of high energy electrons in a metal Synchrotron radiation emitted by relativistic charged particles in particle accelerators Cosmic synchrotron radiation Radiation production mechanisms There are two ways to produce synchrotron radiation: X-ray ray tubes Radiation angular distribution in an X-ray tube Charged particles moving in circular motion radiate Synchrotron light from a storage ring Three types of magnetic systems Animation Radiation angular distribution (a) electrons travelling at low speed (b) electrons travelling at relativistic speed (g = (1-v2/c2)-1/2 ? 10000 at ESRF) Synchrotron radiation angular distribution Top view Properties of synchrotron radiation High collimation Polarization E Temporal structure t I High flux Brillance Wide spectrum Bending magnets Wigglers Wigglers Bending Magnets Wigglers Undulators BM ID ? wavelength flux Spectral distributions of different sources Intensity and spectral range of synchrotron radiation sources are several order of magnitude greater than those of rare gas discharge lamps. The greatest concentration of laboratories in matter Physics in Europe ESRF - Grenoble Als-Nielsen Introduction to Modern X-ray Physics Synchrotron storage ring Spectrometer Monochromator Undulator 300 m Focusing device 10 m 2 m 30 m From the magnetic device to the experimental station 5 m The Grenoble machine The European Synchrotron Radiation Facility (ESRF) ESRF beamlines Each beamline hosts one or more specialized experimental stations ESRF Detector Sample X-rays Small angle scattering angle I X-rays Detector Sample I angle Diffraction Inelastic scattering Detector X-rays Energy shift Detector Sample X-rays Absorption X-rays Sample I wavelength Fluorescence Imaging Detector X-rays Elemental analysis 8800 0.0 8800 9000 9200 9400 9600 9800 10000 1.0 2.0 E (eV) 9000 9200 9400 9600 9800 10000 Energy m Detector Laue Diffraction Synchrotron light: ESRF Laue pattern of a crystal of metabolic enzyme isocitrate deydrogenase NSLS Brookhaven Time resolved crystallography: Exposure time: 10 ms Biology The functions of the life molecules, like proteins and nucleic acids, depend on three-dimensional atomic structure. For instance the knowledge of viruses has allowed the preparation of anti-viruses compounds to be prepared Diffraction is the technique to study the molecular structure of biological Film of molecular process The myoglobine molecule a CO molecule nteracting with a myoglobine molecule iron site The collection of precise information on the molecular structure of chromosomes and their components can improve the knowledge of how the genetic code of DNA is maintained and reproduced Reconstruction of the molecular structure of nucleosome with a resolution of .2 nm The life construction plan reported by the genetic code Study o materials under extreme conditions In laboratory it is possible to reach pressures of some milions of atm (100 Gpa) comparable with those present in the Earth nucleus Diffusion spots Diffuse scattering in crystalline materials Unexpected diffusion peaks appear in a diffraction pattern of a non perfect crystalline structures. Diffraction spots Synchrotron light - Springer Verlag The structure factors for pure silica gel samples treated at different temperatures starting from the as-prepared to 1200oC. Diffuse scattering in amorphous materials WAXS measurements can be carried out in short time at various conditions of temperature and pressure. Microtomogram of illiac crest bone from a female patient undergoing haemodialysis. The three images are of biopsies taken at three ages, 24, 27 and 32 years. The severe loss of bone mass is apparent. The ratios of bone volume to total volume fell from 29.6% to 23.7% between the ages of 24 and 32 X-ray ray micro-tomography Coronary Angiography

    27. imaging of the coronaric veins resorting to a simple injection of a contrast liquid in the arm veinimaging of the coronaric veins resorting to a simple injection of a contrast liquid in the arm vein

    The brilliance versus time Bibliography Synchrotron light, Springer-Verlag Compact Disk 2000, ISBN 3540148884. 100 anni di Raggi X, 2001, P. Fornasini, Università dgli Studi di Trento Dipartimento di Fisica, Compact Disk, 2001 http://www.elettra.trieste.it (web site of Italian Synchrotron Light Source, named ELETTRA, Trieste Italy)) http://www. sesame.htm http://www.esrf.fr (web site of European Synchrotron Radiation Facility, Grenoble, France) http://www.lbl.gov/MicroWorlds/ALSTool/ (web site of theAdvanced Light Source) Time Resolved Macromolecular Crystallography, Physics Today, 54 (2001) 33. Mr. Tompkins in paperback by G. Gamow J Als-Nielsen, Des McMorrow Elements of modern X-ray Physics Wiley Sicily Milan Cagliari Venice Florence Naples Italy Sardinia Trento Palermo Rome Emission from an x-ray tube Charged particles in accelerated motion radiate Storage ring Bunch of relativistic electrons Light Bending magnet N S Storage ring Angular divergence Q ? m0c2/E = 1/g rad e- Electron orbit v ? c Q ? 1/g rad The beam collimation is defined as the photon opening angle Q ? 1/g rad. For GeV electrons Q can be smaller than 0.1 m rad. It means that at 100 m from the source the vertical dimension of the beam, h, is 1 cm. Horizontally the beam opens as a fan. A very thin sheet of light spreads out from the orbit on the orbital plane. h Properties Wiggler N S N N S K/g S N S N S N N S N S N S 1/g Top view Side view Radiation from a wiggler: the horizontal opening is higher than the vertical one: K is around 20 for a wiggler Properties Storage ring S Undulator N S N S N S S N S N S N N S N S N S Top view Side view Radiation from an undulator: typically N = 50 Storage ring Properties Collimation, Why? An X-ray beam at the ESRF facility Are X-rays visible? Properties Flux of synchrotron light . 1012 1013 1014 1015 lc 105 104 Photon flux (Photons / s ·m rad (0.1% band pass)) l (Å) 102 101 100 10-1 103 EC Spectral distribution of synchrotron light . EC Spectra ? Spectral distribution curves from bending magnets of some synchrotron light facilities ESRF is the European facility located in Grenoble, ELETTRA, the Italian facility is located in Trieste. Critical energy Properties Definition of Brilliance The brilliance represents the largest number of photons per second in a given band pass that can be focused by a perfect optics onto the unit area at the sample W Image N (Photons/sec) Source A (mm2) e- Focusing device Mirror Spectra Spectral radiation distribution Properties Brilliance Comparison of brilliances between synchrotron and conventional x-ray sources Properties The relativistic effect on the vertical opening of the light beam Properties

    44. A popular scientific text by the famous physicist Nobel prize Gamow. It’s only a matter of kinematics, i.e. of relative motion between a moving observer and the observer still in the lab reference frame. From the lab observer the source velocity u and the x-ray component od light speed have to be summed. So the angular opening of the emitted light is smaller.A popular scientific text by the famous physicist Nobel prize Gamow. It’s only a matter of kinematics, i.e. of relative motion between a moving observer and the observer still in the lab reference frame. From the lab observer the source velocity u and the x-ray component od light speed have to be summed. So the angular opening of the emitted light is smaller.

    Electron bunches, their trajectory and synchrotron radiation in three different magnetic devices: bending magnets, wigglers, undulators Insertion devices Storage ring Q Q 2Q R t t+Dt Dt Q = 1/g Fourier relationship: Dt ?Dw ? 2p Why a so wide emission spectrum? ? Low wavelengths An undulator as seen in the laboratory reference system l0 = L/n Magnetic pole periodicity L n = number of periods Spectrum E = 1.5 GeV I = 100 mA 1013 1012 1011 10 102 103 104 105 Wiggler 1.85 T Bending magnet Wiggler 6 T Photon energy (eV) Photon Flux By decreasing the curvature radius of the electron trajectory the spectrum shifts to higher photon energies Ec=k/R ID comparison N S N S N S N S N S N S e- Dt Side view Q ? 1/g (?10-4 mrad) Synchrotron light is spread on the orbital plane as a very thin sheet Angular distribution Electron orbital plane Giuseppe Dalba: Ee (GeV) = 1.5 2.5 4 109 101 1010 108 1011 102 103 104 105 Photon Energy (eV) Photon Flux Dependence of the critical photon energy on the electron energy EC EC EC The on-axis synchrotron light is polarized in the orbital plane The synchrotron light out of the orbital plane has circular components with opposite helicities above and below the horizontal plane. Polarization is exploited for studying magnetic interactions. The difference in absorption in left and right hand circularly polarised light by a solid can be directly related to the ferromagnetic magnetization density (circular dichroism). Polarization Orbital plane Circularar polarization Synchrotron light - Springer Verlag Properties Synchrotron light - Springer Verlag Linear polarization Time structure Time pulsed emission is interesting for studying rapid reactions Properties Light pulses Synchrotron-light for Experimental Science and Applications in the Middle East Eleven countries have so far joined the project. These are: Armenia, Cyprus, Egypt, Greece, Iran, Israel, Jordan, Morocco, Oman, Palestinian Authority, and Turkey. The SESAME Project aims to establish the Middle East's first major international research center as a cooperative venture by the scientists of the region The project is being developed under the umbrella of UNESCO and will be located in Allaan, Jordan (30 km from Amman and 30 km from the King Hussein/Allenby Bridge crossing of the Jordan River. Principle of operation of a bending bending magnet Synchrotron light Springer Verlag Principle of operation of a bending magnet Synchrotron light, ESRF
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