Accelerator Physics. Lecture 13. Synchrotron Radiation Basics Free Electron Laser Applications + Facilities. Accelerator Physics WS 2012/13

Transcription

1 Accelerator Physics Lecture 13 Synchrotron Radiation Basics Free Electron Laser Applications + Facilities 1

2 Synchrotron Radiation Atomic Physics Chemistry (Micro-)Biology Solid State Physics Medical Research Wavelengths: Infrared to X-ray

3 Generations of Synchrotrons Brilliance K>>1 3

4 European Synchrotron Radiation Facility (Grenoble) 4

5 Swiss Light Source (Schweiz) 5

6 DESY Synchrotron Complex 6

7 DESY HASYLAB Beamlines for experiments shutdown 01 7

8 DESYTitel PETRA 3 Biggest monolithic concrete plate in the world 8

9 Bragg Scattering in Crystals Regular structure (crystal) Monchromatic light Diffractive Pattern 9

10 Summary of Facilities ANKA (Angströmquelle Karlsruhe) Advanced Photon Source in den USA NSLS (National Synchrotron Light Source) am Brookhaven National Laboratory, Long Island, USA OPTIVUS (Loma Linda University Medical Center in Californien)[1][] USA DESY (Forschungszentrum Deutsches Elektronen-Synchrotron) Diamond (Diamond Light Source) South Oxfordshire, UK Elektronen-Stretcher-Anlage (ELSA) Universität Bonn [3] CERN (frz. Conseil Européen pour la Recherche Nucléaire, das Europäische Kernforschungslabor) GSI (Gesellschaft für Schwerionenforschung mbh, Darmstadt) HIT (Heidelberger Ionenstrahl Therapie, Universitätskliniken Heidelberg) COSY (Cooler Synchrotron im Forschungszentrum Jülich) BESSY (Berliner ElektronenSpeicherringgesellschaft für SYnchrotronstrahlung) DELTA (Dortmunder Elektronen Speicherring Anlage) ESRF (European Synchrotron Radiation Facility) in Grenoble ELETTRA (ELETTRA Synchrotron Light Laboratory) in Triest, Italien MAMI (Mainzer Microtron [4]) Johannes Gutenberg-Universität, Mainz SOLEIL (Synchrotron SOLEIL) in GIF-sur-YVETTE, bei Paris, Frankreich SPring-8 (Super Photon ring-8 GeV) in Japan SLS (Swiss Light Source) am Paul-Scherrer-Institut in der Schweiz CLS (Canadian Light Source) SSLS (Singapore Synchrotron Light Source an der National University of Singapore) SESAME (Synchrotron-light for Experimental Science and Applications in the Middle East) in Allaan, Jordanien 10

11 Soleil, France 11

12 Main Principle 1

13 Wiggler / Undulator 13

14 Synchrotron Radition Calculation Moving electron bunch: β= r From Maxwell Equations: 1 μ ν A = j c ν μ r Solved using retarded Green-Functions Lienard-Wiechert potential: r ' o q Φ= r r ' ( r r ' ) β A= βφ E.M. Fields: = E A Φ t = B A 14

15 Synchrotron Power Moving electron bunch: β= r Poynting Vector S far = c E xb Radiated power per solid angle r a = ( r r ') d P = r r ' ( r r ' ) S far d Ω r ' o integration q β ) P= ( β β 3 3 c (1 β) in magnetic field: β β Radiation power in ring accelerator: 4 q E P= 4 3(m c ) R R = radius 15

16 Synchrotron Energy Spectrum via Fourier Transformation of time dependece: de q a ω = 3 dω dω 3π c ( 1 +Θ γ ) [ (γ Θ ) K / 3 (ξ) + K 1/ 3 (ξ) 1+ γ Θ ] ω = frequency Θ = radiation angle K ν = modified Bessel function r 3 / ωa 1 ξ= +Θ 3c γ ( ) Θ r ' o 16

17 Energyspectrum Power law Exponential fall Energy distribution described by mod. Bessel Function c γ ωc = R 3

18 Syncrotron Radiation Cone 18

19 Undulator versus Wiggler I Wiggler Dipol K>1 e K = λu B me c Undulator superposition of cones K<1 19

20 Undulator Parameter Characteristic Parameter e K = λu B me c Relation to radiation angle θmax p=e R B λu θmax = R r Insertion K = 4 θmax γ If K>1, synchr. Radiation fan larger than cone size 0

21 Undulator versus Wiggler I Wiggler Dipol K>1 Undulator superposition of cones K<1 1

22 Free Electron Lasers (FEL) SASE FEL = Self Amplified Stimulated Emission Very short, and intense light pulses Monochromatic and adjustable in a wide energy range light is coherent! Light is polarised (spin polarised) Produced in long undulators

23 Virus studied in X-FEL Possible to study irregular structures (virus) By Marvin Seibert, Janos Hajdu et al. Nature, Vol. 470, No. 733, February 3,

24 Equation of Motions in Undulator From Lorentz Force γ m e v = e v B Equation of Motion x = e B y z γ me z = e B y x γ me Usual approximations: vx vz v z v Solution: x = K sin (k u z) β γ ku K= eb me c k u 4

25 Electron Velocities Total velocity v=β c x-projection Kc v x = γ cos(k u c t) z-projection vz = v v x v v x vz = [ ( 1 K v z c 1 1+ γ )] Large K value reduces longitudinal velocity 5

26 Energy Transfer between Electrons and Photons Energy transfer: dw q = v E dz vz Condition: photon field ω γ (Δ t e Δ t γ ) =π λu Δ t e= vz λu λu Δ t γ= c ( K λ γ = 1+ γ ) Phase shift = π elecrons gain speed! 6

27 Superposition 7

28 Energy Transfer Energy transfer: dw q = v E dz vz Condition: ω γ (Δ t e Δ t γ ) =π λu Δ t e= vz λu λu Δ t γ= c ( K λ γ = 1+ γ ) Phase shift = π problem: bunch length ~ 50 μm >> photon wave length no effective superposition 8

29 Microbunching + Self Modulation 9

30 Superposition λu ( K λ γ = 1+ γ ) Power scales quadratically with number of particles in microbunch 31

31 Self Amplification Saturation Seeding Photon Power: z P( z)= A P0 exp( ) Lg 3

32 DESY FLASH (Tesla Test Facility) FEL: Energy ~1 GeV Bunchlength 50 μm Undulator Tesla Cavities 33

33 DESY XFEL (in construction) 34

34 DESY XFEL (0 GeV) 35

35 Comparision XFEL - FLASH 36

36 XFEL Accelerator + Experiments 37

37 38