Light Sources based on Storage Rings

Transcription

1 Light Sources based on Storage Rings Lenny Rivkin Paul Scherrer Institute (PSI) and Swiss Federal Institute of Technology Lausanne (EPFL) Electron Beam Dynamics, L. Rivkin, Introduction to Accelerator Physics, Budapest

2 Light sources: > 50 producing synchrotron light users world-wide Electron Beam Dynamics, L. Rivkin, Introduction to Accelerator Physics, Budapest

3 Wavelength continuously tunable!

4 Materials key to our technologies MAXIV that shook the world, L. Rivkin, PSI & EPFL

5 Materials key to our technologies Herzschrittmacher Li-Batterien Neue Materialen für Energie GPS Navigation Funktionale Materialien Air Bag Beschleunigungssensoren Kosmetika TiO 2 Nanopartikel Mobiltelefon SAW Strukturen Künstliches Hüftgelenk Biokompatible Materialien Gläser and Beschichtungen Optische Materialien UV Filter Digitalkamera CCD Chip Artificial Lens Biocompatible Polymers Fahrradrahmen Kohlenstofffasern Composite Materials GMR Lesekopf Magnetische Vielfachschichten LED Display Photonische Materialien Intelligente Kreditkarte Integrated Circuits Genaue Zeit via Satellit Halbleiterbauelemente Micro-Batterien Helmut Dosch, Max Planck Institut für Metallforschung, Stuttgart MAXIV that shook the world, L. Rivkin, PSI & EPFL

6 The brightness of a light source: Source area, S Angular divergence, W Flux, F Brightness = constant x F S x W

7 Steep rise in brightness Undulators XFEL the second wave SLS SOLEIL (F) DIAMOND (UK) ESRF Wigglers SPring8 APS 10 9 Bending magnets Moore s Law for semiconductors Rotating anode Bertha Roentgen s hand (exposure: 20 min)

8 3 types of storage ring sources: 1. Bending magnets: B ~ N e detector short signal pulse broad hn-band time frequency

9 3 types of storage ring sources: 2. Wigglers: large undulations B ~ N e N w x10 Series of short pulses broad hn-band time frequency

10 3 types of storage ring sources: 3. Undulators: small undulations detector continuously illuminated long signal pulse narrow hn-band detector B ~ N e N 2 u x10 3 hn/dhn N time frequency

11 Anatomy of a light source Linac 100 MeV Storage Ring Booster 2.7 GeV Undulators Beam lines

12 Undulator based beamline J.Als-Nielsen, Des Mc Morrow

13 Bright beams of particles: phase space density Incoherent, spontaneous emission of light: Coherent, stimulated emission of light Large phase space

14 Permanent magnet undulators Permanent magnet materials: SmCo 5, NdFeB e.g. a pencil made of such material corresponds to A-turns! Hybrid undulator: permanent magnets and iron Electron Beam Dynamics, L. Rivkin, Introduction to Accelerator Physics, Budapest

15 Click Field to tuning edit Master with gap title style B 1. 8 B r e gap u Permanent magnet material Remanent field [T] SmCo Sm 2 Co NdFeB Electron Beam Dynamics, L. Rivkin, Introduction to Accelerator Physics, Budapest

16 Selection of wavelength in an undulator II N S N(orth) S(outh) A B C electron photon period u v β c c dl= n The path difference K u 1 2 2n 2 θ = K γ 2 dl n (1 ), 1 u detour through slalom mm BT K u 1 2 2

17 Medium energy rings ESRF, APS K-edges Undulator radiation * = mm u 2n 2 1 K * = 1.5 mm 1 K * 1 2 2n 2 u W. Joho

18 In-vacuum undulators / s.c. undulators Gaps down to 3 mm Electron Beam Dynamics, L. Rivkin, Introduction to Accelerator Physics, Budapest

19 Undulator line width Undulator of infinite length N u = D Finite length undulator radiation pulse has as many periods as the undulator the line width is D 1 N u Due to the electron energy spread D = 2 E E

20 Radiation cone of an undulator Undulator radiates from the whole length L into a narrow cone. Propagation of the wave front BC is suppressed under an angle 0, if the path length AC is just shorter by a half wavelength compared to AB (negative interference). This defines the central cone. 0 DL 2 L AB R 0 AC 1 2 L 2 1 cos L Negative interference for L 0 0R0 2 0 DL 2 W. Joho

21 WHAT DO USERS EXPECT FROM A HIGH PERFORMANCE LIGHT SOURCE? PROPER PHOTON ENERGY FOR THEIR EXPERIMENTS BRILLIANCE STABILITY 2 2 x x' y y' FIGURE OF MERIT e x x' ~ x ' x x Photon beam size (U): ' L

22 The electron beam emittance : Source area, S Angular divergence, W The brightness depends on the geometry of the source, i.e., on the electron beam emittance Emittance = S x W

23 Undulator radiation from 6 GeV beam with zero emittance, energy spread (example ESRF) 8 th 9 th 10 th 7 th harmonic Emittance 4 nm rad, 1% coupling, finite energy spread

24 Electron beam phase space Emittance Transverse electron beam distribution Gaussian Units of Typical particle: 1 - ellipse (in a place where a = = 0) m rad Area = x x x x x = x = / = x x = x x

25 Radiation effects in electron storage rings Average radiated power restored by RF Electron loses energy each turn to synchrotron radiation RF cavities accelerate electrons back to the nominal energy Radiation damping Average rate of energy loss produces DAMPING of electron oscillations in all three degrees of freedom (if properly arranged!) Quantum fluctuations Statistical fluctuations in energy loss (from quantized emission of radiation) produce RANDOM EXCITATION of these oscillations Equilibrium distributions The balance between the damping and the excitation of the electron oscillations determines the equilibrium distribution of particles in the beam

26 Small emittance lattices Equilibrium horizontal emittance x0 2 x = C qe 2 J x H mag one tries to optimize the H function in bending magnets the equilibrium emittance can be written as: x 0 = C q E 2 there exists a minimum * = J x H = D 2 + 2aDD + D 2 3 F latt L 2 15, D* = L 24 F min = a = D = 0 L D

27 Theoretical minimum emittance

28 Minimum emittance lattices C E 2 q 3 x0 θ Flatt J x F min =

29 Tight focus in the middle of the bending magnets need space! Many bending magnets need space!

30 X-ray emittance from electron source: a convolution of electron and photon phase space rightness 2 2 x x' y y' e R. Hettel

31 PHOTON ENERGY [ev] HITTING THE DIFFRACTION LIMIT BRIGHTNESS: DIFFRACTION LIMIT Medium E 3 GLS ESRF APS Spring-8 Light of wavelength focused to spot size Dx will diffract with angle D = ~ /Dx

32 Coherence fraction

33 Transverse coherence High brightness gives coherence The knee of a spider Wave optics methods for X-rays (all chapters in Born & Wolf) Holography phase contrast imaging

34 ELECTRON INTENSITY Top-up injection: key to stability TOP-UP INJECTION POSITION < 1 mm TIME

35 A revolution in storage ring technology Pioneer work: MAX IV (Lund, Sweden) Aperture reduction Multi-Bend Achromat (MBA) x y D Technological achievement: NEG coating of small vacuum chambers Small magnet bore High magnet gradient short & strong multipoles short lattice cells many lattice cells low angle per bend emittance (energy) 2 (bend angle) 3 Emittance reduction from nm to pm range

36 The MAX IV Laboratory in Lund, Sweden MAXIV that shook the world, L. Rivkin, PSI & EPFL

37 The world is moving to ever brighter ring sources NSLS-II 2-bend achromat 7- bend achromat 5- bend achromat MAX-IV SIRIUS BNL: NSLS-II (2014): 3 GeV, <1000pm x 8 pm, 500 ma (New) 1 st multi-bend achromat ring upgrade ERSF-II Sweden: MAX-4 (2016): 3 GeV, 230 pm x 8 pm, 500 ma (New) APS-U U.S. Proposals ALS-U Brazil: SIRIUS (2016/17): 3 GeV, 280 pm x 8 pm, 500 ma (New) France: ESRF-II (2020): 6 GeV, 160 pm x 3 pm, 200 ma (New) APS-U: 6 GeV, 60 pm x 8 pm, 200 ma (Upgrade Proposal) ALS-U: 2 GeV, 50 pm x 50 pm, 500 ma (Upgrade proposal) Other international upgrades: Japan (Spring 8, 6 GeV), China (BAPS, 5 GeV), Germany (PETRA-IV, France (SOLEIL), Switzerland (SLS, 2.4 GeV), Italy (ELETTRA) and others are R. Hettel

38 Brightness and coherence of 3 rd and 4 th gen rings Legend: 0.2km/2GeV: ALS-II, 52 pm 0.8km/3GeV: NSLS-III, 30 pm 1.1km/6GeV: APS-II, 80 pm 2.2km/6GeV: PEP-X, 5 pm 6.2km/9GeV: tauusr, 3 pm For 6 GeV rings, a common set of IDs, including advanced SCUs, was assumed M. Borland

39 Sirius: 5 Bend Achromat x/y = /3 3 GeV, 350 ma, C = 518 m gapless flanges NEG coating capability

40 ESRF-II hybrid 7BA 6 GeV, 844 m, 4 nm 0.15 nm High gradient quadrupoles 85 T/m Spec:100 T/m x 335 mm Bore radius: 11 mm Mechanical length: 360 mm 1 kw D1 D2 D3 D4 D5 D6 D7 Quadrupole Around 50 T/m Combined dipole quadrupoles 0.85 T / 45 T/m & 0.34 T / 50 T/m Sextupoles 1700 T/m -2 Permanent magnet dipoles longitudinal gradient T, magnetic gap 22 mm 2 metre long, 5 modules With a small tuning coil 1%

41 APS-U hybrid 7BA x/y = 67/8 6 GeV, 200 ma C = 1.1 km 41-pm.rad option using reverse bend lattice

42 ALS-U hybrid 9 Bend Achromat x/y = 50/50 2 GeV, 500 ma superbend option includes octupoles

43 SLS 2.0 upgrade plans SLS SLS-2 x = GeV Dipole Quadrupole Sextupole New type of lattice cell for low emittance bending magnets with longitudinal field variation (2 T peak) options for 5-6 T peak field superbends anti-bends for beam dynamics star-shaped lattice longitudinal gradient bend anti-bend

44 Diffraction limited rings: the new wave Storage rings in operation ( ) and planned ( ). The old ( ) and the new ( ) generation. R. Bartolini

45 Click to edit Master title style Compact light source COSAMI Conventional, normal conducting magnetic structure Electron Beam Dynamics, L. Rivkin, Introduction to Accelerator Physics, Budapest

46 Injector and storage ring integration MAXIV that shook the world, L. Rivkin, PSI & EPFL

47 Click Whento an edit electron Master collides title style with a photon Also known as Compton or Thomson scattering e - f i ε f = 4γ2 ε i 1 + γ 2 θ 2 backscattered photon has the maximum energy at an angle of 1/ the energy drops by a factor of 2 undulator s periodic magnetic field could be viewed as a «photon», with useful parallels between the two cases Electron Beam Dynamics, L. Rivkin, Introduction to Accelerator Physics, Budapest

48 Compact light source based on Compton scattering