Light Sources based on Storage Rings Lenny Rivkin
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
Light sources: > 50 producing synchrotron light 60‘ 000 users world-wide Electron Beam Dynamics, L. Rivkin, Introduction to Accelerator Physics, Budapest
Wavelength continuously tunable !
Materials – key to our technologies MAXIV that shook the world, L. Rivkin, PSI & EPFL
Materials – key to our technologies Herzschrittmacher Li-Batterien Neue Materialen für Energie Mobiltelefon SAW Strukturen GPS Navigation Funktionale Materialien Künstliches Hüftgelenk Biokompatible Materialien Fahrradrahme n Kohlenstofffasern Composite Materials GMR Lesekopf Magnetische Vielfachschichten Air Bag Kosmetika Beschleunigungssenso ren Gläser and Beschichtungen Optische Materialien UV Filter LED Display Photonische Materialien Ti. O 2 Nanopartikel Digitalkame ra CCD Chip Artificial Lens Biocompatible Polymers 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
The “brightness” of a light source: Source area, S Angular divergence, W Flux, F F Brightness = constant x _____ Sx. W
Steep rise in brightness 1021 the second wave SLS SOLEIL (F) DIAMOND (UK) … XFEL Undulators ESRF SPring 8 1015 APS Wigglers Moore’s Law for semiconductors Bending magnets 109 Rotating anode 1900 Bertha Roentgen’s hand (exposure: 20 min) 1950 2000
3 types of storage ring sources: 1. Bending magnets: B ~ Ne detector short signal pulse time broad hn-band frequency
3 types of storage ring sources: 2. Wigglers: large undulations Series of short pulses time B ~ Ne. Nw x 10 broad hn-band frequency
3 types of storage ring sources: 3. Undulators: small undulations detector continuously illuminated detector long signal pulse time B ~ Ne. N 2 u x 103 narrow hn -band hn/Dhn ≈N frequency
Anatomy of a light source Linac 100 Me. V Storage Ring Booster 2. 7 Ge. V Undulators Beam lines
Undulator based beamline J. Als-Nielsen, Des Mc Morrow
Bright beams of particles: phase space density Incoherent, spontaneous emission of light: Large phase space Coherent, stimulated emission of light
Permanent magnet undulators Permanent magnet materials: Sm. Co 5, Nd. Fe. B e. g. a pencil made of such material corresponds to 15‘ 000 A-turns! Hybrid undulator: permanent magnets and iron Electron Beam Dynamics, L. Rivkin, Introduction to Accelerator Physics, Budapest
Click Field to tuning edit Master with gap title style Permanent magnet material Remanent field [T] Sm. Co 5 0. 9 – 1. 0 Sm 2 Co 17 1. 0 – 1. 1 Nd. Fe. B 1. 0 – 1. 4 Electron Beam Dynamics, L. Rivkin, Introduction to Accelerator Physics, Budapest
Selection of wavelength in an undulator II N A B period lu electron photon N(orth) S C d. L= nl v βc c The path difference detour through slalom S(outh)
Undulator radiation -FE IR l* = 2‘ 500 mm Medium energy ESRF, APSrings K-edges L l* = 1. 5 mm W. Joho
In-vacuum undulators / s. c. undulators Gaps down to 3 mm Electron Beam Dynamics, L. Rivkin, Introduction to Accelerator Physics, Budapest
Undulator line width Undulator of infinite length Finite length undulator • radiation pulse has as many periods as the undulator • the line width is Due to the electron energy spread
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. Negative interference for W. Joho
WHAT DO USERS EXPECT FROM A HIGH PERFORMANCE LIGHT SOURCE ? PROPER PHOTON ENERGY FOR THEIR EXPERIMENTS BRILLIANCE STABILITY FIGURE OF MERIT Photon beam size (U):
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
Undulator radiation from 6 Ge. V 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
Electron beam phase space Emittance Transverse electron beam distribution • Gaussian • “Typical” particle: 1 - ellipse (in a place where a = ’ = 0) x’ x x
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
Small emittance lattices Equilibrium horizontal emittance § one tries to optimize the magnets H function in bending § the equilibrium emittance can be written as: there exists a minimum D L
Theoretical minimum emittance
Minimum emittance lattices
Tight focus in the middle of the bending magnets – need space! Many bending magnets – need space!
X-ray emittance from electron source: a convolution of electron and photon phase space R. Hettel
HITTING THE DIFFRACTION LIMIT BRIGHTNESS: DIFFRACTION LIMIT Medium E 3 GLS ESRF APS Spring-8 Light of wavelength l focused to spot size Dx will diffract with angle D = ~ l/Dx PHOTON ENERGY [e. V]
Coherence fraction
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
Top-up injection: key to stability ELECTRON INTENSITY TOP-UP INJECTION POSITION TIME < 1 mm
A revolution in storage ring technology Pioneer work: MAX IV (Lund, Sweden) Aperture reduction Multi-Bend Achromat (MBA) bx by 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 e (energy)2 (bend angle)3 Emittance reduction from nm to 10. . . 100 pm range
The MAX IV Laboratory in Lund, Sweden MAXIV that shook the world, L. Rivkin, PSI & EPFL
The world is moving to ever brighter ring sources 2 -bend achromat NSLS-II 7 - bend achromat MAX-IV BNL: NSLS-II (2014): 3 Ge. V, <1000 pm x 8 pm, 500 m. A (New) 1 st multi-bend achromat ring upgrade ERSF-II France: ESRF-II (2020): 6 Ge. V, 160 pm x 3 pm, 200 m. A (New) SIRIUS Sweden: MAX-4 (2016): 3 Ge. V, 230 pm x 8 pm, 500 m. A (New) APS-U 5 - bend achromat Brazil: SIRIUS (2016/17): 3 Ge. V, 280 pm x 8 pm, 500 m. A (New) U. S. Proposals ALS-U APS-U: 6 Ge. V, 60 pm x 8 pm, 200 m. A (Upgrade Proposal) ALS-U: 2 Ge. V, 50 pm x 50 pm, 500 m. A (Upgrade proposal) Other international upgrades: Japan (Spring 8, 6 Ge. V), China (BAPS, 5 Ge. V), Germany R. Hettel (PETRA-IV, France (SOLEIL), Switzerland (SLS, 2. 4 Ge. V), Italy (ELETTRA) and others are
Brightness and coherence of 3 rd and 4 th gen rings Legend: 0. 2 km/2 Ge. V: ALS-II, 52 pm 0. 8 km/3 Ge. V: NSLS-III, 30 pm 1. 1 km/6 Ge. V: APS-II, 80 pm 2. 2 km/6 Ge. V: PEP-X, 5 pm 6. 2 km/9 Ge. V: tau. USR, 3 pm For 6 Ge. V rings, a common set of IDs, including advanced SCUs, was assumed M. Borland
Sirius: 5 Bend Achromat ex/y = 190 -270/3 pm. rad @ 3 Ge. V, 350 m. A, C = 518 m • gapless flanges • NEG coating capability
V, ESRF-II – hybrid 7 BA Pe rm D 1 m , 4 High g radient quadru 85 T/m D pol nm es 2 • Spec: 1 00 T/m x 335 m git a • Bore ra m dius: 1 ud • n. Me 1 m m et ina encthanical leng ic • 1 l gk. W m th: 360 mm g r lon ap ad ag n g 2 ie all , 5 2 m nt 0 et tu mo m. 16 dip ni n d o g ule 0. le co s 6 T, s il 1 % 84 4 D 3 D 4 D 5 → 0. 15 nm D 6 C o 0. 8 mbi 5 T ne / 4 d di 5 T po /m le & 0 qua. 34 dru T / po 50 les T/m D 7 Qua Aro drupo und le 50 T /m Se 17 xtup 00 ole T/m s -2
APS-U – hybrid 7 BA • ex/y = 67/8 pm. rad @ 6 Ge. V, 200 m. A • C = 1. 1 km • 41 -pm. rad option using reverse bend lattice
ALS-U – hybrid 9 Bend Achromat ex/y = 50/50 pm. rad @ 2 Ge. V, 500 m. A superbend option includes octupoles
SLS SLS-2 SLS 2. 0 upgrade plans ex = 140 pm. rad @ 2. 4 Ge. V arc 2 S SL rc a SLS Dipole 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 Quadrupole Sextupole longitudinal gradient bend anti-bend
Diffraction limited rings: the new wave Storage rings in operation ( • ) and planned ( • ). The old (—) and the new (—) generation. R. Bartolini
Click to edit Master title. COSAMI style Compact light source Conventional, normal conducting magnetic structure Electron Beam Dynamics, L. Rivkin, Introduction to Accelerator Physics, Budapest
Injector and storage ring integration MAXIV that shook the world, L. Rivkin, PSI & EPFL
Click Whentoanedit electron Master collides title style with a photon… Also known as Compton or Thomson scattering ef eei § backscattered photon has the maximum energy § at an angle of 1/g 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
Compact light source based on Compton scattering www. lynceantech. com
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