Introduction to Synchrotron Beamlines

Dr Richard Garrett Senior Advisor, Strategic Projects Beamline Design Goals • Deliver the required X-ray beam to the experiment: – Energy and bandwidth – Spot size – Divergence/convergence • Preserve source characteristics eg intensity, brightness, coherence • Handle the heat load of the beam • Optimise signal / background • Be very stable and reproducible, in position, intensity and energy • Be safe to operate • Be user friendly to operate • Achieve all the above within a reasonable budget !

(Good Luck!)

R. Garrett 1st AOF Synchrotron School Generation of Synchrotron Radiation: Radiation from Accelerating Charge

Low energy electrons OR electron frame: High energy (relativistic) electrons Radiation in all directions – Laboratory frame: Example: Radio waves Radiation pattern swept into a from a transmitter. narrow cone in the forward direction = High brightness!

E = electron beam energy

R. Garrett 1st AOF Synchrotron School

.7 mrad Singapore γ = 1400 Light Source .04º

700 MeV

Australian .2 mrad γ = 6000 .01º Synchrotron

3 GeV

Spring-8 .06 mrad γ = 16000 .004º

8 GeV

R. Garrett 1st AOF Synchrotron School 2 εc = .665 E B

K>>1

K=0.934.λu[cm].B[T] K ~ 1

(on axis) 2015 Cheiron School High Heat Load

• IMBL SC Wiggler: total power ~30 kW • in vacuum X-ray undulator: peak power density 15 kW/mrad2 at k=1.8.

Consequences of poor design: • Melting holes in things! and other damage. • Thermal distortions of optics resulting in loss of intensity, focus etc • An unstable X-ray beam due to long thermal equilibrium times

Focused wiggler beam emerging into the air: NSLS X25 beamline.

R. Garrett 1st AOF Synchrotron School Synchrotron Optics

R. Garrett 1st AOF Synchrotron School Available x-ray optical techniques

8 Professor David Attwood / UC Berkeley / AST 210/ EE213, Fall 2016, Chapter 10 Mirrors for Synchrotron Beamlines

• Deflection

• Focusing

• Harmonic Rejection

• Power Reduction

R. Garrett 1st AOF Synchrotron School X-ray Mirrors • At grazing angles, below the critical angle, reflectivity is close to 1 • All common geometric figures can be produced with high accuracy: – Flat mirrors – Cylindrical and spherical mirrors (produce spherical aberrations except at 1:1 focus) – Elliptical mirrors: point to point focus – Parabolic mirrors: collimation and point focus from a parallel beam • Due to the highly astigmatic focus (a spherical mirror focuses almost entirely in the meridional direction) toroidal figures or separate horizontal and vertical focusing elements are often used.

R. Garrett 1st AOF Synchrotron School Critical Angle/Reflectivity with Energy: Rhodium Coated Mirror Example

1 keV 10 keV 20 keV Harder X-rays need more grazing angles and longer mirrors:

2 mm high beam needs:

≤ 10 cm mirror at 1 keV ≥ 80 cm mirror at 20 keV

(grazing incidence long mirror does help with heat load )

R. Garrett 1st AOF Synchrotron School Mirror Reflectivity at 2.5 milli-radians Incidence

Pt

Rh

Si

Such adjustable reflectivity/ high energy cutoff is very useful for harmonic rejection. Many beamlines have two or three different metal stripes coated side by side.. 3rd Generation typical Undulator source size SPring-8 2 mm

2 mm y (mm) y

σx = 316 µm σy = 4.9 µm

x (mm)

R. Garrett 1st AOF Synchrotron School Kirkpatrick-Baez Mirror Pair

Orthogonal mirrors cancel astigmatism Elliptical surfaces for point to point imaging Glancing incidence coatings for broad band applications, multilayer coatings for fixed bandpass

Commonly used in synchrotron beamlines – separate vertical and horizontal focusing is a good Courtesy of J. Underwood, LBNL match to the asymmetric source Bent Mirrors • The easiest figures to produce with high accuracy are flats, cylinders and spheres • Large aspheric mirrors become very expensive: common solution is a bent mirror: – Bent flat becomes a cylindrical mirror – Bent sagittal cylinder becomes a toroid

SESO mirror & single actuator bender

R. Garrett 1st AOF Synchrotron School Mirror Cooling Water Channel Thermal loads can easily destroy the Copper fin in mirror figure, degrading focal spots and Ga filled slot losing intensity.

Side cooled mirror. Side cooling results in opposite thermal gradients at the center and the sides of the mirror. These gradients act against each other reducing the thermal deformation of the mirror.

R. Garrett 1st AOF Synchrotron School Diffractive Optics:

Crystals, Gratings and Multilayers

R. Garrett 1st AOF Synchrotron School Monochromators: Crystals and Gratings

Diffraction from periodic structures is used to select the desired energy from the “white” synchrotron radiation.

Crystals used at hard X-ray energies Bragg’s law: θ 2d sinθ = mλ d

Monochromators all produce harmonics: Silicon Miller indices “Rule”: • All Odd or • Divide by 4 So allowed reflections are: • <111>, <333> etc • <220>, <440> etc Double Crystal Monochromator

R. Garrett 1st AOF Synchrotron School Some Crystals used in Synchrotron Monochromators

Crystal 2d Energy Range α-quartz (5052) 1.624 8.0 – 88 keV Silicon (311) 3.274 4.0 – 44 keV Silicon (220) 3.84 3.4 – 37 keV Diamond (111) 4.118 3.2 – 35 keV Silicon (111) 6.2712 2.1 – 23 keV InSb (111) 7.4806 1.7 – 19 keV Beryl (1010) 15.954 0.82 – 9 keV

Source: ALS/CXRO X-ray Data Booklet & XOP At soft X-ray energies crystal diffraction has difficulties: most large d-spacing crystals have significant imperfections, and absorption limits the penetration depth and therefore the resolution. Absorption edges can also result in structure on the monochromatic beam, eg Beryl contains Al with a k-edge at 1560 eV. Crystal Monochromators – Match to Source

• BM & wiggler: divergence >> Si natural width • Normal DCM: 2nd crystal accepts same as first <111> <333> • = worse energy resolution

• Can slit beam but lose flux AS Undulator

Bending Magnet 1/γ

• BM & wiggler – collimating mirrors recover resolution without sacrificing flux • Undulator source – good match

R. Garrett 1st AOF Synchrotron School Graphical Representation of Bragg’s Law

2d sinθ = mλ

R. Garrett 1st AOF Synchrotron School Example: ChemMatCARS High Resolution Monochromator

Dumond diagram at 10 keV

R. Garrett 1st AOF Synchrotron School Effect of Heat Load on Monochromator First Crystal Thermal gradient = “Thermal Bump”

No heating of first crystal

Thermal bump in water cooled Si crystal. Finite element calculation of undulator beam shows a 0.3 micron Heat “bump” on first crystal bump.

R. Garrett 1st AOF Synchrotron School Two Solutions to Monochromator Heat Loads

APS LN2 cooled crystal Photo: D. Mills

Liquid Nitrogen Cooled Silicon “Inclined Geometry” Crystal Silicon coefficient of thermal Beam footprint spread out expansion goes through zero near Thermal bump not in diffraction direction LN2 temperatures. A thermal gradient therefore does not produce a thermal “bump”. Diffraction Gratings

d(sin β − sinα) = mλ

The grating equation. • Diffraction gratings are used d = grating line spacing from visible (and beyond) to soft X-ray energies. Gratings can m = +2 function up to and above 2 keV, m = +1 with decreasing efficiency m = 0 • Practical limit on line spacing is m = -1 about 2000 lines/mm α β • Most monochromators use first order diffraction • Most gratings are “blazed”, ie the groove profile is figured to Unlike crystal diffraction, all energies are optimise for certain diffracted all the time. An exit slit is needed angle/wavelength ranges. to select a monochromatic beam. Zero order is not dispersed (grating acts like a mirror, ie α = β). Multilayer Optics

Multilayers can be deposited on mirrors or gratings to increase the reflectivity, although only over a limited energy range. Double multilayer monochromator has higher bandpass & intensity than DCM.

A schematic multilayer structure and a typical measured reflectivity spectrum. Layer A usually consists of a strongly absorbing material (metal). Layer B is a spacer made of a low-density material. Graded Multilayers

• Multilayers can be graded (layer period varied) laterally or with depth • Lateral grading is needed for focusing multilayers • Depth grading can be used to produce a “Super Mirror” • In example shown, a normal grazing mirror cuts under 10 keV at 0.5 degree incidence. (Erko etal)

R. Garrett 1st AOF Synchrotron School Micro-focus Optics

R. Garrett 1st AOF Synchrotron School Summary of Micro-focus Optics

Focus Spot Energy Range Other Characteristics

Zone Plate 0.1 μm (hard) < 25 keV Good resolution .06 μm (soft) Focus moves with energy K-B Mirror ~10nm (Osaka) < 25keV Resolution improving fast! .3 μm (ESRF) Focus fixed Typical ~1 μm H & V decoupled Refractive Lens ~ 1 μm < 100 keV High X-ray energy Focus moves with energy Capillary .05 μm < 20 keV Very short working distance

R. Garrett 1st AOF Synchrotron School Zone Plates: Basic properties

b • resolution is limited by ∆x smallest feature size b: ∆x = 1.22 b

• highly chromatic: f ~ 1/λ

• mostly have several diffraction orders

R. Garrett 1st AOF Synchrotron School X-ray Zone Plates

Scanning electron micrograph of 40 nm outermost zones Kirkpatrick Baez Optics - O. Hignette et al. (ESRF)

KB mirrorset-up with Xray CCD based With 0.24 x 0.18 mm2 (v x h) acceptance focus spot measurement Spot size = 0.34 x 0.27 µ m2 FWHM

R. Garrett 1st AOF Synchrotron School X-ray nanoprobe based on crossed ellipses

Nanofocus fluorescence beamline @ Spring-8. Elemental distribution maps18 of Cu and Zn, are seen within the nucleus of a single NIH/3T3 cell. Maps of P, S, Cl, Ca and Fe also reported

Courtesy of S. Matsuyama and K. Yamauchi (Osaka university). S. Matsuyama et al., Rev. Sci. Instrum.77, 103102 (2006). 34 Professor David Attwood / UC Berkeley / AST 210/ EE213, Fall 2016, Chapter 10 Compound Refractive Lenses

SEM image of an array of parabolic refractive X-ray lenses made of silicon. The shaded areas (i) and (ii) show an individual and a compound lens, respectively. (ESRF)

• Refractive index is <1 so concave lens focuses • Refraction is very small so many lenses normally stacked • Low absorption materials needed, eg Be, Al Snigirev etal Multilayer Laue Lenses (MLL) for focusing hard x-rays

Optimum performance is obtained with curved multilayer zones of graded d-spacing that satisfy the Bragg condition everywhere.

Courtesy of H.Yan, National Synchrotron Light Source (NSLS), BNL.

36 Professor David Attwood / UC Berkeley / AST 210/ EE213, Fall 2016, Chapter 10 Complete Beamlines

R. Garrett 1st AOF Synchrotron School A Simple X-ray Beamline: the ANBF (1992-2012)

Bending Magnet Beamline Slits Source *

Be Window Channel Cut Safety Hutch Be Window Si<111> Mono Shutter Wall AS Xray Absorption Spectroscopy Beamline

R. Garrett 1st AOF Synchrotron School Undulator Beamlines

Nano-focus fluorescence beamline @ Spring-8

K-B mirror DCM

AS SAXS/WAXS Beamline

R. Garrett 1st AOF Synchrotron School Example Soft X-ray Beamline (NSRRC Taiwan)

R. Garrett 1st AOF Synchrotron School Bio-nanotomography for 3D imaging of cells

Nanotomography of Soft X-Ray Nanotomography Cryogenic Fixed Cells of a Yeast Cell

λ = 2.4 nm (517 eV) Δr = 35 nm N = 320 NA = 0.034 D = 45 µm λ = 2.4 nm f = 650 µm Courtesy of C. Larabell (UCSF & σ = 0.64 LBNL) and M. LeGros (LBNL) Resolution = 60 nm 3 min total time 42 Professor David Attwood / UC Berkeley / AST 210/ EE213, Fall 2016, Chapter 10 New 4th Generation Light Sources

PETRA III @ DESY MAX IV in Lund NSLS II @ BNL

εh = 1 nm rad @ 6 GeV εh = 0.2-0.3 nm rad @ 3.7 GeV εh = 0.55 nm rad @ 3 GeV

Upgrades to 4th Gen

APS @ ANL ESRF in Grenoble Spring-8 in Hyogo, Japan

εh = 0.07 nm rad @ 6 GeV εh = 0.1-0.15 nm rad @ 6 GeV εh = 0.11 nm rad @ 6 GeV

R. Garrett 1st AOF Synchrotron School Comparison of undulator source size SPring-8 SPring-8-II 2 mm 2 mm

2 mm y (mm) y (mm)

σx = 316 µm σx = 27.3 µm σy = 4.9 µm σy = 6.4 µm

x (mm) x (mm)

R. Garrett 1st AOF Synchrotron School Online Resources:

http://xdb.lbl.gov/ X-ray data booklet “the orange book” http://www.csrri.iit.edu/periodic-table.html Periodic table of X- ray absorption edges and emission energies http://www.lightsources.org/regions list of light sources https://www1.aps.anl.gov/Science/Scientific-Software/XOP assembly of codes to calculate BM, wiggler & undulator sources, mirror & filter transmissions & more https://forge.epn-campus.eu/projects/shadow3 Shadow ray tracing package etc

R. Garrett 1st AOF Synchrotron School Thank you

ansto.gov.au