Stanford Synchrotron Radiation Laboratory

Synchrotron Radiation: Brighter than thousand Suns

Apurva Mehta

Apurva Mehta OutlineSynchrotron radiation – How and Why?

History

How is it Produced?

Why is it used?

How is Synchrotron Radiation Used

X-ray Spectroscopy

X-ray Scattering

Microscopy

Apurva MehtaFable

Fast Cars and Flying Tomatoes

Apurva Mehta What good are Flying Tomatoes?

P. Eisenberger, B. Kincaid

~ 10 days using rotating anode. X- Ray tube

~ 20 minutes using synch. rad. from bending magnet

Apurva Mehta Brighter than a Thousand Suns

Apurva Mehta ESRF in Grenoble, France

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54

Operational Rings in 19 countries + 10 under construction + 11

in adv. design

Apurva Mehta What is Synchrotron Radiation?

Natural Synchrotron Radiation

The crab nebula

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Accelerating charges produce Electromagnetic Radiation (i.e., light)

Maxwell’s Equations

Apurva Mehta Electrons in a Storage ring

In Electron’s frame of reference the light radiates

out in a sphere.

But the electrons are moving at almost the speed on light, so from our frame of reference the radiation

“sphere”

undergoes Lorentz contraction and becomes a

very narrow cone

Emmission

pattern is peaked sharply forward

Opening angleΘ

~ mc2/E,

@ SSRL: Θ

~ 0.01 deg

As the E goes up, radiative

power goes

up dramatically.

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Synchrotron radiation from relativistic electrons in a storage ring

Observer only sees the radiation for a brief instant as the beam sweeps across. Therefore (by uncertainty

principle, or Fourier transform of the brief pulse) the energy spectrum

of the radiation must be broad.

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Energy Spectrum of a synchrotron source

The broad spectrum is characterized by a critical energy, where half the radiated power lies above and half below.

Ec

(keV) = 0.7 E2(GeV) B(T)

Flux

Log(E)

Ec

electron energybending magnet field

Apurva Mehta Insertion devicesinsertion device

Storage ring with straight sections

t1t2

Bending Magnet — A “Sweeping Searchlight”

Wiggler — Incoherent Superposition

Dipoles

t3 t4

(10-100) γ –1

t5γ –1

wiggler -

incoherent superposition

bending magnet -

a “sweeping searchlight”

Quasi-monochromatic spectrum with peaks at lower energy than a wiggler

ε1

(keV) =

K = γθ where θ is the angle in each pole

λ1

= λu2γ2

(1 + ) ~

(fundamental)K2

2 γ2

λU

+ harmonics at higher energy

0.95 E2

(GeV)K2λu

(cm)

(1 + )2

Undulator — Coherent Interference

(γ N)–1

undulator -

coherent interference

Like multiple bend magnets

Apurva Mehta BrightnessOne of the most useful metrics for a radiation source (of any kind) is its spectral brightness, or flux density in phase space

Normal units for measuring spectral brightness of a synchrotron source are:

Photons s-1

mm-2

mrad-2

(10-3

BW)-1

As a general rule, a higher brightness beam

implies a higher count rate

in an experiment using the beam

source size source divergencebandwidth

Apurva MehtaA bright synchrotron x-ray beam ionizing air and

causing visible fluorescence.

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Typical Synchrotron Light Source (3rd-gen)

Supports >50 beamlines, operates >6000 hrs/year, supports ~1000 research programs involving several thousand scientists

Apurva Mehta Typical SR Beamline

Apurva Mehta Properties of Synchrotron Radiation

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Properties of Synchrotron Radiation

Well-collimatedDivergence ~ 1/γ

= 5x10-4 / E(GeV)

BroadbandCritical energy Ec

(keV) = 0.7 E2(GeV) B(T)

IntenseSpectral flux density: photons s-1

mrad-1

(10-3

BW)-1= 2.5 x1013

E(GeV) I(A) at critical energy

Linearly polarized in bending plane

Pulsed

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Interaction of radiation with matter

Electrons, neutron, x-rays, or visible light

Absorbtion(Spectroscopy)

Scattering(Diffraction)

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Interaction of radiation with matter

Electrons, neutron, x-rays, or visible light

Absorbtion(Spectroscopy)

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XAS: What you get out of X-ray absorption

Basic Experiment :

Core electron binding energy, Eb

Eb

2.32Å2.46Å

3.43 Å

2.90 Å

Fe2

O3

EXAFSQuantitative Local Structure.

=XANES (X-ay Absorption Near Edge Structure)=NEXAFS (Near Edge X ray Absorption Fine Structure)

XANES / NEXAFSOxidation state, Molecular composition, structure.

0

0.2

0.4

0.6

0.8

1

Abs

orba

nce

Cr(III)

0

0.2

0.4

0.6

0.8

1

5980 6000 6020 6040

Abs

orba

nce

X-ray Energy (eV)

Cr(VI)

(EXAFS = Extended X ray Absorption Fine Structure)

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0

0.2

0.4

0.6

0.8

1

5980 6000 6020 6040A

bsor

banc

e

X-ray Energy (eV)

0

0.2

0.4

0.6

0.8

1

Abs

orba

nce

Cr6+

Cr3+

2.0 Å

1.6 Å

The movie Erin Brockovich was about chromium in water; was it trivalent (no problem) or hexavalent

(deadly) chromium? Synchrotron radiation answers questions like this with ease.

Apurva Mehta X-ray Absorption Spectroscopy

γ

1s

filled 3d

continuumEF

γ

core hole

Apurva Mehta Drinking Water Wars

Apurva Mehta Water Filtration and Desalination Removal of Aqueous Ions

Energy Issue as well

Activated Charcoal and Carbon Nanotubes do it energetically efficient manner

Apurva Mehta How Carbon removes Aq. Halides?

0 1 2 3 4 50.0

0.5

1.0

1.5

2.0

2.5

ampl

itude

R

χ(R) data χ(R) fit

4 6 8 10 12-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

χ(k)

k

k3χ(k) data k3χ(k) fit

4 6 8 10 12-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

χ(k)

k

k3χ(k) data k3χ(k) fit

0 1 2 3 4 5

0.0

0.2

0.4

0.6

0.8

1.0

1.2

ampl

itude

R

χ(R) data χ(R) fit

Br-

Apurva Mehta Defect sites control reactivity

Br-

Br- Br-

Apurva Mehta La1-x

Cax

MnO3

–

Quasicubic

Mn

O La/Ca

• 6 Mn-O in CaMnO3 at ~1.9 Å• Mn-O are distorted in LaMnO3

2 Mn-O at ~1.90 Å2 Mn-O at ~1.97 Å2 Mn-O at ~2.15 Å

P. Schiffer et al., PRL 75, 3336 (1995)

From Bridges Group – UC Santa Cruz

Measure short-range order/distortion

Apurva Mehta XAFS spectra

0 1 2 3 4 5 6

-0.5

0.0

0.5 Mn K edgeT=50 K

Mn-MnMn-CaMn-O

CaMnO3

FT o

f kχ(

k)

r(Å)

Peak position depends on phase shifts, δc and δi, which are calculable.

Peak width depends on back-scattering amplitude F(k), the Fourier transform (FT) range, and the distribution width of g(r), a.k.a. the Debye-Waller σ.

Amplitude envelope[Re2+Im2]1/2

Real part of the complex

transform

0 2 4 6 8 10 12 14-0.8

-0.4

0.0

0.4

0.8

kχ (k

)

k (Å-1)

Mn K-edge (k-space data)

Apurva Mehta σ2

as function of Temperature

0 100 200 300 400

3

4

5

6

7

8

Δ (σ2)

σ2 (1

0-3 Å

2 )

T (K)

0 T 2 T 5 T 8 T11 T

0 100 200 300 4001

2

3

4

5

6

7

Δ (σ2) 0 T 2 T 4 T 7 T 9 T

σ2 (1

0-3 Å

2 )

T (K)0 100 200 300

0

1

2

3

4

5

6

Δ σ2

σ2 (1

0-3 Å

2 )

T (K)0 100 200 300 400

0

1

2

3

4

5

6

Δ σ2

σ2 (1

0-3 Å

2 )T (K)

0 100 200 3001

2

3

4

5

Δ σ2

σ2 (1

0-3 Å

2 )

T (K)

x = 0.21

x = 0.40

x = 0.45

x = 0.35x = 0.30

Apurva Mehta Cartoon model

Red ovals – J-T Mn sites

Blue circles – hole site

Pink and turquoise circles – undistorted electron and hole sites within magnetized domain.

Dimer - one electron shared on 2 Mn sites. Dimers aggregate first. Leads to filamentary magnetized and unmagnetized regions on a unit cell scale – like spagetti.

Dimeron

L. Downward et al., Phy. Rev. Lett., 95, 106401 (2005)

Apurva Mehta

Interaction of radiation with matter

Electrons, neutron, x-rays, or visible light

Scattering(Diffraction)

Apurva Mehta Physics of Diffraction

X-ray Lens not very good

Mathematically

coherence

Better optics

Apurva Mehta How Botox worksBotulism is caused by a neurotoxin that blocks muscle

contractions

SNARE protein delivers

neurotransmitter acetlycholine

to make muscles contract.

Botulism neutrotoxin

binds with SNARE, blocks acetlycholine

delivery

Breidenbach

and Brunger

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Often you know the overall structure

What you really are looking for are

Small Changes

Apurva MehtaMaking Faster CPUs

Staying on the “curve”

So far we have done this by shrinking device size

From microns to 32 nanometers

But Can’t probably go much smaller

Alternative –

increase the speed of the electrons

Strained Si on insulator

Bibee et al.

Apurva MehtaStrained Si on Insulator (sSOI)

004 115113

331

sSi (15 nm)

Oxide (150 nm)

Substrate

Native ox. (~1 nm)

Low density Oxide (1 nm)

Characterization of layered structures

X-ray reflectivity X-ray diffraction

Oxide

15 nm100

nm

100 nm

sSi Strain mapping

Domain structure

Layer misorientation

110

Substrate (331)

Strained Si (331)

Strain: 0.7%

Misorientation:< 0.01º

Low freq. oscillations→ thin strained layer

High freq. oscillations→ thick oxide layer

Q (Å-1)

I/I0

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Thickness of lubricant on hard-drive platters

Toney et al.

X-ray methods are non-contact

Used to calibrate various industrial

methods for measuring films

Apurva Mehta Dating Sea Water Temperature

22 23 24

100

1000

22 23 24

100

1000

N. Pingitore et al.

~ 0.25% SrCO3

CaCO3Calcareous Plankton(Foraminifers)

Inte

nsity

(arb

. uni

ts)

2 θ

Sample = few mg

N. Pinigitore

et alSr/Ca ratio depends on the sea water temperature

Apurva Mehta Imaging vs. DiffractionPictures are pretty

But if the optics is not good than images are distorted and full of artefacts

Not very good at determining ensemble properties

Every point in a diffraction pattern is a Fourier transf. of the sampling volume –automatically averages.Because of automatic averaging diffraction is excellent for

Very precise Atom positions determinationVery accurate Strain determination (0.1 -0.01%)Average particle sizeDetecting small amounts of secondary phase, especially if it is dispersed

Apurva Mehta Xray

MicroscopyBecause pictures are pretty

But also because they show new structures and lead to better understanding

But Traditionally Hard with X-rays

Apurva Mehta Focusing of beams

Refractive index of x-rays in material < vacuum! (but almost nearly ~1 n ~ 0.99991)

Xray’s can be focused – but with difficulty. Long grazing angle cylindrical or torodial mirrors- not paraboloidhence aberrationFresnel zone platesRefractive lenses – hole in a solid focuses x-rays.

But because of inherently low divergence, synchrotron beams can focused to a small spot. Brightness – PEP-X (2.2 km ring –until recently used for HEP – BABAR) more x1000

Routinely to 1x1 mm, lately much smaller (1 micron to 50 nm – 1nm )

Apurva MehtaX-ray Microscopes

Spectroscopy + scatteringScanning

One pixel at a timeTransmission

Full image at once

slit

reflectiveCondenser

MZP

CCD

Si(Li)

xy

X-rays sample

Fluor. detectorD

iff. detector

Fluor. detector

Apurva Mehta Scanning Microscopy

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Araneus diadematus Fangs and Marginal Teeth

Fang 3 Fang 7

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I1

Mn

Zn

Fang2_init_14000_001

Scanning Spectromicroscopy

Scott, Webb et al

Apurva Mehta Transmission Microscopy

Apurva Mehta Ant’s Head

Apurva MehtaStructure of Bone

NASA interested in Changes due to Gravity

Mouse g08 male Ex101 loaded left tibiaCircles are areas for hi-res 3x3 mosaics

Apurva Mehta Materials @ 1 A to 1mmSolar Cell MaterialsProteinsPhotosynthesisBiomaterialsCorelated electron systemsHow materials “break”How bugs make rocksCatalysisStructure of Water

Hydrogen StorageDrug – protein interactionsDeciphering Ancient ManuscriptsPreservation of archeological artifactsScience behind cleanup of superfund sites.Magnetic Storage Devices

Apurva MehtaExamples

Highlight on SSRL Webpage

10 μm Grain/Phase Map

Elastic Strain

Plastic Strain

Apurva Mehta A few WebsitesSSRL: http://www-ssrl.slac.stanford.edu/ALS: http://www-als.lbl.gov/als/APS: http://www.aps.anl.gov/NSLS: http://www.nsls.bnl.gov/ESRF: http://www.esrf.fr/SPring8: http://www.spring8.or.jp/top.html

J. Synchr. Rad. : http://journals.iucr.org/s/journalhomepage.html

Synchr. Rad. News: http://www.tandf.co.uk/journals/titles/08940886.asp

http://www-ssrl.slac.stanford.edu/http://www.aps.anl.gov/

Synchrotron Radiation:�Brighter than thousand SunsOutlineFable�Fast Cars and Flying Tomatoes What good are Flying Tomatoes?Brighter than a Thousand SunsESRF in Grenoble, France54 Operational Rings in 19 countries + 10 under construction + 11 in adv. designWhat is Synchrotron Radiation?Accelerating charges produce Electromagnetic Radiation (i.e., light)Electrons in a Storage ringSynchrotron radiation from relativistic electrons in a storage ringEnergy Spectrum of a synchrotron sourceInsertion devicesBrightnessA bright synchrotron x-ray beam ionizing air and causing visible fluorescence.Typical Synchrotron Light Source (3rd-gen)Typical SR BeamlineProperties of Synchrotron RadiationProperties of Synchrotron RadiationInteraction of radiation with matterInteraction of radiation with matterXAS: What you get out of X-ray absorptionSlide Number 23X-ray Absorption SpectroscopyDrinking Water WarsWater Filtration and Desalination�Removal of Aqueous IonsHow Carbon removes Aq. Halides?Defect sites control reactivityLa1-xCaxMnO3 – Quasicubic XAFS spectraσ2 as function of TemperatureCartoon modelInteraction of radiation with matterPhysics of DiffractionHow Botox worksSlide Number 36Making Faster CPUs�Staying on the “curve”Strained Si on Insulator (sSOI)Thickness of lubricant on hard-drive plattersDating Sea Water TemperatureImaging vs. DiffractionXray MicroscopyFocusing of beamsX-ray Microscopes�Spectroscopy + scatteringScanning MicroscopySlide Number 46Scanning SpectromicroscopyTransmission MicroscopyAnt’s HeadStructure of Bone�NASA interested in Changes due to GravityMaterials @ 1 A to 1mm Examples�Highlight on SSRL WebpageA few Websites