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Stanford Synchrotron Radiation Laboratory
Synchrotron Radiation: Brighter than thousand Suns
Apurva Mehta
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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
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Apurva MehtaFable
Fast Cars and Flying Tomatoes
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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
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Apurva Mehta Brighter than a Thousand Suns
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Apurva Mehta ESRF in Grenoble, France
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Apurva Mehta
54
Operational Rings in 19 countries + 10 under construction + 11
in adv. design
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Apurva Mehta What is Synchrotron Radiation?
Natural Synchrotron Radiation
The crab nebula
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Apurva Mehta
Accelerating charges produce Electromagnetic Radiation (i.e., light)
Maxwell’s Equations
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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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Apurva Mehta
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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Apurva Mehta
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
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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
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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
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Apurva MehtaA bright synchrotron x-ray beam ionizing air and
causing visible fluorescence.
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Apurva Mehta
Typical Synchrotron Light Source (3rd-gen)
Supports >50 beamlines, operates >6000 hrs/year, supports ~1000 research programs involving several thousand scientists
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Apurva Mehta Typical SR Beamline
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Apurva Mehta Properties of Synchrotron Radiation
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Apurva Mehta
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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Apurva Mehta
Interaction of radiation with matter
Electrons, neutron, x-rays, or visible light
Absorbtion(Spectroscopy)
Scattering(Diffraction)
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Apurva Mehta
Interaction of radiation with matter
Electrons, neutron, x-rays, or visible light
Absorbtion(Spectroscopy)
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Apurva Mehta
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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Apurva Mehta
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.
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Apurva Mehta X-ray Absorption Spectroscopy
γ
1s
filled 3d
continuumEF
γ
core hole
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Apurva Mehta Drinking Water Wars
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Apurva Mehta Water Filtration and Desalination Removal of Aqueous Ions
Energy Issue as well
Activated Charcoal and Carbon Nanotubes do it energetically efficient manner
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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-
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Apurva Mehta Defect sites control reactivity
Br-
Br- Br-
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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
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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)
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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
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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)
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Apurva Mehta
Interaction of radiation with matter
Electrons, neutron, x-rays, or visible light
Scattering(Diffraction)
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Apurva Mehta Physics of Diffraction
X-ray Lens not very good
Mathematically
coherence
Better optics
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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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Apurva Mehta
Often you know the overall structure
What you really are looking for are
Small Changes
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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.
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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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Apurva Mehta
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
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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
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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
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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
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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 )
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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
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Apurva Mehta Scanning Microscopy
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Apurva Mehta
Araneus diadematus Fangs and Marginal Teeth
Fang 3 Fang 7
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Apurva Mehta
I1
Mn
Zn
Fang2_init_14000_001
Scanning Spectromicroscopy
Scott, Webb et al
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Apurva Mehta Transmission Microscopy
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Apurva Mehta Ant’s Head
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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
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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
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Apurva MehtaExamples
Highlight on SSRL Webpage
10 μm Grain/Phase Map
Elastic Strain
Plastic Strain
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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