Will Size Define a
New Generation of Light Sources?
David E. Moncton
Future Light Sources Conference
JLab
March 5, 2012
March 2012
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Summary
• The most substantial societal impact of x-rays has come from
small scale sources—x-ray tubes (14 Nobel prizes)
• Synchrotron radiation has made enormous impact in two ways
– Science accomplished (4 Nobel prizes)
– Development of extremely powerful methods based on high brilliance
made possible by incoherent emission from relativistic beams
• X-ray free-electron lasers will also have enormous impact
– Access the fs timescale for the first time with significant flux
– Enable the development of methods exploiting the high peak brilliance
made possible by coherent electron emission from relativistic beams
• Future machine beyond the ultimate single-mode FELs will
combine the features of these three generations of sources
– Small scale, relativistic e-beams, and coherent emission.
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X-ray Science Driven by Beam Brilliance
Synchrotron
Radiation
X-ray Tubes
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Relativity
Coherent
Emission
X-ray Lasers
Roentgen’s X-ray Tubes circa 1895
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The Modern X-ray Tube
Rigaku FR-E flux on crystal ~ 4 x 109 ph/sec
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Spiral CT (Computed Tomography) Imaging
Note: We now know that much
better images can be obtained by
phase contrast methods, but are not
possible with the cathode ray tube
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Nobel Prizes for X-ray Research
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First Reference Proposing Use of Synchrotron X-rays
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Radiation from Charged Particles (1952)
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X-ray Science Driven by Beam Brilliance
Synchrotron
Radiation
X-ray Tubes
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Relativity
Coherent
Emission
X-ray Lasers
Thousands of Protein Structures from One APS Beamline
The Structural
Biology Center
APS
Kappa Goniostat, ROBAC,
Q315 detector
10 Tb NSF
Storage
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Nobel Prizes for Synchrotron X-ray Research
1997 ATP-synthase structure (Boyer, Walker)
2003
Ion channels (Agre, MacKinnon)
2006
Eukaryotic transcription (Kornberg)
2009 Ribosime structure (Ramakrishnan, Steitz, Yonath)
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X-ray Science Driven by Beam Brilliance
Synchrotron
Radiation
X-ray Tubes
March 2012
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Relativity
Coherent
Emission
X-ray Lasers
New Facilities Based on SASE Radiation
SLAC Stanford
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A Tutorial on Peak Brilliance
•New scientific frontiers require access to the spatial and temporal regimes
where new properties emerge that are out of reach with 3rd gen sources
•This challenge requires the highest collimation, the smallest beam size,
the shortest pulses and the best energy resolution—often simultaneously
Peak Brilliance = # photons/Dx Dqx Dy Dqy Dt DE
•The denominator is the phase space volume of the source which can be
as small as the uncertainty principle allows—one photon mode
•Therefore peak brilliance is a direct measure of the # photons in the
most highly occupied mode—aka photon degeneracy
•To convert from peak brilliance to photon degeneracy divide by
2.3 x 1021/ l3 (nm)
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Peak Brilliance
Example—The Advanced Photon Source
with peak brilliance about 1023 at l = 0.1 nm
Degeneracy =
1023
2.3 x 1021/ l3 (nm)
= 0.04
In other words the most highly occupied mode
has, on average, a 4 percent chance of
having one photon in it.
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Peak Brilliance
Example—The LCLS
with peak brilliance about 1034 at l = 0.1 nm
Degeneracy =
2 x 1033
2.3 x 1021/ l3 (nm)
~109
What is the difference between sources with degeneracy of 109
and those sources with degeneracy from .01—100?
It is the fundamentally different process producing the radiation–
coherent vs incoherent emission, laser vs. light bulb
Ring sources produce photons one electron at a time,
proportional to the number N of electrons
Lasing is a coherent electron process proportional to N2
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Two Key Questions
Are SASE sources the ultimate in x-ray
technology?
While SASE sources benefit from exponential
No
gain, the resulting beam has poor quality
compared to a single mode optical laser.
Are billion dollar central facilities the only option?
No
Advances in accelerator, laser, and nano
technology offer opportunities to build high
performance x-ray sources of the scale of a
university laboratory
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SASE Amplifies Random Electron Density Modulations
Dw/w (%)
t (fs)
The SASE radiation is powerful, but noisy!
Solution: Impose a strong coherent modulation with an
external laser source
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A Transform-Limited X-ray Pulse
• Satisfies the Uncertainty Principle in all dimensions
Transverse phase space
Dx , Dy ~ 50 microns
Dkx , Dky ~ 10-5 nm-1
Dx Dkx = ½
Dy Dky = ½
Longitudinal phase space
Dt ~ 1fs - 1ps
2meV
Dw Dt = ½
Dw ~ 2eV -
A 1 milli-Joule pulse contains 5.0 x 1011 12 keV photons
Peak brilliance = 1036
March 2012
3rd Gen: 1025
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Brookhaven Laser Seeding Demonstration
eLaser
output
800 nm
266 nm
Modulator
Buncher
Radiator
High Gain Harmonic
Generation (HGHG)
HGHG
•Suppressed SASE noise
•Amplified coherent signal
SASE x105
•Narrowed bandwidth
•Shifted wavelength
L.H. Yu et al., Phys. Rev. Lett. 91, 74801 (2003).
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X-ray Science Driven by Beam Brilliance
Synchrotron
Radiation
X-ray Tubes
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Relativity
Coherent
Emission
X-ray Lasers
Compact X-ray Sources
• There is a growing and urgent need to fill the large gap between
laboratory x-ray tubes, and large central facilities.
• At nano-centers such as EMSL that are not at synchrotron sources,
advanced x-ray capability is the most important missing probe of matter.
• Advances in accelerator and laser technology make high-brilliance,
short pulses sources possible and affordable.
?
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The Technical Opportunity
Inverse Compton Scattering
• Head-on collision between a relativistic electron and a photon
e-
energy = Ee=  me
q
lL
lX
• Normal Compton Scattering the photon has higher energy than the electron
• The inverse process has the Thomson cross-section when
wX E ee
• The scattered photon satisfies the undulator equation with period lL/2 for
head-on collisions
lX = lL (1+2q2)
4 2
• Therefore, the x-ray energy decreases by a factor of 2 at an angle of 1/
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Lyncean Technologies Compact Source Concept
Courtesy of Ron Ruth
Parameters of Source
Average flux
Source size
109 photons/sec
50 microns
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MIT Inverse Compton Scattering Concept
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Full Calculations of the Photon Spectrum
Normalized emittance = 1.0 mm
Normalized emittance = 0.3 mm
photons/mrad2/eV
photons/mrad2/eV
Photon Energy (keV)
10
10
8
1
6
4
0.1
Photon Energy (keV)
100
12
10
1
8
6
0.1
4
2
2
-40
10
12
-20
0
q (mrad)
20
40
0.01
0.01
-40
-20
0
q (mrad)
Note: Plane Perpendicular to Laser Polarization
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20
40
Intensity Profile of 12 keV X-rays with 0.1% bw
8
8000
6
7000
4
6000
10000
9000
2
5000
0
4000
-2
3000
-4
2000
-6
1000
-8
Intensity (keV/mrad^2)
dy/dz (mrad)
Calculations by Winthrop Brown, MIT LL
8000
7000
6000
5000
4000
3000
2000
1000
0
-9
-8 -6 -4 -2 0 2 4
dx/dz (mrad)
6
-7
-5
8
-3
-1
1
3
q y (mrad)
~1012 photons/sec @ 100 MHz in 0.1% BW
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5
7
9
Conceptual Multi-User Facility based on ICS
1 kW cryo-cooled
Yb:YAG drive
laser
X-ray
beamline 2
Coherent enhancement
cavity with Q=1000
giving 1 MW cavity
power
X-ray
beamline 1
Inverse Compton
scattering
X-ray
beamline 3
6m
Superconducting
RF photoinjector
10 kW
beam dump
Electron beam of
1-100 mA
average current
at 10-30 MeV
Superconducting RF Linac
X-ray
beamline 4
8m
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X-ray Source Parameters
High average
flux
Single-shot
Tunable monochromatic photon energy [keV]
3 – 12
3 – 12
Pulse length [ps]
0.1 – 2
1 – 10
Flux per shot [photons]
5 x 106
1 x 1010
108
1-10
5 x 1014
1 x 1011
FWHM bandwidth [%]
25
25
On-axis bandwidth [%]
1
2
Source RMS divergence [mrad]
1
5
0.002
0.006
Peak brightness [photons/(sec mm2 mrad2
0.1%bw)]
1 x 1020
6 x 1022
Average brightness [photons/(sec mm2 mrad2)]
3 x 1015
6 x 1011
Parameter
Repetition rate [Hz]
Average flux [photons/sec]
Source RMS size [mm]
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X-ray Science Driven by Beam Brilliance
Coherent ICS
Incoherent ICS
Synchrotron
Radiation
X-ray Tubes
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Relativity
Coherent
Emission
X-ray Lasers
Coherent ICS
• How can coherent emission be achieved to boost ICS performance?
Answer: Maybe—by structuring the electron beam,
not by laser seeding, but by using a structured
nanocathode as a electron source, after T.
Akinwande, MIT.
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Coherent ICS
It appears possible to manipulate these structured bunches
in magnet arrays to compress, rotate, and exchange
transverse and longitudinal coordinates, resulting in a
sub nm periodic structure which will then coherently emit
a hard x-ray beam. See talk by Bill Graves on Wednesday
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Protein Crystallography
Small Crystals with Fixed Wavelength and MAD
• Goal: Achieve ICS images with 10 mm crystals of equal or better quality
compared to rotating anode (Rigaku FR-E) with 100 mm crystals.
20 cm
2 mm
Asymmetric Ge (111)
10 µ
or Si (111)
10 mrad
Multilayer
Osmic
Collimator
30 µ
‹ 100 µrad
3.3 mrad
│← 160
Fixed Wavelength:
MAD:
Multilayer
Osmic
Condenser
60 cm
mm →│
Ge(111); DE = 16 eV; R = 67%
Si (111); DE = 7 eV; R = 80%
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Medical Applications
• Medical Imaging—Improved Absorption Images
–
–
–
–
–
–
–
Current radiographs use 5-75 keV Bremstahlung spectrum
Low energy range causes skin dose, no contrast
High portion cause tissue dose with low contrast
Only the range of energies around 30 keV useful
ICS spectrum is ideal at 30 keV with 5-15% bandwidth
Image quality improved and dose reduced
We would establish collaboration with local radiologists to
further study these factors in detail
• Medical Imaging/Therapy—Tuning to specific
wavelengths
– Iodine contrast agent for blood imaging
– Gd or Pt based cancer therapy
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Medical Applications
• Medical Imaging—Phase Contrast Method
– Few micron circular source is ideal
– Many milli-radian divergence illuminates large objects in
short distance
– Few percent bandwidth can be fully utilized and presents
no limitation
– Would improve medical imaging for soft tissue while
reducing dose
– Could also utilize the single-shot mode for time-resolved
images
– Simplest approach requires no optics
– But optics could reduce spot size, increase coherence, and
increase illuminated area
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Ultrafast Science Opportunities
• Pico-second Science
– Synchrotron sources have 50-100 ps pulse lengths
– ICS source may have pulse lengths down to 100 fs
– At 1 ps the single-shot flux could be >109 photons in a 6%
bandwidth
– Large bandwidths are appropriate for Laue method as
pioneered by Wulff and co-workers at ESRF
– ICS could be run in a kHz mode for repetitive experiments
– Both diffraction and PC imaging modes possible
– Flux exceeds plasma sources by many orders of magnitude
– Flux exceeds storage ring pulse chopping schemes
– Would be a stepping stone to the big FELs
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Novartis
Kirk Clark, Novartis Institutes for
Biomedical Research
• Structural Biology is an integral component of many drug discovery programs.
– Guides medicinal chemistry efforts; turn-around time is critical
– Insight into protein function; novel structures benefit from tunable x-rays
– Epitope mapping for antibodies; rapid structures (even low resolution) valuable
• Benefits of bright, local x-ray source
– Time. Quick feedback on quality of small crystals and/or final datasets.
• Small crystals are more readily obtained with less reagents
• Reduced opportunity costs by avoiding needless improvements to good crystals.
– Facilitate expanding structural biology to integral membrane proteins.
– Costs. Reduced travel costs (currently traveling to Chicago/Zurich every 3 to 4 weeks),
proprietary fees, access fees.
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Wyeth
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National High Magnetic Field Laboratory
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NIST Gaithersburg Campus
Ultraviolet
Synchrotron
Radiation
Laser Spectroscopy
Advanced X-ray Facility
SIRCUS
CNST
Nanoscale Science &
Technology
SURF III
AXF
NCNR
Neutron Research
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Louvre Museum
VIS
LC2RMF = Laboratory of analytical chemistry and
scientific imaging located in the Louvre
Objectives: Research, expertise and support for curators
and conservators thanks to physico-chemical analyses.
Ø Necessity of non destructive testing with high sensitivity
because the studied materials are very complex
1989: Installation of the accelerator AGLAE in the Louvre
= ion beam analysis with an external microbeam (elemental
analysis, direct on the artifacts)
1997: Development of synchrotron radiation analysis =
structural and molecular analysis but necessity of samples
2009: Project of combination of AGLAE with an ICS in the
Louvre for non destructive structural and elemental analysis
(XRF, XANES, XRD) as well as for 3D imaging of works of art.
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X-ray
UV
Purdue University
Virus Protein Science at the MIT STC
-M. Rossmann, Biological Sciences
Conduct structure determinations of proteins
associated with viruses, and viral complexes with
antibodies and antiviral agents. Extend current
research efforts into
• bacteriophages
• animal RNA viruses
• large ds DNA viruses
• virus-membrane interactions
This Science & Technology Center could serve as
a model for a future Purdue facility geared to onsite handling of viruses and pathogens difficult to
handle at distant facilities. This would add to the
ds viruses
Flaviviruses
Bacteriophages
new
Hockmeyer Hall
of Structural Biology
and
the Birck Nanotechnology Center at Purdue.
March 2012
Picosecond Physics at the MIT STC
- S. Durbin, Physics Dept.
I. Laser pump deposits energy into the electronic
system, and the lattice response can be tracked with
an x-ray probe beam.
Use high rep rate (>106 Hz), ultrashort pulse length
(0.1-5 ps, not available at ANY synchrotron source))
to observe
• non-thermal melting, coherent phonons
•ferroelectric/complex oxide transitions
• porphyrin dynamics
II. X-ray pump, laser probe in semiconductors: Single
1 ps x-ray pulse (1010 x-rays) focused to 10 microns
can generate up to 1017 cm-3 instantaneous deep core
holes in a semiconductor. Laser monitor of absorption
and reflectivity will reveal the quantum kinetic
response of plasmons and phonons in this new manybody probe.
Alpha viruses
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University College London
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University of Copenhagen
Robert Feidenhans’l, Niels Bohr Institute, University of Copenhagen
Absorption
Phase shift
Aim : Medical Imaging
Franz Pfeiffer et al
Lab source setup
Cancerous
Lymph node
ESRF data
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Conclusions (Predictions)
• Within a decade FEL facilities will achieve single mode laser radiation in the
hard x-ray regime with milli-Joule power levels.
• Within two decades superconducting linac-based facilities will have many such
beamlines operating across a wide spectral range.
• There is no obvious “next generation” large facility. But….
• Within a decade compact sources less than $10M will offer NSLS I level (2nd
generation) x-ray properties.
• Within two decades compact sources will demonstrate coherent emission
revolutionizing laboratory-scale capability.
• Large facilities always be the most powerful sources simply due to the physics
of electromagnetic radiation from energetic charged particles.
• But the most creative science will most likely come from the laboratory sources,
just as with laser sources today, and x-ray sources of the early 20th century.
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