X-Rays and Materials

1
X-Rays and Materials
A Vision of the Future
Joachim Stöhr Stanford Synchrotron Radiation
Laboratory
2
The big Picture US Gross
Domestic Product 10 Trillion
In 's Information technology 800
Billion Chemical Industry 400
Billion Semiconductors 80
Billion Magnetic materials
25 Billion Pharmaceutical
industry 220 Billion Biotech Industry
30 Billion
Modern materials are complex studies require
sophisticated techniques
3
Present Size gt 0.1 mm, Speed gt 1 nsec Future
Size lt 0.1 mm, Speed lt 1 nsec
Ultrafast Nanoscale Dynamics
4
(No Transcript)
5
Growth of X-Ray Brightness and Magnetic Storage
Density
6
Why X-Rays? - Chemical Sensitivity
Core level shifts and Molecular
orbital shifts
Stöhr et.al
7
(No Transcript)
8
Polarization Dependence
Normalized Intensity (a.u.)
F8 22C
Photon Energy (eV)
9
Magnetic Spectroscopy and Microscopy
10
(No Transcript)
11
Real Space Imaging
X-Rays have come a long way
1895
1993
12
Photoemission Electron Microscopy PEEM at ALS
The Future PEEM3
PEEM2 on BL 7.3.1.1
PEEM2 PEEM3 nm nm Resolution 50
nm lt 5 nm (1 transmission) Transmission 1
50 _at_ 50 nm Resolution Relative photon flux
1 20 Relative Flux density 1 gt1000 Source /
bend EPU (arbitrary) Polarization
13
4.0.3 PEEM3 Microscope

• total electron yield imaging
• no LEEM mode (as in SMART)

14
Resolution vs Transmission
15
(No Transcript)
16
Spectromicroscopy of Ferromagnets and
Antiferromagnets
AFM domain structure at surface of NiO substrate
FM domain structure inthin Co film on NiO
substrate
NiO XMLD
Co XMCD
H. Ohldag, A. Scholl et al., Phys. Rev. Lett.
86(13), 2878 (2001).
17
Non Resonant X-Ray Scattering
Relative Intensity (hn / mc2)2
Relative Intensity 1
hn 10 keV, mc2 500 keV
18
Fe metal L edge
Kortright and Kim, Phys. Rev. B 62, 12216 (2000)
19
Resonant Magnetic Soft X-ray Scattering
Fe
charge
magnetic -XMCD
f

e
'

e
-
i
(
e
'

e
)

M
F
(
1
)
F
(
0
)
n
n
n
n
where Fn(i) are complex
f1 i f2
Note at resonance f1 0
Kortright and Kim, Phys. Rev. B 62, 12216 (2000)
20
Incoherent vs. Coherent X-Ray Scattering
Small Angle Scattering Coherence length larger
than domains, but smaller than illuminated area
information about domain statistics
Speckle Coherence length larger than illuminated
area
true information about domain structure
21
Present Pump/Probe Experiments
Laser pulse

• Pump
• Laser
• Probe
• delayed photon pulse
• Vary the delay between laser and x-ray pulses

50 ps
330 ns
X-Ray pulse
?
Can also produce current pulses
22
Development of High Energy Physics and X-Ray
Sources
-- From storage rings to linacs --
SR
HEP
Storage rings
Single pass linear colliders
Single pass linacs Free electron lasers
(FELs) Energy recovery linacs (ERLs)
23
X-Ray Brightness and Pulse Length

• X-ray brightness determined by electron beam
  brightness
• X-ray pulse length determined by electron beam
  pulse length

Storage ring Emittance and bunch length are
result of an equilibrium typical numbers 2 nm
rad, 50 psec
Linac Normalized emittance is determined by gun
Bunch length is determined by compression typical
numbers 0.03 nm rad, 100 fs
Linac beam can be much brighter and pulses much
shorter at cost of jitter
24

• SASE gives 106 intensity gain
• over spontaneous emission
• FELs can produce ultrafast
• pulses (of order 100 fs)

l
25
LINAC COHERENT LIGHT SOURCE
0 Km
2 Km
3 Km
26
Concepts of the LCLS

• Based on single pass free electron laser (FEL)
• Uses high energy linac (15 GeV) to provide
  compressed electron beam to long undulator(s)
  (120 m) 200 fs or less
• Based on SASE physics to produce 800-8,000eV (up
  to 24KeV in 3rd harmonic) radiation - 1012
  photon/shot
• Analogous in concept to XFEL of TESLA project at
  DESY
• Planned operation starting in 2008

27
From Molecules to Solids Ultra-fast Phenomena
Note in quantum regime 1 eV corresponds to
fluctuation time of 4 fs
Chemistry Biology
H2O?OH H about 10 fs
time depends on mass and size
Fundamental atomic and molecular reaction and
dissociation processes
Fundamental motions of charge and spin on the
nanoscale (atomic 100nm size)
28
X-Ray Photon Correlation Spectroscopy Using Split
Pulse
In picoseconds - nanoseconds range Uses high
peak brilliance
sample
transversely coherent X-ray pulse from LCLS
variable delay
sum of speckle patterns from prompt and delayed
pulses recorded on CCD
Analyze contrast as f(delay time)
Contrast
29
Single shot Imaging by Coherent X-Ray Diffraction
Phase problem can be solved by oversampling
speckle image
? 5 ?m (different areas)
S. Eisebitt, M. Lörgen, J. Lüning, J. Stöhr, W.
Eberhardt, E. Fullerton (unpublished)
30
Spin Block Fluctuations around Critical
Temperature
Tc
Magnetization
Temperature
t (T-Tc) / Tc
T lt Tc
T ? Tc
T gt Tc
31
Structural Studies on Single Particles and
Biomolecules
Conventional method x-ray diffraction from
crystal
Proposed method diffuse x-ray scattering from
single protein molecule Neutze, Wouts, van der
Spoel, Weckert, Hajdu Nature 406, 752-757 (2000)
Lysozyme
Calculated scattering pattern from lysozyme
molecule
Implementation limited by radiation damage In
crystals limit to damage tolerance is about 200
x-ray photons/Å2 For single protein molecules
need about 1010 x-ray photons/Å2 (for 2Å
resolution)
32
X-Ray Diffraction from a Single Molecules
A bright idea Use ultra-short, intense x-ray
pulse to produce scattering pattern before
molecule explodes
Just before LCLS pulse
Just after pulse
Long after pulse
The million dollar question Can we produce an
x-ray pulse that is
short enough?
intense enough?
33
Summary
X-FELs will deliver unprecedented brightness and
femtosecond pulses Understanding of laser
physics and technology well founded FELs
promise to be extraordinary scientific
tools Applications in many areas chemistry,
biology, plasma physics, atomic physics,
condensed matter physics
34
The End