Transcript Science Program and Team Leader's Update

Science Program and Team Leaders Update
Brian Stephenson
LUSI XCS Scientific Team Leader
XCS Final Instrument Design Review
June 17, 2009
History
• Scientific case for LCLS developed in September 2000
in “The First Experiments” document
• One of the six themes, “Studies of Nanoscale
Dynamics in Condensed Matter Physics,” focused on
the use of x-ray correlation spectroscopy (XCS)
• XCS Scientific Team formed in summer of 2004 from
scientists submitting Letters of Intent to develop
experiments
• Group has grown to include additional interested
scientists from workshops
XCS Scientific Team
Leader:
Brian Stephenson (Materials Science Div., Argonne)
Co-Leaders:
Karl Ludwig (Dept. of Physics, Boston Univ.),
Gerhard Gruebel (DESY)
Sean Brennan (SSRL)
Steven Dierker (Brookhaven)
Eric Dufresne (Advanced Photon Source, Argonne)
Paul Fuoss (Materials Science Div., Argonne)
Zahid Hasan (Dept. of Physics, Princeton)
Randall Headrick (Dept. of Physics, Univ. of Vermont)
Hyunjung Kim (Dept. of Physics, Sogang Univ.)
Laurence Lurio (Dept. of Physics, Northern Illinois Univ.)
Simon Mochrie (Dept. of Physics, Yale Univ.)
Alec Sandy (Advanced Photon Source, Argonne)
Larry Sorensen (Dept. of Physics, Univ. of Washington)
Mark Sutton (Dept. of Physics, McGill Univ.)
Scattering of a Coherent Beam: Speckle
• Speckle Reveals Dynamics, Even in Equilibrium
• X-ray Speckle Reveals Nanoscale/Atomic-scale Dynamics
Small-Angle Scattering:
Polystyrene Latex Colloid
Wide-Angle Scattering:
Ordering in Fe3Al Alloy
Scientific Impact of X-ray Photon Correlation Spectroscopy
at LCLS
New Frontiers:
• Ultrafast
• Ultrasmall
Time domain
complementary to
energy domain
Both equilibrium and
non-equilibrium
dynamics
Unique Capabilities of LCLS for XPCS Studies
Higher average coherent flux will move the frontier
• smaller length scales
• greater variety of systems
Much higher peak coherent flux will open a new frontier
• picosecond to nanosecond time range
• complementary to inelastic scattering
Wide Scientific Impact of XPCS at LCLS
•Simple Liquids – Transition from the hydrodynamic to the kinetic regime.
•Complex Liquids – Effect of the local structure on the collective dynamics.
•Polymers – Entanglement and reptative dynamics.
•Proteins – Fluctuations between conformations, e.g folded and unfolded.
•Glasses – Vibrational and relaxational modes approaching the glass transition.
•Phase Transitions – Order fluctuations in ferroelectrics, alloys, liquid crystals, etc.
•Charge Density Waves – Direct observation of sliding dynamics.
•Quasicrystals – Nature of phason and phonon dynamics.
•Surfaces – Dynamics of adatoms, islands, and steps during growth and etching.
•Defects in Crystals – Diffusion, dislocation glide, domain dynamics.
•Soft Phonons – Order-disorder vs. displacive nature in ferroelectrics.
•Correlated Electron Systems – Novel collective modes in superconductors.
•Magnetic Films – Observation of magnetic relaxation times.
•Lubrication – Correlations between ordering and dynamics.
XPCS using ‘Sequential’ Mode
• Milliseconds to seconds time resolution
• Uses high average brilliance
transversely coherent
X-ray beam
g2 (t) 
t1
sample
monochromator
t2
I(t) I(t  t)
2
I
t3
g2
 1 (Q)  Rate(Q)

1
t
“movie” of speckle
recorded by CCD
I(Q,t)
Time Correlation Functions for
Various Wavenumbers
Autocorrelations, g2(Q,t) for 70nm-radius PS spheres in glycerol at volume
fractions of 0.28 (left, single exponential) and 0.52 (right, double exponential,
but a stretched exponential can also be used). L.B. Lurio, et al. Physical
Review Letters 84, 785-788 (2000).
Amphiphilic Complex Fluids
Amphiphilic molecules possess two (or more) moieties with very different affinities
e.g. soaps,
lecithin,
block copolymers
..and organize immiscible fluids
XPCS at LCLS using ‘Split Pulse’ Mode
Femtoseconds to nanoseconds time resolution
Uses high peak brilliance
sample
splitter
transversely coherent
X-ray pulse from FEL
variable delay
t
Contrast
10 ps  3mm
Analyze contrast
as f(delay time)

t
sum of speckle patterns
from prompt and delayed pulses
recorded on CCD
I(Q,t)
Relaxor Ferroelectrics
Dielectric relaxation times span picoseconds
to milliseconds near phase transition
Polar nanoregions are believed responsible
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
J. Macutkevic et al., Phys. Rev. B
74, 104106 (2006)
G. Xu et al., Nature Materials 5,
134 (2006)
Dynamics at Surfaces and Interfaces
Study fluctuations at surfaces and
interfaces in:
fluids,
membranes,
…
XFEL:
Onset of non-classical behaviour
(Q > 2 nm-1)
(beyond continuum hydrodynamics)
Capillary wave dynamics at high Q
(=1Å, Q=1 nm-1):
 [s]
Water
Mercury
 25 ps
 0.5 ps
countrate (FEL)
20
0.3
G. Grübel et al., TDR XFEL, DESY (2006)
Design Goals and Challenges
• Use of high x-ray energies, up to 24 keV, for flexibility
in reducing beam heating
• Ability to tailor coherence parameters, e.g. beam size,
monochromaticity
• Versatile geometry diffractometer
• Large sample-to-detector distance at small and large
scattering angles
• Area detector with small pixels and low noise
XCS Scientific Team Input into XCS
Instrument
• Following the requirements determined by the scientific
case, an XCS Instrument was designed by LUSI staff
(this will be described by Aymeric Robert later today)
• The Team helped develop the Physics Requirements
Document for XCS Instrument (see Backup Documents
on FIDR web page)
• The XCS Scientific Team has had extensive input into
the instrument design through initial LOIs, workshops,
and regular meetings of Team Leaders with LUSI staff
and review committees
XCS Instrument is Ready for CD3
• The design of the XCS Instrument is
mature and meets the performance
requirements of XCS experiments at
LCLS
• The new schedule allows delivery of
an Early Science Instrument suitable
for a large class of XCS experiments
a year earlier than previously
possible
• We recommend rapid approval of
CD3 to allow XCS users to take
advantage of the successful early
lasing of LCLS at hard x-ray energies