Science Program and Team Leaders Update

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Science Program and Team Leaders Update
Brian Stephenson LUSI XCS Scientific Team
Leader XCS Final Instrument Design
Review June 17, 2009
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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

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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.)
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Scattering of a Coherent Beam Speckle

• Speckle Reveals Dynamics, Even in Equilibrium
• X-ray Speckle Reveals Nanoscale/Atomic-scale
  Dynamics

Wide-Angle Scattering Ordering in Fe3Al Alloy
Small-Angle Scattering Polystyrene Latex Colloid
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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

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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

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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.

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XPCS using Sequential Mode

• Milliseconds to seconds time resolution
• Uses high average brilliance

sample
transversely coherent X-ray beam
monochromator
movie of speckle recorded by CCD
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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).
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Amphiphilic Complex Fluids
Amphiphilic molecules possess two (or more)
moieties with very different affinities e.g.
soaps, lecithin, block copolymers
..and organize immiscible fluids
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transversely coherent X-ray pulse from FEL
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Relaxor Ferroelectrics
Dielectric relaxation times span picoseconds to
milliseconds near phase transition Polar
nanoregions are believed responsible
G. Xu et al., Nature Materials 5, 134 (2006)
J. Macutkevic et al., Phys. Rev. B 74, 104106
(2006)
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Dynamics at Surfaces and Interfaces
Study fluctuations at surfaces and interfaces
in fluids, membranes, XFEL Onset of
non-classical behaviour (Q gt 2 nm-1) (beyond
continuum hydrodynamics)
Capillary wave dynamics at high Q (?1Å, Q1
nm-1) ? s countrate (FEL) Water ?
25 ps 20 Mercury ? 0.5 ps
0.3
G. Grübel et al., TDR XFEL, DESY (2006)
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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

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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

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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