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

Small-Angle Scattering: Polystyrene Latex Colloid

Wide-Angle Scattering: Ordering in Fe3Al Alloy

• Speckle Reveals Dynamics, Even in Equilibrium

• X-ray Speckle Reveals Nanoscale/Atomic-scale Dynamics

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.

transversely coherent X-ray beam

sample

XPCS using ‘Sequential’ Mode

• Milliseconds to seconds time resolution• Uses high average brilliance

t1

t2

t3

monochromator

“movie” of specklerecorded by CCD

g2(Δt)≡ I(t) I (t+Δt)I 2

1Δt

g2

ττ−1(Q)=Rate(Q)

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 FluidsAmphiphilic molecules possess two (or more) moieties with very different affinities

e.g. soaps, lecithin, block copolymers

..and organize immiscible fluids

transversely coherent X-ray pulse from FEL

sample

XPCS at LCLS using ‘Split Pulse’ Mode

Femtoseconds to nanoseconds time resolutionUses high peak brilliance

sum of speckle patternsfrom prompt and delayed pulses

recorded on CCD

I(Q,Δt)

splitter

variable delay Δt

Δt

τ

Con

trast Analyze contrast

as f(delay time)

10ps⇔ 3mm

Relaxor FerroelectricsDielectric relaxation times span picoseconds to milliseconds near phase transition

Polar nanoregions are believed responsible

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

G. Xu et al., Nature Materials 5, 134 (2006)

J. Macutkevic et al., Phys. Rev. B 74, 104106 (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)

G. Grübel et al., TDR XFEL, DESY (2006)

Capillary wave dynamics at high Q (=1Å, Q=1 nm-1):

[s] countrate (FEL)

Water 25 ps 20 Mercury 0.5 ps 0.3

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