Dynamics of materials with X-ray Photon Correlation Spectroscopy - Opportunities and detector requirements

Transcription

1 Dynamics of materials with X-ray Photon Correlation Spectroscopy - Opportunities and detector requirements Quasi-static speckles from colloidal suspension near random compact packing volume fraction Speckles near the (409) Bragg peak of concanavalin A Andrei Fluerasu fluerasu@bnl.gov Washington DC, August

2 X-ray Photon Correlation Spectroscopy XPCS Mesoscale structure determines most (if not all) macroscopic properties of materials. X-ray Photon Correlation Spectroscopy (XPCS) measures collective meso-scale dynamics a) b) c) d) Scientific opportunities Structure and dynamics of complex materials: colloids, emulsions, polymers, gels and glasses, membranes, liquid crystals, bio-materials crowded systems = structure & dynamics affected by entropy, weak forces Wide range of time & length scales Examples of mesoscale structure: (a) porous silicon; (b) sponge phase in a polymer blend (S. Mochrie) (c) bicontinuous microstructure arrested by interfacial colloidal jamming (A. Moharaz et al.); (d) self-assembled amphiphilic nanotubes (Park C et al. PNAS 2006;103: ) Applications: photonics, lithography, high-tech materials, photovoltaics, paints, food, cosmetics, etc fundamental science: glass transition, rheology, jamming, non-equilibrium physics, complexity ( more is different - P. Anderson) Impact: Understanding dynamics may be the critical element in switching from a science of observation to a science of control. How do we characterize and control matter away especially very far away from equilibrium? Directing Matter and Energy: Five Challenges for Science and Imagination (BESAC) 2

3 XPCS: New Opportunities XPCS XPCSatatNSLS-II: high brightness SR structure determines most (if not all) Mesoscale sources: NSLS-II, APS, ERL(?) macroscopic properties of materials. X-ray Photon Correlation Spectroscopy (XPCS) 1/2 SNR=brightness*τ measures collective meso-scale dynamics Focus on: e.g.matter: NSLS-II >10 emulsions, x brighterpolymers, gels and Soft colloids, than other SRs liquid crystals, bio-materials glasses, membranes, crowded systems = structure & dynamics by time entropy, weak forces 100affected x faster scales Wide range of time & length scales a) b) c) d) 10μm Examples of mesoscale structure: (a) porous silicon; (b) sponge phase in a polymer blend (S. Mochrie) (c) bicontinuous microstructure arrested by interfacial colloidal jamming (A. Moharaz et al.); (d) self-assembled amphiphilic nanotubes (J. Douliez et al.) (i.e. reaching 1 μs) and shorter length scales than was ever Applications: possible before. photonics, lithography, high-tech materials, photovoltaics, paints, food, cosmetics, etc fundamental science: glass transition, rheology, jamming, non-equilibrium physics, complexity ( more is different - P. Anderson) However: Current detector technology is limited to 1-3 khz maximum frame rate New detectors enabling > MHz acquisition are required in order to capitalize on the unprecedented performance of the new, high brightness, light sources 3

4 XPCS 101 From R. Leheny Dynamic structure factor Reference: e.g. M. Sutton, CR Physique 9, 657 (2008) 4

5 What is an ideal XPCS detector? Specifications (from P. Siddons) 1000 Mpixels 1 μm pixels 1 ns frame rate; no dead time 100% efficiency at all energies 100 bit dynamic range free From O. Shpyrko 5

6 Detectors for XPCS - Current State of the Art Maxipix (ESRF) Based on chip developed by Medipix collaboration 1.4 khz, 55 μm pix size, single ph sensitivity, 100% efficiency (8keV), ~12-bit dynamic range C. Ponchut et al., J. Instrumentation 6, (2011) Enabled new science (@ ID10, ESRF) e.g. : cooperative behavior of nanoparticles suspended in a supercooled liquid C. Caronna et al., Phys. Rev. Lett. 100, (2008) Dynamics and rheology under steady shear flow A. Fluerasu et al., New J. of Phys. 12, (2010) Eiger (SLS) To become available ~ khz*, 75 μm pix size, single ph sensitivity, 100% efficiency (8keV), ~12-bit dynamic range B. Schmidt, unpublished * Dectris development 3kHz (but possible future upgrades) 6

7 Next best option for an XPCS detector? Photon counting provides best S/N Specifications 1-9 Mpixels 1 μs frame rate, ~10-20 ns time resolution (time stamping) μm pixels negligible dead time 100% efficiency at 8keV 4 bit dynamic range electronic shutter Preamp X6 Disc. ts=250 ns Inject/ option Feedback 2 3 Th 7 Program latches Two 5 bit counters Sparsification Serializer and LVDS Output Serial Output Line VIPIC project (FNAL/BNL) is close to matching 16 Serial Output Lines (LVDS) these ideal/realistic specs: 10 μs frame rate, ~20 ns time resolution (time stamping) 80 μm pixels, scalable to >1M pixels 7 4X64

8 Applications Example of science that is impossible to do without fast 2D detectors Dynamics in out-of-equilibrium glass complex materials Non-stationary and non-equilibrium dynamics (two-time correlations) Speckle Visibility Spectroscopy (with applications in mitigating beam damage, low scatterers, etc) 8

9 Dynamics of out-of-equilibrium system: complex fluids, glassy and jammed materials Challenges: Wide-range of time/length scales, with samples that are often beam sensitive and/or low scatterers Current experiments photon-limited Samples are often non-ergodig or non-stationary (e.g. aging) see next slide Opportunities: Understanding phenomena such as the colloidal glass transition Understanding the interplay between dynamics and rheology; designing complex fluids with specific viscoelastic properties Correlation functions from hard-sphere suspensions near the colloidal glass transition (P. Kwasniewski et al., unpublished) Self-assembled monodisperse supramolecular assemblies from polydisperse nanoparticles T.D.Nguyen, S. Glotzer, et al. Nature Nanotech

10 Dynamics of out-of-equilibrium system: non-stationary and aging samples Challenges: Most complex system exhibit complex time-dependent behavior (i.e. aging) Dynamics is often heterogeneous Opportunities: Measuring time-dependent dynamics using two-time analysis M. Sutton et al. Optics Express 11, 2268, 2003 Characterize dynamical heterogeneities or rare events A. Duri and L. Cipelletti, Eur. Phys. Lett. 76, 972, 2006 C. Sanborn et al. Phy. Rev. Lett 107, , 2011 Using two-time analysis and higher order correlations to understand and control phenomena such as self-assembling in complex systems Two-time correlation functions showing nonequilibrium effects ( aging ) and heterogeneous dynamics (let) in colloidal gels or dynamical rare events in a colloidal glass (right) (AF et al.) 10

11 Speckles from protein crystals: the low scattering limit Challenges: Beam damage, low scattering Solution: speckles are detected from single images by analyzing the probability of measuring 1,2,3,4,... scattered photons near Bragg spots of PXs Intensity distribution (speckles) Left: Reference sample (colloid) Right: scattering near the (409) Bragg spot of concanavalina incoherent scattering should follow Poisson statistics while speckles from coherent illumination follow neg binomial statistics (J.W. Goodman, 2007) Opportunities: Measuring dynamics of proteins using speckle visibility P.K. Dixon and D. J. Durian, Phys. Rev. Lett. 90, (2003) 11 spectroscopy

12 Conclusions Exciting (& challenging) opportunities for studying microscale dynamics of materials (examples show here focus on soft- and bio- matterials) Unprecedented coherent flux (e.g. NSLS-II) and experimental capabilities become available Fast 2D detectors for coherent scattering (speckles) are the single most important required development. Availability of such detectors would allow experiments that would capitalize on the unprecedented brightness of the new SRs and which are otherwise impossible 12