X-Ray Science Division: Postdoctoral Projects

Researchers in XSD groups use Advanced Photon Source beamlines and techniques to perform a wide variety of experiments across many scientific disciplines. Several Postdoctoral project research opportunities are available within each group. Select a group below for a list of current projects and contact information.

For more information regarding Postdoctoral or other educational opportunities at Argonne, visit the Division of Educational Programs. All open Postdoctoral positions at Argonne are posted here.

• Chemistry, Environmental and Polymer Science

  Peter Chupas (630-252-8651, chupas@anl.gov):

  • Watching Nano-particles Grow:  Probing the Mechanism and Kinetics for the Formation and Growth of Catalytic Nano-Particles with In-situ Pair-Distribution Function Analysis.
    Highly dispersed supported metal nano-particles find widespread application in catalysis, including in hydrocarbon reforming, hydrogen production, and fuel cells. Pivotal to the development of catalytic materials with controlled reactivity, is the understanding of the fundamental mechanisms that drive the formation of catalytic nano-particles.  A key step towards this goal is the ability to discriminate between the separate processes including the initial reaction of precursors and the subsequent nano-particle sintering. Recently, the Pair-Distribution-Function (PDF) method has emerged as a powerful technique to probe the structure of nano-scale materials, with atomic-scale resolution across the entire length scale of the nano-particle, although to date this has been limited to studies of static materials prepared ex situ, i.e., in advance of the measurement.  We have been developing and using time-resolved PDF methods, with resolution as fast as 30 milliseconds, to monitor the structural evolution and kinetics associated with the formation of catalytic nano-particles from.  We apply differential-PDF (d-PDF) methods, which allow the atom-atom correlations involving the metallic nanoparticle (eg. Pt, Ru, Cu, Au, etc.) to be separated from those of the support (oxides such as SiO2, Al2O3, and TiO2), to probe the structure of the nano-particles directly.

  Steve Heald (630-252-9795, heald@aps.anl.gov):

  • Application of x-ray microanalysis to Hanford cleanup problems.
    A legacy of the cold war is a variety of contaminated sites at Hanford and other DOE facilities. In collaboration with researchers at Pacific Northwest National Laboratory, we have been using x-ray fluorescence imaging, micro-XAFS, micro-diffraction and bulk XAFS to study the fate of elements such as U, Tc and Cr in Hanford sediments. The detailed structural information from these measurements have proven to be invaluable in understanding the valence and compositional changes occurring in the field. When combined with other laboratory experiments, these results are used to guide cleanup decisions at the Hanford site and elsewhere.

  Steve Heald (630) 252-9795, heald@aps.anl.gov), Dale Brewe (630) 252-0582, brewe@aps.anl.gov):

  • Time resolved EXAFS studies of the light induced structural phase transition in La2CuO4.
    Femtosecond light pulses have been observed to drive a structural phase transition in La2CuO4 with a lifetime of a few hundred psec. The previous measurements simply observed a c-axis contraction, but provided no information on the detailed mechanism. At sector 20 we have developed an efficient time resolved XAFS facility capable of 100 psec resolution, and we plan to use this facility to study the phase transition in detail. Polarization dependent near edge and EXAFS at the Cu site can provide detailed information on the chemical and structural changes accompanying the transition. There is also an opportunity to get involved in other time resolved experiments ongoing at sector 20 such as laser induced melting, and transient phases in DVD materials.

  Byeongdu Lee (630-252-0395, blee@aps.anl.gov):

  • Small angle X-ray scattering (SAXS) for Research in Chemistry, Environment, and Polymer Science. Currently, we are developing various SAXS techniques/theories, including GISAXS, ASAXS, and time-resolved SAXS, at 12ID at APS and applying for studies in the field of chemistry, environment and polymer science. On-going research projects are listed as follows: Firstly, structural variations of catalysts, which are nano/subnano clusters deposited on substrates, during in-situ reactions, are being monitored by GISAXS and Mass spectroscopy simultaneously. Secondly, thermodynamics determining morphological structures of block copolymer/nanoparticle composites have been studied using SAXS/SANS/GISAXS and microscopy. Finally, growths and structure formations of nano-objects in solutions are of interest. DNA/nanoparticle hybrid and nucleation/growth of inorganics in solutions are being studied in collaborations with outside researchers.

  Randall Winans (630-252-7479, rewinans@anl.gov):

  • In Situ Studies of Catalytic Systems by X-ray Scattering.
    Small-angle X-ray scattering techniques are being used to follow changes in structure of nanocatalysis under realistic conditions.  Systems such as partial oxidation of alkenes to alkene oxides and hydrogen from alcohols are being studied.  The reactivity of these processes with nanocatalysis such as platinum, gold, silver and copper is very dependent on the size and shape of the metal particles which in turn depend on substrates and reaction conditions.
  • Reactivity Studies of Fossil Fuels by X-ray Scattering.
    Both SAXS and high energy scattering with PDF is being used to better understand the reactivity of fossil fuels such as coal, oil shale and heavy petroleum.  The effects of CO2 on coal structure is being studied to model sequestration processes.  Oil shale is a very large hydrocarbon resource in the U.S. but extraction of the hydrocarbons is very difficult. The reactivity of oil shale under high pressures is being explored.

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• Inelastic X-Ray & Nuclear Resonant Scattering

  E. E. Alp (630-252-4775, eea@aps.anl.gov):

  • Momentum-resolved inelastic x-ray scattering with 2 meV resolution for solids and liquids under high-pressure.
  • Nuclear Resonant Inelastic x-ray scattering in materials science
  • Synchrotron Mossbauer Spectroscopy under high pressure and low temperatures
  • Momentum resolved Resonant Inelastic X-Ray scattering for transition metal oxides and other correlated electron systems

  Yuri Shvyd'ko (630-252-2901, shvydko@aps.anl.gov):

  • Excitations of correlated electrons in condensed matter systems using Inelastic x-ray scattering.
    The newly built medium energy resolution inelastic x-ray scattering (MERIX) spectrometer at 30-ID, by far the best in its class, allows state-of-the-art studies of electronic excitations in strongly correlated systems using resonant or non-resonant inelastic x-ray  scattering with medium energy resolution about 0.1 eV. The photon energy  range 5-12 keV. The main focus is on the 3d-transition metal oxide, and  4f rare earth systems: Mott-Habard systems (high-Tc cuprate  superconductors, cobaltite superconductors and thermoelectric materials,  CMR manganites, nikelites, vanadates), multiferroics, heavy fermions, Kondo systems, etc.

  Wolfgang Sturhahn (630-252-0163, sturhahn@anl.gov):

  • Inelastic x-ray scattering under extreme conditions.
    High-resolution inelastic x-ray scattering and nuclear resonant scattering have provided us with completely new avenues to address cross-disciplinary problems. For example, sound velocities in iron-bearing materials of great importance to geophysics were derived under pressure up to 1.5Mbar and temperatures up to 3000K. We are now seeking to extend our capabilities and apply momentum resolved IXS to solids and liquids under high pressure. The latter in particular has not been explored and offers the potential for surprising discoveries.

  Thomas Toellner (630-252-0166, toellner@anl.gov):

  • Ultrahigh-energy-resolution inelastic x-ray scattering.
    Develop and implement an ultrahigh-energy-resolution x-ray monochromator and perform nuclear resonant inelastic scattering measurements on relevant materials. This project involves significant instrumentation development, but offers the post-doctoral candidate with a fresh opportunity to extend inelastic x-ray scattering into unexplored areas.

  Jiyong Zhao (630-252-9195, jzhao@aps.anl.gov):

  • Nuclear resonant scattering studies under high pressure and temperature.
    Sound velocities and densities of Earth and planetary materials measured under high P-T conditions are most important for our understanding and modeling of planetary interiors. These materials are often opaque and cannot be studied with conventional light-scattering methods. Nuclear resonant scattering can fill this gap and provide phonon density of states, valences, and electronic configurations. This project will make use of the unique high-pressure and x-ray capabilities and the Advanced Photon Source.

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• Materials Characterization

  Jon Almer (630-252-1049, almer@aps.anl.gov):

  • Studies of layered systems using microfocused high-energy x-rays.
    At beamline 1-ID we are developing novel high-energy x-ray microfocusing techniques, utilizing both small- and wide-angle scattering for materials analysis. Key features of our capabilities include high penetration power (several mm in most materials), high real-space spatial and temporal resolution, and the ability to simultaneously probe large regions of reciprocal space.  Resulting data is analysed for relevant parameters including quantitative phase fractions, internal strain, particle size, texture and porosity.  An ongoing research goal is to use and extend these techniques for in situ studies of layered systems.  Systems of interest include solid-oxide fuel cells and protective coatings (e.g. thermal barrier coatings, metal-nitride coatings), which have strong relevance in energy applications.

  Chris J. Benmore (630-252-7665, Benmore@anl.gov):

  • High Energy X-ray Diffraction from Liquids and Glasses at Extreme Conditions.
    Glasses are technologically important materials and our understanding of structure-property relations at the atomic level is essential for tuning their optical and electronic properties. We are developing techniques for studying the structure of liquids and supercooled melts at high temperatures through laser heating of aerodynamic levitated droplets, as well as high pressure techniques for studying both abrupt and continuous amorphous to amorphous transitions.

  Dean Haeffner (630-252-0126, haeffner@aps.anl.gov):

  • Combined high-energy x-ray techniques for the study of heterogeneous materials.
    The 1-ID beamline at the APS is one of the premier sources of high-energy x-rays (50-120 keV) in the world. At this beamline, high-energy x-rays are used for a variety of wide-angle scattering, small-angle scattering, and imaging techniques.  This project is focused on using these various techniques in combination to study heterogeneous materials in situ to develop a far more complete understanding of complex materials systems than can be ascertained by any one experimental probe.

  Peter L. Lee (630-252-0162, pllee@aps.anl.gov):

  • Structural Studies Employing High-Energy X-Ray Powder Diffraction.
    The main focus of the research program is exploring new opportunities in the area of in situ pair distribution function, Rietveld powder analysis and resonant powder diffraction structural studies employing high-energy x-rays.  We develop techniques to study reactions in real time, phase transitions under extreme condition such as high pressure and/or high temperature and metal ion distribution at different crystallographic sites in the crystal structure.  Sample publications in this area include: J. Appl.  Cryst., (2003), 36, 1342-1347; JACS, (2004), 126, 4756-4757; J. Appl.  Cryst., (2005), 38, 433 -441; Chem. Comm., (2006), 38, 4013-4015. 

  Ulrich Lienert (630-252-0120, lienert@aps.anl.gov):

  • Structural characterization of polycrystalline materials on the single grain length scale.
    Polycrystalline bulk materials are characterized on the single grain length scale in situ during thermo-mechanical processing employing high energy x-rays. Over the last years dedicated x-ray optics, instrumentation, and software has been developed at the 1-ID beamline in close collaboration with national and international research groups. Ongoing scientific studies include: (1) sub-grain structure formation within FCC metals under tensile deformation, (2) grain growth in aluminum, (3) domain flipping in ferroelectrics, and (4) orientation relationships and strain under phase transformations.

  Wenjun Liu (630-252-0890, wjliu@anl.gov):

  • Structural characterization by three-dimensional x-ray diffraction microscopy.
    The principle research activities in the beamline 34-ID-E involve development of exciting new small-area diffraction techniques for characterization and microscopy at the micro- and nano-scale, in support of material sciences and condensed matter physics. By using Kirkpatrick-Baez (K-B) focusing mirrors and newly developed differential aperture techniques, spatially resolved micro-diffraction measurements can be made with submicron resolution in all three dimensions. Properties that can be measured include local crystalline phase, texture (grain orientation), and strains, which enable detailed studies of fundamental deformation processes, basic grain-growth behavior, and small scale structures.

  Yang Ren (630-252-0363, yren@anl.gov):

  • High-Energy X-ray Diffraction Studies of Materials in Complex Sample Environments.
    Many materials with interesting properties, such as high temperature superconductivity, relaxor ferroelectricity, colossal magneto-resistivity, colossal magneto-elastic effect, and multiferroics, have a propensity to form intrinsically inhomogeneous structures on a variety of length scales, from macroscopic phase separation to nanoscale domains embedded in a matrix. It is of fundamental importance to study those structural inhomogeneities and their real-time responses to the external stimuli. Exploiting the advantages of synchrotron high-energy x-rays, we have been developing experimental facilities for high resolution high-energy x-ray diffraction study of structural changes of samples under multiple simultaneous sample environments, which includes combinations of high/low temperature, high pressure, high magnetic field and electric fields.

  Sarvjit D. Shastri (630-252-0129, shastri@aps.anl.gov):

  • High-Energy X-Ray Optics Development (50-150 keV).
    Standard optics concepts designed to work at conventional x-ray energy ranges encounter problems when pushed to work at high energies, where the 7 GeV APS is an intense source. Given the numerous advantages of employing these photon energies to materials research, the efforts of this program are directed towards developing optimized optics for high-energy x-rays. Research is directed at brilliance-preserving monochromators (of various degrees of energy resolution), some of which operate under extreme heat load, focusing schemes, and stability. In addition to the obviously "hands-on" engineering aspects of such work, conceptual tools include: dynamical diffraction theory (for unstrained and strained crystals), wave propagation through focusing optics, elasticity theory, and heat transfer.

  Brian Toby (630-252-5488, Brian.Toby@anl.gov):

  • Combined Methods in Powder Diffraction.
    Crystallographic studies draw their great power from the large number of independent structural observations that can be made from a single sample. In powder diffraction, the information available is reduced significantly due to radial averaging, so the amount of structural detail that can be learned is often reduced. We have made many studies where multiple techniques (x-ray diffraction, neutron diffraction, molecular mechanics, database mining…) are utilized to provide models of greater complexity than can be derived from a single set of observations and to provide greater confidence in these models. We will continue apply these methods and seek to extend the techniques to utilize more scientific measurement data directly in the model fitting process.

  Robert B. Von Dreele (630-252-8178, vondreele@anl.gov):

  • Protein Powder Diffraction.
    An outstanding problem in our understanding of protein structure and function is the relatively low yield of transforming a gene sequence into a detailed protein crystal structure. Much of the loss is the inability to form protein single crystals of sufficient size (>>20mm) and quality for diffraction. We are developing an alternative approach based on the idea that polycrystalline material (~1mm "perfect" crystallites) is more readily formed than large single crystals. We then use high-resolution powder diffraction for protein structure determination by combining approaches developed for small molecules with those used for single-crystal protein structure determination. Powder diffraction is also ideal for exploring the formation of protein/ligand complexes and determining the details of the interaction.

  Jun Wang (630-252-0324, wangjun@aps.anl.gov):

  • Structural Evolution by Powder Diffraction.
    We are developing novel methods to extract structural changes in typical powder diffraction experiments. By removing/minimizing radiation effects, high-resolution structures can be determined and real structure intermediates can be obtained.  Targeted systems for study include x-ray driven catalysis and x-ray induced structural changes, as well as chemical reaction studies.

  Zhan Zhang (630-252-0863, zhanzhang@anl.gov):

  • Probing the Atomic Scale Structure at the Oxide-Aqueous Solution Interface with X-ray Scattering Methods.
    We are studying the interface structure at the boundaries between solid phase oxides and aqueous solutions in situ with a combination of several X-ray scattering methods, such as the crystal truncation rod (CTR), X-ray standing waves (XSW), and resonant anomalous X-ray reflectivity (RAXR).  A detailed atomic scale structure with element sensitivity is be obtained, which provides critical information to further understand the reactions that occur at such interfaces. Such reactions are important for catalysis, water purification, mineral migration and crystal growth.

  Paul Zschack (630-252-0860, zschack@anl.gov):

  • Structural Properties in Thermoelectric Materials.
    Thermoelectric materials directly convert thermal gradients into electric current (and vice versa). They hold great promise for significant advancements in refrigeration and power generation technology.  The challenge in thermoelectric materials development is to manipulate the structure & physical properties of these systems in order to improve electrical conductivity and simultaneously reduce thermal conductivity. For newly discovered, highly efficient, thermoelectric materials, we use X-ray scattering and diffraction techniques to relate structural details at the nanometer length scale and the interplay between order/disorder to the material’s extremely low thermal conductivities. New synthesis strategies will result from a fundamental understanding of the mechanisms that lead to the enhanced thermoelectric properties.

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• Magnetic Materials

  John Freeland (630-252-9614, freeland@aps.anl.gov):

  • Creating Novel Ground states At the Interface Between Different Complex Oxides
    One of the current problems of intense interest to the condensed matter physics community is the behavior of systems with strongly interacting electrons. These systems contain a variety of competing strong interactions which create a subtle balance to define the lowest energy state (e.g metal, insulator, superconductor.) Now through the use of state of the art sample fabrication, one can create high quality interfaces between dissimilar strongly correlated electron systems. The broken symmetry at the interface though can then drastically upset the subtle balance of these competing energies and lead to significant deviations from the bulk properties. Using the element resolved nature of the x-ray probes, one is able to understand how the electronic and magnetic structure at the interface is modified is systems such as superconductor (YBa2Cu3O7)/ferromagnetic (LaCaMnO3) and antiferromagnetic insulator (CaMnO3)/paramagnetic metal (CaRuO3). At the boundary between the two oxides, the behavior is quite different from the bulk constituents and use of the Advanced Photon Source provides the opportunity to create and study new states created at the interface.

  Zahir Islam (630-252-9252, zahir@aps.anl.gov):

  • Synchrotron studies of materials in high-field pulsed magnets.
    Materials subjected to extreme conditions such as high magnetic fields are of great interest in contemporary condensed matter physics. From basic science point of view, novel states of matter that are crucial for developing a correct theoretical understanding of materials can only be realized by high magnetic fields. Since magnetic field couples directly to the spin and orbital degrees of freedom and it is an integral part of the canonical momentum, it acts as a contact-free and versatile experimental “knob” for tuning properties and states of matter. From applications point of view, inorganic and organic materials can be treated or manipulated by magnetic fields to change their functional behavior. A high-field (30T) portable pulsed magnet project is underway to facilitate numerous x-ray scattering and spectroscopic techniques to study materials on various beamlines at the APS. The characteristic features of the magnets are their small bore requiring only a low-energy capacitor bank to generate milli-second long magnetic pulse. Physical systems of current interests include spin-gap compounds, quantum criticality in novel oxides, and geometrically frustrated magnets, respectively. This instrument is unique in the US and promises to usher in unprecendented studies of non-equilibrium states driven by magnetic fields as well.

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• Optics Fabrication and Metrology

  Albert Macrander (630-252-5672, macrander@aps.anl.gov):

  • Wave-Optical Simulations and Testing of Hard X-ray Optics
    Metrology data obtained in the XSD Metrology Laboratory will be used to simulate the performance of mirrors, multilayers, and crystals designed as optics for the hard x-rays produced by the APS. The position involves testing of the optical performance on beamlines in order to compare to the simulations. The simulations will incorporate true wave optics a priori, and involve as few approximations as possible. The simulation level of complexity and capability is expected to grow in preparation for beamlines at the APS Upgrade/ERL.

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• Time Resolved Research

  Eric Landahl (630-252-0278, elandahl@anl.gov), Eric Dufresne (630-252-0274, dufresne@aps.anl.gov), Jin Wang (630-252-9125, wangj@aps.anl.gov):

  • Science with picosecond source.
    At Sector 7 of the APS, we are developing techniques and applications for a picosecond  6 – 22 keV x-ray beamline.  X-ray pulses as short as one picosecond will be produced using transient orbit deflection at a repetition rate of 120 Hz beginning in 2008 and are subsequently expected to reach kHz and possibly MHz repetition rates eventually.  The x-rays will be tunable, polarized, and contain between 1 – 10 % of the flux of a standard undulator beamline.  Current areas of research include the characterization of these x-ray pulses, synchronization with sub-picosecond jitter to a femtosecond laser, and ultfast x-ray science of pump-probe scattering, spectroscopy, and imaging using this new x-ray source.

  Dohn Arms (630-252-0272, dohnarms@anl.gov) and Eric Landahl (630-252-0278, elandahl@anl.gov):

  • Photochemistry in Solutions.
    We are studying solvation structure around laser excited and produced atoms and ions using time-resolved x-ray spectroscopy.  Specifically, we have adapted microfocus fluorescence spectroscopy techniques (both XANES and EXAFS) to dilute solutions where large photoconversions are possible using harmonic light from an ultrafast Titanium:Sapphire laser.  The dynamics of atom/ion recombination can also be monitored using pump-probe techniques at timescales from tens of picoseconds to microseconds.   We anticipate that x-ray measurements of photochemistry at picosecond and sub picosecond timescales will be possible using either future short x-ray pulses produced by transient orbit deflection for dilute solutions, or by the use of streak cameras in a transmission geometry for solutions with higher concentrations.

  Donald Walko (630-252-0271, d-walko@anl.gov):

  • Ultrafast Surface Science using Laser-pump X-ray Probe.
    We use time resolved x-ray diffraction to study the evolution of surfaces, interfaces, and low dimensional structures on sub-nanosecond timescales.  With excitation provided by an ultrafast laser, we study changes to the structures by measuring the time evolution of the diffuse scattering features associated with them.  Current research has focused on thin metal films undergoing structural phase transitions and on heat transport through semiconducting films.  Future research directions include application of this method to quantum dots and to performing experiments on faster time scales, with the introduction of the ps source at Sector 7.

  Bernhard Adams (630-252-6454, adams@aps.anl.gov):

  • X-ray Streak Camera Development.
    The APS is moving decisively to do x-ray scattering and x-ray spectroscopy at time resolutions of about 1 picosecond. A set of important tools in this effort are x-ray streak cameras. Our initial effort has produced an x-ray streak camera with picosencond temporal resolution. This camera will soon achieve 1 ps or less detecting x-ray beams, which is the best that x-ray streak cameras have reached, to date. We are setting up a program for improving the time resolution for x-rays beyond this limit, using a dedicated test camera for exploring novel concepts for improving the time resolution. We are also working on improving the x-ray photoelectron yield of photocathodes. Future work will also involve the modeling of high-frequency, picosecond photoconductive switches, transmission lines, as well as of high-speed electron optics.

  Bernhard Adams (630-252-6454, adams@aps.anl.gov), Klaus Attenkofer (630-252-0383, klaus.attenkofer@anl.gov) Jin Wang (630-252-9125, wangj@aps.anl.gov):

  • Laser-induced Electronic Structures.
    Laser-induced changes in the electronic structure of materials (semiconductors and metals) are a tool to study their electronics and lattice dynamics with important implications for high-speed electronic devices, solar energy, catalysts and tailored nanoscaled materials. Time-resolved x-ray spectroscopy can play a crucial role in these studies because it supplies local and element-specific information, and because it can discriminate between bulk and interfaces (crucial for nanoscale devices). Most electronic processes are too fast to be resolved with current synchrotron-radiation sources, which typically have about 100 ps time resolution. The APS is now pursuing a decisive effort to reach a time resolution of 1 ps, which will open the door to charge-carrier dynamics in inorganic semiconductors such as GaAs and metals such as Pt. We have recently succeeded in measuring a 250-ps laser-induced electronic excitation in GalAs using x-ray spectroscopy, and will continue this work with the coming picosecond capabilities of the APS. This work will involve laser pump, x-ray probe spectroscopy using the ps-source, fast x-ray detectors and x-ray streak cameras, as well as optical spectroscopy.

  Suresh Narayanan (630-252-0287, sureshn@aps.anl.gov), Alec Sandy (630-252-0281, asandy@aps.anl.gov):

  • Dynamics in Soft Matter.
    X-ray photon correlation spectroscopy (XPCS) has found vast applications in the research of nanostructures and nanocomposites in bulk and at surfaces and interfaces.  The insertion device beamline 8-ID-I is dedicated to the study of equilibrium and non-equilibrium dynamics by XPCS. By improving the area detection techniques and instruments, 8-ID has become the most capable XPCS beamline that promotes research related to dynamics in materials not readily accessible to visible-light based techniques such dynamics light scattering. Through previous studies in this area, we have established a good synergy between kinetics and dynamics in soft matter and complex fluids. The systems studied by XPCS include polymer melts and composites to understand the parameters governing the physics comprises of entanglements in the polymer matrix, interaction between the nanoparticles and the confinement in the case of thin films. The current and future research work in this area is aimed towards carrying out a systematic study probing the parameter space to unravel interesting physics in soft matter systems and complex fluids.

  Michael Sprung (630-252-0283, sprung@aps.anl.gov), Jin Wang (630-252-9125 wangj@aps.anl.gov):

  • In situ Study of Self-Assembly of Nanocomposites.
    Although highly ordered nanostructures can often form in a self-assembled fashion, the formation of the structures can be extremely dynamic, far from commonly believed near-equilibrium conditions. Therefore, a controlled self-assembling of the nanostructure has to be guided by a thorough understanding of system kinetics and dynamics in the complex matrices. Grazing-incident x-ray small-angle scattering (GISAXS) is extremely powerful to probe dynamics and kinetics in the nanostructures. Our objectives, therefore, for this project are as follows: 1. Develop advanced x-ray optics and detectors for GISAXS and x-ray reflectivity measurements at the dedicated beamline 8-ID for various sample environments such as heating, solvent annealing, and evaporation; 2. Develop data collection and data analysis program (e.g. using distorted-wave Born approximation) for GISAXS measurements, 3. Apply these developments to the study of multi-timescale non-equilibrium kinetics and dynamics in nanostructures and nanocomposites of organic and inorganic materials in the research areas of materials science, chemistry and Physics.

  Alec Sandy (630-252-0281, asandy@aps.anl.gov), Michael Sprung (630-252-0283, sprung@aps.anl.gov):

  • Developing Advanced XPCS Experimental Facilities.
    X-ray photon correlation spectroscopy (XPCS) experiments are performed most efficiently and are most capable of addressing important scientific problems in the dynamics of complex materials when XPCS-suitable area detectors are run as fast as possible and as long as possible or necessary to obtain suitably high quality autocorrelation decay functions but such modes of operation are unsustainable with currently developed scalar algorithms and computing resources.  Our objectives, therefore, for this project, involve development and deployment of PC cluster-based parallel processing algorithms for reducing raw XPCS data to multi-t time autocorrelations in very small fractions of time required for data acquisition, development on-the fly firmware compression of XPCS data via firmware development in FPGA's, development of short delay-time time autocorrelation routines that function in the hardware described above, utility of all 3 of these developmental milestones in a single package that allows multi-speckle data to be processed “live” at frame rates up to 500 frames per second, applying these developments to the study of multi-timescale equilibrium and non-equilibrium dynamics in glassy and jammed condensed matter systems.

  Jin Wang (630-252-9125, wangj@aps.anl.gov):

  • Fuel Spray Studies with Ultrafast X-ray Imaging Experiments.
    High-speed liquid jets are responsible for many technological applications ranging from fuel injection. The physical breakup mechanism in those cases has remained largely unknown primarily due to the dearth of experimental methods for effectively probing the in-nozzle flow and the liquid jet near the nozzle exit, and to the lack of realistic multiphase hydrodynamic models. To overcome those difficulties, we use intense synchrotron-based x-radiography and phase-contrast imaging techniques to visualize the transient internal dynamics in injection nozzles and fuel sprays outside of the nozzle during a millisecond injection process.  In the project, we investigate how geometry of the injection nozzles, turbulent flow and cavitations inside the nozzle, injection conditions and timing, and properties of fuels affect the jet flow and spray formation in high-pressure and high-speed injection events.

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• X-ray Microscopy and Imaging

  Zhonghou Cai (630-252-0144, cai@aps.anl.gov):

  • Nanodiffraction in materials research.
    X-ray microdiffraction allows spatially resolved studies of crystallographic phases, phase concentrations, micro/nano-structures, stress/strain fields, and superlattice structures via direct probing of the reciprocal lattices. We are developing nanodiffraction technique that provides new capabilities for x-ray nanoanalysis of structures of individual nanomaterials. Using the technique, we have resolved the internal structures of a 30-nm p-MOSFET channel between SiGe stressors and the zinc oxide nanobelts under coiling stress. Other research opportunities include dependence of material properties on their micro/nanostructures, lattice deformation under external stress, and structures of antiferromagnetic and ferroelectric domains.

  Yong Chu (630-252-0150, ychu@aps.anl.gov):

  • Development of full-field diffraction microscopy.
    We are developing an imaging-based diffraction microscopy method to visualize and quantify crystalline structures at a few microns to tens of nanometers.   Recently, we have demonstrated the feasibility of measuring the lattice distortion at 80 nm spatial resolution using a full-field transmission microscope (TXM). Our aim is to develop a method to quantify the 3D strain at 50~100 nm spatial resolution in various materials such as semiconductors, magnetic, and ferroelectric materials.

  Jan Ilavsky (630-252-0866, ilavsky@aps.anl.gov):

  • USAXS applications in materials science.
    This project involves microstructural characterization of materials with complex microstructures such as solid oxide fuel cell electrodes, ceramic coatings, etc., using small-angle x-ray scattering (USAXS or SAXS, including USAXS imaging) combined with other appropriate x-ray techniques such as tomography, GISAXS, and diffraction.  Interested candidate would develop close collaborations with APS users in his/her area of interest.  Apart from the scientific program, the project would further involve development of USAXS hardware and user support software in the area of expertise of the candidate.

  Barry Lai (630-252-6405, blai@aps.anl.gov): 

  • X-ray fluorescence microanalysis of biological specimens. 
    X-ray fluorescence (XRF) microanalysis presents a unique opportunity to study trace elements and their chemistry at the subcellular level within single biological cells as well as tissues, with the current spatial resolution of ~ 200 nm and elemental sensitivity in the attogram (10-18 g) regime. In collaboration with users, we pursue exciting applications with micro-XRF in cell biology, metalloproteomics, pathogenesis, novel therapeutic approaches including nanomedicine, microbiology, bio-remediation, and more.  We are looking for qualified postdoctoral candidates to improve the technique and analytical methods to meet current and future needs in such areas as cryogenic sample environments, differential phase contrast, large acceptance fluorescence detectors, fluorescence tomography, and high throughput data analysis, data mining, and data reduction.

  Wah-Keat Lee (630-252-7759, wklee@aps.anl.gov):

  • Ultrafast x-ray imaging
    The high x-ray flux at the APS, coupled with its small source size, has enabled for the first time full field x-ray phase-contrast imaging with micrometer-level spatial and sub-microsecond temporal resolutions.  The wide energy range available allows measurements on both soft materials such as biological tissue and hard materials such as steel diesel injectors.  This technique opens up an entirely new approach for the study of many high-speed phenomena such as sprays, microfluidics, crack propagations, and impact damage.  Candidates interested in either developing the technique or to answer specific scientific questions using this technique are encouraged to apply.
  • Phase contrast imaging for studies of small animal physiology.
    The APS imaging group pioneered the use of synchrotron phase contrast imaging for the study of small animal physiology.  This technique has enabled biologists to directly visualize the internal physiological and biomechanical dynamics of small animals.  Unprecedented x-ray movies of respiratory and digestive function have shed new light on small insect physiology and at the same time, have raised many more unanswered questions.  Candidates, especially biologists, who can contribute to this developing field are encouraged to apply.

  Jörg Maser (630-252-1091, maser@anl.gov ):

  • Nanofocusing x-ray optics.
    We study the focusing and imaging properties of high resolution x-ray optics with emphasis on diffractive optics, both theoretically and experimentally. A path towards focusing of x-rays to a few nanometers is Multilayer Laue Lenses (MLL), which we fabricate and characterize in collaboration with the Advanced Photon Source and the Materials Science Division. Scientific applications of MLL's or other optics include the study of nanoscale materials and devices at Argonne's Center for Nanoscale Materials.
  • Scientific applications of hard x-ray nanoprobe.
    The Hard X-ray Nanoprobe Beamline at the APS is used to study nanoscale materials using high-resolution x-ray microscopy. The Nanoprobe provides fluorescence imaging and spectroscopy, nanodiffraction and imaging, tomographic transmission imaging at a spatial resolution of 30 nm or bette, time-resolved stroboscopic imaging with a time resolution of 100 psec, and use of circularly polarized x-rays.  Scientific opportunities include studies of slow and fast dynamics in systems such as ferroelectrics, antiferromagnetics and other nanoscale materials.

  Ian McNulty (630-252-2882, mcnulty@aps.anl.gov):

  • Singular x-ray optics.
    The field of "singular optics" has grown rapidly for visible light and recently, for x-rays. This area of research involves the production and application of coherent helical states of light - optical vortices - that carry orbital as well as spin angular momentum associated with the polarization. We have demonstrated production of x-ray vortices with both refractive and diffractive optics, the latter being capable of focusing the phase singularities down to nanometers. We are exploring novel applications of these optics to high resolution x-ray microscopy, where the phase singularity can be exploited to obtain phase contrast images of a specimen, and to x-ray spectroscopy, where the x-ray orbital angular momentum can be coupled to electronic transitions to exploit dichroism contrast. We are also studying the impact of phase singularities on lensless coherent x-ray diffraction experiments, where they can have a pathologic impact on phase retrieval.  Successful postdoctoral applicant will: (a) design new diffractive singular x-ray optics for fabrication through established collaborations and vendors; (b) characterize their performance; (c) develop nanoscale spiral phase contrast microscopy as an effective tool for life and environmental sciences.
  • Nanoscale materials science by coherent diffraction x-ray microscopy.
    Lensless coherent diffraction x-ray microscopy is promising for imaging structure at a resolution limited only by the available signal from the sample at large momentum transfer. We are developing curved-beam methods for rapid phase retrieval convergence and in particular, to combine curved-beam methods with scanning-spot (ptychographic) coherent diffraction to study extended specimens. Successful postdoctoral applicant will: (a) build up a dedicated coherent diffraction x-ray microscope at 2-ID-B; (b) characterize its performance with test standards for comparison with other coherent diffraction instruments; (c) apply the microscope to study of select problems such as quantum dots and wires, nanoparticulates, and nanocomposites. Opportunities exist to collaborate with key players in the field and to participate in a new initiative to build a dedicated coherent diffraction beamline at APS.

  Qun Shen (630-252-0145, qshen@aps.anl.gov):

  • Development of coherent diffraction imaging technique.
    Coherent x-ray diffraction imaging is an emerging microscopic technique for high-resolution material structural studies at spatial resolutions beyond the x-ray optics limit.  We are developing the necessary instrumentation, methodology, and phase retrieval algorithms to advance this technique to the next level so that a wide range of materials and biological applications can be pursued at current and future APS beamlines as well as with more coherent x-ray sources in the future.  
  • Study of nanofoams by x-ray microscopy.
    We plan to image the formation of nanoporous structures in metal nanofoams by x-ray microscopy techniques.  Although porous metal materials have been used extensively in industries, synthesis of hierarchical porous metal materials is challenging and the formation processes, such as dealloying, are poorly understood.  We use transmission hard x-ray microscopy with <60nm resolution for in-situ studies of nanofoam formations during dealloying process.  The metal foams also provide an opportunity to perform coherent diffraction imaging to <10nm resolution.  Together these studies would advance the knowledge in metal foam formation processes and provide the structural basis for many novel physical and electronic properties in nanoporous materials.

  Stefan Vogt (630-252-3071, vogt@aps.anl.gov):

  • Trace-element mapping in biological specimens.
    Quantitative studies of the distribution of trace elements on the cellular and subcellular level provide important information about functions and pathways of metalloproteins and as well as therapeutic approaches, especially in conjunction with the local chemical state of the elements of interest.  Hard x-ray fluorescence microscopy is uniquely suited to map and quantify element distributions in biological specimens such as cells and bacteria.  We are seeking interested postdoctoral candidates to pursue the following areas of research:
    1. Data mining and analysis: The ability to automatically classify scans into regions corresponding to cells, specific organelles, and background, would allow unsupervised probing of large quantities of data while reducing potential observer bias.  Approaches could involve cluster analysis (hierarchical and k-means) or neuronal networks.
    2. Differential phase contrast: We plan to implement quantitative differential phase contrast imaging in a scanning hard x-ray microprobe in order to obtain underlying sample structures along with elemental maps.  This allows unambiguous one-to-one correlations of elemental distributions with cellular structure, and quantitative measurements of specimen mass to allow those maps to be interpreted as absolute concentrations. It is envisioned that the successful candidates would first develop approaches, and then collaborate with outside users to apply those approaches to analysis of the experimental data.

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