2017 March 15 - April 24
2017 May 17 - June 29
2017 BTR deadline: 04/17/17
2017 October 11 - December 21
2017 Proposal deadline: 08/01/17
2017 BTR deadline: 09/10/17
Friday, December 14, 2007
Arthur Woll, Sr.
"Recent Results from G3: Time-resolved diffuse scattering measurements during strontium titanate pulsed laser deposition"
Friday, December 7, 2007
Kyle Shen, Assistant Professor
Physics, Cornell University
"Photoemission Spectroscopy of the Solid State: The Story from Einstein's Electrons"
Abstract: One of the key problems in modern condensed matter physics lies in understanding novel states of matter and particularly their formative interactions. I will discuss how low-energy synchrotron-based spectroscopies can reveal the underlying electronic structure and interactions in novel quantum materials, such as the high-temperature superconductors or materials which exhibit colossal magnetoresistance. In particular, I will focus on how high-resolution angle-resolved photoemission spectroscopy can provide insights into the electronic structure of these materials in momentum space.
Friday, November 30, 2007
Susan Daniel, Professor of Chemical and Biomolecular Engineering, Cornell University
"Separation of Membrane Components using Bilayer Electrophoresis"
Note Date & Time:
Monday, November 19, 2007 - 11:00am
Elaine DiMasi - Staff Physicist, Brookhaven National Lab
"Biosilica Studied by Pair Distribution Function Measurements at CHESS"
Friday, November 16, 2007
Gerald Guerin, Postdoctoral Fellow
Department of Chemistry, University of Toronto
Growth of Cylindrical Micelles: a step closer to "living self-assembly"
Abstract: Our group has recently discovered a method for controlling the length and architecture of cylindrical block-copolymer micelles (Wang et al. Science, 317, p.844, 2007). Our experiments involve polyferocennyldimethylsilane (PFS) block copolymers, such as PFS-PI (PI: Polyisoprene) which self assemble in n-alkane solvents. Cylindrical micelles form spontaneously upon heating and cooling the solution. These micelles can be shortened by sonication in a n-decane solution. More remarkably, they can be elongated by the addition of small aliquots of PFS-PI free chains dissolved in a good solvent for both blocks (THF). By adding a different polymer to a solution of existing micelles (e.g. PFS-PMVS (PMVS: polymethylvinylsiloxane) to a solution of PFS-PI micelles), we can grow triblock co-micelles, as shown in the figure 1.
Based on Light Scattering (LS) and electron microscopy (EM) studies, we will show how the micelle growth follows the key features of living polymerization to form structures of controlled segment length and composition.
Fig 1: TEM images of triblock co-micelles M(PFS48-PMVS300)-b-M(PFS53-P1320)-b-M(PFS48-PMVS300) formed by adding PFS48-PMVS300 (1.0mg in 0.1 mL THF) to a solution (0.5 mg/mL) of sonicated PFS53-PI320 micelles in decane.
Friday, October 18, 2007
Anna Molder, Postdoc
Friday, August 31, 2007
Chae Un Kim, Postdoc
Biophysics, Cornell University
"High Pressure Cryocooling for Macromolecular Crystallography"
Abstract: A novel high-pressure cryocooling technique to reduce radiation damage in macromolecular crystallography is developed and explored. The method involves cooling macromolecular crystals to cryogenic temperatures (~ 77 K) in high pressure Helium gas (up to 200 MPa). Several different kinds of macromolecular crystals have been successfully high-pressure cryocooled and excellent crystal diffraction has been obtained without adding any penetrating cryoprotectants. This new method has great potential for structural biology and high-throughput crystallography.
The talk details technical aspects of high pressure cryocooling. Recent experimental results are presented, including crystal cryoprotection, extension of the method to Krypton/Xenon single-wavelength anomalous dispersion (SAD) phasing, capillary sample cryoprotection and native sulfur SAD phasing. Finally, a mechanism involving high density amorphous (HDA) ice is proposed to explain why the method works.
Note Date & Time and Location:
Thursday, May 24, 2007 - 3:30pm - Third Floor Wilson Commons
Chandrabhas Narayana - Visiting Scientist
Department of Materials Science and Engineering, Cornell University
"Will Silane be Superconductor at High Pressure - Recent Results from CHESS"
Friday, April 13, 2007
Mechanical and Aerospace Engineering, Cornell University
"Measuring Crystal Level Stress States During In-situ Loading using Synchrotron X-rays"
Abstract: One of the most demanding aspects of multiscale modeling associated with materials design and selection is validation of models on the length scales of interest. In many engineering applications, the crystal level stress is of fundamental importance. Due to single crystal property anisotropy, the stress state (magnitude and direction of the stress tensor) at the crystal scale can be significantly different than the nominal value at the macroscale. Quantification of the three dimensional stress state of loaded metallic crystals requires lattice strain measurements in many different directions. In this talk we describe some recent microbeam experiments we conduced at the Advanced Photon Source on β21's, a bcc titanium alloy. We tracked the evolving stress states of four individual crystals during the in-situ loading of a polycrystalline aggregate. Also, in the talk we contrast this single grain method to the powder technique we developed at the A2 station at CHESS. Recent simulation results are compared to crystal stresses that were determined using our lattice strain pole figure method.
Friday, March 2, 2007
Naval Surface Warfare Center, Indian Head
"Application of X-ray Diffraction for the Determination of Lattice Deformation in Crystalline Explosives Using Synchrotron Radiation"
The main purpose of this presentation is to discuss a future series of tests possibly to be conducted at the CHESS facility to observe lattice deformations in both inert and explosive crystalline materials under shock impact.
This presentation will discuss the development of a dynamic X-ray diffraction capability using synchrotron radiation as a source to observe lattice deformation of materials during shock impact. Within this system a single stage 20mm keyed smooth bore powder gun capable of launching flyer plates up to velocities of 2.3 km/s will be fabricated and used to impact inert and explosive crystals along various planar axes.
Within the investigation, explosive crystal lattice deformation as a function of time will be measured both along and perpendicular to the direction of the shock wave using a high speed X-ray streak camera (temporal resolution 2ps). Lattice deformation observed via diffraction both parallel and perpendicular to the shocked axis will be measured both with and without rarefaction wave interaction due to reflected shock waves through the application of target shape and impedance matching to the inert and explosive crystalline material. Through the diffraction measurements and the inclusion/exclusion of rarefaction waves an investigation of the possible mechanisms of explosive initiation relative to lattice deformation due to shock interaction may be identified.
February 23, 2007
Leon Bellan, Graduate Student
Applied Engineering and Physics,
"Properties and Applications of Electrospun Nanofibers"
February 9, 2007
Ken Finkelstein, Sr. Staff Scientist
Cornell High Energy Synchrotron Source,
Report on LCLS Instruments
February 5, 2007
Oak Ridge National Lab
"Microdiffraction in Crystal with Defects"
Abstract: The grouping of point defects into clusters, microscopic pores, coherent precipitates, dislocation loops and other organized structures, changes the character of the local strain field and results in a redistribution of diffuse scattering intensity.
The diffuse scattering depends on both the local and the average lattice distortions. The average distortion is described by the static Debye-Waller factor exponent (2W). For point defects typically 2W<<1. Grouping of point defects into clusters and small dislocation loops increases this value and eventually results in conditions where 2W>>1. Diffuse scattering distributions for different ranges of static Debye-Waller factor are considered.
In contrast to finite size defects weakly curved dislocations produce broadening in the regular reflections. We describe how x-ray diffraction is modified by various organizations of dislocations. For crystals with geometrically necessary dislocations (GNDs) and/or strain gradients, X-ray diffraction Laue spots are elongated in proportion to the number of GNDs within the probed region. Different slip systems cause distinctly different diffraction images. With microdiffraction it is possible to quantitatively analyze a sample at different structure levels.
February 2, 2007
Richard Talman, Professor of Physics
"The Quick, Cheap, CESR-Reconfigured Route to the Brilliance Frontier"
Abstract: A state of the art 5 GeV, 2.5 nm emittance, light source can be built in the Wilson tunnel using (mainly) the magnets, power supplies, and injection chain of the present CESR ring. New supports and vacuum chamber are required and the bending magnets need modification. A tentative insertion device configuration has two 10m undulator lines and six 5m undulator lines (all having brilliances exceeding those of existing world wide facilities) and a comparable number of lower performance "utility" beamlines. There may be time for (brief) discussion of the appropriatenes and practicality of this layout.
The other frontier (fast timing) will only be accessable once the full energy linac (described recently/shortly by Ivan Bazarov) is available. (As well as enabling femtosecond physics) when used as a topping-off injector to the proposed ring (to counteract the Tousche effect) this linac will give an order of magnitude increase in the brilliances of all the beam lines.