Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session M21: Focus Session: Novel Instrumentation and Measurement Science for X-ray and Neutrons |
Hide Abstracts |
Sponsoring Units: GIMS Chair: Dennis Mills, Argonne National Laboratory Room: 201 |
Wednesday, March 4, 2015 11:15AM - 11:51AM |
M21.00001: Measurement and Instrumentation Challenges at X-ray Free Electron Lasers Invited Speaker: Yiping Feng X-ray Free Electron Laser sources based on the Self Amplified Spontaneous Emission process are intrinsically chaotic, giving rise to pulse-to-pulse fluctuations in all physical properties, including intensity, position and pointing, spatial and temporal profiles, spectral content, timing, and coherence. These fluctuations represents special challenges to users whose experiments are designed to reveal small changes in the underlying physical quantities, which would otherwise be completely washed out without using the proper diagnostics tools. Due to the X-ray FEL's unique characteristics such as the unprecedented peak power and nearly full spatial coherence, there are many technical challenges in conceiving and implementing these devices that are highly transmissive, provide sufficient signal-to-noise ratio, and most importantly work in the single-shot mode. [Preview Abstract] |
Wednesday, March 4, 2015 11:51AM - 12:27PM |
M21.00002: TBD Invited Speaker: Alan Tennant |
Wednesday, March 4, 2015 12:27PM - 12:39PM |
M21.00003: LCLS-II: Upgrade Plans for the Linac Coherent Light Source--Including New Scientific Opportunities William Schlotter The Linac Coherent Light Source (LCLS) is planning a major upgrade that will provide revolutionary new scientific capabilities for exploring materials on the atomic and nano-scale with element specificity and ultrafast temporal resolution.~~ The LCLS is an x-ray free electron laser with six experimental instruments accessible via a peer-reviewed proposal process. The upgraded~LCLS-II facility will continuously deliver ultrafast x-ray pulses at repetition rates greater than 100kHz with photon energies tunable between 250 eV and 5 keV. The upgrade will also produce pulses with photon energies as high as 25 keV at a repetition rate of 120 Hz. These capabilities will enable new scientific methods that will revolutionize the study of highly correlated electron systems, magnetization dynamics and nanoscale fluctuations in soft matter to name a few. Expected capabilities and prospective experimental examples will be presented. [Preview Abstract] |
Wednesday, March 4, 2015 12:39PM - 12:51PM |
M21.00004: Fourier transform inelastic x-ray scattering from phonons using Free Electron Laser pulses Mariano Trigo, Thomas Henighan, David Reis We demonstrate that ultrafast x-ray scattering at Free Electron Lasers (FELs) provides a new approach for measuring phonon dispersion relations spanning the entire Brillouin zone, without the need for complex monochromators and spectrometers. Our method uses an ultrafast optical laser as pump and the dynamics are probed using femtosecond x-ray pulses from an FEL. We obtain the entire transverse acoustic phonon dispersion in germanium with $\sim$ 0.5 meV energy resolution by a simple Fourier transform of the oscillatory dynamics of the scattered x-ray intensity. Using coherent control with a pair of pump pulses, we show that the femtosecond laser couples to pairs of phonons, analogous to a second order Raman scattering mechanism, which also explains the excitation of large-wavevector phonons by the long wavelength (optical) pump pulse. This shows that the generation mechanism is quite general and thus this ultrafast approach could be applicable as a general spectroscopic tool of phonons near to and far from equilibrium. [Preview Abstract] |
Wednesday, March 4, 2015 12:51PM - 1:03PM |
M21.00005: ABSTRACT WITHDRAWN |
Wednesday, March 4, 2015 1:03PM - 1:15PM |
M21.00006: A MEMS-based device used for alignment and manipulation of MLL x-ray focusing optics Weihe Xu, Kenneth Lauer, Hui Yan, Veljko Millanovic, Evgeny Nazaretski Multilayer Laue lenses (MLLs) X-ray microscopy is a powerful tool used for materials research. To push the spatial resolution of x-ray microscopy studies below 10 nm the system needs to be compact and rigid. Applications of MEMS based tip-tilt stages used for alignment and manipulation of nanofocusing optics is a promising route to achieve high stability. In this work, we report characterization and stability testing of a MEMS device suitable for manipulation of nanofocusing optics. We developed two closed-loop circuits implemented in a MEMS tip-tilt device utilizing capacitive and laser interferometry techniques. Test results demonstrate better than 10 mille-degree resolution when using capacitive sensors and better than 0.8 mille-degree resolution when using interferometry sensing respectively. [Preview Abstract] |
Wednesday, March 4, 2015 1:15PM - 1:27PM |
M21.00007: Forbidden Reflections in X-ray Crystal Truncation Rods: Using Surface Reference Waves to Distinguish Charge and Vibrational Asymmetry in Bulk Silicon Jesse Kremenak, Yiyao Chen, Shawn Hayden, Michael Gramlich, Paul Miceli X-ray reflections from diamond crystal structures with Miller indices that satisfy h$+$k$+$l $=$ 4n$+$2, where n is an integer, are considered to be forbidden by crystal symmetry. However, asymmetry from valence charge distribution as well as anharmonic vibrations break the symmetry and result in non-zero intensity ``forbidden reflections.'' Due to the absence of phase information, considerable effort, involving combined temperature-dependent x-ray and neutron scattering studies, was previously required to determine the contributions of charge and vibrations to these reflections. In the present work, we demonstrate that useful phase information can be gained in x-ray reflectivity and crystal truncation rod measurements where there is interference between waves scattered from the bulk and the surface. In this manner, surface reference waves can be used to determine the charge and vibrational asymmetry in the bulk crystal. These effects are demonstrated with in situ synchrotron x-ray scattering measurements on Si(111)7x7 surfaces with and without Ag films. [Preview Abstract] |
Wednesday, March 4, 2015 1:27PM - 1:39PM |
M21.00008: Phonon Mapping in Flowing Equilibrium J.P.C. Ruff When a material conducts heat, a modification of the phonon population occurs. The equilibrium Bose-Einstein distribution is perturbed towards flowing-equilibrium, for which the distribution function is not analytically known. Here I argue that the altered phonon population can be efficiently mapped over broad regions of reciprocal space, via diffuse x-ray scattering or time-of-flight neutron scattering, while a thermal gradient is applied across a single crystal sample. When compared to traditional transport measurements, this technique offers a superior, information-rich new perspective on lattice thermal conductivity, wherein the band and momentum dependences of the phonon thermal current are directly resolved. The proposed method is benchmarked using x-ray thermal diffuse scattering measurements of single crystal diamond under transport conditions. [Preview Abstract] |
Wednesday, March 4, 2015 1:39PM - 1:51PM |
M21.00009: Nanoparticle twinning observed using correlated x-ray scattering at a free electron laser Derek Mendez, Herschel Watkins, Daniel Ratner, Gundolf Schenk, Sebastian Doniach Correlated x-ray scattering (CXS) is a novel technique that aims to extract highly detailed information from many exposures of a solution of particles (e.g. nanoparticles (NPs)). During each exposure, a small fraction of all particles are oriented such that they may scatter into spatially separated pixels on an area detector. When this happens, there is a positive correlation between these pixels. In Powder-XRD, one averages over the azimuth to get the mean intensity into a scattering vector magnitude, however azimuthal information is lost. Consider the (111) family of scattering planes in gold NPs. Occasionally two sets of (111) planes scatter photons into the detector, and a positive correlation will appear at an angle which corresponds to the angle between (111) crystal planes. It is well known that FCC NPs will form twinned structures, in which multiple FCC domains are joined yet rotated relative to one another. With CXS we can resolve this twinning signal and determine the average twinning structure of NPs in solution, a result which cannot be obtained with conventional Powder-XRD. [Preview Abstract] |
Wednesday, March 4, 2015 1:51PM - 2:03PM |
M21.00010: Mapping of Strain Inhomogeneity within a Single Ni-NiO Core-Shell Nanoparticle using Bragg Coherent Diffraction Imaging Erandi Wijerathna, R. Harder, J. Clark, B. Kiefer, E. Fullerton, O. Shpyrko, E. Fohtung We report on recent progress in mapping strain inhomogeneity within a single core/shell ferromagnetic/antiferromagnetic Ni-NiO nanoparticle (NP) using Bragg Coherent X-ray Diffraction Imaging (CXDI). By collecting CXD maps from the NP in the vicinity of two different reciprocal lattice points we observe variations in the sign and maximum displacement gradients within the core and shell regions indicative of anisotropy and inhomogeneity. We utilize computations with atomic resolution to model a guess of the deformations within the core structure. This serves as guide for apriori support. Finite difference analysis is used alongside CXDI to reconstruct the core-shell regions. This approach opens further avenues in studying buried structures and multifunctional properties using CXDI. [Preview Abstract] |
Wednesday, March 4, 2015 2:03PM - 2:15PM |
M21.00011: Measurement of fast dynamic strain generated by focusing of surface acoustic waves Uday Singh, Y. Li, D.A. Walko, S. Adenwalla We have measured the spatial and temporal dependence of high frequency (88 MHz) strain waves in a focused surface acoustic wave (FSAW). Increasing the strain generated by a SAW to levels that are comparable with epitaxial strains in thin films ($\sim$ 1{\%}) necessitate annular inter-digital transducers (AIDT) that follow the constant velocity curve of the piezoelectric surface to focus the strain wave over a small focal area. A detailed analysis of the strain around the focal center of an AIDT patterned on 128 Y-cut LiNbO$_{3}$ shows shifts in the (104) x-ray diffraction peak. The AIDT spacing was chosen to produce a resonance at the ring frequency of the Advanced Photon Source, where x -ray diffraction measurements were carried out with a focus of 7 $\mu$m. The spatial dependence of the strain is identical to that measured using light reflectivity. From x-ray diffraction measurements, we obtained a quantitative measure of the strain amplitude, 0.5{\%} at an AIDT excitation power of 24 dBm. The temporal dependence showed a sinusoidally varying strain that cycles between compressive and tensile at the frequency of the AIDT excitation. Diffraction measurements of a Pt thin film grown on the LiNbO$_{3}$ show significant strain transfer. These data lay the groundwork for future experiments that involve tuning the physical properties of strain sensitive thin film materials at high frequencies. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700