Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session F36: Neutron, X-Rays and Scattering |
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Sponsoring Units: GIMS Room: 299 |
Tuesday, March 14, 2017 11:15AM - 11:27AM |
F36.00001: Neutron Focusing Mirrors for Neutron Radiography of Irradiated Nuclear Fuel at Idaho National Laboratory Durgesh K. Rai, Huarui Wu, Muhammad Abir, Jeffrey Giglio, Boris Khaykovich Post irradiation examination (PIE) of samples irradiated in nuclear reactors is a challenging but necessary task for the development on novel nuclear power reactors. Idaho National Laboratory (INL) has neutron radiography capabilities, which are especially useful for the PIE of irradiated nuclear fuel. These capabilities are limited due to the extremely high gamma-ray radiation from the irradiated fuel, which precludes the use of standard digital detectors, in turn limiting the ability to do tomography and driving the cost of the measurements. In addition, the small 250 kW Neutron Radiography Reactor (NRAD) provides a relatively weak neutron flux, which leads to low signal-to-noise ratio. In this work, we develop neutron focusing optics suitable for the installation at NRAD. The optics would separate the sample and the detector, potentially allowing for the use of digital radiography detectors, and would provide significant intensity enhancement as well. The optics consist of several coaxial nested Wolter mirrors and is suited for polychromatic thermal neutron radiation. [Preview Abstract] |
Tuesday, March 14, 2017 11:27AM - 11:39AM |
F36.00002: Fork Dislocation Hologram Created Using Neutron Interferometry M G Huber, D Sarenac, B Heacock, M Arif, C W Clark, D G Cory, C B Shahi, D A Pushin We report creating a hologram of a fork dislocation image using macroscopic optical elements and a neutron beam. This experiment utilized a perfect-crystal neutron interferometer and our method was a simple adaptation of the two-beam wedge technique introduced by Leith and Upatnieks in the early 1960s. In our case, the object was a spiral phase plate (SPP) that had previously been used to impart orbital angular momentum to neutron waves. In this experiment, one path of the interferometer passes through our neutron-transparent-aluminum, centimeter-sized SPP. The other `reference' path of the interferometer contains linear phase gradient imparted on the neutron's wave function using a fused silica prism. The resulting interference between these two paths generates a hologram that is a fork dislocation image. Digital reconstruction of this hologram provided information about the phase generated by the SPP, and will be useful in the design of the next generation of neutron OAM experiments. This work paves the way for novel applications of neutron holography, diffraction and imaging. [Preview Abstract] |
Tuesday, March 14, 2017 11:39AM - 11:51AM |
F36.00003: Methods of Information Processing for Neutron Scattering Data Patrick Nave, Lin Jiao, Martin Mourigal, Matthew Stone Inferring complex dispersion relations from resolution-limited neutron scattering measurements is a task which has been approached from a variety of perspectives from Monte Carlo (MC) scattering simulations to resolution function methods which convolve an approximate resolution function with a theoretical model dispersion. However, detailed MC simulations require a highly-accurate framework such as MCViNE, which is not available for all neutron scattering facilities and is also time consuming, while resolution function methods are faster yet more dependent on accurate analytical models of the instrument to construct a valid approximation. Our research investigates two methods for analyzing neutron scattering data in a more general context. The first is a numerical covariance method designed to be fast while retaining high enough accuracy to be useful and enough generality to be applicable to any time-of-flight direct geometry neutron spectrometer. The second is a theoretical method based in topological data analysis concepts. In particular, we explore the computation of invariant topological features which may be useful in algorithmically learning from large databases of scattering data and identifying resolution correlations across sets of instrument parameters. [Preview Abstract] |
Tuesday, March 14, 2017 11:51AM - 12:03PM |
F36.00004: The Wide Angle Neutron Diffractometer (WAND) at HFIR: possibilities and future Matthias Frontzek, Katie M. Andrews, Bryan C. Chakoumakos The Wide Angle Neutron Diffractometer (WAND) at the High Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory (ORNL) has been built and continues to be, a joint project between ORNL and the Japan Atomic Energy Agency. Equipped with a 1-dimensional position sensitive detector (PSD), the instrument is a multi-purpose instrument for both powder and single crystal diffraction. WAND is currently in the process of a 2-phase upgrade to become a world class, general purpose instrument. In phase 1, finished in the beginning of 2016, the whole instrument was practically re-built from scratch, keeping only the front end and the 1-D PSD. Phase 2 will replace the 1-D PSD with the state of the art BNL120 2D-PSD which comes from the Lujan Neutron Scattering Center. We are currently integrating the detector off-line into the data acquisition architecture at HFIR. The new instrument, WAND$^2$, will be available for general users in the proposal call 2018A. In our contribution we present results from experiments on WAND after phase 1. The upgrade now allows mounting the whole suite of available sample environment (50 mK to 1500 K, magnetic fields (5 T), high pressures (4 GPa)). We will further discuss the scientific impact the new capabilities of WAND$^2$ will have. [Preview Abstract] |
Tuesday, March 14, 2017 12:03PM - 12:15PM |
F36.00005: Abstract Withdrawn
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Tuesday, March 14, 2017 12:15PM - 12:27PM |
F36.00006: In Situ Sub-cm Chemistry for Assessing Ancient Habitability on Mars with the Alpha Particle X-ray Spectrometer Scott VanBommel, Ralf Gellert, Jeff Berger, Lucy Thompson, John L. Campbell, Ken Edgett, Marie McBride The Alpha Particle X-ray Spectrometer (APXS) is a chemical analysis instrument on board NASA's Mars rovers. Mounted at the end of the rover arm, the APXS conducts high-precision in situ measurements of rocks and regolith, playing a significant role in understanding the surface composition and geochemical processes on Mars. Curium-244 sources provide complementary PIXE and XRF excitation resulting in a slowly varying and high sensitivity across the range of geochemically important elements with the added benefits of low power demand, low mass, and robust durability. We combine oversampled APXS data with pictures from the arm-mounted MAHLI camera to produce a 3D model of the target and deconvolve the sub-cm-scale chemistry of visible endmembers within heterogeneous targets. Quantitative chemistry at these small scales is perfectly tailored for deconvolving chemical differences in the rock record that resulted from aqueous processes, particularly the fluid mobilization of biologically essential elements such as P, S, and Zn. This is critical for understanding the history of ancient Mars and contributes to Curiosity's quest to discover past habitable environments on Mars. [Preview Abstract] |
Tuesday, March 14, 2017 12:27PM - 12:39PM |
F36.00007: Coherent Diffractive Imaging in the Near Field at Large Angles Benjamin A. P, John L. Barber, Kimberly Nguyen, Matthew C. Tyson, Richard L. Sandberg Coherent diffraction imaging (CDI) is a rapidly developing form of lensless imaging where the intensity of the diffraction pattern is directly imaged on a CCD and iterative phase retrieval (IPR) algorithms are used to reconstruct a high resolution image of the sample. This is especially useful at x-ray wavelengths, where lenses are inefficient and difficult to manufacture. However, one challenge with CDI is that the exact relationship between light emerging from the sample and arriving at the detector is nearly impossible to determine, even numerically, but becomes tractable with various assumptions. The standard far-field assumptions require the detector to be placed hundreds or thousands of meters from the sample at hard x-ray energies, which is not practical. A different set of assumptions called the ``distorted object'' approach allows imaging at any distance, but has the strict requirement that a value called the small angle number, An, needs to be much smaller than one. Here we examine where the distorted object approach fails, specifically in regards to An. We have found that we can obtain good quality images with very large An values at visible wavelengths. [Preview Abstract] |
Tuesday, March 14, 2017 12:39PM - 12:51PM |
F36.00008: Ultrafast x-ray absorption in NiO studied using femtosecond laser plasma hard x-ray pulses Mzahar Iqval, Muhammad Ijaz Anwar, Karol Janulewicz, Do Young Noh NiO is a wide band gap and typical antiferromagnetic material having highly correlated electronic system. In this contribution, we present the effect of excitation of valence electrons in NiO by femtosecond laser pulse on the response of the core shell electrons using a femtosecond laser plasma X-ray source. NiO (4 $\mu m$ thick) was pumped with a fluence of 10 $mJ/cm^2$ of NIR pulse in 50 fs. X-ray absorption spectra were registered at various time delays with respect to the probe pulse. A sudden shift of K absorption edge to lower energy was observed followed by the quick recovery when electrons are excited with 1.55 eV (800 nm) possibly to the in-gap states. The shift occurred at the rate of 223 $\pm$ 3 fs, and a maximum of $\sim 3$ eV red shift of K- absorption edge was registered after 400 fs of excitation. On the other hand upon pumping with the combination of NIR and UV (800 nm and 400 nm) an abrupt blue shift of K-absorption edge was recorded after $\sim$ 400 fs at the rate of $234 \pm 5$ fs. This is possibly due to the filling of the lowest unoccupied orbital above the band gap in the conduction band. [Preview Abstract] |
Tuesday, March 14, 2017 12:51PM - 1:03PM |
F36.00009: Probing high-energy final-state lifetimes with attosecond angle-resolved photoelectron spectroscopy Zhensheng Tao, Cong Chen, Wenjing You, Adra Carr, Piotr Matyba, Tibor Szilvási, Manos Mavrikakis, Mark Keller, Peter Oppeneer, Henry Kapteyn, Margaret Murnane Photoelectron spectroscopy is one of the most important methods for extracting information about the material band structure. Final-state effects can complicate the interpretation of photoelectron data and these effects are challenging to address both experimentally and theoretically. In this work, we show that the attosecond pulse trains generated by high harmonic generation process in combination with interferometric time- and angle-resolve photoelectron spectroscopy enables a powerful tool (atto-ARPES) to directly access the final-state lifetimes in the time domain. Through our experiments on transition metals Cu(111) and Ni(111), we find the energy- and angle-dependent lifetime carries essential information about the bulk final states, which can serve as a sensitive probe for the final-state effects in solid-state photoemission. [Preview Abstract] |
Tuesday, March 14, 2017 1:03PM - 1:15PM |
F36.00010: Theoretical Study on Angular Dependence of X-ray Natural Circular Dichroism Hiroshi Katsumoto, Hitoshi Fujii, Tamio Oguchi Natural circular dichroism (NCD) can be detected as a difference in the photo-absorption between right- and left-circularly polarized lights in a non-centrosymmetric crystal. It originates in an interference term of electric dipole (E1) and magnetic dipole (M1) transitions in optical ranges, while in that of E1 and electric quadruple (E2) transition in x-ray ranges. In the latter case, the electronic transitions occur from particular inner core states to empty conduction bands depending on the x-ray energy and polarization, being called selection rules. To cause such an interference, the final states should be parity violated because of the selection rules for the E1 and E2 transitions. In this study, we calculate x-ray NCD (XNCD) spectra by using density-functional-theory electronic structure calculation method and Fermi's golden rule for LiIO$_{3}$ (space group P63) and TeO$_{2}$ (P212121). The dependence of the incident angle in the XNCD spectra is calculated and discussed in detail by comparing with its analytic expression. [Preview Abstract] |
Tuesday, March 14, 2017 1:15PM - 1:27PM |
F36.00011: Resonant Soft X-ray Scattering studies with Transition Edge Sensors Yizhi Fang, Sangjun Lee, Gilberto de la Pena, Xiaolan Sun, Fanny Rodolakis, Jessica McChesney, Joe Fowler, Young Il Joe, William Doriese, Kelsey Morgan, Daniel Swetz, Joel Ullom, Peter Abbamonte Resonant Soft X-ray has been one of the key techniques to study charge orders in high $T_c$ cuperates. To solve the issue of unwanted enhancement of inelastic florescence background at resonance, we have developed an energy-resolving superconducting Transition-Edge Sensor microcalorimeters. These superconducting sensors obtain exquisite energy resolution by exploiting the superconducting-to-normal transition to photon energy and by operating at cryogenic temperatures ($\sim$ 70 mK) where thermal noise is minimal. This TES has demonstrated $\sim$ 1.0 eV resolution below 1 keV. We present first results using this detector to study the (002) Bragg peak and specular elastic scattering from a single crystal of stripe-ordered \ce{La_${2-x}Ba_xCuO_4$} (x=0.125). Use of this detector for studying excitations and rejecting background fluorescence will be discussed. [Preview Abstract] |
Tuesday, March 14, 2017 1:27PM - 1:39PM |
F36.00012: Simulation of electron-material interactions in electron microscopy using quantum trajectories Samantha Rudinsky, Angel S. Sanz, Raynald Gauvin Experimental data obtained from transmission imaging in scanning electron microscopy (SEM) is complex and must be coupled with simulations in order to be properly interpreted. Current methods rely on fast electron assumptions which restrict their applicability to high energy systems. This work utilizes the Bohmian formulation of the quantum theory in order to simulate electron-specimen interactions such as diffraction and particle scattering using parameters specific to SEM, such as low energies and high tilt angles, in order to improve current methods. With this computational technique, trajectories whose equation of motion is dependent upon the wave function can provide a physical representation of the system and indicate the quantum flow. Trajectories representing a beam of electrons incident on a thin specimen show how electron-material interactions affect resulting diffraction data under a variety of initial SEM conditions. Comparisons are made to current dynamical diffraction theories in order to explain their underlying mechanisms. Use of a spectral method to compute the wave function emulates a time-dependent system and can display phenomena such as electron backscattering, currently not possible with existing diffraction image simulation algorithms. [Preview Abstract] |
Tuesday, March 14, 2017 1:39PM - 1:51PM |
F36.00013: The effect of physical properties of spheroidal particles on the scattering pattern Jehan Seneviratne, Matthew Berg The focus of this work is to explain the scattering patterns of wavelength-scale spheroidal particles and apply the knowledge to predict the size, shape, and orientation of a particle based on the scattering pattern. Here, scattering patterns of both oblate and prolate particles are studied. Euler rotations are introduced to rotate the particle. The connection between particle’s internal field and scattering field is explained using phasors. [Preview Abstract] |
Tuesday, March 14, 2017 1:51PM - 2:03PM |
F36.00014: Description of Custom System for Raman Spectroscopy of Thin films Keller Andrews, Alexandra Gordienko, Anthony Kaye Many commercial systems exist for off-the-shelf Raman analysis, but these systems are often cost prohibitive or have included features which may be unnecessary for the particular focus of a research group. Our lab studies properties of thin, uniform films, for which we do not need imaging capabilities or different options for imaging objectives. Thin film Raman analysis also requires tight focus and increased signal collection since Raman scattering has a low cross section and scatters in an incoherent manner. We designed, sourced, and built a very flexible, custom Raman spectroscopy apparatus to suit our needs at a minimum of cost. Our system has been used to characterize thin films created in our lab as well as planned applications for other projects. [Preview Abstract] |
Tuesday, March 14, 2017 2:03PM - 2:15PM |
F36.00015: Nonlinear propagation of partially spatially incoherent Airy beams. Yi Liang, Yi Hu, Donghong Song, Xinzheng Zhang, Zhigang Chen, Jingjun Xu Self-accelerating beams have attracted a lot of attention and inspired a variety of applications in manipulation, biophotonics, and communication etc. In general, most present research on this is focused on the application of coherent beams. However, waves are not necessarily fully phase-coherent. In a recent study, we have theoretically and experimentally generated partially spatially incoherent self-accelerating beams, which still exhibit shape-preserving acceleration as that exhibited by a coherent accelerating beam propagating along the same trajectory. Based on this study, here we report on an experimental study of nonlinear propagation of the partially spatially incoherent Airy beams (PSIABs) in a photorefractive crystal. As we know, a coherent Airy beam initially driven by a self-focusing nonlinearity generally cannot maintain its shape and acceleration in subsequent propagation. Counter to that, in our case, PSIABs could keep their shape better and maintain acceleration even under the action of a self-focusing nonlinearity. [Preview Abstract] |
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