Applications of Neutron Scattering - an Overview
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Resolution Neutron Scattering Technique Using Triple-Axis
1 High -resolution neutron scattering technique using triple-axis spectrometers ¢ ¡ ¡ GUANGYONG XU, ¡ * P. M. GEHRING, V. J. GHOSH AND G. SHIRANE ¢ ¡ Physics Department, Brookhaven National Laboratory, Upton, NY 11973, and NCNR, National Institute of Standards and Technology, Gaithersburg, Maryland, 20899. E-mail: [email protected] (Received 0 XXXXXXX 0000; accepted 0 XXXXXXX 0000) Abstract We present a new technique which brings a substantial increase of the wave-vector £ - resolution of triple-axis-spectrometers by matching the measurement wave-vector £ to the ¥§¦©¨ reflection ¤ of a perfect crystal analyzer. A relative Bragg width of can be ¡ achieved with reasonable collimation settings. This technique is very useful in measuring small structural changes and line broadenings that can not be accurately measured with con- ventional set-ups, while still keeping all the strengths of a triple-axis-spectrometer. 1. Introduction Triple-axis-spectrometers (TAS) are widely used in both elastic and inelastic neutron scat- tering measurements to study the structures and dynamics in condensed matter. It has the £ flexibility to allow one to probe nearly all coordinates in energy ( ) and momentum ( ) space in a controlled manner, and the data can be easily interpreted (Bacon, 1975; Shirane et al., 2002). The resolution of a triple-axis-spectrometer is determined by many factors, including the ¨ incident (E ) and final (E ) neutron energies, the wave-vector transfer , the monochromator PREPRINT: Acta Crystallographica Section A A Journal of the International Union of Crystallography 2 and analyzer mosaic, and the beam collimations, etc. This has been studied in detail by Cooper & Nathans (1967), Werner & Pynn (1971) and Chesser & Axe (1973). -
Neutron Scattering
Neutron Scattering John R.D. Copley Summer School on Methods and Applications of High Resolution Neutron Spectroscopy and Small Angle Neutron Scattering NIST Center for NeutronNCNR Summer Research, School 2011 June 12-16, 2011 Acknowledgements National Science Foundation NIST Center for Neutron (grant # DMR-0944772) Research (NCNR) Center for High Resolution Neutron Scattering (CHRNS) 2 NCNR Summer School 2011 (Slow) neutron interactions Scattering plus Absorption Total =+Elastic Inelastic scattering scattering scattering (diffraction) (spectroscopy) includes “Quasielastic neutron Structure Dynamics scattering” (QENS) NCNR Summer School 2011 3 Total, elastic, and inelastic scattering Incident energy Ei E= Ei -Ef Scattered energy Ef (“energy transfer”) Total scattering: Elastic scattering: E = E (i.e., E = 0) all Ef (i.e., all E) f i Inelastic scattering: E ≠ E (i.e., E ≠ 0) D f i A M M Ef Ei S Ei D S Diffractometer Spectrometer (Some write E = Ef –Ei) NCNR Summer School 2011 4 Kinematics mv= = k 1 222 Emvk2m==2 = Scattered wave (m is neutron’s mass) vector k , energy E 2θ f f Incident wave vector ki, energy Ei N.B. The symbol for scattering angle in Q is wave vector transfer, SANS experiments is or “scattering vector” Q =Q is momentum transfer θ, not 2θ. Q = ki - kf (For x-rays, Eck = = ) (“wave vector transfer”) NCNR Summer School 2011 5 Elastic scattering Q = ki - kf G In real space k In reciprocal space f G G G kf Q ki 2θ 2θ G G k Q i E== 0 kif k Q =θ 2k i sin NCNR Summer School 2011 6 Total scattering, inelastic scattering Q = ki - kf G kf G Q Qkk2kkcos2222= +− θ 2θ G if if ki At fixed scattering angle 2θ, the magnitude (and the direction) of Q varies with the energy transfer E. -
Probing the Minimal Length Scale by Precision Tests of the Muon G − 2
Physics Letters B 584 (2004) 109–113 www.elsevier.com/locate/physletb Probing the minimal length scale by precision tests of the muon g − 2 U. Harbach, S. Hossenfelder, M. Bleicher, H. Stöcker Institut für Theoretische Physik, J.W. Goethe-Universität, Robert-Mayer-Str. 8-10, 60054 Frankfurt am Main, Germany Received 25 November 2003; received in revised form 20 January 2004; accepted 21 January 2004 Editor: P.V. Landshoff Abstract Modifications of the gyromagnetic moment of electrons and muons due to a minimal length scale combined with a modified fundamental scale Mf are explored. First-order deviations from the theoretical SM value for g − 2 due to these string theory- motivated effects are derived. Constraints for the fundamental scale Mf are given. 2004 Elsevier B.V. All rights reserved. String theory suggests the existence of a minimum • the need for a higher-dimensional space–time and length scale. An exciting quantum mechanical impli- • the existence of a minimal length scale. cation of this feature is a modification of the uncer- tainty principle. In perturbative string theory [1,2], Naturally, this minimum length uncertainty is re- the feature of a fundamental minimal length scale lated to a modification of the standard commutation arises from the fact that strings cannot probe dis- relations between position and momentum [6,7]. Ap- tances smaller than the string scale. If the energy of plication of this is of high interest for quantum fluc- a string reaches the Planck mass mp, excitations of the tuations in the early universe and inflation [8–16]. string can occur and cause a non-zero extension [3]. -
Neutron Scattering
Neutron Scattering Basic properties of neutron and electron neutron electron −27 −31 mass mkn =×1.675 10 g mke =×9.109 10 g charge 0 e spin s = ½ s = ½ −e= −e= magnetic dipole moment µnn= gs with gn = 3.826 µee= gs with ge = 2.0 2mn 2me =22k 2π =22k Ek== E = 2m λ 2m energy n e 81.81 150.26 Em[]eV = 2 Ee[]V = 2 λ ⎣⎡Å⎦⎤ λ ⎣⎦⎡⎤Å interaction with matter: Coulomb interaction — 9 strong-force interaction 9 — magnetic dipole-dipole 9 9 interaction Several salient features are apparent from this table: – electrons are charged and experience strong, long-range Coulomb interactions in a solid. They therefore typically only penetrate a few atomic layers into the solid. Electron scattering is therefore a surface-sensitive probe. Neutrons are uncharged and do not experience Coulomb interaction. The strong-force interaction is naturally strong but very short-range, and the magnetic interaction is long-range but weak. Neutrons therefore penetrate deeply into most materials, so that neutron scattering is a bulk probe. – Electrons with wavelengths comparable to interatomic distances (λ ~2Å ) have energies of several tens of electron volts, comparable to energies of plasmons and interband transitions in solids. Electron scattering is therefore well suited as a probe of these high-energy excitations. Neutrons with λ ~2Å have energies of several tens of meV , comparable to the thermal energies kTB at room temperature. These so-called “thermal neutrons” are excellent probes of low-energy excitations such as lattice vibrations and spin waves with energies in the meV range. -
Spallation Neutron Sources for Science and Technology
Proceedings of the 8th Conference on Nuclear and Particle Physics, 20-24 Nov. 2011, Hurghada, Egypt SPALLATION NEUTRON SOURCES FOR SCIENCE AND TECHNOLOGY M.N.H. Comsan Nuclear Research Center, Atomic Energy Authority, Egypt Spallation Neutron Facilities Increasing interest has been noticed in spallation neutron sources (SNS) during the past 20 years. The system includes high current proton accelerator in the GeV region and spallation heavy metal target in the Hg-Bi region. Among high flux currently operating SNSs are: ISIS in UK (1985), SINQ in Switzerland (1996), JSNS in Japan (2008), and SNS in USA (2010). Under construction is the European spallation source (ESS) in Sweden (to be operational in 2020). The intense neutron beams provided by SNSs have the advantage of being of non-reactor origin, are of continuous (SINQ) or pulsed nature. Combined with state-of-the-art neutron instrumentation, they have a diverse potential for both scientific research and diverse applications. Why Neutrons? Neutrons have wavelengths comparable to interatomic spacings (1-5 Å) Neutrons have energies comparable to structural and magnetic excitations (1-100 meV) Neutrons are deeply penetrating (bulk samples can be studied) Neutrons are scattered with a strength that varies from element to element (and isotope to isotope) Neutrons have a magnetic moment (study of magnetic materials) Neutrons interact only weakly with matter (theory is easy) Neutron scattering is therefore an ideal probe of magnetic and atomic structures and excitations Neutron Producing Reactions -
Development, Design & Technology of Neutron Scattering Instruments By
Mitglied der Helmholtz-Gemeinschaft der Mitglied Development, design & technology of neutron scattering instruments by ZAT Dr. R. Hanslik - Central Institute of Technology (ZAT) Overview • FRM II Garching - Overview • ZAT-Projects at the research reactor FRM II in Garching − Some current developments and new options for the neutron scattering instruments in Garching • Neutron Spin Echo Spectrometer for SNS in Oak Ridge (USA) • Summary ZAT – Central Institute of Technology R. Hanslik FRM II in Garching Neutron Guide Hall Reactor building Neutron Guide Hall Reactor building East FRM II West FRM I ZAT – Central Institute of Technology R. Hanslik ZAT projects at the research reactor FRM II in Garching • Upgraded instruments moved from Dido reactor at FZJ to FRM II in Garching • New instruments development and manufacture by ZAT • New beam hole plug SR5 ZAT – Central Institute of Technology R. Hanslik Moved and upgraded instruments Neutron Guide Hall West KWS 2 KWS 1 J-NSE DNS KWS 3 ZAT – Central Institute of Technology R. Hanslik J-NSE Juelich - Neutron Spin Echo Spectrometer Tool to study slow dynamics in soft matter, glasses, magnetic materials, and biological systems at highest energy resolution ZAT – Central Institute of Technology R. Hanslik NSE ZAT Developments und Modifications Adaptation of the Shielding for polarizer support system to and drive polarizer the new neutron adjustment beam height (beam height at FRMII about 270mm lower than by DIDO) Development of Double correction correction coil coil adjustement for two independent XY systems. ZAT – Central Institute of Technology R. Hanslik DNS Diffuse Neutron Scattering Spectrometer Tool to study magnetic structure, superconductivity and diffuse scattering ZAT – Central Institute of Technology R. -
An Introduction to Effective Field Theory
An Introduction to Effective Field Theory Thinking Effectively About Hierarchies of Scale c C.P. BURGESS i Preface It is an everyday fact of life that Nature comes to us with a variety of scales: from quarks, nuclei and atoms through planets, stars and galaxies up to the overall Universal large-scale structure. Science progresses because we can understand each of these on its own terms, and need not understand all scales at once. This is possible because of a basic fact of Nature: most of the details of small distance physics are irrelevant for the description of longer-distance phenomena. Our description of Nature’s laws use quantum field theories, which share this property that short distances mostly decouple from larger ones. E↵ective Field Theories (EFTs) are the tools developed over the years to show why it does. These tools have immense practical value: knowing which scales are important and why the rest decouple allows hierarchies of scale to be used to simplify the description of many systems. This book provides an introduction to these tools, and to emphasize their great generality illustrates them using applications from many parts of physics: relativistic and nonrelativistic; few- body and many-body. The book is broadly appropriate for an introductory graduate course, though some topics could be done in an upper-level course for advanced undergraduates. It should interest physicists interested in learning these techniques for practical purposes as well as those who enjoy the beauty of the unified picture of physics that emerges. It is to emphasize this unity that a broad selection of applications is examined, although this also means no one topic is explored in as much depth as it deserves. -
Astro 282: Problem Set 1 1 Problem 1: Natural Units
Astro 282: Problem Set 1 Due April 7 1 Problem 1: Natural Units Cosmologists and particle physicists like to suppress units by setting the fundamental constants c,h ¯, kB to unity so that there is one fundamental unit. Structure formation cosmologists generally prefer Mpc as a unit of length, time, inverse energy, inverse temperature. Early universe people use GeV. Familiarize yourself with the elimination and restoration of units in the cosmological context. Here are some fundamental constants of nature Planck’s constant ¯h = 1.0546 × 10−27 cm2 g s−1 Speed of light c = 2.9979 × 1010 cm s−1 −16 −1 Boltzmann’s constant kB = 1.3807 × 10 erg K Fine structure constant α = 1/137.036 Gravitational constant G = 6.6720 × 10−8 cm3 g−1 s−2 Stefan-Boltzmann constant σ = a/4 = π2/60 a = 7.5646 × 10−15 erg cm−3K−4 2 2 −25 2 Thomson cross section σT = 8πα /3me = 6.6524 × 10 cm Electron mass me = 0.5110 MeV Neutron mass mn = 939.566 MeV Proton mass mp = 938.272 MeV −1/2 19 Planck mass mpl = G = 1.221 × 10 GeV and here are some unit conversions: 1 s = 9.7157 × 10−15 Mpc 1 yr = 3.1558 × 107 s 1 Mpc = 3.0856 × 1024 cm 1 AU = 1.4960 × 1013 cm 1 K = 8.6170 × 10−5 eV 33 1 M = 1.989 × 10 g 1 GeV = 1.6022 × 10−3 erg = 1.7827 × 10−24 g = (1.9733 × 10−14 cm)−1 = (6.5821 × 10−25 s)−1 −1 −1 • Define the Hubble constant as H0 = 100hkm s Mpc where h is a dimensionless number observed to be −1 −1 h ≈ 0.7. -
The High-Flux Backscattering Spectrometer at the NIST Center For
REVIEW OF SCIENTIFIC INSTRUMENTS VOLUME 74, NUMBER 5 MAY 2003 The high-flux backscattering spectrometer at the NIST Center for Neutron Research A. Meyera) National Institute of Standards and Technology, NIST Center for Neutron Research, Gaithersburg, Maryland 20899-8562 and University of Maryland, Department of Materials and Nuclear Engineering, College Park, Maryland 20742 R. M. Dimeo, P. M. Gehring, and D. A. Neumannb) National Institute of Standards and Technology, NIST Center for Neutron Research, Gaithersburg, Maryland 20899-8562 ͑Received 18 September 2002; accepted 23 January 2003͒ We describe the design and current performance of the high-flux backscattering spectrometer located at the NIST Center for Neutron Research. The design incorporates several state-of-the-art neutron optical devices to achieve the highest flux on sample possible while maintaining an energy resolution of less than 1 eV. Foremost among these is a novel phase-space transformation chopper that significantly reduces the mismatch between the beam divergences of the primary and secondary parts of the instrument. This resolves a long-standing problem of backscattering spectrometers, and produces a relative gain in neutron flux of 4.2. A high-speed Doppler-driven monochromator system has been built that is capable of achieving energy transfers of up to Ϯ50 eV, thereby extending the dynamic range of this type of spectrometer by more than a factor of 2 over that of other reactor-based backscattering instruments. © 2003 American Institute of Physics. ͓DOI: 10.1063/1.1568557͔ I. INTRODUCTION driven monochromator ͑Sec. III E͒, which operates with a cam machined to produce a triangular velocity profile, ex- Neutron scattering is an invaluable tool for studies of the tends the dynamic range of the spectrometer by more than a structural and dynamical properties of condensed matter. -
Small Angle Scattering in Neutron Imaging—A Review
Journal of Imaging Review Small Angle Scattering in Neutron Imaging—A Review Markus Strobl 1,2,*,†, Ralph P. Harti 1,†, Christian Grünzweig 1,†, Robin Woracek 3,† and Jeroen Plomp 4,† 1 Paul Scherrer Institut, PSI Aarebrücke, 5232 Villigen, Switzerland; [email protected] (R.P.H.); [email protected] (C.G.) 2 Niels Bohr Institute, University of Copenhagen, Copenhagen 1165, Denmark 3 European Spallation Source ERIC, 225 92 Lund, Sweden; [email protected] 4 Department of Radiation Science and Technology, Technical University Delft, 2628 Delft, The Netherlands; [email protected] * Correspondence: [email protected]; Tel.: +41-56-310-5941 † These authors contributed equally to this work. Received: 6 November 2017; Accepted: 8 December 2017; Published: 13 December 2017 Abstract: Conventional neutron imaging utilizes the beam attenuation caused by scattering and absorption through the materials constituting an object in order to investigate its macroscopic inner structure. Small angle scattering has basically no impact on such images under the geometrical conditions applied. Nevertheless, in recent years different experimental methods have been developed in neutron imaging, which enable to not only generate contrast based on neutrons scattered to very small angles, but to map and quantify small angle scattering with the spatial resolution of neutron imaging. This enables neutron imaging to access length scales which are not directly resolved in real space and to investigate bulk structures and processes spanning multiple length scales from centimeters to tens of nanometers. Keywords: neutron imaging; neutron scattering; small angle scattering; dark-field imaging 1. Introduction The largest and maybe also broadest length scales that are probed with neutrons are the domains of small angle neutron scattering (SANS) and imaging. -
Conceiving a Backscattering Spectrometer at the European Spallation
ICANS XX, 20th meeting on Collaboration of Advanced Neutron Sources March 4 – 9, 2012 Bariloche, Argentina Conceiving a Backscattering Spectrometer at the European Spallation Source to Bridge Time and Length Scales H.N. Bordallo1,2, R.E. Lechner1, J. Eckert3, K. H. Andersen1 and O. Kirstein1. 1. ESS Design update Programme-Denmark; Niels Bohr Institute, University of Copenhagen, Copenhagen. 2. European Spallation Source ESS AB, Stora Algatan 4, Lund, Sweden. 3. University South Florida, Florida, USA [email protected] Abstract Neutron backscattering spectroscopy has been proposed by Maier-Leibnitz nearly 50 years ago. This method improved the energy resolution of neutron spectrometers pushing it into the μeV range. The prototype BS spectrometer built at the FRM in the 1960s yielded an energy resolution of 0.6 μeV (FWHM). Two experiments were then carried out successfully in a completely new energy transfer window: quasi-elastic scattering in viscous Glycerol and nuclear spin excitations in V2O3.With this experimental breakthrough the term 'microeV' was coined in neutron scattering. The development of the neutron backscattering technique follows the basic idea to use Bragg angles near 90° with moderate collimation for both beam monochromatisation and analysis, in order to obtain very high-energy resolution. Since the early experiments backscattering spectroscopy has largely progressed. Nowadays the need to study systems involving longer length scales, which in turn require an increase of the corresponding time scale, i.e. higher energy resolution, is pressing. Moreover, the rapid rise in computer power, coupled with multi-processor computers and better simulation algorithms has led to significant improvements in the capability of molecular dynamics simulation for aiding the understanding of dynamic molecular order on various time scales. -
Single Crystal Diffuse Neutron Scattering
Review Single Crystal Diffuse Neutron Scattering Richard Welberry 1,* ID and Ross Whitfield 2 ID 1 Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia 2 Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA; whitfi[email protected] * Correspondence: [email protected]; Tel.: +61-2-6125-4122 Received: 30 November 2017; Accepted: 8 January 2018; Published: 11 January 2018 Abstract: Diffuse neutron scattering has become a valuable tool for investigating local structure in materials ranging from organic molecular crystals containing only light atoms to piezo-ceramics that frequently contain heavy elements. Although neutron sources will never be able to compete with X-rays in terms of the available flux the special properties of neutrons, viz. the ability to explore inelastic scattering events, the fact that scattering lengths do not vary systematically with atomic number and their ability to scatter from magnetic moments, provides strong motivation for developing neutron diffuse scattering methods. In this paper, we compare three different instruments that have been used by us to collect neutron diffuse scattering data. Two of these are on a spallation source and one on a reactor source. Keywords: single crystal; diffuse scattering; neutrons; spallation source; time-of-flight 1. Introduction Bragg scattering, which is used in conventional crystallography, gives only information about the average crystal structure. Diffuse scattering from single crystals, on the other hand, is a prime source of local structural information. There is now a wealth of evidence to show that the more local structure is investigated the more we are obliged to reassess our understanding of crystalline structure and behaviour [1].