DOCSLIB.ORG

Principles and Applications of Zone Plate X-Ray Microscopes

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Principles and Applications of Zone Plate X-Ray Microscopes PRINCIPLES AND APPLICATIONS OF ZONE PLATE X-RAY MICROSCOPES Malcolm Howells1, Chris Jacobsen2 and Tony Warwick1 1Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, USA 2Department of Physics & Astronomy, Stony Brook University, Stony Brook, New York, USA CONTENTS 1. INTRODUCTION 1. Background 2. X-ray interactions 3. Focusing optics 2. FRESNEL ZONE PLATES 1. Introduction 2. Zone plate image quality: a. Optical path function analysis b. Ray aberrations c. Spherical aberration d. Astigmatism and field curvature e. Coma f. Relative size of aberrations 3. Zone plate efficiency: a. Idealized structures b. Real structures 4. Zone plates: fabrication and examples a. Fabrication technique b. Resolution-determining zone plates c. Condenser zone plates d Zone plates with shaped grooves e Hard x-ray zone plates f Thick zone plates 3. X-RAY MICROSCOPES 1. Microscope Layouts and illumination schemes a Transmission x-ray microsope (TXM) layout b TXM phase contrast layout c Scanning transmission x-ray microscope (STXM) layout d Scanning fluorescence x-ray microprobe (SFXM) layout 2. Fundamentals of contrast 3. Partial coherence a. History b. Fourier Optics treatment c. Contrast Transfer d. Reciprocity e. The influence of coherence on resolution f. Coherence in dark field and Zernike phase contrast g. Propagation-based phase contrast 4. Tomography in x-ray microscopes 1 5. X-ray spectromicroscopy 4. APPLICATIONS 1. Biology 2. Environmental Science 3. Materials Science 4. Magnetic Materials 5. CONCLUSION 6. ACKNOWLEDGEMENTS 7. TABLES 8. REFERENCES 2 1. INTRODUCTION 1.1. Background In the 1949 issue of Scientific American, an article by Stanford physicist Paul Kirkpatrick on “The x-ray microscope” [Kirkpatrick 1949] was described by the editors as follows: "It would be a big improvement on microscopes using light or electrons, for X-rays combine short wavelengths, giving fine resolution, and penetration. The main problems standing in the way have now been solved". With the perspective of a half century, we might change “improvement on” to “complement to,” and say that further problems were solved after 1949, but here in essence is the character of x-ray microscopes. In this chapter, we outline some of the properties of x-ray microscope systems in operation today, and highlight some of their present applications. We will not discuss the history of x-ray microscopes prior to about 1975 but instead refer the reader to a series of conference proceedings known as "X-ray Optics and X-ray Microanalysis", which began in 1956. Originally these had valuable material on x-ray microscopy but this diminished after about 1970. The first five were at Cambridge (1956) [Cosslett 1957], Stockholm (1959) [Engström 1960], Stanford (1962) [Pattee 1963], Orsay (1965) [Castaing 1966] and Tubingen (1968) [Molenstedt 1969]. We also recommend the historical perspectives by A. Baez [Baez 1989, Baez 1997] and the book by Cosslet and Nixon [Cosslett 1960]. There is a recognisable thread of continuity between today’s status of the field and efforts that began slowly around 1975 [Niemann 1976, Parsons 1978, Kirz 1980c, Parsons 1980] and blossomed with the availability of synchrotron light sources and nanofabrication technologies; this thread can be traced in part via the proceedings of another conference series that began in 1984 [Schmahl 1984a] and has continued until today [Sayre 1988, Michette 1992, Aristov 1994, Thieme 1998b, Meyer-Ilse 2000b, Susini 2003]. Zone-plate x-ray microscopes now exist at roughly two dozen international synchrotron radiation research centers, and commercial lab-based instruments are also available. Three types are in especially widespread use. Transmission x-ray microscopes (TXMs) specialize in the rapid acquisition of 2D images using high flux sources, and in the collection of tilt sequences of projection images for 3D imaging by tomography. Scanning transmission x-ray microscopes (STXMs) specialize in the acquisition of reduced dose images and point spectra with high energy resolution for elemental and chemical state mapping, and require high source brightness. Scanning fluorescence x-ray microprobes (SFXMs) are similar to STXMs except that fluorescence x-rays are collected by energy-resolving 3 detectors for trace element mapping. All three approaches are now working below 100 nm resolution, to the point of reaching 15 nm resolution in some demonstrations [Chao 2003]. While many of the new technical developments continue to be pursued by specialists in x-ray optics and microscopy, much of present-day activity comes from scientists in other fields of research who are using x-ray microscopes to address their particular questions. This chapter is aimed at scientists from the latter group as well as those from the other communities represented in the content of this series of books. 1.1. X-ray interactions A microscope requires illumination, magnification, and contrast. The characteristics of x-ray interactions with matter affect all three. In Fig. 1 we show the cross section [Hubbell 1980] for photoelectric absorption, coherent (elastic or Thomson) scattering, and incoherent (inelastic or Compton) scattering. Below 10 keV, absorption dominates, so multiple scattering is usually not of concern (an x ray is much more likely to be absorbed following any scattering event than scattered again) nor is inelastic scattering. However, what is neglected in Fig. 1 is the fact that the propagation of x-rays in materials can also include refractive effects, and in fact it was Einstein [Einstein 1918] who first pointed out that the refractive index is slightly less than unity. The x-ray refractive index for a wave forward propagated as exp $!i knx! ! "# & is often written as n! = 1! " ! i# where δ represents % ( )' the phase-shifting part of the refractive index and β represents absorption according to a linear coefficient µ = 4"# / ! in the Lambert-Beer law I = I 0 exp[! µt]. In an anomalous dispersion model, 2 the refractive index terms can furthermore be written as ($ + i# )= !" (f1 + if 2 ) with " = na re / 2! , -15 where na = !N A / A gives the number density of atoms, re=2.82×10 m is the classical radius of the electron, and (f1 + if 2 ) represents the frequency-dependent oscillator strength of an atom. This oscillator strength (f1 + if 2 ) has been tabulated with very good absolute accuracy for all elements by Henke, Gullikson et al. [Henke 1993] over the energy range 10-30,000 eV (see Fig. 2). In examining Fig. 2, two features immediately jump out: f1 is somewhat constant except near absorption edges, so the thickness t$ = " / 2# =1/(2!" f1 ) needed to provide a phase advance exp[ik!t! ] equal to π increases as !1 !2 2 " , while, because f2 scales as E or " , the thickness 1/ µ =1/(4!"# f 2 ) that produces an attenuation 4 of 1/e increases as E 3 or !"3 . As a result, phase contrast becomes the dominant contrast mechanism as one goes to shorter wavelengths [Schmahl 1987]. Much of modern x-ray microscopy centers on the exploitation of x-ray absorption edges. X-ray absorption edges arise when the x ray photon reaches the threshold energy needed to completely remove an electron from an inner-shell orbital. The energy at which this occurs is approximately given by the 2 2 Bohr model as En=(13.6 eV)(Z-zshield) /n , where Z is the atomic number, zshield approximates the partial screening of the nucleus’ charge by other inner-shell electrons (zshield≈1 for K edges), and n is the principal quantum number (n=1 for K edges, 2 for L edges, and so on). This produces the step-like rise in the cross section for photoelectric absorption that can be seen in the plots of f 2 in Fig. 2. If one takes one image I1 at an energy E1 just below an element’s absorption edge where the incident flux is I01, and a similar image I2 at an energy just above an absorption edge, one can recover the mass per area mx / A of the element x from [Engström 1946] 3 m (E1 / E2 ) ln(I1 / I01 ) " ln(I2 / I02 ) x = ! . (1) A 3 µ2 " µ1 (E1 / E2 ) This approach works well for mass concentrations greater than about 1%. Another way in which x-ray absorption edges are exploited is by means of the “water window.” At x-ray energies between the carbon and oxygen absorption edges at 290 and 540 eV, respectively, organic materials show strong absorption contrast while water layers up to several µm thick are reasonably transmissive [Wolter 1952]; this is particularly valuable for imaging hydrated biological and environmental science specimens. For those elements which have absorption edges below the energy of incident x rays so that inner-shell ionization occurs, the aftermath of absorption involves the emission of either a fluorescent photon or an Auger electron of characteristic energy. The energy of these fluorescent photons, and the fluorescence yield [Krause 1979] (the fraction of events which result in fluorescence rather than Auger electron emission), are both shown in Fig. 3. At x-ray energies below 1 keV, Auger emission dominates, and scanning photoemission microscopes (SPEM) use electron spectrometers to exploit these electrons for surface studies [Ade 1990a, Günther 1997, Warwick 1997, Ko 1998]. At higher energies, the fluorescence signal dominates and detection of these characteristic x rays provides information on the concentration of various elements in the specimen. Most scanning fluorescence x-ray microprobes 5 (SFXM) [Horowitz 1972, Sparks 1980] use energy dispersive detectors where the number of electron- hole pairs created by each fluorescent photon is used to measure its energy, though crystal-based wavelength dispersive spectrometers can also be used. Exact quantitation of the elemental concentration requires accurate knowledge of a number of factors, including the solid angle acceptance of the detector and its quantum efficiency, the degree to which fluorescent photons are reabsorbed in the specimen, and other factors, so that in most cases comparison is made with standards with known elemental concentration and matrix concentration similar to that of the specimen under study.
Load more

Recommended publications
  • A Computational Study of Gabor Zone Plate Gamma Ray Holography
    A COMPUTATIONAL STUDY OF GABOR ZONE PLATE GAMMA RAY HOLOGRAPHY by CLARE ESTELLE JACKSON A thesis submitted to The University of Birmingham for the degree of DOCTOR OF PHILOSOPHY Scho ol of Physics and Astronomy The University of Birmingham Decemb er University of Birmingham Research Archive e-theses repository This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder. ABSTRACT Gamma ray zone plate holography is a new technique with applications to Nuclear Medicine Unlike other tomographic techniques threedimensional images can b e recon structed from just one pro jection The history of zone plate holography is reviewed and the dierences b etween this technique and conventional holography are outlined Sources of error in the recorded hologram are reviewed and metho ds for the assessment of image quality are given Three image reconstruction techniques are describ ed and compared These techniques are convolution deconvolution and the CLEAN algorithm Simulated diraction is the main image reconstruction metho d which has previously b een used to reconstruct images from
    [Show full text]
  • Elements of Screenology: Toward an Archaeology of the Screen 2006
    Repositorium für die Medienwissenschaft Erkki Huhtamo Elements of screenology: Toward an Archaeology of the Screen 2006 https://doi.org/10.25969/mediarep/1958 Veröffentlichungsversion / published version Zeitschriftenartikel / journal article Empfohlene Zitierung / Suggested Citation: Huhtamo, Erkki: Elements of screenology: Toward an Archaeology of the Screen. In: Navigationen - Zeitschrift für Medien- und Kulturwissenschaften, Jg. 6 (2006), Nr. 2, S. 31–64. DOI: https://doi.org/10.25969/mediarep/1958. Nutzungsbedingungen: Terms of use: Dieser Text wird unter einer Deposit-Lizenz (Keine This document is made available under a Deposit License (No Weiterverbreitung - keine Bearbeitung) zur Verfügung gestellt. Redistribution - no modifications). We grant a non-exclusive, Gewährt wird ein nicht exklusives, nicht übertragbares, non-transferable, individual, and limited right for using this persönliches und beschränktes Recht auf Nutzung dieses document. This document is solely intended for your personal, Dokuments. Dieses Dokument ist ausschließlich für non-commercial use. All copies of this documents must retain den persönlichen, nicht-kommerziellen Gebrauch bestimmt. all copyright information and other information regarding legal Auf sämtlichen Kopien dieses Dokuments müssen alle protection. You are not allowed to alter this document in any Urheberrechtshinweise und sonstigen Hinweise auf gesetzlichen way, to copy it for public or commercial purposes, to exhibit the Schutz beibehalten werden. Sie dürfen dieses Dokument document in public, to perform, distribute, or otherwise use the nicht in irgendeiner Weise abändern, noch dürfen Sie document in public. dieses Dokument für öffentliche oder kommerzielle Zwecke By using this particular document, you accept the conditions of vervielfältigen, öffentlich ausstellen, aufführen, vertreiben oder use stated above. anderweitig nutzen. Mit der Verwendung dieses Dokuments erkennen Sie die Nutzungsbedingungen an.
    [Show full text]
  • Applications of the Fresnel Diffraction of Neutrons
    f\u-*•? 0 *o •? ^- UM-P-78/43 APPLICATIONS OF THE FRESNEL DIFFRACTION OF NEUTRONS A. G. Klein and G. I. Opat School of Physics, University of Melbourne, Parkville, Victoria, Australia 3052 ABSTRACT The place of Fresnel diffraction in the overall scheme of neutron interference experiments is outlined and possible applications are discussed in the areas of: magnetic domain visualisation; measurement of nuclear scattering lengths with ver/ small specimens; focussing of long wavelength neutron beams using zone plates. 1. INTRODUCTION In classical optics, two principal types of interference experiment are distinguished: interference by amplitude division and interference by division of wavefront. The first of these, typified by the Michelson and Mach-Zehnder interferometers and by various thin film interference situations, relies on partial reflection, i.e. beam-splitters. They find their realisation in the case of neutron optics in the highly successful single crystal interferometers , in which the dynamical Bragg diffraction of neutrons provides the beam-splitting. Another situation of inter­ ference by amplitude division has been manifested in thin film 2 experiments with neutrons . Interference by division of the wavefront has as its paradigm Young's two-slit experiment, in which spatially separated parts of a coherent wavefront are recombir.ed. One of the classical variants of this scheme is the Fresnel bi-prism experiment which has also been demonstrated in the case of electrons by X A Mollenstedt and, in the case of neutrons by Maier-Leibnitz et al. An even simpler set-up was used by us in 1976 : Naufron b«om from cold Moneehrofflotor Cryttol. o« 200 mm.
    [Show full text]
  • Design of Fresnel Lenses and Binary-Staircase Kinoforms of Low Value of the Aperture Number
    Optics Communications 260 (2006) 454–461 www.elsevier.com/locate/optcom Design of Fresnel lenses and binary-staircase kinoforms of low value of the aperture number Javier Alda a,*, Jose´ M. Rico-Garcı´a a, Jose´ M. Lo´pez-Alonso a, Brian Lail b, Glenn Boreman c a Optics Department, University Complutense of Madrid, School of Optics, Av. Arcos de Jalo´n s/n, 28037 Madrid, Spain b Department of Electrical and Computer Engineering, University of Central Florida, P.O. Box 162450, Orlando, FL 32816-2450, USA c College of Optics and Photonics, CREOL, University of Central Florida, P.O. Box 162700, Orlando, FL 32816-2700, USA Received 23 March 2005; received in revised form 25 October 2005; accepted 27 October 2005 Abstract The design of plane Fresnel zone plates, and binary-staircase kinoforms, has been analyzed in this paper for a non-imaging applica- tion aimed to increase the performance of point-like detectors. They maximize the irradiance at the focal point of the diffractive element maintaining some constrains in the lateral size of the element. The design of the binary-staircase kinoform has been described as an iter- ative process. Some interesting results have been obtained for the values of the relative aperture number, or F/#. The practical case trea- ted here produces elements with very low F/#. The results shows that the gain of the irradiance at the focal point increases with the focal distance of the binary-staircase kinoform, and decreases with the focal length for a plane Fresnel zone plate having a limited lateral size.
    [Show full text]
  • 1 Introduction
    Investigating Silicon-Based Photoresists with Coherent Anti-Stokes Raman Scattering and X-ray Micro-spectroscopy by Allison G. Caster A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Chemistry in the Graduate Division of the University of California, Berkeley Committee in charge: Professor Stephen R. Leone, Chair Professor Richard Mathies Professor Luke P. Lee Spring 2010 Abstract Investigating Silicon-Based Photoresists with Coherent Anti-Stokes Raman Scattering and X-ray Micro-spectroscopy by Allison G. Caster Doctor of Philosophy in Chemistry University of California, Berkeley Professor Stephen R. Leone, Chair Photoresist lithography is a critical step in producing components for high-density data storage and high-speed information processing, as well as in the fabrication of many novel micro and nanoscale devices. With potential applications in next generation nanolithography, the chemistry of a high resolution photoresist material, hydrogen silsesquioxane (HSQ), is studied with two different state-of-the-art, chemically selective microscope systems. Broadband coherent anti- Stokes Raman scattering (CARS) micro-spectroscopy and scanning transmission X•ray microscopy (STXM) reveal the rate of the photoinduced HSQ cross-linking, providing insight into the reaction order, possible mechanisms and species involved in the reactions. Near infrared (NIR) multiphoton absorption polymerization (MAP) is a relatively new technique for producing sub-diffraction limited structures in photoresists, and in this work it is utilized in HSQ for the first time. By monitoring changes in the characteristic Raman active modes over time with ~500 ms time resolution, broadband CARS micro-spectroscopy provides real-time, in situ measurements of the reaction rate as the HSQ thin films transform to a glass-like network (cross-linked) structure under the focused, pulsed NIR irradiation.
    [Show full text]
  • Transmission of Hologram Image Using a Zone Plate for Hard X-Ray
    REPRODUCTION OF HOLOGRAM IMAGE USING A ZONE PLATE FOR HARD X-RAY RADIATION A. V. Kuyumchyan1, A. Yu. Souvorov2, T. Ishikawa2, A. A. Isoyan1, V.V. Aristov1, K. Trouni3, and E. Sarkisian3 1Institute of Microelectronics Technology and High Purity Materials of RAS, Russian Federation, Chernogolovka, 142432, 2SPring-8, JASRI, 1-1-1 Kouto, Mikazuki-cho, Sayo-gun Hyogo 679 5198, Japan and 3International Academy of Science and Technology, P.O. Box 4385, CA 91222, USA The images of the silicon test object have been studied. An image for in-line hologram for hard X-ray (8 – 18 KeV) is presented. The transmission of a hologram image for hard X-ray radiation using Fresnel phase zone plate has been investigated. The experimental investigations have been conducted on the station BL29XU, Spring-8. Introduction The development of X-ray optics opens new possibilities for diagnostics in the field of Biology, microelectronics and nanotechnologies. Methods of X-ray holography for soft X-ray radiation [1,2] and transmission of the image of phase objects for both hard and soft X-ray radiation [3-5] have rapidly develop in recent years. The absence of coherent beams (X-ray lasers) and recording devices for three-dimension images is the main difficulty to obtain X-ray holograms by optical method. In the present work the following experimental results are given: recordings of a Gabor hologram for hard X-ray radiation and transmission of a hologram image using a silicon phase zone plate (ZP) [6]. Experimental scheme and results The images of the test silicon object consisting of the word-combination “X-RAY phase contrast, IPMT RAS CHERNOGOLOVKA” have been investigated.
    [Show full text]
  • Image Grating Metrology Using a Fresnel Zone Plate Chulmin
    Image Grating Metrology Using a Fresnel Zone Plate by Chulmin Joo B.S. Aerospace Engineering, Korea Advanced Institute of Science and Technology (1998) Submitted to the Department of Mechanical Engineering in partial fulfillment of the requirements for the degree of Master of Science in Mechanical Engineering at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY September 2003 @ Massachusetts Institute of Technology 2003. All rights resH S T OF TECHNOLOGY OCT 0 6 2003 LIBRARIES A uthor ......... .. ........... Department of Mechanical Engineering August 20, 2003 Certified by .. ...... ................ Mark L. Schattenburg Principal Research Scientist Thesis Supervisor C ertified by .... ....................... George Barbastathis Assistant Professor, Mechanical Engineering Thesis Supervisor Accepted by ....... ............. Ain A. Sonin Chairman, Department Committee on Graduate Students BARKER Image Grating Metrology Using a Fresnel Zone Plate by Chulmin Joo Submitted to the Department of Mechanical Engineering on August 20, 2003, in partial fulfillment of the requirements for the degree of Master of Science in Mechanical Engineering Abstract Scanning-beam interference lithography (SBIL) is a novel concept for nanometer- accurate grating fabrication. It can produce gratings with nanometer phase accuracy over large area by scanning a photoresist-coated substrate under phase-locked image grating. For the successful implementation of the SBIL, it is crucial to measure the spatial period, phase, and distortion of the image grating accurately, since it enables the precise stitching of subsequent scans. This thesis describes the efforts to develop an image grating metrology that is capable of measuring a wide range of image periods, regardless of changes in grat- ing orientation. In order to satisfy the conditions, the use of a Fresnel zone plate is proposed.
    [Show full text]
  • Emergency! Preparing for Disasters and Confronting the Unexpected in Conservation: AIC's 44Th Annual Meeting, Joint with CAC/A
    July 2016 Vol. 41, No. 4 Inside From the Board President 2 Emergency! Preparing for AIC News 7 Disasters and Confronting the Annual Meeting News 12 Unexpected in Conservation: FAIC News 13 AIC’s 44th Annual Meeting, JAIC News 18 Joint with CAC/ACCR’s Allied Organizations 19 42nd Annual Conference by Margaret Holben Ellis, AIC Board Vice President, with AIC Staff Health & Safety 19 AIC’s 44th Annual Meeting was a joint meeting with our Canadian counterparts, the New Publications 21 Canadian Association for Conservation of Cultural Property, and was held May 13-17, 2016, in Montreal, Canada, at the Palais des Congrès, Montreal’s beautiful conference People 21 center. The joint meeting gave many attendees the opportunity to meet colleagues face- Worth Noting 22 to-face, and provided a forum for international collaboration and connection. This was reflected in the diversity of attendance at the meeting, with more than 1,450 attendees Conservation Training Programs 23 from over 30 different countries, the largest AIC meeting ever. We greatly enjoyed exploring Montreal’s cultural institutions, culinary scene, and beautiful landscapes, even Specialty Group Columns 23 in the rain and snow! Fifty years after the Arno River breached its banks, the theme for the American Network Columns 27 Institute for Conservation of Historic and Artistic Works (AIC) and the Canadian Association for Conservation (Association Canadienne pour la Conservation et la Courses, Conferences, & Seminars 29 Restauration) (CAC-ACCR)’s Joint 44th Annual Meeting and 42nd Annual Conference was Emergency! Preparing for Disasters and Confronting the Unexpected in Conservation. Dr. Anne Radice was the keynote speaker at the opening general session on Sunday, May 15, and recalled her time spent salvaging artwork during the days of the flood.
    [Show full text]
  • Making Hard X-Ray Micro-Focus Beam and Imaging Microscope with Fresnel Zone Plate Optics
    Making hard x-ray micro-focus beam and imaging microscope with Fresnel zone plate optics -SPring-8 summer school text- September 2008 Revised June 2009, Revised October 2009 (Imaging microscope) Revised Sep. 2010 (minor revisions) Final Revision September 2011 Yoshio Suzuki, JASRI/SPring-8 Contents 1. What is Fresnel zone plate for x-rays? 1.1. A simple and intuitional explanation of Fresnel zone plate (FZP) 3 1.2. More precise treatment 6 1.3. Diffraction efficiency 8 1.4. Actual structure of FZP for hard x-rays, fabrication of zone plates 9 2. Making microfocus beam with Fresnel zone plate 2.1. How small is the limit of focused beam size? Diffraction limit and geometrical limit of resolution 12 2.2. Depth of focus and chromatic aberrations 15 2.3. Preservation of emittance and brilliance 16 2.4. General description of focusing optics 17 3. Application of FZP optics to imaging microscopy and microtomography 3.1. X-ray imaging microscopy 19 3.2. Order selection by spatial filter and illuminating optics for FZP objective 19 3.3. Spatial resolution of FZP microscopy with illuminating optics 21 3.4. Depth of focus 22 3.5. Chromatic aberration and spherical aberration 25 3.6. Off-axis aberration theory based on wave optics 26 3.7. Typical example of imaging microtomography with FZP objective in SPring-8 29 4. References 32 Basic exercises before the experiments 33 Practice at the beamline(s) 34 Advanced exercises 36 2 1. What is Fresnel zone plate for hard x-rays? 1.1. Introduction - a simple and intuitional explanation of Fresnel zone plate (FZP) - It is difficult to use refractive optics in the hard x-ray regions, while the refractive lens is most popular optics for visible light.
    [Show full text]
  • Zone-Plate Coded Imaging of Thermonuclear Burn
    DEFENSE PROGRAMS Zone- Plate Coded Imaging of Thermonuclear Burn The first high-resolution, direct images of the images of thermonuclear burn in such region of thermonuclear burn in laser fusion experi­ experiments. I These measurements provide an ex­ ments have been produced using a novel, two-step plicit demonstration that the thermonuclear burn imaging technique called zone-plate coded imaging. produced by laser-driven implosions does indeed This technique is extremely versatile and well suited occur within a compressed core of the imploded for the microscopy of laser fusion targets. It has a target. tomographic capability, which provides three­ Use of the zone-plate-coded imaging (ZPCI) dimensional images of the source distribution. It is technique in laser fusion experiments involves a equally useful for imaging x-ray and particle emis­ simple two-step procedure, which is outlined sions. Since this technique is much more sensitive below and illustrated in Fig. 1. than competing imaging techniques, it permits us to Step I-Shadowgraph Recording. A Fresnel investigate low-intensity sources. zone-plate camera views the laser-irradiated target. The zone-plate camera is a simple shadow device containing no lenses or shutters. It uses a rn the Laboratory's laser fusion program, we are Fresnel zone plate-a concentric array of alter­ experimenting with thermonuclear explosions on a nately transparent and opaque rings of equal microscopic scale using focused, high-power laser area-as an aperture at the front, an appropriate beams. A typical experiment focuses multiple laser recording film at the rear, and filter foils to keep beams onto a spherical glass pellet about 100,um unwanted radiation from reaching the film.
    [Show full text]
  • Download the Annual Review 2017-18
    SOYUZ HITS ROBOTS ARE A FEAST OF MAGIC OF ILLUMINATING ALL GO AT THE ROAD ON THE MARCH FESTIVALS MATHEMATICS INDIA LOCOMOTION RETURN TO CONTENTS PAGE ILLUMINATING INDIA ‘Thank you for the contribution that the Science Museum made to the UK Commonwealth INDIA IN A Summit, and the visit of Indian Prime Minister, Narendra Modi. I am very grateful for the role you played in making this happen’ SPECIAL LIGHT Matt Hancock, Culture Secretary Illuminating India celebrated the country’s rich cultural and scientific history The Illuminating India season The then Secretary of State for Culture, brought together the Indian diaspora Media and Sport, Karen Bradley, in the UK, culminating in a visit to the sent a recorded message to the Science Museum in April from HRH season launch event to ‘convey my The Prince of Wales and the Indian congratulations and those of the entire Prime Minister, Narendra Modi, UK Government. It is especially fitting during the Commonwealth Heads that tonight the Science Museum, of Government summit. The Living which is the most visited museum in the Bridges event, organised by the UK by school groups, celebrates India’s Foreign and Commonwealth Office, contribution to science, technology saw Prince Charles and the Indian and mathematics.’ She went on to thank PM touring the exhibition Illuminating the British High Commission and British India: 5000 Years of Science and Council, notably Baroness Prashar, Innovation with curator Matt Kimberley deputy chairman; and Alan Gemmell and Science Museum Group director OBE, director, British Council India. Ian Blatchford. The Prince of Wales left the reception in the Jaguar She extended a warm welcome to I-Pace, a new zero-emissions electric the Indian High Commissioner, His car produced by Jaguar Land Rover, Excellency Mr Yashvardhan Sinha, who which is owned by the Indian Tata told the guests that it was important Steel company.
    [Show full text]
  • Simulation of Fresnel Zone Plate Imaging Performance with Number of Zones
    sensors Letter Simulation of Fresnel Zone Plate Imaging Performance with Number of Zones Ying Li 1,2, Ombeline de La Rochefoucauld 2 and Philippe Zeitoun 1,* 1 Laboratoire d’Optique Appliquée, CNRS, ENSTA-Paris, Institut Polytechnique de Paris, 828 Boulevard des Maréchaux, 91120 Palaiseau, France; [email protected] 2 Imagine Optic, rue François Mitterrand, 33400 Talence, France; [email protected] * Correspondence: [email protected] Received: 23 October 2020; Accepted: 18 November 2020; Published: 20 November 2020 Abstract: In recent years, integral imaging, a promising three-dimensional imaging technology, has attracted more and more attention for its broad applications in robotics, computational vision, and medical diagnostics. In the visible spectrum, an integral imaging system can be easily implemented by inserting a micro-lens array between a image formation optic and a pixelated detector. By using a micro-Fresnel Zone Plate (FZP) array instead of the refractive lens array, the integral imaging system can be applied in X-ray. Due to micro-scale dimensions of FZP in the array and current manufacturing techniques, the number of zones of FZP is limited. This may have an important impact on the FZP imaging performance. The paper introduces a simulation method based on the scalar diffraction theory. With the aid of this method, the effect of the number of zones on the FZP imaging performance is numerically investigated, especially the case of very small number of zones. Results of several simulation of FZP imaging are presented and show the image can be formed by a FZP with a number of zones as low as 5.
    [Show full text]