Gamma-Ray Interactions with Matter
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
Lecture 6: Spectroscopy and Photochemistry II
Lecture 6: Spectroscopy and Photochemistry II Required Reading: FP Chapter 3 Suggested Reading: SP Chapter 3 Atmospheric Chemistry CHEM-5151 / ATOC-5151 Spring 2005 Prof. Jose-Luis Jimenez Outline of Lecture • The Sun as a radiation source • Attenuation from the atmosphere – Scattering by gases & aerosols – Absorption by gases • Beer-Lamber law • Atmospheric photochemistry – Calculation of photolysis rates – Radiation fluxes – Radiation models 1 Reminder of EM Spectrum Blackbody Radiation Linear Scale Log Scale From R.P. Turco, Earth Under Siege: From Air Pollution to Global Change, Oxford UP, 2002. 2 Solar & Earth Radiation Spectra • Sun is a radiation source with an effective blackbody temperature of about 5800 K • Earth receives circa 1368 W/m2 of energy from solar radiation From Turco From S. Nidkorodov • Question: are relative vertical scales ok in right plot? Solar Radiation Spectrum II From F-P&P •Solar spectrum is strongly modulated by atmospheric scattering and absorption From Turco 3 Solar Radiation Spectrum III UV Photon Energy ↑ C B A From Turco Solar Radiation Spectrum IV • Solar spectrum is strongly O3 modulated by atmospheric absorptions O 2 • Remember that UV photons have most energy –O2 absorbs extreme UV in mesosphere; O3 absorbs most UV in stratosphere – Chemistry of those regions partially driven by those absorptions – Only light with λ>290 nm penetrates into the lower troposphere – Biomolecules have same bonds (e.g. C-H), bonds can break with UV absorption => damage to life • Importance of protection From F-P&P provided by O3 layer 4 Solar Radiation Spectrum vs. altitude From F-P&P • Very high energy photons are depleted high up in the atmosphere • Some photochemistry is possible in stratosphere but not in troposphere • Only λ > 290 nm in trop. -
VISCOSITY of a GAS -Dr S P Singh Department of Chemistry, a N College, Patna
Lecture Note on VISCOSITY OF A GAS -Dr S P Singh Department of Chemistry, A N College, Patna A sketchy summary of the main points Viscosity of gases, relation between mean free path and coefficient of viscosity, temperature and pressure dependence of viscosity, calculation of collision diameter from the coefficient of viscosity Viscosity is the property of a fluid which implies resistance to flow. Viscosity arises from jump of molecules from one layer to another in case of a gas. There is a transfer of momentum of molecules from faster layer to slower layer or vice-versa. Let us consider a gas having laminar flow over a horizontal surface OX with a velocity smaller than the thermal velocity of the molecule. The velocity of the gaseous layer in contact with the surface is zero which goes on increasing upon increasing the distance from OX towards OY (the direction perpendicular to OX) at a uniform rate . Suppose a layer ‘B’ of the gas is at a certain distance from the fixed surface OX having velocity ‘v’. Two layers ‘A’ and ‘C’ above and below are taken into consideration at a distance ‘l’ (mean free path of the gaseous molecules) so that the molecules moving vertically up and down can’t collide while moving between the two layers. Thus, the velocity of a gas in the layer ‘A’ ---------- (i) = + Likely, the velocity of the gas in the layer ‘C’ ---------- (ii) The gaseous molecules are moving in all directions due= to −thermal velocity; therefore, it may be supposed that of the gaseous molecules are moving along the three Cartesian coordinates each. -
R-Process Elements from Magnetorotational Hypernovae
r-Process elements from magnetorotational hypernovae D. Yong1,2*, C. Kobayashi3,2, G. S. Da Costa1,2, M. S. Bessell1, A. Chiti4, A. Frebel4, K. Lind5, A. D. Mackey1,2, T. Nordlander1,2, M. Asplund6, A. R. Casey7,2, A. F. Marino8, S. J. Murphy9,1 & B. P. Schmidt1 1Research School of Astronomy & Astrophysics, Australian National University, Canberra, ACT 2611, Australia 2ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia 3Centre for Astrophysics Research, Department of Physics, Astronomy and Mathematics, University of Hertfordshire, Hatfield, AL10 9AB, UK 4Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA 5Department of Astronomy, Stockholm University, AlbaNova University Center, 106 91 Stockholm, Sweden 6Max Planck Institute for Astrophysics, Karl-Schwarzschild-Str. 1, D-85741 Garching, Germany 7School of Physics and Astronomy, Monash University, VIC 3800, Australia 8Istituto NaZionale di Astrofisica - Osservatorio Astronomico di Arcetri, Largo Enrico Fermi, 5, 50125, Firenze, Italy 9School of Science, The University of New South Wales, Canberra, ACT 2600, Australia Neutron-star mergers were recently confirmed as sites of rapid-neutron-capture (r-process) nucleosynthesis1–3. However, in Galactic chemical evolution models, neutron-star mergers alone cannot reproduce the observed element abundance patterns of extremely metal-poor stars, which indicates the existence of other sites of r-process nucleosynthesis4–6. These sites may be investigated by studying the element abundance patterns of chemically primitive stars in the halo of the Milky Way, because these objects retain the nucleosynthetic signatures of the earliest generation of stars7–13. -
A Study of the Effects of Pair Production and Axionlike Particle
Washington University in St. Louis Washington University Open Scholarship Arts & Sciences Electronic Theses and Dissertations Arts & Sciences Summer 8-15-2016 A Study of the Effects of Pair Production and Axionlike Particle Oscillations on Very High Energy Gamma Rays from the Crab Pulsar Avery Michael Archer Washington University in St. Louis Follow this and additional works at: https://openscholarship.wustl.edu/art_sci_etds Recommended Citation Archer, Avery Michael, "A Study of the Effects of Pair Production and Axionlike Particle Oscillations on Very High Energy Gamma Rays from the Crab Pulsar" (2016). Arts & Sciences Electronic Theses and Dissertations. 828. https://openscholarship.wustl.edu/art_sci_etds/828 This Dissertation is brought to you for free and open access by the Arts & Sciences at Washington University Open Scholarship. It has been accepted for inclusion in Arts & Sciences Electronic Theses and Dissertations by an authorized administrator of Washington University Open Scholarship. For more information, please contact [email protected]. WASHINGTON UNIVERSITY IN ST. LOUIS Department of Physics Dissertation Examination Committee: James Buckley, Chair Francesc Ferrer Viktor Gruev Henric Krawzcynski Michael Ogilvie A Study of the Effects of Pair Production and Axionlike Particle Oscillations on Very High Energy Gamma Rays from the Crab Pulsar by Avery Michael Archer A dissertation presented to the Graduate School of Arts and Sciences of Washington University in partial fulfillment of the requirements for the degree of Doctor of Philosophy August 2016 Saint Louis, Missouri copyright by Avery Michael Archer 2016 Contents List of Tablesv List of Figures vi Acknowledgments xvi Abstract xix 1 Introduction1 1.1 Gamma-Ray Astronomy............................. 1 1.2 Pulsars...................................... -
Experimental Γ Ray Spectroscopy and Investigations of Environmental Radioactivity
Experimental γ Ray Spectroscopy and Investigations of Environmental Radioactivity BY RANDOLPH S. PETERSON 216 α Po 84 10.64h. 212 Pb 1- 415 82 0- 239 β- 01- 0 60.6m 212 1+ 1630 Bi 2+ 1513 83 α β- 2+ 787 304ns 0+ 0 212 α Po 84 Experimental γ Ray Spectroscopy and Investigations of Environmental Radioactivity Randolph S. Peterson Physics Department The University of the South Sewanee, Tennessee Published by Spectrum Techniques All Rights Reserved Copyright 1996 TABLE OF CONTENTS Page Introduction ....................................................................................................................4 Basic Gamma Spectroscopy 1. Energy Calibration ................................................................................................... 7 2. Gamma Spectra from Common Commercial Sources ........................................ 10 3. Detector Energy Resolution .................................................................................. 12 Interaction of Radiation with Matter 4. Compton Scattering............................................................................................... 14 5. Pair Production and Annihilation ........................................................................ 17 6. Absorption of Gammas by Materials ..................................................................... 19 7. X Rays ..................................................................................................................... 21 Radioactive Decay 8. Multichannel Scaling and Half-life ..................................................................... -
7. Gamma and X-Ray Interactions in Matter
Photon interactions in matter Gamma- and X-Ray • Compton effect • Photoelectric effect Interactions in Matter • Pair production • Rayleigh (coherent) scattering Chapter 7 • Photonuclear interactions F.A. Attix, Introduction to Radiological Kinematics Physics and Radiation Dosimetry Interaction cross sections Energy-transfer cross sections Mass attenuation coefficients 1 2 Compton interaction A.H. Compton • Inelastic photon scattering by an electron • Arthur Holly Compton (September 10, 1892 – March 15, 1962) • Main assumption: the electron struck by the • Received Nobel prize in physics 1927 for incoming photon is unbound and stationary his discovery of the Compton effect – The largest contribution from binding is under • Was a key figure in the Manhattan Project, condition of high Z, low energy and creation of first nuclear reactor, which went critical in December 1942 – Under these conditions photoelectric effect is dominant Born and buried in • Consider two aspects: kinematics and cross Wooster, OH http://en.wikipedia.org/wiki/Arthur_Compton sections http://www.findagrave.com/cgi-bin/fg.cgi?page=gr&GRid=22551 3 4 Compton interaction: Kinematics Compton interaction: Kinematics • An earlier theory of -ray scattering by Thomson, based on observations only at low energies, predicted that the scattered photon should always have the same energy as the incident one, regardless of h or • The failure of the Thomson theory to describe high-energy photon scattering necessitated the • Inelastic collision • After the collision the electron departs -
Key Elements of X-Ray CT Physics Part 2: X-Ray Interactions
Key Elements of X-ray CT Physics Part 2: X-ray Interactions NPRE 435, Principles of Imaging with Ionizing Radiation, Fall 2006 Photoelectric Effect • Photoe- absorption is the preferred interaction for X-ray imging. 2 - •Rem.:Eb Z ; characteristic x-rays and/or Auger e preferredinhigh Zmaterial. • Probability of photoe- absorption Z3/E3 (Z = atomic no.) provide contrast according to different Z. • Due to the absorption of the incident x-ray without scatter, maximum subject contrast arises with a photoe- effect interaction No scattering contamination better contrast • Explains why contrast as higher energy x-rays are used in the imaging process - • Increased probability of photoe absorption just above the Eb of the inner shells cause discontinuities in the attenuation profiles (e.g., K-edge) NPRE 435, Principles of Imaging with Ionizing Radiation, Fall 2017 Photoelectric Effect NPRE 435, Principles of Imaging with Ionizing Radiation, Fall 2017 X-ray Cross Section and Linear Attenuation Coefficient • Cross section is a measure of the probability (‘apparent area’) of interaction: (E) measured in barns (10-24 cm2) • Interaction probability can also be expressed in terms of the thickness of the material – linear attenuation coefficient: (E) = fractional number of photons removed (attenuated) from the beam after traveling through a unit length in media by absorption or scattering -1 - • (E) [cm ]=Z[e /atom] · Navg [atoms/mole] · 1/A [moles/gm] · [gm/cm3] · (E) [cm2/e-] • Multiply by 100% to get % removed from the beam/cm • (E) as E , e.g., for soft tissue (30 keV) = 0.35 cm-1 and (100 keV) = 0.16 cm-1 NPRE 435, Principles of Imaging with Ionizing Radiation, Fall 2017 Calculation of the Linear Attenuation Coefficient To the extent that Compton scattered photons are completely removed from the beam, the attenuation coefficient can be approximated as The (effective) Z value of a material is particular important for determining . -
Arxiv:1809.04815V2 [Physics.Hist-Ph] 28 Jan 2020
Who discovered positron annihilation? Tim Dunker∗ (Dated: 29 January 2020) In the early 1930s, the positron, pair production, and, at last, positron annihila- tion were discovered. Over the years, several scientists have been credited with the discovery of the annihilation radiation. Commonly, Thibaud and Joliot have received credit for the discovery of positron annihilation. A conversation between Werner Heisenberg and Theodor Heiting prompted me to examine relevant publi- cations, when these were submitted and published, and how experimental results were interpreted in the relevant articles. I argue that it was Theodor Heiting— usually not mentioned at all in relevant publications—who discovered positron annihilation, and that he should receive proper credit. arXiv:1809.04815v2 [physics.hist-ph] 28 Jan 2020 ∗ tdu {at} justervesenet {dot} no 2 I. INTRODUCTION There is no doubt that the positron was discovered by Carl D. Anderson (e.g. Anderson, 1932; Hanson, 1961; Leone and Robotti, 2012) after its theoretical prediction by Paul A. M. Dirac (Dirac, 1928, 1931). Further, it is undoubted that Patrick M. S. Blackett and Giovanni P. S. Occhialini discovered pair production by taking photographs of electrons and positrons created from cosmic rays in a Wilson cloud chamber (Blackett and Occhialini, 1933). The answer to the question who experimentally discovered the reverse process—positron annihilation—has been less clear. Usually, Frédéric Joliot and Jean Thibaud receive credit for its discovery (e.g., Roqué, 1997, p. 110). Several of their contemporaries were enganged in similar research. In a letter correspondence with Werner Heisenberg Heiting and Heisenberg (1952), Theodor Heiting (see Appendix A for a rudimentary biography) claimed that it was he who discovered positron annihilation. -
The Use of Gamma in Place of Digamma in Ancient Greek
Mnemosyne (2020) 1-22 brill.com/mnem The Use of Gamma in Place of Digamma in Ancient Greek Francesco Camagni University of Manchester, UK [email protected] Received August 2019 | Accepted March 2020 Abstract Originally, Ancient Greek employed the letter digamma ( ϝ) to represent the /w/ sound. Over time, this sound disappeared, alongside the digamma that denoted it. However, to transcribe those archaic, dialectal, or foreign words that still retained this sound, lexicographers employed other letters, whose sound was close enough to /w/. Among these, there is the letter gamma (γ), attested mostly but not only in the Lexicon of Hesychius. Given what we know about the sound of gamma, it is difficult to explain this use. The most straightforward hypothesis suggests that the scribes who copied these words misread the capital digamma (Ϝ) as gamma (Γ). Presenting new and old evidence of gamma used to denote digamma in Ancient Greek literary and documen- tary papyri, lexicography, and medieval manuscripts, this paper refutes this hypoth- esis, and demonstrates that a peculiar evolution in the pronunciation of gamma in Post-Classical Greek triggered a systematic use of this letter to denote the sound once represented by the digamma. Keywords Ancient Greek language – gamma – digamma – Greek phonetics – Hesychius – lexicography © Francesco Camagni, 2020 | doi:10.1163/1568525X-bja10018 This is an open access article distributed under the terms of the CC BY 4.0Downloaded license. from Brill.com09/30/2021 01:54:17PM via free access 2 Camagni 1 Introduction It is well known that many ancient Greek dialects preserved the /w/ sound into the historical period, contrary to Attic-Ionic and Koine Greek. -
3 Gamma-Ray Detectors
3 Gamma-Ray Detectors Hastings A Smith,Jr., and Marcia Lucas S.1 INTRODUCTION In order for a gamma ray to be detected, it must interact with matteu that interaction must be recorded. Fortunately, the electromagnetic nature of gamma-ray photons allows them to interact strongly with the charged electrons in the atoms of all matter. The key process by which a gamma ray is detected is ionization, where it gives up part or all of its energy to an electron. The ionized electrons collide with other atoms and liberate many more electrons. The liberated charge is collected, either directly (as with a proportional counter or a solid-state semiconductor detector) or indirectly (as with a scintillation detector), in order to register the presence of the gamma ray and measure its energy. The final result is an electrical pulse whose voltage is proportional to the energy deposited in the detecting medhtm. In this chapter, we will present some general information on types of’ gamma-ray detectors that are used in nondestructive assay (NDA) of nuclear materials. The elec- tronic instrumentation associated with gamma-ray detection is discussed in Chapter 4. More in-depth treatments of the design and operation of gamma-ray detectors can be found in Refs. 1 and 2. 3.2 TYPES OF DETECTORS Many different detectors have been used to register the gamma ray and its eneqgy. In NDA, it is usually necessary to measure not only the amount of radiation emanating from a sample but also its energy spectrum. Thus, the detectors of most use in NDA applications are those whose signal outputs are proportional to the energy deposited by the gamma ray in the sensitive volume of the detector. -
Photon Cross Sections, Attenuation Coefficients, and Energy Absorption Coefficients from 10 Kev to 100 Gev*
1 of Stanaaros National Bureau Mmin. Bids- r'' Library. Ml gEP 2 5 1969 NSRDS-NBS 29 . A111D1 ^67174 tioton Cross Sections, i NBS Attenuation Coefficients, and & TECH RTC. 1 NATL INST OF STANDARDS _nergy Absorption Coefficients From 10 keV to 100 GeV U.S. DEPARTMENT OF COMMERCE NATIONAL BUREAU OF STANDARDS T X J ". j NATIONAL BUREAU OF STANDARDS 1 The National Bureau of Standards was established by an act of Congress March 3, 1901. Today, in addition to serving as the Nation’s central measurement laboratory, the Bureau is a principal focal point in the Federal Government for assuring maximum application of the physical and engineering sciences to the advancement of technology in industry and commerce. To this end the Bureau conducts research and provides central national services in four broad program areas. These are: (1) basic measurements and standards, (2) materials measurements and standards, (3) technological measurements and standards, and (4) transfer of technology. The Bureau comprises the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology, the Center for Radiation Research, the Center for Computer Sciences and Technology, and the Office for Information Programs. THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consistent system of physical measurement; coordinates that system with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation’s scientific community, industry, and com- merce. The Institute consists of an Office of Measurement Services and the following technical divisions: Applied Mathematics—Electricity—Metrology—Mechanics—Heat—Atomic and Molec- ular Physics—Radio Physics -—Radio Engineering -—Time and Frequency -—Astro- physics -—Cryogenics. -
How Do Radioactive Materials Move Through the Environment to People?
5. How Do Radioactive Materials Move Through the Environment to People? aturally occurring radioactive materials Radionuclides can be removed from the air in Nare present in our environment and in several ways. Particles settle out of the our bodies. We are, therefore, continuously atmosphere if air currents cannot keep them exposed to radiation from radioactive atoms suspended. Rain or snow can also remove (radionuclides). Radionuclides released to them. the environment as a result of human When these particles are removed from the activities add to that exposure. atmosphere, they may land in water, on soil, or Radiation is energy emitted when a on the surfaces of living and non-living things. radionuclide decays. It can affect living tissue The particles may return to the atmosphere by only when the energy is absorbed in that resuspension, which occurs when wind or tissue. Radionuclides can be hazardous to some other natural or human activity living tissue when they are inside an organism generates clouds of dust containing radionu- where radiation released can be immediately clides. absorbed. They may also be hazardous when they are outside of the organism but close ➤ Water enough for some radiation to be absorbed by Radionuclides can come into contact with the tissue. water in several ways. They may be deposited Radionuclides move through the environ- from the air (as described above). They may ment and into the body through many also be released to the water from the ground different pathways. Understanding these through erosion, seepage, or human activities pathways makes it possible to take actions to such as mining or release of radioactive block or avoid exposure to radiation.