DOCSLIB.ORG

Chapter 2 – General Background Information Chapter 2 General Background Information

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Chapter 2 – General Background Information Chapter 2 General Background Information 16 European Atlas of Natural Radiation | Chapter 2 – General background information Chapter 2 General background information This chapter provides the background information geology of Europe, one can already form a general necessary to understand how ionising radiation works, and large-scale idea of the level of natural radioactiv- why it is present in our environment, and how it can be ity that can be expected. For instance, young and mo- represented on a map. bile unconsolidated sediments (like clay or sand) that are found in many regions in northern and northwest- The ionising radiation discussed in this chapter consists ern Europe contain generally fewer radionuclides than of alpha, beta and neutron particles as well as gamma certain magmatic or metamorphic rocks found in for rays. Each interacts with matter in a specific way, caus- example Scandinavia (Fennoscandian Shield), Central ing biological effects that can be hazardous. Health risk Europe (Bohemian Massif), France (Bretagne and Cen- from radiation is described by the absorbed dose, tral Massif) and in Spain (Iberian Massif). The more equivalent dose and effective dose, calculated using recent alpine mountain belts are composed of many specific weighting factors. The effects of ionising radia- different types of rocks, leading to strong spatial vari- tion on humans can be deterministic and stochastic. All ations in radiological signature and radiological back- this information leads to the general principles of radi- ground. Some types of volcanic rocks have a higher ation protection. Natural ionising radiation is emitted by radionuclide content and can lead to increased indoor a variety of sources, both cosmogenic and terrigenous, gamma dose rates and radon or thoron concentra- and can be primordial (existing since the origin of the tions. Another specific case are karstic limestone are- Solar System) or secondary (created by the interaction as, where the radiological risk varies locally, leading to of radiation with matter). The most important terrestrial strong hot-spots of natural radioactivity. Organic-rich 238 235 primordial radionuclides are uranium ( U and U de- shale and slate can also be enriched in uranium lead- 232 cay series), thorium Th decay series and potassium ing to an increased radiological risk. Other geological 40K. One particular descendant from uranium and thori- factors like fractures such as faults can favour radio- um is radon gas, having a particular impact on human nuclide concentration and radon migration to the sur- health. As radon forms by radioactive decay inside min- face. The topmost layer of the Earth's surface is often eral grains, part of it escapes into the pore-space (em- covered by a soil layer, which can influence the local anation), and migrates to the atmosphere (exhalation). content in radionuclides and affect the natural radio- Once present in indoor air, radon becomes a potential activity presented in this Atlas. source of hazardous exposure to the occupants. Being radioactive, it produces progeny that partly attaches to The final section of this chapter describes the process aerosol particles, leading to an attached fraction and of generating a map based on available knowledge an unattached fraction. The relation between radon and experimental data. Statistical analysis is the tool gas, aerosol particle size and concentration and those used to interpret the data and knowledge and the attached and unattached fractions determines the principles are illustrated and described in detail in this health risk (by inhalation) to humans. In this way, scien- part. Concepts like accuracy and precision have very tists can estimate the different sources and contribu- specific meanings in statistical terms, and it is impor- tions to radiation doses to humans, presented in a dose tant to appreciate them when dealing with data. pie-chart. A case study about Ukraine shows how the Measurement uncertainty, sample bias, choice of highest radiation exposure to the population comes scale and resolution are other examples, just to men- from natural radiation sources. Due to the radiation tion a few of the considerations going into the design protection measures imposed, the exposure due to the of a survey or map. Without data there could be no Chernobyl accident is less. map but without a detailed knowledge of the quality, the limitations and the different ways in which data The composition and structure of the sub-surface, de- could be sampled and interpreted, one cannot hope to scribed by geology, has a strong influence on the local create a useful map. The complexity of the process is level of natural background radiation, along with other demonstrated, and it concludes with a case study on conditions such as altitude and climate. Looking at the designing a soil-gas survey. Clockwise from top-left: Borkum sand island, North Sea coast, Germany. Source: Peter Bossew. Törvajöe variegated limestone in blocks fallen from klint escarpment. Törvajöe, Estonia. Source: Tınis Saadre. The Aurora Borealis, or Northern Lights, shines above Sauðárkrókur, Iceland. Source: Vincent Guth on Unsplash. Folded limestone flysch, San Rocco, Liguria, Italy. Source: Rotraud Stiegler. Chapter 2 – General background information | European Atlas of Natural Radiation 17 General background information 2.1 Radiation physics Ionising radiation (hereafter called radiation) is radiation neutrons), ions or atoms moving at high speeds (usually greater under emitting ionising radiation is called radioactivity. that carries enough energy to liberate electrons from atoms or than 1 % of the speed of light), and electromagnetic waves on the The following section briefly describes radiation, together with molecules, thereby ionising them. Ionising radiation is made up of high-energy end of the electromagnetic spectrum. The ability of its biological effects on humans, and the general principle of energetic subatomic particles (alpha particles, beta particles and atomic nuclei to convert spontaneously (without exterior action) radiation protection. 2.1.1 Different kinds of radiation Alpha 4 + Alpha radiation is the emission of an alpha particle from the alpha particle must overcome to penetrate or escape from the Alpha decay α 2He nucleus of an atom, changing the originating atom to one of an nucleus. element with an atomic number 2 less and mass number 4 less The least penetrating alpha particle is positively charged and Nucleus than it started with. An alpha particle consists of two protons and quite massive in comparison to the more penetrating negatively two neutrons, essentially the nucleus of a helium-4 atom, and charged beta-, and the most penetrating, gamma and neutron Alpha gets out from the nucleus by tunnel effect. radiations. Due to its charge and mass: particle The alpha decay equation may be described in general terms • an alpha particle interacts strongly with matter and stops as follows: within 100 µm in most materials. In air, alpha particles may Proton travel only a few centimetres, e.g. an 5.5 MeV alpha particle A A-4 4 Neutron Z P Z-2 D+ 2He (2-1) travels 4 cm in air and 48 µm in water. A A-4 4 • travel distance depends on several variables including the energy where Z P is theZ-2 D parent+ 2He nucleus of atomic(2-1) number Z and mass with atomic electrons. Thus alpha particle produces thousands of A A-4 4 of the alpha particle, the atomic number and atomic weight of numberZ P A, Z-2 D+ is2 Hethe daughter nucleus of(2-1) atomic number Z-2 and ion pairs until its kinetic energy has been completely dissipated A A-4 4 the absorber and the density of the absorber. mass numberP A-4, andD+ He is the alpha particle.(2-1) The total energy Z Z-2 2 • an alpha particle dissipates its energy in matter mainly by two within the substance it traverses. It is the most ionising radiation released is shared between the alpha particle, recoil daughter mechanisms, ionisation and electron excitation. emitted by natural sources, with the extremely rare exception of nucleus,E γand= hgamma-radiationν = E1 - E 2 from the daughter(2-2) nucleus when the spontaneous fission of uranium. (2-2) • direct collisions with an atomic nucleus are few and far Eit isγ E leftγ == inh hanνν =excitedE=1 - EenergyE 21 - stateE 2 and decays(2-2) to its ground state. between. The energyE ofγ the= h alphaν = E particles1 - E 2 typically ranges(2-2) between 2 and 10 MeV and its value is characteristic of the emitting nucleus. Double positive charge of alpha particles allows ionisation Radionuclidesln 2 emitting alpha particles of low energy decay with within a given substance (solid, liquid, or gas) by the formation of The amount of energy required to produce ion pairs is a function of the = (2-3) λ T long half-lives,ln 2 1/2 whereas those emitting alpha particles of high ion pairs due to coloumbic attraction between a traversing alpha absorbing medium. For example, air absorbs an average of 35 eV, argon = (2-3) λ T particle and atomic electrons of the atoms within the material gas absorbs approximately 25 eV, and a semiconductor material requires energy have1/2 shortln 2 half-lives. The shorter half-lives exhibited = (2-3) λ T only 2-3 eV to produce an ion pair. This gives semiconductor materials by radionuclides1/2 with high alpha decay energies compared to the alpha particle travels. The two neutrons of the alpha particle ln 2 an important advantage as radiation detectors compared to gases when the longer half-lives of nuclides with lower decay energies(2-3) is give it additional mass, which further
Load more

Recommended publications
  • Cherenkov Radiation
    TheThe CherenkovCherenkov effecteffect A charged particle traveling in a dielectric medium with n>1 radiates Cherenkov radiation B Wave front if its velocity is larger than the C phase velocity of light v>c/n or > 1/n (threshold) A β Charged particle The emission is due to an asymmetric polarization of the medium in front and at the rear of the particle, giving rise to a varying electric dipole momentum. dN Some of the particle energy is convertedγ = 491into light. A coherent wave front is dx generated moving at velocity v at an angle Θc If the media is transparent the Cherenkov light can be detected. If the particle is ultra-relativistic β~1 Θc = const and has max value c t AB n 1 cosθc = = = In water Θc = 43˚, in ice 41AC˚ βct βn 37 TheThe CherenkovCherenkov effecteffect The intensity of the Cherenkov radiation (number of photons per unit length of particle path and per unit of wave length) 2 2 2 2 2 Number of photons/L and radiation d N 4π z e 1 2πz 2 = 2 1 − 2 2 = 2 α sin ΘC Wavelength depends on charge dxdλ hcλ n β λ and velocity of particle 2πe2 α = Since the intensity is proportional to hc 1/λ2 short wavelengths dominate dN Using light detectors (photomultipliers)γ = sensitive491 in 400-700 nm for an ideally 100% efficient detector in the visibledx € 2 dNγ λ2 d Nγ 2 2 λ2 dλ 2 2 11 1 22 2 d 2 z sin 2 z sin 490393 zz sinsinΘc photons / cm = ∫ λ = π α ΘC ∫ 2 = π α ΘC 2 −− 2 = α ΘC λ1 λ1 dx dxdλ λ λλ1 λ2 d 2 N d 2 N dλ λ2 d 2 N = = dxdE dxdλ dE 2πhc dxdλ Energy loss is about 104 less hc 2πhc than 2 MeV/cm in water from €
    [Show full text]
  • Cherenkov Radiation Induced by Megavolt X-Ray Beams in the Second Near-Infrared Window
    Cherenkov Radiation Induced by Megavolt X-Ray Beams in the Second Near-Infrared Window XIANGXI MENG,1,2 YI DU,3 ZIYUAN LI,1 SIHAO ZHU, 1 HAO WU,3,7 CHANGHUI LI, 1,8 WEIQIANG CHEN, 4 SHUMING NIE, 5 QIUSHI REN 1 AND YANYE LU 6,9 1Department of Biomedical Engineering, College of Engineering, Peking University, Beijing 100871, China 2The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, Atlanta, GA 30332, USA 3Key laboratory of Carcinogenesis and Translational ResearchÂă(Ministry of Education/Beijing),ÂăDepartmentÂăof Radiation Oncology, Peking University Cancer Hospital & Institute, Beijing 100142, China 4Institute of Modern Physics, Chinese Academy of Sciences, Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Key Laboratory of Basic Research on Heavy Ion Radiation Application in Medicine, Gansu Province, Lanzhou 730000, China 5Department of Biomedical Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA 6Pattern Recognition Lab, Friedrich-Alexander-University Erlangen-Nuremberg, 91058 Erlangen, Germany [email protected] [email protected] [email protected] Abstract: Although the Cherenkov light contains mostly short-wavelength components, it is beneficial in the aspect of imaging to visualize it in the second near-infrared (NIR-II) window. In this study, Cherenkov imaging was performed within the NIR-II range on megavolt X-ray beams delivered by a medical linear accelerator. A shielding system was used to reduce the noises of the NIR-II image, enabling high quality signal acquisition. It was demonstrated that the NIR-II Cherenkov imaging is potentially a tool for radiotherapy dosimetry, and correlates well with different parameters.
    [Show full text]
  • Polarized Light from Black Hole Can Be a Symbol of Cherenkov Radiation Generated by Faster Than Light Movement in Vacuum Under Gravity
    Polarized light from black hole can be a symbol of Cherenkov radiation generated by Faster Than Light movement in vacuum under gravity Sterling-Jilin Liu, An independent researcher, Email: [email protected], Cell phone: +86 18621356287, Profile: https://www.linkedin.com/in/sterling-liu-9016096b/ Abstract Light speed is assumed as a constant in Einstein’s general relativity theory. In this paper, the polarized light from blacK hole Cygnus X-1 is found fit well with CherenKov radiation generated by Faster Than Light movement in vacuum under gravity. Thus, proved the gravitational lens is a real existence, the refractive index of space did increase with the gravity field, and light speed is changeable with gravitational potential energy. Possible experiments to double verify the theory on the earth is discussed. A new way to find more advanced alien civilizations in lower gravitational potential energy area is proposed. Introduction In Einstein’s general relativity theory, Mercury precession, gravitational lens and gravitational red shift, etc. can be considered as geodetic effect while assuming light speed is a constant, hence get time goes slower in gravitational field. However, in another view, all these phenomena can be also explained as space curved in gravitational field, refractive index of vacuum is larger, and light speed become smaller, but time keep no change. These two views are both acceptable based on previous experimental verification of general relativity theory, whether light or time speed changed is indistinguishable. In this paper, the author found polarized light from black hole Cygnus X-1 can be well explained by CherenKov radiation generated by Faster Than Light movement in vacuum under gravity.
    [Show full text]
  • Cherenkov Light Imaging in Astroparticle Physics
    Cherenkov light imaging in astroparticle physics U. F. Katz Erlangen Centre for Astroparticle Physics, Friedrich-Alexander University Erlangen-N¨urnberg, Erwin-Rommel-Str. 1, 91058 Erlangen, Germany Abstract Cherenkov light induced by fast charged particles in transparent dielectric media such as air or water is exploited by a variety of experimental techniques to detect and measure extraterrestrial particles impinging on Earth. A selection of detection principles is discussed and corresponding experiments are presented together with breakthrough-results they achieved. Some future develop- ments are highlighted. Keywords: Astroparticle physics, Cherenkov detectors, neutrino telescopes, gamma-ray telescopes, cosmic-ray detectors 1. Introduction Photomultiplier tubes (PMTs) and, more recently, silicon pho- tomultipliers (SiPMs) [3,4] are the standard sensor types. They In 2018, we commemorate the 60th anniversary of the award are provided by specialised companies who cooperate with the of the Nobel Prize to Pavel Alexeyewich Cherenkov, Ilya experiments in developing and optimising sensors according to Mikhailovich Frank and Igor Yevgenyevich Tamm for the dis- the respective specific needs (see e.g. [5,6]). covery and the interpretation of the Cherenkov effect [1,2]. In the following, the detection principles of different types of The impact of this discovery on astroparticle physics is enor- Cherenkov experiments in astroparticle physics are presented mous and persistent. Cherenkov detection techniques were ins- together with selected technical details and outstanding results. tumental for the dicovery of neutrino oscillations; the detection of high-energy cosmic neutrinos; the establishment of ground- based gamma-ray astronomy; and important for the progress in 2. Ground-based gamma-ray detectors cosmic-ray physics.
    [Show full text]
  • Radiation Safety Manual University of Massachusetts Amherst
    Radiation Safety Manual University of Massachusetts Amherst Environmental Health and Safety 117 Draper Hall 413-545-2682 January, 2007 This manual must be returned to Radiation Safety Services when the Approved Principal Investigator no longer uses radioisotopes or radiation generating machines and all permits issued by the Radiation Use Committee have been deactivated. Table of Contents The Program & Basic User Requirements How The Program Works Radiation Safety Organization As Low as Reasonably Achievable (ALARA) The Definition of Compliance The Regulatory Agencies Audit of the Radiation Safety Office Audit of the Authorized Principal Investigator (API) & the Authorized Laboratory Radiation Safety Standard Operating Procedures (SOP’s) Radiation Safety Records Responsibilities of Radiation Safety Program Personnel and Users License Conditions and Regulations Radiation Use Committee Radiation Safety Officer Authorized Principal Investigator Authorized Users Visitors Obtaining Approval to Use RM Qualifications for Authorized Users Training Requesting an API Permit from the RUC Approval for Radioisotope Work in Experimental Animals Laboratory Requirements & Access Control To Radioisotopes & Radiation Administrative Controls in the Laboratory Controlled Areas Restricted Areas Surface Contamination Limits Physical Controls in Laboratory Radiation Warnings & Posting Requirements for RM Use Laboratories or Areas Labeling Requirements for Containers Decommissioning Requirements Individual Laboratories Records of Decommissioning
    [Show full text]
  • Applications of Cherenkov Light Emission for Dosimetry in Radiation Therapy a Thesis Submitted to the Faculty in Partial Fulfill
    Applications of Cherenkov Light Emission for Dosimetry in Radiation Therapy A Thesis Submitted to the Faculty in partial fulfillment of the requirements for the degree of Doctor of Philosophy by Adam Kenneth Glaser Thayer School of Engineering Dartmouth College Hanover, New Hampshire May 2015 Examining Committee: Chairman_______________________ Brian Pogue, Ph.D. Member________________________ Alexander Hartov, Ph.D. Member________________________ Eric Fossum, Ph.D. Member________________________ David Gladstone, Sc.D. Member________________________ Lei Xing, Ph.D. ___________________ F. Jon Kull Dean of Graduate Studies THIS PAGE IS INTENTIONALLY LEFT BLANK, UNCOUNTED AND UNNUMBERED ADDITIONAL ORIGINAL SIGNED COPIES OF THE PREVIOUS SIGNATURE PAGE ARE RECOMMENDED, JUST IN CASE. Abstract Since its discovery during the 1930's, the Cherenkov effect has been paramount in the development of high-energy physics research. It results in light emission from charged particles traveling faster than the local speed of light in a dielectric medium. The ability of this emitted light to describe a charged particle’s trajectory, energy, velocity, and mass has allowed scientists to study subatomic particles, detect neutrinos, and explore the properties of interstellar matter. However, only recently has the phenomenon been considered in the practical context of medical physics and radiation therapy dosimetry, where Cherenkov light is induced by clinical x-ray photon, electron, and proton beams. To investigate the relationship between this phenomenon and dose deposition, a Monte Carlo plug-in was developed within the Geant4 architecture for medically-oriented simulations (GAMOS) to simulate radiation-induced optical emission in biological media. Using this simulation framework, it was determined that Cherenkov light emission may be well suited for radiation dosimetry of clinically used x-ray photon beams.
    [Show full text]
  • Inter/Intramolecular Cherenkov Radiation Energy Transfer (CRET) from a Fluorophore with a Built-In Radionuclide Yann Bernhard, Bertrand Collin, Richard Decréau
    Inter/intramolecular Cherenkov radiation energy transfer (CRET) from a fluorophore with a built-in radionuclide Yann Bernhard, Bertrand Collin, Richard Decréau To cite this version: Yann Bernhard, Bertrand Collin, Richard Decréau. Inter/intramolecular Cherenkov radiation energy transfer (CRET) from a fluorophore with a built-in radionuclide. Chemical Communications, Royal Society of Chemistry, 2014, 50, pp.6711 - 6713. 10.1039/c4cc01690d. hal-03262965 HAL Id: hal-03262965 https://hal.univ-lorraine.fr/hal-03262965 Submitted on 16 Jun 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Showcasing research from Richard A Decréau, Institut de Chimie Moléculaire de l’Université de Bourgogne, France As featured in: Inter/intramolecular Cherenkov radiation energy transfer (CRET) from a fl uorophore with a built-in radionuclide Some radionuclides emit optical light, the Cerenkov Radiation (CR, i.e. the blue glow in nuclear reactors), which can activate fl uorophores. Key parameters were addressed to optimize such processes (energy of the emitted particle, concentrations, Φ λmax, F × ε, η). See Richard A Decréau et al., Chem. Commun., 2014, 50, 6711. www.rsc.org/chemcomm Registered charity number: 207890 ChemComm View Article Online COMMUNICATION View Journal | View Issue Inter/intramolecular Cherenkov radiation energy transfer (CRET) from a fluorophore with a built-in Cite this: Chem.
    [Show full text]
  • Imaging of Radiation Dose Using Cherenkov Light
    Imaging of Radiation Dose Using Cherenkov Light Eric Brost1, Yoichi Watanabe1, Fadil Santosa2, Adam Green3 1Department of Radiation Oncology, University of Minnesota 2Institute for Mathematics and it’s Applications, University of Minnesota 3Department of Physics, University of St. Thomas Imaging of Cherenkov light during radiation therapy • Quality assurance • Surface dosimetry • Molecular imaging Thesis project goals 1. Determination of optical correction factors necessary to perform Cherenkov dosimetry 2. Examine feasibility of Cherenkov imaging on C‐RAD Catalyst system [2] Outline • Background • Related Research • Cherenkov Imaging Dosimetry Cherenkov Radiation Tissue or other medium Production Incident radiation (gamma or electron) Secondary β electron, c/n Index of refraction: Cherenkov Particle velocity: emission o = 43 (2 MV beam in water) 1 Conical emission angle: Ratio of velocity to speed of light: β β Cherenkov Light Characteristics • The number of photons, N, emitted per unit path due to the Cherenkov effect: 1 1 ∝ 1 Lower limit of Cherenkov emission • For a 6 MeV electron beam delivering 100 cGy to water at a rate of 600 MU/min: 1 • 600 photons/electron • 6‐10 photons/electron from surface • 3 x 1011 detectable photons • 8 x 10‐10 Watts Wavelength () [3] Cherenkov Light ‐ Relationship to Dose Water or tissue Incident radiation (gamma or electron) z (mm) • Mono‐energetic pencil beams, relationship is 1:1 between light emission and dose (<1%) • Poly‐energetic finite beam sizes, error is between 0‐5% Dose: Number of photons: Correlation ratio: C Glaser, et al. Phys Med Biol. 2014 Set‐up of Cherenkov Detection • Camera CMOS, CCD not as viable Triggered to linac output • Target material Water tank or phantom Patient • Computer Timing, camera, software • Radiation source Linear accelerator Radiopharmaceutical Glaser, et.
    [Show full text]
  • Initial Examination Report No. 50-005/OL-13-01, Pennsylvania
    September 3, 2013 Dr. Kenan Unlu, Director Radiation Science and Engineering Center Breazeale Nuclear Reactor Building Pennsylvania State University University Park, PA 16802-2301 SUBJECT: EXAMINATION REPORT NO. 50-005/OL-13-01, PENNSYLVANIA STATE UNIVERSITY BREAZEALE RESEARCH REACTOR Dear Dr. Unlu: During the week of August 12, 2013, the U.S. Nuclear Regulatory Commission (NRC) administered operator licensing examinations at your Breazeale Nuclear Reactor. The examinations were conducted according to NUREG-1478, “Operator Licensing Examiner Standards for Research and Test Reactors,” Revision 2. Examination questions and preliminary findings were discussed at the conclusion of the examination with those members of your staff identified in the enclosed report. In accordance with Title 10, Section 2.390 of the Code of Federal Regulations, a copy of this letter and the enclosures will be available electronically for public inspection in the NRC Public Document Room or from the Publicly Available Records component of NRC’s Agencywide Documents Access and Management System (ADAMS). ADAMS is accessible from the NRC Web site at http://www.nrc.gov/reading-rm/adams.html (the Public Electronic Reading Room). The NRC is forwarding the individual grades to you in a separate letter which will not be released publicly. If you have any questions concerning this examination, please contact Mr. Gregory M. Schoenebeck at (301) 415-6345, or via e-mail at [email protected]. Sincerely, /RA/ Gregory T. Bowman, Chief Research and Test Reactors Oversight Branch Division of Policy and Rulemaking Office of Nuclear Reactor Regulation Docket No.: 50-005 Enclosures: 1. Examination Report No. 50-005/OL-13-01 2.
    [Show full text]
  • ATF Presentation.Pptx
    Coherent Microwave Cherenkov Radiation Michael Sivertz 27 October 2016 Overview • Introduction to Cherenkov radiation • Coherent visible Cherenkov radiation • Microwave Cherenkov radiation • Coherent microwave beam tests at SLAC • Askaryan effect in electromagnetic showers • Neutrino astronomy using Cherenkov radiation - IceCube • Neutrino astronomy using coherent microwave Cherenkov radiation – Arianna • ATF studies Cherenkov Radiation Nothing travels faster than light … in vacuum. In matter, with an index of refraction, n, there is a threshold velocity, βt = vt/c = 1/n, When charged particles travel faster than βt they emit EM radiation, so they glow. Angle of radiation depends on the velocity, β, of the charged particle: cosθ = 1/(nβ) So at threshold, θ = 0 degrees. Visible Cherenkov Radiation When many particles emit CR, they can glow brightly. CR from a reactor core: Electrons from nuclear decay emit CR in water. The CR spectrum is largest at visible wavelengths, scaling like: Note dependence on z2. Microwave Cherenkov Radiation At frequencies of ~1 GHz, λ = 30cm, so the CR intensity is reduced by a factor of 10-5 compared to visible CR (when integrated over the acceptance of an antenna). However, because the wavelength of the microwaves is so long, CR from multiple sources can add coherently to produce very large signal strength. A bunch of 109 electrons (~nC) shorter than 30 cm will radiate microwaves coherently with an intensity that is 1018 times stronger than a single electron. SLAC Measurement First observation (SLAC 2001) made use of Askaryan§ effect where EM showers develop a 20-30% electron excess due to positron annihilation and Compton scattering. 3.6 tons of silica sand §G.
    [Show full text]
  • Xa9951340 Development of an Underwater Cherenkov Detector to Reveal Sources of Technogenic Radionuclides
    IAEA-SM-354/93P XA9951340 DEVELOPMENT OF AN UNDERWATER CHERENKOV DETECTOR TO REVEAL SOURCES OF TECHNOGENIC RADIONUCLIDES A.M.CHERNYAEV, I.A GAPONOV. Russian Research Center "Kurchatov Institute", Moscow, Russia L.V.LAPUSHKINA National Research Institute "Electron", St. Petersburg, Russia For monitoring marine radioactive contamination sources the underwater scintillation detectors are extensively used, permitting in situ detection of radionuclides both from a surface ship and from underwater vehicles [1], Detection of gamma-emitting radionuclides by the underwater scintillation detectors does not involve any difficulties. The problem consists in detection of the nuclides, when their beta-decay is not accompanied by gamma radiation. First of all, it is true for strontium-90, which is the most significant nuclide from ecological viewpoint. To enhance the potentialities of in situ radioactivity monitoring in marine environment, complex research aimed at the development of an underwater Cherenkov detector for measuring of beta-decay nuclides, featuring a high sensitivity not only in deep-sea but in near the surface sea water and characterized by a high level of the natural light background, has been undertaken at RRC KI . To suppress the light background this project makes use of an original method of optical filtration of light fluxes by the wavelength, making allowance for differences in spectral characteristics of the Cherenkov radiation and atmospheric light, as well as the optimal combination of optical and geometrical parameters of basic elements in the photodetector [2], A schematic diagram of the Cherenkov detector being developed is presented in Fig. 1 and it consists of a high-strength capsule (1) with a transparent inlet window (2), enclosing a solar-blind filter (3), a photomultiplier (4) and an electronic module (5).
    [Show full text]
  • Tachyons and Gravitational Cherenkov Radiation
    UC Berkeley UC Berkeley Previously Published Works Title Tachyons and Gravitational Cherenkov Radiation Permalink https://escholarship.org/uc/item/89m0w23g Journal Modern Physics Letters A, 26(30) Author Schwartz, Charles Publication Date 2011 Peer reviewed eScholarship.org Powered by the California Digital Library University of California September 14, 2011 16:40 WSPC/146-MPLA S0217732311036681 Modern Physics Letters A Vol. 26, No. 30 (2011) 2223–2225 c World Scientific Publishing Company DOI: 10.1142/S0217732311036681 TACHYONS AND GRAVITATIONAL CHERENKOV RADIATION CHARLES SCHWARTZ Department of Physics, University of California, Berkeley, CA 94720, USA [email protected] Received 1 July 2011 Revised 23 August 2011 We calculate the rate at which a free tachyon (faster than light particle) would emit gravitational radiation. It is very small. Keywords: Tachyons; gravitational waves; Cherenkov radiation. In a recent work,1 I have suggested considering that faster-than-light particles (tachyons) might exist in the universe and could be a significant element in cosmo- logical models. That study treated tachyons as classical particles, within the Special and General Theories of Relativity, and found a number of new and interesting re- sults. This present paper looks at a possible criticism of that theoretical approach: namely, whether faster-than-light particles can be considered as stable entities in view of Cherenkov-type radiative effects. Traveling faster than c, the speed of light, tachyons would be expected to emit gravitational radiation — analogous to the electromagnetic radiation (Cherenkov radiation) observed when electrically charged particles travel at high speeds through a medium in which light waves propagate at speeds less than c.
    [Show full text]