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Sample records for cosmic positrons

  1. Search for positron anisotropies in cosmic rays with AMS

    Energy Technology Data Exchange (ETDEWEB)

    Machate, Fabian [1. Physikalisches Institut B, RWTH Aachen University (Germany)

    2016-07-01

    The Alpha Magnetic Spectrometer (AMS-02) on the International Space Station has observed a significant excess of cosmic ray positrons over the background expected from secondary production at energies above 10 GeV. Nearby pulsars and annihilating dark matter particles as a primary source of electrons and positrons have been discussed as an explanation. A possible way of distinguishing between pulsar and dark matter origin is the measurement of dipole anisotropies in the positron flux or the positron to electron ratio. Any anisotropy will be reduced by diffusion in galactic magnetic fields to below the percent level. AMS-02 is the leading space-based experiment for cosmic ray detection and well suited for this search. A new analysis procedure for anisotropies using an event sample with large acceptance is presented. It relies on the ability of the Transition Radiation Detector (TRD) to separate positrons from the proton background.

  2. Pulsars as the sources of high energy cosmic ray positrons

    International Nuclear Information System (INIS)

    Hooper, Dan; Blasi, Pasquale; Serpico, Pasquale Dario

    2009-01-01

    Recent results from the PAMELA satellite indicate the presence of a large flux of positrons (relative to electrons) in the cosmic ray spectrum between approximately 10 and 100 GeV. As annihilating dark matter particles in many models are predicted to contribute to the cosmic ray positron spectrum in this energy range, a great deal of interest has resulted from this observation. Here, we consider pulsars (rapidly spinning, magnetized neutron stars) as an alternative source of this signal. After calculating the contribution to the cosmic ray positron and electron spectra from pulsars, we find that the spectrum observed by PAMELA could plausibly originate from such sources. In particular, a significant contribution is expected from the sum of all mature pulsars throughout the Milky Way, as well as from the most nearby mature pulsars (such as Geminga and B0656+14). The signal from nearby pulsars is expected to generate a small but significant dipole anisotropy in the cosmic ray electron spectrum, potentially providing a method by which the Fermi gamma-ray space telescope would be capable of discriminating between the pulsar and dark matter origins of the observed high energy positrons

  3. The stationary non-equilibrium plasma of cosmic-ray electrons and positrons

    Science.gov (United States)

    Tomaschitz, Roman

    2016-06-01

    The statistical properties of the two-component plasma of cosmic-ray electrons and positrons measured by the AMS-02 experiment on the International Space Station and the HESS array of imaging atmospheric Cherenkov telescopes are analyzed. Stationary non-equilibrium distributions defining the relativistic electron-positron plasma are derived semi-empirically by performing spectral fits to the flux data and reconstructing the spectral number densities of the electronic and positronic components in phase space. These distributions are relativistic power-law densities with exponential cutoff, admitting an extensive entropy variable and converging to the Maxwell-Boltzmann or Fermi-Dirac distributions in the non-relativistic limit. Cosmic-ray electrons and positrons constitute a classical (low-density high-temperature) plasma due to the low fugacity in the quantized partition function. The positron fraction is assembled from the flux densities inferred from least-squares fits to the electron and positron spectra and is subjected to test by comparing with the AMS-02 flux ratio measured in the GeV interval. The calculated positron fraction extends to TeV energies, predicting a broad spectral peak at about 1 TeV followed by exponential decay.

  4. HAWC Observations Strongly Favor Pulsar Interpretations of the Cosmic-Ray Positron Excess

    Energy Technology Data Exchange (ETDEWEB)

    Hooper, Dan [Fermilab; Cholis, Ilias [Johns Hopkins U.; Linden, Tim [Ohio State U., CCAPP; Fang, Ke [Maryland U.

    2017-11-17

    Recent measurements of the Geminga and B0656+14 pulsars by the gamma-ray telescope HAWC (along with earlier measurements by Milagro) indicate that these objects generate significant fluxes of very high-energy electrons. In this paper, we use the very high-energy gamma-ray intensity and spectrum of these pulsars to calculate and constrain their expected contributions to the local cosmic-ray positron spectrum. Among models that are capable of reproducing the observed characteristics of the gamma-ray emission, we find that pulsars invariably produce a flux of high-energy positrons that is similar in spectrum and magnitude to the positron fraction measured by PAMELA and AMS-02. In light of this result, we conclude that it is very likely that pulsars provide the dominant contribution to the long perplexing cosmic-ray positron excess.

  5. The rise in the positron fraction. Distance limits on positron point sources from cosmic ray arrival directions and diffuse gamma-rays

    Energy Technology Data Exchange (ETDEWEB)

    Gebauer, Iris; Bentele, Rosemarie [Karlsruhe Institute of Technology, Karlsruhe (Germany)

    2016-07-01

    The rise in the positron fraction as observed by AMS and previously by PAMELA, cannot be explained by the standard paradigm of cosmic ray transport in which positrons are produced by cosmic-ray-gas interactions in the interstellar medium. Possible explanations are pulsars, which produce energetic electron-positron pairs in their rotating magnetic fields, or the annihilation of dark matter. Here we assume that these positrons originate from a single close-by point source, producing equal amounts of electrons and positrons. The propagation and energy losses of these electrons and positrons are calculated numerically using the DRAGON code, the source properties are optimized to best describe the AMS data. Using the FERMI-LAT limits on a possible dipole anisotropy in electron and positron arrival directions, we put a limit on the minimum distance of such a point source. The energy losses that these energetic electrons and positrons suffer on their way through the galaxy create gamma ray photons through bremsstrahlung and Inverse Compton scattering. Using the measurement of diffuse gamma rays from Fermi-LAT we put a limit on the maximum distance of such a point source. We find that a single electron positron point source powerful enough to explain the locally observed positron fraction must reside between 225 pc and 3.7 kpc distance from the sun and compare to known pulsars.

  6. Comment on AMS02 results support the secondary origin of cosmic ray positrons

    OpenAIRE

    Dado, Shlomo; Dar, Arnon

    2015-01-01

    We present a simple calculation of the flux of secondary positrons produced in the ISM that is based only on priors. Our calculated ISM flux agrees very well with that calculated with the elaborate GALPROP code. It confirms that secondary production of positrons in the ISM by the primary cosmic rays cannot explain the observed sub-TeV flux of CR positrons. Moreover, we show that once energy loss of positrons in source and in the ISM are included, secondary production inside the CR sources plu...

  7. COSMIC-RAY POSITRONS FROM MILLISECOND PULSARS

    Energy Technology Data Exchange (ETDEWEB)

    Venter, C.; Kopp, A.; Büsching, I. [Centre for Space Research, North-West University, Potchefstroom Campus, Private Bag X6001, Potchefstroom 2520 (South Africa); Harding, A. K. [Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Gonthier, P. L. [Hope College, Department of Physics, Holland, MI (United States)

    2015-07-10

    Observations by the Fermi Large Area Telescope of γ-ray millisecond pulsar (MSP) light curves imply copious pair production in their magnetospheres, and not exclusively in those of younger pulsars. Such pair cascades may be a primary source of Galactic electrons and positrons, contributing to the observed enhancement in positron flux above ∼10 GeV. Fermi has also uncovered many new MSPs, impacting Galactic stellar population models. We investigate the contribution of Galactic MSPs to the flux of terrestrial cosmic-ray electrons and positrons. Our population synthesis code predicts the source properties of present-day MSPs. We simulate their pair spectra invoking an offset-dipole magnetic field. We also consider positrons and electrons that have been further accelerated to energies of several TeV by strong intrabinary shocks in black widow (BW) and redback (RB) systems. Since MSPs are not surrounded by pulsar wind nebulae or supernova shells, we assume that the pairs freely escape and undergo losses only in the intergalactic medium. We compute the transported pair spectra at Earth, following their diffusion and energy loss through the Galaxy. The predicted particle flux increases for non-zero offsets of the magnetic polar caps. Pair cascades from the magnetospheres of MSPs are only modest contributors around a few tens of GeV to the lepton fluxes measured by the Alpha Magnetic Spectrometer, PAMELA, and Fermi, after which this component cuts off. The contribution by BWs and RBs may, however, reach levels of a few tens of percent at tens of TeV, depending on model parameters.

  8. A self-consistent model of cosmic-ray fluxes and positron excess: roles of nearby pulsars and a sub-dominant source population

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Jagdish C.; Razzaque, Soebur, E-mail: jjagdish@uj.ac.za, E-mail: srazzaque@uj.ac.za [Department of Physics, University of Johannesburg, P. O. Box 524, Auckland Park 2006 (South Africa)

    2017-09-01

    The cosmic-ray positron flux calculated using the cosmic-ray nuclei interactions in our Galaxy cannot explain observed data above 10 GeV. An excess in the measured positron flux is therefore open to interpretation. Nearby pulsars, located within sub-kiloparsec range of the Solar system, are often invoked as plausible sources contributing to the excess. We show that an additional, sub-dominant population of sources together with the contributions from a few nearby pulsars can explain the latest positron excess data from the Alpha Magnetic Spectrometer (AMS). We simultaneously model, using the DRAGON code, propagation of cosmic-ray proton, Helium, electron and positron and fit their respective flux data. Our fit to the Boron to Carbon ratio data gives a diffusion spectral index of 0.45, which is close to the Kraichnan turbulent spectrum.

  9. Electron and Positron Fluxes in Primary Cosmic Rays Measured with the Alpha Magnetic Spectrometer on the International Space Station

    Science.gov (United States)

    Aguilar, M.; Aisa, D.; Alvino, A.; Ambrosi, G.; Andeen, K.; Arruda, L.; Attig, N.; Azzarello, P.; Bachlechner, A.; Barao, F.; Barrau, A.; Barrin, L.; Bartoloni, A.; Basara, L.; Battarbee, M.; Battiston, R.; Bazo, J.; Becker, U.; Behlmann, M.; Beischer, B.; Berdugo, J.; Bertucci, B.; Bigongiari, G.; Bindi, V.; Bizzaglia, S.; Bizzarri, M.; Boella, G.; de Boer, W.; Bollweg, K.; Bonnivard, V.; Borgia, B.; Borsini, S.; Boschini, M. J.; Bourquin, M.; Burger, J.; Cadoux, F.; Cai, X. D.; Capell, M.; Caroff, S.; Casaus, J.; Cascioli, V.; Castellini, G.; Cernuda, I.; Cervelli, F.; Chae, M. J.; Chang, Y. H.; Chen, A. I.; Chen, H.; Cheng, G. M.; Chen, H. S.; Cheng, L.; Chikanian, A.; Chou, H. Y.; Choumilov, E.; Choutko, V.; Chung, C. H.; Clark, C.; Clavero, R.; Coignet, G.; Consolandi, C.; Contin, A.; Corti, C.; Coste, B.; Cui, Z.; Dai, M.; Delgado, C.; Della Torre, S.; Demirköz, M. B.; Derome, L.; Di Falco, S.; Di Masso, L.; Dimiccoli, F.; Díaz, C.; von Doetinchem, P.; Du, W. J.; Duranti, M.; D'Urso, D.; Eline, A.; Eppling, F. J.; Eronen, T.; Fan, Y. Y.; Farnesini, L.; Feng, J.; Fiandrini, E.; Fiasson, A.; Finch, E.; Fisher, P.; Galaktionov, Y.; Gallucci, G.; García, B.; García-López, R.; Gast, H.; Gebauer, I.; Gervasi, M.; Ghelfi, A.; Gillard, W.; Giovacchini, F.; Goglov, P.; Gong, J.; Goy, C.; Grabski, V.; Grandi, D.; Graziani, M.; Guandalini, C.; Guerri, I.; Guo, K. H.; Habiby, M.; Haino, S.; Han, K. C.; He, Z. H.; Heil, M.; Hoffman, J.; Hsieh, T. H.; Huang, Z. C.; Huh, C.; Incagli, M.; Ionica, M.; Jang, W. Y.; Jinchi, H.; Kanishev, K.; Kim, G. N.; Kim, K. S.; Kirn, Th.; Kossakowski, R.; Kounina, O.; Kounine, A.; Koutsenko, V.; Krafczyk, M. S.; Kunz, S.; La Vacca, G.; Laudi, E.; Laurenti, G.; Lazzizzera, I.; Lebedev, A.; Lee, H. T.; Lee, S. C.; Leluc, C.; Li, H. L.; Li, J. Q.; Li, Q.; Li, Q.; Li, T. X.; Li, W.; Li, Y.; Li, Z. H.; Li, Z. Y.; Lim, S.; Lin, C. H.; Lipari, P.; Lippert, T.; Liu, D.; Liu, H.; Lomtadze, T.; Lu, M. J.; Lu, Y. S.; Luebelsmeyer, K.; Luo, F.; Luo, J. Z.; Lv, S. S.; Majka, R.; Malinin, A.; Mañá, C.; Marín, J.; Martin, T.; Martínez, G.; Masi, N.; Maurin, D.; Menchaca-Rocha, A.; Meng, Q.; Mo, D. C.; Morescalchi, L.; Mott, P.; Müller, M.; Ni, J. Q.; Nikonov, N.; Nozzoli, F.; Nunes, P.; Obermeier, A.; Oliva, A.; Orcinha, M.; Palmonari, F.; Palomares, C.; Paniccia, M.; Papi, A.; Pedreschi, E.; Pensotti, S.; Pereira, R.; Pilo, F.; Piluso, A.; Pizzolotto, C.; Plyaskin, V.; Pohl, M.; Poireau, V.; Postaci, E.; Putze, A.; Quadrani, L.; Qi, X. M.; Rancoita, P. G.; Rapin, D.; Ricol, J. S.; Rodríguez, I.; Rosier-Lees, S.; Rozhkov, A.; Rozza, D.; Sagdeev, R.; Sandweiss, J.; Saouter, P.; Sbarra, C.; Schael, S.; Schmidt, S. M.; Schuckardt, D.; von Dratzig, A. Schulz; Schwering, G.; Scolieri, G.; Seo, E. S.; Shan, B. S.; Shan, Y. H.; Shi, J. Y.; Shi, X. Y.; Shi, Y. M.; Siedenburg, T.; Son, D.; Spada, F.; Spinella, F.; Sun, W.; Sun, W. H.; Tacconi, M.; Tang, C. P.; Tang, X. W.; Tang, Z. C.; Tao, L.; Tescaro, D.; Ting, Samuel C. C.; Ting, S. M.; Tomassetti, N.; Torsti, J.; Türkoǧlu, C.; Urban, T.; Vagelli, V.; Valente, E.; Vannini, C.; Valtonen, E.; Vaurynovich, S.; Vecchi, M.; Velasco, M.; Vialle, J. P.; Wang, L. Q.; Wang, Q. L.; Wang, R. S.; Wang, X.; Wang, Z. X.; Weng, Z. L.; Whitman, K.; Wienkenhöver, J.; Wu, H.; Xia, X.; Xie, M.; Xie, S.; Xiong, R. Q.; Xin, G. M.; Xu, N. S.; Xu, W.; Yan, Q.; Yang, J.; Yang, M.; Ye, Q. H.; Yi, H.; Yu, Y. J.; Yu, Z. Q.; Zeissler, S.; Zhang, J. H.; Zhang, M. T.; Zhang, X. B.; Zhang, Z.; Zheng, Z. M.; Zhuang, H. L.; Zhukov, V.; Zichichi, A.; Zimmermann, N.; Zuccon, P.; Zurbach, C.; AMS Collaboration

    2014-09-01

    Precision measurements by the Alpha Magnetic Spectrometer on the International Space Station of the primary cosmic-ray electron flux in the range 0.5 to 700 GeV and the positron flux in the range 0.5 to 500 GeV are presented. The electron flux and the positron flux each require a description beyond a single power-law spectrum. Both the electron flux and the positron flux change their behavior at ˜30 GeV but the fluxes are significantly different in their magnitude and energy dependence. Between 20 and 200 GeV the positron spectral index is significantly harder than the electron spectral index. The determination of the differing behavior of the spectral indices versus energy is a new observation and provides important information on the origins of cosmic-ray electrons and positrons.

  10. Cosmic-ray positron fraction measurement from 1 to 30 GeV with AMS-01

    CERN Document Server

    Aguilar, M; Allaby, James V; Alpat, B; Ambrosi, G; Anderhub, H; Ao, L; Arefev, A; Azzarello, P; Baldini, L; Basile, M; Barancourt, D; Barão, F; Barbier, G; Barreira, G; Battiston, R; Becker, R; Becker, U; Bellagamba, L; Bene, P; Berdugo, J; Berges, P; Bertucci, B; Biland, A; Blasko, S; Bölla, G; Boschini, M; Bourquin, M; Brocco, L; Bruni, G; Buénerd, M; Burger, J D; Burger, W J; Cai, X D; Camps, C; Cannarsa, P; Capell, M; Cardano, F; Casadei, D; Casaus, J; Castellini, G; Chang, Y H; Chen, H F; Chen, H S; Chen, Z G; Chernoplekov, N A; Tzi Hong Chiueh; Cho, K; Choi, M J; Choi, Y Y; Cindolo, F; Commichau, V; Contin, A; Cortina, E; Cristinziani, M; Dai, T S; Delgado, C; Difalco, S; Djambazov, L; D'Antone, I; Dong, Z R; Emonet, P; Engelberg, J; Eppling, F J; Eronen, T; Esposito, G; Extermann, P; Favier, Jean; Fiandrini, E; Fisher, P H; Flügge, G; Fouque, N; Galaktionov, Yu; Gast, H; Gervasi, M; Giusti, P; Grandi, D; Grimm, O; Gu, W Q; Hangarter, K; Hasan, A; Hermel, V; Hofer, H; Hungerford, W; Jongmanns, M; Karlamaa, K; Karpinski, W; Kenney, G; Kim, D H; Kim, G N; Kim, K S; Kim, M Y; Klimentov, A; Kossakowski, R; Kounine, A; Koutsenko, V F; Kraeber, M; Laborie, G; Laitinen, T; Lamanna, G; Lanciotti, E; Laurenti, G; Lebedev, A; Lechanoine-Leluc, C; Lee, M W; Lee, S C; Levi, G; Liu, C L; Liu, H T; Lu, G; Lü, Y S; Lübelsmeyer, K; Luckey, D; Lustermann, W; Maña, C; Margotti, A; Mayet, F; McNeil, R R; Meillon, B; Menichelli, M; Mihul, A; Mujunen, A; Oliva, A; Olzem, J; Palmonari, F; Park, H B; Park, W H; Pauluzzi, M; Pauss, F; Perrin, E; Pesci, A; Pevsner, A; Pilo, F; Pimenta, M; Plyaskin, V; Pozhidaev, V; Pohl, M; Produit, N; Rancoita, P G; Rapin, D; Raupach, F; Ren, D; Ren, Z; Ribordy, M; Richeux, J P; Riihonen, E; Ritakari, J; Ro, S; Röser, U; Rossin, C; Sagdeev, R; Santos, D; Sartorelli, G; Sbarra, C; Schael, S; Schultzvon Dratzig, A; Schwering, G; Seo, E S; Shin, J W; Shoumilov, E; Shoutko, V; Siedenburg, T; Siedling, R; Son, D; Song, T; Spinella, F; Steuer, M; Sun, G S; Suter, H; Tang, X W; Ting, Samuel C C; Ting, S M; Tornikoski, M; Torsti, J; Trumper, J; Ulbricht, J; Urpo, S; Valtonen, E; Vandenhirtz, J; Velikhov, E P; Verlaat, B; Vetlitskii, I; Vezzu, F; Vialle, J P; Viertel, G; Vite, D; Von Gunten, H; Waldmeier-Wicki, S; Wallraff, W; Wang, B C; Wang, J Z; Wiik, K; Williams, C; Wu, S X; Xia, P C; Xu, S; Yan, J L; Yan, L G; Yang, C G; Yang, J; Yang, M; Ye, S W; Xu, Z Z; Zhang, H Y; Zhang, Z P; Zhao, D X; Zhou, Y; Zhu, G Y; Zhu, W Z; Zhuang, H L; Zichichi, A; Zimmermann, B; Zuccon, P

    2007-01-01

    A measurement of the cosmic ray positron fraction e+/(e+ + e-) in the energy range of 1-30 GeV is presented. The measurement is based on data taken by the AMS-01 experiment during its 10 day Space Shuttle flight in June 1998. A proton background suppression on the order of 10^6 is reached by identifying converted bremsstrahlung photons emitted from positrons.

  11. Cosmic-ray positron fraction measurement from 1 to 30 GeV with AMS-01

    International Nuclear Information System (INIS)

    Aguilar, M.; Alcaraz, J.; Allaby, J.

    2007-01-01

    A measurement of the cosmic ray positron fraction e + /(e + +e - ) in the energy range of 1-30 GeV is presented. The measurement is based on data taken by the AMS-01 experiment during its 10 day Space Shuttle flight in June 1998. A proton background suppression on the order of 10 6 is reached by identifying converted bremsstrahlung photons emitted from positrons

  12. Electron and Positron Fluxes in Primary Cosmic Rays Measured with the Alpha Magnetic Spectrometer on the International Space Station

    CERN Document Server

    Aguilar, M; Alvino, A; Ambrosi, G; Andeen, K; Arruda, L; Attig, N; Azzarello, P; Bachlechner, A; Barao, F; Barrau, A; Barrin, L; Bartoloni, A; Basara, L; Battarbee, M; Battiston, R; Bazo, J; Becker, U; Behlmann, M; Beischer, B; Berdugo, J; Bertucci, B; Bigongiari, G; Bindi, V; Bizzaglia, S; Bizzarri, M; Boella, G; de Boer, W; Bollweg, K; Bonnivard, V; Borgia, B; Borsini, S; Boschini, M J; Bourquin, M; Burger, J; Cadoux, F; Cai, X D; Capell, M; Caroff, S; Casaus, J; Cascioli, V; Castellini, G; Cernuda, I; Cervelli, F; Chae, M J; Chang, Y H; Chen, A I; Chen, H; Cheng, G M; Chen, H S; Cheng, L; Chikanian, A; Chou, H Y; Choumilov, E; Choutko, V; Chung, C H; Clark, C; Clavero, R; Coignet, G; Consolandi, C; Contin, A; Corti, C; Coste, B; Cui, Z; Dai, M; Delgado, C; Della Torre, S; Demirköz, M B; Derome, L; Di Falco, S; Di Masso, L; Dimiccoli, F; Díaz, C; von Doetinchem, P; Du, W J; Duranti, M; D’Urso, D; Eline, A; Eppling, F J; Eronen, T; Fan, Y Y; Farnesini, L; Feng, J; Fiandrini, E; Fiasson, A; Finch, E; Fisher, P; Galaktionov, Y; Gallucci, G; García, B; García-López, R; Gast, H; Gebauer, I; Gervasi, M; Ghelfi, A; Gillard, W; Giovacchini, F; Goglov, P; Gong, J; Goy, C; Grabski, V; Grandi, D; Graziani, M; Guandalini, C; Guerri, I; Guo, K H; Habiby, M; Haino, S; Han, K C; He, Z H; Heil, M; Hoffman, J; Hsieh, T H; Huang, Z C; Huh, C; Incagli, M; Ionica, M; Jang, W Y; Jinchi, H; Kanishev, K; Kim, G N; Kim, K S; Kirn, Th; Kossakowski, R; Kounina, O; Kounine, A; Koutsenko, V; Krafczyk, M S; Kunz, S; La Vacca, G; Laudi, E; Laurenti, G; Lazzizzera, I; Lebedev, A; Lee, H T; Lee, S C; Leluc, C; Li, H L; Li, J Q; Li, Q; Li, Q; Li, T X; Li, W; Li, Y; Li, Z H; Li, Z Y; Lim, S; Lin, C H; Lipari, P; Lippert, T; Liu, D; Liu, H; Lomtadze, T; Lu, M J; Lu, Y S; Luebelsmeyer, K; Luo, F; Luo, J Z; Lv, S S; Majka, R; Malinin, A; Mañá, C; Marín, J; Martin, T; Martínez, G; Masi, N; Maurin, D; Menchaca-Rocha, A; Meng, Q; Mo, D C; Morescalchi, L; Mott, P; Müller, M; Ni, J Q; Nikonov, N; Nozzoli, F; Nunes, P; Obermeier, A; Oliva, A; Orcinha, M; Palmonari, F; Palomares, C; Paniccia, M; Papi, A; Pedreschi, E; Pensotti, S; Pereira, R; Pilo, F; Piluso, A; Pizzolotto, C; Plyaskin, V; Pohl, M; Poireau, V; Postaci, E; Putze, A; Quadrani, L; Qi, X M; Rancoita, P G; Rapin, D; Ricol, J S; Rodríguez, I; Rosier-Lees, S; Rozhkov, A; Rozza, D; Sagdeev, R; Sandweiss, J; Saouter, P; Sbarra, C; Schael, S; Schmidt, S M; Schuckardt, D; Schulz von Dratzig, A; Schwering, G; Scolieri, G; Seo, E S; Shan, B S; Shan, Y H; Shi, J Y; Shi, X Y; Shi, Y M; Siedenburg, T; Son, D; Spada, F; Spinella, F; Sun, W; Sun, W H; Tacconi, M; Tang, C P; Tang, X W; Tang, Z C; Tao, L; Tescaro, D; Ting, Samuel C C; Ting, S M; Tomassetti, N; Torsti, J; Türkoğlu, C; Urban, T; Vagelli, V; Valente, E; Vannini, C; Valtonen, E; Vaurynovich, S; Vecchi, M; Velasco, M; Vialle, J P; Wang, L Q; Wang, Q L; Wang, R S; Wang, X; Wang, Z X; Weng, Z L; Whitman, K; Wienkenhöver, J; Wu, H; Xia, X; Xie, M; Xie, S; Xiong, R Q; Xin, G M; Xu, N S; Xu, W; Yan, Q; Yang, J; Yang, M; Ye, Q H; Yi, H; Yu, Y J; Yu, Z Q; Zeissler, S; Zhang, J H; Zhang, M T; Zhang, X B; Zhang, Z; Zheng, Z M; Zhuang, H L; Zhukov, V; Zichichi, A; Zimmermann, N; Zuccon, P; Zurbach, C

    2014-01-01

    Precision measurements by the Alpha Magnetic Spectrometer on the International Space Station of the primary cosmic-ray electron flux in the range 0.5 to 700 GeV and the positron flux in the range 0.5 to 500 GeV are presented. The electron flux and the positron flux each require a description beyond a single power-law spectrum. Both the electron flux and the positron flux change their behavior at ∼30  GeV but the fluxes are significantly different in their magnitude and energy dependence. Between 20 and 200 GeV the positron spectral index is significantly harder than the electron spectral index. The determination of the differing behavior of the spectral indices versus energy is a new observation and provides important information on the origins of cosmic-ray electrons and positrons.

  13. Search for Cosmic-Ray Electron and Positron Anisotropies with Seven Years of Fermi Large Area Telescope Data

    International Nuclear Information System (INIS)

    Abdollahi, S.; Ackermann, M.; Ajello, M.; Albert, A.; Atwood, W. B.

    2017-01-01

    We present the Large Area Telescope on board the Fermi Gamma-ray Space Telescope that has collected the largest ever sample of high-energy cosmic-ray electron and positron events since the beginning of its operation. Potential anisotropies in the arrival directions of cosmic-ray electrons or positrons could be a signature of the presence of nearby sources. We use almost seven years of data with energies above 42 GeV processed with the Pass 8 reconstruction. The present data sample can probe dipole anisotropies down to a level of 10"-"3. We take into account systematic effects that could mimic true anisotropies at this level. We present a detailed study of the event selection optimization of the cosmic-ray electrons and positrons to be used for anisotropy searches. Since no significant anisotropies have been detected on any angular scale, we present upper limits on the dipole anisotropy. Lastly, the present constraints are among the strongest to date probing the presence of nearby young and middle-aged sources.

  14. A self-consistent model for the Galactic cosmic ray, antiproton and positron spectra

    CERN Multimedia

    CERN. Geneva

    2015-01-01

    In this talk I will present the escape model of Galactic cosmic rays. This model explains the measured cosmic ray spectra of individual groups of nuclei from TeV to EeV energies. It predicts an early transition to extragalactic cosmic rays, in agreement with recent Auger data. The escape model also explains the soft neutrino spectrum 1/E^2.5 found by IceCube in concordance with Fermi gamma-ray data. I will show that within the same model one can explain the excess of positrons and antiprotons above 20 GeV found by PAMELA and AMS-02, the discrepancy in the slopes of the spectra of cosmic ray protons and heavier nuclei in the TeV-PeV energy range and the plateau in cosmic ray dipole anisotropy in the 2-50 TeV energy range by adding the effects of a 2 million year old nearby supernova.

  15. Production of positron annihilation radiation by cosmic-rays near sea level

    CERN Document Server

    Puzovic, J M

    2002-01-01

    Production of positron annihilation radiation by cosmic-rays in Al, Fe, Sn and Pb is measured by means of a triggered HPGe detector. The equipment is located in Belgrade, at an absolute height of 125 m a.s.l. The production rate per unit mass is found to be proportional to the square of the atomic number of the material divided by its mass number, with the proportionality constant equal to 8.1(3)x10 sup - sup 6 s sup - sup 1 g sup - sup 1.

  16. Cosmic antimatter

    International Nuclear Information System (INIS)

    Tarle, G.; Swordy, S.

    1998-01-01

    In 1928 Paul Dirac forecasted the existence of antimatter and 4 years later Carl Anderson detected the first antiparticle: the positron in a cloud chamber while studying cosmic radiation. Antiprotons were more difficult to find but in 1955 physicists from Lawrence Berkeley Laboratory got some in a particle accelerator. In 1995 a team from the CERN synthesized atoms of anti-hydrogen by binding positrons to antiprotons in a particle accelerator. Astrophysicists have built more and more complex detectors to study cosmic rays. The detector HEAT (high energy antimatter telescope) has been designed to study positrons above the atmosphere. This detector has been launched for the first time in 1994 and has measured cosmic radiation for 32 hours at an altitude of 37000 meters. The results were challenging: whereas the number of low energy positrons detected agrees with the theory, the number of high energy positrons is too important. It suggests the existence of unknown sources of positrons somewhere in the universe. The massive particles that interact weakly (WIMP) could be such sources. This article draws the history of the quest for antimatter and its implications in cosmology, the detector HEAT is described. (A.C.)

  17. Cosmic Ray Positrons from Pulsars

    Science.gov (United States)

    Harding, Alice K.

    2010-01-01

    Pulsars are potential Galactic sources of positrons through pair cascades in their magnetospheres. There are, however, many uncertainties in establishing their contribution to the local primary positron flux. Among these are the local density of pulsars, the cascade pair multiplicities that determine the injection rate of positrons from the pulsar, the acceleration of the injected particles by the pulsar wind termination shock, their rate of escape from the pulsar wind nebula, and their propagation through the interstellar medium. I will discuss these issues in the context of what we are learning from the new Fermi pulsar detections and discoveries.

  18. Simulating Terrestrial Gamma Ray Flashes due to cosmic ray shower electrons and positrons

    Science.gov (United States)

    Connell, Paul

    2017-04-01

    The University of Valencia has developed a software simulator LEPTRACK to simulate the relativistic runaway electron avalanches, RREA, that are presumed to be the cause of Terrestrial Gamma Ray Flashes and their powerful accompanying Ionization/Excitation Flashes. We show here results of LEPTRACK simulations of RREA by the interaction of MeV energy electrons/positrons and photons in cosmic ray showers traversing plausible electric field geometries expected in storm clouds. The input beams of MeV shower products were created using the CORSIKA software package from the Karlsruhe Institute of Technology. We present images, videos and plots showing the different Ionization, Excitation and gamma-ray photon density fields produced, along with their time and spatial profile evolution, which depend critically on where the line of shower particles intercept the electric field geometry. We also show a new effect of incoming positrons in the shower, which make up a significant fraction of shower products, in particular their apparent "orbiting" within a high altitude negative induced shielding charge layer, which has been conjectured to produce a signature microwave emission, as well as a short range 511 keV annihilation line. The interesting question posed is if this conjectured positron emission can be observed and correlated with TGF orbital observations to show if a TGF originates in the macro E-fields of storm clouds or the micro E-fields of lightning leaders where this positron "orbiting" is not likely to occur.

  19. Measurements of the cosmic-ray electron and positron spectrum and anisotropies with the Fermi LAT

    Science.gov (United States)

    Loparco, F.; Fermi LAT Collaboration

    2017-12-01

    The Large Area Telescope (LAT) onboard the Fermi satellite is a pair-conversion telescope for high-energy gamma rays of astrophysical origin. Although it was designed to be a high-sensitivity gamma-ray telescope, the LAT has proved to be an excellent electron/positron detector. It has been operating in low Earth orbit since June 2008 and has collected more than 16 million cosmic-ray electron and positron (CRE) events in its first seven years of operation. The huge data sample collected by the LAT enables a precise measurement of the CRE energy spectrum up to the TeV region. A search for anisotropies in the arrival directions of CREs was also performed. The upper limits on the dipole anisotropy probe the presence of nearby young and middle-aged CRE sources.

  20. Cosmic Sum Rules

    DEFF Research Database (Denmark)

    T. Frandsen, Mads; Masina, Isabella; Sannino, Francesco

    2011-01-01

    We introduce new sum rules allowing to determine universal properties of the unknown component of the cosmic rays and show how it can be used to predict the positron fraction at energies not yet explored by current experiments and to constrain specific models.......We introduce new sum rules allowing to determine universal properties of the unknown component of the cosmic rays and show how it can be used to predict the positron fraction at energies not yet explored by current experiments and to constrain specific models....

  1. The discrimination between cosmic positrons and protons with the Transition Radiation Detector of the AMS experiment on the International Space Station

    Energy Technology Data Exchange (ETDEWEB)

    Millinger, Mark

    2012-10-08

    The aim of this thesis is the development and validation of a particle identification method with the Transition Radiation Detector (TRD) of the Alpha Magnetic Spectrometer AMS-02 to allow for the determination of the positron fraction in the cosmic lepton flux. Independent measurements indicate that a significant amount of about 23% of the energy density in the universe consists of an unknown mass contribution, the so-called Dark Matter. The Neutralino, as the most popular Dark Matter particle candidate, may produce an additional signal in the spectrum of cosmic rays. The fraction of positrons in the cosmic lepton flux possibly contains such a Dark Matter signal at high particle momenta. The currently most precise measurements in the region of this excess are provided by the satellite-borne PAMELA and Fermi detectors. Momentumdependent systematic uncertainties, especially the mis-identification of protons as positrons, could imitate the signal. However, if this positron excess is produced by Dark Matter the fraction should decrease above a theoretical energy threshold to the expectations, based on particle propagation. The energy region measured up to now does not show such a progress. Due to its significantly increased event statistics and its capability to measure up to higher particle energies, this signature could be observed with AMS-02. The number of events, which can be recorded by a detector, is limited by the combination of aperture and observable solid angle, quantified by the geometrical acceptance, and the observation time. As the cosmic particle flux follows a power-law in particle momentum with exponent {gamma} {approx} -3, the observable momentum interval is thus constrained by statistics. Due to its large geometrical acceptance of about 0.5 m{sup 2}sr, its long observation time of at least 9 years and its high proton suppression factor of >or similar 10{sup 6} AMS-02 will record large and clean lepton samples and thus provide a precise measurement

  2. The discrimination between cosmic positrons and protons with the Transition Radiation Detector of the AMS experiment on the International Space Station

    International Nuclear Information System (INIS)

    Millinger, Mark

    2012-01-01

    The aim of this thesis is the development and validation of a particle identification method with the Transition Radiation Detector (TRD) of the Alpha Magnetic Spectrometer AMS-02 to allow for the determination of the positron fraction in the cosmic lepton flux. Independent measurements indicate that a significant amount of about 23% of the energy density in the universe consists of an unknown mass contribution, the so-called Dark Matter. The Neutralino, as the most popular Dark Matter particle candidate, may produce an additional signal in the spectrum of cosmic rays. The fraction of positrons in the cosmic lepton flux possibly contains such a Dark Matter signal at high particle momenta. The currently most precise measurements in the region of this excess are provided by the satellite-borne PAMELA and Fermi detectors. Momentumdependent systematic uncertainties, especially the mis-identification of protons as positrons, could imitate the signal. However, if this positron excess is produced by Dark Matter the fraction should decrease above a theoretical energy threshold to the expectations, based on particle propagation. The energy region measured up to now does not show such a progress. Due to its significantly increased event statistics and its capability to measure up to higher particle energies, this signature could be observed with AMS-02. The number of events, which can be recorded by a detector, is limited by the combination of aperture and observable solid angle, quantified by the geometrical acceptance, and the observation time. As the cosmic particle flux follows a power-law in particle momentum with exponent γ ∼ -3, the observable momentum interval is thus constrained by statistics. Due to its large geometrical acceptance of about 0.5 m 2 sr, its long observation time of at least 9 years and its high proton suppression factor of >or similar 10 6 AMS-02 will record large and clean lepton samples and thus provide a precise measurement of the cosmic

  3. Measurement of the positron to electron ratio in the cosmic rays above 5 GeV

    International Nuclear Information System (INIS)

    Golden, R.L.; Stochaj, S.J.; Stephens, S.A.; Aversa, F.; Barbiellini, G.; Boezio, M.; Bravar, U.; Colavita, A.; Fratnik, F.

    1995-12-01

    As part of a series of experiments to search for antimatter in cosmic rays, the NMSU balloon-borne magnet spectrometer was configured for a flight to study positrons. Two completely new instruments, a transition radiation detector and a silicon-tungsten imaging calorimeter, were added to the magnet spectrometer. These two detectors provided a proton rejection factor better than (3) (10) 4 . This instrument was flown from Fort Sumner, NM at an average depth of 4.5 g/cm 2 of residual atmosphere for a period of 25 hours. The paper reports the measured fraction of positrons e + /e + +e - from about 5 to 60 GeV at the top of the atmosphere. The measurements do not show any compelling evidence for an increase in this ratio with energy and the results are consistent with a constant fraction of 0.78±0.016 over the entire region

  4. High Statistics Measurement of the Positron Fraction in Primary Cosmic Rays of 0.5-500 GeV with the Alpha Magnetic Spectrometer on the International Space Station

    Science.gov (United States)

    Accardo, L.; Aguilar, M.; Aisa, D.; Alvino, A.; Ambrosi, G.; Andeen, K.; Arruda, L.; Attig, N.; Azzarello, P.; Bachlechner, A.; Barao, F.; Barrau, A.; Barrin, L.; Bartoloni, A.; Basara, L.; Battarbee, M.; Battiston, R.; Bazo, J.; Becker, U.; Behlmann, M.; Beischer, B.; Berdugo, J.; Bertucci, B.; Bigongiari, G.; Bindi, V.; Bizzaglia, S.; Bizzarri, M.; Boella, G.; de Boer, W.; Bollweg, K.; Bonnivard, V.; Borgia, B.; Borsini, S.; Boschini, M. J.; Bourquin, M.; Burger, J.; Cadoux, F.; Cai, X. D.; Capell, M.; Caroff, S.; Casaus, J.; Cascioli, V.; Castellini, G.; Cernuda, I.; Cervelli, F.; Chae, M. J.; Chang, Y. H.; Chen, A. I.; Chen, H.; Cheng, G. M.; Chen, H. S.; Cheng, L.; Chikanian, A.; Chou, H. Y.; Choumilov, E.; Choutko, V.; Chung, C. H.; Clark, C.; Clavero, R.; Coignet, G.; Consolandi, C.; Contin, A.; Corti, C.; Coste, B.; Cui, Z.; Dai, M.; Delgado, C.; Della Torre, S.; Demirköz, M. B.; Derome, L.; Di Falco, S.; Di Masso, L.; Dimiccoli, F.; Díaz, C.; von Doetinchem, P.; Du, W. J.; Duranti, M.; D'Urso, D.; Eline, A.; Eppling, F. J.; Eronen, T.; Fan, Y. Y.; Farnesini, L.; Feng, J.; Fiandrini, E.; Fiasson, A.; Finch, E.; Fisher, P.; Galaktionov, Y.; Gallucci, G.; García, B.; García-López, R.; Gast, H.; Gebauer, I.; Gervasi, M.; Ghelfi, A.; Gillard, W.; Giovacchini, F.; Goglov, P.; Gong, J.; Goy, C.; Grabski, V.; Grandi, D.; Graziani, M.; Guandalini, C.; Guerri, I.; Guo, K. H.; Habiby, M.; Haino, S.; Han, K. C.; He, Z. H.; Heil, M.; Hoffman, J.; Hsieh, T. H.; Huang, Z. C.; Huh, C.; Incagli, M.; Ionica, M.; Jang, W. Y.; Jinchi, H.; Kanishev, K.; Kim, G. N.; Kim, K. S.; Kirn, Th.; Kossakowski, R.; Kounina, O.; Kounine, A.; Koutsenko, V.; Krafczyk, M. S.; Kunz, S.; La Vacca, G.; Laudi, E.; Laurenti, G.; Lazzizzera, I.; Lebedev, A.; Lee, H. T.; Lee, S. C.; Leluc, C.; Li, H. L.; Li, J. Q.; Li, Q.; Li, Q.; Li, T. X.; Li, W.; Li, Y.; Li, Z. H.; Li, Z. Y.; Lim, S.; Lin, C. H.; Lipari, P.; Lippert, T.; Liu, D.; Liu, H.; Lomtadze, T.; Lu, M. J.; Lu, Y. S.; Luebelsmeyer, K.; Luo, F.; Luo, J. Z.; Lv, S. S.; Majka, R.; Malinin, A.; Mañá, C.; Marín, J.; Martin, T.; Martínez, G.; Masi, N.; Maurin, D.; Menchaca-Rocha, A.; Meng, Q.; Mo, D. C.; Morescalchi, L.; Mott, P.; Müller, M.; Ni, J. Q.; Nikonov, N.; Nozzoli, F.; Nunes, P.; Obermeier, A.; Oliva, A.; Orcinha, M.; Palmonari, F.; Palomares, C.; Paniccia, M.; Papi, A.; Pedreschi, E.; Pensotti, S.; Pereira, R.; Pilo, F.; Piluso, A.; Pizzolotto, C.; Plyaskin, V.; Pohl, M.; Poireau, V.; Postaci, E.; Putze, A.; Quadrani, L.; Qi, X. M.; Rancoita, P. G.; Rapin, D.; Ricol, J. S.; Rodríguez, I.; Rosier-Lees, S.; Rozhkov, A.; Rozza, D.; Sagdeev, R.; Sandweiss, J.; Saouter, P.; Sbarra, C.; Schael, S.; Schmidt, S. M.; Schuckardt, D.; von Dratzig, A. Schulz; Schwering, G.; Scolieri, G.; Seo, E. S.; Shan, B. S.; Shan, Y. H.; Shi, J. Y.; Shi, X. Y.; Shi, Y. M.; Siedenburg, T.; Son, D.; Spada, F.; Spinella, F.; Sun, W.; Sun, W. H.; Tacconi, M.; Tang, C. P.; Tang, X. W.; Tang, Z. C.; Tao, L.; Tescaro, D.; Ting, Samuel C. C.; Ting, S. M.; Tomassetti, N.; Torsti, J.; Türkoǧlu, C.; Urban, T.; Vagelli, V.; Valente, E.; Vannini, C.; Valtonen, E.; Vaurynovich, S.; Vecchi, M.; Velasco, M.; Vialle, J. P.; Wang, L. Q.; Wang, Q. L.; Wang, R. S.; Wang, X.; Wang, Z. X.; Weng, Z. L.; Whitman, K.; Wienkenhöver, J.; Wu, H.; Xia, X.; Xie, M.; Xie, S.; Xiong, R. Q.; Xin, G. M.; Xu, N. S.; Xu, W.; Yan, Q.; Yang, J.; Yang, M.; Ye, Q. H.; Yi, H.; Yu, Y. J.; Yu, Z. Q.; Zeissler, S.; Zhang, J. H.; Zhang, M. T.; Zhang, X. B.; Zhang, Z.; Zheng, Z. M.; Zhuang, H. L.; Zhukov, V.; Zichichi, A.; Zimmermann, N.; Zuccon, P.; Zurbach, C.; AMS Collaboration

    2014-09-01

    A precision measurement by AMS of the positron fraction in primary cosmic rays in the energy range from 0.5 to 500 GeV based on 10.9 million positron and electron events is presented. This measurement extends the energy range of our previous observation and increases its precision. The new results show, for the first time, that above ∼200 GeV the positron fraction no longer exhibits an increase with energy.

  5. Reestimation of the production spectra of cosmic ray secondary positrons and electrons in the ISM

    Science.gov (United States)

    Wong, C. M.; Ng, L. K.

    1985-01-01

    A detailed calculation of the production spectra of charged hadrons produced by interactions of cosmic rays in the interstellar medium is presented along with a thorough treatment of pion and muon decays. Newly parameterized inclusive cross sections of hadrons were used and exact kinematic limitations were taken into account. Single parametrized expressions for the production spectra of both secondary positrons and electrons in the energy range .1 to 100 GeV are presented. The results are compared with other authors' predictions. Equilibrium spectra using various models are also presented.

  6. High Statistics Measurement of the Positron Fraction in Primary Cosmic Rays of 0.5–500 GeV with the Alpha Magnetic Spectrometer on the International Space Station

    CERN Document Server

    Accardo, L; Aisa, D; Alpat, B; Alvino, A; Ambrosi, G; Andeen, K; Arruda, L; Attig, N; Azzarello, P; Bachlechner, A; Barao, F; Barrau, A; Barrin, L; Bartoloni, A; Basara, L; Battarbee, M; Battiston, R; Bazo, J; Becker, U; Behlmann, M; Beischer, B; Berdugo, J; Bertucci, B; Bigongiari, G; Bindi, V; Bizzaglia, S; Bizzarri, M; Boella, G; de Boer, W; Bollweg, K; Bonnivard, V; Borgia, B; Borsini, S; Boschini, M J; Bourquin, M; Burger, J; Cadoux, F; Cai, X D; Capell, M; Caroff, S; Carosi, G; Casaus, J; Cascioli, V; Castellini, G; Cernuda, I; Cerreta, D; Cervelli, F; Chae, M J; Chang, Y H; Chen, A I; Chen, H; Cheng, G M; Chen, H S; Cheng, L; Chikanian, A; Chou, H Y; Choumilov, E; Choutko, V; Chung, C H; Cindolo, F; Clark, C; Clavero, R; Coignet, G; Consolandi, C; Contin, A; Corti, C; Coste, B; Cui, Z; Dai, M; Delgado, C; Della Torre, S; Demirköz, M B; Derome, L; Di Falco, S; Di Masso, L; Dimiccoli, F; Díaz, C; von Doetinchem, P; Du, W J; Duranti, M; D’Urso, D; Eline, A; Eppling, F J; Eronen, T; Fan, Y Y; Farnesini, L; Feng, J; Fiandrini, E; Fiasson, A; Finch, E; Fisher, P; Galaktionov, Y; Gallucci, G; García, B; García-López, R; Gast, H; Gebauer, I; Gervasi, M; Ghelfi, A; Gillard, W; Giovacchini, F; Goglov, P; Gong, J; Goy, C; Grabski, V; Grandi, D; Graziani, M; Guandalini, C; Guerri, I; Guo, K H; Haas, D; Habiby, M; Haino, S; Han, K C; He, Z H; Heil, M; Henning, R; Hoffman, J; Hsieh, T H; Huang, Z C; Huh, C; Incagli, M; Ionica, M; Jang, W Y; Jinchi, H; Kanishev, K; Kim, G N; Kim, K S; Kirn, Th; Kossakowski, R; Kounina, O; Kounine, A; Koutsenko, V; Krafczyk, M S; Kunz, S; La Vacca, G; Laudi, E; Laurenti, G; Lazzizzera, I; Lebedev, A; Lee, H T; Lee, S C; Leluc, C; Levi, G; Li, H L; Li, J Q; Li, Q; Li, Q; Li, T X; Li, W; Li, Y; Li, Z H; Li, Z Y; Lim, S; Lin, C H; Lipari, P; Lippert, T; Liu, D; Liu, H; Lolli, M; Lomtadze, T; Lu, M J; Lu, Y S; Luebelsmeyer, K; Luo, F; Luo, J Z; Lv, S S; Majka, R; Malinin, A; Mañá, C; Marín, J; Martin, T; Martínez, G; Masi, N; Massera, F; Maurin, D; Menchaca-Rocha, A; Meng, Q; Mo, D C; Monreal, B; Morescalchi, L; Mott, P; Müller, M; Ni, J Q; Nikonov, N; Nozzoli, F; Nunes, P; Obermeier, A; Oliva, A; Orcinha, M; Palmonari, F; Palomares, C; Paniccia, M; Papi, A; Pauluzzi, M; Pedreschi, E; Pensotti, S; Pereira, R; Pilastrini, R; Pilo, F; Piluso, A; Pizzolotto, C; Plyaskin, V; Pohl, M; Poireau, V; Postaci, E; Putze, A; Quadrani, L; Qi, X M; Rancoita, P G; Rapin, D; Ricol, J S; Rodríguez, I; Rosier-Lees, S; Rossi, L; Rozhkov, A; Rozza, D; Rybka, G; Sagdeev, R; Sandweiss, J; Saouter, P; Sbarra, C; Schael, S; Schmidt, S M; Schuckardt, D; Schulz von Dratzig, A; Schwering, G; Scolieri, G; Seo, E S; Shan, B S; Shan, Y H; Shi, J Y; Shi, X Y; Shi, Y M; Siedenburg, T; Son, D; Spada, F; Spinella, F; Sun, W; Sun, W H; Tacconi, M; Tang, C P; Tang, X W; Tang, Z C; Tao, L; Tescaro, D; Ting, Samuel C C; Ting, S M; Tomassetti, N; Torsti, J; Türkoğlu, C; Urban, T; Vagelli, V; Valente, E; Vannini, C; Valtonen, E; Vaurynovich, S; Vecchi, M; Velasco, M; Vialle, J P; Vitale, V; Volpini, G; Wang, L Q; Wang, Q L; Wang, R S; Wang, X; Wang, Z X; Weng, Z L; Whitman, K; Wienkenhöver, J; Wu, H; Wu, K Y; Xia, X; Xie, M; Xie, S; Xiong, R Q; Xin, G M; Xu, N S; Xu, W; Yan, Q; Yang, J; Yang, M; Ye, Q H; Yi, H; Yu, Y J; Yu, Z Q; Zeissler, S; Zhang, J H; Zhang, M T; Zhang, X B; Zhang, Z; Zheng, Z M; Zhou, F; Zhuang, H L; Zhukov, V; Zichichi, A; Zimmermann, N; Zuccon, P; Zurbach, C

    2014-01-01

    A precision measurement by AMS of the positron fraction in primary cosmic rays in the energy range from 0.5 to 500 GeV based on 10.9 million positron and electron events is presented. This measurement extends the energy range of our previous observation and increases its precision. The new results show, for the first time, that above ∼200  GeV the positron fraction no longer exhibits an increase with energy.

  7. The Fermi Large Area Telescope as a cosmic-ray detector

    International Nuclear Information System (INIS)

    Sgrò, Carmelo

    2013-01-01

    The Fermi Large Area Telescope is an international observatory conceived to study high energy gamma-rays from the universe. It is designed to identify and reconstruct electromagnetic showers and it can collect cosmic-ray electrons and positrons thanks to its triggering and filtering capabilities. The Fermi LAT collaboration has published several results on charged cosmic rays. We measured the inclusive spectrum of electrons and positrons from 7 GeV to 1 TeV and searched for anisotropies in the electron incoming direction. We have recently published a measurement of cosmic-ray positron-only and electron-only spectra for energies between 20 GeV and 200 GeV exploiting the Earth's magnetic field as a charge separator. In this work we describe the techniques and capabilities of the LAT as a cosmic-ray detector and review the recent results and their interpretations. Prospects for future studies and observations will also be discussed

  8. About cosmic gamma ray lines

    Science.gov (United States)

    Diehl, Roland

    2017-06-01

    Gamma ray lines from cosmic sources convey the action of nuclear reactions in cosmic sites and their impacts on astrophysical objects. Gamma rays at characteristic energies result from nuclear transitions following radioactive decays or high-energy collisions with excitation of nuclei. The gamma-ray line from the annihilation of positrons at 511 keV falls into the same energy window, although of different origin. We present here the concepts of cosmic gamma ray spectrometry and the corresponding instruments and missions, followed by a discussion of recent results and the challenges and open issues for the future. Among the lessons learned are the diffuse radioactive afterglow of massive-star nucleosynthesis in 26Al and 60Fe gamma rays, which is now being exploited towards the cycle of matter driven by massive stars and their supernovae; large interstellar cavities and superbubbles have been recognised to be of key importance here. Also, constraints on the complex processes making stars explode as either thermonuclear or core-collapse supernovae are being illuminated by gamma-ray lines, in this case from shortlived radioactivities from 56Ni and 44Ti decays. In particular, the three-dimensionality and asphericities that have recently been recognised as important are enlightened in different ways through such gamma-ray line spectroscopy. Finally, the distribution of positron annihilation gamma ray emission with its puzzling bulge-dominated intensity disctribution is measured through spatially-resolved spectra, which indicate that annihilation conditions may differ in different parts of our Galaxy. But it is now understood that a variety of sources may feed positrons into the interstellar medium, and their characteristics largely get lost during slowing down and propagation of positrons before annihilation; a recent microquasar flare was caught as an opportunity to see positrons annihilate at a source.

  9. Cosmic ray electrons and protons, and their antiparticles

    International Nuclear Information System (INIS)

    Boezio, Mirko

    2014-01-01

    Cosmic rays are a sample of solar, galactic, and extragalactic matter. Their origin, acceleration mechanisms, and subsequent propagation toward Earth have intrigued scientists since their discovery. These issues can be studied via analysis of the energy spectra and composition of cosmic rays. Protons are the most abundant component of the cosmic radiation, and many experiments have been dedicated to the accurate measurement of their spectra. Complementary information is provided by electrons, which comprise about 1% of the cosmic radiation. Because of their low mass, electrons experience severe energy losses through synchrotron emission in the galactic magnetic field and inverse Compton scattering of radiation fields. Electrons therefore provide information on the local galactic environment that is not accessible from the study of the cosmic ray nuclei. Antiparticles, namely antiprotons and positrons, are produced in the interaction between cosmic ray nuclei and the interstellar matter. They are therefore intimately linked to the propagation mechanisms of the parent nuclei. Novel sources of primary cosmic ray antiparticles of either astrophysical (e.g., positrons from pulsars) or exotic origin (e.g., annihilation of dark matter particles) may exist. The nature of dark matter is one of the most prominent open questions in science today. An observation of positrons from pulsars would open a new observation window on these sources. Several experiments equipped with state-of-the art detector systems have recently presented results on the energy spectra of electrons, protons, and their antiparticles with a significant improvement in statistics and better control of systematics The status of the field will be reviewed, with a focus on these recent scientific results. (author)

  10. Propagation of Galactic Cosmic Rays and Dark Matter indirect Detection

    International Nuclear Information System (INIS)

    Delahaye, Timur

    2010-07-01

    This thesis is dedicated to the study of propagation of cosmic electrons and positrons in the Milky Way and to the indirect detection of dark matter. The existence of dark matter is a hypothesis considered as reasonable from the point of view of cosmology, astrophysics and even particle physics. Nevertheless its detection still eludes us and it is not possible to verify this hypothesis by other means than gravitational one. A possible way to detect dark matter is to look for its annihilation or decay products among Galactic cosmic rays. During the last three years, data concerning cosmic ray electrons and positrons have been accumulated and have reached a remarkable precision. Such a precision requires from us to refine the theoretical models and to quantify the errors. This thesis addresses the study of all the sources of uncertainties affecting predictions of cosmic electrons and positron fluxes, primary and secondary, classical or from exotic origin. The greatest care has been dedicated to the sources and the propagation in the Galactic halo. Moreover a study of gamma and radio emissions associated to these cosmic rays is presented, again with the will of sizing uncertainties. Finally a status of the research for detection of annihilation or decay of Galactic dark matter is presented. (author)

  11. Cosmic-ray sum rules

    International Nuclear Information System (INIS)

    Frandsen, Mads T.; Masina, Isabella; Sannino, Francesco

    2011-01-01

    We introduce new sum rules allowing to determine universal properties of the unknown component of the cosmic rays; we show how they can be used to predict the positron fraction at energies not yet explored by current experiments, and to constrain specific models.

  12. Cosmic ray anisotropy searches with AMS-02

    Energy Technology Data Exchange (ETDEWEB)

    Zeissler, Stefan; Gebauer, Iris; Trumpf, Ricarda [Karlsruher Institut fuer Technologie (KIT) (Germany)

    2016-07-01

    The Alpha Magnetic Spectrometer (AMS-02) is a state-of-the-art particle detector designed to operate as an external module on the International Space Station (ISS). In this unique space environment cosmic particles can be measured with high precision over an energy range from GeV up to TeV. The AMS collaboration provided precise measurements of the electron and positron fluxes, which indicate an additional source of positrons among the various cosmic particles. Possible candidates for this source are local pulsars, a local source of positrons produced in proton-gas interactions or dark matter annihilation. In the first two cases a possible anisotropy in the electrons and positrons incoming direction at Earth might be detectable. To determine the level of isotropy the measured data is compared to reference maps, which simulate the measurement of an isotropic sky. A common choice of reference maps are proton count maps or shuffled maps, which redistribute measured incoming directions over the whole measuring time. Both choices lead to difficulties in the reconstruction of a marginal signal with a big expansion over the galactic sky as it would be the case for charged cosmic particles. We developed a method to construct reference maps based on fundamental detector characteristics such as the lifetime and the geometric acceptance. Using this we are able to reconstruct the isotropic sky as it would be seen by the detector. We demonstrate the performance of the method using AMS-02 data.

  13. Measurement of the cosmic positrons' spectrum with the experiment AMS-02 and search for exotic signals; Mesure du spectre de positons cosmiques avec l'experience AMS-02 et recherche de signaux exotiques

    Energy Technology Data Exchange (ETDEWEB)

    Pochon, J

    2005-06-15

    The AMS-02 experiment is a particle detector that will be installed on the international space station (ISS) in 2008 for at least 3 years. The physics motivations are cosmic ray measurements (e-, e+, p, p-bar, {gamma}, He, C,...), antimatter search for Z>2 and gamma ray studies from GeV to TeV. The HEAT experiment has measured positron spectrum up to 30 GeV, and shown a possible distortion around 8 GeV, which can be interpreted as a dark matter signal. The cosmic positrons spectrum measurement needs positron/proton separation close to 10{sup 5}, which will be obtained combining all AMS-02 sub-detectors. A neural network analysis has been developed on test beam data taken in 2002, to estimate the electron/proton rejection for the electromagnetic calorimeter. This technique, based on discriminant variables and which was tuned on data, was used to determine the positron acceptance combining other sub-detectors information. The number of conventional positrons can be estimated and AMS ability to detect cold dark matter signals has been determined. This study was presented for signal from supersymmetric neutralinos and from Kaluza-Klein stable particles. Fluxes are naturally too low to be detected. Signal can be enhanced thanks to local dark matter over-densities which appear naturally in galaxy formation models. A model for those over-densities has been tuned and presented. (author)

  14. PEBS - Positron Electron Balloon Spectrometer

    CERN Document Server

    von Doetinchem, P.; Kirn, T.; Yearwood, G.Roper; Schael, S.

    2007-01-01

    The best measurement of the cosmic ray positron flux available today was performed by the HEAT balloon experiment more than 10 years ago. Given the limitations in weight and power consumption for balloon experiments, a novel approach was needed to design a detector which could increase the existing data by more than a factor of 100. Using silicon photomultipliers for the readout of a scintillating fiber tracker and of an imaging electromagnetic calorimeter, the PEBS detector features a large geometrical acceptance of 2500 cm^2 sr for positrons, a total weight of 1500 kg and a power consumption of 600 W. The experiment is intended to measure cosmic ray particle spectra for a period of up to 20 days at an altitude of 40 km circulating the North or South Pole. A full Geant 4 simulation of the detector concept has been developed and key elements have been verified in a testbeam in October 2006 at CERN.

  15. Observations of cosmic ray positrons during the 1993 flight of the NMSU/WiZard-TS93 balloon borne apparatus

    Energy Technology Data Exchange (ETDEWEB)

    Basini, G. [INFN, Laboratori Nazionali di Frascati, Rome (Italy); Bellotti, R.; Cafagna, F.; Circella, M.; De Cataldo, G.; De Marzo, C.N. [Bari Univ. (Italy)]|[INFN, Bari (Italy); Brunetti, M.T.; Codini, A. [Perugia Univ. (Italy)]|[INFN, Perugia (Italy); De Pascale, M.P. [Rome Univ. `Tor Vergata` (Italy)]|[INFN, Rome (Italy); Aversa, F. [Trieste Univ. (Italy)]|[INFN, Trieste (Italy)

    1995-09-01

    As a part of a series of experiments to search for antimatter in the primary cosmic ray, the NMSU balloon borne apparatus was configured for a flight dedicated to the search of positrons. Two completely new instruments were added to the magnetic spectrometer: a transition radiation detector (TRD) and a silicon-tungsten tracking calorimeter. The function of these two instruments complemented one another and the combined action provided a proton rejection factor better than 5x10{sup 5}. The paper shows the results from the analysis on the complete set of data. All the presented spectra are at the level of the spectrometer.

  16. Radio reconstruction of the mass of ultra-high cosmic rays

    Energy Technology Data Exchange (ETDEWEB)

    Dorosti, Qader [Institut fuer Kernphysik (IKP), KIT (Germany)

    2015-07-01

    Detection of ultra-high energy cosmic rays can reveal the processes of the most violent sources in the Universe, which yet has to be determined. Interaction of cosmic rays with the Earth's atmosphere results in cascades of secondary particles, i.e. air showers. Many of such particles are electrons and positrons. The induced electrons and positrons interact with the geomagnetic field and induce radio emissions. Detection of air showers along with the detection of induced radio emissions can furnish a precise measurement of the direction, energy and mass of ultra-high energy cosmic rays. The Auger Engineering Radio Array consists of 124 radio stations measuring radio emission from air showers, in order to reconstruct the energy, direction and mass of cosmic rays. In this contribution, we present a method which employs a reduced hyperbolic model to describe the shape of radio wave front. We have investigated that the parameters of the reduced hyperbolic model are sensitive to the mass of cosmic rays. The obtained results are presented in this talk.

  17. AMS-02 positron excess and indirect detection of three-body decaying dark matter

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Hsin-Chia [Department of Physics, University of California, Davis, CA 95616 (United States); Huang, Wei-Chih [Fakultät für Physik, Technische Universität Dortmund, 44221 Dortmund (Germany); Huang, Xiaoyuan [Physik-Department T30d, Technische Universität München, James-Franck-Straße, D-85748 Garching (Germany); Low, Ian [High Energy Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Tsai, Yue-Lin Sming [Kavli IPMU (WPI), University of Tokyo, Kashiwa, Chiba 277-8583 (Japan); Yuan, Qiang, E-mail: cheng@physics.ucdavis.edu, E-mail: wei-chih.huang@tu-dortmund.de, E-mail: huangxiaoyuan@gmail.com, E-mail: ilow@northwestern.edu, E-mail: smingtsai@gmail.com, E-mail: yuanq@pmo.ac.cn [Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

    2017-03-01

    We consider indirect detection of meta-stable dark matter particles decaying into a stable neutral particle and a pair of standard model fermions. Due to the softer energy spectra from the three-body decay, such models could potentially explain the AMS-02 positron excess without being constrained by the Fermi-LAT gamma-ray data and the cosmic ray anti-proton measurements. We scrutinize over different final state fermions, paying special attention to handling of the cosmic ray background and including various contributions from cosmic ray propagation with the help of the LIKEDM package. It is found that primary decays into an electron-positron pair and a stable neutral particle could give rise to the AMS-02 positron excess and, at the same time, stay unscathed against the gamma-ray and anti-proton constraints. Decays to a muon pair or a mixed flavor electron-muon pair may also be viable depending on the propagation models. Decays to all other standard model fermions are severely disfavored.

  18. Latest AMS Results: The Positron Fraction and the p-bar/p Ratio

    CERN Multimedia

    CERN. Geneva

    2015-01-01

    A precision measurement by AMS of the positron fraction in primary cosmic rays is presented. The results show that at 275±32 GeV the positron fraction no longer increases with energy. The current status of the anti-proton analysis is also presented.

  19. Cosmic Ray Signatures of Decaying Dark Matter

    International Nuclear Information System (INIS)

    Ibarra, Alejandro

    2011-01-01

    Astrophysical and cosmological observations do not require the dark matter particles to be absolutely stable. If they are indeed unstable, their decay into Standard Model particles might occur at a sufficiently large rate to allow the indirect detection of dark matter through an anomalous contribution to the high energy cosmic ray fluxes. We analyze the implications of the excess in the total electron plus positron flux and the positron fraction reported by the Fermi and PAMELA collaborations, respectively, for the scenario of decaying dark matter. We also discuss the constraints on this scenario from measurements of other cosmic ray species and the predictions for the diffuse gamma ray flux and the neutrino flux. In particular, we expect a sizable dipole-like anisotropy which may be observed in the near future by the Fermi-LAT.

  20. The History of Cosmic Ray Studies after Hess

    Energy Technology Data Exchange (ETDEWEB)

    Grupen, Claus, E-mail: grupen@physik.uni-siegen.de

    2013-06-15

    The discovery of cosmic rays by Victor Hess was confirmed with balloon flights at higher altitudes by Kolhörster. Soon the interest turned into questions about the nature of cosmic rays: gamma rays or particles? Subsequent investigations have established cosmic rays as the birthplace of elementary particle physics. The 1936 Nobel prize was shared between Victor Hess and Carl Anderson. Anderson discovered the positron in a cloud chamber. The positron was predicted by Dirac several years earlier. Many new results came now from studies with cloud chambers and nuclear emulsions. Anderson and Neddermeyer saw the muon, which for some time was considered to be a candidate for the Yukawa particle responsible for nuclear binding. Lattes, Powell, Occhialini and Muirhead clarified the situation by the discovery of the charged pions in cosmic rays. Rochester and Butler found V's, which turned out to be short-lived neutral kaons decaying into a pair of charged pions. Λ's, Σ's and Ξ's were found in cosmic rays using nuclear emulsions. After that period, accelerators and storage rings took over. The unexpected renaissance of cosmic rays started with the search for solar neutrinos and the observation of the supernova 1987A and other accelerators in the sky. With the observation of neutrino oscillations one began to look beyond the standard model of elementary particles. After 100 years of cosmic ray research we are again at the beginning of a new era, and cosmic rays may contribute to solve the many open questions, like dark matter and dark energy, by providing energies well beyond those of earth-bound accelerators.

  1. Use of neural network techniques to identify cosmic ray electrons and positrons during the 1993 balloon flight of the NMSU/Wizard-TS93 instrument

    Energy Technology Data Exchange (ETDEWEB)

    Bellotti, R.; Castellano, M. [Bari Univ. (Italy)]|[INFN, Bari (Italy); Candusso, M.; Casolino, M.; Morselli, A.; Picozza, P. [Rome Univ. `Tor Vergata` (Italy)]|[INFN, Rome (Italy); Aversa, F.; Boezio, M. [Trieste Univ. (Italy)]|[INFN, Trieste (Italy); Barbiellini, G. [Trieste Univ. (Italy)]|[INFN, Trieste (Italy); Basini, G. [INFN, Laboratori Nazionali di Frascati, Rome (Italy)

    1995-09-01

    The detectors used in the TS93 balloon flight produced a large volume of information for each cosmic ray trigger. Some of the data was visual in nature, other portions contained energy deposition and timing information. The data sets are amenable to conventional analysis techniques but there is no assurance that conventional techniques make full use of subtle correlations and relations amongst the detector responses. With the advent of neural network technologies, particularly adept at classification of complex phenomena, it would seem appropriate to explore the utility of neural network techniques to classify particles observed with the instruments. In this paper neural network based methodology for signal/background discrimination in a cosmic ray space experiment is discussed. Results are presented for electron and positron classification in the TS93 flight data set and will be compared to conventional analyses.

  2. High energy physics in cosmic rays

    Energy Technology Data Exchange (ETDEWEB)

    Jones, Lawrence W. [University of Michigan, Ann Arbor, Michigan (United States)

    2013-02-07

    In the first half-century of cosmic ray physics, the primary research focus was on elementary particles; the positron, pi-mesons, mu-mesons, and hyperons were discovered in cosmic rays. Much of this research was carried out at mountain elevations; Pic du Midi in the Pyrenees, Mt. Chacaltaya in Bolivia, and Mt. Evans/Echo Lake in Colorado, among other sites. In the 1960s, claims of the observation of free quarks, and satellite measurements of a significant rise in p-p cross sections, plus the delay in initiating accelerator construction programs for energies above 100 GeV, motivated the Michigan-Wisconsin group to undertake a serious cosmic ray program at Echo Lake. Subsequently, with the succession of higher energy accelerators and colliders at CERN and Fermilab, cosmic ray research has increasingly focused on cosmology and astrophysics, although some groups continue to study cosmic ray particle interactions in emulsion chambers.

  3. Positron astrophysics and areas of relation to low-energy positron physics

    International Nuclear Information System (INIS)

    Guessoum, N.

    2014-01-01

    I briefly review our general knowledge of positron astrophysics, focusing mostly on the theoretical and modelling aspects. The experimental/observational aspects of the topic have recently been reviewed elsewhere [E. Churazov et al., Mon. Nat. R. Astron. Soc. 411, 1727 (2011); N. Prantazos et al., Rev. Mod. Phys. 83, 1001 (2011)]. In particular, I highlight the interactions and cross sections of the reactions that the positrons undergo in various cosmic media. Indeed, these must be of high interest to both the positron astrophysics community and the low-energy positron physics community in trying to find common areas of potential collaboration for the future or areas of research that will help the astrophysics community make further progress on the problem. The processes undergone by positrons from the moments of their birth to their annihilation (in the interstellar medium or other locations) are thus examined. The physics of the positron interactions with gases and solids (dust grains) and the physical conditions and characteristics of the environments where the processes of energy loss, positronium formation, and annihilation take place, are briefly reviewed. An explanation is given about how all the relevant physical information is taken into account in order to calculate annihilation rates and spectra of the 511 keV emission in the ISM; special attention is paid to positron interactions with dust and with polycyclic aromatic hydrocarbons. In particular, an attempt is made to show to what extent the interactions between positrons and interstellar dust grains are similar to laboratory experiments in which beams of low-energy positrons impinge upon solids and surfaces. Sample results are shown for the effect of dust grains on positron annihilation spectra in some phases of the ISM which, together with high resolution spectra measured by satellites, can be used to infer useful knowledge about the environment where the annihilation is predominantly taking place

  4. Simulating TGF and gamma ray emission above and within stormclouds due to the interaction of TeV cosmic ray shower electrons/positrons/photons with plausible electric field geometries generated in stormclouds.

    Science.gov (United States)

    Connell, P. H.

    2017-12-01

    The University of Valencia has developed a software simulator LEPTRACK to simulate lepton and photon scattering in any kind of media with a variable density, and permeated by electric/magnetic fields of any geometry, and which can handle an exponential runaway avalanche. Here we show results of simulating the interaction of electrons/positrons/photons in an incoming TeV cosmic ray shower with the kind of electric fields expected in a stormcloud after a CG discharge which removes much of the positive charge build up at the centre of the cloud. The point is to show not just a Relativistic Runaway Electron Avalanche (RREA) above the upper negative shielding layer at 12 km but other gamma ray emission due to electron/positron interaction in the remaining positive charge around 9km and the lower negative charge at 6km altitude. We present here images, lightcurves, altitude profiles, spectra and videos showing the different ionization, excitation and photon density fields produced, their time evolution, and how they depend critically on where the cosmic ray shower beam intercepts the electric field geometry. We also show a new effect of incoming positrons, which make up a significant fraction of the shower, where they appear to "orbit" within the high altitude negative shielding layer, and which has been conjectured to produce significant microwave emission, as well as a short range 511 keV annihilation line. The interesting question is if this conjectured emission can be observed and correlated with TGF orbital observations to prove that a TGF originates in the macro-fields of stormclouds or the micro-fields of light leaders and streamers where this "positron orbiting" is not likely to occur.

  5. It's About Time: Interpreting AMS Antimatter Data in Terms of Cosmic Ray Propagation

    CERN Multimedia

    CERN. Geneva

    2015-01-01

    If cosmic ray positrons come from a secondary origin, then their production spectrum is correlated with the production spectrum of other secondary particles such as boron and antiprotons through scattering cross sections measured in the laboratory. This allows to define a first-principle upper bound on the positron flux at the Earth, independent of propagation model assumptions. Using currently available B/C and antiproton/proton data, we show that the positron flux reported by AMS is consistent with the bound and saturates it at high energies. This coincidence is a compelling indication for a secondary source. We explain how improved AMS measurements of the high energy boron, antiproton, and secondary radioactive nuclei fluxes can corroborate or falsify the secondary source hypothesis. Assuming that the positrons are secondary, we show that AMS data imply a propagation time in the Galaxy of order 1Myr or less for cosmic rays with magnetic rigidity > 300 GV. This corresponds to an average traversed interstel...

  6. Positron astrophysics and areas of relation to low-energy positron physics

    Science.gov (United States)

    Guessoum, Nidhal

    2014-05-01

    I briefly review our general knowledge of positron astrophysics, focusing mostly on the theoretical and modelling aspects. The experimental/observational aspects of the topic have recently been reviewed elsewhere [E. Churazov et al., Mon. Nat. R. Astron. Soc. 411, 1727 (2011); N. Prantazos et al., Rev. Mod. Phys. 83, 1001 (2011)]. In particular, I highlight the interactions and cross sections of the reactions that the positrons undergo in various cosmic media. Indeed, these must be of high interest to both the positron astrophysics community and the low-energy positron physics community in trying to find common areas of potential collaboration for the future or areas of research that will help the astrophysics community make further progress on the problem. The processes undergone by positrons from the moments of their birth to their annihilation (in the interstellar medium or other locations) are thus examined. The physics of the positron interactions with gases and solids (dust grains) and the physical conditions and characteristics of the environments where the processes of energy loss, positronium formation, and annihilation take place, are briefly reviewed. An explanation is given about how all the relevant physical information is taken into account in order to calculate annihilation rates and spectra of the 511 keV emission in the ISM; special attention is paid to positron interactions with dust and with polycyclic aromatic hydrocarbons. In particular, an attempt is made to show to what extent the interactions between positrons and interstellar dust grains are similar to laboratory experiments in which beams of low-energy positrons impinge upon solids and surfaces. Sample results are shown for the effect of dust grains on positron annihilation spectra in some phases of the ISM which, together with high resolution spectra measured by satellites, can be used to infer useful knowledge about the environment where the annihilation is predominantly taking place

  7. On the cosmic-ray spectra of three-body lepton-flavor-violating dark matter decays

    International Nuclear Information System (INIS)

    Carone, Christopher D.; Cukierman, Ari; Primulando, Reinard

    2011-01-01

    We consider possible leptonic three-body decays of spin-1/2, charge-asymmetric dark matter. Assuming a general Dirac structure for the four-fermion contact interactions of interest, we study the cosmic-ray electron and positron spectra and show that good fits to the current data can be obtained for both charged-lepton-flavor-conserving and flavor-violating decay channels. We find that different choices for the Dirac structure of the underlying decay operator can be significantly compensated by different choices for the dark matter mass and lifetime. The decay modes we consider provide differing predictions for the cosmic-ray positron fraction at energies higher than those currently probed at the PAMELA experiment; these predictions might be tested at cosmic-ray detectors like AMS-02.

  8. Cosmic rays and radiations from the cosmos

    International Nuclear Information System (INIS)

    Parizot, E.

    2005-12-01

    This document gathers a lot of recent information concerning cosmic radiations, it is divided into 4 parts. Part I: energy, mass and angular spectra of cosmic rays. Part II: general phenomenology of cosmic rays, this part deals with the standard model, the maximal energy of protons inside supernova remnants, nucleosynthesis of light elements, and super-bubbles. Part III: radiations from the cosmos, this part deals with high energy gamma rays, non-thermal radiation of super-bubbles, positron transport, and the Compton trail of gamma-ray bursts. Part IV: the Pierre Auger observatory (OPA), this part deals with the detection of gamma ray bursts at OPA, the measurement of anisotropy, and top-down models. (A.C.)

  9. Radio detection of cosmic rays with LOFAR

    NARCIS (Netherlands)

    Hörandel, J. R.; Buitink, S.; Corstanje, A.; Enriquez, J. E.; Falcke, H.; Karskens, T.; Krause, M.; Nelles, A.; Rachen, J. P.; Rossetto, L.; Schellart, P.; Scholten, O.; Ter Veen, S.; Thoudam, S.; Trinh, T. N G

    2015-01-01

    When high-energy cosmic rays (ionized atomic nuclei) impinge on the atmosphere of the Earth they interact with atomic nuclei and initiate cascades of secondary particles - the extensive air showers. Many of the secondary particles in the air showers are electrons and positrons. They cause radiation

  10. Direct detection of a break in the teraelectronvolt cosmic-ray spectrum of electrons and positrons

    Science.gov (United States)

    DAMPE Collaboration; Ambrosi, G.; An, Q.; Asfandiyarov, R.; Azzarello, P.; Bernardini, P.; Bertucci, B.; Cai, M. S.; Chang, J.; Chen, D. Y.; Chen, H. F.; Chen, J. L.; Chen, W.; Cui, M. Y.; Cui, T. S.; D'Amone, A.; de Benedittis, A.; De Mitri, I.; di Santo, M.; Dong, J. N.; Dong, T. K.; Dong, Y. F.; Dong, Z. X.; Donvito, G.; Droz, D.; Duan, K. K.; Duan, J. L.; Duranti, M.; D'Urso, D.; Fan, R. R.; Fan, Y. Z.; Fang, F.; Feng, C. Q.; Feng, L.; Fusco, P.; Gallo, V.; Gan, F. J.; Gao, M.; Gao, S. S.; Gargano, F.; Garrappa, S.; Gong, K.; Gong, Y. Z.; Guo, D. Y.; Guo, J. H.; Hu, Y. M.; Huang, G. S.; Huang, Y. Y.; Ionica, M.; Jiang, D.; Jiang, W.; Jin, X.; Kong, J.; Lei, S. J.; Li, S.; Li, X.; Li, W. L.; Li, Y.; Liang, Y. F.; Liang, Y. M.; Liao, N. H.; Liu, H.; Liu, J.; Liu, S. B.; Liu, W. Q.; Liu, Y.; Loparco, F.; Ma, M.; Ma, P. X.; Ma, S. Y.; Ma, T.; Ma, X. Q.; Ma, X. Y.; Marsella, G.; Mazziotta, M. N.; Mo, D.; Niu, X. Y.; Peng, X. Y.; Peng, W. X.; Qiao, R.; Rao, J. N.; Salinas, M. M.; Shang, G. Z.; H. Shen, W.; Shen, Z. Q.; Shen, Z. T.; Song, J. X.; Su, H.; Su, M.; Sun, Z. Y.; Surdo, A.; Teng, X. J.; Tian, X. B.; Tykhonov, A.; Vagelli, V.; Vitillo, S.; Wang, C.; Wang, H.; Wang, H. Y.; Wang, J. Z.; Wang, L. G.; Wang, Q.; Wang, S.; Wang, X. H.; Wang, X. L.; Wang, Y. F.; Wang, Y. P.; Wang, Y. Z.; Wen, S. C.; Wang, Z. M.; Wei, D. M.; Wei, J. J.; Wei, Y. F.; Wu, D.; Wu, J.; Wu, L. B.; Wu, S. S.; Wu, X.; Xi, K.; Xia, Z. Q.; Xin, Y. L.; Xu, H. T.; Xu, Z. L.; Xu, Z. Z.; Xue, G. F.; Yang, H. B.; Yang, P.; Yang, Y. Q.; Yang, Z. L.; Yao, H. J.; Yu, Y. H.; Yuan, Q.; Yue, C.; Zang, J. J.; Zhang, C.; Zhang, D. L.; Zhang, F.; Zhang, J. B.; Zhang, J. Y.; Zhang, J. Z.; Zhang, L.; Zhang, P. F.; Zhang, S. X.; Zhang, W. Z.; Zhang, Y.; Zhang, Y. J.; Zhang, Y. Q.; Zhang, Y. L.; Zhang, Y. P.; Zhang, Z.; Zhang, Z. Y.; Zhao, H.; Zhao, H. Y.; Zhao, X. F.; Zhou, C. Y.; Zhou, Y.; Zhu, X.; Zhu, Y.; Zimmer, S.

    2017-12-01

    High-energy cosmic-ray electrons and positrons (CREs), which lose energy quickly during their propagation, provide a probe of Galactic high-energy processes and may enable the observation of phenomena such as dark-matter particle annihilation or decay. The CRE spectrum has been measured directly up to approximately 2 teraelectronvolts in previous balloon- or space-borne experiments, and indirectly up to approximately 5 teraelectronvolts using ground-based Cherenkov γ-ray telescope arrays. Evidence for a spectral break in the teraelectronvolt energy range has been provided by indirect measurements, although the results were qualified by sizeable systematic uncertainties. Here we report a direct measurement of CREs in the energy range 25 gigaelectronvolts to 4.6 teraelectronvolts by the Dark Matter Particle Explorer (DAMPE) with unprecedentedly high energy resolution and low background. The largest part of the spectrum can be well fitted by a ‘smoothly broken power-law’ model rather than a single power-law model. The direct detection of a spectral break at about 0.9 teraelectronvolts confirms the evidence found by previous indirect measurements, clarifies the behaviour of the CRE spectrum at energies above 1 teraelectronvolt and sheds light on the physical origin of the sub-teraelectronvolt CREs.

  11. Contribution from individual nearby sources to the spectrum of high-energy cosmic-ray electrons

    International Nuclear Information System (INIS)

    Sedrati, R.; Attallah, R.

    2014-01-01

    In the last few years, very important data on high-energy cosmic-ray electrons and positrons from high-precision space-born and ground-based experiments have attracted a great deal of interest. These particles represent a unique probe for studying local comic-ray accelerators because they lose energy very rapidly. These energy losses reduce the lifetime so drastically that high-energy cosmic-ray electrons can attain the Earth only from rather local astrophysical sources. This work aims at calculating, by means of Monte Carlo simulation, the contribution from some known nearby astrophysical sources to the cosmic-ray electron/positron spectra at high energy (≥10GeV). The background to the electron energy spectrum from distant sources is determined with the help of the GALPROP code. The obtained numerical results are compared with a set of experimental data

  12. Contribution from individual nearby sources to the spectrum of high-energy cosmic-ray electrons

    Energy Technology Data Exchange (ETDEWEB)

    Sedrati, R., E-mail: rafik.sedrati@univ-annaba.org; Attallah, R.

    2014-04-01

    In the last few years, very important data on high-energy cosmic-ray electrons and positrons from high-precision space-born and ground-based experiments have attracted a great deal of interest. These particles represent a unique probe for studying local comic-ray accelerators because they lose energy very rapidly. These energy losses reduce the lifetime so drastically that high-energy cosmic-ray electrons can attain the Earth only from rather local astrophysical sources. This work aims at calculating, by means of Monte Carlo simulation, the contribution from some known nearby astrophysical sources to the cosmic-ray electron/positron spectra at high energy (≥10GeV). The background to the electron energy spectrum from distant sources is determined with the help of the GALPROP code. The obtained numerical results are compared with a set of experimental data.

  13. Cosmic ray signatures of a 2-3 Myr old local supernova

    Science.gov (United States)

    Kachelrieß, M.; Neronov, A.; Semikoz, D. V.

    2018-03-01

    The supernova explosion which deposited Fe 60 isotopes on Earth 2-3 million years ago should have also produced cosmic rays which contribute to the locally observed cosmic ray flux. We show that the contribution of this "local source" causes the "anomalies" observed in the positron and antiproton fluxes and explains why their spectral shapes agree with that of the proton flux. At the same time, this local source component accounts for the difference in the slopes of the spectra of cosmic ray nuclei as the result of the slightly varying relative importance of the "local" and the average component for distinct CR nuclei. Such a "local supernova" model for the spectra of nuclei can be tested via a combined measurement of the energy dependence of the boron-to-carbon (primary-to-secondary cosmic rays) ratio and of the antiproton spectrum: while the antiproton spectrum is predicted to extend approximately as a power law into the TeV range without any softening break, the B/C ratio is expected to show a "plateau" at a level fixed by the observed positron excess in the 30-300 GeV range. We discuss the observability of such a plateau with dedicated experiments for the measurement of the cosmic ray composition in the 10 TeV energy range (NUCLEON, ISS-CREAM).

  14. Precise measurement of cosmic ray fluxes with the AMS-02 experiment

    Energy Technology Data Exchange (ETDEWEB)

    Vecchi, Manuela, E-mail: manuela.vecchi@ifsc.usp.br [Instituto de Física de São Carlos, Universidade de São Paulo, CP 369, 13560-970, São Carlos, SP (Brazil)

    2015-12-17

    The AMS-02 detector is a large acceptance magnetic spectrometer operating onboard the International Space Station since May 2011. The main goals of the detector are the search for antimatter and dark matter in space, as well as the measurement of cosmic ray composition and flux. In this document we present precise measurements of cosmic ray positrons, electrons and protons, collected during the first 30 months of operations.

  15. What can we learn from a sharply falling positron fraction?

    Directory of Open Access Journals (Sweden)

    Delahaye Timur

    2015-01-01

    Full Text Available Recent results from the AMS-02 data have confirmed that the cosmic ray positron fraction increases with energy between 10 and 200 GeV. This quantity should not exceed 50%, and it is hence expected that it will either converge towards 50% or fall. We study the possibility that future data may show the positron fraction dropping down abruptly to the level expected with only secondary production, and forecast the implications of such a feature in term of possible injection mechanisms that include both Dark Matter and pulsars.

  16. ‘Excess’ of primary cosmic ray electrons

    Directory of Open Access Journals (Sweden)

    Xiang Li

    2015-10-01

    Full Text Available With the accurate cosmic ray (CR electron and positron spectra (denoted as Φe− and Φe+, respectively measured by AMS-02 Collaboration, the difference between the electron and positron fluxes (i.e., ΔΦ=Φe−−Φe+, dominated by the propagated primary electrons, can be reliably inferred. In the standard model, the spectrum of propagated primary CR electrons at energies ≥30GeV softens with the increase of energy. The absence of any evidence for such a continuous spectral softening in ΔΦ strongly suggests a significant ‘excess’ of primary CR electrons and at energies of 100–400GeV the identified excess component has a flux comparable to that of the observed positron excess. Middle-age but ‘nearby’ supernova remnants (e.g., Monogem and Geminga are favored sources for such an excess.

  17. The mass composition of cosmic rays measured with LOFAR

    NARCIS (Netherlands)

    Hörandel, Jörg R.; Bonardi, A.; Buitink, S.; Corstanje, A.; Falcke, H.; Mitra, P.; Mulrey, K.; Nelles, A.; Rachen, J. P.; Rossetto, L.; Schellart, P.; Scholten, O.; ter Veen, S.; Thoudam, S.; Trinh, T. N. G.; Winchen, T.

    2017-01-01

    High-energy cosmic rays, impinging on the atmosphere of the Earth initiate cascades of secondary particles, the extensive air showers. The electrons and positrons in the air shower emit electromagnetic radiation. This emission is detected with the LOFAR radio telescope in the frequency range from 30

  18. Cosmic Ray Antimatter

    CERN Multimedia

    CERN. Geneva

    2017-01-01

    Over the last decade, space-born experiments have delivered new measurements of high energy cosmic-ray (CR) antiprotons and positrons, opening new frontiers in energy reach and precision. While being a promising discovery tool for new physics or exotic astrophysical phenomena, an irreducible background of antimatter comes from CR collisions with interstellar matter in the Galaxy. Understanding this irreducible source or constraining it from first principles is an interesting challenge: a game of hide-and-seek where the objective is to identify the laws of basic particle physics among the forest of astrophysical uncertainties. I describe an attempt to obtain such understanding, combining information from a zoo of CR species including massive nuclei and relativistic radioisotopes. I show that: (i) CR antiprotons most likely come from CR-gas collisions; (ii) positron data is consistent with, and suggestive of the same astrophysical production mechanism responsible for antiprotons and dominated by proton-proton c...

  19. Cosmic Ray Results from the CosmoALEPH Experiment

    CERN Document Server

    Grupen, C; Jost, B; Maciuc, F; Luitz, S; Mailov, A; Müller, A S; Putzer, A; Rensch, B; Sander, H G; Schmeling, S; Schmelling, M; Tcaciuc, R; Wachsmuth, H; Ziegler, T; Zuber, K

    2008-01-01

    CosmoALEPH is an experiment operated in conjunction with the ALEPH detector. The ALEPH experiment took data from 1989 until the year 2000 at the Large Electron Positron Collider (LEP) at CERN. It provides, among others, high resolution tracking and calorimetry. CosmoALEPH used this e+e− detector for cosmic ray studies. In addition, six scintillator telescopes were installed in the ALEPH pit and the LEP tunnel. The whole experiment operated underground at a vertical depth of 320 meter water equivalent. Data from ALEPH and the scintillator telescopes provide informaton on the lateral distribution of energetic cosmic ray muons in extensive air showers. The decoherence curve of these remnant air shower muons is sensitive to the chemical composition of primary cosmic rays and to the interaction characteristics of energetic hadrons in the atmosphere. An attempt is made to extract the various interdependencies in describing the propagation of primary and secondary cosmic rays through the atmosphere and the rock ov...

  20. On the Energy Spectra of GeV/TeV Cosmic Ray Leptons

    Energy Technology Data Exchange (ETDEWEB)

    Stawarz, Lukasz; /KIPAC, Menlo Park /Jagiellonian U., Astron. Observ.; Petrosian, Vahe; /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept.; Blandford, Roger D.; /KIPAC, Menlo Park

    2011-08-19

    Recent observations of cosmic ray electrons from several instruments have revealed various degrees of deviation in the measured electron energy distribution from a simple power-law, in a form of an excess around 0.1 to 1 TeV energies. An even more prominent deviation and excess has been observed in the fraction of cosmic ray positrons around 10 and 100 GeV energies. These observations have received considerable attention and many theoretical models have been proposed to explain them. The models rely on either dark matter annihilation/decay or specific nearby astrophysical sources, and involve several additional assumptions regarding the dark matter distribution or particle acceleration. In this paper we show that the observed excesses in the electron spectrum may be easily reproduced without invoking any unusual sources other than the general diffuse Galactic components of cosmic rays. The model presented here assumes a power-law injection of electrons (and protons) by supernova remnants, and evaluates their expected energy spectrum based on a simple kinetic equation describing the propagation of charged particles in the interstellar medium. The primary physical effect involved is the Klein-Nishina suppression of the electron cooling rate around TeV energies. With a very reasonable choice of the model parameters characterizing the local interstellar medium, we can reproduce the most recent observations by Fermi and HESS experiments. Interestingly, in our model the injection spectral index of cosmic ray electrons becomes comparable to, or even equal to that of cosmic ray protons. The Klein-Nishina effect may also affect the propagation of the secondary e{sup {+-}} pairs, and therefore modify the cosmic ray positron-to-electron ratio. We have explored this possibility by considering two mechanisms for production of e{sup {+-}} pairs within the Galaxy. The first is due to the decay of {pi}{sup {+-}}'s produced by interaction of cosmic ray nuclei with ambient

  1. The puzzle of the ultra-high energy cosmic rays

    CERN Document Server

    Tkachev, I I

    2003-01-01

    In early years the cosmic ray studies were ahead of accelerator research, starting from the discovery of positrons, through muons, to that of pions and strange particles. Today we are facing the situation that the puzzling saga of cosmic rays of the highest energies may again unfold in the discovery of new physics, now beyond the Standard Model; or it may bring to life an "extreme" astrophysics. After a short review of the Greisen-Zatsepin-Kuzmin puzzle, I discuss different models which were suggested for its resolution. Are there any hints pointing to the correct model? I argue that the small-scale clustering of arrival directions of cosmic rays gives a clue, and BL Lacs are the probable sources of the observed events. (58 refs).

  2. PRECISE COSMIC RAYS MEASUREMENTS WITH PAMELA

    Directory of Open Access Journals (Sweden)

    A. Bruno

    2013-12-01

    Full Text Available The PAMELA experiment was launched on board the Resurs-DK1 satellite on June 15th 2006. The apparatus was designed to conduct precision studies of charged cosmic radiation over a wide energy range, from tens of MeV up to several hundred GeV, with unprecedented statistics. In five years of continuous data taking in space, PAMELA accurately measured the energy spectra of cosmic ray antiprotons and positrons, as well as protons, electrons and light nuclei, sometimes providing data in unexplored energetic regions. These important results have shed new light in several astrophysical fields like: an indirect search for Dark Matter, a search for cosmological antimatter (anti-Helium, and the validation of acceleration, transport and secondary production models of cosmic rays in the Galaxy. Some of the most important items of Solar and Magnetospheric physics were also investigated. Here we present the most recent results obtained by the PAMELA experiment.

  3. Cosmic radiation and air crew exposure

    International Nuclear Information System (INIS)

    Vukovic, B.; Lisjak, I.; Vekic, B.; Planinic, J.

    2005-01-01

    When the primary particles from space, mainly protons, enter the atmosphere, they interact with the air nuclei and induce cosmic-ray shower. When an aircraft is in the air, the radiation field within includes many types of radiation of large energy range; the field comprises mainly photons, electrons, positrons and neutrons. Cosmic radiation dose for crews of air crafts A 320 and ATR 42 was measured using TLD-100 (LiF: Mg, Ti) detectors and the Mini 6100 semiconductor dosimeter; radon concentration in the atmosphere was measured using the Alpha Guard radon detector. The total annual dose estimated for the A 320 aircraft crew, at altitudes up to 12000 meters, was 5.3 mSv (including natural radon radiation dose of 1.1 mSv).(author)

  4. Performance tests of a full scale prototype of the Belle II TOP counter with cosmic muons and 2.1 GeV/c positron beam

    Energy Technology Data Exchange (ETDEWEB)

    Hayakawa, Tomokatsu

    2014-12-01

    A time-of-propagation detector named TOP is a hadronic particle identification system for the Belle II experiment. We have produced a full scale prototype of the Belle II TOP counter and tested with cosmic muons at KEK and the 2.1 GeV/c positrons at SPring-8 LEPS beamline. The procedures for the quartz acceptance test and assembly worked well and the first quartz radiator was successfully fabricated. The obtained test data shows good agreement with Monte Carlo expectation. - Highlights: • We have successfully produced a full scale prototype of the Belle II TOP counter. • The prototype counter has been tested at KEK and SPring-8 LEPS beamline. • The obtained test data shows good agreement with Monte Carlo expectation.

  5. Bubbles, superbubbles and their impact on cosmic ray transport

    Energy Technology Data Exchange (ETDEWEB)

    Weinreuter, Matthias; Gebauer, Iris; Boer, Wim de; Neumann, Alexander [KIT, Karlsruhe (Germany)

    2016-07-01

    The Fermi-LAT data on diffuse gamma rays show variations in the gamma ray intensity, which are linked to either variations in the gas density or variations in the cosmic ray density. Such small scale variations are not modeled in current state-of-the-art models for galactic cosmic ray propagation. Inhomogeneities in the interstellar material can be formed by cavities like the so-called Local Bubble, an underdense region surrounding our Sun, which was created by several supernova explosions in the past. We show that the Local Bubble can have a strong impact on the cosmic ray energy spectra and density. In particular, it enhances cosmic ray scattering in the surrounding molecular cloud complexes and can significantly distort the cosmic ray arrival directions. We briefly discuss the consequences for pulsar searches in energetic positrons and electrons. By making simple assumptions on the level of inhomogeneity in the interstellar medium we investigate if the observed variations in the diffuse gamma ray emission can indeed be explained by cavities similar to the Local Bubble.

  6. PAMELA mission: heralding a new era in cosmic ray physics

    Directory of Open Access Journals (Sweden)

    Ricciarini S. B.

    2014-04-01

    Full Text Available After seven years of data taking in space, the experiment PAMELA is showing very interesting features in cosmic rays, namely in the fluxes of protons, helium, electrons, that might change our basic vision of the mechanisms of production, acceleration and propagation of cosmic rays in the galaxy. In addition, PAMELA measurements of cosmic antiproton and positron fluxes are setting strong constraints to the nature of Dark Matter. The continuous particle detection is allowing a constant monitoring of the solar activity and detailed study of the solar modulation for a long period, giving important improvements to the comprehension of the heliosphere mechanisms. PAMELA is also measuring the radiation environment around the Earth, and has recently discovered an antiproton radiation belt.

  7. Dark matter "transporting" mechanism explaining positron excesses

    Science.gov (United States)

    Kim, Doojin; Park, Jong-Chul; Shin, Seodong

    2018-04-01

    We propose a novel mechanism to explain the positron excesses, which are observed by satellite-based telescopes including PAMELA and AMS-02, in dark matter (DM) scenarios. The novelty behind the proposal is that it makes direct use of DM around the Galactic Center where DM populates most densely, allowing us to avoid tensions from cosmological and astrophysical measurements. The key ingredients of this mechanism include DM annihilation into unstable states with a very long laboratory-frame life time and their "retarded" decay near the Earth to electron-positron pair(s) possibly with other (in)visible particles. We argue that this sort of explanation is not in conflict with relevant constraints from big bang nucleosynthesis and cosmic microwave background. Regarding the resultant positron spectrum, we provide a generalized source term in the associated diffusion equation, which can be readily applicable to any type of two-"stage" DM scenarios wherein production of Standard Model particles occurs at completely different places from those of DM annihilation. We then conduct a data analysis with the recent AMS-02 data to validate our proposal.

  8. Positron Interactions with Atoms and Ions

    Science.gov (United States)

    Bhatia, Anand K.

    2012-01-01

    Dirac, in 1928, combining the ideas of quantum mechanics and the ideas of relativity invented the well-known relativistic wave equation. In his formulation, he predicted an antiparticle of the electron of spin n-bar/2. He thought that this particle must be a proton. Dirac published his interpretation in a paper 'A theory of electrons and protons.' It was shown later by the mathematician Hermann Weyl that the Dirac theory was completely symmetric between negative and positive particles and the positive particle must have the same mass as that of the electron. In his J. Robert Oppenheimer Memorial Prize Acceptance Speech, Dirac notes that 'Blackett was really the first person to obtain hard evidence for the existence of a positron but he was afraid to publish it. He wanted confirmation, he was really over cautious.' Positron, produced by the collision of cosmic rays in a cloud chamber, was detected experimentally by Anderson in 1932. His paper was published in Physical Review in 1933. The concept of the positron and its detection were the important discoveries of the 20th century. I have tried to discuss various processes involving interactions of positrons with atoms and ions. This includes scattering, bound states and resonances. It has not been possible to include the enormous work which has been carried out during the last 40 or 50 years in theory and measurements.

  9. Positron identification by TRDs in TS93 and PAMELA experiments

    International Nuclear Information System (INIS)

    Bellotti, R.; Cafagna, F.; Castellano, M.; Circella, M.; De Marzo, C.; De Cataldo, G.; Giglietto, N.; Marangelli, B.; Raino, A.; Spinelli, P.

    1997-01-01

    We are involved in a program to study the antimatter components of the cosmic rays in outer space. We present the performances of a transition radiation detector we have built for positron identification during a balloon flight in 1993. The flight (TS93) was dedicated to the measurement of the positron spectrum in the energy range 4-50 GeV. We present also the design and expected performances of a similar detector we intend to build for a future experiment (PAMELA), to be run on a satellite by the end of 1999, in order to complete this program with higher statistics and at higher energies, namely about 200 GeV. (orig.)

  10. Possible Contribution to Electron and Positron Fluxes from Pulsars and their Nebulae

    CERN Document Server

    Della Torre, S.; Rancoita, P.G.; Rozza, D.; Treves, A.

    2014-01-01

    The AMS-02 experiment confirms the excess of positrons in cosmic rays (CRs) for energy above 10 GeV with respect to the secondary production of positrons in the interstellar medium. This is interpreted as evidence of the existence of a primary source of these particles. Possible candidates are dark matter or astrophysical sources. In this work we discuss the possible contribution due to pulsars and their nebulae. Our key assumption is that the primary spectrum of electrons and positrons at the source is the same of the well known photon spectrum observed from gamma-rays telescopes. Using a diffusion model in the Galaxy we propagate the source spectra up to the Solar System. We compare our results with the recent experiments and with the LIS model

  11. Decaying Dark Atom Constituents and Cosmic Positron Excess

    DEFF Research Database (Denmark)

    Belotsky, K.; Khlopov, M.; Kouvaris, C.

    2014-01-01

    We present a scenario where dark matter is in the form of dark atoms that can accommodate the experimentally observed excess of positrons in PAMELA and AMS-02 while being compatible with the constraints imposed on the gamma-ray ux from Fermi/LAT. This scenario assumes that the dominant component...... of dark matter is in the form of a bound state between a helium nucleus and a -2 particle and a small component is in the form of a WIMP-like dark atom compatible with direct searches in underground detectors. One of the constituents of this WIMP-like state is a +2 metastable particle with a mass of 1 Te...... baryons in the universe to be close to -3....

  12. Extended gamma-ray sources around pulsars constrain the origin of the positron flux at Earth

    OpenAIRE

    Abeysekara, A. U.; Albert, A.; Alfaro, R.; Alvarez, C.; Álvarez, J. D.; Arceo, R.; Arteaga-Velázquez, J. C.; Rojas, D. Avila; Solares, H. A. Ayala; Barber, A. S.; Bautista-Elivar, N.; Becerril, A.; Belmont-Moreno, E.; BenZvi, S. Y.; Berley, D.

    2017-01-01

    The unexpectedly high flux of cosmic ray positrons detected at Earth may originate from nearby astrophysical sources, dark matter, or unknown processes of cosmic-ray secondary production. We report the detection, using the HighAltitude Water Cherenkov Observatory (HAWC), of extended tera-electron volt gamma-ray emission coincident with the locations of two nearby middle-aged pulsars (Geminga and PSR B0656+14). The HAWC observations demonstrate that these pulsars are indeed local sources of ac...

  13. AMS-02 data confront acceleration of cosmic ray secondaries in nearby sources

    DEFF Research Database (Denmark)

    Mertsch, Philipp; Sarkar, Subir

    2014-01-01

    We revisit the model proposed earlier to account for the observed increase in the positron fraction in cosmic rays with increasing energy, in the light of new data from the Alpha Magnetic Spectrometer (AMS-02) experiment. The model accounts for the production and acceleration of secondary electrons...

  14. The positron excess as a smoking gun for dynamical dark matter?

    Energy Technology Data Exchange (ETDEWEB)

    Dienes, Keith R. [Department of Physics, University of Arizona, Tucson, AZ 85721 USA and Department of Physics, University of Maryland, College Park, MD 20742 (United States); Kumar, Jason [Department of Physics, University of Hawaii, Honolulu, HI 96822 (United States); Thomas, Brooks [Department of Physics, Carleton University, Ottawa, Ontario, K1S 5B6 (Canada)

    2014-06-24

    One of the most puzzling aspects of recent data from the AMS-02 experiment is an apparent rise in the cosmic-ray positron fraction as a function of energy. This feature is observed out to energies of approximately 350 GeV. One explanation of these results interprets the extra positrons as arising from the decays of dark-matter particles. This in turn typically requires that such particles have rather heavy TeV-scale masses and not undergo simple two-body decays to leptons. In this talk, by contrast, we show that Dynamical Dark Matter (DDM) can not only match existing AMS-02 data on the positron excess, but also accomplish this feat with significantly lighter dark-matter constituents undergoing simple two-body decays to leptons. We also demonstrate that the Dynamical Dark Matter framework makes a fairly robust prediction that the positron fraction should level off and then remain roughly constant out to approximately 1 TeV, without experiencing any sharp downturns. Thus, if we interpret the positron excess in terms of decaying dark matter, the existence of a plateau in the positron fraction at energies less than 1 TeV may be taken as a “smoking gun” of Dynamical Dark Matter.

  15. The positron excess as a smoking gun for dynamical dark matter?

    International Nuclear Information System (INIS)

    Dienes, Keith R.; Kumar, Jason; Thomas, Brooks

    2014-01-01

    One of the most puzzling aspects of recent data from the AMS-02 experiment is an apparent rise in the cosmic-ray positron fraction as a function of energy. This feature is observed out to energies of approximately 350 GeV. One explanation of these results interprets the extra positrons as arising from the decays of dark-matter particles. This in turn typically requires that such particles have rather heavy TeV-scale masses and not undergo simple two-body decays to leptons. In this talk, by contrast, we show that Dynamical Dark Matter (DDM) can not only match existing AMS-02 data on the positron excess, but also accomplish this feat with significantly lighter dark-matter constituents undergoing simple two-body decays to leptons. We also demonstrate that the Dynamical Dark Matter framework makes a fairly robust prediction that the positron fraction should level off and then remain roughly constant out to approximately 1 TeV, without experiencing any sharp downturns. Thus, if we interpret the positron excess in terms of decaying dark matter, the existence of a plateau in the positron fraction at energies less than 1 TeV may be taken as a “smoking gun” of Dynamical Dark Matter

  16. Determining Thunderstorm Electric Fields using Radio Emission from Cosmic-Ray Air Showers

    NARCIS (Netherlands)

    Hare, B.; Scholten, O.; Trinh, G. T. N.; Ebert, U.; Rutjes, C.

    2017-01-01

    We report on a novel non-intrusive way to investigate electric fields in thunderclouds.Energetic cosmic rays penetrating the atmosphere create a particle avalanche called an extensive air shower. The front of the shower is a plasma cloud that contains 10^6 or more free electrons and positrons moving

  17. Cosmic rays and radiations from the cosmos; Rayons cosmiques et rayonnement du cosmos

    Energy Technology Data Exchange (ETDEWEB)

    Parizot, E

    2005-12-01

    This document gathers a lot of recent information concerning cosmic radiations, it is divided into 4 parts. Part I: energy, mass and angular spectra of cosmic rays. Part II: general phenomenology of cosmic rays, this part deals with the standard model, the maximal energy of protons inside supernova remnants, nucleosynthesis of light elements, and super-bubbles. Part III: radiations from the cosmos, this part deals with high energy gamma rays, non-thermal radiation of super-bubbles, positron transport, and the Compton trail of gamma-ray bursts. Part IV: the Pierre Auger observatory (OPA), this part deals with the detection of gamma ray bursts at OPA, the measurement of anisotropy, and top-down models. (A.C.)

  18. Pair production from nuclear collisions and cosmic ray transport

    International Nuclear Information System (INIS)

    Norbury, John W

    2006-01-01

    Modern cosmic ray transport codes, that are capable of use for a variety of applications, need to include all significant atomic, nuclear and particle reactions at a variety of energies. Lepton pair production from nucleus-nucleus collisions has not been included in transport codes to date. Using the methods of Baur, Bertulani and Baron, the present report provides estimates of electron-positron pair production cross sections for nuclei and energies relevant to cosmic ray transport. It is shown that the cross sections are large compared to other typical processes such as single neutron removal due to strong or electromagnetic interactions. Therefore, lepton pair production may need to be included in some transport code applications involving MeV electrons. (brief report)

  19. Antiproton and positron signal enhancement in dark matter mini-spikes scenarios

    International Nuclear Information System (INIS)

    Brun, Pierre; Bertone, Gianfranco; Lavalle, Julien; Salati, Pierre; Taillet, Richard

    2007-04-01

    The annihilation of dark matter (DM) in the Galaxy could produce specific imprints on the spectra of antimatter species in Galactic cosmic rays, which could be detected by upcoming experiments such as PAMELA and AMS02. Recent studies show that the presence of substructures can enhance the annihilation signal by a 'boost factor' that not only depends on energy, but that is intrinsically a statistical property of the distribution of DM substructures inside the Milky Way. We investigate a scenario in which substructures consist of ∼100 'mini-spikes' around intermediate-mass black holes. Focusing on primary positrons and antiprotons, we find large boost factors, up to a few thousand, that exhibit a large variance at high energy in the case of positrons and at low energy in the case of antiprotons. As a consequence, an estimate of the DM particle mass based on the observed cut-off in the positron spectrum could lead to a substantial underestimate of its actual value. (authors)

  20. A new way of air shower detection: measuring the properties of cosmic rays with LOFAR

    NARCIS (Netherlands)

    Nelles, A.; Buitink, S.; Corstanje, A.; Enriquez, J. E.; Falcke, H.; Hörandel, J. R.; Rachen, J. P.; Schellart, P.; Scholten, O.; ter Veen, S.; Thoudam, S.; Trinh, T.N.G.

    2015-01-01

    High-energy cosmic rays impinging onto the atmosphere of the Earth initiate cascades of secondary particles: extensive air showers. Many of the particles in a shower are electrons and positrons. During the development of the air shower and by interacting with the geomagnetic field, the

  1. Cosmic Rays in Thunderstorms

    Science.gov (United States)

    Buitink, Stijn; Scholten, Olaf; van den Berg, Ad; Ebert, Ute

    2013-04-01

    Cosmic Rays in Thunderstorms Cosmic rays are protons and heavier nuclei that constantly bombard the Earth's atmosphere with energies spanning a vast range from 109 to 1021 eV. At typical altitudes up to 10-20 km they initiate large particle cascades, called extensive air showers, that contain millions to billions of secondary particles depending on their initial energy. These particles include electrons, positrons, hadrons and muons, and are concentrated in a compact particle front that propagates at relativistic speed. In addition, the shower leaves behind a trail of lower energy electrons from ionization of air molecules. Under thunderstorm conditions these electrons contribute to the electrical and ionization processes in the cloud. When the local electric field is strong enough the secondary electrons can create relativistic electron run-away avalanches [1] or even non-relativistic avalanches. Cosmic rays could even trigger lightning inception. Conversely, strong electric fields also influence the development of the air shower [2]. Extensive air showers emit a short (tens of nanoseconds) radio pulse due to deflection of the shower particles in the Earth's magnetic field [3]. Antenna arrays, such as AERA, LOFAR and LOPES detect these pulses in a frequency window of roughly 10-100 MHz. These systems are also sensitive to the radiation from discharges associated to thunderstorms, and provide a means to study the interaction of cosmic ray air showers and the electrical processes in thunderstorms [4]. In this presentation we discuss the involved radiation mechanisms and present analyses of thunderstorm data from air shower arrays [1] A. Gurevich et al., Phys. Lett. A 165, 463 (1992) [2] S. Buitink et al., Astropart. Phys. 33, 1 (2010) [3] H. Falcke et al., Nature 435, 313 (2005) [4] S. Buitink et al., Astron. & Astrophys. 467, 385 (2007)

  2. TEACHING PHYSICS: Demonstrating cosmic ray induced electromagnetic cascades in the A-level laboratory

    Science.gov (United States)

    Dunne, Peter

    1999-01-01

    This article indicates how the study of sea-level cosmic ray phenomena can have a role in A-level physics. It describes a simple but far reaching particle physics experiment that can be carried out in the A-level physics laboratory. A simple model of electron-positron-photon cascades, suitable for use at A-level, is described.

  3. The PAMELA Mission: Heralding a new era in precision cosmic ray physics

    International Nuclear Information System (INIS)

    Adriani, O.; Barbarino, G.C.; Bazilevskaya, G.A.; Bellotti, R.; Boezio, M.; Bogomolov, E.A.; Bongi, M.; Bonvicini, V.; Bottai, S.; Bruno, A.; Cafagna, F.; Campana, D.; Carbone, R.; Carlson, P.; Casolino, M.; Castellini, G.

    2014-01-01

    On the 15th of June 2006, the PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) satellite-borne experiment was launched onboard the Russian Resurs-DK1 satellite by a Soyuz rocket from the Baikonur space centre. The satellite was placed in a quasi-polar 70°inclination orbit at an altitude varying between 350 km and 600 km. New results on the antiparticle component of the cosmic radiation were obtained. The positron energy spectrum and positron fraction were measured from 400 MeV up to 200 GeV revealing a positron excess over the predictions of commonly used propagation models. This can be interpreted either as evidence that the propagation models should be revised or in terms of dark matter annihilation or a pulsar contribution. The antiproton spectrum was measured over the energy range from 60 MeV to 350 GeV. The antiproton spectrum is consistent with secondary production and significantly constrains dark matter models. The energy spectra of protons and helium nuclei were measured up to 1.2 TV. The spectral shapes of these two species are different and cannot be described well by a single power law. For the first time the electron spectrum was measured up to 600 GeV complementing the information obtained from the positron data. Nuclear and isotopic composition was obtained with unprecedented precision. The variation of the low energy proton, electron and positron energy spectra was measured from July 2006 until December 2009 accurately sampling the unusual conditions of the most recent solar minimum activity period (2006–2009). Low energy particle spectra were accurately measured also for various solar events that occurred during the PAMELA mission. The Earth’s magnetosphere was studied measuring the particle radiation in different regions of the magnetosphere. Energy spectra and composition of sub-cutoff and trapped particles were obtained. For the first time a belt of trapped antiprotons was detected in the South Atlantic

  4. The PAMELA Mission: Heralding a new era in precision cosmic ray physics

    Energy Technology Data Exchange (ETDEWEB)

    Adriani, O. [University of Florence, Department of Physics, I-50019 Sesto Fiorentino, Florence (Italy); INFN, Sezione di Florence, I-50019 Sesto Fiorentino, Florence (Italy); Barbarino, G.C. [University of Naples “Federico II”, Department of Physics, I-80126 Naples (Italy); INFN, Sezione di Naples, I-80126 Naples (Italy); Bazilevskaya, G.A. [Lebedev Physical Institute, RU-119991 Moscow (Russian Federation); Bellotti, R. [University of Bari, Department of Physics, I-70126 Bari (Italy); INFN, Sezione di Bari, I-70126 Bari (Italy); Boezio, M. [INFN, Sezione di Trieste, I-34149 Trieste (Italy); Bogomolov, E.A. [Ioffe Physical Technical Institute, RU-194021 St. Petersburg (Russian Federation); Bongi, M. [University of Florence, Department of Physics, I-50019 Sesto Fiorentino, Florence (Italy); INFN, Sezione di Florence, I-50019 Sesto Fiorentino, Florence (Italy); Bonvicini, V. [INFN, Sezione di Trieste, I-34149 Trieste (Italy); Bottai, S. [INFN, Sezione di Florence, I-50019 Sesto Fiorentino, Florence (Italy); Bruno, A. [University of Bari, Department of Physics, I-70126 Bari (Italy); INFN, Sezione di Bari, I-70126 Bari (Italy); Cafagna, F. [INFN, Sezione di Bari, I-70126 Bari (Italy); Campana, D. [INFN, Sezione di Naples, I-80126 Naples (Italy); Carbone, R. [INFN, Sezione di Naples, I-80126 Naples (Italy); INFN, Sezione di Trieste, I-34149 Trieste (Italy); Carlson, P. [KTH Royal Institute of Technology, Department of Physics, AlbaNova University Centre, SE-10691 Stockholm (Sweden); The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova University Centre, SE-10691 Stockholm (Sweden); Casolino, M. [INFN, Sezione di Rome “Tor Vergata”, I-00133 Rome (Italy); Castellini, G. [IFAC, I-50019 Sesto Fiorentino, Florence (Italy); and others

    2014-11-30

    On the 15th of June 2006, the PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) satellite-borne experiment was launched onboard the Russian Resurs-DK1 satellite by a Soyuz rocket from the Baikonur space centre. The satellite was placed in a quasi-polar 70°inclination orbit at an altitude varying between 350 km and 600 km. New results on the antiparticle component of the cosmic radiation were obtained. The positron energy spectrum and positron fraction were measured from 400 MeV up to 200 GeV revealing a positron excess over the predictions of commonly used propagation models. This can be interpreted either as evidence that the propagation models should be revised or in terms of dark matter annihilation or a pulsar contribution. The antiproton spectrum was measured over the energy range from 60 MeV to 350 GeV. The antiproton spectrum is consistent with secondary production and significantly constrains dark matter models. The energy spectra of protons and helium nuclei were measured up to 1.2 TV. The spectral shapes of these two species are different and cannot be described well by a single power law. For the first time the electron spectrum was measured up to 600 GeV complementing the information obtained from the positron data. Nuclear and isotopic composition was obtained with unprecedented precision. The variation of the low energy proton, electron and positron energy spectra was measured from July 2006 until December 2009 accurately sampling the unusual conditions of the most recent solar minimum activity period (2006–2009). Low energy particle spectra were accurately measured also for various solar events that occurred during the PAMELA mission. The Earth’s magnetosphere was studied measuring the particle radiation in different regions of the magnetosphere. Energy spectra and composition of sub-cutoff and trapped particles were obtained. For the first time a belt of trapped antiprotons was detected in the South Atlantic

  5. Cosmic AntiParticle Ring Imaging Cerenkov Experiment

    CERN Multimedia

    2002-01-01

    %RE2A \\\\ \\\\ %title \\\\ \\\\The CAPRICE experiment studies antimatter and light nuclei in the cosmic rays as well as muons in the atmosphere. The experiment is performed with the spectrometer shown in the figure which is lifted by a balloon to an altitude of 35-40 km. At this altitude less than half a percent of the atmosphere is above the 2 ton spectrometer which makes it possible to study the cosmic ray flux without too much background from atmospherically produced particles. The spectrometer includes time-of-flight scintillators, a gaseous RICH counter, a drift chamber tracker and a silicon electromagnetic calorimeter. The important feature of the spectrometer is to discriminate between different particles.\\\\ \\\\ The experiment aims at measuring the flux of the antiparticles (antiprotons and positrons) above about 5 GeV and relate the fluxes to models including exotic production of antiparticles like dark matter supersymmetric particles. The flux of muons is measured during descent of the balloon through the at...

  6. Positron Annihilation Study of Ion-irradiated Si

    International Nuclear Information System (INIS)

    Shin, Jung Ki; Kwon, Jun Hyun; Lee, Jong Yong

    2009-01-01

    Structural parts like a spaceship, satellite and solar cell are composed of metal alloy or semiconductor materials. Especially, Si is used as a primary candidate alloy. But, manned and robotic missions to the Earth's moon and Mars are exposed to a continuous flux of Galactic Cosmic Rays (GCR) and occasional, but intense, fluxes of Solar Energetic Particles. These natural radiations impose hazards to manned exploration. Irradiation of cosmic particle induces various changes in the mechanical and physical properties of device steels. It is, therefore, important to investigate radiation damage to the component materials in semiconductor. The evolution of radiation-induced defects leads to degradation of the mechanical properties. One of them includes irradiation embrittlement, which can cause a loss of ductility and further increase the probability of a brittle fracture. It can be more dangerous in the space. Positron annihilation lifetime spectroscopy(PALS) have been applied to investigate the production of vacancy-type defects for Ion-irradiated Si wafer penetrated by H, He, O and Fe ions. Then, we carried out a comparison with an un-irradiated Si wafer

  7. Study of Primary Cosmic Ray Electrons In Energy Range 10^11 - 10^13 Ev By Pamela Instrument.

    Science.gov (United States)

    Voronov, S.; Pamela Collaboration

    The main goal of the magnetic spectrometer PAMELA is the study of antiparticle fluxes with energy up to 300 GeV in cosmic rays on board satellite. A modification of instrument was done by introducing of neutron detector. This device was placed under imaging calorimeter and bottom scintillator counter. It consists of two layers of 36 3He gas counters enveloped by a polyethylene moderator. The neutron detector gives additional possibility to identify the antiprotons going in aperture of spectrome- ter and generating the nuclear cascade in tungsten plates of calorimeter. This shower is followed by big number of neutrons in contrast to electromagnetic one caused by elec- tron or positron. From other side the combination of the imaging calorimeter, bottom scintillator and neutron detector constitute the independent instrument with large field of view which gives the possibility to measure the electron-positron cosmic ray com- ponent in energy range 1011-1013 eV with a rejection factor of order 10-4 regarding to nuclear one.

  8. Cosmic Ray Electron and Positron Excesses from a Fourth Generation Heavy Majorana Neutrino

    DEFF Research Database (Denmark)

    Masina, Isabella; Sannino, Francesco

    2011-01-01

    and positrons originated in the heavy Majorana neutrino decay modes, also including polarization effects. We then compare the prediction of this model with the experimental data, exploiting both the standard direct method and our recently proposed Sum Rules method. We find that the decay modes involving the tau...

  9. Time dependence of electron and positron fluxes measured with the AMS-02 spectrometer

    CERN Document Server

    AUTHOR|(CDS)2081963; Duranti, Matteo

    The electrons (e-) and positrons (e+) are a rare component of Cosmic Rays (CRs) since they constitute respectively only a 1% and 0.1% of cosmic radiation. However, the correct detection of e+- covers a great importance in the astrophysics field since, unlike the hadronic component, they are subjected to strong energy losses through the interaction with Interstellar Medium. As consequence e with energies above GeV that reach the Earth are galactic, with the source inside Kpc and through the study of their primary spectra it is possible to probe the local interstellar medium (LIS) and to indirectly detect new possible sources like pulsar or dark matter. However, these spectra, when measured near Earth, are significantly affected by the solar activity and we have the so-called solar modulation of CRs (SM). The solar activity has a cycle which period is ~11 years, during which it increases reaching a maximum and then decreases again. The intensity of cosmic ray radiation is correlated (or rather anticorrelated...

  10. Development of dark disk model of positron anomaly origin

    Science.gov (United States)

    Belotsky, K. M.; Kirillov, A. A.; Solovyov, M. L.

    Dark disk model could be a remedy for dark matter (DM) explanation of positron anomaly (PA) in cosmic rays (CR). The main difficulty in PA explanation relates to cosmic gamma-radiation which is inevitably produced in DM annihilation or decay leading to tension with respective observation data. Introduction of “active” (producing CR) DM component concentrating in galactic disk alleviates this tension. Earlier, we considered 2-lepton modes, with branching ratios being chosen to fit in the best way all the observation data. Here we considered, in the framework of the same dark disk model, two cases: 2-body final state annihilation and 4-body one, and in each case a quark mode is added to the leptonic ones. It is shown that 4-body mode case is a little better than 2-body one from viewpoint of quality of observation data description at the fixed all other parameters (of CR propagation, background, disk height). The values of DM particle mass around 350GeV and 500GeV are more favorable for 2- and 4-body modes, respectively. Higher values would improve description of data on positrons only but accounting for data on gamma-radiation prevents it because of unwanted more abundant high-energy gamma production. Inclusion of the quark modes improves a little fitting data in both 4- and 2-body mode cases, contrary to naive expectations. In fact, quark mode has a bigger gammas yield than that of most gamma-productive leptonic mode — tau, but they are softer due to bigger final state hadron multiplicity.

  11. Cosmic ray injection spectrum at the galactic sources

    Science.gov (United States)

    Lagutin, Anatoly; Tyumentsev, Alexander; Volkov, Nikolay

    The spectra of cosmic rays measured at Earth are different from their source spectra. A key to understanding this difference, being crucial for solving the problem of cosmic-ray origin, is the determination of how cosmic-ray (CR) particles propagate through the turbulent interstellar medium (ISM). If the medium is a quasi-homogeneous the propagation process can be described by a normal diffusion model. However, during a last few decades many evidences, both from theory and observations, of the existence of multiscale structures in the Galaxy have been found. Filaments, shells, clouds are entities widely spread in the ISM. In such a highly non-homogeneous (fractal-like) ISM the normal diffusion model certainly is not kept valid. Generalization of this model leads to what is known as "anomalous diffusion". The main goal of the report is to retrieve the cosmic ray injection spectrum at the galactic sources in the framework of the anomalous diffusion (AD) model. The anomaly in this model results from large free paths ("Levy flights") of particles between galactic inhomogeneities. In order to evaluate the CR spectrum at the sources, we carried out new calculation of the CR spectra at Earth. AD equation in terms of fractional derivatives have been used to describe CR propagation from the nearby (r≤1 kpc) young (t≤ 1 Myr) and multiple old distant (r > 1 kpc) sources. The assessment of the key model parameters have been based on the results of the particles diffusion in the cosmic and laboratory plasma. We show that in the framework of the anomalous diffusion model the locally observed basic features of the cosmic rays (difference between spectral exponents of proton, He and other nuclei, "knee" problem, positron to electron ratio) can be explained if the injection spectrum at the main galactic sources of cosmic rays has spectral exponent p˜ 2.85. The authors acknowledge support from The Russian Foundation for Basic Research grant No. 14-02-31524.

  12. Positron-molecule interactions and corresponding positron attachment to molecules. As a basis for positron emission tomography (PET)

    International Nuclear Information System (INIS)

    Tachikawa, Masanori; Kimura, Mineo; Pichl, Lukas

    2007-01-01

    Through positron and electron interactions, they annihilate emitting primarily two gamma rays with 180-degree opposite directions. Positron spectroscopy using the characteristics of these gamma rays has been employed for analyzing various properties of material as well as for positron emission tomography (PET). However, its fundamental physics of positron-electron interactions and resulting features of emitting gamma rays are not well understood. By obtaining better understanding of positron interactions, it should become possible to provide the firm bases for positron spectroscopy in finer accuracy and quality. Here, we propose a significant mechanism for positron annihilation through positron attachment process, which may help increase the quality of positron spectroscopy. (author)

  13. Ultra-high energy cosmic rays: analysis of extensive air showers and their associated electromagnetic signal in the MHz domain

    International Nuclear Information System (INIS)

    Revenu, B.

    2012-01-01

    In this HDR (accreditation to supervise research) report, the author proposes a review of the present results in the field of ultra-high energy cosmic rays. After a presentation of some results about the Fermi mechanism to accelerate cosmic rays, the author more particularly addresses the reconstruction of air showers, and the search for sources. He also addresses the radio signal emitted by air shower secondary positrons and electrons. He proposes an overview of the present knowledge on the basis of present experiments. Data show that the electric field is mainly due to the influence of the Earth magnetic field which acts on electrons and positrons, but more recently, the contribution due to electrons in excess seems to appear in data. The author reports the last advances in the field of simulation of the electric field, with notably the prediction of new signal produced by the disappearance of the air shower during its absorption by the soil [fr

  14. Differential flux measurement of atmospheric pion, muon, electron and positron energy spectra at balloon altitudes

    Energy Technology Data Exchange (ETDEWEB)

    Grimani, C.; Brunetti, M.T.; Codino, A. [Perugia Univ. (Italy)]|[INFN, Perugia (Italy); Papini, P.; Massimo Brancaccio, F.; Finetti, N. [Florence Univ. (Italy)]|[INFN, Florence (Italy); Stephens, S.A. [Tata Institute of Fundamental Researc, Bombay (International Commission on Radiation Units and Measurements); Basini, G.; Bongiorno, F. [INFN, Laboratori Nazionali di Frascati, Rome (Italy); Golden, R.L. [New Mexico State Univ. Las Cruces, NM (United States). Particle Astrophysics Lab.

    1995-09-01

    The fluxes of atmospheric electrons, positrons, positive and negative muons and negative pions have been determined using the NMSU Wizard-MASS2 balloons-borne instrument. The instrument was launched from Fort Sumner, New Mexico, (geomagnetic cut-off about 4.5 GV/c) on september 23, 1991. The flight lasted 9.8 hours and remained above 100.000 ft. Muons and negative pions were observed and their momenta were determined. Since these particles are not a part of the primary component, the measurement of their fluxes provides information regarding production and propagation of secondary particles in the atmosphere. Similarly, observations of electrons and positrons well below the geomagnetic cut-off provides insight into electromagnetic cascade processes in the upper atmosphere. In addition, the determination of the energy spectra of rare particles such as positrons can be used for background subtraction for cosmic ray experiments gathering data below a few g/cm{sup 2} of overlying atmosphere.

  15. Perspective on the Cosmic-ray Electron Spectrum above TeV

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Kun; Wang, Bing-Bing; Bi, Xiao-Jun; Lin, Su-Jie; Yin, Peng-Fei [Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)

    2017-02-20

    The AMS-02 has measured the cosmic-ray electron (plus positron) spectrum up to ∼TeV with unprecedented precision. The spectrum can be well described by a power law without any obvious features above 10 GeV. The satellite instrument Dark Matter Particle Explorer (DAMPE), which was launched a year ago, will measure the electron spectrum up to 10 TeV with high-energy resolution. The cosmic electrons beyond TeV may be attributed to few local cosmic-ray sources, such as supernova remnants. Therefore, spectral features, such as cut-off and bumps, can be expected at high energies. In this work, we provide a careful study on the perspective of the electron spectrum beyond TeV. We first examine our astrophysical source models on the latest leptonic data of AMS-02 to give a self-consistent picture. Then we focus on the discussion about the candidate sources, which could be electron contributors above TeV. Depending on the properties of the local sources (especially on the nature of Vela), DAMPE may detect interesting features in the electron spectrum above TeV in the future.

  16. Measurements of the dose due to cosmic rays in aircraft

    International Nuclear Information System (INIS)

    Vukovic, B.; Lisjak, I.; Radolic, V.; Vekic, B.; Planinic, J.

    2006-01-01

    When the primary particles from space, mainly protons, enter the atmosphere, they produce interactions with air nuclei, and cosmic-ray showers are induced. The radiation field at aircraft altitude is complex, with different types of particles, mainly photons, electrons, positrons and neutrons, with a large energy range. The cosmic radiation dose aboard A320 and ATR 42 aircraft was measured with TLD-100 (LiF:Mg,Ti) detectors and the Mini 6100 semiconductor dosimeter; radon concentration in the atmosphere was measured with the Alpha Guard radon detector. The estimated occupational effective dose for the aircraft crew (A320) working 500 h per year was 1.64 mSv. Another experiment was performed by the flights Zagreb-Paris-Buenos Aires and reversely, when one measured cosmic radiation dose; for 26.7 h of flight, the TLD dosimeter registered the total dose of 75 μSv and the average dose rate was 2.7 μSv/h. In the same month, February 2005, a traveling to Japan (24 h flight: Zagreb-Frankfurt-Tokyo and reversely) and the TLD-100 measurement showed the average dose rate of 2.4 μSv/h

  17. Measurements of the dose due to cosmic rays in aircraft

    Energy Technology Data Exchange (ETDEWEB)

    Vukovic, B. [Department of Physics, University of Osijek, Osijek, P.O. Box 125 (Croatia); Lisjak, I. [Croatia Airlines, Zagreb (Croatia); Radolic, V. [Department of Physics, University of Osijek, Osijek, P.O. Box 125 (Croatia); Vekic, B. [Rudjer Boskovic Institute, Zagreb (Croatia); Planinic, J. [Department of Physics, University of Osijek, Osijek, P.O. Box 125 (Croatia)]. E-mail: planinic@ffos.hr

    2006-06-15

    When the primary particles from space, mainly protons, enter the atmosphere, they produce interactions with air nuclei, and cosmic-ray showers are induced. The radiation field at aircraft altitude is complex, with different types of particles, mainly photons, electrons, positrons and neutrons, with a large energy range. The cosmic radiation dose aboard A320 and ATR 42 aircraft was measured with TLD-100 (LiF:Mg,Ti) detectors and the Mini 6100 semiconductor dosimeter; radon concentration in the atmosphere was measured with the Alpha Guard radon detector. The estimated occupational effective dose for the aircraft crew (A320) working 500 h per year was 1.64 mSv. Another experiment was performed by the flights Zagreb-Paris-Buenos Aires and reversely, when one measured cosmic radiation dose; for 26.7 h of flight, the TLD dosimeter registered the total dose of 75 {mu}Sv and the average dose rate was 2.7 {mu}Sv/h. In the same month, February 2005, a traveling to Japan (24 h flight: Zagreb-Frankfurt-Tokyo and reversely) and the TLD-100 measurement showed the average dose rate of 2.4 {mu}Sv/h.

  18. Implications of the cosmic ray electron spectrum and anisotropy measured with Fermi-LAT

    Energy Technology Data Exchange (ETDEWEB)

    Di Bernardo, Giuseppe [Gothenburg Univ. (Sweden). Dept. of Physics; Evoli, Carmelo [SISSA, Trieste (Italy); Gaggero, Daniele; Grasso, Dario [Pisa Univ. (Italy). Dipt. die Fisica; INFN, Pisa (Italy); Maccione, Luca [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Mazziotta, Mario Nicola [Istituto Nazionale di Fisica Nucleare, Bari (Italy)

    2010-11-15

    The Fermi Large Area Telescope (LAT) collaboration recently released the updated results of the measurement of the cosmic ray electron (CRE) spectrum and published its first constraints on the CRE anisotropy. With respect to the previous Fermi-LAT results, the CRE spectrum measurement was extended down from 20 to 7 GeV, thus providing a better lever arm to discriminate theoretical models. Here we show that the new data strengthen the evidence for the presence of two distinct electron and positron spectral components. Furthermore, we show that under such hypothesis most relevant CRE and positron data sets are remarkably well reproduced. Consistent fits of cosmic-ray nuclei and antiproton data, which are crucial to validate the adopted propagation setup(s) and to fix the solar modulation potential, are obtained for the Kraichnan and plain-diffusion propagation setups, while the Kolmogorov one is disfavored. We then confirm that nearby pulsars are viable source candidates of the required e{sup {+-}} extra-component. In that case, we show that the predicted CRE anisotropy is compatible with Fermi-LAT constraints and that a positive detection should be at hand of that observatory. Models assuming that only nearby supernova remnants contribute to the high energy tail of the observed CRE spectrum are in contrast with anisotropy limits. (orig.)

  19. Positron-containing systems and positron diagnostics

    International Nuclear Information System (INIS)

    1978-01-01

    The results of the experimental and theoretical investigations are presented. Considered are quantum-mechanical calculations of wave functions describing the states of positron-containing atomic systems and of cross-sections of the processes characterizing different interactions, and also the calculations of the behaviour of positrons in gases in the presence of an electric field. The results of experimental tests are presented by the data describing the behaviour of positrons and positronium in liquids, polymers and elastomers, complex oxides and in different solids. New equipment and systems developed on the basis of current studies are described. Examined is a possibility of applying the methods of model and effective potentials for studying the bound states of positron systems and for calculating cross-sections of elementary processes of elastic and inelastic collisions with a positron involved. The experimental works described indicate new possibilities of the positron diagnosis method: investigation of thin layers and films of semiconductor materials, defining the nature of chemical bonds in semiconductors, determination of the dislocation density in deformed semiconductors, derivation of important quantitative information of the energy states of radiation defects in them

  20. Measurements of Cosmic-Ray Proton and Helium Spectra from the BESS-Polar Long-Duration Balloon Flights Over Antarctica

    Science.gov (United States)

    Abe, K.; Fuke, H.; Haino, S.; Hams, T.; Hasegawa, M.; Horikoshi, A.; Itazaki, A.; Kim, K. C.; Kumazawa, T.; Kusumoto, A.; hide

    2016-01-01

    The BESS-Polar Collaboration measured the energy spectra of cosmic-ray protons and helium during two long-duration balloon flights over Antarctica in December 2004 and December 2007, at substantially different levels of solar modulation. Proton and helium spectra probe the origin and propagation history of cosmic rays in the galaxy, and are essential to calculations of the expected spectra of cosmic-ray antiprotons, positrons, and electrons from interactions of primary cosmic-ray nuclei with the interstellar gas, and to calculations of atmospheric muons and neutrinos. We report absolute spectra at the top of the atmosphere for cosmic-ray protons in the kinetic energy range 0.2-160 GeV and helium nuclei 0.15-80 GeV/nucleon. The corresponding magnetic rigidity ranges are 0.6-160 GV for protons and 1.1-160 GV for helium. These spectra are compared to measurements from previous BESS flights and from ATIC-2, PAMELA, and AMS-02. We also report the ratio of the proton and helium fluxes from 1.1 GV to 160 GV and compare to ratios from PAMELA and AMS-02.

  1. Cosmic Rays Report from the Structure of Space

    Directory of Open Access Journals (Sweden)

    A. Annila

    2015-01-01

    Full Text Available Spectrum of cosmic rays follows a broken power law over twelve orders of magnitude. Since ubiquitous power laws are manifestations of the principle of least action, we interpret the spectrum accordingly. Our analysis complies with understanding that low-energy particles originate mostly from rapidly receding sources throughout the cosmos. The flux peaks about proton rest energy whereafter it decreases because fewer and fewer receding sources are energetic enough to provide particles with high enough velocities to compensate for the recessional velocities. Above 1015.6 eV the flux from the expanding Universe diminishes below the flux from the nearby nonexpanding part of the Universe. In this spectral feature, known as the “knee,” we relate to a distance of about 1.3 Mpc where the gravitational potential tallies the energy density of free space. At higher energies particles decelerate in a dissipative manner to attain thermodynamic balance with the vacuum. At about 1017.2 eV a distinct dissipative mechanism opens up for protons to slow down by electron-positron pair production. At about 1019.6 eV a more effective mechanism opens up via pion production. All in all, the universal principle discloses that the broad spectrum of cosmic rays probes the structure of space from cosmic distances down to microscopic details.

  2. Primary cosmic radiation

    International Nuclear Information System (INIS)

    Anderson, H.R.

    1972-01-01

    The term cosmic radiation means the charged particle flux that reaches the earth from outside its magnetosphere with energies above the solar wind energy of a few keV. There are two sources of flux. Sporadically the sun produces such particles, generally within the energy range 1--200 MeV, and these solar cosmic rays arrive at the earth for a period ranging from hours to days. There may be a small, rather constant flux from the sun also, but the bulk of the steady flux originates outside the earth's orbit. Although some have conjectured that part of this latter flux may be accelerated in the outer portions of the solar system where the outward flowing interplanetary medium meets the interstellar medium, it is generally thought that most or all of it arises in unique systems such as supernovae, and is distributed throughout the galaxy. These galactic particles range in energy from a few MeV to at least 10 13 MeV and consist primarily of protons with significant numbers of heavier nuclei, positrons and electrons. They are supposed to fill our galaxy, or at least the disc, more or less uniformly. However, the flux with energies below a few GeV that reaches earth's orbit is modulated by the interplanetary medium so that the number at earth varies inversely with solar activity and is always somewhat below the interstellar flux. A discussion is presented of primary galactic radiation at earth, its modulation by solar activity, and its interaction with the geomagnetic field. (U.S.)

  3. Cosmic strings and cosmic structure

    International Nuclear Information System (INIS)

    Albrecht, A.; Brandenberger, R.; Turok, N.

    1987-01-01

    The paper concerns the application of the theory of cosmic strings to explain the structure of the Universe. The formation of cosmic strings in the early Universe is outlined, along with the Big Bang theory, Grand Unified theories, and the first three minutes after the Big Bang. A description is given of the shaping of the Universe by cosmic strings, including the evolution of the string. The possibility for direct observation of cosmic strings is discussed. (U.K.)

  4. Planned Positron Factory project

    International Nuclear Information System (INIS)

    Okada, Sohei

    1990-01-01

    The Japan Atomic Energy Research Institute, JAERI, has started, drafting a construction plan for the 'Positron Factory', in which intense energy-controllable monoenergetic positron beams are produced from pair-production reactions caused by high-energy electrons from a linac. The JAERI organized a planning committee to provide a basic picture for the Positron Factory. This article presents an overview of the interactions of positrons, intense positron sources and the research program and facilities planned for the project. The interactions of positrons and intense positron sources are discussed focusing on major characteristics of positrons in different energy ranges. The research program for the Positron Factory is then outlined, focusing on advanced positron annihilation techniques, positron spectroscopy (diffraction, scattering, channeling, microscopy), basic positron physics (exotic particle science), and positron beam technology. Discussion is also made of facilities required for the Positron Factory. (N.K.)

  5. Positron sources

    International Nuclear Information System (INIS)

    Chehab, R.

    1989-01-01

    A tentative survey of positron sources is given. Physical processes on which positron generation is based are indicated and analyzed. Explanation of the general features of electromagnetic interactions and nuclear β + decay makes it possible to predict the yield and emittance for a given optical matching system between the positron source and the accelerator. Some kinds of matching systems commonly used - mainly working with solenoidal fields - are studied and the acceptance volume calculated. Such knowledge is helpful in comparing different matching systems. Since for large machines, a significant distance exists between the positron source and the experimental facility, positron emittance has to be preserved during beam transfer over large distances and methods used for that purpose are indicated. Comparison of existing positron sources leads to extrapolation to sources for future linear colliders

  6. Positron-acoustic waves in an electron-positron plasma with an electron beam

    International Nuclear Information System (INIS)

    Nejoh, Y.N.

    1996-01-01

    The nonlinear wave structures of large-amplitude positron-acoustic waves are studied in an electron-positron plasma in the presence of an electron beam with finite temperature and hot electrons and positrons. The region where positron-acoustic waves exist is presented by analysing the structure of the pseudopotential. The region depends sensitively on the positron density, the positron temperature and the electron beam temperature. It is shown that the maximum amplitude of the wave decreases as the positron temperature increases, and the region of positron-acoustic waves spreads as the positron temperature increases. 11 refs., 5 figs

  7. Cosmic rays and the search for a Lorentz Invariance Violation

    Energy Technology Data Exchange (ETDEWEB)

    Bietenholz, Wolfgang, E-mail: wolbi@nucleares.unam.mx

    2011-08-15

    This is an introductory review about the ongoing search for a signal of Lorentz Invariance Violation (LIV) in cosmic rays. We first summarise basic aspects of cosmic rays, focusing on rays of ultrahigh energy (UHECRs). We discuss the Greisen-Zatsepin-Kuz'min (GZK) energy cutoff for cosmic protons, which is predicted due to photopion production in the Cosmic Microwave Background (CMB). This is a process of modest energy in the proton rest frame. It can be investigated to a high precision in the laboratory, if Lorentz transformations apply even at factors {gamma}{approx}O(10{sup 11}). For heavier nuclei, the energy attenuation is even faster due to photo-disintegration, again if this process is Lorentz invariant. Hence the viability of Lorentz symmetry up to tremendous {gamma}-factors-far beyond accelerator tests-is a central issue. Next, we comment on conceptual aspects of Lorentz Invariance and the possibility of its spontaneous breaking. This could lead to slightly particle dependent 'Maximal Attainable Velocities'. We discuss their effect in decays, Cerenkov radiation, the GZK cutoff and neutrino oscillation in cosmic rays. We also review the search for LIV in cosmic {gamma}-rays. For multi-TeV {gamma}-rays, we encounter another possible puzzle related to the transparency of the CMB, similar to the GZK cutoff, due to electron/positron creation and subsequent inverse Compton scattering. The photons emitted in a Gamma Ray Burst occur at lower energies, but their very long path provides access to information not that far from the Planck scale. We discuss conceivable nonlinear photon dispersions based on non-commutative geometry or effective approaches. No LIV has been observed so far. However, even extremely tiny LIV effects could change the predictions for cosmic ray physics drastically. An Appendix is devoted to the recent results by the Pierre Auger Collaboration, in particular the hypothesis that nearby Active Galactic Nuclei-or objects next to

  8. Cosmic rays and the search for a Lorentz Invariance Violation

    International Nuclear Information System (INIS)

    Bietenholz, Wolfgang

    2008-11-01

    This is an introductory review about the on-going search for a signal of Lorentz Invariance Violation (LIV) in cosmic rays. We first summarise basic aspects of cosmic rays, focusing on rays of ultra high energy (UHECRs). We discuss the Greisen-Zatsepin-Kuz'min (GZK) energy cutoff for cosmic protons, which is predicted due to photopion production in the Cosmic Microwave Background (CMB). This is a process of modest energy in the proton rest frame. It can be investigated to a high precision in the laboratory, if Lorentz transformations apply even at factors γ ∝ O(10 11 ). For heavier nuclei the energy attenuation is even faster due to photo-disintegration, again if this process is Lorentz invariant. Hence the viability of Lorentz symmetry up to tremendous γ-factors - far beyond accelerator tests - is a central issue. Next we comment on conceptual aspects of Lorentz Invariance and the possibility of its spontaneous breaking. This could lead to slightly particle dependent ''Maximal Attainable Velocities''. We discuss their effect in decays, Cerenkov radiation, the GZK cutoff and neutrino oscillation in cosmic rays. We also review the search for LIV in cosmic γ-rays. For multi TeV γ-rays we possibly encounter another puzzle related to the transparency of the CMB, similar to the GZK cutoff, due to electron/positron creation and subsequent inverse Compton scattering. The photons emitted in a Gamma Ray Burst occur at lower energies, but their very long path provides access to information not far from the Planck scale. We discuss conceivable non-linear photon dispersions based on non-commutative geometry or effective approaches. No LIV has been observed so far. However, even extremely tiny LIV effects could change the predictions for cosmic ray physics drastically. An Appendix is devoted to the recent hypothesis by the Pierre Auger Collaboration, which identifies nearby Active Galactic Nuclei - or objects next to them - as probable UHECR sources. (orig.)

  9. Cosmic rays and the search for a Lorentz Invariance Violation

    Energy Technology Data Exchange (ETDEWEB)

    Bietenholz, Wolfgang [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC

    2008-11-15

    This is an introductory review about the on-going search for a signal of Lorentz Invariance Violation (LIV) in cosmic rays. We first summarise basic aspects of cosmic rays, focusing on rays of ultra high energy (UHECRs). We discuss the Greisen-Zatsepin-Kuz'min (GZK) energy cutoff for cosmic protons, which is predicted due to photopion production in the Cosmic Microwave Background (CMB). This is a process of modest energy in the proton rest frame. It can be investigated to a high precision in the laboratory, if Lorentz transformations apply even at factors {gamma} {proportional_to} O(10{sup 11}). For heavier nuclei the energy attenuation is even faster due to photo-disintegration, again if this process is Lorentz invariant. Hence the viability of Lorentz symmetry up to tremendous {gamma}-factors - far beyond accelerator tests - is a central issue. Next we comment on conceptual aspects of Lorentz Invariance and the possibility of its spontaneous breaking. This could lead to slightly particle dependent ''Maximal Attainable Velocities''. We discuss their effect in decays, Cerenkov radiation, the GZK cutoff and neutrino oscillation in cosmic rays. We also review the search for LIV in cosmic {gamma}-rays. For multi TeV {gamma}-rays we possibly encounter another puzzle related to the transparency of the CMB, similar to the GZK cutoff, due to electron/positron creation and subsequent inverse Compton scattering. The photons emitted in a Gamma Ray Burst occur at lower energies, but their very long path provides access to information not far from the Planck scale. We discuss conceivable non-linear photon dispersions based on non-commutative geometry or effective approaches. No LIV has been observed so far. However, even extremely tiny LIV effects could change the predictions for cosmic ray physics drastically. An Appendix is devoted to the recent hypothesis by the Pierre Auger Collaboration, which identifies nearby Active Galactic Nuclei - or objects

  10. Positron sources

    International Nuclear Information System (INIS)

    Chehab, R.

    1994-01-01

    A tentative survey of positron sources is given. Physical processes on which positron generation is based are indicated and analyzed. Explanation of the general features of electromagnetic interactions and nuclear β + decay makes it possible to predict the yield and emittance for a given optical matching system between the positron source and the accelerator. Some kinds of matching systems commonly used - mainly working with solenoidal field - are studied and the acceptance volume calculated. Such knowledge is helpful in comparing different matching systems. Since for large machines, a significant distance exists between the positron source and the experimental facility, positron emittance has to be preserved during beam transfer over large distances and methods used for that purpose are indicated. Comparison of existing positron sources leads to extrapolation to sources for future linear colliders. Some new ideas associated with these sources are also presented. (orig.)

  11. Some ways for the investigation of the solar modulation of cosmic electrons

    International Nuclear Information System (INIS)

    Mercier, J.

    1969-01-01

    In this report, we are investigating the solar modulation of cosmic electrons, in different ways. By comparing the calculated intensity with the measured intensity of positrons, we can evaluate the solar modulation of positrons, hence the modulation of negatons, since the modulation of negatons is probably the same that for positrons. By comparing the electron spectrum in interstellar space needed to explain the galactic background radio emission with that observed near the earth, we can deduce information about the modulation of electrons. We can investigate the modulation through the observation of its variations during the solar cycle. This different ways lead us to compatible results. In spite of the fact that the precision of the experimental data is poor, the modulation can be represented by: a constant or a form in exp(- K/Roβ) under the rigidity Ro ≅ 0,5 BV; a form in exp(- K/R) or exp(- K/Rβ) above this rigidity. In addition, the investigation of both electrons and protons displays that the diffusion-convection theory is inadequate to explain all the features of the solar modulation. (author) [fr

  12. Measuring extensive air showers with Cherenkov light detectors of the Yakutsk array: the energy spectrum of cosmic rays

    International Nuclear Information System (INIS)

    Ivanov, A A; Knurenko, S P; Sleptsov, I Ye

    2009-01-01

    The energy spectrum of cosmic rays in the range E∼10 15 eV to 6x10 19 eV is studied in this paper using air Cherenkov light detectors of the Yakutsk array. The total flux of photons produced by the relativistic electrons (including positrons as well, hereafter) of extensive air showers in the atmosphere is used as an energy estimator of the primary particle initiating a shower. The resultant differential flux of cosmic rays exhibits, in agreement with previous measurements, a knee and ankle feature at energies of 3x10 15 and ∼10 19 eV, respectively. A comparison of observational data with simulations is made in the knee and ankle regions in order to choose the models of galactic and extragalactic components of cosmic rays that describe well the energy spectrum measured.

  13. Measuring extensive air showers with Cherenkov light detectors of the Yakutsk array: the energy spectrum of cosmic rays

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, A A; Knurenko, S P; Sleptsov, I Ye [Shafer Institute for Cosmophysical Research and Aeronomy, Yakutsk 677980 (Russian Federation)], E-mail: ivanov@ikfia.ysn.ru

    2009-06-15

    The energy spectrum of cosmic rays in the range E{approx}10{sup 15} eV to 6x10{sup 19} eV is studied in this paper using air Cherenkov light detectors of the Yakutsk array. The total flux of photons produced by the relativistic electrons (including positrons as well, hereafter) of extensive air showers in the atmosphere is used as an energy estimator of the primary particle initiating a shower. The resultant differential flux of cosmic rays exhibits, in agreement with previous measurements, a knee and ankle feature at energies of 3x10{sup 15} and {approx}10{sup 19} eV, respectively. A comparison of observational data with simulations is made in the knee and ankle regions in order to choose the models of galactic and extragalactic components of cosmic rays that describe well the energy spectrum measured.

  14. Transmission positron microscopes

    International Nuclear Information System (INIS)

    Doyama, Masao; Kogure, Yoshiaki; Inoue, Miyoshi; Kurihara, Toshikazu; Yoshiie, Toshimasa; Oshima, Ryuichiro; Matsuya, Miyuki

    2006-01-01

    Immediate and near-future plans for transmission positron microscopes being built at KEK, Tsukuba, Japan, are described. The characteristic feature of this project is remolding a commercial electron microscope to a positron microscope. A point source of electrons kept at a negative high voltage is changed to a point source of positrons kept at a high positive voltage. Positional resolution of transmission microscopes should be theoretically the same as electron microscopes. Positron microscopes utilizing trapping of positrons have always positional ambiguity due to the diffusion of positrons

  15. MEASUREMENTS OF COSMIC-RAY PROTON AND HELIUM SPECTRA FROM THE BESS-POLAR LONG-DURATION BALLOON FLIGHTS OVER ANTARCTICA

    Energy Technology Data Exchange (ETDEWEB)

    Abe, K.; Itazaki, A.; Kusumoto, A.; Matsukawa, Y.; Orito, R. [Kobe University, Kobe, Hyogo 657-8501 (Japan); Fuke, H. [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (ISAS/JAXA), Sagamihara, Kanagawa 252-5210 (Japan); Haino, S.; Hasegawa, M.; Horikoshi, A.; Kumazawa, T.; Makida, Y.; Matsuda, S.; Matsumoto, K.; Nozaki, M. [High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801 (Japan); Hams, T.; Mitchell, J. W. [NASA-Goddard Space Flight Center (NASA-GSFC), Greenbelt, MD 20771 (United States); Kim, K. C.; Lee, M. H.; Myers, Z. [IPST, University of Maryland, College Park, MD 20742 (United States); Nishimura, J., E-mail: Kenichi.Sakai@nasa.gov [The University of Tokyo, Bunkyo, Tokyo 113-0033 (Japan); and others

    2016-05-10

    The BESS-Polar Collaboration measured the energy spectra of cosmic-ray protons and helium during two long-duration balloon flights over Antarctica in 2004 December and 2007 December at substantially different levels of solar modulation. Proton and helium spectra probe the origin and propagation history of cosmic rays in the galaxy, and are essential to calculations of the expected spectra of cosmic-ray antiprotons, positrons, and electrons from interactions of primary cosmic-ray nuclei with the interstellar gas, and to calculations of atmospheric muons and neutrinos. We report absolute spectra at the top of the atmosphere for cosmic-ray protons in the kinetic energy range 0.2–160 GeV and helium nuclei in the range 0.15–80 GeV/nucleon. The corresponding magnetic-rigidity ranges are 0.6–160 GV for protons and 1.1–160 GV for helium. These spectra are compared to measurements from previous BESS flights and from ATIC-2, PAMELA, and AMS-02. We also report the ratio of the proton and helium fluxes from 1.1 to 160 GV and compare this to the ratios from PAMELA and AMS-02.

  16. Cosmic ray nuclei detection in the balloon borne nuclear emulsion gamma ray telescope flight in Australia (GRAINE 2015

    Directory of Open Access Journals (Sweden)

    Iyono Atsushi

    2017-01-01

    Full Text Available Nuclear emulsion plates for studying elementary particle physics as well as cosmic ray physics are very powerful tracking tools with sub-micron spatial resolutions of charged particle trajectories. Even if gamma rays have to be detected, electron-positron pair tracks can provide precise information to reconstruct their direction and energy with high accuracy. Recent developments of emulsion analysis technology can digitally handle almost all tracks recorded in emulsion plates by using the Hyper Track Selector of the OPERA group at NAGOYA University. On the other hand, the potential of time resolutions have been equipped by emulsion multilayer shifter technology in the GRAINE (Gamma Ray Astro-Imager with Nuclear Emulsion experiments, the aims of which are to detect cosmic gamma rays such as the Vela pulsar stellar object by precise emulsion tracking analysis and to study cosmic ray particle interactions and chemical compositions. In this paper, we focus on the subject of cosmic ray nuclei detection in the GRAINE balloon flight experiments launched at Alice Springs, Australia in May 2015.

  17. Energy and flux measurements of ultra-high energy cosmic rays observed during the first ANITA flight

    Energy Technology Data Exchange (ETDEWEB)

    Schoorlemmer, H.; Belov, K.; Romero-Wolf, A.; García-Fernández, D.; Bugaev, V.; Wissel, S. A.; Allison, P.; Alvarez-Muñiz, J.; Barwick, S. W.; Beatty, J. J.; Besson, D. Z.; Binns, W. R.; Carvalho Jr., W. R.; Chen, C.; Chen, P.; Clem, J. M.; Connolly, A.; Dowkontt, P. F.; DuVernois, M. A.; Field, R. C.; Goldstein, D.; Gorham, P. W.; Hast, C.; Huege, T.; Heber, C. L.; Hoover, S.; Israel, M. H.; Javaid, A.; Kowalski, J.; Lam, J.; Learned, J. G.; Link, J. T.; Lusczek, E.; Matsuno, S.; Mercurio, B. C.; Miki, C.; Miočinović, P.; Mulrey, K.; Nam, J.; Naudet, C. J.; Ng, J.; Nichol, R. J.; Palladino, K.; Rauch, B. F.; Roberts, J.; Reil, K.; Rotter, B.; Rosen, M.; Ruckman, L.; Saltzberg, D.; Seckel, D.; Urdaneta, D.; Varner, G. S.; Vieregg, A. G.; Walz, D.; Wu, F.; Zas, E.

    2016-04-01

    The first flight of the Antarctic Impulsive Transient Antenna (ANITA) experiment recorded 16 radio signals that were emitted by cosmic-ray induced air showers. The dominant contribution to the radiation comes from the deflection of positrons and electrons in the geomagnetic field, which is beamed in the direction of motion of the air shower. For 14 of these events, this radiation is reflected from the ice and subsequently detected by the ANITA experiment at a flight altitude of ~36 km. In this paper, we estimate the energy of the 14 individual events and find that the mean energy of the cosmic-ray sample is 2.9 × 1018 eV, which is significantly lower than the previous estimate. By simulating the ANITA flight, we calculate its exposure for ultra-high energy cosmic rays. We estimate for the first time the cosmic-ray flux derived only from radio observations and find agreement with measurements performed at other observatories. In addition, we find that the ANITA data set is consistent with Monte Carlo simulations for the total number of observed events and with the properties of those events.

  18. Development of an Electron-Positron Source for Positron Annihilation Lifetime Spectroscopy

    Science.gov (United States)

    2009-12-19

    REPORT Development of an electron- positron source for positron annihilation lifetime spectroscopy : FINAL REPORT 14. ABSTRACT 16. SECURITY...to generate radiation, to accelerate particles, and to produce electrons and positrons from vacuum. From applications using existing high-repetition...theoretical directions. This report reviews work directed toward the application of positron generation from laser interaction with matter 1. REPORT DATE

  19. The L3+C detector, a unique tool-set to study cosmic rays

    International Nuclear Information System (INIS)

    Adriani, O.; Akker, M. van den; Banerjee, S.; Baehr, J.; Betev, B.; Bourilkov, D.; Bottai, S.; Bobbink, G.; Cartacci, A.; Chemarin, M.; Chen, G.; Chen, H.S.; Chiarusi, T.; Dai, C.J.; Ding, L.K.; Duran, I.; Faber, G.; Fay, J.; Grabosch, H.J.; Groenstege, H.; Guo, Y.N.; Gupta, S.; Haller, Ch.; Hayashi, Y.; He, Z.X.; Hebbeker, T.; Hofer, H.; Hoferjun, H.; Huo, A.X.; Ito, N.; Jing, C.L.; Jones, L.; Kantserov, V.; Kawakami, S.; Kittel, W.; Koenig, A.C.; Kok, E.; Korn, A.; Kuang, H.H.; Kuijpers, J.; Ladron de Guevara, P.; Le Coultre, P.; Lei, Y.; Leich, H.; Leiste, R.; Li, D.; Li, L.; Li, Z.C.; Liu, Z.A.; Liu, H.T.; Lohmann, W.; Lu, Y.S.; Ma, X.H.; Ma, Y.Q.; Mil, A. van; Monteleoni, B.; Nahnhauer, R.; Pauss, F.; Parriaud, J.-F.; Petersen, B.; Pohl, M.; Qing, C.R.; Ramelli, R.; Ravindran, K.C.; Rewiersma, P.; Rojkov, A.; Saidi, R.; Schmitt, V.; Schoeneich, B.; Schotanus, D.J.; Shen, C.Q.; Sulanke, H.; Tang, X.W.; Timmermans, C.; Tonwar, S.; Trowitzsch, G.; Unger, M.; Verkooijen, H.; Wang, X.L.; Wang, X.W.; Wang, Z.M.; Wijk, R. van; Wijnen, Th.A.M.; Wilkens, H.; Xu, Y.P.; Xu, Z.Z.; Yang, C.G.; Yang, X.F.; Yao, Z.G.; Yu, Z.Q.; Zhang, S.; Zhu, G.Y.; Zhu, Q.Q.; Zhuang, H.L.; Zwart, A.N.M.

    2002-01-01

    The L3 detector at the CERN electron-positron collider, LEP, has been employed for the study of cosmic ray muons. The muon spectrometer of L3 consists of a set of high-precision drift chambers installed inside a magnet with a volume of about 1000 m 3 and a field of 0.5 T. Muon momenta are measured with a resolution of a few percent at 50 GeV. The detector is located under 30 m of overburden. A scintillator air shower array of 54 m by 30 m is installed on the roof of the surface hall above L3 in order to estimate the energy and the core position of the shower associated with a sample of detected muons. Thanks to the unique properties of the L3+C detector, muon research topics relevant to various current problems in cosmic ray and particle astrophysics can be studied

  20. The L3+C detector, a unique tool-set to study cosmic rays

    CERN Document Server

    Adriani, O; Banerjee, S; Bähr, J; Betev, B L; Bourilkov, D; Bottai, S; Bobbink, Gerjan J; Cartacci, A M; Chemarin, M; Chen, G; Chen He Sheng; Chiarusi, T; Dai Chang Jiang; Ding, L K

    2002-01-01

    The L3 detector at the CERN electron-positron collider, LEP, has been employed for the study of cosmic ray muons. The muon spectrometer of L3 consists of a set of high-precision drift chambers installed inside a magnet with a volume of about 1000 m**3 and a field of 0.5 T. Muon momenta are measured with a resolution of a few percent at 50 GeV. The detector is located under 30 m of overburden. A scintillator air shower array of 54 m by 30 m is installed on the roof of the surface hall above L3 in order to estimate the energy and the core position of the shower associated with a sample of detected muons. Thanks to the unique properties of the L3+C detector, muon research topics relevant to various current problems in cosmic ray and particle astrophysics can be studied.

  1. Determining Thunderstorm Electric Fields using Radio Emission from Cosmic-Ray Air Showers

    Science.gov (United States)

    Hare, B.; Scholten, O.; Trinh, G. T. N.; Ebert, U.; Rutjes, C.

    2017-12-01

    We report on a novel non-intrusive way to investigate electric fields in thunderclouds.Energetic cosmic rays penetrating the atmosphere create a particle avalanche called an extensive air shower. The front of the shower is a plasma cloud that contains 10^6 or more free electrons and positrons moving towards the Earth's surface at the speed of light. The electric fields that exists in thunderclouds induces electric currents in the plasma cloud that emit radio waves. The radio footprint for intensity, linear and circular polarization thus contains the finger print of the atmospheric electric fields along the path of the air shower.Here we report on the analysis of many cosmic-ray radio footprints as have been measured at LOFAR, a dense array of simple radio antennas (several thousands of dual-polarized antennas) primarily developed for radio-astronomy observations. We show that this method can be used to determine the charge structure in thunderclouds and discuss the accuracy of the method. We have observed seasonal dependencies.

  2. Cosmic radiation dose in the aircraft

    International Nuclear Information System (INIS)

    Vukovic, B.; Radolic, V.; Varga, M.; Planinic, J.; Vekic, B.

    2006-01-01

    When primary particles from space, mainly protons, enter the atmosphere, they produce interactions with air nuclei, and cosmic-ray showers are induced. The radiation field at aircraft altitude is complex, with different types of particles, mainly photons, electrons, positrons and neutrons, with a large energy range. The non-neutron component of cosmic radiation dose aboard A 320 and ATR 42 aircraft was measured with TLD-100 (LiF:Mg,Ti) detectors and the Mini 6100 semiconductor dosimeter; the neutron dose was measured with the neutron dosimeter consisted of LR-115 track detector and boron foil BN-1 or 10B converter. The estimated occupational effective dose for the aircraft crew (A320) working 500 h per year was 1.64 mSv. Another experiment was performed at the flights Zagreb - Paris - Buenos Aires and reversely, when one measured cosmic radiation dose; for 26.7 h of flight, the MINI 6100 dosimeter gave an average dose rate of 2.3 μSv/h and the TLD dosimeter registered the total dose of 75 μSv or the average dose rate of 2.7 μSv/h; the neutron dosimeter gave the dose rate of 2.4 μSv/h. In the same month, February 2005, a traveling to the Japan (24 hours-flight: Zagreb - Frankfurt - Tokyo and reversely) and the TLD-100 measurement showed the average dose rate of 2.4 μSv/h; the neutron dosimeter gave the dose rate of 2.5 μSv/h. Comparing dose rates of the non-neutron component (low LET) and the neutron one (high LET) of the radiation field at the aircraft flight level, we could conclude the neutron component curried about 50% of the total dose, that was near other known data. (author)

  3. Investigation of positron moderator materials for electron-linac-based slow positron beamlines

    International Nuclear Information System (INIS)

    Suzuki, Ryoichi; Ohdaira, Toshiyuki; Uedono, Akira

    1998-01-01

    Positron re-emission properties were studied on moderator materials in order to improve the positron moderation system of electron-linac-based intense slow positron beamlines. The re-emitted positron fraction was measured on tungsten, SiC, GaN, SrTiO 3 , and hydrogen-terminated Si with a variable-energy pulsed positron beam. The results suggested that tungsten is the best material for the primary moderator of the positron beamlines while epitaxially grown n-type 6H-SiC is the best material for the secondary moderator. Defect characterization by monoenergetic positron beams and surface characterization by Auger electron spectroscopy were carried out to clarify the mechanism of tungsten moderator degradation induced by high-energy electron irradiation. The characterization experiments revealed that the degradation is due to both radiation-induced vacancy clusters and surface carbon impurities. For the restoration of degraded tungsten moderators, oxygen treatment at ∼900degC is effective. Furthermore, it was found that oxygen at the tungsten surface inhibits positronium formation; as a result, it can increase the positron re-emission fraction. (author)

  4. Positron-atom collisions

    International Nuclear Information System (INIS)

    Drachman, R.J.

    1984-01-01

    The past decade has seen the field of positron-atom collisions mature into an important sub-field of atomic physics. Increasingly intense positron sources are leading towards a situation in which electron and positron collision experiments will be on almost an equal footing, challenging theory to analyze their similarities and differences. The author reviews the advances made in theory, including dispersion theory, resonances, and inelastic processes. A survey of experimental progress and a brief discussion of astrophysical positronics is also included. (Auth.)

  5. Positrons and positronium

    International Nuclear Information System (INIS)

    Jean, Y.C.; Lambrecht, R.M.

    1988-01-01

    This bibliography includes articles, proceedings, abstracts, reports and patents published between 1930 and 1984 on the subject of positrons, positron annihilation and positronium. The subject covers experimental and theoretical results in the areas of physics and chemistry of low and intermediate energy (< 0.6 MeV) positrons and positronium. The topics of interest are: fundamental properties, interactions with matter, nuclear technology, the history and philosophy of antimatter, the theory of the universe, and the applications of positrons in the chemical, physical, and biomedical sciences

  6. The proposed INEL intense slow positron source, beam line, and positron microscope facility

    International Nuclear Information System (INIS)

    Makowitz, H.; Denison, A.B.; Brown, B.

    1993-01-01

    A program is currently underway at the Idaho National Engineering Laboratory (INEL) to design and construct an Intense Slow Positron Beam Facility with an associated Positron Microscope. Positron beams have been shown to be valuable research tools and have potential application in industrial processing and nondestructive evaluation (microelectronics, etc.). The limit of resolution or overall usefulness of the technique has been limited because of lack of sufficient intensity. The goal of the INEL positron beam is ≥ 10 12 slow e+/s over a 0.03 cm diameter which represents a 10 3 to 10 4 advancement in beam current over existing beam facilities. The INEL is an ideal site for such a facility because of the nuclear reactors capable of producing intense positron sources and the personnel and facilities capable of handling high levels of radioactivity. A design using 58 Co with moderators and remoderators in conjunction with electrostatic positron beam optics has been reached after numerous computer code studies. Proof-of-principle electron tests have demonstrated the feasibility of the large area source focusing optics. The positron microscope development is occurring in conjunction with the University of Michigan positron microscope group. Such a Beam Facility and associated Intense Slow Positron Source (ISPS) can also be utilized for the generation and study of positron, and positron electron plasmas at ≤ 10 14 particles/cm 3 with plasma temperatures ranging from an eV to many keV, as well as an intense x-ray source via positron channeling radiation. The possibility of a tunable x-ray laser based on channeling positron radiation also exists. In this discussion the authors will present a progress report on various activities associated with the INEL ISPS

  7. Review of the Theoretical and Experimental Status of Dark Matter Identification with Cosmic-Ray Antideuterons

    Science.gov (United States)

    Aramaki, T.; Boggs, S.; Bufalino, S.; Dal, L.; von Doetinchem, P.; Donato, F.; Fornengo, N.; Fuke, H.; Grefe, M.; Hailey, C.; hide

    2016-01-01

    Recent years have seen increased theoretical and experimental effort towards the first-ever detection of cosmic-ray antideuterons, in particular as an indirect signature of dark matter annihilation or decay. In contrast to indirect dark matter searches using positrons, antiprotons, or gamma-rays, which suffer from relatively high and uncertain astrophysical backgrounds, searches with antideuterons benefit from very suppressed conventional backgrounds, offering a potential breakthrough in unexplored phase space for dark matter. This article is based on the first dedicated cosmic-ray antideuteron workshop, which was held at UCLA in June 2014. It reviews broad classes of dark matter candidates that result in detectable cosmic-ray antideuteron fluxes, as well as the status and prospects of current experimental searches. The coalescence model of antideuteron production and the influence of antideuteron measurements at particle colliders are discussed. This is followed by a review of the modeling of antideuteron propagation through the magnetic fields, plasma currents, and molecular material of our Galaxy, the solar system, the Earth's geomagnetic field, and the atmosphere. Finally, the three ongoing or planned experiments that are sensitive to cosmic-ray antideuterons, BESS, AMS-02, and GAPS, are detailed. As cosmic-ray antideuteron detection is a rare event search, multiple experiments with orthogonal techniques and backgrounds are essential. Therefore, the combination of AMS-02 and GAPS antideuteron searches is highly desirable. Many theoretical and experimental groups have contributed to these studies over the last decade, this review aims to provide the first coherent discussion of the relevant dark matter theories that antideuterons probe, the challenges to predictions and interpretations of antideuteron signals, and the experimental efforts toward cosmic antideuteron detection.

  8. Positron emission tomography

    International Nuclear Information System (INIS)

    Reivich, M.; Alavi, A.

    1985-01-01

    This book contains 24 selections. Some of the titles are: Positron Emission Tomography Instrumentation, Generator Systems for Positron Emitters, Reconstruction Algorithms, Cerebral Glucose Consumption: Methodology and Validation, Cerebral Blood Flow Tomography Using Xenon-133 Inhalation: Methods and Clinical Applications, PET Studies of Stroke, Cardiac Positron Emission Tomography, and Use of PET in Oncology

  9. Cardiac positron emission tomography

    International Nuclear Information System (INIS)

    Eftekhari, M.; Ejmalian, G.

    2003-01-01

    Positron emission tomography is an intrinsically tool that provide a unique and unparalleled approach for clinicians and researchers to interrogate the heart noninvasively. The ability to label substances of physiological interest with positron-emitting radioisotopes has permitted insight into normal blood flow and metabolism and the alterations that occur with disease states. Positron emission tomography of the heart has evolved as a unique, noninvasive approach for the assessment of myocardial perfusion, metabolism, and function. Because of the intrinsic quantitative nature of positron emission tomography measurements as well as the diverse compounds that can be labeled with positron- emitting radioisotopes, studies with positron emission tomography have provided rich insight into the physiology of the heart under diverse conditions

  10. Cosmic radiation dose in aircraft - a neutron track etch detector

    Energy Technology Data Exchange (ETDEWEB)

    Vukovic, B.; Radolic, V.; Miklavcic, I.; Poje, M.; Varga, M. [Department of Physics, University of Osijek, 31000 Osijek, P.O. Box 125, Gajev trg 6 (Croatia); Planinic, J. [Department of Physics, University of Osijek, 31000 Osijek, P.O. Box 125, Gajev trg 6 (Croatia)], E-mail: planinic@ffos.hr

    2007-12-15

    Cosmic radiation bombards us at high altitude by ionizing particles. The radiation environment is a complex mixture of charged particles of solar and galactic origin, as well as of secondary particles produced in interaction of the galactic cosmic particles with the nuclei of atmosphere of the Earth. The radiation field at aircraft altitude consists of different types of particles, mainly photons, electrons, positrons and neutrons, with a large energy range. The non-neutron component of cosmic radiation dose aboard ATR 42 and A 320 aircrafts (flight level of 8 and 11 km, respectively) was measured with TLD-100 (LiF:Mg,Ti) detectors and the Mini 6100 semiconductor dosimeter. The estimated occupational effective dose for the aircraft crew (A 320) working 500 h per year was 1.64 mSv. Other experiments, or dose rate measurements with the neutron dosimeter, consisting of LR-115 track detector and boron foil BN-1 or 10B converter, were performed on five intercontinental flights. Comparison of the dose rates of the non-neutron component (low LET) and the neutron one (high LET) of the radiation field at the aircraft flight level showed that the neutron component carried about 50% of the total dose. The dose rate measurements on the flights from the Middle Europe to the South and Middle America, then to Korea and Japan, showed that the flights over or near the equator region carried less dose rate; this was in accordance with the known geomagnetic latitude effect.

  11. Cosmic radiation dose in aircraft - a neutron track etch detector

    International Nuclear Information System (INIS)

    Vukovic, B.; Radolic, V.; Miklavcic, I.; Poje, M.; Varga, M.; Planinic, J.

    2007-01-01

    Cosmic radiation bombards us at high altitude by ionizing particles. The radiation environment is a complex mixture of charged particles of solar and galactic origin, as well as of secondary particles produced in interaction of the galactic cosmic particles with the nuclei of atmosphere of the Earth. The radiation field at aircraft altitude consists of different types of particles, mainly photons, electrons, positrons and neutrons, with a large energy range. The non-neutron component of cosmic radiation dose aboard ATR 42 and A 320 aircrafts (flight level of 8 and 11 km, respectively) was measured with TLD-100 (LiF:Mg,Ti) detectors and the Mini 6100 semiconductor dosimeter. The estimated occupational effective dose for the aircraft crew (A 320) working 500 h per year was 1.64 mSv. Other experiments, or dose rate measurements with the neutron dosimeter, consisting of LR-115 track detector and boron foil BN-1 or 10B converter, were performed on five intercontinental flights. Comparison of the dose rates of the non-neutron component (low LET) and the neutron one (high LET) of the radiation field at the aircraft flight level showed that the neutron component carried about 50% of the total dose. The dose rate measurements on the flights from the Middle Europe to the South and Middle America, then to Korea and Japan, showed that the flights over or near the equator region carried less dose rate; this was in accordance with the known geomagnetic latitude effect

  12. PAMELA: A Satellite Experiment for Antiparticles Measurement in Cosmic Rays

    Science.gov (United States)

    Bongi, M.; Adriani, O.; Ambriola, M.; Bakaldin, A.; Barbarino, G. C.; Basili, A.; Bazilevskaja, G.; Bellotti, R.; Bencardino, R.; Boezio, M.; Bogomolov, E. A.; Bonechi, L.; Bongiorno, L.; Bonvicini, V.; Boscherini, M.; Cafagna, F. S.; Campana, D.; Carlson, P.; Casolino, M.; Castellini, G.; Circella, M.; De Marzo, C. N.; De Pascale, M. P.; Furano, G.; Galper, A. M.; Giglietto, N.; Grigorjeva, A.; Koldashov, S. V.; Korotkov, M. G.; Krut'kov, S. Y.; Lund, J.; Lundquist, J.; Menicucci, A.; Menn, W.; Mikhailov, V. V.; Minori, M.; Mirizzi, N.; Mitchell, J. W.; Mocchiutti, E.; Morselli, A.; Mukhametshin, R.; Orsi, S.; Osteria, G.; Papini, P.; Pearce, M.; Picozza, P.; Ricci, M.; Ricciarini, S. B.; Romita, M.; Rossi, G.; Russo, S.; Schiavon, P.; Simon, M.; Sparvoli, R.; Spillantini, P.; Spinelli, P.; Stochaj, S. J.; Stozhkov, Y.; Straulino, S.; Streitmatter, R. E.; Taccetti, F.; Vacchi, A.; Vannuccini, E.; Vasilyev, G. I.; Voronov, S. A.; Wischnewski, R.; Yurkin, Y.; Zampa, G.; Zampa, N.

    2004-06-01

    PAMELA is a satellite-borne experiment that will study the antiproton and positron fluxes in cosmic rays in a wide range of energy (from 80 MeV up to 190 GeV for antiprotons and from 50 MeV up to 270 GeV for positrons) and with high statistics, and that will measure the antihelium/helium ratio with a sensitivity of the order of 10/sup -8/. The detector will fly on-board a polar orbiting Resurs DK1 satellite, which will be launched into space by a Soyuz rocket in 2004 from Baikonur cosmodrome in Kazakhstan, for a 3-year-long mission. Particle identification and energy measurements are performed in the PAMELA apparatus using the following subdetectors: a magnetic spectrometer made up of a permanent magnet equipped with double-sided microstrip silicon detectors, an electromagnetic imaging calorimeter composed of layers of tungsten absorber and silicon detectors planes, a transition radiation detector made of straw tubes interleaved with carbon fiber radiators, a plastic scintillator time-of-flight and trigger system, a set of anticounter plastic scintillator detectors, and a neutron detector. The features of the detectors and the main results obtained in beam test sessions are presented.

  13. BEPC II positron source

    International Nuclear Information System (INIS)

    Pei Guoxi; Sun Yaolin; Liu Jintong; Chi Yunlong; Liu Yucheng; Liu Nianzong

    2006-01-01

    BEPC II-an upgrade project of the Beijing Electron Positron Collider (BEPC) is a factory type of e + e - collider. The fundamental requirements for its injector linac are the beam energy of 1.89 GeV for on-energy injection and a 40 mA positron beam current at the linac end with a low beam emittance of 1.6 μm and a low energy spread of ±0.5% so as to guarantee a higher injection rate (≥50 mA/min) to the storage ring. Since the positron flux is proportional to the primary electron beam power on the target, the authors will increase the electron gun current from 4A to 10A by using a new electron gun system and increase the primary electron energy from 120 MeV to 240 MeV. The positron source itself is an extremely important system for producing more positrons, including a positron converter target chamber, a 12kA flux modulator, the 7m focusing module with DC power supplies and the support. The new positron production linac from the electron gun to the positron source has been installed into the tunnel. In what follows, the authors will emphasize the positron source design, manufacture and tests. (authors)

  14. Positron annihilation studies on bulk metallic glass and high intensity positron beam developments

    International Nuclear Information System (INIS)

    Asoka-Kumar, P.; Stoeffl, W.

    2003-01-01

    Positron annihilation spectroscopy is an ideal probe to examine atomic scale open-volume regions in materials. Below, we summarize the recent results on studies of open-volume regions of a multicomponent Zr-Ti-Ni-Cu-Be bulk metallic glass. Our studies establish two types of open-volume regions, one group that is too shallow to trap positrons at room temperature and becomes effective only at low temperatures and the other group that localizes positrons at room temperature and is large enough to accommodate hydrogen. The second half of the paper will concentrate on the high intensity positron program at Lawrence Livermore National Laboratory. A new positron production target is under development and we are constructing two experimental end stations to accommodate a pulsed positron microprobe and an experiment on positron diffraction and holography. Important design considerations of these experiments will be described. (author)

  15. Cosmic radiation

    Energy Technology Data Exchange (ETDEWEB)

    Capdevielle, J N

    1984-01-01

    First, the different instruments and techniques of cosmic particle detection are presented. Then the passage of the cosmic particles through the atmosphere is studied: electrons, photons, muons. The collective behavior of the different categories is also studied, the electromagnetic cascade is distinguished from the hadron cascade. Through the principal physical properties of the radiation and the medium, the ''mean'' aspects of the radiation are then successively dealt with out of the atmosphere, at different altitudes until the sea level, then at great depths. A chapter is devoted to cosmic radiation of more than 10,000 GeV, studied separately. Then solar radiation in universe is studied through their propagation in solar system and their origin. At last, the cosmic radiation effects are studied in environment (cosmic biophysics) and some applications of cosmic radiation are presented.

  16. On the average luminosity of electron positron collider and positron-producing energy

    International Nuclear Information System (INIS)

    Xie Jialin

    1985-01-01

    In this paper, the average luminosity of linac injected electron positron collider is investigated from the positron-producing energy point of view. When the energy of the linac injector is fixed to be less than the operating energy of the storage ring, it has been found that there exists a positron-producing energy to give optimum average luminosity. Two cases have been studied, one for an ideal storage ring with no single-beam instability and the other for practical storage ring with fast head-tail instability. The result indicates that there is a positron-producing energy corresponding to the minimum injection time, but this does not correspond to the optimum average luminosity for the practical storage rings. For Beijing Electron Positron Collider (BEPC), the positron-producing energy corresponding to the optimum average luminosity is about one tenth of the total injector energy

  17. Positron emission tomography

    International Nuclear Information System (INIS)

    Paans, A.M.J.

    1981-01-01

    Positron emitting radiopharmaceuticals have special applications in in-vivo studies of biochemical processes. The combination of a cyclotron for the production of radionuclides and a positron emission tomograph for the registration of the distribution of radioactivity in the body enables the measurement of local radioactivity concentration in tissues, and opens up new possibilities in the diagnosis and examination of abnormalities in the metabolism. The principles and procedures of positron emission tomography are described and the necessary apparatus considered, with emphasis on the positron camera. The first clinical applications using 55 Co bloemycine for tumor detection are presented. (C.F.)

  18. Interactions of cosmic rays in the atmosphere: growth curves revisited

    Energy Technology Data Exchange (ETDEWEB)

    Obermeier, A.; Boyle, P.; Müller, D. [Enrico Fermi Institute, University of Chicago, Chicago, IL 60637 (United States); Hörandel, J., E-mail: a.obermeier@astro.ru.nl [Radboud Universiteit Nijmegen, 6525-HP Nijmegen (Netherlands)

    2013-12-01

    Measurements of cosmic-ray abundances on balloons are affected by interactions in the residual atmosphere above the balloon. Corrections for such interactions are particularly important for observations of rare secondary particles such as boron, antiprotons, and positrons. These corrections either can be calculated if the relevant cross sections in the atmosphere are known or may be empirically determined by extrapolation of the 'growth curves', i.e., the individual particle intensities as functions of atmospheric depth. The growth-curve technique is particularly attractive for long-duration balloon flights where the periodic daily altitude variations permit rather precise determinations of the corresponding particle intensity variations. We determine growth curves for nuclei from boron (Z = 5) to iron (Z = 26) using data from the 2006 Arctic balloon flight of the TRACER detector for cosmic-ray nuclei, and we compare the growth curves with predictions from published cross section values. In general, good agreement is observed. We then study the boron/carbon abundance ratio and derive a simple and energy-independent correction term for this ratio. We emphasize that the growth-curve technique can be developed further to provide highly accurate tests of published interaction cross section values.

  19. Cosmic Education: Formation of a Planetary and Cosmic Personality

    Directory of Open Access Journals (Sweden)

    Bazaluk Oleg

    2012-04-01

    Full Text Available The major stages of development of cosmic pedagogy have been researched. Based on the achievements of the modern neurosciences as well as of psychology, cosmology, and philosophy, the authors provide their reasoning for the cosmic education and its outlooks for the educational systems of the world. Through the studies of how important human mind is for the Earth and the cosmos and by researching the evolution of human mind within the structure of the Universe, the authors create a more advanced scientific and philosophic basis for the cosmic education where the subject is a comprehensive process of formation and directed progress of both an individual mind and a conglomerate of minds called the "psychospace". The cosmic education researches the permanent progress of the intelligent matter of the Earth. The purpose of the cosmic education has been determined as formation of a planetary and cosmic personality. According to the authors, a planetary and cosmic personality is a harmony of mind, soul, and body, and such harmony is directed to use the internal creative potential of mind to the benefit of the intelligent matter of the entire Earth and the cosmos. The properties of such a planetary and cosmic personality are being improved continuously; they are a sample (the ideal of the cosmic pedagogy and the image of a human being of the future. Through the usage of the entire potential and art of upbringing and educating, the cosmic pedagogy is called to embody the major properties of the image of a human being of the future in the new generations of minds and to form a planetary and cosmic personality capable of self-actualization to the benefit of the permanent progress of the intelligent matter.

  20. New techniques of positron annihilation

    International Nuclear Information System (INIS)

    1983-02-01

    Studies on new techniques of positron annihilation and its application to various fields are presented. First, production of slow positron and its characteristic features are described. The slow positron can be obtained from radioisotopes by using a positron moderator, proton beam bombardment on a boron target, and pair production by using an electron linear accelerator. Bright enhancement of the slow positron beam is studied. Polarized positron beam can be used for the study of the momentum distribution of an electron in ferromagnetic substances. Production of polarized positrons and measurements of polarization are discussed. Various phases of interaction between slow positrons and atoms (or molecules) are described. A comparative study of electron scavenging effects on luminescence and on positronium formation in cyclohexane is presented. The positron annihilation phenomena are applicable for the surface study. The microscopic information on the surface of porous material may be obtained. The slow positrons are also useful for the surface study. Production and application of slow muon (positive and negative) are presented in this report. (Kato, T.)

  1. Solvated Positron Chemistry - Positron Reactions with Pseudo-Halide Ions in Water

    DEFF Research Database (Denmark)

    Mogensen, O. E.; Pedersen, Niels Jørgen; Andersen, Jan Rud

    1982-01-01

    The hydrated positron e+aq reactions with SCN−, OCN−, CN−, S2− were studied by means of the angular correlation technique. The positron forms bound states with SCN−, CN−, and S2− but not with OCN−. Apparently, the e+aq reaction with SH− results in a positron bound state with S2−. It was difficult...

  2. The PAMELA experiment on satellite and its capability in cosmic rays measurements

    CERN Document Server

    Adriani, O; Barbarino, G C; Barbier, L M; Bartalucci, S; Bazilevskaja, G; Bellotti, R; Bertazzoni, S; Bidoli, V; Boezio, M; Bogomolov, E A; Bonechi, L; Bonvicini, V; Boscherini, M; Bravar, U; Cafagna, F; Campana, D; Carlson, Per J; Casolino, M; Castellano, M; Castellini, G; Christian, E R; Ciacio, F; Circella, M; D'Alessandro, R; De Marzo, C N; De Pascale, M P; Finetti, N; Furano, G; Gabbanini, A; Galper, A M; Giglietto, N; Grandi, M; Grigorieva, A; Guarino, F; Hof, M; Koldashov, S V; Korotkov, M G; Krizmanic, J F; Krutkov, S; Lund, J; Marangelli, B; Marino, L; Menn, W; Mikhailov, V V; Mirizzi, N; Mitchell, J W; Mocchiutti, E; Moiseev, A A; Morselli, A; Mukhametshin, R; Ormes, J F; Osteria, G; Ozerov, J V; Papini, P; Pearce, M; Perego, A; Piccardi, S; Picozza, P; Ricci, M; Salsano, A; Schiavon, Paolo; Scian, G; Simon, M; Sparvoli, R; Spataro, B; Spillantini, P; Spinelli, P; Stephens, S A; Stochaj, S J; Stozhkov, Yu I; Straulino, S; Streitmatter, R E; Taccetti, F; Tesi, M; Vacchi, A; Vannuccini, E; Vasiljev, G; Vignoli, V; Voronov, S A; Yurkin, Y; Zampa, G; Zampa, N

    2002-01-01

    The PAMELA equipment will be assembled in 2001 and installed on board the Russian satellite Resurs. PAMELA is conceived mainly to study the antiproton and positron fluxes in cosmic rays up to high energy (190 GeV for p-bar and 270 GeV for e sup +) and to search antinuclei, up to 30 GeV/n, with a sensitivity of 10 sup - sup 7 in the He-bar/He ratio. The PAMELA telescope consists of: a magnetic spectrometer made up of a permanent magnet system equipped with double sided microstrip silicon detectors; a transition radiation detector made up of active layers of proportional straw tubes interleaved with carbon fibre radiators; and a silicon-tungsten imaging calorimeter made up of layers of tungsten absorbers and silicon detector planes. A time-of-flight system and anti-coincidence counters complete the PAMELA equipment. In the past years, tests have been done on each subdetector of PAMELA; the main results are presented and their implications on the anti-particles identification capability in cosmic rays are discus...

  3. Positron-Induced Luminescence

    Science.gov (United States)

    Stenson, E. V.; Hergenhahn, U.; Stoneking, M. R.; Pedersen, T. Sunn

    2018-04-01

    We report on the observation that low-energy positrons incident on a phosphor screen produce significantly more luminescence than electrons do. For two different wide-band-gap semiconductor phosphors (ZnS:Ag and ZnO:Zn), we compare the luminescent response to a positron beam with the response to an electron beam. For both phosphors, the positron response is significantly brighter than the electron response, by a factor that depends strongly on incident energy (0-5 keV). Positrons with just a few tens of electron-volts of energy (for ZnS:Ag) or less (for ZnO:Zn) produce as much luminescence as is produced by electrons with several kilo-electron-volts. We attribute this effect to valence band holes and excited electrons produced by positron annihilation and subsequent Auger processes. These results demonstrate a valuable approach for addressing long-standing questions about luminescent materials.

  4. Analytical Model for Estimating Terrestrial Cosmic Ray Fluxes Nearly Anytime and Anywhere in the World: Extension of PARMA/EXPACS.

    Directory of Open Access Journals (Sweden)

    Tatsuhiko Sato

    Full Text Available By extending our previously established model, here we present a new model called "PHITS-based Analytical Radiation Model in the Atmosphere (PARMA version 3.0," which can instantaneously estimate terrestrial cosmic ray fluxes of neutrons, protons, ions with charge up to 28 (Ni, muons, electrons, positrons, and photons nearly anytime and anywhere in the Earth's atmosphere. The model comprises numerous analytical functions with parameters whose numerical values were fitted to reproduce the results of the extensive air shower (EAS simulation performed by Particle and Heavy Ion Transport code System (PHITS. The accuracy of the EAS simulation was well verified using various experimental data, while that of PARMA3.0 was confirmed by the high R2 values of the fit. The models to be used for estimating radiation doses due to cosmic ray exposure, cosmic ray induced ionization rates, and count rates of neutron monitors were validated by investigating their capability to reproduce those quantities measured under various conditions. PARMA3.0 is available freely and is easy to use, as implemented in an open-access software program EXcel-based Program for Calculating Atmospheric Cosmic ray Spectrum (EXPACS. Because of these features, the new version of PARMA/EXPACS can be an important tool in various research fields such as geosciences, cosmic ray physics, and radiation research.

  5. Positron Factory project

    Energy Technology Data Exchange (ETDEWEB)

    Okada, Sohei; Sunaga, Hiromi; Kaneko, Hirohisa; Kawasuso, Atsuo; Masuno, Shin-ichi; Takizawa, Haruki; Yotsumoto, Keiichi [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment

    1997-03-01

    We have started drafting a construction program for the Positron Factory, in which linac-based intense monoenergetic positron beams are planned to be applied for materials science, biotechnology and basic physics and chemistry. A technical survey study confirmed the feasibility of manufacturing a dedicated electron linac of 100 kW class with a beam energy of 100 MeV, which will produce a world-highest monoenergetic positron beam of more than 10{sup 10}/sec in intensity. A self-driven rotating converter (electrons to positrons and photons) suitable for the high power electron beam was devised and successfully tested. The practicability of simultaneous extraction of multi-channel monoenergetic positron beams with multiple moderator assemblies, which had been originated on the basis of a Monte Carlo simulation, was demonstrated by an experiment using an electron linac. An efficient moderator structure, which is composed of honeycomb-like assembled moderator foils and reflectors, is also proposed. (author)

  6. KEK-IMSS Slow Positron Facility

    Energy Technology Data Exchange (ETDEWEB)

    Hyodo, T; Wada, K; Yagishita, A; Kosuge, T; Saito, Y; Kurihara, T; Kikuchi, T; Shirakawa, A; Sanami, T; Ikeda, M; Ohsawa, S; Kakihara, K; Shidara, T, E-mail: toshio.hyodo@kek.jp [High Energy Accelerator Research Organization (KEK) 1-1 Oho, Tsukuba, Ibaraki, 305-0801 (Japan)

    2011-12-01

    The Slow Positron Facility at the Institute of Material Structure Science (IMSS) of High Energy Accelerator Research Organization (KEK) is a user dedicated facility with an energy tunable (0.1 - 35 keV) slow positron beam produced by a dedicated 55MeV linac. The present beam line branches have been used for the positronium time-of-flight (Ps-TOF) measurements, the transmission positron microscope (TPM) and the photo-detachment of Ps negative ions (Ps{sup -}). During the year 2010, a reflection high-energy positron diffraction (RHEPD) measurement station is going to be installed. The slow positron generator (converter/ moderator) system will be modified to get a higher slow positron intensity, and a new user-friendly beam line power-supply control and vacuum monitoring system is being developed. Another plan for this year is the transfer of a {sup 22}Na-based slow positron beam from RIKEN. This machine will be used for the continuous slow positron beam applications and for the orientation training of those who are interested in beginning researches with a slow positron beam.

  7. Positron deposition in plasmas by positronium beam ionization and transport of positrons in tokamak plasmas

    International Nuclear Information System (INIS)

    Murphy, T.J.

    1986-11-01

    In a recently proposed positron transport experiment, positrons would be deposited in a fusion plasma by forming a positronium (Ps) beam and passing it through the plasma. Positrons would be deposited as the beam is ionized by plasma ions and electrons. Radial transport of the positrons to the limiter could then be measured by detecting the gamma radiation produced by annihilation of positrons with electrons in the limiter. This would allow measurements of the transport of electron-mass particles and might shed some light on the mechanisms of electron transport in fusion plasmas. In this paper, the deposition and transport of positrons in a tokamak are simulated and the annihilation signal determined for several transport models. Calculations of the expected signals are necessary for the optimal design of a positron transport experiment. There are several mechanisms for the loss of positrons besides transport to the limiter. Annihilation with plasma electrons and reformation of positronium in positron-hydrogen collisions are two such processes. These processes can alter the signal and place restrictions ons on the plasma conditions in which positron transport experiments can be effectively performed

  8. A transmission positron microscope and a scanning positron microscope being built at KEK, Japan

    International Nuclear Information System (INIS)

    Doyama, M.; Inoue, M.; Kogure, Y.; Kurihara, T.; Yagishita, A.; Shidara, T.; Nakahara, K.; Hayashi, Y.; Yoshiie, T.

    2001-01-01

    This paper reports the plans of positron microscopes being built at KEK (High Energy Accelerator Research Organization), Tsukuba, Japan improving used electron microscopes. The kinetic energies of positron produced by accelerators or by nuclear decays have not a unique value but show a spread over in a wide range. Positron beam will be guided near electron microscopes, a transmission electron microscope (JEM100S) and a scanning electron microscope (JSM25S). Positrons are slowed down by a tungsten foil, accelerated and focused on a nickel sheet. The monochromatic focused beam will be injected into an electron microscope. The focusing of positrons and electrons is achieved by magnetic system of the electron microscopes. Imaging plates are used to record positron images for the transmission electron microscope. (orig.)

  9. Positron emission computed tomography

    International Nuclear Information System (INIS)

    Grover, M.; Schelbert, H.R.

    1985-01-01

    Regional mycardial blood flow and substrate metabolism can be non-invasively evaluated and quantified with positron emission computed tomography (Positron-CT). Tracers of exogenous glucose utilization and fatty acid metabolism are available and have been extensively tested. Specific tracer kinetic models have been developed or are being tested so that glucose and fatty acid metabolism can be measured quantitatively by Positron-CT. Tracers of amino acid and oxygen metabolism are utilized in Positron-CT studies of the brain and development of such tracers for cardiac studies are in progress. Methods to quantify regional myocardial blood flow are also being developed. Previous studies have demonstrated the ability of Positron-/CT to document myocardial infarction. Experimental and clinical studies have begun to identify metabolic markers of reversibly ischemic myocardium. The potential of Positron-CT to reliably detect potentially salvageable myocardium and, hence, to identify appropriate therapeutic interventions is one of the most exciting applications of the technique

  10. Theory, development, and applications of the scanning positron microbeam and positron reemission microscope

    International Nuclear Information System (INIS)

    Brandes, G.R.

    1990-01-01

    The theory, design, development, and applications of two new imaging instruments, the scanning positron microbeam (SPM) and positron reemission microscope (PRM), are discussed. The SPM consists of a sectored lens which focuses and rasters the positrons from the beam across the sample. The results of rastering the 10μm x 50μm beam across a test grid demonstrate the SPM's ability to scan a 500μm diameter region and to resolve features with ∼ 5μm resolution. The SPM was used to examine the location of defects in a Si-on-SiO 2 sample. Possible applications to three dimensional defect spectroscopy and the observation of small samples are considered. In the PRM, the positrons from the brightness-enhanced beam are focused at 5keV to an 8/Am diameter spot (FWHM) onto a thin metal single crystal. An image of the opposing side of the film is formed by accelerating and focusing the reemitted thermalized positrons with a cathode lens objective and a projector lens. The final image (real) is a record of the thermal positron emission intensity versus position. Images of surface and subsurface defect structures, taken at magnifications up to 4400x and with a resolution up to 80nm, are presented and discussed. The ultimate resolution capabilities and possible applications of the PRM are examined. The implantation and diffusion process of positrons was studied with the PRM by examining the positron emission profile of 3-9keV positrons implanted into a 2200 angstrom thick Ni single crystal

  11. Positron studies in catalysis research

    International Nuclear Information System (INIS)

    1994-01-01

    During the past eight months, the authors have made progress in several areas relevant to the eventual use of positron techniques in catalysis research. They have come closer to the completion of their positron microscope, and at the same time have performed several studies in their non-microscopic positron spectrometer which should ultimately be applicable to catalysis. The current status of the efforts in each of these areas is summarized in the following sections: Construction of the positron microscope (optical element construction, data collection software, and electronic sub-assemblies); Doppler broadening spectroscopy of metal silicide; Positron lifetime spectroscopy of glassy polymers; and Positron lifetime measurements of pore-sizes in zeolites

  12. 22 Na positron source for annihilation positron spectroscopy

    International Nuclear Information System (INIS)

    Cimpeanu, Catalina; Craciun, L.; Dragulescu, E.; Dudu, D.; Racolta, P. M.; Voiculescu, Dana; Miron, N.

    2003-01-01

    To extend the nuclear physics applications and to perform the study of vacancy - type defects in metals, semiconductors, polymers etc., we decided to promote positron annihilation techniques. In order to achieve this goal we started a project of dedicated positron sources produced at the IFIN-HH U-120 Cyclotron. We have used the nuclear reaction: 24 Mg(d,α) 22 Na with deuterons of 13 MeV energy. The paper presents the main characteristics of this procedure, as follows: general conditions asked for 22 NaCl sources, reactive chamber and characteristics of Mg target, parameters for the irradiation, radiochemical procedures for separating Na from Mg after the irradiation and geometrical or mechanical requirements for dedicated NaCl source for positron annihilation spectrometry. In the e + lifetime measurements, the e + end - start signals may be obtained from prompt γ -quanta emitted from the NaCl source (1. 275 MeV photons). The 22 NaCl stock solution obtained by radiochemical separation will be kept in quartz sealed ampoules in dry places and will be dropped between the study materials before the use in positron spectrometry. (authors)

  13. Slow positron applications at slow positron facility of institute of materials structure science, KEK

    Science.gov (United States)

    Hyodo, Toshio; Mochizuki, Izumi; Wada, Ken; Toge, Nobukazu; Shidara, Tetsuo

    2018-05-01

    Slow Positron Facility at High Energy Accelerator Research Organization (KEK) is a user dedicated facility with an energy-tunable (0.1 - 35 keV) slow positron beam created by a dedicated ˜ 50 MeV linac. It operates in a short pulse (width 1-12 ns, variable, 5×106 e+/s) and a long pulse (width 1.2 µs, 5×107 e+/s) modes of 50 Hz. High energy positrons from pair creation are moderated by reemission after thermalization in W foils. The reemitted positrons are then electrostatically accelerated to a desired energy up to 35 keV and magnetically transported. A pulse-stretching section (pulse stretcher) is installed in the middle of the beamline. It stretches the slow positron pulse for the experiments where too many positrons annihilating in the sample at the same time has to be avoided. Four experiment stations for TRHEPD (total-reflection high-energy positron diffraction), LEPD (low-energy positron diffraction), Ps- (positronium negative ion), and Ps-TOF (positronium time-of-flight) experiments are connected to the beamline branches, SPF-A3, SPF-A4, SPF-B1 and SPF-B2, respectively. Recent results of these stations are briefly described.

  14. Positron effective mass in silicon

    International Nuclear Information System (INIS)

    Panda, B.K.; Shan, Y.Y.; Fung, S.; Beling, C.D.

    1995-01-01

    The positron effective mass in Si is obtained from the first-principles calculations along various crystallographic directions. The effect of electron-positron correlation on the band mass is examined in this work. A positron pseudopotential scheme is worked out to calculate the isotropic band mass without explicitly solving the band energy. The effective mass 1.46m obtained as a sum of band mass and the positron-plasmon interaction compares very well with 1.5m obtained from the positron mobility data

  15. Positron emission tomography

    International Nuclear Information System (INIS)

    Iio, Masahiro

    1982-01-01

    Utilization of positron emission tomography was reviewed in relation to construction and planned construction of small-size medical cyclotrons, planned construction of positron cameras and utilization of short-lived radionuclides. (Chiba, N.)

  16. Generation of a high-brightness pulsed positron beam for the Munich scanning positron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Piochacz, Christian

    2009-11-20

    Within the present work the prerequisites for the operation of the Munich scanning positron microscope (SPM) at the high intense neutron induced positron source Munich (NEPOMUC) were established. This was accomplished in two steps: Firstly, a re-moderation device was installed at the positron beam facility NEPOMUC, which enhances the brightness of the positron beam for all connected experiments. The second step was the design, set up and initial operation of the SPM interface for the high efficient conversion of the continuous beam into a bunched beam. The in-pile positron source NEPOMUC creates a positron beam with a diameter of typically 7 mm, a kinetic energy of 1 keV and an energy spread of 50 eV. The NEPOMUC re-moderator generates from this beam a low energy positron beam (20 - 200 eV) with a diameter of less than 2 mm and an energy spread well below 2.5 eV. This was achieved with an excellent total efficiency of 6.55{+-}0.25 %. The re-moderator was not only the rst step to implement the SPM at NEPOMUc, it enables also the operation of the pulsed low energy positron beam system (PLEPS). Within the present work, at this spectrometer rst positron lifetime measurements were performed, which revealed the defect types of an ion irradiated uranium molybdenum alloy. Moreover, the instruments which were already connected to the positron beam facility bene ts considerably of the high brightness enhancement. In the new SPM interface an additional re-moderation stage enhances the brightness of the beam even more and will enable positron lifetime measurements at the SPM with a lateral resolution below 1 {mu}m. The efficiency of the re-moderation process in this second stage was 24.5{+-}4.5 %. In order to convert high efficiently the continuous positron beam into a pulsed beam with a repetition rate of 50 MHz and a pulse duration of less than 50 ps, a sub-harmonic pre-bucher was combined with two sine wave bunchers. Furthermore, the additional re-moderation stage of the

  17. Generation of a high-brightness pulsed positron beam for the Munich scanning positron microscope

    International Nuclear Information System (INIS)

    Piochacz, Christian

    2009-01-01

    Within the present work the prerequisites for the operation of the Munich scanning positron microscope (SPM) at the high intense neutron induced positron source Munich (NEPOMUC) were established. This was accomplished in two steps: Firstly, a re-moderation device was installed at the positron beam facility NEPOMUC, which enhances the brightness of the positron beam for all connected experiments. The second step was the design, set up and initial operation of the SPM interface for the high efficient conversion of the continuous beam into a bunched beam. The in-pile positron source NEPOMUC creates a positron beam with a diameter of typically 7 mm, a kinetic energy of 1 keV and an energy spread of 50 eV. The NEPOMUC re-moderator generates from this beam a low energy positron beam (20 - 200 eV) with a diameter of less than 2 mm and an energy spread well below 2.5 eV. This was achieved with an excellent total efficiency of 6.55±0.25 %. The re-moderator was not only the rst step to implement the SPM at NEPOMUc, it enables also the operation of the pulsed low energy positron beam system (PLEPS). Within the present work, at this spectrometer rst positron lifetime measurements were performed, which revealed the defect types of an ion irradiated uranium molybdenum alloy. Moreover, the instruments which were already connected to the positron beam facility bene ts considerably of the high brightness enhancement. In the new SPM interface an additional re-moderation stage enhances the brightness of the beam even more and will enable positron lifetime measurements at the SPM with a lateral resolution below 1 μm. The efficiency of the re-moderation process in this second stage was 24.5±4.5 %. In order to convert high efficiently the continuous positron beam into a pulsed beam with a repetition rate of 50 MHz and a pulse duration of less than 50 ps, a sub-harmonic pre-bucher was combined with two sine wave bunchers. Furthermore, the additional re-moderation stage of the SPM

  18. Positron sources for electron-positron colliders application to the ILC and CLIC

    CERN Multimedia

    CERN. Geneva

    2008-01-01

    The increased demanding qualities for positron sources dedicated to e+e- colliders pushed on investigations oriented on new kinds of e+ sources. The different kinds of positron sources polarized and no polarized are considered. Their main features (intensity, emittance) are described and analysed. Comparison between the different sources is worked out. The characteristics of the positron beam available in the collision point are greatly depending on the capture device and on the positron accelerator. Different kinds of capture systems are considered and their qualities, compared. Intense positron sources which are necessary for the colliders require intense incident beams (electrons or photons). The large number of pairs created in the targets leads to important energy deposition and so, thermal heating, which associated to temperature gradients provoke mechanical stresses often destructive. Moreover, the important Coulomb collisions, can affect the atomic structure in crystal targets and the radiation resist...

  19. High current pulsed positron microprobe

    International Nuclear Information System (INIS)

    Howell, R.H.; Stoeffl, W.; Kumar, A.; Sterne, P.A.; Cowan, T.E.; Hartley, J.

    1997-01-01

    We are developing a low energy, microscopically focused, pulsed positron beam for defect analysis by positron lifetime spectroscopy to provide a new defect analysis capability at the 10 10 e + s -l beam at the Lawrence Livermore National Laboratory electron linac. When completed, the pulsed positron microprobe will enable defect specific, 3-dimensional maps of defect concentrations with sub-micron resolution of defect location. By coupling these data with first principles calculations of defect specific positron lifetimes and positron implantation profiles we will both map the identity and concentration of defect distributions

  20. Efficient Cryosolid Positron Moderators

    Science.gov (United States)

    2012-08-01

    table layout Figure 21 shows the integration of the IR spectroscopy optics with the positron Moderation and Annihilation vacuum chambers on the...Characterization of Cryogenic Moderators The application of Matrix Isolation Spectroscopy (MIS) to characterizing cryogenic solid positron ...Matrix Isolation Spectroscopy capability into our Positron Moderation apparatus, which enables spectroscopic characterization of the cryogenic

  1. Positron annihilation in a metal-oxide semiconductor studied by using a pulsed monoenergetic positron beam

    Science.gov (United States)

    Uedono, A.; Wei, L.; Tanigawa, S.; Suzuki, R.; Ohgaki, H.; Mikado, T.; Ohji, Y.

    1993-12-01

    The positron annihilation in a metal-oxide semiconductor was studied by using a pulsed monoenergetic positron beam. Lifetime spectra of positrons were measured as a function of incident positron energy for a polycrystalline Si(100 nm)/SiO2(400 nm)/Si specimen. Applying a gate voltage between the polycrystalline Si film and the Si substrate, positrons implanted into the specimen were accumulated at the SiO2/Si interface. From the measurements, it was found that the annihilation probability of ortho-positronium (ortho-Ps) drastically decreased at the SiO2/Si interface. The observed inhibition of the Ps formation was attributed to an interaction between positrons and defects at the SiO2/Si interface.

  2. Observation of a VHE Cosmic-Ray Flare-Signal with the L3+C Muon Spectrometer

    CERN Document Server

    Adriani, O; Aziz, T; Bähr, J; Banerjee, S; Becattini, F; Bellucci, L; Betev, B L; Blaising, J J; Bobbink, G J; Bottai, S; Bourilkov, D; Cartacci, A; Chemarin, M; Chen, G; Chen, G M; Chen, H S; Chiarusi, T; Coignet, G; Ding, L K; Duran, I; Eline, A; El Mamouni, H; Faber, G; Fay, J; Filthaut, F; Ganguli, S N; Gong, Z F; Grabosch, H J; Groenstege, H; Guo, Y N; Gupta, S; Gurtu, A; Haller, Ch; Hayashi, Y; He, Z X; Hebbeker, T; Herve, A; Hofer, H; Hoferjun, H; Huo, A X; Ito, N; Jing, C L; Jones, L W; Kantserov, V; Kawakami, S; Kittel, W; König, A C; Kok, E; Kuang, H H; Kuijpers, J; Ladron de Guevara, P; Le Coultre, P; Lei, Y; Leich, H; Leiste, R; Li, L; Li, Z C; Liu, Z A; Lohmann, W; Lu, Y S; Ma, W G; Ma, X H; Ma, Y Q; Mele, S; Meng, X W; Meschini, M; Metzger, W J; van Mil, A; Milcent, H; Mohanty, G B; Monteleoni, B; Nahnhauer, R; Naumov, V A; Nowak, H; Parriaud, J -F; Pauss, F; Petersen, B; Pieri, M; Pohl, M; Pojidaev, V; Qing, C R; Ramelli, R; Ranieri, R; Ravindran, K C; Rewiersma, P; Riemann, S; Rojkov, A; Romero, L; Schmitt, V; Schoeneich, B; Schotanus, D J; Shen, C Q; Spillantini, P; Sulanke, H; Tang, X W; Timmermans, C; Tonwar, S C; Trowitzsch, G; Unger, M; Verkooijen, H; Van de Walle, R T; Vogt, H; Wang, R G; Wang, Q; Wang, X L; Wang, X W; Wang, Z M; Wijk, R van; Wijnen, T A M; Wilkens, H; Xu, Y P; Xu, J S; Xu, Z Z; Yang, C G; Yang, X F; Yao, Z G; Yu, Z Q; Zhang, C; Zhang, F; Zhang, J; Zhang, S; Zhou, S J; Zhu, G Y; Zhu, Q Q; Zhuang, H L; Zwart, A N M

    2010-01-01

    The data collected by the L3+C muon spectrometer at the CERN Large Electron-Positron collider, LEP, have been used to search for short duration signals emitted by cosmic point sources. A sky survey performed from July to November 1999 and from April to November 2000 has revealed one single flux enhancement (chance probability = 2.6X10^{-3}) between the 17th and 20th of August 2000 from a direction with a galactic longitude of (265.02+-0.42)^° and latitude of (55.58+-0.24)^°. The energy of the detected muons was above 15 GeV.

  3. 22 Na positron source for annihilation positron spectroscopy

    International Nuclear Information System (INIS)

    Cimpeanu, Catalina; Craciun, L.; Dragulescu, E.; Dudu, D.; Racolta, P.M.; Voiculescu, Dana; Miron, N.

    2002-01-01

    To extend the nuclear physics applications and to perform the study of vacancy - type defects in metals, semiconductors, polymers etc., we decided to promote positron annihilation techniques. In order to achieve this goal we started a project of dedicated positron sources produced at the IFIN-HH U-120 Cyclotron. We have used the nuclear reaction 24 Mg(d,α) 22 Na and deuterons of 13 MeV energy. The paper presents the main steps of this procedure like: general conditions required for 22 NaCl sources, reactive chamber and characteristics of Mg target, parameters for the irradiation, radiochemical procedures to separate Na from Mg after the irradiation and geometrical or mechanical requirements for dedicated NaCl source for positron annihilation spectrometry. In the e + lifetime measurements the e + 'death - stop' signals are always provided by γ - quanta generated by the e + e - annihilation and the 'birth - start' signals may be obtained from 'prompt' γ - quanta emitted from the NaCl source (the 1.275 MeV photons). The 22 NaCl stock solution obtained by radiochemical separation will be kept in the sealed quartz vials in dry places and will be dropped between the studied materials before use in positron spectrometry. (authors)

  4. Positron Beam Characteristics at NEPOMUC Upgrade

    Science.gov (United States)

    Hugenschmidt, C.; Ceeh, H.; Gigl, T.; Lippert, F.; Piochacz, C.; Reiner, M.; Schreckenbach, K.; Vohburger, S.; Weber, J.; Zimnik, S.

    2014-04-01

    In 2012, the new neutron induced positron source NEPOMUC upgrade was put into operation at FRMII. Major changes have been made to the source which consists of a neutron-γ-converter out of Cd and a Pt foil structure for electron positron pair production and positron moderation. The new design leads to an improvement of both intensity and brightness of the mono-energetic positron beam. In addition, the application of highly enriched 113Cd as neutron-γ-converter extends the lifetime of the positron source to 25 years. A new switching and remoderation device has been installed in order to allow toggling from the high-intensity primary beam to a brightness enhanced remoderated positron beam. At present, an intensity of more than 109 moderated positrons per second is achieved at NEPOMUC upgrade. The main characteristics are presented which comprise positron yield and beam profile of both the primary and the remoderated positron beam.

  5. Positron emission tomography

    International Nuclear Information System (INIS)

    Wienhard, K.; Heiss, W.D.

    1984-01-01

    The principles and selected clinical applications of positron emission tomography are described. In this technique a chemical compound is labeled with a positron emitting isotope and its biochemical pathway is traced by coincidence detection of the two annihilation photons. The application of the techniques of computed tomography allows to reconstruct the spatial distribution of the radioactivity within a subject. The 18 F-deoxyglucose method for quantitative measurement of local glucose metabolism is discussed in order to illustrate the possibilities of positron emission tomography to record physiological processes in vivo. (orig.) [de

  6. Application of mathematical removal of positron range blurring in positron emission tomography

    International Nuclear Information System (INIS)

    Haber, S.F.; Derenzo, S.E.; Uber, D.

    1990-01-01

    The range of positrons in tissue is an important limitation to the ultimate spatial resolution achievable in positron emission tomography. In this work the authors have applied a Fourier deconvolution technique to remove range blurring in images taken by the Donner 600-crystal positron tomograph. Using phantom data, the authors have found significant improvement in the image quality and the FWHM for both 68 Ga and 82 Rb. These were successfully corrected so that the images and FWHM almost matched those of 18 F which has negligible positron range. However, statistical noise was increased by the deconvolution process and it was not practical to recover the full spatial resolution of the tomograph

  7. Electron anisotropy: A tool to discriminate dark matter in cosmic rays

    International Nuclear Information System (INIS)

    Borriello, Enrico; Maccione, Luca; Cuoco, Alessandro

    2012-01-01

    Indirect searches of particle Dark Matter (DM) with high energy Cosmic Rays (CR) are typically affected by large uncertainties. We show that, on the contrary, the DM intrinsic degree of anisotropy in the arrival directions of high energy CR electrons and positrons (CRE) is basically model independent and offers a straightforward criterion to discriminate among CRE from DM or from local discrete sources, like e.g. pulsars. In particular, in absence of the latter, DM sets the maximum degree of total anisotropy. As a consequence, if a larger anisotropy is detected, this would constitute an unambiguous evidence for the presence of astrophysical local discrete CRE sources. The Fermi-LAT will be able to probe such scenarios in the next years.

  8. Positron Annihilation in Insulating Materials

    International Nuclear Information System (INIS)

    Asoka-Kumar, P; Sterne, PA

    2002-01-01

    We describe positron results from a wide range of insulating materials. We have completed positron experiments on a range of zeolite-y samples, KDP crystals, alkali halides and laser damaged SiO 2 . Present theoretical understanding of positron behavior in insulators is incomplete and our combined theoretical and experimental approach is aimed at developing a predictive understanding of positrons and positronium annihilation characteristics in insulators. Results from alkali halides and alkaline-earth halides show that positrons annihilate with only the halide ions, with no apparent contribution from the alkali or alkaline-earth cations. This contradicts the results of our existing theory for metals, which predicts roughly equal annihilation contributions from cation and anion. We also present result obtained using Munich positron microprobe on laser damaged SiO 2 samples

  9. Applications of slow positrons to cancer research: Search for selectivity of positron annihilation to skin cancer

    International Nuclear Information System (INIS)

    Jean, Y.C.; Li Ying; Liu Gaung; Chen, Hongmin; Zhang Junjie; Gadzia, Joseph E.

    2006-01-01

    Slow positrons and positron annihilation spectroscopy (PAS) have been applied to medical research in searching for positron annihilation selectivity to cancer cells. We report the results of positron lifetime and Doppler broadening energy spectroscopies in human skin samples with and without cancer as a function of positron incident energy (up to 8 μm depth) and found that the positronium annihilates at a significantly lower rate and forms at a lower probability in the samples having either basal cell carcinoma (BCC) or squamous cell carcinoma (SCC) than in the normal skin. The significant selectivity of positron annihilation to skin cancer may open a new research area of developing positron annihilation spectroscopy as a novel medical tool to detect cancer formation externally and non-invasively at the early stages

  10. Applications of slow positrons to cancer research: Search for selectivity of positron annihilation to skin cancer

    Energy Technology Data Exchange (ETDEWEB)

    Jean, Y.C. [Department of Chemistry, University of Missouri-Kansas City, 205 Spenscer Chemistry Building, 5009 Rockhill Road, Kansas City, MO 64110 (United States)]. E-mail: jeany@umkc.edu; Li Ying [Department of Chemistry, University of Missouri-Kansas City, 205 Spenscer Chemistry Building, 5009 Rockhill Road, Kansas City, MO 64110 (United States); Liu Gaung [Department of Chemistry, University of Missouri-Kansas City, 205 Spenscer Chemistry Building, 5009 Rockhill Road, Kansas City, MO 64110 (United States); Chen, Hongmin [Department of Chemistry, University of Missouri-Kansas City, 205 Spenscer Chemistry Building, 5009 Rockhill Road, Kansas City, MO 64110 (United States); Zhang Junjie [Department of Chemistry, University of Missouri-Kansas City, 205 Spenscer Chemistry Building, 5009 Rockhill Road, Kansas City, MO 64110 (United States); Gadzia, Joseph E. [Dermatology, Department of Internal Medicine, University of Kansas Medical Center, Kansas City, KS 66103 (United States); Kansas Medical Clinic, Topeka, KS 66614 (United States)

    2006-02-28

    Slow positrons and positron annihilation spectroscopy (PAS) have been applied to medical research in searching for positron annihilation selectivity to cancer cells. We report the results of positron lifetime and Doppler broadening energy spectroscopies in human skin samples with and without cancer as a function of positron incident energy (up to 8 {mu}m depth) and found that the positronium annihilates at a significantly lower rate and forms at a lower probability in the samples having either basal cell carcinoma (BCC) or squamous cell carcinoma (SCC) than in the normal skin. The significant selectivity of positron annihilation to skin cancer may open a new research area of developing positron annihilation spectroscopy as a novel medical tool to detect cancer formation externally and non-invasively at the early stages.

  11. Positron lifetime measurements and positron-annihilation induced auger electron spectroscpy using slow positron beams; Teisoku yodenshi bimu wo mochiita yodenshi jumyo sokutei oyobi yodenshi shometsu reiki oje denshi bunko

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, R. [Electrotechnical Lab., Tsukuba (Japan)

    1996-02-20

    Slow positron beam with less than several eV can be controlled freely such as accelerating, throttling the beam size, shortening the pulse or making pulse with short time width and so forth. These low positron beams are applied to various measurements like Doppler broadening measurement of annihilation {gamma} rays or lifetime measurement of positron, and secondary particle measurements using positron microscope, positron electron ray diffraction, flight time method and so forth. In particular, these recent years, high intensity slow positron beams were possible using accelerators like electron linac and its application is increasing. In this report, pulse shortening method for high intensity slow positron beam, and incidence energy variable positron lifetime measurement method using this slow pulsed beam and flight time type positron-annihilation-induced auger electron spectroscopy are outlined. In future, these measurements can be possible to carry out with high resolution and also with high counting rate if higher intensity monochromatic excellent positron beam than present one is produced. 31 refs., 5 figs.

  12. LLNL pure positron plasma program

    International Nuclear Information System (INIS)

    Hartley, J.H.; Beck, B.R.; Cowan, T.E.; Howell, R.H.; McDonald, J.L.; Rohatgi, R.R.; Fajans, J.; Gopalan, R.

    1995-01-01

    Assembly and initial testing of the Positron Time-of-Flight Trap at the Lawrence Livermore National Laboratory (LLNL) Increase Pulsed Positron Facility has been completed. The goal of the project is to accumulate at high-density positron plasma in only a few seconds., in order to facilitate study that may require destructive diagnostics. To date, densities of at least 6 x 10 6 positrons per cm 3 have been achieved

  13. High resolution positron tomography

    International Nuclear Information System (INIS)

    Brownell, G.L.; Burnham, C.A.

    1982-01-01

    The limits of spatial resolution in practical positron tomography are examined. The four factors that limit spatial resolution are: positron range; small angle deviation; detector dimensions and properties; statistics. Of these factors, positron range may be considered the fundamental physical limitation since it is independent of instrument properties. The other factors are to a greater or lesser extent dependent on the design of the tomograph

  14. Key scientific problems from Cosmic Ray History

    Science.gov (United States)

    Lev, Dorman

    2016-07-01

    -1911, before CR were discovered). 8. Moreover, in the 1930s it was shown by investigations of West-East CR asymmetry that the largest part of primary CR must be positive energetic particles. Later, in the 1940s - 1950s, it was established by direct measurements at high altitudes on balloons and rockets that the most part of cosmic rays are energetic protons, about 10% He nuclei, 1% more heavy nuclei, 1% energetic electrons, and only about 1% energetic gamma rays. Nevertheless, the name 'cosmic rays' (for short, CR) continues to be used up to now (sometimes they are called astroparticles). 9. The importance of CR for fundamental science was understood in the 1930s - 1950s, when has been discovered the first antiparticle predicted by the Quantum Electrodynamics - positron (in 1932), and then muons (1937), pions, K+, K0 mesons (in 1947), Λ0, Ξ-, Σ+ hyperons (accordingly in 1951, 1952, 1953). Cosmic rays became considered as very important natural source of high and very high energies. 10. In 1940s-1950s formatted also geophysical and astrophysical aspects of CR research. In 1936, the Nobel Prize in Physics received Victor Hess for CR discovery and Charles Anderson for discovery of positrons in CR. Later, many other great scientists in CR research received Nobel Prizes.

  15. Positron emission tomography

    NARCIS (Netherlands)

    Paans, AMJ

    Positron Emission Tomography (PET) is a method for determining biochemical and physiological processes in vivo in a quantitative way by using radiopharmaceuticals labelled with positron emitting radionuclides as C-11, N-13, O-15 and F-18 and by measuring the annihilation radiation using a

  16. Positron confinement in embedded lithium nanoclusters

    Science.gov (United States)

    van Huis, M. A.; van Veen, A.; Schut, H.; Falub, C. V.; Eijt, S. W.; Mijnarends, P. E.; Kuriplach, J.

    2002-02-01

    Quantum confinement of positrons in nanoclusters offers the opportunity to obtain detailed information on the electronic structure of nanoclusters by application of positron annihilation spectroscopy techniques. In this work, positron confinement is investigated in lithium nanoclusters embedded in monocrystalline MgO. These nanoclusters were created by means of ion implantation and subsequent annealing. It was found from the results of Doppler broadening positron beam analysis that approximately 92% of the implanted positrons annihilate in lithium nanoclusters rather than in the embedding MgO, while the local fraction of lithium at the implantation depth is only 1.3 at. %. The results of two-dimensional angular correlation of annihilation radiation confirm the presence of crystalline bulk lithium. The confinement of positrons is ascribed to the difference in positron affinity between lithium and MgO. The nanocluster acts as a potential well for positrons, where the depth of the potential well is equal to the difference in the positron affinities of lithium and MgO. These affinities were calculated using the linear muffin-tin orbital atomic sphere approximation method. This yields a positronic potential step at the MgO||Li interface of 1.8 eV using the generalized gradient approximation and 2.8 eV using the insulator model.

  17. Stopped cosmic-ray muons in plastic scintillators on the surface and at the depth of 25 m.w.e

    International Nuclear Information System (INIS)

    Maletić, D; Dragić, A; Banjanac, R; Joković, D; Veselinović, N; Udovicić, V; Savić, M; Anicin, I; Puzović, J

    2013-01-01

    Cosmic ray muons stopped in 5 cm thick plastic scintillators at surface and at depth of 25 m.w.e are studied. Apart from the stopped muon rate we measured the spectrum of muon decay electrons and the degree of polarization of stopped muons. Preliminary results for the Michel parameter yield values lower than the currently accepted one, while the asymmetry between the numbers of decay positrons registered in the upper and lower hemispheres appear higher than expected on the basis of numerous earlier studies.

  18. Cosmic void clumps

    Science.gov (United States)

    Lares, M.; Luparello, H. E.; Garcia Lambas, D.; Ruiz, A. N.; Ceccarelli, L.; Paz, D.

    2017-10-01

    Cosmic voids are of great interest given their relation to the large scale distribution of mass and the way they trace cosmic flows shaping the cosmic web. Here we show that the distribution of voids has, in consonance with the distribution of mass, a characteristic scale at which void pairs are preferentially located. We identify clumps of voids with similar environments and use them to define second order underdensities. Also, we characterize its properties and analyze its impact on the cosmic microwave background.

  19. Simulation of the annihilation emission of galactic positrons; Modelisation de l'emission d'annihilation des positrons Galactiques

    Energy Technology Data Exchange (ETDEWEB)

    Gillard, W

    2008-01-15

    Positrons annihilate in the central region of our Galaxy. This has been known since the detection of a strong emission line centered on an energy of 511 keV in the direction of the Galactic center. This gamma-ray line is emitted during the annihilation of positrons with electrons from the interstellar medium. The spectrometer SPI, onboard the INTEGRAL observatory, performed spatial and spectral analyses of the positron annihilation emission. This thesis presents a study of the Galactic positron annihilation emission based on models of the different interactions undergone by positrons in the interstellar medium. The models are relied on our present knowledge of the properties of the interstellar medium in the Galactic bulge, where most of the positrons annihilate, and of the physics of positrons (production, propagation and annihilation processes). In order to obtain constraints on the positrons sources and physical characteristics of the annihilation medium, we compared the results of the models to measurements provided by the SPI spectrometer. (author)

  20. Observation of the thunderstorm-related ground cosmic ray flux variations by ARGO-YBJ

    Science.gov (United States)

    Bartoli, B.; Bernardini, P.; Bi, X. J.; Cao, Z.; Catalanotti, S.; Chen, S. Z.; Chen, T. L.; Cui, S. W.; Dai, B. Z.; D'Amone, A.; Danzengluobu; De Mitri, I.; D'Ettorre Piazzoli, B.; Di Girolamo, T.; Di Sciascio, G.; Feng, C. F.; Feng, Zhaoyang; Feng, Zhenyong; Gao, W.; Gou, Q. B.; Guo, Y. Q.; He, H. H.; Hu, Haibing; Hu, Hongbo; Iacovacci, M.; Iuppa, R.; Jia, H. Y.; Labaciren; Li, H. J.; Liu, C.; Liu, J.; Liu, M. Y.; Lu, H.; Ma, L. L.; Ma, X. H.; Mancarella, G.; Mari, S. M.; Marsella, G.; Mastroianni, S.; Montini, P.; Ning, C. C.; Perrone, L.; Pistilli, P.; Salvini, P.; Santonico, R.; Shen, P. R.; Sheng, X. D.; Shi, F.; Surdo, A.; Tan, Y. H.; Vallania, P.; Vernetto, S.; Vigorito, C.; Wang, H.; Wu, C. Y.; Wu, H. R.; Xue, L.; Yang, Q. Y.; Yang, X. C.; Yao, Z. G.; Yuan, A. F.; Zha, M.; Zhang, H. M.; Zhang, L.; Zhang, X. Y.; Zhang, Y.; Zhao, J.; Zhaxiciren; Zhaxisangzhu; Zhou, X. X.; Zhu, F. R.; Zhu, Q. Q.; D'Alessandro, F.; ARGO-YBJ Collaboration

    2018-02-01

    A correlation between the secondary cosmic ray flux and the near-earth electric field intensity, measured during thunderstorms, has been found by analyzing the data of the ARGO-YBJ experiment, a full coverage air shower array located at the Yangbajing Cosmic Ray Laboratory (4300 m a. s. l., Tibet, China). The counting rates of showers with different particle multiplicities (m =1 , 2, 3, and ≥4 ) have been found to be strongly dependent upon the intensity and polarity of the electric field measured during the course of 15 thunderstorms. In negative electric fields (i.e., accelerating negative charges downwards), the counting rates increase with increasing electric field strength. In positive fields, the rates decrease with field intensity until a certain value of the field EFmin (whose value depends on the event multiplicity), above which the rates begin increasing. By using Monte Carlo simulations, we found that this peculiar behavior can be well described by the presence of an electric field in a layer of thickness of a few hundred meters in the atmosphere above the detector, which accelerates/decelerates the secondary shower particles of opposite charge, modifying the number of particles with energy exceeding the detector threshold. These results, for the first time to our knowledge, give a consistent explanation for the origin of the variation of the electron/positron flux observed for decades by high altitude cosmic ray detectors during thunderstorms.

  1. Mining the bulk positron lifetime

    International Nuclear Information System (INIS)

    Aourag, H.; Guittom, A.

    2009-01-01

    We introduce a new approach to investigate the bulk positron lifetimes of new systems based on data-mining techniques. Through data mining of bulk positron lifetimes, we demonstrate the ability to predict the positron lifetimes of new semiconductors on the basis of available semiconductor data already studied. Informatics techniques have been applied to bulk positron lifetimes for different tetrahedrally bounded semiconductors in order to discover computational design rules. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Cosmic rays

    International Nuclear Information System (INIS)

    Tkachev, I.I.

    2014-01-01

    In this talk I will review results of cosmic ray observations at the highest energies. This year the new results on energy spectra, composition and the study of arrival directions of cosmic ray primaries came from the Telescope Array collaboration. I present these results in comparison with measurements done by other recent experiments and discuss their implications for the search of cosmic ray sources. Some related results in gamma-ray astronomy and selected recent advances in theory are also covered. (author)

  3. Solvated Positron Chemistry. Competitive Positron Reactions with Halide Ions in Water

    DEFF Research Database (Denmark)

    Christensen, Palle; Pedersen, Niels Jørgen; Andersen, J. R.

    1979-01-01

    It is shown by means of the angular correlation technique that the binding of positrons to halides is strongly influenced by solvation effects. For aqueous solutions we find increasing values for the binding energies between the halide and the positron with increasing mass of the halide...

  4. Signatures of SUSY dark matter at the LHC and in the spectra of cosmic rays

    International Nuclear Information System (INIS)

    Olzem, J.

    2007-01-01

    This thesis discusses the search for supersymmetry at the future Large Hadron Collider (LHC) and the ongoing construction of one of the four large LHC experiments, the Compact Muon Solenoid (CMS), and focuses on the detection of signals from the annihilation of supersymmetric dark matter in the spectra of cosmic rays. The final steps of assembly of 1061 silicon microstrip detector modules for the CMS tracker endcaps are performed at the 1. Physikalisches Institut B at the RWTH Aachen. A laser test facility for these modules was developed and is described in this thesis. In contrast to test procedures based only on the evaluation of pedestal and noise data, the test facility relies on the generation of signals in the silicon sensors by infrared laser illumination. The fully automatic test facility provides high throughput and easy operation for the series production of the modules. Its performance is validated by investigating a reference module with artificially prepared defects of three types: open wirebonds, short-circuited strips and pinholes. It is shown that all defects are clearly detected. In addition to defect detection, an indication for the type of defect is provided. In a further validation step, nine modules from a prototype series are investigated with the laser test facility. Confirming the earlier results on the reference module, defective strips are reliably identified. This thesis describes a novel approach of positron identification with the space-borne AMS-01 experiment, namely through the detection of bremsstrahlung conversion in a silicon microstrip detector. In order to obtain the highest positron selection efficiency possible, novel combinatorial track finding algorithms were developed, particularly optimized for the signature of converted bremsstrahlung. By applying restrictions on the invariant mass of particles the background to the positron sample is largely eliminated. The remaining background contamination is determined from large

  5. A model explaining neutrino masses and the DAMPE cosmic ray electron excess

    DEFF Research Database (Denmark)

    Fan, Yi Zhong; Huang, Wei Chih; Spinrath, Martin

    2018-01-01

    We propose a flavored U(1)eμ neutrino mass and dark matter (DM) model to explain the recent DArk Matter Particle Explorer (DAMPE) data, which feature an excess on the cosmic ray electron plus positron flux around 1.4 TeV. Only the first two lepton generations of the Standard Model are charged under...... the new U(1)eμ gauge symmetry. A vector-like fermion ψ, which is our DM candidate, annihilates into e± and μ± via the new gauge boson Z′ exchange and accounts for the DAMPE excess. We have found that the data favors a ψ mass around 1.5 TeV and a Z′ mass around 2.6 TeV, which can potentially be probed...

  6. Development of a transmission positron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Matsuya, M., E-mail: matsuya@jeol.co.jp [JEOL Ltd., 1-2 Musashino, 3-Chome, Akishima, Tokyo 196-8558 (Japan); Jinno, S. [Department of Applied Chemistry, Chiba University, Yayoi, Inage, Chiba, Chiba 263-8552 (Japan); Ootsuka, T.; Inoue, M. [JEOL Ltd., 1-2 Musashino, 3-Chome, Akishima, Tokyo 196-8558 (Japan); Kurihara, T. [High Energy Accelerator Research Organization, Oho, Tsukuba, Ibaraki 305-0801 (Japan); Doyama, M.; Inoue, M. [Teikyo University of Science and Technology, Uenohara, Yamanashi 409-0913 (Japan); Fujinami, M. [Department of Applied Chemistry, Chiba University, Yayoi, Inage, Chiba, Chiba 263-8552 (Japan)

    2011-07-21

    A practical transmission positron microscope (TPM) JEM-1011B has been developed to survey differences in the interaction of positron and electron beams with materials, and is installed in the Slow Positron Facility of High Energy Accelerator Research Organization (KEK). The TPM can share positron and electron beams, and can also be used as a transmission electron microscope (TEM). Positron transmission images up to magnification 10,000x (resolution: 50 nm) and positron diffraction patterns up to 044 family were successfully obtained by the TPM comparing them with those of electrons. The differences in material transmittances for both beams have been measured, and can be explained by the calculated results of the Monte Carlo simulation code PENELOPE-2008.

  7. Positron annihilation microprobe

    Energy Technology Data Exchange (ETDEWEB)

    Canter, K F [Brandeis Univ., Waltham, MA (United States)

    1997-03-01

    Advances in positron annihilation microprobe development are reviewed. The present resolution achievable is 3 {mu}m. The ultimate resolution is expected to be 0.1 {mu}m which will enable the positron microprobe to be a valuable tool in the development of 0.1 {mu}m scale electronic devices in the future. (author)

  8. Positron lifetimes in deformed copper

    International Nuclear Information System (INIS)

    Hinode, Kenji; Tanigawa, Shoichiro; Doyama, Masao

    1976-01-01

    Positron lifetime measurements were performed for Cu samples with different densities of lattice defects. The lifetime spectra were successfully resolved into two components with the help of the well established analysis program. Obtained results were quite consistent with those expected from the trapping model. The positron trapping mechanism from free to trapped states and the initial condition of the model were especially checked. Deduced values obtained for tau sub(c) (lifetime of free positrons) and tau sub(t) (lifetime of trapped positrons) were 122+-5 psec and 176+-5 psec, respectively. (auth.)

  9. Positron annihilation near fractal surfaces

    International Nuclear Information System (INIS)

    Lung, C.W.; Deng, K.M.; Xiong, L.Y.

    1991-07-01

    A model for positron annihilation in the sub-surface region near a fractal surface is proposed. It is found that the power law relationship between the mean positron implantation depth and incident positron energy can be used to measure the fractal dimension of the fractal surface in materials. (author). 10 refs, 2 figs

  10. High energy positron imaging

    International Nuclear Information System (INIS)

    Chen Shengzu

    2003-01-01

    The technique of High Energy Positron Imaging (HEPI) is the new development and extension of Positron Emission Tomography (PET). It consists of High Energy Collimation Imaging (HECI), Dual Head Coincidence Detection Imaging (DHCDI) and Positron Emission Tomography (PET). We describe the history of the development and the basic principle of the imaging methods of HEPI in details in this paper. Finally, the new technique of the imaging fusion, which combined the anatomical image and the functional image together are also introduced briefly

  11. High intensity positron program at LLNL

    International Nuclear Information System (INIS)

    Asoka-Kumar, P.; Howell, R.; Stoeffl, W.; Carter, D.

    1999-01-01

    Lawrence Livermore National Laboratory (LLNL) is the home of the world's highest current beam of keV positrons. The potential for establishing a national center for materials analysis using positron annihilation techniques around this capability is being actively pursued. The high LLNL beam current will enable investigations in several new areas. We are developing a positron microprobe that will produce a pulsed, focused positron beam for 3-dimensional scans of defect size and concentration with submicron resolution. Below we summarize the important design features of this microprobe. Several experimental end stations will be available that can utilize the high current beam with a time distribution determined by the electron linac pulse structure, quasi-continuous, or bunched at 20 MHz, and can operate in an electrostatic or (and) magnetostatic environment. Some of the planned early experiments are: two-dimensional angular correlation of annihilation radiation of thin films and buried interfaces, positron diffraction holography, positron induced desorption, and positron induced Auger spectroscopy

  12. High intensity positron program at LLNL

    International Nuclear Information System (INIS)

    Asoka-Kumar, P.; Howell, R.H.; Stoeffl, W.

    1998-01-01

    Lawrence Livermore National Laboratory (LLNL) is the home of the world's highest current beam of keV positrons. The potential for establishing a national center for materials analysis using positron annihilation techniques around this capability is being actively pursued. The high LLNL beam current will enable investigations in several new areas. We are developing a positron microprobe that will produce a pulsed, focused positron beam for 3-dimensional scans of defect size and concentration with submicron resolution. Below we summarize the important design features of this microprobe. Several experimental end stations will be available that can utilize the high current beam with a time distribution determined by the electron linac pulse structure, quasi-continuous, or bunched at 20 MHz, and can operate in an electrostatic or (and) magnetostatic environment. Some of the planned early experiments are: two-dimensional angular correlation of annihilation radiation of thin films and buried interfaces, positron diffraction holography, positron induced desorption, and positron induced Auger spectra

  13. Positron and positronium annihilation in silica-based thin films studied by a pulsed positron beam

    International Nuclear Information System (INIS)

    Suzuki, R.; Ohdaira, T.; Kobayashi, Y.; Ito, K.; Shioya, Y.; Ishimaru, T.

    2003-01-01

    Positron and positronium annihilation in silica-based thin films has been investigated by means of measurement techniques with a monoenergetic pulsed positron beam. The age-momentum correlation study revealed that positron annihilation in thermally grown SiO 2 is basically the same as that in bulk amorphous SiO 2 while o-Ps in the PECVD grown SiCOH film predominantly annihilate with electrons of C and H at the microvoid surfaces. We also discuss time-dependent three-gamma annihilation in porous low-k films by two-dimensional positron annihilation lifetime spectroscopy

  14. Positron astronomy with SPI/INTEGRAL

    International Nuclear Information System (INIS)

    Weidenspointner, G.; Diehl, R.; Strong, A.; Weidenspointner, G.; Skinner, G.K.; Skinner, G.K.; Jean, P.; Knoedlseder, J.; Von Ballmoos, P.; Cordier, B.; Schanne, S.; Winkler, C.

    2008-01-01

    We provide an overview of positron astronomy results that have been obtained using the INTEGRAL spectrometer SPI, and discuss their implications for the still mysterious origin of positrons in our Galaxy. It has long been known that the 511 keV positron annihilation emission is strongest from the central region of our Galaxy. Recently, it has been discovered with the SPI spectrometer that the weaker 511 keV line emission from the inner Galactic disk appears to be asymmetric, with the emission to the west of the Galactic center being about twice as strong than that to the east. This distribution of positron annihilation resembles that of low mass X-ray binaries as observed with the INTEGRAL imager IBIS at hard X-ray energies, suggesting that these systems could provide a significant portion of the positrons in our Galaxy. In addition, the spectrometer SPI has permitted unprecedented spectroscopy of annihilation radiation from the bulge and disk regions of the Galaxy, which commences to yield important insights into the conditions of the medium in which the positrons annihilate. (authors)

  15. Positron implantation profile in kapton

    International Nuclear Information System (INIS)

    Plotkowski, K.; Panek, T.J.; Kansj, J.

    1988-01-01

    Measurements of positrons' implantation profile were made with geometry as in the majority of PAT experiments, making use of the difference in values of mean lifetimes of positrons in the absorber and in the detector. The function describing the absorption of positrons in the absorber taking into account measurement geometry was fitted to the experimental data. The correction to the exponential relation occurring in this function is the dominating factor for small thicknesses of the absorber. In this analysis various values of positrons' backscatter coefficients of the nickel and of the kapton were also taken into account

  16. The Positron-Electron Correlation Energy In ZnO Calculated With The Modified Single Wave Function Of Positron

    International Nuclear Information System (INIS)

    Chau Van Tao; Trinh Hoa Lang; Le Hoang Chien; Nguyen Huu Loc; Nguyen Anh Tuan

    2011-01-01

    Positron-electron correlation energy of the ZnO - positron system is studied on assumption that positron binds with the outer shell electrons of Zinc and Oxygen to form the pseudo ZnO - positron molecule before it annihilates with one of these electrons. In this work, the single wave function for positron is form by LCAO approximation and is modified according to the principle of linear superposition, and by using Variational Quantum Monte Carlo method (VQMC) [7] the correlation energy of this system is estimated with the value E c e-p = - 9.3 ± 1.1 eV. In the theoretical aspect it turns out that this result is more reasonable and closer to those of other methods [3] than the one which is done without modifying the wave function of positron [1]. To confirm this legitimate approach, however, the further calculations of positron annihilation rate in ZnO have to be carried out in our next work. (author)

  17. A Southern African positron beam

    International Nuclear Information System (INIS)

    Britton, D.T.; Haerting, M.; Teemane, M.R.B.; Mills, S.; Nortier, F.M.; Van der Walt, T.N.

    1997-01-01

    The first stage of a state of the art positron beam, being constructed at the University of Cape Town, is currently being brought into operation. This is the first positron beam on the African continent, as well as being the first positron beam dedicated to solid and surface studies in the southern hemisphere. The project also contains a high proportion of local development, including the encapsulated 22 Na positron source developed by our collaboration. Novel features in the design include a purely magnetic in-line deflector, working in the solenoidal guiding field, to eliminate unmoderated positrons and block the direct line of sight to the source. A combined magnetic projector and single pole probe forming lens is being implemented in the second phase of construction to achieve a spot size of 10 μm without remoderation

  18. Some cosmic radiation dose measurements aboard flights connecting Zagreb Airport

    International Nuclear Information System (INIS)

    Vukovic, B.; Radolic, V.; Lisjak, I.; Vekic, B.; Poje, M.; Planinic, J.

    2008-01-01

    When primary particles from space, mainly protons, enter the atmosphere, they produce interactions with air nuclei, and cosmic-ray showers are induced. The radiation field at aircraft altitude is complex, with different types of particles, mainly photons, electrons, positrons and neutrons, with a large energy range. The non-neutron component of cosmic radiation dose aboard A320 and ATR40 aircraft was measured with TLD-100 (LiF:Mg,Ti) detectors and the Mini 6100 semiconductor dosimeter; the neutron dose was measured with the neutron dosimeter consisted of LR-115 track detector and boron foil BN-1 or 10 B converter. The estimated occupational effective dose for the aircraft crew (A320) working 500 h per year was 1.64 mSv. Another experiment was performed at the flights Zagreb-Paris-Buenos Aires and reversely, when one measured non-neutron cosmic radiation dose; for 26.7 h of flight, the MINI 6100 dosimeter gave an average dose rate of 2.3 μSv/h and the TLD dosimeter registered the dose equivalent of 75 μSv or the average dose rate of 2.7 μSv/h; the neutron dosimeter gave the dose rate of 2.4 μSv/h. In the same month, February 2005, a traveling to Japan (24-h-flight: Zagreb-Frankfurt-Tokyo and reversely) and the TLD-100 measurement showed the average dose rate of 2.4 μSv/h; the neutron dosimeter gave the dose rate of 2.5 μSv/h. Comparing dose rates of the non-neutron component (low LET) and the neutron one (high LET) of the radiation field at the aircraft flight level, we could conclude that the neutron component carried about 50% of the total dose, that was near other known data

  19. Some cosmic radiation dose measurements aboard flights connecting Zagreb Airport

    Energy Technology Data Exchange (ETDEWEB)

    Vukovic, B.; Radolic, V. [Department of Physics, University of Osijek, Osijek, P.O. Box 125 (Croatia); Lisjak, I. [Croatia Airlines, Zagreb (Croatia); Vekic, B. [Rudjer Boskovic Institute, Zagreb (Croatia); Poje, M. [Department of Physics, University of Osijek, Osijek, P.O. Box 125 (Croatia); Planinic, J. [Department of Physics, University of Osijek, Osijek, P.O. Box 125 (Croatia)], E-mail: planinic@ffos.hr

    2008-02-15

    When primary particles from space, mainly protons, enter the atmosphere, they produce interactions with air nuclei, and cosmic-ray showers are induced. The radiation field at aircraft altitude is complex, with different types of particles, mainly photons, electrons, positrons and neutrons, with a large energy range. The non-neutron component of cosmic radiation dose aboard A320 and ATR40 aircraft was measured with TLD-100 (LiF:Mg,Ti) detectors and the Mini 6100 semiconductor dosimeter; the neutron dose was measured with the neutron dosimeter consisted of LR-115 track detector and boron foil BN-1 or {sup 10}B converter. The estimated occupational effective dose for the aircraft crew (A320) working 500 h per year was 1.64 mSv. Another experiment was performed at the flights Zagreb-Paris-Buenos Aires and reversely, when one measured non-neutron cosmic radiation dose; for 26.7 h of flight, the MINI 6100 dosimeter gave an average dose rate of 2.3 {mu}Sv/h and the TLD dosimeter registered the dose equivalent of 75 {mu}Sv or the average dose rate of 2.7 {mu}Sv/h; the neutron dosimeter gave the dose rate of 2.4 {mu}Sv/h. In the same month, February 2005, a traveling to Japan (24-h-flight: Zagreb-Frankfurt-Tokyo and reversely) and the TLD-100 measurement showed the average dose rate of 2.4 {mu}Sv/h; the neutron dosimeter gave the dose rate of 2.5 {mu}Sv/h. Comparing dose rates of the non-neutron component (low LET) and the neutron one (high LET) of the radiation field at the aircraft flight level, we could conclude that the neutron component carried about 50% of the total dose, that was near other known data.

  20. Our Cosmic Insignificance

    Science.gov (United States)

    Kahane, Guy

    2014-01-01

    The universe that surrounds us is vast, and we are so very small. When we reflect on the vastness of the universe, our humdrum cosmic location, and the inevitable future demise of humanity, our lives can seem utterly insignificant. Many philosophers assume that such worries about our significance reflect a banal metaethical confusion. They dismiss the very idea of cosmic significance. This, I argue, is a mistake. Worries about cosmic insignificance do not express metaethical worries about objectivity or nihilism, and we can make good sense of the idea of cosmic significance and its absence. It is also possible to explain why the vastness of the universe can make us feel insignificant. This impression does turn out to be mistaken, but not for the reasons typically assumed. In fact, we might be of immense cosmic significance—though we cannot, at this point, tell whether this is the case. PMID:25729095

  1. Positron Transport and Annihilation in the Galactic Bulge

    Directory of Open Access Journals (Sweden)

    Fiona Helen Panther

    2018-03-01

    Full Text Available The annihilation of positrons in the Milky Way Galaxy has been observed for ∼50 years; however, the production sites of these positrons remains hard to identify. The observed morphology of positron annihilation gamma-rays provides information on the annihilation sites of these Galactic positrons. It is understood that the positrons responsible for the annihilation signal originate at MeV energies. The majority of sources of MeV positrons occupy the star-forming thin disk of the Milky Way. If positrons propagate far from their sources, we must develop accurate models of positron propagation through all interstellar medium (ISM phases in order to reveal the currently uncertain origin of these Galactic positrons. On the other hand, if positrons annihilate close to their sources, an alternative source of MeV positrons with a distribution that matches the annihilation morphology must be identified. In this work, I discuss the various models that have been developed to understand the origin of the 511 keV line from the direction of the Galactic bulge, and the propagation of positrons in the ISM.

  2. Positron emission tomography

    International Nuclear Information System (INIS)

    Yamamoto, Y.L.; Thompson, C.J.; Diksic, M.; Meyer, E.; Feindel, W.H.

    1984-01-01

    One of the most exciting new technologies introduced in the last 10 yr is positron emission tomography (PET). PET provides quantitative, three-dimensional images for the study of specific biochemical and physiological processes in the human body. This approach is analogous to quantitative in-vivo autoradiography but has the added advantage of permitting non-invasive in vivo studies. PET scanning requires a small cyclotron to produce short-lived positron emitting isotopes such as oxygen-15, carbon-11, nitrogen-13 and fluorine-18. Proper radiochemical facilities and advanced computer equipment are also needed. Most important, PET requires a multidisciplinary scientific team of physicists, radiochemists, mathematicians, biochemists and physicians. The most recent trends are reviewed in the imaging technology, radiochemistry, methodology and clinical applications of positron emission tomography. (author)

  3. Study of the Solar Anisotropy for Cosmic Ray Primaries of about 200 GeV Energy with the L3+C Muon Detector

    CERN Document Server

    Achard, P; Aguilar-Benitez, M; van den Akker, M; Alcaraz, J; Alemanni, G; Allaby, J; Aloisio, A; Alviggi, M G; Anderhub, H; Andreev, Valery P; Anselmo, F; Arefev, A; Azemoon, T; Aziz, T; Bagnaia, P; Bajo, A; Baksay, G; Baksay, L; Bahr, J; Baldew, S V; Banerjee, S; Banerjee, Sw; Barczyk, A; Barillere, R; Bartalini, P; Basile, M; Batalova, N; Battiston, R; Bay, A; Becattini, F; Becker, U; Behner, F; Bellucci, L; Berbeco, R; Berdugo, J; Berges, P; Bertucci, B; Betev, B L; Biasini, M; Biglietti, M; Biland, A; Blaising, J J; Blyth, S C; Bobbink, G J; Bohm, A; Boldizsar, L; Borgia, B; Bottai, S; Bourilkov, D; Bourquin, M; Braccini, S; Branson, J G; Brochu, F; Burger, J D; Burger, W J; Cai, X D; Capell, M; Cara Romeo, G; Carlino, G; Cartacci, A; Casaus, J; Cavallari, F; Cavallo, N; Cecchi, C; Cerrada, M; Chamizo, M; Chiarusi, T; Chang, Y H; Chemarin, M; Chen, A; Chen, G; Chen, G M; Chen, H F; Chen, H S; Chiefari, G; Cifarelli, L; Cindolo, F; Clare, I; Clare, R; Coignet, G; Colino, N; Costantini, S; de la Cruz, B; Cucciarelli, S; van Dalen, J; de Asmundis, R; Deglon, P; Debreczeni, J; Degre, A; Dehmelt, K; Deiters, K; della Volpe, D; Delmeire, E; Denes, P; DeNotaristefani, F; De Salvo, A; Diemoz, M; Dierckxsens, M; Ding, L K; Dionisi, C; Dittmar, M; Doria, A; Dova, M T; Duchesneau, D; Duda, M; Duran, I; Echenard, B; Eline, A; El Hage, A; El Mamouni, H; Engler, A; Eppling, F J; Extermann, P; Faber, G; Falagan, M A; Falciano, S; Favara, A; Fay, J; Fedin, O; Felcini, M; Ferguson, T; Fesefeldt, H; Fiandrini, E; Field, J H; Filthaut, F; Fisher, W; Fisk, I; Forconi, G; Freudenreich, K; Furetta, C; Galaktionov, Iouri; Ganguli, S N; Garcia-Abia, Pablo; Gataullin, M; Gentile, S; Giagu, S; Gong, Z F; Grabosch, H J; Grenier, G; Grimm, O; Groenstege, H; Gruenewald, M W; Guida, M; Guo, Y N; Gupta, S; Gupta, V K; Gurtu, A; Gutay, L J; Haas, D; Haller, Ch; Hatzifotiadou, D; Hayashi, Y; He, Z X; Hebbeker, T; Herve, Alain; Hirschfelder, J; Hofer, H; Hohlmann, M; Holzner, G; Hou, S R; Huo, A X; Hu, Y; Ito, N; Jin, B N; Jing, C L; Jones, Lawrence W; de Jong, P; Josa-Mutuberria, I; Kantserov, V; Kaur, M; Kawakami, S; Kienzle-Focacci, M N; Kim, J K; Kirkby, Jasper; Kittel, W; Klimentov, A; Konig, A C; Kok, E; Korn, A; Kopal, M; Koutsenko, V; Kraber, M; Kuang, H H; Kraemer, R W; Kruger, A; Kuijpers, J; Kunin, A; Ladron de Guevara, P; Laktineh, I; Landi, G; Lebeau, M; Lebedev, A; Lebrun, P; Lecomte, P; Lecoq, P; Le Coultre, P; Le Goff, J M; Lei, Y; Leich, H; Leiste, R; Levtchenko, M; Levtchenko, P; Li, C; Li, L; Li, Z C; Likhoded, S; Lin, C H; Lin, W T; Linde, F L; Lista, L; Liu, Z A; Lohmann, W; Longo, E; Lu, Y S; Luci, C; Luminari, L; Lustermann, W; Ma, W G; Ma, X H; Ma, Y Q; Malgeri, L; Malinin, A; Mana, C; Mans, J; Martin, J P; Marzano, F; Mazumdar, K; McNeil, R R; Mele, S; Meng, X W; Merola, L; Meschini, M; Metzger, W J; Mihul, A; van Mil, A; Milcent, H; Mirabelli, G; Mnich, J; Mohanty, G B; Monteleoni, B; Muanza, y G S; Muijs, A J M; Musicar, B; Musy, M; Nagy, S; Nahnhauer, R; Naumov, V A; Natale, S; Napolitano, M; Nessi-Tedaldi, F; Newman, H; Nisati, A; Novak, T; Kluge, Hannelies; Ofierzynski, R; Organtini, G; Pal, I; Palomares, C; Paolucci, P; Paramatti, R; Parriaud, J -F; Passaleva, G; Patricelli, S; Paul, Thomas Cantzon; Pauluzzi, M; Paus, C; Pauss, F; Pedace, M; Pensotti, S; Perret-Gallix, D; Petersen, B; Piccolo, D; Pierella, F; Pieri, M; Pioppi, M; Piroue, P A; Pistolesi, E; Plyaskin, V; Pohl, M; Pojidaev, V; Pothier, J; Prokofev, D; Quartieri, J; Qing, C R; Rahal-Callot, G; Rahaman, Mohammad Azizur; Raics, P; Raja, N; Ramelli, R; Rancoita, P G; Ranieri, R; Raspereza, A; Ravindran, K C; Razis, P; Ren, D; Rescigno, M; Reucroft, S; Rewiersma, P; Riemann, y S; Riles, Keith; Roe, B P; Rojkov, A; Romero, L; Rosca, A; Rosemann, C; Rosenbleck, C; Rosier-Lees, S; Roth, Stefan; Rubio, J A; Ruggiero, G; Rykaczewski, H; Saidi, R; Sakharov, A; Saremi, S; Sarkar, S; Salicio, J; Sanchez, E; Schafer, C; Schegelsky, V; Schmitt, V; Schoeneich, B; Schopper, H; Schotanus, D J; Sciacca, C; Servoli, L; Shen, C Q; Shevchenko, S; Shivarov, N; Shoutko, V; Shumilov, E; Shvorob, A; Son, D; Souga, C; Spillantini, P; Steuer, M; Stickland, D P; Stoyanov, B; Straessner, A; Sudhakar, K; Sulanke, H; Sultanov, G; Sun, L Z; Sushkov, S; Suter, H; Swain, J D; Szillasi, Z; Tang, X W; Tarjan, P; Tauscher, L; Taylor, L; Tellili, B; Teyssier, D; Timmermans, Charles; Ting, Samuel C C; Ting, S M; Tonwar, S C; Toth, J; Trowitzsch, G; Tully, C; Tung, K L; Ulbricht, J; Unger, M; Valente, E; Verkooijen, H; Van de Walle, R T; Vasquez, R; Veszpremi, V; Vesztergombi, G; Vetlitsky, I; Vicinanza, D; Viertel, G; Villa, S; Vivargent, M; Vlachos, S; Vodopianov, I; Vogel, H; Vogt, H; Vorobev, I; Vorobyov, A A; Wadhwa, M; Wang, R G; Wang, Q; Wang, X L; Wang, X W; Wang, Z M; Weber, M; van Wijk, R; Wijnen, T A M; Wilkens, H; Wynhoff, S; Xia, L; Xu, Y P; Xu, J S; Xu, Z Z; Yamamoto, J; Yang, B Z; Yang, C G; Yang, H J; Yang, M; Yang, X F; Yao, Z G; Yeh, S C; Yu, Z Q; Zalite, An; Zalite, Yu; Zhang, C; Zhang, F; Zhang, J; Zhang, S; Zhang, Z P; Zhao, J; Zhou, S J; Zhu, G Y; Zhu, R Y; Zhuang, H L; Zhu, Q Q; Zichichi, A; Zimmermann, B; Zoller, M; Zwart, A N M

    2008-01-01

    Primary cosmic rays experience multiple deflections in the nonuniform galactic and heliospheric magnetic fields which may generate anisotropies. A study of anisotropies in the energy range between 100 and 500 GeV is performed. This energy range is not yet well explored. The L3 detector at the CERN electron-positron collider, LEP, is used for a study of the angular distribution of atmospheric muons with energies above 20 GeV. This distribution is used to investigate the isotropy of the time-dependent intensity of the primary cosmic-ray flux with a Fourier analysis. A small deviation from isotropy at energies around 200 GeV is observed for the second harmonics at the solar frequency. No sidereal anisotropy is found at a level above 10^-4. The measurements have been performed in the years 1999 and 2000.

  4. High intensity positron program at LLNL

    International Nuclear Information System (INIS)

    Asoka-Kumar, P.; Howell, R.; Stoeffl, W.; Carter, D.

    1999-01-01

    Lawrence Livermore National Laboratory (LLNL) is the home of the world close-quote s highest current beam of keV positrons. The potential for establishing a national center for materials analysis using positron annihilation techniques around this capability is being actively pursued. The high LLNL beam current will enable investigations in several new areas. We are developing a positron microprobe that will produce a pulsed, focused positron beam for 3-dimensional scans of defect size and concentration with submicron resolution. Below we summarize the important design features of this microprobe. Several experimental end stations will be available that can utilize the high current beam with a time distribution determined by the electron linac pulse structure, quasi-continuous, or bunched at 20 MHz, and can operate in an electrostatic or (and) magnetostatic environment. Some of the planned early experiments are: two-dimensional angular correlation of annihilation radiation of thin films and buried interfaces, positron diffraction holography, positron induced desorption, and positron induced Auger spectroscopy. copyright 1999 American Institute of Physics

  5. PF slow positron source

    International Nuclear Information System (INIS)

    Shirakawa, A.; Enomoto, A.; Kurihara, T.

    1993-01-01

    A new slow-positron source is under construction at the Photon Factory. Positrons are produced by bombarding a tantalum rod with high-energy electrons; they are moderated in multiple tungsten vanes. We report here the present status of this project. (author)

  6. Positron spectroscopy of 2D materials using an advanced high intensity positron beam

    Science.gov (United States)

    McDonald, A.; Chirayath, V.; Lim, Z.; Gladen, R.; Chrysler, M.; Fairchild, A.; Koymen, A.; Weiss, A.

    An advanced high intensity variable energy positron beam(~1eV to 20keV) has been designed, tested and utilized for the first coincidence Doppler broadening (CDB) measurements on 6-8 layers graphene on polycrystalline Cu sample. The system is capable of simultaneous Positron annihilation induced Auger electron Spectroscopy (PAES) and CDB measurements giving it unparalleled sensitivity to chemical structure at external surfaces, interfaces and internal pore surfaces. The system has a 3m flight path up to a micro channel plate (MCP) for the Auger electrons emitted from the sample. This gives a superior energy resolution for PAES. A solid rare gas(Neon) moderator was used for the generation of the monoenergetic positron beam. The positrons were successfully transported to the sample chamber using axial magnetic field generated with a series of Helmholtz coils. We will discuss the PAES and coincidence Doppler broadening measurements on graphene -Cu sample and present an analysis of the gamma spectra which indicates that a fraction of the positrons implanted at energies 7-60eV can become trapped at the graphene/metal interface. This work was supported by NSF Grant No. DMR 1508719 and DMR 1338130.

  7. Positron depth profiling

    International Nuclear Information System (INIS)

    Coleman, P.

    2001-01-01

    Wide-ranging studies of defects below the surface of semiconductor structures have been performed at the University of Bath, in collaboration with the University of Surrey Centre for Ion Beam Applications and with members of research teams at a number of UK universities. Positron implantation has been used in conjunction with other spectroscopies such as RBS-channeling and SIMS, and electrical characterisation methods. Research has ranged from the development of a positron-based technique to monitor the in situ annealing of near-surface open-volume defects to the provision of information on defects to comprehensive diagnostic investigations of specific device structures. We have studied Si primarily but not exclusively; e.g., we have investigated ion-implanted SiC and SiO 2 /GaAs structures. Of particular interest are the applications of positron annihilation spectroscopy to ion-implanted semiconductors, where by linking ion dose to vacancy-type defect concentration one can obtain information on ion dose and uniformity with a sensitivity not achievable by standard techniques. A compact, user-friendly positron beam system is currently being developed at Bath, in collaboration with SCRIBA, with the intention of application in an industrial environment. (orig.)

  8. Positron annihilation induced Auger electron spectroscopy and its implementation at accelerator based low energy positron factories

    International Nuclear Information System (INIS)

    Weiss, A.; Koeymen, A.R.; Mehl, D.; Lee, K.H.; Yang Gimo; Jensen, K.

    1991-01-01

    Positron annihilation induced auger electron spectroscopy (PAES) makes use of a beam of low energy positrons to excite Auger transitions by annihilating core electrons. The large secondary electron background usually present in Auger spectra can be eliminated by setting the positron beam energy well below the Auger electron energy. This allows true Auger lineshapes to be obtained. Further, because the positron is localized just outside the surface before it annihilates, PAES is extremely sensitive to the topmost atomic layer. Recent PAES results obtained at the University of Texas at Arlington will be presented. In addition, the use of high resolution energy analyzers with multichannel particle detection schemes to prevent problems due to the high data rates associated with accelerator based positron beams will be discussed. (orig.)

  9. Nonlinear positron acoustic solitary waves

    International Nuclear Information System (INIS)

    Tribeche, Mouloud; Aoutou, Kamel; Younsi, Smain; Amour, Rabia

    2009-01-01

    The problem of nonlinear positron acoustic solitary waves involving the dynamics of mobile cold positrons is addressed. A theoretical work is presented to show their existence and possible realization in a simple four-component plasma model. The results should be useful for the understanding of the localized structures that may occur in space and laboratory plasmas as new sources of cold positrons are now well developed.

  10. Positron emission tomography. Basic principles

    International Nuclear Information System (INIS)

    Rodriguez, Jose Luis; Massardo, Teresa; Gonzalez, Patricio

    2001-01-01

    The basic principles of positron emission tomography (PET) technique are reviewed. lt allows to obtain functional images from gamma rays produced by annihilation of a positron, a positive beta particle. This paper analyzes positron emitters production in a cyclotron, its general mechanisms, and the various detection systems. The most important clinical applications are also mentioned, related to oncological uses of fluor-l8-deoxyglucose

  11. Compressive effect of the magnetic field on the positron range in commonly used positron emitters simulated using Geant4

    Science.gov (United States)

    Li, Chong; Cao, Xingzhong; Liu, Fuyan; Tang, Haohui; Zhang, Zhiming; Wang, Baoyi; Wei, Long

    2017-11-01

    The compressive effect of a magnetic field on the positron range from commonly used positron emitters in PET (Positron Emission Tomography) was simulated using the Geant4 toolkit with H2O as the environmental material. The compression of the positron range, which was different in the directions parallel and perpendicular to the magnetic field, showed finite final variation of relative change rate versus the magnetic field. The variation greatly depended on the positron-emission energy spectrum in the same medium. Furthermore, the volume of the positron annihilation point was dramatically compressed as the magnetic field was set in the range of 3-6T. It was more prominent for 82Rb , which is generally used as a positron source in PET technology.

  12. Positron annihilation studies of mesoporous silica films using a slow positron beam

    International Nuclear Information System (INIS)

    He Chunqing; Muramatsu, Makoto; Ohdaira, Toshiyuki; Kinomura, Atsushi; Suzuki, Ryoichi; Ito, Kenji; Kabayashi, Yoshinori

    2006-01-01

    Positron annihilation lifetime spectra were measured for mesoporous silica films, which were synthesized using triblock copolymer (EO 106 PO 70 EO 106 ) as a structure-directing agent. Different positron lifetime spectra for the deposited and calcined films indicated the formation of meso-structure after calcination, which was confirmed by Fourier transform infrared (FTIR) spectra and field emission-scanning electron microscopy (FE-SEM) observation. Open porosity or pore interconnectivity of a silica film might be evaluated by a two-dimensional positron annihilation lifetime spectrum of an uncapped film. Pore sizes and their distributions in the silica films were found to be affected by thermal treatments

  13. Positron annihilation spectroscopy

    International Nuclear Information System (INIS)

    Sundar, C.S.; Viswanathan, B.

    1996-01-01

    An overview of positron annihilation spectroscopy, the experimental techniques and its application to studies on defects and electronic structure of materials is presented. The scope of this paper is to present the requisite introductory material, that will enable a better appreciation of the subsequent specialized articles on the applications of positron annihilation spectroscopy to investigate various problems in materials science. (author). 31 refs., 3 figs

  14. A cosmic microwave background feature consistent with a cosmic texture.

    Science.gov (United States)

    Cruz, M; Turok, N; Vielva, P; Martínez-González, E; Hobson, M

    2007-12-07

    The Cosmic Microwave Background provides our most ancient image of the universe and our best tool for studying its early evolution. Theories of high-energy physics predict the formation of various types of topological defects in the very early universe, including cosmic texture, which would generate hot and cold spots in the Cosmic Microwave Background. We show through a Bayesian statistical analysis that the most prominent 5 degrees -radius cold spot observed in all-sky images, which is otherwise hard to explain, is compatible with having being caused by a texture. From this model, we constrain the fundamental symmetry-breaking energy scale to be (0) approximately 8.7 x 10(15) gigaelectron volts. If confirmed, this detection of a cosmic defect will probe physics at energies exceeding any conceivable terrestrial experiment.

  15. Cosmic Microwave Background Timeline

    Science.gov (United States)

    Cosmic Microwave Background Timeline 1934 : Richard Tolman shows that blackbody radiation in an will have a blackbody cosmic microwave background with temperature about 5 K 1955: Tigran Shmaonov anisotropy in the cosmic microwave background, this strongly supports the big bang model with gravitational

  16. Light scattering by cosmic particles

    NARCIS (Netherlands)

    Hovenier, J.W.; Min, M.

    2008-01-01

    We define cosmic particles as particles outside the Earth. Two types of cosmic particles can be distinguished, namely liquid and solid particles. The solid particles are often called grains or cosmic dust particles. Cosmic particles occur in a great variety of astronomical objects and environments.

  17. Positron Studies of Oxide-Semiconductor Structures

    OpenAIRE

    Uedono , A.; Wei , L.; Kawano , T.; Tanigawa , S.; Suzuki , R.; Ohgaki , H.; Mikado , T.

    1995-01-01

    The annihilation characteristics of positrons in SiO2 films grown on Si substrates were studied by using monoenergetic positron beams. Doppler broadening profiles of the annihilation radiation and lifetime spectra of positrons were measured as a function of incident positron energy for SiO2/Si structures fabricated by various oxidation techniques. From the measurements, it was found that the formation probability of positronium (Ps) atoms in SiO2 films strongly depends on the growth condition...

  18. Dark matter indirect detection with charged cosmic rays

    International Nuclear Information System (INIS)

    Giesen, Gaelle

    2015-01-01

    Overwhelming evidence for the existence of Dark Matter (DM), in the form of an unknown particle filling the galactic halos, originates from many observations in astrophysics and cosmology: its gravitational effects are apparent on galactic rotations, in galaxy clusters and in shaping the large scale structure of the Universe. On the other hand, a non-gravitational manifestation of its presence is yet to be unveiled. One of the most promising techniques is the one of indirect detection, aimed at identifying excesses in cosmic ray fluxes which could possibly be produced by DM annihilations or decays in the Milky Way halo. The current experimental efforts mainly focus in the GeV to TeV energy range, which is also where signals from WIMPs (Weakly Interacting Massive Particles) are expected. Focussing on charged cosmic rays, in particular antiprotons, electrons and positrons, as well as their secondary emissions, an analysis of current and foreseen cosmic ray measurements and improvements on astrophysical models are presented. Antiproton data from PAMELA imposes constraints on annihilating and decaying DM which are similar to (or even slightly stronger than) the most stringent bounds from gamma ray experiments, even when kinetic energies below 10 GeV are discarded. However, choosing different sets of astrophysical parameters, in the form of propagation models and halo profiles, allows the constraints to span over one or two orders of magnitude. In order to exploit fully the power of antiprotons to constrain or discover DM, effects which were previously perceived as sub-leading turn out to be relevant especially for the analysis of the newly released AMS-02 data. In fact, including energy losses, diffusive re-acceleration and solar modulation can somewhat modify the current bounds, even at large DM masses. A wrong interpretation of the data may arise if they are not taken into account. Finally, using the updated proton and helium fluxes just released by the AMS-02

  19. A model explaining neutrino masses and the DAMPE cosmic ray electron excess

    Science.gov (United States)

    Fan, Yi-Zhong; Huang, Wei-Chih; Spinrath, Martin; Tsai, Yue-Lin Sming; Yuan, Qiang

    2018-06-01

    We propose a flavored U(1)eμ neutrino mass and dark matter (DM) model to explain the recent DArk Matter Particle Explorer (DAMPE) data, which feature an excess on the cosmic ray electron plus positron flux around 1.4 TeV. Only the first two lepton generations of the Standard Model are charged under the new U(1)eμ gauge symmetry. A vector-like fermion ψ, which is our DM candidate, annihilates into e± and μ± via the new gauge boson Z‧ exchange and accounts for the DAMPE excess. We have found that the data favors a ψ mass around 1.5 TeV and a Z‧ mass around 2.6 TeV, which can potentially be probed by the next generation lepton colliders and DM direct detection experiments.

  20. Depth-dependent positron annihilation in different polymers

    Energy Technology Data Exchange (ETDEWEB)

    Yang, J.; Zhang, P.; Cheng, G.D.; Li, D.X.; Wu, H.B.; Li, Z.X.; Cao, X.Z. [Key Laboratory of Nuclear Analysis Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, No. 19 Yuquan Lu, Beijing 100049 (China); Jia, Q.J. [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, No. 19 Yuquan Lu, Beijing 100049 (China); Yu, R.S. [Key Laboratory of Nuclear Analysis Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, No. 19 Yuquan Lu, Beijing 100049 (China); Wang, B.Y., E-mail: wangboy@ihep.ac.cn [Key Laboratory of Nuclear Analysis Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, No. 19 Yuquan Lu, Beijing 100049 (China)

    2013-09-01

    Depth-dependent positron annihilation Doppler broadening measurements were conducted for polymers with different chemical compositions. Variations of the S parameter with respect to incident positron energy were observed. For pure hydrocarbons PP, HDPE and oxygen-containing polymer PC, S parameter rises with increasing positron implantation depth. While for PI and fluoropolymers like PTFE, ETFE and PVF, S parameter decreases with higher positron energy. For chlorine-containing polymer PVDC, S parameter remains nearly constant at all incident positron energies. It is suggested that these three variation trends are resulted from a competitive effect between the depth-dependent positronium formation and the influence of highly electronegative atoms on positron annihilation characteristics.

  1. Simulation of the annihilation emission of galactic positrons; Modelisation de l'emission d'annihilation des positrons Galactiques

    Energy Technology Data Exchange (ETDEWEB)

    Gillard, W

    2008-01-15

    Positrons annihilate in the central region of our Galaxy. This has been known since the detection of a strong emission line centered on an energy of 511 keV in the direction of the Galactic center. This gamma-ray line is emitted during the annihilation of positrons with electrons from the interstellar medium. The spectrometer SPI, onboard the INTEGRAL observatory, performed spatial and spectral analyses of the positron annihilation emission. This thesis presents a study of the Galactic positron annihilation emission based on models of the different interactions undergone by positrons in the interstellar medium. The models are relied on our present knowledge of the properties of the interstellar medium in the Galactic bulge, where most of the positrons annihilate, and of the physics of positrons (production, propagation and annihilation processes). In order to obtain constraints on the positrons sources and physical characteristics of the annihilation medium, we compared the results of the models to measurements provided by the SPI spectrometer. (author)

  2. Experimentation with low-energy positron beams

    International Nuclear Information System (INIS)

    Mills, A.P. Jr.

    1983-01-01

    The capability of studying the interactions of positrons with surfaces has recently been exploited by using ultra-high-vacuum techniques. The result has been a new understanding of how positrons interact with surfaces and because of this we are now able to make much stronger fluxes of slow positrons. The higher beam strengths in turn are opening up new possibilities for experimentation on surfaces and solids and for studying the atomic physics of positronium and positron-molecule scattering at low energies. The lectures are intended to review some of the history of this subject and to outline the present state of our knowledge of experimentation with low-energy positron beams. (orig./TW)

  3. Positron annihilation in vitreous silica glasses

    International Nuclear Information System (INIS)

    Uedono, Akira; Tanigawa, Shoichiro

    1993-01-01

    The annihilation characteristics of positrons in vitreous silica glasses (v-SiO 2 ) were studied by measurements of two-dimensional angular correlation of positron annihilation radiations and positron lifetime spectra. From the measurements, it was found that positrons and positronium (Ps) atoms mainly annihilate from trapped states by vacancy-type defects in v-SiO 2 . For v-SiO 2 specimens with cylindrical porous structures, annihilations of Ps with anisotropic momentum distributions were observed. This fact was attributed to the momentum uncertainty due to localization of Ps in a finite dimension of pores. This investigation showed possibilities for the detection of microstructures in v-SiO 2 by the positron annihilation technique. (author)

  4. Positrons in ionic crystals

    International Nuclear Information System (INIS)

    Pareja, R.

    1988-01-01

    Positron annihilation experiments in ionic crystals are reviewed and their results are arranged. A discussion about the positron states in these materials is made in the light of these results and the different proposed models. The positronium in alkali halides is specially considered. (Author)

  5. Cosmic strings and galaxy formation

    International Nuclear Information System (INIS)

    Bertschinger, E.

    1989-01-01

    Cosmic strings have become increasingly popular candidates as seeds for the formation of structure in the universe. This scenario, remains a serious cosmogonical model despite close scrutiny. In constrast, magnetic monopoles and domain walls - relic topological defects as are cosmic strings - are disastrous for cosmology if they are left over from the early universe. The production of heavy cosmic strings is speculative, as it depends on the details of ultrahigh energy physics. Fortunately, speculation about cosmic strings is not entirely idle because, if they exist and are heavy enough to seed galaxy formation, cosmic strings can be detected astronomically. Failure to detect cosmic strings would impose some constraints on grand unified theories (GUTs); their discovery would have exciting consequences for high energy physics and cosmology. This article reviews the basic physics of nonsuperconducting cosmic strings, highlighting the field theory aspects, and provides a progress report on calculations of structure formation with cosmic strings

  6. Positron annihilation in SiO 2-Si studied by a pulsed slow positron beam

    Science.gov (United States)

    Suzuki, R.; Ohdaira, T.; Uedono, A.; Kobayashi, Y.

    2002-06-01

    Positron and positronium (Ps) behavior in SiO 2-Si have been studied by means of positron annihilation lifetime spectroscopy (PALS) and age-momentum correlation (AMOC) spectroscopy with a pulsed slow positron beam. The PALS study of SiO 2-Si samples, which were prepared by a dry-oxygen thermal process, revealed that the positrons implanted in the Si substrate and diffused back to the interface do not contribute to the ortho-Ps long-lived component, and the lifetime spectrum of the interface has at least two components. From the AMOC study, the momentum distribution of the ortho-Ps pick-off annihilation in SiO 2, which shows broader momentum distribution than that of crystalline Si, was found to be almost the same as that of free positron annihilation in SiO 2. A varied interface model was proposed to interpret the results of the metal-oxide-semiconductor (MOS) experiments. The narrow momentum distribution found in the n-type MOS with a negative gate bias voltage could be attributed to Ps formation and rapid spin exchange in the SiO 2-Si interface. We have developed a two-dimensional positron lifetime technique, which measures annihilation time and pulse height of the scintillation gamma-ray detector for each event. Using this technique, the positronium behavior in a porous SiO 2 film, grown by a sputtering method, has been studied.

  7. Theoretical calculations of positron lifetimes for metal oxides

    International Nuclear Information System (INIS)

    Mizuno, Masataka; Araki, Hideki; Shirai, Yasuharu

    2004-01-01

    Our recent positron lifetime measurements for metal oxides suggest that positron lifetimes of bulk state in metal oxides are shorter than previously reported values. We have performed theoretical calculations of positron lifetimes for bulk and vacancy states in MgO and ZnO using first-principles electronic structure calculations and discuss the validity of positron lifetime calculations for insulators. By comparing the calculated positron lifetimes to the experimental values, it wa found that the semiconductor model well reproduces the experimental positron lifetime. The longer positron lifetime previously reported can be considered to arise from not only the bulk but also from the vacancy induced by impurities. In the case of cation vacancy, the calculated positron lifetime based on semiconductor model is shorter than the experimental value, which suggests that the inward relaxation occurs around the cation vacancy trapping the positron. (author)

  8. Signatures of SUSY dark matter at the LHC and in the spectra of cosmic rays

    Energy Technology Data Exchange (ETDEWEB)

    Olzem, J.

    2007-02-27

    This thesis discusses the search for supersymmetry at the future Large Hadron Collider (LHC) and the ongoing construction of one of the four large LHC experiments, the Compact Muon Solenoid (CMS), and focuses on the detection of signals from the annihilation of supersymmetric dark matter in the spectra of cosmic rays. The final steps of assembly of 1061 silicon microstrip detector modules for the CMS tracker endcaps are performed at the 1. Physikalisches Institut B at the RWTH Aachen. A laser test facility for these modules was developed and is described in this thesis. In contrast to test procedures based only on the evaluation of pedestal and noise data, the test facility relies on the generation of signals in the silicon sensors by infrared laser illumination. The fully automatic test facility provides high throughput and easy operation for the series production of the modules. Its performance is validated by investigating a reference module with artificially prepared defects of three types: open wirebonds, short-circuited strips and pinholes. It is shown that all defects are clearly detected. In addition to defect detection, an indication for the type of defect is provided. In a further validation step, nine modules from a prototype series are investigated with the laser test facility. Confirming the earlier results on the reference module, defective strips are reliably identified. This thesis describes a novel approach of positron identification with the space-borne AMS-01 experiment, namely through the detection of bremsstrahlung conversion in a silicon microstrip detector. In order to obtain the highest positron selection efficiency possible, novel combinatorial track finding algorithms were developed, particularly optimized for the signature of converted bremsstrahlung. By applying restrictions on the invariant mass of particles the background to the positron sample is largely eliminated. The remaining background contamination is determined from large

  9. Calculation of cosmic ray induced single event upsets: Program CRUP (Cosmic Ray Upset Program)

    Science.gov (United States)

    Shapiro, P.

    1983-09-01

    This report documents PROGRAM CRUP, COSMIC RAY UPSET PROGRAM. The computer program calculates cosmic ray induced single-event error rates in microelectronic circuits exposed to several representative cosmic-ray environments.

  10. Production and applications of positron microbeams

    International Nuclear Information System (INIS)

    Brandes, G.R.; Canter, K.F.; Horsky, T.N.; Lippel, P.H.; Mills, A.P. Jr.

    1989-01-01

    The production of a positron microbeam using the high-brightness beam developed at Brandeis University and possible applications of this microbeam to spatially resolved defect studies and positron microscopy are reviewed. The high-brightness beam consists of a W(110) primary moderator and two remoderation stages which provide a 500-fold increase in brightness. With this brightness increase and microbeam optics, we are able to form a 12 μm FWHM beam (48 mrad pencil half-angle) at 5 keV beam energy. The well characterised small-diameter beam is particularly adaptable for determining defect concentration and structure, both laterally and in a depth-profiling mode. In the case of a transmission positron microscope or a positron re-emission microscope operating in a high-magnification mode, efficient image formation requires the use of a microbeam to maximise the number of positrons in the area being imaged. Results of the scanning microbeam tests and the application of a microbeam to positron microscopy and defect studies are reviewed. (author)

  11. Detection of tokamak plasma positrons using annihilation photons

    Energy Technology Data Exchange (ETDEWEB)

    Guanying, Yu; Liu, Jian; Xie, Jinlin [University of Science and Technology, Hefei, Anhui, 230027 (China); Li, Jiangang, E-mail: j_li@ipp.ac.cn [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui 230031 (China)

    2017-05-15

    Highlights: • A design for detection of tokamak plasma positrons is given. • Identify the main obstacle toward experimental confirmation of fusion plasma positrons. • Signal to noise ratio in a plasma disruption is estimated. • Unique potential applications of fusion plasma positrons are discussed. - Abstract: A massive amount of positrons (plasma positrons), produced by the collision between runaway electrons and nuclei during fusion plasma disruption, was first predicted theoretically in 2003. To help confirm this prediction, we report here the design of an experimental system to detect tokamak plasma positrons. Because a substantial amount of positrons (material positrons) are produced when runaway electrons impact plasma-facing materials, we proposed maximizing the ratio of plasma to material positrons by inserting a thin carbon target at the plasma edge as a plasma positron bombing target and producing a plasma disruption scenario triggered by massive gas injection. Meanwhile, the coincidence detection of positron annihilation photons was used to filter out the noise of annihilation photons from locations other than the carbon target and that of bremsstrahlung photons near 511 keV. According to our simulation, the overall signal-to-noise ratio should be more than 10:1.

  12. Time-dependent behavior of positrons in noble gases

    International Nuclear Information System (INIS)

    Wadehra, J.M.

    1990-01-01

    Both equilibrium and nonequilibrium behaviors of positrons in several noble gases are reviewed. Our novel procedure for obtaining the time-dependent behavior of various swarm parameters -- such as the positron drift velocity, average positron energy, positron annihilation rate (or equivalently Z eff ) etc. -- for positrons in pure ambient gases subjected to external electrostatic fields is described. Summaries of time-dependent as well as electric field-dependent results for positron swarms in various noble gases are presented. New time-dependent results for positron swarms in neon are also described in detail. 36 refs., 4 figs., 3 tabs

  13. Solvated Positron Chemistry. II

    DEFF Research Database (Denmark)

    Mogensen, O. E.

    1979-01-01

    The reaction of the hydrated positron, eaq+ with Cl−, Br−, and I− ions in aqueous solutions was studied by means of positron The measured angular correlation curves for [Cl−, e+], [Br−, e+, and [I−, e+] bound states were in good agreement with th Because of this agreement and the fact...... that the calculated positron wavefunctions penetrate far outside the X− ions in the [X−, e+] sta propose that a bubble is formed around the [X−, e+] state, similar to the Ps bubble found in nearly all liquids. F−ions did not react w Preliminary results showed that CN− ions react with eaq+ while OH−ions are non...... in the Cl− case) at higher concentrations. This saturation and the high-concentration effects-in the angular correlation results were interpreted as caused by rather complicated spur effects, wh It is proposed that spur electrons may pick off the positron from the [X−, e+ states with an efficiency which...

  14. Radiation damage of polymers studied by positron annihilation. Positron and gamma-ray irradiation effects

    International Nuclear Information System (INIS)

    Suzuki, T.; Oki, Y.; Numajiri, M.; Miura, T.; Kondo, K.; Ito, Y.

    1995-01-01

    Positron irradiation effects on polypropylene (PP) have been studied using positron sources ( 22 Na) during positron annihilation (PA) experiments. The irradiation effect was measured by the intensity (I 3 ) of the long-lived component of positronium (Ps). At a low temperature of around 100 K, I 3 for unirradiated PP samples increased due to a termination of the thermal motion of the -CH 3 groups. However, the increase in I 3 for γ-ray irradiated samples was reduced in inverse proportion to the amount of irradiation. Although no increase in I 3 was observed for 1 MGy-irradiated PP with γ-rays, an increase was observed again after a 48 h irradiation by positrons emitted from 22 Na. This may be due to a reconstructing of the polymer chains. (author)

  15. Effects of positron density and temperature on large amplitude ion-acoustic waves in an electron-positron-ion plasma

    International Nuclear Information System (INIS)

    Nejoh, Y.N.

    1997-01-01

    The nonlinear wave structures of large amplitude ion-acoustic waves are studied in a plasma with positrons. We have presented the region of existence of the ion-acoustic waves by analysing the structure of the pseudopotential. The region of existence sensitively depends on the positron to electron density ratio, the ion to electron mass ratio and the positron to electron temperature ratio. It is shown that the maximum Mach number increases as the positron temperature increases and the region of existence of the ion-acoustic waves spreads as the positron temperature increases. 12 refs., 6 figs

  16. Importance of non-local electron-positron correlations for positron annihilation characteristics in solids

    International Nuclear Information System (INIS)

    Rubaszek, A.

    2001-01-01

    Several methods to describe the electron-positron (e-p) correlation effects are used in calculations of positron annihilation characteristics in solids. The weighted density approximation (WDA), giving rise to the non-local, state-selective e-p correlation functions, is applied to calculate positron annihilation rates and e-p momentum densities in a variety of metals and silicon. The WDA results are compared to the results of other methods such as the independent particle model, local density approximation, generalised gradient approximation, and also to experiments. The importance of non-locality and state-dependence of the e-p correlation functions is discussed. (orig.)

  17. Positron source based on the 48V isotope dedicated to positron lifetime spectroscopy

    International Nuclear Information System (INIS)

    Dryzek, Jerzy

    2009-01-01

    In the paper we consider application of the 48 V isotope as a source in the positron lifetime spectroscopy. The isotope was produced in the 48 Ti(p,n) 48 V reaction using 15 MeV proton beam. As a target the natural titanium thin plate was used. The measurements using the typical positron lifetime spectrometer have shown the usefulness of the source obtained for this application. Due to its properties, the source may be used for measurements of positron annihilation characteristics in high temperature or aggressive environments. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Applications of positron depth profiling

    Energy Technology Data Exchange (ETDEWEB)

    Hakvoort, R A

    1993-12-23

    In this thesis some contributions of the positron-depth profiling technique to materials science have been described. Following studies are carried out: Positron-annihilation measurements on neon-implanted steel; Void creation in silicon by helium implantation; Density of vacancy-type defects present in amorphous silicon prepared by ion implantation; Measurements of other types of amorphous silicon; Epitaxial cobalt disilicide prepared by cobalt outdiffusion. Positron-annihilation experiments on low-pressure CVD silicon-nitride films. (orig./MM).

  19. Applications of positron depth profiling

    International Nuclear Information System (INIS)

    Hakvoort, R.A.

    1993-01-01

    In this thesis some contributions of the positron-depth profiling technique to materials science have been described. Following studies are carried out: Positron-annihilation measurements on neon-implanted steel; Void creation in silicon by helium implantation; Density of vacancy-type defects present in amorphous silicon prepared by ion implantation; Measurements of other types of amorphous silicon; Epitaxial cobalt disilicide prepared by cobalt outdiffusion. Positron-annihilation experiments on low-pressure CVD silicon-nitride films. (orig./MM)

  20. Positron emission tomography

    International Nuclear Information System (INIS)

    Lindback, Stig

    1995-01-01

    Positron Emission Tomography (PET) is an advanced nuclear medicine technique used for research at major centres. Unique diagnostic information is obtained from tomographic measurements of the biochemistry and physiology of tissues and organs. In theory, diseases are related to biochemical changes and these can be observed with PET long before any anatomical changes are detectable. In PET the radioactive component is a positron-emitting isotope or 'tracer'. The positrons annihilate with electrons in the body to produce two gamma rays 180° apart; coincidence detection of these gammas provides a very efficient method of determining the spatial distribution of the radioisotope tracer. Because physiological measurements are usually required in a single imaging session, very short-lived isotopes are used to label the tracer molecules; isotope production and labelling is usually carried out in situ. The most commonly used radionuclides are carbon- 11 (half-life 20 minutes), nitrogen-13 (10 minutes), oxygen-15 (2 minutes), and fluorine-18 (110 minutes). A PET system has three major components: - a particle accelerator with targets for production of the positron-emitting isotopes; - chemistry modules for synthesis and labelling of the desired tracers; - and a PET camera for in-vivo measurements of the distribution of the tracer in the body

  1. Positron emission tomography

    Energy Technology Data Exchange (ETDEWEB)

    Lindback, Stig [GEMS PET Systems AB, Uppsala (Sweden)

    1995-07-15

    Positron Emission Tomography (PET) is an advanced nuclear medicine technique used for research at major centres. Unique diagnostic information is obtained from tomographic measurements of the biochemistry and physiology of tissues and organs. In theory, diseases are related to biochemical changes and these can be observed with PET long before any anatomical changes are detectable. In PET the radioactive component is a positron-emitting isotope or 'tracer'. The positrons annihilate with electrons in the body to produce two gamma rays 180° apart; coincidence detection of these gammas provides a very efficient method of determining the spatial distribution of the radioisotope tracer. Because physiological measurements are usually required in a single imaging session, very short-lived isotopes are used to label the tracer molecules; isotope production and labelling is usually carried out in situ. The most commonly used radionuclides are carbon- 11 (half-life 20 minutes), nitrogen-13 (10 minutes), oxygen-15 (2 minutes), and fluorine-18 (110 minutes). A PET system has three major components: - a particle accelerator with targets for production of the positron-emitting isotopes; - chemistry modules for synthesis and labelling of the desired tracers; - and a PET camera for in-vivo measurements of the distribution of the tracer in the body.

  2. Cosmic ray diffusion: report of the workshop in cosmic ray diffusion theory

    International Nuclear Information System (INIS)

    Birmingham, T.J.; Jones, F.C.

    1975-02-01

    A workshop in cosmic ray diffusion theory was held at Goddard Space Flight Center on May 16-17, 1974. Topics discussed and summarized are: (1) cosmic ray measurements as related to diffusion theory; (2) quasi-linear theory, nonlinear theory, and computer simulation of cosmic ray pitch-angle diffusion; and (3) magnetic field fluctuation measurements as related to diffusion theory. (auth)

  3. Positron probes of the Ge(1 0 0) surface: The effects of surface reconstructions and electron-positron correlations on positron trapping and annihilation characteristics

    International Nuclear Information System (INIS)

    Fazleev, N.G.; Jung, E.; Weiss, A.H.

    2007-01-01

    Positron annihilation induced Auger electron spectroscopy (PAES) has been applied to study the Ge(1 0 0) surface. The high-resolution PAES spectrum from the Ge(1 0 0) surface displays several strong Auger peaks corresponding to M 4,5 N 1 N 2,3 , M 2,3 M 4,5 M 4,5 , M 2,3 M 4,5 V and M 1 M 4,5 M 4,5 Auger transitions. The integrated peak intensities of Auger transitions are used to obtain experimental annihilation probabilities for the Ge 3d and 3p core level electrons. These experimental results are analyzed by performing calculations of positron surface states and annihilation characteristics of surface trapped positrons with relevant Ge core-level electrons for the non-reconstructed and reconstructed Ge(1 0 0)-p(2 x 1), Ge(1 0 0)-p(2 x 2) and Ge(1 0 0)-c(4 x 2) surfaces. It is found that the positron surface state wave function extends into the Ge lattice in the regions where atoms are displaced from their ideal terminated positions due to reconstructions. Estimates of the positron binding energy and the positron annihilation characteristics reveal their sensitivity to the specific atomic structure of the topmost layers of Ge(1 0 0). A comparison with PAES data reveals an agreement with theoretical core annihilation probabilities for the Auger transitions considered

  4. 11. European cosmic ray symposium

    International Nuclear Information System (INIS)

    1989-03-01

    The biannual Symposium includes all aspects of cosmic ray research. The scientific programme was organized under three main headings: Cosmic rays in the heliosphere, Cosmic rays in the interstellar and extragalactic space, Properties of high-energy interactions as studied by cosmic rays. Seven invited talks were indexed seprately for the INIS database. (R.P.)

  5. The cryogenic source of slow monochromatic positrons

    International Nuclear Information System (INIS)

    Meshkov, I.N.; Pavlov, V.N.; Sidorin, A.O.; Yakovenko, S.L.

    2008-01-01

    The cryogenic source of slow monochromatic positrons based on the 22 Na isotope has been designed and constructed at JINR. Positrons emitted from radioactive source 22 Na have a very broad energy spectrum up to 0.5 MeV. To generate monochromatic beam of slow positrons the solid neon is used as a moderator. The solid neon allows forming slow positron beam of the energy of 1.2 eV at the spectrum width of 1 eV. The efficiency of moderation is 1 % of total positron flux

  6. Probing the positron moderation process using high-intensity, highly polarized slow-positron beams

    Science.gov (United States)

    Van House, J.; Zitzewitz, P. W.

    1984-01-01

    A highly polarized (P = 0.48 + or - 0.02) intense (500,000/sec) beam of 'slow' (Delta E = about 2 eV) positrons (e+) is generated, and it is shown that it is possible to achieve polarization as high as P = 0.69 + or - 0.04 with reduced intensity. The measured polarization of the slow e+ emitted by five different positron moderators showed no dependence on the moderator atomic number (Z). It is concluded that only source positrons with final kinetic energy below 17 keV contribute to the slow-e+ beam, in disagreement with recent yield functions derived from low-energy measurements. Measurements of polarization and yield with absorbers of different Z between the source and moderator show the effects of the energy and angular distributions of the source positrons on P. The depolarization of fast e+ transmitted through high-Z absorbers has been measured. Applications of polarized slow-e+ beams are discussed.

  7. A COSMIC VARIANCE COOKBOOK

    International Nuclear Information System (INIS)

    Moster, Benjamin P.; Rix, Hans-Walter; Somerville, Rachel S.; Newman, Jeffrey A.

    2011-01-01

    Deep pencil beam surveys ( 2 ) are of fundamental importance for studying the high-redshift universe. However, inferences about galaxy population properties (e.g., the abundance of objects) are in practice limited by 'cosmic variance'. This is the uncertainty in observational estimates of the number density of galaxies arising from the underlying large-scale density fluctuations. This source of uncertainty can be significant, especially for surveys which cover only small areas and for massive high-redshift galaxies. Cosmic variance for a given galaxy population can be determined using predictions from cold dark matter theory and the galaxy bias. In this paper, we provide tools for experiment design and interpretation. For a given survey geometry, we present the cosmic variance of dark matter as a function of mean redshift z-bar and redshift bin size Δz. Using a halo occupation model to predict galaxy clustering, we derive the galaxy bias as a function of mean redshift for galaxy samples of a given stellar mass range. In the linear regime, the cosmic variance of these galaxy samples is the product of the galaxy bias and the dark matter cosmic variance. We present a simple recipe using a fitting function to compute cosmic variance as a function of the angular dimensions of the field, z-bar , Δz, and stellar mass m * . We also provide tabulated values and a software tool. The accuracy of the resulting cosmic variance estimates (δσ v /σ v ) is shown to be better than 20%. We find that for GOODS at z-bar =2 and with Δz = 0.5, the relative cosmic variance of galaxies with m * >10 11 M sun is ∼38%, while it is ∼27% for GEMS and ∼12% for COSMOS. For galaxies of m * ∼ 10 10 M sun , the relative cosmic variance is ∼19% for GOODS, ∼13% for GEMS, and ∼6% for COSMOS. This implies that cosmic variance is a significant source of uncertainty at z-bar =2 for small fields and massive galaxies, while for larger fields and intermediate mass galaxies, cosmic

  8. Cosmic Accelerators: An Introduction

    International Nuclear Information System (INIS)

    Kanbach, Gottfried

    2005-01-01

    High energy, relativistic, particles are an essential component of the Universe and play a major role in astrophysics. In a few years we will reach the centennial of the discovery of cosmic rays; all through this century the properties, origin, and effects of this radiation have intrigued researchers in astrophysics and elementary particles alike. We briefly review the history, current status, and future perspectives of cosmic ray research. Emphasis will be placed on the multitude of cosmic accelerators, direct observations of these objects, and the effects of cosmic rays in the Galaxy and beyond

  9. High energy cosmic rays

    CERN Document Server

    Stanev, Todor

    2010-01-01

    Offers an accessible text and reference (a cosmic-ray manual) for graduate students entering the field and high-energy astrophysicists will find this an accessible cosmic-ray manual Easy to read for the general astronomer, the first part describes the standard model of cosmic rays based on our understanding of modern particle physics. Presents the acceleration scenario in some detail in supernovae explosions as well as in the passage of cosmic rays through the Galaxy. Compares experimental data in the atmosphere as well as underground are compared with theoretical models

  10. High efficiency positron moderation

    International Nuclear Information System (INIS)

    Taqqu, D.

    1990-01-01

    A new positron moderation scheme is proposed. It makes use of electric and magnetic fields to confine the β + emitted by a radioactive source forcing them to slow down within a thin foil. A specific arrangement is described where an intermediary slowed-down beam of energy below 10 keV is produced. By directing it towards a standard moderator optimal conversion into slow positrons is achieved. This scheme is best applied to short lived β + emitters for which a 25% moderation efficiency can be reached. Within the state of the art technology a slow positron source intensity exceeding 2 x 10 10 e + /sec is achievable. (orig.)

  11. Positron emission tomography

    International Nuclear Information System (INIS)

    Chandrasekhar, Preethi; Himabindu, Pucha

    2000-01-01

    Positron Emission Tomography (PET) is a non-invasive nuclear imaging technique used to study different molecular pathways and anatomical structures. PET has found extensive applications in various fields of medicine viz. cardiology, oncology, psychiatry/psychology, neuro science and pulmonology. This study paper basically deals with the physics, chemistry and biology behind the PET technique. It discusses the methodology for generation of the radiotracers responsible for emission of positrons and the annihilation and detection techniques. (author)

  12. Positron emission tomography

    International Nuclear Information System (INIS)

    Dvorak, O.

    1989-01-01

    The principle is briefly described of positron emission tomography, and its benefits and constraints are listed. It is emphasized that positron emission tomography (PET) provides valuable information on metabolic changes in the organism that are otherwise only very difficult to obtain, such as brain diagnosis including relationships between mental disorders and the physiology and pathophysiology of the brain. A PET machine is to be installed in Czechoslovakia in the near future. (L.O.)

  13. Relevance of slow positron beam research to astrophysical studies of positron interactions and annihilation in the interstellar medium

    International Nuclear Information System (INIS)

    Guessoum, N.; Jean, P.; Gillard, W.

    2006-01-01

    The processes undergone by positrons in the interstellar medium (ISM) from the moments of their birth to their annihilation are examined. Both the physics of the positron interactions with gases and solids (dust grains), and the physical conditions and characteristics of the environments where the processes of energy loss, positronium formation, and annihilation taking place, are reviewed. An explanation is given as to how all the relevant physical information are taken into account in order to calculate annihilation rates and spectra of the 511 keV emission for the various phases of the ISM; special attention is paid to positron interactions with dust and with polycyclic aromatic hydrocarbons. An attempt is made to show to what extent the interactions between positrons and interstellar dust grains are similar to laboratory experiments in which beams of slow positrons impinge upon solids and surfaces. Sample results are shown for the effect of dust grains on positron annihilation spectra in some phases of the ISM which, together with high resolution spectra measured by satellites, can be used to infer useful knowledge about the environment where the annihilation is predominantly taking place and ultimately about the birth place and history of positrons in the Galaxy. The important complementarity between work done by the astrophysical and the solid-state positron communities is strongly emphasized and specific experimental work is suggested which could assist the modeling of the interaction and annihilation of positrons in the ISM

  14. Relevance of slow positron beam research to astrophysical studies of positron interactions and annihilation in the interstellar medium

    Energy Technology Data Exchange (ETDEWEB)

    Guessoum, N. [American University of Sharjah, Physics Department, P.O. Box 26666, Sharjah (United Arab Emirates)]. E-mail: nguessoum@aus.ac.ae; Jean, P. [Centre d' Etude Spatiale des Rayonnements, Toulouse (France); Gillard, W. [Centre d' Etude Spatiale des Rayonnements, Toulouse (France)

    2006-02-28

    The processes undergone by positrons in the interstellar medium (ISM) from the moments of their birth to their annihilation are examined. Both the physics of the positron interactions with gases and solids (dust grains), and the physical conditions and characteristics of the environments where the processes of energy loss, positronium formation, and annihilation taking place, are reviewed. An explanation is given as to how all the relevant physical information are taken into account in order to calculate annihilation rates and spectra of the 511 keV emission for the various phases of the ISM; special attention is paid to positron interactions with dust and with polycyclic aromatic hydrocarbons. An attempt is made to show to what extent the interactions between positrons and interstellar dust grains are similar to laboratory experiments in which beams of slow positrons impinge upon solids and surfaces. Sample results are shown for the effect of dust grains on positron annihilation spectra in some phases of the ISM which, together with high resolution spectra measured by satellites, can be used to infer useful knowledge about the environment where the annihilation is predominantly taking place and ultimately about the birth place and history of positrons in the Galaxy. The important complementarity between work done by the astrophysical and the solid-state positron communities is strongly emphasized and specific experimental work is suggested which could assist the modeling of the interaction and annihilation of positrons in the ISM.

  15. Three dimensional positron-CT: 3D-PET

    International Nuclear Information System (INIS)

    Ishii, K.

    2000-01-01

    Positron-CT, namely the positron emission tomograph (PET) provides us the metabolism images obtained by the administration of the drug labeled by the positron emission nuclide in the human body. For example, the carbohydrate metabolism image is obtained by the administration of glucose labelled by 18 F-radioisotopes, and it can be applied to early detection of the cancer and research of high-order function of the brain. As well as X-ray CT, the examine receives the exposure in the positron CT. 3D-PET is based on the solid measurement of γ-rays, therefore, the detection sensitivity of 3D-PET becomes very high and it is possible to drastically reduce the dose of the positron emission nuclide. Because the exposure is reduced to the utmost, the positron CT diagnosis would be possible for the child and the exposure of positron CT doctor in charge can be also reduced. This ideal functional diagnostic imaging equipment, namely, 3D-PET is introduced here. (author)

  16. Positron lifetime technique with applications in materials science

    International Nuclear Information System (INIS)

    Vries, J. de.

    1987-01-01

    This thesis deals with the positron lifetime technique as a method to measure extremely low concentrations of extremely small cavities in materials. The method is based upon the fact that the positron lieftime decreases as the electron density increases and upon the fact that a positron preferably annihilates in cavity-like defects in lattices. The theory of positron behaviour in materials and technical aspects of measuring positron liefetimes are described in ch.'s 2 and 3 respectively. Three methods for increasing the time resolution are discussed and some positron sources are described (ch.4). Some applications of the positron lifetime technique and experimental results are shown in chapter 5. 125 refs.; 61 figs.; 18 tabs

  17. Results on positron diffusion in Si

    International Nuclear Information System (INIS)

    Nielsen, B.; Lynn, K.G.; Vehanen, A.; Schultz, P.J.

    1984-10-01

    Positron diffusion in Si(100) and Si(111) has been measured using a variable energy positron beam. The diffusion related parameter, E 0 is found to be 4.2 +- 0.2 keV, significantly longer than previously reported values. The positron diffusion coefficient is estimated at D/sub +/ = 2.3 +- 0.4 cm 2 /sec, the uncertainty arising mainly from the characteristics of the assumed positron implantation profile. A drastic reduction in E 0 is found after heating the sample to 1300 0 K, showing that previously reported low values of E 0 are associated with the thermal history of the sample. A high sensitivity to defects introduced by low energy ion bombardment is found, and the defect recovery was followed during heat treatments. Reconstruction of the Si(111) surface into the so-called 7 x 7 structure had no detectable influence on the positron diffusion behavior. No changes in the positron diffusion was observed after covering the surface with atomic hydrogen. However the yield of positronium formation at the surface was enhanced, attributed to an increased density of states at the surface

  18. Positrons from supernova and the origin of the galactic-center positron-annihilation radiation

    International Nuclear Information System (INIS)

    Colgate, S.A.

    1983-01-01

    The emission of positrons from supernova ejecta is dicussed in terms of the galactic-center annihilation radiation. The positrons from the radioactive sequences 56 Ni→ 56 Co→ 56 Fe are the most numerous source from supernova. Only type I supernova will allow a significant fraction to escape the expanding ejecta. For a neutron star model of a type I SN a fraction 4 x 10 -3 of the escaped positron is enough to create the observed several year fluctuation of the annihilation radiation. The likelihood of this model is discussed in terms of other astrophysical evidence as well as the type I SN light curve

  19. Theoretical aspects of positrons in imperfect solids

    International Nuclear Information System (INIS)

    Puska, M.J.

    1987-01-01

    The efficient use of positron annihilation in defect studies requires a deep understanding of the basic processes of positron-imperfect solid interaction. Three stages, i.e. thermalization, trapping by a defect, and the annihilation can be separated during the evolution of the interaction. The last two processes are the most relevant ones for the positron lifetime spectroscopy and they will be discussed in detail in this review. The complete solution of the problem of a localized positron interacting with the electrons around a defect requires the simultaneous self-consistent calculation of the electronic structure and the positron state. This is in principle possible in the two component density functional theory. However, the approximation, in which the electronic structure without the positron influence is used and the electron-positron correlation effects are described by local enhancement factors, has turned out to be feasible in practice and also accurate enough in predicting positron annihilation characteristics. Moreover, a non-self-consistent electron structure is sufficient in many cases. This enables an efficient calculation method in which the positron wave function can be solved in three dimensions for arbitrary defect geometries. Enhancement models for simple metals, transition metals, and semiconductors are represented. Thereafter, applications to vacancies, vacancy clusters, and vacancy-impurity complexes are shown. The positron trapping by defects is mediated by the transfer of the positron binding energy to the solid in the form of electron-hole pairs and phonons. The trapping phenomenon is discussed in the case of metals and semiconductors. Semiconductors are especially challenging because the existence of the energy gap makes the low energy electron-hole excitations impossible and because the defects have different charge states effecting strongly on the trapping rate. (author)

  20. High Energy Cosmic Electrons: Messengers from Nearby Cosmic Ray Sources or Dark Matter?

    Science.gov (United States)

    Moiseev, Alexander

    2011-01-01

    This slide presentation reviews the recent discoveries by the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM) on board the Fermi Gamma-Ray Telescope in reference to high energy cosmic electrons, and whether their source is cosmic rays or dark matter. Specific interest is devoted to Cosmic Ray electrons anisotropy,

  1. Design of a transmission electron positron microscope

    International Nuclear Information System (INIS)

    Doyama, Masao; Inoue, M.; Kogure, Y.; Hayashi, Y.; Yoshii, T.; Kurihara, T.; Tsuno, K.

    2003-01-01

    This paper reports the plans and design of positron-electron microscopes being built at KEK (High Energy Accelerator Research Organization), Tsukuba, Japan. A used electron microscope is altered. The kinetic energies of positrons produced by accelerators or by nuclear decays are not a unique value but show a spread over in a wide range. Positron beam is guided to a transmission electron microscope (JEM100SX). Positrons are moderated by a tungsten foil, are accelerated and are focused on a nickel sheet. The monochromatic focused beam is injected into an electron microscope. The focusing and aberration of positrons are the same as electrons in a magnetic system which are used in commercial electron microscopes. Imaging plates are used to record positron images for the transmission electron microscope. (author)

  2. Cosmic strings

    International Nuclear Information System (INIS)

    Bennett, D.P.

    1988-07-01

    Cosmic strings are linear topological defects that are predicted by some grand unified theories to form during a spontaneous symmetry breaking phase transition in the early universe. They are the basis for the only theories of galaxy formation aside from quantum fluctuations from inflation that are based on fundamental physics. In contrast to inflation, they can also be observed directly through gravitational lensing and their characteristic microwave background anistropy. It has recently been discovered by F. Bouchet and myself that details of cosmic string evolution are very different from the so-called ''standard model'' that has been assumed in most of the string induced galaxy formation calculations. Therefore, the details of galaxy formation in the cosmic string models are currently very uncertain. 29 refs., 9 figs

  3. Positron deep level transient spectroscopy — a new application of positron annihilation to semiconductor physics

    Science.gov (United States)

    Beling, C. D.; Fung, S.; Au, H. L.; Ling, C. C.; Reddy, C. V.; Deng, A. H.; Panda, B. K.

    1997-05-01

    Recent positron mobility and lifetime measurements made on ac-biased metal on semi-insulating GaAs junctions, which have identified the native EL2 defect through a determination of the characteristic ionization energy of the donor level, are reviewed. It is shown that these measurements point towards a new spectroscopy, tentatively named positron-DLTS (deep level transient spectroscopy), that is the direct complement to conventional DLTS in that it monitors transients in the electric field of the depletion region rather than the inversely related depletion width, as deep levels undergo ionization. In this new spectroscopy, which may be applied to doped material by use of a suitable positron beam, electric field transients are monitored through the Doppler shift of the annihilation radiation resulting from the drift velocity of the positron in the depletion region. Two useful extensions of the new spectroscopy beyond conventional capacitance-DLTS are suggested. The first is that in some instances information on the microstructure of the defect causing the deep level may be inferred from the sensitivity of the positron to vacancy defects of negative and neutral charge states. The second is that the positron annihilation technique is intrinsically much faster than conventional DLTS with the capability of observing transients some 10 6 times faster, thus allowing deep levels (and even shallow levels) to be investigated without problems associated with carrier freeze-out.

  4. Positron probes of the Ge(1 0 0) surface: The effects of surface reconstructions and electron-positron correlations on positron trapping and annihilation characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Fazleev, N.G. [Department of Physics, University of Texas at Arlington, Box 19059, Arlington, TX 76019-0059 (United States) and Department of Physics, Kazan State University, Kazan 420008 (Russian Federation)]. E-mail: Fazleev@uta.edu; Jung, E. [Department of Physics, University of Texas at Arlington, Box 19059, Arlington, TX 76019-0059 (United States); Weiss, A.H. [Department of Physics, University of Texas at Arlington, Box 19059, Arlington, TX 76019-0059 (United States)

    2007-08-15

    Positron annihilation induced Auger electron spectroscopy (PAES) has been applied to study the Ge(1 0 0) surface. The high-resolution PAES spectrum from the Ge(1 0 0) surface displays several strong Auger peaks corresponding to M{sub 4,5}N{sub 1}N{sub 2,3}, M{sub 2,3}M{sub 4,5}M{sub 4,5}, M{sub 2,3}M{sub 4,5}V and M{sub 1}M{sub 4,5}M{sub 4,5} Auger transitions. The integrated peak intensities of Auger transitions are used to obtain experimental annihilation probabilities for the Ge 3d and 3p core level electrons. These experimental results are analyzed by performing calculations of positron surface states and annihilation characteristics of surface trapped positrons with relevant Ge core-level electrons for the non-reconstructed and reconstructed Ge(1 0 0)-p(2 x 1), Ge(1 0 0)-p(2 x 2) and Ge(1 0 0)-c(4 x 2) surfaces. It is found that the positron surface state wave function extends into the Ge lattice in the regions where atoms are displaced from their ideal terminated positions due to reconstructions. Estimates of the positron binding energy and the positron annihilation characteristics reveal their sensitivity to the specific atomic structure of the topmost layers of Ge(1 0 0). A comparison with PAES data reveals an agreement with theoretical core annihilation probabilities for the Auger transitions considered.

  5. Dynamic behavior of ion acoustic waves in electron-positron-ion magnetoplasmas with superthermal electrons and positrons

    Science.gov (United States)

    Saha, Asit; Pal, Nikhil; Chatterjee, Prasanta

    2014-10-01

    The dynamic behavior of ion acoustic waves in electron-positron-ion magnetoplasmas with superthermal electrons and positrons has been investigated in the framework of perturbed and non-perturbed Kadomtsev-Petviashili (KP) equations. Applying the reductive perturbation technique, we have derived the KP equation in electron-positron-ion magnetoplasma with kappa distributed electrons and positrons. Bifurcations of ion acoustic traveling waves of the KP equation are presented. Using the bifurcation theory of planar dynamical systems, the existence of the solitary wave solutions and the periodic traveling wave solutions has been established. Two exact solutions of these waves have been derived depending on the system parameters. Then, using the Hirota's direct method, we have obtained two-soliton and three-soliton solutions of the KP equation. The effect of the spectral index κ on propagations of the two-soliton and the three-soliton has been shown. Considering an external periodic perturbation, we have presented the quasi periodic behavior of ion acoustic waves in electron-positron-ion magnetoplasmas.

  6. Dynamic behavior of ion acoustic waves in electron-positron-ion magnetoplasmas with superthermal electrons and positrons

    Energy Technology Data Exchange (ETDEWEB)

    Saha, Asit, E-mail: asit-saha123@rediffmail.com, E-mail: prasantachatterjee1@rediffmail.com [Department of Mathematics, Sikkim Manipal Institute of Technology, Majitar, Rangpo, East-Sikkim 737136 (India); Department of Mathematics, Siksha Bhavana, Visva Bharati University, Santiniketan-731235 (India); Pal, Nikhil; Chatterjee, Prasanta, E-mail: asit-saha123@rediffmail.com, E-mail: prasantachatterjee1@rediffmail.com [Department of Mathematics, Siksha Bhavana, Visva Bharati University, Santiniketan-731235 (India)

    2014-10-15

    The dynamic behavior of ion acoustic waves in electron-positron-ion magnetoplasmas with superthermal electrons and positrons has been investigated in the framework of perturbed and non-perturbed Kadomtsev-Petviashili (KP) equations. Applying the reductive perturbation technique, we have derived the KP equation in electron-positron-ion magnetoplasma with kappa distributed electrons and positrons. Bifurcations of ion acoustic traveling waves of the KP equation are presented. Using the bifurcation theory of planar dynamical systems, the existence of the solitary wave solutions and the periodic traveling wave solutions has been established. Two exact solutions of these waves have been derived depending on the system parameters. Then, using the Hirota's direct method, we have obtained two-soliton and three-soliton solutions of the KP equation. The effect of the spectral index κ on propagations of the two-soliton and the three-soliton has been shown. Considering an external periodic perturbation, we have presented the quasi periodic behavior of ion acoustic waves in electron-positron-ion magnetoplasmas.

  7. Cosmic-Ray Extremely Distributed Observatory: a global cosmic ray detection framework

    Science.gov (United States)

    Sushchov, O.; Homola, P.; Dhital, N.; Bratek, Ł.; Poznański, P.; Wibig, T.; Zamora-Saa, J.; Almeida Cheminant, K.; Alvarez Castillo, D.; Góra, D.; Jagoda, P.; Jałocha, J.; Jarvis, J. F.; Kasztelan, M.; Kopański, K.; Krupiński, M.; Michałek, M.; Nazari, V.; Smelcerz, K.; Smolek, K.; Stasielak, J.; Sułek, M.

    2017-12-01

    The main objective of the Cosmic-Ray Extremely Distributed Observatory (CREDO) is the detection and analysis of extended cosmic ray phenomena, so-called super-preshowers (SPS), using existing as well as new infrastructure (cosmic-ray observatories, educational detectors, single detectors etc.). The search for ensembles of cosmic ray events initiated by SPS is yet an untouched ground, in contrast to the current state-of-the-art analysis, which is focused on the detection of single cosmic ray events. Theoretical explanation of SPS could be given either within classical (e.g., photon-photon interaction) or exotic (e.g., Super Heavy Dark Matter decay or annihilation) scenarios, thus detection of SPS would provide a better understanding of particle physics, high energy astrophysics and cosmology. The ensembles of cosmic rays can be classified based on the spatial and temporal extent of particles constituting the ensemble. Some classes of SPS are predicted to have huge spatial distribution, a unique signature detectable only with a facility of the global size. Since development and commissioning of a completely new facility with such requirements is economically unwarranted and time-consuming, the global analysis goals are achievable when all types of existing detectors are merged into a worldwide network. The idea to use the instruments in operation is based on a novel trigger algorithm: in parallel to looking for neighbour surface detectors receiving the signal simultaneously, one should also look for spatially isolated stations clustered in a small time window. On the other hand, CREDO strategy is also aimed at an active engagement of a large number of participants, who will contribute to the project by using common electronic devices (e.g., smartphones), capable of detecting cosmic rays. It will help not only in expanding the geographical spread of CREDO, but also in managing a large manpower necessary for a more efficient crowd-sourced pattern recognition scheme to

  8. Simulation of the annihilation emission of galactic positrons

    International Nuclear Information System (INIS)

    Gillard, W.

    2008-01-01

    Positrons annihilate in the central region of our Galaxy. This has been known since the detection of a strong emission line centered on an energy of 511 keV in the direction of the Galactic center. This gamma-ray line is emitted during the annihilation of positrons with electrons from the interstellar medium. The spectrometer SPI, onboard the INTEGRAL observatory, performed spatial and spectral analyses of the positron annihilation emission. This thesis presents a study of the Galactic positron annihilation emission based on models of the different interactions undergone by positrons in the interstellar medium. The models are relied on our present knowledge of the properties of the interstellar medium in the Galactic bulge, where most of the positrons annihilate, and of the physics of positrons (production, propagation and annihilation processes). In order to obtain constraints on the positrons sources and physical characteristics of the annihilation medium, we compared the results of the models to measurements provided by the SPI spectrometer. (author)

  9. Positron probes for mechanical fatigue detection system

    International Nuclear Information System (INIS)

    Holt, W.H.; Mock, W. Jr.

    1976-01-01

    The invention comprises positron-emitting probes for use in testing samples of metals for fatique by positron annihilation techniques comprising a substrate made from the same material as the test sample, positron-emitting material supported by one surface of the substrate, and a cover for the emitting material, the cover is sealed to the substrate and is of such thinness and density as to provide a window through which positron passage is unimpeded

  10. Cosmic rays in space

    International Nuclear Information System (INIS)

    Fujitaka, Kazunobu

    2005-01-01

    Cosmos is a mysterious space by which many researchers are fascinated for many years. But, going into space means that we will receive extra exposure due to existence of cosmic rays. Cosmic rays are mainly composed of highly energetic protons. It was born in the last stage of stellar life. Understanding of cosmos will certainly bring right understanding of radiation energy, or energy itself. As no one could see the very early stage of cosmic rays, there is only a speculation. But it is better to speculate something based on certain side evidences, than to give up the whole. Such attitude shall be welcomed in the space researches. Anyway, cosmic rays were born in the last explosion of a star, which is called as Super Nova. After cosmic rays are emitted from the Super Nova, it will reach to the human surroundings. To indicate its intensity, special unit of ''dose rate'' is used. When a man climbs a mountain, cosmic ray intensity surely increases. It doubles as he goes up every 1500m elevation. It was ascertained by our own measurements. Then what happens when the goes up more? At aviation altitude, where airplanes fly, the dose rate will be increased up to 100times the high mountain cases. And what is expected when he goes up further more, up to space orbit altitude? In this case, the dose rate increases up to 10times the airplane cases. Geomagnetism affects the dose rate very much. As primary cosmic ray particles are charged particles, they cannot do well with existence of the magnetic field. In effect, cosmic rays can penetrate into the polar atmosphere along geomagnetic lines of forces which stand almost vertical, but penetration of low energy cosmic rays will be banned when they intend to penetrate crossing the geomagnetic lines of forces in equatorial region. Therefore, exposure due to cosmic rays will become large in polar region, while it remains small in equatorial region. In effect, airplanes which fly over the equator. Only, we have to know that the cosmos

  11. 4.5 Tesla magnetic field reduces range of high-energy positrons -- Potential implications for positron emission tomography

    International Nuclear Information System (INIS)

    Wirrwar, A.; Vosberg, H.; Herzog, H.; Halling, H.; Weber, S.; Mueller-Gaertner, H.W.; Forschungszentrum Juelich GmbH

    1997-01-01

    The authors have theoretically and experimentally investigated the extent to which homogeneous magnetic fields up to 7 Tesla reduce the spatial distance positrons travel before annihilation (positron range). Computer simulations of a noncoincident detector design using a Monte Carlo algorithm calculated the positron range as a function of positron energy and magnetic field strength. The simulation predicted improvements in resolution, defined as full-width at half-maximum (FWHM) of the line-spread function (LSF) for a magnetic field strength up to 7 Tesla: negligible for F-18, from 3.35 mm to 2.73 mm for Ga-68 and from 3.66 mm to 2.68 mm for Rb-82. Also a substantial noise suppression was observed, described by the full-width at tenth-maximum (FWTM) for higher positron energies. The experimental approach confirmed an improvement in resolution for Ga-68 from 3.54 mm at 0 Tesla to 2.99 mm FWHM at 4.5 Tesla and practically no improvement for F-18 (2.97 mm at 0 Tesla and 2.95 mm at 4.5 Tesla). It is concluded that the simulation model is appropriate and that a homogeneous static magnetic field of 4.5 Tesla reduces the range of high-energy positrons to an extent that may improve spatial resolution in positron emission tomography

  12. Defect characterization with positron annihilation

    International Nuclear Information System (INIS)

    Granatelli, L.; Lynn, K.G.

    1980-01-01

    Positron annihilation in metal crystals is reviewed. A brief introduction to the positron annihilation technique is presented first. Then the ability of the positron technique to perform microstructural characterization of four types of lattice defects (vacancies, voids, dislocations, grain boundaries) is discussed. It is frequently not possible to obtain samples that contain only one type of defect in nonnegligible concentrations. Such situations exist for some alloys and for fatigued metal samples. Finally, the current limitations and some future prospects of the technique are presented. 79 references, 14 figures, 1 table

  13. Fundamentals of positron emission tomography

    International Nuclear Information System (INIS)

    Ostertag, H.

    1989-01-01

    Positron emission tomography is a modern radionuclide method of measuring physiological quantities or metabolic parameters in vivo. The methods is based on: (1) Radioactive labelling with positron emitters; (2) the coincidence technique for the measurement of the annihilation radiation following positron decay; (3) analysis of the data measured using biological models. The basic aspects and problems of the method are discussed. The main fields of future research are the synthesis of new labelled compounds and the development of mathematical models of the biological processes to be investigated. (orig.) [de

  14. Atomic collisions involving pulsed positrons

    DEFF Research Database (Denmark)

    Merrison, J. P.; Bluhme, H.; Field, D.

    2000-01-01

    Conventional slow positron beams have been widely and profitably used to study atomic collisions and have been instrumental in understanding the dynamics of ionization. The next generation of positron atomic collision studies are possible with the use of charged particle traps. Not only can large...... instantaneous intensities be achieved with in-beam accumulation, but more importantly many orders of magnitude improvement in energy and spatial resolution can be achieved using positron cooling. Atomic collisions can be studied on a new energy scale with unprecedented precion and control. The use...

  15. Construction report of the PF slow-positron source. 1

    International Nuclear Information System (INIS)

    Enomoto, Atsushi; Kurihara, Toshikazu; Kobayashi, Hitoshi

    1993-12-01

    The slow positron source utilizing the electron beam of the 2.5 GeV electron beam accelerator which is the synchrotron radiation injector is being constructed. The outline of the project and the present state of construction are reported. As of November, 1993, by injecting the electron beam of about 10 W to the targets for producing positrons, the slow positrons of 4 x 10 4 e + /s has been obtained in the laboratory. Finally, with the electron beam of 30 kW, it is aimed at to obtain the slow positron beam of 2 x 10 9 e + /s. In the slow positron source, the electron beam from the 2.5 GeV linear accelerator is used as the primary beam. This beam is led to the target with electromagnets. Radiation shields were strengthened, and the electrostatic lens system was attached to efficiently extract and send out slow positrons. The conveying system for slow positrons is explained. Primary electron beam, target and moderator for producing slow positrons, the change to continuous current of pulsed slow positron beam and the heightening of luminance of slow positron beam, and the experiment on the utilization of slow positron beam, and the control system for positron conveyance path are reported. (K.I.)

  16. Cosmic ray: Studying the origin

    International Nuclear Information System (INIS)

    Szabelski, J.

    1997-01-01

    Investigations of the origin of cosmic rays are presented. Different methods are discussed: studies of cosmic gamma rays of energy from 30 MeV to about 10 15 eV (since photons point to their places of origin), studies of the mass composition of cosmic rays (because it reflects source morphology), and studies of cosmic rays with energy above 1O 19 eV (for these are the highest energies observed in nature). (author)

  17. Constraints on cosmic strings due to black holes formed from collapsed cosmic string loops

    International Nuclear Information System (INIS)

    Caldwell, R.R.; Gates, E.

    1993-05-01

    The cosmological features of primordial black holes formed from collapsed cosmic string loops are studied. Observational restrictions on a population of primordial black holes are used to restrict f, the fraction of cosmic string loops which collapse to form black holes, and μ, the cosmic string mass-per-unit-length. Using a realistic model of cosmic strings, we find the strongest restriction on the parameters f and μ is due to the energy density in 100MeV photons radiated by the black holes. We also find that inert black hole remnants cannot serve as the dark matter. If earlier, crude estimates of f are reliable, our results severely restrict μ, and therefore limit the viability of the cosmic string large-scale structure scenario

  18. Performance of the Electromagnetic Calorimeter of AMS-02 on the International Space Station ans measurement of the positronic fraction in the 1.5 – 350 GeV energy range

    CERN Document Server

    Basara, Laurent

    The AMS-02 experiment is a particle detector installed on the International Space Station (ISS) since May 2011, which measures the characteristics of the cosmic rays to bring answers to the problematics risen by the astroparticle physics since a few decades, in particular the study of dark matter and the search of antimatter. The phenomenological aspects of the physics of cosmic rays are reviewed in a first part. A second one describes the in-flight performances of the different subdetectors of AMS-02, in particular the electromagnetic calorimeter. It is shown, using particles at the ionizing minimum (MIPs), accounting for the main part of cosmic rays, that the calorimeter works as expected, and we find the same performances as on ground. This study is used to follow in time the evolution of the detector performances. It also allows to develop a charge estimator for the nuclei using the calorimeter. A third and final part, deals with the determination of the positronic fraction. The main difficulty of this me...

  19. A study of positron irradiated porous silicon

    International Nuclear Information System (INIS)

    Huang Yuanming; Xue Qing; Zhai Baogai; Xu Aijun; Liu Shewen; Yu Weizhong

    1998-01-01

    The effect of positron irradiation on photoluminescence (PL) of porous silicon has been studied. After four hour positron irradiation, the red PL spectrum of porous silicon blue shifts into greenish spectral region, and a higher energy luminescence band is introduced into this blueshifted spectrum. The fourier transform infrared absorption experiment shows that the positron irradiation can cause further oxidization of porous silicon. A possible mechanism causing this change of PL spectra after positron irradiation is suggested

  20. Nuclear-charge and positron-energy dependence of the single-quantum annihilation of positrons

    International Nuclear Information System (INIS)

    Palathingal, J.C.; Asoka-Kumar, P.; Lynn, K.G.; Wu, X.Y.

    1995-01-01

    We report an experimental study of the single-quantum annihilation of positrons in a number of elements having atomic numbers between 49 and 90, utilizing a monoenergetic positron beam. Measurements were made of the differential cross sections for the forward direction for the K, L, and M atomic shells in targets of Th, Pb, Au, Hf, Gd, and In, having thicknesses that vary between 2.7 and 4.4 mg/cm 2 . A shielded HPGe detector of high relative photopeak efficiency was used for recording the photon spectrum. Values for the individual atomic shells were obtained in the positron kinetic-energy range 1.02--2.24 MeV. It was observed that the differential cross sections measured for the forward direction varied with energy for each major shell almost alike so that the shell ratios appeared to remain constant while the positron energy varied. The dependence of the cross section on the atomic number Z of the target element was tested for each of the major shells at various energies of measurement. It was seen that the cross sections follow a Z ν relation with ν∼5.1 as the exponent for the K shell. For the higher shells, the exponent is approximately 6.4, which is significantly larger. It was also noted that this pattern is fairly independent of the positron energy. The results on the Z dependence are seen to be clearly at variance with the most updated theoretical predictions

  1. D-term inflation, cosmic strings, and consistency with cosmic microwave background measurements.

    Science.gov (United States)

    Rocher, Jonathan; Sakellariadou, Mairi

    2005-01-14

    Standard D-term inflation is studied in the framework of supergravity. D-term inflation produces cosmic strings; however, it can still be compatible with cosmic microwave background (CMB) measurements without invoking any new physics. The cosmic strings contribution to the CMB data is not constant, nor dominant, contrary to some previous results. Using current CMB measurements, the free parameters (gauge and superpotential couplings, as well as the Fayet-Iliopoulos term) of D-term inflation are constrained.

  2. Explanation of the Knee-like Feature in the DAMPE Cosmic {e}^{-}+{e}^{+} Energy Spectrum

    Science.gov (United States)

    Fang, Kun; Bi, Xiao-Jun; Yin, Peng-Fei

    2018-02-01

    The DArk Matter Particle Explorer, a space-based high precision cosmic-ray detector, has just reported the new measurement of the total electron plus positron energy spectrum up to 4.6 TeV. A notable feature in the spectrum is the spectral break at ∼0.9 TeV, with the spectral index softening from ‑3.1 to ‑3.9. Such a feature is very similar to the knee at the cosmic nuclei energy spectrum. In this work, we propose that the knee-like feature can be explained naturally by assuming that the electrons are accelerated at the supernova remnants (SNRs) and released when the SNRs die out with lifetimes around 105 years. The cut-off energy of those electrons have already decreased to several TeV due to radiative cooling, which may induce the observed TeV spectral break. Another possibility is that the break is induced by a single nearby old SNR. Such a scenario may bring a large electron flux anisotropy that may be observable by the future detectors. We also show that a minor part of electrons escaping during the acceleration in young and nearby SNRs is able to contribute to a several TeV or higher energy region of the spectrum.

  3. Cosmic ray modulation

    International Nuclear Information System (INIS)

    Ueno, Hirosachi

    1974-01-01

    It is important to know the physical state of solar plasma region by the observation of intensity variation of cosmic ray which passed through the solar plasma region, because earth magnetosphere is formed by the interaction between geomagnetic field and solar plasma flow. The observation of cosmic ray intensity is useful to know the average condition of the space of 0.1--3 A.U., and gives the structure of the magnetic field in solar wind affecting the earth magnetosphere. The observation of neutron component in cosmic ray has been carried out at Norikura, Tokyo, Fukushima and Morioka. The lower limit of the energy of incident cosmic ray which can be observed at each station is different, and the fine structure of the variation can be known by comparison. The intensity of meson component in cosmic ray has been measured in underground, and the state of solar plasma region 2--3 A.U. from the earth can be known. The underground measurement has been made at Takeyama and Matsumoto, and a new station at Sakashita is proposed. The measurement at Sakashita will be made by proportional counters at the depth of 100m (water equivalent). Arrangement of detectors is shown. (Kato, T.)

  4. Bulk Materials Analysis Using High-Energy Positron Beams

    International Nuclear Information System (INIS)

    Glade, S C; Asoka-Kumar, P; Nieh, T G; Sterne, P A; Wirth, B D; Dauskardt, R H; Flores, K M; Suh, D; Odette, G.R.

    2002-01-01

    This article reviews some recent materials analysis results using high-energy positron beams at Lawrence Livermore National Laboratory. We are combining positron lifetime and orbital electron momentum spectroscopic methods to provide electron number densities and electron momentum distributions around positron annihilation sites. Topics covered include: correlation of positron annihilation characteristics with structural and mechanical properties of bulk metallic glasses, compositional studies of embrittling features in nuclear reactor pressure vessel steel, pore characterization in Zeolites, and positron annihilation characteristics in alkali halides

  5. Investigation and realization of a slow-positron beam

    International Nuclear Information System (INIS)

    Ruiz, Nicolas

    2011-01-01

    This research thesis first proposes a presentation of the GBAR project (Gravitational Behaviour of Anti-hydrogen at Rest) within which this research took place, and which aims at performing the first direct test of the Weak Equivalence Principle on anti-matter by studying the free fall of anti-hydrogen atoms in the Earth gravitational field. The author presents different aspects of this project: scientific objective, experiment principle and structure, detailed structure (positron beam, positron trap, positron/positronium conversion, anti-proton beam, trapping, slowing down and neutralisation of anti-hydrogen ions). The author then reports the design of the positron beam: study of source technology, studies related to the fast positron source, design of the low positron line (approach, functions, simulations, technology). The two last chapters report the construction and the characterization of the slow-positron line [fr

  6. Ultrarelativistic electron and positron radiation in planar channeling

    International Nuclear Information System (INIS)

    Kalashnikov, N.P.; Olchack, A.S.

    1980-01-01

    The coherent electromagnetic radiation from channeling electrons and positrons is given by similar expression. However for the channeling positrons the close collisions are suppressed due to the fact that the positron wave function is exponentially small near the atoms of the crystal lattice. It follows that the coherent bremsstrahlung decreases for the channeling positrons. We have investigated the ultrarelativistic channeling electron and positron radiations, connected with the electromagnetic transitions from the continuum spectrum states to the quasi-bound spectrum states and between the different quasi-bound spectrum states. The radiation probabilities are calculated by using the model continuum planar potential. It is shown that the radiation from the channeling electrons is several orders of magnitude larger than the positron radiation, while the electron and positron radiation have similar characteristics such as frequency limitation and angular distribution of the radiation. (orig.)

  7. Evaluation of scintillators and semiconductor detectors to image three-photon positron annihilation for positron emission tomography

    International Nuclear Information System (INIS)

    Abuelhia, E.; Spyrou, N.M.; Kacperski, K.; College University, Middlesex Hospital, London

    2008-01-01

    Positron emission tomography (PET) is rapidly becoming the main nuclear imaging modality of the present century. The future of PET instrumentation relies on semiconductor detectors because of their excellent characteristics. Three-photon positron annihilation has been recently investigated as a novel imaging modality, which demands the crucial high energy resolution of semiconductor detector. In this work the evaluation of the NaI(Tl) scintillator and HPGe and CdZTe semiconductor detectors, to construct a simple three-photon positron annihilation scanner has been explored. The effect of detector and scanner size on spatial resolution (FWHM) is discussed. The characteristics: energy resolution versus count rate and point-spread function of the three-photon positron annihilation image profile from triple coincidence measurements were investigated. (author)

  8. Cosmic Humanity: Utopia, Realities, Prospects

    OpenAIRE

    Sergey Krichevsky

    2017-01-01

    The philosophical foundations of the theory and practice of the creation of cosmic humanity as a process of the evolution of human civilization, the emergence into space, with the prospect of resettlement outside the Earth are considered. There is a connection between myths, fantasies, ideas, concepts and projects aimed at the exploration of outer space, the creation of cosmic humanity. A new and voluminous definition of cosmic humanity in the evolutionary paradigm is given. Cosmic humanity i...

  9. Cosmic-ray-veto detector system

    International Nuclear Information System (INIS)

    Miller, D.W.; Menlove, H.O.

    1992-12-01

    To reduce the cosmic-ray-induced neutron background, we are testing a cosmic-ray veto option with a neutron detector system that uses plastic scintillator slabs mounted on the outside of a 3 He-tube detector. The scintillator slabs eliminate unwanted cosmic-ray events, enabling the detector to assay low-level plutonium samples, for which a low-background coincident signature is critical. This report describes the design and testing of the prototype cosmic-ray-veto detector system

  10. Studies of positron induced luminescence from polymers

    International Nuclear Information System (INIS)

    Xu, J.; Hulett, L.D. Jr.; Lewis, T.A.; Tolk, N.H.

    1994-01-01

    Light emission from polymers (anthracene dissolved in polystryrene) induced by low-energy positrons and electrons has been studied. Results indicate a clear difference between optical emissions under positron and electron bombardment. The positron-induced luminescence spectrum is believed to be generated by both collisional and annihilation processes

  11. Cardiac positron tomography

    International Nuclear Information System (INIS)

    Geltmann, E.M.; Roberts, R.; Sobel, B.E.

    1980-01-01

    Positron emission tomography (PET) performed after the administration of the positron-emitting radionuclides carbon-11 ( 11 C), nitrogen-13 ( 13 N), oxygen-15 ( 15 O) and fluorine-18 ( 18 F) has permitted the improved noninvasive assessment of the regional myocardial metabolism of normal physiologic substrates and intermediates and their cogeners. In experimental animals, the rate of oxidation of 11 C-palmitate correlates closely with other indexes of oxygen consumption, and the extraction of 11 C-palmitate (like that of 18 F-fatty acids and 18 F-fluoredoxyglucose) ist markedly diminished in regions of myocardial ischemia. In both experimental animals and in patients, myocardial infarct site and size, determined by positron emission tomography after the intravenous injection of 11 C-palmitate, correlate closely with the electrocardiographic infarct locus and enzymatically estimated infarct size as well as with the location and extent of regional left ventricular wall motion abnormalities. PET offers promise for assessment of flow as well despite the complexities involved. PET with 13 NH 3 appears to provide one useful qualitative index, although this tracer ist actively metabolized. Because of the quantitative capabilities of positron emission tomography and the rapid progress which is being made in the development of fast scan, multi-slice, and gated instrumentation, this technique is likely to facilitate improved understanding and characterization of regional myocardial metabolism and blood flow in man under physiological and pathophysiological conditions. (orig.) [de

  12. Positron lifetime experiments in indium selenide

    International Nuclear Information System (INIS)

    Cruz, R.M. de la; Pareja, R.

    1988-01-01

    Positron lifetime experiments have been performed on as-grown samples which had been isochronally annealed up to 820 K and plastically deformed and these experiments yield a constant lifetime of 282 ± 2 ps which is attributed to bulk positron states in InSe. Electron-irradiated samples exhibit a two-component spectrum, revealing the presence of positron traps which anneal out at about 330 K. The nature of the native shallow donors in InSe is discussed in the light of the results, which support the idea that native donor centres are probably interstitial In atoms rather than Se vacancies. Positron trapping observed in the electron-irradiated samples is attributed to defects related to In vacancies. (author)

  13. Test particle trajectories near cosmic strings

    Indian Academy of Sciences (India)

    We present a detailed analysis of the motion of test particle in the gravitational field of cosmic strings in different situations using the Hamilton–Jacobi (H–J) formalism. We have discussed the trajectories near static cosmic string, cosmic string in Brans–Dicke theory and cosmic string in dilaton gravity.

  14. Cosmic ray: Studying the origin

    Energy Technology Data Exchange (ETDEWEB)

    Szabelski, J. [Cosmic Ray Laboratory, Soltan Institute for Nuclear Studies, Lodz (Poland)

    1997-12-31

    Investigations of the origin of cosmic rays are presented. Different methods are discussed: studies of cosmic gamma rays of energy from 30 MeV to about 10{sup 15} eV (since photons point to their places of origin), studies of the mass composition of cosmic rays (because it reflects source morphology), and studies of cosmic rays with energy above 1O{sup 19} eV (for these are the highest energies observed in nature). (author) 101 refs, 19 figs, 7 tabs

  15. Undulator-based production of polarized positrons

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, G. [Tel-Aviv Univ. (Israel); Barley, J. [Cornell Univ., Ithaca, NY (United States); Batygin, Y. [SLAC, Menlo Park, CA (US)] (and others)

    2009-05-15

    Full exploitation of the physics potential of a future International Linear Collider will require the use of polarized electron and positron beams. Experiment E166 at the Stanford Linear Accelerator Center (SLAC) has demonstrated a scheme in which an electron beam passes through a helical undulator to generate photons (whose first-harmonic spectrum extended to 7.9 MeV) with circular polarization, which are then converted in a thin target to generate longitudinally polarized positrons and electrons. The experiment was carried out with a one-meter-long, 400-period, pulsed helical undulator in the Final Focus Test Beam (FFTB) operated at 46.6 GeV. Measurements of the positron polarization have been performed at five positron energies from 4.5 to 7.5 MeV. In addition, the electron polarization has been determined at 6.7MeV, and the effect of operating the undulator with a ferrofluid was also investigated. To compare the measurements with expectations, detailed simulations were made with an upgraded version of GEANT4 that includes the dominant polarization-dependent interactions of electrons, positrons, and photons with matter. The measurements agree with calculations, corresponding to 80% polarization for positrons near 6 MeV and 90% for electrons near 7 MeV. (orig.)

  16. Positron lifetime study of neutron-irradiated molybdenum

    International Nuclear Information System (INIS)

    Hinode, Kenji; Tanigawa, Shoichiro; Kumakura, Hiroaki; Doyama, Masao; Shiraishi, Kensuke.

    1978-01-01

    Annealing behavior of fast-neutron-irradiated molybdenum was studied by means of positron lifetime technique. It was found that Stage III annealing can be mainly identified as the vacancy migration process from the detailed analyses of data. The void growth after successive high temperature annealings was clearly detected through the changes of positron lifetime parameters. An attempt to analyse the size distribution of voids from positron lifetime spectra was presented, and discussions on the evaluation of void concentration from positron data are also given. (author)

  17. Department of Cosmic Radiation Physics: Overview

    International Nuclear Information System (INIS)

    Gawin, J.

    1999-01-01

    Full text: The Department of Cosmic Ray Physics in Lodz is involved in basic research in the area of high energy physics and cosmic ray physics related to: - Studies of asymptotic properties of hadronic interactions based on the analysis of cosmic ray propagation in the atmosphere. - Experimental and phenomenological studies of Extensive Air Showers induced by cosmic ray particles. - Search for point sources of high energy cosmic rays. - Studies of cosmic ray propagation in the Galaxy and mechanisms of particle acceleration. - Studies of mass composition of cosmic rays in the energy range 10 15 - 10 17 eV. Theoretical and experimental studies of Extensive Air Shower properties are performed mostly based on the results obtained by the Lodz Extensive Air Shower Array. We analysed nearly 100,000 events of energies above 10 15 eV registered by the Lodz hodoscope. We have developed the method of data analysis which allows us to verify different models of cosmic ray mass composition. In our research in high energy cosmic rays we also used experimental data from other collaborating experiments in Karlsruhe, Baksan and THEMISTOCLE. The Lodz group collaborates with many foreign institutes and laboratories in construction and data interpretation of cosmic ray experiments. Our most important partners are: Forschungszentrum in Karlsruhe (Germany), College de France, Institute for Nuclear Studies of the Russian Academy of Science, University of Perpignan and Uppsala University (Sweden). (author)

  18. Department of Cosmic Radiation Physics - Overview

    International Nuclear Information System (INIS)

    Gawin, J.

    1997-01-01

    Full text: The Department of Cosmic Ray Physics in Lodz is involved in basic research in the area of high energy physics and cosmic ray physics related to: -Studies of the asymptotic properties of hadronic interactions from the analysis of cosmic ray propagation in the atmosphere. -Studies of structure and properties of Extensive Air Showers induced by cosmic ray particles. -Search for point sources of high energy cosmic rays. -Studies of cosmic ray propagation in the Galaxy and mechanisms of particle acceleration. -Studies of the mass composition of cosmic rays in the energy range 10 15 -10 17 eV. Theoretical and experimental studies of nuclear interactions for energies exceeding those obtained by modern particle accelerators are performed employing results obtained by the Lodz Extensive Air Shower Array. The Lodz hodoscope can register electromagnetic components of cosmic ray showers in the atmosphere as well as muons at two energy thresholds. Data collected by the Lodz array are also used to study mass composition of cosmic rays in the energy range 10 15 - 10 17 eV. The Lodz group collaborates with foreign institutes and laboratories on construction and data interpretation of cosmic ray experiments. Our most important partners are: Forschungszentrum Karlsruhe (Germany), College de France, the Institute for Nuclear Studies of the Russian Academy of Sciences, the University of Durham, and the University of Perpignan. (author)

  19. Positron annihilation spectroscopy in materials structure studies

    International Nuclear Information System (INIS)

    Grafutin, Viktor I; Prokop'ev, Evgenii P

    2002-01-01

    A relatively new method of materials structure analysis - positron annihilation spectroscopy (PAS) - is reviewed. Measurements of positron lifetimes, the determination of positron 3γ- and 2γ-annihilation probabilities, and an investigation of the effects of different external factors on the fundamental characteristics of annihilation constitute the basis for this promising method. The ways in which the positron annihilation process operates in ionic crystals, semiconductors, metals and some condensed matter systems are analyzed. The scope of PAS is described and its prospects for the study of the electronic and defect structures are discussed. The applications of positron annihilation spectroscopy in radiation physics and chemistry of various substances as well as in physics and chemistry of solutions are exemplified. (instruments and methods of investigation)

  20. Digital positron annihilation spectrometer

    International Nuclear Information System (INIS)

    Cheng Bin; Weng Huimin; Han Rongdian; Ye Bangjiao

    2010-01-01

    With the high speed development of digital signal process, the technique of the digitization and processing of signals was applied in the domain of a broad class of nuclear technique. The development of digital positron lifetime spectrometer (DPLS) is more promising than the conventional positron lifetime spectrometer equipped with nuclear instrument modules. And digital lifetime spectrometer has many advantages, such as low noise, long term stability, flexible online or offline digital processing, simple setup, low expense, easy to setting, and more physical information. Digital constant fraction discrimination is for timing. And a new method of optimizing energy windows setting for digital positron lifetime spectrometer is also developed employing the simulated annealing for the convenient use. The time resolution is 220ps and the count rate is 200cps. (authors)

  1. Positron emission tomography imaging--technical considerations

    International Nuclear Information System (INIS)

    Muehllehner, G.; Karp, J.S.

    1986-01-01

    Positron imaging instrumentation has improved rapidly in the last few years. Scanners currently under development are beginning to approach fundamental limits set by positron range and noncolinearity effects. This report reviews the latest developments in positron emission tomography (PET) instrumentation, emphasizing the development of coding schemes that reduce the complexity and cost of high-resolution scanners. The relative benefits of using time-of-flight (TOF) information is discussed as well. 68 references

  2. Deepening Cosmic Education

    Science.gov (United States)

    Leonard, Gerard

    2013-01-01

    This article is a special blend of research, theory, and practice, with clear insight into the origins of Cosmic Education and cosmic task, while recalling memories of student explorations in botany, in particular, episodes from Mr. Leonard's teaching. Mr. Leonard speaks of a storytelling curriculum that eloquently puts perspective into dimensions…

  3. Generation and application of slow positrons based on a electron LINAC

    International Nuclear Information System (INIS)

    Kurihara, Toshikazu

    2002-01-01

    History of slow positron in Institute of Materials Structure Science High Energy Accelerator Research Organization is explained. The principle of generation and application of intense positron beam is mentioned. Two sources of intense positron are radioactive decay of radioactive isotopes emitting positron and electron-positron pair creation. The radioactive decay method uses 58 Co, 64 Cu, 11 C, 13 N, 15 O and 18 F. The electron-positron pair creation method uses nuclear reactor or electron linear accelerator (LINAC). The positron experimental facility in this organization consists of electron LINAC, slow positron beam source, positron transport and experimental station. The outline of this facility is started. The intense slow positron beam is applied to research positronium work function, electron structure of surface. New method such as combination of positron lifetime measurement and slow positron beam or Auger electron spectroscopy by positron annihilation excitation and positron reemission microscope are developed. (S.Y.)

  4. Experimental Study of a Positron\\\\ Source Using Channeling

    CERN Multimedia

    Gavrykov, V; Kulibaba, V; Baier, V; Beloborodov, K; Bojenok, A; Bukin, A; Burdin, S; Dimova, T; Druzhinin, V; Dubrovin, M; Seredniakov, S; Shary, V; Strakhovenko, V; Keppler, P; Major, J; Bogdanov, A V; Potylitsin, A; Vnoukov, I; Artru, X; Lautesse, P; Poizat, J-C; Remillieux, J

    2002-01-01

    Many simulations have predicted that the yield of positrons, resulting from the interaction of fast electrons in a solid target, increases if the target is a crystal oriented with a major axis parallel to the electron beam. Tests made at Orsay and Tokyo confirmed these expectations. The experiment WA 103 concerns the determination of the main characteristics (emittance, energy spread) of a crystal positron source which could replace advantageously the conventional positron converters foreseen in some linear collider projects. The main element of the set-up is a magnetic spectrometer, using a drift chamber, where the positron trajectories are reconstructed (see Figure 1) A first run has been operated in july 2000 and the first results showed, as expected, a significant enhancement in photon and positron generation along the $$ axis of the tungsten crystal. Indications about a significant increase in the number of soft photons and positrons were also gathered : this point is of importance for the positron colle...

  5. Toward a European Network of Positron Laboratories

    Directory of Open Access Journals (Sweden)

    Karwasz Grzegorz P.

    2015-12-01

    Full Text Available Some applications of controlled-energy positron beams in material studies are discussed. In porous organic polysilicates, measurements of 3γ annihilation by Doppler broadening (DB method at the Trento University allowed to trace pore closing and filling by water vapor. In silicon coimplanted by He+ and H+, DB data combined with positron lifetime measurements at the München pulsed positron beam allowed to explain Si blistering. Presently measured samples of W for applications in thermonuclear reactors, irradiated by W+ and electrons, show vast changes of positron lifetimes, indicating complex dynamics of defects.

  6. Recent developments in the theory of positrons at surfaces

    International Nuclear Information System (INIS)

    Walker, A.B.

    1989-01-01

    Positron beams of ever brighter intensity are now establishing themselves as a novel surface probe enabling a wide variety of spectroscopies. The production of high positron intensities and exploitation of the beams depends critically on our understanding of the complex behaviour of positrons at and near surfaces. I will review progress on the theory of positron-surface interactions and of the implantation and diffusion of low energy positrons. Applications of this theory to a variety of experimental techniques such as ACAR (Angular Correlation by Annihilation Radiation) spectra, angle resolved positronium (Ps) spectroscopy, REPELS (Reemitted Positron Energy Loss Spectroscopy), LEPD (Low Energy Positron Diffraction) and measurements of defect profiles will be discussed. 24 refs. (author)

  7. Department of Cosmic Radiation Physics: Overview

    International Nuclear Information System (INIS)

    Szabelski, J.

    2000-01-01

    Full text: Department of Cosmic Ray Physics in Lodz is involved in basic research in the area of high-energy physics and cosmic ray physics related to: -Studies of asymptotic properties of hadronic interactions based on the analysis of cosmic ray propagation through the atmosphere. -Experimental and phenomenological studies of Extensive Air Showers induced by cosmic ray particles. - Search for high-energy cosmic ray point sources. - Studies of cosmic ray propagation in the Galaxy and particle acceleration mechanisms. -Studies of mass composition of cosmic rays in the energy range 10 15 -10 17 eV. Theoretical and experimental studies of Extensive Air Shower properties are performed mainly on the basis of the results obtained by the Lodz Extensive Air Shower Array. We have analysed nearly 100,000 events of energies above 10 15 eV registered in the Lodz hodoscope. We have developed a method to verify different models of cosmic ray mass composition. The Lodz group collaborates with many foreign institutes and laboratories in construction and data interpretation of cosmic ray experiments. Our most important partners are: Forschungszentrum in Karlsruhe (Germany), College de France, Institute for Nuclear Studies of the Russian Academy of Sciences and Uppsala University (Sweden). (author)

  8. A precision search for WIMPs with charged cosmic rays

    Science.gov (United States)

    Reinert, Annika; Winkler, Martin Wolfgang

    2018-01-01

    AMS-02 has reached the sensitivity to probe canonical thermal WIMPs by their annihilation into antiprotons. Due to the high precision of the data, uncertainties in the astrophysical background have become the most limiting factor for indirect dark matter detection. In this work we systematically quantify and—where possible—reduce uncertainties in the antiproton background. We constrain the propagation of charged cosmic rays through the combination of antiproton, B/C and positron data. Cross section uncertainties are determined from a wide collection of accelerator data and are—for the first time ever—fully taken into account. This allows us to robustly constrain even subdominant dark matter signals through their spectral properties. For a standard NFW dark matter profile we are able to exclude thermal WIMPs with masses up to 570 GeV which annihilate into bottom quarks. While we confirm a reported excess compatible with dark matter of mass around 80 GeV, its local (global) significance only reaches 2.2 σ (1.1 σ) in our analysis.

  9. Design and Characterization of a Three-Dimensional Positron Annihilation Spectroscopy System Using a Low-Energy Positron Beam

    Science.gov (United States)

    2012-03-22

    Technique Applied to Measure Oxygen -Atom Defects in 6H Silicon Carbide”. 2010. [31] Y. C. Jean , P. E. Mallon and D. M. Schrader. Principles and Applications...that result in β+ emission, by photon interactions with nuclei and subsequent pair production, or by β+ decays from radioactive isotopes made by...reactions for creating positrons [7], some of which are used to to create radioactive isotopes that β+ decay. Regardless of the positron source, positrons

  10. Robust constraint on cosmic textures from the cosmic microwave background.

    Science.gov (United States)

    Feeney, Stephen M; Johnson, Matthew C; Mortlock, Daniel J; Peiris, Hiranya V

    2012-06-15

    Fluctuations in the cosmic microwave background (CMB) contain information which has been pivotal in establishing the current cosmological model. These data can also be used to test well-motivated additions to this model, such as cosmic textures. Textures are a type of topological defect that can be produced during a cosmological phase transition in the early Universe, and which leave characteristic hot and cold spots in the CMB. We apply bayesian methods to carry out a rigorous test of the texture hypothesis, using full-sky data from the Wilkinson Microwave Anisotropy Probe. We conclude that current data do not warrant augmenting the standard cosmological model with textures. We rule out at 95% confidence models that predict more than 6 detectable cosmic textures on the full sky.

  11. Cyclotrons and positron emitting radiopharmaceuticals

    International Nuclear Information System (INIS)

    Wolf, A.P.; Fowler, J.S.

    1984-01-01

    The state of the art of Positron Emission Tomography (PET) technology as related to cyclotron use and radiopharmaceutical production is reviewed. The paper discusses available small cyclotrons, the positron emitters which can be produced and the yields possible, target design, and radiopharmaceutical development and application. 97 refs., 12 tabs

  12. Positron emission tomography now and in the future

    International Nuclear Information System (INIS)

    Vaalburg, W.

    1987-01-01

    A survey is given of positron emission tomography used in nuclear medicine. The production of positron emitting radionuclides is discussed. The development of positron detectors is described. The application of positron emission tomography in cardiology, oncology and neurology is treated. The authors conclude that PET is a unique method to examine metabolic processes, although the method is still in its infancy. 7 refs.; 1 table

  13. Department of Cosmic Radiation Physics: Overview

    International Nuclear Information System (INIS)

    Gawin, J.

    1998-01-01

    (full text) The Department of Cosmic Ray Physics in Lodz is involved in basic research in the area of high energy physics and cosmic ray physics related to: -Studies of asymptotic properties of hadronic interactions based on the analysis of cosmic ray propagation in the atmosphere. -Studies of the structure and properties of Extensive Air Showers induced by cosmic ray particles. - Search for point sources of high energy cosmic rays. - Studies of cosmic ray propagation in the Galaxy and mechanisms of particle acceleration. - Studies of mass composition of cosmic rays in the energy range l0 15 -10 17 eV. Theoretical and experimental studies of nuclear interactions for energies exceeding those obtained by modern particle accelerators are performed based on the results obtained by the Lodz Extensive Air Shower Array. The Lodz hodoscope can register the electromagnetic component of cosmic ray showers developing in the atmosphere as well as muons of two energy thresholds. Data collected by the Lodz array are also used to study the mass composition of cosmic rays in the energy range 10 15 -10 17 eV. The Lodz group collaborates with many foreign institutes and laboratories in construction and data interpretation of cosmic ray experiments. Our most important partners are: Forschungszentrum Karlsruhe (Germany), College de' France, the Institute for Nuclear Studies of the Russian Academy of Science, the University of Perpignan (France) and Uppsala University (Sweden). (author)

  14. Positron creation in superheavy quasi-molecules

    International Nuclear Information System (INIS)

    Mueller, B.

    1976-01-01

    The review of positron creation in superheavy quasi-molecules includes spontaneous positron emission from superheavy atoms, supercritical quasi-molecules, background effects, and some implications of the new ground state. 66 references

  15. Progress toward magnetic confinement of a positron-electron plasma: nearly 100% positron injection efficiency into a dipole trap

    Science.gov (United States)

    Stoneking, Matthew

    2017-10-01

    The hydrogen atom provides the simplest system and in some cases the most precise one for comparing theory and experiment in atomics physics. The field of plasma physics lacks an experimental counterpart, but there are efforts underway to produce a magnetically confined positron-electron plasma that promises to represent the simplest plasma system. The mass symmetry of positron-electron plasma makes it particularly tractable from a theoretical standpoint and many theory papers have been published predicting modified wave and stability properties in these systems. Our approach is to utilize techniques from the non-neutral plasma community to trap and accumulate electrons and positrons prior to mixing in a magnetic trap with good confinement properties. Ultimately we aim to use a levitated superconducting dipole configuration fueled by positrons from a reactor-based positron source and buffer-gas trap. To date we have conducted experiments to characterize and optimize the positron beam and test strategies for injecting positrons into the field of a supported permanent magnet by use of ExB drifts and tailored static and dynamic potentials applied to boundary electrodes and to the magnet itself. Nearly 100% injection efficiency has been achieved under certain conditions and some fraction of the injected positrons are confined for as long as 400 ms. These results are promising for the next step in the project which is to use an inductively energized high Tc superconducting coil to produce the dipole field, initially in a supported configuration, but ultimately levitated using feedback stabilization. Work performed with the support of the German Research Foundation (DFG), JSPS KAKENHI, NIFS Collaboration Research Program, and the UCSD Foundation.

  16. Positron studies of metal-oxide-semiconductor structures

    Science.gov (United States)

    Au, H. L.; Asoka-Kumar, P.; Nielsen, B.; Lynn, K. G.

    1993-03-01

    Positron annihilation spectroscopy provides a new probe to study the properties of interface traps in metal-oxide semiconductors (MOS). Using positrons, we have examined the behavior of the interface traps as a function of gate bias. We propose a simple model to explain the positron annihilation spectra from the interface region of a MOS capacitor.

  17. In-situ positron emission of CO oxidation

    NARCIS (Netherlands)

    Vonkeman, K.A.; Jonkers, G.; Wal, van der S.W.A.; Santen, van R.A.

    1993-01-01

    Using a Neuro ECAT positron tomog., the Positron Emission computed Tomog. (PET) was utilized to image the catalytic oxidn. of CO by using CO and CO2, labeled with short lived positron emitting nuclides. Studies were performed over highly dispersed CeO2/g-Al2O3 supported Pt and Rh catalysts. With a

  18. Low-energy positron and electron diffraction and positron-stimulated secondary electron emission from Cu(100)

    International Nuclear Information System (INIS)

    Weiss, A.H.

    1983-01-01

    The results of two series of experiments are reported. In the first, an electrostatically guided beam of low-energy (40-400 eV) positrons, delta/sub p/ was used to study low-energy positron diffraction (LEPD) from a Cu(100) surface under ultrahigh-vacuum conditions. Low-energy electron diffraction (LEED) data were obtained from the same sample in the same apparatus. Comparison of LEPD and LEED intensity versus energy data with model calculations made using computer programs developed by C.B. Duke and collaborators indicated that: LEPD data is adequately modeled using potentials with no exchange-correlation term. The inelastic mean free path, lambda/sub ee/, is shorter for positrons than for electrons at low (< approx.80 eV). LEED is better than LEPD at making a determination of the first-layer spacing of Cu(100) for the particular data set reported. In the second set of experiments, the same apparatus and sample were used to compare positron- and electron-stimulated secondary-electron emission (PSSEE and ESSEE). The results were found to be consistent with existing models of secondary-electron production for metals. The energy distributions of secondary-electrons had broad low-energy (<10 eV) peaks for both positron and electron stimulation. But the PSEE distribution showed no elastic peak. Measurements of secondary-electron angular distributions, found to be cosine-like in both the PSSEE and ESSEE case, were used to obtain total secondary yield ratios, delta, at four beam energies ranging from 40-400 eV. The secondary yield ratio for primary positrons and the yield for primary electrons, delta/sub e/, were similar at these energies. For 400-eV primary particles the secondary yields were found to be delta/sub p/ = 0.94 +/- 0.12 and delta/sub e/ = 0.94 +/- 0./12, giving a ratio of unity for positron-stimulated secondary yield to electron-stimulated secondary yield

  19. Positron emission tomography

    International Nuclear Information System (INIS)

    Bolwig, T.G.; Haunsoe, S.; Dahlgaard Hove, J.; Hesse, B.; Hoejgard, L.; Jensen, M.; Paulson, O.B.; Hastrup Svendsen, J.; Soelvsten Soerensen, S.

    1994-01-01

    Positron emission tomography (PET) is a method for quantitative imaging of regional physiological and biochemical parameters. Positron emitting radioactive isotopes can be produced by a cyclotron, eg. the biologically important carbon ( 11 C), oxygen ( 15 O), and nitrogen ( 13 N) elements. With the tomographic principles of the PET scanner the quantitative distribution of the administered isotopes can be determined and images can be provided as well as dynamic information on blood flow, metabolism and receptor function. In neurology PET has been used for investigations on numerous physiological processes in the brain: circulation, metabolism and receptor studies. In Parkinson's disease PET studies have been able to localize the pathology specifically, and in early stroke PET technique can outline focal areas with living but non-functioning cells, and this could make it possible to intervene in this early state. With positron emission tomography a quantitative evaluation of myocardial blood flow, glucose and fatty acid metabolism can be made as well as combined assessments of blood flow and metabolism. Combined studies of blood flow and metabolism can determine whether myocardial segments with abnormal motility consist of necrotic or viable tissue, thereby delineating effects of revascularisation. In the future it will probably be possible to characterize the myocardial receptor status in different cardiac diseases. The PET technique is used in oncology for clinical as well as more basic research on tumor perfusion and metabolism. Further, tumor uptake of positron labelled cytotoxic drugs might predict the clinical benefit of treatment. (au) (19 refs.)

  20. Positron-attachment to small molecules: Vibrational enhancement of positron affinities with configuration interaction level of multi-component molecular orbital approach

    Energy Technology Data Exchange (ETDEWEB)

    Tachikawa, Masanori [Quantum Chemistry Division, Graduate School of NanoBioScience, Yokohama City University, 22-2 Seto, Kanazawa, Yokohama 236-0027 (Japan)

    2015-12-31

    To theoretically demonstrate the binding of a positron to small polarized molecules, we have calculated the vibrational averaged positron affinity (PA) values along the local vibrational contribution with the configuration interaction level of multi-component molecular orbital method. This method can take the electron-positron correlation contribution into account through single electronic - single positronic excitation configurations. The PA values are enhanced by including the local vibrational contribution from vertical PA values due to the anharmonicity of the potential.

  1. Cyclotrons and positron emitting radiopharmaceuticals

    Energy Technology Data Exchange (ETDEWEB)

    Wolf, A.P.; Fowler, J.S.

    1984-01-01

    The state of the art of Positron Emission Tomography (PET) technology as related to cyclotron use and radiopharmaceutical production is reviewed. The paper discusses available small cyclotrons, the positron emitters which can be produced and the yields possible, target design, and radiopharmaceutical development and application. 97 refs., 12 tabs. (ACR)

  2. Automatic sup sup 1 sup sup 8 F positron source supply system for a monoenergetic positron beam

    CERN Document Server

    Saito, F; Itoh, Y; Goto, A; Fujiwara, I; Kurihara, T; Iwata, R; Nagashima, Y; Hyodo, T

    2000-01-01

    A system which supplies an intense sup sup 1 sup sup 8 F (half life 110 min) positron source produced by an AVF cyclotron through sup sup 1 sup sup 8 O(p,n) sup sup 1 sup sup 8 F reaction has been constructed. Produced sup sup 1 sup sup 8 F is transferred to a low background experiment hall through a capillary. It is electro-deposited on a graphite rod and used for a source of a slow positron beam. In the meantime the next batch of target sup sup 1 sup sup 8 O water is loaded and proton irradiation proceeds. This system makes it possible to perform continuous positron beam experiments using the 18 F positron source.

  3. Positron emission tomography with Positome, 2

    International Nuclear Information System (INIS)

    Nukui, Hideaki; Yamamoto, Y.L.; Thompson, C.J.; Feindel, W.

    1979-01-01

    Positron emission tomography with Positome II using 68 Ga-EDTA was performed in cases with brain tumor and cerebral arteriovenous malformation. A significant focal uptake in static study and hemodynamic changes in dynamic study were noted in all cases except one case with intracranial lipoma. Comparing this method with sup(99m) Tc-pertechnetate cerebral image study and computerized axial tomography, the diagnostic rate for detecting brain tumor was almost equal in all of these three methods. However, detecting and localizing was easier and clearer in static positron emission tomography with 68 Ga-EDTA than in sup(99m) Tc-pertechnetate cerebral image and computerized axial tomography without infusion of contrast medium. Furthermore, static positron emission tomography with 68 Ga-EDTA was superior to computerized axial tomography without infusion of contrast medium for detecting cerebral arteriovenous malformation. Concerning dynamic positron emission tomography with 68 Ga-EDTA, semiquantitative values obtained by this method correlated well with findings of computerized axial tomography and was thought to be more precise and in detail than the findings of sup(99m) Tc-pertechnetate cerebral image study. Summation of the previous studies about dynamic positron emission tomography with 77 Kr in occlusive cerebrovascular disease is also reported. In conclusion, static positron emission tomography with 68 Ga-EDTA is a very useful diagnostic method for detecting and localizing brain tumor and cerebral arteriovenous malformation without any attendant complications. Furthermore, a good combination of static and dynamic positron emission tomography and computerized axial tomography appear to be outstandingly effective for not only detecting the lesion but also understanding the pathophysiological aspect in cases with various intracranial lesions. (author)

  4. Generation and application of slow positrons based on a electron LINAC

    CERN Document Server

    Kurihara, T

    2002-01-01

    History of slow positron in Institute of Materials Structure Science High Energy Accelerator Research Organization is explained. The principle of generation and application of intense positron beam is mentioned. Two sources of intense positron are radioactive decay of radioactive isotopes emitting positron and electron-positron pair creation. The radioactive decay method uses sup 5 sup 8 Co, sup 6 sup 4 Cu, sup 1 sup 1 C, sup 1 sup 3 N, sup 1 sup 5 O and sup 1 sup 8 F. The electron-positron pair creation method uses nuclear reactor or electron linear accelerator (LINAC). The positron experimental facility in this organization consists of electron LINAC, slow positron beam source, positron transport and experimental station. The outline of this facility is started. The intense slow positron beam is applied to research positronium work function, electron structure of surface. New method such as combination of positron lifetime measurement and slow positron beam or Auger electron spectroscopy by positron annihil...

  5. Simulation of a Positron Source for CEBAF

    International Nuclear Information System (INIS)

    S. Golge; A. Freyberger; C. Hyde-Wright

    2007-01-01

    A positron source for the 6 GeV (or the proposed 12 GeV upgrade) recirculating linacs at Jefferson Lab is presented. The proposed 100nA CW positron source has several unique characteristics; high incident beam power (100kW), 10 MeV incident electron beam energy, CW incident beam and CW production. Positron production with 10 MeV electrons has several advantages; the energy is below neutron threshold so the production target will not become activated during use and the absolute energy spread is bounded by the low incident energy. These advantages are offset by the large angular distribution of the outgoing positrons. Results of simulations of the positron production, capture, acceleration and injection into the recirculating linac are presented. Energy flow and thermal management of the production target present a challenge and are included in the simulations

  6. Latest Results from the AMS Experiment on the International Space Station

    CERN Multimedia

    CERN. Geneva

    2018-01-01

    In seven years on the Space Station, AMS has collected more than 115 billion charged cosmic rays with energies up to multi TeV.  The measured positron spectra agrees well with dark matter models. The energy dependence of elementary particles (electrons, positrons, protons and antiprotons)  as well as the rigidity dependence of primary cosmic rays and secondary cosmic rays are unique and distinct.  These results require a new understanding of the cosmos. 

  7. Cosmic Ether

    CERN Document Server

    Tomaschitz, R

    1998-01-01

    A prerelativistic approach to particle dynamics is explored in an expanding Robertson-Walker cosmology. The receding galactic background provides a distinguished frame of reference and a unique cosmic time. In this context the relativistic, purely geometric space-time concept is criticized. Physical space is regarded as a permeable medium, the cosmic ether, which effects the world-lines of particles and rays. We study in detail a Robertson-Walker universe with linear expansion factor and negatively curved, open three-space; we choose the permeability tensor of the ether in such a way that the semiclassical approximation is exact. Galactic red-shifts depend on the refractive index of the ether. In the local Minkowskian limit the ether causes a time variation of mass, which scales inversely proportional to cosmic time. In the globally geodesic rest frames of galactic observers the ether manifests itself in an unbounded speed of signal transfer, in bifurcations of world-lines, and in time inversion effects.

  8. Cosmic vacuum

    International Nuclear Information System (INIS)

    Chernin, Artur D

    2001-01-01

    Recent observational studies of distant supernovae have suggested the existence of cosmic vacuum whose energy density exceeds the total density of all the other energy components in the Universe. The vacuum produces the field of antigravity that causes the cosmological expansion to accelerate. It is this accelerated expansion that has been discovered in the observations. The discovery of cosmic vacuum radically changes our current understanding of the present state of the Universe. It also poses new challenges to both cosmology and fundamental physics. Why is the density of vacuum what it is? Why do the densities of the cosmic energy components differ in exact value but agree in order of magnitude? On the other hand, the discovery made at large cosmological distances of hundreds and thousands Mpc provides new insights into the dynamics of the nearby Universe, the motions of galaxies in the local volume of 10 - 20 Mpc where the cosmological expansion was originally discovered. (reviews of topical problems)

  9. Cosmic vacuum

    Energy Technology Data Exchange (ETDEWEB)

    Chernin, Artur D [P.K. Shternberg State Astronomical Institute at the M.V. Lomonosov Moscow State University, Moscow (Russian Federation)

    2001-11-30

    Recent observational studies of distant supernovae have suggested the existence of cosmic vacuum whose energy density exceeds the total density of all the other energy components in the Universe. The vacuum produces the field of antigravity that causes the cosmological expansion to accelerate. It is this accelerated expansion that has been discovered in the observations. The discovery of cosmic vacuum radically changes our current understanding of the present state of the Universe. It also poses new challenges to both cosmology and fundamental physics. Why is the density of vacuum what it is? Why do the densities of the cosmic energy components differ in exact value but agree in order of magnitude? On the other hand, the discovery made at large cosmological distances of hundreds and thousands Mpc provides new insights into the dynamics of the nearby Universe, the motions of galaxies in the local volume of 10 - 20 Mpc where the cosmological expansion was originally discovered. (reviews of topical problems)

  10. Development of slow positron beam lines and applications

    Science.gov (United States)

    Mondal, Nagendra Nath

    2018-05-01

    A positron is an antiparticle of an electron that can be formed in diverse methods: natural or artificial β-decay process, fission and fusion reactions, and a pair production of electron-positron occurred in the reactor and the high energy accelerator centers. Usually a long-lifetime radio isotope is customized for the construction of a slow positron beam lines in many laboratories. The typical intensity of this beam depends upon the strength of the positron source, moderator efficiency, and guiding, pulsing, focusing and detecting systems. This article will review a few positron beam lines and their potential applications in research, especially in the Positronium Bose-Einstein Condensation.

  11. Cosmic muons in ATLAS calorimetric system

    International Nuclear Information System (INIS)

    Hodak, R.

    2008-01-01

    At the turn of the 20 th and 21 th century detectors for orbital stations (Project Integra) found that 10 43 positrons annihilate every second in our galaxy. Their origin is not entirely clear and, moreover, the processes leading to positrons annihilating in the interstellar space are also not clear. When looking for ways to annihilation of positrons in the interstellar medium using the method of Doppler extension of annihilation gamma quanta we managed partly to show that the contribution of annihilation of positrons in grain of interstellar dust is minimal compared with the contribution of positron annihilation in a hot neutral and ionized phase of interstellar medium [P. Jean, Spectral analysis of the Galactic e + e annihilation emission]. Experimental work has been performed in the laboratory at the Department of Nuclear Physics Institute in Bratislava. (author)

  12. Intense positron beam and its application to surface science

    International Nuclear Information System (INIS)

    Ito, Y.; Hirose, M.; Kanazawa, I.; Sueoka, O.; Takamura, S.; Okada, S.

    1992-01-01

    Intense pulsed slow positron beam has been produced using the 100 MeV electron LINAC of JAERI · Tokai. In order to use the beam for surface studies such as positron diffraction and positron microscopy, it was transferred from the solenoid magnetic field to field free region and then was brightness-enhanced. The beam size was reduced from 10 mmφ (in the magnetic field) to 0.5 mmφ after two stages of re-moderation. Using the intense brightness-enhanced positron beam we have observed for the first time RHEPD (Reflection High-Energy Positron Diffraction) patterns. A design of re-emission positron microscopy is also described. (author)

  13. Closing CMS to hunt cosmic rays

    CERN Multimedia

    Claudia Marcelloni

    2006-01-01

    Every second the Earth is bombarded by billions of cosmic rays and occasionally one of these cosmic particles will collide with the Earth's atmosphere generating a shower of particles known as an 'air shower'. This is similiar to the collisions and subsequent particle showers observed in accelerators such as the LHC. Here the CMS detector is closed so that systems can be tested using muon cosmic rays in the 'Cosmic Challenge'.

  14. Study of a positron generation

    International Nuclear Information System (INIS)

    Nakahara, Kazuo; Enomoto, A.; Ikeda, M.; Ohsawa, S.; Kamitani, T.; Hosoyama, K.; Takei, H.; Emoto, T.; Tani, S.

    1998-03-01

    In the Power Reactor and Nuclear Fuel Development Corporation (PNC), the following are examined as part of an application technology using a high power electron linac: monochromatic gamma ray sources, free electron lasers, and intense positron sources. This report presents the study of an intense positron source, which has been developed jointly by High Energy Accelerator Research Organization (KEK) and PNC. In this report, we describe following items for an adaptive estimate of a superconducting magnet in order to efficiently converge a positron beam. (1) The cryostat which included the superconducting magnet is manufactured. (2) An excitement test of the superconducting magnet is carried out with a magnetic substance such as the electromagnet yoke. (author)

  15. The influence of positron trapping at vacancies on a pattern of the Fermi surface of #betta#-brass studied by positron annihilation

    International Nuclear Information System (INIS)

    Rozenfeld, B.; Chabik, S.; Pajak, J.

    1982-01-01

    Angular correlations of positron annihilation quanta (ACPAQ) have been measured for differently oriented monocrystalline samples of the ordered #betta#-brass under conditions permitting the neglecting of the trapping of positrons at vacancies as well as in the case when almost all the positrons annihilate being trapped at vacancies. It has been shown that trapping of positrons at vacancies can make the observation of the directional anisotropy in electron momentum distribution impossible. (Auth.)

  16. Interplanetary cosmic-ray scintillations

    Energy Technology Data Exchange (ETDEWEB)

    Toptygin, I N; Vasiliev, V N [Kalininskij Sel' skokhozyajstvennyj Inst. (USSR)

    1977-05-01

    The equation for the two-particles cosmic-ray distribution function is derived by means of the Boltzmann kinetic equation averaging. This equation is valid for arbitrary ratio of regular and random parts of the magnetic field. For small energy particles the guiding-center approximation is used. On the basis of the derived equation the dependence between power spectra of cosmic-ray intensity and random magnetic field is obtained. If power spectra are degree functions for high energy particles (approximately 10 GeV nucleon/sup -1/), then the spectral exponent ..gamma.. of magnetic field lies between rho and rho-2, where rho is the spectral exponent of cosmic-ray power spectra. The experimental data concerning moderate energy particles are in accordance with ..gamma..=rho, which demonstrates that the magnetic fluctuations are isotropic or cosmic-ray space gradient is small near the Earth orbit.

  17. Positron beam studies of transients in semiconductors

    International Nuclear Information System (INIS)

    Beling, C.D.; Ling, C.C.; Cheung, C.K.; Naik, P.S.; Zhang, J.D.; Fung, S.

    2006-01-01

    Vacancy-sensing positron deep level transient spectroscopy (PDLTS) is a positron beam-based technique that seeks to provide information on the electronic ionization levels of vacancy defects probed by the positron through the monitoring of thermal transients. The experimental discoveries leading to the concept of vacancy-sensing PDLTS are first reviewed. The major problem associated with this technique is discussed, namely the strong electric fields establish in the near surface region of the sample during the thermal transient which tend to sweep positrons into the contact with negligible defect trapping. New simulations are presented which suggest that under certain conditions a sufficient fraction of positrons may be trapped into ionizing defects rendering PDLTS technique workable. Some suggestions are made for techniques that might avoid the problematic electric field problem, such as optical-PDLTS where deep levels are populated using light and the use of high forward bias currents for trap filling

  18. Positron lifetime measurements on electron irradiated amorphous alloys

    International Nuclear Information System (INIS)

    Moser, P.; Hautojaervi, P.; Chamberod, A.; Yli-Kauppila, J.; Van Zurk, R.

    1981-08-01

    Great advance in understanding the nature of point defects in crystalline metals has been achieved by employing positron annihilation technique. Positrons detect vacancy-type defects and the lifetime value of trapped positrons gives information on the size of submicroscopic vacancy aglomerates and microvoids. In this paper it is shown that low-temperature electron irradiations can result in a considerable increase in the positron lifetimes in various amorphous alloys because of the formation of vacancy-like defects which, in addition of the pre-existing holes, are able to trap positrons. Studied amorphous alloys were Fe 80 B 20 , Pd 80 Si 20 , Cu 50 Ti 50 , and Fe 40 Ni 40 P 14 B 6 . Electron irradiations were performed with 3 MeV electrons at 20 K to doses around 10 19 e - /cm 2 . After annealing positron lifetime spectra were measured at 77 K

  19. Polarized positron sources for the future linear colliders

    International Nuclear Information System (INIS)

    Chaikovska, I.

    2012-01-01

    This thesis introduces the polarized positron source as one of the key element of the future Linear Collider (LC). In this context, the different schemes of the polarized positron source are described highlighting the main issues in this technology. In particular, the main focus is on the Compton based positron source adopted by the CLIC as a preferred option for the future positron source upgrade. In this case, the circularly polarized high energy gamma rays resulting from Compton scattering are directed to a production target where an electromagnetic cascade gives rise to the production of positrons by e + -e - pair conversion. To increase the efficiency of the gamma ray production stage, a multiple collision point line integrated in energy recovery linac is proposed. The simulations of the positron production, capture and primary acceleration allow to estimate the positron production efficiency and provide a simple parametrization of the Compton based polarized positron source in the view of the future LC requirements. The storage ring based Compton source option, so-called Compton ring, is also described. The main constraint of this scheme is given by the beam dynamics resulting in the large energy spread and increased bunch length affecting the gamma ray production rate. An original theoretical contribution is shown to calculate the energy spread induced by Compton scattering. Moreover, an experiment to test the gamma ray production by Compton scattering using a state-of-art laser system developed at LAL has been conducted in the framework of the 'Mighty Laser' project at the ATF, KEK. The experimental layout as well as the main results obtained are discussed in details. The studies carried out in this thesis show that the polarized positron source based on Compton scattering is a promising candidate for the future LC polarized positron source. (author)

  20. ALICE Cosmic Ray Detector

    CERN Multimedia

    Fernandez Tellez, A; Martinez Hernandez, M; Rodriguez Cahuantzi, M

    2013-01-01

    The ALICE underground cavern provides an ideal place for the detection of high energy atmospheric muons coming from cosmic ray showers. ACORDE detects cosmic ray showers by triggering the arrival of muons to the top of the ALICE magnet.

  1. Cosmic Humanity: Utopia, Realities, Prospects

    Directory of Open Access Journals (Sweden)

    Sergey Krichevsky

    2017-07-01

    Full Text Available The philosophical foundations of the theory and practice of the creation of cosmic humanity as a process of the evolution of human civilization, the emergence into space, with the prospect of resettlement outside the Earth are considered. There is a connection between myths, fantasies, ideas, concepts and projects aimed at the exploration of outer space, the creation of cosmic humanity. A new and voluminous definition of cosmic humanity in the evolutionary paradigm is given. Cosmic humanity is (essence and 4 stages of evolution: 1. Humanity living on Earth, sensing, knowing, understanding its cosmic origin, relationship with the cosmos and cosmic destiny. 2. Humanity living on Earth, leading aerospace activity for the purposes of exploration and use of aerospace space (Heaven, Space for survival and development. 3. Humanity living on Earth and outside the Earth — in the solar system, preserving the Earth and mastering the Cosmos for survival and development. 4. Humanity, settled and living in the Cosmos. Now humanity is in the process of transition from the second to the third stage. In the process of this evolution, a complex transformation of man and society takes place. The problem-semantic field of cosmic humanity is described and its general model is presented. The meta-goal-setting is the justification of cosmic humanity with the application of the anthropic principle and its “active” super (post anthropic supplement: “Cosmic humanity has an evolutionary purpose to actively manage evolution: change man, humanity and the universe.” The evolution of the “cosmic dream”, goals and technologies of space activities is formalized in the form of a conceptual model. Challenges and negative trends are considered in connection with the crisis of space activity, criticism and attempts to limit the flights of people into space. The prototype of cosmic humanity, its basis and acting model is the cosmonauts’ community. The main

  2. Theory of the temperature dependence of positron bulk lifetimes-implications for vacancy formation enthalpy measurements via positron experiments

    International Nuclear Information System (INIS)

    Tam, S.W.; Sinha, S.K.; Siegel, R.W.

    1977-02-01

    Temperature dependent effects, which may have a bearing on determinations of vacancy formation enthalpies in metals by positron annihilation, have been observed in certain metals. These effects have been observed to occur both at temperatures below those at which positron annihilation is most sensitive to equilibrium vacancies and at temperatures well within the vacancy-sensitive region. The effect of thermal lattice displacements on positron lifetimes in metals was investigated to help understand these phenomena

  3. New Possibilities of Positron-Emission Tomography

    Science.gov (United States)

    Volobuev, A. N.

    2018-01-01

    The reasons for the emergence of the angular distribution of photons generated as a result of annihilation of an electron and a positron in a positron-emission tomograph are investigated. It is shown that the angular distribution of the radiation intensity (i.e., the probability of photon emission at different angles) is a consequence of the Doppler effect in the center-of-mass reference system of the electron and the positron. In the reference frame attached to the electron, the angular distribution of the number of emitted photons does not exists but is replaced by the Doppler shift of the frequency of photons. The results obtained in this study make it possible to extend the potentialities of the positron-emission tomograph in the diagnostics of diseases and to obtain additional mechanical characteristics of human tissues, such as density and viscosity.

  4. Porous silicon investigated by positron annihilation

    International Nuclear Information System (INIS)

    Cruz, R.M. de la; Pareja, R.

    1989-01-01

    The effect of the anodic conversion in silicon single crystals is investigated by positron lifetime measurements. Anodization at constant current induces changes in the positron lifetime spectrum of monocrystalline silicon samples. It is found that theses changes are primarily dependent on the silicon resistivity. The annihilation parameter behaviour of anodized samples, treated at high temperature under reducing conditions, is also investigated. The results reveal that positron annihilation can be a useful technique to characterize porous silicon formed by anodizing as well as to investigate its thermal behaviour. (author)

  5. New Developments in Positron Scintigraphy and the Application of Cyclotron-Produced Positron Emitters

    Energy Technology Data Exchange (ETDEWEB)

    Brownell, G. L.; Burnham, C. A.; Wilensky, S.; Aronow, S.; Kazemi, H.; Strieder, D. [Massachusetts General Hospital. Boston, MA (United States)

    1969-01-15

    The use of positron-emitting radioisotopes offers unique advantages inscintigraphy and dynamic function studies. The detection of the two annihilation quanta provides, in principle, the possibility of utilization of all the positron annihilations with good resolution. In practice, very high efficiencies can be achieved with large area annihilation quanta detectors. The use of multi-detector matrices as large area detectors permits high levels o f activity and yields very high data acquisition rates. The independence of attenuation with depth of a source offers marked advantages for quantitative measurement. The use of time-of-flight techniques opens the possibility of true three-dimensional visualization. Finally, a number of very short-lived positron emitting radioisotopes such as {sup 15}O, {sup 19}N and {sup 11}C are available. A hybrid positron scanner has been constructed and is undergoing tests for brain tumour localization using {sup 74}As. The scanner uses two rows of detectors each containing 9 Nal scintillators and phototubes. The detector array moves continuously in the horizontal direction and in steps in the vertical direction, producing a scintigram with no line structure. The data is recorded on tape for replay or for computer processing. In either case, the plane of best focus can be positioned at will. The techniques developed for the hybrid scanner will be used in a stationary device employing two two-dimensional arrays of detectors. The design will emphasize the very rapid collection of data and the sequential production of scintigrams. The advantages and techniques of positron annihilation detection are also applicable to devices for study of dynamic function. We have constructed and are testing a fast six-detector coincidence system for pulmonary function studies. The measurement of time-of-flight offers the possibility of three-dimensional visualization of a distribution of positron-emitting radioisotope. We a re studying systems with

  6. Cosmic Connections:. from Cosmic Rays to Gamma Rays, Cosmic Backgrounds and Magnetic Fields

    Science.gov (United States)

    Kusenko, Alexander

    2013-12-01

    Combined data from gamma-ray telescopes and cosmic-ray detectors have produced some new surprising insights regarding intergalactic and galactic magnetic fields, as well as extragalactic background light. We review some recent advances, including a theory explaining the hard spectra of distant blazars and the measurements of intergalactic magnetic fields based on the spectra of distant sources. Furthermore, we discuss the possible contribution of transient galactic sources, such as past gamma-ray bursts and hypernova explosions in the Milky Way, to the observed ux of ultrahigh-energy cosmicrays nuclei. The need for a holistic treatment of gamma rays, cosmic rays, and magnetic fields serves as a unifying theme for these seemingly unrelated phenomena.

  7. Techniques for slow positron beam generation and the applications

    International Nuclear Information System (INIS)

    Okada, Sohei

    1994-01-01

    Slow positron beams have been expected to be a powerful tool for observation of nature in wide range of research fields from materials science to basic physics, chemistry and biology. In this paper, at first, the beam technology is reviewed, which includes the positron generation, the transformation to slow positron beams and the beam manipulation such as beam stretching, bunching and brightness enhancement. Next, the present status of the slow positron beam applications to a variety of fields is demonstrated in terms of special characteristics of positron, that is, depth controllability, surface sensitivity, unique ionization channels and elemental anti-particle properties. Finally, prospects to produce intense slow positron beams are described. (author) 65 refs

  8. Fitting cosmic microwave background data with cosmic strings and inflation.

    Science.gov (United States)

    Bevis, Neil; Hindmarsh, Mark; Kunz, Martin; Urrestilla, Jon

    2008-01-18

    We perform a multiparameter likelihood analysis to compare measurements of the cosmic microwave background (CMB) power spectra with predictions from models involving cosmic strings. Adding strings to the standard case of a primordial spectrum with power-law tilt ns, we find a 2sigma detection of strings: f10=0.11+/-0.05, where f10 is the fractional contribution made by strings in the temperature power spectrum (at l=10). CMB data give moderate preference to the model ns=1 with cosmic strings over the standard zero-strings model with variable tilt. When additional non-CMB data are incorporated, the two models become on a par. With variable ns and these extra data, we find that f10<0.11, which corresponds to Gmicro<0.7x10(-6) (where micro is the string tension and G is the gravitational constant).

  9. Positron emission tomography

    CERN Document Server

    Paans, A M J

    2006-01-01

    Positron Emission Tomography (PET) is a method for measuring biochemical and physiological processes in vivo in a quantitative way by using radiopharmaceuticals labelled with positron emitting radionuclides such as 11C, 13N, 15O and 18F and by measuring the annihilation radiation using a coincidence technique. This includes also the measurement of the pharmacokinetics of labelled drugs and the measurement of the effects of drugs on metabolism. Also deviations of normal metabolism can be measured and insight into biological processes responsible for diseases can be obtained. At present the combined PET/CT scanner is the most frequently used scanner for whole-body scanning in the field of oncology.

  10. Low-energy positron interactions with atoms and molecules

    International Nuclear Information System (INIS)

    Surko, C M; Gribakin, G F; Buckman, S J

    2005-01-01

    This paper is a review of low-energy positron interactions with atoms and molecules. Processes of interest include elastic scattering, electronic and vibrational excitation, ionization, positronium formation and annihilation. An overview is presented of the currently available theoretical and experimental techniques to study these phenomena, including the use of trap-based positron beam sources to study collision processes with improved energy resolution. State-resolved measurements of electronic and vibrational excitation cross sections and measurement of annihilation rates in atoms and molecules as a function of incident positron energy are discussed. Where data are available, comparisons are made with analogous electron scattering cross sections. Resonance phenomena, common in electron scattering, appear to be less common in positron scattering. Possible exceptions include the sharp onsets of positron-impact electronic and vibrational excitation of selected molecules. Recent energy-resolved studies of positron annihilation in hydrocarbons containing more than a few carbon atoms provide direct evidence that vibrational Feshbach resonances underpin the anomalously large annihilation rates observed for many polyatomic species. We discuss open questions regarding this process in larger molecules, as well as positron annihilation in smaller molecules where the theoretical picture is less clear. (topical review)

  11. Probing the defects in nano-semiconductors using positrons

    Energy Technology Data Exchange (ETDEWEB)

    Nambissan, P M G, E-mail: pmg.nambissan@saha.ac.in [Nuclear and Atomic Physics Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India)

    2011-01-10

    Positron annihilation spectroscopy (PAS) is a very useful tool to study the defect properties of nanoscale materials. The ability of thermalized positrons to diffuse over to the surfaces of nanocrystallites prior to annihilation helps to explore the disordered atomic arrangement over there and is very useful in understanding the structure and properties of nanomaterials. As examples, the results of studies on FeS{sub 2} nanorods and ZnS nanoparticles are presented. In semiconductor nanoparticles, there are positron trapping sites within the grains also and these are characterised by using appropriate models on the measured positron lifetimes. We have observed vivid changes in the measured positron lifetimes and Doppler broadened gamma ray spectral lineshapes during structural transformations prompted by substitutional effects in Mn{sup 2+}-doped ZnS nanorods. Interestingly, the nanoparticles did not exhibit the transformation, implying the morphologies of the nanosystems playing a decisive role. Quantum confinement effect in CdS nanoparticles was another phenomenon that could be seen through positron annihilation experiments. Coincidence Doppler broadening measurements have been useful to identify the elemental environment around the vacancy clusters that trap positrons. Recent studies on nanocrystalline oxide and sulphide semiconductors are also discussed.

  12. Probing the defects in nano-semiconductors using positrons

    International Nuclear Information System (INIS)

    Nambissan, P M G

    2011-01-01

    Positron annihilation spectroscopy (PAS) is a very useful tool to study the defect properties of nanoscale materials. The ability of thermalized positrons to diffuse over to the surfaces of nanocrystallites prior to annihilation helps to explore the disordered atomic arrangement over there and is very useful in understanding the structure and properties of nanomaterials. As examples, the results of studies on FeS 2 nanorods and ZnS nanoparticles are presented. In semiconductor nanoparticles, there are positron trapping sites within the grains also and these are characterised by using appropriate models on the measured positron lifetimes. We have observed vivid changes in the measured positron lifetimes and Doppler broadened gamma ray spectral lineshapes during structural transformations prompted by substitutional effects in Mn 2+ -doped ZnS nanorods. Interestingly, the nanoparticles did not exhibit the transformation, implying the morphologies of the nanosystems playing a decisive role. Quantum confinement effect in CdS nanoparticles was another phenomenon that could be seen through positron annihilation experiments. Coincidence Doppler broadening measurements have been useful to identify the elemental environment around the vacancy clusters that trap positrons. Recent studies on nanocrystalline oxide and sulphide semiconductors are also discussed.

  13. Probing the defects in nano-semiconductors using positrons

    Science.gov (United States)

    Nambissan, P. M. G.

    2011-01-01

    Positron annihilation spectroscopy (PAS) is a very useful tool to study the defect properties of nanoscale materials. The ability of thermalized positrons to diffuse over to the surfaces of nanocrystallites prior to annihilation helps to explore the disordered atomic arrangement over there and is very useful in understanding the structure and properties of nanomaterials. As examples, the results of studies on FeS2 nanorods and ZnS nanoparticles are presented. In semiconductor nanoparticles, there are positron trapping sites within the grains also and these are characterised by using appropriate models on the measured positron lifetimes. We have observed vivid changes in the measured positron lifetimes and Doppler broadened gamma ray spectral lineshapes during structural transformations prompted by substitutional effects in Mn2+-doped ZnS nanorods. Interestingly, the nanoparticles did not exhibit the transformation, implying the morphologies of the nanosystems playing a decisive role. Quantum confinement effect in CdS nanoparticles was another phenomenon that could be seen through positron annihilation experiments. Coincidence Doppler broadening measurements have been useful to identify the elemental environment around the vacancy clusters that trap positrons. Recent studies on nanocrystalline oxide and sulphide semiconductors are also discussed.

  14. Descriptions of positron defect analysis capabilities

    International Nuclear Information System (INIS)

    Howell, R.H.

    1994-10-01

    A series of descriptive papers and graphics appropriate for distribution to potential collaborators has been assembled. These describe the capabilities for defect analysis using positron annihilation spectroscopy. The application of positrons to problems in the polymer and semiconductor industries is addressed

  15. Positron annihilation studies on high temperature superconductors

    International Nuclear Information System (INIS)

    Sundar, C.S.; Bharathi, A.

    1996-01-01

    A survey of the positron annihilation studies on high temperature superconductors (HTSC), with results drawn mainly from our work, is presented. These include results of the studies on the temperature dependence of positron lifetime across T c , which have been carried out in the whole gamut of oxide superconductors. These experimental results are discussed in conjunction with the results of theoretically calculated positron density distribution, and it is shown that the observed temperature dependence of lifetime is intimately linked to the probing of the Cu-O network by the positrons. Results on the investigation of oxygen defects, which play a crucial role in HTSC, are presented. The most significant contribution of positrons to HTSC relates to the investigation of Fermi surface and the results of these studies, drawn from literature, are indicated. Some of our recent results in other novel superconducting materials, viz., the fullerenes and borocarbides are also presented. (author). 69 refs., 15 figs

  16. Electron-positron correlations in an electron liquid

    International Nuclear Information System (INIS)

    Stachowiak, H.

    1980-01-01

    The importance of studying electron-positron interaction for the interpretation of angular correlation data obtained for metallic systems is emphasized. The most successful approaches to electron-positron correlations in jellium are presented. Those include the Bethe-Goldstone two-body equation proposed by Kahana, the charge-density-dielectric function approach connected with the names of Singwi, Sjolander, Stott and Bhattacharyya and the Sawada boson-generalized Tamm-Dancoff approach elaborated recently by Arponen and Pajanne. In conclusion, it is reported that one can consider that the behaviour of a positron at rest in jellium is relatively well understood, though the problem of the optimal choice of a two-body electron-positron phenomenological equation is still open. Also, the behaviour of a positron in a real metal is not well understood and so far, serious calculations in this field have been performed only on very simple models while realistic calculations of the ACPAQ curves tend to minimize the importance of the problems which remain to be solved. (K.B.)

  17. Development of positron emitting radionuclides for imaging with improved positron detectors

    International Nuclear Information System (INIS)

    Yano, Y.

    1976-10-01

    Recent advances in positron cameras and positron ring detectors for transverse section reconstruction have created renewed interest in positron emitting radionuclides. This paper reports on: generator-produced 82 Rb; cyclotron-produced 62 Zn; and reactor-produced 64 Cu. Investigation of the 82 Sr (25 d)-- 82 Rb (75 s) generator determined the elution characteristics for Bio-Rex 70, a weakly acidic carboxylic cation exchanger, using 2% NaCl as the eluent. The yield of 82 Rb and the breakthrough of 82 Sr were determined for newly prepared columns and for long term elution conditions. Spallation-produced 82 Sr was used to charge a compact 82 Rb generator to obtain multi-millicurie amounts of 82 Rb for myocardial imaging. Zinc accumulates in the islet cells of the pancreas and in the prostate. Zinc-62 was produced by protons on Cu foil and separated by column chromatography. Zinc-62 was administered as the amino acid chelates and as the ZnCl 2 to tumor and normal animals. Tissue distribution was determined for various times after intravenous injection. Pancreas-liver images of 62 Zn-histidine uptake were obtained in animals with the gamma camera and the liver uptake of /sup 99m/Tc sulfur colloid was computer subtracted to image the pancreas alone. The positron camera imaged uptake of 62 Zn-histidine in the prostate of a dog at 20 h. 64 Cu was chelated to asparagine, a requirement of leukemic cells, and administered to lymphoma mice. Uptake in tumor and various tissues was determined and compared with the uptake of 67 Ga citrate under the same conditions. 64 Cu-asparagine had better tumor-to-soft tissue ratios than 67 Ga-citrate

  18. Impacts of dark matter particle annihilation on recombination and the anisotropies of the cosmic microwave background

    International Nuclear Information System (INIS)

    Zhang Le; Chen Xuelei; Lei Yian; Si Zongguo

    2006-01-01

    The recombination history of the Universe provides a useful tool for constraining the annihilation of dark matter particles. Even a small fraction of dark matter particles annihilated during the cosmic dark age can provide sufficient energy to affect the ionization state of the baryonic gas. Although this effect is too small for neutralinos, lighter dark matter particle candidates, e.g. with mass of 1-100 MeV, which was proposed recently to explain the observed excess of positrons in the galactic center, may generate observable differences in the cosmic microwave background (CMB) temperature and polarization anisotropies. The annihilations at the era of recombination affects mainly the CMB anisotropy at small angular scales (large l), and is distinctively different from the effect of early reionization. We perform a multiparameter analysis of the CMB data, including both the Wilkinson Microwave Anisotropy Probe (WMAP) first year and three year data, and the ACBAR, Boomerang, CBI, and VSA data. Assuming that the observed excess of e + e - pairs in the galactic center region is produced by dark matter annihilation, and that a sizable fraction of the energy produced in the annihilation is deposited in the baryonic gas during recombination, we obtain a 95% dark matter mass limit of M<8 MeV with the current data set

  19. Positron Spectroscopy of Hydrothermally Grown Actinide Oxides

    Science.gov (United States)

    2014-03-27

    actinide oxides . The work described here is an attempt to characterize the quality of crystals using positron annihilation spectroscopy (PALS). The...Upadhyaya, R. V. Muraleedharan, B. D. Sharma and K. G. Prasad, " Positron lifetime studies on thorium oxide powders," Philosohical Magazine A, vol. 45... crystals . A strong foundation for actinide PALS studies was laid, but further work is required to build a more effective system. Positron Spectroscopy

  20. Positron beam studies of solids and surfaces: A summary

    International Nuclear Information System (INIS)

    Coleman, P.G.

    2006-01-01

    A personal overview is given of the advances in positron beam studies of solids and surfaces presented at the 10th International Workshop on Positron Beams, held in Doha, Qatar, in March 2005. Solids studied include semiconductors, metals, alloys and insulators, as well as biophysical systems. Surface studies focussed on positron annihilation-induced Auger electron spectroscopy (PAES), but interesting applications of positron-surface interactions in fields as diverse as semiconductor technology and studies of the interstellar medium serve to illustrate once again the breadth of scientific endeavour covered by slow positron beam investigations

  1. Positron beam studies of solids and surfaces: A summary

    Science.gov (United States)

    Coleman, P. G.

    2006-02-01

    A personal overview is given of the advances in positron beam studies of solids and surfaces presented at the 10th International Workshop on Positron Beams, held in Doha, Qatar, in March 2005. Solids studied include semiconductors, metals, alloys and insulators, as well as biophysical systems. Surface studies focussed on positron annihilation-induced Auger electron spectroscopy (PAES), but interesting applications of positron-surface interactions in fields as diverse as semiconductor technology and studies of the interstellar medium serve to illustrate once again the breadth of scientific endeavour covered by slow positron beam investigations.

  2. Department of Cosmic Ray Physics: Overview

    International Nuclear Information System (INIS)

    Szabelski, J.

    2001-01-01

    Full text: The Department of Cosmic Ray Physics in Lodz is involved in basic research in the area of high-energy physics and cosmic ray physics related to: Experimental and phenomenological studies of Extensive Air Showers induced by cosmic ray particles. Studies of ultra-high energy (above 10 19 eV) cosmic rays: determination of energy and primary particle mass composition. Studies of asymptotic properties of hadronic interactions based on the analysis of cosmic ray propagation through the atmosphere. Studies of mass composition of cosmic rays in the energy range 10 15 -10 17 eV. Registration of cosmic ray intensity variation correlated with solar activity. Theoretical and experimental studies of Extensive Air Shower properties are performed mostly based on the results obtained by the Lodz Extensive Air Shower Array. We have noticed unexplainable delayed signals registered about 500-900 microseconds after the main EAS pulse. We prepared hardware for further experimental study of this effect. In September we have started registration of 5 GeV muon flux with the underground muon telescope. We registered 3 decreases of muon intensity correlated with Forbush decreases registered at lower energies. Variations of primary cosmic ray of energies up to about 100 GeV were responsible for our registrations. These set the upper limits for geometrical size of geomagnetic disturbances in interplanetary space. In construction and data interpretation of cosmic ray experiments, the Lodz group collaborates with many foreign institutes and laboratories: Forschungszentrum in Karlsruhe (Germany), College de France, Institute for Nuclear Studies of the Russian Academy of Sciences and Uppsala University (Sweden). We have organised (together with the Physics Department of the University of Lodz) the 17 th European Cosmic Ray Symposium (24-?8 July 2000) in which about 150 physicists participated (about 100 from abroad). (author)

  3. Low-energy positron-argon collisions by using parameter-free positron correlation polarization potentials

    International Nuclear Information System (INIS)

    Jain, A.

    1990-01-01

    We report differential, integral, and momentum-transfer cross sections and the scattering length (A 0 ) for positron (e + )-argon scattering at low energies below the positronium formation threshold. An optical-potential approach is employed in which the repulsive Coulombic interaction is calculated exactly at the Hartree-Fock level and the attractive polarization and correlation effects are included approximately via a parameter-free positron correlation polarization (PCP) potential recently proposed by us. The PCP model is based on the correlation energy var-epsilon corr of one positron in a homogeneous electron gas; in the outside region, the var-epsilon corr is joined smoothly with the correct asymptotic form of the polarization interaction (-α 0 /2r 4 , where α 0 is the target polarizability) where they cross each other for the first time. The total optical potential of the e + -argon system is treated exactly in a partial-wave analysis to extract the scattering parameters. It is found that the PCP potential gives much better qualitative results, particularly for the differential cross sections and the scattering length, than the corresponding results obtained from an electron polarization potential used as such for the positron case. We also discuss the ''critical'' points (representing the minima in the differential scattering) in the low-energy e + -Ar scattering. The present results involve no fitting procedure

  4. Existence of dark matter with observed properties of cosmic microwave background radiation substantiates three conservation laws of classical physics and all principles of quantum mechanics as creates the value of Planck’s constant

    Science.gov (United States)

    Boriev, I. A.

    2018-03-01

    Astronomical data indicate a presence of dark matter (DM) in the space, what is necessary for explanation of observed dynamics of the galaxies within Newtonian mechanics. DM, at its very low density (∼10-26kg/m3), constitutes main part of the matter in the Universe, 10 times the mass of all visible cosmic bodies. No doubt, namely properties of DM, which fills space, must determine its physical properties and fundamental physical laws. Taking into account observed properties of cosmic microwave background radiation (CMBR), whose energy is ∼90% of all cosmic radiation, and understanding that this radiation is produced by DM motion, conservation laws of classical physics and principles of quantum mechanics receive their materialistic substantiation. Thus, CMBR high homogeneity and isotropy (∼10-4), and hence the same properties of DM (and space) justify momentum and angular momentum conservation laws, respectively, according to E. Noether's theorems. CMBR has black body spectrum at ∼2.7K with maximum wavelength ∼1.9·10-3m, what allows calculate the value of mechanical action produced by DM thermal motion (∼7·10-34 J·s). This value corresponds well to the Planck’s constant, which is the mechanical action too, what gives materialistic basis for all principles of quantum mechanics. Obtained results directly confirm the reality of DM existence, and show that CMBR is an observed display of DM thermal motion. Understanding that namely from DM occur known creation of electron-positron pairs as contrarily rotating material vortexes (according to their spins) let substantiate positron nature of ball lightning what first explains all its observed specific properties.

  5. Binding matter with antimatter: the covalent positron bond.

    Science.gov (United States)

    Charry, Jorge Alfonso; Varella, Marcio T Do N; Reyes, Andrés

    2018-05-16

    We report sufficient theoretical evidence of the energy stability of the e⁺H₂²⁻ molecule, formed by two H⁻ anions and one positron. Analysis of the electronic and positronic densities of the latter compound undoubtedly points out the formation of a positronic covalent bond between the otherwise repelling hydride anions. The lower limit for the bonding energy of the e⁺H₂²⁻ molecule is 74 kJ/mol (0.77 eV), accounting for the zero-point vibrational correction. The formation of a non electronic covalent bond is fundamentally distinct from positron attachment to stable molecules, as the latter process is characterized by a positron affinity, analogous to the electron affinity. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Positron annihilation spectroscopy using high-energy photons

    International Nuclear Information System (INIS)

    Butterling, Maik; Jungmann, Marco; Krause-Rehberg, Reinhard; Krille, Arnold; Anwand, Wolfgang; Brauer, Gerhard; Cowan, Thomas E.; Hartmann, Andreas; Kosev, Krasimir; Schwengner, Ronald; Wagner, Andreas

    2010-01-01

    The superconducting electron accelerator ELBE (Electron Linac with high Brilliance and low Emittance) at the Research Centre Dresden-Rossendorf (Germany) serves as a high-intensity bremsstrahlung photon-source delivering a pulsed beam (26 MHz) with very short bunches (<5 ps). The photons are being converted into positrons by means of pair production inside the target material thus forming an intense positron source. The accelerator machine pulse is used as time reference allowing positron lifetime spectroscopy. We performed positron annihilation spectroscopy by pair production in different sample materials and used coincidence techniques to reduce the background due to scattered photons significantly in order resulting in spectra of extraordinary high quality. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  7. Polymeric membrane studied using slow positron beam

    International Nuclear Information System (INIS)

    Hung, W.-S.; Lo, C.-H.; Cheng, M.-L.; Chen Hongmin; Liu Guang; Chakka, Lakshmi; Nanda, D.; Tung, K.-L.; Huang, S.-H.; Lee, Kueir-Rarn; Lai, J.-Y.; Sun Yiming; Yu Changcheng; Zhang Renwu; Jean, Y.C.

    2008-01-01

    A radioisotope slow positron beam has been built at the Chung Yuan Christian University in Taiwan for the research and development in membrane science and technology. Doppler broadening energy spectra and positron annihilation lifetime have been measured as a function of positron energy up to 30 keV in a polyamide membrane prepared by the interfacial polymerization between triethylenetetraamine (TETA) and trimesoyl chloride (TMC) on modified porous polyacrylonitrile (PAN) asymmetric membrane. The multilayer structures and free-volume depth profile for this asymmetric membrane system are obtained. Positron annihilation spectroscopy coupled with a slow beam could provide new information about size selectivity of transporting molecules and guidance for molecular designs in polymeric membranes

  8. A Magnetic Transport Middle Eastern Positron Beam

    International Nuclear Information System (INIS)

    Al-Qaradawi, I.Y.; Britton, D.T.; Rajaraman, R.; Abdulmalik, D.

    2008-01-01

    A magnetically guided slow positron beam is being constructed at Qatar University and is currently being optimised for regular operation. This is the first positron beam in the Middle East, as well as being the first Arabic positron beam. Novel features in the design include a purely magnetic in-line deflector, working in the solenoid guiding field, to eliminate un-moderated positrons and block the direct line of sight to the source. The impact of this all-magnetic transport on the Larmor radius and resultant beam characteristics are studied by SIMION simulations for both ideal and real life magnetic field variations. These results are discussed in light of the coupled effect arising from electrostatic beam extraction

  9. Cosmic physics: the high energy frontier

    International Nuclear Information System (INIS)

    Stecker, F W

    2003-01-01

    Cosmic rays have been observed up to energies 10 8 times larger than those of the best particle accelerators. Studies of astrophysical particles (hadrons, neutrinos and photons) at their highest observed energies have implications for fundamental physics as well as astrophysics. Thus, the cosmic high energy frontier is the nexus to new particle physics. This overview discusses recent advances being made in the physics and astrophysics of cosmic rays and cosmic γ-rays at the highest observed energies as well as the related physics and astrophysics of very high energy cosmic neutrinos. These topics touch on questions of grand unification, violations of Lorentz invariance as well as Planck scale physics and quantum gravity. (topical review)

  10. Characteristics of the positron annihilation process in the matter

    International Nuclear Information System (INIS)

    Dryzek, J.

    2000-01-01

    In this report the positrons annihilation spectroscopy, as a method for the matter study is described. The interaction of positrons of high as well as thermal energies are discussed and different models of mentioned interactions are presented. Special attention is paid for positrons interaction with crystal lattice and its defects. The influence of positron beams characteristics on measured values are also discussed

  11. Cosmic rays and global warming

    Energy Technology Data Exchange (ETDEWEB)

    Erlykin, A.D. [P.N. Lebedev Physical Institute, Moscow (Russian Federation); Sloan, T. [Lancaster University (United Kingdom); Wolfendale, A.W. [Durham University (United Kingdom)

    2010-07-01

    The possible effects of cosmic rays on clouds could contribute to global warming. The argument is that the observed increased solar activity during the last century caused a decrease in the ionization due to cosmic rays since the lower energy cosmic particles are deflected by the magnetic field created by the increasing solar wind. This would lead to a decrease in cloud cover allowing more heating of the earth by the sun. Meteorological data combined to solar activity observations and simulations show that any effect of solar activity on clouds and the climate is likely to be through irradiance rather than cosmic rays. Since solar irradiance transfers 8 orders of magnitude more energy to the atmosphere than cosmic rays it is more plausible that this can produce a real effect. The total contribution of variable solar activity to global warming is shown to be less than 14% of the total temperature rise. (A.C.)

  12. Impact of Cosmic-Ray Transport on Galactic Winds

    Science.gov (United States)

    Farber, R.; Ruszkowski, M.; Yang, H.-Y. K.; Zweibel, E. G.

    2018-04-01

    The role of cosmic rays generated by supernovae and young stars has very recently begun to receive significant attention in studies of galaxy formation and evolution due to the realization that cosmic rays can efficiently accelerate galactic winds. Microscopic cosmic-ray transport processes are fundamental for determining the efficiency of cosmic-ray wind driving. Previous studies modeled cosmic-ray transport either via a constant diffusion coefficient or via streaming proportional to the Alfvén speed. However, in predominantly cold, neutral gas, cosmic rays can propagate faster than in the ionized medium, and the effective transport can be substantially larger; i.e., cosmic rays can decouple from the gas. We perform three-dimensional magnetohydrodynamical simulations of patches of galactic disks including the effects of cosmic rays. Our simulations include the decoupling of cosmic rays in the cold, neutral interstellar medium. We find that, compared to the ordinary diffusive cosmic-ray transport case, accounting for the decoupling leads to significantly different wind properties, such as the gas density and temperature, significantly broader spatial distribution of cosmic rays, and higher wind speed. These results have implications for X-ray, γ-ray, and radio emission, and for the magnetization and pollution of the circumgalactic medium by cosmic rays.

  13. Positron annihilation studies on high temperature superconductors

    International Nuclear Information System (INIS)

    Sundar, C.S.; Bharathi, A.

    1991-01-01

    The results of positron annihilation measurements as a function of temperature, across Tc, in a variety of high temperature superconductors such as Y-Ba-Cu-O (Y1237), Y-Ba-Cu-O (Y1248), Bi-Sr-Ca-Cu-O, Tl-Ba-Ca-Cu-O, Ba-K-Bi-O and Nd-Ce-Cu-O are presented. It is shown that the variation of annihilation parameters in the superconducting state is correlated with the diposition of the positron density distribution with respect to the superconducting CuO planes. An increase in positron lifetime is observed below Tc when the positrons probe the CuO planes whereas a decrease in lifetime is observed when the positron density overlaps predominantly with the apical oxygen atom. With this correlation, the different temperature variation of annihilation parameters, seen in the various high temperature superconductors, is understood in terms of a local charge transfer from the planar oxygen atom to the apical oxygen atom. The significance of these results in the context of various theoretical models of high temperature superconductivity is discussed. In addition, the application of positron annihilation spectroscopy to the study of oxygen defects in the Y-Ba-Cu-O, Bi-Sr-Ca-Cu-O and Nd-Ce-Cu-O is presented. (author). 53 refs., 17 figs., 2 tabs

  14. Radiation damage analysis by positron annihilation spectroscopy

    International Nuclear Information System (INIS)

    Siegel, R.W.

    1982-01-01

    Positron annihilation spectroscopy (PAS) has in recent years become a valuable new tool for investigating defects in metals. The ability of the positron to localize in a trapped state at various defect sites, in which the positron annihilates with unique characteristics, has enabled the positron to be used as a localized probe of these defect sites. Several reviews of the application of PAS to the study of defects in metals have been published, as have more general treatises on the applications of positron annihilation to the study of solids. PAS has made, and has considerably greater potential for, a significant contribution to radiation damage analysis in two areas of importance: (1) the determination of atomic-defect properties, a knowledge of which is necessary for the modeling required to couple the results of model experiments using electron and ion irradiation with the expected irradiation conditions of reactor systems, and (2) the monitoring and characterization of irradiation-induced microstructure development. A unique aspect of PAS for radiation damage analysis is the defect specificity of the annihilation characteristics of a trapped positron. In addition to its value as an independent analytical tool, PAS can be a useful complement to more traditional techniques for defect studies

  15. Cosmic Topology

    Science.gov (United States)

    Luminet, Jean-Pierre

    2015-08-01

    Cosmic Topology is the name given to the study of the overall shape of the universe, which involves both global topological features and more local geometrical properties such as curvature. Whether space is finite or infinite, simply-connected or multi-connected like a torus, smaller or greater than the portion of the universe that we can directly observe, are questions that refer to topology rather than curvature. A striking feature of some relativistic, multi-connected "small" universe models is to create multiples images of faraway cosmic sources. While the most recent cosmological data fit the simplest model of a zero-curvature, infinite space model, they are also consistent with compact topologies of the three homogeneous and isotropic geometries of constant curvature, such as, for instance, the spherical Poincaré Dodecahedral Space, the flat hypertorus or the hyperbolic Picard horn. After a "dark age" period, the field of Cosmic Topology has recently become one of the major concerns in cosmology, not only for theorists but also for observational astronomers, leaving open a number of unsolved issues.

  16. Polarization Study for NLC Positron Source Using EGS4

    Energy Technology Data Exchange (ETDEWEB)

    Liu, James C

    2000-09-20

    SLAC is exploring a polarized positron source to study new physics for the NLC project. The positron source envisioned in this paper consists of a polarized electron source, a 50-MeV electron accelerator, a thin target less-than-or-equal-to 0.2 radiation length for positron production, and a capture system for high-energy, small angular divergence positrons. The EGS4 code was used to study the yield, energy spectra, emission-angle distribution, and the mean polarization of the positrons emanating from W-Re and Ti targets hit by longitudinally polarized electron and photon beams. To account for polarization within the EGS4 code a method devised by Flottmann was used, which takes into account polarization transfer for pair production, bremsstrahlung, and Compton interactions. A mean polarization of 0.85 for positrons with energies greater than 25 MeV was obtained. Most of the high-energy positrons were emitted within a forward angle of 20 degrees. The yield of positrons above 25 MeV per incident photon was 0.034, which was about 70 times higher than that obtained with an electron beam.

  17. Cosmic ray physics goes to school

    CERN Multimedia

    2002-01-01

    With the help of a CERN physicist, German Schools bring the Largest Cosmic Ray Detector in Europe one step closer to reality   Eric Berthier and Robert Porret (CERN, ST/HM), Frej Torp and Christian Antfolk from the Polytechnics Arcada in Finland, and Karsten Eggert, physicist at CERN who initiated this project, during the installation of cosmic ray detectors in the Pays de Gex, at point 4. Niina Patrikainen and Frej Torp, Finnish students from Rovaniemi and Arcada Polytechnics, installing cosmic ray counters at the Fachhochschule in Duesseldorf. The science of cosmic ray detection is growing, literally. Cosmic rays, energetic particles from space, strike our planet all the time. They collide with the air molecules in our upper atmosphere and initiate large showers of elementary particles (mainly electrons, photons, hadrons and muons) which rain down upon the earth. The shower size and the particle density in the showers reflect the initial energy of the cosmic ray particle, a detail which makes d...

  18. Generation of an intense pulsed positron beam and its applications

    International Nuclear Information System (INIS)

    Suzuki, Ryoichi; Mikado, Tomohisa; Ohgaki, Hideaki; Chiwaki, Mitsukuni; Yamazaki, Tetsuo; Kobayashi, Yoshinori.

    1994-01-01

    A positron pulsing system for an intense positron beam generated by an electron linac has been developed at the Electrotechnical Laboratory. The pulsing system generates an intense pulsed positron beam of variable energy and variable pulse period. The pulsed positron beam is used as a non destructive probe for various materials researches. In this paper, we report the present status of the pulsed positron beam and its applications. (author)

  19. Matrix Isolation Spectroscopy Applied to Positron Moderatioin in Cryogenic Solids

    Science.gov (United States)

    2011-07-01

    Current Positron Applications • 2-γ decay exploited in Positron Emission Tomography (PET) scanners. • Positrons localize & annihilate preferentially at...Air Force  Eglin Air Force Base AFRL-RW-EG-TP-2011-024 Matrix Isolation Spectroscopy Applied to Positron Moderation in Cryogenic Solids Distribution... Spectroscopy Applied to Positron Moderation in Cryogenic Solids 5a. CONTRACT NUMBER 5b. GRANT NUMBER 62602F 5c. PROGRAM ELEMENT NUMBER 6

  20. Separation of gravitational-wave and cosmic-shear contributions to cosmic microwave background polarization.

    Science.gov (United States)

    Kesden, Michael; Cooray, Asantha; Kamionkowski, Marc

    2002-07-01

    Inflationary gravitational waves (GW) contribute to the curl component in the polarization of the cosmic microwave background (CMB). Cosmic shear--gravitational lensing of the CMB--converts a fraction of the dominant gradient polarization to the curl component. Higher-order correlations can be used to map the cosmic shear and subtract this contribution to the curl. Arcminute resolution will be required to pursue GW amplitudes smaller than those accessible by the Planck surveyor mission. The blurring by lensing of small-scale CMB power leads with this reconstruction technique to a minimum detectable GW amplitude corresponding to an inflation energy near 10(15) GeV.

  1. Advanced characterization of lithium battery materials with positrons

    International Nuclear Information System (INIS)

    Barbiellini, Bernardo; Kuriplach, Jan

    2017-01-01

    Cathode materials are crucial to improved battery performance, in part because there are not yet materials that can maintain high power and stable cycling with a capacity comparable to that of anode materials. Our parameter-free, gradient-corrected model for electron-positron correlations predicts that spectroscopies based on positron annihilation can be deployed to study the effect of lithium intercalation in the oxide matrix of the cathode. The positron characteristics in oxides can be reliably computed using methods based on first-principles. Thus, we can enable a fundamental characterization of lithium battery materials involving positron annihilation spectroscopy and first-principles calculations. The detailed information one can extract from positron experiments could be useful for understanding and optimizing both battery materials and bi-functional catalysts for oxygen reduction and evolution. (paper)

  2. Cosmic rays and the interstellar medium

    International Nuclear Information System (INIS)

    Wolfendale, A.W.

    1986-01-01

    It is inevitable that there is a close connection between cosmic rays and the ISM insofar as the propagation of cosmic rays is conditioned by the magnetic field in the ISM and the cosmic rays interact with the gas (and photon fluxes) in this medium. This paper deals with both topics. Propagation effects manifest themselves as an anisotropy in arrival directions and a review is given of anisotropy measurements and their interpretation. The status of studies of cosmic ray interactions is examined whit particular reference to the information about the ISM itself which comes from observations of the flux of secondary γ-rays produced by cosmic ray interactions with gas, the situation regarding molecular as in the Inner Galaxy being of particular concern

  3. Looking for Cosmic Neutrino Background

    Directory of Open Access Journals (Sweden)

    Chiaki eYanagisawa

    2014-06-01

    Full Text Available Since the discovery of neutrino oscillation in atmospheric neutrinos by the Super-Kamiokande experiment in 1998, study of neutrinos has been one of exciting fields in high-energy physics. All the mixing angles were measured. Quests for 1 measurements of the remaining parameters, the lightest neutrino mass, the CP violating phase(s, and the sign of mass splitting between the mass eigenstates m3 and m1, and 2 better measurements to determine whether the mixing angle theta23 is less than pi/4, are in progress in a well-controlled manner. Determining the nature of neutrinos, whether they are Dirac or Majorana particles is also in progress with continuous improvement. On the other hand, although the ideas of detecting cosmic neutrino background have been discussed since 1960s, there has not been a serious concerted effort to achieve this goal. One of the reasons is that it is extremely difficult to detect such low energy neutrinos from the Big Bang. While there has been tremendous accumulation of information on Cosmic Microwave Background since its discovery in 1965, there is no direct evidence for Cosmic Neutrino Background. The importance of detecting Cosmic Neutrino Background is that, although detailed studies of Big Bang Nucleosynthesis and Cosmic Microwave Background give information of the early Universe at ~a few minutes old and ~300 k years old, respectively, observation of Cosmic Neutrino Background allows us to study the early Universe at $sim$ 1 sec old. This article reviews progress made in the past 50 years on detection methods of Cosmic Neutrino Background.

  4. Defects in Czochralski-grown silicon crystals investigated by positron annihilation

    Energy Technology Data Exchange (ETDEWEB)

    Ikari, Atsushi; Kawakami, Kazuto; Haga, Hiroyo [Nippon Steel Corp., Sagamihara, Kanagawa (Japan). Electronics Research Labs.; Uedono, Akira; Wei, Long; Kawano, Takao; Tanigawa, Shoichiro

    1994-10-01

    Positron lifetime and Doppler broadening experiments were performed on Czochralski-grown silicon crystals. A monoenergetic positron beam was also used to measure the diffusion length of positrons in the wafer. From the measurements, it was observed that the value of diffusion length of positrons decreased at the region where microdefects were formed during the crystal growth process. It was also found that the line shape parameter S decreased and the lifetime of positrons increased at the region. These results can be attributed to the annihilation of positrons trapped by vacancy oxygen complexes which are formed in association with the microdefects. (author).

  5. Stress evaluation at the ILC positron source

    Energy Technology Data Exchange (ETDEWEB)

    Ushakov, Andriy; Moortgat-Pick, Gudrid [Universitaet Hamburg, II. Institut fuer Theoretische Physik, Luruper Chaussee 149, 22761 Hamburg (Germany); Riemann, Sabine; Dietrich, Felix [Deutsches Elektronen-Synchrotron (DESY), Standort Zeuthen, Platanenallee 6, 15738 Zeuthen (Germany); Aulenbacher, Kurt; Tyukin, Valery; Heil, Philipp [Johannes Gutenberg-Universitaet Mainz, Institut fuer Kernphysik, Johann-Joachim-Becher-Weg 45, 55128 Mainz (Germany)

    2016-07-01

    High luminosity is required at future Linear Colliders which is particularly challenging for all corresponding positron sources. At the International Linear Collider (ILC), polarized positrons are obtained from electron-positron pairs by converting high-energy photons produced by passing the high-energy main electron beam through a helical undulator. The conversion target undergoes cyclic stress with high peak values. To distribute the thermal load, the target is designed as wheel spinning in vacuum with 100 m/s. However, the cyclic stress over long time at high target temperatures could exceed the fatigue stress limit. In the talk, an overview of the ILC positron source is given. The prospects to study material parameters under conditions as expected at the ILC are discussed.

  6. Ionization and positron emission in giant quasiatoms

    International Nuclear Information System (INIS)

    Soff, G.; Reinhardt, J.; Reus, T. de; Wietschorke, K.H.; Schaefer, A.; Mueller, B.; Greiner, W.; Mueller, U.; Schlueter, P.

    1985-07-01

    Electron excitation processes in superheavy quasiatoms are treated within a relativistic framework. Theoretical results on K-hole production rates as well as delta-electron and positron spectra are compared with experimental data. It is demonstrated that the study of heavy ion collisions with nuclear time delay promises a signature for the spontaneous positron formation in overcritical systems. Corresponding experimental results are confronted with our theoretical hypothesis. Recent speculations on the origin of the observed peak structures in positron spectra are critically reviewed. Atomic excitations are also employed to obtain information on the course of a nuclear reaction. Using a semiclassical picture we calculate the emission of delta-electrons and positrons in deep-inelastic nuclear reactions. Furthermore some consequences of conversion processes in giant systems are investigated. (orig.)

  7. Development of a Simple Positron Age-Momentum Setup

    Science.gov (United States)

    Sheffield, Thomas; Quarles, C. A.

    2009-04-01

    A positron age-momentum setup that uses NIM Bin electronic modules and a conventional multichannel analyzer (MCA) is described. The essential idea is to accumulate a Doppler broadened spectrum (sensitive to the annihilation electron momentum) using a high purity Germanium detector in coincidence with a BaF2 scintillation counter, which also serves as the stop signal in a conventional positron lifetime setup. The MCA that collects the Doppler spectrum is gated by a selected region of the lifetime spectrum. Thus we can obtain Doppler broadening spectra as a function of positron lifetime: an age-momentum spectrum. The apparatus has been used so far to investigate a ZnO sample where the size of different vacancy trapping sites may affect the positron lifetime and the Doppler broadening spectrum. We are also looking at polymer and rubber carbon-black composite samples where differences in the Doppler spectrum may arise from positron trapping or positronium formation in the samples. Correction for background and contribution from the positron source itself to the Doppler spectrum will be discussed.

  8. Channeling crystals for positron production

    International Nuclear Information System (INIS)

    Decker, F.J.

    1991-05-01

    Particles traversing at small angles along a single crystal axis experience a collective scattering force of many crystal atoms. The enormous fields can trap the particles along an axis or plane, called channeling. High energy electrons are attracted by the positive nuclei and therefore produce strongly enhanced so called coherent bremsstrahlung and pair production. These effects could be used in a positron production target: A single tungsten crystal is oriented to the incident electron beam within 1 mrad. At 28 GeV/c the effective radiation length is with 0.9 mm about one quarter of the amorphous material. So the target length can be shorter, which yields a higher conversion coefficient and a lower emittance of the positron beam. This makes single crystals very interesting for positron production targets. 18 refs., 2 figs

  9. Positron spectroscopy for materials characterization

    International Nuclear Information System (INIS)

    Schultz, P.J.; Snead, C.L. Jr.

    1988-01-01

    One of the more active areas of research on materials involves the observation and characterization of defects. The discovery of positron localization in vacancy-type defects in solids in the 1960's initiated a vast number of experimental and theoretical investigations which continue to this day. Traditional positron annihilation spectroscopic techniques, including lifetime studies, angular correlation, and Doppler broadening of annihilation radiation, are still being applied to new problems in the bulk properties of simple metals and their alloys. In addition new techniques based on tunable sources of monoenergetic positron beams have, in the last 5 years, expanded the horizons to studies of surfaces, thin films, and interfaces. In the present paper we briefly review these experimental techniques, illustrating with some of the important accomplishments of the field. 40 refs., 19 figs

  10. 50 years of positrons

    International Nuclear Information System (INIS)

    Anon.

    1982-01-01

    This year marks the 50th anniversary of one of the major landmarks of modern physics - the discovery of the positron, the antimatter counterpart of the electron. This provided the first evidence for antimatter, and it was also unprecedented for the existence of a new particle to have been predicted by theory. The positron and the concepts behind it were to radically change our picture of Nature. It led to the rapid advancement or our understanding, culminating some fifteen years later with the formulation of quantum electrodynamics as we now know it. (orig./HSI).

  11. Positron annihilation in metallic glasses - a general survey

    International Nuclear Information System (INIS)

    Brauer, G.; Kajcsos, Zs.; Kemeny, T.

    1981-08-01

    This report presents a review of the literature on positron annihilation studies concerning metallic glasses. After some general information and overview on structural models of metallic glasses as well as a short description of the positron annihilation method itself are added. Conclusions regarding information on the structure of metallic glasses obtainable by positron annihilation are also given. (author)

  12. PREFACE: The International Workshop on Positron Studies of Defects 2014

    Science.gov (United States)

    Sugita, Kazuki; Shirai, Yasuharu

    2016-01-01

    The International Workshop on Positron Studies of Defects 2014 (PSD-14) was held in Kyoto, Japan from 14-19 September, 2014. The PSD Workshop brought together positron scientists interested in studying defects to an international platform for presenting and discussing recent results and achievements, including new experimental and theoretical methods in the field. The workshop topics can be characterized as follows: • Positron studies of defects in semiconductors and oxides • Positron studies of defects in metals • New experimental methods and equipment • Theoretical calculations and simulations of momentum distributions, positron lifetimes and other characteristics for defects • Positron studies of defects in combination with complementary methods • Positron beam studies of defects at surfaces, interfaces, in sub-surface regions and thin films • Nanostructures and amorphous materials

  13. Positron annihilation in germanium in thermal equilibrium at high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Uedono, Akira; Moriya, Tsuyoshi; Komuro, Naoyuki; Tanigawa, Shoichiro [Tsukuba Univ., Ibaraki (Japan). Inst. of Materials Science; Kawano, Takao; Ikari, Atsushi

    1996-09-01

    Annihilation characteristics of positrons in Ge in thermal equilibrium at high temperature were studied using a monoenergetic positron beam. Precise measurements of Doppler broadening profiles of annihilation radiation were performed in the temperature range between 300 K and 1211 K. The line shape parameters of Doppler broadening profiles were found to be almost constant at 300-600 K. The changes in these parameters were observed to start above 600 K. This was attributed to both the decrease in the fraction of positrons annihilating with core electrons and the lowering of the crystal symmetry around the region detected by positron-electron pairs. This suggests that behaviors of positrons are dominated by some form of positron-lattice coupling in Ge at high temperatures. The temperature dependence of the diffusion length of positrons was also discussed. (author)

  14. Cosmic strings and galaxy formation

    Science.gov (United States)

    Bertschinger, Edmund

    1989-01-01

    The cosmogonical model proposed by Zel'dovich and Vilenkin (1981), in which superconducting cosmic strings act as seeds for the origin of structure in the universe, is discussed, summarizing the results of recent theoretical investigations. Consideration is given to the formation of cosmic strings, the microscopic structure of strings, gravitational effects, cosmic string evolution, and the formation of galaxies and large-scale structure. Simulation results are presented in graphs, and several outstanding issues are listed and briefly characterized.

  15. A simulation study of a method to reduce positron annihilation spread distributions using a strong magnetic field in positron emission tomography

    International Nuclear Information System (INIS)

    Iida, H.; Kanno, I.; Miura, S.; Murakami, M.; Takahashi, V.; Kemura, K.

    1986-01-01

    The positron trajectories have been three-dimensionally simulated using a Monte-Carlo method under various strength of the magnetic field. More than 5 tesla of the field confined the positrons effectively, resulting in increase of the probability of the annihilation within a limited small region, hence the higher spatial resolution in positron emission tomography

  16. Formation of a high intensity low energy positron string

    Science.gov (United States)

    Donets, E. D.; Donets, E. E.; Syresin, E. M.; Itahashi, T.; Dubinov, A. E.

    2004-05-01

    The possibility of a high intensity low energy positron beam production is discussed. The proposed Positron String Trap (PST) is based on the principles and technology of the Electron String Ion Source (ESIS) developed in JINR during the last decade. A linear version of ESIS has been used successfully for the production of intense highly charged ion beams of various elements. Now the Tubular Electron String Ion Source (TESIS) concept is under study and this opens really new promising possibilities in physics and technology. In this report, we discuss the application of the tubular-type trap for the storage of positrons cooled to the cryogenic temperatures of 0.05 meV. It is intended that the positron flux at the energy of 1-5 eV, produced by the external source, is injected into the Tubular Positron Trap which has a similar construction as the TESIS. Then the low energy positrons are captured in the PST Penning trap and are cooled down because of their synchrotron radiation in the strong (5-10 T) applied magnetic field. It is expected that the proposed PST should permit storing and cooling to cryogenic temperature of up to 5×109 positrons. The accumulated cooled positrons can be used further for various physics applications, for example, antihydrogen production.

  17. Formation of a high intensity low energy positron string

    International Nuclear Information System (INIS)

    Donets, E.D.; Donets, E.E.; Syresin, E.M.; Itahashi, T.; Dubinov, A.E.

    2004-01-01

    The possibility of a high intensity low energy positron beam production is discussed. The proposed Positron String Trap (PST) is based on the principles and technology of the Electron String Ion Source (ESIS) developed in JINR during the last decade. A linear version of ESIS has been used successfully for the production of intense highly charged ion beams of various elements. Now the Tubular Electron String Ion Source (TESIS) concept is under study and this opens really new promising possibilities in physics and technology. In this report, we discuss the application of the tubular-type trap for the storage of positrons cooled to the cryogenic temperatures of 0.05 meV. It is intended that the positron flux at the energy of 1-5 eV, produced by the external source, is injected into the Tubular Positron Trap which has a similar construction as the TESIS. Then the low energy positrons are captured in the PST Penning trap and are cooled down because of their synchrotron radiation in the strong (5-10 T) applied magnetic field. It is expected that the proposed PST should permit storing and cooling to cryogenic temperature of up to 5x10 9 positrons. The accumulated cooled positrons can be used further for various physics applications, for example, antihydrogen production

  18. Application of positron annihilation to polymer and development of a radioisotopes-based pulsed slow positron beam apparatus

    International Nuclear Information System (INIS)

    Suzuki, Takenori

    2004-01-01

    Positrons injected into polymer behave as nanometer probes, which can detect the size and amount of intermolecular spaces among polymer structures. Although positrons can probe the characteristics of polymer, they induce a radiation effect on polymer samples. At low temperature, the radiation effect induces free electrons, which can be trapped in a shallow potential created among intermolecular structures after freezing molecular motions. These trapped electrons can be released after the disappearance of the shallow potential due to the reappearance of molecular motion above the relaxation temperature. Thus, positrons can be used as a probe for relaxation studies. Coincidence of Doppler broadening spectroscopy (CDBS) can improve the S/N ratio to 10 7 , which makes it possible to detect trace elements, since CDBS can separate the high-momentum component of core electrons. A pulsed slow positron beam apparatus is necessary for measuring holes in the polymer film and allows the measurement of the characteristics of thin film coated on semiconductors used widely in electronics industries. (author)

  19. The cosmic spiderweb: equivalence of cosmic, architectural and origami tessellations

    Science.gov (United States)

    Neyrinck, Mark C.; Hidding, Johan; Konstantatou, Marina; van de Weygaert, Rien

    2018-04-01

    For over 20 years, the term `cosmic web' has guided our understanding of the large-scale arrangement of matter in the cosmos, accurately evoking the concept of a network of galaxies linked by filaments. But the physical correspondence between the cosmic web and structural engineering or textile `spiderwebs' is even deeper than previously known, and also extends to origami tessellations. Here, we explain that in a good structure-formation approximation known as the adhesion model, threads of the cosmic web form a spiderweb, i.e. can be strung up to be entirely in tension. The correspondence is exact if nodes sampling voids are included, and if structure is excluded within collapsed regions (walls, filaments and haloes), where dark-matter multistreaming and baryonic physics affect the structure. We also suggest how concepts arising from this link might be used to test cosmological models: for example, to test for large-scale anisotropy and rotational flows in the cosmos.

  20. The cosmic spiderweb: equivalence of cosmic, architectural and origami tessellations.

    Science.gov (United States)

    Neyrinck, Mark C; Hidding, Johan; Konstantatou, Marina; van de Weygaert, Rien

    2018-04-01

    For over 20 years, the term 'cosmic web' has guided our understanding of the large-scale arrangement of matter in the cosmos, accurately evoking the concept of a network of galaxies linked by filaments. But the physical correspondence between the cosmic web and structural engineering or textile 'spiderwebs' is even deeper than previously known, and also extends to origami tessellations. Here, we explain that in a good structure-formation approximation known as the adhesion model, threads of the cosmic web form a spiderweb, i.e. can be strung up to be entirely in tension. The correspondence is exact if nodes sampling voids are included, and if structure is excluded within collapsed regions (walls, filaments and haloes), where dark-matter multistreaming and baryonic physics affect the structure. We also suggest how concepts arising from this link might be used to test cosmological models: for example, to test for large-scale anisotropy and rotational flows in the cosmos.

  1. The cosmic spiderweb: equivalence of cosmic, architectural and origami tessellations

    Science.gov (United States)

    Hidding, Johan; Konstantatou, Marina; van de Weygaert, Rien

    2018-01-01

    For over 20 years, the term ‘cosmic web’ has guided our understanding of the large-scale arrangement of matter in the cosmos, accurately evoking the concept of a network of galaxies linked by filaments. But the physical correspondence between the cosmic web and structural engineering or textile ‘spiderwebs’ is even deeper than previously known, and also extends to origami tessellations. Here, we explain that in a good structure-formation approximation known as the adhesion model, threads of the cosmic web form a spiderweb, i.e. can be strung up to be entirely in tension. The correspondence is exact if nodes sampling voids are included, and if structure is excluded within collapsed regions (walls, filaments and haloes), where dark-matter multistreaming and baryonic physics affect the structure. We also suggest how concepts arising from this link might be used to test cosmological models: for example, to test for large-scale anisotropy and rotational flows in the cosmos. PMID:29765637

  2. Ice and Atoms: experiments with laboratory-based positron beams

    International Nuclear Information System (INIS)

    Coleman, P G

    2011-01-01

    This short review presents results of new positron and positronium (Ps) experiments in condensed matter and atomic physics, as an illustration of the satisfying variety of scientific endeavours involving positron beams which can be pursued with relatively simple apparatus in a university laboratory environment. The first of these two studies - on ice films - is an example of how positrons and Ps can provide new insights into an important system which has been widely interrogated by other techniques. The second is an example of how simple positron beam systems can still provide interesting information - here on a current interesting fundamental problem in positron atomic physics.

  3. Positron annihilation studies on nasicon analogues containing cation vacancies

    International Nuclear Information System (INIS)

    Sreeramalu, V.; Sreepad, H.R.; Chandrashekara, A.; Ravindrachary, V.; Gopal, S.

    1990-01-01

    Positron annihilation studies were carried out on the Nasicon analogue Na 2 (La, Al)Zr(PO 4 ) 3 compound for three different concentrations (2.2, 2.8 and 5.2 by wt.%) of ZrO 2 in the nutrient. Angular correlation study of annihilated photons reveals that the defect concentration is maximum for 2.8(wt.%) of ZrO 2 . Further, positron lifetime studies indicate that the positrons are trapped at cation vacancies. Application of a two state trapping model to this system made it possible to evaluate the lifetime of positrons in the Bloch state and of positrons trapped at cation vacancies. (author). 16 refs., 4 figs

  4. Is the positron a light proton. Contrasts of positron/proton analogies in small molecules

    International Nuclear Information System (INIS)

    Cade, P.E.; Kao, C.-M.

    1982-01-01

    The nature of positron behavior in [M - :e + ] systems is explored. Here M - is a molecular anion which combines with a proton to form a stable system, HM. The sharp distinction between the positron and proton dynamics does not entirely remove common characteristics of these systems. Examples are given for HM versus [M - :e + ] systems with M - = (H - , SH - , CN - , and N 3- ). In addition, the possibilities of a 'positronium' bond versus a hydrogen bond are discussed. (Auth.)

  5. Electron-positron pair creation in heavy ion collisions

    International Nuclear Information System (INIS)

    Kienle, P.

    1987-08-01

    We review here the status of experiments to study the electron positron pair creation in heavy ion atom collisions at bombarding energies close to the Coulomb barrier. The disentanglement and characterisation of various sources of positrons observed in such collisions are described with a focus on the monoenergetic electron positron pairs observed. They seem to originate from the two-body decay of a family of neutral particles with masses of about 3 m e and life times in the range of 6x10 -14 s -10 s, produced by high Coulomb fields. First attempts were made to create these particles by resonant Bhabha scattering. First we present some experimental methods for high efficiency positron spectroscopy in heavy ion collisions. Then we describe the discovery of positron creation induced by strong time changing Coulomb fields. (orig./HSI)

  6. Dosimetry of environmental radiations (cosmic ray)

    International Nuclear Information System (INIS)

    Yamasaki, Keizo

    1978-01-01

    Cosmic ray is dominant as environmental radiation, though the experimental determination made on cosmic ray doses is few in Japan. The free air ionization intensity at sea level due to cosmic ray has been estimated in the Bay of Wakasa, Japan, at middle geomagnetic latitude (25 deg. N), in October 1977. The ionization chambers used were two air and one argon types. Where the responses to cosmic and terrestrial gamma rays were equal, the ionization intensity due to cosmic ray was obtained by subtracting the ionization intensity due to terrestrial gamma ray from the total ionization intensity. As the terrestrial gamma ray, (1) U-238 series, Th-232 series, and K-40 in seawater, (2) K-40 in the material of a wooden ship, and (3) Rn-222 and its daughter products in the atmosphere were considered. The result of free air ionization due to cosmic ray with the argon chamber was slightly smaller than those with the other two air chambers; however, both were in good agreement within standard errors. (JPN.)

  7. The generation and development of the moderators for slow positron beam

    International Nuclear Information System (INIS)

    Yu Weizhong; Yuan Jiaping

    2001-01-01

    The positron annihilation technique is a sensitive tool for studying microdefects and phase transitions in various materials. Usually the energy of positrons is on the order of MeV and the implantation depth about 100 microns, so the bulk average defect density can be studied. In a slow positron beam the positron energy is about keV and the implantation depth a few microns, so surface defects can be detected. Positron moderator is the key device for obtaining a slow positron beam. The authors review the history and development of the positron moderator, including four methods that convert fast positrons into slow mono-energetic positrons and five array types. The tungsten moderator is the most widely used one while the inert gas solid moderator is the most efficient. Field-enhanced moderators with their high efficiency have great potential but need to be developed. The vane arrangement is the most commonly found

  8. Origin and annihilation physics of positrons in the Galaxy

    International Nuclear Information System (INIS)

    Alexis, Anthony

    2014-01-01

    A gamma radiation at 511 keV is observed since the early 1970's toward the Galactic bulge region. This emission is the signature of a large number of electron-positron annihilations, the positron being the electron's antiparticle. Unfortunately, the origin of the positrons responsible for this emission is still a mystery. Many positron-source candidates have been suggested but none of them can account for the galactic annihilation emission. The spatial distribution of this emission is indeed very atypical. Since 2002, the SPI spectrometer onboard the INTEGRAL space laboratory revealed an emission strongly concentrated toward the galactic bulge and a weaker emission from the galactic disk. This morphology is unusual because it does not correspond to any of the known galactic astrophysical-object or interstellar-matter distributions. The assumption that positrons annihilate close to their sources (i.e. the spatial distribution of the annihilation emission reflects the spatial distribution of the sources) has consequently been called into question. Recent studies suggest that positrons could propagate far away from their sources before annihilating. This physical aspect could be the key point to solve the riddle of the galactic positron origin. This thesis is devoted to the modelling of the propagation and annihilation of positrons in the Galaxy, in order to compare simulated spatial models of the annihilation emission with recent measurements provided by SPI/INTEGRAL. This method allows to put constraints on the origin of galactic positrons. We therefore developed a propagation Monte-Carlo code of positrons within the Galaxy in which we implemented all the theoretical and observational knowledge about positron physics (sources, transport modes, energy losses, annihilation modes) and the interstellar medium of our Galaxy (interstellar gas distributions, galactic magnetic fields, structures of the gaseous phases). Due to uncertainties in several physical parameters

  9. Department of Cosmic Ray Physics; Overview

    International Nuclear Information System (INIS)

    Szabelski, J.

    2004-01-01

    Full text: Cosmic Rays are energetic particles from outside the Solar System. The energy spectrum (power law energy dependence) suggests a non-thermal origin of these particles. Most of the studies of Cosmic Rays address fundamental problems such as: - the nature of the physical and astrophysical processes responsible for the high energies of particles (up to about 10 20 eV/particle), - estimation of the astrophysical conditions at the acceleration sites and/or a search for sources of Cosmic Rays, - properties of high energy particle interactions at very high energies (nuclear interactions at energies exceeding energies available in the laboratories). Some Cosmic Ray studies might have practical (commercial) implications, e.g. - ''cosmic weather'' forecast - predictions of geomagnetic disturbances related to Solar activity changes (due to large Solar Flares / events of Coronal Mass Ejections); these are important for large electricity networks, gas pipes, radio-wave connections, space missions and satellite experiments. The Department of Cosmic Ray Physics in Lodz is involved in basic research in the high energy Cosmic Ray field. Energetic Cosmic Ray particles produce cascades of particles in the atmosphere, called Extensive Air Showers (EAS). Registering EAS and their properties is the main theme of experimental studies of very high energy Cosmic Rays. In the Lodz Department we run an Extensive Air Shower array where EAS are registered. We concentrate our experimental research on the explanation of particle detection delayed by hundreds of microseconds with respect to the main EAS signals. In the underground (I5 meters) laboratory we continuously register muon (5 GeV energy threshold) flux with the multidirectional telescope. We have observed several disturbances (Forbush Decreases) in muon counting rates. The interpretation of these events for ''cosmic weather'' and for Cosmic Ray transport models in the interplanetary plasma are on going in collaboration with

  10. Department of Cosmic Ray Physics - Overview

    International Nuclear Information System (INIS)

    Szabelski, J.

    2010-01-01

    Full text: The 31 st International Cosmic Ray Conference (31.ICRC) was held in Lodz on 7-15 July 2009. The Conference was organized by the University of Lodz (Department of High Energy Astrophysics and Department of Astrophysics) and IPJ (Department of Cosmic Ray Physics). ICRCs are held every two years and are the largest forums to present and discuss the current status of Cosmic Ray studies. The Conference we co-organized gathered about 750 scientists (including about 50 from Poland). This was a remarkable event. The Department of Cosmic Ray Physics in Lodz is involved in basic research in the field of high energy Cosmic Rays. Cosmic Rays are energetic panicles from outside the Solar System. Most studies of Cosmic Rays address fundamental problems: - the nature of the physical and astrophysical processes responsible for the high energies of the particles. - experimental search for sources of Cosmic Rays, - studies of the astrophysical conditions at the acceleration sites, - properties of particle interactions at very high energies. Presentation of Cosmic Ray registration to high school students has become a popular way to introduce panicle physics detectors and elementary particle detection techniques to young people, in Lodz and Poznan we organize workshops on particle physics for high school students. This is part of the European activity: EPPOG Masterclass - Hands on CERN. Energetic Cosmic Ray particles produce cascades of panicles in the atmosphere, called Extensive Air Showers (EAS). Registering EASs and their properties is the main means of studying experimentally high energy Cosmic Rays: · The satellite experiment JEM-EUSO will observe EASs from the International Space Station. The main target is to find Cosmic Ray Sources for the highest energy Cosmic Rays. JEM-EUSO will collect a large number of events since it will observe a large area of the atmosphere. We are participating in the preparation of this mission. · The KASCADE-Grande addresses

  11. Positron radiography of ignition-relevant ICF capsules

    Science.gov (United States)

    Williams, G. J.; Chen, Hui; Field, J. E.; Landen, O. L.; Strozzi, D. J.

    2017-12-01

    Laser-generated positrons are evaluated as a probe source to radiograph in-flight ignition-relevant inertial confinement fusion capsules. Current ultraintense laser facilities are capable of producing 2 × 1012 relativistic positrons in a narrow energy bandwidth and short time duration. Monte Carlo simulations suggest that the unique characteristics of such positrons allow for the reconstruction of both capsule shell radius and areal density between 0.002 and 2 g/cm2. The energy-downshifted positron spectrum and angular scattering of the source particles are sufficient to constrain the conditions of the capsule between preshot and stagnation. We evaluate the effects of magnetic fields near the capsule surface using analytic estimates where it is shown that this diagnostic can tolerate line integrated field strengths of 100 T mm.

  12. The Effects of Surface Reconstruction and Electron-Positron Correlation on the Annihilation Characteristics of Positrons Trapped at Semiconductor Surfaces

    International Nuclear Information System (INIS)

    Fazleev, N. G.; Jung, E.; Weiss, A. H.

    2009-01-01

    Experimental positron annihilation induced Auger electron spectroscopy (PAES) data from Ge(100) and Ge(111) surfaces display several strong Auger peaks corresponding to M 4,5 N 1 N 2,3 , M 2,3 M 4,5 M 4,5 , M 2,3 M 4,5 V, and M 1 M 4,5 M 4,5 Auger transitions. The integrated peak intensities of Auger transitions have been used to obtain experimental annihilation probabilities for the Ge 3d and 3p core electrons. The experimental data were analyzed by performing theoretical studies of the effects of surface reconstructions and electron-positron correlations on image potential induced surface states and annihilation characteristics of positrons trapped at the reconstructed Ge(100) and Ge(111) surfaces. Calculations of positron surface states and annihilation characteristics have been performed for Ge(100) surface with (2x1), (2x2), and (4x2) reconstructions, and for Ge(111) surface with c(2x8) reconstruction. Estimates of the positron binding energy and annihilation characteristics reveal their sensitivity to the specific atomic structure of the topmost layers of the semiconductor and to the approximations used to describe electron-positron correlations. The results of these theoretical studies are compared with the ones obtained for the reconstructed Si(100)-(2x1) and Si(111)-(7x7) surfaces.

  13. Positron emitter labeled enzyme inhibitors

    International Nuclear Information System (INIS)

    Fowler, J.S.; MacGregor, R.R.; Wolf, A.P.; Langstrom, B.

    1990-01-01

    This invention involves a new strategy for imagining and mapping enzyme activity in the living human and animal body using positron emitter-labeled suicide enzyme inactivators or inhibitors which become covalently bound to the enzyme as a result of enzymatic catalysis. Two such suicide inactivators for monoamine oxidase have been labeled with carbon-11 and used to map the enzyme subtypes in the living human and animal body using PET. By using positron emission tomography to image the distribution of radioactivity produced by the body penetrating radiation emitted by carbon-11, a map of functionally active monoamine oxidase activity is obtained. Clorgyline and L-deprenyl are suicide enzyme inhibitors and irreversibly inhibit monoamine oxidase. When these inhibitors are labeled with carbon-11 they provide selective probes for monoamine oxidase localization and reactivity in vivo using positron emission tomography

  14. Instrumentation for positron emission tomography

    International Nuclear Information System (INIS)

    Budinger, T.F.; Derenzo, S.E.; Huesman, R.H.

    1984-01-01

    Positron emission tomography with a spatial resolution of 2 mm full width at half maximum for quantitation in regions of interest 4 mm in diameter will become possible with the development of detectors that achieve ultrahigh resolution. Improved resolution will be possible using solid-state photodetectors for crystal identification or photomultiplier tubes with many small electron multipliers. Temporal resolution of 2 seconds and gating of cyclic events can be accomplished if statistical requirements are met. The major physical considerations in achieving high-resolution positron emission tomography are the degradation in resolution resulting from positron range, emission angle, parallax error, detector sampling density, the sensitivity of various detector materials and packing schemes, and the tradeoff between temporal resolution and statistical accuracy. The accuracy of data required for physiological models depends primarily on the fidelity of spatial sampling independent of statistical constraints

  15. Nanometer cavities studied by positron annihilation

    International Nuclear Information System (INIS)

    Mogensen, O.E.

    1992-01-01

    Positronium (Ps) is trapped in cavities in insulating solids, and the lifetime of ortho Ps is determined by the size of the cavity. The information on the properties of the cavities obtained by use of the standard slow positron beam and the 'normal' positron annihilation techniques is compared for several selected cases. (author)

  16. A new slow positron beam facility using a compact cyclotron

    International Nuclear Information System (INIS)

    Hirose, Masafumi

    1998-01-01

    In 1993, Sumitomo Heavy Industries became the first in the world to successfully produce a slow positron beam using a compact cyclotron. Slow positron beam production using an accelerator had mainly consisted of using an electron linear accelerator (LINAC). However, the newly developed system that uses a compact cyclotron enabled cost reduction, downsizing of equipment, production of a DC slow positron beam, a polarized slow positron beam, and other benefits. After that, a genuine slow positron beam facility was developed with the construction of compact cyclotron No.2, and beam production in the new facility has already been started. The features of this new slow positron beam facility are explained below. 1) It is the world's first compact slow positron beam facility using a compact cyclotron. 2) It is the only genuine slow positron beam facility in the world which incorporates the production and use of a slow positron beam in the design stage of the cyclotron. To use a slow positron beam for non-destructive detection of lattice defects in semiconductor material, it is necessary to convert the beam into ultra-short pulses of several hundreds of pico-seconds. Sumitomo Heavy Industries has devised a new short-pulsing method (i.e. an induction bunching method) that enables the conversion of a slow positron beam into short pulses with an optimum pulsing electric field change, and succeeded in converting a slow positron beam into short pulses using this method for the first time in the world. Non-destructive detection of lattice defects in semiconductor material using this equipment has already been started, and some information about the depth distribution, size, density, etc. of lattice defects has already been obtained. (J.P.N.)

  17. Plasma Wakefield Acceleration of an Intense Positron Beam

    Energy Technology Data Exchange (ETDEWEB)

    Blue, B

    2004-04-21

    The Plasma Wakefield Accelerator (PWFA) is an advanced accelerator concept which possess a high acceleration gradient and a long interaction length for accelerating both electrons and positrons. Although electron beam-plasma interactions have been extensively studied in connection with the PWFA, very little work has been done with respect to positron beam-plasma interactions. This dissertation addresses three issues relating to a positron beam driven plasma wakefield accelerator. These issues are (a) the suitability of employing a positron drive bunch to excite a wake; (b) the transverse stability of the drive bunch; and (c) the acceleration of positrons by the plasma wake that is driven by a positron bunch. These three issues are explored first through computer simulations and then through experiments. First, a theory is developed on the impulse response of plasma to a short drive beam which is valid for small perturbations to the plasma density. This is followed up with several particle-in-cell (PIC) simulations which study the experimental parameter (bunch length, charge, radius, and plasma density) range. Next, the experimental setup is described with an emphasis on the equipment used to measure the longitudinal energy variations of the positron beam. Then, the transverse dynamics of a positron beam in a plasma are described. Special attention is given to the way focusing, defocusing, and a tilted beam would appear to be energy variations as viewed on our diagnostics. Finally, the energy dynamics imparted on a 730 {micro}m long, 40 {micro}m radius, 28.5 GeV positron beam with 1.2 x 10{sup 10} particles in a 1.4 meter long 0-2 x 10{sup 14} e{sup -}/cm{sup 3} plasma is described. First the energy loss was measured as a function of plasma density and the measurements are compared to theory. Then, an energy gain of 79 {+-} 15 MeV is shown. This is the first demonstration of energy gain of a positron beam in a plasma and it is in good agreement with the predictions

  18. Primary cosmic ray flux

    Energy Technology Data Exchange (ETDEWEB)

    Stanev, Todor

    2001-05-01

    We discuss the primary cosmic ray flux from the point of view of particle interactions and production of atmospheric neutrinos. The overall normalization of the cosmic ray flux and its time variations and site dependence are major ingredients of the atmospheric neutrino predictions and the basis for the derivation of the neutrino oscillation parameters.

  19. High efficiency cyclotron trap assisted positron moderator

    OpenAIRE

    Gerchow, L.; Cooke, D. A.; Braccini, S.; Döbeli, M.; Kirch, K.; Köster, U.; Müller, A.; Van Der Meulen, N. P.; Vermeulen, C.; Rubbia, A.; Crivelli, P.

    2017-01-01

    We report the realisation of a cyclotron trap assisted positron tungsten moderator for the conversion of positrons with a broad keV- few MeV energy spectrum to a mono-energetic eV beam with an efficiency of 1.8(2)% defined as the ratio of the slow positrons divided by the $\\beta^+$ activity of the radioactive source. This is an improvement of almost two orders of magnitude compared to the state of the art of tungsten moderators. The simulation validated with this measurement suggests that usi...

  20. Positron emission tomography. Positronemisionstomografi

    Energy Technology Data Exchange (ETDEWEB)

    Bolwig, T G; Haunsoe, S; Dahlgaard Hove, J; Hesse, B; Hoejgard, L; Jensen, M; Paulson, O B; Hastrup Svendsen, J; Soelvsten Soerensen, S

    1994-10-01

    Positron emission tomography (PET) is a method for quantitative imaging of regional physiological and biochemical parameters. Positron emitting radioactive isotopes can be produced by a cyclotron, eg. the biologically important carbon ([sup 11]C), oxygen ([sup 15]O), and nitrogen ([sup 13]N) elements. With the tomographic principles of the PET scanner the quantitative distribution of the administered isotopes can be determined and images can be provided as well as dynamic information on blood flow, metabolism and receptor function. In neurology PET has been used for investigations on numerous physiological processes in the brain: circulation, metabolism and receptor studies. In Parkinson's disease PET studies have been able to localize the pathology specifically, and in early stroke PET technique can outline focal areas with living but non-functioning cells, and this could make it possible to intervene in this early state. With positron emission tomography a quantitative evaluation of myocardial blood flow, glucose and fatty acid metabolism can be made as well as combined assessments of blood flow and metabolism. Combined studies of blood flow and metabolism can determine whether myocardial segments with abnormal motility consist of necrotic or viable tissue, thereby delineating effects of revascularisation. In the future it will probably be possible to characterize the myocardial receptor status in different cardiac diseases. The PET technique is used in oncology for clinical as well as more basic research on tumor perfusion and metabolism. Further, tumor uptake of positron labelled cytotoxic drugs might predict the clinical benefit of treatment. (au) (19 refs.).

  1. Study of radiation damage in metals by positron annihilation

    International Nuclear Information System (INIS)

    Gauster, W.B.

    1977-01-01

    Positron annihilation is a sensitive technique for probing defects in metals and it has recently been shown to be a valuable tool for the study of radiation damage. After an introduction to the three basic experimental methods (angular correlation, Doppler broadening, and lifetime measurements), the interaction of positrons with lattice defects is reviewed. Results for the annealing of damage after low temperature irradiation are used to show that positron annihilation has provided new information on annealing kinetics. The role of positron techniques in characterizing complex defect structures resulting from high-temperature neutron irradiation is reviewed and the possible utility of positron annihilation as a nondestructive monitor of property changes is pointed out

  2. Imaging optimizations with non-pure and high-energy positron emitters in small animal positron computed tomography

    International Nuclear Information System (INIS)

    Harzmann, Sophie

    2014-01-01

    The contribution on imaging optimizations with non-pure and high-energy positron emitters in small animal positron emission tomography (PET) covers the following topics: physical fundamentals of PET, mathematical image reconstruction and data analyses, Monte-Carlo simulations and implemented correction scheme, quantification of cascade gamma coincidences based on simulations and measurements, sinogram based corrections, restoration of the spatial resolution, implementation of full corrections.

  3. Application of position-sensitive detectors to positron imaging

    International Nuclear Information System (INIS)

    Yamashita, Takaji; Uchida, Hiroshi; Watanabe, Mitsuo; Omura, Tomohide

    1994-01-01

    Positron imaging including positron emission tomography (PET) is expected to be a promising tool for basic and clinical research, because it makes possible the study of regional chemistry within multiple organs of the body in living human beings and experimental animals. New schemes of high resolution block detectors have been developed to improve the performance of positron imaging systems, which employ small segments of bismuth germanate (BGO) arrays and position-sensitive photomultiplier tubes (PS-PMT). The coincidence detector resolution of less than 2.0 mm in full width at half maximum was achieved with the detectors, which is very close to the theoretical resolution limit in positron imaging. (author)

  4. Measurement of cosmic-ray muons with the Distributed Electronic Cosmic-ray Observatory, a network of smartphones

    International Nuclear Information System (INIS)

    Vandenbroucke, J.; Bravo, S.; Karn, P.; Meehan, M.; Plewa, M.; Schultz, D.; Tosi, D.; BenZvi, S.; Jensen, K.; Peacock, J.; Ruggles, T.; Santander, M.; Simons, A.L.

    2016-01-01

    Solid-state camera image sensors can be used to detect ionizing radiation in addition to optical photons. We describe the Distributed Electronic Cosmic-ray Observatory (DECO), an app and associated public database that enables a network of consumer devices to detect cosmic rays and other ionizing radiation. In addition to terrestrial background radiation, cosmic-ray muon candidate events are detected as long, straight tracks passing through multiple pixels. The distribution of track lengths can be related to the thickness of the active (depleted) region of the camera image sensor through the known angular distribution of muons at sea level. We use a sample of candidate muon events detected by DECO to measure the thickness of the depletion region of the camera image sensor in a particular consumer smartphone model, the HTC Wildfire S. The track length distribution is fit better by a cosmic-ray muon angular distribution than an isotropic distribution, demonstrating that DECO can detect and identify cosmic-ray muons despite a background of other particle detections. Using the cosmic-ray distribution, we measure the depletion thickness to be 26.3 ± 1.4 μm. With additional data, the same method can be applied to additional models of image sensor. Once measured, the thickness can be used to convert track length to incident polar angle on a per-event basis. Combined with a determination of the incident azimuthal angle directly from the track orientation in the sensor plane, this enables direction reconstruction of individual cosmic-ray events using a single consumer device. The results simultaneously validate the use of cell phone camera image sensors as cosmic-ray muon detectors and provide a measurement of a parameter of camera image sensor performance which is not otherwise publicly available

  5. The Upgrade of the Neutron Induced Positron Source NEPOMUC

    Science.gov (United States)

    Hugenschmidt, C.; Ceeh, H.; Gigl, T.; Lippert, F.; Piochacz, C.; Pikart, P.; Reiner, M.; Weber, J.; Zimnik, S.

    2013-06-01

    In summer 2012, the new NEutron induced POsitron Source MUniCh (NEPOMUC) was installed and put into operation at the research reactor FRM II. At NEPOMUC upgrade 80% 113Cd enriched Cd is used as neutron-gamma converter in order to ensure an operation time of 25 years. A structure of Pt foils inside the beam tube generates positrons by pair production. Moderated positrons leaving the Pt front foil are electrically extracted and magnetically guided to the outside of the reactor pool. The whole design, including Pt-foils, the electric lenses and the magnetic fields, has been improved in order to enhance both the intensity and the brightness of the positron beam. After adjusting the potentials and the magnetic guide and compensation fields an intensity of about 3·109 moderated positrons per second is expected. During the first start-up, the measured temperatures of about 90°C ensure a reliable operation of the positron source. Within this contribution the features and the status of NEPOMUC upgrade are elucidated. In addition, an overview of recent positron beam experiments and current developments at the spectrometers is given.

  6. The MEG positron spectrometer

    International Nuclear Information System (INIS)

    Nishiguchi, Hajime

    2007-01-01

    We have been developing an innovative spectrometer for the MEG experiment at the Paul Scherrer Institute (PSI) in Switzerland. This experiment searches for a lepton flavour violating decay μ + →e + γ with a sensitivity of 10 -13 in order to explore the region predicted by supersymmetric extensions of the standard model. The MEG positron spectrometer consists of a specially designed superconducting solenoidal magnet with a highly graded field, an ultimate low-mass drift chamber system, and a precise time measuring counter system. This innovative positron spectrometer is described here focusing on the drift chamber system

  7. Depth profiling of boron implanted silicon by positron beam

    International Nuclear Information System (INIS)

    Oevuenc, S.

    2004-01-01

    Positron depth profiling analyses of low energy implants of silicon aim to observe tbe structure and density of the vacancies generating by implantation and the effect of annealing. This work present the results to several set of data starting S and W parameters. Boron implanted Silicon samples with different implantation energies,20,22,24,and 26 keV are analyzed by Slow positron beam (0-40 keV and 10 5 e + /s )(Variable Energy Positron) at the Positron Centre Delf-HOLLAND

  8. Cosmic Ray Physics with ACORDE at LHC

    CERN Document Server

    Pagliarone, C.

    2008-01-01

    The use of large underground high-energy physics experiments, for comic ray studies, have been used, in the past, at CERN, in order to measure, precisely, the inclusive cosmic ray flux in the energy range from 2x10^10 - 2x10^12 eV. ACORDE, ALICE Cosmic Rays DEtector, will act as Level 0 cosmic ray trigger and, together with other ALICE apparatus, will provide precise information on cosmic rays with primary energies around 10^15 - 10^17 eV. This paper reviews the main detector features, the present status, commissioning and integration with other apparatus. Finally, we discuss the ACORDE-ALICE cosmic ray physics program.

  9. Cosmic ray physics with ACORDE at LHC

    International Nuclear Information System (INIS)

    Pagliarone, C; Fernandez-Tellez, A

    2008-01-01

    The use of large underground high-energy physics experiments, for comic ray studies, have been used, in the past, at CERN, in order to measure, precisely, the inclusive cosmic ray flux in the energy range from 2·10 10 to 2· 10 12 eV. ACORDE, ALICE Cosmic Rays DEtector, will act as Level 0 cosmic ray trigger and, together with other ALICE apparatus, will provide precise information on cosmic rays with primary energies around 10 15 to 10 17 eV. This paper reviews the main detector features, the present status, commissioning and integration with other apparatus. Finally, we discuss the ACORDE-ALICE cosmic ray physics program

  10. Characterization of lacunar defects by positrons annihilation

    CERN Document Server

    Barthe, M F; Blondiaux, G

    2003-01-01

    Among the nondestructive methods for the study of matter, the positrons annihilation method allows to sound the electronic structure of materials by measuring the annihilation characteristics. These characteristics depend on the electronic density as seen by the positon, and on the electron momentums distribution which annihilate with the positon. The positon is sensible to the coulombian potential variations inside a material and sounds preferentially the regions away from nuclei which represent potential wells. The lacunar-type defects (lack of nuclei) represent deep potential wells which can trap the positon up to temperatures close to the melting. This article describes the principles of this method and its application to the characterization of lacunar defects: 1 - positrons: matter probes (annihilation of electron-positon pairs, annihilation characteristics, positrons sources); 2 - positrons interactions in solids (implantation profiles, annihilation states, diffusion and trapping, positon lifetime spec...

  11. Positron annihilation spectroscopic studies of 6H silicon carbide

    International Nuclear Information System (INIS)

    Hu, Y.F.; Lam, C.H.; Ling, C.C.; Fung, S.; Beling, C.D.; Weng, H.M.

    2001-01-01

    Positron lifetime measurements have been performed on p-type and n-type 6H-SiC with temperatures varying from 10 K to 290 K. The V C V Si divacancy is observed in both types of 6H-SiC where the V Si related defect is only found in the n-type material. Positron trapping into a defect with lifetime value close to the bulk was found to compete with positron trapping into V Si or V C V Si at temperatures lower than 80 K. The positron diffusion length of the 1400 C annealed n-type 6H-SiC has also been measured at different temperatures with the use of a positron beam. Positron diffusion was found to be limited by acoustic phonon scattering at T=150-300 K. However, at T=50-150 K, D + follows T 2.12±0.02 and the details of the physical process is not yet known. (orig.)

  12. The effects of low-energy scattering on positron implantation

    Energy Technology Data Exchange (ETDEWEB)

    Ritley, K.A. (Dept. of Physics and Materials Research Laboratory, Univ. of Illinois, Urbana, IL (United States)); Lynn, K.G.; Ghosh, V.; Welch, D.O. (Brookhaven National Lab., Upton, NY (United States))

    1992-01-01

    Existing Monte Carlo models are capable of simulating the behavior of positrons incident at keV energies, then following the energy loss process to arbitrary final kinetic energies of from 20 eV to 100 eV. This work describes a Monte Carlo simulation of the final stages of positron thermalization in Al, from 25 eV to thermal energies, via the mechanisms of conduction-electron and longitudinal acoustic phonon scattering. The latter stages of thermalization can have important effects on the stopping profiles and mean depth. A novel way to obtain information about positron energy loss by considering the time-evolution of a point-concentration (delta-function distribution) of positrons is described. The effects of a positive positron work function are examined for the first time in the context of a positron Monte Carlo calculation. Finally, some issues relating to the agreement of Monte Carlo calculations with experimental data are discussed. 6 figs., 16 refs.

  13. The effects of low-energy scattering on positron implantation

    Energy Technology Data Exchange (ETDEWEB)

    Ritley, K.A. [Dept. of Physics and Materials Research Laboratory, Univ. of Illinois, Urbana, IL (United States); Lynn, K.G.; Ghosh, V.; Welch, D.O. [Brookhaven National Lab., Upton, NY (United States)

    1992-12-31

    Existing Monte Carlo models are capable of simulating the behavior of positrons incident at keV energies, then following the energy loss process to arbitrary final kinetic energies of from 20 eV to 100 eV. This work describes a Monte Carlo simulation of the final stages of positron thermalization in Al, from 25 eV to thermal energies, via the mechanisms of conduction-electron and longitudinal acoustic phonon scattering. The latter stages of thermalization can have important effects on the stopping profiles and mean depth. A novel way to obtain information about positron energy loss by considering the time-evolution of a point-concentration (delta-function distribution) of positrons is described. The effects of a positive positron work function are examined for the first time in the context of a positron Monte Carlo calculation. Finally, some issues relating to the agreement of Monte Carlo calculations with experimental data are discussed. 6 figs., 16 refs.

  14. Temperature dependence of positron trapping by vacancies, loops and voids in molybdenum

    International Nuclear Information System (INIS)

    Bentzon, M.D.; Linderoth, S.; Petersen, K.

    1985-01-01

    The temperature dependence of positron trapping by defects in molybdenum has been studied. By resolving positron lifetime spectra into three components, it has been possible to distinguish the temperature dependence of positron trapping into loops and voids. The results show that the positron trapping rate into voids depends linearly on temperature. The temperature dependence of positron trapping by loops can be interpreted as positrons being trapped by jogs, directly or via the dislocation line. The temperature dependence of positrons trapped by loops is argued mainly to be due to the trapping at the dislocation line, and not to detrapping. The observed temperature dependence of positron annihilation parameters in an electron irradiated sample (below stage III), is explained by competitive positron trapping in interstitial loops at low temperatures

  15. Temperature dependence of the fraction of re-emitted positrons, the positron work function, and the positronium fraction for Cu(III)+S

    International Nuclear Information System (INIS)

    Schultz, P.J.; Lynn, K.G.

    1982-01-01

    A beam of 1 keV positrons incident on a Cu(111)+S surface has been used to study the dependence on temperature of the positron work function (phi/sub +/), the yield of re-emitted positrons (Y) and of the positronium (Ps) fraction. A positive dependence of the slow-positron yield on temperature is found which is attributed in part to a reduction in the magnitude of phi/sub +/ (approx. 25%) at 50 K relative to its value at 300 K. A similar, though weaker, positive dependence on temperature was seen for the Ps fraction down to 40 K. We present a suggestion for the apparent lack of reflection

  16. Positron-trapping mechanism at dislocations in Zn

    DEFF Research Database (Denmark)

    Hidalgo, Carlos; Linderoth, Søren; Diego, Nieves de

    1987-01-01

    the average lifetime and the intensity of the long component decrease with increasing temperature. The experimental results are very well described in terms of a generalized trapping model where it is assumed that positrons become trapped in deep traps (jogs) via shallow traps (dislocation lines......). The temperature dependence of the positron-lifetime spectra below 120 K is attributed to the temperature dependence of the trapping rate to the dislocation line. The experimental results have demonstrated that detrapping processes from the dislocation line take place above 120 K. The positron binding energy...

  17. In-situ positron emission of CO oxidation

    OpenAIRE

    Vonkeman, K.A.; Jonkers, G.; Wal, van der, S.W.A.; Santen, van, R.A.

    1993-01-01

    Using a Neuro ECAT positron tomog., the Positron Emission computed Tomog. (PET) was utilized to image the catalytic oxidn. of CO by using CO and CO2, labeled with short lived positron emitting nuclides. Studies were performed over highly dispersed CeO2/g-Al2O3 supported Pt and Rh catalysts. With a math. model of the reaction kinetics, based on the elementary steps of the catalytic reaction and partially on literature surface science data, the effect of CeO2 promotion and the presence of NO we...

  18. Positron emission tomography studies of brain receptors

    International Nuclear Information System (INIS)

    Maziere, B.; Maziere, M.

    1991-01-01

    Probing the regional distribution and affinity of receptors in the brain, in vivo, in human and non human primates has become possible with the use of selective ligands labelled with positron emitting radionuclides and positron emission tomography (PET). After describing the techniques used in positron emission tomography to characterize a ligand receptor binding and discussing the choice of the label and the limitations and complexities of the in vivo approach, the results obtained in the PET studies of various neurotransmission systems: dopaminergic, opiate, benzodiazepine, serotonin and cholinergic systems are reviewed

  19. Positron-emitting raionuclides: present and future status

    International Nuclear Information System (INIS)

    Lambrecht, R.M.

    1979-01-01

    A tabulation of 157 positron-emitting radionuclides that have the physical characteristics deemed appropriate for radiopharmaceutical use in conjunction with positron emission tomography is provided. The most promising radionuclides are within the production capabilities of a variable-energy cyclotron accelerating protons to about 40 MeV and deuterons, helium-3, and helium-4 to compatable energies. To data only 27 positron-emitting radionuclides have been subjected to radiopharmaceutical consideration, whereas only 11 C, 13 N, 15 O, 18 F, 38 K, and 68 Ga have proved to be especially promising. 2 tables

  20. Department of Cosmic Ray Physics; Overview

    International Nuclear Information System (INIS)

    Szabelski, J.

    2003-01-01

    Full text: Department of Cosmic Ray Physics in Lodz is involved in basic research in the area of high-energy physics and cosmic ray physics related to: - Experimental and phenomenological studies of Extensive Air Showers induced by cosmic ray particles. - Studies of ultra-high energy (above 10 19 eV) cosmic rays: determination of energy spectrum and mass composition of primary particles - Studies of asymptotic properties of hadronic interactions based on the analysis of cosmic ray propagation through the atmosphere. - Studies of mass composition of cosmic rays in the energy range 10 15 - 10 17 eV. - Registration of cosmic ray intensity variation correlated with solar activity. Theoretical and experimental studies of Extensive Air Shower properties are performed mostly basing on the results obtained by the Lodz Extensive Air Shower Array. We have noticed unexplainable delayed signals registered about 500-900 microseconds after the main EAS pulse. Neutron transport simulations were performed in collaboration with JINR in Dubna. We prepared hardware for further experimental study of this effect. Continuous registrations of 5 GeV muon flux with the underground muon telescope have been carried on over the year 2001. We have detected several changes of muon intensity correlated with Forbush decreases registered at lower energies. We have also started registrations of muon counting rate in the on-surface scintillation detectors. These measurements will be included to the analysis of the disturbed energy spectrum of primary cosmic rays and its dependence on interplanetary disturbances related to the solar activity. In construction and data interpretation of cosmic ray experiments the Lodz group collaborates with many foreign institutes and laboratories: Forschungszentrum in Karlsruhe (Germany), College de France, Institute for Nuclear Studies of the Russian Academy of Sciences, JINR in Dubna (Russia), Uppsala University (Sweden) and DESY (Germany). We have prepared a

  1. Department of Cosmic Ray Physics: Overview

    International Nuclear Information System (INIS)

    Szabelski, J.

    2002-01-01

    Full text:The Department of Cosmic Ray Physics in Lodz is involved in basic research in the area of high-energy physics and cosmic ray physics related to: * Experimental and phenomenological studies of Extensive Air Showers induced by cosmic ray particles. * Studies of ultra-high energy (above 10 19 eV) cosmic rays: determination of energy spectrum and mass composition of primary particles * Studies of asymptotic properties of hadronic interactions based on the analysis of cosmic ray propagation through the atmosphere. * Studies of mass composition of cosmic rays in the energy range 10 15 -10 17 eV. * Registration of cosmic ray intensity variation correlated with solar activity. Theoretical and experimental studies of Extensive Air Shower properties are performed mostly based on the results obtained by the Lodz Extensive Air Shower Array. We have noticed unexplainable delayed signals registered about 500-900 microseconds after the main EAS pulse. We prepared hardware for further experimental study of this effect. Continuous registrations of 5 GeV muon flux with the underground muon telescope have been carried on during 2001. We detected several changes of muon intensity correlated with Forbush decreases registered at lower energies. We have also started registration of the muon counting rate in on-surface scintillation detectors. These measurements will be included to the analysis of the disturbed energy spectrum of primary cosmic rays and its dependence on interplanetary disturbances related to solar activity. In construction and data interpretation of cosmic ray experiments the Lodz group collaborates with many foreign institutes and laboratories: Forschungszentrum in Karlsruhe (Germany), College de France, Institute for Nuclear Studies of the Russian Academy of Sciences, Uppsala University (Sweden) and DESY (Germany). We have prepared a project of large air shower array for studies of cosmic rays up to 10 20 eV. Detectors would be placed on the roofs of high

  2. Muon reconstruction performance using cosmic rays in CMS

    CERN Document Server

    Calderon, Alicia

    2009-01-01

    After the incident with the Large Hadron Collider (LHC) in September 2008, the Compact Muon Solenoid (CMS) collaboration invested a considerable effort in further refining the understanding of the detector using cosmic muon data. About 300 million cosmic events were recorded with the CMS detector fully operational and the central solenoid switched on at the nominal value of 3.8 Tesla. The resulting data set provides ample statistics to study in great detail the detector performance and allows to analyze properties of cosmic rays. We present recent results on detector performance from the cosmic muon analysis activities and compare cosmic data to dedicated cosmic Monte Carlo samples. These results demonstrate the readiness of the CMS detector to do physics analysis with muons, and the study of cosmic muon properties provides interesting links to astrophysics.

  3. COSMIC-RAY TRANSPORT AND ANISOTROPIES

    Energy Technology Data Exchange (ETDEWEB)

    Biermann, Peter L. [MPI for Radioastronomy, Auf dem Huegel 69, D-53121 Bonn (Germany); Becker Tjus, Julia; Mandelartz, Matthias [Ruhr-Universitaet Bochum, Fakultaet fuer Physik and Astronomie, Theoretische Physik I, D-44780 Bochum (Germany); Seo, Eun-Suk [Department of Physics, University of Maryland, College Park, MD 20742 (United States)

    2013-05-10

    We show that the large-scale cosmic-ray anisotropy at {approx}10 TeV can be explained by a modified Compton-Getting effect in the magnetized flow field of old supernova remnants. Cosmic rays arrive isotropically to the flow field and are then carried along with the flow to produce a large-scale anisotropy in the arrival direction. This approach suggests an optimum energy scale for detecting the anisotropy. Two key assumptions are that propagation is based on turbulence following a Kolmogorov law and that cosmic-ray interactions are dominated by transport via cosmic-ray-excited magnetic irregularities through the stellar wind of an exploding star and its shock shell. A prediction is that the amplitude is smaller at lower energies due to incomplete sampling of the velocity field and also smaller at larger energies due to smearing.

  4. Positron reemission microscopy

    International Nuclear Information System (INIS)

    Brandes, G.F.; Canter, K.F.; Mills, A.P. Jr.

    1991-01-01

    The positron reemission microscope (PRM), originally proposed by Hulett, Dale and Pendyala, operates on principles fundamentally different from those utilized in existing microscopes and offers sensitivity and contrast not available in conventional microscopes

  5. Multi-spectra Cosmic Ray Flux Measurement

    Science.gov (United States)

    He, Xiaochun; Dayananda, Mathes

    2010-02-01

    The Earth's upper atmosphere is constantly bombarded by rain of charged particles known as primary cosmic rays. These primary cosmic rays will collide with the atmospheric molecules and create extensive secondary particles which shower downward to the surface of the Earth. In recent years, a few studies have been done regarding to the applications of the cosmic ray measurements and the correlations between the Earth's climate conditions and the cosmic ray fluxes [1,2,3]. Most of the particles, which reach to the surface of the Earth, are muons together with a small percentage of electrons, gammas, neutrons, etc. At Georgia State University, multiple cosmic ray particle detectors have been constructed to measure the fluxes and energy distributions of the secondary cosmic ray particles. In this presentation, we will briefly describe these prototype detectors and show the preliminary test results. Reference: [1] K.Borozdin, G.Hogan, C.Morris, W.Priedhorsky, A.Saunders, L.Shultz, M.Teasdale, Nature, Vol.422, 277 (2003). [2] L.V. Egorova, V. Ya Vovk, O.A. Troshichev, Journal of Atmospheric and Terrestrial Physics 62, 955-966 (2000). [3] Henrik Svensmark, Phy. Rev. Lett. 81, 5027 (1998). )

  6. Probing Positron Gravitation at HERA

    International Nuclear Information System (INIS)

    Gharibyan, Vahagn

    2015-07-01

    An equality of particle and antiparticle gravitational interactions holds in general relativity and is supported by indirect observations. Here I develop a method based on high energy Compton scattering to measure the gravitational interaction of accelerated charged particles. Within that formalism the Compton spectra measured at HERA rule out the positron's anti-gravity and hint for a positron's 1.3(0.2)% weaker coupling to the gravitational field relative to an electron.

  7. Probing Positron Gravitation at HERA

    Energy Technology Data Exchange (ETDEWEB)

    Gharibyan, Vahagn

    2015-07-15

    An equality of particle and antiparticle gravitational interactions holds in general relativity and is supported by indirect observations. Here I develop a method based on high energy Compton scattering to measure the gravitational interaction of accelerated charged particles. Within that formalism the Compton spectra measured at HERA rule out the positron's anti-gravity and hint for a positron's 1.3(0.2)% weaker coupling to the gravitational field relative to an electron.

  8. Cosmic rays, clouds and climate

    Energy Technology Data Exchange (ETDEWEB)

    Svensmark, Henrik [Danish Space Research Institute, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark)

    2007-07-01

    Changes in the intensity of galactic cosmic rays seems alter the Earth's cloudiness. A recent experiment has shown how electrons liberated by cosmic rays assist in making aerosols, the building blocks of cloud condensation nuclei, while anomalous climatic trends in Antarctica confirm the role of clouds in helping to drive climate change. Variations in the cosmic-ray influx due to solar magnetic activity account well for climatic fluctuations on decadal, centennial and millennial timescales. Over longer intervals, the changing galactic environment of the Solar System has had dramatic consequences, including Snowball Earth episodes.

  9. High-energy cosmic-ray acceleration

    CERN Document Server

    Bustamante, M; de Paula, W; Duarte Chavez, J A; Gago, A M; Hakobyan, H; Jez, P; Monroy Montañez, J A; Ortiz Velasquez, A; Padilla Cabal, F; Pino Rozas, M; Rodriguez Patarroyo, D J; Romeo, G L; Saldaña-Salazar , U J; Velasquez, M; von Steinkirch, M

    2010-01-01

    We briefly review the basics of ultrahigh-energy cosmic-ray acceleration. The Hillas criterion is introduced as a geometrical criterion that must be fulfilled by potential acceleration sites, and energy losses are taken into account in order to obtain a more realistic scenario. The different available acceleration mechanisms are presented, with special emphasis on Fermi shock acceleration and its prediction of a power-law cosmic-ray energy spectrum. We conclude that first-order Fermi acceleration, though not entirely satisfactory, is the most promising mechanism for explaining the ultra-high-energy cosmic-ray flux.

  10. Multi-pair states in electron–positron pair creation

    Directory of Open Access Journals (Sweden)

    Anton Wöllert

    2016-09-01

    Full Text Available Ultra strong electromagnetic fields can lead to spontaneous creation of single or multiple electron–positron pairs. A quantum field theoretical treatment of the pair creation process combined with numerical methods provides a description of the fermionic quantum field state, from which all observables of the multiple electron–positron pairs can be inferred. This allows to study the complex multi-particle dynamics of electron–positron pair creation in-depth, including multi-pair statistics as well as momentum distributions and spin. To illustrate the potential benefit of this approach, it is applied to the intermediate regime of pair creation between nonperturbative Schwinger pair creation and perturbative multiphoton pair creation where the creation of multi-pair states becomes nonnegligible but cascades do not yet set in. Furthermore, it is demonstrated how spin and helicity of the created electrons and positrons are affected by the polarization of the counterpropagating laser fields, which induce the creation of electron–positron pairs.

  11. Multi-pair states in electron–positron pair creation

    Energy Technology Data Exchange (ETDEWEB)

    Wöllert, Anton, E-mail: woellert@mpi-hd.mpg.de; Bauke, Heiko, E-mail: heiko.bauke@mpi-hd.mpg.de; Keitel, Christoph H.

    2016-09-10

    Ultra strong electromagnetic fields can lead to spontaneous creation of single or multiple electron–positron pairs. A quantum field theoretical treatment of the pair creation process combined with numerical methods provides a description of the fermionic quantum field state, from which all observables of the multiple electron–positron pairs can be inferred. This allows to study the complex multi-particle dynamics of electron–positron pair creation in-depth, including multi-pair statistics as well as momentum distributions and spin. To illustrate the potential benefit of this approach, it is applied to the intermediate regime of pair creation between nonperturbative Schwinger pair creation and perturbative multiphoton pair creation where the creation of multi-pair states becomes nonnegligible but cascades do not yet set in. Furthermore, it is demonstrated how spin and helicity of the created electrons and positrons are affected by the polarization of the counterpropagating laser fields, which induce the creation of electron–positron pairs.

  12. Multi-pair states in electron–positron pair creation

    International Nuclear Information System (INIS)

    Wöllert, Anton; Bauke, Heiko; Keitel, Christoph H.

    2016-01-01

    Ultra strong electromagnetic fields can lead to spontaneous creation of single or multiple electron–positron pairs. A quantum field theoretical treatment of the pair creation process combined with numerical methods provides a description of the fermionic quantum field state, from which all observables of the multiple electron–positron pairs can be inferred. This allows to study the complex multi-particle dynamics of electron–positron pair creation in-depth, including multi-pair statistics as well as momentum distributions and spin. To illustrate the potential benefit of this approach, it is applied to the intermediate regime of pair creation between nonperturbative Schwinger pair creation and perturbative multiphoton pair creation where the creation of multi-pair states becomes nonnegligible but cascades do not yet set in. Furthermore, it is demonstrated how spin and helicity of the created electrons and positrons are affected by the polarization of the counterpropagating laser fields, which induce the creation of electron–positron pairs.

  13. Organic synthesis with short-lived positron-emitting radioisotopes

    International Nuclear Information System (INIS)

    Pike, V.W.

    1988-01-01

    Chemistry with short-lived positron-emitting radioisotopes of the non-metals, principally 11 C, 13 N and 18 F, has burgeoned over the last decade. This has been almost entirely because of the emergence of positron emission tomography (PET) as a powerful non-invasive technique for investigating pathophysiology in living man. PET is essentially an external technique for the rapid serial reconstruction of the spatial distribution of any positron-emitting radioisotope that has been administered in vivo. Such a distribution is primarily governed by the chemical form in which the positron-emitting radioisotope is incorporated, and importantly for clinical research, is often perturbed by physical, biological or clinical factors. Judicious choice of the chemical form enables specific biological information to be obtained. For example, the labelling of glucose with a positron-emitting radioisotope could be expected to provide a radiopharmaceutical for the study of glucose utilisation in both health and disease. (author)

  14. Positron trapping at defects in copper oxide superconductors

    International Nuclear Information System (INIS)

    McMullen, T.; Jena, P.; Khanna, S.N.; Li, Y.; Jensen, K.O.

    1991-01-01

    Positron states and lifetimes at defects in the copper oxide superconductors La 2-x Sr x CuO 4 , YBa 2 Cu 3 O 7-x , and Bi 2 Sr 2 CaCu 2 O 8+x are calculated with use of the superposed-atom model. In the Bi 2 Sr 2 CaCu 2 O 8+x compound, we find that the smaller metal-ion vacancies appear to only bind positrons weakly, while missing oxygens do not trap positrons. In contrast, metal-ion vacancies in La 2-x Sr x CuO 4 and YBa 2 Cu 3 O 7-x bind positrons by ∼1 eV, and oxygen-related defects appear to be the weak-binding sites in these materials. The sites that bind positrons only weakly, by energies ∼k BT , are of particular interest in view of the complex temperature dependences of the annihilation characteristics that are observed in these materials

  15. Positrons trapped in polyethylene: Electric field effect

    International Nuclear Information System (INIS)

    Bertolaccini, M.; Bisi, A.; Gambarini, G.; Zappa, L.

    1978-01-01

    The intensity of the iot 2 -component of positrons annihilated in polyethylene is found to increase with increasing electric field, while the formation probability of the positron state responsible for this component remains independent of the field. (orig.) 891 HPOE [de

  16. ANTICOOL: Simulating positron cooling and annihilation in atomic gases

    Science.gov (United States)

    Green, D. G.

    2018-03-01

    The Fortran program ANTICOOL, developed to simulate positron cooling and annihilation in atomic gases for positron energies below the positronium-formation threshold, is presented. Given positron-atom elastic scattering phase shifts, normalised annihilation rates Zeff, and γ spectra as a function of momentum k, ANTICOOL enables the calculation of the positron momentum distribution f(k , t) as a function of time t, the time-varying normalised annihilation rate Z¯eff(t) , the lifetime spectrum and time-varying annihilation γ spectra. The capability and functionality of the program is demonstrated via a tutorial-style example for positron cooling and annihilation in room temperature helium gas, using accurate scattering and annihilation cross sections and γ spectra calculated using many-body theory as input.

  17. Irradiation damage of alkali halide crystals during positron bombardment

    International Nuclear Information System (INIS)

    Arefiev, K.P.; Arefiev, V.P.; Vorobiev, S.A.

    1978-01-01

    The bleaching effect of positron irradiation of KCl and KBr single crystals previously coloured with electrons or protons was investigated. Positrons injection in the coloured alkali halide samples reduced the F-centres concentration considerably. For KCl crystals thicker than the positrons range the appearance of additional bands in the absorption spectra is noticeable. The experimental data show that the bleaching phenomenon should be observed merely throughout the positron exposure both for irradiated and non-irradiated regions of the sample. Irradiation effects, due to positron source, on the peak counting rate of (γ-γ) angular correlation in KCl crystals under applied magnetic field were also investigated. The growth of peak counting rate shows the increase of positronium-like states formation near defects of cation sublattice. (author)

  18. Department of Cosmic Ray Physics - Overview

    International Nuclear Information System (INIS)

    Szabelski, J.

    2008-01-01

    Full text: The Department of Cosmic Ray Physics in Lodz is involved in basic research in the high energy Cosmic Ray field. Cosmic Rays are energetic particles from outside the Solar System. Most of the studies of Cosmic Rays address fundamental problems: · the nature of the physical and astrophysical processes responsible for high energies of particles · an estimation of the astrophysical conditions at the acceleration sites and/or search for sources of Cosmic Rays, · properties of high energy particle interactions at very high energies. Some Cosmic Ray studies might have practical (commercial) implications, e.g. · '' cosmic weather '' forecast - predictions of geomagnetic disturbances related to Solar activity changes (due to large Solar Flares / events of Coronal Mass Ejection); these are important for large electricity networks, gas pipes, radio-wave connections, space missions and satellite experiments. Presentation of Cosmic Ray registration to high school students becomes a popular way to introduce particle physics detectors and elementary particle detection techniques to young people. We organize in Lodz several workshops on particle physics for high school students. This is a part of European activity: EPPOG's Masterclass - Hands on CERN. Energetic Cosmic Ray particles produce cascades of particles in the atmosphere, called Extensive Air Showers (EAS). Registering EAS and their properties is the main way of experimental studies of very high energy Cosmic Rays. In Lodz Department we run Extensive Air Shower array where EAS are continuously being registered. We concentrate on the studies of detection of neutrons correlated with EAS and interpretation of this phenomenon. In 2004 we started realisation of the Roland Maze Project, the network of EAS detectors placed on the roofs of high schools in Lodz. We received funds from the City of Lodz budget to make a pilot project and equip 10 high schools, each with four 1m 2 detectors and GPS. The network is

  19. A question of balance: Kinetic balance for electrons and positrons

    International Nuclear Information System (INIS)

    Dyall, Kenneth G.

    2012-01-01

    Graphical abstract: Kinetic balance for both electrons and positrons is achieved by applying the correct relation for positive and negative energy states separately and then using the electron and positron eigensolutions from the separate diagonalizations of the Hamiltonian as a dual basis. Highlights: ► Kinetic balance for electrons and positrons is achieved in a dual atomic basis. ► Dual atomic balance alleviates, but does not eliminate, energy prolapse. ► Positron affinities converge quicker with basis set size with dual atomic balance. - Abstract: The kinetic balance criterion used in current relativistic basis set codes is satisfied by the electron solutions of the Dirac equation, but not the positron solutions. A proposal for applying kinetic balance to both sets of solutions is presented. The method is applied along with “normal” kinetic balance to one-electron systems, to investigate its possible relation to prolapse, and to the positron affinity of F − , to investigate the kinetic energy deficiency for positron solutions. The new method reduces but does not eliminate prolapse for energy-optimized basis sets, and provides faster and smoother convergence with basis set size for the positron affinity.

  20. Digital positron lifetime spectroscopy: present status and outlook

    International Nuclear Information System (INIS)

    Becvar, F.

    2007-01-01

    This contribution summarizes achievements in instrumentation for positron lifetime measurements with emphasis on digital spectrometric systems. A significant part of the data presented are based on a long-term exploitation of a conventional positron lifetime spectrometer developed at Charles University in early 90s, on bench-mark testing measurements with this spectrometer working temporarily in conjunction with a pair of 8-bit, 4 GS/s digitizers and on analogous measurements with a recently assembled digital positron lifetime spectrometer. In addition, results from testing experiments with microchannel plate photomultipliers are briefly reported. Further development of positron lifetime technique is discussed. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Cosmic rays on earth

    International Nuclear Information System (INIS)

    Allkofer, O.C.; Grieder, P.K.F.

    1984-01-01

    A data collection is presented that covers cosmic rays on earth. Included are all relevant data on flux and intensity measurements, energy spectra, and related data of all primary and secondary components of the cosmic radiation at all levels in the atmosphere, at sea level and underground. In those cases where no useful experimental data have been available, theoretical predictions were substituted. (GSCH)

  2. High-energy cosmic rays

    CERN Document Server

    Cronin, James Watson

    1996-01-01

    Recently two cosmic rays with energy in excess of 2 1020 eV have been recorded. These are some 108 times more energetic than the protons produced by accelerators on earth. There is no credible understanding of the mechanism of acceleration by known a Because of the short mean free path in the cosmic background radiation they must come from nearby distances on a cosmological scale (< 50 Mpc). Their magnetic rigidity suggests that they should point to their source. Lectures will cover the present available data on the highest energy cosmic rays, their detection, possible acceleration mechanisms, their propagation in the galaxy and in extra galactic space and design of new detectors where simulations of air show ers play an important role.

  3. Empirical model for the Earth's cosmic ray shadow at 400 KM: prohibited cosmic ray access

    International Nuclear Information System (INIS)

    Humble, J.E.; Smart, D.F.; Shea, M.A.

    1985-01-01

    The possibility of constructing a unit sphere of access that describes the cosmic radiation allowed to an Earth-orbiting spacecraft is discussed. It is found that it is possible to model the occluded portion of the cosmic ray sphere of access as a circular projection with a diameter bounded by the satellite-Earth horizon. Maintaining tangency at the eastern edge of the spacecraft-Earth horizon, this optically occluded area is projected downward by an angle beta which is a function of the magnetic field inclination and cosmic ray arrival direction. This projected plane, corresponding to the forbidden area of cosmic ray access, is bounded by the spacecraft-Earth horizon in easterly directions, and is rotated around the vertical axis by an angle alpha from the eastern direction, where the angle alpha is a function of the offset dipole latitude of the spacecraft

  4. Cosmic ray physics with ACORDE at LHC

    Energy Technology Data Exchange (ETDEWEB)

    Pagliarone, C [Universita degli Studi di Cassino and INFN Pisa, Largo B. Pontecorvo, 3 - Pisa (Italy); Fernandez-Tellez, A [Benemerita Universidad Autonoma de Puebla (BUAP), Puebla (Mexico)], E-mail: pagliarone@fnal.gov

    2008-05-15

    The use of large underground high-energy physics experiments, for comic ray studies, have been used, in the past, at CERN, in order to measure, precisely, the inclusive cosmic ray flux in the energy range from 2{center_dot}10{sup 10} to 2{center_dot} 10{sup 12} eV. ACORDE, ALICE Cosmic Rays DEtector, will act as Level 0 cosmic ray trigger and, together with other ALICE apparatus, will provide precise information on cosmic rays with primary energies around 10{sup 15} to 10{sup 17} eV. This paper reviews the main detector features, the present status, commissioning and integration with other apparatus. Finally, we discuss the ACORDE-ALICE cosmic ray physics program.

  5. Positron annihilation studies on BeO powders

    International Nuclear Information System (INIS)

    Brauer, G.; Kerbe, F.; Kajcsos, Z.; Ashry, A.

    1984-01-01

    The sintering behaviour of two differently produced BeO powders is studied by positron annihilation. The positron lifetime in dislocations is found to be tau/sub d/ = (185 +- 2) ps, whereas for the perfect lattice tau/sub c/ = (130 +- 2) ps. (author)

  6. Cosmic ray investigations

    International Nuclear Information System (INIS)

    Zatsepin, Georgii T; Roganova, Tat'yana M

    2009-01-01

    The history of cosmic ray research at the Lebedev Institute beginning with the first work and continuing up to now is reviewed. The milestones and main avenues of research are outlined. Pioneering studies on the nuclear cascade process in extensive air showers, investigations of the Vavilov-Cherenkov radiation, and some work on the origin of cosmic rays are discussed. Recent data on ultrahigh-energy particle detection at the Pierre Auger Observatory and the High Resolution Fly's Eye (HiRes) experiments are presented. (conferences and symposia)

  7. Heterotic cosmic strings

    International Nuclear Information System (INIS)

    Becker, Katrin; Becker, Melanie; Krause, Axel

    2006-01-01

    We show that all three conditions for the cosmological relevance of heterotic cosmic strings, the right tension, stability and a production mechanism at the end of inflation, can be met in the strongly coupled M-theory regime. Whereas cosmic strings generated from weakly coupled heterotic strings have the well-known problems posed by Witten in 1985, we show that strings arising from M5-branes wrapped around 4-cycles (divisors) of a Calabi-Yau in heterotic M-theory compactifications solve these problems in an elegant fashion

  8. CO2 absorption of perovskites as seen by positron lifetime spectroscopy

    International Nuclear Information System (INIS)

    Suevegh, K.; Nomura, K.; Juhasz, G.; Homonnay, Z.; Vertes, A.

    2000-01-01

    The CO 2 absorption of several ABO 3 type perovskites was studied by positron lifetime spectroscopy. The longer positron lifetime was associated with positrons trapped by A site vacancies. The evaluated positron lifetime data indicated the relative stability of the crystal structure of Sr(Co 0.5 Fe 0.5 )O 3-δ against Ca doping at low Ca concentrations. Oxygen desorption and CO 2 absorption/desorption could also be followed by positron lifetime spectroscopy. It was shown that the concentration of oxygen vacancies has a large effect on positron lifetime data through the electron density of A site vacancies.

  9. Modelling of radio emission from cosmic ray air showers

    Science.gov (United States)

    Ludwig, Marianne

    2011-06-01

    Cosmic rays entering the Earth's atmosphere induce extensive air showers consisting of up to billions of secondary particles. Among them, a multitude of electrons and positrons are generated. These get deflected in the Earth's magnetic field, creating time-varying transverse currents. Thereby, the air shower emits coherent radiation in the MHz frequency range measured by radio antenna arrays on the ground such as LOPES at the KIT. This detection method provides a possibility to study cosmic rays with energies above 1017 eV. At this time, the radio technique undergoes the change from prototype experiments to large scale application. Thus, a detailed understanding of the radio emission process is needed more than ever. Before starting this work, different models made conflicting predictions on the pulse shape and the amplitude of the radio signal. It turned out that a radiation component caused by the variation of the number of charged particles within the air shower was missed in several models. The Monte Carlo code REAS2 superposing the radiation of the individual air shower electrons and positrons was one of those. At this time, it was not known how to take the missing component into account. For REAS3, we developed and implemented the endpoint formalism, a universal approach, to calculate the radiation from each single particle. For the first time, we achieve a good agreement between REAS3 and MGMR, an independent and completely different simulation approach. In contrast to REAS3, MGMR is based on a macroscopic approach and on parametrisations of the air shower. We studied the differences in the underlying air shower models to explain the remaining deviations. For comparisons with LOPES data, we developed a new method which allows "top-down" simulations of air showers. From this, we developed an air shower selection criterion based on the number of muons measured with KASCADE to take shower-to-shower fluctuations for a single event analysis into account. With

  10. Positron annihilation study in La2CuO4

    International Nuclear Information System (INIS)

    Kubo, Y.; Asano, S.

    1992-01-01

    The positron annihilation study for La 2 CuO 4 are performed using the full-potential linearized augmented-plane-wave(FLAPW) calculated electron and positron densities. The electron-positron momentum density(EPMD) is computed, and the well known Lock-Crisp-West(LCW) zone folding of the EPMD is produced. In the LCW analysis, small residual variations of order about 3 % are observed. The calculations show that the relative weights of the Fermi surface discontinuities are substantially altered due to the positron preferentially sampling the Cu-O plane region

  11. Positron kinetics in an idealized PET environment

    Science.gov (United States)

    Robson, R. E.; Brunger, M. J.; Buckman, S. J.; Garcia, G.; Petrović, Z. Lj.; White, R. D.

    2015-08-01

    The kinetic theory of non-relativistic positrons in an idealized positron emission tomography PET environment is developed by solving the Boltzmann equation, allowing for coherent and incoherent elastic, inelastic, ionizing and annihilating collisions through positronium formation. An analytic expression is obtained for the positronium formation rate, as a function of distance from a spherical source, in terms of the solutions of the general kinetic eigenvalue problem. Numerical estimates of the positron range - a fundamental limitation on the accuracy of PET, are given for positrons in a model of liquid water, a surrogate for human tissue. Comparisons are made with the ‘gas-phase’ assumption used in current models in which coherent scattering is suppressed. Our results show that this assumption leads to an error of the order of a factor of approximately 2, emphasizing the need to accurately account for the structure of the medium in PET simulations.

  12. Monte Carlo simulation of positron induced secondary electrons in thin carbon foils

    International Nuclear Information System (INIS)

    Cai, L H; Yang, B; Ling, C C; Beling, C D; Fung, S

    2011-01-01

    Emission of secondary electrons induced by the passage of low energy positrons through thin carbon foils was studied by the Monte Carlo method. The positron and electron elastic cross sections were calculated by partial wave analysis. The inelastic positron-valence-electron was described by the energy loss function obtained from dielectric theory. The positron-core-electron interaction was modelled by the Gryzinski's excitation function. Positron transport inside the carbon foil was simulated in detail. Secondary electrons created by positrons and high energy secondary electrons through inelastic interactions were tracked through the foil. The positron transmission coefficient and secondary electron yielded in forward and backward geometry are calculated and dependences on positron energy and carbon foil thickness are discussed.

  13. Positron energy distributions from a hybrid positron source based on channeling radiation

    International Nuclear Information System (INIS)

    Azadegan, B.; Mahdipour, A.; Dabagov, S.B.; Wagner, W.

    2013-01-01

    A hybrid positron source which is based on the generation of channeling radiation by relativistic electrons channeled along different crystallographic planes and axes of a tungsten single crystal and subsequent conversion of radiation into e + e − -pairs in an amorphous tungsten target is described. The photon spectra of channeling radiation are calculated using the Doyle–Turner approximation for the continuum potentials and classical equations of motion for channeled particles to obtain their trajectories, velocities and accelerations. The spectral-angular distributions of channeling radiation are found applying classical electrodynamics. Finally, the conversion of radiation into e + e − -pairs and the energy distributions of positrons are simulated using the GEANT4 package

  14. Positron collisions with helium and alkaline earth-like atoms

    International Nuclear Information System (INIS)

    Campbell, C.P.

    1998-09-01

    This doctoral thesis is subdivided into: 1. Theory of positron collisions with helium and alkaline earth-like atoms, 2. Positron collisions with helium, magnesium, calcium, zinc, 3. Intercomparison of positron scattering by all those elements. The appendix of this work gives details of the numerical calculations and expands on the wavefunctions used

  15. Design studies for the Positron Factory

    International Nuclear Information System (INIS)

    Okada, S.; Sunaga, H.; Kaneko, H.; Masuno, S.; Kawasuso, A.; Sakai, T.; Takizawa, H.; Yotsumoto, K.; Honda, Y.; Tagawa, S.

    1996-01-01

    In the design study for the Positron Factory, a feasibility of simultaneous extraction of multi-channel monoenergetic positron beams, which had been proposed at the previous conference (Linac 94), was demonstrated by an experiment using an electron linac. On the basis of the experimental result, an efficient moderator structure, which is composed of honeycomb-like assembled moderator foils and reflectors, is proposed. (author)

  16. Positron emission tomography of the heart

    International Nuclear Information System (INIS)

    Budinger, T.F.; Yano, Y.; Mathis, C.A.; Moyer, B.R.; Huesman, R.H.; Derenzo, S.E.

    1983-01-01

    Positron emission tomography (PET) offers the opportunity to noninvasively measure heart muscle blood perfusion, oxygen utilization, metabolism of fatty acids, sugars and amino acids. This paper reviews physiological principles which are basic to PET instrumentation for imaging the heart and gives examples of the application of positron emission tomography for measuring myocardial flow and metabolism. 33 references, 11 figures, 1 table

  17. Late decaying 2-component dark matter scenario as an explanation of the AMS-02 positron excess

    Energy Technology Data Exchange (ETDEWEB)

    Buch, Jatan; Ralegankar, Pranjal; Rentala, Vikram, E-mail: jatan_buch@brown.edu, E-mail: pranjal6@illinois.edu, E-mail: rentala@phy.iitb.ac.in [Department of Physics, Indian Institute of Technology - Bombay, Powai, Mumbai 400076 (India)

    2017-10-01

    The long standing anomaly in the positron flux as measured by the PAMELA and AMS-02 experiments could potentially be explained by dark matter (DM) annihilations. This scenario typically requires a large 'boost factor' to be consistent with a thermal relic dark matter candidate produced via freeze-out. However, such an explanation is disfavored by constraints from CMB observations on energy deposition during the epoch of recombination. We discuss a scenario called late-decaying two-component dark matter (LD2DM), where the entire DM consists of two semi-degenerate species. Within this framework, the heavier species is produced as a thermal relic in the early universe and decays to the lighter species over cosmological timescales. Consequently, the lighter species becomes the DM which populates the universe today. We show that annihilation of the lighter DM species with an enhanced cross-section, produced via such a non-thermal mechanism, can explain the observed AMS-02 positron flux while avoiding CMB constraints. The observed DM relic density can be correctly reproduced as well with simple s -wave annihilation cross-sections. We demonstrate that the scenario is safe from CMB constraints on late-time energy depositions during the cosmic 'dark ages'. Interestingly, structure formation constraints force us to consider small mass splittings between the two dark matter species. We explore possible cosmological and particle physics signatures in a toy model that realizes this scenario.

  18. Late decaying 2-component dark matter scenario as an explanation of the AMS-02 positron excess

    International Nuclear Information System (INIS)

    Buch, Jatan; Ralegankar, Pranjal; Rentala, Vikram

    2017-01-01

    The long standing anomaly in the positron flux as measured by the PAMELA and AMS-02 experiments could potentially be explained by dark matter (DM) annihilations. This scenario typically requires a large 'boost factor' to be consistent with a thermal relic dark matter candidate produced via freeze-out. However, such an explanation is disfavored by constraints from CMB observations on energy deposition during the epoch of recombination. We discuss a scenario called late-decaying two-component dark matter (LD2DM), where the entire DM consists of two semi-degenerate species. Within this framework, the heavier species is produced as a thermal relic in the early universe and decays to the lighter species over cosmological timescales. Consequently, the lighter species becomes the DM which populates the universe today. We show that annihilation of the lighter DM species with an enhanced cross-section, produced via such a non-thermal mechanism, can explain the observed AMS-02 positron flux while avoiding CMB constraints. The observed DM relic density can be correctly reproduced as well with simple s -wave annihilation cross-sections. We demonstrate that the scenario is safe from CMB constraints on late-time energy depositions during the cosmic 'dark ages'. Interestingly, structure formation constraints force us to consider small mass splittings between the two dark matter species. We explore possible cosmological and particle physics signatures in a toy model that realizes this scenario.

  19. Hydrogen interaction with oxidized Si(111) probed with positrons

    International Nuclear Information System (INIS)

    Lynn, K.G.; Nielsen, B.; Welch, D.O.

    1989-01-01

    A variable-energy positron beam was utilized to study the interface action of hydrogen with Si(111) covered by an ultrahigh-vacuum thermally grown oxide of 2-3 nm thickness. It was observed that positrons implanted at shallow depth (< 100 nm) after diffusion are trapped either at the interface between the oxide and the Si or in the oxide. The positron-annihilation characteristics of these trapped positrons are found to be very sensitive to hydrogen exposure. The momentum distribution of the annihilating positron-electron pair, as observed in the Doppler broadening of the annihilation line, broadens considerably after exposure to hydrogen. The effect recovers after annealing at ≅ 1100 K, suggesting a hydrogen binding at the interface of ∼ 3 ± 0.3 eV. (author). 18 refs., 3 figs

  20. LEP - Large Electron Positron Exhibition LEPFest 2000

    CERN Multimedia

    2000-01-01

    The Large Electron-Positron Collider (LEP) is 27 km long. Its four detectors (ALEPH, DELPHI, L3, OPAL) measure precisely what happens in the collisions of electrons and positrons. These conditions only exist-ed in the Universe when it was about 10 -10 sec old.

  1. Large angle cosmic microwave background fluctuations from cosmic strings with a cosmological constant

    International Nuclear Information System (INIS)

    Landriau, M.; Shellard, E.P.S.

    2004-01-01

    In this paper, we present results for large-angle cosmic microwave background anisotropies generated from high resolution simulations of cosmic string networks in a range of flat Friedmann-Robertson-Walker universes with a cosmological constant. Using an ensemble of all-sky maps, we compare with the Cosmic Background Explorer data to infer a normalization (or upper bound) on the string linear energy density μ. For a flat matter-dominated model (Ω M =1) we find Gμ/c 2 ≅0.7x10 -6 , which is lower than previous constraints probably because of the more accurate inclusion of string small-scale structure. For a cosmological constant within an observationally acceptable range, we find a relatively weak dependence with Gμ/c 2 less than 10% higher

  2. Applications and advances of positron beam spectroscopy: appendix a

    Energy Technology Data Exchange (ETDEWEB)

    Howell, R. H., LLNL

    1997-11-05

    Over 50 scientists from DOE-DP, DOE-ER, the national laboratories, academia and industry attended a workshop held on November 5-7, 1997 at Lawrence Livermore National Laboratory jointly sponsored by the DOE-Division of Materials Science, The Materials Research Institute at LLNL and the University of California Presidents Office. Workshop participants were charged to address two questions: Is there a need for a national center for materials analysis using positron techniques and can the capabilities at Lawrence Livermore National Laboratory serve this need. To demonstrate the need for a national center the workshop participants discussed the technical advantages enabled by high positron currents and advanced measurement techniques, the role that these techniques will play in materials analysis and the demand for the data. There were general discussions lead by review talks on positron analysis techniques, and their applications to problems in semiconductors, polymers and composites, metals and engineering materials, surface analysis and advanced techniques. These were followed by focus sessions on positron analysis opportunities in these same areas. Livermore now leads the world in materials analysis capabilities by positrons due to developments in response to demands of science based stockpile stewardship. There was a detailed discussion of the LLNL capabilities and a tour of the facilities. The Livermore facilities now include the worlds highest current beam of keV positrons, a scanning pulsed positron microprobe under development capable of three dimensional maps of defect size and concentration, an MeV positron beam for defect analysis of large samples, and electron momentum spectroscopy by positrons. This document is a supplement to the written summary report. It contains a complete schedule, list of attendees and the vuegraphs for the presentations in the review and focus sessions.

  3. Analysis of experimental positron-molecule binding energies

    International Nuclear Information System (INIS)

    Danielson, J R; Surko, C M; Young, J A

    2010-01-01

    Experiments show that positron annihilation on molecules frequently occurs via capture into vibrational Feshbach resonances. In these cases, the downshifts in the annihilation spectra from the vibrational mode spectra provide measures of the positron-molecule binding energies. An analysis of these binding energy data is presented in terms of the molecular dipole polarizability, the permanent dipole moment, and the number of π bonds in aromatic molecules. The results of this analysis are in reasonably good agreement with other information about positron-molecule bound states. Predictions for other targets and promising candidate molecules for further investigation are discussed.

  4. Positron production in heavy ion-atom collisions

    International Nuclear Information System (INIS)

    Kienle, P.

    1985-08-01

    Following an introduction into the concept of an atom with an overcritical field, established by a nucleus with a charge larger than 173, the spontaneous positron emission from such an atom with an 1s binding energy exceeding 2mc 2 is presented. Such a process, in which an electron is bound and a monoenergetic positron emitted turns the neutral into a charged vacuum. In a U-U di-nuclear system (Z=184) the spontaneous positron emission proceeds with an energy of about 300 keV corresponding to a decay time of 3x10 -19 sec. (orig./WL)

  5. Cosmic radiation exposure to airline flight passenger

    International Nuclear Information System (INIS)

    Momose, Mitsuhiro

    2000-01-01

    At the high altitudes, airline flight passengers can be exposed to some levels of cosmic radiation. The purpose of this study was to quantify this radiation exposure. Cosmic radiation was measured during 5 flights using a personal dosimeter (PDM-102, Aloka). Cosmic radiation equivalent dose rates ranged from 0.7 to 1.43 microsieverts per hour, the average rate was 1.08. For the passenger who travels only occasionally, the cosmic radiation levels are well below occupational limits, and the risks are extremely small. (author)

  6. Cosmic radiation exposure to airline flight passenger

    Energy Technology Data Exchange (ETDEWEB)

    Momose, Mitsuhiro [Shinshu Univ., Matsumoto, Nagano (Japan). School of Medicine

    2000-08-01

    At the high altitudes, airline flight passengers can be exposed to some levels of cosmic radiation. The purpose of this study was to quantify this radiation exposure. Cosmic radiation was measured during 5 flights using a personal dosimeter (PDM-102, Aloka). Cosmic radiation equivalent dose rates ranged from 0.7 to 1.43 microsieverts per hour, the average rate was 1.08. For the passenger who travels only occasionally, the cosmic radiation levels are well below occupational limits, and the risks are extremely small. (author)

  7. Cosmic ray production curves below reworking zones

    International Nuclear Information System (INIS)

    Blanford, G.E.

    1980-01-01

    A method is presented for calculating cosmic ray production profiles below reworking zones. The method uses an input reworking depth determined from data such as signatures in the depth profile of ferromagnetic resonance intensity and input cosmic ray production profiles for an undisturbed surface. Reworking histories are simulated using Monte Carlo techniques, and depth profiles are used to determine cosmic ray exposure age limits with a specified probability. It is shown that the track density profiles predict cosmic ray exposure ages in lunar cores that are consistent with values determined by other methods. Results applied to neutron fluence and spallation rare gases eliminate the use of reworking depth as an adjustable parameter and give cosmic ray exposure ages that are compatible with each other

  8. Department of Cosmic Ray Physics - Overview

    International Nuclear Information System (INIS)

    Szabelski, J.

    2007-01-01

    The Department of Cosmic Ray Physics in Lodz is involved in basic research in the high energy Cosmic Ray field. Cosmic Rays are energetic particles from outside the Solar System. The energy spectrum (power law energy dependence) suggests non-thermal origin of these particles. Most of the studies of Cosmic Rays address fundamental problems: · the nature of the physical and astrophysical processes responsible for high energies of particles (up to about 1020 eV/particle), · an estimation of the astrophysical conditions at the acceleration sites and/or search for sources of Cosmic Rays, · properties of high energy particle interactions at very high energies (nuclear interactions at energies exceeding energy available in the laboratories). Some Cosmic Ray studies might have practical (commercial) implications, e.g.: · '' cosmic weather '' forecast - predictions of geomagnetic disturbances related to Solar activity changes (due to large Solar Flares / events of Coronal Mass Ejection); these are important for large electricity networks, gas pipes, radio-wave connections, space missions and satellite experiments. Presentation of Cosmic Ray registration to high school students becomes a popular way to introduce particle physics detectors and elementary particle detection techniques to young people. We organize in Lodz several workshops on particle physics for high school students. This is a part of European activity: Masterclass - Hands on CERN. Energetic Cosmic Ray particles produce cascades of particles in the atmosphere, called Extensive Air Showers (EAS). Registering EAS and their properties is the main way of experimental studies of very high energy Cosmic Rays. In Lodz Department we run Extensive Air Shower array where EAS are continuously being registered. We concentrate on the studies of detection of neutrons correlated with EAS and interpretation of this phenomenon. Back in 2004 we started realisation of the Roland Maze Project, the network of EAS detectors

  9. Millimeter positron focusing using a hybrid lens design

    International Nuclear Information System (INIS)

    Cheung, C.K.; Kwan, P.Y.; Shan, Y.Y.; Naik, P.S.; Weng, H.M.; Beling, C.D.; Fung, S.

    2004-01-01

    The study of metal-semiconductor and metal-oxide-semiconductor systems with low energy positrons is made considerably easier if structures of millimeter dimension can be studied. For this reason the production of a positron beam of sub-millimeter dimension has been a long-term goal of the positron research group at the university of Hong Kong. The hybrid lens system employed consists of a standard Soa extraction lens in a magnetic field free region followed by a gridded Einzel lens that focuses positrons into a 100G magnetic funnel at an energy of 10keV for transportation to the target. Here we report on the present progress, by showing the capability of obtaining millimeter diameter focusing at a preliminary 7.5 kV beam energy. (orig.)

  10. Proposal for a slow positron facility at Jefferson National Laboratory

    Science.gov (United States)

    Mills, Allen P.

    2018-05-01

    One goal of the JPos-17 International Workshop on Physics with Positrons was to ascertain whether it would be a good idea to expand the mission of the Thomas Jefferson National Accelerator Facility (JLab) to include science with low energy (i.e. "slow") spin polarized positrons. It is probably true that experimentation with slow positrons would potentially have wide-ranging benefits comparable to those obtained with neutron and x-ray scattering, but it is certain that the full range of these benefits will never be fully available without an infrastructure comparable to that of existing neutron and x-ray facilities. The role for Jefferson Laboratory would therefore be to provide and maintain (1) a dedicated set of machines for making and manipulating high intensity, high brightness beams of polarized slow positrons; (2) a suite of unique and easily used instruments of wide utility that will make efficient use of the positrons; and (3) a group of on-site positron scientists to provide scientific leadership, instrument development, and user support. In this note some examples will be given of the science that might make a serious investment in a positron facility worthwhile. At the same time, the lessons learned from various proposed and successful positron facilities will be presented for consideration.

  11. Proceedings of the 21. European Cosmic Ray Symposium

    International Nuclear Information System (INIS)

    Kiraly, P.; Kudela, K.; Wolfendale, A. W.

    2008-09-01

    Scientific symposium deals with problems of cosmic ray. The Symposium included the following sessions: (1): Relationship of cosmic rays to the environment; (2) Energetic particles and the magnetosphere of the Earth; (3) Energetic particles in the heliosphere; (4) Solar-terrestrial effects on different time scales; (5) Cosmic rays below the knee; (6) Cosmic rays above the knee (7) High energy interactions; (8) GeV and TeV gamma ray astronomy; (9) European projects related to cosmic rays; Future perspectives. Proceedings contains 122 papers dealing with the scope of INIS.

  12. A combined matrix isolation spectroscopy and cryosolid positron moderation apparatus

    Energy Technology Data Exchange (ETDEWEB)

    Molek, Christopher D.; Michael Lindsay, C.; Fajardo, Mario E. [Air Force Research Laboratory, Munitions Directorate, Ordnance Division, Energetic Materials Branch, AFRL/RWME, 2306 Perimeter Road, Eglin AFB, Florida 32542-5910 (United States)

    2013-03-15

    We describe the design, construction, and operation of a novel apparatus for investigating efficiency improvements in thin-film cryogenic solid positron moderators. We report results from solid neon, argon, krypton, and xenon positron moderators which illustrate the capabilities and limitations of our apparatus. We integrate a matrix isolation spectroscopy diagnostic within a reflection-geometry positron moderation system. We report the optical thickness, impurity content, and impurity trapping site structures within our moderators determined from infrared absorption spectra. We use a retarding potential analyzer to modulate the flow of slow positrons, and report positron currents vs. retarding potential for the different moderators. We identify vacuum ultraviolet emissions from irradiated Ne moderators as the source of spurious signals in our channel electron multiplier slow positron detection channel. Our design is also unusual in that it employs a sealed radioactive Na-22 positron source which can be translated relative to, and isolated from, the cryogenic moderator deposition substrate. This allows us to separate the influences on moderator efficiency of surface contamination by residual gases from those of accumulated radiation damage.

  13. Production of slow-positron beams with an electron linac

    International Nuclear Information System (INIS)

    Howell, R.H.; Alvarez, R.A.; Stanek, M.

    1982-01-01

    Intense, pulsed beams of low-energy positrons have been produced by a high-energy beam from an electron linac. The production efficiency for low-energy positrons has been determined for electrons with 60 to 120 MeV energy, low-energy positron beams from a linac can be of much higher intensity than those beams currently derived from radioactive sources

  14. Development of positron diffraction and holography at LLNL

    International Nuclear Information System (INIS)

    Hamza, A.; Asoka-Kumar, P.; Stoeffl, W.; Howell, R.; Miller, D.; Denison, A.

    2003-01-01

    A low-energy positron diffraction and holography spectrometer is currently being constructed at the Lawrence Livermore National Laboratory (LLNL) to study surfaces and adsorbed structures. This instrument will operate in conjunction with the LLNL intense positron beam produced by the 100 MeV LINAC allowing data to be acquired in minutes rather than days. Positron diffraction possesses certain advantages over electron diffraction which are discussed. Details of the instrument based on that of low-energy electron diffraction are described

  15. Positron lifetime spectroscopy of internally oxidised Ag-In alloys

    International Nuclear Information System (INIS)

    Wegner, D.; Lieb, K.P.

    1989-01-01

    The effects of In 2 O 3 precipitates on positron lifetimes after internal oxidation of α-Ag-In alloys have been investigated. A positron trap associated with the lifetime τ 205(3) ps was detected. On the basis of the experimental results obtained for different oxidation kinetics parameters, a trapping model is proposed according to which positrons thermalised in a dislocation field around oxide precipitates are trapped at the oxide/metal phase boundary. The transition from internal to external oxidation of Ag-In was also studied. The positron lifetime in In 2 O 3 was measured to be τ = 263(8) ps. (author)

  16. A Shifting Shield Provides Protection Against Cosmic Rays

    Science.gov (United States)

    Kohler, Susanna

    2017-12-01

    The Sun plays an important role in protecting us from cosmic rays, energetic particles that pelt us from outside our solar system. But can we predict when and how it will provide the most protection, and use this to minimize the damage to both pilotedand roboticspace missions?The Challenge of Cosmic RaysSpacecraft outside of Earths atmosphere and magnetic field are at risk of damage from cosmic rays. [ESA]Galactic cosmic rays are high-energy, charged particles that originate from astrophysical processes like supernovae or even distant active galactic nuclei outside of our solar system.One reason to care about the cosmic rays arriving near Earth is because these particles can provide a significant challenge for space missions traveling above Earths protective atmosphere and magnetic field. Since impacts from cosmic rays can damage human DNA, this risk poses a major barrier to plans for interplanetary travel by crewed spacecraft. And roboticmissions arent safe either: cosmic rays can flip bits, wreaking havoc on spacecraft electronics as well.The magnetic field carried by the solar wind provides a protective shield, deflecting galactic cosmic rays from our solar system. [Walt Feimer/NASA GSFCs Conceptual Image Lab]Shielded by the SunConveniently, we do have some broader protection against galactic cosmic rays: a built-in shield provided by the Sun. The interplanetary magnetic field, which is embedded in the solar wind, deflects low-energy cosmic rays from us at the outer reaches of our solar system, decreasing the flux of these cosmic rays that reach us at Earth.This shield, however, isnt stationary; instead, it moves and changes as the strength and direction of the solar wind moves and changes. This results in a much lower cosmic-ray flux at Earth when solar activity is high i.e., at the peak of the 11-year solar cycle than when solar activity is low. This visible change in local cosmic-ray flux with solar activity is known as solar modulation of the cosmic ray flux

  17. Positron and positronium annihilation in low-dielectric-constant films studied by a pulsed positron beam

    International Nuclear Information System (INIS)

    Suzuki, R.; Ohdaira, T.; Kobayashi, Y.; Ito, K.; Yu, R.S.; Shioya, Y.; Ichikawa, H.; Hosomi, H.; Ishikiriyama, K.; Shirataki, H.; Matsuno, S.; Xu, J.

    2004-01-01

    Positron and positronium annihilation in porous low-dielectric-constant (low-k) films deposited by plasma-enhanced chemical vapor deposition (PECVD) and spin-on dielectric (SOD) have been investigated by means of positron annihilation lifetime spectroscopy (PALS) and age-momentum correlation (AMOC) spectroscopy with a pulsed slow positron beam. The ortho-positronium (o-Ps) lifetime strongly depends on the deposition condition. In general, PECVD low-k films have shorter o-Ps lifetimes than SOD low-k films, indicating PECVD low-k films have smaller pores. Since o-Ps diffusion and escaping from the surface occurs in most of porous SOD films, three-gamma annihilation measurement is important. To investigate o-Ps behavior in SOD films, we have carried out two-dimensional (2D) PALS measurement, which measures annihilation time and pulse-height of the scintillation detector simultaneously. Monte-Carlo simulation of the o-Ps diffusion and escaping in porous films has been carried out to simulate the 2D-PALS results. (orig.)

  18. Bremsstrahlung Based Positron Annihilation Spectroscopy for Material Defect Analysis

    International Nuclear Information System (INIS)

    Selim, F.A.; Wells, D.P.; Harmon, F.; Kwofie, J.; Lancaster, G.; Jones, J.L.

    2003-01-01

    The Idaho Accelerator Center (IAC) has developed new techniques for Positron Annihilation Spectroscopy (PAS) using highly penetrating γ-rays to create positrons inside the material via pair production. γ-Ray induced positron annihilation spectroscopy can provide highly penetrating probes for material characterization and defect analysis. Bremsstrahlung beams from small, pulsed electron Linacs (6 MeV) have been used to bombard the materials to generate positrons, which annihilate with the material electrons emitting 511 keV radiation. We have also synchronized bremsstrahlung pulses with laser irradiation pulses to study dynamic structural changes in material. In addition, we have developed another method using (p,γ) reactions from a 2 MeV proton beam, which induce coincident γ-rays to perform positron life-time spectroscopy. We have showed the feasibility of extending PAS into thick samples and a wide variety of materials and industrial applications

  19. On new developments in the physics of positron swarms

    International Nuclear Information System (INIS)

    Petrovic, Z Lj; Bankovic, A; Dujko, S; Marjanovic, S; Suvakov, M; Malovic, G; Marler, J P; Buckman, S J; White, R D; Robson, R E

    2010-01-01

    Recently a new wave of swarm studies of positrons was initiated based on more complete scattering cross section sets. Initially some interesting and new physics was discovered, most importantly negative differential conductivity (NDC) that occurs only for the bulk drift velocity while it does not exist for the flux property. However the ultimate goal was to develop tools to model positron transport in realistic applications and the work that is progressing along these lines is reviewed here. It includes studies of positron transport in molecular gases, thermalization in generic swarm situations and in realistic gas filled traps and transport of positrons in crossed electric and magnetic fields. Finally we have extended the same technique of simulation (Monte Carlo) to studies of thermalization of positronium molecule. In addition, recently published first steps towards including effects of dense media on positron transport are summarized here.

  20. Positron annihilation in corrosion protective polymeric coatings. Pt. 2

    International Nuclear Information System (INIS)

    Szeles, C.; Vertes, A.; White, M.L.; Leidheiser, H. Jr.; Lehigh Univ., Bethlehem, PA

    1988-01-01

    Positron annihilation was studied in four commercial polymeric coatings on iron. Positron lifetime measurements were performed before and after exposure of the coatings to boiling water for 1 h. A correlation was observed between the effect of water exposure on the lifetime spectra and the protective properties of the coatings when exposed to 0.1M sulfuric acid at 60 0 C for 1010 h. The coatings that provided good corrosion protection in the acid showed minor changes in the positron lifetime spectra upon exposure to water. The spectra of coatings that showed poor corrosion protection in the acid showed minor changes in the positron lifetime spectra upon exposure to water. The spectra of coatings that showed poor corrosion protection, on the other hand, exhibited considerable changes in the positron lifetime spectra upon exposure to water. (orig.)

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