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Sample records for high enery gamma

  1. High energy gamma ray astronomy

    NASA Technical Reports Server (NTRS)

    Fichtel, Carl E.

    1987-01-01

    High energy gamma ray astronomy has evolved with the space age. Nonexistent twenty-five years ago, there is now a general sketch of the gamma ray sky which should develop into a detailed picture with the results expected to be forthcoming over the next decade. The galactic plane is the dominant feature of the gamma ray sky, the longitude and latitude distribution being generally correlated with galactic structural features including the spiral arms. Two molecular clouds were already seen. Two of the three strongest gamma ray sources are pulsars. The highly variable X-ray source Cygnus X-3 was seen at one time, but not another in the 100 MeV region, and it was also observed at very high energies. Beyond the Milky Way Galaxy, there is seen a diffuse radiation, whose origin remains uncertain, as well as at least one quasar, 3C 273. Looking to the future, the satellite opportunities for high energy gamma ray astronomy in the near term are the GAMMA-I planned to be launched in late 1987 and the Gamma Ray Observatory, scheduled for launch in 1990. The Gamma Ray Observatory will carry a total of four instruments covering the entire energy range from 30,000 eV to 3 x 10 to the 10th eV with over an order of magnitude increase in sensitivity relative to previous satellite instruments.

  2. High energy gamma ray balloon instrument

    NASA Technical Reports Server (NTRS)

    Thompson, D. J.; Baker, R. G.; Bertsch, D. L.; Chesney, J. R.; Derdeyn, S. M.; Ehrmann, C. H.; Fichtel, C. E.; Hunter, S. D.; Jacques, J. S.; Laubenthal, N. A.

    1985-01-01

    The High Energy Gamma Ray Balloon Instrument was built in part to verify certain subsystems' performance for the Energetic Gamma Ray Experiment Telescope (EGRET) instrument, the high energy telescope to be carried on the Gamma Ray Observatory. This paper describes the instrument, the performance of some subsystems, and some relevant results.

  3. High Redshift Gamma Ray Bursts

    NASA Technical Reports Server (NTRS)

    Gehrels, Neil

    2012-01-01

    The Swift Observatory has been detecting 100 gamma-ray bursts per year for 7 years and has greatly stimulated the field with new findings. Observations are made of the X-ray and optical afterglow from 1 minute after the burst, continuing for days. GRBs are providing a new tool to study the high redshift universe. Swift has detected several events at z>5 and one at z=9.4 giving information on metallicity, star formation rate and reionization. The talk will present the latest results.

  4. Helios 2-Vela-Ariel 5 gamma-ray burst source position

    NASA Technical Reports Server (NTRS)

    Cline, T. L.; Desai, U. D.; Trainor, J.; Pizzichini, G.; Spizzichino, A.; Klebesadel, R.; Ricketts, M.; Helmken, H.

    1979-01-01

    The gamma-ray burst of January 28, 1976, one of 18 events thus far detected in interplanetary space with Helios 2, was also observed with the Vela 5A and 6A and the Ariel 5 satellites. A small source field is obtained from the intersection of the region derived from the observed time delays between Helios 2 and Vela 5A and 6A, with the source region independently found with the Ariel 5 X-ray detector. This area contains neither any steady X-ray source as scanned by HEAO 1 nor any previously cataloged X-ray, radio, or infrared sources, X-ray transients, quasars, Seyferts, globular clusters, flare stars, pulsars, white dwarfs, or high enery gamma-ray sources. The region is, however, within the source field of a gamma-ray transient observed in 1974 by Jacobson et al. (1978) which exhibited nuclear gamma-ray line structure.

  5. Exploring the High Energy Universe: GLAST Mission and Science

    NASA Technical Reports Server (NTRS)

    McEnery, Julie

    2007-01-01

    GLAST, the Gamma-Ray Large Area Space Telescope, is NASA's next-generation high-energy gamma-ray satellite scheduled for launch in Autumn 2007. GLAST will allow measurements of cosmic gamma-ray sources in the 10 MeV to 100 GeV energy band to be made with unprecedented sensitivity. Amongst its key scientific objectives are to understand particle acceleration in Active Galactic Nuclei, Pulsars and Supernovae Remnants, to provide high resolution measurements of unidentified gamma-ray sources, to study transient high energy emission from objects such as gamma-ray bursts, and to probe Dark Matter and the early Universe. Dr. McEnery will present an overview of the GLAST mission and its scientific goals.

  6. High energy gamma ray imaging

    NASA Astrophysics Data System (ADS)

    Doherty, Michael Richard

    This thesis presents a design study into gamma ray collimation techniques for use in high energy radiation imaging devices for the nuclear industry. Such technology is required to provide information on the nature and location of isotopes within nuclear facilities that have reached the end of their useful life. The work has concentrated on the use of two different techniques, namely mechanical collimation using the Anger camera and electronic collimation using a Compton camera. The work has used computational models to evaluate the performance of such systems and thereby suggest optimal design parameters for use in prototype devices. Ray tracing models have been constructed to simulate both parallel hole and tapered bore diverging collimators. Investigations have been carried out to measure the effects on the spatial resolution of changing various design parameters of the collimators. The effects of varying the hole size, septal thickness and collimator length over a range of source to collimator distances likely to be encountered in an industrial scenario have been examined. Some new insight into the nature of the point spread function of mechanical collimators has been gained and the limitations of the conventional analytical approach to collimator evaluation have been highlighted. Modifications to the standard equations used in collimator design have subsequently been suggested. An analytical description of tapered bore collimators has been derived. Monte Carlo models have been developed to model a single scatter Compton camera. Germanium, silicon and sodium iodide have been investigated as candidates for the scattering detector in such a device. A model of a complete ring array Compton camera system has been used to evaluate performance. The data from the Monte Carlo model has been reconstructed to form images. The quality of the images generated have then been compared with images obtained from parallel hole and focusing mechanical collimators.

  7. Gamma Rays at Very High Energies

    NASA Astrophysics Data System (ADS)

    Aharonian, Felix

    This chapter presents the elaborated lecture notes on Gamma Rays at Very High Energies given by Felix Aharonian at the 40th Saas-Fee Advanced Course on "Astrophysics at Very High Energies". Any coherent description and interpretation of phenomena related to gammarays requires deep knowledge of many disciplines of physics like nuclear and particle physics, quantum and classical electrodynamics, special and general relativity, plasma physics, magnetohydrodynamics, etc. After giving an introduction to gamma-ray astronomy the author discusses the astrophysical potential of ground-based detectors, radiation mechanisms, supernova remnants and origin of the galactic cosmic rays, TeV emission of young supernova remnants, gamma-emission from the Galactic center, pulsars, pulsar winds, pulsar wind nebulae, and gamma-ray loud binaries.

  8. Exploring the High Energy Universe: GLAST Mission and Science

    NASA Technical Reports Server (NTRS)

    McEnery, Julie

    2007-01-01

    GLAST, the Gamma-Ray Large Area Space Telescope, is NASA's next-generation high-energy gamma-ray satellite scheduled for launch in Autumn 2007. GLAST will allow measurements of cosmic gamma-ray sources in t he 10 MeV to 100 GeV energy band to be made with unprecedented sensi tivity. Amongst its key scientific objectives are to understand part icle acceleration in Active Galactic Nuclei, Pulsars and Supernovae Remnants, to provide high resolution measurements of unidentified ga mma-ray sources, to study transient high energy emission from objects such as gamma-ray bursts, and to probe Dark Matter and the early Uni verse. Dr. McEnery will present an overview of the GLAST mission and its scientific goals.

  9. Very High-Energy Gamma-Ray Sources.

    ERIC Educational Resources Information Center

    Weekes, Trevor C.

    1986-01-01

    Discusses topics related to high-energy, gamma-ray astronomy (including cosmic radiation, gamma-ray detectors, high-energy gamma-ray sources, and others). Also considers motivation for the development of this field, the principal results to date, and future prospects. (JN)

  10. Gamma rays and supernova explosions. [high temperature radiation measurement

    NASA Technical Reports Server (NTRS)

    Arnett, W. D.

    1977-01-01

    Thermal radiation associated with the explosion of supernovae is investigated. High temperature is required to produce copious gamma radiation of this sort. It appears that type 11 supernovae do not release much of their energy as gamma ray continuum radiation.

  11. Very high-energy gamma rays from gamma-ray bursts.

    PubMed

    Chadwick, Paula M

    2007-05-15

    Very high-energy (VHE) gamma-ray astronomy has undergone a transformation in the last few years, with telescopes of unprecedented sensitivity having greatly expanded the source catalogue. Such progress makes the detection of a gamma-ray burst at the highest energies much more likely than previously. This paper describes the facilities currently operating and their chances for detecting gamma-ray bursts, and reviews predictions for VHE gamma-ray emission from gamma-ray bursts. Results to date are summarized.

  12. The High Altitude Gamma Ray Observatory, HAWC

    NASA Astrophysics Data System (ADS)

    González, M. M.

    2011-10-01

    The Volcano Sierra Negra in Puebla, Mexico was selected to host HAWC (High Altitude Water Cherenkov), a unique obervatory of wide field of view (2π sr) capable of observing the sky continously at energies from 0.5 TeV to 100 TeV. HAWC is an array of 300 large water tanks (7.3 m diameter × 5 m depth) at an altitude of 4100 m. a. s. l. Each tank is instrumented with three upward-looking photomultipliers tubes. The full array will be capable of observing the most energetic gamma rays from the most violent events in the universe. HAWC will be 15 times more sensitive than its predecesor, Milagro. We present HAWC, the scientific case and capabilities.

  13. Gamma-ray bursts at high and very high energies

    NASA Astrophysics Data System (ADS)

    Piron, Frédéric

    2016-06-01

    Gamma-Ray Bursts (GRBs) are extra-galactic and extremely energetic transient emissions of gamma rays, which are thought to be associated with the death of massive stars or the merger of compact objects in binary systems. Their huge luminosities involve the presence of a newborn stellar-mass black hole emitting a relativistic collimated outflow, which accelerates particles and produces non-thermal emissions from the radio domain to the highest energies. In this article, I review recent progresses in the understanding of GRB jet physics above 100 MeV, based on Fermi observations of bright GRBs. I discuss the physical implications of these observations and their impact on GRB modeling, and I present some prospects for GRB observation at very high energies in the near future. xml:lang="fr"

  14. Perspectives of the GAMMA-400 space observatory for high-energy gamma rays and cosmic rays measurements

    NASA Astrophysics Data System (ADS)

    Topchiev, N. P.; Galper, A. M.; Bonvicini, V.; Adriani, O.; Aptekar, R. L.; Arkhangelskaja, I. V.; Arkhangelskiy, A. I.; Bakaldin, A. V.; Bergstrom, L.; Berti, E.; Bigongiari, G.; Bobkov, S. G.; Boezio, M.; Bogomolov, E. A.; Bonechi, S.; Bongi, M.; Bottai, S.; Castellini, G.; Cattaneo, P. W.; Cumani, P.; Dalkarov, O. D.; Dedenko, G. L.; De Donato, C.; Dogiel, V. A.; Finetti, N.; Gorbunov, M. S.; Gusakov, Yu V.; Hnatyk, B. I.; Kadilin, V. V.; Kaplin, V. A.; Kaplun, A. A.; Kheymits, M. D.; Korepanov, V. E.; Larsson, J.; Leonov, A. A.; Loginov, V. A.; Longo, F.; Maestro, P.; Marrocchesi, P. S.; Men'shenin, A. L.; Mikhailov, V. V.; Mocchiutti, E.; Moiseev, A. A.; Mori, N.; Moskalenko, I. V.; Naumov, P. Yu; Papini, P.; Pearce, M.; Picozza, P.; Rappoldi, A.; Ricciarini, S.; Runtso, M. F.; Ryde, F.; Serdin, O. V.; Sparvoli, R.; Spillantini, P.; Stozhkov, Yu I.; Suchkov, S. I.; Taraskin, A. A.; Tavani, M.; Tiberio, A.; Tyurin, E. M.; Ulanov, M. V.; Vacchi, A.; Vannuccini, E.; Vasilyev, G. I.; Yurkin, Yu T.; Zampa, N.; Zirakashvili, V. N.; Zverev, V. G.

    2016-02-01

    The GAMMA-400 gamma-ray telescope is intended to measure the fluxes of gamma-rays and cosmic-ray electrons and positrons in the energy range from 100 MeV to several TeV. Such measurements concern the following scientific tasks: investigation of point sources of gamma-rays, studies of the energy spectra of Galactic and extragalactic diffuse emission, studies of gamma-ray bursts and gamma-ray emission from the Sun, as well as high precision measurements of spectra of high-energy electrons and positrons. Also the GAMMA- 400 instrument provides the possibility for protons and nuclei measurements up to knee. But the main goal for the GAMMA-400 mission is to perform a sensitive search for signatures of dark matter particles in high-energy gamma-ray emission. To fulfill these measurements the GAMMA-400 gamma-ray telescope possesses unique physical characteristics in comparison with previous and present experiments. The major advantage of the GAMMA-400 instrument is excellent angular and energy resolution for gamma-rays above 10 GeV. The GAMMA-400 experiment will be installed onboard of the Navigator space platform, manufactured by the NPO Lavochkin Association. The expected orbit will be a highly elliptical orbit (with apogee 300.000 km and perigee 500 km) with 7 days orbital period. An important profit of such an orbit is the fact that the full sky coverage will always be available for gamma ray astronomy.

  15. High Energy Neutron Induced Gamma Production

    SciTech Connect

    Brown, D A; Johnson, M; Navratil, P

    2007-09-28

    N Division has an interest in improving the physics and accuracy of the gamma data it provides to its customers. It was asked to look into major gamma producing reactions for 14 MeV incident neutrons for several low-Z materials and determine whether LLNL's processed data files faithfully represent the current state of experimental and theoretical knowledge for these reactions. To address this, we surveyed the evaluations of the requested materials, made recommendations for the next ENDL release and noted isotopes that will require further experimental study. This process uncovered several major problems in our translation and processing of the ENDF formatted evaluations, most of which have been resolved.

  16. Monte Carlo calibration of the SMM gamma ray spectrometer for high energy gamma rays and neutrons

    NASA Technical Reports Server (NTRS)

    Cooper, J. F.; Reppin, C.; Forrest, D. J.; Chupp, E. L.; Share, G. H.; Kinzer, R. L.

    1985-01-01

    The Gamma Ray Spectrometer (GRS) on the Solar Maximum Mission spacecraft was primarily designed and calibrated for nuclear gamma ray line measurements, but also has a high energy mode which allows the detection of gamma rays at energies above 10 MeV and solar neutrons above 20 MeV. The GRS response has been extrapolated until now for high energy gamma rays from an early design study employing Monte Carlo calculations. The response to 50 to 600 MeV solar neutrons was estimated from a simple model which did not consider secondary charged particles escaping into the veto shields. In view of numerous detections by the GRS of solar flares emitting high energy gamma rays, including at least two emitting directly detectable neutrons, the calibration of the high energy mode in the flight model has been recalculated by the use of more sophisticated Monte Carlo computer codes. New results presented show that the GRS response to gamma rays above 20 MeV and to neutrons above 100 MeV is significantly lower than the earlier estimates.

  17. Studying the High Energy Gamma Ray Sky with Gamma Ray Large Area Space Telescope (GLAST)

    NASA Technical Reports Server (NTRS)

    Kamae, T.; Ohsugi, T.; Thompson, D. J.; Watanabe, K.

    1998-01-01

    Building on the success of the Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory, the Gamma Ray Large Area Space Telescope (GLAST) will make a major step in the study of such subjects as blazars, gamma Ray bursts, the search for dark matter, supernova remnants, pulsars, diffuse radiation, and unidentified high energy sources. The instrument will be built on new and mature detector technologies such as silicon strip detectors, low-power low-noise LSI, and a multilevel data acquisition system. GLAST is in the research and development phase, and one full tower (of 25 total) is now being built in collaborating institutes. The prototype tower will be tested thoroughly at Stanford Linear Accelerator Center (SLAC) in the fall of 1999.

  18. Multiwavelength observations of unidentified high energy gamma-ray sources

    NASA Technical Reports Server (NTRS)

    Halpern, Jules P.

    1995-01-01

    As was the case for COS B, the majority of high-energy (greater than 100 MeV) gamma-ray sources detected by the EGRET instrument on GRO are not immediately identifiable with catalogued objects at other wavelengths. These persistent gamma-ray sources are, next to the gamma-ray bursts, the least understood objects in the universe. This two year investigation is intended to support the analysis, correlation, and theoretical interpretation of data that we are obtaining at x-ray, optical, and radio wavelengths in order to render the gamma-ray data interpretable. This second year was devoted to studies of unidentified gamma-ray sources from the first EGRET catalog, similar to previous observations. Efforts have concentrated on the sources at low and intermediate Galactic latitudes, which are the most plausible pulsar candidates.

  19. Spectrometer of high energy gamma quantums

    NASA Technical Reports Server (NTRS)

    Blokhintsev, I. D.; Melioranskiy, A. S.; Kalinkin, L. F.; Nagornykh, Y. I.; Pryakhin, Y. A.

    1979-01-01

    A detailed description of the apparatus GG-2M is given. The spectrometer contains a Cerenkov and scintillation (including anticoincidence) counter. The energies of the gamma quantums are measured by a shower calorimeter, in which scintillation counters are used in the capacity of detectors. Results are given for tuning the device on mu-mesons of cosmic rays. The data of physical tuning allow more reliable interpretation of the results of measurements which are received on the satellites.

  20. High-pressure phase transition in {gamma}-hexanitrohexaazaisowurtzitane

    SciTech Connect

    Russell, T.P.; Miller, P.J.; Piermarini, G.J.; Block, S.

    1992-06-25

    FTIR, EDXD, and PLM; data for a new high-pressure polymorph, {zeta}-HNIW, which is formed from {gamma}-HNIW at 0.7 +/- 0.05 GPa and room temperature. The {gamma}-{zeta} transformation is rapid and reversible in single crystals in a hydrostatic pressure transmitting medium, but the {zeta} form could not be retrieved to ambient conditions. 12 refs., 6 figs., 2 tabs.

  1. Co-axial, high energy gamma generator

    DOEpatents

    Reijonen, Jani Petteri; Gicquel, Frederic

    2011-08-16

    A gamma ray generator includes an ion source in a first chamber. A second chamber is configured co-axially around the first chamber at a lower second pressure. Co-axially arranged plasma apertures separate the two chambers and provide for restricted passage of ions and gas from the first to the second chamber. The second chamber is formed by a puller electrode having at least one long channel aperture to draw ions from the first chamber when the puller electrode is subject to an appropriate applied potential. A plurality of electrodes rings in the third chamber in third pressure co-axially surround the puller electrode and have at least one channel corresponding to the at least one puller electrode aperture and plasma aperture. The electrode rings increase the energy of the ions to a selected energy in stages in passing between successive pairs of the electrodes by application of an accelerating voltage to the successive pairs of accelerator electrodes. A target disposed co-axially around the plurality of electrodes receives the beam of accelerated ions, producing gamma rays.

  2. Very high energy gamma ray astrophysics

    SciTech Connect

    Lamb, R.C.; Lewis, D.A.

    1992-02-01

    The second reflector (project GRANITE) is on schedule. At present (January 1992) it and the 10 m reflector are obtaining stereoscopic views of gamma-ray air showers from the Crab Nebula which verify the expected performance of the twin reflector telescopes. With the additional improvements of the upgrade (a pending DOE proposal) the twin reflectors should reach a limiting intensity of 1% that of the Crab. The astonishing early results from the EGRET detector aboard the Compton Gamma Ray Observatory indicate that distant quasars (powered by supermassive black holes) are active at GeV energies. The Whipple instruments are poised to see if such behavior continues above 100 GeV, as well as perform sensitive observations of previously reported GeV (Geminga) and TeV (Hercules X-1, etc.) sources. In addition to observing sources and identifying their location in the sky to one arcminute, experiments are planned to search for WIMPS in the mass range 0.1 to 1 TeV, and to determine the abundance of anti-protons in the cosmic rays. The successful performance of the stereoscopic reflectors demonstrates the feasibility of the concept of arrays of Cherenkov receivers. Design studies for a much larger array (CASITA) are just beginning.

  3. Very high energy gamma ray extension of GRO observations

    NASA Technical Reports Server (NTRS)

    Weekes, Trevor C.

    1992-01-01

    This has been an exiciting year for high energy gamma-ray astronomy, both from space and from ground-based observatories. It has been a particularly active period for the Whipple Observatory gamma-ray group. In phase 1 of the Compton Gamma Ray Observatory (GRO), there has not been too much opportunity for overlapping observations with the Energetic Gamma Ray Experiment Telescope (EGRET) and the other GRO telescopes; however, significant progress was made in the development of data analysis techniques and in improving the sensitivity of the technique which will have direct application in correlative observations in phase 2. Progress made during the period 1 Jul. 1991 - 31 Dec. 1991 is presented.

  4. Multiwavelength observations of unidentified high energy gamma ray sources

    NASA Technical Reports Server (NTRS)

    Halpern, Jules P.

    1993-01-01

    As was the case for COS B, the majority of high-energy (greater than 100 MeV) gamma-ray sources detected by the EGRET instrument on GRO are not immediately identifiable with cataloged objects at other wavelengths. These persistent gamma-ray sources are, next to the gamma-ray bursts, the least understood objects in the universe. Even a rudimentary understanding of their nature awaits identifications and follow-up work at other wavelengths to tell us what they are. The as yet unidentified sources are potentially the most interesting, since they may represent unrecognized new classes of astronomical objects, such as radio-quiet pulsars or new types of active galactic nuclei (AGN's). This two-year investigation is intended to support the analysis, correlation, and theoretical interpretation of data that we are obtaining at x ray, optical, and radio wavelengths in order to render the gamma-ray data interpretable. According to plan, in the first year concentration was on the identification and study of Geminga. The second year will be devoted to studies of similar unidentified gamma-ray sources which will become available in the first EGRET catalogs. The results obtained so far are presented in the two papers which are reproduced in the Appendix. In these papers, we discuss the pulse profiles of Geminga, the geometry and efficiency of the magnetospheric accelerator, the distance to Geminga, the implications for theories of polar cap heating, the effect of the magnetic field on the surface emission and environment of the neutron star, and possible interpretations of a radio-quiet Geminga. The implications of the other gamma-ray pulsars which were discovered to have high gamma-ray efficiency are also discussed, and the remaining unidentified COS B sources are attributed to a population of efficient gamma-ray sources, some of which may be radio quiet.

  5. High energy neutrinos from gamma-ray burst fireballs

    NASA Astrophysics Data System (ADS)

    Tamborra, Irene

    2016-05-01

    The diffuse high-energy neutrino emission from long and short gamma-ray bursts (GRBs) is studied within the fireball emission model. By requiring that the GRB high-energy neutrino counterparts follow up-to-date gamma-ray luminosity functions and redshift evolutions, we find that GRBs could contribute up to a few percents to the observed IceCube high-energy neutrino flux for sub-PeV energies, if the latter has a diffuse origin. Our findings suggest that larger exposure is mandatory to detect neutrinos from GRBs in future stacking searches.

  6. Spectroscopic gamma camera for use in high dose environments

    NASA Astrophysics Data System (ADS)

    Ueno, Yuichiro; Takahashi, Isao; Ishitsu, Takafumi; Tadokoro, Takahiro; Okada, Koichi; Nagumo, Yasushi; Fujishima, Yasutake; Kometani, Yutaka; Suzuki, Yasuhiko; Umegaki, Kikuo

    2016-06-01

    We developed a pinhole gamma camera to measure distributions of radioactive material contaminants and to identify radionuclides in extraordinarily high dose regions (1000 mSv/h). The developed gamma camera is characterized by: (1) tolerance for high dose rate environments; (2) high spatial and spectral resolution for identifying unknown contaminating sources; and (3) good usability for being carried on a robot and remotely controlled. These are achieved by using a compact pixelated detector module with CdTe semiconductors, efficient shielding, and a fine resolution pinhole collimator. The gamma camera weighs less than 100 kg, and its field of view is an 8 m square in the case of a distance of 10 m and its image is divided into 256 (16×16) pixels. From the laboratory test, we found the energy resolution at the 662 keV photopeak was 2.3% FWHM, which is enough to identify the radionuclides. We found that the count rate per background dose rate was 220 cps h/mSv and the maximum count rate was 300 kcps, so the maximum dose rate of the environment where the gamma camera can be operated was calculated as 1400 mSv/h. We investigated the reactor building of Unit 1 at the Fukushima Dai-ichi Nuclear Power Plant using the gamma camera and could identify the unknown contaminating source in the dose rate environment that was as high as 659 mSv/h.

  7. The very-high-energy gamma-ray sky.

    PubMed

    Aharonian, Felix

    2007-01-01

    Over the past few years, very-high-energy gamma-ray astronomy has emerged as a truly observational discipline, with many detected sources representing different galactic and extragalactic source populations-supernova remnants, pulsar wind nebulae, giant molecular clouds, star formation regions, compact binary systems, and active galactic nuclei. It is expected that observations with the next generation of stereoscopic arrays of imaging atmospheric Cherenkov telescopes over a very broad energy range from 10(10) to 10(15) electron volts will dramatically increase the number of very-high-energy gamma-ray sources, thus having a huge impact on the development of astrophysics, cosmology, and particle astrophysics. PMID:17204642

  8. The very-high-energy gamma-ray sky.

    PubMed

    Aharonian, Felix

    2007-01-01

    Over the past few years, very-high-energy gamma-ray astronomy has emerged as a truly observational discipline, with many detected sources representing different galactic and extragalactic source populations-supernova remnants, pulsar wind nebulae, giant molecular clouds, star formation regions, compact binary systems, and active galactic nuclei. It is expected that observations with the next generation of stereoscopic arrays of imaging atmospheric Cherenkov telescopes over a very broad energy range from 10(10) to 10(15) electron volts will dramatically increase the number of very-high-energy gamma-ray sources, thus having a huge impact on the development of astrophysics, cosmology, and particle astrophysics.

  9. On the possible effects of gluon number fluctuations on {gamma}{gamma} collisions at high energies

    SciTech Connect

    Goncalves, V. P.; De Santana Amaral, J. T.

    2013-03-25

    We investigate the effects of the fluctuations on the total {gamma}{gamma}, {gamma}*{gamma}* cross sections and the real photon structure function F{sup {gamma}}{sub 2}(x,Q{sup 2}), considering a saturation phenomenological model for the dipole-dipole cross section and scattering amplitude with fluctuations included.

  10. (Gamma scattering in condensed matter with high intensity Moessbauer radiation)

    SciTech Connect

    Not Available

    1992-01-01

    This report discusses: quasielastic scattering studies on glycerol; gamma-ray scattering from alkali halides; lattice dynamics in metals; Moessbauer neutron scattering, x-ray diffraction, and macroscopic studies of high {Tc} superconductors containing tungsten; NiAl scattering studies; and atomic interference factors and nuclear Casimir effect.

  11. High-energy gamma radiation from Geminga observed by EGRET

    NASA Technical Reports Server (NTRS)

    Mayer-Hasselwander, H. A.; Bertsch, D. L.; Brazier, K. T. S.; Chiang, J.; Fichtel, C. E.; Fierro, J. M.; Hartman, R. C.; Hunter, S. D.; Kanbach, G.; Kwok, P. W.

    1994-01-01

    The Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (CGRO) has carried out extensive studies of the gamma-ray source Geminga. Following the detection of pulsed X-rays (Halpern and Holt 1992) from Geminga, Bertsch et al. (1992) reported the same 237 ms periodicity to be visible in the EGRET data. A full analysis of the Geminga source shows that the energy spectrum is compatible with a power law with a spectral index of -1.50 +/- 0.08 between 30 MeV and 2 GeV. A falloff relative to the power law is observed for energies above 2 GeV. Phase-resolved spectra also show power laws with high-energy cutoffs, but with significant variation of the spectral index with phase. No unpulsed emission is observed. No evidence for time variation was found within the EGRET observations.

  12. High-energy gamma-ray sources of cosmological origin

    NASA Astrophysics Data System (ADS)

    Brun, Pierre; Cohen-Tanugi, Johann

    2016-06-01

    The current generation of instruments in gamma-ray astrophysics launched a new era in the search for a dark matter signal in the high-energy sky. Such searches are said indirect, in the sense that the presence of a dark matter particle is inferred from the detection of products of its pair-annihilation or decay. They have recently started to probe the natural domain of existence for weakly interacting massive particles (WIMPs), the favorite dark matter candidates today. In this article, we review the basic framework for indirect searches and we present a status of current limits obtained with gamma-ray observations. We also devote a section to another possible class of cosmological gamma-ray sources, primordial black holes, also considered as a potential constituent of dark matter. xml:lang="fr"

  13. Recent gamma background measurements at high mountain altitude.

    PubMed

    Mishev, A L; Hristova, E

    2012-11-01

    Results from recent measurements of radiation gamma background at high mountain altitude, namely at Basic Environmental Observatory Moussala (42.11 N, 23.35 E, 2925 m a.s.l.) are reported. The measurements are fulfilled with several devices, namely IGS-421 gamma probe and MDU Liulin. A comparative analysis with previous measurements performed with SBN-90 SAPHYMO NaI(Tl) gamma probe is carried out. A temperature effect during winter period of SAPHYMO probe is observed. In addition the measurements are compared with CaSO(4):Dy TLD. The obtained results are widely discussed. A numerical model for galactic cosmic ray contribution to the dose rate in air is presented. The model is based on a full Monte Carlo simulation of cosmic ray induced cascade in the atmosphere. The simulation is carried out with CORSIKA 6.52 code using FLUKA 2006b and QGSJET II hadron interaction models. PMID:22659148

  14. High Energy Gamma-Ray Emission from Gamma-Ray Bursts - Before GLAST

    SciTech Connect

    Fan, Yi-Zhong; Piran, Tsvi

    2011-11-29

    Gamma-ray bursts (GRBs) are short and intense emission of soft {gamma}-rays, which have fascinated astronomers and astrophysicists since their unexpected discovery in 1960s. The X-ray/optical/radio afterglow observations confirm the cosmological origin of GRBs, support the fireball model, and imply a long-activity of the central engine. The high-energy {gamma}-ray emission (> 20 MeV) from GRBs is particularly important because they shed some lights on the radiation mechanisms and can help us to constrain the physical processes giving rise to the early afterglows. In this work, we review observational and theoretical studies of the high-energy emission from GRBs. Special attention is given to the expected high-energy emission signatures accompanying the canonical early-time X-ray afterglow that was observed by the Swift X-ray Telescope. We also discuss the detection prospect of the upcoming GLAST satellite and the current ground-based Cerenkov detectors.

  15. Enery Efficient Press and Sinter of Titanium Powder for Low-Cost Components in Vehicle Applications

    SciTech Connect

    Thomas Zwitter; Phillip Nash; Xiaoyan Xu; Chadwick Johnson

    2011-03-31

    This is the final technical report for the Department of Energy NETL project NT01931 Energy Efficient Press and Sinter of Titanium Powder for Low-Cost Components in Vehicle Applications. Titanium has been identified as one of the key materials with the required strength that can reduce the weight of automotive components and thereby reduce fuel consumption. Working with newly developed sources of titanium powder, Webster-Hoff will develop the processing technology to manufacture low cost vehicle components using the single press/single sinter techniques developed for iron based powder metallurgy today. Working with an automotive or truck manufacturer, Webster-Hoff will demonstrate the feasibility of manufacturing a press and sinter titanium component for a vehicle application. The project objective is two-fold, to develop the technology for manufacturing press and sinter titanium components, and to demonstrate the feasibility of producing a titanium component for a vehicle application. The lowest cost method for converting metal powder into a net shape part is the Powder Metallurgy Press and Sinter Process. The method involves compaction of the metal powder in a tool (usually a die and punches, upper and lower) at a high pressure (up to 60 TSI or 827 MPa) to form a green compact with the net shape of the final component. The powder in the green compact is held together by the compression bonds between the powder particles. The sinter process then converts the green compact to a metallurgically bonded net shape part through the process of solid state diffusion. The goal of this project is to expand the understanding and application of press and sinter technology to Titanium Powder applications, developing techniques to manufacture net shape Titanium components via the press and sinter process. In addition, working with a vehicle manufacturer, demonstrate the feasibility of producing a titanium component for a vehicle. This is not a research program, but rather a

  16. High-energy emission in gamma-ray bursts

    NASA Technical Reports Server (NTRS)

    Matz, S. M.; Forrest, D. J.; Vestrand, W. T.; Chupp, E. L.; Share, G. H.; Rieger, E.

    1985-01-01

    Between February 1980 and August 1983 the Gamma-Ray Spectrometer on the Solar Maximum Mission Satellite (SMM) detected 72 events identified as being of cosmic origin. These events are an essentially unbiased subset of all gamma-ray bursts. The measured spectra of these events show that high energy (greater than 1 MeV) emission is a common and energetically important feature. There is no evidence for a general high-energy cut-off or a distribution of cut-offs below about 6 MeV. These observations imply a limit on the preferential beaming of high energy emission. This constraint, combined with the assumption of isotropic low energy emission, implies that the typical magnetic field strength at burst radiation sites is less than 1 x 10 to the 12th gauss.

  17. Recent high energy gamma-ray results from SAS-2

    NASA Technical Reports Server (NTRS)

    Thompson, D. J.; Fichtel, C. E.; Hartman, R. C.; Kniffen, D. A.; Bignami, G. F.; Ogelman, H. B.; Ozel, M. E.; Tumer, T.; Lamb, R. C.

    1977-01-01

    Recent developments in gamma-ray astronomy due to the results from SAS-2 have focused on two areas. First, the emission from the plane of the Galaxy is the dominant feature in the gamma-ray sky. The galactic latitude and longitude distributions are consistent with the concept that the high-energy radiation originates from cosmic rays interacting with interstellar matter, and the measurements support a galactic origin for cosmic rays. Second, searches of the SAS-2 data for emission from localized sources have shown three strong discrete gamma-ray sources: the Crab nebula and PSR 0531 + 21, the Vela supernova remnant and PSR 0833-45, and a source near galactic coordinates 193 deg longitude, +3 deg latitude, which does not appear to be associated with other known celestial objects. Evidence has also been found for pulsed gamma-ray emission from two other radio pulsars, PSR 1818-04 and PSR 1747-46. A localized source near longitudes 76-80 deg may be associated with the X-ray source Cyg X-3.

  18. Characteristics of the Telescope for High Energy Gamma-ray Astronomy Selected for Definition Studies on the Gamma Ray Observatory

    NASA Technical Reports Server (NTRS)

    Hughes, E. B.; Hofstadter, R.; Johansson, A.; Rolfe, J.; Bertsch, D. L.; Cruickshank, W. J.; Ehrmann, C. H.; Fichtel, C. E.; Hartman, R. C.; Kniffen, D. A.

    1979-01-01

    The high energy gamma-ray selected for definition studies on the Gamma Ray Observatory provides a substantial improvement in observational capability over earlier instruments. It will have about 20 times more sensitivity, cover a much broader energy range, have considerably better energy resolution and provide a significantly improved angular resolution. The design and performance are described.

  19. Characteristics of the telescope for high energy gamma-ray astronomy selected for definition studies on the Gamma Ray Observatory

    NASA Technical Reports Server (NTRS)

    Hughes, E. B.; Hofstadter, R.; Rolfe, J.; Johansson, A.; Bertsch, D. L.; Cruickshank, W. J.; Ehrmann, C. H.; Fichtel, C. E.; Hartman, R. C.; Kniffen, D. A.

    1980-01-01

    The high energy gamma-ray telescope selected for definition studies on the Gamma Ray Observatory provides a substantial improvement in observational capability over earlier instruments. It will have about 20 times more sensitivity, cover a much broader energy range, have considerably better energy resolution and provide a significantly improved angular resolution. The design and performance are described.

  20. EXTRAGALACTIC VERY HIGH ENERGY GAMMA-RAY BACKGROUND

    SciTech Connect

    Neronov, A.; Semikoz, D. V.

    2012-09-20

    We study the origin of the extragalactic diffuse gamma-ray background using the data from the Fermi telescope. To estimate the background level, we count photons at high Galactic latitudes |b| > 60 Degree-Sign . Subtracting photons associated with known sources and the residual cosmic-ray and Galactic diffuse backgrounds, we estimate the extragalactic gamma-ray background (EGB) flux. We find that the spectrum of EGB in the very high energy band above 30 GeV follows the stacked spectrum of BL Lac objects. Large Area Telescope data reveal the positive (1 + z) {sup k}, 1 < k < 4 cosmological evolution of the BL Lac source population consistent with that of their parent population, Fanaroff-Riley type I radio galaxies. We show that EGB at E > 30 GeV could be completely explained by emission from unresolved BL Lac objects if k {approx_equal} 3.

  1. Finnish spectrolite as high-dose gamma detector

    NASA Astrophysics Data System (ADS)

    Antonio, Patrícia L.; Caldas, Linda V. E.

    2015-11-01

    A natural material called spectrolite, from Finland, was studied in this work. The purpose was to test it in gamma radiation beams to verify its performance as a high-dose detector. From this material, pellets were manufactured with two different concentrations of Teflon and spectrolite, and their responses were verified using two luminescent techniques: thermoluminescence (TL) and optically stimulated luminescence (OSL). The TL and OSL signals were evaluated by means of characterization tests of the material response, after exposure to a nominal absorbed dose interval of 5 Gy to 10 kGy. The results obtained, for both concentrations, showed a good performance of this material in beams of high-dose gamma radiation. Both techniques were utilized in order to investigate the properties of the spectrolite+Teflon samples for different applications.

  2. Very high energy gamma ray observations of southern hemisphere AGNs

    NASA Astrophysics Data System (ADS)

    Chadwick, P. M.; Lyons, K.; McComb, T. J. L.; Orford, K. J.; Osborne, J. L.; Rayner, S. M.; Shaw, S. E.; Turver, K. E.

    2001-12-01

    A range of AGNs visible from the Southern hemisphere has been observed with the University of Durham Mark 6 very high energy gamma ray telescope. Results of observations of 1ES 0323+022, PKS 0829+046, 1ES 1101-232, Cen A, PKS 1514-24, RKJ 10578-275, 1ES 2316-423, PKS 2005-489 and PKS 0548-322 are presented. .

  3. High energy gamma-rays and hadrons at Mount Fuji

    NASA Technical Reports Server (NTRS)

    Amenomori, M.; Nanjo, H.; Konishi, E.; Hotta, N.; Mizutani, K.; Kasahara, K.; Kobayashi, T.; Mikumo, E.; Sato, K.; Yuda, T.

    1985-01-01

    The energy spectra of high energy gamma-rays and hadrons were obtained by the emulsion chamber with 40 c.u. thickness at Mt. Fuji (3750 m). These results are compared with the Monte Carlo calculation based on the same model which is used in a family analysis. Our data are compatible with the model of heavy-enriched primary and scaling in the fragmentation region.

  4. WINKLER - An imaging high resolution gamma-ray spectrometer

    NASA Astrophysics Data System (ADS)

    Nakano, G. H.; Sandie, W. G.; Kilner, J. R.; Pang, F.; Imai, B. B.

    1991-04-01

    The WINKLER high-resolution gamma-ray spectrometer was originally developed to fly on a high-altitude aircraft. Following the discovery of Supernova 1987A in the Large Magellanic Cloud, arrangements were made to perform balloon-borne observations of this event. The instrument was quickly adapted to fit on a gondola furnished by NASA/MSFC in a collaborative effort and was flown in a series of three successful flights from Alice Springs, Australia. The second flight on October 29-31, 1987 resulted in the first high-resolution detection of the 847-keV line emission from the decay of 56Co and provided definitive confirmation of the explosive nucleosynthesis process. WINKLER comprises an array of nine coaxial n-type germanium detectors which are housed in a common vaccuum cryostat and surrounded by an NaI(Tl) scintillator shield that suppresses Compton interactions and gamma-ray background. Gamma-ray images are obtained with a rotational modulation collimator system attached to the spectrometer. Collimator holes in the upper section of the shield define the angular field of view of the instrument to 22 deg FWHM. The energy range of the spectrometer is 20 eV to 8 MeV, and the composite energy resolution from all detectors is 1.5 keV at 100 keV and about 2.5 keV at 1.33 MeV. The total frontal area of the sensor array is 214 cm2 with a volume of 1177 cm3, providing sufficient detection sensitivity for gamma-ray astronomy as well as for land-based applications such as treaty verification monitoring.

  5. High Energy Electron and Gamma - Ray Detection with ATIC

    NASA Technical Reports Server (NTRS)

    Chang, J.; Schmidt, W. K. H.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    The Advanced Thin Ionization Calorimeter (ATIC) balloon borne ionization calorimeter is well suited to record and identify high energy cosmic ray electrons, and at very high energies gamma-ray photons as well. We have simulated the performance of the instrument, and compare the simulations with actual high energy electron exposures at the CERN accelerator. Simulations and measurements do not compare exactly, in detail, but overall the simulations have predicted actual measured behavior quite well. ATIC has had its first 16 day balloon flight at the turn of the year over Antarctica, and first results obtained using the analysis methods derived from simulations and calibrations will be reported.

  6. High resolution {gamma}-ray spectroscopy: The first 85 years

    SciTech Connect

    Deslattes, R.D.

    2000-02-01

    This opening review attempts to follow the main trends in crystal diffraction spectrometry of nuclear {gamma} rays from its 1914 beginning in Rutherford's laboratory to the ultra-high resolution instrumentation realized in the current generation of spectrometers at the Institute Laue Langeven (ILL). The authors perspective is that of an instrumentalist hoping to convey a sense of intellectual debt to a number of predecessors, each of whom realized a certain elegance in making the tools that have enabled much good science, including that to which the remainder of this workshop is dedicated. This overview follows some of the main ideas along a trajectory toward higher resolution at higher energies, thereby enabling not only the disentangling of dense spectra, but also allowing detailed study of aspects of spectral profiles sensitive to excited state lifetimes and interatomic potentials. The parallel evolution toward increasing efficiency while preserving needed resolution is also an interesting story of artful compromise that should not be neglected. Finally, it is the robustness of the measurement chain connecting {gamma}-ray wavelengths with optical wave-lengths associated with the Rydberg constant that only recently has allowed {gamma}-ray data to contribute to determine of particle masses and fundamental constants, as will be described in more detail in other papers from this workshop.

  7. Software developments for gamma-ray data with high multiplicity

    SciTech Connect

    Lauritsen, T.; Crowell, B.; Ahmad, I.

    1995-08-01

    Software capabilities for angle sort of data from the new powerful gamma detector arrays like Gammasphere and EUROGAM which were developed in preceding years, were enhanced and extended to read new data formats. In addition, we can now sort the data for directional correlation ratios (DCO). This version of the software was exported to a university group. For the analysis of, e.g., the quasi-continuum of gamma-rays it is necessary to angle sort the high multiplicity data and perform a careful background subtraction in order to extract the continuum of gamma rays from the feeding and decay of superdeformed bands. We need to angle sort in order to untangle the parts of the spectra which are of E1 nature from those of quadrupole or of M1/E2 nature. We further developed software running on new fast SUN workstations. We now have two such workstations, each equipped with a stacker and a secondary 8-mm tape drive. We enhanced the software to apply an energy-dependent time gate. We can enhance the events that are in true prompt coincidence, and reject random and signals in the germanium detectors coming from neutrons hitting the detector in coincidence with the gamma-ray burst. By applying energy-dependent time gates, in form of a {open_quotes}reduced time{close_quotes}, we can perform this rejection without the loss of efficiency at low energy. Effort has gone into developing low-level tape reader routines for data from the new EUROGAM array with cluster detectors as well as from the new flexible data format from Gammasphere phase II. In addition, we developed software to read data tapes from the local DAPHNE and MSU data-acquisition systems on the new fast UNIX platforms.

  8. Development and Characterization of a High Resolution Portable Gamma Spectrometer

    NASA Astrophysics Data System (ADS)

    Ali, Muhammad

    The recent disaster of Fukushima in Japan combined with the high demand to enhance nuclear safety and to minimize personal exposure to radioactive materials has a significant impact on research and development of radiation detection instrumentation. Currently, there is ample effort worldwide in the pursuit of radiation detection to maximize the accuracy and meet international standards in terms of size and specifications to enable radiation protection decision making. Among the requirements is the development of a portable, light-weight gamma-ray isotope identifier to be used by first responders in nuclear accidents as well as for radiation security and identification of illicit material isotopes. From nuclear security perspective, research into advanced screening technologies has become a high priority in all aspects, while for occupational safety, and environmental radiation protection, the regulatory authorities are requiring specific performance of radiation detection and measuring devices. At the applied radiation laboratory of the University of Ontario Institute of Technology, UOIT, the development of a high resolution spectrometer for medium and high energy gamma ray has been conducted. The spectrometer used a newly developed scintillator based on a LaBr3(Ce) crystal. The detector has been modeled using advanced Monte Carlo code (MCNP/X code) for the response function simulation and parameter characterization. The simulation results have been validated by experimental investigations using a wide range of gamma radiation energies. The developed spectrometer has been characterized in terms of resolution and response in different fields. It has also been compared with other crystals such as NaI(TI) and LiI(Eu).

  9. High-revolution gamma-ray imaging from the moon

    NASA Technical Reports Server (NTRS)

    Mahoney, William A.

    1990-01-01

    An observatory is suggested for exploiting unique lunar features to perform sensitive, subarcsecond cosmic X-ray and gamma-ray imaging. The observatory would be built in an evolutionary manner and would eventually include several different position-sensitive detector systems which together would cover a broad energy range and address a wide variety of astrophysical problems. High angular resolution would be obtained by using a mobile crane on the flat lunar mare regions to move a coded aperture mask for source tracking with detector/mask separations of up to 5 kilometers.

  10. Zinc oxide nanowire gamma ray detector with high spatiotemporal resolution

    NASA Astrophysics Data System (ADS)

    Mayo, Daniel C.; Nolen, J. Ryan; Cook, Andrew; Mu, Richard R.; Haglund, Richard F.

    2016-03-01

    Conventional scintillation detectors are typically single crystals of heavy-metal oxides or halides doped with rare-earth ions that record the recombination of electron-hole pairs by photon emission in the visible to ultraviolet. However, the light yields are typically low enough to require photomultiplier detection with the attendant instrumental complications. Here we report initial studies of gamma ray detection by zinc oxide (ZnO) nanowires, grown by vapor-solid deposition. The nanowires grow along the c-axis in a wurtzite structure; they are typically 80 nm in diameter and have lengths of 1- 2 μm. The nanowires are single crystals of high quality, with a photoluminescence (PL) yield from band-edge exciton emission in the ultraviolet that is typically one hundred times larger than the PL yield from defect centers in the visible. Nanowire ensembles were irradiated by 662 keV gamma rays from a Cs-137 source for periods of up to ten hours; gamma rays in this energy range interact by Compton scattering, which in ZnO creates F+ centers that relax to form singly-charged positive oxygen vacancies. Following irradiation, we fit the PL spectra of the visible emission with a sum of Gaussians at the energies of the known defects. We find highly efficient PL from the irradiated area, with a figure of merit approaching 106 photons/s/MeV of deposited energy. Over a period of days, the singly charged O+ vacancies relax to the more stable doubly charged O++ vacancies. However, the overall defect PL returns to pre-irradiation values after about a week, as the vacancies diffuse to the surface of these very thin nanowires, indicating that a self-healing process restores the nanowires to their original state.

  11. Creep of highly-porous iron compacts under conditions of cyclic {alpha}{leftrightarrow}{gamma}-transformations

    SciTech Connect

    Kibets, V.I.; Matsokin, V.P.; Gedes, N.

    1994-09-01

    Features of the creep of highly-porous iron compacts with cyclic {alpha}{leftrightarrow}{gamma}-transformation are studied. Possible reasons are explored for acceleration of deformation during {alpha}{yields}{gamma}-transformation and sintering of compacts with {gamma}{yields}{alpha}-transformation.

  12. Prospects for High Energy Detection of Microquasars with the AGILE and GLAST Gamma-Ray Telescopes

    SciTech Connect

    Santolamazza, Patrizia; Pittori, Carlotta; Verrecchia, Francesco

    2007-08-21

    We estimate the sensitivities of the AGILE and GLAST {gamma}-ray experiments taking into account two cases for the galactic {gamma}-ray diffuse background (at high galactic latitude and toward the galactic center). Then we use sensitivities to estimate microquasar observability with the two experiments, assuming the {gamma}-ray emission above 100 MeV of a recent microquasar model.

  13. Search of the energetic gamma-ray experiment telescope (EGRET) data for high-energy gamma-ray microsecond bursts

    NASA Technical Reports Server (NTRS)

    Fichtel, C. E.; Bertsch, D. L.; Dingus, B. L.; Esposito, J. A.; Hartman, R. C.; Hunter, S. D.; Kanbach, G.; Kniffen, D. A.; Lin, Y. C.; Mattox, J. R.

    1994-01-01

    Hawking (1974) and Page & Hawking (1976) investigated theoretically the possibility of detecting high-energy gamma rays produced by the quantum-mechanical decay of a small black hole created in the early universe. They concluded that, at the very end of the life of the small black hole, it would radiate a burst of gamma rays peaked near 250 MeV with a total energy of about 10(exp 34) ergs in the order of a microsecond or less. The characteristics of a black hole are determined by laws of physics beyond the range of current particle accelerators; hence, the search for these short bursts of high-energy gamma rays provides at least the possibility of being the first test of this region of physics. The Compton Observatory Energetic Gamma-Ray Experiment Telescope (EGRET) has the capability of detecting directly the gamma rays from such bursts at a much fainter level than SAS 2, and a search of the EGRET data has led to an upper limit of 5 x 10(exp -2) black hole decays per cu pc per yr, placing constraints on this and other theories predicting microsecond high-energy gamma-ray bursts.

  14. High resolution spectroscopy from low altitude satellites. [gamma ray astronomy

    NASA Technical Reports Server (NTRS)

    Nakano, G. H.; Imhof, W. L.

    1978-01-01

    The P 78 1 satellite to be placed in a synchronous polar orbit at an altitude of 550-660 km will carry two identical high resolution spectrometers each consisting of a single (approximately 85 cc) intrinsic germanium IGE detector. The payload also includes a pair of phoswitch scintillators, an array of CdTe detectors and several particle detectors, all of which are mounted on the wheel of the satellite. The intrinsic high purity IGE detectors receive cooling from two Stirling cycle refrigerators and facilitate the assembly of large and complex detector arrays planned for the next generation of high sensitivity instruments such as those planned for the gamma ray observatory. The major subsystems of the spectrometer are discussed as well as its capabilities.

  15. Detection of high-degree nonradial pulsations in Gamma Bootis

    NASA Technical Reports Server (NTRS)

    Kennelly, E. J.; Yang, S.; Walker, G. A. H.; Hubeny, I.

    1992-01-01

    The line-profile variations of the rapidly rotating Delta-Scuti star Gamma Bootis can be explained by high-degree nonradial pulsations (NRPs) with an apparent period approximately equal to 0.047 days. This same period was derived from two data sets taken three months apart wherein the amplitude increased by 30 percent. Such high-degree NRP cannot explain the apparent reversals previously observed by Auvergne at al. (1979) for this star in the cores of the hydrogen Balmer lines and Ca-II K line. The present radial-velocity variations can be reconciled with their 0.25-day spectroscopic period if an amplitude of about 1 km/s is adopted, an order of magnitude less than previous measurements. The presence of line-profile variations from high-degree modes probably limits the accuracy of radial-velocity measurents and can appear as bumps in the radial-velocity curve.

  16. Experimental determination of gamma-ray discrimination in pillar-structured thermal neutron detectors under high gamma-ray flux

    SciTech Connect

    Shao, Qinghui; Conway, Adam M.; Voss, Lars F.; Radev, Radoslav P.; Nikolić, Rebecca J.; Dar, Mushtaq A.; Cheung, Chin L.

    2015-08-04

    Silicon pillar structures filled with a neutron converter material (10B) are designed to have high thermal neutron detection efficiency with specific dimensions of 50 μm pillar height, 2 μm pillar diameter and 2 μm spacing between adjacent pillars. In this paper, we have demonstrated such a detector has a high neutron-to-gamma discrimination of 106 with a high thermal neutron detection efficiency of 39% when exposed to a high gamma-ray field of 109 photons/cm2s.

  17. High-spin. gamma. -ray spectroscopy: past successes, future hopes

    SciTech Connect

    Diamond, R.M.

    1983-04-01

    Nuclei can carry angular momentum by aligning individual particles along the rotation axis or by rotation of a deformed nucleus as a whole. The interweaving of these modes leads to a variety of behavior that is just beginning to be observed and explained. The discrete ..gamma..-ray studies have led to a new backbending spectroscopy, which is telling us about the details of particle alignments and monopole and quadrupole pairing. The high-spin continuum studies, as yet less well developed, are indicating changes in shape and structure, as well as particle alignments from higher shells. New developments in detector systems and in theory promise much more detailed comparisons of experiment and theory and consequent increase in our knowledge of nuclear behavior at high spin.

  18. The large area high resolution gamma ray astrophysics facility - HR-GRAF

    NASA Astrophysics Data System (ADS)

    Fenyves, E. J.; Chaney, R. C.; Hoffman, J. H.; Cline, D. B.; Atac, M.; Park, J.; White, S. R.; Zych, A. D.; Tumer, Q. T.; Hughes, E. B.

    1990-03-01

    The long-term program is described in terms of its equipment, scientific objectives, and long-range scientific studies. A prototype of a space-based large-area high-resolution gamma-ray facility (HR-GRAF) is being developed to examine pointlike and diffuse gamma-ray sources in the range 1 MeV-100 GeV. The instrument for the facility is proposed to have high angular and energy resolution and very high sensitivity to permit the study of the proposed objects. The primary research targets include the mapping of galactic gamma radiation, observing the angular variations of diffuse gamma rays, and studying the Galactic center with particular emphasis on the hypothetical black hole. Also included in the research plans are obtaining data on gamma-ray bursters, investigating the transmission of gamma rays from cold dark matter, and studying nuclear gamma-ray lines.

  19. High-resolution gamma-ray spectrometry in uranium exploration

    USGS Publications Warehouse

    Moxham, Robert M.; Tanner, Allan B.

    1977-01-01

    Sedimentary-type uranium deposits accumulate at favorable sites along a migration path which may be kilometers in length. Their source is a large volume of rock from which the uranium has been leached. The geochemical mobilities and half lives of uranium and its daughter products vary widely so that they are transported from the source rocks, at different rates, along the migration path to their ultimate site. The radioactive disequilibrium resulting from this process has been well documented in the immediate vicinity of ore deposits, and disequilibrium is commonly recorded on gamma-ray logs up the hydraulic gradient from uranium ore. Little is known about the state of secular equilibrium in the leached host rocks, which often represent the only part of the migration path that is at or near the surface and is thus most accessible to the exploration geophysicist. High-resolution gamma-ray spectrometry provides a means of investigating the disequilibrium associated with uranium leaching and migration. Direct measurement of uranium can be made by this method, and the equivalent weight percents can be determined for six of the seven daughter-product decay groups that characterize the state of radioactive equilibrium. The technique has been used quantitatively in laboratory studies, where the results compare favorably with radiochemical analyses; field experiments suggest that semi-quantitative data may be obtained at the outcrop.

  20. NEW FERMI-LAT EVENT RECONSTRUCTION REVEALS MORE HIGH-ENERGY GAMMA RAYS FROM GAMMA-RAY BURSTS

    SciTech Connect

    Atwood, W. B.; Baldini, L.; Bregeon, J.; Pesce-Rollins, M.; Sgro, C.; Tinivella, M.; Bruel, P.; Cohen-Tanugi, J.; Granot, J.; Longo, F.; Razzaque, S.; Zimmer, S. E-mail: nicola.omodei@stanford.edu

    2013-09-01

    Based on the experience gained during the four and a half years of the mission, the Fermi-LAT Collaboration has undertaken a comprehensive revision of the event-level analysis going under the name of Pass 8. Although it is not yet finalized, we can test the improvements in the new event reconstruction with the special case of the prompt phase of bright gamma-ray bursts (GRBs), where the signal-to-noise ratio is large enough that loose selection cuts are sufficient to identify gamma rays associated with the source. Using the new event reconstruction, we have re-analyzed 10 GRBs previously detected by the Large Area Telescope (LAT) for which an X-ray/optical follow-up was possible and found four new gamma rays with energies greater than 10 GeV in addition to the seven previously known. Among these four is a 27.4 GeV gamma ray from GRB 080916C, which has a redshift of 4.35, thus making it the gamma ray with the highest intrinsic energy ({approx}147 GeV) detected from a GRB. We present here the salient aspects of the new event reconstruction and discuss the scientific implications of these new high-energy gamma rays, such as constraining extragalactic background light models, Lorentz invariance violation tests, the prompt emission mechanism, and the bulk Lorentz factor of the emitting region.

  1. High count rate gamma camera with independent modules

    NASA Astrophysics Data System (ADS)

    Massari, R.; Ucci, A.; Campisi, C.; Scopinaro, F.; Soluri, A.

    2015-11-01

    Advances in nuclear medical imaging are based on the improvements of the detector's performance. Generally the research is focussed on the spatial resolution improvement. However, another important parameter is the acquisition time that can significantly affect performance in some clinical investigation (e.g. first-pass cardiac studies). At present, there are several clinical imaging systems which are able to solve these diagnostic requirements, such as the D-SPECT Cardiac Imaging System (Spectrum Dynamics) or the Nucline Cardiodesk Medical Imaging System (Mediso). Actually, these solutions are organ-specific dedicated systems, while it would be preferable having general purpose planar detectors with high counting rate. Our group has recently introduced the use of scintillation matrices whose size is equal to the overall area of a position sensitive photomultiplier tube (PSPMT) in order to design a modular gamma camera. This study allowed optimising the overall pixel identification by improving and controlling the light collection efficiency of each PSPMT. Although we achieved a solution for the problems about the dead area at the junction of the PSPMTs when they are set side by side. In this paper, we propose a modular gamma camera design as the basis to build large area detectors. The modular detector design allows us to achieve better counting performance. In this approach, each module that is made of one or more PSPMTs, can actually acquire data independently and simultaneously, increasing the overall detection efficiency. To verify the improvement in count rate capability we have built two detectors with a field of view of ~ 5 × 5cm2, by using four R8900-C12 PSPMTs (Hamamatsu Photonics K.K.). Each PSPMT was coupled to a dedicated discrete scintillation structure designed to obtain a good homogeneity, high imaging performance and high efficiency. One of the detectors was designed as a standard gamma camera, while the other was composed by four independent

  2. GAMMA PROPORTIONAL COUNTER CONTAINING HIGH Z GAS AND LOW Z MODERATOR

    DOEpatents

    Fox, R.

    1963-07-23

    A gamma radiation counter employing a gas proportional counter is described. The radiation counter comprises a cylindrical gas proportional counter which contains a high atomic number gas and is surrounded by a low atomic number gamma radiation moderator material. At least one slit is provided in the moderator to allow accident gamma radiation to enter the moderator in the most favorable manner for moderation, and also to allow low energy gamma radiation to enter the counter without the necessity of passing through the moderator. This radiation counter is capable of detecting and measuring gamma radiation in the energy range of 0.5-5 Mev. (AEC)

  3. Neutrino beams from electron capture at high gamma

    NASA Astrophysics Data System (ADS)

    Rolinec, Mark; Sato, Joe

    2007-08-01

    We investigate the potential of a flavor pure high gamma electron capture electron neutrino beam directed towards a large Water Cherenkov detector with 500 kt fiducial mass. The energy of the neutrinos is reconstructed by the position measurement within the detector and superb energy resolution capabilities could be achieved. We estimate the requirements for such a scenario to be competitive to a neutrino/anti-neutrino running at a neutrino factory with less accurate energy resolution. Although the requirements turn out to be extreme, in principle such a scenario could achieve as good abilities to resolve correlations and degeneracies in the search for sin2 2θ13 and δCP as a standard neutrino factory experiment.

  4. High-z Universe with Gamma Ray Bursts

    NASA Technical Reports Server (NTRS)

    Kouveliotou, C.

    2011-01-01

    Gamma-Ray Bursts (GRBs) are the most luminous explosions in space and trace the cosmic star formation history back to the first generations of stars. Their bright afterglows allow us to trace the abundances of heavy elements to large distances, thereby measuring cosmic chemical evolution. To date GRBs have been detected up to distances of z=8.23 and possibly even beyond z9. This makes GRBs a unique and powerful tool to probe the high-z Universe up to the re-ionization era. We discuss the current status of the field, place it in context with other probes, and also discuss new mission concepts that have been planned to utilize GRBs as probes.

  5. Accessing the population of high-redshift Gamma Ray Bursts

    NASA Astrophysics Data System (ADS)

    Ghirlanda, G.; Salvaterra, R.; Ghisellini, G.; Mereghetti, S.; Tagliaferri, G.; Campana, S.; Osborne, J. P.; O'Brien, P.; Tanvir, N.; Willingale, D.; Amati, L.; Basa, S.; Bernardini, M. G.; Burlon, D.; Covino, S.; D'Avanzo, P.; Frontera, F.; Götz, D.; Melandri, A.; Nava, L.; Piro, L.; Vergani, S. D.

    2015-04-01

    Gamma Ray Bursts (GRBs) are a powerful probe of the high-redshift Universe. We present a tool to estimate the detection rate of high-z GRBs by a generic detector with defined energy band and sensitivity. We base this on a population model that reproduces the observed properties of GRBs detected by Swift, Fermi and CGRO in the hard X-ray and γ-ray bands. We provide the expected cumulative distributions of the flux and fluence of simulated GRBs in different energy bands. We show that scintillator detectors, operating at relatively high energies (e.g. tens of keV to the MeV), can detect only the most luminous GRBs at high redshifts due to the link between the peak spectral energy and the luminosity (Epeak-Liso) of GRBs. We show that the best strategy for catching the largest number of high-z bursts is to go softer (e.g. in the soft X-ray band) but with a very high sensitivity. For instance, an imaging soft X-ray detector operating in the 0.2-5 keV energy band reaching a sensitivity, corresponding to a fluence, of ˜10-8 erg cm-2 is expected to detect ≈40 GRBs yr-1 sr-1 at z ≥ 5 (≈3 GRBs yr-1 sr-1 at z ≥ 10). Once high-z GRBs are detected the principal issue is to secure their redshift. To this aim we estimate their NIR afterglow flux at relatively early times and evaluate the effectiveness of following them up and construct usable samples of events with any forthcoming GRB mission dedicated to explore the high-z Universe.

  6. Very High Energy Gamma Ray Extension of GRO Observations

    NASA Technical Reports Server (NTRS)

    Weekes, Trevor C.

    1994-01-01

    The membership, progress, and invited talks, publications, and proceedings made by the Whipple Gamma Ray Collaboration is reported for june 1990 through May 1994. Progress was made in the following areas: the May 1994 Markarian Flare at Whipple and EGRET (Energetic Gamma Ray Experiment Telescope) energies; AGN's (Active Galactic Nuclei); bursts; supernova remnants; and simulations and energy spectra.

  7. Pulsed high-energy gamma rays from PSR 1055-52

    NASA Technical Reports Server (NTRS)

    Fierro, J. M.; Bertsch, D. L.; Brazier, K. T.; Chiang, J.; D'Amico, N.; Fichtel, C. E.; Hartman, R. C.; Hunter, S. D.; Johnston, S.; Kanbach, G.

    1993-01-01

    The Energetic Gamma Ray Experiment Telescope (EGRET) aboard the Compton Gamma Ray Observatory has detected a high-energy gamma-ray source at a position coincident with that of the radio pulsar PSR 1055-52. Analysis of the EGRET data at the radio pulsar period of 197 ms has revealed pulsed gamma-radiation at energies above 300 MeV, making PSR 1055-52 the fifth detected high-energy gamma-ray pulsar. The pulsed radiation from PSR 1055-52 has a very hard photon spectral index of -1.18 +/- 0.16 and a high efficiency for converting its rotational energy into gamma-rays. No unpulsed emission was observed.

  8. Identifying high-redshift gamma-ray bursts with RATIR

    SciTech Connect

    Littlejohns, O. M.; Butler, N. R.; Cucchiara, A.; Watson, A. M.; Lee, W. H.; Richer, M. G.; De Diego, J. A.; Georgiev, L.; González, J.; Román-Zúñiga, C. G.; Kutyrev, A. S.; Troja, E.; Gehrels, N.; Moseley, H.; Klein, C. R.; Fox, O. D.; Bloom, J. S.; Prochaska, J. X.; Ramirez-Ruiz, E.

    2014-07-01

    We present a template-fitting algorithm for determining photometric redshifts, z {sub phot}, of candidate high-redshift gamma-ray bursts (GRBs). Using afterglow photometry, obtained by the Reionization and Transients InfraRed (RATIR) camera, this algorithm accounts for the intrinsic GRB afterglow spectral energy distribution, host dust extinction, and the effect of neutral hydrogen (local and cosmological) along the line of sight. We present the results obtained by this algorithm and the RATIR photometry of GRB 130606A, finding a range of best-fit solutions, 5.6 < z {sub phot} < 6.0, for models of several host dust extinction laws (none, the Milky Way, Large Magellanic Clouds, and Small Magellanic Clouds), consistent with spectroscopic measurements of the redshift of this GRB. Using simulated RATIR photometry, we find that our algorithm provides precise measures of z {sub phot} in the ranges of 4 < z {sub phot} ≲ 8 and 9 < z {sub phot} < 10 and can robustly determine when z {sub phot} > 4. Further testing highlights the required caution in cases of highly dust-extincted host galaxies. These tests also show that our algorithm does not erroneously find z {sub phot} < 4 when z {sub sim} > 4, thereby minimizing false negatives and allowing us to rapidly identify all potential high-redshift events.

  9. Simulating high-z gamma-ray burst host galaxies

    NASA Astrophysics Data System (ADS)

    Salvaterra, R.; Maio, U.; Ciardi, B.; Campisi, M. A.

    2013-03-01

    We investigate the nature of high-z host galaxies of long gamma-ray bursts (LGRBs) by means of state-of-the-art numerical simulations of cosmic structure formation and evolution of galaxies. We combine results from different runs with various box sizes and resolutions. By assigning to each simulated galaxy the probability to host an LGRB, assumed to be proportional to the mass of young stars, we provide a full description of the physical properties of high-z LGRB host galaxy population. We find that LGRBs at z > 6 are hosted in galaxies with typical star formation rates SFR ≃ 0.03-0.3 M⊙ yr-1, stellar masses M⋆ ≃ 106-108 M⊙ and metallicities Z ≃ 0.01-0.1 Z⊙. Furthermore, the ratio between their doubling time and the corresponding cosmic time seems to be universally equal to ˜0.1-0.3, independently from the redshift. The distribution of their UV luminosity places LGRB hosts in the faint end of the galaxy luminosity function, well below the current capabilities of space- or ground-based optical facilities. This is in line with recent reports of non-detection of LGRB hosts using extremely deep Hubble Space Telescope and Very Large Telescope observations. In conclusion, high-z LGRBs are found to trace the position of those faint galaxies that are thought to be the major actors in the re-ionization of the Universe.

  10. Present status of very high energy gamma ray astronomy and plans for an imaging gamma ray telescope in India

    NASA Astrophysics Data System (ADS)

    Bhat, C. L.

    1993-09-01

    The unequivocal detection of the Crab Nebula as the first-ever standard candle in the very high energy (VHE) bracket, made possible by the recently-developed Cerenkov Imaging Technique, marks a water-shed in the 20 year-old history of the TeV gamma-ray astronomy. It gives hope that, as with the Crab today, future detections in the field, too, will be on a firm statistical footing and the attendant investigations, more comprehensive in their content and range. The present mood in the field is one of cautious optimism. This paper gives an overview of the contemporary observational scene in the ground-based gamma-ray astronomy. It closes with an introduction to TACTIC, the first Indian Imaging gamma-ray telescope, presently under-development.

  11. High Resolution Gamma Ray Analysis of Medical Isotopes

    NASA Astrophysics Data System (ADS)

    Chillery, Thomas

    2015-10-01

    Compton-suppressed high-purity Germanium detectors at the University of Massachusetts Lowell have been used to study medical radioisotopes produced at Brookhaven Linac Isotope Producer (BLIP), in particular isotopes such as Pt-191 used for cancer therapy in patients. The ability to precisely analyze the concentrations of such radio-isotopes is essential for both production facilities such as Brookhaven and consumer hospitals across the U.S. Without accurate knowledge of the quantities and strengths of these isotopes, it is possible for doctors to administer incorrect dosages to patients, thus leading to undesired results. Samples have been produced at Brookhaven and shipped to UML, and the advanced electronics and data acquisition capabilities at UML have been used to extract peak areas in the gamma decay spectra. Levels of Pt isotopes in diluted samples have been quantified, and reaction cross-sections deduced from the irradiation parameters. These provide both cross checks with published work, as well as a rigorous quantitative framework with high quality state-of-the-art detection apparatus in use in the experimental nuclear physics community.

  12. The fusion diagnostic gamma experiment: A high-bandwidth fusion diagnostic of the National Ignition Facility

    SciTech Connect

    Moran, M.J.

    1999-01-01

    Diagnostics for the National Ignition Facility/inertial confinement fusion program must include good characterization of the fusion source. Ideally, diagnostics would measure the spatially resolved history of the fusion reaction rate and temperature. Existing diagnostics can satisfy this goal only partially. One class of new techniques that could play a major role in high-yield diagnostics is measurements based on fusion {gamma} rays. The fusion diagnostic gamma experiment can perform energy-resolved measurements of (D,T) fusion reaction rates. This diagnostic is based on the 16.7 MeV {gamma} rays that are produced by (D,T) fusion. The {gamma} rays are free of spectral dispersion and can be detected (via Compton recoil electrons) with a high bandwidth Cherenkov detector. A simple magnetic monochromator selects signals from the 16.7 MeV {gamma} rays and reduces background signals from nonfusion {gamma} rays. {copyright} {ital 1998 American Institute of Physics.}

  13. Indoor and outdoor in situ high-resolution gamma radiation measurements in urban areas of Cyprus.

    PubMed

    Svoukis, E; Tsertos, H

    2007-01-01

    In situ, high-resolution, gamma-ray spectrometry of a total number of 70 outdoor and 20 indoor representative measurements were performed in preselected, common locations of the main urban areas of Cyprus. Specific activities and gamma absorbed dose rates in air due to the naturally occurring radionuclides of (232)Th and (238)U series, and (40)K are determined and discussed. Effective dose rate to the Cyprus population due to terrestrial gamma radiation is derived directly from this work. The results obtained outdoors match very well with those derived previously by high-resolution gamma spectrometry of soil samples, which were collected from the main island bedrock surface. This implies that the construction and building materials in urban areas do not affect the external gamma dose rate; thus they are mostly of local origin. Finally, the indoor/outdoor gamma dose ratio was found to be 1.4 +/- 0.5. PMID:17065195

  14. Design of a compact spectrometer for high-flux MeV gamma-ray beams

    SciTech Connect

    Corvan, D. J. Sarri, G.; Zepf, M.

    2014-06-15

    A novel design for a compact gamma-ray spectrometer is presented. The proposed system allows for spectroscopy of high-flux multi-MeV gamma-ray beams with MeV energy resolution in a compact design. In its basic configuration, the spectrometer exploits conversion of gamma-rays into electrons via Compton scattering in a low-Z material. The scattered electron population is then spectrally resolved using a magnetic spectrometer. The detector is shown to be effective for gamma-ray energies between 3 and 20 MeV. The main properties of the spectrometer are confirmed by Monte Carlo simulations.

  15. Design of a compact spectrometer for high-flux MeV gamma-ray beams.

    PubMed

    Corvan, D J; Sarri, G; Zepf, M

    2014-06-01

    A novel design for a compact gamma-ray spectrometer is presented. The proposed system allows for spectroscopy of high-flux multi-MeV gamma-ray beams with MeV energy resolution in a compact design. In its basic configuration, the spectrometer exploits conversion of gamma-rays into electrons via Compton scattering in a low-Z material. The scattered electron population is then spectrally resolved using a magnetic spectrometer. The detector is shown to be effective for gamma-ray energies between 3 and 20 MeV. The main properties of the spectrometer are confirmed by Monte Carlo simulations.

  16. Effects of Cosmic Infrared Background on High Energy Delayed Gamma-Rays From Gamma-Ray Bursts

    SciTech Connect

    Murase, Kohta; Asano, Katsuaki; Nagataki, Shigehiro; /Kyoto U., Yukawa Inst., Kyoto /KIPAC, Menlo Park

    2007-04-06

    Regenerated high energy emissions from gamma-ray bursts (GRBs) are studied in detail. If the primary emission spectrum extends to TeV range, these very high energy photons will be absorbed by the cosmic infrared background (CIB). The created high energy electron-positron pairs up-scatter not only cosmic microwave background (CMB) photons but also CIB photons, and secondary photons are generated in the GeV-TeV range. These secondary delayed photons may be observed in the near future, and useful for a consistency check for the primary spectra and GRB physical parameters. The up-scattered CIB photons cannot be neglected for low redshift bursts and/or GRBs with a relatively low maximum photon energy. The secondary gamma-rays also give us additional information on the CIB, which is uncertain in observations so far.

  17. Very-high-energy gamma rays from a distant quasar: how transparent is the universe?

    PubMed

    Albert, J; Aliu, E; Anderhub, H; Antonelli, L A; Antoranz, P; Backes, M; Baixeras, C; Barrio, J A; Bartko, H; Bastieri, D; Becker, J K; Bednarek, W; Berger, K; Bernardini, E; Bigongiari, C; Biland, A; Bock, R K; Bonnoli, G; Bordas, P; Bosch-Ramon, V; Bretz, T; Britvitch, I; Camara, M; Carmona, E; Chilingarian, A; Commichau, S; Contreras, J L; Cortina, J; Costado, M T; Covino, S; Curtef, V; Dazzi, F; De Angelis, A; De Cea Del Pozo, E; de Los Reyes, R; De Lotto, B; De Maria, M; De Sabata, F; Mendez, C Delgado; Dominguez, A; Dorner, D; Doro, M; Errando, M; Fagiolini, M; Ferenc, D; Fernández, E; Firpo, R; Fonseca, M V; Font, L; Galante, N; López, R J García; Garczarczyk, M; Gaug, M; Goebel, F; Hayashida, M; Herrero, A; Höhne, D; Hose, J; Hsu, C C; Huber, S; Jogler, T; Kneiske, T M; Kranich, D; La Barbera, A; Laille, A; Leonardo, E; Lindfors, E; Lombardi, S; Longo, F; López, M; Lorenz, E; Majumdar, P; Maneva, G; Mankuzhiyil, N; Mannheim, K; Maraschi, L; Mariotti, M; Martínez, M; Mazin, D; Meucci, M; Meyer, M; Miranda, J M; Mirzoyan, R; Mizobuchi, S; Moles, M; Moralejo, A; Nieto, D; Nilsson, K; Ninkovic, J; Otte, N; Oya, I; Panniello, M; Paoletti, R; Paredes, J M; Pasanen, M; Pascoli, D; Pauss, F; Pegna, R G; Perez-Torres, M A; Persic, M; Peruzzo, L; Piccioli, A; Prada, F; Prandini, E; Puchades, N; Raymers, A; Rhode, W; Ribó, M; Rico, J; Rissi, M; Robert, A; Rügamer, S; Saggion, A; Saito, T Y; Salvati, M; Sanchez-Conde, M; Sartori, P; Satalecka, K; Scalzotto, V; Scapin, V; Schmitt, R; Schweizer, T; Shayduk, M; Shinozaki, K; Shore, S N; Sidro, N; Sierpowska-Bartosik, A; Sillanpää, A; Sobczynska, D; Spanier, F; Stamerra, A; Stark, L S; Takalo, L; Tavecchio, F; Temnikov, P; Tescaro, D; Teshima, M; Tluczykont, M; Torres, D F; Turini, N; Vankov, H; Venturini, A; Vitale, V; Wagner, R M; Wittek, W; Zabalza, V; Zandanel, F; Zanin, R; Zapatero, J

    2008-06-27

    The atmospheric Cherenkov gamma-ray telescope MAGIC, designed for a low-energy threshold, has detected very-high-energy gamma rays from a giant flare of the distant Quasi-Stellar Radio Source (in short: radio quasar) 3C 279, at a distance of more than 5 billion light-years (a redshift of 0.536). No quasar has been observed previously in very-high-energy gamma radiation, and this is also the most distant object detected emitting gamma rays above 50 gigaelectron volts. Because high-energy gamma rays may be stopped by interacting with the diffuse background light in the universe, the observations by MAGIC imply a low amount for such light, consistent with that known from galaxy counts.

  18. Very-high-energy gamma rays from a distant quasar: how transparent is the universe?

    PubMed

    Albert, J; Aliu, E; Anderhub, H; Antonelli, L A; Antoranz, P; Backes, M; Baixeras, C; Barrio, J A; Bartko, H; Bastieri, D; Becker, J K; Bednarek, W; Berger, K; Bernardini, E; Bigongiari, C; Biland, A; Bock, R K; Bonnoli, G; Bordas, P; Bosch-Ramon, V; Bretz, T; Britvitch, I; Camara, M; Carmona, E; Chilingarian, A; Commichau, S; Contreras, J L; Cortina, J; Costado, M T; Covino, S; Curtef, V; Dazzi, F; De Angelis, A; De Cea Del Pozo, E; de Los Reyes, R; De Lotto, B; De Maria, M; De Sabata, F; Mendez, C Delgado; Dominguez, A; Dorner, D; Doro, M; Errando, M; Fagiolini, M; Ferenc, D; Fernández, E; Firpo, R; Fonseca, M V; Font, L; Galante, N; López, R J García; Garczarczyk, M; Gaug, M; Goebel, F; Hayashida, M; Herrero, A; Höhne, D; Hose, J; Hsu, C C; Huber, S; Jogler, T; Kneiske, T M; Kranich, D; La Barbera, A; Laille, A; Leonardo, E; Lindfors, E; Lombardi, S; Longo, F; López, M; Lorenz, E; Majumdar, P; Maneva, G; Mankuzhiyil, N; Mannheim, K; Maraschi, L; Mariotti, M; Martínez, M; Mazin, D; Meucci, M; Meyer, M; Miranda, J M; Mirzoyan, R; Mizobuchi, S; Moles, M; Moralejo, A; Nieto, D; Nilsson, K; Ninkovic, J; Otte, N; Oya, I; Panniello, M; Paoletti, R; Paredes, J M; Pasanen, M; Pascoli, D; Pauss, F; Pegna, R G; Perez-Torres, M A; Persic, M; Peruzzo, L; Piccioli, A; Prada, F; Prandini, E; Puchades, N; Raymers, A; Rhode, W; Ribó, M; Rico, J; Rissi, M; Robert, A; Rügamer, S; Saggion, A; Saito, T Y; Salvati, M; Sanchez-Conde, M; Sartori, P; Satalecka, K; Scalzotto, V; Scapin, V; Schmitt, R; Schweizer, T; Shayduk, M; Shinozaki, K; Shore, S N; Sidro, N; Sierpowska-Bartosik, A; Sillanpää, A; Sobczynska, D; Spanier, F; Stamerra, A; Stark, L S; Takalo, L; Tavecchio, F; Temnikov, P; Tescaro, D; Teshima, M; Tluczykont, M; Torres, D F; Turini, N; Vankov, H; Venturini, A; Vitale, V; Wagner, R M; Wittek, W; Zabalza, V; Zandanel, F; Zanin, R; Zapatero, J

    2008-06-27

    The atmospheric Cherenkov gamma-ray telescope MAGIC, designed for a low-energy threshold, has detected very-high-energy gamma rays from a giant flare of the distant Quasi-Stellar Radio Source (in short: radio quasar) 3C 279, at a distance of more than 5 billion light-years (a redshift of 0.536). No quasar has been observed previously in very-high-energy gamma radiation, and this is also the most distant object detected emitting gamma rays above 50 gigaelectron volts. Because high-energy gamma rays may be stopped by interacting with the diffuse background light in the universe, the observations by MAGIC imply a low amount for such light, consistent with that known from galaxy counts. PMID:18583607

  19. High resolution gamma-ray spectroscopy at GANIL

    SciTech Connect

    France, G. de

    2014-11-11

    Gamma-ray spectroscopy is intensively used at GANIL to measure low lying states in exotic nuclei on the neutron-rich as well as on the neutron-deficient side of the nuclear chart. On the neutron deficient border, gamma-rays have been observed for the first time in {sup 92}Pd. The level scheme which could be established points to the role of isoscalar pairing. On the neutron rich side, the lifetime of excited states in nuclei around {sup 68}Ni have been been measured using the plunger technique. This allows us to study the evolution of collectivity in a broad range of nuclei. In 2014 GANIL will host the AGATA array for a campaign of at least 2 years. This array is based on the gamma-ray tracking technique, which allows an impressive gain in resolving power.

  20. Gamma-ray spectrometer utilizing xenon at high pressure

    SciTech Connect

    Smith, G.C.; Mahler, G.J.; Yu, B.; Kane, W.R.; Markey, J.K.

    1994-08-01

    A prototype gamma-ray spectrometer utilizing xenon gas near the critical point (166{degrees}C, 58 atm) is under development. The spectrometer will function as a room-temperature ionization chamber detecting gamma rays in the energy range 100 keV2 MeV, with an energy resolution intermediate between semiconductor (Ge) and scintillation (NaI) spectrometers. The energy resolution is superior to that of a NaI scintillation spectrometer by a substantial margin (approximately a factor 5), and accordingly, much more information can be extracted from a given gamma-ray spectrum. Unlike germanium detectors, the spectrometer possesses the capability for sustained operation under ambient temperature conditions without a requirement for liquid nitrogen.

  1. Unresolved gamma rays from high-spin states

    SciTech Connect

    Stephens, F.S.

    1985-08-01

    The ..gamma..-rays which are emitted from the highest spin states in nuclei cannot be resolved using present techniques. Nevertheless, methods are being developed to study nuclear structures in this spin range. For example, coincidence data has been used in the study of superdeformations and moments of inertia. While the general properties of these correlation plots are in accord with present expectations, there are several puzzling features of the data which require more study. One unresolved aspect concerns ..gamma..-ray energy spreads in a given decay pathway. In addition, higher-order correlation methods are in various stages of inception. 15 refs., 16 figs. (WRF)

  2. Development of a high resolution gamma camera system using finely grooved GAGG scintillator

    NASA Astrophysics Data System (ADS)

    Yamamoto, Seiichi; Kataoka, Jun; Oshima, Tsubasa; Ogata, Yoshimune; Watabe, Tadashi; Ikeda, Hayato; Kanai, Yasukazu; Hatazawa, Jun

    2016-06-01

    High resolution gamma cameras require small pixel scintillator blocks with high light output. However, manufacturing a small pixel scintillator block is difficult when the pixel size becomes small. To solve this limitation, we developed a high resolution gamma camera system using a finely grooved Ce-doped Gd3Al2Ga3O12 (GAGG) plate. Our gamma camera's detector consists of a 1-mm-thick finely grooved GAGG plate that is optically coupled to a 1-in. position sensitive photomultiplier tube (PSPMT). The grooved GAGG plate has 0.2×0.2 mm pixels with 0.05-mm wide slits (between the pixels) that were manufactured using a dicing saw. We used a Hamamatsu PSPMT with a 1-in. square high quantum efficiency (HQE) PSPMT (R8900-100-C12). The energy resolution for the Co-57 gamma photons (122 keV) was 18.5% FWHM. The intrinsic spatial resolution was estimated to be 0.7-mm FWHM. With a 0.5-mm diameter pinhole collimator mounted to its front, we achieved a high resolution, small field-of-view gamma camera. The system spatial resolution for the Co-57 gamma photons was 1.0-mm FWHM, and the sensitivity was 0.0025%, 10 mm from the collimator surface. The Tc-99m HMDP administered mouse images showed the fine structures of the mouse body's parts. Our developed high resolution small pixel GAGG gamma camera is promising for such small animal imaging.

  3. High-energy gamma-ray beams from Compton-backscattered laser light

    SciTech Connect

    Sandorfi, A.M.; LeVine, M.J.; Thorn, C.E.; Giordano, G.; Matone, G.

    1983-01-01

    Collisions of light photons with relativistic electrons have previously been used to produce polarized ..gamma..-ray beams with modest (-10%) resolution but relatively low intensity. In contrast, the LEGS project (Laser + Electron Gamma Source) at Brookhaven will produce a very high flux (>2 x 10/sup 7/ s/sup -1/) of background-free polarized ..gamma.. rays whose energy will be determined to a high accuracy (..delta..E = 2.3 MeV). Initially, 300(420)-MeV ..gamma.. rays will be produced by backscattering uv light from the new 2.5(3.0)-GeV X-ray storage ring of the National Synchrotron Light Source (NSLS). The LEGS facility will operate as one of many passive users of the NSLS. In a later stage of the project, a Free Electron Laser is expectred to extend the ..gamma..-ray energy up to 700 MeV.

  4. Effect of high doses of gamma radiation on the functional characteristics of amniotic membrane

    NASA Astrophysics Data System (ADS)

    Singh, Rita; Purohit, Sumita; Chacharkar, M. P.

    2007-06-01

    The effect of different doses of gamma radiation viz. 25, 36 and 50 kGy on the chemical and functional characteristics of the amniotic membrane was studied. The change in the chemical structure of amniotic membranes at high doses of gamma irradiation was evaluated by means of Infrared (IR) Spectroscopy. The degradation of amnion on irradiation with gamma rays could produce a relative variation in IR absorption troughs. This kind of variation was absent in the samples irradiated to doses of 25, 36 and 50 kGy indicating no qualitative change in the material property of amnion. No significant differences in the water absorption capacity and water vapour transmission rate of amniotic membranes irradiated to different doses were observed. Impermeability of the amniotic membranes to different microorganisms was also not affected at high doses of gamma radiation. Gamma irradiation at doses of 25-50 kGy did not evoke undesirable changes in the functional properties of the amniotic membrane.

  5. High energy gamma ray results from the second small astronomy satellite

    NASA Technical Reports Server (NTRS)

    Fichtel, C. E.; Hartman, R. C.; Kniffen, D. A.; Thompson, D. J.; Bignami, G. F.; Oegelman, H.; Oezel, M. F.; Tuemer, T.

    1974-01-01

    A high energy (35 MeV) gamma ray telescope employing a thirty-two level magnetic core spark chamber system was flown on SAS 2. The high energy galactic gamma radiation is observed to dominate over the general diffuse radiation along the entire galactic plane, and when examined in detail, the longitudinal and latitudinal distribution seem generally correlated with galactic structural features, particularly with arm segments. The general high energy gamma radiation from the galactic plane, explained on the basis of its angular distribution and magnitude, probably results primarily from cosmic ray interactions with interstellar matter.

  6. A high precision gamma-ray spectrometer for the Mars-94 mission

    SciTech Connect

    Mitrofanov, I.G.; Anfimov, D.S.; Chernenko, A.M.

    1994-06-01

    The high precision gamma-ray spectrometer (PGS) is scheduled to be launched on the Mars-94 mission in October 1994, and to go into an elliptical polar orbit around Mars. The PGS consists of two high-purity germanium (Ge) detectors, associated electronics, and a passive cooler and will be mounted on one of the solar panels. The PGS will measure nuclear gamma-ray emissions from the martian surface, cosmic gamma-ray bursts, and the high-energy component of solar flares in the broad energy range from 50 KeV to 8 MeV using 4096 energy channels.

  7. Specification of High Activity Gamma-Ray Sources.

    ERIC Educational Resources Information Center

    International Commission on Radiation Units and Measurements, Washington, DC.

    The report is concerned with making recommendations for the specifications of gamma ray sources, which relate to the quantity of radioactive material and the radiation emitted. Primary consideration is given to sources in teletherapy and to a lesser extent those used in industrial radiography and in irradiation units used in industry and research.…

  8. Evidence for Temporally-Extended, High-Energy Emission from Gamma Ray Burst 990104

    NASA Technical Reports Server (NTRS)

    Wren, D. N.; Bertsch, D. L.; Ritz, S.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    It is well known that high-energy emission (MeV - GeV) has been observed in several gamma ray bursts and temporally-extended emission from lower-energy gamma rays through radio wavelengths is well established. Observations of extended, high-energy emission are, however, scarce. Here we present evidence for a gamma ray burst emission that is both high-energy and extended, coincident with lower energy emissions. For the very bright and long burst, GRB 990104, we show light curves and spectra that confirm emission above 50 MeV, approximately 152 seconds after the BATSE (Burst and Transient Source Experiment) trigger and initial burst emission. Between the initial output and the main peak, seen at both low and high energy, there was a period of approx. 100 s during which the burst was relatively quiet. This burst was found as part of an ongoing search for high-energy emission in gamma ray bursts.

  9. High and low energy gamma beam dump designs for the gamma beam delivery system at ELI-NP

    NASA Astrophysics Data System (ADS)

    Yasin, Zafar; Matei, Catalin; Ur, Calin A.; Mitu, Iani-Octavian; Udup, Emil; Petcu, Cristian

    2016-03-01

    The Extreme Light Infrastructure - Nuclear Physics (ELI-NP) is under construction in Magurele, Bucharest, Romania. The facility will use two 10 PW lasers and a high intensity, narrow bandwidth gamma beam for stand-alone and combined laser-gamma experiments. The accurate estimation of particle doses and their restriction within the limits for both personel and general public is very important in the design phase of any nuclear facility. In the present work, Monte Carlo simulations are performed using FLUKA and MCNPX to design 19.4 and 4 MeV gamma beam dumps along with shielding of experimental areas. Dose rate contour plots from both FLUKA and MCNPX along with numerical values of doses in experimental area E8 of the facility are performed. The calculated doses are within the permissible limits. Furthermore, a reasonable agreement between both codes enhances our confidence in using one or both of them for future calculations in beam dump designs, radiation shielding, radioactive inventory, and other calculations releated to radiation protection. Residual dose rates and residual activity calculations are also performed for high-energy beam dump and their effect is negligible in comparison to contributions from prompt radiation.

  10. High temperature oxidation behavior of gamma-nickel+gamma'-nickel aluminum alloys and coatings modified with platinum and reactive elements

    NASA Astrophysics Data System (ADS)

    Mu, Nan

    Materials for high-pressure turbine blades must be able to operate in the high-temperature gases (above 1000°C) emerging from the combustion chamber. Accordingly, the development of nickel-based superalloys has been constantly motivated by the need to have improved engine efficiency, reliability and service lifetime under the harsh conditions imposed by the turbine environment. However, the melting point of nickel (1455°C) provides a natural ceiling for the temperature capability of nickel-based superalloys. Thus, surface-engineered turbine components with modified diffusion coatings and overlay coatings are used. Theses coatings are capable of forming a compact and adherent oxide scale, which greatly impedes the further transport of reactants between the high-temperature gases and the underlying metal and thus reducing attack by the atmosphere. Typically, these coatings contain beta-NiAl as a principal constituent phase in order to have sufficient aluminum content to form an Al2O3 scale at elevated temperatures. The drawbacks to the currently-used beta-based coatings, such as phase instabilities, associated stresses induced by such phase instabilities, and extensive coating/substrate interdiffusion, are major motivations in this study to seek next-generation coatings. The high-temperature oxidation resistance of novel Pt+Hf-modified gamma-Ni+gamma'-Ni 3Al-based alloys and coatings were investigated in this study. Both early-stage and 4-days isothermal oxidation behavior of single-phase gamma-Ni and gamma'-Ni3Al alloys were assessed by examining the weight changes, oxide-scale structures, and elemental concentration profiles through the scales and subsurface alloy regions. It was found that Pt promotes Al 2O3 formation by suppressing the NiO growth on both gamma-Ni and gamma'-Ni3Al single-phase alloys. This effect increases with increasing Pt content. Moreover, Pt exhibits this effect even at lower temperatures (˜970°C) in the very early stage of oxidation. It

  11. Laser-driven hole boring and gamma-ray emission in high-density plasmas

    NASA Astrophysics Data System (ADS)

    Nerush, E. N.; Kostyukov, I. Y.

    2015-03-01

    Ion acceleration in laser-produced dense plasmas is a key topic of many recent investigations thanks to its potential applications. Indeed, at forthcoming laser intensities (I ≳ 1023 W cm-2) interaction of laser pulses with plasmas can be accompanied by copious gamma-ray emission. Here we demonstrate the mutual influence of gamma-ray emission and ion acceleration during relativistic hole boring in high-density plasmas with ultra-intense laser pulses. If the gamma-ray emission is abundant, laser pulse reflection and hole-boring velocity are lower and gamma-ray radiation pattern is narrower than in the case of low emission. Conservation of energy and momentum allows one to elucidate the effects of the gamma-ray emission which are more pronounced at higher hole-boring velocities.

  12. Spatial Working Memory in Humans Depends on Theta and High Gamma Synchronization in the Prefrontal Cortex.

    PubMed

    Alekseichuk, Ivan; Turi, Zsolt; Amador de Lara, Gabriel; Antal, Andrea; Paulus, Walter

    2016-06-20

    Previous, albeit correlative, findings have shown that the neural mechanisms underlying working memory critically require cross-structural and cross-frequency coupling mechanisms between theta and gamma neural oscillations. However, the direct causality between cross-frequency coupling and working memory performance remains to be demonstrated. Here we externally modulated the interaction of theta and gamma rhythms in the prefrontal cortex using novel cross-frequency protocols of transcranial alternating current stimulation to affect spatial working memory performance in humans. Enhancement of working memory performance and increase of global neocortical connectivity were observed when bursts of high gamma oscillations (80-100 Hz) coincided with the peaks of the theta waves, whereas superimposition on the trough of the theta wave and low gamma frequency protocols were ineffective. Thus, our results demonstrate the sensitivity of working memory performance and global neocortical connectivity to the phase and rhythm of the externally driven theta-gamma cross-frequency synchronization.

  13. Report on Ultra-high Resolution Gamma- / X-ray Analysis of Uranium Skull Oxide

    SciTech Connect

    Friedrich, S; Velazquez, M; Drury, O; Salaymeh, S

    2009-11-02

    We have utilized the high energy resolution and high peak-to-background ratio of superconducting TES {gamma}-detectors at very low energies for non-destructive analysis of a skull oxide derived from reprocessed nuclear fuel. Specifically, we demonstrate that superconducting detectors can separate and analyze the strong actinide emission lines in the spectral region below 60 keV that are often obscured in {gamma}-measurements with conventional Ge detectors.

  14. High gamma oscillations of sensorimotor cortex during unilateral movement in the developing brain: a MEG study.

    PubMed

    Huo, Xiaolin; Wang, Yingying; Kotecha, Rupesh; Kirtman, Elijah G; Fujiwara, Hisako; Hemasilpin, Nat; Degrauw, Ton; Rose, Douglas F; Xiang, Jing

    2011-01-01

    Recent studies in adults have found consistent contralateral high gamma activities in the sensorimotor cortex during unilateral finger movement. However, no study has reported on this same phenomenon in children. We hypothesized that contralateral high gamma activities also exist in children during unilateral finger movement. Sixty normal children (6-17 years old) were studied with a 275-channel MEG system combined with synthetic aperture magnetometry (SAM). Sixty participants displayed consistently contralateral event-related synchronization (C-ERS) within high gamma band (65-150 Hz) in the primary motor cortices (M1) of both hemispheres. Interestingly, nineteen younger children displayed ipsilateral event-related synchronization (I-ERS) within the high gamma band (65-150 Hz) just during their left finger movement. Both I-ERS and C-ERS were localized in M1. The incidence of I-ERS showed a significant decrease with age. Males had significantly higher odds of having ipsilateral activity compared to females. Noteworthy, high gamma C-ERS appeared consistently, while high gamma I-ERS changed with age. The asymmetrical patterns of neuromagnetic activities in the children's brain might represent the maturational lateralization and/or specialization of motor function. In conclusion, the present results have demonstrated that contralateral high-gamma neuromagnetic activities are potential biomarkers for the accurate localization of the primary motor cortex in children. In addition, the interesting finding of the ipsilateral high-gamma neuromagnetic activities opens a new window for us to understand the developmental changes of the hemispherical functional lateralization in the motor system. PMID:20577795

  15. Gamma rays made on Earth have unexpectedly high energies

    SciTech Connect

    Miller, Johanna

    2011-01-15

    Terrestrial gamma-ray flashes (TGFs) are the source of the highest-energy nonanthropogenic photons produced on Earth. Associated with thunder-storms - and in fact, with individual lightning discharges - they are presumed to be the bremsstrahlung produced when relativistic electrons, accelerated by the storms' strong electric fields, collide with air molecules some 10-20 km above sea level. The TGFs last up to a few milliseconds and contain photons with energies on the order of MeV.

  16. High-energy gamma radiation from extragalactic radio sources

    NASA Technical Reports Server (NTRS)

    Dermer, C. D.; Schlickeiser, R.; Mastichiadis, A.

    1992-01-01

    We propose that the important relationship between 3C 273 and 3C 279, the first two extragalactic sources detected at over 100 MeV energies, is their superluminal nature. In support of this conjecture, we propose a kinematic focusing mechanism, based on Compton scattering of accretion-disk photons by relativistic nonthermal electrons in the jet, that preferentially emits gamma rays in the superluminal direction.

  17. SAS-2 high-energy gamma-ray observations of the Vela pulsar

    NASA Technical Reports Server (NTRS)

    Thompson, D. J.; Fichtel, C. E.; Kniffen, D. A.; Ogelman, H. B.

    1975-01-01

    The Second Small Astronomy Satellite (SAS-2) high-energy (in excess of 35 MeV) gamma-ray telescope has detected pulsed gamma-ray emission at the radio period from PSR 0833-45, the Vela pulsar, as well as an unpulsed flux from the Vela region. The pulsed emission consists of two peaks following the single radio peak by about 13 ms and 48 ms. The luminosity of the pulsed emission above 100 MeV from Vela is about 0.1 that of the pulsar NP 0532 in the Crab nebula, whereas the pulsed emission from Vela at optical wavelengths is less than 0.0002 that from the Crab. The relatively high intensity of the pulsed gamma-ray emission, and the double peak structure, compared with the single pulse in the radio emission, suggest that the high-energy gamma-ray pulsar emission may be produced under different conditions from those at lower energies.

  18. High-Power Laser Pulse Recirculation for Inverse Compton Scattering-Produced Gamma-Rays

    SciTech Connect

    Jovanovic, I; Shverdin, M; Gibson, D; Brown, C

    2007-04-17

    Inverse Compton scattering of high-power laser pulses on relativistic electron bunches represents an attractive method for high-brightness, quasi-monoenergetic {gamma}-ray production. The efficiency of {gamma}-ray generation via inverse Compton scattering is severely constrained by the small Thomson scattering cross section. Furthermore, repetition rates of high-energy short-pulse lasers are poorly matched with those available from electron accelerators, resulting in low repetition rates for generated {gamma}-rays. Laser recirculation has been proposed as a method to address those limitations, but has been limited to only small pulse energies and peak powers. Here we propose and experimentally demonstrate an alternative method for laser pulse recirculation that is uniquely capable of recirculating short pulses with energies exceeding 1 J. Inverse Compton scattering of recirculated Joule-level laser pulses has a potential to produce unprecedented peak and average {gamma}-ray brightness in the next generation of sources.

  19. High gamma activity in response to deviant auditory stimuli recorded directly from human cortex.

    PubMed

    Edwards, Erik; Soltani, Maryam; Deouell, Leon Y; Berger, Mitchel S; Knight, Robert T

    2005-12-01

    We recorded electrophysiological responses from the left frontal and temporal cortex of awake neurosurgical patients to both repetitive background and rare deviant auditory stimuli. Prominent sensory event-related potentials (ERPs) were recorded from auditory association cortex of the temporal lobe and adjacent regions surrounding the posterior Sylvian fissure. Deviant stimuli generated an additional longer latency mismatch response, maximal at more anterior temporal lobe sites. We found low gamma (30-60 Hz) in auditory association cortex, and we also show the existence of high-frequency oscillations above the traditional gamma range (high gamma, 60-250 Hz). Sensory and mismatch potentials were not reliably observed at frontal recording sites. We suggest that the high gamma oscillations are sensory-induced neocortical ripples, similar in physiological origin to the well-studied ripples of the hippocampus. PMID:16093343

  20. Contraband detection using high-energy gamma rays from 16O*

    NASA Astrophysics Data System (ADS)

    Micklich, Bradley J.; Fink, Charles L.; Sagalovsky, Leonid; Smith, Donald L.

    1997-02-01

    High-energy monoenergetic gamma rays (6.13 and 7.12 MeV) from the decay of excited states of the 16O* nucleus are highly penetrating and thus offer potential for non- intrusive inspection of loaded containers for narcotics, explosives, and other contraband items. These excited states can be produced by irradiation of water with 14-MeV neutrons from a DT neutron generator or through the 19F(p,alpha)16O* reaction. Resonances in 19F(p,alpha)16O* at proton energies between 340 keV and 2 MeV allow use of a low-energy accelerator to provide a compact, portable gamma source of reasonable intensity. The present work provides estimates of gamma source parameters and suggests how various types of contraband could be detected. Gamma rays can be used to perform transmission or emission radiography of containers or other objects. Through the use of (gamma,n) and (gamma,fission) reactions, this technique is also capable of detecting special nuclear materials such as deuterium, lithium, beryllium, uranium, and plutonium. Analytic and Monte Carlo techniques are used to model empty and loaded container inspection for accelerator-produced gamma, radioisotope, and x-ray sources.

  1. Contraband detection using high-energy gamma rays from {sup 16}O*

    SciTech Connect

    Micklich, B.J.; Fink, C.L.; Sagalovsky, L.; Smith, D.L.

    1996-12-01

    High-energy monoenergetic gamma rays (6.13 and 7.12 MeV) from the decay of excited states of the {sup 16}O* nucleus are highly penetrating and thus offer potential for non-intrusive inspection of loaded containers for narcotics, explosives, and other contraband items. These excited states can be produced by irradiation of water with 14-MeV neutrons from a DT neutron generator or through the {sup 19}F(p,{alpha}){sup 16}O* reaction. Resonances in {sup 19}F(p,{alpha}){sup 16}O* at proton energies between 340 keV and 2 MeV allow use of a low-energy accelerator to provide a compact, portable gamma source of reasonable intensity. The present work provides estimates of gamma source parameters and suggests how various types of contraband could be detected. Gamma rays can be used to perform transmission or emission radiography of containers or other objects. Through the use of ({gamma}, n) and ({gamma}, fission) reactions, this technique is also capable of detecting special nuclear materials such as deuterium, lithium, beryllium, uranium, and plutonium. Analytic and Monte Carlo techniques are used to model empty and loaded container inspection for accelerator-produced gamma, radioisotope, and x-ray sources.

  2. Damage correlations in semiconductor devices exposed to gamma and high energy swift heavy ions

    NASA Astrophysics Data System (ADS)

    Pushpa, N.; Prakash, A. P. Gnana

    2015-05-01

    NPN rf power transistors and N-channel depletion MOSFETs are irradiated by different high energy swift heavy ions and 60Co gamma radiation in the dose range of 100 krad to 100 Mrad. The damage created by different heavy ions and 60Co gamma radiation in NPN rf power transistors and N-channel depletion MOSFETs have been correlated and studied in the same dose range. The recoveries in the electrical characteristics of different swift heavy ions and 60Co gamma irradiated devices have been studied after annihilation.

  3. Damage correlations in semiconductor devices exposed to gamma and high energy swift heavy ions

    SciTech Connect

    Pushpa, N.; Prakash, A. P. Gnana

    2015-05-15

    NPN rf power transistors and N-channel depletion MOSFETs are irradiated by different high energy swift heavy ions and {sup 60}Co gamma radiation in the dose range of 100 krad to 100 Mrad. The damage created by different heavy ions and {sup 60}Co gamma radiation in NPN rf power transistors and N-channel depletion MOSFETs have been correlated and studied in the same dose range. The recoveries in the electrical characteristics of different swift heavy ions and {sup 60}Co gamma irradiated devices have been studied after annihilation.

  4. Superconducting High Energy Resolution Gamma-ray Spectrometers

    SciTech Connect

    Chow, D T

    2002-02-22

    We have demonstrated that a bulk absorber coupled to a TES can serve as a good gamma-ray spectrometer. Our measured energy resolution of 70 eV at 60 keV is among the best measurements in this field. We have also shown excellent agreement between the noise predictions and measured noise. Despite this good result, we noted that our detector design has shortcomings with a low count rate and vulnerabilities with the linearity of energy response. We addressed these issues by implementation of an active negative feedback bias. We demonstrated the effects of active bias such as additional pulse shortening, reduction of TES change in temperature during a pulse, and linearization of energy response at low energy. Linearization at higher energy is possible with optimized heat capacities and thermal conductivities of the microcalorimeter. However, the current fabrication process has low control and repeatability over the thermal properties. Thus, optimization of the detector performance is difficult until the fabrication process is improved. Currently, several efforts are underway to better control the fabrication of our gamma-ray spectrometers. We are developing a full-wafer process to produce TES films. We are investigating the thermal conductivity and surface roughness of thicker SiN membranes. We are exploring alternative methods to couple the absorber to the TES film for reproducibility. We are also optimizing the thermal conductivities within the detector to minimize two-element phonon noise. We are experimenting with different absorber materials to optimize absorption efficiency and heat capacity. We are also working on minimizing Johnson noise from the E S shunt and SQUID amplifier noise. We have shown that our performance, noise, and active bias models agree very well with measured data from several microcalorimeters. Once the fabrication improvements have been implemented, we have no doubt that our gamma-ray spectrometer will achieve even more spectacular results.

  5. An imaging telescope for high energy gamma-ray astronomy

    NASA Technical Reports Server (NTRS)

    Frye, G.; Jenkins, T. L.; Owen, A.; Ramsden, D.; Carter, J. N.; Hall, C. J.

    1983-01-01

    Recent tests of a gamma-ray imaging telescope, which incorporated a coded aperture mask and multiwire proportional counter system produced good images of a tritium target source which was used to generate the 20 MeV protons at a proton Van de Graaff accelerator. This paper indicates what performance might be expected if a large area drift chamber were used in conjunction with a coded aperture mask. The prospects for achieving significant scientific results if such a system were flown on a variety of space vehicles are discussed.

  6. Detection of high-energy gamma rays from winter thunderclouds.

    PubMed

    Tsuchiya, H; Enoto, T; Yamada, S; Yuasa, T; Kawaharada, M; Kitaguchi, T; Kokubun, M; Kato, H; Okano, M; Nakamura, S; Makishima, K

    2007-10-19

    A report is made on a comprehensive observation of a burstlike gamma-ray emission from thunderclouds on the Sea of Japan, during strong thunderstorms on 6 January 2007. The detected emission, lasting for approximately 40 sec, preceded cloud-to-ground lightning discharges. The burst spectrum, extending to 10 MeV, can be interpreted as consisting of bremsstrahlung photons originating from relativistic electrons. This ground-based observation provides the first clear evidence that strong electric fields in thunderclouds can continuously accelerate electrons beyond 10 MeV prior to lightning discharges. PMID:17995261

  7. Ceramic Matrix Composites Performances Under High Gamma Radiation Doses

    NASA Astrophysics Data System (ADS)

    Cemmi, A.; Baccaro, S.; Fiore, S.; Gislon, P.; Serra, E.; Fassina, S.; Ferrari, E.; Ghisolfi, E.

    2014-06-01

    Ceramic matrix composites reinforced by continuous ceramic fibers (CMCs) represent a class of advanced materials developed for applications in automotive, aerospace, nuclear fusion reactors and in other specific systems for harsh environments. In the present work, the silicon carbide/silicon carbide (SiCf/SiC) composites, manufactured by Chemical Vapour Infiltration process at FN S.p.A. plant, have been evaluated in term of gamma radiation hardness at three different absorbed doses (up to around 3MGy). Samples behavior has been investigated before and after irradiation by means of mechanical tests (flexural strength) and by surface and structural analyses (X-ray diffraction, SEM, FTIR-ATR, EPR).

  8. The future of high energy gamma ray astronomy and its potential astrophysical implications

    NASA Technical Reports Server (NTRS)

    Fichtel, C. E.

    1982-01-01

    Future satellites should carry instruments having over an order of magnitude greater sensitivity than those flown thus far as well as improved energy and angular resolution. The information to be obtained from these experiments should greatly enhance knowledge of: the very energetic and nuclear processes associated with compact objects; the structure of our galaxy; the origin and dynamic pressure effects of the cosmic rays; the high energy particles and energetic processes in other galaxies; and the degree of matter-antimatter symmetry of the universe. The relevant aspects of extragalactic gamma ray phenomena are emphasized along with the instruments planned. The high energy gamma ray results of forthcoming programs such as GAMMA-1 and the Gamma Ray Observatory should justify even more sophisticated telescopes. These advanced instruments might be placed on the space station currently being considered by NASA.

  9. Characterisation of a high resolution small field of view portable gamma camera.

    PubMed

    Bugby, S L; Lees, J E; Bhatia, B S; Perkins, A C

    2014-05-01

    A handheld, high-resolution small field of view (SFOV) pinhole gamma camera has been characterised using a new set of protocols adapted from standards previously developed for large field of view (LFOV) systems. Parameters investigated include intrinsic and extrinsic spatial resolution, spatial linearity, uniformity, sensitivity, count rate capability and energy resolution. Camera characteristics are compared to some clinical LFOV gamma cameras and also to other SFOV cameras in development.

  10. High performance gamma measurements of equipment retrieved from Hanford high-level nuclear waste tanks

    SciTech Connect

    Troyer, G.L.

    1997-03-17

    The cleanup of high level defense nuclear waste at the Hanford site presents several progressive challenges. Among these is the removal and disposal of various components from buried active waste tanks to allow new equipment insertion or hazards mitigation. A unique automated retrieval system at the tank provides for retrieval, high pressure washing, inventory measurement, and containment for disposal. Key to the inventory measurement is a three detector HPGe high performance gamma spectroscopy system capable of recovering data at up to 90% saturation (200,000 counts per second). Data recovery is based on a unique embedded electronic pulser and specialized software to report the inventory. Each of the detectors have different shielding specified through Monte Carlo simulation with the MCNP program. This shielding provides performance over a dynamic range of eight orders of magnitude. System description, calibration issues and operational experiences are discussed.

  11. High-performance gamma spectroscopy for equipment retrieval from Hanford high-level nuclear waste tanks

    NASA Astrophysics Data System (ADS)

    Troyer, Gary L.; Hillesand, K. E.; Goodwin, S. G.; Kessler, S. F.; Killian, E. W.; Legare, D.; Nelson, Joseph V., Jr.; Richard, R. F.; Nordquist, E. M.

    1999-01-01

    The cleanup of high level defense nuclear waste at the Hanford site presents several progressive challenges. Among these is the removal and disposal of various components from buried active waste tanks to allow new equipment insertion or hazards mitigation. A unique automated retrieval system at the tank provides for retrieval, high pressure washing, inventory measurement, and containment for disposal. Key to the inventory measurement is a three detector HPGe high performance gamma spectroscopy system capable of recovering data at up to ninety per cent saturation (200,000 counts per second). Data recovery is based on a unique embedded electronic pulser and specialized software to report the inventory. Each of the detectors have different shielding specified through Monte Carlo simulation with the MCNP program. This shielding provides performance over a dynamic range of eight orders of magnitude. System description, calibration issues and operational experiences are discussed.

  12. Development of a High-Average-Power Compton Gamma Source for Lepton Colliders

    SciTech Connect

    Pogorelsky, Igor; Polyanskiy, Mikhail N.; Yakimenko, Vitaliy; Platonenko, Viktor T.

    2009-01-22

    Gamma-({gamma}{sup -}) ray beams of high average power and peak brightness are of demand for a number of applications in high-energy physics, material processing, medicine, etc. One of such examples is gamma conversion into polarized positrons and muons that is under consideration for projected lepton colliders. A {gamma}-source based on the Compton backscattering from the relativistic electron beam is a promising candidate for this application. Our approach to the high-repetition {gamma}-source assumes placing the Compton interaction point inside a CO{sub 2} laser cavity. A laser pulse interacts with periodical electron bunches on each round-trip inside the laser cavity producing the corresponding train of {gamma}-pulses. The round-trip optical losses can be compensated by amplification in the active laser medium. The major challenge for this approach is in maintaining stable amplification rate for a picosecond CO{sub 2}-laser pulse during multiple resonator round-trips without significant deterioration of its temporal and transverse profiles. Addressing this task, we elaborated on a computer code that allows identifying the directions and priorities in the development of such a multi-pass picosecond CO{sub 2} laser. Proof-of-principle experiments help to verify the model and show the viability of the concept. In these tests we demonstrated extended trains of picosecond CO{sub 2} laser pulses circulating inside the cavity that incorporates the Compton interaction point.

  13. Development of platinum-modified gamma-nickel+gamma-nickel-aluminum-based alloys for high-temperature applications

    NASA Astrophysics Data System (ADS)

    Heidloff, Andrew James

    Nickel-base superalloys have been used extensively in high-temperature applications where strength and structural stability are required, most notably in aero gas turbine engines. To increase the efficiency of such engines, a continuous increase in superalloy operating temperatures has been observed. As temperatures continue to increase, multiple aspects of alloy stability become increasingly important. In that regard, the high-temperature performance of superalloys can be generally discussed from two important standpoints, surface stability and structural stability. Historically, structural stability has been the primary concern to alloy designers, such that superalloys that may be exposed to high-temperature applications exceeding 1100°C typically utilize a coating for environmental protection. However, the use of coatings introduces potential deficiencies. For instance, aluminide coatings can lead to extensive instabilities when in contact with newer generation superalloys. Also, a few niche applications exist where the use of a coating is impractical. In such cases, the alloys require both environmental resistance and high-temperature strength. The primary goal of this study was to develop novel heat-treatable gamma-Ni+gamma'-Ni 3Al-based alloys having excellent resistance to both high-temperature oxidation and creep. The alloys were developed in a systematic manner using multiple alloying additions, including Pt and Ir, i.e., platinum group metals (PGMs). The microstructures and environmental and thermal stabilities of the alloys studied were fully characterized through a series of experiments, including: oxidation (both isothermal and cyclic); hot corrosion (both Type I and Type II); microstructure analysis (including lattice misfit); and phase equilibria calculations with partitioning coefficient analysis. Pt modification was found to significantly affect the lattice misfit of an alloy by expanding the gamma' lattice parameter through its Ni sublattice site

  14. Extended performance gas Cherenkov detector for gamma-ray detection in high-energy density experiments.

    PubMed

    Herrmann, H W; Kim, Y H; Young, C S; Fatherley, V E; Lopez, F E; Oertel, J A; Malone, R M; Rubery, M S; Horsfield, C J; Stoeffl, W; Zylstra, A B; Shmayda, W T; Batha, S H

    2014-11-01

    A new Gas Cherenkov Detector (GCD) with low-energy threshold and high sensitivity, currently known as Super GCD (or GCD-3 at OMEGA), is being developed for use at the OMEGA Laser Facility and the National Ignition Facility (NIF). Super GCD is designed to be pressurized to ≤400 psi (absolute) and uses all metal seals to allow the use of fluorinated gases inside the target chamber. This will allow the gamma energy threshold to be run as low at 1.8 MeV with 400 psi (absolute) of C2F6, opening up a new portion of the gamma ray spectrum. Super GCD operating at 20 cm from TCC will be ∼400 × more efficient at detecting DT fusion gammas at 16.7 MeV than the Gamma Reaction History diagnostic at NIF (GRH-6m) when operated at their minimum thresholds. PMID:25430303

  15. Tabulated data from the SAS-2 high energy gamma ray telescope

    NASA Technical Reports Server (NTRS)

    Fichtel, C. E.; Hartman, R. C.; Kniffen, D. A.; Thompson, D. J.; Ogelman, H. B.; Tuner, T.; Ozel, M. E.

    1978-01-01

    The second small astronomy satellite (SAS-2) carried a high energy gamma ray telescope into an equitorial orbit with a 2 D inclination, an apogee of 610 km, and a perigee of 440 km. The energy threshold of the instrument was about 30 MeV, the energy of the gamma rays could be measured up to about 200 MeV, and the integral intensity above 200 MeV could also be measured. Summary tables of the gamma ray data are presented in two energy bands, 35-100 MeV and 100 MeV. The sky was divided into 144 solid angle elements, and, in each solid angle element for which data exist, the number of gamma rays observed is given and also the exposure factor. Information is provided to permit conversion of these data into approximate intensities.

  16. Discovery of very-high-energy gamma-rays from the Galactic Centre ridge.

    PubMed

    Aharonian, F; Akhperjanian, A G; Bazer-Bachi, A R; Beilicke, M; Benbow, W; Berge, D; Bernlöhr, K; Boisson, C; Bolz, O; Borrel, V; Braun, I; Breitling, F; Brown, A M; Chadwick, P M; Chounet, L-M; Cornils, R; Costamante, L; Degrange, B; Dickinson, H J; Djannati-Ataï, A; Drury, L O'C; Dubus, G; Emmanoulopoulos, D; Espigat, P; Feinstein, F; Fontaine, G; Fuchs, Y; Funk, S; Gallant, Y A; Giebels, B; Gillessen, S; Glicenstein, J F; Goret, P; Hadjichristidis, C; Hauser, D; Hauser, M; Heinzelmann, G; Henri, G; Hermann, G; Hinton, J A; Hofmann, W; Holleran, M; Horns, D; Jacholkowska, A; de Jager, O C; Khélifi, B; Klages, S; Komin, Nu; Konopelko, A; Latham, I J; Le Gallou, R; Lemière, A; Lemoine-Goumard, M; Leroy, N; Lohse, T; Marcowith, A; Martin, J M; Martineau-Huynh, O; Masterson, C; McComb, T J L; de Naurois, M; Nolan, S J; Noutsos, A; Orford, K J; Osborne, J L; Ouchrif, M; Panter, M; Pelletier, G; Pita, S; Pühlhofer, G; Punch, M; Raubenheimer, B C; Raue, M; Raux, J; Rayner, S M; Reimer, A; Reimer, O; Ripken, J; Rob, L; Rolland, L; Rowell, G; Sahakian, V; Saugé, L; Schlenker, S; Schlickeiser, R; Schuster, C; Schwanke, U; Siewert, M; Sol, H; Spangler, D; Steenkamp, R; Stegmann, C; Tavernet, J-P; Terrier, R; Théoret, C G; Tluczykont, M; van Eldik, C; Vasileiadis, G; Venter, C; Vincent, P; Völk, H J; Wagner, S J

    2006-02-01

    The source of Galactic cosmic rays (with energies up to 10(15) eV) remains unclear, although it is widely believed that they originate in the shock waves of expanding supernova remnants. At present the best way to investigate their acceleration and propagation is by observing the gamma-rays produced when cosmic rays interact with interstellar gas. Here we report observations of an extended region of very-high-energy (> 10(11) eV) gamma-ray emission correlated spatially with a complex of giant molecular clouds in the central 200 parsecs of the Milky Way. The hardness of the gamma-ray spectrum and the conditions in those molecular clouds indicate that the cosmic rays giving rise to the gamma-rays are likely to be protons and nuclei rather than electrons. The energy associated with the cosmic rays could have come from a single supernova explosion around 10(4) years ago.

  17. Extended performance gas Cherenkov detector for gamma-ray detection in high-energy density experiments

    SciTech Connect

    Herrmann, H. W. Kim, Y. H.; Young, C. S.; Fatherley, V. E.; Lopez, F. E.; Oertel, J. A.; Batha, S. H.; Malone, R. M.; Rubery, M. S.; Horsfield, C. J.; Stoeffl, W.; Zylstra, A. B.; Shmayda, W. T.

    2014-11-15

    A new Gas Cherenkov Detector (GCD) with low-energy threshold and high sensitivity, currently known as Super GCD (or GCD-3 at OMEGA), is being developed for use at the OMEGA Laser Facility and the National Ignition Facility (NIF). Super GCD is designed to be pressurized to ≤400 psi (absolute) and uses all metal seals to allow the use of fluorinated gases inside the target chamber. This will allow the gamma energy threshold to be run as low at 1.8 MeV with 400 psi (absolute) of C{sub 2}F{sub 6}, opening up a new portion of the gamma ray spectrum. Super GCD operating at 20 cm from TCC will be ∼400 × more efficient at detecting DT fusion gammas at 16.7 MeV than the Gamma Reaction History diagnostic at NIF (GRH-6m) when operated at their minimum thresholds.

  18. Extended performance gas Cherenkov detector for gamma-ray detection in high-energy density experiments.

    PubMed

    Herrmann, H W; Kim, Y H; Young, C S; Fatherley, V E; Lopez, F E; Oertel, J A; Malone, R M; Rubery, M S; Horsfield, C J; Stoeffl, W; Zylstra, A B; Shmayda, W T; Batha, S H

    2014-11-01

    A new Gas Cherenkov Detector (GCD) with low-energy threshold and high sensitivity, currently known as Super GCD (or GCD-3 at OMEGA), is being developed for use at the OMEGA Laser Facility and the National Ignition Facility (NIF). Super GCD is designed to be pressurized to ≤400 psi (absolute) and uses all metal seals to allow the use of fluorinated gases inside the target chamber. This will allow the gamma energy threshold to be run as low at 1.8 MeV with 400 psi (absolute) of C2F6, opening up a new portion of the gamma ray spectrum. Super GCD operating at 20 cm from TCC will be ∼400 × more efficient at detecting DT fusion gammas at 16.7 MeV than the Gamma Reaction History diagnostic at NIF (GRH-6m) when operated at their minimum thresholds.

  19. Extended performance gas Cherenkov detector for gamma-ray detection in high-energy density experimentsa)

    NASA Astrophysics Data System (ADS)

    Herrmann, H. W.; Kim, Y. H.; Young, C. S.; Fatherley, V. E.; Lopez, F. E.; Oertel, J. A.; Malone, R. M.; Rubery, M. S.; Horsfield, C. J.; Stoeffl, W.; Zylstra, A. B.; Shmayda, W. T.; Batha, S. H.

    2014-11-01

    A new Gas Cherenkov Detector (GCD) with low-energy threshold and high sensitivity, currently known as Super GCD (or GCD-3 at OMEGA), is being developed for use at the OMEGA Laser Facility and the National Ignition Facility (NIF). Super GCD is designed to be pressurized to ≤400 psi (absolute) and uses all metal seals to allow the use of fluorinated gases inside the target chamber. This will allow the gamma energy threshold to be run as low at 1.8 MeV with 400 psi (absolute) of C2F6, opening up a new portion of the gamma ray spectrum. Super GCD operating at 20 cm from TCC will be ˜400 × more efficient at detecting DT fusion gammas at 16.7 MeV than the Gamma Reaction History diagnostic at NIF (GRH-6m) when operated at their minimum thresholds.

  20. TL kinetics study of LiF nanophosphors for high exposures of gamma-rays

    SciTech Connect

    Sharma, A. K.; Vij, Ankush; Kumar, Ravi; Kumar, Satinder; Lochab, S. P.

    2013-02-05

    We report the thermoluminescence (TL) kinetics study of LiF nanophosphors synthesized by chemical co-precipitation at 8.00 pH and exposed to high gamma dose. XRD and TEM studies confirm the formation of single phase LiF nanophosphors. TL properties of LiF phosphors irradiated with gamma rays at different doses of 100 Gy - 70 KGy shows a major peak around 395 K in addition to other low intensity peaks. The major peak in the TL glow curve is almost resolved from other peaks, which has been analyzed using Chen's peak shape method to determine the TL kinetic parameters. TL intensity almost increases linearly with gamma dose, however TL glow curve shift slightly to lower temperature values as a function of gamma exposure.

  1. The Prompt and High Energy Emission of Gamma Ray Bursts

    SciTech Connect

    Meszaros, P.

    2009-05-25

    I discuss some recent developments concerning the prompt emission of gamma-ray bursts, in particular the jet properties and radiation mechanisms, as exemplified by the naked-eye burst GRB 080319b, and the prompt X-ray emission of XRB080109/SN2008d, where the progenitor has, for the first time, been shown to contribute to the prompt emission. I discuss then some recent theoretical calculations of the GeV/TeV spectrum of GRB in the context of both leptonic SSC models and hadronic models. The recent observations by the Fermi satellite of GRB 080916C are then reviewed, and their implications for such models are discussed, together with its interesting determination of a bulk Lorentz factor, and the highest lower limit on the quantum gravity energy scale so far.

  2. Design of high density gamma-phase uranium alloys for LEU dispersion fuel applications.

    SciTech Connect

    Hofman, G. L.

    1998-10-19

    Uranium alloys are candidates for the fuel phase in aluminum matrix dispersion fuels requiring high uranium loading. Certain uranium alloys have been shown to have good irradiation performance at intermediate burnup. Previous studies have shown that acceptable fission gas swelling behavior and fuel-aluminum interaction is possible only if the fuel alloy can be maintained in the high temperature body-centered-cubic {gamma}-phase during fabrication and irradiation, i.e., at temperatures at which {alpha}-U is the equilibrium phase. Transition metals in Groups V through VIII are known to allow metastable retention of the gamma phase below the equilibrium isotherm. These metals have varying degrees of effectiveness in stabilizing the gamma phase. Certain alloys are metastable for very long times at the relatively low fuel temperatures seen in research reactor operation. In this paper, the existing data on the gamma stability of binary and ternary uranium alloys is analyzed. The mechanism and kinetics of decomposition of the gamma phase are assessed with the help of metal alloy theory. Alloys with the highest possible uranium content, good gamma-phase stability, and good neutronic performance are identified for further metallurgical studies and irradiation tests. Results from theory will be compared with experimentally generated data.

  3. Design of a Multi-Channel Ultra-High Resolution Superconducting Gamma-Ray Spectrometer

    SciTech Connect

    Friedrich, S; Terracol, S F; Miyazaki, T; Drury, O B; Ali, Z A; Cunningham, M F; Niedermayr, T R; Barbee Jr., T W; Batteux, J D; Labov, S E

    2004-11-29

    Superconducting Gamma-ray microcalorimeters operated at temperatures around {approx}0.1 K offer an order of magnitude improvement in energy resolution over conventional high-purity Germanium spectrometers. The calorimeters consist of a {approx}1 mm{sup 3} superconducting or insulating absorber and a sensitive thermistor, which are weakly coupled to a cold bath. Gamma-ray capture increases the absorber temperature in proportion to the Gamma-ray energy, this is measured by the thermistor, and both subsequently cool back down to the base temperature through the weak link. We are developing ultra-high-resolution Gamma-ray spectrometers based on Sn absorbers and superconducting Mo/Cu multilayer thermistors for nuclear non-proliferation applications. They have achieved an energy resolution between 60 and 90 eV for Gamma-rays up to 100 keV. We also build two-stage adiabatic demagnetization refrigerators for user-friendly detector operation at 0.1 K. We present recent results on the performance of single pixel Gamma-ray spectrometers, and discuss the design of a large detector array for increased sensitivity.

  4. Some aspects of the scientific significance of high energy gamma ray astrophysics

    NASA Technical Reports Server (NTRS)

    Fichtel, Carl E.

    1991-01-01

    The attraction of high energy gamma-ray astronomy lies in this radiation relating directly to those processes in astrophysical situations which deviate most from thermo-dynamic equilibrium. Some examples of these phenomena which are known to or expected to emit gamma rays are cosmic rays as they interact in intergalactic space, the high energy particles in the magnetic fields of neutron stars, the death of a black hole, the explosion and residual of a supernova, lumps of Weakly Interacting Massive Particles, energetic solar particles interacting near the sun, and very high energy particles in the extreme conditions associated with active galaxies. Although the intensities are known to be low as seen near the earth, a partially compensating characteristic is that the very penetrating nature of high energy gamma rays increases the probability that they can escape from their origin and reach the solar system.

  5. DISCOVERY OF HIGH-ENERGY AND VERY HIGH ENERGY {gamma}-RAY EMISSION FROM THE BLAZAR RBS 0413

    SciTech Connect

    Aliu, E.; Archambault, S.; Arlen, T.; Aune, T.; Bouvier, A.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Benbow, W.; Boettcher, M.; Bradbury, S. M.; Byrum, K.; Decerprit, G.; Cannon, A.; Collins-Hughes, E.; Cesarini, A.; Connolly, M. P.; Ciupik, L.; Coppi, P.; Cui, W. E-mail: fortin@llr.in2p3.fr; and others

    2012-05-10

    We report on the discovery of high-energy (HE; E > 0.1 GeV) and very high energy (VHE; E > 100 GeV) {gamma}-ray emission from the high-frequency-peaked BL Lac object RBS 0413. VERITAS, a ground-based {gamma}-ray observatory, detected VHE {gamma} rays from RBS 0413 with a statistical significance of 5.5 standard deviations ({sigma}) and a {gamma}-ray flux of (1.5 {+-} 0.6{sub stat} {+-} 0.7{sub syst}) Multiplication-Sign 10{sup -8} photons m{sup -2} s{sup -1} ({approx}1% of the Crab Nebula flux) above 250 GeV. The observed spectrum can be described by a power law with a photon index of 3.18 {+-} 0.68{sub stat} {+-} 0.30{sub syst}. Contemporaneous observations with the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope detected HE {gamma} rays from RBS 0413 with a statistical significance of more than 9{sigma}, a power-law photon index of 1.57 {+-} 0.12{sub stat}+{sup 0.11}{sub -0.12sys}, and a {gamma}-ray flux between 300 MeV and 300 GeV of (1.64 {+-} 0.43{sub stat}{sup +0.31}{sub -0.22sys}) Multiplication-Sign 10{sup -5} photons m{sup -2} s{sup -1}. We present the results from Fermi-LAT and VERITAS, including a spectral energy distribution modeling of the {gamma}-ray, quasi-simultaneous X-ray (Swift-XRT), ultraviolet (Swift-UVOT), and R-band optical (MDM) data. We find that, if conditions close to equipartition are required, both the combined synchrotron self-Compton/external-Compton and the lepto-hadronic models are preferred over a pure synchrotron self-Compton model.

  6. A new population of very high energy gamma-ray sources in the Milky Way.

    PubMed

    Aharonian, F; Akhperjanian, A G; Aye, K-M; Bazer-Bachi, A R; Beilicke, M; Benbow, W; Berge, D; Berghaus, P; Bernlöhr, K; Boisson, C; Bolz, O; Borgmeier, C; Braun, I; Breitling, F; Brown, A M; Gordo, J Bussons; Chadwick, P M; Chounet, L-M; Cornils, R; Costamante, L; Degrange, B; Djannati-Ataï, A; Drury, L O'C; Dubus, G; Ergin, T; Espigat, P; Feinstein, F; Fleury, P; Fontaine, G; Funk, S; Gallant, Y A; Giebels, B; Gillessen, S; Goret, P; Hadjichristidis, C; Hauser, M; Heinzelmann, G; Henri, G; Hermann, G; Hinton, J A; Hofmann, W; Holleran, M; Horns, D; de Jager, O C; Jung, I; Khélifi, B; Komin, Nu; Konopelko, A; Latham, I J; Le Gallou, R; Lemière, A; Lemoine, M; Leroy, N; Lohse, T; Marcowith, A; Masterson, C; McComb, T J L; de Naurois, M; Nolan, S J; Noutsos, A; Orford, K J; Osborne, J L; Ouchrif, M; Panter, M; Pelletier, G; Pita, S; Pühlhofer, G; Punch, M; Raubenheimer, B C; Raue, M; Raux, J; Rayner, S M; Redondo, I; Reimer, A; Reimer, O; Ripken, J; Rob, L; Rolland, L; Rowell, G; Sahakian, V; Saugé, L; Schlenker, S; Schlickeiser, R; Schuster, C; Schwanke, U; Siewert, M; Sol, H; Steenkamp, R; Stegmann, C; Tavernet, J-P; Terrier, R; Théoret, C G; Tluczykont, M; van der Walt, D J; Vasileiadis, G; Venter, C; Vincent, P; Visser, B; Völk, H J; Wagner, S J

    2005-03-25

    Very high energy gamma-rays probe the long-standing mystery of the origin of cosmic rays. Produced in the interactions of accelerated particles in astrophysical objects, they can be used to image cosmic particle accelerators. A first sensitive survey of the inner part of the Milky Way with the High Energy Stereoscopic System (HESS) reveals a population of eight previously unknown firmly detected sources of very high energy gamma-rays. At least two have no known radio or x-ray counterpart and may be representative of a new class of "dark" nucleonic cosmic ray sources.

  7. The Nature of Unidentified Galactic High-Energy Gamma-Ray Sources

    NASA Astrophysics Data System (ADS)

    Carramiñana, Alberto; Reimer, Olaf; Thompson, David J.

    2001-10-01

    This is the first book dedicated to unidentified celestial gamma-ray sources. The launch of the Compton Gamma-Ray Observatory allowed the first all-sky surveys in gamma-rays, the most energetic form of electromagnetic radiation. The Energetic Gamma-Ray Experiment Telescope discovered more than 270 sources of high-energy protons, more than half of which are not identified with known celestial objects. Most of these objects belong to the Milky Way and more than one class of sources are present among the unidentified sources. Unravelling the nature of all these objects requires the combination of different sorts of instruments, like radio telescopes, optical telescopes, and X-ray satellites, together with the next generations of space and ground-based gamma-ray telescopes. This book presents the current knowledge on the subject and outlines strategies for identification of objects with current astronomical facilities. It provides a forward look by outlining the prospects of future generation gamma-ray telescopes. The contributions are detailed and represent valuable material for undergraduate and postgraduate astrophysics students and researchers in the field. Link: http://www.wkap.nl/prod/b/1-4020-0010-3

  8. Intergalactic Extinction of High Energy Gamma-Rays

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.

    1998-01-01

    We discuss the determination of the intergalactic pair-production absorption coefficient as derived by Stecker and De Jager by making use of a new empirically based calculation of the spectral energy distribution of the intergalactic infrared radiation field as given by Malkan and Stecker. We show that the results of the Malkan and Stecker calculation agree well with recent data on the infrared background. We then show that Whipple observations of the flaring gamma-ray spectrum of Mrk 421 hint at extragalactic absorption and that the HEGRA observations of the flaring spectrum of Mrk 501 appear to strongly indicate extragalactic absorption. We also discuss the determination of the y-ray opacity at higher redshifts, following the treatment of Salamon and Stecker. We give a predicted spectrum, with absorption included for PKS 2155-304. This XBL lies at a redshift of 0.12, the highest redshift source yet observed at an energy above 0.3 TeV. This source should have its spectrum steepened by approx. 1 in its spectral index between approx. 0.3 and approx. 3 TeV and should show an absorption cutoff above approx. 6 TeV.

  9. Isotopic composition analysis and age dating of uranium samples by high resolution gamma ray spectrometry

    NASA Astrophysics Data System (ADS)

    Apostol, A. I.; Pantelica, A.; Sima, O.; Fugaru, V.

    2016-09-01

    Non-destructive methods were applied to determine the isotopic composition and the time elapsed since last chemical purification of nine uranium samples. The applied methods are based on measuring gamma and X radiations of uranium samples by high resolution low energy gamma spectrometric system with planar high purity germanium detector and low background gamma spectrometric system with coaxial high purity germanium detector. The "Multigroup γ-ray Analysis Method for Uranium" (MGAU) code was used for the precise determination of samples' isotopic composition. The age of the samples was determined from the isotopic ratio 214Bi/234U. This ratio was calculated from the analyzed spectra of each uranium sample, using relative detection efficiency. Special attention is paid to the coincidence summing corrections that have to be taken into account when performing this type of analysis. In addition, an alternative approach for the age determination using full energy peak efficiencies obtained by Monte Carlo simulations with the GESPECOR code is described.

  10. Status and future of high energy diffuse gamma-ray astronomy

    NASA Technical Reports Server (NTRS)

    Fichtel, C. E.

    1983-01-01

    There are two distinctly different high energy diffuse gamma-ray components, one well correlated with broad galactic features and the other apparently isotropic and presumably extragalactic. The observed diffuse galactic high energy gamma radiation is generally thought to be produced in interactions between the cosmic rays and the interstellar matter and photons. It should then ultimately be possible to obtain from the diffuse galactic emission a detailed picture of the galactic cosmic-ray distribution, a high contrast view of the general structure of the galaxy, and further insight into molecular clouds. Two of the candidates for the explanation of the extragalactic diffuse radiation are the sum of emission from active galaxies and matter-antimatter annihilation. A major advancement in the study of the properties of both galactic and extragalactic gamma radiation should occur over the next decade.

  11. High energy neutron and gamma-radiation generated during the solar flares

    NASA Technical Reports Server (NTRS)

    Kocharov, G. E.; Mandzhavidze, N. Z.

    1985-01-01

    The problem of high energy neutrons and gamma rays generation in the solar conditions is considered. It is shown that due to a peculiarity of generation and propagation of neutrons corresponding solar flares should be localized at high helio-longitudes.

  12. Common origin of the high energy astronomical gamma rays, neutrinos and cosmic ray positrons?

    NASA Astrophysics Data System (ADS)

    Dado, Shlomo; Dar, Arnon

    2016-03-01

    We show that the observed fluxes, spectra and sky distributions of the high energy astronomical neutrinos, gamma rays and cosmic ray positrons satisfy the simple relations expected from their common production in hadronic collisions in/near source of high energy cosmic rays with diffuse matter.

  13. X- and gamma ray observations in high-altitude thunderstorms in Mexico

    NASA Astrophysics Data System (ADS)

    Kelley, N. A.; Smith, D. M.; Lara, A.

    2014-12-01

    High-energy emission from lightning is more easily measured at high altitudes, close to or within the electric fields accelerating the energetic particles. Gamma rays from long duration glows and x-rays from stepped leaders attenuate with distance. From mountaintops, it may be possible to measure an amplified version of the x-rays commonly seen from stepped leaders. These amplified x-rays could arise from the thunderstorm electric field multiplying the energetic particles via Relativistic Runaway Electron Avalanches (RREA). Amplified stepped leaders may be similar or even the same as terrestrial gamma-ray flashes (TGFs), which need long-range electric fields to produce the intensities seen from space. We deployed two gamma-ray detectors at the High Altitude Water Cherenkov (HAWC) Observatory site on the northeastern slope of the Sierra Negra near Puebla, Mexico at 4100 meters to search for amplified leader events and also for the minutes-long gamma-ray glows observed from thunderstorms by other groups from the ground, balloons, and aircraft. We will also examine the data from HAWC itself, a large array of water tanks viewed by photomultiplier tubes, to look for signals simultaneous with any in our scintillators. In principle, large Cherenkov detectors and small scintillators can give complementary data about the radiation field, emphasizing the total energy content and the number flux of particles, respectively. We will present results from the summer 2014 deployment and talk about future lightning gamma-ray detectors to be deployed at HAWC.

  14. CeBr3 as a Room-Temperature, High-Resolution Gamma-Ray Detector

    SciTech Connect

    Paul Guss, Michael Reed, Ding Yuan, Alexis Reed, and Sanjoy Mukhopadhyay

    2009-09-01

    Cerium bromide (CeBr3) has become a material of interest in the race for high-resolution gamma-ray spectroscopy at room temperature. This investigation quantified the potential of CeBr3 as a room temperature, high-resolution gamma-ray detector. The performance of CeBr3 crystals was compared to other scintillation crystals of similar dimensions and detection environments. Comparison of self-activity of CeBr3 to cerium-doped lanthanum tribromide (LaBr3:Ce) was performed. Energy resolution and relative intrinsic efficiency were measured and are presented.

  15. Gamma-Ray Irradiation and Contact with High-Alkalinity Sludge: Stability Studies of Mercury Fulminate

    SciTech Connect

    Fondeur, F.F.; Wilmarth, W.R.; Peters, T.B.; Fink, S.D

    2005-09-15

    The stability of mercury fulminate under gamma-ray irradiation and in a high-alkalinity sludge environment was determined. Both differential scanning calorimetry and Fourier transform infrared spectroscopy were used to characterize mercury fulminate. Mercury fulminate completely decomposed in a gamma-ray source (0.86 Mrad/h) after a dose of 208 Mrad. This exposure equates to {approx}2.4 to 4 yr in Savannah River Site tanks. Mercury fulminate decomposed in contact with high-alkalinity wet sludge. This study suggests that any mercury fulminate or closely related energetic species decomposed long ago if it ever formed in the tank farm.

  16. High energy (gamma)-ray emission from the starburst nucleus of NGC 253

    SciTech Connect

    Domingo-Santamaria, E; Torres, D F

    2005-06-15

    The high density medium that characterizes the central regions of starburst galaxies and its power to accelerate particles up to relativistic energies make these objects good candidates as {gamma}-rays sources. In this paper, a self-consistent model of the multifrequency emission of the starburst galaxy NGC 253, from radio to gamma-rays, is presented. The model is in agreement with all current measurements and provides predictions for the high energy behavior of the NGC 253 central region. Prospects for observations with the HESS array and GLAST satellite are especially discussed.

  17. Neutron detection in a high gamma ray background with liquid scintillators

    SciTech Connect

    Stevanato, L.; Cester, D.; Viesti, G.; Nebbia, G.

    2013-04-19

    The capability of liquid scintillator (namely 2'' Multiplication-Sign 2'' cells of EJ301 and EJ309) of detecting neutrons in a very high gamma ray background is explored. A weak {sup 252}Cf source has been detected in a high {sup 137}Cs gamma ray background corresponding to a dose rate of 100 {mu}Sv/h with probability of detection in compliance with IEC requirements for hand held instruments. Tests were performed with new generation of CAEN digitizers, in particular the V1720 (8 Channel 12bit 250 MS/s) one.

  18. Modulated high-energy gamma-ray emission from the microquasar Cygnus X-3.

    PubMed

    Abdo, A A; Ackermann, M; Ajello, M; Axelsson, M; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Baughman, B M; Bechtol, K; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Brez, A; Brigida, M; Bruel, P; Burnett, T H; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cecchi, C; Celik, O; Chaty, S; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Cominsky, L R; Conrad, J; Corbel, S; Corbet, R; Dermer, C D; de Palma, F; Digel, S W; do Couto e Silva, E; Drell, P S; Dubois, R; Dubus, G; Dumora, D; Farnier, C; Favuzzi, C; Fegan, S J; Focke, W B; Fortin, P; Frailis, M; Fusco, P; Gargano, F; Gehrels, N; Germani, S; Giavitto, G; Giebels, B; Giglietto, N; Giordano, F; Glanzman, T; Godfrey, G; Grenier, I A; Grondin, M-H; Grove, J E; Guillemot, L; Guiriec, S; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Hill, A B; Hjalmarsdotter, L; Horan, D; Hughes, R E; Jackson, M S; Jóhannesson, G; Johnson, A S; Johnson, T J; Johnson, W N; Kamae, T; Katagiri, H; Kawai, N; Kerr, M; Knödlseder, J; Kocian, M L; Koerding, E; Kuss, M; Lande, J; Latronico, L; Lemoine-Goumard, M; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Makeev, A; Marchand, L; Marelli, M; Max-Moerbeck, W; Mazziotta, M N; McColl, N; McEnery, J E; Meurer, C; Michelson, P F; Migliari, S; Mitthumsiri, W; Mizuno, T; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nolan, P L; Norris, J P; Nuss, E; Ohsugi, T; Omodei, N; Ong, R A; Ormes, J F; Paneque, D; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Piron, F; Pooley, G; Porter, T A; Pottschmidt, K; Rainò, S; Rando, R; Ray, P S; Razzano, M; Rea, N; Readhead, A; Reimer, A; Reimer, O; Richards, J L; Rochester, L S; Rodriguez, J; Rodriguez, A Y; Romani, R W; Ryde, F; Sadrozinski, H F-W; Sander, A; Saz Parkinson, P M; Sgrò, C; Siskind, E J; Smith, D A; Smith, P D; Spinelli, P; Starck, J-L; Stevenson, M; Strickman, M S; Suson, D J; Takahashi, H; Tanaka, T; Thayer, J B; Thompson, D J; Tibaldo, L; Tomsick, J A; Torres, D F; Tosti, G; Tramacere, A; Uchiyama, Y; Usher, T L; Vasileiou, V; Vilchez, N; Vitale, V; Waite, A P; Wang, P; Wilms, J; Winer, B L; Wood, K S; Ylinen, T; Ziegler, M

    2009-12-11

    Microquasars are accreting black holes or neutron stars in binary systems with associated relativistic jets. Despite their frequent outburst activity, they have never been unambiguously detected emitting high-energy gamma rays. The Fermi Large Area Telescope (LAT) has detected a variable high-energy source coinciding with the position of the x-ray binary and microquasar Cygnus X-3. Its identification with Cygnus X-3 is secured by the detection of its orbital period in gamma rays, as well as the correlation of the LAT flux with radio emission from the relativistic jets of Cygnus X-3. The gamma-ray emission probably originates from within the binary system, opening new areas in which to study the formation of relativistic jets. PMID:19965378

  19. Size distributions of air showers accompanied with high energy gamma ray bundles observed at Mt. Chacaltaya

    NASA Technical Reports Server (NTRS)

    Matano, T.; Machida, M.; Tsuchima, I.; Kawasumi, N.; Honda, K.; Hashimoto, K.; Martinic, N.; Zapata, J.; Navia, C. E.; Aquirre, C.

    1985-01-01

    Size distributions of air showers accompanied with bundle of high energy gamma rays and/or large size bursts under emulsion chambers, to study the composition of primary cosmic rays and also characteristics of high energy nuclear interaction. Air showers initiated by particles with a large cross section of interaction may develop from narrow region of the atmosphere near the top. Starting levels of air showers by particles with smaller cross section fluctuate in wider region of the atmosphere. Air showers of extremely small size accompanied with bundle of gamma rays may be ones initiated by protons at lower level after penetrating deep atmosphere without interaction. It is determined that the relative size distribution according to the total energy of bundle of gamma rays and the total burst size observed under 15 cm lead absorber.

  20. Modulated High-Energy Gamma-Ray Emission from the Microquasar Cygnus X-3

    NASA Astrophysics Data System (ADS)

    Fermi LAT Collaboration; Abdo, A. A.; Ackermann, M.; Ajello, M.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Baughman, B. M.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Brez, A.; Brigida, M.; Bruel, P.; Burnett, T. H.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cecchi, C.; Çelik, Ö.; Chaty, S.; Cheung, C. C.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Cominsky, L. R.; Conrad, J.; Corbel, S.; Corbet, R.; Dermer, C. D.; de Palma, F.; Digel, S. W.; do Couto e Silva, E.; Drell, P. S.; Dubois, R.; Dubus, G.; Dumora, D.; Farnier, C.; Favuzzi, C.; Fegan, S. J.; Focke, W. B.; Fortin, P.; Frailis, M.; Fusco, P.; Gargano, F.; Gehrels, N.; Germani, S.; Giavitto, G.; Giebels, B.; Giglietto, N.; Giordano, F.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Grondin, M.-H.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Hanabata, Y.; Harding, A. K.; Hayashida, M.; Hays, E.; Hill, A. B.; Hjalmarsdotter, L.; Horan, D.; Hughes, R. E.; Jackson, M. S.; Jóhannesson, G.; Johnson, A. S.; Johnson, T. J.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kawai, N.; Kerr, M.; Knödlseder, J.; Kocian, M. L.; Koerding, E.; Kuss, M.; Lande, J.; Latronico, J.; Lemoine-Goumard, M.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; Makeev, A.; Marchand, L.; Marelli, M.; Max-Moerbeck, W.; Mazziotta, M. N.; McColl, N.; McEnery, J. E.; Meurer, C.; Michelson, P. F.; Migliari, S.; Mitthumsiri, W.; Mizuno, T.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Omodei, N.; Ong, R. A.; Ormes, J. F.; Paneque, D.; Parent, D.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Piron, F.; Pooley, G.; Porter, T. A.; Pottschmidt, K.; Rainò, S.; Rando, R.; Ray, P. S.; Razzano, M.; Rea, N.; Readhead, A.; Reimer, A.; Reimer, O.; Richards, J. L.; Rochester, L. S.; Rodriguez, J.; Rodriguez, A. Y.; Romani, R. W.; Ryde, F.; Sadrozinski, H. F.-W.; Sander, A.; Saz Parkinson, P. M.; Sgrò, C.; Siskind, E. J.; Smith, D. A.; Smith, P. D.; Spinelli, P.; Starck, J.-L.; Stevenson, M.; Strickman, M. S.; Suson, D. J.; Takahashi, H.; Tanaka, T.; Thayer, J. B.; Thompson, D. J.; Tibaldo, L.; Tomsick, J. A.; Torres, D. F.; Tosti, G.; Tramacere, A.; Uchiyama, Y.; Usher, T. L.; Vasileiou, V.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wang, P.; Wilms, J.; Winer, B. L.; Wood, K. W.; Ylinen, T.; Ziegler, M.

    2009-12-01

    Microquasars are accreting black holes or neutron stars in binary systems with associated relativistic jets. Despite their frequent outburst activity, they have never been unambiguously detected emitting high-energy gamma rays. The Fermi Large Area Telescope (LAT) has detected a variable high-energy source coinciding with the position of the x-ray binary and microquasar Cygnus X-3. Its identification with Cygnus X-3 is secured by the detection of its orbital period in gamma rays, as well as the correlation of the LAT flux with radio emission from the relativistic jets of Cygnus X-3. The gamma-ray emission probably originates from within the binary system, opening new areas in which to study the formation of relativistic jets.

  1. Modulated high-energy gamma-ray emission from the microquasar Cygnus X-3.

    PubMed

    Abdo, A A; Ackermann, M; Ajello, M; Axelsson, M; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Baughman, B M; Bechtol, K; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Brez, A; Brigida, M; Bruel, P; Burnett, T H; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cecchi, C; Celik, O; Chaty, S; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Cominsky, L R; Conrad, J; Corbel, S; Corbet, R; Dermer, C D; de Palma, F; Digel, S W; do Couto e Silva, E; Drell, P S; Dubois, R; Dubus, G; Dumora, D; Farnier, C; Favuzzi, C; Fegan, S J; Focke, W B; Fortin, P; Frailis, M; Fusco, P; Gargano, F; Gehrels, N; Germani, S; Giavitto, G; Giebels, B; Giglietto, N; Giordano, F; Glanzman, T; Godfrey, G; Grenier, I A; Grondin, M-H; Grove, J E; Guillemot, L; Guiriec, S; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Hill, A B; Hjalmarsdotter, L; Horan, D; Hughes, R E; Jackson, M S; Jóhannesson, G; Johnson, A S; Johnson, T J; Johnson, W N; Kamae, T; Katagiri, H; Kawai, N; Kerr, M; Knödlseder, J; Kocian, M L; Koerding, E; Kuss, M; Lande, J; Latronico, L; Lemoine-Goumard, M; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Makeev, A; Marchand, L; Marelli, M; Max-Moerbeck, W; Mazziotta, M N; McColl, N; McEnery, J E; Meurer, C; Michelson, P F; Migliari, S; Mitthumsiri, W; Mizuno, T; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nolan, P L; Norris, J P; Nuss, E; Ohsugi, T; Omodei, N; Ong, R A; Ormes, J F; Paneque, D; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Piron, F; Pooley, G; Porter, T A; Pottschmidt, K; Rainò, S; Rando, R; Ray, P S; Razzano, M; Rea, N; Readhead, A; Reimer, A; Reimer, O; Richards, J L; Rochester, L S; Rodriguez, J; Rodriguez, A Y; Romani, R W; Ryde, F; Sadrozinski, H F-W; Sander, A; Saz Parkinson, P M; Sgrò, C; Siskind, E J; Smith, D A; Smith, P D; Spinelli, P; Starck, J-L; Stevenson, M; Strickman, M S; Suson, D J; Takahashi, H; Tanaka, T; Thayer, J B; Thompson, D J; Tibaldo, L; Tomsick, J A; Torres, D F; Tosti, G; Tramacere, A; Uchiyama, Y; Usher, T L; Vasileiou, V; Vilchez, N; Vitale, V; Waite, A P; Wang, P; Wilms, J; Winer, B L; Wood, K S; Ylinen, T; Ziegler, M

    2009-12-11

    Microquasars are accreting black holes or neutron stars in binary systems with associated relativistic jets. Despite their frequent outburst activity, they have never been unambiguously detected emitting high-energy gamma rays. The Fermi Large Area Telescope (LAT) has detected a variable high-energy source coinciding with the position of the x-ray binary and microquasar Cygnus X-3. Its identification with Cygnus X-3 is secured by the detection of its orbital period in gamma rays, as well as the correlation of the LAT flux with radio emission from the relativistic jets of Cygnus X-3. The gamma-ray emission probably originates from within the binary system, opening new areas in which to study the formation of relativistic jets.

  2. Fermi observations of high-energy gamma-ray emission from GRB 080916C.

    PubMed

    Abdo, A A; Ackermann, M; Arimoto, M; Asano, K; Atwood, W B; Axelsson, M; Baldini, L; Ballet, J; Band, D L; Barbiellini, G; Baring, M G; Bastieri, D; Battelino, M; Baughman, B M; Bechtol, K; Bellardi, F; Bellazzini, R; Berenji, B; Bhat, P N; Bissaldi, E; Blandford, R D; Bloom, E D; Bogaert, G; Bogart, J R; Bonamente, E; Bonnell, J; Borgland, A W; Bouvier, A; Bregeon, J; Brez, A; Briggs, M S; Brigida, M; Bruel, P; Burnett, T H; Burrows, D; Busetto, G; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Ceccanti, M; Cecchi, C; Celotti, A; Charles, E; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Cominsky, L R; Connaughton, V; Conrad, J; Costamante, L; Cutini, S; Deklotz, M; Dermer, C D; de Angelis, A; de Palma, F; Digel, S W; Dingus, B L; do Couto E Silva, E; Drell, P S; Dubois, R; Dumora, D; Edmonds, Y; Evans, P A; Fabiani, D; Farnier, C; Favuzzi, C; Finke, J; Fishman, G; Focke, W B; Frailis, M; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giebels, B; Giglietto, N; Giommi, P; Giordano, F; Glanzman, T; Godfrey, G; Goldstein, A; Granot, J; Greiner, J; Grenier, I A; Grondin, M-H; Grove, J E; Guillemot, L; Guiriec, S; Haller, G; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Hernando Morat, J A; Hoover, A; Hughes, R E; Jóhannesson, G; Johnson, A S; Johnson, R P; Johnson, T J; Johnson, W N; Kamae, T; Katagiri, H; Kataoka, J; Kavelaars, A; Kawai, N; Kelly, H; Kennea, J; Kerr, M; Kippen, R M; Knödlseder, J; Kocevski, D; Kocian, M L; Komin, N; Kouveliotou, C; Kuehn, F; Kuss, M; Lande, J; Landriu, D; Larsson, S; Latronico, L; Lavalley, C; Lee, B; Lee, S-H; Lemoine-Goumard, M; Lichti, G G; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Makeev, A; Marangelli, B; Mazziotta, M N; McBreen, S; McEnery, J E; McGlynn, S; Meegan, C; Mészáros, P; Meurer, C; Michelson, P F; Minuti, M; Mirizzi, N; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Moretti, E; Morselli, A; Moskalenko, I V; Murgia, S; Nakamori, T; Nelson, D; Nolan, P L; Norris, J P; Nuss, E; Ohno, M; Ohsugi, T; Okumura, A; Omodei, N; Orlando, E; Ormes, J F; Ozaki, M; Paciesas, W S; Paneque, D; Panetta, J H; Parent, D; Pelassa, V; Pepe, M; Perri, M; Pesce-Rollins, M; Petrosian, V; Pinchera, M; Piron, F; Porter, T A; Preece, R; Rainò, S; Ramirez-Ruiz, E; Rando, R; Rapposelli, E; Razzano, M; Razzaque, S; Rea, N; Reimer, A; Reimer, O; Reposeur, T; Reyes, L C; Ritz, S; Rochester, L S; Rodriguez, A Y; Roth, M; Ryde, F; Sadrozinski, H F-W; Sanchez, D; Sander, A; Saz Parkinson, P M; Scargle, J D; Schalk, T L; Segal, K N; Sgrò, C; Shimokawabe, T; Siskind, E J; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Stamatikos, M; Starck, J-L; Stecker, F W; Steinle, H; Stephens, T E; Strickman, M S; Suson, D J; Tagliaferri, G; Tajima, H; Takahashi, H; Takahashi, T; Tanaka, T; Tenze, A; Thayer, J B; Thayer, J G; Thompson, D J; Tibaldo, L; Torres, D F; Tosti, G; Tramacere, A; Turri, M; Tuvi, S; Usher, T L; van der Horst, A J; Vigiani, L; Vilchez, N; Vitale, V; von Kienlin, A; Waite, A P; Williams, D A; Wilson-Hodge, C; Winer, B L; Wood, K S; Wu, X F; Yamazaki, R; Ylinen, T; Ziegler, M

    2009-03-27

    Gamma-ray bursts (GRBs) are highly energetic explosions signaling the death of massive stars in distant galaxies. The Gamma-ray Burst Monitor and Large Area Telescope onboard the Fermi Observatory together record GRBs over a broad energy range spanning about 7 decades of gammaray energy. In September 2008, Fermi observed the exceptionally luminous GRB 080916C, with the largest apparent energy release yet measured. The high-energy gamma rays are observed to start later and persist longer than the lower energy photons. A simple spectral form fits the entire GRB spectrum, providing strong constraints on emission models. The known distance of the burst enables placing lower limits on the bulk Lorentz factor of the outflow and on the quantum gravity mass.

  3. Ground-based very high energy gamma ray astronomy: Observational highlights

    NASA Technical Reports Server (NTRS)

    Turver, K. E.

    1986-01-01

    It is now more than 20 years since the first ground based gamma ray experiments involving atmospheric Cerenkov radiation were undertaken. The present highlights in observational ground-based very high energy (VHE) gamma ray astronomy and the optimism about an interesting future for the field follow progress in these areas: (1) the detection at increased levels of confidence of an enlarged number of sources so that at present claims were made for the detection, at the 4 to 5 sd level of significance, of 8 point sources; (2) the replication of the claimed detections with, for the first time, confirmation of the nature and detail of the emission; and (3) the extension of gamma ray astronomy to the ultra high energy (UHE) domain. The pattern, if any, to emerge from the list of sources claimed so far is that X-ray binary sources appear to be copious emitters of gamma rays over at least 4 decades of energy. These X-ray sources which behave as VHE and UHE gamma ray emitters are examined.

  4. Phase stability of {epsilon} and {gamma} HNIW (CL-20) at high-pressure and temperature

    SciTech Connect

    Gump, Jared C.; Stoltz, Chad A.; Peiris, Suhithi M.

    2007-12-12

    Hexanitrohexaazaisowurtzitane (CL-20) is one of the few ingredients developed since World War II to be considered for transition to military use. Five polymorphs have been identified for CL-20 by FTIR measurements ({alpha}, {beta}, {gamma}, {epsilon}, {zeta}). As CL-20 is transitioned into munitions it will become necessary to predict its response under conditions of detonation, for performance evaluation. Such predictive modeling requires a phase diagram and basic thermodynamic properties of the various phases at high pressure and temperature. Therefore, the epsilon and gamma phases of CL-20 at static high-pressure and temperature were investigated using synchrotron angle-dispersive x-ray diffraction experiments. The samples were compressed and heated using diamond anvil cells (DAC). Pressures and temperatures achieved were around 5 GPa and 240 deg. C, respectively. The epsilon phase was stable to 6.3 GPa at ambient temperature. When heated at ambient pressure the epsilon phase was sustained to a temperature of 120 deg. C then underwent a transition to the gamma phase above 125 deg. C and then thermal decomposition occurred above 150 deg. C. Upon compression, the gamma phase underwent a phase transition at both ambient temperature and 140 deg. C. Pressure--volume data for the epsilon and gamma phase at ambient temperature and the epsilon phase at 75 deg. C were fit to the Birch-Murnaghan formalism to obtain isothermal equations of state.

  5. Title: MAGIC detects exceptionally high activity from PKS 1510-089 at very high energy gamma-rays

    NASA Astrophysics Data System (ADS)

    Mirzoyan, Razmik

    2016-06-01

    The MAGIC telescopes have detected an increase in the Very High Energy gamma-ray flux from PKS 1510-089 (RA=15 12 50.5, dec=-09 06 00, J2000.0). The preliminary analysis of the MAGIC data taken on 2016/05/30 for 2.7 hours, indicates a highly significant signal (significance > 60 sigma).

  6. Generating Polarized High-Brightness Muon Beams With High-Energy Gammas

    SciTech Connect

    Yakimenko, Vitaly

    2009-01-22

    Hadron colliders are impractical at very high energies as effective interaction energy is a fraction of the energies of the beams and luminosity must rise as energy squared. Further, the prevailing gluon-gluon background radiation makes it difficult to sort out events. e{sup +}e{sup -} colliders, on other hand, are constrained at TeV energies by beamstrahlung radiation and also by cost as long linacs are required to avoid synchrotron radiation in the rings. A muon collider will have the same advantages in energy reach as an e{sup +}e{sup -} collider, but without prohibitive beamstrahlung- and synchrotron- radiation. Generation of the high-brightness polarized muon ({mu}{sup -}{mu}{sup +}) beams through gamma conversion into pairs in the nuclei field is considered in this paper. The dominant effect in the interaction of the high-energy photons with the solid target will be the production of electron-positron pairs. The low-phase space of the resulting muon beams adequately compensates for the small probability of generating a {mu}{sup -}{mu}{sup +} pair.

  7. Gamma-ray astronomy: From Fermi up to the HAWC high-energy {gamma}-ray observatory in Sierra Negra

    SciTech Connect

    Carraminana, Alberto; Collaboration: HAWC Collaboration

    2013-06-12

    Gamma-rays represent the most energetic electromagnetic window for the study of the Universe. They are studied both from space at MeV and GeV energies, with instruments like the Fermi{gamma}-ray Space Telescope, and at TeV energies with ground based instruments profiting of particle cascades in the atmosphere and of the Cerenkov radiation of charged particles in the air or in water. The Milagro gamma-ray observatory represented the first instrument to successfully implement the water Cerenkov technique for {gamma}-ray astronomy, opening the ground for the more sensitive HAWC {gamma}-ray observatory, currently under development in the Sierra Negra site and already providing early science results.

  8. Radio galaxies dominate the high-energy diffuse gamma-ray background

    NASA Astrophysics Data System (ADS)

    Hooper, Dan; Linden, Tim; Lopez, Alejandro

    2016-08-01

    It has been suggested that unresolved radio galaxies and radio quasars (sometimes referred to as misaligned active galactic nuclei) could be responsible for a significant fraction of the observed diffuse gamma-ray background. In this study, we use the latest data from the Fermi Gamma-Ray Space Telescope to characterize the gamma-ray emission from a sample of 51 radio galaxies. In addition to those sources that had previously been detected using Fermi data, we report here the first statistically significant detection of gamma-ray emission from the radio galaxies 3C 212, 3C 411, and B3 0309+411B. Combining this information with the radio fluxes, radio luminosity function, and redshift distribution of this source class, we find that radio galaxies dominate the diffuse gamma-ray background, generating 77.2+25.4-9.4% of this emission at energies above ~1 GeV . We discuss the implications of this result and point out that it provides support for scenarios in which IceCube's high-energy astrophysical neutrinos also originate from the same population of radio galaxies.

  9. A Luminous High-Mass Gamma-ray Binary in the Large Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Corbet, Robin; Cheung, Chi C.; Chomiuk, Laura; Coe, Malcolm J.; Coley, Joel Barry; Dubus, Guillaume; Edwards, Philip; Martin, Pierrick; McBride, Vanessa; Stevens, Jamie; Strader, Jay; Townsend, Lee

    2016-04-01

    We have been undertaking a search for gamma-ray binaries from the detection of periodic modulation in light curves from all sources in the Fermi LAT 3FGL catalog. From this search we identified a 10 day modulation in the direction of the LMC. A localization of the modulation indicates that it arises from a point source identified in a recent Fermi-LAT survey of the LMC. The nature and identification of this source had been uncertain. We find that the counterpart is a previously reported candidate high-mass X-ray binary with an O6III(f) primary located in a supernova remnant. Swift XRT observations of this source show modulation on the 10 day gamma-ray period, but with a different epoch of maximum flux. ATCA radio observations (5.5 and 9 GHz) also reveal variable radio emission from this source. Optical spectroscopy (SAAO and SOAR) show that while there are no large changes in the spectrum, there is apparent radial velocity modulation. At all wavebands this new gamma-ray binary is significantly more luminous than comparable Galactic systems, even though very few of these are known. The discovery of this extragalactic gamma-ray binary may have implications for the overall population of gamma-ray binaries and their evolutionary pathways and lifetimes.

  10. Microstructural development in high volume fraction gamma prime Ni-base oxide-dispersion-strengthened superalloys

    NASA Astrophysics Data System (ADS)

    Kang, S. K.; Benn, R. C.

    1985-07-01

    The mechanical alloying process has successfully combined oxide-dispersion-strengthening with conventional gamma prime precipitation hardening for advanced gas turbine materials. INCONEL* alloy MA 6000, a mechanically alloyed Ni-base superalloy, has the highest temperature capability among commercially available superalloys. Further improvement of the intermediate temperature strength has been pursued by both increasing the gamma prime content up to 80 vol pct and controlling the additions of refractory metals. The microstructural development of these new experimental alloys is reported in this paper, especially for an alloy, nominally identified as Alloy 51, having the composition Ni-9.3 pct Cr-8.5 pct Al-6.6 pct W-3.4 pct Mo-0.15 pct Zr-0.01 pct B-l.l pct Y2O3 (wt pct). Both the primary and the secondary recrystallized microstructures of the alloy were characterized in terms of gamma grain structure, gamma prime precipitate morphology, orientation relationships, dispersoids, carbide/nitride particles, and chemical composition of intermetallic phases. The microstructural stability of the alloy under stress rupture conditions was also investigated in terms of coarsening/coalescence of gamma prime precipitates. Correlation of the microstructural information with the high temperature properties of the alloy is also briefly discussed.

  11. A review of recent results in gamma-ray astronomy obtained from high-altitude balloons

    NASA Technical Reports Server (NTRS)

    Teegarden, B. J.

    1994-01-01

    This paper reviews recent results in gamma-ray astronomy obtained from experiments flown on high-altitude balloons. New generation balloon-borne imaging experiments have produced the first gamma-ray maps of the Galactic center (GC) region. Balloon flights of new gamma-ray spectrometers with improved sensitivity have provided important new information on the GC annihilation line. For the first time, the narrow 511 keV line as been resolved (FWHM approx. = 3 keV). A very interesting spectral feature at approximately 170 keV has been attributed to backscattered annihilation, probably from the vicinity of a compact object. New results from the Compton Gamma-Ray Observatory (CGRO)/OSSE and Granat/SIGMA experiments on the annihilation line, when considered together with the recent balloon results, have added greatly to our knowledge and understanding of the origin and distribution of this emission. Balloon-borne instruments have made important measurements of gamma-ray continuum and line emission from SN 1987A. The GRIS spectrometer unambiguously resolved the 847 and 1238 keV line emission from radioactive Co-56 synthesized during the explosion. This data indicated that simple spherically symmetric and homogeneous models did not provide an adequate description of the expanding SN shell.

  12. Radio galaxies dominate the high-energy diffuse gamma-ray background

    NASA Astrophysics Data System (ADS)

    Hooper, Dan; Linden, Tim; Lopez, Alejandro

    2016-08-01

    It has been suggested that unresolved radio galaxies and radio quasars (sometimes referred to as misaligned active galactic nuclei) could be responsible for a significant fraction of the observed diffuse gamma-ray background. In this study, we use the latest data from the Fermi Gamma-Ray Space Telescope to characterize the gamma-ray emission from a sample of 51 radio galaxies. In addition to those sources that had previously been detected using Fermi data, we report here the first statistically significant detection of gamma-ray emission from the radio galaxies 3C 212, 3C 411, and B3 0309+411B. Combining this information with the radio fluxes, radio luminosity function, and redshift distribution of this source class, we find that radio galaxies dominate the diffuse gamma-ray background, generating 77.2+25.4‑9.4% of this emission at energies above ~1 GeV . We discuss the implications of this result and point out that it provides support for scenarios in which IceCube's high-energy astrophysical neutrinos also originate from the same population of radio galaxies.

  13. Radio galaxies dominate the high-energy diffuse gamma-ray background

    DOE PAGESBeta

    Hooper, Dan; Linden, Tim; Lopez, Alejandro

    2016-08-09

    It has been suggested that unresolved radio galaxies and radio quasars (sometimes referred to as misaligned active galactic nuclei) could be responsible for a significant fraction of the observed diffuse gamma-ray background. In this study, we use the latest data from the Fermi Gamma-Ray Space Telescope to characterize the gamma-ray emission from a sample of 51 radio galaxies. In addition to those sources that had previously been detected using Fermi data, we report here the first statistically significant detection of gamma-ray emission from the radio galaxies 3C 212, 3C 411, and B3 0309+411B. Combining this information with the radio fluxes,more » radio luminosity function, and redshift distribution of this source class, we find that radio galaxies dominate the diffuse gamma-ray background, generating 77.2(+25.4)(-9.4)% of this emission at energies above ~1 GeV . We discuss the implications of this result and point out that it provides support for scenarios in which IceCube's high-energy astrophysical neutrinos also originate from the same population of radio galaxies.« less

  14. Simulation experiments for gamma-ray mapping of planetary surfaces: Scattering of high-energy neutrons

    NASA Technical Reports Server (NTRS)

    Brueckner, J.; Englert, P.; Reedy, R. C.; Waenke, H.

    1986-01-01

    The concentration and distribution of certain elements in surface layers of planetary objects specify constraints on models of their origin and evolution. This information can be obtained by means of remote sensing gamma-ray spectroscopy, as planned for a number of future space missions, i.e., Mars, Moon, asteroids, and comets. To investigate the gamma-rays made by interactions of neutrons with matter, thin targets of different composition were placed between a neutron-source and a high-resolution germanium spectrometer. Gamma-rays in the range of 0.1 to 8 MeV were accumulated. In one set of experiments a 14-MeV neutron generator using the T(d,n) reaction as neutron-source was placed in a small room. Scattering in surrounding walls produced a spectrum of neutron energies from 14 MeV down to thermal. This complex neutron-source induced mainly neutron-capture lines and only a few scattering lines. As a result of the set-up, there was a considerable background of discrete lines from surrounding materials. A similar situation exists under planetary exploration conditions: gamma-rays are induced in the planetary surface as well as in the spacecraft. To investigate the contribution of neutrons with higher energies, an experiment for the measurement of prompt gamma radiation was set up at the end of a beam-line of an isochronous cyclotron.

  15. SAS-2 observations of high energy gamma rays from discrete sources

    NASA Technical Reports Server (NTRS)

    Kniffen, D. A.; Fichtel, C. E.; Hartman, R. C.; Lamb, R. C.; Thompson, D. J.

    1977-01-01

    The SAS-2 identified six localized high energy (greater than 35 MeV) gamma ray sources. Four of these are the radio pulsars, PSR 0531+21, PSR 0833-45, PSR 1818-04, and PSR 1717-46 discovered in a search of 75 radio pulsars. The fact that only one of these is observed in X-rays, and the significant differences in pulse profiles in the gamma ray and radio observations, leads to the speculation that different mechanisms are involved.

  16. Cygnus X-3 and other ultra-high-energy gamma-ray sources

    NASA Technical Reports Server (NTRS)

    Barnard, John J.

    1987-01-01

    Recently, several binary X-ray sources have been found to be sources of ultrahigh-energy gamma emission. Air-shower observations indicate photon energies above about 1 PeV. Observations from Cyg X-3 are reviewed and compared with data on the sources Her X-1, Vel X-1, and LMC X-4. Current theoretical models for the production of gamma rays and the acceleration of high-energy particles are discussed, and the consequences for the evolution of such systems are examined.

  17. The COS-B experiment and mission. [high energy extraterrestrial gamma radiation

    NASA Technical Reports Server (NTRS)

    1977-01-01

    The COS-B satellite carries a single experiment, capable of detecting gamma rays with energies greater than 30 MeV to study the spatial, energy, and time characteristics of high-energy radiation of galactic and extragalactic origin. The capability to search for gamma ray pulsations is enhanced by the inclusion in the payload of a proportional counter sensitive of X-rays of 2 to 12 keV. The experiment was calibrated using particle accelerators. The results of these measurements are presented, and the performance of the system in orbit is discussed.

  18. A field-deployable gamma-ray spectrometer utilizing xenon at high pressure

    SciTech Connect

    Smith, G.C.; Mahler, G.J.; Yu, B.; Salwen, C.; Kane, W.R.; Lemley, J.R.

    1996-10-01

    Prototype gamma-ray spectrometers utilizing xenon gas at high pressure, suitable for applications in the nuclear safeguards, arms control, and nonproliferation communities, have been developed at Brookhaven National Laboratory (BNL). These spectrometers function as ambient-temperature ionization chambers detecting gamma rays with good efficiency in the energy range 50 keV - 2 MeV, with an energy resolution intermediate between semiconductor (Ge) and scintillation (NaI) spectrometers. They are capable of prolonged, low-power operation without a requirement for cryogenic fluids or other cooling mechanisms, and with the addition of small quantities of {sup 3}He gas, can function simultaneously as efficient thermal neutron detectors.

  19. High spatial resolution X-ray and gamma ray imaging system using diffraction crystals

    DOEpatents

    Smither, Robert K.

    2011-05-17

    A method and a device for high spatial resolution imaging of a plurality of sources of x-ray and gamma-ray radiation are provided. The device comprises a plurality of arrays, with each array comprising a plurality of elements comprising a first collimator, a diffracting crystal, a second collimator, and a detector.

  20. COS-B observations of the high energy gamma radiation from the galactic disc

    NASA Technical Reports Server (NTRS)

    Paul, J.

    1976-01-01

    During the first months of operation, COS-B has observed galactic high energy gamma rays from the galactic disc. In the galactic center and Vela regions the disc emission distribution was measured. From these data the existence of a local ( 1 kpc) and a distant ( 3 kpc) emitting region is apparent in the general direction of the inner galaxy.

  1. Conducting High Cycle Fatigue Strength Step Tests on Gamma TiAl

    NASA Technical Reports Server (NTRS)

    Lerch, Brad; Draper, Sue; Pereira, J. Mike

    2002-01-01

    High cycle fatigue strength testing of gamma TiAl by the step test method is investigated. A design of experiments was implemented to determine if the coaxing effect occurred during testing. Since coaxing was not observed, step testing was deemed a suitable method to define the fatigue strength at 106 cycles.

  2. Monitoring performance of the cameras under the high dose-rate gamma ray environments.

    PubMed

    Cho, Jai Wan; Choi, Young Soo; Jeong, Kyung Min

    2014-05-01

    CCD/CMOS cameras, loaded on a robot system, are generally used as the eye of the robot and monitoring unit. A major problem that arises when dealing with images provided by CCD/CMOS cameras under severe accident situations of a nuclear power plant is the presence of speckles owing to the high dose-rate gamma irradiation fields. To use a CCD/CMOS camera as a monitoring unit in a high radiation area, the legibility of the camera image in such intense gamma-radiation fields should therefore be defined. In this paper, the authors describe the monitoring index as a figure of merit of the camera's legibleness under a high dose-rate gamma ray irradiation environment. From a low dose-rate (10 Gy h) to a high dose-rate (200 Gy h) level, the legible performances of the cameras owing to the speckles are evaluated. The numbers of speckles generated by gamma ray irradiation in the camera image are calculated by an image processing technique. The legibility of the sensor indicator (thermo/hygrometer) owing to the number of speckles is also presented. PMID:24667385

  3. SAS-2 observations of the high energy gamma radiation from the Vela region

    NASA Technical Reports Server (NTRS)

    Thompson, D. J.; Bignami, G. F.; Fichtel, C. E.; Kniffen, D. A.

    1974-01-01

    Data from a scan of the galactic plane by the SAS-B high energy gamma ray experiment in the region 250 deg smaller than 12 smaller than 290 deg show a statistically significant excess over the general radiation from the galactic plane for gamma radiation of energy larger than 100 MeV. If the enhanced gamma radiation results from interactions of cosmic rays with galactic matter, as the energy spectrum suggests, it seems reasonable to associate the enhancement with large scale galactic features, such as spiral arm segments in that direction, or with the region surrounding the Vela supernova remnant with which PSR 0833-45 is associated. If the excess is attributed to cosmic rays released from the supernova interacting with the interstellar matter in that region, than on the order of 3 x 10 to the 50th power ergs would have been released by that supernova in the form of cosmic rays.

  4. High-energy gamma-ray emission from pion decay in a solar flare magnetic loop

    NASA Technical Reports Server (NTRS)

    Mandzhavidze, Natalie; Ramaty, Reuven

    1992-01-01

    The production of high-energy gamma rays resulting from pion decay in a solar flare magnetic loop is investigated. Magnetic mirroring, MHD pitch-angle scattering, and all of the relevant loss processes and photon production mechanisms are taken into account. The transport of both the primary ions and the secondary positrons resulting from the decay of the positive pions, as well as the transport of the produced gamma-ray emission are considered. The distributions of the gamma rays as a function of atmospheric depth, time, emission angle, and photon energy are calculated and the dependence of these distributions on the model parameters are studied. The obtained angular distributions are not sufficiently anisotropic to account for the observed limb brightening of the greater than 10 MeV flare emission, indicating that the bulk of this emission is bremsstrahlung from primary electrons.

  5. Effect of gamma irradiation on high temperature hardness of low-density polyethylene

    NASA Astrophysics Data System (ADS)

    Chen, Pei-Yun; Yang, Fuqian; Lee, Sanboh

    2015-11-01

    Gamma irradiation can cause the change of microstructure and molecular structure of polymer, resulting in the change of mechanical properties of polymers. Using the hardness measurement, the effect of gamma irradiation on the high temperature hardness of low-density polyethylene (LDPE) was investigated. The gamma irradiation caused the increase in the melting point, the enthalpy of fusion, and the portion of crystallinity of LDPE. The Vickers hardness of the irradiated LDPE increases with increasing the irradiation dose, annealing temperature, and annealing time. The activation energy for the rate process controlling the reaction between defects linearly decreases with the irradiation dose. The process controlling the hardness evolution in LDPE is endothermic because LDPE is semi-crystalline.

  6. Fermi Observations of High-energy Gamma-ray Emission from GRB 080825C

    NASA Astrophysics Data System (ADS)

    Abdo, A. A.; Ackermann, M.; Asano, K.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Ballet, J.; Band, D. L.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bhat, P. N.; Bissaldi, E.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Bregeon, J.; Brez, A.; Briggs, M. S.; Brigida, M.; Bruel, P.; Burnett, T. H.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cecchi, C.; Chaplin, V.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Cominsky, L. R.; Connaughton, V.; Conrad, J.; Cutini, S.; Dermer, C. D.; de Angelis, A.; de Palma, F.; Digel, S. W.; Silva, E. do Couto e.; Drell, P. S.; Dubois, R.; Dumora, D.; Farnier, C.; Favuzzi, C.; Focke, W. B.; Frailis, M.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Gibby, L.; Giebels, B.; Giglietto, N.; Giordano, F.; Glanzman, T.; Godfrey, G.; Goldstein, A.; Granot, J.; Grenier, I. A.; Grondin, M.-H.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Hanabata, Y.; Harding, A. K.; Hayashida, M.; Hays, E.; Hughes, R. E.; Jóhannesson, G.; Johnson, A. S.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kataoka, J.; Kawai, N.; Kerr, M.; Knödlseder, J.; Kocevski, D.; Komin, N.; Kouveliotou, C.; Kuehn, F.; Kuss, M.; Latronico, L.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Makeev, A.; Mazziotta, M. N.; McBreen, S.; McEnery, J. E.; McGlynn, S.; Meegan, C.; Meurer, C.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Monte, C.; Monzani, M. E.; Moretti, E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakamori, T.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohno, M.; Ohsugi, T.; Omodei, N.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paciesas, W. S.; Paneque, D.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Piron, F.; Porter, T. A.; Preece, R.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, O.; Reposeur, T.; Ritz, S.; Rochester, L. S.; Rodriguez, A. Y.; Roth, M.; Ryde, F.; Sadrozinski, H. F.-W.; Sanchez, D.; Sander, A.; Saz Parkinson, P. M.; Scargle, J. D.; Sgrò, C.; Siskind, E. J.; Smith, D. A.; Smith, P. D.; Spandre, G.; Spinelli, P.; Stamatikos, M.; Strickman, M. S.; Suson, D. J.; Tajima, H.; Takahashi, H.; Tanaka, T.; Thayer, J. B.; Thayer, J. G.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Uchiyama, Y.; Usher, T. L.; van der Horst, A. J.; Vasileiou, V.; Vilchez, N.; Vitale, V.; von Kienlin, A.; Waite, A. P.; Wang, P.; Wilson-Hodge, C.; Winer, B. L.; Wood, K. S.; Ylinen, T.; Ziegler, M.

    2009-12-01

    The Fermi Gamma-ray Space Telescope has opened a new high-energy window in the study of gamma-ray bursts (GRBs). Here we present a thorough analysis of GRB 080825C, which triggered the Fermi Gamma-ray Burst Monitor (GBM), and was the first firm detection of a GRB by the Fermi Large Area Telescope (LAT). We discuss the LAT event selections, background estimation, significance calculations, and localization for Fermi GRBs in general and GRB 080825C in particular. We show the results of temporal and time-resolved spectral analysis of the GBM and LAT data. We also present some theoretical interpretation of GRB 080825C observations as well as some common features observed in other LAT GRBs.

  7. Opportunities for Fundamental and New Physics with Very High Energy Gamma-ray Telescopes

    NASA Astrophysics Data System (ADS)

    Bechtol, Keith

    2016-04-01

    Astronomical observations with the highest energy gamma rays enable a wide range of fundamental physics measurements as well as searches for new physics beyond the Standard Model. In this presentation, I will discuss indirect dark matter searches, intergalactic magnetic field constraints, and tests of Lorentz invariance with an emphasis on sensitivity gains that could be achieved with two new ground-based gamma-ray telescopes operating at the TeV energy scale: the High-Altitude Water Cherenkov observatory (HAWC) and the Cherenkov Telescope Array (CTA). Multiwavelength and multimessenger observations are an essential component of these studies needed to characterize the environments in which the highest energy gamma rays are produced, the conditions encountered while traversing interstellar and intergalactic distances, and "conventional" astrophysical backgrounds.

  8. THE HIGH ENERGY BUDGET ALLOCATIONS IN SHOCKS AND GAMMA RAY BURSTS

    SciTech Connect

    Eichler, David; Guetta, Dafne; Pohl, Martin

    2010-10-10

    The statistical distribution of energies among particles responsible for long gamma-ray burst (GRB) emission is analyzed in light of recent results of the Fermi Observatory. The all-sky flux, F{sub {gamma}}, recorded by the Gamma-Ray Burst Monitor (GBM) is shown, despite its larger energy range, to be not significantly larger than that reported by the Burst and Transient Explorer, suggesting a relatively small flux in the 3-30 MeV energy range. The present-day energy input rate in {gamma}-rays recorded by the GBM from long GRBs is found, assuming star formation rates in the literature, to be W-dot(0)=0.5 F{sub {gamma}H}/c=5x10{sup 42}erg Mpc{sup -3} yr{sup -1}. The Large Area Telescope fluence, when observed, is about 5%-10% per decade of the total, in good agreement with the predictions of saturated, nonlinear shock acceleration. The high-energy component of long GRBs, as measured by Fermi, is found to contain only {approx}10{sup -2.5} of the energy needed to produce ultrahigh-energy cosmic rays (UHECRs) above 4 EeV, assuming the latter to be extragalactic, when various numerical factors are carefully included, if the cosmic-ray source spectrum has a spectral index of -2. The observed {gamma}-ray fraction of the required UHECR energy is even smaller if the source spectrum is softer than E {sup -2}. The AMANDA II limits rule out such a GRB origin for UHECRs if much more than 10{sup -2} of the cosmic-ray energy goes into neutrinos that are within, and simultaneous with, the {gamma}-ray beam. It is suggested that 'orphan' neutrinos out of the {gamma}-ray beam might be identifiable via orphan afterglow or other wide angle signatures of GRBs in lieu of coincidence with prompt {gamma}-rays, and it is recommended that feasible single neutrino trigger criteria be established to search for such coincidences.

  9. High voltage stability performance of a gamma ray detection device

    SciTech Connect

    Abdullah, Nor Arymaswati; Lombigit, Lojius; Rahman, Nur Aira Abd

    2014-02-12

    An industrial grade digital radiation survey meter device is currently being developed at Malaysian Nuclear Agency. This device used a cylindrical type Geiger Mueller (GM) which acts as a detector. GM detector operates at relatively high direct current voltages depend on the type of GM tube. This thin/thick walled cylindrical type of GM tube operates at 450-650 volts range. Proper value and stability performance of high voltage are important parameters to ensure that this device give a reliable radiation dose measurement. This paper will present an assessment of the stability and performance of the high voltage supply for radiation detector. The assessment is performed using System Identification tools box in MATLAB and mathematical statistics.

  10. High voltage stability performance of a gamma ray detection device

    NASA Astrophysics Data System (ADS)

    Abdullah, Nor Arymaswati; Lombigit, Lojius; Rahman, Nur Aira Abd

    2014-02-01

    An industrial grade digital radiation survey meter device is currently being developed at Malaysian Nuclear Agency. This device used a cylindrical type Geiger Mueller (GM) which acts as a detector. GM detector operates at relatively high direct current voltages depend on the type of GM tube. This thin/thick walled cylindrical type of GM tube operates at 450-650 volts range. Proper value and stability performance of high voltage are important parameters to ensure that this device give a reliable radiation dose measurement. This paper will present an assessment of the stability and performance of the high voltage supply for radiation detector. The assessment is performed using System Identification tools box in MATLAB and mathematical statistics.

  11. SAS-2 High energy gamma-ray observations of the Vela pulsar

    NASA Technical Reports Server (NTRS)

    Thompson, D. J.; Fichtel, C. E.; Kniffen, D. A.; Oegelman, H. B.

    1975-01-01

    The second Small Astronomy Satellite high-energy (35 MeV) gamma-ray telescope detected pulsed gamma-ray emission at the radio period from PSR 0833-45, the Vela pulsar, as well as an unpulsed flux from the Vela region. The pulsed emission consists of two peaks, one following the radio peak by about 13 msec, and the other 0.4 period after the first. The luminosity of the pulsed emission above 100 MeV from Vela is about 0.1 that of the pulsar NP0532 in the Crab nebula, whereas the pulsed emission from Vela at optical wavelengths is less than 0.0004 that from the Crab. The relatively high intensity of the pulsed gamma-ray emission and the double peak structure, compared to the single pulse in the radio emission, suggests that the high energy gamma-ray pulsar emission may be produced under different conditions from those found at lower energies.

  12. High-energy galactic gamma radiation from cosmic rays concentrated in spiral arms

    NASA Technical Reports Server (NTRS)

    Bignami, G. F.; Fichtel, C. E.; Kniffen, D. A.; Thompson, D. J.

    1975-01-01

    A model for the emission of high-energy (exceeding 100 Mev) gamma-rays from the galactic disk has been developed and compared with recent SAS-2 observations. In the calculation, it is assumed that (1) the high energy galactic gamma-rays result primarily from the interaction of cosmic rays with galactic matter, (2) the cosmic-ray density is proportional to the matter density on the scale of galactic arms, and (3) the matter in the Galaxy is distributed in a spiral pattern consistent with density-wave theory and experimental data on the matter distribution that is available, including the 21-cm H I line emission, continuum emission from H II regions, and data currently being used to estimate the H2 density. The calculated galactic-longitude distribution of gamma rays is in good agreement with the SAS-2 observations in relative shape and absolute flux. As a corollary, the nonuniform cosmic-ray distribution of this model tends to support the galactic origin of the fraction of cosmic rays which is important in the production of high-energy photons. Modifications of the basic model show that the gamma-ray flux is relatively sensitive to large variations of the assumed distribution of molecular hydrogen in the Galaxy.

  13. High resolution bone mineral densitometry with a gamma camera

    NASA Technical Reports Server (NTRS)

    Leblanc, A.; Evans, H.; Jhingran, S.; Johnson, P.

    1983-01-01

    A technique by which the regional distribution of bone mineral can be determined in bone samples from small animals is described. The technique employs an Anger camera interfaced to a medical computer. High resolution imaging is possible by producing magnified images of the bone samples. Regional densitometry of femurs from oophorectomised and bone mineral loss.

  14. MEG sensor and source measures of visually induced gamma-band oscillations are highly reliable.

    PubMed

    Tan, H-R M; Gross, J; Uhlhaas, P J

    2016-08-15

    High frequency brain oscillations are associated with numerous cognitive and behavioral processes. Non-invasive measurements using electro-/magnetoencephalography (EEG/MEG) have revealed that high frequency neural signals are heritable and manifest changes with age as well as in neuropsychiatric illnesses. Despite the extensive use of EEG/MEG-measured neural oscillations in basic and clinical research, studies demonstrating test-retest reliability of power and frequency measures of neural signals remain scarce. Here, we evaluated the test-retest reliability of visually induced gamma (30-100Hz) oscillations derived from sensor and source signals acquired over two MEG sessions. The study required participants (N=13) to detect the randomly occurring stimulus acceleration while viewing a moving concentric grating. Sensor and source MEG measures of gamma-band activity yielded comparably strong reliability (average intraclass correlation, ICC=0.861). Peak stimulus-induced gamma frequency (53-72Hz) yielded the highest measures of stability (ICCsensor=0.940; ICCsource=0.966) followed by spectral signal change (ICCsensor=0.890; ICCsource=0.893) and peak frequency bandwidth (ICCsensor=0.856; ICCsource=0.622). Furthermore, source-reconstruction significantly improved signal-to-noise for spectral amplitude of gamma activity compared to sensor estimates. Our assessments highlight that both sensor and source derived estimates of visually induced gamma-band oscillations from MEG signals are characterized by high test-retest reliability, with source derived oscillatory measures conferring an improvement in the stability of peak-frequency estimates. Importantly, our finding of high test-retest reliability supports the feasibility of pharma-MEG studies and longitudinal aging or clinical studies. PMID:27153980

  15. MEG sensor and source measures of visually induced gamma-band oscillations are highly reliable.

    PubMed

    Tan, H-R M; Gross, J; Uhlhaas, P J

    2016-08-15

    High frequency brain oscillations are associated with numerous cognitive and behavioral processes. Non-invasive measurements using electro-/magnetoencephalography (EEG/MEG) have revealed that high frequency neural signals are heritable and manifest changes with age as well as in neuropsychiatric illnesses. Despite the extensive use of EEG/MEG-measured neural oscillations in basic and clinical research, studies demonstrating test-retest reliability of power and frequency measures of neural signals remain scarce. Here, we evaluated the test-retest reliability of visually induced gamma (30-100Hz) oscillations derived from sensor and source signals acquired over two MEG sessions. The study required participants (N=13) to detect the randomly occurring stimulus acceleration while viewing a moving concentric grating. Sensor and source MEG measures of gamma-band activity yielded comparably strong reliability (average intraclass correlation, ICC=0.861). Peak stimulus-induced gamma frequency (53-72Hz) yielded the highest measures of stability (ICCsensor=0.940; ICCsource=0.966) followed by spectral signal change (ICCsensor=0.890; ICCsource=0.893) and peak frequency bandwidth (ICCsensor=0.856; ICCsource=0.622). Furthermore, source-reconstruction significantly improved signal-to-noise for spectral amplitude of gamma activity compared to sensor estimates. Our assessments highlight that both sensor and source derived estimates of visually induced gamma-band oscillations from MEG signals are characterized by high test-retest reliability, with source derived oscillatory measures conferring an improvement in the stability of peak-frequency estimates. Importantly, our finding of high test-retest reliability supports the feasibility of pharma-MEG studies and longitudinal aging or clinical studies.

  16. A New View of the High Energy Gamma-ray Sky with the Fermi Gamma-Ray Space Telescope

    NASA Technical Reports Server (NTRS)

    McEnery, Julie

    2010-01-01

    This slide presentation reviews some of the findings that have been made possible by the use of the Fermi Gamma-ray Space Telescope. It describes the current status of the Fermi Telescope and reviews some of the science highlights.

  17. Phase Stability of Epsilon and Gamma Hniw (CL-20) at High-Pressure and Temperature

    NASA Astrophysics Data System (ADS)

    Gump, Jared C.; Stoltz, Chad A.; Peiris, Suhithi M.

    2007-12-01

    Hexanitrohexaazaisowurtzitane (CL-20) is one of the few ingredients developed since World War II to be considered for transition to military use. Five polymorphs have been identified for CL-20 by FTIR measurements (α, β, γ, ɛ, ζ). As CL-20 is transitioned into munitions it will become necessary to predict its response under conditions of detonation, for performance evaluation. Such predictive modeling requires a phase diagram and basic thermodynamic properties of the various phases at high pressure and temperature. Therefore, the epsilon and gamma phases of CL-20 at static high-pressure and temperature were investigated using synchrotron angle-dispersive x-ray diffraction experiments. The samples were compressed and heated using diamond anvil cells (DAC). Pressures and temperatures achieved were around 5 GPa and 240 °C, respectively. The epsilon phase was stable to 6.3 GPa at ambient temperature. When heated at ambient pressure the epsilon phase was sustained to a temperature of 120 °C then underwent a transition to the gamma phase above 125 °C and then thermal decomposition occurred above 150 °C. Upon compression, the gamma phase underwent a phase transition at both ambient temperature and 140 °C. Pressure—volume data for the epsilon and gamma phase at ambient temperature and the epsilon phase at 75 °C were fit to the Birch-Murnaghan formalism to obtain isothermal equations of state.

  18. The Impact of Electromagnetic Cascades of Very-high Energy Gamma Rays on the Extragalactic Gamma-ray Background

    NASA Technical Reports Server (NTRS)

    Venters, Tonia

    2012-01-01

    As very high energy (VHE) photons propagate through the extragalactic background light (EBL), they interact with the soft photons of the EBL and initiate electromagnetic cascades of photons and electrons. The collective intensity of a cosmological population emitting at VHEs (such as blazars) will be attenuated at the highest energies through interactions with the EBL and enhanced at lower energies by the resulting cascade. As such, depending on the space density and spectra of the sources and the model of the EBL, cascade radiation can provide a significant contribution to the extragalactic gamma-ray background (EGB). Through deflections of the charged particles of the cascade, an intergalactic magnetic field (IGMF) may leave an imprint on the anisotropy properties of the EGB. The impact of a strong IGMF is to isotropize lower energy cascade photons, inducing a modulation in the anisotropy energy spectrum of the EGB. We discuss the implications of cascade radiation for the origins of the EGB and the nature of the IGMF, as well as insight that will be provided by data from the Fermi Large Area Telescope in the upcoming years.

  19. Ultra high energy gamma rays, cosmic rays and neutrinos from accreting degenerate stars

    NASA Technical Reports Server (NTRS)

    Brecher, K.; Chanmugam, G.

    1985-01-01

    Super-Eddington accretion for a recently proposed unipolar induction model of cosmic ray acceleration in accreting binary star systems containing magnetic white dwarfs or neutron stars is considered. For sufficiently high accretion rates and low magnetic fields, the model can account for: (1) acceleration of cosmic ray nuclei up to energies of 10 to the 19th power eV; (2) production of more or less normal solar cosmic ray composition; (3) the bulk of cosmic rays observed with energies above 1 TeV, and probably even down to somewhat lower energies as well; and (4) possibly the observed antiproton cosmic ray flux. It can also account for the high ultra high energy (UHE) gamma ray flux observed from several accreting binary systems (including Cygnus X-3), while allowing the possibility of an even higher neutrino flux from these sources, with L sub nu/L sub gamma is approximately 100.

  20. A field-deployable gamma-ray spectrometer utilizing high pressure xenon

    SciTech Connect

    Smith, G.C.; Mahler, G.J.; Yu, Bo; Kane, W.R.; Lemley, J.R.

    1997-05-01

    Most nuclear materials in the nuclear energy, safeguards, arms control, and nonproliferation regimes emit gamma rays with a unique signature. Currently, two categories of spectrometers are available to evaluate these materials: (1) Semiconductors, with excellent energy resolution, which operate at cryogenic temperatures. (2) Scintillation detectors, which function at ambient temperature, but with poor energy resolution. A detector which functions for extended periods in a range of environments, with an energy resolution superior to that of a scintillation spectrometer, would have evident utility. Recently, in the research community, such a device has evolved, an ionization chamber utilizing xenon gas at very high pressure (60 atm). Its energy resolution, typically, is 20 keV for the 661 keV gamma ray of {sup 137}Cs. With high xenon density and its high atomic number (Z=54), and superior energy resolution, its sensitivity is comparable to that of a scintillator.

  1. High-precision source location of the 1978 November 19 gamma-ray burst

    NASA Technical Reports Server (NTRS)

    Cline, T. L.; Desai, U. D.; Teegarden, B. J.; Pizzichini, G.; Evans, W. D.; Klebesadel, R. W.; Laros, J. G.; Barat, C.; Hurley, K.; Niel, M.

    1981-01-01

    The celestial source location of the November 19, 1978, intense gamma ray burst has been determined from data obtained with the interplanetary gamma-ray sensor network by means of long-baseline wave front timing instruments. Each of the instruments was designed for studying events with observable spectra of approximately greater than 100 keV, and each provides accurate event profile timing in the several millisecond range. The data analysis includes the following: the triangulated region is centered at (gamma, delta) 1950 = (1h16m32s, -28 deg 53 arcmin), at -84 deg galactic latitude, where the star density is very low and the obscuration negligible. The gamma-ray burst source region, consistent with that of a highly polarized radio source described by Hjellming and Ewald (1981), may assist in the source modeling and may facilitate the understanding of the source process. A marginally identifiable X-ray source was also found by an Einstein Observatory investigation. It is concluded that the burst contains redshifted positron annihilation and nuclear first-excited iron lines, which is consistent with a neutron star origin.

  2. Gamma-resonance Contraband Detection using a high current tandem accelerator

    SciTech Connect

    Milton, B. F.; Beis, J.; Dale, D.; Rogers, J.; Ruegg, R.; Debiak, T.; Kamykowski, E.; Melnychuk, S.; Rathke, J.; Sredniawski, J.

    1999-04-26

    TRIUMF and Northrop Grumman have developed a new system for the detection of concealed explosives and drugs. This Contraband Detection System (CDS) is based on the resonant absorption by {sup 14}N of gammas produced using {sup 13}C(p,{gamma}){sup 14}N. The chosen reaction uses protons at 1.75 MeV and the gammas have an energy of 9.17 MeV. By measuring both the resonant and the non-resonant absorption using detectors with good spatial resolution, and applying standard tomographic techniques, we are able to produce 3D images of both the nitrogen partial density and the total density. The images together may be utilized with considerable confidence to determine if small amounts of nitrogen based explosives, heroin or cocaine are present in the interrogated containers. Practical Gamma Resonant Absorption (GRA) scanning requires an intense source of protons. However this proton source must also be very stable, have low energy spread, and have good spatial definition. These demands suggested a tandem as the accelerator of choice. We have therefore constructed a 2 MeV H{sup -} tandem optimized for high current (10 mA) operation, while minimizing the overall size of the accelerator. This has required several special innovations which will be presented in the paper. We will also present initial commissioning results.

  3. VERY HIGH ENERGY {gamma}-RAY EMISSION FROM PASSIVE SUPERMASSIVE BLACK HOLES: CONSTRAINTS FOR NGC 1399

    SciTech Connect

    Pedaletti, G.; Wagner, S. J.; Rieger, F. M.

    2011-09-10

    Very high energy (VHE, >100 GeV) {gamma}-rays are expected to be emitted from the vicinity of supermassive black holes (SMBHs), irrespective of their activity state. In the magnetosphere of rotating SMBH, efficient acceleration of charged particles can take place through various processes. These particles could reach energies up to E {approx} 10{sup 19} eV. VHE {gamma}-ray emission from these particles is then feasible via leptonic or hadronic processes. Therefore, passive systems, where the lack of a strong photon field allows the VHE {gamma}-rays to escape, are expected to be detected by Cherenkov telescopes. We present results from recent VHE experiments on the passive SMBH in the nearby elliptical galaxy NGC 1399. No {gamma}-ray signal has been found, neither by the H.E.S.S. experiment nor in the Fermi data analyzed here. We discuss possible implications for the physical characteristics of the system. We conclude that in a scenario where particles are accelerated in vacuum gaps in the magnetosphere, only a fraction {approx}0.3 of the gap is available for particle acceleration, indicating that the system is unlikely to be able to accelerate protons up to E {approx} 10{sup 19} eV.

  4. High-spin structure and multiphonon {gamma} vibrations in very neutron-rich {sup 114}Ru

    SciTech Connect

    Yeoh, E. Y.; Wang, J. G.; Ding, H. B.; Gu, L.; Xu, Q.; Xiao, Z. G.; Zhu, S. J.; Hamilton, J. H.; Li, K.; Ramayya, A. V.; Hwang, J. K.; Liu, Y. X.; Liu, S. H.; Sheikh, J. A.; Bhat, G. H.; Luo, Y. X.; Rasmussen, J. O.; Lee, I. Y.; Ma, W. C.

    2011-05-15

    High-spin levels of the neutron-rich {sup 114}Ru have been investigated by measuring the prompt {gamma} rays in the spontaneous fission of {sup 252}Cf. The ground-state band and one-phonon {gamma}-vibrational band have been extended up to 14{sup +} and 9{sup +}, respectively. Two levels are proposed as the members of a two-phonon {gamma}-vibrational band. A back bending (band crossing) has been observed in the ground-state band at ({h_bar}/2{pi}){omega}{approx_equal} 0.40 MeV. Using the triaxial deformation parameters, the cranked shell model calculations indicate that this back bending in {sup 114}Ru should originate from the alignment of a pair of h{sub 11/2} neutrons. Triaxial projected shell model calculations for the {gamma}-vibrational band structures of {sup 114}Ru are in good agreement with the experimental data. However, when using the oblate deformation parameters, both of the above-calculated results are not in agreement with the experimental data.

  5. Nonthermal processes around collapsed objects: High energy gamma ray sources in the radio sky

    NASA Technical Reports Server (NTRS)

    Helfand, David J.; Ruderman, Malvin; Applegate, James H.; Becker, Robert H.

    1993-01-01

    In our proposal responding to the initial Guest Observer NRA for the Compton Gamma Ray Observatory, 'Nonthermal Processes Around Collapsed Objects: High Energy Gamma Ray Sources in the Radio Sky', we stated that 'At high energies - the identity of the principal Galactic source population remains unknown' although the 'one certain source of high energy emission is young radio pulsars'. These two statements remain true, although at this writing, eighteen months after the beginning of the Compton allsky survey, much of the gamma-ray data required to greatly extend our knowledge of the Galaxy's high energy emission has been collected. The thrust of the program supported by our grant was to collect and analyze a complementary set of data on the Milky Way at radio wavelengths in order to help identify the dominant Pop 1 component of the Galaxy's gamma ray sources, and to pursue theoretical investigations on the origins and emission mechanisms of young pulsars, the one component of this population identified to date. We summarize here our accomplishments under the grant. In Section 2, we describe our VLA surveys of the Galactic Plane along with the current status of the radio source catalogs derived therefrom; unfortunately, owing to the TDRSS antenna problem and subsequent extension of the Sky Survey, we were not able to carry out a comparison with the EGRET data directly, although everything is now in place to do so as soon as it becomes available. In Section 2, we summarize our progress on the theoretical side, including the substantial completion of a dissertation on pulsar origins and work on the high energy emission mechanisms of isolated pulsars. We list the personnel supported by the grant in section 4 and provide a complete bibliography of publications supported in whole or in part by the grant in the final section.

  6. Spatiotemporal dynamics of affective picture processing revealed by intracranial high-gamma modulations.

    PubMed

    Boucher, Olivier; D'Hondt, Fabien; Tremblay, Julie; Lepore, Franco; Lassonde, Maryse; Vannasing, Phetsamone; Bouthillier, Alain; Nguyen, Dang Khoa

    2015-01-01

    Our comprehension of the neural mechanisms underlying emotional information processing has largely benefited from noninvasive electrophysiological and functional neuroimaging techniques in recent years. However, the spatiotemporal dynamics of the neural events occurring during emotional processing remain imprecise due to the limited combination of spatial and temporal resolution provided by these techniques. This study examines the modulations of high-frequency activity of intracranial electroencephalography recordings associated with affective picture valence, in epileptic patients awaiting neurosurgery. Recordings were obtained from subdural grids and depth electrodes in eight patients while they viewed a series of unpleasant, pleasant and neutral pictures from the International Affective Picture System. Broadband high-gamma (70-150 Hz) power was computed for separate 100-ms time windows and compared according to ratings of emotional valence. Compared to emotionally neutral or pleasant pictures, unpleasant stimuli were associated with an early and long-lasting (≈200-1,000 ms) bilateral increase in high-gamma activity in visual areas of the occipital and temporal lobes, together with a late and transient (≈500-800 ms) decrease found bilaterally in the lateral prefrontal cortex (PFC). Pleasant pictures were associated with increased gamma activity in the occipital cortex, compared to the emotionally neutral stimuli. Consistent with previous studies, our results provide direct evidence of emotion-related modulations in the visual ventral pathway during picture processing. Results in the lateral PFC also shed light on the neural mechanisms underlying its role in negative emotions processing. This study demonstrates the utility of intracranial high-gamma modulations to study emotional process with a high spatiotemporal precision.

  7. High Energy Neutrinos and Cosmic-Rays From Low-Luminosity Gamma-Ray Bursts?

    SciTech Connect

    Murase, Kohta; Ioka, Kunihito; Nagataki, Shigehiro; Nakamura, Takashi; /Kyoto U.

    2006-07-10

    The recently discovered gamma-ray burst (GRB) 060218/SN 2006aj is classified as an X-ray Flash with very long duration driven possibly by a neutron star. Since GRB 060218 is very near {approx} 140 Mpc and very dim, one-year observation by Swift suggests that the true rate of GRB 060218-like events might be very high so that such low luminosity GRBs (LL-GRBs) might form a different population of GRBs from the cosmological high luminosity GRBs (HL-GRBs). We found that the high energy neutrino background from such LL-GRBs could be comparable with or larger than that from HL-GRBs. If each neutrino event is detected by IceCube, later optical-infrared follow-up observations such as by Subaru could identify a Type Ibc supernova associated with LL-GRBs, even if gamma- and X-rays are not observed by Swift. This is in a sense a new window from neutrino astronomy, which might enable us to confirm the existence of LL-GRBs and to obtain information about their rate and origin. We also argue LL-GRBs as high energy gamma-ray and cosmic-ray sources.

  8. Pulse Rise Time Characterization of a High Pressure Xenon Gamma Detector for use in Resolution Enhancement

    SciTech Connect

    TROYER, G.L.

    2000-08-25

    High pressure xenon ionization chamber detectors are possible alternatives to traditional thallium doped sodium iodide (NaI(Tl)) and hyperpure germanium as gamma spectrometers in certain applications. Xenon detectors incorporating a Frisch grid exhibit energy resolutions comparable to cadmium/zinc/telluride (CZT) (e.g. 2% {at} 662keV) but with far greater sensitive volumes. The Frisch grid reduces the position dependence of the anode pulse risetimes, but it also increases the detector vibration sensitivity, anode capacitance, voltage requirements and mechanical complexity. We have been investigating the possibility of eliminating the grid electrode in high-pressure xenon detectors and preserving the high energy resolution using electronic risetime compensation methods. A two-electrode cylindrical high pressure xenon gamma detector coupled to time-to-amplitude conversion electronics was used to characterize the pulse rise time of deposited gamma photons. Time discrimination was used to characterize the pulse rise time versus photo peak position and resolution. These data were collected to investigate the effect of pulse rise time compensation on resolution and efficiency.

  9. Superconducting gamma and fast-neutron spectrometers with high energy resolution

    DOEpatents

    Friedrich, Stephan; , Niedermayr, Thomas R.; Labov, Simon E.

    2008-11-04

    Superconducting Gamma-ray and fast-neutron spectrometers with very high energy resolution operated at very low temperatures are provided. The sensor consists of a bulk absorber and a superconducting thermometer weakly coupled to a cold reservoir, and determines the energy of the incident particle from the rise in temperature upon absorption. A superconducting film operated at the transition between its superconducting and its normal state is used as the thermometer, and sensor operation at reservoir temperatures around 0.1 K reduces thermal fluctuations and thus enables very high energy resolution. Depending on the choice of absorber material, the spectrometer can be configured either as a Gamma-spectrometer or as a fast-neutron spectrometer.

  10. Search for Very High Energy Emission from Gamma-Ray Bursts using Milagro

    SciTech Connect

    Saz Parkinson, P. M.

    2007-07-12

    Gamma-Ray Bursts (GRBs) have been detected at GeV energies by EGRET and models predict emission at > 100 GeV. Milagro is a wide field (2 sr) high duty cycle (> 90%) ground based water Cherenkov detector that records extensive air showers in the energy range 100 GeV to 100 TeV. We have searched for very high energy emission from a sample of 106 gamma-ray bursts (GRB) detected since the beginning of 2000 by BATSE, BeppoSax, HETE-2, INTEGRAL, Swift or the IPN. No evidence for emission from any of the bursts has been found and we present upper limits from these bursts.

  11. Very-High-Energy Gamma-Ray Observations of M 31 with VERITAS

    NASA Astrophysics Data System (ADS)

    Bird, R.

    2014-07-01

    VERITAS, an array of 12 m imaging atmospheric Cherenkov telescopes in southern Arizona, is one of the world's most sensitive detectors of astrophysical very-high-energy (VHE, > 100 GeV) gamma rays. We present the current status of the VERITAS observations of M 31 (Andromeda Galaxy) including an upper limit on the VHE flux and a comparison with theoretical predictions. The dominant mechanism for the formation of diffuse gamma rays is expected to be through the inelastic collision of high-energy cosmic rays with the interstellar medium (ISM). M 31 provides an opportunity to probe this mechanism due to its proximity and spatial extent, with the VERITAS point-spread function sufficient to resolve the ISM dense star-forming ring and the galaxy core with its multiple supernova remnants.

  12. Perspectives for neutron and gamma spectroscopy in high power laser driven experiments at ELI-NP

    NASA Astrophysics Data System (ADS)

    Negoita, F.; Gugiu, M.; Petrascu, H.; Petrone, C.; Pietreanu, D.; Fuchs, J.; Chen, S.; Higginson, D.; Vassura, L.; Hannachi, F.; Tarisien, M.; Versteegen, M.; Antici, P.; Balabanski, D.; Balascuta, S.; Cernaianu, M.; Dancus, I.; Gales, S.; Neagu, L.; Petcu, C.; Risca, M.; Toma, M.; Turcu, E.; Ursescu, D.

    2015-02-01

    The measurement of energy spectra of neutrons and gamma rays emitted by nuclei, together with charge particles spectroscopy, are the main tools for understanding nuclear phenomena occurring also in high power laser driven experiments. However, the large number of particles emitted in a very short time, in particular the strong X-rays flash produced in laser-target interaction, impose adaptation of technique currently used in nuclear physics experiment at accelerator based facilities. These aspects are discussed (Section 1) in the context of proposed studies at high power laser system of ELI-NP. Preliminary results from two experiments performed at Titan (LLNL) and ELFIE (LULI) facilities using plastic scintillators for neutron detection (Section 2) and LaBr3(Ce) scintillators for gamma detection (Section 3) are presented demonstrating the capabilities and the limitations of the employed methods. Possible improvements of these spectroscopic methods and their proposed implementation at ELI-NP will be discussed as well in the last section.

  13. Multipurpose Radiation Resistant Semiconductor Detectors for Alpha, Neutron & Low Energy Gamma Ray Measurements at High Temperatures in High-Intensity Gamma Ray

    SciTech Connect

    Ruddy, Frank H.

    2005-06-01

    Work scheduled under year two of DOE Grant DE-FG02-04ER63734 is on schedule and all year-two milestones have or will be met. Results to date demonstrate that unprecedented silicon carbide (SiC) energy resolution has been obtained, and that SiC detectors may achieve energy resolution that exceeds that obtainable with the best silicon alpha spectrometers. Fast-neutron energy spectrometry measurements indicate that recoil-ion energy spectrometry should be possible with SiC detectors. Furthermore, SiC detectors have been demonstrated to perform well even after gamma-ray exposures of 1.E09 Rad. This result and the previously demonstrated capability of SiC detectors to operate in elevated-temperature environments are very promising for potential DOE EMSP applications. A new class of multipurpose, radiation-resistant semiconductor detectors that can be used in elevated-temperature and high-radiation environments is being developed under this grant. These detectors, based on silicon carbide (SiC) semiconductor are designed to have larger active volumes than previously available SiC detectors, and are being tested for their response to alpha particles, X-rays and low energy gamma rays, and fast neutrons.

  14. Modeling high-energy gamma-rays from the Fermi Bubbles

    SciTech Connect

    Splettstoesser, Megan

    2015-09-17

    In 2010, the Fermi Bubbles were discovered at the galactic center of the Milky Way. These giant gamma-ray structures, extending 55° in galactic latitude and 20°-30° in galactic longitude, were not predicted. We wish to develop a model for the gamma-ray emission of the Fermi Bubbles. To do so, we assume that second order Fermi acceleration requires charged particles and irregular magnetic fields- both of which are present in the disk of the Milky Way galaxy. By solving the steady-state case of the transport equation, I compute the proton spectrum due to second order Fermi acceleration. I compare the analytical solutions of the proton spectrum to a numerical solution. I find that the numerical solution to the transport equation converges to the analytical solution in all cases. The gamma-ray spectrum due to proton-proton interaction is compared to Fermi Bubble data (from Ackermann et al. 2014), and I find that second order Fermi acceleration is a good fit for the gamma-ray spectrum of the Fermi Bubbles at low energies with an injection source term of S = 1.5 x 10⁻¹⁰ GeV⁻¹cm⁻³yr⁻¹. I find that a non-steady-state solution to the gamma-ray spectrum with an injection source term of S = 2 x 10⁻¹⁰ GeV⁻¹cm⁻³yr⁻¹ matches the bubble data at high energies.

  15. Determination of impurities in (124)I samples by high resolution gamma spectrometry.

    PubMed

    de Almeida, M C M; da Silva, R L; Delgado, J U; Poledna, R; de Araújo, M T F; Laranjeira, A S; de Veras, E; Braghirolli, A M S; dos Santos, G R; Lopes, R T

    2016-03-01

    (124)I is a radionuclide used in the diagnosis of tumors. The National Health Agency requires identification and activity measurement of impurities. Using gamma spectrometry with an efficiency calibrated high-purity germanium detector, impurities (125)I and (126)I in an (1)(24)I production sample were identified. Activity ratios of (125)I and (126)I to (124)I were approximately 0.5% and 98%, respectively. PMID:26653211

  16. Diffuse emission of high-energy neutrinos from gamma-ray burst fireballs

    SciTech Connect

    Tamborra, Irene; Ando, Shin'ichiro E-mail: s.ando@uva.nl

    2015-09-01

    Gamma-ray bursts (GRBs) have been suggested as possible sources of the high-energy neutrino flux recently detected by the IceCube telescope. We revisit the fireball emission model and elaborate an analytical prescription to estimate the high-energy neutrino prompt emission from pion and kaon decays, assuming that the leading mechanism for the neutrino production is lepto-hadronic. To this purpose, we include hadronic, radiative and adiabatic cooling effects and discuss their relevance for long- (including high- and low-luminosity) and short-duration GRBs. The expected diffuse neutrino background is derived, by requiring that the GRB high-energy neutrino counterparts follow up-to-date gamma-ray luminosity functions and redshift evolutions of the long and short GRBs. Although dedicated stacking searches have been unsuccessful up to now, we find that GRBs could contribute up to a few % to the observed IceCube high-energy neutrino flux for sub-PeV energies, assuming that the latter has a diffuse origin. Gamma-ray bursts, especially low-luminosity ones, could however be the main sources of the IceCube high-energy neutrino flux in the PeV range. While high-luminosity and low-luminosity GRBs have comparable intensities, the contribution from the short-duration component is significantly smaller. Our findings confirm the most-recent IceCube results on the GRB searches and suggest that larger exposure is mandatory to detect high-energy neutrinos from high-luminosity GRBs in the near future.

  17. Effects of L-dopa priming on cortical high beta and high gamma oscillatory activity in a rodent model of Parkinson’s disease

    PubMed Central

    Dupre, Kristin B.; Cruz, Ana V.; McCoy, Alex J.; Delaville, Claire; Gerber, Colin M.; Eyring, Katherine W.; Walters, Judith R.

    2016-01-01

    Prolonged L-dopa treatment in Parkinson’s disease (PD) often leads to the expression of abnormal involuntary movements known as L-dopa-induced dyskinesia. Recently, dramatic 80 Hz oscillatory local field potential (LFP) activity within the primary motor cortex has been linked to dyskinetic symptoms in a rodent model of PD and attributed to stimulation of cortical dopamine D1 receptors. To characterize the relationship between high gamma (70–110 Hz) cortical activity and the development of L-dopa-induced dyskinesia, cortical LFP and spike signals were recorded in hemiparkinsonian rats treated with L-dopa for 7 days, and dyskinesia was quantified using the abnormal involuntary movements (AIMs) scale. The relationship between high gamma and dyskinesia was further probed by assessment of the effects of pharmacological agents known to induce or modulate dyskinesia expression. Findings demonstrate that AIMs and high gamma LFP power increase between days 1 and 7 of L-dopa priming. Notably, high beta (25–35 Hz) power associated with parkinsonian bradykinesia decreased as AIMs and high gamma LFP power increased during priming. After priming, rats were treated with the D1 agonist SKF81297 and the D2 agonist quinpirole. Both dopamine agonists independently induced AIMs and high gamma cortical activity that were similar to that induced by L-dopa, showing that this LFP activity is neither D1 nor D2 receptor specific. The serotonin 1A receptor agonist 8-OH-DPAT reduced L-dopa- and DA agonist-induced AIMs and high gamma power to varying degrees, while the serotonin 1A antagonist WAY100635 reversed these effects. Unexpectedly, as cortical high gamma power increased, phase locking of cortical pyramidal spiking to high gamma oscillations decreased, raising questions regarding the neural substrate(s) responsible for high gamma generation and the functional correlation between high gamma and dyskinesia. PMID:26586558

  18. High energy gamma-ray spectroscopy with LaBr3 scintillation detectors

    NASA Astrophysics Data System (ADS)

    Quarati, F. G. A.; Owens, Alan; Dorenbos, P.; de Haas, J. T. M.; Benzoni, G.; Blasi, N.; Boiano, C.; Brambilla, S.; Camera, F.; Alba, R.; Bellia, G.; Maiolino, C.; Santonocito, D.; Ahmed, M.; Brown, N.; Stave, S.; Weller, H. R.; Wu, Y. K.

    2011-02-01

    Lanthanum bromide scintillation detectors produce very high light outputs (˜60,000 ph/MeV) within a very short decay time (typically ˜20 ns) which means that high instantaneous currents can be generated in the photocathode and dynode chain of the photomultiplier tube (PMT) used for the scintillation readout. The net result is that signal saturation can occur long before the recommended PMT biasing conditions can be reached.In search of an optimized light readout system for LaBr3, we have tested and compared two different PMT configurations for detection of gamma-rays up to 15 MeV. This range was chosen as being appropriate for gamma-ray remote sensing and medium energy nuclear physics applications. The experiments were conducted at two facilities: the Laboratori Nazionali del Sud (LNS) in Catania, Italy [1] and the High Intensity Gamma-ray Source (HIγS) at Triangle University Nuclear Laboratory, in Durham, North Carolina, USA [2].The PMT configurations we have tested are (1) a standard dynode chain operated under-biased; (2) a 4-stage reduced chain operated at nominal inter-dynode bias.The results are that shortening the number of active stages, as in configuration (2), has advantages in preserving energy resolution and avoiding PMT saturation over a large energy range.However, the use of an under-biased PMT, configuration (1), can still be considered a satisfactory solution, at least in the case of PMTs manufactured by Photonis.The results of this study will be used in support of the Mercury Gamma-ray and Neutron Spectrometer (MGNS) on board of BepiColombo, the joint ESA/JAXA mission to Mercury, scheduled for launch in 2014.

  19. High resolution x-ray and gamma ray imaging using diffraction lenses with mechanically bent crystals

    DOEpatents

    Smither, Robert K.

    2008-12-23

    A method for high spatial resolution imaging of a plurality of sources of x-ray and gamma-ray radiation is provided. High quality mechanically bent diffracting crystals of 0.1 mm radial width are used for focusing the radiation and directing the radiation to an array of detectors which is used for analyzing their addition to collect data as to the location of the source of radiation. A computer is used for converting the data to an image. The invention also provides for the use of a multi-component high resolution detector array and for narrow source and detector apertures.

  20. A data acquisition and control system for high-speed gamma-ray tomography

    NASA Astrophysics Data System (ADS)

    Hjertaker, B. T.; Maad, R.; Schuster, E.; Almås, O. A.; Johansen, G. A.

    2008-09-01

    A data acquisition and control system (DACS) for high-speed gamma-ray tomography based on the USB (Universal Serial Bus) and Ethernet communication protocols has been designed and implemented. The high-speed gamma-ray tomograph comprises five 500 mCi 241Am gamma-ray sources, each at a principal energy of 59.5 keV, which corresponds to five detector modules, each consisting of 17 CdZnTe detectors. The DACS design is based on Microchip's PIC18F4550 and PIC18F4620 microcontrollers, which facilitates an USB 2.0 interface protocol and an Ethernet (IEEE 802.3) interface protocol, respectively. By implementing the USB- and Ethernet-based DACS, a sufficiently high data acquisition rate is obtained and no dedicated hardware installation is required for the data acquisition computer, assuming that it is already equipped with a standard USB and/or Ethernet port. The API (Application Programming Interface) for the DACS is founded on the National Instrument's LabVIEW® graphical development tool, which provides a simple and robust foundation for further application software developments for the tomograph. The data acquisition interval, i.e. the integration time, of the high-speed gamma-ray tomograph is user selectable and is a function of the statistical measurement accuracy required for the specific application. The bandwidth of the DACS is 85 kBytes s-1 for the USB communication protocol and 28 kBytes s-1 for the Ethernet protocol. When using the iterative least square technique reconstruction algorithm with a 1 ms integration time, the USB-based DACS provides an online image update rate of 38 Hz, i.e. 38 frames per second, whereas 31 Hz for the Ethernet-based DACS. The off-line image update rate (storage to disk) for the USB-based DACS is 278 Hz using a 1 ms integration time. Initial characterization of the high-speed gamma-ray tomograph using the DACS on polypropylene phantoms is presented in the paper.

  1. The Third EGRET Catalog of High-Energy Gamma-Ray Sources

    NASA Technical Reports Server (NTRS)

    Hartman, R. C.; Bertsch, D. L.; Bloom, S. D.; Chen, A. W.; Deines-Jones, P.; Esposito, J. A.; Fichtel, C. E.; Friedlander, D. P.; Hunter, S. D.; McDonald, L. M.; Sreekumar, P.; Thompson, D. J.; Jones, B. B.; Lin, Y. C.; Michelson, P. F.; Nolan, P. L.; Tompkins, W. F.; Kanbach, G.; Mayer-Hasselwander, H. A.; Muecke, A.

    1998-01-01

    The third catalog of high-energy gamma-ray sources detected by the EGRET telescope on the Compton Gamma Ray Observatory includes data from 1991 April 22 to 1995 October 3 (Cycles 1, 2, 3, and 4 of the mission). In addition to including more data than the second EGRET catalog (Thompson et al. 1995) and its supplement (Thompson et al. 1996), this catalog uses completely reprocessed data (to correct a number of mostly minimal errors and problems). The 271 sources (E greater than 100 MeV) in the catalog include the single 1991 solar flare bright enough to be detected as a source, the Large Magellanic Cloud, five pulsars, one probable radio galaxy detection (Cen A), and 66 high-confidence identifications of blazars (BL Lac objects, flat-spectrum radio quasars, or unidentified flat-spectrum radio sources). In addition, 27 lower-confidence potential blazar identifications are noted. Finally, the catalog contains 170 sources not yet identified firmly with known objects, although potential identifications have been suggested for a number of those. A figure is presented that gives approximate upper limits for gamma-ray sources at any point in the sky, as well as information about sources listed in the second catalog and its supplement which do not appear in this catalog.

  2. The Third EGRET Catalog of High-Energy Gamma-Ray Sources

    NASA Technical Reports Server (NTRS)

    Hartman, R. C.; Bertsch, D. L.; Bloom, S. D.; Chen, A. W.; Deines-Jones, P.; Esposito, J. A.; Fichtel, C. E.; Friedlander, D. P.; Hunter, S. D.; McDonald, L. M.; Sreekumar, P.; Thompson, D. J.; Jones, B. B.; Lin, Y. C.; Michelson, P. F.; Nolan, P. L.; Tompkins, W. F.; Kanbach, G.; Mayer-Hasselwander, A.; Muecke, A.

    1998-01-01

    The third catalog of high-energy gamma-ray sources detected by the EGRET telescope on the Compton Gamma Ray Observatory includes data from 1991 April 22 to 1995 October 3 (Cycles 1, 2, 3, and 4 of the mission). In addition to including more data than the second EGRET catalog and its supplement, this catalog uses completely reprocessed data (to correct a number of mostly minimal errors and problems). The 271 sources (E greater than 100 MeV) in the catalog include the single 1991 solar flare bright enough to be detected as a source, the Large Magellanic Cloud, five pulsars, one probable radio galaxy detection (Cen A), and 66 high-confidence identifications of blazars (BL Lac objects, flat-spectrum radio quasars, or unidentified flat-spectrum radio sources). In addition, 27 lower-confidence potential blazar identifications are noted. Finally, the catalog contains 170 sources not yet identified firmly with known objects, although potential identifications have been suggested for a number of those. A figure is presented that gives approximate upper limits for gamma-ray sources at any point in the sky, as well as information about sources listed in the second catalog and its supplement which do not appear in this catalog.

  3. The Multi-Messenger Approach to High Energy Gamma-Ray Sources

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.

    2006-01-01

    Recent studies of the shape and polarization of pulse profiles of young radio pulsars have provided evidence that their radio emission originates in wide cone beams at altitudes that are a significant fraction (1 -10%) of their light cylinder radius. Supporting evidence also comes from the relatively high rate of detection of radio pulsars in young supernova remnants. Such wide radio emission beams will be visible at a much larger range of observer angles than the narrow core components thought to originate at lower altitude and would make young, radio-quiet gamma-ray pulsars more of a rarity than previously thought. Radio emission at high altitudes will also have enhanced distortions due to aberration, retardation and caustics. Using 3D geometrical modeling that includes relativistic effects from pulsar rotation, we study the visibility of such radio cone beams as well as that of the gamma-ray beams predicted by polar cap, slot gap and outer gap models. From the results of this study one can obtain revised predictions for the fraction of Geminga-like, radio quiet pulsars present in the gamma-ray pulsar population.

  4. An observation of the Galactic center region with the HEXAGONE high resolution gamma-ray spectrometer

    NASA Technical Reports Server (NTRS)

    Matteson, J.; Pelling, M.; Bowman, B.; Briggs, M.; Gruber, D.; Lingenfelter, R.; Peterson, L.; Lin, R.; Smith, D.; Feffer, P.

    1991-01-01

    The Galactic center region was observed for 6 hours on May 22, 1989 from a high altitude balloon with the HEXAGONE high resolution gamma-ray spectrometer. The instrument had a 285 sq/cm array of cooled germanium detectors with an energy resolution of 2.2 keV at 511 keV and an 18 deg FWHM field of view. The 511 keV gamma-rays from electron-positron annihilation and 1809 keV gamma-rays from the radioactive decay of Al-26 were observed to have fluxes of 8.9 x 10 exp -4 and 1.9 x 10 exp -4 ph/cm-s, respectively. Continuum emission was detected from 20 to 800 keV and preliminary results have been obtained for the spectrum. Below 120 keV this is well described by power law with a slope of -2.6. In the 120-250 keV band the spectrum contains a broad linelike feature. This is interpreted as the result of Compton backscattering of about 511 keV photons from a compact source of electron-positron annihilation radiation.

  5. Are gamma-ray bursts the sources of ultra-high energy cosmic rays?

    NASA Astrophysics Data System (ADS)

    Baerwald, Philipp; Bustamante, Mauricio; Winter, Walter

    2015-03-01

    We reconsider the possibility that gamma-ray bursts (GRBs) are the sources of the ultra-high energy cosmic rays (UHECRs) within the internal shock model, assuming a pure proton composition of the UHECRs. For the first time, we combine the information from gamma-rays, cosmic rays, prompt neutrinos, and cosmogenic neutrinos quantitatively in a joint cosmic ray production and propagation model, and we show that the information on the cosmic energy budget can be obtained as a consequence. In addition to the neutron model, we consider alternative scenarios for the cosmic ray escape from the GRBs, i.e., that cosmic rays can leak from the sources. We find that the dip model, which describes the ankle in UHECR observations by the pair production dip, is strongly disfavored in combination with the internal shock model because (a) unrealistically high baryonic loadings (energy in protons versus energy in electrons/gamma-rays) are needed for the individual GRBs and (b) the prompt neutrino flux easily overshoots the corresponding neutrino bound. On the other hand, GRBs may account for the UHECRs in the ankle transition model if cosmic rays leak out from the source at the highest energies. In that case, we demonstrate that future neutrino observations can efficiently test most of the parameter space - unless the baryonic loading is much larger than previously anticipated.

  6. Effect of particle size in the TL response of natural quartz sensitized with high gamma dose

    NASA Astrophysics Data System (ADS)

    Carvalho, A. B., Jr.; Guzzo, P. L.; Sullasi, H. L.; Khoury, H. J.

    2010-11-01

    The aim of this study is to investigate the effect of particle size in the thermoluminescence (TL) response of natural quartz sensitized with high gamma dose. For this, fragments of a single crystal taken from the Solonópole district (Brazil) were crushed and classified into ten size fractions ranging from 38 μm to 5 mm. Aliquots of each size fraction were sensitized with 25 kGy of gamma dose of 60Co and heat-treated in a muffle furnace at 400oC. The non-sensitized samples were exposed to test doses between 50 Gy and 5 kGy and the sensitized samples were exposed to a unique test dose equal to 50 mGy. For non-sensitized samples, the TL peak near 325 °C increases with the particle size decreasing. However, in the case of sensitized samples, the TL output near 280 °C increases with the increasing of particle size up to mean grain size equal to 308 μm. Above 308 μm, an abrupt reduction in the TL intensity was noticed. These effects are discussed in relation to the specific surface area and the different interaction of high gamma doses with fine and coarse particles of quartz.

  7. High resolution gamma ray tomography scanner for flow measurement and non-destructive testing applications

    NASA Astrophysics Data System (ADS)

    Hampel, U.; Bieberle, A.; Hoppe, D.; Kronenberg, J.; Schleicher, E.; Sühnel, T.; Zimmermann, F.; Zippe, C.

    2007-10-01

    We report on the development of a high resolution gamma ray tomography scanner that is operated with a Cs-137 isotopic source at 662keV gamma photon energy and achieves a spatial image resolution of 0.2linepairs/mm at 10% modulation transfer function for noncollimated detectors. It is primarily intended for the scientific study of flow regimes and phase fraction distributions in fuel element assemblies, chemical reactors, pipelines, and hydrodynamic machines. Furthermore, it is applicable to nondestructive testing of larger radiologically dense objects. The radiation detector is based on advanced avalanche photodiode technology in conjunction with lutetium yttrium orthosilicate scintillation crystals. The detector arc comprises 320 single detector elements which are operated in pulse counting mode. For measurements at fixed vessels or plant components, we built a computed tomography scanner gantry that comprises rotational and translational stages, power supply via slip rings, and data communication to the measurement personal computer via wireless local area network.

  8. SONGS - A high resolution imaging gamma-ray spectrometer for the Space Station

    NASA Technical Reports Server (NTRS)

    Nakano, G. H.; Chase, L. F.; Kilner, J. R.; Sandie, W. G.; Fishman, G. J.; Paciesas, W. S.

    1989-01-01

    The overall design and the instrumental features of the Space-Station Observer for Nuclear Gamma-ray Spectroscopy (SONGS) instrument are described. SONGS comprises an array of 19 two-segment n-type Ge detectors, which have the capability of determining the interaction site in either the upper or the lower segment or in both segments. The detectors provide high energy resolution of 1 keV at 100 keV and of 2 keV at 1 MeV. The close-packed Ge sensor array provides a natural sensitivity for the measurement of gamma ray polarization in the 100 keV to 1 MeV energy range, making it possible to obtain information on the structure of the magnetosphere of neutron stars and of the accretion disk of black holes.

  9. Locating very high energy gamma ray sources with arc minute accuracy

    NASA Technical Reports Server (NTRS)

    Akerlof, C. W.; Cawley, M. F.; Chantell, M.; Fegan, D. J.; Harris, K.; Hillas, A. M.; Jennings, D. G.; Lamb, R. C.; Lawrence, M. A.; Lang, M. J.

    1992-01-01

    The angular accuracy of gamma-ray detectors is intrinsically limited by the physical processes involved in photon detection. Although a number of point-like sources were detected by the COS-B satellite, only two were unambiguously identified by time signature with counterparts at longer wavelengths. By taking advantage of the extended longitudinal structure of Very High Energy gamma-ray showers, measurements in the TeV energy range can pinpoint source coordinates to arc minute accuracy. This was demonstrated using Cerenkov air shower imaging techniques. With two telescopes in coincidence, the individual event circular probable error will be 0.13 deg. The half-cone angle of the field of view is effectively 1 deg.

  10. Very-High-Energy Gamma-Ray Observations of Active Galactic Nuclei with VERITAS

    NASA Astrophysics Data System (ADS)

    Quinn, John

    2016-08-01

    VERITAS is an array of four imaging atmospheric Cherenkov telescopes for very-high-energy (VHE, E>100 GeV) gamma-ray astronomy that has been in full scientific operation since 2007. The VERITAS collaboration is conducting several key science projects, one of which is the study of active galactic nuclei (AGN). So far, VERITAS has invested more than 3000 hours in observations of AGN, with approximately 150 objects observed. The program has resulted in the successful detection of 34 AGN as VHE gamma-ray sources, with the majority belonging to the blazar AGN subclass. Significant effort is made to acquire multiwavelength data coincident with the VERITAS observations. An overview of the VERITAS AGN program and its key results will be presented.

  11. High resolution gamma ray tomography scanner for flow measurement and non-destructive testing applications

    SciTech Connect

    Hampel, U.; Bieberle, A.; Hoppe, D.; Kronenberg, J.; Schleicher, E.; Suehnel, T.; Zimmermann, F.; Zippe, C.

    2007-10-15

    We report on the development of a high resolution gamma ray tomography scanner that is operated with a Cs-137 isotopic source at 662 keV gamma photon energy and achieves a spatial image resolution of 0.2 line pairs/mm at 10% modulation transfer function for noncollimated detectors. It is primarily intended for the scientific study of flow regimes and phase fraction distributions in fuel element assemblies, chemical reactors, pipelines, and hydrodynamic machines. Furthermore, it is applicable to nondestructive testing of larger radiologically dense objects. The radiation detector is based on advanced avalanche photodiode technology in conjunction with lutetium yttrium orthosilicate scintillation crystals. The detector arc comprises 320 single detector elements which are operated in pulse counting mode. For measurements at fixed vessels or plant components, we built a computed tomography scanner gantry that comprises rotational and translational stages, power supply via slip rings, and data communication to the measurement personal computer via wireless local area network.

  12. Pure LiF nanophosphors for high exposures of gamma-rays

    SciTech Connect

    Sharma, A. K.; Kumar, Satinder; Dogra, R.; Lochab, S. P.; Kumar, Ravi

    2012-06-05

    Nanocrystalline lithium fluoride (LiF) phosphors have been prepared by the chemical co-precipitation method at different pH values (7.0, 8.0, 9.0 and 10.00). The formation of nanocrystalline structure has been confirmed by X-ray diffraction and transmission electron microscope. Thermoluminescence (TL) properties of LiF phosphors irradiated with gamma rays at different doses of 10 Gy - 70 kGy have been further studied. The analysis of TL glow curve revealed the existence of three well resolved glow peaks, first low temperature peak at around 82 deg. C, second at 125 deg. C and third one at higher temperature around 303 deg. C. The LiF nano-crystallites synthesized at 8.00 pH with maximum TL sensitivity at studied gamma doses ranging from threshold to high exposures are potential candidate for dosimetry applications.

  13. High resolution gamma-ray spectroscopy applied to bulk sample analysis

    SciTech Connect

    Kosanke, K.L.; Koch, C.D.; Wilson, R.D.

    1980-01-01

    A high resolution Ge(Li) gamma-ray spectrometer has been installed and made operational for use in routine bulk sample analysis by the Bendix Field Engineering Corporation (BFEC) geochemical analysis department. The Ge(Li) spectrometer provides bulk sample analyses for potassium, uranium, and thorium that are superior to those obtained by the BFEC sodium iodide spectrometer. The near term analysis scheme permits a direct assay for uranium that corrects for bulk sample self-absorption effects and is independent of the uranium/radium disequilibrium condition of the sample. A more complete analysis scheme has been developed that fully utilizes the gamma-ray data provided by the Ge(Li) spectrometer and that more properly accounts for the sample self-absorption effect. This new analysis scheme should be implemented on the BFEC Ge(Li) spectrometer at the earliest date.

  14. Constraining the High-Energy Emission from Gamma-Ray Bursts with Fermi

    NASA Technical Reports Server (NTRS)

    Gehrels, Neil; Harding, A. K.; Hays, E.; Racusin, J. L.; Sonbas, E.; Stamatikos, M.; Guirec, S.

    2012-01-01

    We examine 288 GRBs detected by the Fermi Gamma-ray Space Telescope's Gamma-ray Burst Monitor (GBM) that fell within the field-of-view of Fermi's Large Area Telescope (LAT) during the first 2.5 years of observations, which showed no evidence for emission above 100 MeV. We report the photon flux upper limits in the 0.1-10 GeV range during the prompt emission phase as well as for fixed 30 s and 100 s integrations starting from the trigger time for each burst. We compare these limits with the fluxes that would be expected from extrapolations of spectral fits presented in the first GBM spectral catalog and infer that roughly half of the GBM-detected bursts either require spectral breaks between the GBM and LAT energy bands or have intrinsically steeper spectra above the peak of the nuF(sub v) spectra (E(sub pk)). In order to distinguish between these two scenarios, we perform joint GBM and LAT spectral fits to the 30 brightest GBM-detected bursts and find that a majority of these bursts are indeed softer above E(sub pk) than would be inferred from fitting the GBM data alone. Approximately 20% of this spectroscopic subsample show statistically significant evidence for a cut-off in their high-energy spectra, which if assumed to be due to gamma gamma attenuation, places limits on the maximum Lorentz factor associated with the relativistic outflow producing this emission. All of these latter bursts have maximum Lorentz factor estimates that are well below the minimum Lorentz factors calculated for LAT-detected GRBs, revealing a wide distribution in the bulk Lorentz factor of GRB outflows and indicating that LAT-detected bursts may represent the high end of this distribution.

  15. Phase Stability of Epsilon and Gamma HNIW (CL-20) at High-Pressure and Temperature

    NASA Astrophysics Data System (ADS)

    Gump, Jared

    2007-06-01

    Hexanitrohexaazaisowurtzitane (CL-20) is one of the few ingredients developed since World War II to be considered for transition to military use. Five polymorphs have been identified for CL-20 by FTIR measurements (α, β, γ, ɛ, and ζ). As CL-20 is transitioned into munitions it will become necessary to predict its response under conditions of detonation, for performance evaluation. Such predictive modeling requires a phase diagram and basic thermodynamic properties of the various phases at high pressure and temperature. Theoretical calculations have been performed for a variety of explosive ingredients including CL-20, but it was noted that no experimental measurements existed for comparison with the theoretical bulk modulus calculated for CL-20. Therefore, the phase stabilities of epsilon and gamma CL-20 at static high-pressure and temperature were investigated using synchrotron angle-dispersive x-ray diffraction experiments. The samples were compressed and heated using diamond anvil cells (DAC). Pressures and temperatures achieved were around 5GPa and 175^oC, respectively. No phase change (from the starting epsilon phase) was observed under hydrostatic compression up to 6.3 GPa at ambient temperature. Under ambient pressure the epsilon phase was determined to be stable to a temperature of 120^oC. When heating above 125^oC the gamma phase appeared and it remained stable until thermal decomposition occurred above 150^oC. The gamma phase exhibits a phase change upon compression at both ambient temperature and 140^oC. Pressure -- volume data for the epsilon and gamma phase at ambient temperature and the epsilon phase at 75^oC were fit to the Birch-Murnaghan formalism to obtain isothermal equations of state.

  16. High-energy gamma-ray emission from solar flares: Constraining the accelerated proton spectrum

    NASA Technical Reports Server (NTRS)

    Alexander, David; Dunphy, Philip P.; Mackinnon, Alexander L.

    1994-01-01

    Using a multi-component model to describe the gamma-ray emission, we investigate the flares of December 16, 1988 and March 6, 1989 which exhibited unambiguous evidence of neutral pion decay. The observations are then combined with theoretical calculations of pion production to constrain the accelerated proton spectra. The detection of pi(sup 0) emission alone can indicate much about the energy distribution and spectral variation of the protons accelerated to pion producing energies. Here both the intensity and detailed spectral shape of the Doppler-broadened pi(sup 0) decay feature are used to determine the spectral form of the accelerated proton energy distribution. The Doppler width of this gamma-ray emission provides a unique diagnostic of the spectral shape at high energies, independent of any normalisation. To our knowledge, this is the first time that this diagnostic has been used to constrain the proton spectra. The form of the energetic proton distribution is found to be severely limited by the observed intensity and Doppler width of the pi(sup 0) decay emission, demonstrating effectively the diagnostic capabilities of the pi(sup 0) decay gamma-rays. The spectral index derived from the gamma-ray intensity is found to be much harder than that derived from the Doppler width. To reconcile this apparent discrepancy we investigate the effects of introducing a high-energy cut-off in the accelerated proton distribution. With cut-off energies of around 0.5-0.8 GeV and relatively hard spectra, the observed intensities and broadening can be reproduced with a single energetic proton distribution above the pion production threshold.

  17. New insights into the global composition of the lunar surface from high-energy gamma rays measured by Lunar Prospector

    NASA Astrophysics Data System (ADS)

    Peplowski, Patrick N.; Lawrence, David J.

    2013-04-01

    An analysis of the lunar gamma-ray spectrum as measured by the Lunar Prospector Gamma-Ray Spectrometer has revealed that 8-8.9 MeV gamma rays contain information about the elemental composition of near-surface materials. These high-energy gamma rays are found to be primarily sensitive to the total Fe and Mg content of the surface, although other elements also contribute. This information has been used to identify several regions with unique compositions, including the Hertzsprung and Orientale basins. A method for deriving global Mg abundances from high-energy gamma-ray measurements is presented. The physical mechanism for high-energy gamma-ray production is proposed to be radiation produced during the decay of galactic cosmic ray produced pions within the lunar surface. Laboratory measurements of pion production cross sections are found to be consistent with the empirically derived relationship between the lunar Fe, Mg, and Ti abundances and the measured high-energy gamma-ray count rates.

  18. Thermal, tensile and rheological properties of high density polyethylene (HDPE) processed and irradiated by gamma-ray in different atmospheres

    SciTech Connect

    Ferreto, H. F. R. E-mail: ana-feitoza@yahoo.com.br; Oliveira, A. C. F. E-mail: ana-feitoza@yahoo.com.br; Parra, D. F. E-mail: ablugao@ipen.br; Lugão, A. B. E-mail: ablugao@ipen.br; Gaia, R.

    2014-05-15

    The aim of this paper is to investigate structural changes of high density polyethylene (HDPE) modified by ionizing radiation (gamma rays) in different atmospheres. The gamma radiation process for modification of commercial polymers is a widely applied technique to promote new physical-chemical and mechanical properties. Gamma irradiation originates free radicals which can induce chain scission or recombination, providing its annihilation, branching or crosslinking. This polymer was irradiated with gamma source of {sup 60}Co at doses of 5, 10, 20, 50 or 100 kGy at a dose rate of 5 kGy/h. The changes in molecular structure of HDPE, after gamma irradiations were evaluated using thermogravimetric analysis (TGA) and tensile machine and oscillatory rheology. The results showed the variations of the properties depending on the dose at each atmosphere.

  19. Gadolinium-doped water cerenkov-based neutron and high energy gamma-ray detector and radiation portal monitoring system

    DOEpatents

    Dazeley, Steven A; Svoboda, Robert C; Bernstein, Adam; Bowden, Nathaniel

    2013-02-12

    A water Cerenkov-based neutron and high energy gamma ray detector and radiation portal monitoring system using water doped with a Gadolinium (Gd)-based compound as the Cerenkov radiator. An optically opaque enclosure is provided surrounding a detection chamber filled with the Cerenkov radiator, and photomultipliers are optically connected to the detect Cerenkov radiation generated by the Cerenkov radiator from incident high energy gamma rays or gamma rays induced by neutron capture on the Gd of incident neutrons from a fission source. The PMT signals are then used to determine time correlations indicative of neutron multiplicity events characteristic of a fission source.

  20. Correlative studies of astrophysical sources of very high and ultra high energy gamma-rays

    NASA Technical Reports Server (NTRS)

    Akerlof, Carl W.

    1993-01-01

    During the period of this contract, June 1, 1991 to November 14, 1992, the major results of our research effort have come from the Whipple air shower experiment in Tucson, AZ. The most notable development has been the discovery of TeV photons from the BL Lac object, Markarian 421. This result depended critically on the identification of Mrk 421 by the EGRET team as a source of GeV gamma rays.

  1. Final report: VHE [very high energy] gamma-ray astronomy at Iowa State University, 1991-2000

    SciTech Connect

    Carter-Lewis, D.

    2001-01-30

    A brief summary of the important results and a listing of publications which have resulted from the Iowa State University Very High Energy Gamma-ray Astrophysics Program for the decade 1991-2000 are given.

  2. Background Modelling in Very-High-Energy Gamma-Ray Astronomy

    SciTech Connect

    Berge, David; Funk, S.; Hinton, J.; /Heidelberg, Max Planck Inst. /Heidelberg Observ. /Leeds U.

    2006-11-07

    Ground based Cherenkov telescope systems measure astrophysical {gamma}-ray emission against a background of cosmic-ray induced air showers. The subtraction of this background is a major challenge for the extraction of spectra and morphology of {gamma}-ray sources. The unprecedented sensitivity of the new generation of ground based very-high-energy {gamma}-ray experiments such as H.E.S.S. has lead to the discovery of many previously unknown extended sources. The analysis of such sources requires a range of different background modeling techniques. Here we describe some of the techniques that have been applied to data from the H.E.S.S. instrument and compare their performance. Each background model is introduced and discussed in terms of suitability for image generation or spectral analysis and possible caveats are mentioned. We show that there is not a single multi-purpose model, different models are appropriate for different tasks. To keep systematic uncertainties under control it is important to apply several models to the same data set and compare the results.

  3. Modeling High-Energy Gamma-Rays from the Fermi Bubbles - Oral Presentation

    SciTech Connect

    Splettstoesser, Megan

    2015-08-25

    In 2010, the Fermi Bubbles were discovered at the galactic center of the Milky Way. These giant gamma-ray structures, extending 50 degrees in galactic latitude and 20-30 degrees in galactic longitude, were not predicted. We wish to develop a model for the gamma-ray emission of the Fermi Bubbles. To do so, we assume that second order Fermi acceleration is responsible for the high-energy emission of the bubbles. Second order Fermi acceleration requires charged particles and irregular magnetic fields—both of which are present in the disk of the Milky Way galaxy. I use the assumption of second order Fermi acceleration in the transport equation, which describes the diffusion of particles. By solving the steady-state case of the transport equation, I compute the proton spectrum due to Fermi second order acceleration and compare this analytical solution to a numerical solution provided by Dr. P. Mertsch. Analytical solutions to the transport equation are taken from Becker, Le, & Dermer and are used to further test the numerical solution. I find that the numerical solution converges to the analytical solution in all cases. Thus, we know the numerical solution accurately calculates the proton spectrum. The gamma-ray spectrum follows the proton spectrum, and will be computed in the future.

  4. Absorption of very high energy gamma rays in the Milky Way

    NASA Astrophysics Data System (ADS)

    Vernetto, Silvia; Lipari, Paolo

    2016-09-01

    Galactic gamma ray astronomy at very high energy (Eγ≳30 TeV ) is a vital tool in the study of the nonthermal universe. The interpretation of the observations in this energy region requires the precise modeling of the attenuation of photons due to pair production interactions (γ γ →e+e- ) where the targets are the radiation fields present in interstellar space. For gamma rays with energy Eγ≳300 TeV the attenuation is mostly due to the photons of the cosmic microwave background radiation. At lower energy the most important targets are infrared photons with wavelengths in the range λ ≃50 - 500 μ m emitted by dust. The evaluation of the attenuation requires a good knowledge of the density, and energy and angular distributions of the target photons for all positions in the Galaxy. In this work we discuss a simple model for the infrared radiation that depends on only few parameters associated to the space and temperature distributions of the emitting dust. The model allows to compute with good accuracy the effects of absorption for any space and energy distribution of the diffuse Galactic gamma ray emission. The absorption probability due to the Galactic infrared radiation is maximum for Eγ≃150 TeV , and can be as large as Pabs≃0.45 for distant sources on lines of sight that pass close to the Galactic center. The systematic uncertainties on the absorption probability are estimated as Δ Pabs≲0.08 .

  5. The BATSE Gamma-Ray Burst Spectral Catalog. 1; High Time Resolution Spectroscopy of Bright Bursts Using High Energy Resolution Data

    NASA Technical Reports Server (NTRS)

    Preece, Robert D.; Briggs, Michael S.; Mallozzi, Robert S.; Pendleton, Geoffrey N.; Paciesas, W. S.; Band, David L.

    1999-01-01

    This is the first in a series of gamma-ray burst spectroscopy catalogs from the Burst And Transient Source Experiment (BATSE) on the Compton Gamma Ray Abstract: Observatory, each covering a different aspect of burst phenomenology. In this paper, we present time-sequences of spectral fit parameters for 156 bursts selected either for their high peak flux or fluence.

  6. Nonuniform High-Gamma (60–500 Hz) Power Changes Dissociate Cognitive Task and Anatomy in Human Cortex

    PubMed Central

    Gaona, Charles M.; Sharma, Mohit; Freudenburg, Zachary V.; Breshears, Jonathan D.; Bundy, David T.; Roland, Jarod; Barbour, Dennis L.; Schalk, Gerwin

    2011-01-01

    High-gamma-band (>60 Hz) power changes in cortical electrophysiology are a reliable indicator of focal, event-related cortical activity. Despite discoveries of oscillatory subthreshold and synchronous suprathreshold activity at the cellular level, there is an increasingly popular view that high-gamma-band amplitude changes recorded from cellular ensembles are the result of asynchronous firing activity that yields wideband and uniform power increases. Others have demonstrated independence of power changes in the low- and high-gamma bands, but to date, no studies have shown evidence of any such independence above 60 Hz. Based on nonuniformities in time-frequency analyses of electrocorticographic (ECoG) signals, we hypothesized that induced high-gamma-band (60–500 Hz) power changes are more heterogeneous than currently understood. Using single-word repetition tasks in six human subjects, we showed that functional responsiveness of different ECoG high-gamma sub-bands can discriminate cognitive task (e.g., hearing, reading, speaking) and cortical locations. Power changes in these sub-bands of the high-gamma range are consistently present within single trials and have statistically different time courses within the trial structure. Moreover, when consolidated across all subjects within three task-relevant anatomic regions (sensorimotor, Broca's area, and superior temporal gyrus), these behavior- and location-dependent power changes evidenced nonuniform trends across the population. Together, the independence and nonuniformity of power changes across a broad range of frequencies suggest that a new approach to evaluating high-gamma-band cortical activity is necessary. These findings show that in addition to time and location, frequency is another fundamental dimension of high-gamma dynamics. PMID:21307246

  7. Toward ultrafast high-DQE and multi-image CZT gamma-camera prospecting

    NASA Astrophysics Data System (ADS)

    Gerstenmayer, Jean-Louis; Glasser, Francis; Desbat, Laurent; Allouche, Virginie

    2003-07-01

    The development of high frame rate imaging high energy X-rays detector system is discussed. The purpose of this paper is to highlight some of the issues involved in the development of high performance position sensitive X- and gamma-ray cameras for high frame rate imaging. New CZT technology has provided some prototypes offering more than 50% stopping power (and millimetric spatial resolution) for 5 MeV X-ray pulses. Some different CdTe and CdZnTe sensors were tested with MeV energy photons produced by the accelerators ELSA and ARCO (CEA Bruyeres-le-Chatel). The first experimental results obtained at CEA with 20 ps long are very encouraging for high energy high frame rate imaging applications.

  8. Detection of high-energy gamma radiation from quasar 3C 279 by the EGRET telescope on the Compton Gamma Ray Observatory

    NASA Technical Reports Server (NTRS)

    Hartman, R. C.; Bertsch, D. L.; Fichtel, C. E.; Hunter, S. D.; Kwok, P. W.; Thompson, D. J.; Mattox, J. R.; Kanbach, G.; Nel, H. I.; Sreekumar, P.

    1992-01-01

    Intense gamma radiation has been observed from the direction of the quasar 3C 279 throughout the energy range from 30 MeV to over 5 GeV by the Energetic Gamma Ray Experiment Telescope (EGRET) during the period June 15-28, 1991. Its spectrum is well represented by a photon differential power-law exponent of 2.0 +/- 0.1, with a photon intensity above 100 MeV of (2.8 +/- 0.4) x 10 exp -6/sq cm s. For E is greater than 100 MeV, the 2-sigma upper limits were 1.0 x 10 exp -6/sq cm s in 1973 from the SAS 2 observations and 0.3 x 10 exp -6/sq cm s for the combined 1976, 1978, and 1980 COS B observations. Hence, there has been a large increase in high-energy gamma-ray intensity relative to the earlier times, as there has been in the radio, infrared, optical, and X-ray ranges. This source is the most distant and by far the most luminous gamma-ray source yet detected.

  9. The Gamma-Ray Large-Area Space Telescope: An Astro-Particle Mission to Explore the High-Energy Gamma-Ray Sky

    SciTech Connect

    Spandre, Gloria; /INFN, Pisa

    2009-05-12

    The Gamma Ray Large Area Space Telescope (GLAST) is a space mission that will detect photons from the gamma ray sky, in the rich yet poorly explored high energy band between 20MeV and 1TeV. Main instrument on board is the Large Area Telescope (LAT), a gamma-ray pair-conversion telescope, that will measure direction and energy of incoming photons by means of a very large (11.000 sensors), low pitch (228 {micro}m) Silicon strip Tracker and an imaging CsI e.m. calorimeter, supported in the rejection of charged particles background by an outer, segmented Anti-Coincidence Detector built with plastic scintillators. The superior angular resolution of the LAT, coupled to its very large field of view, results in a sensitivity advance of a factor 30 or more with respect to previously flown instruments. This will allow GLAST to locate currently unresolved gamma ray sources and to detect potential new classes of sources. Study of the residual gamma ray background will have a crucial role in connection to cosmological models, supersymmetric dark matter and relics of exotic particle decay searches. An accurate spectroscopy of all gamma ray emitters will be possible with the high energy resolution of the calorimeter, improving our knowledge of the mechanisms that power the cores of blazars and AGNs, and enabling tens of different pulsar emission models. The GLAST mission will have the instrumental capabilities to locate and analyze sources of cosmic rays and investigate on their acceleration mechanism. As for transient phenomena studies, like the spectacular GRBs, known to be the most energetic natural events, GLAST is in a prominent position. This is due to the minimum detection dead time (<100 {micro}s), typical of the silicon detectors used for the LAT tracker, and to the increased field of view and alert capabilities of the second GLAST instrument, the Gamma Burst Monitor (GBM), essentially conceived as a fast transients trigger for the more accurate observations from the LAT

  10. High temperature thermo-mechanical stability of lamellar ({gamma} + {alpha}{sub 2}) Ti-49Al-2V

    SciTech Connect

    Guillard, S.; Rack, H.J.

    1995-12-31

    The high temperature thermo-mechanical stability of lamellar two phase {gamma} + {alpha}{sub 2} Ti-49Al-2V has been examined. At low temperatures and high rates the flow behavior exhibited initial strain hardening, followed by flow softening and steady-state behavior at high strains. As the temperature increased and/or the strain rate decreased, strain hardening was eliminated, flow softening commencing upon yielding. Dynamic material modeling showed that two stable flow regions exist in this alloy and microstructural condition, both stable regimes being associated with dynamic spheroidization of the lamellar {gamma} + {alpha}{sub 2} structure. At higher temperatures and lower rates, dynamic spheroidization involved both the {gamma} and {alpha}{sub 2} lamellae, while at lower temperatures and/or higher rates the {alpha}{sub 2} lamellae remained essentially unchanged, all deformation occurring within the {gamma} phase. Finally, unstable flow is related to lamellae kinking, flow localization and surface cracking.

  11. High-redshift gamma-ray bursts: observational signatures of superconducting cosmic strings?

    PubMed

    Cheng, K S; Yu, Yun-Wei; Harko, T

    2010-06-18

    The high-redshift gamma-ray bursts (GRBs), GRBs 080913 and 090423, challenge the conventional GRB progenitor models by their short durations, typical for short GRBs, and their high energy releases, typical for long GRBs. Meanwhile, the GRB rate inferred from high-redshift GRBs also remarkably exceeds the prediction of the collapsar model, with an ordinary star formation history. We show that all these contradictions could be eliminated naturally, if we ascribe some high-redshift GRBs to electromagnetic bursts of superconducting cosmic strings. High-redshift GRBs could become a reasonable way to test the superconducting cosmic string model because the event rate of cosmic string bursts increases rapidly with increasing redshifts, whereas the collapsar rate decreases. PMID:20867291

  12. I Search of Narrow Proton-Antiproton Bound States: High Resolution Gamma and Charged Flow Pion Spectra from Protonium.

    NASA Astrophysics Data System (ADS)

    Petridou, Chariclia I.

    We studied the pp annihilations at rest looking for narrow bound states in the proton-antiproton system. We looked, with high energy resolution, for radiative and pionic transitions in the gamma and charged pion spectra. The detector for the (gamma)(--->)e+e- and the (pi)('(+OR-)) was a magnetic pair spectrometer. The directions of the incident particles (e(+OR-) and (pi)(+OR-)) were determined by a drift chamber module in front of the magnet and the final directions of the particles, if reflected in the magnet, by the same chamber; if transversing the magnet, by an identical module at the rear of the magnet. The momentum was calculated from the directions of the particle. The following gamma spectra were obtained. Gammas with both e+, e- reflected in the magnet at a field of about 6 Kgauss (RR-gammas). That covers the region between 80 and 180 MeV, corresponding to a missing mass 1794 to 1686 MeV/c. The energy resolution is about 2.5 MeV ((sigma)) at 129 MeV (confirmed by the observed Panofsky gammas from stopping (pi)('-)p data) and 5 MeV ((sigma)) at 80 MeV. We have no evidence for narrow peaks except for the Panofsky gamma produced with a branching ratio of 3.3 x 10('-3) from (pi)('-) stops in the target. Upper limits for (gamma) -transitions in the region between 80 to 180 MeV were set at about 10('-3). Gammas with one e+(e-) reflected and the other transversing the magnet (RP-gammas) for fields of about 6 and 12 Kgauss, covering the region (GREATERTHEQ) 200 MeV, which corresponds to missing mass (LESSTHEQ) 1664 MeV/c('2). The gamma energy resolution in MeV is 51(.)E('2) (GeV) and 25.5(.)E('2)(GeV) for the low and high field respectively. Finally the charged pion spectra for those transversing the magnet are given for both magnet settings and as a function of charge multiplicity, covering the momentum region from (GREATERTHEQ) 150 MeV/c. The momentum resolution is the same as that for the RP-gammas. The two body annihilations (pi)('+)(pi)('-) and (pi

  13. CeBr3 as a High-Resolution Gamma-Ray Detector

    SciTech Connect

    Michael Reed, Paul Guss, Christopher Contreras

    2008-11-13

    Lanthanum halide (LaBr3:Ce) scintillators have been well-documented as high-resolution gamma-ray detectors that are operated at room temperature. These scintillators have better resolution (<3% at 662 keV) relative to sodium iodide (NaI(Tl)) scintillators (7% at 662 keV), but the naturally occurring radioactive isotope 138La causes self-activity in the crystal that occludes portions of the gamma-ray spectrum. This selfactivity limits the use of LaBr3:Ce in high-sensitivity applications. Cerium, the dopant in the LaBr3:Ce matrix possesses useful scintillation properties, and its selfactivity is on the order of 3750 times less than La; however, Ce has not been fully characterized as the chief component in a scintillation detector. This work investigated Ce as the key scintillation matrix component in a scintillation detector with the hypothesis that CeBr3 promises energy resolution comparable or superior to LaBr3:Ce. The researchers involved with this work believe that CeBr3 may be the answer to obtaining high-temperature, high-resolution spectra with greater sensitivity than LaBr3:Ce.

  14. Direct transitions from high-K isomers to low-K bands -- {gamma} softness or coriolis coupling

    SciTech Connect

    Shimizu, Yoshifumi R.; Narimatsu, Kanako; Ohtsubo, Shin-Ichi

    1996-12-31

    Recent measurements of direct transitions from high-K isomers to low-K bands reveal severe break-down of the K-selection rule and pose the problem of how to understand the mechanism of such K-violation. The authors recent systematic calculations by using a simple {gamma}-tunneling model reproduced many of the observed hindrances, indicating the importance of the {gamma} softness. However, there are some data which cannot be explained in terms of the {gamma}-degree of freedom. In this talk, the authors also discuss the results of conventional Coriolis coupling calculations, which is considered to be another important mechanism.

  15. In situ calibration of a high-resolution gamma-ray borehole sonde for assaying uranium-bearing sandstone deposits

    USGS Publications Warehouse

    Day, J.H.

    1985-01-01

    A method is presented for assaying radioactive sandstone deposits in situ by using a high-resolution borehole gamma-ray spectrometer. Gamma-ray photopeaks from the same spectrum acquired to analyze a sample are used to characterize gamma-ray attenuation properties, from which a calibration function is determined. Assay results are independent of differences between properties of field samples and those of laboratory or test-hole standards generally used to calibrate a borehole sonde. This assaying technique is also independent of the state of radioactive disequilibrium that usually exists in nature among members of the natural-decay chains. ?? 1985.

  16. High gamma oscillations in medial temporal lobe during overt production of speech and gestures.

    PubMed

    Marstaller, Lars; Burianová, Hana; Sowman, Paul F

    2014-01-01

    The study of the production of co-speech gestures (CSGs), i.e., meaningful hand movements that often accompany speech during everyday discourse, provides an important opportunity to investigate the integration of language, action, and memory because of the semantic overlap between gesture movements and speech content. Behavioral studies of CSGs and speech suggest that they have a common base in memory and predict that overt production of both speech and CSGs would be preceded by neural activity related to memory processes. However, to date the neural correlates and timing of CSG production are still largely unknown. In the current study, we addressed these questions with magnetoencephalography and a semantic association paradigm in which participants overtly produced speech or gesture responses that were either meaningfully related to a stimulus or not. Using spectral and beamforming analyses to investigate the neural activity preceding the responses, we found a desynchronization in the beta band (15-25 Hz), which originated 900 ms prior to the onset of speech and was localized to motor and somatosensory regions in the cortex and cerebellum, as well as right inferior frontal gyrus. Beta desynchronization is often seen as an indicator of motor processing and thus reflects motor activity related to the hand movements that gestures add to speech. Furthermore, our results show oscillations in the high gamma band (50-90 Hz), which originated 400 ms prior to speech onset and were localized to the left medial temporal lobe. High gamma oscillations have previously been found to be involved in memory processes and we thus interpret them to be related to contextual association of semantic information in memory. The results of our study show that high gamma oscillations in medial temporal cortex play an important role in the binding of information in human memory during speech and CSG production. PMID:25340347

  17. On The Origin Of High Energy Correlations in Gamma-ray Bursts

    SciTech Connect

    Kocevski, Daniel

    2012-04-03

    I investigate the origin of the observed correlation between a gamma-ray burst's {nu}F{sub {nu}} spectral peak E{sub pk} and its isotropic equivalent energy E{sub iso} through the use of a population synthesis code to model the prompt gamma-ray emission from GRBs. By using prescriptions for the distribution of prompt spectral parameters as well as the population's luminosity function and co-moving rate density, I generate a simulated population of GRBs and examine how bursts of varying spectral properties and redshift would appear to a gamma-ray detector here on Earth. I find that a strong observed correlation can be produced between the source frame Epk and Eiso for the detected population despite the existence of only a weak and broad correlation in the original simulated population. The energy dependance of a gamma-ray detector's flux-limited detection threshold acts to produce a correlation between the source frame E{sub pk} and E{sub iso} for low luminosity GRBs, producing the left boundary of the observed correlation. Conversely, very luminous GRBs are found at higher redshifts than their low luminosity counterparts due to the standard Malquest bias, causing bursts in the low E{sub pk}, high E{sub iso} regime to go undetected because their E{sub pk} values would be redshifted to energies at which most gamma-ray detectors become less sensitive. I argue that it is this previously unexamined effect which produces the right boundary of the observed correlation. Therefore, the origin of the observed correlation is a complex combination of the instrument's detection threshold, the intrinsic cutoff in the GRB luminosity function, and the broad range of redshifts over which GRBs are detected. Although the GRB model presented here is a very simplified representation of the complex nature of GRBs, these simulations serve to demonstrate how selection effects caused by a combination of instrumental sensitivity and the cosmological nature of an astrophysical population

  18. Gamma-ray-spectroscopy following high-flux 14-MeV neutron activation

    SciTech Connect

    Williams, R.E.

    1981-10-12

    The Rotating Target Neutron Source (RTNS-I), a high-intensity source of 14-MeV neutrons at the Lawrence Livermore National Laboratory (LLNL), has been used for applications in activation analysis, inertial-confinement-fusion diagnostic development, and fission decay-heat studies. The fast-neutron flux from the RTNS-I is at least 50 times the maximum fluxes available from typical neutron generators, making these applications possible. Facilities and procedures necessary for gamma-ray spectroscopy of samples irradiated at the RTNS-I were developed.

  19. Combined Effects of Gamma Radiation and High Dietary Iron on Peripheral Leukocyte Distribution and Function

    NASA Technical Reports Server (NTRS)

    Crucian, Brian E.; Morgan, Jennifer L. L.; Quiriarte, Heather A.; Sams, Clarence F.; Smith, Scott M.; Zwart, Sara R.

    2012-01-01

    Both radiation and increased iron stores can independently increase oxidative damage, resulting in protein, lipid and DNA oxidation. Oxidative stress increases the risk of many health problems including cancer, cataracts, and heart disease. This study, a subset of a larger interdisciplinary investigation of the combined effect of iron overload on sensitivity to radiation injury, monitored immune parameters in the peripheral blood of rats subjected to gamma radiation, high dietary iron or both. Specific immune measures consisted of: (1) peripheral leukocyte distribution, (2) plasma cytokine levels and (3) cytokine production profiles following whole blood mitogenic stimulation

  20. Calculated Neutron and Gamma-ray Spectra across the Prismatic Very High Temperature Reactor Core

    SciTech Connect

    James W. Sterbentz

    2008-05-01

    Neutron and gamma-ray flux spectra are calculated using the MCNP5 computer code and a one-sixth core model of a prismatic Very High Temperature Reactor based on the General Atomics Gas Turbine-Modular Helium Reactor. Spectra are calculated in the five inner reflector graphite block rings, three annular active core fuel rings, three outer graphite reflector block rings, and the core barrel. The neutron spectra are block and fuel pin averages and are calculated as a function of temperature and burnup. Also provided are the total, fast, and thermal radial profile fluxes and core barrel dpa rates.

  1. Very High Energy Observations of Gamma Ray Bursts with the Whipple/VERITAS Telescopes

    SciTech Connect

    Horan, D.; Badran, H.M.; Blaylock, G.; Bond, I.H.; Boyle, P.J.; Bradbury, S.M.; Buckley, J.H.; Byrum, K.; Carter-Lewis, D.A.; Celik, O.; Cogan, P.; Cui, W.; Daniel, M.K.; Calle Perez, I. de la; Duke, C.; Falcone, A.; Fegan, D.J.; Fegan, S.J.; Finley, J.P.; Fortson, L.F.

    2005-02-21

    Gamma-ray Burst (GRB) observations at Very High Energies (VHE, E > 100 GeV) can impose tight constraints on some GRB emission models. Many GRB after-glow models predict a VHE component similar to that seen in blazars and supernova remnants, in which the GRB spectral energy distribution has a double-peaked shape extending into the VHE regime. Consistent with this afterglow scenario, EGRET detected delayed high energy emission from all five bright BATSE GRBs that occurred within its field of view. GRB observations have had high priority in the observing program at the Whipple 10m Telescope and will continue to be high priority targets when the next generation observatory VERITAS comes online. Upper limits on the VHE emission from ten GRBs observed with the Whipple Telescope are reported here.

  2. High-precision gamma-ray spectroscopy for enhancing production and application of medical isotopes

    NASA Astrophysics Data System (ADS)

    McCutchan, E. A.; Sonzogni, A. A.; Smith, S. V.; Muench, L.; Nino, M.; Greene, J. P.; Carpenter, M. P.; Zhu, S.; Chillery, T.; Chowdhury, P.; Harding, R.; Lister, C. J.

    2015-10-01

    Nuclear medicine is a field which requires precise decay data for use in planning radionuclide production and in imaging and therapeutic applications. To address deficiencies in decay data, sources of medical isotopes were produced and purified at the Brookhaven Linear Isotope Producer (BLIP) then shipped to Argonne National Laboratory where high-precision, gamma-ray measurements were performed using Gammasphere. New decay schemes for a number of PET isotopes and the impact on dose calculations will be presented. To investigate the production of next-generation theranostic or radiotherapeutic isotopes, cross section measurements with high energy protons have also been explored at BLIP. The 100-200 MeV proton energy regime is relatively unexplored for isotope production, thus offering high discovery potential but at the same time a challenging analysis due to the large number of open channels at these energies. Results of cross sections deduced from Compton-suppressed, coincidence gamma-ray spectroscopy performed at Lowell will be presented, focusing on the production of platinum isotopes by irradiating natural platinum foils with 100 to 200 MeV protons. DOE Isotope Program is acknowledged for funding ST5001030. Work supported by the US DOE under Grant DE-FG02-94ER40848 and Contracts DE-AC02-98CH10946 and DE-AC02-06CH11357.

  3. Fermi Observations of High-energy Gamma-ray Emission from GRB 090217A

    NASA Astrophysics Data System (ADS)

    Ackermann, M.; Ajello, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bhat, P. N.; Bissaldi, E.; Blandford, R. D.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Bregeon, J.; Brez, A.; Briggs, M. S.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Carrigan, S.; Casandjian, J. M.; Cecchi, C.; Çelik, Ö.; Charles, E.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Connaughton, V.; Conrad, J.; Cutini, S.; Dermer, C. D.; de Angelis, A.; de Palma, F.; Digel, S. W.; Silva, E. do Couto e.; Drell, P. S.; Dubois, R.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Frailis, M.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Granot, J.; Grenier, I. A.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Hadasch, D.; Hays, E.; Horan, D.; Hughes, R. E.; Jóhannesson, G.; Johnson, A. S.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kippen, R. M.; Knödlseder, J.; Kocevski, D.; Kuss, M.; Lande, J.; Latronico, L.; Lee, S.-H.; Llena Garde, M.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Makeev, A.; Mazziotta, M. N.; McBreen, S.; McEnery, J. E.; McGlynn, S.; Meegan, C.; Mehault, J.; Mészáros, P.; Michelson, P. F.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Moretti, E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakajima, H.; Nakamori, T.; Naumann-Godo, M.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohno, M.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paciesas, W. S.; Paneque, D.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Petrosian, V.; Piron, F.; Porter, T. A.; Preece, R.; Racusin, J. L.; Rainò, S.; Rando, R.; Rau, A.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Ripken, J.; Roth, M.; Ryde, F.; Sadrozinski, H. F.-W.; Sander, A.; Scargle, J. D.; Schalk, T. L.; Sgrò, C.; Siskind, E. J.; Smith, P. D.; Spandre, G.; Spinelli, P.; Stamatikos, M.; Strickman, M. S.; Suson, D. J.; Tajima, H.; Takahashi, H.; Tanaka, T.; Thayer, J. B.; Thayer, J. G.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Uehara, T.; Usher, T. L.; Vandenbroucke, J.; van der Horst, A. J.; Vasileiou, V.; Vilchez, N.; Vitale, V.; von Kienlin, A.; Waite, A. P.; Wang, P.; Wilson-Hodge, C.; Winer, B. L.; Wood, K. S.; Wu, X. F.; Yamazaki, R.; Yang, Z.; Ylinen, T.; Ziegler, M.; Fermi LAT Collaboration; Fermi GBM Collaboration

    2010-07-01

    The Fermi observatory is advancing our knowledge of gamma-ray bursts (GRBs) through pioneering observations at high energies, covering more than seven decades in energy with the two on-board detectors, the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM). Here, we report on the observation of the long GRB 090217A which triggered the GBM and has been detected by the LAT with a significance greater than 9σ. We present the GBM and LAT observations and on-ground analyses, including the time-resolved spectra and the study of the temporal profile from 8 keV up to ~1 GeV. All spectra are well reproduced by a Band model. We compare these observations to the first two LAT-detected, long bursts GRB 080825C and GRB 080916C. These bursts were found to have time-dependent spectra and exhibited a delayed onset of the high-energy emission, which are not observed in the case of GRB 090217A. We discuss some theoretical implications for the high-energy emission of GRBs.

  4. A clinical gamma camera-based pinhole collimated system for high resolution small animal SPECT imaging.

    PubMed

    Mejia, J; Galvis-Alonso, O Y; Castro, A A de; Braga, J; Leite, J P; Simões, M V

    2010-12-01

    The main objective of the present study was to upgrade a clinical gamma camera to obtain high resolution tomographic images of small animal organs. The system is based on a clinical gamma camera to which we have adapted a special-purpose pinhole collimator and a device for positioning and rotating the target based on a computer-controlled step motor. We developed a software tool to reconstruct the target's three-dimensional distribution of emission from a set of planar projections, based on the maximum likelihood algorithm. We present details on the hardware and software implementation. We imaged phantoms and heart and kidneys of rats. When using pinhole collimators, the spatial resolution and sensitivity of the imaging system depend on parameters such as the detector-to-collimator and detector-to-target distances and pinhole diameter. In this study, we reached an object voxel size of 0.6 mm and spatial resolution better than 2.4 and 1.7 mm full width at half maximum when 1.5- and 1.0-mm diameter pinholes were used, respectively. Appropriate sensitivity to study the target of interest was attained in both cases. Additionally, we show that as few as 12 projections are sufficient to attain good quality reconstructions, a result that implies a significant reduction of acquisition time and opens the possibility for radiotracer dynamic studies. In conclusion, a high resolution single photon emission computed tomography (SPECT) system was developed using a commercial clinical gamma camera, allowing the acquisition of detailed volumetric images of small animal organs. This type of system has important implications for research areas such as Cardiology, Neurology or Oncology.

  5. Constraining the High-energy Emission from Gamma-Ray Bursts with Fermi

    NASA Astrophysics Data System (ADS)

    Fermi Large Area Telescope Team; Ackermann, M.; Ajello, M.; Baldini, L.; Barbiellini, G.; Baring, M. G.; Bechtol, K.; Bellazzini, R.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bottacini, E.; Bouvier, A.; Brigida, M.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Cecchi, C.; Charles, E.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Cutini, S.; D'Ammando, F.; de Palma, F.; Dermer, C. D.; Silva, E. do Couto e.; Drell, P. S.; Drlica-Wagner, A.; Favuzzi, C.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Granot, J.; Grenier, I. A.; Grove, J. E.; Hadasch, D.; Hanabata, Y.; Harding, A. K.; Hays, E.; Horan, D.; Jóhannesson, G.; Kataoka, J.; Knödlseder, J.; Kocevski, D.; Kuss, M.; Lande, J.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Mazziotta, M. N.; McEnery, J.; McGlynn, S.; Michelson, P. F.; Mitthumsiri, W.; Monzani, M. E.; Moretti, E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Naumann-Godo, M.; Norris, J. P.; Nuss, E.; Nymark, T.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pesce-Rollins, M.; Piron, F.; Pivato, G.; Racusin, J. L.; Rainò, S.; Rando, R.; Razzaque, S.; Reimer, A.; Reimer, O.; Ritz, S.; Ryde, F.; Sgrò, C.; Siskind, E. J.; Sonbas, E.; Spandre, G.; Spinelli, P.; Stamatikos, M.; Stawarz, Łukasz; Suson, D. J.; Takahashi, H.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Tibaldo, L.; Tinivella, M.; Tosti, G.; Uehara, T.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Waite, A. P.; Fermi Gamma-ray Burst Monitor Team; Connaughton, V.; Briggs, M. S.; Guirec, S.; Goldstein, A.; Burgess, J. M.; Bhat, P. N.; Bissaldi, E.; Camero-Arranz, A.; Fishman, J.; Fitzpatrick, G.; Foley, S.; Gruber, D.; Jenke, P.; Kippen, R. M.; Kouveliotou, C.; McBreen, S.; Meegan, C.; Paciesas, W. S.; Preece, R.; Rau, A.; Tierney, D.; van der Horst, A. J.; von Kienlin, A.; Wilson-Hodge, C.; Xiong, S.

    2012-08-01

    We examine 288 gamma-ray bursts (GRBs) detected by the Fermi Gamma-ray Space Telescope's Gamma-ray Burst Monitor (GBM) that fell within the field of view of Fermi's Large Area Telescope (LAT) during the first 2.5 years of observations, which showed no evidence for emission above 100 MeV. We report the photon flux upper limits in the 0.1-10 GeV range during the prompt emission phase as well as for fixed 30 s and 100 s integrations starting from the trigger time for each burst. We compare these limits with the fluxes that would be expected from extrapolations of spectral fits presented in the first GBM spectral catalog and infer that roughly half of the GBM-detected bursts either require spectral breaks between the GBM and LAT energy bands or have intrinsically steeper spectra above the peak of the νF ν spectra (E pk). In order to distinguish between these two scenarios, we perform joint GBM and LAT spectral fits to the 30 brightest GBM-detected bursts and find that a majority of these bursts are indeed softer above E pk than would be inferred from fitting the GBM data alone. Approximately 20% of this spectroscopic subsample show statistically significant evidence for a cutoff in their high-energy spectra, which if assumed to be due to γγ attenuation, places limits on the maximum Lorentz factor associated with the relativistic outflow producing this emission. All of these latter bursts have maximum Lorentz factor estimates that are well below the minimum Lorentz factors calculated for LAT-detected GRBs, revealing a wide distribution in the bulk Lorentz factor of GRB outflows and indicating that LAT-detected bursts may represent the high end of this distribution.

  6. Gamma-gamma colliders

    SciTech Connect

    Kim, K.J.; Sessler, A.

    1996-06-01

    Gamma-gamma colliders make intense beams of gamma rays and have them collide so as to make elementary particles. The authors show, in this article, that constructing a gamma-gamma collider as an add-on to an electron-positron linear collider is possible with present technology and that it does not require much additional cost. Furthermore, they show that the resulting capability is very interesting from a particle physics point of view. An overview of a linear collider, with a second interaction region devoted to {gamma}{gamma} collisions is shown.

  7. Multipurpose Radiation Resistant Semiconductor Detectors for Alpha, Neutron & Low Energy Gamma Ray Measurements at High Temperatures in High-Intensity Gamma Ray

    SciTech Connect

    Ruddy, Frank H.

    2005-06-01

    Work scheduled under year two of DOE Grant DE-FG02-04ER63734 is on schedule and all year-two milestones have or will be met. Results to date demonstrate that unprecedented silicon carbide (SiC) energy resolution has been obtained, and that SiC detectors may achieve energy resolution that exceeds that obtainable with the best silicon alpha spectrometers. Fast-neutron energy spectrometry measurements indicate that recoil-ion energy spectrometry should be possible with SiC detectors. Furthermore, SiC detectors have been demonstrated to perform well even after gamma-ray exposures of 1.E09 Rad. This result and the previously demonstrated capability of SiC detectors to operate in elevated-temperature environments are very promising for potential DOE EMSP applications. A new class of multipurpose, radiation-resistant semiconductor detectors that can be used in elevated-temperature and high-radiation environments is being developed under this grant. These detectors, based on silicon carbide (SiC) semiconductor are designed to have larger active volumes than previously available SiC detectors, and are being tested for their response to alpha particles, X-rays and low energy gamma rays, and fast neutrons. Specifically, SiC radiation detectors with larger areas and 100-micrometer thick active regions have been designed and manufactured according to detector-design specifications. Detectors based on a Schottky diode design were specified in order to minimize the effects of the detector entrance window on alpha particle measurements. During manufacture of the Schottky diodes, the manufacturer also provided a set of large-volume SiC p-i-n diodes for testing Extensive alpha particle measurements have been carried out to test and quantify the response of the SiC Schottky diodes. Exposures to 148-Gd, 213-Po, 217-At, 221-Fr, 225-Ac, 237-Np, 238-Pu, 240-Pu, and 242-Pu sources were used to obtain detailed alpha response data in the alpha energy range from 3182.787 keV to 8375.9 ke

  8. Multipurpose Radiation Resistant Semiconductor Detectors for Alpha, Neutron & Low Energy Gamma Ray Measurements at High Temperatures in High-Intensity Gamma Ray

    SciTech Connect

    Ruddy, Frank H

    2005-06-01

    Work scheduled under year two of DOE Grant DE-FG02-04ER63734 is on schedule and all year-two milestones have or will be met. Results to date demonstrate that unprecedented silicon carbide (SiC) energy resolution has been obtained, and that SiC detectors may achieve energy resolution that exceeds that obtainable with the best silicon alpha spectrometers. Fast-neutron energy spectrometry measurements indicate that recoil-ion energy spectrometry should be possible with SiC detectors. Furthermore, SiC detectors have been demonstrated to perform well even after gamma-ray exposures of 1.E09 Rad. This result and the previously demonstrated capability of SiC detectors to operate in elevated-temperature environments are very promising for potential DOE EMSP applications. A new class of multipurpose, radiation-resistant semiconductor detectors that can be used in elevated-temperature and high-radiation environments is being developed under this grant.

  9. Sensitivity of the High Altitude Water Cherenkov Experiment to observe Gamma-Ray Bursts

    NASA Astrophysics Data System (ADS)

    González, M. M.

    Ground based telescopes have marginally observed very high energy emission (>100GeV) from gamma-ray bursts(GRB). For instance, Milagrito observed GRB970417a with a significance of 3.7 sigmas over the background. Milagro have not yet observed TeV emission from a GRB with its triggered and untriggered searches or GeV emission with a triggered search using its scalers. These results suggest the need of new observatories with higher sensitivity to transient sources. The HAWC (High Altitute Water Cherenkov) observatory is proposed as a combination of the Milagro tecnology with a very high altitude (>4000m over see level) site. The expected HAWC sensitivity for GRBs is at least >10 times the Milagro sensitivity. In this work HAWC sensitivity for GRBs is discussed for different detector configurations such as altitude, distance between PMTs, depth under water of PMTs, number of PMTs required for a trigger, etc.

  10. High Purity Germanium Gamma-PHA Assay of Uranium Scrap Cans Used in 321-M Facility

    NASA Astrophysics Data System (ADS)

    Salaymeh, S. R.; Dewberry, R. A.; Casella, V.

    2001-12-01

    The Analytical Development Section of SRTC was requested by the Facilities Disposition Division (FDD) to determine the holdup of enriched uranium in the 321-M facility as part of an overall deactivation project of the facility. The 321-M facility was used to fabricate enriched uranium fuel assemblies, lithium-aluminum target tubes, neptunium assemblies, and miscellaneous components for the production reactors. The facility also includes the 324-M storage building and the passageway connecting it to 321-M. The results of the holdup assays are essential for determining compliance with the Solid Waste's Waste Acceptance Criteria, Material Control & Accountability, and to meet criticality safety controls. This report describes and documents the use of a portable HPGe detector and EG&G DART system that contains a high voltage power supply, signal processing electronics, a personal computer with Gamma-Vision software, and space to store and manipulate multiple 4096-channel gamma-ray spectra to assay for 235U content. The system was used to assay a large number of scrap cans used to store highly enriched uranium (HEU) chips and filings. This report includes a description of two efficiency calibration configurations and also the results of the assay. A description of the quality control checks is included as well.

  11. Milagro Search for Very High Energy Emission from Gamma-Ray Bursts in the Swift Era

    SciTech Connect

    Saz Parkinson, P. M.

    2006-05-19

    The recently launched Swift satellite is providing an unprecedented number of rapid and accurate Gamma-Ray Burst (GRB) localizations, facilitating a flurry of follow-up observations by a large number of telescopes at many different wavelengths. The Very High Energy (VHE, >100 GeV) regime has so far been relatively unexplored. Milagro is a wide field of view (2 sr) and high duty cycle (> 90%) ground-based gamma-ray telescope which employs a water Cherenkov detector to monitor the northern sky almost continuously in the 100 GeV to 100 TeV energy range. We have searched the Milagro data for emission from the most recent GRBs identified within our field of view. These include three Swift bursts which also display late-time X-ray flares. We have searched for emission coincident with these flares. No significant detection was made. A 99% confidence upper limit is provided for each of the GRBs, as well as the flares.

  12. High-efficiency scintillation detector for combined of thermal and fast neutrons and gamma radiation

    DOEpatents

    Chiles, Marion M.; Mihalczo, John T.; Blakeman, Edward D.

    1989-02-07

    A scintillation based radiation detector for the combined detection of thermal neutrons, high-energy neutrons and gamma rays in a single detecting unit. The detector consists of a pair of scintillators sandwiched together and optically coupled to the light sensitive face of a photomultiplier tube. A light tight radiation pervious housing is disposed about the scintillators and a portion of the photomultiplier tube to hold the arrangement in assembly and provides a radiation window adjacent the outer scintillator through which the radiation to be detected enters the detector. The outer scintillator is formed of a material in which scintillations are produced by thermal-neutrons and the inner scintillator is formed of a material in which scintillations are produced by high-energy neutrons and gamma rays. The light pulses produced by events detected in both scintillators are coupled to the photomultiplier tube which produces a current pulse in response to each detected event. These current pulses may be processed in a conventional manner to produce a count rate output indicative of the total detected radiation even count rate. Pulse discrimination techniques may be used to distinguish the different radiations and their energy distribution.

  13. High-efficiency scintillation detector for combined detection of thermal and fast neutrons and gamma radiation

    DOEpatents

    Chiles, M.M.; Mihalczo, J.T.; Blakeman, E.D.

    1987-02-27

    A scintillation based radiation detector for the combined detection of thermal neutrons, high-energy neutrons and gamma rays in a single detecting unit. The detector consists of a pair of scintillators sandwiched together and optically coupled to the light sensitive face of a photomultiplier tube. A light tight radiation pervious housing is disposed about the scintillators and a portion of the photomultiplier tube to hold the arrangement in assembly and provides a radiation window adjacent the outer scintillator through which the radiation to be detected enters the detector. The outer scintillator is formed of a material in which scintillations are produced by thermal-neutrons and the inner scintillator is formed of a material in which scintillations are produced by high-energy neutrons and gamma rays. The light pulses produced by events detected in both scintillators are coupled to the photomultiplier tube which produces a current pulse in response to each detected event. These current pulses may be processed in a conventional manner to produce a count rate output indicative of the total detected radiation event count rate. Pulse discrimination techniques may be used to distinguish the different radiations and their energy distribution.

  14. High-efficiency scintillation detector for combined of thermal and fast neutrons and gamma radiation

    DOEpatents

    Chiles, Marion M.; Mihalczo, John T.; Blakeman, Edward D.

    1989-01-01

    A scintillation based radiation detector for the combined detection of thermal neutrons, high-energy neutrons and gamma rays in a single detecting unit. The detector consists of a pair of scintillators sandwiched together and optically coupled to the light sensitive face of a photomultiplier tube. A light tight radiation pervious housing is disposed about the scintillators and a portion of the photomultiplier tube to hold the arrangement in assembly and provides a radiation window adjacent the outer scintillator through which the radiation to be detected enters the detector. The outer scintillator is formed of a material in which scintillations are produced by thermal-neutrons and the inner scintillator is formed of a material in which scintillations are produced by high-energy neutrons and gamma rays. The light pulses produced by events detected in both scintillators are coupled to the photomultiplier tube which produces a current pulse in response to each detected event. These current pulses may be processed in a conventional manner to produce a count rate output indicative of the total detected radiation even count rate. Pulse discrimination techniques may be used to distinguish the different radiations and their energy distribution.

  15. A Concept for a High-Energy Gamma-ray Polarimeter

    NASA Technical Reports Server (NTRS)

    Bloser, P. F.; Hunter, S. D.; Depaola, G. O.; Longo, F.

    2003-01-01

    We present a concept for an imaging gamma-ray polarimeter operating from approx. 50 MeV to approx. 1 GeV. Such an instrument would be valuable for the study of high-energy pulsars, active galactic nuclei, supernova remnants, and gamma-ray bursts. The concept makes use of pixelized gas micro-well detectors, under development at Goddard Space Flight Center, to record the electron-positron tracks from pair-production events in a large gas volume. Pixelized micro-well detectors have the potential to form large-volume 3-D track imagers with approx. 100 micron (rms) position resolution at moderate cost. The combination of high spatial resolution and a continuous low-density gas medium permits many thousands of measurements per radiation length, allowing the particle tracks to be imaged accurately before multiple scattering masks their original directions. The polarization of the incoming radiation may then be determined from the azimuthal distribution of the electron-positron pairs. We have performed Geant4 simulations of these processes to estimate the polarization sensitivity as a function of instrument parameters and event selection criteria.

  16. Perspectives for neutron and gamma spectroscopy in high power laser driven experiments at ELI-NP

    SciTech Connect

    Negoita, F. Gugiu, M. Petrascu, H. Petrone, C. Pietreanu, D.; Fuchs, J.; Chen, S.; Higginson, D.; Vassura, L.; Hannachi, F.; Tarisien, M.; Versteegen, M.; Antici, P.; Balabanski, D.; Balascuta, S.; Cernaianu, M.; Dancus, I.; Gales, S.; Neagu, L.; Petcu, C.; and others

    2015-02-24

    The measurement of energy spectra of neutrons and gamma rays emitted by nuclei, together with charge particles spectroscopy, are the main tools for understanding nuclear phenomena occurring also in high power laser driven experiments. However, the large number of particles emitted in a very short time, in particular the strong X-rays flash produced in laser-target interaction, impose adaptation of technique currently used in nuclear physics experiment at accelerator based facilities. These aspects are discussed (Section 1) in the context of proposed studies at high power laser system of ELI-NP. Preliminary results from two experiments performed at Titan (LLNL) and ELFIE (LULI) facilities using plastic scintillators for neutron detection (Section 2) and LaBr{sub 3}(Ce) scintillators for gamma detection (Section 3) are presented demonstrating the capabilities and the limitations of the employed methods. Possible improvements of these spectroscopic methods and their proposed implementation at ELI-NP will be discussed as well in the last section.

  17. Upright face-preferential high-gamma responses in lower-order visual areas: evidence from intracranial recordings in children

    PubMed Central

    Matsuzaki, Naoyuki; Schwarzlose, Rebecca F.; Nishida, Masaaki; Ofen, Noa; Asano, Eishi

    2015-01-01

    Behavioral studies demonstrate that a face presented in the upright orientation attracts attention more rapidly than an inverted face. Saccades toward an upright face take place in 100-140 ms following presentation. The present study using electrocorticography determined whether upright face-preferential neural activation, as reflected by augmentation of high-gamma activity at 80-150 Hz, involved the lower-order visual cortex within the first 100 ms post-stimulus presentation. Sampled lower-order visual areas were verified by the induction of phosphenes upon electrical stimulation. These areas resided in the lateral-occipital, lingual, and cuneus gyri along the calcarine sulcus, roughly corresponding to V1 and V2. Measurement of high-gamma augmentation during central (circular) and peripheral (annular) checkerboard reversal pattern stimulation indicated that central-field stimuli were processed by the more polar surface whereas peripheral-field stimuli by the more anterior medial surface. Upright face stimuli, compared to inverted ones, elicited up to 23% larger augmentation of high-gamma activity in the lower-order visual regions at 40-90 ms. Upright face-preferential high-gamma augmentation was more highly correlated with high-gamma augmentation for central than peripheral stimuli. Our observations are consistent with the hypothesis that lower-order visual regions, especially those for the central field, are involved in visual cues for rapid detection of upright face stimuli. PMID:25579446

  18. High-energy particle production in the 1997 November 6 flare as viewed from gamma rays and neutrons

    NASA Astrophysics Data System (ADS)

    Yoshimori, M.; Suga, K.; Nakayama, S.; Ogawa, H.; Share, G. H.; Murphy, R. J.

    2001-08-01

    Yohkoh observed hard Xand gamma-rays from a X9.4 flare on November 6, 1997. Strong gamma-rays were emitted in 11:52-11:56 UT (peak phase). After that, weak and extended gamma-ray production lasted for 600s (extended phase). The OSSE aboard CGRO detected neutrons associated with this flare between 12:08 and 12:28 UT. The neutron count-rate time profile exhibit a gradually decrease with time. We derive the proton spectra and the timing of particle acceleration to explain the observed neutron time profile. The proton spectra of E-3.5 in the peak phase and of E-3.0 in the extended phase give a good fit to the observed neutron time profile. We present detailed calculations of the neutron arrival time profiles and discuss high-energy particle production processes from the gamma-ray neutron observations.

  19. The intriguing nature of the high-energy gamma ray source XSS J12270-4859

    NASA Astrophysics Data System (ADS)

    de Martino, D.; Falanga, M.; Bonnet-Bidaud, J.-M.; Belloni, T.; Mouchet, M.; Masetti, N.; Andruchow, I.; Cellone, S. A.; Mukai, K.; Matt, G.

    2010-06-01

    Context. The nature of the hard X-ray source XSS J12270-4859 is still unclear. It was claimed to be a possible magnetic cataclysmic variable of the Intermediate Polar type from its optical spectrum and a possible 860 s X-ray periodicity in RXTE data. However, recent observations do not support the latter variability, leaving this X-ray source still unclassified. Aims: To investigate its nature we present a broad-band X-ray and gamma ray study of this source based on a recent XMM-Newton observation and archival INTEGRAL and RXTE data. Using the Fermi/LAT 1-year point source catalogue, we tentatively associate XSS J12270-4859 with 1FGL J1227.9-4852, a source of high-energy gamma rays with emission up to 10 GeV. We further complement the study with UV photometry from XMM-Newton and ground-based optical and near-IR photometry. Methods: We have analysed both timing and spectral properties in the gamma rays, X-rays, UV and optical/near-IR bands of XSS J12270-4859. Results: The X-ray emission is highly variable, showing flares and intensity dips. The flares consist of flare-dip pairs. Flares are detected in both X-rays and the UV range, while the subsequent dips are present only in the X-ray band. Further aperiodic dipping behaviour is observed during X-ray quiescence, but not in the UV. The broad-band 0.2-100 keV X-ray/soft gamma ray spectrum is featureless and well described by a power law model with Γ = 1.7. The high-energy spectrum from 100 MeV to 10 GeV is represented by a power law index of 2.45. The luminosity ratio between 0.1-100 GeV and 0.2-100 keV is ~0.8, indicating that the GeV emission is a significant component of the total energy output. Furthermore, the X-ray spectrum does not greatly change during flares, quiescence and the dips seen in quiescence. The X-ray spectrum however hardens during the post-flare dips, where a partial covering absorber is also required to fit the spectrum. Optical photometry acquired at different epochs reveals a period of 4

  20. High-gamma band fronto-temporal coherence as a measure of functional connectivity in speech motor control

    PubMed Central

    Kingyon, Johnathan; Behroozmand, Roozbeh; Kelley, Ryan; Oya, Hiroyuki; Kawasaki, Hiroto; Narayanan, Nandakumar S.; Greenlee, Jeremy D. W.

    2015-01-01

    The neural basis of human speech is unclear. Intracranial electrophysiological recordings have revealed that high-gamma band oscillations (70–150 Hz) are observed in frontal lobe during speech production and in the temporal lobe during speech perception. Here, we tested the hypothesis that the frontal and temporal brain regions had high-gamma coherence during speech. We recorded electrocorticography (ECoG) from the frontal and temporal cortices of five humans who underwent surgery for medically intractable epilepsy, and studied coherence between frontal and temporal cortex during vocalization and playback of vocalization. We report two novel results. First, we observed high-gamma band as well as theta (4–8 Hz) coherence between frontal and temporal lobes. Second, both high-gamma and theta coherence were stronger when subjects were actively vocalizing as compared to playback of the same vocalizations. These findings provide evidence that coupling between sensory-motor networks measured by high-gamma coherence plays a key role in feedback-based monitoring and control of vocal output for human vocalization. PMID:26232713

  1. High-gamma band fronto-temporal coherence as a measure of functional connectivity in speech motor control.

    PubMed

    Kingyon, J; Behroozmand, R; Kelley, R; Oya, H; Kawasaki, H; Narayanan, N S; Greenlee, J D W

    2015-10-01

    The neural basis of human speech is unclear. Intracranial electrophysiological recordings have revealed that high-gamma band oscillations (70-150Hz) are observed in the frontal lobe during speech production and in the temporal lobe during speech perception. Here, we tested the hypothesis that the frontal and temporal brain regions had high-gamma coherence during speech. We recorded electrocorticography (ECoG) from the frontal and temporal cortices of five humans who underwent surgery for medically intractable epilepsy, and studied coherence between the frontal and temporal cortex during vocalization and playback of vocalization. We report two novel results. First, we observed high-gamma band as well as theta (4-8Hz) coherence between frontal and temporal lobes. Second, both high-gamma and theta coherence were stronger when subjects were actively vocalizing as compared to playback of the same vocalizations. These findings provide evidence that coupling between sensory-motor networks measured by high-gamma coherence plays a key role in feedback-based monitoring and control of vocal output for human vocalization.

  2. HAND-HELD GAMMA-RAY SPECTROMETER BASED ON HIGH-EFFICIENCY FRISCH-RING CdZnTe DETECTORS.

    SciTech Connect

    CUI,Y.

    2007-05-01

    Frisch-ring CdZnTe detectors have demonstrated good energy resolution, el% FWHM at 662 keV, and good efficiency for detecting gamma rays. This technique facilitates the application of CdZnTe materials for high efficiency gamma-ray detection. A hand-held gamma-ray spectrometer based on Frisch-ring detectors is being designed at Brookhaven National Laboratory. It employs an 8x8 CdZnTe detector array to achieve a high volume of 19.2 cm3, so that detection efficiency is significantly improved. By using the front-end ASICs developed at BNL, this spectrometer has a small profile and high energy resolution. The spectrometer includes signal processing circuit, digitization and storage circuit, high-voltage module, and USB interface. In this paper, we introduce the details of the system structure and report our test results with it.

  3. Thermoluminescence glow-curve characteristics of LiF phosphors at high doses of gamma radiation

    NASA Astrophysics Data System (ADS)

    Benny, P. G.; Khader, S. A.; Sarma, K. S. S.

    2013-05-01

    High doses of ionising radiation are becoming increasingly common for radiation-processing applications of various medical, agricultural and polymer products using gamma and electron beams. The objective of this work was to study thermoluminescence (TL) glow-curve characteristics of commonly used commercial LiF TL phosphors at high doses of radiation with a view to use them in dosimetry of radiation-processing applications. The TL properties of TLD 100 and 700 phosphors, procured from the Thermo-Scientific (previously Harshaw) company, have been studied in the dose range of 1-60 kGy. The shift in glow peaks was observed in this dose range. Integral TL responses of TLD 100 and TLD 700 were found to decrease as a linear function of dose in the range of 5-50 kGy. The paper describes initial results related to the glow-curve characteristics of these phosphors.

  4. The High Altitude Water Cherenlov (HAWC) Gamma ray Detector Response to Atmospheric Electric Field Variations

    NASA Astrophysics Data System (ADS)

    Lara, A.

    2015-12-01

    The High Altitude Water Cherenkov (HAWC) observatory is located at 4100 m a.s.l. in Mexico. HAWC's primary purpose is the study of both: galactic and extra-galactic sources of high energy gamma rays. HAWC consists of 300 large water Cherenkov detectors (WCD), each instrumented with 4 photo-multipliers (PMTs). The HAWC scaler system records the rates of individual PMTs giving the opportunity of study relatively low energy transients as solar energetic particles, the solar modulation of galactic cosmic rays and possible variations of the cosmic ray rate due to atmospheric electric field changes. In this work, we present the observations of scaler rate enhancements associated with thunderstorm activity observed at the HAWC site.In particular, we present preliminary results of the analysis of the time coincidence of the electric field changes and the scaler enhancements.

  5. High-Resolution Gamma-Ray Imaging Measurements Using Externally Segmented Germanium Detectors

    NASA Technical Reports Server (NTRS)

    Callas, J.; Mahoney, W.; Skelton, R.; Varnell, L.; Wheaton, W.

    1994-01-01

    Fully two-dimensional gamma-ray imaging with simultaneous high-resolution spectroscopy has been demonstrated using an externally segmented germanium sensor. The system employs a single high-purity coaxial detector with its outer electrode segmented into 5 distinct charge collection regions and a lead coded aperture with a uniformly redundant array (URA) pattern. A series of one-dimensional responses was collected around 511 keV while the system was rotated in steps through 180 degrees. A non-negative, linear least-squares algorithm was then employed to reconstruct a 2-dimensional image. Corrections for multiple scattering in the detector, and the finite distance of source and detector are made in the reconstruction process.

  6. High-resolution observations of gamma-ray line emission from SN 1987A

    NASA Technical Reports Server (NTRS)

    Sandie, W. G.; Nakano, G. H.; Chase, L. F., Jr.; Fishman, G. J.; Meegan, C. A.; Wilson, R. B.

    1988-01-01

    Observations of SN 1987A made with a balloon-borne gamma-ray spectrometer comprising an array of high-purity germanium detectors on October 29-31, 1987 are presented. High resolution data, typically 2.5 keV at 1.33 MeV, were obtained for two transists of the supernova with interspersed background data. A preliminary estimation of line flux is presented. It is found that there is evidence of dynamical broadening of the 847 keV line. It is suggested that this line may be an emission from the first excited state of Fe-56 due to the radioactive decay of Co-56 providing evidence for nucleosynthesis in the supernova.

  7. Long-term meditators self-induce high-amplitude gamma synchrony during mental practice

    PubMed Central

    Lutz, Antoine; Greischar, Lawrence L.; Rawlings, Nancy B.; Ricard, Matthieu; Davidson, Richard J.

    2004-01-01

    Practitioners understand “meditation,” or mental training, to be a process of familiarization with one's own mental life leading to long-lasting changes in cognition and emotion. Little is known about this process and its impact on the brain. Here we find that long-term Buddhist practitioners self-induce sustained electroencephalographic high-amplitude gamma-band oscillations and phase-synchrony during meditation. These electroencephalogram patterns differ from those of controls, in particular over lateral frontoparietal electrodes. In addition, the ratio of gamma-band activity (25-42 Hz) to slow oscillatory activity (4-13 Hz) is initially higher in the resting baseline before meditation for the practitioners than the controls over medial frontoparietal electrodes. This difference increases sharply during meditation over most of the scalp electrodes and remains higher than the initial baseline in the postmeditation baseline. These data suggest that mental training involves temporal integrative mechanisms and may induce short-term and long-term neural changes. PMID:15534199

  8. Long-term meditators self-induce high-amplitude gamma synchrony during mental practice.

    PubMed

    Lutz, Antoine; Greischar, Lawrence L; Rawlings, Nancy B; Ricard, Matthieu; Davidson, Richard J

    2004-11-16

    Practitioners understand "meditation," or mental training, to be a process of familiarization with one's own mental life leading to long-lasting changes in cognition and emotion. Little is known about this process and its impact on the brain. Here we find that long-term Buddhist practitioners self-induce sustained electroencephalographic high-amplitude gamma-band oscillations and phase-synchrony during meditation. These electroencephalogram patterns differ from those of controls, in particular over lateral frontoparietal electrodes. In addition, the ratio of gamma-band activity (25-42 Hz) to slow oscillatory activity (4-13 Hz) is initially higher in the resting baseline before meditation for the practitioners than the controls over medial frontoparietal electrodes. This difference increases sharply during meditation over most of the scalp electrodes and remains higher than the initial baseline in the postmeditation baseline. These data suggest that mental training involves temporal integrative mechanisms and may induce short-term and long-term neural changes.

  9. Very high-energy gamma ray astronomy. [using the atmospheric cerenkov technique

    NASA Technical Reports Server (NTRS)

    Grindlay, J. E.

    1977-01-01

    Recent results in ground-based very high-energy (less than 10 to the eleventh power eV) gamma-ray astronomy are reviewed. The various modes of the atmospheric Cerenkov technique are described, and the importance of cosmic ray rejection methods is stressed. The positive detections (at approximately less than 10 to the 12th power eV) of the Crab pulsar that suggest a very flat spectrum and time-variable pulse phase are discussed. Observations of other pulsars (particularly Vela) suggest that these features may be general. The steady flux upper limits for the Crab Nebula are thus reconsidered, and a new value of the implied (Compton-synchrotron) magnetic field in the Nebula is reported. Evidence that a 4.8-hour modulated effect was detected at E sub gamma is less than 10 to the 12th power eV from Cyg X-3 is strengthened in that the exact period originally proposed agrees well with a recent determination of the X-ray period. The southern sky observations are reviewed, and the significance of the detection of an active galaxy (NGC 5128) is considered for source models and future observations.

  10. Ultra-High Rate Measurements of Spent Fuel Gamma-Ray Emissions

    NASA Astrophysics Data System (ADS)

    Rodriguez, Douglas; Vandevender, Brent; Wood, Lynn; Glasgow, Brian; Taubman, Matthew; Wright, Michael; Dion, Michael; Pitts, Karl; Runkle, Robert; Campbell, Luke; Fast, James

    2014-03-01

    Presently there are over 200,000 irradiated spent nuclear fuel (SNF) assemblies in the world, each containing a concerning amount of weapons-usable material. Both facility operators and safeguards inspectors want to improve composition determination. Current measurements are expensive and difficult so new methods are developed through models. Passive measurements are limited since a few specific decay products and the associated down-scatter overwhelm the gamma rays of interest. Active interrogation methods produce gamma rays beyond 3 MeV, minimizing the impact of the passive emissions that drop off sharply above this energy. New devices like the Ultra-High Rate Germanium (UHRGe) detector are being developed to advance these novel measurement methods. Designed for reasonable resolution at 106 s-1 output rates (compared to ~ 1 - 10 e 3 s-1 standards), SNF samples were directly measured using UHRGe and compared to models. Model verification further enables using Los Alamos National Laboratory SNF assembly models, developed under the Next Generation Safeguards Initiative, to determine emission and signal expectations. Measurement results and future application requirements for UHRGe will be discussed.

  11. Radioactivity of a Rock Profile from Rio do Rasto Formation Measured by High Resolution Gamma Spectrometry

    NASA Astrophysics Data System (ADS)

    Bastos, Rodrigo O.; Appoloni, Carlos R.; Pinese, José P. P.

    2011-08-01

    Natural occurring radionuclides are present in different concentrations in sedimentary rocks. Generally, their distribution correlates reasonably with their geo-physicochemical behavior during sediment deposition and rock consolidation. This fact permits to study some geological characteristics of the rocks by analyzing the radionuclide distribution in the rocks, as it might reflect the origin of the sediments, the depositional environment, and more recent events such as weathering and erosion. In this work, rocks from an exposed profile of the Rio do Rasto Formation were collected and analyzed in laboratory by high resolution gamma spectrometry for 226Ra, 232Th and 40K determination. It was employed a standard gamma ray spectrometry electronic chain, with a 66% relative efficiency HPGe detector. The efficiency calibration, as well as its validation, was accomplished with eight International Atomic Energy Agency certified samples. The outcrop exposes layers of sandstone and siltstone and, secondarily, claystone, with varying colors (gray, red and green). The rocks were collected along this profile, each of them was dried in the open air during 48 hours, grounded, sieved through 4 mm mesh and sealed in cylindrical recipients. The 226Ra, 232Th and 40K activity concentrations are presented, their distribution and the possible relations among activities are analyzed. The general pattern of radionuclides distribution respects well the hypotheses on geo-physicochemical behavior of radioactive elements.

  12. POCI: A compact high resolution {gamma} camera for intra-operative surgical use

    SciTech Connect

    Menard, L.; Charon, Y.; Solal, M.; Laniece, P.; Mastrippolito, R.; Pinot, L.; Ploux, L.; Valentin, L. |; Ricard, M.

    1998-06-01

    The development of a hand-held {gamma} imaging probe for inside body localization of small tumors is of first interest for radio-guided operative cancer surgery. In that context, the authors have developed a sub-millimeter spatial resolution, small field of view, {gamma} per-operative compact imager (POCI). It consists of a head module composed of a high resolution tungsten collimator and a YAP:Ce crystal plate, optically coupled to an intensified position sensitive diode (IPSD). The authors report here the essential imaging performance characteristics of the POCI camera (spatial resolution, position linearity, efficiency and energy response). These were obtained by studying the influence of the collimator and the crystal design to evaluate the optimal configuration. The present version of POCI has a 24 mm diameter usable field of view and an intrinsic spatial resolution of 0.9 mm to 1.2 mm FWHM at 120 keV. These good detection performance characteristics combined with the small size of the camera make the device well suited to provide intra-operative monitoring in several medical procedures, such as thyroid and breast tumor removal.

  13. High-resolution imaging gamma-ray spectroscopy with externally segmented germanium detectors

    NASA Technical Reports Server (NTRS)

    Callas, J. L.; Mahoney, W. A.; Varnell, L. S.; Wheaton, W. A.

    1993-01-01

    Externally segmented germanium detectors promise a breakthrough in gamma-ray imaging capabilities while retaining the superb energy resolution of germanium spectrometers. An angular resolution of 0.2 deg becomes practical by combining position-sensitive germanium detectors having a segment thickness of a few millimeters with a one-dimensional coded aperture located about a meter from the detectors. Correspondingly higher angular resolutions are possible with larger separations between the detectors and the coded aperture. Two-dimensional images can be obtained by rotating the instrument. Although the basic concept is similar to optical or X-ray coded-aperture imaging techniques, several complicating effects arise because of the penetrating nature of gamma rays. The complications include partial transmission through the coded aperture elements, Compton scattering in the germanium detectors, and high background count rates. Extensive electron-photon Monte Carlo modeling of a realistic detector/coded-aperture/collimator system has been performed. Results show that these complicating effects can be characterized and accounted for with no significant loss in instrument sensitivity.

  14. Connection of Very High Energy Gamma-ray Flares in Blazars to Activity at Lower Frequencies

    NASA Astrophysics Data System (ADS)

    Marscher, Alan P.; Jorstad, Svetlana G.

    2016-04-01

    The author will briefly review the results of multi-wavelength observations of blazars that emit very high-energy (VHE) gamma rays. The VHE gamma-ray emission is generally episodic, including flares that are often very short-lived. While many of these flares have counterparts only at X-ray energies, or no counterparts at all, some events are seen also at optical wavelengths, and a number are associated with the passage of new superluminal knots passing through the core in mm-wave VLBA images. Two explanations for the short-term VHE flares in the relativistic jets are supersonic turbulence and ultra-fast plasma jets resulting from magnetic reconnections. Observations of frequency-dependent linear polarization during flares can potentially decide between these models. VLBA images can help to locate VHE events that are seen at millimeter wavelengths. In some cases, the flares take place near the parsec-scale core, while in others they occur closer to the black hole.This research is supported in part by NASA through Swift Guest Investigator grants NNX15AR45G and NNX15AR34G.

  15. Amorphous and crystalline optical materials used as instruments for high gamma radiation doses estimations

    NASA Astrophysics Data System (ADS)

    Ioan, M.-R.

    2016-06-01

    Nuclear radiation induce some changes to the structure of exposed materials. The main effect of ionizing radiation when interacting with optical materials is the occurrence of color centers, which are quantitatively proportional to the up-taken doses. In this paper, a relation between browning effect magnitude and dose values was found. Using this relation, the estimation of a gamma radiation dose can be done. By using two types of laser wavelengths (532 nm and 633 nm), the optical powers transmitted thru glass samples irradiated to different doses between 0 and 59.1 kGy, were measured and the associated optical browning densities were determined. The use of laser light gives the opportunity of using its particularities: monochromaticity, directionality and coherence. Polarized light was also used for enhancing measurements quality. These preliminary results bring the opportunity of using glasses as detectors for the estimation of the dose in a certain point in space and for certain energy, especially in particles accelerators experiments, where the occurred nuclear reactions are involving the presence of high gamma rays fields.

  16. PoGOLite A high sensitivity balloon-borne soft gamma-ray polarimeter

    NASA Astrophysics Data System (ADS)

    Kamae, Tuneyoshi; Andersson, Viktor; Arimoto, Makoto; Axelsson, Magnus; Marini Bettolo, Cecilia; Björnsson, Claes-Ingvar; Bogaert, Gilles; Carlson, Per; Craig, William; Ekeberg, Tomas; Engdegård, Olle; Fukazawa, Yasushi; Gunji, Shuichi; Hjalmarsdotter, Linnea; Iwan, Bianca; Kanai, Yoshikazu; Kataoka, Jun; Kawai, Nobuyuki; Kazejev, Jaroslav; Kiss, Mózsi; Klamra, Wlodzimierz; Larsson, Stefan; Madejski, Grzegorz; Mizuno, Tsunefumi; Ng, Johnny; Pearce, Mark; Ryde, Felix; Suhonen, Markus; Tajima, Hiroyasu; Takahashi, Hiromitsu; Takahashi, Tadayuki; Tanaka, Takuya; Thurston, Timothy; Ueno, Masaru; Varner, Gary; Yamamoto, Kazuhide; Yamashita, Yuichiro; Ylinen, Tomi; Yoshida, Hiroaki

    2008-09-01

    We describe a new balloon-borne instrument (PoGOLite) capable of detecting 10% polarisation from 200 mCrab point-like sources between 25 and 80 keV in one 6-h flight. Polarisation measurements in the soft gamma-ray band are expected to provide a powerful probe into high energy emission mechanisms as well as the distribution of magnetic fields, radiation fields and interstellar matter. Synchrotron radiation, inverse Compton scattering and propagation through high magnetic fields are likely to produce high degrees of polarisation in the energy band of the instrument. We demonstrate, through tests at accelerators, with radioactive sources and through computer simulations, that PoGOLite will be able to detect degrees of polarisation as predicted by models for several classes of high energy sources. At present, only exploratory polarisation measurements have been carried out in the soft gamma-ray band. Reduction of the large background produced by cosmic-ray particles while securing a large effective area has been the greatest challenge. PoGOLite uses Compton scattering and photo-absorption in an array of 217 well-type phoswich detector cells made of plastic and BGO scintillators surrounded by a BGO anticoincidence shield and a thick polyethylene neutron shield. The narrow field of view (FWHM = 1.25 msr, 2.0 deg × 2.0 deg) obtained with detector cells and the use of thick background shields warrant a large effective area for polarisation measurements (˜228 cm 2 at E = 40 keV) without sacrificing the signal-to-noise ratio. Simulation studies for an atmospheric overburden of 3-4 g/cm 2 indicate that neutrons and gamma-rays entering the PDC assembly through the shields are dominant backgrounds. Off-line event selection based on recorded phototube waveforms and Compton kinematics reduce the background to that expected for a ˜100 mCrab source between 25 and 50 keV. A 6-h observation of the Crab pulsar will differentiate between the Polar Cap/Slot Gap, Outer Gap, and

  17. Observation of solar high energy gamma and X-ray emission and solar energetic particles

    NASA Astrophysics Data System (ADS)

    Struminsky, A.; Gan, W.

    2015-08-01

    We considered 18 solar flares observed between June 2010 and July 2012, in which high energy >100 MeV γ-emission was registered by the Large Area Telescope (LAT) aboard FermiGRO. We examined for these γ-events soft X-ray observations by GOES, hard X-ray observations by the Anti-Coincidence Shield of the SPectrometer aboard INTEGRAL (ACS SPI) and the Gamma-Ray burst Monitor (GBM) aboard FermiGRO. Hard X-ray and π0-decay γ-ray emissions are used as tracers of electron and proton acceleration, respectively. Bursts of hard X-ray were observed by ACS SPI during impulsive phase of 13 events. Bursts of hard X- ray >100 keV were not found during time intervals, when prolonged hard y-emission was registered by LAT/FermiGRO. Those events showing prolonged high-energy gamma-ray emission not accompanied by >100 keV hard X-ray emission are interpreted as an indication of either different acceleration processes for protons and electrons or as the presence of a proton population accelerated during the impulsive phase of the flare and subsequently trapped by some magnetic structure. In-situ energetic particle measurements by GOES and STEREO (High Energy Telescope, HET) shows that five of these y-events were not accompanied by SEP events at 1 AU, even when multi-point measurements including STEREO are taken into account. Therefore accelerated protons are not always released into the heliosphere. A longer delay between the maximum temperature and the maximum emission measure characterises flares with prolonged high energy γ-emission and solar proton events.

  18. A study of the sensitivity of an imaging telescope (GRITS) for high energy gamma-ray astronomy

    NASA Technical Reports Server (NTRS)

    Yearian, Mason R.

    1990-01-01

    When a gamma-ray telescope is placed in Earth orbit, it is bombarded by a flux of cosmic protons much greater than the flux of interesting gammas. These protons can interact in the telescope's thermal shielding to produce detectable gamma rays, most of which are vetoed. Since the proton flux is so high, the unvetoed gamma rays constitute a significant background relative to some weak sources. This background increases the observing time required to pinpoint some sources and entirely obscures other sources. Although recent telescopes have been designed to minimize this background, its strength and spectral characteristics were not previously calculated in detail. Monte Carlo calculations are presented which characterize the strength, spectrum and other features of the cosmic proton background using FLUKA, a hadronic cascade program. Several gamma-ray telescopes, including SAS-2, EGRET and the Gamma Ray Imaging Telescope System (GRITS), are analyzed, and their proton-induced backgrounds are characterized. In all cases, the backgrounds are either shown to be low relative to interesting signals or suggestions are made which would reduce the background sufficiently to leave the telescope unimpaired. In addition, several limiting cases are examined for comparison to previous estimates and calibration measurements.

  19. DISCOVERY OF VERY HIGH ENERGY {gamma}-RAY EMISSION FROM THE SNR G54.1+0.3

    SciTech Connect

    Acciari, V. A.; Benbow, W.; Aliu, E.; Boltuch, D.; Arlen, T.; Aune, T.; Bautista, M.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Dickherber, R.; Bradbury, S. M.; Butt, Y.; Byrum, K.; Cesarini, A.; Ciupik, L.; Cui, W.; Finley, J. P.; Duke, C.; Finnegan, G. E-mail: wakely@uchicago.ed

    2010-08-10

    We report the discovery of very high energy (VHE) gamma-ray emission from the direction of the SNR G54.1+0.3 using the VERITAS ground-based gamma-ray observatory. The TeV signal has an overall significance of 6.8{sigma} and appears pointlike given the resolution of the instrument. The integral flux above 1 TeV is 2.5% of the Crab Nebula flux and significant emission is measured between 250 GeV and 4 TeV, well described by a power-law energy spectrum dN/dE {approx} E {sup -{Gamma}} with a photon index {Gamma} = 2.39 {+-} 0.23{sub stat} {+-} 0.30{sub sys}. We find no evidence of time variability among observations spanning almost two years. Based on the location, the morphology, the measured spectrum, the lack of variability, and a comparison with similar systems previously detected in the TeV band, the most likely counterpart of this new VHE gamma-ray source is the pulsar wind nebula (PWN) in the SNR G54.1+0.3. The measured X-ray to VHE gamma-ray luminosity ratio is the lowest among all the nebulae supposedly driven by young rotation-powered pulsars, which could indicate a particle-dominated PWN.

  20. Sound identification in human auditory cortex: Differential contribution of local field potentials and high gamma power as revealed by direct intracranial recordings.

    PubMed

    Nourski, Kirill V; Steinschneider, Mitchell; Rhone, Ariane E; Oya, Hiroyuki; Kawasaki, Hiroto; Howard, Matthew A; McMurray, Bob

    2015-09-01

    High gamma power has become the principal means of assessing auditory cortical activation in human intracranial studies, albeit at the expense of low frequency local field potentials (LFPs). It is unclear whether limiting analyses to high gamma impedes ability of clarifying auditory cortical organization. We compared the two measures obtained from posterolateral superior temporal gyrus (PLST) and evaluated their relative utility in sound categorization. Subjects were neurosurgical patients undergoing invasive monitoring for medically refractory epilepsy. Stimuli (consonant-vowel syllables varying in voicing and place of articulation and control tones) elicited robust evoked potentials and high gamma activity on PLST. LFPs had greater across-subject variability, yet yielded higher classification accuracy, relative to high gamma power. Classification was enhanced by including temporal detail of LFPs and combining LFP and high gamma. We conclude that future studies should consider utilizing both LFP and high gamma when investigating the functional organization of human auditory cortex.

  1. Imaging of radiocesium uptake dynamics in a plant body by using a newly developed high-resolution gamma camera.

    PubMed

    Kawachi, Naoki; Yin, Yong-Gen; Suzui, Nobuo; Ishii, Satomi; Yoshihara, Toshihiro; Watabe, Hiroshi; Yamamoto, Seiichi; Fujimaki, Shu

    2016-01-01

    We developed a new gamma camera specifically for plant nutritional research and successfully performed live imaging of the uptake and partitioning of (137)Cs in intact plants. The gamma camera was specially designed for high-energy gamma photons from (137)Cs (662 keV). To obtain reliable images, a pinhole collimator made of tungsten heavy alloy was used to reduce penetration and scattering of gamma photons. A single-crystal scintillator, Ce-doped Gd3Al2Ga3O12, with high sensitivity, no natural radioactivity, and no hygroscopicity was used. The array block of the scintillator was coupled to a high-quantum efficiency position sensitive photomultiplier tube to obtain accurate images. The completed gamma camera had a sensitivity of 0.83 count s(-1) MBq(-1) for (137)Cs with an energy window from 600 keV to 730 keV, and a spatial resolution of 23.5 mm. We used this gamma camera to study soybean plants that were hydroponically grown and fed with 2.0 MBq of (137)Cs for 6 days to visualize and investigate the transport dynamics in aerial plant parts. (137)Cs gradually appeared in the shoot several hours after feeding, and then accumulated preferentially and intensively in growing pods and seeds; very little accumulation was observed in mature leaves. Our results also suggested that this gamma-camera method may serve as a practical analyzing tool for breeding crops and improving cultivation techniques resulting in low accumulation of radiocesium into the consumable parts of plants. PMID:25959930

  2. Imaging of radiocesium uptake dynamics in a plant body by using a newly developed high-resolution gamma camera.

    PubMed

    Kawachi, Naoki; Yin, Yong-Gen; Suzui, Nobuo; Ishii, Satomi; Yoshihara, Toshihiro; Watabe, Hiroshi; Yamamoto, Seiichi; Fujimaki, Shu

    2016-01-01

    We developed a new gamma camera specifically for plant nutritional research and successfully performed live imaging of the uptake and partitioning of (137)Cs in intact plants. The gamma camera was specially designed for high-energy gamma photons from (137)Cs (662 keV). To obtain reliable images, a pinhole collimator made of tungsten heavy alloy was used to reduce penetration and scattering of gamma photons. A single-crystal scintillator, Ce-doped Gd3Al2Ga3O12, with high sensitivity, no natural radioactivity, and no hygroscopicity was used. The array block of the scintillator was coupled to a high-quantum efficiency position sensitive photomultiplier tube to obtain accurate images. The completed gamma camera had a sensitivity of 0.83 count s(-1) MBq(-1) for (137)Cs with an energy window from 600 keV to 730 keV, and a spatial resolution of 23.5 mm. We used this gamma camera to study soybean plants that were hydroponically grown and fed with 2.0 MBq of (137)Cs for 6 days to visualize and investigate the transport dynamics in aerial plant parts. (137)Cs gradually appeared in the shoot several hours after feeding, and then accumulated preferentially and intensively in growing pods and seeds; very little accumulation was observed in mature leaves. Our results also suggested that this gamma-camera method may serve as a practical analyzing tool for breeding crops and improving cultivation techniques resulting in low accumulation of radiocesium into the consumable parts of plants.

  3. High resolution phoswich gamma-ray imager utilizing monolithic MPPC arrays with submillimeter pixelized crystals

    NASA Astrophysics Data System (ADS)

    Kato, T.; Kataoka, J.; Nakamori, T.; Kishimoto, A.; Yamamoto, S.; Sato, K.; Ishikawa, Y.; Yamamura, K.; Kawabata, N.; Ikeda, H.; Kamada, K.

    2013-05-01

    We report the development of a high spatial resolution tweezers-type coincidence gamma-ray camera for medical imaging. This application consists of large-area monolithic Multi-Pixel Photon Counters (MPPCs) and submillimeter pixelized scintillator matrices. The MPPC array has 4 × 4 channels with a three-side buttable, very compact package. For typical operational gain of 7.5 × 105 at + 20 °C, gain fluctuation over the entire MPPC device is only ± 5.6%, and dark count rates (as measured at the 1 p.e. level) amount to <= 400 kcps per channel. We selected Ce-doped (Lu,Y)2(SiO4)O (Ce:LYSO) and a brand-new scintillator, Ce-doped Gd3Al2Ga3O12 (Ce:GAGG) due to their high light yield and density. To improve the spatial resolution, these scintillators were fabricated into 15 × 15 matrices of 0.5 × 0.5 mm2 pixels. The Ce:LYSO and Ce:GAGG scintillator matrices were assembled into phosphor sandwich (phoswich) detectors, and then coupled to the MPPC array along with an acrylic light guide measuring 1 mm thick, and with summing operational amplifiers that compile the signals into four position-encoded analog outputs being used for signal readout. Spatial resolution of 1.1 mm was achieved with the coincidence imaging system using a 22Na point source. These results suggest that the gamma-ray imagers offer excellent potential for applications in high spatial medical imaging.

  4. Gamma delta T cells promote inflammation and insulin resistance during high fat diet-induced obesity in mice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Gamma delta T cells are resident in adipose tissue and increase during diet-induced obesity. Their possible contribution to the inflammatory response that accompanies diet-induced obesity was investigated in mice after a 5-10 week high milk fat diet. The high milk fat diet resulted in significant in...

  5. Limits on the high-energy gamma and neutrino fluxes from the SGR 1806-20 giant flare of 27 December 2004 with the AMANDA-II detector.

    PubMed

    Achterberg, A; Ackermann, M; Adams, J; Ahrens, J; Andeen, K; Atlee, D W; Bahcall, J N; Bai, X; Baret, B; Bartelt, M; Barwick, S W; Bay, R; Beattie, K; Becka, T; Becker, J K; Becker, K-H; Berghaus, P; Berley, D; Bernardini, E; Bertrand, D; Besson, D Z; Blaufuss, E; Boersma, D J; Bohm, C; Bolmont, J; Böser, S; Botner, O; Bouchta, A; Braun, J; Burgess, C; Burgess, T; Castermans, T; Chirkin, D; Christy, B; Clem, J; Cowen, D F; D'Agostino, M V; Davour, A; Day, C T; De Clercq, C; Demirörs, L; Descamps, F; Desiati, P; Deyoung, T; Diaz-Velez, J C; Dreyer, J; Dumm, J P; Duvoort, M R; Edwards, W R; Ehrlich, R; Eisch, J; Ellsworth, R W; Evenson, P A; Fadiran, O; Fazely, A R; Feser, T; Filimonov, K; Fox, B D; Gaisser, T K; Gallagher, J; Ganugapati, R; Geenen, H; Gerhardt, L; Goldschmidt, A; Goodman, J A; Gozzini, R; Grullon, S; Gross, A; Gunasingha, R M; Gurtner, M; Hallgren, A; Halzen, F; Han, K; Hanson, K; Hardtke, D; Hardtke, R; Harenberg, T; Hart, J E; Hauschildt, T; Hays, D; Heise, J; Helbing, K; Hellwig, M; Herquet, P; Hill, G C; Hodges, J; Hoffman, K D; Hommez, B; Hoshina, K; Hubert, D; Hughey, B; Hulth, P O; Hultqvist, K; Hundertmark, S; Hülss, J-P; Ishihara, A; Jacobsen, J; Japaridze, G S; Jones, A; Joseph, J M; Kampert, K-H; Karle, A; Kawai, H; Kelley, J L; Kestel, M; Kitamura, N; Klein, S R; Klepser, S; Kohnen, G; Kolanoski, H; Köpke, L; Krasberg, M; Kuehn, K; Landsman, H; Leich, H; Liubarsky, I; Lundberg, J; Madsen, J; Mase, K; Matis, H S; McCauley, T; McParland, C P; Meli, A; Messarius, T; Mészáros, P; Miyamoto, H; Mokhtarani, A; Montaruli, T; Morey, A; Morse, R; Movit, S M; Münich, K; Nahnhauer, R; Nam, J W; Niessen, P; Nygren, D R; Ogelman, H; Olbrechts, Ph; Olivas, A; Patton, S; Peña-Garay, C; Pérez de Los Heros, C; Piegsa, A; Pieloth, D; Pohl, A C; Porrata, R; Pretz, J; Price, P B; Przybylski, G T; Rawlins, K; Razzaque, S; Refflinghaus, F; Resconi, E; Rhode, W; Ribordy, M; Rizzo, A; Robbins, S; Roth, P; Rott, C; Rutledge, D; Ryckbosch, D; Sander, H-G; Sarkar, S; Schlenstedt, S; Schmidt, T; Schneider, D; Seckel, D; Seo, S H; Seunarine, S; Silvestri, A; Smith, A J; Solarz, M; Song, C; Sopher, J E; Spiczak, G M; Spiering, C; Stamatikos, M; Stanev, T; Steffen, P; Stezelberger, T; Stokstad, R G; Stoufer, M C; Stoyanov, S; Strahler, E A; Straszheim, T; Sulanke, K-H; Sullivan, G W; Sumner, T J; Taboada, I; Tarasova, O; Tepe, A; Thollander, L; Tilav, S; Toale, P A; Turcan, D; van Eijndhoven, N; Vandenbroucke, J; Van Overloop, A; Voigt, B; Wagner, W; Walck, C; Waldmann, H; Walter, M; Wang, Y-R; Wendt, C; Wiebusch, C H; Wikström, G; Williams, D R; Wischnewski, R; Wissing, H; Woschnagg, K; Xu, X W; Yodh, G; Yoshida, S; Zornoza, J D

    2006-12-01

    On 27 December 2004, a giant gamma flare from the Soft Gamma-Ray Repeater 1806-20 saturated many satellite gamma-ray detectors, being the brightest transient event ever observed in the Galaxy. AMANDA-II was used to search for down-going muons indicative of high-energy gammas and/or neutrinos from this object. The data revealed no significant signal, so upper limits (at 90% C.L.) on the normalization constant were set: 0.05(0.5) TeV-1 m;{-2} s;{-1} for gamma=-1.47 (-2) in the gamma flux and 0.4(6.1) TeV-1 m;{-2} s;{-1} for gamma=-1.47 (-2) in the high-energy neutrino flux.

  6. THE EXTRAGALACTIC BACKGROUND LIGHT FROM THE MEASUREMENTS OF THE ATTENUATION OF HIGH-ENERGY GAMMA-RAY SPECTRUM

    SciTech Connect

    Gong Yan; Cooray, Asantha

    2013-07-20

    The attenuation of high-energy gamma-ray spectrum due to the electron-positron pair production against the extragalactic background light (EBL) provides an indirect method to measure the EBL of the universe. We use the measurements of the absorption features of the gamma-rays from blazars as seen by the Fermi Gamma-ray Space Telescope to explore the EBL flux density and constrain the EBL spectrum, star formation rate density (SFRD), and photon escape fraction from galaxies out to z = 6. Our results are basically consistent with the existing determinations of the quantities. We find a larger photon escape fraction at high redshifts, especially at z = 3, compared to the result from recent Ly{alpha} measurements. Our SFRD result is consistent with the data from both gamma-ray burst and ultraviolet (UV) observations in the 1{sigma} level. However, the average SFRD we obtain at z {approx}> 3 matches the gamma-ray data better than the UV data. Thus our SFRD result at z {approx}> 6 favors the fact that star formation alone is sufficiently high enough to reionize the universe.

  7. Origin of ultra-high-energy gamma-rays from Cygnus X-3 and related sources

    NASA Technical Reports Server (NTRS)

    Kazanas, D.; Ellison, D. C.

    1986-01-01

    Diffusive shock acceleration of ions is examined as the mechanism responsible for the ultrahigh energy (UHE) gamma ray emission observed from Cygnus X-3 and several other binary X-ray sources at energies of 10 to the 15th eV and higher. The shock acceleration can under reasonable assumptions be sufficiently short to allow acceleration of ions to energies near 10 to the 16th eV. It is proposed that the subsequent proton-proton collisions and photodissociation of He-4 can produce a flux of neutrons that escapes from the acceleration site despite high magnetic fields. These neutrons, by interacting with the binary companion, produce the observed UHE radiation.

  8. Discovery of Very High Energy Gamma-Ray Emission from Rbs 0723 with the Magic Telescopes

    NASA Astrophysics Data System (ADS)

    Mirzoyan, Razmik

    2014-01-01

    The MAGIC collaboration reports the discovery of very high energy (VHE; E>100 GeV) gamma-ray emission from RBS 0723 (RA: 08:47:12.9 DEC: +11:33:50, J2000.0) RBS 0723 is a BL Lac object at redshift z=0.198. The source has been detected by Fermi-LAT, in the Second Fermi-LAT source Catalogue (2FGL; Nolan et al. 2012) with F(>1 GeV) = (5.3+-1.2)e-10 cm^-2 s^-1 and with photon index 1.48+-0.16. It also belongs to the first Fermi-LAT catalog of >10 GeV sources (1FHL; Ackermann et al, 2013), showing a hard (photon index = 1.4 +- 0.4) and bright (photon flux = 9.6e-11 ph cm^-2 s^-1) emission above 10 GeV, and identified as a good candidate for VHE detection.

  9. A Search for Early High-Energy Afterglows in BATSE Gamma-Ray Bursts

    NASA Technical Reports Server (NTRS)

    Giblin, Timothy W.

    2003-01-01

    The scope of this project was to perform a detailed search for the early high-energy afterglow component of gamma-ray bursts (GRBs) in the BATSE GRB data archive. GRBs are believed to be the product of shock waves generated in a relativistic outflow from the demise of extremely massive stars and/or binary neutron star mergers. The outflow undeniably encounters the ambient medium of the progenitor object and another shock wave is set up. A forward shock propagates into the medium and a reverse shock propagates through the ejecta. This "external" shock dissipates the kinetic energy of the ejecta in the form of radiation via synchrotron losses and slows the outflow eventually to a non-relativistic state. Radiation from the forward external shock is therefore expected to be long-lived, lasting days, weeks, and even months. This radiation is referred to as the 'afterglow'.

  10. Beyond VERITAS: High-Energy Gamma-Rays with the Cherenkov Telescope Array

    NASA Astrophysics Data System (ADS)

    Williams, David A.; CTA Consortium

    2016-01-01

    The Cherenkov Telescope Array (CTA) will be a new observatory for the study of very-high-energy gamma-ray sources, designed to achieve an order of magnitude improvement in sensitivity in the ~30 GeV to ~100 TeV energy band compared to currently operating instruments: VERITAS, MAGIC, and H.E.S.S. CTA will probe known sources with unprecedented sensitivity, angular resolution, and spectral coverage, while also detecting hundreds of new sources. CTA will provide access to data in this energy band to members of the wider astronomical community for the first time. The CTA Consortium will also conduct a number of Key Science Projects, including a Galactic Plane survey and a survey of one quarter of the extragalactic sky, creating legacy data sets that will also be available to the public. This presentation will describe how CTA will bring new opportunities for the solution of astrophysical puzzles.

  11. Characterization Studies of Radioactive Waste Drums Using High Resolution Gamma Spectrometric Systems

    SciTech Connect

    Toma, M.; Cristache, C.; Done, L.; Dragolici, F.; Sima, O.

    2010-01-21

    The problem of radioactive waste has become a critical issue in the country and worldwide. The radioactive waste containers, containing different radioactive materials, have to be characterized before their final disposal. Destructive methods, although being the most precise, are also the most expensive and not the easiest ones from the radioprotection point of view. In this situation, high resolution gamma spectrometry proved to be a reliable method for the non destructive assay method. However, the non-homogenous composition of the radioactive waste inside the drum makes the quantitative characterization of the radioactive waste drum a difficult task. Experimental studies and computed results, combined with Monte Carlo simulations using GESPECOR, are presented in this paper as a possibility to achieve this task.

  12. Compact, high-resolution, gamma ray imaging for scintimammography and other medical diagostic applications

    DOEpatents

    Majewski, Stanislaw; Weisenberger, Andrew G.; Wojcik, Randolph F.; Steinbach, Daniela

    1999-01-01

    A high resolution gamma ray imaging device includes an aluminum housing, a lead screen collimator at an opened end of the housing, a crystal scintillator array mounted behind the lead screen collimator, a foam layer between the lead screen collimator and the crystal scintillator array, a photomultiplier window coupled to the crystal with optical coupling grease, a photomultiplier having a dynode chain body and a base voltage divider with anodes, anode wire amplifiers each connected to four anodes and a multi pin connector having pin connections to each anode wire amplifier. In one embodiment the crystal scintillator array includes a yttrium aluminum perovskite (YAP) crystal array. In an alternate embodiment, the crystal scintillator array includes a gadolinium oxyorthosilicate (GSO) crystal array.

  13. High energy galactic gamma radiation from cosmic rays concentrated in spiral arms. [using SAS-B satellite

    NASA Technical Reports Server (NTRS)

    Bignami, G. F.; Fichtel, C. E.; Thompson, D. J.; Kniffen, D. A.

    1974-01-01

    A model for the emission of high energy ( 100 MeV) gamma rays from the galactic disk was developed and compared to recent SAS-2 observations. In the calculation, it is assumed that (1) the high energy galactic gamma rays result primarily from the interaction of cosmic rays with galactic matter; (2) on the basis of theoretical and experimental arguments the cosmic ray density is proportional to the matter density on the scale of galactic arms; and (3) the matter in the galaxy, atomic and molecular, is distributed in a spiral pattern consistent with density wave theory and the experimental data on the matter distribution.

  14. Evaluation of the cosmic-ray induced background in coded aperture high energy gamma-ray telescopes

    NASA Technical Reports Server (NTRS)

    Owens, Alan; Barbier, Loius M.; Frye, Glenn M.; Jenkins, Thomas L.

    1991-01-01

    While the application of coded-aperture techniques to high-energy gamma-ray astronomy offers potential arc-second angular resolution, concerns were raised about the level of secondary radiation produced in a thick high-z mask. A series of Monte-Carlo calculations are conducted to evaluate and quantify the cosmic-ray induced neutral particle background produced in a coded-aperture mask. It is shown that this component may be neglected, being at least a factor of 50 lower in intensity than the cosmic diffuse gamma-rays.

  15. Gamma detectors based on high pressure xenon: their development and application

    NASA Astrophysics Data System (ADS)

    Ulin, Sergey E.; Dmitrenko, Valery V.; Grachev, V. M.; Uteshev, Z. M.; Vlasic, K. F.; Chernysheva, I. V.; Duhvalov, A. G.; Kotler, F. G.; Pushkin, K. N.

    2004-01-01

    Various modifications of xenon detectors and their parameters in comparison with gamma-detectors of other types are considered. Prospects of xenon detectors' applications in gamma-spectroscopy based on experimental results are discussed including detection and control of radioactive and fissile materials displacement, definition of uranium enrichment rate, and measurements of nuclear reactor radioactive gas waste concentration. Possibilities for xenon detector use for environmental control and measurement of cosmic gamma radiation on orbital stations are considered.

  16. Gamma detectors based on high-pressure xenon: their development and application

    NASA Astrophysics Data System (ADS)

    Ulin, Sergey E.; Dmitrenko, Valery V.; Grachev, V. M.; Uteshev, Z. M.; Vlasik, K. F.; Chernysheva, I. V.; Dukhvalov, A. G.; Kotler, F. G.; Pushkin, K. N.

    2004-10-01

    Various modifications of xenon detectors and their parameters in comparison with gamma-detectors of other types are considered. Prospects of xenon detectors' applicatins in gamma-spectroscopy based on experimental results are discussed including detection and control of radioactive and fissile materials displacement, definition of uranium enrichment rate, and measurements of nuclear reactor radioactive gas waste concentration. Possibilities for xenon detector use for environmental control and measurement of cosmic gamma radiation on orbital stations are considered.

  17. On Ultra-high-energy Cosmic Rays and Their Resultant Gamma-Rays

    NASA Astrophysics Data System (ADS)

    Gavish, Eyal; Eichler, David

    2016-05-01

    The Fermi Large Area Telescope collaboration has recently reported on 50 months of measurements of the isotropic extragalactic gamma-ray background (EGRB) spectrum between 100 MeV and 820 GeV. Ultra-high-energy cosmic ray (UHECR) protons interact with the cosmic microwave background photons and produce cascade photons of energies 10 MeV-1 TeV that contribute to the EGRB flux. We examine seven possible evolution models for UHECRs and find that UHECR sources that evolve as the star formation rate (SFR), medium low luminosity active galactic nuclei type-1 (L = 1043.5 erg s-1 in the [0.5-2] KeV band), and BL Lacertae objects (BL Lacs) are the most acceptable given the constraints imposed by the observed EGRB. Other possibilities produce too much secondary γ-radiation. In all cases, the decaying dark matter (DM) contribution improves the fit at high energy, but the contribution of still unresolved blazars, which would leave the smallest role for decaying DM, may yet provide an alternative improvement. The possibility that the entire EGRB can be fitted with resolvable but not-yet-resolved blazars, as recently claimed by Ajello et al., would leave little room in the EGRB to accommodate γ-rays from extragalactic UHECR production, even for many source evolution rates that would otherwise be acceptable. We find that under the assumption of UHECRs being mostly protons, there is not enough room for producing extragalactic UHECRs with active galactic nucleus, gamma-ray burst, or even SFR source evolution. Sources that evolve as BL Lacs, on the other hand, would produce much less secondary γ-radiation and would remain a viable source of UHECRs, provided that they dominate.

  18. The Flux Variability of Markarian 501 in Very High Energy Gamma Rays

    SciTech Connect

    Quinn, J. Dept. of Experimental Physics, University College, Belfield, Dublin 4 ); Bond, I.H. ); Boyle, P.J. ); Bradbury, S.M. ); Breslin, A.C. ); Buckley, J.H. ); Burdett, A.M. Department of Physics, University of Leeds, Leeds, LS2 9JT, West Yorkshire, England ); Gordo, J.B. (Department of

    1999-06-01

    The BL Lacertae object Markarian 501 was identified as a source of [gamma]-ray emission at the Whipple Observatory in 1995 March. Here we present a flux variability analysis on several timescales of the 233 hr data set accumulated over 213 nights (from March 1995 to July 1998) with the Whipple Observatory 10 m atmospheric Cerenkov imaging telescope. In 1995, with the exception of a single night, the flux from Markarian 501 was constant on daily and monthly timescales and had an average flux of only 10[percent] that of the Crab Nebula, making it the weakest very high energy source detected to date. In 1996, the average flux was approximately twice the 1995 flux and showed significant month-to-month variability. No significant day-scale variations were detected. The average [gamma]-ray flux above [approximately]350 GeV in the 1997 observing season rose to 1.4 times that of the Crab Nebula[emdash]14 times the 1995 discovery level[emdash]allowing a search for variability on timescales shorter than 1 day. Significant hour-scale variability was present in the 1997 data, with the shortest, observed on MJD 50,607, having a doubling time of [approximately]2 hr. In 1998 the average emission level decreased considerably from that of 1997 (to [approximately]20[percent] of the Crab Nebula flux), but two significant flaring events were observed. Thus the emission from Markarian 501 shows large amplitude and rapid flux variability at very high energies, as does Markarian 421. It also shows large mean flux level variations on year-to-year timescales, behavior that has not been seen from Markarian 421 so far. [copyright] [ital [copyright] 1999.] [ital The American Astronomical Society

  19. High-level production of recombinant chicken interferon-gamma by Brevibacillus choshinensis.

    PubMed

    Yashiro, K; Lowenthal, J W; O'Neil, T E; Ebisu, S; Takagi, H; Moore, R J

    2001-10-01

    Cytokines, such as interferon-gamma have been shown to have adjuvant and growth promoting activity in poultry and livestock and have the potential to be used as alternatives to antibiotics. We have developed an efficient system for commercial-scale synthesis of recombinant chicken interferon-gamma (ChIFN-gamma) using Brevibacillus choshinensis as the host for protein production. The ChIFN-gamma expression vector, pNCIFN, was constructed using the novel Escherichia coli-B. choshinensis shuttle vector, pNCMO2. ChIFN-gamma expression was optimized by investigating different culture conditions and different host B. choshinensis mutants. The highest level of production was observed using the B. choshinensis HPD31-MB2 strain grown at 30 degrees C, where ChIFN-gamma was produced at approximately 300-500 mg/L. ChIFN-gamma was also produced as a His-tagged fusion protein by using the pNCHis-IFN expression vector, a derivative of pNCMO2. The protein was constitutively secreted into the culture supernatant and could be partially purified in a single step using a Ni-nitrilotriacetic acid column. This recombinant His-ChIFN-gamma was shown to have the same biological activity as native ChIFN-gamma. PMID:11570852

  20. High-energy neutrinos from the gravitational wave event GW150914 possibly associated with a short gamma-ray burst

    NASA Astrophysics Data System (ADS)

    Moharana, Reetanjali; Razzaque, Soebur; Gupta, Nayantara; Mészáros, Peter

    2016-06-01

    High-energy neutrinos (HEN) and gravitational waves (GW) can probe astrophysical sources in addition to electromagnetic observations. Multimessenger studies can reveal the nature of the sources, which may not be discerned from one type of signal alone. We discuss HEN emission in connection with the Advanced Laser Interferometer Gravitational-Wave Observatory event GW150914, which could be associated with a short gamma-ray burst detected by the Fermi Gamma-Ray Burst Monitor 0.4 s after the GW event and within localization uncertainty of the GW event. We calculate HEN flux from this short gamma-ray burst, GW150914-GBM, and show that nondetection of a high-energy starting event by the IceCube Neutrino Observatory can constrain the total isotropic-equivalent jet energy of this short burst to be less than 3 ×1052 erg .

  1. Gamma-ray bursts from the accretion of solid bodies onto high-velocity Galactic neutron stars

    SciTech Connect

    Colgate, S.A.; Leonard, P.J.T.

    1993-12-31

    We propose a simple model for the gamma-ray bursts based on high- velocity Galactic neutron stars that have accretion disks. The latter are formed from a mixture of material from the supernova shell and that ablated from a pre-supernova binary companion. Accretion onto the neutron star from this disk when the disk is still largely gaseous may result in a soft gamma-ray repeater phase. Much later, after the neutron star has moved away from its birthplace, solid bodies form in the disk, and some are perturbed into hitting the neutron star to create gamma-ray bursts. This model makes several predictions that are consistent with the observations. The observed combination of a high degree of isotropy on the sky coupled with the observed value of < V/V{sub max}> is not, at first glance, predicted, but is not impossible to attain in our model.

  2. THE {gamma}-RAY SPECTRUM OF GEMINGA AND THE INVERSE COMPTON MODEL OF PULSAR HIGH-ENERGY EMISSION

    SciTech Connect

    Lyutikov, Maxim

    2012-09-20

    We reanalyze the Fermi spectra of the Geminga and Vela pulsars. We find that the spectrum of Geminga above the break is well approximated by a simple power law without the exponential cutoff, making Geminga's spectrum similar to that of Crab. Vela's broadband {gamma}-ray spectrum is equally well fit with both the exponential cutoff and the double power-law shapes. In the broadband double power-law fits, for a typical Fermi spectrum of a bright {gamma}-ray pulsar, most of the errors accumulate due to the arbitrary parameterization of the spectral roll-off. In addition, a power law with an exponential cutoff gives an acceptable fit for the underlying double power-law spectrum for a very broad range of parameters, making such fitting procedures insensitive to the underlying Fermi photon spectrum. Our results have important implications for the mechanism of pulsar high-energy emission. A number of observed properties of {gamma}-ray pulsars-i.e., the broken power-law spectra without exponential cutoffs and stretching in the case of Crab beyond the maximal curvature limit, spectral breaks close to or exceeding the maximal breaks due to curvature emission, patterns of the relative intensities of the leading and trailing pulses in the Crab repeated in the X-ray and {gamma}-ray regions, presence of profile peaks at lower energies aligned with {gamma}-ray peaks-all point to the inverse Compton origin of the high-energy emission from majority of pulsars.

  3. Application of FEL technique for constructing high-intensity, monochromatic, polarized gamma-sources at storage rings

    SciTech Connect

    Saldin, E.L.; Schneidmiller, E.A.; Ulyanov, Yu.N.

    1995-12-31

    A possibility to construct high-intensity tunable monochromatic{gamma}-source at high energy storage rings is discussed. It is proposed to produce {gamma}-quanta by means of Compton backscattering of laser photons on electrons circulating in the storage. The laser light wavelength is chosen in such a way that after the scattering, the electron does not leave the separatrix. So as the probability of the scattering is rather small, energy oscillations are damped prior the next scattering. As a result, the proposed source can operate in {open_quotes}parasitic{close_quote} mode not interfering with the main mode of the storage ring operation. Analysis of parameters of existent storage rings (PETRA, ESRF, Spring-8, etc) shows that the laser light wavelength should be in infrared, {lambda}{approximately} 10 - 400 {mu}m, wavelength band. Installation at storage rings of tunable free-electron lasers with the peak and average output power {approximately} 10 MW and {approximately} 1 kW, respectively, will result in the intensity of the {gamma}-source up to {approximately} 10{sup 14}s{sup -1} with tunable {gamma}-quanta energy from several MeV up to several hundreds MeV. Such a {gamma}-source will reveal unique possibilities for precision investigations in nuclear physics.

  4. Very-high-energy Gamma-ray Observations Of Synchrotron-dominated Supernova Remnants With H.E.S.S.

    NASA Astrophysics Data System (ADS)

    Chaves, Ryan C. G.; Sushch, I.; Paz Arribas, M.; Volpe, F.; Komin, N.; Kerschhaggl, M.; H.E.S.S. Collaboration

    2011-09-01

    Supernova remnants (SNRs) are expected to produce very-high-energy (VHE; E > 100 GeV) gamma rays through interactions of high-energy particles with the surrounding medium and photon fields. VHE gamma-ray emission has indeed been discovered, by ground-based imaging atmospheric Cherenkov telescopes such as the H.E.S.S. telescope array, from a number of SNRs, establishing them as a prominent source class in the VHE domain. Of particular interest are the handful of SNRs whose X-ray spectra are dominated by non-thermal synchrotron emission; of these, the H.E.S.S. array has detected VHE gamma-ray emission from RX J1713.7-3946, RX J0852.0-4622 (Vela Jr.), RCW 86, SN 1006 and HESS J1731-347. The shell-type SNRs G1.9+0.3 and G330.2+1.0 also belong to this subclass and are further notable for their young ages (< 1 kyr), especially G1.9+0.3, which was recently determined to be the youngest SNR in the Galaxy ( 100 yr). These unique characteristics motivated investigations with H.E.S.S. to search for VHE gamma rays. The results of the H.E.S.S. observations and analyses will be presented, along with implications for potential particle acceleration scenarios, and discussed in comparison with the previously detected VHE gamma-ray shells.

  5. Prospects for exploring the local galaxies through the study of their high-energy gamma-ray emission

    NASA Technical Reports Server (NTRS)

    Ozel, Mehmet E.; Fichtel, Carl E.

    1988-01-01

    In the near future, high-energy (E greater than 20 MeV) gamma-ray astronomy offers the promise of a new means of examining the closest galaxies. Three local galaxies, the SMCs, LMCs, and M31, should be visible to the high-energy gamma-ray telescope on the Gamma Ray Observatory and the first two should be seen by GAMMA-1. It is expected that the intensity and the structure of both of the Magellanic Clouds can be examined in sufficient detail to study the cosmic-ray density and its variation, and, thereby, to determine the relevant scale of coupling for the cosmic rays and diffuse matter. With the assumptions of adequate sources and reasonable magnetic field strengths, both of which should likely be satisfied, very specific predictions of the gamma-ray emission can be made separating the three current cosmic-ray containment concepts, namely that it is on the scale of one to a few kiloparsec mass clustering, the whole galaxy, or some much larger scale. Further, because of the markedly different distributions of molecular and atomic hydrogen in the galaxies and the differences between the galaxies, an independent measure of the normalization of the diffuse molecular hydrogen density is possible.

  6. High Energy Electrons and Gamma Rays from the ATIC-2 Balloon Flight

    NASA Astrophysics Data System (ADS)

    Isbert, J. B.; ATIC Collaboration

    2004-08-01

    The Advanced Thin Ionization Calorimeter (ATIC) Balloon Experiment is primarily designed to measure the spectra of nuclear cosmic rays (protons to nickel). It is composed of a segmented BGO calorimeter (18 radiation lengths deep) following a carbon target (0.75 nuclear interaction lengths) interleaved with scintillator tracking layers. A Silicon matrix detector at the entrance identifies the incident particle charge. Utilizing simulations such as Fluka and Geant we have investigated the ability of this design to differentiate electron (gamma) initiated showers from hadronic showers. The differences in shower development between the two populations are sufficient to differentiate them for measurements of electron spectra into the TeV region, as confirmed by accelerator tests at CERN and by the ATIC-1 test flight in 2000-01. ATIC had a successful science flight in 2002-03 from McMurdo, Antarctica returning about 19 days of flight data. This exposure is sufficient to record electrons into the TeV region and measure gamma rays at 100's of GeV. The majority of gamma rays are of atmospheric origin and provide a test for this technique. The preliminary electron spectrum from the ATIC-2 flight is presented and compared to previous high energy measurements, principally from emulsion chambers. Possible astrophysical interpretations of the results are discussed. The ATIC Collaboration: J.H. Adams,2 H.S. Ahn,3 G.L. Bashindzhagyan,4 K.E. Batkov,4 J. Chang,6,7 M. Christl,2 A.R. Fazely,5, O. Ganel,3 R.M. Gunasingha,5 T.G. Guzik,1 J. Isbert,1 K.C. Kim,3 E.N. Kouznetsov,4 M.I. Panasyuk,4 A.D. Panov,4 W.K.H. Schmidt,6 E.S. Seo,3 N.V. Sokolskaya,4 J.Z. Wang,3 J.P. Wefel,1 J. Wu,3 V.I. Zatsepin,4 (1) Louisiana State University, Baton Rouge, LA, USA (2) Marshall Space Flight Center, Huntsville, AL, USA (3) University of Maryland, College Park, MD, USA (4) Skobeltsyn Institute of Nuclear Physics, Moscow State University, Moscow, Russia (5) Southern University, Baton Rouge, LA, USA (6

  7. EGRET upper limits to the high-energy gamma-ray emission from the millisecond pulsars in nearby globular clusters

    NASA Technical Reports Server (NTRS)

    Michelson, P. F.; Bertsch, D. L.; Brazier, K.; Chiang, J.; Dingus, B. L.; Fichtel, C. E.; Fierro, J.; Hartman, R. C.; Hunter, S. D.; Kanbach, G.

    1994-01-01

    We report upper limits to the high-energy gamma-ray emission from the millisecond pulsars (MSPs) in a number of globular clusters. The observations were done as part of an all-sky survey by the energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (CGRO) during Phase I of the CGRO mission (1991 June to 1992 November). Several theoretical models suggest that MSPs may be sources of high-energy gamma radiation emitted either as primary radiation from the pulsar magnetosphere or as secondary radiation generated by conversion into photons of a substantial part of the relativistic e(+/-) pair wind expected to flow from the pulsar. To date, no high-energy emission has been detected from an individual MSP. However, a large number of MSPs are expected in globular cluster cores where the formation rate of accreting binary systems is high. Model predictions of the total number of pulsars range in the hundreds for some clusters. These expectations have been reinforced by recent discoveries of a substantial number of radio MSPs in several clusters; for example, 11 have been found in 47 Tucanae (Manchester et al.). The EGRET observations have been used to obtain upper limits for the efficiency eta of conversion of MSP spin-down power into hard gamma rays. The upper limits are also compared with the gamma-ray fluxes predicted from theoretical models of pulsar wind emission (Tavani). The EGRET limits put significant constraints on either the emission models or the number of pulsars in the globular clusters.

  8. Managing NIF safety equipment in a high neutron and gamma radiation environment.

    PubMed

    Datte, Philip; Eckart, Mark; Jackson, Mark; Khater, Hesham; Manuel, Stacie; Newton, Mark

    2013-06-01

    The National Ignition Facility (NIF) is a 192 laser beam facility that supports the Inertial Confinement Fusion program. During the ignition experimental campaign, the NIF is expected to perform shots with varying fusion yield producing 14 MeV neutrons up to 20 MJ or 7.1 × 10(18) neutrons per shot and a maximum annual yield of 1,200 MJ. Several infrastructure support systems will be exposed to varying high yield shots over the facility's 30-y life span. In response to this potential exposure, analysis and testing of several facility safety systems have been conducted. A detailed MCNP (Monte Carlo N-Particle Transport Code) model has been developed for the NIF facility, and it includes most of the major structures inside the Target Bay. The model has been used in the simulation of expected neutron and gamma fluences throughout the Target Bay. Radiation susceptible components were identified and tested to fluences greater than 10(13) (n cm(-2)) for 14 MeV neutrons and γ-ray equivalent. The testing includes component irradiation using a 60Co gamma source and accelerator-based irradiation using 4- and 14- MeV neutron sources. The subsystem implementation in the facility is based on the fluence estimates after shielding and survivability guidelines derived from the dose maps and component tests results. This paper reports on the evaluation and implementation of mitigations for several infrastructure safety support systems, including video, oxygen monitoring, pressure monitors, water sensing systems, and access control interfaces found at the NIF.

  9. Semi-automated structural analysis of high resolution magnetic and gamma-ray spectrometry airborne surveys

    NASA Astrophysics Data System (ADS)

    Debeglia, N.; Martelet, G.; Perrin, J.; Truffert, C.; Ledru, P.; Tourlière, B.

    2005-08-01

    A user-controlled procedure was implemented for the structural analysis of geophysical maps. Local edge segments are first extracted using a suitable edge detector function, then linked into straight discontinuities and, finally, organised in complex boundary lines best delineating geophysical features. Final boundary lines may be attributed by a geologist to lithological contacts and/or structural geological features. Tests of some edge detectors, (i) horizontal gradient magnitude (HGM), (ii) various orders of the analytic signal ( An), reduced to the pole or not, (iii) enhanced horizontal derivative (EHD), (iv) composite analytic signal (CAS), were performed on synthetic magnetic data (with and without noise). As a result of these comparisons, the horizontal gradient appears to remain the best operator for the analysis of magnetic data. Computation of gradients in the frequency domain, including filtering and upward continuation of noisy data, is well-suited to the extraction of magnetic gradients associated to deep sources, while space-domain smoothing and differentiation techniques is generally preferable in the case of shallow magnetic sources, or for gamma-ray spectrometry analysis. Algorithms for edge extraction, segment linking, and line following can be controlled by choosing adequate edge detector and processing parameters which allows adaptation to a desired scale of interpretation. Tests on synthetic and real case data demonstrate the adaptability of the procedure and its ability to produce basic layer for multi-data analysis. The method was applied to the interpretation of high-resolution airborne magnetic and gamma-ray spectrometry data collected in northern Namibia. It allowed the delineation of dyke networks concealed by superficial weathering and demonstrated the presence of lithological variations in alluvial flows. The output from the structural analysis procedure are compatible with standard GIS softwares and enable the geologist to (i) compare

  10. A Multi-Contact, Low Capacitance HPGe Detector for High Rate Gamma Spectroscopy

    SciTech Connect

    Cox, Christopher

    2014-12-04

    The detection, identification and non-destructive assay of special nuclear materials and nuclear fission by-products are critically important activities in support of nuclear non-proliferation programs. Both national and international nuclear safeguard agencies recognize that current accounting methods for spent nuclear fuel are inadequate from a safeguards perspective. Radiation detection and analysis by gamma-ray spectroscopy is a key tool in this field, but no instrument exists that can deliver the required performance (energy resolution and detection sensitivity) in the presence of very high background count rates encountered in the nuclear safeguards arena. The work of this project addresses this critical need by developing a unique gamma-ray detector based on high purity germanium that has the previously unachievable property of operating in the 1 million counts-per-second range while achieving state-of-the-art energy resolution necessary to identify and analyze the isotopes of interest. The technical approach was to design and fabricate a germanium detector with multiple segmented electrodes coupled to multi-channel high rate spectroscopy electronics. Dividing the germanium detector’s signal electrode into smaller sections offers two advantages; firstly, the energy resolution of the detector is potentially improved, and secondly, the detector is able to operate at higher count rates. The design challenges included the following; determining the optimum electrode configuration to meet the stringent energy resolution and count rate requirements; determining the electronic noise (and therefore energy resolution) of the completed system after multiple signals are recombined; designing the germanium crystal housing and vacuum cryostat; and customizing electronics to perform the signal recombination function in real time. In this phase I work, commercial off-the-shelf electrostatic modeling software was used to develop the segmented germanium crystal geometry

  11. Multipurpose Radiation Resistant Semiconductor Detectors for Alpha, Neutron & Low Energy Gamma Ray Measurements at High Temperatures in High-Intensity Gamma Ray

    SciTech Connect

    Ruddy, Frank H.

    2005-06-01

    Work scheduled under year two of DOE Grant DE-FG02-04ER63734 is on schedule and all year-two milestones have or will be met. Results to date demonstrate that unprecedented silicon carbide (SiC) energy resolution has been obtained, and that SiC detectors may achieve energy resolution that exceeds that obtainable with the best silicon alpha spectrometers. Fast-neutron energy spectrometry measurements indicate that recoil-ion energy spectrometry should be possible with SiC detectors. Furthermore, SiC detectors have been demonstrated to perform well even after gamma-ray exposures of 1.E09 Rad. This result and the previously demonstrated capability of SiC detectors to operate in elevated-temperature environments are very promising for potential DOE EMSP applications. A new class of multipurpose, radiation-resistant semiconductor detectors that can be used in elevated-temperature and high-radiation environments is being developed under this grant. These detectors, based on silicon carbide (SiC) semiconductor are designed to have larger active volumes than previously available SiC detectors, and are being tested for their response to alpha particles, X-rays and low energy gamma rays, and fast neutrons. Specifically, SiC radiation detectors with larger areas and 100-micrometer thick active regions have been designed and manufactured according to detector-design specifications. Detectors based on a Schottky diode design were specified in order to minimize the effects of the detector entrance window on alpha particle measurements. During manufacture of the Schottky diodes, the manufacturer also provided a set of large-volume SiC p-i-n diodes for testing Extensive alpha particle measurements have been carried out to test and quantify the response of the SiC Schottky diodes. Exposures to 148-Gd, 213-Po, 217-At, 221-Fr, 225-Ac, 237-Np, 238-Pu, 240-Pu, and 242-Pu sources were used to obtain detailed alpha response data in the alpha energy range from 3182.787 keV to 8375.9 ke

  12. High-entropy fireballs and jets in gamma-ray burst sources

    NASA Technical Reports Server (NTRS)

    Meszaros, P.; Rees, M. J.

    1992-01-01

    Two mechanisms whereby compact coalescing binaries can produce relatively 'clean' fireballs via neutrino-antineutrino annihilation are proposed. Preejected mass due to tidal heating will collimate the fireball into jets. The resulting anisotropic gamma-ray emission can be efficient and intense enough to provide an acceptable model for gamma-ray bursts, if these originate at cosmological distances.

  13. Neutron interrogation system using high gamma ray signature to detect contraband special nuclear materials in cargo

    DOEpatents

    Slaughter, Dennis R.; Pohl, Bertram A.; Dougan, Arden D.; Bernstein, Adam; Prussin, Stanley G.; Norman, Eric B.

    2008-04-15

    A system for inspecting cargo for the presence of special nuclear material. The cargo is irradiated with neutrons. The neutrons produce fission products in the special nuclear material which generate gamma rays. The gamma rays are detecting indicating the presence of the special nuclear material.

  14. GeV gamma-ray astronomy telescopes with high angular resolution

    NASA Technical Reports Server (NTRS)

    Mcbreen, B.

    1985-01-01

    Gamma-ray telescopes flown on satellites have poor angular resolution with typical point source error circles of a few square degrees. It is shown that a major improvement in angular resolution for the detection of gamma-rays in the GeV region can be obtained with a single crystal as converter. The electron produced by a gamma ray incident at a small angle to a major crystal axis or plane is captured into channeling and radiates gamma rays. The channeling radiation and the electron-positron pair can be detected and yield point source locations with a precision of 5 arcseconds at 10 GeV. This is an improvement of three orders of magnitude on the angular precision of telescopes sensitive to gamma-rays above 50 MeV flown on Satellites.

  15. Gamma-ray polarization of the synchrotron self-compton process from a highly relativistic jet

    SciTech Connect

    Chang, Zhe; Lin, Hai-Nan

    2014-11-01

    The high polarization observed in the prompt phase of some gamma-ray bursts invites extensive study of the emission mechanism. In this paper, we investigate the polarization properties of the synchrotron self-Compton (SSC) process from a highly relativistic jet. A magnetic-dominated, baryon-loaded jet ejected from the central engine travels with a large Lorentz factor. Shells with slightly different velocities collide with each other and produce shocks. The shocks accelerate electrons to a power-law distribution and, at the same time, magnify the magnetic field. Electrons move in the magnetic field and produce synchrotron photons. Synchrotron photons suffer from the Compton scattering (CS) process and then are detected by an observer located slightly off-axis. We analytically derive the formulae of photon polarization in the SSC process in two magnetic configurations: a magnetic field in the shock plane and perpendicular to the shock plane. We show that photons induced by the SSC process can be highly polarized, with the maximum polarization Π ∼ 24% in the energy band [0.5, 5] MeV. The polarization depends on the viewing angles, peaking in the plane perpendicular to the magnetic field. In the energy band [0.05, 0.5] MeV, in which most γ-ray polarimeters are active, the polarization is about twice that in the Thomson limit, reaching Π ∼ 20%. This implies that the Klein-Nishina effect, which is often neglected in the literature, should be carefully considered.

  16. Multiscale Aspects of Generation of High-Gamma Activity during Seizures in Human Neocortex123

    PubMed Central

    Marcuccilli, Charles J.; Ben-Mabrouk, Faiza; Lew, Sean M.; Goodman, Robert R.; McKhann, Guy M.; Frim, David M.; Kohrman, Michael H.; Schevon, Catherine A.; van Drongelen, Wim

    2016-01-01

    High-gamma (HG; 80-150 Hz) activity in macroscopic clinical records is considered a marker for critical brain regions involved in seizure initiation; it is correlated with pathological multiunit firing during neocortical seizures in the seizure core, an area identified by correlated multiunit spiking and low frequency seizure activity. However, the effects of the spatiotemporal dynamics of seizure on HG power generation are not well understood. Here, we studied HG generation and propagation, using a three-step, multiscale signal analysis and modeling approach. First, we analyzed concurrent neuronal and microscopic network HG activity in neocortical slices from seven intractable epilepsy patients. We found HG activity in these networks, especially when neurons displayed paroxysmal depolarization shifts and network activity was highly synchronized. Second, we examined HG activity acquired with microelectrode arrays recorded during human seizures (n = 8). We confirmed the presence of synchronized HG power across microelectrode records and the macroscale, both specifically associated with the core region of the seizure. Third, we used volume conduction-based modeling to relate HG activity and network synchrony at different network scales. We showed that local HG oscillations require high levels of synchrony to cross scales, and that this requirement is met at the microscopic scale, but not within macroscopic networks. Instead, we present evidence that HG power at the macroscale may result from harmonics of ongoing seizure activity. Ictal HG power marks the seizure core, but the generating mechanism can differ across spatial scales. PMID:27257623

  17. Soft gamma-ray repeaters and anomalous X-ray pulsars as highly magnetized white dwarfs

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, Banibrata; Rao, A. R.

    2016-05-01

    We explore the possibility that soft gamma-ray repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are powered by highly magnetized white dwarfs (B-WDs). We take a sample of SGRs and AXPs and provide the possible parameter space in mass, radius, and surface magnetic field based on their observed properties (period and its derivative) and the assumption that these sources obey the mass-radius relation derived for the B-WDs. The radius and magnetic field of B-WDs are adequate to explain energies in SGRs/AXPs as the rotationally powered energy. In addition, B-WDs also adequately explain the perplexing radio transient GCRT J1745-3009 as a white dwarf pulsar. Note that the radius and magnetic fields of B-WDs are neither extreme (unlike of highly magnetized neutron stars) nor ordinary (unlike of magnetized white dwarfs, yet following the Chandrasekhar's mass-radius relation (C-WDs)). In order to explain SGRs/AXPs, while the highly magnetized neutron stars require an extra, observationally not well established yet, source of energy, the C-WDs predict large ultra-violet luminosity which is observationally constrained from a strict upper limit. Finally, we provide a set of basic differences between the magnetar and B-WD hypotheses for SGRs/AXPs.

  18. Possible production of high-energy gamma rays from proton acceleration in the extragalactic radio source markarian 501

    PubMed

    Mannheim

    1998-01-30

    The active galaxy Markarian 501 was discovered with air-Cerenkov telescopes at photon energies of 10 tera-electron volts. Such high energies may indicate that the gamma rays from Markarian 501 are due to the acceleration of protons rather than electrons. Furthermore, the observed absence of gamma ray attenuation due to electron-positron pair production in collisions with cosmic infrared photons implies a limit of 2 to 4 nanowatts per square meter per steradian for the energy flux of an extragalactic infrared radiation background at a wavelength of 25 micrometers. This limit provides important clues about the epoch of galaxy formation.

  19. REAL-TIME IN-SITU MEASUREMENT OF MATERIAL ELASTIC PROPERTIES IN A HIGH GAMMA IRRADIATION ENVIRONMENT

    SciTech Connect

    Ken Telschow; Rob Schley; Dave Cottle

    2006-05-01

    The first measurements of elastic vibrations of an object in-situ to a high gamma irradiation field using a laser coupled resonant ultrasound method are described. A vibration mode of an Inconel hollow capped cylinder was measured throughout a period of 170 hours as the gamma radiation field was increased to 104 Gray/hour. The vibration mode frequency was observed to change in a manner consistent with the temperature dependence of the elastic stiffness coefficients of the material. These results illustrate the efficacy of the laser approach for real-time resonant ultrasound measurements in this severely hostile nuclear environment.

  20. Observation and Simulations of the Backsplash Effects in High-Energy Gamma-Ray Telescopes Containing a Massive Calorimeter

    NASA Technical Reports Server (NTRS)

    Moiseev, Alexander A.; Ormes, Jonathan F.; Hartman, Robert C.; Johnson, Thomas E.; Mitchell, John W.; Thompson, David J.

    1999-01-01

    Beam test and simulation results are presented for a study of the backsplash effects produced in a high-energy gamma-ray detector containing a massive calorimeter. An empirical formula is developed to estimate the probability (per unit area) of backsplash for different calorimeter materials and thicknesses, different incident particle energies, and at different distances from the calorimeter. The results obtained are applied to the design of Anti-Coincidence Detector (ACD) for the Large Area Telescope (LAT) on the Gamma-ray Large Area Space Telescope (GLAST).

  1. Detection of Very High Energy Gamma-Ray Emission from 1ES 2037+521 with the MAGIC telescopes

    NASA Astrophysics Data System (ADS)

    Mirzoyan, Razmik

    2016-10-01

    The MAGIC collaboration reports the detection of very high energy (VHE) gamma-ray emission from 1ES 2037+521 (RA 20h39m23.5s, DEC +52d19m50s, J2000.0). The object was observed with the MAGIC telescopes for 11 hours between 2016/09/26 and 2016/09/30.

  2. Effects of high-temperature anneals and {sup 60}Co gamma-ray irradiation on strained silicon on insulator

    SciTech Connect

    Park, K.; Canonico, M.; Celler, G. K.; Seacrist, M.; Chan, J.; Gelpey, J.; Holbert, K. E.; Nakagawa, S.; Tajima, M.; Schroder, D. K.

    2007-10-01

    Strained silicon on insulator was exposed to high-temperature annealing and high-dose {sup 60}Co gamma ({gamma})-ray irradiation to study the tenacity of the bond between the strained Si film and the underlying buried oxide. During the high-temperature anneals, the samples were ramped at a rate of 150 deg. C/s to 850 deg. C then ramped to 1200, 1250, and 1300 deg. C at a rate of approximately 5x10{sup 5} deg. C/s for millisecond duration anneals. For the irradiation experiments, the samples were irradiated with {sup 60}Co {gamma} rays to a dose of 51.5 kGy. All samples were characterized by ultraviolet (UV) Raman, pseudo metal-oxide-semiconductor field-effect transistor ({psi}-MOSFET) current voltage, Hall mobility, and photoluminescence (PL) to verify changes in strain. UV Raman, PL, and {psi}-MOSFET measurements show no strain relaxation for the high-temperature annealed samples and only very slight relaxation for the {gamma}-ray irradiated samples.

  3. ATel 7516: VERITAS Detection of Very High-Energy Gamma-Ray Emission from S3 1227+25

    NASA Astrophysics Data System (ADS)

    Mukherjee, Reshmi

    2015-05-01

    The VERITAS Collaboration reports the detection of very high energy(VHE; E > 100 GeV) gamma-ray emission above 120 GeV from the low-synchrotron-peaked BL Lac object S3 1227+25 (z=0.135, see Nass et al. ...

  4. Modeling the Delayed Emission in the 2005 Mkn 501 Very-High-Energy Gamma-Ray Flare

    SciTech Connect

    Bednarek, Wlodek; Wagner, Robert

    2008-12-24

    Recently, the MAGIC collaboration reported evidence for a delay in the arrival times of photons of different energies during a {gamma}-ray flare from the blazar Markarian 501 on 2005 July 9. We describe the observed delayed high-energy emission by applying a homogeneous synchrotron self-Compton (SSC) model under the assumption that the blob, containing relativistic electrons, was observed in its acceleration phase. This modified SSC model predicts the appearance of a {gamma}-ray flare first at lower energies and subsequently at higher energies. Based on the reported time delay, we predict a delay on the order of 1 h if observed between 10 GeV and 100 GeV, which can be tested in the future by simultaneous flare observations using, e.g., the Fermi Gamma-Ray Telescope and Cerenkov telescopes.

  5. SOLIDIFICATION TESTING FOR A HIGH ACTIVITY WASTESTREAM FROM THE SAVANNAH RIVER SITE USING GROUT AND GAMMA RADIATION SHEILDING MATERIALS - 10017

    SciTech Connect

    Burns, H.

    2009-11-10

    The U.S. Department of Energy (DOE) tasked MSE Technology Applications, Inc. (MSE) with evaluating grouts that include gamma radiation shielding materials to solidify surrogates of liquid aqueous radioactive wastes from across the DOE Complex. The Savannah River Site (SRS) identified a High Activity Waste (HAW) that will be treated and solidified at the Waste Solidification Building (WSB) for surrogate grout testing. The HAW, which is produced at the Mixed Oxide Fuel Fabrication Facility (MFFF), is an acidic aqueous wastestream generated by the alkaline treatment process and the aqueous purification process. The HAW surrogate was solidified using Portland cement with and without the inclusion of different gamma radiation shielding materials to determine the shielding material that is the most effective to attenuate gamma radiation for this application.

  6. Dictyostelium possesses highly diverged presenilin/gamma-secretase that regulates growth and cell-fate specification and can accurately process human APP: a system for functional studies of the presenilin/gamma-secretase complex.

    PubMed

    McMains, Vanessa C; Myre, Michael; Kreppel, Lisa; Kimmel, Alan R

    2010-01-01

    Presenilin (PS) is the catalytic moiety of the gamma-secretase complex. PS and other gamma-secretase components are well conserved among metazoa, but their presence and function in more-distant species are not resolved. Because inappropriate gamma-secretase processing of amyloid precursor protein (APP) in humans is associated with familial Alzheimer's disease, understanding essential elements within each gamma-secretase component is crucial to functional studies. Diverged proteins have been identified in primitive plants but experiments have failed to demonstrate gamma-secretase activity. We have identified highly diverged orthologs for each gamma-secretase component in the ancient eukaryote Dictyostelium, which lacks equivalents of APP, Notch and other characterized PS/gamma-secretase substrates. We show that wild-type (WT) Dictyostelium is capable of amyloidogenic processing of ectopically expressed human APP to generate amyloid-beta peptides Abeta(40) and Abeta(42); strains deficient in gamma-secretase cannot produce Abeta peptides but accumulate processed intermediates of APP that co-migrate with the C-terminal fragments alpha- and beta-CTF of APP that are found in mammalian cells. We further demonstrate that Dictyostelium requires PS for phagocytosis and cell-fate specification in a cell-autonomous manner, and show that regulation of phagocytosis requires an active gamma-secretase, a pathway suggested, but not proven, to occur in mammalian and Drosophila cells. Our results indicate that PS signaling is an ancient process that arose prior to metazoan radiation, perhaps independently of Notch. Dictyostelium might serve to identify novel PS/gamma-secretase signaling targets and provide a unique system for high-throughput screening of small-molecule libraries to select new therapeutic targets for diseases associated with this pathway. PMID:20699477

  7. Mechanical Behavior of Gamma-Met PX under Uniaxial Loading at Elevated Temperatures and High Strain Rates

    NASA Technical Reports Server (NTRS)

    Shazly, Mostafa; Prakash, Vikas; Draper, Susan

    2005-01-01

    Gamma titanium aluminides have received considerable attention over the last decade. These alloys are known to have low density, good high temperature strength retention and good oxidation and corrosion resistance. However, poor ductility and low fracture toughness have been the key limiting factors in the full utilization of these alloys. More recently, a new generation of gamma titanium aluminide alloys, commonly referred to as Gamma-met PX, has been developed by GKSS, Germany. These alloys have been observed to have superior strength and better oxidation resistance at elevated temperatures when compared with conventional gamma titanium aluminides. The present paper discusses results of a study to understand the uniaxial mechanical behavior in both compression and tension of Gamma-Met PX at elevated temperatures and high strain rates. The compression and tensile tests are conducted using a modified split-Hopkinson bar apparatus at test temperatures ranging from room temperature to 900 C and strain rates of up to 3500/s. Under uniaxial compression, in the temperature range from room to 600 C, the flow stress is observed to be nearly independent of test temperature. However, at temperatures higher than 600 C thermal softening is observed at all strain rates with the rate of thermal softening increasing dramatically between 800 C and 900 C. The room temperature tensile tests show negligible strain-rate dependence on both yield stress and flow stress. With an increase in test temperature from room to 900 C the material shows a drop in both yield and flow stress at all levels of plastic strain. However, the measured flow stress is still higher when compared to nickel based super-alloys and other gamma titanium aluminides under similar test conditions. Also, no anomaly in yield stress is observed up to 900 C.

  8. Search for high mass photon pairs in p{anti p}{yields}{gamma}{gamma}jj events at {radical}s = 1.8 TeV

    SciTech Connect

    Abbott, B.; D0 Collaboration

    1997-10-01

    A search for new physics in the channel p{anti p} {yields} {gamma}{gamma}jj has been studied. In some extended Higgs models, a light neutral scalar Higgs boson is produced with suppressed couplings to fermions and standard model(SM) strength couplings to vector bosons(bosonic Higgs), thus enhancing the H {yields} {gamma}{gamma} channel. We required one photon in the event with E{sup {gamma}}{sub T} > 20 GeV, {vert_bar}{eta}{sup {gamma}}{vert_bar} < 1.1 or 1.5 < {vert_bar}{eta}{sup {gamma}}{vert_bar} < 2.0 and a second photon with E{sup {gamma}}{sub T} > 15 GeV, {vert_bar}{eta}{sup {gamma}}{vert_bar} < 1.1 or 1.5 < {vert_bar}{eta}{sup {gamma}}{vert_bar} < 2.25. Additionally, we required one hadronic jet in the event with E{sup jet}{sub T} > 20 GeV, {vert_bar}{eta}{sup jet}{vert_bar} < 2.0 and a second hadronic jet with E{sup jet}{sub T} > 15 GeV, {vert_bar}{eta}{sup jet}{vert_bar} < 2.25. The photons are required to have a {summation}{rvec E}{sub T}({gamma}) {>=} 10 GeV, and likewise the jets are required to have a {summation}{rvec E}{sub T}(jet) {>=} 10 GeV. The final M{sub {gamma}{gamma}} distribution is consistent with background and no resonance is observed. A 90(95)% C.L. upper limit cross section vs M{sub {gamma}{gamma}} is calculated, which ranges from 0.6(0.7) pb{sup -1} for M{sub {gamma}{gamma}} = 60 GeV/c{sup 2} to 0.3(0.4) pb{sup -1} for M{sub {gamma}{gamma}} = 130 GeV/c{sup 2}. With standard model coupling strengths between the bosonic Higgs and vector bosons, a 90(95)% C.L. bosonic Higgs lower mass limit is set at 86(81) GeV/c{sup 2}.

  9. IN-SITU ASSAY OF TRANSURANIC RADIONUCLIDES IN THE VADOSE ZONE USING HIGH-RESOLUTION SPECTRAL GAMMA LOGGING - A HANFORD CASE STUDY

    SciTech Connect

    ROHAY VJ; HENWOOD P; MCCAIN R

    2009-11-30

    High-resolution spectral gamma logging in steel-cased boreholes is used to detect and quantify transuranic radionuclides in the subsurface. Pu-239, Pu-241, Am-241, and Np-237 are identified based on characteristic decay gammas. Typical minimum detectable levels are on the order of 20 to 40 nCi/g. In intervals of high transuranic concentrations, gamma rays from other sources may complicate analysis and interpretation. Gamma rays detected in the borehole may originate from three sources: decay of the parent transuranic radionuclide or a daughter; alpha interactions; and interactions with neutrons resulting from either spontaneous fission or alpha particle interactions.

  10. The high-redshift gamma-ray burst GRB 140515A

    SciTech Connect

    Melandri, A.; Bernardini, M. G.; D'Avanzo, P. D.; Sanchez-Ramirez, R.; Nappo, F.; Nava, L.; Japelj, J.; de Ugarte Postigo, A.; Oates, S.; Campana, S.; Covino, S.; D'Elia, V.; Ghirlanda, G.; Gafton, E.; Ghisellini, G.; Gnedin, N.; Goldoni, P.; Gorosabel, J.; Libbrecht, T.; Malesani, D.; Salvaterra, R.; Thone, C. C.; Vergani, S. D.; Xu, D.; Tagliaferri, G.

    2015-09-09

    High-redshift gamma-ray bursts (GRBs) offer several advantages when studying the distant Universe, providing unique information about the structure and properties of the galaxies in which they exploded. Spectroscopic identification with large ground-based telescopes has improved our knowledge of this kind of distant events. We present the multi-wavelength analysis of the high-zSwift GRB GRB 140515A (z = 6.327). The best estimate of the neutral hydrogen fraction of the intergalactic medium towards the burst is xHI ≤ 0.002. The spectral absorption lines detected for this event are the weakest lines ever observed in GRB afterglows, suggesting that GRB 140515A exploded in a very low-density environment. Its circum-burst medium is characterised by an average extinction (AV ~ 0.1) that seems to be typical of z ≥ 6 events. The observed multi-band light curves are explained either with a very hard injected spectrum (p = 1.7) or with a multi-component emission (p = 2.1). In the second case a long-lasting central engine activity is needed in order to explain the late time X-ray emission. Furthermore, the possible origin of GRB 140515A in a Pop III (or in a Pop II star with a local environment enriched by Pop III) massive star is unlikely.

  11. Model-dependent high-energy neutrino flux from gamma-ray bursts.

    PubMed

    Zhang, Bing; Kumar, Pawan

    2013-03-22

    The IceCube Collaboration recently reported a stringent upper limit on the high energy neutrino flux from gamma-ray bursts (GRBs), which provides a meaningful constraint on the standard internal shock model. Recent broadband electromagnetic observations of GRBs also challenge the internal shock paradigm for GRBs, and some competing models for γ-ray prompt emission have been proposed. We describe a general scheme for calculating the GRB neutrino flux, and compare the predicted neutrino flux levels for different models. We point out that the current neutrino flux upper limit starts to constrain the standard internal shock model. The dissipative photosphere models are also challenged if the cosmic ray luminosity from GRBs is at least 10 times larger than the γ-ray luminosity. If the neutrino flux upper limit continues to go down in the next few years, then it would suggest the following possibilities: (i) the photon-to-proton luminosity ratio in GRBs is anomalously high for shocks, which may be achieved in some dissipative photosphere models and magnetic dissipation models; or (ii) the GRB emission site is at a larger radius than the internal shock radius, as expected in some magnetic dissipation models such as the internal collision-induced magnetic reconnection and turbulence model.

  12. High doses of gamma radiation suppress allergic effect induced by food lectin

    NASA Astrophysics Data System (ADS)

    Vaz, Antônio F. M.; Souza, Marthyna P.; Vieira, Leucio D.; Aguiar, Jaciana S.; Silva, Teresinha G.; Medeiros, Paloma L.; Melo, Ana M. M. A.; Silva-Lucca, Rosemeire A.; Santana, Lucimeire A.; Oliva, Maria L. V.; Perez, Katia R.; Cuccovia, Iolanda M.; Coelho, Luana C. B. B.; Correia, Maria T. S.

    2013-04-01

    One of the most promising areas for the development of functional foods lies in the development of effective methods to reduce or eliminate food allergenicity, but few reports have summarized information concerning the progress made with food irradiation. In this study, we investigated the relationship between allergenicity and molecular structure of a food allergen after gamma irradiation and evaluate the profile of the allergic response to irradiated allergens. Cramoll, a lectin isolated from a bean and used as a food allergen, was irradiated and the possible structural changes were accompanied by spectrofluorimetry, circular dichroism and microcalorimetry. Subsequently, sensitized animals subjected to intragastric administration of non-irradiated and irradiated Cramoll were treated for 7 days. Then, body weight, leukocytes, cytokine profiles and histological parameters were also determined. Cramoll showed complete inhibition of intrinsic activity after high radiation doses. Changes in fluorescence and CD spectra with a simultaneous collapse of the tertiary structure followed by a pronounced decrease of native secondary structure were observed after irradiation. After oral challenge, sensitized mice demonstrate an association between Cramoll intake, body weight loss, eosinophilia, lymphocytic infiltrate in the gut and Eotaxin secretion. Irradiation significantly reduces, according to the dose, the effects observed by non-irradiated food allergens. We confirm that high-dose radiation may render protein food allergens innocuous by irreversibly compromising their molecular structure.

  13. High-molecular-weight polymers for protein crystallization: poly-gamma-glutamic acid-based precipitants.

    PubMed

    Hu, Ting Chou; Korczyńska, Justyna; Smith, David K; Brzozowski, Andrzej Marek

    2008-09-01

    Protein crystallization has been revolutionized by the introduction of high-throughput technologies, which have led to a speeding up of the process while simultaneously reducing the amount of protein sample necessary. Nonetheless, the chemistry dimension of protein crystallization has remained relatively undeveloped. Most crystallization screens are based on the same set of precipitants. To address this shortcoming, the development of new protein precipitants based on poly-gamma-glutamic acid (PGA) polymers with different molecular-weight ranges is reported here: PGA-LM (low molecular weight) of approximately 400 kDa and PGA-HM (high molecular weight) of >1,000 kDa. It is also demonstrated that protein precipitants can be expanded further to polymers with much higher molecular weight than those that are currently in use. Furthermore, the modification of PGA-like polymers by covalent attachments of glucosamine substantially improved their solubility without affecting their crystallization properties. Some preliminary PGA-based screens are presented here.

  14. The high-redshift gamma-ray burst GRB 140515A

    DOE PAGESBeta

    Melandri, A.; Bernardini, M. G.; D'Avanzo, P. D.; Sanchez-Ramirez, R.; Nappo, F.; Nava, L.; Japelj, J.; de Ugarte Postigo, A.; Oates, S.; Campana, S.; et al

    2015-09-09

    High-redshift gamma-ray bursts (GRBs) offer several advantages when studying the distant Universe, providing unique information about the structure and properties of the galaxies in which they exploded. Spectroscopic identification with large ground-based telescopes has improved our knowledge of this kind of distant events. We present the multi-wavelength analysis of the high-zSwift GRB GRB 140515A (z = 6.327). The best estimate of the neutral hydrogen fraction of the intergalactic medium towards the burst is xHI ≤ 0.002. The spectral absorption lines detected for this event are the weakest lines ever observed in GRB afterglows, suggesting that GRB 140515A exploded in amore » very low-density environment. Its circum-burst medium is characterised by an average extinction (AV ~ 0.1) that seems to be typical of z ≥ 6 events. The observed multi-band light curves are explained either with a very hard injected spectrum (p = 1.7) or with a multi-component emission (p = 2.1). In the second case a long-lasting central engine activity is needed in order to explain the late time X-ray emission. Furthermore, the possible origin of GRB 140515A in a Pop III (or in a Pop II star with a local environment enriched by Pop III) massive star is unlikely.« less

  15. TARGET: A multi-channel digitizer chip for very-high-energy gamma-ray telescopes

    SciTech Connect

    Bechtol, K.; Funk, S.; Okumura, A.; Ruckman, L.; Simons, A.; Tajima, H.; Vandenbroucke, J.; Varner, G.; /Hawaii U.

    2011-08-11

    The next-generation very-high-energy (VHE) gamma-ray observatory, the Cherenkov Telescope Array, will feature dozens of imaging atmospheric Cherenkov telescopes (IACTs), each with thousands of pixels of photosensors. To be affordable and reliable, reading out such a mega-channel array requires event recording technology that is highly integrated and modular, with a low cost per channel. We present the design and performance of a chip targeted to this application: the TeV Array Readout with GSa/s sampling and Event Trigger (TARGET). This application-specific integrated circuit (ASIC) has 16 parallel input channels, a 4096-sample buffer for each channel, adjustable input termination, self-trigger functionality, and tight window-selected readout. We report the performance of TARGET in terms of sampling frequency, power consumption, dynamic range, current-mode gain, analog bandwidth, and cross talk. The large number of channels per chip allows a low cost per channel ($10 to $20 including front-end and back-end electronics but not including photosensors) to be achieved with a TARGET-based IACT readout system. In addition to basic performance parameters of the TARGET chip itself, we present a camera module prototype as well as a second-generation chip (TARGET 2), both of which have been produced.

  16. New frontiers in nuclear physics with high-power lasers and brilliant monochromatic gamma beams

    NASA Astrophysics Data System (ADS)

    Gales, S.; Balabanski, D. L.; Negoita, F.; Tesileanu, O.; Ur, C. A.; Ursescu, D.; Zamfir, N. V.

    2016-09-01

    The development of high power lasers and the combination of such novel devices with accelerator technology has enlarged the science reach of many research fields, in particular particle and nuclear physics, astrophysics as well as societal applications in material science, nuclear energy and applications for medicine. The European Strategic Forum for Research Infrastructures has selected a proposal based on these new premises called the Extreme Light Infrastructure (ELI). The ELI will be built as a network of three complementary pillars at the frontier of laser technologies. The ELI-NP pillar (NP for nuclear physics) is under construction near Bucharest (Romania) and will develop a scientific program using two 10 PW lasers and a Compton back-scattering high-brilliance and intense low-energy gamma beam, a combination of laser and accelerator technology at the frontier of knowledge. This unique combination of beams that are unique worldwide allows us to develop an experimental program in nuclear physics at the frontiers of present-day knowledge as well as society driven applications. In the present paper, the technical description of the facility as well as the new perspectives in nuclear structure, nuclear reactions and nuclear astrophysics will be presented.

  17. The properties of gamma-radiation and high-energy neutron fluxes in "MIR" station orbit.

    PubMed

    Bogomolov, A V; Bogomolov, V V; Denisov, Yu I; Logachev, Yu I; Svertilov, S I; Kudryavtsev, M I; Lyagushin, V I; Ershova, T V

    2002-10-01

    The study of radiation background components in the near-Earth space is very important for different branches of space research, in particular for space dosimetry and for the planning of gamma-astronomy experiments. Detailed information on the neutral components (gamma-quanta, neutrons) of background radiation was obtained during the Grif-1 experiment onboard Mir orbital station (OS). The measurements of fluxes of 0.05-50 MeV gamma-quanta and >30 MeV neutrons with a large area instrument (approximately 250 cm2 for gamma-quanta, approximately 30 cm2 for neutrons) as well as corresponding charged particle measurements (0.4-1.5 MeV electrons, 1-200 MeV protons) were made during this experiment. The background components induced by the station's own radiation as well as the albedo gamma-rays from the Earth's atmosphere were revealed as the result of data analysis for about 600 h of observation. A mathematical model describing the latitude and energy dependences of atmospheric albedo gamma-rays as well as of those of gamma-quanta produced in the material of the station due to cosmic ray interactions was developed. An analytical approximation of the spectrum of induced gamma-rays from radioactive isotopes stored in the station and instrument's materials is presented. The dynamics of gamma-quantum background fluxes during the geomagnetic disturbances of January 10-11, 1997 are discussed. An analytical representation of the latitude dependence of the integral flux of neutrons with >30 MeV is given.

  18. The properties of gamma-radiation and high-energy neutron fluxes in "MIR" station orbit.

    PubMed

    Bogomolov, A V; Bogomolov, V V; Denisov, Yu I; Logachev, Yu I; Svertilov, S I; Kudryavtsev, M I; Lyagushin, V I; Ershova, T V

    2002-10-01

    The study of radiation background components in the near-Earth space is very important for different branches of space research, in particular for space dosimetry and for the planning of gamma-astronomy experiments. Detailed information on the neutral components (gamma-quanta, neutrons) of background radiation was obtained during the Grif-1 experiment onboard Mir orbital station (OS). The measurements of fluxes of 0.05-50 MeV gamma-quanta and >30 MeV neutrons with a large area instrument (approximately 250 cm2 for gamma-quanta, approximately 30 cm2 for neutrons) as well as corresponding charged particle measurements (0.4-1.5 MeV electrons, 1-200 MeV protons) were made during this experiment. The background components induced by the station's own radiation as well as the albedo gamma-rays from the Earth's atmosphere were revealed as the result of data analysis for about 600 h of observation. A mathematical model describing the latitude and energy dependences of atmospheric albedo gamma-rays as well as of those of gamma-quanta produced in the material of the station due to cosmic ray interactions was developed. An analytical approximation of the spectrum of induced gamma-rays from radioactive isotopes stored in the station and instrument's materials is presented. The dynamics of gamma-quantum background fluxes during the geomagnetic disturbances of January 10-11, 1997 are discussed. An analytical representation of the latitude dependence of the integral flux of neutrons with >30 MeV is given. PMID:12442742

  19. Development of GAMMA Code and Evaluation for a Very High Temperature gas-Cooled Reactor

    SciTech Connect

    Oh, Chang H; Lim, H.S.; Kim, E.S.; NO, H.C.

    2007-06-01

    The very high-temperature gas-cooled reactor (VHTR) is envisioned as a single- or dual-purpose reactor for electricity and hydrogen generation. The concept has average coolant temperatures above 9000C and operational fuel temperatures above 12500C. The concept provides the potential for increased energy conversion efficiency and for high-temperature process heat application in addition to power generation. While all the High Temperature Gas Cooled Reactor (HTGR) concepts have sufficiently high temperature to support process heat applications, such as coal gasification, desalination or cogenerative processes, the VHTR’s higher temperatures allow broader applications, including thermochemical hydrogen production. However, the very high temperatures of this reactor concept can be detrimental to safety if a loss-of-coolant accident (LOCA) occurs. Following the loss of coolant through the break and coolant depressurization, air will enter the core through the break by molecular diffusion and ultimately by natural convection, leading to oxidation of the in-core graphite structure and fuel. The oxidation will accelerate heatup of the reactor core and the release of toxic gasses (CO and CO2) and fission products. Thus, without any effective countermeasures, a pipe break may lead to significant fuel damage and fission product release. Prior to the start of this Korean/United States collaboration, no computer codes were available that had been sufficiently developed and validated to reliably simulate a LOCA in the VHTR. Therefore, we have worked for the past three years on developing and validating advanced computational methods for simulating LOCAs in a VHTR. This paper will also include what improvements will be made in the Gamma code for the VHTR.

  20. Application of Gamma code coupled with turbomachinery models for high temperature gas-cooled reactors

    SciTech Connect

    Chang Oh

    2008-02-01

    The very high-temperature gas-cooled reactor (VHTR) is envisioned as a single- or dual-purpose reactor for electricity and hydrogen generation. The concept has average coolant temperatures above 9000C and operational fuel temperatures above 12500C. The concept provides the potential for increased energy conversion efficiency and for high-temperature process heat application in addition to power generation. While all the High Temperature Gas Cooled Reactor (HTGR) concepts have sufficiently high temperature to support process heat applications, such as coal gasification, desalination or cogenerative processes, the VHTR’s higher temperatures allow broader applications, including thermochemical hydrogen production. However, the very high temperatures of this reactor concept can be detrimental to safety if a loss-ofcoolant accident (LOCA) occurs. Following the loss of coolant through the break and coolant depressurization, air will enter the core through the break by molecular diffusion and ultimately by natural convection, leading to oxidation of the in-core graphite structure and fuel. The oxidation will accelerate heatup of the reactor core and the release of a toxic gas, CO, and fission products. Thus, without any effective countermeasures, a pipe break may lead to significant fuel damage and fission product release. Prior to the start of this Korean/United States collaboration, no computer codes were available that had been sufficiently developed and validated to reliably simulate a LOCA in the VHTR. Therefore, we have worked for the past three years on developing and validating advanced computational methods for simulating LOCAs in a VHTR. GAMMA code is being developed to implement turbomachinery models in the power conversion unit (PCU) and ultimately models associated with the hydrogen plant. Some preliminary results will be described in this paper.

  1. Afferent inputs to cortical fast-spiking interneurons organize pyramidal cell network oscillations at high-gamma frequencies (60-200 Hz).

    PubMed

    Suffczynski, Piotr; Crone, Nathan E; Franaszczuk, Piotr J

    2014-12-01

    High-gamma activity, ranging in frequency between ∼60 Hz and 200 Hz, has been observed in local field potential, electrocorticography, EEG and magnetoencephalography signals during cortical activation, in a variety of functional brain systems. The origin of these signals is yet unknown. Using computational modeling, we show that a cortical network model receiving thalamic input generates high-gamma responses comparable to those observed in local field potential recorded in monkey somatosensory cortex during vibrotactile stimulation. These high-gamma oscillations appear to be mediated mostly by an excited population of inhibitory fast-spiking interneurons firing at high-gamma frequencies and pacing excitatory regular-spiking pyramidal cells, which fire at lower rates but in phase with the population rhythm. The physiological correlates of high-gamma activity, in this model of local cortical circuits, appear to be similar to those proposed for hippocampal ripples generated by subsets of interneurons that regulate the discharge of principal cells. PMID:25210164

  2. Adaptation of high-gamma responses in human auditory association cortex

    PubMed Central

    Eliades, Steven J.; Crone, Nathan E.; Anderson, William S.; Ramadoss, Deepti; Lenz, Frederick A.

    2014-01-01

    This study investigates adaptation of high-frequency cortical responses [>60 Hz; high-gamma (HG)] to simple and complex sounds in human nonprimary auditory cortex. We used intracranial electrocorticographic recordings to measure event-related changes in HG power as a function of stimulus probability. Tone and speech stimuli were presented in a series of traditional oddball and control paradigms. We hypothesized that HG power attenuates with stimulus repetition over multiple concurrent time scales in auditory association cortex. Time-frequency analyses were performed to identify auditory-responsive sites. Single-trial analyses and quantitative modeling were then used to measure trial-to-trial changes in HG power for high (frequent), low (infrequent), and equal (control) stimulus probabilities. Results show strong reduction of HG responses to frequently repeated tones and speech, with no differences in responses to infrequent and equal-probability stimuli. Adaptation of the HG frequent response, and not stimulus-acoustic differences or deviance-detection enhancement effects, accounted for the differential responses observed for frequent and infrequent sounds. Adaptation of HG responses showed a rapid onset (less than two trials) with slower adaptation between consecutive, repeated trials (2–10 s) and across trials in a stimulus block (∼7 min). The auditory-evoked N100 response also showed repetition-related adaptation, consistent with previous human scalp and animal single-unit recordings. These findings indicate that HG responses are highly sensitive to the regularities of simple and complex auditory events and show adaptation on multiple concurrent time scales in human auditory association cortex. PMID:25122702

  3. Detection system for high-resolution gamma radiation spectroscopy with neutron time-of-flight filtering

    DOEpatents

    Dioszegi, Istvan; Salwen, Cynthia; Vanier, Peter

    2014-12-30

    A .gamma.-radiation detection system that includes at least one semiconductor detector such as HPGe-Detector, a position-sensitive .alpha.-Detector, a TOF Controller, and a Digitizer/Integrator. The Digitizer/Integrator starts to process the energy signals of a .gamma.-radiation sent from the HPGe-Detector instantly when the HPGe-Detector detects the .gamma.-radiation. Subsequently, it is determined whether a coincidence exists between the .alpha.-particles and .gamma.-radiation signal, based on a determination of the time-of-flight of neutrons obtained from the .alpha.-Detector and the HPGe-Detector. If it is determined that the time-of-flight falls within a predetermined coincidence window, the Digitizer/Integrator is allowed to continue and complete the energy signal processing. If, however, there is no coincidence, the Digitizer/Integrator is instructed to be clear and reset its operation instantly.

  4. HIGH ENERGY DELAYED GAMMA SPECTROSCOPY FOR PLUTONIUM ASSAY OF SPENT REACTOR FUEL

    SciTech Connect

    Campbell, Luke W.; Smith, L. E.; Misner, Alex C.

    2011-07-18

    Nuclear safeguards requires accountancy of plutonium present in spent reactor fuels. Current non-destructive methods do not directly measure plutonium content but instead rely on indirect measurements that require operator declarations of the fuel history. Delayed gamma spectroscopy is one method being investigated which can overcome these limitations. Delayed gamma rays from fission depend on the isotopic fission yield of the fissile isotope, and thus can be used to fingerprint the isotopes undergoing fission. However, difficulties arise because of the intense background due to long lived fission radionuclides already present in the fuel. We report on progress on simulated measurements of the delayed gamma spectrum in the presence of this background, using neutrons from a D-T source thermalized in an interrogation chamber slipped over a fuel assembly. By focusing on delayed gammas in the 3 to 4 MeV range, the passive spectrum becomes negligible, while allowing the preferential attenuation of the passive background to acceptable levels.

  5. SAS 2 observation of pulsed high-energy gamma radiation from Geminga

    NASA Technical Reports Server (NTRS)

    Mattox, J. R.; Bertsch, D. L.; Fichtel, C. E.; Hartman, R. C.; Kniffen, D. A.; Thompson, D. J.

    1992-01-01

    Following the detection of pulsed X-rays and gamma rays from Geminga, the 1972-1973 SAS 2 data which first revealed this source have been reanalyzed. The 237 ms periodicity is visible in those observations. The phase of the SAS 2 periodicity is consistent with that of COS B suggesting that the gamma-ray data allow an accounting for every revolution of the Geminga pulsar between 1972 and 1982.

  6. Picosecond Pulse Recirculation for High Average Brightness Thomson Scattering-based Gamma-ray Sources

    SciTech Connect

    Semenov, V. A.

    2009-06-12

    Pulse recirculation has been successfully demonstrated with the interaction laser system of LLNL's Thomson-Radiated Extreme X-ray (T-REX) source. The recirculation increased twenty-eight times the intensity of the light coming out of the laser system, demonstrating the capability of increasing the gamma-ray flux emitted by T-REX. The technical approach demonstrated could conceivably increase the average gamma-ray flux output by up to a hundred times.

  7. PKS 1510-089 in high gamma-ray state as detected by AGILE

    NASA Astrophysics Data System (ADS)

    Minervini, G.; Piano, G.; Munar-Adrover, P.; Verrecchia, F.; Pittori, C.; Lucarelli, F.; Tavani, M.; Donnarumma, I.; Bulgarelli, A.; Fioretti, V.; Zoli, A.; Vercellone, S.; Striani, E.; Cardillo, M.; Gianotti, F.; Trifoglio, M.; Giuliani, A.; Mereghetti, S.; Caraveo, P.; Perotti, F.; Chen, A.; Argan, A.; Costa, E.; Del Monte, E.; Evangelista, Y.; Feroci, M.; Lazzarotto, F.; Lapshov, I.; Pacciani, L.; Soffitta, P.; Sabatini, S.; Vittorini, V.; Pucella, G.; Rapisarda, M.; Di Cocco, G.; Fuschino, F.; Galli, M.; Labanti, C.; Marisaldi, M.; Pellizzoni, A.; Pilia, M.; Trois, A.; Barbiellini, G.; Vallazza, E.; Longo, F.; Morselli, A.; Picozza, P.; Prest, M.; Lipari, P.; Zanello, D.; Cattaneo, P. W.; Rappoldi, A.; Colafrancesco, S.; Parmiggiani, N.; Ferrari, A.; Antonelli, A.; Giommi, P.; Salotti, L.; Valentini, G.; D'Amico, F.

    2016-09-01

    The AGILE-GRID is detecting transient gamma-ray emission above 100 MeV from the blazar PKS 1510-089. Integrating from 2016-09-19 UT 01:00:00 to 2016-09-21 UT 01:00:00, a preliminary likelihood analysis provides a gamma-ray flux F( > 100 MeV) = (3.7 +/- 1.2) x 10^-6 photons/cm^2/s with a significance above 5 sigma.

  8. TESTING THE MILLISECOND PULSAR SCENARIO OF THE GALACTIC CENTER GAMMA-RAY EXCESS WITH VERY HIGH ENERGY GAMMA-RAYS

    SciTech Connect

    Yuan, Qiang; Ioka, Kunihito

    2015-04-01

    Recent analyses of Fermi Large Area Telescope data show an extended GeV γ-ray excess on top of the expected diffuse background in the Galactic center region, which can be explained by annihilating dark matter (DM) or a population of millisecond pulsars (MSPs). We propose observations of very high energy (VHE) γ-rays to distinguish the MSP scenario from the DM scenario. GeV γ-ray MSPs should release most of their energy to the relativistic e{sup ±} wind, which will diffuse into the Galaxy and radiate TeV γ-rays through inverse Compton scattering and bremsstrahlung processes. By calculating the spectrum and spatial distribution, we show that such emission is detectable with the next generation VHE γ-ray observatory, the Cherenkov Telescope Array (CTA), under reasonable model parameters. It is essential to search for multi-wavelength counterparts to the GeV γ-ray excess in order to solve this mystery in the high-energy universe.

  9. THE FIRST LIMITS ON THE ULTRA-HIGH ENERGY NEUTRINO FLUENCE FROM GAMMA-RAY BURSTS

    SciTech Connect

    Vieregg, A. G.; Belov, K.; Palladino, K.; Allison, P.; Baughman, B. M.; Beatty, J. J.; Connolly, A.; Grashorn, E. W.; Besson, D. Z.; Detrixhe, M.; Bevan, S.; Binns, W. R.; Dowkontt, P. F.; Chen, C.; Chen, P.; Clem, J. M.; De Marco, D.; DuVernois, M.; Gorham, P. W.; Hill, B.

    2011-07-20

    We set the first limits on the ultra-high energy (UHE) neutrino fluence at energies greater than 10{sup 9} GeV from gamma-ray bursts (GRBs) based on data from the second flight of the Antarctic Impulsive Transient Antenna (ANITA). During the 31 day flight of ANITA-II, 26 GRBs were recorded by Swift or Fermi. Of these, we analyzed the 12 GRBs which occurred during quiet periods when the payload was away from anthropogenic activity. In a blind analysis, we observe 0 events on a total background of 0.0044 events in the combined prompt window for all 12 low-background bursts. We also observe 0 events from the remaining 14 bursts. We place a 90% confidence level limit on the E{sup -4} prompt neutrino fluence between 10{sup 8} GeV < E < 10{sup 12} GeV of E{sup 4}{Phi} = 2.5 x 10{sup 17} GeV{sup 3} cm{sup -2} from GRB090107A. This is the first reported limit on the UHE neutrino fluence from GRBs above 10{sup 9} GeV, and the strongest limit above 10{sup 8} GeV.

  10. An engineering array for the High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory

    NASA Astrophysics Data System (ADS)

    Longo, Megan; Mostafa, Miguel

    2012-03-01

    The High Altitude Water Cherenkov (HAWC) gamma-ray observatory is currently being deployed at 4100 m in Sierra Negra, Mexico. The HAWC observatory will have 300 Water Cherenkov Detectors (WCDs). Each WCD will be instrumented with 4 upward facing baffled photo multiplier tubes (PMTs) anchored to the bottom of a 5 m deep by 7.3 m diameter steel container with a multilayer hermetic plastic bag containing 200,000 liters of purified water. An engineering array of 6 WCDs was deployed in Summer 2011 at the HAWC site and has been operational since then. This array serves to validate the design and construction methods for the HAWC observatory. It has also been collecting data which allows for the development of data collection and analysis tools. Here we will describe the deployment of the engineering array, the lessons learned from this experience and the implications for HAWC, as well as give an introduction into data collection and initial analysis being done, which will be presented jointly.

  11. Galactic sources of high energy neutrinos: Expectation from gamma-ray data

    NASA Astrophysics Data System (ADS)

    Sahakyan, N.

    2016-07-01

    The recent results from ground based γ-ray detectors (HESS, MAGIC, VERITAS) provide a population of TeV galactic γ-ray sources which are potential sources of High Energy (HE) neutrinos. Since the γ-rays and ν-s are produced from decays of neutral and charged pions, the flux of TeV γ-rays can be used to estimate the upper limit of ν flux and vice versa; the detectability of ν flux implies a minimum flux of the accompanying γ-rays (assuming the internal and the external absorption of γ-rays is negligible). Using this minimum flux, it is possible to find the sources which can be detected with cubic-kilometer telescopes. I will discuss the possibility to detect HE neutrinos from powerful galactic accelerators, such as Supernova Remnants (SNRs) and Pulsar Wind Nebulae (PWNe) and show that likely only RX J1713.7-3946, RX J0852.0-4622 and Vela X can be detected by current generation of instruments (IceCube and Km3Net). It will be shown also, that galactic binary systems could be promising sources of HE ν-s. In particular, ν-s and γ-rays from Cygnus X-3 will be discussed during recent gamma-ray activity, showing that in the future such kind of activities could produce detectable flux of HE ν-s.

  12. Design and performance of a new high accuracy combined small sample neutron/gamma detector

    SciTech Connect

    Menlove, H.; Davidson, D.; Verplancke, J.; Vermeulen, P.; Wagner, H.G.; Wellum, R.; Brandelise, B.; Mayer, K.

    1993-08-01

    This paper describes the design of an optimized combined neutron and gamma detector installed around a measurement well protruding from the floor of a glove box. The objective of this design was to achieve an overall accuracy for the plutonium element concentration in gram-sized samples of plutonium oxide powder approaching the {approximately}0.1--0.2% accuracies routinely achieved by inspectors` chemical analysis. The efficiency of the clam-shell neutron detector was increased and the flat response zone extended in axial and radial directions. The sample holder introduced from within the glove box was designed to form the upper reflector, while two graphite half-shells fitted around the thin neck of the high-resolution LEGE detector replaced the lower plug. The Institute for Reference Materials and Measurements (IRMM) in Geel prepared special plutonium oxide test samples whose plutonium concentration was determined to better than 0.05%. During a three week initial performance test in July 1992 at ITU Karlsruhe and in long term tests, it was established that the target accuracy can be achieved provided sufficient care is taken to assure the reproducibility of sample bottling and sample positioning. The paper presents and discusses the results of all test measurements.

  13. Design and performance of a new high accuracy combined small sample neutron/gamma detector

    SciTech Connect

    Menlove, H.; Davidson, D.; Verplancke, J.; Vermeulen, P.; Wagner, H.G.; Wellum, R.; Brandelise, B.; Mayer, K.

    1993-12-31

    This paper describes the design of an optimized combined neutron and gamma detector installed around a measurement well protruding from the floor of a glove box. The objective of this design was to achieve an overall accuracy for the plutonium element concentration in gram-sized samples of plutonium oxide powder approaching the {approximately}0.1--0.2% accuracies routinely achieved by inspectors` chemical analysis. The efficiency of the clam-shell neutron detector was increased and the flat response zone extended in axial and radial directions. The sample holder introduced from within the glove box was designed to form the upper reflector, while two graphite half-shells fitted around the thin neck of the high-resolution LEGe detector replaced the lower plug. The Institute for Reference Materials and Measurements (IRMM) in Geel prepared special plutonium oxide test samples whose plutonium concentration was determined to better than 0.05%. During a three week initial performance test in July 1992 at ITU Karlsruhe and in long term tests, it was established that the target accuracy can be achieved provided sufficient care is taken to assure the reproducibility of sample bottling and sample positioning. The paper presents and discusses the results of all test measurements.

  14. Metal ion blockage of tritium incorporation into gamma-carboxyglutamic acid of prothrombin. Stoichiometry of gamma-carboxyglutamic acid to Gd3+ for the high affinity sites

    SciTech Connect

    Bajaj, S.P.; Saini, R.; Katz, A.; Cai, G.Z.; Maki, S.L.; Brodsky, G.L.

    1988-07-15

    Prothrombin possesses two high affinity and four low affinity gamma-carboxyglutamic acid (Gla)-dependent gadolinium binding sites. Earlier work has shown that tritium can be specifically incorporated at the gamma-carbon of Gla in proteins at pH 5. In the present work we show that inclusion of saturating concentrations of Ca2+ in nondenaturing buffer systems ranging from pH 5.5 to 8.5 prevents the exchange of tritium into all 10 Gla residues of prothrombin. Similarly, saturating concentrations of Gd3+ prevent tritium incorporation into Gla at pH 5.5. Positive cooperativity was observed for the binding of Gd3+ to human prothrombin (at pH 5.5) for the two high affinity sites (Kd congruent to 35 nM). The four low affinity sites bind Gd3+ with a Kd congruent to 5 microM. Incubation of prothrombin ranging in concentrations from 10 to 40 microM with 2 eq of Gd3+ at pH 5.5 prevents 5.7 (average of seven determinations) Gla residues from tritium incorporation. Sedimentation velocity experiments conducted at pH 5.5 indicate that prothrombin in the presence of saturating concentrations of Gd3+ polymerizes, most likely, to a trimer. Further, in the presence of 2 eq of Gd3+, calculated percent weight average concentration of monomer prothrombin is congruent to 100% at 10 microM, approximately equal to 95% at 20 microM, and congruento to 80% at 40 microM protein concentration. Thus, it appears that under conditions in which prothrombin primarily exists as a monomer, occupancy of the initial two metal binding sites by Gd3+ involves six Gla residues.

  15. Exploring the nature of the unidentified very-high-energy gamma-ray source HESS J1507-622

    NASA Astrophysics Data System (ADS)

    Domainko, W.; Ohm, S.

    2012-09-01

    Context. Several extended sources of very-high-energy (VHE; E > 100 GeV) gamma rays have been found that lack counterparts belonging to an established class of VHE gamma-ray emitters. Aims: The nature of the first unidentified VHE gamma-ray source with significant angular offset from the Galactic plane of 3.5°, HESS J1507-622, is explored. Methods.Fermi-LAT data in the high-energy (HE, 100 MeV < E < 100 GeV) gamma-ray range collected over 34 month are used to describe the spectral energy distribution (SED) of the source. Additionally, implications of the off-plane location of the source for a leptonic and hadronic gamma-ray emission model are investigated. Results: HESS J1507-622 is detected in the Fermi energy range and its spectrum is best described by a power law in energy with Γ = 1.7 ± 0.1stat ± 0.2sys and integral flux between (0.3-300) GeV of F = (2.0 ± 0.5stat ± 1.0sys) × 10-9 cm-2 s-1. The SED constructed from the Fermi and H.E.S.S. data for this source does not support a smooth power-law continuation from the VHE to the HE gamma-ray range. With the available data it is not possible to discriminate between a hadronic and a leptonic scenario for HESS J1507-622. The location and compactness of the source indicate a considerable physical offset from the Galactic plane for this object. In case of a multiple-kpc distance, this challenges a pulsar wind nebula (PWN) origin for HESS J1507-622 since the time of travel for a pulsar born in the Galactic disk to reach such a location would exceed the inverse Compton (IC) cooling time of electrons that are energetic enough to produce VHE gamma-rays. However, an origin of this gamma-ray source connected to a pulsar that was born off the Galactic plane in the explosion of a hypervelocity star cannot be excluded. Conclusions: The nature of HESS J1507-622 is still unknown to date, and a PWN scenario cannot be ruled out in general. On the contrary HESS J1507-622 could be the first discovered representative of a

  16. A transportable high-resolution gamma-ray spectrometer and analysis system applicable to mobile, autonomous or unattended applications

    SciTech Connect

    Buckley, W.M.; Neufeld, K.W.

    1995-07-01

    The Safeguards Technology Program at the Lawrence Livermore National Laboratory is developing systems based on a compact electro-mechanically cooled high-purity germanium (HPGe) detector. This detector system broadens the practicality of performing high- resolution gamma-ray spectrometry in the field. Utilizing portable computers, multi-channel analyzers and software these systems greatly improve the ease of performing mobile high-resolution gamma-ray spectrometry. Using industrial computers, we can construct systems that will run autonomously for extended periods of time without operator input or maintenance. These systems can start or make decisions based on sensor inputs rather than operator interactions. Such systems can provide greater capability for wider domain of safeguards, treaty verification application, and other unattended, autonomous or in-situ applications.

  17. Hand-Held Gamma-Ray Spectrometer Based on High-Efficiency Frisch-Ring Cdznte Detectors

    SciTech Connect

    Cui, Y.; Bolotnikov, A; Camarda, G; Hossain, A; James, R; DeGeronimo, G; Fried, J; O'Connor, P; Kargar, A; et. al.

    2008-01-01

    Frisch-ring CdZnTe detectors have demonstrated both good energy resolution, <1% FWHM at 662 keV, and good efficiency in detecting gamma rays, highlighting the strong potential of CdZnTe materials for such applications. We are designing a hand-held gamma-ray spectrometer based on Frisch-ring detectors at Brookhaven National Laboratory. It employs an 8 times 8 CdZnTe detector array to achieve a high volume of 19.2 cm3, so greatly improving detection efficiency. By using the front-end application-specific integrated circuits (ASICs) developed at BNL, this spectrometer has a small profile and high energy-resolution. It includes a signal processing circuit, digitization and storage circuits, a high-voltage module, and a universal serial bus (USB) interface. In this paper, we detail the system's structure and report the results of our tests with it.

  18. {gamma}-ray spectroscopy of neutron-deficient {sup 110}Te. II. High-spin smooth-terminating structures

    SciTech Connect

    Paul, E. S.; Evans, A. O.; Boston, A. J.; Nolan, P. J.; Semple, A. T.; Chiara, C. J.; Fossan, D. B.; Lane, G. J.; Sears, J. M.; Starosta, K.; Devlin, M.; LaFosse, D. R.; Sarantites, D. G.; Freeman, S. J.; Leddy, M. J.; Lee, I. Y.; Macchiavelli, A. O.; Smith, J. F.; Afanasjev, A. V.; Ragnarsson, I.

    2007-09-15

    High-spin states have been populated in {sub 52}{sup 110}Te via {sup 58}Ni({sup 58}Ni,{alpha}2p{gamma}) reactions at 240 and 250 MeV. The Gammasphere {gamma}-ray spectrometer was used in conjunction with the Microball charged-particle detector. The high-spin (I>30) collective level scheme of {sup 110}Te, up to {approx}45({Dirac_h}/2{pi}), is discussed in this paper. Four new decoupled ({delta}I=2) high-spin structures have been observed for the first time, together with two strongly coupled ({delta}I=1) bands. These bands all show the characteristics of smooth band termination, and are discussed within the framework of the cranked Nilsson-Strutinsky approach.

  19. HESPERIA studies on the nature of high-energy solar gamma-ray events

    NASA Astrophysics Data System (ADS)

    Zucca, Pietro; Klein, Karl-Ludwig; Share, Gerry; Vilmer, Nicole; Malandraki, Olga; Miteva, Rositsa; Heber, Bernd; Hamadache, Clarisse; Kiener, Juergen; Tatischeff, Vincent; Vainio, Rami

    2016-04-01

    The FERMI/LAT gamma-ray experiment, thanks to its large effective are, observed about 25 solar events with gamma-ray emission above photon energies of 100 MeV. The emission is attributed to pion-decay photons. This implies that the acceleration of protons in the solar corona to energies above 300 MeV is a frequent phenomenon, probably more so than previously thought. In some cases the emission persists over several hours. In the frame of the HESPERIA project, funded by the Horizon 2020 programme of the European Union, we conduct an extensive study on the relationship between these gamma-ray emissions and electromagnetic signatures of accelerated electrons in the corona on the one hand, solar energetic particles (SEPs) detected in space on the other hand. This contribution is to present first results on the sample of 25 gamma-ray events, mainly addressing two subjects: (1) We compare the durations of the gamma-ray emission with the durations of hard X-ray and microwave signatures of electrons in the solar atmosphere, in the attempt to see if long-duration gamma-ray events are accompanied by signatures of long-duration electron acceleration. (2) We show that in each gamma-ray event electrons had rapid access to interplanetary space since the impulsive flare phase. This suggests that particles accelerated during the flare could escape to interplanetary space. We compare the hardness of the proton spectra detected in interplanetary space with the prediction using the properties of the solar microwave bursts. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 637324.

  20. PKS 2123-463: A Confirmed Gamma-ray Blazar at High Redshift

    NASA Technical Reports Server (NTRS)

    DAmmando, F.; Rau, A.; Schady, P.; Finke, J.; Orienti, M.; Greiner, J.; Kann, D. A.; Ojha, R.; Foley, A. R.; Stevens, J.; Blanchard, J. M.; Edwards, P. G.; Kadler, M.; Lovell, J. E. J.

    2012-01-01

    The flat spectrum radio quasar (FSRQ) PKS 2123-463 was associated in the First Fermi-LAT source catalog with the gamma-ray source 1FGL J2126.1-4603, but when considering the full first two years of Fermi observations, no gamma-ray source at a position consistent with this FSRQ was detected, and thus PKS 2123-463 was not reported in the Second Fermi-LAT source catalog. On 2011 December 14 a gamma-ray source positionally consistent with PKS 2123-463 was detected in flaring activity by Fermi-LAT. This activity triggered radio-to-X-ray observations by the Swift, GROND, ATCA, Ceduna, and KAT-7 observatories. Results of the localization of the gamma-ray source over 41 months of Fermi-LAT operation are reported here in conjunction with the results of the analysis of radio, optical, UV and X-ray data collected soon after the gamma-ray flare. The strict spatial association with the lower energy counterpart together with a simultaneous increase of the activity in optical, UV, X-ray and gamma-ray bands led to a firm identification of the gamma-ray source with PKS 2123-463. A new photometric redshift has been estimated as z = 1.46 +/- 0.05 using GROND and Swift/UVOT observations, in rough agreement with the disputed spectroscopic redshift of z = 1.67. We fit the broadband spectral energy distribution with a synchrotron/external Compton model. We find that a thermal disk component is necessary to explain the optical/UV emis- sion detected by Swift/UVOT. This disk has a luminosity of 1.8x1046 erg s-1, and a fit to the disk emission assuming a Schwarzschild (i.e., nonrotating) black hole gives a mass of 2 x 109 M(solar mass). This is the first black hole mass estimate for this source.

  1. Gamma background studies for the XENON experiment using a High Purity Germanium Detector

    NASA Astrophysics Data System (ADS)

    Angle, Jesse Isaac

    The XENON Dark Matter Experiment, deployed at the Gran Sasso National Laboratory in Italy on March 2006, is a liquid noble gas detector designed to directly detect dark matter. The detector uses a dual-phase (gas/liquid) Xenon target to search for nuclear recoils associated with nucleus-WIMP interactions. Due to the high sensitivity needed in such an experiment, it is vital to not only reduce the background but to also understand the remaining background so as to aid in the understanding of the data as well as to facilitate upgrades beyond the early Research and Development phases. Many of the components of the XENON10 detector have been screened using a High Purity Germanium Detector known as the GATOR detector. Full analysis of the screening data requires Monte Carlo simulations of the GATOR detector and the sample. Results from this screening will be presented. Using the information obtained from the screening operation, Monte Carlo simulations of the XENON10 electron recoil background will be examined and compared to the actual detector data. The success of this simulation to data comparison indicates that we have a good understanding of the XENON10 gamma background and will be able to make more informed decisions regarding the next stage of detector development. This type of analysis has aided in the selection and design of many of the materials and components being incorporated into the new XENON100 detector, the next generation detector which will be capable of improving the limit set by XENON10 by at least an order of magnitude. (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http:/ /www.uflib.ufl.edu/etd.html)

  2. High Resolution Gamma Ray Tomography and its Application to the Measurement of Phase Fractions in Chemical Reactors

    NASA Astrophysics Data System (ADS)

    Hampel, Uwe; Bieberle, Andre; Schleicher, Eckhard; Hessel, Günther; Zippe, Cornelius; Friedrich, Hans-Jürgen

    2007-06-01

    We applied gamma ray tomography to the problem of phase fraction measurement in chemical reactors. Therefore, we used a new tomography device that is operated with a Cs-137 source and a high resolution gamma ray detector. One application example is the reconstruction of the fluid distribution and the measurement of radial gas fraction profiles in a laboratory scale stirred vessel. The tomograph was used to obtain radiographic projections of the averaged gamma ray attenuation for different stirrer speeds along the height of the vessel. With tomographic reconstruction techniques we calculated the angularly averaged radial distribution of the attenuation coefficient for as many as 150 single cross-sectional planes and synthesised from this data set the axial and radial fluid distribution pattern. Further, we exemplarily reconstructed the radial gas fraction distributions induced by the stirrer in the area of the stirrer blades. In a second application the gamma ray measurement system was used to visualise gas inclusions in a water cleaning column that is used to remove hazardous heavy metal species from water.

  3. High-energy cosmic-ray nuclei from high- and low-luminosity gamma-ray bursts and implications for multimessenger astronomy

    SciTech Connect

    Murase, Kohta; Nagataki, Shigehiro; Ioka, Kunihito; Nakamura, Takashi

    2008-07-15

    Gamma-ray bursts (GRBs) are one of the candidates of ultrahigh-energy (> or approx. 10{sup 18.5} eV) cosmic-ray (UHECR) sources. We investigate high-energy cosmic-ray acceleration including heavy nuclei in GRBs by using Geant 4, and discuss its various implications, taking both high-luminosity (HL) and low-luminosity (LL) GRBs into account. This is because LL GRBs may also make a significant contribution to the observed UHECR flux if they form a distinct population. We show that not only protons, but also heavier nuclei can be accelerated up to ultrahigh energies in the internal, (external) reverse, and forward shock models. We also show that the condition for ultrahigh-energy heavy nuclei such as iron to survive is almost the same as that for {approx}TeV gamma rays to escape from the source and for high-energy neutrinos not to be much produced. The multimessenger astronomy by neutrino and GeV-TeV gamma-ray telescopes such as IceCube and KM3Net, GLAST and MAGIC will be important to see whether GRBs can be accelerators of ultrahigh-energy heavy nuclei. We also demonstrate expected spectra of high-energy neutrinos and gamma rays, and discuss their detectabilities. In addition, we discuss implications of the GRB-UHECR hypothesis. We point out, since the number densities of HL GRBs and LL GRBs are quite different, its determination by UHECR observations is also important.

  4. Gamma watermarking

    DOEpatents

    Ishikawa, Muriel Y.; Wood, Lowell L.; Lougheed, Ronald W.; Moody, Kenton J.; Wang, Tzu-Fang

    2004-05-25

    A covert, gamma-ray "signature" is used as a "watermark" for property identification. This new watermarking technology is based on a unique steganographic or "hidden writing" digital signature, implemented in tiny quantities of gamma-ray-emitting radioisotopic material combinations, generally covertly emplaced on or within an object. This digital signature may be readily recovered at distant future times, by placing a sensitive, high energy-resolution gamma-ray detecting instrument reasonably precisely over the location of the watermark, which location may be known only to the object's owner; however, the signature is concealed from all ordinary detection means because its exceedingly low level of activity is obscured by the natural radiation background (including the gamma radiation naturally emanating from the object itself, from cosmic radiation and material surroundings, from human bodies, etc.). The "watermark" is used in object-tagging for establishing object identity, history or ownership. It thus may serve as an aid to law enforcement officials in identifying stolen property and prosecuting theft thereof. Highly effective, potentially very low cost identification-on demand of items of most all types is thus made possible.

  5. Studies on High Energy Radiation Mechanisms and Gamma-Ray Burst Prompt Emissions

    NASA Astrophysics Data System (ADS)

    Zhang, B.

    2014-07-01

    Gamma-Ray Bursts (GRBs) are the most violent high-energy explosion in the universe. They are randomly happened, pulse-like phenomena with short durations. Since its discovery in 1960's by Vela satellite, GRBs have become a hot topic for astrophysical research. In 1997 the BeppoSAX satellite discovered afterglows of GRBs, and then helped to measure GRB redshifts. Thus it was found that GRBs are the events occurred at cosmological distances. Now it is widely accepted that the long bursts with durations longer than 2 s are from the collapsing massive stars, while the short bursts with durations less than 2 s are results of the merging compact binaries. By studying GRBs, the physical processes in ultrarelativistic and very high energy conditions can be investigated, and the researches on other fields, including constraining the cosmological models, can also get helped. The goal of this thesis is to present some discussions on possible radiation mechanisms and prompt light curves of GRBs. Since radiation mechanisms and prompt emissions are related to GRB central engines directly, studying these topics can help us to get a better understanding of some properties of the central engine. In Chapter 1, we review the discovery and observations of GRBs, presenting major achievements from major GRB-monitoring satellites including Compton Gamma-ray Observatory, BeppoSAX satellite, Swift satellite, as well as the latest Fermi Gamma-ray Space Telescope. The multi-wavelength properties of prompt emission as well as afterglows of GRBs are also summarized in Chapter 1. In Chapter 2 the current GRB standard model is presented. According to standard model, a fireball is ejected by the central engine. The internal shock is produced by collisions between various shells with different velocities inside the fireball. The directional kinetic energy of the fireball is then converted to internal energy, and finally the non-thermal radiation (the prompt emission) is produced by internal shocks

  6. Studies on High Energy Radiation Mechanisms and Gamma-Ray Burst Prompt Emissions

    NASA Astrophysics Data System (ADS)

    Zhang, B.

    2014-07-01

    Gamma-Ray Bursts (GRBs) are the most violent high-energy explosion in the universe. They are randomly happened, pulse-like phenomena with short durations. Since its discovery in 1960's by Vela satellite, GRBs have become a hot topic for astrophysical research. In 1997 the BeppoSAX satellite discovered afterglows of GRBs, and then helped to measure GRB redshifts. Thus it was found that GRBs are the events occurred at cosmological distances. Now it is widely accepted that the long bursts with durations longer than 2 s are from the collapsing massive stars, while the short bursts with durations less than 2 s are results of the merging compact binaries. By studying GRBs, the physical processes in ultrarelativistic and very high energy conditions can be investigated, and the researches on other fields, including constraining the cosmological models, can also get helped. The goal of this thesis is to present some discussions on possible radiation mechanisms and prompt light curves of GRBs. Since radiation mechanisms and prompt emissions are related to GRB central engines directly, studying these topics can help us to get a better understanding of some properties of the central engine. In Chapter 1, we review the discovery and observations of GRBs, presenting major achievements from major GRB-monitoring satellites including Compton Gamma-ray Observatory, BeppoSAX satellite, Swift satellite, as well as the latest Fermi Gamma-ray Space Telescope. The multi-wavelength properties of prompt emission as well as afterglows of GRBs are also summarized in Chapter 1. In Chapter 2 the current GRB standard model is presented. According to standard model, a fireball is ejected by the central engine. The internal shock is produced by collisions between various shells with different velocities inside the fireball. The directional kinetic energy of the fireball is then converted to internal energy, and finally the non-thermal radiation (the prompt emission) is produced by internal shocks

  7. Optical and Electrical Studies of Gamma-Irradiated AlGaN/GaN High Electron Mobility Transistors

    NASA Astrophysics Data System (ADS)

    Yadav, Anupama; Flitsiyan, Elena; Chernyak, Leonid; Ahn, Shihyun; Ren, Fan; Pearton, Stephen; Lubomirsky, Igor; Khodorov, Sergey

    The impact of 60Co gamma-irradiation on n-channel AlGaN/GaN High Electron Mobility Transistors (HEMTs) was studied by means of temperature dependent Cathodoluminescence (CL) and Electron Beam Induced Current (EBIC) technique. Increase in diffusion length after low dose of gamma-irradiation (<= 200 Gy) is consistent with the decrease in the CL intensity. The observed effect is explained via the mechanism involving trapping of Compton electrons on irradiation induced nitrogen vacancies. For high dose (>200 Gy), diffusion length was observed to decrease which is presumably associated with the mobility degradation. It is shown that calculated activation from the EBIC and CL measurements follows exactly the same trend, which implies that same underlying phenomenon is responsible for observed findings. In addition, DC current-voltage measurements were conducted on the devices in order to relate the material's fundamental properties to the device performance.

  8. Discovery of a new population of high-energy gamma-ray sources in the Milky Way

    PubMed

    Gehrels; Macomb; Bertsch; Thompson; Hartman

    2000-03-23

    One of the great mysteries of the high-energy gamma-ray sky is the group of approximately 170 unidentified point sources found along the Galactic plane. They are more numerous than all other high-energy gamma-ray sources combined and, despite 20 years of effort, no clear counterparts have been found at other wavelengths. Here we report a new population of such objects. A cluster of approximately 20 faint sources appears north of the Galactic Centre, which is part of a broader class of faint objects at mid-latitudes. In addition, we show in a model-independent way that the mid-latitude sources are distinct from the population of bright unidentified sources along the Galactic plane. The distribution on the sky indicates that the faint mid-latitude sources are associated with the Gould belt of massive stars and gas clouds at approximately 600 light years distance, as has been previously suggested.

  9. Observation of celestial high energy gamma rays from SAS-II

    NASA Technical Reports Server (NTRS)

    Fichtel, C. E.; Hartman, R. C.; Kniffen, D. A.

    1974-01-01

    The Small Astronomy Satellite (SAS)-II, launched on Nov. 15, 1973, carried into orbit a 32-deck magnetic-core digitized-spark-chamber gamma-ray telescope to study celestial gamma radiation in the energy range above 30 MeV. As of May 21, 1973, SAS-II had viewed approximately half the sky, including the galactic center region, the galactic anti-center, and several regions off the galactic plane, and about one-third of the data from eight weeks of viewing has been analyzed. A finite diffuse flux for regions with galactic latitudes greater than 20 deg has been detected with a very steep energy spectrum. Combining this result with low-energy gamma-ray data yields a picture suggesting a cosmological origin for this radiation.

  10. Search for a Correlation Between Very-High-Energy Gamma Rays and Giant Radio Pulses in the Crab Pulsar

    NASA Technical Reports Server (NTRS)

    Aliu, E.; Archambault, S.; Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Bouvier, A.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cesarini, A.; Ciupik, L.; Collins-Hughes, E.; Connolly, M. P.; Cui, W.; Dickherber, R.; Duke, C.; Dumm, J.; Falcone, A.; Federici, S.; Feng, Q.; Finley, J. P.; Finnegan, G.; Fortson, L.; Perkins, J. S.

    2012-01-01

    We present the results of a joint observational campaign between the Green Bank radio telescope and the VERITAS gamma-ray telescope, which searched for a correlation between the emission of very-high-energy (VHE) gamma rays ( E(sub Gamma) > 150 GeV) and giant radio pulses (GRPs) from the Crab pulsar at 8.9 GHz. A total of 15,366 GRPs were recorded during 11.6 hr of simultaneous observations, which were made across four nights in 2008 December and in 2009 November and December. We searched for an enhancement of the pulsed gamma-ray emission within time windows placed around the arrival time of the GRP events. In total, eight different time windows with durations ranging from 0.033 ms to 72 s were positioned at three different locations relative to the GRP to search for enhanced gamma-ray emission which lagged, led, or was concurrent with, the GRP event. Furthermore, we performed separate searches on main pulse GRPs and interpulse GRPs and on the most energetic GRPs in our data sample. No significant enhancement of pulsed VHE emission was found in any of the preformed searches. We set upper limits of 5-10 times the average VHE flux of the Crab pulsar on the flux simultaneous with interpulse GRPs on single-rotation-period timescales. On approx. 8 s timescales around interpulse GRPs, we set an upper limit of 2-3 times the average VHE flux. Within the framework of recent models for pulsed VHE emission from the Crab pulsar, the expected VHE-GRP emission correlations are below the derived limits.

  11. SEARCH FOR A CORRELATION BETWEEN VERY-HIGH-ENERGY GAMMA RAYS AND GIANT RADIO PULSES IN THE CRAB PULSAR

    SciTech Connect

    Aliu, E.; Archambault, S.; Arlen, T.; Aune, T.; Bouvier, A.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Dickherber, R.; Benbow, W.; Byrum, K.; Cesarini, A.; Connolly, M. P.; Ciupik, L.; Collins-Hughes, E.; Cui, W.; Duke, C.; Dumm, J.; Falcone, A.; Federici, S. E-mail: mccann@kicp.uchicago.edu; and others

    2012-12-01

    We present the results of a joint observational campaign between the Green Bank radio telescope and the VERITAS gamma-ray telescope, which searched for a correlation between the emission of very-high-energy (VHE) gamma rays (E {sub {gamma}} > 150 GeV) and giant radio pulses (GRPs) from the Crab pulsar at 8.9 GHz. A total of 15,366 GRPs were recorded during 11.6 hr of simultaneous observations, which were made across four nights in 2008 December and in 2009 November and December. We searched for an enhancement of the pulsed gamma-ray emission within time windows placed around the arrival time of the GRP events. In total, eight different time windows with durations ranging from 0.033 ms to 72 s were positioned at three different locations relative to the GRP to search for enhanced gamma-ray emission which lagged, led, or was concurrent with, the GRP event. Furthermore, we performed separate searches on main pulse GRPs and interpulse GRPs and on the most energetic GRPs in our data sample. No significant enhancement of pulsed VHE emission was found in any of the preformed searches. We set upper limits of 5-10 times the average VHE flux of the Crab pulsar on the flux simultaneous with interpulse GRPs on single-rotation-period timescales. On {approx}8 s timescales around interpulse GRPs, we set an upper limit of 2-3 times the average VHE flux. Within the framework of recent models for pulsed VHE emission from the Crab pulsar, the expected VHE-GRP emission correlations are below the derived limits.

  12. Impulsive and long duration high-energy gamma-ray emission from the very bright 2012 March 7 solar flares

    SciTech Connect

    Ajello, M.; Albert, A.; Allafort, A.; Caliandro, G. A.; Cameron, R. A.; Charles, E.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Buson, S.; Bellazzini, R.; Bregeon, J.; Bissaldi, E.; Bonamente, E.; Cecchi, C.; Brandt, T. J.; Brigida, M.; Bruel, P.; Caraveo, P. A. E-mail: vahep@stanford.edu; and others

    2014-07-01

    The Fermi Large Area Telescope (LAT) detected gamma-rays up to 4 GeV from two bright X-class solar flares on 2012 March 7, showing both an impulsive and temporally extended emission phases. The gamma-rays appear to originate from the same active region as the X-rays associated with these flares. The >100 MeV gamma-ray flux decreases monotonically during the first hour (impulsive phase) followed by a slower decrease for the next 20 hr. A power law with a high-energy exponential cutoff can adequately describe the photon spectrum. Assuming that the gamma rays result from the decay of pions produced by accelerated protons and ions with a power-law spectrum, we find that the index of that spectrum is ∼3, with minor variations during the impulsive phase. During the extended phase the photon spectrum softens monotonically, requiring the proton index varying from ∼4 to >5. The >30 MeV proton flux observed by the GOES satellites also shows a flux decrease and spectral softening, but with a harder spectrum (index ∼2-3). Based on these observations, we explore the relative merits of prompt or continuous acceleration scenarios, hadronic or leptonic emission processes, and acceleration at the solar corona or by the fast coronal mass ejections. We conclude that the most likely scenario is continuous acceleration of protons in the solar corona that penetrate the lower solar atmosphere and produce pions that decay into gamma rays. However, acceleration in the downstream of the shock cannot be definitely ruled out.

  13. Can Life Survive Gamma-Ray Bursts in the High-redshift Universe?

    NASA Astrophysics Data System (ADS)

    Li, Ye; Zhang, Bing

    2015-09-01

    Nearby gamma-ray bursts (GRBs) have been proposed as a possible cause of mass extinctions on Earth. Due to the higher event rate of GRBs at higher redshifts, it has been speculated that life as we know it may not survive above a certain redshift (e.g., z\\gt 0.5). We examine the duty cycle of lethal (life-threatening) GRBs in the solar neighborhood, in the Sloan Digital Sky Survey (SDSS) galaxies, and GRB host galaxies, with the dependence of the long GRB rate on star formation and metallicity properly taken into account. We find that the number of lethal GRBs attacking Earth within the past 500 Myr (˜epoch of the Ordovician mass extinction) is 0.93. The number of lethal GRBs hitting a certain planet increases with redshift, as a result of the increasing star formation rate (SFR) and decreasing metallicity in high-z galaxies. Taking 1 per 500 Myr as a conservative duty cycle for life to survive, as evidenced by our existence, we find that there is still a good fraction of SDSS galaxies beyond z=0.5 where the GRB rate at half-mass radius is lower than this value. We derive the fraction of such benign galaxies as a function of redshift through Monte Carlo simulations, and we find that the fraction is ˜ 50% at z˜ 1.5 and ˜ 10% even at z˜ 3. The mass distribution of benign galaxies is dominated by Milky Way-like ones, due to their commonness, relatively large mass, and low SFR. GRB host galaxies are among the most dangerous ones.

  14. Radioisotope guided surgery with imaging probe, a hand-held high-resolution gamma camera

    NASA Astrophysics Data System (ADS)

    Soluri, A.; Trotta, C.; Scopinaro, F.; Tofani, A.; D'Alessandria, C.; Pasta, V.; Stella, S.; Massari, R.

    2007-12-01

    Since 1997, our group of Physics together with Nuclear Physicians studies imaging probes (IP), hand-held, high-resolution gamma cameras for radio-guided surgery (RGS). Present work is aimed to verify the usefulness of two updated IP in different surgical operations. Forty patients scheduled for breast cancer sentinel node (SN) biopsy, five patients with nodal recurrence of thyroid cancer, seven patients with parathyroid adenomas, five patients with neuroendocrine tumours (NET), were operated under the guide of IP. We used two different IP with field of view of 1 and 4 in. 2, respectively and intrinsic spatial resolution of about 2 mm. Radioisotopes were 99mTc, 123I and 111In. The 1 in. 2 IP detected SN in all the 40 patients and more than one node in 24, whereas anger camera (AC) failed locating SN in four patients and detected true positive second nodes in only nine patients. The 4 in. 2 IP was used for RGS of thyroid, parathyroid and NETs. It detected eight latero-cervical nodes. In the same patients, AC detected five invaded nodes. Parathyroid adenomas detected by IP were 10 in 7 patients, NET five in five patients. One and 4 in. 2 IPs showed usefulness in all operations. Initial studies on SN biopsy were carried out on small series of patients to validate IP and to demonstrate the effectiveness and usefulness of IP alone or against conventional probes. We propose the use of the IP as control method for legal documentation and surgeon strategy guide before and after lesion(s) removal.

  15. MAGIC and VERITAS detect an unprecedented flaring activity from Mrk 421 in very high energy gamma-rays

    NASA Astrophysics Data System (ADS)

    Cortina, Juan; Holder, Jamie

    2013-04-01

    The MAGIC and VERITAS telescopes have observed an unprecedented flaring activity in the Very High Energy (VHE; >100 GeV) gamma-ray flux from Markarian 421 (RA= 11 04 27.31, Dec=38 12 31.8, J2000.0). These observations were initially performed within a pre-planned extensive multi-instrument campaign that started in December 2012, and intensified in the last days because of the extreme VHE activity observed.

  16. Comparative toxicity and micronuclei formation in Tribolium castaneum, Callosobruchus maculatus and Sitophilus oryzae exposed to high doses of gamma radiation.

    PubMed

    Ahmadi, Mehrdad; Mozdarani, Hossein; Abd-Alla, Adly M M

    2015-07-01

    The effects of gamma radiation on mortality and micronucleus formation in Tribolium castaneum Herbst, Callosobruchus maculatus (F.) and Sitophilus oryzae (L.) genital cells were evaluated. Two groups of healthy and active adult insects 1-3 and 8-10 days old were irradiated with various doses (50-200 Gy) gamma ray. Seven days post-irradiation; mortality rates and micronucleus formation were assessed in genital cells of the irradiated insects. The results show that with increasing gamma doses, the mortality rate of each species increased and T. castaneum and S. oryzae showed the low and high sensitivity respectively. It was shown that the micronucleus appearance in the tested insects had correlation with amount and intensity of radiation doses. Moreover our results indicate different levels in the genotoxicity of gamma radiation among the insects' genital cells under study. The frequency of micronuclei in genital cells of 1-3 days old insects exposed to 50 and 200 Gy were 12.6 and 38.8 Mn/1000 cells in T. castaneum, 20.8 and 46.8 Mn/1000 cells in C. maculatus and 16.8 and 57.2 Mn/1000 cells in S. oryzae respectively. A high sensitivity of the genital cells to irradiation exposure was seen in S. oryzae correlated with its high mortality rate compared with the other two species. These results might be indicative of inflicting chromosomal damage expressed as micronucleus in high mortality rates observed in the pest population; an indication of genotoxic effects of radiation on the studied species.

  17. Development of a high resolution liquid xenon imaging chamber for gamma-ray astronomy

    NASA Technical Reports Server (NTRS)

    Aprile, Elena

    1991-01-01

    The objective was to develop the technology of liquid xenon (LXe) detectors for spectroscopy and imaging of gamma rays from astrophysical sources emitting in the low to medium energy regime. In particular, the technical challenges and the physical processes relevant to the realization of the LXe detector operated as a Time Projection Chamber (TPC) were addressed and studied. Experimental results were obtained on the following topics: (1) long distance drift of free electrons in LXe (purity); (2) scintillation light yield for electrons and alphas in LXe (triggering); and (3) ionization yield for electrons and gamma rays in LXe (energy resolution). The major results from the investigations are summarized.

  18. Constraining heavy decaying dark matter with the high energy gamma-ray limits

    NASA Astrophysics Data System (ADS)

    Kalashev, O. E.; Kuznetsov, M. Yu.

    2016-09-01

    We consider decaying dark matter with masses 1 07≲M ≲1 016 GeV as a source of ultrahigh energy (UHE) gamma rays. Using recent limits on UHE gamma-ray flux for energies Eγ>2 ×1 014 eV , provided by extensive air shower observatories, we put limits on masses and lifetimes of the dark matter. We also discuss possible dark matter decay origin of tentative 100 PeV photon flux detected with the EAS-MSU experiment.

  19. Variable very-high-energy gamma-ray emission from the microquasar LS I +61 303.

    PubMed

    Albert, J; Aliu, E; Anderhub, H; Antoranz, P; Armada, A; Asensio, M; Baixeras, C; Barrio, J A; Bartelt, M; Bartko, H; Bastieri, D; Bavikadi, S R; Bednarek, W; Berger, K; Bigongiari, C; Biland, A; Bisesi, E; Bock, R K; Bordas, P; Bosch-Ramon, V; Bretz, T; Britvitch, I; Camara, M; Carmona, E; Chilingarian, A; Ciprini, S; Coarasa, J A; Commichau, S; Contreras, J L; Cortina, J; Curtef, V; Danielyan, V; Dazzi, F; De Angelis, A; de Los Reyes, R; De Lotto, B; Domingo-Santamaría, E; Dorner, D; Doro, M; Errando, M; Fagiolini, M; Ferenc, D; Fernández, E; Firpo, R; Flix, J; Fonseca, M V; Font, L; Fuchs, M; Galante, N; Garczarczyk, M; Gaug, M; Giller, M; Goebel, F; Hakobyan, D; Hayashida, M; Hengstebeck, T; Höhne, D; Hose, J; Hsu, C C; Isar, P G; Jacon, P; Kalekin, O; Kosyra, R; Kranich, D; Laatiaoui, M; Laille, A; Lenisa, T; Liebing, P; Lindfors, E; Lombardi, S; Longo, F; López, J; López, M; Lorenz, E; Lucarelli, F; Majumdar, P; Maneva, G; Mannheim, K; Mansutti, O; Mariotti, M; Martínez, M; Mase, K; Mazin, D; Merck, C; Meucci, M; Meyer, M; Miranda, J M; Mirzoyan, R; Mizobuchi, S; Moralejo, A; Nilsson, K; Oña-Wilhelmi, E; Orduña, R; Otte, N; Oya, I; Paneque, D; Paoletti, R; Paredes, J M; Pasanen, M; Pascoli, D; Pauss, F; Pavel, N; Pegna, R; Persic, M; Peruzzo, L; Piccioli, A; Poller, M; Pooley, G; Prandini, E; Raymers, A; Rhode, W; Ribó, M; Rico, J; Riegel, B; Rissi, M; Robert, A; Romero, G E; Rügamer, S; Saggion, A; Sánchez, A; Sartori, P; Scalzotto, V; Scapin, V; Schmitt, R; Schweizer, T; Shayduk, M; Shinozaki, K; Shore, S N; Sidro, N; Sillanpää, A; Sobczynska, D; Stamerra, A; Stark, L S; Takalo, L; Temnikov, P; Tescaro, D; Teshima, M; Tonello, N; Torres, A; Torres, D F; Turini, N; Vankov, H; Vitale, V; Wagner, R M; Wibig, T; Wittek, W; Zanin, R; Zapatero, J

    2006-06-23

    Microquasars are binary star systems with relativistic radio-emitting jets. They are potential sources of cosmic rays and can be used to elucidate the physics of relativistic jets. We report the detection of variable gamma-ray emission above 100 gigaelectron volts from the microquasar LS I 61 + 303. Six orbital cycles were recorded. Several detections occur at a similar orbital phase, which suggests that the emission is periodic. The strongest gamma-ray emission is not observed when the two stars are closest to one another, implying a strong orbital modulation of the emission or absorption processes. PMID:16709745

  20. Spirogyra varians mutant generated by high dose gamma-irradiation shows increased antioxidant properties

    NASA Astrophysics Data System (ADS)

    Lee, Hak-Jyung; Yoon, Minchul; Sung, Nak-Yun; Choi, Jong-il

    2012-08-01

    The aim of this study was to evaluate the antioxidant properties of a Spirogyra varians mutant (Mut) produced by gamma irradiation. Methanol extracts were prepared from Spirogyra varians wild-type and Mut plants, and their antioxidant activities and total phenolic content (TPC) were determined. Antioxidant parameters, including the 2-diphenyl-1-picrylhydrazyl radical-scavenging activity and ferric-reducing/antioxidant power, were higher in the Mut extract. Moreover, the TPC level was higher (P<0.05) in the Mut methanol extract. Therefore, these results suggest that gamma irradiation-induced S. varians Mut has superior antioxidant properties.

  1. Variable very-high-energy gamma-ray emission from the microquasar LS I +61 303.

    PubMed

    Albert, J; Aliu, E; Anderhub, H; Antoranz, P; Armada, A; Asensio, M; Baixeras, C; Barrio, J A; Bartelt, M; Bartko, H; Bastieri, D; Bavikadi, S R; Bednarek, W; Berger, K; Bigongiari, C; Biland, A; Bisesi, E; Bock, R K; Bordas, P; Bosch-Ramon, V; Bretz, T; Britvitch, I; Camara, M; Carmona, E; Chilingarian, A; Ciprini, S; Coarasa, J A; Commichau, S; Contreras, J L; Cortina, J; Curtef, V; Danielyan, V; Dazzi, F; De Angelis, A; de Los Reyes, R; De Lotto, B; Domingo-Santamaría, E; Dorner, D; Doro, M; Errando, M; Fagiolini, M; Ferenc, D; Fernández, E; Firpo, R; Flix, J; Fonseca, M V; Font, L; Fuchs, M; Galante, N; Garczarczyk, M; Gaug, M; Giller, M; Goebel, F; Hakobyan, D; Hayashida, M; Hengstebeck, T; Höhne, D; Hose, J; Hsu, C C; Isar, P G; Jacon, P; Kalekin, O; Kosyra, R; Kranich, D; Laatiaoui, M; Laille, A; Lenisa, T; Liebing, P; Lindfors, E; Lombardi, S; Longo, F; López, J; López, M; Lorenz, E; Lucarelli, F; Majumdar, P; Maneva, G; Mannheim, K; Mansutti, O; Mariotti, M; Martínez, M; Mase, K; Mazin, D; Merck, C; Meucci, M; Meyer, M; Miranda, J M; Mirzoyan, R; Mizobuchi, S; Moralejo, A; Nilsson, K; Oña-Wilhelmi, E; Orduña, R; Otte, N; Oya, I; Paneque, D; Paoletti, R; Paredes, J M; Pasanen, M; Pascoli, D; Pauss, F; Pavel, N; Pegna, R; Persic, M; Peruzzo, L; Piccioli, A; Poller, M; Pooley, G; Prandini, E; Raymers, A; Rhode, W; Ribó, M; Rico, J; Riegel, B; Rissi, M; Robert, A; Romero, G E; Rügamer, S; Saggion, A; Sánchez, A; Sartori, P; Scalzotto, V; Scapin, V; Schmitt, R; Schweizer, T; Shayduk, M; Shinozaki, K; Shore, S N; Sidro, N; Sillanpää, A; Sobczynska, D; Stamerra, A; Stark, L S; Takalo, L; Temnikov, P; Tescaro, D; Teshima, M; Tonello, N; Torres, A; Torres, D F; Turini, N; Vankov, H; Vitale, V; Wagner, R M; Wibig, T; Wittek, W; Zanin, R; Zapatero, J

    2006-06-23

    Microquasars are binary star systems with relativistic radio-emitting jets. They are potential sources of cosmic rays and can be used to elucidate the physics of relativistic jets. We report the detection of variable gamma-ray emission above 100 gigaelectron volts from the microquasar LS I 61 + 303. Six orbital cycles were recorded. Several detections occur at a similar orbital phase, which suggests that the emission is periodic. The strongest gamma-ray emission is not observed when the two stars are closest to one another, implying a strong orbital modulation of the emission or absorption processes.

  2. PKS 2123-463: A Confirmed Gamma-ray Blazar at High Redshift

    NASA Technical Reports Server (NTRS)

    D'Ammando, F.; Rau, A.; Schady, P.; Finke, J.; Orienti, M.; Greiner, J.; Kann, D. A.; Ojha, R.; Foley, A. R.; Stevens, J.; Blanchard, J. M.; Edwards, P. G.; Kadler, M.; Lovell, J. E.

    2013-01-01

    The flat spectrum radio quasar (FSRQ) PKS 2123-463 was associated in the first Fermi- Large Area Telescope (LAT) source catalogue with the gamma-ray source 1FGL J2126.1-4603, but when considering the full first two years of Fermi observations, no gamma-ray source at a position consistent with this FSRQ was detected, and thus PKS 2123-463 was not reported in the second Fermi-LAT source catalogue. On 2011 December 14 a gamma-ray source positionally consistent with PKS 2123-463 was detected in flaring activity by Fermi-LAT. This activity triggered radio-to-X-ray observations by the Swift,Gamma-ray Optical/Near-Infrared Detector (GROND), Australia Telescope Compact Array (ATCA), Ceduna and Seven Dishes Karoo Array Telescope (KAT-7) observatories. Results of the localization of the gamma-ray source over 41 months of Fermi-LAT operation are reported here in conjunction with the results of the analysis of radio, optical, ultraviolet (UV) and X-ray data collected soon after the gamma-ray flare. The strict spatial association with the lower energy counterpart together with a simultaneous increase of the activity in optical, UV, X-ray and gamma-ray bands led to a firm identification of the gamma-ray source with PKS 2123-463. A new photometric redshift has been estimated as z = 1.46 plus or minus 0.05 using GROND and Swift Ultraviolet/Optical Telescope (UVOT) observations, in rough agreement with the disputed spectroscopic redshift of z = 1.67.We fit the broad-band spectral energy distribution with a synchrotron/external Compton model. We find that a thermal disc component is necessary to explain the optical/UV emission detected by Swift/UVOT. This disc has a luminosity of approximately 1.8 x 10(exp 46) erg s(exp -1), and a fit to the disc emission assuming a Schwarzschild (i.e. non-rotating) black hole gives a mass of approximately 2 x 10(exp 9) solar mass. This is the first black hole mass estimate for this source.

  3. Probing Pre-galactic Metal Enrichment with High-redshift Gamma-Ray Bursts

    NASA Astrophysics Data System (ADS)

    Wang, F. Y.; Bromm, Volker; Greif, Thomas H.; Stacy, Athena; Dai, Z. G.; Loeb, Abraham; Cheng, K. S.

    2012-11-01

    We explore high-redshift gamma-ray bursts (GRBs) as promising tools to probe pre-galactic metal enrichment. We utilize the bright afterglow of a Population III (Pop III) GRB exploding in a primordial dwarf galaxy as a luminous background source, and calculate the strength of metal absorption lines that are imprinted by the first heavy elements in the intergalactic medium (IGM). To derive the GRB absorption line diagnostics, we use an existing highly resolved simulation of the formation of a first galaxy which is characterized by the onset of atomic hydrogen cooling in a halo with virial temperature >~ 104 K. We explore the unusual circumburst environment inside the systems that hosted Pop III stars, modeling the density evolution with the self-similar solution for a champagne flow. For minihalos close to the cooling threshold, the circumburst density is roughly proportional to (1 + z) with values of about a few cm-3. In more massive halos, corresponding to the first galaxies, the density may be larger, n >~ 100 cm-3. The resulting afterglow fluxes are weakly dependent on redshift at a fixed observed time, and may be detectable with the James Webb Space Telescope and Very Large Array in the near-IR and radio wavebands, respectively, out to redshift z >~ 20. We predict that the maximum of the afterglow emission shifts from near-IR to millimeter bands with peak fluxes from mJy to Jy at different observed times. The metal absorption line signature is expected to be detectable in the near future. GRBs are ideal tools for probing the metal enrichment in the early IGM, due to their high luminosities and featureless power-law spectra. The metals in the first galaxies produced by the first supernova (SN) explosions are likely to reside in low-ionization stages (C II, O I, Si II and Fe II). We show that, if the afterglow can be observed sufficiently early, analysis of the metal lines may distinguish whether the first heavy elements were produced in a pair

  4. Probing Pre-Galactic Metal Enrichment with High-Redshift Gamma-Ray Bursts

    NASA Technical Reports Server (NTRS)

    Wang, F. Y.; Bromm, Volker; Greif, Thomas H.; Stacy, Athena; Dai, Z. G.; Loeb, Abraham; Cheng, K. S.

    2012-01-01

    We explore high-redshift gamma-ray bursts (GRBs) as promising tools to probe pre-galactic metal enrichment. We utilize the bright afterglow of a Population III (Pop III) GRB exploding in a primordial dwarf galaxy as a luminous background source, and calculate the strength of metal absorption lines that are imprinted by the first heavy elements in the intergalactic medium (IGM). To derive the GRB absorption line diagnostics, we use an existing highly resolved simulation of the formation of a first galaxy which is characterized by the onset of atomic hydrogen cooling in a halo with virial temperature approximately greater than10(exp 4) K.We explore the unusual circumburst environment inside the systems that hosted Pop III stars, modeling the density evolution with the self-similar solution for a champagne flow. For minihalos close to the cooling threshold, the circumburst density is roughly proportional to (1 + z) with values of about a few cm(exp -3). In more massive halos, corresponding to the first galaxies, the density may be larger, n approximately greater than100 cm(exp -3). The resulting afterglow fluxes are weakly dependent on redshift at a fixed observed time, and may be detectable with the James Webb Space Telescope and Very Large Array in the near-IR and radio wavebands, respectively, out to redshift z approximately greater than 20. We predict that the maximum of the afterglow emission shifts from near-IR to millimeter bands with peak fluxes from mJy to Jy at different observed times. The metal absorption line signature is expected to be detectable in the near future. GRBs are ideal tools for probing the metal enrichment in the early IGM, due to their high luminosities and featureless power-law spectra. The metals in the first galaxies produced by the first supernova (SN) explosions are likely to reside in low-ionization stages (C II, O I, Si II and Fe II). We show that, if the afterglow can be observed sufficiently early, analysis of the metal lines may

  5. SAS-2 high-energy gamma-ray observations of the Vela pulsar. II

    NASA Technical Reports Server (NTRS)

    Thompson, D. J.; Fichtel, C. E.; Kniffen, D. A.; Ogelman, H. B.

    1977-01-01

    Analysis of additional data from SAS-2 experiment and improvements in the orbit-attitude data and analysis procedures have produced revised values for the flux from the Vela gamma-ray source. The pulsar phase plot shows two peaks, neither of which is in phase with the single radio pulse.

  6. On the possibility of observing cosmic ray sources in high energy gamma rays

    NASA Technical Reports Server (NTRS)

    Ormes, J. F.

    1987-01-01

    If cosmic rays are accelerated by strong shocks, then cosmic ray sources should be characterized by spectra, dN/dE alpha E exp -(2.0-2.2), reflecting the strength of those shocks. This is expected from the 'standard leaky box' model of cosmic ray propagation in which the source spectra are harder than the observed spectra because higher energy particles have shorter residence times in the galactic magnetic fields. Furthermore, data on cosmic ray nucleons suggest that these sources might be surrounded by material. If the latter is true, such sources should be observable in gamma rays at energies beyond 1 GeV where the angular resolution of gamma-ray telescopes is optimized and the background is significantly reduced. For identified sources, the source location accuracy can be shown to improve with increasing energy in spite of the decreasing statistics, as long as the gamma-ray spectrum is harder than dN/dE alpha E exp -gamma. A Monte Carlo model is used to predict the photon spectra which would be expected from cosmic ray sources under varying assumptions about the strength of the shocks in the acceleration region.

  7. A LEPTONIC MODEL OF STEADY HIGH-ENERGY GAMMA-RAY EMISSION FROM Sgr A*

    SciTech Connect

    Kusunose, Masaaki; Takahara, Fumio E-mail: takahara@vega.ess.sci.osaka-u.ac.jp

    2012-03-20

    Recent observations of Sgr A* by Fermi and HESS have detected steady {gamma}-ray emission in the GeV and TeV bands. We present a new model to explain the GeV {gamma}-ray emission by inverse Compton scattering by nonthermal electrons supplied by the NIR/X-ray flares of Sgr A*. The escaping electrons from the flare regions accumulate in a region with a size of {approx}10{sup 18} cm and magnetic fields of {approx}< 10{sup -4} G. Those electrons produce {gamma}-rays by inverse Compton scattering off soft photons emitted by stars and dust around the central black hole. By fitting the GeV spectrum, we find constraints on the magnetic field and the energy density of optical-UV radiation in the central 1 pc region around the supermassive black hole. While the GeV spectrum is well fitted by our model, the TeV {gamma}-rays, whose spectral index is different from that of the GeV emission, may be from different sources such as pulsar wind nebulae.

  8. THE STELLAR CONTRIBUTION TO THE EXTRAGALACTIC BACKGROUND LIGHT AND ABSORPTION OF HIGH-ENERGY GAMMA RAYS

    SciTech Connect

    Razzaque, Soebur; Finke, Justin D.; Dermer, Charles D.

    2009-05-20

    TeV {gamma}-rays from distant astrophysical sources are attenuated due to electron-positron pair creation by interacting with ultraviolet/optical to infrared photons which fill the universe and are collectively known as the extragalactic background light (EBL). We model the {approx}0.1-10 eV starlight component of the EBL derived from expressions for the stellar initial mass function (IMF), star formation history of the universe, and wavelength-dependent absorption of a large sample of galaxies in the local universe. These models are simultaneously fitted to the EBL data as well as to the data on the stellar luminosity density in our local universe. We find that the models with modified Salpeter A IMF together with Cole et al. or Hopkins and Beacom star formation history best represent available data. Since no dust emission is included, our calculated EBL models can be interpreted as the lower limits in the {approx}0.1-1 eV range. We present simple analytic fits to the best-fit EBL model evolving with redshift. We then proceed to calculate {gamma}-ray opacities and absorption of {approx}10-300 GeV {gamma}-rays coming from different redshifts. We discuss implications of our results for the Fermi Gamma Ray Space Telescope and ground-based Air Cherenkov Telescopes.

  9. Registration of the high energy muon bundles by the muon detector of the Ani gamma installation

    NASA Astrophysics Data System (ADS)

    Ivanov, V. A.; Eganov, V. S.; Nikolskaya, N. M.; Romakhin, V. A.

    The paper presents analyses of muon component of EAS measured with "GAMMA" installation at Mt. Aragats. It shows a strong dependence of muon lateral distribution shape and of total muon number from the age parameter of EAS electron-photon component. Obtained Nµ/Ne dependence demonstrates abrupt change in the knee region.

  10. A New Paradigm for Identification of Classes of High Energy Gamma-Ray Sources

    SciTech Connect

    Torres, D F; Reimer, O

    2005-04-08

    A large fraction of the expected number of source detections of the forthcoming observatory Gamma-ray Large Area Space Telescope (GLAST) will be initially unidentified. We argue that traditional methodological approaches to identify individual detections and/or populations of gamma-ray sources present procedural limitations. These limitations will hamper our ability to classify the populations lying in the anticipated dataset with the required degree of confidence, in particular for those for which no member has yet been detected convincingly with the predecessor experiment EGRET. Here we suggest a new paradigm for achieving the classification of gamma-ray source populations that is based on implementing an a priori protocol to search for theoretically-motivated candidates. It is essential that such paradigm will be defined before the data is unblinded, in order to protect the discovery potential of the sample. Key to the new procedure is a quantitative assessment of the confidence level by which new populations can be claimed to have been discovered. When needed, small number statistics is applied for population studies in gamma-ray astronomy. Although we refer here explicitly only to the case of GLAST, the scheme we present can certainly be adapted to other experiments confronted with a similar combination of problems.

  11. HAWC: The High-Altitude Water Cherenkov observatory for TeV gamma-rays & cosmic-ray anisotropy

    NASA Astrophysics Data System (ADS)

    DuVernois, Michael

    Currently, the High-Altitude Water Cherenkov (HAWC) Observatory is being built at a site about a two hours drive east of Puebla, Mexico, on the Sierra Negra plateau (4100 m a.s.l.). HAWC is unique among TeV gamma-ray instruments since it can observe large portions of the sky in a 24 hour time period and therefore the detector is particularly well suited to measure extended and large-scale structures in the sky like galactic diffuse gamma-ray emission, and both large and small-scale anisotropies. In addition, discoveries of other extended unidentified objects at TeV energies, for example collocated with the “Fermi Bubbles”, and the observation of transient phenomena such as GRBs are possible. The construction of HAWC funded through NSF, DoE, and CONACyT is expected to be complete by Fall 2014. Data are already being collected during construction with an increasingly sensitive detector allowing for synchronous observations with instruments at other wavebands such as the Fermi Space Telescopes. Analysis of the already recorded data reveal significant anisotropies in the arrival directions of cosmic rays at small and large scales. A number of gamma-ray hot spots are also observed along the Galactic plane and the data are searched for high-energy emission from GRBs detected at lower energies. I will present first results and some of the scientific potential of the observatory.

  12. NEW CLASS OF VERY HIGH ENERGY {gamma}-RAY EMITTERS: RADIO-DARK MINI SHELLS SURROUNDING ACTIVE GALACTIC NUCLEUS JETS

    SciTech Connect

    Kino, Motoki; Kawakatu, Nozomu; Orienti, Monica

    2013-02-20

    We explore non-thermal emission from a shocked interstellar medium, which is identified as an expanding shell, driven by a relativistic jet in active galactic nuclei (AGNs). In this work, we particularly focus on parsec-scale size mini shells surrounding mini radio lobes. From the radio to X-ray band, the mini radio lobe emission dominates the faint emission from the mini shell. On the other hand, we find that inverse-Compton (IC) emission from the shell can overwhelm the associated lobe emission at the very high energy (VHE; E > 100 GeV) {gamma}-ray range, because energy densities of synchrotron photons from the lobe and/or soft photons from the AGN nucleus are large and IC scattering works effectively. The predicted IC emission from nearby mini shells can be detected with the Cherenkov Telescope Array and they are potentially a new class of VHE {gamma}-ray emitters.

  13. Practical considerations for TLD-400/700-based gamma ray dosimetry for BNCT applications in a high thermal neutron fluence.

    PubMed

    Martsolf, S W; Johnson, J E; Vostmyer, C E; Albertson, B D; Binney, S E

    1995-12-01

    Operating experience with thermoluminescent dosimeters used in a boron neutron capture therapy research project is reported. In particular, certain facets of the use of thermoluminescent dosimeters for gamma ray dose measurements in the presence of a high thermal neutron fluence are discussed, including a comparison of TLD-400 and TLD-700 for gamma ray dosimetry, annealing procedures, and the effects of neutrons (56Mn activation) on TLD-400. The TLD-400 were observed to have a thermal neutron sensitivity (due to 56Mn beta decay) of 1.5 x 10(-13) Gy per n cm-2. An algorithm was developed to correct for the 56Mn beta decay thermal neutron-induced effects on TLD-400 by using a two-stage thermoluminescent readout for the thermoluminescent dosimeter chips.

  14. Optical and electron beam studies of gamma-irradiated AlGaN/GaN high-electron-mobility transistors

    NASA Astrophysics Data System (ADS)

    Yadav, Anupama; Glasscock, Cameron; Flitsiyan, Elena; Chernyak, Leonid; Lubomirsky, Igor; Khodorov, Sergey; Salzman, Joseph; Meyler, Boris; Coppola, Carlo; Guay, Sebestian; Boivin, Jasques

    2016-03-01

    The impact of 60Co gamma-irradiation on n-channel AlGaN/GaN high-electron-mobility transistors was studied by means of temperature-dependent electron beam-induced current (EBIC) and cathodoluminescence (CL) techniques. For the doses up to ∼250 Gy, an enhancement of minority carrier transport was observed as evident from the EBIC measurements. This enhancement is associated with internal electron irradiation induced by the primary gamma photons. For the doses above ∼250 Gy, deterioration in minority carrier transport was explained by carrier scattering on radiation-induced defects. It is shown that calculated activation energy from the EBIC and CL measurements follows exactly the same trend, which implies that the same underlying phenomenon is responsible for observed findings.

  15. Lateral distribution of high energy hadrons and gamma ray in air shower cores observed with emulsion chambers

    NASA Technical Reports Server (NTRS)

    Matano, T.; Machida, M.; Kawasumi, N.; Tsushima, I.; Honda, K.; Hashimoto, K.; Navia, C. E.; Matinic, N.; Aquirre, C.

    1985-01-01

    A high energy event of a bundle of electrons, gamma rays and hadronic gamma rays in an air shower core were observed. The bundles were detected with an emulsion chamber with thickness of 15 cm lead. This air shower is estimated to be initiated with a proton with energy around 10 to the 17th power to 10 to the 18th power eV at an altitude of around 100 gmc/2. Lateral distributions of the electromagnetic component with energy above 2 TeV and also the hadronic component of energy above 6 TeV of this air shower core were determined. Particles in the bundle are produced with process of the development of the nuclear cascade, the primary energy of each interaction in the cascade which produces these particles is unknown. To know the primary energy dependence of transverse momentum, the average products of energy and distance for various average energies of secondary particles are studied.

  16. Search for Very High Energy Gamma-ray Emission from Pulsar-Pulsar Wind Nebula Systems with the MAGIC Telescope

    NASA Astrophysics Data System (ADS)

    Anderhub, H.; Antonelli, L. A.; Antoranz, P.; Backes, M.; Baixeras, C.; Balestra, S.; Barrio, J. A.; Bastieri, D.; Becerra González, J.; Becker, J. K.; Bednarek, W.; Berger, al K.; Bernardini, E.; Biland, A.; Bock, R. K.; Bonnoli, G.; Bordas, P.; Borla Tridon, D.; Bosch-Ramon, V.; Bose, D.; Braun, I.; Bretz, T.; Britzger, D.; Camara, M.; Carmona, E.; Carosi, A.; Colin, P.; Commichau, S.; Contreras, J. L.; Cortina, J.; Costado, M. T.; Covino, S.; Dazzi, F.; De Angelis, A.; de Cea del Pozo, E.; De los Reyes, R.; De Lotto, B.; De Maria, M.; De Sabata, F.; Delgado Mendez, C.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Elsaesser, D.; Errando, M.; Ferenc, D.; Fernández, E.; Firpo, R.; Fonseca, M. V.; Font, L.; Galante, N.; García López, R. J.; Garczarczyk, M.; Gaug, M.; Godinovic, N.; Goebel, F.; Hadasch, D.; Herrero, A.; Hildebrand, D.; Höhne-Mönch, D.; Hose, J.; Hrupec, D.; Hsu, C. C.; Jogler, T.; Klepser, S.; Kranich, D.; La Barbera, A.; Laille, A.; Leonardo, E.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; Lorenz, E.; Majumdar, P.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Meucci, M.; Miranda, J. M.; Mirzoyan, R.; Miyamoto, H.; Moldón, J.; Moles, M.; Moralejo, A.; Nieto, D.; Nilsson, K.; Ninkovic, J.; Orito, R.; Oya, I.; Paoletti, R.; Paredes, J. M.; Pasanen, M.; Pascoli, D.; Pauss, F.; Pegna, R. G.; Perez-Torres, M. A.; Persic, M.; Peruzzo, L.; Prada, F.; Prandini, E.; Puchades, N.; Puljak, I.; Reichardt, I.; Rhode, W.; Ribó, M.; Rico, J.; Rissi, M.; Robert, A.; Rügamer, S.; Saggion, A.; Saito, T. Y.; Salvati, M.; Sánchez-Conde, M.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schweizer, T.; Shayduk, M.; Shore, S. N.; Sierpowska-Bartosik, A.; Sillanpää, A.; Sitarek, J.; Sobczynska, D.; Spanier, F.; Spiro, S.; Stamerra, A.; Stark, L. S.; Suric, T.; Takalo, L.; Tavecchio, F.; Temnikov, P.; Tescaro, D.; Teshima, M.; Torres, D. F.; Turini, N.; Vankov, H.; Wagner, R. M.; Zabalza, V.; Zandanel, F.; Zanin, R.; Zapatero, J.; Cognard, I.

    2010-02-01

    The MAGIC collaboration has searched for high-energy gamma-ray emission of some of the most promising pulsar candidates above an energy threshold of 50 GeV, an energy not reachable up to now by other ground-based instruments. Neither pulsed nor steady gamma-ray emission has been observed at energies of 100 GeV from the classical radio pulsars PSR J0205+6449 and PSR J2229+6114 (and their nebulae 3C58 and Boomerang, respectively) and the millisecond pulsar PSR J0218+4232. Here, we present the flux upper limits for these sources and discuss their implications in the context of current model predictions.

  17. The Very Bright and Nearby GRB130427A: the Extra Hard Spectral Component and Implications for Very High-Energy Gamma-Ray Observations of Gamma-Ray Bursts

    NASA Astrophysics Data System (ADS)

    Tam, Pak-Hin Thomas

    2014-03-01

    The extended high-energy gamma-ray (>100 MeV) emission occurring after the prompt gamma-ray bursts (GRBs) is usually characterized by a single power-law spectrum, which has been explained as the afterglow synchrotron radiation. We report on the Fermi Large Area Telescope (LAT) observations of the >100 MeV emission from the very bright and nearby GRB 130427A, up to 100 GeV. By performing time-resolved spectral fits of GRB 130427A, we found a strong evidence of an extra hard spectral component above a few GeV that exists in the extended high-energy emission of this GRB. This extra spectral component may represent the first clear evidence of the long sought-after afterglow inverse Compton emission. Prospects for observations at the very high-energy gamma-rays, i.e., above 100 GeV, are described.

  18. A high-resolution gamma-ray and hard X-ray spectrometer for solar flare observations in Max 1991

    NASA Technical Reports Server (NTRS)

    Lin, R. P.; Curtis, D. W.; Harvey, P.; Hurley, K.; Primbsch, J. H.; Smith, D. M.; Pelling, R. M.; Duttweiler, F.

    1988-01-01

    A long duration balloon flight instrument for Max 1991 designed to study the acceleration of greater than 10 MeV ions and greater than 15 keV electrons in solar flares through high resolution spectroscopy of the gamma ray lines and hard X-ray and gamma ray continuum is described. The instrument, HIREGS, consists of an array of high-purity, n-type coaxial germanium detectors (HPGe) cooled to less than 90 K and surrounded by a bismuth germanate (BGO) anticoincidence shield. It will cover the energy range 15 keV to 20 MeV with keV spectral resolution, sufficient for accurate measurement of all parameters of the expected gamma ray lines with the exception of the neutron capture deuterium line. Electrical segmentation of the HPGe detector into a thin front segment and a thick rear segment, together with pulse-shape discrimination, provides optimal dynamic range and signal-to-background characteristics for flare measurements. Neutrons and gamma rays up to approximately 0.1 to 1 GeV can be detected and identified with the combination of the HPGe detectors and rear BGO shield. The HIREGS is planned for long duration balloon flights (LDBF) for solar flare studies during Max 1991. The two exploratory LDBFs carried out at mid-latitudes in 1987 to 1988 are described, and the LDBFs in Antarctica, which could in principle provide 24 hour/day solar coverage and very long flight durations (20 to 30 days) because of minimal ballast requirements are discussed.

  19. Use of a Shielded High Resolution Gamma Spectrometry System to Segregate LLW from Contact Handleable ILW Containing Plutonium - 13046

    SciTech Connect

    Lester, Rosemary; Wilkins, Colin; Chard, Patrick; Jaederstroem, Henrik; LeBlanc, Paul; Mowry, Rick; MacDonald, Sanders; Gunn, William

    2013-07-01

    Dounreay Site Restoration Limited (DSRL) have a number of drums of solid waste that may contain Plutonium Contaminated Material. These are currently categorised as Contact Handleable Intermediate Level Waste (CHILW). A significant fraction of these drums potentially contain waste that is in the Low Level Waste (LLW) category. A Canberra Q2 shielded high resolution gamma spectrometry system is being used to quantify the total activity of drums that are potentially in the LLW category in order to segregate those that do contain LLW from CHILW drums and thus to minimise the total volume of waste in the higher category. Am-241 is being used as an indicator of the presence of plutonium in the waste from its strong 59.54 keV gamma-ray; a knowledge of the different waste streams from which the material originates allows a pessimistic waste 'fingerprint' to be used in order to determine an upper limit to the activities of the weak and non-gamma-emitting plutonium and associated radionuclides. This paper describes the main features of the high resolution gamma spectrometry system being used by DSRL to perform the segregation of CHILW and LLW and how it was configured and calibrated using the Canberra In-Situ Object Counting System (ISOCS). It also describes how potential LLW drums are selected for assay and how the system uses the existing waste stream fingerprint information to determine a reliable upper limit for the total activity present in each measured drum. Results from the initial on-site commissioning trials and the first measurements of waste drums using the new monitor are presented. (authors)

  20. Effect of annealing on electronic carrier transport properties of gamma-irradiated AlGaN/GaN high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Yadav, Anupama; Schwarz, Casey; Shatkhin, Max; Wang, Luther; Flitsiyan, Elena; Chernyak, Leonid; Liu, Lu; Hwang, Ya; Ren, Fan; Pearton, Stephen; Department of Physics, University of Central Florida Collaboration; Department of Chemical Engineering, University of Florida Collaboration; Department of Materials Science; Engineering, University of Florida Collaboration

    2014-03-01

    AlGaN/GaN High Electron Mobility Transistors were irradiated with 60Co gamma-ray doses from 100Gy to 1000Gy, in order to analyze the effects of irradiation on the devices' transport properties. Temperature dependent Electron Beam Induced Current (EBIC) measurements, conducted on the devices before and after exposure to gamma-irradiation, allowed for the obtaining of activation energy related to radiation-induced defects due to nitrogen vacancies. Later, the devices were annealed at 200o C for 25 minutes. All the measurements were performed again to study the effect of annealing on the gamma-irradiated devices. Annealing of gamma-irradiated transistors shows that partial recovery of device performance is possible at this temperature. DC current-voltage measurements were also conducted on the transistors to assess the impact of gamma-irradiation and annealing on transfer, gate and drain characteristics.

  1. Workshop on Cosmic Ray and High Energy Gamma Ray Experiments for the Space Station Era, Louisiana State University, Baton Rouge, October 17-20, 1984, Proceedings

    NASA Technical Reports Server (NTRS)

    Jones, W. V. (Editor); Wefel, J. P. (Editor)

    1985-01-01

    The potential of the Space Station as a platform for cosmic-ray and high-energy gamma-ray astronomy is discussed in reviews, reports, and specific proposals. Topics examined include antiparticles and electrons, science facilities and new technology, high-energy nuclear interactions, nuclear composition and energy spectra, Space Shuttle experiments, Space Station facilities and detectors, high-energy gamma rays, and gamma-ray facilities and techniques. Consideration is given to universal-baryon-symmetry testing on the scale of galactic clusters, particle studies in a high-inclination orbit, balloon-borne emulsion-chamber results on ultrarelativistic nucleus-nucleus interactions, ionization states of low-energy cosmic rays, a large gamma-ray telescope for point-source studies above 1 GeV, and the possible existence of stable quark matter.

  2. Discovery of Very High Energy Gamma-Ray Emission from MS1221.8+2452 with the MAGIC telescopes

    NASA Astrophysics Data System (ADS)

    Cortina, Juan

    2013-05-01

    The MAGIC collaboration reports the discovery of very high energy (VHE; E>100 GeV) gamma-ray emission from MS1221.8+2452 (12h24m24.2s +24d36m24s, J2000.0). MS1221.8+2452 is a blazar located at a redshift of 0.218 (Sbarufatti et al., 2005, ApJ 635, 173) and classified as a high synchrotron peaked (HSP) BL Lac. It is one of the very few BL Lacs that has been imaged with the Hubble Space Telescope (Jannuzzi et al., 1997, ApJ 491, 146).

  3. A balloon-borne high-resolution spectrometer for observations of gamma-ray emission from solar flares

    NASA Technical Reports Server (NTRS)

    Crannell, C. J.; Starr, R.; Stottlemyre, A. R.; Trombka, J. I.

    1984-01-01

    The design, development, and balloon-flight verification of a payload for observations of gamma-ray emission from solar flares are reported. The payload incorporates a high-purity germanium semiconductor detector, standard NIM and CAMAC electronics modules, a thermally stabilized pressure housing, and regulated battery power supplies. The flight system is supported on the ground with interactive data-handling equipment comprised of similar electronics hardware. The modularity and flexibility of the payload, together with the resolution and stability obtained throughout a 30-hour flight, make it readily adaptable for high-sensitivity, long-duration balloon fight applications.

  4. Characterization of gamma-crystallin from a catfish: structural characterization of one major isoform with high methionine by cDNA sequencing.

    PubMed

    Pan, F M; Chang, W C; Lin, C H; Hsu, A L; Chiou, S H

    1995-04-01

    gamma-Crystallin is the major and most abundant lens protein present in the eye lens of most teleostean fishes. To facilitate structural characterization of gamma-crystallins isolated from the lens of the catfishes (Clarias fuscus), a cDNA mixture was synthesized from the poly(A)+mRNA isolated from fresh eye lenses, and amplification by polymerase chain reaction (PCR) was adopted to obtain cDNAs encoding various gamma-crystallins. Plasmids of transformed E. coli strain JM109 containing amplified gamma-crystallin cDNAs were purified and prepared for nucleotide sequencing by the dideoxynucleotide chain-termination method. Sequencing more than five clones containing DNA inserts of 0.52 kb revealed the presence of one major isoform with a complete reading frame of 534 base pairs, covering a gamma-crystallin (gamma M1) with a deduced protein sequence of 177 amino acids excluding the initiating methionine. It was of interest to find that this crystallin of pI 9.1 contains a high-methionine content of 15.3% in contrast to those gamma-crystallins of low-methionine content from most mammalian lenses. Sequence comparisons of catfish gamma M1-crystallin with those published sequences of gamma-crystallins from carp, bovine and mouse lenses indicate that there is approx. an 82% sequence homology between the catfish and the carp species of piscine class whereas only 51-58% homology is found between mammals and the catfish. Moreover the differences in the hydropathy profiles for these two groups of gamma-crystallins, i.e. one with a high-methionine content from teleostean fishes and the other with a low-methionine content from mammalian species, reflect a distinct variance in the polarity distributions of surface amino acids in these crystallins.(ABSTRACT TRUNCATED AT 250 WORDS)

  5. Locating very high energy gamma-ray sources with arcminute accuracy

    NASA Technical Reports Server (NTRS)

    Akerlof, C. W.; Cawley, M. F.; Chantell, M.; Harris, K.; Lawrence, M. A.; Fegan, D. J.; Lang, M. J.; Hillas, A. M.; Jennings, D. G.; Lamb, R. C.

    1991-01-01

    The angular accuracy of gamma-ray detectors is intrinsically limited by the physical processes involved in photon detection. Although a number of pointlike sources were detected by the COS B satellite, only two have been unambiguously identified by time signature with counterparts at longer wavelengths. By taking advantage of the extended longitudinal structure of VHE gamma-ray showers, measurements in the TeV energy range can pinpoint source coordinates to arcminute accuracy. This has now been demonstrated with new data analysis procedures applied to observations of the Crab Nebula using Cherenkov air shower imaging techniques. With two telescopes in coincidence, the individual event circular probable error will be 0.13 deg. The half-cone angle of the field of view is effectively 1 deg.

  6. On the high-energy gamma-ray signature of cosmic-ray sources

    NASA Technical Reports Server (NTRS)

    Ormes, J. F.; Ozel, M. E.; Morris, D. J.

    1988-01-01

    Monte Carlo simulations of the gamma-ray emission from hypothetical cosmic-ray sources are performed. Sources which might correspond to acceleration by supernova shocks in 'average' interstellar conditions and deep within giant molecular clouds are considered. The consequences of dropping the common assumption that the cosmic-ray spectrum at the sources is the same as that observed at earth are examined. Spectral effects which can be related to the depth of the material shroud and the population of accelerated particles are explored using these simulations and are described. The results are compared with the COS B catalog of gamma-ray sources, and the implications for the underlying particle populations and source mechanisms are discussed.

  7. Effects of stearic acid and gamma irradiation, alone and in combination, on pasting properties of high amylose maize starch.

    PubMed

    Ocloo, Fidelis C K; Minnaar, Amanda; Emmambux, Naushad M

    2016-01-01

    The effects of stearic acid and gamma irradiation on pasting properties of high amylose maize starch (HAMS) were studied. Stearic acid (0%, 1.5%, and 5%) was added to HAMS, and then irradiated at 0, 30, and 60 kGy before pasting. Stearic acid increased the paste viscosity of un-irradiated HAMS from 420 mPas to 557 and 652 mPas for 1.5% and 5% stearic acid, respectively. This observation related well with the formation of type II amylose-lipid complexes, with melting temperatures of about 100-120 °C. Gamma irradiation (30 and 6 0kGy) reduced pasting viscosity of HAMS. Pasting of gamma irradiated HAMS resulted in the formation of type I amylose-lipid complexes, with melting temperatures and enthalpies ranging from 82 to 102 °C and 0.22 to 1.85 J/g, respectively. Stearic acid addition followed by irradiation creates means of producing different types of amylose-lipid complexes from HAMS for industrial utilization.

  8. Time-dependent absorption of very high-energy gamma-rays from the Galactic center by pair-production

    SciTech Connect

    Abramowski, Attila; Horns, Dieter; Ripken, Joachim; Gillessen, Stefan; Eldik, Christopher van

    2008-12-24

    Very high energy (VHE) gamma-rays have been detected from the direction of the Galactic center. The H.E.S.S. Cherenkov telescopes have located this {gamma}-ray source with a preliminary position uncertainty of 8.5'' per axis (6'' statistic+6'' sytematic per axis). Within the uncertainty region several possible counterpart candidates exist: the Super Massive Black Hole Sgr A*, the Pulsar Wind Nebula candidate G359.95-0.04, the Low Mass X-Ray Binary-system J174540.0-290031, the stellar cluster IRS 13, as well as self-annihilating dark matter. It is experimentally very challenging to further improve the positional accuracy in this energy range and therefore, it may not be possible to clearly associate one of the counterpart candidates with the VHE-source. Here, we present a new method to investigate a possible link of the VHE-source with the near environment of Sgr A*(within approximately 1000 Schwarzschild radii). This method uses the time- and energy-dependent effect of absorption of VHE {gamma}-rays by pair-production (in the following named pair-eclipse) with low-energy photons of stars closely orbiting the SMBH Sgr A*.

  9. High-precision (p,t) reaction to determine {sup 25}Al(p,{gamma}){sup 26}Si reaction rates

    SciTech Connect

    Matic, A.; Berg, A. M. van den; Harakeh, M. N.; Woertche, H. J.; Berg, G. P. A.; Couder, M.; Goerres, J.; LeBlanc, P.; O'Brien, S.; Wiescher, M.; Fujita, K.; Hatanaka, K.; Sakemi, Y.; Shimizu, Y.; Tameshige, Y.; Tamii, A.; Yosoi, M.; Adachi, T.; Fujita, Y.; Shimbara, Y.

    2010-08-15

    Since the identification of ongoing {sup 26}Al production in the universe, the reaction sequence {sup 24}Mg(p,{gamma}){sup 25}Al({beta}{sup +{nu}}){sup 25}Mg(p,{gamma}){sup 26}Al has been studied intensively. At temperatures where the radiative capture on {sup 25}Al (t{sub 1/2}=7.2 s) becomes faster than the {beta}{sup +} decay, the production of {sup 26}Al can be reduced due to the depletion of {sup 25}Al. To determine the resonances relevant for the {sup 25}Al(p,{gamma}){sup 26}Si bypass reaction, we measured the {sup 28}Si(p,t){sup 26}Si reaction with high-energy precision using the Grand Raiden spectrometer at the Research Center for Nuclear Physics, Osaka. Several new energy levels were found above the p threshold and for known states excitation energies were determined with smaller uncertainties. The calculated stellar rates of the bypass reaction agree well with previous results, suggesting that these rates are well established.

  10. EGRET detection of high-energy gamma radiation from the OVV quasar 3C 454.3

    NASA Technical Reports Server (NTRS)

    Hartman, R. C.; Bertsch, D. L.; Dingus, B. L.; Fichtel, C. E.; Hunter, S. D.; Kanbach, G.; Kniffen, D. A.; Lin, Y. C.; Mattox, J. R.; Mayer-Hasselwander, H. A.

    1993-01-01

    High-energy gamma radiation has been observed from the optically violent variable quasar 3C 454.3 (PKS 2251 + 158) by the Energetic Gamma-Ray Experiment Telescope on the Compton Observatory. During the 1992 January-February observation, the emission showed a power-law photon spectrum with an exponent of -2.18 +/- 0.08. The flux density (greater than 100 MeV) was observed to vary within the range (0.4-1.4) x 10 exp -6 photon/sq cm s on a time scale of less than a week. Lower sensitivity observations during 1992 April and May also detected emission within that range, but with lower statistical significance. An earlier low-sensitivity exposure during 1991 August gave a 95 percent confidence upper limit of 0.26 x 10 exp 6 photon/sq cm s. The similarity of the gamma-ray emission of 3C 454.3 to that of 3C 279 parallels the similarity of these two objects at lower frequencies.

  11. Chandra X-Ray Observations of the Two Brightest Unidentified High Galactic Latitude Fermi-LAT Gamma-Ray Sources

    NASA Technical Reports Server (NTRS)

    Cheung, C. C.; Donato, D.; Gehrels, N.; Sokolovsky, K. V.; Giroletti, M.

    2012-01-01

    We present Chandra ACIS-I X-ray observations of 0FGL J1311.9-3419 and 0FGL J1653.4-0200, the two brightest high Galactic latitude (absolute value (beta) >10 deg) gamma-ray sources from the three-month Fermi Large Area Telescope (LAT) bright source list that are still unidentified. Both were also detected previously by EGRET, and despite dedicated multi-wavelength follow-up, they are still not associated with established classes of gamma-ray emitters like pulsars or radio-loud active galactic nuclei. X-ray sources found in the ACIS-I fields of view are cataloged, and their basic properties are determined. These are discussed as candidate counterparts to 0FGL J1311.9-3419 and 0FGL J1653.4-0200, with particular emphasis on the brightest of the 9 and 13 Chandra sources detected within the respective Fermi-LAT 95% confidence regions. Further follow-up studies, including optical photometric and spectroscopic observations, are necessary to identify these X-ray candidate counterparts in order to ultimately reveal the nature of these enigmatic gamma-ray objects.

  12. Monte Carlo assessment of soil moisture effect on high-energy thermal neutron capture gamma-ray by 14N.

    PubMed

    Pazirandeh, Ali; Azizi, Maryam; Farhad Masoudi, S

    2006-01-01

    Among many conventional techniques, nuclear techniques have shown to be faster, more reliable, and more effective in detecting explosives. In the present work, neutrons from a 5 Ci Am-Be neutron source being in water tank are captured by elements of soil and landmine (TNT), namely (14)N, H, C, and O. The prompt capture gamma-ray spectrum taken by a NaI (Tl) scintillation detector indicates the characteristic photo peaks of the elements in soil and landmine. In the high-energy region of the gamma-ray spectrum, besides 10.829 MeV of (15)N, single escape (SE) and double escape (DE) peaks are unmistakable photo peaks, which make the detection of concealed explosive possible. The soil has the property of moderating neutrons as well as diffusing the thermal neutron flux. Among many elements in soil, silicon is more abundant and (29)Si emits 10.607 MeV prompt capture gamma-ray, which makes 10.829 MeV detection difficult. The Monte Carlo simulation was used to adjust source-target-detector distances and soil moisture content to yield the best result. Therefore, we applied MCNP4C for configuration very close to reality of a hidden landmine in soil.

  13. Search for High-energy Gamma-ray Emission from Tidal Disruption Events with the Fermi Large Area Telescope

    NASA Astrophysics Data System (ADS)

    Peng, Fang-Kun; Tang, Qing-Wen; Wang, Xiang-Yu

    2016-07-01

    Massive black holes at galaxy center may tear apart a star when the star passes occasionally within the disruption radius, which is the so-called tidal disruption event (TDE). Most TDEs radiate with thermal emission resulting from the acceleration disk, but three TDEs have been detected in bright nonthermal X-ray emission, which is interpreted as arising from the relativistic jets. A search for high-energy gamma-ray emission from one relativistic TDE (Swift J164449.3+573451) with the Fermi Large Area Telescope (LAT) has yielded nondetection. In this paper, we report the search for high-energy emission from the other two relativistic TDEs (Swift J2058.4+0516 and Swift J1112.2-8238) during the flare period. No significant GeV emission is found, with an upper limit fluence in the LAT energy range being less than 1% of that in X-rays. Compared with gamma-ray bursts and blazars, these TDEs have the lowest flux ratio between GeV emission and X-ray emission. The nondetection of high-energy emission from relativistic TDEs could be due to the fact that the high-energy emission is absorbed by soft photons in the source. Based on this hypothesis, upper limits on the bulk Lorentz factors, {{Γ }}≲ 30, are then obtained for the jets in these TDEs. We also search for high-energy gamma-ray emission from the nearest TDE discovered to date, ASASSN-14li. No significant GeV emission is found, and an upper limit of L(0.1{--}10 {GeV})≤slant 4.4× {10}42 erg s‑1 (at 95% confidence level) is obtained for the first 107 s after the disruption.

  14. High resolution gamma-ray astronomy - Observations and predictions of line shapes

    NASA Technical Reports Server (NTRS)

    Bhattacharya, Dipen; Gehrels, Neil

    1991-01-01

    The shapes of gamma-ray lines carry unique information about the physical processes and conditions in astrophysical sites. Galactic center and SN 1987A lines have been observationally resolved allowing their shapes to be studied. There are also significant new theoretical results concerning line shapes from Type I supernovae, supernova remnants and the interstellar medium. New work is presented on a simple treatment of line profiles for rotating disks and spherical shells.

  15. Search for a Correlation between Very-high-energy Gamma Rays and Giant Radio Pulses in the Crab Pulsar

    NASA Astrophysics Data System (ADS)

    Aliu, E.; Archambault, S.; Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Bouvier, A.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cesarini, A.; Ciupik, L.; Collins-Hughes, E.; Connolly, M. P.; Cui, W.; Dickherber, R.; Duke, C.; Dumm, J.; Falcone, A.; Federici, S.; Feng, Q.; Finley, J. P.; Finnegan, G.; Fortson, L.; Furniss, A.; Galante, N.; Gall, D.; Gillanders, G. H.; Godambe, S.; Griffin, S.; Grube, J.; Gyuk, G.; Hanna, D.; Holder, J.; Huan, H.; Hughes, G.; Humensky, T. B.; Kaaret, P.; Karlsson, N.; Khassen, Y.; Kieda, D.; Krawczynski, H.; Krennrich, F.; Lang, M. J.; LeBohec, S.; Lee, K.; Lyutikov, M.; Madhavan, A. S.; Maier, G.; Majumdar, P.; McArthur, S.; McCann, A.; Moriarty, P.; Mukherjee, R.; Nelson, T.; O'Faoláin de Bhróithe, A.; Ong, R. A.; Orr, M.; Otte, A. N.; Park, N.; Perkins, J. S.; Pohl, M.; Prokoph, H.; Quinn, J.; Ragan, K.; Reyes, L. C.; Reynolds, P. T.; Roache, E.; Saxon, D. B.; Schroedter, M.; Sembroski, G. H.; Şentürk, G. D.; Smith, A. W.; Staszak, D.; Telezhinsky, I.; Tešić, G.; Theiling, M.; Thibadeau, S.; Tsurusaki, K.; Varlotta, A.; Vincent, S.; Vivier, M.; Wagner, R. G.; Wakely, S. P.; Weekes, T. C.; Weinstein, A.; Welsing, R.; Williams, D. A.; Zitzer, B.; Kondratiev, V.

    2012-12-01

    We present the results of a joint observational campaign between the Green Bank radio telescope and the VERITAS gamma-ray telescope, which searched for a correlation between the emission of very-high-energy (VHE) gamma rays (E γ > 150 GeV) and giant radio pulses (GRPs) from the Crab pulsar at 8.9 GHz. A total of 15,366 GRPs were recorded during 11.6 hr of simultaneous observations, which were made across four nights in 2008 December and in 2009 November and December. We searched for an enhancement of the pulsed gamma-ray emission within time windows placed around the arrival time of the GRP events. In total, eight different time windows with durations ranging from 0.033 ms to 72 s were positioned at three different locations relative to the GRP to search for enhanced gamma-ray emission which lagged, led, or was concurrent with, the GRP event. Furthermore, we performed separate searches on main pulse GRPs and interpulse GRPs and on the most energetic GRPs in our data sample. No significant enhancement of pulsed VHE emission was found in any of the preformed searches. We set upper limits of 5-10 times the average VHE flux of the Crab pulsar on the flux simultaneous with interpulse GRPs on single-rotation-period timescales. On ~8 s timescales around interpulse GRPs, we set an upper limit of 2-3 times the average VHE flux. Within the framework of recent models for pulsed VHE emission from the Crab pulsar, the expected VHE-GRP emission correlations are below the derived limits.

  16. Active Detection and Imaging of Nuclear Materials with High-Brightness Gamma Rays

    SciTech Connect

    Barty, C J; Gibson, D J; Albert, F; Anderson, S G; Anderson, G G; Betts, S M; Berry, R D; Fisher, S E; Hagmann, C A; Johnson, M S; Messerly, M J; Phan, H H; Semenov, V A; Shverdin, M Y; Tremaine, A M; Hartemann, F V; Siders, C W; McNabb, D P

    2009-02-26

    A Compton scattering {gamma}-ray source, capable of producing photons with energies ranging from 0.1 MeV to 0.9 MeV has been commissioned and characterized, and then used to perform nuclear resonance fluorescence (NRF) experiments. The performances of the two laser systems (one for electron production, one for scattering), the electron photoinjector, and the linear accelerator are also detailed, and {gamma}-ray results are presented. The key source parameters are the size (0.01 mm{sup 2}), horizontal and vertical divergence (6 x 10 mrad{sup 2}), duration (10 ps), spectrum and intensity (10{sup 5} photons/shot). These parameters are summarized by the peak brightness, 1.5 x 10{sup 15} photons/mm{sup 2}/mrad{sup 2}/s/0.1% bandwidth, measured at 478 keV. Additional measurements of the flux as a function of the timing difference between the drive laser pulse and the relativistic photo-electron bunch, {gamma}-ray beam profile, and background evaluations are presented. These results are systematically compared to theoretical models and computer simulations. NRF measurements performed on {sup 7}Li in LiH demonstrate the potential of Compton scattering photon sources to accurately detect isotopes in situ.

  17. The expected high-energy to ultra-high-energy gamma-ray spectrum of the Crab Nebula

    NASA Technical Reports Server (NTRS)

    De Jager, O. C.; Harding, A. K.

    1992-01-01

    The inverse Compton scattering model for the unpulsed TeV emission from the Crab Nebula is reexamined using the magnetic field distribution derived from MHD flow models of the nebula. It is shown that the observed flux can be explained if the average nebular field is indeed about 0.0003, as is predicted by the spectral break between radio and optical. The brightness distribution of the TeV gamma-ray signal is expected to extend out to about 1.5 arcmin from the pulsar. The present estimates predict a steady flux of unpulsed ultrahigh-energy gamma-rays due to the inverse Compton scattering of soft photons by shock-accelerated electrons and/or positrons in the vicinity of the shock.

  18. Suzaku Observation of the Unidentified Very High Energy Gamma-Ray Source HESS J1702-420

    NASA Astrophysics Data System (ADS)

    Fujinaga, Takahisa; Bamba, Aya; Dotani, Tadayasu; Ozaki, Masanobu; Pü:Hlhofer, Gerd; Wagner, Stefan; Reimer, Olaf; Funk, Stefan; Hinton, Jim

    2011-11-01

    A deep X-ray observation of the unidentified very high energy (VHE) gamma-ray source HESS J1702-420, for the first time, was carried out by Suzaku. No bright sources were detected in the XIS field of view (FOV), except for two faint point-like sources. The two sources, however, are considered not to be related to HESS J1702-420, because their fluxes in the 2-10 keV band (˜10-14 erg s-1 cm-2) are ˜3 orders of magnitude smaller than the VHE gamma-ray flux in the 1-10 TeV band (FTeV = 3.1 × 10-11 erg s-1 cm-2). We compared the energy spectrum of diffuse emission, extracted from the entire XIS FOV with those from nearby observations. If we consider the systematic error of background subtraction, no significant diffuse emission was detected with an upper limit of FX < 2.7 × 10-12 erg s-1 cm-2 in the 2-10 keV band for an assumed power-law spectrum of Γ = 2.1 and a source size same as that in the VHE band. The upper limit of the X-ray flux is twelve-times as small as the VHE gamma-ray flux. The large flux ratio (FTeV/FX) indicates that HESS J1702-420 is another example of a ``dark'' particle accelerator. If we use a simple one-zone leptonic model, in which VHE gamma-rays are produced through inverse Compton scattering of the cosmic microwave background and interstellar far-infrared emission, and the X-rays via the synchrotron mechanism, an upper limit of the magnetic field (1.7μG), is obtained from the flux ratio. Because the magnetic field is weaker than the typical value in the galactic plane (3-10 νG), the simple one-zone model may not work for HESS J1702-420 and a significant fraction of the VHE gamma-rays may originate from protons.

  19. Observations of potential ultra high energy gamma-ray sources above 10(15) eV

    NASA Technical Reports Server (NTRS)

    Lambert, A.; Lloyd-Evans, J.; Perrett, J. C.; Watson, A. A.; West, A. A.

    1985-01-01

    The Haverah Park 50 m water-Cerenkov array has been used to examine a number of periodic sources for ultra high energy gamma-ray emission above 10 to the 15th power eV. The data, recorded between 1 Jan. 1979 and 31 Dec. 1984, feature a modest angular resolution of approx 3 deg with millisecond arrival time resolution post 1982. The sources investigated include the Crab pulsar, Her X-1, Au0115 + 63 and Geminga. All objects have been detected by workers in the TeV region, with varying degrees of confidence.

  20. Gamma-ray astronomy using a high pressure gas scintillation drift chamber with a waveshifting fiber readout

    NASA Technical Reports Server (NTRS)

    Wilkerson, J.; Edberg, T. K.; Parsons, A.; Sadoulet, B.; Weiss, S.; Smith, G.

    1992-01-01

    We describe a balloon-borne hard X-ray telescope called SIGHT (Scintillation Imaging Gas-filled Hard X-ray Telescope). SIGHT is a high sensitivity, good energy resolution instrument that images in the 30 to 300 keV region. We discuss the development of a large area, 20 atmosphere, position sensitive xenon gas scintillation drift chamber which is the gamma-ray detector at the heart of the telescope package. Results of the development of the novel waveshifting fiber readout for this chamber are presented.

  1. A high resolution gamma-ray and hard X-ray spectrometer (HIREGS) for long duration balloon flights

    NASA Technical Reports Server (NTRS)

    Pelling, M.; Feffer, P. T.; Hurley, K.; Kane, S. R.; Lin, R. P.; Mcbride, S.; Primbsch, J. H.; Smith, D. M.; Youseffi, K.; Zimmer, G.

    1992-01-01

    The elements of a high resolution gamma-ray spectrometer, developed for observations of solar flares, are described. Emphasis is given to those aspects of the system that relate to its operation on a long duration balloon platform. The performance of the system observed in its first flight, launched from McMurdo Station, Antarctica on 10 January, 1992, is discussed. Background characteristics of the antarctic balloon environment are compared with those observed in conventional mid-latitude balloon flights and the general advantages of long duration ballooning are discussed.

  2. High-energy emissions from the gamma-ray binary LS 5039

    SciTech Connect

    Takata, J.; Leung, Gene C. K.; Cheng, K. S.; Tam, P. H. T.; Kong, A. K. H.; Hui, C. Y. E-mail: gene930@connect.hku.hk

    2014-07-20

    We study mechanisms of multi-wavelength emissions (X-ray, GeV, and TeV gamma-rays) from the gamma-ray binary LS 5039. This paper is composed of two parts. In the first part, we report on results of observational analysis using 4 yr data of the Fermi Large Area Telescope. Due to the improvement of instrumental response function and increase of the statistics, the observational uncertainties of the spectrum in the ∼100-300 MeV bands and >10 GeV bands are significantly improved. The present data analysis suggests that the 0.1-100 GeV emissions from LS 5039 contain three different components: (1) the first component contributes to <1 GeV emissions around superior conjunction, (2) the second component dominates in the 1-10 GeV energy bands, and (3) the third component is compatible with the lower-energy tail of the TeV emissions. In the second part, we develop an emission model to explain the properties of the phase-resolved emissions in multi-wavelength observations. Assuming that LS 5039 includes a pulsar, we argue that emissions from both the magnetospheric outer gap and the inverse-Compton scattering process of cold-relativistic pulsar wind contribute to the observed GeV emissions. We assume that the pulsar is wrapped by two kinds of termination shock: Shock-I due to the interaction between the pulsar wind and the stellar wind and Shock-II due to the effect of the orbital motion. We propose that the X-rays are produced by the synchrotron radiation at the Shock-I region and the TeV gamma-rays are produced by the inverse-Compton scattering process at the Shock-II region.

  3. A new array for the study of ultra high energy gamma-ray sources

    NASA Technical Reports Server (NTRS)

    Brooke, G.; Lambert, A.; Ogden, P. A.; Patel, M.; Ferrett, J. C.; Reid, R. J. O.; Watson, A. A.; West, A. A.

    1985-01-01

    The design and operation of a 32 x 1 10 to the 15th power sq m array of scintillation detectors for the detection of 10 to the 15th power eV cosmic rays is described with an expected angular resolution of 1 deg, thus improving the present signal/background ratio for gamma ray sources. Data are recorded on a hybrid CAMAC, an in-house system which uses a laser and Pockel-Cell arrangement to routinely calibrate the timing stability of the detectors.

  4. COS-B observations of the high-energy gamma radiation from the galactic disk

    NASA Technical Reports Server (NTRS)

    1977-01-01

    The COS-B experiment has observed approximately one-fourth of the galactic disk, including the galactic-center region, the galactic anticenter, and the Vela region. A completely automatic analysis of the events recorded during these observations reveals a galactic gamma ray emission from the three regions. In the galactic center and Vela regions, the disk emission distribution was measured. From these data, the existence of a local (less than 1 kpc) and a distant (greater than 3 kpc) emitting region is apparent in the general direction of the inner galaxy.

  5. Pulsed high-energy gamma-radiation from Geminga (1E0630 + 178)

    NASA Technical Reports Server (NTRS)

    Bertsch, D. L.; Brazier, K. T. S.; Fichtel, C. E.; Hartman, R. C.; Hunter, S. D.; Kanbach, G.; Kniffen, D. A.; Kwok, P. W.; Lin, Y. C.; Mattox, J. R.

    1992-01-01

    The detection of pulsed gamma rays with energy above 50 MeV from the soft X-ray source 1E0630 + 178 is reported, confirming the identification of Geminga with this X-ray source. The period derivative (11.4 +/- 1.7) x 10 exp -15 s/s suggests that Geminga is a nearby isolated rotating neutron star with a magnetic field of 1.6 x 10 exp 12 gauss, a characteristic age of 300,000 yr, and a spin-down energy loss rate of 3.5 x 10 exp 34 erg/s.

  6. Detecting special nuclear materials in containers using high-energy gamma rays emitted by fission products

    DOEpatents

    Norman, Eric B.; Prussin, Stanley G.

    2007-10-02

    A method and a system for detecting the presence of special nuclear materials in a container. The system and its method include irradiating the container with an energetic beam, so as to induce a fission in the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

  7. New room temperature high resolution solid-state detector (CdZnTe) for hard x rays and gamma rays

    NASA Technical Reports Server (NTRS)

    Stewart, Amyelizabeth C.; Desai, Upendra D.

    1993-01-01

    The new CdZnTe high 'Z' material represents a significant improvement in detectors for high energy photons. With the thicknesses available, photons up to 100 keV can be efficiently detected. This material has a wide band gap of 1.5 - 2.2 eV which allows it to operate at room temperature while providing high spectral resolution. Results of resolution evaluations are presented. This detector can be used for high resolution spectral measurements of photons in x-ray and gamma-ray astronomy, offering a significant reduction in the weight, power, and volume of the detector system compared to more conventional detector types such as scintillation counters. In addition, the detector will have the simplicity and reliability of solid-state construction. The CdZnTe detector, as a new development, has not yet been evaluated in space. The Get Away Special program can provide this opportunity.

  8. Magnetic Microcalorimeter Gamma Detectors for High-Precision Non-Destructive Analysis, FY14 Extended Annual Report

    SciTech Connect

    Friedrich, S.

    2015-02-06

    Cryogenic gamma (γ) detectors with operating temperatures of ~0.1 K or below offer 10× better energy resolution than conventional high-purity germanium detectors that are currently used for non-destructive analysis (NDA) of nuclear materials. This can greatly increase the accuracy of NDA, especially at low-energies where gamma rays often have similar energies and cannot be resolved by Ge detectors. We are developing cryogenic γ–detectors based on metallic magnetic calorimeters (MMCs), which have the potential of higher resolution, faster count rates and better linearity than other cryogenic detector technologies. High linearity is essential to add spectra from different pixels in detector arrays that are needed for high sensitivity. Here we discuss the fabrication of a new generation of MMC γ–detectors in FY2014, and the resulting improvements in energy resolution and linearity of the new design. As an example of the type of NDA that cryogenic detectors enable, we demonstrate the direct detection of Pu-242 emissions with our MMC γ–detectors in the presence of Pu-240, and show that a quantitative NDA analysis agrees with the mass spectrometry

  9. The 2010 Very High Energy Gamma-Ray Flare and 10 Years of Multi-Wavelength Observations of M87

    NASA Technical Reports Server (NTRS)

    Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A G.; Anton, G.; Balzer, A.; Barnacka, A.; Barres de Almeida, U.; Becherini, Y.; Becker, J.; Behera, B.; Bernlohr, K.; Birsin, E.; Biteau, J.; Bochow, A.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, P.; Brun, P.; Bulik, T.; Busching, I.; Perkins, J. S.; McConville, W.

    2011-01-01

    The giant radio galaxy M87 with its proximity (16 Mpc), famous jet, and very massive black hole ((3-6) X 10(exp 9) Solar Mass) provides a unique opportunity to investigate the origin of very high energy (VHE; E>100 GeV) gamma-ray emission generated in relativistic outflows and the surroundings of super-massive black holes. M87 has been established as a VHE gamma -ray emitter since 2006. The VHE gamma -ray emission displays strong variability on timescales as short as a day. In this paper, results from a joint VHE monitoring campaign on M87 by the MAGIC and VERITAS instruments in 2010 are reported. During the campaign, a flare at VHE was detected. triggering further observations at VHE (H.E.S.S.), X-rays (Chandra), and radio (43 GHz VLBA). The excellent sampling of the VHE gamma-ray light curve enables one to derive a precise temporal characterization of the flare: the single, isolated flare is well described by a two-sided exponential function with significantly different flux rise and decay times of rise tau ((sup rise sub d) = (1:69 +/- 0:30) days and tau(sup decay sub d = (0:611 +/- 0:080) days, respectively. While the overall variability pattern of the 2010 flare appears somewhat different from that of previous VHE flares in 2005 and 2008, they share very similar timescales (approx day), peak fluxes (Phi (sub > 0:35 TeV) approx. equals (1 - 3) X 10(exp -11) ph / square cm/s), and VHE spectra. 43 GHz VLBA radio observations of the inner jet regions indicate no enhanced flux in 2010 in contrast to observations in 2008, where an increase of the radio flux of the innermost core regions coincided with a VHE flare. On the other hand, Chandra X-ray observations taken approx 3 days after the peak of the VHE gamma -ray emission reveal an enhanced flux from the core (flux increased by factor approx 2; variability timescale < 2 days). The long-term (2001-2010) multi-wavelength (MWL) light curve of M87, spanning from radio to VHE and including data from HST, LT, VLA and

  10. THE 2010 VERY HIGH ENERGY {gamma}-RAY FLARE AND 10 YEARS OF MULTI-WAVELENGTH OBSERVATIONS OF M 87

    SciTech Connect

    Abramowski, A.; Acero, F.; Akhperjanian, A. G.; Anton, G.; Balzer, A.; Barnacka, A.; Barres de Almeida, U.; Becherini, Y.; Becker, J.; Behera, B.; Birsin, E.; Biteau, J.; Bolmont, J.; Collaboration: H.E.S.S. Collaboration; MAGIC Collaboration; VERITAS Collaboration; and others

    2012-02-20

    The giant radio galaxy M 87 with its proximity (16 Mpc), famous jet, and very massive black hole ((3 - 6) Multiplication-Sign 10{sup 9} M{sub Sun }) provides a unique opportunity to investigate the origin of very high energy (VHE; E > 100 GeV) {gamma}-ray emission generated in relativistic outflows and the surroundings of supermassive black holes. M 87 has been established as a VHE {gamma}-ray emitter since 2006. The VHE {gamma}-ray emission displays strong variability on timescales as short as a day. In this paper, results from a joint VHE monitoring campaign on M 87 by the MAGIC and VERITAS instruments in 2010 are reported. During the campaign, a flare at VHE was detected triggering further observations at VHE (H.E.S.S.), X-rays (Chandra), and radio (43 GHz Very Long Baseline Array, VLBA). The excellent sampling of the VHE {gamma}-ray light curve enables one to derive a precise temporal characterization of the flare: the single, isolated flare is well described by a two-sided exponential function with significantly different flux rise and decay times of {tau}{sup rise}{sub d} = (1.69 {+-} 0.30) days and {tau}{sup decay}{sub d} = (0.611 {+-} 0.080) days, respectively. While the overall variability pattern of the 2010 flare appears somewhat different from that of previous VHE flares in 2005 and 2008, they share very similar timescales ({approx}day), peak fluxes ({Phi}{sub >0.35TeV} {approx_equal} (1-3) Multiplication-Sign 10{sup -11} photons cm{sup -2} s{sup -1}), and VHE spectra. VLBA radio observations of 43 GHz of the inner jet regions indicate no enhanced flux in 2010 in contrast to observations in 2008, where an increase of the radio flux of the innermost core regions coincided with a VHE flare. On the other hand, Chandra X-ray observations taken {approx}3 days after the peak of the VHE {gamma}-ray emission reveal an enhanced flux from the core (flux increased by factor {approx}2; variability timescale <2 days). The long-term (2001-2010) multi-wavelength (MWL

  11. Mechanism of action for anti-radiation vaccine in reducing the biological impact of high-dose gamma irradiation

    NASA Astrophysics Data System (ADS)

    Maliev, Vladislav; Popov, Dmitri; Jones, Jeffrey A.; Casey, Rachael C.

    Ionizing radiation is a major health risk of long-term space travel, the biological consequences of which include genetic and oxidative damage. In this study, we propose an original mechanism by which high doses of ionizing radiation induce acute toxicity. We identified biological components that appear in the lymphatic vessels shortly after high-dose gamma irradiation. These radiation-induced toxins, which we have named specific radiation determinants (SRD), were generated in the irradiated tissues and then circulated throughout the body via the lymph circulation and bloodstream. Depending on the type of SRD elicited, different syndromes of acute radiation sickness (ARS) were expressed. The SRDs were developed into a vaccine used to confer active immunity against acute radiation toxicity in immunologically naïve animals. Animals that were pretreated with SRDs exhibited resistance to lethal doses of gamma radiation, as measured by increased survival times and survival rates. In comparison, untreated animals that were exposed to similar large doses of gamma radiation developed acute radiation sickness and died within days. This phenomenon was observed in a number of mammalian species. Initial analysis of the biochemical characteristics indicated that the SRDs were large molecular weight (200-250 kDa) molecules that were comprised of a mixture of protein, lipid, carbohydrate, and mineral. Further analysis is required to further identify the SRD molecules and the biological mechanism by which they mediate the toxicity associated with acute radiation sickness. By doing so, we may develop an effective specific immunoprophylaxis as a countermeasure against the acute effects of ionizing radiation.

  12. Assay for uranium and determination of disequilibrium by means of in situ high resolution gamma-ray spectrometry

    USGS Publications Warehouse

    Tanner, Allan B.; Moxham, Robert M.; Senftle, F.E.

    1977-01-01

    Two sealed sondes, using germanium gamma-ray detectors cooled by melting propane, have been field tested to depths of 79 m in water-filled boreholes at the Pawnee Uranium Mine in Bee Co., Texas. When, used as total-count devices, the sondes are comparable in logging speed and counting rate with conventional scintillation detectors for locating zones of high radioactivity. When used with a multichannel analyzer, the sondes are detectors with such high resolution that individual lines from the complex spectra of the uranium and thorium series can be distinguished. Gamma rays from each group of the uranium series can be measured in ore zones permitting determination of the state of equilibrium at each measurement point. Series of 10-minute spectra taken at 0.3- to 0.5-m intervals in several holes showed zones where maxima from the uranium group and from the 222Rn group were displaced relative to each other. Apparent excesses of 230Th at some locations suggest that uranium-group concentrations at those locations were severalfold greater some tens of kiloyears, ago. At the current state of development a 10-minute count yields a sensitivity of about 80 ppm U308. Data reduction could in practice be accomplished in about 5 minutes. The result is practically unaffected by disequilibrium or radon contamination. In comparison with core assay, high-resolution spectrometry samples a larger volume; avoids problems due to incomplete core recovery, loss of friable material to drilling fluids, and errors in depth and marking; and permits use of less expensive drilling methods. Because gamma rays from the radionuclides are accumulated simultaneously, it also avoids the problems inherent in trying to correlate logs made in separate runs with different equipment. Continuous-motion delayed-gamma activation by a 163-?g 252Cf neutron source attached to the sonde yielded poor sensitivity. A better neutron-activation method, in which the sonde is moved in steps so as to place the detector

  13. Recent progress of MPPC-based scintillation detectors in high precision X-ray and gamma-ray imaging

    NASA Astrophysics Data System (ADS)

    Kataoka, J.; Kishimoto, A.; Fujita, T.; Nishiyama, T.; Kurei, Y.; Tsujikawa, T.; Oshima, T.; Taya, T.; Iwamoto, Y.; Ogata, H.; Okochi, H.; Ohsuka, S.; Ikeda, H.; Yamamoto, S.

    2015-06-01

    The multi-pixel photon counter (MPPC) is a promising light sensor for various applications, not only in physics experiments but also in nuclear medicine, industry, and even high-energy astrophysics. In this paper, we present the current status and most recent progress of the MPPC-based scintillation detectors, such as (1) a high-precision X-ray and gamma-ray spectral image sensor, (2) next-generation PET detectors with MRI, TOF, and DOI measurement capabilities, and (3) a compact gamma camera for environmental radiation surveys. We first present a new method of fabricating a Ce:GAGG scintillator plate (1 or 2 mm thick) with ultra-fine resolution (0.2 mm/pixel), cut using a dicing saw to create 50 μm wide micro-grooves. When the plate is optically coupled with a large-area MPPC array, excellent spatial resolution of 0.48 mm (FWHM) and energy resolution of 14% (FWHM) are obtained for 122 keV gamma rays. Hence, the detector can act as a convenient "multi-color" imaging device that can potentially be used for future SPECT and photon-counting CT. We then show a prototype system for a high-resolution MPPC-based PET scanner that can realize ≃1 mm (FWHM) spatial resolution, even under a strong magnetic field of 4.7 T. We develop a front-end ASIC intended for future TOF-PET scanner with a 16-channel readout that achieves a coincidence time resolution of 489 ps (FWHM). A novel design for a module with DOI-measurement capability for gamma rays is also presented by measuring the pulse height ratio of double-sided MPPCs coupled at both ends of scintillation crystal block. Finally, we present the concept of a two-plane Compton camera consisting of Ce:GAGG scintillator arrays coupled with thin MPPC arrays. As a result of the thin and compact features of the MPPC device, the camera not only achieves a small size (14×14×15 cm3) and light weight (1.9 kg) but also excellent sensitivity, compared to the conventional PMT-based pinhole camera used in Fukushima. Finally, we briefly

  14. Very high energy gamma ray astrophysics. Technical progress report, May 1, 1992--April 30, 1993

    SciTech Connect

    Lamb, R C; Lewis, D A

    1993-02-01

    The Crab-Nebula continues to be the standard candle'' of TeV gamma-ray astronomy. The Whipple Collaboration's observations of it are now confirmed by two French groups. Application of the supercuts'' technique, developed on the Crab database, has resulted in the observation of a distant, active galaxy, Markarian 421. Markarian 421 is one of 16 active galactic nuclei (AGN's) observed by the EGRET instrument on the Compton Gamma Ray Observatory. The EGRET observations and the expected attenuation of TeV photons from very distant AGN's gives added impetus to efforts in upgrading the present steoscopic detection system. The upgrade not only improves the sensitivity of the twin telescopes, but also reduces the energy threshold to 100 GeV, at which energy attenuation effects for distant sources are greatly reduced. During the past year the llm reflector was operated as a 37-pixel camera, with its performance matching design expectations. During the coming year, its camera will be upgraded to 109 pixels, the 10m camera electronics made to conform to the llm electronics, and both systems interfaced to a single, faster computer. Observations of Markarian 421, simultaneous with EGRET, are scheduled for May, 1993.

  15. Timing the Geminga Pulsar with High-Energy Gamma-Rays

    NASA Technical Reports Server (NTRS)

    Halpern, Jules P.

    1997-01-01

    This is a continuing program to extend and refine the ephemeris of the Geminga pulsar with annual observations for the remaining lifetime of EGRET. The data show that every revolution of Geminga is accounted for during the EGRET epoch, and that a coherent timing solution linking the phase between EGRET, COS-B, amd SAS-2, observations has now been achieved. The accuracy of the gamma-ray timing is such that the proper motion of the pulsar can now be detected, consistent with the optical determination. The measured braking index over the 24.2 yr baseline is 17 +/- 1. Further observation is required to ascertain whether this very large braking index truly represents the energy loss mechanism, perhaps related to the theory in which Geminga is near its gamma-ray death line, or whether it is a manifestation of timing noise. Statistically significant timing residuals are detected in the EGRET data; they depart from the cubic ephemeris at a level of 23 milliperiods. The residuals appear to have a sinusoidal modulation with a period of about 5.1 yr. This could simply be a manifestation of timing noise, or it could be consistent with a planet of mass 1.7/sin i solar mass orbiting Geminga at a radius of 3.3/sin i AU.

  16. A Search for High-Energy Neutrino Emission from Gamma-Ray Bursts

    NASA Astrophysics Data System (ADS)

    Whitehorn, Nathan

    2012-05-01

    A century after their discovery, the origin of cosmic rays remains one of the most enduring mysteries in physics. They can have energies that exceed 1020 eV, a hundred million times as energetic as the most powerful Earth-bound particle accelerators and must therefore be produced in the universe's most violent environments. Direct observation of their origins, however, has proven difficult due to deflection of charged cosmic ray particles in galactic and intergalactic magnetic fields, obscuring their true origins. Astronomy using electrically neutral particles, such as photons and neutrinos, does not, however, share this difficulty. This work presents a search for neutrino emission from one of the primary candidates for the sources of the highest-energy cosmic rays, Gamma-Ray Bursts, using the recently-completed IceCube neutrino telescope located at the South Pole. The null result obtained from this search contradicts well-established predictions for the neutrino flux from Gamma-Ray Bursts if they are the cosmic ray sources, forcing a reevaluation of these theoretical models.

  17. A high resolution gamma-ray spectrometer based on superconducting microcalorimeters.

    PubMed

    Bennett, D A; Horansky, R D; Schmidt, D R; Hoover, A S; Winkler, R; Alpert, B K; Beall, J A; Doriese, W B; Fowler, J W; Fitzgerald, C P; Hilton, G C; Irwin, K D; Kotsubo, V; Mates, J A B; O'Neil, G C; Rabin, M W; Reintsema, C D; Schima, F J; Swetz, D S; Vale, L R; Ullom, J N

    2012-09-01

    Improvements in superconductor device fabrication, detector hybridization techniques, and superconducting quantum interference device readout have made square-centimeter-sized arrays of gamma-ray microcalorimeters, based on transition-edge sensors (TESs), possible. At these collecting areas, gamma microcalorimeters can utilize their unprecedented energy resolution to perform spectroscopy in a number of applications that are limited by closely-spaced spectral peaks, for example, the nondestructive analysis of nuclear materials. We have built a 256 pixel spectrometer with an average full-width-at-half-maximum energy resolution of 53 eV at 97 keV, a useable dynamic range above 400 keV, and a collecting area of 5 cm(2). We have demonstrated multiplexed readout of the full 256 pixel array with 236 of the pixels (91%) giving spectroscopic data. This is the largest multiplexed array of TES microcalorimeters to date. This paper will review the spectrometer, highlighting the instrument design, detector fabrication, readout, operation of the instrument, and data processing. Further, we describe the characterization and performance of the newest 256 pixel array.

  18. A high resolution gamma-ray spectrometer based on superconducting microcalorimeters

    SciTech Connect

    Bennett, D. A.; Horansky, R. D.; Schmidt, D. R.; Doriese, W. B.; Fowler, J. W.; Kotsubo, V.; Mates, J. A. B.; Hoover, A. S.; Winkler, R.; Rabin, M. W.; Alpert, B. K.; Beall, J. A.; Fitzgerald, C. P.; Hilton, G. C.; Irwin, K. D.; O'Neil, G. C.; Reintsema, C. D.; Schima, F. J.; Swetz, D. S.; Vale, L. R.; and others

    2012-09-15

    Improvements in superconductor device fabrication, detector hybridization techniques, and superconducting quantum interference device readout have made square-centimeter-sized arrays of gamma-ray microcalorimeters, based on transition-edge sensors (TESs), possible. At these collecting areas, gamma microcalorimeters can utilize their unprecedented energy resolution to perform spectroscopy in a number of applications that are limited by closely-spaced spectral peaks, for example, the nondestructive analysis of nuclear materials. We have built a 256 pixel spectrometer with an average full-width-at-half-maximum energy resolution of 53 eV at 97 keV, a useable dynamic range above 400 keV, and a collecting area of 5 cm{sup 2}. We have demonstrated multiplexed readout of the full 256 pixel array with 236 of the pixels (91%) giving spectroscopic data. This is the largest multiplexed array of TES microcalorimeters to date. This paper will review the spectrometer, highlighting the instrument design, detector fabrication, readout, operation of the instrument, and data processing. Further, we describe the characterization and performance of the newest 256 pixel array.

  19. Applications Using High Flux LCS gamma-ray Beams: Nuclear Security and Contributions to Fukushima

    NASA Astrophysics Data System (ADS)

    Fujiwara, Mamoru

    2014-09-01

    Nuclear nonproliferation and security are an important issue for the peaceful use of nuclear energy. Many countries now collaborate together for preventing serious accidents from nuclear terrorism. Detection of hidden long-lived radioisotopes and fissionable nuclides in a non-destructive manner is useful for nuclear safeguards and management of nuclear wastes as well as nuclear security. After introducing the present situation concerning the nuclear nonproliferation and security in Japan, we plan to show the present activities of JAEA to detect the hidden nuclear materials by means of the nuclear resonance fluorescence with energy-tunable, monochromatic gamma-rays generated by Laser Compton Scattering (LCS) with an electron beam. The energy recovery linac (ERL) machine is now under development with the KEK-JAEA collaboration for realizing the new generation of gamma-ray sources. The detection technologies of nuclear materials are currently developed using the existing electron beam facilities at Duke University and at NewSubaru. These developments in Japan will contribute to the nuclear security program in Japan and to the assay of melted nuclear fuels in the Fukushima Daiichi nuclear power plants.

  20. Can gamma ray bursts be used as effective tracers of star formation to high Z?

    NASA Astrophysics Data System (ADS)

    Beckman, John; Giammanco, Corrado

    Long duration gamma ray bursts (GRB's) have been identified as originating in type II SNa explosions, produced during the late stage evolution of massive stars. As the lifetimes of their progenitors are so short the GRB rate per unit (comoving) volume of space, on scales which include significant numbers of galaxies, could be proportional to the star formation rate (SFR), at least to the formation rate of massive stars. Unfortunately both theory and observation imply that those SNe which give rise to gamma ray bursts occur in stars of low metallicity, less than half an order of magnitude lower than solar. Here we examine the evidence and show that although some workers believe that it is possible to use local galaxies with GRB's to calibrate the SFR in more distant galaxies others claim that this may be possible given independent ways of determining the metallicities of the distant galaxies, while others suggest that it is too difficult, at least with present measurements, to use GRB's to determine the SFR at values of redshift higher than 5. We conclude that although their intrinsic power gives GRB's the facility to guide observers towards star forming galaxies, only by also using complementary indicators will we be able to make plausible determinations of the SFR as a function of epoch beyond z = 5, i.e. during the first 2 Gyr after the Big Bang.

  1. Fermi LAT detection of a new high-energy transient gamma-ray source Fermi J0751-5136

    NASA Astrophysics Data System (ADS)

    Kocevski, D.; Buson, S.

    2016-08-01

    During the week from 18 July through 25 July, 2016, the Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, observed gamma-ray activity from a previously unidentified transient source.

  2. Circulating gamma delta T cells are activated and depleted during progression of high-grade gliomas: Implications for gamma delta T cell therapy of GBM

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Glioblastoma multiforme (GBM) remains frustratingly impervious to any existing therapy. We have previously shown that GBM is sensitive to recognition and lysis by ex vivo activated gamma delta T cells, a minor subset of lymphocytes that innately recognize autologous stress-associated target antigens...

  3. Suitable gamma energy for gamma-spectrometric determination of (238)U in surface soil samples of a high rainfall area in India.

    PubMed

    Lenka, P; Jha, S K; Gothankar, S; Tripathi, R M; Puranik, V D

    2009-06-01

    The paper presents a systematic study on suitability of various gamma lines for monitoring of (238)U activity in soil samples around a uranium mineralized zone of Kylleng Pyndengsohiong Mawthabah (Domiasiat), Meghalaya in India. The area lies in a plateau region which recieves the highest average annual rainfall (12,000mm) in the world. The geochemical behaviour of the uranium and its daughter products at such wet climatic conditions imposes restrictions to assess (238)U through gamma lines of radon decay products. Soil samples were collected from nine locations around the uranium mineralization zone for analysis. The ratio of the concentration of uranium obtained from gamma energies of radium daughter products to the 63.29keV of (234)Th was found to vary from 1.01 to 2.07, which indicates a pronounced disequilibrium between uranium and radium daughters. The results obtained from various gamma energies were validated from the data generated by Instrumental Neutron Activation Analysis (INAA) technique. The (238)U activities from the two analytical methods show a well fitted regression line with correlation coefficient 0.99 which validates the reliability of 63.29keV energy for estimation of uranium in such conditions. PMID:19375833

  4. Simultaneous measurements of indoor radon, radon-thoron progeny and high-resolution gamma spectrometry in Greek dwellings.

    PubMed

    Clouvas, A; Xanthos, S; Antonopoulos-Domis, M

    2006-01-01

    Simultaneous indoor radon, radon-thoron progeny and high-resolution in situ gamma spectrometry measurements, with portable high-purity Ge detector were performed in 26 dwellings of Thessaloniki, the second largest town of Greece, during March 2003-January 2005. The radon gas was measured with an AlphaGUARD ionisation chamber (in each of the 26 dwellings) every 10 min, for a time period between 7 and 10 d. Most of the values of radon gas concentration are between 20 and 30 Bq m(-3), with an arithmetic mean of 34 Bq m(-3). The maximum measured value of radon gas concentration is 516 Bq m(-3). The comparison between the radon gas measurements, performed with AlphaGUARD and short-term electret ionisation chamber, shows very good agreement, taking into account the relative short time period of the measurement and the relative low radon gas concentration. Radon and thoron progeny were measured with a SILENA (model 4s) instrument. From the radon and radon progeny measurements, the equilibrium factor F could be deduced. Most of the measurements of the equilibrium factor are within the range 0.4-0.5. The mean value of the equilibrium factor F is 0.49 +/- 0.10, i.e. close to the typical value of 0.4 adopted by UNSCEAR. The mean equilibrium equivalent thoron concentration measured in the 26 dwellings is EEC(thoron) = 1.38 +/- 0.79 Bq m(-3). The mean equilibrium equivalent thoron to radon ratio concentration, measured in the 26 dwellings, is 0.1 +/- 0.06. The mean total absorbed dose rate in air, owing to gamma radiation, is 58 +/- 12 nGy h(-1). The contribution of the different radionuclides to the total indoor gamma dose rate in air is 38% due to 40K, 36% due to thorium series and 26% due to uranium series. The annual effective dose, due to the different source terms (radon, thoron and external gamma radiation), is 1.05, 0.39 and 0.28 mSv, respectively. PMID:16410290

  5. High-power laser-driven source of ultra-short X-ray and gamma-ray pulses

    NASA Astrophysics Data System (ADS)

    Esirkepov, T. Zh.; Bulanov, S. V.; Zhidkov, A. G.; Pirozhkov, A. S.; Kando, M.

    2009-11-01

    A novel ultra-bright high-intensity source of X-ray and gamma radiation is suggested. It is based on the double Doppler effect, where a relativistic flying mirror reflects a counter-propagating electromagnetic radiation causing its frequency multiplication and intensification, and on the inverse double Doppler effect, where the mirror acquires energy from an ultra-intense co-propagating electromagnetic wave. The role of the flying mirror is played by a high-density thin plasma slab accelerating in the radiation pressure dominant regime. Frequencies of high harmonics generated at the flying mirror by a relativistically strong counter-propagating radiation udergo multiplication with the same factor as the fundamental frequency of the reflected radiation, approximately equal to the quadruple of the square of the mirror Lorentz factor.

  6. High IFN-gamma production of individual CD8 T lymphocytes is controlled by CD152 (CTLA-4).

    PubMed

    Pandiyan, Pushpa; Hegel, J Kolja E; Krueger, Manuela; Quandt, Dagmar; Brunner-Weinzierl, Monika C

    2007-02-15

    CD8 T cell expansion and cytokine production is needed to generate an effective defense against viral invasion of the host. These features of CD8 T lymphocytes are regulated, especially during primary responses, by positive and negative costimulation. We show in this study that surface expression of CD152 is highly up-regulated on activated CD8 T lymphocytes during primary immune responses, suggesting a prominent regulatory role. Indeed, production of the proinflammatory cytokine IFN-gamma, but not TNF-alpha, by CD8 T cells was inhibited by CD152 engagement. The inhibition was regulated independent of proliferation and IL-2 production, but dependent on the quality of the TCR signaling. We show that signals induced by CD152 on activated CD8 T lymphocytes reduce the frequency of IFN-gamma(high)-expressing cells. Our data also show that in activated CD8 T cells, the CD152-mediated inhibition of cytokine production is more pronounced than inhibition of their proliferation.

  7. DISCOVERY OF VARIABILITY IN THE VERY HIGH ENERGY {gamma}-RAY EMISSION OF 1ES 1218+304 WITH VERITAS

    SciTech Connect

    Acciari, V. A.; Benbow, W.; Aliu, E.; Beilicke, M.; Bugaev, V.; Dickherber, R.; Boltuch, D.; Boettcher, M.; Bradbury, S. M.; Byrum, K.; Cesarini, A.; Ciupik, L.; Fortson, L.; Cogan, P.; Cui, W.; Finley, J. P.; Duke, C.; Falcone, A.; Finnegan, G.; Furniss, A.

    2010-02-01

    We present results from an intensive VERITAS monitoring campaign of the high-frequency peaked BL Lac object 1ES 1218+304 in 2008/2009. Although 1ES 1218+304 was detected previously by MAGIC and VERITAS at a persistent level of {approx}6% of the Crab Nebula flux, the new VERITAS data reveal a prominent flare reaching {approx}20% of the Crab. While very high energy (VHE) flares are quite common in many nearby blazars, the case of 1ES 1218+304 (redshift z = 0.182) is particularly interesting since it belongs to a group of blazars that exhibit unusually hard VHE spectra considering their redshifts. When correcting the measured spectra for absorption by the extragalactic background light, 1ES 1218+304 and a number of other blazars are found to have differential photon indices {gamma}{<=} 1.5. The difficulty in modeling these hard spectral energy distributions in blazar jets has led to a range of theoretical {gamma}-ray emission scenarios, one of which is strongly constrained by these new VERITAS observations. We consider the implications of the observed light curve of 1ES 1218+304, which shows day scale flux variations, for shock acceleration scenarios in relativistic jets, and in particular for the viability of kiloparsec-scale jet emission scenarios.

  8. DISCOVERY OF VERY HIGH ENERGY GAMMA RAYS FROM PKS 1424+240 AND MULTIWAVELENGTH CONSTRAINTS ON ITS REDSHIFT

    SciTech Connect

    Acciari, V. A.; Benbow, W.; Aliu, E.; Boltuch, D.; Arlen, T.; Chow, Y. C.; Aune, T.; Bautista, M.; Cogan, P.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Boettcher, M.; Bradbury, S. M.; Byrum, K.; Cannon, A.; Cesarini, A.; Ciupik, L.; Cui, W.; Duke, C. E-mail: amy.furniss@gmail.com

    2010-01-10

    We report the first detection of very high energy{sup 83}Gamma-ray emission above 100 GeV. (VHE) gamma-ray emission above 140 GeV from PKS 1424+240, a BL Lac object with an unknown redshift. The photon spectrum above 140 GeV measured by VERITAS is well described by a power law with a photon index of 3.8 {+-} 0.5{sub stat} {+-} 0.3{sub syst} and a flux normalization at 200 GeV of (5.1 {+-} 0.9{sub stat} {+-} 0.5{sub syst}) x 10{sup -11} TeV{sup -1} cm{sup -2} s{sup -1}, where stat and syst denote the statistical and systematical uncertainties, respectively. The VHE flux is steady over the observation period between MJD 54881 and 55003 (from 2009 February 19 to June 21). Flux variability is also not observed in contemporaneous high-energy observations with the Fermi Large Area Telescope. Contemporaneous X-ray and optical data were also obtained from the Swift XRT and MDM observatory, respectively. The broadband spectral energy distribution is well described by a one-zone synchrotron self-Compton model favoring a redshift of less than 0.1. Using the photon index measured with Fermi in combination with recent extragalactic background light absorption models it can be concluded from the VERITAS data that the redshift of PKS 1424+240 is less than 0.66.

  9. Observations of AGN at very-high energy gamma rays with the H.E.S.S. telescopes

    NASA Astrophysics Data System (ADS)

    Wagner, Robert

    2016-08-01

    At the high-energy end of their electromagnetic spectra, the emission of AGNs is based on non-thermal particle acceleration processes. Ground-based Imaging Atmospheric Cherenkov Telescopes, like the H.E.S.S. array of gamma-ray telescopes, offer excellent sensitivity at E>100 GeV, a superb time resolution, and in combination with multi-wavelength instruments, represent powerful tools for investigating the particle accelerators within AGN. In the past decade, non-thermal emission from relativistic jets in numerous blazars and radio galaxies could be investigated. The gamma-rays are likely due to Compton scattering of lower energy photons, either from within the jet or from the surrounding gas. The physical properties of the jet and the way in which it is produced are still largely a unknown, but are probably related in some way to accretion onto a central supermassive black hole. In the presentation, we will discuss H.E.S.S. results of observations of AGN, both highlighting substantial new lessons learned at the high energy end of the electromagnetic spectrum and in multi wavelength contexts.

  10. Nano {gamma}'/{gamma}'' composite precipitates in Alloy 718

    SciTech Connect

    Phillips, P. J.; McAllister, D.; Gao, Y.; Lv, D.; Williams, R. E. A.; Wang, Y.; Mills, M. J.; Peterson, B.

    2012-05-21

    Nanoscale composite precipitates of Alloy 718 have been investigated with both high-resolution scanning transmission electron microscopy and phase field modeling. Chemical analysis via energy-dispersive x-ray spectroscopy allowed for the differentiation of {gamma}' and {gamma}'' particles, which is not otherwise possible through traditional Z-contrast methods. Phase field modeling was applied to determine the stress distribution and elastic interaction around and between the particles, respectively, and it was determined that a composite particle (of both {gamma}' and {gamma}'') has an elastic energy that is significantly lower than, for example, single {gamma}' and {gamma}'' precipitates which are non-interacting.

  11. Mechanism of Action for Anti-radiation Vaccine in Reducing the Biological Impact of High-dose Gamma Irradiation

    NASA Technical Reports Server (NTRS)

    Maliev, Vladislav; Popov, Dmitri; Jones, Jeffrey A.; Casey, Rachael C.

    2007-01-01

    Ionizing radiation is a major health risk of long-term space travel, the biological consequences of which include genetic and oxidative damage. In this study, we propose an original mechanism by which high doses of ionizing radiation induce acute toxicity. We identified biological components that appear in the lymphatic vessels shortly after gamma irradiation. These radiation-induced toxins, which we have named specific radiation determinants (SRD), were generated in the irradiated tissues and then collected and circulated throughout the body via the lymph circulation and bloodstream. Depending on the type of SRD elicited, different syndromes of acute radiation sickness (ARS) were expressed. The SRDs were developed into a vaccine used to confer active immunity against acute radiation toxicity in immunologically naive animals. Animals that were pretreated with SRDs exhibited resistance to lethal doses of gamma radiation, as measured by increased survival times and survival rates. In comparison, untreated animals that were exposed to similar large doses of gamma radiation developed acute radiation sickness and died within days. This phenomenon was observed in a number of mammalian species. Initial analysis of the biochemical characteristics indicated that the SRDs were large molecular weight (200-250 kDa) molecules that were comprised of a mixture of protein, lipid, carbohydrate, and mineral. Further analysis is required to further identify the SRD molecules and the biological mechanism by which the mediate the toxicity associated with acute radiation sickness. By doing so, we may develop an effective specific immunoprophylaxis as a countermeasure against the acute effects of ionizing radiation.

  12. Cesium hafnium chloride: A high light yield, non-hygroscopic cubic crystal scintillator for gamma spectroscopy

    SciTech Connect

    Burger, Arnold; Rowe, Emmanuel; Groza, Michael; Morales Figueroa, Kristle; Cherepy, Nerine J.; Beck, Patrick R.; Hunter, Steven; Payne, Stephen A.

    2015-10-05

    We report on the scintillation properties of Cs{sub 2}HfCl{sub 6} (cesium hafnium chloride or CHC) as an example of a little-known class of non-hygroscopic compounds having the generic cubic crystal structure of K{sub 2}PtCl{sub 6}. The crystals are easily growable from the melt using the Bridgman method with minimal precursor treatments or purification. CHC scintillation is centered at 400 nm, with a principal decay time of 4.37 μs and a light yield of up to 54 000 photons/MeV when measured using a silicon CCD photodetector. The light yield is the highest ever reported for an undoped crystal, and CHC also exhibits excellent light yield nonproportionality. These desirable properties allowed us to build and test CHC gamma-ray spectrometers providing energy resolution of 3.3% at 662 keV.

  13. Development of a High Resolution Liquid Xenon Imaging Telescope for Medium Energy Gamma Ray Astrophysics

    NASA Technical Reports Server (NTRS)

    Aprile, Elena

    1992-01-01

    In the third year of the research project, we have (1) tested a 3.5 liter prototype of the Liquid Xenon Time Projection Chamber, (2) used a prototype having a 4.4 cm drift gap to study the charge and energy resolution response of the 3.5 liter chamber, (3) obtained an energy resolution as good as that previously measured by us using chambers with drift gaps of the order of millimeters, (4) observed the induction signals produced by MeV gamma rays, (4) used the 20 hybrid charge sensitive preamplifiers for a nondestructive readout of the electron image on the induction wires, (5) performed extensive Monte Carlo simulations to obtain results on efficiency, background rejection capability, and source flux sensitivity, and (6) developed a reconstruction algorithm for events with multiple interaction points.

  14. Time correlations between low and high energy gamma rays from discrete sources

    NASA Technical Reports Server (NTRS)

    Ellsworth, R. W.

    1995-01-01

    Activities covered the following areas: (1) continuing analysis of the Cygnus Experiment data on the shadowing of cosmic rays by the moon and sun, which led to a direct confirmation of the angular resolution of the CYGNUS EAS array; and (2) development of analysis methods for the daily search overlapping with EGRET targets. To date, no steady emission of ultrahigh energy (UHE) gamma rays from any source has been detected by the Cygnus Experiment, but some evidence for sporadic emission had been found. Upper limits on steady fluxes from 49 sources in the northern hemisphere have been published. In addition, a daily search of 51 possible sources over the interval April 1986 to June 1992 found no evidence for emission. From these source lists, four candidates were selected for comparison with EGRET data.

  15. gamma* N --> Delta at JLab: Exploring the High Q2 Regime

    SciTech Connect

    Maurizio Ungaro; Kyungseon Jo; Paul Stoler

    2007-04-01

    We report a new measurement of the exclusive electroproduction reaction gamma* p --> pi0 p to explore the evolution from soft non-perturbative physics to hard processes via the Q2 dependence of the magnetic (M1+), electric (E1+) and scalar (S1+) multipoles in the N --> Delta transition. 9000 differential cross section data points cover W from threshold to 1.4 GeV/c2, 4pi center-of-mass solid angle, and Q2 from 3 to 6 GeV2/c2, the highest yet achieved. It is found that the magnetic form factor GM* decreases with Q2 more steeply than the proton magnetic form factor, the ratio E1+/M1+ is small and negative, indicating strong helicity non-conservation, and the ratio S1+/M1+ is negative, while its magnitude increases with Q2.

  16. High performance gamma-ray spectrometer for runaway electron studies on the FT-2 tokamak

    NASA Astrophysics Data System (ADS)

    Shevelev, A. E.; Khilkevitch, E. M.; Lashkul, S. I.; Rozhdestvensky, V. V.; Altukhov, A. B.; Chugunov, I. N.; Doinikov, D. N.; Esipov, L. A.; Gin, D. B.; Iliasova, M. V.; Naidenov, V. O.; Nersesyan, N. S.; Polunovsky, I. A.; Sidorov, A. V.; Kiptily, V. G.

    2016-09-01

    A gamma-ray spectrometer based on LaBr3(Ce) scintillator has been used for measurements of hard X-ray emission generated by runaway electrons in the FT-2 tokamak plasmas. Using of the fast LaBr3(Ce) has allowed extending count rate range of the spectrometer by a factor of 10. A developed digital processing algorithm of the detector signal recorded with a digitizer sampling rate of 250 MHz has provided a pulse height analysis at count rates up to 107 s-1. A spectrum deconvolution code DeGaSum has been applied for inferring the energy distribution of runaway electrons escaping from the plasma and interacting with materials of the FT-2 limiter in the vacuum chamber. The developed digital signal processing technique for LaBr3(Ce) spectrometer has allowed studying the evolution of runaways energy distribution in the FT-2 plasma discharges with time resolution of 1-5 ms.

  17. Detection of high-energy gamma-ray emission from the globular cluster 47 Tucanae with Fermi.

    PubMed

    Abdo, A A; Ackermann, M; Ajello, M; Atwood, W B; Axelsson, M; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Baughman, B M; Bechtol, K; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bregeon, J; Brez, A; Brigida, M; Bruel, P; Burnett, T H; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cecchi, C; Celik, O; Charles, E; Chaty, S; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; Cutini, S; Dermer, C D; de Palma, F; Digel, S W; Dormody, M; do Couto e Silva, E; Drell, P S; Dubois, R; Dumora, D; Farnier, C; Favuzzi, C; Fegan, S J; Focke, W B; Frailis, M; Fukazawa, Y; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giebels, B; Giglietto, N; Giordano, F; Glanzman, T; Godfrey, G; Grenier, I A; Grove, J E; Guillemot, L; Guiriec, S; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Horan, D; Hughes, R E; Jóhannesson, G; Johnson, A S; Johnson, R P; Johnson, T J; Johnson, W N; Kamae, T; Katagiri, H; Kawai, N; Kerr, M; Knödlseder, J; Kuehn, F; Kuss, M; Lande, J; Latronico, L; Lemoine-Goumard, M; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Makeev, A; Mazziotta, M N; McConville, W; McEnery, J E; Meurer, C; Michelson, P F; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nolan, P L; Norris, J P; Nuss, E; Ohsugi, T; Omodei, N; Orlando, E; Ormes, J F; Paneque, D; Panetta, J H; Parent, D; Pelassa, V; Pepe, M; Pierbattista, M; Piron, F; Porter, T A; Rainò, S; Rando, R; Razzano, M; Rea, N; Reimer, A; Reimer, O; Reposeur, T; Ritz, S; Rochester, L S; Rodriguez, A Y; Romani, R W; Roth, M; Ryde, F; Sadrozinski, H F-W; Sanchez, D; Sander, A; Saz Parkinson, P M; Sgrò, C; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Starck, J-L; Strickman, M S; Suson, D J; Tajima, H; Takahashi, H; Tanaka, T; Thayer, J B; Thayer, J G; Thompson, D J; Tibaldo, L; Torres, D F; Tosti, G; Tramacere, A; Uchiyama, Y; Usher, T L; Vasileiou, V; Vilchez, N; Vitale, V; Wang, P; Webb, N; Winer, B L; Wood, K S; Ylinen, T; Ziegler, M

    2009-08-14

    We report the detection of gamma-ray emissions above 200 megaelectron volts at a significance level of 17sigma from the globular cluster 47 Tucanae, using data obtained with the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope. Globular clusters are expected to emit gamma rays because of the large populations of millisecond pulsars that they contain. The spectral shape of 47 Tucanae is consistent with gamma-ray emission from a population of millisecond pulsars. The observed gamma-ray luminosity implies an upper limit of 60 millisecond pulsars present in 47 Tucanae.

  18. Studies of Avalanche Photodiodes (APDS) as Readout Devices for Scintillating Fibers for High Energy Gamma-Ray Astronomy Telescopes

    NASA Technical Reports Server (NTRS)

    Vasile, Stefan; Shera, Suzanne; Shamo, Denis

    1998-01-01

    New gamma ray and charged particle telescope designs based on scintillating fiber arrays could provide low cost, high resolution, lightweight, very large area and multi radiation length instrumentation for planned NASA space exploration. The scintillating fibers low visible light output requires readout sensors with single photon detection sensitivity and low noise. The sensitivity of silicon Avalanche Photodiodes (APDS) matches well the spectral output of the scintillating fibers. Moreover, APDs have demonstrated single photon capability. The global aim of our work is to make available to NASA a novel optical detector concept to be used as scintillating fiber readouts and meeting the requirements of the new generations of space-borne gamma ray telescopes. We proposed to evaluate the feasibility of using RMD's small area APDs ((mu)APD) as scintillating fiber readouts and to study possible alternative (mu)APD array configurations for space borne readout scintillating fiber systems, requiring several hundred thousand to one million channels. The evaluation has been conducted in accordance with the task description and technical specifications detailed in the NASA solicitation "Studies of Avalanche Photodiodes (APD as readout devices for scintillating fibers for High Energy Gamma-Ray Astronomy Telescopes" (#8-W-7-ES-13672NAIS) posted on October 23, 1997. The feasibility study we propose builds on recent developments of silicon APD arrays and light concentrators advances at RMD, Inc. and on more than 5 years of expertise in scintillating fiber detectors. In a previous program we carried out the initial research to develop a high resolution, small pixel, solid-state, silicon APD array which exhibited very high sensitivity in the UV-VIS spectrum. This (mu)APD array is operated in Geiger mode and results in high gain (greater than 10(exp 8)), extremely low noise, single photon detection capability, low quiescent power (less than 10 (mu)W/pixel for 30 micrometers sensitive

  19. A new regime for highly robust gamma oscillation with co-exist of accurate and weak synchronization in excitatory-inhibitory networks.

    PubMed

    Wang, Zhijie; Fan, Hong; Han, Fang

    2014-08-01

    A great number of biological experiments show that gamma oscillation occurs in many brain areas after the presentation of stimulus. The neural systems in these brain areas are highly heterogeneous. Specifically, the neurons and synapses in these neural systems are diversified; the external inputs and parameters of these neurons and synapses are heterogeneous. How the gamma oscillation generated in such highly heterogeneous networks remains a challenging problem. Aiming at this problem, a highly heterogeneous complex network model that takes account of many aspects of real neural circuits was constructed. The network model consists of excitatory neurons and fast spiking interneurons, has three types of synapses (GABAA, AMPA, and NMDA), and has highly heterogeneous external drive currents. We found a new regime for robust gamma oscillation, i.e. the oscillation in inhibitory neurons is rather accurate but the oscillation in excitatory neurons is weak, in such highly heterogeneous neural networks. We also found that the mechanism of the oscillation is a mixture of interneuron gamma (ING) and pyramidal-interneuron gamma (PING). We explained the mixture ING and PING mechanism in a consistent-way by a compound post-synaptic current, which has a slowly rising-excitatory stage and a sharp decreasing-inhibitory stage.

  20. Topics in Particle Astrophysics: Dark Matter, Gamma-Ray Bursts, and the Origin of Ultra-High-Energy Cosmic Rays

    NASA Astrophysics Data System (ADS)

    Calvez, Antoine

    Since the first observation of cosmic rays in the early 1900's, intensive astronomical and cosmological observations, and improvements in particle detectors have generated important discoveries such as the existence of gamma-ray bursts and pulsars; they have also generated puzzling evidence for dark matter and dark energy, and for the existence of particles in the interstellar medium with energy beyond 1020 eV. In this dissertation, I will investigate some of the current theoretical challenges posed by the latest cosmological and astrophysical observations, and attempt to provide a unifying solution to the problems. X-ray and gamma-ray observations can help understand the origin of the electron and positron signals reported by ATIC, PAMELA, PPB-BETS , and Fermi. It remains unclear whether the observed high-energy electrons and positrons are produced by relic particles, or by astrophysical sources. To distinguish between the two possibilities, one can compare the electron population in the local neighborhood with that in Dwarf Spheroidal Galaxies (dSphs), which are not expected to host as many gamma-ray bursts, pulsars, or other astrophysical sources. This can be accomplished using X-ray and gamma-ray observations. Assuming the signal detected by Fermi and ATIC comes from dark matter, we calculate the photon spectrum produced by electrons via inverse Compton scattering with the Cosmic Microwave Background radiation (CMB). Since little is known about the magnetic fields in dwarf spheroidals, we consider the propagation of charged particles with and without diffusion. Extending the analysis of the Fermi collaboration for the Draco dwarf spheroidal galaxy, we find that even in the absence of diffusion, the expected gamma-ray signal lies above the upper limits set by the Fermi telescope, thus favoring astrophysical sources such as gamma-ray bursts and pulsars. Furthermore, if one assumes that a local magnetic field exists in the dwarf spheroidal galaxy, the diffusion of

  1. [Development of a high-resolution pinhole SPECT system using dual-head gamma camera for small animal studies].

    PubMed

    Yokoi, T; Kishi, H

    1998-11-01

    We developed a high-resolution pinhole SPECT system using dual-head gamma camera (PRISM-2000XP) for small animal, and evaluated the performance of this system. Two pinhole-inserts (Pb) were mounted on the same unit, and it was not attached to the detector but the gantry of gamma camera. We designed two kinds of pinhole collimators with different rotating radii, 40 mm (Type-I) and 50 mm (Type-II). The diameter of the pinhole is 1 mm for both types. The field of view (FOV) and magnification were 45.8 mm phi and 4.25 for Type-I, 57.4 mm phi and 3.40 for Type-II, respectively. We measured full width at half maximum (FWHM) of line spread function using a 99mTc line source. Measured FWHM values were 1.65 mm using Type-I and 1.91 mm using Type-II at the center of FOV in the center slice. The volume sensitivity of this system was 8.54 kcps/MBq/ml (Type-I) and 5.68 kcps/MBq/ml (Type-II). We could observed 1.2 mm phi cold spot in the resolution phantom using Type-I. In conclusion, this system is available for SPECT measurement of small animal studies.

  2. Discovery of Very High Energy Gamma-Ray Emission from 1FGL J2001.1 4351 by MAGIC

    SciTech Connect

    Berger, Karsten; Paneque, David; Giavitto, Gianluca; /Barcelona, IFAE

    2012-05-07

    We report the discovery of Very High Energy (VHE; >100 GeV) gamma-ray emission from the source 1FGL J2001.1+4351, (RA 20 01 13.5, dec 43 53 02.8, J2000), which is positionally consistent with the location of the flat spectrum radio source MG4 J200112+4352 (RA 20 01 12.9, dec 43 52 52.8, J2000). The VHE detection is based on a 1.5 hour-long observation performed on July 16th in stereoscopic mode with the two 17m diameter imaging Cherenkov telescopes on La Palma, Canary Islands, Spain. The preliminary analysis of the MAGIC data using the standard cuts optimized for soft energy spectra sources yields a detection of 125 gamma-rays above 90 GeV, corresponding to a pre-trail statistical significance of 7.6 standard deviations. The observed flux is estimated to be {approx}20% of the Crab nebula flux above 100 GeV. Earlier MAGIC observations indicated a substantially lower flux; hence indicating that the source is variable on a few days timescale.

  3. ROLE OF LINE-OF-SIGHT COSMIC-RAY INTERACTIONS IN FORMING THE SPECTRA OF DISTANT BLAZARS IN TeV GAMMA RAYS AND HIGH-ENERGY NEUTRINOS

    SciTech Connect

    Essey, Warren; Kusenko, Alexander; Kalashev, Oleg; Beacom, John F.

    2011-04-10

    Active galactic nuclei (AGNs) can produce both gamma rays and cosmic rays. The observed high-energy gamma-ray signals from distant blazars may be dominated by secondary gamma rays produced along the line of sight by the interactions of cosmic-ray protons with background photons. This explains the surprisingly low attenuation observed for distant blazars, because the production of secondary gamma rays occurs, on average, much closer to Earth than the distance to the source. Thus, the observed spectrum in the TeV range does not depend on the intrinsic gamma-ray spectrum, while it depends on the output of the source in cosmic rays. We apply this hypothesis to a number of sources and, in every case, we obtain an excellent fit, strengthening the interpretation of the observed spectra as being due to secondary gamma rays. We explore the ramifications of this interpretation for limits on the extragalactic background light and for the production of cosmic rays in AGNs. We also make predictions for the neutrino signals, which can help probe the acceleration of cosmic rays in AGNs.

  4. Selection and molecular characterization of a high tocopherol accumulation rice mutant line induced by gamma irradiation.

    PubMed

    Hwang, Jung Eun; Ahn, Joon-Woo; Kwon, Soon-Jae; Kim, Jin-Baek; Kim, Sang Hoon; Kang, Si-Yong; Kim, Dong Sub

    2014-11-01

    Tocopherols are micronutrients with antioxidant properties. They are synthesized by photosynthetic bacteria and plants, and play important roles in animal and human nutrition. In this study, we isolated a new rice mutant line with elevated tocopherol content (MRXII) from an in vitro mutagenized population induced by gamma irradiation. The mutant exhibited greater seed longevity than the control, indicating a crucial role for tocopherols in maintaining viability during quiescence, and displayed faster seedling growth during the early growth stage. To study the molecular mechanism underlying vitamin E biosynthesis, we examined the expression patterns of seven rice genes encoding vitamin E biosynthetic enzymes. Accumulation levels of the OsVTE2 transcript and OsVTE2 protein in the MRXII mutant were significantly higher than in the control. Sequence analysis revealed that the MRXII mutant harbored a point mutation in the OsVTE2 promoter region, which resulted in the generation of MYB transcription factor-binding cis-element. These results help identify the promoter regions that regulate OsVTE2 transcription, and offer insights into the regulation of tocopherol content.

  5. A High Sensitivity Balloon-Borne Soft Gamma-ray Polarimeter PoGOLite

    NASA Astrophysics Data System (ADS)

    Kamae, Tuneyoshi; Craig, W.; Madejski, G.; Ng, J.; Tajima, H.; Varner, G.; Carlson, P.; Klamra, W.; Pearce, M.; Bjornsson, C.; Larsson, S.; Ryde, F.; Kataoka, J.; Kawai, N.; Mizuno, T.; Takahashi, T.

    2006-09-01

    Development status of a new balloon-borne polarimeter, PoGOLite, will be presented. PoGOLite is designed to detect 10% polarization of a 100 mCrab source in one 6 hour balloon observation in the 25 keV - 100 keV energy range. Its design is based on the well-type phoswich counter technology. Polarization is measured by recording Compton scattering and photo-absorption in an array of 217 phoswich detector cells made of plastic and BGO scintillators, surrounded by active BGO shields. The design has been optimized through 4 rounds of tests at synchrotron beams and a proton beam, and flight model production has began: it can reduce the large background produced by cosmic-ray particles to about 10 mCrab level in most of its energy coverage. Potential systematic instrumental bias to the polarization measurement will be removed by rotating the polarimeter telescope around its axis. We plan to observe northern sky sources including the Crab pulsar/nebula, Cygnus X-1, and Hercules X-1 in the first flight scheduled in 2009. Our future plans include long duration balloon flights from Sweden to North America, and launching within a few weeks of gamma-ray flare detection from jet sources such as Mkn 501 by GLAST.

  6. The Search for High Energy Extended Emission by Fermi-LAT from Swift-Localized Gamma-Ray Bursts

    SciTech Connect

    Chiang, J.; Racusin, J.L.; /NASA, Goddard

    2012-05-01

    The brighter Fermi-LAT bursts have exhibited emission at energies >0.1 GeV that persists as late as {approx}2 ks after the prompt phase has nominally ended. This so-called 'extended emission' could arise from continued activity of the prompt burst mechanism or it could be the start of a high energy afterglow component. The high energy extended emission seen by the LAT has typically followed a t{sup -}{gamma} power-law temporal decay where {gamma} {approx} 1.2-1.7 and has shown no strong indication of spectral evolution. In contrast, the prompt burst emission generally displays strong spectral variability and more complex temporal changes in the LAT band. This differing behavior suggests that the extended emission likely corresponds to an early afterglow phase produced by an external shock. In this study, we look for evidence of high energy extended emission from 145 Swift-localized GRBs that have occurred since the launch of Fermi. A majority of these bursts were either outside of the LAT field-of-view or were otherwise not detected by the LAT during the prompt phase. However, because of the scanning operation of the Fermi satellite, the long-lived extended emission of these bursts may be detectable in the LAT data on the {approx}few ks time scale. We will look for emission from individual bursts and will perform a stacking analysis in order to set bounds on this emission for the sample as a whole. The detection of such emission would have implications for afterglow models and for the overall energy budget of GRBs.

  7. A Mechanically-Cooled, Highly-Portable, HPGe-Based, Coded-Aperture Gamma-Ray Imager

    SciTech Connect

    Ziock, Klaus-Peter; Boehnen, Chris Bensing; Hayward, Jason P; Raffo-Caiado, Ana Claudia

    2010-01-01

    Coded-aperture gamma-ray imaging is a mature technology that is capable of providing accurate and quantitative images of nuclear materials. Although it is potentially of high value to the safeguards and arms-control communities, it has yet to be fully embraced by those communities. One reason for this is the limited choice, high-cost, and low efficiency of commercial instruments; while instruments made by research organizations are frequently large and / or unsuitable for field work. In this paper we present the results of a project that mates the coded-aperture imaging approach with the latest in commercially-available, position-sensitive, High Purity Germanium (HPGe) detec-tors. The instrument replaces a laboratory prototype that, was unsuitable for other than demonstra-tions. The original instrument, and the cart on which it is mounted to provide mobility and pointing capabilities, has a footprint of ~ 2/3 m x 2 m, weighs ~ 100 Kg, and requires cryogen refills every few days. In contrast, the new instrument is tripod mounted, weighs of order 25 Kg, operates with a laptop computer, and is mechanically cooled. The instrument is being used in a program that is ex-ploring the use of combined radiation and laser scanner imaging. The former provides information on the presence, location, and type of nuclear materials while the latter provides design verification information. To align the gamma-ray images with the laser scanner data, the Ge imager is fitted and aligned to a visible-light stereo imaging unit. This unit generates a locus of 3D points that can be matched to the precise laser scanner data. With this approach, the two instruments can be used completely independently at a facility, and yet the data can be accurately overlaid based on the very structures that are being measured.

  8. Comparison of high energy gamma rays from absolute value of b greater than 30 deg with the galactic neutral hydrogen distribution

    NASA Technical Reports Server (NTRS)

    Ozel, M. E.; Ogelman, H.; Tumer, T.; Fichtel, C. E.; Hartman, R. C.; Kniffen, D. A.; Thompson, F. J.

    1978-01-01

    High-energy gamma-ray (energy above 35 MeV) data from the SAS 2 satellite have been used to compare the intensity distribution of gamma rays with that of neutral hydrogen (H I) density along the line of sight, at high galactic latitudes (absolute values greater than 30 deg). A model has been constructed for the case where the observed gamma-ray intensity has been assumed to be the sum of a galactic component proportional to the H I distribution plus an isotropic extragalactic emission. A chi-squared test of the model parameters indicates that about 30% of the total high-latitude emission may originate within the Galaxy.

  9. -G gamma A gamma-Thalassemia and gamma-chain variants in Chinese newborn babies.

    PubMed

    Zeng, Y T; Huang, S Z; Nakatsuji, T; Huisman, T H

    1985-03-01

    The occurrence of gamma-chain abnormal hemoglobins and of gamma-thalassemia in Chinese newborns was evaluated through analyses of the Hb F of over 1,100 babies and of the DNA from one baby and his parents. Gene mapping data identified this baby as a homozygote for -G gamma A gamma-thalassemia, which is caused by a deletion of about 5 kb due to an unequal crossing-over between the -G gamma- and -A gamma- genes. This condition is the same as that observed in Indian and Japanese babies [2,3]. Its gene frequency among babies from the Shanghai area was 0.012. A previously unrecognized G gamma chain variant, Hb F-Shanghai or alpha 2 G gamma 266(E10)Lys----Arg, was observed in one newborn. This variant was not detected by conventional techniques but only by high performance liquid chromatography, as the G gamma 66 Lys and G gamma 66 Arg chains had slightly different chromatographic mobilities. Lys at position gamma 66 participates in contacts with the heme group, and its substitution by another amino acid residue might interfere with physiochemical and/or functional properties. No other gamma-chain variants have been detected except the well-known A gamma T or F-Sardinia chain (f.A gamma T = 0.076).

  10. Gamma-ray emission from globular clusters. Shock high energy emission from the Be-Star/Pulsar System PSR 1259-63. Echoes in x-ray novae

    NASA Technical Reports Server (NTRS)

    Kaaret, Philip

    1995-01-01

    This grant covers work on the Compton phase 3 investigation, 'Shock High Energy Emission from the Be- Star/Pulsar System PSR 1259-63' and cycle 4 investigations 'Diffuse Gamma-Ray Emission at High Latitudes' and 'Echoes in X-Ray Novae'. Work under the investigation 'Diffuse Gamma-Ray Emission at High Latitudes' has lead to the publication of a paper (attached), describing gamma-ray emissivity variations in the northern galactic hemisphere. Using archival EGRET data, we have found a large irregular region of enhanced gamma-ray emissivity at energies greater 100 MeV. This is the first observation of local structure in the gamma-ray emissivity. Work under the investigation 'Echoes in X-Ray Novae' is proceeding with analysis of data from OSSE from the transient source GRO J1655-40. The outburst of this source last fall triggered this Target of Opportunity investigation. Preliminary spectral analysis shows emission out to 600 keV and a pure power low spectrum with no evidence of an exponential cutoff. Work is complete on the analysis of BATSE data from the Be-Star/Pulsar Sustem PSR 1259-63.

  11. High gamma power in ECoG reflects cortical electrical stimulation effects on unit activity in layers V/VI

    NASA Astrophysics Data System (ADS)

    Yazdan-Shahmorad, Azadeh; Kipke, Daryl R.; Lehmkuhle, Mark J.

    2013-12-01

    Objective. Cortical electrical stimulation (CES) has been used extensively in experimental neuroscience to modulate neuronal or behavioral activity, which has led this technique to be considered in neurorehabilitation. Because the cortex and the surrounding anatomy have irregular geometries as well as inhomogeneous and anisotropic electrical properties, the mechanism by which CES has therapeutic effects is poorly understood. Therapeutic effects of CES can be improved by optimizing the stimulation parameters based on the effects of various stimulation parameters on target brain regions. Approach. In this study we have compared the effects of CES pulse polarity, frequency, and amplitude on unit activity recorded from rat primary motor cortex with the effects on the corresponding local field potentials (LFP), and electrocorticograms (ECoG). CES was applied at the surface of the cortex and the unit activity and LFPs were recorded using a penetrating electrode array, which was implanted below the stimulation site. ECoGs were recorded from the vicinity of the stimulation site. Main results. Time-frequency analysis of LFPs following CES showed correlation of gamma frequencies with unit activity response in all layers. More importantly, high gamma power of ECoG signals only correlated with the unit activity in lower layers (V-VI) following CES. Time-frequency correlations, which were found between LFPs, ECoGs and unit activity, were frequency- and amplitude-dependent. Significance. The signature of the neural activity observed in LFP and ECoG signals provides a better understanding of the effects of stimulation on network activity, representative of large numbers of neurons responding to stimulation. These results demonstrate that the neurorehabilitation and neuroprosthetic applications of CES targeting layered cortex can be further improved by using field potential recordings as surrogates to unit activity aimed at optimizing stimulation efficacy. Likewise, the signatures

  12. Variation in the topography of the speech production cortex verified by cortical stimulation and high gamma activity.

    PubMed

    Babajani-Feremi, Abbas; Rezaie, Roozbeh; Narayana, Shalini; Choudhri, Asim F; Fulton, Stephen P; Boop, Frederick A; Wheless, James W; Papanicolaou, Andrew C

    2014-12-17

    In this study, we have addressed the question of functional brain reorganization for language in the presence and absence of anatomical lesions in two patients with epilepsy using cortical stimulation mapping and high gamma (HG) activity in subdural grid recordings. In both, the expressive language cortex was defined as the cortical patch below the electrode(s) that when stimulated resulted in speech arrest, and during speech expression tasks generated HG activity. This patch fell within the borders of Broca's area, as defined anatomically, in the case of the patient with a lesion, but outside that area in the other, lesion-free patient. Such results highlight the necessity for presurgical language mapping in all cases of surgery involving the language-dominant hemisphere and suggest that HG activity during expressive language tasks can be informative and helpful in conjunction with cortical stimulation mapping for expressive language mapping.

  13. A Search for Enhanced Very High Energy Gamma-Ray Emission from the 2013 March Crab Nebula Flare

    NASA Astrophysics Data System (ADS)

    Aliu, E.; Archambault, S.; Aune, T.; Benbow, W.; Berger, K.; Bird, R.; Bouvier, A.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cerruti, M.; Chen, X.; Ciupik, L.; Connolly, M. P.; Cui, W.; Dumm, J.; Errando, M.; Falcone, A.; Federici, S.; Feng, Q.; Finley, J. P.; Fortin, P.; Fortson, L.; Furniss, A.; Galante, N.; Gillanders, G. H.; Griffin, S.; Griffiths, S. T.; Grube, J.; Gyuk, G.; Hanna, D.; Holder, J.; Hughes, G.; Humensky, T. B.; Kaaret, P.; Kertzman, M.; Khassen, Y.; Kieda, D.; Krennrich, F.; Kumar, S.; Lang, M. J.; Lyutikov, M.; Maier, G.; McArthur, S.; McCann, A.; Meagher, K.; Millis, J.; Moriarty, P.; Mukherjee, R.; O'Faoláin de Bhróithe, A.; Ong, R. A.; Otte, A. N.; Park, N.; Perkins, J. S.; Pohl, M.; Popkow, A.; Quinn, J.; Ragan, K.; Rajotte, J.; Reyes, L. C.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Sembroski, G. H.; Sheidaei, F.; Smith, A. W.; Staszak, D.; Telezhinsky, I.; Theiling, M.; Tucci, J. V.; Tyler, J.; Varlotta, A.; Wakely, S. P.; Weekes, T. C.; Weinstein, A.; Welsing, R.; Williams, D. A.; Zajczyk, A.; Zitzer, B.

    2014-01-01

    In 2013 March, a flaring episode from the Crab Nebula lasting ~2 weeks was detected by Fermi-LAT (Large Area Telescope on board the Fermi Gamma-ray Space Telescope). The Very Energetic Radiation Imaging Telescope Array System (VERITAS) provides simultaneous observations throughout this period. During the flare, Fermi-LAT detected a 20 fold increase in flux above the average synchrotron flux >100 MeV seen from the Crab Nebula. Simultaneous measurements with VERITAS are consistent with the non-variable long-term average Crab Nebula flux at TeV energies. Assuming a linear correlation between the very high energy flux change >1 TeV and the flux change seen in the Fermi-LAT band >100 MeV during the period of simultaneous observations, the linear correlation factor can be constrained to be at most 8.6 × 10-3 with 95% confidence.

  14. Performance of A Compact Multi-crystal High-purity Germanium Detector Array for Measuring Coincident Gamma-ray Emissions

    SciTech Connect

    Howard, Chris; Daigle, Stephen; Buckner, Matt; Erikson, Luke E.; Runkle, Robert C.; Stave, Sean C.; Champagne, Art; Cooper, Andrew; Downen, Lori; Glasgow, Brian D.; Kelly, Keegan; Sallaska, Anne

    2015-02-18

    The Multi-sensor Airborne Radiation Survey (MARS) detector is a 14-crystal array of high-purity germanium (HPGe) detectors housed in a single cryostat. The array was used to measure the astrophysical S-factor for the 14N(p,γ)15O* reaction for several transition energies at an effective center of mass energy of 163 keV. Owing to the segmented nature of the MARS detector, the effect of gamma-ray summing was greatly reduced in comparison to past experiments which utilized large, single-crystal detectors. The new S-factor values agree within the uncertainties with the past measurements. Details of the analysis and detector performance will be presented.

  15. Variation in the topography of the speech production cortex verified by cortical stimulation and high gamma activity

    PubMed Central

    Rezaie, Roozbeh; Narayana, Shalini; Choudhri, Asim F.; Fulton, Stephen P.; Boop, Frederick A.; Wheless, James W.; Papanicolaou, Andrew C.

    2014-01-01

    In this study, we have addressed the question of functional brain reorganization for language in the presence and absence of anatomical lesions in two patients with epilepsy using cortical stimulation mapping and high gamma (HG) activity in subdural grid recordings. In both, the expressive language cortex was defined as the cortical patch below the electrode(s) that when stimulated resulted in speech arrest, and during speech expression tasks generated HG activity. This patch fell within the borders of Broca’s area, as defined anatomically, in the case of the patient with a lesion, but outside that area in the other, lesion-free patient. Such results highlight the necessity for presurgical language mapping in all cases of surgery involving the language-dominant hemisphere and suggest that HG activity during expressive language tasks can be informative and helpful in conjunction with cortical stimulation mapping for expressive language mapping. PMID:25371284

  16. A SEARCH FOR ENHANCED VERY HIGH ENERGY GAMMA-RAY EMISSION FROM THE 2013 MARCH CRAB NEBULA FLARE

    SciTech Connect

    Aliu, E.; Errando, M.; Archambault, S.; Aune, T.; Benbow, W.; Cerruti, M.; Berger, K.; Bird, R.; Bouvier, A.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Chen, X.; Ciupik, L.; Connolly, M. P.; Cui, W.; Feng, Q.; Dumm, J.; Falcone, A.; Federici, S. E-mail: gtrichards@gatech.edu; and others

    2014-01-20

    In 2013 March, a flaring episode from the Crab Nebula lasting ∼2 weeks was detected by Fermi-LAT (Large Area Telescope on board the Fermi Gamma-ray Space Telescope). The Very Energetic Radiation Imaging Telescope Array System (VERITAS) provides simultaneous observations throughout this period. During the flare, Fermi-LAT detected a 20 fold increase in flux above the average synchrotron flux >100 MeV seen from the Crab Nebula. Simultaneous measurements with VERITAS are consistent with the non-variable long-term average Crab Nebula flux at TeV energies. Assuming a linear correlation between the very high energy flux change >1 TeV and the flux change seen in the Fermi-LAT band >100 MeV during the period of simultaneous observations, the linear correlation factor can be constrained to be at most 8.6 × 10{sup –3} with 95% confidence.

  17. Evaluation of the Combined Effects of Gamma Radiation and High Dietary Iron on Peripheral Leukocyte Distribution and Function

    NASA Technical Reports Server (NTRS)

    Crucian, Brian E.; Morgan, Jennifer L. L.; Quiriarte, Heather A.; Sams, Clarence F.; Smith, Scott M.; Zwart, Sara R.

    2011-01-01

    NASA is concerned with the health risks to astronauts, particularly those risks related to radiation exposure. Both radiation and increased iron stores can independently increase oxidative damage, resulting in protein, lipid and DNA oxidation. Oxidative stress increases the risk of many health problems including cancer, cataracts, and heart disease. This study, a subset of a larger interdisciplinary investigation of the combined effect of iron overload on sensitivity to radiation injury, monitored immune parameters in the peripheral blood of rats subjected to gamma radiation, high dietary iron or both. Specific immune measures consisted of (A) peripheral leukocyte distribution; (B) plasma cytokine levels; (C) cytokine production profiles following whole blood stimulation of either T cells or monocytes.

  18. Effects of film thickness on scintillation characteristics of columnar CsI:Tl films exposed to high gamma radiation doses

    NASA Astrophysics Data System (ADS)

    Shinde, Seema; Singh, S. G.; Sen, S.; Gadkari, S. C.

    2016-02-01

    Oriented columnar films of Tl doped CsI (CsI:Tl) of varying thicknesses from 50 μm to 1000 μm have been deposited on silica glass substrates by a thermal evaporation technique. The SEM micrographs confirmed the columnar structure of the film while the powder X-ray diffraction pattern recorded for the films revealed a preferred orientation of the grown columns along the <200> direction. Effects of high energy gamma exposure up to 1000 Gy on luminescence properties of the films were investigated. Results of radio-luminescence, photo-luminescence and scintillation studies on the films are compared with those of a CsI:Tl single crystal with similar thickness. A possible correlation between the film thicknesses and radiation damage in films has been observed.

  19. Performance of a compact multi-crystal high-purity germanium detector array for measuring coincident gamma-ray emissions

    NASA Astrophysics Data System (ADS)

    Howard, Chris; Daigle, Stephen; Buckner, Matt; Erikson, Luke E.; Runkle, Robert C.; Stave, Sean C.; Champagne, Arthur E.; Cooper, Andrew; Downen, Lori; Glasgow, Brian D.; Kelly, Keegan; Sallaska, Anne

    2015-05-01

    The Multi-sensor Airborne Radiation Survey (MARS) detector is a 14-crystal array of high-purity germanium (HPGe) detectors housed in a single cryostat. The array was used to measure the astrophysical S-factor for the 14N(p,γ)15O* reaction for several transition energies at an effective center-of-mass energy of 163 keV. Owing to the granular nature of the MARS detector, the effect of gamma-ray summing was greatly reduced in comparison to past experiments which utilized large, single-crystal detectors. The new S-factor values agree within their uncertainties with the past measurements. Details of the analysis and detector performance are presented.

  20. High-resolution gamma-ray spectroscopy with a microwave-multiplexed transition-edge sensor array

    SciTech Connect

    Noroozian, Omid; Mates, John A. B.; Bennett, Douglas A.; Brevik, Justus A.; Fowler, Joseph W.; Gao, Jiansong; Hilton, Gene C.; Horansky, Robert D.; Irwin, Kent D.; Schmidt, Daniel R.; Vale, Leila R.; Ullom, Joel N.; Kang, Zhao

    2013-11-11

    We demonstrate very high resolution photon spectroscopy with a microwave-multiplexed two-pixel transition-edge sensor (TES) array. We measured a {sup 153}Gd photon source and achieved an energy resolution of 63 eV full-width-at-half-maximum at 97 keV and an equivalent readout system noise of 86 pA/√(Hz) at the TES. The readout circuit consists of superconducting microwave resonators coupled to radio-frequency superconducting-quantum-interference-devices and transduces changes in input current to changes in phase of a microwave signal. We use flux-ramp modulation to linearize the response and evade low-frequency noise. This demonstration establishes one path for the readout of cryogenic X-ray and gamma-ray sensor arrays with more than 10{sup 3} elements and spectral resolving powers R=λ/Δλ>10{sup 3}.

  1. Modelling gamma-ray photon emission and pair production in high-intensity laser–matter interactions

    SciTech Connect

    Ridgers, C.P.; Kirk, J.G.; Duclous, R.; Blackburn, T.G.; Brady, C.S.; Bennett, K.; Arber, T.D.; Bell, A.R.

    2014-03-01

    In high-intensity (>10{sup 21} Wcm{sup −2}) laser–matter interactions gamma-ray photon emission by the electrons can strongly affect the electron's dynamics and copious numbers of electron–positron pairs can be produced by the emitted photons. We show how these processes can be included in simulations by coupling a Monte Carlo algorithm describing the emission to a particle-in-cell code. The Monte Carlo algorithm includes quantum corrections to the photon emission, which we show must be included if the pair production rate is to be correctly determined. The accuracy, convergence and energy conservation properties of the Monte Carlo algorithm are analysed in simple test problems.

  2. Development of the 3-D Track Imager for Medium and High-Energy Gamma-Ray Telescopes

    NASA Technical Reports Server (NTRS)

    Hunter, Stanley D.

    2006-01-01

    The Advanced Compton Telescope (ACT) and Advanced Pair Telescope (APT) are envisioned as the next medium (0.3 ^ 50 MeV) and high-energy (30 MeV - greater than 100 GeV) gamma-ray missions. These missions will address many research focus areas of the Structure and Evolution of the Universe Roadmap. These areas include: element formation, matter, energy, & magnetic field interactions in galaxies, AGN & GRB emission, and behavior of matter in extreme environments of black holes & pulsars. Achieving these science goals requires a substantial increases in telescope sensitivity and angular resolution. This talk will discuss how these goals can be met with the three-dimensional track imager (3-DTI), a large volume, low density, time projection chamber with two-dimensional micro-well detector readout and report on our development of a 10 cm x 10 cm x 30 prototype instrument.

  3. High time resolved electron temperature measurements by using the multi-pass Thomson scattering system in GAMMA 10/PDX

    NASA Astrophysics Data System (ADS)

    Yoshikawa, Masayuki; Yasuhara, Ryo; Ohta, Koichi; Chikatsu, Masayuki; Shima, Yoriko; Kohagura, Junko; Sakamoto, Mizuki; Nakashima, Yousuke; Imai, Tsuyoshi; Ichimura, Makoto; Yamada, Ichihiro; Funaba, Hisamichi; Minami, Takashi

    2016-11-01

    High time resolved electron temperature measurements are useful for fluctuation study. A multi-pass Thomson scattering (MPTS) system is proposed for the improvement of both increasing the TS signal intensity and time resolution. The MPTS system in GAMMA 10/PDX has been constructed for enhancing the Thomson scattered signals for the improvement of measurement accuracy. The MPTS system has a polarization-based configuration with an image relaying system. We optimized the image relaying optics for improving the multi-pass laser confinement and obtaining the stable MPTS signals over ten passing TS signals. The integrated MPTS signals increased about five times larger than that in the single pass system. Finally, time dependent electron temperatures were obtained in MHz sampling.

  4. Exit Dose Measurement in Therapeutic High Energy Photon Beams and Cobalt-60 Gamma Rays

    NASA Astrophysics Data System (ADS)

    Sathiyan, S.; Ravikumar, M.

    2007-01-01

    To estimate the skin dose to the patient from the treatment planning, the knowledge about exit dose is essential, which is calculated from the percentage depth dose. In this study 6 MV and 18 MV beams from linear accelerator and cobalt-60 beams were used. The ionometric measurements were carried out with parallel plate chamber of sensitive volume 0.16 cc. Parallel plate chamber was fitted in to 30 x 30 cm2 polystyrene phantom at a fixed FSD with the measuring entrance window facing farther from the source. The field size for this measuring condition was maintained at 10 x 10 cm2. The ionization measurements were also carried out by changing the thickness of the polystyrene phantom at the entrance side of the point of measurement. In order to find out the variation of relative exit dose (RED) with field size the measurements were carried out without and with the full back-scattering material (27.2 gm/cm2) placed beyond the entrance window of the chamber. The measurements were also done for the entrance polystyrene phantom thicknesses of 10, 20 and 30 cm for the field size ranging from 5 x 5 cm2 to 30 x 30 cm2. The dose at the exit surface with no backscatter material is about 4.4%, 3.7% and 5.8% less than the dose with the full backscatter material present beyond the point of measurement for 6 MV, 18 MV X-rays and cobalt-60 gamma rays. The reduction in exit dose does not depend much of the phantom thickness through which the beam traverses before exiting at the chamber side. Dose enhancements of about 1.03 times were observed for a field size of 5 x 5 cm2 for 6 MV, 18 MV X-rays and cobalt-60 gamma rays. The dose enhancement factor (DEF) values were noticed to vary with field size beyond 15 x 15 cm2 for all the energies studied. Also it can be observed that the dose enhancement factor (DEF) values do not depend on the thickness of the phantom material through which the beam has traversed. The DEF values were found to vary marginally for different phantom material

  5. The use of an active coded aperture for improved directional measurements in high energy gamma-ray astronomy

    NASA Technical Reports Server (NTRS)

    Johansson, A.; Beron, B. L.; Campbell, L.; Eichler, R.; Hofstadter, R.; Hughes, E. B.; Wilson, S.; Gorodetsky, P.

    1980-01-01

    The coded aperture, a refinement of the scatter-hole camera, offers a method for the improved measurement of gamma-ray direction in gamma-ray astronomy. Two prototype coded apertures have been built and tested. The more recent of these has 128 active elements of the heavy scintillator BGO. Results of tests for gamma-rays in the range 50-500 MeV are reported and future application in space discussed.

  6. BLAZARS AS ULTRA-HIGH-ENERGY COSMIC-RAY SOURCES: IMPLICATIONS FOR TeV GAMMA-RAY OBSERVATIONS

    SciTech Connect

    Murase, Kohta; Dermer, Charles D.; Takami, Hajime; Migliori, Giulia

    2012-04-10

    The spectra of BL Lac objects and Fanaroff-Riley I radio galaxies are commonly explained by the one-zone leptonic synchrotron self-Compton (SSC) model. Spectral modeling of correlated multiwavelength data gives the comoving magnetic field strength, the bulk outflow Lorentz factor, and the emission region size. Assuming the validity of the SSC model, the Hillas condition shows that only in rare cases such sources accelerate protons to much above 10{sup 19} eV, so {approx}> 10{sup 20} eV ultra-high-energy cosmic rays (UHECRs) are likely to be heavy ions if powered by this type of radio-loud active galactic nuclei (AGNs). Survival of nuclei is shown to be possible in TeV BL Lacs and misaligned counterparts with weak photohadronic emissions. Another signature of hadronic production is intergalactic UHECR-induced cascade emission, which is an alternative explanation of the TeV spectra of some extreme non-variable blazars such as 1ES 0229+200 or 1ES 1101-232. We study this kind of cascade signal, taking into account effects of the structured extragalactic magnetic fields in which the sources should be embedded. We demonstrate the importance of cosmic-ray deflections on the {gamma}-ray flux, and show that required absolute cosmic-ray luminosities are larger than the average UHECR luminosity inferred from UHECR observations and can even be comparable to the Eddington luminosity of supermassive black holes. Future TeV {gamma}-ray observations using the Cerenkov Telescope Array and the High Altitude Water Cerenkov detector array can test for UHECR acceleration by observing >25 TeV photons from relatively low redshift sources such as 1ES 0229+200, and {approx}>TeV photons from more distant radio-loud AGNs.

  7. Sparse Spectro-Temporal Receptive Fields Based on Multi-Unit and High-Gamma Responses in Human Auditory Cortex

    PubMed Central

    Jenison, Rick L.; Reale, Richard A.; Armstrong, Amanda L.; Oya, Hiroyuki; Kawasaki, Hiroto; Howard, Matthew A.

    2015-01-01

    Spectro-Temporal Receptive Fields (STRFs) were estimated from both multi-unit sorted clusters and high-gamma power responses in human auditory cortex. Intracranial electrophysiological recordings were used to measure responses to a random chord sequence of Gammatone stimuli. Traditional methods for estimating STRFs from single-unit recordings, such as spike-triggered-averages, tend to be noisy and are less robust to other response signals such as local field potentials. We present an extension to recently advanced methods for estimating STRFs from generalized linear models (GLM). A new variant of regression using regularization that penalizes non-zero coefficients is described, which results in a sparse solution. The frequency-time structure of the STRF tends toward grouping in different areas of frequency-time and we demonstrate that group sparsity-inducing penalties applied to GLM estimates of STRFs reduces the background noise while preserving the complex internal structure. The contribution of local spiking activity to the high-gamma power signal was factored out of the STRF using the GLM method, and this contribution was significant in 85 percent of the cases. Although the GLM methods have been used to estimate STRFs in animals, this study examines the detailed structure directly from auditory cortex in the awake human brain. We used this approach to identify an abrupt change in the best frequency of estimated STRFs along posteromedial-to-anterolateral recording locations along the long axis of Heschl’s gyrus. This change correlates well with a proposed transition from core to non-core auditory fields previously identified using the temporal response properties of Heschl’s gyrus recordings elicited by click-train stimuli. PMID:26367010

  8. High-Quality Early-Time Light Curves of GRB 060206: Implications for Gamma-Ray Burst Environments and Energetics

    NASA Astrophysics Data System (ADS)

    Monfardini, A.; Kobayashi, S.; Guidorzi, C.; Carter, D.; Mundell, C. G.; Bersier, D. F.; Gomboc, A.; Melandri, A.; Mottram, C. J.; Smith, R. J.; Steele, I. A.

    2006-09-01

    The 2 m robotic Liverpool Telescope (LT) reacted promptly to the high-redshift (z=4.048) gamma-ray burst GRB 060206. The afterglow was identified automatically, and the multicolor r'i'z' imaging program was triggered without human intervention. Combining our data with those obtained from later follow-ups provides a well-sampled optical light curve from 5 minutes to more than 2days after the gamma event. The light curve is highly structured, with at least three bumps evident in the first 75 minutes, including a major rebrightening (Δr'~-1.6 at t~3000 s), interpreted as late energy injection. At early time (t~440 s), we find evidence for fast (Δtrest<4 s<

  9. A New Population of High-Redshift Short-Duration Gamma-Ray Bursts

    NASA Astrophysics Data System (ADS)

    Berger, E.; Fox, D. B.; Price, P. A.; Nakar, E.; Gal-Yam, A.; Holz, D. E.; Schmidt, B. P.; Cucchiara, A.; Cenko, S. B.; Kulkarni, S. R.; Soderberg, A. M.; Frail, D. A.; Penprase, B. E.; Rau, A.; Ofek, E.; Burnell, S. J. Bell; Cameron, P. B.; Cowie, L. L.; Dopita, M. A.; Hook, I.; Peterson, B. A.; Podsiadlowski, P.; Roth, K. C.; Rutledge, R. E.; Sheppard, S. S.; Songaila, A.

    2007-08-01

    The redshift distribution of the short-duration gamma-ray bursts (GRBs) is a crucial, but currently fragmentary, clue to the nature of their progenitors. Here we present optical observations of nine short GRBs obtained with Gemini, Magellan, and the Hubble Space Telescope. We detect the afterglows and host galaxies of two short bursts, and host galaxies for two additional bursts with known optical afterglow positions, and five with X-ray positions (<~6" radius). In eight of the nine cases we find that the most probable host galaxies are faint, R~23-26.5 mag, and are therefore starkly different from the first few short GRB hosts with R~17-22 mag and z<~0.5. Indeed, we measure spectroscopic redshifts of z~0.4-1.1 for the four brightest hosts. A comparison to large field galaxy samples, as well as the hosts of long GRBs and previous short GRBs, indicates that the fainter hosts likely reside at z>~1. Our most conservative limit is that at least half of the five hosts without a known redshift reside at z>0.7 (97% confidence level), suggesting that about 1/3 to 2/3 of all short GRBs originate at higher redshifts than previously determined. This has two important implications: (1) we constrain the acceptable age distributions to a wide lognormal (σ>~1) with τ*~4-8 Gyr, or to a power law, P(τ)~τn, with -1<~n<~0 and (2) the inferred isotropic energies, Eγ,iso~1050-1052 ergs, are significantly larger than ~1048-1049 ergs for the low-redshift, short GRBs, indicating a large spread in energy release or jet opening angles. Finally, we reiterate the importance of short GRBs as potential gravitational-wave sources and find a conservative detection rate with the advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) of ~2-6 yr-1.

  10. An Investigation of 154Eu as a High-Precision Multi-{gamma}-Ray Intensity Calibration Standard for Detector Arrays

    SciTech Connect

    Kulp, W.D.; Wood, J.L.; Krane, K. S.; Loats, J.; Schmelzenbach, P.D.; Stapels, C.J.; Norman, E.B.

    2005-05-24

    The decay of 154Eu has been studied using {gamma}-ray singles and {gamma} - {gamma} coincidence spectroscopy with an array of Compton-suppressed Ge detectors. Particular attention to coincidence summing in the analysis, with consideration of detailed decay cascades and angular correlation effects, suggests that previous studies have overlooked necessary corrections. It is concluded that 154Eu provides 26 {gamma} rays that can be used for relative efficiency calibrations from 120 to 1600 keV at the 0.7% precision level and that this precision could be improved in the future.

  11. Gamma/neutron analysis for SNM signatures at high-data rates(greater than 107 cps) for single-pulse active interrogation

    SciTech Connect

    Forman L.; Dioszegi, I.; Salwen, C.

    2011-04-26

    We are developing a high data gamma/neutron spectrometer suitable for active interrogation of special nuclear materials (SNM) activated by a single burst from an intense source. We have tested the system at Naval Research Laboratory's (NRL) Mercury pulsed-power facility at distances approaching 10 meters from a depleted uranium (DU) target. We have found that the gamma-ray field in the target room 'disappears' 10 milliseconds after the x-ray flash, and that gamma ray spectroscopy will then be dominated by isomeric states/beta decay of fission products. When a polyethylene moderator is added to the DU target, a time-dependent signature of the DU is produced by thermalized neutrons. We observe this signature in gamma-spectra measured consecutively in the 0.1-1.0 ms time range. These spectra contain the Compton edge line (2.2 MeV) from capture in hydrogen, and a continuous high energy gamma-spectrum from capture or fission in minority constituents of the DU.

  12. Gamma-ray Bursts

    NASA Astrophysics Data System (ADS)

    Kouveliotou, Chryssa; Wijers, Ralph A. M. J.; Woosley, Stan

    2012-11-01

    Prologue C. Kouveliotou, R. A . M. J. Wijers and S. E. Woosley; 1. The discovery of the gamma-ray burst phenomenon R. W. Klebesadel; 2. Instrumental principles E. E. Fenimore; 3. The BATSE era G. J. Fishman and C. A. Meegan; 4. The cosmological era L. Piro and K. Hurley; 5. The Swift era N. Gehrels and D. N. Burrows; 6. Discoveries enabled by multi-wavelength afterglow observations of gamma-ray bursts J. Greiner; 7. Prompt emission from gamma-ray bursts T. Piran, R. Sari and R. Mochkovitch; 8. Basic gamma-ray burst afterglows P. Mészáros and R. A. M. J. Wijers; 9. The GRB-supernova connection J. Hjorth and J. S. Bloom; 10. Models for gamma-ray burst progenitors and central engines S. E. Woosley; 11. Jets and gamma-ray burst unification schemes J. Granot and E. Ramirez-Ruiz; 12. High-energy cosmic rays and neutrinos E. Waxman; 13. Long gamma-ray burst host galaxies and their environments J. P. U. Fynbo, D. Malesani and P. Jakobsson; 14. Gamma-ray burst cosmology V. Bromm and A. Loeb; 15. Epilogue R. D. Blandford; Index.

  13. VTEM airborne EM, aeromagnetic and gamma-ray spectrometric data over the Cerro Quema high sulphidation epithermal gold deposits, Panama

    NASA Astrophysics Data System (ADS)

    Kwan, Karl; Prikhodko, Alexander; Legault, Jean M. Plastow, Geoffrey C.; Kapetas, John; Druecker, Michael

    2016-03-01

    In March 2012, a helicopter-borne versatile time-domain electromagnetic (VTEM), magnetic and radiometric survey was flown over the Cerro Quema high sulphidation (HS) epithermal gold deposits and the surrounding area. The Cerro Quema deposits are located in the Azuero Peninsula, Panama, approximately 8 km east of Güerita. The gold mineralisation is associated with clay-pyrite alterations topped by an acid-leached resistive cap, and the principal ores are pyrite-rich sulphides located within mineralised vuggy silica rocks. The geophysical data over the Cerro Quema deposits have been analysed. The electromagnetic (EM) responses over the deposits are characterised by resistivity highs and chargeability lows, surrounded by resistivity lows and chargeability highs. Radiometric Th/K ratio highs and magnetic susceptibility lows are observed over the deposits. These geophysical signatures over the Cerro Quema deposits are characteristic responses from HS epithermal gold deposits. The success of the VTEM survey points to the applicability of the regional helicopter electromagnetic, magnetic and gamma-ray spectrometry (EM-Mag-Spec) surveys for the exploration of similar HS epithermal gold deposits to depths < 500 m in weathered terrains.

  14. CORRELATED X-RAY AND VERY HIGH ENERGY EMISSION IN THE GAMMA-RAY BINARY LS I +61 303

    SciTech Connect

    Anderhub, H.; Biland, A.; Antonelli, L. A.; Antoranz, P.; Balestra, S.; Barrio, J. A.; Backes, M.; Becker, J. K.; Baixeras, C.; Bastieri, D.; Bock, R. K.; Gonzalez, J. Becerra; Bednarek, W.; Berger, K.; Bernardini, E.; Bigas, O. Blanch; Bonnoli, G.; Bordas, P.; Bosch-Ramon, V.; Tridon, D. Borla E-mail: jogler@mppmu.mpg.d

    2009-11-20

    The discovery of very high energy (VHE) gamma-ray emitting X-ray binaries has triggered an intense effort to better understand the particle acceleration, absorption, and emission mechanisms in compact binary systems, which provide variable conditions along eccentric orbits. Despite this, the nature of some of these systems, and of the accelerated particles producing the VHE emission, is unclear. To answer some of these open questions, we conducted a multiwavelength campaign of the VHE gamma-ray emitting X-ray binary LS I +61 303 including the MAGIC telescope, XMM-Newton, and Swift during 60% of an orbit in 2007 September. We detect a simultaneous outburst at X-ray and VHE bands, with the peak at phase 0.62 and a similar shape at both wavelengths. A linear fit to the simultaneous X-ray/VHE pairs obtained during the outburst yields a correlation coefficient of r = 0.97, while a linear fit to all simultaneous pairs provides r = 0.81. Since a variable absorption of the VHE emission towards the observer is not expected for the data reported here, the correlation found indicates a simultaneity in the emission processes. Assuming that they are dominated by a single particle population, either hadronic or leptonic, the X-ray/VHE flux ratio favors leptonic models. This fact, together with the detected photon indices, suggests that in LS I +61 303 the X-rays are the result of synchrotron radiation of the same electrons that produce VHE emission as a result of inverse Compton scattering of stellar photons.

  15. Influence of gamma-irradiation sterilization and temperature on the fracture toughness of ultra-high-molecular-weight polyethylene.

    PubMed

    Pascaud, R S; Evans, W T; McCullagh, P J; FitzPatrick, D P

    1997-05-01

    Surface damage of the tibial plateau components of knee prostheses made from medical grade ultra-high-molecular-weight polyethylene (UHMW-PE) has been attributed to delamination wear caused by a fatigue fracture mechanism. It has been proposed that factors such as component design and method of sterilization contribute to such failure mechanisms. Understanding the fracture behaviour of UHMW-PE is therefore critical in optimizing the in vivo life-span of total joint components. The elastic-plastic fracture toughness parameter J was consequently determined for a commercial UHMW-PE at ambient and body temperatures, before and after gamma-irradiation sterilization in air at a minimum dose of 29 kGy. Both ductile stability theory and experimental data suggest that cracks propagate in a stable manner, although stability is affected by the sterilization process. Sterilization with gamma-irradiation results in a loss in fracture toughness JIc of 50% and a decrease in tearing modulus (Tm) of 30%. This dramatic reduction could result in a 50% decrease in the residual strength of the components, maximum permissible crack size under service loading and service life (assuming flaws such as fusion defects exist). The time required for a crack to grow from its original size to the maximum permissible size could be decreased by 30%, resulting in earlier failure. In terms of the design of joint replacement components the critical factor to envisage is the design stress level, which should be halved to account for the irradiation process. A scanning electron microscope study reveals that the material fails in layers parallel to the fracture surface. PMID:9158855

  16. Correlated X-Ray and Very High Energy Emission in the Gamma-Ray Binary LS I +61 303

    NASA Astrophysics Data System (ADS)

    Anderhub, H.; Antonelli, L. A.; Antoranz, P.; Backes, M.; Baixeras, C.; Balestra, S.; Barrio, J. A.; Bastieri, D.; Becerra González, J.; Becker, J. K.; Bednarek, W.; Berger, K.; Bernardini, E.; Biland, A.; Blanch Bigas, O.; Bock, R. K.; Bonnoli, G.; Bordas, P.; Borla Tridon, D.; Bosch-Ramon, V.; Bose, D.; Braun, I.; Bretz, T.; Britzger, D.; Camara, M.; Carmona, E.; Carosi, A.; Colin, P.; Commichau, S.; Contreras, J. L.; Cortina, J.; Costado, M. T.; Covino, S.; Dazzi, F.; De Angelis, A.; de Cea del Pozo, E.; De los Reyes, R.; De Lotto, B.; De Maria, M.; De Sabata, F.; Delgado Mendez, C.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Elsaesser, D.; Errando, M.; Ferenc, D.; Fernández, E.; Firpo, R.; Fonseca, M. V.; Font, L.; Galante, N.; García López, R. J.; Garczarczyk, M.; Gaug, M.; Godinovic, N.; Goebel, F.; Hadasch, D.; Herrero, A.; Hildebrand, D.; Höhne-Mönch, D.; Hose, J.; Hrupec, D.; Hsu, C. C.; Jogler, T.; Klepser, S.; Kranich, D.; La Barbera, A.; Laille, A.; Leonardo, E.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; Lorenz, E.; Majumdar, P.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Meucci, M.; Miranda, J. M.; Mirzoyan, R.; Miyamoto, H.; Moldón, J.; Moles, M.; Moralejo, A.; Nieto, D.; Nilsson, K.; Ninkovic, J.; Orito, R.; Oya, I.; Paoletti, R.; Paredes, J. M.; Pasanen, M.; Pascoli, D.; Pauss, F.; Pegna, R. G.; Perez-Torres, M. A.; Persic, M.; Peruzzo, L.; Prada, F.; Prandini, E.; Puchades, N.; Puljak, I.; Reichardt, I.; Rhode, W.; Ribó, M.; Rico, J.; Rissi, M.; Robert, A.; Rügamer, S.; Saggion, A.; Saito, T. Y.; Salvati, M.; Sánchez-Conde, M.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schweizer, T.; Shayduk, M.; Shore, S. N.; Sidro, N.; Sierpowska-Bartosik, A.; Sillanpää, A.; Sitarek, J.; Sobczynska, D.; Spanier, F.; Spiro, S.; Stamerra, A.; Stark, L. S.; Suric, T.; Takalo, L.; Tavecchio, F.; Temnikov, P.; Tescaro, D.; Teshima, M.; Torres, D. F.; Turini, N.; Vankov, H.; Wagner, R. M.; Zabalza, V.; Zandanel, F.; Zanin, R.; Zapatero, J.; MAGIC Collaboration; Falcone, A.; Vetere, L.; Gehrels, N.; Trushkin, S.; Dhawan, V.; Reig, P.

    2009-11-01

    The discovery of very high energy (VHE) gamma-ray emitting X-ray binaries has triggered an intense effort to better understand the particle acceleration, absorption, and emission mechanisms in compact binary systems, which provide variable conditions along eccentric orbits. Despite this, the nature of some of these systems, and of the accelerated particles producing the VHE emission, is unclear. To answer some of these open questions, we conducted a multiwavelength campaign of the VHE gamma-ray emitting X-ray binary LS I +61 303 including the MAGIC telescope, XMM-Newton, and Swift during 60% of an orbit in 2007 September. We detect a simultaneous outburst at X-ray and VHE bands, with the peak at phase 0.62 and a similar shape at both wavelengths. A linear fit to the simultaneous X-ray/VHE pairs obtained during the outburst yields a correlation coefficient of r = 0.97, while a linear fit to all simultaneous pairs provides r = 0.81. Since a variable absorption of the VHE emission towards the observer is not expected for the data reported here, the correlation found indicates a simultaneity in the emission processes. Assuming that they are dominated by a single particle population, either hadronic or leptonic, the X-ray/VHE flux ratio favors leptonic models. This fact, together with the detected photon indices, suggests that in LS I +61 303 the X-rays are the result of synchrotron radiation of the same electrons that produce VHE emission as a result of inverse Compton scattering of stellar photons.

  17. Gamma-ray and neutrino backgrounds as probes of the high-energy universe: hints of cascades, general constraints, and implications for TeV searches

    SciTech Connect

    Murase, Kohta; Beacom, John F.; Takami, Hajime E-mail: beacom.7@osu.edu

    2012-08-01

    Recent observations of isotropic diffuse backgrounds by Fermi and IceCube allow us to get more insight into distant very-high-energy (VHE) and ultra-high-energy (UHE) gamma-ray/neutrino emitters, including cosmic-ray accelerators/sources. First, we investigate the contribution of intergalactic cascades induced by gamma-rays and/or cosmic rays (CRs) to the diffuse gamma-ray background (DGB) in view of the latest Fermi data. We identify a possible 'VHE Excess' from the fact that the Fermi data are well above expectations for an attenuated power law, and show that cascades induced by VHE gamma rays (above ∼ 10 TeV) and/or VHECRs (below ∼ 10{sup 19} eV) may significantly contribute to the DGB above ∼ 100 GeV. The relevance of the cascades is also motivated by the intergalactic cascade interpretations of extreme TeV blazars such as 1ES 0229+200, which suggest very hard intrinsic spectra. This strengthens the importance of future detailed VHE DGB measurements. Then, more conservatively, we derive general constraints on the cosmic energy budget of high-energy gamma rays and neutrinos based on recent Fermi and IceCube observations of extragalactic background radiation. We demonstrate that these multi-messenger constraints are useful and the neutrino limit is very powerful for VHE/UHE hadronic sources. Furthermore, we show the importance of constraints from individual source surveys by future imaging atmospheric Cherenkov telescopes such as Cherenkov Telescope Array, and demonstrate that the cascade hypothesis for the VHE DGB can be tested by searching for distant emitters of cascaded gamma rays.

  18. Characterization of the promoter of the human gene encoding the high-affinity IgG receptor: Transcriptional induction by. gamma. -interferon is mediated through common DNA response elements

    SciTech Connect

    Pearse, R.N.; Feinman, R.; Ravetch, J.V. )

    1991-12-15

    Expression of the high-affinity receptor for IgG (Fc{sub {gamma}}RI) is restricted to cells of myeloid lineage and is induced by {gamma}-interferon (IFN-{gamma}) but not by IFN-{alpha}/{beta}. The organization of the human Fc{sub {gamma}}RI gene has been determined and the DNA elements governing its cell type-restricted transcription and IFN-{gamma} induction are reported here. A 39-nucleotide sequence (IFN-{gamma} response region, or GRR) is defined that is both necessary and sufficient for IFN-{gamma} inducibility. Sequence analysis of the GRR reveals the presence of promoter elements initially defined for the major histocompatibility complex class 2 genes: i.e., X, H, and {gamma}-IRE sequences. Comparison of a number of genes whose expression is induced selectively by IFN-{gamma} indicated that the presence of these elements is a general feature of IFN-{gamma}-responsive genes. The studies suggest that the combination of X, H, and {gamma}-IRE elements is a common motif in the pathway of transcriptional induction by this lymphokine.

  19. The Swift gamma-ray burst redshift distribution: selection biases and optical brightness evolution at high z?

    NASA Astrophysics Data System (ADS)

    Coward, D. M.; Howell, E. J.; Branchesi, M.; Stratta, G.; Guetta, D.; Gendre, B.; Macpherson, D.

    2013-07-01

    We employ realistic constraints on astrophysical and instrumental selection effects to model the gamma-ray burst (GRB) redshift distribution using Swift triggered redshift samples acquired from optical afterglows and The Optically Unbiased GRB Host survey. Models for the Malmquist bias, redshift desert, and the fraction of afterglows missing because of host galaxy dust extinction are used to show how the `true' GRB redshift distribution is distorted to its presently observed biased distribution. We also investigate another selection effect arising from a correlation between Eiso and Lopt. The analysis, which accounts for the missing fraction of redshifts in the two data subsets, shows that a combination of selection effects (both instrumental and astrophysical) can describe the observed GRB redshift distribution. Furthermore, the observed distribution is compatible with a GRB rate evolution that tracks the global star formation rate, although the rate at high z cannot be constrained with confidence. Taking optical selection effects into account, it may not be necessary to invoke high-energy GRB luminosity evolution with redshift to explain the observed GRB rate at high z.

  20. Fermi LAT detection of increasing GeV gamma-ray activity from the high-energy peaked BL Lac object 1ES 1959+650

    NASA Astrophysics Data System (ADS)

    Ciprini, Stefano; Fermi Large Area Telescope Collaboration

    2015-10-01

    The Large Area Telescope (LAT), one of two instruments on the Fermi Gamma-ray Space Telescope, has observed increasing gamma-ray emission from a source positionally consistent with the very-high energy peaked BL Lac object 1ES 1959+650 (also known as TXS 1959+650 and 3FGL J2000.0+6509, Acero et al. 2015, ApJS 218, 23) with radio coordinates (J2000) R.A.: 299.999384 deg, Dec.: 65.148514 deg (Beasley et al. 2002, ApJS, 141, 13). This source has a redshift z=0.047 (Schachter et al. 1993, ApJ, 412, 541).