Sample records for ultrahigh resolution gamma-ray

  1. A Liquid-Cryogen-Free Cryostat for Ultrahigh Resolution Gamma-Ray Spectrometers

    SciTech Connect

    Dreyer, J G; Hertrich, T; Drury, O B; Hohne, J; Friedrich, S

    2008-06-30

    We are developing ultra-high energy resolution gamma-ray detectors based on superconducting transition edge sensors (TESs) for nuclear non-proliferation and fundamental science applications. They use bulk tin absorbers attached to molybdenum-copper multilayer TESs, and have achieved an energy resolution between 50 and 90 eV FWHM for gamma-ray energies below 122 keV. For increased user-friendliness, we have built a cryostat that attains the required detector operating temperature of 0.1 K at the push of a button without the use of cryogenic liquids. It uses a two-stage mechanical pulse tube refrigerator for precooling to {approx}3 K, and a two-stage adiabatic demagnetization refrigerator for cooling to the base temperature. The cryostat is fully automated, attains a base temperature below 30 mK without the use of cryogenic liquids, and has a hold time of {approx}2 days at 0.1 K between 1-hour demagnetization cycles. Here we discuss the performance of the cryostat for operation in a Gamma-spectrometer with 112-pixel arrays of superconducting TES detectors.

  2. Ultrahigh resolution gamma-ray spectrometer development for nuclear attribution and non-proliferation applications

    Microsoft Academic Search

    Stephane F. Terracol; Shafinaz Ali; I. Niedermayr; D. Hau; Owen B. Drury; Zaheer A. Ali; Toshiyuki Miyazaki; Mark F. Cunningham; Jonathan G. Dreyer; John D. Leacock; Stephan Friedrich

    2004-01-01

    Cryogenic gamma-ray spectrometers based on superconducting thermistors provide more than an order of magnitude improvement in energy resolution over conventional high-purity germanium detectors. They are based on measuring the temperature increase upon gamma-ray absorption with a sensor operated at the transition between its superconducting and normal state. We are developing gamma-ray calorimeters using Mo\\/Cu multilayer sensors with an attached Sn

  3. The gamma ray content of ultrahigh energy cosmic radiation

    SciTech Connect

    Kolodziejczak, J.J.

    1990-01-01

    Data from the Utah-Michigan (UM) extensive air shower (EAS) array at Dugway, Utah are examined for evidence of a gamma ray component in the UHE cosmic rays. The UM array consist of a 3 {times} 10{sup 4} sq m surface array with 40 sq m of charged particle detectors, and a 1200 sq m buried array for detecting muons. Data from the large muon array are used to search for a gamma ray signature, since gamma rays are expected to produce far fewer muons in EAS than hadronic cosmic ray primaries. When no evidence for gamma rays is found, limits are set based on expected gamma ray behavior. For a photon energy threshold of 200 TeV, results include: a limit on the omnidirectional gamma ray fraction of cosmic rays at 0.2 pct; a limit on the galactic gamma ray fraction of cosmic rays at 7 {times} 10{sup {minus}5}; no strong evidence for enduring gamma ray point sources at fluxes approx. = 4 {times} 10{sup {minus}14}/sq cm/s; and no strong evidence for bursts on a one day time scale at a flux sensitivity {approx} 2 {times} 10{sup {minus}12}/sq cm/s. These limits and measurements are based on muon poor data. While no strong signal of UHE gamma rays is found, future application to the large Chicago Air Shower Array-Michigan Array (CASA-MIA) is possible.

  4. The GAMMA-400 gamma-ray telescope angular resolution

    NASA Astrophysics Data System (ADS)

    Kheymits, Maxim; Leonov, Alexey

    The measurements of gamma-ray fluxes and cosmic-ray electrons and positrons in the energy range from 100 MeV to several TeV, which will be realized by the specially designed GAMMA-400 gamma-ray telescope, concern with the following broad range of science topics. Search for signatures of dark matter, surveying the celestial sphere in order to study point and extended sources of gamma-rays, measuring the energy spectra of Galactic and extragalactic diffuse gamma-ray emission, study of gamma-ray bursts and gamma-ray emission from the Sun. To clarify these scientific problems with the new experimental data the GAMMA-400 gamma-ray telescope possesses unique physical characteristics comparing with previous and present experiments. For gamma-ray energies more than 100 GeV GAMMA-400 provides the energy resolution nearby 1% and angular resolution better than 0.02 deg. The methods, developed to reconstruct the direction of incident gamma photon, are presented in this paper. The main point concerns with the space topology of high energy gamma photon interaction in the matter of GAMMA-400. Multiple secondary particles, generated inside gamma-ray telescope, produce significant problems to restore the direction of initial gamma photon. Also back-splash particles, i.e., charged particles and gamma photons generated in calorimeter and moved upward, mask the initial tracks of electron/positron pair from conversion of incident gamma photon. The processed methods allow us to reconstruct the direction of electromagnetic shower axis and extract the electron/positron trace. As a result, the direction of incident gamma photon with the energy of 100 GeV is calculated with an accuracy of more than 0.02 deg.

  5. PANGU: A high resolution gamma-ray space telescope

    NASA Astrophysics Data System (ADS)

    Wu, Xin; Su, Meng; Bravar, Alessandro; Chang, Jin; Fan, Yizhong; Pohl, Martin; Walter, Roland

    2014-07-01

    We describe the instrument concept of a high angular resolution telescope dedicated to the sub-GeV (from >=10 MeV to >=1 GeV) gamma-ray photon detection. This mission, named PANGU (PAir-productioN Gamma-ray Unit), has been suggested as a candidate for the joint small mission between the European Space Agency (ESA) and the Chinese Academy of Science (CAS). A wide range of topics of both astronomy and fundamental physics can be attacked with PANGU, covering Galactic and extragalactic cosmic-ray physics, extreme physics of a variety of extended (e.g. supernova remnants, galaxies, galaxy clusters) and compact (e.g. black holes, pulsars, gamma-ray bursts) objects, solar and terrestrial gamma-ray phenomena, and searching for dark matter decay and/or annihilation signature etc. The unprecedented point spread function can be achieved with a pair-production telescope with a large number of thin active tracking layers to precisely reconstruct the pair-produced electron and positron tracks. Scintillating fibers or thin silicon micro-strip detectors are suitable technology for such a tracker. The energy measurement is achieved by measuring the momentum of the electrons and positrons through a magnetic field. The innovated spectrometer approach provides superior photon pointing resolution, and is particular suitable in the sub-GeV range. The level of tracking precision makes it possible to measure the polarization of gamma rays, which would open up a new frontier in gamma-ray astronomy. The frequent full-sky survey at sub-GeV with PANGU's large field of view and significantly improved point spread function would provide crucial information to GeV-TeV astrophysics for current/future missions including Fermi, DAMPE, HERD, and CTA, and other multi-wavelength telescopes.

  6. PANGU: A High Resolution Gamma-Ray Space Telescope

    NASA Astrophysics Data System (ADS)

    Su, Meng

    2014-08-01

    We propose a high angular resolution telescope dedicated to the sub-GeV gamma-ray astronomy as a candidate for the CAS-ESA joint small mission. This mission, called PANGU (PAir-productioN Gamma-ray Unit), will open up a unique window of electromagnetic spectrum that has never been explored with great precision. A wide range of topics of both astronomy and fundamental physics can be attacked with a telescope that has an angular resolution about one order of magnitude better than the currently operating Fermi Gamma-ray Space Telescope (Fermi) in the sub-GeV range, covering galactic and extragalactic cosmic-ray physics, extreme physics of a variety of extended (e.g. supernova remnants, galaxies, galaxy clusters) and compact (e.g. black holes, pulsars, gamma-ray bursts) objects, solar and terrestrial gamma-ray phenomena, and searching for Dark Matter (DM) decay and/or annihilation signature etc. The unprecedented resolution can be achieved with a pair-production telescope that, instead of the high-Z converter commonly used, relies on a large number of thin active tracking layers to increase the photon conversion probability, and to precisely reconstruct the pair-produced electron and positron tracks. Scintillating fibers or thin silicon micro-strip detectors are suitable technology for such a tracker. The energy measurement is achieved by measuring the momentum of the electrons and positrons through a magnetic field. The innovated spectrometer approach provides superior photon conversion identification and photon pointing resolution, and is particular suitable in the sub-GeV range, where the opening angle between the electron and positron is relatively large. The level of tracking precision makes it possible to measure the polarization of gamma rays, which would open up a new frontier in gamma-ray astronomy. The sub-GeV full sky survey by PANGU would provides crucial link with GeV to TeV maps from current/future missions including Fermi, DAMPE, HERD, and CTA.

  7. High-Resolution Spectroscopy of Gamma-Ray Bursts with the Transient Gamma-Ray Spectrometer

    NASA Astrophysics Data System (ADS)

    Kurczynski, P.; Palmer, D.; Seifert, H.; Teegarden, B. J.; Gehrels, N.; Cline, T. L.; Ramaty, R.; Hurley, K.; Madden, N. W.; Pehl, R. H.

    2000-11-01

    A search for spectral lines in gamma-ray bursts detected with the Transient Gamma-Ray Spectrometer has been unable to confirm their existence. The spectrometer, aboard the Wind spacecraft, has detected gamma-ray bursts and other transients since 1995. We have performed a systematic search for narrow spectral lines in gamma-ray bursts detected with this instrument that augments and extends the results of a similar search of bursts detected with BATSE. This search procedure tests for statistically significant lines at all possible times and durations during a burst using the method of maximum likelihood and C-statistic. Simulations demonstrated the effectiveness of this procedure, particularly on Poisson distributed data, for distinguishing real features from statistical fluctuations. The most promising line candidates were consistent with chance fluctuations, given the large number of spectra searched.

  8. Ultra-high energy cosmic rays and the extragalactic gamma ray flux

    E-print Network

    Erlykin, A D

    2014-01-01

    Ultra-high energy cosmic rays interacting with the radiation fields in the universe cause electromagnetic cascades resulting in a flux of extragalactic gamma rays, detectable to some 100 GeV. Recent precise measurements of the extragalactic gamma ray flux by Fermi-LAT, coupled with estimates of the background from active galactic nuclei of various types, allows limits to be set on the cascade component. By comparison with prediction and, making various assumptions, ie taking a particular model, limits can be set on the maximum energy to which ultra-high energy particle can be accelerated. If our model is correct, it is unlikely that the maximum energy is above 100 EeV, in turn, the apparent 'GZK' cut-off in the measured ultra-high energy spectrum could instead be due to a fall-off in the intrinsic emergent particle spectrum. However, it is not plausible to be dogmatic at the present time because of uncertainty in many of the parameters involved. We have used recent estimates of the range of parameters and hav...

  9. Pointlike gamma ray sources as signatures of distant accelerators of ultrahigh energy cosmic rays.

    PubMed

    Gabici, Stefano; Aharonian, Felix A

    2005-12-16

    We discuss the possibility of observing distant accelerators of ultrahigh energy cosmic rays in synchrotron gamma rays. Protons propagating away from their acceleration sites produce extremely energetic electrons during photopion interactions with cosmic microwave background photons. If the accelerator is embedded in a magnetized region, these electrons will emit high energy synchrotron radiation. The resulting synchrotron source is expected to be pointlike, steady, and detectable in the GeV-TeV energy range if the magnetic field is at the nanoGauss level. PMID:16384444

  10. 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.

  11. On the spectrum of Ultrahigh Energy Cosmic Rays and the Gamma Ray Burst Origin Hypothesis

    E-print Network

    S. T. Scully; F. W. Stecker

    2001-03-21

    It has been suggested that cosmological gamma-ray bursts (GRBs) can produce the observed flux of cosmic rays at the highest energies. However, recent studies of GRBs indicate that their redshift distribution likely follows that of the average star formation rate and that GRBs were more numerous at high redshifts. As a consequence, we show that photomeson production energy losses suffered by ultrahigh energy cosmic rays coming from GRBs would produce too sharp a spectral high energy cutoff to be consistent with the air shower data. Furthermore, we show that cosmological GRBs fail to supply the energy input required to account for the cosmic ray flux above 10 EeV by a factor of 100-1000.

  12. Very-high-energy gamma-ray signal from nuclear photodisintegration as a probe of extragalactic sources of ultrahigh-energy nuclei

    SciTech Connect

    Murase, Kohta [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto, 606-8502 (Japan); CCAPP, Ohio State University, Columbus, Ohio 43210 (United States); Beacom, John F. [CCAPP, Ohio State University, Columbus, Ohio 43210 (United States); Department of Physics, Ohio State University, Columbus, Ohio 43210 (United States); Department of Astronomy, Ohio State University, Columbus, Ohio 43210 (United States)

    2010-08-15

    It is crucial to identify the ultrahigh-energy cosmic-ray sources and probe their unknown properties. Recent results from the Pierre Auger Observatory favor a heavy nuclear composition for the ultrahigh-energy cosmic rays. Under the requirement that heavy nuclei survive in these sources, using gamma-ray bursts as an example, we predict a diagnostic gamma-ray signal, unique to nuclei--the emission of deexcitation gamma rays following photodisintegration. These gamma rays, boosted from MeV to TeV-PeV energies, may be detectable by gamma-ray telescopes such as VERITAS, HESS, and MAGIC, and especially the next-generation CTA and AGIS. They are a promising messenger to identify and study individual ultrahigh-energy nuclei accelerators.

  13. CONSTRAINING THE EMISSIVITY OF ULTRAHIGH ENERGY COSMIC RAYS IN THE DISTANT UNIVERSE WITH THE DIFFUSE GAMMA-RAY EMISSION

    SciTech Connect

    Wang Xiangyu; Liu Ruoyu [Department of Astronomy, Nanjing University, Nanjing 210093 (China); Aharonian, Felix [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany)

    2011-08-01

    Ultrahigh cosmic rays (UHECRs) with energies {approx}> 10{sup 19} eV emitted at cosmological distances will be attenuated by cosmic microwave and infrared background radiation through photohadronic processes. Lower energy extragalactic cosmic rays ({approx}10{sup 18}-10{sup 19} eV) can only travel a linear distance smaller than {approx}Gpc in a Hubble time due to the diffusion if the extragalactic magnetic fields are as strong as nano-Gauss. These prevent us from directly observing most of the UHECRs in the universe, and thus the observed UHECR intensity reflects only the emissivity in the nearby universe within hundreds of Mpc. However, UHECRs in the distant universe, through interactions with the cosmic background photons, produce UHE electrons and gamma rays that in turn initiate electromagnetic cascades on cosmic background photons. This secondary cascade radiation forms part of the extragalactic diffuse GeV-TeV gamma-ray radiation and, unlike the original UHECRs, is observable. Motivated by new measurements of extragalactic diffuse gamma-ray background radiation by Fermi/Large Area Telescope, we obtained upper limit placed on the UHECR emissivity in the distant universe by requiring that the cascade radiation they produce not exceed the observed levels. By comparison with the gamma-ray emissivity of candidate UHECR sources (such as gamma-ray bursts (GRBs) and active galactic nuclei) at high redshifts, we find that the obtained upper limit for a flat proton spectrum is {approx_equal} 10{sup 1.5} times larger than the gamma-ray emissivity in GRBs and {approx_equal} 10 times smaller than the gamma-ray emissivity in BL Lac objects. In the case of iron nuclei composition, the derived upper limit of UHECR emissivity is a factor of 3-5 times higher. Robust upper limit on the cosmogenic neutrino flux is further obtained, which is marginally reachable by the Icecube detector and the next-generation detector JEM-EUSO.

  14. Simulating gamma-ray energy resolution in scintillators due to electron–hole pair statistics

    Microsoft Academic Search

    R. D. Narayan; R. Miranda; P. Rez

    2011-01-01

    The best-possible limit to gamma-ray energy resolution in scintillators is given by the statistics of the number of electron–hole pairs produced by an incident gamma-ray, characterized by the Fano factor. The Fano factor is primarily controlled by the inelastic scattering during the electron cascade, which could be modeled by Monte Carlo simulation. Commonly used radiation transport codes do not follow

  15. High resolution, in situ, gamma-ray spectrometry procedures manual

    Microsoft Academic Search

    Sautter

    1987-01-01

    Procedures used for environmental in situ gamma-ray spectroscopy of the Los Alamos National Laboratory are documented. These procedures are based on techniques developed at other laboratories, principally by H.L. Beck et al., of the Department of Energy's Environmental Measurements Laboratory. The procedures are limited to use of large-volume, lithium-drifted or high-purity germanium diode detectors for quantification of the contributions of

  16. 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.

  17. Search for very high energy gamma rays from possible ultra-high energy cosmic ray sources by the MAGIC Telescope

    E-print Network

    K. Shinozaki; M. Teshima; for the MAGIC Collaboration

    2007-09-17

    The origin of ultra-high energy (UHE) cosmic rays is still an open question. In the present work, we searched the possible UHE cosmic ray sources using the MAGIC telescope for the associated very high energy (VHE) gamma ray emission. Due to constrained propagation distance of such cosmic rays, we selected nearby galaxies in vicinity of the direction of the AGASA triplet and a HiRes UHE cosmic ray event: NGC 3610 and NGC 3613 (quasar remnants); Arp 299 (a system of colliding galaxies). No significant excess in the VHE region was found found from these objects or their surrounding region. At multi-100 GeV regime, the upper limits on fluxes were given against gamma ray sources in surrounding region. The presented limits constrain the flux of a new hypothetical source in the region, provided the cosmic rays are emitted from a single point-like origin.

  18. Very-High-Energy Gamma-Ray Signal from Nuclear Photodisintegration as a Probe of Extragalactic Sources of Ultrahigh-Energy Nuclei

    E-print Network

    Kohta Murase; John F. Beacom

    2010-07-29

    It is crucial to identify the ultrahigh-energy cosmic-ray (UHECR) sources and probe their unknown properties. Recent results from the Pierre Auger Observatory favor a heavy nuclear composition for the UHECRs. Under the requirement that heavy nuclei survive in these sources, using gamma-ray bursts as an example, we predict a diagnostic gamma-ray signal, unique to nuclei - the emission of de-excitation gamma rays following photodisintegration. These gamma rays, boosted from MeV to TeV-PeV energies, may be detectable by gamma-ray telescopes such as VERITAS, HESS, and MAGIC, and especially the next-generation CTA and AGIS. They are a promising messenger to identify and study individual UHE nuclei accelerators.

  19. Development of Superconducting High-Resolution Gamma-Ray Spectrometers for Nuclear Safeguards

    NASA Astrophysics Data System (ADS)

    Dreyer, Jonathan Glen

    Superconducting high-resolution gamma-ray spectrometers based on molybdenum/ copper transition edge sensors (TES) with tin absorbers have been developed for nuclear safeguard applications. This dissertation focuses on plutonium analysis, specifically the direct measurement of the 242Pu gamma-ray signature at 44.915 keV. As existing nondestructive analysis methods cannot directly measure this or any other 242Pu signature, the feasibility of making such a measurement using a TES based system is presented. Analysis from of Monte Carlo simulations and analytical noise models shows that the direct detection of this gamma-ray line of is possible and can be quantified in the presence of a 240Pu gamma-ray line with a line separation of 324 eV, even if the emission from the 240Pu is several orders of magnitude stronger. Spectroscopic measurements conducted in a liquid cryogen system offered an energy resolution of 180 eV, adequate for the measurement of 242Pu; however, TES operation in a liquid-cryogen-free pulse tube refrigerator degraded sensor performance such that this measurement was no longer possible. The numerical noise model indicates that the energy resolution of this device is adequate to demonstrate a direct measurement of 242Pu if the noise pickup from the mechanical cooler can be suppressed. This work shows that the precise measurement of low-intensity gamma-ray signatures, such as the 44.915 keV gamma ray from 242Pu, will require arrays of low-noise TES sensors and that such a system would offer invaluable information in the analysis of plutonium bearing materials.

  20. Gamma ray spectroscopy at high energy and high time resolution at JET

    SciTech Connect

    Tardocchi, M.; Proverbio, L. I.; Gorini, G.; Grosso, G.; Locatelli, M. [Universita degli Studi di Milano-Bicoccae Istituto di Fisica del Plasma, EURATOM-ENEA-CNR Association, I-20125 Milan (Italy); Chugonov, I. N.; Gin, D. B.; Shevelev, A. E. [A. F. Ioffe Physico-Technical Institute, St. Petersburg 194021 (Russian Federation); Murari, A.; Kiptily, V. G.; Syme, B. [EURATOM-UKAEA Association, Culham Science Centre, OX14 3DB Abingdon (United Kingdom); Fernandes, A. M.; Pereira, R. C.; Sousa, J. [Associacao EURATOM/IST Centro de Fusao Nuclear, Instituto Superior Tecnico, 1049-001 Lisboa (Portugal)

    2008-10-15

    In fusion plasmas gamma ray emission is caused by reactions of fast particles, such as fusion alpha particles, with impurities. Gamma ray spectroscopy at JET has provided valuable diagnostic information on fast fuel as well as fusion product ions. Improvements of these measurements are needed to fully exploit the flux increase provided by future high power experiments at JET and ITER. Limiting aspects are, for instance, the count rate capability due to a high neutron/gamma background combined with slow detector response and a modest energy resolution due to the low light yield of the scintillators. This paper describes the solutions developed for achieving higher energy resolution, signal to background, and time resolution. The detector design is described based on the new BrLa{sub 3} scintillator crystal. The paper will focus on hardware development, including a photomultiplier tube capable of stable operation at counting rate as high as 1 MHz, the magnetic shielding, and the fast digital data acquisition system.

  1. Compact high-resolution gamma-ray computed tomography system for multiphase flow studies

    SciTech Connect

    Bieberle, A.; Nehring, H.; Berger, R.; Arlit, M.; Haerting, H.-U.; Schubert, M. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Fluid Dynamics, Bautzner Landstrasse 400, 01328 Dresden (Germany); Hampel, U. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Fluid Dynamics, Bautzner Landstrasse 400, 01328 Dresden (Germany); Technische Universitaet Dresden, AREVA Endowed Chair of Imaging Techniques in Energy and Process Engineering, 01062 Dresden (Germany)

    2013-03-15

    In this paper, a compact high-resolution gamma-ray Computed Tomography (CompaCT) measurement system for multiphase flow studies and tomographic imaging of technical objects is presented. Its compact and robust design makes it particularly suitable for studies on industrial facilities and outdoor applications. Special care has been given to thermal ruggedness, shock resistance, and radiation protection. Main components of the system are a collimated {sup 137}Cs isotopic source, a thermally stabilised modular high-resolution gamma-ray detector arc with 112 scintillation detector elements, and a transportable rotary unit. The CompaCT allows full CT scans of objects with a diameter of up to 130 mm and can be operated with any tilting angle from 0 Degree-Sign (horizontal) to 90 Degree-Sign (vertical).

  2. 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.

  3. High resolution GRB spectra from the Transient Gamma-Ray Spectrometer (TGRS)

    NASA Astrophysics Data System (ADS)

    Palmer, D. M.; Seifert, H.; Teegarden, B. J.; Gehrels, N.; Cline, T. L.; Ramaty, R.; Hurley, K.; Pehl, R.; Madden, N.; Owens, A.

    1996-08-01

    The Transient Gamma-Ray Spectrometer (TGRS) is a germanium spectrometer designed to produce high-resolution (2-3 keV) spectra of bright gamma-ray bursts. In its first year of operation it has triggered on 62 GRBs, of which ~33 were bright enough for spectroscopy. Almost all of these bursts were also seen by the Konus detectors on the same spacecraft, and about half were also observed by BATSE. This allows the instruments and their results to be compared and will allow line candidates seen by any of the instruments to be confirmed or refuted by the others. This paper presents some typical spectra from GRBs observed by TGRS, and includes for comparison the corresponding BATSE and Konus spectra.

  4. A transportable high-resolution gamma-ray spectrometer and analysis system applicable to mobile, autonomous or unattended applications

    Microsoft Academic Search

    W. M. Buckley; K. W. Neufeld

    1995-01-01

    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,

  5. X-ray interferometry with transmissive beam combiners for ultra-high angular resolution astronomy

    Microsoft Academic Search

    Gerald K. Skinner; John F. Krizmanic

    2009-01-01

    Interferometry provides one of the possible routes to ultra-high angular resolution for X-ray and gamma-ray astronomy. Sub-micro-arc-second angular resolution, necessary to achieve objectives such as imaging the regions around the event horizon of a super-massive black hole at the center of an active galaxy, can be achieved if beams from parts of the incoming wavefront separated by 100s of meters

  6. X-ray interferometry with transmissive beam combiners for ultra-high angular resolution astronomy

    Microsoft Academic Search

    Gerald K. Skinner; John F. Krizmanic

    2009-01-01

    Interferometry provides one of the possible routes to ultra-high angular resolution for X-ray and gamma-ray astronomy. Sub-micro-arc-second\\u000a angular resolution, necessary to achieve objectives such as imaging the regions around the event horizon of a super-massive\\u000a black hole at the center of an active galaxy, can be achieved if beams from parts of the incoming wavefront separated by 100s\\u000a of meters

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

    DOEpatents

    Smither, Robert K. (Hinsdale, IL)

    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.

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

    NASA Astrophysics Data System (ADS)

    Sandie, W. G.; Nakano, G. H.; Chase, L. F.; Fishman, G. J.; Meegan, C. A.; Wilson, R. B.; Paciesas, W. S.; Lashe, G. P.

    1988-09-01

    A balloon-borne gamma-ray spectrometer comprising an array of high-purity germanium (HPGE) detectors was flown from Alice Springs, Australia, on October 29-30-31, norminally 250 days after the observed neutrino pulse. High-resolution data, typically 2.5 keV at 1.33 MeV, for two transists of the supernova SN 1987A were obtained along with interspersed background data. A significant net flux of gamma rays with energy 847 keV was observed from the direction of SN 1987A on each transit. No prominent gamma-ray features were seen at other energies, although data analysis is still in progress. A preliminary estimate of the line flux at 847 keV is ~5×10-4 photons cm-2 s-1 with statistical significance greater than three sigma. This line may be interpreted as emission from the first excited state of 56Fe due to the radioactive decay of 56Co, providing strong evidence for nucleosynthesis in the supernova. No emission was seen from the second excited state of 56Fe at 1238 keV. A preliminary upper limit for the 1238-keV line is ~5×10-4 photons cm-2 s-1. The flux estimates may be considerably altered as the systematics of the experiment are better understood.

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

    USGS Publications Warehouse

    Day, J.H., Jr.

    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.

  10. A high-resolution gamma-ray and hard X-ray spectrometer for solar flare observations in Max 1991

    Microsoft Academic Search

    R. P. Lin; D. W. Curtis; P. Harvey; K. Hurley; J. H. Primbsch; D. M. Smith; R. M. Pelling; F. Duttweiler

    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

  11. High resolution CdTe detectors for the next-generation multi-Compton gamma-ray telescope

    Microsoft Academic Search

    Tadayuki Takahashi; Kazuhiro Nakazawa; Tuneyoshi Kamae; Hiroyasu Tajima; Yasushi Fukazawa; Masaharu Nomachi; Motohide Kokubun

    2003-01-01

    A multi-Compton gamma-ray telescope based on high resolution semiconductor materials (Semiconductor Multi-Compton Telescope (SMCT) or Advanced Compton Telescope (ACT)) is a promising approach to achieve high sensitivity for gamma-rays with energies from several hundred keV up to several MeV. A SMCT utilizing several tens of layers of thin CdTe (Cadmium Telluride) detector is an attractive concept to obtain higher detection

  12. 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.

  13. In situ subterranean determination of actinides by high-resolution gamma-ray spectrometry

    Microsoft Academic Search

    Brodzinski

    1981-01-01

    A system utilizing high resolution germanium diode gamma-ray spectroscopy for the simple, safe, and economical in situ determination of actinides is described. Six isotopes, ²³⁵U, ²³⁸U, ²³⁷Np, ²³⁹Pu, ²⁴¹Pu, and ²⁴¹Am, can be simultaneously measured at the 10 nCi g⁻¹ level in less than 7 minutes. Collimators provide for measurement of horizontal strata as thin as 1 cm or solid

  14. High resolution gamma-ray spectra for {sup 235}U(n{sub th},ff)

    SciTech Connect

    Pullen, D.J.; Campbell, J.M.; Couchell, G.P.; Li, Shengjie; Nguyen, Hung V.; Schier, W.A.; Seabury, E.H.; Tipnis, S.V. [Univ. of Massachusetts, Lowell, MA (United States); England, T.R. [Los Alamos National Lab., NM (United States)

    1994-12-31

    High-resolution gamma ray spectra from thermal fission of {sup 235}U have been measured for 21 delay time intervals in the range 0.2s to nearly 100,000s. More than 170 gamma transitions have so far been studied out to 1000s in 27 different fission products. Relative line intensities and time evolutions for the gamma lines provide information on relative production probabilities for fission products, direct-vs.-beta chain production ratios, isomeric to ground-state production ratios, as well as precursor halflives, for comparison with ENDF/B-VI.

  15. Hard X-ray and Gamma-ray Emission Induced by Ultra-High Energy Protons in Cluster Accretion Shocks

    E-print Network

    Susumu Inoue; Felix A. Aharonian; Naoshi Sugiyama

    2005-06-05

    All sufficiently massive clusters of galaxies are expected to be surrounded by strong accretion shocks, where protons can be accelerated to $\\sim 10^{18}$-$10^{19}$ eV under plausible conditions. Such protons interact with the cosmic microwave background and efficiently produce very high energy electron-positron pairs, which then radiate synchrotron and inverse Compton emission, peaking respectively at hard X-ray and TeV gamma-ray energies. Characterized by hard spectra (photon indices $\\sim 1.5$) and spatial distribution tracing the accretion shock, these can dominate over other nonthermal components depending on the shock magnetic field. HESS and other Cerenkov telescopes may detect the TeV emission from nearby clusters, notwithstanding its extended nature. The hard X-rays may be observable by future imaging facilities such as NeXT, and possibly also by ASTRO-E2/HXD. Such detections will not only provide a clear signature of ultra-high energy proton acceleration, but also an important probe of the accretion shock itself as well as magnetic fields in the outermost regions of clusters.

  16. Topics in gamma ray astronomy

    NASA Technical Reports Server (NTRS)

    Ramaty, R.; Lingenfelter, R. E.

    1986-01-01

    Observations of gamma rays from solar flares, gamma ray bursts, the Galactic center, galactic nucleosynthesis, SS433, and Cygnus X-3, and their effects on astrophysical problems are discussed. It is observed that gamma ray spectra from solar flares are applicable to the study of particle acceleration and confinement and the determination of chemical abundances in the solar atmosphere. The gamma ray lines from the compact galactic object SS433 are utilized to examine the acceleration of jets, and analysis of the gamma ray lines of Cygnus X-3 reveal that particles can be accelerated in compact sources to ultrahigh energies.

  17. 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.

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

    PubMed

    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 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. PMID:17979425

  19. A High-Resolution GE Spectrometer for Gamma-Ray Burst Astronomy

    NASA Astrophysics Data System (ADS)

    Owens, A.; Baker, R.; Cline, T. L.; Gehrels, N.; Jermakian, J.; Nolan, T.; Ramaty, R.; Seifert, H.; Shephard, D. A.; Smith, G.; Stilwell, D. E.; Teegarden, B. J.; Cork, C. P.; Landis, D. A.; Luke, P. N.; Madden, N. W.; Malone, D.; Pehl, R. H.; Yaver, H.; Hurley, K.; Mathias, S.; Post, A. H., Jr.

    1995-02-01

    The Transient Gamma-Ray Spectrometer (TGRS) to be flown aboard the WIND spacecraft is primarily designed to perform high resolution spectroscopy of transient ?-ray events, such as cosmic ?-ray bursts and solar flares over the energy range 25 keV to 8.2 MeV with an expected spectroscopic resolution of ˜ 3 keV at 1 MeV. The detector itself consists of a 215 cm3 high purityn-type Ge crystal kept at cryogenic temperatures by a passive radiative cooler. The geometric field of view defined by the cooler is ˜ 1.8 ? steradian. To avoid continuous triggers by soft solar events, a thin BeCu Sun-shield around the sides of the cooler has been provided. A passive Mo/Pb occulter, which modulates signals from within ±5° of the ecliptic plane at the spacecraft spin frequency, is used to identify and study solar flares, as well as emission from the galactic plane and center. Thus, in addition to transient event measurements, the instrument will allow the search for possible diffuse background lines and monitor the 511 keV positron annihilation radiation from the galactic center. In order to handle the typically large burst count rates, which can be in excess of 100 kHz, burst data are stored directly in an onboard 2.75 Mbit burst memory with an absolute timing accuracy of ±1.5 ms after ground processing. The memory is capable of storing the entire spectral data set of all but the largest bursts. WIND is scheduled to be launched on a Delta II launch vehicle from Cape Canaveral on November 1, 1994. After injection into a phasing orbit, the spacecraft will execute a double lunar swing-by before being moved into a controlled ‘halo’ orbit about theL1 Lagrangian point (˜250R e towards the Sun). This will provide a 5 light-second light travel time with which to triangulate gamma-ray burst sources with Earth-orbiting systems, such as those on-board the Gamma-Ray Observatory (GRO). The response of instrument to transient ?-ray events such as GRB's and solar flares will be presented as well as the expected response to steady state point sources and galactic center line emission.

  20. Constraints on the Ultra-High Energy Neutrino Flux from Gamma-Ray Bursts from a Prototype Station of the Askaryan Radio Array

    E-print Network

    Allison, P; Bard, R; Beatty, J J; Besson, D Z; Bora, C; Chen, C -C; Chen, P; Connolly, A; Davies, J P; DuVernois, M A; Fox, B; Gorham, P W; Hanson, K; Hill, B; Hoffman, K D; Hong, E; Hu, L -C; Ishihara, A; Karle, A; Kelley, J; Kravchenko, I; Landsman, H; Laundrie, A; Li, C -J; Liu, T; Lu, M -Y; Maunu, R; Mase, K; Meures, T; Miki, C; Nam, J; Nichol, R J; Nir, G; O'Murchadha, A; Pfendner, C G; Ratzlaff, K; Richman, M; Rotter, B; Sandstrom, P; Seckel, D; Shultz, A; Song, M; Stockham, J; Stockham, M; Sullivan, M; Touart, J; Tu, H -Y; Varner, G S; Yoshida, S; Young, R; Guetta, D

    2015-01-01

    We searched for ultra-high energy (UHE) neutrinos from Gamma-Ray Bursts (GRBs) with the Askaryan Radio Array (ARA) Testbed station's 2011-2012 data set. Among 589 GRBs monitored by the Gamma Ray Coordinate Network (GCN) catalog from Jan. 2011 to Dec. 2012 over the entire sky, 57 GRBs were selected for analysis. These GRBs were chosen because they occurred during a period of low anthropogenic background and high stability of the station and fell within our geometric acceptance. We searched for UHE neutrinos from 57 GRBs and observed 0 events, which is consistent with 0.11 expected background events. With this result, we set the limits on the UHE GRB neutrino fluence and quasi-diffuse flux from $10^{16}$ to $10^{19}$~eV. This is the first limit on the UHE GRB neutrino quasi-diffuse flux at energies above $10^{16}$~eV.

  1. On Gamma Ray Burst and Blazar AGN Origins of the Ultra-High Energy Cosmic Rays in Light of First Results from Auger

    E-print Network

    Charles D. Dermer

    2007-12-14

    The discoveries of the GZK cutoff with the HiRes and Auger Observatories and the discovery by Auger of clustering of >~60 EeV ultra-high energy cosmic rays (UHECRs) towards nearby <~75 Mpc) AGNs along the supergalactic plane establishes the astrophysical origin of the UHECRs. The likely sources of the UHECRs are gamma-ray bursts and radio-loud AGNs because: (1) they are extragalactic; (2) they are sufficiently powerful; (3) acceleration to ultra-high energies can be achieved in their relativistic ejecta; (4) anomalous X-ray and gamma-ray features can be explained by nonthermal hadron acceleration in relativistic blast waves; and (5) sources reside within the GZK radius. Two arguments for acceleration to UHE are presented, and limits on UHECR ion acceleration are set. UHECR ions are shown to be able to survive without photodisintegrating while passing through the AGN scattered radiation field, even if launched deep in the broad line region. UHECR injection throughout cosmic time fits the measured energy spectrum of UHECRs, at least for protons. Local UHECR proton and ion interaction and energy-loss mean free paths are calculated using an empirical fit to the extragalactic background light (EBL) at IR and optical energies. Minimum intergalactic magnetic (IGM) fields ~1e-11 G are derived from clustering assuming specific source origins, e.g., Cen A, nearby AGNs, or GRBs for the super-GZK CRs seen with Auger. Besides distinct cosmic-ray induced gamma-ray signatures that should be observed with the Gamma ray Large Area Space Telescope (GLAST), source and GZK neutrino detections and the arrival distribution of UHECR in direction and time can finally decide the sources of cosmic rays at the highest energies.

  2. Hybrid ultrahigh resolution optical coherence / photoacoustic microscopy

    NASA Astrophysics Data System (ADS)

    Hermann, B.; Liu, M.; Schmitner, N.; Maurer, B.; Meyer, D.; Weninger, W. J.; Drexler, W.

    2015-03-01

    We present an ultrahigh resolution dual modality optical resolution photoacoustic microsopy (OR-PAM) and spectral domain optical coherence microscopy (SD-OCM) system. The ultrahigh sub-micron lateral resolution is provided by the high numerical aperture of the objective lens used while the ultrahigh axial resolution is provided by the broadband OCT laser that covers 107 nm with a central wavelength of 840 nm. The synchronized simultaneous acquisition for the two modalities is achieved using a 40MHz FPGA. 2D-scanning is realized by two orthogonal translation stages (PI, 400 nm resolution). The transversal resolution of the system is 0.5 ?m, the axial resolutions are 30 ?m (PAM) and 4 ?m (OCM), respectively. The values have been determined experimentally using nanospheres (diameter 10-200nm). For a demonstration of the imaging capability we present images from thin slices of different biological samples as well as in vivo imaging in the zebrafish embryo.

  3. High resolution gamma ray spectroscopy of flares on the east and west limbs of the Sun

    E-print Network

    M. J. Harris; V. Tatischeff; J. Kiener; M. Gros; G. Weidenspointner

    2006-10-29

    A new generation of Ge-based high-resolution gamma-ray spectrometers has allowed accurate measurements to be made of the profiles, widths and energies of the gamma-ray lines emitted in the impulsive phases of solar flares. Here we present measurements in two flares of the energies of the de-excitation lines of 12C and 16O at 4.4 and 6.1 MeV respectively by the Ge spectrometer SPI on board INTEGRAL, from which Doppler shifts are derived and compared with those expected from the recoil of 12C and 16O nuclei which were excited by the impacts of flare-accelerated ions. An anomalous Doppler measurement (in terms of recoil theory) has been reported by the Ge spectrometer RHESSI in a flare near the east limb, and explained by a tilt of the magnetic field lines at the footpoint of a magnetic loop away from the vertical, and towards the observer. This might be interpreted to imply a significant difference between the Doppler shifts on the east and west limbs, if it is a general phenomenon. SPI observed both east and west limb flares and found no significant difference in Doppler shifts. We also measured the shapes and fluences of these lines, and their fluence ratio to the 2.2 MeV line from the capture of flare-generated neutrons. Analyses of both quantities using thick-target models parametrized by solar physical and geometric quantities suggest that the two flares studied here also have magnetic fields tilted towards the observer, though the significance of the measurements is not high.

  4. A gamma-ray imager with multiplexer read-out for use in ultra-high-resolution brain SPECT

    SciTech Connect

    Barber, H.B.; Barret, H.H. (Univ. of Arizona, Tucson, AZ (United States). Div. of Nuclear Medicine Univ. of Arizona, Tucson, AZ (United States). Optical Sciences Center); Dereniak, E.L.; Hartsough, N.E.; Perry, D.L.; Rogulski, M.M. (Univ. of Arizona, Tucson, AZ (United States). Optical Sciences Center); Roberts, P.C.T. (Litton Electron Devices, Tempe, AZ (United States)); Woolfenden, J.M. (Univ.of Arizona, Tucson, AZ (United States). Div. of Nuclear Medicine); Young, E.T. (Univ. of Arizona, Tucson, AZ (United States). Steward Observatory)

    1993-08-01

    The authors developing an ultra-high-resolution SPECT system for brain imaging. The system uses a multiple-pinhole aperture and many modular detectors,each composed of an array of semiconductor detectors read out by a monolithic integrated circuit called a multiplexer (MUX). The modular detectors, being passive integrators, can detect individual gamma rays with good energy resolution. They will also have sub-millimeter spatial resolution and high count-rate capability. In this paper the authors describe the basic concept of these detectors and review some of the design considerations for them. They also report some preliminary experiments that demonstrate that semiconductor detectors with multiplexer read-out act as gamma ray detectors.

  5. REM Optical Slitless Spectrograph (ROSS): an instrument for prompt low resolution spectroscopy of Gamma Ray Bursts

    E-print Network

    Eliana Palazzi; Elena Pian

    2001-09-07

    Since the discovery of Gamma-Ray Bursts (GRBs), attempts have been made to detect correlated optical transient emission from these objects. In January 1999, the ROTSE I robotic telescope detected a bright optical flash simultaneous with a GRB, thanks to the prompt dissemination to the ground of the high energy event coordinates. To date, that single observation remains unique as no other prompt flashes have been seen for other bursts observed with comparably short response times. This suggests that in general GRB prompt optical emission may be considerably dimmer than observed for the GRB990123 event. To exploit the better angular localization accuracy of the flying (HETE-2) or soon to fly (INTEGRAL, AGILE, SWIFT, GLAST) missions for high energy astrophysics, a new generation of robotic telescopes is being developed. These will have response times as short as a few seconds and will be sensitive to signals as faint as m_v ~ 20, thus increasing the chance of detecting even weak prompt emission. Results from these experiments should provide important new data about the dynamics and local medium composition of GRBs. In this paper we describe one of the new instruments, ROSS, to be mounted on the robotic facility REM, designed to perform low resolution spectroscopy on the prompt optical flares associated with GRBs.

  6. Hot-Electron Tunneling sensors for high-resolution x-ray and gamma-ray spectroscopy

    SciTech Connect

    Mears, C.A.; Labov, S.E.; Frank, M.; Netel, H.

    1997-02-07

    Over the past 2 years, we have been studying the use of Hot Electron Tunneling sensors for use in high-energy-resolution x-ray and gamma-ray spectrometers. These sensors promise several advantages over existing cryogenic sensors, including simultaneous high count rate and high resolution capability, and relative ease of use. Using simple shadow mask lithography, we verified the basic principles of operation of these devices and discovered new physics in their thermal behavior as a function applied voltage bias. We also began to develop ways to use this new sensor in practical x-ray and gamma-ray detectors based on superconducting absorbers. This requires the use of quasiparticle trapping to concentrate the signal in the sensing elements.

  7. Gamma Rays

    MedlinePLUS

    ... Life Decay Chains Radioactive Equilibrium Curies Alpha Particles Beta Particles Gamma Rays Other Decay Modes A gamma ray is a packet of ... energy. It often follows the emission of a beta particle. What happens ... an example of radioactive decay by gamma radiation. When a neutron transforms to ...

  8. Ultrahigh-resolution X-ray tomography

    Microsoft Academic Search

    W. S. Haddad; J. E. Trebes; R. A. Levesque; I. McNulty; L. Yang; E. H. Anderson

    1994-01-01

    Ultrahigh-resolution three-dimensional images of a microscopic test object were made with soft x-rays collected with a scanning transmission x-ray microscope. The test object consisted of two different patterns of gold bars on silicon nitride windows that were separated by 5 micrometers. Depth resolution comparable to the transverse resolution was achieved by recording nine two-dimensional images of the object at angles

  9. Measurement of the atmospheric 0.511 MeV gamma rays with a high resolution spectrometer

    NASA Astrophysics Data System (ADS)

    Ayre, C. A.; Owens, A.; Summers, W. M.; Thompson, M. G.; Bhat, P. N.

    A report is presented of the measurement of the 511 keV gamma-rays in the atmosphere using an actively collimated solid state detector. This high resolution (1.7 keV at 511 keV) gamma-ray spectrometer was flown on a balloon over Palestine, Texas, USA, on 28th August 1979. The counting rates of 511 keV photons were measured at various atmospheric depths. It is concluded that the observed rate mainly owes its origin to two components: atmospheric 511 keV photons leaking through the shield and annihilation photons resulting from the beta(plus) decay of the radioactive nuclei produced locally as a result of proton and neutron interactions in the atmosphere.

  10. 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.

  11. Analysis of high resolution satellite data for cosmic gamma ray bursts

    NASA Technical Reports Server (NTRS)

    Imhof, W. L.; Nakano, G. H.; Reagan, J. B.

    1976-01-01

    Cosmic gamma ray bursts detected a germanium spectrometer on the low altitude satellite 1972-076B were surveyed. Several bursts with durations ranging from approximately 0.032 to 15 seconds were found and are tabulated. The frequency of occurrence/intensity distribution of these events was compared with the S to the -3/2 power curve of confirmed events. The longer duration events fall above the S to the -3/2 power curve of confirmed events, suggesting they are perhaps not all true cosmic gamma-ray bursts. The narrow duration events fall closely on the S to the -3/2 power curve. The survey also revealed several counting rate spikes, with durations comparable to confirmed gamma-ray bursts, which were shown to be of magnetospheric origin. Confirmation that energetic electrons were responsible for these bursts was achieved from analysis of all data from the complete payload of gamma-ray and energetic particle detectors on board the satellite. The analyses also revealed that the narrowness of the spikes was primarily spatial rather than temporal in character.

  12. Optimizing the angular resolution of the HEGRA telescope system to study the emission region of VHE gamma rays in the Crab Nebula

    NASA Astrophysics Data System (ADS)

    Aharonian, F. A.; Akhperjanian, A. G.; Barrio, J. A.; Bernlöhr, K.; Bojahr, H.; Bolz, O.; Börst, H.; Contreras, J. L.; Cortina, J.; Denninghoff, V.; Fonseca, S.; Gonzalez, J. C.; Götting, N.; Heinzelmann, G.; Hermann, G.; Heusler, A.; Hofmann, W.; Horns, D.; Ibarra, A.; Iserlohe, C.; Jung, I.; Kankanyan, R.; Kestel, M.; Kettler, J.; Kohnle, A.; Konopelko, A.; Kornmeyer, H.; Kranich, D.; Krawczynski, H.; Lampeitl, H.; Lorenz, E.; Lucarelli, F.; Magnussen, N.; Mang, O.; Meyer, H.; Mirzoyan, R.; Moralejo, A.; Padilla, L.; Panter, M.; Plaga, R.; Plyasheshnikov, A.; Prahl, J.; Pühlhofer, G.; Rhode, W.; Röhring, A.; Rowell, G.; Sahakian, V.; Samorski, M.; Schilling, M.; Schröder, F.; Siems, M.; Stamm, W.; Tluczykont, M.; Völk, H. J.; Wiedner, C.; Wittek, W.

    2000-09-01

    The HEGRA system of imaging atmospheric Cherenkov telescopes provides for specially selected classes of events an angular resolution of better than 3'. By comparing the measured angular distribution of TeV gamma rays from the Crab Nebula with the distribution expected on the basis of Monte Carlo simulations, and with measurements of gamma rays from the point source Mrk 501, we conclude that the rms size of the VHE gamma-ray emission region in the Crab Nebula is less than 1.5'.

  13. 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.

  14. A position sensitive gamma-ray scintillator detector with enhanced spatial resolution, linearity, and field of view.

    PubMed

    Domingo-Pardo, César; Goel, Namita; Engert, Tobias; Gerl, Juergen; Isaka, Masahiro; Kojouharov, Ivan; Schaffner, Henning

    2009-12-01

    The performance of a position sensitive gamma-ray scintillator detector (PSD) is described. This PSD is based on a lutetium yttrium oxyorthosilicate (LYSO) crystal read out by a crossed-wire anode position sensitive photomultiplier tube (PSPMT). The main difference with respect to similar existing devices is the individual multi-anode readout (IMAR) approach that is followed here. This method allows to exploit better the intrinsic characteristics of the PSPMT, thus yielding better linearity, improved spatial resolution, and a larger field of view. The new detector is intended for the characterization of 3-D position sensitive germanium detectors. PMID:19628451

  15. 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.

  16. High energy resolution hard X-ray and gamma-ray imagers using CdTe diode devices

    E-print Network

    Watanabe, Shin; Aono, Hiroyuki; Takeda, Shin'ichiro; Odaka, Hirokazu; Kokubun, Motohide; Takahashi, Tadayuki; Nakazawa, Kazuhiro; Tajima, Hiroyasu; Onishi, Mitsunobu; Kuroda, Yoshikatsu

    2008-01-01

    We developed CdTe double-sided strip detectors (DSDs or cross strip detectors) and evaluated their spectral and imaging performance for hard X-rays and gamma-rays. Though the double-sided strip configuration is suitable for imagers with a fine position resolution and a large detection area, CdTe diode DSDs with indium (In) anodes have yet to be realized due to the difficulty posed by the segmented In anodes. CdTe diode devices with aluminum (Al) anodes were recently established, followed by a CdTe device in which the Al anodes could be segmented into strips. We developed CdTe double-sided strip devices having Pt cathode strips and Al anode strips, and assembled prototype CdTe DSDs. These prototypes have a strip pitch of 400 micrometer. Signals from the strips are processed with analog ASICs (application specific integrated circuits). We have successfully performed gamma-ray imaging spectroscopy with a position resolution of 400 micrometer. Energy resolution of 1.8 keV (FWHM: full width at half maximum) was ob...

  17. Sigma - A new gamma-ray space observatory with high angular resolution for 1985 and beyond

    NASA Astrophysics Data System (ADS)

    Debouzy, G.

    The primary objective of the Satellite d'Imagerie Gamma Montesur Ariane (SIGMA) is the acquisition of images of the sky in the hard X-ray/low energy gamma-ray domains, which cover the 30 keV-2 MeV range, with an angular accuracy of a few arcmin and a point source sensitivity as low as a few UHURU Flux Units. In order to fulfill these requirements, a large, position-sensitive detector operating with a coded aperture mask will be employed. While the sensitivity of the SIGMA detector can be derived easily in the low energy domain, where the photoelectric effect predominates, background estimation has required detailed Monte-Carlo simulations.

  18. Sigma: a new gamma-ray space observatory with high angular resolution for 1985 and beyond

    SciTech Connect

    Debouzy, G.

    1983-01-01

    The primary objective of the Satellite d'Imagerie Gamma Montesur Ariane (SIGMA) is the acquisition of images of the sky in the hard X-ray/low energy gamma-ray domains, which cover the 30 keV-2 MeV range, with an angular accuracy of a few arcmin and a point source sensitivity as low as a few UHURU Flux Units. In order to fulfill these requirements, a large, position-sensitive detector operating with a coded aperture mask will be employed. While the sensitivity of the SIGMA detector can be derived easily in the low energy domain, where the photoelectric effect predominates, background estimation has required detailed Monte-Carlo simulations.

  19. High energy resolution hard X-ray and gamma-ray imagers using CdTe diode devices

    E-print Network

    Shin Watanabe; Shin-nosuke Ishikawa; Hiroyuki Aono; Shin'ichiro Takeda; Hirokazu Odaka; Motohide Kokubun; Tadayuki Takahashi; Kazuhiro Nakazawa; Hiroyasu Tajima; Mitsunobu Onishi; Yoshikatsu Kuroda

    2008-11-04

    We developed CdTe double-sided strip detectors (DSDs or cross strip detectors) and evaluated their spectral and imaging performance for hard X-rays and gamma-rays. Though the double-sided strip configuration is suitable for imagers with a fine position resolution and a large detection area, CdTe diode DSDs with indium (In) anodes have yet to be realized due to the difficulty posed by the segmented In anodes. CdTe diode devices with aluminum (Al) anodes were recently established, followed by a CdTe device in which the Al anodes could be segmented into strips. We developed CdTe double-sided strip devices having Pt cathode strips and Al anode strips, and assembled prototype CdTe DSDs. These prototypes have a strip pitch of 400 micrometer. Signals from the strips are processed with analog ASICs (application specific integrated circuits). We have successfully performed gamma-ray imaging spectroscopy with a position resolution of 400 micrometer. Energy resolution of 1.8 keV (FWHM: full width at half maximum) was obtained at 59.54 keV. Moreover, the possibility of improved spectral performance by utilizing the energy information of both side strips was demonstrated. We designed and fabricated a new analog ASIC, VA32TA6, for the readout of semiconductor detectors, which is also suitable for DSDs. A new feature of the ASIC is its internal ADC function. We confirmed this function and good noise performance that reaches an equivalent noise charge of 110 e- under the condition of 3-4 pF input capacitance.

  20. Monte Carlo Simulations of Ultra-High Energy Resolution Gamma Detectors for Nuclear Safeguards

    SciTech Connect

    Robles, A; Drury, O B; Friedrich, S

    2009-08-19

    Ultra-high energy resolution superconducting gamma-ray detectors can improve the accuracy of non-destructive analysis for unknown radioactive materials. These detectors offer an order of magnitude improvement in resolution over conventional high purity germanium detectors. The increase in resolution reduces errors from line overlap and allows for the identification of weaker gamma-rays by increasing the magnitude of the peaks above the background. In order to optimize the detector geometry and to understand the spectral response function Geant4, a Monte Carlo simulation package coded in C++, was used to model the detectors. Using a 1 mm{sup 3} Sn absorber and a monochromatic gamma source, different absorber geometries were tested. The simulation was expanded to include the Cu block behind the absorber and four layers of shielding required for detector operation at 0.1 K. The energy spectrum was modeled for an Am-241 and a Cs-137 source, including scattering events in the shielding, and the results were compared to experimental data. For both sources the main spectral features such as the photopeak, the Compton continuum, the escape x-rays and the backscatter peak were identified. Finally, the low energy response of a Pu-239 source was modeled to assess the feasibility of Pu-239 detection in spent fuel. This modeling of superconducting detectors can serve as a guide to optimize the configuration in future spectrometer designs.

  1. 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 at the previous activation point, could not be evaluated because of equipment failure.

  2. Influence of the thorium decay series on the background of high-resolution gamma-ray spectrometers.

    PubMed

    Bu?ar, K; Korun, M; Vodenik, B

    2012-06-01

    The background induced by the members of the thorium decay sequence in six high-resolution, gamma-ray spectrometers was analyzed. For the analysis, the count rates in the peaks of the background spectra, normalized to the unit of emission probability and detection probability, were used. The energy dependence of these normalized count rates carries information about the location of the sources of contamination. The contributions of the detector contamination, the contamination of the shielding material and the radiation penetrating the shield were calculated. The comparison of these contributions among the spectrometers pointed to the weaknesses of some shields, making such a comparison a useful tool for assessing the effectiveness of the shields. PMID:22464929

  3. Arcminute Resolution Gamma-ray Images of Cosmic Sources Taken with the Balloon-borne GRATIS Payload

    Microsoft Academic Search

    W. W. Craig; C. J. Hailey; J. Hong; S. M. Kahn; J. W. Keck; R. McLean; M. J. Pivovaroff; G. Sprehn; R. E. Wurtz; K. P. Ziock; F. A. Harrison; J. G. Jernigan; P. M. Lubin; M. Seiffert

    1996-01-01

    We present the first arcminute images of the gamma-ray sky. These images were taken with the Gamma Ray Arcminute Telescope and Imaging System (GRATIS). Using a combination of rotated one-dimensional coded aperture masks and a novel state of the art aspect reconstruction system we imaged a number of gamma ray sources, including CenA and GRS 1915 during the Fall 1995

  4. Gamma Ray Bursts and CETI

    E-print Network

    Frank D. Smith Jr

    1993-02-10

    Gamma ray burst sources are isotropically distributed. They could be located at distances $\\sim 1000$ AU. (Katz \\cite{JK92}) GRB signals have many narrow peaks that are unresolved at the millisecond time resolution of existing observations. \\cite{JK87} CETI could use stars as gravitational lenses for interstellar gamma ray laser beam communication. Much better time resolution of GRB signals could rule out (or confirm?) the speculative hypothesis that GRB = CETI.

  5. Analytic treatment of resolution precision in electronically collimated SPECT imaging involving multiple-interaction gamma rays

    Microsoft Academic Search

    J. W. Durkee Jr.; P. P. Antich; E. N. Tsyganov; A. Constantinescu; P. V. Kulkarni; B. J. Smith; G. M. Arbique; M. A. Lewis; T. Nguyen; A. Raheja; G. Thambi; R. W. Parkey

    1998-01-01

    The widely applied single-interaction analytic expression characterizing the energy resolution component of the angular resolution precision for an electronically collimated point source is extended to include multiple-interaction Compton scatter sequences as well as sequences terminated by photoelectric absorption. The analytic formulation is developed using the statistical variance of the mean for components comprising composite, multivariate resolution precision estimators. It is

  6. Digital pulse processing in high resolution, high throughput, gamma-ray spectroscopy

    Microsoft Academic Search

    Andrey Georgiev; Werner Gast

    1993-01-01

    A new method for processing signals produced by high resolution, large volume semiconductor detectors is described. These detectors, to be used in the next generation of spectrometer arrays for nuclear research (i.e., EUROBALL, etc.), present a set of problems, such as resolution degradation due to charge trapping and ballistic deficit effects, poor resolution at a high count rate, long term

  7. High resolution gamma ray spectroscopy with CdTe detector systems

    Microsoft Academic Search

    M. Richter; P. Siffert

    1992-01-01

    Energy resolution and photopeak efficiency of the nowadays CdTe detector material can be improved using several detector shapes or electronic signal processing. Current results obtained in our laboratory with different detector geometries and pulse discrimination methods are presented and compared. Finally, we report on a new charge loss compensation method which improves both energy resolution and photopeak efficiency.

  8. Ultrahigh Resolution Multicolor Colocalization of Single Fluorescent Nanocrystals.

    E-print Network

    Michalet, Xavier

    Ultrahigh Resolution Multicolor Colocalization of Single Fluorescent Nanocrystals. Xavier Michaleta and distance measurement between biomolecules is described, based on semiconductor nanocrystal probes-spread- function (PSF) of various colors nanocrystals while maintaining perfect registry between the channels. Fit

  9. Prospects for High Energy Resolution Gamma Ray Spectroscopy with Europium-Doped Strontium Iodide

    SciTech Connect

    Cherepy, N J; Payne, S A; Hawrami, R; Burger, A; Boatner, L; Van Loef, E; Shah, K

    2009-04-03

    Europium-doped strontium iodide scintillators offer a light yield exceeding 100,000 photons/MeV and excellent light yield proportionality, while at the same time, SrI{sub 2} is readily grown in single crystal form. Thus far, our collaboration has demonstrated an energy resolution with strontium iodide of 2.6% at 662 keV and 7.6% at 60 keV, and we have grown single crystals surpassing 30 cm{sup 3} in size (with lower resolution). Our analysis indicates that SrI{sub 2}(Eu) has the potential to offer 2% energy resolution at 662 keV with optimized material, optics, and read-out. In particular, improvements in feedstock purity may result in crystal structural and chemical homogeneity, leading to improved light yield uniformity throughout the crystal volume, and consequently, better energy resolution. Uniform, efficient light collection and detection, is also required to achieve the best energy resolution with a SrI{sub 2}(Eu) scintillator device.

  10. Arcminute Resolution Gamma-ray Images of Cosmic Sources Taken with the Balloon-borne GRATIS Payload

    NASA Astrophysics Data System (ADS)

    Craig, W. W.; Hailey, C. J.; Hong, J.; Kahn, S. M.; Keck, J. W.; McLean, R.; Pivovaroff, M. J.; Sprehn, G.; Wurtz, R. E.; Ziock, K. P.; Harrison, F. A.; Jernigan, J. G.; Lubin, P. M.; Seiffert, M.

    1996-12-01

    We present the first arcminute images of the gamma-ray sky. These images were taken with the Gamma Ray Arcminute Telescope and Imaging System (GRATIS). Using a combination of rotated one-dimensional coded aperture masks and a novel state of the art aspect reconstruction system we imaged a number of gamma ray sources, including CenA and GRS 1915 during the Fall 1995 Alice Springs, Australia balloon campaign. We discuss the specifics of the observations and preliminary results. The performance of the aspect system provides a straightforward development path to the production of a system capable of the 1-3 arcsecond localizations required for potential gamma-ray burst detection from either small satellite or long duration balloon platforms.

  11. The effect of gain variation in micro-channel plates on gamma-ray energy resolution

    NASA Astrophysics Data System (ADS)

    Han, Ling; Barrett, Harrison H.; Barber, H. Bradford; Furenlid, Lars R.

    2013-09-01

    A Monte Carlo simulation of micro-channel plate (MCP) with particular interest in its effect on energy resolution performance is presented. Important physical processes occurring in MCP channels are described and modeled, including secondary electron (SE) yield, SE emission, and primary electron reflection. The effects causing channel saturation are also introduced. A two dimensional Monte Carlo simulation is implemented under the assumption of unsaturated channel. Simulation results about basic MCP performances and especially gain and energy resolution performances are presented and analyzed. It's found that energy resolution as an intrinsic property of MCP cannot be improved simply by adjusting system parameters; however it can be improved by increasing input signal or number of photoelectrons (PEs) in the context of image intensifier. An initial experiment with BazookaSPECT detector and CsI(Tl) scintillator is performed to validate and correlate with the simulation results and good agreement is achieved.

  12. Renal basement membranes by ultrahigh resolution scanning electron microscopy

    Microsoft Academic Search

    Kazue Hironaka; Hirofumi Makino; Yasushi Yamasaki; Zensuke Ota

    1993-01-01

    Renal basement membranes by ultrahigh resolution scanning electron microscopy. Three-dimensional ultrastructures of basement membranes of the rat kidney were investigated with an ultrahigh resolution scanning electron microscope (HSEM) equipped with a resolving power of 0.5 nm. All cellular components were extracted from renal cortical tissues by sequential-detergent treatment. Four types of acellular basement membranes were observed after tannin-osmium conductive staining:

  13. A high resolution gamma-ray and hard x-ray spectrometer (HIREGS) for long duration balloon flights

    NASA Astrophysics Data System (ADS)

    Boggs, S. E.; Lin, R. P.; Feffer, P. T.; Slassi-Sennou, S.; McBride, S.; Primbsch, J. H.; Youssefi, K.; Zimmer, G.; Cork, C.; Luke, P.; Madden, N.; Malone, D.; Pehl, R.; Pelling, M.; Cotin, F.; Vedrenne, G.

    The HIREGS gamma-ray spectrometer made a 23-day Long Duration Balloon Flight (LDBF) from Antarctica in January 1995 to observe Galactic sources of gamma-ray and hard X-ray line and continuum emission. The scientific instrument itself is discussed, followed by a more extensive discussion of the characteristics of the instrument unique to LDBFs. The flight performance and preliminary results are briefly summarized.

  14. Inter-pulse high-resolution gamma-ray spectra using a 14 MeV pulsed neutron generator

    USGS Publications Warehouse

    Evans, L.G.; Trombka, J.I.; Jensen, D.H.; Stephenson, W.A.; Hoover, R.A.; Mikesell, J.L.; Tanner, A.B.; Senftle, F.E.

    1984-01-01

    A neutron generator pulsed at 100 s-1 was suspended in an artificial borehole containing a 7.7 metric ton mixture of sand, aragonite, magnetite, sulfur, and salt. Two Ge(HP) gamma-ray detectors were used: one in a borehole sonde, and one at the outside wall of the sample tank opposite the neutron generator target. Gamma-ray spectra were collected by the outside detector during each of 10 discrete time windows during the 10 ms period following the onset of gamma-ray build-up after each neutron burst. The sample was measured first when dry and then when saturated with water. In the dry sample, gamma rays due to inelastic neutron scattering, neutron capture, and decay were counted during the first (150 ??s) time window. Subsequently only capture and decay gamma rays were observed. In the wet sample, only neutron capture and decay gamma rays were observed. Neutron capture gamma rays dominated the spectrum during the period from 150 to 400 ??s after the neutron burst in both samples, but decreased with time much more rapidly in the wet sample. A signal-to-noise-ratio (S/N) analysis indicates that optimum conditions for neutron capture analysis occurred in the 350-800 ??s window. A poor S/N in the first 100-150 ??s is due to a large background continuum during the first time interval. Time gating can be used to enhance gamma-ray spectra, depending on the nuclides in the target material and the reactions needed to produce them, and should improve the sensitivity of in situ well logging. ?? 1984.

  15. High energy gamma ray astronomy

    NASA Technical Reports Server (NTRS)

    Fichtel, C. E.

    1974-01-01

    The SAS-2 gamma ray experiment and its detection of celestial gamma rays are described. Data also cover intensity of high energy gamma rays, gamma ray distribution, gamma ray origin, and diffuse radiation.

  16. Mercuric iodine room temperature gamma-ray detectors

    NASA Technical Reports Server (NTRS)

    Patt, Bradley E.; Markakis, Jeffrey M.; Gerrish, Vernon M.; Haymes, Robert C.; Trombka, Jacob I.

    1990-01-01

    high resolution mercuric iodide room temperature gamma-ray detectors have excellent potential as an essential component of space instruments to be used for high energy astrophysics. Mercuric iodide detectors are being developed both as photodetectors used in combination with scintillation crystals to detect gamma-rays, and as direct gamma-ray detectors. These detectors are highly radiation damage resistant. The list of applications includes gamma-ray burst detection, gamma-ray line astronomy, solar flare studies, and elemental analysis.

  17. Ultra?high resolution array painting facilitates breakpoint sequencing

    PubMed Central

    Gribble, S M; Kalaitzopoulos, D; Burford, D C; Prigmore, E; Selzer, R R; Ng, B L; Matthews, N S W; Porter, K M; Curley, R; Lindsay, S J; Baptista, J; Richmond, T A; Carter, N P

    2007-01-01

    Objective To describe a considerably advanced method of array painting, which allows the rapid, ultra?high resolution mapping of translocation breakpoints such that rearrangement junction fragments can be amplified directly and sequenced. Method Ultra?high resolution array painting involves the hybridisation of probes generated by the amplification of small numbers of flow?sorted derivative chromosomes to oligonucleotide arrays designed to tile breakpoint regions at extremely high resolution. Results and discussion How ultra?high resolution array painting of four balanced translocation cases rapidly and efficiently maps breakpoints to a point where junction fragments can be amplified easily and sequenced is demonstrated. With this new development, breakpoints can be mapped using just two array experiments: the first using whole?genome array painting to tiling resolution large insert clone arrays, the second using ultra?high?resolution oligonucleotide arrays targeted to the breakpoint regions. In this way, breakpoints can be mapped and then sequenced in a few weeks. PMID:16971479

  18. Fundamental physics using ultrahigh resolution gamma spectroscopy

    NASA Astrophysics Data System (ADS)

    Dewey, M. S.; Kessler, E. G.; Greene, G. L.; Deslattes, R. D.; Börner, H.; Jolie, J.

    1989-11-01

    GAMS4, a double-flat-crystal spectrometer, is operated as a joint NIST/ILL facility at the High Flux Reactor at the Institut Laue-Langevin (ILL) in Grenoble, France. It was designed and has been used successfully for the absolute determination of gamma-ray energies in the region <5 MeV. Such measurements can lead to a unification of the atomic mass scale and the wavelength scale. Recently, new directions of research that exploit details of measured line shapes have been identified. We discuss the status of the absolute wavelength program and these new programs.

  19. Diagnosis of physical parameters of fast particles in high power fusion plasmas with high resolution neutron and gamma-ray spectroscopy

    NASA Astrophysics Data System (ADS)

    Tardocchi, M.; Nocente, M.; Gorini, G.

    2013-07-01

    High resolution neutron emission spectroscopy (NES) and gamma-ray spectroscopy (GRS) measurements of fast ions in high power fusion plasmas are reviewed. NES is a well established diagnostics of the velocity distribution of fast fuel ions and was recently used to investigate the interaction of energetic ions with MHD instabilities. High energy resolution GRS on fusion plasmas is a more recent application and was shown to provide information on the distribution function of fast minority ions accelerated by ICRH, such as 4He and 3He. Starting from measurements on today's high power D plasmas, fast ion measurements with NES and GRS in a DT burning plasma of next step tokamaks, such as ITER, are discussed. The enhanced neutron and gamma-ray fluxes expected on ITER will allow for time-resolved measurements of the fast fuel and minority ion dynamics in the ms time scale. The intensity of the alpha knock-on component in the 14 MeV neutron spectrum and of the 4.44 and 3.21 MeV gamma-ray peaks from the 9Be(?,n?)12C reaction is studied as a diagnostics for the ? particle slowing down distribution in a DT plasma. The results show that the two techniques are sensitive to different regions of the ? particle phase space and thus provide complementary information.

  20. Preliminary results from the high resolution gamma-ray and hard x-ray spectrometer (HIREGS) '92-'93 long duration balloon flight in Antarctica

    SciTech Connect

    Lin, R.P.; Feffer, P.T.; Slassi, S.; Whiteside, W.; Smith, D.M.; Hurley, K.C.; Kane, S.R.; McBride, S.; Primbsch, J.H.; Youssefi, K.; Zimmer, G. (Univ. of California, Berkeley, CA (United States)); Pelling, R.M. (Univ. of California, San Diego, CA (United States)); Cotin, F.; Lavigne, J.M.; Rouaix, G.; Vedrenne, G.; Pehl, R.; Cork, C.; Luke, P.; Madden, N.; Malone, D.

    1993-01-01

    HIREGS consists of an array of twelve 6.7 cm diameter x 6.1 cm long liquid nitrogen-cooled segmented germanium detectors enclosed in a bismuth germanate (BGO) active anticoincidence shield. A CsI front collimator defines a 24 degree FWHM field-of-view. The energy resolution is one to several keV FWHM over the instrument energy range of 20 keV to 16 MeV. HIREGS was flown on a 10-day (31 Dec 92--10 Jan 93) circumpolar balloon flight from McMurdo Station, Antarctica. 30.5 hours of observation were obtained between 31 Dec 0400-2130 UT and 1 Jan 0600-1900 UT. Because the Sun was inactive during the flight, only one small flare was detected on 31 Dec 1933 UT. Excellent high resolution [open quotes]quiet[close quotes] Sun hard X-ray and gamma-ray spectra were obtained. These provide stringent upper limits for solar gamma-ray line and hard X-ray and gamma-ray continuum emission, which in turn can constrain the storage and/or continuous acceleration of ions and electrons by the Sun.

  1. Ultra-High Resolution Imaging by Fluorescence Photoactivation Localization Microscopy

    E-print Network

    La Rosa, Andres H.

    Ultra-High Resolution Imaging by Fluorescence Photoactivation Localization Microscopy Samuel T-field visible light microscopy suffers from limited resolution. A new method for fluorescence imaging has been-nm) laser and are then fluorescent when excited at a lower frequency. The fluorescence is imaged

  2. 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.

  3. High resolution inelastic gamma-ray measurements with a white neutron source from 1 to 200 MeV

    SciTech Connect

    Nelson, R.O.; Laymon, C.M.; Wender, S.A.

    1990-01-01

    Measurements of prompt gamma rays following neutron-induced reactions have recently been made at the spallation neutron source at the WNR target area of LAMPF using germanium detectors. These experiments provide extensive excitation function data for inelastic neutron scattering as well as for other reactions such as (n,{alpha}), (n,n{alpha}), (n,p), (n,np), (n,nnp) and (n,xn) for 1 {le} {times} {le} 11. The continuous energy coverage available from 1 MeV to over 200 MeV is ideal for excitation function measurements and greatly extends the energy range for such data. The results of these measurements will provide a database for interpretation of gamma-ray spectra from the planned Mars Observer mission, aid in radiation transport calculations, allow verification of nuclear reaction models, and improve the evaluated neutron reaction data base.

  4. Adaptive-optics ultrahigh-resolution optical coherence tomography

    Microsoft Academic Search

    B. Hermann; E. J. Fernández; A. Unterhuber; H. Sattmann; A. F. Fercher; W. Drexler; P. Artal

    2004-01-01

    Merging of ultrahigh-resolution optical coherence tomography (UHR OCT) and adaptive optics (AO), resulting in high axial (3 µm) and improved transverse resolution (5-10 µm) is demonstrated for the first time to our knowledge in in vivo retinal imaging. A compact (300 mm × 300 mm) closed-loop AO system, based on a real-time Hartmann-Shack wave-front sensor operating at 30 Hz and

  5. Towards Ultra-High Resolution Models of Climate and Weather

    SciTech Connect

    Wehner, Michael; Oliker, Leonid; Shalf, John

    2007-01-01

    We present a speculative extrapolation of the performance aspects of an atmospheric general circulation model to ultra-high resolution and describe alternative technological paths to realize integration of such a model in the relatively near future. Due to a superlinear scaling of the computational burden dictated by stability criterion, the solution of the equations of motion dominate the calculation at ultra-high resolutions. From this extrapolation, it is estimated that a credible kilometer scale atmospheric model would require at least a sustained ten petaflop computer to provide scientifically useful climate simulations. Our design study portends an alternate strategy for practical power-efficient implementations of petaflop scale systems. Embedded processor technology could be exploited to tailor a custom machine designed to ultra-high climate model specifications at relatively affordable cost and power considerations. The major conceptual changes required by a kilometer scale climate model are certain to be difficult to implement. Although the hardware, software, and algorithms are all equally critical in conducting ultra-high climate resolution studies, it is likely that the necessary petaflop computing technology will be available in advance of a credible kilometer scale climate model.

  6. Energy resolution of gamma-ray spectroscopy of JET plasmas with a LaBr{sub 3} scintillator detector and digital data acquisition

    SciTech Connect

    Nocente, M.; Tardocchi, M.; Grosso, G.; Perelli Cippo, E.; Pietropaolo, A.; Proverbio, I.; Gorini, G. [Dipartimento di Fisica, Universita degli Studi di Milano-Bicocca and Istituto di Fisica del Plasma, Associazione EURATOM-ENEA-CNR, 20125 Milano (Italy); Chugunov, I.; Gin, D.; Shevelev, A. [A. F. Ioffe Physico-Technical Institute, St. Petersburg 194021 (Russian Federation); Pereira, R. C.; Fernandes, A. M.; Neto, A.; Sousa, J. [Associacao EURATOM/IST Centro de Fusao Nuclear, Instituto Superior Tecnico, 1049-001 Lisboa (Portugal); Edlington, T.; Kiptily, V.; Syme, B. [Culham Centre for Fusion Energy, Culham OX143DB (United Kingdom); Murari, A. [Consorzio RFX, 35127 Padova (Italy); Collaboration: JET-EFDA Contributors

    2010-10-15

    A new high efficiency, high resolution, fast {gamma}-ray spectrometer was recently installed at the JET tokamak. The spectrometer is based on a LaBr{sub 3}(Ce) scintillator coupled to a photomultiplier tube. A digital data acquisition system is used to allow spectrometry with event rates in excess of 1 MHz expected in future JET DT plasmas. However, at the lower rates typical of present day experiments, digitization can degrade the energy resolution of the system, depending on the algorithms used for extracting pulse height information from the digitized pulses. In this paper, the digital and analog spectrometry methods were compared for different experimental conditions. An algorithm based on pulse shape fitting was developed, providing energy resolution equivalent to the traditional analog spectrometry method.

  7. Preliminary Results from the HIgh REsolution Gamma-ray and hard x-ray Spectrometer (HIREGS) Long Duration Balloon Flight in Antarctica

    NASA Astrophysics Data System (ADS)

    Feffer, P. T.; Lin, R. P.; Smith, D. M.; Hurley, K. C.; Kane, S. R.; McBride, S.; Primbsch, J. H.; Youssefi, K.; Zimmer, G.; Pelling, R. M.; Cotin, F.; Lavigne, J. M.; Rouaix, G.; Slassi, S.; Vedrenne, G.; Pehl, R.; Cork, C.; Luke, P.; Madden, N.; Malone, D.

    1992-05-01

    The HIgh REsolution Gamma-ray and hard x-ray Spectrometer (HIREGS) was flown on a 14 day balloon flight from McMurdo Station, Antarctica in January 1992. For this flight, HIREGS consists of an array of four 6.7cm diameter x 6.1cm long liquid nitrogen-cooled segmented germanium detectors enclosed in a bismuth germanate (BGO) shield. A CsI front collimator defines a 24 degree FWHM field-of-view, while passive collimation reduces the field-of-view to roughly 3 x 12 degrees for hard X-rays (<200 keV). The energy resolution is one to several keV from 20 keV to 16 MeV. 178 hours of observations were obtained: Jan 10 0943UT - Jan 12 1026UT, Jan 13 0528UT - Jan 15 0823UT, Jan 17 2000UT - Jan 18 1909UT, Jan 20 0245UT - Jan 22 1522UT. Out of these 178 hours, 128 hours were spent on the sun. We have analyzed the data for two M class flares on Jan 13 1913UT and Jan 14 1937UT. No significant hard x-ray or gamma-ray emission was detected for either flare. We are currently searching for hard x-ray emission from smaller C class flares.

  8. Ultrahigh resolution photoacoustic microscopy via transient absorption

    NASA Astrophysics Data System (ADS)

    Shelton, Ryan; Applegate, Brian E.

    2011-03-01

    We have developed a novel, hybrid imaging modality, Transient Absorption Ultrasonic Microscopy (TAUM), which fuses photoacoustic microscopy with non-linear microscopy. Photoacoustic microscopy is well known for its ability to image chromophores deep (> 1 mm) in scattering media with spatial resolutions in the 10s of microns. Non-linear microscopy is well known for its exquisite spatial resolution in three dimensions. This superior spatial resolution is attributed to the fact that the collected signal has a non-linear dependence on the light intensity. This dependence confines the signal to a very small focal volume, producing optically resolved voxels. Transient absorption is a non-linear process often used to map the excited state lifetimes of molecules exhibiting low fluorescence quantum efficiency. This sensitivity to non-radiative transitions makes transient absorption an attractive process to combine with photoacoustic imaging. We have built a prototype transient absorption ultrasonic microscope, implementing off-axis photoacoustic detection to allow the use of a high-quality, high numerical aperture objective. This high-quality, commercial lens is required to provide the tight focusing needed to optimize non-linear effects. We have demonstrated the increased spatial resolution of TAUM by imaging Rhodamine 6G in a capillary tube. The capillary cross-section is fully resolved, suggesting an axial resolution of < 10 microns. A 6 MHz transducer was used in this experiment, which results in an axial resolution of ~ 400 microns when used in a traditional photoacoustic microscope. Boasting the superior penetration depth and absorption contrast offered by photoacoustic emission and complemented by spatial resolutions comparable to confocal microscopy, we believe that Transient Absorption Ultrasonic Microscopy has excellent potential for producing volumetric images with cellular/subcellular resolution in three dimensions deep inside living tissue.

  9. Ultrahigh-resolution endoscopic optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Chen, Yu; Herz, Paul R.; Hsiung, Pei-Lin; Aguirre, Aaron D.; Mashimo, Hiroshi; Desai, Saleem; Pedrosa, Macos; Koski, Amanda; Schmitt, Joseph M.; Fujimoto, James G.

    2005-01-01

    Early detection of gastrointestinal cancer is essential for the patient treatment and medical care. Endoscopically guided biopsy is currently the gold standard for the diagnosis of early esophageal cancer, but can suffer from high false negative rates due to sampling errors. Optical coherence tomography (OCT) is an emerging medical imaging technology which can generate high resolution, cross-sectional images of tissue in situ and in real time, without the removal of tissue specimen. Although endoscopic OCT has been used successfully to identify certain pathologies in the gastrointestinal tract, the resolution of current endoscopic OCT systems has been limited to 10 - 15 m for clinical procedures. In this study, in vivo imaging of the gastrointestinal tract is demonstrated at a three-fold higher resolution (< 5 m), using a portable, broadband, Cr4+:Forsterite laser as the optical light source. Images acquired from the esophagus, gastro-esophageal junction and colon on animal model display tissue microstructures and architectural details at high resolution, and the features observed in the OCT images are well-matched with histology. The clinical feasibility study is conducted through delivering OCT imaging catheter using standard endoscope. OCT images of normal esophagus, Barrett's esophagus, and esophageal cancers are demonstrated with distinct features. The ability of high resolution endoscopic OCT to image tissue morphology at an unprecedented resolution in vivo would facilitate the development of OCT as a potential imaging modality for early detection of neoplastic changes.

  10. SMART: a planned ultrahigh-resolution spectromicroscope for BESSY II

    Microsoft Academic Search

    R. Fink; M. R. Weiss; E. Umbach; D. Preikszas; H. Rose; R. Spehr; P. Hartel; W. Engel; R. Degenhardt; R. Wichtendahl; H. Kuhlenbeck; W. Erlebach; K. Ihmann; R. Schlögl; H.-J. Freund; A. M. Bradshaw; G. Lilienkamp; Th. Schmidt; E. Bauer; G. Benner

    1997-01-01

    A new UHV spectromicroscope called SMART (spectromicroscope for all relevant techniques) is currently under construction for a soft X-ray undulator beamline at BESSY II. The instrument consists of a plane-grating monochromator with an aspherical focusing mirror and an ultrahigh-resolution, low-energy electron microscope containing an energy filter. It can be used as a photoemission microscope for a variety of electron spectroscopies

  11. Ultrahigh resolution optical biopsy with endoscopic optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Herz, Paul R.; Chen, Yu; Aguirre, Aaron D.; Fujimoto, James G.; Mashimo, Hiroshi; Schmitt, Joseph; Koski, Amanda; Goodnow, John; Petersen, Chris

    2004-07-01

    Optical coherence tomography (OCT) is an emerging medical imaging technology that can generate high resolution, cross-sectional images of tissue in situ and in real time. Although endoscopic OCT has been used successfully to identify certain pathologies in the gastrointestinal tract, the resolution of current endoscopic OCT systems has been limited to 10-15 µm for in vivo studies. In this study, in vivo imaging of the rabbit gastrointestinal tract is demonstrated at a three-fold higher resolution (< 5 µm), using a broadband Cr4+:Forsterite laser as the optical light source. Images acquired from the esophagus, trachea, and colon reveal high resolution details of tissue architecture. Definitive correlation of architectural features in OCT images and histological sections is shown. The ability of ultrahigh resolution endoscopic OCT to image tissue morphology at an unprecedented resolution in vivo advances the development of OCT as a potential imaging tool for the early detection of neoplastic changes in biological tissue.

  12. Ultrahigh resolution optical biopsy with endoscopic optical coherence tomography.

    PubMed

    Herz, Paul; Chen, Yu; Aguirre, Aaron; Fujimoto, James; Mashimo, Hiroshi; Schmitt, Joseph; Koski, Amanda; Goodnow, John; Petersen, Chris

    2004-07-26

    Optical coherence tomography (OCT) is an emerging medical imaging technology that can generate high resolution, cross-sectional images of tissue in situ and in real time. Although endoscopic OCT has been used successfully to identify certain pathologies in the gastrointestinal tract, the resolution of current endoscopic OCT systems has been limited to 10-15 microm for in vivo studies. In this study, in vivo imaging of the rabbit gastrointestinal tract is demonstrated at a three-fold higher resolution (< 5 microm), using a broadband Cr(4+):Forsterite laser as the optical light source. Images acquired from the esophagus, trachea, and colon reveal high resolution details of tissue architecture. Definitive correlation of architectural features in OCT images and histological sections is shown. The ability of ultrahigh resolution endoscopic OCT to image tissue morphology at an unprecedented resolution in vivo advances the development of OCT as a potential imaging tool for the early detection of neoplastic changes in biological tissue. PMID:19483882

  13. 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.

  14. Gamma ray detector shield

    DOEpatents

    Ohlinger, R.D.; Humphrey, H.W.

    1985-08-26

    A gamma ray detector shield comprised of a rigid, lead, cylindrical-shaped vessel having upper and lower portions with an pneumatically driven, sliding top assembly. Disposed inside the lead shield is a gamma ray scintillation crystal detector. Access to the gamma detector is through the sliding top assembly.

  15. Gamma Ray Astronomy with Magnetized Zevatrons

    E-print Network

    Eric Armengaud; Guenter Sigl; Francesco Miniati

    2005-11-09

    Nearby sources of cosmic rays up to a ZeV(=10^21 eV) could be observed with a multi-messenger approach including secondary gamma-rays and neutrinos. If cosmic rays above ~10^18 eV are produced in magnetized environments such as galaxy clusters, the flux of secondary gamma-rays below ~1 TeV can be enhanced up to several orders of magnitudes compared to unmagnetized sources. A particular source of enhancement are synchrotron and cascade photons from e^+e^- pairs produced by protons from sources with relatively steep injection spectra proportional to E^-2.6. Such sources should be visible at the same time in ultra-high energy cosmic ray experiments and gamma-ray telescopes.

  16. Gamma-Ray Pulsar Studies With GLAST

    SciTech Connect

    Thompson, D.J.; /NASA, Goddard

    2011-11-23

    Some pulsars have their maximum observable energy output in the gamma-ray band, offering the possibility of using these high-energy photons as probes of the particle acceleration and interaction processes in pulsar magnetospheres. After an extended hiatus between satellite missions, the recently-launched AGILE mission and the upcoming Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) will allow gamma-ray tests of the theoretical models developed based on past discoveries. With its greatly improved sensitivity, better angular resolution, and larger energy reach than older instruments, GLAST LAT should detect dozens to hundreds of new gamma-ray pulsars and measure luminosities, light curves, and phase-resolved spectra with unprecedented resolution. It will also have the potential to find radio-quiet pulsars like Geminga, using blind search techniques. Cooperation with radio and X-ray pulsar astronomers is an important aspect of the LAT team's planning for pulsar studies.

  17. Ultrahigh resolution optical spectrometry based on Brillouin dynamic grating

    NASA Astrophysics Data System (ADS)

    Dong, Yongkang; Jiang, Taofei; Teng, Lei; Zhang, Hongying; Chen, Liang; Bao, Xiaoyi; Lu, Zhiwei

    2014-05-01

    We demonstrate an ultrahigh resolution optical spectrometry based on Brillouin dynamic grating (BDG). Taking advantage of creating a long grating in an optical fiber, an ultra-narrow bandwidth optical filter is realized by operating a BDG in a long single-mode fiber (SMF), and the optical spectrometry is performed by sweeping the center wavelength of the filter through swept-tuned laser. In experiment, a 4-fm (0.5 MHz) spectral resolution is achieved by operating a BDG in a 400-m SMF, and the wavelength coverage can be readily extended to C+L band with a commercial tunable laser.

  18. Development of a high-resolution imaging capability for observing cosmic sources in the hard x-ray/soft gamma-ray band

    NASA Astrophysics Data System (ADS)

    Harrison, Fiona Anne

    1993-01-01

    Astronomical observations in the Hard X-ray/Soft Gamma-ray (20 keV-a few hundred keV) region of the electromagnetic spectrum provide insight into astrophysical phenomena distinct from studies in the more classical X-ray band (0.2-15 keV). High-energy non-thermal processes in a variety of sources are best observed above 20 keV, where they are not masked by the intense thermal emission which dominates the spectra of many astronomical objects at lower energies. In spite of the promise of the hard X-ray band, its development into a prominent field in astrophysics has been protracted. This has been due in part to the lack of imaging observations which have been made at these energies. Early observations were made by coarsely-collimated (approximately few degrees) instruments which frequently confused or misidentified sources, making detailed studies impossible. Recent observations with imaging instruments have demonstrated the need for angular resolution on the sub-degree level in order to avoid source confusion and measure in detail the spectra of individual objects. There are, however, also a number of exciting and important investigations requiring an imaging capability at least a factor of five better than this, and it is these investigations which motivated the development of the instrument, the Gamma-Ray Arcminute Telescope Imaging System (GRATIS) which is the subject of this thesis. Imaging capability at the few arcminute level is required to resolve diffuse non-thermal radiation in galaxy clusters, to position accurately transient hard X-ray sources in the galactic center region, and to study diffuse non-thermal emission in giant elliptical galaxies. This thesis describes both the scientific motivation for developing the GRATIS instrument as well as the technological advances required to achieve the high angular resolution (2 arcminutes) of GRATIS. This instrument is a balloon-borne coded mask experiment with operates in the 20-200 keV portion of the hard X-ray/soft Gamma-ray band. The design and characterization of the instrument are discussed in detail. In addition, background measurements from a balloon flight from Palestine, TX are presented, and implications for observations of specific sources are discussed.

  19. Gamma-Ray Bursts

    NASA Technical Reports Server (NTRS)

    Fishman, Gearld J.

    2003-01-01

    Gamma-ray bursts originate from cosmological distances and represent the largest known explosions in the Universe. The observed temporal and spectral characteristics of bursts in the gamma-ray region, primarily from data obtained with the BATSE experiment on the Compton Observatory, will be described. The talk will concentrate on recent studies of burst properties, correlations of GRB parameters and other statistical studies that have recently come to light. A summary of recent discoveries and observations in other wavelength regions will also be presented, along with their implications for models of the burst emission mechanism. Various models for the energy source of gamma-ray bursts will be described.

  20. Gamma-ray Astronomy

    E-print Network

    Jim Hinton

    2007-12-20

    The relevance of gamma-ray astronomy to the search for the origin of the galactic and, to a lesser extent, the ultra-high-energy cosmic rays has long been recognised. The current renaissance in the TeV gamma-ray field has resulted in a wealth of new data on galactic and extragalactic particle accelerators, and almost all the new results in this field were presented at the recent International Cosmic Ray Conference (ICRC). Here I summarise the 175 papers submitted on the topic of gamma-ray astronomy to the 30th ICRC in Merida, Mexico in July 2007.

  1. Gamma ray astrophysics to the year 2000. Report of the NASA Gamma Ray Program Working Group

    NASA Technical Reports Server (NTRS)

    1988-01-01

    Important developments in gamma-ray astrophysics up to energies of 100 GeV during the last decade are reviewed. Also, the report seeks to define the major current scientific goals of the field and proposes a vigorous program to pursue them, extending to the year 2000. The goals of gamma-ray astronomy include the study of gamma rays which provide the most direct means of studying many important problems in high energy astrophysics including explosive nucleosynthesis, accelerated particle interactions and sources, and high-energy processes around compact objects. The current research program in gamma-ray astronomy in the U.S. including the space program, balloon program and foreign programs in gamma-ray astronomy is described. The high priority recommendations for future study include an Explorer-class high resolution gamma-ray spectroscopy mission and a Get Away Special cannister (GAS-can) or Scout class multiwavelength experiment for the study of gamma-ray bursts. Continuing programs include an extended Gamma Ray Observatory mission, continuation of the vigorous program of balloon observations of the nearby Supernova 1987A, augmentation of the balloon program to provide for new instruments and rapid scientific results, and continuation of support for theoretical research. Long term recommendations include new space missions using advanced detectors to better study gamma-ray sources, the development of these detectors, continued study for the assembly of large detectors in space, collaboration with the gamma-ray astronomy missions initiated by other countries, and consideration of the Space Station attached payloads for gamma-ray experiments.

  2. GAMMA-RAY DETECTION WITH PbO GLASS CONVERTERS IN MWPC: ELECTRON CONVERSION EFFICIENCY AND TIME RESOLUTION

    SciTech Connect

    Lum, G.K.; Perez-Mendez, V.; Sleaford, B.

    1980-06-01

    The development of glass tubing converters for efficient gamma-ray detection in multiwire proportional chambers (MWPC) has led to an investigation on the improvement of conductivity on glass surfaces and to an investigation of gas mixtures which will improve on the electron conversion efficiency and electron transit time within the tubes. Efforts to establish uniform electric field lines within small diameter tubes has resulted in an improved H{sub 2} reducing treatment. For a 0.91 mm I.D., 1.10 mm O.D., 2 cm thick converter the electron conversion efficiency {epsilon} was measured to be 9.0% and 10.4% at 511 keV, using Ar mixtures containing 10% CF{sub 4} and 30% isobutane, respectively. The effects of gas mixtures on {epsilon} and on {tau}, the mean transit time on conversion electrons within the converter, and the projection of these results on the performance of a modified MWPC positron camera will be presented.

  3. Ultrahigh-resolution endoscopic optical coherence tomography for gastrointestinal imaging

    NASA Astrophysics Data System (ADS)

    Chen, Yu; Herz, Paul R.; Hsiung, Pei-Lin; Aguirre, Aaron D.; Schneider, Karl; Fujimoto, James G.; Mashimo, Hiroshi; Desai, Saleem; Pedrosa, Marcos; Schmitt, Joseph M.; Koski, Amanda

    2005-04-01

    Optical coherence tomography (OCT) is an emerging medical imaging technology which can generate high resolution, cross-sectional images of tissue in situ and in real time, without the removal of tissue specimen. Although endoscopic OCT has been used successfully to identify certain pathologies in the gastrointestinal tract, the resolution of current endoscopic OCT systems has been limited to 10-15 um for clinical procedures. In this study, in vivo imaging of the gastrointestinal tract is demonstrated at a three-fold higher axial resolution (<5 um), using a portable, broadband, Cr4+:Forsterite laser as the optical light source. Images acquired from the esophagus and colon on animal model display tissue microstructures and architectural details at ultrahigh resolution, and the features observed in the OCT images are well-matched with histology. The clinical feasibility study is conducted through delivering OCT imaging catheter using the standard endoscope. OCT images of normal esophagus and Barrett's esophagus are demonstrated with distinct features.

  4. Gamma ray astronomy

    NASA Technical Reports Server (NTRS)

    Paciesas, William S.

    1991-01-01

    Miscellaneous tasks related to the development of the Bursts and Transient Source Experiment on the Gamma Ray Observatory and to analysis of archival data from balloon flight experiments were performed. The results are summarized and relevant references are included.

  5. High Energy Gamma Rays

    E-print Network

    R. Mukherjee

    2000-09-22

    This article reviews the present status of high energy gamma-ray astronomy at energies above 30 MeV. Observations in the past decade using both space- and ground-based experiments have been primarily responsible for giving a tremendous boost to our knowledge of the high energy Universe. High energy gamma-rays have been detected from a wide range of Galactic and extragalactic astrophysical sources, such as gamma-ray bursters, pulsars, and active galaxies. These observations have established high energy gamma-ray astronomy as a vital and exciting field, that has a bright future. This review summarizes the experimental techniques, observations and results obtained with recent experiments, and concludes with a short description of future prospects.

  6. Gamma-ray astronomy

    NASA Technical Reports Server (NTRS)

    Ramaty, R.; Lingenfelter, R. E.

    1982-01-01

    Cosmic gamma rays, the physical processes responsible for their production and the astrophysical sites from which they were seen are reported. The bulk of the observed gamma ray emission is in the photon energy range from about 0.1 MeV to 1 GeV, where observations are carried out above the atmosphere. There are also, however, gamma ray observations at higher energies obtained by detecting the Cerenkov light produced by the high energy photons in the atmosphere. Gamma ray emission was observed from sources as close as the Sun and the Moon and as distant as the quasar 3C273, as well as from various other galactic and extragalactic sites. The radiation processes also range from the well understood, e.g. energetic particle interactions with matter, to the still incompletely researched, such as radiation transfer in optically thick electron positron plasmas in intense neutron star magnetic fields.

  7. Gamma-Ray Bursts

    E-print Network

    P. Meszaros

    2006-05-30

    Gamma-ray bursts are the most luminous explosions in the Universe, and their origin and mechanism are the focus of intense research and debate. More than three decades after their discovery, and after pioneering breakthroughs from space and ground experiments, their study is entering a new phase with the recently launched Swift satellite. The interplay between these observations and theoretical models of the prompt gamma ray burst and its afterglow is reviewed.

  8. Gamma ray camera

    SciTech Connect

    Robbins, C.D.; Wang, S.

    1980-09-09

    An anger gamma ray camera is improved by the substitution of a gamma ray sensitive, proximity type image intensifier tube for the scintillator screen in the anger camera, the image intensifier tube having a negatively charged flat scintillator screen and a flat photocathode layer and a grounded, flat output phosphor display screen all of the same dimension (Unity image magnification) and all within a grounded metallic tube envelope and having a metallic, inwardly concaved input window between the scintillator screen and the collimator.

  9. Precision X-Band Linac Technologies for Nuclear Photonics Gamma-Ray Sources

    SciTech Connect

    Hartemann, F V; Albert, F; Anderson, S G; Bayramian, A J; Cross, R R; Ebbers, C A; Gibson, D J; Houck, T L; Marsh, R A; Messerly, M J; Siders, C W; McNabb, D P; Barty, C J; Adolphsen, C E; Chu, T S; Jongewaard, E N; Tantawi, S G; Vlieks, A E; Wang, F; Wang, J W; Raubenheimer, T O; Ighigeanu, D; Toma, M; Cutoiu, D

    2011-08-31

    Nuclear photonics is an emerging field of research requiring new tools, including high spectral brightness, tunable gamma-ray sources; high photon energy, ultrahigh-resolution crystal spectrometers; and novel detectors. This presentation focuses on the precision linac technology required for Compton scattering gamma-ray light sources, and on the optimization of the laser and electron beam pulse format to achieve unprecedented spectral brightness. Within this context, high-gradient X-band technology will be shown to offer optimal performance in a compact package, when used in conjunction with the appropriate pulse format, and photocathode illumination and interaction laser technologies. The nascent field of nuclear photonics is enabled by the recent maturation of new technologies, including high-gradient X-band electron acceleration, robust fiber laser systems, and hyper-dispersion CPA. Recent work has been performed at LLNL to demonstrate isotope-specific detection of shielded materials via NRF using a tunable, quasi-monochromatic Compton scattering gamma-ray source operating between 0.2 MeV and 0.9 MeV photon energy. This technique is called Fluorescence Imaging in the Nuclear Domain with Energetic Radiation (or FINDER). This work has, among other things, demonstrated the detection of {sup 7}Li shielded by Pb, utilizing gamma rays generated by a linac-driven, laser-based Compton scattering gamma-ray source developed at LLNL. Within this context, a new facility is currently under construction at LLNL, with the goal of generating tunable {gamma}-rays in the 0.5-2.5 MeV photon energy range, at a repetition rate of 120 Hz, and with a peak brightness in the 10{sup 20} photons/(s x mm{sup 2} x mrad{sup 2} x 0.1% bw).

  10. The gamma-ray observatory

    NASA Technical Reports Server (NTRS)

    1991-01-01

    An overview is given of the Gamma Ray Observatory (GRO) mission. Detection of gamma rays and gamma ray sources, operations using the Space Shuttle, and instruments aboard the GRO, including the Burst and Transient Source Experiment (BATSE), the Oriented Scintillation Spectrometer Experiment (OSSE), the Imaging Compton Telescope (COMPTEL), and the Energetic Gamma Ray Experiment Telescope (EGRET) are among the topics surveyed.

  11. Gamma ray optics

    SciTech Connect

    Jentschel, M.; Guenther, M. M.; Habs, D.; Thirolf, P. G. [Institut Laue-Langevin, F38042 Grenoble (France); Max-Planck-Institut fuer Quantenoptik, D-85748 Garching (Germany); Max-Planck-Institut fuer Quantenoptik, D-85748 Garching, Germany and Ludwig-Maximilians-Universitaet Muenchen, D-85748 Garching (Germany); Ludwig-Maximilians-Universitaet Muenchen, D-85748 Garching (Germany)

    2012-07-09

    Via refractive or diffractive scattering one can shape {gamma} ray beams in terms of beam divergence, spot size and monochromaticity. These concepts might be particular important in combination with future highly brilliant gamma ray sources and might push the sensibility of planned experiments by several orders of magnitude. We will demonstrate the experimental feasibility of gamma ray monochromatization on a ppm level and the creation of a gamma ray beam with nanoradian divergence. The results are obtained using the inpile target position of the High Flux Reactor of the ILL Grenoble and the crystal spectrometer GAMS. Since the refractive index is believed to vanish to zero with 1/E{sup 2}, the concept of refractive optics has never been considered for gamma rays. The combination of refractive optics with monochromator crystals is proposed to be a promising design. Using the crystal spectrometer GAMS, we have measured for the first time the refractive index at energies in the energy range of 180 - 2000 keV. The results indicate a deviation from simple 1/E{sup 2} extrapolation of X-ray results towards higher energies. A first interpretation of these new results will be presented. We will discuss the consequences of these results on the construction of refractive optics such as lenses or refracting prisms for gamma rays and their combination with single crystal monochromators.

  12. Ultra-high resolution crystal structure of recombinant caprine ?-lactoglobulin.

    PubMed

    Crowther, Jennifer M; Lassé, Moritz; Suzuki, Hironori; Kessans, Sarah A; Loo, Trevor S; Norris, Gillian E; Hodgkinson, Alison J; Jameson, Geoffrey B; Dobson, Renwick C J

    2014-11-01

    ?-Lactoglobulin (?lg) is the most abundant whey protein in the milks of ruminant animals. While bovine ?lg has been subjected to a vast array of studies, little is known about the caprine ortholog. We present an ultra-high resolution crystal structure of caprine ?lg complemented by analytical ultracentrifugation and small-angle X-ray scattering data. In both solution and crystalline states caprine ?lg is dimeric (K(D)<5 ?M); however, our data suggest a flexible quaternary arrangement of subunits within the dimer. These structural findings will provide insight into relationships among structural, processing, nutritional and immunological characteristics that distinguish cow's and goat's milk. PMID:25241165

  13. GRI: the gamma-ray imager mission

    E-print Network

    Jürgen Knödlseder

    2006-08-07

    Observations of the gamma-ray sky reveal the most powerful sources and the most violent events in the Universe. While at lower wavebands the observed emission is generally dominated by thermal processes, the gamma-ray sky provides us with a view on the non-thermal Universe. Here particles are accelerated to extreme relativistic energies by mechanisms which are still poorly understood, and nuclear reactions are synthesizing the basic constituents of our world. Cosmic accelerators and cosmic explosions are the major science themes that are addressed in the gamma-ray regime. With the INTEGRAL observatory, ESA has provided a unique tool to the astronomical community revealing hundreds of sources, new classes of objects, extraordinary views of antimatter annihilation in our Galaxy, and fingerprints of recent nucleosynthesis processes. While INTEGRAL provides the global overview over the soft gamma-ray sky, there is a growing need to perform deeper, more focused investigations of gamma-ray sources. In soft X-rays a comparable step was taken going from the Einstein and the EXOSAT satellites to the Chandra and XMM/Newton observatories. Technological advances in the past years in the domain of gamma-ray focusing using Laue diffraction and multilayer-coated mirror techniques have paved the way towards a gamma-ray mission, providing major improvements compared to past missions regarding sensitivity and angular resolution. Such a future Gamma-Ray Imager will allow to study particle acceleration processes and explosion physics in unprecedented detail, providing essential clues on the innermost nature of the most violent and most energetic processes in the Universe.

  14. 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.

  15. 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.

  16. Gamma ray camera

    DOEpatents

    Perez-Mendez, Victor (Berkeley, CA)

    1997-01-01

    A gamma ray camera for detecting rays emanating from a radiation source such as an isotope. The gamma ray camera includes a sensor array formed of a visible light crystal for converting incident gamma rays to a plurality of corresponding visible light photons, and a photosensor array responsive to the visible light photons in order to form an electronic image of the radiation therefrom. The photosensor array is adapted to record an integrated amount of charge proportional to the incident gamma rays closest to it, and includes a transparent metallic layer, photodiode consisting of a p-i-n structure formed on one side of the transparent metallic layer, and comprising an upper p-type layer, an intermediate layer and a lower n-type layer. In the preferred mode, the scintillator crystal is composed essentially of a cesium iodide (CsI) crystal preferably doped with a predetermined amount impurity, and the p-type upper intermediate layers and said n-type layer are essentially composed of hydrogenated amorphous silicon (a-Si:H). The gamma ray camera further includes a collimator interposed between the radiation source and the sensor array, and a readout circuit formed on one side of the photosensor array.

  17. Ultrahigh resolution multicolor colocalization of single fluorescent nanocrystals

    SciTech Connect

    Michalet, X.; Lacoste, T.D.; Pinaud, F.; Chemla, D.S.; Alivisatos, A.P.; Weiss, S.

    2000-12-20

    A new method for in vitro and possibly in vivo ultrahigh-resolution colocalization and distance measurement between biomolecules is described, based on semiconductor nanocrystal probes. This ruler bridges the gap between FRET and far-field (or near-field scanning optical microscope) imaging and has a dynamic range from few nanometers to tens of micrometers. The ruler is based on a stage-scanning confocal microscope that allows the simultaneous excitation and localization of the excitation point-spread-function (PSF) of various colors nanocrystals while maintaining perfect registry between the channels. Fit of the observed diffraction and photophysics-limited images of the PSFs with a two-dimensional Gaussian allows one to determine their position with nanometer accuracy. This new high-resolution tool opens new windows in various molecular, cell biology and biotechnology applications.

  18. GAMMA RAY IMAGING FOR ENVIRONMENTAL REMEDIATION

    EPA Science Inventory

    The research is a three year development program to apply high resolution gamma-ray imaging technologies to environmental remediation of radioactive hazards. High resolution, position-sensitive germanium detectors are being developed at the Naval Research Laboratory for space app...

  19. Effect of tissue preservation on imaging using ultrahigh resolution optical coherence tomography

    E-print Network

    Hsiung, Pei-Lin

    Ultrahigh resolution optical coherence tomography (OCT) is an emerging imaging modality that enables noninvasive imaging of tissue with 1- to 3-?m resolutions. Initial OCT studies have typically been performed using harvested ...

  20. Gamma Ray Bursts

    NASA Technical Reports Server (NTRS)

    Gehrels, Neil; Meszaros, Peter

    2012-01-01

    Gamma-ray bursts (GRBs) are bright flashes of gamma-rays coming from the cosmos. They occur roughly once per day ,last typically lOs of seconds and are the most luminous events in the universe. More than three decades after their discovery, and after pioneering advances from space and ground experiments, they still remain mysterious. The launch of the Swift and Fermi satellites in 2004 and 2008 brought in a trove of qualitatively new data. In this review we survey the interplay between these recent observations and the theoretical models of the prompt GRB emission and the subsequent afterglows.

  1. Gamma-ray bursts.

    PubMed

    Gehrels, Neil; Mészáros, Péter

    2012-08-24

    Gamma-ray bursts (GRBs) are bright flashes of gamma rays coming from the cosmos. They occur roughly once per day, typically last for tens of seconds, and are the most luminous events in the universe. More than three decades after their discovery, and after pioneering advances from space and ground experiments, they still remain mysterious. The launch of the Swift and Fermi satellites in 2004 and 2008 brought in a trove of qualitatively new data. In this Review, we survey the interplay between these recent observations and the theoretical models of the prompt GRB emission and the subsequent afterglow. PMID:22923573

  2. High-resolution neutron-induced [gamma]-ray production cross sections for oxygen and beryllium for neutron energies from 4 to 200 MeV.

    SciTech Connect

    Nelson, R. O. (Ronald O.); Michaudon, A. F. (André F.); Chadwick, M. B. (Mark B.); Young, P. G. (Phillip Gaffney),

    2001-01-01

    Measurements of discrete gamma-ray spectra from neutron-induced reactions on a Be0 sample have been performed using the broad-spectrum neutron spallation source of the WNR facility at LANSCE. Incident neutron energies were determined by the time-of-flight technique. Two high-purity Ge detectors were used to detect gamma rays in the energy range from 0.150 to 9.0 MeV. Spectra were measured at seven angles. Absolute gamma-ray production cross sections were delermined from the measured neutron fluence and detector efficiencies. A new evaluation of the reaction cross sections has been performed based on this data. GNASH model calculations were performed for 20 < E, < 150 MeV, and are compared with the data. KEY WOlWS: neutron-induced reactions, gamma-ray cross section, measurement, evaluation, oxygen, beryllium, germanium detector

  3. Soft gamma rays from black holes versus neutron stars

    NASA Technical Reports Server (NTRS)

    Liang, Edison P.

    1992-01-01

    The recent launches of GRANAT and GRO provide unprecedented opportunities to study compact collapsed objects from their hard x ray and gamma ray emissions. The spectral range above 100 keV can now be explored with much higher sensitivity and time resolution than before. The soft gamma ray spectral data is reviewed of black holes and neutron stars, radiation, and particle energization mechanisms and potentially distinguishing gamma ray signatures. These may include soft x ray excesses versus deficiencies, thermal versus nonthermal processes, transient gamma ray bumps versus power law tails, lines, and periodicities. Some of the highest priority future observations are outlines which will shed much light on such systems.

  4. Evaluation of natural radioactivity content in high-volume surface water samples along the northern coast of Oman Sea using portable high-resolution gamma-ray spectrometry.

    PubMed

    Zare, Mohammad Reza; Kamali, Mahdi; Omidi, Zohre; Khorambagheri, Mahdi; Mortazavi, Mohammad Seddigh; Ebrahimi, Mahmood; Akbarzadeh, Gholamali

    2015-06-01

    Portable high-resolution gamma-ray spectrometry was carried out to determine the natural radioactivity levels in high volume surface water samples of the northern coast of Oman Sea, covering the coastal strip from Hormoz strait to Goatr seaport, for the first time. The water samples from 36 coastal and near shore locations were collected for analysis. Analyses on the samples collected were carried out to determine (226)Ra, (232)Th and (40)K contents. The concentration of (226)Ra, (232)Th and (40)K in surface water samples ranged between 2.19 and 2.82 Bq/L, 1.66-2.17 Bq/L and 132.6-148.87 Bq/L, respectively. The activity profile of radionuclides shows low activity across the study area. The study also examined some radiation hazard indices. The external hazard index was found to be less than 1, indicating a low dose. The results of measurements will serve as background reference level for Oman Sea coastlines. PMID:25847859

  5. Gamma-Ray Bursts

    NASA Technical Reports Server (NTRS)

    Meegan, Charles A.; Six, N. Frank (Technical Monitor)

    2002-01-01

    Gamma-Ray Bursts (GRBs) are now known to be the most powerful explosions in the Universe. I will summarize the history of observations of GRBs, and how we came to know that the sources are so distant. I will also give an overview of the most prominent theories as to the cause of bursts.

  6. Celestial gamma ray study

    NASA Technical Reports Server (NTRS)

    Michelson, Peter F.

    1995-01-01

    This report documents the research activities performed by Stanford University investigators as part of the data reduction effort and overall support of the Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Observatory. This report is arranged chronologically, with each subsection detailing activities during roughly a one year period of time, beginning in June 1991.

  7. “Ultra-high resolution optical trap with single fluorophore sensitivity”

    PubMed Central

    Comstock, Matthew J; Ha, Taekjip; Chemla, Yann R

    2013-01-01

    We present a single-molecule instrument that combines a timeshared ultra-high resolution dual optical trap interlaced with a confocal fluorescence microscope. In a demonstration experiment, individual single-fluorophore labeled DNA oligonucleotides were observed to bind and unbind to complementary DNA suspended between two trapped beads. Simultaneous with the single-fluorophore detection, coincident angstrom-scale changes in tether extension could be clearly observed. Fluorescence readout allowed us to determine the duplex melting rate as a function of force. The new instrument will enable the simultaneous measurement of angstrom-scale mechanical motion of individual DNA-binding proteins (e.g., single base pair stepping of DNA translocases) along with the detection of fluorescently labeled protein properties (e.g., internal configuration). PMID:21336286

  8. Gamma-Ray Burst Wallsheet

    NSDL National Science Digital Library

    2005-01-01

    The Gamma-ray Burst Wallsheet was developed to illustrate the properties of light emanating from a gamma-ray burst as seen by three distant satellites, including NASA's Swift. The back of the wallsheet has one of the three activities in the accompanying educator guide (Angling for Gamma-ray Bursts).

  9. Gamma ray spectrometer for Lunar Scout 2

    NASA Technical Reports Server (NTRS)

    Moss, C. E.; Burt, W. W.; Edwards, B. C.; Martin, R. A.; Nakano, George H.; Reedy, R. C.

    1993-01-01

    We review the current status of the Los Alamos program to develop a high-resolution gamma-ray spectrometer for the Lunar Scout-II mission, which is the second of two Space Exploration Initiative robotic precursor missions to study the Moon. This instrument will measure gamma rays in the energy range of approximately 0.1 - 10 MeV to determine the composition of the lunar surface. The instrument is a high-purity germanium crystal surrounded by an CsI anticoincidence shield and cooled by a split Stirling cycle cryocooler. It will provide the abundance of many elements over the entire lunar surface.

  10. Gamma-Ray Imaging for Explosives Detection

    NASA Technical Reports Server (NTRS)

    deNolfo, G. A.; Hunter, S. D.; Barbier, L. M.; Link, J. T.; Son, S.; Floyd, S. R.; Guardala, N.; Skopec, M.; Stark, B.

    2008-01-01

    We describe a gamma-ray imaging camera (GIC) for active interrogation of explosives being developed by NASA/GSFC and NSWCICarderock. The GIC is based on the Three-dimensional Track Imager (3-DTI) technology developed at GSFC for gamma-ray astrophysics. The 3-DTI, a large volume time-projection chamber, provides accurate, approx.0.4 mm resolution, 3-D tracking of charged particles. The incident direction of gamma rays, E, > 6 MeV, are reconstructed from the momenta and energies of the electron-positron pair resulting from interactions in the 3-DTI volume. The optimization of the 3-DTI technology for this specific application and the performance of the GIC from laboratory tests is presented.

  11. Gamma ray astronomy

    NASA Technical Reports Server (NTRS)

    Paciesas, William S.

    1994-01-01

    The Burst and Transient Source Experiment (BATSE) is one of four instruments on the Compton observatory which was launched by the space shuttle Atlantis on April 5, 1991. As of mid-March, 1994, BATSE detected more than 925 cosmic gamma-ray bursts and more than 725 solar flares. Pulsed gamma rays have been detected from at least 16 sources and emission from at least 28 sources (including most of the pulsed sources) has been detected by the earth occultation technique. UAH participation in BATSE is extensive but can be divided into two main areas, operations and data analysis. The daily BATSE operations tasks represent a substantial level of effort and involve a large team composed of MSFC personnel as well as contractors such as UAH. The scientific data reduction and analysis of BATSE data is also a substantial level of effort in which UAH personnel have made significant contributions.

  12. Ultrahigh-speed ultrahigh-resolution adaptive optics: optical coherence tomography system for in-vivo small animal retinal imaging

    NASA Astrophysics Data System (ADS)

    Jian, Yifan; Xu, Jing; Zawadzki, Robert J.; Sarunic, Marinko V.

    2013-03-01

    Small animal models of human retinal diseases are a critical component of vision research. In this report, we present an ultrahigh-resolution ultrahigh-speed adaptive optics optical coherence tomography (AO-OCT) system for small animal retinal imaging (mouse, fish, etc.). We adapted our imaging system to different types of small animals in accordance with the optical properties of their eyes. Results of AO-OCT images of small animal retinas acquired with AO correction are presented. Cellular structures including nerve fiber bundles, capillary networks and detailed double-cone photoreceptors are visualized.

  13. Gamma ray collimator

    NASA Technical Reports Server (NTRS)

    Casanova, Edgar J. (inventor)

    1991-01-01

    A gamma ray collimator including a housing having first and second sections is disclosed. The first section encloses a first section of depleted uranium which is disposed for receiving and supporting a radiation emitting component such as cobalt 60. The second section encloses a depleted uranium member which is provided with a conical cut out focusing portion disposed in communication with the radiation emitting element for focusing the emitted radiation to the target.

  14. Gamma ray collimator

    NASA Technical Reports Server (NTRS)

    Casanova, Edgar J. (Inventor)

    1993-01-01

    A gamma ray collimator including a housing having first and second sections. The first section encloses a first section of depleted uranium which is disposed for receiving and supporting a radiation emitting component such as cobalt 60. The second section encloses a depleted uranium member which is provided with a conical cut-out focusing portion disposed in communication with the radiation emitting element for focusing the emitted radiation to the target.

  15. Gamma-ray tracking method for pet systems

    DOEpatents

    Mihailescu, Lucian; Vetter, Kai M.

    2010-06-08

    Gamma-ray tracking methods for use with granular, position sensitive detectors identify the sequence of the interactions taking place in the detector and, hence, the position of the first interaction. The improved position resolution in finding the first interaction in the detection system determines a better definition of the direction of the gamma-ray photon, and hence, a superior source image resolution. A PET system using such a method will have increased efficiency and position resolution.

  16. Performance of the EGRET astronomical gamma ray telescope

    SciTech Connect

    Nolan, P.L.; Hofstadter, R.; Hughes, E.B.; Lin, Y.C.; Michelson, P.F. (Stanford Univ., CA (United States)); Bertsch, D.L.; Fichtel, C.E.; Hartman, R.C.; Hunter, S.D.; Mattox, J.R.; Sreekumar, P.; Thompson, D.J. (National Aeronautics and Space Administration, Greenbelt, MD (United States). Goddard Space Flight Center)

    1992-08-01

    On April 5, 1991, the Space Shuttle Atlantis carried the Compton Gamma Ray Observatory (CGRO) into orbit, deploying the satellite on April 7. This paper reports on the EGRET instrument which was activated on April 15, and the first month of operations was devoted to verification of the instrument performance. Measurements made during that month and in the subsequent sky survey phase have verified that the instrument time resolution, angular resolution, and gamma ray detection efficiency are all within nominal limits.

  17. The Extragalactic Gamma Ray Background

    E-print Network

    Charles D. Dermer

    2007-05-10

    One way to understand the nonthermal history of the universe is by establishing the origins of the unresolved and truly diffuse extragalactic gamma rays. Dim blazars and radio/gamma galaxies certainly make an important contribution to the galactic gamma-ray background given the EGRET discoveries, and previous treatments are reviewed and compared with a new analysis. Studies of the gamma-ray intensity from cosmic rays in star-forming galaxies and from structure formation shocks, as well as from dim GRBs, are briefly reviewed. A new hard gamma-ray source class seems required from the predicted aggregate intensity compared with the measured intensity.

  18. Gamma Ray Astronomy with Muons

    E-print Network

    F. Halzen; T. Stanev; G. B. Yodh

    1996-08-29

    Although gamma ray showers are muon-poor, they still produce a number of muons sufficient to make the sources observed by GeV and TeV telescopes observable also in muons. For sources with hard gamma ray spectra there is a relative `enhancement' of muons from gamma ray primaries as compared to that from nucleon primaries. All shower gamma rays above the photoproduction threshold contribute to the number of muons $N_\\mu$, which is thus proportional to the primary gamma ray energy. With gamma ray energy 50 times higher than the muon energy and a probability of muon production by the gammas of about 1\\%, muon detectors can match the detection efficiency of a GeV satellite detector if their effective area is larger by $10^4$. The muons must have enough energy for sufficiently accurate reconstruction of their direction for doing astronomy. These conditions are satisfied by relatively shallow neutrino detectors such as AMANDA and Lake Baikal and by gamma ray detectors like MILAGRO. TeV muons from gamma ray primaries, on the other hand, are rare because they are only produced by higher energy gamma rays whose flux is suppressed by the decreasing flux at the source and by absorption on interstellar light. We show that there is a window of opportunity for muon astronomy with the AMANDA, Lake Baikal and MILAGRO detectors.

  19. {gamma} ray astronomy with muons

    SciTech Connect

    Halzen, F. [Department of Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States)] [Department of Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States); Stanev, T. [Bartol Research Institute, University of Delaware, Newark, Delaware 19716 (United States)] [Bartol Research Institute, University of Delaware, Newark, Delaware 19716 (United States); Yodh, G.B. [Department of Physics and Astronomy, University of California, Irvine, California 92715 (United States)] [Department of Physics and Astronomy, University of California, Irvine, California 92715 (United States)

    1997-04-01

    Although {gamma} ray showers are muon poor, they still produce a number of muons sufficient to make the sources observed by GeV and TeV telescopes observable also in muons. For sources with hard {gamma} ray spectra there is a relative {open_quotes}enhancement{close_quotes} of muons from {gamma} ray primaries as compared to that from nucleon primaries. All shower {gamma} rays above the photoproduction threshold contribute to the number of muons N{sub {mu}}, which is thus proportional to the primary {gamma} ray energy. With {gamma} ray energy 50 times higher than the muon energy and a probability of muon production by the {gamma}{close_quote}s of about 1{percent}, muon detectors can match the detection efficiency of a GeV satellite detector if their effective area is larger by 10{sup 4}. The muons must have enough energy for sufficiently accurate reconstruction of their direction for doing astronomy. These conditions are satisfied by relatively shallow neutrino detectors such as AMANDA and Lake Baikal, and by {gamma} ray detectors such as MILAGRO. TeV muons from {gamma} ray primaries, on the other hand, are rare because they are only produced by higher energy {gamma} rays whose flux is suppressed by the decreasing flux at the source and by absorption on interstellar light. We show that there is a window of opportunity for muon astronomy with the AMANDA, Lake Baikal, and MILAGRO detectors. {copyright} {ital 1997} {ital The American Physical Society}

  20. The obscured gamma-ray and UHECR universe

    E-print Network

    Charles D. Dermer

    2008-04-15

    Auger results on clustering of > 60 EeV ultra-high energy cosmic ray (UHECR) ions and the interpretation of the gamma-ray spectra of TeV blazars are connected by effects from the extragalactic background light (EBL). The EBL acts as an obscuring medium for gamma rays and a reprocessing medium for UHECR ions and protons, causing the GZK cutoff. The study of the physics underlying the coincidence between the GZK energy and the clustering energy of UHECR ions favors a composition of > 60 EeV UHECRs in CNO group nucleons. This has interesting implications for the sources of UHECRs. We also comment on the Auger analysis.

  1. Digital Pulse Processing and Gamma Ray Tracking

    NSDL National Science Digital Library

    Two of the big changes in new generations of Nuclear Physics instrumentation will be the incorporation of digital processing and the use of gamma ray tracking. The Nuclear Physics Group at Daresbury has set up a project to investigate digital pulse processing for gamma ray detectors and how best to implement gamma ray tracking in large Germanium gamma ray detectors. Topics on this site include but are not limited to: gamma ray tracking, overview of the Gamma Ray Tracking Project, pictures of one of the tracking gamma ray detectors (TIGRE), pictures of test experiment, gamma ray tracking project publications, and links to other gamma ray tracking pages.

  2. Development of a high-resolution imaging capability for observing cosmic sources in the hard x-ray\\/soft gamma-ray band

    Microsoft Academic Search

    Fiona Anne Harrison

    1993-01-01

    Astronomical observations in the Hard X-ray\\/Soft Gamma-ray (20 keV-a few hundred keV) region of the electromagnetic spectrum provide insight into astrophysical phenomena distinct from studies in the more classical X-ray band (0.2-15 keV). High-energy non-thermal processes in a variety of sources are best observed above 20 keV, where they are not masked by the intense thermal emission which dominates the

  3. EGRET - The high energy gamma ray telescope for NASA's Gamma Ray Observatory

    NASA Technical Reports Server (NTRS)

    Fichtel, C. E.; Bertsch, D. L.; Hartman, R. C.; Kniffen, D. A.; Thompson, D. J.; Hofstadter, R.; Hughes, E. B.; Campbell-Finman, L. E.; Pinkau, K.; Mayer-Hasselwander, H.

    1983-01-01

    The EGRET high energy gamma-ray telescope under development for NASA's Gamma Ray Observatory will have an energy range of approximately 12 to 30,000 MeV, energy resolution of about 15 percent FWHM over most of that range, an effective area of about 2000 sq cm at high energies, and single photon angular accuracy of approximately 2 deg at 100 MeV, less than 0.1 deg above 5 GeV. This instrument can locate strong sources to an accuracy of about 5 arc min. The instrument utilizes a set of digital spark chambers interleaved with tantalum foils for detection and identification of gamma-ray events, and a large NaI(Tl) scintillator for energy determination. The system is triggered by a coincidence matrix using two arrays of plastic scintillation counters and a large plastic scintillator anticoincidence dome that rejects incident charged particles.

  4. Towed seabed gamma ray spectrometer

    Microsoft Academic Search

    1994-01-01

    For more than 50 years, the measurement of radioactivity has been used for onshore geological surveys and in laboratories. The British Geological Survey (BGS) has extended the use of this type of equipment to the marine environment with the development of seabed gamma ray spectrometer systems. The present seabed gamma ray spectrometer, known as the Eel, has been successfully used

  5. The Compton Gamma Ray Observatory

    Microsoft Academic Search

    N. Gehrels; E. Chipman; D. Kniffen

    1994-01-01

    The Arthur Holly Compton Gamma Ray Observatory Compton) is the second in NASA's series of great Observatories. Launched on 1991 April 5, Compton represents a dramatic increase in capability over previous gamma-ray missions. The spacecraft and scientific instruments are all in good health, and many significant discoveries have already been made. We describe the capabilities of the four scientific instruments,

  6. The Compton Gamma Ray Observatory

    NASA Technical Reports Server (NTRS)

    Gehrels, N.; Chipman, E.; Kniffen, D.

    1994-01-01

    The Arthur Holly Compton Gamma Ray Observatory Compton) is the second in NASA's series of great Observatories. Launched on 1991 April 5, Compton represents a dramatic increase in capability over previous gamma-ray missions. The spacecraft and scientific instruments are all in good health, and many significant discoveries have already been made. We describe the capabilities of the four scientific instruments, and the observing program of the first 2 years of the mission. Examples of early discoveries by Compton are enumerated, including the discovery that gamma-ray bursts are isotropic but spatially inhomogeneous in their distribution; the discovery of a new class of high-energy extragalacatic gamma-ray sources, the gamma-ray AGNs; the discovery of emission from SN 1987A in the nuclear line of Co-57; and the mapping of emission from Al-26 in the interstellar medium (ISM) near the Galactic center. Future observations will include deep surveys of selected regions of the sky, long-tem studies of individual objects, correlative studies of objects at gamma-ray and other energies, a Galactic plane survey at intermediate gamma-ray energies, and improved statistics on gamma-ray bursts to search for small anisotropies. After completion of the all-sky survey, a Guest Investigator program is in progress with guest observers' time share increasing from 30% upward for the late mission phases.

  7. The Compton Gamma Ray Observatory

    NASA Astrophysics Data System (ADS)

    Gehrels, N.; Chipman, E.; Kniffen, D.

    1994-06-01

    The Arthur Holly Compton Gamma Ray Observatory Compton) is the second in NASA's series of great Observatories. Launched on 1991 April 5, Compton represents a dramatic increase in capability over previous gamma-ray missions. The spacecraft and scientific instruments are all in good health, and many significant discoveries have already been made. We describe the capabilities of the four scientific instruments, and the observing program of the first 2 years of the mission. Examples of early discoveries by Compton are enumerated, including the discovery that gamma-ray bursts are isotropic but spatially inhomogeneous in their distribution; the discovery of a new class of high-energy extragalacatic gamma-ray sources, the gamma-ray AGNs; the discovery of emission from SN 1987A in the nuclear line of Co-57; and the mapping of emission from Al-26 in the interstellar medium (ISM) near the Galactic center. Future observations will include deep surveys of selected regions of the sky, long-tem studies of individual objects, correlative studies of objects at gamma-ray and other energies, a Galactic plane survey at intermediate gamma-ray energies, and improved statistics on gamma-ray bursts to search for small anisotropies. After completion of the all-sky survey, a Guest Investigator program is in progress with guest observers' time share increasing from 30% upward for the late mission phases.

  8. Development of a gamma-ray detector with iridium transition edge sensor coupled to a Pb absorber

    E-print Network

    Leman, Steven W.

    We have recently started to develop a high-resolution gamma-ray spectrometer for material defect analysis. Our gamma-ray detector is a microcalorimeter consisting of an iridium/gold bilayer transition edge sensor (TES) ...

  9. Simulation of Gamma Rays from Proton Interaction in Local Galaxies

    SciTech Connect

    Karlsson, Niklas; /SLAC /Stockholm U.; Cohen-Tanugi, Johann; Kamae, Tuneyoshi; Tajima, Hiroyasu; /SLAC /KIPAC, Menlo Park

    2007-06-06

    The GLAST Large Area Telescope will provide unprecedented opportunities to detect cosmic GeV gamma rays, thanks to its large effective area, field of view and angular resolution compared with earlier telescopes. We present here the possibility of detecting GeV gamma rays produced by interactions of accelerated protons (or hadrons) with surrounding ambient material. Sources where such detection could be made include local galaxies, such as the Large Magellanic Cloud (LMC), molecular clouds and other extended sources. We have calculated the expected gamma-ray spectrum for an isotropic distribution of protons in the LMC and simulated a one-year GLAST-LAT observation.

  10. Gamma Ray Bursts

    NASA Technical Reports Server (NTRS)

    Gehrels, Neil

    2006-01-01

    Gamma-ray bursts are among the most fascinating occurrences in the cosmos. They are thought to be the birth cries of black holes throughout the universe. There has been tremendous recent progress in our understanding of bursts with the new data from the Swift mission. Swift was launched in November 2004 and is a multiwave length observatory designed to determine the origin of bursts and use them to probe the early Universe. It was developed and is being operated by an international team of scientists from the US, UK and Italian. The first year of findings from the mission will be presented. A large step forward has been made in our understanding of the mysterious short GRBs. High redshift bursts have been detected leading to a better understanding of star formation rates and distant galaxy environments. GRBs have been found with giant X-ray flares occurring in their afterglow. These, and other topics, will be discussed.

  11. Gamma Ray Bursts - Observations

    NASA Technical Reports Server (NTRS)

    Gehrels, N.; Cannizzo, J. K.

    2010-01-01

    We are in an exciting period of discovery for gamma-ray bursts. The Swift observatory is detecting 100 bursts per year, providing arcsecond localizations and sensitive observations of the prompt and afterglow emission. The Fermi observatory is observing 250 bursts per year with its medium-energy GRB instrument and about 10 bursts per year with its high-energy LAT instrument. In addition, rapid-response telescopes on the ground are providing new capabilities to study optical emission during the prompt phase and spectral signatures of the host galaxies. The combined data set is enabling great advances in our understanding of GRBs including afterglow physics, short burst origin, and high energy emission.

  12. Ultrahigh-resolution optical coherence tomography by broadband continuum generation from a photonic crystal fiber

    Microsoft Academic Search

    Yimin Wang; Yonghua Zhao; J. S. Nelson; Zhongping Chen; Robert S. Windeler

    2003-01-01

    We have developed an ultrahigh-resolution optical coherence tomographic system in which broadband continuum generation from a photonic crystal fiber is used to produce high longitudinal resolution. Longitudinal resolution of 1.3-mum has been achieved in a biological tissue by use of continuum light from 800 to 1400 nm. The system employed a dynamic-focusing tracking method to maintain high lateral resolution over

  13. Adaptive optics using a liquid crystal spatial light modulator for ultrahigh-resolution optical coherence tomography

    Microsoft Academic Search

    Enrique J. Fernández; Boris Povazay; Boris M. Hermann; Angelika Unterhuber; Harald Sattmann; Pedro M. Prieto; Rainer Leitgeb; Peter K. Ahnelt; Pablo Artal; Wolfgang Drexler

    2006-01-01

    Three-dimensional ultrahigh resolution optical coherence tomography (UHR OCT) and adaptive optics (AO) are combined using a liquid crystal programmable phase modulator (PPM) as a correcting device for the first time. AO is required for correcting ocular aberrations in moderate and large pupils in order to achieve high resolution retinal images. The capabilities of the PPM are studied using polychromatic light.

  14. Gamma Ray Astronomy at TeV Energies

    Microsoft Academic Search

    Trevor C. Weekes

    1994-01-01

    Cosmic sources of gamma-rays of energy in excess of 0.25 TeV are now well-established using the ground-based atmospheric Cherenkov technique. Recently high resolution cameras (arrays of phototubes) on large optical reflectors have achieved significant improvements in flux sensitivity. Observations with the Compton Gamma Ray Observatory have shown that many sources have significant fluxes at the highest useful energy of EGRET

  15. Studies of Cosmic Rays with GeV Gamma Rays

    E-print Network

    Hiroyasu Tajima; Tuneyoshi Kamae; Stefano Finazzi; Johann Cohen-Tanugi; James Chiang

    2007-05-10

    We describe the role of GeV gamma-ray observations with GLAST-LAT (Gamma-ray Large Area Space Telescope - Large Area Telescope) in identifying interaction sites of cosmic-ray proton (or hadrons) with interstellar medium (ISM). We expect to detect gamma rays from neutral pion decays in high-density ISM regions in the Galaxy, Large Magellanic Cloud, and other satellite galaxies. These gamma-ray sources have been detected already with EGRET (Energetic Gamma Ray Experiment Telescope) as extended sources (eg. LMC and Orion clouds) and GLAST-LAT will detect many more with a higher spatial resolution and in a wider spectral range. We have developed a novel image restoration technique based on the Richardson-Lucy algorithm optimized for GLAST-LAT observation of extended sources. Our algorithm calculates PSF (point spread function) for each event. This step is very important for GLAST-LAT and EGRET image analysis since PSF varies more than one order of magnitude from one gamma ray to another depending on its energy as well as its impact point and angle in the instrument. The GLAST-LAT and EGRET image analysis has to cope with Poisson fluctuation due to low number of detected photons for most sources. Our technique incorporates wavelet filtering to minimize effects due to the fluctuation. Preliminary studies on some EGRET sources are presented, which shows potential of this novel image restoration technique for the identification and characterisation of extended gamma-ray sources.

  16. HARPO: beam characterization of a TPC for gamma-ray polarimetry and high angular-resolution astronomy in the MeV-GeV range

    E-print Network

    Wang, Shaobo; Bruel, Philippe; Frotin, Mickael; Geerebaert, Yannick; Giebels, Berrie; Gros, Philippe; Horan, Deirdre; Louzir, Marc; Poilleux, Patrick; Semeniouk, Igor; Attié, David; Calvet, Denis; Colas, Paul; Delbart, Alain; Sizun, Patrick; Götz, Diego; Amano, Sho; Kotaka, Takuya; Hashimoto, Satoshi; Minamiyama, Yasuhito; Takemoto, Akinori; Yamaguchi, Masashi; Miyamoto, Shuji; Daté, Schin; Ohkuma, Haruo

    2015-01-01

    A time projection chamber (TPC) can be used to measure the polarization of gamma rays with excellent angular precision and sensitivity in the MeV-GeV energy range through the conversion of photons to e+e- pairs. The Hermetic ARgon POlarimeter (HARPO) prototype was built to demonstrate this concept. It was recently tested in the polarized photon beam at the NewSUBARU facility in Japan. We present this data-taking run, which demonstrated the excellent performance of the HARPO TPC.

  17. Fission-fragment gamma-ray multiplicities

    SciTech Connect

    Hook, D.E.

    1987-01-01

    The gamma ray multiplicity (M{gamma}) of fission fragments is a valuable experimental clue to the physics of the fission process in particular and the dynamics of heavy-ion collisions in general. Apparatus for measuring M{gamma} as a function of mass asymmetry was constructed and commissioned. The apparatus consisted of a time-of-flight telescope with a time resolution for fission fragments of {approx}1.5 ns and a solid angle of some 0.04 strad. The telescope was constructed using a micro-channel plate start detector and a parallel plate avalanche counter as a stop detector. Gamma rays from the fragments were detected in an array of three 5{double prime} {times} 6{double prime} NaI(Tl) detectors placed approximately 55 cm from the target. When used in beam this apparatus provided sufficient mass resolution for the detected fission fragments and allowed excellent separation of the {gamma}-rays and neutrons from the reaction on the basis of their time-of-flight.

  18. Gamma Ray Bursts: a 1983 Overview

    NASA Technical Reports Server (NTRS)

    Cline, T. L.

    1983-01-01

    Gamma ray burst observations are reviewed with mention of new gamma-ray and optical transient measurements and with discussions of the controversial, contradictory and unresolved issues that have recently emerged: burst spectra appear to fluctuate in time as rapidly as they are measured, implying that any one spectrum may be incorrect; energy spectra can be obligingly fitted to practically any desired shape, implying, in effect, that no objective spectral resolution exists at all; burst fluxes and temporal quantities, including the total event energy, are characterized very differently with differing instruments, implying that even elementary knowledge of their properties is instrumentally subjective; finally, the log N-log S determinations are deficient in the weak bursts, while there is no detection of a source direction anisotropy, implying that Ptolemy was right or that burst source distance estimates are basically guesswork. These issues may remain unsolved until vastly improved instruments are flown.

  19. Gamma ray bursts: a 1983 overview

    SciTech Connect

    Cline, T.L.

    1983-10-01

    Gamma ray burst observations are reviewed with mention of new gamma-ray and optical transient measurements and with discussions of the controversial, contradictory and unresolved issues that have recently emerged: burst spectra appear to fluctuate in time as rapidly as they are measured, implying that any one spectrum may be incorrect. Energy spectra can be obligingly fitted to practically any desired shape, implying, in effect, that no objective spectral resolution exists at all. Burst fluxes and temporal quantities, including the total event energy, are characterized very differently with differing instruments, implying that even elementary knowledge of their properties is instrumentally subjective. Finally, the log N-log S determinations are deficient in the weak bursts, while there is no detection of a source direction anisotropy, implying that Ptolemy was right or that burst source distance estimates are basically guesswork. These issues may remain unsolved until vastly improved instruments are flown.

  20. Very High Energy Gamma Ray Astronomy.

    NASA Astrophysics Data System (ADS)

    Goodman, Jordan

    2008-04-01

    In the last decade the number of detected TeV gamma ray sources has gone up by more than an order of magnitude. This is due to the increased sensitivity of the current generation of telescopes. Imaging Atmospheric Cherenkov Telescopes such as HESS, Magic and VERITAS have exploited their high sensitivity and excellent angular resolution to discovered and map new classes of galactic gamma ray sources while continuing to discover and monitor extra-galactic AGN. In addition, Milagro, using water Cherenkov technology, has used its large field of view and continuous exposure to observe large scale diffuse emission from the Galactic plane and extended sources. In addition it has detected galactic sources with flat spectra extending beyond 100 TeV. The combination of these techniques are giving us a new view of the TeV sky and providing tantalizing evidence of the sources of Galactic cosmic rays. This talk will review recent results and discuss prospects for future detectors.

  1. SuperAGILE and Gamma Ray Bursts

    SciTech Connect

    Pacciani, Luigi; Costa, Enrico; Del Monte, Ettore; Donnarumma, Immacolata; Evangelista, Yuri; Feroci, Marco; Frutti, Massimo; Lazzarotto, Francesco; Lapshov, Igor; Rubini, Alda; Soffitta, Paolo; Tavani, Marco [IASF-INAF Rome (Italy); Barbiellini, Guido [INFN Trieste (Italy); Mastropietro, Marcello [CNR Montelibretti (Italy); Morelli, Ennio [IASF-INAF-Bologna (Italy); Rapisarda, Massimo [ENEA Frascati (Italy)

    2006-05-19

    The solid-state hard X-ray imager of AGILE gamma-ray mission -- SuperAGILE -- has a six arcmin on-axis angular resolution in the 15-45 keV range, a field of view in excess of 1 steradian. The instrument is very light: 5 kg only. It is equipped with an on-board self triggering logic, image deconvolution, and it is able to transmit the coordinates of a GRB to the ground in real-time through the ORBCOMM constellation of satellites. Photon by photon Scientific Data are sent to the Malindi ground station at every contact. In this paper we review the performance of the SuperAGILE experiment (scheduled for a launch in the middle of 2006), after its first onground calibrations, and show the perspectives for Gamma Ray Bursts.

  2. September 1, 1999 / Vol. 24, No. 17 / OPTICS LETTERS 1221 Invivo ultrahigh-resolution optical coherence tomography

    E-print Network

    Boppart, Stephen

    September 1, 1999 / Vol. 24, No. 17 / OPTICS LETTERS 1221 Invivo ultrahigh-resolution optical Ultrahigh-resolution optical coherence tomography (OCT) by use of state of the art broad with a Kerr-lens mode-locked Ti:sapphire laser with double-chirped mirrors that emits sub-two- cycle pulses

  3. Gamma Rays from Dark Matter

    E-print Network

    R. J. Protheroe

    2000-11-02

    I give a brief review of high energy gamma-ray signatures of dark matter. The decay of massive $X$-particles and subsequent hadronization have been suggested as the origin of the highest energy cosmic rays. Propagation over cosmological distances to Earth (as would be the case in some topological defect origin models for the $X$-particles) results in potentially observable gamma-ray fluxes at GeV energies. Massive relic particles on the other hand, would cluster in galaxy halos, including that of our Galaxy, and may give rise to anisotropic gamma ray and cosmic ray signals at ultra high energies. Future observations above 100 Gev of gamma rays due to WIMP annihilation in the halo of the Galaxy may be used to place constraints on supersymmetry parameter space.

  4. Gamma-Ray Burst Lines

    E-print Network

    Michael S. Briggs

    1999-10-20

    The evidence for spectral features in gamma-ray bursts is summarized. As a guide for evaluating the evidence, the properties of gamma-ray detectors and the methods of analyzing gamma-ray spectra are reviewed. In the 1980's, observations indicated that absorption features below 100 keV were present in a large fraction of bright gamma-ray bursts. There were also reports of emission features around 400 keV. During the 1990's the situation has become much less clear. A small fraction of bursts observed with BATSE have statistically significant low-energy features, but the reality of the features is suspect because in several cases the data of the BATSE detectors appear to be inconsistent. Furthermore, most of the possible features appear in emission rather than the expected absorption. Analysis of data from other instruments has either not been finalized or has not detected lines.

  5. Early Time Optical Emission from Gamma-Ray Bursts

    NASA Astrophysics Data System (ADS)

    Kopac, D.; Gomboc, A.; Japelj, J.

    We present the study of a sample of Gamma-Ray Bursts (GRBs) with contemporaneous early time optical and gamma-ray detections. By performing detailed temporal and spectral analysis of 18 GRBs which show optical peaks during prompt gamma-ray emission, we find that in most cases early time optical emission shows sharp and steep behavior, with a rich diversity of GRBs' broadband spectral properties. These observational results, supported by a simple internal shock dissipation model, show that the standard external shock interpretation for early time optical emission is disfavored in most cases where early time optical peaks are sharp (Delta t/t < 1$) and have steep rise/decay indices. Although the sample of GRBs with contemporaneous optical and gamma-ray detections has become sufficiently larger after the launch of the Swift satellite, this field of research is still poorly developed, mainly due to inadequate optical time resolution and often too long response time of robotic optical telescopes.

  6. Multiwavelength Astronomy: Gamma Ray Science

    NSDL National Science Digital Library

    Dieter Hartmann, a high-energy physicist, presents a story-based lesson on the science of Gamma-Ray astronomy. The lesson focuses on gamma-ray bursts; examining their sources, types, and links to the origin and evolution of the Universe. The story-based format of the lesson also provides insights into the nature of science. Students answer questions based on the reading guide. A list of supplemental websites is also included.

  7. Improving the Compatibility of Polycarbonate\\/UHMWPE Blends through Gamma-Ray Irradiation

    Microsoft Academic Search

    Ping Fan; Wen Xu; Canhui Lu; Huawei Zou; Bo Wang

    2006-01-01

    Gamma-ray irradiation treatment in air has been used as an alternative to the common surface treatment of ultrahigh molecular weight polyethylene (UHMWPE) powders to induce some oxygen-containing groups onto the molecular chain of UHMWPE to enhance its compatibility with polycarbonate (PC). The effect of gamma-ray irradiation on the structure and properties of UHMWPE was studied by FTIR, gel content measurement,

  8. Observations of Spin-Powered Pulsars with the EGRET Gamma Ray Telescope

    NASA Astrophysics Data System (ADS)

    Fierro, Joseph Miguel

    The Energetic Gamma Ray Experiment Telescope (EGRET) on board the Compton Gamma Ray Observatory (CGRO) covers the energy range from 30 MeV to 30 GeV with more than an order of magnitude greater sensitivity than any previous experiment in this energy range, as well as improved resolution in spectral, spatial, and timing measurements. The first three and a half years of observations are analyzed to determine the characteristics of the detected gamma-ray pulsars, establish upper limits on high-energy gamma-ray emission from other radio pulsars, and differentiate the unidentified EGRET point sources which have behavior consistent with the detected gamma-ray pulsars. Pulsed high-energy gamma-ray emission has been detected from six spin-powered pulsars. Using the EGRET observations, the total flux and photon spectra, phase -resolved behavior, and efficiency for converting the rotational power into gamma-rays are derived for each of these pulsars. In addition, time variability, pulse nulling, and the relative phases of the radio and gamma-ray pulses are investigated. Radio pulsars which are possible candidates for gamma-ray emission are studied for evidence of pulsed or steady state emission. The properties of the detected gamma-ray pulsars, as well as the upper limits on gamma-radiation from the other radio pulsars, are considered in the context of current models for gamma-ray emission from rotation-driven pulsars.

  9. Multicavity X-Ray Fabry-Perot Resonance with Ultrahigh Resolution and Contrast

    SciTech Connect

    Huang X. R.; Siddons D.; Macrander, A.T.; Peng, R.W.; Wu, X.S.

    2012-05-31

    Realization of x-ray Fabry-Perot (FP) resonance in back-Bragg-reflection crystal cavities has been proposed and explored for many years, but to date no satisfactory performance has been achieved. Here we show that single-cavity crystal resonators intrinsically have limited finesse and efficiency. To break this limit, we demonstrate that monolithic multicavity resonators with equal-width cavities and specific plate thickness ratios can generate ultrahigh-resolution FP resonance with high efficiency, steep peak tails, and ultrahigh contrast simultaneously. The resonance mechanism is similar to that of sequentially cascaded single-cavity resonators. The ultranarrow-bandwidth FP resonance is anticipated to have various applications, including modern ultrahigh-resolution or precision x-ray monochromatization, spectroscopy, coherence purification, coherent diffraction, phase contrast imaging, etc.

  10. Ultrahigh-resolution adaptive optics - optical coherence tomography: toward isotropic 3 mum resolution for in vivo retinal imaging

    Microsoft Academic Search

    Robert J. Zawadzki; Yan Zhang; Steven M. Jones; R. Daniel Ferguson; Stacey S. Choi; Barry Cense; Julia W. Evans; Diana Chen; Donald T. Miller; Scot S. Olivier; John S. Werner

    2007-01-01

    Ultrahigh axial resolution in adaptive optics - optical coherence tomography (AO-OCT) is fundamentally limited by the intrinsic chromatic aberrations of the human eye. Variation in refractive index of the ocular media with wavelength causes the spectral content of broadband light sources to focus at different depths in the retina for light entering the eye and at the imaging detector for

  11. The Animated Gamma-ray Sky Revealed by the Fermi Gamma-ray Space Telescope

    ScienceCinema

    Isabelle Grenier

    2010-01-08

    The Fermi Gamma-ray Space Telescope has been observing the sky in gamma-rays since August 2008.  In addition to breakthrough capabilities in energy coverage (20 MeV-300 GeV) and angular resolution, the wide field of view of the Large Area Telescope enables observations of 20% of the sky at any instant, and of the whole sky every three hours. It has revealed a very animated sky with bright gamma-ray bursts flashing and vanishing in minutes, powerful active galactic nuclei flaring over hours and days, many pulsars twinkling in the Milky Way, and X-ray binaries shimmering along their orbit. Most of these variable sources had not been seen by the Fermi predecessor, EGRET, and the wealth of new data already brings important clues to the origin of the high-energy emission and particles powered by the compact objects. The telescope also brings crisp images of the bright gamma-ray emission produced by cosmic-ray interactions in the interstellar medium, thus allowing to measure the cosmic nuclei and electron spectra across the Galaxy, to weigh interstellar clouds, in particular in the dark-gas phase. The telescope sensitivity at high energy will soon provide useful constraints on dark-matter annihilations in a variety of environments. I will review the current results and future prospects of the Fermi mission.

  12. The Animated Gamma-ray Sky Revealed by the Fermi Gamma-ray Space Telescope

    SciTech Connect

    Isabelle Grenier

    2009-04-01

    The Fermi Gamma-ray Space Telescope has been observing the sky in gamma-rays since August 2008.  In addition to breakthrough capabilities in energy coverage (20 MeV-300 GeV) and angular resolution, the wide field of view of the Large Area Telescope enables observations of 20% of the sky at any instant, and of the whole sky every three hours. It has revealed a very animated sky with bright gamma-ray bursts flashing and vanishing in minutes, powerful active galactic nuclei flaring over hours and days, many pulsars twinkling in the Milky Way, and X-ray binaries shimmering along their orbit. Most of these variable sources had not been seen by the Fermi predecessor, EGRET, and the wealth of new data already brings important clues to the origin of the high-energy emission and particles powered by the compact objects. The telescope also brings crisp images of the bright gamma-ray emission produced by cosmic-ray interactions in the interstellar medium, thus allowing to measure the cosmic nuclei and electron spectra across the Galaxy, to weigh interstellar clouds, in particular in the dark-gas phase. The telescope sensitivity at high energy will soon provide useful constraints on dark-matter annihilations in a variety of environments. I will review the current results and future prospects of the Fermi mission.

  13. Ultrahigh Resolution Simulations of Mode Converted Ion Cyclotron Waves and Lower Hybrid Waves

    E-print Network

    Wright, John C.

    Full Wave studies of mode conversion (MC) processes in toroidal plasmas have required prohibitiveUltrahigh Resolution Simulations of Mode Converted Ion Cyclotron Waves and Lower Hybrid Waves J. C. By distributing the large linear system across many processors in conjunction with the out-of-core technique

  14. A DFB fiber laser sensor system with ultra-high resolution and its noise analysis

    Microsoft Academic Search

    Hao Xiao; Yuliang Liu; Jun He; Fang Li

    2008-01-01

    We describe a distributed feedback fiber laser (DFB FL) sensor system with ultra-high resolution. The sensor is made by writing distributed feedback structures into a high gain active fiber, and the system employs an unbalanced Michelson interferometer to translate laser wavelength shifts induced by weak measurands into phase shifts. A digital phase generated carrier demodulation scheme is introduced to achieve

  15. In vivo measurement of retinal physiology with high-speed ultrahigh-resolution optical

    E-print Network

    Srinivasan, Vivek J.

    optical imaging of the intact retina is demonstrated by using high-speed, ultrahigh-resolution optical of OCT functional imaging in the intact retina. © 2006 Optical Society of America OCIS codes: 110 was used for functional imaging in the rat retina. The spectrometer has been described previously13

  16. Ultrahigh-resolution FT-ICR mass spectrometry characterization of a -pinene ozonolysis SOA

    EPA Science Inventory

    Secondary organic aerosol (SOA) of a-pinene ozonolysis with and without hydroxyl radical scavenging hexane was characterized by ultrahigh-resolution. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Molecular formulas for more than 900 negative ions were i...

  17. The Ultrahigh Resolution Mass Spectrometry of Natural Organic Matter from Different Sources

    Microsoft Academic Search

    Lori Beth Tremblay

    2006-01-01

    Gas phase mass spectral analysis is now showing great promise in the characterization of natural organic matter. With the routine availability of the soft electrospray ionization (ESI) technique, volatilization and ionization of a sample is no longer a problem. Also, resolving power and mass accuracy of the mass spectrometers has increased greatly. Electrospray ionization combined with ultrahigh resolution Fourier transform-ion

  18. A Comparison of Hurricane Eye Determination Using Standard and Ultra-High Resolution

    E-print Network

    Long, David G.

    A Comparison of Hurricane Eye Determination Using Standard and Ultra-High Resolution QuikSCAT Winds of hurricanes. I. INTRODUCTION Space-borne scatterometers such as SeaWinds on QuikSCAT are instruments designed these is the observation and tracking of tropical cyclones including hurricanes. Several fea- tures of interest

  19. Ultra-high Resolution Optics for EUV and Soft X-ray Inelastic Scattering

    E-print Network

    have developed a new technology for achieving both of these goals which should allow high throughput gratings, multilayer EUV, soft x-rays, lithography, anisotropic etch PACS: 07.85.Fv, 07.85.Qe INTRODUCTION Recent accomplishments in the development of ultra-high resolution diffraction gratings for EUV and soft

  20. The Compton Gamma Ray Observatory

    NASA Astrophysics Data System (ADS)

    Gehrels, N.; Chipman, E.; Kniffen, D. A.

    1993-01-01

    The Arthur Holly Compton Gamma Ray Observatory (Compton) was launched by the Space Shuttle Atlantis on 5 April 1991. The spacecraft and instruments are in good health and returning exciting results. The mission provides nearly six orders of magnitude in spectral coverage, from 30 keV to 30 GeV, with sensitivity over the entire range an order of magnitude better than that of previous observations. The 16,000 kilogram observatory contains four instruments on a stabilized platform. The mission began normal operations on 16 May 1991 and is now over half-way through a full-sky survey. The mission duration is expected to be from six to ten years. A Science Support Center has been established at Goddard Space Flight Center for the purpose of supporting a vigorous Guest Investigator Program. New scientific results to date include: (1) the establishment of the isotropy, combined with spatial inhomogeneity, of the distribution of gamma-ray bursts in the sky; (2) the discovery of intense high energy (100 MeV) gamma-ray emission from 3C 279 and other quasars and BL Lac objects, making these the most distant and luminous gamma-ray sources ever detected; (3) one of the first images of a gamma-ray burst; (4) the observation of intense nuclear and position-annihilation gamma-ray lines and neutrons from several large solar flares; and (5) the detection of a third gamma-ray pulsar, plus several other transient and pulsing hard X-ray sources.

  1. Ultrahigh resolution OCT imaging with a two-dimensional MEMS scanning endoscope

    NASA Astrophysics Data System (ADS)

    Aguirre, Aaron D.; Herz, Paul R.; Chen, Yu; Fujimoto, James G.; Piyawattanametha, Wibool; Fan, Li; Hsu, ShuTing; Fujino, Makoto; Wu, Ming C.; Kopf, Daniel

    2005-04-01

    This paper reports preliminary results from the development and application of a two-dimensional MEMS endoscopic scanner for OCT imaging. A 1 mm diameter mirror provides high aperture over large scan angle and can scan at rates of hundreds of Hz in both axes. The mirror is integrated with focusing optics and a fiber-optic collimator into a package of ~5 mm diameter. Using a broadband femtosecond laser light source, ultrahigh axial image resolution of < 5 um in tissue is achieved at 1.06 um center wavelength. Ultrahigh resolution cross-sectional and three-dimensional OCT imaging is demonstrated with the endoscope with ~12 um transverse resolution and < 5 um axial resolution.

  2. Observation of New Rydberg Series and Resonances in Doubly Excited Helium at Ultrahigh Resolution

    Microsoft Academic Search

    K. Schulz; Gunter Kaindl; Michael Domke; John D. Bozek; Philip A. Heimann; Alfred S. Schlachter; J. M. Rost

    1996-01-01

    We report on a striking improvement in spectral resolution in the soft x-ray range to 1.0 meV at 64.1 eV, measured via the mueV-wide 2, -13 double-excitation resonance of helium. This ultrahigh resolution combined with the high photon flux at undulator beam line 9.0.1 of the Advanced Light Source have allowed observation of new Rydberg series and resonances below the

  3. Solar Submillimeter and Gamma-Ray Burst Emission

    NASA Astrophysics Data System (ADS)

    Kaufmann, P.; Raulin, J.-P.; Melo, A. M.; Correia, E.; Costa, J. E. R.; de Castro, C. G. Giménez; Silva, A. V. R.; Yoshimori, M.; Hudson, H. S.; Gan, W. Q.; Gary, D. E.; Gallagher, P. T.; Levato, H.; Marun, A.; Rovira, M.

    2002-08-01

    Solar flare emission was measured at 212 GHz in the submillimeter range by the Submillimeter Solar Telescope in the 1.2-18 GHz microwave range by the Owens Valley Solar Array and in the gamma-ray energy range (continuum) by experiments on board the Yohkoh (>1.2 MeV) and Shenzhou 2 (>0.2 MeV) satellites. At the burst onset, the submillimeter and microwave time profiles were well correlated with gamma rays to the limit of the temporal resolution (<=10 s). At 212 GHz, fast pulses (<1 s), defined as time structures in excess of the bulk emission, were identified as the flux increased. Their spatial positions were scattered by tens of arcseconds with respect to the main burst emission position. Correlation of submillimeter emission with gamma-ray fast time structures shorter than 500 ms is suggested at the gamma-ray maximum. The time variation of the rate of occurrence of the submillimeter rapid pulses was remarkably well correlated with gamma-ray intensities in the energy range (>1.2 MeV), attaining nearly 50 pulses per minute at the maximum. These results suggest that gamma rays might be the response to multiple rapid pulses at 212 GHz and might be produced at different sites within the flaring region.

  4. A model of unpulsed very high energy gamma rays from the Crab Nebula and pulsar

    NASA Technical Reports Server (NTRS)

    Kwok, P. W.; Cheng, K. S.; Lau, M. M.

    1991-01-01

    The angular resolution of gamma-ray detectors does not allow one to separate the nebula from the pulsar in the Crab. It is generally assumed that the steady emission of gamma rays comes from the nebula. Using the 'outer magnetospheric gap' model, an alternative mechanism in which the steady emission of gamma rays could come from a compact region, a couple of light cylinder radii beyond the pulsar.

  5. Gamma rays from molecular clouds

    E-print Network

    Stefano Gabici; Felix Aharonian; Pasquale Blasi

    2006-10-02

    It is believed that the observed diffuse gamma ray emission from the galactic plane is the result of interactions between cosmic rays and the interstellar gas. Such emission can be amplified if cosmic rays penetrate into dense molecular clouds. The propagation of cosmic rays inside a molecular cloud has been studied assuming an arbitrary energy and space dependent diffusion coefficient. If the diffusion coefficient inside the cloud is significantly smaller compared to the average one derived for the galactic disk, the observed gamma ray spectrum appears harder than the cosmic ray spectrum, mainly due to the slower penetration of the low energy particles towards the core of the cloud. This may produce a great variety of gamma ray spectra.

  6. Surface and Coatings Technology, 68/69 (1994) 439--445 439 Ultrahigh vacuum high resolution transmission electron microscopy of

    E-print Network

    Marks, Laurence D.

    1994-01-01

    Surface and Coatings Technology, 68/69 (1994) 439--445 439 Ultrahigh vacuum high resolution of sputter-deposited MoS 2 coatings under both conventional and ultrahigh vacuum (UHV) conditions particles vacuum systems contain 5--15 at.% oxygen (and/or early in operation [1,4,5]. In addition, the edge

  7. Calibration of the Energetic Gamma-Ray Experiment Telescope (EGRET) for the Compton Gamma-Ray Observatory

    Microsoft Academic Search

    D. J. Thompson; D. L. Bertsch; C. E. Fichtel; R. C. Hartman; R. Hofstadter; E. B. Hughes; S. D. Hunter; B. W. Hughlock; G. Kanbach; D. A. Kniffen; Y. C. Lin; J. R. Mattox; H. A. Mayer-Hasselwander; C. von Montigny; P. L. Nolan; H. I. Nel; K. Pinkau; H. Rothermel; E. J. Schneid; M. Sommer; P. Sreekumar; D. Tieger; A. H. Walker

    1993-01-01

    The calibration of the (EGRET) prior to its launch aboard the Compton Gamma Ray Observatory, the continuing calibration after launch, and instrument-performance results based on calibrations and early postlaunch data, are described. Particular attention is given to the effective area, the annular resolution, and the energy resolution.

  8. Application of high resolution NMR, ESR, and gamma-ray scintillation spectroscopy to the study of ligand binding in proteins. [Torpedo californica

    SciTech Connect

    Lancione, G.V.

    1982-01-01

    Electron spin resonance spectroscopy has been employed to study the nature of the ligand binding site of alpha-1-antitrypsin. Spectra of spin-labeled alpha-1-antitrypsin were recorded at pH's ranging from 2.4 to 12.5. This data demonstrates the tight binding of the spin-label to the protease, and the sensitivity of the bound spin-label to informational changes in the protease inhibitor. A molecular dipstick approach has also been applied to this system and has yielded information on the geometry of the cleft accommodating the spin-label. /sup 160/Terbium(III) exchange experiments have been performed on the acetylcholine receptor protein isolated from Torpedo californica, employing a specially designed flow dialysis apparatus constructed in the laboratory. The apparatus is designed to allow continuous monitoring of /sup 160/Tb(III) gamma-ray emission from the protein compartment of the flow dialysis cell. Nicotinic ligand-induced displacement of /sup 160/Tb(III) from the nicotinic binding site of the receptor was monitored as a funtion of (1) the concentration of nicotinic ligand in the washout buffer, and (2) the nature of the nicotinic ligand in the buffer. Measured /sup 160/Tb(III) exchange half-lives indicate (1) a direct relationship between /sup 160/Tb(III) displacement and nicotinic ligand concentration in the wash-out buffer, and (2) an enhanced /sup 160/Tb(III) displacement for nicotinic agents possessing quaternary ammonium functions.

  9. Gamma ray flares in AGN

    NASA Technical Reports Server (NTRS)

    Kafatos, M.

    1992-01-01

    The inner regions of accretion disks of supermassive black holes can become unstable when the existing temperatures are sufficiently high. This naturally occurs for two-temperature disks in the case of rapidly spinning (Kerr) black holes. Physical effects in the hot, inner regions are such that non-steady flows can result. Effects which would be relevant in producing variability in intense gamma-ray sources (MeV to GeV range), such as the recent discovery of strong gamma-ray emission in 3C 279, are discussed.

  10. Towed seabed gamma ray spectrometer

    SciTech Connect

    Jones, D.G. (British Geological Survey, Nottingham (United Kingdom))

    1994-08-01

    For more than 50 years, the measurement of radioactivity has been used for onshore geological surveys and in laboratories. The British Geological Survey (BGS) has extended the use of this type of equipment to the marine environment with the development of seabed gamma ray spectrometer systems. The present seabed gamma ray spectrometer, known as the Eel, has been successfully used for sediment and solid rock mapping, mineral exploration, and radioactive pollution studies. The range of applications for the system continues to expand. This paper examines the technological aspects of the Eel and some of the applications for which it has been used.

  11. Feasibility study of gamma-ray medical radiography.

    PubMed

    Alyassin, Abdalmajeid M; Maqsoud, Hamza A; Mashat, Ahmad M; Al-Mohr, Al-Sayed; Abdulwajid, Subhan

    2013-02-01

    This research explores the feasibility of using gamma-ray radiography in medical imaging. We will show that gamma-ray medical radiography has the potential to provide alternative diagnostic medical information to X-ray radiography. Approximately one Ci Am-241 radioactive source which emits mono-energetic 59.5 keV gamma rays was used. Several factors that influence the feasibility of this study were tested. They were the radiation source uniformity, image uniformity, and image quality parameters such as contrast, noise, and spatial resolution. In addition, several gamma-ray and X-ray images were acquired using humanoid phantoms. These images were recorded on computed radiography image receptors and displayed on a standard monitor. Visual assessments of these images were then conducted. The Am-241 radioactive source provided relatively uniform radiation exposure and images. Image noise and image contrast were mainly dependent on the exposure time and source size, whereas spatial resolution was dependent on source size and magnification factor. The gamma-ray humanoid phantom images were of lower quality than the X-ray images mainly due to the low radioactivity used and not enough exposure time. Nevertheless, the gamma-ray images displayed most of the main structures contained in the humanoid phantoms. Higher exposure rates and thus lower exposure times were estimated for different pure Am-241 source sizes that are hypothesized to provide high quality images similar to X-ray images. For instance, a 10mm source size of pure Am-241 with 7s exposure time should produce images similar in contrast and noise to X-ray images. This research paves the way for the production and usage of a highly radioactive Am-241 source with the potential to lead to the feasibility of acceptable quality medical gamma-ray radiography. PMID:23208227

  12. Recommended Priorities for NASA's Gamma Ray Astronomy Program 1999-2013

    NASA Technical Reports Server (NTRS)

    Carol, Ladd

    1999-01-01

    The Gamma-Ray Astronomy Program Working Group (GRAPWG) recommends priorities for the NASA Gamma-Ray Astronomy Program. The highest priority science topic is nuclear astrophysics and sites of gamma ray line emission. Other high priority topics are gamma ray bursts, hard x-ray emission from accreting black holes and neutron stars, the Advanced Compton Telescope (ACT), the High-resolution Spectroscopic Imager (HSI), and the Energetic X-ray Imaging Survey Telescope (EXIST). The recommendations include special consideration for technology development, TeV astronomy, the ultra-long duration balloon (ULDB) program, the International Space Station, optical telescope support, and data analysis and theory.

  13. Performance evaluation of ASPECT: a high resolution desktop pinhole SPECT system for imaging small animals

    Microsoft Academic Search

    David P. McElroy; Lawrence R. MacDonald; Freek J. Beekman; Yuchuan Wang; Bradley E. Patt; Jan S. Iwanczyk; Benjamin M. W. Tsui; Edward J. Hoffman

    2002-01-01

    Pinhole collimation of gamma rays to image distributions of radiolabeled tracers is considered promising for use in small animal imaging. The recent availability of transgenic mice, coupled with the development of 125I and 99mTc labeled tracers, has allowed the study of a range of human disease models while creating demand for ultrahigh resolution imaging devices. We have developed a compact

  14. Transient Gamma-Ray Spectrometer Observation of the Bright Gamma-Ray Burst GRB 950822

    NASA Astrophysics Data System (ADS)

    Seifert, H.; Teegarden, B. J.; Cline, T. L.; Gehrels, N.; Zand, J. J. M. in't.; Palmer, D. M.; Ramaty, R.; Hurley, K.; Madden, N. W.; Pehl, R.

    1997-12-01

    The Transient Gamma-Ray Spectrometer (TGRS) on the Wind satellite is designed to perform spectroscopy of bright gamma-ray bursts in the ~20-8000 keV energy range, having a resolution 5-30 times better than that of earlier generation detectors. GRB 950822 was the brightest burst observed by TGRS in its first year of operation, with a peak flux (1024 ms) of ~78.3 photons cm-2 s-1 and a fluence (50-300 keV) of ~1.4 × 10-4 ergs cm-2 therefore, the GRB data in this paper represent the first high-resolution spectroscopy ever performed on a burst of this brightness. The continuum spectrum of GRB 950822 has the classical gamma-ray burst shape and exhibits typical evolution from hard to soft over the course of the burst. We found no evidence of line features or any other spectral fine structure with significance greater than 3.5 ? in our data.

  15. Diffractive catheter for ultrahigh-resolution spectral-domain volumetric OCT imaging.

    PubMed

    Xi, Jiefeng; Zhang, Anqi; Liu, Zhenyu; Liang, Wenxuan; Lin, Lih Y; Yu, Shaoyong; Li, Xingde

    2014-04-01

    We present a novel design for an endoscopic imaging catheter utilizing diffractive optics for ultrahigh-resolution optical coherence tomography (OCT) imaging at 800 nm. A diffractive microlens was developed to alleviate severe chromatic aberration when a broadband light source was employed at the 800 nm wavelength range. Combined with a home-built fiber rotary joint and a broadband Ti:sapphire laser, the imaging catheter achieved a lateral resolution of 6.2 ?m and an axial resolution of 3.0 ?m in air. The performance of the catheter was demonstrated by three-dimensional full-circumferential endoscopic OCT imaging of guinea pig esophagus in vivo. PMID:24686663

  16. Ultra-high resolution optical CT dosimetry for the visualisation of synchrotron microbeam therapy doses

    NASA Astrophysics Data System (ADS)

    Doran, S. J.; Rahman, A. T. Abdul; Bräuer-Krisch, E.; Brochard, T.; Adamovics, J.

    2013-06-01

    Optical CT is a method that can potentially provide both accurate dosimetry at high spatial resolution and 3-D visualisation over a large field-of-view in a single dataset. The major factors limiting spatial resolution in previous studies are analysed here and it is shown that improvements in equipment specification can overcome many of these. The need for ultra-high spatial resolution in the verification of microbeam radiation therapy verification is demonstrated and example images of a PRESAGE® sample are presented.

  17. Ultrahigh Speed Imaging of the Rat Retina Using Ultrahigh Resolution Spectral/Fourier Domain OCT

    E-print Network

    Liu, Jonathan Jaoshin

    We performed OCT imaging of the rat retina at 70,000 axial scans per second with ~3 ?m axial resolution. Three-dimensional OCT (3D-OCT) data sets of the rat retina were acquired. The high speed and high density data sets ...

  18. A preliminary report on the determination of natural radioactivity levels of the State of Qatar using high-resolution gamma-ray spectrometry

    NASA Astrophysics Data System (ADS)

    Al-Sulaiti, H.; Regan, P. H.; Bradley, D. A.; Malain, D.; Santawamaitre, T.; Habib, A.; Matthews, M.; Bukhari, S.; Al-Dosari, M.

    2010-07-01

    This study is aimed at the determination of the activity concentrations of naturally occuring and technically enhanced levels of radiation in soil samples collected across the landscape of Qatar. Representative soil samples from various locations across the Qatarian peninsula have been collected and analyzed in order to establish activity concentrations associated with the 235,8U and 232Th natural decay chains and also the long-lived naturally occurring radionuclide 40K. The activity concentrations have been measured using a hyper-pure germanium detector. Details of the sample preparation and the gamma-ray spectroscopic analysis techniques are presented, together with the preliminary values of the activity concentrations associated with the naturally occuring radionuclide chains for six soil samples collected from the Qatarian peninsula. Sample 228, which has been collected from an inshore oil-field area, was observed to have the highest observed value of 226Ra concentration among the six samples. The weighted mean values of the activity concentrations of the radionuclides 238U, 232Th and 40K in one particular sample (sample 228) were, respectively, found to be 213.9±1.4, 4.55±0.11 and 111.4±3.6 Bq/kg, which compare with the worldwide weighted mean values in soil samples, 33, 45 and 420 Bq/kg, respectively. The deduced activity concentration of 238U in sample 228 in the current work was found to be significantly higher than the worldwide average value and was also significantly higher than the values determined for the five other initial samples discussed here. The mean values of the activity concentration of the 232Th series, 40K and 137Cs in Bq/kg from the six investigated soil samples were found to be 9.4±1.3, 204±22 and 5.8±5.6, respectively, with the quoted uncertainty referring to the standard deviation among these measurements.

  19. POSITION SENSITIVE GERMANIUM DETECTORS FOR GAMMA-RAY IMAGING AND SPECTROSCOPY

    EPA Science Inventory

    Gamma-ray imaging with position-sensitive germanium detectors offers the advantages of excellent energy resolution, high detection efficiency, and potentially good sptial resolution. The development of the amorphous-semiconductor electrical contact technology for germanium detec...

  20. Cosmological gamma-ray bursts

    NASA Technical Reports Server (NTRS)

    Paczynski, Bohdan

    1991-01-01

    The distribution in angle and flux of gamma-ray bursts indicates that the majority of gamma-ray bursters are at cosmological distances, i.e., at z of about 1. The rate is then about 10 exp -8/yr in a galaxy like the Milky Way, i.e., orders of magnitude lower than the estimated rate for collisions between neutron stars in close binary systems. The energy per burst is about 10 exp 51 ergs, assuming isotropic emission. The events appear to be less energetic and more frequent if their emission is strongly beamed. Some tests for the distance scale are discussed: a correlation between the burst's strength and its spectrum; the absorption by the Galactic gas below about 2 keV; the X-ray tails caused by forward scattering by the Galactic dust; about 1 month recurrence of some bursts caused by gravitational lensing by foreground galaxies; and a search for gamma-ray bursts in M31. The bursts appear to be a manifestation of something exotic, but conventional compact objects can provide an explanation. The best possibility is offered by a decay of a bindary composed of a spinning-stellar-mass black-hole primary and a neutron or a strange-quark star secondary. In the final phase the secondary is tidally disrupted, forms an accretion disk, and up to 10 exp 54 ergs are released. A very small fraction of this energy powers the gamma-ray burst.

  1. Swift: Gamma-Ray Bursts

    NSDL National Science Digital Library

    2005-12-17

    In this video segment adapted from Penn State Public Broadcasting's Swift: Eyes Through Time, learn about the Swift satellite — a NASA mission with international participation — and how it is collecting data about gamma-ray bursts that may yield important discoveries about the Universe.

  2. Gamma ray bursters: a solution?

    Microsoft Academic Search

    G. M. Hurst

    2003-01-01

    We certainly live in exciting astronomical times. Recently a Gamma Ray Burster, designated GRB 030329, produced an optical afterglow or transient (OT), which at one stage on March 29, was observed at magnitude 12.4. There has been discussion that it may have been as bright as magnitude 3 and therefore a naked eye object at the moment of outburst but

  3. The Compton Gamma Ray Observatory

    Microsoft Academic Search

    N. Gehrels; E. Chipman; D. A. Kniffen

    1993-01-01

    The Arthur Holly Compton Gamma Ray Observatory (Compton) was launched by the Space Shuttle Atlantis on 5 April 1991. The spacecraft and instruments are in good health and returning exciting results. The mission provides nearly six orders of magnitude in spectral coverage, from 30 keV to 30 GeV, with sensitivity over the entire range an order of magnitude better than

  4. Gamma ray astrophysics: the EGRET results

    E-print Network

    D J Thompson

    2008-11-05

    Cosmic gamma rays provide insight into some of the most dynamic processes in the Universe. At the dawn of a new generation of gamma-ray telescopes, this review summarizes results from the Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory, the principal predecessor mission studying high-energy photons in the 100 MeV energy range. EGRET viewed a gamma-ray sky dominated by prominent emission from the Milky Way, but featuring an array of other sources, including quasars, pulsars, gamma-ray bursts, and many sources that remain unidentified. A central feature of the EGRET results was the high degree of variability seen in many gamma-ray sources, indicative of the powerful forces at work in objects visible to gamma-ray telescopes.

  5. In situ gamma-ray spectrometry for the measurement of uranium in surface soils

    Microsoft Academic Search

    K. M. Miller; P. Shebell; G. A. Klemic

    1994-01-01

    The application of the technique of in situ gamma-ray spectrometry to the measurement of uranium isotopes in surface soils is described. A basic review of the in situ methodology using high resolution germanium gamma-ray spectrometers is given and specifics on calculated fluences, dose rates in air, and calibration factors are provided for relevant uranium isotopes and their progeny. The influence

  6. Ultrahigh-resolution soft x-ray tomography

    NASA Astrophysics Data System (ADS)

    Haddad, Waleed S.; Trebes, James E.; Goodman, Dennis M.; Lee, Heung-Rae; McNulty, Ian; Anderson, Erik H.; Zalensky, Andrei O.

    1995-09-01

    Ultra high resolution three-dimensional images of a microscopic test object were made with soft x rays using a scanning transmission x-ray microscope. The test object consisted of two different patterns of gold bars on silicon nitride windows that were separated by approximately 5 micrometer. A series of nine 2-D images of the object were recorded at angles between -5 to +55 degrees with respect to the beam axis. The projections were then combined tomographically to form a 3-D image by means of an algebraic reconstruction technique (ART) algorithm. A transverse resolution of approximately 1000 angstrom was observed. Artifacts in the reconstruction limited the overall depth resolution to approximately 6000 angstrom, however some features were clearly reconstructed with a depth resolution of approximately 1000 angstrom. A specially modified ART algorithm and a constrained conjugate gradient (CCG) code were also developed as improvements over the standard ART algorithm. Both of these methods made significant improvements in the overall depth resolution, bringing it down to approximately 1200 angstrom overall. Preliminary projection data sets were also recorded with both dry and re-hydrated human sperm cells over a similar angular range.

  7. All-fiber CW Raman continuum light source for ultrahigh resolution optical coherence tomography

    Microsoft Academic Search

    Pei-Lin Hsiung; Yu Chen; N. Nishizawa; Tony H. Ko; James G. Fujimoto; Christiano J. S. de Matos; Sergei V. Popov; James R. Taylor; J. Broeng; Valentin P. Gapontsev

    2005-01-01

    High performance, short coherence length light sources with broad bandwidths and high output powers are critical for high speed, ultrahigh resolution OCT imaging. We demonstrate an all-fiber continuous-wave Raman light source based on a photonic crystal fiber, pumped by a continuous-wave Yb-fiber laser, which generates 330 mW output power and 140 nm bandwidths. The light source is compact, robust, turnkey

  8. Ocular Tissue Imaging Using Ultrahigh-Resolution, Full-Field Optical Coherence Tomography

    Microsoft Academic Search

    Kate Grieve; Michel Paques; Arnaud Dubois; Claude Boccara

    2004-01-01

    PURPOSE. Ultrahigh-resolution, full-field optical coherence to- mography (OCT), which uses a white light source, allows bidimensional, noninvasive tomographic imaging without scanning. The goal of the present study was to apply full-field OCT to ocular tissue imaging in an attempt to explore the capabilities of the technique. METHODS. This full-field OCT system uses a Linnik-type inter- ferometer with a tungsten-halogen source.

  9. Enhanced visualization of choroidal vessels using ultrahigh resolution ophthalmic OCT at 1050 nm

    Microsoft Academic Search

    B. Povazay; K. Bizheva; B. Hermann; A. Unterhuber; H. Sattmann; A. F. Fercher; W. Drexler; C. Schubert; P. K. Ahnelt; M. Mei; R. Holzwarth; W. J. Wadsworth; J. C. Knight; P. St. J. Russell

    2003-01-01

    In this article the ability of ultrahigh resolution ophthalmic optical coherence tomography (OCT) to image small choroidal blood vessels below the highly reflective and absorbing retinal pigment epithelium is demonstrated for the first time. A new light source (lc= 1050 nm, Dl = 165 nm, Pout= 10 mW), based on a photonic crystal fiber pumped by a compact, self-starting Ti:Al2O3

  10. The Universe Viewed in Gamma-Rays 1 Concept of new gamma ray detector

    E-print Network

    Enomoto, Ryoji

    The Universe Viewed in Gamma-Rays 1 Concept of new gamma ray detector Satoko Osone Institute for Cosmic Ray Research, University of Tokyo, 5-1-5 Kashiwa-no-Ha, Kashiwa City,Chiba 277-8582, Japan Abstract We present a concept of a new gamma ray detector in order to observe undetected TeV gamma ray

  11. Nuclear gamma rays from energetic particle interactions

    NASA Technical Reports Server (NTRS)

    Ramaty, R.; Kozlovsky, B.; Lingenfelter, R. E.

    1978-01-01

    Gamma ray line emission from nuclear deexcitation following energetic particle reactions is evaluated. The compiled nuclear data and the calculated gamma ray spectra and intensities can be used for the study of astrophysical sites which contain large fluxes of energetic protons and nuclei. A detailed evaluation of gamma ray line production in the interstellar medium is made.

  12. Gamma ray spectroscopy in astrophysics. [conferences

    NASA Technical Reports Server (NTRS)

    Cline, T. L. (editor); Ramaty, R. (editor)

    1978-01-01

    Experimental and theoretical aspects of gamma ray spectroscopy in high energy astrophysics are discussed. Line spectra from solar, stellar, planetary, and cosmic gamma rays are examined as well as HEAO investigations, the prospects of a gamma ray observatory, and follow-on X-ray experiments in space.

  13. Gamma ray astrophysics. [emphasizing processes and absorption

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.

    1974-01-01

    Gamma ray production processes are reviewed, including Compton scattering, synchrotron radiation, bremsstrahlung interactions, meson decay, nucleon-antinucleon annihilations, and pion production. Gamma ray absorption mechanisms through interactions with radiation and with matter are discussed, along with redshifts and gamma ray fluxes.

  14. Enhanced visualization of choroidal vessels using ultrahigh resolution ophthalmic OCT at 1050 nm

    NASA Astrophysics Data System (ADS)

    Povazay, B.; Bizheva, K.; Hermann, B.; Unterhuber, A.; Sattmann, H.; Fercher, A. F.; Drexler, W.; Schubert, C.; Ahnelt, P. K.; Mei, M.; Holzwarth, R.; Wadsworth, W. J.; Knight, J. C.; Russell, P. St. J.

    2003-08-01

    In this article the ability of ultrahigh resolution ophthalmic optical coherence tomography (OCT) to image small choroidal blood vessels below the highly reflective and absorbing retinal pigment epithelium is demonstrated for the first time. A new light source (lc= 1050 nm, Dl = 165 nm, Pout= 10 mW), based on a photonic crystal fiber pumped by a compact, self-starting Ti:Al2O3 laser has therefore been developed. Ex-vivo ultrahigh resolution OCT images of freshly excised pig retinas acquired with this light source demonstrate enhanced penetration into the choroid and better visualization of choroidal vessels as compared to tomograms acquired with a state-of-the art Ti:Al2O3 laser (Femtolasers Compact Pro, lc= 780 nm, Dl= 160 nm, Pout= 400 mW), normally used in clinical studies for in vivo ultrahigh resolution ophthalmic OCT imaging. These results were also compared with retinal tomograms acquired with a novel, spectrally broadened fiber laser (MenloSystems, lc= 1350 nm, Dl= 470 nm, Pout = 4 mW) permitting even greater penetration in the choroid. Due to high water absorption at longer wavelengths retinal OCT imaging at ~1300 nm may find applications in animal ophthalmic studies. Detection and follow-up of choroidal neovascularization improves early diagnosis of many retinal pathologies, e.g. age-related macular degeneration or diabetic retinopathy and can aid development of novel therapy approaches.

  15. Enhanced visualization of choroidal vessels using ultrahigh resolution ophthalmic OCT at 1050 nm.

    PubMed

    Povazay, B; Bizheva, K; Hermann, B; Unterhuber, A; Sattmann, H; Fercher, A; Drexler, W; Schubert, C; Ahnelt, P; Mei, M; Holzwarth, R; Wadsworth, W; Knight, J; Russell, P St J

    2003-08-25

    In this article the ability of ultrahigh resolution ophthalmic optical coherence tomography (OCT) to image small choroidal blood vessels below the highly reflective and absorbing retinal pigment epithelium is demonstrated for the first time. A new light source (lambdac= 1050 nm, Deltalambda = 165 nm, Pout= 10 mW), based on a photonic crystal fiber pumped by a compact, self-starting Ti:Al2O3 laser has therefore been developed. Ex-vivo ultrahigh resolution OCT images of freshly excised pig retinas acquired with this light source demonstrate enhanced penetration into the choroid and better visualization of choroidal vessels as compared to tomograms acquired with a state-of-the art Ti:Al2O3 laser (Femtolasers Compact Pro, lc= 780 nm, Deltalambda= 160 nm, Pout= 400 mW), normally used in clinical studies for in vivo ultrahigh resolution ophthalmic OCT imaging. These results were also compared with retinal tomograms acquired with a novel, spectrally broadened fiber laser (MenloSystems, lambdac= 1350 nm, Deltalambda= 470 nm, Pout = 4 mW) permitting even greater penetration in the choroid. Due to high water absorption at longer wavelengths retinal OCT imaging at ~1300 nm may find applications in animal ophthalmic studies. Detection and follow-up of choroidal neovascularization improves early diagnosis of many retinal pathologies, e.g. age-related macular degeneration or diabetic retinopathy and can aid development of novel therapy approaches. PMID:19466083

  16. UltraHigh Resolution Imaging by Fluorescence Photoactivation Localization Microscopy

    Microsoft Academic Search

    Samuel T. Hess; Thanu P. K. Girirajan; Michael D. Mason

    2006-01-01

    Biological structures span many orders of magnitude in size, but far-field visible light microscopy suffers from limited resolution. A new method for fluorescence imaging has been developed that can obtain spatial distributions of large numbers of fluorescent molecules on length scales shorter than the classical diffraction limit. Fluorescence photoactivation localization microscopy (FPALM) analyzes thousands of single fluorophores per acquisition, localizing

  17. Adaptive optics for ophthalmic ultrahigh-resolution optical coherence tomography

    Microsoft Academic Search

    E. J. Fernandez; B. Hermann; A. Unterhuber; B. Povazay; H. Sattmann; W. Drexler; P. M. Prieto; P. Artal

    2005-01-01

    The prospects to combine AO and OCT both theoretically and experimentally are presented. The possibility to significantly improve the performance of ophthalmic UHR OCT systems by means of AO is proved. Moreover, the expected transversal resolution when using larger pupil sizes in the eye in combination with AO should enable the study for the first time of many retinal structures

  18. HIGH-RESOLUTION X-RAY OBSERVATIONS OF THE PULSAR WIND NEBULA ASSOCIATED WITH THE GAMMA-RAY SOURCE HESS J1640-465

    SciTech Connect

    Lemiere, A.; Slane, P.; Murray, S. [Harvard-Smithonian Center For Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Gaensler, B. M. [Institute of Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia)

    2009-12-01

    We present a Chandra X-ray observation of the very high energy gamma-ray source HESS J1640 - 465. We identify a point source surrounded by a diffuse emission that fills the extended object previously detected by XMM-Newton at the centroid of the HESS source, within the shell of the radio supernova remnant (SNR) G338.3 - 0.0. The morphology of the diffuse emission strongly resembles that of a pulsar wind nebula (PWN) and extends asymmetrically to the southwest of a point source presented as a potential pulsar. The spectrum of the putative pulsar and compact nebula are well characterized by an absorbed power-law model which, for a reasonable N{sub H} value of 14 x 10{sup 22} cm{sup -2}, exhibit an index of 1.1 and 2.5 respectively, typical of Vela-like PWNe. We demonstrate that, given the H I absorption features observed along the line of sight, the SNR and the H II surrounding region are probably connected and lie between 8 kpc and 13 kpc. The resulting age of the system is between 10 and 30 kyr. For a 10 kpc distance (also consistent with the X-ray absorption) the 2-10 keV X-ray luminosities of the putative pulsar and nebula are L{sub PSR} approx 1.3 x 10{sup 33} d {sup 2}{sub 10kpc} erg s{sup -1} and L{sub PWN} approx 3.9 x 10{sup 33} d {sup 2}{sub 10} erg s{sup -1} (d {sub 10} = d/10 kpc). Both the flux ratio of L {sub PWN}/L{sub PSR} approx 3.4 and the total luminosity of this system predict a pulsar spin-down power around E-dotapprox4 x 10{sup 36} erg s{sup -1}. We finally consider several reasons for the asymmetries observed in the PWN morphology and discuss the potential association with the HESS source in terms of a time-dependent one-zone leptonic model.

  19. Ultrahigh resolution fiber-optic quasi-static strain sensors for geophysical research

    NASA Astrophysics Data System (ADS)

    He, Zuyuan; Liu, Qingwen; Tokunaga, Tomochika

    2013-12-01

    A review of our recent work on ultrahigh resolution optical fiber sensors in the quasi-static region is presented, and their applications in crustal deformation measurement are introduced. Geophysical research such as studies on earthquake and volcano requires monitoring the earth's crustal deformation continuously with a strain resolution on the order of nano-strains (n?) in static to low frequency region. Optical fiber sensors are very attractive due to their unique advantages such as low cost, small size, and easy deployment. However, the resolution of conventional optical fiber strain sensors is far from satisfactory in the quasi-static domain. In this paper, several types of recently developed fiber-optic sensors with ultrahigh resolution in the quasi-static domain are introduced, including a fiber Bragg grating (FBG) sensor interrogated with a narrow linewidth tunable laser, an FBG based fiber Fabry-Perot interferometer (FFPI) sensor by using a phase modulation technique, and an FFPI sensor with a sideband interrogation technique. Quantificational analyses and field experimental results demonstrated that the FBG sensor can provide nano-order strain resolution. The sub-nano strain resolution was also achieved by the FFPI sensors in laboratory. Above achievements provide the basis to develop powerful fiber-optic tools for geophysical research on crustal deformation monitoring.

  20. Technical evaluation of software for gamma-ray logging system

    SciTech Connect

    Stromswold, D.C.

    1994-05-01

    This report contains results of a technical review of software, identified as LGCALC, that processes data collected by a high-resolution gamma-ray borehole logging system. The software presently operates within Westinghouse Hanford Company, Department of Geosciences, to process data collected by the Radionuclide Logging System. The software has been reviewed for its suitability for processing data to be collected by new high-resolution gamma-ray logging trucks scheduled to begin operational tests within Westinghouse Tank Waste Remediation Systems during 1994. Examination of the program code and hands-on operational tests have shown that this software is suitable for its intended use of processing high-resolution gamma-ray data obtained from borehole logging. Most of the code requires no changes, but in a few limited cases, suggestions have been made to correct errors or improve operation. Section 4 describes these changes. The technical review has confirmed the appropriateness, correctness, completeness, and coding accuracy of algorithms used to process spectral gamma-ray data, leading to a calculation of subsurface radionuclide contaminants. Running the program with test data from calibration models has confirmed that the program operates correctly. Comparisons with hand calculations have shown the correctness of the output from the program, based on known input data. Section 3 describes these tests. The recommended action is to make the near term programming changes suggested in Section 4.1 and then use the LGCALC analysis program with the new high-resolution logging systems once they have been properly calibrated.

  1. The Fermi Gamma-ray Burst Monitor Instrument

    SciTech Connect

    Bhat, P. N.; Briggs, M. S.; Connaughton, V.; Paciesas, W. S.; Preece, R. D. [University of Alabama in Huntsville, Huntsville AL (United States); Meegan, C. A. [Universities Space Research Association, Huntsville AL (United States); Lichti, G. G.; Diehl, R.; Greiner, J.; Kienlin, A. von [Max-Planck-Institut fuer extraterrestrische Physik, Garching (Germany); Fishman, G. J.; Kouveliotou, C. [NASA Marshall Space Flight Center, Huntsville AL (United States); Kippen, R. M. [Los Alamos National Laboratory, Los Alamos NM (United States)

    2009-05-25

    The Fermi Gamma-ray Space Telescope launched on June 11, 2008 carries two experiments onboard--the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM). The primary mission of the GBM instrument is to support the LAT in observing {gamma}-ray bursts (GRBs) by providing low-energy measurements with high temporal and spectral resolution as well as rapid burst locations over a large field-of-view ({>=}8 sr). The GBM will complement the LAT measurements by observing GRBs in the energy range 8 keV to 40 MeV, the region of the spectral turnover in most GRBs. The GBM detector signals are processed by the onboard digital processing unit (DPU). We describe some of the hardware features of the DPU and its expected limitations during intense triggers.

  2. The imaging compton telescope COMPTEL on the gamma ray observatory

    SciTech Connect

    Schonfelder, V.; Aarts, H.; Deerenberg, A.J.M.; Diehl, R.; Lichti, G.G.; Lockwood, J.; Steinle, H.; Swanburg, B.N.

    1984-02-01

    This instrument is based on a newly established concept of ..gamma..-ray detection in the very difficult 1-30 MeV range. It employs the unique feature of a two-step interaction of the ..gamma..-ray: a Compton scattering collision in a first detector followed by an interaction in a second detector element. COMPTEL has been designed to perform a very sensitive survey of the ..gamma..-ray sky. Extreme care has been taken to minimize background so that the detection limits of COMPTEL will be dominated by source counting statistics. It combines a wide field of view (about 1 steradian) with a good angular resolution. The design criteria of COMPTEL and the performance of a Science Model are described.

  3. Pulsed Photofission Delayed Gamma Ray Detection for Nuclear Material Identification

    SciTech Connect

    John Kavouras; Xianfei Wen; Daren R. Norman; Dante R. Nakazawa; Haori Yang

    2012-11-01

    Innovative systems with increased sensitivity and resolution are in great demand to detect diversion and to prevent misuse in support of nuclear materials management for the U.S. fuel cycle. Nuclear fission is the most important multiplicative process involved in non-destructive active interrogation. This process produces the most easily recognizable signature for nuclear materials. High-energy gamma rays can also excite a nucleus and cause fission through a process known as photofission. After photofission reactions, delayed signals are easily distinguishable from the interrogating radiation. Linac-based, advanced inspection techniques utilizing the fission signals after photofission have been extensively studied for homeland security applications. Previous research also showed that a unique delayed gamma ray energy spectrum exists for each fissionable isotope. Isotopic composition measurement methods based on delayed gamma ray spectroscopy will be the primary focus of this work.

  4. Miniature gamma-ray camera for tumor localization

    SciTech Connect

    Lund, J.C.; Olsen, R.W.; James, R.B.; Cross, E. [and others

    1997-08-01

    The overall goal of this LDRD project was to develop technology for a miniature gamma-ray camera for use in nuclear medicine. The camera will meet a need of the medical community for an improved means to image radio-pharmaceuticals in the body. In addition, this technology-with only slight modifications-should prove useful in applications requiring the monitoring and verification of special nuclear materials (SNMs). Utilization of the good energy resolution of mercuric iodide and cadmium zinc telluride detectors provides a means for rejecting scattered gamma-rays and improving the isotopic selectivity in gamma-ray images. The first year of this project involved fabrication and testing of a monolithic mercuric iodide and cadmium zinc telluride detector arrays and appropriate collimators/apertures. The second year of the program involved integration of the front-end detector module, pulse processing electronics, computer, software, and display.

  5. Future directions in experimental gamma ray astronomy. [technology assessment

    NASA Technical Reports Server (NTRS)

    Haymes, R. C.

    1978-01-01

    Better vehicles and instruments are needed if gamma ray spectroscopy in astrophysics and cosmology is to advance. A gamma ray observatory will (1) permit long-term observations of selected sources to measure their variability and to achieve high sensitivity; (2) measure periods in days or weeks; and (3) assess the entire sky to observe various predicted sources, to measure the energy spectrum, and to map the isotropy of the cosmic ray background over larger collecting areas (of the order of a square meter). Conventional and unconventional instruments must cover the energy range from 0.1 MeV to 20 MeV with improved sensitivity. Angular resolution must be improved one degree or more to study discrete X-ray sources in the galactic center. Actively collimated detectors, improved double Compton instruments, and gamma ray correlators to actively synthesize the absolute energy spectrum of the sky protons are discussed as well as the need for scientific balloons.

  6. Gamma ray astronomy. [source mechanisms review

    NASA Technical Reports Server (NTRS)

    Fichtel, C. E.; Kniffen, D.

    1974-01-01

    The various source mechanisms for celestial gamma rays are reviewed. The gamma-ray data are examined as a source of information about the processes and source locations for the production of charged particle cosmic rays, galactic structure, explosive nucleosynthesis in supernovae, regions of confinement for cosmic rays, regions where matter-antimatter annihilation occurs, and the general condition in cosmological space both in the past and present. Topics include gamma rays from pi mesons by nuclear interactions, nuclear and supernovae lines, diffuse emission and discrete sources, interstellar absorption and detection of gamma rays, and others. A brief view of the available gamma-ray detection systems and techniques is presented.

  7. Terrestrial Gamma-Ray Flashes (TGFs)

    NASA Technical Reports Server (NTRS)

    Fishman, Gerald J.

    2010-01-01

    This slide presentation reviews the observation of Terrestrial Gamma Ray Flashes (TGFs) by Gamma-Ray Telescopes. These were: (1) BATSE /Compton Observatory, (2) Solar Spectroscopic Imager, (3) AGILE Gamma-ray Telescope, and (4) Gamma-ray Burst Monitor (GBM) on the Fermi Gamma-ray Space Telescope. It contains charts which display the counts over time, a map or the TGFs observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). and a map showing the latitude and longitude of 85 of the TGFs observed by the Fermi GBM.

  8. Ultrahigh-resolution, high-speed spectral domain optical coherence phase microscopy.

    PubMed

    Ansari, Rehman; Myrtus, Christian; Aherrahrou, Redouane; Erdmann, Jeanette; Schweikard, Achim; Hüttmann, Gereon

    2014-01-01

    We present an ultrahigh-resolution, high-speed spectral domain optical coherence phase microscopy (SD-OCPM) system that combines submicrometer transverse spatial resolution and subnanometer optical path length sensitivity, with an acquisition speed of over 217,000 voxels/s. The proposed SD-OCPM system overcomes two significant drawbacks of traditional common-path interferometers-limited transverse spatial resolution and suboptimal detection sensitivity-while maintaining phase stability that is comparable with common-path interferometer setups. The transverse and axial spatial resolution of the setup is measured to be 0.6 and 1.9 ?m, respectively, with a phase sensitivity of 0.0027 rad (corresponds to optical path length sensitivity of 110 pm). High-speed acquisition allows for phase-sensitive 4D imaging of biological samples with subcellular resolution. PMID:24365818

  9. Ultrahigh-resolution spin-resolved photoemission spectrometer with a mini Mott detector

    SciTech Connect

    Souma, S.; Sugawara, K. [WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Takayama, A.; Sato, T. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Takahashi, T. [WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Department of Physics, Tohoku University, Sendai 980-8578 (Japan); CREST, Japan Science and Technology Agency (JST), Kawaguchi 332-0012 (Japan)

    2010-09-15

    We have developed an ultrahigh-resolution spin-resolved photoemission spectrometer with a highly efficient mini Mott detector and an intense xenon plasma discharge lamp. The spectrometer achieves the energy resolutions of 0.9 and 8 meV for non-spin-resolved and spin-resolved modes, respectively. Three-dimensional spin-polarization is determined by using a 90 deg. electron deflector situated before the Mott detector. The performance of spectrometer is demonstrated by observation of a clear Rashba splitting of the Bi(111) surface states.

  10. Ultrahigh-resolution spin-resolved photoemission spectrometer with a mini Mott detector.

    PubMed

    Souma, S; Takayama, A; Sugawara, K; Sato, T; Takahashi, T

    2010-09-01

    We have developed an ultrahigh-resolution spin-resolved photoemission spectrometer with a highly efficient mini Mott detector and an intense xenon plasma discharge lamp. The spectrometer achieves the energy resolutions of 0.9 and 8 meV for non-spin-resolved and spin-resolved modes, respectively. Three-dimensional spin-polarization is determined by using a 90° electron deflector situated before the Mott detector. The performance of spectrometer is demonstrated by observation of a clear Rashba splitting of the Bi(111) surface states. PMID:20887002

  11. Gamma rays and cosmic rays at Venus: The Pioneer Venus gamma ray detector and considerations for future measurements

    NASA Astrophysics Data System (ADS)

    Lorenz, Ralph D.; Lawrence, David J.

    2015-05-01

    We draw attention to, and present a summary archive of the data from, the Pioneer Venus Orbiter Gamma-ray Burst Detector (OGBD), an instrument not originally conceived with Venus science in mind. We consider the possibility of gamma-ray flashes generated by lightning and model the propagation of gamma rays in the Venusian atmosphere, finding that if gamma rays originate at the upper range of reported cloud top altitudes (75 km altitude), they may be attenuated by factors of only a few, whereas from 60 km altitude they are attenuated by over two orders of magnitude. The present archive is too heavily averaged to reliably detect such a source (and we appeal to investigators who may have retained a higher-resolution archive), but the data do provide a useful and unique record of the cosmic ray flux at Venus 1978-1993. We consider other applications of future orbital gamma ray data, such as atmospheric occultations and the detection of volcanic materials injected high in the atmosphere.

  12. Outburst in the Gamma-ray Bright Quasar CTA26

    NASA Astrophysics Data System (ADS)

    Foord, Adi; Jorstad, S. G.; Marscher, A. P.

    2014-01-01

    We analyze multi-waveband space- and ground-based observations of the z=0.852 quasar CTA26 (PKS 0336-019) over a 6-year time span that includes two gamma-ray outbursts. The instruments used include the Fermi Gamma-ray Space Telescope, the Very Long Baseline Array (VLBA), the Perkins Telescope at Lowell Observatory, and a number of other optical telescopes. We cross-correlate the time variations from the different wavebands and compare the timing of the gamma-ray events with changes in the jet seen in VLBA images at 43 GHz, with a resolution of 100 micro-arcseconds, to determine the relationship between the conditions in the jet and the high-energy outbursts. A total of 39 VLBA images were collected from June 2007 to February 2013 at near bimonthly intervals. We analyze the multi-frequency behavior of the quasar during two prominent gamma-ray outbursts, in late 2010 and late 2011. An increase in the flux in the VLBA images during mid to late 2010 marked the appearance of a new superluminal knot that proceeded to emerge from the mm-wave core as a gamma-ray flare erupted. A similar sequence of events occurred almost a year before the outburst in late 2011, although the associated superluminal knot was not as fast. Our analysis shows radio, optical, and gamma-ray fluxes peaking contemporaneously during these two events, with the maximum of the optical/gamma-ray correlation agreeing within a few days, and with the radio peak occurring about 1 month earlier. Each outburst ended after 3 months at gamma-ray energies, while the radio emission decayed more slowly, with a plateau between the two outbursts. We infer the degree of order and geometry of the magnetic field during the outbursts by studying the linear polarization at both radio (in the images) and optical wavelengths. We use the changing positions of the superluminal knots to locate the gamma-ray flares in the parsec-scale jet. Armed with this information, we compare the evolution of the jet of CTA26 with the expectations of current models, such as those that include moving and/or standing shocks in the parsec-scale jet. This research was supported in part by NASA through Fermi Guest Investigator grant NNX11AQ03G.

  13. Gamma-ray free-electron lasers: Quantum fluid model

    E-print Network

    Silva, H M

    2014-01-01

    A quantum fluid model is used to describe the interacion of a nondegenerate cold relativistic electron beam with an intense optical wiggler taking into account the beam space-charge potential and photon recoil effect. A nonlinear set of coupled equations are obtained and solved numerically. The numerical results shows that in the limit of plasma wave-breaking an ultra-high power radiation pulse are emitted at the$\\gamma$-ray wavelength range which can reach an output intensity near the Schwinger limit depending of the values of the FEL parameters such as detuning and input signal initial phase at the entrance of the interaction region.

  14. Energy resolution of gamma-ray spectroscopy of JET plasmas with a LaBr3 scintillator detector and digital data acquisition.

    PubMed

    Nocente, M; Tardocchi, M; Chugunov, I; Pereira, R C; Edlington, T; Fernandes, A M; Gin, D; Grosso, G; Kiptily, V; Murari, A; Neto, A; Perelli Cippo, E; Pietropaolo, A; Proverbio, I; Shevelev, A; Sousa, J; Syme, B; Gorini, G

    2010-10-01

    A new high efficiency, high resolution, fast ?-ray spectrometer was recently installed at the JET tokamak. The spectrometer is based on a LaBr3(Ce) scintillator coupled to a photomultiplier tube. A digital data acquisition system is used to allow spectrometry with event rates in excess of 1 MHz expected in future JET DT plasmas. However, at the lower rates typical of present day experiments, digitization can degrade the energy resolution of the system, depending on the algorithms used for extracting pulse height information from the digitized pulses. In this paper, the digital and analog spectrometry methods were compared for different experimental conditions. An algorithm based on pulse shape fitting was developed, providing energy resolution equivalent to the traditional analog spectrometry method. PMID:21058454

  15. The Impact of Multiple-Site Interactions on the Energy Resolution of a High-Pressure Xenon Gamma-Ray Spectrometer

    SciTech Connect

    Kiff, Scott D.; He, Zhong

    2007-11-30

    High-pressure xenon (HPXe) ionization chambers have generated interest as a radiation detection medium for purposes requiring good energy resolution, high detection efficiency, and uniform response over a broad temperature range, such as homeland security and well logging applications. These chambers generally exhibit a substantial degradation of the measured energy resolution relative to theoretical limits. This investigation studies the impact of the number of interaction sites in an event sequence on the measured energy resolution using a benchmarked simulation package. The prominence of single and multiple-site interactions is investigated in addition to the photopeak broadening due to each event class. A radial position-sensing technique developed for coplanar-anode HPXe chambers is shown to have benefit for only single-site events.

  16. Low-resolution Spectroscopy of Gamma-ray Burst Optical Afterglows: Biases in the Swift Sample and Characterization of the Absorbers

    NASA Astrophysics Data System (ADS)

    Fynbo, J. P. U.; Jakobsson, P.; Prochaska, J. X.; Malesani, D.; Ledoux, C.; de Ugarte Postigo, A.; Nardini, M.; Vreeswijk, P. M.; Wiersema, K.; Hjorth, J.; Sollerman, J.; Chen, H.-W.; Thöne, C. C.; Björnsson, G.; Bloom, J. S.; Castro-Tirado, A. J.; Christensen, L.; De Cia, A.; Fruchter, A. S.; Gorosabel, J.; Graham, J. F.; Jaunsen, A. O.; Jensen, B. L.; Kann, D. A.; Kouveliotou, C.; Levan, A. J.; Maund, J.; Masetti, N.; Milvang-Jensen, B.; Palazzi, E.; Perley, D. A.; Pian, E.; Rol, E.; Schady, P.; Starling, R. L. C.; Tanvir, N. R.; Watson, D. J.; Xu, D.; Augusteijn, T.; Grundahl, F.; Telting, J.; Quirion, P.-O.

    2009-12-01

    We present a sample of 77 optical afterglows (OAs) of Swift detected gamma-ray bursts (GRBs) for which spectroscopic follow-up observations have been secured. Our first objective is to measure the redshifts of the bursts. For the majority (90%) of the afterglows, the redshifts have been determined from the spectra. We provide line lists and equivalent widths (EWs) for all detected lines redward of Ly? covered by the spectra. In addition to the GRB absorption systems, these lists include line strengths for a total of 33 intervening absorption systems. We discuss to what extent the current sample of Swift bursts with OA spectroscopy is a biased subsample of all Swift detected GRBs. For that purpose we define an X-ray-selected statistical sample of Swift bursts with optimal conditions for ground-based follow-up from the period 2005 March to 2008 September; 146 bursts fulfill our sample criteria. We derive the redshift distribution for the statistical (X-ray selected) sample and conclude that less than 18% of Swift bursts can be at z > 7. We compare the high-energy properties (e.g., ?-ray (15-350 keV) fluence and duration, X-ray flux, and excess absorption) for three subsamples of bursts in the statistical sample: (1) bursts with redshifts measured from OA spectroscopy; (2) bursts with detected optical and/or near-IR afterglow, but no afterglow-based redshift; and (3) bursts with no detection of the OA. The bursts in group (1) have slightly higher ?-ray fluences and higher X-ray fluxes and significantly less excess X-ray absorption than bursts in the other two groups. In addition, the fractions of dark bursts, defined as bursts with an optical to X-ray slope ?OX < 0.5, is 14% in group (1), 38% in group (2), and >39% in group (3). For the full sample, the dark burst fraction is constrained to be in the range 25%-42%. From this we conclude that the sample of GRBs with OA spectroscopy is not representative for all Swift bursts, most likely due to a bias against the most dusty sight lines. This should be taken into account when determining, e.g., the redshift or metallicity distribution of GRBs and when using GRBs as a probe of star formation. Finally, we characterize GRB absorption systems as a class and compare them to QSO absorption systems, in particular the damped Ly? absorbers (DLAs). On average GRB absorbers are characterized by significantly stronger EWs for H I as well as for both low and high ionization metal lines than what is seen in intervening QSO absorbers. However, the distribution of line strengths is very broad and several GRB absorbers have lines with EWs well within the range spanned by QSO-DLAs. Based on the 33 z > 2 bursts in the sample, we place a 95% confidence upper limit of 7.5% on the mean escape fraction of ionizing photons from star-forming galaxies. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, under programs 275.D-5022 (PI: Chincarini), 075.D-0270 (PI: Fynbo), 077.D-0661 (PI: Vreeswijk), 077.D-0805 (PI: Tagliaferri), 177.A-0591 (PI: Hjorth), 078.D-0416 (PI: Vreeswijk), 079.D-0429 (PI: Vreeswijk), 080.D-0526 (PI: Vreeswijk), 081.A-0135 (PI: Greiner), 281.D-5002 (PI: Della Valle), and 081.A-0856 (PI: Vreeswijk). Also based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. Some of the data obtained herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck foundation.

  17. GLAST: Exploring Nature's Highest Energy Processes with the Gamma-ray Large Area Space Telescope

    NASA Technical Reports Server (NTRS)

    Digel, Seth; Myers, J. D.; White, Nicholas E. (Technical Monitor)

    2001-01-01

    The Gamma-ray Large Area Space Telescope (GLAST) is an international and multi-agency space mission that will study the cosmos in the energy range 10 keV-300 GeV. Several successful exploratory missions in gamma-ray astronomy led to the Energetic Gamma Ray Experiment Telescope (EGRET) instrument on the Compton Gamma Ray Observatory (CGRO). Launched in 1991, EGRET made the first complete survey of the sky in the 30 MeV-10 GeV range. EGRET showed the high-energy gamma-ray sky to be surprisingly dynamic and diverse, with sources ranging from the sun and moon to massive black holes at large redshifts. Most of the gamma-ray sources detected by EGRET remain unidentified. In light of the discoveries with EGRET, the great potential of the next generation gamma-ray telescope can be appreciated. GLAST will have an imaging gamma-ray telescope vastly more capable than instruments flown previously, as well as a secondary instrument to augment the study of gamma-ray bursts. The main instrument, the Large Area Telescope (LAT), will have superior area, angular resolution, field of view, and deadtime that together will provide a factor of 30 or more advance in sensitivity, as well as provide capability for study of transient phenomena. The GLAST Burst Monitor (GBM) will have a field of view several times larger than the LAT and will provide spectral coverage of gamma-ray bursts that extends from the lower limit of the LAT down to 10 keV. The basic parameters of the GBM are compared to those of the Burst and Transient Source Experiment (BATSE) instrument on CGRO in Table 1-2. With the LAT and GBM, GLAST will be a flexible observatory for investigating the great range of astrophysical phenomena best studied in high-energy gamma rays. NASA plans to launch GLAST in late 2005.

  18. Measurements of gamma-ray production cross sections for shielding materials of space nuclear systems

    NASA Technical Reports Server (NTRS)

    Orphan, V. J.; John, J.; Hoot, C. G.

    1972-01-01

    Measurements of secondary gamma ray production from neutron interactions have been made over the entire energy range of interest in shielding applications. The epithermal capture gamma ray yields for both resolved gamma ray lines and continuum have been measured from thermal energies to 100 KeV for natural tungsten and U-238, two important candidate shield materials in SNAP reactor systems. Data are presented to illustrate the variation of epithermal capture gamma ray yields with neutron energy. The gamma ray production cross sections from (n,xy) reactions have been measured for Fe and Al from the threshold energies for inelastic scattering to approximately 16 MeV. Typical Fe and Al cross sections obtained with high-neutron energy resolution and averaged over broad neutron-energy groups are presented.

  19. Gamma-ray burst spectra and time histories from 2 to 400 keV

    SciTech Connect

    Fenimore, E.E.

    1998-07-01

    The Gamma-Ray burst detector on Ginga consisted of a proportional counter to observe the x-rays and a scintillation counter to observe the gamma-rays. Both instrument recorded the time histories in phase with each other and with 0.03125 s temporal resolution. The author compares the average of 21 gamma-ray bursts to determine the delay, in any, between the peak of the x-rays and the peak of the gamma-rays. The delay is less than or about equal to 30 msec. Thus, models must content with two average features of the temporal behavior. First, as a function of energy, the time structure scales as {approximately}E{sup {minus}0.45}. Second, the x-rays are not appreciable delayed relative to the gamma-rays. Some cooling models might have difficulties explaining these features.

  20. Simultaneous dual wavelength eye-tracked ultrahigh resolution retinal and choroidal optical coherence tomography.

    PubMed

    Unterhuber, A; Považay, B; Müller, A; Jensen, O B; Duelk, M; Le, T; Petersen, P M; Velez, C; Esmaeelpour, M; Andersen, P E; Drexler, W

    2013-11-01

    We demonstrate an optical coherence tomography device that simultaneously combines different novel ultrabroad bandwidth light sources centered in the 800 and 1060 nm regions, operating at 66 kHz depth scan rate, and a confocal laser scanning ophthalmoscope-based eye tracker to permit motion-artifact-free, ultrahigh resolution and high contrast retinal and choroidal imaging. The two wavelengths of the device provide the complementary information needed for diagnosis of subtle retinal changes, while also increasing visibility of deeper-lying layers to image pathologies that include opaque media in the anterior eye segment or eyes with increased choroidal thickness. PMID:24177081

  1. 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.

  2. High Energy Emission from Gamma Ray Bursts

    SciTech Connect

    Meszaros, P.; Razzaque, S.; Wang, X. Y. [Dept. of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Dept. of Physics, Pennsylvania State University, University Park, PA 16802 (United States)

    2006-07-11

    Gamma-Ray Bursts (GRB) are powerful sources of MeV gamma-rays, whose prompt emission has been detected in some case up to tens of GeV. Leptonic emission mechanisms could produce also TeV gamma-rays, and if proton acceleration takes place, hadronic and photopion processes are expected to produce TeV neutrino emission as well. Current models for the production of GeV-TeV photons and neutrinos are discussed.

  3. Gamma-ray emission from thunderstorm discharges

    Microsoft Academic Search

    A. V. Gurevich; A. P. Chubenko; A. N. Karashtin; G. G. Mitko; A. S. Naumov; M. O. Ptitsyn; V. A. Ryabov; A. L. Shepetov; Yu. V. Shlyugaev; L. I. Vildanova; K. P. Zybin

    2011-01-01

    Fine features of gamma-ray radiation registered during a thunderstorm at Tien-Shan Mountain Cosmic Ray Station are presented. Long duration (100–600 ms) gamma-ray bursts are found. They are for the first time identified with atmospheric discharges (lighting). Gamma-ray emission lasts all the time of the discharge and is extremely non-uniform consisting of numerous flashes. Its peak intensity in the flashes exceeds

  4. Understanding Doppler Broadening of Gamma Rays

    SciTech Connect

    Rawool-Sullivan, Mohini [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Sullivan, John P. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-07-03

    Doppler-broadened gamma ray peaks are observed routinely in the collection and analysis of gamma-ray spectra. If not recognized and understood, the appearance of Doppler broadening can complicate the interpretation of a spectrum and the correct identification of the gamma ray-emitting material. We have conducted a study using a simulation code to demonstrate how Doppler broadening arises and provide a real-world example in which Doppler broadening is found. This report describes that study and its results.

  5. Fermi large area telescope measurements of the diffuse gamma-ray emission at intermediate galactic latitudes.

    PubMed

    Abdo, A A; Ackermann, M; Ajello, M; Anderson, B; 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; Charles, E; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; Dereli, H; Dermer, C D; de Angelis, A; de Palma, F; Digel, S W; Di Bernardo, G; Dormody, M; do Couto e Silva, E; Drell, P S; Dubois, R; Dumora, D; Edmonds, Y; Farnier, C; Favuzzi, C; Fegan, S J; Focke, W B; Frailis, M; Fukazawa, Y; Funk, S; Fusco, P; Gaggero, D; Gargano, F; Gehrels, N; Germani, S; 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; Hughes, R E; Jóhannesson, G; Johnson, A S; Johnson, R P; Johnson, T J; Johnson, W N; Kamae, T; Katagiri, H; Kataoka, J; Kawai, N; Kerr, M; Knödlseder, J; Kocian, M L; Kuehn, F; Kuss, M; Lande, J; Latronico, L; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; 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; Nuss, E; Ohsugi, T; Okumura, A; Omodei, N; Orlando, E; Ormes, J F; Paneque, D; Panetta, J H; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Piron, F; Porter, T A; Rainò, S; Rando, R; Razzano, M; Reimer, A; Reimer, O; Reposeur, T; Ritz, S; Rodriguez, A Y; Roth, M; Ryde, F; Sadrozinski, H F-W; Sanchez, D; Sander, A; Saz Parkinson, P M; Scargle, J D; Sellerholm, A; Sgrò, C; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Starck, J-L; Stecker, F W; Striani, E; Strickman, M S; Strong, A W; 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; Waite, A P; Wang, P; Winer, B L; Wood, K S; Ylinen, T; Ziegler, M

    2009-12-18

    The diffuse galactic gamma-ray emission is produced by cosmic rays (CRs) interacting with the interstellar gas and radiation field. Measurements by the Energetic Gamma-Ray Experiment Telescope (EGRET) instrument on the Compton Gamma-Ray Observatory indicated excess gamma-ray emission greater, > or approximately equal to 1 GeV relative to diffuse galactic gamma-ray emission models consistent with directly measured CR spectra (the so-called "EGRET GeV excess"). The Large Area Telescope (LAT) instrument on the Fermi Gamma-Ray Space Telescope has measured the diffuse gamma-ray emission with improved sensitivity and resolution compared to EGRET. We report on LAT measurements for energies 100 MeV to 10 GeV and galactic latitudes 10 degrees < or = |b| < or = 20 degrees. The LAT spectrum for this region of the sky is well reproduced by a diffuse galactic gamma-ray emission model that is consistent with local CR spectra and inconsistent with the EGRET GeV excess. PMID:20366246

  6. Distribution of iron&titanium on the lunar surface from lunar prospector gamma ray spectra

    SciTech Connect

    Prettyman, T. H. (Thomas H.); Feldman, W. C. (William C.); Lawrence, David J. (David Jeffery),; Elphic, R. C. (Richard C.); Gasnault, O. M. (Olivier M.); Maurice, S. (Sylvestre); Moore, K. R. (Kurt R.); Binder, A. B.

    2001-01-01

    Gamma ray pulse height spectra acquired by the Lunar Prospector (LP) Gamma-Ray Spectrometer (GRS) contain information on the abundance of major elements in the lunar surface, including O, Si, Ti, Al, Fe, Mg, Ca, K, and Th. With the exception of Th and K, prompt gamma rays produced by cosmic ray interactions with surface materials are used to determine elemental abundance. Most of these gamma rays are produced by inelastic scattering of fast neutrons and by neutron capture. The production of neutron-induced gamma rays reaches a maximum deep below the surface (e.g. {approx}140 g/cm{sup 2} for inelastic scattering and {approx}50 g/cm{sup 2} for capture). Consequently, gamma rays sense the bulk composition of lunar materials, in contrast to optical methods [e.g. Clementine Spectral Reflectance (CSR)], which only sample the top few microns. Because most of the gamma rays are produced deep beneath the surface, few escape unscattered and the continuum of scattered gamma rays dominates the spectrum. In addition, due to the resolution of the spectrometer, there are few well-isolated peaks and peak fitting algorithms must be used to deconvolve the spectrum in order to determine the contribution of individual elements.

  7. Response of AGATA segmented HPGe detectors to gamma-rays up to 15.1 MeV

    Microsoft Academic Search

    F. C. L. Crespi; R. Avigo; F. Camera; G. Benzoni; N. Blasi; S. Bottoni; A. Bracco; S. Brambilla; P. Casati; F. Coniglio; A. Corsi; A. Giaz; S. Leoni; B. Million; R. Nicolini; L. Pellegri; S. Riboldi; V. Vandone; O. Wieland; S. Akkoyun; A. Atac; D. Bazzacco; M. Bellato; D. Bortolato; E. Calore; M. Ciemala; E. Farnea; A. Gadea; A. Gottardo; M. Kmiecik; A. Maj; D. Mengoni; C. Michelagnoli; D. Montanari; D. R. Napoli; J. Nyberg; F. Recchia; E. Sahin; P.-A. Soderstrom; C. Ur; J. J. Valiente Dobon

    2011-01-01

    In many in-beam gamma spectroscopy experiments the detection of high-energy gamma rays in the range up to 10–20 MeV is of primary importance. New generation high-resolution gamma-ray spectrometers like AGATA and GRETA are composed of position sensitive segmented HPGe detectors and provide a reconstruction of the gamma-ray tracks. The performance of AGATA detectors in this energy range has, however, never

  8. The Mystery of Gamma-Ray Bursts

    NASA Technical Reports Server (NTRS)

    Fishman, Gerald J.

    2004-01-01

    Gamma-ray bursts remain one of the greatest mysteries in astrophysics. Observations of gamma-ray bursts made by the BATSE experiment on the Compton Gamma-Ray Observatory will be described. Most workers in the field now believe that they originate from cosmological distances. This view has been reinforced by observations this year of several optical afterglow counterparts to gamma-ray bursts. A summary of these recent discoveries will be presented, along with their implications for models of the burst emission mechanism and the energy source of the bursts.

  9. Gamma rays from compact binary system

    E-print Network

    Josep M. Paredes

    2008-10-24

    Some of the very high energy (VHE) gamma-ray sources detected with the modern generation of Cherenkov telescopes have been identified with previously known X-ray binary systems. These detections demonstrate the richness of non-thermal phenomena in compact galactic objects containing relativistic outflows or winds produced near black holes and neutron stars. Recently, the well-known microquasar Cygnus X-3 seems to be associated with a gamma-ray source detected with AGILE. Here I summarise the main observational results on gamma-ray emission from X-ray binaries, as well as some of the proposed scenarios to explain the production of VHE gamma-rays.

  10. Low-level gamma-ray spectrometry

    SciTech Connect

    Brodzinski, R.L.

    1990-10-01

    Low-level gamma-ray spectrometry generally equates to high-sensitivity gamma-ray spectrometry that can be attained by background reduction, selective signal identification, or some combination of both. Various methods for selectively identifying gamma-ray events and for reducing the background in gamma-ray spectrometers are given. The relative magnitude of each effect on overall sensitivity and the relative cost'' for implementing them are given so that a cost/benefit comparison can be made and a sufficiently sensitive spectrometer system can be designed for any application without going to excessive or unnecessary expense. 10 refs., 8 figs.

  11. Gamma-ray background: a review

    E-print Network

    Tanja M. Kneiske

    2007-11-29

    The gamma-ray background is still a subject under great debate. All phenomena in the universe emitting gamma-rays can contribute directly as diffuse emission or as an isotropic component from unresolved point sources. The question of the origin of the extragalactic component cannot be answered without determining the galactic emission. To discuss in detail all models resulting in gamma-ray background contributions is far beyond the scope of this paper. Therefore the focus will be on recent publications on the extragalactic high energy (>100 MeV) part of the gamma-ray background.

  12. Observations of Gamma-Ray Bursts

    NASA Technical Reports Server (NTRS)

    Fishman, Gerald J.

    1999-01-01

    Gamma-ray bursts are now generally believed to originate from cosmological distances and represent the largest known explosions in the Universe. These lectures will describe the temporal and spectral characteristic of gamma-ray bursts, their intensity and sky distribution, and other observed characteristics in the gamma-ray region, primarily from data obtained with the BATSE experiment on the Compton Observatory. A summary of recent discoveries and observations in other wavelength regions will also be presented, along with their implications for models of the burst emission mechanism. Various possibilities and models for the energy source(s) of gamma-ray bursts will be described.

  13. Future prospects for gamma-ray

    NASA Technical Reports Server (NTRS)

    Fichtel, C.

    1980-01-01

    Astrophysical phenomena discussed are: the very energetic and nuclear processes associated with compact objects; astrophysical nucleo-synthesis; solar particle acceleration; the chemical composition of the planets and other bodies of the solar system; 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, especially active ones; and the degree of matter antimater symmetry of the universe. The gamma ray results of GAMMA-I, the gamma ray observatory, the gamma ray burst network, solar polar, and very high energy gamma ray telescopes on the ground provide justification for more sophisticated telescopes.

  14. A thick anger camera for gamma-ray astronomy

    SciTech Connect

    Cook, W.R.; Finger, M.; Prince, T.A.

    1985-02-01

    The NaI(T1) Anger camera is a natural candidate for a position sensitive detector in imaging of astrophysical ..gamma..-ray sources. Here we present laboratory measurements of the response of a relatively thick (5.1 cm) NaI(T1) Anger camera designed for coded aperture imaging in the 50 keV to 2 MeV energy range. We obtained a position resolution of 10.5 mm FWHM at 122 keV and 6.3 mm FWHM at 662 keV. The energy resolution was 7% FWHM at 662 keV. We discuss the ability of the detector to resolve the depth of the ..gamma..-ray interaction and the use of this depth resolution to reduce back-incident and internal background.

  15. A thick Anger camera for gamma-ray astronomy

    NASA Technical Reports Server (NTRS)

    Cook, W. R.; Finger, M.; Prince, T. A.

    1985-01-01

    The NaI(Tl) Anger camera is a natural candidate for a position sensitive detector in imaging of astrophysical gamma-ray sources. Here laboratory measurements are presented of the response of a relatively thick (5.1 cm) NaI(Tl) Anger camera designed for coded aperture imaging in the 50 keV to 2 MeV energy range. A position resolution of 10.5 mm FWHM at 122 keV and 6.3 mm FWHM at 662 keV. The energy resolution was 7 percent FWHM at 662 keV. The ability of the detector to resolve the depth of the gamma-ray interaction and the use of this depth resolution to reduce back-incident and internal background is discussed.

  16. Gamma-ray burst models.

    PubMed

    King, Andrew

    2007-05-15

    I consider various possibilities for making gamma-ray bursts, particularly from close binaries. In addition to the much-studied neutron star+neutron star and black hole+neutron star cases usually considered good candidates for short-duration bursts, there are also other possibilities. In particular, neutron star+massive white dwarf has several desirable features. These systems are likely to produce long-duration gamma-ray bursts (GRBs), in some cases definitely without an accompanying supernova, as observed recently. This class of burst would have a strong correlation with star formation and occur close to the host galaxy. However, rare members of the class need not be near star-forming regions and could have any type of host galaxy. Thus, a long-duration burst far from any star-forming region would also be a signature of this class. Estimates based on the existence of a known progenitor suggest that this type of GRB may be quite common, in agreement with the fact that the absence of a supernova can only be established in nearby bursts. PMID:17293332

  17. Gamma-ray observations with the Transient Gamma-Ray Spectrometer (TGRS).

    NASA Astrophysics Data System (ADS)

    Seifert, H.; Teegarden, B. J.; Cline, T. L.; Gehrels, N.; Hurley, K. H.; Madden, N.; Owens, A.; Palmer, D. M.; Pehl, R.; Ramaty, R.

    1996-12-01

    The Transient Gamma-Ray Spectrometer (TGRS), a high-resolution germanium detector, was launched aboard the WIND satellite on November 1, 1994. After ~2 years and several deep space orbits the spacecraft will eventually be injected into a halo orbit around the Sun-Earth L_1_ point. Although TGRS is primarily designed to perform high resolution spectroscopy of gamma-ray bursts (GRBs) and solar flares, it equally well lends itself to the study of transient X-ray sources and, using an on-board passive occulter, the long-term monitoring of steady sources such as the Crab and the Galactic Center. Since launch, TGRS has been working exceedingly well and has proven to be very stable in its performance. TGRS has been detecting on the average ~5 GRBs per month and to date has observed three solar flares. Preliminary analysis of our data also indicates that TGRS is indeed sensitive to sources such as the X-ray transient GRO J1655-40, the Crab, and the Galactic Center.

  18. Future Gamma-Ray Imaging of Solar Eruptive Events

    NASA Astrophysics Data System (ADS)

    Shih, Albert Y.; Lin, R. P.; Hurford, G. J.; Duncan, N. A.; Saint-Hilaire, P.; Bain, H. M.; Smith, D. M.

    2012-05-01

    Solar eruptive events, the combination of large solar flares and coronal mass ejections (CMEs), accelerate ions to tens of Gev and electrons to hundreds of MeV. The energy in accelerated particles can be a significant fraction (up to tens of percent) of the released energy and is roughly equipartitioned between ions and electrons. Observations of the gamma-ray signatures produced by these particles interacting with the ambient solar atmosphere probes the distribution and composition of the accelerated population, as well as the atmospheric parameters and abundances of the atmosphere, ultimately revealing information about the underlying physics. Gamma-ray imaging provided by RHESSI showed that the interacting 20 MeV/nucleon ions are confined to flare magnetic loops rather than precipitating from a large CME-associated shock. Furthermore, RHESSI images show a surprising, significant spatial separation between the locations where accelerated ions and electrons are interacting, thus indicating a difference in acceleration or transport processes for the two types of particles. Future gamma-ray imaging observations, with higher sensitivity and greater angular resolution, can investigate more deeply the nature of ion acceleration. The technologies being proven on the Gamma-Ray Imager/Polarimeter for Solar flares (GRIPS), a NASA balloon instrument, are possible approaches for future instrumentation. We discuss the GRIPS instrument and the future of studying this aspect of solar eruptive events.

  19. Galactic Diffuse Gamma Ray Emission Is Greater than 10 Gev

    NASA Technical Reports Server (NTRS)

    Hunter, Stanley D.; White, Nicholas E. (Technical Monitor)

    2000-01-01

    AGILE and Gamma-ray Large Area Telescope (GLAST) are the next high-energy gamma-ray telescopes to be flown in space. These instruments will have angular resolution about 5 times better than Energetic Gamma-Ray Experiment Telescope (EGRET) above 10 GeV and much larger field of view. The on-axis effective area of AGILE will be about half that of EGRET, whereas GLAST will have about 6 times greater effective area than EGRET. The capabilities of ground based very high-energy telescopes are also improving, e.g. Whipple, and new telescopes, e.g. Solar Tower Atmospheric Cerenkov Effect Experiment (STACEE), Cerenkov Low Energy Sampling and Timing Experiment (CELESTE), and Mars Advanced Greenhouse Integrated Complex (MAGIC) are expected to have low-energy thresholds and sensitivities that will overlap the GLAST sensitivity above approximately 10 GeV. In anticipation of the results from these new telescopes, our current understanding of the galactic diffuse gamma-ray emission, including the matter and cosmic ray distributions is reviewed. The outstanding questions are discussed and the potential of future observations with these new instruments to resolve these questions is examined.

  20. Extracting and compensating dispersion mismatch in ultrahigh-resolution Fourier domain OCT imaging of the retina.

    PubMed

    Choi, WooJhon; Baumann, Bernhard; Swanson, Eric A; Fujimoto, James G

    2012-11-01

    We present a numerical approach to extract the dispersion mismatch in ultrahigh-resolution Fourier domain optical coherence tomography (OCT) imaging of the retina. The method draws upon an analogy with a Shack-Hartmann wavefront sensor. By exploiting mathematical similarities between the expressions for aberration in optical imaging and dispersion mismatch in spectral / Fourier domain OCT, Shack-Hartmann principles can be extended from the two-dimensional paraxial wavevector space (or the x-y plane in the spatial domain) to the one-dimensional wavenumber space (or the z-axis in the spatial domain). For OCT imaging of the retina, different retinal layers, such as the retinal nerve fiber layer (RNFL), the photoreceptor inner and outer segment junction (IS/OS), or all the retinal layers near the retinal pigment epithelium (RPE) can be used as point source beacons in the axial direction, analogous to point source beacons used in conventional two-dimensional Shack-Hartman wavefront sensors for aberration characterization. Subtleties regarding speckle phenomena in optical imaging, which affect the Shack-Hartmann wavefront sensor used in adaptive optics, also occur analogously in this application. Using this approach and carefully suppressing speckle, the dispersion mismatch in spectral / Fourier domain OCT retinal imaging can be successfully extracted numerically and used for numerical dispersion compensation to generate sharper, ultrahigh-resolution OCT images. PMID:23187353

  1. Quantification of photoreceptor layer thickness in different macular pathologies using ultrahigh-resolution optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Drexler, Wolfgang; Hermann, Boris; Unterhuber, Angelika; Sattmann, Harald; Wirtitsch, Matthias; Stur, Michael; Scholda, Christoph; Ergun, Erdem; Anger, Elisabeth; Ko, Tony H.; Schubert, Christian; Ahnelt, Peter K.; Fujimoto, James G.; Fercher, Adolf F.

    2004-07-01

    In vivo ultrahigh resolution ophthalmic OCT has been performed in more than 300 eyes of 200 patients with several retinal pathologies, demonstrating unprecedented visualization of all major intraretinal layers, in particular the photoreceptor layer. Visualization as well as quantification of the inner and outer segment of the photoreceptor layer especially in the foveal region has been acvhieved. In normal subjects the photoreceptor layer thickness in the center of the fovea is about of 90 ?m, approximately equally distributed to the inner and the outer photoreceptor segment. In the parafoveal region this thickness is reduced to ~50 ?m (~30 ?m for the inner and ~20 ?m for the outer segment). This is in good agreement with well known increase of cone outer segments in the central foveal region. Photoreceptor layer impairment in different macular pathologies like macular hole, central serous chorioretinopathy, age related macular degeneration, foveomacular dystrophies, Stargardt dystrophy as well as retinitis pigmentosa has been investigated. Photoreceptor layer loss significantly correlated with visual acuity (R2 = 0.6, p < 0.001) and microperimetry findings for the first time in 22 eyes with Stargardt dystrophy. Visualization and quantification of photoreceptor inner and outer segment using ultrahigh resolution OCT has the potential to improve early ophthalmic diagnosis, contributes to a better understanding of pathogenesis of retinal diseases as well as might have impact in the development and monitoring of novel therapy approaches.

  2. Automated Segmentation of Hippocampal Subfields From Ultra-High Resolution In Vivo MRI

    PubMed Central

    Van Leemput, Koen; Bakkour, Akram; Benner, Thomas; Wiggins, Graham; Wald, Lawrence L.; Augustinack, Jean; Dickerson, Bradford C.; Golland, Polina; Fischl, Bruce

    2009-01-01

    Recent developments in MRI data acquisition technology are starting to yield images that show anatomical features of the hippocampal formation at an unprecedented level of detail, providing the basis for hippocampal subfield measurement. However, a fundamental bottleneck in MRI studies of the hippocampus at the subfield level is that they currently depend on manual segmentation, a laborious process that severely limits the amount of data that can be analyzed. In this article, we present a computational method for segmenting the hippocampal subfields in ultra-high resolution MRI data in a fully automated fashion. Using Bayesian inference, we use a statistical model of image formation around the hippocampal area to obtain automated segmentations. We validate the proposed technique by comparing its segmentations to corresponding manual delineations in ultra-high resolution MRI scans of 10 individuals, and show that automated volume measurements of the larger subfields correlate well with manual volume estimates. Unlike manual segmentations, our automated technique is fully reproducible, and fast enough to enable routine analysis of the hippocampal subfields in large imaging studies. PMID:19405131

  3. Gamma ray emission from radiative supernova remnants

    NASA Astrophysics Data System (ADS)

    Asvarov, Abdul

    In this presentation we have considered Gamma-ray emission from supernova remnants (SNRs) evolving in high density environments, for which the radiative phase of evolution is more typical. Gamma-rays from such objects are believed to have hadronic origin, i.e. as a result of decay of neutral pi-mesons, created in the p-p collisions of relativistic hadrons (protons, etc.) with interstellar medium protons. DSA mechanism is considered as the main mechanism of acceleration of relativistic particles. We assume that SNR evolves in more or less homogeneous interstellar medium. This is contrary to two main models of origin of Gamma-rays from shell type SNRs, which are: 1) Runaway CR model which considers Gamma-ray emission from molecular clouds illuminated by runaway CRs that have escaped from the SNRs; 2) Crushed Cloud model, which considers the shocked interstellar clouds being responsible for the gamma-ray emission of the SNR. The considered model gives the largest conversion rate of SN energy to gamma-rays. It has been found that under certain (close to real) conditions considered here type of SNRs can easily provide the flux of gamma-rays with energies > 100 MeV, typical for the large number of unidentified sources listed in the recent Fermi LAT source catalog. We have obtained conditions under which SNRs are better observable in gamma-rays than in other bands of the electromagnetic spectrum.

  4. The Compton Gamma Ray Observatory: mission status

    Microsoft Academic Search

    N. Gehrels; E. Chipman; D. A. Kniffen

    1994-01-01

    The Arthur Holly Compton Gamma Ray Observatory (Compton) is the second in NASA's series of Great Observatories. Compton has now been operating for over two and a half years, and has given a dramatic increase in capability over previous gamma-ray missions. The spacecraft and scientific instruments are all in good health, and many significant discoveries have already been made and

  5. A 16N gamma-ray facility

    NASA Astrophysics Data System (ADS)

    Hull, Ethan L.; Pehl, Richard H.; Stanley, Michelle R.; Foster, Charles C.; Komisarcik, Kevin; East, Gary W.; Vanderwerp, John D.; Friesel, Dennis L.

    1997-02-01

    A practical 16N gamma-ray source is created in a medium-energy cyclotron environment. A 16N source emits 6129 and 7115 keV gamma rays. The viability of this several ?Ci source for detector calibration and studying detector physics is established.

  6. 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. PMID:17293337

  7. Characteristics of gamma-ray line flares

    NASA Technical Reports Server (NTRS)

    Bai, T.; Dennis, B.

    1983-01-01

    Observations of solar gamma rays by the Solar Maximum Mission (SMM) demonstrate that energetic protons and ions are rapidly accelerated during the impulsive phase. To understand the acceleration mechanisms for these particles, the characteristics of the gamma ray line flares observed by SMM were studied. Some very intense hard X-ray flares without detectable gamma ray lines were also investigated. Gamma ray line flares are distinguished from other flares by: (1) intense hard X-ray and microwave emissions; (2) delay of high energy hard X-rays; (3) emission of type 2 and/or type 4 radio bursts; and (4) flat hard X-ray spectra (average power law index: 3.1). The majority of the gamma ray line flares shared all these characteristics, and the remainder shared at least three of them. Positive correlations were found between durations of spike bursts and spatial sizes of flare loops as well as between delay times and durations of spike bursts.

  8. Atmospheric gamma-ray and neutron flashes

    SciTech Connect

    Babich, L. P., E-mail: babich@elph.vniief.ru; Kudryavtsev, A. Yu., E-mail: kay@sar.ru; Kudryavtseva, M. L., E-mail: kay@sar.ru; Kutsyk, I. M. [All-Russian Research Institute of Experimental Physics (VNIIEF), Russian Federal Nuclear Center (Russian Federation)

    2008-01-15

    Gamma-ray pulses are calculated from 2D numerical simulations of an upward atmospheric discharge in a self-consistent electric field using the multigroup approach to the kinetics of relativistic runaway electrons (REs). Computed {gamma}-ray numbers and spectra are consistent with those of terrestrial {gamma}-ray flashes (TGFs) observed aboard spacecrafts. The RE flux is concentrated mainly within the domain of the Blue Jet fluorescence. This confirms that exactly the domain adjacent to a thundercloud is the source of the observed {gamma}-ray flashes. The yield of photonuclear neutrons is calculated. One {gamma}-ray pulse generates {approx}10{sup 14}-10{sup 15} neutrons. The possibility of the direct deposition of REs to the detector readings and the origin of the lightning-advanced TGFs are discussed.

  9. Gamma-Ray Bursts: An Overview

    NASA Technical Reports Server (NTRS)

    Fishman, Gerald J.

    1995-01-01

    A history and overview of the observed properties of gamma-ray bursts are presented. The phenomenon of gamma-ray bursts is without precedent in astronomy, having no observed property that would be a direct indicator of their distance and no counterpart object in another wavelength region. Their brief, random appearance only in the gamma-ray region has made their study difficult. The observed time profiles, spectral properties, and durations of gamma-ray bursts cover a wide range. All proposed models for their origin must be considered speculative. It is humbling to think that even after 25 years since their discovery, the distance scale of gamma-ray bursts is still very much debatable.

  10. Terrestrial Gamma-ray Flashes After CGRO: Prospects From HESSI

    NASA Astrophysics Data System (ADS)

    Barrington-Leigh, C. P.

    2001-12-01

    Brief (1--5~ms) flashes of gamma-rays coming from the direction of Earth's atmosphere were discovered by the BATSE instrument aboard the Compton Gamma Ray Observatory (CGRO) in 1994. CGRO was deorbited in June 2000, but during its lifetime 75 Terrestrial Gamma-ray Flashes (TGFs) were observed. The source of the photons is generally assumed to lie at atmospheric altitudes of 60--70~km, and to consist of bremmstrahlung radiation from highly relativistic electrons energized by strong mesospheric electric fields overlying thunderstorms. Because of the high altitude and upward-directed nature of this radiation, neither the gamma-rays nor the assumed causative runaway electron beams can be directly observed except by satellite. To date, no clear optical or in situ electron data exist to shed light on this phenomenon. Since CGRO's demise, there is no longer an orbiting gamma-ray instrument that is well suited for detecting TGF's. We describe the prospects for detecting TGFs with the High Energy Solar Spectroscopic Imager (HESSI), whose launch is imminent. While the BATSE main detectors had an upper energy band of 300~keV -- ~1~MeV, which was too low to resolve the hard (>1~MeV) TGF spectrum, the nine HESSI rear germanium detectors have spectral resolution of 0.1% -- 3% up to >10~MeV. In addition, BATSE's triggering circuitry integrated for at least 64~ms (much longer than the duration of a TGF) while the HESSI spacecraft records and telemeters the energy and time of arrival of each photon event. On the other hand, the geometric factor for the HESSI detectors is small compared with that of BATSE. Altogether, we expect a comparable TGF detection rate from HESSI but superior spectral (and temporal) information, which may provide key new evidence for the underlying mechanisms behind TGFs.

  11. ISGRI: The INTEGRAL Soft Gamma-Ray Imager

    Microsoft Academic Search

    F. Lebrun; J. P. Leray; P. Lavocat; J. Crétolle; M. Arquès; C. Blondel; C. Bonnin; A. Bouère; C. Cara; T. Chaleil; F. Daly; F. Desages; H. Dzitko; B. Horeau; P. Laurent; O. Limousin; F. Mathy; V. Mauguen; F. Meignier; F. Molinié; E. Poindron; M. Rouger; A. Sauvageon; T. Tourrette

    2003-01-01

    For the first time in the history of high energy astronomy, a large CdTe gamma-ray camera is operating in space. ISGRI is the low-energy camera of the IBIS telescope on board the INTEGRAL satellite. This paper details its design and its in-flight behavior and performances. Having a sensitive area of 2621 cm2 with a spatial resolution of 4.6 mm, a

  12. Advances in CdTe Gamma-Ray Detectors

    Microsoft Academic Search

    H. B. Serreze; G. Entine; R. O. Bell; F. V. Wald

    1974-01-01

    Performance of halogen-doped CdTe gamma - ray detectors has been improved significantly by the development of new device fabrication methods. In particular, these detectors do not exhibit any of the previously observed polarization effects. Room temperature resolution of 7% at 122 keV has been achieved using applied fields of less than 50 V\\/mm for detectors up to 100 mm3 in

  13. Research in particle and gamma-ray astrophysics

    NASA Technical Reports Server (NTRS)

    Stone, E. C.; Davis, L., Jr.; Mewaldt, R. A.; Prince, T. A.

    1988-01-01

    This research program is directed toward the investigation of the astrophysical aspects of cosmic rays and gamma rays and of the radiation and electromagnetic field environment of the Earth and other planets. The emphasis was on precice measurements with high resolution in charge, mass and energy. These investigations were carried out by means of energetic particle and photon detector systems flown on spacecraft and balloons.

  14. Application of HEALpix Pixelization to Gamma-ray Data

    Microsoft Academic Search

    T. H. Burnett; B. Lesnick; M. Roth

    2007-01-01

    The HEALpix scheme for tessellating the sky is a natural way to represent all-sky data that is naturally binned in sky coordinates. Gamma-ray data are collected and saved as individual photons, and usually analyzed as such. We present a summary data representation that is compact, saves energy information, and is consistent with the energy-dependent resolution. We take advantage of the

  15. ATCA data acquisition system for gamma-ray spectrometry

    Microsoft Academic Search

    R. C. Pereira; J. Sousa; A. M. Fernandes; F. Patrício; B. Carvalho; A. Neto; C. A. F. Varandas; G. Gorini; M. Tardocchi; D. Gin; A. Shevelev

    2008-01-01

    The gamma-ray spectrometer JET EP2 (Joint European Torus enhancement project 2) project aims to perform high-resolution gamma spectroscopy at very high count rate (up to few MHz). Traditional analogue electronic has count rate and pulse processing limitations (long dead-time, pile-up challenge). Digital pulse processing (DPP) systems have been shown to have better performance than analogue ones for processing neutrons or\\/and

  16. Gamma-ray line investigations with the Durham gamma-ray spectrometer

    NASA Astrophysics Data System (ADS)

    Ayre, C. A.; Owens, A.; Summers, W. M.; Thompson, M. G.; Bhat, P. N.

    1981-06-01

    A description is presented of a program undertaken to investigate gamma-ray lines with the aid of an actively shielded high purity Ge detector cooled by liquid nitrogen. The active NaI(Tl) shielding elements limit the opening angle of the telescope to 5.2 deg. The basic crystal has a gamma-ray detection efficiency of 23% relative to a standard 3 in. x 3 in. NaI(Tl) detector at 1.33 MeV and an energy resolution of 2.5 keV at the same energy. The first flight of the apparatus was in August 1979 at Palestine, Texas and it lasted about 6 1/2 hours. Attention is given to the variation of counting rate of the Ge detector in the energy range from 0.09 to 8.8 MeV, the atmospheric background spectra from the Ge(HP) detector, and the minimum sensitivity of the spectrometer.

  17. Radioactivity Levels and Gamma-Ray Dose Rate in Soil Samples from Kohistan (Pakistan) Using Gamma-Ray Spectrometry

    Microsoft Academic Search

    M. Khan Hasan; M. Ismail; K. Khan; P. Akhter

    2011-01-01

    The analysis of naturally occurring radionuclides (226Ra, 232Th and 40K) and an anthropogenic radionuclide 137Cs is carried out in some soil samples collected from Kohistan district of N.W.F.P. (Pakistan), using gamma-ray spectrometry. The gamma spectrometry is operated using a high purity Germanium (HPGe) detector coupled with a computer based high resolution multi channel analyzer. The specific activity in soil ranges

  18. Ultra-high resolution 3D upper airway MRI with compressed sensing and parallel imaging , S. S. Narayanan1

    E-print Network

    Southern California, University of

    Ultra-high resolution 3D upper airway MRI with compressed sensing and parallel imaging Y-C. Kim1) was demonstrated [2] by utilizing compressed sensing MRI [3] with a single channel receive coil. When imaging with multiple channel receive coil, the benefit of combining compressed sensing (CS) and parallel imaging has

  19. Ultrahigh-resolution endoscopic optical coherence tomography for in vivo mouse colonoscopy

    NASA Astrophysics Data System (ADS)

    Tumlinson, Alexandre Rex

    In vivo monitoring of mouse models of colon cancer promises to reduce the cost of research by improving sacrifice timing and allowing serial studies that observe the progression of disease and drug efficacy in a relatively small set of animals. Optical coherence tomography (OCT) is an optical analog of ultrasound imaging, capable of minimally-invasive mapping of light scatter intensity up to 2 mm deep in tissue. In this work, factors limiting resolution in OCT were examined and devices were created and applied to mouse colon imaging that extended the state-of-the-art in endoscopic ultrahigh-resolution OCT. First, axial chromatic aberration of the objective optics acts as a spectral filter in the sample arm limiting the effective bandwidth of the system. An achromatized endoscope design was demonstrated that achieved axial resolution of 2.3 mum in tissue and 4.4 mum lateral spot diameter with 101 dB sensitivity when interfaced with a time domain OCT system utilizing a 10-femtosecond laser (Deltalambda=150 nm FWHM, lambdac=800 nm). Second, dispersion matching between the sample and reference arms presents the practical resolution limit to endoscopic implementations including a separate, fiber-based reference arm. A second endoscope incorporated the reference arm into the tip of the endoscope using a novel custom beamsplitter prism and achieved 2.4 mum axial resolution in tissue without adjustments for pathlength or dispersion matching when interfaced with a spectrometer-based frequency domain OCT system and a similar laser. Third, non-linear dispersion of the sample media with respect to wavelength causes distortion and broadening of the axial point spread function when data are sampled uniformly in optical frequency. An experiment was performed on high dispersion glass to demonstrate that dispersion artifact free imaging can be achieved without post process corrections if the samples are acquired at equal intervals of media index of refraction divided by vacuum wavelength. Finally, other microscopic modalities that depend on tissue scatter intensity are used to find the origins of scatter in the mouse colonic mucosa. These observations are used to explain unexpected features found in ultrahigh-resolution tomograms collected with the two endoscopes presented.

  20. Application of nondestructive gamma-ray and neutron techniques for the safeguarding of irradiated fuel materials

    SciTech Connect

    Phillips, J.R.; Halbig, J.K.; Lee, D.M.; Beach, S.E.; Bement, T.R.; Dermendjiev, E.; Hatcher, C.R.; Kaieda, K.; Medina, E.G.

    1980-05-01

    Nondestructive gamma-ray and neutron techniques were used to characterize the irradiation exposures of irradiated fuel assemblies. Techniques for the rapid measurement of the axial-activity profiles of fuel assemblies have been developed using ion chambers and Be(..gamma..,n) detectors. Detailed measurements using high-resolution gamma-ray spectrometry and passive neutron techniques were correlated with operator-declared values of cooling times and burnup.

  1. Light Transmission From Extended Air Showers Produced By Cosmic-Rays and Gamma-Rays

    Microsoft Academic Search

    S. F. Taylor; T. Abu-Zayyad; K. Belov; Z. Cao; G. Chen; C. C. H. Jui; D. B. Kieda; J. N. Matthews; M. Salamon; P. V. Sokolsky; J. D. Smith; P. Sommers; R. W. Springer; B. T. Stokes; S. B. Thomas; L. R. Wiencke; J. A. J. Matthews; R. W. Clay; B. R. Dawson; K. Simpson; J. Bells; J. Boyer; B. Knapp; B. H. Song; X. Z. Zhang

    1999-01-01

    Cosmic-ray and gamma-ray experiments that use the atmosphere as a calorimeter, such as the High Resolution Fly's Eye (HiRes) and the Telescope Array (TA), require understanding the transmission of the light from the air shower of particles produced by the cosmic-ray or gamma-ray striking the atmosphere. To better understand the scattering and transmission of light to the detectors, HiRes measures

  2. CdZnTe gamma-ray spectrometer for orbital planetary missions

    Microsoft Academic Search

    Thomas H. Prettyman; William C. Feldman; Kenneth R. Fuller; Steven A. Storms; Stephen A. Soldner; Csaba Szeles; Frank P. Ameduri; David J. Lawrence; Michael C. Browne; Calvin E. Moss

    2002-01-01

    We present the design and analysis of a new gamma-ray spectrometer for planetary science that uses an array of CdZnTe detectors to achieve the detection efficiency needed for orbital measurements. The use of CdZnTe will provide significantly improved pulse-height resolution relative to scintillation-based detectors, with commensurate improvement in the accuracy of elemental abundances determined by gamma-ray and neutron spectroscopy. The

  3. Bismuth Germanate: A High-Z Gamma-Ray and Charged Particle Detector

    Microsoft Academic Search

    O. H. Nestor; C. Y. Huang

    1975-01-01

    The room-temperature scintillation characteristics of single crystals of Bi4Ge3O2 under gamma-ray and alpha-particle excitation have been determined. The wavelength of maximum intensity in the scintillation spectrum is 480 nm. A decay constant of 0.30 microseconds was measured. Scintillation efficiency (pulse height) varied linearly with gamma-ray energy, E, and the resolution varied as E-1\\/2. 8% pulse height relative to NaI(Tl) with

  4. Fermi LAT measurements of diffuse gamma-ray emission: results at the first-year milestone

    SciTech Connect

    Tibaldo, Luigi [INFN-Sezione di Padova and Dipartimento di Fisica 'G. Galilei'-Universita di Padova, I-35131 Padova, Italy and Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d'Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France)

    2010-03-26

    For more than one year the Fermi Large Area Telescope has been surveying the gamma-ray sky from 20 MeV to more than 300 GeV with unprecedented statistics and angular resolution. One of the key science targets of the Fermi mission is diffuse gamma-ray emission. Galactic interstellar gamma-ray emission is produced by interactions of high-energy cosmic rays with the interstellar gas and radiation field. We review the most important results on the subject obtained so far: the non-confirmation of the excess of diffuse GeV emission seen by EGRET, the measurement of the gamma-ray emissivity spectrum of local interstellar gas, the study of the gradient of cosmic-ray densities and of the X{sub CO} = N(H{sub 2})/W{sub CO} ratio in the outer Galaxy. We also catch a glimpse at diffuse gamma-ray emission in the Large Magellanic Cloud. These results allow the improvement of large-scale models of Galactic diffuse gamma-ray emission and new measurements of the extragalactic gamma-ray background.

  5. Gamma-rays from star-forming regions: from SNOBs to dark accelerators

    E-print Network

    Montmerle, Thierry

    2009-01-01

    Observational gamma-ray astronomy was born some forty years ago, when small detectors were flown in satellites, following a decade of theoretical predictions of its potential to discover the origin of cosmic rays via the pi-zero decay mechanism. The seventies were a golden era for gamma-ray and cosmic-ray astrophysics, with the (re)discovery of the "diffuse shock acceleration" theory for cosmic rays, and the first CO and GeV gamma-ray surveys of the galactic plane, verifying the importance of pi-zero decay in the large-scale gamma-ray emission of the Galaxy. But because of this strong galactic background, GeV gamma-ray sources were hard to identify. The first such sources definitely identified were three pulsars, with a suggestion that supernova remnants interacting with molecular clouds in massive star-forming regions ("SNOBs") were also gamma-ray sources. Because of their improved sensitivity and spatial resolution, ground-based Cerenkov telescopes, detecting gamma-rays at > TeV energies, are now able to re...

  6. An imaging neutron/gamma-ray spectrometer

    NASA Astrophysics Data System (ADS)

    Madden, Amanda C.; Bloser, Peter F.; Fourguette, Dominique; Larocque, Liane; Legere, Jason S.; Lewis, Matt; McConnell, Mark L.; Rousseau, Marissa; Ryan, James M.

    2013-05-01

    We present the test results of a neutron/gamma-ray imaging spectrometer for the identification and location of radioactive and special nuclear materials. Radioactive materials that could be fashioned into a radiation dispersal device typically emit gamma rays, while fissile materials such as uranium and plutonium emit both neutrons and gamma rays via spontaneous or induced fission. The simultaneous detection of neutrons and gamma rays is a clear indication of the presence of fissile material. The instrument works as a double-scatter telescope, requiring a neutron or gamma ray to undergo an interaction in two detectors to be considered a valid event. While this requirement reduces the detector efficiency, it yields information about the direction and energy of the incident particle, which is then used to reconstruct an image of the emitting source. Because of this imaging capability background events can be rejected, decreasing the number of events required for high confidence detection and thereby greatly improving its sensitivity. The instrument is optimized for the detection of neutrons with energies from 1-20 MeV and gamma rays from 0.4 to 10 MeV. Images and energy spectra for neutron and gamma rays are reported for several sources including depleted uranium and plutonium. In addition, the effect of neutron source shielding is investigated.

  7. Gamma-Ray Burst Physics with GLAST

    SciTech Connect

    Omodei, N.; /INFN, Pisa

    2006-10-06

    The Gamma-ray Large Area Space Telescope (GLAST) is an international space mission that will study the cosmos in the energy range 10 keV-300 GeV, the upper end of which is one of the last poorly observed region of the celestial electromagnetic spectrum. The ancestor of the GLAST/LAT was the Energetic Gamma Ray Experiment Telescope (EGRET) detector, which flew onboard the Compton Gamma Ray Observatory (CGRO). The amount of information and the step forward that the high energy astrophysics made thanks to its 9 years of observations are impressive. Nevertheless, EGRET uncovered the tip of the iceberg, raising many questions, and it is in the light of EGRET's results that the great potential of the next generation gamma-ray telescope can be appreciated. GLAST will have an imaging gamma-ray telescope, the Large Area Telescope (LAT) vastly more capable than instruments own previously, as well as a secondary instrument, the GLAST Bursts Monitor, or GBM, to augment the study of gamma-ray bursts. Gamma-Ray Bursts (GRBs) science is one of the most exciting challenges for the GLAST mission, exploring the high energy emission of one of the most intense phenomena in the sky, shading light on various problems: from the acceleration of particles to the emission processes, to more exotic physics like Quantum Gravity effect. In this paper we report the work done so far in the simulation development as well as the study of the LAT sensitivity to GRB.

  8. Gamma-Ray Bursts: An Update

    NASA Technical Reports Server (NTRS)

    Fishman, Gerald J.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Gamma-ray bursts are now known to originate from cosmological distances and represent the largest known explosions in the Universe. The observed characteristics of bursts in the gamma-ray region, primarily from data obtained with the BATSE experiment on the Compton Observatory, will be described. These include the temporal and spectral characteristic of bursts, and their intensity and sky distribution. A summary of recent discoveries and observations in other wavelength regions will also be presented, along with their implications for models of the burst emission mechanism. Various models for the energy source of gamma-ray bursts will be described.

  9. Detecting axionlike particles with gamma ray telescopes.

    PubMed

    Hooper, Dan; Serpico, Pasquale D

    2007-12-01

    We propose that axionlike particles (ALPs) with a two-photon vertex, consistent with all astrophysical and laboratory bounds, may lead to a detectable signature in the spectra of high-energy gamma-ray sources. This occurs as a result of gamma rays being converted into ALPs in the magnetic fields of efficient astrophysical accelerators according to the "Hillas criterion", such as jets of active galactic nuclei or hot spots of radio galaxies. The discovery of such an effect is possible by GLAST in the 1-100 GeV range and by ground-based gamma-ray telescopes in the TeV range. PMID:18233353

  10. Gamma-Ray Bursts and Particle Astrophysics

    E-print Network

    B. Gendre

    2008-07-24

    Gamma-ray bursts are violent events occurring randomly in the sky. In this review, I will present the fireball model, proposed to explain the phenomenon of gamma-ray bursts. This model has important consequences for the production and observation at Earth of gravitational waves, high energy neutrinos, cosmic rays and high energy photons, and the second part of this review will be focused on these aspects. A last section will briefly discuss the topic of the use of gamma-ray bursts as standard candles and possible cosmological studies.

  11. Ultrahigh resolution adaptive optics: optical coherence tomography for in vivo imaging of healthy and diseased retinal structures

    Microsoft Academic Search

    Robert J. Zawadzki; Yan Zhang; Steven M. Jones; Stacey S. Choi; Barry Cense; Julia W. Evans; Donald T. Miller; Scot S. Olivier; John S. Werner

    2008-01-01

    Ultra-high isotropic resolution imaging of retinal structures was made possible with an adaptive optics system using dual deformable mirrors and a Fourier-domain optical coherence tomography (Fd-OCT) system with correction for longitudinal chromatic aberration. This system was used to image microscopic retinal structures of healthy as well as diseased retinas in vivo. The improved resolution and contrast enhanced visualization of morphological

  12. Ultra-high resolution Fourier domain optical coherence tomography for old master paintings.

    PubMed

    Cheung, C S; Spring, M; Liang, H

    2015-04-20

    In the last 10 years, Optical Coherence Tomography (OCT) has been successfully applied to art conservation, history and archaeology. OCT has the potential to become a routine non-invasive tool in museums allowing cross-section imaging anywhere on an intact object where there are no other methods of obtaining subsurface information. While current commercial OCTs have shown potential in this field, they are still limited in depth resolution (> 4 ?m in paint and varnish) compared to conventional microscopic examination of sampled paint cross-sections (~1 ?m). An ultra-high resolution fiber-based Fourier domain optical coherence tomography system with a constant axial resolution of 1.2 ?m in varnish or paint throughout a depth range of 1.5 mm has been developed. While Fourier domain OCT of similar resolution has been demonstrated recently, the sensitivity roll-off of some of these systems are still significant. In contrast, this current system achieved a sensitivity roll-off that is less than 2 dB over a 1.2 mm depth range with an incident power of ~1 mW on the sample. The high resolution and sensitivity of the system makes it convenient to image thin varnish and glaze layers with unprecedented contrast. The non-invasive 'virtual' cross-section images obtained with the system show the thin varnish layers with similar resolution in the depth direction but superior clarity in the layer interfaces when compared with conventional optical microscope images of actual paint sample cross-sections obtained micro-destructively. PMID:25969057

  13. Miniaturization in x ray and gamma ray spectroscopy

    NASA Technical Reports Server (NTRS)

    Iwanczyk, Jan S.; Wang, Yuzhong J.; Bradley, James G.

    1993-01-01

    The paper presents advances in two new sensor technologies and a miniaturized associated electronics technology which, when combined, can allow for very significant miniaturization and for the reduction of weight and power consumption in x-ray and gamma-ray spectroscopy systems: (1) Mercuric iodide (HgI2) x-ray technology, which allows for the first time the construction of truly portable, high-energy resolution, non-cryogenic x-ray fluorescence (XRF) elemental analyzer systems, with parameters approaching those of laboratory quality cryogenic instruments; (2) the silicon avalanche photodiode (APD), which is a solid-state light sensitive device with internal amplification, capable of uniquely replacing the vacuum photomultiplier tube in scintillation gamma-ray spectrometer applications, and offering substantial improvements in size, ruggedness, low power operation and energy resolution; and (3) miniaturized (hybridized) low noise, low power amplification and processing electronics, which take full advantage of the favorable properties of these new sensors and allow for the design and fabrication of advanced, highly miniaturized x-ray and gamma-ray spectroscopy systems. The paper also presents experimental results and examples of spectrometric systems currently under construction. The directions for future developments are discussed.

  14. Seabed gamma-ray spectrometry: applications at IAEA-MEL.

    PubMed

    Osvath, I; Povinec, P P

    2001-01-01

    The technique of underwater gamma-ray spectrometry has been developed to complement or replace the traditional sampling-sample analysis approach for applications with space-time constraints, e.g. large areas of investigation, emergency response or long-term monitoring. IAEA-MEL has used both high-efficiency NaI(Tl) and high-resolution HPGe spectrometry to investigate contamination with anthropogenic radionuclides in a variety of marine environments. Surveys at the South Pacific nuclear test sites of Mururoa and Fangataufa have been used to guide sampling in areas of high contamination around ground zero points. In the Irish Sea offshore from the Sellafield nuclear reprocessing plant, a gamma-ray survey of seabed sediment was carried out to obtain estimates of the distribution and subsequently, for the inventory of 137Cs in the investigated area. PMID:11379061

  15. Scintillator and photodetector array optimization for gamma-ray imaging

    NASA Astrophysics Data System (ADS)

    Bakkali, Aboubakr; Tamda, Najia; Parmentier, Michel; Chavanelle, Jerome; Pousse, Annie; Kastler, Bruno

    2004-10-01

    Needs of improved medical diagnostics, specially for early and reliable breast cancer detection, lead us to consider developments in scintillation crystals and position sensitive photomultiplier tubes (PSPMT) in order to develop a high resolution medium field g-ray imaging device. However, gamma rays detector need to find a compromise between many conflicting requirements. In order to optimize different parameters involved in the detection process, we have developed a Monte Carlo simulation software. Its aims were to optimize a gamma ray imaging system based on pixellated scintillation crystal coupled to a PSPMT array. Several crystal properties were taken into account as well as the measured intrinsic response of PSPMTs. Images obtained by simulations are compared with experimental results. Agreement between simulation and experimental results validate our simulation model.

  16. Solar Gamma Rays Powered by Secluded Dark Matter

    E-print Network

    Brian Batell; Maxim Pospelov; Adam Ritz; Yanwen Shang

    2009-10-08

    Secluded dark matter models, in which WIMPs annihilate first into metastable mediators, can present novel indirect detection signatures in the form of gamma rays and fluxes of charged particles arriving from directions correlated with the centers of large astrophysical bodies within the solar system, such as the Sun and larger planets. This naturally occurs if the mean free path of the mediator is in excess of the solar (or planetary) radius. We show that existing constraints from water Cerenkov detectors already provide a novel probe of the parameter space of these models, complementary to other sources, with significant scope for future improvement from high angular resolution gamma-ray telescopes such as Fermi-LAT. Fluxes of charged particles produced in mediator decays are also capable of contributing a significant solar system component to the spectrum of energetic electrons and positrons, a possibility which can be tested with the directional and timing information of PAMELA and Fermi.

  17. Gamma-ray bursts: Potential sources of ultra high energy cosmic-rays

    E-print Network

    E. Waxman

    2004-12-21

    The arguments suggesting an association between the sources of cosmological gamma-ray bursts (GRBs) and the sources of ultra-high energy cosmic rays (UHECRs) are presented. Recent GRB and UHECR observations are shown to strengthen these arguments. Predictions of the GRB model for UHECR production, that may be tested with large area high energy cosmic-ray detectors which are either operating or under construction, are outlined.

  18. Ultrahigh resolution optical coherence tomography for quantitative topographic mapping of retinal and intraretinal architectural morphology

    NASA Astrophysics Data System (ADS)

    Ko, Tony H.; Hartl, Ingmar; Drexler, Wolfgang; Ghanta, Ravi K.; Fujimoto, James G.

    2002-06-01

    Quantitative, three-dimensional mapping of retinal architectural morphology was achieved using an ultrahigh resolution ophthalmic OCT system. This OCT system utilizes a broad bandwidth titanium-sapphire laser light source generating bandwidths of up to 300 nm near 800 nm center wavelength. The system enables real-time cross-sectional imaging of the retina with ~3 micrometers axial resolution. The macula and the papillomacular axis of a normal human subject were systematically mapped using a series of linear scans. Edge detection and segmentation algorithms were developed to quantify retinal and intraretinal thicknesses. Topographic mapping of the total retinal thickness and the total ganglion cell/inner plexiform layer thickness was achieved around the macula. A topographic mapping quantifying the progressive thickening of the nerve fiber layer (NFL) nasally approaching the optic disk was also demonstrated. The ability to create three-dimensional topographic mapping of retinal architectural morphology at ~3 micrometers axial resolution will be relevant for the diagnosis of many retinal diseases. The topographic quantification of these structures can serve as a powerful tool for developing algorithms and clinical scanning protocols for the screening and staging of ophthalmic diseases such as glaucoma.

  19. Analysis of protein hydration in ultrahigh-resolution structures of the SRP GTPase Ffh

    PubMed Central

    Ramirez, Ursula D.; Freymann, Douglas M.

    2013-01-01

    Two new structures of the SRP GTPase Ffh have been determined at 1.1 Å resolution and provide the basis for comparative examination of the extensive water structure of the apo conformation of these GTPases. A set of well defined water-binding positions have been identified in the active site of the two-domain ‘NG’ GTPase, as well as at two functionally important interfaces. The water hydrogen-bonding network accommodates alternate conformations of the protein side chains by undergoing local rearrangements and, in one case, illustrates binding of a solute molecule within the active site by displacement of water molecules without further disruption of the water-interaction network. A subset of the water positions are well defined in several lower resolution structures, including those of different nucleotide-binding states; these appear to function in maintaining the protein structure. Consistent arrangements of surface water between three different ultrahigh-resolution structures provide a framework for beginning to understand how local water structure contributes to protein–ligand and protein–protein binding in the SRP GTPases. PMID:17139088

  20. Direct surface analysis of time-resolved aerosol impactor samples with ultrahigh-resolution mass spectrometry.

    PubMed

    Fuller, Stephen J; Zhao, Yongjing; Cliff, Steven S; Wexler, Anthony S; Kalberer, Markus

    2012-11-20

    Aerosol particles in the atmosphere strongly influence the Earth's climate and human health, but the quantification of their effects is highly uncertain. The complex and variable composition of atmospheric particles is a main reason for this uncertainty. About half of the particle mass is organic material, which is very poorly characterized on a molecular level, and therefore it is challenging to identify sources and atmospheric transformation processes. We present here a new combination of techniques for highly time-resolved aerosol sampling using a rotating drum impactor (RDI) and organic chemical analysis using direct liquid extraction surface analysis (LESA) combined with ultrahigh-resolution mass spectrometry. This minimizes sample preparation time and potential artifacts during sample workup compared to conventional off-line filter or impactor sampling. Due to the high time resolution of about 2.5 h intensity correlations of compounds detected in the high-resolution mass spectra were used to identify groups of compounds with likely common sources or atmospheric history. PMID:23110367

  1. Energetics of Gamma Ray Bursts

    E-print Network

    Jiménez, R; Piran, T; Jimenez, Raul; Band, David; Piran, Tsvi

    2001-01-01

    We determine the distribution of total energy emitted by gamma-ray bursts for bursts with fluences and distance information. Our core sample consists of eight bursts with BATSE spectra and spectroscopic redshifts. We extend this sample by adding four bursts with BATSE spectra and host galaxy R magnitudes. From these R magnitudes we calculate a redshift probability distribution; this method requires a model of the host galaxy population. From a sample of ten bursts with both spectroscopic redshifts and host galaxy R magnitudes (some do not have BATSE spectra) we find that the burst rate is proportional to the galaxy luminosity at the epoch of the burst. Assuming that the total energy emitted has a log-normal distribution, we find that the average emitted energy (assumed to be radiated isotropically) is $ = 1.3^{+1.2}_{-1.0} \\times 10^{53}$ ergs (for H$_0$ = 65 km s$^{-1}$ Mpc$^{-1}$, $\\Omega_m=0.3$ and $\\Omega_\\Lambda=0.7$); the distribution has a logarithmic width of $\\sigma_\\gamma=1.7^{+0.7}_{-0.3}$. The cor...

  2. Gamma-ray Burst Cosmology

    E-print Network

    Wang, F Y; Liang, E W

    2015-01-01

    Gamma-ray bursts (GRBs) are the most luminous electromagnetic explosions in the Universe, which emit up to $8.8\\times10^{54}$ erg isotropic equivalent energy in the hard X-ray band. The high luminosity makes them detectable out to the largest distances yet explored in the Universe. GRBs, as bright beacons in the deep Universe, would be the ideal tool to probe the properties of high-redshift universe: including the cosmic expansion and dark energy, star formation rate, the reionization epoch and the metal enrichment history of the Universe. In this article, we review the luminosity correlations of GRBs, and implications for constraining the cosmological parameters and dark energy. Observations show that the progenitors of long GRBs are massive stars. So it is expected that long GRBs are tracers of star formation rate. We also review the high-redshift star formation rate derived from GRBs, and implications for the cosmic reionization history. The afterglows of GRBs generally have broken power-law spectra, so it...

  3. Ultrahigh-resolution full-field optical coherence tomography for imaging of a developing embryo

    NASA Astrophysics Data System (ADS)

    Wang, Bo; Zheng, Jinggao; Wang, Rui; Chen, Dieyan; Xue, Ping

    2009-07-01

    Optical coherence tomography (OCT) is a new emerging technique for cross-sectional imaging with high spatial resolution of micrometer scale. It enables in vivo and non-invasive imaging with no need to contact the sample and is widely used in biological and clinic application. In this paper a white-light interference microscope is developed for ultrahigh-resolution full-field optical coherence tomography (Full-Field OCT) to implement 3D imaging of biological tissue. The experimental setup is based on a Linnik-type interferometer illuminated by a tungsten halogen lamp via a bundle of fiber. En-face tomographic images are obtained by demodulation of a combination of interferometric images recorded by a CCD camera. We use a PZT synchronized with the CCD in the reference arm to get the modulated interferometric image and use a programmed precisely controlled electric lift stage in the sample arm to get a 3D image. To fulfill the requirement of in vivo measurement and better match the index of bio-tissue, a pair of high numerical-aperture water immersion microscope objectives is used. Spatial resolution of 1.8?m×1.12?m (transverse×axial) is achieved owing to the extremely short coherence length of the light source and optimized compensation of dispersion mismatch. A shot-noise limited detection sensitivity of 80 dB is obtained at an acquisition time of 5 seconds per image. The development of a mouse embryo is studied layer by layer with our ultrahigh-resolution full-filed OCT. 3D imaging of the embryo can be reconstructed by the OCT images. Information of cell shape, centroid, reflectivity, mitosis period in the development process can be obtained. The variance of the relative reflectivity of an oocyte with time is calculated as well. It is found that the reflectivity of a living oocyte is much lower than that of a dead. Therefore the reflectivity of the cytoplasm can be a signal of the cell activity. In fact, all these parameters above could be very useful for distinguishing the healthy embryos from the morbid, showing high potential for early diagnosis of procreation diseases at cellular level in clinic. More experimental study is still in progress.

  4. Thermal neutron capture gamma-rays

    SciTech Connect

    Tuli, J.K.

    1983-01-01

    The energy and intensity of gamma rays as seen in thermal neutron capture are presented. Only those (n,..cap alpha..), E = thermal, reactions for which the residual nucleus mass number is greater than or equal to 45 are included. These correspond to evaluations published in Nuclear Data Sheets. The publication source data are contained in the Evaluated Nuclear Structure Data File (ENSDF). The data presented here do not involve any additional evaluation. Appendix I lists all the residual nuclides for which the data are included here. Appendix II gives a cumulated index to A-chain evaluations including the year of publication. The capture gamma ray data are given in two tables - the Table 1 is the list of all gamma rays seen in (n,..gamma..) reaction given in the order of increasing energy; the Table II lists the gamma rays according to the nuclide.

  5. POPULATION SYNTHESIS AND GAMMA RAY BURST PROGENITORS

    SciTech Connect

    C. L. FREYER

    2000-12-11

    Population synthesis studies of binaries are always limited by a myriad of uncertainties from the poorly understood effects of binary mass transfer and common envelope evolution to the many uncertainties that still remain in stellar evolution. But the importance of these uncertainties depends both upon the objects being studied and the questions asked about these objects. Here I review the most critical uncertainties in the population synthesis of gamma-ray burst progenitors. With a better understanding of these uncertainties, binary population synthesis can become a powerful tool in understanding, and constraining, gamma-ray burst models. In turn, as gamma-ray bursts become more important as cosmological probes, binary population synthesis of gamma-ray burst progenitors becomes an important tool in cosmology.

  6. Gamma-ray bursts: An overview

    NASA Technical Reports Server (NTRS)

    Lestrade, John Patrick

    1990-01-01

    Gamma Ray Bursts were discovered by researchers studying data from gamma ray detectors aboard the Vela satellites. Since the original discovery, over 500 bursts have been observed by more than a dozen experiments on planetary spacecraft, earth orbiters, balloon flights, and even ground based instruments. Unfortunately, a description of the nature of these transient phenomena is no closer today than two decades ago. Part of the problem lies in the large variability in their physical characteristics. This variability has spawned more than 40 gamma ray burst models. Each model claims some subset of the 500 observed bursts that conclusively proves its validity. A very brief overview is presented of the gamma ray burst phenomenon.

  7. Gravitational waves and gamma-ray bursts

    E-print Network

    Alessandra Corsi; for the LIGO Scientific Collaboration; for the Virgo Collaboration

    2012-05-11

    Gamma-Ray Bursts are likely associated with a catastrophic energy release in stellar mass objects. Electromagnetic observations provide important, but indirect information on the progenitor. On the other hand, gravitational waves emitted from the central source, carry direct information on its nature. In this context, I give an overview of the multi-messenger study of gamma-ray bursts that can be carried out by using electromagnetic and gravitational wave observations. I also underline the importance of joint electromagnetic and gravitational wave searches, in the absence of a gamma-ray trigger. Finally, I discuss how multi-messenger observations may probe alternative gamma-ray burst progenitor models, such as the magnetar scenario.

  8. Studying Gamma Ray Bursts from a

    E-print Network

    Â?umer, Slobodan

    Studying Gamma Ray Bursts from a new perspective! {... Unraveling some mysteries and adding new Radio Op0cal X-ray Short ( energy -ray photons... ... accompained by a considerable long las0ng emission

  9. Optical reprocessing of gamma-ray bursts

    SciTech Connect

    Melia, F.; Rappaport, S.; Joss, P.C.

    1986-06-01

    One model for the optical flashes associated with three cosmic gamma-ray burst sources invokes the reprocessing of some of the gamma-radiation emitted by a hypothesized collapsed object in the surface layers of a nearby companion star. This model was investigated by carrying out detail, fully hydrodynamical calculations of such reprocessing in the surface layers of very low mass stars. It is found that, at most, 7 percent of the gamma-ray fluence incident on the companion star is reprocessed into the blue band; the time scale for this reprocessing is typically 100 s, which is long compared to the duration of the gamma-ray burst itself. Using this result, it is shown that there is marginal agreement between the observed and calculated ratios of gamma-ray fluence to optical fluence at earth. 18 references.

  10. Ultrahigh Energy Activity in Giant Magnetar Outbursts

    E-print Network

    David Eichler

    2005-04-20

    The recent superflare of 27 December 2004 from the magnetar SGR 1806-20 was the brightest extrasolar flash ever recorded in the modern era. The chances for seeing exotic ultrahigh energy (UHE) radiation - neutrons, neutrinos, gamma rays and charged cosmic rays - from it are far better from an energetic point of view than from cosmological gamma ray bursts (GRBs). The chances for detecting the various components are discussed in light of recent data from the 27 December event.

  11. The BATSE experiment on the Gamma Ray Observatory: Solar flare hard x ray and gamma-ray capabilities

    NASA Technical Reports Server (NTRS)

    Fishman, G. J.; Meegan, C. A.; Wilson, R. B.; Parnell, T. A.; Paciesas, W. S.; Pendleton, G. N.; Hudson, H. S.; Matteson, J. L.; Peterson, L. E.; Cline, T. L.

    1989-01-01

    The Burst and Transient Source Experiment (BATSE) for the Gamma Ray Observatory (GRO) consists of eight detector modules that provide full-sky coverage for gamma-ray bursts and other transient phenomena such as solar flares. Each detector module has a thin, large-area scintillation detector (2025 sq cm) for high time-resolution studies, and a thicker spectroscopy detector (125 sq cm) to extend the energy range and provide better spectral resolution. The total energy range of the system is 15 keV to 100 MeV. These 16 detectors and the associated onboard data system should provide unprecedented capabilities for observing rapid spectral changes and gamma-ray lines from solar flares. The presence of a solar flare can be detected in real-time by BATSE; a trigger signal is sent to two other experiments on the GRO. The launch of the GRO is scheduled for June 1990, so that BATSE can be an important component of the Max '91 campaign.

  12. Non-photonic emission from gamma-ray bursts

    E-print Network

    E. Waxman

    2007-03-16

    gamma-ray bursts (GRBs) are likely sources of ultra-high energy, >10^{19} eV, protons and high energy, >1 TeV, neutrinos. Large volume detectors of ultra high energy cosmic rays (UHECRs) and high energy neutrinos, which are already operating and are being expanded, may allow to test in the coming few years the predictions of the GRB model for high energy proton and neutrino production. Detection of the predicted signals will allow to identify the sources of UHECRs and will provide a unique probe, which may allow to resolve open questions related to the underlying physics of GRB models. Moreover, detection of GRB neutrinos will allow to test for neutrino properties (e.g., flavor oscillations for which tau's would be a unique signature, and coupling to gravity) with an accuracy many orders of magnitude better than is currently possible.

  13. Particle Acceleration in Gamma-Ray Burst Jets

    E-print Network

    Frank M. Rieger; Peter Duffy

    2005-11-02

    Gradual shear acceleration of energetic particles in gamma-ray burst (GRB) jets is considered. Special emphasis is given to the analysis of universal structured jets, and characteristic acceleration timescales are determined for a power-law and a Gaussian evolution of the bulk flow Lorentz factor $\\gamma_b$ with angle $\\phi$ from the jet axis. The results suggest that local power-law particle distributions may be generated and that higher energy particles are generally concentrated closer to the jet axis. Taking several constraints into account we show that efficient electron acceleration in gradual shear flows, with maximum particle energy successively decreasing with time, may be possible on scales larger than $r \\sim 10^{15}$ cm, provided the jet magnetic field becomes sufficiently weak and/or decreases rapidly enough with distance, while efficient acceleration of protons to ultra-high energies $> 10^{20}$ eV may be possible under a wide range of conditions.

  14. Digital discrimination of neutrons and gamma-rays in organic scintillation detectors using moment analysis

    SciTech Connect

    Xie Xufei; Zhang Xing; Yuan Xi; Chen Jinxiang; Li Xiangqing; Zhang Guohui; Fan Tieshuan [School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing (China); Yuan Guoliang; Yang Jinwei; Yang Qingwei [Southwestern Institute of Physics, Chengdu (China)

    2012-09-15

    Digital discrimination of neutron and gamma-ray events in an organic scintillator has been investigated by moment analysis. Signals induced by an americium-beryllium (Am/Be) isotropic neutron source in a stilbene crystal detector have been sampled with a flash analogue-to-digital converter (ADC) of 1 GSamples/s sampling rate and 10-bit vertical resolution. Neutrons and gamma-rays have been successfully discriminated with a threshold corresponding to gamma-ray energy about 217 keV. Moment analysis has also been verified against the results assessed by a time-of-flight (TOF) measurement. It is shown that the classification of neutrons and gamma-rays afforded by moment analysis is consistent with that achieved by digital TOF measurement. This method has been applied to analyze the data acquired from the stilbene crystal detector in mixed radiation field of the HL-2A tokamak deuterium plasma discharges and the results are described.

  15. Digital discrimination of neutrons and gamma-rays in organic scintillation detectors using moment analysis

    NASA Astrophysics Data System (ADS)

    Xie, Xufei; Zhang, Xing; Yuan, Xi; Chen, Jinxiang; Li, Xiangqing; Zhang, Guohui; Fan, Tieshuan; Yuan, Guoliang; Yang, Jinwei; Yang, Qingwei

    2012-09-01

    Digital discrimination of neutron and gamma-ray events in an organic scintillator has been investigated by moment analysis. Signals induced by an americium-beryllium (Am/Be) isotropic neutron source in a stilbene crystal detector have been sampled with a flash analogue-to-digital converter (ADC) of 1 GSamples/s sampling rate and 10-bit vertical resolution. Neutrons and gamma-rays have been successfully discriminated with a threshold corresponding to gamma-ray energy about 217 keV. Moment analysis has also been verified against the results assessed by a time-of-flight (TOF) measurement. It is shown that the classification of neutrons and gamma-rays afforded by moment analysis is consistent with that achieved by digital TOF measurement. This method has been applied to analyze the data acquired from the stilbene crystal detector in mixed radiation field of the HL-2A tokamak deuterium plasma discharges and the results are described.

  16. The Measurements of Gamma-ray Spectrometers from China's Chang'E-1/2 Spacecrafts

    NASA Astrophysics Data System (ADS)

    Zhu, Meng-Hua; Chang, Jin; Ma, T.

    2012-07-01

    Gamma ray spectrometers, as one of the major payloads onboard China's Chang'E-1/2 spacecrafts, were aimed to provide maps of the abundances of major elements, O, Si, Mg, Al, Ca, Ti, Na, and Fe, and of the natural radioactive elements, U, Th, and K, in the subsurface of the Moon. These elements presented on the lunar surface are the end products of a series of processes (i.e., accumulation, collision, and modification), their measurements, therefore, could provide many important clues to understand the formation and evolution of the Moon. Gamma ray spectrometer onboard Chang'E-1spacecraft used a large CsI(Tl) crystal as its main detector to measure gamma rays from the Moon with energy resolution of ˜9%@662 keV while Chang'E-2 gamma ray spectrometer firstly used big LaBr3 crystal in the planetary detection with energy resolution of ˜3.61%@662 keV. Both gamma ray spectrometers used coincident technique to suppress the Compton effects and reduce the background gamma rays from the interactions from GCRs with spacecraft materials. Gamma rays from the Moon were measured in the energy range of 0.3 ˜ 10 MeV with 512-channel spectrum every 3 seconds from a circle, polar-orbit but at a nominal altitude of 200 km and 100 km, respectively. Thorium and Potassium maps were derived from the one-year gamma ray measurements of Chang'E-1spacecraft. All these maps show good consistent with previous results from Lunar Prospector and Kaguya missions. Lunar terrains could be clearly classified on the basis of these compositions in relation with other characteristics. Chang'E-2 gamma ray spectrometer has only half-year detections, but since large LaBr3 crystal has higher energy resolution and higher detection efficiency, element distribution across the lunar surface could be obtained with higher precision. With the data set from Chang'E-2 gamma ray spectrometer, radioactive elements (K, and Th), and major elements (Fe, Ti, Si, Mg, Al, O, and Ca) distributions on the lunar surface have been derived. From present research, several new features have been found that are different from the results of Lunar Prospector gamma ray spectrometer.

  17. Photoabsorption of Gamma Rays in Relativistic Jets

    E-print Network

    Charles Dermer

    2004-02-18

    A derivation of the \\gamma\\gamma --> e^+ e^- optical depth for \\gamma rays produced in a comoving spherical emitting region is presented. Employing a simplified expression for the \\gamma\\gamma absorption cross section, analytic expressions for the minimum Doppler factor implied by the requirement of gamma-ray transparency are derived for a broken power-law spectrum of target photons which are isotropically distributed in the comoving frame. Application to specific systems is illustrated.

  18. Diffuse continuum gamma rays from the Galaxy

    E-print Network

    A. W. Strong; I. V. Moskalenko; O. Reimer

    2000-02-24

    A new study of the diffuse Galactic gamma-ray continuum radiation is presented, using a cosmic-ray propagation model which includes nucleons, antiprotons, electrons, positrons, and synchrotron radiation. Our treatment of the inverse Compton (IC) scattering includes the effect of anisotropic scattering in the Galactic interstellar radiation field (ISRF) and a new evaluation of the ISRF itself. Models based on locally measured electron and nucleon spectra and synchrotron constraints are consistent with gamma-ray measurements in the 30-500 MeV range, but outside this range excesses are apparent. A harder nucleon spectrum is considered but fitting to gamma rays causes it to violate limits from positrons and antiprotons. A harder interstellar electron spectrum allows the gamma-ray spectrum to be fitted above 1 GeV as well, and this can be further improved when combined with a modified nucleon spectrum which still respects the limits imposed by antiprotons and positrons. A large electron/IC halo is proposed which reproduces well the high-latitude variation of gamma-ray emission. The halo contribution of Galactic emission to the high-latitude gamma-ray intensity is large, with implications for the study of the diffuse extragalactic component and signatures of dark matter. The constraints provided by the radio synchrotron spectral index do not allow all of the <30 MeV gamma-ray emission to be explained in terms of a steep electron spectrum unless this takes the form of a sharp upturn below 200 MeV. This leads us to prefer a source population as the origin of the excess low-energy gamma rays.

  19. Solar Two High Energy Gamma Ray Observatory

    Microsoft Academic Search

    T. O. Tumer; D. Bhattacharya; M. Chantell; Z. Conner; P. Coppi; C. E. Covault; M. Dragovan; D. T. Gregorich; D. S. Hanna; U. Mohideen; R. A. Ong; S. Oser; K. Ragan; H. Tom; D. A. Williams

    1997-01-01

    The Solar Two Gamma-Ray Telescope is planned as an extension to the STACEE Sandia experiment that is being developed for ground-based gamma-ray astronomy using the atmospheric Cherenkov detection technique in the energy range of 20 to 250 GeV. Because of its large effective light collection area, the STACEE and Solar Two Observatory will be able to reach low energy thresholds

  20. Neutrinos and Gamma Rays from Galaxy Clusters

    E-print Network

    Brandon Wolfe; Fulvio Melia; Roland M. Crocker; Raymond R. Volkas

    2008-07-04

    The next generation of neutrino and gamma-ray detectors should provide new insights into the creation and propagation of high-energy protons within galaxy clusters, probing both the particle physics of cosmic rays interacting with the background medium and the mechanisms for high-energy particle production within the cluster. In this paper we examine the possible detection of gamma-rays (via the GLAST satellite) and neutrinos (via the ICECUBE and Auger experiments) from the Coma cluster of galaxies, as well as for the gamma-ray bright clusters Abell 85, 1758, and 1914. These three were selected from their possible association with unidentified EGRET sources, so it is not yet entirely certain that their gamma-rays are indeed produced diffusively within the intracluster medium, as opposed to AGNs. It is not obvious why these inconspicuous Abell-clusters should be the first to be seen in gamma-rays, but a possible reason is that all of them show direct evidence of recent or ongoing mergers. Their identification with the EGRET gamma-ray sources is also supported by the close correlation between their radio and (purported) gamma-ray fluxes. Under favorable conditions (including a proton spectral index of 2.5 in the case of Abell 85, and sim 2.3 for Coma, and Abell 1758 and 1914), we expect ICECUBE to make as many as 0.3 neutrino detections per year from the Coma cluster of galaxies, and as many as a few per year from the Abell clusters 85, 1758, and 1914. Also, Auger may detect as many as 2 events per decade at ~ EeV energies from these gamma-ray bright clusters.

  1. Research in cosmic and gamma ray astrophysics

    NASA Technical Reports Server (NTRS)

    Stone, E. C.; Davis, L., Jr.; Mewaldt, R. A.; Prince, T. A.

    1989-01-01

    Research activities in cosmic rays, gamma rays, and astrophysical plasmas are covered. The activities are divided into sections and described, followed by a bibliography. The astrophysical aspects of cosmic rays, gamma rays, and of the radiation and electromagnetic field environment of the Earth and other planets are investigated. These investigations are performed by means of energetic particle and photon detector systems flown on spacecraft and balloons.

  2. Observing with a space-borne gamma-ray telescope: selected results from INTEGRAL

    E-print Network

    S. Schanne

    2006-06-22

    The International Gamma-Ray Astrophysics Laboratory, i.e. the INTEGRAL satellite of ESA, in orbit since about 3 years, performs gamma-ray observations of the sky in the 15 keV to 8 MeV energy range. Thanks to its imager IBIS, and in particular the ISGRI detection plane based on 16384 CdTe pixels, it achieves an excellent angular resolution (12 arcmin) for point source studies with good continuum spectrum sensitivity. Thanks to its spectrometer SPI, based on 19 germanium detectors maintained at 85 K by a cryogenic system, located inside an active BGO veto shield, it achieves excellent spectral resolution of about 2 keV for 1 MeV photons, which permits astrophysical gamma-ray line studies with good narrow-line sensitivity. In this paper we review some goals of gamma-ray astronomy from space and present the INTEGRAL satellite, in particular its instruments ISGRI and SPI. Ground and in-flight calibration results from SPI are presented, before presenting some selected astrophysical results from INTEGRAL. In particular results on point source searches are presented, followed by results on nuclear astrophysics, exemplified by the study of the 1809 keV gamma-ray line from radioactive 26Al nuclei produced by the ongoing stellar nucleosynthesis in the Galaxy. Finally a review on the study of the positron-electron annihilation in the Galactic center region, producing 511 keV gamma-rays, is presented.

  3. Gamma-ray Albedo of the Moon

    SciTech Connect

    Moskalenko, Igor V.; Porter, Troy A.

    2007-06-14

    We use the GEANT4 Monte Carlo framework to calculate the gamma-ray albedo of the Moon due to interactions of cosmic ray (CR) nuclei with moon rock. Our calculation of the albedo spectrum agrees with the EGRET data. We show that the spectrum of gamma-rays from the Moon is very steep with an effective cutoff around 3 GeV (600 MeV for the inner part of the Moon disc). Since it is the only (almost) black spot in the gamma-ray sky, it provides a unique opportunity for calibration of gamma-ray telescopes, such as the forthcoming Gamma Ray Large Area Space Telescope (GLAST). The albedo flux depends on the incident CR spectrum which changes over the solar cycle. Therefore, it is possible to monitor the CR spectrum using the albedo gamma-ray flux. Simultaneous measurements of CR proton and helium spectra by the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA), and observations of the albedo -rays by the GLAST Large Area Telescope (LAT), can be used to test the model predictions and will enable the GLAST LAT to monitor the CR spectrum near the Earth beyond the lifetime of PAMELA.

  4. On Gamma-Ray Bursts

    E-print Network

    Remo Ruffini; Maria Grazia Bernardini; Carlo Luciano Bianco; Letizia Caito; Pascal Chardonnet; Christian Cherubini; Maria Giovanna Dainotti; Federico Fraschetti; Andrea Geralico; Roberto Guida; Barbara Patricelli; Michael Rotondo; Jorge Armando Rueda Hernandez; Gregory Vereshchagin; She-Sheng Xue

    2008-04-17

    (Shortened) We show by example how the uncoding of Gamma-Ray Bursts (GRBs) offers unprecedented possibilities to foster new knowledge in fundamental physics and in astrophysics. After recalling some of the classic work on vacuum polarization in uniform electric fields by Klein, Sauter, Heisenberg, Euler and Schwinger, we summarize some of the efforts to observe these effects in heavy ions and high energy ion collisions. We then turn to the theory of vacuum polarization around a Kerr-Newman black hole, leading to the extraction of the blackholic energy, to the concept of dyadosphere and dyadotorus, and to the creation of an electron-positron-photon plasma. We then present a new theoretical approach encompassing the physics of neutron stars and heavy nuclei. It is shown that configurations of nuclear matter in bulk with global charge neutrality can exist on macroscopic scales and with electric fields close to the critical value near their surfaces. These configurations may represent an initial condition for the process of gravitational collapse, leading to the creation of an electron-positron-photon plasma: the basic self-accelerating system explaining both the energetics and the high energy Lorentz factor observed in GRBs. We then turn to recall the two basic interpretational paradigms of our GRB model. [...] We then turn to the special role of the baryon loading in discriminating between "genuine" short and long or "fake" short GRBs [...] We finally turn to the GRB-Supernova Time Sequence (GSTS) paradigm: the concept of induced gravitational collapse. [...] We then present some general conclusions.

  5. Nucleotide-binding flexibility in ultrahigh-resolution structures of the SRP GTPase Ffh

    SciTech Connect

    Ramirez, Ursula D.; Focia, Pamela J.; Freymann, Douglas M., E-mail: freymann@northwestern.edu [Department of Molecular Pharmacology and Biological Chemistry, Northwestern University, Chicago, IL 60611 (United States)

    2008-10-01

    Crystal structures of the Ffh NG GTPase domain at < 1.24 Å resolution reveal multiple overlapping nucleotide binding modes. Two structures of the nucleotide-bound NG domain of Ffh, the GTPase subunit of the bacterial signal recognition particle (SRP), have been determined at ultrahigh resolution in similar crystal forms. One is GDP-bound and one is GMPPCP-bound. The asymmetric unit of each structure contains two protein monomers, each of which exhibits differences in nucleotide-binding conformation and occupancy. The GDP-bound Ffh NG exhibits two binding conformations in one monomer but not the other and the GMPPCP-bound protein exhibits full occupancy of the nucleotide in one monomer but only partial occupancy in the other. Thus, under the same solution conditions, each crystal reveals multiple binding states that suggest that even when nucleotide is bound its position in the Ffh NG active site is dynamic. Some differences in the positioning of the bound nucleotide may arise from differences in the crystal-packing environment and specific factors that have been identified include the relative positions of the N and G domains, small conformational changes in the P-loop, the positions of waters buried within the active site and shifts in the closing loop that packs against the guanine base. However, ‘loose’ binding may have biological significance in promoting facile nucleotide exchange and providing a mechanism for priming the SRP GTPase prior to its activation in its complex with the SRP receptor.

  6. Gamma-ray identification of nuclear weapon materials

    SciTech Connect

    Gosnell, T. B., LLNL; Hall, J. M.; Jam, C. L.; Knapp, D. A.; Koenig, Z. M.; Luke, S. J.; Pohl, B. A.; Schach von Wittenau, A.; Wolford, J. K.

    1997-02-03

    There has been an accelerating national interest in countering nuclear smuggling. This has caused a corresponding expansion of interest in the use of gamma-ray spectrometers for checkpoint monitoring, nuclear search, and within networks of nuclear and collateral sensors. All of these are fieldable instruments--ranging from large, fixed portal monitors to hand-held and remote monitoring equipment. For operational reasons, detectors with widely varying energy resolution and detection efficiency will be employed. In many instances, such instruments must be sensitive to weak signals, always capable of recognizing the gamma-ray signatures from nuclear weapons materials (NWM), often largely insensitive to spectral alteration by radiation transport through intervening materials, capable of real-time implementation, and able to discriminate against signals from commonly encountered legitimate gamma-ray sources, such as radiopharmaceuticals. Several decades of experience in classified programs have shown that all of these properties are not easily achieved and successful approaches were of limited scope--such as the detection of plutonium only. This project was originally planned as a two-year LDRD-ER. Since funding for 1997 was not sustained, this is a report of the first year's progress.

  7. Historical aspects of gamma-ray astronomy

    NASA Astrophysics Data System (ADS)

    Sreekantan, B. V.

    2002-03-01

    Over the entire 20th century, Cosmic Rays proved to be the watershed of fundamental knowledge from which poured out several streams that made us familiar with aspects of the universe that could never have been known through optical and radio astronomies alone. Cosmic ray interaction studies opened up the field of elementary particles and high energy physical processes. Gamma-ray astronomy enabled us to study celestial environments characterised by the dominance of high energy particles and their interactions with matter, magnetic and electric fields in the neighbourhood of these special environments. While neutrino astronomy is still in its infancy, it has the potential of becoming the most exciting field of study in the current century. Gamma-ray astronomy has had a chequered career. In the early part of the 20th century, Millikan proposed that cosmic rays are merely gamma rays. This was disproved by Compton, through the establishment of the latitude effect. The soviet astrophysicist Shklovskii pointed out at the III International conference on cosmic rays held at Guanjuato, Mexico, the possibility of supernova remants like the Crab Nebula being sources of TeV gamma rays. This was based on his realisation that the high degree of polarized light from the Crab could be due to Synchrotron emission by TeV energy electrons spiralling round the filamentary magnetic fields of the nebula. He argued that the same mechanism that accelerated electrons could also accelerate the protons which through their interaction with the surrounding matter generate pi-zero measons that would immediately decay into gamma rays. However, the efforts by the soviet experimentalists, who used the night air cerenkov technique for detection of the TeV gamma rays, proved negative; only upper limits could be set on the fluxew of TeV gamma rays from several of the SN-remnants; the negative results were first reported at the 7th ICRC held at Jaipur, India in 1963. High energy gamma ray astronomy had a remarkable revival with the discovery of Pulsars in 1967 and their identification with Neutron stars. The field has thrived since then has been extended even to the PeV range. Beginning with 1965, gamma ray astronomy in the energy range MeV to tens of GeV has also been successfully pursued with ballons, and satellites. The most perplexing in this energy range has been the discovery of the Gamma ray bursts. In the keynote address the historical aspects of this field will be covered with some references to the work in India.

  8. Prompt gamma rays from thermal-neutron capture

    Microsoft Academic Search

    M. A. Lone; R. A. Leavitt; D. A. Harrison

    1981-01-01

    A catalog of ..gamma..-rays emitted following thermal-neutron capture in natural elements is presented. In Table I, ..gamma..-rays are arranged in order of increasing energy. Each line contains the ..gamma..-ray energy, intensity, element identification, thermal-neutron radiative-capture cross section, and the energies and intensities of two of the more abundant ..gamma..-rays associated with that element. In Table II, ..gamma..-rays are arranged by

  9. The MESSENGER Gamma-Ray and Neutron Spectrometer

    NASA Astrophysics Data System (ADS)

    Goldsten, John O.; Rhodes, Edgar A.; Boynton, William V.; Feldman, William C.; Lawrence, David J.; Trombka, Jacob I.; Smith, David M.; Evans, Larry G.; White, Jack; Madden, Norman W.; Berg, Peter C.; Murphy, Graham A.; Gurnee, Reid S.; Strohbehn, Kim; Williams, Bruce D.; Schaefer, Edward D.; Monaco, Christopher A.; Cork, Christopher P.; Del Eckels, J.; Miller, Wayne O.; Burks, Morgan T.; Hagler, Lisle B.; Deteresa, Steve J.; Witte, Monika C.

    2007-08-01

    A Gamma-Ray and Neutron Spectrometer (GRNS) instrument has been developed as part of the science payload for NASA’s Discovery Program mission to the planet Mercury. Mercury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) launched successfully in 2004 and will journey more than six years before entering Mercury orbit to begin a one-year investigation. The GRNS instrument forms part of the geochemistry investigation and will yield maps of the elemental composition of the planet surface. Major elements include H, O, Na, Mg, Si, Ca, Ti, Fe, K, and Th. The Gamma-Ray Spectrometer (GRS) portion detects gamma-ray emissions in the 0.1- to 10-MeV energy range and achieves an energy resolution of 3.5 keV full-width at half-maximum for 60Co (1332 keV). It is the first interplanetary use of a mechanically cooled Ge detector. Special construction techniques provide the necessary thermal isolation to maintain the sensor’s encapsulated detector at cryogenic temperatures (90 K) despite the intense thermal environment. Given the mission constraints, the GRS sensor is necessarily body-mounted to the spacecraft, but the outer housing is equipped with an anticoincidence shield to reduce the background from charged particles. The Neutron Spectrometer (NS) sensor consists of a sandwich of three scintillation detectors working in concert to measure the flux of ejected neutrons in three energy ranges from thermal to ˜7 MeV. The NS is particularly sensitive to H content and will help resolve the composition of Mercury’s polar deposits. This paper provides an overview of the Gamma-Ray and Neutron Spectrometer and describes its science and measurement objectives, the design and operation of the instrument, the ground calibration effort, and a look at some early in-flight data.

  10. Low energy {gamma}-rays scintillation detection with large area avalanche photodiodes

    SciTech Connect

    Moszynski, M.; Kapusta, M.; Zalipska, J.; Balcerzyk, M.; Wolski, D. [Soltan Inst. for Nuclear Studies, Swierk-Otwock (Poland)] [Soltan Inst. for Nuclear Studies, Swierk-Otwock (Poland); Szawlowski, M. [Advanced Photonix, Inc., Camarillo, CA (United States)] [Advanced Photonix, Inc., Camarillo, CA (United States); Klamra, W. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Physics] [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Physics

    1999-08-01

    Energy resolution of NaI(Tl), CsI(Tl), LSO and YAP crystals coupled to 16 mm diameter Large Area Avalanche Photodiodes (LAAPD) was studied for low energy {gamma}-rays. Energy resolutions of 11.3% and 8.4% were obtained for 59.6 keV {gamma}-rays from {sup 241}Am and 122 keV {gamma}-rays from {sup 57}Co sources, respectively, as measured with a 10 mm diameter by 10 mm high NaI(Tl) crystal. The optimization of the LAAPD performance is presented, being essential for improvement of energy resolution at low energy {gamma}-rays. Measured numbers of primary electron-hole pairs produced in LAAPDs and evaluation of noise contribution of these devices allowed for quantitative discussion of the results. Particularly, the intrinsic energy resolution of the crystals vs. energy of {gamma}-rays has been evaluated. Obtained data for NaI(Tl) crystal showed a good agreement (within 30%) with calculated component due to nonproportional light yield for energies above 50 keV.

  11. High-Energy Cosmology: gamma rays and neutrinos from beyond the galaxy

    E-print Network

    Charles D. Dermer

    2006-11-06

    Our knowledge of the high-energy universe is undergoing a period of rapid change as new astronomical detectors of high-energy radiation start to operate at their design sensitivities. Now is a boomtime for high-energy astrophysics, with new discoveries from Swift and HESS, results from MAGIC and VERITAS starting to be reported, the upcoming launches of the gamma-ray space telescopes GLAST and AGILE, and anticipated data releases from IceCube and Auger. A formalism for calculating statistical properties of cosmological gamma-ray sources is presented. Application is made to model calculations of the statistical distributions of gamma-ray and neutrino emission from (i) beamed sources, specifically, long-duration GRBs, blazars, and extagalactic microquasars, and (ii) unbeamed sources, including normal galaxies, starburst galaxies and clusters. Expressions for the integrated intensities of faint beamed and unbeamed high-energy radiation sources are also derived. A toy model for the background intensity of radiation from dark-matter annihilation taking place in the early universe is constructed. Estimates for the gamma-ray fluxes of local group galaxies, starburst, and infrared luminous galaxies are briefly reviewed. Because the brightest extragalactic gamma-ray sources are flaring sources, and these are the best targets for sources of PeV -- EeV neutrinos and ultra-high energy cosmic rays, rapidly slewing all-sky telescopes like MAGIC and an all-sky gamma-ray observatory beyond Milagro will be crucial for optimal science return in the multi-messenger age.

  12. Neutron-induced gamma-ray spectroscopy: simulations for chemical mapping of planetary surfaces

    SciTech Connect

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

    1986-01-01

    Cosmic rays interact with the surface of a planetary body and produce a cascade of secondary particles, such as neutrons. Neutron-induced scattering and capture reactions play an important role in the production of discrete gamma-ray lines that can be measured by a gamma-ray spectrometer on board of an orbiting spacecraft. These data can be used to determine the concentration of many elements in the surface of a planetary body, which provides clues to its bulk composition and in turn to its origin and evolution. To investigate the gamma rays made by neutron interactions, thin targets were irradiated with neutrons having energies from 14 MeV to 0.025 eV. By means of foil activation technique the ratio of epithermal to thermal neutrons was determined to be similar to that in the Moon. Gamma rays emitted by the targets and the surrounding material were detected by a high-resolution germanium detector in the energy range of 0.1 to 8 MeV. Most of the gamma-ray lines that are expected to be used for planetary gamma-ray spectroscopy were found in the recorded spectra and the principal lines in these spectra are presented. 58 refs., 7 figs., 9 tabs.

  13. Structure and nature of gamma-ray binaries by means of VLBI observations

    NASA Astrophysics Data System (ADS)

    Moldón, J.

    2015-05-01

    Gamma-ray binaries are extreme systems that produce non-thermal emission from radio to very-high-energy (>TeV) gamma rays, with the energy output in the spectral energy distribution (SED) dominated by the MeV-GeV photons. Their broadband emission is usually modulated by the orbital cycle of the system, which suggests that the physical conditions are also periodic and reproducible. The diversity of systems, together with the reproducibility of the conditions within each system, makes gamma-ray binaries excellent physical laboratories. These systems produce outflows of relativistic particles emitting synchrotron radio emission that extend up to several astronomical units, which correspond to projected angular scales of a few milliarcseconds (mas) at typical distances of 2-3 kpc. Very Long Baseline Interferometry (VLBI) provide mas resolution and therefore can be used to directly see this radio outflow. Here we present VLBI observations of five of the six gamma-ray binaries known. We have revealed for the first time the radio structure of two gamma-ray binaries, and found periodic changes in the structure of other two. Based on these results we have established the basic properties and behaviour of the radio emission of gamma-ray binaries on AU scales, and we have contributed to find characteristics that are common to all of them.

  14. Measuring planetary neutron albedo fluxes by remote gamma-ray sensing

    NASA Technical Reports Server (NTRS)

    Haines, E. L.; Metzger, A. E.

    1984-01-01

    In order to measure the planetary neutron albedo fluxes, a neutron-absorbing shield which emits gamma rays of characteristic energy and serves as a neutron detector, is added to a gamma-ray spectrometer (GRS). The gamma rays representing the neutron flux are observed against interference consisting of cosmic gamma rays, planetary continuum and line emission, and gamma rays arising from the interaction of cosmic rays with the GRS and the spacecraft. The uncertainty and minimum detection limits in neutron albedo fluxes are calculated for two missions, a lunar orbiter and a comet nucleus rendezvous. A GRS on a lunar orbiter at 100 km altitude detects a thermal neutron albedo flux as low as 0.002/sq cm/s and an expected flux of about 0.6/sq cm/s is measured with an uncertainty of 0.001/sq cm/s, for a 100 h observation period. For the comet nucleus, again in a 100 h observing period, a thermal neutron albedo flux is detected at a level of 0.006/sq cm/s and an expected flux of about 0.4/sq cm/s is measured with an uncertainty of 0.004/sq cm/s. The expanded geological capabilities made possible by this technique include improvements in H sensitivity, spatial resolution, and measurement depth; and an improved model of induced gamma-ray emission.

  15. COMBINED GAMMA-RAY AND NEUTRON DETECTOR FOR MEASURING THE CHEMICAL COMPOSITION OF AIRLESS PLANETARY BODIES.

    SciTech Connect

    Lawrence, David J. (David Jeffery),; Barraclough, B. L. (Bruce L.); Feldman, W. C. (William C.); Prettyman, T. H. (Thomas H.); Wiens, R. C. (Roger C.)

    2001-01-01

    Galactic cosmic rays (GCR) constant1,y itnpinge all planetary bodies and produce characteristic gamma-ray lines and leakage neutrons as reaction products. Together with gamma-ray lines produced by radioactive decay, these nuclear emissions provide a powerful technique for remotely measuring the chemical composition of airless planetary surfaces. While lunar gamma-ray spectroscopy was first demonstrated with Apollo Gamma-Ray measurements, the full value of combined gamma-ray and neutron spectroscopy was shown for the first time with the Lunar Prospector Gamma-Ray (LP-GRS) and Neutron Spectrometers (LP-NS). Any new planetary mission will likely have the requirement that instrument mass and power be kept to a minimum. To satisfy such requirements, we have been designing a GR/NS instrument which combines all the functionality of the LP-GRS and LP-NS for a fraction of the mass and power. Specifically, our design uses a BGO scintillator crystal to measure gamma-rays from 0.5-10 MeV. A borated plastic scintillator and a lithium gliiss scintillator are used to separately measure thermal, epithermal, and fast neutrons as well as serve as an anticoincidence shield for the BGO. All three scintillators are packaged together in a compact phoswich design. Modifications to this design could include a CdZnTe gamma-ray detector for enhanced energy resolution at low energies (0.5-3 MeV). While care needs to be taken to ensure that an adequate count rate is achieved for specific mission designs, previous mission successes demonstrate that a cornbined GR/NS provides essential information about planetary surfaces.

  16. A search for optical counterparts of gamma-ray bursts. Final report

    SciTech Connect

    Park, Hye-Sook

    1995-03-09

    Gamma Ray Bursts (GRBS) are mysterious flashes of gamma rays lasting several tens to hundreds of seconds that occur approximately once per day. NASA launched the orbiting Compton Gamma Ray Observatory to study GRBs and other gamma ray phenomena. CGRO carries the Burst and Transient Experiment (BATSE) specifically to study GRBS. Although BATSE has collected data on over 600 GRBS, and confirmed that GRBs are localized, high intensity point sources of MeV gamma rays distributed isotropically in the sky, the nature and origin of GRBs remains a fundamental problem in astrophysics. BATSE`s 8 gamma ray sensors located on the comers of the box shaped CGRO can detect the onset of GRBs and record their intensity and energy spectra as a function of time. The position of the burst on the sky can be determined to < {plus_minus}10{degrees} from the BATSE data stream. This position resolution is not sufficient to point a large, optical telescope at the exact position of a GRB which would determine its origin by associating it with a star. Because of their brief duration it is not known if GRBs are accompanied by visible radiation. Their seemingly large energy output suggests thatthis should be. Simply scaling the ratio of visible to gamma ray intensities of the Crab Nebula to the GRB output suggests that GRBs ought to be accompanied by visible flashes of magnitude 10 or so. A few photographs of areas containing a burst location that were coincidentally taken during the burst yield lower limits on visible output of magnitude 4. The detection of visible light during the GRB would provide information on burst physics, provide improved pointing coordinates for precise examination of the field by large telescope and provide the justification for larger dedicated optical counterpart instruments. The purpose of this experiment is to detect or set lower limits on optical counterpart radiation simultaneously accompanying the gamma rays from

  17. Gamma-Ray Emission from Galaxy Clusters : DARK MATTER AND COSMIC-RAYS

    NASA Astrophysics Data System (ADS)

    Pinzke, Anders

    The quest for the first detection of a galaxy cluster in the high energy gamma-ray regime is ongoing, and even though clusters are observed in several other wave-bands, there is still no firm detection in gamma-rays. To complement the observational efforts we estimate the gamma-ray contributions from both annihilating dark matter and cosmic-ray (CR) proton as well as CR electron induced emission. Using high-resolution simulations of galaxy clusters, we find a universal concave shaped CR proton spectrum independent of the simulated galaxy cluster. Specifically, the gamma-ray spectra from decaying neutral pions, which are produced by CR protons, dominate the cluster emission. Furthermore, based on our derived flux and luminosity functions, we identify the galaxy clusters with the brightest galaxy clusters in gamma-rays. While this emission is challenging to detect using the Fermi satellite, major observations with Cherenkov telescopes in the near future may put important constraints on the CR physics in clusters. To extend these predictions, we use a dark matter model that fits the recent electron and positron data from Fermi, PAMELA, and H.E.S.S. with remarkable precision, and make predictions about the expected gamma-ray flux from nearby clusters. In order to remain consistent with the EGRET upper limit on the gamma-ray emission from Virgo, we constrain the minimum mass of substructures for cold dark matter halos. In addition, we find comparable levels of gamma-ray emission from CR interactions and dark matter annihilations without Sommerfeld enhancement.

  18. Three-dimensional adaptive optics ultrahigh-resolution optical coherence tomography using a liquid crystal spatial light modulator

    Microsoft Academic Search

    Enrique J. Fernández; Boris Považay; Boris Hermann; Angelika Unterhuber; Harald Sattmann; Pedro M. Prieto; Rainer Leitgeb; Peter Ahnelt; Pablo Artal; Wolfgang Drexler

    2005-01-01

    A liquid crystal programmable phase modulator (PPM) is used as correcting device in an adaptive optics system for three-dimensional ultrahigh-resolution optical coherence tomography (UHR OCT). The feasibility of the PPM to correct high order aberrations even when using polychromatic light is studied, showing potential for future clinical use. Volumetric UHR OCT of the living retina, obtained with up 25,000A-scans\\/s and

  19. Challenges and possibilities for developing adaptive optics: ultra-high resolution optical coherence tomography for clinical in vivo retinal imaging

    Microsoft Academic Search

    Robert J. Zawadzki; Stacey S. Choi; Julia W. Evans; John S. Werner

    2008-01-01

    Recent developments in adaptive optics - optical coherence tomography (AO-OCT) allow for ultra-high isotropic resolution imaging of the in-vivo retina, offering unprecedented insight into its volumetric microscopic and cellular structures. In addition to this promising achievement, the clinical impact and application of this technology still needs to be explored. This includes assessment of limitations and challenges for existing as well

  20. Evaluation of the Doppler-Broadening of Gamma-Ray Spectra from Neutron Inelastic Scattering on Light Nuclei

    NASA Astrophysics Data System (ADS)

    Womble, Phillip C.; Barzilov, Alexander; Novikov, Ivan; Howard, Joseph; Musser, Jason

    2009-03-01

    Neutron-induced gamma-ray reactions are extensively used in the nondestructive analysis of materials and other areas where the information about the chemical composition of a substance is crucial. The common technique to find the intensity of the gamma ray is to fit gamma-ray line shape with an analytical function, for example, a Gaussian. However, the Gaussian fitting may fail if the gamma-ray peak is Doppler-broadened since this leads to the miscalculation of the area of the peak and, therefore, to misidentification of the material. Due to momentum considerations, Doppler-broadening occurs primarily with gamma rays from neutron-induced inelastic scattering reactions with light nuclei. The recoiling nucleus of interest must have excited states whose lifetimes are much smaller than the time of flight in the material. We have examined various light nuclei bombarded by 14 MeV neutrons to predict when the peak shape of a neutron-induced gamma ray emitted from these nuclei will be Doppler-broadened. We have found that nearly all the gamma rays from neutron-induced gamma-ray reactions on light elements (A<20) are Doppler-broadened with only a few exceptions. This means that utilization of resolution curves derived from isotopic sources or thermal neutron capture reactions have little value in the analysis.

  1. Observing Gamma-ray Bursts with GLAST

    NASA Technical Reports Server (NTRS)

    McEnery, Julie

    2008-01-01

    The Gamma-ray Large Area Telescope (GLAST) is a satellite-based observatory to study the high-energy gamma-ray sky. The Large Area Telescope, the main instrument, is a pair-conversion telescope which will survey the sky in the energy range 20 MeV to greater than 300 GeV. The LAT's wide field of view (greater than 2 sr), large effective area and low deadtime combine to provide excellent high-energy gamma-ray observations of GRB. To tie these frontier high-energy observations to the better-known properties at lower energies, a second instrument, the GLAST Burst Monitor (GBM) will provide important spectra and timing in the 8 keV to 30 MeV range. Upon detection of a GRB by the LAT or the GBM, the spacecraft can autonomously repoint to keep the GRB location within the LAT field of view, allowing high-energy afterglow observations. We describe how the instruments, spacecraft, and ground system work together to provide observations of gamma-ray bursts from 8 keV to over 300 GeV and provide rapid notification of these observations to the wider gamma-ray burst community. Analysis and simulation tools dedicated to the GRB science have been developed. In this contribution we show the expected LAT sensitivity obtained with such simulations, and illustrate the results we expect from GLAST observations with spectral and temporal analysis of simulated GRB.

  2. Gamma-ray Emission from Nova Outbursts

    NASA Astrophysics Data System (ADS)

    Hernanz, M.

    2014-12-01

    Classical novae produce radioactive nuclei which are emitters of gamma-rays in the MeV range. Some examples are the lines at 478 and 1275 keV (from 7Be and 22Na) and the positron-electron annihilation emission, with the 511 keV line and a continuum. Gamma-ray spectra and light curves are potential unique tools to trace the corresponding isotopes and to give insights on the properties of the expanding envelope. Another possible origin of gamma-rays is the acceleration of particles up to very high energies, so that either neutral pions or inverse Compton processes produce gamma-rays of energies larger than 100 MeV. MeV photons during nova explosions have not been detected yet, although several attempts have been made in the last decades; on the other hand, GeV photons from novae have been detected with the Fermi satellite in V407 Cyg, a nova in a symbiotic binary, where the companion is a red giant with a wind, instead of a main sequence star as in the cataclysmic variables hosting classical novae. Two more novae have been detected recently (summer 2012) by Fermi, apparently in non symbiotic binaries, thus challenging our understanding of the emission mechanism. Both scenarios (radioactivities and acceleration) of gamma-ray production in novae are discussed.

  3. Low-noise double-sided silicon strip detector for multiple-compton gamma-ray telescope

    Microsoft Academic Search

    Hiroyasu Tajima; Tuneyoshi Kamae; Shingo Uno; Tatsuya Nakamoto; Yasushi Fukazawa; Takefumi Mitani; Tadayuki Takahashi; Kazuhiro Nakazawa; Yu Okada; Masaharu Nomachi

    2003-01-01

    The Semiconductor Multiple-Compton Telescope (SMCT) is being developed to explore the gamma-ray universe in an energy band 0.1--20 MeV, which is not well covered by the present or near-future gamma-ray telescopes. The key feature of the SMCT is the high energy resolution that is crucial for high angular resolution and high background rejection capability. We have developed prototype modules for

  4. Fast Super-Resolution Imaging with Ultra-High Labeling Density Achieved by Joint Tagging Super-Resolution Optical Fluctuation Imaging

    PubMed Central

    Zeng, Zhiping; Chen, Xuanze; Wang, Hening; Huang, Ning; Shan, Chunyan; Zhang, Hao; Teng, Junlin; Xi, Peng

    2015-01-01

    Previous stochastic localization-based super-resolution techniques are largely limited by the labeling density and the fidelity to the morphology of specimen. We report on an optical super-resolution imaging scheme implementing joint tagging using multiple fluorescent blinking dyes associated with super-resolution optical fluctuation imaging (JT-SOFI), achieving ultra-high labeling density super-resolution imaging. To demonstrate the feasibility of JT-SOFI, quantum dots with different emission spectra were jointly labeled to the tubulin in COS7 cells, creating ultra-high density labeling. After analyzing and combining the fluorescence intermittency images emanating from spectrally resolved quantum dots, the microtubule networks are capable of being investigated with high fidelity and remarkably enhanced contrast at sub-diffraction resolution. The spectral separation also significantly decreased the frame number required for SOFI, enabling fast super-resolution microscopy through simultaneous data acquisition. As the joint-tagging scheme can decrease the labeling density in each spectral channel, thereby bring it closer to single-molecule state, we can faithfully reconstruct the continuous microtubule structure with high resolution through collection of only 100 frames per channel. The improved continuity of the microtubule structure is quantitatively validated with image skeletonization, thus demonstrating the advantage of JT-SOFI over other localization-based super-resolution methods. PMID:25665878

  5. Energy-momentum uncertainties as possible origin of threshold anomalies in UHECR and TeV-gamma ray events

    E-print Network

    Y. Jack Ng; D. -S. Lee; M. C. Oh; H. van Dam

    2000-10-24

    A threshold anomaly refers to a theoretically expected energy threshold that is not observed experimentally. Here we offer an explanation of the threshold anomalies encountered in the ultra-high energy cosmic ray events and the TeV-gamma ray events, by arguing that energy-momentum uncertainties due to quantum gravity, too small to be detected in low-energy regime, can affect particle kinematics so as to raise or even eliminate the energy thresholds. A possible modification of the energy-momentum dispersion relation, giving rise to time-of-flight differences between photons of different energies from gamma ray bursts, is also discussed.

  6. Development of the gamma-ray analysis digital filter multi-channel analyzer (GMCA)

    Microsoft Academic Search

    M. Dambacher; A. Zwerger; A. Fauler; C. Disch; U. Stöhlker; M. Fiederle

    2011-01-01

    Gamma-ray spectroscopic systems with high efficiency and energy resolution have become important in many fields. Conventional systems with analog shaping are being replaced by digital systems that can provide higher throughput, better energy resolution and better stability. Therefore, we present the development of our new versatile real time Multi-Channel Analyzer with digital signal processing, the GMCA. The device has two

  7. Dislocations in high-purity germanium and its relation to gamma-ray detector performance

    Microsoft Academic Search

    M. van Sande; L. van Goethem; L. de Laet; H. Guislain

    1986-01-01

    The presence of dislocations in high-purity germanium influences the resolution of radiation detectors made from it. The four dislocation types found with electron microscopy are studied by DLTS to understand their influence on trapping in a gamma-ray detector. Only three DLTS bands were found in commercially produced material. Statistical correlation with the detector resolution reported by various detector manufacturers finally

  8. Ultrahigh resolution total organic carbon analysis using Fourier Transform Near Infrarred Reflectance Spectroscopy (FT-NIRS)

    NASA Astrophysics Data System (ADS)

    Pearson, Emma J.; Juggins, Steve; Tyler, Jonathan

    2014-01-01

    Fourier transform near infrared reflectance spectroscopy (FT-NIRS) is a cheap, rapid, and nondestructive method for analyzing organic sediment components. Here, we examine the robustness of a within lake FT-NIRS calibration using a data set of almost 400 core samples from Lake Suigetsu, Japan, as a means to rapidly reconstruct % total organic carbon (TOC). We evaluate the best spectra pretreatment, examine different statistical approaches, and provide recommendations for the optimum number of calibration samples required for accurate predictions. Results show that the most robust method is based on first-order derivatives of all spectra modeled with partial least squares regression. We construct a TOC model training set using 247 samples and a validation test set using 135 samples (for test set R2 = 0.951, RMSE = 0.280) to determine TOC and illustrate the use of the model in an ultrahigh resolution (e.g., 1 mm/annual) study of a long sediment core from a climatically sensitive archive.

  9. Ultrahigh resolution optical coherence tomography imaging of diseased rat lung using Gaussian shaped super continuum sources

    NASA Astrophysics Data System (ADS)

    Nishizawa, N.; Ishida, S.; Kitatsuji, M.; Ohshima, H.; Hasegawa, Y.; Matsushima, M.; Kawabe, T.

    2012-02-01

    We have been investigating ultrahigh resolution optical coherence tomography (UHR-OCT) imaging of lung tissues using fiber super continuum sources. The high power, low-noise, Gaussian shaped supercontinuum generated with ultrashort pulses and optical fibers at several wavelengths were used as the broadband light sources for UHR-OCT. For the 800 nm wavelength region, the axial resolution was 3.0 um in air and 2.0 um in tissue. Since the lung consists of tiny alveoli which are separated by thin wall, the UHR-OCT is supposed to be effective for lung imaging. The clear images of alveoli of rat were observed with and without index matching effects by saline. In this work, we investigated the UHR-OCT imaging of lung disease model. The lipopolysaccharide (LPS) induced acute lung injury / acute respiratory distress syndrome (ALI/ARDS) model of rat was prepared as the sample with disease and the UHR-OCT imaging of the disease part was demonstrated. The increment of signal intensity by pleural thickening was observed. The accumulation of exudative fluid in alveoli was also observed for two samples. By the comparison with normal lung images, we can obviously show the difference in the ALI/ARDS models. Since the lung consists of alveolar surrounded by capillary vessels, the effect of red-blood cells (RBC) is considered to be important. In this work, ex-vivo UHR-OCT imaging of RBC was demonstrated. Each RBC was able to be observed individually using UHR-OCT. The effect of RBC was estimated with the rat lung perfused with PBS.

  10. Gamma rays from pulsar wind shock acceleration

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.

    1990-01-01

    A shock forming in the wind of relativistic electron-positron pairs from a pulsar, as a result of confinement by surrounding material, could convert part of the pulsar spin-down luminosity to high energy particles through first order Fermi acceleration. High energy protons could be produced by this mechanism both in supernova remnants and in binary systems containing pulsars. The pion-decay gamma-rays resulting from interaction of accelerated protons with surrounding target material in such sources might be observable above 70 MeV with EGRET (Energetic Gamma-Ray Experimental Telescope) and above 100 GeV with ground-based detectors. Acceleration of protons and expected gamma-ray fluxes from SN1987A, Cyg X-3 type sources and binary pulsars are discussed.

  11. Solar gamma rays and neutron observations

    NASA Technical Reports Server (NTRS)

    Chupp, E. L.; Forrest, D. J.; Suri, A. N.

    1972-01-01

    The present status of knowledge concerning the impulsive and the continuous emission of solar gamma rays and neutrons is reviewed in the light of the recent solar activity in early August 1972. The gamma ray spectrometer on OSO-7 has observed the sun continuously for most of the activity period except for occultation by the earth. In association with the 2B flare on 4 August 1972 and the 3B flare on 7 August 1972, the monitor provides evidence for solar gamma ray line emission in the energy range from 300 keV to 10 MeV. A summary of all the results available from preliminary analysis of the data will be given. Significant improvements in future experiments can be made with more sensitive instruments and more extensive time coverage of the sun.

  12. Mars Neutron/Gamma-ray Data Clustering

    NASA Astrophysics Data System (ADS)

    Campbell, Carl

    2010-02-01

    Neutron detectors on spacecraft at Mars and the Moon were designed to look for signs of water; at Mars a gamma-ray spectrometer was used to measure elemental abundances but no such instrument was added to the current lunar probe. The goal of this research is to determine if there are correlations between neutron and gamma-ray data at Mars so as to be able to measure elemental abundances at the Moon. To achieve this goal I am using a clustering algorithm to group similar data between neutron and gamma-ray sets. So far for N clusters, usually chosen here to be between five and eight, the results have excellent repeatability between runs and shapes recognizable with the mars albedo map. )

  13. Ground-Based Gamma Ray Astronomy

    NASA Astrophysics Data System (ADS)

    Holder, Jamie

    2014-10-01

    This paper is the write-up of a rapporteur talk given by the author at the 33rd International Cosmic Ray Conference in Rio de Janeiro, Brazil, in 2013. It attempts to summarize results and developments in ground-based gamma-ray observations and instrumentation from among the ˜300 submissions to the gamma-ray sessions of the meeting. Satellite observations and theoretical developments were covered by a companion rapporteur (Stawarz, L., 33rd ICRC, Rio de Janeiro, Brazil, Rapporteur talk: Space-based Gamma-Ray Astronomy, 2013). Any review of this nature is unavoidably subjective and incomplete. Nevertheless, the article should provide a useful status report for those seeking an overview of this exciting and fast-moving field.

  14. Distance and spectrum of the Apollo gamma-ray burst

    SciTech Connect

    Gilman, D.; Metzger, A.E.; Parker, R.H.; Evans, L.G.; Trombka, J.I.

    1980-03-15

    The ..gamma..-ray spectrometer on Apollo 16 obtained spectral information with good energy resolution from more than 2500 burst photons in the energy range 0.06--5.16 MeV. The spectrum from 2 keV to 2 MeV, observed at X-ray energies by the Apollo X-ray spectrometer, is fitted by a thermal bremsstrahlung spectrum with kT=500 keV. The success of the fit implies that the source is optically thin, and it follows that it must be closer than 50 pc. Absence of spectral variability suggests that the burst results from isothermal changes in emission measure.

  15. Quasielastic gamma-ray scattering from polydimethylsiloxane in benzene solutions

    SciTech Connect

    Hammouda, B.; Schupp, G.; Maglic, S. (Research Reactor, University of Missouri-Columbia, Columbia, MO (USA) Department of Physics, University of Missouri-Columbia, Columbia, MO (USA))

    1990-10-15

    Quasielastic gamma-ray scattering of 46.5-keV Moessbauer photons by polydimethylsiloxane has been studied at room temperature as a function of dilution in benzene. The high energy resolution of this novel technique allowed the separation of the scattering signal into a narrow component associated with stiff motions along the polymer chain backbone and a quasielastic component associated with softer side group motions. The narrow component disappears upon dilution in benzene while the intensity of the quasielastic component grows proportionately. This result is interpreted as a softening of the backbone normal modes upon dilution.

  16. Evidence for a Galactic gamma ray halo

    E-print Network

    D. D. Dixon; D. H. Hartmann; E. D. Kolaczyk; J. Samimi; R. Diehl; G. Kanbach; H. Mayer-Hasselwander; A. W. Strong

    1998-08-19

    We present quantitative statistical evidence for a $\\gamma$-ray emission halo surrounding the Galaxy. Maps of the emission are derived. EGRET data were analyzed in a wavelet-based non-parametric hypothesis testing framework, using a model of expected diffuse (Galactic + isotropic) emission as a null hypothesis. The results show a statistically significant large scale halo surrounding the center of the Milky Way as seen from Earth. The halo flux at high latitudes is somewhat smaller than the isotropic gamma-ray flux at the same energy, though of the same order (O(10^(-7)--10^(-6)) ph/cm^2/s/sr above 1 GeV).

  17. Gamma-ray Bursts: The Prompt Emission

    NASA Technical Reports Server (NTRS)

    Fishman, Jerry

    2005-01-01

    Gamma-ray bursts are the largest explosions in the Universe. The radiation is thought to come from a hypernova initiated from the collapse of a massive star or perhaps the merger of two compact stars such s neutron stars and/or black holes. Most of the observed energy is radiated as gamma rays, usually lasting from a fraction of a second to several hundred seconds. The energy generation process is usually referred to as the "central engine". Observed properties of this prompt emission, including spectra, time profiles and durations will be discussed. The history of these observations and future GRB spacecraft will also be described.

  18. Gamma Ray Bursts in the HAWC Era

    E-print Network

    Mészáros, Peter; Murase, Kohta; Fox, Derek; Gao, He; Senno, Nicholas

    2015-01-01

    Gamma-Ray Bursts are the most energetic explosions in the Universe, and are among the most promising for detecting multiple non-electromagnetic signals, including cosmic rays, high energy neutrinos and gravitational waves. The multi-GeV to TeV gamma-ray range of GRB could have significant contributions from hadronic interactions, mixed with more conventional leptonic contributions. This energy range is important for probing the source physics, including overall energetics, the shock parameters and the Lorentz factor. We discuss some of the latest observational and theoretical developments in the field.

  19. Gamma-Ray Burst observations with Fermi

    E-print Network

    Bissaldi, Elisabetta; Omodei, Nicola; Vianello, Giacomo; von Kienlin, Andreas

    2015-01-01

    After seven years of science operation, the Fermi mission has brought great advances in the study of Gamma-ray Bursts (GRBs). Over 1600 GRBs have been detected by the Gamma-ray Burst Monitor, and more than 100 of these are also detected by the Large Area Telescope above 30 MeV. We will give an overview of these observations, presenting the common properties in the GRB temporal and spectral behavior at high energies. We will also highlight the unique characteristics of some individual bursts. The main physical implications of these results will be discussed, along with open questions regarding GRB modeling in their prompt and temporally-extended emission phases.

  20. Status of the Milagro Gamma Ray Observatory

    E-print Network

    R. Atkins; W. Benbow; D. Berley; M. -L. Chen; D. G. Coyne; R. S. Delay; B. L. Dingus; D. E. Dorfan; R. W. Ellsworth; D. Evans; A. Falcone; L. Fleysher; R. Fleysher; G. Gisler; J. A. Goodman; T. J. Haines; C. M. Hoffman; S. Hugenberger; L. A. Kelley; I. Leonor; J. Macri; M. McConnell; J. F. McCullough; J. E. McEnery; R. S. Miller; A. I. Mincer; M. F. Morales; P. Nemethy; J. M. Ryan; M. Schneider; B. Shen; A. Shoup; G. Sinnis; A. J. Smith; G. W. Sullivan; T. N. Thompson; O. T. Tumer; K. Wang; M. O. Wascko; S. Westerhoff; D. A. Williams; T. Yang; G. B. Yodh

    1999-06-24

    The Milagro Gamma Ray Observatory is the world's first large-area water Cherenkov detector capable of continuously monitoring the sky at TeV energies. Located in northern New Mexico, Milagro will perform an all sky survey of the Northern Hemisphere at energies between ~250 GeV and 50 TeV. With a high duty cycle, large detector area (~5000 square meters), and a wide field-of-view (~1 sr), Milagro is uniquely capable of searching for transient and DC sources of high-energy gamma-ray emission. Milagro has been operating since February, 1999. The current status of the Milagro Observatory and initial results will be discussed.

  1. Statistics of cosmological gamma-ray bursts

    NASA Technical Reports Server (NTRS)

    Dermer, Charles D.

    1992-01-01

    A phenomenological model of gamma-ray burst spectra is used to calculate the statistics of gamma-ray bursts originating at cosmological distances. A model of bursters with no source evolution in a q sub 0 = 1/2 Friedmann cosmology is in accord with recent observations of the differential V/Vmax distribution. The data are best fit with an average peak-burst luminosity of (4 +/- 2) x 10 exp 51 ergs/s and a present-day source emissivity of 940 +/- 440 bursts/(10 exp 10 yr) cu Mpc. A spectral test of the cosmological hypothesis is proposed.

  2. Gamma-ray Burst Skymap Website

    NSDL National Science Digital Library

    2012-12-06

    The Gamma-ray Burst Skymap website automatically updates for each gamma-ray burst as it occurs, whether detected by Swift or other orbiting satellites. For each burst, the location on the sky, star map, constellation and detecting mission are generated automatically. It is then quickly updated by hand to include a written description of the burst properties and scientific significance, as observations continue. Note: In order to view the content of the website, users need to download and install Silverlight on their computers.

  3. Status of the Transient Gamma-Ray Spectrometer

    NASA Astrophysics Data System (ADS)

    Seifert, H.; Teegarden, B. J.; Palmer, D.; Gehrels, N.; Cline, T. L.; Ramaty, R.; Owens, A.; Hurley, K.; Pehl, R.; Madden, N.

    1995-09-01

    The Transient Gamma-Ray Spectrometer (TGRS) was launched aboard the GGS/WIND spacecraft on November 1, 1994. After several deep space orbits (˜2 yrs) WIND will eventually be injected into a halo orbit around the Sun-EarthL 1 point. TGRS consists of a 215 cm3 high purityn-type Ge crystal which is kept at cryogenic temperatures by a passive radiative cooler. The energy range covered by the instrument is ˜25 8000 keV with an energy resolution of ˜2 3 keV. The primary task of TGRS is to perform high resolution spectroscopy of gamma-ray bursts and solar flares. Additional objectives are the study of transient x-ray pulsars and, using an on-board passive occulter, the long-term monitoring of sources such as the Crab and the Galactic Center. Since launch, TGRS has been performing exceedingly well, and all the important experiment parameters such as background levels, gain, and resolution have proven to be very stable. To date, TGRS has detected 27 GRBs and three solar flares. Preliminary analysis of our data also indicates that TGRS is indeed sensitive to sources such as the Crab and the Galactic Center.

  4. EGRET Gamma-Ray Blazars: Luminosity Function and Contribution to the Extragalactic Gamma-Ray Background

    E-print Network

    R. Mukherjee; J. Chiang

    1999-01-30

    We describe the properties of the blazars detected by EGRET and summarize the results on the calculations of the evolution and luminosity function of these sources. Of the large number of possible origins of extragalactic diffuse gamma-ray emission, it has been postulated that active galaxies might be one of the most likely candidates. However, some of our recent analyses indicate that only 25 percent of the diffuse extragalactic emission measured by SAS-2 and EGRET can be attributed to unresolved gamma-ray blazars. Therefore, other sources of diffuse extragalactic gamma-ray emission must exist. We present a summary of these results in this article.

  5. Real time method and computer system for identifying radioactive materials from HPGe gamma-ray spectroscopy

    DOEpatents

    Rowland, Mark S. (Alamo, CA); Howard, Douglas E. (Livermore, CA); Wong, James L. (Dublin, CA); Jessup, James L. (Tracy, CA); Bianchini, Greg M. (Livermore, CA); Miller, Wayne O. (Livermore, CA)

    2007-10-23

    A real-time method and computer system for identifying radioactive materials which collects gamma count rates from a HPGe gamma-radiation detector to produce a high-resolution gamma-ray energy spectrum. A library of nuclear material definitions ("library definitions") is provided, with each uniquely associated with a nuclide or isotope material and each comprising at least one logic condition associated with a spectral parameter of a gamma-ray energy spectrum. The method determines whether the spectral parameters of said high-resolution gamma-ray energy spectrum satisfy all the logic conditions of any one of the library definitions, and subsequently uniquely identifies the material type as that nuclide or isotope material associated with the satisfied library definition. The method is iteratively repeated to update the spectrum and identification in real time.

  6. Ultra-High Resolution Spectroscopic Remote Sensing: A Microscope on Planetary Atmospheres

    NASA Technical Reports Server (NTRS)

    Kostiuk, Theodor

    2010-01-01

    Remote sensing of planetary atmospheres is not complete without studies of all levels of the atmosphere, including the dense cloudy- and haze filled troposphere, relatively clear and important stratosphere and the upper atmosphere, which are the first levels to experience the effects of solar radiation. High-resolution spectroscopy can provide valuable information on these regions of the atmosphere. Ultra-high spectral resolution studies can directly measure atmospheric winds, composition, temperature and non-thermal phenomena, which describe the physics and chemistry of the atmosphere. Spectroscopy in the middle to long infrared wavelengths can also probe levels where dust of haze limit measurements at shorter wavelength or can provide ambiguous results on atmospheric species abundances or winds. A spectroscopic technique in the middle infrared wavelengths analogous to a radio receiver. infrared heterodyne spectroscopy [1], will be describe and used to illustrate the detailed study of atmospheric phenomena not readily possible with other methods. The heterodyne spectral resolution with resolving power greater than 1,000.000 measures the true line shapes of emission and absorption lines in planetary atmospheres. The information on the region of line formation is contained in the line shapes. The absolute frequency of the lines can be measured to I part in 100 ,000,000 and can be used to accurately measure the Doppler frequency shift of the lines, directly measuring the line-of-sight velocity of the gas to --Im/s precision (winds). The technical and analytical methods developed and used to measure and analyze infrared heterodyne measurements will be described. Examples of studies on Titan, Venus, Mars, Earth, and Jupiter will be presented. 'These include atmospheric dynamics on slowly rotating bodies (Titan [2] and Venus [3] and temperature, composition and chemistry on Mars 141, Venus and Earth. The discovery and studies of unique atmospheric phenomena will also be described, such as non-thermal and lasing phenomena on Mars and Venus, mid-infrared aurora on Jupiter [5], and results of small body impacts on Jupiter [6]. The heterodyne technique can also be applied for detailed study of the Earth's stratosphere and mesosphere by measuring trace constituent abundances and temporal and spatial variability as well as winds, which provide information of transport. All ground-based measurements will be described as complementary and supporting studies for on-going and future space missions [7] (Mars Express, Venus Express, Cassini Huygens, JUNO, ExoMars Trace Gas Orbiter, and the Europa Jupiter System Mission, an Earth Science Venture Class missions), Proposed instrument and technology development for a space flight infrared heterodyne spectrometer will be described.

  7. EXPLORING THE NATURE OF THE GALACTIC CENTER {gamma}-RAY SOURCE WITH THE CHERENKOV TELESCOPE ARRAY

    SciTech Connect

    Linden, Tim; Profumo, Stefano [Department of Physics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)

    2012-11-20

    Observations from multiple {gamma}-ray telescopes have uncovered a high-energy {gamma}-ray source spatially coincident with the Galactic center. Recently, a compelling model for the broadband {gamma}-ray emission has been formulated, which posits that high-energy protons emanating from Sgr A* could produce {gamma}-rays through {pi}{sup 0} decays resulting from inelastic collisions with the traversed interstellar gas in the region. Models of the gas distribution in the Galactic center region imply that the resulting {gamma}-ray morphology would be observed as a point source with all current telescopes, but that the upcoming Cherenkov Telescope Array (CTA) may be able to detect an extended emission profile with an unmistakable morphology. Here, we critically evaluate this claim, employing a three-dimensional gas distribution model and a detailed Monte Carlo simulation, and using the anticipated effective area and angular resolution of CTA. We find that the impressive angular resolution of CTA will be key to test hadronic emission models conclusively against, for example, point source or dark matter annihilation scenarios. We comment on the relevance of this result for searches for dark matter annihilation in the Galactic center region.

  8. Gamma Ray Astronomy ALDO MORSELLI

    E-print Network

    Morselli, Aldo

    of view is enhanced now, in respect to EGRET, with the use of silicon detectors, that allows a further the angular resolution, b) the possibility to use the silicon detectors themselves for the trigger from a refined study of the GILDA project (A.Morselli 1994),(G.Barbiellini et al. 1995),(A.Morselli et

  9. Search for. gamma. rays from the supernova 1987A at energies greater than 100 TeV

    SciTech Connect

    Bond, I.A.; Budding, E.; Conway, M.J.; Fenton, K.B.; Fujii, H.; Fujii, Z.; Hasegawa, H.; Hayashida, N.; Honda, M.; Hotta, N.

    1988-03-21

    We searched for ultrahigh-energy ..gamma.. rays emitted by the supernova 1987A with a new cosmic-ray facility installed at the Black Birch Range in New Zealand. The observations from 13 October to 3 December 1987 suggest no clear clustering of events around the direction of the supernova. We conclude that an upper limit on the flux ..gamma.. rays of energies greater than 100 TeV is 1.1 x 10/sup -12/ cm/sup -2/ s/sup -1/ (95% confidence limit) for a differential spectral index ..cap alpha.. = 2.0 and source distance d = 50 kpc. This value gives an upper bound on the ..gamma..-ray luminosity of the supernova of 5.5 x 10/sup 38/ erg s/sup -1/ for 10/sup 14/--10/sup 17/ eV

  10. The Characterization of Dissolved Organic Nitrogen in Wetlands by Ultrahigh Resolution Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Podgorski, D. C.; Osborne, D.; Cooper, W. T.

    2009-12-01

    Dissolved Organic Nitrogen (DON) in agricultural runoff water can prove to be troublesome to wetland ecosystems. Therefore, Water Quality Treatment Areas (WQTAs) have been developed to reduce total nitrogen (TN) concentrations, specifically, organic nitrogen. At present the only parameter available for judging the effectiveness of WQTAs is total DON. However, total DON does not account for the biogeochemistry of individual organic nitrogen compounds. There are no doubt many organic-N species that are refractory and present no threat to receiving waters, but they are nevertheless counted as TN. Unfortunately, there is no general method for determining which DON molecules are biodegradable and which are refractory. The purpose of this research is to provide an analytical method that will drive the design of WTQAs that more effectively reduce organic nitrogen concentrations. We coupled Atmospheric Pressure Photo-ionization (APPI) with Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) to specifically focus on the characterization of DON compounds. Atmospheric pressure photoionization (APPI) represents an attractive alternative to the more conventional electrospray ionization (ESI) method. APPI has the ability to ionize both polar and nonpolar compounds, many of which are unobservable by ESI. APPI coupled with the ultrahigh resolution and mass accuracy provided by FT-ICR MS allowed us to unambiguously assign molecular formulas to the specific DON compounds. Therefore, we were able to determine the degree of oxidation and presence of other hetero-atoms, such as sulfur, in these DON compounds. Comparative analysis of the influent and effluent waters from the WTQAs provided valuable data about what types of molecules are successfully removed during the treatment process. This molecular level information was previously unavailable with other analytical techniques, and it may be used to design more effective WQTAs in the future.

  11. Molecular composition of boreal forest aerosol from Hyytiälä, Finland, using ultrahigh resolution mass spectrometry.

    PubMed

    Kourtchev, Ivan; Fuller, Stephen; Aalto, Juho; Ruuskanen, Taina M; McLeod, Matthew W; Maenhaut, Willy; Jones, Rod; Kulmala, Markku; Kalberer, Markus

    2013-05-01

    Organic compounds are important constituents of fine particulate matter (PM) in the troposphere. In this study, we applied direct infusion nanoelectrospray (nanoESI) ultrahigh resolution mass spectrometry (UHR-MS) and liquid chromatography LC/ESI-UHR-MS for the analysis of the organic fraction of PM1 aerosol samples collected over a two week period at a boreal forest site (Hyytiälä), southern Finland. Elemental formulas (460-730 in total) were identified with nanoESI-UHR-MS in the negative ionization mode and attributed to organic compounds with a molecular weight below 400. Kendrick Mass Defect and Van Krevelen approaches were used to identify compound classes and mass distributions of the detected species. The molecular composition of the aerosols strongly varied between samples with different air mass histories. An increased number of nitrogen, sulfur, and highly oxygenated organic compounds was observed during the days associated with continental air masses. However, the samples with Atlantic air mass history were marked by a presence of homologous series of unsaturated and saturated C12-C20 fatty acids suggesting their marine origin. To our knowledge, we show for the first time that the highly detailed chemical composition obtained from UHR-MS analyses can be clearly linked to meteorological parameters and trace gases concentrations that are relevant to atmospheric oxidation processes. The additional LC/ESI-UHR-MS analysis revealed 29 species, which were mainly attributed to oxidation products of biogenic volatile compounds BVOCs (i.e., ?,?-pinene, ?3-carene, limonene, and isoprene) supporting the results from the direct infusion analysis. PMID:23469832

  12. Gamma Ray Burst Detectives (Elementary School)

    NSDL National Science Digital Library

    2010-04-28

    This interactive resource invites students to join NASA to find the source of gamma ray bursts, the single biggest explosions in the Universe since the Big Bang. The web site features an animation, information on three possible star sources, and a check yes or no for each star with feedback.

  13. Gamma Ray Burst Detectives (High School)

    NSDL National Science Digital Library

    2011-04-26

    >This WPSU interactive resource invites students to join NASA to find the source of gamma ray bursts, the single biggest explosions in the Universe since the Big Bang by exploring three aspects of the death of stars: energy, duration, and variability.

  14. Observations of Gamma-Ray Bursts

    NASA Technical Reports Server (NTRS)

    Meegan, C. A.; Six, N. Frank (Technical Monitor)

    2001-01-01

    Observations of Gamma-ray bursts (GRBs) remain one of the most baffling phenomena in astrophysics. This talk will summarize the observations of GRBs with particular emphasis on those that present the greatest difficulty for theoretical interpretation. These include the short and highly variable temporal structure, the hard non-thermal spectra, and the enormous total energy output.

  15. Gamma-Ray Bursts: progress, problems & prospects

    Microsoft Academic Search

    Bing Zhang; Peter Mészáros

    2004-01-01

    The cosmological gamma-ray burst (GRB) phenomenon is reviewed. The broad observational facts and empirical phenomenological relations of the GRB prompt emission and afterglow are outlined. A well-tested, successful fireball shock model is introduced in a pedagogical manner. Several important uncertainties in the current understanding of the phenomenon are reviewed, and prospects of how future experiments and extensive observational and theoretical

  16. Physics issues of gamma ray burst emissions

    NASA Technical Reports Server (NTRS)

    Liang, Edison

    1987-01-01

    The critical physics issues in the interpretation of gamma-ray-burst spectra are reviewed. An attempt is made to define the emission-region parameter space satisfying the maximum number of observational and theoretical constraints. Also discussed are the physical mechanisms responsible for the bursts that are most consistent with the above parameter space.

  17. Fitting and Updating Gamma-Ray Energies

    SciTech Connect

    Guimaraes-Filho, Zwinglio O.; Helene, Octaviano; Vanin, Vito R.; Maidana, Nora L. [Laboratorio do Acelerador Linear, Instituto de Fisica, Universidade de Sao Paulo, Travessa R 187, Cidade Universitaria, CEP: 05508-900 Sao Paulo, SP (Brazil)

    2005-05-24

    The procedure for obtaining the updated version of the recommended gamma-ray transition energies for detector calibration is described. The energies were recalculated to account for the 2002 CODATA Recommended Values of Fundamental Physical Constants. The re-evaluation methodology considered the statistical correlations and used the appropriate covariance matrices in all steps.

  18. Fitting and Updating Gamma-Ray Energies

    NASA Astrophysics Data System (ADS)

    Guimarães-Filho, Zwinglio O.; Helene, Octaviano; Vanin, Vito R.; Maidana, Nora L.

    2005-05-01

    The procedure for obtaining the updated version of the recommended gamma-ray transition energies for detector calibration is described. The energies were recalculated to account for the 2002 CODATA Recommended Values of Fundamental Physical Constants. The re-evaluation methodology considered the statistical correlations and used the appropriate covariance matrices in all steps.

  19. Cascade model of gamma-ray bursts

    NASA Technical Reports Server (NTRS)

    Sturrock, P. A.; Harding, A. K.; Daugherty, J. K.

    1989-01-01

    If, in a neutron star magnetosphere, an electron is accelerated to an energy of 10 to the 11th or 12th power eV by an electric field parallel to the magnetic field, motion of the electron along the curved field line leads to a cascade of gamma rays and electron-positron pairs. This process is believed to occur in radio pulsars and gamma ray burst sources. Results are presented from numerical simulations of the radiation and photon annihilation pair production processes, using a computer code previously developed for the study of radio pulsars. A range of values of initial energy of a primary electron was considered along with initial injection position, and magnetic dipole moment of the neutron star. The resulting spectra was found to exhibit complex forms that are typically power law over a substantial range of photon energy, and typically include a dip in the spectrum near the electron gyro-frequency at the injection point. The results of a number of models are compared with data for the 5 Mar., 1979 gamma ray burst. A good fit was found to the gamma ray part of the spectrum, including the equivalent width of the annihilation line.

  20. Gamma ray production in interstellar space

    NASA Technical Reports Server (NTRS)

    Badhwar, G. D.; Stephens, S. A.

    1978-01-01

    A simple representation of the observed invariant cross section for the production of neutral pions in pp collisions has been obtained. This representation is used to calculate the differential and integral production spectra of gamma rays in galactic space from the interactions of cosmic-ray nuclei with interstellar gas. These spectra are compared with those from existing calculations.

  1. The Supernova Gamma-Ray Burst Connection

    Microsoft Academic Search

    Stan Woosley; A. Heger

    2006-01-01

    The chief distinction between ordinary supernovae and long-soft gamma-ray bursts (GRBs) is the degree of differential rotation in the inner several solar masses when a massive star dies, and GRBs are rare mainly because of the difficulty achieving the necessary high rotation rate. Models that do provide the necessary angular momentum are discussed, with emphasis on a new single star

  2. Neutron production in terrestrial gamma ray flashes

    Microsoft Academic Search

    B. E. Carlson; N. G. Lehtinen

    2010-01-01

    Terrestrial gamma ray flashes (TGFs) are brief bursts of photons with energies up to 20 MeV typically observed in association with lightning. Such energetic photons may undergo photonuclear reactions with nontrivial cross section in the vicinity of the giant dipole resonance. Pulses of neutrons have been observed experimentally in coincidence with lightning, suggesting such reactions are observable. We present simulations

  3. Study of gamma-ray strength functions

    SciTech Connect

    Gardner, D.G.; Gardner, M.A.; Dietrich, F.S.

    1980-08-07

    The use of gamma-ray strength function systematics to calculate neutron capture cross sections and capture gamma-ray spectra is discussed. The ratio of the average capture width, GAMMA/sub ..gamma../-bar, to the average level spacing, D/sub obs/, both at the neutron separation energy, can be derived from such systematics with much less uncertainty than from separate systematics for values of GAMMA/sub ..gamma../-bar and D/sub obs/. In particular, the E1 gamma-ray strength function is defined in terms of the giant dipole resonance (GDR). The GDR line shape is modeled with the usual Lorentzian function and also with a new energy-dependent, Breit-Wigner (EDBW) function. This latter form is further parameterized in terms of two overlapping resonances, even for nuclei where photonuclear measurements do not resolve two peaks. In the mass ranges studied, such modeling is successful for all nuclei away from the N = 50 closed neutron shell. Near the N = 50 shell, a one-peak EDBW appears to be more appropriate. Examples of calculated neutron capture excitation functions and capture gamma-ray spectra using the EDBW form are given for target nuclei in the mass-90 region and also in the Ta-Au mass region. 20 figures.

  4. Cascade model of gamma-ray bursts

    NASA Astrophysics Data System (ADS)

    Sturrock, P. A.; Harding, A. K.; Daugherty, J. K.

    1989-11-01

    If, in a neutron star magnetosphere, an electron is accelerated to an energy of 10 to the 11th or 12th power eV by an electric field parallel to the magnetic field, motion of the electron along the curved field line leads to a cascade of gamma rays and electron-positron pairs. This process is believed to occur in radio pulsars and gamma ray burst sources. Results are presented from numerical simulations of the radiation and photon annihilation pair production processes, using a computer code previously developed for the study of radio pulsars. A range of values of initial energy of a primary electron was considered along with initial injection position, and magnetic dipole moment of the neutron star. The resulting spectra was found to exhibit complex forms that are typically power law over a substantial range of photon energy, and typically include a dip in the spectrum near the electron gyro-frequency at the injection point. The results of a number of models are compared with data for the 5 Mar., 1979 gamma ray burst. A good fit was found to the gamma ray part of the spectrum, including the equivalent width of the annihilation line.

  5. Gamma-Ray Telescope and Uncertainty Principle

    ERIC Educational Resources Information Center

    Shivalingaswamy, T.; Kagali, B. A.

    2012-01-01

    Heisenberg's Uncertainty Principle is one of the important basic principles of quantum mechanics. In most of the books on quantum mechanics, this uncertainty principle is generally illustrated with the help of a gamma ray microscope, wherein neither the image formation criterion nor the lens properties are taken into account. Thus a better…

  6. Gamma Ray Telescope Senses High-Energy Radiation

    NSDL National Science Digital Library

    WNET

    2011-11-02

    This video from NASA describes the GLAST satellite, which is equipped with a gamma-ray telescope, and shares some background about the kinds of extreme universal phenomena indicated by the presence of gamma rays.

  7. Gamma-ray induced Doppler broadening and the determination of lifetimes of excited nuclear states

    SciTech Connect

    Boerner, H.G.; Jolie, J.; Robinson, S.J. (Institut Laue-Langevin, 38 - Grenoble (France)); Kessler, E.G.; Dewey, S.M.; Greene, G.; Deslattes, R. (National Inst. of Standards and Technology, Gaithersburg, MD (USA)); Ulbig, S.; Lieb, K.P. (Goettingen Univ. (Germany, F.R.)); Casten, R.F. (Brookhaven National Lab., Upton, NY (USA)); Krusche, B. (Giessen Univ. (Germany, F.R.)); Cizewski, J.A. (Rutgers--the

    1990-01-01

    Measurements of lifetimes of excited states in nuclei yield crucial information for sensitive tests of nuclear models. Here a novel method will be discussed which involves the GRID (Gamma Ray Induced Doppler broadening) technique, in which Doppler broadening is observed in a transition from a nucleus recoiling from the emission of a previous gamma ray. As the recoil energy is extremely small, ultra-high energy resolving power has to be used. To date all such experiments have been carried out at ILL using the GAMS4 double flat crystal spectrometer which is operated in a NIST-ILL collaboration. The method can be used for all lifetimes below a few picoseconds. The wide range of applicability, together with the very exhaustive set of data often obtained, is an advantage with respect to many other methods. The characteristic features of GRID will be discussed using some selected examples. 21 refs., 8 figs.

  8. Preliminary observations of the SELENE Gamma Ray Spectrometer

    NASA Astrophysics Data System (ADS)

    Forni, O.; Diez, B.; Gasnault, O.; Munoz, B.; D'Uston, C.; Reedy, R. C.; Hasebe, N.

    2008-09-01

    Introduction We analyze the spectra measured by the Gamma Ray Spectrometer (GRS) on board the SELENE satellite [1]. SELENE was inserted in lunar orbit on 4 Oct. 2007. After passing through a health check and a function check, the GRS was shifted to nominal observation on 21 Dec. 2007. The spectra consist in various lines of interest (O, Mg, Al, Si, Ti, Ca, Fe, K, Th, U, and possibly H) superposed on a continuum. The energies of the gamma rays identify the nuclides responsible for the gamma ray emission and their intensities relate to their abundance. Data collected through 17 Feb. 2008 are studied here, corresponding to an accumulation time (Fig. 1) sufficiently good to allow preliminary mapping. Analysis of the global gamma ray spectrum In order to obtain spectra with counting statistics sufficient for peak analysis, we accumulate all observations. The identification of lines is performed on this global lunar spectrum (Fig 2). Fit of individual lines The gamma ray lines that arise from decay of longlived radioactive species are among the easiest to analyze. So far the abundance of two species is studied thanks to such lines: potassium (1461 keV) and thorium (2614 keV). Secondary neutrons from cosmic ray interactions also produce gamma ray when reacting with the planetary material, according to scattering or absorption reactions. However these lines need substantial corrections before an interpretation in terms of abundance can be performed. Lines have been examined with different techniques. The simplest method consists in summing the spectra in a window containing the line of interest. The continuum is adjusted with a polynomial and removed. Such a method was used for the gamma ray spectra collected by Lunar Prospector [2]. This method is especially robust for isolated lines, such as those of K and Th mentioned above, or with very low statistics. The second method consists in fitting the lines by summing a quadratic continuum with Gaussian lines and exponential tails. We presently fit the spectra thanks to a program developed at CESR: Aquarius. Afterwards the areas associated with the parameters of these ideal lines are calculated. This method is welladapted for interfering lines, such as U, Al, and H around 2210 keV, but it requires good statistics. These two methods were used to analyze the Mars Odyssey gamma-ray spectra [3]. Prettyman et al. [4] applied a third method where theoretical spectra are simulated and matched against the observations. Below we propose a fourth approach based on statistical analyzes. Mapping of elemental abundances Data returned by the spacecraft are time-tagged records acquired with a resolution of 17 seconds. The angular distance covered by the spacecraft during this interval corresponds to about 1° at the surface. However the true resolution of the instrument is lower because gamma rays come from all directions onto the spacecraft. The resolution is therefore set by the field of view of the instrument, which depends on the spacecraft altitude and the geometry of the instrument. The full width half maximum of the instrumental response has been estimated to be 130 km at 1 MeV by the SELENE GRS team. We have tiled the data in agreement with the better resolution we could obtain depending on the intensity of a given line. The thorium line at 2614 keV was thus mapped at a resolution of 3° with the first method described above (sum over 2550-2640 keV). Then this map was smoothed with a 5° filter (152 km radius) to approximate the response function of the instrument. Finally the counting rate was converted into abundance (Fig. 3), using the compositions at landing sites and in the highlands as did Gillis et al. [5]. Statistical analysis We have also analysed the data with various multivariate techniques, one of them being the Independent Component Analysis (ICA) [6, 7]. ICA defines a generative model for the observed multivariate data, which is typically given as a large database of samples. In the model, the data variables are assumed to be linear mixtures of some unknown latent variables,

  9. Gamma ray lines from the Galactic Center and gamma ray transients

    NASA Technical Reports Server (NTRS)

    Ramaty, R.; Leiter, D.; Lingenfelter, R. E.

    1981-01-01

    The observations and interpretations of cosmic (nonsolar) gamma ray lines are discussed. The most prominent of these lines is the e(+)e(-) annihilation line which was observed from the Galactic Center and from several gamma ray transients. At the Galactic Center the e(+)e(-) pairs are probably produced by an accreting massive black hole (solar mass of approximately one million) and annihilate within the central light year to produce a line at almost exactly 0.511 MeV. In gamma ray transients the annihilation line is redshifted by factors consistent with neutron star surface redshifts. Other observed transient gamma ray lines appear to be due to cyclotron absorption in the strong magnetic fields of neutron stars, and nuclear deexcitations and neutron capture, which could also occur on or around these objects.

  10. Ultrahigh-resolution low-voltage SEM reveals ultrastructure of the glucan network formation from fission yeast protoplast.

    PubMed

    Osumi, M; Yamada, N; Yaguchi, H; Kobori, H; Nagatani, T; Sato, M

    1995-08-01

    The refined field emission SEM, S-900 LV which gives better resolution especially at low voltages below 5 kV was developed for ultrahigh resolution scanning electron microscopy. A visualization test at x 300,000 was made using a gold-evaporated magnetic tape, and the resolution was found to be about 1 nm at 2.5 kV. The ultrastructure of the cell wall, especially the reverting glucan network, from the protoplast of Schizosaccharomyces pombe was studied using this improved ultrahigh-resolution low-voltage SEM (UHR-LVSEM). The results with uncoated reverting protoplasts observed with this microscope revealed that the network was originally formed as secreted particles scattered on the protoplast surface and these were subsequently stretched to microfibrils about 2 nm thick. The microfibrils were twisted around each other and joined together so that they developed into 8-nm-thick fibrils, forming a ribbon-shaped network of glucans about 16-nm-thick which covered the entire protoplast surface. The UHR-LVSEM images of reverting protoplasts treated with glucanase confirmed that the particles scattered on the protoplast surface in the initial stage of regeneration were glucan in nature. PMID:8568444

  11. Retinal Structure of Birds of Prey Revealed by Ultra-High Resolution Spectral-Domain Optical Coherence Tomography

    PubMed Central

    Ruggeri, Marco; Major, James C.; McKeown, Craig; Knighton, Robert W.; Puliafito, Carmen A.

    2010-01-01

    Purpose. To reveal three-dimensional (3-D) information about the retinal structures of birds of prey in vivo. Methods. An ultra-high resolution spectral-domain optical coherence tomography (SD-OCT) system was built for in vivo imaging of retinas of birds of prey. The calibrated imaging depth and axial resolution of the system were 3.1 mm and 2.8 ?m (in tissue), respectively. 3-D segmentation was performed for calculation of the retinal nerve fiber layer (RNFL) map. Results. High-resolution OCT images were obtained of the retinas of four species of birds of prey: two diurnal hawks (Buteo platypterus and Buteo brachyurus) and two nocturnal owls (Bubo virginianus and Strix varia). These images showed the detailed retinal anatomy, including the retinal layers and the structure of the deep and shallow foveae. The calculated thickness map showed the RNFL distribution. Traumatic injury to one bird's retina was also successfully imaged. Conclusions. Ultra-high resolution SD-OCT provides unprecedented high-quality 2-D and 3-D in vivo visualization of the retinal structures of birds of prey. SD-OCT is a powerful imaging tool for vision research in birds of prey. PMID:20554605

  12. Report of the x ray and gamma ray sensors panel

    NASA Technical Reports Server (NTRS)

    Szymkowiak, Andrew; Collins, S.; Kurfess, J.; Mahoney, W.; Mccammon, D.; Pehl, R.; Ricker, G.

    1991-01-01

    Overall five major areas of technology are recommended for development in order to meet the science requirements of the Astrotech 21 mission set. These are: detectors for high resolution gamma ray spectroscopy, cryogenic detectors for improved x ray spectral and spatial resolution, advanced x ray charge coupled devices (CCDs) for higher energy resolution and larger format, extension to higher energies, liquid and solid position sensitive detectors for improving stopping power in the energy range 5 to 500 keV and 0.2 to 2 MeV. Development plans designed to achieve the desired capabilities on the time scales required by the technology freeze dates have been recommended in each of these areas.

  13. Report of the X ray and gamma ray sensors panel

    NASA Astrophysics Data System (ADS)

    Szymkowiak, Andrew; Collins, S.; Kurfess, J.; Mahoney, W.; McCammon, D.; Pehl, R.; Ricker, G.

    1991-08-01

    Overall five major areas of technology are recommended for development in order to meet the science requirements of the Astrotech 21 mission set. These are: detectors for high resolution gamma ray spectroscopy, cryogenic detectors for improved x ray spectral and spatial resolution, advanced x ray charge coupled devices (CCDs) for higher energy resolution and larger format, extension to higher energies, liquid and solid position sensitive detectors for improving stopping power in the energy range 5 to 500 keV and 0.2 to 2 MeV. Development plans designed to achieve the desired capabilities on the time scales required by the technology freeze dates have been recommended in each of these areas.

  14. Gamma ray bursts of black hole universe

    NASA Astrophysics Data System (ADS)

    Zhang, T. X.

    2015-07-01

    Slightly modifying the standard big bang theory, Zhang recently developed a new cosmological model called black hole universe, which has only a single postulate but is consistent with Mach's principle, governed by Einstein's general theory of relativity, and able to explain existing observations of the universe. In the previous studies, we have explained the origin, structure, evolution, expansion, cosmic microwave background radiation, quasar, and acceleration of black hole universe, which grew from a star-like black hole with several solar masses through a supermassive black hole with billions of solar masses to the present state with hundred billion-trillions of solar masses by accreting ambient matter and merging with other black holes. This study investigates gamma ray bursts of black hole universe and provides an alternative explanation for the energy and spectrum measurements of gamma ray bursts according to the black hole universe model. The results indicate that gamma ray bursts can be understood as emissions of dynamic star-like black holes. A black hole, when it accretes its star or merges with another black hole, becomes dynamic. A dynamic black hole has a broken event horizon and thus cannot hold the inside hot (or high-frequency) blackbody radiation, which flows or leaks out and produces a GRB. A star when it collapses into its core black hole produces a long GRB and releases the gravitational potential energy of the star as gamma rays. A black hole that merges with another black hole produces a short GRB and releases a part of their blackbody radiation as gamma rays. The amount of energy obtained from the emissions of dynamic star-like black holes are consistent with the measurements of energy from GRBs. The GRB energy spectra derived from this new emission mechanism are also consistent with the measurements.

  15. Fermi Gamma-Ray Imaging of a Radio Galaxy

    Microsoft Academic Search

    A. A. Abdo; M. Ackermann; M. Ajello; W. B. Atwood; L. Baldini; J. Ballet; G. Barbiellini; D. Bastieri; B. M. Baughman; K. Bechtol; R. Bellazzini; B. Berenji; R. D. Blandford; E. D. Bloom; E. Bonamente; A. W. Borgland; J. Bregeon; A. Brez; M. Brigida; P. Bruel; T. H. Burnett; S. Buson; G. A. Caliandro; R. A. Cameron; P. A. Caraveo; J. M. Casandjian; E. Cavazzuti; C. Cecchi; Ö. Çelik; A. Chekhtman; C. C. Cheung; J. Chiang; S. Ciprini; R. Claus; J. Cohen-Tanugi; S. Colafrancesco; L. R. Cominsky; J. Conrad; L. Costamante; S. Cutini; D. S. Davis; C. D. Dermer; A. de Angelis; F. de Palma; S. W. Digel; E. do Couto e Silva; P. S. Drell; R. Dubois; D. Dumora; C. Farnier; C. Favuzzi; S. J. Fegan; J. Finke; W. B. Focke; P. Fortin; Y. Fukazawa; S. Funk; P. Fusco; F. Gargano; D. Gasparrini; N. Gehrels; M. Georganopoulos; S. Germani; B. Giebels; N. Giglietto; F. Giordano; M. Giroletti; T. Glanzman; G. Godfrey; I. A. Grenier; J. E. Grove; L. Guillemot; S. Guiriec; Y. Hanabata; A. K. Harding; M. Hayashida; E. Hays; R. E. Hughes; M. S. Jackson; Jóhannesson G; S. Johnson; T. J. Johnson; W. N. Johnson; T. Kamae; H. Katagiri; J. Kataoka; N. Kawai; M. Kerr; J. Knödlseder; M. L. Kocian; M. Kuss; J. Lande; L. Latronico; M. Lemoine-Goumard; F. Loparco; B. Lott; M. N. Lovellette; P. Lubrano; G. M. Madejski; A. Makeev; M. N. Mazziotta; W. McConville; J. E. McEnery; C. Meurer; P. F. Michelson; W. Mitthumsiri; T. Mizuno; A. A. Moiseev; C. Monte; M. E. Monzani; A. Morselli; I. V. Moskalenko; S. Murgia; P. L. Nolan; J. P. Norris; E. Nuss; T. Ohsugi; N. Omodei; E. Orlando; J. F. Ormes; D. Paneque; D. Parent; V. Pelassa; M. Pesce-Rollins; F. Piron; T. A. Porter; S. Rainò; R. Rando; M. Razzano; S. Razzaque; A. Reimer; O. Reimer; T. Reposeur; S. Ritz; L. S. Rochester; A. Y. Rodriguez; R. W. Romani; M. Roth; F. Ryde; H. F.-W. Sadrozinski; R. Sambruna; D. Sanchez; A. Sander; P. M. Saz Parkinson; J. D. Scargle; C. Sgrò; J. Siskind; D. A. Smith; P. D. Smith; G. Spandre; P. Spinelli; J.-L. Starck; L. Stawarz; M. S. Strickman; D. J. Suson; H. Takahashi; T. Takahashi; T. Tanaka; J. B. Thayer; J. G. Thayer; D. J. Thompson; L. Tibaldo; D. F. Torres; G. Tosti; A. Tramacere; Y. Usher Uchiyama T. L; V. Vasileiou; N. Vilchez; V. Vitale; A. P. Waite; E. Wallace; P. Wang; B. L. Winer; K. S. Wood; T. Ylinen; M. Ziegler; M. J. Hardcastle; D. Kazanas

    2010-01-01

    The Fermi Gamma-ray Space Telescope has detected the gamma-ray glow emanating from the giant radio lobes of the radio galaxy Centaurus A. The resolved gamma-ray image shows the lobes clearly separated from the central active source. In contrast to all other active galaxies detected so far in high-energy gamma-rays, the lobe flux constitutes a considerable portion (greater than one-half) of

  16. Simultaneous optical/gamma-ray observations of GRBs

    NASA Technical Reports Server (NTRS)

    Greiner, J.; Wenzel, W.; Hudec, R.; Moskalenko, E. I.; Metlov, V.; Chernych, N. S.; Getman, V. S.; Ziener, Rainer; Birkle, K.; Bade, N.

    1994-01-01

    Details on the project to search for serendipitous time correlated optical photographic observations of Gamma Ray Bursters (GRB's) are presented. The ongoing photographic observations at nine observatories are used to look for plates which were exposed simultaneously with a gamma ray burst detected by the gamma ray instrument team (BATSE) and contain the burst position. The results for the first two years of the gamma ray instrument team operation are presented.

  17. Gamma ray constraints on the Galactic supernova rate

    NASA Technical Reports Server (NTRS)

    Hartmann, D.; The, L.-S.; Clayton, Donald D.; Leising, M.; Mathews, G.; Woosley, S. E.

    1991-01-01

    We perform Monte Carlo simulations of the expected gamma ray signatures of Galactic supernovae of all types to estimate the significance of the lack of a gamma ray signal due to supernovae occurring during the last millenium. Using recent estimates of the nuclear yields, we determine mean Galactic supernova rates consistent with the historic supernova record and the gamma ray limits. Another objective of these calculations of Galactic supernova histories is their application to surveys of diffuse Galactic gamma ray line emission.

  18. Gamma-Ray Background Variability in Mobile Detectors

    NASA Astrophysics Data System (ADS)

    Aucott, Timothy John

    Gamma-ray background radiation significantly reduces detection sensitivity when searching for radioactive sources in the field, such as in wide-area searches for homeland security applications. Mobile detector systems in particular must contend with a variable background that is not necessarily known or even measurable a priori. This work will present measurements of the spatial and temporal variability of the background, with the goal of merging gamma-ray detection, spectroscopy, and imaging with contextual information--a "nuclear street view" of the ubiquitous background radiation. The gamma-ray background originates from a variety of sources, both natural and anthropogenic. The dominant sources in the field are the primordial isotopes potassium-40, uranium-238, and thorium-232, as well as their decay daughters. In addition to the natural background, many artificially-created isotopes are used for industrial or medical purposes, and contamination from fission products can be found in many environments. Regardless of origin, these backgrounds will reduce detection sensitivity by adding both statistical as well as systematic uncertainty. In particular, large detector arrays will be limited by the systematic uncertainty in the background and will suffer from a high rate of false alarms. The goal of this work is to provide a comprehensive characterization of the gamma-ray background and its variability in order to improve detection sensitivity and evaluate the performance of mobile detectors in the field. Large quantities of data are measured in order to study their performance at very low false alarm rates. Two different approaches, spectroscopy and imaging, are compared in a controlled study in the presence of this measured background. Furthermore, there is additional information that can be gained by correlating the gamma-ray data with contextual data streams (such as cameras and global positioning systems) in order to reduce the variability in the background. This is accomplished by making many hours of background measurements with a truck-mounted system, which utilizes high-purity germanium detectors for spectroscopy and sodium iodide detectors for coded aperture imaging. This system also utilizes various peripheral sensors, such as panoramic cameras, laser ranging systems, global positioning systems, and a weather station to provide context for the gamma-ray data. About three hundred hours of data were taken in the San Francisco Bay Area, covering a wide variety of environments that might be encountered in operational scenarios. These measurements were used in a source injection study to evaluate the sensitivity of different algorithms (imaging and spectroscopy) and hardware (sodium iodide and high-purity germanium detectors). These measurements confirm that background distributions in large, mobile detector systems are dominated by systematic, not statistical variations, and both spectroscopy and imaging were found to substantially reduce this variability. Spectroscopy performed better than the coded aperture for the given scintillator array (one square meter of sodium iodide) for a variety of sources and geometries. By modeling the statistical and systematic uncertainties of the background, the data can be sampled to simulate the performance of a detector array of arbitrary size and resolution. With a larger array or lower resolution detectors, however imaging was better able to compensate for background variability.

  19. Gamma Rays to Blame for Mass Extinction Brandon Lohman

    E-print Network

    Wysin, Gary

    Abstract: Gamma Rays to Blame for Mass Extinction Brandon Lohman Abstract: A new hypothesis triggered by cosmic events. A high intensity gamma ray burst directed toward Earth may have irradiated our, evolutionary patterns, and geological evidence tend to support a hypothesis that a gamma-ray burst may have

  20. Gamma-ray Sky Observed with Fermi Large Area Telescope

    E-print Network

    Yamamoto, Hirosuke

    Gamma-ray Sky Observed with Fermi Large Area Telescope RESCEU Symposium on Astroparticle Physics) Measure the photon direction Identification of the gamma-ray shower 36 planes of Si strip detectors (228 m) Calorimeter(CAL) Measure the photon energy Image the gamma-ray shower CsI(Tl) crystals in 8 layers. Anticoinc

  1. Results from the Milagro Gamma-Ray Observatory

    E-print Network

    California at Santa Cruz, University of

    Results from the Milagro Gamma-Ray Observatory E. Blaufuss for the Milagro Collaboration a,1 , aUniversity of Maryland, College Park, MD 20742, USA Abstract The Milagro Gamma-Ray Observatory, located at an altitude The Milagro Detector The Milagro Gamma-Ray Observatory is located in the Jemez Mountains just outside of Los

  2. Performance of a chamber for studying the liquid xenon response to \\/spl gamma\\/-rays and nuclear recoils

    Microsoft Academic Search

    F. Neves; V. Chepel; V. Solovov; A. Pereira; M. I. Lopes; J. Pinto da Cunha; P. Mendes; A. Lindote; C. P. Silva; R. Ferreira Marques; A. J. P. L. Policarpo

    2005-01-01

    The design and performance of a 1.2 liter liquid xenon chamber equipped with 7 two-inch photomultiplier tubes, with the purpose of studying the scintillation response of xenon to gamma-rays and neutrons, is described. Measurements with gamma-rays indicate a high VUV light collection efficiency resulting in ~5.5 photoelectrons per 1 keV of deposited energy. The energy resolution (FWHM) is 18% and

  3. Exploring the Gamma Ray Horizon with the next generation of Gamma Ray Telescopes. Part 1: Theoretical predictions

    E-print Network

    O. Blanch; M. Martinez

    2004-06-17

    The physics potential of the next generation of Gamma Ray Telescopes in exploring the Gamma Ray Horizon is discussed. It is shown that the reduction in the Gamma Ray detection threshold might open the window to use precise determinations of the Gamma Ray Horizon as a function of the redshift to either put strong constraints on the Extragalactic Background Light modeling or to obtain relevant independent constraints in some fundamental cosmological parameters.

  4. Gamma-ray emitting radio galaxies

    NASA Astrophysics Data System (ADS)

    Beckmann, Volker; Soldi, Simona; De Jong, Sandra

    A number of radio galaxies has been detected by Fermi/LAT in the gamma-ray domain. The question remains why these objects, where the relativistic jet is not pointed at the observer, are observable gamma-ray emitters in the first place, and what distinguishes them from the vast majority of gamma-ray silent radio galaxies. In some cases, like Cen A and M 87, these objects have been seen even in the TeV range by Cherenkov telescopes. Whereas the gamma-ray emission is likely to be connected with the non-thermal jet emission, dominating also the radio band, the situation is less clear at hard X-rays. While the smoothly curved continuum emission and the overall spectral energy distribution indicate non-thermal emission, other features such as the iron line emission and the low variability appear to be rather of Seyfert type, i.e. created in the accretion disk and corona around the central black hole. We analysed the case of the 15 gamma-ray detected radio galaxies known so far. Using X-ray data from the soft X-ray band (e.g. Chandra, XMM-Newton, Suzaku/XIS) to the hard X-ray band (e.g. Suzaku/PIN, INTEGRAL, Swift) we determine the emission processes dominant between 0.5 keV and several 100 keV. In the case of M87 we report, for the first time, a detection in the 10-50 keV band. In most cases, the X-ray band of gamma-ray detected radio galaxies is produced in the inverse Compton branch, which can be seen in the fact that most have X-ray spectrum with a photon index <2.0 (i.e. a rising spectral energy distribution). Three different origins of the X-ray flux can be identified. The emission can be purely non-thermal and caused by the jet, as in the case of M 87, or thermal inverse Compton emission from the Seyfert type core (Cen A), or appears to be a superposition of non-thermal and thermal inverse Compton emission, as we observe in 3C 111. The iron fluorescence line Fe Kalpha is visible in the X-ray spectra of some, but not all radio galaxies. In three cases (OH-342, M87, and 3C 78) the X-ray emission is dominated by synchrotron processes, as indicated by X-ray photon indices >2.0. Gamma-ray bright radio galaxies host all kinds of AGN cores, Seyfert 1 and 2, BL Lacs, and also LINER, and can appear as FR-I and FR-II types. But the overall emission as seen in the spectral energy distribution can be modeled by a simple synchrotron self Compton model as typical for BL Lac objects, i.e. no additional strong photon field giving rise to an external Compton component is required. This indicates that the site of the gamma-ray emission is not exposed to a luminous broad line region or other dense photon field, as observed for example in FSRQ. Based on the number counts, it appears that within the Fermi/LAT data there are a dozen gamma-ray bright radio galaxies already detected but not yet identified as radio galaxies.

  5. Characterization of Thermal Cross-talk in a {gamma}-ray Microcalorimeter Array

    SciTech Connect

    Jethava, N. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Ullom, J. N.; Bennett, D. A.; Irwin, K. D.; Horansky, R. D.; Beall, J. A.; Hilton, G. C.; Vale, L. R. [NIST, 325 Broadway, Boulder, CO 80305 (United States); Hoover, A.; Bacrania, M. K.; Rabin, M. W. [Los Alamos National Laboratory, Los Alamos, NM, 87545 (United States)

    2009-12-16

    We present experimental data describing cross-talk within an array of gamma-ray microcalorimeters during gamma-ray irradiation. The microcalorimeters consist of Mo/Cu transition-edge sensors (TESs) with attached Sn absorbers. We observe both thermal and electrical cross-talk with peak cross-talk amplitudes as large as 0.4%. We have developed an analytical model for thermal cross-talk and make a preliminary comparison to data. Cross-talk must be understood and minimized for high resolution spectroscopy at high input count rates.

  6. Model-independent dark matter annihilation bound from the diffuse gamma ray flux

    E-print Network

    M. Kachelriess; P. D. Serpico

    2007-09-30

    An upper limit on the total annihilation cross section of dark matter (DM) has recently been derived from the observed atmospheric neutrino background. We show that comparable bounds are obtained for DM masses around the TeV scale by observations of the diffuse gamma-ray flux by EGRET, because electroweak bremsstrahlung leads to non-negligible electromagnetic branching ratios, even if DM particles only couple to neutrinos at tree level. A better mapping and the partial resolution of the diffuse gamma-ray background into astrophysical sources by the GLAST satellite will improve this bound in the near future.

  7. On the observability of the gamma-ray line flux from dark matter annihilation

    NASA Technical Reports Server (NTRS)

    Rudaz, S.; Stecker, F. W.

    1991-01-01

    The limits on the possible cosmic gamma-ray line flux from the two-photon annihilation of dark matter in the Galaxy are discussed. These limits are derived using both particle physics and cosmological constraints on dark matter candidates which arise in supersymmetric extensions of the standard model of particle physics. Results are given in terms of allowed and prescribed areas in the flux-energy plane. Then these bounds are used to consider the observability of the line flux above continuum background fluxes using future high-resolution gamma-ray telescopes.

  8. Germanium gamma-ray detector operation with a flight-like mechanical cooler

    NASA Astrophysics Data System (ADS)

    Gully, W. J.; Hopkins, R. A.; Cork, C. P.; Luke, P. N.; Madden, N. W.; Malone, D. F.; Pehl, R. H.

    Ball Aerospace and Lawrence Berkeley Laboratory (LBL) have successfully integrated a large germanium gamma-ray detector with a long-lifetime Stirling-cycle mechanical cooler. Testing performed at LBL in March 1995 demonstrated for the first time the compatibility of a space-quality mechanical cooler with a high-resolution germanium gamma-ray detector. The focus of the test was to investigate noise pick-up on the detector signal output caused by electromagnetic/electrostatic interference or vibration from the mechanical cooler.

  9. Spectroscopy of bright bursts with the transient gamma-ray spectrometer (TGRS)

    NASA Astrophysics Data System (ADS)

    Seifert, H.; Cline, T. L.; Palmer, D. M.; Ramaty, R.; Teegarden, B. J.; Hurley, K.; Madden, N. W.; Pehl, R. H.

    1998-05-01

    The Transient Gamma-Ray Spectrometer (TGRS) on the WIND spacecraft is designed to perform spectroscopy of bright gamma-ray bursts (GRBs) in the ~20-8000 keV energy range, with a spectroscopic resolution which is 5-30 times better than that of earlier-generation detectors. During its first ~2.5 years of operation, TGRS detected ~90 GRBs, of which about one third are suitable for statistically interesting spectroscopy. We present preliminary comparative results for some of the brightest of those bursts, and which were also observed by CGRO/BATSE.

  10. The detector response matrices of the Transient Gamma-Ray Spectrometer (TGRS)

    NASA Astrophysics Data System (ADS)

    Seifert, H.; Cline, T. L.; Gehrels, N.; Mitra, B.; Palmer, D. M.; Ramaty, R.; Teegarden, B. J.; Hurley, K.; Madden, N.; Pehl, R.; Owens, A.

    1996-08-01

    The Transient Gamma-Ray Spectrometer (TGRS) on the WIND spacecraft is a germanium detector primarily designed to measure high-resolution (~2-3 keV) spectra of bright gamma-ray bursts. The instrument response matrix, used to unfold photon spectra from the measured count spectra, has been obtained by modelling TGRS/WIND with the GEANT detector description and simulation package from CERN. The simulations were verified using laboratory measurements. We present a brief description of the TGRS instrument, as well as an outline of the measurements, simulations and software algorithms used in the generation of the detector response matrices.

  11. Origin of the 871-keV gamma ray and the ``oxide'' attribute

    SciTech Connect

    AJ Peurrung; RJ Arthur; BD Geelhood; RD Scheele; RJ Elovich; SL Pratt

    2000-03-22

    This work concludes the investigation of the oxide attribute of current interest for the characterization of stored plutonium. Originally it was believed that the presence of oxide could be ascertained by measurement of the 871-keV line in a high-resolution gamma-ray spectrum. However, recent work has suggested that the 871-keV gamma ray in plutonium oxide arises from the reaction {sup 14}N({alpha},p){sup 17}O rather than the inelastic scattering reaction {sup 17}O({alpha},{alpha}{prime}){sup 17}O*. This conclusion, though initially surprising, was obtained during efforts to determine the relative importance of americium and plutonium alpha-particle decay for the production of the 871-keV gamma ray. Several questions were raised by previous experiments: What role, if any does {sup 17}O have in the generation of the 871-keV gamma ray? How does sufficient nitrogen come to be present in plutonium oxide? Under what conditions is the 871-keV gamma ray measurable in plutonium oxide? This paper describes the answers to these questions.

  12. THE MORPHOLOGY OF HADRONIC EMISSION MODELS FOR THE GAMMA-RAY SOURCE AT THE GALACTIC CENTER

    SciTech Connect

    Linden, Tim; Profumo, Stefano [Department of Physics, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Lovegrove, Elizabeth [Department of Astronomy and Astrophysics, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States)

    2012-07-01

    Recently, detections of a high-energy {gamma}-ray source at the position of the Galactic center have been reported by multiple {gamma}-ray telescopes, spanning the energy range between 100 MeV and 100 TeV. Analysis of these signals strongly suggests the TeV emission to have a morphology consistent with a point source up to the angular resolution of the HESS telescope (approximately 3 pc), while the point-source nature of the GeV emission is currently unsettled, with indications that it may be spatially extended. In the case that the emission is hadronic and in a steady state, we show that the expected {gamma}-ray morphology is dominated by the distribution of target gas, rather than by details of cosmic-ray injection and propagation. Specifically, we expect a significant portion of hadronic emission to coincide with the position of the circumnuclear ring, which resides between 1 and 3 pc from the Galactic center. We note that the upcoming Cherenkov Telescope Array (CTA) will be able to observe conclusive correlations between the morphology of the TeV {gamma}-ray source and the observed gas density, convincingly confirming or ruling out a hadronic origin for the {gamma}-ray emission.

  13. GAMMA RAYS FROM MAJOR ELEMENTS BY THERMAL NEUTRON CAPTURE REACTIONS: EXPERIMENT AND SIMULATION FOR PLANETARY GAMMA-RAY SPECTROSCOPY.

    E-print Network

    Berezhnoi, Aleksei A.

    GAMMA RAYS FROM MAJOR ELEMENTS BY THERMAL NEUTRON CAPTURE REACTIONS: EXPERIMENT AND SIMULATION FOR PLANETARY GAMMA-RAY SPECTROSCOPY. N. Yamashita1 , N. Hasebe1 , M. -N. Kobayashi1 , T. Miyachi1 , O. Okudaira of planetary surface can be determined by remotely measuring the energies and intensities of gamma rays

  14. Imaging interactions of metal oxide nanoparticles with macrophage cells by ultra-high resolution scanning electron microscopy techniques.

    PubMed

    Plascencia-Villa, Germán; Starr, Clarise R; Armstrong, Linda S; Ponce, Arturo; José-Yacamán, Miguel

    2012-11-01

    Use of engineered metal oxide nanoparticles in a plethora of biological applications and custom products has warned about some possible dose-dependent cytotoxic effects. Macrophages are key components of the innate immune system used to study possible toxic effects and internalization of different nanoparticulate materials. In this work, ultra-high resolution field emission scanning electron microscopy (FE-SEM) was used to offer new insights into the dynamical processes of interaction of nanomaterials with macrophage cells dosed with different concentrations of metal oxide nanoparticles (CeO(2), TiO(2) and ZnO). The versatility of FE-SEM has allowed obtaining a detailed characterization of processes of adsorption and endocytosis of nanoparticles, by using advanced analytical and imaging techniques on complete unstained uncoated cells, including secondary electron imaging, high-sensitive backscattered electron imaging, X-ray microanalysis and stereoimaging. Low voltage BF/DF-STEM confirmed nanoparticle adsorption and internalization into endosomes of CeO(2) and TiO(2), whereas ZnO develop apoptosis after 24 h of interaction caused by dissolution and invasion of cell nucleus. Ultra-high resolution scanning electron microscopy techniques provided new insights into interactions of inorganic nanoparticles with macrophage cells with high spatial resolution. PMID:23023106

  15. Gamma-Ray Bursts: A Mystery Story

    NASA Technical Reports Server (NTRS)

    Parsons, Ann

    2007-01-01

    With the success of the Swift Gamma-Ray Burst Explorer currently in orbit, this is quite an exciting time in the history of Gamma Ray Bursts (GRBs). The study of GRBs is a modern astronomical mystery story that began over 30 years ago with the serendipitous discovery of these astronomical events by military satellites in the late 1960's. Until the launch of BATSE on the Compton Gamma-ray Observatory, astronomers had no clue whether GRBs originated at the edge of our solar system, in our own Milky Way Galaxy or incredibly far away near the edge of the observable Universe. Data from BATSE proved that GRBs are distributed isotropically on the sky and thus could not be the related to objects in the disk of our Galaxy. Given the intensity of the gamma-ray emission, an extragalactic origin would require an astounding amount of energy. Without sufficient data to decide the issue, a great debate continued about whether GRBs were located in the halo of our own galaxy or were at extragalactic - even cosmological distances. This debate continued until 1997 when the BeppoSAX mission discovered a fading X-ray afterglow signal in the same location as a GRB. This discovery enabled other telescopes, to observe afterglow emission at optical and radio wavelengths and prove that GRBs were at cosmological distances by measuring large redshifts in the optical spectra. Like BeppoSAX Swift, slews to new GRB locations to measure afterglow emission. In addition to improved GRB sensitivity, a significant advantage of Swift over BeppoSAX and other missions is its ability to slew very quickly, allowing x-ray and optical follow-up measurements to be made as early as a minute after the gamma-ray burst trigger rather than the previous 6-8 hour delay. Swift afterglow measurements along with follow-up ground-based observations, and theoretical work have allowed astronomers to identify two plausible scenarios for the creation of a GRB: either through core collapse of super massive stars or colliding compact objects in distant galaxies. The pieces of the puzzle are beginning to fall into place and yet the story isn't quite finished. I will frame the history of gamma-ray bursts as a mystery story and will end with a description of what we still don't know and what we'll have to do to get the next clues.

  16. A measurement control program for plutonium isotopic gamma-ray systems at the Rocky Flats Plant

    Microsoft Academic Search

    Fleissner

    1986-01-01

    A sound measurement control (MC) program should be an integral part of every nondestructive assay measurement system used for the assay of special nuclear materials. This paper will describe a measurement control program for plutonium isotopic composition measurements, using high-resolution gamma-ray spectroscopy, that has been implemented in the analytical Laboratories and the Chemistry Standards Laboratory at the Rocky Flats Plant.

  17. A measurement control program for plutonium isotopic gamma-ray systems at the Rocky Flats Plant

    Microsoft Academic Search

    Fleissner

    1986-01-01

    A sound measurement control (MC) program should be an integral part of every nondestructive assay measurement system used for the assay of special nuclear materials. This paper describes a measurement control program for plutonium isotopic composition measurements, using high-resolution gamma-ray spectroscopy, that has been implemented in the Analytical Laboratories and the Chemistry Standards Laboratory at the Rocky Flats Plant. This

  18. Monitoring of multi-frequency polarization of gamma-ray bright AGNs

    E-print Network

    Lee, Sang-Sung; Kang, Sincheol; Seen, Jungmin; Byun, Do-Young; Baek, Jun-Hyun; Kim, Soon-Wook; Kim, Jeong-Sook

    2013-01-01

    We started two observing programs with the Korean VLBI Network (KVN) monitoring changes in the flux density and polarization of relativistic jets in gamma-ray bright AGNs simultaneously at 22, 43, 86, 129 GHz. One is a single-dish weekly-observing program in dual polarization with KVN 21-m diameter radio telescopes beginning in 2011 May. The other is a VLBI monthly-observing program with the three-element VLBI network at an angular resolution range of 1.0--9.2 mas beginning in 2012 December. The monitoring observations aim to study correlation of variability in gamma-ray with that in radio flux density and polarization of relativistic jets when they flare up. These observations enable us to study the origin of the gamma-ray flares of AGNs.

  19. 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.

  20. Fermi Large Area Telescope Measurements of the Diffuse Gamma-Ray Emission at Intermediate Galactic Latitudes

    NASA Astrophysics Data System (ADS)

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Anderson, B.; 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.; Charles, E.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Dereli, H.; Dermer, C. D.; de Angelis, A.; de Palma, F.; Digel, S. W.; di Bernardo, G.; Dormody, M.; Do Couto E Silva, E.; Drell, P. S.; Dubois, R.; Dumora, D.; Edmonds, Y.; Farnier, C.; Favuzzi, C.; Fegan, S. J.; Focke, W. B.; Frailis, M.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gaggero, D.; Gargano, F.; Gehrels, N.; Germani, S.; 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.; Hughes, R. E.; Jóhannesson, G.; Johnson, A. S.; Johnson, R. P.; Johnson, T. J.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kataoka, J.; Kawai, N.; Kerr, M.; Knödlseder, J.; Kocian, M. L.; Kuehn, F.; Kuss, M.; Lande, J.; Latronico, L.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; 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.; Nuss, E.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ormes, J. F.; Paneque, D.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Piron, F.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Reimer, A.; Reimer, O.; Reposeur, T.; Ritz, S.; Rodriguez, A. Y.; Roth, M.; Ryde, F.; Sadrozinski, H. F.-W.; Sanchez, D.; Sander, A.; Saz Parkinson, P. M.; Scargle, J. D.; Sellerholm, A.; Sgrò, C.; Smith, D. A.; Smith, P. D.; Spandre, G.; Spinelli, P.; Starck, J.-L.; Stecker, F. W.; Striani, E.; Strickman, M. S.; Strong, A. W.; 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.; Waite, A. P.; Wang, P.; Winer, B. L.; Wood, K. S.; Ylinen, T.; Ziegler, M.

    2009-12-01

    The diffuse galactic ?-ray emission is produced by cosmic rays (CRs) interacting with the interstellar gas and radiation field. Measurements by the Energetic Gamma-Ray Experiment Telescope (EGRET) instrument on the Compton Gamma-Ray Observatory indicated excess ?-ray emission ?1GeV relative to diffuse galactic ?-ray emission models consistent with directly measured CR spectra (the so-called “EGRET GeV excess”). The Large Area Telescope (LAT) instrument on the Fermi Gamma-Ray Space Telescope has measured the diffuse ?-ray emission with improved sensitivity and resolution compared to EGRET. We report on LAT measurements for energies 100 MeV to 10 GeV and galactic latitudes 10°?|b|?20°. The LAT spectrum for this region of the sky is well reproduced by a diffuse galactic ?-ray emission model that is consistent with local CR spectra and inconsistent with the EGRET GeV excess.

  1. Comparisons between digital gamma-ray spectrometer (DSPec) and standard nuclear instrumentation methods (NIM) systems

    SciTech Connect

    Vo, D.T.; Russo, P.A.; Sampson, T.E.

    1998-03-01

    Safeguards isotopic measurements require the best spectrometer systems with excellent resolution, stability and throughput. Up until about a year ago, gamma ray spectroscopy has always been done using the analog amplifier, which processes the pulses from the preamplifier to remove the noise, reject the pile up signals, and shape the signals into some desirable form before sending them to the analog to digital converter (ADC) to be digitized. In late 1996, EG and G Ortec introduced a digital gamma ray spectrometer (DSPec) which uses digital technology to analyze the preamplifiers` pulses from all types of germanium and silicon detectors. Considering its performance, digital based spectroscopy may become the way of future gamma ray spectroscopy.

  2. COMPTEL upper limits on gamma-ray line emission from Supernova 1991T

    NASA Technical Reports Server (NTRS)

    Lichti, G. G.; Bennett, K.; Herder, J. W. Den; Diehl, R.; Morris, D.; Ryan, J.; Schoenfelder, V.; Steinle, H.; Strong, A. W.; Winkler, C.

    1994-01-01

    The imaging Compton telescope COMPTEL on board the Compton Gamma-Ray Observatory (CGRO) measures gamma-rays in the energy range 0.75-30 MeV with an energy resolution of 9.7% full width at half maximum (FWHM) at 1 MeV. From June 15 to 28, 1991 and again from October 3 to 17, 1991 the region containing the supernova SN 1991T was observed. A search for gamma-ray line emission from the supernova yields no detection of line emission from the supernova. 2 sigma upper limits for the two predicted lines at 847 keV and at 1.238 MeV of approximately equal to 3 x 10(exp -5) photons/(sq cm)(s) were derived. These limits are compared with the predictions of some theoretical models and constraints imposed by these limits on these models are discussed.

  3. Amorphous-semiconductor-contact germanium-based detectors for gamma-ray imaging and spectroscopy

    NASA Astrophysics Data System (ADS)

    Amman, M.; Luke, P. N.; Boggs, S. E.

    2007-09-01

    Germanium-based detectors are the standard technology used for gamma-ray spectroscopy when high efficiency and excellent energy resolution are desired. By dividing the electrical contacts on these detectors into segments, the locations of the gamma-ray interaction events within the detectors can be determined as well as the deposited energies. This enables simultaneous gamma-ray imaging and spectroscopy and leads to applications in the areas of astronomy, nuclear physics, environmental remediation, nuclear nonproliferation, and homeland security. Producing the fine-pitched electrode segmentation often required for imaging has been problematic in the past. To address this issue, we have developed an amorphous-semiconductor contact technology. Using this technology, fully passivated detectors with closely spaced contacts can be produced using a simple fabrication process. The current state of the amorphous-semiconductor contact technology and the challenges that remain are given in this paper.

  4. Image Artifacts Resulting from Gamma-Ray Tracking Algorithms Used with Compton Imagers

    SciTech Connect

    Seifert, Carolyn E.; He, Zhong

    2005-10-01

    For Compton imaging it is necessary to determine the sequence of gamma-ray interactions in a single detector or array of detectors. This can be done by time-of-flight measurements if the interactions are sufficiently far apart. However, in small detectors the time between interactions can be too small to measure, and other means of gamma-ray sequencing must be used. In this work, several popular sequencing algorithms are reviewed for sequences with two observed events and three or more observed events in the detector. These algorithms can result in poor imaging resolution and introduce artifacts in the backprojection images. The effects of gamma-ray tracking algorithms on Compton imaging are explored in the context of the 4? Compton imager built by the University of Michigan.

  5. A redshifted Kalpha line from the peculiar gamma-ray source PMN J1603-4904

    NASA Astrophysics Data System (ADS)

    Mueller, C.; Krauß, F.; Kreikenbohm, A.; Kadler, M.; Ojha, R.; Wilms, J.; Markowitz, A.; Pottschmidt, K.; Stawarz, L.; Taylor, G.

    2015-07-01

    We present the latest results on the bright hard-spectrum gamma-ray source PMN J1603-4904, observed in the framework of the multiwavelength monitoring program TANAMI. High-resolution radio observations reveal a symmetric brightness distribution with the brightest, most compact component at the center of the emission region. Its broadband spectral energy distribution and other multiwavelength properties point to a very atypical blazar. Here, we focus on recent XMM-Newton and Suzaku observations. We detect a narrow iron line which allows for a first measurement of the redshift of the system (z˜ 0.18) and further challenges the earlier blazar classification. This result suggests that the source is observed at a larger angle to the line of sight than expected for blazars, and thus the source would add to the elusive class of gamma-ray loud misaligned-jet objects, possibly a gamma-ray bright young radio galaxy.

  6. Observation of SN 1987A with the gamma-ray spectrometer HEXAGONE

    NASA Astrophysics Data System (ADS)

    Chapuis, C. G. L.; Wallyn, P.; Durouchoux, Ph.; Matteson, J.; Pelling, M.; Bowman, B.; Briggs, M.; Gruber, D.; Peterson, L.; Lingenfelter, R.; Cork, C.; Landis, D.; Luke, P.; Madden, N.; Malone, D.; Pehl, R.; Pollard, M.; Lin, R.; Smith, D.; Feffer, P.; Hurley, K.; Vedrenne, G.; Niel, M.; von Ballmoos, P.

    1993-01-01

    The HEXAGONE balloon-borne spectrometer was flown from Alice Springs (Australia) on 1989 May 22. HEXAGONE is a high-resolution gamma-ray spectrometer and consists of an array of twelve cooled germanium detectors. One of the observed targets was the supernova 1987A and it was seen during 9.9hr, 818 days after the initial optical outburst. No significant hard X-ray or gamma-ray emission is detected in the final spectrum of SN 1987A. We report the upper limits of the flux values for the gamma-ray lines coming from the decay of radionuclides synthesized in this star such as Co56, Co-57, or Ti-44. The results are consistent with models incorporating mixing of the radioactive nuclei in the ejecta, 0.073 solar mass of Co-56, 3.1 10 exp -3 solar mass of Co-57, and 1.2 10 expo -4 solar mass of Ti-44.

  7. A search for spectral lines in gamma-ray bursts using TGRS

    NASA Astrophysics Data System (ADS)

    Kurczynski, P.; Palmer, D.; Seifert, H.; Teegarden, B. J.; Gehrels, N.; Cline, T. L.; Ramaty, R.; Hurley, K.; Madden, N. W.; Pehl, R. H.

    1998-05-01

    We present the results of an ongoing search for narrow spectral lines in gamma-ray burst data. TGRS, the Transient Gamma-Ray Spectrometer aboard the Wind satellite is a high energy-resolution Ge device. Thus it is uniquely situated among the array of space-based, burst sensitive instruments to look for line features in gamma-ray burst spectra. Our search strategy adopts a two tiered approach. An automated `quick look' scan searches spectra for statistically significant deviations from the continuum. We analyzed all possible time accumulations of spectra as well as individual spectra for each burst. Follow-up analysis of potential line candidates uses model fitting with F-test and ?2 tests for statistical significance.

  8. A performance study of an electron-tracking Compton camera with a compact system for environmental gamma-ray observation

    NASA Astrophysics Data System (ADS)

    Mizumoto, T.; Tomono, D.; Takada, A.; Tanimori, T.; Komura, S.; Kubo, H.; Matsuoka, Y.; Mizumura, Y.; Nakamura, K.; Nakamura, S.; Oda, M.; Parker, J. D.; Sawano, T.; Bando, N.; Nabetani, A.

    2015-06-01

    An electron-tracking Compton camera (ETCC) is a detector that can determine the arrival direction and energy of incident sub-MeV/MeV gamma-ray events on an event-by-event basis. It is a hybrid detector consisting of a gaseous time projection chamber (TPC), that is the Compton-scattering target and the tracker of recoil electrons, and a position-sensitive scintillation camera that absorbs of the scattered gamma rays, to measure gamma rays in the environment from contaminated soil. To measure of environmental gamma rays from soil contaminated with radioactive cesium (Cs), we developed a portable battery-powered ETCC system with a compact readout circuit and data-acquisition system for the SMILE-II experiment [1,2]. We checked the gamma-ray imaging ability and ETCC performance in the laboratory by using several gamma-ray point sources. The performance test indicates that the field of view (FoV) of the detector is about 1 sr and that the detection efficiency and angular resolution for 662 keV gamma rays from the center of the FoV is (9.31 ± 0.95) × 10?5 and 5.9° ± 0.6°, respectively. Furthermore, the ETCC can detect 0.15 ?Sv/h from a 137Cs gamma-ray source with a significance of 5? in 13 min in the laboratory. In this paper, we report the specifications of the ETCC and the results of the performance tests. Furthermore, we discuss its potential use for environmental gamma-ray measurements.

  9. High-resolution study of the {sup 12}C({gamma},p{gamma}{sup '}){sup 11}B reaction using a HpGe detector to resolve excited states of {sup 11}B through the observation of their {gamma}-ray decays

    SciTech Connect

    Morrow, S.A.; Branford, D.; Foehl, K. [School of Physics, University of Edinburgh, Edinburgh EH9 3JZ (United Kingdom); McGeorge, J.C.; MacGregor, I.J.D. [Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Adler, J.-O.; Hansen, K.; Isaksson, L.; Lundin, M.; Schroder, B. [Department of Nuclear Physics, University of Lund, S-223 62 Lund (Sweden)

    2006-04-15

    Relative populations of states in {sup 11}B following the {sup 12}C({gamma},p){sup 11}B reaction have been measured with high resolution using a 70% HpGe {gamma} detector to observe decay {gamma} rays from the residual nucleus. The triplet of states near 7 MeV in {sup 11}B are resolved and the measured populations compared to previous data. The analysis includes a consideration of {gamma}-proton angular correlations, which was not made in the previous measurement. The new and previous results corrected for angular correlation effects agree reasonably well with calculations that include one- and two-body nuclear currents, pion exchange, and {delta} currents, under the assumption that the photons are mainly absorbed on exchanged pions.

  10. Multichannel CdZnTe gamma ray spectrometer

    NASA Astrophysics Data System (ADS)

    Doty, F. P.; Lingren, C. L.; Apotovsky, B. A.; Brunsch, J.; Butler, J. F.; Collins, T.; Conwell, R. L.; Friesenhahn, S.; Gormley, J.; Pi, B.; Zhao, S.; Augustine, F. L.; Bennett, B. A.; Cross, E.; James, R. B.

    1999-02-01

    A 3 cm 3 multichannel gamma spectrometer for DOE applications is under development by Digirad Corporation. The device is based on a position sensitive detector packaged in a compact multi-chip module (MCM) with integrated readout circuitry. The modular, multichannel design will enable identification and quantitative analysis of radionuclides in extended sources, or sources containing low levels of activity. The MCM approach has the advantages that the modules are designed for imaging applications, and the sensitivity can be arbitrarily increased by increasing the number of pixels, i.e. adding modules to the instrument. For a high sensitivity probe, the outputs for each pixel can be corrected for gain and offset variations, and summed digitally. Single pixel results obtained with discrete low noise readout indicate energy resolution of 3 keV can be approached with currently available CdZnTe. The energy resolution demonstrated to date with MCMs for 511 keV gamma rays is 10 keV.

  11. The GAMCIT gamma ray burst detector

    NASA Technical Reports Server (NTRS)

    Mccall, Benjamin J.; Grunsfeld, John M.; Sobajic, Srdjan D.; Chang, Chinley Leonard; Krum, David M.; Ratner, Albert; Trittschuh, Jennifer E.

    1993-01-01

    The GAMCIT payload is a Get-Away-Special payload designed to search for high-energy gamma-ray bursts and any associated optical transients. This paper presents details on the design of the GAMCIT payload, in the areas of battery selection, power processing, electronics design, gamma-ray detection systems, and the optical imaging of the transients. The paper discusses the progress of the construction, testing, and specific design details of the payload. In addition, this paper discusses the unique challenges involved in bringing this payload to completion, as the project has been designed, constructed, and managed entirely by undergraduate students. Our experience will certainly be valuable to other student groups interested in taking on a challenging project such as a Get-Away-Special payload.

  12. Nuclear isomer suitable for gamma ray laser

    NASA Technical Reports Server (NTRS)

    Jha, S.

    1979-01-01

    The operation of gamma ray lasers (gasers) are studied. It is assumed that the nuclear isomers mentioned in previously published papers have inherent limitations. It is further assumed that the judicious use of Bormann effect or the application of the total external reflection of low energy gamma radiation at grazing angle of incidence may permit the use of a gaser crystal sufficiently long to achieve observable stimulated emission. It is suggested that a long lived 0(+) isomer decaying by low energy gamma ray emission to a short lived 2(+) excited nuclear state would be an attractive gaser candidate. It is also suggested that the nuclear isomer be incorporated in a matrix of refractory material having an electrostatic field gradient whose principal axis lies along the length of the medium. This results in the preferential transmission of electric quadrupole radiation along the length of the medium.

  13. Gamma Ray Signatures from Ordinary Cosmic Strings

    E-print Network

    Jane H. MacGibbon; Robert H. Brandenberger

    1992-06-19

    We calculate the flux of ultra high energy photons from individual ordinary (i.e. non-superconducting) cosmic strings and compare the results with the sensitivity of current and proposed TeV and EeV telescopes. Our calculations give only upper limits for the gamma ray flux, since the source of the photons, jets from particle production at cusps, may be weakened by back reaction effects. For the usual cosmic distribution of strings, the predicted bursts from strings with the value of mass per unit length associated with galaxy formation or light strings may just be detectable. A diffuse gamma ray background from light strings may also be seen by the Fly's Eye detector at above $7 \\times 10^{10}$ GeV.

  14. Gamma Ray Imaging for Environmental Remediation

    SciTech Connect

    Johnson, W. Neil; Luke, Paul N.; Kurfess, J.D.; Phlips, Bernard F.; Kroeger, R.A.; Phillips, G.W.

    1999-06-01

    The goal of this project is the development of field portable gamma-ray detectors that can both image gamma rays from radioactive emission and determine the isotopic composition by the emitted spectrum. Most instruments to date have had either very good imaging with no spectroscopy, or very good spectroscopy with no imaging. The only instruments with both imaging and spectroscopy have had rather poor quality imaging and spectroscopy (e.g. NaI Anger Cameras). The technology would have widespread applications, from laboratory nuclear physics, to breast cancer imaging, to astronomical research. For this project, we focus on the applications in the field of fissile materials, spent nuclear fuels and decontamination and decommissioning.

  15. Fissile interrogation using gamma rays from oxygen

    DOEpatents

    Smith, Donald; Micklich, Bradley J.; Fessler, Andreas

    2004-04-20

    The subject apparatus provides a means to identify the presence of fissionable material or other nuclear material contained within an item to be tested. The system employs a portable accelerator to accelerate and direct protons to a fluorine-compound target. The interaction of the protons with the fluorine-compound target produces gamma rays which are directed at the item to be tested. If the item to be tested contains either a fissionable material or other nuclear material the interaction of the gamma rays with the material contained within the test item with result in the production of neutrons. A system of neutron detectors is positioned to intercept any neutrons generated by the test item. The results from the neutron detectors are analyzed to determine the presence of a fissionable material or other nuclear material.

  16. Stirling Colgate and Gamma-Ray Bursts

    NASA Astrophysics Data System (ADS)

    Lamb, Donald

    2014-10-01

    Even before the discovery of gamma-ray bursts (GRBs), Stirling Colgate proposed that bursts of x rays and gamma rays might be produced by a relativistic shock created in the supernova explosion of a massive star. We trace the scientific story of GRBs from their detection to the present, highlighting along the way Stirling's interest in them and his efforts to understand them. We summarize our current understanding that short, soft, repeating bursts are produced by magnetic neutron stars; short, hard bursts are produced by the mergers of neutron star-neutron star binaries; and long, hard bursts are produced by the core collapse of massive stars that have lost their hydrogen and helium envelopes. We then discuss some important open questions about GRBs and how they might be answered. We conclude by describing the recent serendipitous discovery of an x-ray burst of exactly the kind he proposed, and the insights into core collapse supernovae and GRBs that it provided.

  17. SUB-LUMINOUS {gamma}-RAY PULSARS

    SciTech Connect

    Romani, R. W.; Kerr, M.; Craig, H. A. [Department of Physics, Stanford University, Stanford, CA 94305 (United States); Johnston, S. [Australia Telescope National Facility, CSIRO, Epping, NSW 1710 (Australia); Cognard, I. [Laboratoire de Physique et Chimie de l'Environnement, LPCE UMR 6115 CNRS, 45071 Orleans Cedex 02 (France); Smith, D. A., E-mail: rwr@astro.stanford.edu [Centre d'Etudes Nucleaires de Bordeaux Gradignan, Universite Bordeaux 1, CNRS/IN2p3, 33175 Gradignan (France)

    2011-09-01

    Most pulsars observed by the Fermi Large Area Telescope have {gamma}-ray luminosities scaling with spin-down power E-dot as L{sub {gamma}}{approx}(E-dot x 10{sup 33} erg s{sup -1}){sup 1/2}. However, there exist one detection and several upper limits an order of magnitude or more fainter than this trend. We describe these 'sub-luminous' {gamma}-ray pulsars and discuss the case for this being an orientation effect. Of the 12 known young radio pulsars with E-dot >10{sup 34} erg s{sup -1} and d {<=} 2 kpc several are substantially sub-luminous. The limited available geometrical constraints favor aligned geometries for these pulsars, although no one case for alignment is compelling. In this scenario GeV emission detected from such sub-luminous pulsars can be due to a lower altitude, lower-power accelerator gap.

  18. Real time gamma-ray signature identifier

    SciTech Connect

    Rowland, Mark (Alamo, CA); Gosnell, Tom B. (Moraga, CA); Ham, Cheryl (Livermore, CA); Perkins, Dwight (Livermore, CA); Wong, James (Dublin, CA)

    2012-05-15

    A real time gamma-ray signature/source identification method and system using principal components analysis (PCA) for transforming and substantially reducing one or more comprehensive spectral libraries of nuclear materials types and configurations into a corresponding concise representation/signature(s) representing and indexing each individual predetermined spectrum in principal component (PC) space, wherein an unknown gamma-ray signature may be compared against the representative signature to find a match or at least characterize the unknown signature from among all the entries in the library with a single regression or simple projection into the PC space, so as to substantially reduce processing time and computing resources and enable real-time characterization and/or identification.

  19. Research in cosmic and gamma ray astrophysics

    NASA Technical Reports Server (NTRS)

    Stone, Edward C.; Mewaldt, Richard A.; Prince, Thomas A.

    1992-01-01

    Discussed here is research in cosmic ray and gamma ray astrophysics at the Space Radiation Laboratory (SRL) of the California Institute of Technology. The primary activities discussed involve the development of new instrumentation and techniques for future space flight. In many cases these instrumentation developments were tested in balloon flight instruments designed to conduct new investigations in cosmic ray and gamma ray astrophysics. The results of these investigations are briefly summarized. Specific topics include a quantitative investigation of the solar modulation of cosmic ray protons and helium nuclei, a study of cosmic ray positron and electron spectra in interplanetary and interstellar space, the solar modulation of cosmic rays, an investigation of techniques for the measurement and interpretation of cosmic ray isotopic abundances, and a balloon measurement of the isotopic composition of galactic cosmic ray boron, carbon, and nitrogen.

  20. Lorentz violation from gamma-ray bursts

    E-print Network

    Shu Zhang; Bo-Qiang Ma

    2014-06-18

    The constancy of light speed is a basic assumption in Einstein's special relativity, and consequently the Lorentz invariance is a fundamental symmetry of space-time in modern physics. However, it is speculated that the speed of light becomes energy-dependent due to the Lorentz invariance violation~(LV) in various new physics theories. We analyse the data of the energetic photons from the gamma-ray bursts (GRBs) by the Fermi Gamma-Ray Space Telescope, and find more events to support the energy dependence in the light speed with both linear and quadratic form corrections. We provide two scenarios to understand all the new-released Pass~8 data of bright GRBs by the Fermi-LAT Collaboration, with predictions from such scenarios being testable by future detected GRBs.

  1. Are gamma-ray bursts cosmological?

    E-print Network

    Horvath, I

    2015-01-01

    Gamma-ray burst sources are distributed with a high level of isotropy, which is compatible with either a cosmological origin or an extended Galactic halo origin. The brightness distribution is another indicator used to characterize the spatial distribution in distance. In this paper the author discusses detailed fits of the BATSE gamma-ray burst peak-flux distributions with Friedmann models taking into account possible density evolution and standard candle luminosity functions. A chi-square analysis is used to estimate the goodness of the fits and the author derives the significance level of limits on the density evolution and luminosity function parameters. Cosmological models provide a good fit over a range of parameter space which is physically reasonable

  2. The Compton Gamma Ray Observatory: mission status.

    NASA Astrophysics Data System (ADS)

    Gehrels, N.; Chipman, E.; Kniffen, D. A.

    The Arthur Holly Compton Gamma Ray Observatory (Compton) is the second in NASA's series of Great Observatories. Compton has now been operating for over two and a half years, and has given a dramatic increase in capability over previous gamma-ray missions. The spacecraft and scientific instruments are all in good health, and many significant discoveries have already been made and continue to be made. The authors describe the capabilities of the four scientific instruments and the observing programs for the first three years of the mission. During Phases 2 and 3 of the mission a Guest Investigator program has been in progress with the Guest Observers' time share increasing from 30% to over 50% for the later mission phases.

  3. Ground-Based Gamma-Ray Astronomy

    E-print Network

    Michael Catanese

    1999-11-09

    Ground-based gamma-ray astronomy has become an active astrophysical discipline with four confirmed sources of TeV gamma rays, two plerionic supernova remnants (SNRs) and two BL Lac objects (BL Lacs). An additional nine objects (one plerion, three shell-type SNRs, one X-ray binary, and four BL Lacs) have been detected but have not been confirmed by independent detections. None of the galactic sources require the presence of hadronic cosmic rays, so definitive evidence of their origin remains elusive. Mrk 421 and Mrk 501 are weak EGRET sources but they exhibit extremely variable TeV emission with spectra that extend beyond 10 TeV. They also exhibit correlations with lower energy photons during multi-wavelength campaigns, providing tests of emission models. Next generation telescopes like VERITAS hold the promise of moving this field dramatically forward.

  4. Gamma-ray Output Spectra from 239Pu Fission

    NASA Astrophysics Data System (ADS)

    Ullmann, John

    2015-05-01

    Gamma-ray multiplicities, individual gamma-ray energy spectra, and total gamma energy spectra following neutron-induced fission of 239Pu were measured using the DANCE detector at Los Alamos. Corrections for detector response were made using a forward-modeling technique based on propagating sets of gamma rays generated from a paramaterized model through a GEANT model of the DANCE array and adjusting the parameters for best fit to the measured spectra. The results for the gamma-ray spectrum and multiplicity are in general agreement with previous results, but the measured total gamma-ray energy is about 10% higher. A dependence of the gamma-ray spectrum on the gamma-ray multplicity was also observed. Global model calculations of the multiplicity and gamma energy distributions are in good agreement with the data, but predict a slightly softer total-energy distribution.

  5. Physical constraints on models of gamma-ray bursters

    SciTech Connect

    Epstein, R.I.

    1985-01-01

    This report deals with the constraints that can be placed on models of gamma-ray burst sources based on only the well-established observational facts and physical principles. The premise is developed that the very hard x-ray and gamma-ray continua spectra are well-established aspects of gamma-ray bursts. Recent theoretical work on gamma-ray bursts are summarized with emphasis on the geometrical properties of the models. Constraints on the source models which are implied by the x-ray and gamma-ray spectra are described. The allowed ranges for the luminosity and characteristic dimension for gamma-ray burst sources are shown. Some of the deductions and inferences about the nature of the gamma-ray burst sources are summarized. 67 refs., 3 figs.

  6. SN2014J gamma rays from the 56Ni decay chain

    NASA Astrophysics Data System (ADS)

    Diehl, Roland; Siegert, Thomas; Hillebrandt, Wolfgang; Krause, Martin; Greiner, Jochen; Maeda, Keiichi; Röpke, Friedrich K.; Sim, Stuart A.; Wang, Wei; Zhang, Xiaoling

    2015-02-01

    Context. The detection and measurement of gamma-ray lines from the decay chain of 56Ni provides unique information about the explosion in supernovae. SN2014J at 3.3 Mpc is a sufficiently-nearby supernova of type Ia so that such measurements have been feasible with the gamma-ray spectrometer SPI on ESA's INTEGRAL gamma-ray observatory. Aims: The 56Ni freshly produced in the supernova is understood to power the optical light curve, because it emits gamma rays upon its radioactive decay first to 56Co and then to 56Fe. Gamma-ray lines from 56Co decay are expected to become directly visible through the white dwarf material several weeks after the explosion, as they progressively penetrate the overlying material of the supernova envelope, which is diluted as it expands. The lines are expected to be Doppler-shifted or broadened from the kinematics of the 56Ni ejecta. We aim to exploit high-resolution gamma-ray spectroscopy with the SPI spectrometer on INTEGRAL toward constraining the 56Ni distribution and kinematics in this supernova. Methods: We use the observations with the SPI spectrometer on INTEGRAL, together with an improved instrumental background method. Results: We detect the two main lines from 56Co decay at 847 and 1238 keV, which are significantly Doppler-broadened, and at intensities (3.65 ± 1.21) × 10-4 and (2.27 ± 0.69) × 10-4 ph cm-2 s-1, respectively, at their brightness maximum. We measure their rise toward a maximum after about 60-100 days and a decline thereafter. The intensity ratio of the two lines is found to be consistent with expectations from 56Co decay (0.62 ± 0.28 at brightness maximum, the expected ratio is 0.68). We find that the broad lines seen in the late, gamma-ray transparent phase are not representative of the early gamma-ray emission, and notice instead that the emission spectrum is complex and irregular until the supernova is fully transparent to gamma rays, with progressive uncovering of the bulk of 56Ni. We infer that the explosion morphology is not spherically symmetric, both in the distribution of 56Ni and in the unburnt material which occults the 56Co emission. After we compare light curves from different plausible models, the resulting 56Ni mass is determined to be 0.49 ± 0.09 M?.

  7. The Tools of Gamma Ray Astronomy

    NSDL National Science Digital Library

    NASA scientist, Neil Gehrels, serves as your guide to this online lesson on gamma ray tools, which focuses on advances in detector technologies since the 1980s that have enabled us to capture and image high-energy phenomena. Dr. Gehrels explains different methods for detecting and imaging high-energy particles, how they work, and the advantages and disadvantages of each, using examples and imagery from NASA missions.

  8. Gamma Ray Observatory over Baja California, Mexico

    NASA Technical Reports Server (NTRS)

    1991-01-01

    In this view of the Gamma Ray Observatory over Baja California, Mexico (31.5N, 113.0W), the Salton Sea and Imperial Valley region of California where the mouth of the Colorado River empties into the Sea of Cortez is clearly visible. The Los Angeles basin is partially visible below the GRO's left solar panel. Looking due east, across Mexico and south Texas, toward the Earth limb, the Texas Gulf coast is faintly visible.

  9. Gamma rays from extragalactic radio sources

    NASA Technical Reports Server (NTRS)

    Dermer, Charles D.; Schlickeiser, Reinhard; Mastichiadis, Apostolos

    1992-01-01

    It is proposed that the important connection between 3C 273 and 3C 279, the first two extragalactic sources detected at greater than 100 MeV energies, is their superluminal nature. In support of this conjecture, we propose a radiation mechanism that focuses gamma rays in the superluminal direction, due to Compton scattering of accretion-disk photons by relativistic nonthermal electrons in the jet.

  10. Gamma-ray Bursts in Wavelet Space

    E-print Network

    Z. Bagoly; I. Horvath; A. Meszaros; L. G. Balazs

    2005-08-31

    The gamma-ray burst's lightcurves have been analyzed using a special wavelet transformation. The applied wavelet base is based on a typical Fast Rise-Exponential Decay (FRED) pulse. The shape of the wavelet coefficients' total distribution is determined on the observational frequency grid. Our analysis indicates that the pulses in the long bursts' high energy channel lightcurves are more FRED-like than the lower ones, independently from the actual physical time-scale.

  11. Prospects for Nuclear-gamma-ray Astronomy

    NASA Technical Reports Server (NTRS)

    Clayton, D. D.

    1973-01-01

    An analysis was made of prospects for gamma rays coming from two sources outside the solar system: (1) radioactive decay of fresh nuclear products to explosive nucleosynthesis, and (2) scattering of low energy cosmic rays. The former should be detectable and will provide a factual base for many suppositions about the site and history of nucleosynthesis. The latter may be detectable and, if so, will probably provide factual information about high-flux regions of cosmic radiation.

  12. Gamma-Ray Line Observations with RHESSI

    E-print Network

    David M. Smith

    2004-04-30

    The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) has been observing gamma-ray lines from the Sun and the Galaxy since its launch in February 2002. Here I summarize the status of RHESSI observations of solar lines (nuclear de-excitation, neutron capture, and positron annihilation), the lines of $^{26}$Al and $^{60}$Fe from the inner Galaxy, and the search for positron annihilation in novae.

  13. Observational Review of Gamma-Ray Bursts

    NASA Technical Reports Server (NTRS)

    Fishman, Gerald J.

    1999-01-01

    The observed gamma-ray temporal, spectral, intensity and spatial distribution characteristics of GRBs, primarily from data obtained from the Compton Observatory, will be described. The talk will concentrate on recent studies of burst properties, correlations of GRB parameters and other statistical studies that have only recently come to light with the unprecedented sample of over two thousand GRBs, along with some mention of studies in progress by members of the BATSE team.

  14. Cosmological Time Dilation in Gamma Ray Bursts?

    E-print Network

    David Band

    1994-07-01

    Norris et al. (1994) report that the temporal structure of faint gamma ray bursts is longer than that of bright bursts, as expected for time dilation in the cosmological models of burst origin. I show that the observed trends can easily be produced by a burst luminosity function and thus may not result from cosmological effects. A cosmological signature may be present, but the tests Norris et al. present are not powerful enough to detect these signatures.

  15. Supernovae and Gamma-Ray Bursts

    Microsoft Academic Search

    Massimo Della Valle

    2006-01-01

    I review the observational status of the Supernova\\/Gamma-Ray Burst (GRB) connection. Available data suggest that Supernovae (SNe) associated with GRBs form an heterogeneous class of objects including bright and faint hypernovae (Hyp) and perhaps also `standard' Ib\\/c events. Current estimates of SN and GRB rates and beaming angles yield ratios GRB\\/SNe-Ibc ?2% and GRB\\/Hyp ?25%. In the few SN\\/GRB associations

  16. Cosmological parametrization of gamma ray burst models

    E-print Network

    Eric V. Linder

    1996-07-02

    Using three parametrizations of the gamma ray burst count data comparison is made to cosmological source models. While simple models can fit and faint end slope constraints, the addition of a logarithmic count range variable describing the curvature of the counts shows that models with no evolution or evolution power law in redshift with index less than 10 fail to satisfy simultaneously all three descriptors of the burst data. The cosmological source density that would be required for a fit is illustrated.

  17. Gamma rays from active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Kazanas, Demosthenes

    1990-01-01

    The general properties of Active Galactic Nuclei (AGN) and quasars are reviewed with emphasis on their continuum spectral emission. Two general classes of models for the continuum are outlined and critically reviewed in view of the impending GRO (Gamma Ray Observatory) launch and observations. The importance of GRO in distinguishing between these models and in general in furthering the understanding of AGN is discussed. The very broad terms the status of the current understanding of AGN are discussed.

  18. Gamma ray spectroscopy and timing using LSO and PIN photodiodes

    SciTech Connect

    Moses, W.W.; Derenzo, S.E. [Lawrence Berkeley Lab., CA (United States)] [Lawrence Berkeley Lab., CA (United States); Melcher, C.L.; Manente, R.A. [Schlumberger-Doll Research, Ridgefield, CT (United States)] [Schlumberger-Doll Research, Ridgefield, CT (United States)

    1995-08-01

    The high density, high light output, and short decay time of LSO (lutetium orthosilicate, Lu{sub 2}SiO{sub 5}:Ce) make it an attractive scintillator for gamma ray spectroscopy. The low cost, small size, high quantum efficiency, and ruggedness of silicon photodiodes make them attractive photodetectors for this same application, although their high noise (compared to a photomultiplier tube) reduces their appeal. In this work the authors measure the gamma ray energy resolution, timing accuracy, and conversion factor from gamma energy to number of electron-hole pairs produced with a 3 x 3 x 22 mm{sup 3} LSO scintillator crystal read out with a 3 x 3 mm{sup 2} silicon PIN photodiode. When the detector is excited with 511 keV photons, a photopeak centered at 4,910 e{sup {minus}} with 149 keV fwhm is observed and a timing signal with 25 ns fwhm jitter is produced. While these performance measures are inferior to those obtained with photomultiplier tubes, they are acceptable for some applications.

  19. Bulk crystal growth of scintillator materials for gamma ray detectors

    NASA Astrophysics Data System (ADS)

    Aggarwal, Mohan

    2008-10-01

    Within the past few years, it has been demonstrated that several new rare earth halide scintillation detector crystals such as cerium doped lanthanum bromide (LaBr3:Ce) have high output and improved energy deposit to light linearity and thus they can substantially enhance the performance of the next generation of gamma ray detectors. These detectors have a variety of applications in NASA hard x-ray and gamma ray missions, high energy physics, home land security and medical imaging applications. This cerium doped lanthanum bromide crystal has ˜1100% the light output of BGO, resulting in better energy resolution than conventional scintillators. This is equivalent to 60000 photons per MeV of deposited energy. This new series of scintillator materials promise to usher a breakthrough in the field, if sufficiently large and clear crystals of this material can be grown. These halides however are highly hygroscopic and hence pose some difficulty in growing crystals. Efforts are being made to grow this and other materials in this family of crystals and successful results have been achieved. An overview of the challenges encountered during the synthesis and melt crystal growth of these rare earth halide scintillators shall be presented.

  20. Gamma ray spectroscopy and timing using LSO and PIN photodiodes

    SciTech Connect

    Moses, W.W.; Derenzo, S.E. [Lawrence Berkeley Lab., CA (United States); Melcher, C.L.; Manente, R.A. [Schlumberger-Doll Research, Ridgefield, CT (United States)

    1994-11-01

    The high density, high light output, and short decay time of LSO (lutetium orthosilicate, Lu{sub 2}SiO{sub 5}:Ce) make it an attractive scintillator for gamma ray spectroscopy. The low cost, small size, high quantum efficiency, and ruggedness of silicon photodiodes make them attractive photodetectors for this same application, although their high noise (Compared to a photomultiplier tube) reduces their appeal. In this work the authors measure the gamma ray energy resolution, timing accuracy, and conversion factor from gamma energy to number of electron-hole pairs produced with a 3 x 3 x 22 mm{sup 3} LSO scintillator crystal read out with a 3 x 3 mm{sup 2} silicon PIN photodiode. When the detector is excited with 511 keV photons, a photopeak centered at 1,940 e{sup {minus}} with 149 keV fwhm is observed and a timing signal with 35 ns fwhm jitter is produced. When the detector is excited with 1,275 keV photons, a photopeak centered at 4,910 e{sup {minus}} with 149 keV fwhm is observed and a timing signal with 25 ns fwhm jitter is produced. While these performance measures are inferior to those obtained with photomultiplier tubes, they are acceptable for some applications.

  1. THE FERMI GAMMA-RAY BURST MONITOR

    SciTech Connect

    Meegan, Charles [Universities Space Research Association, NSSTC, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Lichti, Giselher; Bissaldi, Elisabetta; Diehl, Roland; Greiner, Jochen; Von Kienlin, Andreas; Steinle, Helmut [Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse Postfach 1312, Garching 85748 (Germany); Bhat, P. N.; Briggs, Michael S.; Connaughton, Valerie; Paciesas, W. S.; Preece, Robert; Wilson, Robert B. [University of Alabama in Huntsville, NSSTC, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Fishman, Gerald; Kouveliotou, Chryssa [Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Hoover, Andrew S.; Kippen, R. Marc; Wallace, Mark S. [Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545 (United States); Van der Horst, Alexander J. [NSSTC, 320 Sparkman Drive, Huntsville, AL 35805 (United States); McBreen, Sheila [University College, Dublin, Belfield, Stillorgan Road, Dublin 4 (Ireland)] (and others)

    2009-09-01

    The Gamma-Ray Burst Monitor (GBM) will significantly augment the science return from the Fermi Observatory in the study of gamma-ray bursts (GRBs). The primary objective of GBM is to extend the energy range over which bursts are observed downward from the energy range of the Large Area Telescope (LAT) on Fermi into the hard X-ray range where extensive previous data sets exist. A secondary objective is to compute burst locations onboard to allow re-orienting the spacecraft so that the LAT can observe delayed emission from bright bursts. GBM uses an array of 12 sodium iodide scintillators and two bismuth germanate scintillators to detect gamma rays from {approx}8 keV to {approx}40 MeV over the full unocculted sky. The onboard trigger threshold is {approx}0.7 photons cm{sup -2} s{sup -1} (50-300 keV, 1 s peak). GBM generates onboard triggers for {approx}250 GRBs per year.

  2. The Extrgalactic Gamma-Ray Background

    E-print Network

    F. W. Stecker; M. H. Salamon

    2001-04-23

    The COMPTEL and EGRET detectors aboard the Compton Gamma-Ray Observatory measured an extragalactic gamma-ray background extending from MeV energies up to about 100 GeV. Calculations performed making reasonable assumptions indicate that blazars can account for the background between about 10 MeV and at least 10 GeV. Below 30 MeV, the background flux and spectrum are not very well determined and a dedicated satellite detector will be required to remedy this situation. Below 10 MeV, supernovae and possibly AGN may contribute to the extragalactic background flux. Above 10 GeV, the role of blazars in contributing to the background is unclear because we do not have data on their spectra at these energies and because theoretical models predict that many of them will have spectra which should cut off in this energy range. At these higher energies, a new component, perhaps from topological defects, may contribute to the background, as well as X-ray selected BL Lac objects. The future GLAST detector should provide important data on the emission of extragalactic sources above 10 GeV and help resolve this issue. GLAST may also be able to detect the signature of intergalactic absorption by pair production interactions of background gamma-rays of energy above 20 GeV with starlight photons, this signature being a steepening of the background spectrum.

  3. Gamma Ray Astronomy with Underground Detectors

    E-print Network

    F. Halzen; T. Stanev

    1995-07-20

    Underground detectors measure the directions of up-coming muons of neutrino origin. They can also observe down-going muons made by gamma rays in the Earth's atmosphere. Although gamma ray showers are muon-poor, they produce a sufficient number of muons to detect the sources observed by GeV and TeV telescopes. With a threshold higher by one hundred and a probability of muon production of about $1\\%$ for the shallower AMANDA and Lake Baikal detectors, these instruments can, for a typical GRO source, match the detection efficiency of a GeV satellite detector since their effective area is larger by a factor $10^4$. The muons must have enough energy for accurate reconstruction of their direction. Very energetic muons on the other hand are rare because they are only produced by higher energy gamma rays whose flux is suppressed by the decreasing flux at the source and by absorption on interstellar light. We show that there is a window of opportunity for muon astronomy in the 100~GeV energy region which nicely matches the threshold energies of the AMANDA and Lake Baikal detectors.

  4. Radio Flares from Gamma-ray Bursts

    NASA Astrophysics Data System (ADS)

    Kopa?, D.; Mundell, C. G.; Kobayashi, S.; Virgili, F. J.; Harrison, R.; Japelj, J.; Guidorzi, C.; Melandri, A.; Gomboc, A.

    2015-06-01

    We present predictions of centimeter and millimeter radio emission from reverse shocks (RSs) in the early afterglows of gamma-ray bursts (GRBs) with the goal of determining their detectability with current and future radio facilities. Using a range of GRB properties, such as peak optical brightness and time, isotropic equivalent gamma-ray energy, and redshift, we simulate radio light curves in a framework generalized for any circumburst medium structure and including a parameterization of the shell thickness regime that is more realistic than the simple assumption of thick- or thin-shell approximations. Building on earlier work by Mundell et al. and Melandri et al. in which the typical frequency of the RS was suggested to lie at radio rather than optical wavelengths at early times, we show that the brightest and most distinct RS radio signatures are detectable up to 0.1–1 day after the burst, emphasizing the need for rapid radio follow-up. Detection is easier for bursts with later optical peaks, high isotropic energies, lower circumburst medium densities, and at observing frequencies that are less prone to synchrotron self-absorption effects—typically above a few GHz. Given recent detections of polarized prompt gamma-ray and optical RS emission, we suggest that detection of polarized radio/millimeter emission will unambiguously confirm the presence of low-frequency RSs at early time.

  5. Neutrino bursts from gamma-ray bursts

    NASA Technical Reports Server (NTRS)

    Paczynski, Bohdan; Xu, Guohong

    1994-01-01

    If gamma-ray bursts originate at cosmological distances, as strongly indicated by the results from Burst and Transient Source Experiment (BATSE) on the Compton Gamma-Ray Observatory (CGRO), then ultrarelativistic ejecta are the likely consequence of the highly super-Eddington luminosity of the sources. If the energy injection rate varies with time, then the Lorentz factor of the wind also varies, and the shells of ejected matter collide with each other. The collisions between baryons produce pions which decay into high-energy photons, electrons, electron positron pairs, and neutrino pairs. The bulk Lorentz factor of approximately 300 is required if our model is to be compatible with the observed millisecond variability. The strongest gamma-ray bursts are observed to deliver approximately 10(exp -4) ergs/sq cm in 100-200 keV photons. In our scenario more energy may be delivered in a neutrino burst. Typical neutrinos may be approximately 30 GeV if the protons have a Maxwellian energy distribution, and up to approximately TeV if the protons have a power-law distribution. Such neutrino bursts are close to the detection limit of the DUMAND II experiment.

  6. Blood oxygenation level-dependent functional MRI signal turbulence caused by ultrahigh spatial resolution: numerical simulation and theoretical explanation.

    PubMed

    Chen, Zikuan; Chen, Zeyuan; Calhoun, Vince

    2013-03-01

    High-spatial-resolution functional MRI (fMRI) can enhance image contrast and improve spatial specificity for brain activity mapping. As the voxel size is reduced, an irregular magnetic fieldmap will emerge as a result of less local averaging, and will lead to abnormal fMRI signal evolution with respect to the image acquisition TE. In this article, we report this signal turbulence phenomenon observed in simulations of ultrahigh-spatial-resolution blood oxygenation level-dependent (BOLD) fMRI (voxel size of less than 50?×?50?×?50 µm³). We present a four-level coarse-to-fine multiresolution BOLD fMRI signal simulation. Based on the statistical histogram of an intravoxel fieldmap, we reformulate the intravoxel dephasing summation (a form of Riemann sum) into a new formula that is a discrete Fourier transformation of the intravoxel fieldmap histogram (a form of Lebesgue sum). We interpret the BOLD signal formation by relating its magnitude (phase) to the even (odd) symmetry of the fieldmap histogram. Based on multiresolution BOLD signal simulation, we find that the signal turbulence mainly emerges at the vessel boundary, and that there are only a few voxels (less than 10%) in an ultrahigh-resolution image that reveal turbulence in the form of sparse point noise. Our simulation also shows that, for typical human brain imaging of the cerebral cortex with millimeter resolution, TE?< 30 ms and B? ?=?3 T, we are unlikely to observe BOLD signal turbulence. Overall, the main causes of voxel signal turbulence include a high spatial resolution, high field, long TE and large vessel. PMID:22927163

  7. Performance of a low noise front-end ASIC for Si\\/CdTe detectors in Compton gamma-ray telescope

    Microsoft Academic Search

    Hiroyasu Tajima; Tatsuya Nakamoto; Takaaki Tanaka; Shingo Uno; Takefumi Mitani; Ed. Ce. Silva; Yasushi Fukazawa; Tuneyoshi Kamae; Grzegorz Madejski; Daniel Marlow; Kazuhiro Nakazawa; Masaharu Nomachi; Y. Okada; Tadayuki Takahashi

    2004-01-01

    Compton telescopes based on semiconductor technologies are being developed to explore the gamma-ray universe in an energy band 0.1-20 MeV, which is not well covered by the present or near-future gamma-ray telescopes. The key feature of such Compton telescopes is the high energy resolution that is crucial for high angular resolution and high background rejection capability. The energy resolution around

  8. Performance of a low noise front-end ASIC for Si\\/CdTe detectors in Compton gamma-ray telescope

    Microsoft Academic Search

    Hiroyasu Tajima; Tatsuya Nakamoto; Takaaki Tanaka; Shingo Uno; Takefumi Mitani; E. do Couto e Silva; Y. Fukazawa; T. Kamae; G. Madejski; D. Marlow; K. Nakazawa; M. Nomachi; Y. Okada; T. Takahashi

    2003-01-01

    Compton telescopes based on semiconductor technologies are being developed to explore the gamma-ray universe in an energy band 0.1-20 MeV, which is not well covered by the present or near-future gamma-ray telescopes. The key feature of such Compton telescopes is the high energy resolution that is crucial for high angular resolution and high background rejection capability. The energy resolution around

  9. Response of AGATA Segmented HPGe Detectors to Gamma Rays up to 15.1 MeV

    E-print Network

    F. C. L. Crespi; R. Avigo; F. Camera; S. Akkoyun; A. Atac; D. Bazzacco; M. Bellato; G. Benzoni; N. Blasi; D. Bortolato; S. Bottoni; A. Bracco; S. Brambilla; B. Bruyneel; S. Cerutia; M. Ciemala; S. Coelli; J. Eberth; C. Fanin; E. Farnea; A. Gadea; A. Giaz; A. Gottardo; H. Hess; M. Kmiecik; S. Leoni; A. Maj; D. Mengoni; C. Michelagnoli; B. Million; D. Montanari; L. Pellegri; F. Recchia; P. Reiter; S. Riboldi; C. A. Ur; V. Vandone; J. J. Valiente-Dobon; O. Wieland; A. Wiens; The AGATA Collaboration

    2012-09-06

    The response of AGATA segmented HPGe detectors to gamma rays in the energy range 2-15 MeV was measured. The 15.1 MeV gamma rays were produced using the reaction d(11B,ng)12C at Ebeam = 19.1 MeV, while gamma-rays between 2 to 9 MeV were produced using an Am-Be-Fe radioactive source. The energy resolution and linearity were studied and the energy-to-pulse-height conversion resulted to be linear within 0.05%. Experimental interaction multiplicity distributions are discussed and compared with the results of Geant4 simulations. It is shown that the application of gamma-ray tracking allows a suppression of background radiation following neutron capture by Ge nuclei. Finally the Doppler correction for the 15.1 MeV gamma line, performed using the position information extracted with Pulse-shape Analysis, is discussed.

  10. Design and performance of soft gamma-ray detector for NeXT mission

    SciTech Connect

    Tajima, H.; Kamae, T.; Madejski, G.; /KIPAC, Menlo Park; Takahashi, T.; Nakazawa, K.; Watanabe, S.; Mitani, T.; Tanaka, T.; /JAXA, Sagamihara; Fukazawa, Y.; /Hiroshima U.; Kataoka, J.; Ikagawa, T.; /Tokyo Inst. Tech.; Kokubun, M.; Makishima, K.; /Tokyo U.; Terada, Y.; /Wako, RIKEN; Nomachi, M.; /Osaka U.; Tashiro, M.; /Saitama U.

    2005-05-04

    The Soft Gamma-ray Detector (SGD) on board NeXT (Japanese future high energy astrophysics mission) is a Compton telescope with narrow field of view, which utilizes Compton kinematics to enhance its background rejection capabilities. It is realized as a hybrid semiconductor gamma-ray detector which consists of silicon and Cadmium Telluride (CdTe) detectors. It can detect photons in an energy band 0.05-1 MeV at a background level of 5 x 10{sup -7} counts/s/cm{sup 2}/keV; the silicon layers are required to improve the performance at a lower energy band (<0.3 MeV). Excellent energy resolution is the key feature of the SGD to achieve both high angular resolution and good background rejection capability. Its ability to measure gamma-ray polarization opens up a new window to study gamma-ray emission in the universe. We will present the development of key technologies to realize the SGD; high quality CdTe, low noise front-end VLSI and bump bonding technology. Energy resolutions of 1.7 keV (FWHM) for CdTe pixel detectors and 1.1 keV for silicon strip detectors have been measured. We also present the validation of Monte Carlo simulation used to evaluate the performance of the SGD.

  11. Design and Performance of Soft Gamma-ray Detector for NeXT Mission

    NASA Astrophysics Data System (ADS)

    Tajima, H.; Kamae, T.; Madejski, G.; Takahashi, T.; Nakazawa, K.; Watanabe, S.; Mitani, T.; Tanaka, T.; Fukazawa, Y.; Kataoka, J.; Ikagawa, T.; Kokubun, M.; Makishima, K.; Terada, Y.; Nomachi, M.; Tashiro, M.

    The Soft Gamma-ray Detector (SGD) on board NeXT (Japanese future high energy astrophysics mission) is a Compton telescope with narrow field of view, which utilizes Compton kinematics to enhance its background rejection capabilities. It is realized as a hybrid semiconductor gamma-ray detector which consists of silicon and Cadmium Telluride (CdTe) detectors. It can detect photons in an energy band 0.05-1 MeV at a background level of 5×10-7 counts/s/cm2/keV; the silicon layers are required to improve the performance at a lower energy band (<0.3 MeV). Excellent energy resolution is the key feature of the SGD to achieve both high angular resolution and good background rejection capability. Its ability to measure gamma-ray polarization opens up a new window to study gamma-ray emission in the universe. We will present the development of key technologies to realize the SGD; high quality CdTe, low noise front-end VLSI and bump bonding technology. Energy resolutions of 1.7 keV (FWHM) for CdTe pixel detectors and 1.1 keV for silicon strip detectors have been measured. We also present the validation of Monte Carlo simulation used to evaluate the performance of the SGD.

  12. The Gamma-ray Large Area Space Telescope and Gamma-Ray Bursts

    NASA Technical Reports Server (NTRS)

    McEnery, Julie; Ritz, Steve

    2006-01-01

    The Gamma-ray Large Area Telescope (GLAST) is a satellite-based observatory to study the high energy gamma-ray sky. The main instrument on GLAST, the Large Area Telescope (LAT) is a pair-conversion telescope that will survey the sky from 20 MeV to greater than 300 GeV. With the GLAST launch in 2007, the LAT will open a new and important window on a wide variety of high energy phenomena, including supermassive black holes and active galactic nuclei, gamma-ray bursts, supernova remnants and cosmic ray acceleration and dark matter. A second instrument, the GLAST Burst Monitor (GBM), greatly enhances GLAST s capability to study GRB by providing important spectral and timing information in the 10 keV to 30 MeV range. We describe how the instruments, spacecraft and ground system work together to provide observations of gamma-ray bursts from 8 keV - 300 GeV and to provide rapid notification of bursts to the wider gamma-ray burst community.

  13. HIGH-ENERGY GAMMA-RAY AFTERGLOWS FROM LOW-LUMINOSITY GAMMA-RAY BURSTS

    SciTech Connect

    He Haoning; Wang Xiangyu; Yu Yunwei [Department of Astronomy, Nanjing University, Nanjing 210093 (China); Meszaros, Peter [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States)

    2009-12-01

    The observations of gamma-ray bursts (GRBs) such as 980425, 031203 and 060218, with luminosities much lower than those of other classic bursts, lead to the definition of a new class of GRBs-LL-GRBs. The nature of the outflow responsible for them is not yet clear. Two scenarios have been suggested: one is the conventional relativistic outflow with initial Lorentz factor of order of GAMMA{sub 0} approx> 10 and the other is a trans-relativistic outflow with GAMMA{sub 0} approx = 1-2. Here, we compare the high-energy gamma-ray afterglow emission from these two different models, taking into account both synchrotron self-inverse Compton (SSC) scattering and the external inverse Compton scattering due to photons from the cooling supernova or hypernova envelope (SNIC). We find that the conventional relativistic outflow model predicts a relatively high gamma-ray flux from SSC at early times (<10{sup 4} s for typical parameters) with a rapidly decaying light curve, while in the trans-relativistic outflow model, one would expect a much flatter light curve of high-energy gamma-ray emission at early times, which could be dominated by both the SSC emission and the SNIC emission, depending on the properties of the underlying supernova and the shock parameter epsilon{sub e} and epsilon{sub B}. The Fermi Gamma-ray Space Telescope should be able to distinguish between the two models in the future.

  14. Geolocation of Terrestrial Gamma Ray Flashes in Gamma Rays Using the Fermi Large Area Telescope

    NASA Astrophysics Data System (ADS)

    Grove, J. Eric; Schaal, Meagan M.; Chekhtman, Alexandre; Briggs, Michael S.; Connaughton, Valerie; Holzworth, Robert H.; Heckman, Stan; Cummer, Steven A.

    2015-04-01

    We derive geolocations of bright Terrestrial Gamma ray Flashes (TGFs) directly in gamma rays using the Fermi Large Area Telescope (LAT) and compare with geolocations given by LF and VLF radio networks intended to study lightning discharges. We show that the Fermi LAT, which was designed to perform an imaging survey of the high-energy gamma ray sky, can geolocate bright TGFs in favorable geometries with accuracies <100 km, a factor of a few larger than radio geolocation accuracies. A large fraction of TGFs appear to be temporally coincident with radio pulses detected by lightning geolocation network. Recent work by Cummer et al. (2011), Connaughton et al. (2013), and Dwyer and Cummer (2013) strongly suggests that the pulse of relativistic electrons that generates the gamma rays via bremsstrahlung also generates the radio signal via its secondary ionization electrons. Our analysis confirms this picture by establishing that the radio and gamma ray signals are indeed temporally and spatially coincident. Portions of this work were performed at NRL under sponsorship of NASA.

  15. A Link between Prompt Optical and Prompt Gamma-Ray Emission in Gamma-Ray Bursts

    E-print Network

    Vestrand, W T; Wren, J A; Fenimore, E E; Sakamoto, T; White, R R; Casperson, D; Davis, H; Evans, S; Galassi, M; McGowan, K E; Schier, J A; Asa, J W; Barthelmy, S D; Cummings, J R; Gehrels, N; Hullinger, D; Krimm, H A; Markwardt, C B; McLean, K; Palmer, D; Tüller, J

    2005-01-01

    The prompt optical emission that arrives with gamma-rays from a cosmic gamma-ray burst (GRB) is a signature of the engine powering the burst, the properties of the ultra-relativistic ejecta of the explosion, and the ejecta's interactions with the surroundings. Until now, only GRB 990123 had been detected at optical wavelengths during the burst phase. Its prompt optical emission was variable and uncorrelated with the prompt gamma-ray emission, suggesting that the optical emission was generated by a reverse shock arising from the ejecta's collision with the surrounding material. Here we report prompt optical emission from GRB 041219a. It is variable and correlated with the prompt gamma-rays, indicating a common origin for the optical light and the gamma-rays. Within the context of the standard fireball model of GRBs, we attribute this new optical component to internal shocks driven into the burst ejecta by variations of the inner engine. The correlated optical emission is a direct probe of the jet isolated from...

  16. A Link between Prompt Optical and Prompt Gamma-Ray Emission in Gamma-Ray Bursts

    E-print Network

    W. T. Vestrand; P. R. Wozniak; J. A. Wren; E. E. Fenimore; T. Sakamoto; R. R. White; D. Casperson; H. Davis; S. Evans; M. Galassi; K. E. McGowan; J. A. Schier; J. W. Asa; S. D. Barthelmy; J. R. Cummings; N. Gehrels; D. Hullinger; H. A. Krimm; C. B. Markwardt; K. McLean; D. Palmer; A. Parsons; J. Tueller

    2005-04-05

    The prompt optical emission that arrives with gamma-rays from a cosmic gamma-ray burst (GRB) is a signature of the engine powering the burst, the properties of the ultra-relativistic ejecta of the explosion, and the ejecta's interactions with the surroundings. Until now, only GRB 990123 had been detected at optical wavelengths during the burst phase. Its prompt optical emission was variable and uncorrelated with the prompt gamma-ray emission, suggesting that the optical emission was generated by a reverse shock arising from the ejecta's collision with the surrounding material. Here we report prompt optical emission from GRB 041219a. It is variable and correlated with the prompt gamma-rays, indicating a common origin for the optical light and the gamma-rays. Within the context of the standard fireball model of GRBs, we attribute this new optical component to internal shocks driven into the burst ejecta by variations of the inner engine. The correlated optical emission is a direct probe of the jet isolated from the medium. The timing of the uncorrelated optical emission is strongly dependent on the nature of the medium.

  17. Evidence of outer retinal changes in glaucoma patients as revealed by ultrahigh-resolution in vivo retinal imaging

    PubMed Central

    Choi, Stacey S; Zawadzki, Robert J; Lim, Michele C; Brandt, James D; Keltner, John L; Doble, Nathan; Werner, John S

    2010-01-01

    Aims It is well established that glaucoma results in a thinning of the inner retina. To investigate whether the outer retina is also involved, ultrahigh-resolution retinal imaging techniques were utilised. Methods Eyes from 10 glaucoma patients (25–78 years old), were imaged using three research-grade instruments: (1) ultrahigh-resolution Fourier-domain optical coherence tomography (UHR-FD-OCT), (2) adaptive optics (AO) UHR-FD-OCT and (3) AO-flood illuminated fundus camera (AO-FC). UHR-FD-OCT and AO-UHR-FD-OCT B-scans were examined for any abnormalities in the retinal layers. On some patients, cone density measurements were made from the AO-FC en face images. Correlations between retinal structure and visual sensitivity were measured by Humphrey visual-field (VF) testing made at the corresponding retinal locations. Results All three in vivo imaging modalities revealed evidence of outer retinal changes along with the expected thinning of the inner retina in glaucomatous eyes with VF loss. AO-UHR-FD-OCT images identified the exact location of structural changes within the cone photoreceptor layer with the AO-FC en face images showing dark areas in the cone mosaic at the same retinal locations with reduced visual sensitivity. Conclusion Losses in cone density along with expected inner retinal changes were demonstrated in well-characterised glaucoma patients with VF loss. PMID:20956277

  18. Diagnosing ICF gamma-ray physics

    SciTech Connect

    Herrmann, Hans W [Los Alamos National Laboratory; Kim, Y H [Los Alamos National Laboratory; Mc Evoy, A [Los Alamos National Laboratory; Young, C S [Los Alamos National Laboratory; Mack, J M [Los Alamos National Laboratory; Hoffman, N [Los Alamos National Laboratory; Wilson, D C [Los Alamos National Laboratory; Langenbrunner, J R [Los Alamos National Laboratory; Evans, S [Los Alamos National Laboratory; Sedillo, T [Los Alamos National Laboratory; Batha, S H [Los Alamos National Laboratory; Dauffy, L [LLNL; Stoeffl, W [LLNL; Malone, R [Los Alamos National Laboratory; Kaufman, M I [Los Alamos National Laboratory; Cox, B C [Los Alamos National Laboratory; Tunnel, T W [Los Alamos National Laboratory; Miller, E K [NSTEC/SB; Ali, Z A [NSREC/LIVERMORE; Horsfield, C J [AWE; Rubery, M [AWE

    2010-01-01

    Gamma rays produced in an ICF environment open up a host of physics opportunities we are just beginning to explore. A branch of the DT fusion reaction, with a branching ratio on the order of 2e-5 {gamma}/n, produces 16.7 MeV {gamma}-rays. These {gamma}-rays provide a direct measure of fusion reaction rate (unlike x-rays) without being compromised by Doppler spreading (unlike neutrons). Reaction-rate history measurements, such as nuclear bang time and burn width, are fundamental quantities that will be used to optimize ignition on the National Ignition Facility (NIF). Gas Cherenkov Detectors (GCD) that convert fusion {gamma}-rays to UV/visible Cherenkov photons for collection by fast optical recording systems established their usefulness in illuminating ICF physics in several experimental campaigns at OMEGA. Demonstrated absolute timing calibrations allow bang time measurements with accuracy better than 30 ps. System impulse response better than 95 ps fwhm have been made possible by the combination of low temporal dispersion GCDs, ultra-fast microchannel-plate photomultiplier tubes (PMT), and high-bandwidth Mach Zehnder fiber optic data links and digitizers, resulting in burn width measurement accuracy better than 10ps. Inherent variable energy-thresholding capability allows use of GCDs as {gamma}-ray spectrometers to explore other interesting nuclear processes. Recent measurements of the 4.44 MeV {sup 12}C(n,n{prime}) {gamma}-rays produced as 14.1 MeV DT fusion neutrons pass through plastic capsules is paving the way for a new CH ablator areal density measurement. Insertion of various neutron target materials near target chamber center (TCC) producing secondary, neutron-induced {gamma}y-rays are being used to study other nuclear interactions and as in-situ sources to calibrate detector response and DT branching ratio. NIF Gamma Reaction History (GRH) diagnostics, based on the GCD concept, are now being developed based on optimization of sensitivity, bandwidth, dynamic range, cost, and NIF-specific logistics, requirements and extreme radiation environment. Implementation will occur in two phases: (1) four PMT-based channels mounted to the outside of the target chamber at {approx}6m from TCC (GRH-6m) for the 3e13-3e16 DT neutron yield range expected during the early ignition-tuning campaigns; and (2) several channels located just inside the target bay shield wall at 15 m from TCC (GRH-15m) with optical paths leading through the cement shield wall to well-shielded streak cameras and PMTs for the 1e16-1e20 yield range expected during the DT ignition campaign. Multiple channels at each phase will allow for increased redundancy, reliability, accuracy and flexibility. This suite of diagnostics will make possible exploration of interesting {gamma}-ray physics well beyond the ignition campaign.

  19. In VivoFunctional Imaging of Intrinsic Scattering Changes in the Human Retina with High-speed Ultrahigh Resolution OCT

    PubMed Central

    Srinivasan, V. J.; Chen, Y.; Duker, J. S.; Fujimoto, J. G.

    2009-01-01

    Non-invasive methods of probing retinal function are of interest for the early detection of retinal disease. While retinal function is traditionally directly measured with the electroretinogram (ERG), recently functional optical imaging of the retina has been demonstrated. In this manuscript, stimulus-induced, intrinsic optical scattering changes in the human retina are measured in vivo with high-speed, ultrahigh resolution optical coherence tomography (OCT) operating at 50,000 axial scans per second and ?3.3 micron axial resolution. A stimulus and measurement protocol that enables measurement of functional OCT retinal signals is described. OCT signal changes in the photoreceptors are demonstrated. Two distinct responses having different temporal and spatial properties are reported. These results are discussed in the context of optical intrinsic signals measured previously in the retina by fundus imaging and scanning laser ophthalmoscopy. Finally, challenges associated with in vivo functional retinal imaging in human subjects are discussed. PMID:19259228

  20. GAMMA RAYS FROM STAR FORMATION IN CLUSTERS OF GALAXIES

    SciTech Connect

    Storm, Emma M.; Jeltema, Tesla E.; Profumo, Stefano [Department of Physics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)

    2012-08-20

    Star formation in galaxies is observed to be associated with gamma-ray emission, presumably from non-thermal processes connected to the acceleration of cosmic-ray nuclei and electrons. The detection of gamma rays from starburst galaxies by the Fermi Large Area Telescope (LAT) has allowed the determination of a functional relationship between star formation rate and gamma-ray luminosity. Since star formation is known to scale with total infrared (8-1000 {mu}m) and radio (1.4 GHz) luminosity, the observed infrared and radio emission from a star-forming galaxy can be used to quantitatively infer the galaxy's gamma-ray luminosity. Similarly, star-forming galaxies within galaxy clusters allow us to derive lower limits on the gamma-ray emission from clusters, which have not yet been conclusively detected in gamma rays. In this study, we apply the functional relationships between gamma-ray luminosity and radio and IR luminosities of galaxies derived by the Fermi Collaboration to a sample of the best candidate galaxy clusters for detection in gamma rays in order to place lower limits on the gamma-ray emission associated with star formation in galaxy clusters. We find that several clusters have predicted gamma-ray emission from star formation that are within an order of magnitude of the upper limits derived in Ackermann et al. based on non-detection by Fermi-LAT. Given the current gamma-ray limits, star formation likely plays a significant role in the gamma-ray emission in some clusters, especially those with cool cores. We predict that both Fermi-LAT over the course of its lifetime and the future Cerenkov Telescope Array will be able to detect gamma-ray emission from star-forming galaxies in clusters.

  1. Ultra-High Resolution Four Dimension Imaging Across the Earth Sciences (Invited)

    NASA Astrophysics Data System (ADS)

    Bawden, G. W.

    2010-12-01

    Geodesy in the 21st century is embracing two distinct areas of research: “Geodetic Science” — the scientific discipline that deals with the measurement and representation of the kinematics and dynamics of the Earth’s size, shape, orientation, and gravity field; and “Geodetic Applications”— the wide range of applied geodetic techniques contributing to research not only within the geodetic community, but also across the broad natural science spectrum including, hazards, hydrology, ecosystems, geomorphology, and climate change. Ground-based LiDAR, known as Tripod/Terrestrial LiDAR (T-LiDAR) and Terrestrial Laser Scanning, is a rapidly evolving emergent ‘geodetic science’ technology that is also a forefront ‘geodetic application’ tool that will allow researchers from multiple disciplines to address questions that were unanswerable only 5 years ago. T-LiDAR has unsurpassed ability to collect ultra-high resolution detailed (cm to sub-centimeter) 3D and 4D point cloud measurements that are on scales ranging from individual tree branches and small outcrops to landscapes and glaciers upwards of a few square kilometers in extent. T-LiDAR is ushering in a new era of geodetically driven mesoscopic scale science with true 3D site characterization and 4D change detection. T-LiDAR has made it possible to image 4D postseismic surface change through tracking how elements on the land surface move over time; fence post, bridges, buildings, trees, and the unique land surface morphology elements are now becoming tractable benchmark-like objects whose 3D positions change. Similar approaches have been applied to a wide range of applications including landslides, rock falls, glacial motion, fissure growth, breakwater/structural stability, and mine collapses. T-LiDAR can image how basins respond to aeolian and fluvial processes following major fires through detailed 4D time-series that show how sediment and material move through a denuded landscape via dry ravel, fluvial, slumping, and debris flow processes. It is now possible to track material volume as a function of basin slope, rainfall intensity and transport mode through detailed geomorphologic analysis and repeat laser surveys. Similar approaches also are being used to track the ice mass-balance during glacier retreat, and spatially variable snow mass balance as a function of solar radiation on north vs. south facing slopes. Furthermore, T-LiDAR is making it possible to accurately and non-destructively measure biomass using a methodology that preserves the target while providing a wealth of information about the target in its surrounding ecosystem. Detailed laser scans of excavated tree root systems are providing detailed biomorphic information that relates surface slope, solar angle, and water source with root growth as a function of depth below the land surface and distance from the tree. The analysis of dense point cloud data has necessitated the development of new 3D workspace environments such that data quality can be assess and the science/applications objectives can be achieved. This presentation will discuss geodetic science applications of ground based T-LiDAR spanning the broad range of earth science. A stereo 3D projection system will be used to visualize specific science elements and 3D glasses will be provided.

  2. Prospects for Dark Matter Measurements with the Advanced Gamma Ray Imaging System (AGIS)

    NASA Astrophysics Data System (ADS)

    Buckley, James

    2009-05-01

    AGIS, a concept for a future gamma-ray observatory consisting of an array of 50 atmospheric Cherenkov telescopes, would provide a powerful new tool for determining the nature of dark matter and its role in structure formation in the universe. The advent of more sensitive direct detection experiments, the launch of Fermi and the startup of the LHC make the near future an exciting time for dark matter searches. Indirect measurements of cosmic-ray electrons may already provide a hint of dark matter in our local halo. However, gamma-ray measurements will provide the only means for mapping the dark matter in the halo of our galaxy and other galaxies. In addition, the spectrum of gamma-rays (either direct annihilation to lines or continuum emission from other annihilation channels) will be imprinted with the mass of the dark matter particle, and the particular annihilation channels providing key measurements needed to identify the dark matter particle. While current gamma-ray instruments fall short of the generic sensitivity required to measure the dark matter signal from any sources other than the (confused) region around the Galactic center, we show that the planned AGIS array will have the angular resolution, energy resolution, low threshold energy and large effective area required to detect emission from dark matter annihilation in Galactic substructure or nearby Dwarf spheroidal galaxies.

  3. LaBr3:Ce scintillators for gamma-ray spectroscopy

    Microsoft Academic Search

    K. S. Shah; J. Glodo; M. Klugerman; W. W. Moses; S. E. Derenzo; M. J. Weber

    2003-01-01

    In this paper, we report on a relatively new scintillator - LaBr3:Ce for gamma-ray spectroscopy. Crystals of this scintillator have been grown using Bridgman process. This material when doped with cerium has high light output (?60000 photons\\/MeV) and fast principal decay constant (?25 ns). Furthermore, it shows excellent energy resolution for ?-ray detection. Energy resolution of 3.2% (FWHM) has been

  4. Gamma-Ray Bursts: Sans Second Postulate

    NASA Astrophysics Data System (ADS)

    Fritzius, R.

    In 1950, Albert Einstein intimated to Robert Shankland that in the years prior to 1905 he had considered using an emission theory [similar to that which Swiss Physicist Walter Ritz propounded in 1908.] In Ritz's theory the velocity of light with respect to an observer is c + v, where c is the velocity of light with respect to its source, and v is the relative velocity between the source and the observer. Einstein abandoned the c+v approach because he could think of no form of differential equation that could have solutions representing waves whose velocity depended [in part] on the motion of the source. For binary stars the c + v approach would predict "observed" phase relations for light arriving from different parts of a given component's orbit, such that the observed light would be, according to Einstein, all badly "mixed up" and might even "back up on itself." In 1913, the Dutch astronomer, Willem de Sitter, urged abandonment of Ritz's c + v relativity by showing that binary stars failed to provide evidence of the "mixed up" light phasing. (Apparent departures from Keplerian motion, including seeing the same star on opposite sides of its orbit at the same time [at the appropriate observer distance] were predicted by Ritz's c +v relativity.) In 1987, Vladimir Sekerin, at Tomsk University, announced that de Sitter failed to address the fact that for the observer-distances required to produce the star-in-two-places-at-once phenomenon, the angular diameter of the binary component's orbit (from the observer's viewpoint) would be too small for our atmospherically limited earth-borne "seeing" to resolve the images. In essence, de Sitter did not "de throne" Ritz. Sekerin then showed how de Sitter's binary star scenario could be interpreted as evidence "for" the Ritzian theory. (Two images briefly on top of one another will be briefly twice as bright as a single image.) He used de Sitter's equations to analog compute light curves of a number of different kinds variable stars starting with Cepheid variables. The author cleared up a critical flaw in Sekerin's reasoning regarding the computed value of the periodic spectral variations involved, and created software simulations of binary star orbits which produce the light curves and spectral variations predicted by the Ritzian theory. (Constant speed-of-light simulations do not produce the variations.) A limited number of these simulations including some for various kinds of Gamma-Ray Bursts (GRBs) are to be shown as part of this presentation. High-resolution spectral studies of variable stars, including GRBs, may eventually help us decide whether or not Ritz was as wrong as is currently generally thought. Further information on this topic is available at: http://www.ebicom.net/~rsf1/binaries.htm

  5. Radioactive pollutant determinations using gamma-ray spectroscopy.

    PubMed

    Eldridge, J S; Oakes, T W; Pruitt, M E

    1978-06-01

    Qualitative and quantitative determination of radionuclide contamination in environmental samples is often complicated by the presence of uranium- and thorium-series radioelements as well as 40K. High resolution gamma-ray spectroscopy with lithium-drifted germanium detectors provides a method for the determination of man-made radio-nuclide contaminants in many matrices with a minimum of chemical separation. Methods have been studied for increasing the efficiency of such determinations by using large samples in reentrant beakers ("Merinelli beakers") and small samples inside the well of a recently developed Ge(Li) well detector. Specific examples for the determination of 129I(16 m.y. half-life) in the well detector and recent fall-out in grass samples are presented. PMID:685825

  6. Gamma-ray computed tomography to characterize soil surface sealing.

    PubMed

    Pires, Luiz F; de Macedo, Jose R; de Souza, Manoel D; Bacchi, Osny O S; Reichardt, Klaus

    2002-09-01

    The application of sewage sludge as a fertilizer on soils may cause compacted surface layers (surface sealing), which can promote changes on soil physical properties. The objective of this work was to study the use of gamma-ray computed tomography, as a diagnostic tool for the evaluation of this sealing process through the measurement of soil bulk density distribution of the soil surface layer of samples subjected to sewage sludge application. Tomographic images were taken with a first generation tomograph with a resolution of 1 mm. The image analysis opened the possibility to obtain soil bulk density profiles and average soil bulk densities of the surface layer and to detect the presence of soil surface sealing. The sealing crust thickness was estimated to be in the range of 2-4 mm. PMID:12201145

  7. Application of HEALpix Pixelization to Gamma-ray Data

    NASA Astrophysics Data System (ADS)

    Burnett, T. H.; Lesnick, B.; Roth, M.

    2007-07-01

    The HEALpix scheme for tessellating the sky is a natural way to represent all-sky data that is naturally binned in sky coordinates. Gamma-ray data are collected and saved as individual photons, and usually analyzed as such. We present a summary data representation that is compact, saves energy information, and is consistent with the energy-dependent resolution. We take advantage of the equal-area, hierarchical characteristics of the HEALpix representation by relating pixel size to energy. The data set is a sparse list of variable-size pixels, arranged to group regions of the sky. Thus numerous low-energy photons share pixels, while rare high-energy photons often are represented by single pixels. Of course, time variation is lost. We will show how this is used for generating sky pictures, efficiently finding and localizing point sources, and even construction WMAP-like angular power spectra.

  8. Fermi gamma-ray imaging of a radio galaxy.

    PubMed

    Abdo, A A; Ackermann, M; Ajello, M; Atwood, W B; 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; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cavazzuti, E; Cecchi, C; Celik, O; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Colafrancesco, S; Cominsky, L R; Conrad, J; Costamante, L; Cutini, S; Davis, D S; Dermer, C D; de Angelis, A; de Palma, F; Digel, S W; do Couto e Silva, E; Drell, P S; Dubois, R; Dumora, D; Farnier, C; Favuzzi, C; Fegan, S J; Finke, J; Focke, W B; Fortin, P; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Georganopoulos, M; Germani, S; Giebels, B; Giglietto, N; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Grenier, I A; Grove, J E; Guillemot, L; Guiriec, S; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Hughes, R E; Jackson, M S; Jóhannesson, G; Johnson, A S; Johnson, T J; Johnson, W N; Kamae, T; Katagiri, H; Kataoka, J; Kawai, N; Kerr, M; Knödlseder, J; Kocian, M L; 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; 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; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Piron, F; Porter, T A; Rainò, S; Rando, R; Razzano, M; Razzaque, S; 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; Sambruna, R; 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; Starck, J-L; Stawarz, ?; Strickman, M S; Suson, D J; Tajima, H; Takahashi, H; Takahashi, T; 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; Waite, A P; Wallace, E; Wang, P; Winer, B L; Wood, K S; Ylinen, T; Ziegler, M; Hardcastle, M J; Kazanas, D

    2010-05-01

    The Fermi Gamma-ray Space Telescope has detected the gamma-ray glow emanating from the giant radio lobes of the radio galaxy Centaurus A. The resolved gamma-ray image shows the lobes clearly separated from the central active source. In contrast to all other active galaxies detected so far in high-energy gamma-rays, the lobe flux constitutes a considerable portion (greater than one-half) of the total source emission. The gamma-ray emission from the lobes is interpreted as inverse Compton-scattered relic radiation from the cosmic microwave background, with additional contribution at higher energies from the infrared-to-optical extragalactic background light. These measurements provide gamma-ray constraints on the magnetic field and particle energy content in radio galaxy lobes, as well as a promising method to probe the cosmic relic photon fields. PMID:20360067

  9. A model of the diffuse galactic gamma ray emission

    NASA Technical Reports Server (NTRS)

    Sreekumar, Parameswaran

    1990-01-01

    The galaxy was observed to be a source of high energy gamma rays as shown by the two successful satellite experiments, SAS-2 and COS-B. It is generally understood that these diffuse gamma rays result from interactions between energetic cosmic rays and interstellar gas. This work makes use of the most recent data on the distribution of atomic and molecular hydrogen in the galaxy along with new estimates of gamma ray production functions to model the diffuse galactic gamma ray emission. The model allows various spatial distributions for cosmic rays in the Galaxy including non-axisymmetric ones. In the light of the expected data from EGRET (Energetic Gamma-Ray Experiment Telescope), an improved model of cosmic ray-matter-gamma ray interaction will provide new insights into the distribution of cosmic rays and the strength of its coupling to matter.

  10. Highlights of GeV Gamma-Ray Astronomy

    NASA Technical Reports Server (NTRS)

    Thompson, David J.

    2010-01-01

    Because high-energy gamma rays are primarily produced by high-energy particle interactions, the gamma-ray survey of the sky by the Fermi Gamma-ray Space Telescope offers a view of sites of cosmic ray production and interactions. Gamma-ray bursts, pulsars, pulsar wind nebulae, binary sources, and Active Galactic Nuclei are all phenomena that reveal particle acceleration through their gamma-ray emission. Diffuse Galactic gamma radiation, Solar System gamma-ray sources, and energetic radiation from supernova remnants are likely tracers of high-energy particle interactions with matter and photon fields. This paper will present a broad overview of the constantly changing sky seen with the Large Area Telescope (LAT) on the Fermi spacecraft.

  11. High Energy Observations of X-Ray Binaries and Gamma-Ray Blazars

    NASA Technical Reports Server (NTRS)

    Vestrand, W. Thomas

    1999-01-01

    The report discusses the CGRO observation of X-ray binary systems and studies of gamma-ray blasars. Numerous authors have suggested mechanisms for particle acceleration within X-Ray Binary (XRB) systems. Among the acceleration mechanisms that have been applied are pulsar acceleration, shock acceleration at an accretion shock front, shock acceleration at a pulsar wind termination shock, plasma turbulence excited by the accretion flow, and a number of electrodynamic mechanisms. There are therefore many mechanisms which are capable of generating very energetic particles in the XRB environment. If the reports of TeV/PeV gamma-ray generation in XRBs are correct, then one can show that the accelerated particles must be hadrons and that the most likely gamma-ray production mechanism is the decay of collisionally-produced (or photoproduced) neutral pions. At these ultra-high energies, the emission is so strongly beamed that the target conditions are constrained by the requirement that the column depth be large enough to efficiently generate gamma-rays, but not so large that the gamma-rays are absorbed. These constraints naturally lead to models that explain the periodic, narrow duty-cycle pulses observed at TeV/PeV energies as arising from interactions with, either, the atmosphere of the binary companion, an accretion column, or an accretion disk. The production of these TeV/PeV gamma-rays by the decay of pions from "leading isobars" must also be accompanied by a more isotropic emission component in the EGRET energy band from the decay of slower pions (i.e. the "pionization" component). Since the attenuation of 35 MeV-1 GeV photons by photon-photon pair production is not likely to be significant in most XRBs, the TeV/PeV reports therefore strongly suggest sporadic emission in the EGRET energy band. One of the key unresolved issues for understanding AGN is the relationship between XBLs and RBLs.To test the "reunification" hypothesis, authors conducted a multiwavelength campaign during Cycle 7 of the CGRO observing program. The analysis of the cycle 4 through cycle 6 CGRO measurements was completed. Two previously unknown EGRET sources was discovered.

  12. Classification of Fermi Gamma-RAY Bursts

    E-print Network

    Horvath, I; Hakkila, J; Bagoly, Z; Preece, R D

    2015-01-01

    The Fermi GBM Catalog has been recently published. Previous classification analyses of the BATSE, RHESSI, BeppoSAX, and Swift databases found three types of gamma-ray bursts. Now we analyzed the GBM catalog to classify the GRBs. PCA and Multiclustering analysis revealed three groups. Validation of these groups, in terms of the observed variables, shows that one of the groups coincides with the short GRBs. The other two groups split the long class into a bright and dim part, as defined by the peak flux. Additional analysis is needed to determine whether this splitting is only a mathematical byproduct of the analysis or has some real physical meaning.

  13. Directions in gamma-ray spectroscopy

    NASA Technical Reports Server (NTRS)

    Gehrels, Neil; Candey, Robert M.

    1990-01-01

    Current and future instrumentation for gamma-ray spectroscopy in the spectral range from 10 keV to 10 MeV is described. New technologies for Germanium (Ge) spectrometers and emerging detector technologies are highlighted. Scientific objectives are considered, with emphasis on capabilities beyond those of the Nuclear Astrophysics Explorer (NAE). A list of instrument requirements is given. Technologies under development for an NAE-era spectrometer are presented. Spectrometers beyond NAE and other types of future technologies are discussed, and a partial list of current and future spectrometers is provided.

  14. Gamma Ray Bursts: back to the blackboard

    E-print Network

    Lyutikov, Maxim

    2009-01-01

    Exceptional observational breakthroughs in the field of Gamma Ray Burst research are not paralleled by theoretical advances. In this review, based on the introductory talk given at the "The Shocking Universe" meeting, I argue that any present day model of GRBs, especially of Short type, is grossly incomplete. I will highlight various contradictions with observations that many models face and briefly mention a number of ideas that might or might not work. In particular, I will discuss (i) a possibility that early X-ray afterglows are coming from internal dissipation, and not from the forwards shock; (ii) that prompt radiation is beamed in the outflow frame.

  15. Observational Review of Gamma-Ray Bursts

    NASA Technical Reports Server (NTRS)

    Fishman, Gerald J.

    1999-01-01

    The observed gamma-ray temporal, spectral, intensity and spatial distribution characteristics of GRBs, primarily from data obtained from the Compton Observatory, will be described. The talk will concentrate on recent studies of burst properties, correlations of GRB parameters and other statistical studies that have only recently come to light with the unprecedented sample of over two thousand GRBs, along with some mention of studies in progress by members of the BATSE team. Recent studies of possible observational biases, un-triggered GRBs and threshold calculations for BATSE will also be described.

  16. Gamma Ray Bursts: Explaining the Universe's Biggest Bangs

    NSDL National Science Digital Library

    This radio broadcast discusses research into gamma ray bursts, the largest explosions in the universe. Topics include the SWIFT satellite mission and discoveries; the immense energy output of a gamma ray burst, and the causes of long and short gamma ray bursts (long bursts caused by core collapse into a black hole, and the short bursts from binary stellar system mergers, such as a neutron star colliding with a black hole). The broadcast is 28 minutes and 50 seconds in length.

  17. Factors influencing in situ gamma-ray measurements

    Microsoft Academic Search

    E. H. Loonstra; F. M. van Egmond

    2009-01-01

    Introduction In situ passive gamma-ray sensors are very well suitable for mapping physical soil properties. In order to make a qualitative sound soil map, high quality input parameters for calibration are required. This paper will focus on the factors that affect the output of in situ passive gamma-ray sensors, the primary source, soil, not taken into account. Factors The gamma-ray

  18. The Gamma-ray Large Area Space Telescope (GLAST) Mission

    Microsoft Academic Search

    Steven M. Ritz; P. F. Michelson; C. Meegan; J. Grindlay

    2007-01-01

    The Gamma-ray Large Area Space Telescope, GLAST, is a mission to measure the cosmic gamma-ray flux in the energy range 20 MeV to >300; GeV, with supporting measurements for gamma-ray bursts from 8 keV to 30 MeV. The very large field of view will make it possible to observe 20% of the sky at any instant, and the entire sky

  19. The Gamma-ray Large Area Space Telescope (GLAST) Mission

    Microsoft Academic Search

    S. Ritz; J. Grindlay; C. Meegan; P. F. Michelson

    2005-01-01

    The Gamma-ray Large Area Space Telescope, GLAST, is a mission under construction to measure the cosmic gamma-ray flux in the energy range 20 MeV to >300 GeV, with supporting measurements for gamma-ray bursts from 10 keV to 25 MeV. With its launch in 2007, GLAST will open a new and important window on a wide variety of high-energy phenomena, including

  20. The Gamma-ray Large Area Space Telescope (GLAST) Mission

    Microsoft Academic Search

    Steven M. Ritz; P. F. Michelson; C. Meegan; J. E. Grindlay

    2006-01-01

    The Gamma-ray Large Area Space Telescope, GLAST, is a mission to measure the cosmic gamma-ray flux in the energy range 20 MeV to >300 GeV, with supporting measurements for gamma-ray bursts from 10 keV to 25 MeV. With its launch in 2007, GLAST will open a new and important window on a wide variety of phenomena, including black holes and