A fast, high light output scintillator for gamma ray and neutron detection. Fifth Semi-Annual Report

International Nuclear Information System (INIS)

Entine, Gerald; Kanai, S.; Shah, M.S.; Leonard Cirignano, M.S.; Jarek Glodo; Van Loef, Edgar V.

2003-01-01

In view of the attractive properties of RbGd2Br7:Ce for gamma-ray and thermal neutron detection, and the lack of larger volume crystals, the goal of the Phase I project was to perform a rigorous investigation of the crystal growth of this exciting material and explore its capabilities for gamma-ray and thermal neutron detection. The Phase I research was very successful. All technical objectives were met and in many cases exceeded expectations. We were able to produce large (>1 cm3) RbGd2Br7:Ce crystals with excellent scintillation properties and demonstrated the possibility to detect thermal neutrons. As far as we are aware, our Phase I experiment was the first to demonstrate thermal neutron detection with RbGd2Br7:Ce. Clearly, the feasibility of the proposed research was adequately proven. The Phase II research builds on the successful results obtained during Phase I. Phase II will initially focus on optimizing the RbGd2Br7:Ce growth process to produce high quality, larger volume RbGd2Br7:Ce crystals. We will continue to use the versatile Bridgman technique. During this process, crystal growth parameters will be adjusted for optimal growth conditions. Our goal is to produce high quality RbGd2Br7:Ce crystals of size 1 inch x 1 inch x 1 inch (∼16 cm3). We will work on packaging aspects that allow efficient light collection and prevent crystal degradation. We will study and measure emission spectra, light yield, scintillation decay, energy and time resolution. The effects of variation in Ce concentration on the scintillation properties of RbGd2Br7:Ce will be examined in detail. Comprehensive gamma-ray spectroscopic and imaging studies will be conducted. Also, optimization of RbGd2Br7:Ce for thermal neutron detection will be addressed. Our initial studies will determine the optimal geometry of the RbGd2Br7:Ce crystals for neutron detection. For thermal neutron detection experiments, we will produce large area, thin samples in order to minimize gamma-ray sensitivity

Cosmic very high-energy {gamma}-rays

Energy Technology Data Exchange (ETDEWEB)

Plaga, R. [Max-Planck-Institut fur Physik, Muenchen (Germany)

1998-12-31

The article gives a brief overview, aimed at nonspecialists, about the goals and selected recent results of the detection of very-high energy {gamma}-rays (energies above 100 GeV) with ground based detectors. The stress is on the physics questions, specially the origin of Galactic Cosmic Rays and the emission of TeV {gamma}-radiation from active galaxies. Moreover some particle-physics questions which are addressed in this area are discussed.

Very high energy gamma-ray astronomy

International Nuclear Information System (INIS)

Weekes, T.C.

1988-01-01

Current interest in gamma-ray astronomy at energies above 100 GeV comes from the identification of Cygnus X-3 and other X-ray binaries as sources. In addition there are reports of emission from radio pulsars and a variety of other objects. The statistical significance of many of the observations is not high and many reported effects await confirmation, but there are a sufficient number of independent reports that very high energy gamma-ray astronomy must now be considered to have an observational basis. The observations are summarized with particular emphasis on those reported since 1980. The techniques used - the detection of small air showers using the secondary photons and particles at ground level - are unusual and are described. Future prospects for the field are discussed in relation to new ground-based experiments, satellite gamma-ray studies and proposed neutrino astronomy experiments. (orig.) With 296 refs

High-energy Neutrino Emission from Short Gamma-Ray Bursts: Prospects for Coincident Detection with Gravitational Waves

Energy Technology Data Exchange (ETDEWEB)

Kimura, Shigeo S.; Murase, Kohta; Mészáros, Peter [Department of Physics, Pennsylvania State University, University Park, PA 16802 (United States); Kiuchi, Kenta [Center for Gravitational Physics, Yukawa Institute for Theoretical Physics, Kyoto, Kyoto 606-8502 (Japan)

2017-10-10

We investigate current and future prospects for coincident detection of high-energy neutrinos and gravitational waves (GWs). Short gamma-ray bursts (SGRBs) are believed to originate from mergers of compact star binaries involving neutron stars. We estimate high-energy neutrino fluences from prompt emission, extended emission (EE), X-ray flares, and plateau emission, and we show that neutrino signals associated with the EE are the most promising. Assuming that the cosmic-ray loading factor is ∼10 and the Lorentz factor distribution is lognormal, we calculate the probability of neutrino detection from EE by current and future neutrino detectors, and we find that the quasi-simultaneous detection of high-energy neutrinos, gamma-rays, and GWs is possible with future instruments or even with current instruments for nearby SGRBs having EE. We also discuss stacking analyses that will also be useful with future experiments such as IceCube-Gen2.

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

Energy Technology Data Exchange (ETDEWEB)

Atwood, W. B. [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Baldini, L. [Universita di Pisa and Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Bregeon, J.; Pesce-Rollins, M.; Sgro, C.; Tinivella, M. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Bruel, P. [Laboratoire Leprince-Ringuet, Ecole polytechnique, CNRS/IN2P3, Palaiseau (France); Chekhtman, A. [Center for Earth Observing and Space Research, College of Science, George Mason University, Fairfax, VA 22030 (United States); Cohen-Tanugi, J. [Laboratoire Univers et Particules de Montpellier, Universite Montpellier 2, CNRS/IN2P3, F-34095 Montpellier (France); Drlica-Wagner, A.; Omodei, N.; Rochester, L. S.; Usher, T. L. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Granot, J. [Department of Natural Sciences, The Open University of Israel, 1 University Road, P.O. Box 808, Ra' anana 43537 (Israel); Longo, F. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Razzaque, S. [Department of Physics, University of Johannesburg, Auckland Park 2006 (South Africa); Zimmer, S., E-mail: melissa.pesce.rollins@pi.infn.it, E-mail: nicola.omodei@stanford.edu, E-mail: granot@openu.ac.il [Department of Physics, Stockholm University, AlbaNova, SE-106 91 Stockholm (Sweden)

2013-09-01

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

Prompt Gamma Ray Spectroscopy for process monitoring

International Nuclear Information System (INIS)

Zoller, W.H.; Holmes, J.L.

1991-01-01

Prompt Gamma Ray Spectroscopy (PGRS) is a very powerful analytical technique able to measure many metallic, contamination problem elements. The technique involves measurement of gamma rays that are emitted by nuclei upon capturing a neutron. This method is sensitive not only to the target element but also to the particular isotope of that element. PGRS is capable of measuring dissolved metal ions in a flowing system. In the field, isotopic neutron sources are used to produce the desired neutron flux ( 252 Cf can produce neutron flux of the order of 10 8 neutrons/cm 2 --sec.). Due to high penetrating power of gamma radiation, high efficiency gamma ray detectors can be placed in an appropriate geometry to maximize sensitivity, providing real-time monitoring with low detection level capabilities

Neutron detection in a high gamma-ray background with EJ-301 and EJ-309 liquid scintillators

International Nuclear Information System (INIS)

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

2012-01-01

Using a fast digitizer, the neutron–gamma discrimination capability of the new liquid scintillator EJ-309 is compared with that obtained using standard EJ-301. Moreover the capability of both the scintillation detectors to identify a weak neutron source in a high gamma-ray background is demonstrated. The probability of neutron detection is PD=95% at 95% confidence level for a gamma-ray background corresponding to a dose rate of 100 μSv/h.

Very high energy gamma ray astrophysics

International Nuclear Information System (INIS)

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

1990-02-01

Our scientific goal is to discover and study by means of gamma-ray astronomy those regions of the universe where particles are accelerated to extreme energies. The atmospheric Cherenkov technique provides a unique and potentially sensitive window in the region of 10 11 to approximately 10 14 eV for this purpose. The Whipple Observatory Collaboration is currently engaged in the development of a Cherenkov camera which has the ultimate capability of distinguishing gamma-ray showers from the numerous cosmic-ray background showers by imaging the Cherenkov light from each shower. We have recently demonstrated the potential of the imaging technique with our 18 sigma detection of TeV photons from the Crab Nebula using a camera of 10 elements, pixel spacing 0.25 degrees. This detection represents a factor of 10 improvement in sensitivity compared to a non-imaging detector. The next step in the development of the detector is to obtain a second large reflector, similar to the present 10 meter instrument, for stereoscopic viewing of showers. This project, named GRANITE, is now approved by DOE. With GRANITE it should be possible to probe more deeply in space by a factor of 7, and to fully investigate the possibility of new physics which has been suggested by reports of anomalous radiation from Hercules X-1. 18 refs

ESA's Integral detects closest cosmic gamma-ray burst

Science.gov (United States)

2004-08-01

be just sensitive enough to reveal a few more of them in the years to come. These could be just the tip of the iceberg and future gamma-ray observatories, such as the planned NASA's Swift mission, should be able to extend this search to a much larger volume of the Universe and find many more sub-energetic GRBs. Notes for editors The results of this investigation are presented in two articles that have appeared in today's issue of the scientific journal Nature. One of them, by S. Sazonov, A. Lutovinov and R. Sunyaev, is entitled "An apparently normal gamma-ray burst with unusually low luminosity". The other, entitled "The sub-energetic GRB 031203 as a cosmic analogue to GRB 980425", is signed by A. Soderberg, S. Kulkarni, E. Berger, D. Fox, M. Sako, D. Frail, A. Gal-Yam, D. Moon, S. Cenko, S. Yost, M. Phillips, E. Persson, W. Freedman, P. Wyatt, R. Jayawardhana and D. Paulson. The original announcement of the Integral detection of GRB 031203 was made by D. Goetz, S. Mereghetti, M. Beck, J. Borkowski and N. Mowlavi, via the Circular Service of the GRB Co-ordinates Network. More about Integral The International Gamma Ray Astrophysics Laboratory (Integral) is the first space observatory that can simultaneously observe celestial objects in gamma rays, X-rays and visible light. Integral was launched on a Russian Proton rocket on 17 October 2002 into a highly elliptical orbit around Earth. Its principal targets include regions of the galaxy where chemical elements are being produced and compact objects, such as black holes. For more information about Integral please see: http://www.esa.int/esaSC/spk.html More about XMM-Newton ESA's XMM-Newton can detect more X-ray sources than any previous satellite and is helping to solve many cosmic mysteries of the violent Universe, from black holes to the formation of galaxies. It was launched on 10 December 1999, using an Ariane-5 rocket, from French Guiana. It is expected to return data for a decade. XMM-Newton's high-tech design uses

Proceedings of the workshop on multiple prompt gamma-ray analysis

International Nuclear Information System (INIS)

Ebihara, Mitsuru; Hatsukawa, Yuichi; Oshima, Masumi

2006-10-01

The workshop on 'Multiple Prompt Gamma-ray Analysis' was held on March 8, 2006 at Tokai. It is based on a project, 'Developments of real time, non-destructive ultra sensitive elemental analysis using multiple gamma-ray detections and prompt gamma ray analysis and its application to real samples', one of the High priority Cooperative Research Programs performed by Japan Atomic Energy Agency and the University of Tokyo. In this workshop, the latest results of the Multiple Prompt Gamma ray Analysis (MPGA) study were presented, together with those of Neutron Activation Analysis with Multiple Gamma-ray Detection (NAAMG). The 9 of the presented papers are indexed individually. (J.P.N.)

Multiple Gamma-Ray Detection Capability of a CeBr3 Detector for Gamma Spectroscopy

Directory of Open Access Journals (Sweden)

A. A. Naqvi

2017-01-01

Full Text Available The newly developed cerium tribromide (CeBr3 detector has reduced intrinsic gamma-ray activity with gamma energy restricted to 1400–2200 keV energy range. This narrower region of background gamma rays allows the CeBr3 detector to detect more than one gamma ray to analyze the gamma-ray spectrum. Use of multiple gamma-ray intensities in elemental analysis instead of a single one improves the accuracy of the estimated results. Multigamma-ray detection capability of a cylindrical 75 mm × 75 mm (diameter × height CeBr3 detector has been tested by analyzing the chlorine concentration in water samples using eight chlorine prompt gamma rays over 517 to 8578 keV energies utilizing a D-D portable neutron generator-based PGNAA setup and measuring the corresponding minimum detection limit (MDC of chlorine. The measured MDC of chlorine for gamma rays with 517–8578 keV energies varies from 0.07 ± 0.02 wt% to 0.80 ± 0.24. The best value of MDC was measured to be 0.07 ± 0.02 wt% for 788 keV gamma rays. The experimental results are in good agreement with Monte Carlo calculations. The study has shown excellent detection capabilities of the CeBr3 detector for eight prompt gamma rays over 517–8578 keV energy range without significant background interference.

Very high energy gamma-ray astronomy

International Nuclear Information System (INIS)

Weekes, T.C.

1989-01-01

It is apparent that very high gamma-ray astronomy, at the very end of the electromagnetic spectrum, is just at the threshold of becoming an important channel of astronomical information. The author discusses how, to fully develop, it requires telescopes with improved minimum flux sensitivity; development of techniques that characterize the nature of the primary; more overlapping observations to remove any question of the reality of the detected phenomenon; more consistency in the application of statistics among experimenters and more openness about methods used; development of models that will predict the phenomenon to be expected rather than explain what has been observed; and more accurate calibrations to determine absolute fluxes and energies

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

Science.gov (United States)

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.

Very high energy gamma ray astronomy from Hanle

International Nuclear Information System (INIS)

Chitnis, Varsha R.

2015-01-01

Over a past decade very high energy (VHE) gamma ray astronomy has emerged as a major astronomical discipline. In India, we have a long tradition of experiments in this field. Few years ago, multi-institutional Himalayan Gamma Ray Observatory (HiGRO) collaboration was formed to set up VHE gamma rays experiments at Hanle, a high altitude location in Himalayas. HAGAR, the first phase of this collaboration is operational since 2008. HAGAR has successfully detected VHE gamma ray emission from some of the extragalactic objects like Mrk 421, Mrk 501 as well as galactic sources including Crab nebula/pulsar. Details of HAGAR telescope system and results obtained will be discussed. HiGRO is now gearing up for the next phase, i.e. 21 m diameter MACE telescope, which is being installed at Hanle at present. Details of MACE telescope system and future plans will be discussed. (author)

High energy photons and neutrinos from gamma ray bursts

International Nuclear Information System (INIS)

Dar, A.

1998-01-01

The Hubble space telescope has recently discovered thousands of gigantic comet-like objects in a ring around the central star in the nearest planetary nebula. It is suggested that such circumstellar rings exist around most of stars. Collisions of the relativistic debris from gamma ray bursts in dense stellar regions with such gigantic comet-like objects, which have been stripped off from the circumstellar rings by gravitational perturbations, produce detectable fluxes of high energy gamma-rays and neutrinos from gamma ray bursts

Sensitivity of self-powered detector probes to electron and gamma-ray fields

Energy Technology Data Exchange (ETDEWEB)

Lone, M A; Wong, P Y [Atomic Energy of Canada Ltd., Chalk River, ON (Canada)

1996-12-31

A self-powered detector (SPD) is a simple, passive device that consists of a coaxial probe with a metallic outer sleeve, a mineral oxide insulating layer, and a metallic inner core. SPD`s are used in nuclear reactors to monitor neutron and gamma fields. Responses of SPD`s to electrons and {gamma}-rays of various energies were investigated with Monte Carlo simulations. Transmission filters were studied for the design of threshold SPD probes used for online monitoring of the energy spectrum of high-power industrial electron accelerator beams. Filters were also investigated for the enhancement of {gamma}-ray sensitivity of an SPD placed in a mixed electron and {gamma}-ray field. (author). 30 refs., 1 tab., 8 figs.

Millisecond Pulsars at Gamma-Ray Energies: Fermi Detections and Implications

Science.gov (United States)

Harding, Alice K.

2011-01-01

The Fermi Gamma-Ray Space Telescope has revolutionized the study of pulsar physics with the discovery of new populations of radio quiet and millisecond gamma-ray pulsars. The Fermi Large Area Telescope has so far discovered approx.20 new gamma-ray millisecond pulsars (MSPs) by both folding at periods of known radio MSPs or by detecting them as gamma-ray sources that are followed up by radio pulsar searches. The second method has resulted in a phenomenally successful synergy, with -30 new radio MSPs (to date) having been discovered at Fermi unidentified source locations and the gamma-ray pulsations having then been detected in a number of these using the radio timing solutions. Many of the newly discovered MSPs may be suitable for addition to the collection of very stable MSPs used for gravitational wave detection. Detection of such a large number of MSPs was surprising, given that most have relatively low spin-down luminosity and surface field strength. I will discuss their properties and the implications for pulsar particle acceleration and emission, as well as their potential contribution to gamma-ray backgrounds and Galactic cosmic rays.

AGILE: A gamma-ray mission

International Nuclear Information System (INIS)

Tavani, M.; Caraveo, P.; Mereghetti, S.; Perotti, F.; Vercellone, S.; Barbiellini, G.; Budini, G.; Longo, F.; Prest, M.; Vallazza, E.; Cocco, V.; Morselli, A.; Picozza, P.; Pittori, C.; Costa, E.; Feroci, M.; Lapshov, I.; Morelli, E.; Rubini, A.; Soffitta, P.

2000-01-01

AGILE is an innovative, cost-effective gamma-ray mission selected by the Italian Space Agency for a Program of Small Scientific Missions. The AGILE gamma-ray imaging detector (GRID, made of a Silicon tracker and CsI Mini-Calorimeter) is designed to detect and image photons in the 30 MeV-50 GeV energy band with good sensitivity and very large field of view (FOV ∼3 sr). The X-ray detector, Super-AGILE, sensitive in the 10-40 keV band and integrated on top of the GRID gamma-ray tracker will provide imaging (1-3 arcmin) and moderate spectroscopy. For selected sky areas, AGILE might achieve a flux sensitivity (above 100 MeV) better than 5x10 -8 ph cm 2 s -1 at the completion of its scientific program. AGILE will operate as an Observatory open to the international community and is planned to be operational during the year 2002 for a nominal 2-year mission. It will be an ideal 'bridge' between EGRET and GLAST, and the only mission entirely dedicated to high-energy astrophysics above 30 MeV during that period

A Very High Energy Gamma-Ray Spectrum of 1ES 2344+514

OpenAIRE

Schroedter, M.; Badran, H. M.; Buckley, J. H.; Gordo, J. Bussons; Carter-Lewis, D. A.; Duke, C.; Fegan, D. J.; Fegan, S. F.; Finley, J. P.; Gillanders, G. H.; Grube, J.; Horan, D.; Kenny, G. E.; Kertzman, M.; Kosack, K.

2005-01-01

The BL Lacertae (BL Lac) object 1ES 2344+514 (1ES 2344), at a redshift of 0.044, was discovered as a source of very high energy (VHE) gamma rays by the Whipple Collaboration in 1995 \\citep{2344Catanese98}. This detection was recently confirmed by the HEGRA Collaboration \\citep{2344Hegra03}. As is typical for high-frequency peaked blazars, the VHE gamma-ray emission is highly variable. On the night of 20 December, 1995, a gamma-ray flare of 5.3-sigma significance was detected, the brightest ou...

Method of incident low-energy gamma-ray direction reconstruction in the GAMMA-400 gamma-ray space telescope

International Nuclear Information System (INIS)

Kheymits, M D; Leonov, A A; Zverev, V G; Galper, A M; Arkhangelskaya, I V; Arkhangelskiy, A I; Yurkin, Yu T; Bakaldin, A V; Suchkov, S I; Topchiev, N P; Dalkarov, O D

2016-01-01

The GAMMA-400 gamma-ray space-based telescope has as its main goals to measure cosmic γ-ray fluxes and the electron-positron cosmic-ray component produced, theoretically, in dark-matter-particles decay or annihilation processes, to search for discrete γ-ray sources and study them in detail, to examine the energy spectra of diffuse γ-rays — both galactic and extragalactic — and to study gamma-ray bursts (GRBs) and γ-rays from the active Sun. Scientific goals of GAMMA-400 telescope require fine angular resolution. The telescope is of a pair-production type. In the converter-tracker, the incident gamma-ray photon converts into electron-positron pair in the tungsten layer and then the tracks are detected by silicon- strip position-sensitive detectors. Multiple scattering processes become a significant obstacle in the incident-gamma direction reconstruction for energies below several gigaelectronvolts. The method of utilising this process to improve the resolution is proposed in the presented work. (paper)

Deduction of solar neutron fluences from large gamma-ray flares

International Nuclear Information System (INIS)

Yoshimori, Masato; Watanabe, Hiroyuki; Takahashi, Kazuyoshi.

1986-01-01

Solar neutron fluences from large gamma-ray flares are deduced from accelerated proton spectra and numbers derived from the gamma-ray observations. The deduced solar neutron fluences range from 1 to 200 neutrons cm -2 . The present result indicates a possibility that high sensitivity ground-based neutron monitors can detect solar neutron events, just as detected by the Jungfraujoch and Rome neutron monitors. (author)

Basics of Gamma Ray Detection

Energy Technology Data Exchange (ETDEWEB)

Stinnett, Jacob [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Venkataraman, Ram [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2017-09-13

The objective of this training is to explain the origin of x-rays and gamma rays, gamma ray interactions with matter, detectors and electronics used in gamma ray-spectrometry, and features of a gamma-ray spectrum for nuclear material that is safeguarded.

Population Studies of Radio and Gamma-Ray Pulsars

Science.gov (United States)

Harding, Alice K; Gonthier, Peter; Coltisor, Stefan

2004-01-01

Rotation-powered pulsars are one of the most promising candidates for at least some of the 40-50 EGRET unidentified gamma-ray sources that lie near the Galactic plane. Since the end of the EGRO mission, the more sensitive Parkes Multibeam radio survey has detected mere than two dozen new radio pulsars in or near unidentified EGRET sources, many of which are young and energetic. These results raise an important question about the nature of radio quiescence in gamma-ray pulsars: is the non-detection of radio emission a matter of beaming or of sensitivity? The answer is very dependent on the geometry of the radio and gamma-ray beams. We present results of a population synthesis of pulsars in the Galaxy, including for the first time the full geometry of the radio and gamma-ray beams. We use a recent empirically derived model of the radio emission and luminosity, and a gamma-ray emission geometry and luminosity derived theoretically from pair cascades in the polar slot gap. The simulation includes characteristics of eight radio surveys of the Princeton catalog plus the Parkes MB survey. Our results indicate that EGRET was capable of detecting several dozen pulsars as point sources, with the ratio of radio-loud to radio-quiet gamma-ray pulsars increasing significantly to about ten to one when the Parkes Survey is included. Polar cap models thus predict that many of the unidentified EGRET sources could be radio-loud gamma- ray pulsars, previously undetected as radio pulsars due to distance, large dispersion and lack of sensitivity. If true, this would make gamma-ray telescopes a potentially more sensitive tool for detecting distant young neutron stars in the Galactic plane.

Selective Beta and Gamma-ray Discrimination by CdWO{sub 4} and PlasticScintillator

Energy Technology Data Exchange (ETDEWEB)

Bae, Jun Woo; Kim, Hee Reyoung [Dept. of Nuclear Engineering, Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of)

2017-04-15

Radiation monitoring technique has been used for monitoring of decommissioning site of nuclear facility, radioactive waste disposal site, or in case of radioactivity accident. For rapid measurement of gamma-ray and beta-ray, many portable radiation detectors were developed but they are sensitive to specific radiation type. For example, portable detectors using NaI(Tl) or high purity germanium (HPGe) are suitable to detect gamma-ray. Otherwise, Geiger-müller (GM) tube or ionization chamber are suitable to detect all-types of radiation but it is hard to determine which particle is detected in the detector. In this reason, phoswich detectors for discrimination of beta-ray and gamma-ray were developed by using pulse shape discrimination. In this study, another approach to discriminate the beta-ray and gamma-ray is carried out. Two scintillators are used, cadmium tungstate (CdWO{sub 4}) and plastic scintillator. They have huge difference in their effective atomic number and mass density, thus they have huge difference in their gamma-ray sensitivity while the sensitivity of beta-ray is similar. The characterization of beta-ray and gamma-ray discrimination by using this characteristics is include. A technique of discrimination between beta-ray and gamma-ray was suggested. The method was verified by Monte Carlo simulation and experiment. This work showed feasibility on in field measurement of radiation with discrimination of beta-ray and gamma-ray.

Detection of gamma-ray bursts from Andromeda

International Nuclear Information System (INIS)

Bulik, Tomasz; Coppi, Paolo S.; Lamb, Donald Q.

1996-01-01

If gamma-ray bursts originate in a corona around the Milky Way, it should also be possible to detect them from a similar corona around Andromeda. Adopting a simple model of high velocity neutron star corona, we evaluate the ability of instruments on existing missions to detect an excess of bursts toward Andromeda. We also calculate the optimal properties of an instrument designed to detect such an excess. We find that if the bursts radiate isotropically, an experiment with a sampling distance d max > or approx. 500 kpc could detect a significant excess of bursts in the direction of Andromeda in a few years of observation. If the radiation is beamed along the neutron star's direction of motion, an experiment with d max > or approx. 800 kpc would detect such an excess in a similar amount of time, provided that the width of the beam is greater than 10 deg. Lack of an excess toward Andromeda would therefore be compelling evidence that the bursts are cosmological in origin if made by an instrument at least 50 times more sensitive than BATSE, given current constraints on Galactic corona models. Comparisons with detailed dynamical calculations of the spatial distribution of high velocity neutron stars in the coronae around the Milky Way and Andromeda confirm these conclusions

Detection of 16 Gamma-Ray Pulsars Through Blind Frequency Searches Using the Fermi LAT

International Nuclear Information System (INIS)

Anderson, B.; Atwood, W.B.; Dormody, M.; Johnson, R.P.; Porter, T.A.; Primack, J.R.; Sadrozinski, H.F.W.; Parkinson, P.M.S.; Ziegler, M.; Abdo, A.A.; Dermer, C.D.; Grove, J.E.; Gwon, C.; Johnson, W.N.; Lovellette, M.N.; Makeev, A.; Ray, P.S.; Strickman, M.S.; Wolff, M.T.; Wood, K.S.; Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Blandford, R.D.; Borgland, A.W.; Cameron, R.A.; Chiang, J.; Claus, R.; Digel, S.W.; Silva, E.D.E.; Drell, P.S.; Dubois, R.; Funk, S.; Glanzman, T.; Godfrey, G.; Hayashida, M.; Johannesson, G.; Kamae, T.; Kocian, M.L.; Lande, J.; Madejski, G.M.; Michelson, P.F.; Mitthumsiri, W.; Monzani, M.E.; Moskalenko, I.V.; Murgia, S.; Nolan, P.L.; Paneque, D.; Reimer, A.; Reimer, O.; Rochester, L.S.; Romani, R.W.; Tajima, H.; Tanaka, T.; Thayer, J.G.; Tramacere, A.; Uchiyama, Y.; Usher, T.L.; Van Etten, A.; Waite, A.P.; Wang, P.; Watters, K.; Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Bloom, E.D.; Borgland, A.W.; Cameron, R.A.; Chiang, J.; Claus, R.; Digel, S.W.; Silva, E.D.E.; Drell, P.S.; Dubois, R.; Glanzman, T.; Godfrey, G.; Hayashida, M.; Johannesson, G.; Kamae, T.; Kocian, M.L.; Lande, J.; Madejski, G.M.; Michelson, P.F.; Mitthumsiri, W.; Monzani, M.E.; Moskalenko, I.V.; Murgia, S.; Nolan, P.L.; Paneque, D.; Reimer, A.; Reimer, O.; Rochester, L.S.; Romani, R.W.; Tajima, H.; Tanaka, T.; Thayer, J.G.; Tramacere, A.; Uchiyama, Y.; Usher, T.L.; Van Etten, A.; Waite, A.P.; Wang, P.; Watters, K.; Axelsson, M.; Conrad, J.; Meurer, C.; Ryde, F.; Ylinen, T.; Axelsson, M.; Baldini, L.; Bellazzini, R.; Bregeon, J.; Brez, A.; Kuss, M.; Latronico, L.; Omodei, N.; Pesce-Rollins, M.; Razzano, M.; Sgro, C.; Spandre, G.; Ballet, J.; Casandjian, J.M.; Grenier, I.A.; Pierbattista, M.; Starck, J.L.

2009-01-01

Pulsars are rapidly rotating, highly magnetized neutron stars emitting radiation across the electromagnetic spectrum. Although there are more than 1800 known radio pulsars, until recently only seven were observed to pulse in gamma rays, and these were all discovered at other wavelengths. The Fermi Large Area Telescope (LAT) makes it possible to pinpoint neutron stars through their gamma-ray pulsations. We report the detection of 16 gamma-ray pulsars in blind frequency searches using the LAT. Most of these pulsars are coincident with previously unidentified gamma-ray sources, and many are associated with supernova remnants. Direct detection of gamma-ray pulsars enables studies of emission mechanisms, population statistics, and the energetics of pulsar wind nebulae and supernova remnants. (authors)

High energy X-ray observations of COS-B gamma-ray sources from OSO-8

Science.gov (United States)

Dolan, J. F.; Crannell, C. J.; Dennis, B. R.; Frost, K. J.; Orwig, L. E.; Caraveo, P. A.

1985-01-01

During the three years between satellite launch in June 1975 and turn-off in October 1978, the high energy X-ray spectrometer on board OSO-8 observed nearly all of the COS-B gamma-ray source positions given in the 2CG catalog (Swanenburg et al., 1981). An X-ray source was detected at energies above 20 keV at the 6-sigma level of significance in the gamma-ray error box containing 2CG342 - 02 and at the 3-sigma level of significance in the error boxes containing 2CG065 + 00, 2CG195 + 04, and 2CG311 - 01. No definite association between the X-ray and gamma-ray sources can be made from these data alone. Upper limits are given for the 2CG sources from which no X-ray flux was detected above 20 keV.

Gamma ray polarimetry using a position sensitive germanium detector

CERN Document Server

Kroeger, R A; Kurfess, J D; Phlips, B F

1999-01-01

Imaging gamma-ray detectors make sensitive polarimeters in the Compton energy regime by measuring the scatter direction of gamma rays. The principle is to capitalize on the angular dependence of the Compton scattering cross section to polarized gamma rays and measure the distribution of scatter directions within the detector. This technique is effective in a double-sided germanium detector between roughly 50 keV and 1 MeV. This paper reviews device characteristics important to the optimization of a Compton polarimeter, and summarizes measurements we have made using a device with a 5x5 cm active area, 1 cm thickness, and strip-electrodes on a 2 mm pitch.

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

International Nuclear Information System (INIS)

Yearian, M.R.

1990-08-01

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

Fermi Detection of a Luminous gamma-ray Pulsar in a Globular Cluster

Science.gov (United States)

Freire, P. C. C.; Abdo, A. A.; Ajello, M.; Allafort, A.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Blandford, R. D.;

Collimatorless imaging of gamma rays with help of gamma-ray tracking

CERN Document Server

Marel, J V D

2001-01-01

In many gamma-ray detector systems that are built for imaging purposes Compton scattered photons are suppressed as much as possible. However, the information from photons that scattered inside a detector system can be used to reconstruct the tracks of the photons with help of gamma-ray tracking. Estimates of the incident directions of the photons can be made and an image can be created. Examples of potential applications for this technique are the use as a gamma-camera in medical imaging (e.g. SPECT) or as a detector for PET. Due to the omission of collimators, much higher detection efficiencies can be achieved, reducing the doses required for an image. A gamma-ray tracking method, called backtracking, has been developed for nuclear spectroscopy. The method tracks gamma-rays originating from a point source in the center of a spherical detector system consisting of position-sensitive germanium detectors. This method can also be used as a tracking technique for imaging of an unknown source distribution. With he...

High energy neutrinos from gamma-ray bursts with precursor supernovae.

Science.gov (United States)

Razzaque, Soebur; Mészáros, Peter; Waxman, Eli

2003-06-20

The high energy neutrino signature from proton-proton and photo-meson interactions in a supernova remnant shell ejected prior to a gamma-ray burst provides a test for the precursor supernova, or supranova, model of gamma-ray bursts. Protons in the supernova remnant shell and photons entrapped from a supernova explosion or a pulsar wind from a fast-rotating neutron star remnant provide ample targets for protons escaping the internal shocks of the gamma-ray burst to interact and produce high energy neutrinos. We calculate the expected neutrino fluxes, which can be detected by current and future experiments.

High-energy neutrinos from gamma ray bursts

International Nuclear Information System (INIS)

Dermer, Charles D.; Atoyan, Armen

2003-01-01

We treat high-energy neutrino production in gamma ray bursts (GRBs). Detailed calculations of photomeson neutrino production are presented for the collapsar model, where internal nonthermal synchrotron radiation is the primary target photon field, and the supranova model, where external pulsar-wind synchrotron radiation provides important additional target photons. Detection of > or approx. 10 TeV neutrinos from GRBs with Doppler factors > or approx. 200, inferred from γ-ray observations, would support the supranova model. Detection of or approx. 3x10 -4 erg cm -2 offer a realistic prospect for detection of ν μ

Gamma-Ray Pulsar Studies With GLAST

Energy Technology Data Exchange (ETDEWEB)

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.

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

Science.gov (United States)

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

2008-06-27

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

The opacity of the universe for high and very high energy {gamma}-rays

Energy Technology Data Exchange (ETDEWEB)

Meyer, Manuel

2013-08-15

}{sub {gamma}{gamma}}<1 to {tau}{sub {gamma}{gamma}}{>=}2 is investigated. The absorption-corrected spectra consistently show an upturn at high optical depths, significant at the 4{sigma} level. A source intrinsic effect is unlikely to produce such a feature, since the transition to the {tau}{sub {gamma}{gamma}}{>=}2 regime occurs at different energies for each source. Systematic uncertainties that could mimic the effect are studied but found unlikely as a possible explanation. A similar study is conducted for photons detected with the Fermi-LAT. To this end, the number of expected photons in the optical thick regime is compared to the number of photons observed with the LAT. Above {tau}{sub {gamma}{gamma}}{>=}2, three photons are associated with AGN with high confidence. Under the assumption of certain EBL models, extrapolating the unattenuated spectrum from low to high energies results in a probability of 1.2 x 10{sup -4} to observe these photons. However, the probability for detecting the high optical depth photons when all LAT detected AGN with known redshift are considered sensitively depends on the choice of the intrinsic spectral model. The indication for a reduced opacity might be explained by the oscillation of photons into hypothetical axion-like particles (ALPs) in ambient magnetic fields. Such particles propagate unimpeded over cosmological distances, thereby reducing the {gamma}-ray opacity. Photon-ALP conversions are studied in different magnetic field configurations, including intracluster and intergalactic magnetic fields, as well as the field of the Milky Way. Optimistic values of the field strength and coherence length result in lower limits on the photon-ALP coupling, g{sub a{gamma}}>or similar 10{sup -12} GeV{sup -1}. For more realistic magnetic field parameters, couplings above g{sub a{gamma}}>or similar 2 x 10{sup 11} GeV{sup -1} are necessary to explain the indication for the reduced opacity. The lower limits are in reach of future dedicated ALP

High-pressure {sup 3}He-Xe gas scintillators for simultaneous detection of neutrons and gamma rays over a large energy range

Energy Technology Data Exchange (ETDEWEB)

Tornow, W., E-mail: tornow@tunl.duke.edu [Department of Physics, Duke University, Durham, NC 27708 (United States); Triangle Universities Nuclear Laboratory, Durham, NC 27708 (United States); Esterline, J.H. [Department of Physics, Duke University, Durham, NC 27708 (United States); Triangle Universities Nuclear Laboratory, Durham, NC 27708 (United States); Leckey, C.A. [Department of Physics, The College of William and Mary, Williamsburg, VA 23187 (United States); Weisel, G.J. [Department of Physics, Penn State Altoona, Altoona, PA 16601 (United States)

2011-08-11

We report on features of high-pressure {sup 3}He-Xe gas scintillators which have not been sufficiently addressed in the past. Such gas scintillators can be used not only for the efficient detection of low-energy neutrons but at the same time for the detection and identification of {gamma}-rays as well. Furthermore, {sup 3}He-Xe gas scintillators are also very convenient detectors for fast neutrons in the 1-10 MeV energy range and for high-energy {gamma}-rays in the 7-15 MeV energy range. Due to their linear pulse-height response and self calibration via the {sup 3}He(n,p){sup 3}H reaction, neutron and {gamma}-ray energies can easily be determined in this high-energy regime.

Highly accurate determination of relative gamma-ray detection efficiency for Ge detector and its application

International Nuclear Information System (INIS)

Miyahara, H.; Mori, C.; Fleming, R.F.; Dewaraja, Y.K.

1997-01-01

When quantitative measurements of γ-rays using High-Purity Ge (HPGe) detectors are made for a variety of applications, accurate knowledge of oy-ray detection efficiency is required. The emission rates of γ-rays from sources can be determined quickly in the case that the absolute peak efficiency is calibrated. On the other hand, the relative peak efficiencies can be used for determination of intensity ratios for plural samples and for comparison to the standard source. Thus, both absolute and relative detection efficiencies are important in use of γ-ray detector. The objective of this work is to determine the relative gamma-ray peak detection efficiency for an HPGe detector with the uncertainty approaching 0.1% . We used some nuclides which emit at least two gamma-rays with energies from 700 to 2400 keV for which the relative emission probabilities are known with uncertainties much smaller than 0.1%. The relative peak detection efficiencies were calculated from the measurements of the nuclides, 46 Sc, 48 Sc, 60 Co and 94 Nb, emitting two γ- rays with the emission probabilities of almost unity. It is important that various corrections for the emission probabilities, the cascade summing effect, and the self-absorption are small. A third order polynomial function on both logarithmic scales of energy and efficiency was fitted to the data, and the peak efficiency predicted at certain energy from covariance matrix showed the uncertainty less than 0.5% except for near 700 keV. As an application, the emission probabilities of the 1037.5 and 1212.9 keV γ-rays for 48 Sc were determined using the function of the highly precise relative peak efficiency. Those were 0.9777+0,.00079 and 0.02345+0.00017 for the 1037.5 and 1212.9 keV γ-rays, respectively. The sum of these probabilities is close to unity within the uncertainty which means that the certainties of the results are high and the accuracy has been improved considerably

Terrestrial Gamma-Ray Flashes (TGFs) Observed with the Fermi-Gamma-Ray Burst Monitor: The First Hundred TGFs

Science.gov (United States)

Fishman, G J.; Briggs, M. S.; Connaughton, V.; Bhat, P. N.

2010-01-01

The Gamma-ray Burst Monitor (GBM) on the Fermi Gamma-ray Space Telescope Observatory (Fermi) is now detecting 2.1 TGFs per week. At this rate, nearly a hundred TGFs will have been detected by the time of this Meeting. This rate has increased by a factor of 8 since new flight software was uploaded to the spacecraft in November 2009 in order to increase the sensitivity of GBM to TGFs. The high time resolution (2 microseconds) allows temporal features to be resolved so that some insight may be gained on the origin and transport of the gamma-ray photons through the atmosphere. The absolute time of the TGFs, known to several microseconds, also allows accurate correlations of TGFs with lightning networks and other lightning-related phenomena. The thick bismuth germanate (BGO) scintillation detectors of the GBM system have observed photon energies from TGFs at energies above 40 MeV. New results on the some temporal aspects of TGFs will be presented.

High Sensitivity Detection of Xe Isotopes Via Beta-Gamma Coincidence Counting

International Nuclear Information System (INIS)

Bowyer, Ted W.; McIntyre, Justin I.; Reeder, Paul L.

1999-01-01

Measurement of xenon fission product isotopes is a key element in the global network being established to monitor the Comprehensive Nuclear-Test-Ban Treaty. Pacific Northwest National Laboratory has developed an automated system for separating Xe from air which includes a beta-gamma counting system for 131mXe, 133mXe, 133Xe, and 135Xe. Betas and conversion electrons are detected in a plastic scintillation cell containing the Xe sample. The counting geometry is nearly 100% for beta and conversion electrons. The resolution in the pulse height spectrum from the plastic scintillator is sufficient to observe distinct peaks for specific conversion electrons. Gamma and X-rays are detected in a NaI(Tl) scintillation detector which surrounds the plastic scintillator sample cell. Two-dimensional pulse height spectra of gamma energy versus beta energy are obtained. Each of the four xenon isotopes has a distinctive signature in the two-dimensional energy array. The details of the counting system, examples of two-dimensional beta-gamma data, and operational experience with this counting system will be described

Modulated High-Energy Gamma-Ray Emission from the Micro-quasar Cygnus X-3

International Nuclear Information System (INIS)

Abdo, A.A.; Cheung, C.C.; Dermer, C.D.; Grove, J.E.; Johnson, W.N.; Lovellette, M.N.; Makeev, A.; Ray, P.S.; Strickman, M.S.; Wood, K.S.; Abdo, A.A.; Cheung, C.C.; Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Blandford, R.D.; Bloom, E.D.; Borgland, A.W.; Cameron, R.A.; Chiang, J.; Claus, R.; Digel, S.W.; Silva, E.D.E.; Drell, P.S.; Dubois, R.; Focke, W.B.; Glanzman, T.; Godfrey, G.; Hayashida, M.; Johannesson, G.; Johnson, A.S.; Kamae, T.; Kocian, M.L.; Lande, J.; Madejski, G.M.; Michelson, P.F.; Mitthumsiri, W.; Monzani, M.E.; Moskalenko, I.V.; Murgia, S.; Nolan, P.L.; Paneque, D.; Reimer, A.; Reimer, O.; Rochester, L.S.; Romani, R.W.; Tanaka, T.; Thayer, J.B.; Tramacere, A.; Uchiyama, Y.; Usher, T.L.; Waite, A.P.; Wang, P.; Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Blandford, R.D.; Bloom, E.D.; Borgland, A.W.; Cameron, R.A.; Chiang, J.; Claus, R.; Digel, S.W.; Silva, E.D.E.; Drell, P.S.; Dubois, R.; Focke, W.B.; Glanzman, T.; Godfrey, G.; Hayashida, M.; Johannesson, G.; Johnson, A.S.; Kamae, T.; Kocian, M.L.; Lande, J.; Madejski, G.M.; Michelson, P.F.; Mitthumsiri, W.; Monzani, M.E.; Moskalenko, I.V.; Murgia, S.; Nolan, P.L.; Paneque, D.; Reimer, A.; Reimer, O.; Rochester, L.S.; Romani, R.W.; Tanaka, T.; Thayer, J.B.; Tramacere, A.; Uchiyama, Y.; Usher, T.L.; Waite, A.P.; Wang, P.; Axelsson, M.; Hjalmarsdotter, L.; Axelsson, M.; Conrad, J.; Hjalmarsdotter, L.; Jackson, M.S.; Meurer, C.; Ryde, F.; Ylinen, T.; Baldini, L.; Bellazzini, R.; Brez, A.; Kuss, M.; Latronico, L.; Omodei, N.; Pesce-Rollins, M.; Razzano, M.; Sgro, C.; Ballet, J.; Casandjian, J.M.; Chaty, S.; Corbel, S.; Grenier, I.A.; Koerding, E.; Rodriguez, J.; Starck, J.L.; Tibaldo, L.

2009-01-01

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

Exploring the extreme gamma-ray sky with HESS

International Nuclear Information System (INIS)

Sol, Helene

2006-01-01

The international HESS experiment. High Energy Stereoscopic System, fully operational since January 2004, is opening a new era for extreme gamma-ray astronomy. Located in Namibia, it is now the most sensitive detector for cosmic sources of very high energy (VHE) gamma-rays, in the tera-electron-volt (TeV) range. In July 2005, it had already more than double the number of sources detected at such energies, with the discovery of several active galactic nuclei (AGN), supernova remnants and plerions, a binary pulsar system, a microquasar candidate, and a sample of yet unidentified sources. HESS has also provide for the first time gamma-ray images of extended sources with the first astrophysical jet resolved in gamma-rays, and the first mapping of a shell supernova remnant, which proves the efficiency of in situ acceleration of particles up to 100 TeV and beyond

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

Science.gov (United States)

Slaughter, Dennis R [Oakland, CA; Pohl, Bertram A [Berkeley, CA; Dougan, Arden D [San Ramon, CA; Bernstein, Adam [Palo Alto, CA; Prussin, Stanley G [Kensington, CA; Norman, Eric B [Oakland, CA

2008-04-15

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

Detection of gamma-ray bursts with the ECLAIRs instrument onboard the space mission SVOM

International Nuclear Information System (INIS)

Antier-Farfar, Sarah

2016-01-01

Discovered in the early 1970's, gamma-ray bursts (GRBs) are amazing cosmic phenomena appearing randomly on the sky and releasing large amounts of energy mainly through gamma-ray emission. Although their origin is still under debate, they are believed to be produced by some of the most violent explosions in the Universe leading to the formation of stellar black-holes. GRBs are detected by their prompt emission, an intense short burst of gamma-rays (from a few milliseconds to few minutes), and are followed by a lived-afterglow emission observed on longer timescales from the X-ray to the radio domain. My thesis participates to the development of the SVOM mission, which a Chinese-French mission to be launched in 2021, devoted to the study of GRBs and involving space and ground instruments. My work is focussed on the main instrument ECLAIRs, a hard X-ray coded mask imaging camera, in charge of the near real-time detection and localization of the prompt emission of GRBs. During my thesis, I studied the scientific performances of ECLAIRs and in particular the number of GRBs expected to be detected by ECLAIRs and their characteristics. For this purpose, I performed simulations using the prototypes of the embedded trigger algorithms combined with the model of the ECLAIRs instrument. The input data of the simulations include a background model and a synthetic population of gamma-ray bursts generated from existing catalogs (CGRO, HETE-2, Fermi and Swift). As a result, I estimated precisely the ECLAIRs detection efficiency of the algorithms and I predicted the number of GRBs to be detected by ECLAIRs: 40 to 70 GRBs per year. Moreover, the study highlighted that ECLAIRs will be particularly sensitive to the X-ray rich GRB population. My thesis provided additional studies about the localization performance, the rate of false alarm and the characteristics of the triggers of the algorithms. Finally, I also proposed two new methods for the detection of GRBs.The preliminary

The high intensity {gamma}-ray source (HI{gamma}S) and recent results

Energy Technology Data Exchange (ETDEWEB)

Tonchev, A.P. [Duke University and TUNL, Triangle University Nuclear Laboratory, P.O. Box 90308, Durham, NC 27708 0308 (United States)]. E-mail: tonchev@tunl.duke.edu; Boswell, M. [University of North Carolina at Chapel Hill and TUNL, Chapel Hill, NC 27599 (United States); Howell, C.R. [Duke University and TUNL, Triangle University Nuclear Laboratory, P.O. Box 90308, Durham, NC 27708 0308 (United States); Karwowski, H.J. [University of North Carolina at Chapel Hill and TUNL, Chapel Hill, NC 27599 (United States); Kelley, J.H. [North Carolina State University and TUNL, Raleigh, NC 27695 (United States); Tornow, W. [Duke University and TUNL, Triangle University Nuclear Laboratory, P.O. Box 90308, Durham, NC 27708 0308 (United States); Wu, Y.K. [Duke University and Duke Free Electron Laser Laboratory, Durham, NC 27708-0319 (United States)

2005-12-15

The high intensity {gamma}-ray source (HI{gamma}S) utilizes intra-cavity backscattering of free electron laser photons from the Duke electron storage ring to produce a unique monoenergetic beam of high-flux {gamma}-rays with high polarization and selectable energy resolution. At present, {gamma}-ray beams with energies from 2 to 58 MeV are available with intensities as high as 10{sup 5}-5 x 10{sup 6} {gamma}/s, energy spreads of 3% or better, and nearly 100% linear polarization. The quality and intensity of the {gamma}-ray beams at HI{gamma}S are responsible for the unprecedented performance of this facility in a broad range of research programs in nuclear structure, nuclear astrophysics and nuclear applications. Recent results from excitation of isomeric states in ({gamma}, n) reactions and parity assignments of dipole states determined via the ({gamma}, {gamma}') reaction are presented.

Decreasing of the detection limit for gamma-ray Spectrometry with the influence of sample treatment

International Nuclear Information System (INIS)

Karami, M.; Sadighzadeh, A.; Asgharizadeh, F.; Sardari, D.; Tavassoli, A.; Arbabi, A.; Hochaghani, O.

2009-01-01

Full text: In this study the ash method has been applied for environmental sample treatment in order to decrease of the detection limit in gamma-ray spectrometry for low level radioactivity measurements. Detection limit in gamma ray spectrometry is the smallest expectation value of the net counting rate that can be detected on given probabilities. The environmental test samples have been changed into ash using a suitable oven. The heating were made under controlled temperature to avoid the escape of some radionuclides such as radiocaesium. The ash samples were measured by high resolution gamma-ray spectrometry system. (author)

Extragalactic Gamma-Ray Astrophysics

CERN Multimedia

CERN. Geneva

2016-01-01

During the last decades, various classes of radio-loud active galactic nuclei have been established as sources of high-energy radiation extending over a very broad range from soft gamma-rays (photon energies E~MeV) up to very-high-energy gamma-rays (E>100 GeV). These include blazars of different types, as well as young and evolved radio galaxies. The observed gamma-ray emission from such implies efficient particle acceleration processes taking place in highly magnetized and relativistic jets produced by supermassive black holes, processes that have yet to be identified and properly understood. In addition, nearby starforming and starburst galaxies, some of which host radio-quiet Seyfert-type nuclei, have been detected in the gamma-ray range as well. In their cases, the observed gamma-ray emission is due to non-thermal activity in the interstellar medium, possibly including also a contribution from accretion disks and nuclear outflows. Finally, the high-energy emission from clusters of galaxies remains elusive...

Large-area atmospheric Cherenkov detectors for high-energy gamma-ray astronomy

International Nuclear Information System (INIS)

Ong, R.A.

1996-01-01

This paper describes the development of new ground-based gamma-ray detectors to explore the energy region between 20 and 200 GeV. This region in energy is interesting because it is currently unexplored by any experiment. The proposed detectors use the atmospheric Cherenkov technique, in which Cherenkov radiation produced in the gamma-ray air showers is detected using mirrors and light-sensitive devices. The important feature of the proposed experiments is the use of large mirror collection areas, which should allow for a significant improvement (i.e. reduction) in energy threshold over existing experiments. Large mirror areas are available for relatively low cost at central tower solar power plants, and there are two groups developing gamma-ray experiments using solar heliostat arrays. This paper summarizes the progress in the design of experiments using this novel approach

DETECTION OF GAMMA-RAY EMISSION FROM THE ETA-CARINAE REGION

International Nuclear Information System (INIS)

Tavani, M.; Viotti, R. F.; Argan, A.; Cocco, V.; D'Ammando, F.; Costa, E.; Sabatini, S.; Pian, E.; Bulgarelli, A.; Caraveo, P.; Giuliani, A.; Vercellone, S.; Mereghetti, S.; Chen, A. W.; Corcoran, M. F.; Pittori, C.; Verrecchia, F.; Barbiellini, G.; Boffelli, F.; Cattaneo, P. W.

2009-01-01

We present the results of extensive observations by the gamma-ray AGILE satellite of the Galactic region hosting the Carina nebula and the remarkable colliding wind binary Eta Carinae (η Car) during the period 2007 July-2009 January. We detect a gamma-ray source (1AGL J1043-5931) consistent with the position of η Car. If 1AGL J1043-5931 is associated with the Car system, our data provide the long sought first detection above 100 MeV of a colliding wind binary. The average gamma-ray flux above 100 MeV and integrated over the preperiastron period 2007 July-2008 October is F γ = (37 ± 5) x 10 -8 ph cm -2 s -1 corresponding to an average gamma-ray luminosity of L γ = 3.4 x 10 34 erg s -1 for a distance of 2.3 kpc. We also report a two-day gamma-ray flaring episode of 1AGL J1043-5931 on 2008 October 11-13 possibly related to a transient acceleration and radiation episode of the strongly variable shock in the system.

Very high energy gamma ray astrophysics. Progress report, August 1, 1980-July 31, 1981

International Nuclear Information System (INIS)

Lamb, R.C.

1981-04-01

Very high energy (VHE) gamma ray astronomy gives insight into fundamental questions regarding the origins of cosmic rays and the types of particle acceleration mechanisms which operate in nature. VHE photons are detected by means of the Cerenkov light their secondaries produce in the atmosphere. During June - September 1981 the solar collectors at Edwards Air Force Base will be used to detect the Cerenkov light from the photons from Cygnus X-3 thus extending its observation into a previously unexplored region. The time of each detector event will be recorded to the nearest 0.5 ms. If Cygnus X-3 is the neutron star remnant of a recent (unseen) supernova, then the VHE gamma rays may be pulsed at its rotation rate, and the data obtained will allow a sensitive test of this possibility. The equipment for the summer observations is nearly ready and will be tested in May prior to any early run in June

Validation of gamma-ray detection techniques for safeguards monitoring at natural uranium conversion facilities

Energy Technology Data Exchange (ETDEWEB)

Dewji, S.A., E-mail: dewjisa@ornl.gov [Oak Ridge National Laboratory, 1 Bethel Valley Road, MS-6335, Oak Ridge, TN 37831-6335 (United States); Lee, D.L.; Croft, S. [Oak Ridge National Laboratory, 1 Bethel Valley Road, MS-6335, Oak Ridge, TN 37831-6335 (United States); Hertel, N.E. [Oak Ridge National Laboratory, 1 Bethel Valley Road, MS-6335, Oak Ridge, TN 37831-6335 (United States); Nuclear and Radiological Engineering Program, Georgia Institute of Technology, 770 State Street, Atlanta, GA 30332-0745 (United States); Chapman, J.A.; McElroy, R.D.; Cleveland, S. [Oak Ridge National Laboratory, 1 Bethel Valley Road, MS-6335, Oak Ridge, TN 37831-6335 (United States)

2016-07-01

Recent IAEA circulars and policy papers have sought to implement safeguards when any purified aqueous uranium solution or uranium oxides suitable for isotopic enrichment or fuel fabrication exists. Under the revised policy, IAEA Policy Paper 18, the starting point for nuclear material under safeguards was reinterpreted, suggesting that purified uranium compounds should be subject to safeguards procedures no later than the first point in the conversion process. In response to this technical need, a combination of simulation models and experimental measurements were employed to develop and validate concepts of nondestructive assay monitoring systems in a natural uranium conversion plant (NUCP). In particular, uranyl nitrate (UO{sub 2}(NO{sub 3}){sub 2}) solution exiting solvent extraction was identified as a key measurement point (KMP), where gamma-ray spectroscopy was selected as the process monitoring tool. The Uranyl Nitrate Calibration Loop Equipment (UNCLE) facility at Oak Ridge National Laboratory was employed to simulate the full-scale operating conditions of a purified uranium-bearing aqueous stream exiting the solvent extraction process in an NUCP. Nondestructive assay techniques using gamma-ray spectroscopy were evaluated to determine their viability as a technical means for drawing safeguards conclusions at NUCPs, and if the IAEA detection requirements of 1 significant quantity (SQ) can be met in a timely way. This work investigated gamma-ray signatures of uranyl nitrate circulating in the UNCLE facility and evaluated various gamma-ray detector sensitivities to uranyl nitrate. These detector validation activities include assessing detector responses to the uranyl nitrate gamma-ray signatures for spectrometers based on sodium iodide, lanthanum bromide, and high-purity germanium detectors. The results of measurements under static and dynamic operating conditions at concentrations ranging from 10–90 g U/L of natural uranyl nitrate are presented. A range of

Swift: A gamma ray burst MIDEX

International Nuclear Information System (INIS)

Barthelmy, Scott

2001-01-01

Swift is a first of its kind multiwavelength transient observatory for gamma-ray burst astronomy. It has the optimum capabilities for the next breakthroughs in determining the origin of gamma-ray bursts and their afterglows as well as using bursts to probe the early Universe. Swift will also perform the first sensitive hard X-ray survey of the sky. The mission is being developed by an international collaboration and consists of three instruments, the Burst Alert Telescope (BAT), the X-ray Telescope (XRT), and the Ultraviolet and Optical Telescope (UVOT). The BAT, a wide-field gamma-ray detector, will detect ∼1 gamma-ray burst per day with a sensitivity 5 times that of BATSE. The sensitive narrow-field XRT and UVOT will be autonomously slewed to the burst location in 20 to 70 seconds to determine 0.3-5.0 arcsec positions and perform optical, UV, and X-ray spectrophotometry. On-board measurements of redshift will also be done for hundreds of bursts. Swift will incorporate superb, low-cost instruments using existing flight-spare hardware and designs. Strong education/public outreach and follow-up programs will help to engage the public and astronomical community. Swift has been selected by NASA for development and launch in late 2003

Detection of pseudo gamma-ray bursts of long duration

International Nuclear Information System (INIS)

Frontera, F.; Fuligni, F.; Morelli, E.; Pizzichini, G.; Ventura, G.

1981-01-01

It is known that the counting rate of both Na I and Cs I hard X-ray detectors can have intense enhancements of brief (< 1 s) duration, which appear like very short cosmic gamma-ray bursts but probably are due to phosphorescence in the detector itself. Unfortunately, this problem is not limited to short bursts. We present here three much longer (up to 80 s) pseudo-gamma-ray bursts observed during a transatlantic balloon flight. We conclude that detections of gamma-ray bursts (and probably also of hard X-ray source flares) based only on a rate increase by a single scintillator should always be confirmed by at least one other instrument. (orig.)

The application of two-dimensional imaging to very high energy gamma ray astronomy

International Nuclear Information System (INIS)

Weekes, T.C.

1992-05-01

A technique has been developed to distinguish air showers generated by gamma rays from those generated by hadronic cosmic rays. The method involves the registration of the Cherenkov light images by a large aperture multi-phototube telescope at the Whipple Observatory in southern Arizona. The energy threshold is 0.4 TeV. The efficacy of the technique has been demonstrated by the detection of a signal from the Crab Nebula, a supernova remnant. The physics of shower development at TeV energies is demonstrated to be what is expected, and no support is found for the detection of anomalous signals from binary sources. The sensitivity of the technique is such that a five sigma gamma-ray signal from the Crab can be detected in just an hour of observation. Further improvements in the technique are under way; in particular, a second large aperture camera is now operated in conjunction with the original camera to give stereoscopic images of showers. When completed, this system will give a flux sensitivity a factor of ten below that now available

Public List of LAT-Detected Gamma-Ray Pulsars

Data.gov (United States)

National Aeronautics and Space Administration — The following is a compilation of all publicly-announced gamma-ray pulsars detected using the Fermi LAT. Each of the detections has been vetted by the LAT team,...

Detection circuit for gamma-ray burst

International Nuclear Information System (INIS)

Murakami, Hiroyuki; Yamagami, Takamasa; Mori, Kunishiro; Uchiyama, Sadayuki.

1982-01-01

A new gamma-ray burst detection system is described. The system was developed as an environmental monitor of an accelerator, and can be used as the burst detection system. The system detects the arrival time of burst. The difference between the arrival times detected at different places will give information on the burst source. The frequency of detecting false burst was estimated, and the detection limit under the estimated frequency of false burst was also calculated. Decision whether the signal is false or true burst was made by the statistical treatment. (Kato, T.)

Design and expected performance of a novel hybrid detector for very-high-energy gamma-ray astrophysics

Science.gov (United States)

Assis, P.; Barres de Almeida, U.; Blanco, A.; Conceição, R.; D'Ettorre Piazzoli, B.; De Angelis, A.; Doro, M.; Fonte, P.; Lopes, L.; Matthiae, G.; Pimenta, M.; Shellard, R.; Tomé, B.

2018-05-01

Current detectors for Very-High-Energy γ-ray astrophysics are either pointing instruments with a small field of view (Cherenkov telescopes), or large field-of-view instruments with relatively large energy thresholds (extensive air shower detectors). In this article, we propose a new hybrid extensive air shower detector sensitive in an energy region starting from about 100 GeV. The detector combines a small water-Cherenkov detector, able to provide a calorimetric measurement of shower particles at ground, with resistive plate chambers which contribute significantly to the accurate shower geometry reconstruction. A full simulation of this detector concept shows that it is able to reach better sensitivity than any previous gamma-ray wide field-of-view experiment in the sub-TeV energy region. It is expected to detect with a 5σ significance a source fainter than the Crab Nebula in one year at 100 GeV and, above 1 TeV a source as faint as 10% of it. As such, this instrument is suited to detect transient phenomena making it a very powerful tool to trigger observations of variable sources and to detect transients coupled to gravitational waves and gamma-ray bursts.

High Energy Gamma-rays from FR I Jets

CERN Document Server

Sikora, M

2003-01-01

Thanks to Hubble and Chandra telescopes, some of the large scale jets in extragalactic radio sources are now being observed at optical and X-ray frequencies. For the FR I objects the synchrotron nature of this emission is surely established, although a lot of uncertainties--connected for example with the particle acceleration processes involved--remain. In this paper we study production of high energy gamma-rays in FR I kiloparsec-scale jets by inverse-Compton emission of the synchrotron-emitting electrons. We consider different origin of seed photons contributing to the inverse-Compton scattering, including nuclear jet radiation as well as ambient, stellar and circumstellar emission of the host galaxies. We discuss how future detections or non-detections of the evaluated gamma-ray fluxes can provide constraints on the unknown large scale jet parameters, i.e. the magnetic field intensity and the jet Doppler factor. For the nearby sources Centaurus A and M 87, we find measurable fluxes of TeV photons resulting...

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

Directory of Open Access Journals (Sweden)

Iyono Atsushi

2017-01-01

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

Isolation of cell cycle-dependent gamma ray-sensitive Chinese hamster ovary cell

International Nuclear Information System (INIS)

Stamato, T.D.; Weinstein, R.; Giaccia, A.; Mackenzie, L.

1983-01-01

A technique for the isolation of gamma ray-sensitive Chinese hamster ovary (CHO) cell mutants is described, which uses nylon cloth replica plating and photography with dark-field illumination to directly monitor colonies for growth after gamma irradiation. Two gamma ray-sensitive mutants were isolated using this method. One of these cells (XR-1) had a two-slope survival curve: an initial steep slope and then a flattening of the curve at about 10% survival. Subsequently, it was found that this cell is sensitive to gamma irradiation in G1, early S, and late G2 phases of the cell cycle, whereas in the resistant phase (late S phase) its survival approaches that of the parental cells. The D37 in the sensitive G1 period is approximately 30 rads, compared with 300 rads of the parental cell. This mutant cell is also sensitive to killing by the DNA breaking agent, bleomycin, but is relatively insensitive to UV light and ethyl methane sulfonate, suggesting that the defect is specific for agents that produce DNA strand breakage

Lunar occultations for gamma-ray source measurements

Science.gov (United States)

Koch, David G.; Hughes, E. B.; Nolan, Patrick L.

1990-01-01

The unambiguous association of discrete gamma-ray sources with objects radiating at other wavelengths, the separation of discrete sources from the extended emission within the Galaxy, the mapping of gamma-ray emission from nearby galaxies and the measurement of structure within a discrete source cannot presently be accomplished at gamma-ray energies. In the past, the detection processes used in high-energy gamma-ray astronomy have not allowed for good angular resolution. This problem can be overcome by placing gamma-ray detectors on the moon and using the horizon as an occulting edge to achieve arcsec resolution. For purposes of discussion, this concept is examined for gamma rays above 100 MeV for which pair production dominates the detection process and locally-generated nuclear gamma rays do not contribute to the background.

Ultimate detection sensitivity of Ge-Li γ-ray spectrometers

International Nuclear Information System (INIS)

1978-06-01

This paper presents the principal results of a study concerning low-level counting capabilities of GeLi gamma-ray spectrometers. The expression adopted for the theoretical sensitivity limit of gamma spectrometers has been experimentally verified with very low activity samples, using 17 installations of various characteristics. This expression sets off the influence of the efficiency, the environmental conditions on the sensitivity limits. It can be used also to eliminate the fraudulents peaks in automatical analysis of gamma-ray spectras. At last, it provides a list of criteria to determine the most suitable characteristics of a detector according to a special problem. Informations which have to be obtained from the manufacturers are specified [fr

Formation properties from high resolution neutron activation gamma-ray spectra

International Nuclear Information System (INIS)

Mellor, D.W.; Underwood, M.C.

1985-01-01

A neutron activation logging tool has been developed comprising a Five Curie /sup 241/ Am-Be neutron source and a large n-type hyper-pure germanium gamma-ray detector. The tool maintains a constant temperature cryogenic environment for periods in excess of twenty hours. No liquid nitrogen or other consumable material is used in the operating or recharging stages. A large calibration tank in simulated well-bore geometry has been constructed with sand bodies saturated with oil and low salinity water (14,000 ppm NaCl). In the water zone prompt neutron capture gamma-rays from silicon, hydrogen and chlorine were prominent; gamma-rays from inelastic scattering on oxygen and silicon were detected. No gamma-rays arising from inelastic scattering on carbon were detected. These data have been interpreted to yield the porosity, fluid saturations, salinity and matrix composition. In the oil zone, gamma-rays arising from inelastic scattering on oxygen, silicon and carbon were detected. The intensity of the carbon line was very poor, and inadequate for quantitative purposes

Gamma-Ray Imaging Spectrometer (GRIS): a new balloon-borne experiment for gamma-ray line astronomy

International Nuclear Information System (INIS)

Teegarden, B.J.; Cline, T.L.; Gehrels, N.; Porreca, G.; Tueller, J.; Leventhal, M.; Huters, A.F.; Maccallum, C.J.; Stang, P.D.; Sandia Labs., Albuquerque, NM)

1985-01-01

High resolution gamma-ray spectroscopy is a relatively new field that holds great promise for further understanding of high energy astrophysical processes. When the high resolution gamma-ray spectrometer (GRSE) was removed from the GRO payload, a balloon program was initiated to permit continued development and improvement of instrumentation in this field, as well as continued scientific observations. The Gamma-Ray Imaging Spectrometer (GRIS) is one of the experiments selected as part of this program. The instrument contains a number of new and innovative features that are expected to produce a significant improvement in source location accuracy and sensitivity over previous balloon and satellite experiments

High-energy gamma-ray emission in compact binaries

International Nuclear Information System (INIS)

Cerutti, Benoit

2010-01-01

Four gamma-ray sources have been associated with binary systems in our Galaxy: the micro-quasar Cygnus X-3 and the gamma-ray binaries LS I +61 degrees 303, LS 5039 and PSR B1259-63. These systems are composed of a massive companion star and a compact object of unknown nature, except in PSR B1259-63 where there is a young pulsar. I propose a comprehensive theoretical model for the high-energy gamma-ray emission and variability in gamma-ray emitting binaries. In this model, the high-energy radiation is produced by inverse Compton scattering of stellar photons on ultra-relativistic electron-positron pairs injected by a young pulsar in gamma-ray binaries and in a relativistic jet in micro-quasars. Considering anisotropic inverse Compton scattering, pair production and pair cascade emission, the TeV gamma-ray emission is well explained in LS 5039. Nevertheless, this model cannot account for the gamma-ray emission in LS I +61 degrees 303 and PSR B1259-63. Other processes should dominate in these complex systems. In Cygnus X-3, the gamma-ray radiation is convincingly reproduced by Doppler-boosted Compton emission of pairs in a relativistic jet. Gamma-ray binaries and micro-quasars provide a novel environment for the study of pulsar winds and relativistic jets at very small spatial scales. (author)

Ultra-high energy cosmic rays and prompt TeV gamma rays from ...

Indian Academy of Sciences (India)

physics pp. 789-792. Ultra-high energy cosmic rays and prompt. TeV gamma rays from gamma ray bursts ... The origin of the observed ultra-high energy cosmic ray (UHECR) events with ... are proton and electron rest mass, respectively.

The Dynamic Range of Ultra-High Resolution Cryogenic Gamma-ray Spectrometers

International Nuclear Information System (INIS)

Ali, S; Terracol, S F; Drury, O B; Friedrich, S

2005-01-01

We are developing high-resolution cryogenic gamma-ray spectrometers for nuclear science and non-proliferation applications. The gamma-ray detectors are composed of a bulk superconducting Sn foil absorber attached to multilayer Mo/Cu transition-edge sensors (TES). The energy resolution achieved with a 1 x 1 x 0.25 mm 3 Sn absorber is 50 -90eV for γ-rays up to 100 keV and it decreases for large absorber sizes. We discuss the trade-offs between energy resolution and dynamic range, as well as development of TES arrays for higher count rates and better sensitivity

Gamma-Ray, Cosmic Ray and Neutrino Tests of Lorentz Invariance and Quantum Gravity Models

Science.gov (United States)

Stecker, Floyd

2011-01-01

High-energy astrophysics observations provide the best possibilities to detect a very small violation of Lorentz invariance such as may be related to the structure of space-time near the Planck scale of approximately 10(exp -35) m. I will discuss here the possible signatures of Lorentz invariance violation (LIV) from observations of the spectra, polarization, and timing of gamma-rays from active galactic nuclei and gamma-ray bursts. Other sensitive tests are provided by observations of the spectra of ultrahigh energy cosmic rays and neutrinos. Using the latest data from the Pierre Auger Observatory one can already derive an upper limit of 4.5 x 10(exp -23) to the amount of LIV of at a proton Lorentz factor of approximately 2 x 10(exp 11). This result has fundamental implications for quantum gravity models. I will also discuss the possibilities of using more sensitive space based detection techniques to improve searches for LIV in the future.

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

Science.gov (United States)

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.

Characterization of Compton-suppressed TIGRESS detectors for high energy gamma-rays

International Nuclear Information System (INIS)

Kshetri, R.; Andreoiu, C.; Cross, D.S.; Galinski, N.; Ball, G.C.; Djongolov, M.; Garnsworthy, A.B.; Hackman, G.; Orce, J.N.; Pearson, C.; Triambak, S.; Williams, S.J.; Drake, T.; Smalley, D.; Svensson, C.E.

2009-01-01

The TRIUMF-ISAC Gamma-Ray Escape- Suppressed Spectrometer (TIGRESS) will consist of 12 large-volume, 32-fold segmented HPGe clover detectors. Each detector is shielded by a 20-fold segmented Compton suppression shield. For performing discrete gamma-ray spectroscopy of light mass nuclei with TIGRESS, we need information about full energy peak efficiency, resolution and lineshape of full energy peaks for high energy gamma-rays. However, suitable radioactive sources having decay gamma-rays of energies greater than ∼ 3.5 MeV are not easily available. So the characteristics of gamma spectrometers at energies higher than 3.5 MeV are usually determined from simulation data. Predictions from GEANT4 simulations (experimentally validated from 0.3 to 3 MeV) indicate that TIGRESS will be capable for single 10 MeV gamma-rays of absolute detection efficiency of 1.5% for backward configuration of the array. It has been observed experimentally that simulation results work well up to certain energies and might deviate at higher energies. So, it is essential to check the validity of simulation results for energies above 3.3 MeV. We have investigated the high energy performance of seven TIGRESS detectors up to 8 MeV

Sensitivity of P-Channel MOSFET to X- and Gamma-Ray Irradiation

Directory of Open Access Journals (Sweden)

Milić Pejović

2013-01-01

Full Text Available Investigation of Al-gate p-channel MOSFETs sensitivity following irradiation using 200 and 280 kV X-ray beams as well as gamma-ray irradiation of 60Co in the dose range from 1 to 5 Gy was performed in this paper. The response followed on the basis of threshold voltage shift and was studied as a function of absorbed dose. It was shown that the most significant change in threshold voltage was in the case of MOSFET irradiation in X-ray fields of 200 kV and when the gate voltage was +5 V. For practical applications in dosimetry, the sensitivity of the investigated MOSFETs was also satisfactory for X-ray tube voltage of 280 kV and for gamma rays. Possible processes in gate oxide caused by radiation and its impact on the response of MOSFETs were also analyzed in this paper.

Gamma-Ray Background Variability in Mobile Detectors

Science.gov (United States)

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

Enhanced gamma ray sensitivity in bismuth triiodide sensors through volumetric defect control

International Nuclear Information System (INIS)

Johns, Paul M.; Baciak, James E.; Nino, Juan C.

2016-01-01

Some of the more attractive semiconducting compounds for ambient temperature radiation detector applications are impacted by low charge collection efficiency due to the presence of point and volumetric defects. This has been particularly true in the case of BiI_3, which features very attractive properties (density, atomic number, band gap, etc.) to serve as a gamma ray detector, but has yet to demonstrate its full potential. We show that by applying growth techniques tailored to reduce defects, the spectral performance of this promising semiconductor can be realized. Gamma ray spectra from >100 keV source emissions are now obtained from high quality Sb:BiI_3 bulk crystals with limited concentrations of defects (point and extended). The spectra acquired in these high quality crystals feature photopeaks with resolution of 2.2% at 662 keV. Infrared microscopy is used to compare the local microstructure between radiation sensitive and non-responsive crystals. This work demonstrates that BiI_3 can be prepared in melt-grown detector-grade samples with superior quality and can acquire the spectra from a variety of gamma ray sources.

Early warning for VHE gamma-ray flares with the ARGO-YBJ detector

Energy Technology Data Exchange (ETDEWEB)

Bartoli, B. [Dipartimento di Fisica dell' Universita di Napoli ' Federico II' , Complesso Universitario di Monte Sant' Angelo, via Cinthia, 80126 Napoli (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, Complesso Universitario di Monte Sant' Angelo, via Cinthia, 80126 Napoli (Italy); Bernardini, P. [Dipartimento di Fisica dell' Universita del Salento, via per Arnesano, 73100 Lecce (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Lecce, via per Arnesano, 73100 Lecce (Italy); Bi, X.J. [Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, P.O. Box 918, 100049 Beijing (China); Bleve, C. [Dipartimento di Fisica dell' Universita del Salento, via per Arnesano, 73100 Lecce (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Lecce, via per Arnesano, 73100 Lecce (Italy); Bolognino, I. [Dipartimento di Fisica Nucleare e Teorica dell' Universita di Pavia, via Bassi 6, 27100 Pavia (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, via Bassi 6, 27100 Pavia (Italy); Branchini, P.; Budano, A. [Istituto Nazionale di Fisica Nucleare, Sezione di Roma Tre, via della Vasca Navale 84, 00146 Roma (Italy); Calabrese Melcarne, A.K. [Istituto Nazionale di Fisica Nucleare - CNAF, Viale Berti-Pichat 6/2, 40127 Bologna (Italy); Camarri, P. [Dipartimento di Fisica dell' Universita di Roma ' Tor Vergata' , via della Ricerca Scientifica 1, 00133 Roma (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Roma Tor Vergata, via della Ricerca Scientifica 1, 00133 Roma (Italy); Cao, Z. [Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, P.O. Box 918, 100049 Beijing (China); and others

2011-12-11

Detecting and monitoring emissions from flaring gamma-ray sources in the very-high-energy (VHE, > 100 GeV) band is a very important topic in gamma-ray astronomy. The ARGO-YBJ detector is characterized by a high duty cycle and a wide field of view. Therefore, it is particularly capable of detecting flares from extragalactic objects. Based on fast reconstruction and analysis, real-time monitoring of 33 selected VHE extragalactic sources is implemented. Flares exceeding a specific threshold are reported timely, hence enabling the follow-up observation of these objects using more sensitive detectors, such as Cherenkov telescopes.

Development of a Gamma-Ray Detector for Z-Selective Radiographic Imaging

International Nuclear Information System (INIS)

Brandis, Michal

2013-11-01

Dual-Discrete Energy Gamma-Radiography (DDEGR) is a method for Special Nuclear Materials (SNM) detection. DDEGR utilizes 15.11 and 4.43 MeV gamma-rays produced in the 11B(d,n)12C reaction, in contrast to the conventional use of continuous Bremsstrahlung radiation. The clean and well separated gamma-rays result in high contrast sensitivity, enabling detection of small quantities of SNM. The most important aspects of a DDEGR system were discussed, simulated, measured and demonstrated. An experimental measurement of gamma-ray yields from the 11B(d,n)12C reaction showed that the yields from deuterons with 3{12 MeV energy are 2{201010 N/sr/mC 4.4 MeV gamma- rays and 2{5109 N/sr/mC 15.1 MeV gamma-rays. The measured neutron yields show that the neutron energies extend to 15-23 MeV for the same deuteron energy range. A simplied inspection system was simulated with GEANT4, showing that the ect of scattering on the signal measured in the detector is acceptable. Considering the reaction gamma yields, 1.8 mA deuteron current is required for separation of high-Z materials from medium- and low-Z materials and a 4.5 mA current is required for the additional capability of separating benign high-Z materials from SNM. The main part of the work was development of a detector suitable for a DDEGR system | Time Resolved Event Counting Optical Radiation (TRECOR) detector. TRECOR detector is a novel spectroscopic imaging detector for gamma-rays within the MeV energy range that uses an event counting image intensier with gamma-rays for the rst time. Neutrons that accompany the gamma radiation enable to implement, in parallel, Fast Neutron Resonance Radiography (FNRR), a method for explosives detection. A second generation detector, TRECOR-II, is capable of detecting gamma-rays and neutrons in parallel, separating them to create particle-specic images and energy-specic images for each particle, thus enabling simultaneous implementation of the two detection methods. A full DDEGR laboratory

The Advanced Gamma-ray Imaging System (AGIS)-Science Highlights

Science.gov (United States)

Buckley, J.; Coppi, P.; Digel, S.; Funk, S.; Krawczynski, H.; Krennrich, F.; Pohl, M.; Romani, R.; Vassiliev, V.

2008-12-01

The Advanced Gamma-ray Imaging System (AGIS), a future gamma-ray telescope consisting of an array of ~50 atmospheric Cherenkov telescopes distributed over an area of ~1 km2, will provide a powerful new tool for exploring the high-energy universe. The order-of-magnitude increase in sensitivity and improved angular resolution could provide the first detailed images of γ-ray emission from other nearby galaxies or galaxy clusters. The large effective area will provide unprecedented sensitivity to short transients (such as flares from AGNs and GRBs) probing both intrinsic spectral variability (revealing the details of the acceleration mechanism and geometry) as well as constraining the high-energy dispersion in the velocity of light (probing the structure of spacetime and Lorentz invariance). A wide field of view (~4 times that of current instruments) and excellent angular resolution (several times better than current instruments) will allow for an unprecedented survey of the Galactic plane, providing a deep unobscured survey of SNRs, X-ray binaries, pulsar-wind nebulae, molecular cloud complexes and other sources. The differential flux sensitivity of ~10-13 erg cm-2 sec-1 will rival the most sensitive X-ray instruments for these extended Galactic sources. The excellent capabilities of AGIS at energies below 100 GeV will provide sensitivity to AGN and GRBs out to cosmological redshifts, increasing the number of AGNs detected at high energies from about 20 to more than 100, permitting population studies that will provide valuable insights into both a unified model for AGN and a detailed measurement of the effects of intergalactic absorption from the diffuse extragalactic background light. A new instrument with fast-slewing wide-field telescopes could provide detections of a number of long-duration GRBs providing important physical constraints from this new spectral component. The new array will also have excellent background rejection and very large effective area

Bursts of the Crab Nebula gamma-ray emission at high and ultra-high energies

Directory of Open Access Journals (Sweden)

Lidvansky A.S.

2017-01-01

Full Text Available Characteristics of the flares of gamma rays detected from the Crab Nebula by the AGILE and Fermi-LAT satellite instruments are compared with those of a gamma ray burst recorded by several air shower arrays on February 23, 1989 and with one recent observation made by the ARGO-YBJ array. It is demonstrated that though pulsar-periodicity and energy spectra of emissions at 100 MeV (satellite gamma ray telescopes and 100 TeV (EAS arrays are different, their time structures seem to be similar. Moreover, maybe the difference between “flares” and “waves” recently found in the Crab Nebula emission by the AGILE team also exists at ultra-high energies.

High energy gamma-ray production in nuclear reactions

International Nuclear Information System (INIS)

Pinston, J.A.; Nifenecker, H.; Nifenecker, H.

1989-01-01

Experimental techniques used to study high energy gamma-ray production in nuclear reactions are reviewed. High energy photon production in nucleus-nucleus collisions is discussed. Semi-classical descriptions of the nucleus-nucleus gamma reactions are introduced. Nucleon-nucleon gamma cross sections are considered, including theoretical aspects and experimental data. High energy gamma ray production in proton-nucleus reactions is explained. Theoretical explanations of photon emission in nucleus-nucleus collisions are treated. The contribution of charged pion currents to photon production is mentioned

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

Science.gov (United States)

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.

Angular resolution study of a combined gamma-neutron coded aperture imager for standoff detection

International Nuclear Information System (INIS)

Ayaz-Maierhafer, Birsen; Hayward, Jason P.; Ziock, Klaus P.; Blackston, Matthew A.; Fabris, Lorenzo

2013-01-01

Nuclear threat source observables at standoff distances of tens of meters from mCi class sources include both gamma-rays and neutrons. This work uses simulations to investigate the effects of the angular resolution of a mobile gamma-ray and neutron coded aperture imaging system upon orphan source detection significance and specificity. The design requires maintaining high sensitivity and specificity while keeping the system size as compact as possible to reduce weight, footprint, and cost. A mixture of inorganic and organic scintillators was considered in the detector plane for high sensitivity to both gamma-rays and fast neutrons. For gamma-rays (100 to 2500 keV) and fission spectrum neutrons, angular resolutions of 1–9° and radiation angles of incidence appropriate for mobile search were evaluated. Detection significance for gamma-rays considers those events that contribute to the photopeak of the image pixel corresponding the orphan source location. For detection of fission spectrum neutrons, energy depositions above a set pulse shape discrimination threshold were tallied. The results show that the expected detection significance for the system at an angular resolution of 1° is significantly lower compared to its detection significance an angular resolution of ∼3–4°. An angular resolution of ∼3–4° is recommended both for better detection significance and improved false alarm rate, considering that finer angular resolution does not result in improved background rejection when the coded aperture method is used. Instead, over-pixelating the search space may result in an unacceptably high false alarm rate

Gamma ray astronomy with COS-B

International Nuclear Information System (INIS)

Swanenburg, B.N.

1981-01-01

Observational results in the field of gamma-ray astronomy that have been obtained to date with the COS-B satellite are discussed and questions raised by these observations are summarized. Following a brief review of the instrumental characteristics of COS-B and the extent of COS-B gamma-ray coverage of the sky, particular attention is given to the questions raised by the discovery of many unidentified gamma-ray sources with no apparent optical, X-ray or radio counterparts and the detection of high-energy gamma radiation from the quasar 3C 273, which suggests the role of gamma-ray emission in the creation of other radiation

Discoveries by the Fermi Gamma Ray Space Telescope

Science.gov (United States)

Gehrels, Neil

2011-01-01

Fermi is a large space gamma-ray mission developed by NASA and the DOE with major contributions from France, Germany, Italy, Japan and Sweden. It was launched in June 2008 and has been performing flawlessly since then. The main instrument is the Large Area Telescope (LAT) operating in the 20 MeV to 300 GeV range and a smaller monitor instrument is the Gamma-ray Burst Monitor (GBM) operating in the 8 keV to 40 MeV range. New findings are occurring every week. Some of the key discoveries are: 1) Discovery of many new gamma-ray pulsars, including gamma-ray only and millisecond pulsars. 2) Detection of high energy gamma-ray emission from globular clusters, most likely due to summed emission from msec pulsars. 3) Discovery of delayed and extended high energy gamma-ray emission from short and long gamma-ray busts. 4) Detection of approximately 250 gamma-ray bursts per year with the GBM instrument. 5) Most accurate measurement of the cosmic ray electron spectrum between 30 GeV and 1 TeV, showing some excess above the conventional diffusion model. The talk will present the new discoveries and their implications.

Performance characteristics of high resolution semiconductor gamma ray spectrometry system

Energy Technology Data Exchange (ETDEWEB)

Naing, Ko Ko

1994-05-01

A high purity germanium (HPGe) gamma-ray detector has been used in Nuclear Research Laboratory, Department of Physics, Yangon University for over fourteen years. Now it is still being used and it is coupled to new peripheral devices, such as spectroscopy amplifier, analog to digital converter and computer fit-in S-100 multichannel analyser. Therefore, it is necessary to determine the important parameters: energy resolution, detecting efficiency and relative efficiency of the system. In the present work, these parameters were obtained by using mixed calibrated source. The results were compared to the data given by the manufacturer. Moreover, the parameters of another {gamma}-ray detecting system NaI(T1) were also determined. In conclusion the results obtained from the above two measurements were compared and discussed

The CTA Sensitivity to Lorentz-Violating Effects on the Gamma-Ray Horizon

CERN Document Server

Fairbairn, Malcolm; Ellis, John; Hinton, Jim; White, Richard

2014-01-01

The arrival of TeV-energy photons from distant galaxies is expected to be affected by their QED interaction with intergalactic radiation fields through electron-positron pair production. In theories where high-energy photons violate Lorentz symmetry, the kinematics of the process $\\gamma + \\gamma\\rightarrow e^+ + e^-$ is altered and the cross-section suppressed. Consequently, one would expect more of the highest-energy photons to arrive if QED is modified by Lorentz violation than if it is not. We estimate the sensitivity of Cherenkov Telescope Array (CTA) to changes in the $\\gamma$-ray horizon of the Universe due to Lorentz violation, and find that it should be competitive with other leading constraints.

Very high energy gamma ray astrophysics

International Nuclear Information System (INIS)

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

1991-01-01

The Whipple Observatory High Resolution Camera will be used in a vigorous program of observations to search for new sources of very-high-energy gamma rays. In addition, a search for antimatter using the moon-earth system as an ion spectrometer will be begun. The first phase of GRANITE, the new 37-element 11-m camera, will be concluded with first light scheduled for September, 1991. The two cameras will operate in support of the Gamma Ray Observatory mission in the winter of 1991/2

High gamma-ray measurement using optical emission of ceramic material

Energy Technology Data Exchange (ETDEWEB)

Kakuta, Tsunemi; Sakasai, Kaoru; Yamagishi, Hideshi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Nakazawa, Masaharu

1996-07-01

This paper describes the fluorescence phenomena in Zr-O ceramic under expose to high gamma-ray and fission neutron source. In addition, the paper also discusses the possibility of ionizing radiation detection in the core region of reactor. (J.P.N.)

Gamma-ray spectrometer utilizing xenon at high pressure

International Nuclear Information System (INIS)

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

1994-01-01

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

Gamma-ray pulsars: Emission zones and viewing geometries

Science.gov (United States)

Romani, Roger W.; Yadigaroglu, I.-A.

1995-01-01

There are now a half-dozen young pulsars detected in high-energy photons by the Compton Gamma-Ray Observatory (CGRO), showing a variety of emission efficiencies and pulse profiles. We present here a calculation of the pattern of high-energy emission on the sky in a model which posits gamma-ray production by charge-depleted gaps in the outer magnetosphere. This model accounts for the radio to gamma-ray pulse offsets of the known pulsars, as well as the shape of the high-energy pulse profiles. We also show that about one-third of emitting young radio pulsars will not be detected due to beaming effects, while approximately 2.5 times the number of radio-selected gamma-ray pulsars will be viewed only high energies. Finally we compute the polarization angle variation and find that the previously misunderstood optical polarization sweep of the Crab pulsar arises naturally in this picture. These results strongly support an outer magnetosphere location for the gamma-ray emission.

Terrestrial Gamma-ray Flashes (TGFs) Observed with the Fermi-Gamma-ray Burst Monitor: Temporal and Spectral Properties

Science.gov (United States)

Fishman, G. J.; Briggs, M. S.; Connaughton, W.; Wilson-Hodge, C.; Bhat, P. N.

2010-01-01

The Gamma-ray Burst Monitor (GBM) on the Fermi Gamma-ray Space Telescope Observatory (Fermi) was detecting 2.1 TGFs per week. This rate has increased by a factor of 8 since new flight software was uploaded to the spacecraft in November 2009 in order to increase the sensitivity of GBM to TGFs. Further upgrades to Fermi-GBM to allow observations of weaker TGFs are in progress. The high time resolution (2 s) allows temporal features to be resolved so that some insight may be gained on the origin and transport of the gamma-ray photons through the atmosphere. The absolute time of the TGFs, known to several microseconds, also allows accurate correlations of TGFs with lightning networks and other lightning-related phenomena. The thick bismuth germanate (BGO) scintillation detectors of the GBM system have observed photon energies from TGFs at energies above 40 MeV. New results on the some temporal aspects of TGFs will be presented along with spectral characteristics and properties of several electron-positron TGF events that have been identified.

Gamma Ray Bursts - Observations

Science.gov (United States)

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.

Study and realization of pixelated APD Geiger photodetectors of very high sensitivity for Very High Energy gamma astronomy

International Nuclear Information System (INIS)

Jradi, K.

2010-07-01

Very High Energy gamma ray astronomy uses till now exclusively as detector the Photomultiplier Tube (PMT) to collect weak light flux of atmospheric showers. But an alternative is now emerging: Avalanche Photodiodes polarized in Geiger mode called 'Geiger-APD'. The PMT is a detector designed in the 70's which presents many advantages but also suffers from several drawbacks: size, weight, cost, sensitivity to magnetic field but especially difficulty to realize its pixelation in matrix. Geiger-APDs are semi-conductor devices made of PN junction integrated in a special technology to detect very low light flux, thanks to the polarization beyond the avalanche voltage. Geiger-APD presents very high photoelectron gain (∼106) strongly dependant on the polarization voltage beyond avalanche. These photodiodes present many advantages with respect to PMT, mainly as concerns miniaturization for applications based on imaging, such as the detection of Cerenkov flashes in gamma ray astronomy. In this thesis, we present the study, the design and the realization of a technological structure, based on Silicon. This structure has shown reliability to detect weak luminous flux with breakdown voltage at 12 V and dark current below 10 pA at breakdown. We also developed several models, physical and electrical, necessary to the technological optimization, as well to the development of control and readout circuits, i.e. the basis of any imaging technology. The work presented here consists in the study, the design and the realization of a matrix of high sensitivity pixels. A project of a Cerenkov telescope based on this innovative technology is also presented. (author)

Principles and techniques of gamma ray tracers

International Nuclear Information System (INIS)

Claxton, K.T.

1978-01-01

Radioactive tracer techniques provide a very sensitive means of studying physical and chemical processes in a whole variety of different media. Some of the techniques and principles of radioactive tracers and their application to practical engineering systems are discussed. Information which has been found useful in the design of high temperature liquid sodium facilities employing radio-tracers, is presented. The report deals solely with the use of gamma-emitting species as the tracer. These find particular application for in-situ studies on engineering systems where the highly penetrating properties of gamma rays are needed for detection through strongly absorbent media such as stainless steel pepe walls. (author)

Found: A Galaxy's Missing Gamma Rays

Science.gov (United States)

Kohler, Susanna

2016-04-01

Recent reanalysis of data from the Fermi Gamma-ray Space Telescope has resulted in the first detection of high-energy gamma rays emitted from a nearby galaxy. This discovery reveals more about how supernovae interact with their environments.Colliding Supernova RemnantAfter a stellar explosion, the supernovas ejecta expand, eventually encountering the ambient interstellar medium. According to models, this generates a strong shock, and a fraction of the kinetic energy of the ejecta is transferred into cosmic rays high-energy radiation composed primarily of protons and atomic nuclei. Much is still unknown about this process, however. One open question is: what fraction of the supernovas explosion power goes into accelerating these cosmic rays?In theory, one way to answer this is by looking for gamma rays. In a starburst galaxy, the collision of the supernova-accelerated cosmic rays with the dense interstellar medium is predicted to produce high-energy gamma rays. That radiation should then escape the galaxy and be visible to us.Pass 8 to the RescueObservational tests of this model, however, have beenstumped by Arp 220. This nearby ultraluminous infrared galaxy is the product of a galaxy merger ~700 million years ago that fueled a frenzy of starbirth. Due to its dusty interior and extreme levels of star formation, Arp 220 has long been predicted to emit the gamma rays produced by supernova-accelerated cosmic rays. But though weve looked, gamma-ray emission has never been detected from this galaxy until now.In a recent study, a team of scientists led by Fang-Kun Peng (Nanjing University) reprocessed 7.5 years of Fermi observations using the new Pass 8 analysis software. The resulting increase in resolution revealed the first detection of GeV emission from Arp 220!Acceleration EfficiencyGamma-ray luminosity vs. total infrared luminosity for LAT-detected star-forming galaxies and Seyferts. Arp 220s luminosities are consistent with the scaling relation. [Peng et al. 2016

Searches for hard X-ray gamma-ray burst afterglows with the BAT on Swift

International Nuclear Information System (INIS)

Krimm, Hans A.; Ozawa, Hideki; Weidenspointner, Georg; Barbier, Louis M.; Barthelmy, Scott D.; Gehrels, Neil; Parsons, Ann M.; Tueller, Jack; Eftekharzadeh, Ardeshir; Hullinger, Derek D.; Markwardt, Craig; Fenimore, Edward E.; Palmer, David M.

2003-01-01

The Burst Alert Telescope (BAT) on the Swift gamma ray burst mission will continue to observe the fields of all detected gamma-ray bursts for several days after the prompt emission has faded. Utilizing first event-by-event data, then one minute and later five minute survey accumulations, the BAT will be extremely sensitive to the hard X-ray afterglow known to be associated with many bursts. This data will cover the crucial transition of the afterglow from rapid variability to the smoothly decaying power law in time and will extend observations of the tails of individual bursts to longer time scales than have been achievable so far. Since Swift is sensitive to short duration GRBs, we will also be able to determine whether hard X-ray afterglows are associated with short GRBs. The BAT will provide high resolution spectra of burst afterglows, allowing us to study in detail the time evolution of GRB spectra

Gamma-rays from decaying dark matter

Energy Technology Data Exchange (ETDEWEB)

Bertone, G. [Paris-6 Univ., 75 (France). Inst. d' Astrophysique; Buchmueller, W.; Covi, L.; Ibarra, A. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

2007-10-15

We study the prospects for detecting gamma-rays from decaying Dark Matter (DM), focusing in particular on gravitino DM in R-parity breaking vacua. Given the substantially different angular distribution of the predicted gamma-ray signal with respect to the case of annihilating DM, and the relatively poor (of order 0.1 ) angular resolution of gamma-ray detectors, the best strategy for detection is in this case to look for an exotic contribution to the gamma-ray flux at high galactic latitudes, where the decaying DM contribution would resemble an astrophysical extragalactic component, similar to the one inferred by EGRET observations. Upcoming experiments such as GLAST and AMS-02 may identify this exotic contribution and discriminate it from astrophysical sources, or place significant constraints on the mass and lifetime of DM particles. (orig.)

Searches for Particle Dark Matter with gamma-rays.

CERN Multimedia

CERN. Geneva

2012-01-01

In this contribution I review the present status and discuss some prospects for indirect detection of dark matter with gamma-rays. Thanks to the Fermi Large Area Telescope, searches in gamma-rays have reached sensitivities that allow to probe the most interesting parameter space of the weakly interacting massive particles (WIMP) paradigm. This gain in sensitivity is naturally accompanied by a number of detection claims or indications, the most recent being the claim of a line feature at a dark matter particle mass of ∼ 130 GeV at the Galactic Centre, a claim which requires confirmation from the Fermi-LAT collaboration and other experiments, for example HESS II or the planned Gamma-400 satellite. Predictions for the next generation air Cherenkov telescope, Cherenkov Telescope Array (CTA), together with forecasts on future Fermi-LAT constraints arrive at the exciting possibility that the cosmological benchmark cross-section could be probed from masses of a few GeV to a few TeV. Consequently, non-detection wou...

Reset charge sensitive amplifier for NaI(Tl) gamma-ray spectrometer

International Nuclear Information System (INIS)

Zeng, Guoqiang; Tan, Chengjun; Li, Qiang; Ge, Liangquan; Liu, Xiyao; Luo, Qun

2015-01-01

The time constant of the output signal of the front-end readout circuit of a traditional gamma-ray spectrometer with a NaI(Tl)+PMT structure is affected by temperature, measurement environment and the signal transmission cable, so it is difficult to get a good resolution spectrum, especially at higher counting rates. In this paper, a reset charge sensitive amplifier (RCSA) is designed for the gamma-ray spectrometer with a NaI(Tl)+PMT structure. The designed RCSA outputs a step signal, thus enabling the acquisition of double-exponential signals with a stable time constant by using the next stage of a CR differentiating circuit. The designed RCSA is mainly composed of a basic amplifying circuit, a reset circuit and a dark current compensation circuit. It provides the output step signal through the integration of the PMT output charge signal. When the amplitude of the step signal exceeds a preset voltage threshold, it triggers the reset circuit to generate a reset pulse (about 5 µs pulse width) to reset the output signal. Experimental results demonstrated that the designed RCSA achieves a charge sensitivity of 4.26×10 10 V/C, with a zero capacitance noise of 51.09 fC and a noise slope of 1.98 fC/pF. Supported by the digital shaping algorithm of the digital multi-channel analyzer (DMCA), it can maintain good energy resolution with high counting rates up to 150 kcps and with a temperature range from −19 °C to 50 °C. - Highlights: • A new reset type charge sensitive amplifier for gamma-ray spectrometer based on a photomultiplier tube is proposed. • Reset circuit formed by constant current source output a fixed width pulse to reset charge sensitive amplifier. • Photomultiplier tube dark current compensation circuit could increase the pulse through rate by decreasing reset frequency. • This amplifier outputs a step function signal that could match next stage circuit easily

Gamma-ray burst polarimeter (GAP)

International Nuclear Information System (INIS)

Mihara, Tatehiro; Murakami, Toshio; Yonetoku, Daisuke; Gunji, Shuichi; Kubo, Shin

2013-01-01

The gamma-ray burst polarimeter (GAP: GAmma-ray burst Polarimeter), which had been almost handcrafted by scientists, has succeeded in working normally in interplanetary space, and in detecting the polarization of the gamma-ray from a mysterious astronomical object 'gamma-ray burst'. It is the first result of the detectors in the world exclusively aiming at detecting gamma-ray polarization. We mainly describe the hardware of our GAP equipment and show the method of preparing equipment to work in the cosmic space with a tight budget. The mechanical structure, the electronic circuits, the software on the equipment, the data analysis on the earth, and the scientific results gained by the observation just over one year, are presented after explaining the principle of gamma-ray polarization detection. Our design to protect equipment against mechanical shock and cosmic radiation may provide useful information for future preparation of compact satellite. (J.P.N.)

CeBr3 as a room-temperature, high-resolution gamma-ray detector

International Nuclear Information System (INIS)

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

2009-01-01

Cerium bromide (CeBr 3 ) has become a material of interest in the race for high-resolution gamma-ray spectroscopy at room temperature. This investigation quantified the potential of CeBr 3 as a room-temperature, high-resolution gamma-ray detector. The performance of CeBr 3 crystals was compared to other scintillation crystals of similar dimensions and detection environments. Comparison of self-activity of CeBr 3 to cerium-doped lanthanum tribromide (LaBr 3 :Ce) was performed. Energy resolution and relative intrinsic efficiency were measured and are presented.

On response operator in semiconductor gamma ray spectrometry

Energy Technology Data Exchange (ETDEWEB)

Krnac, S [Slovak Technical Univ., Bratislava (Slovakia); Povinec, P [International Atomic Energy Agency, Monaco (Monaco). MEL; Ragan, R [Inst. of Preventive and Clinical Medicine, Bratislava (Slovakia)

1996-12-31

Some results of the scaling confirmation factor analysis (SCFA) application in semiconductor gamma-ray spectrometry presented in this contribution points out to a new ground for evaluation the gamma-ray spectra. This whole-spectrum processing approach considerably increases detection sensitivity, especially, if significant interferences being present in the measured spectrum. Precision of the SCFA method is determined by choice of a sufficient number of suitable calibration gamma-ray sources in the energy region of interest, by setting up an acceptable latent hypothesis and by chosen experimental quantification of spectra. The SCFA method is very advantageous to use, for instance, in ultra low-level gamma-spectrometry where counting rates in full energy peaks are extremely low as compared with background interferences. It enables to increase of the sensitivity by the 5-10 times in comparison with the traditional full energy peak net area method (J.K.). 1 fig., 2 tabs., 6 refs.

On response operator in semiconductor gamma ray spectrometry

International Nuclear Information System (INIS)

Krnac, S.; Povinec, P.

1995-01-01

Some results of the scaling confirmation factor analysis (SCFA) application in semiconductor gamma-ray spectrometry presented in this contribution points out to a new ground for evaluation the gamma-ray spectra. This whole-spectrum processing approach considerably increases detection sensitivity, especially, if significant interferences being present in the measured spectrum. Precision of the SCFA method is determined by choice of a sufficient number of suitable calibration gamma-ray sources in the energy region of interest, by setting up an acceptable latent hypothesis and by chosen experimental quantification of spectra. The SCFA method is very advantageous to use, for instance, in ultra low-level gamma-spectrometry where counting rates in full energy peaks are extremely low as compared with background interferences. It enables to increase of the sensitivity by the 5-10 times in comparison with the traditional full energy peak net area method (J.K.). 1 fig., 2 tabs., 6 refs

New stage in high-energy gamma-ray studies with GAMMA-400 after Fermi-LAT

Directory of Open Access Journals (Sweden)

Topchiev N.P.

2017-01-01

Full Text Available Fermi-LAT has made a significant contribution to the study of high-energy gamma-ray diffuse emission and the observations of 3000 discrete sources. However, one third of all gamma-ray sources (both galactic and extragalactic are unidentified, the data on the diffuse gamma-ray emission should be clarified, and signatures of dark matter particles in the high-energy gamma-ray range are not observed up to now. GAMMA-400, the currently developing gamma-ray telescope, will have angular (∼0.01∘ at 100 GeV and energy (∼1% at 100 GeV resolutions in the energy range of 10–1000 GeV which are better than Fermi-LAT (as well as ground gamma-ray telescopes by a factor of 5–10. It will observe some regions of the Universe (such as the Galactic Center, Fermi Bubbles, Crab, Cygnus, etc. in a highly elliptic orbit (without shading the telescope by the Earth continuously for a long time. It will allow us to identify many discrete sources, to clarify the structure of extended sources, to specify the data on the diffuse emission, and to resolve gamma rays from dark matter particles.

High-energy photons and neutrinos from gamma-ray bursts

International Nuclear Information System (INIS)

Dar, A.

1998-01-01

The Hubble Space Telescope has recently discovered thousands of gigantic cometlike objects in a ring around the central star in the nearest planetary nebula. It is assumed that such circumstellar rings exist around the majority of stars. Collisions of relativistic debris from gamma-ray bursts (GRB) in dense stellar regions with such gigantic cometlike objects, which have been stripped off from the circumstellar rings by gravitational perturbations, produce detectable fluxes of high energy γ rays and neutrinos from GRBs

Photodetectors for the Advanced Gamma-ray Imaging System (AGIS)

Science.gov (United States)

Wagner, Robert G.; Advanced Gamma-ray Imaging System AGIS Collaboration

2010-03-01

The Advanced Gamma-Ray Imaging System (AGIS) is a concept for the next generation very high energy gamma-ray observatory. Design goals include an order of magnitude better sensitivity, better angular resolution, and a lower energy threshold than existing Cherenkov telescopes. Each telescope is equipped with a camera that detects and records the Cherenkov-light flashes from air showers. The camera is comprised of a pixelated focal plane of blue sensitive and fast (nanosecond) photon detectors that detect the photon signal and convert it into an electrical one. Given the scale of AGIS, the camera must be reliable and cost effective. The Schwarzschild-Couder optical design yields a smaller plate scale than present-day Cherenkov telescopes, enabling the use of more compact, multi-pixel devices, including multianode photomultipliers or Geiger avalanche photodiodes. We present the conceptual design of the focal plane for the camera and results from testing candidate! focal plane sensors.

FERMI OBSERVATIONS OF HIGH-ENERGY GAMMA-RAY EMISSION FROM GRB 080825C

International Nuclear Information System (INIS)

Abdo, A. A.; Ackermann, M.; Bechtol, K.; Berenji, B.; Bloom, E. D.; Borgland, A. W.; Bouvier, A.; Asano, K.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Bellazzini, R.; Bregeon, J.; Ballet, J.; Band, D. L.; Barbiellini, G.; Bastieri, D.; Bhat, P. N.; Bissaldi, E.; Bonamente, E.

2009-01-01

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

Future prospects for. gamma. -ray astronomy

Energy Technology Data Exchange (ETDEWEB)

Fichtel, C [National Aeronautics and Space Administration, Greenbelt, MD (USA). Goddard Space Flight Center

1981-06-30

As ..gamma..-ray astronomy moves from the discovery to the exploratory phase, the promise of ..gamma..-ray astrophysics noted by theorists in the late 1940s and 1950s is beginning to be realized. In the future, satellites should carry instruments that will have over an order of magnitude greater sensitivity than those flown thus far, and, for at least some portions of the ..gamma..-ray energy range, these detectors will also have substantially improved energy and angular resolution. The information to be obtained from these experiments should greatly enhance our knowledge of several astrophysical phenomena including the very energetic and nuclear processes associated with compact objects, astrophysical nucleosynthesis, 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, high energy particles and energetic processes in other galaxies especially active ones, and the degree of matter-antimatter symmetry of the Universe. The ..gamma..-ray results of the forthcoming programs such as Gamma-I, the Gamma Ray Observatory, the ..gamma..-ray burst network, Solar Polar, and very high energy ..gamma..-ray telescopes on the ground will almost certainly provide justification for more sophisticated telescopes. These advanced instruments might be placed on the Space Platform currently under study by N.A.S.A.

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

Science.gov (United States)

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

1993-01-01

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

Integrated neutron/gamma-ray portal monitors for nuclear safeguards

International Nuclear Information System (INIS)

Fehlau, P.E.

1994-01-01

Radiation monitoring is one nuclear-safeguards measure used to protect against the theft of special nuclear materials (SNM) by pedestrians departing from SNM access areas. The integrated neutron/gamma-ray portal monitor is an ideal radiation monitor for the task when the SNM is plutonium. It achieves high sensitivity for detecting both bare and shielded plutonium by combining two types of radiation detector. One type is a neutron-chamber detector, comprising a large, hollow, neutron moderator that contains a single thermal-neutron proportional counter. The entrance wall of each chamber is thin to admit slow neutrons from plutonium contained in a moderating shield, while the other walls are thick to moderate fast neutrons from bare or lead-shielded plutonium so that they can be detected. The other type of detector is a plastic scintillator that is primarily for detecting gamma rays from small amounts of unshielded plutonium. The two types of detector are easily integrated by making scintillators part of the thick back wall of each neutron chamber or by inserting them into each chamber void. The authors compared the influence of the two methods of integration on detecting neutrons and gamma rays, and they examined the effectiveness of other design factors and the methods for signal detection as well

Portable high energy gamma ray imagers

International Nuclear Information System (INIS)

Guru, S.V.; Squillante, M.R.

1996-01-01

To satisfy the needs of high energy gamma ray imagers for industrial nuclear imaging applications, three high energy gamma cameras are presented. The RMD-Pinhole camera uses a lead pinhole collimator and a segmented BGO detector viewed by a 3 in. square position sensitive photomultiplier tube (PSPMT). This pinhole gamma camera displayed an energy resolution of 25.0% FWHM at the center of the camera at 662 keV and an angular resolution of 6.2 FWHM at 412 keV. The fixed multiple hole collimated camera (FMCC), used a multiple hole collimator and a continuous slab of NaI(Tl) detector viewed by the same PSPMT. The FMCC displayed an energy resolution of 12.4% FWHM at 662 keV at the center of the camera and an angular resolution of 6.0 FWHM at 412 keV. The rotating multiple hole collimated camera (RMCC) used a 180 antisymmetric rotation modulation collimator and CsI(Tl) detectors coupled to PIN silicon photodiodes. The RMCC displayed an energy resolution of 7.1% FWHM at 662 keV and an angular resolution of 4.0 FWHM at 810 keV. The performance of these imagers is discussed in this paper. (orig.)

Detecting gamma-ray anisotropies from decaying dark matter. Prospects for Fermi LAT

International Nuclear Information System (INIS)

Ibarra, Alejandro; Tran, David

2009-09-01

Decaying dark matter particles could be indirectly detected as an excess over a simple power law in the energy spectrum of the diffuse extragalactic gamma-ray background. Furthermore, since the Earth is not located at the center of the Galactic dark matter halo, the exotic contribution from dark matter decay to the diffuse gamma-ray flux is expected to be anisotropic, offering a complementary method for the indirect search for decaying dark matter particles. In this paper we discuss in detail the expected dipole-like anisotropies in the dark matter signal, taking also into account the radiation from inverse Compton scattering of electrons and positrons from dark matter decay. A different source for anisotropies in the gamma-ray flux are the dark matter density fluctuations on cosmic scales. We calculate the corresponding angular power spectrum of the gamma-ray flux and comment on observational prospects. Finally, we calculate the expected anisotropies for the decaying dark matter scenarios that can reproduce the electron/positron excesses reported by PAMELA and the Fermi LAT, and we estimate the prospects for detecting the predicted gamma-ray anisotropy in the near future. (orig.)

VERY HIGH ENERGY OBSERVATIONS OF GAMMA-RAY BURSTS WITH STACEE

International Nuclear Information System (INIS)

Jarvis, A.; Ong, R. A.; Ball, J.; Carson, J. E.; Zweerink, J.; Williams, D. A.; Aune, T.; Covault, C. E.; Driscoll, D. D.; Fortin, P.; Mukherjee, R.; Gingrich, D. M.; Hanna, D. S.; Kildea, J.; Lindner, T.; Mueller, C.; Ragan, K.

2010-01-01

Gamma-ray bursts (GRBs) are the most powerful explosions known in the universe. Sensitive measurements of the high-energy spectra of GRBs can place important constraints on the burst environments and radiation processes. Until recently, there were no observations during the first few minutes of GRB afterglows in the energy range between 30 GeV and ∼1 TeV. With the launch of the Swift GRB Explorer in late 2004, GRB alerts and localizations within seconds of the bursts became available. The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) was a ground-based, gamma-ray telescope with an energy threshold of ∼150 GeV for sources at zenith. At the time of Swift's launch, STACEE was in a rare position to provide >150 GeV follow-up observations of GRBs as fast as three minutes after the burst alert. In addition, STACEE performed follow-up observations of several GRBs that were localized by the HETE-2 and INTEGRAL satellites. Between 2002 June and 2007 July, STACEE made follow-up observations of 23 GRBs. Upper limits are placed on the high-energy gamma-ray fluxes from 21 of these bursts.

Depth of interaction detection for {gamma}-ray imaging

Energy Technology Data Exchange (ETDEWEB)

Lerche, Ch.W. [Instituto de Aplicaciones de las Tecnologias de la Informacion y de las Comunicaciones Avanzadas, (UPV) Camino de Vera s/n, E46022 (Spain)], E-mail: lerche@ific.uv.es; Doering, M. [Institut fuer Kernphysik, Forschungszentrum Juelich GmbH, D52425 Juelich (Germany); Ros, A. [Institute de Fisica Corpuscular (CSIC-UV), 22085, Valencia E46071 (Spain); Herrero, V.; Gadea, R.; Aliaga, R.J.; Colom, R.; Mateo, F.; Monzo, J.M.; Ferrando, N.; Toledo, J.F.; Martinez, J.D.; Sebastia, A. [Instituto de Aplicaciones de las Tecnologias de la Informacion y de las Comunicaciones Avanzadas, (UPV) Camino de Vera s/n, E46022 (Spain); Sanchez, F.; Benlloch, J.M. [Institute de Fisica Corpuscular (CSIC-UV), 22085, Valencia E46071 (Spain)

2009-03-11

A novel design for an inexpensive depth of interaction capable detector for {gamma}-ray imaging has been developed. The design takes advantage of the strong correlation between the width of the scintillation light distribution in monolithic crystals and the interaction depth of {gamma}-rays. We present in this work an inexpensive modification of the commonly used charge dividing circuits which enables the instantaneous and simultaneous computation of the second order moment of light distribution. This measure provides a good estimate for the depth of interaction and does not affect the determination of the position centroids and the energy release of {gamma}-ray impact. The method has been tested with a detector consisting of a monolithic LSO block sized 42x42x10mm{sup 3} and a position-sensitive photomultiplier tube H8500 from Hamamatsu. The mean spatial resolution of the detector was found to be 3.4mm for the position centroids and 4.9mm for the DOI. The best spatial resolutions were observed at the center of the detector and yielded 1.4mm for the position centroids and 1.9mm for the DOI.

A directional gamma-ray detector based on scintillator plates

Energy Technology Data Exchange (ETDEWEB)

Hanna, D., E-mail: hanna@physics.mcgill.ca; Sagnières, L.; Boyle, P.J.; MacLeod, A.M.L.

2015-10-11

A simple device for determining the azimuthal location of a source of gamma radiation, using ideas from astrophysical gamma-ray burst detection, is described. A compact and robust detector built from eight identical modules, each comprising a plate of CsI(Tl) scintillator coupled to a photomultiplier tube, can locate a point source of gamma rays with degree-scale precision by comparing the count rates in the different modules. Sensitivity to uniform environmental background is minimal.

Direction-Sensitive Hand-Held Gamma-Ray Spectrometer

Energy Technology Data Exchange (ETDEWEB)

Mukhopadhyay, S.

2012-10-04

A novel, light-weight, hand-held gamma-ray detector with directional sensitivity is being designed. The detector uses a set of multiple rings around two cylindrical surfaces, which provides precise location of two interaction points on two concentric cylindrical planes, wherefrom the source location can be traced back by back projection and/or Compton imaging technique. The detectors are 2.0 × 2.0 mm europium-doped strontium iodide (SrI2:Eu2+) crystals, whose light output has been measured to exceed 120,000 photons/MeV, making it one of the brightest scintillators in existence. The crystal’s energy resolution, less than 3% at 662 keV, is also excellent, and the response is highly linear over a wide range of gamma-ray energies. The emission of SrI2:Eu2+ is well matched to both photo-multiplier tubes and blue-enhanced silicon photodiodes. The solid-state photomultipliers used in this design (each 2.0 × 2.0 mm) are arrays of active pixel sensors (avalanche photodiodes driven beyond their breakdown voltage in reverse bias); each pixel acts as a binary photon detector, and their summed output is an analog representation of the total photon energy, while the individual pixel accurately defines the point of interaction. A simple back-projection algorithm involving cone-surface mapping is being modeled. The back projection for an event cone is a conical surface defining the possible location of the source. The cone axis is the straight line passing through the first and second interaction points.

Camera Concepts for the Advanced Gamma-Ray Imaging System (AGIS)

Science.gov (United States)

Nepomuk Otte, Adam

2009-05-01

The Advanced Gamma-Ray Imaging System (AGIS) is a concept for the next generation observatory in ground-based very high energy gamma-ray astronomy. Design goals are ten times better sensitivity, higher angular resolution, and a lower energy threshold than existing Cherenkov telescopes. Each telescope is equipped with a camera that detects and records the Cherenkov-light flashes from air showers. The camera is comprised of a pixelated focal plane of blue sensitive and fast (nanosecond) photon detectors that detect the photon signal and convert it into an electrical one. The incorporation of trigger electronics and signal digitization into the camera are under study. Given the size of AGIS, the camera must be reliable, robust, and cost effective. We are investigating several directions that include innovative technologies such as Geiger-mode avalanche-photodiodes as a possible detector and switched capacitor arrays for the digitization.

Gamma Ray Burst Discoveries by the Swift Mission

Science.gov (United States)

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. The NASA swift mission is an innovative new multiwavelength observatory designed to determine the origin of bursts and use them to probe the early Universe. Swift is now in orbit since November 20, 2004 and all hardware is performing well. A new-technology wide-field gamma-ray camera is detecting a hundred bursts per year. sensitive narrow-field X-ray and uv/optical telescopes, built in collaboration with UK and Italian partners, are pointed at the burst location in 50-100 sec by an autonomously controlled "swift" spacecraft. For each burst, arcsec positions are determined and optical/UV/X-ray/gamma-ray spectrophotometry performed. Information is also rapidly sent to the ground to a team of more than 50 observers at telescopes around the world. The first year of findings from the mission will be presented. There has been a break-through in the longstanding mystery of short GRBs; they appear to be caused by merging neutron stars. 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.

Gamma Ray Burst Discoveries by the Swift Mission

Science.gov (United States)

Gehrels, Neil

2006-04-01

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. The NASA Swift mission is an innovative new multiwavelength observatory designed to determine the origin of bursts and use them to probe the early Universe. Swift is now in orbit since November 20, 2004 and all hardware is performing well. A new-technology wide-field gamma-ray camera is detecting a hundred bursts per year. Sensitive narrow-field X-ray and UV/optical telescopes, built in collaboration with UK and Italian partners, are pointed at the burst location in 50-100 sec by an autonomously controlled ``swift'' spacecraft. For each burst, arcsec positions are determined and optical/UV/X-ray/gamma-ray spectrophotometry performed. Information is also rapidly sent to the ground to a team of more than 50 observers at telescopes around the world. The first year of findings from the mission will be presented. There has been a break-through in the long-standing mystery of short GRBs; they appear to be caused by merging neutron stars. 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.

Design and development of a PMOSFET gamma ray dosimeter

International Nuclear Information System (INIS)

Khanna, V.K.; Kumar, A.; Gupta, R.P.; Pandya, A.; Roy, Rajesh

2005-01-01

A P-channel MOSFET chip has been designed for detection of gamma radiations. The chip consists of three MOSFETs of different geometrical parameters for achieving sensitivity to low and high dose ranges. One of the MOSFET structures has a closed geometry to reduce the leakage current. The developed dosimeter being a MOSFET, its IC (Integrated Circuit)-compatibility helps in easy interfacing with readout circuitry. The dosimeter fabrication process is based on metal-gate MOSFET technology with thick gate oxide to increase the effective number of electron-hole pairs generated by the gamma rays impinging on the device. The process for the chip realization has been designed and simulated to achieve the required impurity diffusion profile. The chip has been fabricated using the above process and electrically characterized. The device has been exposed to gamma ray source and its characteristics measured. The change in threshold voltage of the MOSFET after exposure has been used to calculate the sensitivity of the device. The developed dosimeter has potential applications in personnel dosimetry and cancer treatment. This paper describes the basic detection mechanism of the MOSFET, the design approach, and fabrication process of the MOSFET dosimeter. (author)

The goals of gamma-ray spectroscopy in high energy astrophysics

Science.gov (United States)

Lingenfelter, Richard E.; Higdon, James C.; Leventhal, Marvin; Ramaty, Reuven; Woosley, Stanford E.

1990-01-01

The use of high resolution gamma-ray spectroscopy in astrophysics is discussed with specific attention given to the application of the Nuclear Astrophysics Explorer (NAE). The gamma-ray lines from nuclear transitions in radionucleic decay and positron annihilation permits the study of current sites, rates and models of nucleosynthesis, and galactic structure. Diffuse galactic emission is discussed, and the high-resolution observations of gamma-ray lines from discrete sites are also described. Interstellar mixing and elemental abundances can also be inferred from high-resolution gamma-ray spectroscopy of nucleosynthetic products. Compact objects can also be examined by means of gamma-ray emissions, allowing better understanding of neutron stars and the accreting black hole near the galactic center. Solar physics can also be investigated by examining such features as solar-flare particle acceleration and atmospheric abundances.

100 MH/sub z/ fiber optic single transient gamma ray detection system

International Nuclear Information System (INIS)

Ogle, J.W.; Smith, R.C.; Ward, M.; Ramsey, R.; Hollabaugh, J.

1984-01-01

A fiber optic system has been developed to measure single transient gamma rays. The gamma ray signature is converted to light by the Cerenkov process in a 20 cm length of radiation resistant optical fiber. The signal is transmitted over 1 km of optical fiber and detected by state-of-the-art, 175 MHz analog receivers. The receivers are based on silicon PIN detectors with transimpedance hybrid amplifiers and two stages of power amplification. The dc coupled receivers have less than 2% distortion up to 5 volts with less than 10 mV rms noise and a responsivity of 37,500 V/watt at 800 nm. A calibration system measures relative fiber to fiber transit time delays and system sensitivity. System bandwidth measurements utilized an electron linear accelerator (Linac) with a 50 ps electron pulse as the Cerenkov light source. The system will be described with supporting calibration and characterization data of parts of the system and the whole system. 5 references, 7 figures, 4 tables

Sensitivity of self-powered detector probes to electron and gamma-ray fields

International Nuclear Information System (INIS)

Lone, M.A.; Wong, P.Y.

1995-01-01

A self-powered detector (SPD) is a simple, passive device that consists of a coaxial probe with a metallic outer sleeve, a mineral oxide insulating layer, and a metallic inner core. SPD's are used in nuclear reactors to monitor neutron and gamma fields. Responses of SPD's to electrons and γ-rays of various energies were investigated with Monte Carlo simulations. Transmission filters were studied for the design of threshold SPD probes used for online monitoring of the energy spectrum of high-power industrial electron accelerator beams. Filters were also investigated for the enhancement of γ-ray sensitivity of an SPD placed in a mixed electron and γ-ray field. (author). 30 refs., 1 tab., 8 figs

Use of water-Cherenkov detectors to detect Gamma Ray Bursts at the Large Aperture GRB Observatory (LAGO)

International Nuclear Information System (INIS)

Allard, D.; Allekotte, I.; Alvarez, C.; Asorey, H.; Barros, H.; Bertou, X.; Burgoa, O.; Gomez Berisso, M.; Martinez, O.; Miranda Loza, P.; Murrieta, T.; Perez, G.; Rivera, H.; Rovero, A.; Saavedra, O.; Salazar, H.; Tello, J.C.; Ticona Peralda, R.; Velarde, A.; Villasenor, L.

2008-01-01

The Large Aperture GRB Observatory (LAGO) project aims at the detection of high energy photons from Gamma Ray Bursts (GRB) using the single particle technique in ground-based water-Cherenkov detectors (WCD). To reach a reasonable sensitivity, high altitude mountain sites have been selected in Mexico (Sierra Negra, 4550 m a.s.l.), Bolivia (Chacaltaya, 5300 m a.s.l.) and Venezuela (Merida, 4765 m a.s.l.). We report on detector calibration and operation at high altitude, search for bursts in 4 months of preliminary data, as well as search for signal at ground level when satellites report a burst

Use of water-Cherenkov detectors to detect Gamma Ray Bursts at the Large Aperture GRB Observatory (LAGO)

Energy Technology Data Exchange (ETDEWEB)

Allard, D. [APC, CNRS et Universite Paris 7 (France); Allekotte, I. [Centro Atomico Bariloche, Instituto Balseiro (Argentina); Alvarez, C. [Facultad de Ciencias Fisico-Matematicas de la BUAP (Mexico); Asorey, H. [Centro Atomico Bariloche, Instituto Balseiro (Argentina); Barros, H. [Laboratorio de Fisica Nuclear, Universidad Simon Bolivar, Caracas (Venezuela, Bolivarian Republic of); Bertou, X. [Centro Atomico Bariloche, Instituto Balseiro (Argentina)], E-mail: bertou@cab.cnea.gov.ar; Burgoa, O. [Instituto de Investigaciones Fisicas, UMSA (Bolivia); Gomez Berisso, M. [Centro Atomico Bariloche, Instituto Balseiro (Argentina); Martinez, O. [Facultad de Ciencias Fisico-Matematicas de la BUAP (Mexico); Miranda Loza, P. [Instituto de Investigaciones Fisicas, UMSA (Bolivia); Murrieta, T.; Perez, G. [Facultad de Ciencias Fisico-Matematicas de la BUAP (Mexico); Rivera, H. [Instituto de Investigaciones Fisicas, UMSA (Bolivia); Rovero, A. [Instituto de Astronomia y Fisica del Espacio (Argentina); Saavedra, O. [Dipartimento di Fisica Generale and INFN, Torino (Italy); Salazar, H. [Facultad de Ciencias Fisico-Matematicas de la BUAP (Mexico); Tello, J.C. [Laboratorio de Fisica Nuclear, Universidad Simon Bolivar, Caracas (Venezuela, Bolivarian Republic of); Ticona Peralda, R.; Velarde, A. [Instituto de Investigaciones Fisicas, UMSA (Bolivia); Villasenor, L. [Facultad de Ciencias Fisico-Matematicas de la BUAP (Mexico); Instituto de Fisica y Matematicas, Universidad de Michoacan (Mexico)

2008-09-21

The Large Aperture GRB Observatory (LAGO) project aims at the detection of high energy photons from Gamma Ray Bursts (GRB) using the single particle technique in ground-based water-Cherenkov detectors (WCD). To reach a reasonable sensitivity, high altitude mountain sites have been selected in Mexico (Sierra Negra, 4550 m a.s.l.), Bolivia (Chacaltaya, 5300 m a.s.l.) and Venezuela (Merida, 4765 m a.s.l.). We report on detector calibration and operation at high altitude, search for bursts in 4 months of preliminary data, as well as search for signal at ground level when satellites report a burst.

High-energy gamma-ray astronomy and the COS-B mission

International Nuclear Information System (INIS)

Wills, R.D.

1977-01-01

The most significant results in gamma-ray astronomy have been produced by satellite- and balloon-borne instruments sensitive in the range 30 MeV to approximately 10 GeV. The COS-B instrument which is described is typical of this type of detector. For this reason the review of gamma-ray production mechanisms gives greater attention to those processes which are specifically important in that energy range. (orig.) [de

Technology Needs for Gamma Ray Astronomy

Science.gov (United States)

Gehrels, Neil

2011-01-01

Gamma ray astronomy is currently in an exciting period of multiple missions and a wealth of data. Results from INTEGRAL, Fermi, AGILE, Suzaku and Swift are making large contributions to our knowledge of high energy processes in the universe. The advances are due to new detector and imaging technologies. The steps to date have been from scintillators to solid state detectors for sensors and from light buckets to coded aperture masks and pair telescopes for imagers. A key direction for the future is toward focusing telescopes pushing into the hard X-ray regime and Compton telescopes and pair telescopes with fine spatial resolution for medium and high energy gamma rays. These technologies will provide finer imaging of gamma-ray sources. Importantly, they will also enable large steps forward in sensitivity by reducing background.

Studies of weak capture-gamma-ray resonances via coincidence techniques

CERN Document Server

Rowland, C; Champagne, A E; Dummer, A K; Fitzgerald, R; Harley, E C T; Mosher, J; Runkle, R

2002-01-01

A method for measuring weak capture-gamma-ray resonances via gamma gamma-coincidence counting techniques is described. The coincidence apparatus consisted of a large-volume germanium detector and an annular NaI(Tl) crystal. The setup was tested by measuring the weak E sub R =227 keV resonance in sup 2 sup 6 Mg(p,gamma) sup 2 sup 7 Al. Absolute germanium and NaI(Tl) counting efficiencies for a range of gamma-ray energies and for different detector-target geometries are presented. Studies of the gamma-ray background in our spectra are described. Compared to previous work, our method improves the detection sensitivity for weak capture-gamma-ray resonances by a factor of approx 100. The usefulness of the present technique for investigations of interest to nuclear astrophysics is discussed.

NEUTRINO EMISSION FROM HIGH-ENERGY COMPONENT GAMMA-RAY BURSTS

International Nuclear Information System (INIS)

Becker, Julia K.; Olivo, Martino; Halzen, Francis; O Murchadha, Aongus

2010-01-01

Gamma-ray bursts (GRBs) have the potential to produce the particle energies (up to 10 21 eV) and energy budget (10 44 erg yr -1 Mpc -3 ) to accommodate the spectrum of the highest energy cosmic rays; on the other hand, there is no observational evidence that they accelerate hadrons. The Fermi Gamma-ray Space Telescope recently observed two bursts that exhibit a power-law high-energy extension of a typical (Band) photon spectrum that extends to ∼30 GeV. On the basis of fireball phenomenology we argue that these two bursts, along with GRB941017 observed by EGRET in 1994, show indirect evidence for considerable baryon loading. Since the detection of neutrinos is the only unambiguous way to establish that GRBs accelerate protons, we use two methods to estimate the neutrino flux produced when they interact with fireball photons to produce charged pions and neutrinos. While the number of events expected from the two Fermi bursts discussed is small, should GRBs be the sources of the observed cosmic rays, a GRB941017-like event that has a hadronic power-law tail extending to several tens of GeV will be detected by the IceCube neutrino telescope.

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

International Nuclear Information System (INIS)

Grenier, Isabelle

2009-01-01

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.

Gamma-ray imaging spectrometer (GRIS): a new balloon-borne experiment for gamma-ray line astronomy

International Nuclear Information System (INIS)

Teegarden, B.J.; Cline, T.L.; Gehrels, N.; Porreca, G.; Tueller, J.; Leventhal, M.; Huters, A.F.; MacCallum, C.J.; Stang, P.D.

1985-01-01

High resolution gamma-ray spectroscopy is a relatively new field that holds great promise for further understanding of high energy astrophysical processes. Preliminary results such as the annihilation radiation from the galactic center, the 26 Al line from the galactic plane and cyclotron lines from neutron stars may well be just the initial discoveries of a rich and as yet undeveloped field. When the high resolution gamma-ray spectrometer (GRSE) was removed from the GRO payload NASA decided to initiate a balloon program to permit continued development and improvement of instrumentation in this field, as well as continued scientific observations. The Gamma-Ray Imaging Spectrometer (GRIS) is one of the experiments selected as part of this program. The instrument contains a number of new and innovative features that are expected to produce a significant improvement in source location accuracy and sensitivity over previous balloon and satellite experiments. 6 refs., 2 figs

Loop-induced dark matter direct detection signals from gamma-ray lines

DEFF Research Database (Denmark)

Frandsen, Mads Toudal; Haisch, Ulrich; Kahlhoefer, Felix

2012-01-01

Improved limits as well as tentative claims for dark matter annihilation into gamma-ray lines have been presented recently. We study the direct detection cross section induced from dark matter annihilation into two photons in a model-independent fashion, assuming no additional couplings between...... dark matter and nuclei. We find a striking non-standard recoil spectrum due to different destructively interfering contributions to the dark matter nucleus scattering cross section. While in the case of s-wave annihilation the current sensitivity of direct detection experiments is insufficient...... to compete with indirect detection searches, for p-wave annihilation the constraints from direct searches are comparable. This will allow to test dark matter scenarios with p-wave annihilation that predict a large di-photon annihilation cross section in the next generation of experiments....

X-Ray Spectral Characteristics of Ginga Gamma-Ray Bursts

International Nuclear Information System (INIS)

Strohmayer, T.E.; Fenimore, E.E.; Murakami, T.; Yoshida, A.

1998-01-01

We have investigated the spectral characteristics of a sample of bright gamma-ray bursts detected with the gamma-ray burst sensors aboard the satellite Ginga. This instrument employed a proportional and scintillation counter to provide sensitivity to photons in the 2 endash 400 keV region and as such provided a unique opportunity to characterize the largely unexplored X-ray properties of gamma-ray bursts. The photon spectra of the Ginga bursts are well described by a low-energy slope, a bend energy, and a high-energy slope. In the energy range where they can be compared, this result is consistent with burst spectral analyses obtained from the BATSE experiment aboard the Compton Gamma-Ray Observatory. However, below 20 keV we find evidence for a positive spectral number index in approximately 40% of our burst sample, with some evidence for a strong rolloff at lower energies in a few events. There is a correlation (Pearson's r = -0.62) between the low-energy slope and the bend energy. We find that the distribution of spectral bend energies extends below 10 keV. There has been some concern in cosmological models of gamma-ray bursts (GRBs) that the bend energy covers only a small dynamic range. Our result extends the observed dynamic range, and, since we observe bend energies down to the limit of our instrument, perhaps observations have not yet limited the range. The Ginga trigger range was virtually the same as that of BATSE, yet we find a different range of fit parameters. One possible explanation might be that GRBs have two break energies, one often in the 50 endash 500 keV range and the other near 5 keV. Both BATSE and Ginga fit with only a single break energy, so BATSE tends to find breaks near the center of its energy range, and we tend to find breaks in our energy range. The observed ratio of energy emitted in the X-rays relative to the gamma rays can be much larger than a few percent and, in fact, is sometimes larger than unity. The average for our 22 bursts

ICF ignition capsule neutron, gamma ray, and high energy x-ray images

Science.gov (United States)

Bradley, P. A.; Wilson, D. C.; Swenson, F. J.; Morgan, G. L.

2003-03-01

Post-processed total neutron, RIF neutron, gamma-ray, and x-ray images from 2D LASNEX calculations of burning ignition capsules are presented. The capsules have yields ranging from tens of kilojoules (failures) to over 16 MJ (ignition), and their implosion symmetry ranges from prolate (flattest at the hohlraum equator) to oblate (flattest towards the laser entrance hole). The simulated total neutron images emphasize regions of high DT density and temperature; the reaction-in-flight neutrons emphasize regions of high DT density; the gamma rays emphasize regions of high shell density; and the high energy x rays (>10 keV) emphasize regions of high temperature.

Gamma-ray tracking: Characterisation of the AGATA symmetric prototype detectors

International Nuclear Information System (INIS)

Boston, A.J.; Boston, H.C.; Cresswell, J.R.; Dimmock, M.R.; Nelson, L.; Nolan, P.J.; Rigby, S.; Lazarus, I.; Simpson, J.; Medina, P.; Santos, C.; Parisel, C.

2007-01-01

Each major technical advance in gamma-ray detection devices has resulted in significant new insights into the structure of atomic nuclei. The next major step in gamma-ray spectroscopy involves achieving the goal of a 4pi ball of Germanium detectors by using the technique of gamma-ray energy tracking in electrically segmented Germanium crystals. The resulting spectrometer will have an unparalleled level of detection power for nuclear electromagnetic radiation. Collaborations have been established in Europe (AGATA) [J. Simpson, Acta Phys. Pol. B 36 (2005) 1383. ] and the USA (GRETA/GRETINA) to build gamma-ray tracking spectrometers. This paper discusses the performance of the AGATA (Advanced Gamma Tracking Array) symmetric prototype detectors that have been tested at University of Liverpool. The use of a fully digital data acquisition system has allowed detector charge pulse shapes from a selection of well defined photon interaction positions to be analysed, yielding important information on the position sensitivity of the detector

Gamma-ray tracking: Characterisation of the AGATA symmetric prototype detectors

Energy Technology Data Exchange (ETDEWEB)

Boston, A.J. [Oliver Lodge Laboratory, University of Liverpool, Oxford Street, Liverpool L69 7ZE (United Kingdom)]. E-mail: ajboston@liv.ac.uk; Boston, H.C. [Oliver Lodge Laboratory, University of Liverpool, Oxford Street, Liverpool L69 7ZE (United Kingdom); Cresswell, J.R. [Oliver Lodge Laboratory, University of Liverpool, Oxford Street, Liverpool L69 7ZE (United Kingdom); Dimmock, M.R. [Oliver Lodge Laboratory, University of Liverpool, Oxford Street, Liverpool L69 7ZE (United Kingdom); Nelson, L. [Oliver Lodge Laboratory, University of Liverpool, Oxford Street, Liverpool L69 7ZE (United Kingdom); Nolan, P.J. [Oliver Lodge Laboratory, University of Liverpool, Oxford Street, Liverpool L69 7ZE (United Kingdom); Rigby, S. [Oliver Lodge Laboratory, University of Liverpool, Oxford Street, Liverpool L69 7ZE (United Kingdom); Lazarus, I. [STFC Daresbury Laboratory, Daresbury, Warrington WA4 4AD (United Kingdom); Simpson, J. [STFC Daresbury Laboratory, Daresbury, Warrington WA4 4AD (United Kingdom); Medina, P. [Institut de Recherches Subatomiques, Strasbourg BP28 67037 (France); Santos, C. [Institut de Recherches Subatomiques, Strasbourg BP28 67037 (France); Parisel, C. [Institut de Recherches Subatomiques, Strasbourg BP28 67037 (France)

2007-08-15

Each major technical advance in gamma-ray detection devices has resulted in significant new insights into the structure of atomic nuclei. The next major step in gamma-ray spectroscopy involves achieving the goal of a 4pi ball of Germanium detectors by using the technique of gamma-ray energy tracking in electrically segmented Germanium crystals. The resulting spectrometer will have an unparalleled level of detection power for nuclear electromagnetic radiation. Collaborations have been established in Europe (AGATA) [J. Simpson, Acta Phys. Pol. B 36 (2005) 1383. ] and the USA (GRETA/GRETINA) to build gamma-ray tracking spectrometers. This paper discusses the performance of the AGATA (Advanced Gamma Tracking Array) symmetric prototype detectors that have been tested at University of Liverpool. The use of a fully digital data acquisition system has allowed detector charge pulse shapes from a selection of well defined photon interaction positions to be analysed, yielding important information on the position sensitivity of the detector.

Local gamma ray events as tests of the antimatter theory of gamma ray bursts

International Nuclear Information System (INIS)

Sofia, S.; Wilson, R.E.

1976-01-01

Nearby examples of the antimatter 'chunks' postulated by Sofia and Van Horn to explain the cosmic gamma ray bursts may produce detectable gamma ray events when struck by solar system meteoroids. These events would have a much shorter time scale and higher energy spectrum than the bursts already observed. In order to have a reasonably high event rate, the local meteoroid population must extend to a distance from the Sun of the order of 0.1 pc, but the required distance could become much lower if the instrumental threshold is improved. The expected gamma ray flux for interaction of the antimatter bodies with the solar wind is also examined, and found to be far below present instrumental capabilities. (Auth.)

Very high energy gamma ray astrophysics

International Nuclear Information System (INIS)

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

1986-01-01

The Whipple Observatory's atmospheric Cerenkov camera has detected TeV radiation from four galactic sources: the Crab Nebula, Cygnus X-3, Hercules X-1, and 4U0115+63. Recent simulations encourage the view that unwanted cosmic-ray background showers may be suppressed by a large factor. Emphasis in the coming year will be on determining optimum selection criteria for enhancing gamma-ray signals and in developing a prototype camera with finer angular resolution as a first step towards implementation of the HERCULES concept

Gamma-ray detection and Compton camera image reconstruction with application to hadron therapy

International Nuclear Information System (INIS)

Frandes, M.

2010-09-01

A novel technique for radiotherapy - hadron therapy - irradiates tumors using a beam of protons or carbon ions. Hadron therapy is an effective technique for cancer treatment, since it enables accurate dose deposition due to the existence of a Bragg peak at the end of particles range. Precise knowledge of the fall-off position of the dose with millimeters accuracy is critical since hadron therapy proved its efficiency in case of tumors which are deep-seated, close to vital organs, or radio-resistant. A major challenge for hadron therapy is the quality assurance of dose delivery during irradiation. Current systems applying positron emission tomography (PET) technologies exploit gamma rays from the annihilation of positrons emitted during the beta decay of radioactive isotopes. However, the generated PET images allow only post-therapy information about the deposed dose. In addition, they are not in direct coincidence with the Bragg peak. A solution is to image the complete spectrum of the emitted gamma rays, including nuclear gamma rays emitted by inelastic interactions of hadrons to generated nuclei. This emission is isotropic, and has a spectrum ranging from 100 keV up to 20 MeV. However, the measurement of these energetic gamma rays from nuclear reactions exceeds the capability of all existing medical imaging systems. An advanced Compton scattering detection method with electron tracking capability is proposed, and modeled to reconstruct the high-energy gamma-ray events. This Compton detection technique was initially developed to observe gamma rays for astrophysical purposes. A device illustrating the method was designed and adapted to Hadron Therapy Imaging (HTI). It consists of two main sub-systems: a tracker where Compton recoiled electrons are measured, and a calorimeter where the scattered gamma rays are absorbed via the photoelectric effect. Considering a hadron therapy scenario, the analysis of generated data was performed, passing trough the complete

Energy- and time-resolved detection of prompt gamma-rays for proton range verification.

Science.gov (United States)

Verburg, Joost M; Riley, Kent; Bortfeld, Thomas; Seco, Joao

2013-10-21

In this work, we present experimental results of a novel prompt gamma-ray detector for proton beam range verification. The detection system features an actively shielded cerium-doped lanthanum(III) bromide scintillator, coupled to a digital data acquisition system. The acquisition was synchronized to the cyclotron radio frequency to separate the prompt gamma-ray signals from the later-arriving neutron-induced background. We designed the detector to provide a high energy resolution and an effective reduction of background events, enabling discrete proton-induced prompt gamma lines to be resolved. Measuring discrete prompt gamma lines has several benefits for range verification. As the discrete energies correspond to specific nuclear transitions, the magnitudes of the different gamma lines have unique correlations with the proton energy and can be directly related to nuclear reaction cross sections. The quantification of discrete gamma lines also enables elemental analysis of tissue in the beam path, providing a better prediction of prompt gamma-ray yields. We present the results of experiments in which a water phantom was irradiated with proton pencil-beams in a clinical proton therapy gantry. A slit collimator was used to collimate the prompt gamma-rays, and measurements were performed at 27 positions along the path of proton beams with ranges of 9, 16 and 23 g cm(-2) in water. The magnitudes of discrete gamma lines at 4.44, 5.2 and 6.13 MeV were quantified. The prompt gamma lines were found to be clearly resolved in dimensions of energy and time, and had a reproducible correlation with the proton depth-dose curve. We conclude that the measurement of discrete prompt gamma-rays for in vivo range verification of clinical proton beams is feasible, and plan to further study methods and detector designs for clinical use.

The noise analysis and optimum filtering techniques for a two-dimensional position sensitive orthogonal strip gamma ray detector employing resistive charge division

International Nuclear Information System (INIS)

Gerber, M.S.; Muller, D.W.

1976-01-01

The analysis of an orthogonal strip, two-dimensional position sensitive high purity germanium gamma ray detector is discussed. Position sensitivity is obtained by connecting each electrode strip on the detector to a resistor network. Charge, entering the network, divides in relation to the resistance between its entry point and the virtual earth points of the charge sensitive preamplifiers located at the end of each resistor network. The difference of the voltage pulses at the output of each preamplifier is proportional to the position at which the charge entered the resistor network and the sum of the pulse is proportional to the energy of the detected gamma ray. The analysis and spatial noise resolution is presented for this type of position sensitive detector. The results of the analysis show that the position resolution is proportional to the square root of the filter amplifier's output pulse time constant and that for energy measurement the resolution is maximized at the filter amplifier's noise corner time constant. The design of the electronic noise filtering system for the prototype gamma ray camera was based on the mathematical energy and spatial resolution equations. For the spatial channel a Gaussian trapezoidal filtering system was developed. Gaussian filtering was used for the energy channel. The detector noise model was verified by taking rms noise measurements of the filtered energy and spatial pulses from resistive readout charge dividing detectors. These measurements were within 10% of theory. (Auth.)

Gamma ray energy tracking in GRETINA

Science.gov (United States)

Lee, I. Y.

2011-10-01

The next generation of stable and exotic beam accelerators will provide physics opportunities to study nuclei farther away from the line of stability. However, these experiments will be more demanding on instrumentation performance. These come from the lower production rate for more exotic beams, worse beam impurities, and large beam velocity from the fragmentation and inverse reactions. Gamma-ray spectroscopy will be one of the most effective tools to study exotic nuclei. However, to fully exploit the physics reach provided by these new facilities, better gamma-ray detector will be needed. In the last 10 years, a new concept, gamma-ray energy tracking array, was developed. Tracking arrays will increase the detection sensitivity by factors of several hundred compared to current arrays used in nuclear physics research. Particularly, the capability of reconstructing the position of the interaction with millimeters resolution is needed to correct the Doppler broadening of gamma rays emitted from high velocity nuclei. GRETINA is a gamma-ray tracking array which uses 28 Ge crystals, each with 36 segments, to cover ¼ of the 4 π of the 4 π solid angle. The gamma ray tracking technique requires detailed pulse shape information from each of the segments. These pulses are digitized using 14-bit 100 MHz flash ADCs, and digital signal analysis algorithms implemented in the on-board FPGAs provides energy, time and selection of pulse traces. A digital trigger system, provided flexible trigger functions including a fast trigger output, and also allows complicated trigger decisions to be made up to 20 microseconds. Further analyzed, carried out in a computer cluster, determine the energy, time, and three-dimensional positions of all gamma-ray interactions in the array. This information is then utilized, together with the characteristics of Compton scattering and pair-production processes, to track the scattering sequences of the gamma rays. GRETINA construction is completed in

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

Energy Technology Data Exchange (ETDEWEB)

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

1983-01-01

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

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

International Nuclear Information System (INIS)

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

1996-01-01

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

The Advanced Gamma-ray Imaging System (AGIS): Simulation Studies

Science.gov (United States)

Fegan, Stephen; Buckley, J. H.; Bugaev, S.; Funk, S.; Konopelko, A.; Maier, G.; Vassiliev, V. V.; Simulation Studies Working Group; AGIS Collaboration

2008-03-01

The Advanced Gamma-ray Imaging System (AGIS) is a concept for the next generation instrument in ground-based very high energy gamma-ray astronomy. It has the goal of achieving significant improvement in sensitivity over current experiments. We present the results of simulation studies of various possible designs for AGIS. The primary characteristics of the array performance, collecting area, angular resolution, background rejection, and sensitivity are discussed.

EJ-309 pulse shape discrimination performance with a high gamma-ray-to-neutron ratio and low threshold

Energy Technology Data Exchange (ETDEWEB)

Kaplan, A.C., E-mail: Alexis.C.Kaplan@gmail.com [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Blvd., Ann Arbor, MI 48104 (United States); Nuclear Engineering and Nonproliferation Division, Los Alamos National Laboratory, Los Alamos, NM 87544 (United States); Flaska, M.; Enqvist, A.; Dolan, J.L.; Pozzi, S.A. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Blvd., Ann Arbor, MI 48104 (United States)

2013-11-21

Measuring neutrons in the presence of high gamma-ray fluence is a challenge with multi-particle detectors. Organic liquid scintillators such as the EJ-309 are capable of accurate pulse-shape discrimination (PSD) but the chance for particle misclassification is not negligible for some applications. By varying the distance from an EJ-309 scintillator to a strong-gamma-ray source and keeping a weak-neutron source at a fixed position, various gamma-to-neutron ratios can be measured and PSD performance can be quantified. Comparing neutron pulse-height distributions allows for pulse-height specific PSD evaluation, and quantification and visualization of deviation from {sup 252}Cf alone. Even with the addition of the misclassified gamma-rays, the PSD is effective in separating particles so that neutron count rate can be predicted with less than 10% error up to a gamma-to-neutron ratio of almost 650. For applications which can afford a reduction in neutron detection efficiency, PSD can be sufficiently effective in discriminating particles to measure a weak neutron source in a high gamma-ray background. -- Highlights: •We measure neutrons in a high photon background with EJ-309 liquid scintillators. •A low threshold is used to test the limits of particle discrimination. •A weak neutron signal is detectable with a gamma/neutron ratio as high as 770. •Photon pileup most commonly adds to error in classification of neutrons. •Neutron count rates are within 10% of expected rate under high gamma background.

EJ-309 pulse shape discrimination performance with a high gamma-ray-to-neutron ratio and low threshold

International Nuclear Information System (INIS)

Kaplan, A.C.; Flaska, M.; Enqvist, A.; Dolan, J.L.; Pozzi, S.A.

2013-01-01

Measuring neutrons in the presence of high gamma-ray fluence is a challenge with multi-particle detectors. Organic liquid scintillators such as the EJ-309 are capable of accurate pulse-shape discrimination (PSD) but the chance for particle misclassification is not negligible for some applications. By varying the distance from an EJ-309 scintillator to a strong-gamma-ray source and keeping a weak-neutron source at a fixed position, various gamma-to-neutron ratios can be measured and PSD performance can be quantified. Comparing neutron pulse-height distributions allows for pulse-height specific PSD evaluation, and quantification and visualization of deviation from 252 Cf alone. Even with the addition of the misclassified gamma-rays, the PSD is effective in separating particles so that neutron count rate can be predicted with less than 10% error up to a gamma-to-neutron ratio of almost 650. For applications which can afford a reduction in neutron detection efficiency, PSD can be sufficiently effective in discriminating particles to measure a weak neutron source in a high gamma-ray background. -- Highlights: •We measure neutrons in a high photon background with EJ-309 liquid scintillators. •A low threshold is used to test the limits of particle discrimination. •A weak neutron signal is detectable with a gamma/neutron ratio as high as 770. •Photon pileup most commonly adds to error in classification of neutrons. •Neutron count rates are within 10% of expected rate under high gamma background

Gamma ray induced sensitization in CaSO4:Dy and competing trap model

International Nuclear Information System (INIS)

Nagpal, J.S.; Kher, R.K.; Gangadharan, P.

1979-01-01

Gamma ray induced sensitization in CaSO 4 :Dy has been compared (by measurement of TL glow curves) for different temperatures during irradiation (25 0 , 120 0 and 250 0 C). Enhanced sensitization at elevated temperatures seems to support the competing trap model for supralinearity and sensitization in CaSO 4 :Dy. (author)

Position sensitive detection of neutrons in high radiation background field.

Science.gov (United States)

Vavrik, D; Jakubek, J; Pospisil, S; Vacik, J

2014-01-01

We present the development of a high-resolution position sensitive device for detection of slow neutrons in the environment of extremely high γ and e(-) radiation background. We make use of a planar silicon pixelated (pixel size: 55 × 55 μm(2)) spectroscopic Timepix detector adapted for neutron detection utilizing very thin (10)B converter placed onto detector surface. We demonstrate that electromagnetic radiation background can be discriminated from the neutron signal utilizing the fact that each particle type produces characteristic ionization tracks in the pixelated detector. Particular tracks can be distinguished by their 2D shape (in the detector plane) and spectroscopic response using single event analysis. A Cd sheet served as thermal neutron stopper as well as intensive source of gamma rays and energetic electrons. Highly efficient discrimination was successful even at very low neutron to electromagnetic background ratio about 10(-4).

IMRT QA: Selecting gamma criteria based on error detection sensitivity

Energy Technology Data Exchange (ETDEWEB)

Steers, Jennifer M. [Department of Radiation Oncology, Cedars-Sinai Medical Center, Los Angeles, California 90048 and Physics and Biology in Medicine IDP, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California 90095 (United States); Fraass, Benedick A., E-mail: benedick.fraass@cshs.org [Department of Radiation Oncology, Cedars-Sinai Medical Center, Los Angeles, California 90048 (United States)

2016-04-15

Purpose: The gamma comparison is widely used to evaluate the agreement between measurements and treatment planning system calculations in patient-specific intensity modulated radiation therapy (IMRT) quality assurance (QA). However, recent publications have raised concerns about the lack of sensitivity when employing commonly used gamma criteria. Understanding the actual sensitivity of a wide range of different gamma criteria may allow the definition of more meaningful gamma criteria and tolerance limits in IMRT QA. We present a method that allows the quantitative determination of gamma criteria sensitivity to induced errors which can be applied to any unique combination of device, delivery technique, and software utilized in a specific clinic. Methods: A total of 21 DMLC IMRT QA measurements (ArcCHECK®, Sun Nuclear) were compared to QA plan calculations with induced errors. Three scenarios were studied: MU errors, multi-leaf collimator (MLC) errors, and the sensitivity of the gamma comparison to changes in penumbra width. Gamma comparisons were performed between measurements and error-induced calculations using a wide range of gamma criteria, resulting in a total of over 20 000 gamma comparisons. Gamma passing rates for each error class and case were graphed against error magnitude to create error curves in order to represent the range of missed errors in routine IMRT QA using 36 different gamma criteria. Results: This study demonstrates that systematic errors and case-specific errors can be detected by the error curve analysis. Depending on the location of the error curve peak (e.g., not centered about zero), 3%/3 mm threshold = 10% at 90% pixels passing may miss errors as large as 15% MU errors and ±1 cm random MLC errors for some cases. As the dose threshold parameter was increased for a given %Diff/distance-to-agreement (DTA) setting, error sensitivity was increased by up to a factor of two for select cases. This increased sensitivity with increasing dose

High-energy Emission from Nonrelativistic Radiative Shocks: Application to Gamma-Ray Novae

Science.gov (United States)

Vurm, Indrek; Metzger, Brian D.

2018-01-01

The observation of GeV gamma-rays from novae by Fermi/LAT demonstrates that the nonrelativistic radiative shocks in these systems can accelerate particles to energies of at least ∼10 GeV. The low-energy extension of the same nonthermal particle distribution inevitably gives rise to emission in the hard X-ray band. Above ≳ 10 {keV}, this radiation can escape the system without significant absorption/attenuation, and can potentially be detected by NuSTAR. We present theoretical models for hard X-ray and gamma-ray emission from radiative shocks in both leptonic and hadronic scenarios, accounting for the rapid evolution of the downstream properties due to the fast cooling of thermal plasma. We find that due to strong Coulomb losses, only a fraction of {10}-4{--}{10}-3 of the gamma-ray luminosity is radiated in the NuSTAR band; nevertheless, this emission could be detectable simultaneously with the LAT emission in bright gamma-ray novae with a ∼50 ks exposure. The spectral slope in hard X-rays is α ≈ 0 for typical nova parameters, thus serving as a testable prediction of the model. Our work demonstrates how combined hard X-ray and gamma-ray observations can be used to constrain properties of the nova outflow (velocity, density, and mass outflow rate) and particle acceleration at the shock. A very low X-ray to gamma-ray luminosity ratio ({L}{{X}}/{L}γ ≲ 5× {10}-4) would disfavor leptonic models for the gamma-ray emission. Our model can also be applied to other astrophysical environments with radiative shocks, including SNe IIn and colliding winds in massive star binaries.

Terrestrial gamma-ray flashes

Science.gov (United States)

Marisaldi, Martino; Fuschino, Fabio; Labanti, Claudio; Tavani, Marco; Argan, Andrea; Del Monte, Ettore; Longo, Francesco; Barbiellini, Guido; Giuliani, Andrea; Trois, Alessio; Bulgarelli, Andrea; Gianotti, Fulvio; Trifoglio, Massimo

2013-08-01

Lightning and thunderstorm systems in general have been recently recognized as powerful particle accelerators, capable of producing electrons, positrons, gamma-rays and neutrons with energies as high as several tens of MeV. In fact, these natural systems turn out to be the highest energy and most efficient natural particle accelerators on Earth. Terrestrial Gamma-ray Flashes (TGFs) are millisecond long, very intense bursts of gamma-rays and are one of the most intriguing manifestation of these natural accelerators. Only three currently operative missions are capable of detecting TGFs from space: the RHESSI, Fermi and AGILE satellites. In this paper we review the characteristics of TGFs, including energy spectrum, timing structure, beam geometry and correlation with lightning, and the basic principles of the associated production models. Then we focus on the recent AGILE discoveries concerning the high energy extension of the TGF spectrum up to 100 MeV, which is difficult to reconcile with current theoretical models.

Terrestrial gamma-ray flashes

International Nuclear Information System (INIS)

Marisaldi, Martino; Fuschino, Fabio; Labanti, Claudio; Tavani, Marco; Argan, Andrea; Del Monte, Ettore; Longo, Francesco; Barbiellini, Guido; Giuliani, Andrea; Trois, Alessio; Bulgarelli, Andrea; Gianotti, Fulvio; Trifoglio, Massimo

2013-01-01

Lightning and thunderstorm systems in general have been recently recognized as powerful particle accelerators, capable of producing electrons, positrons, gamma-rays and neutrons with energies as high as several tens of MeV. In fact, these natural systems turn out to be the highest energy and most efficient natural particle accelerators on Earth. Terrestrial Gamma-ray Flashes (TGFs) are millisecond long, very intense bursts of gamma-rays and are one of the most intriguing manifestation of these natural accelerators. Only three currently operative missions are capable of detecting TGFs from space: the RHESSI, Fermi and AGILE satellites. In this paper we review the characteristics of TGFs, including energy spectrum, timing structure, beam geometry and correlation with lightning, and the basic principles of the associated production models. Then we focus on the recent AGILE discoveries concerning the high energy extension of the TGF spectrum up to 100 MeV, which is difficult to reconcile with current theoretical models

Prompt gamma-ray imaging for small animals

Science.gov (United States)

Xu, Libai

Small animal imaging is recognized as a powerful discovery tool for small animal modeling of human diseases, which is providing an important clue to complete understanding of disease mechanisms and is helping researchers develop and test new treatments. The current small animal imaging techniques include positron emission tomography (PET), single photon emission tomography (SPECT), computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound (US). A new imaging modality called prompt gamma-ray imaging (PGI) has been identified and investigated primarily by Monte Carlo simulation. Currently it is suggested for use on small animals. This new technique could greatly enhance and extend the present capabilities of PET and SPECT imaging from ingested radioisotopes to the imaging of selected non-radioactive elements, such as Gd, Cd, Hg, and B, and has the great potential to be used in Neutron Cancer Therapy to monitor neutron distribution and neutron-capture agent distribution. This approach consists of irradiating small animals in the thermal neutron beam of a nuclear reactor to produce prompt gamma rays from the elements in the sample by the radiative capture (n, gamma) reaction. These prompt gamma rays are emitted in energies that are characteristic of each element and they are also produced in characteristic coincident chains. After measuring these prompt gamma rays by surrounding spectrometry array, the distribution of each element of interest in the sample is reconstructed from the mapping of each detected signature gamma ray by either electronic collimations or mechanical collimations. In addition, the transmitted neutrons from the beam can be simultaneously used for very sensitive anatomical imaging, which provides the registration for the elemental distributions obtained from PGI. The primary approach is to use Monte Carlo simulation methods either with the specific purpose code CEARCPG, developed at NC State University or with the general purpose

The First Fermi-LAT Gamma-Ray Burst Catalog

NARCIS (Netherlands)

Ackermann, M.; et al., [Unknown; van der Horst, A.J.

2013-01-01

In three years of observations since the beginning of nominal science operations in 2008 August, the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope has observed high-energy (gsim 20 MeV) γ-ray emission from 35 gamma-ray bursts (GRBs). Among these, 28 GRBs have been detected

The First FERMI-LAT Gamma-Ray Burst Catalog

Science.gov (United States)

Ackermann, M.; Ajello, M.; Asano, K.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.;

Coincidence gamma-ray spectrometry

DEFF Research Database (Denmark)

Markovic, Nikola; Roos, Per; Nielsen, Sven Poul

2017-01-01

Gamma-ray spectrometry with high-purity germanium (HPGe) detectors is often the technique of choice in an environmental radioactivity laboratory. When measuring environmental samples associated activities are usually low so an important parameter that describes the performance of the spectrometer...... for a nuclide of interest is the minimum detectable activity (MDA). There are many ways for lowering the MDAs in gamma spectrometry. Recently, developments of fast and compact digital acquisition systems have led to growing number of multiple HPGe detector spectrometers. In these applications all detected...

Gamma-Ray Pulsars Models and Predictions

CERN Document Server

Harding, A K

2001-01-01

Pulsed emission from gamma-ray pulsars originates inside the magnetosphere, from radiation by charged particles accelerated near the magnetic poles or in the outer gaps. In polar cap models, the high energy spectrum is cut off by magnetic pair production above an energy that is dependent on the local magnetic field strength. While most young pulsars with surface fields in the range B = 10^{12} - 10^{13} G are expected to have high energy cutoffs around several GeV, the gamma-ray spectra of old pulsars having lower surface fields may extend to 50 GeV. Although the gamma-ray emission of older pulsars is weaker, detecting pulsed emission at high energies from nearby sources would be an important confirmation of polar cap models. Outer gap models predict more gradual high-energy turnovers at around 10 GeV, but also predict an inverse Compton component extending to TeV energies. Detection of pulsed TeV emission, which would not survive attenuation at the polar caps, is thus an important test of outer gap models. N...

Shielding system for the detection of radioisotopes gamma-rays emitters

International Nuclear Information System (INIS)

Nascimento Filho, V.F. do

1983-01-01

A shielding system for detection of radioisotopes gamma-rays emitters in samples of big volumes (plants, animals, soils) is presented. The detection between the beaker Marinelli and the glass tube (inside of the scintillator crystal well) is compared. The beaker Marinelli method allows a drastic reduction in the time detection of the sample. (M.A.C.) [pt

Point source search techniques in ultra high energy gamma ray astronomy

International Nuclear Information System (INIS)

Alexandreas, D.E.; Biller, S.; Dion, G.M.; Lu, X.Q.; Yodh, G.B.; Berley, D.; Goodman, J.A.; Haines, T.J.; Hoffman, C.M.; Horch, E.; Sinnis, C.; Zhang, W.

1993-01-01

Searches for point astrophysical sources of ultra high energy (UHE) gamma rays are plagued by large numbers of background events from isotropic cosmic rays. Some of the methods that have been used to estimate the expected number of background events coming from the direction of a possible source are found to contain biases. Search techniques that avoid this problem are described. There is also a discussion of how to optimize the sensitivity of a search to emission from a point source. (orig.)

Detection of SNM by delayed gamma rays from induced fission

International Nuclear Information System (INIS)

Rennhofer, H.; Crochemore, J.-M.; Roesgen, E.; Pedersen, B.

2011-01-01

The Pulsed Neutron Interrogation Test Assembly (PUNITA) is an experimental device for research in NDA methods and field applicable instrumentation for nuclear safeguards and security applications. PUNITA incorporates a standard 14-MeV (D-T) pulsed neutron generator inside a large graphite mantle. The generator target is surrounded by a thick tungsten filter with the purpose to increase the neutron output and to tailor the neutron energy spectrum. In this configuration a sample may be exposed to a relatively high average thermal neutron flux of about (2.2±0.1)x10 3 s -1 cm -2 at only 10% of the maximum target neutron emission. The sample cavity is large enough to allow variation of the experimental setup including the fissile sample, neutron and gamma detectors, and shielding materials. The response from SNM samples of different fissile material content was investigated with various field-applicable scintillation gamma detectors such as the 3x2 in. LaBr 3 detector. Shielding in the form of tungsten and cadmium was applied to the detector to improve the signal to background ratio. Gamma and neutron shields surrounding the samples were also tested for the purpose of simulating clandestine conduct. The energy spectra of delayed gamma rays were recorded in the range 100 keV-9 MeV. In addition time spectra of delayed gamma rays in the range 3.3-8 MeV were recorded in the time period of 10 ms-120 s after the 14-MeV neutron burst. The goal of the experiment was to optimize the sample/detector configuration including the energy range and time period for SNM detection. The results show, for example, that a 170 g sample of depleted uranium can be detected with the given setup in less than 3 min of investigation. Samples of higher enrichment or higher mass are detected in much shorter time.

THE DETECTABILITY OF DARK MATTER ANNIHILATION WITH FERMI USING THE ANISOTROPY ENERGY SPECTRUM OF THE GAMMA-RAY BACKGROUND

International Nuclear Information System (INIS)

Hensley, Brandon S.; Pavlidou, Vasiliki; Siegal-Gaskins, Jennifer M.

2010-01-01

The energy dependence of the anisotropy (the anisotropy energy spectrum) of the large-scale diffuse gamma-ray background can reveal the presence of multiple source populations. Annihilating dark matter in the substructure of the Milky Way halo could give rise to a modulation in the anisotropy energy spectrum of the diffuse gamma-ray emission measured by Fermi, enabling the detection of a dark matter signal. We determine the detectability of a dark-matter-induced modulation for scenarios in which unresolved blazars are the primary contributor to the measured emission above ∼1 GeV and find that in some scenarios pair-annihilation cross sections on the order of the value expected for thermal relic dark matter can produce a detectable feature. We anticipate that the sensitivity of this technique to specific dark matter models could be improved by tailored likelihood analysis methods.

High energy astrophysics with ground-based gamma ray detectors

International Nuclear Information System (INIS)

Aharonian, F; Buckley, J; Kifune, T; Sinnis, G

2008-01-01

Recent advances in ground-based gamma ray astronomy have led to the discovery of more than 70 sources of very high energy (E γ ≥ 100 GeV) gamma rays, falling into a number of source populations including pulsar wind nebulae, shell type supernova remnants, Wolf-Rayet stars, giant molecular clouds, binary systems, the Galactic Center, active galactic nuclei and 'dark' (yet unidentified) galactic objects. We summarize the history of TeV gamma ray astronomy up to the current status of the field including a description of experimental techniques and highlight recent astrophysical results. We also discuss the potential of ground-based gamma ray astronomy for future discoveries and describe possible directions for future instrumental developments

Search for very high-energy gamma-ray emission from the microquasar Cygnus X-1 with the MAGIC telescopes

Science.gov (United States)

Ahnen, M. L.; Ansoldi, S.; Antonelli, L. A.; Arcaro, C.; Babić, A.; Banerjee, B.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Berti, A.; Bhattacharyya, W.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Carosi, R.; Carosi, A.; Chatterjee, A.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Cumani, P.; da Vela, P.; Dazzi, F.; de Angelis, A.; de Lotto, B.; de Oña Wilhelmi, E.; di Pierro, F.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher Glawion, D.; Elsaesser, D.; Engelkemeier, M.; Fallah Ramazani, V.; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Fruck, C.; Galindo, D.; García López, R. J.; Garczarczyk, M.; Gaug, M.; Giammaria, P.; Godinović, N.; Gora, D.; Guberman, D.; Hadasch, D.; Hahn, A.; Hassan, T.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Ishio, K.; Konno, Y.; Kubo, H.; Kushida, J.; Kuveždić, D.; Lelas, D.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; Maggio, C.; Majumdar, P.; Makariev, M.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Minev, M.; Mirzoyan, R.; Moralejo, A.; Moreno, V.; Moretti, E.; Neustroev, V.; Niedzwiecki, A.; Nievas Rosillo, M.; Nilsson, K.; Ninci, D.; Nishijima, K.; Noda, K.; Nogués, L.; Paiano, S.; Palacio, J.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Pedaletti, G.; Peresano, M.; Perri, L.; Persic, M.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Garcia, J. R.; Reichardt, I.; Rhode, W.; Ribó, M.; Rico, J.; Righi, C.; Saito, T.; Satalecka, K.; Schroeder, S.; Schweizer, T.; Sitarek, J.; Šnidarić, I.; Sobczynska, D.; Stamerra, A.; Strzys, M.; Surić, T.; Takalo, L.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Torres, D. F.; Torres-Albà, N.; Treves, A.; Vanzo, G.; Vazquez Acosta, M.; Vovk, I.; Ward, J. E.; Will, M.; Zarić, D.; MAGIC Collaboration; Bosch-Ramon, V.; Pooley, G. G.; Trushkin, S. A.; Zanin, R.

2017-12-01

The microquasar Cygnus X-1 displays the two typical soft and hard X-ray states of a black hole transient. During the latter, Cygnus X-1 shows a one-sided relativistic radio-jet. Recent detection of the system in the high energy (HE; E ≳ 60 MeV) gamma-ray range with Fermi-LAT associates this emission with the outflow. Former MAGIC observations revealed a hint of flaring activity in the very high-energy (VHE; E ≳ 100 GeV) regime during this X-ray state. We analyse ∼97 h of Cygnus X-1 data taken with the MAGIC telescopes between July 2007 and October 2014. To shed light on the correlation between hard X-ray and VHE gamma rays as previously suggested, we study each main X-ray state separately. We perform an orbital phase-folded analysis to look for variability in the VHE band. Additionally, to place this variability behaviour in a multiwavelength context, we compare our results with Fermi-LAT, AGILE, Swift-BAT, MAXI, RXTE-ASM, AMI and RATAN-600 data. We do not detect Cygnus X-1 in the VHE regime. We establish upper limits for each X-ray state, assuming a power-law distribution with photon index Γ = 3.2. For steady emission in the hard and soft X-ray states, we set integral upper limits at 95 per cent confidence level for energies above 200 GeV at 2.6 × 10-12 photons cm-2 s-1 and 1.0 × 10-11 photons cm-2 s-1, respectively. We rule out steady VHE gamma-ray emission above this energy range, at the level of the MAGIC sensitivity, originating in the interaction between the relativistic jet and the surrounding medium, while the emission above this flux level produced inside the binary still remains a valid possibility.

Gamma-ray detectors for breast imaging

Science.gov (United States)

Williams, Mark B.; Goode, Allen R.; Majewski, Stan; Steinbach, Daniela; Weisenberger, Andrew G.; Wojcik, Randolph F.; Farzanpay, Farzin

1997-07-01

Breast cancer is the most common cancer of American women and is the leading cause of cancer-related death among women aged 15 - 54; however recent years have shown that early detection using x-ray mammography can lead to a high probability of cure. However, because of mammography's low positive predictive value, surgical or core biopsy is typically required for diagnosis. In addition, the low radiographic contrast of many nonpalpable breast masses, particularly among women with radiographically dense breasts, results in an overall rate of 10% to 25% for missed tumors. Nuclear imaging of the breast using single gamma emitters (scintimammography) such as (superscript 99m)Tc, or positron emitters such as F-18- fluorodeoxyglucose (FDG) for positron emission tomography (PET), can provide information on functional or metabolic tumor activity that is complementary to the structural information of x-ray mammography, thereby potentially reducing the number of unnecessary biopsies and missed cancers. This paper summarizes recent data on the efficacy of scintimammography using conventional gamma cameras, and describes the development of dedicated detectors for gamma emission breast imaging. The detectors use new, high density crystal scintillators and large area position sensitive photomultiplier tubes (PSPMTs). Detector design, imaging requirements, and preliminary measured imaging performance are discussed.

Observation of solar gamma-ray by Hinotori

International Nuclear Information System (INIS)

Yoshimori, Masato; Okudaira, Kiyoaki; Hirashima, Yo; Kondo, Ichiro.

1982-01-01

The solar gamma-ray emitted by solar flare was observed. The gamma-ray is the electromagnetic radiation with the energy more than 300 keV. The line gamma-ray intensity and the time profile were observed. The gamma-ray detector CsI (Tl) was loaded on Hinotori, and the observed gamma-ray was analyzed by a multi-channel analyzer. The observed line gamma-ray was the radiation from Fe-56 and Ne-20. The line gamma-ray from C-12 and O-16 was also seen. These gamma-ray is the direct evidence of the nuclear reaction on the sun. The observed spectrum suggested the existence of the lines from Mg-24 and Si-28. The intensity of the 2.22 MeV gamma-line was small. This fact showed that the origin of this line was different from other nuclear gamma-ray. Two kinds of hard X-ray bursts were detected. The one was impulsive burst, and the other was gradual burst. There was no time difference between the hard X-ray and the gamma-ray of the impulsive burst. The impulsive burst may be explained by the beam model. The delay of time profile in the high energy gamma-ray of the gradual burst was observed. This means that the time when accelerated electrons cause bremsstrahlung depends on the electron energy. The long trapping of electrons at the top of magnetic loop is suggested. (Kato, T.)

The Advanced Gamma-ray Imaging System (AGIS): Galactic Astrophysics

Science.gov (United States)

Digel, Seth William; Funk, S.; Kaaret, P. E.; Tajima, H.; AGIS Collaboration

2010-03-01

The Advanced Gamma-ray Imaging System (AGIS), a concept for a next-generation atmospheric Cherenkov telescope array, would provide unprecedented sensitivity and resolution in the energy range >50 GeV, allowing great advances in the understanding of the populations and physics of sources of high-energy gamma rays in the Milky Way. Extrapolation based on the known source classes and the performance parameters for AGIS indicates that a survey of the Galactic plane with AGIS will reveal hundreds of TeV sources in exquisite detail, for population studies of a variety of source classes, and detailed studies of individual sources. AGIS will be able to study propagation effects on the cosmic rays produced by Galactic sources by detecting the diffuse glow from their interactions in dense interstellar gas. AGIS will complement and extend results now being obtained in the GeV range with the Fermi mission, by providing superior angular resolution and sensitivity to variability on short time scales, and of course by probing energies that Fermi cannot reach.

Gamma-ray-burst beaming and gravitational-wave observations.

Science.gov (United States)

Chen, Hsin-Yu; Holz, Daniel E

2013-11-01

Using the observed rate of short-duration gamma-ray bursts (GRBs) it is possible to make predictions for the detectable rate of compact binary coalescences in gravitational-wave detectors. We show that the nondetection of mergers in the existing LIGO/Virgo data constrains the beaming angles and progenitor masses of gamma-ray bursts, although these limits are fully consistent with existing expectations. We make predictions for the rate of events in future networks of gravitational-wave observatories, finding that the first detection of a neutron-star-neutron-star binary coalescence associated with the progenitors of short GRBs is likely to happen within the first 16 months of observation, even in the case of only two observatories (e.g., LIGO-Hanford and LIGO-Livingston) operating at intermediate sensitivities (e.g., advanced LIGO design sensitivity, but without signal recycling mirrors), and assuming a conservative distribution of beaming angles (e.g., all GRBs beamed within θ(j) = 30°). Less conservative assumptions reduce the waiting time until first detection to a period of weeks to months, with an event detection rate of >/~10/yr. Alternatively, the compact binary coalescence model of short GRBs can be ruled out if a binary is not seen within the first two years of operation of a LIGO-Hanford, LIGO-Livingston, and Virgo network at advanced design sensitivity. We also demonstrate that the gravitational wave detection rate of GRB triggered sources (i.e., those seen first in gamma rays) is lower than the rate of untriggered events (i.e., those seen only in gravitational waves) if θ(j)≲30°, independent of the noise curve, network configuration, and observed GRB rate. The first detection in gravitational waves of a binary GRB progenitor is therefore unlikely to be associated with the observation of a GRB.

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

Science.gov (United States)

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

2012-01-01

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

DETECTION OF GAMMA-RAY POLARIZATION IN PROMPT EMISSION OF GRB 100826A

Energy Technology Data Exchange (ETDEWEB)

Yonetoku, Daisuke; Murakami, Toshio; Sakashita, Tomonori; Morihara, Yoshiyuki; Takahashi, Takuya; Fujimoto, Hirofumi; Kodama, Yoshiki [College of Science and Engineering, School of Mathematics and Physics, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192 (Japan); Gunji, Shuichi; Toukairin, Noriyuki [Department of Physics, Faculty of Science, Yamagata University, 1-4-12, Koshirakawa, Yamagata, Yamagata 990-8560 (Japan); Mihara, Tatehiro [Cosmic Radiation Laboratory, RIKEN, 2-1, Hirosawa, Wako City, Saitama 351-0198 (Japan); Toma, Kenji [Department of Earth and Space Science, Osaka University, Toyonaka 560-0043 (Japan); Kubo, Shin, E-mail: yonetoku@astro.s.kanazawa-u.ac.jp [Clear Pulse Co. Ltd., 6-25-17, Chuo, Ohta-ku, Tokyo 143-0024 (Japan); Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1, Yoshinodai, Sagamihara, Kanagawa 229-8510 (Japan)

2011-12-20

We report the polarization measurement in prompt {gamma}-ray emission of GRB 100826A with the Gamma-Ray Burst Polarimeter on board the small solar-power-sail demonstrator IKAROS. We detected the firm change of polarization angle (PA) during the prompt emission with 99.9% (3.5{sigma}) confidence level, and the average polarization degree ({Pi}) of 27% {+-} 11% with 99.4% (2.9{sigma}) confidence level. Here the quoted errors are given at 1{sigma} confidence level for the two parameters of interest. The systematic errors have been carefully included in this analysis, unlike other previous reports. Such a high {Pi} can be obtained in several emission models of gamma-ray bursts (GRBs), including synchrotron and photospheric models. However, it is difficult to explain the observed significant change of PA within the framework of axisymmetric jet as considered in many theoretical works. The non-axisymmetric (e.g., patchy) structures of the magnetic fields and/or brightness inside the relativistic jet are therefore required within the observable angular scale of {approx}{Gamma}{sup -1}. Our observation strongly indicates that the polarization measurement is a powerful tool to constrain the GRB production mechanism, and more theoretical works are needed to discuss the data in more detail.

Localization of Gamma-Ray Bursts Using the Fermi Gamma-Ray Burst Monitor

NARCIS (Netherlands)

Connaughton, V.; Briggs, M.S.; Goldstein, A.; Meegan, C.A.; Paciesas, W.S.; Preece, R.D.; Wilson-Hodge, C.A.; Gibby, M.H.; Greiner, J.; Gruber, D.; Jenke, P.; Kippen, R.M.; Pelassa, V.; Xiong, S.; Yu, H-F.; Bhat, P.N.; Burgess, J.M.; Byrne, D.; Fitzpatrick, G.; Foley, S.; Giles, M.M.; Guiriec, S.; van der Horst, A.J.; von Kienlin, A.; McBreen, S.; McGlynn, S.; Tierney, D.; Zhang, B..B.

2015-01-01

The Fermi Gamma-ray Burst Monitor (GBM) has detected over 1400 gamma-ray bursts (GRBs) since it began science operations in 2008 July. We use a subset of over 300 GRBs localized by instruments such as Swift, the Fermi Large Area Telescope, INTEGRAL, and MAXI, or through triangulations from the

The Advanced Gamma-Ray Imaging System (AGIS)

Science.gov (United States)

Otte, Nepomuk

The Advanced Gamma-ray Imaging System (AGIS) is a concept for the next generation of imag-ing atmospheric Cherenkov telescope arrays. It has the goal of providing an order of magnitude increase in sensitivity for Very High Energy Gamma-ray ( 100 GeV to 100 TeV) astronomy compared to currently operating arrays such as CANGAROO, HESS, MAGIC, and VERITAS. After an overview of the science such an array would enable, we discuss the development of the components of the telescope system that are required to achieve the sensitivity goal. AGIS stresses improvements in several areas of IACT technology including component reliability as well as exploring cost reduction possibilities in order to achieve its goal. We discuss alterna-tives for the telescopes and positioners: a novel Schwarzschild-Couder telescope offering a wide field of view with a relatively smaller plate scale, and possibilities for rapid slewing in order to address the search for and/or study of Gamma-ray Bursts in the VHE gamma-ray regime. We also discuss options for a high pixel count camera system providing the necessary finer solid angle per pixel and possibilities for a fast topological trigger that would offer improved realtime background rejection and lower energy thresholds.

Reduction of Compton background from hydrogen in prompt gamma-ray analysis by multiple photon detection

International Nuclear Information System (INIS)

Toh, Y.; Oshima, M.; Kimura, A.; Koizumi, M.; Furutaka, K.; Hatsukawa, Y.

2008-01-01

Low-energy photons produced by the Compton scattering from hydrogen increase the background in the lower-energy region of the gamma-ray spectrum. This results in an increase in the detection limit for trace elements. In multiple photon detection prompt gamma-ray analysis (MPGA), only those elements that simultaneously emit two or more prompt gamma-rays, which have cascade relation and are emitted within a short interval, can be measured. Therefore, the influence of hydrogen can be reduced. In this study, standard polymer and food samples are measured. The hydrogen background is reduced in MPGA. (author)

The Gamma-Ray Imager GRI

Science.gov (United States)

Wunderer, Cornelia B.; GRI Collaboration

2008-03-01

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 major science themes that are addressed in the gamma-ray regime. ESA's INTEGRAL observatory currently provides the astronomical community with a unique tool to investigate the sky up to MeV energies and hundreds of sources, new classes of objects, extraordinary views of antimatter annihilation in our Galaxy, and fingerprints of recent nucleosynthesis processes have been discovered. NASA's GLAST mission will similarly take the next step in surveying the high-energy ( GeV) sky, and NuSTAR will pioneer focusing observations at hard X-ray energies (to 80 keV). There will be clearly a growing need to perform deeper, more focused investigations of gamma-ray sources in the 100-keV to MeV regime. Recent technological advances 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 the study of 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.

Plastic Gamma Sensors: An Application in Detection of Radioisotopes

International Nuclear Information System (INIS)

Mukhopadhyay, S.

2003-01-01

A brief survey of plastic scintillators for various radiation measurement applications is presented here. The utility of plastic scintillators for practical applications such as gamma radiation monitoring, real-time radioisotope detection and screening is evaluated in laboratory and field measurements. This study also reports results of Monte Carlo-type predictive responses of common plastic scintillators in gamma and neutron radiation fields. Small-size plastic detectors are evaluated for static and dynamic gamma-ray detection sensitivity of selected radiation sources

Constraints on Short, Hard Gamma-Ray Burst Beaming Angles from Gravitational Wave Observations

Science.gov (United States)

Williams, D.; Clark, J. A.; Williamson, A. R.; Heng, I. S.

2018-05-01

The first detection of a binary neutron star merger, GW170817, and an associated short gamma-ray burst confirmed that neutron star mergers are responsible for at least some of these bursts. The prompt gamma-ray emission from these events is thought to be highly relativistically beamed. We present a method for inferring limits on the extent of this beaming by comparing the number of short gamma-ray bursts (SGRBs) observed electromagnetically with the number of neutron star binary mergers detected in gravitational waves. We demonstrate that an observing run comparable to the expected Advanced LIGO (aLIGO) 2016–2017 run would be capable of placing limits on the beaming angle of approximately θ \\in (2\\buildrel{\\circ}\\over{.} 88,14\\buildrel{\\circ}\\over{.} 15), given one binary neutron star detection, under the assumption that all mergers produce a gamma-ray burst, and that SGRBs occur at an illustrative rate of {{ \\mathcal R }}grb}=10 {Gpc}}-3 {yr}}-1. We anticipate that after a year of observations with aLIGO at design sensitivity in 2020, these constraints will improve to θ \\in (8\\buildrel{\\circ}\\over{.} 10,14\\buildrel{\\circ}\\over{.} 95), under the same efficiency and SGRB rate assumptions.

Detection and measurement of gamma-ray self-attenuation in plutonium residues

International Nuclear Information System (INIS)

Prettyman, T.H.; Foster, L.A.; Estep, R.J.

1996-01-01

A new method to correct for self-attenuation in gamma-ray assays of plutonium is presented. The underlying assumptions of the technique are based on a simple but accurate physical model of plutonium residues, particularly pyrochemical salts, in which it is assumed that the plutonium is divided into two portions, each of which can be treated separately from the standpoint of gamma-ray analysis: a portion that is in the form of plutonium metal shot; and a dilute portion that is mixed with the matrix. The performance of the technique is evaluated using assays of plutonium residues by tomographic gamma scanning at the Los Alamos Plutonium Facility. The ability of the method to detect saturation conditions is examined

Gamma Ray Burst Discoveries with the Swift Mission

Science.gov (United States)

Gehrels, Neil; Tueller, Jack

2007-01-01

There is a great synergy between the Swift and INTEGRAL missions. Swift provides wide-field hard x-ray monitoring and sensitive x-ray and UV/optical observations. INTEGRAL provides optical through gamma-ray coverage with emphasis on hard xray imaging and gamma-ray spectroscopy. For hard x-ray survey studies, the BAT and IBIS instruments are complementary with BAT covering the full sky every day and IBIS scanning the galactic plane. For GRBs, Swift follows up bursts detected by INTEGRAL. X-ray and optical observations give arcsecond positions and afterglow lightcurves. For IGR sources, X-ray observations identify counterparts. The joint BAT and IBIS survey data are giving the most complete picture of the hard x-ray sky ever obtained. This talk will review Swift capabilities and discuss joint observations that are taking place and planned

Finding Sub-threshold Short Gamma-ray Bursts in Fermi GBM Data

Science.gov (United States)

Burns, Eric; Fermi Gamma-ray Burst Monitor Team

2018-01-01

The all-sky monitoring capability of Fermi GBM makes it ideal for finding transients, and the most prolific detector of short gamma-ray bursts with about 40 on-board triggers per year. Because the observed brightness of short gamma-ray bursts has no correlation with redshift, weak short gamma-ray bursts are important during the gravitational wave era. With this in mind, we discuss two searches of GBM data to find short gamma-ray which were below the on-board trigger threshold. The untargeted search looks for significant background-subtracted signals in two or more detectors at various timescales in the continuous data, detecting ~80 additional short GRB candidates per year. The targeted search is the most sensitive search for weak gamma-ray signals in GBM data and is run over limited time intervals around sources of interest like gravitational waves.

Neutron counting and gamma spectroscopy with PVT detectors

International Nuclear Information System (INIS)

Mitchell, Dean James; Brusseau, Charles A.

2011-01-01

Radiation portals normally incorporate a dedicated neutron counter and a gamma-ray detector with at least some spectroscopic capability. This paper describes the design and presents characterization data for a detection system called PVT-NG, which uses large polyvinyl toluene (PVT) detectors to monitor both types of radiation. The detector material is surrounded by polyvinyl chloride (PVC), which emits high-energy gamma rays following neutron capture reactions. Assessments based on high-energy gamma rays are well suited for the detection of neutron sources, particularly in border security applications, because few isotopes in the normal stream of commerce have significant gamma ray yields above 3 MeV. Therefore, an increased count rate for high-energy gamma rays is a strong indicator for the presence of a neutron source. The sensitivity of the PVT-NG sensor to bare 252 Cf is 1.9 counts per second per nanogram (cps/ng) and the sensitivity for 252 Cf surrounded by 2.5 cm of polyethylene is 2.3 cps/ng. The PVT-NG sensor is a proof-of-principal sensor that was not fully optimized. The neutron detector sensitivity could be improved, for instance, by using additional moderator. The PVT-NG detectors and associated electronics are designed to provide improved resolution, gain stability, and performance at high-count rates relative to PVT detectors in typical radiation portals. As well as addressing the needs for neutron detection, these characteristics are also desirable for analysis of the gamma-ray spectra. Accurate isotope identification results were obtained despite the common impression that the absence of photopeaks makes data collected by PVT detectors unsuitable for spectroscopic analysis. The PVT detectors in the PVT-NG unit are used for both gamma-ray and neutron detection, so the sensitive volume exceeds the volume of the detection elements in portals that use dedicated components to detect each type of radiation.

GBM Observations of Terrestrial Gamma-Ray Flashes

Science.gov (United States)

Briggs, M. S.; Fishman, G. J.; Connaughton, V.; Bhat, P. N.; Paciesas, W. S.; Preece, R. D.; Wilson-Hodge, C.; Chaplin, V. L.; Kippen, R. M.; vonKienlin, A.;

Standard guide for high-resolution gamma-ray spectrometry of soil samples

CERN Document Server

American Society for Testing and Materials. Philadelphia

2004-01-01

1.1 This guide covers the identification and quantitative determination of gamma-ray emitting radionuclides in soil samples by means of gamma-ray spectrometry. It is applicable to nuclides emitting gamma rays with an approximate energy range of 20 to 2000 keV. For typical gamma-ray spectrometry systems and sample types, activity levels of about 5 Bq (135 pCi) are measured easily for most nuclides, and activity levels as low as 0.1 Bq (2.7 pCi) can be measured for many nuclides. It is not applicable to radionuclides that emit no gamma rays such as the pure beta-emitting radionuclides hydrogen-3, carbon-14, strontium-90, and becquerel quantities of most transuranics. This guide does not address the in situ measurement techniques, where soil is analyzed in place without sampling. Guidance for in situ techniques can be found in Ref (1) and (2). This guide also does not discuss methods for determining lower limits of detection. Such discussions can be found in Refs (3), (4), (5), and (6). 1.2 This guide can be us...

Limits to the Fraction of High-energy Photon Emitting Gamma-Ray Bursts

Science.gov (United States)

Akerlof, Carl W.; Zheng, WeiKang

2013-02-01

After almost four years of operation, the two instruments on board the Fermi Gamma-ray Space Telescope have shown that the number of gamma-ray bursts (GRBs) with high-energy photon emission above 100 MeV cannot exceed roughly 9% of the total number of all such events, at least at the present detection limits. In a recent paper, we found that GRBs with photons detected in the Large Area Telescope have a surprisingly broad distribution with respect to the observed event photon number. Extrapolation of our empirical fit to numbers of photons below our previous detection limit suggests that the overall rate of such low flux events could be estimated by standard image co-adding techniques. In this case, we have taken advantage of the excellent angular resolution of the Swift mission to provide accurate reference points for 79 GRB events which have eluded any previous correlations with high-energy photons. We find a small but significant signal in the co-added field. Guided by the extrapolated power-law fit previously obtained for the number distribution of GRBs with higher fluxes, the data suggest that only a small fraction of GRBs are sources of high-energy photons.

LIMITS TO THE FRACTION OF HIGH-ENERGY PHOTON EMITTING GAMMA-RAY BURSTS

International Nuclear Information System (INIS)

Akerlof, Carl W.; Zheng, WeiKang

2013-01-01

After almost four years of operation, the two instruments on board the Fermi Gamma-ray Space Telescope have shown that the number of gamma-ray bursts (GRBs) with high-energy photon emission above 100 MeV cannot exceed roughly 9% of the total number of all such events, at least at the present detection limits. In a recent paper, we found that GRBs with photons detected in the Large Area Telescope have a surprisingly broad distribution with respect to the observed event photon number. Extrapolation of our empirical fit to numbers of photons below our previous detection limit suggests that the overall rate of such low flux events could be estimated by standard image co-adding techniques. In this case, we have taken advantage of the excellent angular resolution of the Swift mission to provide accurate reference points for 79 GRB events which have eluded any previous correlations with high-energy photons. We find a small but significant signal in the co-added field. Guided by the extrapolated power-law fit previously obtained for the number distribution of GRBs with higher fluxes, the data suggest that only a small fraction of GRBs are sources of high-energy photons.

Room temperature X- and gamma-ray detectors using thallium bromide crystals

CERN Document Server

Hitomi, K; Shoji, T; Suehiro, T; Hiratate, Y

1999-01-01

Thallium bromide (TlBr) is a compound semiconductor with wide band gap (2.68 eV) and high X- and gamma-ray stopping power. The TlBr crystals were grown by the horizontal travelling molten zone (TMZ) method using purified material. Two types of room temperature X- and gamma-ray detectors were fabricated from the TlBr crystals: TlBr detectors with high detection efficiency for positron annihilation gamma-ray (511 keV) detection and TlBr detectors with high-energy resolution for low-energy X-ray detection. The detector of the former type demonstrated energy resolution of 56 keV FWHM (11%) for 511 keV gamma-rays. Energy resolution of 1.81 keV FWHM for 5.9 keV was obtained from the detector of the latter type. In order to analyze noise characteristics of the detector-preamplifier assembly, the equivalent noise charge (ENC) was measured as a function of the amplifier shaping time for the high-resolution detector. This analysis shows that parallel white noise and 1/f noise were dominant noise sources in the detector...

Detection of Primordial Magnetic Fields in TeV gamma-ray data

Science.gov (United States)

Wingler, A.

The analysis of the time-variable flux of γ-ray photons from extragalactic sources is currently the only proposed way to directly determine the magnetic field strengths in intergalactic space - far away from galaxies and clusters (in the cosmological "voids") - in the range below about 10,10 Gauss (Plaga 1995). Remnant magnetic fields with field strengths much below this, which may well have formed in early cosmological times, could exist in these voids. Due to their interaction with infrared photons TeV gamma-rays induce pair production in intergalactic space. The electrons and positrons are deflected by ambient magnetic fields and produce γ-rays via inverse Compton scattering that are delayed with respect to the original photons in an energy-dependent, characteristic manner. A standard method to identify these delayed events in a data sample of a source with a variable VHE γ-ray flux (as available from several Cherenkov telescope experiments for the high-emission phase of the AGN Mrk 501 in 1997) is described. Monte-Carlo simulations of existing data sets (taking into backgrounds and instrumental limitations) are used to explore how sensitive data sets similar to the existing ones are to primordial magnetic fields. We find that about 22000 (15000) events from a source with characteristics similar to Mrk 501 are needed to detect a primordial B field of 3 (10) atto Gauss (10,18 G) with a 3 significance.

A study of gamma-ray bursts and a new detector for gamma-ray astronomy

International Nuclear Information System (INIS)

Carter, J.N.

1979-09-01

Three gamma-ray experiments flown on balloons between August 1975 and August 1976 are described in detail. The successful Transatlantic balloon flight enabled a rate of 3 bursts year -1 with energies > 7 x 10 -7 ergs cm -2 to be established. This result is discussed in the light of other work. The choice of γ-ray detector for optimum sensitivity is presented. In addition various techniques for determining the arrival direction of gamma-ray bursts are compared. A new balloon borne γ-ray burst telescope is proposed. The design, testing and results of the beam calibration of a new drift chamber detector system for high energy (> 50 MeV) γ-rays are presented. A projected angular resolution of 0.8 0 was obtained at 300 MeV. Techniques for the measurement of γ-ray energies are discussed in relation to this instrument. Finally the use of drift chambers in an integrated free flying satellite is illustrated, and the expected performance is presented. (author)

Development of software for the determination of gamma ray detection efficiency

International Nuclear Information System (INIS)

Silva, Antonio C.O. da; Genezini, Frederico A.; Zahn, Guilherme S.

2009-01-01

Gamma spectrometry is frequently used as a tool in analytical chemistry or environmental analyses. The efficiency of the detection setup is one of most important steps of the analyses, but users don't always calculate their own efficiency curve because this procedure is not trivial, and therefore they adapt their measurement geometry to work in a setup that has been previously calibrated, which will often cause limitations. In order to solve this problem, a software was developed that helps a non-experienced user to compute the detection efficiency curve and to determine the detection efficiency at a given gamma-ray energy. (author)

Active neutron and gamma-ray imaging of highly enriched uranium for treaty verification.

Science.gov (United States)

Hamel, Michael C; Polack, J Kyle; Ruch, Marc L; Marcath, Matthew J; Clarke, Shaun D; Pozzi, Sara A

2017-08-11

The detection and characterization of highly enriched uranium (HEU) presents a large challenge in the non-proliferation field. HEU has a low neutron emission rate and most gamma rays are low energy and easily shielded. To address this challenge, an instrument known as the dual-particle imager (DPI) was used with a portable deuterium-tritium (DT) neutron generator to detect neutrons and gamma rays from induced fission in HEU. We evaluated system response using a 13.7-kg HEU sphere in several configurations with no moderation, high-density polyethylene (HDPE) moderation, and tungsten moderation. A hollow tungsten sphere was interrogated to evaluate the response to a possible hoax item. First, localization capabilities were demonstrated by reconstructing neutron and gamma-ray images. Once localized, additional properties such as fast neutron energy spectra and time-dependent neutron count rates were attributed to the items. For the interrogated configurations containing HEU, the reconstructed neutron spectra resembled Watt spectra, which gave confidence that the interrogated items were undergoing induced fission. The time-dependent neutron count rate was also compared for each configuration and shown to be dependent on the neutron multiplication of the item. This result showed that the DPI is a viable tool for localizing and confirming fissile mass and multiplication.

THE ORIGIN OF GAMMA RAYS FROM GLOBULAR CLUSTERS

International Nuclear Information System (INIS)

Cheng, K. S.; Chernyshov, D. O.; Dogiel, V. A.; Hui, C. Y.; Kong, A. K. H.

2010-01-01

Fermi has detected gamma-ray emission from eight globular clusters (GCs). It is commonly believed that the energy sources of these gamma rays are millisecond pulsars (MSPs) inside GCs. Also it has been standard to explain the spectra of most Fermi Large Area Telescope pulsars including MSPs resulting from the curvature radiation (CR) of relativistic electrons/positrons inside the pulsar magnetosphere. Therefore, gamma rays from GCs are expected to be the collection of CR from all MSPs inside the clusters. However, the angular resolution is not high enough to pinpoint the nature of the emission. In this paper, we calculate the gamma rays produced by the inverse Compton (IC) scattering between relativistic electrons/positrons in the pulsar wind of MSPs in the GCs and background soft photons including cosmic microwave/relic photons, background star lights in the clusters, the galactic infrared photons, and the galactic star lights. We show that the gamma-ray spectrum from 47 Tucanae can be explained equally well by upward scattering of either the relic photons, the galactic infrared photons, or the galactic star lights, whereas the gamma-ray spectra from the other seven GCs are best fitted by the upward scattering of either the galactic infrared photons or the galactic star lights. We also find that the observed gamma-ray luminosity is correlated better with the combined factor of the encounter rate and the background soft photon energy density. Therefore, the IC scattering may also contribute to the observed gamma-ray emission from GCs detected by Fermi in addition to the standard CR process. Furthermore, we find that the emission region of high-energy photons from GCs produced by the IC scattering is substantially larger than the cores of GCs with a radius >10 pc. The diffuse radio and X-rays emitted from GCs can also be produced by the synchrotron radiation and IC scattering, respectively. We suggest that future observations including radio, X-rays, and gamma rays

THE FIRST FERMI-LAT GAMMA-RAY BURST CATALOG

Energy Technology Data Exchange (ETDEWEB)

Ackermann, M. [Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen (Germany); Ajello, M. [Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720-7450 (United States); Asano, K. [Interactive Research Center of Science, Tokyo Institute of Technology, Meguro City, Tokyo 152-8551 (Japan); Axelsson, M. [Department of Astronomy, Stockholm University, SE-106 91 Stockholm (Sweden); Baldini, L. [Università di Pisa and Istituto Nazionale di Fisica Nucleare, Sezione di Pisa I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Université Paris Diderot, Service d' Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bechtol, K.; Bloom, E. D. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Bellazzini, R.; Bregeon, J. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Bhat, P. N. [Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Bissaldi, E. [Institut für Astro- und Teilchenphysik and Institut für Theoretische Physik, Leopold-Franzens-Universität Innsbruck, A-6020 Innsbruck (Austria); Bonamente, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Bonnell, J.; Brandt, T. J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Bouvier, A., E-mail: nicola.omodei@stanford.edu, E-mail: giacomov@slac.stanford.edu [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); and others

2013-11-01

In three years of observations since the beginning of nominal science operations in 2008 August, the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope has observed high-energy (∼> 20 MeV) γ-ray emission from 35 gamma-ray bursts (GRBs). Among these, 28 GRBs have been detected above 100 MeV and 7 GRBs above ∼20 MeV. The first Fermi-LAT catalog of GRBs is a compilation of these detections and provides a systematic study of high-energy emission from GRBs for the first time. To generate the catalog, we examined 733 GRBs detected by the Gamma-Ray Burst Monitor (GBM) on Fermi and processed each of them using the same analysis sequence. Details of the methodology followed by the LAT collaboration for the GRB analysis are provided. We summarize the temporal and spectral properties of the LAT-detected GRBs. We also discuss characteristics of LAT-detected emission such as its delayed onset and longer duration compared with emission detected by the GBM, its power-law temporal decay at late times, and the fact that it is dominated by a power-law spectral component that appears in addition to the usual Band model.

THE FIRST FERMI-LAT GAMMA-RAY BURST CATALOG

International Nuclear Information System (INIS)

Ackermann, M.; Ajello, M.; Asano, K.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bloom, E. D.; Bellazzini, R.; Bregeon, J.; Bhat, P. N.; Bissaldi, E.; Bonamente, E.; Bonnell, J.; Brandt, T. J.; Bouvier, A.

2013-01-01

In three years of observations since the beginning of nominal science operations in 2008 August, the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope has observed high-energy (∼> 20 MeV) γ-ray emission from 35 gamma-ray bursts (GRBs). Among these, 28 GRBs have been detected above 100 MeV and 7 GRBs above ∼20 MeV. The first Fermi-LAT catalog of GRBs is a compilation of these detections and provides a systematic study of high-energy emission from GRBs for the first time. To generate the catalog, we examined 733 GRBs detected by the Gamma-Ray Burst Monitor (GBM) on Fermi and processed each of them using the same analysis sequence. Details of the methodology followed by the LAT collaboration for the GRB analysis are provided. We summarize the temporal and spectral properties of the LAT-detected GRBs. We also discuss characteristics of LAT-detected emission such as its delayed onset and longer duration compared with emission detected by the GBM, its power-law temporal decay at late times, and the fact that it is dominated by a power-law spectral component that appears in addition to the usual Band model

FERMI OBSERVATIONS OF HIGH-ENERGY GAMMA-RAY EMISSION FROM GRB 090217A

International Nuclear Information System (INIS)

Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Borgland, A. W.; Bouvier, A.; Baldini, L.; Bellazzini, R.; Bregeon, J.; Brez, A.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Bhat, P. N.; Briggs, M. S.; Bissaldi, E.; Bonamente, E.; Brigida, M.

2010-01-01

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

INTEGRAL Detection of the First Prompt Gamma-Ray Signal Coincident with the Gravitational-wave Event GW170817

DEFF Research Database (Denmark)

Savchenko, V.; Ferrigno, C.; Kuulkers, E.

2017-01-01

We report the INTernational Gamma-ray Astrophysics Laboratory (INTEGRAL) detection of the short gamma-ray burst GRB 170817A (discovered by Fermi-GBM) with a signal-to-noise ratio of 4.6, and, for the first time, its association with the gravitational waves (GWs) from binary neutron star (BNS......) merging event GW170817 detected by the LIGO and Virgo observatories. The significance of association between the gamma-ray burst observed by INTEGRAL and GW170817 is 3.2σ, while the association between the Fermi-GBM and INTEGRAL detections is 4.2σ. GRB 170817A was detected by the SPI-ACS instrument about...

The γ rays sensitivity measurement of CeF3 scintillator detector

International Nuclear Information System (INIS)

Hu Mengchun; Zhou Dianzhong; Li Rurong; Wang Zhentong; Yang Hongqiong; Zhang Jianhua; Hu Qingyuan; Peng Taiping

2003-01-01

The CeF 3 is an abio-scintillator developed in recent years, which are insensitive to neutron and sensitive to gamma rays and respond quickness. The relationship of CeF 3 scintillation detector gamma rays sensitivity with the change of crystal thickness was measured. The CeF 3 scintillation detector is composed by high liner current photomultiplier tube of CHφT3, CHφT5 and CeF 3 scintillator. The detector gamma rays sensitivity of purple photocell and common photocell with CeF 3 scintillator were measured too

The Advanced Gamma-ray Imaging System (AGIS)-Simulation Studies

Science.gov (United States)

Maier, G.; Buckley, J.; Bugaev, V.; Fegan, S.; Funk, S.; Konopelko, A.; Vassiliev, V. V.

2008-12-01

The Advanced Gamma-ray Imaging System (AGIS) is a US-led concept for a next-generation instrument in ground-based very-high-energy gamma-ray astronomy. The most important design requirement for AGIS is a sensitivity of about 10 times greater than current observatories like Veritas, H.E.S.S or MAGIC. We present results of simulation studies of various possible designs for AGIS. The primary characteristics of the array performance, collecting area, angular resolution, background rejection, and sensitivity are discussed.

Gamma-ray identification of nuclear weapon materials

International Nuclear Information System (INIS)

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

1997-01-01

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

Detection of gamma-ray emission from the Vela pulsar wind nebula with AGILE.

Science.gov (United States)

Pellizzoni, A; Trois, A; Tavani, M; Pilia, M; Giuliani, A; Pucella, G; Esposito, P; Sabatini, S; Piano, G; Argan, A; Barbiellini, G; Bulgarelli, A; Burgay, M; Caraveo, P; Cattaneo, P W; Chen, A W; Cocco, V; Contessi, T; Costa, E; D'Ammando, F; Del Monte, E; De Paris, G; Di Cocco, G; Di Persio, G; Donnarumma, I; Evangelista, Y; Feroci, M; Ferrari, A; Fiorini, M; Fuschino, F; Galli, M; Gianotti, F; Hotan, A; Labanti, C; Lapshov, I; Lazzarotto, F; Lipari, P; Longo, F; Marisaldi, M; Mastropietro, M; Mereghetti, S; Moretti, E; Morselli, A; Pacciani, L; Palfreyman, J; Perotti, F; Picozza, P; Pittori, C; Possenti, A; Prest, M; Rapisarda, M; Rappoldi, A; Rossi, E; Rubini, A; Santolamazza, P; Scalise, E; Soffitta, P; Striani, E; Trifoglio, M; Vallazza, E; Vercellone, S; Verrecchia, F; Vittorini, V; Zambra, A; Zanello, D; Giommi, P; Colafrancesco, S; Antonelli, A; Salotti, L; D'Amico, N; Bignami, G F

2010-02-05

Pulsars are known to power winds of relativistic particles that can produce bright nebulae by interacting with the surrounding medium. These pulsar wind nebulae are observed by their radio, optical, and x-ray emissions, and in some cases also at TeV (teraelectron volt) energies, but the lack of information in the gamma-ray band precludes drawing a comprehensive multiwavelength picture of their phenomenology and emission mechanisms. Using data from the AGILE satellite, we detected the Vela pulsar wind nebula in the energy range from 100 MeV to 3 GeV. This result constrains the particle population responsible for the GeV emission and establishes a class of gamma-ray emitters that could account for a fraction of the unidentified galactic gamma-ray sources.

Advances in gamma-ray burst astronomy

International Nuclear Information System (INIS)

Cline, T.L.; Desai, U.D.

1976-01-01

Work at Goddard is presently being carried out in three major areas of gamma-ray burst research: (1) A pair of simultaneously operating 0.8-m 2 burst detectors were successfully balloon-borne at locations 800 miles apart on 9 May, 1975, each to atmospheric depths of 3 to 4 g cm -2 , for a 20-h period of coincident data coverage. This experiment investigates the size spectrum of bursts in the 10 -7 to 10 -6 erg cm -2 size region where dozens of events per day are expected on a -1.5 index integral power-law extrapolation. Considerable separation in latitude was used to avoid possible atmospheric and auroral secondary effects. Its results are not yet available. (2) A deep-space burst detector, the first spacecraft instrument built specifically for gamma-ray burst studies, was recently successfully integrated into the Helios-B space probe. Its use at distances of up to 2 AU will make possible the first high-resolution directional study of gamma-ray burst source locations. Similar modifications to several other space vehicles are also being prepared. (3) The gamma-ray instrument on the IMP-7 satellite is presently the most sensitive burst detector still operating in orbit. Its results have shown that all measured event-average energy spectra are consistent with being alike. Using this characteristic spectrum to select IMP-7 candidate events of smaller size than those detected using other spacecraft in coincidence, a size spectrum is constructed which fits the -1.5 index power law down to 2.5 x 10 -5 erg cm -2 per event, at an occurrence rate of about once per month. (Auth.)

Development of a high sensitivity pinhole type gamma camera using semiconductors for low dose rate fields

Science.gov (United States)

Ueno, Yuichiro; Takahashi, Isao; Ishitsu, Takafumi; Tadokoro, Takahiro; Okada, Koichi; Nagumo, Yasushi; Fujishima, Yasutake; Yoshida, Akira; Umegaki, Kikuo

2018-06-01

We developed a pinhole type gamma camera, using a compact detector module of a pixelated CdTe semiconductor, which has suitable sensitivity and quantitative accuracy for low dose rate fields. In order to improve the sensitivity of the pinhole type semiconductor gamma camera, we adopted three methods: a signal processing method to set the discriminating level lower, a high sensitivity pinhole collimator and a smoothing image filter that improves the efficiency of the source identification. We tested basic performances of the developed gamma camera and carefully examined effects of the three methods. From the sensitivity test, we found that the effective sensitivity was about 21 times higher than that of the gamma camera for high dose rate fields which we had previously developed. We confirmed that the gamma camera had sufficient sensitivity and high quantitative accuracy; for example, a weak hot spot (0.9 μSv/h) around a tree root could be detected within 45 min in a low dose rate field test, and errors of measured dose rates with point sources were less than 7% in a dose rate accuracy test.

GAMMA RAYS FROM STAR FORMATION IN CLUSTERS OF GALAXIES

International Nuclear Information System (INIS)

Storm, Emma M.; Jeltema, Tesla E.; Profumo, Stefano

2012-01-01

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 μm) 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.

High-Z Nanoparticle/Polymer Nanocomposites for Gamma-Ray Scintillation Detectors

Science.gov (United States)

Liu, Chao

An affordable and reliable solution for spectroscopic gamma-ray detection has long been sought after due to the needs from research, defense, and medical applications. Scintillators resolve gamma energy by proportionally converting a single high-energy photon into a number of photomultiplier-tube-detectable low-energy photons, which is considered a more affordable solution for general purposes compared to the delicate semiconductor detectors. An ideal scintillator should simultaneously exhibit the following characteristics: 1) high atomic number (Z) for high gamma stopping power and photoelectron production; 2) high light yield since the energy resolution is inversely proportional to the square root of light yield; 3) short emission decay lifetime; and 4) low cost and scalable production. However, commercial scintillators made from either inorganic single crystals or plastics fail to satisfy all requirements due to their intrinsic material properties and fabrication limitations. The concept of adding high-Z constituents into plastic scintillators to harness high Z, low cost, and fast emission in the resulting nanocomposite scintillators is not new in and of itself. Attempts have been made by adding organometallics, quantum dots, and scintillation nanocrystals into the plastic matrix. High-Z organometallics have long been used to improve the Z of plastic scintillators; however, their strong spin-orbit coupling effect entails careful triplet energy matching using expensive triplet emitters to avoid severe quenching of the light yield. On the other hand, reported quantum dot- and nanocrystal-polymer nanocomposites suffer from moderate Z and high optical loss due to aggregation and self-absorption at loadings higher than 10 wt%, limiting their potential for practical application. This dissertation strives to improve the performance of nanoparticle-based nanocomposite scintillators. One focus is to synthesize transparent nanocomposites with higher loadings of high

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

International Nuclear Information System (INIS)

Baerwald, Philipp

2014-07-01

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

System for Gamma an X rays fluorescence spectrometric

International Nuclear Information System (INIS)

Alonso Abad, D.; Arista Romeu, E.; Bolanos Perez, L. and others

1997-01-01

A system for spectrometry of gamma or fluorescence X rays is presented. It sis composed by a Si(Li) semiconductors detector, a charge sensitive preamplifier, a high voltage power supply, a spectrometric amplifier and a monolithic 1024 channels multichannel analyzers or an IBM compatible 4096 channels add - on- card multichannel analyzer. The system can be configured as a 1024 or 4096 channels gamma or fluorescent X rays spectrometer

AGIS -- the Advanced Gamma-ray Imaging System

Science.gov (United States)

Krennrich, Frank

2009-05-01

The Advanced Gamma-ray Imaging System, AGIS, is envisioned to become the follow-up mission of the current generation of very high energy gamma-ray telescopes, namely, H.E.S.S., MAGIC and VERITAS. These instruments have provided a glimpse of the TeV gamma-ray sky, showing more than 70 sources while their detailed studies constrain a wealth of physics and astrophysics. The particle acceleration, emission and absorption processes in these sources permit the study of extreme physical conditions found in galactic and extragalactic TeV sources. AGIS will dramatically improve the sensitivity and angular resolution of TeV gamma-ray observations and therefore provide unique prospects for particle physics, astrophysics and cosmology. This talk will provide an overview of the science drivers, scientific capabilities and the novel technical approaches that are pursued to maximize the performance of the large array concept of AGIS.

Constraints on the bulk Lorentz factor of gamma-ray bursts with the detection rate by Fermi LAT

Science.gov (United States)

Chen, Ye; Liu, Ruo-Yu; Wang, Xiang-Yu

2018-05-01

The bulk Lorentz factor(Γ) of the outflow is an essential parameter to understanding the physics of gamma-ray burst (GRB). Informations about the Lorentz factors of some individual GRBs have been obtained from the spectral features of the high-energy gamma-ray emissions (>100 MeV), assuming that the spectral breaks or cutoffs are due to the pair-production attenuation (i.e., γγ → e+e-). In this paper, we attempt to interpret the dependence of the LAT detection rate of GRBs on the number of high-energy gamma-rays, taking into account the attenuation effect. We first simulate a long-GRB sample with Monte Carlo method using the luminosity function, rate distribution with redshift and properties of the GRB spectrum. To characterize the distribution of the Lorentz factors, we assume that the Lorentz factors follow the relation Γ =Γ _0E_iso,52k, where Eiso, 52 is the isotropic photon energy in unit of 1052erg. After taking into account the attenuation effect related with the above Lorentz factor distribution, we are able to reproduce the LAT-detected rate of GRBs as the function of the number of gamma-rays for suitable choice of the values of Γ0 and k. The result suggests that the distribution of the bulk Lorentz factor for the majority of GRBs is in the range of 50 - 250.

Performance characteristics of high resolution semiconductor gamma ray spectrometry system

International Nuclear Information System (INIS)

Ko Ko Naing

1994-05-01

A high purity germanium (HPGe) gamma-ray detector has been used in Nuclear Research Laboratory, Department of Physics, Yangon University for over fourteen years. Now it is still being used and it is coupled to new peripheral devices, such as spectroscopy amplifier, analog to digital converter and computer fit-in S-100 multichannel analyser. Therefore, it is necessary to determine the important parameters: energy resolution, detecting efficiency and relative efficiency of the system. In the present work, these parameters were obtained by using mixed calibrated source. The results were compared to the data given by the manufacturer. Moreover, the parameters of another γ-ray detecting system NaI(T1) were also determined. In conclusion the results obtained from the above two measurements were compared and discussed

Systematic search for very-high-energy gamma-ray emission from bow shocks of runaway stars

Science.gov (United States)

H.E.S.S. Collaboration; Abdalla, H.; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Andersson, T.; Angüner, E. O.; Arakawa, M.; Arrieta, M.; Aubert, P.; Backes, M.; Balzer, A.; Barnard, M.; Becherini, Y.; Becker Tjus, J.; Berge, D.; Bernhard, S.; Bernlöhr, K.; Blackwell, R.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Bregeon, J.; Brun, F.; Brun, P.; Bryan, M.; Büchele, M.; Bulik, T.; Capasso, M.; Carr, J.; Casanova, S.; Cerruti, M.; Chakraborty, N.; Chalme-Calvet, R.; Chaves, R. C. G.; Chen, A.; Chevalier, J.; Chrétien, M.; Coffaro, M.; Colafrancesco, S.; Cologna, G.; Condon, B.; Conrad, J.; Cui, Y.; Davids, I. D.; Decock, J.; Degrange, B.; Deil, C.; Devin, J.; deWilt, P.; Dirson, L.; Djannati-Ataï, A.; Domainko, W.; Donath, A.; Drury, L. O.'C.; Dutson, K.; Dyks, J.; Edwards, T.; Egberts, K.; Eger, P.; Ernenwein, J.-P.; Eschbach, S.; Farnier, C.; Fegan, S.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Förster, A.; Funk, S.; Füßling, M.; Gabici, S.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Gottschall, D.; Goyal, A.; Grondin, M.-H.; Hahn, J.; Haupt, M.; Hawkes, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hinton, J. A.; Hofmann, W.; Hoischen, C.; Holler, M.; Horns, D.; Ivascenko, A.; Iwasaki, H.; Jacholkowska, A.; Jamrozy, M.; Janiak, M.; Jankowsky, D.; Jankowsky, F.; Jingo, M.; Jogler, T.; Jouvin, L.; Jung-Richardt, I.; Kastendieck, M. A.; Katarzyński, K.; Katsuragawa, M.; Katz, U.; Kerszberg, D.; Khangulyan, D.; Khélifi, B.; Kieffer, M.; King, J.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Kraus, M.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lau, J.; Lees, J.-P.; Lefaucheur, J.; Lefranc, V.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Leser, E.; Lohse, T.; Lorentz, M.; Liu, R.; López-Coto, R.; Lypova, I.; Marandon, V.; Marcowith, A.; Mariaud, C.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; Meintjes, P. J.; Meyer, M.; Mitchell, A. M. W.; Moderski, R.; Mohamed, M.; Mohrmann, L.; Morå, K.; Moulin, E.; Murach, T.; Nakashima, S.; de Naurois, M.; Niederwanger, F.; Niemiec, J.; Oakes, L.; O'Brien, P.; Odaka, H.; Öttl, S.; Ohm, S.; Ostrowski, M.; Oya, I.; Padovani, M.; Panter, M.; Parsons, R. D.; Pekeur, N. W.; Pelletier, G.; Perennes, C.; Petrucci, P.-O.; Peyaud, B.; Piel, Q.; Pita, S.; Poon, H.; Prokhorov, D.; Prokoph, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Richter, S.; Rieger, F.; Romoli, C.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Saito, S.; Salek, D.; Sanchez, D. A.; Santangelo, A.; Sasaki, M.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwemmer, S.; Seglar-Arroyo, M.; Settimo, M.; Seyffert, A. S.; Shafi, N.; Shilon, I.; Simoni, R.; Sol, H.; Spanier, F.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stycz, K.; Sushch, I.; Takahashi, T.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tibaldo, L.; Tiziani, D.; Tluczykont, M.; Trichard, C.; Tsuji, N.; Tuffs, R.; Uchiyama, Y.; van der Walt, D. J.; van Eldik, C.; van Rensburg, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter, C.; Viana, A.; Vincent, P.; Vink, J.; Voisin, F.; Völk, H. J.; Vuillaume, T.; Wadiasingh, Z.; Wagner, S. J.; Wagner, P.; Wagner, R. M.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zabalza, V.; Zaborov, D.; Zacharias, M.; Zanin, R.; Zdziarski, A. A.; Zech, A.; Zefi, F.; Ziegler, A.; Żywucka, N.

2018-04-01

Context. Runaway stars form bow shocks by ploughing through the interstellar medium at supersonic speeds and are promising sources of non-thermal emission of photons. One of these objects has been found to emit non-thermal radiation in the radio band. This triggered the development of theoretical models predicting non-thermal photons from radio up to very-high-energy (VHE, E ≥ 0.1 TeV) gamma rays. Subsequently, one bow shock was also detected in X-ray observations. However, the data did not allow discrimination between a hot thermal and a non-thermal origin. Further observations of different candidates at X-ray energies showed no evidence for emission at the position of the bow shocks either. A systematic search in the Fermi-LAT energy regime resulted in flux upper limits for 27 candidates listed in the E-BOSS catalogue. Aim. Here we perform the first systematic search for VHE gamma-ray emission from bow shocks of runaway stars. Methods: Using all available archival H.E.S.S. data we search for very-high-energy gamma-ray emission at the positions of bow shock candidates listed in the second E-BOSS catalogue release. Out of the 73 bow shock candidates in this catalogue, 32 have been observed with H.E.S.S. Results: None of the observed 32 bow shock candidates in this population study show significant emission in the H.E.S.S. energy range. Therefore, flux upper limits are calculated in five energy bins and the fraction of the kinetic wind power that is converted into VHE gamma rays is constrained. Conclusions: Emission from stellar bow shocks is not detected in the energy range between 0.14 and 18 TeV.The resulting upper limits constrain the level of VHE gamma-ray emission from these objects down to 0.1-1% of the kinetic wind energy.

TEV GAMMA-RAY OBSERVATIONS OF THE GALACTIC CENTER RIDGE BY VERITAS

Energy Technology Data Exchange (ETDEWEB)

Archer, A.; Buckley, J. H.; Bugaev, V. [Department of Physics, Washington University, St. Louis, MO 63130 (United States); Benbow, W.; Cerruti, M. [Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645 (United States); Bird, R.; Collins-Hughes, E. [School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland); Buchovecky, M. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Byrum, K. [Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439 (United States); Cardenzana, J. V; Eisch, J. D. [Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); Chen, X. [Institute of Physics and Astronomy, University of Potsdam, D-14476 Potsdam-Golm (Germany); Ciupik, L. [Astronomy Department, Adler Planetarium and Astronomy Museum, Chicago, IL 60605 (United States); Connolly, M. P. [School of Physics, National University of Ireland Galway, University Road, Galway (Ireland); Falcone, A. [Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802 (United States); Feng, Q.; Finley, J. P. [Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907 (United States); Fleischhack, H. [DESY, Platanenallee 6, D-15738 Zeuthen (Germany); Flinders, A. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Fortson, L., E-mail: asmith44@umd.edu [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States); and others

2016-04-20

The Galactic Center ridge has been observed extensively in the past by both GeV and TeV gamma-ray instruments revealing a wealth of structure, including a diffuse component and the point sources G0.9+0.1 (a composite supernova remnant) and Sgr A* (believed to be associated with the supermassive black hole located at the center of our Galaxy). Previous very high energy (VHE) gamma-ray observations with the H.E.S.S. experiment have also detected an extended TeV gamma-ray component along the Galactic plane in the >300 GeV gamma-ray regime. Here we report on observations of the Galactic Center ridge from 2010 to 2014 by the VERITAS telescope array in the >2 TeV energy range. From these observations we (1) provide improved measurements of the differential energy spectrum for Sgr A* in the >2 TeV gamma-ray regime, (2) provide a detection in the >2 TeV gamma-ray emission from the composite SNR G0.9+0.1 and an improved determination of its multi-TeV gamma-ray energy spectrum, and (3) report on the detection of VER J1746-289, a localized enhancement of >2 TeV gamma-ray emission along the Galactic plane.

Gamma ray astronomy from satellites and balloons

International Nuclear Information System (INIS)

Schoenfelder, V.

1986-01-01

A survey is given of gamma ray astronomy topics presented at the Cosmic Ray Conference. The major conclusions at the Cosmic Ray Conference in the field of gamma ray astronomy are given. (1) MeV-emission of gamma-ray bursts is a common feature. Variations in duration and energy spectra from burst to burst may explain the discrepancy between the measured log N - log S dependence and the observed isotropy of bursts. (2) The gamma-ray line at 1.809 MeV from Al(26) is the first detected line from a radioactive nucleosynthesis product. In order to understand its origin it will be necessary to measure its longitude distribution in the Milky Way. (3) The indications of a gamma-ray excess found from the direction of Loop I is consistent with the picture that the bulk of cosmic rays below 100 GeV is produced in galactic supernova remnants. (4) The interpretation of the large scale distribution of gamma rays in the Milky Way is controversial. At present an extragalactic origin of the cosmic ray nuclei in the GeV-range cannot be excluded from the gamma ray data. (5) The detection of MeV-emission from Cen A is a promising step towards the interesting field of extragalactic gamma ray astronomy

Gamma-Ray Imager With High Spatial And Spectral Resolution

Science.gov (United States)

Callas, John L.; Varnell, Larry S.; Wheaton, William A.; Mahoney, William A.

1996-01-01

Gamma-ray instrument developed to enable both two-dimensional imaging at relatively high spatial resolution and spectroscopy at fractional-photon-energy resolution of about 10 to the negative 3rd power in photon-energy range from 10 keV to greater than 10 MeV. In its spectroscopic aspect, instrument enables identification of both narrow and weak gamma-ray spectral peaks.

Detecting special nuclear materials in suspect containers using high-energy gamma rays emitted by fission products

Science.gov (United States)

Norman, Eric B [Oakland, CA; Prussin, Stanley G [Kensington, CA

2009-01-27

A method and a system for detecting the presence of special nuclear materials in a suspect container. The system and its method include irradiating the suspect container with a beam of neutrons, so as to induce a thermal fission in a portion of the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the thermal fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

Inverse Compton gamma-rays from galactic dark matter annihilation. Anisotropy signatures

International Nuclear Information System (INIS)

Zhang, Le; Sigl, Guenter; Miniati, Francesco

2010-08-01

High energy electrons and positrons from annihilating dark matter can imprint unique angular anisotropies on the diffuse gamma-ray flux by inverse Compton scattering off the interstellar radiation field. We develop a numerical tool to compute gamma-ray emission from such electrons and positrons diffusing in the smooth host halo and in substructure halos with masses down to 10 -6 M s un. We show that, unlike the total gamma-ray angular power spectrum observed by Fermi-LAT, the angular power spectrum from inverse Compton scattering is exponentially suppressed below an angular scale determined by the diffusion length of electrons and positrons. For TeV scale dark matter with a canonical thermal freeze-out cross section 3 x 10 -26 cm 3 /s, this feature may be detectable by Fermi-LAT in the energy range 100-300 GeV after more sophisticated foreground subtraction. We also find that the total flux and the shape of the angular power spectrum depends sensitively on the spatial distribution of subhalos in the Milky Way. Finally, the contribution from the smooth host halo component to the gamma-ray mean intensity is negligibly small compared to subhalos. (orig.)

Inverse Compton gamma-rays from galactic dark matter annihilation. Anisotropy signatures

Energy Technology Data Exchange (ETDEWEB)

Zhang, Le; Sigl, Guenter [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Miniati, Francesco [ETH Zuerich (Switzerland). Physics Dept.

2010-08-15

High energy electrons and positrons from annihilating dark matter can imprint unique angular anisotropies on the diffuse gamma-ray flux by inverse Compton scattering off the interstellar radiation field. We develop a numerical tool to compute gamma-ray emission from such electrons and positrons diffusing in the smooth host halo and in substructure halos with masses down to 10{sup -6}M{sub s}un. We show that, unlike the total gamma-ray angular power spectrum observed by Fermi-LAT, the angular power spectrum from inverse Compton scattering is exponentially suppressed below an angular scale determined by the diffusion length of electrons and positrons. For TeV scale dark matter with a canonical thermal freeze-out cross section 3 x 10{sup -26} cm{sup 3}/s, this feature may be detectable by Fermi-LAT in the energy range 100-300 GeV after more sophisticated foreground subtraction. We also find that the total flux and the shape of the angular power spectrum depends sensitively on the spatial distribution of subhalos in the Milky Way. Finally, the contribution from the smooth host halo component to the gamma-ray mean intensity is negligibly small compared to subhalos. (orig.)

High energy particles from {gamma}-ray bursts

Energy Technology Data Exchange (ETDEWEB)

Waxman, E [Weizmann Institute of Science, Rehovot (Israel)

2001-11-15

A review is presented of the fireball model of {gamma}-ray bursts (GRBs), and of the production in GRB fireballs of high energy protons and neutrinos. Constraints imposed on the model by recent afterglow observations, which support the association of GRB and ultra-high energy cosmic-ray (UHECR) sources, are discussed. Predictions of the GRB model for UHECR production, which can be tested with planned large area UHECR detectors and with planned high energy neutrino telescopes, are reviewed. (author)

TeV Gamma-Ray Observations of Geminga with HAWC

Science.gov (United States)

Zhou, Hao; HAWC Collaboration

2016-03-01

Geminga is a radio-quiet pulsar that was first detected at GeV energies. Its pulsations were first discovered in X-rays. It is one of the closest middle-aged pulsars at approximately 250 parsecs from Earth. The Geminga pulsar is one of the brightest sources in the GeV sky but there is no unambiguous evidence for the existence of a pulsar wind nebula at GeV energies. Milagro reported an extended TeV source spatially consistent with Geminga, but IACT observations using standard analysis techniques have only provided upper limits. Geminga has been interpreted as a nearby cosmic-ray accelerator, which would possibly explain the observed multi-GeV positron excess. TeV observations of Geminga are crucial to test this interpretation. The High Altitude Water Cherenkov (HAWC) Observatory, located at 4100 m above see level in central Mexico, is sensitive to gamma rays between 100 GeV and 100 TeV. Thanks to its large field of view of 2 steradians, HAWC has a good sensitivity to extended sources. We will present the preliminary results for TeV gamma-ray emission from Geminga from HAWC data. Spectral and morphological analyses are on-going with a growing data set.

Radio Observations of Gamma-ray Novae

Science.gov (United States)

Linford, Justin D.; Chomiuk, L.; Ribeiro, V.; project, E.-Nova

2014-01-01

Recent detection of gamma-ray emission from classical novae by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope surprised many in the astronomical community. We present results from radio observations, obtained using the Karl G. Jansky Very Large Array (VLA), of three gamma-ray novae: Mon2012, Sco2012, and Del2013. Radio observations allow for the calculation of ejecta masses, place limits on the distances, and provide information about the gamma-ray emission mechanism for these sources.

LATTES: a new gamma-ray detector concept for South America

Directory of Open Access Journals (Sweden)

Assis P.

2017-01-01

Full Text Available Currently the detection of Very High Energy gamma-rays for astrophysics rely on the measurement of the Extensive Air Showers (EAS either using Cherenkov detectors or EAS arrays with larger field of views but also larger energy thresholds. In this talk we present a novel hybrid detector concept for a EAS array with an improved sensitivity in the lower energies (~ 100 GeV. We discuss its main features, capabilities and present preliminary results on its expected perfomances and sensitivities.This wide field of view experiment is planned to be installed at high altitude in South America making it a complementary project to the planned Cherenkov telescope experiments and a powerful tool to trigger further observations of variable sources and to detect transients phenomena.

Development of advanced sensing system for antipersonnel mines with neutron capture gamma-ray analysis

International Nuclear Information System (INIS)

Iguchi, Tetsuo

2006-01-01

Neutron induced prompt gamma-ray analysis (NPGA) for survey of antipersonnel landmines is developed. A concept of sensor system with compact strong accelerator neutron source, simulation of detection and simulation results by trial examinations are stated. The measurement principles, objects, system construction, development of compact accelerator neutron source and high performance neutron capture gamma-ray detector, simulation of detection of landmine are reported. It can detect 10.8 MeV gamma-rays and estimate the incident angle of gamma-ray. Schematic layouts of the compact accelerator neutron resource, the compact Compton gamma camera and sensor unit, the estimation principle of incident angle of gamma-ray, experiments and comparison between the experimental results and the estimation results, a preliminary trial experiment system for sensing antipersonnel mines with neutron capture gamma-ray analysis are illustrated. (S.Y.)

The 2HWC HAWC Observatory Gamma-Ray Catalog

Energy Technology Data Exchange (ETDEWEB)

Abeysekara, A. U.; Barber, A. S. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT (United States); Albert, A. [Physics Division, Los Alamos National Laboratory, Los Alamos, NM (United States); Alfaro, R.; Becerril, A.; Belmont-Moreno, E. [Instituto de Física, Universidad Nacional Autónoma de México, Mexico City (Mexico); Alvarez, C.; Arceo, R.; Caballero-Mora, K. S. [Universidad Autónoma de Chiapas, Tuxtla Gutiérrez, Chiapas (Mexico); Álvarez, J. D.; Arteaga-Velázquez, J. C. [Universidad Michoacana de San Nicolás de Hidalgo, Morelia (Mexico); Solares, H. A. Ayala; Brisbois, C. [Department of Physics, Michigan Technological University, Houghton, MI (United States); Baughman, B.; Berley, D. [Department of Physics, University of Maryland, College Park, MD (United States); Bautista-Elivar, N. [Universidad Politecnica de Pachuca, Pachuca, Hidalgo (Mexico); Gonzalez, J. Becerra [NASA Goddard Space Flight Center, Greenbelt, MD (United States); BenZvi, S. Y. [Department of Physics and Astronomy, University of Rochester, Rochester, NY (United States); Bernal, A. [Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico City (Mexico); Braun, J., E-mail: riviere@umdgrb.umd.edu [Department of Physics, University of Wisconsin-Madison, Madison, WI (United States); and others

2017-07-01

We present the first catalog of TeV gamma-ray sources realized with data from the newly completed High Altitude Water Cherenkov Observatory (HAWC). It is the most sensitive wide field-of-view TeV telescope currently in operation, with a one-year survey sensitivity of ∼5%–10% of the flux of the Crab Nebula. With an instantaneous field of view >1.5 sr and >90% duty cycle, it continuously surveys and monitors the sky for gamma-ray energies between hundreds of GeV and tens of TeV. HAWC is located in Mexico, at a latitude of 19° N, and was completed in 2015 March. Here, we present the 2HWC catalog, which is the result of the first source search performed with the complete HAWC detector. Realized with 507 days of data, it represents the most sensitive TeV survey to date for such a large fraction of the sky. A total of 39 sources were detected, with an expected number of false detections of 0.5 due to background fluctuation. Out of these sources, 19 are new sources that are not associated with previously known TeV sources (association criteria: <0.°5 away). The source list, including the position measurement, spectrum measurement, and uncertainties, is reported, then each source is briefly discussed. Of the 2HWC associated sources, 10 are reported in TeVCat as PWN or SNR: 2 as blazars and the remaining eight as unidentified.

Galactic sources of high energy neutrinos: Expectation from gamma-ray data

Directory of Open Access Journals (Sweden)

Sahakyan N.

2016-01-01

Full Text Available The recent results from ground based γ-ray detectors (HESS, MAGIC, VERITAS provide a population of TeV galactic γ-ray sources which are potential sources of High Energy (HE neutrinos. Since the γ-rays and ν-s are produced from decays of neutral and charged pions, the flux of TeV γ-rays can be used to estimate the upper limit of ν flux and vice versa; the detectability of ν flux implies a minimum flux of the accompanying γ-rays (assuming the internal and the external absorption of γ-rays is negligible. Using this minimum flux, it is possible to find the sources which can be detected with cubic-kilometer telescopes. I will discuss the possibility to detect HE neutrinos from powerful galactic accelerators, such as Supernova Remnants (SNRs and Pulsar Wind Nebulae (PWNe and show that likely only RX J1713.7-3946, RX J0852.0-4622 and Vela X can be detected by current generation of instruments (IceCube and Km3Net. It will be shown also, that galactic binary systems could be promising sources of HE ν-s. In particular, ν-s and γ-rays from Cygnus X-3 will be discussed during recent gamma-ray activity, showing that in the future such kind of activities could produce detectable flux of HE ν-s.

What Can Simbol-X Do for Gamma-ray Binaries?

Science.gov (United States)

Cerutti, B.; Dubus, G.; Henri, G.; Hill, A. B.; Szostek, A.

2009-05-01

Gamma-ray binaries have been uncovered as a new class of Galactic objects in the very high energy sky (>100 GeV). The three systems known today have hard X-ray spectra (photon index ~1.5), extended radio emission and a high luminosity in gamma-rays. Recent monitoring campaigns of LSI +61°303 in X-rays have confirmed variability in these systems and revealed a spectral hardening with increasing flux. In a generic one-zone leptonic model, the cooling of relativistic electrons accounts for the main spectral and temporal features observed at high energy. Persistent hard X-ray emission is expected to extend well beyond 10 keV. We explain how Simbol-X will constrain the existing models in connection with Fermi Space Telescope measurements. Because of its unprecedented sensitivity in hard X-rays, Simbol-X will also play a role in the discovery of new gamma-ray binaries, giving new insights into the evolution of compact binaries.

What Can Simbol-X Do for Gamma-ray Binaries?

International Nuclear Information System (INIS)

Cerutti, B.; Dubus, G.; Henri, G.; Hill, A. B.; Szostek, A.

2009-01-01

Gamma-ray binaries have been uncovered as a new class of Galactic objects in the very high energy sky (>100 GeV). The three systems known today have hard X-ray spectra (photon index ∼1.5), extended radio emission and a high luminosity in gamma-rays. Recent monitoring campaigns of LSI +61 deg. 303 in X-rays have confirmed variability in these systems and revealed a spectral hardening with increasing flux. In a generic one-zone leptonic model, the cooling of relativistic electrons accounts for the main spectral and temporal features observed at high energy. Persistent hard X-ray emission is expected to extend well beyond 10 keV. We explain how Simbol-X will constrain the existing models in connection with Fermi Space Telescope measurements. Because of its unprecedented sensitivity in hard X-rays, Simbol-X will also play a role in the discovery of new gamma-ray binaries, giving new insights into the evolution of compact binaries.

High-z Universe with Gamma Ray Bursts

Science.gov (United States)

Kouveliotou, C.

2011-01-01

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

DO THE FERMI GAMMA-RAY BURST MONITOR AND SWIFT BURST ALERT TELESCOPE SEE THE SAME SHORT GAMMA-RAY BURSTS?

International Nuclear Information System (INIS)

Burns, Eric; Briggs, Michael S.; Connaughton, Valerie; Zhang, Bin-Bin; Lien, Amy; Goldstein, Adam; Pelassa, Veronique; Troja, Eleonora

2016-01-01

Compact binary system mergers are expected to generate gravitational radiation detectable by ground-based interferometers. A subset of these, the merger of a neutron star with another neutron star or a black hole, are also the most popular model for the production of short gamma-ray bursts (GRBs). The Swift Burst Alert Telescope (BAT) and the Fermi Gamma-ray Burst Monitor (GBM) trigger on short GRBs (SGRBs) at rates that reflect their relative sky exposures, with the BAT detecting 10 per year compared to about 45 for GBM. We examine the SGRB populations detected by Swift BAT and Fermi GBM. We find that the Swift BAT triggers on weaker SGRBs than Fermi GBM, providing they occur close to the center of the BAT field of view, and that the Fermi GBM SGRB detection threshold remains flatter across its field of view. Overall, these effects combine to give the instruments the same average sensitivity, and account for the SGRBs that trigger one instrument but not the other. We do not find any evidence that the BAT and GBM are detecting significantly different populations of SGRBs. Both instruments can detect untriggered SGRBs using ground searches seeded with time and position. The detection of SGRBs below the on-board triggering sensitivities of Swift BAT and Fermi GBM increases the possibility of detecting and localizing the electromagnetic counterparts of gravitational wave (GW) events seen by the new generation of GW detectors

DO THE FERMI GAMMA-RAY BURST MONITOR AND SWIFT BURST ALERT TELESCOPE SEE THE SAME SHORT GAMMA-RAY BURSTS?

Energy Technology Data Exchange (ETDEWEB)

Burns, Eric; Briggs, Michael S. [University of Alabama in Huntsville, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Connaughton, Valerie [Universities Space Research Association, Science and Technology Institute, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Zhang, Bin-Bin [Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Lien, Amy [Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Goldstein, Adam [NASA Postdoctoral Program, Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Pelassa, Veronique [Smithsonian Astrophysical Observatory, P.O. Box 97, Amado, AZ 85645 (United States); Troja, Eleonora, E-mail: eb0016@uah.edu [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2016-02-20

Compact binary system mergers are expected to generate gravitational radiation detectable by ground-based interferometers. A subset of these, the merger of a neutron star with another neutron star or a black hole, are also the most popular model for the production of short gamma-ray bursts (GRBs). The Swift Burst Alert Telescope (BAT) and the Fermi Gamma-ray Burst Monitor (GBM) trigger on short GRBs (SGRBs) at rates that reflect their relative sky exposures, with the BAT detecting 10 per year compared to about 45 for GBM. We examine the SGRB populations detected by Swift BAT and Fermi GBM. We find that the Swift BAT triggers on weaker SGRBs than Fermi GBM, providing they occur close to the center of the BAT field of view, and that the Fermi GBM SGRB detection threshold remains flatter across its field of view. Overall, these effects combine to give the instruments the same average sensitivity, and account for the SGRBs that trigger one instrument but not the other. We do not find any evidence that the BAT and GBM are detecting significantly different populations of SGRBs. Both instruments can detect untriggered SGRBs using ground searches seeded with time and position. The detection of SGRBs below the on-board triggering sensitivities of Swift BAT and Fermi GBM increases the possibility of detecting and localizing the electromagnetic counterparts of gravitational wave (GW) events seen by the new generation of GW detectors.

Gamma-ray bursts at high redshift

NARCIS (Netherlands)

Wijers, R.A.M.J.

1999-01-01

Gamma-ray bursts are much brighter than supernovae, and could therefore possibly probe the Universe to high redshift. The presently established GRB redshifts range from 0.83 to 5, and quite possibly even beyond that. Since most proposed mechanisms for GRB link them closely to deaths of massive

The beginning of gamma-ray astronomy with Fermi

International Nuclear Information System (INIS)

Paneque, D.

2008-01-01

The Fermi observatory is designed to perform gamma-ray astronomy in the energy range 20 MeV to 300 GeV, with supporting measurements for gamma-ray bursts from 10 keV to 30 MeV. Fermi was successfully launched on June 11 (2008) from the Kennedy Space Center at Cape Canaveral. The main instrument of Fermi is the Large Area Telescope (LAT), which provides break-through high-energy measurements using techniques typically used in particle detectors for collider experiments. The LAT consists of 16 identical towers in a four-by-four grid, each one containing a pair conversion tracker and a hodoscopic crystal calorimeter, all covered by a segmented plastic scintillator anti-coincidence shield. The LAT is currently monitoring the GeV gamma-ray sky with rather uniform exposure (covering 20% of the sky at any instant and the entire sky on a timescale of a few hours) and a sensitivity ∼ 30 times better than its predecessor, EGRET. The large performance improvement of LAT opens a new and important window on a wide variety of high-energy astrophysical phenomena, as well as potential to discover/study non-conventional physics. In the talk I will report the instrument performance, the mission status and science opportunities and will present some results derived from the first months of operation, which includes astronomical telegrams on AGN flares, 2 GCN circulars on LAT-detected GRBs and the monitoring of some selected sources (22 blazars and 1 high mass X-ray Binary). (author)

The X-ray Telescope for the SWIFT Gamma-Ray Burst Mission

International Nuclear Information System (INIS)

Wells, A.; Abbey, A.F.; Beardmore, A.; Mukerjee, K.; Osborne, J.P.; Watson, D.J.; Willingale, R.; Burrows, D. N.; Hill, J. E.; Nousek, J.A.; Miles, B.J.; Mori, K.; Morris, D.C.; Zugger, M.; Chincarini, G.; Campana, S.; Citterio, O.; Moretti, A.; Tagliaferri, G.; Bosworth, J.

2004-01-01

The X-ray Telescope (XRT) for the SWIFT mission, built by the international consortium from Pennsylvania State University (United States), University of Leicester (UK) and Osservatorio Astronomico di Brera (Italy), is already installed on the SWIFT spacecraft. The XRT has two key functions on SWIFT; to determine locations of GRBs to better than 5 arc seconds within 100 seconds of initial detection of a burst and to measure spectra and light curves of the X-ray afterglow over around four orders of magnitude of decay in the afterglow intensity. This paper summarises the XRT performance, operating modes and sensitivity for the detection of prompt and extended X-ray afterglows from gamma-ray bursts. The performance characteristics have been determined from data taken during the ground calibration campaign at MPE's Panter facility in September 2002

Full energy peak efficiency of composite detectors for high energy gamma-rays

International Nuclear Information System (INIS)

Kshetri, Ritesh

2015-01-01

Experiments involving radioactive beams demand high detection efficiencies. One of the ways to obtain high detection efficiency without deteriorating the energy resolution or timing characteristics is the use of composite detectors which are composed of standard HPGe crystals arranged in a compact way. Two simplest composite detectors are the clover and cluster detectors. The TRIUMF-ISAC Gamma-Ray Escape-Suppressed Spectrometer (TIGRESS) comprises of 16 large volume, 32-fold segmented HPGe clover detectors, where each detector is shielded by a 20-fold segmented escape suppression shield (ESS)

SN 1987A gamma-ray line profiles and fluxes

International Nuclear Information System (INIS)

Bussard, R.W.; Burrows, A.; The, L.S.

1989-01-01

Results for the time dependence of the line profiles and integrated fluxes for the 0.847 and 1.238 MeV gamma rays from the decay of cobalt to excited states of iron are presented for several models of the ejectum of SN 1987A. The relatively early detection of these lines has led several workers to propose that some degree of mixing has brought the cobalt closer to the electron-scattering photosphere than standard models predict. Constraints on the amount of mixing from recent observations are discussed using calculations of the energy-integrated line fluxes as a function of time since the explosion. Implications for the line profiles at various times are considered, and it is found that they show strong time dependences and are quite sensitive to the degree of mixing. The two primary effects are Doppler broadening due to the presence of radioactive material at higher velocities and a strong blueshift at early times resulting from optical depth effects. These results have important implications for gamma-ray observations, especially with high-resolution germanium instruments. Finally, the consequences of the fragmentation of the debris for the early emergence of the gamma-ray lines are considered. 32 refs

Gamma-ray Emission from Globular Clusters

Directory of Open Access Journals (Sweden)

Pak-Hin T. Tam

2016-03-01

Full Text Available Over the last few years, the data obtained using the Large Area Telescope (LAT aboard the Fermi Gamma-ray Space Telescope has provided new insights on high-energy processes in globular clusters, particularly those involving compact objects such as MilliSecond Pulsars (MSPs. Gamma-ray emission in the 100 MeV to 10 GeV range has been detected from more than a dozen globular clusters in our galaxy, including 47 Tucanae and Terzan 5. Based on a sample of known gammaray globular clusters, the empirical relations between gamma-ray luminosity and properties of globular clusters such as their stellar encounter rate, metallicity, and possible optical and infrared photon energy densities, have been derived. The measured gamma-ray spectra are generally described by a power law with a cut-off at a few gigaelectronvolts. Together with the detection of pulsed γ-rays from two MSPs in two different globular clusters, such spectral signature lends support to the hypothesis that γ-rays from globular clusters represent collective curvature emission from magnetospheres of MSPs in the clusters. Alternative models, involving Inverse-Compton (IC emission of relativistic electrons that are accelerated close to MSPs or pulsar wind nebula shocks, have also been suggested. Observations at >100 GeV by using Fermi/LAT and atmospheric Cherenkov telescopes such as H.E.S.S.-II, MAGIC-II, VERITAS, and CTA will help to settle some questions unanswered by current data.

High dose gamma-ray standard

International Nuclear Information System (INIS)

Macrin, R.; Moraru, R.

1999-01-01

The high gamma-ray doses produced in a gamma irradiator are used, mainly, for radiation processing, i.e. sterilization of medical products, processing of food, modifications of polymers, irradiation of electronic devices, a.s.o. The used absorbed doses depend on the application and cover the range 10 Gy to 100 MGy. The regulations in our country require that the response of the dosimetry systems, used for the irradiation of food and medical products, be calibrated and traceable to the national standards. In order to be sure that the products receive the desired absorbed dose, appropriate dosimetric measurements must be performed, including the calibration of the dosemeters and their traceability to the national standards. The high dose gamma-ray measurements are predominantly based on the use of reference radiochemical dosemeters. Among them the ferrous sulfate can be used as reference dosemeter for low doses (up to 400 Gy) but due to its characteristics it deserves to be considered a standard dosemeter and to be used for transferring the conventional absorbed dose to other chemical dosemeters used for absorbed doses up to 100 MGy. The study of the ferrous sulfate dosemeter consisted in preparing many batches of solution by different operators in quality assurance conditions and in determining for all batches the linearity, the relative intrinsic error, the repeatability and the reproducibility. The principal results are the following: the linear regression coefficient: 0.999, the relative intrinsic error: max.6 %, the repeatability (for P* = 95 %): max.3 %, the reproducibility (P* = 95%): max.5 %. (authors)

X ray sensitive area detection device

Science.gov (United States)

Carter, Daniel C. (Inventor); Witherow, William K. (Inventor); Pusey, Marc L. (Inventor); Yost, Vaughn H. (Inventor)

1990-01-01

A radiation sensitive area detection device is disclosed which comprises a phosphor-containing film capable of receiving and storing an image formed by a pattern of incoming x rays, UV, or other radiation falling on the film. The device is capable of fluorescing in response to stimulation by a light source in a manner directly proportional to the stored radiation pattern. The device includes: (1) a light source capable of projecting light or other appropriate electromagnetic wave on the film so as to cause it to fluoresce; (2) a means to focus the fluoresced light coming from the phosphor-containing film after light stimulation; and (3) at least one charged coupled detector or other detecting element capable of receiving and digitizing the pattern of fluoresced light coming from the phosphor-containing film. The device will be able to generate superior x ray images of high resolution from a crystal or other sample and will be particularly advantageous in that instantaneous near-real-time images of rapidly deteriorating samples can be obtained. Furthermore, the device can be made compact and sturdy, thus capable of carrying out x ray or other radiation imaging under a variety of conditions, including those experienced in space.

$\\gamma$-Ray Pulsars: Emission Zones and Viewing Geometries

OpenAIRE

Romani, Roger W.; Yadigaroglu, I. -A.

1994-01-01

There are now a half dozen young pulsars detected in high energy photons by the Compton GRO, showing a variety of emission efficiencies and pulse profiles. We present here a calculation of the pattern of high energy emission on the sky in a model which posits $\\gamma$-ray production by charge depleted gaps in the outer magnetosphere. This model accounts for the radio to $\\gamma$-ray pulse offsets of the known pulsars, as well as the shape of the high energy pulse profiles. We also show that $...

Testing and Performance Validation of a Sensitive Gamma Ray Camera Designed for Radiation Detection and Decommissioning Measurements in Nuclear Facilities-13044

International Nuclear Information System (INIS)

Mason, John A.; Looman, Marc R.; Poundall, Adam J.; Towner, Antony C.N.; Creed, Richard; Pancake, Daniel

2013-01-01

This paper describes the measurements, testing and performance validation of a sensitive gamma ray camera designed for radiation detection and quantification in the environment and decommissioning and hold-up measurements in nuclear facilities. The instrument, which is known as RadSearch, combines a sensitive and highly collimated LaBr 3 scintillation detector with an optical (video) camera with controllable zoom and focus and a laser range finder in one detector head. The LaBr 3 detector has a typical energy resolution of between 2.5% and 3% at the 662 keV energy of Cs-137 compared to that of NaI detectors with a resolution of typically 7% to 8% at the same energy. At this energy the tungsten shielding of the detector provides a shielding ratio of greater than 900:1 in the forward direction and 100:1 on the sides and from the rear. The detector head is mounted on a pan/tile mechanism with a range of motion of ±180 degrees (pan) and ±90 degrees (tilt) equivalent to 4 π steradians. The detector head with pan/tilt is normally mounted on a tripod or wheeled cart. It can also be mounted on vehicles or a mobile robot for access to high dose-rate areas and areas with high levels of contamination. Ethernet connects RadSearch to a ruggedized notebook computer from which it is operated and controlled. Power can be supplied either as 24-volts DC from a battery or as 50 volts DC supplied by a small mains (110 or 230 VAC) power supply unit that is co-located with the controlling notebook computer. In this latter case both power and Ethernet are supplied through a single cable that can be up to 80 metres in length. If a local battery supplies power, the unit can be controlled through wireless Ethernet. Both manual operation and automatic scanning of surfaces and objects is available through the software interface on the notebook computer. For each scan element making up a part of an overall scanned area, the unit measures a gamma ray spectrum. Multiple radionuclides may be

Testing and Performance Validation of a Sensitive Gamma Ray Camera Designed for Radiation Detection and Decommissioning Measurements in Nuclear Facilities-13044

Energy Technology Data Exchange (ETDEWEB)

Mason, John A.; Looman, Marc R.; Poundall, Adam J.; Towner, Antony C.N. [ANTECH, A. N. Technology Ltd., Unit 6, Thames Park, Wallingford, Oxfordshire, OX10 9TA (United Kingdom); Creed, Richard; Pancake, Daniel [Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439 (United States)

2013-07-01

This paper describes the measurements, testing and performance validation of a sensitive gamma ray camera designed for radiation detection and quantification in the environment and decommissioning and hold-up measurements in nuclear facilities. The instrument, which is known as RadSearch, combines a sensitive and highly collimated LaBr{sub 3} scintillation detector with an optical (video) camera with controllable zoom and focus and a laser range finder in one detector head. The LaBr{sub 3} detector has a typical energy resolution of between 2.5% and 3% at the 662 keV energy of Cs-137 compared to that of NaI detectors with a resolution of typically 7% to 8% at the same energy. At this energy the tungsten shielding of the detector provides a shielding ratio of greater than 900:1 in the forward direction and 100:1 on the sides and from the rear. The detector head is mounted on a pan/tile mechanism with a range of motion of ±180 degrees (pan) and ±90 degrees (tilt) equivalent to 4 π steradians. The detector head with pan/tilt is normally mounted on a tripod or wheeled cart. It can also be mounted on vehicles or a mobile robot for access to high dose-rate areas and areas with high levels of contamination. Ethernet connects RadSearch to a ruggedized notebook computer from which it is operated and controlled. Power can be supplied either as 24-volts DC from a battery or as 50 volts DC supplied by a small mains (110 or 230 VAC) power supply unit that is co-located with the controlling notebook computer. In this latter case both power and Ethernet are supplied through a single cable that can be up to 80 metres in length. If a local battery supplies power, the unit can be controlled through wireless Ethernet. Both manual operation and automatic scanning of surfaces and objects is available through the software interface on the notebook computer. For each scan element making up a part of an overall scanned area, the unit measures a gamma ray spectrum. Multiple

Gamma-ray emission from internal shocks in novae

Science.gov (United States)

Martin, P.; Dubus, G.; Jean, P.; Tatischeff, V.; Dosne, C.

2018-04-01

Context. Gamma-ray emission at energies ≥100 MeV has been detected from nine novae using the Fermi Large Area Telescope (LAT), and can be explained by particle acceleration at shocks in these systems. Eight out of these nine objects are classical novae in which interaction of the ejecta with a tenuous circumbinary material is not expected to generate detectable gamma-ray emission. Aim. We examine whether particle acceleration at internal shocks can account for the gamma-ray emission from these novae. The shocks result from the interaction of a fast wind radiatively-driven by nuclear burning on the white dwarf with material ejected in the initial runaway stage of the nova outburst. Methods: We present a one-dimensional model for the dynamics of a forward and reverse shock system in a nova ejecta, and for the associated time-dependent particle acceleration and high-energy gamma-ray emission. Non-thermal proton and electron spectra are calculated by solving a time-dependent transport equation for particle injection, acceleration, losses, and escape from the shock region. The predicted emission is compared to LAT observations of V407 Cyg, V1324 Sco, V959 Mon, V339 Del, V1369 Cen, and V5668 Sgr. Results: The ≥100 MeV gamma-ray emission arises predominantly from particles accelerated up to 100 GeV at the reverse shock and undergoing hadronic interactions in the dense cooling layer downstream of the shock. The emission rises within days after the onset of the wind, quickly reaches a maximum, and its subsequent decrease reflects mostly the time evolution of the wind properties. Comparison to gamma-ray data points to a typical scenario where an ejecta of mass 10-5-10-4 M⊙ expands in a homologous way with a maximum velocity of 1000-2000 km s-1, followed within a day by a wind with a velocity values of which result in the majority of best-fit models having gamma-ray spectra with a high-energy turnover below 10 GeV. Our typical model is able to account for the main

Gamma-Ray Bursts: 4th Huntsville Symposium. Proceedings

International Nuclear Information System (INIS)

Meegan, C.A.; Preece, R.D.; Koshut, T.M.

1998-01-01

These proceedings represent papers presented at the Fourth Huntsville Gamma-Ray Bursts Symposium held in September, 1997 in Huntsville, Alabama, USA. This conference occurred at a crucial time in the history of the gamma-ray burst research. In early 1997, 30 years after the detection of the first gamma-ray burst by the Vela satellites, counterparts to bursts were finally detected at optical and radio wavelengths. The symposium attracted about 200 scientists from 16 countries. Some of the topics discussed include gamma-ray burst spectra, x-ray observations, optical observations, radio observations, host galaxies, shocks and afterglows and models of gamma-ray bursts. There were 183 papers presented, out of these, 16 have been abstracted for the Energy Science and Technology database

Annihilation vs. decay: constraining dark matter properties from a gamma-ray detection

International Nuclear Information System (INIS)

Palomares-Ruiz, Sergio; Siegal-Gaskins, Jennifer M.

2010-01-01

Most proposed dark matter candidates are stable and are produced thermally in the early Universe. However, there is also the possibility of unstable (but long-lived) dark matter, produced thermally or otherwise. We propose a strategy to distinguish between dark matter annihilation and/or decay in the case that a clear signal is detected in gamma-ray observations of Milky Way dwarf spheroidal galaxies with gamma-ray experiments. The sole measurement of the energy spectrum of an indirect signal would render the discrimination between these cases impossible. We show that by examining the dependence of the intensity and energy spectrum on the angular distribution of the emission, the origin could be identified as decay, annihilation, or both. In addition, once the type of signal is established, we show how these measurements could help to extract information about the dark matter properties, including mass, annihilation cross section, lifetime, dominant annihilation and decay channels, and the presence of substructure. Although an application of the approach presented here would likely be feasible with current experiments only for very optimistic dark matter scenarios, the improved sensitivity of upcoming experiments could enable this technique to be used to study a wider range of dark matter models

Annihilation vs. decay: constraining dark matter properties from a gamma-ray detection

Energy Technology Data Exchange (ETDEWEB)

Palomares-Ruiz, Sergio [Centro de Física Teórica de Partículas, Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal); Siegal-Gaskins, Jennifer M., E-mail: sergio.palomares.ruiz@ist.utl.pt, E-mail: jsg@mps.ohio-state.edu [Center for Cosmology and AstroParticle Physics, The Ohio State University, 191 W. Woodruff Ave., Columbus OH 43210 (United States)

2010-07-01

Most proposed dark matter candidates are stable and are produced thermally in the early Universe. However, there is also the possibility of unstable (but long-lived) dark matter, produced thermally or otherwise. We propose a strategy to distinguish between dark matter annihilation and/or decay in the case that a clear signal is detected in gamma-ray observations of Milky Way dwarf spheroidal galaxies with gamma-ray experiments. The sole measurement of the energy spectrum of an indirect signal would render the discrimination between these cases impossible. We show that by examining the dependence of the intensity and energy spectrum on the angular distribution of the emission, the origin could be identified as decay, annihilation, or both. In addition, once the type of signal is established, we show how these measurements could help to extract information about the dark matter properties, including mass, annihilation cross section, lifetime, dominant annihilation and decay channels, and the presence of substructure. Although an application of the approach presented here would likely be feasible with current experiments only for very optimistic dark matter scenarios, the improved sensitivity of upcoming experiments could enable this technique to be used to study a wider range of dark matter models.

DAMPE: A gamma and cosmic ray observatory in space

Science.gov (United States)

D'Urso, D.; Dampe Collaboration

2017-05-01

DAMPE (DArk Matter Particle Explorer) is one of the five satellite missions in the framework of the Strategic Pioneer Research Program in Space Science of the Chinese Academy of Sciences (CAS). Launched on December 17th 2015 at 08:12 Beijing time, it is taking data into a sun-synchronous orbit, at the altitude of 500km. The main scientific objective of DAMPE is to detect electrons and photons in the range 5GeV-10TeV with unprecedented energy resolution, in order to identify possible Dark Matter signatures. It will also measure the flux of nuclei up to 100TeV with excellent energy resolution. The satellite is equipped with a powerful space telescope for high energy gamma-ray, electron and cosmic rays detection. It consists of a plastic scintillator strips detector (PSD) that serves as anti-coincidence detector, a silicon-tungsten tracker (STK), a BGO imaging calorimeter of about 32 radiation lengths, and a neutron detector. With its excellent photon detection capability and its detector performances (at 100GeV energy resolution ˜1% , angular resolution ˜0.1° , the DAMPE mission is well placed to make strong contributions to high-energy gamma-ray observations: it covers the gap between space and ground observation; it will allow to detect a line signature in the gamma-ray spectrum, if present, in the sub-TeV to TeV region; it will allow a high precision gamma-ray astronomy. A report on the mission goals and status will be discussed, together with in-orbit first data coming from space.

Use of gamma-rays sensitivity for discrimination of upland cultivars of groups Indican and Japonica

International Nuclear Information System (INIS)

Rodrigues, Luis Roberto Franco

2003-01-01

Sixty-five upland rice cultivars (Oryza sativa L.) were evaluated in relation to gamma-ray sensitivity. Seeds were subjected to seven doses of gamma-radiation and sown in wooden boxes in randomised complete block design with three replications. The experiment was conducted in greenhouse during the year of 1992. Physiological effects caused by radiation in the M 1 generation, were evaluated. The results showed that the sensitivity to the radiation at doses 300 and 360 Gy was useful for distinguishing Indican and Japonica groups. (author)

Continued Development of a Soft Gamma-Ray Concentrator

Science.gov (United States)

Bloser, Peter

We propose to continue our development of a concept for a soft gamma-ray (E > 100 keV) concentrator using thin-film multilayer structures. Alternating layers of low- and high-density materials will channel soft gamma-ray photons via total external reflection. A suitable arrangement of bent structures will then concentrate the incident radiation to a point. Gamma-ray optics made in this way offer the potential for soft gamma-ray telescopes with focal lengths of less than 10 m, removing the need for formation flying spacecraft and opening the field up to balloon-borne instruments. Under previous APRA funding we have been investigating methods for efficiently producing such multilayer structures and modeling their performance. We now propose to pursue magnetron sputtering (MS) techniques to quickly produce structures with the required smoothness and thickness, to measure their channeling efficiency and compare with calculations, and to design a "lens" with optimized bandpass and throughput and predict its scientific performance. If successful, this work will confirm that this innovative optics concept is suitable for a balloon-born soft gamma-ray telescope with unprecedented sensitivity.

Gamma detection: an unusual application for surface barrier detectors

Energy Technology Data Exchange (ETDEWEB)

Fichtenbaum de Iacub, S; Matatagui, E

1983-02-01

The silicon surface barrier detectors (SBD), may be ideal devices to be used in dose indicators for the monitoring of gamma radiations; the SBD working as a cavity sensor. The measurement consists in counting the number of pulses that exceeds a certain level of discrimination, this number being proportional to the absorbed dose. The spectral distribution of the pulses gives an idea of the existing photon field's energy. Characteristic spectra obtained with different gamma and X-ray sources are described and analyzed, and tests are carried out by using different sensitive volumes of the detector in order to determine significant parameters for a gamma-monitor system. The results from the measurements indicate: a) high sensitivity of the system with SBD (high density of material); b) low background: enviromental backgrounds are reliably registered (approx. 10 R/h); c) minimum detectable energies of the order of 60 keV; d) possibility to determine high exposure rates (approx. 100 R/h); e) for emitters of low Z, the result is approximately independent from the gamma energy. These results suggest the possibility of constructing fixed and portable systems, appropriate for gamma monitoring, which utilize SBD as sensors; these devices are adequate for working at enviroment temperatures, being compact, reliable, with low polarization voltages, and of relatively low cost.

Radio Flares from Gamma-ray Bursts

Science.gov (United States)

Kopač, 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.

RADIO FLARES FROM GAMMA-RAY BURSTS

International Nuclear Information System (INIS)

Kopač, D.; Mundell, C. G.; Kobayashi, S.; Virgili, F. J.; Harrison, R.; Japelj, J.; Gomboc, A.; Guidorzi, C.; Melandri, A.

2015-01-01

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

BiI₃ Crystals for High Energy Resolution Gamma-Ray Spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Nino, Juan C. [Univ. of Florida, Gainesville, FL (United States); Baciak, James [Univ. of Florida, Gainesville, FL (United States); Johns, Paul [Univ. of Florida, Gainesville, FL (United States); Sulekar, Soumitra [Univ. of Florida, Gainesville, FL (United States); Totten, James [Univ. of Florida, Gainesville, FL (United States); Nimmagadda, Jyothir [Univ. of Florida, Gainesville, FL (United States)

2017-04-12

BiI₃ had been investigated for its unique properties as a layered compound semiconductor for many decades. However, despite the exceptional atomic, physical, and electronic properties of this material, good resolution gamma ray spectra had never been reported for BiI₃. The shortcomings that previously prevented BiI₃ from reaching success as a gamma ray sensor were, through this project, identified and suppressed to unlock the performance of this promising compound. Included in this work were studies on a number of methods which have, for the first time, enabled BiI₃ to exhibit spectral performance rivaling many other candidate semiconductors for room temperature gamma ray sensors. New approaches to crystal growth were explored that allow BiI₃ spectrometers to be fabricated with up to 2.2% spectral resolution at 662 keV. Fundamental studies on trap states, dopant incorporation, and polarization were performed to enhance performance of this compound. Additionally, advanced detection techniques were applied to display the capabilities of high quality BiI₃ spectrometers. Overall, through this work, BiI₃ has been revealed as a potentially transformative material for nuclear security and radiation detection sciences.

SEARCH FOR GAMMA-RAYS FROM THE UNUSUALLY BRIGHT GRB 130427A WITH THE HAWC GAMMA-RAY OBSERVATORY

Energy Technology Data Exchange (ETDEWEB)

Abeysekara, A. U. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI (United States); Alfaro, R. [Instituto de Física, Universidad Nacional Autónoma de México, México D. F. (Mexico); Alvarez, C.; Arceo, R. [CEFyMAP, Universidad Autónoma de Chiapas, Tuxtla Gutiérrez, Chiapas (Mexico); Álvarez, J. D.; Arteaga-Velázquez, J. C.; Cotti, U.; De León, C. [Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán (Mexico); Solares, H. A. Ayala [Department of Physics, Michigan Technological University, Houghton, MI (United States); Barber, A. S. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT (United States); Baughman, B. M.; Braun, J. [Department of Physics, University of Maryland, College Park, MD (United States); Bautista-Elivar, N. [Universidad Politécnica de Pachuca, Municipio de Zempoala, Hidalgo (Mexico); BenZvi, S. Y. [Department of Physics and Astronomy, University of Rochester, Rochester, NY (United States); Rosales, M. Bonilla; Carramiñana, A. [Instituto Nacional de Astrofísica, Óptica y Electrónica, Tonantzintla, Puebla (Mexico); Caballero-Mora, K. S. [Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, México D. F. (Mexico); Castillo, M.; Cotzomi, J. [Facultad de Ciencias Físico Matemáticas, Benemérita Universidad Autónoma de Puebla, Ciudad Universitaria, Puebla (Mexico); De la Fuente, E., E-mail: dirk.lennarz@gatech.edu [Departamento de Física, Centro Universitario de Ciencias Exactas e Ingenierías, Universidad de Guadalajara, Guadalajara (Mexico); Collaboration: HAWC collaboration; and others

2015-02-20

The first limits on the prompt emission from the long gamma-ray burst (GRB) 130427A in the >100 GeV energy band are reported. GRB 130427A was the most powerful burst ever detected with a redshift z ≲ 0.5 and featured the longest lasting emission above 100 MeV. The energy spectrum extends at least up to 95 GeV, clearly in the range observable by the High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory, a new extensive air shower detector currently under construction in central Mexico. The burst occurred under unfavorable observation conditions, low in the sky and when HAWC was running 10% of the final detector. Based on the observed light curve at MeV-GeV energies, eight different time periods have been searched for prompt and delayed emission from this GRB. In all cases, no statistically significant excess of counts has been found and upper limits have been placed. It is shown that a similar GRB close to zenith would be easily detected by the full HAWC detector, which will be completed soon. The detection rate of the full HAWC detector may be as high as one to two GRBs per year. A detection could provide important information regarding the high energy processes at work and the observation of a possible cut-off beyond the Fermi Large Area Telescope energy range could be the signature of gamma-ray absorption, either in the GRB or along the line of sight due to the extragalactic background light.

DEVELOPMENT OF DEPOSIT DETECTION SYSTEM IN PIPELINES OF THE STEELWORKS USING CS-137 GAMMA-RAY

International Nuclear Information System (INIS)

Song, Won-Joon; Lee, Seung-Hee; Jeong, Hee-Dong

2008-01-01

The deposit is built up in the pipeline of the steelworks by the chemical reaction among COG (coke oven gas), BFG (blast furnace gas), moisture, and steel in the high temperature environment and obstructs the smooth gas flow. In this study a gamma-ray system is developed to detect the deposit accumulated in pipelines and calculate the accumulation rate with respect to the cross section area of pipes. Cs-137 is used as the gamma-ray source and the system is designed to apply to pipes of various diameters. This system also includes the DB for storage and display of the measurement results so that it can be used for the efficient management of the pipelines

Very high-frequency gravitational waves from magnetars and gamma-ray bursts

Science.gov (United States)

Wen, Hao; Li, Fang-Yu; Li, Jin; Fang, Zhen-Yun; Beckwith, Andrew

2017-12-01

Extremely powerful astrophysical electromagnetic (EM) systems could be possible sources of high-frequency gravitational waves (HFGWs). Here, based on properties of magnetars and gamma-ray bursts (GRBs), we address “Gamma-HFGWs” (with very high-frequency around 1020 Hz) caused by ultra-strong EM radiation (in the radiation-dominated phase of GRB fireballs) interacting with super-high magnetar surface magnetic fields (˜1011 T). By certain parameters of distance and power, the Gamma-HFGWs would have far field energy density Ω gw around 10-6, and they would cause perturbed signal EM waves of ˜10-20 W/m2 in a proposed HFGW detection system based on the EM response to GWs. Specially, Gamma-HFGWs would possess distinctive envelopes with characteristic shapes depending on the particular structures of surface magnetic fields of magnetars, which could be exclusive features helpful to distinguish them from background noise. Results obtained suggest that magnetars could be involved in possible astrophysical EM sources of GWs in the very high-frequency band, and Gamma-HFGWs could be potential targets for observations in the future. Supported by National Natural Science Foundation of China (11605015, 11375279, 11205254, 11647307) and the Fundamental Research Funds for the Central Universities (106112017CDJXY300003, 106112017CDJXFLX0014)

Prompt gamma-ray activation analysis (PGAA)

International Nuclear Information System (INIS)

Kern, J.

1996-01-01

The paper deals with a brief description of the principles of prompt gamma-ray activation analysis (PGAA), with the detection of gamma-rays, the PGAA project at SINQ and with the expected performances. 8 figs., 3 tabs., 10 refs

Prompt gamma-ray activation analysis (PGAA)

Energy Technology Data Exchange (ETDEWEB)

Kern, J [Fribourg Univ. (Switzerland). Inst. de Physique

1996-11-01

The paper deals with a brief description of the principles of prompt gamma-ray activation analysis (PGAA), with the detection of gamma-rays, the PGAA project at SINQ and with the expected performances. 8 figs., 3 tabs., 10 refs.

Constraining Gamma-Ray Pulsar Gap Models with a Simulated Pulsar Population

Science.gov (United States)

Pierbattista, Marco; Grenier, I. A.; Harding, A. K.; Gonthier, P. L.

2012-01-01

With the large sample of young gamma-ray pulsars discovered by the Fermi Large Area Telescope (LAT), population synthesis has become a powerful tool for comparing their collective properties with model predictions. We synthesised a pulsar population based on a radio emission model and four gamma-ray gap models (Polar Cap, Slot Gap, Outer Gap, and One Pole Caustic). Applying gamma-ray and radio visibility criteria, we normalise the simulation to the number of detected radio pulsars by a select group of ten radio surveys. The luminosity and the wide beams from the outer gaps can easily account for the number of Fermi detections in 2 years of observations. The wide slot-gap beam requires an increase by a factor of 10 of the predicted luminosity to produce a reasonable number of gamma-ray pulsars. Such large increases in the luminosity may be accommodated by implementing offset polar caps. The narrow polar-cap beams contribute at most only a handful of LAT pulsars. Using standard distributions in birth location and pulsar spin-down power (E), we skew the initial magnetic field and period distributions in a an attempt to account for the high E Fermi pulsars. While we compromise the agreement between simulated and detected distributions of radio pulsars, the simulations fail to reproduce the LAT findings: all models under-predict the number of LAT pulsars with high E , and they cannot explain the high probability of detecting both the radio and gamma-ray beams at high E. The beaming factor remains close to 1.0 over 4 decades in E evolution for the slot gap whereas it significantly decreases with increasing age for the outer gaps. The evolution of the enhanced slot-gap luminosity with E is compatible with the large dispersion of gamma-ray luminosity seen in the LAT data. The stronger evolution predicted for the outer gap, which is linked to the polar cap heating by the return current, is apparently not supported by the LAT data. The LAT sample of gamma-ray pulsars

Extra-light gamma-ray imager for safeguards and homeland security

Energy Technology Data Exchange (ETDEWEB)

Ivanov, Oleg P.; Semin, Ilya A.; Potapov, Victor N.; Stepanov, Vyacheslav E. [National Research Centre Kurchatov Institute, Moscow, 123182, (Russian Federation)

2015-07-01

Gamma-ray imaging is the most important way to identify unknown gamma-ray emitting objects in decommissioning, security, overcoming accidents. Over the past two decades a system for producing of gamma images in these conditions became more or less portable devices. But in recent years these systems have become the hand-held devices. This is very important, especially in emergency situations, and measurements for safety reasons. We describe the first integrated hand-held instrument for emergency and security applications. The device is based on the coded aperture image formation, position sensitive gamma-ray (X-ray) detector Medipix2 (detectors produces by X-ray Imaging Europe) and tablet computer. The development was aimed at creating a very low weight system with high angular resolution. We present some sample gamma-ray images by camera. Main estimated parameters of the system are the following. The field of view video channel ∼ 490 deg. The field of view gamma channel ∼ 300 deg. The sensitivity of the system with a hexagonal mask for the source of Cs-137 (Eg = 662 keV), is in units of dose D ∼ 100 mR. This option is less then order of magnitude worse than for the heavy, non-hand-held systems (e.g., gamma-camera Cartogam, by Canberra.) The angular resolution of the gamma channel for the sources of Cs-137 (Eg = 662 keV) is about 1.20 deg. (authors)

Natural background gamma-ray spectrum. List of gamma-rays ordered in energy from natural radionuclides

Energy Technology Data Exchange (ETDEWEB)

Ichimiya, Tsutomu [Japan Radioisotope Association, Tokyo (Japan); Narita, Tsutomu; Kitao, Kensuke

1998-03-01

A quick index to {gamma}-rays and X-rays from natural radionuclides is presented. In the list, {gamma}-rays are arranged in order of increasing energy. The list also contains {gamma}-rays from radioactive nuclides produced in a germanium detector and its surrounding materials by interaction with cosmic neutrons, as well as direct {gamma}-rays from interaction with the neutrons. Artificial radioactive nuclides emitting {gamma}-rays with same or near energy value as that of the natural {gamma}-rays and X-rays are also listed. In appendix, {gamma}-ray spectra from a rock, uranium ore, thorium, monazite and uraninite and also background spectra obtained with germanium detectors placed in iron or lead shield have been given. The list is designed for use in {gamma}-ray spectroscopy under the conditions of highly natural background, such as in-situ environmental radiation monitoring or low-level activity measurements, with a germanium detector. (author)

Scanning of Cargo Containers by Gamma-Ray and Fast Neutron Radiography

International Nuclear Information System (INIS)

Yousri, A.M.; Bashter, I.I.; Megahid, M.R.; Osman, A.M.; Kansouh, W.A.; Reda, A.M.

2011-01-01

This paper describes the combined systems which were installed and tested to detect contraband smuggled in cargo containers. These combined systems are based on radiographers work by gamma-rays emitted from point source 60 Co with 0.5 Ci activity and neutrons emitted from point isotopic sources of Pu-α-Be as well as 14 MeV neutrons emitted from sealed tube neutron generator. The transmitted gamma ray through the inspected object was measured by gamma detection system with NaI(Tl) detector while the transmitted fast neutron beam was measured by a neutron gamma detection system with stilbene organic scintillator. The later possess the capability of discrimination between between gamma and neutron pulses using a discrimination system based on pulse shape discrimination method. The measured intensities of primary incident and transmitted beams of gamma-rays and fast neutrons were used to construct 2D cross-sectional images of the inspected objects hidden directly within benign materials of the container and for object screened by high dense material to stop object detection by gamma or X-rays. The constructed images for the inspected objects show the good capability and effectiveness of the installed gamma and neutron radiographers to detect illicit materials hidden in air cargo containers and sea containers of med size. They have also indicated that the developed scanning systems possess the ease of mobility and low cost of scanning

Multi-dimensional analysis of high resolution {gamma}-ray data

Energy Technology Data Exchange (ETDEWEB)

Flibotte, S.; Huettmeier, U.J.; France, G. de; Haas, B.; Romain, P.; Theisen, Ch.; Vivien, J.P.; Zen, J. [Strasbourg-1 Univ., 67 (France). Centre de Recherches Nucleaires

1992-12-31

A new generation of high resolution {gamma}-ray spectrometers capable of recording high-fold coincidence events with a large efficiency will soon be available. Algorithms are developed to analyze high-fold {gamma}-ray coincidences. As a contribution to the software development associated with the EUROGAM spectrometer, the performances of computer codes designed to select multi-dimensional gates from 3-, 4- and 5-fold coincidence databases were tested. The tests were performed on events generated with a Monte Carlo simulation and also on real experimental triple data recorded with the 8{pi} spectrometer and with a preliminary version of the EUROGAM array. (R.P.) 14 refs.; 3 figs.; 3 tabs.

Observational techniques of gamma rays astronomy in low energy

International Nuclear Information System (INIS)

Costa, J.M. da.

1982-02-01

Due to the absorption of great part of the gamma-ray spectrum of cosmic origin, by the earth's atmosphere at heights above 20Km, gamma-ray astronomy achieved its full development only after the advent of the space age. Ballons and satellites are the space vehicles which have been used to transport gamma-ray telescopes to observational heights in the atmosphere, or out of it. The results of these experiments can determine the sources, the energy spectra and the intensities of the cosmic gamma-rays, and provide other important information of astrophysical interest. The detection of gamma-rays of cosmic origin is very difficult. The observational techniques used in gamma-ray astronomy are dependent on the energy range of the gamma-rays which one desires to detect. The most common telescopes of low energy gamma-ray astronomy (50KeV - 20MeV) use NaI(Tl) scintillators, or germanium diodes, as principal detectors, surrounded by an active shield (anticoincidence) of organic or inorganic scintillators. (Author) [pt

Numerical simulations on efficiency and measurement of capabilities of BGO detectors for high energy gamma ray

CERN Document Server

Wen Wan Xin

2002-01-01

The energy resolution and time resolution of two phi 75 x 100 BGO detectors for high energy gamma ray newly made were measured with sup 1 sup 3 sup 7 Cs and sup 6 sup 0 Co resources. The two characteristic gamma rays of high energy emitted from the thermal neutron capture of germanium in BGO crystal were used for the energy calibration of gamma spectra. The intrinsic photopeak efficiency, single escape probability and double escape probabilities of BGO detectors in photon energy range of 4-30 MeV are numerically calculated with GEANT code. The real count response and count ratio of the uniformly distributed incident photons in energy range of 0-30 MeV are also calculated. The distortion of gamma spectra caused by the photon energy loss extension to lower energy in detection medium is discussed

Highlights of GeV Gamma-Ray Astronomy

Science.gov (United States)

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.

In-flight observation of long duration gamma-ray glows by aircraft

Science.gov (United States)

Kochkin, Pavlo; (Lex) van Deursen, A. P. J.; de Boer, Alte; Bardet, Michiel; Allasia, Cedric; Boissin, Jean Francois; Ostgaard, Nikolai

2017-04-01

The Gamma-Ray Glow is a long-lasting (several seconds to minutes) X- and gamma radiation presumably originated from high-electric field of thunderclouds. Such glows were previously observed by aircraft, balloons, and from the ground. When detected on ground with other particles, i.e. electrons and neutrons, they are usually called Thunderstorm Ground Enhancements (TGEs). Their measured spectra are often consistent with Relativistic Runaway Electron Avalanche (RREA) mechanism. That is why RREA is a commonly accepted explanation for their existence. The gamma-ray glows are observed to be interrupted by lightning discharge, which terminates the high-electric field region. In January 2016 an Airbus A340 factory test aircraft was performing intentional flights through thunderstorms over Northern Australia. The aircraft was equipped with a dedicated in-flight lightning detection system called ILDAS (http://ildas.nlr.nl). The system also contained two scintillation detectors each with 38x38 mm cylinder LaBr3 crystals. While being at 12 km altitude the system detected a gamma-ray flux enhancement 30 times the background counts. It lasted for 20 seconds and was abruptly terminated by a lightning flash. The flash hit the aircraft and its parameters were recorded with 10 ns sampling time including gamma radiation. Ground-based lightning detection network WWLLN detected 4 strikes in the nearby region, all in association with the same flash. The ILDAS system recorded the time-resolved spectrum of the glow. In 6 minutes, after making a U-turn, the aircraft passed the same glow region. Smaller gamma-ray enhancement was again detected. In this presentation we will show the mapped event timeline including airplane, gamma-ray glow, WWLLN, and cloud data. We will discuss the glow's properties, i.e. intensity and differential spectrum, and its possible origin. This result will also be compared to previously reported observations.

Effect of gamma rays on M1 generation in basmati rice

International Nuclear Information System (INIS)

Ashraf, M.; Cheema, A.A.; Rashid, M.; Zia-ul-Qamar

2003-01-01

To estimate the sensitivity to gamma rays in Basmati rice, five varieties namely Basmati 370, Basmati Pak, Basmati 385, Super Basmati and Basmati 2000were exposed to different doses of gamma rays ranging 150- 350 Gy with an increment of 50 Gy among the doses. Plant growth parameters such as seedling shoot and root lengths were measured in the laboratory. Highly significant differences were observed among the varieties for seedling shoot and root lengths. Radiations showed highly significant negative correlations with seedling shoot length (-0.998), seedling root length (-0.941) showing dose dependent responses. Highly significant negative correlations with panicle fertility (-0.941) and grain yield (-0.971), and significant negative correlation for seedling emergence (-0.941) showed detrimental dose dependent responses.Seedling emergence, panicle fertility and grain yield declined with increasing dose level in all the varieties. The dose at which panicle fertility halved was 260.37 Gy. Basmati 2000 was observed to be the most sensitive followed by Basmati 370, Super Basmati and Basmati Pak, but Basmati 385 was found to be the least sensitive variety to gamma rays

Research on self-powered detectors for gamma-ray monitoring

International Nuclear Information System (INIS)

Cho, S.W.; Lee, Y.J.

1984-01-01

Self-powered neutron detectors are used extensively in power reactors both for flux mapping and for power control and over-power protection, because of their small size, ruggedness and simplicity. But they have a few disadvantages such as high burn-up rate and background signal produced by the gamma-rays from the reactor itself. In order to overcome these disadvantages and to achieve a better understanding of gamma-ray effects of self-power detectors, a new type of self-powered detectors was designed and fabricated by the author,and experiments have carried out in the 10kCi sup(60)Co gamma irradiation facility in Korea Advanced Energy Research Institute. The configuration of the new type detectors is not of coaxial type but of paralled plate in order to obtain directional effects of gamma-ray incidence. Detector materials and dimensions are so chosen that the output current signal is large enough to be detected using some commercial measuring divice even at low dose rate and the contribution of the lead cable to the total signal is negligibly small. The results are 1)sensitivity is depended primarily on the materials of the insulator, 2)output signal has a good linearity to gamma dose rate, 3) response of detectors is prompt, but not perfect, 4) critical thickness for satusation of the output current is thinner than the range of photoelectron in the materials. (Author)

Research on self-powered detectors for gamma-ray monitoring

International Nuclear Information System (INIS)

Cho, S.W.

1983-01-01

Self-powered neutron detectors are used extensively in power reactors both for flux mapping and for power control and over-power protection, because of their small size, ruggedness and simplicity. But they have a few disadvantages such as high burn-up rate and background signal produced by the gamma-rays from the reactor itself. In order to overcome these disadvantages and to achieve a better understanding of gamma-ray effects of self-powered detectors, a new type of self-powered detectors was designed and fabricated by the author, and experiments have been carried out in the 10kCi sup(60)Co gamma irradiation facility in Korea Advanced Energy Research Institute. The configuration of the new type detectors is not of coaxial type but of paralled plate in order to obtain directional effects of gamma-ray incidence. Detector materials and dimensions are so chosen that the output current signal is large enough to be detected using some commercial measuring divice even at low dose rate and the contribution of the lead cable to the totel signal is negligibly small. The results are 1) sensitivity is depended primarily on the materials of the insulator, 2) output signal has a good linearity to gamma dose rate, 3) response of detectors is prompt, but not perfect, 4) critical thickness for satusation of the output current is thinner than the range of photoelectron in the materials. (Author) πT

The Advanced Gamma-ray Imaging System (AGIS): Extragalactic Science

Science.gov (United States)

Coppi, Paolo S.; Extragalactic Science Working Group; AGIS Collaboration

2010-03-01

The Advanced Gamma-ray Imaging System (AGIS), a proposed next-generation array of Cherenkov telescopes, will provide an unprecedented view of the high energy universe. We discuss how AGIS, with its larger effective area, improved angular resolution, lower threshold, and an order of magnitude increase in sensitivity, impacts the extragalactic science possible in the very high energy domain. Likely source classes detectable by AGIS include AGN, GRBs, clusters, star-forming galaxies, and possibly the cascade radiation surrounding powerful cosmic accelerators. AGIS should see many of the sources discovered by Fermi. With its better sensitivity and angular resolution, AGIS then becomes a key instrument for identifying and characterizing Fermi survey sources, the majority of which will have limited Fermi photon statistics and localizations.

REVEALING TYPE Ia SUPERNOVA PHYSICS WITH COSMIC RATES AND NUCLEAR GAMMA RAYS

International Nuclear Information System (INIS)

Horiuchi, Shunsaku; Beacom, John F.

2010-01-01

Type Ia supernovae (SNe Ia) remain mysterious despite their central importance in cosmology and their rapidly increasing discovery rate. The progenitors of SNe Ia can be probed by the delay time between progenitor birth and explosion as SNe Ia. The explosions and progenitors of SNe Ia can be probed by MeV nuclear gamma rays emitted in the decays of radioactive nickel and cobalt into iron. We compare the cosmic star formation and SN Ia rates, finding that their different redshift evolution requires a large fraction of SNe Ia to have large delay times. A delay-time distribution of the form t -α with α = 1.0 ± 0.3 provides a good fit, implying that 50% of SNe Ia explode more than ∼1 Gyr after progenitor birth. The extrapolation of the cosmic SN Ia rate to z = 0 agrees with the rate we deduce from catalogs of local SNe Ia. We investigate prospects for gamma-ray telescopes to exploit the facts that escaping gamma rays directly reveal the power source of SNe Ia and uniquely provide tomography of the expanding ejecta. We find large improvements relative to earlier studies by Gehrels et al. in 1987 and Timmes and Woosley in 1997 due to larger and more certain SN Ia rates and advances in gamma-ray detectors. The proposed Advanced Compton Telescope, with a narrow-line sensitivity ∼60 times better than that of current satellites, would, on an annual basis, detect up to ∼100 SNe Ia (3σ) and provide revolutionary model discrimination for SNe Ia within 20 Mpc, with gamma-ray light curves measured with ∼10σ significance daily for ∼100 days. Even more modest improvements in detector sensitivity would open a new and invaluable astronomy with frequent SN Ia gamma-ray detections.

Advanced Laser-Compton Gamma-Ray Sources for Nuclear Materials Detection, Assay and Imaging

Science.gov (United States)

Barty, C. P. J.

2015-10-01

Highly-collimated, polarized, mono-energetic beams of tunable gamma-rays may be created via the optimized Compton scattering of pulsed lasers off of ultra-bright, relativistic electron beams. Above 2 MeV, the peak brilliance of such sources can exceed that of the world's largest synchrotrons by more than 15 orders of magnitude and can enable for the first time the efficient pursuit of nuclear science and applications with photon beams, i.e. Nuclear Photonics. Potential applications are numerous and include isotope-specific nuclear materials management, element-specific medical radiography and radiology, non-destructive, isotope-specific, material assay and imaging, precision spectroscopy of nuclear resonances and photon-induced fission. This review covers activities at the Lawrence Livermore National Laboratory related to the design and optimization of mono-energetic, laser-Compton gamma-ray systems and introduces isotope-specific nuclear materials detection and assay applications enabled by them.

Prospects for Dark Matter Measurements with the Advanced Gamma Ray Imaging System (AGIS)

Science.gov (United States)

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.

Stacked search for time shifted high energy neutrinos from gamma ray bursts with the Antares neutrino telescope

Energy Technology Data Exchange (ETDEWEB)

Adrian-Martinez, S.; Ardid, M.; Felis, I.; Martinez-Mora, J.A.; Saldana, M. [Universitat Politecnica de Valencia, Institut d' Investigacio per a la Gestio Integrada de les Zones Costaneres (IGIC), Gandia (Spain); Albert, A.; Drouhin, D.; Racca, C. [GRPHE-Institut Universitaire de Technologie de Colmar, 34 rue du Grillenbreit, BP 50568, Colmar (France); Andre, M. [Technical University of Catalonia, Laboratory of Applied Bioacoustics, Vilanova i la Geltru, Barcelona (Spain); Anghinolfi, M. [INFN-Sezione di Genova, Genoa (Italy); Anton, G.; Eberl, T.; Enzenhoefer, A.; Fehn, K.; Folger, F.; Geisselsoeder, S.; Geyer, K.; Gleixner, A.; Graf, K.; Hallmann, S.; Hoessl, J.; Hofestaedt, J.; James, C.W.; Kalekin, O.; Katz, U.; Kiessling, D.; Lahmann, R.; Richter, R.; Roensch, K.; Schmid, J.; Schnabel, J.; Seitz, T.; Sieger, C.; Tselengidou, M.; Wagner, S. [Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Erlangen Centre for Astroparticle Physics, Erlangen (Germany); Aubert, J.J.; Bertin, V.; Brunner, J.; Busto, J.; Carr, J.; Costantini, H.; Coyle, P.; Dornic, D.; Mathieu, A.; Vallee, C. [CPPM, Aix-Marseille Universite, CNRS/IN2P3, Marseille (France); Baret, B.; Barrios-Marti, J.; Hernandez-Rey, J.J.; Sanchez-Losa, A.; Toennis, C.; Zornoza, J.D.; Zuniga, J. [CSIC-Universitat de Valencia, IFIC-Instituto de Fisica Corpuscular, Edificios Investigacion de Paterna, Paterna, Valencia (Spain); Basa, S.; Marcelin, M.; Nezri, E. [Pole de l' Etoile Site de Chateau-Gombert, LAM-Laboratoire d' Astrophysique de Marseille, Marseille Cedex 13 (France); Biagi, S.; Coniglione, R.; Distefano, C.; Piattelli, P.; Riccobene, G.; Sapienza, P.; Trovato, A. [INFN-Laboratori Nazionali del Sud (LNS), Catania (Italy); Bormuth, R.; Jong, M. de; Samtleben, D.F.E. [Nikhef, Science Park, Amsterdam (Netherlands); Universiteit Leiden, Leids Instituut voor Onderzoek in Natuurkunde, Leiden (Netherlands); Bouwhuis, M.C.; Heijboer, A.J.; Michael, T.; Steijger, J.J.M.; Visser, E. [Nikhef, Science Park, Amsterdam (Netherlands); Bruijn, R. [Nikhef, Science Park, Amsterdam (Netherlands); Universiteit van Amsterdam, Instituut voor Hoge-Energie Fysica, Amsterdam (Netherlands); Capone, A.; De Bonis, G.; Fermani, P.; Perrina, C. [INFN-Sezione di Roma, Rome (Italy); Dipartimento di Fisica dell' Universita La Sapienza, Rome (Italy); Caramete, L.; Pavalas, G.E.; Popa, V. [Institute for Space Sciences, Bucharest, Magurele (Romania); Chiarusi, T. [INFN-Sezione di Bologna, Bologna (Italy); Circella, M. [INFN-Sezione di Bari, Bari (Italy); Creusot, A.; Galata, S.; Gracia-Ruiz, R.; Van Elewyck, V. [APC, Universite Paris Diderot, CNRS/IN2P3, CEA/IRFU, Observatoire de Paris, Sorbonne Paris Cite, Paris (France); Dekeyser, I.; Lefevre, D.; Tamburini, C. [Aix-Marseille University, Mediterranean Institute of Oceanography (MIO), Marseille Cedex 9 (France); Universite du Sud Toulon-Var, CNRS-INSU/IRD UM 110, La Garde Cedex (France); Deschamps, A.; Hello, Y. [Geoazur, Universite Nice Sophia-Antipolis, CNRS/INSU, IRD, Observatoire de la Cote d' Azur, Sophia Antipolis (France); Donzaud, C. [APC, Universite Paris Diderot, CNRS/IN2P3, CEA/IRFU, Observatoire de Paris, Sorbonne Paris Cite, Paris (France); Universite Paris-Sud, Orsay Cedex (France); Dumas, A.; Gay, P. [Clermont Universite, Universite Blaise Pascal, CNRS/IN2P3, Laboratoire de Physique Corpusculaire, BP 10448, Clermont-Ferrand (France); Elsaesser, D.; Kadler, M.; Kreter, M.; Mueller, C. [Universitaet Wuerzburg, Institut fuer Theoretische Physik und Astrophysik, Wuerzburg (Germany); Fusco, L.A.; Margiotta, A.; Pellegrino, C.; Spurio, M. [INFN-Sezione di Bologna, Bologna (Italy); Dipartimento di Fisica dell' Universita, Bologna (Italy); Giordano, V. [INFN-Sezione di Catania, Catania (Italy); Haren, H. van [Royal Netherlands Institute for Sea Research (NIOZ), ' t Horntje, Texel (Netherlands); Hugon, C.; Taiuti, M. [INFN-Sezione di Genova, Genoa (Italy); Dipartimento di Fisica dell' Universita, Genoa (Italy); Kooijman, P. [Nikhef, Science Park, Amsterdam (Netherlands); Universiteit Utrecht, Faculteit Betawetenschappen, Utrecht (Netherlands); Universiteit van Amsterdam, Instituut voor Hoge-Energie Fysica, Amsterdam (Netherlands); Kouchner, A. [APC, Universite Paris Diderot, CNRS/IN2P3, CEA/IRFU, Observatoire de Paris, Sorbonne Paris Cite, Paris (France); Institut Universitaire de France, Paris (France); Kreykenbohm, I.; Wilms, J. [Universitaet Erlangen-Nuernberg, Dr. Remeis-Sternwarte and ECAP, Bamberg (Germany); Kulikovskiy, V. [INFN-Laboratori Nazionali del Sud (LNS), Catania (Italy); Moscow State University, Skobeltsyn Institute of Nuclear Physics, Moscow (Russian Federation); Leonora, E. [INFN-Sezione di Catania, Catania (Italy); Dipartimento di Fisica ed Astronomia dell' Universita, Catania (Italy); Loucatos, S. [APC, Universite Paris Diderot, CNRS/IN2P3, CEA/IRFU, Observatoire de Paris, Sorbonne Paris Cite, Paris (France); CEA Saclay, Direction des Sciences de la Matiere, Institut de recherche sur les lois fondamentales de l' Univers, Service de Physique des Particules, Gif-sur-Yvette Cedex (France); Marinelli, A. [INFN-Sezione di Pisa, Pisa (Italy); Dipartimento di Fisica dell' Universita, Pisa (Italy); Migliozzi, P. [INFN-Sezione di Napoli, Naples (IT); Moussa, A. [University Mohammed I, Laboratory of Physics of Matter and Radiations, Oujda (MA); Pradier, T. [Universite de Strasbourg et CNRS/IN2P3, IPHC-Institut Pluridisciplinaire Hubert Curien, 23 rue du Loess, BP 28, Strasbourg Cedex 2 (FR); Sanguineti, M. [Dipartimento di Fisica dell' Universita, Genoa (IT); Schuessler, F.; Stolarczyk, T.; Vallage, B. [CEA Saclay, Direction des Sciences de la Matiere, Institut de recherche sur les lois fondamentales de l' Univers, Service de Physique des Particules, Gif-sur-Yvette Cedex (FR); Vivolo, D. [INFN-Sezione di Napoli, Naples (IT); Dipartimento di Fisica dell' Universita Federico II di Napoli, Naples (IT)

2017-01-15

A search for high-energy neutrino emission correlated with gamma-ray bursts outside the electromagnetic prompt-emission time window is presented. Using a stacking approach of the time delays between reported gamma-ray burst alerts and spatially coincident muon-neutrino signatures, data from the Antares neutrino telescope recorded between 2007 and 2012 are analysed. One year of public data from the IceCube detector between 2008 and 2009 have been also investigated. The respective timing profiles are scanned for statistically significant accumulations within 40 days of the Gamma Ray Burst, as expected from Lorentz Invariance Violation effects and some astrophysical models. No significant excess over the expected accidental coincidence rate could be found in either of the two data sets. The average strength of the neutrino signal is found to be fainter than one detectable neutrino signal per hundred gamma-ray bursts in the Antares data at 90% confidence level. (orig.)

Stacked search for time shifted high energy neutrinos from gamma ray bursts with the Antares neutrino telescope

International Nuclear Information System (INIS)

Adrian-Martinez, S.; Ardid, M.; Felis, I.; Martinez-Mora, J.A.; Saldana, M.; Albert, A.; Drouhin, D.; Racca, C.; Andre, M.; Anghinolfi, M.; Anton, G.; Eberl, T.; Enzenhoefer, A.; Fehn, K.; Folger, F.; Geisselsoeder, S.; Geyer, K.; Gleixner, A.; Graf, K.; Hallmann, S.; Hoessl, J.; Hofestaedt, J.; James, C.W.; Kalekin, O.; Katz, U.; Kiessling, D.; Lahmann, R.; Richter, R.; Roensch, K.; Schmid, J.; Schnabel, J.; Seitz, T.; Sieger, C.; Tselengidou, M.; Wagner, S.; Aubert, J.J.; Bertin, V.; Brunner, J.; Busto, J.; Carr, J.; Costantini, H.; Coyle, P.; Dornic, D.; Mathieu, A.; Vallee, C.; Baret, B.; Barrios-Marti, J.; Hernandez-Rey, J.J.; Sanchez-Losa, A.; Toennis, C.; Zornoza, J.D.; Zuniga, J.; Basa, S.; Marcelin, M.; Nezri, E.; Biagi, S.; Coniglione, R.; Distefano, C.; Piattelli, P.; Riccobene, G.; Sapienza, P.; Trovato, A.; Bormuth, R.; Jong, M. de; Samtleben, D.F.E.; Bouwhuis, M.C.; Heijboer, A.J.; Michael, T.; Steijger, J.J.M.; Visser, E.; Bruijn, R.; Capone, A.; De Bonis, G.; Fermani, P.; Perrina, C.; Caramete, L.; Pavalas, G.E.; Popa, V.; Chiarusi, T.; Circella, M.; Creusot, A.; Galata, S.; Gracia-Ruiz, R.; Van Elewyck, V.; Dekeyser, I.; Lefevre, D.; Tamburini, C.; Deschamps, A.; Hello, Y.; Donzaud, C.; Dumas, A.; Gay, P.; Elsaesser, D.; Kadler, M.; Kreter, M.; Mueller, C.; Fusco, L.A.; Margiotta, A.; Pellegrino, C.; Spurio, M.; Giordano, V.; Haren, H. van; Hugon, C.; Taiuti, M.; Kooijman, P.; Kouchner, A.; Kreykenbohm, I.; Wilms, J.; Kulikovskiy, V.; Leonora, E.; Loucatos, S.; Marinelli, A.; Migliozzi, P.; Moussa, A.; Pradier, T.; Sanguineti, M.; Schuessler, F.; Stolarczyk, T.; Vallage, B.; Vivolo, D.

2017-01-01

A search for high-energy neutrino emission correlated with gamma-ray bursts outside the electromagnetic prompt-emission time window is presented. Using a stacking approach of the time delays between reported gamma-ray burst alerts and spatially coincident muon-neutrino signatures, data from the Antares neutrino telescope recorded between 2007 and 2012 are analysed. One year of public data from the IceCube detector between 2008 and 2009 have been also investigated. The respective timing profiles are scanned for statistically significant accumulations within 40 days of the Gamma Ray Burst, as expected from Lorentz Invariance Violation effects and some astrophysical models. No significant excess over the expected accidental coincidence rate could be found in either of the two data sets. The average strength of the neutrino signal is found to be fainter than one detectable neutrino signal per hundred gamma-ray bursts in the Antares data at 90% confidence level. (orig.)

Prospects for joint observations of gravitational waves and gamma rays from merging neutron star binaries

Energy Technology Data Exchange (ETDEWEB)

Patricelli, B.; Razzano, M.; Fidecaro, F. [Dipartimento di Fisica, Università di Pisa, Largo B. Pontecorvo, 3, 56127 Pisa (Italy); Cella, G. [INFN—Sezione di Pisa, Largo B. Pontecorvo, 3, 56127 Pisa (Italy); Pian, E.; Stamerra, A. [Scuola Normale Superiore, Piazza dei Cavalieri, 7, 56126 Pisa (Italy); Branchesi, M., E-mail: barbara.patricelli@pi.infn.it, E-mail: massimiliano.razzano@unipi.it, E-mail: giancarlo.cella@pi.infn.it, E-mail: francesco.fidecaro@unipi.it, E-mail: elena.pian@sns.it, E-mail: marica.branchesi@uniurb.it, E-mail: stamerra@oato.inaf.it [Universit\\a di Urbino, Via Aurelio Saffi, 2, 61029 Urbino (Italy)

2016-11-01

The detection of the events GW150914 and GW151226, both consistent with the merger of a binary black hole system (BBH), opened the era of gravitational wave (GW) astronomy. Besides BBHs, the most promising GW sources are the coalescences of binary systems formed by two neutron stars or a neutron star and a black hole. These mergers are thought to be connected with short Gamma Ray Bursts (GRBs), therefore combined observations of GW and electromagnetic (EM) signals could definitively probe this association. We present a detailed study on the expectations for joint GW and high-energy EM observations of coalescences of binary systems of neutron stars with Advanced Virgo and LIGO and with the Fermi gamma-ray telescope. To this scope, we designed a dedicated Montecarlo simulation pipeline for the multimessenger emission and detection by GW and gamma-ray instruments, considering the evolution of the GW detector sensitivities. We show that the expected rate of joint detection is low during the Advanced Virgo and Advanced LIGO 2016–2017 run; however, as the interferometers approach their final design sensitivities, the rate will increase by ∼ a factor of ten. Future joint observations will help to constrain the association between short GRBs and binary systems and to solve the puzzle of the progenitors of GWs. Comparison of the joint detection rate with the ones predicted in this paper will help to constrain the geometry of the GRB jet.

Multidimensional analysis of high resolution. gamma. -ray data

Energy Technology Data Exchange (ETDEWEB)

Flibotte, S.; Huettmeier, U.J.; France, G. de; Haas, B.; Romain, P.; Theisen, C.; Vivien, J.P.; Zen, J. (Centre de Recherches Nucleaires, 67 - Strasbourg (France)); Bednarczyk, P. (Inst. of Nuclear Physics, Krakow (Poland))

1992-08-15

Algorithms are developed to analyze high-fold {gamma}-ray coincidences. Performances of the programs have been tested in 3, 4 and 5 dimensions using events generated with a Monte Carlo simulation. (orig.).

Monitoring and Detecting X-ray Transients with the Swift Observatory

Science.gov (United States)

Markwardt, Craig

2002-01-01

Swift is a multi-wavelength observatory specifically designed to detect transients sources in the gamma-ray energy band 15-200 keV. The primary goals of the mission involve gamma ray burst (GRB) astronomy, namely to determine the origin of GRBs and their afterglows, and use bursts to probe the early Universe. However, Swift will also discover new X-ray transient sources, and it will be possible to bring Swift's considerable multi-wavelength capabilities to bear on these sources, and those discovered by other means. The Burst Alert Telescope (BAT) is a coded mask instrument sensitive to 15-200 keV gamma rays, and has a field of view which covers approximately 1/8th of the sky in a single pointing. Over a typical observing day, the almost the entire sky will be observed and monitored for new transient sources. Sources will be detected within several hours of observation. The two narrow field instruments, the X-ray Telescope and Ultra-Violet Optical Telescope, can provide sensitive simultaneous imaging and spectroscopy observations in the optical through soft X-ray bands. The Swift science operations team will entertain requests for targets of opportunity for sources which are astrophysically significant. Swift will be ideally suited for the detection of transients which produce hard X-rays, such as black hole binaries and some neutron star systems.

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

International Nuclear Information System (INIS)

Schanne, Stephane

2006-01-01

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 26 Al 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

Gamma-ray production cross sections for MeV neutrons

International Nuclear Information System (INIS)

Kitazawa, Hideo; Harima, Yoshiko; Yamakoshi, Hisao; Sano, Yuji; Kobayashi, Tsuguyuki.

1979-01-01

Gamma-ray production cross section and spectra for 1- to 20-MeV neutrons were theoretically obtained, which were requested for heating calculations, for shielding design calculations, and for material damage estimates. Calculations were carried out for Al, Si, Ca, Fe, Ni, Cu, Nb, Ta, Au, and Pb, using a spin-dependent evaporation model without the parity conservation and including the dipole and quardupole gamma-ray transitions. The results were compared with the experimental data measured in ORNL to confirm the availability of this model in applications. In addition, the effects on the gamma-ray production cross section of the optical potential, level density, yrast level, and radiation width were investigated in detail. The conclusions are: 1) the use of the optical potential which gives the correct total reaction cross section is essential to gamma-ray production calculations, 2) the gamma-ray production cross section is not so sensitive to the choice of level density parameters, 3) the inclusion of yrast levels is necessary in dealing with the competition of the neutron and gamma-ray emissions from highly excited states, and 4) the Brink-Axel type's radiation width is unsuitable to be applied to radiative capture processes. (author)

Modeling high-energy gamma-rays from the Fermi Bubbles

Energy Technology Data Exchange (ETDEWEB)

Splettstoesser, Megan

2015-09-17

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

A high energy gamma ray astronomy experiment

International Nuclear Information System (INIS)

Hofstadter, R.

1988-01-01

The author describes work involving NASA's Gamma Ray Observatory (GRO). GRO exemplifies the near zero principle because it investigates new gamma ray phenomena by relying on the space program to take us into the region of zero interference above the earth's atmosphere. In its present form GRO has four experiments

Gamma detector for use with luggage X-ray systems

International Nuclear Information System (INIS)

McHugh, H.; Quam, W.

1998-01-01

A new gamma radiation sensor has been designed for installation on several types of luggage x-ray machines and mobile x-ray vans operated by the U.S. Customs Service and the U.S. Department of State. The use of gamma detectors on x-ray machines imposed difficulties not usually encountered in the design of gamma detectors because the spectrum of scattered x-rays, which varied from machine to machine, extended to energies significantly higher than those of the low-energy isotopic emissions. In the original design, the lower level discriminator was raised above the x-ray end point energy resulting in the loss of the americium line associated with plutonium. This reduced the overall sensitivity to unshielded plutonium by a factor of approximately 100. An improved method was subsequently developed wherein collimation was utilized in conjunction with a variable counting threshold to permit accommodation of differing conditions of x-ray scattering. This design has been shown to eliminate most of the problems due to x-ray scattering while still capturing the americium emissions. The overall sensitivity has remained quite high, though varying slightly from one model of x-ray machine to another, depending upon the x-ray scattering characteristics of each model. (author)

A relativistic type Ibc supernova without a detected gamma-ray burst.

Science.gov (United States)

Soderberg, A M; Chakraborti, S; Pignata, G; Chevalier, R A; Chandra, P; Ray, A; Wieringa, M H; Copete, A; Chaplin, V; Connaughton, V; Barthelmy, S D; Bietenholz, M F; Chugai, N; Stritzinger, M D; Hamuy, M; Fransson, C; Fox, O; Levesque, E M; Grindlay, J E; Challis, P; Foley, R J; Kirshner, R P; Milne, P A; Torres, M A P

2010-01-28

Long duration gamma-ray bursts (GRBs) mark the explosive death of some massive stars and are a rare sub-class of type Ibc supernovae. They are distinguished by the production of an energetic and collimated relativistic outflow powered by a central engine (an accreting black hole or neutron star). Observationally, this outflow is manifested in the pulse of gamma-rays and a long-lived radio afterglow. Until now, central-engine-driven supernovae have been discovered exclusively through their gamma-ray emission, yet it is expected that a larger population goes undetected because of limited satellite sensitivity or beaming of the collimated emission away from our line of sight. In this framework, the recovery of undetected GRBs may be possible through radio searches for type Ibc supernovae with relativistic outflows. Here we report the discovery of luminous radio emission from the seemingly ordinary type Ibc SN 2009bb, which requires a substantial relativistic outflow powered by a central engine. A comparison with our radio survey of type Ibc supernovae reveals that the fraction harbouring central engines is low, about one per cent, measured independently from, but consistent with, the inferred rate of nearby GRBs. Independently, a second mildly relativistic supernova has been reported.

Cosmic and solar gamma-ray x-ray and particle measurements from high altitude balloons in Antarctica

International Nuclear Information System (INIS)

Lin, R.P.

1990-01-01

For measurements of cosmic and solar gamma-rays, hard X-rays, and particles, Antarctica offers the potential for very long, 10--20 day, continuous, twenty-four-hour-a-day observations, with balloon flights circling the South Pole during austral summer. For X-ray/gamma-ray sources at high south latitude the overlying atmosphere is minimized, and for cosmic ray measurements the low geomagnetic cutoff permits entry of low rigidity particles. The first Antarctic flight of a heavy (∼2400 lb.) payload on a large (11.6x10 6 cu. ft.) balloon took place in January, 1988, to search for the gamma-ray lines of 56 Co produced in the new supernova SN 1987A in the Large Magellanic Cloud. The long duration balloon flights presently planned from Antarctica include those for further gamma-ray/hard X-ray studies of SN 1987A and for the NASA Max '91 program for solar flare studies

Remote planetary geochemical exploration with the NEAR X-ray/gamma-ray spectrometer

International Nuclear Information System (INIS)

Trombka, J.I.; Boynton, W.V.; Brueckner, J.; Squyres, S.; Clark, P.E.; Starr, R.; Evans, L.G.; Floyd, S.R.; McClanahan, T.P.; Goldsten, J.; Mcnutt, R.; Schweitzer, J.S.

1999-01-01

The X-ray/gamma-ray spectrometer (XGRS) instrument onboard the Near Earth Asteroid Rendezvous (NEAR) spacecraft will map asteroid 433 Eros in the 0.2 keV to 10 MeV energy region. Measurements of the discrete line X-ray and gamma-ray emissions in this energy domain can be used to obtain both qualitative and quantitative elemental composition maps of the asteroid surface. The NEAR X-ray/gamma-ray spectrometer (XGRS) was turned on for the first time during the week of 7 April 1996. Rendezvous with Eros 433 is expected during December 1998. Observations of solar X-ray spectra during both quiescent and active periods have been made. A gamma-ray transient detection system has been implemented and about three gamma-ray transient events a week have been observed which are associated with either gamma-ray bursts or solar flares

Sensitivity of Canola Seeds Associated Fungi to Gamma Rays During Storage

International Nuclear Information System (INIS)

Botros, H.W.

2011-01-01

The present study was carried out to investigate the possibility of using the gamma radiation to elongate the storage periods of canola seeds (Brassica naps L.). In this respect, canola seeds were irradiated at doses of 0.5, 1.5, 2.5, 3.5, 5.0 and 7.5 kGy gamma rays and stored at room temperature for periods 0, 3, 6, 9 and 12 months. The isolated fungi from non-irradiated post-harvest canola seeds included different species identified as Aspergillus flavus, A. niger, A. condidus, A. fumigatus, A. ochraceus, A. parasiticus, Fusarium oxysporium, F. moniliforme, Penicillium expansum, P. crysogenum, Alternaria brassicae, A. raphani and Trichoderma spp. It was noticed that the predominant species were A. ochraceus, A. flavus, A. niger and F. oxysporium at percentages 16.18, 14.73, 11.00 and 10.53%, respectively. The effective gamma irradiation on the predominant fungi (the sub-lethal dose) was 3.5 kGy for A. ochraceus and 5.0 kGy for F. oxysporium and F. moniliforme. Increasing the irradiated dose up to 7.5 kGy decreased significantly the growth of most isolated fungi. The data also showed that there was a decrease in the total fungal count in stored seeds under the effect of gamma rays for 12 months storage. Also, mycotoxins at the stored seeds were not detected after 12 months storage

First detection of very-high-energy gamma-ray emission from the extreme blazar PGC 2402248 with the MAGIC telescopes

Science.gov (United States)

Mirzoyan, Razmik

2018-04-01

The MAGIC collaboration reports the first detection of very-high-energy (VHE; E > 100 GeV) gamma-ray emission from PGC 2402248, also known as 2WHSP J073326.7+515354 (Chang et al. 2016, A & A, 598, A17) with coordinates R.A.: 07:33:26.7 h, Dec: +51:53:54.99 deg. The source is classified as an extreme high-energy peaked BL Lacertae object of unknown redshift, included in the 2WHSP catalog with a synchrotron peak located at 10^17.9 Hz. PGC 2402248 was observed with the MAGIC telescopes from 2018/01/23 to 2018/04/18 (MJD 58141-58226) for about 23 h. The preliminary analysis of these data resulted in the detection of PGC 2402248 with a statistical significance of more than 6 standard deviations.

GEM gas detectors for soft X-ray imaging in fusion devices with neutron–gamma background

Energy Technology Data Exchange (ETDEWEB)

Pacella, Danilo, E-mail: danilo.pacella@enea.it [Associazione EURATOM-ENEA, C.R. Frascati, Via E. Fermi 45, 00044 Frascati, Roma (Italy); Romano, Afra; Gabellieri, Lori [Associazione EURATOM-ENEA, C.R. Frascati, Via E. Fermi 45, 00044 Frascati, Roma (Italy); Murtas, Fabrizio [Istituto Nazionale di Fisica Nucleare, Via E. Fermi 45, 00044 Frascati, Roma (Italy); Mazon, Didier [Association EURATOM-CEA, CEA Cadarache, DSM/IRFM, 13108 St. Paul Lez Durance Cedex (France)

2013-08-21

A triple gas electron multiplier (GEM) detector has been built and characterized in a collaboration between ENEA, INFN and CEA to develop a soft X-ray imaging diagnostic for magnetic fusion plasmas. It has an active area of 5×5 cm{sup 2}, 128 pixels and electronics in counting mode. Since burning plasma experiments will have a very large background of radiation, this prototype has been tested with contemporary X-ray, neutron and gamma irradiation, to study the detection efficiencies, and the discrimination capabilities. The detector has been preliminarily characterized under DD neutron irradiation (2.45 MeV) up to 2.2×10{sup 6} n/s on the detector active area, showing a detection efficiency of about 10{sup −4}, while the detection efficiency of X-rays is more than three orders of magnitude higher. The detector has been also tested under DT neutron flux (14 MeV) up to 2.8×10{sup 8} n/s on the whole detector, with a detection efficiency of about 10{sup −5}. The calibration of the γ-rays detection has been done by means of a source of {sup 60}Co (gamma rays of energy 1.17 MeV and 1.33 MeV) and the detection efficiency was found of the order of 10{sup −4}. Thanks to the adjustable gain of the detector and the discrimination threshold of the electronics, it is possible to minimize the sensitivity to neutrons and gamma, and discriminate the X-ray signals even with very high radiative background.

X-Ray and Gamma-Ray Radiation Detector

DEFF Research Database (Denmark)

2015-01-01

Disclosed is a semiconductor radiation detector for detecting X-ray and / or gamma-ray radiation. The detector comprises a converter element for converting incident X-ray and gamma-ray photons into electron-hole pairs, at least one cathode, a plurality of detector electrodes arranged with a pitch...... (P) along a first axis, a plurality of drift electrodes, a readout circuitry being configured to read out signals from the plurality of detector electrodes and a processing unit connected to the readout circuitry and being configured to detect an event in the converter element. The readout circuitry...... is further configured to read out signals from the plurality of drift electrodes, and the processing unit is further configured to estimate a location of the event along the first axis by processing signals obtained from both the detector electrodes and the drift electrodes, the location of the event along...

All-sky x-ray ampersand gamma-ray monitor (AXGAM)

International Nuclear Information System (INIS)

Tuemer, T.O.; O'Neill, T.J.; Hurley, K.

1996-01-01

A wide field-of-view, arcsecond imaging, high energy resolution x-ray and low energy gamma ray detector is proposed for a future space mission. It is specifically designed to detect and find counterparts at other wavelengths for Gamma Ray Bursts (GRBs). Detection of GRBs require wide field-of-view (π to 2 π field-of-view) and high sensitivity. This will be achieved by using high quantum efficiency CdZnTe pixel detectors, low energy threshold (few keV) to observe larger flux levels that may be possible at lower energies and large effective area (625 to 1,000 cd) per coded aperture imaging module. Counterpart searches can only be done with ultra high angular resolution (10 to 30 arcsecond FWHM) which gives 1 to 5 arcsecond position determination especially for strong GRBs. A few arcsecond resolution error box is expected to contain only one counterpart observed at another wavelength. This will be achieved by using ultra high spatial resolution pixel detectors (50 x 50 to 100 X 100 micron) and a similar resolution coded aperture to achieve the required angular resolution. AXGAM also has two other important advantages over similar detectors: (1) excellent low energy response (> 1 keV) and (2) high energy resolution (<6% at sign 5.9 keV, <3% at sign 14 keV, <4% at sign 122 keV). The low energy range may provide important new information on their cause and the high energy resolution is expected to help in the observation and identification of emission and absorption lines in the GRB spectrum. The effective energy range is planned to be 2 to 200 keV which is exceptionally wide for such a detector. AXGAM will be built in the form of a open-quotes Bucky Ballclose quotes using a coded aperture mask in a semi geodesic dome arrangement placed over a two-dimensional, high resolution CdZnTe pixel detector array using newly developed p-i-n detector technology. The p-i-n structure decreases the electron and hole trapping effect and increases energy resolution significantly

Development of a Telescope for Medium-Energy Gamma-ray Astronomy

Science.gov (United States)

Sunter, Stan

2012-01-01

Since the launch of AGILE and FERMI, the scientific progress in high-energy (Eg greater than approximately 200 MeV) gamma-ray science has been, and will continue to be dramatic. Both of these telescopes cover a broad energy range from approximately 20 MeV to greater than 10 GeV. However, neither instrument is optimized for observations below approximately 200 MeV where many astrophysical objects exhibit unique, transitory behavior, such as spectral breaks, bursts, and flares. Hence, while significant progress from current observations is expected, there will nonetheless remain a significant sensitivity gap in the medium-energy (approximately 0.1-200 MeV) regime; the lower end of this range remains largely unexplored whereas the upper end will allow comparison with FERMI data. Tapping into this unexplored regime requires significant improvements in sensitivity. A major emphasis of modern detector development, with the goal of providing significant improvements in sensitivity in the medium-energy regime, focuses on high-resolution electron tracking. The Three-Dimensional Track Imager (3-DTI) technology being developed at GSFC provides high resolution tracking of the electron-positron pair from gamma-ray interactions from 5 to 200 MeV. The 3-DTI consists of a time projection chamber (TPC) and 2-D cross-strip microwell detector (MWD). The low-density and homogeneous design of the 3-DTI, offers unprecedented sensitivity by providing angular resolution near the kinematic limit. Electron tracking also enables measurement of gamma-ray polarization, a new tool to study astrophysical phenomenon. We describe the design, fabrication, and performance of a 30x30x30 cm3 3-DTI detector prototype of a medium-energy gamma-ray telescope.

Characterization and Applications of a CdZnTe-Based Gamma-Ray Imager

Science.gov (United States)

Galloway, Michelle Lee

Detection of electromagnetic radiation in the form of gamma rays provides a means to discover the presence of nuclear sources and the occurrence of highly-energetic events that occur in our terrestrial and astrophysical environment. The highly penetrative nature of gamma rays allows for probing into objects and regions that are obscured at other wavelengths. The detection and imaging of gamma rays relies upon an understanding of the ways in which these high-energy photons interact with matter. The applications of gamma-ray detection and imaging are numerous. Astrophysical observation of gamma rays expands our understanding of the Universe in which we live. Terrestrial detection and imaging of gamma rays enable environmental monitoring of radioactivity. This allows for identification and localization of nuclear materials to prevent illicit trafficking and to ultimately protect against harmful acts. This dissertation focusses on the development and characterization of a gamma-ray detection and imaging instrument and explores its capabilities for the aforementioned applications. The High Efficiency Multimode Imager, HEMI, is a prototype instrument that is based on Cadmium Zinc Telluride (CdZnTe) semiconductor detectors. The detectors are arranged in a two-planar configuration to allow for both Compton and coded-aperture imaging. HEMI was initially developed as a prototype instrument to demonstrate its capabilities for nuclear threat detection, spectroscopy, and imaging. The 96-detector instrument was developed and fully characterized within the laboratory environment, yielding a system energy resolution of 2.4% FWHM at 662 keV, an angular resolution of 9.5 deg. FWHM at 662 keV in Compton mode, and a 10.6 deg. angular resolution in coded aperture mode. After event cuts, the effective area for Compton imaging of the 662 keV photopeak is 0.1 cm 22. Imaging of point sources in both Compton and coded aperture modes have been demonstrated. The minimum detectable activity of

Overview of high intensity x-ray and gamma-ray sources

International Nuclear Information System (INIS)

Prestwich, K.R.; Lee, J.R.; Ramirez, J.J.; Sanford, T.W.L.; Agee, F.J.; Frazier, G.B.; Miller, A.R.

1987-01-01

The requirements for intense x-ray and gamma-ray sources to simulate the radiation effects from nuclear weapons has led to the development of several types of terawatt-pulsed power systems. One example of a major gamma-ray source is Aurora, a 10-MV, 1.6-MA, 120-ns four-module, electron-beam generator. Recent requirements to improve the dose rate has led to the Aurora upgrade program and to the development of the 20-MV, 800-kA, 40-ns Hermes-III electron-beam accelerator. The Aurora program includes improvements to the pulsed power system and research on techniques to improve the pulse shape of the electron beam. Hermes III will feature twenty 1-MV, 800-kA induction accelerator cavities supplying energy to a magnetically insulated transmission line adder. Hermes III will become operational in 1988. Intense x-ray sources consist of pulsed power systems that operate with 1-MV to 2-MV output voltages and up to 25-TW output powers. These high powers are achieved with either low impedance electron-beam generators or multimodular pulsed power systems. The low-impedance generators have high voltage Marx generators that store the energy and then sequentially transfer this energy to pulse-forming transmission lines with lower and lower impedance until the high currents are reached. In the multimode machines, each module produces 0.7-TW to 4-TW output pulses, and all of the modules are connected together to supply energy to a single diode

An extremely bright gamma-ray pulsar in the Large Magellanic Cloud.

Science.gov (United States)

2015-11-13

Pulsars are rapidly spinning, highly magnetized neutron stars, created in the gravitational collapse of massive stars. We report the detection of pulsed giga-electron volt gamma rays from the young pulsar PSR J0540-6919 in the Large Magellanic Cloud, a satellite galaxy of the Milky Way. This is the first gamma-ray pulsar detected in another galaxy. It has the most luminous pulsed gamma-ray emission yet observed, exceeding the Crab pulsar's by a factor of 20. PSR J0540-6919 presents an extreme test case for understanding the structure and evolution of neutron star magnetospheres. Copyright © 2015, American Association for the Advancement of Science.

Precision Gamma-Ray Branching Ratios for Long-Lived Radioactive Nuclei

Energy Technology Data Exchange (ETDEWEB)

Tonchev, Anton [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2017-10-19

Many properties of the high-energy-density environments in nuclear weapons tests, advanced laser-fusion experiments, the interior of stars, and other astrophysical bodies must be inferred from the resulting long-lived radioactive nuclei that are produced. These radioactive nuclei are most easily and sensitively identified by studying the characteristic gamma rays emitted during decay. Measuring a number of decays via detection of the characteristic gamma-rays emitted during the gamma-decay (the gamma-ray branching ratio) of the long-lived fission products is one of the most straightforward and reliable ways to determine the number of fissions that occurred in a nuclear weapon test. The fission products ¹⁴⁷Nd, ¹⁴⁴Ce, ¹⁵⁶Eu, and certain other long-lived isotopes play a crucial role in science-based stockpile stewardship, however, the large uncertainties (about 8%) on the branching ratios measured for these isotopes are currently limiting the usefulness of the existing data [1,2]. We performed highly accurate gamma-ray branching-ratio measurements for a group of high-atomic-number rare earth isotopes to greatly improve the precision and reliability with which the fission yield and reaction products in high-energy-density environments can be determined. We have developed techniques that take advantage of new radioactive-beam facilities, such as DOE's CARIBU located at Argonne National Laboratory, to produce radioactive samples and perform decay spectroscopy measurements. The absolute gamma-ray branching ratios for ¹⁴⁷Nd and ¹⁴⁴Ce are reduced <2% precision. In addition, high-energy monoenergetic neutron beams from the FN Tandem accelerator in TUNL at Duke University was used to produce ¹⁶⁷Tm using the ¹⁶⁹Tm(n,3n) reaction. Fourtime improved branching ratio of ¹⁶⁷Tm is used now to measure reaction-in-flight (RIF) neutrons from a burning DT capsule at NIF [10]. This represents the

The dynamic range of ultra-high-resolution cryogenic gamma-ray spectrometers

Energy Technology Data Exchange (ETDEWEB)

Ali, Shafinaz [Advanced Detector Group, Lawrence Livermore National Laboratory, 7000 East Avenue, L-270, Livermore, CA 94550 (United States); Terracol, Stephane F. [Advanced Detector Group, Lawrence Livermore National Laboratory, 7000 East Avenue, L-270, Livermore, CA 94550 (United States); Drury, Owen B. [Advanced Detector Group, Lawrence Livermore National Laboratory, 7000 East Avenue, L-270, Livermore, CA 94550 (United States); Friedrich, Stephan [Advanced Detector Group, Lawrence Livermore National Laboratory, 7000 East Avenue, L-270, Livermore, CA 94550 (United States)]. E-mail: friedrich1@llnl.gov

2006-04-15

We are developing high-resolution cryogenic gamma-ray spectrometers for nuclear science and non-proliferation applications. The gamma-ray detectors are composed of a bulk superconducting Sn foil absorber attached to a multilayer Mo/Cu transition-edge sensor (TES). The energy resolution of a detector with a 1x1x0.25 mm{sup 3} Sn absorber is 50-90 eV FWHM for {gamma}-rays up to 100 keV, and it decreases for larger absorbers. Here, we present the detector performance for different absorber volumes, and discuss the trade-offs between energy resolution and dynamic range.

Gamma detection: an unusual application for surface barrier detectors

International Nuclear Information System (INIS)

Fichtenbaum de Iacub, Silvana; Matatagui, Emilio

1983-01-01

The silicon surface barrier detectors (SBD), may be ideal devices to be used in dose indicators for the monitoring of gamma radiations; the SBD working as a cavity sensor. The measurement consists in counting the number of pulses that exceeds a certain level of discrimination, this number being proportional to the absorbed dose. The spectral distribution of the pulses gives an idea of the existing photons field's energy. Characteristic spectra obtained with different gamma-and X ray sources are described and analyzed, and tests are carried out by using different sensitive volumes of the detector in order to determine significant parameters for a gamma-monitor system. The results from the measurements indicate: a) high sensitivity of the system with SBD (high density of material); b) low background: enviromental backgrounds are reliably registered (approx. 10μ R/h); c) minimum detectable energies of the order of 60 keV; d) possibility to determine high exposure rates (approx. 100 R/h); e) for emitters of low Z, the result is approximately independent from the gamma energy. These results suggest the possibility of constructing fixed and portable systems, appropriate for gamma monitoring, which utilize SBD as sensors; these devices are adequate for working at enviroment temperatures, being compact, reliable, with low polarization voltages, and of relatively low cost. (M.E.L.) [es

X-ray and. gamma. -ray sources: a comparison of their characteristics

Energy Technology Data Exchange (ETDEWEB)

Freund, A K [Institut Max von Laue - Paul Langevin, 38 - Grenoble (France)

1979-11-01

A comparison of the various source characteristics, in particular the available fluxes of radiation in the X-ray/..gamma..-ray region from (1) high power rotary anode X-ray generators, (2) radioactive ..gamma..-ray sources and (3) high energy electron storage rings is presented. Some of the specific characteristics and possible applications of synchrotron radiation as a source are discussed in detail, together with problems associated with the monochromatization of the continuous radiation in the X-ray/..gamma..-ray region. The new high energy machines PEP at Stanford, the 8 GeV storage ring CESR at Cornell and the PETRA storage ring in Hamburg, which will soon come into operation provide a spectrum of high intensity radiation reaching well above h..gamma..sub(photon)=100 keV. The possibilities of using ondulators (wigglers), and laser-electron scattering for constructing high repetition rate tunable ..gamma..-ray sources are also discussed. Finally the potentials of using the powerful spontaneous emission of ..gamma..-quanta by relativistic channeled particles are mentioned.

Detection prospects for GeV neutrinos from collisionally heated gamma-ray bursts with IceCube/DeepCore.

Science.gov (United States)

Bartos, I; Beloborodov, A M; Hurley, K; Márka, S

2013-06-14

Jet reheating via nuclear collisions has recently been proposed as the main mechanism for gamma-ray burst (GRB) emission. In addition to producing the observed gamma rays, collisional heating must generate 10-100 GeV neutrinos, implying a close relation between the neutrino and gamma-ray luminosities. We exploit this theoretical relation to make predictions for possible GRB detections by IceCube + DeepCore. To estimate the expected neutrino signal, we use the largest sample of bursts observed by the Burst and Transient Source Experiment in 1991-2000. GRB neutrinos could have been detected if IceCube + DeepCore operated at that time. Detection of 10-100 GeV neutrinos would have significant implications, shedding light on the composition of GRB jets and their Lorentz factors. This could be an important target in designing future upgrades of the IceCube + DeepCore observatory.

Feasibility study for an airborne high-sensitivity gamma-ray survey of Alaska. Phase II (final) report: 1976--1979 program

International Nuclear Information System (INIS)

1975-01-01

This study constitutes a determination of the extent to which it is feasible to use airborne, high-sensitivity gamma spectrometer systems for uranium reconnaissance in the State of Alaska, and specification of a preliminary plan for surveying the entire state of the 1975--1979 time frame. Phase I included the design of a program to survey the highest priority areas in 1975 using available aircraft and spectrometer equipment. This has now resulted in a contract for 10,305 flight line miles to cover about 11 of the 1:250,000 scale quadrangles using a DC-3 aircraft with an average 6.25 x 25 mile grid of flight line. Phase II includes the design of alternative programs to cover the remaining 128 quadrangles using either a DC-3 and a Bell 205A helicopter or a Helio Stallion STOL aircraft and a Bell 205A helicopter during 1976-1979. The 1976-1979 time frame allows some time for possible new system developments in both airborne gamma-ray spectrometers and in ancillary equipment, and these are outlined. (auth)

Simulation Study on Identifiability of UHE Gamma-ray Air Showers

International Nuclear Information System (INIS)

Wada, Y.; Inoue, N.; Miyazawa, K.; Vankov, H.P.

2008-01-01

The chemical composition of Ultra-High-Energy (UHE) comic rays is one of unsolved mysteries, and its study will give us fruitful information on the origin and acceleration mechanism of UHE cosmic rays. Especially, a detection of UHE gamma-rays by hybrid experiments, such as AUGER and TA, will be a key to solve these questions. The characteristics of UHE gamma-ray showers have been studied by comparing the lateral and longitudinal structures of shower particles calculated with AIRES and our own simulation code, so far. There are apparent differences in a slope of lateral distribution (η) and a depth of shower maximum (Xmax) between gamma-ray and proton induced showers because UHE gamma-ray showers are affected by the LPM effect and the geomagnetic cascading process in an energy region of >10 19.5 eV. Different features between gamma-ray and proton showers are pointed out from the simulation study and an identifiability of gamma-ray showers from proton ones is also discussed by the method of Neural-Network-Analysis

Simulation Study on Identifiability of UHE Gamma-ray Air Showers

Energy Technology Data Exchange (ETDEWEB)

Wada, Y.; Inoue, N.; Miyazawa, K. [Graduate School of Science and Engineering, Saitama University, Saitama 338-8570 (Japan); Vankov, H.P. [Institute for Nuclear Research and Nuclear Energy, Bulgaria Academy, Sofia (Bulgaria)

2008-01-15

The chemical composition of Ultra-High-Energy (UHE) comic rays is one of unsolved mysteries, and its study will give us fruitful information on the origin and acceleration mechanism of UHE cosmic rays. Especially, a detection of UHE gamma-rays by hybrid experiments, such as AUGER and TA, will be a key to solve these questions. The characteristics of UHE gamma-ray showers have been studied by comparing the lateral and longitudinal structures of shower particles calculated with AIRES and our own simulation code, so far. There are apparent differences in a slope of lateral distribution ({eta}) and a depth of shower maximum (Xmax) between gamma-ray and proton induced showers because UHE gamma-ray showers are affected by the LPM effect and the geomagnetic cascading process in an energy region of >10{sup 19.5}eV. Different features between gamma-ray and proton showers are pointed out from the simulation study and an identifiability of gamma-ray showers from proton ones is also discussed by the method of Neural-Network-Analysis.

The agile alert system for gamma-ray transients

Energy Technology Data Exchange (ETDEWEB)

Bulgarelli, A.; Trifoglio, M.; Gianotti, F.; Fioretti, V. [INAF/IASF-Bologna, Via Gobetti 101, I-40129 Bologna (Italy); Tavani, M.; Argan, A.; Trois, A.; Scalise, E. [INAF/IASF-Roma, Via del Fosso del Cavaliere 100, I-00133 Roma (Italy); Parmiggiani, N.; Beneventano, D. [University of Modena and Reggio Emilia, Dipartimento di Science e Metodi dell' Ingegneria (Italy); Chen, A. W. [INAF/IASF-Milano, Via E. Bassini 15, I-20133 Milano (Italy); Vercellone, S. [School of Physics, University of the Witwatersrand, Johannesburg Wits 2050 (South Africa); Pittori, C.; Verrecchia, F.; Lucarelli, F.; Santolamazza, P.; Fanari, G.; Giommi, P. [INAF/IASF-Palermo, Via U. La Malfa 153, I-90146 Palermo (Italy); Longo, F. [ASI-ASDC, Via G. Galilei, I-00044 Frascati (Roma) (Italy); Pellizzoni, A. [INFN Trieste, I-34127 Trieste (Italy); and others

2014-01-20

In recent years, a new generation of space missions has offered great opportunities for discovery in high-energy astrophysics. In this article we focus on the scientific operations of the Gamma-Ray Imaging Detector (GRID) on board the AGILE space mission. AGILE-GRID, sensitive in the energy range of 30 MeV-30 GeV, has detected many γ-ray transients of both galactic and extragalactic origin. This work presents the AGILE innovative approach to fast γ-ray transient detection, which is a challenging task and a crucial part of the AGILE scientific program. The goals are to describe (1) the AGILE Gamma-Ray Alert System, (2) a new algorithm for blind search identification of transients within a short processing time, (3) the AGILE procedure for γ-ray transient alert management, and (4) the likelihood of ratio tests that are necessary to evaluate the post-trial statistical significance of the results. Special algorithms and an optimized sequence of tasks are necessary to reach our goal. Data are automatically analyzed at every orbital downlink by an alert pipeline operating on different timescales. As proper flux thresholds are exceeded, alerts are automatically generated and sent as SMS messages to cellular telephones, via e-mail, and via push notifications from an application for smartphones and tablets. These alerts are crosschecked with the results of two pipelines, and a manual analysis is performed. Being a small scientific-class mission, AGILE is characterized by optimization of both scientific analysis and ground-segment resources. The system is capable of generating alerts within two to three hours of a data downlink, an unprecedented reaction time in γ-ray astrophysics.

The agile alert system for gamma-ray transients

International Nuclear Information System (INIS)

Bulgarelli, A.; Trifoglio, M.; Gianotti, F.; Fioretti, V.; Tavani, M.; Argan, A.; Trois, A.; Scalise, E.; Parmiggiani, N.; Beneventano, D.; Chen, A. W.; Vercellone, S.; Pittori, C.; Verrecchia, F.; Lucarelli, F.; Santolamazza, P.; Fanari, G.; Giommi, P.; Longo, F.; Pellizzoni, A.

2014-01-01

In recent years, a new generation of space missions has offered great opportunities for discovery in high-energy astrophysics. In this article we focus on the scientific operations of the Gamma-Ray Imaging Detector (GRID) on board the AGILE space mission. AGILE-GRID, sensitive in the energy range of 30 MeV-30 GeV, has detected many γ-ray transients of both galactic and extragalactic origin. This work presents the AGILE innovative approach to fast γ-ray transient detection, which is a challenging task and a crucial part of the AGILE scientific program. The goals are to describe (1) the AGILE Gamma-Ray Alert System, (2) a new algorithm for blind search identification of transients within a short processing time, (3) the AGILE procedure for γ-ray transient alert management, and (4) the likelihood of ratio tests that are necessary to evaluate the post-trial statistical significance of the results. Special algorithms and an optimized sequence of tasks are necessary to reach our goal. Data are automatically analyzed at every orbital downlink by an alert pipeline operating on different timescales. As proper flux thresholds are exceeded, alerts are automatically generated and sent as SMS messages to cellular telephones, via e-mail, and via push notifications from an application for smartphones and tablets. These alerts are crosschecked with the results of two pipelines, and a manual analysis is performed. Being a small scientific-class mission, AGILE is characterized by optimization of both scientific analysis and ground-segment resources. The system is capable of generating alerts within two to three hours of a data downlink, an unprecedented reaction time in γ-ray astrophysics.

The AGILE Alert System for Gamma-Ray Transients

Science.gov (United States)

Bulgarelli, A.; Trifoglio, M.; Gianotti, F.; Tavani, M.; Parmiggiani, N.; Fioretti, V.; Chen, A. W.; Vercellone, S.; Pittori, C.; Verrecchia, F.; Lucarelli, F.; Santolamazza, P.; Fanari, G.; Giommi, P.; Beneventano, D.; Argan, A.; Trois, A.; Scalise, E.; Longo, F.; Pellizzoni, A.; Pucella, G.; Colafrancesco, S.; Conforti, V.; Tempesta, P.; Cerone, M.; Sabatini, P.; Annoni, G.; Valentini, G.; Salotti, L.

2014-01-01

In recent years, a new generation of space missions has offered great opportunities for discovery in high-energy astrophysics. In this article we focus on the scientific operations of the Gamma-Ray Imaging Detector (GRID) on board the AGILE space mission. AGILE-GRID, sensitive in the energy range of 30 MeV-30 GeV, has detected many γ-ray transients of both galactic and extragalactic origin. This work presents the AGILE innovative approach to fast γ-ray transient detection, which is a challenging task and a crucial part of the AGILE scientific program. The goals are to describe (1) the AGILE Gamma-Ray Alert System, (2) a new algorithm for blind search identification of transients within a short processing time, (3) the AGILE procedure for γ-ray transient alert management, and (4) the likelihood of ratio tests that are necessary to evaluate the post-trial statistical significance of the results. Special algorithms and an optimized sequence of tasks are necessary to reach our goal. Data are automatically analyzed at every orbital downlink by an alert pipeline operating on different timescales. As proper flux thresholds are exceeded, alerts are automatically generated and sent as SMS messages to cellular telephones, via e-mail, and via push notifications from an application for smartphones and tablets. These alerts are crosschecked with the results of two pipelines, and a manual analysis is performed. Being a small scientific-class mission, AGILE is characterized by optimization of both scientific analysis and ground-segment resources. The system is capable of generating alerts within two to three hours of a data downlink, an unprecedented reaction time in γ-ray astrophysics.

Fermi-LAT Gamma-Ray Bursts and Insights from Swift

Science.gov (United States)

Racusin, Judith L.

2010-01-01

A new revolution in Gamma-ray Burst (GRB) observations and theory has begun over the last two years since the launch of the Fermi Gamma-ray Space Telescope. The new window into high energy gamma-rays opened by the Fermi-Large Area Telescope (LAT) is providing insight into prompt emission mechanisms and possibly also afterglow physics. The LAT detected GRBs appear to be a new unique subset of extremely energetic and bright bursts compared to the large sample detected by Swift over the last 6 years. In this talk, I will discuss the context and recent discoveries from these LAT GRBs and the large database of broadband observations collected by the Swift X-ray Telescope (XRT) and UV/Optical Telescope (UVOT). Through comparisons between the GRBs detected by Swift-BAT, G8M, and LAT, we can learn about the unique characteristics, physical differences, and the relationships between each population. These population characteristics provide insight into the different physical parameters that contribute to the diversity of observational GRB properties.

Fast-ion energy resolution by one-step reaction gamma-ray spectrometry

DEFF Research Database (Denmark)

Salewski, Mirko; Nocente, M.; Gorini, G.

2016-01-01

The spectral broadening of γ-rays from fusion plasmas can be measured in high-resolution gamma-ray spectrometry (GRS). We derive weight functions that determine the observable velocity space and quantify the velocity-space sensitivity of one-step reaction high-resolution GRS measurements in magne...

Observations Of Gamma-ray Loud Blazars With The VLBA At 5 GHz

Science.gov (United States)

Linford, Justin; Taylor, G. B.; Romani, R.; Readhead, A. C. S.; Reeves, R.; Richards, J. L.; Helmboldt, J. F.

2011-01-01

The Fermi Gamma-ray Space Telescope has been scanning the sky for more than a year. About half of the sources detected by Fermi's Large Area Telesope (LAT) are active galactic nuclei (AGN). Nearly all of these gamma-ray loud AGN are blazars; strong, compact radio emitters that exhibit variability in their flux and apparent superluminal motion in their jets. Several groups are currently monitoring the radio properties of these gamma-ray loud blazars. We present results from both archival and contemporaneous observations of 200 LAT-detected blazars using the Very Long Baseline Array (VLBA) at a frequency of 5 GHz (wavelength of 6 cm). Our large, flux-limited sample provides unique insights into the mechanism that produces strong gamma-ray emissions. We explore the parsec-scale properties of the cores and jets of these highly energetic objects, including core polarization. We compare the gamma-ray loud blazars to their gamma-ray quiet counterparts in the VLBA Imaging and Polarimetry Survey (VIPS). We also investigate the differences between the BL Lacertae objects (BL Lacs) and flat-spectrum radio quasars (FSRQs).

The Future of Gamma Ray Astrophysics

CERN Multimedia

CERN. Geneva

2016-01-01

Over the past decade, gamma ray astrophysics has entered the astrophysical mainstream. Extremely successful space-borne (GeV) and ground-based (TeV) detectors, combined with a multitude of partner telescopes, have revealed a fascinating “astroscape" of active galactic nuclei, pulsars, gamma ray bursts, supernova remnants, binary stars, star-forming galaxies, novae much more, exhibiting major pathways along which large energy releases can flow. From  a basic physics perspective, exquisitely sensitive measurements have constrained the nature of dark matter, the cosmological origin of magnetic field and the properties of black holes. These advances have motivated the development of new facilities, including HAWC, DAMPE, CTA and SVOM, which will further our understanding of the high energy universe. Topics that will receive special attention include merging neutron star binaries, clusters of galaxies, galactic cosmic rays and putative, TeV dark matter.

Gamma-ray detection and Compton camera image reconstruction with application to hadron therapy; Detection des rayons gamma et reconstruction d'images pour la camera Compton: Application a l'hadrontherapie

Energy Technology Data Exchange (ETDEWEB)

Frandes, M.

2010-09-15

A novel technique for radiotherapy - hadron therapy - irradiates tumors using a beam of protons or carbon ions. Hadron therapy is an effective technique for cancer treatment, since it enables accurate dose deposition due to the existence of a Bragg peak at the end of particles range. Precise knowledge of the fall-off position of the dose with millimeters accuracy is critical since hadron therapy proved its efficiency in case of tumors which are deep-seated, close to vital organs, or radio-resistant. A major challenge for hadron therapy is the quality assurance of dose delivery during irradiation. Current systems applying positron emission tomography (PET) technologies exploit gamma rays from the annihilation of positrons emitted during the beta decay of radioactive isotopes. However, the generated PET images allow only post-therapy information about the deposed dose. In addition, they are not in direct coincidence with the Bragg peak. A solution is to image the complete spectrum of the emitted gamma rays, including nuclear gamma rays emitted by inelastic interactions of hadrons to generated nuclei. This emission is isotropic, and has a spectrum ranging from 100 keV up to 20 MeV. However, the measurement of these energetic gamma rays from nuclear reactions exceeds the capability of all existing medical imaging systems. An advanced Compton scattering detection method with electron tracking capability is proposed, and modeled to reconstruct the high-energy gamma-ray events. This Compton detection technique was initially developed to observe gamma rays for astrophysical purposes. A device illustrating the method was designed and adapted to Hadron Therapy Imaging (HTI). It consists of two main sub-systems: a tracker where Compton recoiled electrons are measured, and a calorimeter where the scattered gamma rays are absorbed via the photoelectric effect. Considering a hadron therapy scenario, the analysis of generated data was performed, passing trough the complete

Gamma-Ray Bursts: A Radio Perspective

Directory of Open Access Journals (Sweden)

Poonam Chandra

2016-01-01

Full Text Available Gamma-ray bursts (GRBs are extremely energetic events at cosmological distances. They provide unique laboratory to investigate fundamental physical processes under extreme conditions. Due to extreme luminosities, GRBs are detectable at very high redshifts and potential tracers of cosmic star formation rate at early epoch. While the launch of Swift and Fermi has increased our understanding of GRBs tremendously, many new questions have opened up. Radio observations of GRBs uniquely probe the energetics and environments of the explosion. However, currently only 30% of the bursts are detected in radio bands. Radio observations with upcoming sensitive telescopes will potentially increase the sample size significantly and allow one to follow the individual bursts for a much longer duration and be able to answer some of the important issues related to true calorimetry, reverse shock emission, and environments around the massive stars exploding as GRBs in the early Universe.

Determination of Proton dose distal fall-off location by detecting right-angled prompt gamma rays

International Nuclear Information System (INIS)

Seo, Kyu Seok

2006-02-01

The proton beam has a unique advantage over the electron and photon beams in that it can give very high radiation dose to the tumor volume while effectively sparing the neighboring healthy tissue and organs. The number of proton therapy facility is very rapidly increasing in the world. And now the 230 MeV cyclotron facility for proton therapy is constructing at National Cancer Center, this facility until 2006. The distal fall-off location of proton beam is simply calculated by analytical method, but this method has many uncertain when anatomical structure is very complicated. It is very important to know the exact position of the proton beam distal fall-off, or beam range, in the patient's body for both the safety of the patient and the effectiveness of the treatment itself. In 2003, Stichelbaut and Jongen reported the possibility of using the right-angled prompt gamma rays, which are emitted at 90 .deg. from the incident proton beam direction, to determine the position of the proton beam distal fall-off. They studied the interactions of the protons and other secondary particles in a water phantom and concluded that there is a correlation between the position of the distal fall-off and the distribution of the right-angled prompt gamma rays. We have recently designed a prompt gamma scanning system to measure the proton range in situ by using Monte Carlo technique employing MCNPX, FLUKA, and Sabrina TM . The prompt gamma scanning system was designed to measure only the right-angled prompt gamma rays passing through a narrow collimation hole in order to correlate the position with the dose distribution. The collimation part of the scanning system, which has been constructed to measure the gamma rays at 70 MeV of proton energy, is made of a set of paraffin, boron carbide, and lead layers to shield the high-energy neutrons and secondary photons. After the different proton energies and SOBP beam widths are irradiated at the water phantom. we detected prompt gamma at 5 cm

A link between prompt optical and prompt gamma-ray emission in gamma-ray bursts.

Science.gov (United States)

Vestrand, W T; Wozniak, P R; 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; Parsons, A; Tueller, J

2005-05-12

The prompt optical emission that arrives with the 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 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.

Development of a bottom-hole gamma-ray diagnostic capability for high-level environments, during CTBT on-site inspection drilling

International Nuclear Information System (INIS)

Fontenot, R.; Shakir, S.; Heuze, F.; Butler, M.

1998-05-01

Testing completed at NTS confirmed that the Anadrill gamma-ray tool was fully operational up to 50,000 API, as specified in the initial objective. Recorded results were within expected ranges when compared to the hand-held detector. The gamma-ray module will require special 'high-rate' detection software to be loaded prior to drilling operations. The other components within the VIPER system have been modified to operate with either software (normal or 'high-rate') installed in the gamma-ray module. The successful completion of this test is but one step towards the main goal. The next step will be testing this module in the VIPER tool during an actual 're-entry' drilling operation, which could be performed at NTS on a former U.S. event. (author)

On the correlation between radio and gamma-ray luminosities of active galactic nuclei

DEFF Research Database (Denmark)

Mücke, A.; Pohl, M.

1997-01-01

in flux-limited samples if intrinsic scatter does not exceed similar to 40 % of the original gamma-ray luminosity. However, if mean flux values of high variable sources are used we find the chance probability of high Spearman's correlation coefficient be significant underestimated. The analysis presented......The possibility of a correlation between the radio (cm)- and gamma-ray luminosity of variable AGN seen by EGRET is investigated. We perform Monte-Carlo simulations of typical data sets and apply different correlation techniques (partial correlation analysis, chi(2)-test applied on flux......-flux relations) in view of a truncation bias caused by sensitivity limits of the surveys. For K-corrected flux densities, we find that with the least squares method only a linear correlation can be recovered. Partial correlation analysis on the other side provides a robust tool to detect correlations even...

Observation of cosmic gamma ray burst by Hinotori

International Nuclear Information System (INIS)

Okudaira, Kiyoaki; Yoshimori, Masato; Hirashima, Yo; Kondo, Ichiro.

1982-01-01

The solar gamma ray detecor (SGR) on Hinotori has no collimator, and the collimator of a hard X-ray monitor is not effective for gamma ray with energy more than 100 KeV. Accordingly, the detection system can detect cosmic gamma ray burst, and two bursts were observed. The first burst was detected on February 28, 1981, and the source of the burst was in the direction of 81 degree from Venus. The time profile and the spectrum were observed. In July 21, 1981, the second burst was detected. The time profile obtained with the SGR was compared with those of PVO (Pioneer Venus Orbiter) and LASL-ISEE. The time difference among the data of time profiles indicated that the source of the burst was not the sun. The spectrum was also measured. (Kato, T.)

Properties of a large NaI(Tl) spectrometer for the energy measurement of high-energy gamma rays on the Gamma Ray Observatory

International Nuclear Information System (INIS)

Hughes, E.B.; Finman, L.C.; Hofstadter, R.; Lepetich, J.E.; Lin, Y.C.; Mattox, J.R.; Nolan, P.L.; Parks, R.; Walker, A.H.

1986-01-01

A large NaI(T1) spectrometer is expected to play a crucial role in the measurement of the energy spectra from an all-sky survey of high-energy celestial gamma rays on the Gamma Ray Observatory. The crystal size and requirements of space flight have resulted in a novel crystal-packaging and optics combination. The structure of this spectrometer and the operating characteristics determined in a test program using high energy positrons are described

Population Synthesis of Radio & Gamma-Ray Millisecond Pulsars

Science.gov (United States)

Frederick, Sara; Gonthier, P. L.; Harding, A. K.

2014-01-01

In recent years, the number of known gamma-ray millisecond pulsars (MSPs) in the Galactic disk has risen substantially thanks to confirmed detections by Fermi Gamma-ray Space Telescope (Fermi). We have developed a new population synthesis of gamma-ray and radio MSPs in the galaxy which uses Markov Chain Monte Carlo techniques to explore the large and small worlds of the model parameter space and allows for comparisons of the simulated and detected MSP distributions. The simulation employs empirical radio and gamma-ray luminosity models that are dependent upon the pulsar period and period derivative with freely varying exponents. Parameters associated with the birth distributions are also free to vary. The computer code adjusts the magnitudes of the model luminosities to reproduce the number of MSPs detected by a group of ten radio surveys, thus normalizing the simulation and predicting the MSP birth rates in the Galaxy. Computing many Markov chains leads to preferred sets of model parameters that are further explored through two statistical methods. Marginalized plots define confidence regions in the model parameter space using maximum likelihood methods. A secondary set of confidence regions is determined in parallel using Kuiper statistics calculated from comparisons of cumulative distributions. These two techniques provide feedback to affirm the results and to check for consistency. Radio flux and dispersion measure constraints have been imposed on the simulated gamma-ray distributions in order to reproduce realistic detection conditions. The simulated and detected distributions agree well for both sets of radio and gamma-ray pulsar characteristics, as evidenced by our various comparisons.

New readout and data-acquisition system in an electron-tracking Compton camera for MeV gamma-ray astronomy (SMILE-II)

Energy Technology Data Exchange (ETDEWEB)

Mizumoto, T., E-mail: mizumoto@cr.scphys.kyoto-u.ac.jp [Department of Physics, Kyoto University, 606-8502 Kyoto (Japan); Matsuoka, Y. [Department of Physics, Kyoto University, 606-8502 Kyoto (Japan); Mizumura, Y. [Unit of Synergetic Studies for Space, Kyoto University, 606-8502 Kyoto (Japan); Department of Physics, Kyoto University, 606-8502 Kyoto (Japan); Tanimori, T. [Department of Physics, Kyoto University, 606-8502 Kyoto (Japan); Unit of Synergetic Studies for Space, Kyoto University, 606-8502 Kyoto (Japan); Kubo, H.; Takada, A.; Iwaki, S.; Sawano, T.; Nakamura, K.; Komura, S.; Nakamura, S.; Kishimoto, T.; Oda, M.; Miyamoto, S.; Takemura, T.; Parker, J.D.; Tomono, D.; Sonoda, S. [Department of Physics, Kyoto University, 606-8502 Kyoto (Japan); Miuchi, K. [Department of Physics, Kobe University, 658-8501 Kobe (Japan); Kurosawa, S. [Institute for Materials Research, Tohoku University, 980-8577 Sendai (Japan)

2015-11-11

For MeV gamma-ray astronomy, we have developed an electron-tracking Compton camera (ETCC) as a MeV gamma-ray telescope capable of rejecting the radiation background and attaining the high sensitivity of near 1 mCrab in space. Our ETCC comprises a gaseous time-projection chamber (TPC) with a micro pattern gas detector for tracking recoil electrons and a position-sensitive scintillation camera for detecting scattered gamma rays. After the success of a first balloon experiment in 2006 with a small ETCC (using a 10×10×15 cm{sup 3} TPC) for measuring diffuse cosmic and atmospheric sub-MeV gamma rays (Sub-MeV gamma-ray Imaging Loaded-on-balloon Experiment I; SMILE-I), a (30 cm){sup 3} medium-sized ETCC was developed to measure MeV gamma-ray spectra from celestial sources, such as the Crab Nebula, with single-day balloon flights (SMILE-II). To achieve this goal, a 100-times-larger detection area compared with that of SMILE-I is required without changing the weight or power consumption of the detector system. In addition, the event rate is also expected to dramatically increase during observation. Here, we describe both the concept and the performance of the new data-acquisition system with this (30 cm){sup 3} ETCC to manage 100 times more data while satisfying the severe restrictions regarding the weight and power consumption imposed by a balloon-borne observation. In particular, to improve the detection efficiency of the fine tracks in the TPC from ~10% to ~100%, we introduce a new data-handling algorithm in the TPC. Therefore, for efficient management of such large amounts of data, we developed a data-acquisition system with parallel data flow.

Observations of cosmic gamma ray bursts with WATCH on EURECA

DEFF Research Database (Denmark)

Brandt, Søren; Lund, N.; Castro-Tirado, A. J.

1995-01-01

19 Cosmic Gamma-Ray Bursts were detected by the WATCH wide field X-ray monitor during the 11 months flight of EURECA. The identification of the bursts were complicated by a high frequency of background of events caused by high energy cosmic ray interactions in the detector and by low energy, trap...

A novel background reduction strategy for high level triggers and processing in gamma-ray Cherenkov detectors

International Nuclear Information System (INIS)

Cabras, G.; De Angelis, A.; De Lotto, B.; De Maria, M. M.; De Sabata, F.; Mansutti, O.; Frailis, M.; Persic, M.; Bigongiari, C.; Doro, M.; Mariotti, M.; Peruzzo, L.; Saggion, A.; Scalzotto, V.; Paoletti, R.; Scribano, A.; Turini, N.; Moralejo, A.; Tescaro, D.

2008-01-01

Gamma ray astronomy is now at the leading edge for studies related both to fundamental physics and astrophysics. The sensitivity of gamma detectors is limited by the huge amount of background, constituted by hadronic cosmic rays (typically two to three orders of magnitude more than the signal) and by the accidental background in the detectors. By using the information on the temporal evolution of the Cherenkov light, the background can be reduced. We will present here the results obtained within the MAGIC experiment using a new technique for the reduction of the background. Particle showers produced by gamma rays show a different temporal distribution with respect to showers produced by hadrons; the background due to accidental counts shows no dependence on time. Such novel strategy can increase the sensitivity of present instruments

Physics and astrophysics with gamma-ray telescopes

Energy Technology Data Exchange (ETDEWEB)

Vandenbroucke, J. [Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States)

2012-08-15

In the past few years gamma-ray astronomy has entered a golden age. A modern suite of telescopes is now scanning the sky over both hemispheres and over six orders of magnitude in energy. At {approx}TeV energies, only a handful of sources were known a decade ago, but the current generation of ground-based imaging atmospheric Cherenkov telescopes (H.E.S.S., MAGIC, and VERITAS) has increased this number to nearly one hundred. With a large field of view and duty cycle, the Tibet and Milagro air shower detectors have demonstrated the promise of the direct particle detection technique for TeV gamma rays. At {approx}GeV energies, the Fermi Gamma-ray Space Telescope has increased the number of known sources by nearly an order of magnitude in its first year of operation. New classes of sources that were previously theorized to be gamma-ray emitters have now been confirmed observationally. Moreover, there have been surprise discoveries of GeV gamma-ray emission from source classes for which no theory predicted it was possible. In addition to elucidating the processes of high-energy astrophysics, gamma-ray telescopes are making essential contributions to fundamental physics topics including quantum gravity, gravitational waves, and dark matter. I summarize the current census of astrophysical gamma-ray sources, highlight some recent discoveries relevant to fundamental physics, and describe the synergetic connections between gamma-ray and neutrino astronomy. This is a brief overview intended in particular for particle physicists and neutrino astronomers, based on a presentation at the Neutrino 2010 conference in Athens, Greece. I focus in particular on results from Fermi (which was launched soon after Neutrino 2008), and conclude with a description of the next generation of instruments, namely HAWC and the Cherenkov Telescope Array.

gamma-ray tracking in germanium the backtracking method

CERN Document Server

Marel, J V D

2002-01-01

In the framework of a European TMR network project the concept for a gamma-ray tracking array is being developed for nuclear physics spectroscopy in the energy range of approx 10 keV up to several MeV. The tracking array will consist of a large number of position-sensitive germanium detectors in a spherical geometry around a target. Due to the high segmentation, a Compton scattered gamma-ray will deposit energy in several different segments. A method has been developed to reconstruct the tracks of multiple coincident gamma-rays and to find their initial energies. By starting from the final point the track can be reconstructed backwards to the origin with the help of the photoelectric and Compton cross-sections and the Compton scatter formula. Every reconstructed track is given a figure of merit, thus allowing suppression of wrongly reconstructed tracks and gamma-rays that have scattered out of the detector system. This so-called backtracking method has been tested on simulated events in a shell-like geometry ...

Discovery of a point-like very-high-energy gamma-ray source in Monoceros

International Nuclear Information System (INIS)

Aharonian, F.A.; Benbow, W.; Berge, D.; Bernlohr, K.; Bolz, O.; Braun, I.; Buhler, R.; Carrigan, S.; Costamante, L.; Domainko, W.; Egberts, K.; Forster, A.; Funk, S.; Hauser, D.; Hermann, G.; Hinton, J.A.; Hofmann, W.; Hoppe, S.; Khelifi, B.; Kosack, K.; Masterson, C.; Panter, M.; Rowell, G.; van Eldik, C.; Volk, H.J.; Akhperjanian, A.G.; Sahakian, V.; Bazer-Bachi, A.R.; Borrel, V.; Marcowith, A.; Olive, J.P.; Beilicke, M.; Cornils, R.; Heinzelmann, G.; Raue, M.; Ripken, J.; Bernlohr, K.; Funk, Seb.; Fussling, M.; Kerschhaggl, M.; Lohse, T.; Schlenker, S.; Schwanke, U.; Boisson, C.; Martin, J.M.; Sol, H.; Brion, E.; Glicenstein, J.F.; Goret, P.; Moulin, E.; Rolland, L.

2007-01-01

Aims. The complex Monoceros Loop SNR/Rosette Nebula region contains several potential sources of very-high-energy (VHE) γ-ray emission and two as yet unidentified high-energy EGRET sources. Sensitive VHE observations are required to probe acceleration processes in this region. Methods. The HESS telescope array has been used to search for very high-energy gamma-ray sources in this region. CO data from the NANTEN telescope were used to map the molecular clouds in the region, which could act as target material for γ-ray production via hadronic interactions. Results. We announce the discovery of a new γ-ray source, HESS J0632+057, located close to the rim of the Monoceros SNR. This source is unresolved by HESS and has no clear counterpart at other wavelengths but is possibly associated with the weak X-ray source 1RXS J063258.3+054857, the Be-star MWC148 and/or the lower energy γ-ray source 3EGJ0634+0521. No evidence for an associated molecular cloud was found in the CO data. (authors)

A model problem for restricted-data gamma ray emission tomography of highly active nuclear waste

International Nuclear Information System (INIS)

Cattle, Brian A.

2007-01-01

This paper develops the work of Cattle et al. [Cattle, B.A., Fellerman, A.S., West, R.M., 2004. On the detection of solid deposits using gamma ray emission tomography with limited data. Measurement Science and Technology 15, 1429-1439] by considering a generalization of the model employed therein. The focus of the work is the gamma ray tomographic analysis of high-level waste processing. The work in this paper considers a two-dimensional model for the measurement of gamma ray photon flux, as opposed to the previous one-dimensional analysis via the integrated Beer-Lambert law. The mathematical inverse problem that arises in determining physical quantities from the photon count measurements is tackled using Bayesian statistical methods that are implemented computationally using a Markov chain Monte Carlo (MCMC) approach. In a further new development, the effect of the degree of collimation of the detector on the reliability of the solutions is also considered

Scene data fusion: Real-time standoff volumetric gamma-ray imaging

Energy Technology Data Exchange (ETDEWEB)

Barnowski, Ross [Department of Nuclear Engineering, UC Berkeley, 4155 Etcheverry Hall, MC 1730, Berkeley, CA 94720, United States of America (United States); Haefner, Andrew; Mihailescu, Lucian [Lawrence Berkeley National Lab - Applied Nuclear Physics, 1 Cyclotron Road, Berkeley, CA 94720, United States of America (United States); Vetter, Kai [Department of Nuclear Engineering, UC Berkeley, 4155 Etcheverry Hall, MC 1730, Berkeley, CA 94720, United States of America (United States); Lawrence Berkeley National Lab - Applied Nuclear Physics, 1 Cyclotron Road, Berkeley, CA 94720, United States of America (United States)

2015-11-11

An approach to gamma-ray imaging has been developed that enables near real-time volumetric (3D) imaging of unknown environments thus improving the utility of gamma-ray imaging for source-search and radiation mapping applications. The approach, herein dubbed scene data fusion (SDF), is based on integrating mobile radiation imagers with real-time tracking and scene reconstruction algorithms to enable a mobile mode of operation and 3D localization of gamma-ray sources. A 3D model of the scene, provided in real-time by a simultaneous localization and mapping (SLAM) algorithm, is incorporated into the image reconstruction reducing the reconstruction time and improving imaging performance. The SDF concept is demonstrated in this work with a Microsoft Kinect RGB-D sensor, a real-time SLAM solver, and a cart-based Compton imaging platform comprised of two 3D position-sensitive high purity germanium (HPGe) detectors. An iterative algorithm based on Compton kinematics is used to reconstruct the gamma-ray source distribution in all three spatial dimensions. SDF advances the real-world applicability of gamma-ray imaging for many search, mapping, and verification scenarios by improving the tractiblity of the gamma-ray image reconstruction and providing context for the 3D localization of gamma-ray sources within the environment in real-time.

Advanced techniques for high resolution spectroscopic observations of cosmic gamma-ray sources

International Nuclear Information System (INIS)

Matteson, J.L.; Pelling, M.R.; Peterson, L.E.

1985-08-01

We describe an advanced gamma-ray spectrometer that is currently in development. It will obtain a sensitivity of -4 ph/cm -2 -sec in a 6 hour balloon observation and uses innovative techniques for background reduction and source imaging

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

Science.gov (United States)

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

1994-01-01

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

Gamma ray camera

International Nuclear Information System (INIS)

Wang, S.-H.; Robbins, C.D.

1979-01-01

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 has a negatively charged flat scintillator screen, a flat photocathode layer, and a grounded, flat output phosphor display screen, all of which have the same dimension to maintain unit image magnification; all components are contained within a grounded metallic tube, with a metallic, inwardly curved input window between the scintillator screen and a collimator. The display screen can be viewed by an array of photomultipliers or solid state detectors. There are two photocathodes and two phosphor screens to give a two stage intensification, the two stages being optically coupled by a light guide. (author)

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

Science.gov (United States)

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

1994-01-01

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

High-z semiconductor nuclear radiation detectors for room-temperature gamma-ray spectrometry

International Nuclear Information System (INIS)

Bornand, Bernard; Friant, Alain.

1978-09-01

A bibliographical review (182 articles of periodicals, conferences, reports, thesis and french patents) is presented, as addendum of the report CEA-BIB-210 (1974) on high-Z semiconductor compounds used as materials for the gamma and X-ray detection and spectrometry. This publication reviews issues from 1974 to 1977. References and summaries (in french) are incorporated into 182 bibliograhical notices. Index for authors, corporate authors, documents and periodicals, and subjects is included [fr

Uses of neutron capture gamma-rays in environmental pollution applications

International Nuclear Information System (INIS)

AbdAl-Samad, M.A.

1998-01-01

As a sensitive and accurate technique, the prompt gamma-rays neutron activation is used with success for elemental analysis. The advantages of this method over the other techniques are rapidity, usage of relatively large sample size and high reliability, beside the detection of the elements which have no gamma activity during the delayed neutron activation analysis or very short lived isotopes. Actually different techniques could be used for estimating the trace, minor and major elements of these environmental samples which are considered as complex samples. In the mean time the neutron activation analysis techniques have been improved and have become an excellent tool for elemental analysis of complex samples (Duffey et al., 1970; Senftle et al., 1971; Henkelmm and Born, 1973 ; Hassan et al., .; 1981, 1982, 1983; Clyton et al., 1983; Zaghloul et al., 1993) and the advantages of the prompt γ- ray neutron activation analysis over the other techniques put this technique in the fore front

Gamma-ray flares from the Crab Nebula.

Science.gov (United States)

Abdo, A A; Ackermann, M; Ajello, M; Allafort, A; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bouvier, A; Brandt, T J; Bregeon, J; Brez, A; Brigida, M; Bruel, P; Buehler, R; Buson, S; Caliandro, G A; Cameron, R A; Cannon, A; Caraveo, P A; Casandjian, J M; Çelik, Ö; Charles, E; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Costamante, L; Cutini, S; D'Ammando, F; Dermer, C D; de Angelis, A; de Luca, A; de Palma, F; Digel, S W; do Couto e Silva, E; Drell, P S; Drlica-Wagner, A; Dubois, R; Dumora, D; Favuzzi, C; Fegan, S J; Ferrara, E C; Focke, W B; Fortin, P; Frailis, M; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giglietto, N; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Grenier, I A; Grondin, M-H; Grove, J E; Guiriec, S; Hadasch, D; Hanabata, Y; Harding, A K; Hayashi, K; Hayashida, M; Hays, E; Horan, D; Itoh, R; Jóhannesson, G; Johnson, A S; Johnson, T J; Khangulyan, D; Kamae, T; Katagiri, H; Kataoka, J; Kerr, M; Knödlseder, J; Kuss, M; Lande, J; Latronico, L; Lee, S-H; Lemoine-Goumard, M; Longo, F; Loparco, F; Lubrano, P; Madejski, G M; Makeev, A; Marelli, M; Mazziotta, M N; McEnery, J E; Michelson, P F; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nakamori, T; Naumann-Godo, M; Nolan, P L; Norris, J P; Nuss, E; Ohsugi, T; Okumura, A; Omodei, N; Ormes, J F; Ozaki, M; Paneque, D; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Pierbattista, M; Piron, F; Porter, T A; Rainò, S; Rando, R; Ray, P S; Razzano, M; Reimer, A; Reimer, O; Reposeur, T; Ritz, S; Romani, R W; Sadrozinski, H F-W; Sanchez, D; Saz Parkinson, P M; Scargle, J D; Schalk, T L; Sgrò, C; Siskind, E J; Smith, P D; Spandre, G; Spinelli, P; Strickman, M S; Suson, D J; Takahashi, H; Takahashi, T; Tanaka, T; Thayer, J B; Thompson, D J; Tibaldo, L; Torres, D F; Tosti, G; Tramacere, A; Troja, E; Uchiyama, Y; Vandenbroucke, J; Vasileiou, V; Vianello, G; Vitale, V; Wang, P; Wood, K S; Yang, Z; Ziegler, M

2011-02-11

A young and energetic pulsar powers the well-known Crab Nebula. Here, we describe two separate gamma-ray (photon energy greater than 100 mega-electron volts) flares from this source detected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The first flare occurred in February 2009 and lasted approximately 16 days. The second flare was detected in September 2010 and lasted approximately 4 days. During these outbursts, the gamma-ray flux from the nebula increased by factors of four and six, respectively. The brevity of the flares implies that the gamma rays were emitted via synchrotron radiation from peta-electron-volt (10(15) electron volts) electrons in a region smaller than 1.4 × 10(-2) parsecs. These are the highest-energy particles that can be associated with a discrete astronomical source, and they pose challenges to particle acceleration theory.

Gamma-ray flares from the Crab nebula

International Nuclear Information System (INIS)

Abdo, A.A.; Ackermann, M.; Ajello, M.; Allafort, A.; Baldini, L.; Ballet, J.; Casandjian, J.M.; Grenier, I.A.; Naumann-Godo, M.; Pierbattista, M.; Tibaldo, L.

2011-01-01

A young and energetic pulsar powers the well-known Crab Nebula. Here, we describe two separate gamma-ray (photon energy greater than 100 mega-electron volts) flares from this source detected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The first flare occurred in February 2009 and lasted approximately 16 days. The second flare was detected in September 2010 and lasted approximately 4 days. During these outbursts, the gamma-ray flux from the nebula increased by factors of four and six, respectively. The brevity of the flares implies that the gamma rays were emitted via synchrotron radiation from peta-electron-volt (10 15 electron volts) electrons in a region smaller than 1.4 * 10 -2 parsecs. These are the highest-energy particles that can be associated with a discrete astronomical source, and they pose challenges to particle acceleration theory. (authors)

Detection of explosive substances by tomographic inspection using neutron and gamma-ray spectroscopy

International Nuclear Information System (INIS)

Farahmand, M.; Boston, A.J.; Grint, A.N.; Nolan, P.J.; Joyce, M.J.; Mackin, R.O.; D'Mellow, B.; Aspinall, M.; Peyton, A.J.; Silfhout, R. van

2007-01-01

In recent years the detection and identification of hazardous materials has become increasingly important. This work discusses research and development of a technique which is capable of detecting and imaging hidden explosives. It is proposed to utilise neutron interrogation of the substances under investigation facilitating the detection of emitted gamma radiation and scattered neutrons. Pulsed fast neutron techniques are attractive because they can be used to determine the concentrations of the light elements (hydrogen, carbon, nitrogen, and oxygen) which can be the primary components of explosive materials. Using segmented High Purity Ge (HPGe) detectors and digital pulse processing [R.J. Cooper, G. Turk, A.J. Boston, H.C. Boston, J.R. Cresswell, A.R. Mather, P.J. Nolan, C.J. Hall, I. Lazarus, J. Simpson, A. Berry, T. Beveridge, J. Gillam, R.A. Lewis, in: Proceedings of the 7th International Conference on Position Sensitive Detectors, Nuclear Instruments and Methods A, in press; I. Lazarus, D.E. Appelbe, A. J. Boston, P.J. Coleman-Smith, J.R. Cresswell, M. Descovich, S.A.A. Gros, M. Lauer, J. Norman, C.J. Pearson, V.F.E. Pucknell, J.A. Sampson, G. Turk, J.J. Valiente-Dobon, IEEE Trans. Nucl. Sci., 51 (2004) 1353; R.J. Cooper, A.J. Boston, H.C. Boston, J.R. Cresswell, A.N. Grint, A.R. Mather, P.J. Nolan, D.P. Scraggs, G. Turk, C.J. Hall, I. Lazarus, A. Berry, T. Beveridge, J. Gillam, R.A. Lewis, in: Proceedings of the 11th International Symposium on Radiation Measurements and Application, 2006. ] the scatter path of incident photons can be reconstructed to determine the origin of the gamma-rays without the need for mechanical collimation by applying the Compton camera principle [V. Schonfelder, A. Hirner, K. Schneider, Nucl. Instr. and Meth. 107 (1973) 385; R.W. Todd, J.M. Nightingale, D.B. Everett, Nature 251 (1974) 132. ]. In addition, it is proposed to utilise the scattered neutrons which recoil from the materials being assayed, detecting them with a fast

Examining the nature of very-high-energy gamma-ray emission from the AGN PKS 1222+216 and 3C 279

Science.gov (United States)

Price, Sharleen; Brill, Ari; Mukherjee, Reshmi; VERITAS

2018-01-01

Blazars are a type of active galactic nuclei (AGN) that emit jets of ionized matter which move towards the Earth at relativistic speeds. In this research we carried out a study of two objects, 3C 279 and PKS 1222+216, which belong to the subset of blazars known as FSRQs (flat spectrum radio quasars), the most powerful TeV-detected sources at gamma-ray energies with bolometric luminosities exceeding 1048 erg/s. The high-energy emission of quasars peaks in the MeV-GeV band, making these sources very rarely detectable in the TeV energy range. In fact, only six FSRQs have ever been detected in this range by very-high-energy gamma-ray telescopes. We will present results from observing campaigns on 3C 279 in 2014 and 2016, when the object was detected in high flux states by Fermi-LAT. Observations include simultaneous coverage with the Fermi-LAT satellite and the VERITAS ground-based array spanning four decades in energy from 100 MeV to 1 TeV. We will also report VERITAS observations of PKS 1222+216 between 2008 and 2017. The detection/non-detection of TeV emission during flaring episodes at MeV energies will further contribute to our understanding of particle acceleration and gamma-ray emission mechanisms in blazar jets.

THERMAL X-RAY EMISSION FROM THE SHOCKED STELLAR WIND OF PULSAR GAMMA-RAY BINARIES

Energy Technology Data Exchange (ETDEWEB)

Zabalza, V.; Paredes, J. M. [Departament d' Astronomia i Meteorologia, Institut de Ciencies del Cosmos (ICC), Universitat de Barcelona (IEEC-UB), Marti i Franques 1, E08028 Barcelona (Spain); Bosch-Ramon, V., E-mail: vzabalza@am.ub.es [Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2 (Ireland)

2011-12-10

Gamma-ray-loud X-ray binaries are binary systems that show non-thermal broadband emission from radio to gamma rays. If the system comprises a massive star and a young non-accreting pulsar, their winds will collide producing broadband non-thermal emission, most likely originated in the shocked pulsar wind. Thermal X-ray emission is expected from the shocked stellar wind, but until now it has neither been detected nor studied in the context of gamma-ray binaries. We present a semi-analytic model of the thermal X-ray emission from the shocked stellar wind in pulsar gamma-ray binaries, and find that the thermal X-ray emission increases monotonically with the pulsar spin-down luminosity, reaching luminosities of the order of 10{sup 33} erg s{sup -1}. The lack of thermal features in the X-ray spectrum of gamma-ray binaries can then be used to constrain the properties of the pulsar and stellar winds. By fitting the observed X-ray spectra of gamma-ray binaries with a source model composed of an absorbed non-thermal power law and the computed thermal X-ray emission, we are able to derive upper limits on the spin-down luminosity of the putative pulsar. We applied this method to LS 5039, the only gamma-ray binary with a radial, powerful wind, and obtain an upper limit on the pulsar spin-down luminosity of {approx}6 Multiplication-Sign 10{sup 36} erg s{sup -1}. Given the energetic constraints from its high-energy gamma-ray emission, a non-thermal to spin-down luminosity ratio very close to unity may be required.

Gamma ray generator

Science.gov (United States)

Firestone, Richard B; Reijonen, Jani

2014-05-27

An embodiment of a gamma ray generator includes a neutron generator and a moderator. The moderator is coupled to the neutron generator. The moderator includes a neutron capture material. In operation, the neutron generator produces neutrons and the neutron capture material captures at least some of the neutrons to produces gamma rays. An application of the gamma ray generator is as a source of gamma rays for calibration of gamma ray detectors.

A gamma-ray tracking detector for molecular imaging

International Nuclear Information System (INIS)

Hall, C.J.; Lewis, R.A.; Helsby, W.I.; Nolan, P.; Boston, A.

2003-01-01

A design for a gamma-ray detector for molecular imaging is presented. The system is based on solid-state strip detector technology. The advantages of position sensitivity coupled with fine spectral resolution are exploited to produce a tracking detector for use with a variety of isotopes in nuclear medicine. Current design concepts employ both silicon and germanium layers to provide an energy range from 60 keV to >1 MeV. This allows a reference X-ray image to be collected simultaneously with the gamma-ray image providing accurate anatomical registration. The tracking ability of the gamma-ray detector allows ambiguities in the data set to be resolved which would otherwise cause events to be rejected in standard non-tracking system. Efficiency improvements that high solid angle coverage and the use of a higher proportion of events make time resolved imaging and multi-isotope work possible. A modular detector system, designed for viewing small animals has been accepted for funding

GAMMA-RAYS FROM THE QUASAR PKS 1441+25: STORY OF AN ESCAPE

Energy Technology Data Exchange (ETDEWEB)

Abeysekara, A. U. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Archambault, S. [Physics Department, McGill University, Montreal, QC H3A 2T8 (Canada); Archer, A.; Buckley, J. H.; Bugaev, V. [Department of Physics, Washington University, St. Louis, MO 63130 (United States); Aune, T. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Barnacka, A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Benbow, W.; Cerruti, M. [Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645 (United States); Bird, R. [School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland); Biteau, J. [Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, CA 95064 (United States); Cardenzana, J. V. [Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); Chen, X. [Institute of Physics and Astronomy, University of Potsdam, D-14476 Potsdam-Golm (Germany); Christiansen, J. L. [Physics Department, California Polytechnic State University, San Luis Obispo, CA 94307 (United States); Ciupik, L. [Astronomy Department, Adler Planetarium and Astronomy Museum, Chicago, IL 60605 (United States); Connolly, M. P. [School of Physics, National University of Ireland Galway, University Road, Galway (Ireland); Coppi, P. [Department of Astronomy, Yale University, New Haven, CT 06520-8101 (United States); Cui, W. [Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907 (United States); Dickinson, H. J.; Dumm, J., E-mail: matteo.cerruti@cfa.harvard.edu, E-mail: caajohns@ucsc.edu, E-mail: jbiteau@ucsc.edu, E-mail: biteau@ipno.in2p3.fr, E-mail: mcerruti@lpnhe.in2p3.fr, E-mail: mark.lang@nuigalway.ie [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States); Collaboration: VERITAS; SPOL; ASAS-SN; OVRO; NuSTAR; CRTS; and others

2015-12-20

Outbursts from gamma-ray quasars provide insights on the relativistic jets of active galactic nuclei and constraints on the diffuse radiation fields that fill the universe. The detection of significant emission above 100 GeV from a distant quasar would show that some of the radiated gamma-rays escape pair-production interactions with low-energy photons, be it the extragalactic background light (EBL), or the radiation near the supermassive black hole lying at the jet’s base. VERITAS detected gamma-ray emission up to ∼200 GeV from PKS 1441+25 (z = 0.939) during 2015 April, a period of high activity across all wavelengths. This observation of PKS 1441+25 suggests that the emission region is located thousands of Schwarzschild radii away from the black hole. The gamma-ray detection also sets a stringent upper limit on the near-ultraviolet to near-infrared EBL intensity, suggesting that galaxy surveys have resolved most, if not all, of the sources of the EBL at these wavelengths.

Processing of gamma-ray spectrometric logs

International Nuclear Information System (INIS)

Umiastowski, K.; Dumesnil, P.

1984-10-01

CEA (Commissariat a l'Energie Atomique) has developped a gamma-ray spectrometric tool, containing an analog-to-digital converter. This new tool permits to perform very precise uranium logs (natural gamma-ray spectrometry), neutron activation logs and litho-density logs (gamma-gamma spectrometric logs). Specific processing methods were developped to treate the particular problems of down-hole gamma-ray spectrometry. Extraction of the characteristic gamma-ray peak, even if they are superposed on the background radiation of very high intensity, is possible. This processing methode enables also to obtain geological informations contained in the continuous background of the spectrum. Computer programs are written in high level language for SIRIUS (VICTOR) and APOLLO computers. Exemples of uranium and neutron activation logs treatment are presented [fr

Open high-level data formats and software for gamma-ray astronomy

Science.gov (United States)

Deil, Christoph; Boisson, Catherine; Kosack, Karl; Perkins, Jeremy; King, Johannes; Eger, Peter; Mayer, Michael; Wood, Matthew; Zabalza, Victor; Knödlseder, Jürgen; Hassan, Tarek; Mohrmann, Lars; Ziegler, Alexander; Khelifi, Bruno; Dorner, Daniela; Maier, Gernot; Pedaletti, Giovanna; Rosado, Jaime; Contreras, José Luis; Lefaucheur, Julien; Brügge, Kai; Servillat, Mathieu; Terrier, Régis; Walter, Roland; Lombardi, Saverio

2017-01-01

In gamma-ray astronomy, a variety of data formats and proprietary software have been traditionally used, often developed for one specific mission or experiment. Especially for ground-based imaging atmospheric Cherenkov telescopes (IACTs), data and software are mostly private to the collaborations operating the telescopes. However, there is a general movement in science towards the use of open data and software. In addition, the next-generation IACT instrument, the Cherenkov Telescope Array (CTA), will be operated as an open observatory. We have created a Github organisation at https://github.com/open-gamma-ray-astro where we are developing high-level data format specifications. A public mailing list was set up at https://lists.nasa.gov/mailman/listinfo/open-gamma-ray-astro and a first face-to-face meeting on the IACT high-level data model and formats took place in April 2016 in Meudon (France). This open multi-mission effort will help to accelerate the development of open data formats and open-source software for gamma-ray astronomy, leading to synergies in the development of analysis codes and eventually better scientific results (reproducible, multi-mission). This write-up presents this effort for the first time, explaining the motivation and context, the available resources and process we use, as well as the status and planned next steps for the data format specifications. We hope that it will stimulate feedback and future contributions from the gamma-ray astronomy community.

Supernova sheds light on gamma-ray bursts

CERN Multimedia

2003-01-01

On 29 March the HETE-II satellite detected the most violent explosion in the universe to date - an enormous burst of gamma rays. Observers across the world recorded and studied the event. It appears to prove that gamma ray bursts originate in supernovae (1 page)

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

Science.gov (United States)

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.

Self-powered neutron and gamma-ray flux detector

International Nuclear Information System (INIS)

Allan, C.J.; Shields, R.B.; Lynch, G.F.; Cuttler, J.M.

1980-01-01

A new type of self-powered neutron detector was developed which is sensitive to both the neutron and gamma-ray fluxes. The emitter comprises two parts. The central emitter core is made of materials that generate high-energy electrons on exposure to neutrons. The outer layer acts as a gamma-ray/electron converter, and since it has a higher atomic number and higher back-scattering coefficient than the collector, increases the net outflow or emmission of electrons. The collector, which is around the emitter outer layer, is insulated from the outer layer electrically with dielectric insulation formed from compressed metal-oxide powder. The fraction of electrons given off by the emitter that is reflected back by the collector is less than the fraction of electrons emitted by the collector that is reflected back by the emitter. The thickness of the outer layer needed to achieve this result is very small. A detector of this design responds to external reactor gamma-rays as well as to neutron capture gamma-rays from the collector. The emitter core is either nickel, iron or titanium, or alloys based on these metals. The outer layer is made of platinum, tantalum, osmium, molybdenum or cerium. The detector is particularly useful for monitoring neutron and gamma ray flux intensities in nuclear reactor cores in which the neutron and gamma ray flux intensities are closely proportional, are unltimately related to the fission rate, and are used as measurements of nuclear reactor power. (DN)

Prompt gamma-ray analysis using JRR-3M cold and thermal neutron guide beams

International Nuclear Information System (INIS)

Yonezawa, C.; Haji Wood, A.K.; Magara, M.; Hoshi, M.; Tachikawa, E.; Sawahata, H.; Ito, Y.

1993-01-01

A permanent and stand-alone neutron-induced prompt gamma-ray analysis (PGA) system, usable at both cold and thermal neutron beam guides of JRR-3M has been constructed. Neutron flux at the sample positions were 1.4x10 8 and 2.4x10 7 n cm -2 s -1 for the cold and thermal neutrons, respectively. The γ-ray spectrometer is equipped to acquire three modes of spectra simultaneously: single mode, Compton suppression mode and pair mode, in an energy range up to 12 MeV. Owing to the cold neutron guide beam and the low γ-ray background system, analytical sensitivities and detection limits better than those in other PGA systems have been achieved. Analytical sensitivity and detection limit for 73 elements were measured. Boron, Gd, Sm and Cd are the most sensitive elements with detection limits down to 1 to 10 ng. For some elements such as F, Al, V, Eu and Hf, decay γ-rays are more sensitive compared to their respective prompt γ-ray. Analytical sensitivity of several heavy elements through detection of characteristic X-rays was higher than that through the prompt γ-ray detection. Analytical applicability of some sensitive elements such as B, H, Gd and Sm were examined. Isotopic analysis of Ni and Si were also examined. (author)

ICF burn-history measurments using 17-MeV fusion gamma rays