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1

Design of a MultiChannel UltraHigh Resolution Superconducting Gamma-Ray Spectrometer  

Microsoft Academic Search

Superconducting Gamma-ray microcalorimeters operated at temperatures around 0.1 K offer an order of magnitude improvement in energy resolution over conventional high-purity Germanium spectrometers. The calorimeters consist of a 1 mm³ superconducting or insulating absorber and a sensitive thermistor, which are weakly coupled to a cold bath. Gamma-ray capture increases the absorber temperature in proportion to the Gamma-ray energy, this is

Stephan Friedrich; Stephane F. Terracol; Toshiyuki Miyazaki; Owen B. Drury; Zaheer A. Ali; Mark F. Cunningham; Thomas R. Niedermayr; Troy W. Barbee Jr; Jan D. Batteux; Simon E. Labov

2004-01-01

2

Detecting Gamma-Ray Bursts with Ultra-High Energy Neutrinos  

NASA Astrophysics Data System (ADS)

Gamma-ray bursts are candidate sources of ultra-high energy cosmic rays and neutrinos. While cosmic rays are scattered in the intervening magnetic field, neutrinos point back to their sources being charge neutral and make neutrino astronomy possible. Detection of ultrahigh energy neutrinos by future experiments such as ANITA, ANTARES, Ice-Cube and RICE can provide useful information such as particle acceleration, radiation mechanism and magnetic field about the sources and their progenitors. Detection of ultrahigh energy neutrinos which point back to their sources may establish gamma-ray bursts as the sources of GZK cosmic rays.

Razzaque, Soebur; Mészáros, Peter; Waxman, Eli

3

PANGU: A High Resolution Gamma-Ray Space Telescope  

NASA Astrophysics Data System (ADS)

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

Su, Meng

2014-08-01

4

Development of a high resolution scintillating fiber gamma ray telescope  

Microsoft Academic Search

We report on the initia development and testing of a Compton telescope that is composed of scintillating fibers and position sensitive photomultiphers. Initial tests of the telescope result in a 17.5 mrad (rms) angular resolution for 1.2 MeV photons from a collimated 60Co gamma source. This type of device can be used for constructing large area telescopes for gamma ray

P. Antich; M. Atac; R. Chaney; D. Chrisman; D. Cline; E. Fenyves

1990-01-01

5

WINKLER - An imaging high resolution gamma-ray spectrometer  

Microsoft Academic Search

The WINKLER high-resolution gamma-ray spectrometer was originally developed to fly on a high-altitude aircraft. Following the discovery of Supernova 1987A in the Large Magellanic Cloud, arrangements were made to perform balloon-borne observations of this event. The instrument was quickly adapted to fit on a gondola furnished by NASA\\/MSFC in a collaborative effort and was flown in a series of three

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

1991-01-01

6

WINKLER: An imaging high resolution gamma-ray spectrometer  

Microsoft Academic Search

The WINKLER high-resolution gamma-ray spectrometer was originally developed to fly on a high-altitude aircraft. Following the discovery of Supernova 1987A in the Large Magellanic Cloud arrangements were made to perform balloon-borne observations of this event. The instrument was quickly adapted to fit on a gondola furnished by NASA\\/MSFC in a collaborative effort and was flown in a series of three

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

1991-01-01

7

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

NASA Astrophysics Data System (ADS)

Ultra-high energy cosmic rays interacting with the radiation fields in the universe cause electromagnetic cascades resulting in a flux of extragalactic gamma rays, detectable to some 100 GeV. Recent precise measurements of the extragalactic gamma ray flux by Fermi-LAT, coupled with estimates of the background from active galactic nuclei of various types, allows limits to be set on the cascade component. By comparison with prediction and, making various assumptions, i.e. taking a particular model, limits can be set on the maximum energy to which ultra-high energy particles can be accelerated. If our model is correct, it is unlikely that the maximum energy is above 100 EeV, in turn, the apparent ‘GZK’ cut-off in the measured ultra-high energy spectrum could instead be due to a fall-off in the intrinsic emergent particle spectrum. However, it is not possible to be dogmatic at the present time because of uncertainty in many of the parameters involved. We have used recent estimates of the range of parameters and have found that although our model has parameters in the allowable ranges the uncertainties are so large that our result is not unique, although the method is satisfactory. The result must thus, so far, be taken as an indication only.

Erlykin, A. D.; Wolfendale, A. W.

2014-07-01

8

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

PubMed

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

Gabici, Stefano; Aharonian, Felix A

2005-12-16

9

Superconducting High Energy Resolution Gamma-ray Spectrometers  

SciTech Connect

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

Chow, D T

2002-02-22

10

Generation of ultrahigh-energy gamma rays in accreting x ray pulsars  

NASA Technical Reports Server (NTRS)

Relativistic protons producing ultrahigh energy gamma rays as a result of nuclear collisions ought to be generated in close proximity to the surface of a neutron star due to accretion. The main features of the mechanism in question are a high efficiency of conversion of the gravitational energy of the accreting matter into acceleration energy and a high efficiency of the acceleration itself. It is shown that in accretion to a neutron star with a strong magnetic field, a loss cone type distribution of accreting protons is formed, which due to instability effectively generates small scale Alfven and proton cyclotron waves, as well as nonlinear waves (magneto-acoustic and Alfven solitons). The electric field of the moving solitons may accelerate the protons to energies of greater than 10(exp 15) eV. The region of acceleration is not locally isolated, but extends from its surface. New possible sources of ultrahigh energy gamma rays are predicted. They may be binary x ray systems containing neutron stars with magnetic fields of about 10(exp 9) gauss.

Gnedin, Yu. N.; Ikhsanov, N. R.

1991-01-01

11

High-resolution gamma-ray spectrometry in uranium exploration  

USGS Publications Warehouse

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

Moxham, Robert M.; Tanner, Allan B.

1977-01-01

12

High Resolution Radionuclide Imaging Using Focusing Gamma-Ray Optics  

SciTech Connect

Significant effort is being devoted to the development of noninvasive imaging systems that allow in vivo assessment of biological and biomolecular interactions in mice and other small animals. Although single-photon emission tomography (SPECT) and positron emission tomography (PET) are well-matched to the study of physiological function in small animals, the spatial resolutions of 1-2 mm currently achievable with these techniques limits the types of research possible. For this reason, we are developing a small animal radionuclide imaging system using grazing incidence optics to focus the low-energy gamma-rays emitted by {sup 125}I, {sup 95m}Tc, {sup 96}Tc, and {sup 99m}Tc. We compare this approach to the more traditional use of absorptive collimation.

Pivovaroff, M; Craig, W; Ziock, K; Barber, W; Funk, T; Hasegawa, B; Taylor, C

2004-02-27

13

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

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

14

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

NASA Astrophysics Data System (ADS)

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

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

1990-03-01

15

Design of a multichannel ultra-high-resolution superconducting gamma-ray spectrometer  

Microsoft Academic Search

Superconducting Gamma-ray microcalorimeters operated at temperatures around ~0.1 K offer an order of magnitude improvement in energy resolution over conventional high-purity Germanium spectrometers. The calorimeters consist of a ~1 mm3 superconducting or insulating absorber and a sensitive thermistor, which are weakly coupled to a cold bath. Gamma-ray capture increases the absorber temperature in proportion to the Gamma-ray energy, this is

Stephan F. Friedrich; Stephane F. Terracol; Toshiyuki Miyazaki; Owen B. Drury; Zaheer A. Ali; Mark F. Cunningham; Thomas R. Niedermayr; Troy W. Barbee Jr.; Jan D. Batteux; Simon E. Labov

2004-01-01

16

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

SciTech Connect

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

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

2011-08-01

17

The First Limits on the Ultra-high Energy Neutrino Fluence from Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

We set the first limits on the ultra-high energy (UHE) neutrino fluence at energies greater than 109 GeV from gamma-ray bursts (GRBs) based on data from the second flight of the Antarctic Impulsive Transient Antenna (ANITA). During the 31 day flight of ANITA-II, 26 GRBs were recorded by Swift or Fermi. Of these, we analyzed the 12 GRBs which occurred during quiet periods when the payload was away from anthropogenic activity. In a blind analysis, we observe 0 events on a total background of 0.0044 events in the combined prompt window for all 12 low-background bursts. We also observe 0 events from the remaining 14 bursts. We place a 90% confidence level limit on the E -4 prompt neutrino fluence between 108 GeV < E < 1012 GeV of E 4? = 2.5 × 1017 GeV3 cm-2 from GRB090107A. This is the first reported limit on the UHE neutrino fluence from GRBs above 109 GeV, and the strongest limit above 108 GeV.

Vieregg, A. G.; Palladino, K.; Allison, P.; Baughman, B. M.; Beatty, J. J.; Belov, K.; Besson, D. Z.; Bevan, S.; Binns, W. R.; Chen, C.; Chen, P.; Clem, J. M.; Connolly, A.; Detrixhe, M.; De Marco, D.; Dowkontt, P. F.; DuVernois, M.; Gorham, P. W.; Grashorn, E. W.; Hill, B.; Hoover, S.; Huang, M.; Israel, M. H.; Javaid, A.; Liewer, K. M.; Matsuno, S.; Mercurio, B. C.; Miki, C.; Mottram, M.; Nam, J.; Nichol, R. J.; Romero-Wolf, A.; Ruckman, L.; Saltzberg, D.; Seckel, D.; Varner, G. S.; Wang, Y.

2011-07-01

18

Origin of Ultra-High Energy Cosmic Rays: Nuclear Composition of Gamma-Ray Burst Jets  

NASA Astrophysics Data System (ADS)

Ultra-high energy cosmic rays (UHECRs) are the most energetic particles flying from space and their source is not clarified yet. Recently, the Pierre Auger Observatory (PAO) suggests that UHECRs involve heavy nuclei. The PAO results require that a considerable fraction of metal nuclei must exist in the accelerating site, which can be realized only in the stellar interior. This puts strong constraints on the origin of UHECRs. In order to definitize the constraints from PAO results, we investigate the fraction of metal nuclei in a relativistic jet in gamma-ray burst associated with core-collapse supernova. If the jet is initially dominated by radiation field, quasi-statistical equilibrium (QSE) is established and heavy nuclei are dissociated to light particles such as 4He during the acceleration and expansion. On the other hand, if the jet is mainly accelerated by magnetic field heavy or intermediate mass nuclei can survive. The criterion to contain the metal nuclei is that the temperature at the launch site is below 4.5 × 109K. Therefore, if the composition of UHECRs is dominated by metal nuclei, a GRB with the magnetized jet is the most plausible candidate of the accelerating site.

Shibata, Sanshiro; Tominaga, Nozomu

2012-09-01

19

Origin of Ultra-High Energy Cosmic Rays: Nuclear Composition of Gamma-ray Burst Jets  

NASA Astrophysics Data System (ADS)

Recent results from the Pierre Auger Observatory (PAO) suggest that ultra-high energy cosmic rays (UHECRs) involve heavy or intermediate mass nuclei. This indicates that a considerable fraction of heavy nuclei must exist in the accelerating sites. Here, we focus on relativistic jets in gamma-ray bursts associated with core-collapse supernovae, which could contain large amount of metal. We investegate the dependence of nuclear composition on the outflow parameters. We show that when ratio of thermal to total energy density at initial radius of the outflow is high, heavy nuclei are dissociated to light particles such as ?-particles during the expansion, even if the outflow initially consists of heavy and intermediate nuclei. This result demonstrates that nuclear composition of the outflow in standard fireball model is dominated by light particles after the acceleration. However, we suggest that if the jets are accelerated by magnetic field, fraction of thermal energy in the jets is not necessarily high and metal nuclei could survive in the jets.

Shibata, Sanshiro; Tominaga, Nozomu

2011-09-01

20

Ultra-high resolution computed tomography imaging  

DOEpatents

A method for ultra-high resolution computed tomography imaging, comprising the steps of: focusing a high energy particle beam, for example x-rays or gamma-rays, onto a target object; acquiring a 2-dimensional projection data set representative of the target object; generating a corrected projection data set by applying a deconvolution algorithm, having an experimentally determined a transfer function, to the 2-dimensional data set; storing the corrected projection data set; incrementally rotating the target object through an angle of approximately 180.degree., and after each the incremental rotation, repeating the radiating, acquiring, generating and storing steps; and, after the rotating step, applying a cone-beam algorithm, for example a modified tomographic reconstruction algorithm, to the corrected projection data sets to generate a 3-dimensional image. The size of the spot focus of the beam is reduced to not greater than approximately 1 micron, and even to not greater than approximately 0.5 microns.

Paulus, Michael J. (Knoxville, TN); Sari-Sarraf, Hamed (Knoxville, TN); Tobin, Jr., Kenneth William (Harriman, TN); Gleason, Shaun S. (Knoxville, TN); Thomas, Jr., Clarence E. (Knoxville, TN)

2002-01-01

21

CeBr 3 as a room-temperature, high-resolution gamma-ray detector  

Microsoft Academic Search

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

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

2009-01-01

22

High resolution gamma-ray spectroscopy with high-Z thermal detectors  

NASA Astrophysics Data System (ADS)

A massive thermal detector consisting of a 73 g TeO2 crystal, to be used to search for double beta decay of Te-130 and to detect high energy gamma-rays, is operating at aprox. 15 mK in the Gran Sasso Underground Laboratory. The FWHM resolution achieved with this detector is 5-8 KeV, slightly dependent on energy from 100 KeV to 3 MeV, showing the competitive performances of this detector in gamma-ray spectroscopy comparable with those of conventional Ge solid state detectors. Moreover this is the first massive high-resolution gamma-ray detector of atomic number larger than 32, which implies a peak to Compton ratio comparable to that of a Ge diode of a mass larger by an order of magnitude.

Alessandrello, A.; Brofferio, C.; Camin, D. V.; Cremonesi, O.; Fiorini, E.; Gervasio, G.; Giuliani, A.; Pavan, M.; Pessina, G.; Previtali, E.

1992-12-01

23

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

DOEpatents

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

Smither, Robert K. (Hinsdale, IL) [Hinsdale, IL

2011-05-17

24

Search for point sources of ultrahigh energy gamma rays in the southern sky  

Microsoft Academic Search

A search for point sources of gamma rays with energies >~100 TeV which has been made by the JANZOS Collaboration using an array of plastic scintillators located at Black Birch mountain in New Zealand is reported. The physical characteristics of the array are described, and also the techniques which have been used to analyze the data. Measurements of the angular

W. H. Allen; I. A. Bond; E. Budding; M. J. Conway; A. Daniel; K. B. Fenton; H. Fujii; Z. Fujii; N. Hayashida; K. Hibino; M. Honda; J. E. Humble; S. Kabe; K. Kasahara; T. Kifune; G. D. Lythe; A. Masaike; Y. Matsubara; K. Mitsui; Y. Miura; M. Mori; Y. Muraki; M. Nagano; T. Nakamura; M. Nishizawa; P. M. Morris; S. Ogio; To. Saito; M. Sakata; H. Sato; H. M. Shimizu; M. Spencer; J. R. Storey; T. Tanimori; M. Teshima; S. Torii; A. Wadsworth; Y. Watase; M. D. Woodhams; Y. Yamamoto; P. C. Yock; T. Yuda

1993-01-01

25

High resolution gamma ray detection in a dual phase xenon time projection chamber  

NASA Astrophysics Data System (ADS)

Dual phase Xenon Time Projection Chambers (XeTPCs) are being used by several experiments as a promising technique for direct detection of dark matter. We report on the design and performance of a small 3-D sensitive dual phase XeTPC. The position resolution is 2 mm in the center of detector, limited by the hole size of the mesh at the proportional scintillation region. An energy resolution of 1.6%(?/E) for 662 keV gamma rays is achieved in the very center of the detector by combining the ionization and scintillation signals at a drift field of 0.5 kV/cm. This represents the best energy resolution achieved among liquid xenon detectors to date. The energy resolution is only slightly dependent on the drift field. Better than 2% energy resolution (?/E) for 662 keV gamma rays was achieved for drift fields between 100 V/cm and 2 kV/cm. If such a high position and energy resolution can be achieved in a large volume detector, the dual phase XeTPC will have potential applications in surveys of neutrinoless double-beta decay and in gamma ray imaging.

Lin, Q.; Wei, Y.; Bao, J.; Hu, J.; Li, X.; Lorenzon, W.; Ni, K.; Schubnell, M.; Xiao, M.; Xiao, X.

2014-04-01

26

TeV Gamma Rays from Ultrahigh Energy Cosmic Ray Interactions in the Cores of Active Galactic Nuclei: Lessons from Centaurus A  

NASA Astrophysics Data System (ADS)

TeV gamma rays have been observed from blazars as well as from radio galaxies like M 87 and Centaurus A. In leptonic models, gamma rays above the pair production threshold can escape from the ultra-relativistic jet, because large Lorentz factors reduce the background photon densities compared to those required for isotropic emission. Here we discuss an alternative scenario, where very high energy photons are generated as secondaries from ultrahigh energy cosmic rays interactions in the cores of active galactic nuclei. We show that TeV gamma-rays can escape from the core despite large infrared and ultraviolet backgrounds. For the special case of Centaurus A, we study whether the various existing observations from the far infrared to the ultrahigh energy range can be reconciled within this picture.

Kachelrieß, M.; Ostapchenko, S.; Tomàs, R.

2010-10-01

27

Ge-diode detector combined with crystal-diffraction spectrometer permits high-resolution gamma ray spectroscopy  

NASA Technical Reports Server (NTRS)

Crystal-diffraction spectrometer, combined with a lithium-drifted Ge-diode detector, performs high-resolution gamma ray spectroscopy on the complicated neutron-capture gamma ray spectra. The system is most useful in the 1-3 MeV energy range and improves the signal to background ratio.

Namenson, A. I.; Smither, R. K.

1969-01-01

28

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

SciTech Connect

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

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

2013-03-15

29

Effect of stainless-steel containers on high-resolution gamma-ray analysis of plutonium  

Microsoft Academic Search

The goal of this work was to determine the effects on plutonium isotopic analysis of having plutonium inside of a 0.25 inch thick stainless steel can. To do this, they analyzed plutonium samples with a U-Pu InSpector (which uses a high-resolution gamma-ray detector and the analysis code MGA (Multi Group Analysis)), to determine both the 240-Pu\\/239-Pu ratio and the years

R Dougan; Z Koenig; B Kitt

2000-01-01

30

Spatial variation of energy resolution in 3-D position sensitive CZT gamma-ray spectrometers  

Microsoft Academic Search

This paper reports the energy resolutions obtained from two 3-D CZT ?-ray spectrometers. Each device is a 1 cm3 cube CZT crystal with an 11×11 pixellated anode. For single-interaction events in the detector, the gamma ray interaction location can be determined in 3-D. With the volume of each detector conceptually divided into 11×11×18 voxels, the spectra of single-interaction events from

W. Li; Z. He; G. F. Knoll; D. K. Wehe; C. M. Stahle

1999-01-01

31

VOID MEASUREMENT IN BOILING WATER REACTOR ROD BUNDLES USING HIGH RESOLUTION GAMMA RAY TOMOGRAPHY  

Microsoft Academic Search

We present a high resolution gamma ray computed tomography (CT) system that can be used for averaged void distribution measurements in sub-channels of fuel rod bundles. This measurement system generates cross sectional void fraction profiles through the pressure vessel for true-to-scale fuel rod bundles operating under typical nuclear reaction conditions and in steady state. Measurements are non invasive, thus the

André Bieberle; Dietrich Hoppe; Cornelius Zippe; Eckhard Schleicher; Martin Tschofen; Tobias Suehnel; Wilfried Zimmermann; Uwe Hampel

32

High resolution X- and gamma-ray spectroscopy of cosmic X-ray sources  

NASA Technical Reports Server (NTRS)

A high resolution X-ray spectrometer and large area phoswich detector were designed and co-aligned in a common elevation mounting in order to measure solar and cosmic X-ray and gamma ray emission in the 13 to 600 KeV energy range from a balloon. The instrument is described and results obtained for the Crab Nebula, the supernova remnant Cas A, and the Sun are discussed and analyzed.

Lin, R. P.

1983-01-01

33

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

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

34

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

DOEpatents

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

Smither, Robert K. (Hinsdale, IL)

2008-12-23

35

High resolution X- and gamma-ray spectroscopy of solar flares  

NASA Technical Reports Server (NTRS)

A balloon-borne X- and gamma-ray instrument was developed, fabricated, and flown. This instrument has the highest energy resolution of any instrument flown to date for measurements of solar and cosmic X-ray and gamma-ray emission in the 13 to 600 keV energy range. The purpose of the solar measurements was to study electron acceleration and solar flare energy release processes. The cosmic observations were to search for cyclotron line features from neutron stars and for low energy gamma-ray lines from nucleosynthesis. The instrument consists of four 4 cm diameter, 1.3 cm thick, planar intrinsic germanium detectors cooled by liquid nitrogen and surrounded by CsI and NaI anti-coincidence scintillation crystals. A graded z collimator limited the field of view to 3 deg x 6 deg and a gondola pointing system provided 0.3 deg pointing accuracy. A total of four flights were made with this instrument. Additional funding was obtained from NSF for the last three flights, which had primarily solar objectives. A detailed instrument description is given. The main scientific results and the data analysis are discussed. Current work and indications for future work are summarized. A bibliography of publications resulting from this work is given.

Lin, R. P.

1984-01-01

36

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

NASA Astrophysics Data System (ADS)

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

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

1988-09-01

37

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

USGS Publications Warehouse

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

Day, Jr. , J. H.

1985-01-01

38

CeBr3 as a High-Resolution Gamma-Ray Detector  

SciTech Connect

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

Michael Reed, Paul Guss, Christopher Contreras

2008-11-13

39

A balloon investigation of galactic gamma-ray lines with a high resolution Ge\\/Li\\/ spectrometer  

Microsoft Academic Search

An experimental search for diffuse galactic gamma-ray lines using a balloon-borne Ge(Li) detector is reported. The high-resolution Ge(Li) detector surrounded by a plastic scintillator shield was used to search for 0.2- to 6-MeV gamma ray lines during a 26-hour scan of the galactic plane between longitudes of 40 to 210 deg. Upper limits to the intensity of galactic plane emission

M. Yoshimori; H. Watanabe; K. Okudaira; Y. Hirasima; H. Murakami

1979-01-01

40

Large-Area Microcalorimeter Detectors for Ultra-High-Resolution X-Ray and Gamma-Ray Spectroscopy  

Microsoft Academic Search

We discuss recent developments in using cryogenic microcalorimeter detectors for x- and gamma-ray spectroscopy. We are currently operating a detector array consisting of thirteen pixels with time-domain multiplexed readout. With a single pixel from this detector, we have measured 97.43-keV gamma rays from 153-Gd with 22-eV resolution (FWHM). We have also made the first multiplexed array measurements of plutonium x-

M. K. Bacrania; A. S. Hoover; P. J. Karpius; M. W. Rabin; C. R. Rudy; D. T. Vo; J. A. Beall; D. A. Bennett; W. B. Doriese; G. C. Hilton; R. D. Horansky; K. D. Irwin; N. Jethava; E. Sassi; J. N. Ullom; L. R. Vale

2009-01-01

41

Paradoxes of steady-state and pulse operational mode characteristics of silicon detectors irradiated by ultra-high doses of gamma-rays  

Microsoft Academic Search

Detectors processed from standard and oxygenated Si are compared with respect to radiation hardness to ultra-high dose of gamma-rays up to 1.76Grad. The detectors are processed by different manufactures: Silicon Detector Development and Processing Lab (SDDPL) of BNL (USA), CIS (Germany) and Micron Semiconductor (UK). Oxygenation was performed either by using High Temperature, Long Time (HTLT) oxidation in oxygen-based ambient,

Z. Li; E. Verbitskaya; E. Fretwurst; J. Kierstead; V. Eremin; I. Ilyashenko; R. Röder; C. Wilburn

2003-01-01

42

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

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

43

Novel high-resolution PeV gamma-ray telescope  

Microsoft Academic Search

Most high energy Cosmic Rays are charged but a few are gamma rays generated by extremely energetic processes which are not understood. Precise directions for the gamma rays will indicate their sources. The most energetic gamma rays produce Extensive Air Showers (EAS) in the atmosphere. From the earliest days of radar there have been attempts to use radio techniques to

John E. Baruch; N. J. McEwan; R. I. Davis

1993-01-01

44

High vertical resolution spectral gamma ray logging in shallow water carbonates  

NASA Astrophysics Data System (ADS)

Spectral gamma-ray logs provide one of the best means to investigate the mineralogy of thin-bedded sedimentary sequences, to correlate among different logging runs, and to compare logging data and core measurements. Increasing vertical resolution over currently available tools provides new opportunities for: a) log analysis in reservoirs with rapidly changing lithology, and b) extracting high-frequency climate changes from sedimentary cycles. Given known borehole geometry, optimal logging speed and sampling rate, the vertical resolution can only be enhanced by decreasing the detector length. The low counting efficiency and high statistical fluctuation inherent in small crystals, however, limit the improvement in resolution achievable in this manner. To overcome these limitations, we use an innovative approach based on real-time stacking of output signals from an array of small detectors that has been implemented in a Multi-sensor spectral Gamma ray Tool (MGT) developed for the Ocean Drilling Program. The MGT uses an array of independent, self-contained gamma spectrometry modules with 2-ft spacing. Each module comprises a 2"x4" NaI detector, a programmable 256-channel amplitude analyzer, and an individual spectrum stabilization system based on an Am241 calibration source. The spectral resolution of the stacked data is therefore the same as for each individual detector ( ~8%). The tool also includes an accelerometer to improve data stacking based on the precise measurement of logging speed. A specialized telemetry system developed for the MGT allows it to be combined with other commercial logging devices. The results of field tests using this tool are presented from the shallow water carbonates drilled by ODP Leg 194, Site 1194, offshore eastern Australia on the Marion Plateau. Comparison of MGT and Schlumberger gamma-ray tool data confirms that the MGT has vertical resolution 3 to 4 times better than conventional logging tools at common logging speeds. The improved vertical resolution enables the identification of high order cycles (<1 m thickness) in the thinly bedded successions of hemipelagic sediments. This result is of major interest for paleoceanographic studies of drilled sequences.

Delius, H.; Goldberg, D.; Meltser, A.; Eberli, G.

2001-05-01

45

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

PubMed

We report on the development of a high resolution gamma ray tomography scanner that is operated with a Cs-137 isotopic source at 662 keV gamma photon energy and achieves a spatial image resolution of 0.2 line pairs/ mm at 10% modulation transfer function for noncollimated detectors. It is primarily intended for the scientific study of flow regimes and phase fraction distributions in fuel element assemblies, chemical reactors, pipelines, and hydrodynamic machines. Furthermore, it is applicable to nondestructive testing of larger radiologically dense objects. The radiation detector is based on advanced avalanche photodiode technology in conjunction with lutetium yttrium orthosilicate scintillation crystals. The detector arc comprises 320 single detector elements which are operated in pulse counting mode. For measurements at fixed vessels or plant components, we built a computed tomography scanner gantry that comprises rotational and translational stages, power supply via slip rings, and data communication to the measurement personal computer via wireless local area network. PMID:17979425

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

2007-10-01

46

Development of a High Resolution Liquid Xenon Imaging Telescope for Medium Energy Gamma Ray Astrophysics  

NASA Technical Reports Server (NTRS)

In the third year of the research project, we have (1) tested a 3.5 liter prototype of the Liquid Xenon Time Projection Chamber, (2) used a prototype having a 4.4 cm drift gap to study the charge and energy resolution response of the 3.5 liter chamber, (3) obtained an energy resolution as good as that previously measured by us using chambers with drift gaps of the order of millimeters, (4) observed the induction signals produced by MeV gamma rays, (4) used the 20 hybrid charge sensitive preamplifiers for a nondestructive readout of the electron image on the induction wires, (5) performed extensive Monte Carlo simulations to obtain results on efficiency, background rejection capability, and source flux sensitivity, and (6) developed a reconstruction algorithm for events with multiple interaction points.

Aprile, Elena

1992-01-01

47

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

NASA Astrophysics Data System (ADS)

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

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

2007-10-01

48

Heavy nuclei synthesized in gamma-ray burst outflows as the source of ultrahigh energy cosmic rays  

NASA Astrophysics Data System (ADS)

Recent measurements by the Pierre Auger Observatory suggest that the composition of ultrahigh energy cosmic rays (UHECRs) becomes dominated by heavy nuclei at high energies. However, until now there has been no astrophysical motivation for considering a source highly enriched in heavy elements. Here we demonstrate that the outflows from gamma-ray bursts (GRBs) may indeed be composed primarily of nuclei with masses A˜ 40-200, which are synthesized as hot material expands away from the central engine. In particular, if the jet is magnetically dominated (rather than a thermally driven fireball) its low entropy enables heavy elements to form efficiently. Adopting the millisecond protomagnetar model for the GRB central engine, we show that heavy nuclei both are synthesized in protomagnetar winds and can in principle be accelerated to energies ?1020 eV in the shocks or regions of magnetic reconnection that are responsible for powering the GRB. Similar results may apply to accretion-powered GRB models if the jet originates from a magnetized disc wind. Depending on the precise distribution of nuclei synthesized, we predict that the average primary mass may continue to increase beyond Fe group elements at the highest energies, possibly reaching the A? 90 (zirconium), A? 130 (tellurium) or even A? 195 (platinum) peaks. Future measurements of the UHECR composition at energies ?1020 eV can thus confirm or constrain our model and, potentially, probe the nature of GRB outflows. The longer attenuation length of ultra-heavy nuclei through the extragalactic background light greatly expands the volume of accessible sources and alleviates the energetic constraints on GRBs as the source of UHECRs.

Metzger, B. D.; Giannios, D.; Horiuchi, S.

2011-08-01

49

CAN ULTRAHIGH-ENERGY COSMIC RAYS COME FROM GAMMA-RAY BURSTS? COSMIC RAYS BELOW THE ANKLE AND GALACTIC GAMMA-RAY BURSTS  

SciTech Connect

The maximum cosmic-ray energy achievable by acceleration by a relativistic blast wave is derived. It is shown that forward shocks from long gamma-ray bursts (GRBs) in the interstellar medium accelerate protons to large enough energies, and have a sufficient energy budget, to produce the Galactic cosmic-ray component just below the ankle at 4 x 10{sup 18} eV, as per an earlier suggestion. It is further argued that, were extragalactic long GRBs responsible for the component above the ankle as well, the occasional Galactic GRB within the solar circle would contribute more than the observational limits on the outward flux from the solar circle, unless an avoidance scenario, such as intermittency and/or beaming, allows the present-day local flux to be less than 10{sup -3} of the average. Difficulties with these avoidance scenarios are noted.

Eichler, David [Physics Department, Ben-Gurion University, Be'er-Sheva 84105 (Israel); Pohl, Martin [Institut fuer Physik und Astronomie, Universitaet Potsdam, 14476 Potsdam-Golm (Germany)

2011-09-10

50

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

DOEpatents

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

Majewski, Stanislaw (Grafton, VA); Weisenberger, Andrew G. (Grafton, VA); Wojcik, Randolph F. (Yorktown, VA); Steinbach, Daniela (Williamsburg, VA)

1999-01-01

51

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

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

52

A high resolution flat crystal spectrometer for neutron gamma-ray studies  

Microsoft Academic Search

A flat-crystal diffraction spectrometer, constructed for the measurement ; of gamma rays resulting from neutron capture, is discussed both experimentally ; and theoretically. The spectrometer is used either as a single crystal or a ; double crystal instrument. In the single crystal arrangement a Laue diffracted ; gamma -ray beam from a broad source proceeds through a Soller slit which

J. W. Knowles

1959-01-01

53

High sensitivity high resolution double scatter 1-30 MeV gamma ray telescope  

NASA Technical Reports Server (NTRS)

The design and performance of the double-scatter 1-30-MeV gamma-ray telescope developed at the University of California for balloon-borne observations are reported and illustrated with drawings, diagrams, and graphs. The telescope comprises an upper array of 16 6.03 x 6.03 x 100-cm plastic scintillator bars viewed by photomultiplier tubes (PMTs) at both ends, a lower array (at 100-cm distance) of 16 4.83 x 4.83 x 100-cm NaI(Tl) bars viewed at both ends by PMTs, and four 122 x 122 x 0.64-cm plastic sheets viewed by four PMTs each as charged-particle anticoincidence shielding. The operating principle of the telescope, the tests conducted on the NaI(Tl) bars, the on-board data-processing electronics, and the overall performance are characterized. Performance parameters include area 1 sq m, field of view pi sr, 4-sigma sensitivity above 1 MeV 0.00004 gamma/sq cm sec over 25 h, angular resolution about 3.5 deg FWHM, and energy resolution 10 percent at 1 MeV and 6 percent at 6 MeV.

Zych, A. D.; Tumer, O. T.; White, R. S.; Dayton, B.

1983-01-01

54

A high resolution gamma-ray spectrometer based on superconducting microcalorimeters  

NASA Astrophysics Data System (ADS)

Improvements in superconductor device fabrication, detector hybridization techniques, and superconducting quantum interference device readout have made square-centimeter-sized arrays of gamma-ray microcalorimeters, based on transition-edge sensors (TESs), possible. At these collecting areas, gamma microcalorimeters can utilize their unprecedented energy resolution to perform spectroscopy in a number of applications that are limited by closely-spaced spectral peaks, for example, the nondestructive analysis of nuclear materials. We have built a 256 pixel spectrometer with an average full-width-at-half-maximum energy resolution of 53 eV at 97 keV, a useable dynamic range above 400 keV, and a collecting area of 5 cm2. We have demonstrated multiplexed readout of the full 256 pixel array with 236 of the pixels (91%) giving spectroscopic data. This is the largest multiplexed array of TES microcalorimeters to date. This paper will review the spectrometer, highlighting the instrument design, detector fabrication, readout, operation of the instrument, and data processing. Further, we describe the characterization and performance of the newest 256 pixel array.

Bennett, D. A.; Horansky, R. D.; Schmidt, D. R.; Hoover, A. S.; Winkler, R.; Alpert, B. K.; Beall, J. A.; Doriese, W. B.; Fowler, J. W.; Fitzgerald, C. P.; Hilton, G. C.; Irwin, K. D.; Kotsubo, V.; Mates, J. A. B.; O'Neil, G. C.; Rabin, M. W.; Reintsema, C. D.; Schima, F. J.; Swetz, D. S.; Vale, L. R.; Ullom, J. N.

2012-09-01

55

A high resolution gamma-ray spectrometer based on superconducting microcalorimeters  

SciTech Connect

Improvements in superconductor device fabrication, detector hybridization techniques, and superconducting quantum interference device readout have made square-centimeter-sized arrays of gamma-ray microcalorimeters, based on transition-edge sensors (TESs), possible. At these collecting areas, gamma microcalorimeters can utilize their unprecedented energy resolution to perform spectroscopy in a number of applications that are limited by closely-spaced spectral peaks, for example, the nondestructive analysis of nuclear materials. We have built a 256 pixel spectrometer with an average full-width-at-half-maximum energy resolution of 53 eV at 97 keV, a useable dynamic range above 400 keV, and a collecting area of 5 cm{sup 2}. We have demonstrated multiplexed readout of the full 256 pixel array with 236 of the pixels (91%) giving spectroscopic data. This is the largest multiplexed array of TES microcalorimeters to date. This paper will review the spectrometer, highlighting the instrument design, detector fabrication, readout, operation of the instrument, and data processing. Further, we describe the characterization and performance of the newest 256 pixel array.

Bennett, D. A.; Horansky, R. D. [National Institute of Standards and Technology, Boulder, Colorado 80305 (United States); University of Denver, Denver, Colorado 80208 (United States); Schmidt, D. R.; Doriese, W. B.; Fowler, J. W.; Kotsubo, V.; Mates, J. A. B. [National Institute of Standards and Technology, Boulder, Colorado 80305 (United States); University of Colorado, Boulder, Colorado 80309 (United States); Hoover, A. S.; Winkler, R.; Rabin, M. W. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Alpert, B. K.; Beall, J. A.; Fitzgerald, C. P.; Hilton, G. C.; Irwin, K. D.; O'Neil, G. C.; Reintsema, C. D.; Schima, F. J.; Swetz, D. S.; Vale, L. R. [National Institute of Standards and Technology, Boulder, Colorado 80305 (United States); and others

2012-09-15

56

Avalanche photodiode arrays for a high-angular resolution X-ray and gamma-ray imaging telescopes  

Microsoft Academic Search

Avalanche photodiodes (APDs) have been investigated as the basis for a very high angular resolution coded aperture telescope with sensitivity over a wide energy range. Using custom electronics, software and a unique shadow-masking technique, we have achieved angular resolution from an X-ray point source of about 30arcsec. In addition we have demonstrated imaging of higher gamma-ray energies by coupling to

M. R. Squillante; R. A. Myers; F. Robertson; R. Farrell; J. F. Christian; G. Entine

2007-01-01

57

Recent progress of avalanche photodiodes in high-resolution X-rays and gamma-rays detection  

Microsoft Academic Search

We have studied the performance of large area avalanche photodiodes (APDs) recently developed by Hamamatsu Photonics K.K, in high-resolution X-rays and gamma-rays detections. We show that reach-through APD can be an excellent soft X-ray detector operating at room temperature or moderately cooled environment. We obtain the best energy resolution ever achieved with APDs, 6.4% for 5.9 keV X-rays, and obtain

J. Kataoka; T. Saito; Y. Kuramoto; T. Ikagawa; Y. Yatsu; J. Kotoku; M. Arimoto; N. Kawai; Y. Ishikawa; N. Kawabata

2005-01-01

58

The Gamma-ray Large Area Space Telescope (GLAST): a Wide Field, High Angular Resolution Observatory for High Energy Astrophysics  

NASA Astrophysics Data System (ADS)

The Gamma-ray Large Area Space Telescope (GLAST) is a proposed next-generation high-energy gamma-ray telescope for studying emission from astrophysical sources in the 10 MeV to 300 GeV energy range. It has been se;ected by NASA for a Mission Concept Study. The primary scientific targets include active galactic nuclei, gamma-ray bursts, neutron stars, and diffuse galactic and extragalactic high-energy radiation. GLAST relies on the unambigious identification of incident gamma-rays by detection of the electron and positron that result from pair creation in a thin converter material. Measurement of the energy and direction of the electron-positron shower provides information about the energy and direction of the incident gamma-ray. The GLAST design utilizes modern solid-state particle detector technology and recently developed advanced space-qualified computers. In particular, position-sensitive silicon strip detectors, interleaved between thin converters, are used to track particles. Because of this technical approach, the telescope design can be easily optimized to a range of sizes. For example, accomodation of GLAST within a Delta II size launch system results in an instrument with capabilities well beyond those of the highly successful EGRET currently operating on the Compton Observatory; namely, a broader energy range, larger effective area, wider field of view, and single-photon angular resolution 2 to 5 times more precise than EGRET's resolution. GLAST will have a maximum effective area of 8000 cm(2) above 300 MeV, a field of view of 2.6 sr, and a single photon angular resolution (rms projected) of 0.3deg at 1 GeV, approaching 0.03deg above 20 GeV.

Wood, K.; Michelson, P.; GLAST Collaboration

1995-12-01

59

Design of a high-resolution gamma-ray detector module for tomography applications  

Microsoft Academic Search

We present a modular gamma-ray detector design for gamma-ray tomography applications. As a key electronic component we use the APD array S8550 of Hamamatsu Corp. with 4×8 single APD elements each of 1.6mm×1.6mm size. For this APD array we tested and evaluated different configurations of 2mm wide lutetium yttrium orthosilicate scintillation crystals. Emphasize was given to high counting efficiency and

A. Bieberle; J. Kronenberg; E. Schleicher; U. Hampel

2007-01-01

60

Gamma Rays  

MedlinePLUS

... infrared, and ultraviolet light, are part of the electromagnetic spectrum. While gamma rays and x-rays pose the same kind of hazard, they differ in their origin. Gamma rays originate in the nucleus. X-rays originate in the electron fields surrounding the nucleus or are machine-produced. What ...

61

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

SciTech Connect

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

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

1997-02-07

62

Coupled multi-group neutron photon transport for the simulation of high-resolution gamma-ray spectroscopy applications  

Microsoft Academic Search

The accurate and efficient simulation of coupled neutron-photon problems is necessary for several important radiation detection applications. Examples include the detection of nuclear threats concealed in cargo containers and prompt gamma neutron activation analysis for nondestructive determination of elemental composition of unknown samples. In these applications, high-resolution gamma-ray spectrometers are used to preserve as much information as possible about the

Kimberly Ann Burns; Kimberly A

2009-01-01

63

Ultrahigh resolution Fourier domain optical coherence tomography  

Microsoft Academic Search

We present, for the first time, in vivo ultrahigh resolution (~2.5 µm in tissue), high speed (10000 A-scans\\/second equivalent acquisition rate sustained over 160 A-scans) retinal imaging obtained with Fourier domain (FD) OCT employing a commercially available, compact (500x260mm), broad bandwidth (120 nm at full-width-at-half-maximum centered at 800 nm) Titanium:sapphire laser (Femtosource Integral OCT, Femtolasers Produktions GmbH). Resolution and sampling

R. A. Leitgeb; W. Drexler; A. Unterhuber; B. Hermann; T. Bajraszewski; T. Le; A. Stingl; A. F. Fercher

2004-01-01

64

Atomic Resolution {ital {gamma}} -ray Holography Using the M{umlt o}ssbauer Effect  

SciTech Connect

We have observed a strong (2{percent}) angular modulation of the total backscattered conversion electron yield, measured as a function of the incidence angle of the 14.4keV {gamma} rays from a {sup 57}Co M{umlt o}ssbauer source irradiating thin epitaxial {sup 57}Fe film grown on MgO(001). The measured 2D pattern is the first hologram of the local surrounding of the absorbing nuclei obtained due to nuclear resonant scattering of {gamma} rays. The real space holographic reconstruction shows distinct features corresponding to the nearest neighbor sites in the bcc {alpha} -Fe structure. {copyright} {ital 1997} {ital The American Physical Society}

Korecki, P. [Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow (Poland)] [Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow (Poland); Korecki, J.; Slezak, T. [Department of Solid State Physics, Faculty of Physics and Nuclear Techniques, University of Mining and Metallurgy, 30-059 Krakow (Poland)] [Department of Solid State Physics, Faculty of Physics and Nuclear Techniques, University of Mining and Metallurgy, 30-059 Krakow (Poland)

1997-11-01

65

Determination of the natural radioactivity in Qatarian building materials using high-resolution gamma-ray spectrometry  

NASA Astrophysics Data System (ADS)

This study is aimed at the determination of the activity concentrations of naturally occurring and technically enhanced levels of radiation in building materials used across the State of Qatar. Samples from a range of common building materials, including Qatarian cement, Saudi cement, white cement, sand and washed sand, have been analyzed, in addition to other samples of cement's raw materials and additives collected from the main suppliers in Qatar. In order to establish the activity concentrations associated with the 235,8U and 232Th natural decay chains and 40K, the samples have been studied using a high-resolution, low-background gamma-ray spectrometry set-up. Details of the sample preparation and the gamma-ray spectroscopic analysis techniques are presented, together with the preliminary results of the activity concentrations associated with the naturally occurring radionuclide chains for the building materials collected across the Qatarian peninsula.

Al-Sulaiti, Huda; Alkhomashi, N.; Al-Dahan, N.; Al-Dosari, M.; Bradley, D. A.; Bukhari, S.; Matthews, M.; Regan, P. H.; Santawamaitre, T.

2011-10-01

66

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

NASA Technical Reports Server (NTRS)

A long duration balloon flight instrument for Max 1991 designed to study the acceleration of greater than 10 MeV ions and greater than 15 keV electrons in solar flares through high resolution spectroscopy of the gamma ray lines and hard X-ray and gamma ray continuum is described. The instrument, HIREGS, consists of an array of high-purity, n-type coaxial germanium detectors (HPGe) cooled to less than 90 K and surrounded by a bismuth germanate (BGO) anticoincidence shield. It will cover the energy range 15 keV to 20 MeV with keV spectral resolution, sufficient for accurate measurement of all parameters of the expected gamma ray lines with the exception of the neutron capture deuterium line. Electrical segmentation of the HPGe detector into a thin front segment and a thick rear segment, together with pulse-shape discrimination, provides optimal dynamic range and signal-to-background characteristics for flare measurements. Neutrons and gamma rays up to approximately 0.1 to 1 GeV can be detected and identified with the combination of the HPGe detectors and rear BGO shield. The HIREGS is planned for long duration balloon flights (LDBF) for solar flare studies during Max 1991. The two exploratory LDBFs carried out at mid-latitudes in 1987 to 1988 are described, and the LDBFs in Antarctica, which could in principle provide 24 hour/day solar coverage and very long flight durations (20 to 30 days) because of minimal ballast requirements are discussed.

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

1988-01-01

67

Ultrahigh-Resolution X-ray Tomography  

NASA Astrophysics Data System (ADS)

Ultrahigh-resolution three-dimensional images of a microscopic test object were made with soft x-rays collected with a scanning transmission x-ray microscope. The test object consisted of two different patterns of gold bars on silicon nitride windows that were separated by ~5 micrometers. Depth resolution comparable to the transverse resolution was achieved by recording nine two-dimensional images of the object at angles between -50 and +55 degrees with respect to the beam axis. The projections were then combined tomographically to form a three-dimensional image by means of an algorithm using an algebraic reconstruction technique. A transverse resolution of ~1000 angstroms was observed. Artifacts in the reconstruction limited the overall depth resolution to ~6000 angstroms; however, some features were clearly reconstructed with a depth resolution of ~1000 angstroms.

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

1994-11-01

68

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

Microsoft Academic Search

Nuclear photonics is an emerging field of research requiring new tools, including high spectral brightness, tunable gamma-ray sources; high photon energy, ultrahigh-resolution crystal spectrometers; and novel detectors. This presentation focuses on the precision linac technology required for Compton scattering gamma-ray light sources, and on the optimization of the laser and electron beam pulse format to achieve unprecedented spectral brightness. Within

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

2011-01-01

69

Design of a high-resolution gamma-ray detector module for tomography applications  

NASA Astrophysics Data System (ADS)

We present a modular gamma-ray detector design for gamma-ray tomography applications. As a key electronic component we use the APD array S8550 of Hamamatsu Corp. with 4×8 single APD elements each of 1.6 mm×1.6 mm size. For this APD array we tested and evaluated different configurations of 2 mm wide lutetium yttrium orthosilicate scintillation crystals. Emphasize was given to high counting efficiency and low dead time in order to secure applicability of the detector to tomography of objects with highly attenuating materials. For electronic processing, we designed a low-cost low-power charge-sensitive preamplifier circuit using commercially available operational amplifier ICs. The modular design of the detectors allows us to build up larger line or arc detectors.

Bieberle, A.; Kronenberg, J.; Schleicher, E.; Hampel, U.

2007-03-01

70

High resolution cluster method for topological studies of the light curves of gamma-ray pulsars  

Microsoft Academic Search

The authors describe a non-parametric, binning-free, adaptive method for the detection and the analysis of structures in the light curves of gamma-ray pulsars, based on a clustering technique. They use computer simulated data and a sample of COS-B data relative to the Vela pulsar to show its behavior and robustness. As a main result they find that the method is

R. Buccheri; M. C. Maccarone; B. Sacco; V. di Gesu

1988-01-01

71

High resolution gamma-ray astronomy - Observations and predictions of line shapes  

NASA Technical Reports Server (NTRS)

The shapes of gamma-ray lines carry unique information about the physical processes and conditions in astrophysical sites. Galactic center and SN 1987A lines have been observationally resolved allowing their shapes to be studied. There are also significant new theoretical results concerning line shapes from Type I supernovae, supernova remnants and the interstellar medium. New work is presented on a simple treatment of line profiles for rotating disks and spherical shells.

Bhattacharya, Dipen; Gehrels, Neil

1991-01-01

72

An ultra-high-throughput, high-resolution gamma-ray spectroscopy system  

Microsoft Academic Search

A high-throughput gamma-ray spectroscopy system is described. It consists of the following: a high-purity Ge (HPGe) detector; a transistor-reset preamplifier (TRP); a gated integrator, shaping amplifier; an analog-to-digital converter (ADC); and digital control and storage circuits. The gated integrator uses a quasi-rectangular prefilter. With the detector used, this prefilter provided ~16% less noise than a gated integrator using a conventional

M. L. Simpson; T. H. Becker; R. D. Bingham; R. C. Trammell

1991-01-01

73

A balloon-borne high-resolution spectrometer for observations of gamma-ray emission from solar flares  

NASA Technical Reports Server (NTRS)

The design, development, and balloon-flight verification of a payload for observations of gamma-ray emission from solar flares are reported. The payload incorporates a high-purity germanium semiconductor detector, standard NIM and CAMAC electronics modules, a thermally stabilized pressure housing, and regulated battery power supplies. The flight system is supported on the ground with interactive data-handling equipment comprised of similar electronics hardware. The modularity and flexibility of the payload, together with the resolution and stability obtained throughout a 30-hour flight, make it readily adaptable for high-sensitivity, long-duration balloon fight applications.

Crannell, C. J.; Starr, R.; Stottlemyre, A. R.; Trombka, J. I.

1984-01-01

74

Gamma-ray Polarimetry  

SciTech Connect

An astrophysics application of a low noise Double-sided Silicon Strip Detector (DSSD) is described. A Semiconductor Multiple-Compton Telescope (SMCT) is being developed to explore the gamma-ray universe in the 0.1-20 MeV energy band. Excellent energy resolution and polarization sensitivity are key features of the SMCT. We have developed prototype modules for a low-noise DSSD system, which reached an energy resolution of 1.3 keV (FWHM) for 122 keV at 0 C. Results of a gamma-ray imaging test are also presented.

Tajima, Hiroyasu

2003-02-05

75

High resolution spectroscopy of two gamma-ray bursts in November 1978  

NASA Technical Reports Server (NTRS)

The first results from the ISSEE-3 radiatively colled germanium gamma ray burst spectrometer are presented. Spectra and time histories from two events on the 1978 November 4 and 1978 November 19 are given. A significant difference in the continuum spectra for the two events was observed. Evidence is presented for two spectral features in the features in the November 19 events, a broad one at approximately 420 key KeV and a narrower one at 740 KeV with a suggestion of an accompanying high energy tail.

Teegarden, B. J.; Cline, T. L.

1979-01-01

76

High-resolution gamma-ray spectroscopy with a microwave-multiplexed transition-edge sensor array  

NASA Astrophysics Data System (ADS)

We demonstrate very high resolution photon spectroscopy with a microwave-multiplexed two-pixel transition-edge sensor (TES) array. We measured a 153Gd photon source and achieved an energy resolution of 63 eV full-width-at-half-maximum at 97 keV and an equivalent readout system noise of 86 pA/?Hz at the TES. The readout circuit consists of superconducting microwave resonators coupled to radio-frequency superconducting-quantum-interference-devices and transduces changes in input current to changes in phase of a microwave signal. We use flux-ramp modulation to linearize the response and evade low-frequency noise. This demonstration establishes one path for the readout of cryogenic X-ray and gamma-ray sensor arrays with more than 103 elements and spectral resolving powers R =?/??>10.

Noroozian, Omid; Mates, John A. B.; Bennett, Douglas A.; Brevik, Justus A.; Fowler, Joseph W.; Gao, Jiansong; Hilton, Gene C.; Horansky, Robert D.; Irwin, Kent D.; Kang, Zhao; Schmidt, Daniel R.; Vale, Leila R.; Ullom, Joel N.

2013-11-01

77

High-resolution gamma-ray spectroscopy with a microwave-multiplexed transition-edge sensor array  

SciTech Connect

We demonstrate very high resolution photon spectroscopy with a microwave-multiplexed two-pixel transition-edge sensor (TES) array. We measured a {sup 153}Gd photon source and achieved an energy resolution of 63 eV full-width-at-half-maximum at 97 keV and an equivalent readout system noise of 86 pA/?(Hz) at the TES. The readout circuit consists of superconducting microwave resonators coupled to radio-frequency superconducting-quantum-interference-devices and transduces changes in input current to changes in phase of a microwave signal. We use flux-ramp modulation to linearize the response and evade low-frequency noise. This demonstration establishes one path for the readout of cryogenic X-ray and gamma-ray sensor arrays with more than 10{sup 3} elements and spectral resolving powers R=?/??>10{sup 3}.

Noroozian, Omid [National Institute of Standards and Technology, Boulder, Colorado 80305 (United States) [National Institute of Standards and Technology, Boulder, Colorado 80305 (United States); Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, Colorado 80309 (United States); Mates, John A. B.; Bennett, Douglas A.; Brevik, Justus A.; Fowler, Joseph W.; Gao, Jiansong; Hilton, Gene C.; Horansky, Robert D.; Irwin, Kent D.; Schmidt, Daniel R.; Vale, Leila R.; Ullom, Joel N. [National Institute of Standards and Technology, Boulder, Colorado 80305 (United States)] [National Institute of Standards and Technology, Boulder, Colorado 80305 (United States); Kang, Zhao [Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States)] [Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States)

2013-11-11

78

A portable medium-resolution gamma-ray spectrometer and analysis software  

SciTech Connect

There is a strong need for portable radiometric instrumentation that can both accurately confirm the presence of nuclear materials and allow isotopic analysis of radionuclides in the field. To fulfill this need the Safeguards Technology Program at LLNL has developed a hand-held, non-cryogenic, low-power gamma-ray and x-ray measurements and analysis instrument that can both search for and then accurately verify the presence of nuclear materials. We will report on the use of cadmium zinc telluride (CZT) detectors, detector electronics, and the new field-portable instrument being developed. We will also describe the isotopic analysis that allows enrichment measurements to be made accurately in the field. These systems provide capability for safeguards inspection and verification applications and could find application in counter-smuggling operations.

Lavietes, A.D.; McQuaid, J.H.; Ruhter, W.D.; Buckley, W.M.; Clark, D-L. [Lawrence Livermore National Lab., CA (United States); Paulus, T.J. [EG and G ORTEC, Oak Ridge, TN (United States)

1996-07-01

79

The Application of High-Resolution Gamma-Ray Spectrometry (HRGS) to Nuclear Safeguards, Nonproliferation, and Arms Control Activities  

SciTech Connect

While well-developed methodologies exist for the employment of high- resolution gamma ray spectrometry (HRGS) in determining the isotopic composition of plutonium samples, the potential capabilities of such measurements in determining the properties of nuclear materials otherwise remain largely unexploited. These measurements contain information sufficiently detailed such that not only can the isotopic composition of uranium and plutonium materials be determined, but the details of the spectrum obtained will depend reproducibly upon other factors including the total mass, density, chemical composition, and geometrical configuration of the material, and for certain materials, the elapsed time since chemical processing. The potential thus exists to obtain a `gamma-ray fingerprint` for typical containers or assemblies of nuclear material which will then serve to identify that class of item in a later confirmatory measurement. These measurements have the additional advantage that, by comparison with active interrogation techniques which usually require the introduction of some extraneous form of radiation or other intrusive activity, they are totally passive, and thus impose only minimal additional safety or regulatory burdens on the operators. In the application of these measurements to the verification of treaty-limited items, where the information acquired may be sensitive in nature, the use of the CIVET (Controlled Intrusiveness Verification Technique) approach, where a computer-based interface is employed to limit access to the information obtained, may be followed.

Kane, Walter R.; Lemley, James R.; Forman, Leon

1997-12-31

80

Use of an iterative convolution approach for qualitative and quantitative peak analysis in low resolution gamma-ray spectra  

NASA Astrophysics Data System (ADS)

In many applications, low resolution gamma-ray spectrometers, such as sodium iodide scintillation detectors, are widely used primarily due to their relatively low cost and high detection efficiency. There is widespread interest in improved methods for analyzing spectral data acquired with such devices, using inverse analysis. Peak means and peak areas in gamma- and X-ray spectra are needed for both qualitative and quantitative analysis. This paper introduces the PEAKSI code package that was developed at the Center for Engineering Applications of Radioisotopes (CEAR). The basic approach described here is to use accurate forward models and iterative convolution instead of direct deconvolution. Rather than smoothing and differentiation a combination of linear regression and non-linear searching is used to minimize the reduced chi-square, since this approach retains the capability of establishing uncertainties in the estimated peak parameters. The PEAKSI package uses a Levenberg-Marquardt (LM) non-linear search method combined with multiple linear regression (MLR) to minimize the reduced chi-square value for fitting single or multiple overlapping peaks to determine peak parameters, including peak means, peak standard deviations or full width at half maximum (FWHM), net peak counts, and background counts of peaks in experimental gamma-ray spectra. This approach maintains the natural error structure so that parameter uncertainties can be estimated. The plan is to release this code to the public in the near future.

Gardner, Robin P.; Ai, Xianyun; Peeples, Cody R.; Wang, Jiaxin; Lee, Kyoung; Peeples, Johanna L.; Calderon, Adan

2011-10-01

81

High-Resolution Hard X-Ray and Gamma-Ray Spectrometers Based on Superconducting Absorbers Coupled to Superconducting Transition Edge Sensors.  

National Technical Information Service (NTIS)

We are developing detectors based on bulk superconducting absorbers coupled to superconducting transition edge sensors (TES) for high-resolution spectroscopy of hard X-rays and soft gamma-rays. We have achieved an energy resolution of 70 eV FWHM at 60 keV...

M. van den Berg D. Chow A. Loshak M. F. Cunningham T. W. Barbee F. Matthias S. E. Labov

2000-01-01

82

A Satellite-Borne High-Resolution Ge(Li) Gamma-Ray Spectrometer System Part 1: Description of the Instrument and Gamma-Ray Backgrounds in Earth Orbit  

Microsoft Academic Search

Gamma radiation from terrestrial and extraterrestrial sources has been investigated for the first time with a high-resolution lithium-drifted germanium spectrometer-cryogen system flown on board a low-altitude, spin-stabilized, polar-orbiting satellite (1972-076B) launched on October 2, 1972. Gamma-ray pulses corresponding to energies between 40 keV and ~ 2.8 MeV are analyzed by a 4096-channel pulse-height analyzer with an overall system resolution of

G. H. Nakano; W. L. Imhof; R. G. Johnson

1974-01-01

83

Assay for uranium and determination of disequilibrium by means of in situ high resolution gamma-ray spectrometry  

USGS Publications Warehouse

Two sealed sondes, using germanium gamma-ray detectors cooled by melting propane, have been field tested to depths of 79 m in water-filled boreholes at the Pawnee Uranium Mine in Bee Co., Texas. When, used as total-count devices, the sondes are comparable in logging speed and counting rate with conventional scintillation detectors for locating zones of high radioactivity. When used with a multichannel analyzer, the sondes are detectors with such high resolution that individual lines from the complex spectra of the uranium and thorium series can be distinguished. Gamma rays from each group of the uranium series can be measured in ore zones permitting determination of the state of equilibrium at each measurement point. Series of 10-minute spectra taken at 0.3- to 0.5-m intervals in several holes showed zones where maxima from the uranium group and from the 222Rn group were displaced relative to each other. Apparent excesses of 230Th at some locations suggest that uranium-group concentrations at those locations were severalfold greater some tens of kiloyears, ago. At the current state of development a 10-minute count yields a sensitivity of about 80 ppm U308. Data reduction could in practice be accomplished in about 5 minutes. The result is practically unaffected by disequilibrium or radon contamination. In comparison with core assay, high-resolution spectrometry samples a larger volume; avoids problems due to incomplete core recovery, loss of friable material to drilling fluids, and errors in depth and marking; and permits use of less expensive drilling methods. Because gamma rays from the radionuclides are accumulated simultaneously, it also avoids the problems inherent in trying to correlate logs made in separate runs with different equipment. Continuous-motion delayed-gamma activation by a 163-?g 252Cf neutron source attached to the sonde yielded poor sensitivity. A better neutron-activation method, in which the sonde is moved in steps so as to place the detector at the previous activation point, could not be evaluated because of equipment failure.

Tanner, Allan B.; Moxham, Robert M.; Senftle, F. E.

1977-01-01

84

Angular resolution of an EAS array for gamma ray astronomy energies 5 X 10 (13) eV  

NASA Astrophysics Data System (ADS)

A 24 detector extensive air shower array is being operated at Ootacamund (2300 m altitude, 11.4 deg N latitude) in southern India for a study of arrival directions of showers of energies greater than 5 x 10 to the 13th power eV. Various configurations of the array of detectors have been used to estimate the accuracy in determination of arrival angle of showers with such an array. These studies show that it is possible to achieve an angular resolution of better than 2 deg with the Ooty array for search for point sources of Cosmic gamma rays at energies above 5 x 10 to the 13th power eV.

Apte, A. R.; Gopalakrishnan, N. V.; Tonwar, S. C.; Uma, V.

1985-08-01

85

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

PubMed

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

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

2012-06-01

86

Analysis of scattered radiation cross-talk in a high-resolution gamma ray tomography detector with GATE Monte-Carlo simulation  

Microsoft Academic Search

Limited energy resolution in scintillation type gamma ray detectors leads to systematic errors in photon counting because the pulse height discrimination stages cannot accurately discriminate interactions with full respectively partial deposition of isotopic emission energy. The resulting error is a systematic positive count rate offset originating from erroneously counted scattered photons. The origin of scattering may be the detector itself

N. Kießling; A. Bieberle; U. Hampel

2008-01-01

87

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

Microsoft Academic Search

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

Andrey Georgiev; Werner Gast

1993-01-01

88

High resolution gamma ray spectroscopy with CdTe detector systems  

Microsoft Academic Search

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

M. Richter; P. Siffert

1992-01-01

89

High resolution, high speed ultrahigh vacuum microscopy  

SciTech Connect

The history and future of transmission electron microscopy (TEM) is discussed as it refers to the eventual development of instruments and techniques applicable to the real time in situ investigation of surface processes with high resolution. To reach this objective, it was necessary to transform conventional high resolution instruments so that an ultrahigh vacuum (UHV) environment at the sample site was created, that access to the sample by various in situ sample modification procedures was provided, and that in situ sample exchanges with other integrated surface analytical systems became possible. Furthermore, high resolution image acquisition systems had to be developed to take advantage of the high speed imaging capabilities of projection imaging microscopes. These changes to conventional electron microscopy and its uses were slowly realized in a few international laboratories over a period of almost 40 years by a relatively small number of researchers crucially interested in advancing the state of the art of electron microscopy and its applications to diverse areas of interest; often concentrating on the nucleation, growth, and properties of thin films on well defined material surfaces. A part of this review is dedicated to the recognition of the major contributions to surface and thin film science by these pioneers. Finally, some of the important current developments in aberration corrected electron optics and eventual adaptations to in situ UHV microscopy are discussed. As a result of all the path breaking developments that have led to today's highly sophisticated UHV-TEM systems, integrated fundamental studies are now possible that combine many traditional surface science approaches. Combined investigations to date have involved in situ and ex situ surface microscopies such as scanning tunneling microscopy/atomic force microscopy, scanning Auger microscopy, and photoemission electron microscopy, and area-integrating techniques such as x-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, Auger electron spectroscopy, low-energy electron diffraction, temperature programmed desorption, high-resolution electron energy-loss and Fourier-transform infrared spectroscopies, and others. Material systems ranging from atomic layers of metals and semiconductors to biology related depositions are being investigated. In the case of biological materials, however, strict limitations to high-resolution applications are imposed by electron radiation damage considerations.

Poppa, Helmut [National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2004-09-01

90

Ocular Imaging Combining Ultrahigh Resolution and High Speed OCT  

NASA Astrophysics Data System (ADS)

The impact of ultrahigh-resolution and ultrahigh-speed OCT technique on corneal and retinal imaging is shown. The capabilities of advanced OCT system for imaging of the cornea and the thickness determination of the tear film, corneal epithelium, and Bowman's layer over a wide field of view are demonstrated. The high transverse and axial resolution of OCT system allowing one to image individual nerve fiber bundles, the parafoveal capillary network, and individual cone photoreceptors is described.

Schmoll, Tilman; Leitgeb, Rainer A.

91

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

SciTech Connect

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

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

2009-04-03

92

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

93

The Effect of Gamma-ray Detector Energy Resolution on the Ability to Identify Radioactive Sources  

SciTech Connect

This report describes the results of an initial study on radiation detector spectral resolution, along with the underlying methodology used. The study was done as part of an ongoing effort in Detection Modeling and Operational Analysis (DMOA) for the DNDO System Architecture Directorate. The study objective was to assess the impact of energy resolution on radionuclide identification capability, measured by the ability to reliably discriminate between spectra associated with 'threats' (defined as fissile materials) and radioactive 'non-threats' that might be present in the normal stream of commerce. Although numerous factors must be considered in deciding which detector technology is appropriate for a specific application, spectral resolution is a critical one for homeland security applications in which a broad range of non-threat sources are present and very low false-alarm rates are required. In this study, we have proposed a metric for quantifying discrimination capability, and have shown how this metric depends on resolution. In future work we will consider other important factors, such as efficiency and volume, and the relative frequency of spectra known to be discrimination challenges in practical applications.

Nelson, K E; Gosnell, T B; Knapp, D A

2009-03-05

94

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

USGS Publications Warehouse

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.

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

95

Array-compatible transition-edge sensor microcalorimeter {gamma}-ray detector with 42 eV energy resolution at 103 keV  

SciTech Connect

The authors describe a microcalorimeter {gamma}-ray detector with measured energy resolution of 42 eV full width at half maximum for 103 keV photons. This detector consists of a thermally isolated superconducting transition-edge thermometer and a superconducting bulk tin photon absorber. The absorber is attached with a technique compatible with producing arrays of high-resolution {gamma}-ray detectors. The results of a detailed characterization of the detector, which includes measurements of the complex impedance, detector noise, and time-domain pulse response, suggest that a deeper understanding and optimization of the thermal transport between the absorber and thermometer could significantly improve the energy resolution of future detectors.

Zink, B. L.; Ullom, J. N.; Beall, J. A.; Irwin, K. D.; Doriese, W. B.; Duncan, W. D.; Ferreira, L.; Hilton, G. C.; Horansky, R. D.; Reintsema, C. D.; Vale, L. R. [National Institute of Standards and Technology, 325 Broadway MC 817.03, Boulder, Colorado 80305 (United States)

2006-09-18

96

Background radiation reduction for a high-resolution gamma-ray spectrometer used for environmental radioactivity measurements  

NASA Astrophysics Data System (ADS)

A detailed analysis is presented of background radiation spectra for a high-resolution gamma-ray spectrometer used to measure environmental radioactivity, for various shielding configurations. The main goal is to improve the detection limits of low-level activity measurements by reducing the background as much as possible. Passive shielding configurations are used to decrease the total background counting rate by adding new layers. Subsequently, for the maximum shielding configuration, the Minimum Detectable Activity (MDA) is improved by at least 13-fold for 137Cs, 8-fold for 214Bi (609.31 keV), 7-fold for 40K and 5.5-fold for 208Tl (2614.53 keV). A reduction factor of 240 for the 137Cs peak (counting rate) at maximum shielding and an insignificant peak for this radionuclide was determined. For other radionuclides, peaks below the detection limit of the detector system were also found. These results show that the shielding was successful in reducing and removing peaks from the background spectrum.

Radulescu, I.; Blebea-Apostu, A. M.; Margineanu, R. M.; Mocanu, N.

2013-07-01

97

The effect of energy resolution on the extraction of information content from gamma-ray spectra  

NASA Astrophysics Data System (ADS)

Rapid unambiguous identification of illicit radioactive materials is a matter of international concern that has yet to be fully attained. This is particularly true for shielded fissile materials in the presence of background radiation and routinely encountered benign radionuclides. We present a systematic treatment of the effect of detector resolution on the identification of nuclides in simple and complex shielded ?-ray spectra. Case studies of some problematic spectra with 1000 counts suggest that, at moderate count rates, near-unambiguous identification (<1% probability of misidentification) of potential fissile sources requires a detector with an energy resolution of at least 1-2% at 662 keV. While somewhat limited in scope, the study establishes a quantitative basis for the comparative evaluation of detectors of comparable efficiency.

Nelson, Karl E.; Gosnell, Thomas B.; Knapp, David A.

2011-12-01

98

Development of 2 cm-square Hamamatsu avalanche photodiodes for high-resolution X-rays and gamma-rays detection  

Microsoft Academic Search

The avalanche photodiodes (APDs) have attracted considerable attention in various field of experimental physics, but their uses are still limited in only a few experiments, possibly due to their small surface areas. Here, we report the development of the large-area (˜20mm square) APDs, for future applications to high-resolution X-rays and gamma-rays detection. We have made two prototypes of reverse-type APDs

R. Sato; J. Kataoka; Y. Kanai; Y. Ishikawa; N. Kawabata; T. Ikagawa; T. Saito; Y. Kuramoto; N. Kawai

2006-01-01

99

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

Microsoft Academic Search

A new high efficiency, high resolution, fast gamma-ray spectrometer was recently installed at the JET tokamak. The spectrometer is based on a LaBr3(Ce) scintillator coupled to a photomultiplier tube. A digital data acquisition system is used to allow spectrometry with event rates in excess of 1 MHz expected in future JET DT plasmas. However, at the lower rates typical of

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

2010-01-01

100

Mercuric iodine room temperature gamma-ray detectors  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

101

Mercuric iodide room temperature gamma-ray detectors  

NASA Astrophysics Data System (ADS)

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

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

1989-07-01

102

Gamma-Ray Spectrum of Centaurus A: A High-Resolution Observation Between 70 Kev and 8 Mev.  

National Technical Information Service (NTIS)

The NASA/Goddard Space Flight Center Low Energy Gamma ray Spectrometer (LEGS) observed the nearby active nucleus galaxy Centaurus A (NGC 5128) during a balloon flight on 1981 November 19. There is no evidence of a break in the spectrum or of any line feat...

N. Gehrels T. L. Cline B. J. Teegarden W. S. Paciesas J. Tueller

1983-01-01

103

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

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

104

GRETINA: A gamma ray energy tracking array  

NASA Astrophysics Data System (ADS)

A gamma-ray energy tracking array (GRETA) is a new concept for the detection of gamma radiation. In such an array, the individual interactions of all the gamma rays are identified by their energies and positions. Then, using tracking algorithms based on the properties of gamma ray interactions, the scattering sequences are reconstructed. GRETA will give high peak efficiency, peak-to-background ratio, and position resolution. Recent research and development efforts have demonstrated that the construction of a gamma ray tracking array is feasible, and a plan for constructing a US array GRETINA is in place.

Lee, I. Y.; Clark, R. M.; Cromaz, M.; Deleplanque, M. A.; Descovich, M.; Diamond, R. M.; Fallon, P.; Macchiavelli, A. O.; Stephens, F. S.; Ward, D.

2004-12-01

105

Ultrahigh resolution multicolor colocalization of single fluorescent nanocrystals.  

National Technical Information Service (NTIS)

A new method for in vitro and possibly in vivo ultrahigh-resolution colocalization and distance measurement between biomolecules is described, based on semiconductor nanocrystal probes. This ruler bridges the gap between FRET and far-field (or near-field ...

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

2000-01-01

106

Investigation of gamma-ray families originating from nucleus-nucleus interactions at ultrahigh energies E 0 in excess of 1016 eV  

NASA Astrophysics Data System (ADS)

Various spatial and energy features of gamma-ray families originating from the interactions of primary nuclei of galactic cosmic rays with nuclei of atmospheric atoms ( AA interactions) are studied. The mass composition of galactic cosmic rays is analyzed on the basis of data from x-ray emulsion chambers of the Pamir experiment with the aid of a criterion for selecting gamma-ray families originating from AA interactions ( A families) at energies E 0 of primary galactic cosmic rays in excess of 1016 eV. According to the results obtained in this way only the experimental spatial parameters R 1 E and ? differ from their counterparts in the MC0 model.

Yuldashbaev, T. S.; Nuritdinov, Kh.

2013-12-01

107

Gamma ray camera  

Microsoft Academic Search

A gamma ray camera is disclosed for detecting rays emanating from a radiation source such as an isotope. The gamma ray camera includes a sensor array formed of a visible light crystal for converting incident gamma rays to a plurality of corresponding visible light photons, and a photosensor array responsive to the visible light photons in order to form an

1997-01-01

108

Gamma ray camera  

Microsoft Academic Search

A gamma ray camera for detecting rays emanating from a radiation source such as an isotope. The gamma ray camera includes a sensor array formed of a visible light crystal for converting incident gamma rays to a plurality of corresponding visible light photons, and a photosensor array responsive to the visible light photons in order to form an electronic image

Victor

1997-01-01

109

Design and performance of a new pixelated LSO\\/PSPMT gamma-ray detector for high resolution PET imaging  

Microsoft Academic Search

The gamma-ray detector developed for the Siemens Inveontrade small animal PET systems affords improved light collection and reduced number of photodetectors, while providing 67% greater axial field of view over the previous Focustrade system design. This is achieved using a tapered, multiple-element lightguide to couple the detector's 1.6 mm pitch, 20 times 20 LSO crystal array (32 mm square) to

Robert A. Mintzer; Stefan B. Siegel

2007-01-01

110

Adaptive-optics ultrahigh-resolution optical coherence tomography  

Microsoft Academic Search

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

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

2004-01-01

111

X-ray Interferometry with Transmissive Beam Combiners for Ultra-High Angular Resolution Astronomy  

NASA Technical Reports Server (NTRS)

Abstract Interferometry provides one of the possible routes to ultra-high angular resolution for X-ray and gamma-ray astronomy. Sub-micro-arc-second angular resolution, necessary to achieve objectives such as imaging the regions around the event horizon of a super-massive black hole at the center of an active galaxy, can be achieved if beams from parts of the incoming wavefront separated by 100s of meters can be stably and accurately brought together at small angles. One way of achieving this is by using grazing incidence mirrors. We here investigate an alternative approach in which the beams are recombined by optical elements working in transmission. It is shown that the use of diffractive elements is a particularly attractive option. We report experimental results from a simple 2-beam interferometer using a low-cost commercially available profiled film as the diffractive elements. A rotationally symmetric filled (or mostly filled) aperture variant of such an interferometer, equivalent to an X-ray axicon, is shown to offer a much wider bandpass than either a Phase Fresnel Lens (PFL) or a PFL with a refractive lens in an achromatic pair. Simulations of an example system are presented.

Skinner, G. K.; Krismanic, John F.

2009-01-01

112

Towards Ultra-High Resolution Models of Climate and Weather  

SciTech Connect

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

Wehner, Michael; Oliker, Leonid; Shalf, John

2007-01-01

113

Gamma-ray waveguides  

SciTech Connect

We have developed an approach for gamma-ray optics using layered structures acting as planar waveguides. Experiments demonstrating channeling of 122 keV gamma rays in two prototype waveguides validate the feasibility of this technology. Gamma-ray waveguides allow one to control the direction of radiation up to a few MeV. The waveguides are conceptually similar to polycapillary optics, but can function at higher gamma-ray energies. Optics comprised of these waveguides will be able to collect radiation from small solid angles or concentrate radiation into small area detectors. Gamma-ray waveguides may find applications in medical imaging and treatment, astrophysics, and homeland security.

Tournear, D. M.; Hoffbauer, M. A.; Akhadov, E. A.; Chen, A. T.; Pendleton, S. J.; Williamson, T. L.; Cha, K. C.; Epstein, R. I. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2008-04-14

114

Bridgman growth of LaBr 3:Ce and LaCl 3:Ce crystals for high-resolution gamma-ray spectrometers  

Microsoft Academic Search

Single crystals of LaBr3:Ce and LaCl3:Ce have been grown by the vertical Bridgman technique. Crystals of these scintillators are used in the fabrication of high-resolution, gamma-ray spectrometers. The LaBr3:Ce and LaCl3:Ce crystals we have grown have high light outputs of ?80,000 and 50,000 photons\\/MeV, respectively, and fast principal decay constants of <30ns. The emission wavelength for the LaBr3:Ce and LaCl3:Ce

W. M. Higgins; J. Glodo; E. Van Loef; M. Klugerman; T. Gupta; L. Cirignano; P. Wong; K. S. Shah

2006-01-01

115

Optimal bandgap variants of Cd 1? x Zn x Te for high-resolution X-ray and gamma-ray spectroscopy  

Microsoft Academic Search

We show that the trade-off between noise and charge generation statistics in Cd1?xZnxTe leads to an optimal band gap of approximately 2.0 eV at room temperature. This implies a ZnTe fraction of approximately 0.7–0.8. We show that for X-rays and relatively low energy gamma-rays Cd0.2Zn0.8Te theoretically offers a significant potential improvement in energy resolution over Cd0.9Zn0.1Te even if compensation of

J. E Toney; T. E Schlesinger; R. B James

1999-01-01

116

14-pixel, multiplexed array of gamma-ray microcalorimeters with 47 eV energy resolution at 103 keV  

SciTech Connect

The authors present a prototype for a high-energy-resolution, high-count-rate, gamma-ray spectrometer intended for nuclear forensics and international nuclear safeguards. The prototype spectrometer is an array of 14 transition-edge-sensor microcalorimeters with an average energy resolution of 47 eV (full width at half maximum) at 103 keV. The resolution of the best pixel is 25 eV. A cryogenic, time-division multiplexer reads out the array. Several important topics related to microcalorimeter arrays are discussed, including cross-talk, the uniformity of detector bias conditions, fabrication of the arrays, and the multiplexed readout. The measurements and calculations demonstrate that a kilopixel array of high-resolution microcalorimeters is feasible.

Doriese, W. B.; Ullom, J. N.; Beall, J. A.; Duncan, W. D.; Ferreira, L.; Hilton, G. C.; Horansky, R. D.; Irwin, K. D.; Mates, J. A. B.; Reintsema, C. D.; Vale, L. R.; Xu, Y.; Zink, B. L.; Rabin, M. W.; Hoover, A. S.; Rudy, C. R.; Vo, D. T. [National Institute of Standards and Technology, 325 Broadway, MC 817.03, Boulder, Colorado 80305 (United States); Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2007-05-07

117

Determination of the natural radioactivity levels in north west of Dukhan, Qatar using high-resolution gamma-ray spectrometry.  

PubMed

This study is aimed at the determination of the activity concentrations of naturally occuring and technologically enhanced levels of radiation in 34 representative soil samples that have been collected from an inshore oil field area which was found to have, in a previous study, the highest observed value of 226Ra concentration among 129 soil samples. The activity concentrations of 238U and 226Ra have been inferred from gamma-ray transitions associated with their decay progenies and measured using a hyper-pure germanium detector. Details of the sample preparation and the gamma-ray spectroscopic analysis techniques are presented, together with the values of the activity concentrations associated with the naturally occuring radionuclide chains for all the samples collected from NW Dukhan. Discrete-line, gamma-ray energy transitions from spectral lines ranging in energy from ?100 keV up to 2.6 MeV have been associated with characteristic decays of the various decay products within the 235.8U and 232Th radioactive decay chains. These data have been analyzed, under the assumption of secular equilibrium for the U and Th decay chains. Details of the sample preparation and the gamma-ray spectroscopic analysis techniques are presented. The weighted mean value of the activity concentrations of 226Ra in one of the samples was found to be around a factor of 2 higher than the values obtained in the previous study and approximately a factor of 10 higher than the accepted worldwide average value of 35 Bq/kg. The weighted mean values of the activity concentrations of 232Th and 40K were also deduced and found to be within the worldwide average values of 30 and 400 Bq/kg, respectively. Our previous study reported a value of 201.9±1.5Stat.±13Syst.Bq/kg for 226Ra in one sample and further investigation in the current work determined a measured value for 226Ra of 342.00±1.9Stat.±25Syst.Bq/kg in a sample taken from the same locality. This is significantly higher than all the other investigated soil samples in the current and previous works. Notably, the Th levels in the same sample are within the worldwide average expectations, implying that the increased 226Ra concentration arises from TENORM processes. PMID:22244196

Al-Sulaiti, Huda; Nasir, Tabassum; Al Mugren, K S; Alkhomashi, N; Al-Dahan, N; Al-Dosari, M; Bradley, D A; Bukhari, S; Matthews, M; Regan, P H; Santawamaitre, T; Malain, D; Habib, A

2012-07-01

118

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

SciTech Connect

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

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

2010-10-15

119

Probing the Radio Emission from Gamma Ray Blazars  

Microsoft Academic Search

The Energetic Gamma Ray Experiment Telescope on the Compton Gammay Ray Observatory discovered nearly 70 blazars with high confidence. The mechanics that results in the detectable gamma ray emission from these sources, is not completely understood, however. We obtained high resolution VLBA polarization imaging of two such gamma ray sources. We present our analysis of the superluminal motions discovered in

R. J. Cool; G. A. Moellenbrock

2003-01-01

120

Energy resolution and throughput of a new real time digital pulse processing system for x-ray and gamma ray semiconductor detectors  

NASA Astrophysics Data System (ADS)

New generation spectroscopy systems have advanced towards digital pulse processing (DPP) approaches. DPP systems, based on direct digitizing and processing of detector signals, have recently been favoured over analog pulse processing electronics, ensuring higher flexibility, stability, lower dead time, higher throughput and better spectroscopic performance. In this work, we present the performance of a new real time DPP system for X-ray and gamma ray semiconductor detectors. The system is based on a commercial digitizer equipped with a custom DPP firmware, developed by our group, for on-line pulse shape and height analysis. X-ray and gamma ray spectra measurements with cadmium telluride (CdTe) and germanium (Ge) detectors, coupled to resistive-feedback preamplifiers, highlight the excellent performance of the system both at low and high rate environments (up to 800 kcps). A comparison with a conventional analog electronics showed the better high-rate capabilities of the digital approach, in terms of energy resolution and throughput. These results make the proposed DPP system a very attractive tool for both laboratory research and for the development of advanced detection systems for high-rate-resolution spectroscopic imaging, recently proposed in diagnostic medicine, industrial imaging and security screening.

Abbene, L.; Gerardi, G.; Raso, G.; Basile, S.; Brai, M.; Principato, F.

2013-07-01

121

Solar gamma-ray experiment on Astro-A satellite  

Microsoft Academic Search

The instrumentation and performance parameters of the Japanese Astro-A satellite for measuring solar gamma ray lines and continua associated with solar flares are described. A gamma ray spectrometer which is a phoswich scintillator covers the gamma ray range from 0.24-6.48 MeV with a resolution of 10 percent at 662 keV. Techniques to discern gamma ray from particle events are discussed,

K. Okudaira; Y. Hirasima; M. Yoshimori; I. Kondo

1981-01-01

122

Gamma-Ray Pulsars  

Microsoft Academic Search

Gamma-ray photons from young pulsars allow the deepest insight into the properties and interactions of high-energy particles with magnetic and photon fields in a pulsar magnetosphere. Measurements with the Compton Gamma-Ray Observatory have led to the detection of nearly ten Gamma-ray pulsars. Although quite a variety of individual signatures is found for these pulsars, some general characteristics can be summarized:

Gottfried Kanbach

2002-01-01

123

Gamma ray transients  

NASA Technical Reports Server (NTRS)

The discovery of cosmic gamma ray bursts was made with systems designed at Los Alamos Laboratory for the detection of nuclear explosions beyond the atmosphere. HELIOS-2 was the first gamma ray burst instrument launched; its initial results in 1976, seemed to deepen the mystery around gamma ray transients. Interplanetary spacecraft data were reviewed in terms of explaining the behavior and source of the transients.

Cline, Thomas L.

1987-01-01

124

Ultrahigh resolution optical biopsy with endoscopic optical coherence tomography  

NASA Astrophysics Data System (ADS)

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

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

2004-07-01

125

Instrumentation for gamma-ray astronomy  

NASA Astrophysics Data System (ADS)

The current status of gamma-ray-telescope technology for ground, airborne, and space observations is surveyed and illustrated with drawings, diagrams, and graphs and tables of typical data. For the low- and medium-energy ranges, consideration is given to detectors and detector cooling systems, background-rejection methods, radiation damage, large-area detectors, gamma-ray imaging, data analysis, and the Compton-interaction region. Also discussed are the gamma-ray interaction process at high energies; multilevel automated spark-chamber gamma-ray telescopes; the Soviet Gamma-1 telescope; the EGRET instrument for the NASA Gamma-Ray Observatory; and Cerenkov, air-shower, and particle-detector instruments for the TeV and PeV ranges. Significant improvements in resolution and sensitivity are predicted for the near future.

Bertsch, David L.; Fichtel, Carl E.; Trombka, Jacob I.

1988-03-01

126

Instrumentation for gamma-ray astronomy  

NASA Technical Reports Server (NTRS)

The current status of gamma-ray-telescope technology for ground, airborne, and space observations is surveyed and illustrated with drawings, diagrams, and graphs and tables of typical data. For the low- and medium-energy ranges, consideration is given to detectors and detector cooling systems, background-rejection methods, radiation damage, large-area detectors, gamma-ray imaging, data analysis, and the Compton-interaction region. Also discussed are the gamma-ray interaction process at high energies; multilevel automated spark-chamber gamma-ray telescopes; the Soviet Gamma-1 telescope; the EGRET instrument for the NASA Gamma-Ray Observatory; and Cerenkov, air-shower, and particle-detector instruments for the TeV and PeV ranges. Significant improvements in resolution and sensitivity are predicted for the near future.

Bertsch, David L.; Fichtel, Carl E.; Trombka, Jacob I.

1988-01-01

127

Geolocation of Terrestrial Gamma Ray Flashes in Gamma Rays Using the Fermi Large Area Telescope  

NASA Astrophysics Data System (ADS)

We derive geolocations of bright Terrestrial Gamma ray Flashes (TGFs) directly in gamma rays using the Fermi Large Area Telescope (LAT) and compare with geolocations derived from LF and VLF (radio) networks. Imaging of the gamma ray direction is made possible by the fine spatial resolution of the LAT instrument, which is intended to make maps of the high-energy gamma ray astrophysical sky. Simulations show that LAT can geolocate very bright TGFs in favorable geometries with accuracies of several tens of km. Recent work by Connaughton et al. (2013) strongly suggests that the broadband radio signal is produced by the same bulk flow of relativistic electrons that create the gamma ray signal through bremsstrahlung interactions in the atmosphere. Our analysis confirms this picture by establishing that the radio and gamma ray signals are both temporally and spatially coincident. This work was performed at NRL and sponsored by NASA DPR S-15633-Y.

Schaal, Meagan; Grove, J. E.; Chekhtman, A.; Xiong, S.; Fitzpatrick, G.; Cummer, S.; Holzworth, R. H.

2014-01-01

128

Geolocation of Terrestrial Gamma Ray Flashes in Gamma Rays Using the Fermi Large Area Telescope  

NASA Astrophysics Data System (ADS)

We derive geolocations of bright Terrestrial Gamma ray Flashes (TGFs) directly in gamma rays using the Fermi Large Area Telescope (LAT) and compare with geolocations derived from LF and VLF (radio) networks. Imaging of the gamma ray direction is made possible by the fine spatial resolution of the LAT instrument, which is intended to make maps of the high-energy gamma ray astrophysical sky. Simulations show that LAT can geolocate very bright TGFs in favorable geometries with accuracies of several tens of km. Recent work by Connaughton et al. (2013) strongly suggests that the broadband radio signal is produced by the same bulk flow of relativistic electrons that create the gamma ray signal through bremsstrahlung interactions in the atmosphere. Our analysis confirms this picture by establishing that the radio and gamma ray signals are both temporally and spatially coincident. This work was performed at NRL and sponsored by NASA DPR S-15633-Y.

Schaal, M.; Grove, J.; Chekhtman, A.; Xiong, S.; Fitzpatrick, G.; Cummer, S. A.; Holzworth, R. H.

2013-12-01

129

Gamma-Ray Burst Detection with Icecube  

NASA Astrophysics Data System (ADS)

With their narrow emission window gamma-ray bursts (GRBs) are among the most promising objects for the first identification of high-energy cosmic neutrinos. If a considerable fraction of the ultra-high energy cosmic rays is indeed produced in GRBs, IceCube, which is now more than half-way completed, should be able to detect the associated neutrinos in the next few years. Furthermore, optical follow-up observations of neutrino multiplets will enhance IceCube's sensitivity to choked GRBs which do not produce a gamma-ray signal.

Kappes, Alexander

130

Ultrahigh resolution optical coherence tomography of human skin  

NASA Astrophysics Data System (ADS)

Ultrahigh resolution OCT (UHR OCT) was performed on normal and pathologic human skin biopsies using an ultrabroad-bandwidth (260 nm) Titanium:sapphire laser, enabling sub-micrometer (0.9 ?m) axial UHR OCT resolution. Penetration, image contrast as well as resolution capabilities achieved are analyzed for optimum UHR OCT in vivo performance. With the achieved resolution and the penetration depth, the transition between the dermis and the epidermis is clearly visible by UHR OCT, and also the anomalies of pathologies, which have been confirmed performing a comparison with histological analysis. Three dimensional UHR OCT of normal skin is demonstrated with less than 3 ?m axial resolution at video-rate with up to 50 B-scans/second, each tomogram consisting of 512×1024 pixels, resulting in 25 Megavoxels/second.

Povazay, B.; Unterhuber, A.; Hermann, B.; Gasparoni, S.; Kittler, H.; Sattmann, H.; Roka, F.; Binder, M.; Bizheva, K.; Leitgeb, R.; Pehamberger, H.; Drexler, W.

2005-08-01

131

Gamma Ray Bursts.  

National Technical Information Service (NTIS)

Gamma-ray bursts (GRBs) are bright flashes of gamma-rays coming from the cosmos. They occur roughly once per day, last typically lOs of seconds and are the most luminous events in the universe. More than three decades after their discovery, and after pion...

N. Gehrels P. Meszaros

2012-01-01

132

Gamma-Ray Pulsars  

NASA Technical Reports Server (NTRS)

The Fermi Gamma-Ray Space Telescope has revolutionized the study of pulsar physics with the detection of over 80 gamma-ray pulsars. Several new populations have been discovered, including 24 radio quiet pulsars found through gamma-ray pulsations alone and about 20 millisecond gamma-ray pulsars. The gamma-ray pulsations from millisecond pulsars were discovered by both folding at periods of known radio millisecond pulsars 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 -35 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. The higher sensitivity and larger energy range of the Fermi Large Area Telescope has produced detailed energy-dependent light curves and phase-resolved spectroscopy on brighter pulsars, that have ruled out polar cap models as the major source of the emission in favor of outer magnetosphere accelerators. The large number of gamma-ray pulsars now allows for the first time meaningful population and sub-population studies that are revealing surprising properties of these fascinating sources.

Harding, Alice K.

2011-01-01

133

Gamma-ray Bursts  

NASA Astrophysics Data System (ADS)

Prologue C. Kouveliotou, R. A . M. J. Wijers and S. E. Woosley; 1. The discovery of the gamma-ray burst phenomenon R. W. Klebesadel; 2. Instrumental principles E. E. Fenimore; 3. The BATSE era G. J. Fishman and C. A. Meegan; 4. The cosmological era L. Piro and K. Hurley; 5. The Swift era N. Gehrels and D. N. Burrows; 6. Discoveries enabled by multi-wavelength afterglow observations of gamma-ray bursts J. Greiner; 7. Prompt emission from gamma-ray bursts T. Piran, R. Sari and R. Mochkovitch; 8. Basic gamma-ray burst afterglows P. Mészáros and R. A. M. J. Wijers; 9. The GRB-supernova connection J. Hjorth and J. S. Bloom; 10. Models for gamma-ray burst progenitors and central engines S. E. Woosley; 11. Jets and gamma-ray burst unification schemes J. Granot and E. Ramirez-Ruiz; 12. High-energy cosmic rays and neutrinos E. Waxman; 13. Long gamma-ray burst host galaxies and their environments J. P. U. Fynbo, D. Malesani and P. Jakobsson; 14. Gamma-ray burst cosmology V. Bromm and A. Loeb; 15. Epilogue R. D. Blandford; Index.

Kouveliotou, Chryssa; Wijers, Ralph A. M. J.; Woosley, Stan

2012-11-01

134

Gamma ray detector shield  

DOEpatents

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

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

1985-08-26

135

Optimal bandgap variants of Cd 1- xZn xTe for high-resolution X-ray and gamma-ray spectroscopy  

NASA Astrophysics Data System (ADS)

We show that the trade-off between noise and charge generation statistics in Cd 1- xZn xTe leads to an optimal band gap of approximately 2.0 eV at room temperature. This implies a ZnTe fraction of approximately 0.7-0.8. We show that for X-rays and relatively low energy gamma-rays Cd 0.2Zn 0.8Te theoretically offers a significant potential improvement in energy resolution over Cd 0.9Zn 0.1Te even if compensation of shallow levels is less complete and carrier lifetimes are an order of magnitude lower for the higher x variant. We also show that these calculations are consistent with observed detector performance reported by many workers over a large period of time.

Toney, J. E.; Schlesinger, T. E.; James, R. B.

1999-06-01

136

A High Resolution Liquid Xenon Imaging Telescope for 0.3-10 MeV Gamma Ray Astrophysics: Construction and Initial Balloon Flights  

NASA Technical Reports Server (NTRS)

The results achieved with a 3.5 liter liquid xenon time projection chamber (LXe-TPC) prototype during the first year include: the efficiency of detecting the primary scintillation light for event triggering has been measured to be higher than 85%; the charge response has been measured to be stable to within 0.1% for a period of time of about 30 hours; the electron lifetime has been measured to be in excess of 1.3 ms; the energy resolution has been measured to be consistent with previous results obtained with small volume chambers; X-Y gamma ray imaging has been demonstrated with a nondestructive orthogonal wires readout; Monte Carlo simulation results on detection efficiency, expected background count rate at balloon altitude, background reduction algorithms, telescope response to point-like and diffuse sources, and polarization sensitivity calculations; and work on a 10 liter LXe-TPC prototype and gas purification/recovery system.

Aprile, Elena

1993-01-01

137

Gamma-Ray Pulsar Studies With GLAST  

SciTech Connect

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.

Thompson, D.J.; /NASA, Goddard

2011-11-23

138

Gamma-Ray Pulsar Studies with GLAST  

SciTech Connect

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.

Thompson, D. J. [Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2008-02-27

139

Gamma-ray spectroscopy - Requirements and prospects  

NASA Technical Reports Server (NTRS)

The only previous space instrument which had sufficient spectral resolution and directionality for the resolution of astrophysical sources was the Gamma-Ray Spectrometer carried by HEAO-3. A broad variety of astrophysical investigations entail gamma-ray spectroscopy of E/Delta-E resolving power of the order of 500 at 1 MeV; it is presently argued that a sensitivity to narrow gamma-ray lines of a few millionths ph/sq cm, from about 10 keV to about 10 MeV, should typify the gamma-ray spectrometers of prospective missions. This performance is achievable with technology currently under development, and could be applied to the NASA's planned Nuclear Astrophysics Explorer.

Matteson, James L.

1991-01-01

140

Gamma Ray Pulsars: Observations  

NASA Technical Reports Server (NTRS)

High-energy gamma rays are a valuable tool for studying particle acceleration and radiation in the magnetospheres of energetic pulsars. The six or more pulsars seen by CGRO/EGRET show that: the light curves usually have double-peak structures (suggesting a broad cone of emission); gamma rays are frequently the dominant component of the radiated power; and all the spectra show evidence of a high-energy turnover. Unless a new pulsed component appears at higher energies, progress in gamma-ray pulsar studies will be greatest in the 1-20 GeV range. Ground-based telescopes whose energy ranges extend downward toward 10 GeV should make important measurements of the spectral cutoffs. The Gamma-ray Large Area Space Telescope (GLAST), now in planning for a launch in 2005, will provide a major advance in sensitivity, energy range, and sky coverage.

Thompson, David J.; White, Nicholas E. (Technical Monitor)

2000-01-01

141

Gamma-Ray Detectors  

NASA Astrophysics Data System (ADS)

The common methods of analyzing gamma-ray spectra obtained from detectors capable of energy discrimination are discussed. Gamma-ray spectra generally are in the form of detector response versus discrete channel number. The methods considered for gamma-ray spectroscopy are somewhat general and can be applied to other types of spectroscopy. The general objective of spectroscopy is to obtain, at a minimum, the qualitative identification of the source (e.g., source energies or nuclides present). However, most spectroscopy applications seek quantitative information also, as expressed by, e.g., the source strength or the nuclide concentration. Various different methods for qualitative and quantitative analysis are summarized, and an illustrative example is provided. A review of detectors used for gamma-ray spectroscopy is included.

Dunn, William L.; McGregor, Douglas S.

142

A novel gamma-ray detector with submillimeter resolutions using a monolithic MPPC array with pixelized Ce:LYSO and Ce:GGAG crystals  

NASA Astrophysics Data System (ADS)

We have developed a large-area monolithic Multi-Pixel Photon Counter (MPPC) array consisting of 4×4 channels with a three-side buttable package. Each channel has a photosensitive area of 3×3 mm2 and 3600 Geiger mode avalanche photodiodes (APDs). For typical operational gain of 7.5×105 at +20 °C, gain fluctuation over the entire MPPC device is only ±5.6%, and dark count rates (as measured at the 1 p.e. level) amount to ?400 kcps per channel. We first fabricated a gamma-ray camera consisting of the MPPC array with one-to-one coupling to a Ce-doped (Lu, Y)2(SiO4)O (Ce:LYSO) crystal array (4×4 array of 3×3×10 mm3 crystals). Energy and time resolutions of 11.5±0.5% (FWHM at 662 keV) and 493±22 ps were obtained, respectively. When using the charge division resistor network, which compiles signals into four position-encoded analog outputs, the ultimate positional resolution is estimated as 0.19 mm in both X and Y directions, while energy resolution of 10.2±0.4% (FWHM) was obtained. Finally, we fabricated submillimeter Ce:LYSO and Ce-doped Gd3Ga3Al2O12 (Ce:GGAG) scintillator matrices each consisting of 1.0×1.0, 0.7×0.7 and 0.5×0.5 mm2 pixels, to further improve the spatial resolution. In all types of Ce:LYSO and Ce:GGAG matrices, each crystal was clearly resolved in the position histograms when irradiated by a 137Cs source. The energy resolutions for 662 keV gamma-rays for each Ce:LYSO and Ce:GGAG scintillator matrix were ?14.3%. These results suggest excellent potential for its use as a high spatial medical imaging device, particularly in positron emission tomography (PET).

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

2013-01-01

143

Cloaked Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

It is suggested that many gamma-ray bursts (GRBs) are cloaked by an ultrarelativistic baryonic shell that has high optical depth when the photons are manufactured. Such a shell would not fully block photons reflected or emitted from its inner surface, because the radial velocity of the photons can be less than that of the shell. This avoids the standard problem associated with GRBs that the thermal component should be produced where the flow is still obscured by high optical depth. The radiation that escapes high optical depth obeys the Amati relation. Observational implications may include (1) anomalously high ratios of afterglow to prompt emission, such as may have been the case in the recently discovered PTF 11agg, and (2) ultrahigh-energy neutrino pulses that are non-coincident with detectable GRB. It is suggested that GRB 090510, a short, very hard GRB with very little afterglow, was an exposed GRB, in contrast to those cloaked by baryonic shells.

Eichler, David

2014-06-01

144

Gamma ray pulsars: Observations  

Microsoft Academic Search

High-energy gamma rays are a valuable tool for studying particle acceleration and radiation in the magnetospheres of energetic pulsars. The six or more pulsars seen by CGRO\\/EGRET show that: the light curves usually have double-peak structures (suggesting a broad cone of emission); gamma rays are frequently the dominant component of the radiated power; and all the spectra show evidence of

David J. Thompson

2001-01-01

145

Ultrahigh resolution multicolor colocalization of single fluorescent nanocrystals  

SciTech Connect

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

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

2000-12-20

146

gamma ray astronomy with muons  

Microsoft Academic Search

Although gamma ray showers are muon poor, they still produce a number of muons sufficient to make the sources observed by GeV and TeV telescopes observable also in muons. For sources with hard gamma ray spectra there is a relative ``enhancement'' of muons from gamma ray primaries as compared to that from nucleon primaries. All shower gamma rays above the

Francis Halzen; Todor Stanev; Gaurang B. Yodh

1997-01-01

147

The gamma-ray observatory  

NASA Technical Reports Server (NTRS)

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

1991-01-01

148

Bridgman growth of LaBr 3:Ce and LaCl 3:Ce crystals for high-resolution gamma-ray spectrometers  

NASA Astrophysics Data System (ADS)

Single crystals of LaBr 3:Ce and LaCl 3:Ce have been grown by the vertical Bridgman technique. Crystals of these scintillators are used in the fabrication of high-resolution, gamma-ray spectrometers. The LaBr 3:Ce and LaCl 3:Ce crystals we have grown have high light outputs of ˜80,000 and 50,000 photons/MeV, respectively, and fast principal decay constants of <30 ns. The emission wavelength for the LaBr 3:Ce and LaCl 3:Ce scintillators are ?=360 and 350 nm, respectively. Both materials have excellent energy resolutions of ˜3% FWHM for 662 keV photons at room temperature. In this paper, we will report on our results to date for vertical Bridgman crystal growth and characterization of Ce-doped LaBr 3 and LaCl 3 crystals. We will also describe the handling and processing procedures developed for these oxygen and moisture sensitive materials.

Higgins, W. M.; Glodo, J.; Van Loef, E.; Klugerman, M.; Gupta, T.; Cirignano, L.; Wong, P.; Shah, K. S.

2006-01-01

149

Gamma ray optics  

NASA Astrophysics Data System (ADS)

Via refractive or diffractive scattering one can shape ? ray beams in terms of beam divergence, spot size and monochromaticity. These concepts might be particular important in combination with future highly brilliant gamma ray sources and might push the sensibility of planned experiments by several orders of magnitude. We will demonstrate the experimental feasibility of gamma ray monochromatization on a ppm level and the creation of a gamma ray beam with nanoradian divergence. The results are obtained using the inpile target position of the High Flux Reactor of the ILL Grenoble and the crystal spectrometer GAMS. Since the refractive index is believed to vanish to zero with 1/E2, the concept of refractive optics has never been considered for gamma rays. The combination of refractive optics with monochromator crystals is proposed to be a promising design. Using the crystal spectrometer GAMS, we have measured for the first time the refractive index at energies in the energy range of 180 - 2000 keV. The results indicate a deviation from simple 1/E2 extrapolation of X-ray results towards higher energies. A first interpretation of these new results will be presented. We will discuss the consequences of these results on the construction of refractive optics such as lenses or refracting prisms for gamma rays and their combination with single crystal monochromators.

Jentschel, M.; Günther, M. M.; Habs, D.; Thirolf, P. G.

2012-07-01

150

Gamma ray camera  

DOEpatents

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

Perez-Mendez, Victor (Berkeley, CA)

1997-01-01

151

Gamma ray camera  

DOEpatents

A gamma ray camera is disclosed for detecting rays emanating from a radiation source such as an isotope. The gamma ray camera includes a sensor array formed of a visible light crystal for converting incident gamma rays to a plurality of corresponding visible light photons, and a photosensor array responsive to the visible light photons in order to form an electronic image of the radiation therefrom. The photosensor array is adapted to record an integrated amount of charge proportional to the incident gamma rays closest to it, and includes a transparent metallic layer, photodiode consisting of a p-i-n structure formed on one side of the transparent metallic layer, and comprising an upper p-type layer, an intermediate layer and a lower n-type layer. In the preferred mode, the scintillator crystal is composed essentially of a cesium iodide (CsI) crystal preferably doped with a predetermined amount impurity, and the p-type upper intermediate layers and said n-type layer are essentially composed of hydrogenated amorphous silicon (a-Si:H). The gamma ray camera further includes a collimator interposed between the radiation source and the sensor array, and a readout circuit formed on one side of the photosensor array. 6 figs.

Perez-Mendez, V.

1997-01-21

152

The project of a high-resolution and sensitivity (HRS) instrument for solar flare gamma-ray spectroscopy  

Microsoft Academic Search

Fine-structure measurements of solar gamma-emission lines are possible in the framework of high-resolution and sensitivity (HRS) spectroscopy only. Here we present the project of HRS instrument which includes Germanium and scintillator spectrometers. The Ge-spectrometer will cover the range 0.015–10 MeV with a resolution of ?0.2% at 1 MeV. It consists of an array of Ge-detectors cooled to <90K. The scintillator

H. V. Kladpor-Kleingrothaus; J. Hellmig; A. Mueller; H. Strecker; S. I. Svertilov; V. G Stolpovskii; A. V. Bogomolov; M. I. Kudryavtsev; V. F Melnikov; I. V. Krivosheina

1998-01-01

153

"Ultra-high resolution optical trap with single fluorophore sensitivity"  

PubMed Central

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

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

2013-01-01

154

Gamma ray pulsars  

NASA Technical Reports Server (NTRS)

Recent data from the high energy gamma ray experiment have revealed the existence of four pulsars emitting photons above 35 MeV. An attempt is made to explain the gamma ray emission from these pulsars in terms of an electron-photon cascade that develops in the magnetosphere of the pulsar. Although there is very little material above the surface of the pulsar, the very intense magnetic fields correspond to many radiation lengths which cause electrons to emit photons via magnetic bremsstrahlung and these photons to pair produce. The cascade develops until the mean photon energy drops below the pair production threshold which happens to be in the gamma ray range; at this stage the photons break out from the source.

Oegelman, H.; Ayasli, S.; Hacinliyan, A.

1976-01-01

155

Imaging brain morphology with ultrahigh-resolution optical coherence tomography  

NASA Astrophysics Data System (ADS)

The morphology of healthy and pathological human brain tissue, as well as the brain structural organization of various animal models has been imaged in-vitro using ultrahigh resolution optical coherence tomography (UHR OCT). Micrometer-scale OCT resolution (< 2 ?m axial resolution) was achieved at different central wavelengths by interfacing three state-of-the-art broad bandwidth light sources (Ti:Al2O3, ?c = 790 nm, ?? = 260 nm and Pout = 50 mW; PCF based laser, ?c = 1150 nm, ?? = 350 nm and Pout = 2 W; Fiber laser based light source, ?c = 1350 nm, ?? = 470 nm and Pout = 4 mW) to a modular free-space OCT system, utilizing a dynamic focusing and designed for optimal performance in the appropriate wavelength regions. Images acquired from a fixed honeybee brain demonstrated the ability of UHR OCT to image the globular structure of the brain, some fine morphological details such as the nerve fiber bundles connecting the medulla (visual center) to the honeybee eyes, and the interfaces between different tissue layers in the medulla. Tomograms of various human neuropathologies demonstrated the feasibility of UHR OCT to visualize morphological details such as small (~20 ?m) calcifications typical for fibrous meningioma, and enlarged nuclei of cancer cells (~10-15 ?m) characteristic for many other neuropathologies. In addition UHR OCT was used to image cellular morphology in living ganglion cells.

Bizheva, Kostadinka K.; Unterhuber, Angelika; Hermann, Boris; Povazay, Boris; Sattmann, Harald; Mei, Michael; Holzwarth, Ronald; Preusser, Matthias; Reitsamer, Herbert; Seefeldt, Michael; Menzel, Ralf; Budka, Herbert; Fercher, Adolf F.; Drexler, Wolfgang

2003-10-01

156

Characteristics of the telescope for high energy gamma-ray astronomy selected for definition studies on the gamma ray observatory  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

157

Impact of temperature variation on the energy resolution of 3D position sensitive CZT gamma- ray spectrometers  

Microsoft Academic Search

Prototype 3D position sensitive CZT gamma spectrometers have been developed using 10x10x10 mm3 pixellated CZT detectors and a RENA-3 readout system from NOVA R&D. Under stable room temperature, excellent energy resolution of ~1% FWHM at 662 keV is consistently demonstrated for single interaction events in the detector with one time pre-measurement calibration. To test the feasibility of using the 3D

Wen Li; Yanfeng Du; Brian D. Yanoff; Jeffrey S. Gordon

2007-01-01

158

Position Profiling of the Gamma-Ray Beam at the High Intensity Gamma-Ray Source (HIGS)  

Microsoft Academic Search

A multi-wire proportional chamber has been constructed to be used as a gamma-ray position profiling device at the High Intensity Gamma-Ray Source (HIGS) located in the Duke Free Electron Laser Laboratory. The chamber will provide a means of locating the central axis of the gamma-ray beam with an enhanced position resolution as compared to current methods. The determination of the

David Westerly

2002-01-01

159

Gamma-ray telescopes  

Microsoft Academic Search

The last half-century has seen dramatic developments in ??ray telescopes, from their initial conception and development through to their blossoming into full maturity as a potent\\u000a research tool in astronomy. Gamma-ray telescopes are leading research in diverse areas such as ??ray bursts, blazars, Galactic transients, and the Galactic distribution of 26Al.

Neil Gehrels; John K. Cannizzo

2009-01-01

160

Gamma ray astronomy  

NASA Technical Reports Server (NTRS)

Miscellaneous tasks related to mission operations and data analysis for the Burst and Transient Source Experiment on the Gamma Ray Observatory, to collection, analysis, and interpretation of data from the Marshall Space Flight Center Very Low Frequency transient monitoring program, and to compilation and analysis of induced radioactivity data were performed. The results are summarized and relevant references are included.

Paciesas, William S.

1992-01-01

161

Gamma-Ray Bursts  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

162

Gamma-ray Astronomy.  

National Technical Information Service (NTIS)

The Burst and Transient Source Experiment (BATSE) is one of four instruments on the Compton observatory which was launched by the space shuttle Atlantis on April 5, 1991. As of mid-March, 1994, BATSE detected more than 925 cosmic gamma-ray bursts and more...

W. S. Paciesas

1994-01-01

163

Gamma Ray Astronomy  

NASA Technical Reports Server (NTRS)

The project has progressed successfully during this period of performance. The highlights of the Gamma Ray Astronomy teams efforts are: (1) Support daily BATSE data operations, including receipt, archival and dissemination of data, quick-look science analysis, rapid gamma-ray burst and transient monitoring and response efforts, instrument state-of-health monitoring, and instrument commanding and configuration; (2) On-going scientific analysis, including production and maintenance of gamma-ray burst, pulsed source and occultation source catalogs, gamma-ray burst spectroscopy, studies of the properties of pulsars and black holes, and long-term monitoring of hard x-ray sources; (3) Maintenance and continuous improvement of BATSE instrument response and calibration data bases; (4) Investigation of the use of solid state detectors for eventual application and instrument to perform all sky monitoring of X-Ray and Gamma sources with high sensitivity; and (5) Support of BATSE outreach activities, including seminars, colloquia and World Wide Web pages. The highlights of this efforts can be summarized in the publications and presentation list.

Wu, S. T.

2000-01-01

164

Response of a high-resolution high-energy photon spectrometer (HHS) to monochromatic high-energy gamma rays  

NASA Astrophysics Data System (ADS)

The response function of a high-resolution high-energy photon spectrometer (HHS), consisting of a twin Ge detector and BGO (Bi 3Ge 4O 12) anti-coincidence shields, has been measured for 10.763 MeV monochromatic ?-rays generated in a resonant reaction 27Al(p,?) 28Si. The experimental response functions measured with and without the anti-coincidence were compared with results by Monte Carlo simulations, in which a pulse-height degradation effect associated with a surface channel of the twin Ge detector has been included. Excellent agreement was obtained between the experimental response functions and the simulations.

Harada, H.; Furutaka, K.; Nakamura, S.; Osaka, K.; Akimune, H.; Utsunomiya, H.; Ohsaki, T.; Igashira, M.

2005-12-01

165

Liquid xenon gamma ray imager  

US Patent & Trademark Office Database

A gamma ray imager includes a chamber containing a scintillation liquid such as xenon and several mutually optically isolated interaction modules immersed in the scintillation liquid within the chamber. Multiple photodetectors optically coupled to the modules separately detect scintillation light resulting from gamma ray interactions in the modules. Charge readout devices coupled to the modules provide time projection chamber-class detection of ionization charges produced by gamma ray interactions within the modules. A signal processor connected to the multiple photodetectors and charge readout devices analyzes signals produced by gamma ray interactions within the modules and calculates from the signals gamma ray energy and gamma ray angle. The calculations use Compton scattering formula inversion and also use anti-correlation of prompt scintillation light signals from gamma ray interactions and charge signals from gamma ray interactions.

2013-07-02

166

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

NASA Astrophysics Data System (ADS)

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

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

167

Soft gamma rays from black holes versus neutron stars  

NASA Technical Reports Server (NTRS)

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

Liang, Edison P.

1992-01-01

168

Hybrid gamma ray imaging—Model and results  

Microsoft Academic Search

We report on a hybrid gamma-ray radiation imaging system for industrial applications that combine the advantages of a multi-aperture mechanical collimator with electronic collimation. The combination offers both efficiency and good angular resolution, and is unique since a single gamma ray can contribute information to both modalities simultaneously. The mechanically collimated camera is most effective for imaging lower energy photons

Wonho Lee; David Wehe

2007-01-01

169

Ultrahigh-resolution multicolor colocalization of single fluorescent probes.  

PubMed

An optical ruler based on ultrahigh-resolution colocalization of single fluorescent probes is described in this paper. It relies on the use of two unique families of fluorophores, namely energy-transfer fluorescent beads (TransFluoSpheres) and semiconductor nanocrystal quantum dots, that can be excited by a single laser wavelength but emit at different wavelengths. A multicolor sample-scanning confocal microscope was constructed that allows one to image each fluorescent light emitter, free of chromatic aberrations, by scanning the sample with nanometer scale steps with a piezo-scanner. The resulting spots are accurately localized by fitting them to the known shape of the excitation point-spread function of the microscope. We present results of two-dimensional colocalization of TransFluoSpheres (40 nm in diameter) and of nanocrystals (3-10 nm in diameter) and demonstrate distance-measurement accuracy of better than 10 nm using conventional far-field optics. This ruler bridges the gap between fluorescence resonance energy transfer, near- and far-field imaging, spanning a range of a few nanometers to tens of micrometers. PMID:10931959

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

2000-08-15

170

Retinal oximetry using ultrahigh-resolution optical coherence tomography  

PubMed Central

Background The purpose of this study was to investigate the repeatability of retinal oximetry using slit-lamp adapted ultrahigh-resolution optical coherence tomography (SL-UHR-OCT). Methods SL-UHR-OCT was developed and fringe patterns were obtained for a major retinal artery and a major retinal vein. A-scans at the central wavelengths of 805 nm and 855 nm were analyzed for calculating optical density ratios (ODRs), from which the percentage oxygen saturation was calculated. Measurements were made on two occasions for each person. Repeatability and coefficients of repeatability were calculated. Results The mean ODRs of the artery were 0.79 ± 0.86 and 0.88 ± 0.97 in sessions 1 and 2, respectively. The mean ODRs of the vein were ?0.08 ± 0.69 and 0.14 ± 0.77 between the two sessions, and were significantly lower than that of the artery (P < 0.05). The coefficients of repeatability were 1.44 and 1.81 for the artery and vein, respectively. The mean oxygen saturation of the major retinal artery was 94% ± 45% and 98% ± 51% in sessions 1 and 2, respectively, and the mean oxygen saturation of the major retinal vein was 48% ± 36% and 60% ± 40% between sessions. Conclusion Optical coherence tomographic oximetry for evaluating retinal oxygen saturation was subject to variation, although the averaged measurements in repeated sessions were matched. Further work on reducing variation will be needed.

Ye, Yufeng; Jiang, Hong; Shen, Meixiao; Lam, Byron L; DeBuc, Delia Cabrera; Ge, Lili; Sehi, Mitra; Wang, Jianhua

2012-01-01

171

Gamma-Ray Imaging for Explosives Detection  

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

172

Gamma-ray imaging for explosives detection  

NASA Astrophysics Data System (ADS)

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

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

2008-05-01

173

Technology Needs for Gamma Ray Astronomy  

NASA Technical Reports Server (NTRS)

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.

Gehrels, Neil

2011-01-01

174

Gamma-ray burst and spectroscopy instrumentation development at the Goddard Space Flight Center  

NASA Technical Reports Server (NTRS)

This paper summarizes the activities that are specifically related to the development of instrumentation for gamma-ray astronomy. Three programs are described: (1) the Gamma-Ray Imaging Spectrometer (GRIS), a balloon-borne array of seven germanium detectors for high-resolution spectrographic studies of persistent gamma-ray sources; (2) the Transient Gamma-Ray Spectrometer (TGRS), a single radiatively-cooled germanium detector for the spectrographic study of gamma-ray bursts, and (3) the Rapidly Moving Telescope (RMT), a ground-based optical telescope for the detection and study of short-lived optical transients, particularly those that occur in coincidence with gamma-ray bursts.

Teegarden, B. J.

1986-01-01

175

Unidentified Gamma-Ray Sources: Hunting Gamma-Ray Blazars  

SciTech Connect

One of the main scientific objectives of the ongoing Fermi mission is unveiling the nature of the unidentified {gamma}-ray sources (UGSs). Despite the large improvements of Fermi in the localization of {gamma}-ray sources with respect to the past {gamma}-ray missions, about one third of the Fermi-detected objects are still not associated to low energy counterparts. Recently, using the Wide-field Infrared Survey Explorer (WISE) survey, we discovered that blazars, the rarest class of Active Galactic Nuclei and the largest population of {gamma}-ray sources, can be recognized and separated from other extragalactic sources on the basis of their infrared (IR) colors. Based on this result, we designed an association method for the {gamma}-ray sources to recognize if there is a blazar candidate within the positional uncertainty region of a generic {gamma}-ray source. With this new IR diagnostic tool, we searched for {gamma}-ray blazar candidates associated to the UGS sample of the second Fermi {gamma}-ray catalog (2FGL). We found that our method associates at least one {gamma}-ray blazar candidate as a counterpart each of 156 out of 313 UGSs analyzed. These new low-energy candidates have the same IR properties as the blazars associated to {gamma}-ray sources in the 2FGL catalog.

Massaro, F.; D'Abrusco, R.; Tosti, G.; Ajello, M.; Gasparrini, A.Paggi.D.

2012-04-02

176

UNIDENTIFIED {gamma}-RAY SOURCES: HUNTING {gamma}-RAY BLAZARS  

SciTech Connect

One of the main scientific objectives of the ongoing Fermi mission is unveiling the nature of unidentified {gamma}-ray sources (UGSs). Despite the major improvements of Fermi in the localization of {gamma}-ray sources with respect to the past {gamma}-ray missions, about one-third of the Fermi-detected objects are still not associated with low-energy counterparts. Recently, using the Wide-field Infrared Survey Explorer survey, we discovered that blazars, the rarest class of active galactic nuclei and the largest population of {gamma}-ray sources, can be recognized and separated from other extragalactic sources on the basis of their infrared (IR) colors. Based on this result, we designed an association method for the {gamma}-ray sources to recognize if there is a blazar candidate within the positional uncertainty region of a generic {gamma}-ray source. With this new IR diagnostic tool, we searched for {gamma}-ray blazar candidates associated with the UGS sample of the second Fermi {gamma}-ray LAT catalog (2FGL). We found that our method associates at least one {gamma}-ray blazar candidate as a counterpart to each of 156 out of 313 UGSs analyzed. These new low-energy candidates have the same IR properties as the blazars associated with {gamma}-ray sources in the 2FGL catalog.

Massaro, F.; Ajello, M. [SLAC National Laboratory and Kavli Institute for Particle Astrophysics and Cosmology, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States); D'Abrusco, R.; Paggi, A. [Harvard-Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Tosti, G. [Dipartimento di Fisica, Universita degli Studi di Perugia, 06123 Perugia (Italy); Gasparrini, D. [ASI Science Data Center, ESRIN, I-00044 Frascati (Italy)

2012-06-10

177

A high resolution liquid xenon imaging telescope for 0.3-10 MeV gamma-ray astrophysics: Construction and initial balloon flights  

NASA Technical Reports Server (NTRS)

An instrument is described which will provide a direct image of gamma-ray line or continuum sources in the energy range 300 keV to 10 MeV. The use of this instrument to study the celestial distribution of the (exp 26)Al isotope by observing the 1.809 MeV deexcitation gamma-ray line is illustrated. The source location accuracy is 2' or better. The imaging telescope is a liquid xenon time projection chamber coupled with a coded aperture mask (LXe-CAT). This instrument will confirm and extend the COMPTEL observations from the Compton Gamma-Ray Observatory (CGRO) with an improved capability for identifying the actual Galactic source or sources of (exp 26)Al, which are currently not known with certainty. sources currently under consideration include red giants on the asymptotic giant branch (AGB), novae, Type 1b or Type 2 supernovae, Wolf-Rayet stars and cosmic-rays interacting in molecular clouds. The instrument could also identify a local source of the celestial 1.809 MeV gamma-ray line, such as a recent nearby supernova.

Aprile, Elena

1994-01-01

178

Gamma-ray localization of terrestrial gamma-ray flashes.  

PubMed

Terrestrial gamma-ray flashes (TGFs) are very short bursts of high-energy photons and electrons originating in Earth's atmosphere. We present here a localization study of TGFs carried out at gamma-ray energies above 20 MeV based on an innovative event selection method. We use the AGILE satellite Silicon Tracker data that for the first time have been correlated with TGFs detected by the AGILE Mini-Calorimeter. We detect 8 TGFs with gamma-ray photons of energies above 20 MeV localized by the AGILE gamma-ray imager with an accuracy of ?5-10° at 50 MeV. Remarkably, all TGF-associated gamma rays are compatible with a terrestrial production site closer to the subsatellite point than 400 km. Considering that our gamma rays reach the AGILE satellite at 540 km altitude with limited scattering or attenuation, our measurements provide the first precise direct localization of TGFs from space. PMID:20867680

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

2010-09-17

179

Ultra-high resolution and high-brightness AMOLED  

NASA Astrophysics Data System (ADS)

As part of its continuing effort to improve both the resolution and optical performance of AMOLED microdisplays, eMagin has recently developed an SXGA (1280×3×1024) microdisplay under a US Army RDECOM CERDEC NVESD contract that combines the world's smallest OLED pixel pitch with an ultra-high brightness green OLED emitter. This development is aimed at next-generation HMD systems with "see-through" and daylight imaging requirements. The OLED pixel array is built on a 0.18-micron CMOS backplane and contains over 4 million individually addressable pixels with a pixel pitch of 2.7 × 8.1 microns, resulting in an active area of 0.52 inches diagonal. Using both spatial and temporal enhancement, the display can provide over 10-bits of gray-level control for high dynamic range applications. The new pixel design also enables the future implementation of a full-color QSXGA (2560 × RGB × 2048) microdisplay in an active area of only 1.05 inch diagonal. A low-power serialized low-voltage-differential-signaling (LVDS) interface is integrated into the display for use as a remote video link for tethered systems. The new SXGA backplane has been combined with the high-brightness green OLED device developed by eMagin under an NVESD contract. This OLED device has produced an output brightness of more than 8000fL with all pixels on; lifetime measurements are currently underway and will presented at the meeting. This paper will describe the operational features and first optical and electrical test results of the new SXGA demonstrator microdisplay.

Wacyk, Ihor; Ghosh, Amal; Prache, Olivier; Draper, Russ; Fellowes, Dave

2012-05-01

180

Application of Proportional Scintillation gamma-Ray Counters to the Determination of Radioactive Decay Schemes  

Microsoft Academic Search

THE determination of all but the simplest radioactive decay schemes necessitates a means of analysis of the gamma-rays emitted, so that coincidences may be measured between the various gamma-rays, and also between a particular gamma-ray and the primary beta-ray spectrum. Many nuclei emit gamma-rays well spaced in energy, and a spectrometer of quite poor resolution would separate them sufficiently well

Patrick E. Cavanagh

1950-01-01

181

Gamma-Ray Library and Uncertainty Analysis: Passively Emitted Gamma Rays Used in Safeguards Technology  

SciTech Connect

Non-destructive gamma-ray analysis is a fundamental part of nuclear safeguards, including nuclear energy safeguards technology. Developing safeguards capabilities for nuclear energy will certainly benefit from the advanced use of gamma-ray spectroscopy as well as the ability to model various reactor scenarios. There is currently a wide variety of nuclear data that could be used in computer modeling and gamma-ray spectroscopy analysis. The data can be discrepant (with varying uncertainties), and it may difficult for a modeler or software developer to determine the best nuclear data set for a particular situation. To use gamma-ray spectroscopy to determine the relative isotopic composition of nuclear materials, the gamma-ray energies and the branching ratios or intensities of the gamma-rays emitted from the nuclides in the material must be well known. A variety of computer simulation codes will be used during the development of the nuclear energy safeguards, and, to compare the results of various codes, it will be essential to have all the {gamma}-ray libraries agree. Assessing our nuclear data needs allows us to create a prioritized list of desired measurements, and provides uncertainties for energies and especially for branching intensities. Of interest are actinides, fission products, and activation products, and most particularly mixtures of all of these radioactive isotopes, including mixtures of actinides and other products. Recent work includes the development of new detectors with increased energy resolution, and studies of gamma-rays and their lines used in simulation codes. Because new detectors are being developed, there is an increased need for well known nuclear data for radioactive isotopes of some elements. Safeguards technology should take advantage of all types of gamma-ray detectors, including new super cooled detectors, germanium detectors and cadmium zinc telluride detectors. Mixed isotopes, particularly mixed actinides found in nuclear reactor streams can be especially challenging to identify. The super cooled detectors have a marked improvement in energy resolution, allowing the possibility of deconvolution of mixtures of gamma rays that was unavailable with high purity germanium detectors. Isotopic analysis codes require libraries of gamma rays. In certain situations, isotope identification can be made in the field, sometimes with a short turnaround time, depending on the choice of detector and software analysis package. Sodium iodide and high purity germanium detectors have been successfully used in field scenarios. The newer super cooled detectors offer dramatically increased resolution, but they have lower efficiency and so can require longer collection times. The different peak shapes require software development for the specific detector type and field application. Libraries can be tailored to specific scenarios; by eliminating isotopes that are certainly not present, the analysis time may be shortened and the accuracy may be increased. The intent of this project was to create one accurate library of gamma rays emitted from isotopes of interest to be used as a reliable reference in safeguards work. All simulation and spectroscopy analysis codes can draw upon this best library to improve accuracy and cross-code consistency. Modeling codes may include MCNP and COG. Gamma-ray spectroscopy analysis codes may include MGA, MGAU, U235 and FRAM. The intent is to give developers and users the tools to use in nuclear energy safeguards work. In this project, the library created was limited to a selection of actinide isotopes of immediate interest to reactor technology. These isotopes included {sup 234-238}U, {sup 237}Np, {sup 238-242}Pu, {sup 241,243}Am and {sup 244}Cm. These isotopes were examined, and the best of gamma-ray data, including line energies and relative strengths were selected.

Parker, W

2009-09-18

182

Gamma-ray energy tracking array: GRETINA  

NASA Astrophysics Data System (ADS)

A Gamma-ray energy tracking array can provide higher efficiency, better peak-to-total ratio and higher position resolution than the current generation of detector arrays. Particularly, the capability of reconstructing the position of the interaction with millimetre resolution is needed to fully exploit the physics opportunities provided by current and next generation radioactive beam facilities. This paper presents the basic concepts of energy tracking, examples of physics opportunities, and the status of the GRETINA/GRETA project.

Lee, I.-Yang

2013-03-01

183

Gamma Ray Pulsars: Multiwavelength Observations  

Microsoft Academic Search

High-energy gamma rays are a valuable tool for studying particle acceleration\\u000aand radiation in the magnetospheres of energetic pulsars. The seven or more\\u000apulsars seen by instruments on the Compton Gamma Ray Observatory (CGRO) show\\u000athat: the light curves usually have double-peak structures (suggesting a broad\\u000acone of emission); gamma rays are frequently the dominant component of the\\u000aradiated power;

David J. Thompson

2003-01-01

184

The Gamma Ray Pulsar Population  

Microsoft Academic Search

We apply a likelihood analysis to pulsar detections, pulsar upper limits, and\\u000adiffuse background measurements from the OSSE and EGRET instruments on the\\u000aCompton Gamma Ray Observatory to constrain the luminosity law for gamma-ray\\u000apulsars and some properties of the gamma-ray pulsar population. We find that\\u000athe dependence of luminosity on spin period and dipole magnetic field is much\\u000asteeper

M. A. McLaughlin; J. M. Cordes

1999-01-01

185

{gamma} ray astronomy with muons  

SciTech Connect

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

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

1997-04-01

186

Advances in Physics using Gamma-Ray Tracking and GRETA  

NASA Astrophysics Data System (ADS)

The detection of gamma-ray emission from excited states in atomic nuclei plays a vital and ubiquitous role in nuclear science experiments and with each step forward in gamma-ray detector technology there has been a significant advance in our understanding of nuclei. It is now understood that large gains in resolving power are possible by applying the concept of gamma-ray energy tracking to a detector shell consisting of electrically segmented germanium crystals. This talk will concentrate on such a national detector initiative GRETA (and Gretina). This major advance in technology promises to revolutionize gamma-ray detector design and will enable new classes of high-resolution gamma-ray experiments in nuclear structure, nuclear astrophysics, and weak interactions at existing facilities, and at the future Rare Isotope Accelerator.

Riley, Mark

2003-11-01

187

Gamma-ray burst variability above 4 MeV  

NASA Astrophysics Data System (ADS)

The relationship between the hard X-ray and gamma ray emissions during four bursts using the anti-coincidence shields of the High Energy Astronomy Observatory 3 (HEAO 3) Gamma Ray Spectrometer is explored. Recent observations of gamma ray bursts by the Solar Maximum Mission Gamma Ray Spectrometer (GRS) have shown that high energy emission above 1 MeV is a common and energetically important feature (Matz et al. 1985). Time histories of four gamma ray bursts in 3 energy bands ( keV, around 511 keV, and 4 MeV) with 10.24 a resolution show that the 4 MeV flux is only weakly coupled to the spectrum below approximately 600 keV.

Schwartz, R. A.; Ling, J. C.; Mahoney, W. A.; Wheaton, W. A.; Jacobson, A. S.

1985-08-01

188

The LXeCAT instrument for gamma-ray astrophysics  

NASA Technical Reports Server (NTRS)

The Liquid Xenon Coded Aperture Telescope (LXeCAT) and its capability to image astrophysical gamma-ray sources in the MeV region is described. The gamma-ray detector is a Liquid Xenon Time Projection Chamber (LXeTPC) triggered by the primary scintillation light. Effective background rejection is a direct consequence of the intrinsic three-dimensional imaging capability of the LXeTPC. Initial results with a 10 liter prototype confirm an energy resolution of 6% FWHM, a position resolution of 1 mm RMS and a light triggering efficiency higher than 90% for 1 MeV gamma-rays.

Aprile, E.; Xu, F.; Zhou, M.; Doke, T.; Kikuchi, J.; Masuda, K.; Chupp, E. L.; Dunphy, P. P.; Fishman, G.; Pendelton, G.

1995-01-01

189

Recent improvements in plutonium gamma-ray analysis using MGA.  

National Technical Information Service (NTIS)

MGA is a gamma-ray spectrum analysis program for determining relative plutonium isotopic abundances. It can determine plutonium isotopic abundances better than 1% using a high-resolution, low-energy, planar germanium detector and measurement times ten min...

W. D. Ruhter R. Gunnink

1992-01-01

190

Gamma-ray spectrum of Centaurus A: a high-resolution observation between 70 keV and 8 MeV  

SciTech Connect

The NASA/Goddard Space Flight Center Low Energy Gamma ray Spectrometer (LEGS) observed the nearby active nucleus galaxy Centaurus A (NGC 5128) during a balloon flight on 1981 November 19. There is no evidence of a break in the spectrum or of any line features. The 1.6 MeV limit is a factor of 8 lower than the 1974 line flux, indicating that, if the 1974 feature was real, and, if it was narrow, then the line intensity decreased significantly between 1974 and 1981. The lack of observed annihilation radiation from Cen A, combined with the temporal variations that are seen in the X-ray and gamma-ray intensities, constrain the size of the emission region to be between 10 to the 13th power and 5 x 10 to the 17th power cm.

Gehrels, N.; Cline, T.L.; Teegarden, B.J.; Paciesas, W.S.

1983-08-01

191

The gamma-ray spectrum of Centaurus A - A high-resolution observation between 70 keV and 8 MeV  

NASA Technical Reports Server (NTRS)

The NASA/Goddard Space Flight Center Low Energy Energy Gamma ray Spectrometer (LEGS) observed the nearby active nucleus galaxy Centaurus A (NGC 5128) during a balloon flight on 1981 November 19. There is no evidence of a break in the spectrum or of any line features. The 1.6 MeV limit is a factor of 8 lower than the 1974 line flux, indicating that, if the 1974 feature was real, and, if it was narrow, then the line intensity decreased significantly between 1974 and 1981. The lack of observed annihilation radiation from Cen A, combined with the temporal variations that are seen in the X-ray and gamma-ray intensities, constrain the size of the emission region to be between 10 to the 13th power and 5 x 10 to the 17th power cm. Previously announced in STAR as N83-35990

Gehrels, N.; Cline, T. L.; Teegarden, B. J.; Paciesas, W. S.; Tueller, J.; Durouchoux, PH.; Hameury, J. M.

1984-01-01

192

The gamma-ray spectrum of Centaurus A: A high-resolution observation between 70 keV and 8 MeV  

NASA Technical Reports Server (NTRS)

The NASA/Goddard Space Flight Center Low Energy Gamma ray Spectrometer (LEGS) observed the nearby active nucleus galaxy Centaurus A (NGC 5128) during a balloon flight on 1981 November 19. There is no evidence of a break in the spectrum or of any line features. The 1.6 MeV limit is a factor of 8 lower than the 1974 line flux, indicating that, if the 1974 feature was real, and, if it was narrow, then the line intensity decreased significantly between 1974 and 1981. The lack of observed annihilation radiation from Cen A, combined with the temporal variations that are seen in the X-ray and gamma-ray intensities, constrain the size of the emission region to be between 10 to the 13th power and 5 x 10 to the 17th power cm.

Gehrels, N.; Cline, T. L.; Teegarden, B. J.; Paciesas, W. S.; Tueller, J.; Durouchoux, P.; Hameury, J. M.

1983-01-01

193

Spectral interference corrections for the measurement of (238)U in materials rich in thorium by a high resolution gamma-ray spectrometry.  

PubMed

In this study, the spectral interferences are investigated for the analytical peaks at 63.3 keV of (234)Th and 1001.0 keV of (234m)Pa, which are often used in the measurement of (238)U activity by the gamma-ray spectrometry. The correction methods are suggested to estimate the net peak areas of the gamma-rays overlapping the analytical peaks, due to the contribution of (232)Th that may not be negligible in materials rich in natural thorium. The activity results for the certified reference materials (CRMs) containing U and Th were measured with a well type Ge detector. The self-absorption and true coincidence-summing (TCS) effects were also taken into account in the measurements. It is found that ignoring the contributions of the interference gamma-rays of (232)Th and (235)U to the mixed peak at 63.3 keV of (234)Th ((238)U) leads to the remarkably large systematic influence of 0.8-122% in the measured (238)U activity, but in case of ignoring the contribution of (232)Th via the interference gamma-ray at 1000.7 keV of (228)Ac to the mixed peak at 1001 keV of (234m)Pa ((238)U) results in relatively smaller systematic influence of 0.05-3%, depending on thorium contents in the samples. The present results showed that the necessary correction for the spectral interferences besides self-absorption and TCS effects is also very important to obtain more accurate (238)U activity results. Additionally, if one ignores the contribution of (232)Th to both (238)U and (40)K activities in materials, the maximum systematic influence on the effective radiation dose is estimated to be ~6% and ~1% via the analytical peaks at 63.3 and 1001 keV for measurement of the (238)U activity, respectively. PMID:19683454

Yücel, H; Solmaz, A N; Köse, E; Bor, D

2009-11-01

194

Arcsec source location measurements in gamma-ray astronomy from a lunar observatory  

NASA Astrophysics Data System (ADS)

The physical processes typically used in the detection of high energy gamma-rays do not permit good angular resolution, which makes difficult the unambiguous association of discrete gamma-ray sources with objects emitting at other wavelengths. 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 the purpose of discussion, this concept is examined for gamma rays above about 20 MeV for which pair production dominates the detection process and locally-generated nuclear gamma rays do not contribute to the background.

Koch, D. G.; Hughes, B. E.

1990-03-01

195

Digital Pulse Processing and Gamma Ray Tracking  

NSDL National Science Digital Library

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

2010-09-21

196

The gamma ray spectrometer for the Solar Maximum Mission  

Microsoft Academic Search

The Solar Maximum Mission Gamma Ray Experiment (SMM GRE) utilizes an actively shielded, multicrystal scintillation spectrometer to measure the flux of solar gamma rays. The instrument provides a 476-channel pulse height spectrum (with energy resolution of ~7% at 662 keV) every 16.38 s over the energy range 0.3–9 MeV. Higher time resolution (2 s) is available in three windows between

D. J. Forrest; E. L. Chupp; J. M. Ryan; M. L. Cherry; I. U. Gleske; C. Reppin; K. Pinkau; E. Rieger; G. Kanbach; R. L. Kinzer; G. Share; W. N. Johnson; J. D. Kurfess

1980-01-01

197

Gamma-ray spectrometer utilizing xenon at high pressure  

Microsoft Academic Search

A prototype gamma-ray spectrometer utilizing xenon gas near the critical point (166°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

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

1994-01-01

198

Performance of the EGRET astronomical gamma ray telescope  

NASA Astrophysics Data System (ADS)

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

Nolan, P. L.; Bertsch, D. L.; Fichtel, C. E.; Hartman, R. C.; Hofstadter, R.; Hughes, E. B.; Hunter, S. D.; Kanbach, G.; Kniffen, D. A.; Lin, Y. C.

1992-08-01

199

Performance of the EGRET astronomical gamma ray telescope  

SciTech Connect

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

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

1992-08-01

200

Gamma-ray astronomy comes of age  

NASA Astrophysics Data System (ADS)

The 'spark chamber' detector used for energies greater than 10 MeV in gamma-ray astronomy is a pictorial device in which the ionization trails left by an electron-positron pair can be seen as a series of sparks. Such a detector, although yielding comparatively low angular resolution, has been used in the COS-B satellite observations of pulsars and molecular clouds that began in 1975. Preliminary COS-B analysis results indicate an abundance of cosmic ray protons in the Milky Way 60,000 light years from the galactic center; some of these protons may be of extragalactic origin. Another significant discovery of the COS-B mission has been a population of unidentified gamma-ray objects (UGOs). UGOs are unique in emitting gamma rays preferentially over all other forms of electromagnetic radiation, thereby posing many theoretical problems and compelling efforts toward their identification with objects emitting at other wavelengths. The only probable identification of this type that has thus far been accomplished is of the 'Geminga' gamma-ray source in Gemini; both an X-ray counterpart and possible optical counterparts have been proposed.

Bignami, G. F.

1985-10-01

201

Gamma-ray bursters  

NASA Technical Reports Server (NTRS)

Current theoretical models developed to explain the observational data (from spaceborne detectors) on gamma-ray bursters are summarized and illustrated with drawings, diagrams, graphs, and photographic images. Although the data are fragmentary and often flawed by instrument defects, models involving neutron stars with strong magnetic fields are generally favored, and it is assumed that most observed bursters lie within the Galaxy. The neutron-star origin of the bursts is suggested by their intensity and rapid variability (implying a very compact high-energy source) and the presence in some burster spectra of a line at 420 keV which is explained by the combination of electron-positron annihilation and gravitational reddening. Consideration is also given to optical flashes observed to occur about once per year in the direction of gamma bursters, and the need for further searches for lower-energy emissions from bursters is stressed.

Schaefer, B. E.

1985-01-01

202

Astrophysical gamma-ray spectroscopy  

NASA Technical Reports Server (NTRS)

Observations of gamma-ray lines from solar flares, the Galactic Center, and transient celestial events are reviewed. The lines observed in each case are identified, and possible emission sources are considered. Future prospects for gamma-ray line astronomy are briefly discussed.

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

1979-01-01

203

Bridgman growth of Cs 2LiYCl 6:Ce and 6Li-enriched Cs 2 6LiYCl 6:Ce crystals for high resolution gamma ray and neutron spectrometers  

Microsoft Academic Search

Single crystals of small and large diameter Cs2LiYCl6:Ce and 6Li-enriched Cs26LiYCl6:Ce have been grown by the vertical Bridgman technique. These scintillator crystals are used in the fabrication of high resolution, gamma ray and neutron spectrometers. The Cs2LiYCl6:Ce and 6Li-enriched Cs26LiYCl6:Ce crystals we have grown have high light outputs of up to ?22,000 photons\\/MeV. The emission wavelength for the Cs2LiYCl6:Ce and

William M. Higgins; Jarek Glodo; Urmila Shirwadkar; Alexei Churilov; Edgar Van Loef; Rastgo Hawrami; Guido Ciampi; Craig Hines; Kanai S. Shah

2010-01-01

204

Preliminary results from the first satellite of a high-resolution germanium gamma-ray spectrometer: Description of instrument, some activation lines encountered, and studies of the diffuse spectra  

NASA Technical Reports Server (NTRS)

Gamma radiation from terrestrial and extraterrestrial sources were investigated with a high resolution Ge(Li) spectrometer-cryogen system flown onboard a low altitude, spin stabilized, polar orbiting satellite. A brief description is given of the instrument and preliminary results obtained from earth orbit are discussed. Attempts were made to use angular distributions and geomagnetic latitude spectral variations to determine diffuse background spectrum, detect gamma ray line emissions from solar flares, and search for positron annihilation radiation coming from the direction of the galactic center.

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

1973-01-01

205

The solar gamma ray and neutron capabilities of COMPTEL on the Gamma Ray Observatory  

NASA Technical Reports Server (NTRS)

The imaging Compton telescope COMPTEL on the Gamma Ray Observatory (GRO) has unusual spectroscopic capabilities for measuring solar gamma-ray and neutron emission. The launch of the GRO is scheduled for June 1990 near the peak of the sunspot cycle. With a 30 to 40 percent probability for the Sun being in the COMPTEL field-of-view during the sunlit part of an orbit, a large number of flares will be observed above the 800 keV gamma-ray threshold of the telescope. The telescope energy range extends to 30 MeV with high time resolution burst spectra available from 0.1 to 10 MeV. Strong Compton tail suppression of instrumental gamma-ray interactions will facilitate improved spectral analysis of solar flare emissions. In addition, the high signal to noise ratio for neutron detection and measurement will provide new neutron spectroscopic capabilities. Specifically, a flare similar to that of 3 June 1982 will provide spectroscopic data on greater than 1500 individual neutrons, enough to construct an unambiguous spectrum in the energy range of 20 to 200 MeV. Details of the instrument and its response to solar gamma-rays and neutrons will be presented.

Ryan, James M.; Lockwood, John A.

1989-01-01

206

Planetary gamma-ray spectroscopy  

NASA Technical Reports Server (NTRS)

The measured intensities of certain gamma rays of specific energies escaping from a planetary surface can be used to determine the abundances of a number of elements. The fluxes of the more intense gamma-ray lines emitted from 32 elements were calculated using current nuclear data and existing models for the source processes. The source strengths for neutron-capture reactions were modified from those previously used. The fluxes emitted form a surface of average lunar composition are reported for 292 gamma-ray lines. These theoretical fluxes were used elsewhere to convert the data from the Apollo gamma-ray spectrometers to elemental abundances and can be used with measurements from future missions to map the concentrations of a number of elements over a planet's surface. Detection sensitivities for these elements are examined and applications of gamma-ray spectroscopy for future orbiters to Mars and other solar-system objects are discussed.

Reedy, R. C.

1978-01-01

207

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

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

208

CdZnTe gamma ray spectrometer for orbital gamma ray spectroscopy.  

SciTech Connect

We present the design and analysis of a new gamma ray spectrometer for planetary science that uses an array of CdZnTe detectors to achieve the detection efficiency needed for orbital measurements. The use of CdZnTe will provide significantly improved pulse height resolution relative to scintillation-based detectors, with commensurate improvement in the accuracy of elemental abundances determined by gamma ray and neutron spectroscopy. The spectrometer can be flown either on the instrument deck of the spacecraft or on a boom. For deck-mounted systems, a BGO anticoincidence shield is included in the design to suppress the response of the CdZnTe detector to gamma rays that originate in the spacecraft. The BGO shield also serves as a backup spectrometer, providing heritage from earlier planetary science missions and reducing the risk associated with the implementation of new technology.

Prettyman, T. H. (Thomas H.); Feldman, W. C. (William C.); Fuller, K. R. (Kenneth R.); Storms, S. A. (Steven A.); Soldner, S. A.; Lawrence, David J. (David Jeffery),; Browne, M. C. (Michael C.); Moss, C. E. (Calvin E.)

2001-01-01

209

Multiwavelength Study of Gamma-Ray Bright Blazars  

NASA Astrophysics Data System (ADS)

We investigate total intensity radio images of 6 gamma-ray bright blazars (BL Lac, 3C 279, 3C 273, W Com, PKS 1510-089, and 3C 66A) and their optical and gamma-ray light curves to study connections between gamma-ray and optical brightness variations and changes in the parsec-scale radio structure. We use high-resolution maps obtained by the BU group at 43 GHz with the VLBA, optical light curves constructed by the St.Petersburg State U. (Russia) team using measurements with the 0.4 m telescope of St.Petersburg State U. (LX200) and the 0.7 m telescope of the Crimean Astrophysical Observatory (AZT-8), and gamma-ray light curves, which we have constructed with data provided by the Fermi Large Area Telescope. Over the period from August 2008 to November 2009, superluminal motion is found in all 6 objects with apparent speed ranging from 2c to 40c. The blazars with faster apparent speeds, 3C 273, 3C 279, PKS 1510-089, and 3C 66A, exhibit stronger variability of the gamma-ray emission. There is a tendency for sources with sharply peaked gamma-ray flares to have faster jet speed than sources with gamma-ray light curves with no sharp peaks. Gamma-ray light curves with sharply peaked gamma-ray flares possess a stronger gamma-ray/optical correlations. The research at St.Petersburg State U. was funded by the Minister of Education and Science of the Russian Federation (state contract N#P123). The research at BU was funded in part by NASA Fermi Guest Investigator grant NNX08AV65G and by NSF grant AST-0907893. The VLBA is an instrument of the National Radio Astronomy Observatory, a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

Morozova, Daria; Larionov, V. M.; Hagen-Thorn, V. A.; Jorstad, S. G.; Marscher, A. P.; Troitskii, I. S.

2011-01-01

210

Gamma-Ray Polarimetry with Compton Telescope  

SciTech Connect

Compton telescope is a promising technology to achieve very high sensitivity in the soft gamma-ray band (0.1-10 MeV) by utilizing Compton kinematics. Compton kinematics also enables polarization measurement which will open new windows to study gamma-ray production mechanism in the universe. CdTe and Si semiconductor technologies are key technologies to realize the Compton telescope in which their high energy resolution is crucial for high angular resolution and background rejection capability. We have assembled a prototype module using a double-sided silicon strip detector and CdTe pixel detectors. In this paper, we present expected polarization performance of a proposed mission (NeXT/SGD). We also report results from polarization measurements using polarized synchrotron light and validation of EGS4 MC simulation.

Tajima, H

2004-07-06

211

The gamma-ray telescope Gamma-1  

NASA Astrophysics Data System (ADS)

The telescope 'Gamma-1' is designed to investigate cosmic gamma rays in the energy range from 50 MeV to 5000 MeV. The geometrical sensitive area of the telescope amounts to 1500 cm2, the angular resolution in each direction is equal to 1.2° at the energy 300 MeV and is about 20arcmin when including a coded mask in the telescope, the energy resolution changes from 70% at 100 MeV to 35% at 550 MeV. The characteristics of the telescope and its systems have been determined by the Monte-Carlo method as well as by accelerator calibrations. Discrete sources at the intensity level of 10-7quanta cm-2s-1 may be recorded in a year of observations with the gamma-ray telescope 'Gamma-1' with a source location accuracy of ?10 arc min.

Akimov, V. V.; Balebanov, V. M.; Belousov, A. S.; Blokhintsev, I. D.; Veselova, G. V.

212

A total throughput transient spectrometer for gamma-ray bursters  

NASA Astrophysics Data System (ADS)

The present instrument concept for a high-throughput/high-time/high-energy resolution gamma-ray detector based on an array of 12 high-purity Ge detectors; sensitivities thus obtainable would be sufficient not only to obtain data on the energy spectra of gamma-ray bursts, but also to accomplish polarization measurements. This spectrometer is envisioned as ideally suited for a large platform with substantial telemetry capacity, such as the NASA Space Station. Secondary objectives for the instrument would include solar gamma radiation spectroscopy and the monitoring of X-ray and gamma-ray pulsars, as well as surveying the sky for slow transients.

Hurley, K.

213

Simulation of Gamma Rays from Proton Interaction in Local Galaxies  

SciTech Connect

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

Karlsson, Niklas [Stanford Linear Accelerator Center, Menlo Park, CA 94025 (United States); Royal Institute of Technology, AlbaNova University Center, SE-106 91 Stockholm (Sweden); Cohen-Tanugi, Johann; Kamae, Tuneyoshi; Tajima, Hiroyasu [Stanford Linear Accelerator Center, Menlo Park, CA 94025 (United States); Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Menlo Park, CA 94025 (United States)

2007-07-12

214

Simulation of Gamma Rays from Proton Interaction in Local Galaxies  

SciTech Connect

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

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

2007-06-06

215

The gamma-ray telescope Gamma1  

Microsoft Academic Search

The telescope ‘Gamma-1’ is designed to investigate cosmic gamma rays in the energy range from 50 MeV to 5000 MeV. The geometrical sensitive area of the telescope amounts to 1500 cm2, the angular resolution in each direction is equal to 1.2° at the energy 300 MeV and is about 20' when including a coded mask in the telescope, the energy

V. V. Akimov; V. M. Balebanov; A. S. Belousov; I. D. Blokhintsev; G. V. Veselova; M. B. Dobrijan; L. F. Kalinkin; S. V. Kovalenko; V. D. Kozlov; N. G. Leikov; N. K. Mordvov; Y. I. Nagornih; V. E. Nesterov; O. F. Prilutsky; V. L. Prohin; V. G. Rodin; S. R. Tabaldiev; V. N. Chuprov; V. I. Fuks; I. A. Gerasimov; V. S. Ovtchinnikov; V. P. Poluektov; A. V. Serov; V. Y. Tugaenko; L. V. Kurnosova; M. A. Rusakovich; N. P. Topchiev; M. I. Fradkin; I. F. Bugakov; G. M. Gorodinsky; E. I. Chuikin; S. A. Voronov; A. M. Galper; V. A. Grigoriev; M. V. Guzenko; V. G. Kirillov-Ugriumov; S. V. Koldashov; M. G. Korotkov; B. I. Luchkov; A. A. Moiseev; Yu. V. Ozerov; A. V. Popov; V. A. Rud'ko; M. F. Runtso; B. Yu. Chesnokov; B. Agrinier; A. Bouere; M. Gros; J. P. Leray; A. Leconte; P. Masse; B. Mougin; P. Keirle; J. Cretolle; J. Paul; A. Raviart; B. Parlier; M. Poiviller; C. Hugot; F. Soroka; G. Serra; A. R. Bazer-Bachi; C. Doulade; J. Ducros; G. Vedrenne; F. Cotin; Y. M. Lavigne; P. Mandrou; E. Orsal; M. Avignon; J. Durand; J. Joli; F. Gardon; J. Mouli; M. Nobileau; D. Fournier

1989-01-01

216

GAMANAL. Interpretation of Gamma-Ray Spectra  

Microsoft Academic Search

GAMANAL provides a complete qualitative and quantitative analysis of mixtures of radioactive species such as fission products by computer interpretation of high-resolution gamma-ray spectra. The program first determines and removes the background or Compton continuum under the peaks in a spectrum to locate the peak regions. This is done by examining the pulse-height spectrum data for background and peak regions

Gunnink

1986-01-01

217

Survey of candidate gamma-ray sources at TeV energies using a high-resolution Cerenkov imaging system - 1988-1991  

NASA Technical Reports Server (NTRS)

The steady TeV gamma-ray emission from the Crab Nebula has been used to optimize the sensitivity of the Whipple Observatory atmospheric Cerenkov imaging telescope. Using this method, which is of order 20 times more sensitive than the standard method using a simple non-imaging detector, it is possible to detect the Crab Nebula at a significance level in excess of 6 standard deviations (6 sigma) in under 1 hr on source (with a corresponding time observing a background comparison region); a source one-tenth the strength of the Crab Nebula can be detected at the 4 sigma level after 40 hr on the source (and 40 hr on a background region). A variety of sources have been monitored using this technique over the period 1988-1991, but none were detected apart from the Crab Nebula. Upper limits are presented which in many instances are a factor of 10 below the flux of the Crab Nebula. These upper limits assume steady emission from the source and cannot rule out sporadic gamma-ray emission with short duty cycles.

Reynolds, P. T.; Akerlof, C. W.; Cawley, M. F.; Chantell, M.; Fegan, D. J.; Hillas, A. M.; Lamb, R. C.; Lang, M. J.; Lawrence, M. A.; Lewis, D. A.

1993-01-01

218

Ultrahigh-speed imaging of the rat retina using ultrahigh-resolution spectral/Fourier domain OCT  

NASA Astrophysics Data System (ADS)

We performed OCT imaging of the rat retina at 70,000 axial scans per second with ~3 ?m axial resolution. Three-dimensional OCT (3D-OCT) data sets of the rat retina were acquired. The high speed and high density data sets enable improved en face visualization by reducing eye motion artifacts and improve Doppler OCT measurements. Minimal motion artifacts were visible and the OCT fundus images offer more precise registration of individual OCT images to retinal fundus features. Projection OCT fundus images show features such as the nerve fiber layer, retinal capillary networks and choroidal vasculature. Doppler OCT images and quantitative measurements show pulsatility in retinal blood vessels. Doppler OCT provides noninvasive in vivo quantitative measurements of retinal blood flow properties and may benefit studies of diseases such as glaucoma and diabetic retinopathy. Ultrahigh speed imaging using ultrahigh resolution spectral / Fourier domain OCT promises to enable novel protocols for measuring small animal retinal structure and retinal blood flow. This non-invasive imaging technology is a promising tool for monitoring disease progression in rat and mouse models to assess ocular disease pathogenesis and response to treatment.

Liu, Jonathan J.; Potsaid, Benjamin; Chen, Yueli; Gorczynska, Iwona; Srinivasan, Vivek J.; Duker, Jay S.; Fujimoto, James G.

2010-02-01

219

Pulsars as gamma ray sources.  

NASA Astrophysics Data System (ADS)

Aspects of the physics of rotation powered pulsars as gamma ray sources are discussed. The shock excitation of pulsar powered nebulae (plerions) is discussed, based on recent theoretical work on the structure of relativistic, collisionless magnetosonic shock waves. This theory is used to outline a model in which the ?^-2^ injection spectrum of the Crab Nebula is satisfactorily accounted for. The same theory suggests a model of the ``wisp'' features in the Crab Nebula which accounts for these time variable features in the surface bightness as compressions associated with the magnetic overshoots within the shock structure. It is pointed out that this theory suggests observable variability in the high energy gamma rays from the Crab Nebula (?>50MeV.) The energetics of pulsed gamma ray emission from the six known EGRET pulsars are reviewed and shown to fit a simple efficiency {prop.to}{PHI}_open_^-k^ law, where k~0.8 and {PHI}_open_={OMEGA}_*_^2mu/c^2^=10^13^(?(P)_15_ /P^3^)^1/2^ is a measure of the total voltage available on a pulsar's open field lines. Here ?(P)_15_=?(P)/10^-15^. This result is used to define a criterion for cessation of gamma ray emission in voltage-P space, such that empirically pulsars should stop being gamma ray emitters when the total spindown luminosity falls to ~2x10^32^ergs/sec. A simple result of the same form as the empirical gamma ray emission efficency is derived for the acceleration efficiency of particle beams extracted from the polar cap, and for high voltage pulsars, where curvature radiation reaction is important, equated to the gamma ray efficiency. However, it is also argued that since radio emission from the polar caps continues to lower voltages and spin down luminosities than inferred for the gamma ray emission, that this correspondence is a coincidence and that the EGRET gamma rays come from the outer magnetosphere. The most popular of outer magnetosphere models are shown to be unable to simultanously account for gamma ray efficiencies approaching unity and having most of the gamma ray luminosity in sharp pulses, suggesting that the gamma ray emission has something to do with dense return current boundary layers whose physics has yet to be quantified.

Arons, J.

1996-11-01

220

X-ray and gamma ray astronomy detectors  

NASA Technical Reports Server (NTRS)

X-ray and gamma ray astronomy was made possible by the advent of space flight. Discovery and early observations of celestial x-rays and gamma rays, dating back almost 40 years, were first done with high altitude rockets, followed by Earth-orbiting satellites> once it became possible to carry detectors above the Earth's atmosphere, a new view of the universe in the high-energy part of the electromagnetic spectrum evolved. Many of the detector concepts used for x-ray and gamma ray astronomy were derived from radiation measuring instruments used in atomic physics, nuclear physics, and other fields. However, these instruments, when used in x-ray and gamma ray astronomy, have to meet unique and demanding requirements related to their operation in space and the need to detect and measure extremely weak radiation fluxes from celestial x-ray and gamma ray sources. Their design for x-ray and gamma ray astronomy has, therefore, become a rather specialized and rapidly advancing field in which improved sensitivity, higher energy and spatial resolution, wider spectral coverage, and enhanced imaging capabilities are all sought. This text is intended as an introduction to x-ray and gamma ray astronomy instruments. It provides an overview of detector design and technology and is aimed at scientists, engineers, and technical personnel and managers associated with this field. The discussion is limited to basic principles and design concepts and provides examples of applications in past, present, and future space flight missions.

Decher, Rudolf; Ramsey, Brian D.; Austin, Robert

1994-01-01

221

X-ray and gamma ray astronomy detectors  

NASA Astrophysics Data System (ADS)

X-ray and gamma ray astronomy was made possible by the advent of space flight. Discovery and early observations of celestial x-rays and gamma rays, dating back almost 40 years, were first done with high altitude rockets, followed by Earth-orbiting satellites> once it became possible to carry detectors above the Earth's atmosphere, a new view of the universe in the high-energy part of the electromagnetic spectrum evolved. Many of the detector concepts used for x-ray and gamma ray astronomy were derived from radiation measuring instruments used in atomic physics, nuclear physics, and other fields. However, these instruments, when used in x-ray and gamma ray astronomy, have to meet unique and demanding requirements related to their operation in space and the need to detect and measure extremely weak radiation fluxes from celestial x-ray and gamma ray sources. Their design for x-ray and gamma ray astronomy has, therefore, become a rather specialized and rapidly advancing field in which improved sensitivity, higher energy and spatial resolution, wider spectral coverage, and enhanced imaging capabilities are all sought. This text is intended as an introduction to x-ray and gamma ray astronomy instruments. It provides an overview of detector design and technology and is aimed at scientists, engineers, and technical personnel and managers associated with this field. The discussion is limited to basic principles and design concepts and provides examples of applications in past, present, and future space flight missions.

Decher, Rudolf; Ramsey, Brian D.; Austin, Robert

222

Monte Carlo simulation of discrete gamma-ray detectors  

Microsoft Academic Search

Needs in medical diagnosis, especially for early and reliable breast cancer detection, lead us to consider developments in scintillation crystals and position sensitive photomultiplier tubes (PSPMT) in order to develop a high-resolution medium field gamma-ray imaging device. However the ideal detector for gamma-rays represents a compromise between many conflicting requirements. In order to optimize different parameters involved in the detection

A. Bakkali; N. Tamda; M. Parmentier; J. Chavanelle; A. Pousse; B. Kastler

2005-01-01

223

Low-level gamma-ray spectrometry for environmental samples  

Microsoft Academic Search

Low-level gamma-ray spectrometry with large volume HPGe detectors has been widely used in analysis of environmental radionuclides.\\u000a The reasons are excellent energy resolution and high efficiency that permits selective and non-destructive analyses of several\\u000a radionuclides in composite samples. Although the most effective way of increasing the sensitivity of a gamma-ray spectrometer\\u000a is to increase counting efficiency and the amount of

P. P. Povinec

2008-01-01

224

Gamma-ray imaging with position-sensitive HPGe detectors  

Microsoft Academic Search

Due to advances in manufacturing large and highly segmented HPGe detectors along with the availability of fast and high-precision digital electronics, it is now possible to build efficient and high-resolution Compton cameras. Two-dimensionally segmented semi-conductor detectors along with pulse-shape analysis allow to obtain three-dimensional positions and energies of individual gamma-ray interactions. By employing gamma-ray tracking procedures it is possible to

K. Vetter; M. Burks; L. Mihailescu

2004-01-01

225

Gamma rays and large scale galactic structure  

NASA Technical Reports Server (NTRS)

Gamma ray astronomy is now beginning to provide a new look at the galactic structure and the distribution of cosmic rays, both electrons and nucleons, within the galaxy. The observations are consistent with a galactic spiral-arm model in which the cosmic rays are linearly coupled to the interstellar gas on the scale of the spiral arms. The agreement between the predictions of the model and the observations for regions of the plane where both 21-cm and 2.6-mm CO surveys exist emphasizes the need to extend these observations to include the entire plane. Future gamma-ray observations with more sensitivity and better angular resolutions, combined with these radio surveys, should shed new light on the distribution of cosmic rays, the nature of the galaxy, and the location and intensity of the spiral arms.

Kniffen, D. A.; Fichtel, C. E.; Thompson, D. J.

1977-01-01

226

Nucleosynthesis and astrophysical gamma ray spectroscopy  

NASA Technical Reports Server (NTRS)

The HEAO-3 gamma ray spectrometer has provided evidence in the quest for the understanding of complex element formation in the universe with the discovery of Al-26 in the interstellar medium. It has demonstrated that the synthesis of intermediate mass nuclei is currently going on in the galaxy. This discovery was confirmed by the Solar Maximum Mission. The flux is peaked near the galactic center and indicates about 3 solar masses of Al-26 in the interstellar medium, with an implied ratio of Al-26/Al-27 = .00001. Several possible distributions were studied but the data gathered thus far do not allow discrimination between them. It is felt that only the spaceflight of a high resolution gamma ray spectrometer with adequate sensitivity will ultimately resolve the issue of the source of this material.

Jacobson, Allan S.

1987-01-01

227

Gamma ray spectroscopic measurements of Mars.  

PubMed

A gamma ray spectrometer placed in orbit around Mars is expected to yield significant compositional data which can be related to the evolution of that planet. Components of the observable gamma ray flux come from the Martian surface, galactic and intergalactic space, and the spacecraft itself. The flux can be detected by a scintillation crystal or solid state detector, either of which combines efficiency of detection with energy resolution, and returns information to the earth as a pulse height distribution in order to detect characteristic energy line structure. The data will be evaluated for evidence of elemental differentiation with reference to terrestrial, meteoritic, solar, and lunar abundances. A lengthy mission will allow the surface of Mars to be mapped in a search for possible correlations between composition and topography or albedo. PMID:20076376

Metzger, A E; Arnold, J R

1970-06-01

228

Ultra-high resolution spectral domain optical coherence tomography of traumatic maculopathy.  

PubMed

The authors describe a patient who suffered traumatic maculopathy following blunt trauma to the eye with commotio retinae, subretinal and preretinal hemorrhage, traumatic macular hole, and outer retinal and retinal pigment epithelium disruption. Serial imaging with commercially available and ultra-high resolution spectral domain optical coherence tomography characterized the evolution of the injury. PMID:19772281

Seider, Michael I; Seider, Michael; Lujan, Brandon J; Gregori, Giovanni; Jiao, Shuliang; Murray, Timothy G; Puliafito, Carmen A

2009-01-01

229

Gamma-Ray Pulsars: Observations  

NASA Technical Reports Server (NTRS)

High-energy gamma rays are a valuable tool for studying particle acceleration and radiation in the magnetospheres of energetic pulsars. The six or more pulsars seen by CGRO/EGRET show that the light curves usually have double-peak structures (suggesting a broad cone of emission); gamma rays are frequently the dominant component of the radiated power; and all the spectra show evidence of a high-energy turnover. Unless a new pulsed component appears at higher energies, progress in gamma-ray pulsar studies will be greatest in the 1-10 GeV range . Ground-based telescopes whose energy ranges extend downward toward 10 GeV should make important measurements of the spectral cutoffs. The Gamma-ray Large Area Space Telescope (GLAST), now in planning for a possible launch in 2005, will provide a major advance in sensitivity, energy range, and sky coverage.

Thompson, David J.

2000-01-01

230

Jet Shockwaves Produce Gamma Rays  

NASA Video Gallery

Theorists believe that GRB jets produce gamma rays by two processes involving shock waves. Shells of material within the jet move at different speeds and collide, generating internal shock waves th...

231

Gamma-ray spectrometer experiment  

NASA Technical Reports Server (NTRS)

The experiments in gamma-ray spectrometry to determine the geochemical composition of the lunar surface are reported. The theory is discussed of discrete energy lines of natural radioactivity, and the lines resulting from the bombardment of the lunar surface by high energy cosmic rays. The gamma-ray spectrometer used in lunar orbit and during transearth coast is described, and a preliminary analysis of the results is presented.

Arnold, J. R.; Peterson, L. E.; Metzger, A. E.; Trombka, J. I.

1972-01-01

232

Direct observation of hydrogen atom dynamics and interactions by ultrahigh resolution neutron protein crystallography  

PubMed Central

The 1.1 ?, ultrahigh resolution neutron structure of hydrogen/deuterium (H/D) exchanged crambin is reported. Two hundred ninety-nine out of 315, or 94.9%, of the hydrogen atom positions in the protein have been experimentally derived and resolved through nuclear density maps. A number of unconventional interactions are clearly defined, including a potential O?H…? interaction between a water molecule and the aromatic ring of residue Y44, as well as a number of potential C?H…O hydrogen bonds. Hydrogen bonding networks that are ambiguous in the 0.85 ? ultrahigh resolution X-ray structure can be resolved by accurate orientation of water molecules. Furthermore, the high resolution of the reported structure has allowed for the anisotropic description of 36 deuterium atoms in the protein. The visibility of hydrogen and deuterium atoms in the nuclear density maps is discussed in relation to the resolution of the neutron data.

Chen, Julian C.-H.; Hanson, B. Leif; Fisher, S. Zoe; Langan, Paul; Kovalevsky, Andrey Y.

2012-01-01

233

Improvement of {gamma}-ray energy resolution of LaBr{sub 3}:Ce{sup 3+} scintillation detectors by Sr{sup 2+} and Ca{sup 2+} co-doping  

SciTech Connect

Commercially available LaBr{sub 3}:5% Ce{sup 3+} scintillators show with photomultiplier tube readout about 2.7% energy resolution for the detection of 662 keV {gamma}-rays. Here we will show that by co-doping LaBr{sub 3}:Ce{sup 3+} with Sr{sup 2+} or Ca{sup 2+} the resolution is improved to 2.0%. Such an improvement is attributed to a strong reduction of the scintillation light losses that are due to radiationless recombination of free electrons and holes during the earliest stages (1-10 ps) inside the high free charge carrier density parts of the ionization track.

Alekhin, M. S.; Haas, J. T. M. de; Khodyuk, I. V.; Dorenbos, P. [Department of Radiation Science and Technology, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands)] [Department of Radiation Science and Technology, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands); Kraemer, K. W. [Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern (Switzerland)] [Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern (Switzerland); Menge, P. R. [Saint-Gobain Crystals, 17900 Great Lakes Parkway, Hiram, Ohio 44234 (United States)] [Saint-Gobain Crystals, 17900 Great Lakes Parkway, Hiram, Ohio 44234 (United States); Ouspenski, V. [Saint Gobain Recherche, 39, Quai Lucien Lefranc, 93303 Aubervilliers (France)] [Saint Gobain Recherche, 39, Quai Lucien Lefranc, 93303 Aubervilliers (France)

2013-04-22

234

Ultrahigh resolution photographic films for X-ray\\/EUV\\/FUV astronomy  

Microsoft Academic Search

The quest for ultrahigh resolution full-disk images of the sun at soft X-ray\\/EUV\\/FUV wavelengths has increased the demand for photographic films with broad spectral sensitivity, high spatial resolution, and wide dynamic range. These requirements were made more stringent by the recent development of multilayer telescopes and coronagraphs capable of operating at normal incidence at soft X-ray\\/EUV wavelengths. Photographic films are

Richard B. Hoover; Arthur B. C. Walker Jr.; Craig E. Deforest; Richard Watts; Charles Tarrio

1993-01-01

235

Developments in large gamma-ray detector arrays  

NASA Astrophysics Data System (ADS)

Gamma-ray spectroscopy was revolutionized with the introduction of high energy-resolution semiconductor germanium (Ge) detectors in the early 1960s. This led to the large increase in sensitivity realized by today's arrays of Compton-suppressed Ge detectors. A still larger increase in sensitivity is expected by implementing the new concept of tracking. A tracking array consists of highly segmented Ge detectors (that can cover the full 4pi solid-angle) in which gamma rays will be identified by measuring and tracking every gamma ray interaction. This article reviews the physics motivation for such detectors and the development of the new technologies involved. The concept of tracking is explained using the example of a proposed array called gamma-ray energy tracking array (GRETA).

Lee, I. Y.; Deleplanque, M. A.; Vetter, K.

2003-07-01

236

Prototype design of multiple compton gamma-ray camera  

SciTech Connect

The authors found that the first Compton scattering of the gamma-ray energy degrading process can be correctly reconstructed with a high probability, if energies and positions of recoil electrons are recorded within a few keV (rms) and approx. =1X1X1mm/sup 3/ for the first 4-5 steps. Such a device, called the Multiple Compton Gamma-ray Camera, allows us to measure the energy, direction, and polarization of gamma-rays in sub-MeV to few MeV range. The authors present here the design of a prototype optimized to 150-600keV gamma-rays. Monte Carlo studies of the design predict that one gets a high detection efficiency, a high polarization analyzing power, and a reasonable angular resolution without collimators.

Kamae, T.; Hanada, N.; Enomoto, R.

1988-02-01

237

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

NASA Astrophysics Data System (ADS)

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

Fierro, Joseph Miguel

238

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

ScienceCinema

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.

239

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

ScienceCinema

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.

Isabelle Grenier

2010-01-08

240

LOW-RESOLUTION SPECTROSCOPY OF GAMMA-RAY BURST OPTICAL AFTERGLOWS: BIASES IN THE SWIFT SAMPLE AND CHARACTERIZATION OF THE ABSORBERS  

SciTech Connect

We present a sample of 77 optical afterglows (OAs) of Swift detected gamma-ray bursts (GRBs) for which spectroscopic follow-up observations have been secured. Our first objective is to measure the redshifts of the bursts. For the majority (90%) of the afterglows, the redshifts have been determined from the spectra. We provide line lists and equivalent widths (EWs) for all detected lines redward of Ly{alpha} covered by the spectra. In addition to the GRB absorption systems, these lists include line strengths for a total of 33 intervening absorption systems. We discuss to what extent the current sample of Swift bursts with OA spectroscopy is a biased subsample of all Swift detected GRBs. For that purpose we define an X-ray-selected statistical sample of Swift bursts with optimal conditions for ground-based follow-up from the period 2005 March to 2008 September; 146 bursts fulfill our sample criteria. We derive the redshift distribution for the statistical (X-ray selected) sample and conclude that less than 18% of Swift bursts can be at z > 7. We compare the high-energy properties (e.g., {gamma}-ray (15-350 keV) fluence and duration, X-ray flux, and excess absorption) for three subsamples of bursts in the statistical sample: (1) bursts with redshifts measured from OA spectroscopy; (2) bursts with detected optical and/or near-IR afterglow, but no afterglow-based redshift; and (3) bursts with no detection of the OA. The bursts in group (1) have slightly higher {gamma}-ray fluences and higher X-ray fluxes and significantly less excess X-ray absorption than bursts in the other two groups. In addition, the fractions of dark bursts, defined as bursts with an optical to X-ray slope {beta}{sub OX} < 0.5, is 14% in group (1), 38% in group (2), and >39% in group (3). For the full sample, the dark burst fraction is constrained to be in the range 25%-42%. From this we conclude that the sample of GRBs with OA spectroscopy is not representative for all Swift bursts, most likely due to a bias against the most dusty sight lines. This should be taken into account when determining, e.g., the redshift or metallicity distribution of GRBs and when using GRBs as a probe of star formation. Finally, we characterize GRB absorption systems as a class and compare them to QSO absorption systems, in particular the damped Ly{alpha} absorbers (DLAs). On average GRB absorbers are characterized by significantly stronger EWs for H I as well as for both low and high ionization metal lines than what is seen in intervening QSO absorbers. However, the distribution of line strengths is very broad and several GRB absorbers have lines with EWs well within the range spanned by QSO-DLAs. Based on the 33 z > 2 bursts in the sample, we place a 95% confidence upper limit of 7.5% on the mean escape fraction of ionizing photons from star-forming galaxies.

Fynbo, J. P. U.; Malesani, D.; Vreeswijk, P. M.; Hjorth, J.; Sollerman, J.; Thoene, C. C. [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Oe (Denmark); Jakobsson, P.; Bjoernsson, G.; De Cia, A. [Centre for Astrophysics and Cosmology, Science Institute, University of Iceland, Dunhagi 5, IS-107 ReykjavIk (Iceland); Prochaska, J. X. [Department of Astronomy and Astrophysics, UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States); Ledoux, C.; De Ugarte Postigo, A. [European Southern Observatory, Alonso de Cordova 3107, Vitacura, Casilla 19001, Santiago 19 (Chile); Nardini, M. [SISSA, Via Beirut 2/4, I-34014 Trieste (Italy); Wiersema, K. [Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH (United Kingdom); Chen, H.-W. [Department of Astronomy and Astrophysics and Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637 (United States); Bloom, J. S. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Castro-Tirado, A. J.; Gorosabel, J. [IAA-CSIC, P.O. Box 03004, E-18080 Granada (Spain); Christensen, L. [European Southern Observatory, Karl-Schwarzschildstrasse 2, D-85748 Garching (Germany); Fruchter, A. S. [Space Telescope Science Institute, Department of Physics and Astronomy, Johns Hopkins University, 3700 San Martin Drive, Baltimore, MD 21218 (United States)] (and others)

2009-12-01

241

The project EGRET (Energetic Gamma-Ray Experiment Telescope) on NASA's Gamma-Ray Observatory (GRO)  

NASA Technical Reports Server (NTRS)

The design, predicted performance, and scientific objectives of the 20-30,000-MeV gamma-ray telescope EGRET for the NASA GRO spacecraft (scheduled for Space Shuttle launch to a 450-km 28.5-deg orbit in 1990) are reviewed. The other GRO instruments are briefly characterized, including the burst and transient-source experiment, the oriented scintillation spectrometer, and the imaging Compton telescope. EGRET comprises an anticoincidence system, a spark chamber, a triggering telescope, an NaI total-absorption spectrometer, a gas supply capable of refilling the chamber four times, and support electronics. EGRET will operate with energy resolution about 15 percent, effective area about 2000 sq cm, sensitivity about 5 x 10 to the -8th/sq cm sec, angular resolution 0.1-0.4 deg, and FOV about 40 deg FWHM. Observations of Galactic point sources, Galactic and extragalactic diffuse emission, gamma-ray bursts, and solar flares are planned.

Kanbach, G.; Bertsch, D. L.; Fichtel, C. E.; Hartman, R. C.; Hunter, S. D.; Kniffen, D. A.; Hughlock, B. W.; Favale, A.; Hofstadter, R.; Hughes, E. B.

1988-01-01

242

The project EGRET (Energetic Gamma-Ray Experiment Telescope) on NASA's Gamma-Ray Observatory (GRO)  

NASA Astrophysics Data System (ADS)

The design, predicted performance, and scientific objectives of the 20-30,000-MeV gamma-ray telescope EGRET for the NASA GRO spacecraft (scheduled for Space Shuttle launch to a 450-km 28.5-deg orbit in 1990) are reviewed. The other GRO instruments are briefly characterized, including the burst and transient-source experiment, the oriented scintillation spectrometer, and the imaging Compton telescope. EGRET comprises an anticoincidence system, a spark chamber, a triggering telescope, an NaI total-absorption spectrometer, a gas supply capable of refilling the chamber four times, and support electronics. EGRET will operate with energy resolution about 15 percent, effective area about 2000 sq cm, sensitivity about 5 x 10 to the -8th/sq cm sec, angular resolution 0.1-0.4 deg, and FOV about 40 deg FWHM. Observations of Galactic point sources, Galactic and extragalactic diffuse emission, gamma-ray bursts, and solar flares are planned.

Kanbach, G.; Bertsch, D. L.; Fichtel, C. E.; Hartman, R. C.; Hunter, S. D.; Kniffen, D. A.; Hughlock, B. W.; Favale, A.; Hofstadter, R.; Hughes, E. B.

243

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

SciTech Connect

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

Lancione, G.V.

1982-01-01

244

Time correlations between low and high energy gamma rays from discrete sources  

NASA Technical Reports Server (NTRS)

Activities covered the following areas: (1) continuing analysis of the Cygnus Experiment data on the shadowing of cosmic rays by the moon and sun, which led to a direct confirmation of the angular resolution of the CYGNUS EAS array; and (2) development of analysis methods for the daily search overlapping with EGRET targets. To date, no steady emission of ultrahigh energy (UHE) gamma rays from any source has been detected by the Cygnus Experiment, but some evidence for sporadic emission had been found. Upper limits on steady fluxes from 49 sources in the northern hemisphere have been published. In addition, a daily search of 51 possible sources over the interval April 1986 to June 1992 found no evidence for emission. From these source lists, four candidates were selected for comparison with EGRET data.

Ellsworth, R. W.

1995-01-01

245

Ultrahigh-resolution soft x-ray tomography  

NASA Astrophysics Data System (ADS)

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

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

1995-09-01

246

The Gamma-ray Sky with Fermi  

NASA Technical Reports Server (NTRS)

Gamma rays reveal extreme, nonthermal conditions in the Universe. The Fermi Gamma-ray Space Telescope has been exploring the gamma-ray sky for more than four years, enabling a search for powerful transients like gamma-ray bursts, novae, solar flares, and flaring active galactic nuclei, as well as long-term studies including pulsars, binary systems, supernova remnants, and searches for predicted sources of gamma rays such as dark matter annihilation. Some results include a stringent limit on Lorentz invariance derived from a gamma-ray burst, unexpected gamma-ray variability from the Crab Nebula, a huge gamma-ray structure associated with the center of our galaxy, surprising behavior from some gamma-ray binary systems, and a possible constraint on some WIMP models for dark matter.

Thompson, David

2012-01-01

247

Terrestrial gamma-ray flashes  

NASA Astrophysics Data System (ADS)

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.

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

248

Imaging retinal nerve fiber bundles at ultrahigh-speed and ultrahigh-resolution using OCT with adaptive optics  

NASA Astrophysics Data System (ADS)

Ultrahigh speed line scan detectors based on CMOS technology have been recently demonstrated in ultrahigh resolution spectral-domain optical coherence tomography (UHR-SD-OCT) for retinal imaging. While successful, fundamental tradeoffs exist been image acquisition time, image sampling density, and sensitivity, all of which impact the extent of motion artifacts, visualization of fine spatial detail, and detection of faint reflections. Here we investigate these tradeoffs for imaging retinal nerve fiber bundles (RNFBs) using UHR-SD-OCT with adaptive optics (AO). Volume scans of 3°x3° and 1.5°x1.5° were acquired at retinal locations of 3° nasal and 6° superior to the fovea on a healthy subject. Dynamic AO compensation across a 6 mm pupil provided near-diffraction-limited performance. The acquisition rates were 22.5k lines/s and 125k lines/s with A-lines spaced at 0.9 ?m and 1.8 ?m and B-scans at 1.8 ?m and 9 ?m. Focus was optimized for visualizing the retinal nerve fiber bundles (RNFBs). En face projection and crosssectional views of the RNFBs were extracted from the volumes and compared to images acquired with established conventional CCD-based line-scan camera. The projection view was found highly sensitive to eye motion artifacts, yet could only be partially compensated with coarser sampling, since fine sampling was necessary to observe the microscopic features in the RNFBs. For the cross-sectional view, speckle noise rather than eye motion artifacts limited bundle clarity. The highest B-scan density (1.8 ?m spacing) coupled with B-scan averaging proved the best combination. Regardless of view, the higher line rate provided better RNFB clarity.

Kocaoglu, Omer Pars; Cense, Barry; Wang, Qiang; Bruestle, Jeremy; Besecker, Jason; Gao, Weihua; Jonnal, Ravi; Miller, Donald T.

2010-02-01

249

Gamma-ray Imaging Methods  

SciTech Connect

In this document we discuss specific implementations for gamma-ray imaging instruments including the principle of operation and describe systems which have been built and demonstrated as well as systems currently under development. There are several fundamentally different technologies each with specific operational requirements and performance trade offs. We provide an overview of the different gamma-ray imaging techniques and briefly discuss challenges and limitations associated with each modality (in the appendix we give detailed descriptions of specific implementations for many of these technologies). In Section 3 we summarize the performance and operational aspects in tabular form as an aid for comparing technologies and mapping technologies to potential applications.

Vetter, K; Mihailescu, L; Nelson, K; Valentine, J; Wright, D

2006-10-05

250

History of gamma-ray telescopes and astronomy  

NASA Astrophysics Data System (ADS)

Gamma-ray astronomy is devoted to study nuclear and elementary particle astrophysics and astronomical objects under extreme conditions of gravitational and electromagnetic forces, and temperature. Because signals from gamma rays below 1 TeV cannot be recorded on ground, observations from space are required. The photoelectric effect is dominant <100 keV, Compton scattering between 100 keV and 10 MeV, and electron-positron pair production at energies above 10 MeV. The sun and some gamma ray burst sources are the strongest gamma ray sources in the sky. For other sources, directionality is obtained by shielding / masks at low energies, by using the directional properties of the Compton effect, or of pair production at high energies. The power of angular resolution is low (fractions of a degree, depending on energy), but the gamma sky is not crowded and sometimes identification of sources is possible by time variation. The gamma ray astronomy time line lists Explorer XI in 1961, and the first discovery of gamma rays from the galactic plane with its successor OSO-3 in 1968. The first solar flare gamma ray lines were seen with OSO-7 in 1972. In the 1980’s, the Solar Maximum Mission observed a multitude of solar gamma ray phenomena for 9 years. Quite unexpectedly, gamma ray bursts were detected by the Vela-satellites in 1967. It was 30 years later, that the extragalactic nature of the gamma ray burst phenomenon was finally established by the Beppo-Sax satellite. Better telescopes were becoming available, by using spark chambers to record pair production at photon energies >30 MeV, and later by Compton telescopes for the 1-10 MeV range. In 1972, SAS-2 began to observe the Milky Way in high energy gamma rays, but, unfortunately, for a very brief observation time only due to a failure of tape recorders. COS-B from 1975 until 1982 with its wire spark chamber, and energy measurement by a total absorption counter, produced the first sky map, recording galactic continuum emission, mainly from interactions of cosmic rays with interstellar matter, and point sources (pulsars and unidentified objects). An integrated attempt at observing the gamma ray sky was launched with the Compton Observatory in 1991 which stayed in orbit for 9 years. This large shuttle-launched satellite carried a wire spark chamber “Energetic Gamma Ray Experiment Telescope” EGRET for energies >30 MeV which included a large Cesium Iodide crystal spectrometer, a “Compton Telescope” COMPTEL for the energy range 1-30 MeV, the gamma ray “Burst and Transient Source Experiment” BATSE, and the “Oriented Scintillation-Spectrometer Experiment” OSSE. The results from the “Compton Observatory” were further enlarged by the SIGMA mission, launched in 1989 with the aim to closely observe the galactic center in gamma rays, and INTEGRAL, launched in 2002. From these missions and their results, the major features of gamma ray astronomy are: Diffuse emission, i.e. interactions of cosmic rays with matter, and matter-antimatter annihilation; it is found, “...that a matter-antimatter symmetric universe is empirically excluded....”

Pinkau, Klaus

2009-08-01

251

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

Microsoft Academic Search

The Gamma-Ray burst detector on Ginga consisted of a proportional counter to observe the x-rays and a scintillation counter to observe the gamma-rays. Both instrument recorded the time histories in phase with each other and with 0.03125 s temporal resolution. The author compares the average of 21 gamma-ray bursts to determine the delay, in any, between the peak of the

Fenimore

1998-01-01

252

Hard X-ray and low-energy gamma-ray spectrometers  

Microsoft Academic Search

Basic principles of operation and characteristics of scintillation and semi-conductor detectors used for solar hard X-ray and gamma-ray spectrometers are presented. Scintillation materials such as NaI offer high stopping power for incident gamma rays, modest energy resolution, and relatively simple operation. They are, to date, the most often used detector in solar gamma-ray spectroscopy. The scintillator BGO has higher stopping

N. GEHRELSI; C. J. Crannell; D. J. Forrest; R. P. Lin; L. E. Orwig; R. Starr

1988-01-01

253

Gamma-ray detectors; Proceedings of the Meeting, San Diego, CA, July 21, 22, 1992  

Microsoft Academic Search

The present status of research and development, and future trends in gamma-ray detectors for nuclear medical imaging, astrophysics, nuclear and particle physics, oil-well logging, and radiation monitoring and control are reviewed. Particular attention is given to well-type phoswich counters for low-flux X-ray\\/gamma-ray detection; energy resolution and other properties of CsI(TI) crystals; gamma-ray astronomy using a high-pressure gas scintillation drift chamber

Elena Aprile

1992-01-01

254

Investigation of photoreceptor layer impairment in macular pathologies using ultrahigh-resolution ophthalmic optical coherence tomography  

NASA Astrophysics Data System (ADS)

Ultrahigh resolution ophthalmic OCT has been performed in more than 250 eyes of 160 patients, demonstrating unprecedented visualization of intraretinal morphology of several retinal pathologies. and therefore the potential to enhance sensitivity and specificity for early ophthalmic diagnosis as well as to monitor the efficacy of therapy. In addition, it might contribute to a better understanding of ocular pathogenesis. This is demonstrated by investigating both normal retinal morphology in an animal model and the impairment of the photoreceptor layer in different macular pathologies.

Drexler, Wolfgang; Hermann, Boris; Unterhuber, Angelika; Sattmann, Harald; Stur, Michael; Wirtitsch, Mathias; Glosmann, Martin; Schubert, Christian; Scholda, Christoph; Findl, Oliver; Ko, Tony H.; Ahnelt, Peter K.; Fujimoto, James G.; Fercher, Adolf F.

2003-10-01

255

Observation of d-t fusion gamma rays (invited)  

NASA Astrophysics Data System (ADS)

Deuterium-tritium (DT) reaction rates of imploding capsules have historically been measured using neutron detectors. Temporal resolution is limited by the size of the detector and distance from the source to detector. The reaction rates can also be measured using the 16.7 MeV gamma ray, which is produced by the same DT reaction, but statistically far less often than the 14.1 MeV neutron. Cherenkov detectors detect gamma rays by converting the gamma rays to electrons, which in turn produce Cherenkov light and record this visible light using a fast optical detector. These detectors can be scaled to large volumes in order to increase detection efficiency with little degradation in time resolution, and placed well away from the source since gamma rays do not suffer velocity dispersion between the source and detector. Gas-based Cherenkov detectors can also discriminate against lower-energy photons produced in and around the target. A prototype gas Cherenkov detector has been built and tested for detector response at the Idaho State University electron linear accelerator (LINAC). Later tests at the University of Rochester's OMEGA laser facility proved the feasibility of this diagnostic by successfully recording the 16.7 MeV gamma ray. A second version has now been built to demonstrate the temporal resolution.

Caldwell, S. E.; Berggren, R. R.; Davis, B. A.; Evans, S. C.; Faulkner, J. R.; Garcia, J. A.; Griffith, R. L.; Lash, D. K.; Lerche, R. A.; Mack, J. M.; Morgan, G. L.; Moy, K. J.; Ortel, J. A.; Sturges, R. E.; Young, C. S.

2003-03-01

256

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

NASA Astrophysics Data System (ADS)

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

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

2010-07-01

257

Single photon imaging at ultra-high resolution  

Microsoft Academic Search

We present a detection system capable of imaging both single photon\\/positive ion and multiple coincidence photons\\/positive ions with extremely high spatial resolution. In this detector the photoelectrons excited by the incoming photons are multiplied by microchannel plate(s) (MCP). The process of multiplication is spatially constrained within an MCP pore, which can be as small as 4?m for commercially available MCPs.

R. Bellazzini; G. Spandre; M. Minuti; A. Brez; L. Baldini; L. Latronico; N. Omodei; C. Sgrò; J. Bregeon; M. Razzano; M. Pinchera; A. Tremsin; J. McPhate; J. V. Vallerga; O. Siegmund

2008-01-01

258

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

NASA Astrophysics Data System (ADS)

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

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

2003-08-01

259

Ultra-High Resolution Atom Imaging in a Light - Gradient  

NASA Astrophysics Data System (ADS)

In this thesis, we develop and demonstrate an all-optical technique for measuring the transverse positions of atoms moving in a beam. This technique is based on Raman induced resonance imaging in which a spatially varying potential correlates the atomic center-of-mass position with the resonance frequency of a Raman transition between two long-lived atomic states. The use of optical fields to induce atomic transitions permits access to very small volumes over which large potential gradients can be maintained. Under reasonable laboratory conditions, the spatial resolution of the technique can be two orders of magnitude smaller than an optical wavelength and is ultimately limited only by the Heisenberg uncertainty principle. We present a complete quantum mechanical calculation and analysis of the technique, including the limits placed on the spatial resolution by the motion of the atoms along the measurement direction. By using the Wigner phase space functions, we are able to treat the statistical velocity distribution of atoms in the beam on the same footing as the diffraction velocities of the atomic wavefronts. The results are given in terms of a spatial resolution function that predicts the shape of the measured spatial pattern in terms of the input phase space distribution. In the limit that the statistical velocities of the atoms dominate their diffractive velocities, this function is shown to take the form of a normalized gaussian sampling function that describes the shape of the spatial region in which Raman transitions occur. For an input atomic beam whose atomic distribution is initially uniform, we show that the outgoing beam has impressed in it a gaussian spatial distribution whose width Delta{x} is identical to the width of the gaussian resolution function. The measurement technique can be used to create spatial patterns as well as to measure them. For highly collimated atomic beams in which the transverse coherence length is large compared to the localization distance Delta{x}, the outgoing atomic distribution can take the form of minimum-uncertainty gaussian wavepacket for which Delta{x}Delta {p} = hbar/2. As an experimental demonstration of the technique, we have used a super-sonic beam of samarium atoms and a spatially varying light-shift potential to create and to measure localized atomic distributions. By using copropagating Raman fields to induce transitions between long-lived atomic ground states, we have achieved a spatial resolution of 200 nm, which is in excellent agreement with the theoretical predictions.

Gardner, Jeffrey Ray

260

Feasibility study of gamma-ray medical radiography.  

PubMed

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

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

2013-02-01

261

Ultra-High Resolution Imaging by Fluorescence Photoactivation Localization Microscopy  

PubMed Central

Biological structures span many orders of magnitude in size, but far-field visible light microscopy suffers from limited resolution. A new method for fluorescence imaging has been developed that can obtain spatial distributions of large numbers of fluorescent molecules on length scales shorter than the classical diffraction limit. Fluorescence photoactivation localization microscopy (FPALM) analyzes thousands of single fluorophores per acquisition, localizing small numbers of them at a time, at low excitation intensity. To control the number of visible fluorophores in the field of view and ensure that optically active molecules are separated by much more than the width of the point spread function, photoactivatable fluorescent molecules are used, in this case the photoactivatable green fluorescent protein (PA-GFP). For these photoactivatable molecules, the activation rate is controlled by the activation illumination intensity; nonfluorescent inactive molecules are activated by a high-frequency (405-nm) laser and are then fluorescent when excited at a lower frequency. The fluorescence is imaged by a CCD camera, and then the molecules are either reversibly inactivated or irreversibly photobleached to remove them from the field of view. The rate of photobleaching is controlled by the intensity of the laser used to excite the fluorescence, in this case an Ar+ ion laser. Because only a small number of molecules are visible at a given time, their positions can be determined precisely; with only ?100 detected photons per molecule, the localization precision can be as much as 10-fold better than the resolution, depending on background levels. Heterogeneities on length scales of the order of tens of nanometers are observed by FPALM of PA-GFP on glass. FPALM images are compared with images of the same molecules by widefield fluorescence. FPALM images of PA-GFP on a terraced sapphire crystal surface were compared with atomic force microscopy and show that the full width at half-maximum of features ?86 ± 4 nm is significantly better than the expected diffraction-limited optical resolution. The number of fluorescent molecules and their brightness distribution have also been determined using FPALM. This new method suggests a means to address a significant number of biological questions that had previously been limited by microscope resolution.

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

2006-01-01

262

Gamma-ray pulsar model  

Microsoft Academic Search

Extremely high energy bursts of pulsed gamma-rays have recently been detected from several binary X-ray pulsars and young radio pulsars. It is proposed that curvature synchrotron radiation from electrons (accelerated along the open magnetic field lines) is a possible origin of this emission. The electric and magnetic fields in the present model are computed in the near zone (close to

Jeffrey M. Cohen; Errol Mustafa

1987-01-01

263

Diffuse galactic gamma ray lines  

NASA Technical Reports Server (NTRS)

The production rate of 4.44-MeV line for a variety of assumed cosmic ray spectra is evaluated. These results are compared with reported galactic gamma-ray line intensities and are consistent with a low energy cosmic ray density which increases toward the galactic center in proportion to the molecular gas density.

Lingenfelter, R. E.; Ramaty, R.

1977-01-01

264

The GRAD gamma ray spectrometer  

SciTech Connect

A gamma-ray spectrometer for an upcoming space shuttle mission is described. Consisting of a 150 cm/sup 3/ n-type germanium detector set inside active shielding of bismuth germanate and plastic scintillator, the instrument will be used in studies of the Orbiter background and the galactic center.

Rester, A.C.; Piercey, R.B.; Eichhorn, G.; Coldwell, R.L.; McKisson, J.M.; Ely, D.W.; Mann, H.M.; Jenkins, D.A.

1986-02-01

265

Gamma-ray camera flyby  

ScienceCinema

Animation based on an actual classroom demonstration of the prototype CCI-2 gamma-ray camera's ability to image a hidden radioactive source, a cesium-137 line source, in three dimensions. For more information see http://newscenter.lbl.gov/feature-stories/2010/06/02/applied-nuclear-physics/.

266

Gamma-ray camera flyby  

SciTech Connect

Animation based on an actual classroom demonstration of the prototype CCI-2 gamma-ray camera's ability to image a hidden radioactive source, a cesium-137 line source, in three dimensions. For more information see http://newscenter.lbl.gov/feature-stories/2010/06/02/applied-nuclear-physics/.

None

2010-01-01

267

Cosmological gamma-ray bursts  

NASA Technical Reports Server (NTRS)

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

Paczynski, Bohdan

1991-01-01

268

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

NASA Astrophysics Data System (ADS)

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

He, Zuyuan; Liu, Qingwen; Tokunaga, Tomochika

2013-12-01

269

Labr3:Ce scintillators for gamma ray spectroscopy  

SciTech Connect

In this paper, we report on a relatively new scintillator -LaBr3 for gamma ray spectroscopy. Crystals of this scintillator have beengrown using Bridgman process. This material when doped with cerium hashigh light output (~;60,000 photons/MeV) and fast principal decayconstant (less than 25 ns). Furthermore, it shows excellent energyresolution for gamma-ray detection. Energy resolution of 3.2 percent(FWHM) has been achieved for 662 keV photons (137Cs source) at roomtemperature. High timing resolution (260 ps - FWHM) has been recordedwith LaBr3-PMT and BaF2-PMT detectors operating in coincidence mode using511 keV positron annihilation gamma-ray pairs. Details of itsscintillation properties, and variation of these properties with changingcerium concentration are reported. Potential applications of thismaterial are also addressed.

Shah, K.S.; Glodo, J.; Klugerman, M.; Moses, W.W.; Derenzo, S.E.; Weber, M.J.

2002-12-02

270

Continuous Energy gamma-Ray Spectrometry.  

National Technical Information Service (NTIS)

Compton recoil gamma-ray spectroscopy provides absolute measurements of continuous gamma-ray spectra. Peaks which possess sufficient intensity above the continuum level can be observed. Since the inception of this spectrometric method, this method has evo...

R. Gold B. J. Kaiser J. P. McNeece

1983-01-01

271

High Altitude Balloons and gamma Ray Astronomy.  

National Technical Information Service (NTIS)

The author's experience with scientific high altitude ballooning will be presented. Usefulness of satellite versus balloon platforms will be contrasted in the context of gamma ray astronomy. General principles of gamma ray astronomy instrumentation will b...

C. J. MacCallum

1988-01-01

272

The Gamma-ray Universe through Fermi  

NASA Technical Reports Server (NTRS)

Gamma rays, the most powerful form of light, reveal extreme conditions in the Universe. The Fermi Gamma-ray Space Telescope and its smaller cousin AGILE have been exploring the gamma-ray sky for several years, enabling a search for powerful transients like gamma-ray bursts, novae, solar flares, and flaring active galactic nuclei, as well as long-term studies including pulsars, binary systems, supernova remnants, and searches for predicted sources of gamma rays such as dark matter annihilation. Some results include a stringent limit on Lorentz invariance derived from a gamma-ray burst, unexpected gamma-ray variability from the Crab Nebula, a huge ga.nuna-ray structure associated with the center of our galaxy, surprising behavior from some gamma-ray binary systems, and a possible constraint on some WIMP models for dark matter.

Thompson, David J.

2012-01-01

273

Laser frequency-noise-limited ultrahigh resolution remote fiber sensing  

NASA Astrophysics Data System (ADS)

When a fiber Fabry-Perot is used in an ultra-sensitive strain detection system via a radio-frequency interrogation scheme, its frequency discrimination properties can be enhanced by reducing the linewidth of its resonance. This increases the signal-to-noise ratio, and thus suppresses the strain equivalent noise floor. We demonstrate this improvement in a long-distance high performance remote sensing system and show that in reflection, it can mitigate the effects of random phase noise introduced by Rayleigh back-scattering. In transmission, it improves the remote system sensitivity to sub-picostrain resolution, which surpasses any other long-distance remote sensing system to date. With the reduced fiber Fabry-Perot linewidth, all noise sources in the delivery fiber become irrelevant, as the transmission system is limited only by the pre-stabilized laser frequency noise.

Chow, Jong H.; Littler, Ian C.; McClelland, David E.; Gray, Malcolm B.

2006-05-01

274

Laser frequency-noise-limited ultrahigh resolution remote fiber sensing.  

PubMed

When a fiber Fabry-Perot is used in an ultra-sensitive strain detection system via a radio-frequency interrogation scheme, its frequency discrimination properties can be enhanced by reducing the linewidth of its resonance. This increases the signal-to-noise ratio, and thus suppresses the strain equivalent noise floor. We demonstrate this improvement in a long-distance high performance remote sensing system and show that in reflection, it can mitigate the effects of random phase noise introduced by Rayleigh back-scattering. In transmission, it improves the remote system sensitivity to sub-picostrain resolution, which surpasses any other long-distance remote sensing system to date. With the reduced fiber Fabry-Perot linewidth, all noise sources in the delivery fiber become irrelevant, as the transmission system is limited only by the pre-stabilized laser frequency noise. PMID:19516615

Chow, Jong H; Littler, Ian C; McClelland, David E; Gray, Malcolm B

2006-05-29

275

Zone-Doubling Technique to Produce Ultrahigh-Resolution X-Ray Optics  

SciTech Connect

A method for the fabrication of ultrahigh-resolution Fresnel zone plate lenses for x-ray microscopy is demonstrated. It is based on the deposition of a zone plate material (Ir) onto the sidewalls of a prepatterned template structure (Si) using an atomic layer deposition technique. This results in a doubling of the effective zone density, thus improving the achievable resolution of x-ray microscopes. Test structures with lines and spaces down to 15 nm were resolved in a scanning transmission x-ray microscope at 1 keV photon energy.

Jefimovs, K. [Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); EMPA, CH-8600 Duebendorf (Switzerland); Vila-Comamala, J. [Laboratori de Llum Sincrotro, E-08193 Bellaterra (Spain); Pilvi, T.; Ritala, M. [Laboratory of Inorganic Chemistry, University of Helsinki, FI-00014 Helsinki (Finland); Raabe, J.; David, C. [Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland)

2007-12-31

276

Zone-doubling technique to produce ultrahigh-resolution x-ray optics.  

PubMed

A method for the fabrication of ultrahigh-resolution Fresnel zone plate lenses for x-ray microscopy is demonstrated. It is based on the deposition of a zone plate material (Ir) onto the sidewalls of a prepatterned template structure (Si) using an atomic layer deposition technique. This results in a doubling of the effective zone density, thus improving the achievable resolution of x-ray microscopes. Test structures with lines and spaces down to 15 nm were resolved in a scanning transmission x-ray microscope at 1 keV photon energy. PMID:18233580

Jefimovs, K; Vila-Comamala, J; Pilvi, T; Raabe, J; Ritala, M; David, C

2007-12-31

277

Ultrahigh resolution optical coherence tomography with femtosecond Ti:sapphire laser and photonic crystal fiber  

PubMed Central

Optical coherence tomography (OCT) with ultrahigh axial resolution was achieved by the super-continuum generated by coupling femtosecond pulses from a commercial Ti:sapphire laser into an air-silica microstructure fiber. The visible spectrum of the super-continuum from 450 to 700 nm centered at 540 nm can be generated. A free-space axial OCT resolution of 0.64 ?m was achieved. The sensitivity of OCT system was 108 dB with incident light power 3 mW at sample, only 7dB below the theoretical limit. Subcellular OCT imaging was also demonstrated, showing great potential for biomedical application.

Ping, XUE; FUJIMOTO, James G

2010-01-01

278

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

SciTech Connect

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

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

2010-09-15

279

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

PubMed

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

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

2010-09-01

280

Future directions in X-ray/gamma-ray observations  

NASA Technical Reports Server (NTRS)

Facilities available for X ray and gamma ray astronomical observations in the late 1980s are described, with an emphasis on NASA programs. Current European programs for launching Rosat and Exosat will provide coverage in the 0.4-60 keV energy range. The proposed NASA advanced X ray astrophysics facility is intended to cover the 0.1-8 keV range with higher than 0.5 arcsec resolution. The Japanese Astro-B, scheduled for launch in 1983, observes in the 1-60 keV range. X ray and gamma ray observations are also scheduled for Spacelab flights. The French-Soviet Gamma-1 spark chamber high energy gamma ray telescope is intended for LEO orbit and observations in the energy range above 50 MeV with a 2 deg, 1-5 arcmin resolution. The NASA gamma ray observatory is set for 1988 launch and will feature four instruments to monitor the 60 keV-300 GeV range. Balloon-borne instrumentation will also be launched, with attention given to the medium gamma ray energy range from 1-30 MeV.

Kniffen, D. A.

1982-01-01

281

Photo-nuclear Science using laser Compton scattering gamma-rays in JAEA  

NASA Astrophysics Data System (ADS)

The laser Compton scattering gamma-rays are a new generation of gamma-rays which have advantages of tunable energy, high energy resolution, and almost 100% polarization. These gamma-rays have been used for wide fields as nuclear physics, nuclear astrophysics, and atomic energy engineering. One of the most important topics is a management of nuclear waste. We have proposed a novel non-destructive assay method for isotopes using nuclear resonance fluorescence measurement with the Compton scattering gamma-rays. This assay system is useful for the nuclear waste management. We have successfully demonstrated the detection of a target isotope hidden in heavy metals. We used these gamma-rays for the study of the nuclear physics and nuclear astrophysics. We also have developed a new Compton scattering gamma-ray source with an energy region of sub-MeV.

Hayakawa, Takehito; Hajima, Ryoichi

2008-06-01

282

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

PubMed

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

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

2014-01-01

283

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

NASA Technical Reports Server (NTRS)

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

Carol, Ladd

1999-01-01

284

The gamma-ray spectrometer experiment on the solar maximum mission satellite  

NASA Technical Reports Server (NTRS)

The major activities summarized include: Gamma-Ray Spectrometer (GRS) instrument response and flight operation; solar flare studies; cosmic gamma-ray studies; summary of computer operations; search for flare-precursor protons; diffuse galactic annihilation radiation; cosmic ray bursts; atmospheric gamma ray spectrum; gamma ray line emission from supernovae and novae; improved angular resolutions using Earth occultation; and production processing of NASA IPD data. In addition, an updated list of published papers and invited papers or contributed papers presented at scientific meetings is provided.

Chupp, E. L.

1987-01-01

285

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

PubMed

A novel design for a compact gamma-ray spectrometer is presented. The proposed system allows for spectroscopy of high-flux multi-MeV gamma-ray beams with MeV energy resolution in a compact design. In its basic configuration, the spectrometer exploits conversion of gamma-rays into electrons via Compton scattering in a low-Z material. The scattered electron population is then spectrally resolved using a magnetic spectrometer. The detector is shown to be effective for gamma-ray energies between 3 and 20 MeV. The main properties of the spectrometer are confirmed by Monte Carlo simulations. PMID:24985864

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

2014-06-01

286

Portable compton gamma-ray detection system  

SciTech Connect

A Compton scattered gamma-ray detector system. The system comprises a gamma-ray spectrometer and an annular array of individual scintillators. The scintillators are positioned so that they are arrayed around the gamma-ray spectrometer. The annular array of individual scintillators includes a first scintillator. A radiation shield is positioned around the first scintillator. A multi-channel analyzer is operatively connected to the gamma-ray spectrometer and the annular array of individual scintillators.

Rowland, Mark S. (Alamo, CA); Oldaker, Mark E. (Pleasanton, CA)

2008-03-04

287

Gamma-Ray Spectroscopy of 166Er  

Microsoft Academic Search

Relative intensities of gamma rays of 166Er from the decays of 166mHo were precisely measured with a calibrated Ge(Li) detector. Errors of relative gamma-ray intensities are about 0.5% for strong gamma rays. Angular correlations for 11 cascades were measured with Ge(Li) and NaI(T1) detectors. The B(E2) ratios were deduced from the relative gamma-ray intensities and the adopted values of the

Kazuo Kato; Masaharu Hoshi; Yasukazu Yoshizawa

1981-01-01

288

Gamma ray spectroscopy in astrophysics. [conferences  

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

289

High altitude balloons and gamma ray astronomy  

Microsoft Academic Search

The author's experience with scientific high altitude ballooning will be presented. Usefulness of satellite versus balloon platforms will be contrasted in the context of gamma ray astronomy. General principles of gamma ray astronomy instrumentation will be discussed and illustrated in terms of our current instrument, the Gamma Ray Imaging Spectrometer (GRIS). Some words about the supernova phenomenon and its necessity

Crawford J. MacCallum

1988-01-01

290

Gamma ray astrophysics. [emphasizing processes and absorption  

NASA Technical Reports Server (NTRS)

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

Stecker, F. W.

1974-01-01

291

Gamma Ray Spectroscopy of Mn54  

Microsoft Academic Search

Internal conversion electrons of 0.84 Mev gamma ray were measured by a two-directional focusing beta-ray spectrometer, and it was determined that Egamma{=}837.9± 0.3 kev and K\\/L+M{=}8.5± 0.7. Weak gamma rays were searched, using scintillation counters, but no gamma ray was observed.

Toshio Katoh; Masao Nozawa; Yasukazu Yoshizawa; Yujiro Koh

1958-01-01

292

POSITION SENSITIVE GERMANIUM DETECTORS FOR GAMMA-RAY IMAGING AND SPECTROSCOPY  

EPA Science Inventory

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

293

The goals of gamma-ray spectroscopy in high energy astrophysics  

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

294

Gamma ray imaging using a cadmium zinc telluride crystal and micro-channel plates  

Microsoft Academic Search

Cadmium zinc telluride has proven to be a useful crystal for detecting gamma rays. It shows great promise for filling the need for a high energy and spatial resolution detector for gamma ray imaging. One of the challenges for the use of this device is in the storage and readout of the charge produced by the gamma interaction. The current

R. Chaney; J. Estrera; T. Sinor; K. Passmore

1996-01-01

295

Bridgman growth of Cs 2LiYCl 6:Ce and 6Li-enriched Cs 26LiYCl 6:Ce crystals for high resolution gamma ray and neutron spectrometers  

NASA Astrophysics Data System (ADS)

Single crystals of small and large diameter Cs 2LiYCl 6:Ce and 6Li-enriched Cs 26LiYCl 6:Ce have been grown by the vertical Bridgman technique. These scintillator crystals are used in the fabrication of high resolution, gamma ray and neutron spectrometers. The Cs 2LiYCl 6:Ce and 6Li-enriched Cs 26LiYCl 6:Ce crystals we have grown have high light outputs of up to ˜22,000 photons/MeV. The emission wavelength for the Cs 2LiYCl 6:Ce and 6Li-enriched Cs 26LiYCl 6:Ce is ?=373 nm. This material has an excellent energy resolution at room temperature of ˜4% FWHM for 662 keV photons (using a super bialkali photomultiplier). Cs 2LiYCl 6:Ce exhibits different temporal responses to gamma and neutron radiation. This difference results in effective pulse shape discrimination. In this paper, we will report on our results to date for vertical Bridgman crystal growth and characterization of Ce-doped Cs 2LiYCl 6:Ce and 6Li-enriched Cs 26LiYCl 6:Ce crystals.

Higgins, William M.; Glodo, Jarek; Shirwadkar, Urmila; Churilov, Alexei; Van Loef, Edgar; Hawrami, Rastgo; Ciampi, Guido; Hines, Craig; Shah, Kanai S.

2010-04-01

296

Ultra-high aspect ratio high-resolution nanofabrication for hard X-ray diffractive optics.  

PubMed

Although diffractive optics have played a major role in nanoscale soft X-ray imaging, high-resolution and high-efficiency diffractive optics have largely been unavailable for hard X-rays where many scientific, technological and biomedical applications exist. This is owing to the long-standing challenge of fabricating ultra-high aspect ratio high-resolution dense nanostructures. Here we report significant progress in ultra-high aspect ratio nanofabrication of high-resolution, dense silicon nanostructures using vertical directionality controlled metal-assisted chemical etching. The resulting structures have very smooth sidewalls and can be used to pattern arbitrary features, not limited to linear or circular. We focus on the application of X-ray zone plate fabrication for high-efficiency, high-resolution diffractive optics, and demonstrate the process with linear, circular, and spiral zone plates. X-ray measurements demonstrate high efficiency in the critical outer layers. This method has broad applications including patterning for thermoelectric materials, battery anodes and sensors among others. PMID:24970569

Chang, Chieh; Sakdinawat, Anne

2014-01-01

297

Compton Gamma Ray Observatory Guest Investigator Program  

NASA Technical Reports Server (NTRS)

This paper presents a final report for the Compton Gamma Ray Observatory Guest Investigator Program from 06/01/91-07/31/97. The topics include: 1) Solar Flare Neutron Spectra and Accelerated Ions; 2) Gamma Ray Lines From The Orion Complex; 3) Implications of Nuclear Line Emission From The Orion Complex; 4) Possible Sites of Nuclear Line Emission From Massive OB Associations; 5) Gamma-Ray Burst Repitition and BATSE Position Uncertainties; 6) Effects of Compton Scattering on BATSE Gamma-Ray Burst Spectra; and 7) Selection Biases on the Spectral and Temporal Distribution of Gamma Ray Bursts.

Lingenfelter, Richard E.

1997-01-01

298

Terrestrial Gamma-Ray Flashes (TGFs)  

NASA Technical Reports Server (NTRS)

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

Fishman, Gerald J.

2010-01-01

299

A balloon-borne imaging gamma-ray telescope  

NASA Technical Reports Server (NTRS)

A balloon-borne coded-aperture gamma-ray telescope for galactic and extragalactic astronomy observations is described. The instrument, called GRIP (Gamma Ray Imaging Payload), is designed for measurements in the energy range from 30 keV to 5 MeV with an angular resolution of 0.6 deg over a 20 deg field of view. Distinguishing characteristics of the telescope are a rotating hexagonal coded-aperture mask and a thick NaI scintillation camera. Rotating hexagonal coded-apertures and the development of thick scintillation cameras are discussed.

Althouse, W. E.; Cook, W. R.; Cummings, A. C.; Finger, M. H.; Prince, T. A.; Schindler, S. M.; Starr, C. H.; Stone, E. C.

1985-01-01

300

Pinhole imaging of gamma rays  

Microsoft Academic Search

An approximate calculation is made of the effective area of pinhole collimators allowing for penetration of the metal by gamma -rays of two energies (364 and 140 keV). The particular case of normally-incident rays is treated without approximation. At 364 keV the performance even of heavy alloy (90% tungsten) collimators is dominated by penetration. The effective radius may approach twice

D. Paix

1967-01-01

301

Possible observation of 100 TeV gamma rays from the active galaxy Centaurus A  

Microsoft Academic Search

We have searched for evidence of ultra-high energy gamma rays from the active galaxy Centaurus A in the data set of the JANZOS experiment during the period 13 October 1987 to 18 January 1992. No significant DC excess was found from this source. Excess events were found, however, in the period 14 April - 3 June 1990. The duration of

W. H. Allen; I. A. Bond; E. Budding; M. J. Conway; A. Daniel; K. B. Fenton; H. Fujii; Z. Fujii; N. Hayashida; K. Hibino; M. Honda; J. E. Humble; S. Kabe; K. Kasahara; T. Kifune; G. D. Lythe; A. Masaike; Y. Matsubara; K. Mitsui; Y. Miura; M. Mori; Y. Muraki; M. Nagano; T. Nakamura; M. Nishizawa; P. M. Norris; S. Ogio; To. Saito; M. Sakata; H. Sato; H. M. Shimizu; M. Spencer; J. R. Storey; T. Tanimori; M. Teshima; S. Torii; A. Wadsworth; Y. Watase; M. D. Woodhams; Y. Yamamoto; P. C. M. Yock; T. Yuda

1993-01-01

302

Gamma Ray Spectroscopy in the Pre-HESSI Era  

Microsoft Academic Search

HESSI will provide the high-resolution ?-ray spectroscopy not available in early missions. In spite of these spectral limitations the experiments on SMM, Yohkoh, GRANAT and the Compton Gamma Ray Observatory have provided data for fundamental discoveries over the past decades relating to particle acceleration, transport and energetics in flares and to the ambient abundance of the corona and chromosphere. These

Gerald H. Share; Ronald J. Murphy

303

Which unidentified EGRET sources are gamma-ray pulsars?  

Microsoft Academic Search

We consider high energy gamma -ray radiation from the radio pulsars associated with some unidentified EGRET gamma -ray sources. Calculated efficiencies for the conversion of spin-down power to gamma -rays and the energy spectra of the high energy gamma -rays from these possible gamma -ray pulsars in outer gap models are compared with observed results. Of these possible gamma -ray

L. Zhang; K. S. Cheng

1998-01-01

304

Diffuse galactic gamma ray lines  

NASA Technical Reports Server (NTRS)

The origin and observability were studied of diffuse gamma ray line emission from the galaxy. It was found that such lines could be formed by nuclear excitation interactions of low energy cosmic rays with both interstellar gas and dust grains. The gamma ray emission lines from deexcitation of grain nuclei are sharp with Doppler widths of the order of 10 kev or less; the lines from gas nuclei are also relatively sharp with widths of the order of 100 kev for the most intense line; and the lines from cosmic ray nuclei are broad with widths of the order of several hundred kev. A detailed evaluation is presented of the production rate of the 4.44 Mev line for a variety of assumed cosmic ray spectra. Results are compared with reported galactic gamma ray line intensities and it is concluded that the measurements are consistent with a low energy cosmic ray density which increases toward the galactic center in proportion to the molecular gas density.

Lingenfelter, R. E.; Ramaty, R.

1976-01-01

305

Gamma-ray imaging with coaxial HPGe detector  

SciTech Connect

We report on the first experimental demonstration of Compton imaging of gamma rays with a single coaxial high-purity germanium (HPGe) detector. This imaging capability is realized by two-dimensional segmentation of the outside contact in combination with digital pulse-shape analysis, which enables to image gamma rays in 4{pi} without employing a collimator. We are able to demonstrate the ability to image the 662keV gamma ray from a {sup 137}Cs source with preliminary event selection with an angular accuracy of 5 degree with an relative efficiency of 0.2%. In addition to the 4{pi} imaging capability, such a system is characterized by its excellent energy resolution and can be implemented in any size possible for Ge detectors to achieve high efficiency.

Niedermayr, T; Vetter, K; Mihailescu, L; Schmid, G J; Beckedahl, D; Kammeraad, J; Blair, J

2005-04-12

306

Pulsed Photofission Delayed Gamma Ray Detection for Nuclear Material Identification  

SciTech Connect

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

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

2012-11-01

307

Observations of Gamma-Ray Bursts with INTEGRAL  

SciTech Connect

The INTEGRAL satellite has two coded-mask {gamma}-ray instruments; the spectrometer (SPI) which is optimised for high resolution {gamma}-ray line spectroscopy, and the imager (IBIS) which can localise GRBs to a precision of a few arcminutes. INTEGRAL was launched 3 years ago and the INTEGRAL Burst Alert System (IBAS) has detected 33 long duration GRBs, the most intense burst by far being GRB 041219 which also had prompt optical emission associated with it. The {gamma}-ray properties of some of these bursts are presented with particular emphasis on spectral results. A subset of 6 GRBs were observed with XMM-Newton and a selection of these results is presented. New results from recent GRBs are also discussed.

McGlynn, S.; Hanlon, L.; McBreen, B.; Foley, S.; French, J.; Melady, G. [School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland); McBreen, S. [Astrophysics Missions Division, RSSD of ESA, ESTEC, Noordwijk (Netherlands); Kienlin, A. von [Max-Planck-Institut fur extraterrestrische Physik, 85748 Garching (Germany); Preece, R. [Department of Physics, University of Alabama at Huntsville (United States)

2006-05-19

308

The transient gamma-ray spectrometer  

SciTech Connect

This paper describes the Transient Gamma- Ray Spectrometer (TGRS) to be flown on board the WIND spacecraft. This instrument is designed to detect cosmic {gamma}-ray bursts over the energy range 20 keV to 10 MeV with an expected spectroscopic resolution of 2 keV at 1 MeV (E/{Delta}E = 500). The active detection element is a 215 cm{sup 3} high purity n-type Ge crystal cooled to cryogenic temperatures by a passive radiative cooler. The geometric field of view (FOV) defined by the cooler is 170{degrees} FWFM. Burst data are stored directly in an on board 2.75 Mbit burst memory with an absolute timing accuracy of {plus minus} 1.5 ms. This capacity is sufficient to store the entire spectral data set of all but the largest bursts. In addition to burst measurement, the instrument will also study solar flares, search for possible diffuse background lines and monitor the 511 keV positron annihilation radiation from the galactic center.

Owens, A.; Baker, R.; Cline, T.L.; Gehrels, N.; Jermakian, J.; Nolan, T.; Ramaty, R.; Smith, G.; Stilwell, D.E.; Teegarden, B.J.; Trombka, J.; Yaver, H. (National Aeronautics and Space Administration, Greenbelt, MD (United States). Goddard Space Flight Center); Cork, C.P.; Landis, D.A.; Luke, P.N.; Madden, N.W.; Malone, D.; Pehl, R.H. (Lawrence Berkeley Lab., CA (United States)); Hurley, K. (California Univ., Berkeley, CA (United States). Space Sciences Lab.); Mathias, S.; Post, A.H. Jr. (Little (Arthur D.), Inc., Cambridge, MA (United States))

1991-04-01

309

The gamma ray energy tracking array  

NASA Astrophysics Data System (ADS)

Gamma-ray tracking is a new concept for the detection of ? radiation. One proposed implementation of this concept, called GRETA for Gamma Ray Energy Tracking Array, aims at an improvement in nuclear physics and is based on an array of highly segmented HPGe detectors. We have developed new techniques to determine three-dimensional positions and energies of interactions based on pulse-shape analysis in a two-dimensionally segmented Ge detector and algorithms which use this information to reconstruct the scattering sequence of ? rays, even if many ? rays hit the array at the same time. Such a detector will have a high efficiency and a good peak-to-background ratio, an excellent Doppler-shift correction and high count rate capability, as well as a high polarization sensitivity. However, the concept will not only improve the sensitivity for ? rays in nuclear physics but large potential gain is also possible in other areas, such as ?-ray imaging used in astrophysics or medicine. Only recently we have shown the proof-of-principle of the proposed concept based on the measured position resolution of better than 1 mm in three dimensions in a 36-fold segmented Ge detector at an ?-ray energy of 374 keV. .

Vetter, K.

2001-07-01

310

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

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

311

Outburst in the Gamma-ray Bright Quasar CTA26  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

312

Fabrication and characterization of ultra-high resolution multilayer-coated blazed gratings  

SciTech Connect

Multilayer coated blazed gratings with high groove density are the most promising candidate for ultra-high resolution soft x-ray spectroscopy. They combine the ability of blazed gratings to concentrate almost all diffraction energy in a desired high diffraction order with high reflectance soft x-ray multilayers. However in order to realize this potential, the grating fabrication process should provide a near perfect groove profile with an extremely smooth surface of the blazed facets. Here we report on successful fabrication and testing of ultra-dense saw-tooth substrates with 5,000 and 10,000 lines/mm.

Voronov,, Dmitriy; Anderson, Erik; Cambie, Rossana; Dhuey, Scott; Gullikson, Eric; Salmassi, Farhad; Yashchuk, Tony; Padmore, Howard

2011-07-26

313

In vivo volumetric imaging of chicken retina with ultrahigh-resolution spectral domain optical coherence tomography  

PubMed Central

The chicken retina is an established animal model for myopia and light-associated growth studies. It has a unique morphology: it is afoveate and avascular; oxygen and nutrition to the inner retina is delivered by a vascular tissue (pecten) that protrudes into the vitreous. Here we present, to the best of our knowledge, the first in vivo, volumetric high-resolution images of the chicken retina. Images were acquired with an ultrahigh-resolution optical coherence tomography (UHROCT) system with 3.5 µm axial resolution in the retina, at the rate of 47,000 A-scans/s. Spatial variations in the thickness of the nerve fiber and ganglion cell layers were mapped by segmenting and measuring the layer thickness with a semi-automatic segmentation algorithm. Volumetric visualization of the morphology and morphometric analysis of the chicken retina could aid significantly studies with chicken retinal models of ophthalmic diseases.

Moayed, Alireza Akhlagh; Hariri, Sepideh; Song, Eun Sun; Choh, Vivian; Bizheva, Kostadinka

2011-01-01

314

Position Profiling of the Gamma-Ray Beam at the High Intensity Gamma-Ray Source (HIGS)  

NASA Astrophysics Data System (ADS)

A multi-wire proportional chamber has been constructed to be used as a gamma-ray position profiling device at the High Intensity Gamma-Ray Source (HIGS) located in the Duke Free Electron Laser Laboratory. The chamber will provide a means of locating the central axis of the gamma-ray beam with an enhanced position resolution as compared to current methods. The determination of the gamma-beam's position will enable symmetrical collimation of the gamma-beam about the central axis. This in turn, for a given diameter of collimator, will maximize the beam's intensity while simultaneously minimizing the beam's energy spread. Design specifications, construction procedures, projected performance and preliminary test results will be presented.

Westerly, David

2002-10-01

315

Period differences between X-ray and very high energy gamma-ray observations of accreting X-ray pulsars  

Microsoft Academic Search

Very high energy pulsed gamma-rays have been reported from several accreting X-ray binaries. A model is considered here which gives efficient gamma-ray production in 1000-second bursts and period differences of the observed magnitude. The key feature is acceleration of ultrahigh energy particles through the inner accretion disk in which there is radial flow toward the star as well as Keplerian

K. S. Cheng; Malvin Ruderman

1989-01-01

316

New generation gamma-ray camera for planetary science application: High pressure xenon time projection chamber  

NASA Astrophysics Data System (ADS)

Elemental composition on lunar and planetary surface gives key insights into the formation and crustal evolution. Gamma-ray spectrometer is a powerful tool for the global observation of elemental distribution by measuring MeV gamma-ray lines from many elements (O, Si, Mg, Al, Fe, Ti, Ca, K, U, Th, etc.) on planetary surfaces. Since gamma-ray spectrometers carried on the spacecraft so far could not determine arrival direction of gamma-rays, spatial resolution of those spectrometers was given by the altitude of the spacecraft. New generation gamma-ray camera we have been developing is based on the detection of a Compton scattering interaction of a gamma-ray. The camera is realized by High-pressure Xe Time Projection Chamber (HPXe-TPC), which allows for the simultaneous determination of gamma-ray direction and energy. HPXe-TPC features radiation- and heat-resistance detector and also has relatively a good energy resolution at room temperature compared to scintillation detectors. HPXe-TPC provides global mapping of composition as the remote sensing spectrometer. Current status of gamma-ray detection using HPXe-TPC and preliminary results simulated by GEANT4 codes are reported.

Hasebe, N.; Doke, T.; Pouchkine, K. N.; Kobayashi, M.-N.; Kobayashi, S.; Miyachi, T.; Miyajima, M.; Tezuka, C.; Shibamura, E.; Xenon Detector Team

317

Matter-antimatter gigaelectron volt gamma ray laser rocket propulsion  

NASA Astrophysics Data System (ADS)

It is shown that the idea of a photon rocket through the complete annihilation of matter with antimatter, first proposed by Sänger, is not a utopian scheme as it is widely believed. Its feasibility appears to be possible by the radiative collapse of a relativistic high current pinch discharge in a hydrogen-antihydrogen ambiplasma down to a radius determined by Heisenberg's uncertainty principle. Through this collapse to ultrahigh densities the proton-antiproton pairs in the center of the pinch can become the upper gigaelectron volt laser level for the transition into a coherent gamma ray beam by proton-antiproton annihilation, with the magnetic field of the collapsed pinch discharge absorbing the recoil momentum of the beam and transmitting it by the Moessbauer effect to the spacecraft. The gamma ray laser beam is launched as a photon avalanche from one end of the pinch discharge channel. Because of the enormous technical problems to produce and store large amounts of anti-matter, such a propulsion concept may find its first realization in small unmanned space probes to explore nearby solar systems. The laboratory demonstration of a gigaelectron volt gamma ray laser by comparison requiring small amounts of anti-matter may be much closer.

Winterberg, F.

2012-12-01

318

Anomalous Thermal Behavior in Microcalorimeter Gamma-Ray Detectors  

SciTech Connect

Improving the resolution of gamma-ray detectors is important for many fields, including determinations of the Lamb shift in atoms with high atomic numbers, nuclear treaty verification, and environmental monitoring. High-purity germanium detectors are currently the tool of choice for precision gamma-ray spectroscopy. The resolution of these detectors is limited to about 500 eV full-width-at-half-maximum at 100 keV by Fano statistics. In comparison, low-temperature microcalorimeters can provide over an order of magnitude improvement in photon resolution. For instance, a gamma-ray microcalorimeter has achieved 25 eV FWHM resolution at 103 keV. These calorimeters consist of two components, a bulk absorber to stop incident gamma rays and a thermometer made from a thin film electrically biased in the superconducting-to-normal phase transition, called a Transition Edge Sensor, or TES. The standard absorber is bulk, superconducting tin. While tin has historically been the best performing absorber, pulse decays in Sn devices are much slower than predicted. We have begun a systematic study of absorber behavior in order to assess and improve response times. This study leverages two capabilities: the ability to microfabricate highly uniform arrays of gamma-ray detectors and the ability to read out many detectors in a single cool-down using SQUID multiplexer circuits. Here, we present two experiments to identify the source of thermal time constants. The first involves varying properties of the Sn absorber including purity, vendor, and crystal grain size. The second examines the role of the other elements in the microcalorimeter assembly.

Horansky, Robert D.; Beall, James A.; Irwin, Kent D.; Ullom, Joel N. [National Institute of Standards and Technology, 325 Broadway, Boulder, CO 80305 (United States)

2009-12-16

319

Ultrahigh resolution mass spectrometry and accurate mass measurements for high-throughput food lipids profiling.  

PubMed

In the present study, accurate mass measurements by ultrahigh resolution mass spectrometry with Orbitrap-Exactive working at resolving power R: 100,000 (m/z 200, full width at half maximum) with an accuracy better than 2?ppm in all the mass range (m/z 200 to 2000) were used to show a detailed molecular composition of diverse edible oils and fats. Flow injection was used to introduce samples into the mass spectrometer, obtaining a complete analysis of each sample in less than 10 min, including blanks. Meticulous choice of organic solvents and optimization of the ion source and Orbitrap mass analyzer parameters were carried out, in order to achieve reproducible mass spectra giving reliable elemental compositions of the lipid samples and to prevent carry over. More than 200 elemental compositions attributable to diacylglycerols, triacylglycerols (TAGs), and their oxidation products have been found in the spectra of food lipids from different origin. Several compounds with very close molecular mass could only be resolved through ultrahigh resolution, allowing detailed and robust TAG profiling with a high characterization potential. PMID:22972786

Vichi, Stefania; Cortés-Francisco, Nuria; Caixach, Josep

2012-09-01

320

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

PubMed

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

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

2012-11-01

321

Quasars, blazars, and gamma rays  

NASA Technical Reports Server (NTRS)

The paper discusses the extragalactic sources that have been discovered with the Energetic Gamma Ray Experiment Telescope. All of the sources demonstrate evidence of blazar properties at other wavelengths, including high optical polarization, extreme optical variability, flat-spectrum radio emission associated with a compact core, and apparent superluminal motion. These properties are believed to be produced by those few rare extragalactic quasars and radio galaxies that are favorably aligned to make it possible to observe almost directly down a relativistically outflowing jet of matter expelled from a supermassive black hole.

Dermer, Charles D.; Schlickeiser, Reinhard

1992-01-01

322

Ultra-high resolution optical coherence tomography for encapsulation quality inspection  

NASA Astrophysics Data System (ADS)

We present the application of ultra-high resolution optical coherence tomography (UHR-OCT) in evaluation of thin, protective films used in printed electronics. Two types of sample were investigated: microscopy glass and organic field effect transistor (OFET) structure. Samples were coated with thin (1-3 ?m) layer of parylene C polymer. Measurements were done using experimental UHR-OCT device based on a Kerr-lens mode locked Ti:sapphire femtosecond laser, photonic crystal fibre and modified, free-space Michelson interferometer. Sub-micron resolution offered by the UHR-OCT system applied in the study enables registration of both interfaces of the thin encapsulation layer. Complete, volumetric characterisation of protective layers is presented, demonstrating possibility to use OCT for encapsulation quality inspection.

Czajkowski, J.; Fabritius, T.; Ula?ski, J.; Marsza?ek, T.; Gazicki-Lipman, M.; Nosal, A.; ?li?, R.; Alarousu, E.; Prykäri, T.; Myllylä, R.; Jabbour, G.

2011-11-01

323

Telescope for x ray and gamma ray studies in astrophysics  

NASA Technical Reports Server (NTRS)

Imaging of x-rays has been achieved by various methods in astrophysics, nuclear physics, medicine, and material science. A new method for imaging x-ray and gamma-ray sources avoids the limitations of previously used imaging devices. Images are formed in optical wavelengths by using mirrors or lenses to reflect and refract the incoming photons. High energy x-ray and gamma-ray photons cannot be reflected except at grazing angles and pass through lenses without being refracted. Therefore, different methods must be used to image x-ray and gamma-ray sources. Techniques using total absorption, or shadow casting, can provide images in x-rays and gamma-rays. This new method uses a coder made of a pair of Fresnel zone plates and a detector consisting of a matrix of CsI scintillators and photodiodes. The Fresnel zone plates produce Moire patterns when illuminated by an off-axis source. These Moire patterns are deconvolved using a stepped sine wave fitting or an inverse Fourier transform. This type of coder provides the capability of an instantaneous image with sub-arcminute resolution while using a detector with only a coarse position-sensitivity. A matrix of the CsI/photodiode detector elements provides the necessary coarse position-sensitivity. The CsI/photodiode detector also allows good energy resolution. This imaging system provides advantages over previously used imaging devices in both performance and efficiency.

Weaver, W. D.; Desai, Upendra D.

1993-01-01

324

Development of an ultrahigh resolution Si-PM based PET system for small animals  

NASA Astrophysics Data System (ADS)

Since a high resolution PET system is needed for small animal imaging, especially for mouse studies, we developed a new small animal PET system that decreased the size of the scintillators to less than 1 mm. Our developed PET system used 0.5 × 0.7 × 5 mm3 LYSO pixels arranged in an 11 × 13 matrix to form a block with a 0.1 mm BaSO4 reflector between the pixels. Two LYSO blocks were optically coupled to two optical fiber based angled image guides. These LYSO blocks and image guides were coupled to a Si-PM array (Hamamatsu MPPC S11064-050P) to form a block detector. Eight block detectors (16 LYSO blocks) were arranged in a 34 mm inner diameter ring to form a small animal PET system. The block detector showed good separation for the 22 × 13 LYSO pixels in the two-dimensional position histogram. The energy resolution was 20% full-with at half-maximum (FWHM) for 511 keV gamma photons. The transaxial resolution reconstructed by filtered backprojection was 0.71 to 0.75 mm FWHM and the axial resolution was 0.70 mm. The point source sensitivity was 0.24% at the central axial field-of-view. High resolution mouse images were obtained using our PET system. The developed ultrahigh resolution PET system showed attractive images for small animal studies and has a potential to provide new findings in molecular imaging researches.

Yamamoto, Seiichi; Watabe, Hiroshi; Kanai, Yasukazu; Watabe, Tadashi; Kato, Katsuhiko; Hatazawa, Jun

2013-11-01

325

gamma Rays Following Thermal Neutron Capture in Titanium  

Microsoft Academic Search

The gamma rays following thermal neutron capture in titanium have been studied with two high resolution spectrometers and with an angular correlation arrangement using two sodium iodide scintillation spectrometers. The high resolution instruments were a pair spectrometer for the energy range 2.8 to 11.0 Mev and a double flat crystal diffraction spectrometer for the energy range 0.14 to 5 Mev.

J. W. Knowles; G. Manning; G. A. Bartholomew; P. J. Campion

1959-01-01

326

Cooled germanium spectrometers for X- and gamma-ray astronomy  

Microsoft Academic Search

The techniques of applying cooled germanium detectors to obtain high resolution measurements of hard X-ray and gamma-ray spectra from cosmic sources are discussed. Energy resolutions of better than 2 keV (FWHM) in the MeV region are achieved in the laboratory, representing an improvement of about a factor of 40 over conventional scintillators. Recent development of large intrinsic (pure) germanium detectors

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

1976-01-01

327

LaBr3:Ce scintillators for gamma ray spectroscopy  

Microsoft Academic Search

In this paper, we report on a relatively new scintillator - LaBr3 for gamma ray spectroscopy. Crystals of this scintillator have been grown using Bridgman process. This material when doped with cerium has high light output (?60,000 photons\\/MeV) and fast principal decay constant (?25 ns). Furthermore, it shows excellent energy resolution for ?-ray detection. Energy resolution of 3.2% (FWHM) has

K. S. Shah; J. Glodo; M. Klugerman; W. W. Moses; S. E. Derenzo; M. J. Weber

2002-01-01

328

Ultrahigh resolution optical coherence tomography imaging of lung structure using Gaussian shaped super continuum sources  

NASA Astrophysics Data System (ADS)

Optical coherence tomography (OCT) is an emerging technology for non-invasive cross-sectional imaging of biological tissue and material with um resolution. In the field of pulmonary medicine, non-invasive high resolution cross-sectional imaging is desired for investigation of diseases in lung. So far, a few works have been reported about OCT imaging of lung. Since the lung consists of alveoli separated by thin wall, ultrahigh resolution (UHR) OCT is supposed to be effective for the imaging of fine structure in lung tissue. In this work, ex vivo cross-sectional imaging of isolated rat and hamster lungs was demonstrated using UHR-OCT. A 120 nm-wide, high-power, Gaussian-like supercontinuum (SC) was generated at wavelength of 0.8 um region. The generated SC was used in a time-domain OCT system, and UHR-OCT imaging was demonstrated. An ultrahigh resolution of 2.9 um in air and 2.1 um in tissue was obtained. The achieved sensitivity was 105 dB. Using this system, ex vivo UHR-OCT imaging of isolated rat and hamster lungs was demonstrated for the first time. The structures of the trachea, visceral pleura, and alveoli were observed clearly. When saline was instilled into the lung, the penetration depth was improved, and clear images of the fine structure of the lung, including alveoli, were observed owing to the index matching effect. We have also demonstrated the UHR-OCT imaging of lung tissue using 1.3 um and 1.7 um SC sources. As the results, owing to the precise structures of lung tissues and index matching by saline, the finest images were observed with 0.8 um UHR-OCT system.

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

2011-02-01

329

Gamma-ray pulsar studies with COMPTEL  

Microsoft Academic Search

Since the launch of the Compton Gamma-Ray Observatory (CGRO) the number of detected gamma-ray pulsars increased from two to six. COMPTEL, on-board CGRO and sensitive to gamma-rays with energies between approximately 0.7 and 30 MeV, detected three of these unambiguously. The classical Crab and Vela pulsars have been observed on several occasions and detailed pulse patterns and spectral parameters have

W. Hermsen; L. Kuiper; R. Diehl; G. Lichti; V. Schoenfelder; A. W. Strong; A. Connors; J. Ryan; K. Bennett; M. Busetta; A. Carraminana; R. Buccheri; I. A. Grenier

1994-01-01

330

Gamma-Ray Pulsar Studies with GLAST  

Microsoft Academic Search

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

D. J. Thompson; GAMMA-RAY PULSARS

2008-01-01

331

Gamma-Ray Pulsar Studies with GLAST  

NASA Technical Reports Server (NTRS)

This viewgraph presentation reviews the prospects of extending the understanding of gamma ray pulsars, and answering the open questions left from the limited observations that are available from current observatories. There are 2 new gamma ray observatories that are either on orbit or will be shortly launched: (1) Astro-rivelatore Gamma a Immagini LEggero (AGILE), and Gamma-ray Large Area Space Telescope (GLAST). On board GLAST there will be two instruments Large Area Telescope (LAT), and GLAST Burst Monitor (GBM).

Thompson, David J.

2007-01-01

332

Gamma-Ray Pulsar Candidates for GLAST  

Microsoft Academic Search

The Gamma-ray Large Area Space Telescope (GLAST) will be launched less than a year from now, and its Large Area Telescope (LAT) is expected to discover scores to hundreds of gamma-ray pulsars. This poster discusses which of the over 1700 known pulsars, mostly visible only at radio frequencies, are likely to emit >100 MeV gamma rays with intensities detectable by

David J. Thompson; D. A. Smith; D. Dumora; L. Guillemot; D. Parent; T. Reposeur; J. E. Grove; R. W. Romani; S. E. Thorsett

2006-01-01

333

Gamma-Ray Pulsar Candidates for GLAST  

Microsoft Academic Search

The Gamma-ray Large Area Space Telescope (GLAST) will be launched this year, and its Large Area Telescope (LAT) is expected to discover scores to hundreds of gamma-ray pulsars. This poster discusses which of the over 1700 known pulsars, mostly visible only at radio frequencies, are likely to emit >100; MeV gamma rays with intensities detectable by the LAT. The main

David John Thompson

2008-01-01

334

Gamma-Ray Astronomy Technology Needs  

NASA Technical Reports Server (NTRS)

In recent decades gamma-ray observations have become a valuable tool for studying the universe. Progress made in diverse 8re1lS such as gamma-ray bursts (GRBs), nucleosynthesis, and active galactic nuclei (AGNs) has complimented and enriched our astrophysical understanding in many ways. We present an overview of current and future planned space y-ray missions and discussion technology needs for- the next generation of space gamma-ray instruments.

Gehrels, N.; Cannizzo, J. K.

2012-01-01

335

Very High Energy Gamma-Ray Astronomy  

Microsoft Academic Search

We present a review of the current status of very high energy gamma-ray astronomy. The development of the atmospheric Cerenkov imaging technique for ground-based gamma-ray astronomy has led to a rapid growth in the number of observatories. The detection of TeV gamma-rays from active galactic nuclei was unexpected and is providing new insights into the emission mechanisms in the jets.

Michael Catanese; Trevor C. Weekes

1999-01-01

336

GAMCIT: A gamma ray burst detector  

NASA Technical Reports Server (NTRS)

The origin of celestial gamma ray bursts remains one of the great mysteries of modern astrophysics. The GAMCIT Get-Away-Special payload is designed to provide new and unique data in the search for the sources of gamma ray bursts. GAMCIT consists of three gamma ray detectors, an optical CCD camera, and an intelligent electronics system. This paper describes the major components of the system, including the electronics and structural designs.

Surka, Derek M.; Grunsfeld, John M.; Warneke, Brett A.

1992-01-01

337

Astrophysical constraints from gamma-ray spectroscopy  

Microsoft Academic Search

Gamma-ray lines from cosmic sources provide unique isotopic information, since they originate from energy level transitions in the atomic nucleus. Gamma-ray telescopes explored this astronomical window in the past three decades, detecting radioactive isotopes that have been ejected in interstellar space by cosmic nucleosynthesis events and nuclei that have been excited through collisions with energetic particles. Astronomical gamma-ray telescopes feature

Roland Diehl; Nikos Prantzos; Peter von Ballmoos

2006-01-01

338

BATSE observations of gamma-ray bursts  

NASA Astrophysics Data System (ADS)

Gamma-ray bursts are being detected with unprecedented sensitivity by the Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray observatory since its launch in April, 1991. The experiment is detecting about one gamma-ray burst per day. A brief description is presented of the on-orbit performance of BATSE, the methods of identification of bursts, and examples of the diverse time profiles of the gamma-ray bursts observed. The most significant finding thus far is the apparent isotropy of the bursts together with the observed inhomogeneity of the sources.

Fishman, G. J.; Meegan, C. A.; Wilson, R. B.; Horack, J. M.; Brock, M. N.; Paciesas, W. S.; Pendleton, G. N.; Kouveliotou, C.

1991-09-01

339

BATSE observations of gamma-ray bursts  

NASA Astrophysics Data System (ADS)

Gamma-ray bursts are being detected with unprecedented sensitivity by the Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory since its launch in April, 1991. The experiment is detecting about one gamma-ray burst per day. A brief description is presented of the on-orbit performance of BATSE, the methods of identification of bursts, and examples of the diverse time profiles of the gamma-ray bursts observed. The most significant finding thus far is the apparent isotropy of the bursts together with the observed inhomogeneity of the sources.

Fishman, Gerald J.; Meegan, C. A.; Wilson, R. B.; Horack, J. M.; Brock, M. N.; Paciesas, William S.; Pendleton, G. N.; Kouveliotou, C.

340

Radio Observations of Gamma-ray Novae  

NASA Astrophysics Data System (ADS)

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.

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

2014-01-01

341

Low-level gamma-ray spectrometry  

SciTech Connect

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

Brodzinski, R.L.

1990-10-01

342

Future prospects for gamma-ray  

NASA Technical Reports Server (NTRS)

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

Fichtel, C.

1980-01-01

343

Gamma-ray burst populations  

NASA Astrophysics Data System (ADS)

Over the last fifty years the field of gamma-ray bursts has shown incredible growth, but the amassing of data has also left observers and theorists alike wondering about some of the basic questions surrounding these phenomena. Additionally, these events show remarkable individuality and extrema, ranging in redshift throughout the observable universe and over ten orders of magnitude in energy. This work focuses on analyzing groups of bursts that are different from the general trend and trying to understand whether these bursts are from different intrinsic populations and if so, what can be said about their progenitors. This is achieved through numerical Monte Carlo simulations and statistical inference in conjunction with current GRB observations. Chapter 1 gives a general introduction of gamma-ray burst theory and observations in a semi-historical context. Chapter 2 provides an introduction to the theory and practical issues surrounding the numerical simulations and statistics. Chapters 3--5 are each dedicated to a specific problem relating to a different type of GRB population: high-luminosity v. low-luminosity bursts, constraints from high-redshift bursts, and Type I v. Type II bursts. Chapter 6 follows with concluding remarks.

Virgili, Francisco Javier

344

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

SciTech Connect

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

Fenimore, E.E.

1998-07-01

345

Gamma rays of 1-30 MeV from the Galactic Center Region  

NASA Astrophysics Data System (ADS)

Preliminary results are reported for gamma rays from the Galactic Center Region at 1-30 MeV made with a balloon-borne double Compton scatter gamma ray telescope. The Compton scatter angle, energy, and arrival time of the incident gamma ray and direction of the Compton scattered secondary for downward-moving gamma rays were measured. The handling of the data is described, and the results of Monte Carlo simulation angular resolutions and absolute efficiencies for different zenith angles of incident gamma rays are given. A contour sky map of the weighted fluxes for a southern sky region is shown whose primary feature is a significant enhancement in the Galactic Center Region. It is concluded that several discrete sources contribute to broaden the maximum in the horizontal or RA direction. Less broadening is indicated along the galactic plane.

Oneill, T.; Long, J.; Zanrosso, E.; Zych, A.; White, R. S.; Dayton, B.

1983-08-01

346

High-Energy gamma-Ray BEAMS from Compton-Backscattered Laser Light.  

National Technical Information Service (NTIS)

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...

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

1983-01-01

347

Possible Detection of Gamma Ray Air Showers in Coincidence with BATSE Gamma Ray Bursts  

Microsoft Academic Search

Project GRAND presents the results of a search for coincident high-energy gamma ray events in the direction and at the time of nine Gamma Ray Bursts (GRBs) detected by BATSE. A gamma ray has a non-negligible hadron production cross section; for each gamma ray of energy of 100 GeV, there are 0.015 muons which reach detection level (Fasso & Poirier,

T. F. Lin; J. Carpenter; S. Desch; J. Gress; J. Poirier; A. Roesch

2000-01-01

348

Possible Detection of Gamma Ray Air Showers in Coincidence with BATSE Gamma Ray Bursts  

Microsoft Academic Search

Project GRAND presents the results of a search for coincident high-energy gamma ray events in the direction and at the time of nine Gamma Ray Bursts (GRBs) detected by BATSE. A gamma ray has a non-negligible hadron production cross section; for each gamma ray of energy of 100 GeV, there are 0.015 muons which reach detection level (Fasso & Poirier,

Tzu-Fen Lin

1999-01-01

349

Gamma rays in a spectrum from the Mars Odyssey gamma-ray spectrometer.  

NASA Astrophysics Data System (ADS)

The gamma-ray spectrum from a long sum over the middle latitudes of Mars measured by the Mars Odyssey Gamma Ray Spectrometer was analyzed. About 250 peaks and features were observed, including many seen during the cruise to Mars. The sources of about 85% of these gamma rays were identified. Most were background lines from the Ge detector or from Ti, Mg, and Zn near the detector. Many gamma rays from Mars are present.

Brückner, J.; Reedy, R. C.; Evans, L. G.; Kim, K. J.; Boynton, W. V.

2003-04-01

350

Fermi Large Area Telescope Measurements of the Diffuse Gamma-Ray Emission at Intermediate Galactic Latitudes  

SciTech Connect

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

Abdo, A.A.; /Naval Research Lab, Wash., D.C.; Ackermann, M.; Ajello, M.; /SLAC; Anderson, B.; Atwood, W.B.; /UC, Santa Cruz; Axelsson, M.; /Stockholm U. /Stockholm U., OKC; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Barbiellini, G.; /INFN, Trieste /Trieste U.; Bastieri, D.; /INFN, Padua /Padua U.; Baughman, B.M.; /Taiwan, Natl. Taiwan U. /Ohio State U.; Bechtol, K.; /SLAC; Bellazzini, R.; /INFN, Pisa; Berenji, B.; Blandford, R.D.; Bloom, E.D.; /SLAC; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /SLAC; Bregeon, J.; Brez, A.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari /Ecole Polytechnique /Washington U., Seattle /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /IASF, Milan /DAPNIA, Saclay /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Naval Research Lab, Wash., D.C. /George Mason U. /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Montpellier U. /Stockholm U. /Stockholm U., OKC /Royal Inst. Tech., Stockholm /Padua U. /Naval Research Lab, Wash., D.C. /Udine U. /INFN, Trieste /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /INFN, Pisa /UC, Santa Cruz /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /CENBG, Gradignan /CENBG, Gradignan /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Montpellier U. /Bari U. /INFN, Bari /Ecole Polytechnique /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Udine U. /INFN, Trieste /Hiroshima U. /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Bari U. /INFN, Bari /INFN, Pisa /INFN, Bari /NASA, Goddard /Maryland U.; /more authors..

2012-04-11

351

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

PubMed

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

Abdo, A A; Ackermann, M; Ajello, M; Anderson, B; Atwood, W B; Axelsson, M; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Baughman, B M; Bechtol, K; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bregeon, J; Brez, A; Brigida, M; Bruel, P; Burnett, T H; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cecchi, C; Charles, E; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; Dereli, H; Dermer, C D; de Angelis, A; de Palma, F; Digel, S W; Di Bernardo, G; Dormody, M; do Couto e Silva, E; Drell, P S; Dubois, R; Dumora, D; Edmonds, Y; Farnier, C; Favuzzi, C; Fegan, S J; Focke, W B; Frailis, M; Fukazawa, Y; Funk, S; Fusco, P; Gaggero, D; Gargano, F; Gehrels, N; Germani, S; Giebels, B; Giglietto, N; Giordano, F; Glanzman, T; Godfrey, G; Grenier, I A; Grondin, M-H; Grove, J E; Guillemot, L; Guiriec, S; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Hughes, R E; Jóhannesson, G; Johnson, A S; Johnson, R P; Johnson, T J; Johnson, W N; Kamae, T; Katagiri, H; Kataoka, J; Kawai, N; Kerr, M; Knödlseder, J; Kocian, M L; Kuehn, F; Kuss, M; Lande, J; Latronico, L; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Makeev, A; Mazziotta, M N; McConville, W; McEnery, J E; Meurer, C; Michelson, P F; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nolan, P L; Nuss, E; Ohsugi, T; Okumura, A; Omodei, N; Orlando, E; Ormes, J F; Paneque, D; Panetta, J H; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Piron, F; Porter, T A; Rainò, S; Rando, R; Razzano, M; Reimer, A; Reimer, O; Reposeur, T; Ritz, S; Rodriguez, A Y; Roth, M; Ryde, F; Sadrozinski, H F-W; Sanchez, D; Sander, A; Saz Parkinson, P M; Scargle, J D; Sellerholm, A; Sgrò, C; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Starck, J-L; Stecker, F W; Striani, E; Strickman, M S; Strong, A W; Suson, D J; Tajima, H; Takahashi, H; Tanaka, T; Thayer, J B; Thayer, J G; Thompson, D J; Tibaldo, L; Torres, D F; Tosti, G; Tramacere, A; Uchiyama, Y; Usher, T L; Vasileiou, V; Vilchez, N; Vitale, V; Waite, A P; Wang, P; Winer, B L; Wood, K S; Ylinen, T; Ziegler, M

2009-12-18

352

New concepts for scintillator\\/HgI\\/sub 2\\/ gamma ray spectroscopy  

Microsoft Academic Search

The construction of a high energy resolution gamma ray detector consisting of a scintillator\\/mercuric iodide photodetector combination has been investigated. Several HgI[sub 2] photodetectors have been fabricated and tested with standard NIM electronics. The energy resolution of a scintillator\\/HgI[sub 2] pair was found to be 4.75%, full width at half maximum, for 662 keV [sup 137]Cs gamma ray photons. Of

Y. J. Wang; J. S. Iwanczyk; B. E. Patt

1994-01-01

353

LaCl3:Ce scintillator for gamma-ray detection  

Microsoft Academic Search

In this paper, we report on a relatively new cerium-doped scintillator-LaCl3 for gamma-ray spectroscopy. Crystals of this scintillator have been grown using Bridgman method. This material when doped with 10% cerium has high light output (~50,000 photons\\/MeV) and fast principal decay time constant (~20ns). Furthermore, it shows excellent energy resolution for gamma-ray detection. For example, energy resolution as low as

K. S. Shah; J. Glodo; M. Klugerman; L. Cirignano; W. W. Moses; S. E. Derenzo; M. J. Weber

2003-01-01

354

New Concepts For Scintillator\\/HgI2 Gamma Ray Spectroscopy  

Microsoft Academic Search

The construction of a high energy resolution gamma ray detector consisting of a scintillator\\/mercuric iodide photodetector combination has been investigated. Several HgI, photodetectors have been fabricated and tested with standard NIM electronics. The energy resolution of a scintillator\\/HgI, pair was found to be 4.75%, full width at half maximum, for 662 keV 13'Cs gamma ray photons. New design concepts for

Y. J. Wang; J. S. Iwanczyk; B. E. Patt

1993-01-01

355

Computer design of a low background germanium detector for astrophysical gamma-ray spectroscopy  

Microsoft Academic Search

Real progress in gamma-ray line astronomy depends on the availability of high energy resolution, low background detectors. New large volume germanium (Ge) detectors have an excellent energy resolution (E\\/DeltaE ~ 500 at 1 MeV) but they do not yet reach good sensitivity for gamma-ray spectroscopy of astrophysical sources. We review the various techniques which are or may be employed to

A. S. Slassi-Sennou; F. Albernhe; G. Vedrenne

1991-01-01

356

New concepts for scintillator\\/HgI2 gamma ray spectroscopy  

Microsoft Academic Search

The construction of a high energy resolution gamma ray detector consisting of a scintillator\\/mercuric iodide photodetector combination has been investigated. Several HgI2 photodetectors have been fabricated and tested with standard NIM electronics. The energy resolution of a scintillator\\/HgI2 pair was found to be 4.75%, full width at half maximum, for 662 keV 137Cs gamma ray photons. Of five detectors fabricated

Y. J. Wang; J. S. Iwanczyk; B. E. Patt

1994-01-01

357

Development of a Gamma-Ray Detector With Iridium Transition Edge Sensor Coupled to a Pb Absorber  

Microsoft Academic Search

We have recently started to develop a high-resolution gamma-ray spectrometer for material defect analysis. Our gamma-ray detector is a microcalorimeter consisting of an iridium\\/gold bilayer transition edge sensor (TES) thermometer and a bulk Pb absorber, which is directly coupled to a TES with Stycast 2850FT epoxy. This paper describes our TES based gamma-ray detector and the first experimental results for

Rathnayaka Mudiyanselage Thushara Damayanthi; Steven W. Leman; Hiroyuki Takahashi; Masashi Ohno; Yasuhiro Minamikawa; Kentaro Nishimura; Naoko Iyomoto

2009-01-01

358

Large-scale components of radio galaxies in gamma rays  

NASA Astrophysics Data System (ADS)

The populations of relativistic electrons and high-energy cosmic rays in the extended components of radio-loud active galaxies-kiloparsec-scale jets, hotspots and lobes-make them, in principle, interesting sources of gamma-ray photons up to the highest (TeV) energies. Here I discuss the few detections of extended gamma-ray emission with Fermi and show what constraints they put on the physical conditions in radio galaxies. Although detections of radio galaxies at TeV energy are rare, I show that the information we do have can already put interesting constraints on radio galaxy physics: the CTA should have the sensitivity and resolution to improve this situation considerably, and to resolve the expected arcmin-scale gamma-ray jet in the nearest radio galaxy, Centaurus A. Finally, I review the connection between the gamma-ray observations and the acceleration of ultra-high-energy cosmic rays, and suggest that, while radio galaxies may well be the sources of the highest-energy cosmic rays observed, they may constitute a `disappointing' population in the sense that only very nearby sources, such as Cen A, will ever be identified as discrete cosmic-ray sources.

Hardcastle, Martin J.

2012-12-01

359

Future Gamma-Ray Imaging of Solar Eruptive Events  

NASA Technical Reports Server (NTRS)

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

Shih, Albert

2012-01-01

360

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

NASA Astrophysics Data System (ADS)

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

Tumlinson, Alexandre Rex

361

Ultra-high vacuum scanning thermal microscopy for nanometer resolution quantitative thermometry.  

PubMed

Understanding energy dissipation at the nanoscale requires the ability to probe temperature fields with nanometer resolution. Here, we describe an ultra-high vacuum (UHV)-based scanning thermal microscope (SThM) technique that is capable of quantitatively mapping temperature fields with ?15 mK temperature resolution and ?10 nm spatial resolution. In this technique, a custom fabricated atomic force microscope (AFM) cantilever, with a nanoscale Au-Cr thermocouple integrated into the tip of the probe, is used to measure temperature fields of surfaces. Operation in an UHV environment eliminates parasitic heat transport between the tip and the sample enabling quantitative measurement of temperature fields on metal and dielectric surfaces with nanoscale resolution. We demonstrate the capabilities of this technique by directly imaging thermal fields in the vicinity of a 200 nm wide, self-heated, Pt line. Our measurements are in excellent agreement with computational results-unambiguously demonstrating the quantitative capabilities of the technique. UHV-SThM techniques will play an important role in the study of energy dissipation in nanometer-sized electronic and photonic devices and the study of phonon and electron transport at the nanoscale. PMID:22530657

Kim, Kyeongtae; Jeong, Wonho; Lee, Woochul; Reddy, Pramod

2012-05-22

362

Gamma rays from 'hidden' millisecond pulsars  

NASA Technical Reports Server (NTRS)

The properties were studied of a new class of gamma ray sources consisting of millisecond pulsars totally or partially surrounded by evaporating material from irradiated companion stars. Hidden millisecond pulsars offer a unique possibility to study gamma ray, optical and radio emission from vaporizing binaries. The relevance of this class of binaries for GRO observations and interpretation of COS-B data is emphasized.

Tavani, M.

1993-01-01

363

Gamma-Ray Pulsar Candidates for GLAST  

NASA Technical Reports Server (NTRS)

The Gamma-ray Large Area Space Telescope (GLAST) will be launched less than a year from now, and its Large Area Telescope (LAT) is expected to discover scores to hundreds of gamma-ray pulsars. This poster discusses which of the over 1700 known pulsars, mostly visible only at radio Erequencies, are likely to emit greater than l00 MeV gamma rays with intensities detectable by the LAT. The main figure of merit used to select gamma-ray pulsar candidates is sqrt(E-dot)/d^2, where E-dot is the energy loss due to rotational spindown, and d is the distance to the pulsar. The figure of merit incorporates spin-down flux at earth (proportional to E-dot/d^2) times efficiency, assumed proportional to 1/sqrt(E-dot). A few individual objects are cited to illustrate the issues. Since large E-dot pulsars also tend to have large timing noise and occasional glitches, their ephemerides can become inaccurate in weeks to months. To detect and study the gamma-ray emission the photons must be accurately tagged with the pulse phase. With hours to days between gamma-ray photon arrival times from a pulsar and months to years of LAT exposure needed for good detections, GLAST will need timing measurements throughout the continuous gamma-ray observations. The poster will describe efforts to coordinate pulsar timing of the candidate gamma-ray pulsars.

Thompson, David J.; Smith, D. A.; Dumora, D.; Guillemot, L.; Parent, D.; Reposeur, T.; Grove, E.; Romani, R. W.; Thorsett, S. E.

2007-01-01

364

Gamma rays from hidden millisecond pulsars  

NASA Technical Reports Server (NTRS)

The properties were studied of a new class of gamma ray sources consisting of millisecond pulsars totally or partially surrounded by evaporating material from irradiated companion stars. Hidden millisecond pulsars offer a unique possibility to study gamma ray, optical and radio emission from vaporizing binaries. The relevance of this class of binaries for GRO observations and interpretation of COS-B data is emphasized.

Tavani, Marco

1992-01-01

365

Fermi Gamma-Ray Space Telescope.  

National Technical Information Service (NTIS)

The nonthermal nature of high-energy gamma-ray emission almost assures that gamma-ray sources will be radio sources. The VLBA/Fermi cooperative effort has already produced some excellent science, and more is anticipated from ongoing programs. The Fermi Gu...

D. Thompson J. McEnery

2011-01-01

366

Gamma-Ray Pulsar Candidates for GLAST  

NASA Technical Reports Server (NTRS)

The Gamma-ray Large Area Space Telescope (GLAST) will be launched this year, and its Large Area Telescope (LAT) is expected to discover scores to hundreds of gamma-ray pulsars. This poster discusses which of the over 1700 known pulsars, mostly visible only at radio frequencies, are likely to emit greater than 100 MeV gamma rays with intensities detectable by the LAT. The main figure of merit used to select gamma-ray pulsar candidates is sqrt(E-dot)/d2, where E-dot is the energy loss due to rotational spin-down, and d is the distance to the pulsar. The figure of merit incorporates spin-down flux at earth (proportional to E-dot/d2) times efficiency, assumed proportional to l/sqrt(E-dot). A few individual objects are cited to illustrate the issues. Since large E-dot pulsars also tend to have large timing noise and occasional glitches, their ephemerides can become inaccurate in weeks to months. To detect and study the gamma-ray emission the photons must be accurately tagged with the pulse phase. With hours to days between gamma-ray photon arrival times from a pulsar and months to years of LAT exposure needed for good detections, GLAST will rely on radio and X-ray timing measurements throughout the continuous gamma-ray observations. The poster will describe efforts to coordinate pulsar timing of the candidate gamma-ray pulsars.

Thompson, D. J.

2008-01-01

367

Gamma-ray emission from slow pulsars  

Microsoft Academic Search

The gamma-ray flux to be expected from three slow pulsars is calculated, neglecting the problem of the reliability of the observations. The principal hypothesis here is that since the gamma-ray luminosity is a substantial fraction of the intrinsic energy loss, it should be produced in the vicinity of the speed of light radius. This is from the argument of simultaneous

M. Morini; A. Treves

1981-01-01

368

Gamma-Ray Astronomy Technology Needs.  

National Technical Information Service (NTIS)

In recent decades gamma-ray observations have become a valuable tool for studying the universe. Progress made in diverse 8re1lS such as gamma-ray bursts (GRBs), nucleosynthesis, and active galactic nuclei (AGNs) has complimented and enriched our astrophys...

J. K. Cannizzo N. Gehrels

2012-01-01

369

GAMMA-RAY SPECTROSCOPY IN WELL LOGGING  

Microsoft Academic Search

Thermal neutron capture gamma rays have been observed in boreholes ; drilled in shales, sandstones, and limestones. A capsuled source of neutrons and ; a scintillation crystal detector, connected through 5,000 ft of logging cable to ; a transistorized, multichannel, pulse-height analyzer, were used. Resolved peaks ; were identified on the basis of the known energies of expected gamma rays

Richard L. Caldwell; W. F. Baldwin; J. D. Bargainer; J. E. Berry; G. N. Salaita; R. W. Sloan

1963-01-01

370

SIMULATE Program: a gamma ray spectroscopy tool  

Microsoft Academic Search

A software package which simulates the virtual creation of gamma ray spectra emitted from a combination of radioactive sources, as seen by a semiconductor or scintillation detector, is presented . It partially utilizes Monte Carlo techniques based on the physics of gamma ray spectroscopy. In addition, certain algorithms are used to compensate for the premature termination of the fate of

C. A Kalfas; E. Tsoulou

2003-01-01

371

Neutron Capture gamma-Ray Facility.  

National Technical Information Service (NTIS)

A neutron capture gamma-ray facility was constructed for prompt gamma-ray spectrometry, and its characteristics were measured. In the facility, a neutron beam is extracted from the H-6 horizontal experimental hole of Japan Research Reactor No.3, JAERI, an...

T. Tojo C. Yonezawa S. Koura S. Arai T. Komori

1980-01-01

372

Hard X-ray and low-energy gamma-ray spectrometers  

NASA Technical Reports Server (NTRS)

Basic principles of operation and characteristics of scintillation and semi-conductor detectors used for solar hard X-ray and gamma-ray spectrometers are presented. Scintillation materials such as NaI offer high stopping power for incident gamma rays, modest energy resolution, and relatively simple operation. They are, to date, the most often used detector in solar gamma-ray spectroscopy. The scintillator BGO has higher stopping power than NaI, but poorer energy resolution. The primary advantage of semi-conductor materials such as Ge is their high-energy resolution. Monte-Carlo simulations of the response of NaI and Ge detectors to model solar flare inputs show the benefit of high resoluton for studying spectral lines. No semi-conductor material besides Ge is currently available with adequate combined size and purity to make general-use hard X-ray and gamma-ray detectors for solar studies.

Gehrels, N.; Crannell, C. J.; Orwig, L. E.; Forrest, D. J.; Lin, R. P.; Starr, R.

1988-01-01

373

Atmospheric gamma-ray and neutron flashes  

SciTech Connect

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

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

2008-01-15

374

Gamma-Ray Spectral Calculations for Uranium Borehole Logging.  

National Technical Information Service (NTIS)

Gamma-ray transport calculations were performed to determine the energy distribution of gamma rays inside a borehole introduced into an infinite medium. The gamma rays from the naturally occurring radioactive isotopes of potassium, thorium, and uranium we...

D. A. Close M. L. Evans M. Jain

1980-01-01

375

In vivo volumetric imaging of the human upper eyelid with ultrahigh-resolution optical coherence tomography  

NASA Astrophysics Data System (ADS)

The upper eyelid is a biological tissue with complex structure, essential for the maintenance of an optically clear ocular surface due to its physical (blinking) effect. The Meibomian glands (MGs) are structures that lie beneath the surface of the inner eyelid and are partially responsible for the production of the superficial oily layer of the tear film. The MGs are only superficially visible under magnification when the eyelid is everted. We present for the first time in vivo 3-D images of healthy and inflamed human MGs. Tomograms were acquired from the tarsal plate of everted human eyelids with a 1060-nm ultrahigh-resolution optical coherence tomography (UHOCT) system, with ~3 ?m×10 ?m (axial×lateral) resolution in biological tissue at the rate of 91,911 A-scans/s. Comparison with histology shows that the UHOCT images reveal a spatial distribution of structures that appear to correspond with the MGs' acini and ducts (in healthy subjects), and accumulation of heterogeneous, highly scattering biological material and clear fluids in the visibly blocked glands. Noninvasive, volumetric high-resolution morphological imaging of the human tarsal area could have a significant impact in the clinical diagnosis of inflammatory and noninflammatory lid pathologies.

Bizheva, Kostadinka; Lee, Patrick; Sorbara, Luigina; Hutchings, Natalie; Simpson, Trefford

2010-07-01

376

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

NASA Astrophysics Data System (ADS)

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

Kusenko, Alexander

2013-12-01

377

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

NASA Astrophysics Data System (ADS)

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

Kusenko, Alexander

2013-01-01

378

Miniaturization in x ray and gamma ray spectroscopy  

Microsoft Academic Search

The paper presents advances in two new sensor technologies and a miniaturized associated electronics technology which, when combined, can allow for very significant miniaturization and for the reduction of weight and power consumption in x-ray and gamma-ray spectroscopy systems: (1) Mercuric iodide (HgI2) x-ray technology, which allows for the first time the construction of truly portable, high-energy resolution, non-cryogenic x-ray

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

1993-01-01

379

Research in particle and gamma-ray astrophysics  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

380

CdWO4 crystal in gamma-ray spectrometry  

Microsoft Academic Search

The properties of CdWO4 (CWO) crystals in gamma spectrometry were studied. Several small samples of 10×10×3 mm size, typically used in CT X-ray detectors, were tested and then compared to the performance of a larger crystal of 20 mm in diameter and 20 mm in height. The light output, energy resolution, and non-proportionality of the CWO response versus gamma-ray energy,

M. Moszynski; M. Balcerzyk; M. Kapusta; A. Syntfeld; D. Wolski; G. Pausch; J. Stein; P. Schotanus

2004-01-01

381

ISGRI: The INTEGRAL Soft Gamma-Ray Imager  

Microsoft Academic Search

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

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

2003-01-01

382

Large volume imaging arrays for gamma-ray spectroscopy  

Microsoft Academic Search

We report for the first time on the characteristics of large volume (4 cm4 cm0.5 cm) cadmium zinc telluride gamma-ray imaging\\u000a arrays produced by IMARAD Imaging Systems. These arrays are shown to posses high uniformity of response to gamma-photons in\\u000a the energy range of about 50 to over 600 keV. High resolution photopeaks have been obtained without any pulse processing

T. E. Schlesinger; B. Brunett; H. Yao; J. M. Vanscyoc; R. B. James; S. U. Egarievwe; K. Chattopadhyay; X.-Y. Ma; A. Burger; N. Giles; U. El-Hanany; A. Shahar; A. Tsigelman

1999-01-01

383

Digital signal processing for high rate gamma-ray spectroscopy  

Microsoft Academic Search

A fully digital system for acquisition of NaI gamma-ray spectra was developed and tested. A fast digitizer is used to digitize unprocessed photomultiplier anode pulses to 8-bit resolution at 5 ns intervals. Digital filtering and a pulse searching algorithm are used to identify pulses, detect and correct for pileup and determine pileup corrected pulse areas. A pulse height distribution is

V. Drndarevic; P. Ryge; T. Gozani

1989-01-01

384

Gamma ray spectroscopy in astrophysics: Future role of scintillation detectors  

NASA Technical Reports Server (NTRS)

The future role of conventional scintillation detector telescopes for line gamma-ray astronomy is discussed. Although the energy resolution of the germanium detectors now being used by several groups is clearly desirable, the larger effective areas and higher efficiencies available with scintillation detectors is advantageous for many observations. This is particularly true for those observations of astrophysical phenomena where significant line broadening is expected.

Kurfess, J. D.

1978-01-01

385

Modeling gamma-ray bursts  

NASA Astrophysics Data System (ADS)

Discovered serendipitously in the late 1960s, gamma-ray bursts (GRBs) are huge explosions of energy that happen at cosmological distances. They provide a grand physical playground to those who study them, from relativistic effects such as beaming, jets, shocks and blastwaves to radiation mechanisms such as synchrotron radiation to galatic and stellar populations and history. Through the Swift and Fermi space telescopes dedicated to observing GRBs over a wide range of energies (from keV to GeV), combined with accurate pinpointing that allows ground based follow-up observations in the optical, infrared and radio, a rich tapestry of GRB observations has emerged. The general picture is of a mysterious central engine (CE) probably composed of a black hole or neutron star that ejects relativistic shells of matter into intense magnetic fields. These shells collide and combine, releasing energy in "internal shocks" accounting for the prompt emission and flaring we see and the "external shock" or plowing of the first blastwave into the ambient surrounding medium has well-explained the afterglow radiation. We have developed a shell model code to address the question of how X-ray flares are produced within the framework of the internal shock model. The shell model creates randomized GRB explosions from a central engine with multiple shells and follows those shells as they collide, merge and spread, producing prompt emission and X-ray flares. We have also included a blastwave model, which can constrain X-ray flares and explain the origin of high energy (GeV) emission seen by the Fermi telescope. Evidence suggests that gamma-ray prompt emission and X-ray flares share a common origin and that at least some flares can only be explained by long-lasting central engine activity. We pay special attention to the time history of central engine activity, internal shocks, and observed flares. We calculate the gamma-ray (Swift/BAT band) and X-ray (Swift/XRT band) lightcurves for arbitrary central engine activity and compare the model results with the observational data. We show that the observed X-ray flare phenomenology can be explained within the internal shock model. The number, width and occurring time of flares are then used to diagnose the central engine activity, putting constraints on the energy, ejection time, width and number of ejected shells. We find that the observed X-ray flare time history generally reflects the time history of the central engine, which reactivates multiple times after the prompt emission phase with progressively reduced energy. This shell model code can be used to constrain broadband observations of GRB 090926A, which showed two flares in both the Swift UVOT and XRT bands. Using the prompt emission fluence to constrain the total energy contained in the blastwave, the internal shock model requires that Lorentz factors of the shells causing flares must be less than the Lorentz factor of the blastwave when the shells are ejected. Recent observations of Gamma-Ray Bursts (GRBs) by the Fermi Large Area Telescope (LAT) revealed a power law decay feature of the high energy emission (above 100 MeV), which led to the suggestion that it originates from an external shock. We analyze four GRBs (080916C, 090510, 090902B and 090926A) jointly detected by Fermi LAT and Gamma-ray Burst Monitor (GBM), which have high quality lightcurves in both instrument energy bands. Using the MeV prompt emission (GBM) data, we can record the energy output from the central engine as a function of time. Assuming a constant radiative efficiency, we are able to track energy accumulation in the external shock using our internal/external shell model code and show that the late time lightcurves fit well within the external shock model, but the early time lightcurves are dominated by the internal shock component which has a shallow decay phase due to the initial pile-up of shells onto the blast wave.

Maxham, Amanda

386

Large gamma-ray detector arrays and electromagnetic separators  

NASA Astrophysics Data System (ADS)

The use of large gamma-ray detector arrays with electromagnetic separators is a powerful combination. Various types of gamma-ray detectors have been used; some provide high detector efficiency such as scintillation detector array, others use Ge detectors for good energy resolution, and recently developed Ge energy tracking arrays gives both high peak-to-background ratio and position resolution. Similarly, different types of separators were used to optimize the performance under different experimental requirements and conditions. For example, gas-filled separators were used in heavy element studies for their large efficiency and beam rejection factor. Vacuum separators with good isotope resolution were used in transfer and fragmentation reactions for the study of nuclei far from stability. This paper presents results from recent experiments using gamma-ray detector arrays in combination with electromagnetic separators, and discusses the physics opportunities provided by these instruments. In particular, we review the performance of the instruments currently in use, and discuss the requirements of instruments for future radioactive beam accelerator facilities.

Lee, I.-Yang

2013-12-01

387

An imaging neutron/gamma-ray spectrometer  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

388

Observations of Gamma-Ray Bursts  

NASA Technical Reports Server (NTRS)

Some basic observed properties of gamma-ray bursts are reviewed. Although some properties were known 25 years ago, new and more detailed observations have been made by the Compton Observatory in the past three years. The new observation with the greatest impact has been the observed isotropic distribution of bursts along with a deficiency of weak bursts which would be expected from a homogeneous burst distribution. This is not compatible with any known Galactic population of objects. Gamma-ray bursts show an enormous variety of burst morphologies and a wide spread in burst durations. The spectra of gamma-ray bursts are characterized by rapid variations and peak power which is almost entirely in the gamma-ray energy range. Delayed gamma-ray burst photons extending to GeV energies have been detected for the first time. A time dilation effect has also been reported to be observed in gamma-ray, bursts. The observation of a gamma-ray burst counterpart in another wavelength region has yet to be made.

Fishman, G. J.

1995-01-01

389

High-purity germanium Gamma-Ray Spectrometer with stirling cycle cryocooler  

NASA Astrophysics Data System (ADS)

The Japanese lunar polar orbiter SELENE carries a gamma-ray spectrometer which uses a high-purity Ge detector cooled to 80-90 K by a Stirling mechanical cooler. The Gamma-Ray Spectrometer (GRS) consists of a large volume n-type Ge detector (252 cc) as the main detector and bismuth-germanate (BGO) and plastic scintillators as an active shielding. The engineering model still maintains excellent energy resolution even after severe vibration testing. The Gamma-Ray Spectrometer will globally map of the Moon for the major elements of O, Mg, Al, Si, Ti, Fe, etc. and natural radioisotopes of K, Th and U with a high precision. The energy resolution of the GRS is such that it would identify prompt gamma-ray line from hydrogen and the location and the amount of ice, if it exists at the polar regions.

Kobayashi, M. N.; Hasebe, N.; Miyachi, T.; Doke, T.; Kikuchi, J.; Okada, H.; Oka, A.; Okudaira, O.; Souri, H.; Yamashita, N.; Shibamura, E.; Kashiwagi, T.; Takashima, T.; Narasaki, K.; Tsurumi, K.; Mori, K.; d'Uston, C.; Maurice, S.; Grande, M.; Reedy, R. C.

390

gamma. -ray diagnostic for the CIT  

SciTech Connect

We have examined the feasibility of a fusion ..gamma..-ray diagnostic for the Compact Ignition Tokamak (CIT), which is expected to produce 10/sup 20/ (d, t) fusion reactions per second. Gamma rays at 16.7 MeV are produced by the t(d, ..gamma..)He/sup 5/ fusion reaction. A Monte Carlo coupled neutron--photon transport code is used to model the expected ..gamma..-ray spectrum incident upon a Compton spectrometer backed by a Cerenkov detector. The results indicate that a signal of approx.3 x 10/sup 4/ counts/s and a signal-to-noise ratio of approx.30 can be achieved.

Petrasso, R.D.; Fiore, C.L.; Li, C.

1988-08-01

391

GRETA - Gamma Ray Energy Tracking Array  

NASA Astrophysics Data System (ADS)

Gamma ray energy tracking is a new concept for detecting gamma rays. It can be implemented as a 4? array of highly segmented Ge detector, which would advance detection sensitivity by three orders of magnitude in certain applications. Such an array will provide tremendous discovery potential at current stable and exotic beam facilities, as well as at future facilities. The development of a tracking array for nuclear structure physics has brought together scientists from different areas. Technical advances made in the last 5 years have demonstrated that the construction of a gamma ray energy-tracking array is feasible, and a plan for constructing a US array is in place.

Lee, I.-Yang

2003-03-01

392

NEAR Gamma Ray Spectrometer Characterization and Repair  

NASA Technical Reports Server (NTRS)

This report covers the work completed in the third year of the contract. The principle activities during this period were (1) the characterization of the NEAR 2 Gamma Ray Spectrometer using a neutron generator to generate complex gamma ray spectra and a large Ge Detecter to identify all the major peaks in the spectra; (2) the evaluation and repair of the Engineering Model Unit of the Gamma Ray Spectrometer for the NEAR mission; (3) the investigation of polycapillary x-ray optics for x-ray detection; and (4) technology transfer from NASA to forensic science.

Groves, Joel Lee; Vajda, Stefan

1998-01-01

393

IR observations in gamma-ray blazars  

NASA Technical Reports Server (NTRS)

The infrared photometric and spectral observation of five gamma ray blazars in coordination with the energetic gamma ray experiment telescope (EGRET) onboard the Compton Gamma Ray Observatory is reported. The infrared measurements were made with a Cassegrain infrared camera and the mid-infrared large well imager at the Mt. Palomar 5 m telescope. The emphasis is on the three blazars observed simultaneously by EGRET and the ground-based telescope during viewing period 519. In addition to the acquisition of broadband spectral measurements for direct correlation with the 100 MeV EGRET observations, near infrared images were obtained, enabling a search for intra-day variability to be carried out.

Mahoney, W. A.; Gautier, T. N.; Ressler, M. E.; Wallyn, P.; Durouchoux, P.; Higdon, J. C.

1997-01-01

394

Fermi Gamma-Ray Space Telescope  

NASA Technical Reports Server (NTRS)

The Fermi Gamma-ray Space Telescope, launched in June 2008, is an observatory designed to survey the high-energy gamma-ray sky. The primary instrument, the Large Area Telescope (LAT), provides observations from 20 MeV to greater than 300 GeV. A second instrument, the Gamma-ray Burst Monitor (GBM), provides observations of transients from less than 10 keV to 40 MeV. We describe the design and performance of the instruments and their subsystems, the spacecraft and the ground system.

McEnery, Julie E.; Michelson, Peter F.; Paclesas, William S.; Ritz, Steven

2012-01-01

395

Gamma-Ray Spectroscopy of 42K  

Microsoft Academic Search

Decay of 42K was investigated by a Ge(Li) detector and a 5''phi× 4'' NaI scintillation counter. Two gamma-ray peaks were newly observed at 0.692 and 1.228 MeV in the gamma-gamma coincidence spectrum. The 0.587 MeV gamma-ray, previously reported by McCullen et al., could not be seen and the upper limit of the intensity of this gamma-ray relative to the 0.900

Kiyoshi Kawade; Hiroshi Yamamoto; Kanzo Yoshikawa; Katsuyuki Iizawa; Isao Kitamura; Susumu Amemiya; Toshio Katoh; Yasukazu Yoshizawa

1970-01-01

396

Imaging of oocyte development using ultrahigh-resolution full-field optical coherence tomography.  

PubMed

In this paper, a white-light full-field optical coherence tomography is developed to provide three-dimensional imaging of the development of a mouse embryo with ultrahigh-resolution. Spatial resolution of 1.8???m×1.12???m (transverse×axial) is achieved owing to the extremely short coherence length of the light source and optimized compensation of dispersion mismatch. A shot-noise limited detection sensitivity of 80 dB is obtained at an acquisition time of 5 seconds per image. To enable in vivo imaging of the mouse embryo development, a homemade incubator is applied to provide appropriate CO2 concentration, temperature, and humidity. An electronic light shutter is used to control the light source in order to avoid unnecessary exposure to the embryo development when the sample is not being scanned. To demonstrate our method, in vivo time series two-dimensional images of the in vitro fertilization process of mouse oocytes at the germinal vesicles stage are presented. PMID:22695605

Xiao, Jiaying; Wang, Bo; Lu, Guangyin; Zhu, Ziqiang; Huang, Yujiao

2012-06-01

397

The AGILE gamma ray satellite  

NASA Astrophysics Data System (ADS)

AGILE (Light Imager for Gamma-ray Astrophysics) will be launched on an equatorial orbit in 2007 by the PSLV Indian launcher. It is a small scientific satellite for the detection of ?-ray cosmic sources in the energy range 50 MeV 30 GeV with a field of view of 15 of the sky, and will become the only detector in that energy range till the launch of GLAST. Three different detectors and an anticoincidence system are the components of the scientific instrument. The main detector is a silicon tungsten tracker. The second detector is a X-ray detector in the range 15 45 keV; its main aim is to highlight the X-ray emission associated to the gamma emissions. The third detector is a small calorimeter made of 30 CsI scintillating bars read out by photodiodes; its energy range is 150 300 keV. The large number of channels (about 37 000, with analog read out), requires very reliable components. Each part of the instrument has undergone several tests during the assembly phase; then the whole instrument has been calibrated on a dedicated photon tagged beam-line developed at the DAPHNE BTF (Beam Test Facility, INFN Frascati) and has been integrated with the satellite.

Basset, M.; AGILE Team

2007-03-01

398

Interpretations and implications of gamma ray lines from solar flares, the galactic center in gamma ray transients  

NASA Technical Reports Server (NTRS)

Observations and theories of astrophysical gamma ray line emission are reviewed and prospects for future observations by the spectroscopy experiments on the planned Gamma Ray Observatory are discussed.

Ramaty, R.; Lingenfelter, R. E.

1980-01-01

399

The time structure of the gamma-ray emission from the Crab and Vela pulsars  

NASA Technical Reports Server (NTRS)

High resolution data on the pulsed gamma-ray emission from the Crab and Vela pulsars are presented. The light curves of these two pulsars at gamma-ray energies show striking similarities. The measured pulsed intensity from Vela at energies greater than 50 MeV was found to be .000013 sq cm/sec. The energy spectrum is not consistent with a power law.

1977-01-01

400

Gamma-ray spectrometers using superconducting transition edge sensors with external active feedback bias  

Microsoft Academic Search

We are developing X-ray and gamma-ray spectrometers with high absorption efficiency and high energy-resolution for X-ray and gamma-ray spectroscopy. They are microcalorimeters consisting of a bulk Sn absorber coupled to a Mo\\/Cu multilayer superconducting transition edge sensor (TES). We have operated these microcalorimeters with an external active feedback bias to linearize the detector response, improve the count rate performance, and

D. T. Chow; M. L. van den Berg; A. Loshak; M. Frank; S. E. Labov

2001-01-01

401

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

Microsoft Academic Search

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

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

1996-01-01

402

High-pressure xenon gamma-ray spectrometers: recent developments and applications  

Microsoft Academic Search

One of the most challenging and topical problems in modern gamma-ray spectroscopy is the need for thermally stable, high-resolution detectors. Temperature variations affect sensitive performance parameters in existing spectrometers such as leakage current in semiconductor photo-conductors and light output in scintillation-based spectrometers. For this reason, commercial gamma-ray detectors are restricted to operation over a very limited and often inconvenient temperature

Gary C. Tepper; Robert L. Palmer; Jon R. Losee

1999-01-01

403

Multiple gamma-ray detection method and its application to nuclear chemistry  

Microsoft Academic Search

A new radionuclide quantification method is proposed on the basis of multiple gamma-ray detection, which is two or higher\\u000a fold gamma-ray coincidence method. The coincidence method has so far been used for nuclear structure study. We apply this\\u000a method for quantification of radioactive nuclei. The advantage of this method consists of high energy resolution and high\\u000a sensitivity. It is successfully

M. Oshima; Y. Toh; Y. Hatsukawa; M. Koizumi; A. Kimura; A. Haraga; M. Ebihara; K. Sushida

2008-01-01

404

CdZnTe gamma-ray spectrometer for orbital planetary missions  

Microsoft Academic Search

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

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

2002-01-01

405

Gamma-ray measurements of naturally occurring radioactive samples from Cyprus characteristic geological rocks  

Microsoft Academic Search

Using high-resolution gamma-ray spectroscopy, the terrestrial gamma radiation in all the predominant types of geological rock formations appearing in Cyprus was measured. Soil samples were collected from each rock type, sealed in 1l plastic Marinelli beakers, and measured in the laboratory for 24h each. From the measured gamma-ray spectra, activity concentrations were determined for 232Th (range from 1.3 to 52.8Bqkg?1),

Michalis Tzortzis; Haralabos Tsertos; Stelios Christofides; George Christodoulides

2003-01-01

406

Miniaturization in x ray and gamma ray spectroscopy  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

407

Gamma-ray line observations from cosmic nuclei  

NASA Astrophysics Data System (ADS)

Gamma-ray line astronomy is capable to probe recent and current nucleosynthesis in the nearby universe. Interstellar 26Al (?=1.04 106 y) confirms currently-active nucleosynthesis in the Galaxy, and could be attributed to massive stars as dominating sources. Nearby or well-known 26Al emission regions are now studied in detail to test consistency of models for the evolution of groups of massive stars and their impacts on the ISM. Interesting directions are towards Cygnus, Vela, Orion, and Sco-Cen. 26Al line shape details, and measurement of correlated 60Fe may be needed to resolve the massive-star degeneracy and quantify specific 26Al sources. In spite of the 44Ti detection (?=89 y) from the Cas A supernova remnant 44Ti gamma-rays from other young SNRs, such as SN1987A or otherwise occulted SNRs in the inner Galaxy or nearby active regions, are difficult. The apparent paucity of 44Ti sources seems to suggest that 44Ti ejection is from rather non-typical core-collapse supernovae. Spectral resolution of the 44Ti line shape with future instruments could be a unique SN/SNR diagnostic. Transients from nova nucleosynthesis positron annihilation, and 7Be or more longlived 22Na radioactivities still have to wait for future more sensitive instruments or nearby events. High spectral-resolution experiments such as INTEGRAL (launch Oct 2002) will address some of the open questions through measurements of nucleosynthesis gamma-ray line shapes.

Diehl, Roland

2003-05-01

408

Gamma-ray spectrometer (GRS) for lunar polar orbiter SELENE  

NASA Astrophysics Data System (ADS)

The high-precision gamma-ray spectrometer (GRS) on the lunar polar orbiter SELENE is designed to measure 200 keV-12 MeV gamma rays in order to determine elemental compositions of the lunar surface. The GRS consists of a large germanium (Ge) crystal as a main detector and a massive bismuth germanate crystal and a plastic scintillator as anticoincidence detectors. The Ge detector is cooled by a Stirling cryocooler with its compressor attached to a passive radiator facing the cold space. The cooling system maintains the Ge detector below 90 K during the observation. The flight model of the GRS has achieved an energy resolution of 3.0 keV (FWHM) at 1333 keV. Energy spectra obtained by the GRS will show sharp gamma-ray lines whose energies identify the elements and whose intensities determine the concentrations of the elements, permitting global mapping of the elemental abundances in the sub-surface of the Moon. The elemental maps obtained by the GRS with such high-energy resolution enable us to study lunar geoscience problems.

Hasebe, N.; Shibamura, E.; Miyachi, T.; Takashima, T.; Kobayashi, M.; Okudaira, O.; Yamashita, N.; Kobayashi, S.; Ishizaki, T.; Sakurai, K.; Miyajima, M.; Fujii, M.; Narasaki, K.; Takai, S.; Tsurumi, K.; Kaneko, H.; Nakazawa, M.; Mori, K.; Gasnault, O.; Maurice, S.; D'Uston, C.; Reedy, R. C.; Grande, M.

2008-04-01

409

Further development of IDGS: Isotope dilution gamma-ray spectrometry  

SciTech Connect

The isotope dilution gamma-ray spectrometry (IDGS) technique for determining the plutonium concentration and isotopic composition of highly radioactive spent-fuel dissolver solutions has been further developed. Both the sample preparation and the analysis have been improved. The plutonium isotopic analysis is based on high-resolution, low-energy gamma-ray spectrometry. The plutonium concentration in the dissolver solutions then is calculated from the measured isotopic differences among the spike, the dissolver solution, and the spiked dissolver solution. Plutonium concentrations and isotopic compositions of dissolver solutions analyzed from this study agree well with those obtained by traditional isotope dilution mass spectrometry (IDMS) and are consistent with the first IDGS experimental result. With the current detector efficiency, sample size, and a 100-min count time, the estimated precision is {approximately}0.5% for {sup 239}Pu and {sup 240}Pu isotopic analyses and {approximately}1% for the plutonium concentration analysis. 5 refs., 2 figs., 7 tabs.

Li, T.K.; Parker, J.L. (Los Alamos National Lab., NM (United States)); Kuno, Y.; Sato, S.; Kamata, M.; Akiyama, T. (Power Reactor and Nuclear Fuel Development Corp., Tokai, Ibaraki (Japan))

1991-01-01

410

Dark matter annihilation bound from the diffuse gamma ray flux  

SciTech Connect

An upper limit on the total annihilation rate of dark matter (DM) has been recently derived from the observed atmospheric neutrino background. It is a very conservative upper bound based on the sole hypothesis that the DM annihilation products are the least detectable final states in the Standard Model (SM), neutrinos. Any other decay channel into SM particles would lead to stronger constraints. We show that comparable bounds are obtained for DM masses around the TeV scale by observations of the diffuse gamma ray flux by EGRET, because electroweak bremsstrahlung leads to non-negligible electromagnetic branching ratios, even if DM particles only couple to neutrinos at tree level. A better mapping and the partial resolution of the diffuse gamma-ray background into astrophysical sources by the GLAST satellite will improve this bound in the near future.

Kachelriess, M.; /Norwegian U. Sci. Tech.; Serpico, P.D.; /Fermilab

2007-07-01

411

Terrestrial Gamma-ray Flash (TGFs) Above Thunderstorms  

NASA Technical Reports Server (NTRS)

Terrestrial gamma-ray flashes (TGFs) are being observed with the Gamma-ray Burst Monitor (GBM) detectors on Fermi about once every four weeks. These intense millisecond flashes of MeV photons have been observed with four space-borne experiments since their initial discovery by the BATSE-CGRO experiment in the early 1990s. TGFs have extremely hard spectra (harder than GRBs) and photons are seen to extend to over 30 MeV. The GBM-Fermi observations have the highest temporal resolution of any previous TGF observations and time-resolved coarse spectra can be derived. These features will be crucial for testing the leading current model of TGF production: relativistic run-away electron cascades formed in the intense electric fields within thunderstorms.

Fishman, Gerald J.

2009-01-01

412

Gamma-Ray Heating in Power Reactors.  

National Technical Information Service (NTIS)

The objective of this work is to examine gamma ray heating in commercial nuclear power reactors. Design methods, computer codes, data libraries, and experimental data are examined. Some recommendations are made as to extensions of existing methods and cod...

A. P. Olson

1976-01-01

413

Gamma-Ray Burst Smashes a Record  

NSF Publications Database

... the most distant explosion ever seen The Birth of a Gamma-Ray Burst: one scenario Credit and ... via e-mail, Web sites and cell phone. One of the first groups to respond was Reichart's team from ...

414

Positron annihilation gamma rays from novae  

NASA Technical Reports Server (NTRS)

The potential for observing annihilation gamma rays from novae is investigated. These gamma rays, a unique signature of the thermonuclear runaway models of novae, would result from the annihilation of positrons emitted by beta(+)-unstable nuclei produced near the peak of the runaway and carried by rapid convection to the surface of the nova envelope. Simple models, which are extensions of detailed published models, of the expansion of the nova atmospheres are evolved. These models serve as input into investigations of the fate of nearby Galactic fast novae could yield detectable fluxes of electron-positron annihilation gamma rays produced by the decay of N-13 and F-18. Although nuclear gamma-ray lines are produced by other nuclei, it is unlikely that the fluxes at typical nova distances would be detectable to present and near-future instruments.

Leising, Mark D.; Clayton, Donald D.

1987-01-01

415

Gamma-ray bursts: An overview  

NASA Technical Reports Server (NTRS)

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

Lestrade, John Patrick

1990-01-01

416

The EGRET high energy gamma ray telescope  

NASA Technical Reports Server (NTRS)

The Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (GRO) is sensitive in the energy range from about 20 MeV to about 30,000 MeV. Electron-positron pair production by incident gamma photons is utilized as the detection mechanism. The pair production occurs in tantalum foils interleaved with the layers of a digital spark chamber system; the spark chamber records the tracks of the electron and positron, allowing the reconstruction of the arrival direction of the gamma ray. If there is no signal from the charged particle anticoincidence detector which surrounds the upper part of the detector, the spark chamber array is triggered by two hodoscopes of plastic scintillators. A time of flight requirement is included to reject events moving backward through the telescope. The energy of the gamma ray is primarily determined by absorption of the energies of the electron and positron in a 20 cm deep NaI(Tl) scintillator.

Hartman, R. C.; Bertsch, D. L.; Fichtel, C. E.; Hunter, S. D.; Kanbach, G.; Kniffen, D. A.; Kwok, P. W.; Lin, Y. C.; Mattox, J. R.; Mayer-Hasselwander, H. A.

1992-01-01

417

Gamma rays from the magellanic clouds  

NASA Technical Reports Server (NTRS)

Predicted gamma ray fluxes from the Megallanic Clouds, obtained by using updated parameters, are significantly above the values previously determined, and well within the capabilities of observation from COS-B satellite. Concepts relating galactic gamma ray production and other Population 1 phenomena in the Milky Way were used to postulate a factor of four increase in predicted flux, based on the galactic origin hypothesis. The values obtained provide a possible test of two interpretations of gamma ray emission: enhancement in the inner galaxy from gas and cosmic ray sources alone, or increases produced by the trapping of cosmic rays in spiral arms. Because spiral structure is absent in the small cloud, and questionable in the large cloud, and both clouds are classed as irregular galaxies, the predicted enhancement in gamma ray flux may not be as great in the absence of clear spiral structure.

Stecker, F. W.

1977-01-01

418

Thermal neutron capture gamma-rays  

SciTech Connect

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

Tuli, J.K.

1983-01-01

419

The EGRET high energy gamma ray telescope  

NASA Astrophysics Data System (ADS)

The Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (GRO) is sensitive in the energy range from about 20 MeV to about 30,000 MeV. Electron-positron pair production by incident gamma photons is utilized as the detection mechanism. The pair production occurs in tantalum foils interleaved with the layers of a digital spark chamber system; the spark chamber records the tracks of the electron and positron, allowing the reconstruction of the arrival direction of the gamma ray. If there is no signal from the charged particle anticoincidence detector which surrounds the upper part of the detector, the spark chamber array is triggered by two hodoscopes of plastic scintillators. A time of flight requirement is included to reject events moving backward through the telescope. The energy of the gamma ray is primarily determined by absorption of the energies of the electron and positron in a 20 cm deep NaI(Tl) scintillator.

Hartman, R. C.; Bertsch, D. L.; Fichtel, C. E.; Hunter, S. D.; Kanbach, G.; Kniffen, D. A.; Kwok, P. W.; Lin, Y. C.; Mattox, J. R.; Mayer-Hasselwander, H. A.

1992-02-01

420

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

NASA Astrophysics Data System (ADS)

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

Bellazzini, R.; Spandre, G.

2003-09-01

421

A versatile system for ultrahigh resolution, low temperature, and polarization dependent laser-angle-resolved photoemission spectroscopy.  

PubMed

We have developed a low temperature ultrahigh resolution system for polarization dependent angle-resolved photoemission spectroscopy (ARPES) using a vacuum ultraviolet (vuv) laser (hnu=6.994 eV) as a photon source. With the aim of addressing low energy physics, we show the system performance with angle-integrated PES at the highest energy resolution of 360 mueV and the lowest temperature of 2.9 K. We describe the importance of a multiple-thermal-shield design for achieving the low temperature, which allows a clear measurement of the superconducting gap of tantalum metal with a T(c)=4.5 K. The unique specifications and quality of the laser source (narrow linewidth of 260 mueV, high photon flux), combined with a half-wave plate, facilitates ultrahigh energy and momentum resolution polarization dependent ARPES. We demonstrate the use of s- and p-polarized laser-ARPESs in studying the superconducting gap on bilayer-split bands of a high T(c) cuprate. The unique features of the quasi-continuous-wave vuv laser and low temperature enables ultrahigh-energy and -momentum resolution studies of the spectral function of a solid with large escape depth. We hope the present work helps in defining polarization dependent laser excited angle-resolved photoemission spectroscopy as a frontier tool for the study of electronic structure and properties of materials at the sub-meV energy scale. PMID:18315282

Kiss, T; Shimojima, T; Ishizaka, K; Chainani, A; Togashi, T; Kanai, T; Wang, X-Y; Chen, C-T; Watanabe, S; Shin, S

2008-02-01

422

Gamma-Ray Pulsars Expected in the Outer Gap Model of Gamma-Ray Emission  

Microsoft Academic Search

We study the possibility of high-energy gamma-ray emission from the known 1130 radio pulsars based on the outer gap model of high-energy emission from pulsars. We estimate the fractional size of outer gap, the integrated flux, the gamma-ray luminosity for each known radio pulsar, and find that only 14% of the known radio pulsars are gamma-ray emitters according to the

Li Zhang; Jie Wu; Ze-Jun Jiang; Dong-Cheng Mei

2003-01-01

423

Low-State Gamma-Ray Emission from Blazars and the Gamma-Ray Background  

Microsoft Academic Search

We examine the contribution of flat spectrum radio sources (FSRSs), or blazars, to the diffuse gamma-ray background (DGRB), prompted by the association of the extragalactic gamma -ray sources detected by the EGRET instrument aboard the Compton Gamma Ray Observatory (CGRO) with this class of objects by using their well-studied log N--log S distribution. The basic assumption of our study are

Demosthenes Kazanas; Eric Perlman

1997-01-01

424

Comparison of gamma-ray coincidence and low-background gamma-ray singles spectrometry  

Microsoft Academic Search

Aerosol samples have been studied under different background conditions using gamma-ray coincidence and low-background gamma-ray singles spectrometric techniques with High-Purity Germanium detectors. Conventional low-background gamma-ray singles counting is a competitive technique when compared to the gamma–gamma coincidence approach in elevated background conditions. However, measurement of gamma–gamma coincidences can clearly make the identification of different nuclides more reliable and efficient than

J. Konki; P. T. Greenlees; U. Jakobsson; P. Jones; R. Julin; S. Juutinen; S. Ketelhut; K. Hauschild; R. Kontro; A.-P. Leppänen; A. Lopez-Martens; A. Mattila; P. Nieminen; M. Nyman; K. Peräjärvi; P. Peura; P. Rahkila; P. Ruotsalainen; J. Sarén; C. Scholey; J. Sorri; H. Toivonen; J. Turunen; J. Uusitalo

425

Gamma-Ray Library and Uncertainty Analysis: Passively Emitted Gamma Rays Used in Safeguards Technology  

Microsoft Academic Search

Non-destructive gamma-ray analysis is a fundamental part of nuclear safeguards, including nuclear energy safeguards technology. Developing safeguards capabilities for nuclear energy will certainly benefit from the advanced use of gamma-ray spectroscopy as well as the ability to model various reactor scenarios. There is currently a wide variety of nuclear data that could be used in computer modeling and gamma-ray spectroscopy

2009-01-01

426

First results on terrestrial gamma ray flashes from the Fermi Gamma-ray Burst Monitor  

Microsoft Academic Search

The Gamma-ray Burst Monitor (GBM) on the Fermi Gamma-ray Space Telescope detected 12 intense terrestrial gamma ray flashes (TGFs) during its first year of observation. Typical maximum energies for most of the TGFs are ?30 MeV, with one TGF having a 38 MeV photon; two of the TGFs are softer and longer than the others. After correcting for instrumental effects,

M. S. Briggs; G. J. Fishman; V. Connaughton; P. N. Bhat; W. S. Paciesas; R. D. Preece; C. Wilson-Hodge; V. L. Chaplin; R. M. Kippen; A. von Kienlin; C. A. Meegan; E. Bissaldi; J. R. Dwyer; D. M. Smith; R. H. Holzworth; J. E. Grove; A. Chekhtman

2010-01-01

427

Swift: A gamma ray burst MIDEX  

Microsoft Academic Search

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

2001-01-01

428

Swift gamma-ray burst MIDEX  

Microsoft Academic Search

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 a 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

Neil A. Gehrels

2000-01-01

429

The swift gamma-ray burst MIDEX  

Microsoft Academic Search

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

Neil Gehrels

2000-01-01

430

Compton scattering gamma-ray source optimization  

NASA Astrophysics Data System (ADS)

The interaction of a bright relativistic electron beam with an intense laser pulse via Compton scattering can generate tunable gamma-rays for precision nuclear photonics applications. The properties of the gamma-ray phase space will be outlined, in relation with the 6D electron bunch and 6D laser pulse phase space, along with collimation, nonlinear effects and other sources of spectral broadening. Optimization strategies will be outlines within the context of nuclear photonics applications.

Hartemann, Frederic; Wu, Sheldon; Albert, Félicie; Barty, Chris

2012-10-01

431

Research in cosmic and gamma ray astrophysics  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

432

Very high energy gamma-ray spectroscopy  

Microsoft Academic Search

The cosmic gamma-ray spectrum in the relatively unexplored energy range 1 ⪅ E? ⪅ 103GeV may have several interesting features. It may contain the gamma-ray lines from photino annihilation in the galactic halo, if photinos indeed comprise the unidentified dark matter in typical galaxies. There could also be a detectable diffuse background at E? > 30 GeV. These and other

David Eichler; James H. Adams Jr.

1987-01-01

433

GAMMA-RAY BURSTS AS HYPERNOVAE  

Microsoft Academic Search

The energetics of optical and radio afterglows following BeppoSAX and BATSE gamma-ray bursts (GRBs) suggests that gamma-ray emission is not narrowly collimated, but a moderate beaming is possible, so the total energy of a GRB may be in the range ? 1050 1051 erg. All attempts to generate a fireball powered by neutrino-antineutrino annihilation have failed so far, and a

Bohdan Paczynski

434

Gamma-ray Albedo of the Moon  

SciTech Connect

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

Moskalenko, Igor V.; Porter, Troy A.

2007-06-14

435

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

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

436

Method and apparatus for gamma ray well logging  

Microsoft Academic Search

A radioactive logging source carried by a logging tool injects gamma rays into the formation. A detector generates a pulse for each gamma ray incident upon the detector having an amplitude proportional to the gamma ray energy. Electrical signals corresponding to each such amplitude are delivered to the surface. These incident gamma rays originate from the formation as well as

Hubner

1985-01-01

437

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

SciTech Connect

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.

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

1983-01-01

438

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

439

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

PubMed

Digital discrimination of neutron and gamma-ray events in an organic scintillator has been investigated by moment analysis. Signals induced by an americium-beryllium (Am/Be) isotropic neutron source in a stilbene crystal detector have been sampled with a flash analogue-to-digital converter (ADC) of 1 GSamples/s sampling rate and 10-bit vertical resolution. Neutrons and gamma-rays have been successfully discriminated with a threshold corresponding to gamma-ray energy about 217 keV. Moment analysis has also been verified against the results assessed by a time-of-flight (TOF) measurement. It is shown that the classification of neutrons and gamma-rays afforded by moment analysis is consistent with that achieved by digital TOF measurement. This method has been applied to analyze the data acquired from the stilbene crystal detector in mixed radiation field of the HL-2A tokamak deuterium plasma discharges and the results are described. PMID:23020376

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

2012-09-01

440

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

SciTech Connect

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

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

2012-09-15

441

Gamma-400 Science Objectives Built on the Current HE Gamma-Ray and CR Results  

NASA Technical Reports Server (NTRS)

The main scientific interest of the Russian Gamma-400 team: Observe gamma-rays above approximately 50 GeV with excellent energy and angular resolution with the goals of: (1) Studying the fine spectral structure of the isotropic high-energy gamma-radiation, (2) Attempting to identify the many still-unidentified Fermi-LAT gamma-ray sources. Gamma-400 will likely be the only space-based gamm