Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Gamma Ray”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,801 records · Page 100
All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

What Can Geolocated Sferics Tell Us About Terrestrial Gamma-Ray Flashes?

The Fermi Gamma-ray Burst Monitor (GBM) has been detecting TGFs with increasing sensitivity over the past two years, owing to changes in flight software that have lowered its threshold for triggering and, recently, allowed a search for TGFs weaker than those which would cause an onboard trigger. Associations between TGFs detected in the first 18 months of operation and sferics detected using the World Wide Lightning Location Network (WWLLN) show that TGF peaks and lightning discharges are simultaneous to within tens of microseconds, and that GBM triggered on TGFs that occurred up to a distance of 300 km from the sub-spacecraft position. In the work presented here, we look for associations between TGFs detected by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and WWLLN sferics over the same 18 months, and we compare the match rate and detection horizon of the two instruments. We also look for associations between WWLLN sferics and more recent GBM TGFs, both triggered events and weaker TGFs uncovered in our untriggered search. We discuss whether in this new mode, GBM is detecting TGFs that are more distant from the sub-spacecraft point than 300 km, or whether the weaker TGFs are instead indicative of a luminosity distribution, either because the weaker ones originate deeper in the atmosphere or because they are intrinsically dimmer.

Connaughton, V.↗
NASA NTRS2011

PING Gamma Ray and Neutron Measurements of a Meter-Sized Carbonaceous Asteroid Analog

Determining the elemental composition of carbonaceous (spectral type C) asteroids is still one of the basic problems when studying these objects. The only main source of elemental composition information for asteroids is from their optical, NIR and IR properties, which include their spectral reflectance characteristics, albedo, polarization, and the comparison of optical spectroscopy with meteorite groups corresponding to asteroids of every spectral type. Unfortunately, these sources reflect observations from widely contrasting spatial scales that presently yield a void in the continuum of microscopic and macroscopic evidence, a lack of in situ measurement confirmation, and require deeper sensing techniques to discern the nature of these asteroids. The Probing In situ with Neutrons and Gamma rays (PING) instrument is ideally suited to address this problem because it can be used to determine the bulk elemental composition, H and C content, the average atomic weight and density of the surface and subsurface layers of C-type asteroids, and can provide measurements used to determine the difference between and distinguish between different types of asteroids. We are currently developing the PING instrument that combines gamma ray and neutron detectors with a 14 Me V pulsed neutron generator to determine the in-situ bulk elemental abundances and geochemistry of C-type asteroids with a spatial resolution of 1 m down to depths of tens of cm to 1 m. One aspect of the current work includes experimentally testing and optimizing PING on a known meter-sized Columbia River basalt C-type asteroid analog sample that has a similar composition and the same neutron response as that of a C-type asteroid. An important part of this effort focuses on utilizing timing measurements to isolate gamma rays produced by neutron inelastic scattering, neutron capture and delayed activation processes. Separating the gamma ray spectra by nuclear processes results in higher precision and sensitivity elemental composition measurements. Using gated data acquisition techniques allows for the unambiguous identification of gamma ray lines from different isotopes and nuclear processes, especially in situations when limited detector resolution results in overlapping gamma ray lines that cannot be individually resolved. In this paper, we will present the PING basalt layering experimental data, taken at the test facility at NASA Goddard Space Flight Center using the time tagged event-by-event data analysis technique, compared to our MCNPX computer simulation results for the C-type asteroid and basalt layering simulant models. Comparison of these data will show the advantages, validity, and measurement sensitivity of PING's nuclear interrogation methods to obtain more precise and sensitive in situ bulk elemental composition and density measurements of the subsurface of asteroids.

Bodnarik, J.↗
DOE OSTI2018

Simulation of Space Experiments for Nuclear Planetology: Measurement of Relative Intensities of Lines of Gamma Ray Emitted upon Thermal-Neutron Capture by Nuclei

The results obtained by experimentally studying gamma rays emitted by samples prepared as analogs of planetary matter and irradiated with thermal neutrons are presented. The intensities of spectral lines of gamma rays emitted by such samples differing in chemical composition are compared. These results will be used in processing data on gamma-ray spectra of the Moon and Mercury from measurements performed onboard spacecrafts with the aim of studying the composition of the surface of these celestial bodies.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1976

A cosmic gamma-ray burst on 1975 May 14

A cosmic gamma-ray burst is described which was observed from a balloon with a double-scatter gamma-ray telescope. The observed burst had a rise time of about 0.15 sec, a duration of 0.11 sec, and variations on a time scale of 5 msec. The variations are shown to imply a maximum source dimension of 1500 km. The integral energy distribution of the burst is determined along with the total energy above 0.5 MeV. The direction of the source is found, with 90% confidence, to be limited to a circle with a radius of 25 deg centered at +39 deg galactic latitude and 40 deg galactic longitude. Two additional candidate bursts observed with the same telescope are briefly discussed.

Herzo, D.↗
NASA NTRS2018

MoonBEAM: A Beyond Earth-Orbit Gamma-Ray Burst Detector for Gravitational-Wave Astronomy

Moon Burst Energetics All-sky Monitor (MoonBEAM) is a CubeSat concept of deploying gamma-ray detectors in cislunar space to improve localization precision for gamma-ray bursts by utilizing the light travel time difference between different orbits. We present here a gamma-ray SmallSat concept in Earth-Moon L3 halo orbit that is capable of rapid response and provide a timing baseline for localization improvement when partnered with an Earth-orbit instrument. Such an instrument would probe the extreme processes in cosmic collision of compact objects and facilitate multi-messenger time-domain astronomy to explore the end of stellar life cycles and black hole formations.

gamma-ray burst cubesat↗
DOE OSTI2019

Measuring the Elemental Composition of Phobos: The Mars-moon Exploration with GAmma rays and NEutrons (MEGANE) Investigation for the Martian Moons eXploration (MMX) Mission

The Mars-moon Exploration with GAmma rays and NEutrons (MEGANE) investigation will use gamma-ray and neutron spectroscopy to measure the elemental composition of Mars' moon Phobos. MEGANE is part of the Japanese Martian Moons eXploration (MMX) mission that will make comprehensive remote sensing measurements of both of Mars' moons Phobos and Deimos. MMX will also return to Earth regolith samples of Phobos. The science goals of the MEGANE investigation mirror those of the MMX mission. MEGANE will use elemental composition measurements to determine if Phobos is a captured asteroid or the end result of a giant impact event on Mars, study Phobos surface processes, provide reconnaissance to support the sample site selection, and supply compositional context for the returned samples. To accomplish its measurements, MEGANE will use a high-purity Ge gamma-ray spectrometer (GRS), and a neutron spectrometer (NS) that consists of two 3He gas proportional neutron sensors. The GRS derives heritage from similar instruments from NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging mission and the Psyche mission that is currently in development; the NS is based on similar instruments used for NASA's Lunar Prospector and Psyche missions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Science Case for a Wide Field-of-View Very-High-Energy Gamma-ray Observatory in the Southern Hemisphere

This white paper outlines the wide science program that would be enabled by the construction of a next-generation gamma-ray observatory using ground-level particle detectors in the Southern Hemisphere: the Southern Gamma-ray Survey Observatory (SGSO). This science case rests on four main pillars: unveiling galactic and extragalactic particle accelerators, monitoring the transient sky at very high energies, probing particle physics beyond the Standard Model, and the characterization of the cosmic ray flux. Several currently ongoing efforts to advance the technical performance of such an observatory will briefly be discussed in Section 8. However, the focus of this document will be on the broad spectrum of astrophysical questions SGSO will address, rather than the details of the technical implementation of a detector. To assess the potential to specific astrophysical applications, a “straw man” detector design is used. This design provides an increase in effective area, number of channels, and a lower energy threshold compared to existing observatories such as the HAWC gamma-ray observatory. Intrinsic figures of merit that quantify the potential performance of SGSO (like angular resolution and background rates) are based on the demonstrated performance of HAWC. Details on this design and its performance are given in Section 3. This approach is chosen as a balance to obtain both an ambitious and feasible performance, suitable to a wide range of applications, while keeping the assumptions about the technical implementation to a minimum. It is foreseen that some applications could benefit from enhanced performance over the straw man design in certain energy ranges; the feasibility and need of reaching enhanced performance will be discussed case by case. The outcome of the studies presented in this document will give an overview of the scientific potential of a next-generation gamma-ray observatory in the southern hemisphere and provide guidance to the finalization of the design of such an observatory.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

Gamma ray shielding and structural properties of Bi{sub 2}O{sub 3}−PbO−B{sub 2}O{sub 3}−V{sub 2}O{sub 5} glass system

The present work has been undertaken to evaluate the applicability of Bi{sub 2}O{sub 3}−PbO−B{sub 2}O{sub 3}−V{sub 2}O{sub 5} glass system as gamma ray shielding material. Gamma ray mass attenuation coefficient has been determined theoretically using WinXcom computer software developed by National Institute of Standards and Technology. A meaningful comparison of their radiation shielding properties has been made in terms of their half value layer parameter with standard radiation shielding concrete 'barite'. Structural properties of the prepared glass system have been investigated in terms of XRD and FTIR techniques in order to check the possibility of their commercial utility as alternate to conventional concrete for gamma ray shielding applications.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2020

Gamma Rays from Kilonova: A Potential Probe of r-process Nucleosynthesis

The mergers of compact binaries with at least one neutron star component are the potential leading sites of the production and ejection of r-process elements. Discoveries of galactic binary pulsars, short gamma-ray bursts, and gravitational-wave detections have all been constraining the rate of these events, while the gravitational wave plus broadband electromagnetic coverage of binary neutron star merger (GW170817) has also placed constraints on the properties (mass and composition) of the merger ejecta. But uncertainties and ambiguities in modeling the optical and infrared emission make it difficult to definitively measure the distribution of heavy isotopes in these mergers. In contrast, gamma rays emitted in the decay of these neutron-rich ejecta may provide a more direct measurement of the yields. We calculate the gamma production in remnants of neutron star mergers, considering two epochs: a kilonova epoch, lasting about two weeks, and a much later epoch of tens and hundreds of thousands of years after the merger. For the kilonova epoch, when the expanding ejecta is still only partially transparent to gamma radiation, we use 3D radiative transport simulations to produce the spectra. Futhermore, we show that the gamma-ray spectra associated with beta- and alpha-decay provide a fingerprint of the ejecta properties and, for a sufficiently nearby remnant, may be detectable, even for old remnants. We compare our gamma spectra with the potential detection limits of next generation detectors, including the Lunar Occultation Explorer (LOX), the All-sky Medium Energy Gamma-ray Observatory (AMEGO), and the Compton Spectrometer and Imager (COSI). We show that fission models can be discriminated via the presence of short-lived fission fragments in the remnant spectra.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1989

Development of liquid xenon detectors for gamma ray astronomy

The application of liquid xenon in high-resolution detectors for gamma-ray astronomy is being investigated. Initial results from a pulse-shape analysis of ionization signals in a liquid-xenon gridded chamber indicate that it is possible to achieve the necessary liquid purity for the transport of free electrons with simple techniques. The energy resolution has been measured as a function of applied electric field, using electrons and gamma-rays from a 207Bi source. At a field of 12 kV/cm the noise-substracted energy resolution of the dominant 569-keV gamma-ray line is 34 keV FWHM (full width at half maximum). This value is mostly determined by recombination of electron-ion pairs on delta-electron tracks.

Aprile, Elena↗
DOE OSTI2015

Towards a realistic astrophysical interpretation of the gamma-ray Galactic center excess

A spherical-symmetric gamma-ray emission from (the inner region of the Galaxy (at least up to roughly 10° in latitude and longitude)) has been recently identified in Fermi-LAT data, and initially associated to dark matter particle annihilations. Guided by the evidence for a high gas density in the inner kpc of the Galaxy correlated with a very large Supernova rate, and hence with ongoing cosmic-ray acceleration, we investigate instead the possibility of addressing this excess in terms of ordinary cosmic-ray sources and standard steady-state diffusion. We (alter the source term, and consistently the correlated gamma-ray emissions, in the context of a template-fitting analysis. We focus on a region of interest (ROI) defined as: |l| < 20°; 2° < |b| < 20°, with l and b the Galactic longitude and latitude coordinates.) We analyze in detail the overall goodness of the fit of our framework, and perform a detailed direct comparison against data examining profiles in different directions. Remarkably, the test statistic of the fit related to our scenario turns out to be as good as the Dark Matter one in the ROI here considered.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

A scintillator attenuation spectrometer for intense gamma-rays

A new type of compact high-resolution high-sensitivity gamma-ray spectrometer for short-pulse intense gamma-rays (250 keV to 50 MeV) has been developed by combining the principles of scintillators and attenuation spectrometers. The first prototype of this scintillator attenuation spectrometer (SAS) was tested successfully in Trident laser experiments at LANL. Later versions have been used extensively in the Texas Petawatt laser experiments in Austin, TX, and more recently in OMEGA-EP laser experiments at LLE, Rochester, NY. The SAS is particularly useful for high-repetition-rate laser applications. Furthermore, we give a concise description of the design principles, capabilities, and sample preliminary results of the SAS.

47 OTHER INSTRUMENTATION↗
NASA NTRS1992

Gamma ray burst astrometry 2: Numerical tests

Since the announcement of the discovery of sources of gamma ray radiation in 1973, many more reports of such bursts have been published. Numerous artificial satellites have been equipped with gamma ray detectors including GRO. Unfortunately, almost no progress has been made in identifying the sources of this high energy radiation. Only one visible counterpart is known. It is suspected that this is a consequence of the methods currently used to define gamma ray burst source 'error boxes'. An alternative procedure was proposed in 1988 by Taff. Herein, Monte Carlo simulations are reported of the efficacy of this technique using realistic burst timing uncertainties and satellite location errors as well as a variety of satellite constellations. Since these are controlled numerical experiments, the dependence is examined of the statistics of the errors in the deduced burst wavefront normal as a function of the timing inconsistencies, detector location standard deviations, and especially the number and distribution of the detectors. The results clearly show that an arc minute prediction of a unique burst location is routinely obtainable once there are at least two interplanetary detectors.

Taff, L. G.↗
NASA NTRS2012

Five New Millisecond Pulsars from a Radio Survey of 14 Unidentified Fermi-LAT Gamma-Ray Sources

We have discovered five millisecond pulsars (MSPs) in a survey of 14 unidentified Ferm;'LAT sources in the southern sky using the Parkes radio telescope. PSRs J0101-6422, J1514-4946, and J1902-5105 reside in binaries, while PSRs J1658-5324 and J1747-4036 are isolated. Using an ephemeris derived from timing observations of PSR JOl01-6422 (P=2.57ms, DH=12pc/cubic cm ), we have detected gamma-ray pulsations and measured its proper motion. Its gamma-ray spectrum (a power law of Gamma = 0.9 with a cutoff at 1.6 GeV) and efficiency are typical of other MSPs, but its radio and gamma-ray light curves challenge simple geometric models of emission. The high success rate of this survey -- enabled by selecting gamma-ray sources based on their detailed spectral characteristics -- and other similarly successful searches indicate that a substantial fraction of the local population of MSPs may soon be known.

Kerr, M.↗
DOE OSTI2021

A fully kinetic model for orphan gamma-ray flares in blazars

ABSTRACT Blazars emit a highly variable non-thermal spectrum. It is usually assumed that the same non-thermal electrons are responsible for the IR-optical-UV emission (via synchrotron) and the gamma-ray emission (via inverse Compton). Hence, the light curves in the two bands should be correlated. Orphan gamma-ray flares (i.e. lacking a luminous low-frequency counterpart) challenge our theoretical understanding of blazars. By means of large-scale two-dimensional radiative particle-in-cell simulations, we show that orphan gamma-ray flares may be a self-consistent by-product of particle energization in turbulent magnetically dominated pair plasmas. The energized particles produce the gamma-ray flare by inverse Compton scattering an external radiation field, while the synchrotron luminosity is heavily suppressed since the particles are accelerated nearly along the direction of the local magnetic field. The ratio of inverse Compton to synchrotron luminosity is sensitive to the initial strength of turbulent fluctuations (a larger degree of turbulent fluctuations weakens the anisotropy of the energized particles, thus increasing the synchrotron luminosity). Our results show that the anisotropy of the non-thermal particle population is key to modelling the blazar emission.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1987

Gamma-ray bursts from superconducting cosmic strings at large redshifts

The relation between cusp events and gamma-rays bursts is investigated. The optical depth of the universe to X-rays and gamma-rays of various energies is calculated and discussed. The cosmological evolution of cosmic strings is examined, and the energetics and time-scales related to the cusp phenomena are estimated. It is noted that it is possible to have energy bursts with a duration of a few seconds or less from cusps at z = 1000; the maximum amount of energy associated with such an event is limited to 10 to the 7th ergs/sq cm.

Babul, Arif↗
NASA NTRS1992

High-energy spectral breaks in gamma-ray bursts

Model fits are presented for 18 gamma-ray burst spectra from 100 keV to 27 MeV made with the BATSE spectroscopy detectors on the Compton Gamma Ray Observatory. Most of the bursts are well fitted as power laws with spectral indices between -1.36 and -2.29; however, five bursts show definite departures from a simple power-law fit at high energies. Three of these bursts are well fitted with broken power-law spectra and break energies of from 400 to 690 keV, such as might arise from photon-photon interactions. If so, then the source compactness and hence distance will be sharply constrained. Two of the bursts have spectra with sharply confined slope changes and are well fitted with broken power-law spectra with break energies of 1.2 and 1.6 MeV at peak, such as might arise from photon-magnetic field interactions. If so, then these spectral breaks provide strong evidence for the existence of high magnetic fields in the burst emission region.

Schaefer, Bradley E.↗
NASA NTRS1988

Upper limits to the high-energy gamma-ray and hard X-ray flux from SN 1987A on day 55

A balloon-borne experiment was carried out on April 19, 1987 from Alice Springs, Australia to detect high-energy gamma-rays and hard X-rays from the supernova SN 1987A in the Large Magellanic Cloud. An optical spark chamber for measuring the high-energy gamma-rays and a multiwire proportional counter for measuring the hard X-rays shared a common balloon platform. No positive emission was observed by either detector. The gamma-ray upper limit obtained indicates that either the expanding supernova shell was opaque to gamma-rays at the time of the flight, or that the supernova cosmic ray luminosity was less than about 10 to the 40th erg/s. The X-ray upper limit obtained confirms the opacity of the shell to Comptonized hard X-rays.

Sood, R. K.↗

Refine your search to explore more results.