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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.

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At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Liquid xenon time projection chamber for gamma rays in the MeV region: Development status

The feasibility of a large volume Liquid Xenon Time Projection Chamber (LXe-TPC) for three dimensional imaging and spectroscopy of cosmic gamma ray sources, was tested with a 3.5 liter prototype. The observation of induction signals produced by MeV gamma rays in liquid xenon is reported, with a good signal-to-noise ratio. The results represent the first experimental demonstration with a liquid xenon ionization chamber of a nondestructive readout of the electron image produced by point-like charges, using a sense wire configuration of the type originally proposed in 1970 by Gatti et al. An energy resolution as good as that previously measured by the millimeter size chambers, was achieved with the large prototype of 4.4 cm drift gap.

Aprile, E.↗
NASA NTRS1982

Gamma-ray burst spectra

A review of recent results in gamma-ray burst spectroscopy is given. Particular attention is paid to the recent discovery of emission and absorption features in the burst spectra. These lines represent the strongest evidence to date that gamma-ray bursts originate on or near neutron stars. Line parameters give information on the temperature, magnetic field and possibly the gravitational potential of the neutron star. The behavior of the continuum spectrum is also discussed. A remarkably good fit to nearly all bursts is obtained with a thermal-bremsstrahlung-like continuum. Significant evolution is observed of both the continuum and line features within most events.

Teegarden, B. J.↗
NASA NTRS1988

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

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.↗
NASA NTRS2001

Testing the Physical Mechanisms of Gamma-Ray Bursts with Multi-Instrument Time-Resolved Spectroscopy

We have continued the project of time-resolved spectral analyses of gamma-ray bursts observed jointly by the BATSE and the Wide-Field Camera on board BeppoSAX. We are making progress understanding the systematic differences between the two data sets. These data comprise the most important joint analysis set for our project. In several meetings, we have reported on metal efforts to understand the blackbody portion of the time series of spectra from GRB970111. Clearly, a fading thermal component can provide a 'seed' spectrum for Compton upscattering. It is very likely the X-ray excess that has been observed previously in BATSE data alone continues into the X-ray band observed by the WFC. We have also made progress in joint fitting of BATSE Large Area Detector and Spectroscopy Detector data with that of the Total Absorption Scintillation Calorimeter (TASC) of the EGRET experiment on CGRO. The TASC data are important to understanding the high-energy response of the BATSE data. We have produced time-sequences of spectra for two important GRB with data from both instruments. The Summer workshop on GRBs at the Aspen Center for Physics provided an opportunity for in-depth discussion of our on-going work. To aid our effort, we continue to make improvements in our spectral analysis software, RMFIT (rewritten from WINGSPAN).

Briggs, Michael S.↗
NASA NTRS2022

Ramaty High Energy Solar Spectroscopic Imager (RHESSI)

This chapter describes the X-ray and gamma-ray imaging spectroscopy capabilities of the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). It also outlines RHESSI’s major scientific accomplishments during the 16 years of operations from 2002 to 2018. These include unique contributions to solar flare research and to other aspects of solar physics (oblateness), astrophysics (magnetars), and Earth sciences (terrestrial gamma-ray flashes).

Brian Dennis↗
NASA NTRS2012

Geochemistry at 4 Vesta: Observations Using Fast Neutrons

Dawn is currently in orbit around the asteroid 4 Vesta, and one of the major objectives of the mission is to probe the relationship of Vesta to the Howardite, Eucrite, and Diogenite (HED) meteorites. As Vesta is an example of a differentiated planetary embryo, Dawn will also provide fundamental information about planetary evolution in the early solar system [1]. To help accomplish this overall goal, the Dawn spacecraft carries the Gamma-Ray and Neutron Detector (GRaND). GRaND uses planetary gamma-ray and neutron spectroscopy to measure the surface elemental composition of Vesta and will provide information that is unique and complementary to that provided by the other Dawn instruments and investigations. Gamma-ray and neutron spectroscopy is a standard technique for measuring planetary compositions [2], having successfully made measurements at near-Earth asteroids, the Moon, Mars, Mercury and now Vesta. GRaND has made the first measurements of the neutron spectrum from any asteroid (previous asteroid measurements were only made with gamma-rays). Dawn has been collecting data at Vesta since July 2011. The prime data collection period for GRaND is the Low-Altitude Mapping Orbit (LAMO), which started on 12 December 2011 and will last through spring 2012. During LAMO, the Dawn spacecraft orbits at an average altitude of ~210 km above the surface of Vesta, which allows good neutron and gamma-ray signals to be detected from Vesta. A description of the overall goals of GRaND and a summary of the initial findings are given elsewhere [3,4]. The subject of this study is to present the information that will be returned from GRaND using fast neutron measurements. Here, we discuss what fast neutrons can reveal about Vesta s surface composition, how such data can address Dawn science goals, and describe fast neutron measurements made in the early portion of the Vesta LAMO phase.

Lawrence, David J.↗
NASA NTRS1986

Optical imaging spectroscopy

During the recent solar maximum the combination of imaging and spectroscopy in the visible part of the spectrum became a powerful tool for observational study of flares primarily because of the development of two-dimensional charge-coupled-device (CCD) arrays. In combination with appropriate new operational methods, this has led to the ability to observe, for the first time, the preflare and impulsive-phase physical processes associated with spatially resolved features of flare loops. As a result of concurrent theoretical developments, modeling progressed from an empirical to a physical level. This made it possible to interpret imaging spectra in terms of coronal pressure and heat flux, particle beam heating, chromospheric evaporation, and explosive chromospheric dynamics at the footpoints of flare loops. There is clear potential for further advances in the near future, taking advantage of improvements in digital recording speed (approx. 10-fold), number of photosensitive elements per array (approx. 10-fold), real-time data pre-reduction (potentially 10- to 100-fold), and using multiple CCD arrays. By the time of the next solar maximum imaging spectroscopy is expected to achieve spatial resolution or approx. arc 1 arc s, temporal resolution or approx. 5 s, and simultaneous critically-sampled spectroscopy of several lines and continua. As a result, continued increase in our understanding of the physical processes and configurations of solar flares in the chromosphere, temperature minimum region, and photosphere can be anticipated. Even greater progress toward a more global understanding of flares will obviously come about when simultaneous optical, X-ray, and gamma-ray imaging spectroscopy are possible.

Canfield, R. C.↗
NASA NTRS2000

Gamma Ray Astronomy

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.↗
DOE OSTI2026

Evidence for an isomeric {pi}½{sup +}[411] state in {sup 183}Ta

We report on the identification of a new isomeric state in Ta populated via the ground-state -decay of Hf. The experiment was performed at the KISS setup at RIKEN, where neutron-rich hafnium isotopes were produced via multi-nucleon transfer (MNT) reactions, followed by laser ionization of hafnium atoms, mass separation, and detection using an electron-gamma coincidence system. Isomeric spectroscopy was carried out by gating on different electron-gamma time correlations. A 459.1 keV -ray transition was identified in delayed spectra, and a half-life of μ was extracted through time-distribution fitting. The 459.1 keV state in Ta is known from previous work and has been assigned a Nilsson orbital configuration of , while a proposed new isomeric state above it is interpreted as a configuration that decays to via a low-energy, unobserved E2 transition. This is consistent with the systematic trends in neighbouring odd-A nuclei and transition rate calculations. Similar content being viewed by others

Doshi, S.↗
NASA NTRS1992

Gamma-ray monitoring of AGN and galactic black hole candidates by the Gamma-Ray Observatory

The Burst and Transient Spectroscopy Experiment (BATSE) on the Compton Gamma-Ray Observatory has a powerful capability to provide nearly uninterrupted monitoring in the 25 keV-10 MeV range of both AGN and Galactic black hole candidates such as Cygnus X-1, using the occultation of cosmic sources by the Earth. Progress in background modeling indicates that the data accept region, or fit window tau, around the occultation step can be substantially increased over that conservatively assumed in earlier estimates of BATSE's Earth occultation sensitivity. We show samples of large-tau fits to background and source edges. As a result we expect to be able to perform long-term monitoring of Cygnus X-1 and many of the brighter AGN for the duration of the CGRO mission.

Wheaton, Wm. A.↗
NASA NTRS2010

The Design and Capabilities of the EXIST Optical and Infra-Red Telescope (IRT)

The Infra-Red Telescope is a critical element of the EXIST (Energetic X-Ray Imaging Survey Telescope) observatory. The primary goal of the IRT is to obtain photometric and spectroscopic measurements of high redshift (> or =6) gamma ray reaching to the epoque of reionization. The photometric and spectral capabilities of the IRT will allow to use GRB afterglow as probes of the composition and ionization state of the intergalactic medium of the young universe. A prompt follow up (within three minutes) of the transient discovered by the EXIST makes IRT a unique tool for detection and study of these events in the infrared and optical wavelength, which is particularly valuable at wavelengths unavailable to the ground based observatories. We present the results of the mission study development on the IRT as part of the EXIST observatory. Keywords: infrared spectroscopy, space telescope, gamma ray bursts, early universe

Kutyrev, A S.↗
NASA NTRS1991

Development of a high resolution liquid xenon imaging chamber for gamma-ray astronomy

The objective was to develop the technology of liquid xenon (LXe) detectors for spectroscopy and imaging of gamma rays from astrophysical sources emitting in the low to medium energy regime. In particular, the technical challenges and the physical processes relevant to the realization of the LXe detector operated as a Time Projection Chamber (TPC) were addressed and studied. Experimental results were obtained on the following topics: (1) long distance drift of free electrons in LXe (purity); (2) scintillation light yield for electrons and alphas in LXe (triggering); and (3) ionization yield for electrons and gamma rays in LXe (energy resolution). The major results from the investigations are summarized.

Aprile, Elena↗
NASA NTRS1992

BATSE spectroscopy results

We present preliminary analyses of gamma-ray burst spectra from the BATSE Spectroscopy Detectors. Our conclusions are: (1) No spectral lines have yet been detected in BATSE data from any cosmic gamma-ray burst. This is not surprising as the data for few bright bursts is available, and previous experiments saw lines in only a small fraction of the bursts. (2) Burst spectra show emission up to 20 MeV, with four of eight examined bursts having significant spectral breaks from 1 to 2 MeV. These breaks are consistent with opacity effects due to the interaction of photons with a high magnetic field. (3) Various distance independent parameters from burst spectra and time histories have no correlation with parameters related to distance. In other words, bright bursts look the same as faint bursts. This places a strong constraint on two population models of bursts. (4) The detection time of individual photons is not correlated from detector to detector, as predicted by Mitrofanov's pulsed emission model.

Schaefer, Bradley E.↗
DOE OSTI2025

Steam-Assisted Ammonolysis of MoO2 as a Synthetic Pathway to Oxygenated δ-MoN

A common route for the synthesis of molybdenum nitrides is through the temperature-programmed reaction of molybdenum oxides with NH3, or ammonolysis. In this work, the role of precursor phase, gas phase chemistry (impact of H2O), and temperature profile on the reaction outcome (700 °C) was examined, which resulted in varying amounts of MoO2, H2MoO5, and the nitride phases—cubic γ (nominally Mo2N) and hexagonal δ (nominally MoN). The phase fraction of the δ phase increased with precursor in the sequence MoO2 > MoO3 > H2MoO5. Steam in the reaction gas also favored the production of δ over γ, but with too much steam, MoO2 was obtained in the product. Synthesis conditions for obtaining nearly phase-pure δ were identified: MoO2 as the precursor, 2% H2O in the gas stream, and a moderate heating rate (3 °C/min). In situ X-ray diffraction provided insights into the reaction pathway. Extensive physico-chemical analysis of the δ phase, including synchrotron X-ray and neutron diffraction, electron microscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, and prompt gamma activation analysis, revealed its stoichiometry to be MoO0.108(8)N0.892(8)H0.012(5), indicating non-trivial oxygen incorporation. The presence of N/O ordering and an impurity phase Mo5N6 were also revealed, detectable only by neutron diffraction. Notably, a computationally predicted MoON phase (doi: 10.1103/PhysRevLett.123.236402), of interest due to its potential to display a metal-insulator transition, did not appear under any reaction condition examined.

Pandey, Shobhit↗
NASA NTRS1966

Intermediate energy physics, volume I

Conference on proton, pion, and muon interactions - phase shift analyses of pion-nucleon and nucleon-nucleon scattering, charge distributions and pion decay into gamma rays

SPECTROSCOPY↗
NASA NTRS2012

Chemical Mapping of Vesta

Vesta s surface mineralogy and composition have been studied for decades via telescopic spectroscopy and laboratory analyses of the howardite, eucrite, and diogenite (HED) meteorites, which are thought to originate from Vesta. Visible and infrared reflectance measurements by Dawn have broadly confirmed the paradigm established by Earth-based work, strengthening the Vesta-HED connection. The Dawn mission has achieved a milestone by completing the first chemical measurements of a main-belt asteroid using nuclear spectroscopy. Dawn s Gamma Ray and Neutron Detector (GRaND) has globally mapped the composition of Vesta, including the portions of the northern hemisphere not illuminated by solar radiation. GRaND is sensitive to the composition of the bulk regolith to depths of several decimeters. Abundances and/or detection limits for specific elements and elemental ratios, such as H, Fe, Si, Fe/O, Fe/Si, and K, have been measured. Variations in the average atomic mass and neutron macroscopic absorption cross section have been characterized. The measurements constrain the relative proportions of HED whole-rock end-members, providing measurements of the pyroxene and plagioclase content of the regolith, thereby constraining the processes underlying Vesta s differentiation and crustal evolution. The spatial resolution of GRaND is sufficient to determine basin-average compositions of Veneneia and Rheasilvia, which may contain outcrops of Vesta s olivine-rich mantle. While the elemental composition of Vesta s regolith is similar to the meteorites, there are notable departures from HED whole-rock compositions. While these differences are not sufficient to topple the Vesta-HED paradigm, they provide insight into global-scale processes that have shaped Vesta s surface. Questions addressed by the analysis of GRaND data include: (i) Is Vesta the source of the Fe-rich mesosiderites? (ii) Are evolved, igneous lithologies present on Vesta s surface? (iii) What are the origins of exogenic materials found in Vesta s regolith? (iv) Is the vestan mantle exposed within the southern basins?

Prettyman, Thomas H.↗
NASA NTRS2018

The fraction of ionizing radiation from massive stars that escapes to the intergalactic medium

Whether stars could have driven the reionization of the intergalactic medium depends critically on the proportion of ionizing radiation that escapes the galaxies in which it is produced. Spectroscopy of gamma-ray burst (GRB) afterglows can be used to estimate the opacity to extreme ultraviolet (EUV) radiation along the lines-of-sight to the bursts. Assuming that long-duration GRBs trace the locations of the massive stars dominating EUV production, the average escape fraction of ionizing radiation can be calculated independently of galaxy size or luminosity. Here we present a compilation of HI column density (N(HI)) measures for 140 GRBs in the range 1.6 < z <6.7. Although the sample is heterogeneous, in terms of spectral resolution and signal-to-noise ratio, fits to the Ly α absorption line provide robust constraints on N(HI), even for spectra of insufficient quality for other purposes. Thus we establish an escape fraction at the Lyman limit of {f(esc)} ≈ 0.005, with a 98 per cent confidence upper limit of {f(esc)} ≈ 0.015. This analysis suggests that stars provide a small contribution to the ionizing radiation budget at z < 5. At higher redshifts firm conclusions are limited by the small size of the GRB sample (7/140), but any decline in average HI column density seems to be modest. We also find no significant correlation of N(HI) with galaxy UV luminosity or host stellar mass. We discuss in some detail potential biases and argue that, while not negligible, systematic errors in f(esc) are unlikely to be more than a factor ∼2 in either direction, and so would not affect the primary conclusions. Given that many GRB hosts are low-metallicity dwarf galaxies with high specific star-formation rates, these results present a particular problem for the hypothesis that such galaxies dominated the reionization of the Universe.

N R Tanvir↗
NASA NTRS1999

Analysis of Line Candidates in Gamma-Ray Bursts Observed by BATSE

A comprehensive search of BATSE Spectroscopy Detector data from 117 Gamma Ray Bursts (GRBs) has uncovered 13 statistically significant line candidates. The case of a candidate in GRB-930916 is discussed. In the data of SD-2 there appears to be a emission line at 46 keV, however the line is not seen in the data of SD-7. Simulations indicate that the lack of agreement between the results from SD-2 and SD-7 is implausible but not impossible.

Briggs, M. S.↗