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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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Time sequence gamma-spectrometry of irradiated salt
Persisted Memory Mapping File (MMF) techniques have developed for the processing and analysis of time-stamped list (TLIST) mode data collected from an irradiated salt sample. This is a new technique that is unique to this research and enables additional information to be obtained from a conventional pulse height analysis (PHA) gamma-spectrometry acquisition. A salt sample was irradiated using a DT neutron generator and immediately measured using TLIST acquisition for 1 month to generate a 22 GB data file. MMF techniques were used to process the file without size restrictions at a rate of 388.5 MB minute-1, with instant access to any position within the file, separating the file into a series of time sequenced spectra suitable for PHA analysis. This enabled 14 activation products to be identified at different time intervals (41Ar, 80Br, 80mBr, 47Ca, 34mCl, 38Cl, 42K, 43K, 56Mn, 22Na, 24Na, 85Sr, 87mSr and 69mZn), and 6 radionuclides (80Br, 47Ca, 34mCl, 56Mn, 24Na and 87mSr) to be definitively confirmed based upon their measured half-life. Using this technique, the detection of 47Ca, and in-growth of its 47Sc progeny, was demonstrated as useful for calculating the time since irradiation.
H Atom Production and Reaction in the Gamma Radiolysis of Thermally Modified Boehmite
The correlation between the formation of H atoms and H2 was observed in the radiolysis of thermally modified boehmite (?-AlOOH). Boehmite was pretreated by heating to 300, 400, and 550°C, loaded with adsorbed water, and irradiated with gamma rays. Long-lived H atoms trapped in the interstitial matrix was observed by electron paramagnetic resonance techniques and the amount of gaseous H2 by gas chromatography. Heating the boehmite to 400°C before radiolysis results in the collapse of the matrix with loss of trapped H atoms and a substantial increase in the production of H2. Samples without added water post-heating showed no production of H2 suggesting that it is formed by the diffusion of H atoms to the surface followed by an abstraction reaction with water. Boehmite heated to 550°C has completely converted to alumina and the radiolytic responses of each are similar. Post-irradiation heating of boehmite to 300°C results in a doubling of the H2 yield at pretreated temperatures below 300°C due to the release of trapped H atoms.
New determination of the millisecond pulsar gamma-ray luminosity function and implications for the Galactic Center gamma-ray excess
It has been suggested that the Galactic Center gamma-ray excess (GCE) could be produced by a large number of centrally located millisecond pulsars. The fact that no such pulsar population has been detected implies that these sources must be very faint and very numerous. Here, in this study, we use the contents of Fermi’s recently released Third Pulsar Catalog (3PC) to measure the luminosity function of the millisecond pulsars in the Milky Way’s disk. We find that this source population exhibits a luminosity function with a mean γ -ray luminosity of ⟨ L γ ⟩ ∼ 6 × 10 32 erg / s (integrated above 0.1 GeV). If the GCE were generated by millisecond pulsars with the same luminosity function, we find that ∼ 20 such sources from the inner Galaxy population should have already been detected by Fermi and included in the 3PC. Given the lack of such observed sources, we exclude the hypothesis that the GCE is generated by pulsars with the same luminosity function as those in the Galactic disk with a significance of 3.4 σ . We conclude that either less than 39% of the GCE is generated by pulsars, or that the millisecond pulsars in the inner Galaxy are at least 5 times less luminous on average than those found in the Galactic disk.
Meson Photo-Production in GEANT4 for $E_\gamma = 0.225$ E γ = 0 . 225 -3.0 GeV using the $\gamma + p \rightarrow p + \pi^{0}$ reaction
The study of nuclear resonances in the intermediate energy regime requires accurate modeling of the experimental physics background. The cross sections in the GEANT4 toolkit do not adequately treat meson photo-production. The purpose of this study is to compare experimental data and theoretical models implemented in version 9.6.p02 of the GEANT4 Monte Carlo simulation toolkit for the exclusive and differential cross sections of $\pi^0$ photo-production. Two models were studied: the Chiral Invariant Phase Space (CHIPS) and Bertini Cascade (BERT). The cross section data from the models were compared to the experimental data from the CEBAF Large Acceptance Spectrometer (CLAS) of Jefferson Lab and the phenomenological Scattering Analysis Interactive Dial-in (SAID) model. Relativistic Breit-Wigner fits were used to compare the $\Delta(1232)$, N*(1520), N*(1650) and N*(1875) resonances from SAID, CLAS and CHIPS, giving agreements to within 3% for the mass of each resonance. The limited tabulated data set of BERT does not allow for an accurate description of the energy distribution, even following its improvement in version 10p02. The angular distributions of the cross sections show significant differences between CHIPS and both CLAS and SAID data, the latter being the most accurate model to describe the $\gamma p\rightarrow p\pi ^0$ exclusive cross section. Finally, the physics in CHIPS appears to be correct but it needs further development for the individual resonances contributions that could be useful since it is also the only model able to treat electromagnetically induced meson production for $A>1$.
Electronic transition moments and their effects on the band gamma strengths and absorption oscillator strengths of the beta and gamma systems
Electronic transition moments and effects on band strength - absorption oscillator strengths of nitric oxide beta and gamma systems
Synthesis of calculational methods for the design and analysis of radiation shields for nuclear rocket systems. Volume 7 - NAGS, a Fortran 4 data processing program for calculation of neutron and gamma ray sources and neutron and gamma ray heating in two dimensional geometries Final progress report
Neutron flux and gamma ray source edit computer program for design and analysis of radiation shields in nuclear rocket systems
The production of cosmic gamma rays in interstellar and intergalactic cosmic-ray collisions. 4 - Gamma-ray production from cosmic proton-antiproton interactions
Production of cosmic gamma rays by annihilation of antimatter
The production of cosmic gamma rays in interstellar and intergalactic cosmic-ray collisions. 4 - Gamma-ray production from cosmic proton-antiproton interactions
Gamma ray production from cosmic proton-antiproton interactions
Alpha-gamma angular correlations in the reaction carbon 12/alpha, alpha prime gamma/ 4.433 MeV/
Alpha-gamma angular correlations with scattering cross sections
Alpha-gamma angular correlations in the reaction tin-120/alpha, alpha prime gamma sub 1.18MeV/
Alpha-gamma angular correlation model for particle scattering from even tin isotope
Alpha-gamma angular correlations in the reaction nickel-58/alpha, alpha prime gamma sub 1.452MeV/
Alpha-gamma angular correlations for excitation of 1.452-MeV state of nickel-58
A study of bone mineral content performed by the gamma ray absorption technique in prolonged bed rest subjects maintained in a metabolically controlled environment - The ultimate application of gamma ray absorption techniques to in-flight bone mineral measurements, exhibit B Terminal report
Bone mineral changes in prolonged bed rest subjects determined by gamma ray absorption technique
Gamma ray background analysis at the NASA Langley Research Center SREL 600 Mev proton synchrocyclotron of the relatively short- and long-lived gamma rays
Gamma ray background near proton synchrocyclotron beam degrader at NASA-LRC Space Radiation Effects Laboratory
The isotropy of the cosmic gamma ray flux between 1 and 6 MeV and its implications for future gamma ray investigations
Galactic and extragalactic origin of cosmic gamma ray flux between 1 and 6 MeV
Gamma-ray bursts during neutron star formation. Gamma-ray bursts and transient X-ray sources
Discussions are presented of the associations between cosmic gamma ray bursts and transient X-ray sources, and the release of gravitational binding energy during the formation of neutron stars. The model for studying the associations is described along with the release of neutrinos during the collapse of white dwarfs.
Interpretation of various radiation backgrounds observed in the gamma-ray spectrometer experiments carried on the Apollo missions and implications for diffuse gamma-ray measurements
Since the report of a preliminary analysis of cosmic gamma-ray measurements made during the Apollo 15 mission, an improved calculation of the spallation activation contribution has been made including the effects of short-lived spallation fragments, which can extend the correction to 15 MeV. In addition, a difference between Apollo 15 and 16 data enables an electron bremsstrahlung contribution to be calculated. A high level of activation observed in a crystal returned on Apollo 17 indicates a background contribution from secondary neutrons. These calculations and observations enable an improved extraction of spurious components and suggest important improvements for future detectors.
Gamma ray cosmology: The extra galactic gamma spectrum and methods to detect the underlying source
The possible sources of extragalactic gamma rays and methods to distinguish the different sources are discussed. The sources considered are early universe decays and annihilation of Particles, active galactic nuclei (AGN) sources, and baryon-antibaryon annihilation in a baryon symmetric cosmology. The energy spectrum and possible angular fluctuations due to these sources are described.