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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Gamma-Ray Spectra of r -process Nuclei

The radioactive decay of unstable nuclei created in the rapid neutron capture process releases a large amount of γ-rays. When the ejecta are optically thick, these γ-rays may contribute to an associated kilonova. Once transparent, prominent spectral features will be directly observable in current and future γ-ray detectors. In this work, we study and compare the γ-ray spectra of different representative r-process trajectories across a broad range of timescales, from hours to 50,000 yr, identifying the nuclei that significantly contribute. We discuss these findings in the context of observability, noting that there are several practical challenges to connecting observed signatures to specific nuclei. However, if these challenges can be overcome, direct observation of γ-rays from r-process sites can provide insight into the fundamental physics underpinning the r-process.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1963

HIGH-ENERGY GAMMA-RAY ASTRONOMY

Brief review of the present status of high-energy gamma-ray astronomy and a report of results from the orbiting solar observatory

EXTRATERRESTRIAL RADIATION↗
NASA NTRS1968

Gamma-ray astronomy.

Space gamma radiation in form of quanta with extremely high energies, discussing satellite- borne detectors, spark chambers, etc

Fichtel, C. E.↗
NASA NTRS1970

Gamma-ray astronomy balloon results

Gamma ray astronomical point sources by balloon flight and satellite observation, discussing detector system and telescope for flux and energy spectrum

Fichtel, C. E.↗
NASA NTRS1973

Gamma-ray observations of the galactic centre.

Review of observation data obtained with a portable gas-Cerenkov gamma-ray telescope flown twice from Parana, Argentina (31.8 deg S), to search for gamma radiation from the galactic center. The angular resolution of this detector is not good enough to resolve the source structure controversy, i.e. whether the gamma radiation is coming from point sources or from a diffuse source along the galactic plane. Comparisons with observation data of other investigators are presented and discussed.

Helmken, H. F.↗
NASA NTRS1973

HEAO gamma-ray astronomy experiments

Two gamma ray experiments designed to measure and map the cosmic gamma ray spectrum in the 0.1 to 10 MeV region are outlined. The sensitivity and capability of the instruments- a high resolution gamma ray spectrometer that uses solid state detectors and a combined UCSD-MIT scintillation system are also given. These experiment were designed for the HEAO program.

Metzger, A. E.↗
NASA NTRS1974

Observation of a cosmic gamma-ray burst on Apollo 16. II - X-ray time profile and source location

A burst of X-rays was detected during the trans-earth coast phase of Apollo 16 on Apr. 27, 1972 at 10:68 UT, simultaneously with the observation of a transient event by a gamma-ray spectrometer aboard the same spacecraft. The two instruments provide a broad energy range of more than three orders of magnitude for describing the spectral distribution of this event. The conclusion that the incident flux was X-rays and not charged particles is based on the fact that the particle flux detectors in the Apollo gamma ray spectrometer and on the Vela 6A, which also observed the event, did not respond. The time variation of the total count rate in the X-ray range before and after corrections for detector geometry and the analysis for source direction is presented.

Trombka, J. I.↗
NASA NTRS1977

The hard X-ray pulse profile of the transient source A0535+26

Measurements of the 104 sec pulse profile of A0535+26 at energies near 50 keV are reported. The data were obtained with a balloon-borne detector system which was launched on May 22, 1975 with the objective to observe transient or periodic emissions from X-ray or gamma-ray sources. The presence of the source was detected by a superposed epoch analysis. The pulse profile of A0535+26 in two energy channels is presented in a graph.

Fishman, G. J.↗
NASA NTRS1977

Reanalysis of the Apollo cosmic gamma-ray spectrum in the 0.3 to 10 MeV energy region

Additional data obtained from the Apollo 16 and 17 missions, together with collateral calculations on background radiation effects, have made possible an improved subtraction of unwanted backgrounds from the diffuse cosmic gamma ray data previously reported from Apollo 15. As a result, the 1 to 10 MeV spectrum is lowered significantly and connects smoothly with recent data at other energies. The inflection reported previously is much less pronounced and has no more than 1.5 sigma significance. Sky occultation by the Apollo 16 spacecraft shows the bulk of the 0.3 to 1 MeV radiation to be diffuse. The analysis of spurious backgrounds points to important improvements for future experiments designed for this spectral region. A light-weight satellite design can give a fourfold improvement in the signal to noise for such a measurement. Use of an anisotropic central crystal, which spins quickly compared with possible time variations in detector background, would enable sensitive limits to be set on galactic plane and point source contributions.

Dyer, C. S.↗
NASA NTRS1977

Apollo-Soyuz pamphlet no. 2: X-rays, gamma-rays

The nature of high energy radiation and its penetration through earth's atmosphere is examined with emphasis on X-rays, gamma rays, and cosmic radiation and the instruments used in their detection. The history of radio astronomy and the capabilities of the Uhuru satellite are summarized. The ASTP soft X-ray experiment (MA-048) designed to study the spectra in the range from 0.1 to 10 keV and survey the background over a large section of the sky is described, as well as the determination of SMC C-1 as an X-ray pulsar. The crystal activation experiment (MA-151) used to measure the radioactive isotopes created by cosmic rays in crystals used for gamma ray detectors is also discussed.

Page, L. W.↗
NASA NTRS1978

Cross sections relevant to gamma ray astronomy

Gamma-ray production cross sections were measured for protons and alpha particles incident on targets consisting of nuclei of high cosmic abundance: C-12, N-14, O-16, Ne-20, Mg-24, Si-28 and Fe-56. Solid or gaseous targets were bombarded by monoenergetic beams of protons and alpha particles, and gamma rays were detected by two Ge(Li) detectors. The proton energy for each target was varied from threshold to about 24 MeV (lab); for alphas the range was from threshold to about 27 MeV. For most transitions, it was possible to measure the total cross section by placing the detectors at 30.5 deg and 109.9 deg where the fourth-order Legendre polynomial is zero. For the case of the 16O (E sub gamma = 6.13 MeV, multipolarity E3) cross sections, yields were measured at four angles. Absolute cross sections were obtained by integrating the beam current and by measuring target thicknesses and detector efficiencies. The Ge(Li) detector resolution was a few keV (although the peak widths were greater, due to Doppler broadening).

Dyer, P.↗
NASA NTRS1977

Design and performance of an actively collimated phoswich system for X-ray astronomy

The design and performance of a phoswich type scintillation detector system having 34 sq cm effective collecting area and a sensitivity of 3 x 10 to the -5th power photons/sq cm/s/keV for balloon-borne cosmic X-ray source observations are discussed. The various shield anticoincidence systems are evaluated for effectiveness in reduction of the system background. The total background of nominally 4 x 10 to the -4th power counts/sq cm/s/keV is analyzed and found to consist of aperture flux, K-escape X-rays from the shielding, leakage, and degradation of gamma-rays through the shielding, and several particle induced effects. The background analysis suggests an ultimate practical upper limit of about 8 x 10 to the -5th power counts/sq cm/s/keV might be attainable beyond which further sensitivity improvements will require increased collecting area or a basically differing design approach.

Matteson, J. L.↗
NASA NTRS1978

Large scale telescopes for high resolution X-ray and gamma-ray astronomy

This paper shows that angular-resolution, energy-range, and structural constraints on image-modulated X-ray telescopes are not fundamental and that the limits on angular resolution can be overcome by constructing such telescopes on a very large spatial scale. It is proposed that widely separated satellites be used for the modulating mask and detector array. Implementation of this concept is discussed in terms of a simple system consisting of a pinhole camera (i.e., a hole in an opaque mask on one subsatellite and a detector array on another). Advantages and problems of such systems are briefly discussed, and a solar X-ray telescope intended for deployment from a Shuttle orbiter is described. It is noted that such large-scale telescopes can be constructed to image gamma rays and even energetic neutrons as well.

Hudson, H. S.↗
NASA NTRS1979

Search for an X-ray identification of a strong gamma-ray source

X-rays from Cygnus X-3 were observed during early 1978 with the detectors of the SAS-3 satellite. These observations in conjunction with earlier UHURU and ANS data indicate that the 4.8 hr period of Cygnus X-3 is increasing at the rate of P/P = (5/1 plus or minus 1.3) x 10 to the minus 6 power/1 yr. The sign and magnitude for this change are incompatible with a rotation model for the period and are in reasonable agreement with model predictions for orbital changes associated with mass loss and transfer in a binary system.

Lamb, R. C.↗