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Nakano, G. H.

Publications and source records attributed to Nakano, G. H..

14 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

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

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.↗
NASA NTRS1988

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

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.↗
NASA NTRS1988

Gamma-ray observations of SN 1987A with an array of high-purity germanium detectors

A balloonborne gamma-ray spectrometer comprising an array of high-purity n-type germanium (HPGe) detectors surrounded by an active NaI(T1) collimator and Compton suppressing anticoincidence shield was flown on May 29-30, 1987. The average column depth of residual atmosphere in the direction of SN 1987A at float altitude was 6.3 g/sq cm during the observation. The 3-sigma upper limit obtained for the 1238-keV line from Co-56 is 0.0013 photons/sq cm s. The corresponding limit for the 847-keV line is 0.0017 photons/sq cm s.

Sandie, W. G.↗
NASA NTRS1985

Locations and time histories of five 1979 gamma-ray bursts

The locations and time histories of five gamma-ray bursts that occurred between 1979 March 7 and March 31 were studied. The error box for GB 790325 has a typical dimension of about 1.5 arcmin. The other localizations, while not precise enough for thorough optical examination, contribute to distribution studies and allow radio and X-ray observations, catalog searches, and other archival work. A search through selected catalogs did reveal one object, the star FY Aql (cataloged as a Mira-type variable but probably a dwarf nova) inside one of the gamma-ray burst boxes. Given the parameters of this particular search, the probability of at least one chance association is 0.03. Both recent and archival optical examinations of some of the error boxes were carried out, and no indications of any actual physical associations were seen. One event, GB 790331, had an interesting spectral behavior, in that the leading edges of the two main peaks within the burst had harder spectra than the remainder of the event.

Laros, J. G.↗
NASA NTRS1983

Computer simulation study of multiple germanium gamma-ray sensor arrays

Design studies of large high resolution gamma-ray spectrometer systems employing multiple sensors are greatly facilitated by the use of computer simulation techniques. A study has been made by interfacing a detector geometry code with the EGS-3 version of the Stanford Linear Accelerator Center Monte-Carlo Code which has been modified to run on our VAX computer. The detector responses have been simulated for input photons with energies between 0.1 and 10 MeV. Examples are given to illustrate the performance of complex sensor arrays with different configurations of the anticoincidence system. Of particular interest is a design composed of an array of 7 detector elements each consisting of a thin planar Ge (1 cm thick) detector mounted in front of and in tandem with a large coaxial Ge detector.

Nakano, G. H.↗
NASA NTRS1978

High resolution spectroscopy from low altitude satellites

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.↗
NASA NTRS1977

Fine energy resolution survey of the sky with a germanium gamma-ray spectrometer

A fine-energy-resolution survey (38 to 2700 keV) of the sky has been performed from a spinning polar-orbiting satellite with a cooled germanium spectrometer. The measurements, performed with a fast time resolution (32 ms), permit one to analyze the energy spectra from repeated noon-midnight orbits in selected portions of the local daytime or nighttime sky. During the initial period of the experiment, the sky was surveyed in two broad intervals spanning the galactic plane at longitudes of approximately 255 to 328 deg and 99 to 168 deg, respectively. In the former interval a significant increase in counting rate was observed when the spectrometer viewed the galactic plane. Locally generated backgrounds were removed from the galactic-plane spectrum by subtracting, on a spin-for-spin basis, the contribution measured at a viewing direction with a comparable declination north of the celestial equator. The net spectra from the galactic plane have been examined for evidence of gamma-ray lines. The possible presence of lines near 1121 and 1369 keV emitted from the galactic plane over the galactic longitudinal interval approximately 255 deg to approximately 328 deg is suggested by the data, but better statistics are needed to establish their existence firmly. Comparisons are made with previously reported extraterrestrial lines with assumed normalizations made for the different viewing directions in the two experiments.

Imhof, W. L.↗
NASA NTRS1977

Narrow spikes in the selective precipitation of relativistic electrons in mid-latitudes

Relativistic electron precipitation spikes were observed in the quasi-trapped population at midlatitudes by an array of electron detectors aboard the low-altitude polar-orbiting satellite 1972-076B. The fluxes of electrons of energies not less than 4 MeV may undergo pronounced enhancements, while the intensities of electrons in the few hundred keV range may not be significantly affected. Energy spectra and pitch angle distributions were measured over the energy range 160 keV to 2.4 MeV with a combination of three spectrometers. Fluxes of energetic electrons (greater than 4 MeV) were measured with high sensitivity in each of two large plastic scintillator anticoincidence counters surrounding a germanium spectrometer.

Imhof, W. L.↗
NASA NTRS1976

Analysis of high resolution satellite data for cosmic gamma ray bursts

Cosmic gamma ray bursts detected a germanium spectrometer on the low altitude satellite 1972-076B were surveyed. Several bursts with durations ranging from approximately 0.032 to 15 seconds were found and are tabulated. The frequency of occurrence/intensity distribution of these events was compared with the S to the -3/2 power curve of confirmed events. The longer duration events fall above the S to the -3/2 power curve of confirmed events, suggesting they are perhaps not all true cosmic gamma-ray bursts. The narrow duration events fall closely on the S to the -3/2 power curve. The survey also revealed several counting rate spikes, with durations comparable to confirmed gamma-ray bursts, which were shown to be of magnetospheric origin. Confirmation that energetic electrons were responsible for these bursts was achieved from analysis of all data from the complete payload of gamma-ray and energetic particle detectors on board the satellite. The analyses also revealed that the narrowness of the spikes was primarily spatial rather than temporal in character.

Imhof, W. L.↗
NASA NTRS1973

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

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.↗
NASA NTRS1973

Preliminary results from the first satellite of a high-resolution germanium gamma-ray spectrometer: Backgrounds from electron bremsstrahlung and from electron-positron annihilation

Detailed data are presented on the bremsstrahlung backgrounds measured by a satellite-borne high resolution Ge(Li) gamma ray spectrometer. Two bremsstrahlung classes were discussed: (1) those arising from radiation belt electrons stopping in the vicinity of the spectrometer, and (2) bremsstrahlung produced by electrons precipitating into the earth's atmosphere.

Imhof, W. L.↗