Engineering topics

Radocinski, R. G.

Publications and source records attributed to Radocinski, R. G..

3 records

NASA NTRS1993

Gamma-ray imaging with germanium detectors

Externally segmented germanium detectors promise a breakthrough in gamma-ray imaging capabilities while retaining the superb energy resolution of germanium spectrometers. By combining existing position-sensitive detectors with an appropriate code aperture, two-dimensional imaging with 0.2-deg angular resolution becomes practical for a typical balloon experiment. Much finer resolutions are possible with larger separations between detectors and the coded aperture as would be applicable for space-based or lunar-based observatories. Two coaxial germanium detectors divided into five external segments have been fabricated and have undergone extensive performance evaluation and imaging testing in our laboratory. These tests together with detailed Monte Carlo modeling calculations have demonstrated the great promise of this sensor technology for future gamma-ray missions.

Mahoney, W. A.↗

NASA NTRS1988

Gamma-ray observations of Co-56 in SN 1987A

During observations of SN 1987A 286 days after the supernova explosion using a JPL high-resolution gamma-ray spectrometer, a line feature was found in the net supernova spectrum at an energy of 1240.8 + or - 1.7 keV, with an intrinsic width of 8.2 + or - 3.4 keV FWHM, and a net flux of 0.0021 + or - 0.0007 photons/sq cm per s. This feature is interpreted as the 1238 keV line from the decay of Co-56 in the supernova remnant. The blueshift and intrinsic broadening of the 1238 keV line are consistent with models incorporating mixing of the radioactive cobalt in the expanding eject.

Mahoney, W. A.↗

NASA NTRS1977

Thorium concentrations in the lunar surface. I - Regional values and crustal content

The reported investigation is based on data which have been obtained with the aid of a gamma-ray spectrometer which had been installed on the Apollo 15 and 16 spacecraft to map the composition of the overflown lunar regolith to a maximum depth of about 1 m. Two additional techniques for the analysis of orbital gamma-ray data have been developed. These techniques have provided basic confirmation for the Th results reported previously and one of them, the energy band method, has yielded results for Th with a sensitivity greater than previous analyses, particularly at low concentrations. Significant variations of radioactivity exist in highland areas. The lowest concentrations of radioactivity mapped by Apollo are found near the western limb, contrasting with concentrations in the eastern limb which run roughly a factor of two higher. An inverse relation has been found between Th concentration and crustal thickness. It is suggested that Th, once uniformly distributed, has been extracted from a zone of constant depth over much of the moon, and concentrated in crustal blocks of varying thickness.

Metzger, A. E.↗