Engineering topics
Publications and source records attributed to Stang, P. D..
A coded aperture imaging system was designed for the Gamma-Ray imaging spectrometer (GRIS). The system is optimized for imaging 511 keV positron-annihilation photons. For a galactic center 511-keV source strength of 0.001 sq/s, the source location accuracy is expected to be + or - 0.2 deg.
High resolution gamma-ray spectroscopy is a relatively new field that holds great promise for further understanding of high energy astrophysical processes. When the high resolution gamma-ray spectrometer (GRSE) was removed from the GRO payload, a balloon program was initiated to permit continued development and improvement of instrumentation in this field, as well as continued scientific observations. The Gamma-Ray Imaging Spectrometer (GRIS) is one of the experiments selected as part of this program. The instrument contains a number of new and innovative features that are expected to produce a significant improvement in source location accuracy and sensitivity over previous balloon and satellite experiments.
A balloon-borne gamma ray telescope with an approximately 130 cu cm high purity germanium detector was flown over Australia to detect sharp spectral features from the galactic center direction. A 511 keV positron annihilation line was observed at a flux level of (1.21 plus or minus 0.22) x (10/cu cm) photons/sec/sp cm. Suggestive evidence for the detection of the three-photon positronium continuum is presented. The possible origin of the positrons is discussed.