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Proceedings Paper

Spectrometer SPI of the INTEGRAL mission
Author(s): Giselher G. Lichti; Volker Schoenfelder; Roland Diehl; Robert Georgii; Thomas Kirchner; Gilbert Vedrenne; Pierre Mandrou; Peter von Ballmoos; Pierre Jean; Francis Albernhe; Philippe Durouchoux; Bertrand Cordier; Nene Diallo; Filomeno Sanchez; Pierre Leleux; Patricia A. Caraveo; Bonnard J. Teegarden; James L. Matteson; Robert P. Lin; Gerald K. Skinner; Paul Connell
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Paper Abstract

INTEGRAL is ESA's high-energy astrophysics mission to be launched into a high eccentric orbit early in the next decade. One of the two mission's main telescopes is the gamma-ray spectrometer SPI. This instrument features a compact array of 19 high-purity germanium detectors shielded by a massive anticoincidence system. A coded aperture of the HURA type modulates the astrophysical signal. We present the spectrometer system and its characteristics and discuss the choices that led to the present design. The instrument properties like imaging capability, energy resolution and sensitivity have been evaluated by extensive Monte-Carlo simulations. The expected performance for narrow-line spectroscopy is characterized by an energy resolution of approximately 1.6 keV at 1 MeV, an angular resolution of approximately 2 degrees within a totally coded field of view of approximately 15 degrees, and a sensitivity of (2 - 5) multiplied by 10-6 gamma/(cm2 s) for 4 multiplied by 106 s observation time in the nominal energy range from approximately 20 keV and approximately 8 MeV. With these characteristic features it will be possible for the first time to explore the gamma-ray sky in greater depth and detail than it was possible with previous gamma- ray telescopes like SIGMA, OSSE and COMPTEL. In particular the field of nuclear astrophysics will be addressed with an unprecedented combination of sensitivity and energy. Especially the high-energy resolution allows for the first time measuring gamma-ray line profiles. Such lines are emitted by the debris of nucleosynthesis processes, by the annihilation process near compact objects and by the nuclear interaction between cosmic rays and interstellar matter. Lines of all these processes have been measured so far, but, owing to the relatively poor energy resolution, details of the emission processes in the source regions could not be studied. With the high-resolution spectroscopy of SPI such detailed investigations will be possible opening a wealth of astrophysical investigations.

Paper Details

Date Published: 18 October 1996
PDF: 17 pages
Proc. SPIE 2806, Gamma-Ray and Cosmic-Ray Detectors, Techniques, and Missions, (18 October 1996); doi: 10.1117/12.253981
Show Author Affiliations
Giselher G. Lichti, Max-Planck-Institut fuer Extraterrestrische Physik (Germany)
Volker Schoenfelder, Max-Planck-Institut fuer Extraterrestrische Physik (Germany)
Roland Diehl, Max-Planck-Institut fuer Extraterrestrische Physik (Germany)
Robert Georgii, Max-Planck-Institut fuer Extraterrestrische Physik (Germany)
Thomas Kirchner, Max-Planck-Institut fuer Extraterrestrische Physik (Germany)
Gilbert Vedrenne, Ctr. d'Etude Spatiale des Rayonnements (France)
Pierre Mandrou, Ctr. d'Etude Spatiale des Rayonnements (France)
Peter von Ballmoos, Ctr. d'Etude Spatiale des Rayonnements (France)
Pierre Jean, Ctr. d'Etude Spatiale des Rayonnements (France)
Francis Albernhe, Ctr. d'Etude Spatiale des Rayonnements (France)
Philippe Durouchoux, CEA Saclay/SAP (France)
Bertrand Cordier, CEA Saclay/SAP (France)
Nene Diallo, CEA Saclay/SAP (France)
Filomeno Sanchez, Univ. de Valencia (Spain)
Pierre Leleux, Univ. de Louvain (Belgium)
Patricia A. Caraveo, Istituto di Fisica Cosmica e Tecnologie Relative (Italy)
Bonnard J. Teegarden, NASA Goddard Space Flight Ctr. (United States)
James L. Matteson, Univ. of California/San Diego (United States)
Robert P. Lin, Univ. of California/Berkeley (United States)
Gerald K. Skinner, Univ. of Birmingham (France)
Paul Connell, Univ. of Birmingham (United Kingdom)

Published in SPIE Proceedings Vol. 2806:
Gamma-Ray and Cosmic-Ray Detectors, Techniques, and Missions
Brian D. Ramsey; Thomas A. Parnell, Editor(s)

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