Spectrometer SPI

Co-Principal Investigators: with collaborating scientific institutes in France (CESR Tolouse, CEA Saclay, CNES Toulouse), Germany (MPE Garching), Italy (IFCTR Milano), Spain (U Valencia), Belgium (U Louvain), United Kingdom (U Birmingham), USA (UC San Diego, LBL Berkeley, NASA/GSFC Greenbelt). 
The spectrometer SPI (SPectrometer on INTEGRAL) performs spectral analysis of gamma-ray point sources and extended regions in the 18 keV - 8 MeV energy range with an energy resolution of 2.2 keV (FWHM) at 1.33 MeV. This is accomplished using an array of 19 hexagonal high purity Germanium detectors cooled by a Stirling cooler system to an operating temperature of 85 K. A hexagonal coded aperture mask is located 1.7 m above the detection plane in order to image large regions of the sky (fully coded field of view = 16 degrees) with an angular resolution of 2.5 degrees. In order to reduce background radiation, the detector assembly is shielded by a veto (anticoincidence) system which extends around the bottom and side of the detector almost completely up to the coded mask. The aperture (and hence contribution by cosmic diffuse radiation) is limited to ~ 30 degr. A plastic veto is provided below the mask to further reduce the 511 keV background.

Further details of the current design can be accessed here:

Spectrometer SPI WWW home page at MPE Garching, Germany
Spectrometer SPI WWW home page at CESR Toulouse, France

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