Spectrometer SPI

Co-Principal Investigators:

Jean-Pierre Roques, CESR Toulouse, France

Roland Diehl, MPE Garching, Germany

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:

Overall design
Detector plane (EM)
Cryostat (STM)
Detector plane (FM) #1
Detector plane (FM) #2
The veto subsystem: Lower collimator ring : side-view, top-view, and the rear shield
The flight model: Fig.1, Fig. 2, Fig. 3,Fig. 4, Fig. 5
The flight model being mounted on the spacecraftFig.1, Fig. 2
The SPI flight model Fig.1, Fig. 2, Fig. 3 in Bruyeres-le-Chatel (science calibrations) with preliminary results using sources at long (~ 125 m) distance.
The SPI Calibration WWW page including latest results and pictures can be found here
A spectrum obtained during calibration
An image obtained during calibration (Co60 cal sources, 2 deg apart)
Coded mask

Narrow-line sensitivity (3, 10**6 s, July 2000)
Narrow line sensitivity (AO-2, June 2003)
Narrow line sensitivities (comparison with other missions, August 2003)
Continuum sensitivity (3, 10**6 s,E = E/2, July 2000)
Continuum sensitivities (JEM-X, SPI, IBIS, 3, 10**6 s, AO-1, Nov. 2000)
Continuum sensitivity (AO-2, July 2003)
Continuum sensitivities (comparison with other instruments, August 2003)
Key performance parameters of the SPI Spectrometer

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

Back to the Integral Payload page