The INTEGRAL experiment

The International Gamma-ray Astrophysics Laboratory (INTEGRAL) is conceived as the next logical step in gamma-ray astronomy after the US Compton Gamma-Ray Observatory (CGRO) and the French/Russian SIGMA mission. The INTEGRAL scientific payload consists of two main instruments (Imager and Spectrometer) and two monitor instruments (X-Ray Monitor and Optical Transient Camera). The INTEGRAL spectrometer "SPI" is optimized for detailed measurements of gamma-ray lines and mapping of diffuse sources. It combines a coded aperture mask with an array of large volume, high-purity germanium detectors. The detectors make precise measurements of the gamma-ray energies over the 20 keV-8 MeV energy range. This paper presents the instrument characteristics these properties have been evaluated by means of Monte Carlo calculations. With the characteristic features It will be possible to study gamma-ray emission from compact objects or line profiles with a high-energy resolution and a good angular resolution.