Continuum Background

The continuum background can be split into several components, depending on their origin. On the one hand, the radiation coming from outside the instrument. This can be the cosmic diffuse gamma ray flux that comes in through the instrument aperture, or leakage through the BGO shield of cosmic diffuse gamma ray radiation and gamma continuum radiation from the spacecraft (induced by energetic cosmic ray particles). On the other hand, scattering in the germanium detectors of neutrons that were produced in the spacecraft or other parts of the instrument. Finally, there are background components produced inside the spectrometer detectors. These consist of localized decays, non localized decays and decays. The continuum emission from the mask and the BGO emission when the veto electronics are blacked out (veto dead time) are negligible. The individual components and the total continuum background emission are illustrated in Figure .

Figure: The continuum background components for SPI. The individual components are identified. The total background spectrum is indicated with the black line.