Different types of events recorded by SPI detectors. From the three cosmic photons (green, 1−3), single events (SE, 1), multiple events (ME, 2), or self-vetoed events (3) may arise. Background event types are from photons (blue) which may be prompt cosmic-ray (red dashed) related (4, 5), or delayed and radioactivity events (6); some of these may, or may not, be vetoed by the anticoincidence. Structural elements with different materials may create continuum photons and lines at different, characteristic, energies.