High Purity Germanium (HPGe) and BGO

Figure 1. A closeup of BGO and HPGe in a detector.

Gammasphere's detectors use high purity germanium in order to increase a detector's probability of gamma-ray interaction. BGO (Bismuth Germanate) detectors surround each Ge Detector in Gammasphere to help with Compton scattering suppression. They form a hexagonal shape around the cylindrical Ge, and have an additional BGO "backplug", meaning each detector has 7 BGO contacts. Each detector produces ten different signals for the DAQ system known as the GeCenter, GeSide and 7 BGO signals, which are compacted by the analog pre-processing into four differential signals (GeCenter, GeSide, BGOSum & BGOPattern). Note that in figure 1, the actual outer portion of the detector has sides that are made up of a metal called hevimets, which are dense materials that form a shield around the Ge at a detector's point. The hexagonal closeup in the diagram shows the arrangement of Ge and BGO inside the detector.

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