This array consists of six Compton-suppressed, high purity Germanium gamma detectors (HPGe) and a Sum-Energy and Multiplicity Spectrometer (SMS) made up of 14 independent Bismuth Germanate (BGO) scintillation crystals.
Each HPGe is a high energy resolution detector (≈ 2keV for gammas ∼ 1MeV) with a sixfold reduced background from Compton-scattered γ's. Decay schemes such as those in figure H.2 are obtained by detecting, simultaneously (within ∼ 20 nanosec.) two or more γ's.