Detection of gamma rays using a coupled array of high-purity germanium detectors

The characteristics of a seven-element hexagonal close-packed array of high-purity germanium detectors were measured. The energy resolution or full width at half maximum (FWHM) and full width at 10% maximum (FW.1M) were measured in both the uncoupled mode and the sum-coincidence mode between 333 keV and 2.612 MeV. The fractional peak efficiency improvement obtained in sum-coincidence mode compared with the uncoupled mode increased from 0% at 80 keV to 19.7% at 2.612 MeV. A Monte Carlo code developed to compare these results with theoretical models shows substantial agreement with experiments from 80 keV to 1.332 MeV. A description of the detector, signal processing electronics, data acquisition system, and software is given. A technique based on real-time compensation of gain and offset drift is developed to minimize the peak broadening in real-time sum-coincidence spectra. This technique allows data acquisition to commence shortly after turn-on while the system approaches temperature stabilization.