Compton suppression tests on Ge and BGO prototype detectors for gammasphere

During the last decade the application of arrays of 10--30 Compton Suppressed germanium (CSG) detectors in the field of γ-ray spectroscopy has led to a number of significant advances in studies of nuclear structure. Despite the success of these instruments, most of them are limited to detecting two-fold (and in a few cases three-fold) coincidences from highmultiplicity cascades. To increase the detection sensitivity for weak cascades, proposals have recently emerged for construction of much larger arrays. In the USA, the proposed array, called GAMMASPHERE, is to have 110 large CSG detectors which will subtend a solid angle of almost 2π steradians, sufficient to permit routine acquisition of up to 5-fold coincidences from high-multiplicity cascades. This together with other improvements, will yield a resolving power several orders of magnitude greater than currents arrays. In Europe, an array of similar size and power, called EUROGAM, is currently being constructed. In this paper, we report on measurements of the Compton suppression and overall P/T ratio of two Ge detectors in a BGO shield of the honeycomb pattern. These were the first prototype CSG detector assemblies for GAMMASPHERE