ABSTRACT
The Berkeley High-Resolution Ball involved the first use of bismuth germanate (BGO) for anti-Compton shields for Ge detectors. The system efficiency involves the questions of how many Ge detectors at what distance from the target. The Ge detectors are out of sight inside the BGO shields, but their small liquidnitrogen dewars are visible, as are the pre-amps for the shields. In theory such a system would have an intrinsic resolution only a factor of two worse than solid-state Ge detectors, and it has a number of attractive properties including a much better response function. It has become quite clear that the use of Compton-suppressed Ge detectors is an exciting step forward in nuclear γ-ray spectroscopy. The resulting compact shield permitted rather close packing of 21 detectors around a target. In addition, a small central BGO ball gives the total γ-ray energy and multiplicity, as well as the angular pattern of the γ rays.
