Development of a Gamma-Ray Box (GARBO)

Isomer decays, β–γ and electron–γ spectroscopy, α–γ fine structure studies, and Coulomb excitation are cases of nuclear structure experiments where the ideal detector is a compact, highly segmented, very efficient germanium (Ge) detector box. In order to develop such a structure, we are working on the R&D of large, segmented, high-purity planar Ge strip detectors (HPGeDSSD) which form the walls of such a box. We have developed a 92 mm×92 mm×20 mm HPGeDSSD, which has 16×16 orthogonal strips of 5 mm width. We are in the process of designing a focal plane detector for the Argonne fragment mass analyzer which consists of a five-sided box, each side having a HPGeDSSD backed by a large segmented clover HPGe detector. MCNP simulations indicate this detector would have an efficiency of ∼60% for 122 keV gamma rays and ∼15% for 1.33 MeV radiation, which is ideal for studying the decays of nuclei far from stability that are usually produced with very low cross-sections.