Anti-Compton shield for Compex germanium detector modules

A bismuth-germanate (BGO) anti-Compton shield (ACS) for Compex germanium detector modules was designed, built, and characterised. BGO performance was evaluated for light output and energy resolution. The response of the ACS shield and its impact on germanium detector spectra was measured for standard 60Co, 133Ba, and 137Cs sources. The results were compared to comprehensive Geant4 simulations. The ~70% improvement of the peak-to-total ratio for the 137Cs 662-keV γ-ray peak is in good agreement with expectations from the simulations. A 133Ba source exemplifies decay schemes of odd-A superheavy nuclei. Congruence between measured and simulated spectra indicates that the Compex plus ACS multi-detector module is well understood

Search for Weak Side Branches in the Electromagnetic Decay Paths of the 6526-keV 10+ Isomer in 54Fe

High-spin nuclear isomers in (Formula presented.) nuclei between doubly magic (Formula presented.) Ca and (Formula presented.) Ni provide an excellent testing ground for the nuclear shell model and questions related to isospin symmetry breaking in the vicinity of the proton drip line. The purpose of the present study is to investigate the possibility of weak electromagnetic decay branches along the decay paths of the 6526-keV (Formula presented.) isomer in (Formula presented.) Fe. The isomer was strongly populated by means of the fusion-evaporation reaction (Formula presented.) Mg((Formula presented.) Ar, (Formula presented.)) (Formula presented.) Fe. The Gammasphere array was used to detect (Formula presented.) -ray cascades emitted from the isomeric state. By means of (Formula presented.) coincidences, weak non-yrast decay branches can be discriminated, with the isomer’s half-life confirmed at (Formula presented.) ns. The yrast (Formula presented.)   (Formula presented.) cross-over transition was interrogated. The observations are compared with shell-model calculations