Design and characterization of a compact multi-detector gamma array for studies of induced gamma emission: spontaneous decay of 178m2Hf as a test case

Recent scientific attention has focused on the m2 isomeric state of Hafnium, 178m2Hf. The spontaneous decay of 178m2Hf takes the form of a cascade of gamma photons, totaling 2.4 MeV of energy per nucleus, or approximately 1.3 GigaJoules/gram. If all the decays were simultaneous, exawatt (10$^18$) energy outputs could be realized. A class of isomers called ``K-isomers'' has been studied to determine the possibility of xray-induced decay of the excited isomeric state. The purpose of the ``miniball'' detector system was to separate out possible induced cascades from the spontaneous decay cascades using nuclear calorimetry, in order to settle a recent scientific controversy involving claims of induced decay and counter-claims of null results.