Application of GEANT4 for Efficiency Modeling of an Implantation Detector System used in Beta-Decay Studies of Exotic Nuclei

Beta decay is a highly sensitive and selective means for assessing the properties of exotic nuclei when there are only a small number of atoms available for study. One method of performing beta decay studies involves the implantation of radioactive ions of exotic nuclear species directly into a detector. Following implantation and subsequent decay, event by event reconstructions using spatial and temporal information allow for the unique identification of the parent and daughter decays. A feature of performing beta decay studies using an implantation detector is that one cannot determine the absolute efficiencies of the detectors via source measurements alone. Instead, source measurements must be reproduced in simulation where the origin of the source is moved physically inside the detector in order to reproduce the experimental conditions for implantation. A new CeBr₃ implantation scintillator was utilized in a recent beta decay experiment at the National Superconducting Cyclotron Laboratory that was performed in July, 2018. Efforts are underway to simulate the efficiencies and response of the  CeBr₃ detector and ancillary LaBr₃ and high-purity Germanium detection systems used. Preliminary results modeling the systems and a NIST-calibrated  ^154,155Eu source will be presented.