Optimization of Gamma-ray Detector Systems at the Target Location of the SECAR Recoil Separator

The SEparator for CApture Reactions (SECAR) at the Facility for Rare Isotope Beams (FRIB) is designed for studying low-energy reactions for nuclear astrophysics, including but not limited to (p, γ) and (α, γ) reactions. A set of 26 Bismuth Germinate (BGO) detectors can be positioned around the target to serve two primary purposes: to determine the location of the reaction and to provide coincidence measurements for downstream detectors. As part of SECAR’s commissioning, an algorithm was developed to apply Gaussian fits to GEANT4 gamma-ray spectra and return the average z position of the reaction for 11 known positions; preliminary analysis indicates a position-dependent accuracy of 2–5 mm. Further simulations were taken to optimize the performance of this algorithm, alongside ongoing experimental testing, the results of which will be presented. This work will continue to be refined using data from measurements of well-studied (p, γ) reactions and will play a key role in future experiments.