Segment Geometry Optimization and Prototype Studies of a Multi-Coincidence GAGG Solar Neutrino Detector

A GAGG detector capable of dissecting a multi-coincidence solar neutrino interaction on ${}^{71}$Ga is under development for potential space-based applications. We identify three distinct detection signatures when ${}^{71}$Ge$^*$ is produced, two of which are significantly delayed in time and could be detected within a single large GAGG volume. Further optimizations can be made by optically isolating smaller segments of GAGG to maximize the probability of a spatial separation between the prompt/delayed signals. We construct and test prototype GAGG detectors capable of sub 7% energy resolution @ ${}^{137}$Cs and reliable detection of spatially-separated ${}^{57}$Co double-pulse decays.