Gamma ray detection efficiency of GAGG crystal scintillator using three tagged gamma ray techniques

A CubeSat with a prototype scintillating detector with a sensitive volume of Gadolinium-Aluminum-Gallium-Garnet crystal is being developed with a possible launch date of 2025. Its purpose is to characterize the background signals that mimic the neutrino interaction that the nu SOL (Neutrino Solar Orbiting Laboratory) team is looking for. An important part of the characterization of the backgrounds and the expected real signal is understanding the gamma ray photopeak efficiency of the prototype detector when compared to simulations performed in Geant4. To this end we have used three techniques to do a measurement of the gamma ray efficiency compared to simulation. The first is using electron capture sources that emit an X-ray before prompt emission of a de-excitation gamma ray, specifically Zn-65 and Mn-54. The second is using a beta(+) decay source wherein a positron annihilates on anatomic shell electron producing two back-to-back 511 keV gammas followed promptly by a de-excitation gamma, specifically (22) Na. The third is using a gamma cascade of two near-simultaneous de-excitation gammas from the same nucleus, specifically from Co-60 decay.