Exploring large-volume GAGG scintillators for use in MeV gamma-ray astrophysics

Gamma-ray astrophysics in the MeV band is an exciting field in astronomy due to its potential for multi- messenger astrophysics. It has, however, remained under-explored when compared to other wavelengths. One reason for this observational gap is the difficulties with measuring these high-energy photons and the requirement of large amounts of detection material. In this work, we investigate the usage of large-volume GAGG scintillators for use as a calorimeter in future MeV telescopes. We developed a 5 x 5 array calorimeter utilizing 1 x 1 x 6 cm3 GAGG crystals with onsemi C-series SiPM readout. We tested the calorimeter at the High Intensity Gamma-ray Facility (HIGS) with monoenergetic beams ranging from 2-25 MeV. Finally, we also investigate larger 1 x 1 x 8 cm3 crystals and characterize their response across their depth when their surface treatment is either polished or frosted.