Resolution measurement of next generation scintillator GAGG at high energy using the 992 keV resonance of the ²⁷Al(p,γ)²⁸Si reaction

For in-beam γ-ray spectroscopy experiments with fast beams, the resolution after Doppler correction depends strongly on the position and energy resolution of γ-ray detectors. Scintillator based detector arrays usually have rather low energy and position resolution. For experiments at RIKEN RIBF a new detector array based on cerium doped Gd₃Al₂Ga₃O₁₂, or GAGG(Ce), crystals is being developed. The prime objective of this research project is to measure the energy resolution of the GAGG especially for high energy γ-rays. To produce these high energy γ-rays, the ²⁷Al(p,γ)²⁸Si reaction was used. The experiment was performed at the RIKEN Pelletron which provides proton beams up to 3 MeV. Four GAGGs, including the biggest crystal with a size of 35mm*35mm*100mm, and 9 NaI crystals of the existing detector array, DALI2, were arranged around the ²⁷Al target. Different combinations of PMTs and GAGG detector geometries were employed for the test experiment. Standard calibration sources, and γ-ray transitions from resonances in ²⁸Si up to 10.5 MeV were used to determine the energy resolution of GAGG detectors coupled with various types of PMTs. In this presentation we show the current status of the data analysis and first results on the performance of GAGG as a detector for high energy γ-rays.