The Large-Scale Modular BGO Detection Array (LAMBDA) Design and Test

Total absorption gamma-ray spectroscopy (TAGS) is a powerful tool for measuring complex γ transitions, which has been effectively applied to the study of reactor decay heat. This paper presents the design of a new TAGS detector, the large-scale modular BGO detection array (LAMBDA), tailored for measuring β -decay intensity distributions of fission products. The modular design allows the LAMBDA detectors to be assembled in various configurations. The final version of LAMBDA consists of 102 identical 60 mm × 60 mm × 120 mm BGO crystals and exhibits a high full-energy peak efficiency exceeding 80 ∼ 8 MeV based on a Monte Carlo simulation. Currently, approximately half of the LAMBDA modules have been manufactured. Tests using γ -ray sources and nuclear reactions demonstrated favorable energy resolution, energy linearity, and efficiency uniformity across the modules. Forty-eight modules have been integrated into the prototype LAMBDA-I. The capability of LAMBDA-I in β -delayed γ -decay experiments was evaluated by commissioning measurements using the ^152 Eu source.