The large-scale modular BGO detection array (LAMBDA) design and test

Total absorption gamma-ray spectroscopy (TAGS) is a powerful tool for measuring complex \(\gamma\) $\gamma$ 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 \(\beta\) $\beta$ -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 \(\times\) $\times$ 60 mm \(\times\) $\times$ 120 mm BGO crystals and exhibits a high full-energy peak efficiency exceeding 80% at 0.5 \(\sim\) $\sim$ 8 MeV based on a Monte Carlo simulation. Currently, approximately half of the LAMBDA modules have been manufactured. Tests using \(\gamma\) $\gamma$ -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 \(\beta\) $\beta$ -delayed \(\gamma\) $\gamma$ -decay experiments was evaluated by commissioning measurements using the \(^{152}\) $_{}^{152}$ Eu source.