Construction of a 6×6 BGO array and its measurement of low-energy photons

A 6×6 BGO array as a prototype of precise fully active electromagnetic calorimeter has been constructed. It consists of 36 Chinese-made BGO crystals, each being 20mm by 20mm in cross section and 200mm in. depth, equipped with photomultiplier readout. To obtain linearity over a wide dynamic range, both the anode signal and a dynode signal were digitized. The array has been tested with monochromatic photons produced via (p,γ) reactions at the IHEP Van de Graaff accelerator in the energy range up to 21MeV. The response for photons has shown to be linear in this energy range. The FWHMenergy resolution obtained follows a E~(-(1/2)) dependence and is superior to that of BGO arrays reported in the literature.