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 20 mm by 20 mm in cross section and 200 mm 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 21 MeV. The response for photons has shown to be linear in this energy range