Among the variety of crystal calorimeters recently designed for several physics facilities, CALIFA (CALorimeter for In-Flight emitted gAmmas and light-charged particles) has
especially demanding requirements since it must perform within a
very complicated energy domain (gamma-ray energies from 0.1 to 20 MeV
and up to 300 MeV protons). As part of the R&D program for the Barrel
section of CALIFA, a reduced geometry prototype was constructed. This
prototype consisted of a 3 × 5 array of CsI(Tl) crystals of varying
dimensions, coupled to large area avalanche photodiodes. Here reported
are the details regarding the construction of the prototype and the
experimental results obtained at the NEPTUN tagged gamma beam
facility, reconstructing gamma energies up to 10 MeV. Dedicated Monte
Carlo simulations of the setup were also performed, enabling a deeper
understanding of the experimental data. The experimental results
demonstrate the effectiveness of the reconstruction method and helped
to establish the most suitable crystal geometry to be employed within
the forthcoming calorimeter.