Proton in-beam tests of the Lund R3BR3B calorimeter prototype

A small-scale prototype of the CALIFA calorimeter, which is a subsystem of the R3BR3B detector, has been constructed and tested using the 179 MeV proton beam at The Svedberg Laboratory, Uppsala, Sweden. The prototype consists of 15 CsI(Tl) elements with a size of 10×30×130mm3, assembled in a 3×53×5 array. Each crystal was individually tested using γ-rayγ-ray sources and the light output uniformity along the longitudinal axes was adjusted to better than 0.6%. An energy resolution of ∼0.5%∼0.5% has been achieved with a technique consisting of non-uniform polishing/lapping of the crystal side facets. The performance of the prototype is evaluated using experimental data and GEANT4 simulations. Results from the experiment, including multiplicity and sum spectra, show good agreement with simulations. The quality requirements for CsI(Tl) elements for construction of a high precision calorimeter/spectrometer are summarized.