Design and test of a prototype gas-sampling electromagnetic calorimeter of high granularity for the CPLEAR experiment

Abstract We have designed and tested a gas-sampling calorimeter of high granularity as a prototype for the electromagnetic calorimeter of the CPLEAR experiment. The prototype calorimeter, consisting of 18 layers of 1.5 mm thin lead converters interleaved with a total of 1152 high-gain tubes and 2304 pick-up strips, was tested in a tagged photon beam with photons in the energy range of 50 to 350 MeV. It well fulfilled the requirements of a good detection efficiency for photons above 50 MeV with a spatial resolution σ ≈ 5 mm for the photon conversion point and an energy resolution σ ( E )/ E ≈ 15%/√ E [GeV].