A SILICON IMAGING CALORIMETER PROTOTYPE FOR ANTIMATTER SEARCH IN-SPACE - EXPERIMENTAL RESULTS

This report presents the results obtained with a prototype silicon-tun gsten (Si-W) electromagnetic calorimeter, conceived as a fine-grained imaging device to carry out studies of the antimatter component in pri mary cosmic radiation. The calorimeter prototype contains 20 x, y samp ling layers interleaved with 19 showering material planes. One sensiti ve layer is obtained with two silicon strip detectors (Si-D) (60 x 60) mm2, each divided into 16 strips, 3.6 mm wide; the two detectors are assembled back to back with perpendicular strips. This allows the tran sverse distributions of the shower in both coordinates at each samplin g (0.5 X0) to be pictured. The basic characteristics of the design and the experimental results obtained on a test beam at the CERN proton s ynchrotron (PS) for electrons and pions are reported. The main results presented are the response of the calorimeter to the electron at vari ous energies (1-7 GeV), and the transverse shower profiles at differen t calorimeter depths as well as the patterns of the electromagnetic sh ower and those of the interacting and non-interacting pions. The capab ility of the calorimeter in measuring the direction of the incoming el ectromagnetic particle from the pattern of the shower has been evaluat ed at different energies. These results are encouraging in view of the possible use of this detector to search for high-energy gamma sources in space.