High Resolution Calorimetry with PWO-II

The light output of PbWO/sub 4/ crystals, produced at BTCP, has been significantly enhanced by an improved manufacturing technology. First large size crystals of 150 and 200 mm length have been tested assembled in 3/spl times/3 arrays using tagged photons between 64 MeV and 520 MeV energy. The scintillation light has been detected either with commercial photomultiplier tubes or new developed large area silicon avalanche photo diodes of 10/spl times/10 mm/sup 2/ active area. Excellent energy resolutions have been obtained in both cases. For the first time, a timing resolution well below 1 ns has been achieved with diode readout.