Endcap calorimeter for SuperBelle based on pure CsI crystals

The design of the Belle endcap calorimeter based on pure CsI is presented. The suggested calorimeter consists of pure CsI crystals with readout by vacuum photopentodes followed by the analysis of the shape of the output signal. The results of tests of the counters are presented. Photopentodes provide a gain factor about 150–200 without magnetic field. Tests with magnetic field show that the gain factor drops down about 3.5 times in axial magnetic field of 1.5 T. The preamplifier-shaper has been developed which provides electronics noise of 1000 photoelectrons. The beam test results showed the energy resolution about 2.2% for 100 MeV photons and time resolution better than 2 ns. Radiation hardness tests of the counters have been carried out.