New gamma-ray calorimeter have been develop ed for the MEGA Compton camera. They consist of arrays of small CsI(Tl) scintillator bars read out by Silicon PIN- diodes and low noise, self triggering frontend electronics. The length of the bars (the thickness of the calorimeter) can b e varied for different applications to fit the stopping power needed and the light loss tolerable. In this paper we present calibration results from 2cm long bars with diodes on one side, and 8 ...