The scientific calibration of the PICsIT Engineering Model detector of the IBIS telescope

IBIS is the imaging telescope onboard the European Space Agency's (ESA) satellite INTEGRAL, which will be launched in September, 2001. IBIS will produce images of the gamma-ray sky in the region between 15 keV and 10 MeV by means of a position sensitive detection plane coupled with a coded aperture mask. The detection plane of IBIS comprises two position sensitive layers: ISGRI and PICsIT. PICsIT is a 64x64 unit array of equivalent to 0.75 cm(2) crystals operative in the energy range between 150 keV and 10 MeV. The engineering model (EM) of PICsIT has now been calibrated and delivered to ESA. In this work we present the preliminary results obtained from the PICsIT EM scientific calibrations. These tests were the first occasion for measuring the general behaviour of the detector in terms of the key scientific performances. The gain, linearity, energy resolution, lower energy threshold and background counting rate for each detection unit and the variation of these parameters as a function of pixel position and were measured. Preliminary results regarding event multiplicity distribution, and energy resolution degradation for multiple events are also presented.