ECAL0 is a new electromagnetic calorimeter designed for studying generalized parton distributions at the COMPASS II experiment at CERN. It will be located next to the target and will cover larger photon angles (up to 30 degrees). It is a modular high-granularity Shashlyk device with total number of individual channels are more than 1700. Since it operating in the magnetic field the light readout is based on solid state photodetectors – micropixel avalance photodiodes (MAPD). To provide high linearity in a wide dynamic range of energies MAPD with high pixel density ($\sim10^4 mm^{-2}$) can be used only. In this talk studying of the performance of the various types of MAPD with ECAL0 modules is presented.

Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna 141980, Russia

Warsaw University of Technology, Institute of Radioelectronics, Nowowiejska 15/19, Warsaw 00-665, Poland