A new position-sensitive silicon photomultiplier with submillimeter spatial resolution for photon-cluster identification

We present a new Silicon Photo-Multiplier topology (Interpolating SiPM, ISiPM), able to reach sub-millimeter spatial resolution in photon cluster identification. SiPMs are becoming widely used in different applications, from medical imaging to high energy physics, as gamma ray detectors, coupled with suited scintillating crystals. The intrinsic spatial resolution in such application is limited by the crystal size: smaller crystals can be identified only if many SiPMs (and then many readout channels) are read out. In the ISiPM the avalanche photodiodes are connected to few different readout channels, instead of the common output used in standard device. The cells are assigned to one of the available electrodes in such a way that the center of gravity of any arbitrary shaped group of cells can be reconstructed from a weighted function of the outputs. The devices have been fabricated with standard technologies, use a very limited number of readout channels, have reduced noise and can easily identified sub-millimeter crystals. The energy resolution achieved from the ISiPMs is still in an acceptable range for many applications. We present the prototyped sensor design and the results we obtained coupling it with different LYSO scintillators. Due to its very good results and the reduced number of readout channels, we consider the ISiPM a very promising alternative for photon-cluster detection systems.