Interpolating Silicon Photo-Multiplier: a Novel Position Sensitive Device with Submillimeter Spatial Resolution and Depth of Interaction Capability

Silicon Photo Multiplier are becoming widely used, coupled with suited scintillating crystals, as gamma-ray detectors in high energy physics and medical imaging applications. We present a novel device topology, able to reach sub-millimeter spatial resolution with very few readout channels. The basic idea consists to connect each cell of a SiPM to one of the several readout channels. A cluster of photons, for example from a scintillator, illuminates the cells and the signal is shared between the readout channels, in such a way that the amplitudes include the spatial information. Two prototype generations have already been produced and they both have shown very good results in terms of spatial resolution: they are able to identify crystal arrays down to 0.8 x 0.8mm2 crystals, with only four readout channels. The measurements with the prototyped devices and future outlook are presented.