A compact, water-cooled, 144-channel photo sensor module for γ detection in PET

We present a very compact photo sensor module with an area of 32.8 × 32.0mm2 containing 12 × 12 Silicon Photomultipliers (SiPMs) in a pitch of (2.5mm)2. The readout of the 144 channels is done by highly specialized PETA5 ASICs (Position Energy Timing Asic) which offer self triggered hit detection (including neighbor logic and fast veto mechanisms), time stamping with 50ps bin width and digital amplitude measurement. The module uses a substrate which is cooled by a fluid running in internal channels. The SiPMs are glued and wire bonded in a regular pattern on the top side, the ASICs are flip chip mounted at the bottom side. Several modules will be plugged into a control and data readout PCB. The full height of these parts is below 1cm. The module can be used to read scintillator crystal arrays with a pitch of only 2.5mm in a 1 : 1 coupling, or smaller crystals with light spreaders. We present the module design and the first results obtained with 1 : 1 coupled LYSO crystal arrays.