Efficient and cost effective “sum of rows and columns” readout for large numbers of SiPM arrays

In systems with many 1000 SiPM pixels and with one electronic channel per SiPM pixel, the total cost is usually dominated by the cost of the electronics. We present a simple and low-cost solution for reducing the cost of the electronics without significantly affecting the time and energy resolution. The method requires no active electronic components. We tested the method using the PETsys TOFPET2 ASIC and its readout system. The CTR time resolution is reduced by $12 \%$ compared to a readout with one electronic channel per SiPM pixel. We observed no measurable degradation of the energy resolution and negligible cross talk.