Readout Electronics Development Based on an ASIC for PET Detector using PMT-Quadrant-Sharing

In this work, a new readout electronics system based on an eight-channel readout ASIC is developed for PET detector using PMT-quadrant-sharing (PQS) design. A PQS detector module consists of a 9x9 LYSO crystal block (2.1x2.1x10mm(3) each crystal) coupled to four PMTs. We propose a compact design of readout electronics with time based readout ASIC and Time-Digital-Convertor (TDC) programmed in Field-Programmable-Gated-Array (FPGA). The function of the ASIC is to convert both signal charge and timing information into digital timing pulses which will be processed by back-end TDC. In this way, highly flexible and low cost electronics is developed because the traditional Analog-Digital-Convertor (ADC) and Constant-Fraction-Discriminator (CFD) are replaced. Preliminary tests show that the ASIC has demonstrated good linearity and uniformity. To test the performance of our ASIC based electronics, we compared it with a traditional high speed ADC based data acquisition system which was previously developed in our lab. Crystal flood map was acquired on both acquisition systems and the crystals were clearly identifiable. A coincidence timing resolution of about 1.8 ns was achieved, which can be furthered improved through time walk error correction. We conclude that the proposed electronics is feasible for PQS PET detectors.