An ASIC for ToF-PET application with MCP-PMTs

Abstract The micro-channel plate photomultiplier tube (MCP-PMT) demonstrates excellent sensitivity to single photoelectrons, with a rise time of less than 100 ps. It offers an exceptionally low transit time spread, around 10 ps for multi-photoelectrons and under 50 ps for single photoelectrons. This performance has the potential to enhance coincidence timing, improving image quality in positron emission tomography (PET) and advancing next-generation physics experiments. To meet the stringent demands of picosecond-level time resolution, we developed a prototype frond-end circuit, the FPMROC, designed to accurately measure the time of arrival from the MCP-PMT with a gain of 10 5 . For a target coincidence time resolution of 100 ps, the MCP-PMT contribution is limited to approximately 30 ps, requiring the FPMROC jitter to remain below 10 ps. The FPMROC is implemented using a 55 nm CMOS process and integrates 8 readout channels, a data builder, a high-speed serializer, periphery, and test circuits. Each channel comprises a low-noise preamplifier, discriminator, and time-to-digital converter (TDC) for both time of arrival and time-over-threshold measurements. Digital-to-analog converters, a phase-locked loop, and an serial peripheral interface are used for calibration and threshold adjustment, providing low jitter clocks, and slow control, respectively. Additionally, a charge injection circuit is incorporated for testing and calibration. A prototype design was submitted in July 2024, and the following sections present the architecture, key circuits and simulation results.