Picosecond Timing Electronics for a DIRC-Like Detector at the Super Tau-Charm Facility

Abstract

The DIRC-like time-of-flight detector (DTOF) at the Super Tau-Charm Facility (STCF) in China is a Cherenkov light detector that uses the TOF technique to identify charged particles. To achieve the expected target that provides a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\sigma \pi $ </tex-math></inline-formula> /K separation at 2-Ge/c momentum, a single-photon time resolution of better than 50 ps is required, while the contribution from electronics should be lower than 15 ps. To meet the requirements with high channel count integration, the timing electronics using leading-edge discrimination and field-programmable gate array (FPGA)-based time-to-digital converters (TDCs) are employed in the DTOF detector. This article reports the results of the first phase of project where the timing electronics with 128 channels has been constructed and its performance has been evaluated. Including the uncertainty of system clock distribution and synchronization, the intrinsic timing resolution of the electronics is better than 10-ps rms. Taking fast microchannel plate photomultiplier tubes (MCP-PMTs) as Cherenkov photodetectors and adopting time-over-threshold (TOT) measurement for time walk correction, the measured single-photon time resolutions are better than 40-ps rms. The test results confirm that the proposed timing electronics has advantages of high precision and high integration, which is highly demanded in future picosecond timing detectors.