Prototype Design of the Time Measurement Circuit for SiPM-based T0 Detector of CEE

Inhalt:
In Cooling Storage Ring (CSR) External-target Experiment (CEE), the T0 detector, based on plastic scintillator and SiPM, is located in the front portion of the beam target. It is designed to record the beam's arrival time and provide the start time to the other detectors. In this paper, a prototype design of the readout electronics system for the T0 detector is presented. This design aims to reach a high precision time measurement and requires a resolution under 50 ps RMS each channel for the whole system — the combination of T0 detectors and readout electronics system. To achieve high precision time measurement, a circuit divided into two parts is implemented — the pre-amplification and discrimination circuit based on NINO chip and the circuit that realizes Time-to-Digital Converter (TDC) based on FPGA. Meanwhile, the temperature compensation circuit for the SiPMs is implemented to eliminate the temperature drift by altering the operating voltage (Vop) of the SiPM. By conducting a series of tests to evaluate the performance of this prototype circuit, the function has been proven to be successful with a resolution of the readout electronic system better than 15 ps RMS within the dynamic range of detector output signals. A high resolution of voltage adjustment can be made using the temperature compensation circuits.