Design of a multi-channel high-resolution TDC based on FPGA

High-resolution multi-channel time-to-digital converters (TDC) is an important tool in many physical experiments. In the HL-2A tokamak device,a real-time double-ring neutron time-of-flight (TOFII) spectrometer system used to measure the neutron energy spectrum requires the TDC to have a measurement accuracy of 100 ps and a number of 90 channels. In the measurement-device-independent quantum key distribution (MDI-QKD) system, multi-channel and high-precision TDC is also one of the key factors affecting the final bit rate. In this paper, we propose the field programmable gate array (FPGA) method to develop the TDC. By using the coarse-fine combined measurement method, we complete the TDC design through the tapped delay line formed by the internal carry chain of the FPGA. Our method achieves a time measurement of 90 channels and a time resolution of 52 ps.