Performance study of a prototype readout electronics for the time-of-flight detectors of HIAF-HFRS facility

Abstract: In the High Energy FRagment Separator (HFRS) at the High Intensity heavy-ion Accelerator Facility (HIAF), plastic scintillation detectors are used for high-precision time-of-flight (ToF) measurements to identify the secondary ions from the reaction between the primary beam and the target. During the day-one experiments, the readout electronics for the ToF detectors is required to achieve a time resolution of 40 ps with a single-channel counting rate up to $10^6$ counts per second (cps). This study presents a prototype readout electronics for plastic scintillation ToF detectors, the system comprises a constant-fraction discriminator (ORTEC Model-935), a level conversion board, and a time digitization board. We developed an octal logic signal adapter to convert NIM signals into LVDS differential signals. For time digitization, a Filed Programmable Gare Array (FPGA) is utilized through the internal tapped delay line (TDL). The performance of time resolution and counting rate of the electronics system is evaluated using a high-precision pulse generator and a picosecond pulsed laser. The test results indicate that the single-channel time resolution is around 10 ps, with a maximum counting rate of 1.6 $\times$ $10^6$ cps. The overall average ToF resolution achieves 17.9 ps during the laser test at a repetition rate of 1 MHz. These results validate that the developed system meets the HFRS beamline's requirements for ToF resolution and counting rate.