To meet the stringent time calibration requirements for the Belle II experiment upgrade, particularly for its large-size KL and Muon Detector comprising tens of thousands of scintillator channels with time resolutions better than 100 ps, we developed a compact and high-speed time calibration system. The system utilizes a laser diode as its light source, integrated with a fast pulse laser drive circuit that employs high-speed switching GaN FETs and gate drivers. A prototype was constructed and rigorously evaluated using scintillators, achieving timing resolutions of about 13 ps for a single calibration channel. Furthermore, internal deviations among calibration channels were analyzed, with most measurements remaining within 250 ps. These results highlight the system's precision, scalability, and suitability for large-scale particle physics experiments.
@article{arxiv.2509.20029,
title = {Development of a time calibration system for the KLM upgrade in the Belle II experiment},
author = {Ziyu Liu and Xiyang Wang and Shiming Zou and Xiaolong Wang and Junhao Yin and Minggang Zhao},
journal= {arXiv preprint arXiv:2509.20029},
year = {2026}
}