Development of a time calibration system for the KLM upgrade in the Belle II experiment

Abstract

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.

Figures (10)

• Figure 1: Schematic of the laser calibration system, depicting laser heads positioned on one side and photodetectors on the opposite side, with $T_i$ (where $i = 1,~2,~3, ...,~N$) representing the time recorded by DAQ.
• Figure 2: The schematic of the laser driver.
• Figure 3: Workflow of single channel. Only critical components are demonstrated.
• Figure 4: Schematic of the power supply. The system utilizes two sets of power.
• Figure 5: Schematic of the laser diode circuit. The diode and resistor $R3$ are included to minimize the influence of reverse current.