The scintillating FIber Tracker (FIT) has been designed as a tracking detector for the upcoming High Energy cosmic-Radiation Detection (HERD) facility. The FIT combines excellent angular resolution with precise charge reconstruction measurements for cosmic-ray detection. The tracker consists of multiple tracking planes made of fiber mats, arranged in two orthogonal directions, and read out with Hamamatsu S13552-10 SiPM arrays. A custom-made ASIC, the BETA ASIC, has been developed to fulfill the stringent requirements for noise, linearity, dynamic range, and power consumption of space applications. This work reports the performance of the SiPMs and the BETA read-out system used in FIT. Our setup has been optimized, characterized, and calibrated using an LED light source. Additionally, we discuss the system's performance in generating efficient triggers for the identification of ionizing particles.
Lathika et al. (2025) studied this question.