Study of Calibration for the Dual-Threshold Hybrid Pixel Array Detector of HEPS-BPIX40

This article details the calibration process for the upgraded HEPS-BPIX40, a hybrid array pixel detector designed for the High-Energy Photon Source (HEPS) in China. The detector comprises 40 modules spliced together to form a 6M detector system, enabling a significant enhancement from a single threshold to dual thresholds. Following new design requirements, a dual-threshold calibration was conducted, encompassing the relationships between energy and thresholds, the local DAC (LDAC) S-curve scan, and the fine global DAC (GDAC) and LDAC thresholds for each pixel. An accurate algorithm based on LDAC characteristics was introduced for threshold fine-tuning. The study investigates pixel gain, chip-to-chip bias differences, and the mutual influence of dual thresholds. With the refined algorithm and adjusted gain and dual thresholds, the incidence of dead pixels was reduced to 0.5‰, and the minimum threshold energy reached approximately 3.0 keV. This work marks significant progress in large-scale pixel calibration. A 6M engineering prototype detector is planned for future construction at the HEPS, China.