The Study of Calibration for the Hybrid Pixel Detector With Single Photon Counting in HEPS-BPIX

Abstract

The calibration process for a hybrid pixel detector designed for the High Energy Photon Source in China, called HEPS-BPIX, is presented in this article. The relationship between the energy and threshold is quantified for the threshold calibration based on a threshold scanning. For threshold trimming, a precise algorithm based on local digital to analog converter (LDAC) characteristics and a fast algorithm based on LDAC scanning are proposed in this article to study the performance of threshold digital to analog converters (DACs) that will be applied to pixels. The threshold dispersion was reduced from 46.28 mV without the algorithm to 6.78 mV with the precise algorithm, whereas it was 7.61 mV with the fast algorithm. For temperatures from 5 °C to 60 °C, the threshold dispersion of the precise algorithm varies in the range of 5.69 mV. In contrast, it is 33.21 mV with the fast algorithm, which can be recorrected to 1.49 mV. The measurement results show that the fast algorithm could obtain the applicable threshold dispersion for a silicon pixel module and took less time. In comparison, the precise algorithm could obtain better threshold dispersion but was time-consuming. The temperature dependence of the silicon pixel module noise was also studied to assess the detector working status. The minimum detectable energy threshold could be reduced to 0.83-4.36 keV at a temperature of 5 °C.