The solar X-ray detector (SXD) is the main scientific instrument onboard the Macau Science Satellite-1B (MSS-1B). It consists of two parts—a soft X-ray detection unit and a hard X-ray detection unit—with a dual-channel design comprising a silicon drift detector (SDD) and a cadmium zinc telluride detector (CZT). Both the precise energy spectrum and intensity of the Sun can be simultaneously obtained by the SXD, hence to quantify the level of solar flares and study their evolutionary process.

This study aims to calibrate the detection efficiencies of the SDD and CZT, so as to invert the observed data for obtaining real solar X-ray data.

The Monte Carlo code MCNP5 (Monte Carlo N-Particle 5) was employed to calculate the SDD and CZT efficiencies by simulation. Soft and hard X-ray detection efficiency calibration experiments were performed using a monochromatic X-ray ground calibration facility via relative measurement methods.

The experimental results for the SDD-1 and CZT-1 efficiency calibration agree well with the predicted results of the simulation. In particular, the maximum relative error between the experimental and simulated efficiencies of SDD-1 dose not exceed 3.59%@16 keV, and the maximum relative error between the experimental and simulated efficiencies of CZT-1 dose not exceed 9.54%@120 keV. The relative expanded uncertainty of the monochromatic X-ray flow intensity measurement is 3.8% (k=2), and the uncertainty of the simulation results for the SXD is 0.12%.

This study provides not only data support for SXD onboard MSS-1B satellite, but also valuable guidance for the calibration of other astronomical satellites' detectors in the future.