Ground Calibration Result of the Wide-field X-ray Telescope (WXT) onboard the Einstein Probe

Huaqing Cheng; Chen Zhang; Zhixing Ling; Xiaojin Sun; Shengli Sun; Yuan Liu; Yanfeng Dai; Zhenqing Jia; Haiwu Pan; Wenxin Wang; Donghua Zhao; Yifan Chen; Zhiwei Cheng; Wei Fu; Yixiao Han; Junfei Li; Zhengda Li; Xiaohao Ma; Yulong Xue; Ailiang Yan; Qiang Zhang; Yusa Wang; Xiongtao Yang; Zijian Zhao; Longhui Li; Ge Jin; Weimin Yuan

arXiv · 2505.18939

Ground Calibration Result of the Wide-field X-ray Telescope (WXT) onboard the Einstein Probe

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Abstract

We report on results of the on-ground X-ray calibration of the Wide-field X-ray Telescope (WXT) built from novel lobster-eye micro-pore optics, onboard the Einstein Probe (EP) satellite. To fully characterize the instrumental performance and properties, a series of tests and calibrations have been carried out at different levels of devices, assemblies and the complete module before the launch of EP. In this paper, we present the calibration results of three flight model modules (FM1, FM5 and FM11) obtained during their end-to-end module calibration experiments carried out at the 100-m X-ray Test Facility (100XF) of IHEP, CAS. Measurements of the Point Spread Function (PSF), effective area, and energy response were performed for multiple incident directions and several characteristic X-ray emission line energies. Specifically, the distributions of the PSF and effective areas are found to be roughly uniform across the FoV, in large agreement with the prediction of lobster-eye optics. Their energy dependence behavior aligns well with theoretical predictions and Monte Carlo simulations. At 1.25 keV, the full width at half maximum (FWHM) of the focal spot is in range of 3-7 arcmin (a median of 4.2) and the effective area in range of 2-3 $cm^2$. Noticeably, the flight model instruments demonstrate a $\sim1.5$ arcmin spatial resolution improvement over the previously launched Lobster Eye Imager for Astronomy. The properties of the complementary metal-oxide semiconductor (CMOS) sensors were also calibrated. The gain coefficients are in range of 6.4-6.9 eV/DN. The energy resolutions are in range of 120-140 eV at 1.25 keV, meeting design requirements. These calibration results have been ingested into the first version of calibration database (CALDB) and applied to the analysis of the scientific data acquired by WXT after the launch of EP.

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Huaqing Cheng, Chen Zhang, Zhixing Ling, Xiaojin Sun, Shengli Sun, Yuan Liu, Yanfeng Dai, Zhenqing Jia, Haiwu Pan, Wenxin Wang, Donghua Zhao, Yifan Chen, Zhiwei Cheng, Wei Fu, Yixiao Han, Junfei Li, Zhengda Li, Xiaohao Ma, Yulong Xue, Ailiang Yan, Qiang Zhang, Yusa Wang, Xiongtao Yang, Zijian Zhao, Longhui Li, Ge Jin, Weimin Yuan. 2025-05-25. Ground Calibration Result of the Wide-field X-ray Telescope (WXT) onboard the Einstein Probe. https://arxiv.org/abs/2505.18939

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