Characterization of a pnCCD-based Camera for Applications at the 100 m X-Ray Test Facility*

The 100 m long X-ray test facility (100XF for clarity) in Institute of High Energy Physics of CAS has been playing an increasingly important role in the X-ray astronomy field in China. 100XF has been contributing to the missions under development, such as the Einstein Probe mission. The facility has also been providing support to R & D of focusing X-ray optics in China that will enable future X-ray telescopes to be realized, such as the enhanced X-ray Timing and Polarization (eXTP) mission. A pnCCD-based camera has been employed at 100XF to rapidly measure the performance of the X-ray optics. In this work, we study the performance of the camera and its spectral and imaging applications at 100XF. The camera system can provide a high frame readout rate, with a low readout noise <3 e(-). It is sensitive to X-ray photons in the 3-10 keV energy band with a high quantum efficiency exceeding 90%. Actually, the low threshold of detection energy range can reach down to 0.2 keV. The energy resolution can reach 145.2 eV for single events and 154.8 eV for all valid events (including single events and split events) at 6.4 keV. The camera also exhibits excellent imaging capability in both the full frame mode and the windowing mode, with a readout rate of up to 1000 Hz. Finally, a prototype of a focusing X-ray mirror shell of eXTP was smoothly measured with this camera. The obtained on-axis point-spread function and half-power diameter are consistent with expectations. It is proven that the camera can improve the capability of 100XF in characterizing the X-ray optics. This camera will be very useful for performing on-ground calibrations for future X-ray telescope missions.