China’s Einstein Probe (EP) mission is designed for time-domain astrophysics with energy band of 0.5-4 keV. The payloads of EP include a wide-field X-ray telescope (WXT) and a follow-up X-ray telescope (FXT). The field of view (FOV) of WXT is about 3600 square degrees with sensitivity at least 10 times better than traditional X-ray all-sky monitors applying collimators or coded-masks. Back-side illuminated scientific CMOS (BSI sCMOS) is the best choice for WXT after several types of X-ray detectors are investigated. In this work, we study a BSI sCMOS sensor, GSENSE400BSI developed by Gpixel Inc., which is treated as a pathfinder for the focal plane detector of WXT. GSENSE400BSI has a pixel array of 2048×2048 with pixel size of 11 μm. We have characterized this BSI sCMOS as an X-ray detector. Based on the excellent performance of GSENSE400BSI, a new BSI sCMOS device with large sensitive area of 6×6 cm2 has been proposed as the focal plane detector for WXT.
The Einstein Probe (EP) is a small satellite dedicated to time-domain astronomy to monitor the sky in the soft X-ray band. It is a mission led by the Chinese Academy of Sciences and developed in its space science programme with international collaboration. Its wide-field imaging capability is achieved by using established technology of the micro-pore lobster-eye X-ray focusing optics. Complementary to this is deep X-ray follow-up capability enabled by a Wolter-I type X-ray telescope. EP is also capable of fast transient alerts triggering and downlink, aiming at multi-wavelength follow-up observations by the world-wide community. EP will enable systematic survey and characterisation of high-energy transients at unprecedented sensitivity, spatial resolution, grasp and monitoring cadence. Its scientific goals are mainly concerned with discovering new or rare types of transients, including tidal disruption events, supernova shock breakouts, high-redshift GRBs, and of particular interest, electromagnetic sources of gravitational wave events.