Description
Historically, charge-coupled devices (CCDs) have been the detector of choice for soft X-ray astronomy, successfully deployed on numerous missions over several decades, including XMM-Newton, Swift XRT, Suzaku, Chandra, and the upcoming ESA SMILE SXI mission. While highly successful, CCDs are particularly susceptible to radiation damage and must be operated at cold temperatures, typically around -100 °C.
For the upcoming ESA M7 candidate mission, THESEUS, it was determined that the focal plane of the SXI could only be cooled to approximately -40 °C, rendering CCDs unsuitable and necessitating alternative detector technologies. CMOS image sensors (CIS) have already proven effective for optical instruments, as seen in ESA’s flagship JUICE JANUS instrument. However, as of 2019, CIS technology lacked the full depletion and efficient charge collection required for high-performance X-ray spectroscopy, prompting further development.
In response, ESA engaged the Centre for Electronic Imaging (CEI) and Teledyne e2v (Te2v) to develop the world’s first bespoke X-ray-optimized CIS. Between 2019 and 2024, the CIS221-X sensor was designed, manufactured, and characterized. This 2 × 2 cm device achieves an energy resolution of 126 eV at 5.9 keV at -40 °C and meets all focal plane requirements except detector size. This talk will present the performance of the current sensor and the development of the next-generation 4.5 × 9 cm CIS321, which will enable the SXI on THESEUS and lead to the largest X-ray imaging array ever flown.
