Single‐shot experiments at the soft X‐FEL FERMI using a back‐side‐illuminated scientific CMOS detector

The latest Complementary Metal Oxide Semiconductor (CMOS) 2D sensors now rival the performance of state‐of‐the‐art photon detectors for optical application, combining a high‐frame‐rate speed with a wide dynamic range. While the advent of high‐repetition‐rate hard X‐ray free‐electron lasers (FELs) has boosted the development of complex large‐area fast CCD detectors in the extreme ultraviolet (EUV) and soft X‐ray domains, scientists lacked such high‐performance 2D detectors, principally due to the very poor efficiency limited by the sensor processing. Recently, a new generation of large back‐side‐illuminated scientific CMOS sensors (CMOS‐BSI) has been developed and commercialized. One of these cost‐efficient and competitive sensors, the GSENSE400BSI, has been implemented and characterized, and the proof of concept has been carried out at a synchrotron or laser‐based X‐ray source. In this article, we explore the feasibility of single‐shot ultra‐fast experiments at FEL sources operating in the EUV/soft X‐ray regime with an AXIS‐SXR camera equipped with the GSENSE400BSI‐TVISB sensor. We illustrate the detector capabilities by performing a soft X‐ray magnetic scattering experiment at the DiProi end‐station of the FERMI FEL. These measurements show the possibility of integrating this camera for collecting single‐shot images at the 50 Hz operation mode of FERMI with a cropped image size of 700 × 700 pixels. The efficiency of the sensor at a working photon energy of 58 eV and the linearity over the large FEL intensity have been verified. Moreover, on‐the‐fly time‐resolved single‐shot X‐ray resonant magnetic scattering imaging from prototype Co/Pt multilayer films has been carried out with a time collection gain of 30 compared to the classical start‐and‐stop acquisition method performed with the conventional CCD‐BSI detector available at the end‐station. We demonstrate the possibility of using a CMOS 2D sensor for time‐resolved pump–probe XUV FEL experiments. We gained a factor of 30 in acquisition time compared to the use of a commercial CCD‐BSI.