Characterization of a Single DEPFET Module of DSSC X-Ray Camera at the Small Quantum System Instrument of the European XFEL

The European XFEL exhibits the capacity to generate both soft and hard X-rays, showcasing exceptional brightness, pulse duration, and coherence. Delivering up to 27,000 intense X-ray pulses per second at a maximum repetition rate of 4.5 MHz, it enables researchers to carry out groundbreaking time-resolved experiments in several research fields like chemistry, physics, and biology at an unprecedented speed, unlocking access to previously undiscovered realms. Nevertheless, optimal utilization of the European XFEL's capabilities requires the essential integration of advanced X-ray detectors. While the European XFEL already employs cutting-edge X-ray detectors operating at MHz frame rate, the growing demand for high-performance X-ray detector technology has spurred the development of innovative alternatives, such as the DEPFET Sensor with Signal Compression (DSSC). Tailored to meet the specific requirements of the European XFEL facility, particularly its repetition rate, the DSSC is capable of capturing up to 800 frames at a maximum frame rate of 4.5 MHz. During the calibration campaign in November 2022 at the Small Quantum System (SQS) instrument of the European XFEL, a single DEPFET module of the DSSC camera was instrumented, tested, characterized, and calibrated. Our key findings presented here reveal the outstanding performance of the DEPFET module. Notably, it shows a remarkable non-linear response of the pixels to incoming FEL photons, achieves single photon detection with an impressive Signal-to-Noise Ratio of approximately 50, and maintains a minimum noise level of around 8 Equivalent Noise Charge (ENC). In addition, the pixel exhibits the capacity to detect several thousand Aluminum K-alpha photons of 1.48 keV, highlighting its ample dynamic range for conducting single shot imaging experiments at MHz frame rate. The DEPFET sensor proves to meet the stringent specifications of the facility, thereby unlocking new imaging possibilities relevant for investigating samples with nanosecond time-scale resolution.