Experimental Validation of a Front-End Stage for Future XFEL Detectors

New X-Ray pixel detectors are required to satisfy the challenging requirements from XFEL (X-ray Free Electron Laser) sources, including high frame rates, wide dynamic range, and low noise for single-photon sensitivity. In this work, we present a novel front-end architecture based on a Charge Sensitive Amplifier with predictive gain switching, and a Flip-Capacitor filter. The CSA is designed to achieve both a single photon resolution and a high dynamic range up to 10000 photons by employing an active control of the gain. The predictive gain switching circuit dynamically sets the proper gain by adding feedback capacitances in parallel. The predictive gain switching is based on the time instant at which the signal exceeds a specified threshold. When the CSA is in its highest gain configuration, a filter is connected to reduce the electronic noise and achieve the single photon resolution at 1 keV. To couple the CSA with the filter, a voltage-tocurrent converter has been designed. The filter is based on an architecture called Flip-Capacitor Filter and implements a fast trapezoidal weighting function. The first prototype of this front-end has been designed in 65 nm CMOS technology, and has already been submitted. We expect to show the experimental results at the conference.