Abstract: For time-resolved X-ray measurements, the ability to acquire many images quickly is perhaps the most important requirement of the experiment. We have developed a photon counting hybrid pixel array detector based on the 128 x 256-pixel UFXC32k application specific integrated circuit (ASIC), namely the Rigaku ultrahigh-speed sensor (UHSS).
The first UHSS detector is a 1024 x 512 (500k) pixel array of 76-µm pixels comprised of 16 UFXC ASICs coupled to a 320-mm-thick silicon sensor. The design of the UFXC ASIC provides for an effectively gapless collection area enhancing image quality and ease of use for applications such as ptychography and small-angle X-ray scattering. Flexible configuration of the dual gates (thresholds) and dual 14-bit counters per pixel provide high performance for a variety of applications. For example, one configuration provides zero-readout-deadtime (<100 nsec) continuous measurement at up to more than 50 kfps (2-bit counter). In another configuration, burst-mode operation provides data acquisition at over 1 Mfps with 8% duty cycle (2-bit counter). Other configurations provide high dynamic range by combining the two counters per pixel to make a 28-bit counter per pixel or (limited) energy selectivity by setting different thresholds for the dual gates per pixel. The combination of high count rate, small pixel size, and fast frame rate makes this an excellent detector for time-resolved X-ray measurements including but not limited to diffraction, scattering, absorption, and photon correlation spectroscopy experiments down to sub-micro-second time scales while the flexible counters and gates and the effectively gapless sensor provide superior performance for additional applications like ptychography.
In this presentation we will review the properties of the detector in detail and describe some preliminary time-resolved coherent scattering results from measurements performed at Advanced Photon Source Beamline 8-ID.