Characterization of a Fast-Framing X-Ray Camera With Wide Dynamic Range for High-Energy Imaging

We present first characterization results, with a focus on high-flux measurements, of a fast-framing, wide-dynamic-range x-ray camera intended for high-energy imaging. The MM-PAD-2.1 uses an integrating pixel front-end with a charge removal architecture and in-pixel counter to extend the pixel well depth while maintaining low read noise across the full dynamic range. The charge-removal mechanism is dead-time-less (i.e., incoming signal continues to be integrated by the front-end while charge removal is taking place). The purpose of the high-flux characterization was to determine the maximum sustained incident flux that could be measured while still exhibiting linear behavior. To this end, a 16 × 16 pixel prototype was tested at the Advanced Photon Source at Argonne National Laboratory using 10 keV photons generated by an undulator source. The intensity of the incident beam was varied over 3 orders of magnitude using a series of attenuators, and the signal integrated by the MM-PAD-2.1 prototype was compared to that measured by a He-filled ion chamber directly upstream. Initial results indicate linear performance up to ca. 10
¹⁰
ph/s in a spot spanning approximately 2 × 1.5 pixels (FWHM). The onset of transient radiation damage was observed during these measurements, characterized primarily by failure of digital readout from the detector ASIC. These effects were observed to reverse after annealing at 30° C for several hours, with full recovery of the detector readout.