An Accumulating Pixel Array Detector for Single-Bunch Synchrotron Experiments

We describe the development of a CMOS read-out chip for an X-ray pixel array detector that accumulates into analog storage elements with time resolution typical of synchrotron bunch spacings. Each pixel contains multiple analog storage elements to allow capture of full-frame images at submicrosecond separation. Additionally, each storage element is re-addressable, which allows accumulation of signal from temporally distinct acquisition windows. Test results show the ability to slew and settle the equivalent of 650 8-keV x-rays (1.21 Me^-) in less than 100 ns. The detector RMS read-noise was measured to be 2350 e^- and grows with the square-root of the number of accumulations with a coefficient of 415 e^- (equivalent to 1.07 and 0.19 8-keV x-rays respectively). The saturation value for each storage element, in terms of 8 keV x-rays, was measured to exceed 1880 x-rays (6.42 Me^-). The complete detector is anticipated to contain around 400 times 200 pixels with pixel size near 150 mum times 150 mum. Possible experimental applications include study of material failures, transient phase transformations, and high-speed X-radiography.