Photon-counting detectors for pump-probe science

Many areas of science use x-ray, pump-probe techniques to explore how atomic-scale systems react to an excitation. If a short-duration pump is used to stimulate the sample, the state of the sample can be followed on very fast time scales by varying the delay between the exciting pump and the x-ray probe. Often the difference between excited and static samples is subtle and challenging to determine due to changes in the sample, beam variability, and other systematic uncertainties. To address this, a new hybrid x-ray detector incorporating a pair of counters within each pixel is being developed. A global gate selects which of these two counters is active and will allow for one counter to be dedicated to collecting pumped and the other un-pumped data in a time-interleaved manner, which should result in more accurate measurements. The cycle response time of the detector will be under 100 ns and so be compatible with the camshaft mode at SSRL and 24-bunch mode at the APS, as well as various bunch structures at many synchrotrons.