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Reducing radiation damage in X-ray photon correlation spectroscopy with non-uniform pulse timing
What is it about?
X-ray photon correlation spectroscopy (XPCS) tracks nanoscale motion by recording time series of coherent X-ray speckle patterns. To see fast or weak dynamics we often need intense beams and many images, but the accumulated dose can change or damage soft and biological materials, distorting the measured dynamics. We show that recording only 11 speckle images at carefully chosen non-uniform (log-spaced) time intervals can provide 55 distinct delay times spanning milliseconds to tens of seconds in a single run. Using the same dataset, both standard XPCS analysis and an independent speckle-visibility (XSVS) analysis give consistent relaxation behavior in a polymer gel, while the total exposure is ~100× lower than a conventional 1000-frame measurement. This simple acquisition strategy widens the range of samples and conditions where reliable XPCS can be performed.
Why is it important?
As X-ray sources continue to become brighter—from 4th-generation synchrotrons to X-ray free-electron lasers (XFELs)—radiation damage is increasingly the limiting factor for studying soft and biological materials. Our non-uniform interval-pulse acquisition extracts a densely sampled correlation function from only 11 exposures (55 delay times), reducing dose by ~two orders of magnitude while preserving quantitative relaxation parameters. This makes XPCS-based dynamics measurements more practical for radiation-sensitive samples.