Wavefront sensing at a high-repetition-rate X-ray free-electron laser

Guest, T.; Vagovič, P.; Adriano, L.; Bielecki, J.; Birnsteinova, S.; Graceffa, R.; Koliyadu, J.; Morgan, K.; Moriyama, H.; Mosko, D.; Riessen, G.; Sabol, K.; Sato, T.; Szeles, P.; Taylor, Z.; Uličný, J.; Bean, R.; Mancuso, A.P.; Abbey, B.

doi:10.1107/S1600577526005898

Figure 4
Probability density distributions of transverse pointing-angle fluctuations at the entrance to the SPB/SFX instrument of the European XFEL. Histograms show the distribution of pointing deviations after centering on the inter-train, intra-train and single-shot mean angles (virtual references), where κ denotes the kurtosis of the intra-train pointing-angle distributions. Shot-to-shot pointing-angle measurements reflect the spatial averaging of discrete speckle displacements derived from finite detector sampling. As the intrinsic single-shot pointing uncertainty is substantially smaller than the effective discretization interval of the estimator, the inter-train distributions exhibit an apparent multi-peak structure. Gaussian mixture models of order n_g are therefore used to capture the underlying envelope of these distributions and estimate their overall range and variance.

JOURNAL OF
SYNCHROTRON
RADIATION

ISSN: 1600-5775

Volume 33| Part 5| September 2026| Pages 1255-1268

https://doi.org/10.1107/S1600577526005898

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