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Rayleigh scattering is the dominant contribution to the elastic scattering of hard X-rays on atoms for photon energies below 1 MeV. It is the scattering of a photon on atomic electrons without gain or loss of energy. The angular distribution of Rayleigh scattering strongly depends on the polarization of the
incident photon beam [1]. Thus, determining the angular distribution of Rayleigh scattering of a highly linearly polarized photon beam allows for a sensitive test of the underlying theoretical calculations. Vice versa, relying on the calculations, this process allows for a precise determination of the linear polarization of the incident photon beam.
In an experiment at the synchrotron PETRA III at DESY we analyzed the angular distribution of Rayleigh scattering for a linearly polarized X-ray beam with a photon energy of 175 keV on a thin gold target. The scattered radiation was analyzed inside and out of the polarization plane with a Ge(i) detector and a 2D
sensitive Compton polarimeter. By relying on the theoretical calculations of the scattering process, we were able to determine the polarization characteristics of the incident synchrotron beam with high accuracy. In contrast to the common assumption of a fully linearly polarized synchrotron beam, we can
show a slight depolarization of the incident beam as seen already in a previous experiment [2].
[1] A. Surzhykov et al., Phys. Rev. A98, 053403 (2018)
[2] K. H. Blumenhagen et al., New J. Phys.18, 103034 (2016)
