Time dependence of the polarization of short X-ray pulses after crystal reflection

The short X-ray pulses coming out of a SASE FEL (self-amplified stimulated emission free-electron laser) have stimulated a closer inspection of the response of a crystal reflection to them. As the reflectivity of a crystal reflection depends on the polarization of the incident radiation, the time response does so as well. The response to a δ-pulse incident either under 45° linearly polarized with respect to the reflection plane of a monochromator crystal or circularly polarized is investigated in more detail. In contrast to the purely linear polarization perpendicular and parallel to the reflection plane, these mixed states show a very pronounced time dependence. In addition, a simulated SASE FEL bunch is investigated as an incident intensity distribution.