Progress Report on the XUV Online Diagnostic Unit for the Highly Accurate Determination of SR Properties

Recent results from simultaneous long-term stability measurements of the beam position and photon energy of the synchrotron beam at the soft X-ray beamline PO4 at PETRA III (DESY, Hamburg) are presented. The data was obtained by operating the built-in, non-invasive diagnostic unit directly upstream the beamline focus in parallel with a user experiment. We demonstrate that a sophisticated data evaluation based on principal component analysis results a high positional accuracy better than a few micron and a stable photon energy measurement with an uncertainty in the low ppm regime. Even subtle effects caused by abnormalities in the electron storage ring operation (e.g. short interruptions of the electron injection) are revealed hereby. Utilizing online diagnostic data for feedback controls will enable unprecedented stability of beamline operation at synchrotrons and FEL sources in the future.