• G. Kube, J. Gonschior, U. Hahn, G. Priebe, H. Schulte-Schrepping, Ch. Wiebers
  DESY, Hamburg
• P. Ilinski
  BNL, Upton, Long Island, New York
• C.G. Schroer
  TUD, Dresden
• S. Weisse
  DESY Zeuthen, Zeuthen

PETRA III is the new 3rd generation hard X-ray synchrotron light source at DESY, operating at a beam energy of 6 GeV. Machine commissioning began in April 2009 and user operation starts in 2010. In order to achieve a high brilliance, damping wigglers with a total length of 80 m are installed to reduce the horizontal emittance down to an extremely low value of 1 nm rad. For a precise emittance online control, a dedicated diagnostics beamline was built up to image the beam profile with synchrotron radiation from a bending magnet in the X-ray region. The beamline is equipped with two interchangeable X-ray optical systems, a pinhole optic for standard operation and a high resolution compound refractive lens optic. In addition, the synchrotron radiation angular distribution can be exploited at high photon energies. In this presentation, first experience with the system will be reported.