• R. Wanzenberg, K. Balewski
  DESY, Hamburg

At DESY the PETRA ring has been converted into a synchrotron radiation facility, called PETRA III. The commissioning with beam started in April 2009. The betatron tune versus beam intensity was measured for different configurations of the wiggler magnets which are installed in PETRA III to achieve the small emittance of 1 nm. These measurements are compared with predictions from the impedance model. The measured tune shift is well within the impedance budget and the design single bunch intensities of up-to 2.5 mA can be stored in PETRA III. The predicted vertical tune shift is about 30 % smaller than the measured one.