DESY, Hamburg, Germany
The main linac of the superconducting accelerator of the European XFEL presently consists of 96 accelerator modules, each housing eight 1.3 GHz TESLA-type cavi-ties, with an average design gradient of 23.6 MV/m. The performance of each individual module has been tested after module assembly in the Accelerator Module Test Facility (AMTF) at DESY. The 2-year period of module installation to the accelerator tunnel was finished in August 2016. In order to recheck and re-establish the performance of the input power couplers, warm processing of nearly all installed modules was performed before the first cool-down during Dec 2016 / Jan 2017. Four consecutive modules are connected to one 10 MW klystron and form a so-called RF station, which is powered and controlled individually during operation. By June 2017 23 of 25 RF stations have been commissioned for beam acceleration including frequency tuning, various calibrations and LLRF adjustments. A preliminary beam energy of 14 GeV was achieved, which is sufficient for first lasing experiments. No significant performance degradation has been observed so far. The commissioning experience and the available RF performance data will be presented.
