Experience on In-Situ Module Repair and Set up of Non XFEL Cavity Strings at DESY

All components installed to the European XFEL cavity string modules underwent an intensive inspection and quality control before acceptance for installation to cavities or modules. Even though some RF feed throughs for HOM coupler- and Pick Up antennas showed leaks at the ceramic insulation after module test at 2 K. Due to time restriction and continuity of production the exchange of these parts needed to be done without reentering the cleanroom. Successful repair of these modules took place by setting up a local cleanroom onto the cavity string.In collaboration with Helmholtz-Zentrum Dresden-Rossendorf (HZDR), a cavity string for the ELBE Project was assembled at DESY and transported to HZDR for installation to the vacuum vessel.A spare module with 3.9 GHz resonators for the Euro-pean XFEL was set up at DESY and will be tested and qualified for the European XFEL. Due to delay in delivery of the power couplers, four power couplers were installed after string assembly

Final Acceptance Test of SRF Photo injector Cold String for the BERLinPro Energy Recovery Linac

Helmholtz Zentrum Berlin HZB is currently designing and building an high average current all superconducting CW driven ERL as a prototype to demonstrate low normalized beam emittance of 1 mm mrad at 100 mA and short pulses of about 2 ps. In order to achieve these demanding goals HZB started a staged program for developing this class of required high current, high brightness SRF electron sources. In this contribution we will present the current status of the module assembly and testing of the prototype SRF photoinjector cavity cold string. The steps taken to install the cathode insert system with the cavity in the clean room and the following horizontal test of the cold string as final acceptance test prior installation into its cryostat are shown. First beam in a dedicated diagnostics test stand called Gunlab are planned for this winte

Performance in the vertical test of the 832 nine-cell 1.3 GHz cavities for the European X-ray Free Electron Laser

The successful production and associated vertical testing of over 800 superconducting 1.3 GHz accelerating cavities for the European X-ray Free Electron Laser (XFEL) represents the culmination of over 20 years of superconducting radio-frequency R&D. The cavity production took place at two industrial vendors under the shared responsibility of INFN Milano–LASA and DESY. Average vertical testing rates at DESY exceeded 10 cavities per week, peaking at up to 15 cavities per week. The cavities sent for cryomodule assembly at Commissariat à l’énergie atomique (CEA) Saclay achieved an average maximum gradient of approximately 33  MV/m, reducing to ∼30  MV/m when the operational specifications on quality factor (Q) and field emission were included (the so-called usable gradient). Only 16% of the cavities required an additional surface retreatment to recover their low performance (usable gradient less than 20  MV/m). These cavities were predominantly limited by excessive field emission for which a simple high pressure water rinse (HPR) was sufficient. Approximately 16% of the cavities also received an additional HPR, e.g. due to vacuum problems before or during the tests or other reasons, but these were not directly related to gradient performance. The in-depth statistical analyses presented in this report have revealed several features of the series produced cavities

Production of superconducting 1.3-GHz cavities for the European X-ray Free Electron Laser

The production of over 800 1.3-GHz superconducting (SC) cavities for the European X-ray Free Electron Laser (EXFEL), the largest in the history of cavity fabrication, has now been successfully completed. In the past, manufacturing of SC resonators was only partly industrialized; the main challenge for the EXFEL production was transferring the high-performance surface treatment to industry. The production was shared by the two companies RI Research Instruments GmbH (RI) and Ettore Zanon S.p.A. (EZ) on the principle of “build to print”. DESY provided the high-purity niobium and NbTi for the resonators. Conformity with the European Pressure Equipment Directive (PED) was developed together with the contracted notified body TUEV NORD. New or upgraded infrastructure has been established at both companies. Series production and delivery of fully-equipped cavities ready for cold rf testing was started in December 2012, and finished in December 2015. More than half the cavities delivered to DESY as specified (referred to “as received”) fulfilled the EXFEL specification. Further improvement of low-performing cavities was achieved by supplementary surface treatment at DESY or at the companies. The final achieved average gradient exceeded the EXFEL specification by approximately 25%. In the following paper, experience with the 1.3-GHz cavity production for EXFEL is reported and the main lessons learned are discussed