Results Of The Magnetic Measurements Of The Superconducting Magnets For The European Xfel

A new linear accelerator, i.e., the European X-ray Free-Electron Laser (XFEL), is under construction at DESY in Hamburg. The construction started in early 2009, and the commissioning is planned for 2016. The design energy of the electron beam is 17.5 GeV (0.05-4.7 nm wavelength), and more than 27 000 flashes/s are expected. The accelerator contains 102 cryomodules equipped with a string of eight superconducting RF cavities and one superconducting magnet package. Each magnet consists of two cos-theta-type correction dipoles, horizontal and vertical deflecting. They are glued onto the surface of the beam pipe and are surrounded by a superferric quadrupolemagnet. The package is mounted inside of a compact stainless steel vessel with a length of 30 cm and a diameter of 20 cm. Each package and current lead assembly was tested separately at room temperature and together at 2 K in a dedicated superfluid helium cryostat at DESY. A summary of the results is reported here. During the cold test, special emphasis was given to hysteresis and persistent current effects, as the operating current varies from very low currents at the beginning of the accelerator to the full design current 50 A at the end.