Final Design and Prototyping of the Superconducting Magnet Package for the Linear Accelerator of the European XFEL

The electron beam of the European XFEL will be accelerated to an energy up to 17 GeV in a linear accelerator that is divided into 101 modules. Each module will be equipped with eight superconducting cavities and a superconducting magnet package. That package consists of a main superferric quadrupole and two nested corrector dipoles, horizontal and vertical, enclosed in a stainless steel vessel. Conduction-cooled current leads are used. Up to four prototypes were produced between 2005 and 2009. Some problems were detected, which may complicate the series production, mainly that the wire diameter was too small for the winding process, the solid iron yoke was too expensive to be machined and the magnetization effects on the magnet transfer function were too high. Therefore, it was decided to revisit the design to ease fabrication. The new magnet design is presented in this paper. The fabrication process and test results of the prototype are reported as well. Finally, the helium vessel around the magnet needs to satisfy the European Standard for Pressure Vessels, namely PED 97/23/EC. This paper also describes the modifications necessary in the original design to achieve that specification.