Vertical Electro Polishing of Superconducting Single and Multi Cell Gun Resonators

At DESY activities on surface treatment of superconducting RF gun cavity resonators at 1.3 GHz are ongoing. Due to the small opening on the endplate for insertion of cathodes, no reasonable acid flow can be realized with the existing set up for horizontal electro polishing. To benefit from electro polishing of Niobium surfaces, an adapter to the existing horizontal electro polishing bench at DESY was set up and is in operation now. Vertical EP was applied on 1.3 GHz SRF gun resonators with 1.6 and 3.5 cell geometry. Work flow,process conditions as well as test results of gun cavities treated so far at DESY are described

A New High Resolution Optical System for Inspection of Gun- and Multi-Cell Resonators in ISO-4 Cleanrooms

Optical inspection of the inner surface of superconducting resonators was established during European XFEL cavity production by usage of the so called OBACHT optical inspection [1]. In addition to the surface inspection by OBACHT a new optical inspection system with integrated high resolution camera is set up at DESY. It allows inspection of multi-cell resonators aswell as gun cavity resonators with only single side accessibility to the inner surface. A prototype was commissioned and optical inspections were done with OBACHT and the new system in parallel. Two SRF gun cavities were inspected by this optical system and origin f limitations of the resonators were identified

A New High Resolution Optical System for Inspection of Gun – and Multi-Cell Resonators in ISO-4 Cleanrooms

Optical inspection of the inner surface of superconducting resonators was established during European XFEL cavity production by usage of the so called OBACHT optical inspection. In addition to the surface inspection by OBACHT a new optical inspection system with integrated high resolution camera is set up at DESY. It allows inspection of multi-cell resonators as well as gun resonators with only single side accessibility to the inner surface. A prototype was commissioned and optical inspections done with OBACHT and the new system in parallel. Two SRF gun cavities were inspected by this optical system and origin of limitations of the resonator were identified

Vertical Electro-Polishing at DESY of a 1.3 GHz Gun Cavity for CW Application

Superconducting gun cavities for cw operation in accelerators are under study. In 2003 a three-and-a-half cell gun cavity was chemically treated with buffered chemical polishing and tested successfully in a collaboration between Helmholtz-Zentrum Dresden-Rossendorf and DESY. For several years a 1.3-GHz 1.6-cell resonator has been under study, which has been built and tested at DESY and elsewhere. For further studies and optimization the gun cavity needed to be electro-polished, which was conducted at DESY for the first time using vertical electro-polishing. The technical set-up for the vertical electro-polishing and high pressure rinsing as well as the processing parameters applied and the adaptation of the existing infrastructure to the 1.6-cell geometry at DESY are presented

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

Abstract—The electron beam of the European XFEL will beaccelerated to an energy up to 17 GeV in a linear acceleratorwhich is divided into 101 modules. Each module will be equippedwith eight superconducting cavities and a superconductingmagnet package. That package consists of a main superferricquadrupole and two nested corrector dipoles, horizontal andvertical, enclosed in a stainless steel vessel. Conduction cooledcurrent leads are used.Up to four prototypes were produced between 2005 and 2009.Some problems were detected which may complicate the seriesproduction, mainly that the wire diameter was too small for thewinding process, the solid iron yoke was too expensive to bemachined and the magnetization effects on the magnet transferfunction were too high. Therefore, it was decided to revisit thedesign to ease fabrication. The new magnet design is presented inthis paper. The fabrication process and test results of theprototype are reported as well.Finally, the helium vessel around the magnet needs to satisfythe European Standard for Pressure Vessels, namely PED97/23/EC. This paper also describes the modifications necessaryin the original design to achieve that specification

Experience on Series Production of the Superconducting Magnet Package for the Linear Accelerator of the European XFEL

Abstract—The procurement of 103 superconducting magnetpackages is part of the Spanish in-kind contribution to theEuropean X-FEL. Each package consists of a main superferricquadrupole and two steerers, vertical and horizontal, fed byconduction-cooled current leads and enclosed in a stainless steelvessel. The operation temperature is 2 K, as they are embeddedin a superfluid helium bath. The magnetic and mechanicaldesigns are published elsewhere. The magnets are beingproduced in the Spanish company ANTEC, while the vessels arefabricated by another Spanish company, Trinos Vacuum-Projects, which is also responsible for the integration, under thesupervision of CIEMAT. The helium vessel manufacturer needsto accomplish the requirements given by the European PressureEquipment Directive, namely PED 97/23/EC. This paperdescribes the series fabrication techniques, the production followup,the quality assurance and the magnet testing at themanufacturer site. Cold tests are realized at DESY premises. Themain problems found during the fabrication of the first half ofthe series are also reported: a) the reproducibility of thequadrupole coil dimensions; b) the accuracy of the beam positionmonitor housing after final welding of the vessel; and c) theminimization of the magnetization effects on the transfer functionof the magnets