Development and Adjustment of Tools for Superconducting RF Gun Cavities

For the superconducting radio frequency (SRF), 1.6-cell gun cavities (CV) developed at DESY, a similar fabrication andtreatment process, as for the European XFEL 9-cell cavities is foreseen. The different length and geometry of thesecavities lead to a number of adjustments to existing and the development of new tools. This paper covers the newdesigns and adaptations of a tuning tool, chemistry flanges, a wall thickness measurement device, as well as a new high pressure rinsing spray head and an optical inspection camera for the 1.6-cell, 1.3 GHz DESY SRF gun cavities

Retreatment of European XFEL Series Cavities at DESY as Part of the Repair of the European XFEL Accelerating Modules

For the European XFEL 102 accelerating modules were built and tested. Several accelerating modules had to be reworked due to different kinds of non-conformities. The extent of this rework varied greatly. At the end of production four accelerating modules could not be qualified in time before the tunnel installation was to be finished in September 2016. Meanwhile the cavity strings of two of these accelerating modules have been disassembled in the DESY clean room. The cavities have been retreated at DESY either by additional high pressure water rinsing or BCP flash chemical treatment. All cavities were vertically tested and 15 out of 16 were qualified for the reassembly of the cavity strings. One accelerating module will be reassembled completely and tested until the end of 2018; the other will follow in the first half of 2019. We report on retreatment procedures and performance of these cavities

Accelerator Module Repair for the European XFEL Installation

International audienceRepair actions of different extent have been performed at 61 modules of the 100 accelerating series modules for the European XFEL to qualify them for the tunnel installation. Four modules could not be repaired in time. CEA Saclay managed to perform three major repairs in parallel to the series module integration, the residual repair actions took place at DESY Hamburg. In this paper we will give an overview on the various technical problems which required being fixed before the tunnel installation and on the repair actions performed

SRF Accelerating Modules Repair at DESY

Eight SRF cavities assembled in an accelerating module represent a building block of the particle linear accelerator based onTESLA SRF technology. DESY has two machines, European XFEL and FLASH. Both use almost same module and cavity types.During the module assembly many factors can deteriorate the cavity performance and cause a need for a repair action. Currentlytwo European XFEL modules and two FLASH ones underwent reassembly procedures. The repair was not immediately successfulon every of these modules and re‐iterations did follow. The degradation causes were investigated. SRF modules were tested onboth test‐stands at DESY: AMTF and CMTB. The results of the described actions are presented and discussed

SRF Gun Development at DESY

A future upgrade of the European XFEL (E-XFEL) foresees an additional CW operation mode, which will increase the flexibility in the photon beam time structure [1–3]. One of the challenges of this operational mode is the need fora CW operating photo injector. We believe that using an SRF gun is the preferred approach as the beam parameters of normal conducting pulsed guns can be potentially met by SRF guns operating CW. For more than a decade DESY, incollaboration with TJNAF, NCBJ, BNL, HZB and HZDR, has performed R&D to develop an all superconducting RFgun with a lead cathode. In the frame of E-XFEL CW upgrade feasibility studies, the SRF-gun R&D program gained more attention and support. Within the next few years we would like to demonstrate the performance of the all superconducting injector required for the E-XFEL upgrade. The selected approach offers advantages w.r.t. the cleanliness of the superconducting surface, but requires a complete disassembly of a cryostat and stripping the gun cavity in a cleanroom to exchange the cathode. Thus it is practical only when the life time of the cathode is at least several months. In this paper we present the actual status of the R&D program, next steps and the longer term plans