DESY, Hamburg
The internationally organized European XFEL free-electron laser is under construction at the Deutsches Elektronen-Synchrotron (DESY). Compared to present-day synchrotron radiation sources, its peak brilliance will be more than 100 million times higher, the radiation has a high degree of transverse coherence, and the pulse duration is reduced from the 100 picosecond range down to the 10 fs time domain. The possible wavelength will be down to 0.1 nm. The electron beam energy of up to 17.5 GeV will be achieved by using superconducting accelerator technology. The project is the first large scale application of the TESLA technology developed over the last 15 years. The talk will briefly summarize the XFEL design before presenting details about the status of the superconducting linac. The international collaboration with its contributions will be described. Final prototyping, industrialization and new infrastructure are the actual challenges.
DESY, Hamburg
About 50 nine-cell cavities of the recent fine-grain niobium cavity productions have been analysed with respect to maximum gradient and critical field emission onset in the first and final vertical acceptance test, respectively. Parameters of the analysis were the manufacturer of the cavities, the location of the main EP (=> industry or in-house), the final surface treatment (=> final 40μm EP or short 10μm "flash" BCP) and the cavity preparation strategy (=> vertical acceptance test with or without He-Tank welded). Moreover the effect of a re-processing of field emission loaded cavities by additional ultra pure high pressure water rinsing has been investigated.
