The SwissFEL X-ray Free Electron Laser (XFEL) facility started construction at the Paul Scherrer Institute (Villigen, Switzerland) in 2013 and will be ready to accept its first users in 2018 on the Aramis hard X-ray branch. In the following sections we will summarize the various aspects of the project, including the design of the soft and hard X-ray branches of the accelerator, the results of SwissFEL performance simulations, details of the photon beamlines and experimental stations, and our first commissioning results.

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The conceptual design for a nonscaling fixed field alternating gradient accelerator suitable for charged particle therapy (the use of protons and other light ions to treat some forms of cancer) is described.

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In this work we investigate superconducting properties of niobium samples via application of the muon spin rotation/relaxation (SR) technique. We employ for the first time the SR technique to study samples that are cut out from large and small grain 1.5 GHz radio frequency (rf) single cell niobium cavities. The rf test of these cavities was accompanied by full temperature mapping to characterize the rf losses in each of the samples. Results of the SR measurements show that standard cavity surface treatments like mild baking and buffered chemical polishing performed on the studied samples affect their surface pinning strength. We find an interesting correlation between high field rf losses and field dependence of the sample magnetic volume fraction measured via SR. The SR line width observed in zero-field-SR measurements matches the behavior of Nb samples doped with minute amounts of Ta or N impurities. A lower and an upper bound for the upper critical field H c2 of these cutouts is found.