The Materials Science beamline at the Swiss Light Source has been operational since 2001. In late 2010, the original wiggler source was replaced with a novel insertion device, which allows unprecedented access to high photon energies from an undulator installed in a medium-energy storage ring. In order to best exploit the increased brilliance of this new source, the entire front-end and optics had to be redesigned. In this work, the upgrade of the beamline is described in detail. The tone is didactic, from which it is hoped the reader can adapt the concepts and ideas to his or her needs.

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A new technique of undulator field correction for cryogenic permanent magnet undulators (CPMUs) is proposed to correct the phase error induced by temperature gradient. This technique takes advantage of two important instruments: one is the in-vacuum self-aligned field analyzer with laser instrumentation system to precisely measure the distribution of the magnetic field generated by the permanent magnet arrays placed in vacuum, and the other is the differential adjuster to correct the local variation of the magnet gap. The details of the two instruments are described together with the method of how to analyze the field measurement data and deduce the gap variation along the undulator axis. The correction technique was applied to the CPMU with a length of 1.7 m and a magnetic period of 14 mm. It was found that the phase error induced during the cooling process was attributable to local gap variations of around 30 m, which were then corrected by the differential adjuster.

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The effect of transverse compressive stress on the critical current of solder-fiiled and unfiiled Nb3Sn cables is reported. The conductor used in this study is a Nb3Sn Rutherford cable manufactured with a bronze-process wire of 0.92 m m diameter. Like epoxy-impregnated cables, solderfilled cables exhibit much less degradation than wire samples when subjected to the same stresses. On the other hand, unfded specimens are irreversibly damaged at the thin edge when loaded to 160MPa, and show significantly higher degradation than similar specimens of the solder-filled cable. A finite-element calculation of the stress state inside a particular composite superconductor indicates that more compressive stress is developed in the virgin wire than in a straight wire segment in a real cable environment. A /Magnetic FieldFig. 1. Schematic view of the test S a m p l e showing the two investigated strands of