Magnetic design and field measurements of a VUV-undulator for MAX-lab

The magnetic design of a permanent magnet undulator for generation of vacuum-ultraviolet (VUV) radiation in a 550-MeV storage ring is described. The undulator utilizes ferrite permanent magnets in a hybrid configuration. The periodic magnetic field of the undulator is realized by arrays of permanent magnets and iron poles situated symmetrically on the upper and lower side of the vacuum chamber containing the electron beam (i.e. the hybrid configuration). Magnetic-field measurement methods and results obtained in the finished device are reviewed. From measurements of the peak field values for various gap settings, it was concluded that ferrite is not a good choice for high-uniformity hybrid undulators.