Magnetic Design and Measurement Results of a CPMU Prototype at SSRF

A cryogenic permanent-magnet undulator is under development at SSRF in order to reach larger magnetic field and to produce higher brilliance in the hard rays domain. The undulator has a period of 20 mm of hybrid type, with pure iron poles and NdFeB magnet blocks, and a magnet length of 1.6 m. In order to verify the performance of the device under cryogenic conditions, a new in-vacuum measuring system is developed. The detailed magnetic design and local measurement results under cryogenic in-vacuum conditions will be presented.