Permanent Magnet phase shifters for FLASH2020+ FEL

The development of a simple and compact permanent magnet (PM) phase shifter is presented in this paper. The design is based on four PM blocks per girder (8 PM blocks in total), and uses only one type PM block with horizontal magnetization and 15mm length. The magnetic field provides a net zero and second field integral and a phase integral of 2 · 10–6 T 2 m 3 for 60mm overall magnet length. The study of the numerical model with Radia shows that this design is mainly sensitive to angular magnetization errors. The correction strategy is based on pairing the PM blocks in order to cancel the sum of magnetization angle error, and the remaining magnetic field error is corrected with a stack of magic fingers located around the magnet. Finally, a prototype was built, and the magnetic measurements results are presented here.