A phase shifter magnet is placed between two insertion devices in order to delay the electron beam trajectory. The aim is to phase the radiation of the adjacent undulators to interfere constructively and radiate coherently. Generally, a phase shifter is designed to provide a maximum phase advance value of 2π, and the phase tuning in the range of 0 to 2π is done by varying the magnetic gap.
In the course of the upgrade of the FLASH 1 beamline towards a seeded FEL line, the FEL layout was modified to consist of 12 variable polarization undulators (APPLE III) of 2.5 m length each. The space between the undulators is about 0.8 m in length and contains various electron beam diagnostics, vacuum instrumentation, a quadrupole magnet and a phase shifter chicane magnet. Since this longitudinal space is constraint, a compact design is required for the phase shifters and a permanent magnet-based device was developed.
The FLASH2020+ design uses only four permanent magnet (PM) blocks per array with horizontal magnetization. This design allows for using one type of PM block which simplifies the sorting as the PM blocks can be swapped.
Contact: K. Götze, P. Vagin, P. Neumann
Publications:
P. N’gotta, P. Vagin, M.Tischer: "Permanent Magnet phase shifters for FLASH2020+ FEL", J. Phys.: Conf. Ser. 2380(1), 012007 (2022)
