Permanent magnet wigglers for reducing the emittance of the Petra III synchrotron radiation source

The Petra III synchrotron radiation source was developed based on the Petra-II 6-GeV electron accelerator (DESY). After installing the system for radiation damping, the horizontal emittance of the electron beam of Petra III decreased from 5 nm rad to 1 nm rad, which is a record parameter for this class of installations. The system of radiation damping includes 20 permanent magnet wigglers installed in two straight sections, 50 m each. The total radiation power of the wigglers reaches 800 kW. The wigglers used in the radiation damping system of Petra III were developed in collaboration with DESY (Hamburg) and fabricated by the Budker Institute of Nuclear Physics. The wiggler length is 4.04 m, the gap between the poles is 24 mm, the maximum magnetic field is B = 1.52−1.56 T, and the period is λ = 20 cm. This paper describes the design features of the permanent magnet wigglers and the methods and results of adjustment of the wiggler operating parameters.