Fabrication of a Short-Period Nb3Sn Superconducting Undulator

Lawrence Berkeley National Laboratory develops high-field Nb₃Sn magnets for HEP applications. In the past few years, this experience has been extended to the design and fabrication of undulator magnets. Some undulator applications require devices that can operate in the presence of a heat load from a beam. The use of Nb₃Sn permits operation of a device at both a marginally higher temperature (5-8 K) and a higher J_c, compared to NbTi devices, without requiring a larger magnetic gap. A half-undulator device consisting of 6 periods (12 coil packs) of 14.5 mm period was designed, wound, reacted, potted and tested. It reached the short sample current limit of 717 A in 4 quenches. The non-Cu J_c of the strand was over 7,600 A /mm² and the Cu current density at quench was over 8,000 A/mm² . Magnetic field models show that if a complete device was fabricated with the same parameters one could obtain beam fields of 1.1 T and 1.6 T for pole gaps of 8 mm and 6 mm, respectively.