A superconducting undulator for 3rd-generation light sources

Third-generation light sources are considering full aperture superconducting short-period undulators for new applications. One novel proposal is based on super-imposed fields generated by simple helical windings around a rectangular form. Each layer would be bifilar wound from a single superconducting strand with an alternating pitch between layers. The alternating pitch of "right-hand" and "left-hand" layers produces an overall linear undulating field. A single superconducting strand over the entire magnet eliminates all internal joints. To enhance the field, we have incorporated ferromagnetic iron in the pole regions, and propose to use it for minor field adjustments. This paper describes the magnetic concept, the winding scheme, and reports the field analysis and harmonic calculations.