High-temperature superconducting undulator designs for compact free electron lasers, CLIC and FCC-ee

The application of high-temperature superconductor (HTS) in form of coated REBCO tape conductors to undulators and wigglers allows reaching higher magnetic fields and larger operating margins. Simulations have shown the capability to provide magnetic fields greater than 2 T for undulator periods of 13 mm. Undulator prototype coils are being designed and their performance will be evaluated to make a final design choice for a six period short model. This paper discusses and summarizes the potential of HTS for the major superconducting undulator geometries (helical, horizontal and vertical racetracks). Further, studies of prototype coils for an undulator period of 13 mm, to be built from 4 mm wide REBCO tape, are presented including first results from winding tests.