Superconducting Helical Undulator with Superimposed Focusing Gradient for High Efficiency Tapered X-Ray FELs

Undulator tapering can significantly improve the X-ray Free Electron Laser (XFEL) efficiency by keeping the decelerating electron beam within the FEL bandwidth. Helical superconducting undulator (h- SCU) is an emerging technology, which realization can significantly improve tapering capabilities and enable TW X-ray beam generation, as well as improve XFEL coverage at hard X-rays. The challenge for realizing h-SCU is showing that current fabrication and assembly techniques can realize an undulator system of sufficient quality for the free-electron laser applications. RadiaBeam Technologies is developing h-SCU prototype sector and will develop a cryogenic testing set-up to validate the h-SCU prototype compliance with the FEL field quality requirements. In Phase II, the helical bifilar SCU undulator system has been designed and optimized via 3D magnetic simulations and engineered for manufacturing. The superconducting magnetic winding system was specified and is being procured, and the manufacturing studies are currently under way. To complete this work, however, we need to develop an important additional capability presently not commercially available; namely, cryogenic magnetic testing, which is the focus of this Phase IIA proposal. A cold magnetic metrology system will be developed and will be utilized to perform magnetic measurements and optimization of the h-SCU prototype developed during the base Phase II period. The evolution of the light source has been historically inseparable from the evolution of the insertion devices, and a successful development of the h-SCU in this project would represent a major technological step towards improving both the peak brightness and average power of existing and future light sources. Such possibility represents an excellent commercial opportunity for RadiaBeam, and simultaneously facilitates significant savings for the US taxpayers in maintaining and improving state-of-the-art research infrastructure.