UNDULATOR OPTIONS FOR SOFT X-RAY FREE ELECTRON LASERS ∗

Soft X-ray free electron laser sources require significant photon energy tuning and ideally provide variable polarization to users. The proposed LBNL facility will provide multiple FEL lines with varying spectral characteristics to satisfy a broad array of soft X-ray physics. A variety of undulator technologies are being investigated to satisfy these requirements. We evaluate the performance characteristics of the key competing technologies, including superconducting options, and outline the impact of technology choice on overall facility design and cost. We review the key R&D issues that must be addressed to validate the different technologies for soft X-ray FEL application.