Design, fabrication, and test results of undulators using Nb3Sn superconductor

An R&D effort is underway at Lawrence Berkeley National Laboratory (LBNL) to develop the technology of Nb₃Sn superconducting undulators (SCUs). Issues relating to the selection of the appropriate conductor are discussed. The design and fabrication of SCUs using Nb₃Sn is presented. Two prototype devices have been designed and fabricated at LBNL. The first device concentrated on basic fabrication issues and on magnet protection, a key concern due to extremely high copper current densities during a quench. Test on the first prototype demonstrated that such devices can be passively protected in a scalable manner. The second device incorporated design improvements as well as trim coils that are designed to serve as the basic element of a future active phase error correction approach. Preliminary tests on the second device are presented. The trim coils were successfully tested at a variety of field levels. Two quench runs were performed, both occurring at ∼70% of short-sample J_c. Stability issues associated with flux-jumps and possible epoxy cracking are discussed.