Nb3Sn is a basic superconducting material for the high-field magnets used in accelerators for high energy physics research. However, as the number of subelements in the restacks is increased, problems of ductility and piece length have been encountered in multi-barrier Nb3Sn. There are indications that piece length and ease of manufacture are both easier to achieve in single barrier materials. Unfortunately, the problems of testing high current materials had not been overcome at the time when the single barrier was abandoned. In particular, the method of reporting Jc masked the fact that the current carried by the single barrier materials was significantly higher than that of the multi-barrier material. This project will develop technology for conducting an accurate comparison of the properties of single barrier and multi-barrier materials. In Phase I, two 88.8 mm Ø billets, one with fins and one without, both containing Nb7.5wt.%Ta filaments and no barriers, will be extruded. These billets will be made into 19- (fins) and 54/61-subelement (no fins) restacks with a single Ta barrier around all the subelements in the restacks. The properties of the subelements will be compared with similar designs for multi-barrier materials, which were made in a previous project. In Phase II, the best single barrier material will be scaled up in bigger billets for coil testing.
Commercial Applications and Other Benefits as described by the awardee: In addition to being used for high-energy-physics accelerator applications, the technology should find use in open area magnetic resonance imaging (MRI), small magnets for high field laboratory applications, and nuclear magnetic resonance. MRI is the largest commercial application of low temperature superconductors
