Increasing the Jc of Tube-Type Nb3Sn Strands

In this Phase I, we successfully made strands with better Cu/Sn ratio to reduce the coarse Nb3Sn grain region, thereby providing the potential of increasing the non-Cu Jc in the Phase II and scaling up to 2” billets with 331 subelements. In order to improve the strand’s high field properties, we successfully doped low amount of Ti in the subelements and made a 217-subelement wire which has been drawn down to 0.7 mm without any breakage. This strand gave subelement size of 35 µm. We will scale up the Ti-doped billet to 271-subelement in 1.5” billet in this proposed Phase II. The hexagonal shaped subelements with round Nb-Sn have been developed for a 61-subelement restack. Thus the results indicated that for 217-subelement restack in a 2” billet we have the potential to draw down this type of construction without problems while maintaining a good array to react more Nb to get higher non-Cu Jc in the Phase II