Increasing the Jc of Tube-Type Nb3Sn Strands

This proposal is submitted in response to the SBIR/STTR High Energy Physics Solicitation Topic 64(a). High-Field Superconductor and Superconducting Magnet Technologies for High Energy Particle Colliders, (a) High-Field Superconducting Wire Technologies for Magnets. The need is for strands that can operate in the 15/17T or higher regime, and have deff. values of 30 m or less, with non-Cu Jc values at 3000 A/mm2 at 12T-4.2K or greater and 1500 A/mm2 at 15T-4.2K or greater, and have stable operation throughout their operational fields. Strands close to these values are starting to be obtained, but the instability in the low field and defects due to cabling are issues to be solved. Hyper Tech has a desire to increase non-copper Jc at high field at 4.2K. We would like to see the achievement of non-Cu Jcs of around 3000 A/mm2 at 12T-4.2K for the Tube type strands with filament size of 30~35 m. The goal of this research is to increase non-copper Jc at 12T-4.2K to above 3000 A/mm2 for tube type strands with filament size of 30~35 m. In order to do so, we plan to optimize Nb/Sn, Cu/Sn ratios to get a good combination of RRR and non-Cu Jc, make round filament to improve the filament array, and evaluate the possibility and effect of putting small amount of Ti in high count subelement restack strands. The goal of this Phase I program is to investigate various innovative approaches and determine which approaches to pursue in a Phase II to develop a conductor with target Jc values of 3000 A/mm2 at 12T-4.2K, 1500-1800 A/mm2 at 15T-4.2 K with a subelement count of more than 200, and deff values of 35 m or less. Commercial Applications and Other Benefits: The success of this SBIR will lead to a fully stable strand with high Is and Js for DOE-HEP that will have a demonstrated non-Cu Jc of about 3000A/mm2 (12 T-4.2K) and 1500-1800 A/mm2 (15T- 4.2K) while keeping good RRR and small deff. The design will be able to be fabricated into a Rutherford cable without subelement breakage.