A Scalable APC Approach to Increase Layer and nonCu Critical Current in High Field in Nb3Sn Conductors

Superconducting Wire Technologies for Magnets. The need is for strands that operate at a minimum of 12 Tesla (T) field, with preference for production scale (> 3 km continuous lengths) wire technologies at 15 to 25 T. The strands are preferred to have higher engineering current densities, at least 400 amperes per square millimeter of strand cross section at the target field of operation and 4.2 K temperature, and have reduced effective filament diameter, in particular to less than 30 micrometers at 1 mm wire diameter, with minimal concomitant reduction of the thermal conductivity of the stabilizer or strand critical density. Hyper Tech has fabricated Nb3Sn strands with our tube approach strand with 200900 filaments at 0.7 mm OD in kilometer lengths. While the deff sizes and stabilities of these strands are excellent, and the conductor performance is very good at 2500 A/mm2 at 12 T, it would be very useful for HEP applications to push the nonCu Jc in these strands with high filament counts way beyond the 3000 + A/mm2 12T4.2K level (potential for 50% plus improvement over today’s commercial wires). GenIenr aPlh Sastaet eI,m wene ts oufc cheoewd etdh iisn p mroabkleinmg issu bbeeilnegm aendtdsr easnsde dr estacks with refined grain size in the reacted Nb3Sn superconductors. We have made 61subelement Nb1%Zr restack strands and drew them down to diameters of 0.7 mm, 0.5 mm, 0.4 mm and 0.25 mm with sub element size of 65 m, 45m, 35 m and 25m respectively. We obtained both magnetic and transport layer Jc of 10,000 A/mm2 at 12T4.2K in the binary Nb3Sn with ZrO2 in sub element. For the proposed Phase II program, we will first optimize the heat treatment schedule of the restack wires made in Phase I, and then further optimize the chemistry in the sub element. We will make 217 Sub element restack strands using the optimized sub elements and draw strands down to 0.7 mm diameter with sub element size of 35 m. We will demonstrate strand variants for easy ternary alloying. Through this Phase II, we will fabricate strands targeting to obtain a 50% Je performance of the best presently available commercial conductors at 15 T and 16T. Commercial applications and other benefits The success of this SBIR will lead to a Nb3Sn superconductors for next generation accelerators, fusion reactors, and medical applications such as NMR, MRI, and accelerators for medical purposes. Key Words 3Sn, Ternary Nb3Sn, TubeType, deff, NonCu Jc SumTmhiasr yp rfoogrr mamem pbuerrssu eosf tchoen gdreevsesl opment of improved Nbare used for understanding physics, and various computer and3 Smne cdoicnadlu acptoprlisc afotiro nasc.