Artificial pinning in Nb3Sn

Nov. 30 10:00-10:25

*Xingchen Xu1, Xuan Peng2, Fang Wan1, Jacob Rochester3, Mike Sumption3
Fermi National Accelerator Laboratory, US1
Hyper Tech Reserach Inc., US2
Ohio State University, US3

The record Jc of Nb3Sn conductors has been at a plateau since the early 2000s; however, much higher Jc than the state of the art is required for future energy-frontier circular colliders. For example, the non-Cu Jc required by the planned Future Circular Collider (FCC) is ~50% higher than what present Nb3Sn conductors can deliver. In the past few years a new type of Nb3Sn conductors with artificial pinning centers (APC) have demonstrated significantly superior performance relative to the state of the art. Such APC wires are based on the internal oxidation method, which generates nano-size oxide particles in Nb3Sn. It was found that this method improves high-field Jc via four mechanisms: (1) refining Nb3Sn grain size, (2) the particles directly serving as flux pinning centers, (3) shifting flux pinning force (Fp-B) curve peak to higher field, (4) enhancing Birr and Bc2. In 2019 the APC wires we developed first reached the FCC Jc specification. Since then the efforts have been mainly focused on pushing the APC wires toward readiness for practical applications, including improvement of stability. In this talk a comprehensive review of the APC Nb3Sn conductors will be given, including its opportunities, challenges, current status and future plans.

Keywords: Nb3Sn, Artificial Pinning Center, APC, Internal Oxidation