Conveners
M1OrF - Focused Session: Pushing Nb3Sn Conductors Beyond the State of the Art
- Xingchen Xu (FNAL)
- Peter Lee (NHMFL / FSU / ASC)
Over the past couple of years we have carried out the thus far most extensive neutron irradiation study on Nb3Sn. Samples of five types of state-of-the-art multifilamentary wires as well as high-purity polycrystals were exposed to sequential fast neutron irradiation in the TRIGA Mark-II reactor in Vienna. Irradiation induced changes in the superconducting properties were assessed by means of...
The record Jc of Nb3Sn conductors has plateaued since the early 2000s; however, new target has been put forward for the planned future circular colliders. This presentation aims to discuss prospects for further improvement of Nb3Sn conductors. The factors determining the non-Cu Jc are summarized, which include current-carrying Nb3Sn fraction in subelements, Nb3Sn Bc2, and pinning capacity;...
The heat treatment of internal tin Nb3Sn wires has historically used multiple low temperature stages designed to mix the Cu and Sn as to minimize liquid contact with the Nb filaments, to inhibit Kirkendall void formation, or to increase the Sn concentration surrounding the Nb filaments prior to the A15 reaction. Our recent studies have shown that the unique geometry of high-Jc RRP® wires,...
For cost-effective 15-16 T accelerator magnets, the critical current density Jc(15T,4.2K) of commercial Nb3Sn composite wires has to be pushed from the present state-of-the-art for RRP® wires of ~1,650 A/mm2 to ~2,000 A/mm2. Only so much improvement can be obtained through heat treatment optimization. Wire development was therefore carried out in collaboration with Oxford Instruments -...
Prior to his passing in late 2016, Leszek Motowidlo
developed a method of applying the Nb-1Zr/SnO2 internal oxidation method
to APC Nb3Sn through a powder-in-tube (PIT) approach that used low-cost
Cu5Sn4 powder as the Sn source. Two designs of
multifilamentary PIT wire were successfully produced and fine-grain A15 layers
with average grain diameters...
The relatively low cost of multifilamentary Nb$_3$Sn strand compared to HTS alternatives makes it highly valuable to magnet builders to improve the critical current densities (J$_c$) beyond the current production limits of ~ 3 kA/mm$^2$ (12 T,4.2 K) available today. Future applications such as the proposed Future Circular Collider demand increased J$_c$ at higher fields (≥16 T) that current...
