Significant reduction in the low-field magnetization of Nb3Sn superconducting strands using the internal oxidation APC approach
[1];
[2];
[1];
- Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
- The Ohio State University, Columbus, OH (United States)
- Hyper Tech Research Incorporated, Columbus, OH (United States)
- Florida State University, Tallahassee, FL (United States). National High Magnetic Field Laboratory (MagLab)
Nb3Sn superconductors are promising for building accelerator magnets for future energy-frontier circular colliders. A critical factor for this application is the low-field persistent-current magnetization because it leads to several critical issues: e.g. low-field instability (including flux jumps), hysteresis loss, and field errors in magnet bores. Suppression of low-field magnetization requires reduction of low-field critical current density (Jc) or effective subelement size (deff). However, reduction of deff of state-of-the-art Nb3Sn conductors—the restacked-rod-process (RRP®) type—below 40–50 μm without a pronounced decrease in high-field Jc is difficult. On the other hand, the internal oxidation method which forms artificial pinning centers (APC) in Nb3Sn offers an alternative approach to reducing the low-field magnetization. Compared with a conventional Nb3Sn conductor whose flux pinning force versus field (Fp–B) curve peaks at ~20% of its irreversibility field (Birr), the Fp–B curve peaks of APC conductors shift to higher fields due to the point pinning effect, leading to flattening of the Jc–B curves. The goal of this paper is to quantitatively study how much the APC approach can reduce the low-field magnetization. Here we measured the Jc–B curves of an RRP® conductor and two APC conductors (reacted at 700 °C) from zero field to Birr using a high-field vibrating sample magnetometer. Here the results showed that the APC conductors have higher non-Cu Jc at high fields (e.g. 32%–41% higher at 16 T) and simultaneously lower non-Cu Jc at low fields (e.g. 28%–34% lower at 1 T) compared with the RRP®. This effect is due to a competition between their Nb3Sn layer fraction ratios and layer Fp ratios. Suppose they reach the same 16 T non-Cu Jc, then the 1 T non-Cu Jc and magnetization of the APC conductors are only half or even less compared with the RRP® conductor.
- Research Organization:
- Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP); National Science Foundation (NSF)
- Grant/Contract Number:
- AC02-07CH11359; SC0017755; DMR-1644779
- OSTI ID:
- 1971789
- Report Number(s):
- FERMILAB-PUB-23-099-TD; oai:inspirehep.net:2654022
- Journal Information:
- Superconductor Science and Technology, Vol. 36, Issue 8; ISSN 0953-2048
- Publisher:
- IOP PublishingCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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