Evaluation of isotopic boron (11B) for the fabrication of low activation Mg11B2 superconductor for next generation fusion magnets. Issue 10 (25th April 2020)

• Record Type: Journal Article
• Authors: Jie, Hyunseock; Luzin, Vladimir; Zaman, Mukter; Valiyaparambil Abdulsalam, Anvar; Chae, Keun Hwa; Choi, Hyung‐il; Levchenko, Vladimir; Nijhuis, Arend; Kim, Jung H.; Mustapić, Mislav; Dou, Shi Xue; Yamauchi, Yusuke; Khan, Aslam; Shahriar A. Hossain, Md.
• Is Part Of: Journal of the American Ceramic Society. Volume 103:Issue 10(2020)
• Page Start: 5488
• Page End: 5495
• Publication Date: 2020-04-25
• Subjects: boron isotope -- critical current density -- magnesium diboride -- superconductors; Ceramics -- Periodicals; 620.1405
• DOI: 10.1111/jace.17156
• Languages: English
• ISSNs: 0002-7820

Abstract

Abstract: In this study, we analyze the properties of boron isotope ( 11 B)‐rich powders from three different sources, that is, American, Cambridge, and Pavezyum, to fabricate the bulk Mg 11 B2 superconductors and evaluate their superconducting properties. While 11 B‐rich powder is an essential precursor to fabricate Mg 11 B2 superconductors for fusion magnet applications, the properties of the 11 B powder turned out to be critical to determine the quality of the final superconducting product. Therefore, appropriate control of processing conditions is needed to comply with the requirements of the nuclear fusion application. Analysis of the B isotope ratio by accelerator mass spectroscopy and neutron transmission revealed that all three types of powder are enriched with 11 B to better than 99 at % quality. In addition, Pavezyum's 11 B shows the lowest crystallinity and smallest crystalline domain size as evidenced by the high‐resolution X‐ray diffractometer and scanning electron microscopy. The chemical states of the boron isotope investigated with near edge X‐ray absorption fine structure spectroscopy and X‐ray photoemission spectroscopy also reveals that Pavezyum boron has amorphous structure. Mg 11 B2 bulks and multi‐filamentary (12‐filament) wires have been manufactured, sintered at different temperatures and characterized via the transport critical current density. The wire with Pavezyum 11 B shows three times higher current carrying capacity at a particular magnetic field compared to the wire using Cambridge 11 B and hence, Pavezyum 11 B boron has the potential for manufacturing fusion grade Mg 11 B2 based magnets. The results of this study demonstrated that Boron powders with higher purity, smaller grain size and lower crystallinity are critical for improving the superconducting and electronic properties of Mg 11 B2 samples fabricated from the powder. Thus, the low‐neutron‐activation Mg 11 B2 is possibly an affordable and technically viable candidate to replace NbTi superconductors in the low field poloidal field and correction coils for the next‐generation fusion reactors.