Effect of uranium doping and thermal neutron irradiation on the flux-pinning of silver-clad Bi-Sr-Ca-Cu-O tapes

• Published in: IEEE transactions on applied superconductivity Vol. 11; no. 1; pp. 3896 - 3899
• Main Authors: Marinaro, D.G., Dou, S.X., Horvat, J., Boldeman, J., Weinstein, R., Sawh, R.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York, NY IEEE 01-03-2001; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Anisotropy; Applied sciences; Australia; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Critical currents; Doping; Effects of crystal defects, doping and substitution; Electrical engineering. Electrical power engineering; Exact sciences and technology; Flux pinning; High temperature superconductors; IRRADIATION; Magnetic flux; Magnetic materials; Materials; Neutrons; Physics; Properties of type I and type II superconductors; RADIATION; RADIOACTIVITY; REDUCTION; Silver; Superconducting materials; Superconducting tapes; Superconductivity; TAPE; Thermal neutrons; Transition temperature variations; Weight reduction
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/77.919920

Ag/Bi-2223 tapes doped with small quantities of /sup 235/UO/sub 4/ powder were prepared by the powder-in-tube process and irradiated in a thermal neutron environment. Substantial improvements in critical current density (J/sub c/)-applied field (H) performance and anisotropy have been previously reported. However, the radioactivity of the silver sheath is a limiting factor for commercial and industrial applications of this technique. Here we report the performance of the technique using various doping levels (from 0.15 to 2 percent by weight (wt.%) UO/sub 4/) and thermal neutron fluences (/spl Phi//sub n/), in order to further reduce the silver radioactivity. Optimum fluence levels are identified and an optimum combination in terms of J/sub c/ - H performance is discussed. At a doping level of 2% /sup 235/UO/sub 4/, a normalised J/sub c/ enhancement of 250 times is observed for an 0.8 T field aligned along the c-axis, and 25 times at 3 T along the ab-plane at 77 K, compared to pre-irradiation values. At 0.6%, these figures are 500 and 10 times, respectively. The effects of the uranium doping and thermal neutron irradiation on the flux pinning strengths are also directly probed using dynamic relaxation techniques. The results show an increase in the effective pinning potential after doping and irradiation.