Quench energy and fatigue degradation properties of Cu- and Al/Cu-stabilized Nb-Ti epoxy-impregnated superconductor coils

• Published in: IEEE transactions on applied superconductivity 1995-06, Vol.5 (2), p.222-225
• Main Authors: Bray, S.L., Ekin, J.W., Waltman, D.J., Superczynski, M.J.
• Format: Article
• Language: English
• Subjects: Conductivity; Current measurement; Degradation; Energy measurement; Fatigue; Mechanical variables measurement; Saturation magnetization; Superconducting coils; Superconducting magnets; Testing
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/77.402529

In comparative measurements of small-scale epoxy-impregnated Cu-stabilized and Al/Cu-stabilized Nb-Ti test coils at 4 K and 5 T, the heat energy required to quench the Al/Cu-stabilized coil was 4 to 12 times greater than for the Cu-stabilized coil, depending on the relative operating current. Also, the coils' stabilizer resistivity (/spl rho/) was measured as a function of mechanical fatigue to test for strain-induced degradation. The /spl rho/ of the Cu-stabilized coil is relatively unaffected by fatigue, while that of the Al/Cu-stabilized coil increases with fatigue. However, in these coils, having a typical stabilizer:superconductor ratio of 4:1, the degradation of the Al/Cu-stabilized coil begins to saturate after several hundred fatigue cycles; after 2000 fatigue cycles to 0.2% strain, the /spl rho/ of the Al/Cu-stabilized coil is still 2.6 times lower than the /spl rho/ of the Cu-stabilized coil. Furthermore, after annealing the Al/Cu-stabilized coil at room temperature for 48 hours, the /spl rho/ degradation was reduced by 76%. Thus, the use of Al/Cu stabilizer may offer substantial improvements in magnet stability, even where the magnet is subjected to fatigue degradation from repeatedly energizing the magnet.< >