Strain Studies on Superconducting Nb3Sn Tape Using Differential Thermal Contraction and Other Methods
Nb3Sn tape, manufactured by the General Electric Company for cryocooled, magnetic resonance imaging (MRI) magnets, was examined to determine the influence of strain on critical current, Ic, over a wide range of magnetic fields and temperatures. Copper stabilized Nb3Sn tapes were strained by differential thermal contraction by waxing or epoxying the samples to 4.7 cm diameter short sample test bobbins made of brass, stainless steel, Inconel, nickel, niobium and molybdenum. These samples were measured for Ic in transverse fields ranging from 0 to 7 Tesla (T) and over a temperature range of 4 2 to 16 Kelvin (K). Additionally, Nb3Sn tape, subjected to bend, twist and pressure stresses, was measured for Ic degradation to determine handling limits during manufacture and insulation of the tape, as well as magnet winding. Finally, unstabilized, reacted Nb3Sn foil subjected to various tensile loads was tested for Ic degradation. Surface metallography was used to relate cracking of the Nb3Sn layer to Ic degradation.
KeywordsNickel Zirconium Epoxy Brittle Molybdenum
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