GB/T 21546-2008 Critical current measurement—DC critical current of Nb-Ti composite superconductors

Scope

This standard test method is applicable to the determination of the DC critical current of copper/niobium-titanium (Cu/Nb-Ti) composite superconductors with a copper-to-superconductor ratio greater than 1. It is also applicable to the determination of the DC critical current of copper/copper-nickel/niobium-titanium (Cu/Cu-Ni/Nb-Ti) superconductors with a niobium-titanium core wire diameter greater than 1 μm, a copper-to-superconductor ratio greater than 0.9, and a copper-nickel alloy (Cu-Ni)-superconductor ratio greater than 0.2. Since the critical current test methods for copper/niobium-titanium (Cu/Nb-Ti) composite superconductors and copper/copper-nickel/niobium-titanium (Cu/Cu-Ni/Nb-Ti) superconductors are slightly different, Appendix C (normative) of this standard will introduce the special provisions that need to be followed when measuring copper/copper-nickel/niobium-titanium (Cu/Cu-Ni/Nb-Ti) superconductors. This standard test method is applicable to superconductors under standard test conditions where the magnetic field is less than or equal to 0.7 times their upper critical magnetic field, the critical current is less than 1,000 A, and the n value is greater than 12. During measurement, the tested samples should be immersed in liquid helium at a known temperature. The tested conductors should be integrated superconducting wires with a circular or rectangular cross-section and a cross-sectional area less than 2 mm2. The tested samples should have a spiral coil geometry. This standard also specifies the allowable deviations and other specific limitations for this experimental method in daily testing. Conductors with a critical current greater than 1,000 A or a cross-sectional area greater than 2 mm2 can also be measured using this method, but the measurement uncertainty will increase, and the self-field effect will be more pronounced (see Appendix B). In addition, for the sake of simplicity and maintaining relatively low measurement uncertainty, this standar

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