超导性.第2部分:临界电流测量.Nb3Sn复合超导体的直流临界电流

[中文适用范围]： IEC 61788 的这一部分涵盖了测定 Nb3Sn 复合超导体直流临界电流的测试方法，该超导体由青铜工艺或内部锡扩散工艺制造，铜/非铜比大于 0.2。该方法适用于在标准测试条件下以及在小于或等于上临界磁场 0.7 倍的磁场下临界电流小于 1 000 A 且 n 值大于 12 的超导体。测试过程中将测试样品浸入已知温度的液氦浴中。 Nb3Sn复合测试导体具有整体结构，总圆形横截面积小于2mm2。该测试方法中使用的样本几何形状是感应线圈样本。本标准给出了例行试验所允许的与本试验方法的偏差以及其他具体限制。临界电流高于 1 000 A 或总横截面积大于 2 mm2 的 Nb3Sn 导体可以用本方法测量，但精度预计会降低，自场效应会更显着（见附录 C）。其他更专业的样本测试几何形状可能更适合较大的导体测试，为简单起见并保持精度，本标准已省略这些几何形状。本标准给出的试验方法原则上适用于任何其他工艺制造的Nb3Sn复合丝。该方法经过适当修改后也有望适用于其他超导复合线材。 [外文原描述]： This part of IEC 61788 covers a test method for the determination of the d.c. critical current of Nb3Sn composite superconductors which are fabricated by either the bronze process or the internal tin diffusion process and have a copper/non-copper ratio larger than 0,2. This method is intended for use with superconductors which have critical currents of less than 1 000 A and n-values larger than 12 under standard test conditions and at magnetic fields of less than or equal to 0,7 times the upper critical magnetic field. The test specimen is immersed in a liquid helium bath at a known temperature during testing. The Nb3Sn composite test conductor has a monolithic structure with a total round-cross-sectional area that is less than 2 mm2. The specimen geometry used in this test method is an inductively coiled specimen. Deviations from this test method which are allowed for routine tests and other specific restrictions are given in this standard. Nb3Sn conductors with critical currents above 1 000 A or total cross-sectional areas greater than 2 mm2 can be measured with the present method with an anticipated reduction in precision and a more significant self-field effect (see Annex C). Other, more specialized, specimen test geometries may be more appropriate for larger conductor testing which have been omitted from this present standard for simplicity and to retain precision. The test method given in this standard should in principle apply to Nb3Sn composite wires fabricated by any other process. This method is also expected to apply to other superconducting composite wires after some appropriate modifications.