Ekin Jack, Cheggour Najib, Goodrich Loren, Splett Jolene, Bordini Bernardo, Richter David, Bottura Luca
National Institute of Standards and Technology, Boulder, CO 80305 USA.
University of Colorado, Boulder, CO 80309 USA.
IEEE Trans Appl Supercond. 2017 Jun;27(4). doi: 10.1109/TASC.2017.2647852.
Scaling analysis of several thousand NbSn critical-current measurements is used to derive the extrapolative scaling expression (ESE), a fitting equation that can quickly and accurately extrapolate (or interpolate) limited datasets to obtain full three-dimensional dependences of on magnetic field , temperature , and mechanical strain . Unlike nonextrapolative fitting equations, the ESE relation is determined completely by fundamental raw scaling data from master pinning-force curves. The results show that extrapolation errors with ESE approach typical measurement errors. The scaling expression is simple and robust, providing straightforward extrapolation capability for conductor characterization and magnet design. The ESE relation offers the prospect for extrapolations in several new areas, including: a reduction in the measurement space required for full characterization to about one fifth the size; ability to combine data from separate temperature and strain apparatuses; extrapolation of transport data from above 4 K to lower temperatures, where heating effects and instabilities are problematic for transport measurements; and extrapolation of full datasets from as little as a single curve when several core parameters have been measured in similar conductors (particularly applicable to qualifying production wires). Accuracies are evaluated for concatenations of these different extrapolation capabilities. Examples are given for practical NbSn conductors, including those for high luminosity-LHC magnets, ITER, and cryo-cooled NMR magnets.
通过对数千次铌锡临界电流测量进行标度分析，推导出外推标度表达式（ESE），这是一个拟合方程，它能够快速且准确地对外推（或内插）有限数据集，以获得临界电流(I_c)对磁场(B)、温度(T)和机械应变(\epsilon)的完整三维依赖关系。与非外推拟合方程不同，ESE关系完全由来自主钉扎力曲线的基本原始标度数据确定。结果表明，采用ESE方法的外推误差与典型的测量误差相当。该标度表达式简单且稳健，为导体特性描述和磁体设计提供了直接的外推能力。ESE关系为在几个新领域进行外推提供了前景，包括：将完整(I_c)特性描述所需的测量空间减少到约五分之一大小；能够合并来自单独温度和应变装置的数据；将传输(I_c)数据从4K以上外推到更低温度，在低温下加热效应和不稳定性对传输测量存在问题；以及当在类似导体中测量了几个核心参数时（特别适用于合格生产导线），从仅一条(I_c)曲线外推完整的(I_c)数据集。评估了这些不同外推能力组合的精度。给出了实际铌锡导体的示例，包括用于高亮度大型强子对撞机磁体、国际热核聚变实验堆（ITER）和低温冷却核磁共振磁体的导体。
