0~3.5 T直流背景磁场下第二代高温超导带材临界电流各向异性测试与分析

Test and analysis of critical current anisotropy of second generation superconducting tape under 0~3.5 T DC background magnetic field

为掌握第二代(2G)高温超导(HTS)带材在0~3. 5 T直流背景磁场下的临界电流(Ic)和n值变化趋势,构造和应用了一种新型分裂背场磁体系统,通过测试分析获得了背景磁场对Ic和n值的影响规律。采用4. 2 K运行温度、两个同轴分裂的NbTi线圈构成的超导磁体和样品保持器来改变背景磁场的大小和角度(0~3. 5 T、0~90°),2G HTS带材置于液氮环境(77 K),设置电流源上升速率为1 A/s,基于四引线法原理与直流失超判据(1μV/cm)获得2G HTS带材在高直流背景磁场下的Ic和n值,实验结果表明,2G HTS带材的Ic和n值变化趋势一致,均随外界磁场强度B和带材表面与磁场夹角θ的增大而退化,在背景磁场为1. 4 T时,2G HTS带材在垂直场下的临界电流衰减了84. 6%,是平行场下临界电流衰减程度的1. 47倍。

In order to master the trend of critical current(I c)and value n of second generation(2G)high temperature superconducting(HTS)tape under 0~3.5 T DC background magnetic field,a new type of split back field magnet system was constructed and utilized.The law of influence of the background magnetic field on I c and value n was obtained by test analysis.Superconducting magnets and sample holders with 4.2 K operating temperature and two coaxially split NbTi coils are used to change the magnitude and angle of the background magnetic field(0~3.5 T,0~90°).2G HTS tape was placed in a liquid nitrogen environment(77 K),and the current source rise rate was set to 1 A/s.Based on the four-lead method principle and the criterion of loss of DC superconductance(1μV/cm),I c and n of the 2G HTS tape under DC background magnetic field were obtained.The experimental results show that the I c and n values of 2G HTS tape show the same trend,which are degraded with the external magnetic field strength B and the increase of the angleθbetween the tape surface and the magnetic field.When the background magnetic field is 1.4 T,the 2G HTS tape is vertical,I c under the field is attenuated by 84.6%,which is 1.47 times the degree of parallel field critical current attenuation.