Detection of Critical Current Distribution of YBCO-Coated Conductors Using Permanent Magnet Method

We developed a non-destructive and contactless system for measuring the critical current (I
_c
) in YBa
₂
Cu
₃
O
_7-δ
(YBCO)-coated conductors by using a permanent magnet (Sm
₂
Co
₁₇
). This I
_c
measurement method is based on the repulsive force (F
_r
) between the magnet and the shielding current in high-temperature superconductor-coated conductors. We measured F
_r
using a high-resolution load sensor and found that accurate F
_r
could be determined without the effect of thick copper film on the YBCO thin film and Hastelloy tape of the substrate. We can determine I
_c
from F
_r0
, which is the maximum repulsive force determined from an extrapolated value of the F
_r
vs. L curve for L = 0 mm, described in our previous paper. We show that the permanent magnet method can be used to determine the longitudinal I
_c
distribution and large-scale defects in YBCO-coated conductors. In addition, it turned out from this experiment that the permanent magnet method was effective to rapidly measure the longitudinal I
_c
distribution of long-scale coated conductors.