Measurement of the transverse Jc profiles of coated conductors using a magnetic knife of permanent magnets

The transverse Jc distribution in YBCO coated conductors was measured non-destructively with high resolution using a 'magnetic knife' made of permanent magnets. The method utilizes the strong depression of Jc in applied magnetic fields. A narrow region of low (including zero) magnetic field, in a surrounding higher field, is moved transversely across the sample in order to reveal the critical-current density distribution. The net resolution of this device is approximately 65 μm, and the Jc resolution is better than 0.5%. A Fourier series inversion process was used to determine the transverse Jc distribution in the sample. The Jc profile was correlated with other sample properties of coated conductors prepared by pulsed laser deposition. Because of its straightforward and inexpensive design, this Jc imaging technique can be a powerful tool for quality control in coated-conductor production.