Reduction of Error in Magnetic Knife Method to Measure$J_rm c$Distribution of YBCO Coated Conductor

The cause of error in the
$J_ c$
distribution determined by the magnetic knife method is discussed. The YBCO coated conductor sample was displaced from the center of the gap and the
$J_ c$
distribution of the sample was determined. The error in the determined
$J_ c$
distribution increases with the displacement of the sample. A measurement and numerical analysis of the magnetic field distribution in the gap revealed that the sample was exposed to the magnetic flux density parallel to its wide face. This magnetic flux density component could influence the
$J_ c$
of the sample, but it was not considered in the magnetic knife method, thus causing an error. Placing the sample at the center of the gap was important for accurate measurements. The influence of the displacement of the sample on the error decreased when the gap was widened.