Wideband-RL-cancel circuit for the E-J property measurement using the third-harmonic voltage method

Abstract

A precise and generalisable non-destructive measurement technique is required for evaluation of critical current density JC and electric field E vs. current density J properties in large-area and long-length high-temperature superconducting films. We measured E-J properties of a 2-inch ϕ Y-123 standard film for the calibration of our inductive measurement system using the third-harmonic voltage method. With adoption of a wideband-RL-cancel circuit, frequency normalised third-harmonic resistance contained noise less than 0.2 μΩs and power-law E-J dependencies were in the relatively wide electric field range of 1.4×10-6-1.6×10-4 V/m. Critical current density JC at 10-4 V/m on 7 different positions changed from an average of 2.839×1010A/m2 by a maximum of ±0.52%. As the JC distribution was also included, the maximum error margin of JC became remarkably small in the V3 inductive method. E-J properties of a 20×20mm square Dy-123 film agreed well with the properties measured by another research group. JC at 10-4 V/m and n value were 2.23×1010 A/m2 and 26.74 on the average of four different positions, with estimated systematic errors of -8.6% and +1.4%, respectively, by comparison of the averages of 16 positions measured by the same research group.