Calculation of AC magnetic losses from the experimental field profiles in a coated conductor under various external fields and temperatures

Abstract

We developed a method for the estimation of AC loss in superconducting tapes. First we measured the field profiles, H(x, H-a), near the surface of a coated conductor (CC) using the scanning Hall probe method. Here, the x axis was parallel to the in-plane transverse direction of the CC tape and H-a is the external field applied in normal direction with respect to the tape surface. Then from H(x, H-a), we calculated the current profiles, J(x, H-a), by the inversion method. From J(x, H-a) and the corresponding flux densities, we calculated the hysteretic energy losses per cycle, Q(M). H-a was decreased from H-peak to -H-peak stepwise, and the temperatures were 77 K and 72 K. We estimated Q(M) for various values of H-peak. We calculated the dimensionless characteristic function, g, which are defined by Q(M)/(mu I-0(c)2). Here I-c is the critical current. Our g is similar to the Brandt's theoretical g although the current profile, J(x, Ha), is somewhat different.