Calculation of AC Magnetic Losses from the Experimental Field Profiles in a Coated Conductor Under Various External Fields and Temperatures

摘要

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 $Q_{M}/(mu_{0}I_{c}^{2})$. Here $I_{c}$ is the critical current. Our g is similar to the Brandt''s theoretical g although the current profile, $J(x,H_{a})$, is somewhat different.