Field Angular Dependence of Hysteresis Losses of Coated Conductor for High Field Magnets

Hysteresis loss (Qhyst) of REBCO coated conductors strongly depends on magnetic field orientation. This is mostly due to the shape and critical current (Ic) anisotropy of the coated conductors. For example, while Qhyst in a field parallel to the ab plane is negligibly small, Qhyst in a field perpendicular to the ab plane is much greater than what is typical in a multifilamentary LTS wire. Therefore, during a field ramp of a high-field magnet made of coated conductor tape, at locations where the radial field component is significant, the heat generated by Qhyst will significantly affect the design temperature margin, and increase the operation cost associated the liquid helium consumption. Therefore, it is very important to characterize and understand the field angular dependence of Qhyst. In this paper, we use a vibrating sample magnetometer to measure the field angular dependence of Qhyst of a coated conductor made by SuperPower Inc. Most of the measurements were performed at 4.2 K in ±9 T magnetic field cycle with different field orientations. Our results of Qhyst angular dependence and the correlation between Qhyst and the Ic angular dependence are presented. The factors affecting measurement accuracy such as sample size, field angle uncertainty due to the magnetic torque will be discussed. Based on our experimental data, a practical formulation calculating Qhyst(B, θ, T, I) is proposed.