Influence of Shielding Currents in Coated Conductors on Field Quality of Iron-Dominated HTS Magnets Estimated by Numerical Analyses

Abstract

Additional magnetic fields induced by shielding currents (persistent eddy current induced in superconductor) are called shielding-current induced fields (SCIFs). SCIFs are serious problem in magnets using tape-shaped high-temperature superconductor (HTS) wires, because it would worsen the accuracy and stability of the generated magnetic field of the magnets. In iron-dominated HTS magnets, magnetic field distribution at air gap between iron magnetic poles is dominated by poles' shape, so the influence of SCIFs on the quality of generated magnetic field is usually considered negligible. However, quantitative estimation of SCIFs is required to support this assumption. Therefore, we developed a practical method to estimate SCIF distributions in iron-dominated HTS magnets and use it to estimate temporal change of SCIF distribution in an iron-dominated HTS magnet. According to the analysis results, we confirmed relative error of magnetic field caused by SCIFs is in the order of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> , which is negligible in many magnet applications.