Suppression of Influence of AC External Magnetic Field on Trapped Magnetic Flux in the HTS Bulk by Use of HTS Shielding Rings

Trapped magnetic fields in high temperature superconductor (HTS) bulks are decayed when the bulks are subjected to perturbation of magnetic fields. This phenomenon is inconvenient for the applications of HTS bulks and it is necessary to develop methods to suppress the decay. It was found in a previous study that the decay is caused by temperature rises of the bulks due to AC losses in the bulks. Therefore, it is necessary to develop a method to reduce the AC losses. In this work, a method is proposed to reduce the AC losses by putting HTS shield rings around the bulk and shielding performance of the rings were investigated. The experimental result shows that the shielding rings can drastically suppress the decay, even if the bulk is used in the same cooling condition and the effectiveness of the method was demonstrated.