Trapped Field Profiles for 40-mm Wide Superconducting Tape Pieces
Stacks of superconducting tape can be magnetized to form a new type of permanent magnet due to their ability to circulate persistent currents. Previous work has mostly focussed on magnetization of smaller stacks made of 12-mm tape, but this study reports the trapped field from both field cooling and pulsed field magnetization at 77 K for larger 40-mm wide, high-temperature superconducting tape produced by Bruker HTS. The tape used in this study had a critical current of approximately 570 A at 77 K (self-field). The trapped field profile is reported for a stack of eight octagonal tape pieces showing very high symmetry, and detailed Hall probe scans of the individual tape layers at 77 K reveal the uniformity of the pieces and presence of any defects which divert current flow. The effect of cutting the layers and also applying compressive strain on the tape pieces was investigated. It was found that cutting the 40-mm large squares into octagons had negligible effect on trapped field whilst compressing the layers, which are naturally curved, can lead to reversible degradation of trapped field for large enough compression. Magnetized stacks of tape of a large size and relatively uniform current density represent an attractive technology for trapped field permanent magnets with high magnetic field and flux.
KeywordsYBCO Coated conductor Superconducting tape Trapped field Pulsed magnetization
Authors would like to acknowledge the financial support of the Engineering and Physical Sciences Research Council, UK, for the work reported.
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