Damage Caused by Magnetic Pressure at High Trapped Field in Quasi-PermanentMagnets Composed of Melt-Textured Y-Ba-Cu-O Superconductor

摘要

Quasi-permanent magnets made of melt-textured YBa2Cu3O7 - delta (MT-YBCO)superconductor can now trap multi-tesla fields, B sub t. The interaction of the trapped field and the critical current causes an outward pressure, proportional to B sub t (2), which can crack the magnet. We have done an experiment to observe such cracking in a mini-magnet fabricated from four MT-YBCO discs activated at 49 K using an applied field of 14 T. We have compared the results to existing theories which describe magnetic pressure in a trapped-field magnet (TFM) previously activated. We find that a modification is needed to describe magnetic pressure during the process of activation. We present the experimental results and the expanded theory, based on the simple Bean model. Theory and experiment show good agreement. We find that cracking is more likely during activation, and conclude that 10 T is achievable in TFM's composed of present materials. Cracking is most probable at the center of a TFM, with the cracks running radially outward.