Magnetic induction and its evaluation in superconducting disc under electromagnetic exposure

Abstract The distribution of the magnetic induction in a superconducting (SC) disk under electromagnetic influence was studied using the magneto-optical (MO) method. Particular attention was paid to the behavior of the trapped flux in a disk, being a SC permanent magnet, used in technical devices (motors, generators, etc). These magnets endure repeated electromagnetic ‘shocks’ during operation, which may influence their performance. Our results reveal a direct correlation between the electromagnetic exposure and the trapped flux response, with each increase or decrease in the field inducing a corresponding 40%–50% change in trapped flux for a 600 G step at 5 K. The magnitude of these changes depends on various external conditions, which could lead to additional energy dissipation and potential heating, which can affect the reliability of SC magnets in applications. MO imaging of the penetration field reveals the formation of a highly irregular flux front structure, which may reflect the distribution of pinning centers. The transformation of this induction structure demonstrates an enhancement in shielding properties as a result of extruded alloy annealing. A scaling analysis of the induction flux profiles reveals roughness exponents in the range of 0.435–0.475 and Hausdorff dimensions in the range of 1.525–1.565, both of them influenced by magnetic field strength, temperature, and annealing.