Modeling cross-field demagnetization of superconducting stacks and bulks for up to 100 tapes and 2 million cycles

TL;DR

This paper presents a fast numerical model to simulate the demagnetization of superconducting stacks and bulks under ripple magnetic fields over millions of cycles, revealing their long-term magnetization behavior and stability.

Contribution

A novel, computationally efficient model based on dynamic magneto-resistance for simulating long-term demagnetization in superconducting materials.

Findings

Superconducting stacks reach a non-zero stationary magnetization after many cycles.

Bulks maintain higher stationary magnetization than stacks at high ripple amplitudes.

Stacks lose less magnetization in early cycles compared to bulks.

Abstract

Superconducting stacks and bulks can act as very strong magnets (more than 17 T), but they lose their magnetization in the presence of alternating (or ripple) transverse magnetic fields, due to the dynamic magneto-resistance. This demagnetization is a major concern for applications requiring high run times, such as motors and generators, where ripple fields are of high amplitude and frequency. We have developed a numerical model based on dynamic magneto-resistance that is much faster than the conventional Power-Law-resistivity model, enabling us to simulate high number of cycles with the same accuracy. We simulate demagnetization behavior of superconducting stacks made of 10-100 tapes for up to 2 million cycles of applied ripple field. We found that for high number of cycles, the trapped field reaches non-zero stationary values for both superconducting bulks and stacks; as long as the ripple field amplitudes are below the parallel penetration field, being determined by the penetration field for a single tape in stacks. Bulks keep substantial stationary values for much higher ripple field amplitudes than the stacks, being relevant for high number of cycles. However, for low number of cycles, stacks lose much less magnetization as compared to bulks.