Field and current distributions and ac losses in a bifilar stack of superconducting strips

TL;DR

This paper analytically investigates magnetic-field and current distributions, as well as ac losses, in an infinite stack of superconducting strips with opposite currents, providing formulas and numerical estimates for practical applications.

Contribution

It introduces analytical expressions for magnetic-field, current distributions, and ac losses in a bifilar stack of superconducting strips, incorporating critical-state theory and flux penetration effects.

Findings

Derived explicit formulas for magnetic-field and current distributions.

Provided analytical and numerical estimates of ac losses.

Enhanced understanding of flux penetration and loss mechanisms in superconducting stacks.

Abstract

In this paper I first analytically calculate the magnetic-field and sheet-current distributions generated in an infinite stack of thin superconducting strips of thickness d, width 2a >> d, and arbitrary separation D when adjacent strips carry net current of magnitude I in opposite directions. Each strip is assumed to have uniform critical current density Jc, critical sheet-current density Kc = Jc d, and critical current Ic = 2a Kc, and the distribution of the current density within each strip is assumed to obey critical-state theory. I then derive expressions for the ac losses due to magnetic-flux penetration both from the strip edges and from the top and bottom of each strip, and I express the results in terms of integrals involving the perpendicular and parallel components of the magnetic field. After numerically evaluating the ac losses for typical dimensions, I present analytic expressions from which the losses can be estimated.