Transverse ac susceptibility of superconducting bars with elliptical cross-section andconstant critical-current density

Abstract

The complex ac susceptibility χ = χ′−j χ′′ of an infinitely long hard superconducting bar with an elliptical cross-section of semi-axesa and b is numerically calculated with a uniform ac field applied along theb axis, based on the critical-state model with a constantJc. Normalized to theexact low-field limit of −χ′, χ0,−χ′ andχ′′ as functions of thefield amplitude Hm normalized to the exact full penetration fieldHp are given in tablesand figures for 0.01≤b/a≤100. It isshown for any value of b/a that, with increasing Hm/Hp, χ′′ is proportional to and inversely proportional toHm at and , respectively. Defining a characteristic point as whereχ′′ takes its maximumχ′′m, it is shown that,with increasing b/a,χ′′m/χ0 increases from 0.188 to0.229, whereas Hm(χ′′m)/Hp increasesfrom 0.35 to 1.18 and −χ′(χ′′m)/χ0 displays a minimum at b/a≈0.5. The results are used for comparing with some experimental data of a mono-filamentaryBi-2223/Ag tape.