Strain induced irreversible critical current degradation in highly dense Bi-2212 round wire

Abstract

The strain induced critical current degradation of overpressure processed straight Bi-2212/Ag wires has been studied at 77 K in self-field. For the first time superconducting properties, lattice distortions, composite wire stress and strain have been measured simultaneously in a high energy synchrotron beamline. A permanent Ic degradation of 5% occurs when the wire strain exceeds 0.60%. At a wire strain of about 0.65% a drastic n-value and Ic reduction occur, and the composite stress and the Bi-2212 lattice parameter reach a plateau, indicating Bi-2212 filament fracturing. The XRD measurements show that Bi-2212 exhibits linear elastic behaviour up to the irreversible strain limit.

Comparison of Electromechanical Properties and Lattice Distortions of Different Cuprate High-Temperature Superconductors

“…With the UTM integrated in the ID15 beamline of ESRF the lattice parameter changes, I c , stress and strain of the Bi-2223 HT-CA tape were measured as described in [8]. A critical current of I c =193 A is measured before application of an external load, which is in good agreement with the I c =194 A value that is reported in [19].…”

“…This test configuration also enables simultaneous X-ray diffraction (XRD) measurements in transmission geometry in a high energy synchrotron beamline for studying the lattice distortions in the composite wire [6,7]. Here we present the results of a simultaneous XRD, I c , stress-strain study of a Bi-2223 tape, and compare the results with those reported previously for a Bi-2212 wire [8].…”

“…The outer wire sheath is made of a Ag-0.2wt.%Mg alloy. After OP processing the wire has been submitted to an optimisation heat treatment for maximizing I c at 77 K. For more information about the Bi-2212 wire see reference [8]. The samples have largely different cross sections and aspect ratios (see Table I).…”

“…Diffraction peaks were fitted with Gaussian functions to follow the relative d-spacing changes as a function of the wire strain measured with the extensometer. For more information about the diffraction experiment see reference [8].…”

Advances in the Development of a 10-kA Class REBCO Cable for the EuCARD2 Demonstrator Magnet

“…Cycling within the initial loading range is however quasireversible. More recent data [31], [32] indicate an extended reversible range. It is not clear how much of this behavior is affected by the porosity and connectivity features of early wires.…”